INDUSTRIAL CHEMISTRY 
 
 A MANUAL 
 
 FOE USE IN TECHNICAL COLLEGES OR SCHOOLS 
 AND FOE MANUFACTUEEES ETC. 
 
 BASED UPON A TRANSLATION (PARTLY BY DR T. D. BARRY) 
 OF STOHMANN & ENGLER'S GERMAN EDITION 
 
 OK 
 
 PATEN'S 'PRECIS DE CfflMIE INDUSTRIELLE 
 
 rb 
 
 /ayeo 
 
 EDITED THROUGHOUT 
 
 AND SUPPLEMENTED WITH CHAPTERS ON THE CHEMISTRY OP THE METALS fcc. 
 
 BY 
 
 B. H. PAUL, PH.D. 
 
 ILLUSTRATED WITH 698 ENGRAVINGS ON WOOD 
 
 UITI7ERSIT7 
 
 LONDON 
 LONGMANS, GEEEN, AND CO 
 
 1878 
 
PREFACE. 
 
 ONE of the most noteworthy characteristics of the present time 
 is the growing recognition of science as the highest form of 
 practical knowledge, and of the fact that, since the processes of 
 industrial art are but particular instances of the general habitudes 
 of nature, the successful conduct of technical operations, no less 
 than the improvement of particular branches of industry, involves 
 acquaintance with natural facts and principles, which it is the 
 special business of abstract science to deal with altogether apart 
 from considerations of utility. 
 
 In this respect no branch of science is more important than 
 Chemistry, because there is scarcely any great industry in which 
 the materials operated upon are not, at some stage or other, 
 made to undergo chemical alteration. In the extraction of the 
 useful metals from their ores, in the making of glass and pottery- 
 ware, in dyeing and calico-printing, as well as in the preparation 
 of various articles of food, such as bread, beer, etc., the desired 
 results are obtained by producing suitable chemical alterations. 
 
 The various branches of industry involving a knowledge of 
 Chemistry are moreover of such vast national importance that, 
 while special practical experience is- essential for their conduct, 
 some general acquaintance with them is calculated to be useful 
 to those not directly engaged in such pursuits ; since the develop- 
 ment or modification of old-established industries, as well as the 
 introduction of new ones by the application' of chemical dis- 
 coveries, often determine radical and far-reaching changes that 
 influence general commerce not less than particular departments 
 of trade. 
 
vi PREFACE. 
 
 A knowledge of Chemistry is, therefore, to be regarded as one 
 of the most essential qualifications of those engaged in manu- 
 facturing pursuits, and on this account it has long been made a 
 subject of study in Continental schools. The desirability of 
 adopting a similar course in this country is gradually becoming 
 recognised, and it is believed that a work treating of the technical 
 applications of Chemistry, in a concise and systematic manner, 
 will be of service in promoting the general introduction of its 
 study in schools and technical colleges. 
 
 From these points of view Payen's Precis de Chimie industrielle 
 has been selected as the basis of this work, because it has always 
 held a high position in France where the study of Chemistry 
 in its practical relations has long been systematically carried out 
 as well as in Germany where the technical value of science 
 is most of all appreciated and most successfully realised. 
 
 The' systematic treatment of the subject in the original work 
 has been rendered more complete by the addition of several 
 chapters on the general chemistry of the metals and metal- 
 lurgical operations, as well as several other branches of industry 
 not dealt with in the French or German editions ; so that the book 
 will serve as a manual of Chemistry no less than as a source of 
 information as to the nature of particular industrial operations. 
 
 BENJAMIN H. PAUL. 
 
 CHEMICAL LABORATORY, 
 1 VICTORIA STREET, 
 
 WESTMINSTER. 
 
INDUSTRIAL CHEMISTEY. 
 
 GENERAL INTRODUCTION. 
 
 Nature of Chemical Phenomena In most of the operations of nature and 
 art there is some obvious alteration of the material substances concerned in them. 
 Such phenomena are the sensible manifestations of the activity inherent in all sub- 
 stances, and they are of two kinds. Thus, for instance, a, bar of iron, when sufficiently 
 heated, changes colour and becomes luminous : a mass of lead, under similar condi- 
 tions, becomes liquid ; and a lump of sugar placed in water gradually disappears, com- 
 municating its-sweet taste to the water. Otherwise than in those particulars, however, 
 the several substances remain unaltered in all these instances : although the heated 
 iron is red, luminous, and softer than it was before being heated, it is just as much 
 iron ; while the liquid lead is essentially the same substance that it was before being 
 melted. So, likewise, the solution of sugar in water is, like most other cases of simple 
 solution, a phenomenon in which the alteration of either substance extends only so 
 far as is indicated by the sugar becoming liquid and the water sweet ; with these ex- 
 ceptions, both substances maintain their individuality, and they may be separated by 
 simply evaporating the water, when the sugar will remain behind unchanged in 
 quantity or in any of its characters. Phenomena of this kind are termed Physical in 
 the more restricted sense of the word, and their consideration belongs to the science of 
 Physics. 
 
 But a more radical alteration of material substances is the specially characteristic 
 feature of many phenomena. Thus, when iron is exposed to the air, it becomes coated 
 with a reddish crust, which gradually becomes thicker, and after a sufficient length of 
 time the entire mass of the iron is converted into a red substance. Again, when a 
 lump of sugar is suddenly heated, it melts, assumes a dark colour and swells up, 
 giving off a quantity of vapour, until at last there remains a black coaly mass. The 
 alteration in both instances is of such a nature that the distinctive characters of the 
 original substances totally disappear and what remains is, in each case, not iron or 
 sugar. 
 
 The changes that take place in the rusting of iron and in the charring of sugar 
 serve to illustrate, in a general way, the nature of chemical action, and of the pheno 
 mena which are termed Chemical, in contradistinction to Physical or Mechanical 
 phenomena, that do not involve any such radical alteration of material substances. 
 The peculiar characteristic of chemical phenomena is the production of substances 
 altogether different from those concerned in their formation. In this respect the 
 effect of chemical action differs essentially from that of mere mechanical mixture or 
 separation. Thus, for instance, if powdered sulphur be intimately mixed with very 
 finely divided iron filings until the mixture appears to the eye as a perfectly uniform 
 grey powder, there is still no alteration of the two substances beyond intermixture. 
 The particles of sulphur and iron may be seen by the aid of a powerful microscope, 
 and they may even be separated mechanically by mixing some of the powder with 
 alcohol, and stirring with a magnet, to which the particles of iron will adhere, leaving 
 the sulphur as a yellow powder. The separation may also be effected by digest imr 
 the powder with some liquid that dissolves sulphur without acting upon iron or the- 
 reverse. 
 
 B 
 
2 PHYSICAL CHARACTERS OF SUBSTANCES. 
 
 If, however, some of the mixed powder be heated on an iron plate, it becomes in- 
 candescent, cakes together, and assumes a darker colour. After this has taken place, 
 it is no longer possible to recognise distinct particles of iron and sulphur in the 
 ma>- that remains, nor is it possible to separate those substances as before by any of 
 the means above described. In fact, the substance that remains is neither iron nor 
 sulphur: the alteration of these substances, as a result of chemical action, being of 
 such a nature that both the sulphur and the iron disappear as such, and another sub- 
 stance distinct from both of them is produced. In all cases of chemical action there 
 is such a positive metamorphosis of material substances, and phenomena of this kind 
 constitute the subject-matter of chemical science. 
 
 Many phenomena connected with agriculture, animal nutrition and domestic 
 economy, as well as many of the processes of manufacturing industry, are essentially 
 chemical ; hence the successful conduct of various operations of the Industrial arts 
 presupposes an acquaintance with the general principles of Chemistry as well as 
 special practical experience. 
 
 Definition of Chemistry. In conformity with the distinction already pointed 
 out as existing between physical and chemical phenomena, Chemistry may be defined 
 as that branch of physical science which treats of the nature and relations of material 
 substances, as regards their constitution and the metamorphoses of which they are sus- 
 ceptible. The extension of this knowledge and the elucidation of general principles by 
 research, altogether apart from considerations of utility, constitute the special object of 
 abstract chemistry. The object of technical chemistry, on the contrary, is the practical 
 application of chemical knowledge for particular purposes and its utilisation, either in 
 explaining the chemical processes that take place in various cases, or in modifying 
 those processes to answer particular ends. It is from the latter point of view that the 
 subject will be dealt with in detail in the following pages ; but it is desirable, in the 
 first place, to describe some of the characters most intimately connected with the 
 physical constitution of substances, and to give a brief resume of the general principles 
 of Chemical Science. 
 
 PHYSICAL CHARACTERS OF SUBSTANCES. 
 
 The individuality of different substances is indicated to our senses by certain 
 definite associations of characters, which are intimately connected with the constitu- 
 tion or special nature of the particular substances to which they belong. 
 
 The physical characters of substances are therefore of great interest to the chemist 
 since they serve to distinguish a great number of substances from each other. Among 
 the most important are the state of aggregation, density or the relation of weight 
 and volume; colour, expansion, fusibility, and other relations to light and heat 
 solubility, o<lour, taste, etc. 
 
 State of Aggregation. The physical condition-solid, liquid, or gaseous 
 which a substance presents under certain conditions, is often an important Distinc- 
 tive character. 
 
 Some substances are ordinarily known only in a single state of aggregation for 
 mrtance. lime and carbon as solids ; atmospheric air, hydrogen, etc., algases. Other 
 substances are known in two states of aggregation, as, for instance, alcohol in the liquid 
 I n i^!^ l8 _ 8 ! a ^ *** ! < he ** and liquid states. But many substances^ e 
 
 , u saes. ut many substances 
 
 capable of assuming all three of these conditions. Sulphur, for instance, under ordinary 
 
 Tu IsZeTdl "f ^h T y 1>e T 11 * 1 by meaUS f heat and converted iSoS 
 state, and by further heating made to assume thegaseous state. The same holds 
 good w.th water, which unto ordinary conditions a liquid-may be converted bv ah 
 
 8tra nt S0l<l 8t 
 
 Cein l ' o e 
 
 Certain physical charae ore, such as hardness, crystalline form and struc- 
 ture, etc., appertain specially to the solid state; fluidity or internal mobffltvfc a 
 common, character of the liquid and gaseous states ; and Jhigh degree oTex pins i* 
 bihty is characteristic of the gaseous state. 
 
 In each of these states substances are capable of being subdivided to -in exten- 
 ar ,-xceeding the power of observation ; but since the occupation of ptedenoLd 
 by the term ,xt, ; ns,,,,, is inseparable from the idea of substance and inconsistent wfth 
 .nfin,t.-d,y 1 s 1 lMl,ty, substances are regarded from a physical point of ~W 
 constituted of extr,m,ly minute particles or molec-uh'-s, and the activTv that 
 some form or other, a general character of natural sul,,.,,,^, is wL^e 
 ing * these ultimate particles or molecules, the cons.itut i,,,, ,,r internal structure of 
 
DENSITY AND SPECIFIC GRAVITY. 3 
 
 The internal consistence of a solid or a liquid is indicative of a cohesive action 
 between the molecules or ultimate particles of individual substances. This action is 
 greatest in solids, less in liquids, and almost nothing in gases. 
 
 The cohesion of different substances varies very considerably, as is indicated by 
 the degree of resistance which they offer to tearing, breaking, or disintegration; and 
 the characters of toughness, brittleness, malleability, etc., as well as the diversity of 
 internal structure indicated by differences in the surfaces of fracture of solids, and by 
 the degree of viscosity of liquids, are results of the varied exercise of molecular 
 action. Crystallisation is one of the most remarkable modes in which the exercise of 
 force is manifested as influencing the internal structure of many solid substances. 
 The regular geometrical forms which cry stalli sable substances are capable of assuming 
 are often sufficiently characteristic to be of considerable assistance in distinguishing 
 such substances from each other : thus, for instance, the crystals of ordinary nitre are 
 hexagonal prisms, while those of the corresponding substance called sodium nitre are 
 cubes. 
 
 Density : Specific Gravity. Substances differ considerably as regards 
 density, or the ratio of quantity to volume denoted in ordinary language by the terms 
 heavy and light. Thus, for instance, gold is called a heavy substance, cork a light 
 substance ; the one sinks in water since its density is greater, the other floats because 
 its density is less than that of water ; but both substances sink with equal facility 
 through air, the density of which is very considerably less than that of water or of 
 cork. Platinum and hydrogen furnish an extreme illustration of the differences 
 existing in respect to density, the one being nearly 24,000 times as dense as the other. 
 The density of a substance is also a character that is constant under like conditions, 
 and therefore it often serves the purpose of identification in conjunction with other 
 characters. 
 
 Equal volumes of different substances necessarily differ in weight proportionately 
 to their difference in density; and the numerical expression of the relative weights of 
 substances, as compared with some standard, is termed their specific gravity. 
 Water is generally taken as the standard of comparison for liquids and solids ; while 
 the standard for gases is either atmospheric air or hydrogen. 
 
 The cubic inch of water weighs under normal conditions of temperature and 
 atmospheric pressure 252-5 grains, and this is the unit to which specific gravities are 
 referred according to the English system ; and the differences in specific gravity are 
 expressed in thousandths. Thus, a cubic inch of sulphuric acid weighs 465'62, and 
 consequently its specific gravity is T848 
 
 252-5 : 465-62 = I'OOO : 1'848. 
 
 According to the French system of weights and measures, in which the litre is the 
 unit of volume and the gram the unit of weight, the hundredth part of a litre of water 
 weighs 1 gram at 4 C. and the weight of a cubic centimetre of 'any other substance 
 expressed in grams is also the specific gravity of the substance. 
 
 Practically considerable use is made of specific gravity. From the specific gravity 
 of liquids containing various substances in solution, the amounts of such substances 
 may be ascertained. Water containing another substance dissolved in it is rendered 
 specifically heavier or lighter according to the nature of the dissolved substance. If 
 the substance dissolved be specifically lighter than water, the specific gravity of the 
 solution is reduced ; as, for instance, in the case of a mixture of alcohol and water. 
 The specific gravity is increased when the substance dissolved is specifically heavier 
 than water, as, for instance, in the case of a solution of salt or a mixture of sulphuric 
 acid and water. In the same way the specific gravity of water is increased or reduced 
 by the solution of gases. The specific gravity of a solution of ammonia is less than 
 that of water, while that of a solution of hydrochloric acid gas is greater. 
 
 A very convenient instrument for determining the specific gravity of liquids is 
 the hydrometer, which consists of a hollow globe or cylinder, with a stem con- 
 structed so as to float upright when immersed in a liquid. The volume and weight of 
 the instrument are so regulated that it sinks in water either to the point A or A' 
 according as it is required to indicate the specific gravity of liquids specifically 
 heavier or lighter than water, and the points to which the hydrometer sinks in liquids 
 of various specific gravity are indicated upon the stem, either by figures corresponding 
 to actual specific gravity or by arbitrary degrees. If such'an hydrometer be placed in 
 a liquid, the specific gravity can be at once read off. An instrument of this kind is, 
 however, only serviceable for a definite temperature, because the specific gravity of 
 liquids alters with the temperature. 
 
 Hydrometers are also constructed so as to indicate directly the amounts of par- 
 ticular substances in mixtures or solutions : e.g. the alcoholometer for determining 
 the alcoholic contents of a liquid, the saccharimeter for determining the saccharine 
 contents of solutions of sugar, etc. 
 
 B2 
 
4 PHYSICAL CHARACTERS OF SUBSTANCES. 
 
 Melting Point: Boiling Point. Every solid body that is capable of assuming 
 a different state of aggregation must, for its conversion into the liquid condition, be 
 raised to a temperature peculiar to itself: this temperature is termed the melting 
 point of the substance. In like manner every liquid for its conversion under the 
 ordinary atmospheric pressure into the gaseous state, must be raised to a temperature 
 peculiar to itself, and this temperature is termed the boiling poi nt of the liquid. 
 
 The state of aggregation of substances is influenced not only by heat, but likewise 
 
 by the pressure to which they are subject. For instance, if a vessel containing water 
 be placed under the receiver of an air-pump, and the atmospheric pressure upon the 
 surface of the water is reduced by pumping out the air, the water will boil and assume 
 the gaseous condition at the ordinary temperature. On the other hand, a gas may be 
 converted, by means of pressure, into the liquid state. Quite recently hydrogen, 
 oxygen, and nitrogen, which have hitherto been regarded as permanently gaseous, have 
 been liquefied, and probably all gases admit of being thus converted by pressure into 
 the liquid or the solid condition. 
 
 Specific Beat. Equal quantities of different substances require unequal quantities 
 of heat to raise their temperature equally. 
 
 . By the specific heat of a substance is understood the relative amount of heat which 
 it requires in order to produce a certain increase of temperature. The quantity of 
 heat requisite for raising the temperature of a kilogram of water from 4 to 5 Cent, 
 is taken as the unit, and this is termed the heat-unit. 
 
 The quantity of heat requisite to produce an equal increase of temperature in a 
 kilogram of mercury is only 0'033 of the heat unit, and this fraction expresses the 
 specific heat of mercury relatively to water = TOGO ; in other words, the same quan- 
 tity of heat that raises the temperature of a kilogram of water one degree, Centi- 
 grade, would produce an equal increase of temperature in about 30 kilograms of 
 mercury. 
 
 The heat unit, however, is not an absolute quantity; it varies according to the 
 unit of weight and the thermometric scale to which it refers. According to British 
 usage the heat unit is the quantity of heat that raises the temperature cf a pound of 
 water from 40 to 41 Fahrenheit. The kilogram being about 2^ times as much as 
 the pound, and the Centigrade degree T8 times the Fahrenheit degree, there is a 
 proportionate difference between the British and French heat units. 
 
 British heat unit. French heat unit. 
 
 1- = 0-251996 
 
 3-96832 = 1- 
 
 Specific heat is of practical importance, for the quantity of heat requisite for raising 
 the temperature of a definite weight of any substance can be calculated if the specific 
 heat of the substance in question be known. The greater the specific heat is, the greater 
 is the quantity of heat which has to be communicated to the liquid in order to 
 raise its temperature to any given degree, and the less the specific heat the smaller 
 is the quantity of heat which is requisite. 
 
 NATURE OF CHEMICAL ACTION. 
 
 If the experiments already mentioned as illustrative of the distinction between 
 physical and chemical phenomena were made under such conditions that the weights of 
 the substances could be ascertained both before and after the alteration produced in 
 each case, it would be found that, while the iron bar weighed just the same after 
 being heated as it did before, and while the weight of the solution of sugar in water 
 was exactly equal to the joint weights of the sugar and the water used, considerable 
 alterations of weight accompanied the chemical alteration of the iron in rusting ami 
 that of the sugar by charring it. The reddish substance resulting from the alteration 
 of the iron would weigh nearly half as much again as the iron before it underwent 
 that change. On the contrary, the black cinder left after heating the sugar would 
 not weigh more than about one-third as much as the original sugar. Such alteration 
 in weight is invariably recognisable when substances undergo chemical change, and it 
 constitutes one of the most marked characteristics of chemical phenomena. By further 
 examination, it would be found that in the rusting of iron another substance is added 
 to the iron, and that this addition exactly accounts for the observed increase of weight. 
 The substance thus added to the iron is oxygen, derived from atmospheric air, and the 
 change that takes place consists in the union of these two substances, iron and oxy- 
 gen, in such a way as to produce another substance quite distinct from either of them, 
 just the same as, by heating the mixture of iron and sulphur previously mentioned, 
 another substance is produced. Chemical change of this kind is termed combination] 
 
CHEMICAL ACTION. 5 
 
 By a similar examination of the other instance given as illustrating chemical change, 
 it would be found that the substances given off as vapour on heating sugar would 
 exactly make up the difference in weight between the cinder and the original sugar, 
 and that the change consists in the resolution or breaking up of an individual sub- 
 stance into several other substances distinct from it. Chemical change of this kind is 
 termed decomposition. 
 
 All substances are susceptible, under the influence of various conditions, of being 
 transformed by chemical action in one or other of the modes just described, and by 
 such means a vast number of substances may be produced from those actually met with 
 in nature. Some of the most important operations of industrial art have for their 
 object the production of such chemical alterations. 
 
 But though all material substances can be chemically altered either by decomposi- 
 tion or by combination, chemical research has led to the discovery of certain sub- 
 stances which are in so far peculiar that they cannot be decomposed by any known 
 means. No one of the substances belonging to this class can be transformed into any- 
 thing that is different, and at the same time less in quantity. The peculiarity of these 
 substances consists in their being capable of chemical change only by combination 
 with other substances ; consequently, the chemical alteration of these substances is 
 invariably attended with increase of weight, as in the rusting of iron. The alteration 
 iron undergoes in rusting consists in combination with atmospheric oxygen ; and as 
 iron is a substance of the kind now referred to, it is only by such combination with 
 some other substance that it undergoes chemical change. Some of the characters of 
 iron may indeed be altered by various means : by very intense heating it may even be 
 converted into a liquid state ; it may also be rendered magnetic; and it may be reduced 
 to such an extremely minute state of subdivision as to appear an impalpable black 
 powder ; but in all these cases the alteration is merely of that kind already described 
 as physical and affecting only the internal structure of the substance ; the quantity of 
 material is neither increased nor decreased, the essential nature of the substance remains 
 unaltered : and even in the minute particles of the black powder the distinctive cha- 
 racters of metallic iron may be recognised by the aid of the microscope. 
 
 Substances of this kind, which cannot be decomposed, are therefore termed simple 
 s ub s ta n c e s, in contradistinction to c o m p o u n d s, or those substances which are capable 
 of being decomposed. All substances of the latter class may, however, be resolved by 
 chemical action into two or more simple substances ; and, for this reason, the simple 
 substances are, from a chemical point of view, regarded as the primary materials or 
 ultimate constituents of which all compound substances are made up. Hence they are 
 termed elementary substances or chemical elements. 
 
 The elementary substances of modern chemistry are at least sixty-three in number, 
 as detailed in the first column of the accompanying table, and the distribution of these 
 elementary substances, under different conditions, is indicated by the asterisks in 
 columns 4 to 13. 
 
 Only a few of the elementary substances occur naturally in the free state, as \t is 
 termed in chemical language, when they are uncombined with other substances (see 
 column 11 of the table). The greater number of them are always met with in various 
 states of combination with each other. However, the compounds of the several 
 elementary substances occurring naturally are not, generally speaking, very numerous 
 as compared with the multiplicity of compound substances that can be obtained 
 artificially by various methods of chemical treatment. 
 
 Some of the chemical elements are extremely rare, and the substances containing 
 them are of little or no importance for practical purposes ; but some others, on the 
 contrary, are of very general occurrence, either in the free state or as constituents 
 of some of the most abundant and most important materials concerned in the chemical 
 phenomena of nature and of industrial art. These latter are thirty-five in number, 
 and they are distinguished in the table by the large type in which their names arc 
 printed. Out of these thirty-five elementary substances there are eighteen, indicated 
 by the asterisks in the fourth column, which occur very abundantly and very 
 frequently in all kinds of materials belonging to the mineral kingdom. The thirteenth 
 column shows that precisely the same eighteen elementary substances are distributed 
 throughout the materials originating from plants and animals. Only four of these 
 elementary substances carbon, oxygen, nitrogen, sulphur occur naturally to any 
 considerable extent in the uncombined state. 
 
 Eelatively the greatest number of elementary substances occur in mineral veins 
 or lodes, where nearly all the more rare elementary substances are found, excepting 
 those associated with platinum (see column 8). In granite rocks, also, there is a very 
 general distribution of elementary substances (column 7), while in basaltic and 
 Icanic rocks the number of elementary substances is smaller (see columns 5 and 6). 
 The elementary substances that have been found in the melted masses of lava, and 
 
ELEMENTARY SUBSTANCES. 
 
 Aluminum 
 
 Antimony . 
 
 Arsenic 
 
 Barium 
 
 Bismuth 
 
 Boron 
 
 Bromine 
 
 Cadmium 
 
 Caesium 
 
 Calcium 
 
 Carbon 
 
 Cerium . 
 
 Cblorine 
 
 Chromium . 
 
 Cobalt 
 
 Copper 
 
 Didymium 
 
 Erbium 
 
 Fluorine 
 
 Glucinum 
 
 Gold . 
 
 Hydrogen . 
 
 Indium . 
 
 Iodine 
 
 Iridium 
 
 Iron 
 
 Lanthanum . 
 
 lead . 
 
 Lithium 
 
 Magnesium 
 
 Manganese 
 
 Mercury 
 
 Molybdenum . 
 
 XTickel 
 
 Niobium 
 
 Nitrogen . 
 
 Osmium 
 
 Oxygen 
 
 Palladium 
 
 Phosphorus 
 
 Platinum . 
 
 Potassium . 
 
 Rhodium 
 
 Rubidium 
 
 Ruthenium . 
 
 Selenium 
 
 Silicon 
 
 Silver . 
 
 Sodium 
 
 Strontium . 
 
 Sulphur 
 
 Tantalum 
 
 Tellurium 
 
 Thallium 
 
 Thorium 
 
 Tin 
 
 Titanium 
 
 Tungsten 
 
 Uranium 
 
 Vanadium 
 
 Yttrium 
 
 Zinc . 
 
 Zirconium 
 
 2 
 
 3 
 
 4 
 
 5 
 
 (i 
 
 7 
 
 8 
 
 9 
 
 10 
 
 11 
 
 u 
 
 IS 
 
 A1 
 
 
 
 
 
 
 
 
 
 
 
 
 Sb 
 
 122 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 # 
 
 
 
 
 
 As 
 Ba 
 Bi 
 B 
 Br 
 Cd 
 
 Cs 
 r\ 
 
 75 
 137 
 210 
 11 
 80 
 112 
 133 
 
 
 
 
 
 
 
 # 
 * 
 
 
 M- 
 # 
 # 
 * 
 
 # 
 
 ft 
 # 
 
 
 
 
 
 
 
 # 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Co 
 
 Pi 
 
 138 
 
 - 
 
 
 
 
 
 
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 n 
 
 
 
 
 
 
 
 
 
 
 Or 
 Co 
 PH 
 
 52 
 
 59-8 
 
 
 
 
 
 * 
 # 
 
 # 
 
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 n 
 
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 ft 
 ft 
 
 
 
 Di 
 
 Eb 
 
 TTl 
 
 95 
 168-9 
 
 1 Q 
 
 
 
 
 
 
 
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 v 
 
 
 
 
 
 
 
 
 
 
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 Au 
 
 9-4 
 
 197 
 j 
 
 
 
 
 
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 ft 
 
 
 ft 
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 - 
 
 
 
 
 
 
 
 
 In 
 I 
 Ir 
 
 "Fft 
 
 113-4 
 127 
 198 
 
 ec 
 
 * 
 
 
 
 # 
 
 ! 
 
 I 
 
 * 
 
 = 
 
 * 
 
 z 
 
 
 
 La 
 Pb 
 
 93-6 
 207 
 
 
 
 
 
 
 * 
 
 * 
 
 
 
 
 
 
 
 
 
 
 
 L 
 
 Mo- 
 
 7 
 
 94. 
 
 
 
 
 
 
 
 * 
 
 # 
 
 fc 
 
 
 
 
 
 
 
 
 
 iug 
 Mn 
 
 ^r 
 
 
 
 
 
 
 
 
 
 
 "* 
 
 Hg 
 Mo 
 
 Ni 
 Nb 
 N 
 Os 
 
 o 
 
 200 
 96 
 59 
 94 
 14 
 199-2 
 16 
 
 # 
 
 
 
 # 
 
 * 
 # 
 
 K 
 V 
 
 H 
 
 
 * 
 
 # 
 
 * 
 
 
 
 # 
 
 # 
 
 * 
 
 ft 
 
 Pd 
 p 
 
 106-5 
 31 
 
 
 
 
 
 * 
 
 *? 
 
 * 
 
 
 
 
 
 ?( 
 
 
 
 
 
 Pt 
 K 
 
 197-1 
 39 
 
 
 
 
 
 # 
 
 
 
 # 
 
 
 
 
 
 X 
 
 
 
 
 
 Eh 
 Rb 
 Ku 
 
 Se 
 Si 
 
 104-4 
 85-4 
 104-4 
 80 
 28'5 
 
 
 
 
 * 
 * 
 
 
 
 * 
 
 
 ^ 
 
 * 
 
 * 
 * 
 
 * 
 
 
 Ag 
 Na 
 
 108 
 23 
 
 
 ~ 
 
 
 
 ft 
 
 * 
 
 
 
 
 
 * 
 
 
 
 Sr 
 
 s 
 
 88 
 32 
 
 $. 
 
 * 
 
 
 
 
 ( 
 
 
 
 
 
 
 
 
 
 
 Ta 
 Te 
 
 182 
 128 
 
 
 
 
 # 
 
 # 
 
 
 
 
 
 
 
 
 
 
 Tl 
 Th 
 Sn 
 Ti 
 W 
 U 
 V 
 Y 
 Zn 
 Zr 
 
 204 
 231-5 
 118 
 50 
 184 
 240 
 51-3 
 92 
 65 
 89-5 
 
 
 
 * 
 
 * 
 
 * 
 
 * 
 
 # 
 
 tf 
 # 
 * 
 # 
 
 f 
 # 
 
 V 
 
 tt 
 * 
 # 
 # 
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CHEMICAL CLASSIFICATION. 
 
 in the various other solid, liquid, and gaseous materials, ejected from the interior of 
 the earth during volcanic eruptions (see column 10), as well as in the water of mineral 
 springs rising from very great depths (see column 9), are the same as those existing in 
 rock at and near the earth's surface (see columns 4, 5, 6, and 7): hence it is inferred that 
 the material of the earth is in this respect the same throughout. The chemical nature 
 of volcanic products admits, moreover, of the conclusion that in the interior of the earth, 
 with some few exceptions, the elementary substances exist, in the same relative pro- 
 portions and in the same states of combination as at the surface. 
 
 Column 12 indicates the elementary substances that have been found in meteor- 
 ites. 
 
 Classification of Elementary Substances. The elementary substances are 
 commonly classified as metals and metalloids, according to their physical characters in 
 the uncombined state, and partly also, on account of their relations in a chemical 
 point of view. The metals most generally known are, with the single exception 
 of mercury, solid under ordinary conditions : they are absolutely opaque and present a 
 peculiar lustre or brilliancy that may be increased by polishing. Another physical 
 character, which, in combination with those already mentioned, has been regarded as 
 most distinctive of metallic substances, is an internal mobility, in virtue of which the 
 shape of a mass of metal may be altered by pressure, hammering, or other mechanical 
 means, without disintegration or disruption of the substance. This character is 
 expressed by the terms malleability denoting a capability of flattening or spreading 
 out under the hammer or between rollers and ductility denoting a capability of 
 lengthening, and becoming thinner by stretching or being drawn through a hole of 
 less area than the transverse section of the piece of metal. Metals are also excellent 
 conductors of heat and electricity. In regard to these characters, however, the metals 
 present marked differences of degree, and some of the elementary substances comprised 
 among metalloids also differ only in degree from those popularly known as metals. 
 The distinction is, therefore, to a great extent arbitrary, and so far as such characters 
 are concerned the classification of certain elementary substances as metalloids merely 
 signifies that those substances resembling metals, in so far as they are elementary, 
 possess in a less marked degree the characters distinctive of metals. 
 
 METALS. 
 
 
 METALLOIDS. 
 
 Oxygen 
 Sulphur 
 
 Selenium 
 Tellurium 
 
 Chlorine 
 Bromine 
 Iodine 
 Fluorine 
 
 Nitrogen 
 
 Phosphorus 
 
 Arsenic 
 
 Carbon 
 
 Boron 
 
 Silicon 
 
 The difference between metals and metalloids in regard to chemical characters and 
 relations is manifested chiefly in the functions which the substances of one or the 
 other class perform in their compounds. Probably all elementary substances are 
 capable of existing in a state of combination with each other in pairs : but as a rule 
 this capability is greater in proportion to the difference between the elementary sub- 
 stances. Thus, for instance, compounds of the metals with each other possess far less 
 stability and individuality than the compounds of metals with oxygen or sulphur, 
 chlorine. &c., and they present greater resemblance to mere mechanical mixtures than 
 compounds of the latter class, which generally possess characters totally different from 
 :hose of their constituents in the uncombined state. This is also the case, to some 
 
 Hydrogen 
 Potassium 
 
 Cobalt 
 Nickel 
 
 2sr 
 
 Sodium 
 
 Uranium 
 
 Thallium 
 
 Lithium 
 
 Iron 
 
 Indium 
 
 Caesium 
 
 Chromium 
 
 
 Rubidium 
 
 
 Mercury 
 
 
 Tin 
 
 Silver 
 
 Bari um 
 
 Titanium 
 
 Gold 
 
 Strontium 
 
 Zirconium 
 
 Platinum 
 
 Calcium 
 
 Thorium 
 
 Palladium 
 
 
 Molybdenum 
 
 Rhodium 
 
 Aluminum 
 
 Tungsten 
 
 Ruthenium 
 
 Glucinium 
 
 Niobium 
 
 Osmium 
 
 Yttrium 
 
 Tantalum 
 
 Iridium 
 
 Erbium 
 
 Vanadium 
 
 
 Cerium 
 
 Antimony 
 
 
 Lanthanum 
 
 Bismuth 
 
 
 Didymium 
 
 
 
 Magnesium 
 
 
 
 Zinc 
 
 
 
 Cadmium 
 
 
 
8 COMBINING PROPORTIONS. 
 
 extent, with the compounds of certain metalloids with each other, though as a rule the 
 metalloids have a greater capability of forming definite and distinct compounds with 
 each other than the metals have. 
 
 Combining Proportions. In compound substances possessing chemical indivi- 
 duality, the elementary substances of which they consist, always bear a definite quantita- 
 tive ratio to each other by weight, which is constant for any particular substance under 
 all conditions in which it is capable of existing. Thus in the case of water, which is a 
 compound of oxygen with hydrogen, the ratio of these elements is as 8 : 1 by weight. 
 The same ratio of elementary constituents obtains in ice and steam, which are merely 
 different molecular forms of the same substance. In chemical action also similar 
 definite relations are always recognizable between the weights of the original sub- 
 stances and the weights of those produced from them either by combination or by 
 decomposition. When oxygen unites with hydrogen to form water it is always in the 
 proportion of 8 : 1 by weight, and whenever water is decomposed the hydrogen 
 produced amounts to | of the water decomposed, while the oxygen produced at the 
 same time amounts to eight times the quantity of the hydrogen by weight. 
 
 The existence of such definite relations of weight among the substances concerned 
 in chemical changes, and between the constituent elements of compound substances, 
 has already been mentioned as one of the most important features of chemical 
 phenomena, and the investigation of this general fact has led to the establishment of 
 the fundamental principle of chemical science, that the elementary substances combine 
 with each other only in definite proportions by weight, the ratio of the elementary 
 constituents of any given substance being constant. 
 
 While in water hydrogen is always combined with eight times its weight of 
 oxygen, in hydrochloric acid it is combined with 35'5 times its weight of chlorine, in 
 hydrobromic acid with 80 times its weight of bromine, in hydriodic acid, with 127 
 times its weight of iodine, in sulphuretted hydrogen, with 16 times its weight of 
 sulphur, in ammonia, with 4'67 times its weight of nitrogen, and in marsh gas, with 
 3 times its weight of carbon. 
 
 Again in the compound of oxygen and chlorine to which the peculiar characters of 
 bleaching powder are due, a quantity of oxygen, equal to that which combines with 
 one part of hydrogen to form water, is combined with 35'5 parts of chlorine, and 
 in carbonic acid gas an equal quantity of oxygen is combined with three parts of 
 carbon. In common salt a quantity of chlorine equal to that which combines with one 
 part of hydrogen to form hydrochloric acid is combined with 23 parts of sodium, and 
 in sodium oxide the proportion of sodium to oxygen is as 23 : 8. 
 
 These quantities of oxygen, chlorine, etc., are relatively to hydrogen the combining 
 proportions of those elementary substances, and since they exactly replace each other 
 in certain compounds they are termed equivalent proportions. 
 
 The relations of the elementary substances to each other in this respect may 
 therefore be expressed by numbers representing the relative proportions by weight in 
 which these substances combine or otherwise take part in the various kinds of chemical 
 change ; and if such numbers represent the proportions in which the several substances 
 combine with the unit of hydrogen or with the quantity of oxygen equivalent to it, 
 they will also represent the proportions in which those substances combine with each 
 other or act chemically upon each other, as shown below: 
 
 Hydrogen 1 
 
 Oxygen ] 8 
 
 Chlorine 35.5 
 
 Bromine 80 
 
 Iodine 127 
 
 Sulphur . ....... .16 
 
 Sodium 23 
 
 Silver ; . . 10 8 
 
 Thus hydrogen and chlorine combine in the proportions of 1 to 35'5 hydrogen 
 and sulphur in the proportions of 1 to 16; chlorine and silver in the proportions of 
 3o'o to 108 ; chlorine and sodium in the proportions of 35'5 to 23 ; oxygen and silver 
 in the proportions of 8 to 108, and so on. 
 
 In the combination of substances which are themselves compound the same rule 
 obtains, and the equivalent of a compound substance is the sum of the equivalents of 
 its constituents. Thus the equivalent of hydrochloric acid is 36-5 = 3o'5 + 1 the 
 equivalent of sodium oxide is 31 = 23 + 8, and when hydrochloric acid reacts 'with 
 sodium oxide it is in the proportion of 36'5 to 31 ; when hydrochloric acid reacts 
 with silver oxide it is in the proportions of 36'5 to 116. 
 
 In many cases, however, the elementary substances are capable of combining with 
 
ATOMIC THEORY. 9 
 
 each other in more than one proportion; for example, there is besides water another 
 compound of hydrogen with oxygen, containing a larger amount of oxygen than water 
 does : there are also two compounds of carbon with oxygen, in which the amounts of 
 oxygen are severally 57' 14 and 7272 per cent., and there are two compounds of 
 iron with oxygen, containing respectively 30 per cent, and 22'22 per cent, of oxygen. 
 But the ratios of the elementary constituents in these compounds bear very simple 
 relations to each other ; the proportions of the constituents in one compound being 
 simply multiples or submultiples of the proportions in which these constituents are 
 combined in another compound of them. Thus, in the two compounds of hydrogen 
 the ratios are as 8 : 1 and as 16 ." 1, the one containing relatively to the hydrogen 
 exactly twice as much oxygen as the other does. In the two compounds of carbon 
 with oxygen, also, the ratios of the constituents are respectively as 3 : 8 and 6 : 8, 
 .the one containing relatively to oxygen just twice as much carbon as the others. In 
 one of the compounds of iron with oxygen the ratio of the constituents is as 28 iron to 
 8 oxygen, while in the other it is as 18'67 iron to 8 oxygen, or 28 x 2 : 8 x 3 = 56 .' 24. 
 This fact is well illustrated by the compounds of nitrogen with oxygen, of which 
 there are five, as follow : 
 
 Nitrogen Oxygen 
 
 4-67 x 3 14 
 4-67x3 - 14 
 
 14 
 4-67x3 - 14 
 
 4-67 x 3 * 14 
 
 Nitrous oxide 
 16 = 8x2 Nitric oxide 
 
 4-67 o i 
 
 or [ Nitrous anhydride 
 
 24 - 8x3* 
 
 32 = 8x4 Peroxide of nitrogen. 
 
 40 ff 8x5 Nitric anhydride. 
 
 Here it will be seen that the quantities of oxygen combined with nitrogen in the 
 last four substances are, relatively to the nitrogen, in the proportions of two, three, 
 four, and five times as much as is combined with the unit of hydrogen in water, or 
 with 14 parts of nitrogen in the first-named substance, the general expression of this 
 fact being that when any elementary substance is capable of combining with another 
 in several proportions, those proportions bear a simple multiple relation to each other. 
 
 A theoretical interpretation of the general fact that in all kinds of chemical 
 change there are such definite and fixed relations of ,jveight between the elementary 
 substances, is furnished by the application of the atomic hypothesis of the constitution 
 of material substances. For this purpose it is assumed that each elementary sub- 
 stance consists of extremely minute particles which are incapable of further sub- 
 division, and are therefore termed atoms. According to this view, chemical change 
 consists in the union or separation of the ultimate particles or atoms of different 
 elementary substances, and the relations of weight observed in all cases of chemical 
 change are due to the relative weights of the atoms of the particular elementary sub- 
 stances taking part in those changes. Thus, for instance, in the combination of hydrogen 
 and chlorine, the weight of the chlorine is thirty-five and a half times as much as that of 
 the hydrogen with which it unites ; in the combination of hydrogen and bromine, the 
 weight of the bromine is eighty times that of the hydrogen, and in the combination of 
 hydrogen and iodine the weight of the iodine is one hundred and twenty-seven times that 
 of the hydrogen. Taking hydrogen as the unit, the relative weights of the atoms of 
 hydrogen, chlorine, bromine, and iodine will therefore be 1, 35'5, 80, and 127. This 
 conclusion presupposes the assumption that in the combination of chlorine, bromine, 
 or iodine with hydrogen, a single atom of each of these substances unites with a 
 single atom of hydrogen, and that is the view adopted in regard to these elementary 
 substances. 
 
 The numbers thus arrived at from a study of the chemistry of the several 
 elementary substances, as representing the relative weights of their ultimate particles 
 or atoms, are termed the atomic weights, and in the cases just mentioned the atomic 
 weights coincide with the equivalents of the substances referred to. But there is not 
 always this coincidence between the atomic weight and the equivalent of an element- 
 ary substance. Thus, for instance, in the combination of hydrogen with oxygen to 
 form water, the weight of the oxygen is eight times as much as that of the hydrogen 
 with which it unites ; but a variety of considerations have led chemists to regard the 
 relative weight of the atom of oxygen as being sixteen times as great as that of the 
 hydrogen atom. According to this view, therefore, the molecule of water will consist 
 of three atoms, viz., two of hydrogen united with one of oxygen. In like manner the 
 compound of hydrogen and nitrogen contains 4*67 times as much nitrogen as hydrogen, 
 but the relative weight of the atom of nitrogen is taken as being fourteen times as 
 freat as that of the hydrogen atom, and therefore the molecule of ammonia is repre- 
 sented as consisting of four atoms, viz., three of hydrogen united with one of nitrogen. 
 
10 QUANTIVALENCE. 
 
 In marsh gas, again, hydrogen is combined with three times its weight of carbon ; but 
 as the relative weight of the atom of carbon is taken as being twelve times as great 
 as that of the hydrogen atom, the molecule of marsh gas is represented as consisting 
 of five atoms viz., four of hydrogen united with one of carbon. 
 
 In other words, the chemical value or combining capacity of the atoms of the 
 elementary bubstances is supposed to differ, and that the atoms of some of them are 
 in this respect equivalent to two, three, or four, or even as many as seven hydrogen 
 atoms ; and this difference in the equivalent value of the atomic proportion of any 
 elementary substance relatively to hydrogen generally extends through all its 
 compounds : thus, for instance, the compounds of the bivalent elementary substance 
 sulphur are generally bivalent also, as in the case of sulphuric acid, etc. 
 
 Those elementary substances which combine with each other in simple atomic 
 proportions, like hydrogen, silver, chlorine, bromine, and iodine, are termed monatomic 
 or univalent ; those which combine with two atomic proportions of hydrogen or 
 chlorine, like oxygen or sulphur, are termed diatomic or bivalent ; those which com- 
 bine with three atomic proportions of hydrogen or chlorine are termed triatomic or 
 trivalent ; while others are termed tetratomic or quadrivalent, pentatomic or quinqui- 
 valent, hexatomic or sexvalent, according to the number of atomic proportions of 
 hydrogen that one atomic proportion of the respective elementary substances is equal 
 to in combining capacity. 
 
 This difference in the chemical value of the atomic proportions of the several 
 elementary substances is in some cases a constant characteristic of elementary sub- 
 stances ; in other cases, however, the same substance is capable of exhibiting different 
 relations of atomicity or chemical value as regards hydrogen and other substances: 
 thus, for example, iron is in some compounds bivalent, in others quadrivalent or 
 sexvalent ; nitrogen in some compounds is trivalent, in others quinquivalent ; molyb- 
 denum is in some compounds bivalent, in others quadrivalent, and in others sexvalent, 
 while even chlorine and oxygen must be regarded in some compounds as being re- 
 spectively septivalent and quadrivalent. 
 
 The numbers placed opposite to the several elementary substances in the third 
 column of the table on page 6 represent the atomic proportions of the several 
 elementary substances, and are termed the atomic weights, inasmuch as they are 
 assumed in accordance with the atomic theory to represent the relative weights of 
 their respective atoms. 
 
 Combination by volume. In addition to-the definite relations of weight existing 
 among the substances concerned in all kinds' of chemical change, there is, in the case 
 of elementary substances that are gaseous, a further remarkable relation between the 
 volumes of the combining proportions. For example, taking hydrogen gas as the unit 
 of volume and of weight in comparing the densities and combining proportions of the 
 elementary substances, the density of chlorine gas is to that of hydrogen gas as 35'46 : 1 ; 
 and these numbers expressing the relative weights of equal volumes exactly coincide with 
 the numbers representing the proportions by weight in which chlorine and hydrogen 
 are chemically combined together in hydrochloric acid. In other words, the elementary 
 constituents of any given quantity of hydrochloric acid would occupy exactly equal 
 volumes when in the free state, under equal conditions of temperature and pressure. 
 Again, the density of oxygen gas is to that of hydrogen gas as 16 : 1, and in water 
 these elements are combined in the proportion of 8 : 1 by weight, consequently the 
 volume of the hydrogen in this compound is to that of the oxygen combined with it as 
 
 2 : i. 
 
 In like manner the density of nitrogen gas is to that of hydrogen gas 14 : 1, and 
 as in ammonia these elements are combined together in the proportion of 4*67 I J by 
 weight, the gaseous volume of the hydrogen in this compound is to that of the nitrogen 
 combined with it as 3 : 1. 
 
 In the case of compound substances that are, under ordinary conditions, gaseous, 
 or are capable of assuming the gaseous condition, and whose constituent elements are 
 also gaseous, there are analogous simple relations between tho gaseous volumes of the 
 compound substances and the volumes of their constituents when in the free state, 
 under equal conditions of temperature and pressure. Thus the density of hydrochloric 
 acid gas is the mean of the densities of its constituents, and is to that of hydrogen as 
 18'25 : 1, since the volume of this gas is equal to the joint volumes of its constituents : 
 
 Hydrogen Chlorine Hydrochloric acid 
 
 I II I I 
 
 1 + 3-55 = 36-5 
 In water the volume of the hydrogen is twice that of the oxygen combined with it, 
 
COMBINATION BY VOLUME. 1] 
 
 and this substance m the state of vapour occupies the same volume as the hydrogen it 
 
 contains : 
 
 Hydrogen Hydr. Oxygen Water 
 
 II II II III 
 
 J + 1 + 16 = 18 
 
 In this case therefore the combination of the elements is attended with a reduction 
 of volume, or, as it is termed, condensation, amounting to one-third of the joint volumes 
 of the constituents in the free state, and the density of water in the state of steam is 
 to that of hydrogen as 9 : 1 . 
 
 The volume of gaseous ammonia is equal to one- half the joint volumes of its con- 
 stituents in the free state : 
 
 Hydrogen Hydr. Hydr. Nitrogen Ammonia 
 
 ~~~ " II I I I I II ill 
 
 1 + 1 + 1 + 14 = 17 
 
 and consequently its density is to that of hydrogen as 8'5 : 1, as there is a condensa- 
 tion amounting to one-half the joint volumes of the constituents. 
 
 NOMENCLATURE AND NOTATION. 
 
 The technical language of Chemistry is of a twofold nature, comprising a system of 
 naming substances according to their composition and a system of representing their 
 composition by certain signs or symbols. 
 
 The nomenclature of the elementary substances is to a great extent arbitrary ; and 
 it would probably be impossible as well as useless to regulate it by any uniform 
 principle. 
 
 The names by which many of the chemical elements are known date back to 
 periods long antecedent to the recognition of the elementary nature of the substances 
 they are now used to represent, as in the case of gold, silver, copper, iron, etc. ; and in 
 some instances certain of these names, such as mercury, sulphur, etc., had formerly a 
 significance very different from what they now possess. Many of the more modern 
 names of elementary substances, such as hydrogen, oxygen, chlorine, etc., are derived 
 from Greek words denoting some characteristic properties of the several substances, 
 or some circumstance connected with their occurrenofe. Thus the name hydrogen is 
 derived from u'Scop water and yswaca to generate, in reference to the fact that water is 
 produced by the combustion of hydrogen. The name oxygen is derived from ovs sour 
 and yfvvtiu} to generate, and it was adopted in reference to a premature assumption 
 that the element it represents was a specific acidifying principle, since many of its 
 compounds possess chemical characters analogous to vinegar. The name phosphorus 
 again is derived from 0o>s light and Qopfoo bear to, on account of the peculiar luminous 
 appearance of the substance it represents. Lanthanum is so named from \av6dvo} to 
 lie hidden, because its oxide had for some time been confounded with that of another 
 elementary substance (cerium); while clidymium is so named from SfSi^uos twin, in refer- 
 ence to its frequent association with lanthanum. The name chlorine is derived from 
 X^capbs green, because of the greenish-yellow colour of this substance, and iodine is so 
 named from loetSrjs violet, on account of the colour of its vapour. The name's of other 
 chemical elements are derived from the names of the substances in which they were 
 discovered, as aluminum from alum, potassium from potash ; or from the names of 
 places where the substances containing them were first found, as strontium from 
 Strontian in Scotland, yttrium from Ytterby in Sweden. In some instances the names 
 of elementary substances are more fanciful, as vanadium, derived from Vanadis. n 
 Scandinavian deity. 
 
 The signs or symbols by which the elementary substances are represented are 
 either the initial letters of their ordinary names, as in the case of carbon, hydrogen, 
 and oxygen, or the initial letter of the Latin name, as in the case of potassium, the 
 symbol of which is K (Kalium), or else the symbol is formed of the initial letter together 
 with some other letter of the name, which serves best to make the symbol distinctive, 
 as in the case of Chlorine Cl, Calcium Ca, Nickel Ni, Iron Fe (ferrum), Strontium Sr, 
 Tin Sn (stannum), and Mercury Hg (hydrargyrum). 
 
 As regards compound substances, the object of systematic chemical nomenclature is 
 not only to give them distinctive names, but at the same time to indicate by those 
 names the elementary composition as well as the chemical nature of the substances 
 they represent. Generally speaking, this is easily done in the case of substances con- 
 taining only two or three elementary constituents ; but the numerous compounds of 
 carbon with hydrogen, oxygen, nitrogen, etc., are to a great extent exceptions to this 
 rule, inasmuch as the constitution of these substances is often very complex. 
 
12 CHEMICAL FORMULAE. 
 
 For the purpose of classification, compounds consisting of two elementary substances, 
 are named according to the elementary constituents which a number of them contain in 
 common. Thus, for instance, compounds of oxygen with another substance are termed 
 oxides ; similar compounds of sulphur or phosphorus are termed sulphides or phos- 
 phides; and compounds of chlorine, bromine, or iodine are termed chlorides, bromides, 
 or iodides, these names indicating the generic character of the substances. 
 
 In naming individual substances of this kind the names of the constituents of a 
 particular substance are coupled together in such a way that while the name of one 
 constituent is made to indicate the generic character of the compound, the name of the 
 other constituent is used as an adjective to indicate its specific characters. Thus, for 
 instance, water, which is a compound of hydrogen with oxygen, is termed hydric oxide, 
 a compound of copper with oxygen is termed cupric oxide, and common salt, a com- 
 pound of sodium with chlorine, is termed sodic chloride. 
 
 Substances composed of the same elementary constituents in different proportions are 
 distinguished by adding a prefix to their generic or specific names, as the case may re- 
 quire, or by varyi ng the termination of their specific names. Thus, for instance, the com- 
 pound of hydrogen and oxygen, containing twice the proportion of oxygen that water 
 does, is termed hydric dioxide, and the compound of copper with oxygen, containing 
 twice the proportion of copper that cupric oxide does, is termed dicupric oxide. Again, 
 two of the compounds of iron and oxygen are respectively named ferric oxide and 
 ferrous oxide. 
 
 The symbols by which the elementary substances are represented indicate not 
 only the nature of these substances but also a definite proportion of each substance, and 
 compounds are represented by formulae constructed by the juxtaposition of the symbols 
 of their constituent elements. Thus, for instance, hydrochloric acid is represented 
 by the formula HC1, which indicates that it is a compound of chlorine and hydrogen 
 in the proportions of 35*5 to 1, and that the molecules of hydrochloric acid or the 
 smallest particles into which it can be separated consist of an atom of chlorine united 
 with an atom of hydrogen. When the molecules of a compound contain more than 
 one atom of an elementary substance a small figure is placed against the symbol ; 
 thus water is represented by the formula H 2 0, to show that the molecule consists of 
 two atoms of hydrogen united with one atom of oxygen. In like manner ammonia is 
 represented by the formula NH 3 , sulphuric acid by the formula H 2 S0 4 , and caustic 
 soda by the formula KHO. 
 
 These formulae represent molecules of the respective compounds, -while the symbols 
 of the elementary substances represent atoms or the smallest quantities which unite 
 chemically, and the molecules of elementary substances are represented as consisting 
 of pairs of similar atoms, thus : HH, 00, NN, etc. 
 
 The chemical value or atomicity of an elementary substance is represented in for- 
 mulae by dashes or roman numerals placed against the symbol, thus : 0" S" N 1 " C iv . 
 
 Chemical change can be represented by arranging the formulae of the substances 
 concerned in the form of an equation ; thus the decomposition of sulphuric acid by 
 zinc is represented as follows : 
 
 H2S0 4 + Zn = ZnS0 4 + 2H. 
 
 A chemical formula is intended to serve as an indication not only of the particular 
 elementary substances contained in a compound, but also of their relative proportions ; 
 thus, for instance, the formula of water, H 2 0, indicates that this substance is not only 
 a compound of hydrogen and oxygen, but that it is a compound consisting of two 
 atomic proportions of hydrogen united with one atomic proportion of oxygen. 
 Chemical formulae are therefore to some extent a means of expressing the constitution 
 of the substances they represent ; but it is only in the case of the most simple com- 
 pounds that this is strictly true ; and, as regards the greater number of compound 
 substances, chemical formulas merely express the modes in which particular substances 
 are capable of undergoing chemical alteration. Many substances are capable of 
 chemical alteration in several different ways, and hence they may be represented by 
 as many different formulae. Thus, for instance, sulphuric acid may be represented by 
 the formula H.,80^ which will serve to represent those alterations that correspond 
 to the reaction between this substance and metallic zinc, consisting in the dis- 
 placement of the hydrogen from sulphuric acid and the substitution of zinc in its 
 place, forming a substance called zinc sulphate. In this ease the displacement of the 
 hydrogen takes place in accordance with the law of equivalents, and it is replaced 1>y 
 32-5 times its weight of zinc. But in representing the change according to the 
 atomic theory, it must be borne in mind that while hydrogen is a monovalent sub- 
 stance, zinc is bivalent. Consequently the two atomic proportions of hydrogen that 
 are united with the bivalent radicle S0 4 in sulphuric acid are replaced by one atomic 
 proportion of the bivalent metal zinc, and the formula of the zinc sulphate produced 
 by this change is ZnS0 4 . 
 
TYPICAL FORMULA. 13 
 
 Again sulphuric acid can be split up into water and sulphuric oxide, and this 
 change is represented by the formula H 2 0,S0 3 according to which sulphuric acid 
 appears as a compound of water and sulphuric oxide. 
 
 Another decomposition of which sulphuric acid is capable is effected by the reac- 
 tion with carbon, which gives rise to the formation of sulphurous oxide, S0 2 , carbonic 
 dioxide, C0 2 , and water, H.,0 ; the change consisting in the abstraction of one-fourth 
 of the oxygen from sulphuric acid by the carbon, with the consequent elimination of 
 sulphurous oxide and water, and accordingly sulphuric acid maybe represented by the 
 formula S0 2 OH 2 0, as consisting of the radicle S0 2 , combined with oxygen and water. 
 
 This illustration will serve to show that chemical formulae, except in the case of 
 such extremely simple compounds as hydrochloric acid, are to be regarded rather as a 
 means of representing the possible changes that a substance may undergo than as an 
 actual expression of their constitution, and this fact should always be borne in mind 
 in making use of chemical formulae, especially so in the case of substances of a com- 
 plex nature. 
 
 A formula which merely indicates the relative atomic proportions of the elemen- 
 tary substances contained in the compound it represents is termed an empirical 
 formula ; but when it also indicates the constitution of the substance it is termed a 
 rational formula. 
 
 In representing the constitution of compounds, it is frequently possible to regard 
 a group of atoms as acting the part of an elementary substance. This is chiefly the 
 case with complex compounds, and more especially those carbon compounds which 
 are commonly called organic substances. Thus, for instance, alcohol which is repre- 
 sented by the empirical formula C 2 H 6 may be regarded as the hydrate of such an 
 atomic group or radicle, C 2 H 5 performing in alcohol the same kind of function that 
 one of the atomic proportions of hydrogen does in water ; and ether, having the 
 empirical formula C 4 H, 0, may be represented as the oxide of the same radicle, and 
 aoetic acid as the hydrate of the oxygenated radicle C 2 H 3 0. 
 
 Another method of representing the constitution as well as the composition of 
 substances is based upon the assumption that all compounds admit of classification 
 in one or other of four groups, each comprising substances of analogous constitution 
 or molecular type, the most simple instances of which are furnished by the substances 
 hydrochloric acid, water, ammonia, and marsh gas. Substances of the most simple 
 constitution, such as the chlorides, bromides, and i<|dides of monatomic elementary 
 substances or radicles, are referrible to the hydrogen type, since their molecules may 
 be regarded as consisting either of a pair of monovalent atoms, or of such an atom 
 united with a monovalent radicle. Thus, for example, the molecules of hydrogen, 
 of hydrochloric acid, and of ammonium chloride or ethyl chloride, are represented 
 according to the hydrogen type by the formulas : 
 
 Hydrogen. Hydrochloric acid. Ammonium chloride. Ethyl chloride. 
 
 AA HH HC1 NH 4 C1 C 2 H 5 C1. 
 
 Another large class of substances are referrible to the water type, inasmuch as 
 their molecules may be regarded as consisting either of a bivalent atom united 
 with two monovalent atoms or radicles, or of a pair of bivalent atoms or radicles. So, 
 for example, the molecules of water, caustic soda, and lime or alcohol, are represented 
 by the typical formulae : 
 
 Water. Caustic soda. Lime. Alcohol. 
 
 o Jo cao 
 
 Substances which contain a trivalent atom or radicle are in like manner referrible 
 to the ammonia type, as for example, the molecules of ammonia, ethylamine. phos- 
 phorus trichloride, and triethylamine : 
 
 Ammonia. Phosphorus trichloride. Ethylamine. Triethylamine. 
 
 A! A'" HJN CIJP 2 HJN 
 
 A' H) OP JBP 
 
 Lastly, the substances which contain a tetravalent atom or radicle are referred to 
 the marsh gas type : 
 
 Marsh gas. Carbon tetrachloride. 
 
 A^ H^ Cl\ 
 
 01 1 
 Clf G 
 A] HJ Clj 
 
 The substances referrible to the water type are very numerous and varied, coin- 
 
14 TYPICAL FORMULAE. 
 
 prising many of the acids, salts, alcohols, ethers, etc. In these typical formulae, com- 
 pound radicles are represented as occupying the place of one or both of the hydrogen 
 atoms in the molecule of water. Thus, for example, the acids are represented as 
 being derived from water by the substitution of oxygenated radicles, as follows : 
 Nitric acid. Acetic acid. 
 
 C 2 H 8 0> 
 
 The corresponding salts are represented as being derived from water by the 
 substitution of an oxygenated radicle for one atom of hydrogen, and a monatomic 
 elementary atom for the other, as follows : 
 
 Potassium nitrate. Sodium acetate. 
 
 The composition of the several members of the alcohol and ether series can be 
 represented by substituting for one or both hydrogen atoms in the water type one or 
 two molecules of an alcohol radicle, as follows : 
 
 Ethy lie alcohol. Amylic alcohol. Ether. Amylic ether. 
 
 The anhydrides may also be represented as being derived from water by the sub- 
 stitution of oxygenated radicles for both of the hydrogen atoms as follows : 
 Acetic anhydride. Nitric anhydride. 
 
 2 H,0) n NO^ 
 
 C 2 H,oi N0 2 } 
 
 A very considerable extension of the typical representation of substances is 
 attained by means of multiple or mixed types. Thus, for instance, the duplication of 
 the hydrogen type affords a means of expressing the composition of such substances 
 as ethylene chloride, C 2 H 4 C1 2 , inasmuch as two hydrogen atoms in the typical 
 
 TT ) 
 formula TJ [ may be represented as replaced by the bivalent radicle ethylene, C 2 H 4 , 
 
 and the other two by two monovalent atoms or radicles, or by a bivalent atom or 
 radicle. Thus, for instance, by substitution of the bivalent radicle C 2 H 4 for two 
 
 TT \ 
 
 hydrogen atoms in the double hydrogen type TT Z [ it is possible to represent the com- 
 position of ethylene chloride and analogous compounds of bivalent elementary sub- 
 stances, as follows : 
 
 Ethylene chloride. Calcium chloride. Calcium oxide. 
 H 2 / C 2 H 4 Ca"> Ca"j 
 
 H 2 ( Cl, C1 2 J 01 
 
 By multiplying the water type in the same manner the composition of many other 
 substances may be represented, for example, the compounds of bivalent elementary 
 substances and radicles, such as the polybasic acids, etc., by substituting for two or 
 more atoms of the typical hydrogen in these formulae acid radicles or metals, as 
 follows : 
 
 Sulphuric Calcium Oxalic acid. Glycol. Phosphoric acid. 
 
 acid. hydrate. 
 
 H 2 ) ft S0 2 ( n Ca"/ n C 2 2 > C 2 HJ n H s ) n P<T) ft 
 
 The formulae of the corresponding salts are obtained by substituting for the rest 
 of the hydrogen equivalent quantities of the metals : 
 
 Zinc sulphate. Sodium sulphate Sodium phosphate. 
 
 soJ 
 
 Acid salts are similarly represented as follows : 
 
 Acid sodium sulphate. Acid sodium phosphates. 
 
 S0 2 Q FO ? PO { 
 
 HNaj* HNa^ ' H 2 Na| ( 
 
INORGANIC CHEMISTRY. 
 
 SUBSTANCES OCCURRING AS 
 
 The separate consideration of the general chemical relations of the elementary 
 substances, and of those compounds of them which either occur among the materials 
 constituting the mass of the earth, or can be produced from these latter by making 
 them act upon each other under the influence of heat or other conditions, has long 
 been found convenient, because the facts to be dealt -with are for the most part of a 
 more simple character than those relating to the chemistry of the materials of which 
 plants and animals consist. Hence the distinction that is made between inorganic 
 chemistry and organic chemistry is one justified to some extent by the nature of the 
 subject matter appertaining to each section of the science. But at the same time it 
 must be remembered that this distinction is otherwise merely an artificial one. There 
 is no longer any reason, even of a theoretical kind, for retaining the opinion formerly 
 entertained that the chemical phenomena presented by the organised structure of 
 plants or animals are in any way essentially different from those presented by 
 mineral substances. Both classes of phenomena are subject to the same general laws, 
 and, although the individual substances produced by plants and animals, or artificially 
 derived from their products, are as a class characterised by a peculiarity of compo- 
 sition, inasmuch as they all consist of only a small number of the elementary sub- 
 stance, and always contain carbon as a prominemt constituent, they differ from 
 mineral or inorganic substances only in the same manner that certain classes of these 
 latter substances, as, for example, the compounds of iron or the compounds of copper, 
 differ from other classes of inorganic substances. 
 
 Moreover, there is in many instances considerable difficulty in deciding whether 
 certain substances should be included amongst inorganic or organic compounds, and 
 one of the most important results of modern progress in chemical science has been 
 the discovery of methods by which a large number of substances, ordinarily produced 
 by plants or animals, can be obtained by the direct or indirect combination of their 
 elementary constituents. 
 
 Consequently the separation of the subjects treated of in the subsequent pages, 
 under the two heads of inorganic chemistry and organic chemistry, is to be regarded 
 as a purely arbitrary device, having for its object merely the convenience of treating 
 of the general chemical relations of all the elementary substances and their compounds, 
 under the first head, while the consideration of the carbon compounds derived from 
 plants and animals is specially dealt with under the second head. 
 
 Among the substances which are properly classed as inorganic, there are many 
 which occur naturally as minerals in a state which cannot be reproduced by artificial 
 means. Thus, for instance, some of the metallic compounds constituting ores are 
 often found in the form of crystals, and presenting physical characters widely 
 different from those of the same substances prepared by the combination of elementary 
 substances. This circumstance is referable to the difference in the conditions under 
 which such substances have been formed. The crystallised metallic compounds oc- 
 curring in ores, and the various crystallised minerals occurring as constituents of 
 different rocks, such as granite, hornblende schist, micaceous schist, etc., are most 
 probably the products of very gradual and long-continued chemical action, and perhaps 
 also their formation has been the result of other determining conditions which it is 
 impossible to imitate. In like manner the physical condition of extensive masses of 
 rocks such as marble, granular limestone, slate, sandstone, etc., is the result of long- 
 continued chemical action. 
 
 The several rocks comprised under the general term of metamorphic rocks have 
 always furnished wide scope for speculation as to the mode in which they have acquire 
 
16 GEOLOGICAL CHEMISTRY. 
 
 their present condition. These rocks, presenting evident signs of stratification, fossil- 
 remains and, sometimes, all the features of sedimentary strata, also possess a crystal- 
 line structure, and sometimes resemble massive crystalline rocks so closely as to be 
 distinguishable from them only by retaining faint signs of stratification which reveal 
 their sedimentary origin. Hence it is impossible to regard the present condition of 
 these rocks otherwise than as having been brought about by the chemical no less than 
 the physical alteration of sedimentary strata. Similar evidence of chemical alteration 
 is afforded by crystalline minerals which almost always contain substances not belong- 
 ing to their chemical constitution, 
 
 In seeking to arrive at a knowledge of the means by which such gradually pro- 
 gressive alterations of minerals and rocks are effected, it is necessary to take into 
 account a variety of influences which, though infinitesimal in themselves within ordi- 
 nary periods of observation, are nevertheless capable of producing, by long continu- 
 ance, effects which appear, at first sight, disproportionate. Chief among these are 
 the actions exercised by water as a solvent, and by the substances it holds in solution 
 when brought into contact with rocks or minerals. The uniformity in the characters 
 of the water of mineral springs shows that processes of chemical alteration are 
 continuous and of considerable magnitude at great depths below the earth's surface, 
 while the occurrence of large masses of minerals such as kaolin, evidently originating 
 from felspathic rocks by the abstraction of some of their constituents, indicates that 
 they are the result of similar slow chemical action. 
 
 The masses of metallic compounds occurring in the form of veins extending 
 through the older rocks, and known by the name of lodes, are especially interesting 
 in this respect, as they offer a striking illustration of the way in which chemical 
 action in past conditions of the earth's existence has been operative in effecting a 
 concentration of the materials from which industrial art now derives some of its most 
 important products. 
 
 In regard to other geological phenomena in which the effect of chemical action can 
 be more distinctly traced it soon becomes apparent, in considering them from a 
 chemical point of view, that there are two forms in which chemical action has in- 
 fluenced the successive changes which it is the province of geology to study, and of 
 which the superficial strata of the earth furnish the evidence and record. At the 
 present time chemical action is abundantly exerted in various ways, in effecting the 
 alteration of existing materials, and there are likewise some instances where it may 
 be observed as producing a constructive effect ; but in this latter aspect, chemical 
 action is far more rarely susceptible of direct observation as an element of geological 
 phenomena than it is in its destructive phase. For the most part, the constructive 
 influence of chemical action in regard to geological phenomena can be observed only 
 indirectly, and the evidence of its exercise is much of the same nature as that which 
 serves to determine the relative age of the earth's strata, the climatic or other con- 
 ditions prevailing at the time of their formation as well as their marine or freshwater 
 origin. 
 
OXYGEN. 
 
 SYMBOL 0. ATOMIC WEIGHT 16. 
 
 History. This substance was discovered in 1774 by Priestley in England, and 
 also about the same time by Scheele in Sweden. These chemists studied some of the 
 most important properties of the gas, which was at last called dephlogisticated or vital 
 air. Lavoisier was, however, the most active and successful in this respect, since he 
 made the important discovery that the combustion of substances in atmospheric air con- 
 sists in their chemical combination with oxygen. This discovery of Lavoisier's was one 
 of great moment for the development of chemical science, since it served to overthrow 
 the fundamental hypothesis of the phlogistic theory, according to which the sub- 
 stance burnt in any such case of combustion was supposed to be converted into 
 ' Calx ' and ' Phlogiston.' From this discovery of oxygen, and the knowledge of its 
 most essential properties, dates the modern era of chemical science. 
 
 Occurrence. Oxygen is a very abundant substance, constituting about one- 
 third of the known terraqueous globe. In the free or tincombined state it constitutes 
 nearly one-fifth part by weight of atmospheric air. Oxygen occurs in still greater 
 quantity chemically combined with other substances, as in water, eight-ninths by weight 
 of which is oxygen, in almost all minerals and rocks, and in most organic stibstances. 
 
 Characters. Oxygen in the uncombined state is a colourless and odourless gas 
 that has hitherto resisted all attempts to render it liquid or solid by means of pres- 
 sure and cold. It is slightly denser than atmospheric air, having a specific gravity of 
 1-1056 (air^l); and, relatively to hydrogen = 1, the density of oxygen is 16. Its 
 power of refractiiig light is less than that of any otheB|gas. 
 
 Oxygen is sparingly soluble in water, which at the ordinary temperature dissolves 
 about 3 per cent, of its volume. 
 
 Oxygen possesses considerable chemical activity, and it is capable of combining 
 directly with a great number of elementary and compound substances. The chemical 
 change thus produced is termed oxidation. This character of oxygen is manifested in 
 a variety of ways by the oxygen existing in the atmosphere, although there it exists 
 largely diluted with another gas ; hence many of the changes that substances undergo 
 when in contact with atmospheric air are due to oxidation. The rusting of iron is a 
 familiar instance of change resulting from combination with atmospheric oxygen, and 
 a number of other phenomena are essentially though less obviously of a similar nature. 
 
 Under the influence of the electric current, oxygen gas is converted into an allo- 
 tropic condition, in which it possesses other special properties, and acts far more 
 energetically as an oxidising agent. 
 
 Preparation. Several metallic oxides, such as auric oxide, argentic oxide, mer- 
 curic oxide, disengage their oxygen when merely heated to a temperature ranging from 
 100 to 150 C. Consequently it is very easy to prepare oxygen by heating some one of 
 these oxides in a close vessel furnished with a bent delivery-tube terminating under a 
 bell glass filled with water and immersed with its mouth downwards in a vessel of 
 water. 
 
 Mercuric oxide, when heated in a glass tube, is decomposed into metallic mercury 
 and oxygen in the following proportions : 
 
 HgO = Hg + 
 216 200 16 
 
 And for preparing small quantities of oxygen it is a very convenient material. 
 
 But the high price of such metallic oxides would render the preparation of oxygen 
 from them on a large scale very costly, for with the greatest care in manipulation a 
 loss of some portion of the substance employed is not to be avoided. 
 
 A more economical method of preparing oxygen consists in decomposing the per- 
 oxide of manganese, which occurs abundantly in Spain, England, Germany, and 
 France as a mineral, and is known as manganese-ore. 
 
 When manganese peroxide is heated to redness, it gives up a portion of its 
 
 C 
 
18 
 
 OXYGEN. 
 
 oxygen, and a compound, of manganic and manganous oxides remains. This change is 
 represented by the following equation : 
 
 3Mn0 2 = Mn 3 4 + 20. 
 261 229 32. 
 
 According to this, manganese peroxide will yield one-third of its oxygen, and as 
 it contains 36'78 per cent, by weight of oxygen, the yield from manganese-ore, when 
 pure, will amount to 12-26 per cent. 
 
 The apparatus employed for this purpose is represented in section by fig. 1 ; it 
 consists of a wrought-iron cylindrical vessel (A) with a narrow neck, into which is 
 fitted one end of an iron delivery -tube (B), while the other end is connected by means 
 of a cork (c) with a bent glass tube dipping under the shelf of a pneumatic trough (E E) 
 filled with water. 
 
 The iron cylinder (A), partly filled with manganese-ore, is heated in the furnace (a G G) 
 
 FIG. 1. 
 
 until the decomposition of the peroxide commences and bubbles of gas escape through 
 the water in the pneumatic trough from the end of the glass tube. A bottle (B), com- 
 pletely filled with water, is then inverted over the end of the tube so as to collect the 
 gas. 
 
 The first portion of gas given off carries with it the air contained in the apparatus, 
 so that if pure oxygen be required, it is necessary to wait until all the air has been 
 driven out before beginning to collect the gas. 
 
 It is possible to obtain from manganese ore one-half of the oxygen it contains, or 
 18'39 per cent, by weight instead of 12'26, by carefully treating a mixture of the 
 powdered mineral with an excess of sulphuric acid. The reaction in this case is 
 represented by the following equation : 
 
 Mn0 2 
 87 
 
 H 2 S0 4 
 98 
 
 MnS0 4 
 151 
 
 18 
 
 As the temperature at which sulphuric acid acts upon manganese peroxide with 
 evolution of oxygen is not very high, this operation can be safely conducted in a glass 
 flask (A, fig. 2) heated over a gas flame, the bottom of the flask being protected by a piece 
 of wire gauze. 
 
 Since commercial manganese ore often contains carbonates, a,nd carbonic acid is 
 sometimes liberated even when the mineral is treated alone or more certainly when it 
 is treated with sulphuric acid, the gas obtained from this source is often impure. For 
 
PREPARATION OF OXYGEN. 
 
 19 
 
 its purification it is passed through a Woulfe's bottle (B) half filled with a strong solution 
 of soda or potash. In this way all the carbonic acid is absorbed, and the oxygen pass- 
 ing out through the delivery tube of B can be collected either in an inverted glass 
 cylinder (c) over a pneumatic trough, or in a gasholder. 
 
 FIG. 2. 
 
 Potassium chlorate is a convenient source of oxygen, inasmuch as it is decomposed 
 by heating and, giving up the whole of its oxygen, is converted into potassium chloride 
 according to the following equation : 
 
 KC10 3 = KC1 + 30 
 122-5 74-5 48 
 
 This salt is therefore capable of yielding 39' 16 per cent, by weight of oxygen, and, 
 when all the gas has been expelled by heat, 60-84 per cent, of potassium chloride, 
 which remains in the generating apparatus as a solid mass easily soluble in water. 
 
 This decomposition really takes place in two stages, the first resulting in the con- 
 version of part of the chlorate into perchlorate as follows : 
 
 2KC10 3 - KC1 + KC10 4 + 20 
 245 74-5 138-5 32 
 
 and then, by the application of a more intense heat, the perchlorate gives up all its 
 oxygen, potassium chloride remaining : 
 
 KC10 4 = KC1 + 40 
 138'5 74-5 64 
 
 In this latter stage of the process the decomposition is so sudden that the melted 
 potassium chloride is liable to froth over, and the heat requisite is so great that glass 
 flasks often soften and give way. 
 
 Potassium chlorate decomposes, however, at a comparatively low temperature, when 
 mixed with manganese peroxide, while the manganese peroxide remains unaltered, 
 acting simply as a diluting material, and mechanically by the surface it presents. 
 
 In order to obtain a constant and strong development of oxygen, it is better to 
 make use of a mixture of equal parts of powdered manganese ore and potassium 
 chlorate. The apparatus represented by fig. 2 serves for this purpose. 
 
 During the last few years attempts have been made to isolate the oxygen from 
 atmospheric air, where it exists in such large quantity. One of the most practicable 
 methods for this purpose consists in heating moist cuprous chloride, with access of air, 
 to a temperature ranging from 100 to 200 C., in a rotatory cast-iron retort, the 
 interior of which is protected against the action of the charge or of the products de- 
 veloped from it by a suitable coating. Under these conditions oxygen is absorbed 
 from the air, cuprous oxychloride being formed ; and when this is heated to 400 C., 
 it gives up again the oxygen it had absorbed from the air. In carrying out this pro- 
 cess, it is of practical advantage to mix the cuprous chloride with sand or powdered 
 kaolin, in order to prevent it from melting. In this way cuprous chloride mixed with 
 sand yields, for each 100 kilograms, from 3 to 3 ciibic metres of oxygen; and 
 as the operation can be repeated four or five times daily, it is possible to produce in 
 
 c2 
 
20 
 
 OXYGEN. 
 
 this space of time from 15 to 18 cubic metres of oxygen from 100 kilograms of 
 cuprous chloride. Other methods of isolating oxygen from the atmospheric air, as, 
 for instance, by means of peroxide of barium, do not appear to be practically advan- 
 tageous. 
 
 COLLECTION AND STOBAGE or GASES. The glass vessels represented in figs. 1 and 
 2 are only suitable for collecting small quantities of gas by means of the pneumatic 
 trough, when required for immediate use. 
 
 If larger quantities of gas are required than can be conveniently collected in glass 
 vessels, it is necessary to use a gasholder made of sheet copper, as represented by fig. 3, 
 consisting of a close cylinder (A B) furnished with a glass gauge (h k), and at the bottom 
 with a lateral neck (g) that can be closed with a screw plug or a cork. A smaller cylin- 
 drical vessel (CD), open at the top, is supported upon three pillars above AB. These 
 cylinders are connected together internally by the tubes (/), both furnished with taps so 
 that the communication between the cylinders may be shut off at pleasure. The tube 
 / extends from the bottom of c D nearly to the bottom of A B, while the tube e is imme- 
 diately inside the top of A B. 
 
 In order to prepare the gasholder for collecting a gas, the neck (g) is closed and both 
 the taps e and /opened. Water poured into the upper cylinder will then flow down 
 
 the tube /, while the air in AB escapes 
 through the tube e. When the cylinder 
 ( A B) is quite filled with water, the taps are 
 closed and the lateral neck (g} is opened so 
 as to allow the delivery-tube from the gas- 
 generating apparatus to be inserted. The 
 gas streaming into A B will then displace 
 the water, and force it out through the 
 neck (g) into the pan (jf). As soon as A B 
 is filled with gas, which maybe ascertained 
 by the water-level in the glass gauge (k h), 
 the gas delivery-tube is removed and the 
 neck (g) closed. 
 
 In using the gasholder thus charged 
 with a gas, the cylinder (CD) is filled with 
 water and the tap in the tube (/) opened so 
 as to allow water to flow into A B and com- 
 press the gas it contains. Then, on open- 
 ing the tap in the tube e, the gas will 
 escape as water flows in through /, and it 
 may be collected in a glass jar filled with 
 water and inverted over the mouth of the 
 tube e. Sometimes it is convenient to 
 have a lateral tube with a tap attached to 
 the side of A B at the top, so as to obtain 
 a continuous stream of gas. 
 
 Uses. In confined spaces, where the 
 air cannot be replaced, it has been at- 
 ,-, _ tempted with good success to make use of 
 
 IG * 6 ' oxygen in order to maintain the air in a 
 
 respirable condition. Many such experi- 
 ments have been made, with diving-bells more especially. Oxygen is also much used 
 in chemical laboratories, chiefly for oxidising various substances in chemical analysis. 
 In a subsequent chapter it will be explained how oxygen is used in combination with 
 hydrogen for obtaining high temperatures. 
 
 Without doubt, oxygen gas would be very much used for the production of light 
 and heat, for the oxidation of sulphur, and for the roasting of certain ores, etc., if it 
 could be more cheaply prepared. But up to the present time, notwithstanding many 
 attempts in this direction, there is still no method of preparation known which would 
 admit of the general use of oxygen for such purposes. 
 
 Compounds. With the probable exception of fluorine, all the elementary sub- 
 stances form compounds with oxygen, which are termed oxides. Many of these 
 substances occur naturally in great abundance, arid some of them are of great impor- 
 tance as the sources of various metals. Others are prepared artificially, and extensively 
 used for a variety of purposes. 
 
 Oxides are classified according to the atomic proportions of oxygen they contain, 
 as monoxides, dioxides, trioxides, tetroxides, pentoxides, etc., the prefix in 
 each case indicating the number of oxygen atoms in the molecule. When a substance 
 
COMPOSITION OF OXIDES. 
 
 21 
 
 combines with oxygen in more than one proportion, the oxide containing the least 
 oxygen is often called protoxide and one of those containing more oxygen is some- 
 times called peroxide. Several of the ,-trioxides are also termed sesquioxides 
 when they contain half as much oxygen again as the corresponding protoxides. 
 Oxides containing different proportions of oxygen are often distinguished by adding 
 to the name of the substance they contain in common, the terminations ous and ic ; 
 for example, sulphurous oxide and sulphuric oxide, ferrous oxide and ferric oxide, 
 cuprous oxide and cupric oxide. 
 
 The formulae in the accompanying table represent the composition of the more 
 important oxides of the elementary substances. 
 
 
 Monoxides 
 
 Dioxides 
 
 Trioxides 
 
 Tetroxides 
 
 Pentoxides 
 
 Carbon . 
 
 
 
 CO 
 
 
 
 C0 2 
 
 
 
 
 
 
 
 
 
 __ 
 
 
 
 Silicon . 
 
 
 
 
 
 
 
 Si0 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Titanium 
 
 
 
 
 
 
 
 Ti0 2 
 
 
 
 
 
 
 
 L , 
 
 
 
 
 
 Sulphur 
 
 
 
 
 
 
 
 S0 2 
 
 
 
 so s 
 
 
 
 
 
 
 
 
 
 Selenium 
 
 
 
 . 
 
 
 
 Se0 2 
 
 
 
 Se0 3 
 
 
 
 
 
 
 
 
 
 Tellurium 
 
 
 
 
 
 
 
 Te0 2 
 
 
 
 Te0 3 
 
 
 
 
 
 
 
 
 
 Molybdenum . 
 
 
 
 
 
 
 
 Mo0 2 
 
 
 
 Mo0 3 
 
 
 
 
 
 
 
 
 
 Tungsten 
 
 
 
 
 
 
 
 
 
 
 
 W0 3 
 
 
 
 
 
 
 
 
 
 Boron . 
 
 
 
 
 
 
 
 
 
 B 2 3 
 
 
 
 
 
 
 
 
 
 
 
 Chlorine 
 
 C1 2 
 
 
 
 
 
 CIO, 
 
 CIA 
 
 
 
 
 
 
 
 
 
 
 
 Iodine . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I 
 
 Nitrogen 
 Phosphorus . 
 
 N 2 
 
 NO 
 
 ~ 
 
 N0 2 
 
 NA 
 
 PA 
 
 ~ 
 
 z 
 
 
 
 
 
 PA 
 
 Arsenic . 
 
 
 
 
 
 
 
 
 
 As 2 3 
 
 
 
 
 
 
 
 
 
 AsA 
 
 Antimony 
 
 
 
 
 
 
 
 
 
 Sb 2 3 
 
 
 
 Sb 2 4 
 
 
 
 
 
 Sb 2 ~o 5 
 
 Bismuth 
 
 
 
 
 
 
 
 
 
 Bi 2 3 
 
 
 
 
 
 
 
 
 
 BiA 
 
 Gold . 
 
 Au 2 
 
 
 
 
 
 
 
 Au 2 3 
 
 
 
 
 
 
 
 
 
 
 Tin 
 
 
 
 SnO 
 
 . 
 
 Sn0 2 
 
 Sn 2 3 
 
 
 
 
 
 
 
 
 
 
 
 Platinum 
 
 
 
 PtO 
 
 
 
 Pt0 2 
 
 
 
 
 
 
 
 
 
 
 
 
 Palladium 
 
 
 
 PdO 
 
 
 
 Pd0 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Aluminium 
 
 
 
 
 
 
 
 
 
 A1A 
 
 ~ 
 
 
 
 
 
 
 
 
 
 Uranium 
 
 
 
 uo 
 
 
 
 
 
 UA 
 
 
 
 
 
 U 3 4 
 
 U 4 5 
 
 
 
 Cobalt . 
 
 
 
 CoO 
 
 
 
 
 
 Co 2 3 
 
 
 
 
 
 CoA 
 
 
 
 
 
 Nickel . 
 
 
 
 NiO 
 
 
 
 
 
 Ni 2 3 
 
 
 
 
 
 Ni 3 4 
 
 
 
 
 
 Iron 
 
 
 
 FeO 
 
 
 
 
 
 Fe 2 3 
 
 
 
 
 
 Fe 3 4 
 
 
 
 
 
 Manganese . 
 
 
 
 MnO 
 
 
 
 Mn0 2 
 
 Mn 2 3 
 
 
 
 
 
 Mn 3 4 
 
 
 
 
 
 Chromium 
 
 
 
 CrO 
 
 
 
 Cr0 2 
 
 Cr 2 3 
 
 Cr0 3 
 
 
 
 Cr 3 4 
 
 
 
 
 
 Lead . 
 
 Pb 2 
 
 PbO 
 
 
 
 Pb0 2 
 
 
 
 
 
 
 Pb 3 4 
 
 
 
 
 
 Mercury 
 
 Hg 2 
 
 HgO 
 
 
 
 " 
 
 
 
 
 
 
 
 
 
 
 
 
 Copper . 
 
 Cu 2 
 
 CuO 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Silver . 
 
 Ag 2 
 
 
 
 Ag.,0 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Barium . 
 
 BaO 
 
 
 
 Ba0 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Strontium 
 
 SrO 
 
 
 
 Sr0 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Calcium 
 
 CaO 
 
 
 
 Ca0 2 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Potassium 
 
 K 2 
 
 
 
 KA 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Sodium . 
 
 Na 2 
 
 
 
 Na 2 2 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Hydrogen 
 
 H 2 
 
 
 
 HA 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 With the exception of water, and some oxides of the metalloids which are gaseous 
 under ordinary conditions of temperature, most of the oxides of elementary substances 
 are solid. Many of them melt at various degrees of heat, and a few are volatilisable ; 
 some are readily and entirely decomposed by heating, others are merely converted into 
 lower oxides with partial evolution of oxygen ; and several of them are not in any way 
 altered by the highest temperatures that can be produced. 
 
 Many of the oxides are capable of combining with each other and form compounds 
 termed salts, in which the characters of the constituents are masked or neutralised, 
 and those oxides which are most dissimilar in themselves or in the characters of the 
 elementary substances they contain are most susceptible of such combination. Thus, 
 for instance, nitric pentoxide or sulphur trioxide combines with metallic oxides, 
 forming two series of saline compounds called nitrates and sulphates, the com- 
 pounds with sodium monoxide being cubic nitre, or sodium nitrate, and sodium 
 sulphate, or the substance known as Glauber's salt. 
 
 2NaN0 3 and S0 3 + Na 2 = Na 2 S0 4 
 
22 OXYGEN. 
 
 The oxides which, like iodic, nitric, phosphoric, boracic, arsenic oxides, etc., cor- 
 respond with sulphuric oxide in this respect are called acid oxides, and they form 
 several series of salts called iodates, nitrates, phosphates, borates, arsenates, etc. The 
 oxides corresponding witli sodium monoxide are called basic oxides. This distinction 
 between oxides on the ground of their chemical relations is, to a certain extent, con- 
 sistent with the distinction between elementary substances as metals and metalloids, 
 inasmuch as the acid oxides are chiefly oxides of metalloids, while the oxides of the 
 metals are chiefly basic oxides. 
 
 The acid or basic character of an oxide seems, however, to be in some cases as 
 much determined by the proportion of oxygen it contains as by the nature of its other 
 elementary constituents, since several of the lower oxides of metals are basic oxides 
 and the corresponding higher oxides are acid oxides. Thus, for instance, chromous 
 oxide (CrO) is a decidedly basic oxide, while the trioxide (Cr0 3 ) is as decidedly an 
 acid oxide. 
 
 The capability of assuming in this respect opposite chemical relations is especially 
 marked in the case of hydrogen monoxide, or water, which combines with acid oxides, 
 as well as basic oxides, forming compounds which differ in some respects from the 
 generality of salts. Thus, for instance, sulphuric oxide combines with water, forming 
 a compound corresponding to sodium sulphate S0 3 + H 2 = H 2 S0 4 or hydrogen sul- 
 phate, in which the acid character of the oxide is rather intensified than neutralised 
 as in other sulphates. This is the case with all the acid oxides, and hence the corre- 
 sponding hydrogen salts are specially designateda cids ; hydrogen sulphate, for instance, 
 being ordinary sulphuric acid and hydrogen nitrate HN0 3 nitric acid. 
 
 In the compounds of basic oxides with water likewise the basic characters of those 
 oxides are not neutralised as in ordinary salts, but are even more marked than in the 
 oxides themselves, as in the case of the compounds of calcium oxide, or quicklime, 
 and sodium monoxide with water CaO + H 2 = H^CaC-jand Na 2 + H 2 = 2HNaO. 
 On this account the compounds of basic oxides with water are often termed hydrated 
 oxides or hydrates, as calcic hydrate, sodium hydrate, or sometimes bases, to dis- 
 tinguish them from salts generally, and from acids or the hydrogen salts of acid 
 oxides. The distinction, however, is merely conventional, since the compounds of 
 acid oxides with water might equally be termed hydrates of those oxides, e.g. sul- 
 phuric hydrate, nitric hydrate, etc. 
 
 COMBUSTION. The direct combination of oxygen with other substances is always 
 attended with considerable evolution of heat, and in many natural operations some 
 process of oxidation is the principal source of heat. It is also the only means by 
 which heat is produced artificially. In many instances when oxidation takes place 
 rapidly it gives rise to the phenomenon of combustion, the temperature of the substance 
 produced by the combination being raised to such a degree by the heat evolved as 
 to render it luminous, as in the burning of fuel or of the materials used for obtaining 
 light. These effects are also produced by some other kinds of chemical action, but 
 they are so much more frequently the result of oxidation that the term combustion 
 is specially applied to the evolution of heat and light attending oxidation. In all 
 ordinary cases of combustion the burning substance combines with oxygen derived 
 from the atmospheric air immediately surrounding it ; sulphur in burning being 
 oxidised to sulphurous oxide, phosphorus to phosphoric oxide, carbon to carbonic 
 dioxide, and hydrogen to hydric oxide or water. Oxygen is therefore termed a 
 supporter of combustion, and substances that are capable of combining with 
 oxygen in this way are termed combustible substances. 
 
 The combination of oxygen with substances in this way does not take place at the 
 ordinary temperature except in a few very rare instances ; and in order to make any 
 substance burn it must be heated to the particular temperature or burning-point 
 at which it enters into combination with oxygen, or in ordinary language takes fire. 
 When this combination has once commenced it is generally maintained by the heat 
 always evolved in the process, so long at least as there is an available supply of oxygen 
 and any of the combustible substance remains unburnt. 
 
 A number of substances that do not burn readily or at all in atmospheric air can 
 be burnt in pure oxygen. Iron-wire, for instance, burns with brilliant coruscations 
 when made red-hot at the end and introduced into pure oxygen gas. Carbon, sulphur, 
 phosphorus, and other combustible substances, also burn in oxygen with much greater 
 luminous intensity than in atmospheric air. Phosphorus especially burns with such a 
 dazzling light that the eye cannot bear it. The fact admits of oxygen being easily 
 recognised. If, for instance, an incandescent wood splinter bo inserted into a vessel 
 containing oxygen it immediately begins to burn with an intensely bright light. 
 Nitrous oxide is the only other gas that produces a similar effect, and that can be dis- 
 tinguished from oxygen by its greater solubility in water, and by not forming red 
 fumes with nitric oxide gas as oxygen does. 
 
COMBUSTION. 
 
 23 
 
 The particular phenomena presented by substances in burning depend to a great 
 extent upon the physical condition of the combustible substances themselves and of 
 the products of their oxidation. Thus, for instance, substances that are gaseous burn 
 with flame, and this is also the case with solids or liquids that are capable of assuming 
 the state either of gas or vapour. Substances that do not assume the gaseous condition 
 in burning give no flame. In both cases combination with oxygen takes place when 
 the burning substance is in contact with atmospheric air ; and while a non-volatilisable 
 substance, such as charcoal or iron, burns without any considerable alteration in the 
 bulk of the unoxidised mass, the phenomenon of flame presented in the combustion of a 
 gas or vapour is simply a result of the mobility and expansibility belonging to sub- 
 stances in that physical condition. Flame is, in fact, merely intensely heated gas. 
 
 When oxidisable gases are mixed with a sufficient proportion of oxygen gas or 
 atmospheric air for their oxidation and brought into contact with flame, combination 
 takes place suddenly through the entire mass, and the expansion of the gas by the 
 heat evolved causes a violent concussion. Combination taking place in this way is 
 termed explosion. 
 
 The quantity of heat evolved in oxidation differs according to the nature of the 
 substance oxidised, and according to the proportion of oxygen with which the substance 
 combines. Thus hydrogen evolves considerably more heat when burnt than an equal 
 weight of carbon does, and when carbon is burnt to carbonic dioxide the quantity of 
 heat evolved is much greater than when it is burnt to carbonic oxide. 
 
 The following table gives the quantities as well as the relative amounts of heat 
 evolved in the direct oxidation of several elementary substances : 
 
 
 Product of 
 oxidation 
 
 Quantity of heat 
 generated 
 
 Eelative heal* 
 of oxidation 
 
 
 
 Heat-units 
 
 
 Hydrogen 
 
 H 2 
 
 33881 
 
 4-23 
 
 Carbon 
 
 CO, 
 
 8000 
 
 1- 
 
 Sulphur . 
 
 so; 
 
 2307 
 
 0-29 
 
 Phosphorus 
 
 PA 
 
 5747 
 
 0-72 
 
 Iron 
 
 Fe,0 
 
 1582 
 
 0-19 
 
 Zinc ... 
 
 ZnO 
 
 1 1330 
 
 0-17 
 
 Tin ... 
 
 SnOo 
 
 1147 
 
 0-14 
 
 Copper . 
 
 Cud 
 
 603 
 
 0-07 
 
 According to these data the actual quantity of heat evolved in the oxidation of 
 1 gram of carbon to carbonic dioxide is sufficient to raise the temperature of 8,000 
 grams of water one degree, or of 80 grams from to 100. The heat generated in 
 the oxidation of hydrogen is more than four times as much. 
 
 The immediate effect of the heat evolved in combustion is to raise the temperature 
 of the substance produced, and then the heat is gradually dispersed by conduction 
 throughout the mass of contiguous substances as well as by radiation. The increase 
 of temperature thus produced is to a great extent dependent upon and proportionate 
 to the rate of oxidation, and the higher degrees are distinguished according to the 
 colour of the light emitted by the heated substa,nce, as red heat, white heat, etc. 
 In every case, however, there is a limit to the temperature that a substance can pro- 
 duce by its combustion. The conditions that influence this will be treated of under 
 the head of ' Fuel.' 
 
 The light emitted in combustion depends very much upon the temperature produced ; 
 but it is also considerably influenced by the physical condition of the combustible sub- 
 stance and that of the product of oxidation, as well as by the temperature to which 
 it is heated. Solids such as carbon or iron, that burn without vapouring, are 
 capable of emitting a very intense light in combustion. The flame of hydrogen, how- 
 ever, is but very feebly luminous, although its temperature is much higher than that 
 produced by the combustion of iron or of carbon. The luminous intensity of flame is 
 also greater in proportion to the density of the vapour or gas burnt and of the gaseous 
 products formed ; paraffin, for instance, burns with a very luminous flame, while marsh 
 gas, a substance of the same chemical composition, burns with only a faint light, the 
 density of this gas being very considerably less than that of paraffin vapour. The 
 presence of solid particles in a flame, as a result either of the change produced by 
 oxidation or of other conditions, is another circumstance that considerably augments 
 the luminous intensity, especially if the temperature be high. Thus zinc and phos- 
 phorus, both furnishing solid products by oxidation, give intensely luminous flames when 
 burnt. The light emitted by the flame of a candle or of coal gas is probably due in 
 
24 OXYGEN. 
 
 some degree to the presence of solid particles of carbon originating from the decompo- 
 sition of carbonaceous vapours. 
 
 Since free oxygen is everywhere present as a constituent of the atmosphere upon 
 the earth's stirface, a great number of processes of oxidation are continually going on ; 
 but in many cases the oxidation takes place so slowly that no development of heat or 
 light can be perceived. Thus several metallic sulphides, when exposed to the air, are 
 gradually oxidised to sulphates ; many organic substances absorb oxygen from the air, 
 and by combining with it produce other compounds. This last kind of oxidation is 
 called slow combustion, in opposition to that rapid combustion which is accom- 
 panied by the obvious development of light and heat. The actual amount of heat 
 evolved is, however, the same, whether the oxidation of a substance takes place slowly 
 or rapidly, the only difference being in the intensity of the effect produced. 
 
 Many substances which oxidise but slowly when in compact masses are much more 
 readily oxidised when they are in a state of minute subdivision and there is relatively 
 to the mass a very much larger surface exposed to contact with atmospheric air. Thus, 
 for instance, when the finely divided metallic iron obtained by the action of hydrogen 
 upon powdered ferric oxide at a red heat is brought into contact with atmospheric air, 
 it is suddenly oxidised with evolution of heat and light. In such cases oxidation may 
 also be promoted to some extent by the capability which most porous substances possess 
 of absorbing and condensing gases. The spontaneous combustion of greasy rags, 
 cotton, tow, etc., when heaped up in a confined space, is due to the accelerated oxida- 
 tion of the fatty substance with which these porous materials are impregnated, and the 
 consequent heating of the mass to a temperature at which rapid combustion takes place. 
 
 The process of animal respiration, regarded from a chemical point of view, is a case 
 of slow combustion. Animals, by the operation of breathing, supply their bodies con- 
 tinually with oxygen from the air ; the oxygen thus inhaled combines with the 
 carbon and hydrogen of organic substances, and is again exhaled as carbonic acid and 
 water-vapour. This process serves especially to illustrate the fact that in slow com- 
 bustion heat is liberated, for it is by this means that the supply of heat necessary for 
 the life of animals is generated. The liberation of heat, however, takes place very 
 slowly, and therefore it is not so easily recognisable as in cases of rapid combustion. 
 
 OZONE. 
 
 History. The fact that a peculiar alliaceous odour is sometimes communicated 
 to atmospheric air by a flash of lightning or other forms of electrical discharge, has long 
 been known and frequently observed in various ways. In 1785 Van Marum found 
 that it was the oxygen of the atmosphere which acquired this odour. In 1840 
 Schonbein specially investigated this subject, and having ascertained that the peculiar 
 smell observed in the proximity of the electrical machine, and other electrical appa- 
 ratus, was due to the presence of a peculiar gas, which is also formed when water 
 is decomposed by electrolysis, he gave the name of ozone to the substance possessing 
 this character. It is only recently, however, that the researches of Andrews, Soret, 
 and others have shown that ozone is an allotropic form of oxygen. 
 
 Occurrence. Ozone occurs in the atmosphere in varying proportions, according 
 to locality and season, and it is probably produced chiefly by the action of atmospheric 
 electricity. In country places it is most abundant, but does not amount to more than 
 pJ-ooth part by weight, or 75^55^1 part by volume of atmospheric air. The amount 
 is greatest in spring and least in winter. 
 
 Characters. Ozone is very different in its characters from ordinary oxygen. 
 It possesses a penetrating smell, acts violently upon the organs of respiration like 
 chlorine, and is the most energetic oxidising agent that is known. While oxygen at 
 the ordinary temperature acts directly upon only a few substances, almost all oxi- 
 disable substances are oxidised upon being brought into contact with ozone. The 
 density of ozone appears to be 1-5 times that of oxygen : it is less soluble than oxygen 
 in water, which dissolves only about 0'5 per cent, of its volume. Ozone, placed in 
 contact with potassium iodide, sets the iodine free. Upon this reaction depends a 
 delicate means of ascertaining the presence of ozone. If air or a liquid containing 
 ozone be brought into contact with a dilute aqueous solution of potassium iodide, to 
 which a small quantity of starch paste has been added, the liquid is coloured blue by 
 the liberated iodine combining with the starch. When air has to be tested for ozone, 
 it is more convenient to make use of a strip of bibulous paper which has been saturated 
 with a solution of starch containing potassium iodide. But since iodine is similarly 
 liberated from potassium iodide by chlorine, by some nitrogen oxides, and other sub- 
 stances, this test cannot be relied upon implicitly. 
 
ALLOTEOPIC FORM OF OXYGEN. 25 
 
 The instruments termed ozonometers consist essentially of strips of paper prepared 
 in the way above mentioned : when brought into air containing ozone, they would 
 indicate the amount of ozone contained in the air by the degree of intensity of the blue 
 coloration produced. Since the actual quantity of ozone corresponding to a par- 
 ticular degree of blue coloration is not known, such ozonometers only indicate the 
 relative amounts of ozone in the air. The possible presence of nitrogen oxides in 
 atmospheric air renders the indications of these instruments very uncertain. A better 
 test consists of red litmus paper, with half its surface impregnated with a one per 
 cent, solution of potassium iodide. The portion of the paper thus impregnated 
 becomes blue by contact with air containing ozone, in consequence of oxidation and 
 the formation of potash. The unimpregnated portion of the paper is not at all altered 
 unless the air contains ammoniacal vapours, and then the paper becomes blue over its 
 entire surface. 
 
 Ozone exerts an oxidising action upon many organic substances, destroying some 
 entirely, oxidising others only to a certain extent. Thus, for instance, ozone destroys 
 the colour of many plants, bleaching them entirely ; but tincture of guaiacum is only 
 rendered blue by this agent. 
 
 If ozone be conducted through a glass tube heated to redness, it is decomposed, the 
 volume of the gas is permanently increased, and ordinary oxygen is formed. Ozone is 
 also converted into ordinary oxygen at a temperature of 250 to 300. 
 
 Ozone acts in a very remarkable manner upon certain peroxides. When brought 
 into contact with barium peroxide, hydrogen peroxide, or other peroxides, it is con- 
 verted into ordinary oxygen, while the peroxides also give up a part of their oxygen 
 and are converted into lower oxides. 
 
 Preparation. Though ozone is always present in small quantity in the atmo- 
 sphere, still it cannot be obtained from that source in such a concentrated condition 
 that all its characteristic properties are evident. It is not, in fact, possible to pre- 
 pare pure ozone, and what is called ozone is only air or oxygen containing some 
 admixture of ozone. 
 
 Ozone is produced in every case where electrical discharges take place in the air, 
 as in the production of sparks by electrical machines, etc. During a thunderstorm 
 also a strong odour of ozone is often noticeable. Ozone is formed, moreover, in con- 
 siderable amount when phosphorus, partially immersed in water, is exposed to the air, 
 and when dry potassium permanganate is decomposed with strong sulphuric acid, 
 also in the combustion of hydrogen in the air. 
 
 Lastly, there are many substances called ozone bearers, which exhibit the ozone 
 reaction with potassium iodide, and are therefore supposed to become ozonised upon 
 prolonged contact with the air. To this class of bodies belong especially a number of 
 ethereal oils, oil of turpentine, oil of citron, etc. It is, however, probable that the 
 reaction these oils produce, after exposure to the air, is due to compounds of the oils 
 with oxygen. 
 
 Uses. Ozone has often been proposed as a bleaching agent, for decolorising 
 stearin, wax, and other organic substances, which either cannot stand the process of 
 bleaching with sulphurous acid and chlorine, or are not sufficiently bleached by these 
 substances. However, bleaching with ozonised air has not at present supplanted the 
 natural bleaching of those organic materials. Ozone has also been proposed for disin- 
 fection ; and it would no doiibt prove very suitable for this purpose if it could be 
 more easily and cheaply obtained, for on account of its energetic action upon most 
 organic substances, it is to be presumed that it would destroy the organic miasma of 
 bad air. Whether ozone might be employed as a preservative against cholera, and 
 whether any 'connection exists between the ozonic contents of the air and the appear- 
 ance of that disease, is at present uncertain. 
 
HYDROGEN. 
 
 SYMBOL H. ATOMIC WEIGHT 1. 
 
 History. The statements of the older chemists as to the properties of hy- 
 drogen are very vague, and partly inexact, since the inflammable gas produced by 
 dissolving metals in dilute acids was confounded with other inflammable gases of a 
 different nature, such as marsh gas, etc. Cavendish was the first who made exact 
 experiments with this gas. It was at first named inflammable air; afterwards the anti- 
 phlogistic chemists gave it the name hydrogen from 85wp water, and yzvva<a to generate 
 for the purpose of indicating that, by its combination with oxygen, it produces 
 water. 
 
 Occurrence. Hydrogen seldom occurs naturally in the free state, and only in 
 very small quantities, as in volcanic exhalations. It has also been detected in the 
 expired gases of mammals. It occurs, however, very abundantly in chemical combi- 
 nation ; as with oxygen in the form of water, of which it constitutes one-ninth part 
 by weight, also with carbon in the form of gas known as marsh gas that is exhaled 
 from coal-pits ; with nitrogen in the form of ammonia ; with sulphur as sulphuretted 
 hydrogen ; with chlorine as hydrochloric acid, and as a constituent of very many of 
 the substances of which plants and animals are made up. 
 
 Characters. Hydrogen is an elementary substance known in the free state 
 only as a gas which has not as yet been condensed by the greatest cold and pressure 
 combined. It is without colour, taste, or smell ; very slightly soluble in water, and 
 burns with a pale bluish flame. Hydrogen is the lightest substance known. Its 
 specific gravity, air being taken as unity, is 0'069. Under normal atmospheric 
 pressure, and at the temperature of 0, a litre of hydrogen weighs only 0-0896 
 
 FIG. 4. 
 
 FIG. 5. 
 
 FIG. 6. 
 
 gram. It is therefore possible to decant hydrogen from a cylinder (A) filled with it 
 into another cylinder (B) in the way described by figs. 4 and 5. As soon as the 
 cylinder (A) is placed, with the aperture upwards, vertically under the cylinder (B), 
 all the hydrogen will rise into the upper cylinder, as may be shown by inserting a 
 burning taper into B. The flame of the taper sets fire to the hydrogen at the mouth 
 of the cylinder, where the gas is in contact with the air, but if the taper is raised 
 further up the cylinder, into the pure hydrogen, the flame is at once extinguished. 
 When the extinguished taper is withdrawn, it is again lighted at the mouth of the 
 cylinder by the burning hydrogen gas. 
 
 This experiment proves also that hydrogen cannot burn without a supply of 
 oxygen from the air or otherwise, and that the flame of burning bodies is extinguished 
 in pure hydrogen gas. 
 
 In setting fire to hydrogen gas, it is necessary to proceed with caution ; for if the 
 
PREPARATION OF HYDROGEN. 
 
 27 
 
 FIG. 7. 
 
 gas becomes mixed with atmospheric air, a mixture may, under certain conditions be 
 produced which, on contact with flame, will explode with great violence, shattering 'the 
 vessels in which it is contained. 
 
 Preparation. The methods generally employed for obtaining hydrogen depend 
 either upon the decomposition of water by any easily oxidisable metal, or upon the 
 fact that hydrogen is readily displaced from some of its saline compounds. Thus 
 hydrogen can be prepared by passing steam over iron filings heated to redness in 
 an iron tube. The steam is generated in a glass flask with a delivery-tube fitted air- 
 tight into the iron tube. At the other end of the iron tube is fitted another deliverv- 
 tube, by which the hydrogen is collected over water or mercury. 
 
 The reaction that takes place in this case is easy to understand : iron at a high 
 temperature deprives water of its oxygen, and thus, becoming oxidised itself, the 
 hydrogen is liberated. The first portion of gas evolved contains the air with which 
 the apparatus was originally filled, and therefore this must be allowed to escape, in 
 order to obtain pure hydrogen. If 
 the hydrogen gas be desired free 
 from moisture, it must be passed 
 through tubes filled with pieces of 
 fused calcium chloride, and then 
 collected over mercury. Generally 
 a simpler process is employed in 
 the laboratory. Some granulated 
 zinc is placed in a three-necked 
 bottle (A, fig. 7), of about a litre 
 capacity, nearly half-tilled with 
 water. In one tubulus of the flask 
 is fitted with a cork a funnel tube 
 (b) reaching to the bottom of the 
 flask ; in the other tubulus is fitted 
 one end of a bent delivery-tube 
 
 (c), the other end dipping into a pneumatic trough (E), under the level of the 
 liquid contained in the trough. Above this end of the tube a vessel (D) filled 
 with water is placed in an inverted position on a shelf. The apparatus being 
 thus arranged, concentrated sulphuric acid is poured carefully in small quantities 
 at a time through the tube (5), when a brisk evolution of gas commences at once. 
 This evolution of gas may be so violent if too much sulphuric acid be added at once 
 that the liquid in A overflows. By a regular development the hydrogen escapes 
 through the delivery -tube (c) and is collected in D. In this case also the first portion of 
 the gas contains the air which originally filled the apparatus, and it must be allowed 
 to escape. Even then the hydrogen obtained by the action of zinc upon sulphuric 
 acid is never quite pure, as shown by the unpleasant smell of the gas, pure hydrogen 
 being absolutely inodorous. This smell is due to admixtures of various kinds, espe- 
 cially hydrocarbons, formed from carbon contained in the zinc; also to the pre- 
 sence of arseniuretted and sulphuretted hydrogen, originating from arsenic and 
 sulphur in the zinc, and from arsenical sulphuric acid. 
 
 Hydrogen can be freed from these impurities by passing it first through a tube 
 filled with pieces of pumice-stone saturated with concentrated solution of caustic 
 potash, then through a tube containing pumice-stone saturated with solution of cor- 
 rosive sublimate. The impurities are retained by the potash and corrosive sublimate. 
 If the purified hydrogen be required dry, it must then be passed through a tube con- 
 taining pieces of fused chloride of calcium, or pieces of pumice-stone saturated with 
 concentrated sulphuric acid, before it is collected for use, and in that case the gas 
 must of course be either collected over mercury or at once conducted into the appa- 
 ratus where it is to be used. The gasholder, described on page 20, is as well suited 
 for hydrogen as for oxygen. From such a gasholder the gas can be transferred to 
 flasks and cylinders at pleasure, or it can be passed in a regular stream into the appa- 
 ratus where it is to be used. 
 
 The process which takes place in this preparation of hydrogen consists in the 
 substitution of zinc for the hydrogen of the sulphuric acid, zinc sulphate being thus 
 formed and hydrogen set free in the state of gas, according to the following equation : 
 
 H 2 S0 4 + Zn = ZnS0 4 + H 2 
 98 + 65 = 161 + 2 
 
 163 163 
 
 In this equation no account is taken either of the water, which must be added in 
 great excess, in order that the sulphate of zinc formed may be dissolved, or of the 
 excess of sulphuric acid, which is contained in the liquid when it no longer evolves 
 hydrogen by contact with zinc. 
 
28 HYDROGEN. 
 
 Hydrogen can be obtained more readily by means of an apparatus in which the 
 development of gas is regulated by the quantity consumed. An apparatus of the kind 
 is represented by fig. 8. A is a glass vessel furnished with a tubulus (6), to which is 
 fitted a cock (B). This vessel (A) is three parts filled with dilute sulphuric acid (1 : 5). 
 Into its neck a large globular glass vessel (c), with a long tube gradually narrowing 
 towards its lower extremity and reaching nearly to the bottom, is fitted air-tight. A 
 thick ring of zinc (d) is fastened at the lower end of c, and is held fast by means of 
 a cork placed at the extremity of the tube. 
 
 While the zinc is immersed in the acid, hydrogen is developed, and collecting in 
 the upper part of the vessel (A) presses the liquid into the 
 globular vessel (c), from which the air escapes by the neck, 
 as the stopper H is only lightly fitted into it. 
 
 In proportion as the liquid is forced up into the globe 
 (c) so its level sinks in the flask (A); and when it has sunk 
 to about e, the acid being no longer in contact with the 
 zinc cylinder (d) no more hydrogen can be evolved. Then, 
 if the cock (B) be opened, the liquid, which was driven up 
 into c by the pressure of the evolved hydrogen gas, 
 presses out the gas through the cock (B). In proportion as 
 gas escapes from B, the liquid again falls from c into A, 
 until it again comes into contact with the zinc cylinder (d), 
 and continues to develop gas so long as the cock is allowed 
 to remain open. But as soon as the cock (B) is closed the 
 hydrogen generated presses the liquid anew into the 
 glass globe (c), until the acid is out of contact with the 
 zinc, and the evolution of gas ceases. 
 
 For the preparation of hydrogen on a large scale as, 
 for instance, in the manufacture of aniline, where large 
 quantities of nascent hydrogen are required, and for like 
 purposes crude acetic acid and old iron are employed 
 F IG . g. with advantage. The action of iron upon acetic acid is 
 
 entirely analogous to the action of zinc upon sulphuric 
 
 acid ; the iron displacing the hydrogen of the acetic acid, and forming ferrous acetate. 
 In like manner hydrogen is evolved when zinc or iron is brought into contact with 
 solutions of caustic potash or soda. 
 
 Uses. One of the chief purposes to which hydrogen gas is applied is the pro- 
 duction of an extremely high temperature by its combustion with oxygen. The 
 amount of heat generated in the combustion of hydrogen gas, viz. 33,881 heat units 
 for each kilogram of hydrogen burnt ( = 60,986 British heat units per pound) ex- 
 ceeds that produced in the combustion of any other substance, and when the combustion 
 is supported by oxygen gas the flame has a temperature of more than 6000 C. 
 
 Oxy hydrogen Blowpipe. In consequence of the gaseous condition of hydrogen it can 
 be conveniently burnt so as to produce a small flame of extremely high temperature. 
 Sometimes hydrogen is, for this purpose, mixed with half its volume of oxygen, and 
 compressed in a strong iron vessel furnished with a tap and jet by which the mixed 
 gases can be allowed to escape and burn as required. More frequently, however, a 
 jet of oxygen is mixed with twice its volume of hydrogen immediately before issuing 
 from the jet where the mixed gas is burnt. A piece of lime brought into the oxy- 
 hydrogen flame is heated to whiteness and yields a light nearly as bright as the elec- 
 tric light. 
 
 This intense light is employed in the illumination of microscopic objects, and is 
 called the Druinmond or Oxyhydrogen Lime Light. 
 
 Doeberdner's Lamp. When a jet of hydrogen is made to impinge upon a ball of 
 spongy platinum the combination of the gas with oxygen takes place at the ordinary 
 temperature and the platinum ball is made red hot by the heat thus generated. From 
 an apparatus of similar construction to that shown in fig. 8, it is possible to direct a 
 jet of hydrogen gas, through the cock (B), upon a piece of spongy platinum (/), fastened 
 to the holder Q?) by means of platinum wire. This holder has at g a joint by which 
 the spongy platinum may be turned aside when not required to be used. If the spongy 
 platinum be brought exactly opposite to the cock (B), and this is opened, hydrogen 
 escapes, and coming into contact with the spongy platinum, renders it red hot and takes 
 fire. 
 
 Autogenous soldering. The flame of a jet of hydrogen is much used for uniting 
 the edges of the sheets of lead with which vessels are made for the purpose of hold- 
 ing acids. Joints made in this way are more durable than those made with solder. 
 The soldering apparatus is constructed on the same principle as that represented by 
 
APPLICATION OF HYDROGEN. 
 
 29 
 
 fig. 8, except that it is made^ of copper-plate lined internally with lead, and fitted 
 with arrangements which admit of the easy renewal of the zinc, the removal of the 
 sulphate of zinc formed, and the replenishing of the apparatus with fresh sulphuric 
 acid. This apparatus gives a very constant flame, which can be used with advantage 
 for soldering lead in the manner practised in constructing sulphuric acid chambers. 
 
 It consists essentially of three parts, a gas-generator, a bellows, and a jet. In fig. 9, 
 A, the lower compartment, represents-the vessel for generating hydrogen gas. It is 
 made of sheet copper lined with lead. Pieces of zinc are placed upon the perforated 
 bottom (L) through a side door. When the zinc has been thrown in this door is 
 closed hermetically, the stopper (D) taken out, and the copper reservoir filled with 
 sulphuric acid diluted with eight or nine times its volume of water. The union of the 
 flexible tube (gg, fig. 11) is then connected with the gas generator at c, fig. 9, and the 
 tube (g' g', fig. 11) with the bellows, fig. 10, at/. Both the tubes (g g and//) are 
 connected together by means of the copper tube (d 1 d'}, fitted with another piece 
 of flexible tube (cc), terminating in the blow pipe mouth-piece (b a) of bronze, or 
 platinum. When this apparatus is required for soldering the cocks (/, fig. 9, and 
 /, fig. 11) are opened; the air from the interior of the apparatus then escapes 
 through them in proportion as the sulphuric acid entering through G H (fig. 9), 
 rises in the lower division of the gasholder. When the level of the sulphuric acid 
 in this lower vessel has risen higher than the perforated bottom (K. r), hydrogen 
 gas is generated and passes through the cock (/) and the tube (b a), into the small 
 wash vessel B, containing either a small quantity of water or a solution of caustic soda 
 for the retention of any particles of sulphuric acid that may happen to be carried over 
 with the gas. The hydrogen generator having been in operation a short time, a work- 
 man sets the bellows in motion with his foot by means of the pedal (0). This causes 
 the two ends of the bellows to be pressed together towards their centre, and the air 
 to be forced out through the tube (g'g', fig. 11). The cocks (/and/) must be so 
 regulated that the mixture of hydrogen and air gives a finely-pointed flame. So long 
 as the cocks remain open, hydrogen gas continues to be generated. When the 
 soldering operation is finished and the apparatus is no longer required, the cocks 
 
 
 FIG. 9. 
 
 FIG. 10. 
 
 FIG. 11. 
 
 (/, fig. 9, and/ fig. 11) are closed. The closing of these cocks puts a stop to the 
 further development of gas, since the pressure exerted by gas in the interior of the 
 apparatus causes the sulphuric acid to rise through G H into the uppermost vessel, 
 leaving the zinc out of contact with the acid ; the hydrogen gas consequently ceases 
 to be evolved. When the apparatus is again required for use it is only necessary to 
 re-open the cocks and set the bellows in motion as above described. 
 
 When the sulphuric acid is nearly saturated with zinc sulphate it is drawn off 
 through the opening at B, and fresh acid poured into the apparatus at D. After each 
 fresh re-charging of the apparatus, whether it be with acid or zinc, air finds its way 
 into the interior of the apparatus and forms with the hydrogen gas an explosive 
 mixture. On this account it is necessary after each re-charging to allow the gas to 
 escape for a few minutes from the mouth-piece of the blowpipe (ca, fig. 11), before 
 igniting it, dangerous explosions being apt to occur from a neglect of this precaution. 
 
 Air Balloons. The first air balloons were raised by means of heated air, and had a 
 
30 HYDROGEK 
 
 very irregular uncertain motion, owing to the unequal heating. It is only since the 
 gases specifically lighter than atmospheric air have been used for filling balloons that 
 it has been possible to secure a more regular motion. 
 
 Hydrogen was at one time employed for this purpose, and produced by the action 
 of iron upon a dilute acid. In order to fill a balloon of 500 cubic metres capacity 1,500 
 kilograms of scrap-iron are required, as free as possible from oxide, 15,000 kilos of 
 water, and 2,500 kilograms of sulphuric acid. As a by-product, a solution is ob- 
 tained from which, by means of evaporation, crystallising, and drying, about 7,500 
 kilograms of green vitriol (ferrous sulphate) can be gained. 
 
 Assuming that 1 cubic metre of hydrogen weighs 89'6 grams, and 1 cubic metre of 
 atmospheric air weighs 1,293 grams, the rising power which a cubic metre of hydrogen 
 exerts is equal to 1203'4 grams. If the total difference between the weight of the 
 hydrogen and the weight of the same volume of atmospheric air be greater than the 
 weight of the covering and the other solid parts of the balloon, the balloon rises, and 
 rises the quicker the greater this difference is in proportion to the weight of the 
 covering, etc. 
 
 More recently, ordinary illuminating gas made from coal has been used for inflat- 
 ing balloons, but since this gas is about six times as dense as hydrogen gas, the 
 balloons filled with it must be much larger. Small balloons consisting either of 
 goldbeaters' skin or very thin caoutchouc, either globular, oval, or in the shape of dif- 
 ferent animals, etc., can be filled with hydrogen in the same manner. Such small 
 balloons only remain a short time suspended in the air, because diffusion takes 
 place through the membranes or the caoutchouc covering, hydrogen passing out. 
 
 Compounds. Hydrogen forms a number of important compounds with other 
 elementary substances. 
 
 There are two compounds of hydrogen and oxygen, the monoxide, or water, which 
 is in many respects one of the most important substances in nature, and the dioxide 
 or peroxide, which contains relatively to hydrogen twice as much oxygen as water. 
 
 With nitrogen it forms ammonia NH 3 , and with phosphorus, arsenic, and anti- 
 mony the analogous compound PH 3 ; AsH 3 ; SbH 3 . With carbon it forms a great number 
 of compounds termed hydrocarbons. Several of the compounds of hydrogen with 
 fluorine, chlorine, bromine, iodine, and sulphur correspond in their chemical relations 
 to the hydrogen salts of acid oxides. On this account they are distinguished, as forming 
 a particular class of acids, by the term hydroacids, and like oxyacids they are 
 largely employed for various purposes. With some of the metals hydrogen forms 
 compounds termed hydrides. 
 
 But though hydrogen is a constituent of so many compounds, its chemical activity 
 is but slight under ordinary conditions of temperature, and it combines directly only 
 with chlorine and oxygen. For its combination with oxygen a considerable elevation 
 of temperature is necessary, but when the union of the two gases is once commenced, 
 as in lighting a jet of hydrogen, the heat generated by the combination determines 
 its continuation. Hydrogen combines more readily with chlorine, and when a mixture 
 of these gases is exposed to direct sunlight they combine with explosion. Other 
 compounds of hydrogen with elementary substances are obtained indirectly, and several 
 of them that are of especial value in the arts will be described in the following 
 pages, under the heads of the particular elementary substances they contain. 
 
 WATER. 
 
 FORMULA H 2 0. MOLECULAR WEIGHT 18. 
 
 History. Thales held water to be the principle, or element, from which all other 
 substances were formed, and still later water was regarded as an elementary substance, 
 constituting one of the four elements of Aristotle: water, fire, air, and earth. The 
 opinion that water could be converted by means of heat into earthy or solid 
 substances was also long prevalent. Cavendish first demonstrated the fact that water 
 consists of hydrogen and oxygen. 
 
 Occurrence. Water occurs naturally in the solid, the liquid, and the gaseous 
 conditions. In the solid condition water is known as ice, snow, or hail ; in the liquid 
 condition water occurs as sea, river, spring, mineral, and rain water, etc.' ; and besides 
 the absolute gaseous condition of water, it occurs in the form of steam, a peculiar 
 intermediate stage between the gaseous and the liquid conditions. 
 
 Atmospheric air always contains at the ordinary temperature' a considerable quan- 
 tity of water vapour or gaseous water. The amount varies according to the tempera- 
 ture and the direction of the wind. On the average, it may be assumed that the air 
 
CHARACTERS OF WATER. 31 
 
 contains 0'8 per cent, by weight of water. This water is a very necessary constituent 
 of the air, for neither animals nor plants are able to live in absolutely dry air. By 
 reduction of the temperature of the atmosphere the water vapour is condensed and 
 receives then the appellations cloud, fog, rain, snow, hail, and frost. 
 
 Water also exists in vast quantity, chemically combined in mineral substances, as 
 water of hydration or of crystallisation. It constitutes a large part of the mass of all 
 organic structures. The soft organs of animals contain generally more than three- 
 fourths of their weight of water ; the young parts of plants from 80 to 90 per cent. ; 
 indeed, there are plants which contain as much as 95 per cent, of water. The thickest 
 trunks of large trees at the time of felling always contain as much as 45 to 55 per 
 cent, of water. 
 
 Composition. Water is a compound of hydrogen with eight times its weight 
 of oxygen, the volume of the oxygen in the free' state being half that of the hydrogen. 
 The relation by volume of the constituents of water can easily be proved either by 
 exploding in a suitable vessel a mixture of hydrogen with half its volume of oxygen, 
 whereupon all the gas disappears and water alone is formed, or by decomposing 
 water eleatrolytically and collecting the gases evolved. In this latter process the 
 volume of the hydrogen evolved is exactly double that of the oxygen. 
 
 Characters. In a chemically pure condition water is colourless ; it is only in 
 thick masses that it appears of a faint greenish-blue colour. It is odourless and taste- 
 less ; it attains its greatest density at a temperature of + 4 C., and forms in this respect 
 an exception to the general rule that liquids become denser as the temperature is 
 reduced, until they assume the solid state. Cooled to C., water congeals to ice. 
 From the moment when a few crystals of ice are formed, the temperature of the still 
 liquid water does not, in spite of strong refrigeration, sink any further, until the last 
 drop of liquid water is converted into ice. On the other hand, though heat be 
 applied to water in which solid ice is immersed, its temperature does not rise above 
 until the last particle of ice is melted. Under certain conditions it is possible to 
 retain water in the liquid state at a temperature below the freezing point. If 1 kept 
 perfectly at rest, and cooled slowly down to a temperature below 0, it sometimes 
 remains liquid even at 12 C. So soon, however, as water thus cooled is set in motion, 
 it congeals suddenly throughout its entire mass to a lump of ice. 
 
 The fact above mentioned, that water has its greatest density at + 4 C., and that 
 consequently in becoming ice it again expands, is on$ of the highest importance as 
 regards the upper stratum of the earth's crust. The disintegration of rocks is due in 
 part to this property of water, for since water penetrates into their pores and crevices 
 as into a sponge, its expansion upon becoming ice is sufficient to disintegrate the 
 most compact rocks. So long as the ice thus formed continues to serve as a con- 
 necting material, these fragments are held together by it, but upon the setting in of 
 a thaw, the ice melts and the rocks fall to pieces. 
 
 On account of the great force with which water expands in its transition to ice, 
 vessels, made of a brittle material, when left in the cold filled with water, are liable 
 to be burst by the formation of ice within them. 
 
 As ice occupies a greater space than an equal weight of water at 0, it follows that 
 ice is specifically lighter than water. The fact that ice floats upon water is certainly 
 one of great importance. If ice were heavier than water, it would sink to the bottom from 
 the surface of brooks, rivers, seas, etc., upon which it was formed by the cold of 
 winter, a new ice crust would be formed, which would also sink to the bottom, and so 
 on, in consequence of which the brooks, rivers, seas, etc., would very rapidly freeze 
 up. But since ice is lighter than water, it forms a sheltering cover for the water 
 underneath it. 
 
 The form of ice crystals is difficult to ascertain, as such crystals are generally im- 
 perfectly formed. The best way of observing that ice crystals are six-sided prisms is 
 the examination of the arborescence which forms on window-panes in winter. 
 
 Water boils at a temperature of 100 C. under the normal atmospheric pressure, equal 
 to a column of mercury 760 mm. in height, and, with the phenomenon of bubbling, it is 
 converted into tbe gaseous condition. The temperature at which water boils is lower 
 in proportion as the pressure exerted upon its surface is reduced. Therefore, since 
 the pressure of the atmosphere is less upon the top of high mountains than in valleys 
 or at low levels, water boils at a much lower temperature at considerable elevations. 
 Upon the top of Mont Blanc, for instance, where the atmospheric pressure is only 
 equal to a column of mercury 423'7 mm. high, water boils at a temperature of 84*4 C. In 
 a vacuum it boils at 0. Owing to the tension of water vapour, water assumes the 
 gaseous state at a temperature below its boiling point, and the vapour diffuses into 
 spaces filled with other gases that are indifferent to it. This tension is the cause of 
 water being always present in the atmosphere in the form of gas or vapour. The 
 
32 HYDROGEN. 
 
 evaporation of water is more considerable the greater the surface exposed, and the 
 higher the temperature of the water and of the surrounding air. Thus cold air saturated 
 with water vapour is capable of absorbing a fresh quantity when warmed, and on the 
 other hand warm air saturated with water deposits the water in the liquid state when 
 cooled. Hence it is that cold objects become covered with moisture when brought into 
 contact with warm air as, for instance, the glasses of spectacles when a person 
 enters a warm room, or the window-panes of heated rooms. 
 
 Certain solid and liquid substances, such as calcium chloride or magnesium chlo- 
 ride, dry potassium carbonate, concentrated sulphuric acid, etc., possess the property of 
 withdrawing water from moist air, while at the same time they dissolve in the water 
 thus attracted. These substances are, therefore, termed deliquescent. Other sub- 
 stances, on the contrary, which upon crystallising have taken up much water e.g. 
 sodium sulphate, carbonate or phosphate give up a portion of their water when 
 exposed to the air, losing their crystalline form and falling to powder. These are 
 called efflorescent substances. Many solid substances also attract moisture from 
 the air without dissolving and are for this reason termed hygroscopic. Organised 
 substances, such as wool, hair, etc., and many pulverulent substances, present this 
 character in a marked degree. 
 
 Water is a general solvent. As a rule, it dissolves a given substance in greater 
 proportion the higher its temperature is. Still there are exceptions to this rule as, 
 for instance, Glauber's salt, the solubility of which in water increases only to a defi- 
 nite degree of temperature, and upon further elevation of the temperature decreases. 
 In consequence of the solubility of most substances in water being greater the higher 
 the temperature is, hot saturated solutions deposit upon cooling a portion of the sub- 
 stances dissolved, for water at a low temperature is not capable of dissolving the 
 same quantity of a salt as water of a higher temperature, and, as a rule, the sub- 
 stances deposited in this way assume the crystalline form. 
 
 Water dissolves, or, as it is generally expressed, absorbs, less of a particular gaseous 
 substance the higher its temperature is. In like manner, water absorbs less of a gas 
 the smaller the pressure is with which the gas presses upon the surface of the water. 
 
 Natural Water. Water, as it occurs naturally, is never chemically pure, on 
 account of its great solvent power ; and since it is always in contact with other sub- 
 stances, which it dissolves ; even the potable water of springs, wells, reservoirs, or 
 brooks, always contains in solution varying amounts of foreign substances. These 
 consist of oxygen, nitrogen, and carbonic acid gases ; alkaline and earthy salts, chiefly 
 carbonates and sulphates, and chlorides of potassium, sodium, and magnesium, to- 
 gether with traces of organic substances and silicic acid. 
 
 Eain or snow water, as it falls, is generally contaminated only with the gases 
 contained in the atmosphere. Only that water which falls when it first begins to rain 
 contains the dust always to be found in the air that is in motion. 
 
 This rain or snow water is in part retained in the earth by its porosity, con- 
 veying to the roots of plants the constituents of the soil necessary for their nourish- 
 ment ; another part penetrates deeper into the earth, saturating itself with the soluble 
 constituents of the earth's crust through which it passes, and then collects again in the 
 form of streams and rivers, along the course of which it flows into the sea. Here, 
 and partly also from the moist surface of the land, it is evaporated by means of the 
 heat of the earth and the sun, and the evaporated water, on reaching high cold 
 regions of the atmosphere, is again condensed, and falls once more in the form of rain, 
 etc., upon the earth. 
 
 Well water is water which accumulates above an impermeable stratum, generally 
 of clay at little depth below the surface. Such water is termed hard when it contains 
 in solution large amounts of calcium carbonate or sulphate. Calcium carbonate is 
 retained in solution by means of carbonic acid, for it is dissolved in far larger pro- 
 portion by water containing free carbonic acid than by water free from that substance. 
 If, however, water of this kind be boiled, the solvent agent, the carbonic acid, is 
 expelled in the form of gas, and carbonate of lime is then precipitated in the solid 
 state, the water becoming turbid. In like manner, on evaporating water, all other 
 salts dissolved in it are deposited, and the more readily the less soluble they are, 
 forming the scale of boilers. 
 
 Spring water is essentially the same as well water, only that, by flowing along 
 steep impermeable mountain strata, it finds an outlet for itself where these strata 
 crop out at lower points of the earth's surface, and thus appears in the form of 
 springs. 
 
 The various kinds of mineral water are spring water, holding in solution sub- 
 stances to which their especial medicinal properties are due. Thus, sulphuretted water 
 contains sulphuretted hydr6gen ; acidulous water contains much carbonic acid ; and 
 bitter water contains magnesium sulphate, sodium sulphate, etc. 
 
CHARACTERS OF NATURAL WATER. 
 
 33 
 
 There are besides these some kinds of mineral water the action of which is due to 
 the temperature at which they issue from the earth. The water of the hot springs at 
 Carlsbad has a temperature of 74, that of the springs of Baden-Baden 7H, those of 
 Wiesbaden of 70, those of Teplitz 49 , and those of Vichy of 45^. 
 
 Kiver water is generally soft, though originating from spring water i.e. it does 
 not contain in solution any large amount of calcareous salts. This is owing to the fact 
 that spring water, by long contact with the atmosphere, loses the greater portion of its 
 carbonic acid, and consequently deposits its calcium carbonate together with traces of 
 calcium sulphate. For the same reason river water tastes insipid as compared with 
 the fresh-tasting well or spring water, which still contains carbonic acid. 
 
 Sea water differs from ordinary potable water in the large proportion of saline 
 substances contained in it. It contains over 3f per cent, of salts in solution, amongst 
 which common salt preponderates. 
 
 The average composition of sea water is as follows : 
 
 Water 
 
 Sodium chloride (common salt) .... 
 
 Potassium chloride 
 
 Magnesium chloride 
 
 Calcium sulphate (gypsum) 
 
 Magnesium sulphate 
 
 Potassium sulphate 
 
 Calcium and magnesium carbonates 
 
 Bromine and iodine compounds, together with organic ]> 
 
 substances \ 
 
 Carbonic acid and volatilisable organic substances . 
 
 96-470 
 
 2700 
 0-020 
 0-360 
 0-140 
 0-240 
 0-005 
 0-004 
 
 0-011 
 
 0-OoOj 
 
 3-530 
 
 100 
 
 The composition of sea water is not everywhere the same. The water of the 
 Mediterranean Sea, for instance, contains less magnesian salts than the water of the 
 ocean, and at great depths sea water is salter than near the surface. 
 
 In the Dead Sea, the amount of salt varies considerably according to the depth. 
 
 In the following table are given the results of analyses by Terreil. In the first 
 column the constituents of the water at the surface of the Dead Sea are given, in the 
 second the constituents of the same water at a depth oft, 000 feet. 
 
 1,000 parts of water contain 
 
 Minimum 
 at the surface 
 
 Maximum 
 at the depth of 
 1,000 feet 
 
 
 17-628 
 
 174-985 
 
 
 0-167 
 
 7-093 
 
 
 0-202 
 
 0-523 
 
 
 traces 
 
 traces 
 
 Sulphuretted hydrogen . . ..-./. 
 
 traces 
 4-197 
 
 traces 
 41-428 
 
 
 2-150 
 
 17-269 
 
 
 0-885 
 
 14-300 
 
 
 0-474 
 
 4-386 
 
 Ammonia, alumina, oxide of iron, organic substances . 
 
 traces 
 0-006 
 
 traces 
 traces 
 
 
 
 
 
 25-709 
 
 259-984 
 
 Residue directly determined 
 Water 
 
 27-078 
 972-922 
 
 278-135 
 
 721-865 
 
 
 
 
 It is evident from this that at a depth of 1,000 feet most salts in the water of 
 the Dead Sea are contained in solution in a ten times greater amount than at the 
 surface. 
 
 The large quantities of bromine and of potassium salts contained in the water of 
 the Dead Sea admit of the probability of the Dead Sea being worked at some future 
 period for those substances. 
 
 Salts of calcium and magnesium in water communicate to it the power of forming 
 an insoluble curd with soap, and render the water hard ; the greater the amount of 
 these substances, the harder is the water. 
 
34 HYDROGEN. 
 
 When the saline substances are present only in moderate proportion, as in river 
 water, their presence is not objectionable for most of the purposes to which water is 
 applied ; indeed these substances render water more pleasant to drink, and perhaps 
 they may in some degree contribute to nutrition. 
 
 In household economy and for manufacturing purposes the water most often used 
 is spring, well, or river water ; in dry countries, rain water is collected in tanks. 
 
 An idea of the characters of natural water in this respect is given by the accom- 
 panying table of analyses. 
 
 In judging of the quality of water, account is to be taken of its hardness, its tem- 
 perature, and its purity. It is also of importance to determine whether the hardness 
 is due to earthy carbonates or to the corresponding sulphates and chlorides. In the 
 former case, if the water be allowed to remain for a short time with a considerable 
 surface exposed to the air, the greater part of the calcium and magnesium carbonates 
 are gradually deposited, owing to the f scape of the carbonic acid which determined 
 their solution by the water, and thus the water becomes softer. Such water is also 
 rendered soft by boiling. On the contrary, if calcium and magnesium are present in 
 the state of sulphates or chlorides, the water remains hard after exposure to the air, as 
 well as after boiling. Hence it is easy to understand the reason why many kinds 
 of spring water which are very hard when first escaping from the earth, afterwards 
 become soft when they have flowed for a certain distance down a brook or river. In 
 such cases the carbonic acid escapes, and consequently the carbonates which caused 
 the hardness of the water are deposited in the form of mud. 
 
 Good potable water should be clear, colourless, cool, and clean i.e. it should be free 
 from mechanically suspended impurities, such as clay, organic substances, etc. ; it 
 should contain in solution small amounts of the acid calcium carbonate, common salt, 
 with nitrogen and oxygen gases, and especially carbonic acid. The presence of other 
 compounds of calcium and magnesium than the carbonates is detrimental in propor- 
 tion to the amount of those substances. 
 
 Good potable water may contain in 100,000 parts from 10 to 30 parts of solid 
 contents that remain behind when the water is evaporated, and one half of the solid 
 contents may consist of calcium carbonate. If water contains less than 10 parts of 
 solid contents per 100,000, it is too soft, and is less suitable as potable water than 
 water that is richer in salts. For this reason, rain water is not good for drinking. 
 As regards the aeration of potable water, it ought to contain by measure about 0'8 per 
 cent, of oxygen, 1'7 per cent, of nitrogen, and besides these gases a considerable quan- 
 tity of carbonic acid. 
 
 For industrial purposes soft water is generally preferable. For certain purposes, 
 however, such as the dyeing of some colours, hard water is more suitable. For other 
 purposes, it is a matter of indifference whether water be hard or soft. For cooling 
 purposes, that water would be chosen which indicated the lowest temperature. Hard 
 water is not at all suitable for steam boilers, on account of the formation of scale by 
 the deposition of its solid contents in the boiler. In this respect also, the state of com- 
 bination in which the calcium exists is a matter of great moment : calcium carbonate 
 and calcium chloride are comparatively harmless, the latter being very soluble, and 
 the former producing a scale of a loose nature which is easily removed, while calcium 
 sulphate (gypsum) gives rise to a very hard and adhesive scale, and when present in 
 any considerable quantity in water renders it utterly useless for steam boilers unless 
 it is submitted to a process of purification beforehand. 
 
 Purification. In many cases it is necessary to adopt some means of separating 
 impurities from natural water, to render it suitable for use. 
 
 A very efficient method of preventing this objectionable action of gypsum consists 
 in the addition of sodium carbonate (common soda), which converts the gypsum into 
 calcium carbonate, that is deposited in the state of mud and not as a hard scale ; for 
 every degree of hardness of water rich in gypsum, about 5 parts of soda crystals, or 
 2 parts of calcined soda, are added to each 100,000 parts of water. Barium chloride 
 has also been proposed for the decomposition of gypsum, and by its use water very 
 suitable for steam boilers can be obtained. But at present this salt is too dear for the 
 purpose. Sal-ammoniac would be applicable for preventing the formation of scale by 
 water containing gypsum, were it not that the steam might become ammoniacal, and 
 then act injuriously upon the working parts of the steam engine. Substances contain- 
 ing tannin have been found very serviceable for this purpose, and have lately been 
 much used. Decoction of oak bark has been used, and more recently catechu. 
 
 If it be desired to get rid of the hardness of water for washing, all the calcium 
 salts held in solution must be precipitated. This is most easily effected by the use of 
 common soda, whereby all the calcium is precipitated as carbonate. 
 
 FILTBATION. Muddy water can be easily rendered clear by filtration. In places 
 
 
ERS. 
 
 To face page 34. 
 
 1 
 
 Thames j 
 
 KCl 
 
 NITRATES 
 
 
 rganic 
 sub- 
 tance 
 
 a2N0 3 
 
 g2NO s 
 
 NaNO 3 
 
 KNO 3 
 
 SiO 2 
 
 Al'O 3 
 
 Fe a 3 
 
 96 
 
 38 
 
 
 
 
 
 
 
 88 
 
 14 
 
 3-27 
 
 '< 
 
 
 
 
 
 
 
 
 
 
 
 39 
 
 
 
 
 
 4-97 
 
 i 
 
 
 
 
 
 50 
 
 
 
 1-09 
 
 
 
 49 
 
 2-20 
 
 i 
 
 33 
 
 
 
 
 
 
 
 18 
 
 trace 
 
 trace 
 
 10-00 
 
 j 
 
 
 
 
 
 
 
 
 
 1-13 
 
 
 
 ,, 
 
 5-82 
 
 Rhine at 
 
 ' 
 
 
 
 
 
 
 
 
 
 19 
 
 14 
 
 
 
 at 
 
 
 
 
 
 
 
 
 
 38 
 
 4-88 
 
 25 
 
 58 
 
 
 
 a-V/ 
 
 15 
 
 
 
 
 
 
 
 
 
 89 
 
 
 
 28 
 
 
 
 Seine ab 
 
 
 
 
 
 trace 
 
 
 
 80 
 
 trace 
 
 be]_ 
 
 
 
 
 
 >} 
 
 
 
 2-40 
 
 ,, 
 
 Rh6ne a 
 
 
 
 
 
 
 
 85 
 
 
 
 2-38 
 
 39 
 
 j 
 
 ag 
 
 
 
 
 
 
 
 
 
 
 
 trace 
 
 
 
 trace 
 
 Spree at 
 
 
 
 
 
 
 
 30 
 
 
 
 
 
 1-3 
 
 
 
 Maes at 
 
 
 
 
 
 
 
 
 
 
 
 28 
 
 23 
 
 
 
 at 
 
 
 
 
 
 
 
 
 
 ** 
 
 2-00 
 
 50 
 
 trace 
 
 Elbe nea 
 
 
 -^_ 
 
 
 
 
 
 
 
 54 
 
 12 
 
 
 
 Exe nea: 
 
 trace 
 
 
 
 
 
 23 
 
 
 
 trace 
 
 
 
 
 
 2-30 
 
 Deeneai-gg 
 
 
 
 
 
 
 
 
 
 20 
 
 
 
 
 
 2-60 
 
 Aar neai 
 
 
 
 
 
 
 
 
 
 
 
 27 
 
 
 
 trace 
 
 trace 
 
 Arve (F 
 
 . 
 
 
 
 
 
 
 
 
 
 20 
 
 
 
 
 
 40 
 
 (Ai 
 
 
 
 
 
 
 
 
 
 
 
 10 
 
 
 
 
 
 ?o 
 
 Doubs J 
 
 
 
 
 
 
 
 80 
 
 
 
 1-59 
 
 
 
 trace 
 
 
 
 Marne . 
 
 
 
 
 
 
 
 
 
 
 
 60 
 
 
 
 
 
 trace 
 
 Bievre n 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Ouroy ni 
 
 
 
 
 
 
 
 trace 
 
 
 
 2-00 
 
 
 
 
 
 trace 
 
 Yonne n 
 
 
 
 
 
 
 
 
 
 
 
 1-90 
 
 
 
 
 
 ,, 
 
 Beuvron 
 
 
 
 
 
 
 
 
 
 
 
 
 
 _ 
 
 
 
 
 
 Therouei 
 
 
 
 
 
 _ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Gergogn 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Vesle ne 
 Liitschin 
 
 22 
 
 
 
 
 
 I 
 
 
 
 18 
 35 
 
 11 
 10 
 
 36 
 
 79 
 
 M611,nes-09 
 
 
 
 
 
 
 
 
 
 72 
 
 trace 
 
 10 
 
 
 
 Oetz nea 
 
 
 
 
 
 
 
 
 
 
 
 86 
 
 
 
 
 
 
 
 
 
PURIFICATION OF WATER. 35 
 
 where the only available water is muddy, it is purified in filtering tanks. These 
 consist of large water-tight basins at the bottom of which is placed a layer of coarse 
 stones, over this a layer of coarse sand or gravel, then a layer of fine sand, and on 
 the top a layer of river sand. The water is led in above, and filters through the 
 several layers, collecting in the lowest one. Prom thence it passes into reservoirs or 
 shafts built vertically in the basin, and having their walls so perforated at the lower 
 part, where they are in contact with the coarse stones, that only filtered water can 
 enter them. The filtered water is pumped out from these reservoirs, and conducted to 
 its destination. Iron tubes perforated below are often used instead of brickwork 
 reservoirs. The greater portion of the suspended impurities contained in the water is 
 retained in the uppermost layer of sand, and consequently this has to be renewed from 
 time to time. 
 
 By filtering water through powdered charcoal, not only are mechanically suspended 
 substances got rid of, but substances that are present in solution are also removed to 
 some extent for instance, foul gases, and decaying organic substances and in this 
 way water coloured by such substances may often be rendered colourless. However, 
 the charcoal soon becomes saturated with the absorbed substances, and rendered use- 
 less, so that filtration through charcoal cannot be conducted advantageously on a 
 large scale. It may even happen that charcoal which has become thus saturated at a 
 low temperature will give up a portion of the absorbed substance when the water to 
 be filtered has a higher temperature. On a small scale, however, carbon filters in 
 various forms are frequently used for purifying water. 
 
 At present no means are known of rendering sea water potable by simple filtra- 
 tion. Many experiments have been made in this direction, but no cheap material has 
 been found capable of retaining the salt. 
 
 DISTILLATION. Water that is to be used for analysis and other chemical pur- 
 poses must be purified by distillation, for all kinds of natural water are too impure for 
 such purposes ; even rain water contains impurities originating from the atmosphere, 
 such for instance as dust, salts of ammonia, etc., which render it unfit for many pur- 
 poses. 
 
 The purification of water by distillation is very simple. For this purpose, the 
 purest natural water obtainable should be selected, and especially that most free 
 from smell. The apparatus in which the distillation is carried out varies in shape 
 and arrangement. Generally it consists of a copper still^eated from beneath so as 
 to boil the water in the still. The steam is conducted, by means of a head, fastened 
 air-tight to the still, into a cooling apparatus, where it is condensed and flows out 
 below. The condenser generally consists of a serpentine tube, fitted into a tub filled 
 with cold water in such a way that the interior of the tube cannot communicate with 
 the cold water surrounding it. The first portion of water which distils over is thrown 
 away, since it contains all the gaseous products which were dissolved in the water. 
 The collection of the distillate is not begun until one-fourth of the water has distilled 
 over, and then, provided the operation has been properly conducted, the distilled water is 
 chemically pure. In purifying water by this method, care must be taken to avoid too 
 violent boiling, by which some of the water from the still might be spirted into the 
 condensing apparatus, and also to prevent the water in the still from being evapo- 
 rated to dryness, in which case the solid contents, reduced to a dry state, might be 
 decomposed, yielding gaseous products, which would pass into the distillate. In either 
 case the distilled water would be rendered impure. 
 
 Distillation of sea water. In order to obtain pure water from sea water, a plan is 
 adopted similar to that just described, only that in this case greater precaution is 
 necessary. Sea water contains in solution a much greater amount of salts than 
 ordinary well or river water, and upon evaporation these salts form a thick crust in 
 the still, which adheres firmly to the bottom. Consequently, overheating of the 
 bottom of the still easily occurs, whereby on the one hand salts are decomposed, and 
 on the other hand the still itself suffers. This difficulty has to a great extent been 
 overcome by the use of an apparatus, constructed by Dr. Normandy, which is exten- 
 sively used in ships making long voyages. 
 
 The distillation of sea water for the purpose of rendering it potable has attracted 
 the attention of many. The first to occupy himself with the matter was an English- 
 man of the name of Hanton, and later on, in 1714, a Frenchman named Gautier. Their 
 apparatus, however, was very imperfect, and found on this account no general employ- 
 ment. Peyre and Kochere have recently constructed an apparatus of the kind in which 
 the heat of combustion is not only used for the distillation of water, but at the same 
 time, by means of a suitable condenser, for culinary purposes. 
 
 The first and last portions of the distillation are collected separately, and serve for 
 washing purposes, The intermediate portion is used for drinking. This water is 
 
36 HYDROGEN. 
 
 rendered more potable by heating it in a kind of drum in which the air is constantly 
 renewed. By this means the water absorbs oxygen and carbonic acid in the propor- 
 tion in which these gases are contained in river water. This water would be ren- 
 dered better and more palatable by adding to it one tenth per cent, of water saturated 
 with calcium carbonate and free carbonic acid. 
 
 Uses. There is no substance that is made use of on so large a scale as water, 
 both in manufactures and in household economy. It is employed for the purpose 
 of transferring heat to other substances which cannot with advantage be submitted to 
 the direct action of fire, either by means of bringing them in contact with hot water, 
 or by the application of steam. Water is used for purposes of purification, for dis- 
 solving or crystallising a number of substances, for producing and promoting numerous 
 chemical and physiological changes which set in activity the industrial^ energy of 
 mankind in manufactories, in agriculture, horticulture, etc. Lastly, water is the sub- 
 stance by means of which heat is converted in steam engines into force. 
 
 If all the uses thus cursorily alluded to be considered, it will be evident that there 
 is no substance of more general and higher importance than water. 
 
 Compounds. Water combines with a number of substances in a variety of ways, 
 forming compounds which are generally termed hydrates, though in many instances 
 they probably do not actually contain water, but are to be regarded rather as derivatives 
 of water, by the substitution of elementary or compound substances for a portion of its 
 hydrogen. Thus, for instance, nitric hydrate, or ordinary nitric acid, and sodium 
 
 hydrate should be represented by the formulae jj | an( * g > 0, as derivatives of 
 
 water, half of the hydrogen being replaced by the monovalent radicle N0 2 , and by the 
 monovalent element Na respectively. 
 
 Sulphuric hydrate, or ordinary sulphuric acid, corresponds in like manner to a 
 
 double molecule of water, and may be represented by the formula -n- 2 > 2 , half the 
 
 hydrogen being replaced by the bivalent radicle S0 2 . 
 
 The composition of ethyl hydrate, or ordinary alcohol, and of its analogues, may 
 
 C^ TT "^ 
 
 also be represented as bearing the same relation to water 2 -rr > 0, half of the hydro- 
 gen being replaced by the monovalent radicle, or pseudo-metal, ethyl C 2 H 5 . 
 
 A number of carbonaceous substances, such as starch, sugar, etc., containing, 
 besides carbon, hydrogen and oxygen in the same proportions as water, may on that 
 account be regarded as compounds of carbon with water, or hydrates of carbon, and 
 they are often termed carbohydrates; but other considerations give greater proba- 
 bility to the opinion that the constitution of these substances, or the mode in which 
 their elementary constituents are arranged, is very much more complex. 
 
 In many compounds, however, some part of the hydrogen and oxygen they con- 
 tain actually exists as water. This is especially the case with many crystalline salts ; 
 
 2S0 2 -| 
 for instance, potassic aluminum sulphate AL, S0 4 is capable of combining with 
 
 KJ 
 
 twelve molecules of water, forming the crystalline salt called alum, KA1 2 2S0 4 12H 2 0, 
 containing nearly half its weight of water, which can be separated by heating the salt 
 to redness. Water in this state of combination is termed water of crystallisation. 
 
 HYDROGEN PEROXIDE. 
 
 FORMULA. H 2 2 . MOLECULAR WEIGHT 34. 
 
 Composition. This compound of hydrogen and oxygen contains relatively to 
 hydrogen twice as much oxygen as water does, and its composition is represented by 
 the formula H 2 2 . 
 
 Characters. Hydrogen peroxide is a colourless liquid, in its outward appearance 
 not distinguishable from water, but very different from that substance in its chemical 
 and physical properties. Its density is almost one-and-a-half times that of water, the 
 specific gravity being 1-45. It does not become solid at 30 C. At a temperature 
 of from 15 to 20 it decomposes, yielding water and oxygen ; it cannot, therefore, 
 be converted by means of heat into the gaseous condition, but it can easily be 
 evaporated in a vacuum. Hydrogen peroxide bleaches vegetable colours ; and causes 
 violent irritation of the skin ; its taste is acrid and bitter. It is soluble in all pro- 
 portions in water ; and is soluble in ether in considerable amount. The ethereal 
 
PREPARATION OF HYDROGEN PEROXIDE. 37 
 
 solution is very stable, indeed hydrogen peroxide will partly distil over with the ether 
 vapour. 
 
 Hydrogen peroxide yields its oxygen with readiness to oxidisable substances, and 
 is therefore a powerful oxidising agent. It oxidises arsenic to arsenic acid, phos- 
 phorous acid to phosphoric acid, protoxide of iron to peroxide of iron, etc. 
 
 Hydrogen peroxide also acts as a reducing agent. If it be brought, for instance, into 
 contact with easily reducible oxides, such as oxide of gold, oxide of silver, or oxide of 
 platinum, evolution of gas takes place, the oxygen of the metallic oxides escaping, 
 together with the half of the oxygen of the hydrogen peroxide, water and metal re- 
 maining behind. In the same way, it reduces manganic acid, chromic acid, peroxide 
 of lead, etc., to lower oxides. 
 
 Hydrogen peroxide manifests a still more remarkable behaviour with certain other 
 substances. In contact with finely divided platinum, gold, silver, peroxide of 
 manganese, and other finely divided substances, the half of its oxygen escapes, accom- 
 panied by a rise of temperature of the whole mass ; water remains behind ; but the 
 substances which cause this decomposition do not undergo any alteration whatever. 
 Berzelius termed this phenomenon contact act ion. 
 
 Some of the reactions of hydrogen peroxide are very marked and admit of its 
 presence being readily detected. Thus, if a few drops of a dilute solution of potas- 
 sium chromate, with a few drops of dilute sulphuric acid, are added to a liquid 
 containing only minute quantities of hydrogen peroxide, and the whole is shaken with a 
 little ether, perchromic acid is formed, which colours the ether intensely blue. Mere 
 traces of hydrogen peroxide can be detected by adding a small quantity of starch 
 paste containing potassium iodide to the liquid to be tested, together with from two 
 to three drops of an extremely dilute solution of sulphate of iron. The smallest quan- 
 tity of hydrogen peroxide causes the formation of blue iodide of starch. Of course 
 the liquid to be tested must not contain any substance that likewise produces a blue 
 coloration of starch paste containing potassium iodide. 
 
 Preparation. The preparation of hydrogen peroxide is based upon the fact that 
 certain metallic peroxides as, for instance, potassium peroxide, or barium peroxide, 
 upon treatment with dilute acids yield oxygen which is not separated in the free state, 
 but combines with the water present, forming hydrogen peroxide. It is best to use 
 barium peroxide for this purpose. This decomposes with dilute sulphuric acid accord- 
 ing to the following equation : 
 
 Ba0 2 + * 2 = 2 + H 2 2 . 
 
 Hydrochloric acid is better suited for this purpose than sulphuric acid, because it 
 forms a soluble salt of barium, which does not hinder the further action of the acid 
 upon the peroxide, as the barium sulphate does. But carbonic acid is the most suit- 
 able for the preparation of pure hydrogen peroxide. In order to prepare it by the 
 action of carbonic acid, an abundant stream of the washed gas is passed through dis- 
 tilled water in a beaker. To this water finely-powdered barium peroxide is added from 
 time to time in very small quantities, so that there is never any great excess of barium 
 peroxide present in the liquid containing hydrogen peroxide, which in such case would 
 be decomposed into water, with the evolution of oxygen. After this operation has been 
 carried on for some time the barium carbonate is filtered off, and the solution 
 evaporated in vacuo over sulphuric acid until the liquid assumes a syrupy consistence. 
 
 Hydrogen peroxide cannot be preserved long in this condition. In order to pre- 
 serve it, it must be diluted with water, and made slightly acid with hydrochloric acid. 
 Even in this state, it gradually decomposes, especially when exposed to light. 
 
 Uses. Hydrogen peroxide has been used, according to the recommendation of 
 its discoverer Thenard, for restoring the white colours in pictures that had turned grey or 
 black. It acts in this case by giving off its oxygen, which oxidises the black sulphide 
 of lead and converts it into white sulphate of that metal. In this way the blackened 
 colours of oil-paintings have been restored by making use of water containing only 2 
 per cent, by measure of hydrogen peroxide. If hydrogen peroxide were cheaper, it 
 might be used with advantage for cloth-bleaching. 
 
 Hydrogen peroxide has been used in medicine, but at present only externally. 
 
NITROGEN. 
 
 SYMBOL N. ATOMIC WEIGHT 14. 
 
 History. Kutherford discovered in 1772 that atmospheric air contains a pecu- 
 liar gas, which remains when an animal respires in a closed space, and is not capable 
 of supporting either respiration or combustion. Not long afterwards Scheele and 
 Lavoisier ascertained that atmospheric air consists chiefly of this gas, together with 
 oxygen. Lavoisier gave it the name of Azote, and Chaptal called it Ni'trogene, 
 because the same gas occurs in nitric acid ; hence its designation with the letter or 
 symbol N. 
 
 Occurrence. Nitrogen occurs abundantly in the free state, constituting about 
 four-fifths of the volume of atmospheric air, or rather more than three-fourths of its 
 weight. 
 
 It also occurs largely in a state of combination with oxygen and potassium, sodium, 
 or calcium, as a constituent of the corresponding nitrates, saltpetre, cubic nitre, and 
 nitrocalcite. Oxides of nitrogen-also exist in small proportion in the atmosphere. 
 Nitrogen in combination with hydrogen occurs as ammonia in the atmosphere, in 
 some kinds of natural water, and in volcanic exhalations. Many substances, such as 
 albumin, casein, etc., that are of great importance in connection with the vital phe- 
 nomena of plants and animals, contain nitrogen as an essential constituent, and other 
 nitrogenous substances of like origin are remarkable either for their powerful 
 medicinal properties or for their applicability as dyes, etc. 
 
 Characters. Nitrogen gas is characterised by its chemical indifference towards 
 other substances, and it is on this account impossible to separate it from the air by 
 means of another substance. It is colourless, tasteless, and odourless ; as compared 
 with hydrogen its density is 14, and relatively to atmospheric air its specific gravity is 
 0'9713. It has not been possible as yet, by the agency of the most powerful pressure, 
 combined with the most intense cold, to condense nitrogen gas to a liquid condition. 
 Nitrogen gas is slightly soluble in water ; at 0C. the amount dissolved is only a little 
 above 2 per cent, by measure. It is not inflammable ; on the contrary, burning substances 
 are immediately extinguished when brought into an atmosphere of nitrogen gas ; it 
 is equally irrespirable, for if it does not act as a positive poison upon the animal 
 organism, still animals are suffocated in an atmosphere of the pure gas. 
 
 Preparation. Nitrogen is generally prepared from atmospheric air, of which it 
 constitutes nearly three-fourths by weight. All inflammable substances burn in the air 
 at the expense of the oxygen ; therefore if combustion is carried on in a closed 
 space, it continues only so long as oxygen is present. Combustion ceases as soon as 
 all the oxygen is used up, nitrogen and the products of combustion remaining behind. 
 If, for instance, a glass bell jar be placed over a small dish containing a piece of 
 phosphorus, floating upon water contained in a trough, and thus allowed to remain 
 for twenty-four hours, slow combustion of the phosphorus takes place, the products 
 of combustion, phosphorous and phosphoric acids dissolve in the water, and nitrogen 
 alone remains in the bell jar. 
 
 In order to obtain nitrogen from the air more speedily, it is convenient to proceed 
 in the following manner: A large flat cork, somewhat hollowed out in the middle, is 
 allowed to float upon the surface of water contained in a pneumatic trough, and 
 upon it is placed a small porcelain dish containing a piece of dry phosphorus. The 
 phosphorus is ignited, and over the whole is inverted a large glass bell jar, in such 
 a manner that the rim at the bottom dips at least an inch deep into the water. 
 The burning phosphorus rapidly withdraws all the oxygen from the air con- 
 tained in the bell jar, forming phosphoric acid, which fills the jar with white clouds, and 
 gradually dissolves in the water. As the volume of air in the bell jar is diminished, 
 in consequence of the withdrawal of oxygen, the water rises in the jar and occupies 
 eventually the space that the oxygen had previously occupied. Nitrogen obtained in 
 this manner is never absolutely pure, for it contains still the carbonic acid which was 
 contained in the air, as well as a small quantity of oxygen, since the phosphorus ceases 
 to burn before all the oxygen has disappeared. 
 
PREPARATION OF NITROGEN. 39 
 
 Pure nitrogen can be obtained by freeing atmospheric air from water-vapour and 
 carbonic acid, and conducting such purified air over ignited metallic copper. For this 
 purpose, a gas-holder, such as that described on p. 20 (fig. 3), is filled with air, which 
 is conducted first of all through a glass U-tube filled with pieces of fused calcium 
 chloride, then through a similar tube filled with pieces of fused potassium hydrate. 
 After the air has by this means been freed from water and carbonic acid, it is passed 
 through a horizontal tube of difficultly fusible glass, filled with copper turnings and 
 heated to redness. In this tube oxygen is absorbed by combining with the red-hot 
 copper, forming oxide of copper, and it is only necessary to collect the escaping gas 
 over water in a suitable vessel in order to obtain pure nitrogen gas. 
 
 Nitrogen gas in the pure state can also be obtained by conducting chlorine gas 
 through a solution of ammonia in water. Chlorine deprives part of the ammonia of 
 its hydrogen, forming first of all hydrochloric acid, and this combining with another 
 portion of ammonia, forms sal-ammoniac (ammonium chloride), according to the 
 equation ; this method of preparation is attended with some danger in consequence of 
 the possible formation of explosive nitrogen chloride : 
 
 4NH 3 + 301 = 3NH 4 C1 + N. 
 
 Lastly, pure nitrogen gas can be obtained by heating ammonium nitrite in a 
 retort, the delivery tube of which opens under a glass bell jar over water contained 
 in a pneumatic trough. Upon the application of heat to the nitrite, its hydrogen 
 combines with the oxygen of the nitrous acid, forming water, which condenses, and 
 nitrogen is liberated, according to the equation : 
 
 NO > Q 
 NH 4 ! H 
 
 Nitrogen is often set free as a by-product upon heating nitrogenous organic sub- 
 stances for various purposes. 
 
 Uses. Nitrogen gas has been employed with advantage for replacing atmo- 
 spheric air in vessels in which easily decomposible organic substances are preserved. 
 There are a number of substances, especially organic substances, which decom- 
 pose upon long contact with the air. In order to prevent this, the vessels in which 
 such substances are to be preserved are filled with nitrogen gas. Instead of filling 
 the vessel with nitrogen, the substance to be preservedfcmay be mixed with a substance 
 which on the one hand deprives air of its oxygen, and on the other hand prevents fer- 
 mentation and decay. Such substances are the sulphides of the alkali metals, sul- 
 phurous acid, the proto-salts of iron, certain ethereal oils, etc. In chemical laboratories 
 also, advantage is taken of the chemical indifference of nitrogen, by .filling with the 
 gas apparatus which contain easily oxidisable substances. 
 
 Compounds of Nitrogen. Notwithstanding the marked chemical indifference 
 of nitrogen in the free state, many of its compounds are remarkable for their chemical 
 energy. 
 
 There are five oxides of nitrogen, three of which form with water or metallic oxides 
 salts, which are respectively termed hyponitrites, nitrites, and nitrates, the 
 several hydrogen salts being commonly called acids. The composition of these oxides 
 and of the corresponding hydrogen and potassium salts is shown in the following table : 
 
 Monoxide or nitrous oxide . . N.O (Hyponitrous acid H 2 ON 2 or HNO 
 
 \Potassium hypomtnteK 2 ON 2 KNO 
 Dioxide or nitric oxide . . . N 2 
 
 Trioxide or nitrous anhydride . N 2 3 /^trous acid . . H 2 ON 2 3 or HN0 2 
 
 3 \Potassium nitrite . K 2 ON 2 3 KN0 2 
 Tetroxide or peroxide . . . N 2 4 
 
 Pentosideornitrihydride . . N A 
 
 The compound of nitrogen with hydrogen, called ammonia, has a composition 
 represented by the formula NH 3 . This substance is the type of a number of substances 
 termed compound ammonias or amines, in the composition of which the place 
 of one or more of the hydrogen atoms in ammonia is occupied by an alcohol radical ; 
 one of the most important of these substances, in a technical point of view, is aniline, 
 G 6 H 7 N, the source from which a great number of dyes are now prepared. It contains, 
 in the place of one of the hydrogen atoms of ammonia, the compound radical phenyl, 
 
 5TT 
 C^ 
 
 With carbon, nitrogen forms cyanogen, ON, a substance that is remarkable for 
 its analogy to chlorine, and its pseudo-elementary characters. 
 
40 NITROGEN. 
 
 The compounds of nitrogen with chlorine, bromine, and iodine, though interesting, 
 are not of technical importance. 
 
 Nitrogen appears to form definite compounds with iron, copper, and other metals. 
 
 NITROUS OXIDE. 
 
 FORMULA N 2 0. MOLECULAR WEIGHT 44. 
 
 Composition. This substance contains rather more than one-third its weight 
 of oxygen. The normal volume of nitrogen is double that of the oxygen, and the 
 joint volume of the gases is condensed one-third in combination. 
 
 Characters. Nitrous oxide is, at ordinary temperatures, a colourless gas, having 
 a faint odour and sweet taste. Its density is 22 as compared with hydrogen, and re- 
 latively to air its specific gravity is 1'525. At 15 it dissolves in rather more than its 
 own volume of water, and at in less than its volume. It condenses to a liquid 
 under a pressure of about 50 atmospheres, and more readily when cooled to 0. In 
 the liquid state nitrous oxide has a specific gravity of 0'9 and by cooling to - 99 it 
 solidifies. 
 
 Nitrous oxide gas supports combustion ; but less actively than oxygen, and it can 
 be readily distinguished from oxygen by its greater solubility in water. 
 
 Preparation. Nitrous oxide is formed by the action of zinc upon a mixture of 
 equal parts of nitric acid and sulphuric acid ; but the best method of preparing the 
 gas is to heat ammonium nitrate NH 4 N0 3 in a glass flask to a temperature not ex- 
 ceeding 25-0, when the salt melts and is decomposed according to the following equa- 
 tion, giving off the gas with the appearance of ebullition. 
 NH 4 N0 3 = 2H 2 + N 2 0. 
 
 On account of the solubility of the gas in cold water, it must be collected over 
 mercury or warm water or a solution of salt. 
 
 Uses. Nitrous oxide, when inhaled, produces temporary insensibility, and on 
 this account it is used as an anaesthetic in surgical operations. 
 
 Compounds. Nitrous oxide forms a series of saline compounds called hypo - 
 nitrites, which are very instable and can be obtained only indirectly by the reduction 
 of nitrates. 
 
 NITRIC OXIDE. 
 
 FORMULA NO OR N 2 2 . MOLECULAR WEIGHT 30 OR 60. 
 
 Composition. This substance contains nearly half its weight of oxygen, and is 
 a compound of nitrogen and oxygen in equal atomic proportions. The normal 
 volumes of the constituent gases are equal, and they are combined without condensa- 
 tion. 
 
 Characters. Nitric oxide is a colourless gas, that has not been liquefied by 
 cold or pressure. Its density is 15 as compared with hydrogen, and relatively to air 
 the specific gravity is T039. Nitric oxide is very sparingly soluble in water, which 
 takes up only about one-twentieth of its volume of the gas ; but it is copiously dissolved 
 by solutions of ferrous salts, forming a brown liquid which absorbs oxygen from the 
 air. Nitric acid also dissolves the gas, forming a blue, green, or brown liquid, accord- 
 ing to the concentration of the acid. 
 
 Nitric oxide is a very stable compound, and when dry it is not decomposed at a red 
 heat. It combines readily with oxygen, producing reddish-brown fumes, which dis- 
 solve in water, and probably consist in part of nitrous anhydride N 2 3 and partly of 
 nitrogen peroxide N0 2 . When mixed with water-vapour it is converted into nitric 
 acid and oxygen under the influence of a succession of electric sparks. Nitric oxide 
 extinguishes the flame of a taper, and it gives up its oxygen only when heated to a 
 high temperature with readily oxidisable substances, such as phosphorus. 
 
 Preparation. Nitric oxide is prepared by the action of copper or mercury on 
 nitric acid diluted with an equal bulk of water and without the aid of heat, 
 
 8HN0 3 + 3Cu = 3(Cu2N0 3 ) + 2NO + 4H 2 0, 
 
 or by decomposing potassium nitrate by dilute sulphuric acid in the presence of 
 ferrous sulphate, 
 
 2KNO, + 6FeS0 4 + 5H 2 S0 4 = 2HKS0 4 + 3Fe 2 3(S0 4 ) + 4H 2 + 2NO. 
 
OXIDES OF NITROGEN. 41 
 
 NITROUS ANHYDRIDE. 
 
 FORMULA N 2 3 . MOLECULAR WEIGHT 76. 
 
 Composition. This substance contains rather more than six-tenths of its weight of 
 oxygen, the nitrogen being combined with one and a half times its volume of oxygen. 
 
 Characters. Nitrous anhydride is a reddish-coloured gas, that condenses to a 
 blue liquid at 18. 
 
 Preparation. By gently heating a mixture of nitric acid and arsenous oxide, or 
 a mixture of starch and nitric acid of T25 sp. gr., brown vapours are given off which 
 may be condensed in a tube surrounded by a freezing mixture to a blue liquid, after 
 having been passed over calcium chloride. The reaction that takes place is repre- 
 sented by the following equation : ^ 
 
 As 2 O s + 2HN0 3 <rll 2 = 2H 3 As0 4 + N 2 3 . 
 
 Compounds. Nitrous anhydride combines with water forming nitrous acid 
 HN0 2 , the representative of a series of saline compounds called nitrites. 
 
 It is a very unstable compound, and is readily decomposed into nitric acid, nitric 
 oxide, and water, as shown by the following equation : 
 
 3HN0 2 = HN0 3 + 2N04-H 2 0. 
 
 The nitrites are generally cry stalli sable and soluble in water, the silver and lead 
 salts being the least soluble ; when heated they melt, and on raising the temperature 
 they are decomposed, giving off a mixture of oxygen and nitrogen. An acidulated 
 solution of a nitrate acts both as a reducing and as an oxidising agent. Permanganic 
 acid is at once reduced in this way, as well as chromic acid, salts of gold and mercury, 
 etc. On the contrary, iodine is liberated from potassium iodide by an acidulated 
 solution of a nitrite, ferrous salts are converted into ferric salts, and indigo is bleached 
 by oxidation. Nitrites frequently occur in water contaminated by surface drainage. 
 
 NITROGEN* PEROXIDE. 
 
 FORMULA N0 2 OR N 2 4 . MOLECULAR WEIGHT 93-^ 46. CTL <f }. 
 
 Composition. This substance contains nearly seven-tenths of its weight of 
 oxygen, the nitrogen being combined with twice its volume of oxygen, and the joint 
 volume of the constituent gases is condensed to one-third by their combination. 
 
 Characters. At the ordinary temperature nitrogen peroxide is an orange- 
 coloured liquid, having a specific gravity of 1'45. When cooled, the colour fades and 
 it becomes greenish or even quite colourless, and at a very low temperature it crystal- 
 lises. It boils at 22, giving off reddish -brown vapour, which becomes darker-coloured 
 when heated somewhat above that temperature, and at 40 almost black. The density 
 of the gas as compared with hydrogen is 38'3 at 267, but at 135 it is only 23. 
 
 Nitrogen peroxide is decomposed by water, forming nitrous acid and nitric acid, as 
 shown by the following equation: 
 
 2N0 2 + H 2 = HN0 2 + HN0 3 . 
 
 When liquid nitrogen peroxide is gradually mixed with water the liquid be- 
 comes blue, then green, and lastly orange- coloured, nitric oxide being evolved and 
 nitric acid formed, 
 
 3N0 2 H 2 = NO + 2HN0 3 . 
 
 Nitrogen peroxide is decomposed by basic oxides, such as potash, forming nitrate 
 and nitrite, 
 
 2N0 2 + 2KHO = KN0 2 + KN0 3 + H 2 0. 
 
 The gas has a suffocating odour ; it does not extinguish the flame of a taper ; it is 
 not decomposed at a moderate red-heat ; but heated phosphorus or carbon abstract 
 oxygen from it potassium does the same at the ordinary temperature. 
 
 Preparation. By heating dry lead nitrate in a glass retort or flask, dark-red 
 vapour is given off, consisting of a mixture of the peroxide with oxygen gas ; and by 
 passing the dry vapour through a cooled tube the peroxide is condensed. The reac- 
 tion is represented by the following equation : 
 
 2(Pb2N0 3 ) = 2PbO + 4N0 2 + 20. 
 
 Compounds. Nitrogen peroxide does not form saline compounds ; but it com- 
 bines with sulphuric acid, forming a crystalline substance. 
 
42 NITROGEN. 
 
 NITROGEN PENTOXIDE. 
 
 FORMULA N 2 5 . MOLECULAR WEIGHT 108. 
 
 Composition. This substance contains nearly three-fourths of its weight of 
 oxygen, and it is very unstable, decomposing gradually at the ordinary temperature. 
 
 Characters. Nitrogen pentoxide is colourless and crystalline, melts at 30, and 
 boils at 45. It has a powerful action on oxidisable substances, such as sulphur, phos- 
 phorus, etc. 
 
 Preparation. By passing dry chlorine gas over dry crystals of silver nitrate 
 heated to about 90, and lowering the temperature when decomposition commences, a 
 compound of nitric peroxide and chlorine is formed, as shown by the following equation : 
 
 AgNOg + Cl = AgCl + N0 2 C1 + 0. 
 
 This substance then acts upon the undecomposed silver nitrate, forming nitrogen 
 pentoxide. 
 
 N0 2 CHA.gN0 3 = AgCl + N 2 5 . 
 
 Compounds. Nitrogen pentoxide combines with water, forming hydrogen 
 nitrate or nitric acid, which is the representative of a series of saline compounds 
 called nitrates. 
 
 The nitrates are mostly soluble crystallisable salts ; some few are decomposed by 
 water into basic salts that are insoluble or sparingly soluble in water. By heat 
 nitrates are readily decomposed, either giving off oxygen and being converted into 
 nitrites, as in the case of the potassium salts, or yielding nitrogen peroxide and 
 oxygen, as in the case of lead nitrate. Other nitrates, like bismuth and aluminum 
 nitrates, give off nitric acid even when moderately heated. 
 
 When nitrates are heated with oxidisable substances in the dry state, they de- 
 flagrate or are decomposed with explosive violence, and their oxygen is transferred to 
 the substance mixed with them : thus, for instance, carbon is converted into carbon 
 dioxide, sulphur into sulphuric oxide, and these acid oxides combine with the basic 
 oxide of the nitrate used, forming carbonate or sulphate. 
 
 Nitrates occur abundantly in the soil of some parts of India and South America, 
 and they are formed by the gradual oxidation of nitrogenous organic substances in 
 contact with chalk, limestone, or other earthy materials capable of forming bases. 
 The potassium, sodium, and calcium salts are the most abundant. Magnesium nitrate 
 sometimes occurs in water. 
 
 NITRIC ACID. 
 
 FORMULA HN0 3 . MOLECULAR WEIGHT 63. 
 
 History. The first description of the preparation of nitric acid was given by 
 the Arabian chemist Geber, towards the end of the eighth century. He called it 
 generally aqua dissolutiva, and sometimes aqua fortis. Glauber was the first to give 
 it the name spiritus acidus nitri, which appellation was changed in the eighteenth 
 century to acidum nitricum and nitric acid. 
 
 The characters of nitric acid were studied by Geber, and afterwards by Boyle, 
 Mayf r, Bergmann, and others. The knowledge of its composition is due to Cavendish, 
 who in 1784 prepared nitric acid by the direct combination of nitrogen and oxygen 
 by means of the electric spark. 
 
 The first directions for preparing nitric acid on a large scale, by distilling a mixture 
 of clay and saltpetre, were given by Raymond Lully in the thirteenth century. 
 ^ Occurrence. Nitric acid does not occur to any extent naturally in the free state. 
 Since it is a very strong acid, it expels weaker acids from their compounds and forms 
 nitrates. The nitrates most often met with are those of potassium, sodium, calcium, 
 and magnesium. Small quantities of ammonium nitrate are always present in the 
 air, this salt being formed partly during thunderstorms, by the action of lightning 
 upon the nitrogen, oxygen, and water of the air, and partly by the gradual oxidation 
 of ammonium nitrite, small quantities of which are formed by the burning of most 
 nitrogenous organic substances. 
 
STRENGTH OF NITRIC ACID.. 43 
 
 Composition. In its most concentrated form, nitric acid, orhydric nitrate, 
 contains more than three-fourths its weight of oxygen ; its constitution is represented 
 
 in accordance with the water type, by the formula -r? 
 
 Characters. Nitric acid is an extremely corrosive liquid, fuming in the air, and 
 possessing an irritating smell. When pure, it is colourless ; but it assumes a yellow 
 colour very quickly when exposed to the light, owing to the formation of nitrogen 
 peroxide. When mixed with water this decomposition does not take place so readily. 
 At a temperature of 50 nitric acid becomes solid; it boils at 86, but does not 
 distil without partial decomposition. When passed through a porcelain tube heated 
 to redness, nitric acid is for the greater part decomposed into nitrogen peroxide, oxygen, 
 and water ; at a still higher temperature nitrogen is liberated, and some nitric oxide 
 is formed. Nitric acid at has a specific gravity of 1-559 ; at 15 a specific gravity 
 of 1-530. The specific gravity of an aqueous solution of the acid decreases with the 
 amount of water, hence it is easy to determine the relative strength of solutions of 
 nitric acid from their specific gravity. The following table shows the percentage of 
 nitric anhydride and nitric acid monohydrate in solutions of nitric acid of different 
 specific gravities at a temperature of 15. 
 
 Specific 
 Gravity 
 
 Nitric 
 Monohydrate 
 
 Nitric 
 Anhydride 
 
 Specific 
 Gravity 
 
 Nitric 
 Monohydrate 
 
 Nitric 
 Anhydride 
 
 530 
 
 100-00 
 
 85-71 
 
 1-368 
 
 68-88 
 
 50-47 
 
 529 
 
 99-52 
 
 85-30 
 
 1-363 
 
 58-00 
 
 4971 
 
 523 
 
 97-89 
 
 83-90 
 
 1-358 
 
 57-00 
 
 48-86 
 
 520 
 
 97-00 
 
 83-14 
 
 1-353 
 
 56-10 
 
 48-08 
 
 516 
 
 96-00 
 
 82-28 
 
 1-346 
 
 55-00 
 
 47-14 
 
 514 
 
 95-27 
 
 81-66 
 
 1-341 
 
 54-00 
 
 46-29 
 
 509 
 
 94-00 
 
 80-57 
 
 1-339 
 
 53-81 
 
 46-12 
 
 506 
 
 93-01 
 
 79-79 
 
 1-335 
 
 53-00 
 
 45-40 
 
 1-503 
 
 92-00 
 
 78-85 
 
 1-331 
 
 52-33 
 
 44-55 
 
 1-499 
 
 91-00 
 
 78-00 
 
 1-323 
 
 50-99 
 
 43-70 
 
 1-495 
 
 90-00 
 
 77-15 
 
 1-317 
 
 49-97 
 
 42-83 
 
 1-494 
 
 89-56 
 
 76-77 
 
 1-312 
 
 49-00 
 
 42-00 
 
 1-488 
 
 88-00 
 
 75-43 
 
 1-304 
 
 48-00 
 
 41-14 
 
 1-486 
 
 87-45 
 
 74-59 
 
 1-298 
 
 47*18 
 
 40-44 
 
 1-482 
 
 86-17 
 
 73-86 
 
 1-295 
 
 46-64 
 
 39-97 
 
 1-478 
 
 85-00 
 
 72-86 
 
 1-284 
 
 45-00 
 
 38-57 
 
 1-474 
 
 84-00 
 
 72-00 
 
 1-274 
 
 43-53 
 
 37-31 
 
 1-470 
 
 83-00 
 
 71-14 
 
 1-264 
 
 42-00 
 
 36-00 
 
 1-467 
 
 82-00 
 
 70-28 
 
 1-257 
 
 41-00 
 
 35-14 
 
 1-463 
 
 80-96 
 
 69-39 
 
 1-251 
 
 40-00 
 
 34-28 
 
 1-460 
 
 8000 
 
 68'57 
 
 1-244 
 
 39-00 
 
 33-43 
 
 1-456 
 
 79-00 
 
 67-71 
 
 1237 
 
 37-95 
 
 3253 
 
 1-451 
 
 77-66 
 
 66-56 
 
 1-225 
 
 36-00 
 
 30-89 
 
 1-445 
 
 76-00 
 
 65-14 
 
 1-218 
 
 35-00 
 
 29-29 
 
 1-442 
 
 75-00 
 
 64-28 
 
 1-211 
 
 33-86 
 
 29-02 
 
 1-438 
 
 74-01 
 
 63-44 
 
 1-198 
 
 32-00 
 
 27-43 
 
 1-435 
 
 73-00 
 
 62-57 
 
 1-192 
 
 31-00 
 
 26-57 
 
 1-432 
 
 72-39 
 
 62-05 
 
 1-185 
 
 30-00 
 
 25-71 
 
 1-429 
 
 71-24 
 
 61-06 
 
 1-179 
 
 29-00 
 
 2485 
 
 1-423 
 
 69-96 
 
 60-00 
 
 1-172 
 
 28-00 
 
 24-00 
 
 1-419 
 
 69-20 
 
 59-31 
 
 1-166 
 
 27-00 
 
 23-14 
 
 1-414 
 
 68-00 
 
 58-29 
 
 1-157 
 
 25-71 
 
 22-04 
 
 1-410 
 
 67-00 
 
 57-43 
 
 1-138 
 
 23-00 
 
 19-71 
 
 1-405 
 
 66-00 
 
 56-57 
 
 1-120 
 
 20-00 
 
 17-14 
 
 1-400 
 
 6507 
 
 5577 
 
 1-105 
 
 17-47 
 
 14-97 
 
 1-395 
 
 64-00 
 
 54-85 
 
 1-089 
 
 15-00 
 
 12-85 
 
 1-393 
 
 63-59 
 
 54-50 
 
 1-077 
 
 13-00 
 
 11-14 
 
 1-386 
 
 62-00 
 
 53-14 
 
 1-067 
 
 11-41 
 
 9-77 
 
 1-381 
 
 61-21 
 
 52-46 
 
 1-045 
 
 7-22 
 
 6-62 
 
 1-374 
 
 60-00 
 
 51-43 
 
 1-022 
 
 400 
 
 3-42 
 
 1-372 
 
 59-59 
 
 51-08 
 
 1-010 
 
 2-00 
 
 1-71 
 
NITROGEN. 
 
 The following table shows the percentage of nitric monohydrate and nitric an- 
 hydride in nitric acid solutions of different degrees Baume, and at a temperature of 15. 
 
 Degrees 
 Baumfi 
 
 Nitric 
 Monohydrate 
 
 Nitric 
 Anhydride 
 
 Degrees 
 
 Baume 
 
 Nitric 
 Monohydrate 
 
 Nitric 
 Anhydride 
 
 
 
 0-2 
 
 o-i 
 
 26 
 
 35-5 
 
 30-4 
 
 1 
 
 1-5 
 
 1-3 
 
 27 
 
 37-0 
 
 31-7 
 
 2 
 
 2-6 
 
 2-2 
 
 28 
 
 38-6 
 
 33-1 
 
 3 
 
 4-0 
 
 3-4 
 
 29 
 
 40-2 
 
 34-5 
 
 4 
 
 5-1 
 
 4-4 
 
 30 
 
 41-5 
 
 35-6 
 
 5 
 
 6-3 
 
 5-4 
 
 31 
 
 43-5 
 
 37'3 
 
 6 
 
 7-6 
 
 6-5 
 
 32 
 
 45-0 
 
 38'6 
 
 7 
 
 9-0 
 
 77 
 
 33 
 
 47-1 
 
 40-4 
 
 8 
 
 10-2 
 
 8-7 
 
 34 
 
 48-6 
 
 417 
 
 9 
 
 11-4 
 
 9-8 
 
 35 
 
 507 
 
 43-5 
 
 10 
 
 127 
 
 10-9 
 
 36 
 
 52-9 
 
 45-3 
 
 11 
 
 14-0 
 
 12-0 
 
 37 
 
 55-0 
 
 47-1 
 
 12 
 
 15-3 
 
 13-1 
 
 38 
 
 57-3 
 
 49-1 
 
 13 
 
 16-8 
 
 14-4 
 
 39 
 
 59-6 
 
 51-1 
 
 14 
 
 18-0 
 
 15-4 
 
 40 
 
 61-7 
 
 52-9 
 
 15 
 
 19-4 
 
 16-6 
 
 41 
 
 64-5 
 
 55-3 
 
 16 
 
 20-8 
 
 17-8 
 
 42 
 
 67-5 
 
 57-9 
 
 17 
 
 22-2 
 
 190 
 
 43 
 
 70-6 
 
 60-5 
 
 18 
 
 23-6 
 
 20-2 
 
 44 
 
 74-4 
 
 63-8 
 
 19 
 
 24-9 
 
 21-3 
 
 45 
 
 78-4 
 
 67-2 
 
 20 
 
 26-3 
 
 22-5 
 
 46 
 
 83-0 
 
 71-1 
 
 21 
 
 27'8 
 
 23-8 
 
 47 
 
 87-1 
 
 747 
 
 22 
 
 29-2 
 
 25-0 
 
 48 
 
 92-6 
 
 79-4 
 
 23 
 
 30-7 
 
 26-3 
 
 49 
 
 96-0 
 
 82-3 
 
 24 
 
 32-1 
 
 27-5 
 
 49-5 
 
 98-0 
 
 84-0 
 
 25 
 
 33-8 
 
 28-9 
 
 49-5 
 
 100-0 
 
 857 
 
 When nitric monohydrate is mixed with water, heat is set free, and the mixture 
 thus obtained has a higher boiling point than the pure monohydrate. Upon distil- 
 ling a mixture of nitric monohydrate and water, in which the proportion of water is 
 relatively small compared with the acid, a stronger acid passes over at first, and 
 there remains behind a more dilute acid, the boiling point of which remains constant 
 at 123. On the other hand, if a mixture of nitric acid with much water be distilled, 
 the first portions of the distillate consist of nearly pure water, concentrated acid 
 remaining behind in the retort. Upon continuing the distillation, the boiling point 
 rises to 123, and then remains constant, as in the former case. The acid which thus 
 distils over has a specific gravity of T42, and has a composition corresponding to 
 the formula (2HN0 3 ,3H 2 0). This applies, however, only to a distillation under the 
 ordinary. pressure, change of pressure influencing the composition of the distillate. 
 
 The most important property of nitric acid is the oxidising action which it exerts 
 in virtue of its capacity of yielding up to other bodies a portion of its oxygen^ Thus, 
 nitric acid easily oxidises carbon to carbonic acid, sulphur and sulphurous acid to 
 sulphuric acid, and the metals to oxides, etc. The extensive application of nitric acid 
 to industrial purposes is chiefly owing to its oxidising property. 
 
 Another important property of nitric acid is its nitrifying action, i.e., its property 
 of replacing the hydrogen of certain organic compounds by N0 2 . An example of the 
 kind is found in the case of the preparation of gun-cotton, formed by treating cotton 
 (cellulose) with strong nitric acid: 
 
 C a H 10 6 + 8*5' JO = C 6 H 7 (N0 2 ) 3 5 + 3H 2 0. 
 
 Testing of Nitric Acid. The strength of nitric acid is ascertained from its specific 
 gravity. It is also necessary to test nitric acid for certain impurities with which it is 
 always liable to be contaminated. Thus a yellowish colour may be due either to the 
 presence of nitrogen peroxide or to the presence of compounds of chlorine or iodine. 
 The presence of nitrogen peroxide is detected by dropping into a small quantity of the 
 acid, in a test-glass, a few drops of a solution of potassium permanganate, the colour 
 of which is discharged if nitrogen peroxide bo present. Chlorine is found by 
 diluting a small quantity of the acid, and adding a drop of a solution of silver nitrate, 
 which gives a curdy precipitate if chlorine be present. Free iodine is detected with 
 
PREPARATION OF NITRIC ACID. 
 
 45 
 
 starch paste, or by shaking the diluted acid with carbon bisulphide, which assumes a 
 red tint if free iodine be present. Sulphuric acid is detected by diluting the nitric 
 acid very considerably with water, and then adding a small quantity of a solution of 
 barium nitrate, a white precipitate indicating the presence of sulphuric acid. Further, 
 nitric acid ought not to leave a residue when evaporated upon a watch-glass or on 
 platinum foil ; a residue in such case would indicate the presence of substances, such as 
 sodium sulphate, with which nitric acid may be contaminated by the spirting of the 
 materials in the process of distillation. 
 
 Preparation. Nitric acid is prepared on a small scale by distilling a mixture 
 of equal parts of saltpetre and sulphuric acid in a retort. The following equation 
 represents the change that takes place : 
 
 On the large scale the same materials are used, but Chili saltpetre (sodium nitrate) 
 is generally substituted for potassium nitrate, the proportions in which these 
 materials are used being 116 parts of Chili saltpetre to 100 parts of sulphuric acid. 
 When a weaker acid is required, sulphuric acid of sp. gr. 1-551 is used, but the quantity 
 taken must be larger in proportion to the degree of dilution. 
 
 Distillation of Nitric Acid. In the distillation of nitric acid, gallery furnaces are 
 often employed, in which a number of glass retorts charged with the mixture of 
 saltpetre and sulphuric acid are heated in sand baths, the distillate being collected in 
 spacious receivers of glass. 
 
 According to another process, the apparatus represented by fig. 12 is used, c is a 
 retort of cast iron about four feet in diameter and three feet deep, with an opening 
 above for admitting the mixture of saltpetre and sulphuric acid. This opening is 
 
 FIG. 12. 
 
 closed with a lid, luted on with clay and gypsum. The furnace is also closed with a 
 lid (n ri). The retort is connected with the receivers by means of an iron tube lined 
 with clay, and a glass adapter (D). The condensers consist of a number of stoneware 
 bottles (E, E', E", etc.), connected with one another by means of stoneware tubes (F, F', F", 
 etc.) Each of these bottles holds from forty to fifty gallons, and is furnished with a 
 cock below for running off the acid, as well as with an opening above closed by a 
 stopper, through which the height of the acid in the jar may be ascertained, or water 
 poured in. A condensing arrangement of this kind consists of ten or twelve bottles, 
 the first few of which are left empty, while the last ones of the series contain a small 
 quantity of water for the complete absorption of the nitric acid vapours. The retort 
 is heated by means of the furnace (B), the heated air surrounding the retort on all 
 sides, and escaping through the flue 1 N. At the beginning of the process the damper 
 at the further end of the flue is so placed that the hot air is compelled to pass through 
 the flue M. This is done so as to warm the first few stone receivers, whereby the 
 risk of their cracking when the hot nitric vapours are admitted is avoided. As soon 
 
46 
 
 NITROGEN. 
 
 as the nitric acid in the first few bottles has attained a height of from three to five 
 inches, the damper is so placed that the hot air escapes through the flue L. If con- 
 centrated sulphuric acid has been employed, the first products of distillation are of a 
 reddish brown colour, owing to the great excess of sulphuric acid at the beginning of 
 the operation decomposing a portion of the nitric acid into nitrogen peroxide, oxygen, 
 and water. In proportion, however, as the sulphuric acid is saturated by its action upon 
 the saltpetre, the red vapours gradually disappear, until towards the end of the process, 
 when they are again produced, owing to a decomposition that will be described when 
 treating of fuming nitric acid (p. 48). It is easy to judge of the progress of the 
 distillation by observing the colour of the vapours passing through the glass tube (D). 
 
 Formerly, and even now in some places, the distillation was conducted in cast-iron 
 retorts placed in a horizontal position, and furnished above with a lining of fire-bricks 
 as a protection against the acid vapours. Two such retorts are heated by a single 
 furnace, the condensation being effected by an arrangement similar to that shown in 
 fig. 12. 
 
 At the end of the operation the residue in the retort, after cooling, contracts, and 
 is taken out. When ordinary saltpetre has been used, it is worked for potassium sul- 
 phate, or when Chili saltpetre has been employed, for neutral sodium sulphate. The 
 residue can also be employed in the preparation of fuming sulphuric acid. In order 
 to save time when retorts are used, the residue may be removed without waiting until 
 it has cooled. To effect this, it is only necessary to furnish the lid of the retort at its 
 lowest point with a small opening closed with a stopper or plug, which is cemented 
 in with a luting of clay during the heating. Upon removal of the stopper directly 
 the distillation is over, the molten residue flows out, and the retort can be charged 
 again immediately. 
 
 The preparation of nitric acid as well as soda from Chili saltpetre may be effected, 
 according to M. Walz, by mixing the saltpetre intimately with chalk, and heating 
 such mixture in a retort, in a current of steam, when nitric acid distils over, and is 
 collected in receivers of the usual form. 
 
 Bleaching of Nitric Acid. The crude distillate is always coloured yellow by nitrogen 
 peroxide. To remove this the raw acid is heated in vessels having the form shown 
 in fig. 13, placed in a water bath that can be heated to 80 or 85, until no further 
 
 FIG. 13. 
 
 evolution of coloured vapour is observed. The vapour escaping is passed through 
 a tube into a cool carboy, where a small quantity of liquid acid collects, and finally 
 it is discharged into the air, or into lead chambers for the production of sulphuric 
 acid. 
 
 Direct Preparation of Bleached Add. Since brown vapours are formed only at the 
 
 FIG. 14. 
 
 FIG. 15. 
 
 beginning and end of the process, it is possible to separate such coloured products 
 from the colourless portion by a simple fractional distillation. For this purpose the 
 
PREPARATION OF NITRIC ACID. 47 
 
 glass adapter (D , fig. 14) through which the vapours escape from the distilling vessel, 
 is connected with a stoneware cock (G) so constructed that by turning the cock (G) the 
 vapours pass either through h or h', and are conducted into different receivers, one 
 serving for the coloured and the other for the colourless products. The same end is 
 attained by the arrangement shown by fig. 15. One of the limbs of a three-limbed 
 lute (K K.') fits over the end of the glass adapter of the distilling vessel, and admits of 
 being turned so that the two other limbs are respectively raised or lowered, and the 
 vapours passing through them passed into one or other of two receivers, one of which 
 receives the coloured, the other the colourless vapours. During the time that the one 
 limb of the lute (K K') is lowered and placed in connection with the receiver, the other 
 end is closed with a glass plug. By the use of either of the above arrangements an 
 acid may be obtained which can be sent direct into the market. 
 
 Improved Condensing Apparatus of MM. Severs and Plisson. This is shown in 
 fig. 18. A is a glass adapter, through which the nitric acid vapours from the 
 generators (in this case cast-iron retorts) escape. The end of the adapter is luted 
 air-tight into the tubulus of the carboy (B), which rests upon a flue, serving to heat it. 
 The acid which condenses in B flows through a syphon (d, fig. 16), the outer limb of 
 which is shorter than the inner, thus preventing the complete emptying of the carboy, 
 and forming an hydraulic joint. From Bthe acid flows into another vessel (B) beneath 
 it. The carboys (c E F H) have the same construction as B, and the acid condensed in 
 them flows through the syphons into a stoneware tube, and finally collects in a 
 receiver (o). The upper part of the carboy (B) is furnished with a funnel of the form 
 shown in fig. 17, which admits of water being poured into the carboy. Conical- 
 shaped vessels (D D G G), having an aperture at their lower extremity, and furnished 
 
 FIG. 16. 
 
 FIG. 18. 
 
 above with funnels (PP) of the same construction as that shown in fig. 17, fit into the 
 necks of the carboys (c E F H). The vapours from B pass through a stoneware tube 
 into the second carboy c, and from thence into D, placed above c, through D B j? a o H. 
 
48 NITROGEN. 
 
 The vapours are thereby compelled to traverse a long distance, -which secures 
 their complete condensation. The condensed acid flows from the upper vessels D D G o 
 into the lower ones c E F H, and from thence into the receiver o. The concentration, 
 as well as the condensation, of the acid may be regulated by pouring small quantities 
 of water or very dilute acid, at intervals, through the funnels P P. The uncondensed 
 vapour passes from the last carboy H into the three carboys 1 1' i", filled with pieces of 
 moist pumice and placed one above another. For the condensation of the last traces of 
 vapour, it can be passed from the carboy i" into a stoneware worm condenser j, through 
 which a current of cold water is allowed to flow downwards from the cock M, passing 
 over the pieces of pumice, which it keeps constantly moist. The moist pumice 
 favours the action of oxygen upon the vapour of nitrogen peroxide, formed at the 
 beginning and end of the operation, and causes its reconversion into nitric acid, which 
 collects in the vessel N below. 
 
 This condensing apparatus has the great advantage that it requires emptying and 
 reconstruction much less frequently (every two or four weeks), and thereby saves 
 labour. At the same time the consumption of luting is considerably less, and the 
 vapours are more thoroughly condensed than in any other form of apparatus at 
 present employed. 
 
 The amount of acid obtained by the use of this apparatus is 120 or 130 parts, 
 containing 50 per cent, of nitric monohydrate for every 100 parts of Chili saltpetre. 
 
 The complete purification of nitric acid from unavoidable admixture of sodium 
 sulphate, chlorine, etc., is effected by submitting it to a further distillation, one or 
 two per cent, of lead nitrate being previously mixed with the acid to effect the re- 
 tention of both impurities. 
 
 Fuming Nitric Acid. When a mixture of saltpetre and sulphuric acid in equiva- 
 lent proportions is distilled, the distillate does not consist of an acid so pure as that 
 obtained by distilling the saltpetre with two equivalents of sulphuric acid, but is a 
 mixture of nitrogen peroxide and nitric acid, which bears the name of fuming nitric 
 acid. The formation of the large quantities of nitrogen peroxide depends upon the 
 fact that in the first stage of the process acid potassium sulphate and nitric mono- 
 hydrate are formed (vide p. 45). When the temperature is raised to 220, the acid 
 potassium sulphate is decomposed into neutral potassium sulphate and sulphuric acid, 
 which acts upon the saltpetre present in the retort. The nitric acid thus set free is 
 partly decomposed at this elevated temperature into oxygen and nitrogen peroxide, 
 which passes over with the distillate, and is absorbed by the nitric acid. 
 
 Ked fuming nitric acid must therefore be considered as a mixture of nitric acid 
 and nitrogen peroxide. It is extremely corrosive and exerts a very energetic oxidising 
 action. When slightly heated it gives off nitrogen peroxide, a reaction which serves 
 for the preparation in the pure state of this substance. Upon gradually mixing red 
 fuming nitric acid with water, its colour passes through various shades from reddish 
 yellow to green and blue, and when enough water has been added, it finally becomes 
 colourless. These changes of colour are due to the transitory formation of blue 
 nitrous acid by the action of water upon nitrogen peroxide. At the same time red 
 vapours escape which owe their origin in part to the oxidising action of the air upon 
 nitric oxide formed by the reaction, and in part either to the direct formation of 
 nitrous acid or to the evaporation of nitrogen peroxide. 
 
 Brunner's method of preparing red fuming nitric acid consists in distilling salt- 
 petre with an equal weight of sulphuric acid and 3 J per cent, of starch, which de- 
 composes some nitric acid and produces nitrogen peroxide. 
 
 Uses. Nitric acid owes its large consumption partly to its powerful oxidising 
 and dissolving action, and partly to its nitrifying properties. It is extensively 
 used in the preparation of sulphuric acid, in preparing chemically pure phosphoric 
 acid from phosphorus, also in preparing iodic and arsenic acids. It is used for 
 etching bronze, brass, and copper, for separating gold from silver ; further, by 
 engravers for etching copper plates ; in the preparation of aqua regia, the latter 
 serving as a solvent for gold, platinum, etc. Nitric acid is also employed in the 
 preparation of various nitrates, such as silver (lunar caustic of the surgeon), mer- 
 cury, copper, and lead nitrates ; in the preparation of tin chloride, the neutral and 
 basic nitrates of bismuth ; in the manufacture of pure oxalic acid, gun-cotton, nitro- 
 glycerine, and nitrobenzol, the substance from which aniline colours are prepared ; 
 nitric acid is also used in the preparation of anthraquinone, from which artificial aliza- 
 rine is obtained ; in the preparation of phthalic acid, nitromannite, Martin's yellow, 
 and picric acid. Nitric acid is further used for colouring silk, wool, and other animal 
 substances, for the conversion of starch into dextrin, for the decomposition of indigo 
 in cotton-printing, for preparing iron liquor (rouille) used for colouring silk black, 
 etc. 
 
 
CHARACTERS OF AMMONIA. 49 
 
 Aqua Ecgia, or nitre-muriatic acid, is prepared by mixing nitric acid with four times 
 its volume of hydrochloric acid. It is a solvent for a number of metals, such as gold, 
 iridium, platinum, etc., which are not attacked by the strongest acids. The action of 
 this mixture is due to the presence of free chlorine, which is liberated on heating, 
 HN0 3 + 3HC1 = NO + 2H 2 + 3C1. 
 
 The liberated chlorine combines with the metal to be dissolved, forming with it a 
 chloride. 
 
 Under certain conditions aqua regia exerts an oxidising action ; thus by its means 
 sulphur is oxidised to sulphuric acid, arsenic to arsenic acid, etc. 
 
 ^Upon heating aqua regia and collecting the vapours evolved, the first product 
 which distils over consists of nitric oxydichloride, NOC1 2 , a substance boiling at 7, 
 and afterwards a product passes into the receiver having a composition represented 
 by the formula NOC1, and termed nitrous oxychloride. 
 
 FORMULA NH 3 . MOLECULAR WEIGHT 17. 
 
 History. This substance was certainly known as early as the thirteenth century, 
 a solution of it having -been prepared from urine by Eaymond Lully. A similar 
 solution has long been known under the name ofspiritsofhartshorn. The capability 
 of forming saline compounds with acid, which constitutes the analogy between 
 ammonia and the mineral alkalies, was also known to the ancient chemists. In the 
 gaseous state ammonia was first obtained and described under the name of alkaline 
 air by Priestley in 1774. Bergman gave it the name ammonia in 1782 on account 
 of its having been obtained from sal ammoniac, which was prepared by the distillation 
 of camels' dung near the temple of Jupiter Ammon in Egypt. The composition of 
 ammonia was ascertained by Berthollet in 1 785. 
 
 Occurrence. Ammonia does not occur naturally in the free state. Combined 
 with carbonic acid, and sometimes with nitrous or nitric acids, it exists, in small 
 proportion, in the atmosphere. It is also met with, probably in the state of chloride, 
 in sea water, and in the water of many springs. In vSlcanic districts ammonia occurs 
 abundantly in the state of chloride, and considerable quantities of the carbonate are 
 sometimes found in deposits of guano. At the present time, however, the chief source 
 of ammonia is the gas liquor obtained in the distillation of coal for the preparation 
 of illuminating gas. In all cases of the decomposition of carbonaceous materials 
 containing nitrogen, either by putrefaction or destructive distillation, ammonia is 
 found among the products. 
 
 The presence of a small proportion of ammonia in the atmosphere is of great im- 
 portance for agriculture, since ammonia is essential for the nutrition of plants, and 
 owing to its solubility it is washed out by dew, rain, etc., falling on the earth's surface. 
 The ammonia in the air is generally combined with nitrous acid, which is formed in 
 considerable quantities during thunderstorms by the electric discharges. Whether 
 the ammonia in the air is also itself produced in part by electricity, or whether the 
 ammonium nitrite is formed by the combination of already existing ammonia with 
 nitrous acid, is not determined. At any rate, a number of chemical processes taking 
 place upon the earth give rise to the formation of considerable quantities of ammonia, 
 as, for instance, the putrefaction of nitrogenous organic materials such as animal re- 
 mains. Traces of ammonia are also contained in the air exhaled from the lungs of 
 animals. 
 
 Composition. Ammonia contains rather more than four-fifths of its weight of 
 nitrogen, and nearly one-fifth its weight of hydrogen. The hydrogen it contains has, 
 in the free state, a normal volume three times that of the nitrogen. 
 
 Characters. Ammonia is gaseous at the ordinary temperature : and therefore 
 it is represented as a compound of three atomic proportions of hydrogen with one 
 atomic proportion of nitrogen, and the joint volume of its constituents in the free state 
 is condensed to one half ; its density is 8 '5 times that of hydrogen. Its specific gravity 
 (air = 1) is 0-5893. It can be converted into the liquid state either by the application 
 of a pressure of from 6 to 7 atmospheres, or by cooling to a temperature of 40. At 
 a temperature of 80 it assumes a crystalline condition. Ammonia gas is colourless : 
 it possesses an extremely penetrating smell, and excites a copious flow of tears. When 
 an ^electric current is passed through the gas, it is decomposed into its constituents. 
 It is decomposed in the same way when passed through a porcelain tube heated to 
 
 E 
 
50 
 
 NITROGEN. 
 
 redness. This decomposition takes place more readily if the tube be filled with pieces 
 of porcelain, and easiest of all if pieces of platinum, silver, iron, or copper, be placed 
 in the tube. 
 
 If ammonia gas be conducted by means of a narrow tube into an atmosphere of 
 oxygen, it may be inflamed by the application of a light, and will continue to burn. 
 It is not, however, capable of burning in atmospheric air, except when kept continu- 
 ally in contact with a flame of some other more combustible substance. Ammonia is 
 extremely soluble in water, which at a temperature of 0, and under a pressure of 
 760 mm., dissolves 1,500 times its volume of the gas. The liquid ammonia of commerce 
 is a solution of the gas in water. Water absorbs ammonia with such energy that it 
 rushes into a space filled with ammonia just as it would into a vacuum, and a tube 
 may often be shattered in this way. At higher temperatures, the solubility of ammonia 
 in water is very much less, water at 15 C. absorbing only 727 times its volume of 
 ammonia, and at a temperature of 25 only 586 times its volume. In the absorption 
 of ammonia gas by water there is a considerable increase in the volume, and a corre- 
 sponding reduction in the density of the liquid. Therefore, specific gravity affords a 
 ready means of determining the ammoniacal contents of the solution, as shown by the 
 following table. 
 
 TABLE SHOWING THE AMOUNT OF AMMONIA IN SOLUTIONS OF AMMONIA. 
 TEMPERATURE 14 (Carius.) 
 
 Ammonia 
 
 
 Ammonia 
 
 
 Ammonia 
 
 
 Ammonia 
 
 
 in 100 
 
 Specific 
 
 in 100 
 
 Specific 
 
 in 100 
 
 Specific 
 
 in 100 
 
 Specific 
 
 parts 
 solution 
 
 Gravity 
 
 parts 
 solution 
 
 Gravity 
 
 parts 
 solution 
 
 Gravity 
 
 parts 
 solution 
 
 Gravity 
 
 1 
 
 9959 
 
 10 
 
 9593 
 
 19 
 
 9283 
 
 28 
 
 9026 
 
 2 
 
 9915 
 
 11 
 
 9556 
 
 20 
 
 9251 
 
 29 
 
 9001 
 
 3 
 
 9873 
 
 12 
 
 9520 
 
 21 
 
 9221 
 
 30 
 
 8976 
 
 4 
 
 9831 
 
 13 
 
 9484 
 
 22 
 
 9191 
 
 31 
 
 8953 
 
 5 
 
 9790 
 
 14 
 
 9449 
 
 23 
 
 9162 
 
 32 
 
 8929 
 
 6 
 
 9749 
 
 15 
 
 9414 
 
 24 
 
 9133 
 
 33 
 
 8907 
 
 7 
 
 9709 
 
 16 
 
 9380 
 
 25 
 
 9106 
 
 34 
 
 8885 
 
 8 
 
 9670 
 
 17 
 
 9347 
 
 26 
 
 9078 
 
 35 
 
 8864 
 
 9 
 
 9631 
 
 18 
 
 9314 
 
 27 
 
 9052 
 
 36 
 
 8844 
 
 Aqueous solutions of ammonia occur in commerce under various appellations, such 
 as solution of ammonia, liquid ammonia, spirits of hartshorn, etc. 
 
 Ammonia combines with hydrochloric acid, forming solid sal ammoniac ; hence 
 arise the white fumes observed when an open vessel containing ammonia is brought 
 into the vicinity of one containing hydrochloric acid. This property of ammonia is 
 made use of for ascertaining its presence. A glass rod is moistened with hydrochloric 
 acid, and held over the liquid that is to be tested for ammonia. If a fume of sal 
 ammoniac is formed, the presence of ammonia is proved. 
 
 Preparation. Ammonia is prepared from its saline compounds, principally from 
 the sulphate or chloride. The salts of ammonia, as well as free ammonia, are ob- 
 tained as by-products of the manufacture of illuminating gas, or by the destructive dis- 
 tillation of nitrogenous organic substances, such as animal refuse, old leather, blood, 
 etc., and in Egypt from camel's dung. 
 
 For the preparation of ammonia on a small scale, finely -powdered sal ammoniac 
 is mixed with freshly slaked lime, and the mixture introduced into an iron retort. 
 The neck of the retort is connected with a Woulfe's washbottle containing a very small 
 quantity of water, so that the ammonia gas produced upon heating the retort may 
 be washed free from any solid particles carried over mechanically. If it be desired 
 to use the gas in a dry state, it must then be passed through a JJ-tube filled with 
 pieces 'of fused potassium hydrate and collected over mercury. 
 
 When ammonia has to be prepared on a large scale, a large iron still is employed 
 upon which a head is fixed air-tight by means of luting and screws. The head is 
 connected with a condenser delivering into a glass flask. A delivery tube is fitted 
 with a cork into the neck of the flask and made to dip into a vessel two-thirds filled 
 with pure water. The still is charged with 100 pounds of sal ammoniac or ammonium 
 sulphate, and an equal weight of fresh-burnt lime, previously mixed with four times 
 its weight of water, the whole being mixed together by stirring. The bead is then 
 luted and screwed down air-tight upon the still, and heat is applied, gently at first, 
 
COMPOUNDS OF AMMONIA. 51 
 
 the temperature being ^ gradually raised. Th process that takes place is represented 
 by the following equation : 
 
 _ Ca? 
 " C1 2 J + 
 
 Together with ammonia gas, aqueous vapour is also given off, but this condenses 
 in the cooling apparatus, and collects in the flask, while the ammonia passes into the 
 water of the second vessel, where it is absorbed. Since the solution of ammonia pro- 
 duced is lighter than water, and therefore rises to the surface, the delivery tube is 
 made to terminate in the lowest part of the absorption vessel. 
 
 Uses. Ammonia is much employed in medicine. Its use for this purpose is 
 owing to its strong caustic action, producing blisters when applied to the skin, to its 
 action upon the sensorium, acting in cases of syncope as a restoring agent, and to its 
 strong basic properties. Advantage is taken of this property for neutralising the 
 carbonic acid and sulphuretted hydrogen which are formed in a certain disease of the 
 herbivora, in consequence of over-feeding with green food. Ammonia is further ex- 
 tensively used in chemical laboratories for all sorts of purposes, both in analysis and 
 in the manufacture of preparations. Its use in this way is generally owing to its 
 strong basic properties, rendering it possible to neutralise by its means the strongest 
 acids, and to precipitate nearly all the oxides of the metals 'in a solid condition from 
 solutions of their salts. It is further employed on a large scale in cotton-printing, 
 in bleaching, and for the preparation of lakes and colours. 
 
 Compounds. Ammonia forms numerous compounds with hydracids and with 
 the hydrogen salts of acid oxides. These compounds are termed ammoniacal salts, 
 and they correspond closely with the potassium and sodium salts of acid oxides, but 
 contain, instead of the metals potassium or sodium, a compound molecule NH 4 which 
 takes their place as a pseudo-metal, and is termed ammonium. Thus, for instance, 
 the compounds of ammonia with hydrochloric acid and with nitric or sulphuric acid 
 can be represented by the formulae : 
 
 NH 3 HC1 or NH 4 C1 corresponding to KC1 
 
 NH,HN0 3 or NH 4 N0 3 KN0 3 
 
 2(NH 3 ),H 2 S0 4 or 2(NH 4 ),S0 4 K 2 S0 4 
 
 Ammonia also combines with many chlorides, nitrates, sulphates, and other salts, 
 forming compounds which are probably so constituted that they contain compound 
 molecules analogous to ammonium, with one or more atomic proportions of a metal in 
 the place of part or the whole of the hydrogen of ammonium. Thus the compound 
 NH 2 HgCl, formed by the action of ammonia upon mercuric chloride, may be regarded 
 as the chloride salt of mercurammonium, corresponding to ordinary ammonium 
 chloride, but with two atomic proportions of hydrogen replaced by the divalent metal 
 mercury. 
 
 CHLORIDE. 
 
 FORMULA NH 4 C1. MOLECULAR WEIGHT 53 '5. 
 
 History. This substance, commonly known as sal ammoniac, was at one time 
 obtained almost exclusively from Egypt, and was prepared by sublimation from the 
 soot produced by burning camel's dung as fuel. 
 
 Occurrence. Ammonium chloride occurs naturally in volcanic districts as an 
 incrustation on the surfaces of fissures ; also in sea water and in very small amount in 
 the water of some springs. 
 
 Characters. Ammonium chloride is a colourless translucent substance, crystal- 
 lisable in octahedra, which are generally grouped together in arborescent forms. It 
 sometimes occurs in the cubic form. The salt dissolves in about three times its 
 weight of cold water, and in its own weight of boiling water ; its solution in cold 
 water is attended with considerable reduction of temperature. Ammonium chloride 
 volatilises without melting. 
 
 Preparation. Ammonium chloride is prepared by sublimation from a mixture 
 of ammonium sulphate and sodium chloride or from the ammoniacal liquor of gas 
 works, by neutralising it with hydrochloric acid, evaporating the solution until the 
 salt crystallises, and then purifying by sublimation. 
 
 Uses. Ammonium chloride is largely used for cleaning the surface of metals in 
 tinning and soldering; also in the manufacture of alum, and for preparing freezing 
 mixtures. 
 
52 
 
 NITROGEN. 
 
 AMMONIUM SULPHATE. 
 
 FORMULA 2(NH 4 ),S0 4 . MOLECULAR WEIGHT 132 
 
 Occurrence. Ammonium sulphate occurs naturally as a mineral called mas- 
 cagnin in volcanic districts, also in the water of the Tuscan lagunes, and sometimes 
 as an efflorescence on the surface of the earth. 
 
 Characters. Ammonium sulphate forms colourless transparent prismatic 
 crystals, isomorphous with potassium sulphate. It dissolves in twice its weight of 
 cold water, and in its own weight of boiling water. It is hygroscopic ; when heated 
 it decrepitates, melts at 140, and is decomposed at a higher temperature. 
 
 Preparation. Ammonium sulphate is prepared from gas liquor, and from the 
 ammoniacal liquor obtained in distilling bituminous shale, by neutralising with sul- 
 phuric acid or filtering the liquors through layers of gypsum, by which the carbonate 
 of ammonia they contain is converted into sulphate ; then evaporating and crystal- 
 lising the salt. 
 
 Uses. Ammonium sulphate is largely used as a manure. 
 
 AMMONIUM CARBONATES. 
 
 There are three definite ammonium carbonates : the neutral carbonate 2(NH 4 ), 
 C0 3 H 2 the acid carbonate NH 4 HCO g , commonly called bicarbonate, and the sesqui- 
 carbonate 4(NH 5 ),H 2 3(C0 3 ), called also volatile salt or salts of hartshorn. 
 
 The substance commonly met with as carbonate of ammonia, consists chiefly of the 
 latter compound. It is a translucent fibrous mass, having a strong ammoniacal smell, 
 and is obtained by sublimation from a mixture of ammonium sulphate and chalk. 
 
 PREPARATION OF AMMONIA FROM GAS LIQUOR. The watery liquor obtained in the 
 manufacture of gas from coal contains most of the nitrogen of the coal in the form of 
 ammonia. Its composition varies according to the kind of coal employed, as shown by 
 the following table of analyses by Grerlach : 
 
 100 cub. cent, contain grains. grams. grams. 
 
 Ammonium Hyposulphite , -1036 0'1628 '5032 
 
 Sulphide -0340 -0646 '6222 
 
 Carbonate (NH 4 )HCOyl050 -1470 -2450 
 
 2(NH 4 ),C0 3 -4560 "7680 3-3120 
 
 Sulphate -0462 0'0858 0-1320 
 
 Chloride 3-0495 1-7120 0*3745 
 
 Besides these salts, gas liquor contains some ammonium sulphocyanide and ben- 
 zoate, and on the average it contains from 1 to 5 per cent, of ammonia. 
 
 The gas liquor is mixed with lime and subjected to distillation in a boiler 
 (A, figs. 19 and 20) set over a furnace, the flue of which passes round a second boiler (B), 
 containing a similar mixture of gas liquor and lime. The ammonia gas driven off by the 
 
 FIG. 19. 
 
 heat, passes through the tube (a a) into the second boiler (B), where it is washed, and 
 then passes- by the tube (b) into the washing vessels (c and c'), which are charged with 
 milk of lime for the purpose of separating impurities from the ammonia. It then 
 
AMMONIA FROM GAS LIQUOR. 53 
 
 passes through the worms of the condensers (D and E), and is thus to a great extent 
 deprived of water- vapour. The gas is then passed through several smaller washing 
 vessels (F o G'G") into a leaden vessel (H) surrounded with cold water, and containing 
 water for the absorption of the gas. The vessel i serves for condensing any ammonia 
 that may escape from the leaden vessel (H), and its contents can from time to time be 
 run into the leaden vessel. 
 
 The liquid condensing in the vessel F is raised by the pump (F') into the washing 
 vessel (c), and a stream of fresh gas liquor is occasionally run from a tank (j) into the 
 condenser (D), so as to serve for cooling, and to become warmed before it is run into 
 the washing vessel (c) on its way into the boilers (B and A). In order to save any 
 
 FIG. 20. 
 
 ammonia given off by the heating of the gas liquor thus passed through the condenser 
 (D), this vessel is connected by means of a pipe (K) with a leaden tank (K'), contain- 
 ing sulphuric acid. When the whole of the ammonia has been expelled from the 
 liquid in the boiler (A), the contents are drawn off, and the liquid already heated in the 
 second boiler (B) is run into A, the boiler B being also charged again with heated gas 
 liquor from D, and heated milk of lime from c and c', and then the operation is con- 
 tinued as before. 
 
 Instead of using milk of lime for the purification of ammonia gas, freshly ignited 
 charcoal is sometimes employed, and the gas is passed through closed iron cylinders 
 filled either with that material or coke, which is kept\noist with the refuse oil ob- 
 tained in the distillation of tar or in the manufacture of paraffin oil. This plan has 
 the advantage of separating the napthalin with which ammonia obtained from gas 
 liquor is liable to be contaminated, and it also prevents the stoppage of the condens- 
 ing worms by the napthalin carried over by the hot gas. 
 
 In order to prepare ammonium sulphate the ammonia gas is passed entirely into a 
 lead-lined tank containing sulphuric acid of about T512 sp. gr. The sulphate sepa- 
 rating in small crystals is raked out of the tank into strainers placed so that the liquor 
 runs back into the tank, and when the salt is sufficiently drained it is dried. In 
 proportion as the salt is removed fresh sulphuric acid is added, and the operation is 
 continued in this way until the mother-liquor becomes charged with empyreumatic 
 substances, oil, etc., when it is evaporated separately, and the tank charged with fresh 
 sulphuric acid as before. The ammonia salt contains less oily impurity when the 
 liquor in the tank is kept slightly acid. 
 
 Ammonium chloride is prepared in the same way by substituting hydrochloric 
 acid for sulphuric acid, and passing the cooled ammonia gas into it. In order to ob- 
 tain it pure, it must be recrystallised after the solution has been boiled with some 
 nitric acid to destroy empyreumatic impurities. 
 
 THE ATMOSPHERE. 
 
 History. Auaximenes, who flourished in the sixth century before Christ, re- 
 garded air as the principle or element out of which all other substances took their 
 origin either by dilution or condensation. In the ' natural system ' of Aristotle, also, 
 air constituted one of his four elements earth, air, fire, and water and together with 
 the belief in the four elements of Aristotle, the opinion that air was an elementary 
 body held its ground until near the end of the eighteenth century. 
 
 Lavoisier was the first to point out that atmospheric air consists of several 
 substances. His views upon the chemical nature of the atmosphere have not been 
 materially altered by the numerous researches of later chemists. 
 
 Composition. The atmosphere contains several different gases which are not, 
 however, chemically combined with one another, but only mechanically mixed. The 
 principal constituents are nitrogen and oxygen ; beside these, atmospheric air contains 
 appreciable quantities of water-vapour and carbonic acid. Nitric and nitrous 
 
54 NITROGEN. 
 
 acids, ammonia, ozone, and hydrogen are also present in the air, but in such small 
 proportions that their amount cannot well be determined with certainty. Air con- 
 tains on an average, in 100 volumes : 
 
 By measure By weight 
 
 Nitrogen 78 -492 77 
 
 Oxygen 20'627 23 
 
 Water-vapour 0'840 
 
 Carbonic acid 0'041 
 
 lOO'OOO 
 
 Since these gases differ in density, there is a corresponding difference in their 
 relative proportions by weight and by volume. 
 
 By comparing the composition of the air in the deepest valleys with the composi- 
 tion of the air on the highest mountain summits, it is found that the relations 
 between nitrogen, oxygen, and carbonic acid remain the same, except under certain 
 local influences, such as the proximity of active volcanoes emitting vast streams of 
 carbonic acid, or extraordinarily luxuriant vegetation using up a large amount of 
 carbonic acid, and producing on the other hand a great quantity of oxygen. 
 
 This constancy in the relative proportions of the constituents of atmospheric air is 
 due to ' diffusion,' according to which gases intermix uniformly with each other, how- 
 ever much they may differ in density. 
 
 Modern researches have shown that there are contained suspended in the air in 
 the form of very tine dust, besides inorganic and organic substances, minute organised 
 particles which are recognisable under the microscope as spores and germs which upon 
 contact with materials favourable to their nourishment are developed and form 
 ferments. Thus yeast, or the ferment which causes alcoholic fermentation, is only 
 produced when the liquid to be fermented comes into contact with the air, provided 
 the liquid does not already contain the ferment. It is the same as regards lactic fer- 
 mentation, and other processes of fermentation and putrefaction. How far the hypo- 
 thesis is justified, that certain epidemic diseases, such as cholera, etc., are determined 
 by the presence of germs or spores in the air, which, owing to a process similar to fer- 
 mentation, bring about a diseased condition of the animal organism, cannot be here 
 discussed. 
 
 Condition of the Atmosphere in Nature. The atmosphere surrounding our planet 
 as a gaseous envelope is retained in this position by the attraction of the earth, and 
 consequently it partakes of the motion of the earth. As a result of the attraction 
 of the atmosphere by the earth, the upper portion exerts a pressure upon the lower 
 portion, and, since atmospheric air is compressible, the lower portion of the aerial 
 envelope is therefore denser than the upper portion. The higher a mountain 
 is ascended the smaller does the density of the air become. This is the reason why 
 respiration is more difficult at great heights. The lungs require a certain quantity of 
 air, and as the density of the air is less at great heights, a larger volume of such air 
 is required than of the denser air of lower elevations ; respiration must therefore be 
 more rapid. 
 
 The atmosphere exerts pressure upon the entire surface of the earth. At the sea- 
 level this pressure equals that exerted by a column of mercury 760 mm. in height 
 (29'922 inches). The pressure iipon each square decimetre is therefore 103'33 kilos, 
 or nearly 15 Ibs. upon the square inch. 
 
 At a height of ,5,528 metres (18,136 feet) the atmospheric pressure amounts to 
 only H Ibs. upon the square inch, or half of what it is at the level of the sea. 
 
 From the refraction of the rays of light it has been approximately computed that 
 the atmosphere does not extend beyond a height of 72'419 kilometres (45 miles) above 
 the sea-level, and at that height the pressure would be 0. 
 
 The atmosphere appears of a blue colour, owing to the white sunlight being decom- 
 posed by particles of water contained in the atmosphere and reflected from them of 
 a blue colour. The greater the quantity of light which is thus dispersed the brighter 
 does the atmosphere appear, and it is brightest in the direction in which the greater 
 number of particles are found, in which the atmospheric medium has the greatest 
 extension and density i.e. in a horizontal direction. On the contrary, the atmosphere 
 is darkest in that direction in which the aerial stratum is thinnest i.e. in a vertical 
 direction. In fact the sky always appears much darker in the zenith than towards 
 the horizon. Hence it happens that in ascending above the sea-level the sky becomes 
 darker and at last entirely black. The stratum of atmospheric particles reflecting 
 light becomes thinner and thinner, and in the same proportion does the lightless space 
 beyond become more evident. 
 
 The red colour of the sky at sunset is caused by the aqueous vapour of the atmo- 
 sphere. In a certain state of condensation it transmits white sunlight in shades 
 between yellow and red. As the rays of the sun at evening have to traverse such 
 vapour a longer distance, the sky appears of a hue varying from yellow to red. 
 
ATMOSPHERIC AIR. 55 
 
 One of the most interesting questions in respect to the atmosphere is whether the 
 proportions by weight of the three gases, nitrogen, oxygen, and carbonic acid, always 
 remain the same. Considering the immense quantities of carbonic acid poured into 
 the air from the many sources of this gas, such as active volcanoes, processes of decay, 
 combustion, animal respiration, etc., it might be thought that the amount of carbonic 
 acid in the atmosphere would be constantly on the increase, while its contents of 
 oxygen would be, on the other hand, decreasing. If that were the case,' all animal life 
 would ultimately perish from suffocation. 
 
 This production of carbonic acid and consumption of oxygen is, however, fully 
 compensated by'the action of plants, which, contrary to animals, absorb carbonic acid 
 from the air, and exhale oxygen in its place. This action of plants is so energetic that, 
 in plains where a tolerably luxuriant vegetation exists, the atmosphere always contains 
 a somewhat smaller proportion of carbonic acid and more oxygen than the air of very 
 high regions. On the whole, so far as can be deduced from analyses of air, the present 
 composition of the atmosphere is kept in equilibrium by this vital action of plants. 
 
 When many persons remain for some time in a small and ill-ventilated room, 
 analysis of the air contained in it certainly shows an increase of carbonic acid. How- 
 ever, in our dwelling-rooms, there is a greater change of air than is generally sup- 
 posed, owing to the porosity of the walls. How readily air passes through an ordinary 
 brick is evidenced by the following experiment : A brick is covered with wax, with 
 the exception of the two opposite narrower extremities, and to each of these free ends 
 is fastened an air-passage made of sheet-metal. By blowing through one of these 
 passages the air can only escape by passing through the brick. This happens with 
 such facility, that by blowing into the brick at one side it is easy to extinguish a 
 lighted candle at the other side of the brick. 
 
 As in moist walls the pores are filled with water, rooms surrounded by such moist 
 walls are unhealthy, because, amongst other reasons, the free passage of air is hindered. 
 
 Uses. Atmospheric air is made use of in a great number of mechanical and 
 chemical processes serving technical ends. From the most ancient times man has 
 employed the motive power of wind as, for instance, for turning the sails of wind- 
 mills, for the purification of corn from dust and chaff, and in general for the separation 
 of substances having different specific gravities by the agency of specially constructed 
 vanes, by means of which the lighter bodies are got rid of. 
 
 Atmospheric air is further employed for drying purposes. The newly-built walls 
 of houses, as well as a number of products of agriculture and manufactures, may be 
 deprived of moisture by simple contact with the air. An important use is made of 
 atmospheric air in getting rid of bad smelling and unhealthy gases and vapours from 
 rooms occupied by human beings, often by means of artificial ventilation. 
 
 Atmospheric pressure is applied for forcing preservative or colouring solutions into 
 the fibres of wood. 
 
 If the pressure of the air upon boiling liquids be diminished by conducting the 
 operation of boiling in hermetically-closed vessels, from which the air is pumped out, 
 evaporation takes place at a much lower temperature, and by this means solutions of a 
 number of substances can be evaporated without undergoing decomposition, although 
 many of them would be decomposed to a considerable extent if they were boiled or 
 evaporated under the ordinary atmospheric pressure, and at the corresponding boiling 
 temperature. 
 
 Atmospheric air plays an important part in the process of fermentation and its 
 kindred phenomena of decay and putrefaction. It contains in the form of germs and 
 spores the conditions for the production of ferments which bring about these pro- 
 cesses, and in the form of oxygen gas a body which favours these processes in a high 
 degree. It is often possible by admitting or excluding atmospheric air, either 
 to start or prevent processes of the kind, and even to stop fermentation or putrefac- 
 tion that has already begun, by subsequent exclusion of air. In various industrial 
 operations advantage is frequently taken of these facts. 
 
 But the most extensive application of air is for the production of heat and light. 
 Nearly all artificially produced heat and light are the results of processes of combus- 
 tion, and in all these processes, the burning bodies, such as coal, fats, oil, coal-gas, etc., 
 enter into combination with the oxygen of the air. 
 
 In the same way that rapid processes of oxidation with the evolution of light and 
 heat take place in the air by the aid of the oxygen it contains, so likewise do gradual 
 oxidising actions take place. The formation of nitrates may be instanced as one of 
 the most important of these, the nitric acid being produced from ammonia by slow 
 oxidation under the influence of air, in presence of bases, the ammonia itself being a 
 product of the decay of nitrogenous organic substances. 
 
 The importance of air in the process of animal respiration has been already 
 alluded to (p. 24). 
 
CARBON. 
 
 SYMBOL C. ATOMIC WEIGHT 12. 
 
 History. Until the latter end of the eighteenth century, very little was known 
 of the chemical nature or relations of carbon as an elementary substance, and it was 
 not until Lavoisier demonstrated that carbonic acid gas or fixed air as it was then 
 called is the sole gaseous product of the combustion, either of organic substances or 
 of charcoal and the diamond, that correct opinions on this subject began to prevail. 
 
 Newton conjectured that the diamond must be combustible on account of its strong 
 refraction of light. The first experiment by which the combustibility of the diamond 
 was proved was made by the Academy of Florence, when it was found that a diamond 
 burned in the focus of a large concave reflector. The diamond is not absolutely pure 
 carbon, for after its combustion there remains a minute quantity of ash, which is said 
 to contain silicic acid. The very small amount of this ash, and the high price of the 
 diamond, have up to the present prevented a thorough determination of the ash, although 
 that would be desirable, since an exact knowledge of the composition of this residue 
 might afford some indications as to the substances out of which the diamond has been 
 formed, and as to the manner of its formation, which is at present enveloped in un- 
 certainty. 
 
 For some time it was supposed that besides carbon the diamond must contain 
 hydrogen. This opinion was, however, refuted by the researches of Davy and others, 
 which proved that by the combustion of the diamond in oxygen gas only carbonic acid, 
 and no water, is produced. 
 
 Occurrence. Carbon occurs naturally in the free state, but very much less 
 abundantly than it occurs in various states of combination. 
 
 In the free state, carbon is met with in three very distinct conditions as diamond 
 and as graphite, which occur naturally, and as charcoal which is obtained in a great 
 variety of forms when animal or vegetable materials are strongly heated out of contact 
 with air. 
 
 Diamonds, or carbon crystals, are generally found in alluvial deposits of the most recent 
 geological date, and situated at no great depth below the surface ; they occur especially 
 in the low ground of wide valleys, and but seldom in mountain districts of any great 
 elevation. 
 
 Diamonds, as they occur in these alluvial beds, together with quartz pebbles, 
 ferruginous sand, itaberite, brown iron ore, jasper, and sometimes also with topazes and 
 emeralds, are never pure and sparkling, but always coated with an earthy incrustation, 
 so that it is only with difficulty that they can be recognised by the naked eye. 
 
 The only diamond districts of importance, are East India, Brazil, and the Cape. 
 There are also less extensive diamond yielding deposits in Siberia and the Island of 
 Borneo. Eecently, a diamond deposit has been found in Mundjee in New South Wales. 
 The chief localities where diamonds occur in India, are situated in the kingdoms of 
 Grolconda and Visapur, extending down, however, towards Bengal. In Brazil, it is 
 principally in the bed and on the shores of the river Igitonhona that diamonds are 
 found in great quantity, especially in the district of Serro di Frio. Another diamond 
 yielding stream in Brazil, is the Eio Pardo. 
 
 The Brazilian diamond washings yield annually from 25,000 to 30,000 carats, or 
 nearly 13 pounds of raw diamonds, from which, however, only about 900 carats of 
 finely polished diamonds are obtained. 
 
 Graphite occurs both in the amorphous and crystalline state. The amorphous 
 variety called plumbago or blacklead, occurs at Borrowdale in Cumberland and at 
 Passau in Bavaria ; it is also found in Liberia, New Brunswick and other places. The 
 crystalline variety occurs at Travancore in Ceylon, in Australia and in America. 
 
 Carbon also occurs naturally in the amorphous condition as anthra cite, a mineral 
 containing a much larger amount of carbon than ordinary coal, though closely related 
 to it and most probably of similar origin. 
 
 In a state of combination carbon occurs very abundantly, constituting about one- 
 third of the mass of all animals and plants. Carbon also occurs, combined with 
 
CHARACTERS OF CARBON. 57 
 
 varying proportions of hydrogen, oxygen, and nitrogen, in the form of coa 1 and analogous 
 materials, originating from plants belonging to a remote epoch. In combination with 
 hydrogen, it occurs as petroleum and pit gas or marsh gas, substances intimately 
 connected with coal and with the alteration of organised substances by decay. 
 
 In combination with oxygen carbon occurs in the atmosphere as carbonic acid, and 
 though the proportion of this gas in atmospheric air is but small, this is the chief if 
 not the only source from which plants derive carbon. This compound of carbon also 
 occurs combined with various basic oxides, especially lime, magnesia, and ferrous oxide, 
 as carbonates, in immense quantities, and it constitutes from one-ninth to one-seventh 
 part of the vast masses of limestone and dolomite existing at different parts of the 
 earth. 
 
 Characters. Carbon in the free state is a solid infusible non-volatile substance 
 without taste or odour ; it exhibits very great diversity in some of the physical charac- 
 ters appertaining to it in the several conditions of diamond, graphite, and 
 amorphous carbon or charcoal. 
 
 The diamond is distinguished from graphite, and still more from amorphous char- 
 coal, by its crystalline structure, hardness, transparency, brilliancy, etc. 
 
 Carbon in the crystalline form of diamond is perfectly transparent, and possesses 
 great brilliance. It is generally colourless, sometimes yellow or brown, and very rarely 
 of a blue, green, or rose tint. The diamond is especially characterised by its hardness;, 
 for a long time it was held to be the hardest substance, and it is but recently that 
 crystallised boron has been found to excel the diamond in hardness. The diamond has 
 a specific gravity ranging from 3'50 to 3'55 ; it is infusible, and insoluble in all liquids. 
 
 The diamond occurs either in the form of cr} T stals or as irregular rounded pebbles. 
 The crystalline forms are the octahedron, the cube, the rhomboiclal dodecahedron, etc. 
 The diamond pebbles generally have somewhat curved surfaces and blunt edges that 
 appear to have been worn, and they are on that account very suitable for cutting glass. 
 
 The diamond refracts light either doubly or singly according to its outward crystal- 
 line structure. Besides its great refractive power, it possesses in a very high degree 
 the property of dispersing coloured light after refraction and decomposition, and to 
 this property is to be especially attributed the magnificent play of colours exhibited 
 by the diamond. 
 
 If a diamond be heated to redness out of contact with air, or in a gas by which it 
 is not chemically acted upon, it is not altered even by the highest temperature attain- 
 able, but still retains its characteristic properties. If, nowever, it be placed between 
 the carbon terminals of a powerful galvanic battery, it is converted, with evolution of 
 most brilliant light, into a graphite-like mass having a metallic lustre, which cannot 
 be reconverted into diamond. 
 
 When heated in the air the diamond burns with great difficulty, the combustion 
 beginning only at a temperature of about 1000 C. and then very sluggishly. It burns 
 rapidly, however, in an atmosphere of oxygen. Indeed, when brought red-hot into 
 this gas it burns without the application of further heat. 
 
 The largest known diamond is that of the Rajah of Mattan in the island of Eorneo. 
 It weighs 367 carats (carat = 3^- grains troy), and is of the purest water. The 
 diamond that was formerly in the possession of the Great Mogul, and supposed to be 
 still in his country, weighed 279 carats, but it is said to have been reduced to about 
 half its original weight by the process of polishing. Its value was estimated by Taver- 
 nier to be about 420, GOO/. The Emperor of Russia has in his possession a diamond 
 which weighs 193 carats. It was bought in 1772 by the Empress Catherine of a Greek 
 merchant for the sum of 90,000. besides an annuity to the Greek merchant of 4,00(). 
 The diamond in the possession of the Emperor of Austria weighs 1 39 carats ; the 
 Regent or Pitt diamond of the late Emperor of the French weighs 136 carats. The 
 former is valued at about 105,000^., the latter at about 97,500<L, or according to other 
 estimates at 185,000^. 
 
 The diamond called the Koh-i-noor (mountain of light) weighs 186 carats. The 
 opinion that the Koh-i-noor is identical with the Great Mogul appears to be incorrect, 
 since the sketch which Tavernier gave of the Great Mogul represents this diamond as 
 differing considerably in form from the Koh-i-noor. 
 
 Graphite sometimes possesses a definite crystalline form, but it belongs to a system 
 entirely different from that of the diamond. Graphite is opaque, of a black or grey 
 colour ; it has a metallic lustre and is a good conductor of heat and electricity, while 
 the diamond is not so good a conductor of heat as graphite, and is a non-conductor of 
 electricity. The specific gravity of graphite varies from 1-8 to 2'4. 
 
 Amorphous carbon in the form of anthracite, is a hard black substance possessing 
 considerable lustre. It has a laminated structure, gives a black streak on paper, and 
 is very friable. Its specific gravity is from 13 to T8. 
 
 When substances containing carbon in combination with hydrogen and oxygen 
 
58 CARBON. 
 
 sometimes also with nitrogen, sulphur, etc., are strongly heated out of contact with air, 
 hydrogen, oxygen, nitrogen, and sulphur escape, together with a portion of the carbon 
 in the form of various volatile compounds, but the greater part of the carbon remains 
 behind as charcoal. This charcoal contains, besides the ash-constituents of the organic 
 substance, also a small quantity of hydrogen, which clings to the residual carbon so 
 strongly, that it must be kept at a white heat for a considerable time before it gives 
 up the last portion of hydrogen. If it be desired to prepare chemically pure carbon, 
 pure organic compounds must be employed. Thus for instance, sugar after being heated 
 in a closed vessel for a long time, and the residue eventually exposed to a white heat, 
 yields chemically pure carbon. Amorphous charcoal, obtained by the heating of 
 organic substances with exclusion of air, is a good conductor of electricity and a bad 
 conductor of heat. 
 
 When a carburetted gas, or the vapour of a volatilisable organic substance, is 
 passed through a red hot tube it is decomposed, and carbon is deposited upon the inner 
 surface of the tube. If such a deposition of carbon continues gradually for a consider- 
 able length of time, the deposited carbon forms a very dense, compact hard crust. 
 Carbon in this condition, is found in the retorts used in the manufacture of coal-gas, 
 and it is sometimes sufficiently hard to scratch glass. 
 
 The carbon obtained from any organic substance by heating it out of contact with 
 air, is always amorphous and generally soft and friable. It is further black and opaque, 
 and the fracture is sometimes lustrous, but more generally dull. Its specific gravity 
 varies from 1'5 to 2'0; the compact carbon deposited in gas retorts has sometimes a 
 density of 2;36. 
 
 Some kinds of charcoal present no indication of the form and structure of the 
 organic substances they are obtained from, and the carbonaceous residue is either spongy, 
 vesicular, or porous, as that from gum, sugar, starch, and other substances. In this 
 case, the charcoal presents that form which the carbonised substances assumed at the 
 moment of carbonisation. If these substances first of all melt upon the application 
 of heat, the molten mass froths in consequence of the escape of gases, and as this 
 aerated mass solidifies in carbonisation, it retains its spongy texture. 
 
 Charcoal in a pulverulent form is obtained when infusible substances in a finely- 
 divided state are carbonised, as, for instance, saw-dust; further, when an organic 
 substance is mixed with a large quantity of a refractory body in a state of fine division, 
 such as sand. Carbon is obtained in the finest state of division when it is deposited 
 from a gas in a state of imperfect combustion, as, for instance, when the flame of 
 highly carbonaceous materials, such as pitch, tar, etc., burnt with a limited supply of 
 air, is suddenly cooled. Soot, lamp-black, etc., consist of carbon in this condition. 
 
 The characters which the three modifications of carbon possess in common are the 
 following : they are solid, without taste or smell ; when heated out of contact with air 
 they are unaltered, and they resist the action of every known solvent, but when heated 
 in contact with air they burn, yielding carbonic acid. 
 
 As regards combustibility the three modifications of carbon present considerable 
 differences ; for while charcoal burns easily when heated in the air, graphite, and more 
 especially diamond, can only be burnt when exposed to the highest temperatures. 
 
 Carbon does not manifest any marked chemical activity at ordinary temperatures. 
 A very remarkable proof, amongst others, of this, is to be found in the unaltered state 
 of the ink upon manuscripts found in Herculaneum, which are about 2,000 years old. 
 This ink consists of finally divided carbon that had been ground up with some 
 mucilaginous liquid. This unchangeability of carbon is the reason why wood that has 
 been superficially carbonised, lasts even in moist earth for a very long time without 
 decaying. 
 
 At high temperatures, however, carbon combines readily with oxygen and forms 
 carbon dioxide, a gaseous compound equal in volume to the oxygen combined with the 
 carbon ; but carbon does not burn with flame because it is incapable of volatilising. 
 
 According to the conditions under which carbon is burnt, two different products 
 may be produced. If it be burnt with an abundant supply of air, or as is commonly 
 the case in contact with a large excess of air, it combines with 2'67 times its weight 
 of oxygen, forming carbonic acid, C0 2 . On the contrary when carbon is burnt with a 
 deficient supply of air, the lower product of oxidation, carbonic oxide, CO, is formed 
 either entirely or to a great extent ; in the application of carbon for heating purposes it 
 is therefore one of the chief conditions that so much oxygen shall be supplied to the 
 burning carbon, that it may be entirely converted into carbonic acid. 
 
 Besides the direct combination with free oxygen, which takes place when carbon or 
 any combustible carbonaceous substance is burnt in atmospheric air, carbon is, under 
 certain conditions, also capable of abstracting oxygen from many compounds, and com- 
 bining with it. Thus, for instance, at a bright red heat carbon decomposes carbonic 
 dioxide, combining with half of its oxygen, and thus converting it into carbonic oxide, 
 
CHARACTERS OF CARBON. 59 
 
 C0 2 + C = 2CO, while at the same time forming an additional quantity of the same 
 substance. Water-vapour is also decomposed by carbon at a red heat, the oxygen com- 
 bining with carbon, while the hydrogen is separated in the free state. Carbon com- 
 bines in like manner with part or the whole of the oxygen of most metallic oxides, 
 when heated in contact with them to a sufficiently high temperature, and in many 
 cases the metals are reduced or separated in the free state as regulus. This pro- 
 cess is termed reduction, and the capability of effecting deoxidation in this way is a 
 character that renders carbon a very useful agent in many industrial operations. 
 
 Other compound substances containing oxygen, such as sulphuric, nitric, and other 
 oxyacids, as well as their corresponding salts, are decomposed in the same manner 
 when heated with carbon. The deoxidation thus effected is often only partial, as in 
 the case of sulphuric acid, which yields, when heated with carbon, a mixture of 
 sulphurous acid and carbonic dioxide. The metallic salts may, however, be completely 
 deoxidised by heating them with excess of carbon, and then the metals often remain 
 combined with the other elementary constituents of the acid oxides, if the compound 
 is not itself decomposed by the high temperature required. In such cases the carbonic 
 dioxide formed in the first instance is decomposed by contact with the excess of 
 carbon, 'and converted into carbonic oxide. Thus barium sulphate yields barium 
 sulphide and carbonic oxide, when ignited with carbon. BaS0 4 + 4C BaS -I- 4CO. 
 When nitrates, chlorates, iodates, etc., are heated with carbon or carbonaceous sub- 
 stances, the combination of their oxygen with carbon takes place suddenly and with 
 explosive violence and great evolution of heat, rendering the mass red hot. This phe- 
 nomenon is called deflagration. 
 
 Carbon also combines directly with sulphur vapour at a red heat, forming carbon 
 disulphide, C S 2 . 
 
 In the presence of alkaline substances, and at high temperatures, carbon combines 
 with nitrogen, forming cyanogen, CN. Under the influence of the electric arc, it combines 
 with hydrogen, forming acetylene, C 2 H 2 , and at very high temperature, it combines in 
 small proportion with some metals, for instance, in the manufacture of iron, which 
 always contains a small amount of carbon. 
 
 COKE. This form of carbon, is obtained by heating certain kinds of coal out of 
 access of air. The process is entirely analogous to that of the carbonisation of wood ; 
 hydrogen and oxygen, contained in the coal, are driven off chiefly in the form of water, 
 together with a certain amount of carbon in the fornfr of hydrocarbons and other 
 volatile carbon compounds, while the greater portion of the carbon remains mixed with 
 the mineral constituents of the coal, As compared with coal, coke is generally very 
 hard (sometimes even scratching glass), compact, and lustrous ; its coloiir varies between 
 grey and black ; it is also a good conductor of electricity and heat. In consequence 
 of the very compact texture of coke, it is difficult to set fire to it, and consequently, 
 when used as fuel, it requires a good draught or a blast for maintaining its combustion. 
 When once in a state of combustion, it produces a very considerable degree of heat. 
 
 According to the kind of coal carbonised, as well as the mode of conducting the 
 operation, coke presents very diverse characters, being more or less compact or 
 vesicular, hard or friable, and sometimes even pulverulent. 
 
 WOOD CHARCOAL. Charcoal often retains the form and structure of the organic 
 substance from which it is prepared. This is especially the case with wood charcoal, 
 which always shows quite distinctly the structure of the wood that has been carbon- 
 ised. 
 
 But though wood charcoal presents, in ite outward appearance, the peculiarities of 
 the wood from which it has been made, the charcoal of a particular kind of wood is 
 not always of the same character, but varies somewhat according to the age of the 
 wood, and the conditions uuder which it has been grown, partly also according to the 
 temperature at which the carbonisation has been conducted. The denser the wood, 
 and the drier the soil upon which it has been grown, the denser is the charcoal it yields. 
 Charcoal is also denser the higher the temperature of carbonisation. 
 
 A knowledge of these facts is of practical importance. If it be desired, for instance, 
 to produce charcoal which shall conduct electricity, only such charcoal is serviceable 
 for the purpose as has been prepared at the highest possible temperature, for it is only 
 the denser kind of charcoal that is a good conductor of electricity. On the other 
 hand, when readily combustible charcoal is required, the carbonisation must not be 
 carried on at too high a temperature, since the denser sorts of charcoal burn with 
 difficulty. 
 
 Charcoal, like all porous substances, possesses the property of absorbing gases into 
 its pores. The more porous the charcoal, the greater is its absorbent power, and on 
 thab account, wood charcoal possesses this property in the highest degree. The 
 absorption of gases by charcoal at a temperature of 100 is very slight, but it 
 
60 CARBON. 
 
 begins at a temperature very little below 100, and increases as the temperature falls. 
 It follows therefore that, by the application of heat, the whole absorbed gas may be 
 expelled from charcoal that has become saturated with any gas at the ordinary 
 temperature. In like manner, the gas absorbed by charcoal escapes when the char- 
 coal is placed in vacuum. 
 
 In order to determine the absorbent action of charcoal in reference to any particular 
 gas, a piece of charcoal that has been freshly heated to redness is weighed, and then 
 placed in a graduated glass cylinder containing the gas and inverted over mercury. 
 Owing to the absorption of the gas, part of it disappears, and the diminution of 
 volume indicates the absorbing power of charcoal for the particular gas. 
 
 Although wood charcoal possesses the greatest absorbent power of all varieties of 
 charcoal, still this capacity of absorption varies considerably, according to the kind 
 of wood from which the charcoal has been prepared. Very light kinds of charcoal, 
 with very large pores, as well as very dense kinds, absorb very much less of a gas 
 than charcoal of average porosity. For instance, the light charcoal of pine wood, 
 with very large pores, absorbs only half as much gas as the more dense charcoal pre- 
 pared from oak wood. The mechanical division of the charcoal is in like manner of 
 importance. Very finely powdered charcoal, as well as very large pieces of charcoal, 
 condense less gas than moderate sized pieces. The reason of this is obvious. In very 
 fine charcoal powder, the pores are lessened by a too great state of division ; in large 
 pieces, the communication of the pores from their interior to the surface, is rendered 
 very difficult, on account of the distance ; some of the pores do not communicate with 
 the surface at all, while in the smaller pieces, more of the pores are exposed, and 
 communicate with the surface. The charcoal of cocoanut shell appears to have the 
 greatest capacity of absorbing gases. 
 
 When charcoal is already saturated with a gas, it absorbs extremely little of any 
 other kind ; on this account, charcoal exposed to the air loses its absorbent property, 
 by becoming saturated with gases contained in the atmosphere, and it is only fit for 
 use as an absorbing agent soon after having been heated to redness. The amount of 
 different gases that the same kind of charcoal, when freshly heated to redness, is 
 capable of absorbing varies considerably, as shown by the following table. 
 
 Beechwood Charcoal Cocoanut Charcoal 
 
 (Saussure). (Hunter). 
 
 90 times its volume of ammonia gas . . . .171*7 
 85 , of hydrochloric oxide gas 
 
 65 
 
 55 
 
 40 
 
 35 
 
 9-4 
 
 9-25 
 
 7-5 
 
 1-75 
 
 of sulphurous oxide 
 
 of sulphuretted hydrogen 
 
 of nitrous oxide 
 
 of carbonic dioxide , . . 67*7 
 
 of carbonic oxide . . . .21*2 
 
 of oxygen 17'9 
 
 of nitrogen 
 of hydrogen. 
 
 Freshly burnt charcoal, or charcoal freshly heated to redness, can therefore be used 
 for removing from rooms injurious and bad smelling gases. 
 
 In consequence of the condensation of gases in the pores of charcoal, the chemical 
 activity of these gases is often augmented in a high degree. Thus, for instance, if a 
 piece of wood charcoal saturated with suphurctted hydrogen gas be placed in an 
 atmosphere of oxygen, a violent reaction takes place, sometimes amounting to explo- 
 sion, water arid sulphurous acid being produced. If ordinary atmospheric air be 
 employed in the place of pure oxygen, the oxygen it contains combines more slowly 
 with the hydrogen of suphuretted hydrogen, but not with the sulphur, which is there- 
 fore deposited. This reaction occurs frequently where air comes into contact with 
 sulphuretted hydrogen in the presence of porous substances. 
 
 The oxygen of atmospheric air absorbed by charcoal is converted into carbonic 
 dioxide by combining with the carbon, and consequently the gas expelled from char- 
 coal that has been exposed to the air for some time consists entirely of nitrogen and 
 carbon dioxide. 
 
 Since charcoal absorbs most fetid substances with great energy, the absorbent 
 action of charcoal is also taken advantage of in order to remove bad smelling impuri- 
 ties from liquids, in the same way that it is made useful in removing bad odours 
 from the air. In order, for example, to deprive crude alcohol made from corn, or 
 potatoes, of the unpleasant fusel oil it is contaminated with, the spirit is allowed to 
 remain a short time in contact with charcoal, before being distilled (vide ' Alcohol '). 
 
 Charcoal lying exposed to the air, absorbs moisture ; and this takes place with 
 euch rapidity, that in course of only a few days, the charcoal will have taken up from 
 the air as much water as it is capable of absorbing. 
 
CHARACTERS OF CARBON. 
 
 61 
 
 According to Chevreuse, 100 parts of charcoal exposed to an atmosphere almost 
 saturated with moisture, exhibit the following degrees of absorption : 
 
 
 Charcoal of poplar 
 wood : not heated 
 to redness. 
 
 Charcoal of poplar 
 wood : heated to 
 redness. 
 
 Charcoal of guaia- 
 cum wood : not 
 heated to redness. 
 
 Charcoal of guaia- 
 cum wood: heated 
 to redness. 
 
 1st day . 
 3rd day . 
 30th day. 
 
 176 
 2-35 
 2-35 
 
 1-53 
 2-30 
 2-35 
 
 0-58 
 0-82 
 1-19 
 
 0-21 
 0-40 
 0-94 
 
 When charcoal is immersed in water, it absorbs much more. In this case, the 
 absorption is, for 100 parts: 
 
 Of poplar wood charcoal, not heated to redness . . . 75*3 
 
 Of heated to redness . . . 48'2 
 
 Of guaiacum wood charcoal, not heated to redness . . . 77 
 
 Of heated to redness . . . 4'6 
 
 Since charcoal is sold by weight, regard must be had to its property for absorbing 
 water : for any water thus absorbed, has a double disadvantage, inasmuch as it not 
 only increases the weight of the charcoal, but having also to be evaporated, it lessens 
 its heating effect. The charcoal of commerce is never entirely free from mechanically 
 adhering water, but always contains from eight to twelve per cent of water. 
 
 ANIMAL CHARCOAL. A further peculiar action of charcoal is exercised upon 
 dissolved colouring matters, especially by bone charcoal, which deprives most coloured 
 liquids of their colour-substances, by condensing them into its pores. Thus, red wine, 
 solutions of cochineal or madder, or a neutral solution of indigo in sulphuric acid, etc., 
 may be decolorised by charcoal. This decolorising action of charcoal is frequently 
 employed on a large scale in various industrial operations, especially in the manufac- 
 ture of sugar, for decolorising the cane-juice in the preparation of raw sugar and for 
 decolorising the solution of raw sugar in refining (vide ' Sugar Manufacture '). 
 
 The various kinds of charcoal differ very considerably in regard to their respective 
 decolorising powers. The charcoal most efficacious for decolorising is the nitrogenous 
 charcoal obtained by carbonising bones or other animal substances, and it is this kind 
 chiefly that is practically employed for the purpose. 
 
 The decolorising action of charcoal was discovered in the year 1790 by the Eussian 
 chemist Lowitz. By the year 1798, this property of charcoal was already turned to 
 account in the sugar manufacture, it being employed in the decolorisation of the beet 
 juice. Wood charcoal, however, which at that time was exclusively used, accomplished 
 this end only imperfectly ; but in 1811, Figuier of Montpellier discovered that animal 
 charcoal had a much more powerful decolorising action than wood charcoal, and two 
 years later its use was introduced by Derosne, Payen, and Pluvinet, into the sugar 
 manufacture in the place of that of wood charcoal. 
 
 When charcoal is saturated with colouring matter, it does not exercise any further 
 decolorising action ; but, if the colour- substances it has absorbed be separated by 
 solvents or destroyed, either by fermentation or by heating the charcoal to redness 
 with exclusion of air, it again acquires its decolorising power. This process is termed 
 the revivification of the charcoal. 
 
 Preparation. A number of different methods of preparing carbon are practised 
 for various purposes, but all of them consist essentially of subjecting combustible 
 carbonaceous materials to the action of heat, either entirely out of contact with atmo- 
 spheric air, or in such a way that the supply of air is only sufficient for the combustion 
 of the volatilisable portion of the materials. In a general way, this process is termed 
 carbonisation or charring. It is practised most extensively for the purpose of 
 rendering certain materials more suitable for use as fuel in many metallurgical, and 
 other operations. 
 
 WOOD CHARCOAL. The carbonisation or charring of wood, is generally carried out 
 in heaps, or piles built up of logs or billets of wood, arranged either vertically or 
 horizontally, and covered with earth in order to keep out air. The heat required is 
 produced by setting fire to the heap at the interior, and allowing a portion of the wood 
 to burn slowly with a very limited supply of air, in such a way that the requisite heat 
 is produced by the wood which is undergoing carbonisation. In this carbonising 
 process, volatile by-products are produced (pyroligneous acid, tar, etc.), and as these 
 are of value, the carbonisation of wood is, in many cases, carried out in closed ovens, 
 provided with condensing apparatus for the condensation of the volatile products. 
 
G2 
 
 CARBON. 
 
 The mode of heating wood has very great influence upon the amount of charcoal 
 produced. If wood be heated in such a way that the temperature rises gradually, 
 more charcoal is obtained than when the wood is rapidly brought to a high tempera- 
 ture. Karsten obtained the following results from comparative experiments made in 
 this direction. 
 
 Kind of Wood Charred. 
 
 Percentage amount 
 Eapid heating. 
 
 jf Charcoal obtained. 
 Slow heating. 
 
 Young oak wood 
 
 16-54 
 
 25-60 
 
 Old oak wood 
 
 15-91 
 
 25-71 
 
 Young red beech wood .... 
 
 14-87 
 
 25-87 
 
 Old red beech wood 
 
 14-15 
 
 26-15 
 
 Young white beech wood .... 
 
 13-12 
 
 25-22 
 
 Old white beech wood 
 
 13-65 
 
 26-45 
 
 Young alder wood 
 
 14-45 
 
 25-65 
 
 Old alder wood 
 
 15-30 
 
 25-65 
 
 Young birch wood 
 
 13-05 
 
 25-05 
 
 Old birch wood 
 
 12-20 
 
 2470 
 
 Young pine wood 
 
 14-25 
 
 25-25 
 
 Old pine wood 
 
 14-05 
 
 25-00 
 
 Young fir wood 
 
 16-22 
 
 2772 
 
 Old fir wood 
 
 15-35 
 
 24-75 
 
 Young Scotch fir wood .... 
 
 15-52 
 
 26-07 
 
 Old Scotch fir wood 
 
 1375 
 
 25-95 
 
 
 13-30 
 
 24-60 
 
 
 
 
 COKE. The carbonisation of coal is conducted very much in the same manner as 
 wood charcoal is prepared, and with the same general result of obtaining a material 
 consisting chiefly of carbon. But in addition to the separation of the volatilisable 
 portion of coal by which that result is produced, the carbonisation of coal has, in many 
 cases, a further important influence upon its applicability as fuel for many purposes. 
 This consists in the total or partial separation of the sulphur, with which some kinds 
 of coal are largely contaminated in the state of pyrites, a mineral consisting of sulphur 
 in combination with iron. At the temperature requisite for carbonising coal, this 
 substance is decomposed, giving off a considerable portion of its sulphur, which escapes 
 with the other volatilised products of carbonisation. 
 
 Coke is prepared both in heaps or ridges like wood charcoal and in close ovens; but 
 when coke is prepared for use as fuel, the ovens are never heated externally for the 
 purpose of effecting the carbonisation, as is sometimes the case with wood. 
 
 Fio. 21. 
 
 The coke ovens employed for carbonising coal, are generally large arched chambers 
 of strong brickwork, with a door in front for charging in the coal and an aperture on 
 the crown of the arch for the escape of the volatilised products of carbonisation. A 
 range of such ovens is represented by fig. 21. 
 
 
PREPARATION OF ANIMAL CHARCOAL. 63 
 
 In using these ovens for making coke, they are first made red hot by burning fuel 
 in them, and then are charged with a sufficient quantity of raw coal, which is ignited by 
 the hot brickwork, and is allowed to burn by keeping the front doors of the ovens open 
 as long as dense smoke or flame escapes through the aperture at the top of the ovens. 
 When this discharge of smoke and flame has nearly subsided, the doors are closed and 
 the apertures at the top covered up. The ovens are left in this .condition for several 
 hours, and then water is thrown upon the incandescent mass of coke, to cool it 
 sufficiently for its being drawn out without continuing to burn. 
 
 ANIMATE CHARCOAL. The manufacture of animal charcoal is generally carried on 
 in the neighbourhood of large towns, because it is in such places that the requisite 
 supply of bones can be best secured. 
 
 When bones are heated, the organic substances are decomposed and carbonised. 
 Volatile substances are formed, some of which are combustible gases that do not con- 
 dense upon cooling, but escape, while others condense and form a heavy oily layer (bone 
 oil) and an aqueous layer, which has a tarry smell and colour, and contains ammo- 
 niacal salts in solution. In the residue are found the inorganic constituents of the 
 bones, uniformly mixed with more or less finely divided carbon, and constituting 
 animal charcoal. Upon heating this in the air the carbon is burned and the inorganic 
 constituents of the bones remain as a grey or white substance, known as bone ash. 
 But if the charcoal be treated with warm dilute hydrochloric acid, the inorganic salts 
 are removed and pure carbon remains behind. 
 
 The carbonised bone, coarsely powdered, is used under the name of animal black 
 for decolorising purposes; finely powdered, it is termed burnt ivory or bone 
 black, and is used in the production of black paint, and especially of blacking for 
 boots. 
 
 The carbonisation is conducted differently according as it is desired to obtain only 
 the charcoal, or to collect also the condensible volatile products. In the latter case 
 the carbonisation is conducted in retorts like those used in the production of wood 
 vinegar (vide ' Acetic Acid '), and the watery distillate can be worked for ammonium 
 salts (chloride and sulphate). If the operation is confined to obtaining the non-vola- 
 tile animal charcoal, only a simple apparatus is necessary, and an important saving in 
 fuel is effected. 
 
 According to the method at one time generally adopted, cast-iron crucibles 12 
 inches in diameter and 16 inches high were used. These^rucibles, filled with broken- 
 up bones, were put into large furnaces, five crucibles being placed one on another, so that 
 the covers of the lower ones were formed by the crucible next above them, and only 
 the top crucible required a special lid. More recently, crucibles made of fire-clay 
 have been used, the size and form remaining the same. These fire-clay crucibles 
 have the advantage, that from an equal quantity of bones more charcoal is obtained, 
 because they do not lose their round form upon being heated. Consequently they fit 
 closer upon one another, less air can penetrate, and therefore less charcoal is burnt. 
 Moreover, since the clay is a bad condenser of heat, the carbonisation takes place 
 more slowly in the fire-clay crucibles, and less volatile products are formed. 
 
 It has also been found advantageous not to place the crucibles one upon another, 
 but side by side ; only one row of crucibles being then placed in the furnace. With the 
 exception of the height of the oven, the other arrangements remain the same. 
 
 The furnace consists of a flat hearth, having a superficial area of about 40 square 
 yards, covered in with a flat arch. The fireplace is in the middle of this space ; the 
 crucibles are introduced and removed through doors at the front upon ironbars, let in 
 to the brickwork, and they are easily moved to and fro by means of long hooked rods. 
 Each furnace holds eighteen crucibles. The lids are luted on to the crucibles with 
 clay. As soon as the furnace is filled, the doors are bricked up with a double row of 
 bricks. 
 
 It is advisable to build several such furnaces adjoining each other, and especially 
 to couple two back to back, so as to economise heat and fuel. It is advantageous also 
 to have a revivification furnace between two pair of carbonising furnaces, so that the 
 flame of the four furnaces serves for the heating of the fifth. 
 
 When the crucibles have been placed in the furnace, the temperature is gradually 
 raised to a red heat, and is maintained at that point for six or eight hours. As soon 
 as the decomposition of the bones commences, a large quantity of combustible vapour 
 is evolved, which takes fire and burns in the furnace. So much heat is thus developed 
 that only a small quantity of fuel is required. When the decomposition is completed 
 the crucibles are drawn without waiting for the cooling of the oven, and the furnace 
 is at once charged with fresh crucibles, whilst the others are cooling. 
 
 A uniform and sufficient temperature is especially important in the carbonisation 
 of bones. Insufficient heating yields a charcoal containing a portion of organic sub- 
 
64 CARBON. 
 
 stance not yet decomposed, which dissolves in the aqueous fluid to be decolorised and 
 communicates to it a strong loathsome smell. A charcoal burnt at too high or too 
 long continued a temperature yields too dense a product, the surface exposed, and 
 therefore the decolorising power of the charcoal, being propoitionally reduced. It is 
 consequently necessary not only to burn the bones sufficiently, but also to prevent 
 the temperature from rising too high. 
 
 In two furnaces such as are here described, more than a ton of bones can be carbon- 
 ised at one time, and four charges may be worked daily. The yield is about 60 per 
 cent., or altogether about 2 tons of animal charcoal. 
 
 After cooling in the crucible, the charcoal is crushed. If it be required for de- 
 colorising purposes, care must be taken to avoid as much as possible the production 
 of a fine powder, as this is less valuable than charcoal in small lumps. In order to 
 obtain the charcoal in lumps rather than in powder, the burnt bones are broken up by 
 means of grooved rollers consisting of toothed disks alternately of 10 and 12 inches in 
 diameter. Two such cylinders are so arranged that the smaller disks of one are oppo- 
 site the larger disks of the other, and in revolving, the bones are crushed between 
 them without being pulverised. To obtain the charcoal in sufficiently small lumps 
 without much fine powder, the bones are passed through six of these mills, the rollers 
 of each successive mill being set closer together than those of the previous one. By 
 an arrangement of sieves, the fine powder is separated from the lumps, and these 
 are again separated according to their size. 
 
 Bones are sometimes carbonised in perpendicular iron cylinders, several of which 
 are heated by one common fire. At the bottom of each cylinder is a slide for the 
 removal of the charcoal ; on the top is a lid with a tube for evolved gases and 
 vapour. These tubes extend into the flue by which the distillation products escape. 
 The charging of the cylinders is effected from above through the lids, which are then 
 luted with clay. After heating for two hours, the charcoal is withdrawn by opening 
 the slides underneath ; it is cooled in iron boxes closed from the air as much as pos- 
 sible. These retorts can be so arranged that the distillation products, are condensed 
 and thereby gained in addition. 
 
 The preparation of animal charcoal can also be carried on in combination with 
 that of gas for lighting. This method, however, has not hitherto presented sufficient 
 advantages over the manufacture of such gas from other materials. 
 
 LAMP-BLACK. The finely divided carbon known as lamp-black is prepared on a 
 large scale in the following manner. Fat, oil, rosin or resinous wood, tar, etc., are 
 allowed to burn with an imperfect supply of air, either in a brick furnace, or in cast- 
 iron chambers, and the products of combustion are conducted through a long brick- 
 work flue into a large chamber of timber or brickwork. From the ceiling of this 
 chamber is suspended a large hood of woollen cloth, which nearly fills the chamber, 
 and upon its surface most of the lamp-black is deposited ; only the loose light soot 
 finds its way into this chamber, the more dense or heavy soot remaining behind in the 
 brickwork flue. In many places, the products of combustion, after being evolved in 
 the flue, are conducted through a number of sacks placed in connection with it, in which 
 the lamp-black is collected. 
 
 In some districts of France, lamp-black is obtained in a very simple way. Eesinous 
 substances are burnt in a wooden chamber, the walls of which are hung with coarse 
 cloth. The resinous materials are ignited in vessels of clay or iron. The soot produced 
 deposits itself upon the rough surface of the cloth, from which it is afterwards scraped 
 off. 
 
 An especially fine quality of lamp-black is obtained from oil, waste fat, mineral 
 oils, and the like, by means of lamps constructed for the purpose. 
 
 The arrangement of an apparatus of this kind is shown by figs. 22 and 23. The 
 vessel (A) contains oil, the level of which is kept constant by means of a globular vessel 
 (B) also filled with oil, and inverted over A. From the vessel (A) the oil flows into 
 the tube (c), bent at right angles at its other extremity, which must be on a level 
 with the oil in A. This tube is furnished with a cotton wick, and at c' is a spout, by 
 means of which any overflowing oil is conducted into the vessel c" placed beneath it. 
 The flame is surrounded by a conical hood (d), which terminates in a tube (d'}. Through 
 this tube, the sooty products of combustion are conducted into the broad horizontal 
 tube (d'd 1 ). This latter tube receives the products of combustion from eight or ten or 
 more lamps placed at intervals of about six feet from one another, as shown by 
 fig. 23. 
 
 The wide tube (d'} serves to cool the smoke, as well as to collect water and other 
 liquids) which the smoke deposits. From this tube, the smoke passes into the first 
 sack (e) made of linen of close texture, the length of which is about ten to twelve feet, 
 and the diameter three feet : this is closed below with a trap or slide (e'}. The upper 
 

 PREPARATION OF LAMP-BLACK. 
 
 65 
 
 and lower ends of the sack consist of funnel-shaped tubes, made of sheet copper. The 
 upper tube terminates in a further additional pipe (/), through which the smoke passes 
 into the second sack (g), which has exactly the same construction as the first. From 
 the second sack, the smoke finds its way into the third ; from thence through Jc, and so 
 on, into the last (0). 
 
 The lower extremity of the last sack of each row is connected with a horizontal 
 flue (P), containing frames covered with wire gauze, and mounted on hinges. This 
 
 FIG. 23. 
 
 arrangement serves to retain the last portions of lamp-black carried over with the 
 smoke from the sack. Since the wire gauze (Q) very soon becomes choked with soot, the 
 draught is checked and it has to be cleaned at intervals : this operation is performed 
 by means of the rod (T), which being raised and allowed to fall suddenly, jerks the soot 
 off the sieve. The other end of the flue (P) terminates in a chimney, by which the 
 draught of air flowing through the entire apparatus can be regulated. 
 
 The removal of the black is effected by opening the mouth-pieces at the lower end 
 of the sacks, and shaking out the contents. 
 
 This arrangement admits of the products of the different sacks being separately 
 collected. The product in the first sack is generally kept apart from that of the rest, 
 as it is not so pure, containing resinous or tarry substances. 
 
 In the neighbourhood of Saarbriicken, a coarse sort of lamp-black is obtained by 
 the combustion of highly bituminous coal. The apparatus consists of a long slightly 
 
 F 
 
66 CARBON. 
 
 ascending brickwork flue, in whkh the coal is burnt with a supply of air insufficient 
 for complete combustion. The sooty products of combustion pass into a vaulted 
 chamber, where a part of the soot is deposited. This chamber is connected with three 
 others, decreasing in size, and placed vertically above one another. The products 
 obtained from each of the three chambers are collected separately, since they differ 
 in quality, the best being found in the last chamber. The amount of lamp-black thus 
 obtained is very small : one thousand parts of coal yielding only about thirty -three parts 
 of lamp-black. The coke obtained at the same time, and amounting to about 40 or 
 50 per cent., is, however, a valuable product. 
 
 Before lamp-black is packed, it has generally to undergo the operation of sifting. 
 It is packed either in sacks, barrels, or casks. If it be packed in sacks, they should be 
 previously soaked in water containing clay, which stops up the meshes, and thus 
 prevents loss of the lamp-black. 
 
 Commercial lamp-black is not altogether pure carbon : but always contains small 
 proportions of other substances, as shown by the following analysis by Braconnot : 
 
 Carbon 79-1 
 
 Resinous substances 5 -3 
 
 Combustible oily substances 1'7 
 
 Ulmin 0-5 
 
 Ammonium sulphate 3-3 
 
 Potassium sulphate 0'4 
 
 Calcium sulphate 0'8 
 
 Calcium phosphate (containing a large percentage of iron) . 0'3 
 
 Potassium chloride traces 
 
 Silicious sand 0'6 
 
 Water 8'0 
 
 Commercial lamp-black can be purified by heating it to redness in well-closed cru- 
 cibles or cylinders, to decompose resin and other organic substances. In order to get 
 rid of mineral substances, it must be treated with hydrochloric acid, and the excess of 
 acid afterwards removed by frequent washing with water. After lamp-black has gone 
 through these processes, pure carbon remains, contaminated only with a very small 
 quantity of sand. 
 
 Uses. Besides the extreme rarity of the diamond and its hardness, which is 
 only excelled by boron, its lustre and refractive power also add to its high value. 
 Until the method of cutting and polishing rough diamonds was known, they possessed 
 a comparatively small value. It is curious that the Roman stone polishers made use 
 of diamond powder for polishing other stones, but never for polishing the diamond 
 itself. 
 
 The art of cutting and polishing the diamond was discovered in 1476 by Louis de 
 Berguen. This substance can be easily split in the direction of the octahedral surfaces 
 of a regular octahedron, and since the grinding of diamonds is an extremely tedious 
 operation, advantage is taken of this cleavage in order to give them before polishing 
 the approximately desired form. For this purpose it is necessary to determine the 
 direction of the cleavage of the diamond with precision, and this requires great experi- 
 ence as well as great manipulative skill. When the direction of cleavage is ascertained, 
 the parts to be removed are split off by the application of a knife aided by a blow with 
 a small hammer. This being accomplished, the formation of facets is proceeded 
 with. For this purpose, the diamond is so fastened in the end of a stick, or handle, of 
 iron by means of a cement made of tin solder that the part which is to be ground 
 down is left projecting. This projecting part is rubbed with strong pressure against 
 a second diamond also fixed in a similar manner, and thus the two stones are mutually 
 abraded and acquire the flat surfaces or facettes desired. Other facettes are formed 
 in like manner after shifting the diamond into fresh positions in the cement. 
 
 The last operation of polishing is executed in the following way. The diamond to 
 be polished, is fastened in a small socket of copper with tin solder, and by means of a 
 special contrivance this socket is pressed against a rapidly rotating disc of steel, upon 
 the surface of which a small quantity of diamond powder (bort) mixed with oil, has 
 been previously placed. The polishing is continued until a facette is complete, then 
 the stone is reset and the other facets polished in like manner. 
 
 The bort is obtained, either by the mutual abrasion of rough diamonds or by 
 crushing useless diamonds and diamond chippings to powder in a steel mortar. 
 
 Some diamonds are' so hard that they cannot be polished. These can only be used 
 as glazier's diamonds, or for polishing other diamonds and precious stones. 
 
 The most simple form of the polished diamond is that of the rose, which is flat 
 beneath, while the upper portion, which has in all 24 facets, forms a pyramid having 
 triangular faces. 
 
APPLICATIONS OF CARBON. 67 
 
 A more valued form of the diamond is the brilliant, the greatest diameter of which 
 is at two-thirds of its height. The upper part which projects beyond the setting and 
 is termed the pavilion or crown is half the height of the under part within the setting 
 which is termed the collet (culasse). 
 
 Besides the application of diamonds for purposes of dress and decoration, as being 
 the most valuable of all precious stones, they are of considerable use industrially. On 
 account of their great hardness they are used as bearings for the pivots of delicate 
 watches. They serve further, as has already been mentioned, for polishing other pre- 
 cious stones, for drilling, rock boring, and especially for cutting glass. 
 
 For a long time it was supposed that the action of the diamond in cutting glass 
 depended upon the hardness of the diamond and upon its simply scratching when it 
 was passed over the surface of a piece of glass ; but Wollaston's researches showed 
 that in cutting glass with a diamond, though the rounded edge of the diamond cer- 
 tainly does in the first instance scratch the glass, it then penetrates the glass like a 
 wedge and thus produces, under the part scratched, a continuous crack. It is for this 
 reason that polished diamonds with perfectly even faces are useless for the purposes of 
 the glazier, it being necessary, in order that the diamond may act like a wedge, that 
 the edge made use of should be formed by curved faces, as is the case in the rough 
 diamond. 
 
 One of the chief applications of graphite is for making lead pencils. Graphite is 
 also used, mixed with clay, for the production of plumbago crucibles, which are cap- 
 able of bearing a high temperature. 
 
 Carbon has long been employed in drawing and writing. The most suitable kind 
 for this purpose is vegetable charcoal ; for owing to its softness, it more readily makes 
 a mark upon paper. In ancient times, ink was prepared from wood charcoal, which 
 was first finely powdered, and then mixed with a mucilaginous liquid. 
 
 China ink, or Indian ink, as it is called, is prepared from the soot obtained by 
 burning the oil of Sesamum orientale, less frequently from other forms of soot, 
 mixed with size or gum water, and dried. Frequently, the ink is mixed with some 
 aromatic material, such as camphor; but its essential characters are not thereby 
 altered. Printers' ink consists of carbon in a very fine state of division, mixed with 
 boiled linseed oil to a thin pap. 
 
 The other pigments made of vegetable charcoal are named according to their origin, 
 since they present different degrees of density and blackness, according to the material 
 from which they are prepared. 
 
 For instance, vine black is obtained by carbonising the wood of the grape vine. 
 Spanish black consists of the carbon of cork chippings. It is a charcoal, remarkable 
 for its great softness and loose consistency. 
 
 Charcoal crayons are made of alder-wood charcoal, obtained by carbonising suitable 
 pieces of the wood of the alder in iron cylinders heated to redness, and closed so as to 
 leave only a small aperture for the escape of the products of distillation. 
 
 Frankfort black is the carbon obtained from a mixture of vine twigs, lees of wine, 
 and sometimes also peach stones, bones, and ivory refuse. According as the vegetable 
 or animal charcoal is predominant, so do the pigments vary in shade : when vegetable 
 charcoal is predominant, it has a bluish hue, and a brownish tinge when there is a 
 preponderance of animal charcoal. As a rule, soluble mineral substances are generally 
 removed by washing before the charcoal is used. This black is used in copper-plate 
 printing. 
 
 Lamp-black, or the finely divided carbon obtained by imperfect combustion of fats, 
 oils, resins, pitch, coal, etc., is chiefly used as a pigment. 
 
 The consumption of animal black every year acquires greater dimensions. It is 
 used in sugar manufactories, for the decolorisation of the juice and of the syrup in 
 the working of the after products, as well as in the refining. The use of animal black 
 in sugar boiling has also been commenced in the colonies. 
 
 An important application is made of carbon in metallurgy, on account of its 
 capability of abstracting oxygen from metallic oxides, and in fact it is either directly 
 or indirectly the principal reducing agent employed for this purpose in metallurgical 
 operations. 
 
 But the chief application of carbon, or of combustible carbonaceous materials, is for 
 use as fuel to produce heat. 
 
 Compounds. Carbon forms a number of compounds with other elementary 
 substances, and some of the more complex compounds of carbon, such as vegetable 
 acids, alcohols, starch, sugar, cellulose, albumin, casein, etc., constitute a peculiar class 
 of substances, which are termed organic substances, since they are generally 
 produced by, and occur only as constituents of the organs of plants and animals. 
 
 With oxygen, carbon forms two compounds one, a neutral oxiue, is called 
 carbonic oxide: the other, carbon dioxide, C0 2 , containing twice as much oxygen 
 
 72 
 
68 CARBON. 
 
 in proportion to carbon, presents most of the characters of an acid oxide, and it forms 
 with basic oxides saline compounds called carbonates, several of which occur natu- 
 rally in great abundance and are of great technical importance. The hydrogen salt of 
 carbon dioxide, H 2 C0 3 , or true carbonic acid, is not known. With sulphur, carbon forms 
 adisulphide, CS 2 , sulpho-carbonic acid, corresponding to the dioxide, but containing 
 sulphur in place of oxygen. With nitrogen, it forms the pseudo-elementary substance, 
 cyanogen, ON, and several other compounds which are closely related to cyanogen. 
 The compounds of carbon with hydrogen are very numerous. As a class they are 
 termed hydrocarbons. 
 
 There are several groups of hydrocarbons whose individual members differ from 
 each other by CH 2 , or by a multiple of CH 2 . These are termed homologous groups, and 
 they are named after the lowest members. Marsh gas and the several substances 
 termed paraffins constitute a group of this kind. The following are the most impor- 
 tant of such groups : 
 
 The Marsh gas group. 
 
 Marsh gas, or hydride of methyl, CH 4 . . . CI ^> 
 
 Hydride of ethyl (dimethyl), C 2 H 6 . = C - I *j>j 
 
 Hydride of propyl, C 3 H 8 = CsH jl etc. 
 
 Higher homologues of this series are contained in petroleum, solar oil, etc. 
 
 The Ethylene group. 
 
 Olefiant gas, or ethylene . . . . . . . . C.,H 4 
 
 Propylene . . . . ' C~H 6 
 
 Butylene ....;-, C 4 H 8 
 
 Amylene C 5 H JO etc. 
 
 The Benzol group. 
 
 Benzol . . ; ' . " C 6 H 6 
 
 Toluol . . . .... . . . CjH^ 
 
 Xylol C 8 H 10 
 
 Cumol . 9 H, 2 
 
 Cymol . . . : .' C 10 H 14 
 
 There are many hydrocarbons, which are totally distinct substances, but have 
 exactly the same percentage composition ; as, for instance, olefiant gas (ethylene), 
 propylene, butylene, amylene, etc., but these substances are essentially different in 
 their physical and chemical properties. They all contain 14'3 per cent, hydrogen and 
 85*7 per cent, carbon; but the molecules of these compounds require to be repre- 
 sented by different formulae, though the proportions of hydrogen and carbon are the 
 same in all. 
 
 A few of the hydrocarbon compounds are gaseous at the ordinary temperature : 
 the greater number are liquid; such as, oil of turpentine, benzol, naphtha, etc. ; or 
 solid, like naphthalin, and some of the hydrocarbons of the paraffin series. 
 
 Although the number of hydrocarbons is extraordinarily great, only one of them 
 has been obtained by the direct combination of hydrogen with carbon. This substance 
 is acetylene, C 2 H 2 , which is formed when the electric arc is allowed to play for some 
 time between two carbon electrodes in an atmosphere of hydrogen. 
 
 The substances which have the'same composition as oil of turpentine, Ci H 16 , consti- 
 tute an important group of hydrocarbons. 
 
 The marsh gas series, hydride of ethyl, hydride of propyl, etc., are isomeric with 
 the radicals of the alcohols. So far as industrial art is concerned, the most impor- 
 tant member of the ethylene series is olefiant gas. The other members, propylene. 
 butylene, etc., are formed together with olefiant gas in the destructive distillation of 
 various organic substances for the manufacture of gas for purposes of illumination, 
 and they exert considerable influence upon its illuminating power. 
 
 The hydrocarbons of the benzol series are formed in the destructive distillation of 
 coal, as in the manufacture of coal-gas. They are found in the tar ; from which 
 material they are- obtained by distillation. Benzol and toluol especially have now 
 attained a great value, owing to their being the source from which aniline colours are 
 prepared. Cymol is contained in the volatile oil of cumin. 
 
 Naphthalin and anthracene, C, 4 H, , are likewise products of the destructive distil- 
 lation of coal, that have also recently been made use of in the preparation of colouring 
 materials. 
 
CARBON COMPOUNDS. 69 
 
 Finally, the hydrocarbon termed acetylene, having a composition represented by 
 the formula C 2 H 2 , occurs in coal-gas; and as it burns with a very bright flame, 
 it also exerts an influence upon the illuminating power of the gas. Its presence 
 in coal-gas can easily be detected by passing a stream of the gas through an ammo- 
 niacal solution of cuprous chloride. A reddish-brown precipitate is formed, consist- 
 ing of a compound of acetylene with copper, 2(C 2 HCu2)0, and possessing the property 
 of exploding when dried and heated. 
 
 The carbon compounds that occur naturally as constituents of plants and animals, 
 are much more numerous than those of any other elementary substance, and by various 
 kinds of chemical alteration, a still greater number of derivative products may be 
 obtained from them. 
 
 These organic substances are generally characterised by containing only carbon, 
 hydrogen, oxygen and nitrogen ; but their constitution is much more complex than 
 that of other carbon compounds. In many cases, this circumstance is due to the fact 
 that certain portions of the molecules of these substances present the characters of ele- 
 mentary substances, inasmuch as they perform the same functions as metals, or 
 chlorine, sulphur, etc., in the compounds that are termed inorganic, just in the 
 same way that in ammoniacal salts the group NH 4 acts the part of a metal. Thus, 
 for instance, ordinary wine alcohol consists of carbon, hydrogen, and oxygen, C 2 H 6 0, and 
 
 the composition of its molecule is represented by the formula |r 5 > 0, as being 
 
 analogous to that of the molecule of water H 2 0, with the difference that the place of one 
 atomic proportion of hydrogen is occupied by the group C 2 H 5 , which is termed ethyl or 
 the radicle of wine alcohol, and this pseudo-elementary substance is'capable of forming 
 compounds with chlorine, iodine, etc., that are analogous to the corresponding com- 
 pounds of metals. There are several other substances similar in this respect to 
 ordinary wine alcohol, and they constitute a class of carbon compounds which are on 
 that account termed alcohols. The compounds of alcohol radicles with oxygen re- 
 presented by ordinary ether C 4 H, are in like manner analogous to water, both 
 atomic proportions of hydrogen being replaced by ethyl, as in potassium oxide they are 
 replaced by potassium, as shown by the following formulae : 
 
 Ethyl oxide "Water Potassium oxide 
 
 C 2 H 5 j Q H( Kj 
 
 C 2 H 5 i Hi Kl 
 
 The ethers constitute a very numerous class of substances which differ in character 
 according to the nature of the alcohol radicles contained in them. 
 
 Several other classes of carbon compounds of a similar nature are designated by 
 general terms, such as aldehydes, ketones, etc., which indicate resemblance to the 
 particular representative substances that were originally known by these names, but 
 have since become types of classes, as in the case of the aldehyde obtained from ordi- 
 nary alcohol, and thus named because it was considered to be alcohol dehydrogenised. 
 
 The organic acids constitute another important class of carbon compounds, con- 
 taining radicles, which are, in this case, analogous to the acid oxides of sulphur, phos- 
 phorus, etc. Acetic acid, for instance, C 2 H 4 2 , is represented as containing a mono- 
 basic acid radicle C 2 H 3 0, called acetyl, corresponding to nitric oxide, in nitrates and the 
 composition of the molecules of hydrogen acetate, or acetic acid, and of acetates, is 
 represented, in conformity with that of the molecule of water, by the following 
 formulae : 
 
 Acetic acid Potassium acetate Water Nitric acid 
 
 f|o 
 
 Oxalic acid and oxalates are represented in a similar manner as compounds con- 
 taining the dibasic acid radicle C 2 2 , and corresponding to the double molecule of 
 water and to sulphuric acid, as in the following formulae : 
 
 Oxalic acid Potassium oxalate Water Sulphuric acid 
 
 Another class of carbon compounds, comprising many substances of great utility, is 
 that of the alkaloids, such as quinine, morphia, strychnine, etc. These substances 
 all contain nitrogen, and their constitution is very complex, but in general they 
 present great analogy with ammonia and those derivatives of ammonia which contain 
 alcohol radicles in the place of one or more atomic proportions of the hydrogen in 
 ammonia. 
 
 The substances which resemble starch, sugar, etc., in containing carbon com- 
 bined with hydrogen and oxygen in the same proportions as in water, and on that 
 
70 CARBON. 
 
 account are termed carbohydrates, form an important class of carbon compounds. 
 Their constitution is in many cases very complex, and the mode of representing it has 
 not yet been assimilated to that of more simple compounds. 
 
 Lastly, the substances corresponding to albumen, casein, gelatin, etc., constitute 
 another class of carbon compounds which are remarkable for containing nitrogen and 
 sulphur, in addition to the usual elementary constituents of organic substances. The 
 percentage composition of all these substances varies very little, but scarcely anything 
 is known of their chemical constitution, beyond the fact that it is probably very 
 complex. 
 
 The substances belonging to these different classes of carbon compounds which 
 require to be treated of in this work, as being of interest from an industrial point of 
 view, will be described subsequently either as general oonstituents of plants, etc., or 
 in connection with the materials from which they are usually derived. 
 
 CARBONIC DIOXIDE. 
 
 FORMULA C0 2 . MOLECDIAH WEIGHT 44. 
 
 History. This substance commonly called carbonic acid has been known 
 for a very long time, although Van Helmont was the first to distinguish this gas de- 
 finitely from others. Its true composition was first ascertained by Lavoisier. 
 
 Occurrence. The natural sources of carbonic acid are very numerous, some of 
 them furnishing enormous quantities; and, as has been mentioned in treating of the 
 atmosphere, this is the reason that the amount of the carbonic acid in atmospheric air 
 (about 0'04 per cent.), does not diminish, although it is constantly being consumed by 
 plants. The respiration of animals is one of the principal sources of carbonic acid : it 
 is also produced in a large number of processes of combustion, occurring either naturally 
 or as the result of the industrial activity of man ; as for instance, in the combus- 
 tion of fuel, and in the various contrivances for the purpose of illumination, etc. In 
 nearly all processes of fermentation, in every process of decay and putrefaction, car- 
 bonic acid is a product of the decomposition. Large quantities of carbonic acid are 
 further poured into the atmosphere from active volcanoes ; and sometimes, indeed, so 
 abundantly that there is not time for it to diffuse itself equally into the surrounding 
 air ; and, owing to the great density of the gas, it flows, like a stream of lava, down the 
 sides of the volcanoes, accumulating sometimes in hollows on their sides. On this 
 account, it is often dangerous to pass through such places, in the neighbourhood of 
 volcanoes. At other parts of the earth also, large quantities of carbonic acid are 
 often met with, issuing from crevices and fissures, as for instance in the ' Dog's Grotto,' 
 in the neighbourhood of Naples, at a few places near Treves, and other parts of the 
 Rhine district, as well as at Eger, Pyrmont, etc. A great quantity of carbonic acid 
 is also discharged from the water of mineral springs. As already mentioned, the 
 water of these springs has been saturated with carbonic acid at great depths, and 
 under considerable pressure ; but as the gas cannot be retained in solution at the 
 ordinary pressure of the atmosphere, it is consequently given off when the water comes 
 to the surface. 
 
 Though the quantity of carbonic acid existing in the free state is very great, it is 
 far exceeded by that which occurs chemically, combined principally in the state of 
 carbonates, as limestone, chalk, marble, dolomite, and magnesite, etc. 
 
 Composition. Carbonic acid contains nearly one-fourth its weight of carbon : 
 the normal volume of the oxygen it contains is equal to the volume of gas itself, and 
 the gaseous volume of the carbon it contains is assumed to be half that of the oxygen, 
 the combination being attended with a condensation of one-third the joint volumes of 
 the constituents in the free state. It is therefore a compound of one atomic propor- 
 tion of carbon with two atomic proportions of oxygen, and its composition is repre- 
 sented by the formula C0 2 . 
 
 Characters. Carbonic acid is at the ordinary temperature a colourlessgns, pos- 
 sessing a very slight smell. It is not combustible, nor does it under ordinary conditions 
 support the combustion of other bodies: neither is it a supporter of respiration, and 
 hence it is that animals are suffocated in an atmosphere of the gas. It is, however, 
 very different from carbonic oxide in its action upon the animal organism, for while 
 carbonic oxide is positively poisonous, as is evident from the fact that air containing 
 only a small amount of it causes death ; carbonic acid maybe inhaled in compara- 
 tively large quantities, without the slightest harm. 
 
 Carbonic avid gas is moderately soluble in water ; at a temperature of 15 C. water 
 
CARBONATES. 7i 
 
 dissolves about its own volume (1-002 vol.), and at under a barometric pressure 
 of 760 mm. it dissolves 1797 times its volume of the gas. As in the case of every other gas 
 in respect to solubility, carbonic acid dissolves in water in larger proportion when the 
 pressure is increased. Hence it is that the water of a spring, which has been saturated 
 with carbonic acid at a great depth below the earth's surface, and under great pressure, 
 gives off this gas upon coming to the surface of the earth. The same thing happens 
 with various other liquids, such as champagne, soda water, etc., which are saturated 
 with carbonic acid under considerable pressure, and give off the gas with effervescence 
 when the pressure is removed. 
 
 Carbonic acid may be condensed to a colourless liquid by cooling it to a temperature 
 of under a pressure of 36 atmospheres. When the liquid is allowed to evapo- 
 rate in the air, such an intense degree of cold is produced that a large portion becomes 
 solid. Solid carbonic acid is a white, snow-like substance, which evaporates but slowly 
 in the air, and melts at 57. 
 
 The density of gaseous carbonic acid is 22 as compared with hydrogen ; and its 
 specific gravity relatively to air is 1'529 ; the specific gravity of the liquid acid is 
 - 830 as compared with water. 
 
 Preparation. Carbonic acid is generally obtained by one of the three following 
 methods: 1. Expulsion of the gas from its salts by means of strong acids. 2. Expul- 
 sion from its salts by heat. 3. By burning carbon or carbonaceous substances. 
 
 For the preparation of carbonic acid on a small scale, the first method is the most 
 suitable. Calcium carbonate, a substance occurring very abundantly in various forms, 
 as chalk, limestone, etc., is employed for this purpose, together with hydrochloric acid, 
 the reaction that takes place giving rise to the formation of calcium chloride, while 
 carbonic acid gas is set free. 
 
 CaC0 3 + 2HC1 = CaCl, + H 2 + C0 2 ' 
 
 The calcium carbonate (marble or chalk being the most convenient), is placed in a 
 Woulfe's bottle, fitted with a funnel and a delivery tube connected with a wash bottle 
 containing a small quantity of water for the purpose of removing from the gas any 
 hydrochloric acid that might be mechanically mixed with it. The gas may be collected 
 either in a gasholder or over water by means of a pneumatic trough. After a quantity 
 of water has been poured through the funnel into the generating bottle sufficient to 
 cover the marble or chalk, hydrochloric acid is addjed in small quantities at a time 
 through the funnel. Carbonic acid is then developed with strong effervescence, and is 
 purified by passing through the water in the wash bottle. 
 
 Instead of this apparatus, one of a similar kind to that described on page 28, fig. 8, 
 may be employed ; the only difference being that the zinc ring is replaced by a per- 
 forated vessel containing marble, and resting upon a small glass tripod : hydrochloric 
 acid being, of course, substituted for sulphuric acid. 
 
 Ordinary limestone may be used instead of marble or chalk in the preparation of 
 carbonic acid ; but this is not advisable on account of the impurity of the gas thus 
 produced. Magnesite, a mineral consisting of magnesium carbonate, is very suitable 
 as a source of carbonic acid, the gas obtained from it being very pure. 
 
 The second method of preparing carbonic acid, by the action of heat upon its 
 salts, is not suitable for operations on a small scale. This process takes place in lime 
 burning : the limestone, a substance occurring very abundantly, being converted by 
 strong heat into calcium oxide (burnt lime), and carbonic acid : 
 CaC0 3 = CaO + C0 2 
 
 The carbonic acid produced in this process has of late been collected and made use 
 of for various purposes. 
 
 The third method of obtaining carbonic acid, like the one just described, is only 
 adapted for producing the gas on a large scale. It consists either in burning charcoal 
 or coke in a special apparatus, with the sole object of obtaining carbonic acid, or as is 
 sometimes the case obtaining the carbonic acid as a by-product of the ordinary com- 
 bustion of fuel, by collecting the waste gases from furnaces. (Vide 'Sugar Manu- 
 facture.') 
 
 Carbonic acid may also be obtained as a by-product in alcoholic fermentation ; sugar 
 being in this case resolved into alcohol and carbonic acid ; according to the equation : 
 C 6 H 12 6 = 2C 2 H 6 + 2C0 2 
 
 Further, carbonic acid is produced in a number of chemical processes ; by heating 
 charcoal with concentrated sulphuric or nitric acid ; also when any organic substance 
 is melted with nitre or some other powerful oxidising agent ; in the combustion o: 
 carbonic oxide, and in every process of putrefaction and decay, etc. 
 
 Uses Carbonic acid is very extensively employed in manufacturing industry. 
 
 It is made use of in the preparation of artificial aerated water, and other liquids con- 
 
72 CARBON. 
 
 taining carbonic acid. It is largely used for separating lime from the juice of the 
 sugar-cane, the lime being for the most part precipitated as carbonate, by passing a 
 stream of the gas into the heated juice. 
 
 Further, carbonic acid plays an important part in bread making ; the gas being 
 formed in the fermentation of the dough, and remaining dissolved, until the dough is 
 heated in the operation of baking ; when it expands and converts the dough into a 
 spongy porous mass. In the fermentation of dough, a considerable quantity of material 
 is lost in the shape of products of fermentation (alcohol and carbonic acid), and it 
 has therefore, been attempted to produce the carbonic acid in the dough by artificial 
 additions (Liebig bread, etc.) A process of the kind, which has been carried out on a 
 large scale in London and other places by Dr. Dauglish, consists in charging water 
 with carbonic acid, prepared either by the action of dilute sulphuric acid, or heat 
 upon chalk, and mixing this carbonic acid water with flour under pressure. The 
 resulting dough which becomes vesicular on the removal of the pressure, is divided 
 into loaves and baked (vide article ' Bread '). The production of carbonic acid by the 
 combustion of carbon compounds affords a means of analysing such substances. The 
 carbon is converted by combustion into carbonic acid, which is collected in an 
 apparatus containing caustic potash. From the difference between the weight of the 
 apparatus, before and after the combustion, it is easy to ascertain the amount of 
 carbon contained in the substance operated upon. 
 
 Attention has already been drawn (page 24) to the importance of carbonic acid in 
 the nutrition of plants. Many other effects are referrible to the presence of carbonic 
 acid in the atmosphere ; for instance, the setting of mortar is due to the combination 
 of carbonic acid with ..the lime of the mortar and the formation of calcium carbonate. 
 
 Compounds. The important class of saline substances known as carbonates 
 contain the elements of carbon dioxide combined with basic oxides. Carbonates are 
 generally represented as compounds of the dibasic acid oxide C0 3 with metals. Thus 
 the molecule of neutral calcium carbonate chalk or marble containing C0 2 + CaO is 
 represented by the formula CaC0 3 . Besides the neutral carbonates, there are a great 
 number of carbonates containing excess of base, and the carbonates of monovalent 
 metals form acid salts by the replacement of one atomic proportion of metal by 
 hydrogen. Thus, for instance, ordinary sodium carbonate, Na 2 C0 3 , by combining 
 with water and an additional proportion of carbon dioxide, furnishes two molecules of 
 the salt, NaHCO s , commonly called bicarbonate. With the exception of the carbo- 
 nates of the alkalies and of ammonia, the carbonates are insoluble or only sparingly 
 soluble in water. Ammonium carbonate is the only one soluble in alcohol. Most 
 carbonates are decomposed by heat, some at a comparatively low temperature, like 
 lead or zinc carbonate, giving off carbon dioxide and leaving lead or zinc oxides : cal- 
 cium carbonate requires a greater heat, and the alkaline carbonates are scarcely at all 
 decomposed by heat alone. When heated in contact with an atmosphere of water 
 vapour carbonates are more readily decomposed. Carbonates are decomposed by the 
 greater number of acids in the presence of water, and the liberation of the gas from 
 the liquid gives rise to the phenomenon of effervescence. Carbonates are also de- 
 composed in a similar manner by heating them with fixed acids, such as silicic, and 
 when heated in contact with carbon they are decomposed with evolution of carbonic 
 oxide. 
 
 The compound of carbon dioxide with ammonia, formed when the dry gases are 
 mixed, and sometimes called anhydrous ammonia carbonate, is the ammonium salt of 
 an acid called carbamic acid, HNH 2 C0 2 , the composition of the salt being repre- 
 sented by the formula NH 4 NH 2 C0 2 . This substance is contained in the ordinary am- 
 monia carbonate of commerce. It is a white flocculent mass readily soluble in water, 
 yielding, by combination with the elements of water, a solution of neutral ammonium 
 carbonate. 
 
 ARTIFICIAL AERATED OR MINERAL WATERS. 
 
 The various kinds of effervescent water known as soda water and seltzer water are 
 prepared from ordinary potable water, with or without addition of saline substances, 
 by charging it with carbonic acid under a pressure of from 4 to 6 atmospheres. 
 Consequently, good soda water or seltzer water should contain from 4 to 6 times as 
 much carbonic acid as well aerated potable water contains under ordinary conditions. 
 It is evident that water thus charged with carbonic acid under pressure requires to 
 be kept in well-corked bottles. Should the cork fit imperfectly, the carbonic acid 
 gradually escapes, and when the cork is removed altogether, the gas is given off with 
 brisk effervescence. 
 
 The material used in the preparation of the carbonic acid is generally limestone 
 or marble, which is decomposed with hydrochloric acid. Sometimes chalk or magnesite 
 is employed, and decomposed by means of sulphuric acid. For the preparation of 
 
AERATED WATER. 
 
 73 
 
 carbonic acid on a small scale, double sodium carbonate is very suitable, as it yields 
 very pure carbonic acid, free from the bituminous and earthy smell which carbonic 
 acid prepared from lime, chalk, etc., sometimes possesses. 
 
 The use of carbonic acid produced by fermentation has been recommended for the 
 preparation of effervescing beverages by MM. G-ressler and Wachler. Many different 
 forms of apparatus are in use for preparing carbonic acid water, one of the most com- 
 mon of which is represented by fig. 24. 
 
 This apparatus consists essentially of two parts, viz., the apparatus in which the 
 carbonic acid is generated (from A to E), and that in which water is saturated with 
 the gas (from E' to H). 
 
 Fig. 24. 
 
 The vessel (B) in which the gas is generated is made of lead ; the opening (b"), 
 admitting of being closed with a screw plug, is for putting in the carbonate to be 
 decomposed, and the pipe (b) is for supplying acid, which is poured into the leaden 
 vessel (A) through the opening (a) at the top. For the purpose of accelerating the 
 evolution of carbonic acid, a stirrer is fitted inside, and when set in motion by means 
 of the crank (w), it has the effect of distributing the acid flowing in through the pipe 
 (i), and bringing it into more intimate contact with the pieces of chalk or marble in 
 the vessel B. 
 
 The chemical change that takes place in B is very simple, the carbonic acid of the 
 magnesium or calcium carbonate being expelled by the stronger mineral acid used. It 
 is represented by the following equations : 
 With sulphuric acid 
 
 MgC0 3 + H 2 S0 4 =- MgS0 4 f H 2 + C0 2 . 
 With hydrochloric acid 
 
 CaC0 3 + 2HC1 = CaCl, + H 2 + C0 2 . 
 
 The carbonic acid evolved in B escapes through the tube (c), which passes into the 
 wash vessel (D) made of wood and lined with lead. This vessel is filled with water 
 up to the level (ww), and the gas delivery tube (c), extending above the water level, 
 turns down again so as to dip into the water. In this way the gas is made to pass 
 through the water, which serves to retain particles of mineral acid or salt carried over 
 by it. The washed gas then collects in the gas-holder (E), consistingof a sheet iron 
 or copper bell, which rises and falls in the vessel in which it hangs, according to the 
 quantity of carbonic acid present. The height of the bell is, therefore, an indication by 
 which the supply of acid to the generator (B) may be regulated. 
 
 The solution of the gas in water is effected in a strong copper cylinder (H) lined 
 with tin and fitted with a pressure gauge (r), a safety valve, and a tap for drawing off 
 the aerated water for bottling. This cylinder (H) is connected by means of a tube 
 with the pump (E'), by which gas is drawn out of the gas-holder, and at the same time 
 water is drawn from the small cistern (/), and both are then forced into the cylinder 
 (H) until the pressure indicated by the gauge (r) shows that the water is sufficiently 
 charged with gas. The flow of water and of carbonic acid into the condenser admits 
 
74 
 
 CARBON. 
 
 of being regulated by the cocks (p and#>'), so that water, rich or poor in carbonic acid, 
 may be obtained at pleasure, and the saturation of the water with carbonic acid is 
 aided by a stirrer fitted inside the cylinder, and turned by the toothed wheel ($') upon 
 the shaft of the fly wheel. In warm weather it is sometimes necessary to cool the 
 water before charging it with gas. 
 
 This apparatus can be worked either by manual labour or by steam power, and 
 when once the cylinder is charged with sufficiently aerated water, it works continuously, 
 when the supply of water and gas to the cylinder (n)is regulated by means of the cocks 
 (p and p'), according to the rate at which the aerated water is bottled off. 
 
 In the apparatus represented by fig. 25, carbonic acid is generated in the cylin- 
 drical vessel (G) which contains the calcium carbonate, and is fitted with a safety valve 
 (s) and with an agitator worked by the handle (H). Acid is supplied from the reservoir 
 (A) by opening a valve worked by the handle (v). and when a sufficient quantity has been 
 run in, the valve is again closed. The water to be charged with carbonic acid is con- 
 tained in the cylinder (c), which is also fitted with an agitator worked by the handle 
 
 FIG. 25. 
 
 (i), and between this cylinder and the generator (G) there are two small cylinders (w V) 
 containing water for washing the carbonic acid gas. The small cylinders or washers 
 are connected with the cylinders (c and G) in such a way that when the outlet tap (o), by 
 which the gas is allowed to escape from the generator, is opened, the escaping gas 
 passes successively through w and w' before entering c. In this arrangement the 
 pressure exerted by the evolution of carbonic acid gas in G is made to do the work of 
 forcing the gas into solution in the cylinder c, which is fitted with a pressure gauge (g) 
 for indicating when the water is sufficiently charged with gas and ready for bottling. 
 When this result has been produced, the communication between c and a is shut off 
 and the water is bottled in the usual way. 
 
 In order to carry on work continuously with this apparatus, two cylinders like c 
 are fitted side by side with connecting pipes and stop valves arranged in such a 
 way that either one can be placed in communination with the generator. As soon as 
 the water in one cylinder is charged with gas, the valves between it and the generator 
 are closed, and those between the other cylinder and the generator are opened. While 
 the second cylinder is being charged with gas, the water in the first cylinder is bottled 
 off, and so on alternately. When the cylinders are emptied, they are charged with 
 water again by means of the pump (p) worked by the crank (c). 
 
 Bottling. In filling bottles with water highly charged with carbonic acid, each 
 bottle (&) is set in a semicylindrical frame, so as to protect the workmen from splinters 
 of glass should the bottle burst during the operation. The mouth of the bottle is 
 pressed up by the lever (N) against a small caoutchouc plate with a hole in the middle, 
 which is fitted into a metal collar communicating on one side with the cock (m) and 
 on the other side with a valve (n) capable of being adjusted by a spring. In the 
 cavity above the caoutchouc plate is fixed at (I) a cork, which has been previously 
 softened in water. On opening the cock (w) the aerated water passes into the 
 bottle in proportion as the air escapes from the valve (n). 
 
PREPARATION OF CARBONIC OXIDE, 75 
 
 Directly a bottle is filled up to the neck with aerated water, the cock (m) is closed 
 and the cork (I) pressed by means of a plunger worked by the lever (k) into the neck 
 of the bottle. 
 
 The bottle is removed by lowering the lever (N). It is then placed on a table, and 
 the cork held fast by means of a couple of bent iron rods, while a workman secures it 
 with wire or string. 
 
 It is advisable to test the bottles before filling by exposing them to a pressure of 
 from 10-16 atmospheres, so as to avoid injury to the workman during the filling. 
 The condenser in which the water is saturated with carbonic acid is tested before use 
 by exposing it to a pressure of 20 atmospheres. The testing is without danger, water 
 being used, and water has such very little elasticity that, even if a vessel containing 
 ' it under great pressure should happen to spring, the pieces of the broken vessel are 
 not scattered about with any great violence. 
 
 It is evident that the apparatus above described for preparing aerated water admits 
 of being employed in the preparation of all effervescing beverages : such as artificial 
 sparkling wines, lemonade, etc., it being only necessary to fill the compressor with the 
 liquid required. 
 
 CARBONIC OXIDE. 
 
 FORMULA CO. MOLECULAR WEIGHT 28. 
 
 Composition. Carbonic oxide has the composition represented by the formula 
 CO : it was discovered by Priestley in 1799. 
 
 Characters. Carbonic oxide is a colourless, tasteless, and inodorous gas, that 
 has at present resisted all attempts to condense it to the liquid state. Its specific 
 gravity is 0'968. Carbonic oxide is only slightly soluble in water; 100 volumes of 
 water at absorbing only about 3*3 volumes of the gas ; it is, on the contrary, 
 easily soluble in a solution of cuprous chloride. Carbonic oxide is combustible, and 
 it burns with a beautiful blue flame, which is very characteristic. The product of its 
 combustion is carbonic acid. 
 
 Carbonic oxide does not possess the characters either of an acid or of a base ; it is 
 chemically an indifferent, or neutral, body. At high temperatures carbonic oxide acts 
 as a powerful reducing agent, abstracting oxygen from most metallic oxides, when 
 brought into contact with them at a red heat. 
 
 When respired, carbonic oxide acts as a powerful poison, probably by robbing the 
 blood of oxygen. Its poisonous action upon the animal organism is so powerful, that 
 small animals die in a very short time when placed in an atmosphere containing only 
 1 per cent, of carbonic oxide gas. In still smaller quantities, it causes an unpleasant 
 feeling ; headache, dizziness, and even syncope. 
 
 The fatal effect of burning charcoal in a closed room, with insufficient ventilation, 
 is owing to the formation of carbonic oxide. It is supposed that in this case, carbonic 
 oxide is not a direct product of combustion ; but that here, as in every other case of 
 combustion, whether the access of air be limited or not, carbon probably burns in the 
 first instance to carbonic acid ; and that this gas is afterwards reduced to carbonic 
 oxide by contact with the red-hot fuel. 
 
 Preparation. Carbonic oxide is easily obtained by passing carbonic acid gas 
 through a tube filled with pieces of charcoal and heated to redness. Under these con- 
 ditions, the carbonic acid combines with an additional proportion of carbon, and is thus 
 converted into carbonic oxide according to the following equation 
 
 C0 2 + C = 2 CO 
 44 12 56 
 
 Carbonic oxide can also be prepared by heating a mixture of finely powdered 
 calcium carbonate with one-sixth of its weight of charcoal powder in an iron retort. 
 At a red heat, the calcium carbonate gives off its carbonic acid, and this reacts with 
 the charcoal present in the manner above described. 
 
 The most convenient method, however, of preparing carbonic oxide is to heat 
 oxalic acid, or an oxalate with strong sulphuric acid. For this purpose, either crude 
 oxalic acid, or salt of sorrel, is placed in a capacious flask, covered with seven or eight 
 times its weight of concentrated sulphuric acid, and the mixture heated. Carbonic 
 oxide is then evolved, mixed with some carbonic acid, the mass frothing considerably. 
 On this account, the flask should not be more than half filled. The formation of 
 carbonic oxide in this case depends upon the fact, that when the sulphuric acid ab- 
 stracts either from the oxalic acid the whole of its water, or from the oxalate the 
 
76 CARBON. 
 
 whole of its base, the oxalic anhydride, thus set free, is resolved into carbonic oxide 
 and carbonic acid : 
 
 C 2 H 2 4 = H 2 + C0 2 + CO 
 90 18 44 28 
 
 A method, very much to be recommended for the production of carbonic oxide, 
 consists in heating in a glass flask a mixture of yellow prussiate of potash (potassium 
 ferrocyanide) with nine times its weight of concentrated sulphuric acid. 
 
 In all the processes above described for the preparation of carbonic oxide, the 
 gas is accompanied by carbonic acid. To remove this, the gas must be passed through 
 milk of lime or a solution of caustic potash contained in two or three "Woulfe's 
 bottles. 
 
 MARSH GAS. 
 
 FORMULA CH V MOLECULAR WEIGHT 16. 
 
 Occurrence. Marsh gas is formed in considerable quantities in marshes and 
 stagnant pools, at the bottom of which vegetable remains are under going decay, the 
 decomposition of such materials under water, without access of air, being favourable 
 to the production of the gas. The gas often observed rising to the surface of stagnant 
 water, more especially if the bottom be stirred with a stick, consists chiefly of marsh 
 gas, mixed with nitrogen and carbonic acid. In order to collect the gas, it is only 
 necessary to invert a bottle filled with water over the spot where the gas is issuing, 
 and to conduct the bubbles into the bottle by means of a funnel. 
 
 In certain districts, marsh gas is found escaping from the surface of the earth. 
 Such gaseous exhalations occur in Italy, on the northern slopes of the Apennines, at 
 Velleja, Pietramala, Barigazzo, etc. ; in France, at St.-Barthelemy ; in this country in 
 the neighbourhood of Lancaster and Brosely, as well as in Persia and in Mexico. The 
 gas generally issues from the ground, accompanied by mud containing common salt ; 
 whence those springs have obtained the name of mud volcanoes. It does not appear 
 probable that these springs are always volcanic, since they often occur in districts 
 far removed from volcanoes. The occurrence of the gas together with mud in such 
 springs, probably indicates that it has been formed by the decay of plant remains. 
 
 Marsh gas occurs in very large quantities in coal-mines, and is on this account 
 sometimes called pit gas. Being confined under great pressure in the interstitial 
 spaces of the coal, it rushes into the passages of the mines when such interstitial 
 spaces are opened in course of working a seam of coal. Here it comes in contact with 
 air, forming an explosive mixture, which often causes the greatest devastation, if the 
 miners incautiously approach with a naked light. Miners term the gas fire damp. 
 
 The reason why these explosions are so dangerous, is the enormous expansion of 
 the gases that takes place suddenly owing to the heat developed : by the violent con- 
 cussion thus caused, the workmen are hurled from the spot with great violence, or 
 the walls and roof of the passages are shattered and the mine choked lip. 
 
 Characters. Marsh gas, or light carburetted hydrogen, is a colourless, tasteless 
 gas, very sparingly soluble in water : it has not as yet been condensed to a liquid, 
 either by the application of cold or pressure. As compared with hydrogen its density 
 is 8, and its specific gravity in relation to air is 0'554. 
 
 When respired, marsh gas does not act as a direct poison, but it is not a supporter 
 of respiration. It is combustible, and burns with a yellowish flame of feeble illumi- 
 nating power, the products of combustion being water and carbonic acid. A mixture 
 of this gas with ten times its volume of air, or with twice its volume of oxygen, ex- 
 plodes with great violence when brought into contact with a flame. 
 
 Composition. This substance contains three-fourths its weight of carbon, and 
 twice its own volume of hydrogen. 
 
 Preparation. In order to prepare pure marsh gas, the best method is that of 
 heating together a mixture of sodium acetate and calcium hydrate, collecting the gas 
 evolved in a gas-holder (fig. 3, p. 20), or by means of a pneumatic trough over 
 water (fig. 1, p. 18). The residue in the retort after the operation is over, consists 
 of the carbonates of sodium and calcium. 
 
 Circulation of air in coal mines. One plan of preventing explosions consists in main- 
 taining a rapid change of the air in coal-pits, by means of artificial ventilation. Even 
 in coal-mines where fire damp is only occasionally met with a circulation of air is 
 necessary, for the reason, that without due ventilation, the explosive gases gradually 
 accumulate. For, though large quantities of fire damp seldom appear suddenly, there 
 is in many coal-pits a continual evolution of marsh gas, which, when it has time to 
 collect in any particular part of the pit, may easily give rise to an explosion. 
 
SAFETY LAMPS. 77 
 
 Coal obtained from pits where fire damp is prevalent generally contains marsh 
 gas in its cavities ; this is shown by the fact that such coal explodes with a loud re- 
 port when heated, and sometimes indeed spontaneously at the ordinary temperature. 
 When coal is freshly taken from pits of this kind, it often gives off such a quantity of 
 gas that it may be burnt at the mouths of the hutches in which the coal is brought up 
 from the mine. 
 
 The arrangement for obtaining an artificial current of air is generally the following. 
 Two air-shafts lead into the mine, and at the mouth of one of them is a furnace, with a 
 chimney fifty or sixty feet high. This furnace is so connected with the shaft of the 
 mine, that it can only obtain the necessary supply of air out of the shaft itself. This 
 shaft being in communication with the galleries of the mine, the bad air is thus drawn 
 from the mine and replaced by pure air which enters by the other air shaft. 
 
 In order to prevent the flame of the furnace from setting fire to inflammable gases 
 in the pit, the ventilating tube connecting the furnace with the shaft is fitted with 
 partitions of wire gauze, through which flame cannot pass. 
 
 The vicinity of fire damp is indicated to the miner by the flame of his lamp. The 
 presence of a small quantity of fire damp in the air at a considerable distance from the 
 explosive mixture, causes the flame to lengthen and burn with a blue colour, which 
 increases in depth as the amount of fire damp in the air increases. If there is danger 
 of an explosion, it is advisable for the workman to lie down fiat upon the ground, 
 for in that position, he offers less resistance, should an explosion take place. 
 
 Davy's Safety Lamp. The problem of lighting coal-mines in such a manner, that 
 the source of light should not cause the firing of inflammable gases, has been the object 
 of many researches. Davy especially conducted a number of experiments with this 
 end in view, and at last effected a solution of the problem. First of all, he experi- 
 mented with phosphorescent substances, which after having been exposed to sunlight, 
 possess an illuminating power in the dark, without evolving any perceptible heat. 
 However, the light emitted by all such substances is too weak for lighting up a 
 mine. 
 
 Davy next studied the degree of inflammability of various mixtures of marsh-gas 
 and air ; and upon setting light to them with a flame, he obtained the following 
 results : 
 
 Marsh gas Air 
 
 1 vol. 2 vols. The mixture burns without detonation. 
 
 3 
 4 
 
 The mixture burns with weak detonation. 
 The mixture burns with stronger detonation. 
 
 The mixture burns again with weaker detonation. 
 The mixture no longer ignites ; the flame of a candle 
 
 6 
 
 7 
 8 
 
 9-10 
 15 
 
 immersed in it lengthens. 
 16-30 The mixture does not ignite; the lengthening of the 
 candle-flame is less. 
 
 From these results, it is evident that a mixture of one volume of marsh gas and 
 eight volumes of air is the most explosive. One volume of pure marsh gas would re- 
 quire ten volumes of air for the combustion of the whole of its carbon and hydrogen 
 to carbonic acid and water. 
 
 Davy also found that a red-hot substance, such as a piece of red-hot charcoal, 
 might be introduced into an explosive mixture of air and marsh gas without setting 
 fire to it. Marsh gas is, therefore, less inflammable than carbonic oxide, olefiant gas, 
 sulphuretted hydrogen, or pure hydrogen ; all of which are set fire to when a Apiece of 
 red-hot charcoal is brought in contact with them. ^ Accordingly, since a mixture of 
 marsh gas and air is not easily ignited, Davy conceived the idea of preventing ex- 
 plosions by cooling the flame. Experimenting with an explosive mixture of hydrogen 
 and air, he found that, although it was more easily inflammable than one containing 
 marsh gas, the flame did not extend through metallic tubes of very narrow aperture, 
 nor even through very fine holes made in a piece of thin sheet metal. Eventually, 
 he employed wire gauze, and found that it prevented flame from extending throughout 
 the entire mass of an inflammable gas, by the cooling effect it produced, just like a 
 metallic tube of small diameter, or a plate with fine holes. 
 
 Consequently, by using a lamp with the flame surrounded by w^ire gauze, so 
 the air necessary for combustion, as well as the products of combustion, can enter and 
 escape only through the wire gauze, the firing of an inflammable gas surrounding the 
 lamp is rendered impossible. The cooling effect of the wire gauze prevents the pro- 
 pagation of flame. 
 
78 CARBON. 
 
 In the lamp used originally, and to a great extent even at the present time, a 
 cylinder of wire gauze closed above was fixed round the flame in such a way that it 
 rested on the oil vessel of the lamp. To prevent a miner being suddenly left in the 
 dai'k from the flame of his lamp being extinguished by an atmosphere of marsh gas, 
 Davy fitted his lamp with an arrangement by means of which, after the extinction of 
 the flame the man would still have light enough to find his way back. This arrange- 
 ment consisted of a spiral of platinum wire, surrounding the flame of the lamp and 
 kept red hot by it. If the flame is extinguished by contact with marsh gas, the 
 platinum spiral continues red hot, since the gas which comes in contact with it 
 'continues to burn slowly, and thus produces a feeble light. 
 
 The safety lamps made according to Davy's construction give only a feeble light, 
 on account of the wire gauze through which it has to penetrate. The consequence of 
 this is that, in order to obtain more light, the workmen often partially remove the 
 wire gauze ; and thus accidents have often occurred in spite of the safety lamps. On 
 this account the construction of the lamps has been improved, so that greater illumi- 
 nating effect, as well as greater safety, have been obtained. 
 
 Safety lamps give considerably more light when constructed as follows : The 
 flame is surrounded by a globe or cylinder of thick glass ; this glass is fitted into a 
 double cylinder of wire gauze, closed above also with double wire gauze, through 
 which the products of combustion escape, and air for the support of the flame enters 
 the interior of the glass cylinder through a double wire gauze. By the use of double 
 wire gauze, the inner one is protected by the outer from coal-dust, while the outer one 
 is prevented by the inner one from becoming too hot. 
 
 The metal of which the wire gauze is made is not immaterial. If platinum wire 
 be heated only moderately in an explosive mixture of marsh gas and air, it soon ac- 
 quires such a temperature that it is capable of causing the explosion of the gas. 
 This is also the case with wire made of silver or gold ; on which account these metals 
 are not suitable as material for the wire gauze of safety lamps ; although, on the 
 other hand, owing to their not becoming oxidised when heated, they would be in that 
 respect very suitable for the purpose. Davy's experiments in this direction showed 
 that the wire gauze is best made either of copper, brass, or iron wire. 
 
 OX.EFX.ajrT GAS. 
 
 FORMULA C 3 H,. MOLECULAR WEIGHT 28. 
 
 Characters. Olefiant gas, also called heavy carburetted hydrogen, or ethylene, 
 is at the ordinary temperature a colourless gas, which under strong pressure at- 110 
 is condensed to a colourless liquid. It possesses a peculiar ethereal smell ; burns with 
 a luminous flame; is very sparingly soluble in water, but is rapidly absorbed by con- 
 centrated sulphuric acid. A saturated solution of defiant gas in sulphuric acid when 
 diluted with water yields alcohol, which may be distilled from the mixture. 
 
 Olefiant gas is considerably denser than marsh gas ; as compared with hydrogen, 
 its density is 14, and relatively to air its specific gravity is 0'9784. 
 
 When passed through a tube heated to redness olefiant gas is decomposed, yielding 
 marsh gas and hydrogen together with carbon, which is deposited on the sides of the 
 tube. This property of olefiant gas must be considered in the manufacture of coal- 
 gas, the lighting effect of which is chiefly due to the ethylene it contains. 
 
 A mixture of ethylene with about fifteen times its volume of air explodes upon 
 contact with the electric spark, or other flame, yielding water and carbonic acid. 
 
 Olefiant gas enters into direct combination with concentrated sulphuric acid. As 
 marsh gas does not combine with sulphuric acid, this reaction serves for the separa- 
 tion of the two gases. If olefiant gas be brought into contact with chlorine in the dark, 
 it forms with it an oily liquid, having a composition corresponding to the formula 
 C 2 H 4 C1 2 , which, from its discovery by four Dutch chemists, has been called Dutch 
 liquid ; and from the oily appearance of this product, the gas itself received its name 
 4 olefiant.' If chlorine be allowed to act upon olefiant gas in the sunlight, there is 
 formed chiefly a product represented by the formula C 2 H 3 C1 3 . 
 
 Preparation. Olefiant gas may be prepared on a small scale, by heating 
 together, in a retort OP flask, a mixture of alcohol and from four to five times its 
 weight of concentrated sulphuric acid. This mixture froths considerably when heated 
 and especially towards the end of the operation; therefore the generating vessel 
 should not be more than half filled. The frothing may also be prevented by mixing 
 the acid and alcohol with enough sand to form a pasty mass. The gas evolved upon 
 the application of heat to this mixture is very impure, containing carbonic and sul- 
 
CYANOGEN. 79 
 
 phuric acids, alcohol and ether ; to remove which the gas is passed through two Woulfe's 
 bottles, containing caustic soda, and through a third, containing some concentrated 
 sulphuric acid. After having undergone this process of purification, the gas may be 
 collected over water, or in a gasometer. 
 
 Taking the empirical formula of alcohol as C,H 6 0, it is evident that it can be re- 
 solved into C 2 H 4 ,H.,0, and that accordingly alcohol contains the elements of olefiant 
 gas and of water. If pure alcohol be heated to 170-180, together with concentrated 
 sulphuric acid, the dehydrating affinity of the latter causes the decomposition of the 
 alcohol into water, which combines with the sulphuric acid, and into olefiant gas 
 which escapes. 
 
 When wood, coal, or resins and other allied organic bodies are heated with exclusion 
 of air, olefiant gas is formed together with various other products. A very extensive 
 application is made of this mode of formation of olefiant gas, in the manufacture of 
 illuminating gas, in which ethylene is the most important product. (Fide ' Gas Manu- 
 facture. 1 ) 
 
 Uses. Olefiant gas, mixed with allied hydrocarbons and other gases, is a con- 
 stituent of the different kinds of illuminating gases. Besides this, attempts have 
 been made to prepare alcohol from olefiant gas, or from mixtures of it with the other 
 hydrocarbons obtained by destructive distillation. 
 
 CYANOGEN". 
 
 FORMULA ON. MOLECULAR WEIGHT 26 
 
 History. This substance, which is interesting chiefly on account of its pseudo- 
 elementary character, was first obtained in a separate state by Gay-Lussac in 1815, 
 but many of its compounds had long been known as articles of technical utility. On 
 account of the blue colour of its compound with iron, known as Prussian blue, it was 
 named from Kvav6s blue, and yevvdca to produce. 
 
 Composition. Cyanogen contains nearly half its weight of carbon and its own 
 volume of nitrogen, and assuming the normal gaseous volume of the carbon it contains 
 to be equal to that of the nitrogen, the combination is attended with a condensation 
 amounting to one-half the total volume of the constituents. 
 
 Characters. Cyanogen is a colourless gas of peculiar odour. Its density is 
 13 as compared with that of hydrogen, and its* specific gravity in relation to air is 
 T806; by cooling or compression it condenses readily to a liquid of 0*866 specific 
 gravity as compared with water, and by further cooling it solidifies. The gas dissolves 
 in one-fourth its volume of water and still more copiously in alcohol. It is very 
 poisonous. Cyanogen is combustible, and burns with a blue flame yielding carbon 
 dioxide and nitrogen : 
 
 CN + 20 ~ C0 2 + N. 
 
 One of the most remarkable characteristics of cyanogen is the analogy between it 
 and chlorine in its chemical relations as a pseudo-elementary substance, and on this 
 account it is often represented by the symbol Cy ; it combines directly with metals, 
 forming saline compounds, called cyanides, which are analogous to the chlorides. 
 The hydrogen compound corresponding to hydrochloric acid, and known as hydro- 
 cyanic or prussic acid, cannot be formed directly, but is readily obtained by the action 
 of strong acids upon the metallic cyanides. 
 
 Many of the cyanides combine w r ith each other, forming a large number of com- 
 pounds, which may be regarded as double cyanides, or as containing a still more complex 
 molecular group than cyanogen, that also acts, like it, the part of an elementary sub- 
 stance, as in the ferrocyanides, which contain the elements of ferrous cyanide FeCy 2 
 and of 4 molecules of the cyanide of a univalent element or radicle, as in the case of 
 the salt called yellow potassium prussiate or potassium ferrocyanide, the formula of 
 which is K 4 Fe"Cy 6 = 4KCy + Fe''Cy 2 . Ked potassium prussiate K 6 Fe 2 '"Cy 12 represents 
 another class of compound cyanides termed ferricyanides, and there are several 
 analogous series of compounds containing cobalt or other metals in the place of the 
 iron of ferrocyanides and ferricyanides. These substances are regarded as containing 
 compound radicles termed ferrocyanogen, ferricyanogen, cobaltocyanogen, etc., which are, 
 like cyanogen, analogous to chlorine and act the part of pseudo-elementary substances. 
 Two other cyanogen compounds corresponding respectively to water and sulphuretted 
 hydrogen, in which half the hydrogen has been replaced by_ cyanogen, possess the 
 characters of acids, viz. cyanic acid HCyO and sulphocyanic acid HCyS. and they are 
 the representatives of two series of salts called cya nates and sulphocyanates, some 
 of which are of technical importance. 
 
80 CARBON. 
 
 POTASSIUM CYANIDE. 
 
 FORMULA KCy. MOLECULAR WEIGHT 65'1. 
 
 Cbaracters. This substance is commonly met with in the state of a white 
 opaque mass, which gives off the odour of hydrocyanic acid ; it is deliquescent and 
 very soluble in water, crystallises in transparent colourless cubes, and is extremely 
 poisonous. It melts readily at a low red heat, and is volatilisable at a much higher 
 temperature, apparently without decomposition. 
 
 Preparation. Potassium cyanide is prepared by the action of heat on well- 
 dried potassium ferrocyanide, the decomposition being represented by the following 
 equation : 
 
 K 4 C 6 N 6 Fe = 4KCN + FeC 2 + 2N. 
 
 Generally the ferrocyanide is mixed with potassium carbonate in order to prevent 
 decomposition of part of the cyanogen, and to obtain a larger yield of cyanide ; but in 
 this case the product contains some potassium cyanate, as shown by the following 
 equation : 
 
 K 4 C 6 N 6 Fe + K 2 C0 3 = 5KCN + KCNO + Fe + C0 2 . 
 
 A mixture of anhydrous ferrocyanide with three-eighths of its weight of dry carbonate 
 is thrown in successive small portions into a red-hot cast-iron crucible, and the heat 
 maintained until the evolution of gas has nearly ceased and the melted mass becomes 
 colourless. The crucible is then gradually withdrawn from the fire, and after its con- 
 tents have been allowed to settle, the clear melted cyanide is poured out upon an iron 
 slab. 
 
 Uses. Potassium cyanide is largely used in electro-plating, in photography, and 
 as a chemical reagent. 
 
 POTASSIUM FERROC7ANIDE. 
 
 FORMULA K 4 FeCy 6 . MOLECULAR WEIGHT 368-4. 
 
 History. This substance, commonly called yellow prussiate, was first prepared 
 by Macquer about the middle of the eighteenth century, and is largely used in dyeing 
 and calico-printing, as well as for the preparation of several other cyanogen com- 
 pounds. 
 
 Potassium ferrocyanide may be regarded either as the potassium salt of a com- 
 pound radicle, f errocyanogen C 6 N 6 Fe, sometimes represented by the symbol Cfy, or as 
 a double compound of potassium cyanide and ferrous cyanide. The crystallised salt 
 contains water, and its composition is represented by the formula K 4 FeCy 6 + 3H 2 0. 
 
 Characters. Potassium ferrocyanide crystallises in yellow transparent tables ; 
 it dissolves in 4 parts of cold water and in 2 parts of hot water. Heated to 100, the 
 salt gradually loses its water of crystallisation, and is converted into a white powder 
 consisting of the anhydrous salt. At a red heat it decomposes, giving off nitrogen and 
 leaving a mixture of potassium cyanide and iron carbide. 
 
 An aqueous solution of potassium ferrocyanide produces in solutions of ferric salts a 
 dark blue precipitate called prussian blue ; protosalts of iron yield with potassium 
 ferrocyanide a bluish precipitate which by contact with the air is gradually converted 
 into prussian blue. Solutions of copper salts yield with potassium ferrocyanide a dark 
 reddish-brown precipitate. 
 
 Preparation. On the large scale potassium ferrocyanide is prepared by adding 
 nitrogenous organic substances, such as horn, feathers, dried blood, etc., to fused potas- 
 sium carbonate, lixiviating the residual mass with water and bringing it into contact with 
 a salt of iron. During the melting process potassium cyanide is formed from the 
 potassium of the potash and the nitrogen and carbon of the organic substance, and that 
 salt when brought into contact with iron in the lixiviation yields potassium ferrocyan- 
 ide, according to the equation : 
 
 6KCy + Fe + 2H 2 = K 4 FeCy 6 + 2KHO + H 2 . 
 
 Since it has been observed that the iron vessels in which the mixture is melted are 
 very much attacked, it is now usual to add iron in a fine state of division to the melted 
 mass. By the reduction of potassium sulphate contained in the crude potash, potas- 
 sium sulphide and a double sulphide of iron and potassium are produced, which dis- 
 

 POTASSIUM FERROCYANIDE. 
 
 81 
 
 solve on subsequent lixiviation of the mass, and the iron sulphide and potassium 
 cyanide react upon one another, forming potassium ferrocyanide and potassium sul- 
 phide according to the following equation : 
 
 6KCy + FeS = K 4 FeCy 6 + K 2 S. 
 
 Some potassium sulphocyanide is also formed during the melting process, but it 
 is decomposed by the iron, with the formation of iron sulphide and potassium cyanide. 
 The destruction of the iron vessels, observed in cases where no iron was added to the 
 melted mass, is therefore simply explained by the iron required for the above reactions 
 having been taken from the sides of the iron vessels. 
 
 The great loss of nitrogen which takes place in the manufacture of potassium 
 ferrocyanide is very disadvantageous. At the most only one-fourth of the nitrogen 
 added in the form of animal substances is obtained in the form of potassium ferro- 
 cyanide, and the remaining three- fourths escaping for the greater part as free nitrogen, 
 together with a small quantity of ammonia. 
 
 The potash used in the preparation of potassium ferrocyanide must be very pure, 
 in order to avoid accumulation of foreign salts in the mother liquor. The organic 
 substances are carbonised previously to being mixed with the fused potash, so as to 
 get rid as far as possible of the sulphur they contain. The nitrogenous organic sub- 
 stances consist chiefly of animal refuse. 
 
 The proportion of organic substance required, as well as its value, depends upon 
 the percentage of nitrogen it contains. The following table by Karmrodt gives the 
 percentage of nitrogen in different kinds of animal refuse : 
 
 Horn 
 
 Dried blood 
 Woollen rags . 
 Sheep shearings 
 Calves-hair 
 Bristles . 
 Feathers 
 
 Amount of 
 Nitrogen 
 per cent. 
 15 to 17 
 15 , 17 
 
 Hide clippings . . " 
 
 Old shoes .... 
 
 Charcoal from horn according to 
 the heat to which it has been 
 subjected , . ; , ; ' ." 
 
 Charcoal from rags . ... 
 
 Amount of 
 Nitrogen 
 per cent. 
 4 to R 
 6 7 
 
 The iron required in the preparation of yellow prussiate is employed as filings or 
 turnings, or in some other finely divided state, the fine division being necessary so 
 that the melted mass may act upon it more readily than upon the sides of the iron 
 
 vessels. 
 
 FIG. 26. 
 
 FIG. 27. 
 
 The melting vessels consist either of strong spherical or shallow cast-iron pans, 
 which are set in the brickwork in such a way that the flame of a furnace can play 
 round or over them, as shown in figs. 26 and 27. Great care must be taken that 
 no air has access to the melting space, for in that case some organic substance would 
 be burnt, and some of the potassium cyanide would be oxidised to cyanate. To pre- 
 vent this, the combustion of the fuel must be so regulated that no excess of air passes 
 with the flame into the melting space, but rather undecomposed carbonaceous gases. 
 This is best effected by generating carburetted gas from the fuel in a special apparatus, 
 and mixing it carefully with a sufficient quantity of air before it passes into the 
 melting space. 
 
 G 
 
82 CARBON. 
 
 The older form of apparatus, represented by fig. 27, consists of a spherical cast-iron 
 pot (A) set in the furnace (B), so that the flame plays round it before escaping by the 
 flue (/) into the chimney (c), and a space is left between the mouth of the iron pot and 
 the arch of the furnace for the escape of volatile products. Opposite the mouth of 
 the iron pot, is an opening (0) in the wall of the furnace, capable of being closed by an 
 iron door (D) and the materials used are thrown into the pot through this opening. 
 
 Keverberatory furnaces are sometimes employed, as shown by fig. 26. In this case 
 the operation is conducted in a shallow iron pan (A), heated by the flame passing 
 over it from the fire at B, and at o is the door for changing the pan. 
 
 The method of operating is as follows : The potash (some few cwts. being taken) 
 is first melted, and then the nitrogenous organic substance mixed with iron filings is 
 gradually added. A strong evolution of gas takes place at first, blue flames of car- 
 bonic oxide are observed, while at the same time the organic substance dissolves and 
 potassium cyanide is formed. After all the organic substance has been added, and 
 the whole mass, which is termed the melt, has come to a state of tranquil fusion, it 
 is ladled out into iron pans to cool. 
 
 The melted mass, when cold, is lixiviated, and for this purpose it is broken up into 
 pieces about the size of an egg and thrown into iron lixiviating vessels. It is there 
 covered with water, and the ley heated for a day to 70 80 bypassing steam into the 
 lixivating vessel, the liquor being thus concentrated to a specific gravity of 1-16 to 
 1-22. During this operation the potassium cyanide dissolves, and reacts upon the 
 iron and iron salts in the way previously described to form potassium ferrocyanide. 
 After being allowed to clear, the liquor is drawn off and evaporated to a specific gravity 
 of 1'27, when it yields crystals of potassium ferrocyanide upon cooling. 
 
 The mother liquor contains a considerable quantity of undecomposed potassium 
 carbonate. It is therefore evaporated, and the product, called blue salt, is mixed 
 with half its weight of pure potassium carbonate for use in a subsequent melting 
 operation. 
 
 Blue salt contains, besides potassium carbonate, potassium sulphide, sulphate, 
 silicate, and chloride, as well as traces of other salts. Blue salt is often treated for 
 the production of impure Prussian blue. 
 
 The insoluble residue remaining after the first lixiviation of the melted mass is 
 washed once or twice with fresh quantities of water, and the liquor thus obtained is 
 used for the lixiviation of fresh material. The residue remaining contains over 10 
 per cent, of potash, but it is thrown away as worthless, and thus considerable loss is 
 occasioned. This loss of potash is less in proportion to the purity of the animal sub- 
 stances used. 
 
 Havrez recommends treating suint of sheep for both potassium carbonate and 
 ferrocyanide. When suint of sheep is incinerated potassium carbonate is obtained, 
 mixed with a considerable quantity of potassium cyanide, and on this account it 
 would be suitable for the preparation of potassium ferrocyanide. The direct use of 
 wool suint as nitrogenous material is also recommended by the above chemist. 
 
 Eecry sterilisation of the Crude Salt. The crude salt is dissolved in hot water, or 
 in the mother liquor of a previous crystallisation, and the solution cooled down very 
 slowly, so as to secure the formation of large and clear crystals. For the same 
 purpose pieces of string are often supported in the crystallising vessels, in order that 
 crystals may adhere to them. 
 
 Uses. Potassium ferrocyanide is chiefly used for the preparation of potassium 
 cyanide, hydrocyanic acid, and Prussian blue ; also in dyeing and calico-printing for 
 producing blue colours. It is also useful as a reagent in analytical operations. 
 
 POTASSIUM FERRICYAWIDS. 
 
 FORMULA K 6 Fe 2 Cy, 2 . MOLECULAR WEIGHT GoS'G. 
 
 Composition. This salt, also known as red prussiate, or as Gmelin's 
 salt, etc., is the representative of a number of saline compounds, that may be 
 regarded as containing a compound radicle Ci 2 N, 2 Fe 2 , which is sometimes represented 
 by the symbol Cfdy. 
 
 Characters. It forms beautiful transprent garnet red crystals, which belong 
 to the monoclinic system. The salt is easily soluble in water, but scarcely at all 
 soluble in alcohol. 
 
 Preparation. Potassium ferricyanide is obtained by acting upon potassium 
 
POTASSIUM FERRIC YANIDE. 83 
 
 ferrocyanide with chlorine, the reaction consisting in the removal of one atom of 
 potassium from the molecule of the salt : 
 
 2K 4 FeCy e + 2C1 = K 6 Fe 2 Cy,, + 2KC1. 
 
 Potassium ferricyanide is prepared on a large scale by passing chlorine gas into a 
 hot solution of potassium ferrocyanide having a specific gravity of T085, until a 
 sample no longer gives a dark blue precipitate when tested with a solution of ferric 
 salt, but only a clear brown liquid. When this point has been reached the liquid is 
 evaporated in a copper vessel to a specific gravity of T216. The boiling hot liquor is 
 then made slightly alkaline by the addition of a solution of potash filtered through 
 linen, and left to crystallise in copper vessels. The potassium ferricyanide forms 
 beautiful prismatic crystals, while the potassium chloride remains in the mother liquor, 
 together with some potassium ferricyanide, which may be obtained in a less pure state 
 by further evaporation. 
 
 A preparation known as blue powder is prepared by treating finely-powdered 
 potassium ferrocyanide with chlorine. It consists of a mixture of potassium ferri- 
 cyanide and potassium chloride. By treating the salt with water and crystallising 
 once or twice it is easy to obtain from it pure potassium ferricyanide. 
 
 Eeichardt suggests the use of bromine in the place of chlorine for preparing 
 potassium ferricyanide. There is no doubt that the required change would be brought 
 about as well by bromine as by chlorine, but probably bromine would prove too dear 
 for the preparation of potassium ferricyanide on a large scale. 
 
 Uses. Potassium ferricyanide is used in dyeing and calico-printing, for producing 
 blue colours on wool and cotton fabrics. It is also useful as a reagent in analysis. 
 
 PRUSSIAN BX.VE. 
 
 Under the name of Prussian blue are comprised three different kinds of blue 
 pigment, all of which owe their colour to ferrous or ferric cyanide. The purest of them 
 is Paris blue, consisting entirely of ferric ferrocyanide, Fe 4 3(FeCy 6 ) ; after it comes 
 Prussian blue, which is contaminated with alumina, starch, and similar substances ; the 
 third pigment, called mineral blue, is the most impure, being mixed with large 
 quantities of chalk, heavy spar, clay, starch, etc., and it is of a lighter colour than 
 the others. 
 
 Pure ferric ferrocyanide, or Paris blue, is prepared by mixing an aqueous solution 
 of potassium ferrocyanide with an excess of a solution of ferric salt, such as ferric 
 nitrate. The reaction which takes place is as follows : 
 
 3K 4 FeCy 6 + t = Fe 4 3FeCy 6 + 12 
 
 The precipitate formed is washed several times with water by a process of decantation, 
 and then thrown upon a linen bag to drain off the moisture, and allowed to dry slowly, 
 When it has attained a sufficient consistency for moulding it is either cut into squares 
 or pressed into moulds, and the pieces are afterwards dried in the air. 
 
 Prussian blue is prepared by mixing an aqueous solution of potassium ferro- 
 cyanide with an excess of ferrous salt dissolved in water. A white precipitate is thus 
 produced, which is converted into the dark ferric-ferrocyanide, or Prussian blue, by 
 treating it with hydrochloric acid and calcium hypochlorite. The precipitate consists 
 of potassio-ferrous ferrocyanide, K 2 Fe(FeCy 6 ), if the air is excluded, and there is 
 no ferric salt present; it is formed according to the following equation : 
 K 4 FeCy 6 + FeCl 2 = K 2 Fe(FeCy 6 ) + 2KC1. 
 
 The precipitate rapidly turns blue by exposure to the air and by other oxidising 
 agents, owing to the production of ferric ferrocyanide, as shown by the following 
 equation : 
 
 Potassio-ferrous Potassium 
 
 ferrocyanide Prussian blue ferrocyanide Feme oxide 
 
 6K 2 Fe(FeCy 6 ) + 30 = Fe 4 3(FeCy a ) + 3K 4 (FeCy 6 ) + Fe 2 s 
 
 The oxidised blue product is not entirely ferric ferrocyanide, for another reaction 
 
 also takes place when the white precipitate is treated with oxidising agents, which 
 
 is usually done in making Prussian blue, and as is shown by the following equation, 
 
 part of the potassio-ferrous ferrocyanide is converted into potassio-ferrous ferricyanide : 
 
 2K 2 Fe(FeCy 6 ) + = 2KFe(FeCy 6 ) + K 2 0. 
 
 Ordinary Prussian blue is, therefore, generally a mixture of ferric ferrocyanide 
 
84 CARBON. 
 
 with potassio-ferrous ferricyanide, the proportions varying according to the method 
 of manufacture. 
 
 In the preparation of ordinary Prussian blue very crude potassium fcrrocyanide is 
 chiefly used, which contains considerable quantities of potassium carbonate, and iron 
 alum is often added for the purpose of neutralising it. In this way potassium sulphate and 
 aluminum hydrate are formed, and the alumina remains mixed with the Prussian blue. 
 When it is desired to retain the aluminum hydrate which is generally the case the 
 oxidation must not be effected by the agency of calcium hypochlorite and hydro- 
 chloric acid, which would dissolve the aluminum hydrate, but the oxidation is in such 
 case effected by exposing the mixture to the action of the air. 
 
 Mineral blue is produced by mixing Prussian blue with the above-mentioned 
 foreign ingredients, the Prussian blue itself being for this purpose prepared from the 
 most impure liquors of the potassium ferrocyanide manufacture. 
 
 TurnbuWs Blue. This pigment likewise consists of ferrous and ferric cyanides, but 
 its constitution differs from that of Prussian blue. This may be seen from the follow- 
 ing equation, which represents the formation of Turnbuil's blue by the action of 
 potassium ferricyanide upon a solution of a ferrous salt : 
 
 Potassium Ferrous Ferrous 
 
 ferricyanide chloride ferricyanide 
 
 K 6 (Fe 2 Cy 12 ) + 3FeCl 2 = Fe 3 (Fe 2 Cy 12 ) + 6KC1. 
 
 Soluble Prussian blue is obtained most conveniently according to Briicke in the 
 following way : A solution of 1 part ferric chloride, in 10 parts water, is mixed with 
 double its volume of a saturated solution of Glauber's salt, and the whole stirred up 
 with an equal volume of a mixture consisting of a solution of potassium ferrocyanide 
 (containing per litre 217 grams of the salt), with double its volume of a saturated 
 solution of Glauber's salt. The precipitate formed is washed by decantation with dis- 
 tilled water, until the waste water becomes coloured. The residue is dried at the 
 ordinary temperature and dissolves in water, forming a dark blue liquid. 
 
 Eeindel prepares soluble Prussian blue by dissolving 1 part iron wire in aqua regia, 
 and adding to the solution an aqueous solution containing 7'5 parts of potassium ferro- 
 cyanide and a small quantity of alcohol ; the precipitate thus obtained is washed with 
 a small quantity of water and dried in the air. The precipitate is rendered insoluble 
 by heating it to 100. 
 
 TTse. Prussian blue is chiefly used as a pigment in oil and water-colour painting, 
 also in dyeing and calico-printing, the colour being produced within the fibres them- 
 selves, or printed upon the fabrics. 
 
 FUEL. 
 
 History. The application of artificially produced heat for cooking food and for 
 various domestic purposes appears to have been always a prominent feature of distinc- 
 tion between mankind and the lower animals ; but until a comparatively recent date, 
 the use of combustible materials as a source of heat (fuel) was for the most part re- 
 stricted to the warming of dwellings and the preparation of food, and, beyond the 
 forging of iron and the smelting of other metals, its industrial applications seem to 
 have been but few. In later times, however, as the industrial arts developed, the 
 artificial production of heat by the use of fuel became one of the most important, 
 means of effecting the chemical changes that take place in manufacturing operations ; 
 and since the invention of the steam engine furnished the means of converting heat 
 into motive power, the use of fuel as a source of heat has become so extensive in con- 
 nection with industrial art and commercial intercourse, that there is scarcely any 
 branch of industry or trade that is not to some extent dependent upon it, either 
 directly or indirectly. 
 
 Up to the thirteenth century, wood was probably the chief, if not the only, 
 material used to any great extent as fuel, and the burning of coal for any purpose in 
 the city of London was for a long time rigorously prohibited by law. Even so late 
 as the year 1779, the quantity of coal imported into London was only about 800,000 tons. 
 But in the fifteenth century, the consumption of wood in the smelting of iron had be- 
 come so considerable, and the consequent destruction of timber so serious, that Acts of 
 Parliament were passed to restrict its use for that purpose. Shortly afterwards coal was 
 successfully substituted for wood in iron smelting, and since the middle of the 
 eighteenth century it has been the chief fuel used in the manufacture of iron, as well 
 as in most other industrial operations. 
 
 Composition and Characters. The various materials used as fuel are all, 
 
COMPOSITION OF FUEL. 
 
 85 
 
 either directly or indirectly, of vegetable origin, and they consist either of the unaltered 
 ligneous tissue of plants, as in the case of wood and some varieties of turf and peat, or of 
 products resulting from the alteration of vegetable materials by decay, as in the case 
 of the various kinds of peat, lignite, coal, etc. In all kinds of fuel consequently there 
 is a general similarity of elementary composition, accompanied, however, by consider- 
 able difference in the relative proportions of the elementary constituents, and by 
 specific differences of character, depending sometimes more upon the physical struc- 
 ture and constitution of particular kinds of wood, peat and coal, or the mode in which 
 their elementary constituents are chemically arranged, than upon their actual amounts. 
 
 In all cases, the chief elementary constituents of the materials used as fuel are 
 carbon and hydrogen, combined with some oxygen, and a very small proportion of 
 nitrogen. Besides these constituents, which together make up the principal mass of 
 all kinds of fuel materials, and constitute the organic combustible portion, there is 
 always some proportion of incombustible earthy or inorganic substance that remains 
 as ash when the fuel is burnt, and originates either entirely from plant tissues, as in 
 the case of wood, or partly also from mechanical admixture of earthy substances, such 
 as mud, sand, etc., with the carbonaceous materials from which a particular kind of fuel 
 has been formed, as in the case of coal. Some of the materials used as fuel also con- 
 tain, in the raw state, a considerable amount of water, according to the porous or com- 
 pact texture of the material and its hygroscopic character ; this is especially the case 
 with wood, peat, and lignite, but the amount of water in coal is seldom considerable. 
 
 The amount of ash in different kinds of fuel varies considerably. In wood it is 
 seldom much more than 1 per cent. ; but in some kinds of lignite and coal it rises 
 as high as 10 or even 20 per cent. ; as a general average, 5 per cent, is as much as there 
 should be in fuel of good quality. 
 
 The water actually existing in fresh wood and in air-dried turf and peat may 
 amount to upwards of 40 per cent, and even in ordinary air-dried wood as well as in 
 peat and lignite it is seldom less than 20 per cent. ; in coal the amount of water is 
 always very much less. 
 
 The following tables give the average composition of different kinds of fuel. 
 
 
 CELLULOSE 
 or 
 LlGNDf 
 
 WOOD 
 
 TURF 
 
 PEAT 
 
 LIGNITE 
 
 air-dried 
 
 dried at 140 
 
 air-dried 
 
 air-dried 
 
 kiln-dried 
 
 air-dried 
 
 Carbon . 
 
 44-44 
 
 40-36 
 
 50-45 
 
 35-3 
 
 46-1 
 
 60-0 
 
 49-24 
 
 Hydrogen 
 Oxygen 
 
 6'17 
 49-39 
 
 4-91 
 32-66 
 
 6-14 
 
 40-83 
 
 3-6 
 19-2 
 
 4-6 
 23-6 
 
 6-9 
 30-0 
 
 4-18 
 16-97 
 
 Nitrogen 
 
 
 
 90 
 
 1 11 
 
 7 
 
 1-0 
 
 1-2 
 
 0'41 
 
 Sulphur . i 
 
 
 
 
 
 
 
 
 
 
 
 1-75 
 
 Ash . 
 
 
 
 1-17 
 
 1-47 
 
 1-1 
 
 1-5 
 
 1-9 
 
 1-69 
 
 Water . . 
 
 20-00 
 
 
 
 40-1 
 
 23-2 
 
 
 
 25-75 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 99-99 
 
 Wood. There is but little difference in wood as regards its composition, which ap- 
 proximates closely to that of pure woody fibre, and its applicability as fuel depends 
 chiefly upon its density and structural peculiarities, according to which, the different 
 kinds of wood are distinguished as hard, like oak, beech, elm, alder, etc., or soft, like 
 pine, fir, willow, and poplar woods. The weight of a cubic foot of wood varies from 
 26 to 42 Ibs. 
 
 Turf and Peat consist of the remains of mosses and other plants that have 
 undergone some degree of alteration. In many cases, the plant structure remains al- 
 most perfect, and the material has a spongy fibrous character. Sometimes, however, 
 the entire mass has been converted into a pasty condition like clay, with only slight 
 indications of the organised structure, and the term peat should be restricted to these 
 varieties. In consequence of this difference of texture, the density of turf and peat 
 varies from 0'2 to I 1 23, and the weight of a cubic foot from 12 pounds to 78 pounds. 
 
 Both peat and turf, as they usually occur in bogs or on the side of mountains, 
 contain from 80 to 90 per cent, of water, and in the ordinary air-dried condition they 
 contain from 20 to 40 per cent. . 
 
 As regards composition, there is but little difference between the various kinds of 
 turf and peat, and their applicability as fuel depends chiefly upon their physical 
 character. They are generally somewhat more carbonaceous than wood. 
 
 Lignite or brown coal consists of plant remains still retaining their struc- 
 
86 
 
 CAEBON. 
 
 ture in a distinctly recognisable condition, though they have undergone alteration to 
 greater extent than turf or peat. The density of lignite is generally much greater 
 than that of peat, varying from ri to 1'85, and the cubic foot weighs on the average 
 about 80 pounds. 
 
 In composition, lignite approximates to wood, but it is more highly carbonaceous 
 in proportion to the degree of alteration it has undergone. . 
 
 Coal. Under this name are comprised the different kinds of mineral carbon and 
 a great variety of highly carbonaceous combustible minerals that are capable of being 
 used as fuel, and indeed are by far the most important materials applied to this pur- 
 pose. Coal has probably in all cases originated, like other combustible carbonaceous 
 minerals, from the gradual alteration of vast masses of the remains of plants which 
 flourished in great luxuriance at very remote periods of earth's history. The general 
 chemical features of this alteration, by which the ligneous tissues of plants have been 
 gradually converted into coal, consist in the elimination of water as well as oxygen 
 and hydrogen, existing as constituents of the original plant remains, and the conse- 
 quent proportionate increase of the amount of carbon in the residual mass. But dif- 
 ferences in the particular nature of the original materials from which coal has been 
 thus formed, as well as in the conditions under which the alteration took place and 
 the extent to which it has advanced, have frequently influenced very considerably the 
 character of the product, and consequently there are numerous varieties of coal pre- 
 senting differences in their composition and characters that are sometimes very 
 marked, though in general they are more differences of degree than otherwise. 
 
 The several kinds of coal may be conveniently classified under the two heads of 
 Anthracite and Bituminous Coal ; but this classification is entirely conventional, 
 and is based only upon the presence or absence of certain characteristics affecting the 
 practical application of coal as fuel. 
 
 A similar conventionality and vagueness attaches to the general definition of coal 
 as a fuel material, and its distinction even in this respect alone from other analogous 
 minerals, such as the carbonaceous shales, etc., that are frequently associated with 
 coal, and have probably been formed from similar materials and in the same manner 
 as coal, but are distinguished chiefly by containing large amounts of incombustible 
 earthy admixture. From a practical point of view, any carbonaceous mineral that 
 will burn may in a general way be regarded as coal ; but, in some respects, its ap- 
 plicability as fuel may be greatly influenced by the amount of earthy substance it 
 contains, and this often constitutes a good criterion as to whether a particular mineral 
 should be regarded as coal or not. 
 
 
 Anthracite 
 
 Merthyr 
 
 Duffryn 
 
 Hartley 
 
 Oldcastle 
 
 Hartley 
 
 Wigiin 
 
 Carbon 
 
 91-44 
 
 90-27 
 
 88-26 
 
 81-18 
 
 87-68 
 
 80-26 
 
 80-07 
 
 Hydrogen . 
 
 3-46 
 
 4-12 
 
 4-66 
 
 5-56 
 
 4-89 
 
 5-28 
 
 5-53 
 
 Oxygen 
 
 2-58 
 
 2-53 
 
 0-60 
 
 8-03 
 
 3-39 
 
 2-40 
 
 8-10 
 
 Nitrogen . 
 
 0-21 
 
 0-63 
 
 1-45 
 
 72 
 
 1-31 
 
 1-16 
 
 2-12 
 
 Sulphur 
 
 079 
 
 1-20 
 
 1-77 
 
 1-44 
 
 09 
 
 1-78 
 
 1-50 
 
 Ash . 
 
 1-52 
 
 2-53 
 
 3-26 
 
 3-07 
 
 2-64 
 
 9-12 
 
 2-70 
 
 
 100 
 
 101-28 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100-02 
 
 Anthracite is characterised by containing a larger amount of carbon than any 
 other kind of coal. It is very dense, hard, and brittle. It is less readily combustible 
 than almost any other kind of fuel, and it requires a strong draught or blast for its 
 combustion. When suddenly heated, anthracite decrepitates and crumbles into small 
 fragments, a character which makes anthracite difficult to burn without considerable 
 waste. 
 
 The various kinds of bituminous coal are generally less carbonaceous than anthra- 
 cite, and they contain relatively larger proportions of hydrogen and oxygen. There 
 is not, however, any recognisable relation between their specific characters and their 
 elementary composition. Bituminous coal is generally characterised by containing a 
 considerable amount of bituminous substance which is decomposed by heat, yielding 
 volatile tarry and gaseous products, and consequently burns with flame. In this respect 
 it differs widely from anthracite, which contains little volatilisable substance and burns 
 without flame. Some bituminous coal undergoes a kind of imperfect fusion when 
 heated, softening and swelling up considerably from the evolution of gas while de- 
 composing, and ultimately forming a bulky porous mass of carbon. Coal of this kind 
 is termed caking coal. Other kinds of bituminous coal which retain their solidity 
 
CALORIFIC POWER OF FUEL. 87 
 
 and form when heated, but split into columnar fragments when burnt, are commonly 
 termed dry or free-burning coals. Another kind of bituminous coal, containing 
 a large amount of bituminous substance volatilisable by heat, is termedcannelcoal. 
 The specific gravity of bituminous coal varies from 1*2 to 1'5, the cubic foot weighing 
 from 70 to 90 pounds. 
 
 Since the value of any material as fuel is proportionate to the combustible sub- 
 stance it contains, the presence of any considerable amount of earthy substance or of 
 water is objectionable on that account alone. The presence of earthy substances has 
 likewise the disadvantage of causing inconvenience when the fuel is burnt, by the 
 melting or caking of the earthy residuum and the formation of slag or clinker upon 
 the fire bars of the furnace. The presence of water in fuel is also attended with a 
 further disadvantage, consisting in the consumption of heat for the vaporisation of this 
 water, so that some portion of the heat actually produced by burning the fuel is thus 
 expended uselessly and with a proportionately inferior practical effect. 
 
 When any material containing water is used as fuel, the quantity requisite for pro- 
 ducing a given effect is therefore proportionally greater than it would be if the fuel 
 were free from water. For some purposes, such as evaporation or heating liquids, no 
 great advantage would be gained by drying the fuel artificially before burning it, 
 since the consumption of heat in drying would be equal to the waste attending the use 
 of the fuel in its raw state. The case is different, however, when fuel is used with the 
 special object of producing a high temperature, for the temperature attainable by 
 the combustion of a material is absolutely limited by the presence of water in any 
 considerable amount, and it is only by previously drying the fuel that it is possible to 
 produce a high temperature. It is on this account that wood and similar materials 
 are subjected to the operation of kiln drying to render them more suitable for use as 
 fuel, when high temperature is one of the effects they are intended to produce. 
 
 The amount of heat that any material is capable of producing when used as fuel, 
 depends principally upon the composition of the combustible portion, and to some ex- 
 tent also upon special peculiarities of its constitution, structure, and condition, by 
 which its combustion is influenced. Carbon and hydrogen, the heat-producing con- 
 stituents of all kinds of fuel, differ considerably in regard to the amount of heat they 
 produce when burnt. Carbon burnt to carbonic dioxide evolves heat sufficient to 
 raise the temperature of 8,000 times its weight of water one degree, and hydrogen 
 when burnt evolves heat sufficient to raise the temperature of 3,3881 times its weight 
 of water one degree, or 4-23 times as much as an equal weight of carbon. For the 
 purpose of expressing the relative heat-producing power of fuel, carbon is taken as the 
 standard of comparison, and the heat it evolves when burnt to carbonic dioxide as the 
 unit of calorific power. 
 
 When the combustible portion of fuel consists entirely of carbon, as in the case of 
 charcoal or coke, its relative calorific power p corresponds with the amount of carbon C, 
 in the fuel. 
 
 When the combustible portion of fuel contains hydrogen as well as carbon, the 
 calorific power referrible to this constituent is found by multiplying its percentage 
 amount by 4'23, and adding the product to the number expressing the amount of 
 carbon ; thus p = C + 4'23 H. 
 
 When fuel contains oxygen, this constituent must be regarded as being ^ already in 
 combination with an equivalent quantity of hydrogen, and when the fuel is burnt a 
 corresponding quantity of water is produced in addition to that actually existing in 
 the material. Thus, for instance, kiln-dried wood containing about 41 per cent, of 
 oxygen and 6 per cent, of hydrogen will produce in burning more than half its weight 
 of water, the greater part of which is formed by the combination of some of the hydrogen 
 with the oxygen that constitutes part of the wood. This combination of hydrogen 
 with oxygen existing in the wood is not attended with evolution of heat, and only the 
 carbon and the surplus hydrogen over and above the quantity equivalent to the oxygen 
 present in the fuel evolve heat in the combustion of a material containing oxygen. 
 Practically, therefore, the heat-producing capability of such a material as wood, even 
 when kiln dried, is limited by the amount of oxygen it contains. In other words, wnen 
 materials containing oxygen are burnt as fuel, only those portions of the carbon and 
 hydrogen are capable of evolving heat which can be regarded as though existing in 
 the free state. As a result of this important fact, the efficiency of wood or any other 
 material containing a considerable amount of oxygen is very much less tnan tnat ( 
 materials containing no oxygen. In the case of kiln-dried wood only the carbon and 
 about one-sixth part of the hydrogen it contains, generate heat when tne wood is 
 burnt. Therefore, in expressing the relative calorific power of a material containing 
 oxygen, a deduction must be made from the total amount of hydrogen equal to < 
 eighth of the oxygen present, and in such cases p = C + 4'23 (H 0). ^ 
 
 In all kinds of fuel containing hydrogen and oxygen, the hydrogen is in excess of 
 
88 CARBON. 
 
 the quantity requisite for forming water with the oxygen. This is the case even with 
 wood, although the cellulose of which it chiefly consists has the composition of a 
 carbohydrate. This excess of hydrogen in wood is due to the presence of resin and 
 similar substances. In other kinds of fuel, such as peat, lignite, and coal, the excess 
 of hydrogen over and above that requisite to form water with the oxygen they contain 
 is still greater. The excess of hydrogen in these cases appears to indicate that in the 
 alteration of plant remains, by which these materials have been formed, oxygen has 
 been to a great extent eliminated in combination with carbon and not altogether as 
 water. A similar result may sometimes be produced in the combustion of fuel, and 
 in that case, according to the amount of hydrogen capable of being burnt, a propor- 
 tionately greater amount of heat would be produced, since the calorific power of 
 hydrogen is 4*23 times that of carbon. In such cases p = C -|0 -f 4'23 H. 
 
 The calorific power of fuel may be expressed in heat-units by multiplying the 
 amount of carbon and the amount of available hydrogen in one part of the fuel re- 
 spectively by the numbers expressing in heat- units the calorific power of carbon and 
 of hydrogen ; the sum of these two products represents the calorific power of the fuel 
 in heat-units : 
 
 Fuel containing only carbon . . p = 8000 C 
 
 Fuel containing carbon and hydrogen p 8000C -t- 33881 H 
 
 n ' h7drogen ' = 800 c + 33881 H -- 
 
 The numerical expression of calorific power in heat units will of course be different 
 according as the thermometric scale to which it refers is that of Celsius, Fahrenheit, or 
 Eeaumur, since the degrees of these scales are in the ratio of 1 : 1'8 : 0'8. The value 
 of the heat unit as a definite quantity will also be different according to the unit or 
 weight as well as the thermometric scale referred to. According to the centigrade 
 scale and the metrical system of weights, the heat unit is the quantity of heat which 
 raises the temperature of one kilogram of water from 4 to 8C, while the heat unit, 
 according to the Fahrenheit scale and the British system of weights, is the quantity of 
 heat which raises the temperature of a pound of water from 40 to 41 F. Conse- 
 quently these two values bear the following ratio to each other : 
 British heat unit French heat unit 
 
 1 = 0-251996 
 
 3-96832 = 1- 
 
 In the following table the calorific power of several combustible materials is given 
 both relatively and in heat-units of the centigrade as well as the Fahrenheit scales. 
 
 The figures in column 2 represent the average in decimal parts of the respective 
 proportions of the elementary constituents, ash, etc., in one part of the different 
 materials. Column 3 gives the weight of oxygen requisite for converting the combus- 
 tible carbon and hydrogen in one part of each material into carbon dioxide and water. 
 
 The numbers in column 7 of the accompanying table are obtained by dividing those 
 in column 5 by 100 or those in column 6 by 180, upon the assumption that equal quan- 
 tities of heat are requisite for raising the temperature of x parts of water y degrees 
 or y parts of water x degrees. Thus the heat evolved by the combustion of one 
 pound of carbon would be sufficient to raise the temperature of 8000 pounds of water 
 from 4 to 5 or of 80 pounds of water from to 100. This assumption, however, 
 is not-strictly correct, since the specific heat of water increases slightly as the tem- 
 perature exceeds 4, the point of its maximum density; but the data in the table are 
 sufficiently exact for ordinary purposes. 
 
 The numbers in column 8 are obtained by dividing those in column 7 by 5-37, on 
 the assumption that the quantity of heat requisite to convert water at the boiling 
 point into steam under the normal atmospheric pressure,, is 5'37 times a,s much as is 
 requisite for raising the temperature of the same weight of water from to 100. 
 
 A comparison of the data given in this table will show clearly the influence ex- 
 ercised by the presence of oxygen in the materials used as fuel, not only by reducing 
 the actual amount of carbon and hydrogen, but also by rendering some portion of one or 
 both of those substances useless for the production of heat, inasmuch as they are already 
 combined with the oxygen. This is very evident in the case of carbonic oxide, which 
 gives 1731 heat units by combustion, or only half as much heat as would be produced by 
 the combustion of a quantity of carbon equal to that contained in the unit of weight of 
 carbonic oxide. In fact, so far as regards the production of heat corresponding to the 
 oxidation of carbon to carbon dioxide, one-half of the carbon in carbonic oxide may be 
 regarded as if it were already in the state of carbon dioxide, since the heat evolved by 
 the combustion of carbonic oxide is only half that evolved by the combustion of a 
 quantity of carbon equal to the carbon contained in that gas. 
 
PRACTICAL EFFECT OF FUEL. 
 
 89 
 
 1 
 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 
 Composition of Fuel 
 
 Oxygen 
 
 Calorie c power 
 
 Water 
 
 Water 
 
 
 
 requi- 
 site for 
 
 I 
 
 heat-units 
 
 heated 
 from 
 
 at 100 
 converted 
 
 
 
 
 
 
 
 Car- 
 bon 
 
 Hy- 
 dro- 
 gen 
 
 Oxy- 
 gen 
 
 Ash 
 
 Water 
 
 com- 
 bustion 
 
 1 
 
 i 
 
 Centi- 
 grade 
 
 Fahr. 
 
 0to 
 100 
 
 into 
 steam 
 
 HYDROGEN . 
 
 _ 
 
 1 
 
 _ 
 
 
 
 8- 
 
 4-23 
 
 33881 
 
 60986 
 
 338-81 
 
 63- 
 
 MARSH GAS 
 
 0-75 
 
 0-25 
 
 
 
 
 
 
 
 4- 
 
 1-81 
 
 14470 
 
 26046 
 
 144-7 
 
 26-9 
 
 OLEFIANTGAS 
 
 0-857 
 
 0-143 
 
 
 
 
 
 
 
 3-43 
 
 1-46 
 
 11701 
 
 21062 
 
 117-0 
 
 21-8 
 
 COAL: 
 
 
 
 
 
 
 
 
 
 
 
 
 Welsh 
 
 0-838 
 
 0-048 
 
 0-041 
 
 0-049 
 
 
 
 2-58 
 
 1-02 
 
 8161 
 
 14690 
 
 81-6 
 
 15-2 
 
 Newcastle . 
 
 0-821 
 
 0-053 
 
 0-057 
 
 0-038 
 
 
 
 2-56 
 
 1-01 
 
 8126 
 
 14627 
 
 81-2 
 
 15-1 
 
 Carbon . 
 
 r 
 
 
 
 _ 
 
 _ 
 
 
 
 2-67 
 
 r 
 
 8000 
 
 14400 
 
 800 
 
 14-9 
 
 COAL: 
 
 
 
 
 
 
 
 
 
 
 
 
 Scotch. 
 
 0-785 
 
 0-056 
 
 0-097 
 
 0-040 
 
 
 
 2-53 
 
 0-97 
 
 7771 
 
 13988 
 
 77-7 
 
 14-5 
 
 Derbyshire . 
 
 0-797 
 
 0-049 
 
 0-101 
 
 0-026 
 
 
 
 2-42 
 
 0-95 
 
 7596 
 
 13673 
 
 75-9 
 
 14-1 
 
 Lancashire 
 
 0-779 
 
 0-053 
 
 0-095 
 
 0-049 
 
 
 
 2-41 
 
 0-95 
 
 7621 
 
 13718 
 
 76-2 
 
 14-2 
 
 PEAT: 
 
 
 
 
 
 
 
 
 
 
 
 
 Kilu-dried . 
 
 0-60 
 
 0-060 
 
 0-307 
 
 0-020 
 
 
 
 1-78 
 
 0-69 
 
 5545 
 
 9981 
 
 55-4 
 
 10-3 
 
 Air-dried . 
 
 0-461 
 
 0-046 
 
 0-246 
 
 0-015 
 
 0-232 
 
 1-23 
 
 0-52 
 
 4196 
 
 7553 
 
 41-9 
 
 7-8 
 
 WOOD : 
 
 
 
 
 
 
 
 
 
 
 
 
 Dried at 140 
 
 0-503 
 
 0-061 
 
 0-407 
 
 _ 
 
 
 
 1-42 
 
 0-54 
 
 4363 
 
 7853 
 
 43-6 
 
 8-1 
 
 Air-dried 
 
 0-404 
 
 0-049 
 
 0-327 
 
 
 
 0-200 
 
 1-14 
 
 0-44 
 
 3503 
 
 6305 
 
 35-0 
 
 C-5 
 
 CARBONIC ) 
 
 OXIDE . J 
 
 0-43 
 
 
 
 0-57 
 
 
 
 
 
 0-57 
 
 0-21 
 
 1731 
 
 3116 
 
 17-3 
 
 3-1 
 
 
 
 
 
 
 
 
 
 
 
 
 The practical effect produced by any material used as fuel is always less than its 
 calorific power would indicate, and the amount of this difference depends upon a 
 number of conditions, among which the elementary composition is one of the most im- 
 portant in its influence. To illustrate the nature of this difference between the calo- 
 rific power of fuel and its practical efficiency, it will be necessary to consider how the 
 heat actually evolved in burning fuel is disposed of. In any case of the combustion of 
 fuel, the total heat evolved is communicated to the product of combustion, which is in 
 all ordinary cases gaseous, producing in it at the moment of combustion a temperature 
 determined partly by the calorific power of the fuel, and partly by the nature as well 
 as the amount of the product of combustion. Thus, for instance, taking the simplest 
 case, carbon requires for its combustion to carbonic dioxide 2'67 times its weight of 
 oxygen, and by combining with oxygen, it produces 3'67 times its weight of carbonic 
 dioxide. Since atmospheric air is the source of the oxygen that supports the combus- 
 tion, and since it contains only 23 per cent, of oxygen by weight, the quantity of air 
 containing the 2'67 parts of oxygen requisite for the combustion of the carbon will be 
 11-61 times the weight of the carbon burnt, and the 3'67 parts of carbonic dioxide 
 produced will be mixed with the 8*94 parts of nitrogen contained in that quantity of 
 air, making the gaseous product of combustion in all 12'61 times the weight of the 
 carbon burnt. 
 
 The heat evolved by the combustion and distributed throughout the quantity of 
 mixed gas is 8000 heat units, and it is sufficient to raise the temperature of a quan- 
 tity of water 8000 times the weight of the carbon burnt one degree, or of a quantity of 
 water equal to the weight of mixed gas resulting from the combustion 635 degrees. 
 
 8000 x 1 = 12-61 x 635. 
 
 Bat since the specific heat of carbonic dioxide, as well as that of nitrogen, or the 
 quantities of heat requisite to raise the temperature of these gases one degree, is much 
 less than the specific heat of water, the increase of temperature of the mixed gas re- 
 sulting from the combustion is proportionately greater than 635. 
 
 The specific heat of carbon dioxide is only 0-2164 as compared with that of water 
 = 1-, and the specific heat of nitrogen is 0*244: hence the quantity of heat requisite 
 to raise the temperature of the mixed gas produced by the combustion of the unit of 
 weight of carbon will be as follows : 
 
 Weight 
 
 Products of relatively Specific Heat . units 
 
 combustion to carbon heat 
 
 burnt 
 
 Carbon dioxide . . 3*67 x -2164 = 0'794J _ -975 heat-units' 
 Nitrogen . . . 8'94 x -244 = 2-181} 
 and the 8000 heat-units will therefore raise the temperature of the mixed gas: 
 
 2689 = -5222. 
 2-975 
 
90 CARBON. 
 
 Under ordinary circumstances, however, the effect produced by burning fuel is 
 considerably less than that indicated by the above calculation ; for by the combination 
 of oxygen with carbon and hydrogen there is a constant tendency to the production of 
 an atmosphere of carbonic dioxide, water vapour, and nitrogen in the furnace ;' and 
 in order to maintain a sufficiently rapid combustion, it is necessary to remove these 
 products of combustion and to supply air in greater proportion than is necessary for 
 the mere oxidation of the carbon and hydrogen, so as to sweep the products of com- 
 bustion out of the furnace, and keep the fuel surrounded with an excess of oxygen. 
 Practically the quantity of air requisite for this purpose, when fuel is burnt with a 
 chimney-draught, amounts to about twice as much as is necessary for converting the 
 combustible constituents of fuel into carbon dioxide and water- vapour. 
 
 In this way the product of combustion throughout which the heat is distributed is 
 doubled in quantity, and there is in consequence a proportionate reduction in the tem- 
 perature produced. The specific heat of atmospheric air is 0-2377, and the quantity 
 requisite for raising the temperature of 11 '61 pounds of air one degree will therefore 
 be 2-7596 11 -61 x -2377; and this quantity, added to the 2-975 in the above cal- 
 culation, gives 57346 heat-units as the quantity of heat requisite for raising the tem- 
 perature of the total mixed gas one degree, and therefore the 8000 heat-units will 
 
 produce an increase of temperature of only 1,394 = - , or half as much as the re- 
 
 5*7346 
 suit previously calculated, .because the quantity of gas to be heated is twice as great. 
 
 It will therefore be evident that the admission into a furnace of more air than is 
 actually requisite will be attended with proportionate waste of heat ; and so far at 
 least as the production of a high temperature is concerned, it is always desirable to 
 effect combustion with the smallest possible amount of air. If air be forced into a 
 furnace by means of a fan or other kind of blowing apparatus, as in a forge, fuel may 
 be burnt rapidly with much less air than when combustion is supported by a chimney- 
 draught. 
 
 The amount of heat evolved in the combustion of hydrogen is much greater than 
 that evolved in the combustion of carbon, but the effect produced as regards increase 
 of temperature is not much greater than in the combustion of carbon, for hydrogen 
 requires for combustion three times as much oxygen as carbon does, and therefore the 
 mixed gas resulting from its combustion amounts to three times as much as in the 
 case of carbon. In the formation of water vapour by the combustion of hydrogen, 
 heat is rendered latent and ineffective for increasing the temperature of the gaseous 
 product. The latent heat of water, or the quantity of heat requisite to convert the 
 unit of weight of water at 100 into steam, is 537 times as much as is requisite to 
 raise the temperature of an equal weight of water one degree. Therefore the quantity 
 of heat that becomes latent in the nine parts of water vapour produced in the com- 
 bustion of hydrogen will be 4833 heat-units = 9 x 537, and this must be deducted 
 from the total heat evolved in order to ascertain the quantity available for producing 
 increase of temperature. Moreover, the specific heat of water vapour the product 
 of combustion is more than double that of carbon dioxide. Consequently the heat 
 evolved in the combustion of hydrogen, amounting to 33,881 heat-units for the unit of 
 weight, is not only distributed through a greater quantity of mixed gas, but part of it 
 becomes latent by the formation of water vapour, and a greater proportion of the re- 
 mainder is required to raise the temperature of the gas. 
 
 The specific heat of water vapour is 0-475 as compared with that of water in the 
 liquid state, and the quantity of heat requisite to raise the temperature of the mixed 
 gas resulting from the combustion of hydrogen will be as follows : 
 
 Weight 
 
 Products of relatively to Specific TT O ,.* ,-+= 
 
 combustion hydrogen heat 
 
 burnt 
 
 Water vapour . . . 9- x 0'475 = 4-2750) 
 
 Nitrogen .... 26'78 x 0-244 = 6-5340 [ = 19-076. 
 
 Surplus air . . . 34'78 x 0-2377 = 8'2672j 
 
 Consequently the available heat, amounting to 29,048 heat-units = 33881 4833, 
 will raise the temperature of the mixed gas only 1,522 = ,7-,- 
 
 This comparison of the effects produced by carbon and hydrogen serves to illustrate 
 the influence exercised .by the presence of water vapour in the products of combustion 
 upon the efficacy of fuel, so far as regards the production of high temperature. When 
 the water vapour is formed either from water actually existing in materials used as 
 fuel or from hydrogen and oxygen that do not evolve heat by their combination, as is 
 the case when wood or materials of similar composition are burnt as fuel, its presence 
 
SMOKE AND SOOT. 91 
 
 is especially disadvantageous, since its influence in reducing the temperature of com- 
 bustion is not compensated for by the large amount of heat evolved in the combustion 
 of hydrogen. 
 
 It is for this reason that the practice of charring or carbonisation has been adopted 
 whenever materials such as wood have to be used as fuel for producing high tem- 
 peratures. In charring any kind of fuel the whole of the water that it actually contains 
 is separated, as well as that corresponding to, and capable of being produced by, the 
 oxygen in the material. At the same time some of the carbon is volatilised partly in 
 the state of carbonic oxide and dioxide, partly also in the state of hydrocarbon com- 
 pounds. But though carbonisation always involves absolute loss of some portion of 
 heat-producing material, and though in the case of wood it furnishes, in the form of 
 charcoal, little more than one-half of the carbon existing in the wood, the practice is 
 advantageous on account of the greater efficacy of the carbonaceous product obtained. 
 
 The same principle holds good in regard to other materials besides wood, though 
 the advantage gained, so far as removal of water is concerned, is in this case only 
 proportionate to the amount of oxygen in the materials. There are, however, other 
 effects produced by the carbonisation of some materials which are equally, if not more, 
 beneficial as regards their applicability as fuel. 
 
 In burning certain kinds of raw coal and other materials, a considerable portion of 
 the carbon they contain is volatilised in the form of hydrocarbon compounds. Such 
 materials burn with flame, and for some purposes, such as the heating of steam boilers, 
 this character is to a certain extent ' advantageous. But when the amount of volati- 
 li sable substance is large, it gives rise to such copious evolution of highly carburetted 
 gas and vapour that complete combustion of the fuel is scarcely possible. In many 
 cases where fuel has to be burnt rapidly, as in steam-boiler furnaces, the hot carbona- 
 ceous gases are swept away towards the chimney before being burnt, and as their 
 temperature is reduced by contact with the boiler flues, the unoxidised carbon they 
 contain is deposited in the form of soot and smoke. The tendency to the production 
 of soot and smoke in this way is proportionate to the amount of volatilisable carbona- 
 ceous substance in the material burnt, and to the amount of carbon in the vapour 
 produced. Besides the waste of heating power resulting from the production of soot 
 and smoke, there are manifold other in conveniences attending the use of such materials 
 as fuel, and for these reasons it is often more advantageous to carbonise them than to 
 use them in the raw state. Moreover, caking coal, which undergoes a kind of im- 
 perfect fusion when heated, and becomes pasty while decomposing, is on this account 
 unsuitable for some metallurgical operations until, by the process of carbonisation, it 
 is converted into hard coke that will burn without softening or volatilising, and be 
 more capable of supporting the superincumbent weight of large masses of heavy 
 material. 
 
 The extent to which volatilisation of carbonaceous substance takes place in carbon- 
 ising different materials depends very much upon their nature, and likewise upon the 
 mode in which the operation is conducted. As a rule the amount of carbonaceous 
 residue obtainable from any given material is greatest when the carbonisation is con- 
 ducted slowly. In the case of wood the difference between the result of rapid and 
 slow carbonisation may amount to as much as 9 or 10 per cent, of the wood carbonised. 
 In carbonising coal the difference is not so great, and in a general way the amount of 
 coke obtainable depends more upon the particular character of the coal. 
 
 In the foregoing considerations it has been assumed that in the use of any material 
 as fuel the whole of its combustible constituents are completely converted into carbonic 
 acid and water vapour, and the calculated effects express the highest capabilities of 
 fuel as compared with pure carbon and when burnt under the most favourable con- 
 ditions. 
 
SULPHUR. 
 
 SYMBOL S. ATOMIC WEIGHT 32. 
 
 History. This substance has been known from the earliest times under the 
 name of brimstone (from Brennestein, the burning stone). Its elementary nature was 
 not recognised until the time of Lavoisier. 
 
 Occurrence. Sulphur is found abundantly in the free state, and in chemical 
 combination with other substances it occurs in still larger quantities. 
 
 In the free state sulphur is chiefly found in volcanic districts, where, amongst other 
 modes of formation, it is often produced by the action of sulphurous oxide upon 
 sulphuretted hydrogen, both of which substances occur in volcanic exhalations. The 
 decomposition takes place according to the equation : 
 
 S0 2 + 2H 2 S = 2H 2 + 3S. 
 
 Sulphur is also eliminated when sulphuretted hydrogen gas comes into contact with 
 water vapour and a small quantity of air at a high temperature ; it is also set free by 
 the decomposition of the higher metallic sulphides, which give up a portion of their 
 sulphur when heated. The sulphur thus given off in the state of vapour con- 
 denses in the form of a moist mud, and gives rise to beds of sulphur, such as those 
 occurring in Sicily, Poland, etc. Sulphur is also produced by the reduction that sul- 
 phates (especially gypsum) undergo in contact with decaying vegetable remains. The 
 largest deposits of native sulphur occur in Sicily, where entire beds of rock, generally 
 limestone or blue clay, are found highly impregnated with it. Sulphur is also found 
 in the native state at Urbino Eeggio in Italy, in Croatia, near Liineburg in Poland, on 
 the shores of the Bed Sea, and in smaller quantities in many other places. It occurs 
 likewise, in the volcanic exhalations of Vesuvius and Etna, also in Iceland, in the 
 Lipari Isles, and in the Solfatara of Naples and Tuscany. 
 
 Sulphur exists in various states of chemical combination with a very large number 
 of metals : iron pyrites, copper pyrites, galena, and blende being the most frequent 
 among the compounds of sulphur with metals. It exists also in the form of sulphates, 
 of which the most abundant are gypsum, Epsom salts, heavy spar, and copperas. 
 Free sulphuric acid has been detected among the products of volcanic activity. 
 Mineral water frequently contains sulphur as sulphuretted hydrogen and as sulphides. 
 
 Lastly, sulphur exists very extensively in the organised products of the vegetable 
 and animal kingdom, being found in the ethereal oils of mustard, horse-radish, onions, 
 etc. ; also in albumen, gluten, and casein, as well as in hair and wool, etc. 
 
 Characters. At the ordinary temperature sulphur is solid, and of a pale yellow 
 colour. At a temperature of 50 it becomes almost colourless. When rubbed, it 
 emits a peculiar odour ; it is brittle, a bad conductor of electricity and of heat, and has 
 a specific gravity of 2-050. 
 
 Sulphur melts at 114'5, exhibiting very peculiar phenomena when heated above 
 that temperature, passing gradually from the condition of a pale yellow liquid into a 
 viscous and dark coloured state, until at 250-260 it becomes quite thick and almost 
 black. Heated still further, it again becomes liquid, beginning to boil at a tempera- 
 ture of 420, and being converted into a reddish brown vapour, the specific gravity of 
 which relatively to air is 6 '6 17 and its density as compared with hydrogen 96 : it is 
 only at a temperature of 1000 that sulphur vapour acquires its normal density of 32 
 as compared with hydrogen. 
 
 If sulphur heated to 350 or 400 be suddenly cooled by pouring it in a thin stream 
 into cold water, it forms a soft brownish mass, which may be kneaded like dough, and 
 has in this condition a specific gravity of only T957 ; after a time it passes again 
 into the ordinary pale yellow brittle state. When a mass of melted sulphur is allowed 
 to cool, it crystallises in long prismatic needles, which after a time are converted 
 into octahedra, the ordinary form in which sulphur crystallises. When melted sulphur 
 is cooled quickly, it forms a crystalline mass called roll sulphur. When sulphur 
 vapour is rapidly condensed in chambers containing cold air, it forms a finely 
 divided yellow crystalline powder, and in this state is called flowers of sulphur. 
 
CHARACTERS OF SULPHUR. 
 
 93 
 
 Milk of sulphur consists of sulphur in an extremely fine state of division, as it is 
 precipitated from a solution of alkaline sulphides Ly means of acids. 
 
 Sulphur is insoluble in water, and sparingly soluble in alcohol, ether, or solution of 
 ammonia ; it is more easily dissolved by fat oils and by oil of turpentine. The best 
 solvents for sulphur are carbon disulphide, chloride of sulphur, and ethyl sulphide. 
 The solubility of sulphur in various solvents is shown in the following table : 
 
 100 parts 
 
 Dissolve the following parts by weight of sulphur 
 
 At 100 
 
 At 16 
 
 Of carbon disulphide . 
 light coal oil . 
 benzol ..... 
 oil of turpentine . 
 petroleum .... 
 carbolic acid 
 ether 
 absolute alcohol 
 
 73-46 
 26-98 
 17-04 
 16-16 
 10-56 
 5-47 
 0-54 
 0-42 
 
 38-70 
 1-51 
 1-79 
 1-30 
 2-77 
 0-66 (at 35) 
 0-18 
 0'12 
 
 Sulphur burns in the air with a blue flame. The product of combustion is sul- 
 phurous oxide, to which the unpleasant smell of burning sulphur is due. The process 
 is one of simple oxidation, the sulphur combining with its own weight of oxygen : 
 
 S 
 32 
 
 20 
 32 
 
 S0 2 
 64 
 
 By combustion, sulphur yields 2221 units of heat, or less than an equal quantity 
 of charcoal or coal. It is oxidised slowly when heated with nitric acid, and more 
 rapidly when melted with nitrates. 
 
 In its chemical relations sulphur closely resembles oxygen, and many of the com- 
 pounds of sulphur correspond with those of oxygen. Sulphur, like oxygen, is 
 bivalent. It combines directly with hydrogen, chlorine, carbon, and some other 
 elementary substances under the influence of a high temperature. Sulphur is also 
 dissolved when heated with solutions of basic hydrates, with formation of sulphides. 
 
 Sulphur combines with most metals in several proportions ; but combination takes 
 place only at a high temperature. In the state of vapour sulphur combines with 
 many metals with considerable evolution of heat and light. 
 
 Preparation. Sulphur as it occurs naturally is always mixed with earthy 
 material, stones, etc., and is separated from them by melting. Sulphur is also 
 obtained from pyrites, a mineral consisting chiefly of iron disulphide, which is de- 
 composed by heat with separation of one-third of its sulphur. 
 
 3FeS 2 - Fe 3 S 4 + 2S. 
 
 Sulphur is also obtained as a by-product in roasting copper ores, and a considerable 
 quantity is extracted from the ' soda waste ' obtained in the manufacture of soda, as 
 well as from the ferric hydrate used for purifying coal gas. 
 
 EXTRACTION OF NATIVE SULPHUR. Native sulphur is obtained at a number of 
 places in Sicily ; but there are only about fifty places where the works are at all ex- 
 tensive. The most important sources are situated in the provinces of Caltanizetta, 
 Girgenti, Catania, and Palermo. Bad roads, want of capital, imperfect methods of 
 extracting and working the ores, have so far prevented the utilisation of these abun- 
 dant deposits of sulphur, that it is often found more profitable to use pyrites as a 
 source of sulphur. 
 
 The sulphur deposits in Sicily are worked very imperfectly. _ Steam-power is 
 seldom employed for hauling up the excavated material, which is in most cases 
 carried up from the mines in baskets by boys. The depth of the mines is inconsider- 
 able ; generally about 60 feet, and seldom as much as 100 feet. 
 
 On the shores of the Eed Sea, in the neighbourhood of Suez, there are two beds or 
 deposits of sulphur of comparatively pure quality, viz., Djemah and Eanga. At the 
 first-mentioned place, a large mass of sulphur rises above the sand in the form of a 
 hill 600 feet in height. This deposit has of late been worked by blasting, as in an 
 ordinary stone quarry. The sulphur found at Eanga does not lie so near the surface 
 as is the case at Djemah; it is, however, lighter coloured and purer. 
 
 Extraction of raw Sulphur in Kilns (calcarelty.Fig. 28 represents a kiln, called 
 calcarelle, which was universally in use up to 1851. It has the shape of an ordinary 
 lime kiln, and is charged in the same way. Large lumps of earthy sulphur ore are 
 
94 
 
 SULPHUR. 
 
 built up in the form of an arch at the bottom of the kiln, and the space above 
 this arch is filled in with pieces continually decreasing in size, the top being covered 
 
 with fine ore dust, and lastly with straw. Either 
 the straw is set on fire, or the sulphur is ignited below, 
 and a portion of it burns in either case; but the 
 greater part is melted by the "heat, and trickles down 
 into the lower part of the kiln, flowing out from the 
 opening (g~) into a vessel (A) beneath, in which it 
 solidifies. As it is necessary that a part of the 
 sulphur should be burnt, in order to heat the whole 
 mass, the kiln is furnished with lateral openings 
 (///), for admitting the necessary supply of air. 
 
 Kilns of this kind hold about 4 tons of ore ; 
 they yield only from 8 to 10 per cent, of sulphur 
 from ore containing 30 per cent., or about one-third 
 of the sulphur contained in the ore. 
 
 This method of refining sulphur has the disad- 
 vantage that a great deal of sulphur is lost, and large 
 . 28. quantities of sulphurous acid are produced, which act 
 
 very injuriously upon the surrounding vegetation. 
 
 Extraction in Stacks (calcaroni). This method of extracting sulphur has an 
 advantage over that just described, because less sulphurous acid is produced, and 
 consequently less sulphur is lost. The sulphur ore is built up in stacks on a sloping 
 hearth, and in the interior of the heap vertical spaces are left, open above, and capable 
 of being covered with slabs of stone. Bundles of hay, which have been dipped in 
 melted sulphur, are thrown into these openings, and set fire to, for the purpose of 
 firing the entire heap. Twelve hours after the introduction of the burning bundles, 
 the openings are closed with the stone slabs, and the whole heap or stack is covered 
 with a layer of clay, earth, etc. At the lowest part of the sloping hearth of the 
 stack there is a tap-hole, which is closed with a clay plug, so that all the melted 
 sulphur flowing down from the sloping hearth collects at that point. This tap-hole 
 is opened at intervals, and the sulphur run off into suitable vessels. 
 
 Small stacks are sometimes made containing from 3500 to 5000 cubic feet, but 
 larger ones measuring 30,000 to 35,000 cubic feet are preferable. A stack of the 
 latter size burns about two months. 
 
 By means of the apparatus of Emile and Pierre Thomas, figs. 29 and 30, the 
 sulphur ore is rapidly heated to 130; and if the operation be repeated ten times a 
 
 FIG. 29. 
 
 day, as much ore can be worked up in a comparatively small space, without loss of 
 sulphur and formation of sulphurous acid, as in a calcarone of 14,000 cubic feet 
 capacity. The sheet-iron cylinder (A), about 3 feet in diameter, contains a tram- 
 way (rr), upon which a truck laden with ore can be pushed over the vertical 
 cylinder (D). After running in the truck, the cylinder (A) is hermetically closed, and 
 steam, having a tension of from 4 to 5 atmospheres, is passed through the pipe (t t), 
 whence it escapes in fine jets, through a number of small holes. By opening the 
 cock (a), the air contained in the apparatus at the beginning of the operation is driven 
 out, attd when that is closed any remaining air, together with the steam, is allowed 
 only a narrow exit by the cock (F). In case a stoppage should occur at F, the discharge 
 can take place at F'. The temperature in the interior of the cylinder rises rapidly to 
 130, the pressure being indicated by the gauge (s). The sulphur molts and flows 
 through the perforated sides of the truck into the conical leaden vessel (D') underneath 
 
DISTILLATION OF SULPHUR. 
 
 95 
 
 (fig. 30). Within an hour and a half the operation is completed, and the steam is 
 transferred from the first cylinder, through the cock v, into a second cylinder, from 
 which it expels the air, and at the same time serves to heat it. The receiver'^ D), 
 furnished with wheels, being then detached and let down upon a tramway, placed at 
 no great distance beneath, is run into the magazine, where the leaden cone D' is 
 emptied of its contents. The trucks, containing the exhausted residues, are then 
 drawn out, and recharged with fresh ore. 
 
 At many places where the sulphur ore is rich, the sulphur is simply melted in 
 pans (B, fig. 31), made of cast iron, the mass being heated to 120 or 150. In this 
 
 FIG. 30. 
 
 FIG. 32. 
 
 case, a rise of temperature to 250 must be avoided, for at that temperature sulphur 
 becomes thick and viscous. After the impurities have been deposited, the sulphur is 
 removed by means of the ladle (c), and poured into a vessel ready at hand, made of 
 wood or sheet iron. 
 
 The earthy residues, deposited from the molten sulphur, are sometimes worked in 
 another way for the further extraction of sulphur. 
 
 Extraction by Distillation. The distilling apparatus admits of the working of an 
 ore containing only about 12 per cent, of sulphur. This apparatus consists of large 
 crucibles (A A, fig. 32), of which from 12 to 16, in a double row, stand together in a 
 furnace in such a way that between the two rows there is room for fuel. Each crucible is 
 charged with 50 pounds of ore, and the mouth of the crucible is closed with slabs of 
 fire clay, smeared with loam. A delivery pipe conducts the sulphur vapour into a 
 second crucible or receiver (B), where it condenses, the liquid sulphur flowing through 
 the opening (c) into the vessel (D) beneath. Twelve crucibles, which contain together 
 600 pounds of raw material, require for fuel about 140 pounds of wood, and they yield 
 in a single operation, which lasts 7 hours, about 192 pounds of sulphur. 
 
 Although in this way distilled sulphur is obtained, it is never quite pure, since the 
 boiling of the sulphur causes impurities to be carried over with the sulphur vapour. 
 This sort of raw sulphur contains from 3 to 10 per cent, of impurity. 
 
 The amount of impurity in sulphur may be easily estimated. A small weighed 
 portion is submitted to distillation, and the weight of the distilled portion, consisting 
 of pure sulphur, or that of the residue, is ascertained, or both. 
 
 The production of raw sulphur in Sicily is very large, in spite of its imperfections. 
 According to Payen, Sicily exports annually about 200,000 tons of sulphur. 
 
 The raw sulphur obtained by any of the operations described above is generally 
 far from being pure, as will be seen by the following analyses : 
 
96 
 
 SULPHUR. 
 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 Sulphur (sol. in CS.,) . 
 
 90-1 
 
 96-2 
 
 91-3 
 
 90-0 
 
 88-7 
 
 Carbonaceous material . 
 
 ro 
 
 0-5 
 
 0-7 
 
 1-1 
 
 1*0 
 
 Sulphur (insol. in CS,) . 
 
 2-0 
 
 
 
 1-5 
 
 2-1 
 
 1-7 
 
 Siliceous substances 
 
 2-3 
 
 1-5 
 
 3-3 
 
 2-8 
 
 5-5 
 
 Limestone (and celestine) 
 
 4-1 
 
 1-8 
 
 2-5 
 
 3-0 
 
 2-1 
 
 Loss 
 
 0-5 
 
 
 
 0-7 
 
 1-0 
 
 0-3 
 
 Refining. The object of refining raw sulphur is the removal of earthy substances 
 mechanically intermixed with it, as well as those bodies which, like sulphur itself, are 
 volatile. The separation of these latter impurities, however, is very difficult, and is 
 never completely effected. 
 
 These volatile substances are selenium and arsenic, the latter being in many cases 
 very injurious. A further object in refining sulphur is to give it a marketable form. 
 The most common forms in which sulphur occurs commercially are roll sulphur and 
 the fine sublimate called flowers of sulphur. 
 
 For the purpose of purifying sulphur, an apparatus was formerly employed similar 
 to that represented "by fig. 31 (see p. 95). The raw sulphur was simply re-melted 
 therein, and ladled out after the impurities had subsided. According to an improved 
 method, it was distilled; but the product obtained was still impure. At the present 
 time, both operations of re-melting and distillation are combined, and conducted in a 
 single apparatus. By this means, the sulphur can be obtained either in the form of 
 roll sulphur, or as flowers of sulphur. 
 
 An apparatus of this kind, employed in the neighbourhood of Marseilles, whence 
 this branch of industry started, is represented by fig. 33. It consists of two iron 
 
 FIG. 33. 
 
 cylinders (B) about 5 feet in length, and If feet in diameter, which can be closed in 
 front by means of an iron plate (B') 3 feet in length. The whole apparatus is set in 
 fire brick. Underneath the cylinder (B) is a fire-place (A), suitable for firing either 
 with coal, wood, or turf. The flame plays first under the cylinder (B), and then, by 
 means of the flue (c c), under the vessel (D), in which the sulphur is melted. This 
 melting vessel, 3 feet in diameter, and 3 feet in height, can be shut by means of a 
 lid, and communicates with the cylinder (B) by means of a cock and the pipe (F). 
 The cylinders (B) open into the brick chamber (G) through connecting pieces (B"). 
 By means of a slide (i), moved by the rod (i'), the aperture at B" can be opened and 
 shut at pleasure. The brick chamber is about 23 feet long, 16 feet deep, and 7 feet 
 high, having a capacity of about 2500 cubic feet. At one end is a door (Q), made of 
 sheet iron, covered with lead, and externally closed with light brickwork serving to 
 
REFINING OF SULPHUR. 97 
 
 admit a workman into the chamber. At the lower part of one side of the chamber is 
 an opening, closed by a cast-iron plate (j), having in it a hole inch in diameter. A 
 moveable rod (K) fits into this hole, so as not only to shut it, but also to allow of 
 the size of the aperture being regulated. In order to have more command over the 
 movement of the rod, there is a screw attached to it, which works in a cross piece, 
 built in on both sides. The melted sulphur, flowing through the opening at (j), falls 
 first on an inclined plate of cast iron, and then into the vessel (L), below which is a 
 furnace. Near this furnace is a revolving tube (M), divided by partitions into six or 
 eight parts. N is a stand for holding the sulphur sticks. 
 
 This combined process of purifying raw sulphur by re-melting and distilling has 
 not yet been introduced in many places ; but atKosenau, in Silesia, the raw sulphur is 
 heated in iron cauldrons, and the vapour given off is condensed in clay receivers. 
 
 At Alsattel, in Bohemia, sulphur is distilled from iron retorts, and collected in 
 receivers of the same metal. 
 
 Eoll Sulphur. When the apparatus, represented by fig. 33, is employed for the 
 manufacture of roll sulphur, the following method is adopted. For the first operation, 
 both the cylinders (B) are charged each with 6 cwts. of raw sulphur, as dry and free 
 from impurity as possible, and closed by means of the luted lid (B'). The two retorts 
 are not heated at once, but one after the other ; the second one being heated when the 
 distillation in the first is half completed. The hot air from the furnace passes through 
 c c to the cauldron (D), which is charged with about | of a ton of sulphur. Here the 
 sulphur is melted, and undergoes a preparatory purification, the water evaporating, 
 while the lighter mechanical impurities, such as wood, etc., float on the surface, and 
 the heavier admixtures, such as sand, pyrites, limestone, etc., sink to the bottom. 
 
 As soon as the distillation in the first cylinder is completed, melted sulphur from 
 D is allowed to flow through a pipe (r) into the retort (B), thus charging it afresh. By 
 the sinking of the level in the cauldron (D), the workman judges when enough has run 
 out for a charge. The cock is then closed, the pipe removed, and the hole in the 
 lid (B'), through which it passed, is closed with a plug of burnt earthenware. 
 
 During the operation, the hot expanded air escapes through a safety-valve made of 
 metal plate, kept nearly in a state of equilibrium by means of a weight, so that any 
 pressure likely to damage the walls is prevented. 
 
 Each distillation lasts eight hours, and every alternate four hours one of the 
 cylinders is charged. In this way 1| tons of raw sulphur are distilled from the six 
 charges worked in twenty-four hours. By this continuous distillation, the chamber 
 is kept continually at a temperature higher than the melting-point of sulphur ; so that 
 sulphur condenses there in the liquid form. As soon as the level of melted sulphur in 
 the chamber has risen to the height of twelve or eighteen centimetres, the cock (K) is 
 opened, and the sulphur is allowed to flow into the vessel (L), which has been previously 
 heated ; while a workman ladles it continually into the moulds (p p'), made of boxwood 
 (which are shown on a magnified scale in fig. 33). 
 
 In order that the work of casting may be continued without interruption, a child 
 takes the filled and cooled moulds from the tub (M and M', fig. 33), empties them, 
 and hands them to the caster, who fills them again, and places them in the partitions 
 containing water. In this manner one division after the other is filled, and during 
 the time required for cooling down others are filled in the same manner. 
 
 In order to remove the sticks of sulphur from the moulds, the somewhat conical 
 plug at the bottom of the mould is pushed upwards, whereupon the sulphur sticks, 
 which have undergone some contraction in cooling, easily fall out upon inverting the 
 mould. They are piled upon the stand (N), and are there thoroughly cooled down. 
 
 The sulphur, when freshly cast, is semi-transparent, of a colour varying from 
 yellow to orange, but it gradually becomes opaque and assumes the ordinary light 
 yellow colour. 
 
 Eoll sulphur is generally exported in casks of soft wood, lined with white paper. 
 
 Flowers of Sulphur. When the vapour of sulphur is rapidly cooled down to a 
 temperature below the melting-point of sulphur, it condenses in the form of a powder, 
 consisting of small microscopical crystals called flowers of sulph ur. 
 
 In preparing flowers of sulphur the apparatus employed is the same as that used 
 in the production of roll sulphur (fig. 33). The temperature of the chamber, 
 however, must not rise higher than 111, so as to avoid the melting -of the sulphur. 
 In order to accomplish this, only two distillations are carried out within twenty-four 
 hoxirs, and the charge for each distillation is only 3 cwts. of raw sulphur. With 
 such slow distillation the temperature of the chamber never reaches the melting point 
 of sulphur, and the flowers of sulphur retain their form. 
 
 As soon as the layer of condensed flowers of sulphur has attained a height of 20 or 
 24 inches the door is opened and the sulphur raked out. 
 
 H 
 
98 
 
 SULPHUR. 
 
 The dry flowers of sulphur are packed either in casks lined with paper or in 
 sacks of stout linen. 
 
 It is evident that flowers of sulphur must always have a slightly higher price than 
 roll sulphur, seeing that the preparation requires more time. 
 
 The fine division of flowers of sulphur augments the inflammability of the material, 
 and renders it more suitable for mixing than roll sulphur. But it is less pure than roll 
 sulphur, containing more moisture, together with a small quantity of sulphuric and 
 sulphurous acids, and even traces of hydrocarbons. Flowers of sulphur may, however, 
 be easily purified by washing with water, and drying. 
 
 On account of its greater purity, roll sulphur is preferred even in the manufacture 
 of gunpowder, for which purpose it has first of all to be powdered. 
 
 The use of flowers of sulphur as a remedy for the disease of the vine has considerably 
 increased of late, and it has caused experiments to be, made with the object of avoid- 
 ing loss and other disadvantages in the preparation. Favourable results were 
 obtained by enlarging the surface of the distilling apparatus, and the cubic contents of 
 the condensing chambers. 
 
 The improved apparatus of Dujardin and Bailly is represented by figs. 34 and 35. 
 
 FIG. 34. 
 
 FIG. 35. 
 
 The cast-iron distillatory vessel (K) is considerably expanded in the middle, and it 
 ends in two contracted necks, bent upwards, one of them being generally closed with 
 a lid (B), while the other conducts the sulphur vapour into the chamber. 
 
 The arrangement of the fire-place (i i) protects the distilling vessel from direct con- 
 tact with the flame, and from becoming too strongly heated. The gases of combustion 
 play first round the distilling vessel (E), and pass through a flue (j) under the cauldron 
 (A) in which the raw sulphur is melted, or into the chimney, according to the position 
 of the damper (K), and the heavy mechanical admixtures are deposited in the annular 
 gutters at c. The valve (5) being opened, the melted sulphur flows through a pipe (d) 
 into the distilling vessel, and the charging of the distilling vessel is effected without 
 the use of the movable pipe necessary in the apparatus previously described. 
 
 The slide (FF') serves to interrupt the communication of the distilling vessel with 
 the chamber, so that the latter may be entered for the purpose of removing its contents. 
 This chamber differs only in size from that of the older system ; it is 40 feet long, 
 33 feet wide, and 16 feet high, thus having a capacity of more than 20,000 cubic feet. 
 
 The distilling vessel (E) has sectionally (fig. 34) a height of 21^ inches and a 
 breadth of 32 inches. Its length is 6 feet 4 inches. Accordingly, this distilling 
 vessel is much larger than the old one, and can receive at each charge f of a ton of 
 sulphur. With this apparatus, the rate of production is doubled, and the cost of 
 working is less than with the old one. 
 
 A considerable improvement of this apparatus consists in giving the distilling 
 vessel an elliptical shape, and conducting the hot air from the furnace, first over the 
 upper part of the distilling vessel, which must be surrounded with fire clay, and then 
 under it into the flue, either directly or after passing underneath a cauldron for melt- 
 ing sulphur. 
 
 Figs. 36 and 37 represent two vertical sections, and fig. 38 a horizontal section 
 of the apparatus. BB". roasting and fire room; c"c, flue through which the hot air 
 passes, either direct into the chimney, or is conducted underneath a cauldron (E) ; A is 
 the distilling vessel, having a diameter of 5;V feet and a depth of 18 inches. The 
 mouth, 9 in. wide and 11 in. deep, is closed with a lid by means of a cross bar. The 
 pipe of the distilling apparatus, which leads into the chamber, is 2^ feet in width and 
 17 in. deep. The pipe (H), through which the melted sulphur flows into tho distilling 
 vessel, has8i in. diameter ; the elliptical ly-shapod preparatory heating cauldron (E) has 
 
SULPHUR FROM PYRITES. 
 
 99 
 
 at its widest part a diameter of 3 feet ; and at its narrowest a diameter of 26 in 
 and a depth of 3* feet. 
 
 If a chamber of 10,000 cubic feet capacity is connected with an apparatus of the 
 kind for refining raw sulphur, where there are two distilling vessels, each of which 
 
 FIG. 36. 
 
 FIG. 37. 
 
 can be charged with 12 cwts. of raw sulphur every twenty-four hours, it is possible 
 to work up 4f tons in this space of time. If, however, a chamber of the same capacity 
 be adapted for the production of flowers of 
 sulphur, nearly 2^- tons of manufactured pro- 
 duct will be obtained in twenty-four hours. 
 
 Considering the causes which have led to 
 the various changes in the refining apparatus 
 in use since 1825 (the date of the introduction 
 of the process of distillation by Michel in 
 Marseilles), it is obvious that all improvements 
 aimed at diminishing the depth of the distilling 
 vessel, increasing the surface of the liquid sul- 
 phur, and raising the temperature of the upper 
 part of the distilling vessel. Deep boilers were 
 changed for cylinders, the latter for slightly 
 curved retorts ; and finally an elliptical dis- 
 tilling apparatus has been employed. These 
 alterations are closely connected with the cir- FIG. 38. 
 
 cumstance that the latent heat of sulphur vapour is so inconsiderable that in the older 
 forms of apparatus a large portion of the sulphur vapour was condensed upon the 
 surface of the boiling sulphur, and falling back into it had to be evaporated again. 
 In this way there was much loss of time and fuel, which has been avoided as far as 
 possible in the newer constructions. 
 
 EXTRACTION FROM PYRITES. The extraction of sulphur from iron pyrites is advan- 
 tageous only in districts where wages are low, and fuel and ore are both cheap and 
 abundant. The process was originally introduced into France by Dartigues, at the 
 time of the French ^Revolution, when France was no longer able to obtain sulphur from 
 Sicily. 
 
 The composition of iron pyrites is represented by the formula FeS 2 , and it contains 
 53*33 per cent, of sulphur, of which about one-half, or 26'66 per cent., is capable of 
 being driven off by strongly heating the ore. In order, however, to get as much 
 sulphur as this from iron pyrites, it would be necessary to heat it to a temperature 
 high enough to melt the residue, and that would soon destroy the fire-clay cylinders. 
 The iron pyrites is, therefore, only heated enough to drive off from it 13 or 16 per 
 cent, of sulphur, and then the residue, not being fused, can be more easily removed 
 from the retort. 
 
 The operation is conducted in furnaces, in which conical retorts of fire clay are 
 placed in an inclined position in rows over each other. The narrow ends of the 
 retorts project outside the furnace, and communicate with a pipe extending along the 
 front ; the opposite ends also projecting a little beyond the furnace on the other side 
 serve for charging the retorts with pyrites, and can be closed with lids. Upon heat- 
 ing the retorts, the sulphur condenses in the anterior part, and flows into the common 
 condenser. At one time, instead of a common condenser, and in some places it is 
 even now the case, the mouth of each retort was connected with a vessel filled with 
 water into which the sulphur dropped. Each retort is charged with .} cwt. of pyrites. 
 
 H2 
 
100 SULPHUR. 
 
 In some parts of France sulphur is extracted from iron pyrites in shaft furnaces 
 which resemble lime kilns. 
 
 According to Mene, a continuous working kiln, which is in use in Sweden, deserves 
 especial notice. The pyrites is placed in a kiln somewhat like that used in burning 
 lime, but terminating above in a flue, at first inclined, and finally horizontal, where 
 the sulphur is condensed. The kiln charged with pyrites is set fire to with wood 
 and turf, the further heating taking- place at the cost of the burning pyrites itself. 
 In proportion as the exhausted pyrites is removed from a side opening below, fresh 
 pyrites is thrown in from above. By means of this kiln, according to Mene, one half 
 of the sulphur contained in iron pyrites is extracted, while only about one third is ex- 
 tracted when fire-clay retorts are employed. 
 
 It may here be mentioned that it has often of late been attempted, and with 
 partial success, to obtain sulphur from iron pyrites indirectly. For this purpose the 
 iron pyrites is burnt, and the sulphurous acid thus formed is either made to pass over 
 red-hot charcoal, or coke, or it is in some cases reduced by means of sulphuretted 
 hydrogen. In all cases the residue obtained in distilling sulphur from pyrites can 
 be converted by oxidation into ferrous sulphate and worked up for green vitriol either 
 directly or after a supplementary roasting. 
 
 In Sweden, and in the Harz, sulphur is obtained as a by-product in roasting copper 
 pyrites, or ores containing galena. 
 
 SULPHUR FROM SODA WASTK. After attempts had been made for a long time to 
 utilise soda waste, which contains a considerable amount of sulphur, and obtain the 
 sulphur from it, success was at last achieved in 1863 by Mond, and shortly after hitn 
 by Schaffner, both of whom devised methods which have been employed of late on a 
 large scale (vide ' Soda Manufacture '). 
 
 Schaffners Process. Soda waste contains a compound of calcium sulphide with 
 lime, from which polysulphurets of lime and hyposulphite of lime are formed when 
 such waste is permitted to lie in heaps in the air for a long time. When the mass 
 is lixiviated with water, these lime salts are dissolved. The liquor thus obtained is 
 heated and decomposed with hydrochloric acid, which precipitates part of the sulphur, 
 while another part escapes in the form of sulphurous acid. In order not to lose the 
 sulphurous acid, it is passed into a second vessel containing fresh liquor, and re-acting 
 upon the polysulphurets, the sulphur of both compounds is precipitated at the same 
 time. The precipitated sulphur is washed, and melted under pressure in iron boiloi'.s 
 with water and a little caustic lime, by means of steam, and is then cast into moulds. 
 The sulphur, obtained by this process, has the same degree of purity as roll sulphur. 
 This method of recovering sulphur from alkali-makers' waste is chiefly adopted in 
 Germany ; in this country, as well as in France, the process of Mond has been intro- 
 duced into most large manufactories. This process also depends upon the partial 
 oxidation and precipitation of the sulphur with hydrochloric acid. It differs, how- 
 ever, from the method proposed by Schaffner in practical details. 
 
 Besides these methods, there are a number of others, according to which the 
 sulphur of soda waste is first of all converted in part or entirely into either sulphurous 
 acid or into sulphuretted hydrogen, and is precipitated from these compounds in the 
 iree condition. 
 
 Sulphur has been obtained of late from the by-products of the purification of coal- 
 gas by means of ferric hydrate ; also from sodium sulphide ; and finally from the 
 gases containing sulphurous acid produced in roasting blende. 
 
 Uses. Raw sulphur is employed in the manufacture of sulphuric and sulphurous 
 acids and of sulphuretted hydrogen ; and, generally speaking, nearly all the artificial 
 compounds of sulphur are either directly or indirectly obtained from raw sulphur. 
 
 Refined sulphur is used in the preparation of lucifer matches ; on a large scale in 
 the manufacture of gunpowder and blasting powder, and in pyrotechnics. The use of 
 sulphur for the above purpose is owing to its property of igniting at a temperature of 
 250. 
 
 Owing to the fusibility of sulphur, and its readily assuming the liquid state at a 
 temperature between 111 and 140, sulphur is especially adapted for taking casts of 
 medals, etc. As it easily combines with metals, it is employed in the preparation of a 
 number of metallic sulphides, such as those of mercury (artificial cinnabar), copper, 
 iron, etc. It serves further in the preparation of various lutes. An iron cement, 
 which, owing to the formation of basic ferric sulphate, hardens in contact with the 
 air, is obtained by mixing 100 parts by weight of iron filings with 3, 5, 10, or 20 
 parts by weight of flowers of sulphur, and from 3 to 5 parts by weight of sal-ammoniac, 
 and kneading the mixture with water. This cement is used chiefly for filling in be- 
 tween the joints of steam boilers, for cementing together iron pipes, etc. 
 
 When caoutchouc is treated with sulphur in a state of solution, it absorbs from 
 
tTSES OF SULPHUR. 101 
 
 one to two per cent., yielding vulcanised india-rubber, a very elastic mass, which retains 
 its elasticity at a low temperature, and does not stick like pure caoutchouc. This kind 
 of caoutchouc has recently been extensively employed ; and the branch of industry to 
 which it has given rise will be detailed in a later chapter. 
 
 Coarse linen dipped in melted sulphur becomes coated with it. In this way are 
 prepared the sulphurated or quick matches, used for burning in the inside of moist 
 casks and vats, so as to produce sulphurous acid, which serves for preventing too 
 violent fermentation, or the decomposition of easily decomposable liquids. Thus, for 
 instance, casks intended for the reception of wine or beer are ' sulphured ' before these 
 liquids are put into them. In the same way blood may be preserved, and many 
 boiled leguminous plants. Sulphuring with burning sulphur serves also to destroy 
 noxious insects in feathers or corn ; to remove fruit stains from linen ; and on a large 
 scale for bleaching silk, wool, gut strings, straw hats, isinglass, sponge, etc. Bleaching 
 with the gas of burning sulphur or sulphurous acid is conducted in well-closed 
 round chambers, about 16 feet high, and with a capacity of about 3600 cubic feet; 
 they are entirely filled with the articles that are to undergo the bleaching operation. 
 These articles, previously washed with soda and soap and water, and pressed, are 
 then in a still moist condition hung out in rows upon wooden supports in the bleaching 
 chamber, in such a manner that a space of about an inch is left between each row. 
 Sulphur sufficient to yield the sulphurous acid required is then burnt in all four corners 
 of the chamber. 
 
 Chimney fires can be extinguished by means of sulphur. Sulphur is thrown upon 
 the fire and the draught cut off, and thus the chimney gets filled with gaseous sulphu- 
 rous acid which extinguishes the fire. Powders for extinguishing fire also contain 
 sulphur, which, owing to the formation of sulphurous acid, suffocates the flame. 
 
 According to Heeren, Bucher's powder for extinguishing fire has the following 
 percentage composition : 
 
 Nitre . . . . J. [,.-': .&<-" . 66 
 Sulphur . . . .,' ;. ,,',., *...- . 30 . 
 Charcoal . . . , . * ;,- '*,. .- , *; > 4 
 
 A solution of sulphur in linseed oil is used for impregnating gypsum casts, build- 
 ing stones, etc. 
 
 The use of flowers of sulphur as a remedy for the disease of the vine, produced by 
 a peculiar fungus, the O'idium Tucfceri, or Eresiphe, which is especially prevalent in the 
 south of France, has caused a considerable increase in the consumption of this article. 
 The fungus is destroyed by dusting the vines with flowers of sulphur, which operation 
 is performed, 1, before the flowering, 2, during the flowering period, and 3, when the 
 fruit begins to form. In hot-houses, the same effect may be produced by strewing 
 the heating pipes with flowers of sulphur. 
 
 Flowers of sulphur have been found to act equally efficiently in the analogous 
 diseases of the peach tree, the rose tree, and the hop, which are caused by similar 
 fungi. 
 
 In order to distribute the sulphur equally over all the infected parts of the plants, 
 various forms of apparatus have been employed. One of them, which was in general 
 use up to 1856, introduced by a gardener of the name of Groutier, had the form of a 
 
 FIG. 39. 
 
 bellows. Since then, Ouin and Frank have introduced an apparatus, simple in its con- 
 struction, and cheaper, the so-called boitc a houppe (tarsel box), which is represented by 
 figs. 39,40,41 and 42. It consists of a conical tube of tin plate, which, as ng. 4J w>, 
 is filled to one-half with flowers of sulphur, or about one pound. The upper P ortl .a. 
 which forms the characteristic feature of the apparatus, consists of ? oa. 
 
 The lid is furnished with five rows of woollen wick fastened in concentric* 
 metal plate by means of fine wire, and between the rows of wick are concenti. 
 
102 
 
 SULPHUK. 
 
 openings, as shown by fig. 40. Inside the tube, at about three-fourths of its length, 
 there is a cross of fine bands of tin-plate which serves to loosen any sulphur that mav 
 have got conglomerated together. 
 
 Fm. 40. 
 
 FIG. 41. 
 
 FIG. 42. 
 
 Upon shaking the box, the sulphur passes througn the openings between the rows 
 of wick, and becomes thereby so finely divided, that it covers with a fine dust all parts 
 of the plant operated upon. Not even this fine division of the sulphur would, how- 
 ever, suffice, were it not that a part of it evaporates under the influence of the sun's 
 rays, the volatilised portion settling on other parts of the plant. If a still greater 
 distribution of sulphur be required, wicks of horse-hair are employed in the place of 
 the woollen ones. When the tarsel box is used for dusting the tops of tall vines or 
 trees, it is furnished with a long handle (fig. 39). 
 
 On account of the high price of flowers of sulphur, it has been attempted to make 
 use of powdered sulphur, but it is not at present certain whether this has the same 
 effect. According to Payen, good results have been obtained with flowers of sulphur ; 
 while, on the other hand, vine-dressers often give powdered sulphur the preference, 
 probably, however, on account of its being cheaper. 
 
 Owing to flowers of sulphur being dearer than powdered sulphur, they are often 
 adulterated with the latter, which can, however, be easily detected by means of the 
 microscope. When examined under the microscope, flowers of sulphur, when un- 
 adulterated, are found to consist of small crystals, or groups of crystals ; whereas, 
 when they contain powdered sulphur, this is recognised by its irregular angular struc- 
 ture. Another way of detecting this adulteration is the following. Five grams of 
 the sulphur to be tested are placed together with 25 c.c. of ether in a cylindrical glass 
 
 FIG. 43. 
 
 jar of 25 c.c. capacity, graduated into 100 equal parts, and shaken together, and then 
 allowed to stand quiet for some time. If the flowers of sulphur are pure, the sedi- 
 
COMPOUNDS OF SULPHUR. 103 
 
 ment which is formed after standing occupies a greater volume (50-60 grad.) than is 
 the case when powdered sulphur alone is treated in like manner ; the sediment in the 
 latter case occupying a volume of about 24-40 grad. 
 
 Sulphur may be spared and labour reduced by using a bellows without valve, as 
 constructed by Lavergne, represented by fig. 43. Finely-divided sulphur is intro- 
 duced at c, gets agitated by the inflowing air, and is thrown out again at A each 
 time the bellows is pressed, forming a cloud of sulphur dust. 
 
 By means of this apparatus, a labourer is able to distribute 22 Ibs. of sulphur in 
 7 hoiirs, five times this quantity sufficing for 2 acres of land. As has already been 
 mentioned, the dusting is performed three times, shortly before, during, and shortly 
 after the flowering period. 
 
 The wine must produced from vines that have bt.n sulphured always gives an indi- 
 cation of sulphuretted hydrogen. The sulphi vetted hydrogen, however, disappears 
 during the fermentation, its sulphur becoming converted into sulphate and dissolved. 
 
 Compounds. Sulphur forms with other elementary substances a large number 
 of compounds which are termed sulphides, and as a class they are very analogous to 
 the oxides in their constitution and chemical relations. Only two oxides of sulphur 
 are known, the dioxide or sulphurous oxide S0 2 , and the trioxide or sul- 
 phuric oxide. Both of these substances combine with water, and with basic oxides, 
 forming two series of salts termed sulphi tes and sulphates, the respective hydrogen 
 salts being sulphurous acid H 2 S0 3 and sulphuric acid H 2 S0 4 . 
 
 Besides these oxygen compounds of sulphur there are several other series of ana- 
 logous compounds of sulphur with oxygen and hydrogen or metals. The composition 
 of the hydrogen compounds or acids is given in the following table : 
 
 Hyposulphurous acid H 2 SO., Trithionic acid H 2 S 3 6 
 
 Thiosulphuric acid H,S 2 2 Tetrathionic acid H 2 S 4 4 
 
 Dithionic acid H 2 S 2 O e Pehtathionic acid H 2 S 5 6 
 
 Sulphides are classified like oxides according to the atomic proportions of sulphur 
 they contain, as monosulphides, disulphides, etc. 
 
 The sulphides of the metals are solid substances which are generally insoluble in 
 water, except the sulphides of the alkali metals. Some of them melt more readily 
 than the corresponding oxides ; some are partially and others entirely decomposed by 
 heating, and a few are volatilisable. The sulphides as they occur naturally are often 
 crystalline, brittle, and dark-coloured, and several of them have a metallic lustre. 
 Many of the sulphides are, like oxides, capable of combining together and forming 
 saline compounds termed sulpho-salts, which are analogous to oxy -salts ; the sul- 
 phides of the metalloids having the characters of acid sulphides, and those of the 
 metals having generally the characters of basic sulphides. Thus potassium sulph- 
 senite K 3 AsS 3 corresponds to the oxyarsenite K 3 As0 3 . 
 
 Hydrogen monosulphide H 2 S, commonly called sulphuretted hydrogen, corresponds 
 to water, and it forms compounds with other sulphides, which are called sulphydrates, 
 and are analogous to the oxyhydrates ; as, for instance, potassium sulphydrate KHS, 
 corresponding to the hydrate KHO. 
 
 Many sulphides and sulpho-salts occur naturally as minerals, and are of great 
 technical importance, as the principal sources from which several metals are obtained. 
 
 Carbon disulphide CS 2 , corresponding to carbon dioxide C0 2 , combines with basic 
 sulphides forming salts called sulpho-carbonates, which correspond to carbonates 
 but contain sulphur in place of oxygen : 
 
 Calcium carbonate CaC0 3 
 
 sulpho-carbonate CaCS 3 
 
 Sulphur forms several compounds with phosphorus, iodine, bromine, and chlorine, 
 but the only one of these compounds that is used for industrial purposes is the 
 chloride S,C1 2 . 
 
 SULPHUROUS OXIDE. 
 
 FORMULA S0 2 . MOLECULAR WEIGHT 64. 
 
 History.-This substance, commonly called sulphurous acid, was long known 
 as the gaseous product into which sulphur is converted when it is burnt : but its con 
 position was not ascertained until the latter part of the last century. 
 
 Occurrence. Sulphurous oxide docs not frequently occur naturally ; it is present 
 in the gaseous exhalations of volcanic districts, and more rarely in the wat( 
 mineral springs. 
 
104 
 
 SULPHUR. 
 
 Composition. Sulphurous oxide consists of equal weights of sulphur and oxygen ; 
 it contains its own volume of oxygen and half its volume of gaseous sulphur, the joint 
 volume being reduced one-third in the combination. 
 
 Characters. Sulphurous oxide is at the ordinary temperature a colourless gas 
 having a strong suffocating odour. Its density is 32 relatively to hydrogen, and its 
 specific gravity as compared with air 2'247. It condenses at a temperature of 10 
 to a colourless liquid having a specific gravity of 1-490 as compared with water. 
 When the liquid is evaporated, it absorbs a large quantity of heat, causing a very 
 speedy reduction of the temperature of the surrounding atmosphere. This property of 
 liquid sulphurous oxide is taken advantage of in laboratories for the production of 
 great cold. If, for instance, liquid sulphurous oxide be poured over the bulb of an 
 alcohol thermometer surrounded with cotton wool, the thermometer sinks to 50 or 
 60, while, if a mercury thermometer be xised, the mercury solidifies. Chlorine and 
 ammonia gas may be condensed to liquids by passing them through bulb-shaped 
 tubes, surrounded with cotton wool and kept moist with liquid sulphurous oxide. 
 
 When liquid sulphurous oxide is evaporated under the air-pump, a thermometer 
 placed in it sinks to 80, and the non-volatilised portion is converted into a 
 crystalline solid. 
 
 Sulphurous oxide is soluble in water, the specific gravity of the water increasing in 
 proportion as the gas is absorbed ; consequently the specific gravity of an aqueous 
 solution of sulphurous oxide varies according to the amount of dissolved gas, as shown 
 in the following table by M. Anton : 
 
 Specific Gravity 
 
 ^S*L Specific Gravity 
 
 Percentage of 
 Sulphurous Oxide 
 
 1-046 
 
 9-54 
 
 1-020 
 
 4-77 
 
 1-036 
 
 8-59 
 
 1-016 
 
 3-82 
 
 1-031 
 
 7-63 
 
 1-013 
 
 2-86 
 
 1-027 
 
 6-68 
 
 1-009 
 
 1-90 
 
 1-023 
 
 575 
 
 1-005 
 
 0-95 
 
 At a temperature of water dissolves 68-8 volumes per cent, of sulphurous oxide 
 gas, at 10 51-4 volumes, and at 20 only 36'2 volumes. This difference in the 
 solubility of sulphurous oxide in water at different temperatures has often caused 
 accidents, which have arisen from hermetically-sealed bottles or tubes being filled 
 with a saturated aqueous solution of the gas at some low temperature. When such 
 bottles or tubes are brought into a room at the ordinary temperature, the sulphurous 
 oxide tends to free itself, and the pressure thus exerted is often great enough either to 
 drive out the stopper or to burst the vessel. 
 
 Sulphurous oxide is very useful on account of its action upon nitric acid, which is 
 reduced by it to nitric oxide, a reaction which plays an important part in the 
 manufacture of sulphuric acid (vide Sulphuric Acid). 
 
 Sulphuretted hydrogen and sulphurous oxide mixed together in presence of water 
 undergo a mutual decomposition, water being formed, and sulphur eliminated ; but the 
 decomposition is not complete, and a considerable amount of pentathionic acid is 
 formed, probably according to the following equation : 
 
 10S0 2 
 
 8H 2 + 10S + 2H 2 S 5 O e . 
 
 This decomposition does not take place when the gases come into contact in a dry 
 condition. 
 
 A further very important property of sulphurous oxide is its action on vegetable 
 colours, especially so because the common bleaching agent, chlorine, cannot be used 
 for bleaching nitrogenous substances, since silk, wool, feathers, and straw fabrics are 
 rendered yellow by chlorine, and have therefore to be bleached with sulphurous oxide. 
 
 Preparation. There are various methods of preparing sulphurous oxide, the 
 principal of which consist in burning sulphur or some metallic sulphide, and in the 
 reduction of sulphuric acid. The most important methods are the following : 
 
 BY BURNING SULPHUR. For the preparation of either sulphurous oxide, or of 
 aqueous solutions, or lyes containing sulphurous acid in combination with potassium, 
 sodium or calcium, the apparatus shown in fig. 4-1 (p. 105) may be employed : 
 
PREPARATION OF SULPHUROUS OXIDE. 105 
 
 Sulphur is burnt in a vessel of sheet metal on the hearth of a furnace A. The 
 hot sulphurous oxide passes through a kind of chimney into the condensing tube 
 (B B% and from thence through c into a long leaden vessel (B"), the bottom of which 
 is sloping, and the interior is fitted with partitions (d'd 1 ), in the manner shown in 
 horizontal projection, fig. 45, This receiver is closed with a lid, kept cool by water 
 
 FIG. 44. 
 
 trickling over it. The liquid, consisting either of water or of a solution of potash, soda, 
 or lime, flows from the reservoir (E) into the upper part of the absorption chamber, and 
 from thence into the other divisions successively, escaping eventually through the 
 tube K and the pipe L. The sulphurous oxide, entering at the lowest division, passes 
 in the contrary direction, indicated by the arrows (fig. 45), escaping finally through F, 
 
 FIG. 45. 
 
 which is connected with a vessel (G) filled with moist soda crystals, so as to absorb any 
 free gas. The soda retains the last traces of sulphurous exide, the carbonic acid thus 
 liberated escaping through the tube (j) into a chimney. 
 
 The sodium sulphite thus formed is more soluble than sodium carbonate, conse- 
 quently when the mixture is treated with water it passes through the perforated 
 bottom of the vessel g. and the pipe i into the receiver M. 
 
 When lime is used in the place of soda, the apparatus is fitted with a contrivance for 
 stirring the lime. 
 
 For the preparation of solutions of sulphurous acid in water, Calvert recommends 
 the use of a tower about 40 feet high and 4 feet wide, filled with pieces of pumice, 
 into which the gas is conducted from below, a moderate stream of water being per- 
 mitted to trickle through the pieces of pumice from above. 
 
 For the method of preparing gaseous sulphurous oxide for bleaching purposes, and 
 in the manufacture of sulphuric acid, see p. 101 and the article 'Sulphuric Acid. 
 
106 
 
 SULPHUR. 
 
 BY KEDUCTION OF SULPHURIC ACID. Although this method of preparing sulphur- 
 ous oxide is decidedly more expensive than that just described, it is still sometimes 
 employed. 
 
 The deoxidation of the sulphuric acid is effected by various substances, of which 
 the principal are charcoal, metals, and sulphur. 
 
 By Charcoal. An. apparatus for the reduction of sulphuric acid is represented by 
 fig. 46. It consists of two or three balloons (A), of glass or stoneware, fitted into a 
 furnace, and heated from beneath by means of a sand bath. The balloons are half 
 filled with charcoal and concentrated sulphuric acid, which mixture yields, when 
 heated, carbonic acid, water, and sulphurous oxide, according to the equation : 
 2H 2 S0 4 + C = CO, + 2H 2 + 2S0 2 . 
 
 A small quantity of carbonic oxide is formed in this reaction. 
 
 The larger proportion, however, of the gases consists of carbonic dioxide and sulphur- 
 ous oxide, which are passed through a wide delivery tube into three receivers, similar 
 to Woulfe's bottles in shape and arrangement. These receivers are filled with water 
 to a third or half their height; the first serving to retain any sulphuric acid carried 
 over with the gas, the two others for the absorption of sulphurous oxide. The carbon 
 dioxide escapes into the air through c'. As soon as the water in the receivers is 
 saturated with sulphurous oxide, the solution is drawn off by cocks placed a little 
 above their bottom. The receivers can, of course, be charged with alkaline solutions 
 instead of water, in which case the corresponding sulphites would be formed. 
 
 Eetorts may be advantageously used in the place of balloons for heating the 
 mixture of sulphuric acid and charcoal, being like them filled to one half, and heated 
 in the same way. 
 
 FIG. 46. 
 
 Reduction of Sulphuric Acid by Metals. The preparation of sulphurous oxide by 
 reducing sulphuric acid with metals is chiefly employed on a small scale in chemical 
 laboratories. The most suitable metal for the purpose is copper, which reacts upon 
 sulphuric acid according to the equation: 
 
 2H 2 S0 4 + Cu CuS0 4 + 2H 2 + S0 2 . 
 
 Copper turnings (dirty scraps may also be used) are brought into a capacious glass 
 flask or retort, and covered with from two to three times their weight of concentrated 
 sulphuric acid. The generating vessel being connected by means of glass tubes with 
 a Woulfe's bottle containing water, and this with another vessel containing some 
 liquid for absorbing the sulphurous oxide, the mixture of copper and sulphuric acid 
 is heated gradually over a sand bath up to the boiling point of sulphuric acid. When 
 this point is attained, a development of sulphurous oxide gas begins, which continues 
 so long as undecomposed copper and sulphuric acid are present in the generator. A 
 stronger heat towards the end of the operation is advisable. 
 
 Reduction of Sulphuric Acid by Sulphur. -When six parts of sulphuric acid are 
 heated together with one part of sulphur a very strong development of sulphurous 
 oxide takes place, according to the equation : 
 
 2H 2 S0 4 + S - 3S0 2 + 2H 8 0. 
 
 The reaction is, however, often so violent that for the preparation of sulphurous oxide 
 on a small scale, the' reduction of sulphuric acid by copper is preferable. 
 
 Instead of sulphuric acid, sulphates may be used for preparing sulphurous oxide. 
 Thus, according to M. Stolba, sulphurous oxide in a state of great purity may be ob- 
 tained by heating together four parts of anhydrous ferrous sulphate (green vitriol) 
 and one part of sulphur. 
 
COMPOUNDS OJP SULPHUROUS OXIDE. 107 
 
 Copper sulphate (blue vitriol) may be also employed for preparing sulphurous oxide 
 in the above way. 
 
 MANUFACTUfiE OP SULPHUROUS OXIDE FROM PYRITES. When iron pyrites or other 
 metallic sulphides are heated in contact with air, a process which is technically termed 
 roasting, the sulphur is oxidised to sulphurous oxide (less cften to sulphuric acid) and 
 the metal to its oxide, part of which combines with the acid. The sulphurous oxide set 
 free in this process was formerly allowed to escape into the atmosphere, a plan not 
 only involving waste of a valuable substance, but also at the same time the destruction 
 of all vegetation in the vicinity. This sulphurous oxide is now collected and used 
 for the preparation of sulphuric acid in lead chambers ; some sulphuric acid manu- 
 facturers indeed employing pyrites alone as the source of sulphuric acid. The fol- 
 lowing formula will serve to explain the roasting process : 
 
 2FeS 2 + 110 = Fe 2 3 + 4S0 2 . 
 
 A further method of obtaining sulphurous oxide may be mentioned, which consists 
 in heating to redness, in fire-clay retorts, an intimate mixture of 4 parts of sulphur 
 with 6 parts of manganese peroxide. The decomposition takes place according to the 
 equation : 
 
 2S + Mn0 2 = MnS + S0 2 . 
 
 A small quantity of manganese oxide always remains behind mixed with the sul- 
 phide, which is owing to portions of manganese getting heated to redness without 
 coming into contact with sulphur. 
 
 Sulphurous oxide occurs also as a by-product in a number of industrial operations ; 
 as for instance in the manufacture of glass ; in the preparation of ultramarine, when 
 Glauber's salt is employed ; also in the saponification of soap with sulphuric acid for 
 separating the stearic acid, in burning fuel containing pyrites, etc. 
 
 Uses. Sulphurous oxide is extensively used, its most important application being 
 the manufacture of sulphuric acid. Another important application of sulphurous 
 oxide is in bleaching, especially in the case of silk and woollen goods, which cannot 
 be bleached with chlorine, owing to their being rendered yellow by that substance. 
 
 Compounds. Sulphurous oxide combines chemically with water to form hydro- 
 gen sulphite, H 2 S0 3 , or sulphurous acid; but this compound is readily decom- 
 posed, and upon boiling a solution of sulphurous acid for a short time the whole of 
 the sulphurous oxide is expelled as gas. There is another compound of the gas 
 with water, having a composition represented by the formula H 2 S0 3 8H 2 0, which i? 
 obtainable in the crystallised state by cooling a saturated solution of sulphurous acid tc 
 6, while a current of sulphurous oxide gas is passed through it. 
 
 Sulphurous oxide also combines with basic oxides, forming a series of saline sub- 
 stances called sulphites, some of which, such as the alkaline sulphites, are freely 
 soluble in water, while others, like barium sulphite, are only sparingly soluble. 
 These salts are readily decomposed by hydrochloric acid, with evolution of sulphurous 
 oxide gas ; they also absorb oxygen from the air, and are thus converted into sulphates. 
 
 By passing vapour of nitrogen peroxide into liquid sulphurous oxide there is 
 formed, together with nitrous anhydride, a solid substance having the composition 
 2NO,S 2 7 , according to the following equation : 
 
 2S0 2 + 4N0 2 = 2NO,S 2 7 + N 2 3 . 
 
 This substance melts when heated, and volatilises without decomposition ; it dissolves 
 in concentrated sulphuric acid without change, and with slightly diluted acid it forms 
 a bulky crystalline substance, probably H,NO,S0 4 (vide Sulphuric Oxide, Compounds : 
 and Manufacture of Sulphuric Acid ; Chamber Crystals). 
 
 SULPHUROUS ACID. 
 
 FORMULA H 2 S0 3 . MOLECULAR WEIGHT 82. 
 
 This substance, which exists in the aqueous solution of sulphurous oxide, can be 
 obtained in a crystalline state by passing moist sulphurous oxide gas through a 
 cooled by a freezing mixture, or by cooling a saturated solution to . Ine crystals 
 melt at a temperature a little above 0, and decompose giving off sulphurous oxide 
 gas. Most of the reactions of sulphurous oxide in the presence of moisture are 
 due to sulphurous acid. . , 
 
 In a perfectly dry state, sulphurous acid exerts no action on organic colouring 
 matters, it is therefore necessary in bleaching with this substance to insure the pre- 
 sence of moisture. The way in which the bleaching action takes place is not at 
 
108 SULPHITE. 
 
 present definitely determined, but there must be at any rate two distinct kmas of 
 bleaching action, for there are vegetable colours, which after bleaching with sul- 
 phurous acid, reappear upon treatment with very dilute acids, and again others, 
 which no known re-agent restores. Thus, for instance, the red colouring matter of the 
 rose is completely bleached by sulphurous acid, but reappears upon dipping the rose 
 into very dilute sulphuric acid. On the other hand, the red colouring substance of 
 the beet root, which is also bleached by sulphurous acid, cannot be recovered by any 
 re-agent. In the first case, it is supposed that the bleaching property of the sulphur- 
 ous acid is due to its forming a colourless compound with the colouring matter of the 
 rose, which can be separated again by a weak acid, while in the other case it is sup- 
 posed that the bleaching action of the sulphurous acid is due to a decomposition and 
 reduction of the colouring matter. 
 
 Some vegetable colouring matters, such as chlorophyll, withstand completely the 
 influence of sulphurous acid. 
 
 Sulphurous acid acts as an antiseptic in the case of several organic substances, 
 which property is probably due to its preventing the growth of organic ferments. 
 
 Sulphurous acid oxidises very readily to sulphuric acid, and is on this account a 
 powerful reducing agent. Sulphuric acid is formed in an aqueous solution of sul- 
 phurous acid, exposed to light and air. For this reason, when it is desired to preserve 
 a solution of sulphurous acid for any length of time in a state of purity, the bottles 
 must be completely filled, and kept in a dark place ; it is further necessary to expel, 
 by boiling, the air dissolved in the water, before dissolving the gas. 
 
 Sulphurous acid readily deprives substances of oxygen. Thus, for instance, it 
 liberates iodine from iodic acid, reduces permanganic acid, and precipitates silver and 
 mercury from solutions of their salts. 
 
 Uses. Sulphurous acid is used as a disinfectant and deodoriser, as it destroys 
 miasms, and decomposes bad-smelling substances, such as sulphuretted hydrogen, 
 ammonium sulphide, etc. Another use of sulphurous acid, which is not less im- 
 portant than the latter, is for preserving wine, hops, and other substances. 
 
 Calvert has recommended the addition of ^ of a 10 per cent, solution of sul- 
 phurous acid to sugar juice before boiling in vacuum, for lessening the coloration of 
 the syrup, and for stopping any fermentation that may have set in. 
 
 Sulphurous acid is also employed for bleaching starch, cane sugar, malt, etc. 
 
 A farther use of sulphurous acid which may be here mentioned, is for the preser- 
 vation of corpses for anatomical purposes. Sulphurous acid that has been treated 
 with an excess of zinc is injected into the corpse, which may be then kept for 
 several days. The effect is not to be attributed to sulphurous acid alone, but also 
 to zinc sulphite and hyposulphite. 
 
 SULPHURIC OXIDE. 
 
 FORMULA S0 3 . MOLECULAB WEIGHT 80. 
 
 Characters. This substance, which is also called sulphuric anhydride, is 
 a white fibrous mass resembling asbestos in appearance ; it melts at about 18, and at 
 a higher temperature it volatilises ; the vapour is decomposed at a red heat into sul- 
 phurous oxide S0 2 and oxygen gas. In the dry state sulphuric oxide is a neutral 
 substance, and it does not alter the colour of blue litmus paper, or exercise any corro- 
 sive action on organic substances, but it attracts water from the atmosphere with 
 great avidity, combining with it and forming sulphuric acid ; it also gradually causes 
 the decomposition of organic substances, converting them into water, with which it com- 
 bines, and carbon, which remains as a finely divided black mass. The specific gravity 
 of solid sulphuric oxide is 1-946 at 13, that of the melted substance 1*970 at 20. 
 
 Preparation. Sulphuric oxide may be obtained by heating perfectly dry ferric 
 sulphate, Fe 2 3S0 4 , in ? dose vessel connected with a condenser. The decomposition 
 that takes place is represented by the following equation : 
 
 Fe,3S0 4 Fe 2 3 + 3S0 3 . 
 
 It may also be obtained by distilling the fuming acid known as Nordhausen oil of vitriol. 
 
 Compounds. Sulphuric oxide combines roadily with water, forming hydrogen 
 sulphate, H 2 S0 4 , or sulphuric acid, which is the representative of a very important 
 series of saline substances called sulphates, containing in the place of the 
 hydrogen of sulphuric acid two atomic proportions of monovalent metals, or one atomic 
 proportion of divalent metals for each molecule of sulphuric oxide. 
 
 The sulphates are mostly crystalli sable substances ; with some few exceptions 
 
SULPHURIC ACID. 109 
 
 they are soluble in water, but some of them dissolve only m very small proportions 
 Many sulphates occur naturally, and in some instances they have originated from 
 metallic sulphides by oxidation. 
 
 Sulphuric oxide absorbs the vapour of nitrogen peroxide, forming a crystalline 
 substar.ce having the composition N0 2 S0 3 , which, when sufficiently heated, is decom- 
 posed into oxygen gas and the same substance that is produced by the action of 
 nitrogen peroxide upon sulphurous oxide (see p. 107). This substance, 2NO,S 2 7 , is 
 also formed, together with sulphurous oxide, by the action of nitric oxide upon sul- 
 phuric oxide, according to the following equation : 
 
 3S0 3 + 2NO = 2NO,S 2 7 + S0 2 . 
 
 The crystals sometimes formed in the lead chambers of sulphuric acid works when 
 there is an insufficient supply of steam are closely related to these compounds (vide 
 Sulphuric Acid, Chamber Crystals). 
 
 SULPHURIC ACID. 
 
 FORMULA H 2 S0 4 . MOLECULAR WEIGHT 98. 
 
 History. -Most probably the Arabian chemist, Greber, who lived in Spain in the 
 eighth century, was the first to prepare sulphuric acid, for it is hardly possible that 
 the 'spirit' which he got by distilling alum can have been anything else. In the 
 twelfth century, Albertus Magnus mentions a spiritus vitreoli romani, which 
 must likewise have been sulphuric acid. Basil Valentin, who lived in the fifteenth 
 century, was the first to describe comprehensively and exactly the different methods 
 of preparing sulphuric acid, but even he considered the sulphuric acid prepared in 
 different ways to be distinct substances. Libavius was the first to recognise the 
 identity of the sulphuric acid prepared according to various methods. 
 
 The composition of sulphuric acid was long a matter of doubt. Stahl considered 
 it to be a constituent of sulphur ; and Mayow, who lived in the seventeenth century, 
 maintained that sulphur was a constituent of sulphuric acid. It was not until 1777 
 that Lavoisier established the true composition of sulphuric acid. 
 
 Occurrence. -Sulphuric acid seldom occurs naturally in the free state, since it 
 is one of the strongest acids, and readily unites with metallic oxides and other bases. 
 Its occurrence in the free state is therefore limited to volcanic sources. Thus, for 
 instance, according to Boussingault, the water of the Eio Vinagre, a river rising in 
 the Andes, in South America, contains, in addition to hydrochloric acid, about one-tenth 
 per cent, of free sulphuric acid. M. Boussingault calculated that this river brings to 
 the surface daily more than 38 tons of sulphuric acid. The water of some other 
 volcanic springs in the Andes also contains sulphuric acid. Another spring of water, 
 ?ery rich in sulphuric acid, occxirs in New Granada. It is a hot spring from a volcano 
 called Paramo de Ruiz, 3800 metres above the sea level, and according to Lewy its 
 water contains upwards of one fourth per cent, of free sulphuric acid. The water has 
 a temperature of 69'4, and contains free hydrochloric acid as well as sulphuric acid. 
 
 Sulphuric acid exists far more abundantly in combination with bases as sulphates. 
 The commonest of these compounds are gypsum (calcium sulphate); heavy spar 
 (barium sulphate); celestine (strontium sulphate); angle site (lead sulphate); 
 green copperas (iron sulphate); blue vitriol (copper sulphate); and alunito 
 (aluminum and potassium sulphate), etc. 
 
 Composition. Sulphuric acid or hydric sulphate contains more than six 
 tenths its weight of oxygen in combination with sulphur and hydrogen, and its con- 
 
 titutionis represented in accordance with the double water type -g 2 > 2 , by the formula 
 
 2 ' or as a mon hydrate of sulph 11 " ox ide by the formula SO S H 2 0. 
 Characters. In its most concentrated state sulphuric acid is a colourless, in- 
 
 tin- or carbonising action upon such substances, and the sulphuric ncid met with in 
 commerce is often coloured brown in this way by dust or smalt fragments of straw, etc. 
 It solidifies at a temperature considerably below the freezing point of water and then 
 melts at 10-5 The liquid acid commences to boil at 290 and is partially decom- 
 posed givino- off some vapour of sulphuric oxide, the temperature of t 
 
110 
 
 SULPHUR. 
 
 liquid rising meanwhile, until at about 338 it becomes constant, and the acid that 
 distils over contains Ijg molecule of water for each molecule of sulphuric oxide. 
 
 Sulphuric acid mixes readily with water in all proportions, evolving great heat. 
 On this account water should not be poured into concentrated sulphuric acid ; for un- 
 less this is done with very great caution the heat evolved may suddenly convert the 
 water into steam, and cause the acid to be thrown about with great violence. In 
 mixing the acid with water, it is therefore always preferable to pour the acid gradu- 
 ally into the water. Sulphuric acid also forms several definite crystallisable com- 
 pounds with water. 
 
 The specific gravity of sulphuric acid decreases in proportion to the amount of 
 water it contains. The following table shows the strength of sulphuric acid of differ- 
 ent densities at 15. 
 
 
 1 
 
 
 Specific Gravity 
 
 H 2 S0 4 
 per cent. 
 
 so 
 
 per cent. 
 
 Specific Gravity 
 
 H 2 SO., 
 per cent. 
 
 so s 
 
 per cent. 
 
 1-8426 
 
 100 
 
 81-63 
 
 1-398 
 
 50 
 
 40-81 
 
 1-842 99 
 
 80-81 
 
 1-3886 
 
 49 
 
 40-00 
 
 1-8406 98 
 
 80-00 
 
 1-379 
 
 48 
 
 39-18 
 
 1-840 97 
 
 79-18 
 
 1-370 
 
 47 
 
 38-36 
 
 1-8384 96 
 
 78-36 
 
 1-361 
 
 46 
 
 37-55 
 
 1-8376 95 
 
 77-55 
 
 1-351 
 
 45 
 
 36-73 
 
 1-8356 
 
 94 
 
 76-73 
 
 1-342 
 
 44 
 
 35-82 
 
 1-834 
 
 93 
 
 75-91 
 
 1-333 
 
 43 
 
 35-10 
 
 1-831 92 
 
 75-10 
 
 1-324 
 
 42 
 
 34-28 
 
 1-827 91 
 
 74-28 
 
 1-315 
 
 41 
 
 33-47 
 
 1-822 90 
 
 73-47 
 
 1-306 
 
 40 
 
 32-65 
 
 1-816 89 
 
 72-65 
 
 1-2976 
 
 39 
 
 31-83 
 
 1-809 88 
 
 71-83 
 
 1-289 
 
 38 
 
 31-02 
 
 1-802 87 
 
 71-02 
 
 1-281 
 
 37 
 
 30-20 
 
 1-794 86 
 
 70-10 
 
 1-272 
 
 36 
 
 29-38 
 
 1-786 85 
 
 69-38 
 
 1-264 
 
 35 
 
 28-57 
 
 1-777 84 
 
 68-57 
 
 1-256 
 
 34 
 
 27-75 
 
 1-767 83 
 
 6775 
 
 1-2476 
 
 33 
 
 26-94 
 
 1-756 82 
 
 66-94 
 
 1-239 
 
 32 
 
 26-12 
 
 1-745 81 
 
 66-12 
 
 1-231 
 
 31 
 
 25-30 
 
 1-734 
 
 80 
 
 65-30 
 
 1-223 
 
 30 
 
 24-49 
 
 1-722 
 
 79 
 
 64-48 
 
 1-215 
 
 29 
 
 23-67 
 
 1-710 
 
 78 
 
 63-67 
 
 1-2066 
 
 28 
 
 22-85 
 
 1-698 
 
 77 
 
 62-85 
 
 1-198 
 
 27 
 
 22-03 
 
 1-686 76 
 
 62-04 
 
 1-190 
 
 26 
 
 21-22 
 
 1-675 75 
 
 61-22 
 
 1-182 
 
 25 
 
 20-40 
 
 1-663 74 
 
 60-40 
 
 1-174 
 
 24 
 
 19-58 
 
 1-651 73 
 
 59-59 
 
 1-167 
 
 23 
 
 18-77 
 
 1-639 72 
 
 58-77 
 
 1-159 
 
 22 
 
 17-95 
 
 1-627 71 
 
 57-95 
 
 1-1516 
 
 21 
 
 17-14 
 
 1-615 70 
 
 57-14 
 
 1-144 
 
 20 
 
 16-32 
 
 1-604 69 
 
 56-32 
 
 1-136 
 
 19 
 
 15-51 
 
 1-592 68 
 
 55-59 
 
 1-129 
 
 18 
 
 14-69 
 
 1-580 67 
 
 54-69 
 
 1-121 
 
 17 
 
 13-87 
 
 1-578 
 
 66 
 
 53-87 
 
 1-1136 
 
 16 
 
 13-06 
 
 1-557 
 
 65 
 
 53-05 
 
 1-106 
 
 15 
 
 12-24 
 
 1-545 
 
 64 
 
 52-24 
 
 1-0938 
 
 14 
 
 11-42 
 
 1-534 
 
 63 
 
 51-42 
 
 1-091 
 
 13 
 
 10-61 
 
 1-523 
 
 62 
 
 50-61 
 
 1-083 
 
 12 
 
 9-79 
 
 1-512 
 
 61 
 
 49-79 
 
 1-0756 
 
 11 
 
 8-98 
 
 1-501 
 
 60 
 
 48-98 
 
 1-068 
 
 10 
 
 8-16 
 
 1-490 
 
 59 
 
 48-16 
 
 1-061 
 
 9 
 
 7-34 
 
 1-480 58 
 
 47-34 
 
 1-0536 
 
 8 
 
 6-53 
 
 1-469 57 
 
 46-53 
 
 1-0464 
 
 7 
 
 5-71 
 
 1:4586 56 
 
 45-71 
 
 1-039 
 
 6 
 
 4-89 
 
 1-448 
 
 55 
 
 44-89 
 
 1-032 
 
 5 
 
 4-08 
 
 1-438 
 
 54 
 
 44-07 
 
 1-0256 
 
 4 
 
 3-26 
 
 1-428 53 
 
 43-26 
 
 1-019 
 
 3 
 
 2-445 
 
 1-418 52 
 
 42-45 
 
 1-013 
 
 2 
 
 1-63 
 
 1-408 51 
 
 41-63 
 
 1-0064 
 
 1 
 
 0-816 
 
 i 
 
 
 
 
MANUFACTURE OF SULPHURIC ACID. 
 
 Ill 
 
 The following table shows, in degrees Baume, the proportion per cent, of sulphuric 
 acid and of sulphuric anhydride in sulphuric acid of different densities at a tempera- 
 ture of 15. 
 
 Degrees 
 Baume 
 
 H 2 SO 4 
 per cent. 
 
 SO 3 
 per cent. 
 
 Degrees 
 Baum6 
 
 H 2 S0 4 
 per cent. 
 
 S0 3 
 per cent. 
 
 5 
 
 5-4 
 
 4-3 
 
 49 
 
 61-1 
 
 50-0 
 
 10 
 
 10-9 
 
 8-9 
 
 50 
 
 62-6 
 
 51-1 
 
 15 
 
 16-3 
 
 13-3 
 
 51 
 
 63-9 
 
 52-2 
 
 20 
 
 22-4 
 
 18-3 
 
 52 
 
 65-4 
 
 53-4 
 
 25 
 
 28-3 
 
 23-1 
 
 53 
 
 66-9 
 
 54-6 
 
 30 
 
 34-8 
 
 28-4 
 
 54 
 
 68-4 
 
 55-8 
 
 33 
 
 38-9 
 
 31-8 
 
 55 
 
 70-0 
 
 57-1 
 
 35 
 
 41-6 
 
 34-0 
 
 56 
 
 71-6 
 
 58-4 
 
 36 
 
 43-0 
 
 35-1 
 
 57 
 
 73-2 
 
 597 
 
 37 
 
 44-3 
 
 36-2 
 
 58 
 
 74-7 
 
 61-0 
 
 38 
 
 45-5 
 
 37-2 
 
 59 
 
 76-3 
 
 62-3 
 
 39 
 
 46-9 
 
 38-3 
 
 60 
 
 78-0 
 
 63-6 
 
 40 
 
 48-4 
 
 39-5 
 
 61 
 
 79-8 
 
 65-1 
 
 41 
 
 49-9 
 
 40-7 
 
 62 
 
 81-7 
 
 66-7 
 
 42 
 
 51-2 
 
 41 8 
 
 63 
 
 83-9 
 
 68-5 
 
 43 
 
 52-5 
 
 42-9 
 
 64 
 
 86-3 
 
 70-4 
 
 44 
 
 54-0 
 
 44-1 
 
 65 
 
 89-5 
 
 73-0 
 
 45 
 
 55'4 
 
 45-2 
 
 65-5 
 
 91-8 
 
 74-9 
 
 46 
 
 56-9 
 
 46-4 
 
 65-8 
 
 94-5 
 
 77-1 
 
 47 
 
 58-2 
 
 47-5 
 
 66 
 
 100-0 
 
 81-6 
 
 48 
 
 59-6 
 
 48-7 
 
 1 
 
 
 
 i 
 
 1 
 
 
 One of the most important properties of sulphuric acid is its solvent action. It 
 dissolves nearly all metals, either when diluted or in the concentrated state ; in the 
 former case with development of hydrogen gas, in the latter under reduction to sul- 
 phurous acid. Thus, the metals iron, zinc, cadmium, etc., dissolve in diluted sulphuric 
 acid with evolution of hydrogen ; the metals mercury, copper, silver, etc. dissolve in 
 concentrated sulphuric acid with evolution of sulphurous acid. The chemical change 
 in the first case is represented by the equation : 
 
 that in the second case by the equation : 
 
 + Cu = 
 
 S0 
 
 + SO., + 2 
 
 Other reducing agents, such as carbon, sulphur, phosphorus, etc., also exert a 
 deoxidising action upon concentrated sulphuric acid, like the metals ; but a higher 
 temperature is necessary. 
 
 Sulphuric acid combines very energetically with free bases forming sulphates, 
 and it is only by a few other acids, and in a few instances, that it can be separated 
 from such compounds without the aid of heat. 
 
 Nordhausen oil of vitriol, or fuming sulphuric acid, must be considered as a 
 mixture of variable quantities of sulphuric anhydride and sulphuric acid monohydrate. 
 Its preparation and properties have been known longer than the ordinary acid. 
 
 Preparation. Sulphuric acid is formed by the hydration of sulphuric oxide, also 
 by the oxidation of sulphurous oxide, and by the action of concentrated nitric acid or 
 of aqua regia upon sulphur, but these processes are seldom had recourse to except for 
 special purposes. In the preparation of sulphuric acid on a large scale, sulphurous 
 oxide produced by burning sulphur or pyrites is converted into sulphuric acid by 
 means of some powerful oxidising agent Although sulphurous oxide in aqueous 
 solution is gradually oxidised to sulphuric acid by exposure to the air, this change 
 does not admit of practical application when large quantities of acid are required. 
 
 The oxidising agent now universally employed for oxidising. sulphurous oxide to 
 sulphuric acid is nitric acid. The greater part of the oxygen, however, is not 
 derived from the nitric acid, but is obtained indirectly from the air as the result of 
 a complex chemical process that takes place in the lead chambers used for the 
 purpose. The presence of water ie very important, as will be seeu presently. 
 
112 
 
 SULPHUR. 
 
 MANUFACTURE OP FUMING OIL OF VITRIOL. A comparatively small quantity of 
 sulphuric acid is made in Saxony and Bohemia by distillation from calcined ferrous 
 sulphate or ' green vitriol,' also recently from acid sodium sulphate. 
 
 Preparation from Vitriol. The method of procedure in Bohemia is the following. 
 Pyrites, freed by elutriation from admixtures of clay, is heated to redness in fireclay 
 retorts, out of contact with air, according to the method described on page 99, and the 
 sulphur distilling off, amounting generally to 14 or 15 per cent., is collected. The 
 residue left in the retorts is ferrous sulphide, which is allowed to disintegrate and 
 oxidise in the air, a process which requires several years. The oxidised product is 
 lixiviated and the lye evaporated to crystallisation by the heat of the retort furnaces. 
 The first crystallisation yields tolerably pure ferrous sulphate (green vitriol). The 
 mother liquor is evaporated to dryness, and the residue calcined so as to convert the 
 ferrous sulphate into basic ferric sulphate. This conversion is, however, never entirely 
 accomplished, the calcined material always containing small quantities of ferrous sul- 
 phate, and with this some water which is'given off in the process of heating to redness. 
 The ferrous sulphate also decomposes with formation of sulphuric anhydride and sul- 
 phurous oxide, according to the equation : 
 
 2FeS0 4 = Fe 2 3 + SO S + S0 2 . 
 
 The basic and neutral ferric sulphates, when heated to redness, yield ferric oxide and 
 sulphuric oxide or anhydride. The small quantity of water contained in every sample of 
 Nordhausen oil of vitriol is derived from the water contained in the ferrous sulphate, 
 and given off when the calcined vitriol is heated to redness. 
 
 The distillation of fuming sulphuric acid from calcined vitriol is carried out in a 
 kind of galley furnace, both sides of which are fitted with a double row of retorts, 34 
 in number, lying over each other, and above these often a third row of 32 retorts. The 
 retorts (BE) are made of fire clay, and have a bore of about 8 inches and a length of 
 32 inches^ Each retort is furnished with a receiver (A), of the same size and form as 
 
 FIG. 47- 
 
 itself. The 200 retorts hold 5 cwts. of calcined vitriol, and are so heated (2 tons of 
 brown coal being used) as to yield 2 cwts. of acid and 2* cwts. of residue (colcothar 
 or ferric oxide). At the beginning of the process only water escapes, then sulphurous 
 oxide and oxygen, and finally sulphuric anhydride and hydrated sulphuric acid distil 
 over, which mix and condense in the receivers. 
 
 Since the manufacture of fuming sulphuric acid in the above way involves con- 
 siderable loss of sulphuric acid, which escapes as sulphurous oxide and oxygen, it has of 
 late been the custom to prepare Nordhausen oil of vitriol from ferric sulphate ; the 
 latter being obtained by the treatment of colcothar with ordinary sulphuric acid, and 
 evaporating the product to dryness. On distilling this ferric sulphate, sulphuric 
 anhydride of great purity is obtained and a small quantity of ordinary sulphuric acid 
 is placed in the receivers, with which the nnhydride readily mixes. The residue in the 
 retorts is used again for the preparation of ferric sulphate. 
 
MANUFACTURE OF SULPHURIC ACID. 113 
 
 Fuming Sulphuric Acid from Sodium Eisulphate. This method of preparing 
 fuming sulphuric acid, which has recently been much adopted in France, is analogous 
 to that above described. Ketorts of a similar kind are used, in which the sodium 
 bisulphate is heated until sulphuric anhydride begins to distil over, when glass 
 receivers are attached to the necks of the retorts. 
 
 Fuming sulphuric acid is further manufactured by heating to redness dried Glauber's 
 salt with boracic acid, and condensing the vapour in receivers containing ordinary 
 sulphuric acid. The residue in the retorts is employed in the preparation of borax. 
 
 MANUFACTURE OF SULPHURIC ACID IN LEAD CHAMBERS. The preparation of this 
 acid on a large scale in leaden chambers dates from the year 1746, when Dr. Koebuck, 
 of Birmingham, erected the first leaden chamber at Prestonpans, near Edinburgh. 
 
 The formation of sulphuric acid from sulphurous oxide by the agency of nitric 
 acid and the lower oxides of nitrogen depends upon a number of consecutive chemical 
 changes. Till recently the following three changes wore supposed to take place : 
 
 1. Conversion of sulphurous oxide and concentrated nitric acid into sulphuric acid 
 and nitrogen peroxide according to the equation : 
 
 S0 2 + 2 N 2JO - S ^ 2 |0 2 + 2N0 2 . 
 
 2. Keproduct ion of nitric acid from a portion of the nitrogen peroxide by tne action 
 of water; another portion of it becoming reduced to nitric oxide, according to the 
 equation : 
 
 3N0 2 + **JO = 2 N 2 }0 + NO. 
 
 3. The nitric oxide fowned in the second process combines with oxygen from 
 atmospheric air admitted into the chamber, and is thus converted into nitrogen per- 
 oxide, according to the equation : 
 
 NO + - N0 2 . 
 
 This nitrogen peroxide is again decomposed by the action of water producing a 
 further quantity of nitric acid. According to the changes thus given the nitric acid 
 originally employed is first of all deoxidised, and then by means of two consecutive 
 chemical changes the products of the deoxidation are again converted into nitric acid : 
 theoretically, therefore, it would appear from this that a small quantity of nitric acid 
 should be capable of con verting unlimited quantities of sulphurous oxide into sulphuric 
 acid. But in the manufacture of sulphuric acid it is necessary to keep up a continual 
 supply of nitric acid to the lead chambers, because the nitrogen introduced into the 
 chambers in the form of atmospheric air, and escaping, after the oxygen associated 
 with it has been absorbed, carries with it various oxides of nitrogen. 
 
 According to this view, it is nitrogen peroxide that effects the transfer of oxygen 
 from the air to the sulphurous oxide by a constantly recurring conversion into nitric 
 acid. Weber has suggested another view of the change, according to which it is not 
 nitrogen peroxide, but nitrous anhydride which performs the important function of 
 transferring oxygen from atmospheric air to the sulphurous oxide in the lead chambers. 
 lie assumes the following consecutive changes to take place : 
 
 1. By the contact of sulphurous oxide with a dilute mixture of sulphuric acid and 
 nitric acid, such as is found in the lead chamber, it is oxidised to sulphuric acid, the 
 nitric acid being reduced to nitrous anhydride, according to the equation : 
 
 2S0 2 + 2(*o + H 2 - 
 
 2. The nitrous anhydride in the first instance dissolves in the sulphuric acid. By 
 die reaction of nitrous anhydride thus formed with further portions of sulphurous 
 oxide, it is reduced to nitric oxide, while the sulphurous acid is oxidised to sulphuric 
 acid according to the equation : 
 
 S0 2 + N 2 3 + H 2 = S 2 + 2NO. 
 
 3. Conversion of the nitric oxide into nitrous anhydride by contact with atmo- 
 spheric air according to the equation 2NO + = NA- Inthiswaythesubstanc 
 is reproduced which acts upon sulphurous oxide in the manner above described. 
 
 The important fact that, in the lead chambers, nitric oxide gas MO^JJ" 
 nitrous anhydride, and not to nitrogen peroxide, has been confirmed by W inkier, wn 
 has proved that in presence of sulphuric acid, nitric oxide is never oxidi 
 gen peroxide, but always to nitrous anhydride. 
 
 Accordingly, nitrous anhydride, and not nitrogen peroxide, must be considered as 
 the medium by which oxygen is transferred from atmospheric air to sulpnn 
 in the manufacture of sulphuric acid. 
 
114 
 
 SULPHUR. 
 
 An apparatus for the preparation of sulphuric acid is represented in section by figs. 
 48 and 49. A is the furnace in which the sulphur is burnt, the hearth consisting of a 
 
 "Pro. 48. 
 
 plate of cast or sheet iron, with the edges turned up from 3 to 4 inches high. A steam 
 boiler is often fitted above this furnace, so as to be heated by the burning sulphur, 
 and furnish the steam required in the chamber. The more general plan, however, is 
 to have at least an additional boiler ready to do duty in case of repairs. The acid 
 vapour of the chambers is prevented from getting into the boiler by a valve, which is 
 opened by the steam escaping from the boiler, but prevents the access of gas from the 
 chambers. The figure represents two furnaces for the production of sulphurous acid ; 
 one shown in section (A), the other in elevation with a sliding door (a). The gas from 
 these furnaces, consisting of sulphurous acid and air, escapes through the tubes (B B) and 
 (cc')into a small lead chamber (c' c 7 ),and from thence into the first lead chamber (E'). The 
 tubes (c c') and (D) have a sectional area double that of the tubes (B B), since they have to 
 convey the entire quantity of gas passing through B and B. The tube (c) is sufficiently 
 high to cause a draught, by which the gas is drawn forward from the sulphur burner. 
 The draught is further increased by passing a jet of steam in the direction of D into 
 the chamber (E') and another through a pipe(c") into the chamber (c"c 7 ). The gas passes 
 from the first chamber (E') through the pipe (E") into the second chamber (B'''), where 
 stoneware dishes (g g') are placed terrace-like above one another, into which nitric acid 
 
 is supplied from vessels (/) outside the 
 chamber, and overflows from them so as to 
 offer an extended surface to the gas in 
 the chamber. The supply of nitric acid 
 is either continual or intermittent. In 
 the latter case an apparatus is placed 
 between the acid holders and the cham- 
 bers, which allows about 1 1 Ibs. of nitric 
 acid to flow into the chamber every half 
 hour, or whatever quantity may be re- 
 quired. This apparatus consists of a 
 vessel into which nitric acid is permitted 
 to flow, and from which it cannot escape 
 until the acid has reached the level of 
 the discharge aperture. The discharge 
 
 F IO 50. is regulated by a syphon arrangement, 
 
 so that when it has once begun it does 
 
 not cease until the vessel is emptied. Although nitric acid is constantly dropping 
 into this vessel, the discharge is interrupted while it is being filled, because the syphon 
 is then filled will air. 
 

 MANUFACTURE OF SULPHURIC ACID 
 
 115 
 
 Instead of introducing the nitric acid into the chamber by means of the dishes just 
 described, the arrangement represented by fig. 50 is sometimes employed. It consists 
 
 FIG. 49. 
 
 of a number of vertical tubes of stoneware having a funnel-shaped mouth provided 
 with a lip. These tubes are arranged like the pipes of an organ, along the sides of 
 the second chamber. The nitric acid is supplied from vessels outside the chamber 
 into the tallest of theso tubes, and when that is full it flows into the next, and so 
 on, until it reaches the lowest (D"). In its long passage from the first to the 
 last of the tubes, the nitric acid exposes a considerable surface to the surrounding 
 vapours of sulphurous acid, air, and steam, and is to a great extent reduced to nitric 
 oxide. 
 
 Since the sulphuric acid formed in this chamber contains much nitric acid 
 and other oxides of nitrogen, it is conducted back, through a pipe (e'e, fig. 48) into the 
 first chamber (E'), the floor of which is somewhat lower. Here it is exposed to a 
 fresh mixture of gases containing a large amount of sulphurous acid which reduces 
 the nitric acid contained in it. From this chamber the sulphuric acid is conducted 
 through a tube (//') into the third chamber (F), where the whole of the acid produced by 
 the series of chambers eventually collects, and from whence it is drawn off at intervals 
 or in a continuous stream. The floor of this chamber is therefore lower than that of 
 the other chambers. The gas escaping from the chamber (E"') also passes through the 
 tube (E 4 ) into the larger chamber (F). only the ends of which are shown in figs. 48 and 
 49. In order to increase the draught necessary for the complete mixing and decom- 
 position of the gas, a jet of steam is passed into F, in the same direction as the gas 
 travels ; while at the bottom of the chamber there are several tubes (h h"), which 
 supply the steam required for the production of sulphuric acid. The most judicious 
 arrangement of these steam tubes is to fit them in at the sides or roof of the chambers, 
 so as to avoid joints at the bottom. The gas that is not condensed in this chamber 
 passes through a tube (GG") into a fourth chamber (H), into which steam is passed 
 as before, both in the direction of the gases, and also through a tube (A"') fitted in 
 either the side, top, or bottom of the chamber. The gas then passes through the 
 tube (H' H") into a closed reservoir (M M), furnished with partitions, in which it circulates 
 before passing through the tube (H'") into the fifth chamber (a. 4 ). Steam is passed into 
 this chamber to force the gas into a second reservoir (M' M") similar to the last, and 
 then it either escapes through the tube (j K) direct into the atmosphere, or through 
 (j j') into an apparatus, where the remaining portion of nitrous gas is condensed. 
 The tube conducting the gas into the air or into the condenser is furnished at (j) with 
 an arrangement for regulating the rate at which the gas passes. This is effected bj 
 means of a horizontal partition fitted into the box, and perforated with round holes 
 an inch wide, the joint area of which exactly corresponds to the sectional area of the 
 tube. The rate of passage of the gas is regulated bv closing these holes with 
 
 i 2 
 
116 SULPHUR 
 
 leaden plugs, the regulator for this purpose being furnished with a wooden door 
 covered with lead. 
 
 Condensation of the Nitrous Gas (containing nitrogen peroxide and nitrous anhydride}, 
 escaping from the Chamber. The gas escaping from the chimney (IK) still contains con- 
 siderable quantities of nitrogen oxides, which would be lost if not condensed by means 
 of a special apparatus. An apparatus for this purpose was invented by Gay-Lussac ; 
 its construction is represented in fig. 49. It consists of a cylinder (j'j), into which the 
 gas passes from the tube (j j') after having circulated through the reservoir (M'M"). Thif 
 cylinder has a perforated bottom supporting a column of pieces of coke. Sulphuric 
 acid of sp. gr. T690 to 1'727 is allowed to trickle slowly from the reservoir (N) over 
 the coke, its equal dispersion being secured by means of a cup (I), divided into two parts 
 by a partition parallel to its axis, and turning on an axis on which it oscillates between 
 two cross-bars. When one division is filled with sulphuric acid, it topples over and 
 empties itself, and the acid flows into the other division, and so on. The sulphuric 
 acid flowing down over the coke meets the ascending chamber gas, and absorbs the 
 nitrogen peroxide and nitrous anhydride, and the gas, which then contains only very 
 slight traces of nitrous gases, escapes through the chimney (o). The amount of nitrous 
 gases absorbed amounts to 3^ per cent. Since the absorption of the nitrous gases is 
 more complete in proportion to the dryness of the gas, it is passed through a layer of 
 concentrated sulphuric acid in the reservoir (M' M'), before it enters the Gray-Lussac's 
 condenser. 
 
 The sulphuric acid which collects on the floor of the cylinder, and contains dis- 
 solved in it nitrogen peroxide and nitrous anhydride, is conducted for further use 
 through a long tube into the reservoir (j"), and is pumped from thence into another 
 reservoir QJ). From p this acid flows into the vessel (j), and from thence through a 
 funnel and a swinging cup similar to the one marked I into the anterior chamber (c", c 7 ). 
 The acid trickles down over the shelves (c 6 , c 5 , c 4 , c'") to the floor of this chamber, 
 finding its way eventually into the first leadpn chamber (E'). The shelves (c 6 , c 5 , c 4 , c'") 
 serve to present a large surface of the acid to the joint action of the sulphurous acid 
 and air passing into the anterior chamber (c", c 7 ), through the tube c c', and the steam 
 let in at c". The nitrous gases contained in the sulphuric acid are thereby reduced 
 and the sulphurous acid oxidised to sulphuric acid. By the use of this apparatus 
 oxides of nitrogen are again rendered serviceable, which would otherwise be lost, and 
 be injurious to the neighbourhood surrounding the manufactory. 
 
 MODIFICATIONS IN THE APPARATUS, ETC. Since the introduction of the manufac- 
 ture of sulphuric acid on a large scale, many improvements have been made in the 
 details of the chamber system, the most important of which are the following : 
 
 The Sulphur-Burner or Furnace. These furnaces have various forms and arrange- 
 ments. In their construction it must be remembered that the combustion of 100 
 pounds of sulphur per day of 24 hours requires a burning area of about 5 square 
 feet. Consequently, the number of such burners depends upon the extent of the 
 manufacture. In many works four or six sulphur furnaces are employed, their 
 gaseous products passing into the chambers through a common tube. 
 
 Since it is important that the combustion of the sulphur should admit of being 
 regulated, so as to avoid the too rapid supply of sulphurous oxide to the chambers, and 
 to prevent its entering too hot, some sulphur burners are furnished with an arrange- 
 ment for admitting cold air beneath the iron plate upon which the sulphur is burnt. 
 The grating admitting air into the furnace for the combustion of the sulphur is 
 furnished with a register for regulating the draught. 
 
 In some works, for instance one at Corbetha, near Weissenfels in Prussia, the gas 
 from* the burners is passed through a long brick flue furnished with partitions, in 
 order to cool it sufficiently before passing into the lead chambers. In Kuhlmnnn's 
 works, the sulphur is burnt in cast-iron retorts having a hemispherical cross section. 
 Each furnace holds four such retorts, the retorts having a door in front for charging 
 with sulphur, and regulating the draught, the gas escaping from an opening at the other 
 extremity and passing through long tubes into a suitable cooling chamber. In other 
 works the sulphur burners, instead of being surrounded with brickwork, are fitted on one 
 or two sides with cast-iron plates which serve to cool the gases to a considerable 
 extent. 
 
 Very well worth notice are the so-called continuous burners, in which a constant 
 and uniform combustion of sulphur to sulphurous oxide is effected. 
 
 In a burner of this kind invented by Petrie, a cast-iron plate with the rim bent 
 upwards is supported on brickwork, and forms the floor of the burner. Openings are 
 left in the brickwork basement, so that when necessary air can circulate under the 
 iron plate to cool it. The cover of the burner consists of .in iron plate, also with a 
 rim bent upwards, into which water is poured to cool the gases. The burner has a 
 
MANUFACTURE OF SULPHURIC ACID. 117 
 
 door in front for admitting the air necessary for combustion and for the removal of 
 the burnt residues. Opposite the cast-iron plate which forms the hearth of the burner 
 is a grate forming with the hearth an angle of about 45, upon which the sulphur 
 to be burnt is placed. This grate is heated by the combustion of the sulphur in the 
 burner, causing the sulphur laid on it to melt and trickle down upon the iron plato 
 below, where, coming into contact with atmospheric air from the door in front of the 
 furnace, it is burnt, and by its combustion generates heat enough to melt a fresh por- 
 tion of the sulphur in the grate above, so that in this way a continual supply and 
 combustion of sulphur takes place. The gaseous product of combustion escapes into a 
 long brickwork flue, where it is cooled before passing into the lead chambers. In 
 order to prevent the grating from being too strongly heated and the sulphur from 
 melting too rapidly, a screen of sheet iron is placed parallel to the iron hearth between 
 it and the grate. Up to the present time it has not been found possible to construct 
 the burners so as to insure a perfectly equal flow of sulphur. 
 
 Blair has constructed an apparatus depending upon other principles. The action of 
 his burner depends upon the sulphur being vaporised in a separate chamber, and 
 then burnt in another chamber, the sulphurous oxide and air being then passed into a 
 chamber immediately above the combustion furnace, in which the nitrous vapours are 
 ovolved, the mixture of nitre and sulphuric acid being charged into this chamber from 
 the side, either in pots or small trucks. The quantity of air admitted into the chamber 
 where the sulphur is vaporised is just sufficient to produce, by combining with some 
 of the sulphur, heat enough to vaporise the remainder. 
 
 Production of Sulphurous Oxide. The use of sulphur for this purpose has been 
 largely superseded by the production of sulphurous oxide by roasting native metallic 
 sulphides, which now constitute the chief source of the sulphur used in the manufac- 
 ture of sulphuric acid. (See ante, p. 107.) 
 
 Among the different native metallic sulphides, iron pyrites is so abundant that 
 it is largely employed in the manufactiire of sulphuric acid. Copper pyrites, or at 
 least pyrites containing copper, is also roasted for the preparation of sulphuric acid 
 as well as blende. 
 
 Assuming that pyrites contains on the average 47 per cent, of sulphur, this would re- 
 present from 40 to 42 per cent, of sulphur available in the manufacture of sulphuric acid. 
 The amount of sulphur in pyrites varies somewhat considerably according to the 
 locality from which it is obtained. Pure iron pyrites contains 53'33 per cent, of 
 sulphur, but it is never found of such purity in great quantities. Besides this, the ad- 
 mixtures occurring in pyrites which lessen its amount of sulphur may sometimes have 
 a directly injurious effect. Among these are the compounds of arsenic which pass over 
 into the sulphuric acid itself, and lead compounds which retain the sulphuric acid, etc. 
 A further point of importance in the use of pyrites is the nature of the burnt 
 pyrites. In many cases this is not further worked, but it often happens when copper 
 pyrites is used that the roasted material may be profitably worked for copper. Some 
 sulphuric acid works indeed are supplied with pyrites almost gratis by the proprietors 
 of copper works in exchange for the burnt pyrites. The burnt pyrites is also often 
 worked for green vitriol and for Nordhausen sulphuric acid. 
 
 The use of pyrites as compared with sulphur has, however, many decided disadvan- 
 tages which must be taken into consideration. The acid obtained from pyrites is not so 
 pure, generally containing much arsenic ; the loss of chamber gas is greater, owing to 
 the larger quantities of air employed ; more especially is the consumption of nitric 
 acid greater, being nearly 50 per cent, more than that required when pure sulphur is 
 burnt. The process is more difficult to regulate ; the pipes or tubes conducting the 
 gas from the furnaces to the lead chambers must be of greater length, on account of 
 the high temperature required for roasting the pyrites. Another point of very great 
 importance in the use of pyrites is that the leaden chambers last on an average h 
 over a third as long as they do when sulphur is used. 
 
 As already mentioned, pyrites varies in value according to locality. The . chi. 
 pyrites deposits are the following '. Spain ; from Tharsis, province Huelva and B 
 The pyrites found here contains from 46-50 per cent, sulphur, and from 3-5 per 
 copper. Portugal : province Alemtejo. This pyrites has the same composition as 
 that found at Huelva in Spain, and forms a continuation of that bed. France n; 
 large beds of pyrites in the Kh6ne and Gard departments. This pyrites is worked in 
 France at Chessy, St. Fonds, St. Christ, Oseraie, Pontet, as well as at Chauny, Munl- 
 hausen, Mannheim, Thann, Dieuze, Lille, Eouen, and Paris. It contains from 45-47 
 per cent, of sulphur, and yields from 120-126 per cent, of sulphuric acid of sp. gr. 1-767. 
 The copper amounts to 3 or 4 per cent., and this metal is worked up on a large scale, 
 especially at Chessy. The pyrites from Alais, departemerit du Gard, contains ^ par 
 of gold. The Belgian pyrites from the provinces Namur and laege contains fro, 
 47-49 per cent sutphurf and also as a rule much arsenic. Pyrites is found atCharleroi 
 
118 
 
 SULPHUR. 
 
 which does not contain more than traces of arsenic. Germany has large beds of pyrites 
 at Meggen in Westphalia. The amount of sulphur in this is 45 or 46 per cent., and that 
 of arsenic very small. Beds of pyrites are also found in Ireland, but the sulphur does 
 not exceed 44 per cent., and is generally only 30 per cent. The amount of copper 
 contained in the Irish pyrites varies between and 1 \ per cent. Norway possesses 
 very large beds of pyrites, yielding as much as 44 per cent, of sulphur. Italy has 
 also considerable pyritical beds. St. Domingo exports to this country copper pyrites 
 containing from 3 -4 per cent, of copper. 
 
 Pelouze determines the amount of sulphur in pyrites by melting it with potassium 
 chlorate, sodium chloride, and an exactly weighed quantity of calcined soda, which is 
 partly converted into sodium sulphate and the remainder is titrated with normal acid. 
 Lunge oxidises with concentrated nitric acid; De Kicqles with nitric acid and 
 potassium chlorate, precipitating the sulphuric acid with barium chloride. According 
 to Anthon the amount of pure pyrites in a sample of ore may be ascertained from its 
 specific gravity. 
 
 Before pyrites is roasted it requires breaking up into equal pieces from 1 to \\ 
 inches in diameter, so that the air penetrates a layer of such pieces 30 or 32 inches 
 in depth. 
 
 Well-arranged roasting furnaces only require to be heated with coal or wood at 
 the beginning of the operation, the heat necessary for the continuation of the process 
 being furnished by the combustion of the pyrites itself. The construction of the 
 roasting furnaces varies with their age, the kind of ore to be roasted, and the amount 
 of heat required. Pyrites that has afterwards to be worked for copper is not roasted 
 at so great a heat as that containing little or no copper. 
 
 Shaft Furnaces or Kilns. Figs. 51 and 52 represent a very simple kind of furnace 
 for roasting pyrites. This consists of the fire-place (A), with strong horizontal grate, 
 
 surrounded by thick brickwork. 
 In order to set the furnace going, 
 it is heated to bright redness 
 internally with fuel, and pieces 
 of pyrites, in small quantities at 
 a time, are then thrown in through 
 the opening (e), fresh portions 
 being added according to the 
 rate of combustion at the surface, 
 until the layer of pyrites is about 
 32 inches high. Air passes into 
 the furnace through the open- 
 ing A, fig. 52, its passage being 
 regulated by the damper (B). 
 The roasted pieces of pyrites are 
 poked down with a rod thrust 
 
 between the bars of the grate, whereby the circulation of air is assisted. At every 
 fresh charging the lower opening is closed by letting down the damper B, so as to 
 
 cause the draught to enter for a 
 moment through c, and thereby 
 protect the workman from the 
 vapours. The gaseous product 
 of combustion escapes through 
 the tube d. A number of fur- 
 naces of the kind (A B c D E r, 
 fig. 53) are built round a common 
 chimney (/), through which the 
 gas passes into the lead cham- 
 bers. The chimney (/) must 
 bo also in communication with 
 the air, so that the smoke from 
 the fuel used at the beginning 
 of the operation may escape. 
 
 The arrangement shown by 
 figs. 54, 55, and 56, used at 
 Chessy, is of similar construc- 
 tion. A A are the pyrites furnaces, 
 sixteen of which are arranged 
 arounda chimney (u). This chim- 
 ney is formed of fire bricks below, 
 and of a cast-iron tube (i, fig. 55), 
 ending in a tube of sheet iron (j) 
 
 FIG. 51. 
 
 FIG. 52. 
 
 FIG. 53. 
 
MANUFACTURE OF SULPHURIC ACID. 
 
 119 
 
 fitting into the lead chamber at K. The fire-place of each furnace is 5 feet long, 32 
 inches wide, and 40 inches high. Beneath are lateral openings (bb, fig. 56), each 8 inches 
 
 FIG. 54. 
 
 FIG. 56. 
 
 wide and 10 inches high, closed by doors of sheet or cast iron. Each of these doors 
 has five' round holes about ^ inch wide, for admitting air. An opening at the side, higher 
 up, serves for admitting the charge of pyrites. Four furnaces of the kind are arranged 
 together, and communicate with one another through horizontal flues (c c, fig. 54). The 
 combustion gas passes from these flues through the tunnel (B',fig. 56) into the chimney (H). 
 The dampers (a a' a" a'") are for the purpose of regulating the draught of 'each furnace. 
 Above the opening of the side tunnels in the large chimney is a perforated fire-clay plate 
 4^ inches thick, and covered with pieces of coke or bricks, serving to retain the 
 smoke. When it is desired to set these pyrites furnaces going, the elbow (j, fig. 55) which 
 connects the chimney with the lead chamber is removed, and each furnace is charged 
 with a layer of burnt pyrites to a height of about 24 inches in such a manner that 
 it sinks towards the discharge aperture. The next thing to be done is to throw in dry 
 fuel, to heat the furnace to bright redness, to remove the still glowing coals, and to 
 charge them with about 1 cwt. of pyrites. When the furnaces have been thus set in opera- 
 tion, the elbow (j) is again fitted on, and luted, and fresh charges of 1 cwt. at a time 
 are added at intervals of three hours. At intervals of twelve hours the roasted product 
 is removed through the openings b b. Should the temperature of any one of the furnaces 
 rise too high, the roasted product is removed after eight hours, and by opening one 
 of the doors (b b) the temperature is lowered to a red glow, so as to prevent the pyrites 
 from fusing. 
 
 After the heating of the sixteen furnaces the pyrites burns without any fuel. This 
 
120 
 
 SULPHITE. 
 
 furnace arrangement of sixteen furnaces admits of the roasting of 65 tons of pyrites 
 every 24 hours, and assuming that to contain 40 per cent, of available sulphur, it cor- 
 responds with 7 2 tons of sulphuric acid. 
 
 Freiberg Pyrites Burner. This has a form something like a blast furnace ; the 
 hearth is arched like a saddle and inclines towards the discharge aperture. 
 
 Hearth Furnaces. In a few works where easily combustible pyrites is used, burners 
 are employed having the construction represented by fig. 57- After the brickwork 
 
 FIG. 58. 
 
 FIG. 59. 
 
 has been brought to a red heat, the pyrites 
 is thrown upon the grate (B) in a'layer 
 thick enough to effect the continuation of 
 the combustion without the further use of 
 fuel. The calcined product falls through 
 the bars of the grate into the ash-pit (A). 
 The gaseous products of combustion, con- 
 sisting of sulphurous oxide, nitrogen, air, 
 dr. ex-ape over a brickwork partition into 
 a chamber (c), where a number of cast-iron 
 pots charged -with nitre and sulphuric acid 
 are placed, in order to be heated by the 
 hot gas. Instead of pots, pans of cast iron 
 are sometimes employed. The nitrous 
 vapours thereby evolved mix -with the 
 other gas, which passes through a brick- 
 work flue, indicated in the figure by dotted lines, and through E into a reverberatory 
 
MANUFACTURE OF SULPHURIC ACID. 
 
 121 
 
 FIG. 61. 
 
 furnace (D), where ore dust can be roasted. From thence the gas escapes through the 
 horizontal flue into the chief chimney, and finally into the lead chambers. 
 
 Many improvements have recently been made in pyrites furnaces, with the object 
 of effecting more perfect calcination of the pyrites and greater economy of heat Figs. 
 58, 59, and 60 represent a pyrites furnace employed at the same time for concentrating 
 the chamber acid to sp. gr. 1'65. A A are a couple of calcining furnaces, the arrange- 
 ment of the grate of which presents characteristic features. This grate consists of 
 square iron fears, the sides of which are each If inches wide. The ends of these bars 
 are rounded, and they lie in ring-shaped iron frames, in which they can be turned 
 by means of a key. "When the bars lie so that two of the sides are vertical and 
 two horizontal, and the corresponding sides of all the bars are parallel, the distance 
 between each pair of bars is l inches, sufficient to allow the roasted pieces to pass down 
 between the bars into the ash pit ; but when all the bars are turned 45, the distance 
 between each pair is not more than half an inch ; and this lessens the draught. The 
 grates have each a length of 6 feet and a width of 3f feet. The entire charge of the 
 furnace amounts to 8 cwt. of pyrites, eight charges being thrown in in the course 
 of 24 hours, in charges of 1 cwt. at a time and at intervals of 3 hours between each 
 charge. The pyrites is thrown in through the doors, at the upper part of the arch of 
 each furnace ; the calcined residues being drawn out through the doors of the ash-pit. 
 The doors of the ash-pits are furnished with holes lj inches in diameter, through 
 which air passes under the 
 grate, the draught being 
 regulated by opening or clos- 
 ing the holes. The entire 
 charge remains in the furnace 
 2- to 3 feet high for 48 hours. 
 The gaseous products of com- 
 bustion ascend in the flues 
 (B), pass underneath an iron 
 plate supporting a leaden pan, 
 and escape through the flues 
 (cc)into a horizontal flue (D). 
 Figs. 61 and 62 represent 
 an entire system of pyrites 
 burners of the above kind, 
 connected with the lead 
 chambers. A A A are the 
 furnaces ; A A', the horizontal 
 furnace flues, supported by 
 iron plates and rings ; B B , 
 a brickwork tower, wht-re 
 the gases combine and a 
 quantity of flue -dust collects ; 
 c, an elbow of cast iron, fitted 
 into a leaden flange, through 
 which the gases are conducted 
 into the first small lead cham- 
 ber (D), which servos to con- 
 dense arsenical vapour, at 
 the same time the flue-dust, 
 which contains selenium and 
 thallium, is here deposited. 
 From this chamber the gas 
 passes into the second cham- 
 ber (E, fig. 62), and comes 
 into contact with nitric acid, 
 trickling down in a series 
 of cascades. 
 
 Calcination of Pyrites 
 Dust. Many propositions 
 have been made with the 
 view of utilising this mate- 
 rial. In some places the 
 
 heated, thus stopping up the grate and preventang due circulatio 
 
SULPHITE. 
 
 Figs. 63 and 64 represent a calcining furnace for ore dust constructed by Olivier 
 and Peuret. The ore dust is spread upon six trays (c c' c"c"' c 4 c 5 ), through the open- 
 ings (g g}, which are closed during the roasting, and is heated by the current of hot 
 air and sulphurous acid passing up from the grate (B) of the furnace (A), where the 
 pyrites is burnt. The gases escape through the uppermost division (D) and the flue 
 (i>' ) into the chimney, from whence they are passed into the lead chambers. If at any 
 
 FIG. 63. 
 
 FIG. 64. 
 
 period of the operation the roasting pyrites should have raised the temperature of the 
 furnace too much, or have absorbed all the oxygen, air is admitted through an 
 opening at the side on a level with the third tray. In proportion as the calcining 
 progresses, the hard calcined mass is pushed with a bent rod inserted through G o 
 into a vertical flue, and falls into a pit beneath the furnace, whence it is removed by a 
 lateral aperture. This roasting apparatus is worked at Chessy, St. Bel, etc. A 
 somewhat similar arrangement has been introduced by Mr. Hills for extracting 
 sulphur from the ferric oxide that has been used for purifying coal gas. 
 
 In Spence's furnace the dust is strewn upon an inclined hearth of fire-clay slabs 
 80 to 100 feet long. The clay slabs are heated from beneath by direct fire, the 
 calcination being effected by passing a current of air over the heated pyrites dust, 
 which is spread upon the hearth at the end furthest from the fire in a layer two or 
 three inches thick. After some time, when it has become hot, it is pushed forward 
 towards the other extremity of the hearth and a fresh quantity is put in its place. 
 This operation is repeated at intervals until the portion of pyrites first spread on the 
 hearth has been transferred to the end where the fire is, and the whole of the hearth 
 has been covered with a layer of pyrites. The length of time that must elapse before 
 the ore is pushed forward must be determined for each kind of ore by experience, and 
 it should be regulated so that by the time the ore reaches the further end of the hearth 
 the sulphur should be completely burnt off. This roasting furnace is figured under 
 the head of Copper Smelting. 
 
 In preparing many ores for the operation of smelting the removal of the sulphur 
 they contain is very often a necessary preliminary, and in most instances the sulphur 
 is not only wasted, but is likewise a source of great annoyance and injury to the 
 neighbourhood. Therefore the adoption of some such method of roasting sulphuretted 
 ores as that above described would be attended with considerable economy, inasmuch 
 as the sulphurous oxide then produced could be converted into sulphuric acid. This 
 furnace requires, however, too much air and fuel to render it practically useful and 
 economical. 
 
 GerstcnJioefer 's Kiln. This kiln, which has been introduced of late into many 
 places, serves also for roasting small ore, and is the best kind of kiln at present 
 known. Fig. 65 represents this kiln in section along the line x z (fig. 66), and fig. 
 66 a section along the line v T (fig. 65) ; A A is the grate, about 15 feet wide, 7-J- feet 
 deep, and 40 feet high. The small ore brought in upon a special charging contrivance 
 falls through the slit (D) upon the fire-clay bars (ra), or ore distributors, and from these 
 upon the first row of ore holders (n), from these on to the second, third, and following 
 rows, until all the 15 rows have been passed, and it finally falls into a hollow, whence 
 it is removed through a side opening at K. In order to set the oven going, a number 
 of grate bars (r) are let in at i, and wood or other fuel admitted at h is then burnt 
 npon the grate thus formed. The oven is thus made red hot, and when the ore begins 
 to roast, it continues to do so without further application of heat. 
 
OF SULPHURIC ACID. m 
 
 When this has been done the grate bars (r) are removed and the necessary air 
 admitted through the flue (a), the draught being regulated by a damper (t) in the arch 
 (D). Opposite the upper surface of each row of ore bearers is a flue (b b b) leading out- 
 wards, and closed by an iron box (c) ; in the middle of each box is a hole closed by 
 a clay plug, through which the state of the roasting charge may be observed. The 
 gas passes from the upper part of the space (A) into the vertical flue (B), and from 
 thence through g into the chambers (c and E) where the flue dust is deposited, and 
 finally it is led into the vitriol chambers. 
 
 FIG. 65. 
 
 FIG. 66. 
 
 The further conversion of the sulphurous oxide into sulphuric acid is performed in 
 the same way as when sulphur is used. The acid obtained is, however, generally 
 contaminated with arsenic, from which it can be freed according to one of the methods 
 described on page 134. Where acid is required absolutely free from arsenic, pyrites i< 
 not used, pyrites being only employed as a source of sulphuric acid when it is of no 
 consequence whether the acid contains arsenic or not, as for instance in the preparation 
 of superphosphates, or of sodium sulphate in the manufacture of soda, etc. 
 
 Since the pyrites used as a source of sulphur in the manufacture of sulphuric acid 
 generally contains as much as 40 per cent, of iron, the residue left after the sulphur 
 has been burnt off as sulphurous oxide would be worth working as an iron ore, 
 and in some instances this has been done with some advantage. But besides iron, 
 very many of the different kinds of pyrites worked in sulphuric acid factories con- 
 tain copper, the amount varying from a mere fraction per cent, to 1*5 or 2 per cent, 
 and upwards. The residue from the pyrites burners is therefore frequently as rich 
 as some copper ores that are worked specially for the extraction of the metal, and on 
 this account the extraction of copper has become an important feature of the operations 
 carried on in works where sulphuric acid is manufactured upon a large scale from 
 pyrites. 
 
 In this way, and by reason of the possible utilisation of the sulphurous oxide pro- 
 duced in roasting copper ores for the manufacture of sulphuric acid, copper smelting 
 and the manufacture of soda, two branches of industry which were formerly quite 
 
124 
 
 SULPHUK. 
 
 distinct, both as regards locality and the objects with which they were carried out, 
 have come to be so intimately connected together that it seems a question whether 
 the manufacture of sulphuric acid and soda in the districts of the Tyne, and parts of 
 Lancashire, or the smelting of copper in South Wales, may not eventually be displaced 
 and carried on concurrently. As it is, the extraction of copper from burnt pyrites is 
 carried on to a considerable extent, either in alkali works or in their immediate 
 proximity, and the methods by which this is done will be described in the section 
 treating of Copper Smelting. 
 
 Methods of using the Nitrous Gases. In many works, instead of liquid nitric acid, 
 a mixture of nitre and sulphuric acid is used in the burners. For this purpose, cast- 
 iron crucibles filled with equal parts by weight of nitre and sulphuric acid (specific 
 gravity T551) are placed on the hearth of the sulphur burner. The crucibles are heated 
 
 by the burning sulphur, and 
 by decomposition of their 
 contents, nitric acid, nitrogen 
 peroxide, and nitrous anhy- 
 dride are evolved, and pass 
 along with the other gas into 
 the lead chambers. Accord- 
 ing as Chili saltpetre or 
 potassium nitrate are em- 
 ployed, sodium sulphate or 
 potassium sulphate remains 
 behind in the crucibles. 
 
 As soon as the decomposi- 
 tion is over, the crucibles are 
 removed from the burner and 
 replaced by others that have 
 been fresh charged. The po- 
 tassium or sodium sulphate 
 is removed from the crucibles 
 when cold, and admits of 
 useful application. 
 
 The mixture of sodium or 
 potassium nitrate and sul- 
 phuric acid is often brought 
 into the burners in small 
 trucks, which may be seen in 
 the furnace (A), depicted in fig. 67. The trucks (d'cT) are made of cast iron and are run 
 into the furnace on a small tramway set a little above the bed of the burner. Where 
 trucks are employed, the burners are generally so constructed that the trucks may 
 be run in at one end and out at the other. 
 
 The use of this mixture for the development of nitrous gases, instead of nitric 
 acid itself, has some disadvantages, amongst the most important of which are, 
 first, the fact that the vapour of nitric acid in the nascent state partly decomposes 
 into nitrogen peroxide and oxygen, thus causing the transmission into the lead 
 chambers of inactive oxide of nitrogen, and, secondly, the vapour, on account of the 
 sulphuric acid it contains, attacks the tubes through which it passes much more ener- 
 getically than the sulphurous oxide evolved by the simple combustion of sulphur. 
 
 Condensation of the Nitrons Gases. Since the condensation of the nitrogen oxides, 
 which escape from the lead chambers together with other gases, is a matter of great 
 importance, inasmuch as the consumption of nitric acid maybe thereby reduced to one- 
 third, a number of contrivances have been proposed for effecting such absorption or con- 
 densation. The most important forms of apparatus that have been constructed for this 
 purpose are the following. 
 
 The Gay-Lussac coke cylinder has been already described. It has received of 
 late several improvements. For instance, there is placed between the swinging trough 
 (I, fig. 49) and the coke layer, a lead plate, into which are fitted from 20 to 25 tubes 
 of the same metal. When the sulphuric acid is tipped out of the trough into this plate, 
 it flows through the tubes, and is thereby better dispersed over the coke than in the 
 old arrangement. .Further the perforated leaden floor of the cylinder for supporting 
 the coke is now sometimes replaced by fire-bricks laid crossways over one another. 
 
 At some places, instead of the gases being passed through a reservoir with compart- 
 ments (M'M', fig. 49), they are conducted through a long flue, from the other extremity 
 of which a continual flow of sulphuric acid is kept up. By this moans the gas is 
 thoroughly dried, which is a matter of importance for the complete absorption. The 
 pieces of coke in the Gay Lussac apparatus are replaced in some works by broken glass. 
 
 FIG. 67. 
 
MANUFACTURE OF SULPHURIC ACID. 
 
 125 
 
 In Finkenhoher's apparatus the chamber gas passes into the bottom of a wide stone- 
 ware cylinder made of several pieces. Sulphuric acid flows down from above over 
 alternating and inclined porous clay plates, and is drawn off below. 
 
 In all these forms of apparatus for the absorption of the nitrous gases, the chief 
 thing is to secure an equally distributed flow of sulphuric acid from above. This is 
 secured either by the use of Mariotti's vessel or by an ingeniously constructed 
 balancing apparatus, which consists of a leaden vessel from which the sulphuric acid 
 flows out below through a horizontal tube, terminating in a vertical cylinder. A 
 leaden bucket floats upon the surface of the sulphuric acid in the cylinder attached to 
 one of the arms of a lever, the other arm of the lever being in connection with a 
 valve which opens and shuts the outlet of the leaden reservoir. Upon opening a cock 
 at the lower part of the cylinder containing the leaden bucket the sulphuric acid flows 
 out and consequently its level sinks, and the bucket sinks with it until it opens the 
 valve of the reservoir and admits a fresh supply of sulphuric acid into the cylinder 
 until the sulphuric acid in the cylinder has attained its former level. An apparatus 
 of this kind when once properly set admits of a perfectly regular flow of sulphuric 
 acid being obtained. 
 
 Condensation of Nitrous Gases in Absorption Bottles. An apparatus of the kind is 
 represented by figs. 68 and 69. The chamber gas passes from the last chamber 
 
 FIG. 68. 
 
 through the tube (f) into the vessel (j), and circulating from a to a is partly condensed. 
 From J' the gas passes through the tube (K) into the first carboy, thence into tt 
 second, third, etc., circulating through the three rows (L, i/, L"), and finally e* 
 into the chimne M. A glass tube of the same width as the tube (x) is gee 
 
 FIG. 69. 
 
 1t into the litter for the purpose of watching the colour of the gases escaping from 
 he ^e^ ^STaGeL of colour or only very slight coloration -dicaes 
 an insufficiency in the chambers either of nitrous gases or of steam. When the pro 
 cess is conducted properly the escaping gas is invariably of an orange colour 
 
 The regulation of the draught in this apparatus is effected by ^^*g^ 
 
126 SULPHUR. 
 
 hour, their contents being run into the first chamber, and the carboys again charged 
 with the acid from the second row of carboys ; these again with the acid contents of the 
 third row, and the latter are charged with fresh sulphuric acid of sp. gr. 1732. 
 
 When the necessary contrivances are at hand the filling operation may be performed 
 by a single workman. Since each carboy is emptied and recharged once daily, it 
 follows that a given quantity of acid requires three days for its passage through the 
 series before being run into the first chamber. 
 
 A carboy of the kind with funnel (qp} for filling, and cock (r) for running off the 
 acid, is shown in section by 3, fig. 68 ; 4 shows in section the tubulatures in which 
 the connecting tubes are fastened ; 5 shows the construction of a cylindrical carboy ; 
 and, finally, 6 shows the construction of the stone cock for running off the acid. 
 
 The emptying and refilling of the carboys is simplified by an arrangement repre- 
 sented by fig. 70. This consists of lateral tubulatures (e e), in which the level of the 
 
 acid stands about an inch higher than 
 the mouths of small glass siphons(//). The 
 latter when filled place the acid contents of 
 the carboys in communication ; for upon 
 fresh acid being poured into the last carboy, 
 this passes into the one next behind it, etc., 
 until it finally reaches the first, becoming 
 saturated with nitrous gases on its long 
 journey. The gas is passed through the 
 connecting tubes (c c) and (KB) in a direction 
 contrary to the acid, thus coming on its 
 FIG. 70. way in contact with acid of continually 
 
 increasing purity. 
 
 As regards the use of sulphuric acid for the absorption of nitrous vapour, experi- 
 ence has shown that the stronger it is, the more nitrous vapour is it capable of 
 absorbing. Direct experiments made with sulphuric acid that had been treated with 
 air and nitric oxide gave the following results : 
 
 Sulphuric acid having a specific gravity of 1'711 absorbed 2'5 per cent, of nitrous 
 anhydride, whilst that of specific gi-avity T846 absorbed 7'9 per cent. 
 
 According to the results of the above experiment, sulphuric acid having a specific 
 gravity of 1*767 absorbs three times as much nitrous anhydrideasacidofsp.gr. 1'7H. 
 In some works the absorption of the nitrous vapour is effected by other substances 
 than sulphuric acid ; thus for instance milk of lime is sometimes employed, with which 
 nitric oxide, nitrous anhydride, etc. combine, forming calcium nitrate. Further witherite 
 (barium carbonate) in a state of fine powder and suspended in water is taken, for 
 preparing by this means barium nitrate, and finally, in some cases, pure water is 
 employed, which is allowed to trickle down through high towers something like the 
 coke towers in the Gay Lussac apparatus. 
 
 Construction of the Chambers. Propositions have often been made, but at present 
 without success, to replace the lead used in making the chambers by a substance 
 cheaper than lead. Thus amongst others the following substances have been pro- 
 posed : zeiodolite, a compound consisting of sulphur and stoneware ; panes of glass 
 cemented together with a resinous cement ; different kinds of stone plates joined 
 together with a cement made of sulphur and sand, etc. Very well worth notice is the 
 use of vulcanised caoutchouc or of gutta-percha, both of which substances have the 
 advantage over lead of being cheaper and lighter than lead. On the other hand, they 
 are more readily attacked by the chamber gas than lead is. 
 
 The number and size of the lead chambers, as already mentioned, are dependent upon 
 the amount of sulphur that is to be burnt. The chief point in constructing chambers 
 is to present as large a surface as possible to the chamber gases, so that they may 
 mix intimately together and easily condense. For this reason it has recently been 
 the practice to place a number of chambers one after another in a series, but it is 
 possible to obtain the desired effect as well with two chambers as with six, provided 
 contrivances are employed for increasing the surface. Fig. 67 represents an arrange- 
 ment of this kind, in which the chamber is fitted with several partitions (E) made of 
 iron rods extending from the floor of the chambers to the roof which they support. 
 These rods are entirely covered with lead and are furnished with sheets of glass sup- 
 ported upon leaden hooks, as shown at 2, fig. 67. These partitions are shorter than 
 the width of the chambers, and are so placed alternately as to make the gas travel in 
 a zigzag direction from one side to the other, increasing thereby the length of the pas- 
 sage and presenting to the gas a greater surface, by contact with which it is more easily 
 intermixed and condensed. Chambers thus constructed have a more constant tempe- 
 rature than those which have only side walls. 
 
 In some works built upon this system, only one chnmber is employed having a 
 
MANUFACTURE OF SULPHURIC ACID. 
 
 127 
 
 capacity of 100,000 to 140,000 cubic feet. At the same time better results have 
 been obtained in works where a second and smaller chamber with one or two curtains is 
 attached to the large one. Of course, in chambers constructed on this system the 
 acid collecting in the second chamber is made to flow back into the principal chamber, 
 as in other cases. 
 
 Another plan may be here mentioned where only a single chamber is employed, 
 but it is divided by curtains into three parts. These curtains are made of lead plates, 
 reaching nearly but not quite to the bottom of the chamber, so that each division is 
 separated from the other by the acid lying in the bottom of the chamber. The 
 chamber gas is passed from one division into the other through tubes, the mouths of 
 which are a little above the level of the acid in the chamber, while the other ends are 
 inserted through the curtains at the upper part. 
 
 Arrangement of Chambers. The general method of arranging vitriol chambers is 
 that represented by figs. 48 and 49 where they are set one after another supported upon 
 wooden frames. In this country, our temperate climate admits of the chambers 
 being in the open air, but in France, Germany, and other parts of the continent 
 they are generally roofed in and surrounded by light brickwork, on account of tho 
 more severe cold of winter. 
 
 The most convenient arrangement of the chambers is that in which the ex- 
 tremities are placed near each other, affording thereby a better opportunity of 
 observing the process, inasmuch as these parts of the system are the most important 
 and require the most attention. An arrangement of this kind is shown by fig. 71. 
 
 FIG. 71. 
 
 A A' are burners, the plates of which are each 6 feet long and 13 feet wide. A tube 
 from 28 to 32 inches in width conducts the products of combustion, together with an 
 excess of atmospheric air, into the small chamber (B), which is 23 feet in length, 13 
 feet wide, and 16^ feet in height, and receives back from the second chamber the 
 acid formed there, passing it on into the principal chamber. B' is the second chamber, 
 of the same dimensions as the first, with which it is in communication by means of 
 the tube bb, which has a diameter of 24 to 27 inches, c c is the principal chamber, 
 the floor of which is made lower than the floors of the other chambers, as it receives 
 the condensed acid of the entire system. This principal chamber is about 120 feet 
 long, 30 feet wide, and 20 feet high. D is the fourth chamber, having a length of 46 
 feet, a width of 20 feet, and is 16 feet high; it communicates with the principal 
 chamber by the tube dd. //is a refrigerator furnished with divisions (similar to the 
 one MM, shown in fig. 49), in which a part of the vapour is condensed. D'is the fifth 
 chamber, of the same size, as D, into which no steam is conducted : ii is a refrigerator 
 similar to//. The total capacity of the five chambers is therefore upwards of 100,000 
 cubic feet. These chambers receive every twenty-four hours the gas produced by the 
 combustion of about ] ton and a half of sulphur. FF is a series of carboys charged 
 with sulphuric acid of sp. gr. 1*711. a is a box with perforated divisions for regulat- 
 ing the draught. 
 
 CONDUCT OF THE CHAMBER PROCESS. When a chamber system has to be set in 
 operation, this is effected in the following manner. Sulphuric acid, of sp. gr. 1-357, 
 is poured upon the floor of the principal chamber, in quantity sufficient to shut out the 
 external air completely from the interior of the chamber. Water is not to be recom- 
 
128 SULPHUR. 
 
 mended for this purpose, both on account of its absorbing sulphurous and nitrous 
 acids, which attack the leaden floor, and also on account of its partly decomposing 
 nitrous anhydride with evolution of nitrogen oxide. As soon as sulphuric acid in 
 sufficient quantity has been poured into the principal chamber, sulphurous oxide is 
 passed from the burners into the chamber. When the air has been displaced from the 
 chamber the supply of nitric acid or of vapours of nitric acid to the chambers is com- 
 menced as above described, an excess being employed at the beginning. The tempera- 
 ture of the chambers is gradually raised by the hot gas, and as soon as it is per- 
 ceptible through the sides of the chambers, the supply of nitric acid or of nitrous 
 vapour is reduced to the normal standard. Earthen plugs fitted into the chamber 
 in various parts serve by an inspection of their surface as a guide to the stage at 
 which the process has arrived, and when the proper point is attained, steam is then 
 passed into the chambers. 
 
 Introduction of Sulphurous Oxide. The relation of the amount of sulphur to the 
 surface of the chambers has been already sufficiently treated of. Where non-con- 
 tinuous burners are employed the sulphur must be thrown in in small portions, at 
 intervals of an hour at a time. The temperature of the sulphur furnace should never 
 be allowed to rise too high, as thereby the sulphur is apt to burn too rapidly, and 
 too much sulphurous oxide is sent into the chambers. A reduction of the temperature 
 of the furnace is effected either by reducing the draught, or by less frequent charging, 
 etc. of the burners. As a matter of course the regulation of the process is easier in 
 proportion to the number of burners employed. 
 
 The Supply rf Atmospheric Air. This depends upon the quantity of sulphur burnt. 
 Sulphur requires for its combustion to sulphurous oxide (S0 2 ) its own weight of 
 oxygen, and for oxidation to sulphuric anhydride (S0 3 ) half as much more ; so that it 
 would require the oxygen contained in rather more than six and a half times its 
 weight of atmospheric air. But since the oxygen of the air admitted is not perfectly 
 absorbed, some excess of air is used containing oxygen amounting to six-tenths the 
 weight of the sulphur burnt. Accordingly every pound of sulphur requires 1 + 0-5 
 + 0'6 = 2-1 pounds of oxygen in the form of atmospheric air. Assuming that 1 
 cubic foot of atmospheric air at a temperature of 0, and under a pressure of 760 mm 
 of mercury, contains -21 cubic foot or (H87 pound of oxygen, the above 2-1 pounds 
 would correspond to a volume of air equal to 113 cubic feet. 
 
 The admission of air is generally regulated by sliding doors attached to the 
 burners, and sometimes by means of a special apparatus which admits of the air being 
 measured and regulated. 
 
 The Supply of Steam. This may be estimated as follows : The chamber acid, 
 when it has a strength corresponding to sp. gr. 1-530, contains 51-1 per cent, of sul- 
 phuric anhydride, corresponding to 20'44 sulphur and 48-9 water. Accordingly every 
 20-44 parts of sulphur requires for its conversion into acid ofsp.gr. 1'530, 48'9 parts of 
 water, or, what is the same, 1 part of sulphur requires theoretically 2-392 parts of 
 water. But since a portion of the water employed is invariably carried off with the 
 other gases, it is usual to pass into th'e chambers 2-5 or 3 parts of water in the form of 
 steam, for every part of sulphur burnt. 
 
 Chamber Crystals. When vitriol chambers are worked with an insufficient 
 supply of moisture, this compound is always formed. Its production is consequently a 
 result of bad management. Different views are held as to the composition of these 
 crystals. According to Weltzien and E. Muller, it is a compound of nitrogen peroxide 
 with sulphuric acid (2H 2 0, 3S0 3 , 2N0 2 ) ; according to Weber it is a compound of 
 sulphuric acid with nitrous anhydride (H 2 S0 4 + N 2 3 S0 3 ). Considering the various 
 ways in which this substance has been prepared artificially, it is easy to understand its 
 formation in vitriol chambers. Thus, it has been formed by the reaction of sulphurous 
 oxide and nitrogen peroxide at a moderate temperature in presence of water; by the 
 action of nitrogen peroxide upon sulphuric acid monohydrate ; by mixing red fuming 
 nitric acid with concentrated sulphuric acid ; by conducting nitric oxide gas and air 
 simultaneously into sulphuric acid ; by bringing together sulphurous oxide, nitric oxide 
 gas, air, and a small quantity of steam ; by conducting sulphurous oxide into very con- 
 centrated nitric acid, or into a mixture of nitric and sulphuric acid, etc. 
 
 Although it seems most probable that the crystals are formed in the lead chambers 
 by the mutual action of nitric oxide, sulphurous oxide, air, and steam, this by no 
 means excludes the possibility of the crystals being formed, under certain conditions, 
 by one or other of the reactions above given. 
 
 The substance is deliquescent; it is soluble in concentrated sulphuric acid ; less so 
 in nitric acid. It is decomposed in contact with an excess of water into sulphuric acid 
 and nitric acid, evolving at the same time copious red fumes of nitrous anhydride. 
 This action of water upon the chamber crystals is of great practical importance, 
 
MANUFACTURE OF SULPHURIC ACID. 
 
 129 
 
 
 because it affords a means of effecting the decomposition of this substance, even when 
 dissolved in sulphuric acid. When it has been formed in the chambers, the admission 
 of steam suffices for the purpose. 
 
 It is evident, from the foregoing, that in the manufacture of sulphuric acid great 
 care must be taken to maintain the right proportion between sulphurous oxide, nitric 
 acid, air, and water. When too much sulphurous oxide is present it escapes into the 
 chimney unoxidised ; when nitric acid is used in excess, nitric oxide, nitrous anhydride, 
 etc. are also carried into the chimney with the residual nitrogen of the air ; when 
 insufficient water is present, chamber crystals are formed, and, finally, when too much 
 air is sent into the chambers, the gases have not sufficient time for reacting upon 
 one another, and thus escape in part unaltered. 
 
 The temperature most suitable for the formation of sulphuric acid is between 40 
 and 60. It is regulated either by the rate of admission of steam or by the extent to 
 which the sulphurous oxide is heated. 
 
 Introduction of the Nitric Acid. At the beginning of the operation the calculated 
 quantity of nitric acid required is about 10 or 15 per cent, of the weight of sulphur 
 burnt ; during the process, however, the quantity of nitric acid necessary is reckoned 
 at about 5 or 6 per cent. Theoretically, when the process is once in operation, no 
 further addition of nitric acid ought to be required ; but in reality oxides of nitrogen 
 are carried away in such quantity by the residual nitrogen of the air that a continual 
 supply of fresh nitric acid is necessary. If a cheap method of preparing oxygen gas 
 were known, it would be possible not only to effect a great saving of nitric acid, but 
 at the same time the operation of manufacturing sulphuric acid might then be con- 
 ducted in very much smaller chambers. 
 
 Temperature of the Chambers. The proper regulation of the temperature of the 
 chambers is a matter of great importance. The process of sulphuric acid manufacture 
 is found to be most successful when a thermometer placed at a distance of 5 feet 
 from the floor of the principal chamber shows a temperature of 40 or 44. The tem- 
 perature, however, in the interior of the chambers varies far more, fluctuating between 
 40 and 60. The other chambers are also furnished with thermometers. The regu- 
 lation of the temperature in the chambers is effected by increasing or diminishing the 
 supply of nitric acid or nitrous gas ; the greater the quantity of nitric acid admitted 
 in a given time the higher is the temperature. In order to prevent the sulphurous 
 oxide from entering the chambers too hot, the gas from the burners is first conducted 
 either through a brickwork flue, or, in some sulphuric acid works, through condensers 
 kept cold by a stream of water. 
 
 In judging as to the proper course of the process, two points have to be con- 
 sidered, viz. the specific gravity of the chamber acid and the character of the 
 chamber gas. 
 
 The Specific Gravity of the Chamber Acid. For the purpose of determining this, 
 funnel-shaped arrangements of lead (A A, figs. 72 and 73), placed about 3 feet above the 
 floor of the chambers, are attached to the chambers in different parts. These serve to 
 collect the sulphuric acid as it trickles down the sides of the chambers, the acid flow- 
 
 FIG. 72. 
 
 FIG. 73. 
 
 ing out through the tube (A') which passes through the wall of ^ 
 
 vessel (B), containing an hydrometer, and then flowing back again into 
 
 through the tube (d). ,, ,, . 
 
 The Character of the 6w.-This is determined by the odour and colour^ 
 is ascertained by test tappings, the latter by means of windows i 
 
130 
 
 SULPHUR. 
 
 another in the sides of the chambers. The colour of the escaping gas is likewise 
 determined either by the aid of windows placed opposite one another, or by wide glass 
 tubes. The gas ought to have a reddish-yellow colour. If the coloration is too 
 light, sulphurous oxide and sulphuric acid are apt to escape ; if too dark, too much 
 nitric acid has been employed. In the former case the supply of nitric acid must be 
 increased. 
 
 Determination of the Absorption of the Nitrous Gases in the Coke Tower, or other Con- 
 densing Arrangements. This is most advantageously effected by means of Hart's titra- 
 tion method, which depends upon the fact that urea and nitrous anhydride decompose 
 one another, forming water and nitrogen. When, therefore, a small quantity of the 
 sulphuric acid to be tested is dropped by means of a burette into a solution containing 
 a definite quantity of urea, paste containing potassium iodide is not coloured blue by 
 the solution so long as undecomposed urea is present, as the nitrous anhydride which 
 is the cause of the blue coloration is decomposed by it. The amount of nitrous 
 anhydride in the sulphuric acid to be examined may therefore be easily determined by 
 the quantity of such sulphuric acid necessary for the decomposition of a known quan- 
 tity of a solution of urea. 
 
 CONCENTRATION OF SULPHURIC ACID. This operation is conducted in two stages : 
 first, the concentration in open lead pans to sp. gr. 1752, and then the concentration 
 up to sp. gr. 1'842, in vessels of platinum or glass, other substances not being able to 
 resist either the action of the hot acid or the high temperature. 
 
 An apparatus for concentrating sulphuric acid which is much used is shown on 
 fig. 74. It consists of two leaden pans (A and B) supported on cast-iron plates, and 
 
 FIG. 74. 
 
 heated by the hot air from the furnace (c). Immediately above c is a platinum retort 
 (D), into which flows the acid that has been concentrated in the pan (B) to sp. gr. l - 752, 
 and is therein heated to the boiling point. Platinum is not acted upon by either 
 cold or boiling sulphuric acid; its melting point (1800 1900) is far above the boil- 
 ing point of concentrated sulphuric acid, which is only 338. However, the platinum 
 vessels used for concentrating sulphuric acid are often considerably corroded, partly 
 by the action of oxides of nitrogen, and partly by chlorine, when the saltpetre used in 
 the nitre pots contained sodium chloride. 
 
 The sulphuric acid is run from the chambers through a leaden tube into the pan 
 (A), where it is often submitted to a process of purification, consisting in a treatment 
 with sulphurous oxide gas while in a hot state, the oxides of nitrogen being thus re- 
 duced, and the sulphurous oxide itself converted into sulphuric acid. For this purpose 
 the pan (A) has a lid made of sheet lead arranged bell-like over the sulphuric'acid in 
 it. The four vertical sides close the apparatus hermetically, while the partitions 
 inside do not quite reach the sides, and so the sulphurous oxide gas, entering at a, has 
 to pass backwards and forwards, and comes as much as possible in contact with the 
 sulphuric acid. 
 
 The sulphurous oxide used for this purpose is drawn from the sulphur burner (A, 
 fig. 48) and passed through a tube (a, fig. 74) under the leaden lid above mentioned. 
 It then circulates over the heated sulphuric acid, any excess of it escaping, together 
 with nitric oxide and nitrous oxide thus formed and the steam carried over, through a 
 into the wide leaden tube (D, fig. 48), whence the gas passes into the chamber (F/). In 
 order to draw the sulphurous oxide from the burner through the entire apparatus, a 
 
MANUFACTURE OF SULPHURIC ACID. 131 
 
 steam aspirator is fitted at D, fig. 48, consisting of a steam-pipe an inch in diameter 
 from which steam is ejected through an opening one fifth of an inch in diameter 
 at a tension of about two atmospheres. The sulphuric acid flows from the pan (A) 
 through a syphon into a second pan (B), where a further concentration to about sp gr 
 1750 is effected. In this pan the last portions of oxides of nitrogen are often de- 
 stroyed by the addition of from i to 1 part of ammonium sulphate per 1000 parts of 
 acid. The sulphuric acid then flows through a syphon (c) into the regulator (d), the 
 interior arrangement of which controls the flow of acid into the still (D). This re- 
 gulator consists of a cylindrical vessel (d), with an outflow pipe about half-way up 
 the side, and supported upon chains to admit of being drawn up or lowered at pleasure. 
 The level of the acid in which the end of the syphon terminates is thus raised or 
 lowered ; the flow of sulphuric acid into the funnel of the platinum retort is accord- 
 ingly made quicker or slower, or stopped altogether. 
 
 Often, instead of two lead pans, three or four are arranged terrace-like one above 
 the other, and they generally have a separate furnace. It may be here mentioned that 
 the first concentration is in many works effected by passing the gas from the furnace 
 through a brickwork chamber above the surface of the acid in the evaporating pans. 
 
 The final concentration of sulphuric acid is generally carried out in platinum 
 stills ; a distinction being made between intermittent and continuous working. 
 
 In intermittent working the platinum still (D, fig. 74) is three quarters filled 
 with acid, the quantity of acid poured in being observed by means of a platinum float, 
 and as soon as about two tenths of the liquid has distilled over, a further quantity of 
 acid is run into the still. The vapour of the boiling acid escapes through the head 
 of the still (D) into a condensing worm at the side not shown in the drawing, where 
 it is condensed and flows into a leaden reservoir. 
 
 The distillate thus obtained contains at first a great quantity of water and very 
 little acid, but in proportion as the acid in the still becomes concentrated, and its 
 boiling-point rises, a stronger acid distils over, and it would be possible in this way 
 to raise the temperature so high that at last pure acid would distill over. It is, 
 however, not customary to raise the temperature of the acid in the platinum still so 
 high as this, except when an extra concentrated acid is required. This acid ought to 
 have a specific gravity of T842. 
 
 On account especially of the high temperature required in the production of this 
 acid, the reduction of temperature caused by the flow of much cooler acid from the 
 leaden pans is so great, that the sides of the still contract very considerably, often 
 producing cracks in the still, after a number of operations have been carried out. 
 The sulphuric acid is distilled generally only up to the point where the distillate 
 shows a specific gravity of T152. Payen represents this acid distillate as having a 
 specific gravity of 1*420, and it would be therefore stronger. The acid remaining in 
 the platinum still shows a specific gravity of 1'846. 
 
 The Continuous Process. This process, in which the acid is kept continually 
 flowing in and out of the platinum vessel, is as a rule to be preferred to the inter- 
 mittent process. By the continuous process an acid is obtained which has a specific 
 gravity of only T819, but for most purposes it is as good as the acid of sp. gr. 1-848. 
 The continuous process has this further advantage, that about half as much acid 
 again is produced as by the intermittent process; and owing to the level being 
 constant in the platinum stills, no sudden cooling is apt to take place, the platinum 
 stills being on this account far less attacked. 
 
 When the sulphuric acid has attained the desired degree of concentration, it is 
 drawn off with a platinum syphon (g g' g" h, fig. 74) reaching to within a distance 
 of one third of an inch from the bottom of the still. In order to set the flow of acid 
 going, both the platinum plugs g'g' are removed, and sulphuric acid poured through one 
 of the two small funnels into the long arm of the syphon ; the other funnel serves for 
 the escape of the air. As soon as the syphon arm is full up to the mouth of the 
 funnel the platinum plugs are again fitted in, and the cock h opened, whereupon the 
 concentrated acid flows out into carboys. Since the acid as it comes from the platinum 
 retort has a high temperature, it is necessary to cool it before running it into the 
 carboys, so as to avoid cracking them. For this purpose it is passed through a tube 
 fitted into a condenser, the latter being so arranged that cold water is kept flowing 
 in at its lowest point, and the heated water is let off above. Other forms of apparatus 
 something like a Liebig's condenser are sometimes used, the limb of the syphon passing 
 through a large tub (K) filled with water. The syphon limb has often several branches, 
 so as to increase the cooling surface. In such a case, however, the branches all taken 
 together do not represent a greater sectional area than the syphon at its upper or 
 lower end, where the branches unite. Other contrivances consist in allowing the acid 
 to flow from the syphon through a funnel into a worm condenser, whereby the cooling 
 
 K2 
 
132 
 
 SULPHUR. 
 
 is very thoroughly effected. When it is desired to despatch the carboys as soon as 
 filled, a float of glass or platinum is placed in the mouth of each carboy extending 
 beyond its neck, and connected with a mechanical arrangement which sets a bell 
 ringing as soon as the acid in the carboy has risen to within 1^ or 2 inches of the 
 mouth of the carboy, thereby intimating to a workman when it is necessary to close 
 the cock and remove the carboy. 
 
 An improved apparatus introduced by Chapuis, Demoutis, and Quenessen, is repre- 
 sented by figs. 75 and 76. The platinum still rests upon a bed of fire bricks, and is 
 heated by the hot air from the furnace (E) circulating round the still in the flues (o o'). 
 The still is fitted with a head (A), through the neck of which the vapour is conducted 
 into a leaden condensing worm (B s s B). The hollow globular vessel (B) is kept continu- 
 ally half filled with condensed acid, and is consequently not attacked by the acid 
 dropping into it from the still. The continual influx of acid of sp.gr. 1-580 is here also 
 effected by means of the apparatus (d, fig. 74). From this the acid flows into the funnel 
 (b) fitted with a dropping arrangement with holes (c), which serves to distribute the acid 
 over the interior and heated sides of the still, by which it is considerably concentrated 
 before it gets to the remaining contents of the still. On the other side of the still is 
 fitted a syphon (tt) for the removal of the concentrated acid, which runs off in a continual 
 stream. The process of clarification, coding, and filling into carboys is considerably 
 
 Fro. 75. 
 
 C.UPLWK 
 
 FIG. 76. 
 
 assisted by the use of the apparatus shown in fig. 77. The acid flows from the end of 
 the cooling syphon through the cock b into a number of "Woulfe's bottles (cVY'V"), 
 arranged in a long trough filled with cold water, and communicating with one another 
 by means of syphons (dd! d"). A fourth syphon (d"") of platinum closed by the cock 
 () serves for drawing off the cooled acid into carboys for exportation. For the sake of 
 sparing platinum and thereby rendering the whole apparatus cheaper, theso stills are 
 
MANUFACTURE OF SULPHURIC ACID. 133 
 
 sometimes constructed with a leaden head fitting upon the platinum vessels The 
 upper edge of the platinum still is then bent round over an iron gutter, and the conical 
 
 Fia. 77. 
 
 leaden head fits into this gutter and closes the retort with an hydraulic joint. At 
 present a suitable cooling apparatus is wanting for the leaden cap, which, when too 
 hot, sinks in by virtue of its own weight. A cap with double sides, between which the 
 chamber acid might be made to flow, so as to give it the required temperature, would 
 possibly remove the difficulty.' 
 
 An apparatus entirely of platinum costs several thousand pounds. With an appa- 
 ratus of this kind as much as four tons of ordinary sulphuric acid maybe produced daily. 
 The daily wear and tear and interest on first cost it. however, less than the cost in- 
 volved in the use of the glass retorts in many cases, apart from the risk incurred by 
 the workmen when they are used. The conditions are still more favourable where 
 platinum stills are employed in the continuous process. 
 
 Concentration of Sulphuric Acid in Glass Retorts. -At the time when the manu- 
 facture of sulphuric acid was in its infancy, the acid was concentrated in large glass 
 retorts of ordinary form, each retort being set upon a sand bath. A number of 
 retorts, varying from ten to twelve and more, were placed in a double row and 
 heated by a single fire. Each retort was connected by an adapter with a carboy, into 
 which the weaker acid distilled over. This arrangement was simplified, and the 
 consumption of fuel reduced by covering the retorts with a coating of clay before 
 heating them. 
 
 This apparatus is still in use in several places, as, for instance, in the neighbour- 
 hood of Montpellier, and generally in the vicinity of glass works, where large retorts 
 are cheap. Platinum apparatus has of late met with severe competition from glass 
 retorts of a new kind. These glass vessels are cylindrical in shape, their bottoms 
 arching outwards ; they are furnished above with a neck, into which one end of the 
 delivery tube fits tightly, while the other end dips into a leaden receiver for collecting 
 the distilled acid. The glass vessel stands in a sand bath, the bottom of which alone is 
 covered with sand, each sand bath being heated by a separate fire, the flame imping- 
 ing round the bath on all sides. When the concentration has proceeded far enough 
 the tubes connecting the retort with the leaden receivers are removed, and the acid 
 drawn off from the retorts with a syphon. The retorts are then again filled with 
 acid previously made hot. A retort of the kind holds about 30 gallons, and it yields 
 at each operation 3 cwts. of concentrated acid. Balloon-shaped vessels have also 
 recently been employed in the concentration of sulphuric acid. 
 
 Great attention to the most suitable construction of the glass retorts has led^ of 
 late to such perfection in their manufacture that in some localities the cost of working 
 them is less than that involved in the use of platinum stills. 
 
 Several other methods of concentrating sulphuric acid have been proposed, none 
 of which have met with success, and on this account they need only cursory mention. 
 Kuhlman and Keller recommend concentrating sulphuric acid in vacuum, so as to 
 reduce the boiling point of the acid and enable vessels of lead to be employed. It 
 has, however, been found that notwithstanding the reduction of the boiling point, the 
 leaden vessels are far too much acted upon to render this method practicable. Clough 
 proposed concentrating the acid in leaden pans, kept cool by a constant current of 
 cold water ; the removal of water from the acid being effected by passing heated air 
 from a furnace over the surface of the acid. Gossage suggested a method according to 
 which the acid is allowed to trickle down over flints piled up in a high tower, hot air 
 being passed through the flints in an opposite direction. 
 
134 
 
 SULPHUR. 
 
 PURIFICATION OF CHAMBER ACID. The chamber acid generally contains impuri- 
 ties derived from the raw materials used in its preparation, and when it has to be 
 concentrated is first submitted to a process of purification which is often combined 
 with the concentration. The commonest impurities are sulphurous acid, selenium, 
 thallium, lead, organic substances, arsenous acid, and the oxides of nitrogen (nitric 
 acid, nitrous anhydride, etc.) As a rule, the purification is limited to the removal of 
 the last-mentioned substances. 
 
 The Oxides of Nitrogen. Nitric acid, nitrous anhydride, etc., would be destroyed 
 when sulphuric acid is deprived of its arsenical impurities by sulphuretted hydrogen ; 
 but if this is not done they may be easily removed by adding to the sulphuric acid a 
 small quantity of ammonium sulphate. On the application of heat, ammonia reacts 
 with the nitrous anhydride according to the following equation : 
 
 2NH 3 + N 2 3 = 4N + 3H 2 0. 
 
 The oxides of nitrogen may be also completely removed by heating the sulphuric 
 acid with a little oxalic acid. Carbonic oxide is ttms formed which acts as a reducing 
 agent upon the oxides of nitrogen. Nitric acid may be got rid of most easily according 
 to Wackenroder by heating the sulphuric acid with sugar or starch, or according to 
 Barruel with some sulphur. By treatment with sulphurous oxide gas alone the greater 
 portion of the oxides of nitrogen may be removed. 
 
 Chamber acid, having as it comes from the chambers a sp. gr. of 1*535 to 1*550, 
 may be concentrated to sp. gr. 1*583, and at the same time freed from the oxides of 
 
 nitrogen by means 
 of the arrangement 
 shown in section 
 and projection by 
 78 and 79. 
 The chamber acid 
 passes through the 
 tube (a) into a lead 
 pan (b b b), sur- 
 rounded by brick- 
 work (ccc). The 
 acid flows slowly 
 round the tongue 
 (d d) towards the 
 tube (e), through 
 which it passes into 
 the lead pans next 
 the platinum still. 
 On its way the sul- 
 phuric acid meets 
 with a stream of 
 sulphurous oxide 
 and air passing in 
 a contrary direction, 
 as shown by the ar- 
 rows, fig. 79. The 
 sulphurous oxide is 
 prepared in the fur- 
 nace (/) by burning 
 sulphur, and it 
 passes, mixed with 
 air, through the 
 cast-iron tube (g g) 
 into the chamber 
 (h h), where the 
 greater portion of 
 the sulphur vapour 
 condenses. From 
 
 thence it takes the way above mentioned, passing over the sulphuric acid, abstract- 
 ing from the latter some of its moisture, and destroying the nitrous admixtures, 
 escaping finally through the tube (i) into the first vitriol chamber. 
 
 Arsenous acid may be got rid of by conducting sulphuretted hydrogen gas into the 
 acid diluted to sp. gr. 1*420, accelerating the action by the application of heat, and 
 filtering off the arsenous sulphide. The sulphuretted hydrogen is either prepared by 
 the action of dilute sulphuric acid upon iron sulphide, or, according to Du Pasquier's 
 method, it is evolved in the acid to be purified by throwing in some pieces of barium 
 
 FIG. 78. 
 
 FIG. 79. 
 
MANUFACTURE OF SULPHURIC ACID. 135 
 
 sulphide. Sulphuretted hydrogen may also be produced by the action of carburetted 
 gas upon red-hot pyrites. When the arsenic in sulphuric acid is in the form of arse- 
 nous acid alone, it may be easily got rid of by Buchner's method. For this purpose 
 the arsenic is converted into arsenous chloride by passing hydrochloric acid gas into 
 the sulphuric acid ; by subsequently heating the acid to a temperature of 132 the 
 volatile arsenous chloride is driven off. When arsenic acid is present, it must be re- 
 duced to arsenous acid by passing into the acid to be purified sulphurous oxide gas, or 
 heating it with some charcoal before treatment with hydrochloric acid. 
 
 Attempts to utilise atmospheric air for the oxidation of sulphurous oxide by con- 
 ducting a mixture of the two over porous substances, such as mixtures of clay with 
 the oxides of iron and chromium, or of copper and chromium oxides, pumice, etc., 
 have not as yet led to any useful results, and no method has yet been devised which 
 would supersede the indirect oxidation of sulphurous oxide by nitric acid, and the use 
 of large leaden chambers for bringing about the reaction. 
 
 Wo'hler and Mahla suggested conducting a mixture of sulphurous oxide and air 
 over red-hot oxides, such as a mixture of copper and chromium oxides, etc. Petrie 
 suggested that a mixture of sulphurous oxide and air at a temperature of 300 should 
 be passed upwards through a high tower filled with pieces of granite kept moist with 
 water. Persoz proposed passing sulphurous oxide into diluted nitric acid, by which 
 the sulphurous oxide is converted into sulphuric acid and remains in solution, while 
 the nitrogen peroxide formed escapes, and may be again converted into nitric acid by 
 the action of air and water. In this reaction the nitric acid may be replaced by a 
 nitrate mixed with hydrochloric acid. In the latter case nitrogen oxydichloride is 
 formed, which by the action of air and water is, like nitrogen peroxide, reconverted 
 into nitric acid. Hahner and Macfarlane suggest oxidising sulphurous oxide by 
 chlorine in the presence of steam. 
 
 But although such methods hare not yet been rendered practicable on the large 
 scale for the production of sulphuric acid, the oxidation of sulphurous oxide by atmo- 
 spheric air : and without the intervention of nitric acid, has been so far successfully 
 applied by Hargreaves in the direct production of sodium sulphate from sodium 
 chloride, that his method promises to do away with the necessity for sulphuric acid in 
 the manufacture of soda, for which purpose greater part of the sulphuric acid now 
 made is used. So far as this manufacture is concerned therefore, the adoption of Har- 
 greaves' method would render the use of lead chambers unnecessary. (See ' Soda 
 Manufacture.') 
 
 Methods have also been proposed for separating the sulphuric acid contained in 
 gypsum, Fremy suggesting heating gypsum with sand, and Tilghman proposing to 
 pass steam over red-hot pieces of gypsum, the products in both cases being passed 
 into the lead chambers. Kohsel suggests heating gypsum with charcoal, thus form- 
 ing carbonic acid and calcium sulphide. The carbonic acid hereby evolved is 
 made to decompose a solution of calcium sulphide from a former operation, the 
 sulphuretted hydrogen thus formed being burnt, and the gaseous product conducted 
 into the lead chambers. A number of other propositions have been made for making 
 use of gypsum as a source of sulphuric acid, which for want of space cannot be detailed 
 here. 
 
 Uses. Sulphuric acid is used in the preparation of most other acids, as, for 
 instance, sulphurous, hydrochloric, nitric, phosphoric, boracic, fluoric, tartaric, citric, 
 stearic, and other fatty acids. 
 
 Sulphuric acid is employed in the preparation of most sulphates, such as those of 
 sodium (Glauber's salt), potassium, ammonium, aluminum, iron, copper, magnesium 
 (Epsom salt), mercury, the latter being again used for the preparation of mercury 
 chloride (corrosive sublimate), and protochloride (calomel) ; alum also is indirectly 
 prepared by the agency of sulphuric acid. 
 
 Sulphuric acid in a diluted state is used for dissolving iron and zinc ; the hydrogen 
 thus evolved being employed for filling air balloons, for Dobereiner's fire apparatus, 
 for the oxhydrogen flame used for melting purposes and for illuminating microscopic 
 objects, also for the detection of arsenic in Marsh's apparatus. Diluted sulphuric acid 
 is also made use of in exciting an electric current between zinc and copper and c 
 substances, for electro-plating, telegraphic and other purposes. 
 
 Sulphuric acid is further a valuable reagent in the hands of the chemist, in 
 alkalimetrical and acidimetrical determinations, in the quantitative determination 
 barium and lead, etc. Sulphuric acid is also used for cleaning the si 
 plates ; in the manufacture of tin plate and galvanised iron ; for cleaning copper an< 
 silver before coining; for refining of gold and silver; for separating gold irom 
 alloys of copper ; further, in the dissolving of indigo. It w also xised in 
 preparation of ether, madder dyes, in the purification of various oils, for giving : 
 dark colour to wood, in the manufacture of blacking, of sugar from starch, and 
 
136: SULPHUR 
 
 for preparing guncotton, collodion, nitrobenzol, nitroglycerin, picric acid and its salts, 
 vegetable parchment, etc. Sulphuric acid mixed with from 20 to 30 times its weight of 
 blood coagulates and preserves it ; it also acts in the same way upon urine, preventing 
 in it the unpleasant alkaline fermentation, and is on this account used for disinfecting 
 purposes. Sulphuric acid is also used for precipitating the lime from molasses, for ex- 
 tracting fa to from woollen or cotton goods, for separating out the pure hydrocarbons and 
 other constituents from different kinds of tars. Sulphuric acid is also very effective for 
 the removal from casks or vats of bad smells caused by fungoid growths, such vessels 
 being treated for a short time with sulphuric acid and afterwards rinsed out with clean 
 water to remove adhering acid. 
 
 A very extensive use is now made of sulphuric acid in the manufacture of super- 
 phosphates, for converting the insoluble calcium phosphate of various substances into 
 a soluble condition. The manufactories of superphosphates at Barking, Plaistow, 
 Deptford and Birmingham consume annually several thousand tons of sulphuric acid 
 in the manufacture of superphosphates. 
 
 Finalty, sulphuric acid is extensively employed as a drying agent in chemical 
 laboratories, in virtue of its strong hygroscopic properties. 
 
 SULPHURETTED HYDROGEN. 
 
 FORMULA H 2 S. MOLECULAR WEIGHT 34. 
 
 History. Although this gas must have been frequently observed by the old 
 chemists, its existence as a distinct substance was not recognised until the seventeenth 
 century, and it was not until the end of the eighteenth century that its chemical nature 
 was definitely established by Berthollet. 
 
 Occurrence. Sulphuretted hydrogen often occurs naturally in the water of 
 springs. The best known of the sulphuretted springs are those of Harrogate, Aix- 
 la-Chapelle, Baden near Vienna, Eilsen, Burtscheid, Bagneres, Bareges, etc. Sul- 
 phuretted hydrogen is also found wherever nitrogenous organic substances containing 
 sulphur, or in contact with sulphates, are undergoing decay. 
 
 Characters. Sulphuretted hydrogen is, at ordinary temperatures, a colourless 
 gas; its density as compared with hydrogen gas is 1 7, and its specific gravity re- 
 latively to atmospheric air is 1'1912. When submitted to a pressure of 16 atmo- 
 spheres, sulphuretted hydrogen gas condenses to a colourless mobile liquid, having a 
 specific gravity of 0'9 as compared with water, and this solidifies to a crystalline mass 
 at a temperature of 85. Sulphuretted hydrogen has a penetrating, disgusting 
 smell, resembling that of rotten eggs : it is irrespirable, very poisonous, and combustible, 
 burning with a bluish flame, the products of its combustion being sulphurous oxide and 
 water. Sulphuretted hydrogen imparts a wine red colour to the blue colouring matter of 
 vegetables, a property which it shares in common with boracic, carbonic, and other 
 weak acids, and on this account it is also called hydrosulphuric acid. When passed 
 through a tube heated to redness, sulphuretted hydrogen is decomposed with depo- 
 sition of sulphur. Water dissolves from 2-5 to 3 times its volume of sulphuretted 
 hydrogen gas. The solution is clear when freshly prepared, but gradually becomes 
 muddy by keeping, owing to the separation of sulphur as a result of partial oxidation. 
 For this reason sulphuretted hydrogen water requires to be kept in well -stoppered 
 bottles. 
 
 Sulphuretted hydrogen absorbed by humus or other porous substances decomposes 
 in contact with air, its hydrogen oxidising to water, while sulphur is at the same time 
 set free. When a mixture of sulphuretted hydrogen and air is heated in contact 
 with porous bodies to 40 50, a portion of the sulphur is oxidised as well as the 
 hydrogen, water and sulphuric acid being formed. 
 
 Sulphuretted hydrogen is an unstable substance ; chlorine readily abstracts its hy- 
 drogen, forming hydrochloric acid and liberating sulphur, which then combines with 
 chlorine when it is present in excess. Chlorine is therefore employed as an antidote in 
 cases of poisoning with sulphuretted hydrogen. Bromine and iodine act in a similar 
 manner upon sulphuretted hydrogen. Fuming nitric acid decomposes sulphuretted 
 hydrogen with explosive violence. Sulphuretted hydrogen is decomposed by most 
 motals with the aid of heat, hydrogen gas being liberated and a sulphide of the metal 
 formed. The property possessed by sulphuretted hydrogen of precipitating several 
 metals in the form of sulphides from solutions of their salts renders it a very valuable 
 reagent in analytical operations. 
 
SULPHURETTED HYDROGEN. 137 
 
 Preparation. "When required on a small scale, sulphuretted hydrogen is 
 generally prepared by pouring dilute sulphuric acid or hydrochloric acid upon pieces 
 of ferrous sulphide contained in a good-sized glass flask. The reaction is represented 
 by the following equation : 
 
 FeS + H 2 S0 4 = FeS0 4 + H 2 S. 
 
 The gas is passed through aWoulfe's bottle, containing some water, to free it from 
 any particles of acid carried over with the stream of gas. 
 
 For the preparation of sulphuretted hydrogen free from uncombined hydrogen, it is 
 better to use antimonous sulphide, instead of ordinary ferrous sulphide which always 
 contains some metallic iron that gives rise to evolution of hydrogen. The crude anti- 
 monous sulphide of commerce suffices for this purpose, and hydrochloric acid is used for 
 decomposing it. 
 
 Sulphuretted hydrogen is also prepared on a large scale from ferrous sulphide and 
 dilute sulphuric acid. The ferrous sulphide is obtained by melting together 28 parts 
 of iron scraps with 16 parts of sulphur in graphite crucibles two feet high. At Oker 
 the ferrous sulphide is prepared by melting together 2 parts of iron pyrites poor in 
 copper with 1 part of copper ore slag, containing about 50 per cent, iron and 1 per 
 cent, copper. The excess of sulphur of the iron pyrites combines with the iron of the 
 slag, forming ferrous sulphide. Upon treating the product with acid, the copper 
 sulphide remains unaltered. A similar method is employed at Freiberg. 
 
 The ferrous sulphide obtained in either of the above ways is placed in leaden vessels 
 and covered with dilute sulphuric acid, the sulphuretted hydrogen evolved being 
 passed before using through a vessel containing water. 
 
 Weltz's method of preparing sulphuretted hydrogen depends upon the fact that 
 hydrogen and hydrocarbon gases in contact with red-hot iron pyrites yield sulphu- 
 retted hydrogen. The gas employed for this purpose is obtained by imperfect com- 
 bustion of fuel, conducted in such a way that the air supplied for the combustion, in- 
 stead of ascending through the burning material, is made to pass downwards 
 through the heated fuel and thus produce, by the heat generated, a kind of distillation 
 of the unburnt fuel, by which means the gas becomes charged with hydrogen and car- 
 buretted compounds. 
 
 The generator employed has the form of a shaft furnace ; it is completely filled 
 with charcoal, which is ignited above the grate, and while the furnace 'is open above, 
 air is blown in from below, so as to bring the entire mass to a red heat. The generator 
 is then well closed above and the gas is compelled to pass downwards through the 
 grate and through a brick flue, into the pyrites furnaces. The pyrites furnaces are 
 built of fire bricks, and are entirely filled with pyrites. The gas from the generator 
 enters the pyrites furnaces through a fire bridge, through which air is passed at the 
 same time, sufficient to cause partial combustion of the gas and the heating of the 
 pyrites up to the temperature required for its decomposition by the unburnt gas in 
 the manner already mentioned. 
 
 Uses. -Sulphuretted hydrogen is employed principally as an analytical reagent in 
 chemical laboratories, in a state of solution as well as in the gaseous state. It is used 
 in qualitative analysis for separating one group of metals from another, the metals of 
 the one group being precipitated by it from acidulated solutions of their salts, while 
 the metals of the other group are not precipitated, but remain in the filtrate. 
 
 Sulphuretted hydrogen is also often employed in quantitative analysis and for the 
 preparation of ammonium sulphide and potassium sulphide, etc. , 
 
 Sulphuretted hydrogen is used on a large scale for removing arsenic from sulphuric 
 acid, for precipitating copper from solutions of the salts of that metal, and for pre 
 cipitating gold in the extraction of gold and silver, from waste materials containing 
 them, by the chlorine process. 
 
 CARBON BISULPHIDE. 
 
 FORMULA CS 2 . MOLECULAR WEIGHT 76. 
 
 History-Bisulphide of carbon was accidentally discovered b> Lam pad i us in 
 1796, while heating charcoal to redness with pyrites. He described the proper ies of the 
 body, but he did not succeed in obtaining it again according to the old meth 
 1803. Meanwhile Clement and Desormes obtained the same substance by t e actio 
 of sulphur upon charcoal, and named it sulfurc <k carbone J^P^'^t 
 disputed. Berthollet asserted that the compound obtained by O^*^"*? 
 contained no carbon, but consisted of sulphur and hydrogen only, and Vauquehn ez- 
 
138 SULPHUR. 
 
 pressed the same opinion. In 1811 Cluzel laid before the French Academy a paper 
 containing the results of experiments, according to which, carbon bisulphide was 
 asserted to contain, besides carbon, nitrogen and hydrogen as well. The consequence 
 of this assertion of Cluzel's was that Vauquelin began a new series of researches into 
 the nature of the body, and eventually succeeded in establishing its true composition. 
 
 Characters. Carbon bisulphide at the ordinary temperature is a mobile, 
 strongly refracting liquid, having a specific gravity of T293. It is colourless, 
 and has a peculiar unpleasant odour. The smell of commercial carbon bisulphide is, 
 however, partly owing to its containing small quantities of sulphuretted hydrogen ; 
 it may therefore be got rid of by shaking the carbon bisulphide up with water 
 containing hydrated oxide of lead suspended in it, decanting, and distilling; the 
 sulphuretted hydrogen combines with the hydrated lead oxide, and the smell dis- 
 appears. According to Cloez, it is better to make use of small pieces of mercuric 
 chloride, in the place of hydrated lead oxide, the carbon bisulphide being shaken up 
 with the mercuric chloride, and then slowly distilled in a water bath. Pure carbon 
 bisulphide boils at 48, the specific gravity of its vapour is 2'66. The latent heat of 
 the vapour of carbon bisulphide is much less than that of steam. It follows, as a 
 consequence of this, that carbon bisulphide vapour need be deprived of only a small 
 quantity of heat in order to insure its condensation ; and that on this account it is 
 advisable to surround vessels from which carbon bisulphide is distilled with bad 
 conductors of heat, otherwise a large quantity of the vapour condenses before getting 
 into the condenser, and flows back into the distilling vessel. 
 
 When burnt, carbon bisulphide develops a heat equal to 3400 heat-units, less 
 than half that of wood charcoal. It burns with a beautiful blue flame, yielding 
 carbonic dioxide and sulphurous oxide, according to the equation : 
 
 CS 2 + 60 = C0 2 + 2S0 2 
 
 Its tension is so considerable that it takes fire at the ordinary temperature (18- 
 22 C.) when a burning body is brought near the surface of the liquid, it not being 
 necessary, in order to cause ignition, that the burning body should come in contact 
 with the liquid itself ; a property which very much increases its dangerous nature. A 
 mixture of carbon bisulphide with air explodes, under certain conditions, with great 
 violence. For this reason, it is necessary to exercise great caution with vessels con- 
 taining carbon bisulphide, for an explosion of a vessel containing this substance may 
 very easily cause the contents of neighbouring vessels to take fire ; and in addition to 
 the danger arising from the explosion itself, suffocating gases are produced, such as 
 sulphurous oxide and carbonic dioxide, as well as the unburnt nitrogen of the air. 
 
 Carbon bisulphide is almost insoluble in water, but is very easily soluble in 
 alcohol, benzol, oil of turpentine, and other ^liquid hydrocarbons; it is an excellent 
 solvent for iodine, ordinary phosphorus, and crystallised sulphur. Payen succeeded 
 in freeing illuminating gas from carbon bisulphide, bj' passing the gas through vessels 
 containing pieces of crystalline sulphur. In order to regain both the sulphur and 
 the carbon bisulphide it was then only necessary to distill off the latter. 
 
 If a few drops of nitric acid be poured into a jar containing carbon bisulphide 
 vapour, sulphur is deposited, and a reddish gas is formed ; the reaction being accom- 
 panied by the appearance of a bluish white flame, a portion of the sulphur 
 being oxidised to sulphurous oxide. Carbon bisulphide deports itself to some extent 
 as an acid. It combines with metallic sulphides, such as potassium sulphide and 
 sodium sulphide, etc., forming crystallisable salts. Brought into contact with the 
 alkalies and soluble earthy bases, carbon bisulphide replaces the oxygen in them with 
 sulphur, forming carbonic acid and metallic sulphides which combine with a further 
 portion of carbon bisulphide, forming salts. It reacts in an analogous manner with 
 the insoluble metallic oxides, when its vapour is passed over them at a red heat. 
 
 The characteristic coloration of a weak solution of iodine in carbon bisulphide is 
 taken advantage of as a test for iodides. One tenth part by volume of carbon 
 bisulphide is added to the liquid to be tested, forming according to the density of the 
 liquid a well-defined stratum either above or below it. A few drops of chlorine 
 water are then added to set the iodine free, and the whole well shaken. After standing 
 for a moment, a beautiful violet coloration of the carbon bisulphide is observed ; with 
 traces of iodine the coloration is of a rose tint. Carbon bisulphide is not decomposed 
 by boiling water under the ordinary pressure of the atmosphere : a fact of importance 
 in the rectification 'of crude carbon bisulphide, and its use on a large scale. 
 
 Sulphuretted hydrogen dissolves readily in carbon bisulphide, forming with it, 
 according to Zeise, an unstable chemical compound. The following substances are 
 either partly or entirely soluble in carbon bisulphide, viz., the resins, the varieties of 
 gum resin, the balsams, asphalt, camphor, wax, the fats and fatty acids, the acids of 
 camphor, benzoic and cinnamic acids, paraffin, etc. 
 
CARBON BISULPHIDE. 139 
 
 Owing to the great volatility of carbon bisulphide, great cold may be produced by 
 its evaporation, and if this takes place very quickly under the air pump a cold of - 60 
 may be obtained. 
 
 Preparation Carbon bisulphide may be prepared on a small scale by means 
 of the apparatus shown in fig. 80, consisting of a stoneware retort (A) with a tubulus 
 
 FIG. 80 
 
 (B),in which is fixed, by means of a lute consisting of clay and water, a porcelain tube 
 (c) open at both ends. The retort is filled up to the neck with pieces of charcoal, 
 placed upon a furnace (B) and fitted air tight with an adapter (F). This adapter is 
 connected with a Liebig's condenser (G), the glass tube of which (j) passes into a 
 doubly tubulated receiver (K). A glass tube (I) is fitted into the neck of the second 
 tubulus of the receiver to conduct the uncondensed gases into a flue with a good 
 draught. 
 
 When the whole apparatus has been proved to be air tight, the retort is heated to 
 bright redness, and small pieces of sulphur are thrown into it, at intervals of about 
 two minutes, through c ; the porcelain tube being closed with a cork as soon as possible 
 after each fresh addition of sulphur. According to the development of carbon 
 bisulphide, which is observed in the adapter (F), the operator can judge f the rapidity 
 with which sulphur is to be added. 
 
 The sulphur upon falling into the retort is volatilised, and coming into contact 
 with an excess of charcoal at a high temperature, combines with it, forming carbon 
 bisulphide. The product, which escapes very rapidly at so high a temperature, carries 
 with it considerable quantities of sulphur. The vapour condenses partly in the adapter 
 (F) and partly in the condenser (G), the liquid collecting in the receiver (K). 
 
 Care must be taken to insure a constant flow of water in the condenser (G), which 
 consists of an outer metallic tube, through the axis of which is passed a long glass tube 
 supported by perforated corks. The vapour which has to be condensed is passed 
 through the inner glass tube, while the space between the two tubes is continually 
 supplied with cold water by a funnel (H) near the lower extremity, while the hot 
 water, being specifically lighter, escapes at the other end (i). 
 
 In order to free the carbon bisulphide collected in the receiver from sulphur, it is 
 submitted to distillation in a glass retort over a water bath, the sulphur remaining in 
 the retort. Carbon bisulphide thus treated is however not quite pure ; it still contains 
 sulphuretted hydrogen. To get rid of this, the carbon bisulphide is allowed to 
 stand first of all in contact with hydrated lead oxide, then dried over calcium 
 chloride, and finally distilled. Calcium chloride may be with advantage replaced by 
 concentrated sulphuric acid, from which it is easy to separate the carbon bisulphide 
 by means of a separating funnel. 
 
 By using the apparatus just described, it is easy to produce in a single day 4( 
 ounces of carbon bisulphide, but the preparation in this way is seldom carried out, as 
 carbon bisulphide is manufactured on a very large scale. 
 
 The preparation of carbon bisulphide for industrial purposes was introduced by 
 Deiss and Jesse Fisher. The first forms of apparatus consisted of cast-iron cylinders, 
 in which sulphur vapour was passed over charcoal heated to redness. A single 
 cylinder yielded daily about 2 cwts. of carbon bisulphide. Fire-clay retorts were 
 then employed, glazed internally, so as to prevent the escape of carbon bisulphide 
 through their pores, and a number of such retorts were arranged in a furnace. An 
 apparatus of the kind, as constructed by Deiss, is represented by figs. 81 and 82. _ 
 
 A is a furnace, containing four retorts (c) so arranged that the flame can play quit 
 round them. The interior of the retorts is divided into two parts, by means of 
 perforated fire-clay plate ; the upper part, which is the larger of the two, serves to 
 
140 
 
 SULPHITE. 
 
 receive pieces of charcoal, thrown in through an opening in the lid ; the lower part 
 serves to receive the sulphur, which is thrown in through a somewhat conical tube 
 
 Fm. 81. 
 
 FIG. 82. 
 
 2 inches in diameter. The vapour formed upon heating the retorts passes through 
 the pipes (D), which have a diameter of 3 inches, and then into the condensers. 
 
 A condenser of the kind is shown in section in fig. 83 ; as many as eighteen 
 
 of them are connected together with 
 tubes. The condensers are made of 
 sheet zinc, and consist of a cylin- 
 drically shaped vessel, 26 inches in 
 diameter, provided with perforations 
 (s s) below, and standing in water in 
 a trough up to the upper extremity of 
 the perforations (s s). Two wide tubes 
 pass through the lid of the cylindrical 
 vessel into its interior, and serve for 
 the transmission of the vapour. The 
 lid is further furnished with a rim (c), 
 i inches high, into which water is 
 poured in order to cool it. The con- 
 tents can either be removed from each 
 receiver separately by means of a 
 
 FIG. 83. syphon, or the entire number of re- 
 
 ceivers are so connected with one 
 another, that it is only necessary to draw off the liquid from the last one. 
 
 The process of manufacture is the following : The four retorts are filled with char- 
 coal, and then, after closing the openings through which the charcoal was introduced, 
 the retorts are heated to bright redness by a coal fire. The next operation consists 
 in dropping pieces of sulphur, done up in cylindrical paper packets, through the tube 
 which passes through the lid of the retort to beneath the perforated fire-clay plate. 
 Two such packets each containing about 5 ozs. of sulphur are thrown in at intervals 
 of three minutes,, the opening at the upper end of the porcelain tube being closed 
 with a plug of clay after each addition. The charcoal is renewed every seven hours, 
 being each time heated for about an hour and three quarters before the temperature 
 requisite for the combination with sulphur is attained. The vapour of carbon bisul- 
 phide mixed with vapour of sulphur escapes through the delivery tubes (n), passing 
 into the first row of condensers, where it is partly condensed, together with some 
 
CARBON BISULPHIDE. 141 
 
 sulphur, that is deposited in the solid state and is used again ; from thence the un- 
 condensed vapour passes into the second, third, etc. condensers, until at last the sas 
 from the four retorts is conducted either through a chimney into the air, or through 
 vessels containing a mixture of hydrated ferric oxide and calcium sulphate (vide 'Gas 
 Manufacture ), by which means the sulphuretted hydrogen is retained. 
 
 Gerard in Grenelle has considerably improved the apparatus for the production 
 of carbon bisulphide. An improved form of apparatus, as constructed by him, is 
 shown m fig. 84. 
 
 Fia. 84. 
 
 The vessel (c) in which the charcoal is heated is made of cast iron, having sides 
 1 1 inches thick and, as shown sectionally in the centre, is elliptical in form ; it has a 
 diameter of 4 feet 8 inches, and is 6i feet high. It stands upon a brickwork arch, 
 and is heated from B by the flame which entirely surrounds it. Near the bottom is a 
 pipe (D), fitted with a valve (E), through which the sulphur is thrown in. p is a tube 
 of cast iron, having a somewhat conical shape toward its upper extremity, which 
 can be closed with a lid. It is connected by means of a metal tube, furnished with 
 a tubulus (o) which can be closed, with the receiver (H), from which the vapour passes 
 through the tube (i) into the condensers (j, K, L), which are connected with one another 
 by means of two tubes. To the uppermost condenser is attached a delivery pipe (M), 
 through which the uncondensed gas and vapour escape. The whole of the condensed 
 carbon bisulphide collects in the lowest vessel (j), that portion which condenses in K 
 and L flowing down into J through the communicating tubes, and it is drawn off 
 by means of the cock (N). The three cylindrical condensers (j, K, and L) are con- 
 tained in a large tank 5 feet high and 5 feet wide, filled with cold water, which can 
 be renewed at pleasure. 
 
 The cast-iron vessel (c) is charged with dry wood charcoal broken into small 
 pieces, which are thrown in through a funnel (fig. 84), and it is then heated to bright 
 redness. Sulphur is next thrown in at intervals at E, and upon coming into contact 
 with the red-hot vessel, melts, is converted into vapour, and passing over the red-hot 
 
142 
 
 SULPHUR. 
 
 charcoal, forms with it carbon bisulphide. As was the case with the other forms 
 of apparatus, so also here sulphur vapour is carried over with the carbon bisulphide, 
 and is condensed in the vessel (H), from which the sulphur can be easily removed, 
 the more volatile carbon bisulphide passing through the pipe (i) into the condensers 
 (j, K, L). 
 
 The addition of sulphur is carried on ten hours daily ; in portions of about 3 Ibs. 
 at intervals of three minutes. The oven is heated during the night in order to com- 
 pletely volatilise all the sulphur ; the residue of charcoal left the next morning is 
 allowed to remain, and a new charge is added to it. For the purpose of recharging, 
 the communication between the developing vessel and H is broken, by opening the 
 tubulus (G) and stuffing it with a piece of moist rag. The vessel (c) is then recharged 
 with fresh charcoal, the vapours of carbon bisulphide which are always thexeby 
 formed escaping through the chimney (p). The receiver (H) is emptied, connected again 
 with c, G is closed, and the charcoal again heated to redness. 
 
 This apparatus yields in twenty-four hours about 44 gallons, or 570 Ibs. of carbon 
 bisulphide, which requires theoretically 480 Ibs. of sulphur and 90 Ibs. of carbon, 
 but in practice 530 Ibs. of sulphur and 242 Ibs. of wood charcoal are used. 
 
 Gerard has recently found it expedient to surround the cast-iron vessels with 
 brickwork, which renders them more durable and capable of lasting two or three 
 months, whereas before they only lasted a fortnight at the most. 
 
 In fig. 85 is given a horizontal section of the new arrangement as adopted by Gerard. 
 A is the cast-iron vessel in which the charcoal is heated, bent twice inwards, in order to 
 increase the radiating surface ; B brickwork covering ; c fire-place, in which the flame 
 circulates ; and o the brickwork of the entire furnace. 
 
 FIG. 85. 
 
 PURIFICATION OF CRUDE CAEBON BISULPHIDE. The purification' of crude carbon 
 
 bisulphide which contains considerable quan- 
 tities of sulphur may be effected by distilla- 
 tion. The distilling vessel (B, fig. 86) made 
 of sheet zinc, is fitted into a water bath (A). 
 which is slightly heated, the vapours of 
 carbon bisulphide passing through a wide 
 tube (c) into a serpentine pipe (E) surrounded 
 by cold water, where they condense ; the 
 liquid carbon bisulphide free from sulphur 
 trickling into a vessel placed beneath E' to 
 receive it. 
 
 Deiss rectifies carbon bisulphide from 
 large boilers with a flat bottom, which are 
 10 feet in length, 63 feet in diameter, and 3| 
 feet high. Tho covers are domed, and protected 
 externally by a bad conductor of heat, in order that as little carbon bisulphide as 
 possible may be condensed and returned to the boiler. The boiler is capable of re- 
 ceiving 5 tons of crude carbon bisulphide at a single charge. A man-hole is con- 
 structed at the upper part of the boiler, and also six delivery tubes which terminate 
 in six vertically placed condensers. At the bottom of the boiler there are two serpen- 
 tine pipes, through which fstoam can bo passed. Steam being passed through one of 
 
 FIG. 86. 
 
CARBON BISULPHIDE. 
 
 143 
 
 these pipes, the crude carbon bisulphide is heated to its boiling point (48). The 
 distillation of 5 tons lasts three or four days; the latent heat of 100 parts of 
 steam sufficing to heat to its boiling point 650 parts of carbon bisulphide. The pro- 
 ducts of the different stages of distillation are separately collected, by which means 
 carbon bisulphide is obtained of different degrees of purity, and serving different pur- 
 poses. The first portions which pass over contain the easily volatile, and especially 
 the odoriferous constituents, such as sulphuretted hydrogen, etc. The middle portions 
 are the purest, while the last portions are impure from containing sulphur. For the 
 purpose of distilling off the very last portions of carbon bisulphide, steam is passed 
 through the second pipe, direct into the boiler, by which means the remainder of the 
 carbon bisulphide mixed with steam passes over into the condensers, where both con- 
 dense, the carbon bisulphide forming a layer at the bottom of the water. 
 
 When the operation is over, a workman enters the boiler, which has been pre- 
 viously ventilated, through the manhole, and removes the sulphur residues. 
 
 This apparatus has essentially the same arrangement as that employed in the 
 extraction of oils, which is represented by figs. 90 and 91. 
 
 For the removal of the sulphuretted hydrogen, a small quantity of caustic soda is 
 thrown into the boiler, which retains the sulphuretted hydrogen by combining with it. 
 
 In Boniere's apparatus the carbon bisulphide is run from a large reservoir into 
 a still containing concentrated caustic soda, and heated externally by steam ; the 
 vapour is then made to pass through several other vessels of the same kind, some 
 containing alkaline liquids, and some containing solutions of salts of iron, lead, or 
 copper ; from which it is distilled, and finally condensed in a condenser furnished 
 with a serpentine tube. 
 
 Millon patented a process in which the carbon bisulphide is mixed with half its 
 volume of milk of lime, and then carefully distilled off. 
 
 Carbon bisulphide thus obtained and purified by rectification, comes into the 
 market in sheet-iron drums, which have a form represented 
 by fig. 87. The plates forming the top and bottom are bent 
 inwards, and the upper one has an opening closed by means 
 of a screw. 
 
 METHOD OF STOKING. In the manufacture, storing, and 
 use of carbon bisulphide, great precaution is necessary, owing 
 to the fact that at the ordinary temperature, so much carbon 
 bisulphide may volatilise as to render the air in the vici- 
 nity irrespirable. Further (as has already been mentioned) 
 the vapour of carbon bisulphide, mixed with atmospheric 
 air in certain proportions, forms an explosive mixture, which 
 is the more dangerous owing to the products of such an ex- 
 plosion being three irrespirable gases, viz., carbonic dioxide, 
 sulphurous oxide, and the unburnt residue of the air itself, 
 nitrogen. 
 
 Rooms in which carbon bisulphide is stored, or in which it is used, ought there- 
 fore to be isolated from other buildings and well ventilated. The vessels in which 
 the substance is stored must be tolerably large, and so placed that they are not likely 
 to receive a blow, or get thrown over. 
 
 Fig. 88 represents a vessel for storing carbon bisulphide, as introduced by trerard. 
 It is made of sheet zinc of a cylindrical shape, holding as 
 much as 20 or 30 gallons. Eeceivers of the kind, to the num- 
 ber of 10, 20, 30, or more, are placed upon a wooden platform 
 raised three feet from the ground. Each receiver has a_ cylin- 
 drical cavity at the bottom in which a tube (B B) terminates. 
 This tube has a rim above turned outwards, which serves to 
 secure it firmly upon the cover of the reservoir. The reservoirs 
 are filled by fitting a funnel into the mouth of the tube (BB), 
 and pouring carbon bisulphide through it into the reservoir ; 
 the air in the reservoir escaping through the open cock (c). 
 When sufficient carbon bisulphide has been poured into the 
 reservoirs, a small quantity of water is poured in to prevent 
 the evaporation of the carbon bisulphide, the cock (c) is closed 
 and the mouth of the tube (B) is plugged up. 
 
 When required for use, the carbon bisulphide is drawn off 
 from such reservoirs by means of a syphon (fig. 89), which is plunged in th ) tube (B ) 
 the cock (F) is opened and carbon bisulphide to the required amount is drawn oft nit< 
 a vessel held beneath it. A single syphon serves for the entire number of reserv 
 
 Uses. The low price of carbon bisulphide has rendered it possible to mako 
 of it for a number of purposes. 
 
 FIG. 87. 
 
 Fro. 88. 
 
144 
 
 SULPHUR. 
 
 Thus it has been recently used for the extraction of fatty oils from oil seads and 
 pressed residues from which no more oil can be pressed out, and also in the extraction 
 from crude wool of fat, which was formerly lost. The chief use of 
 carbon bisulphide is, however, in the preparation of vulcanised caout- 
 chouc. Carbon bisulphide is further used for purifying paraffin, for 
 the extraction of sulphur from its ore, for the preparation of a 
 caoutchouc solution and cement, and for filling prisms, for which pur- 
 pose it is used on account of its refractive properties ; it is also used 
 as a poison for vermin, in the manufacture of aluminum, various 
 colours, ammonium sulphocyanide, and other preparations, for dis- 
 solving phosphorus in electro-plating, etc. 
 
 Finally, it may be mentioned that attempts have been made to re- 
 place the water in steam boilers by carbon bisulphide, since it does 
 not require so much heat for its conversion into vapour as water 
 does. 
 
 EXTRACTION OF FAT, OIL, ETC. Deiss first employed carbon bi- 
 sulphide for extracting fatty oils from seeds, oil cakes, and other 
 pressed residues, and its application for such purposes has since 
 Fia. 89. attained considerable dimensions. 
 
 The arrangement of Deiss' apparatus is represented by figs. 90 and 91. A is a cemen- 
 ted brickwork reservoir, with a manhole, which is generally kept closed. The tail pipe ( j) 
 
 FIG. 90. 
 
 of the condenser, and the supply pipe (h') of the pump (h h), dip into this reservoir, 
 which is about 22 feet long, 6 feet in diameter, and nearly 6 feet deep, and lined with 
 lead up to the height at which it is filled with carbon bisulphide and water. 
 
 The reservoir and condensers are made of iron ; but since it often happens that 
 acid residues from stearic acid manufactories have to be treated, the bottom and side 
 walls of the extracting apparatus are made of lead, the lid only being made of iron. 
 
 The extracting apparatus (B) has a domed cover tightly screwed upon the flange of 
 the extractor, has a capacity of 4400 gallons, and may be charged with 12 tons of 
 oil cake. At a height of 6 inches from the floor is a perforated shelf (d d) which can 
 be removed at pleasure. In the space between the bottom and this perforated shelf 
 is a perforated coil of pipe, through which steam can be passed. At the upper part 
 of the extractor there is a second moveable perforated shelf (d' d 1 ), having above it, 
 at the side, two pipes, which place the extractor in direct communication with the 
 distilling vessel (D) and allow the carbon bisulphide saturated with oil to flow into the 
 still (D) as soon as" it rises to the level of the upper shelf. 
 
 Just below the lid of the extracting vessel, on a level with one another, are nine tubes 
 (e e\ 8 inches diameter at the extremity nearest the extractor, and 6 inches diameter 
 at the other extremity, through which the vapour is conducted into the condenser (c), 
 At each end of the extractor, between the bottom and the perforated shelf, is a tube 
 
EXTRACTION OF OIL, ETC. 145 
 
 connected with the pump (h Ji), through which carbon bisulphide is pumped up from 
 the reservoir (A) into the extractor. At the bottom of the extractor there is also -i 
 tube (6 6 ) which upon the opening of a cock serves to let out the entire liquid contents 
 into the reservoir (A). Two other tubes placed at the ends, and at the bottom of the 
 extractor, give exit to the water used in washing or steaming the apparatus. Parallel 
 
 FIG. 91. 
 
 with the extractor (B) is a large distilling vessel (D) about 11 feet long, 5 feet wide, 
 and, without the arching of the roof, 15 inches deep, holding, when half filled, about 
 400 gallons. During the entire course of the operation this distilling vessel is sup- 
 plied, by means of two pipes, with carbon bisulphide, that flows over above the level 
 of the upper shelf in the extractor (B), after having macerated its contents. The 
 vapour from this still passes through 9 tubes (e 1 e") into the condenser (c), and by this 
 means the whole of the carbon bisulphide volatilised in the apparatus is condensed and 
 collected into the reservoir (A), from whence it can be again pumped up into the ex- 
 tractor (B). In order to lessen the evaporation of carbon bisulphide in the reservoirs 
 (A) it is covered with a small quantity of water. 
 
 The liquid in the still (D) is heated by means of steam supplied through the pipe 
 (/) to two pipes coiled several times upon the bottom of the still, the condensed steam 
 flowing back again into the boiler. By means of two other pipes, steam may be ad- 
 mitted directly into the still. 
 
 In working this apparatus, the first thing to be done is to remove the lid of the 
 extractor (B), and fill the space between the shelves (d d) and (d f d') with the material 
 to be operated upon. The lid of the extractor is then fastened down,' and carbon bi- 
 sulphide forced into the extractor (B) by means of the pumps (h h). As the bisulphide 
 penetrates the mass it becomes specifically lighter, owing to the fact that the oil with 
 which it mixes has a specific gravity of about O'OOO, while carbon bisulphide has a 
 specific gravity of 1-293. From the macerating vessel, the liquid containing extracted 
 oil flows in a continual stream into the distilling vessel, which is heated by the steam 
 pipe at its bottom, and the carbon bisulphide is distilled off through the pipes (e r e') 
 and the condenser into the reservoir (A). In order to deprive the oil of the last traces 
 of carbon bisulphide, when the extracting operation is over, steam is passed directly 
 into the vessel (D), through the other pipes at its bottom, which are perforated, and 
 this is continued until all the carbon bisulphide has been carried away by the steam. 
 
 The point of exhaustion of the material in the extractor is ascertained either from 
 the duration of the filtration, or by watching the colour of the carbon bisulphide 
 through a glass tube let into each of the pipes conducting the liquid from the extractor 
 into the still. Although the oil is of itself colourless, there are still sufficient colouring 
 substances dissolved out by the carbon bisulphide to admit of an opinion being formed 
 as to whether the extracting process is complete or not ; as soon as the carbon bisul- 
 
146 
 
 SULPHUR. 
 
 phide passes over colourless, the extraction is considered to be complete. The cock b 
 is then opened, and the liquid contents of the extractor (B) run into the reservoir. 
 
 After this operation is over, superheated steam is passed into the extractor from 
 the perforated serpentine pipe at the bottom, and thus the whole mass is soon brought 
 up to 100 C., any adhering carbon bisulphide being thus volatilised, and passing with 
 the steam through the condenser into the reservoir. 
 
 The filling of the macerating vessel with carbon bisulphide takes eight hours, the 
 maceration itself four hours ; the emptying of the macerating vessel into the reservoir 
 at the end of the operation takes two hours, and the steaming of the oil in order to 
 free it from carbon bisulphide requires from eight to twelve hours. 
 
 After the exhausted material has been sufficiently steamed, a cock at the bottom of 
 the vessel is opened, the condensed water is let out, the lid and upper shelf removed, 
 and the residues spread out in the air to dry. 
 
 "Working with an apparatus of the above dimensions, about 2^ tons of oil can be 
 obtained in thirty hours from 25 tons of olive oil cake. The residues from the macer- 
 ating vessel are used in Pisa for heating the boiler, which produces the steam for the 
 whole apparatus. 
 
 The extraction of fat from bones is at present generally carried out by boiling 
 them in closed vessels with water, an operation by which a good deal of fat is still 
 left in the bones ; its extraction may be effected with greater advantage and more com- 
 pletely by means of carbon bisulphide. 
 
 When bones are treated in the apparatus, a temperature of 140 C. is necessary for 
 extraction, and this is attained by passing hot water or steam into the digester through 
 a serpentine tube. 
 
 Bones exhausted of their fat by maceration with carbon bisulphide are very suit- 
 able for preparing bone charcoal, while on the other hand they are not fit for the 
 purposes of the glue boiler, owing to the fact that the action of carbon bisulphide in 
 the presence of water at 100 C. causes a decomposition of the organic substance, which 
 renders the glue brittle. 
 
 This effect is apparently similar to that exerted upon wool when it is treated with 
 carbon bisulphide for purposes of extracting its fat in the above manner. 
 
 Extraction of Fat from Wool. The apparatus used for this purpose by Moison 
 and Jerome is represented by fig. 92. The extractor consists of a large cylindrical 
 
 FIG. 92. 
 
 vessel (A) of sheet iron, with a close-fitting cover and double walls, between which hot 
 water circulates. At a short distance from the bottom there is a perforated shelf 
 upon which the wool to be extracted is placed. A perforated plate can be pressed 
 down upon the wool by means of screws. A pump (c) forces the carbon bisulphide 
 from the reservoir (D) into the cylinder (A) beneath the perforated shelf, and a pipe 
 placed as near as possible to the centre of the extractor conducts the fat dissolved out 
 by the carbon bisulphide into the still (B), which is heated by a coil of pipe at the 
 bottom, and has a cock for the purpose of letting out the fat freed from carbon bisul- 
 phide. By a second coil of perforated pipe superheated steam can be passed directly 
 into the fat, so as to remove the last portions of carbon bisulphide. 
 
 
EXTRACTION OF OIL, ETC. 147 
 
 A worm tube (L) placed in the vessel (j) condenses the vapour of carbon bisulphide 
 escaping from ^the still (B) and delivers it into the reservoir (D). By means of the 
 air pump (E) air is pumped out of the reservoir (D) and pressed into the extractor (A), 
 through a tube several times bent and fitted towards the end with a jacket (M) through 
 which water is passed at a temperature of 70 C. The heated air being at the end of 
 the operation forced through the wool, carries with it the last portion of carbon bisul- 
 phide, through a pipe at the bottom of the macerating vessel into the condenser (H), 
 where the vapour is condensed and flows into the general reservoir (D). The entire 
 apparatus is in communication with the interior of a gasometer (g ), which serves to 
 regulate the pressure in the interior of the apparatus in such a way that it is always 
 the same as the pressure outside. In the tube leading from the macerating vessel (A) 
 into the distilling vessel (B), as well as at the ends (o and N) of the condensing worms, 
 pieces of glass are let in, which serve to show the colour of the liquid flowing from A 
 to B, and also the rapidity of the distillation. Close to each of these glass windows is 
 a small cock, from which a small quantity of liquid may be drawn off to test whether 
 the extracting process is still going on or not ; for which purpose a little of the liquid is 
 placed upon a watch glass, and allowed to evaporate in order to see if a residue of fat 
 remains. 
 
 The cock (x) between the reservoir (D) and the air pump (E), and the cock (Y) 
 between the macerating vessel (A) and the condensing worm (H), have a double perfor- 
 ation, so as to admit of these parts of the apparatus being, at pleasure, either placed 
 in communication with one another, or of air being drawn in by means of the air pump 
 (E) through the cock (x), forced through the apparatus, and expelled by the cock (Y). 
 
 The macerating vessel (A) is charged with about 10 tons of wool, and the press 
 plate screwed down so as to reduce its bulk to at least one half. The pump (c) is 
 then set going and the macerator gradually filled with carbon bisulphide, which enters 
 underneath the perforated false bottom, penetrates the wool gradually from below 
 upwards, passes through the holes of the press plate, and flows at last into the distill- 
 ing vessel (B). The filtration of the carbon bisulphide through the wool is continued 
 until the liquid flowing from A to B, when examined through the glass window, appears 
 colourless, and a portion of it drawn off and allowed to evaporate leaves no residue 
 of fat. 
 
 In proportion as the carbon bisulphide containing dissolved fat flows into the dis- 
 tilling vessel, it is evaporated by means of the serpentine tube at the bottom, the 
 vapour condensing in the worm (L). When the extracting process is complete, the 
 cock connecting the pump (c) with the macerator (A) is closed, and the air pump (E) 
 set in motion. By this means the air is drawn from the extractor (A) through the 
 tube containing the cock (Y), the greater portion of the carbon bisulphide adhering to 
 the wool being carried with it at the first few strokes of the pump, through the con- 
 denser (H) into the reservoir (D). When no more liquid is observed to flow past the" 
 glass window (N), water at a temperature of 70 C. is allowed to circulate in the 
 jacket (M) ; the air thus warmed penetrates the wool, removing the greater part of 
 the adherent carbon bisulphide as vapour which is condensed in the worm (H). At 
 the end of the process the cocks (x) and (Y) are set so that air can enter through the 
 former and, after having passed through the wool, escape through the latter ; it always 
 contains traces of carbon bisulphide and is therefore conducted into the open air. 
 The wool thus deprived of fat and dried, is taken out and freed mechanically from 
 particles of dust. 
 
 By this method, a considerable amount of fatty substance is obtained from sheep's 
 wool, and it may be employed advantageously in the preparation of soap. 
 
 The materials treated with carbon bisulphide in order to obtain the fatty ingre- 
 dients they contain are : 
 
 I. The dark-coloured tar-like residues of stearic acid manufactories, which are 
 products of the treatment with sulphuric acid. They yield to carbon bisulphide from 
 18 to 20 per cent, of fatty acid, which was almost entirely lost before. The residues 
 are mixed with sawdust in order to facilitate the filtration of the dissolved portion. 
 
 II. The dark brown cart grease which oozes from the axles of cart and carriage 
 wheels, becoming hard. For obtaining the fatty acids from this kind of refuse, it is 
 first of all treated with sulphuric acid, washed, and dried. 
 
 III. Tow and rags used in cleaning and oiling machinery. These can be treated 
 at once with carbon bisulphide without the addition of sawdust. This treatment of 
 rags, etc.. has a threefold advantage : recovery of fat or fatty acids ; purification of 
 rags so tliat they can be used again ; and the prevention of danger arising Iron 
 liability to spontaneous ignition which oily rags or other greasy materials pos 
 when piled together in heaps. . , , ., 
 
 IV. The refuse of the preparation of bees' wax, which yields with carbon bisulphide 
 a certain amount of yellow wax that is useful for many purposes. 
 
 ' 12 
 
148 SULPHUR. 
 
 V. Sawdust that has been used for filtering oils after purification with sulphuric 
 acid. 
 
 VI. The dirty sediment produced by the treatment of various oils with sulplrarie 
 acid contains about 50 per cent, of oil, which maybe extracted with carbon bisulphide, 
 after treating the sediment with boiling water, to destroy the sulpho-fatty acids, dry- 
 ing, and mixing it with sawdust. 
 
 VII. Bones from slaughter-houses and kitchens, that are to be used in the prepa- 
 ration of bone black, yield with carbon bisulphide from 10 to 12 per cent, of fat. 
 
 VIII. The expressed residues of oil seeds, such as rape, sesame, nettle, flax, etc., 
 when they cannot be profitably employed as fodder. In all cases it is necessary to 
 break up the oil cakes into small pieces before treating them with carbon bisulphide, 
 so as to insure thorough penetration of this substance. The residue left after extract- 
 ing the fat is hardly suitable for fodder, but it is a valuable manure. 
 
 IX. The cracklings, or greaves, obtained by the melting of tallow. 
 
 X. The pressed cacao beans, from which no further cacao butter can be obtained 
 by mere pressing. 
 
 XI. The pressed residues obtained in the preparation of olive oil ; there are two 
 sorts, according to the way in which the expressing operation has been performed. 
 Sanza is the residue obtained by simply crushing and pressing the olive. It con- 
 tains, besides the pulp of the flesh, also the kernels, which increase the weight and 
 volume of the mass very considerably, without being of any intrinsic value. Buccia 
 is prepared from sanza by boiling it for a short time with water, until the kernels are 
 detached, and fall to the bottom of the pan ; while the flesh of the fruit remains sus- 
 pended in the liquid. This is skimmed off, placed on a sieve, and pressed. Although 
 a small quantity of oil is thus pressed out with the water, the buccia or doubly pressed 
 residue contains a larger amount of oil than sanza, because the kernels have been re- 
 moved. This rich oily residue is used in Italy as fuel, and especially in cases of fes 
 tivity, on account of the bright flame yielded by it. On this account its price is so 
 high, that although it contains from 22 to 25 per cente of oil that from Calabria, 
 indeed, often containing 28 per cent. there is difficulty in obtaining a sufficient quan- 
 tity at a price cheap enough to render its working up practicable. 
 
 SELENIUIVI AlffD TEXiXiURXUM. 
 
 Se SYMBOL Te. 
 
 79'5 . . ATOMIC WEIGHT . 128. 
 
 These two rare elementary substances are closely analogous to sulphur in their 
 chemical relations. Sel enium occurs naturally either with sulphur or combined with 
 other elementary substances as selenides, which resemble sulphides and are often pre- 
 sent in small proportions in some kinds of pyrites ; hence selenium is frequently found in 
 the flue dust deposited in the chambers of sulphuric acid works where pyrites is burnt as 
 a source of sulphur. A mineral occurring in the Harz mountains and consisting of lead, 
 selenide, and cupric selenide, is one of the chief sources of selenium. Tellurium 
 occurs naturally in the free state and in combination chiefly with bismuth as tetra- 
 dymit e, also with gold, silver and lead ; combined with oxygen, it occurs as tellurite. 
 
 Selenium is a solid substance of a brown colour and considerable lustre; it is, like 
 sulphur, capable of assuming two allotropic conditions, one of which has a vitreous tex- 
 ture and a specific gravity of 4*3 ; the other is crystalline, has a specific gravity of 
 4-8, melts at 217 and is volatilisable. 
 
 Tellurium is a crystalline brittle substance of a white metallic colour, very con- 
 siderable lustre, and decided metallic characters. Its specific gravity is about 6'2, it 
 melts at about 500, and is volatilisable at a higher temperature. 
 
 The compounds of selenium and of tellurium closely resemble in constitution the 
 compounds of sulphur as shown by the formulae of the compounds corresponding to 
 sulphuretted hydrogen, sulphurous acid, and sulphuric acid. 
 
 Hydrides H 2 S H 2 Se H 2 Te 
 
 . . , < H 2 S0 3 H 2 Se0 3 (Selenous Acid) H 2 Te0 3 (Tellurous Acid). 
 
 \ H 2 S0 4 H,Se0 4 (Selenic Acid) H 2 Te0 4 (Telluric Acid). 
 
 The general characters of the corresponding compounds also approximate. 
 The selenates are frequently isomorphous with and otherwise resemble the corre- 
 sponding sulphates, but the tellurates as well as the tellurites present more the characters 
 of salts containing an acid oxide of a metal. 
 
 
PHOSPHORUS. 
 
 SYMBOL P. ATOMIC WEIGHT 31. 
 
 History. This substance was discovered in 1669, by Brandt of Hamburg, and 
 shortly afterwards by Kunkel, but it is probable that he was in some way aware of 
 Brandt's method of preparation, which consisted in distilling the residue from the 
 evaporation of urine with charcoal. In 1743 Marggraf prepared phosphorus from 
 other substances, such as mustard seed, garden cress seeds, wheat, etc. 
 
 Many opinions were formed as to the chemical constitution of phosphorus. Accord- 
 ing to Stahl, it was a compound of phlogiston and hydrochloric acid. Boerhave con- 
 sidered it to be a compound of phlogiston and sulphuric acid. The former view was 
 the one most generally adopted, until it was proved to be incorrect by Marggraf, who 
 considered phosphorus to be a combination of phlogiston and phosphoric acid. 
 Lavoisier showed however, that when phosphorus is burnt it combines with oxygen, 
 being thus converted into phosphoric acid, and that phosphorus ought therefore to be 
 considered as a constituent of phosphoric acid. 
 
 Occurrence. Owing to the readiness with which phosphorus combines with 
 oxygen, it does not occur nafurally in the free condition ; but it occurs abundantly in 
 combination with oxygen and metallic bases as phosphates. Thus calcium phosphate 
 occurs as a mineral called apatite (a compound of calcium phosphate with calcium 
 chloride and fluoride) and as osteolite; aluminum phosphate as wavellite; 
 ferrous and ferric phosphates as green iron-stone; lead phosphate as pyromor- 
 phite. Sombrerite, a mineral found in the Antilles, under guano beds, probably 
 is limestone partly converted into calcium phosphate by the action of solution of guano 
 salts ; it contains about 65 per cent, calcium phosphate and 17 per cent, aluminum phos- 
 phate. Large quantities of calcium phosphate also occur in gu a no, the excrementitious 
 deposit of sea birds, which sometimes contains from 75-80 per cent. A guano which 
 is imported from Navassa in North America, and is related to sombrerite in composi- 
 tion, contains 30 per cent, of calcium phosphate. Coprolites are also rich in calcium 
 phosphate. 
 
 Phosphorus is also very widely distributed in the vegetable kingdom, where it is 
 chiefly found as phosphates. Seeds are especially rich in phosphates ; thus the ash 
 of wheat contains from 39-47 per cent, of phosphates ; that of peas and beans about 
 40 per cent.; maize ash contains about 50 per cent. Other parts of plants are less 
 rich in phosphates, the ash of maize and pea straw containing only 12-15 per cent. ; 
 that of hay, clover, bean straw, etc., from 7-8 per cent. only. 
 
 Phosphorus is also abundant in the state of phosphates in the animal kingdom, 
 where it occurs chiefly in the bones, which contain from 25 to 27 per cent, of phos- 
 phoric acid. A still greater percentage of phosphorus is found iu the teeth and their 
 enamel. The other organs of animals also contain more or less phosphorus. 
 
 Characters. There are two modifications of phosphorus; the ordinary crystal- 
 Usable phosphorus, and the red or amorphous phosphorus. Ordinary phosphorus is 
 colourless, or of a slightly yellow tinge, and is often quite transparent; it has an un- 
 pleasant smell and taste. At a moderately warm temperature it has a waxy con- 
 sistency, and may be easily cut ; but at lower temperatures phosphorus is. hard 
 and brittle ; a small admixture (^) of sulphur has the same effect. Phosphorus 
 melts at 44, forming a thick oily liquid that may be cooled much below the melting 
 point without solidifying ; it boils at 290, and the vapour has a density of 62, as com- 
 pared with hydrogen, even when heated above 1000. When heated above its melting 
 point, phosphorus takes fire in the air, and at the ordinary temperature it gradually 
 oxidises, giving off a faint light. This phenomenon is termed phosphorescence. 
 Even at the ordinary temperature this process of oxidation is apt to cause sufficient 
 heating of the phosphorus to make it melt and burn, and on this account phosphorus 
 must be kept under water out of contact with the air. Phosphorus has a specific gravity 
 of 1-826-1-840. It is insoluble in water, and almost insoluble in alcohol ; slightly 
 
150 PHOSPHORUS. 
 
 soluble in ether, volatile, and fat oils ; but very readily soluble in sulphur chloride 
 and carbon bisuphide. 
 
 When phosphorus is allowed to oxidise slowly in contact with a limited amount of 
 air, the product of oxidation consists of the trioxide or phosphorous oxide only 
 (P 2 3 ), but when the oxidation is more rapid, pentoxide or phosphoric oxide (P 2 5 ) 
 is formed. It is remarkable that phosphorus scarcely emits any light in an atmosphere 
 of pure oxygen, but upon rarefying the gas, or diluting it with another gas that 
 itself exerts no action upon phosphorus, the phosphorescence increases in proportion 
 to such dilution. Phosphorus which is only partly covered with water induces oxida- 
 tion of atmospheric nitrogen and the formation of dense vapours of ammonium nitrite, 
 ozone being produced at the same time. 
 
 Phosphorus, even when entirely protected by water, undergoes a change in direct 
 sunlight, passing into the amorphous condition. The clear transparent sticks of 
 phosphorus become gradually less transparent, the change beginning at the surface 
 and gradually penetrating the entire mass. For this reason phosphorus requires not 
 only to be kept under water, but also to be protected from sunlight. 
 
 Phosphorus abstracts oxygen from a number of substances, such as nitric acid, 
 chromic acid, chloric acid, etc., which are either thus reduced to lower oxides, or 
 entirely decomposed. 
 
 Phosphorus combines readily with chlorine, bromine, iodine, and sulphur. It does 
 not combine directly with hydrogen ; but upon heating phosphorus with concentrated 
 solutions of the caustic alkalies, phosphoretted hydrogen is formed. 
 
 Amorphous phosphorus has been long known ; it was however for some time 
 considered to be a lower oxide of phosphorus, until, in 1848, Schrotter proved it to 
 be an allotropic modification of phosphorus. "When ordinary phosphorus is exposed 
 under water to the action of sunlight, an opaque reddish crust is formed upon its 
 surface, which increases in depth until the crust formed is so thick that the sun's rays 
 can no longer penetrate through it. This change consists in the conversion of ordinary 
 or crystallisable phosphorus into the amorphous or allotropic form. The change may 
 be effected with greater rapidity by heating phosphorus in an atmosphere free from 
 oxygen to a temperature of 160, either alone, or in the presence of a small quantity 
 of iodine, which accelerates the alteration. 
 
 Amorphous phosphorus has a brownish red colour ; it is odourless, opaque, hard 
 and friable. It has a specific gravity of 2'106, the spec. grav. of ordinary phosphorus 
 being r826-l*840. Amorphous phosphorus begins to burn at a temperature of 200; 
 exposed to the light, however, it takes fire at a temperature of 55-60. It undergoes 
 no change when exposed to the atmosphere, and is insoluble in all those mixtures 
 which dissolve ordinary phosphorus, such as alcohol, ether, fat oils, carbon bisulphide, 
 etc. Owing to its not being poisonous, and to its taking fire when rubbed with 
 potassium chlorate, amorphous phosphorus is used in the manufacture of matches. 
 
 Preparation. The raw material used in the manufacture of phosphorus is bone 
 ash, obtained by removing the cartilaginous tissue from bones by burning them. Bone 
 ash varies somewhat in composition, the amount of calcium phosphate generally 
 varying between 82'5 and 84'5 per cent. Besides this, it contains from 2 to 3 per 
 cent, of magnesium phosphate, from 8 to 10 per cent, of calcium carbonate, and 3 to 4 
 per cent, of calcium fluoride. 
 
 The calcined bone ash is decomposed with sulphuric acid, and thus the insoluble 
 neutral tricalcium phosphate is converted into the soluble acid calcium phosphate, 
 according to the equation : 
 
 Ca 3 P 2 8 f 2H 2 S0 4 = CaH 4 P 2 8 + 2Ca S0 4 . 
 
 After separating the calcium sulphate, the clear solution is evaporated nearly to 
 dryness, the residual acid calcium phosphate intimately mixed with charcoal and dried, 
 so as to deprive it of water and form calcium metaphosphate : 
 
 CaH 4 P 2 8 = CaP 2 6 + 2H 2 0. 
 
 The mixture is then heated to redness, and a part of the calcium metaphosphate is 
 reduced and phosphorus liberated, as shown by the following equation : 
 Calcium metaphosphate Tricalcic phosphate 
 
 3CaP 2 6 + IOC = Ca 3 P 2 8 + 10CO + 4P. 
 
 Calcination of the Bones. This operation has for its object the destruction of the 
 organic substance of the bones, and it is generally carried out in^kilns similar to those 
 used in lime burning. 
 
 Fig. 93 represents a kiln of the kind, which is so constructed that the escaping 
 gasos are burnt, and thus nuisance is avoided. A is a cylindrical shaft furnace, the 
 mouth (A') of which is contracted and closed by a lid of cast iron. By means of lateral 
 
MANUFACTURE OF PHOSPHORUS. 151 
 
 apertures (B) opening into a circular flue extending entirely round the body of the 
 kiln, the lower part of it near the furnace communicates with the chimney (i> n). The 
 bars of the grate (c) are moveable, and are supported 
 upon cross bars. To set the operation going, the door 
 (E) is opened, and the fire bars laid in and covered with 
 some easily combustible material, which is set fire to. 
 As soon as the fire burns brightly, the door (B) is 
 closed and a fire of shavings made at (D'), in the 
 chimney (D), so as to draw out and burn the gas es- 
 caping from the fire-grate (c), through the side open- 
 ings (B), and upon closing the door (D') through the 
 chimney (D D) into the air. When the oven has been 
 heated in this way, bones are thrown in through the 
 mouth (A') until the kiln is full ; then A is closed for 
 a moment and the fire bars are drawn out, so that 
 the burnt bones fall down upon the lowest part of the 
 kiln, whence they are drawn out through the open- 
 ing (E). Directly the burnt bones have been drawn 
 out, this opening is closed and more bones are thrown 
 in at A'. The kiln is thus kept in constant operation, 
 the organic substance of the bones sufficing for the! 
 calcination after combustion has been once started. 
 
 Fleck's furnace consists of a shaft which is charged F IG . 93. 
 
 through a lateral opening above, the combustion being 
 
 started by some easily combustible fuel. The products of combustion escape 
 through the highest part of the shaft into a horizontal flue, at the mouth of which a 
 fire is kept up through which the noxious gases pass and are burnt, the heat evolved 
 being used for evaporation. The horizontal flue terminates in a chimney. The yield 
 of calcined bone ash obtained in this operation amounts to from 50 to 56 per cent, of 
 the weight of the bones employed. 
 
 Crushing the burnt Bones. The extent to which the crushing of the bones is carried 
 varies. In some places the bones are reduced to powder, and sometimes only to pieces 
 about the size of peas. The crushing of the bones to pieces of the size of lentils is the 
 most suitable for further working. The crushing operation is effected either between 
 rollers or stampers. 
 
 Treatment with acid. The quantity of sulphuric acid required for the decomposi- 
 tion of the bones depends upon its concentration. 100 parts of bone ash require for 
 decomposition 66 parts by weight of concentrated sulphuric acid, or 100 parts of acid 
 of sp. gr. 1-49. 
 
 According to other authorities 
 
 100 parts of bone-ash require 106*73 parts of sulphuric acid, sp. gr. 1*490. 
 85-68 1*652. 
 
 73*63 1747. 
 
 The decomposition of the bone ash by sulphuric acid is carried out in tubs lined 
 with lead, in which 100 parts by weight of boiling water is mixed with 20 parts of 
 sulphuric acid of sp. gr. 1-490; into this mixture is then thrown, in small quantities 
 at a time, 20 parts of bone ash powder. A lively frothing takes place, owing to the evolu- 
 tion of carbonic acid. As soon as this has ceased, further quantities of boiling water, 
 sulphuric acid, and bone ash are added, this being repeated until four separate charges 
 have been thrown into the tub, making in all 80 parts of bone ash and 80 parts of 
 sulphuric acid of sp. gr. 1-490. The mass is kept warm for twenty-four hours, during 
 which time, it is often stirred, and is then left at rest for ten hours. The clear liquid 
 is then drawn off from the precipitate through a leaden pipe into a wooden gutter lined 
 with lead, then passed first through a filter, and afterwards into leaden evaporating 
 pans. The precipitate which remains in the tubs is covered with a quantity of water 
 equal to that originally used, stirred up and left to settle. The clear liquid is then 
 drawn off and used to wash the residues of four or five other tubs. In this way the 
 liquid of the fifth or sixth tub is brought up to a concentration represented by sp. gr. 
 1-070 to 1*085. The last portions of wash water are used for preparing fresh 
 liquors. 
 
 This kind of washing is sometimes replaced by a process of filtration. For this 
 purpose the residues are placed in a tub with a double bottom. The residues are laid 
 upon the upper perforated bottom of the tub, which is covered with a cloth, and are 
 washed out by pouring water upon them. Gentele covers the perforated bottom of 
 the vat with quartz sand, instead of with a cloth. Recently it has been proposed to 
 use centrifugal machines for the washing. 
 
152 
 
 PHOSPHORUS. 
 
 Concentration of the Liquor. The combined liquid is concentrated to a sp. gr. 
 T188, and left .to cool in large leaden vessels. It is afterwards decanted from die 
 gypsum deposited, and filtered by passing it through a filter of sand or wool. It is 
 next evaporated until it has a specific gravity of 1-277, left to cool and settle, and 
 once more decanted and filtered. The filtered liquid of the last operation is then 
 evaporated to a syrupy consistency (about sp. gr. 1'49), and mixed with dry powdered 
 wood charcoal, in the proportion of 100 parts of syrup to 20 parts of charcoal. This 
 mixture is dried in cast-iron pans, by heating and constantly stirring, and finally 
 heated to low redness. The excess of sulphuric acid is thus decomposed by the 
 charcoal, carbonic oxide, carbonic acid, and sulphurous oxide escaping, which are 
 passed into a chimney. 
 
 Distillation of Phosphorus. The mixture submitted to distillation consists of acid 
 calcium phosphate, charcoal, and a small quantity of water. It is put into retorts of 
 stoneware or fire clay, which are three fourths filled, then smeared over with clay, 
 carefully dried, and placed in furnaces. The furnaces employed are galley furnaces 
 (fig. 94). Each furnace holds ten retorts, which are heated by a common fire, five on 
 each side. The hot air from the furnace passes through the flue (A) underneath the 
 retorts, round which it plays, and finally escapes into the common flue (D). Above 
 (D) is an evaporating pan (j), in which liquors are concentrated. The neck of each 
 retort is connected with a copper adapter (K), terminating in^the copper receiver (E). 
 The copper adapter is luted to the neck of the retort with a luting consisting either of 
 lime, blood, iron filings, and powdered sulphur, or of dry loam moistened with linseed 
 
 FIG. 94. 
 
 oil. The receiver (E) is furnished with a wide opening above, closed air-tight by the 
 lid (h); g is a small tube through which air and other gases escape from the 
 apparatus ; f is a tube for allowing the excess of water contained in the receiver to 
 escape in proportion as phosphorus collects in the receiver. The retorts having been 
 charged and placed in the furnace in the above manner, the niches (c c) are bricked in, 
 and the fire lighted. At first a fire of turf is made, care being taken to heat the re- 
 torts gradually, the temperature continually increasing for 12 hours, and finally wood 
 is thrown into the fire, and the heat kept up so long as anything distils over or gases 
 are seen to escape. The gases first evolved consist of air and steam ; then follow 
 hydrogen and carbonic oxide, the latter being formed by the action of wood charcoal 
 upon the water of the acid calcium phosphate. A small quantity of sulphurous oxide 
 is also formed. After a short time combustible gases escape, which ignite upon 
 coming into contact with the air ; these consist of phosphoretted hydrogen and carbonic- 
 oxide. This point indicates to the workman that the distillation of phosphorus has 
 begun. In proportion as phosphorus collects in the receivers, the level of the water 
 in them rises, and it flows out through the tube (/), so that the pressure does not 
 become great enough to cause injury to the lutings of the retorts. If in course of 
 the operation however the lutings crack, and an escape of phosphorus vapour takes 
 place, the cracks are smeared over again carefully with luting. The heat is continued 
 as long as inflammable vapours escape at</; the distillation occupying in all about 
 60 hours. During the distillation, especially towards the end, when less easily fusible 
 mixtures of phosphorus and charcoal, small quantities of red phosphorus, and perhaps 
 some silicon, pass over, a stoppage may easily take place in the adapters. In such case, 
 a workman, whose hand is protected by a long wet leather glove, removes at intervals 
 such solid pieces. ' In like manner, the first portions of phosphorus which distil 
 over and, being inflated with gas, float on the surface of the water in the receivers, 
 are pressed down under water with the hand. Upon the receivers becoming too hot, 
 either cold water is poured in at h from a can, or the receivers are sprinkled with 
 
MANUFACTURE OP PHOSPHORUS. 153 
 
 water issuing in a fine jet from the pipe (). The water collects in a common gutter 
 which conducts it away. 
 
 As soon as the distillation is over, the retorts and receivers are taken to pieces, the 
 
 adapters thrown into cold water, and the raw phosphorus removed from the receivers. 
 
 f Since the gas which escapes during the distillation would, if breathed, be highly 
 
 injurious to the workmen, the receivers are covered with a wooden roof, connected 
 
 with a ventilating chimney, by which this gas is drawn off. 
 
 Several changes have of late been made in the construction of the furnaces. A 
 furnace similar to the one above described, which is still in use in France, holds from 
 24-36 retorts, in rows of 12 or 18 respectively, placed against each other, and each 
 row is heated by a separate fire. The retorts have a globular form, and are placed 
 horizontally. The necks of the retorts are bent slightly upwards. 
 
 In a few phosphorus works in Germany furnaces are employed which hold as 
 many as 42 retorts. These furnaces are galley furnaces, in which the retorts are 
 placed above one another, each side of the furnace holding 21 retorts. Each side is 
 heated by a special fire, and both furnaces communicate above in a common flue. 
 The retorts are made of stoneware ; they have a cylindrical shape, and are prolonged 
 so as to form a neck. The products of distillation pass into an upright copper 
 tube, and from thence into the receivers. 
 
 The receivers have also been altered both in shape and material. At one time it 
 was usual to employ copper receivers ; these were succeeded by receivers of glass ; the 
 material now chiefly employed is earthenware. The receivers are generally made in 
 the form of jars, and are placed in couples before each retort. Bell-shaped receivers 
 are also employed, secured by an hydraulic joint. 
 
 _ ^ A furnace may here be mentioned, constructed by Fleck, which is suitable for 
 firing with coal or coke, all the other furnaces yet mentioned being only suitable for 
 turf and wood. Fleck's furnace consists of arched fire chambers, separated from one 
 another, and each heated by itself. Each of these chambers contains five cylindrical 
 retorts placed directly over the fire. The retorts are made of fire clay, and are in 
 communication with bell-shaped receivers. The heated air of each furnace passes 
 through an opening in the arched roof, into a common horizontal flue, above which 
 are placed pans for concentrating the liquors. 
 
 Fleck's method of preparing phosphorus consists in digesting one part of broken 
 bones, which have been deprived of their fat, for 6 or 7 days, with four parts of hydro- 
 chloric acid of sp. gr. T048, after which time the liquor is drawn off, and the residue 
 again treated with hydrochloric acid having a strengthequaltosp.gr. r020. The 
 result of this second treatment is a dilute liquor which is used in the digestion of fresh 
 bones. The hydrochloric acid decomposes the tribasic calcium phosphate into acid 
 calcium phosphate and calcium chloride. A liquor is thus obtained of sp. gr. 1*118, 
 which, on account of its containing large quantities of free hydrochloric acid, is 
 evaporated either in earthenware vessels or brickwork pans. The liquor when cooled 
 forms a crystalline mass, which is then pressed, and mixed with one fourth its weight 
 of powdered wood charcoal, and submitted to distillation in Fleck's furnace. There 
 remains in the retorts, after the distillation is over, a mixture of tribasic calcium 
 phosphate and charcoal. This residue is incinerated, treated with concentrated hydro- 
 chloric acid, and the liquor thus obtained treated for phosphorus as before. 
 
 This process possesses the advantage that glue is obtained, as a by-product, from 
 the bones treated with hydrochloric acid. 
 
 In Gentele's process bone ash powder is macerated with hydrochloric acid, and the 
 liquor neutralised with a solution of ammonium carbonate. There is thus formed a 
 precipitate of tribasic calcium phosphate, and a solution of sal ammoniac, which is 
 drawn off and treated for sal ammoniac, while the precipitate is treated with sulphuric 
 acid and charcoal, and distilled. Ammonium carbonate is obtained by carbonising the 
 bones, and if its amount is not sufficient, it is partly replaced by lime. 
 
 In the method of Cari-Montrand a mixture of bone ash and charcoal is placed in 
 stoneware retorts, heated to redness, and hydrochloric acid gas passed over it'. Tho 
 
 excess 
 
 in the receivers, ... 
 
 charcoal powder. For this purpose the bones are covered with the dilute hydrochloric 
 acid, the requisite quantity of powdered charcoal is added, and the mixture obtained is 
 dried and distilled in a current of hydrochloric acid gas. The residue in the retorts 
 consists essentially of calcium chloride and charcoal. 
 
 In Donovan's method, lead phosphate is heated to redness with charcoal. The 
 lead phosphate is prepared by acting upon bone ash with nitric ncid, and precipitating 
 the liquor thus obtained with sugar of lead, so that the whole of the phosphoric acid 
 is precipitated as lead phosphate. The precipitate is separated from the liquid, 
 thoroughly dried, mixed with charcoal, and then heated to redness. 
 
154 
 
 PHOSPHORUS. 
 
 G-erland proposes treating bone ash powder with aqueous sulphurous acid, and 
 heating the liquor thus obtained. Tribasic calcium phosphate is precipitated and ip 
 treated for phosphorus in the ordinary way. The sulphurous oxide which escapes is 
 condensed in a coke tower for further use. 
 
 In Claude Brison's process, calcium phosphate, silica, combustible material, and 
 soda are melted together in a shaft furnace. The mouth of the furnace is closed, and 
 the escaping vapour Conducted through a lateral aperture into the condensing apparatus. 
 It is necessary in this process that the draught should be strong enough to overcome 
 the pressure of the column of water in the condensers. The furnace is recharged at 
 intervals and the operation is, therefore, continuous. The rationale of the process is 
 that silica liberates phosphoric acid, which is then reduced to phosphorus by the action 
 of the charcoal furnished from the combustible material. 
 
 Purification of crude Phosphorus. There are various methods of purifying the 
 product obtained as above described ; it generally contains some amorphous phos- 
 
 FIG. 95. 
 
 FIG. 97. 
 
 phorus, carbon, silicon, etc. The process of purifying raw phosphorus consisted 
 formerly in throwing it into earthenware vessels containing water, and then melting 
 it at a temperature of 60. After it had cooled and become solid, it was bound up 
 tightly in a sack of moist chamois leather (c, fig. 95), which was then laid upon a 
 copper strainer standing in a vessel (A A) containing water heated to 50. Upon the 
 phosphorus melting, a semi-globular dish (D D) was laid upon the sack and pressed 
 down upon it by means of the rod (E) and the lever (G G), the pressure being at first 
 slight and gradually increased. The melted phosphorus pressed through the leather 
 collected at the bottom of the vessel A A. 
 
 A more modern method of purifying raw phosphorus consists in passing melted 
 phosphorus first of all through a layer of animal charcoal, and finally through a piece 
 of chamois leather. The apparatus is shown in figs. 96 and 97. The bone charcoal 
 is laid upon the perforated bottom (b b) of the vessel (A) in a layer of about 6 inches. 
 The vessel (A) is about two thirds filled with water, the temperature of which is raised 
 to 60 by means of the water bath (c c), and then the raw phosphorus is laid upon 
 the layer of charcoal. The phosphorus soon begins to melt, filters through the layer 
 of charcoal and the perforated bottom, collecting at D. Upon opening a cock (E) it 
 flows through a tube (F, fig. 97) into a second vessel (B) filled with water, kept also 
 by the aid of a water bath at the same temperature as the water in A. In B is also 
 a perforated bottom (c c) covered with a piece of chamois leather, upon which the 
 phosphorus collects. So soon as phosphorus has passed into B, the tube (F) is con- 
 nected with a pump which forces warm water into A. The melted phosphorus is then 
 pressed through the' leather and collects at E, whence it is drawn off through a 
 cock (o). 
 
 Another method consists in pressing melted phosphorus by the aid of steam through 
 cylinders furnished with plates of porous brick. The raw phosphorus is previously 
 mixed with powdered charcoal in order to prevent too rapid stoppage of the porous 
 
MANUFACTURE OF PHOSPHORUS. 155 
 
 brick plates. The charcoal powder forms a layer above the porous brick plates, and 
 is removed and submitted to distillation in order to obtain the phosphorus retained 
 by it. 
 
 According to K. Wagner, Messrs. Violet of Paris purify raw phosphorus in the 
 following manner : Eaw phosphorus is melted in a copper boiler and mixed with 3-5 
 per cent, of ^ordinary sulphuric acid and 3 '5 per cent, of acid potassium chromate. A 
 slight frothing takes place, and the phosphorus appears beneath the green liquid clear 
 and colourless. It is then taken out, washed, and cast into sticks. 100 parts of raw 
 phosphorus, thus treated, yield 96 parts of refined phosphorus. 
 
 In Germany the refining or purifying of raw phosphorus is effected by a process 
 of distillation. The raw phosphorus is melted under water in a copper pan, and in 
 order to prevent ignition upon pouring it out, it is mixed with 15 per cent, of sand. 
 This mixture is then put into cast-iron retorts which are placed in a furnace, each re- 
 tort being supported upon a couple of iron bars over the grate, in such a position that 
 its neck inclines downwards, protruding from a niche in the wall of the furnace, with its 
 mouth dipping ^ to f in. into water contained in a wooden tub placed in front of the 
 furnace. The retorts are heated slowly in order to drive off as much adherent moisture 
 as possible, as, upon strongly heating in presence of water, large quantities of phospho- 
 retted hydrogen are formed. After the greater part of the water has been driven off, 
 inflammable gas containing phosphoretted hydrogen is observed, which indicates 
 that the distillation of phosphorus has begun. Immediately beneath the necks of the 
 retorts are leaden dishes for collecting the phosphorus, which is removed from time to 
 time. Since, in case of neglect on the part of the workman, explosions are apt to occur 
 which scatter about the phosphorus in the receivers, it is advisable not to allow too 
 great quantities of phosphorus to collect in the receivers. 
 
 Phosphorus is moulded in various ways, the most general form given to it being 
 that of sticks. 
 
 In order to form phosphorus sticks, the plan adopted in some works is to dip glass 
 tubes of the required aperture into melted phosphorus, which is drawn up in the 
 tubes by sucking with the mouth, care being, however, taken that there is a layer of 
 water between the mouth and the phosphorus. The opening of the tube is then 
 closed with the thumb and the whole quickly dipped into cold water ; the phosphorus 
 then solidifies and contracts, and may be readily removed. Glass tubes have been of 
 late employed in France to which an iron tube is attached furnished with a cock. The 
 glass tube is dipped into the phosphorus, which is drawn up with the mouth, the cock 
 then closed, and the tube immersed in cold water. 
 
 By K. Seubert's method, which has recently received much application, phosphorus 
 is melted in a vessel (i, fig. 98) contracted below and supported in the water bath (H H). 
 The vessel (i) terminates in a tube 
 closed by the cock (j) and communi- 
 cating with the vessel (LI), which is 
 filled with water. A glass tube (M M) 
 is pushed into this tube at M. Upon 
 opening the cock the phosphorus flows 
 into the glass tube until within 1 to 1 1 
 in. of the furthest end, and solidifies 
 in it. The cock is then closed, and 
 also the end of the glass tube, either 
 
 with the stopper (N) or with the thumb. - bIG - ys - 
 
 The glass tube is taken out, immersed in cold water, and the phosphorus stick removed. 
 The tube is then again fitted into the mouth of the cock, and once more filled with 
 phosphorus in the above manner. 
 
 Granular Phosphorus. In order to obtain granular phosphorus, for the prepara- 
 tion of which Seubert's machine is available, it is only necessary to pour a layer of 
 hot water at a temperature of 45-50 from 2 to 3 in. in height, very carefully, upon a 
 board into the vessel (L L) containing cold water, in such a way that a mixing of the ho 
 and cold water is prevented. The cock (j) is then opened so as to allow the phos- 
 phorus to drop, each drop solidifying immediately upon contact with the lower layer 
 of cold water. Phosphorus in the form of very fine grains may be obtained by melt- 
 ing it beneath water, or better under alcohol, agitating it violently while coolin 
 
 g The proportion of refined phosphorus obtained by careful working does no 
 exceed 8 or 10 per cent, of the bone ash employed, since, owing to breakage of retoi 
 and combustion, some phosphorus is always lost. 
 
 na Phosphorus is packed in water in hermetically closed tin canisters, each 
 hSSffSI to 6 L. of phosphorus. In order to test if the soldering IB 
 tight Jhe canTstLs are placed upon sheets of white blotting paper, amoistemng 
 
156 
 
 PHOSPHORUS. 
 
 of the paper indicating an imperfection in the soldering. The canisters are then 
 packed in barrels or boxes. In order to prevent bursting of the canisters in winter, 
 by the freezing of the water, a small quantity of alcohol is often added to the water 
 before the canisters are soldered up. Messrs. Albright and Wilson avoid the use of 
 much water in packing phosphorus by cutting a large cylindrical block of phosphorus 
 into discs, each disc being then cut in a radial direction from the centre, and the pieces 
 fitted into cylindrical tin canisters and covered with water. 
 
 AMORPHOUS PHOSPHORUS maybe prepared on a small scale by heating ordinary 
 phosphorus for some time to a temperature of 260, in a glass flask, the air of which 
 has been expelled by carbonic acid. The glass flask is heated in an oil bath. 
 
 On the large scale this operation is conducted in an apparatus, patented by Al- 
 bright of Birmingham, which consists of a cylindrical vessel of glass or porcelain, 
 surrounded by a casing of cast iron fitting into a cast-iron sand bath, that stands 
 in a cast-iron boiler containing an alloy composed of equal parts of lead and tin. A 
 large hemispherical cast-iron dome covers the whole. The inner porcelain or glass vessel 
 is also furnished with a lid connected with a spring in such a way that, in case of 
 sudden internal pressure, the lid is raised, and the gas causing the pressure escapes. 
 A tube furnished with a cock passes from the inner lid through the large outer arched 
 dome, terminating in a vessel containing water or mercury, so that gases escaping 
 from the glass or porcelain vessel may escape into the air without causing a return of 
 air into the vessel. The apparatus is charged and set in action in the following way. 
 Well-dried phosphorus is placed in the interior porcelain vessel, and the vessel con- 
 taining the alloy of tin and lead heated by a fire underneath it. The alloy gradually 
 melts, heating in succession the sand bath and the porcelain or glass vessel containing 
 
 i'io. 99. 
 
 the phosphorus, driving out at first air, and afterwards gases which ignite spon- 
 taneously upon coming in contact with the air. The temperature of the metal bath is 
 then brought up to 260, and kept at this temperature until the conversion of the 
 phosphorus into the amorphous condition is complete, a process which requires about 
 10 days. During the entire course of the operation the tube through which the gases 
 escape from the interior vessel containing the phosphorus is kept hot by means of a 
 lamp, so as to avoid stoppage from the condensation of any phosphorus that may distil 
 over. When the operation is completed the cock of the delivery tube is closed so as 
 to avoid the ingress of water from the receivers, or of air into the phosphorus vessel, 
 upon the cooling down of the apparatus. 
 
 Coignetof Lyons prepares amorphous phosphorus by heating ordinary phosphorus 
 in a cast-iron boiler, without employing either of the baths above described. The 
 apparatus is shown in fig. 99. A is a crucible-shaped boiler of cast iron, standing in 
 a furnace directly above the fire, the furnace being heated with coke. The tube (B) 
 
FRICTION MATCHES. 157 
 
 serves for regulating the draught of air to the fire, and keeping the temperature of the 
 boiler under control. The boiler is about two thirds filled with phosphorus, and 
 gradually heated, the temperature being shown by four thermometers (c c'), which 
 pass through the lid of the boiler. D is an iron tube for the exit of air and other 
 gases. The evolution of gas at D must be moderate throughout the entire operation. 
 Condensed products of distillation are pushed back into the boiler with the iron 
 bar (E). 
 
 Purification. Eaw amorphorus phosphorus always contains small quantities of 
 ordinary phosphorus, which have to be removed by some process of purification. The 
 raw amorphous phosphorus is cut into pieces and powdered under water. This powder 
 is next dried and washed with carbon bisulphide, in which ordinary phosphorus is 
 soluble. Since this method is somewhat dangerous, owing to the tendency to sponta- 
 neous combustion of carbon bisulphide containing phosphorus, raw amorphous phos- 
 phorus is purified in some places by roasting it in iron pans, the mass being constantly 
 stirred. Ordinary phosphorus is thus burnt to phosphoric acid, which is afterwards 
 washed out with water. 
 
 Coignet's method consists in boiling raw amorphous phosphorus with a solution of 
 caustic soda, by which ordinary phosphorus is converted into sodium hypophosphite. 
 which dissolves, and gaseous phosphoretted hydrogen, which escapes. The raw amor- 
 phous phosphorus is boiled with fresh quantities of caustic soda solution, until the 
 unpleasant odour of phosphoretted hydrogen is no longer observed. It is then well 
 washed with water and dried. 
 
 Nickles proposes shaking raw amorphous phosphorus with a solution of calcium 
 chloride, having a specific gravity of from T83 to T85, which lies between that of 
 ordinary phosphorus (T83) and that of amorphous phosphorus (2-106). Ordinary 
 phosphorus, therefore, collects on the surface of the solution, while the amorphous 
 phosphorus sinks to the bottom, and is afterwards washed and dried ; the ordinary 
 phosphorus is removed with carbon bisulphide. 
 
 Uses. The chief application of phosphorus is in the preparation of friction 
 matches. The remaining consumption of phosphorus is for preparing various labora- 
 tory reagents, pharmaceutical preparations, poison for vermin, etc. 
 
 FBICTION MATCHES. In prehistoric times fire was produced, as indeed it is at 
 the present day among savages, by rubbing together two polished wooden surfaces. 
 The production of fire by striking together flint and steel dates from the fourteenth 
 century. 
 
 In 1805 an apparatus of peculiar construction was invented by Chancel, which 
 consisted of a small bottle filled with asbestos that had been saturated with concentrated 
 sulphuric acid. Splints partly coated with sulphur, and having the points coated with 
 a mixture of sulphur and sugar, caught fire when pressed against the moist asbestos, 
 the ignition being communicated to the splint by the sulphur covering. 
 
 In the year 1823 Dobereiner, at Jena, discovered that finely divided or spongy 
 platinum possesses the property of igniting a mixture of atmospheric air and hydrogen. 
 Dobereiner's apparatus has been already described on page 28. The apparatus is in 
 use at the present day. 
 
 The first friction matches appeared in England in April 1827, and were the in- 
 vention of a chemist and druggist named Walker, residing at Stockton. They con- 
 sisted of thin slips of wood 2| inches in length, covered with sulphur to one third 
 their length, tipped probably with a mixture of sulphide of antimony, chlorate of 
 
 C' ,sh and gum, and were sold for half-a-crown a box containing fifty matches. The 
 dongas newspaper of January 10, 1830, describes them as being supplied in 
 tin boxes, accompanied by a piece of glass paper, between the folds of which the 
 match to be inflamed was pinched, and then suddenly drawn out. Phosphorus friction 
 matches were not known on the continent until the year 1833, and, very curiously, 
 several nations seem to have simultaneously produced this kind of match, so that it is 
 difficult to say who was the discoverer of the first phosphorus matches. As early as 
 1815 Derosne appears to have been acquainted with the preparation of phosphorus 
 matches. The first phosphorus matches consisted essentially of a mixture of phos- 
 phorus and potassium chlorate, and they were so dangerous that their manufacture 
 was, in many countries, prohibited by law. The next attempt was made with a mix- 
 ture of potassium chlorate, red lead, manganese, and phosphorus, which was succeeded 
 by one consisting of lead peroxide and phosphorus, and finally of a mixture consisting 
 of red lead, salpetre, and phosphorus. The modifications of modern date will be 
 treated of further on. 
 
 The use of amorphous phosphorus instead of ordinary phosphorus is of great im- 
 portance for this branch of industry, and although the consumption of this substance 
 has not yet attained the dimensions which might bo expected, still its advantages 
 
158 PHOSPHORUS. 
 
 over ordinary phosphorus are so great, that its consumption is sure before long to 
 assume very considerable dimensions, and, probably, to exceed that of ordinary phos- 
 phorus. The use of amorphous phosphorus would prevent the terrible disease of the 
 jaws from which the workpeople employed in the manufacture of matches containing 
 ordinary phosphorus suffer, and besides this, cases of poisoning with the heads of 
 lucifer matches would be rendered impossible. 
 
 The wood employed in the manufacture of matches is generally that of fir, pine, 
 or aspen trees, less often poplar, birch, or beech, etc. The method of preparing the 
 splints varies with the form to be given to them. 
 
 For the preparation of cylindrical splints a kind of plane is used, the edge of 
 which is fluted, and it has a number of holes, generally three. When this plane is 
 forced along a lath of wood, in a direction parallel to the fibres, the tool penetrates 
 into the wood, cutting it up into cylindrical splints, each spliut having a length eqiial 
 to that of the lath taken. The lath is then again planed true with an ordinary plane, 
 and the former operation repeated. This kind of work is generally conducted in the 
 forest where the trees grow; thus, for instance, in the Black Forest, in several parts of 
 Bohemia, and in Austria, etc. 
 
 The next operation, viz. that of cutting the splints into lengths suitable for the 
 match manufacturer, is generally performed in the match factories. A machine of the 
 kind consists of a narrow trough provided with a slit, in which works a knife moved 
 by a lever. Wrana has invented an apparatus, by means of which manual skill is in 
 part supplanted by machinery. The plane of this machine is impelled forwards by 
 mechanism, and is simply guided by the workman. In Krutzsch's apparatus, manual 
 labour is entirely supplanted by machinery. His machine consists of a steel plate, 
 with about 400 holes placed as near together as possible ; the edges of these holes are 
 sharpened, and a block of wood is forced in the direction of the fibres against the 
 plate, and thus divided into splints. 
 
 Svlphuration of the Splints. For the purpose of sulphuring, the splints are packed 
 in frames in such a way that when dipped in sulphur, sufficient room is left between each 
 splint for the excess of sulphur to drop off. The frames are square, and consist of a 
 number of parallel divisions, between which the splints are so laid that on one side of 
 the frame their ends lie like the fibres of a brush. A single frame generally has 32 
 divisions, and each division holds 40 splints, making a total of 1,280 splints. The 
 placing of the splints in the frame was formerly performed by hand, but at the 
 present day a very ingeniously constructed apparatus is employed, which saves a con- 
 siderable loss of time. The splints are made to fall, by a process of shaking, through 
 the holes of a perforated metal plate, into the divisions in the frames, which are for 
 this purpose slightly loosened. As soon as the frames are full, they are drawn 
 together so as to secure the splints firmly, and removed. 
 
 The frames holding the splints are next placed in a horizontal position over 
 melted sulphur, and lowered so that the protruding ends of the splints are covered to 
 about ^ in. with sulphur. The sulphur is contained in a shallow pan, the bottom 
 of which consists of a perfectly even and horizontally placed stone slab, heated 
 sufficiently to retain the layer of sulphur one-third of an inch deep, at a temperature of 
 from 125 -130C. The frames are so lowered into this sulphur trough that the 
 ends of the splints just rest upon the bottom of the plate. The frames are then taken 
 out, and the excess of sulphur adhering to the splints removed by shaking them, so 
 that only a thin covering of sulphur adheres to each splint. 
 
 Matches are now often dipped in stearin or paraffin instead of sulphur, both of 
 which are preferable to sulphur, as in burning they do not evolve the penetrating and 
 disagreable smell afforded by it. 
 
 The tipping of the splints with the ignitable mixture is effected in the same way 
 as that just described in coating with sulphur, etc., the only difference being that the 
 layer of ignitable mixture is only in. in depth. 
 
 A special machine for dipping the splints in the ignitable composition has been 
 constructed by Higgins. This consists of an endless chain, supporting the frames, 
 which are thus drawn over the vessel containing the composition. In the ignitable 
 composition itself is a rotating grooved roller, the grooves of which are filled with the 
 mixture as it revolves, and the splints are caught one after the other, and are pressed 
 by a special contrivance against the ignitable composition in the grooves of the roller. 
 The entire apparatus is covered with a glass case, so as to shield the workmen from 
 the injurious effects of phosphorus vapours. 
 
 The composition of the combustible composition varies considerably, being in part 
 a trade secret, each manufactory having its own. The following tables will, however, 
 serve to give some idea of the compositions most in use. Such compositions generally 
 contain a small quantity of phosphorus, the chief mass consisting of oxidising 
 substances, together with some adhesive substance, such HP glue or gum. In this 
 
FRICTION MATCHES. 
 
 159 
 
 country glue is generally used, in consequence of the liability of gum to absorb mois- 
 ture from the air. Among the older recipes, by Bottcher, and which are now in part 
 in use, are the two following : 
 
 Phosphorus . 
 Saltpetre 
 Ked lead . 
 Glue 
 
 II. 
 
 Phosphorus . 
 Saltpetre 
 
 Manganese peroxide 
 Gum 
 
 Payen obtained, by analysis, the following results : 
 
 m. 
 
 IV. 
 
 V. 
 
 
 
 Stearin dips 
 
 2-5 
 
 2-5 v 
 
 3-0 
 
 2-0 
 
 Gum 2-5 
 
 2-5 
 
 4-5 
 
 3-0 
 
 3-0 
 
 2-0 
 
 2-0 
 
 2-0 
 
 0-5 
 
 0'5 
 
 3 
 
 o-i 
 
 o-i 
 
 0-1-0-5 
 
 Phosphorus 
 
 Glue 
 
 Water . 
 
 Fine sand 
 
 Ked ochre 
 
 Cinnabar or Prussian blue 
 
 Potassium chlorate . 
 
 German manufacturers, on the whole, use less phosphorus, as may be seen from the 
 following analytical results : 
 
 VI: 
 
 Phosphorus . . . .. . ' . . 47 
 
 Gum ........ 14'0 
 
 Water . . . '. . -^ . 12-0 
 
 Ked lead . . .. 1 . . . 40'OJ 'Oxidised 
 
 Nitric acid . . . . 1**, . 25'0 i red lead.' 
 
 VII. VIII. 
 
 Phosphorus . . 8 4 Phosphorus . . 2-0 
 
 Glue . . . 21-0 Glue tf -' 5-0 
 
 Lead peroxide . . 24-0 Chalk . .. v-. 3-0 
 
 Saltpetre . . . 24-0 Lamp-black . . 0-12 
 
 Manganese peroxide . TO 
 
 When glue is used, it is cut in pieces and soaked in water for three hours, until it 
 swells up. It is then brought into a boi'er (A, fig. 100), heated by a water bath 
 
 FIG. 100. 
 
 Fio. 101. 
 
 <BB) to 100. When the glue has melted, the pot is taken out ana placed upon a 
 wooden frame (fig. 101), the phosphorus mixture is thrown into the pot and 
 whole stirred with the stirrer (a) until cool. The starrer is furnished with bristles 
 and by this means an emulsion of glue and phosphorus is produced which is mixed 
 with the sand, red lead, and other ingredients of ^composition The mass is then 
 again heated in the water bath until liquid, when it is poured out upon ho marble or 
 stone pMe used in the dipping process, and heated by a water bath placed beneath 
 
16C PHOSPHORUS. 
 
 it. When gum is used in the place of glue, the process is conducted in a similar way, 
 the only difference being that it is not necessary to pour the mixture in a warm state 
 upon the dipping plate, or to heat the latter. 
 
 Less phosphorus is required, according to Wagner, when the phosphorus has been 
 previously dissolved in carbon bisulphide, and the other ingredients added to the solu- 
 tion. After the evaporation of the carbon bisulphide, the phosphorus remains in so 
 fine a state of division, that it is very easily ignited. The recipe vii., above given, 
 refers to a case of the kind. In some cases dextrin may conveniently take the place 
 of glue or gum as adhesive material. 
 
 Drying of the Splints. After the dipping is over, the splints are allowed to dry 
 in the air for a short time. When glue has been used, the frames are hung out in the 
 air for two or three hours ; in cases where gum has been used the frames are exposed 
 to the air for 24 hours. The preliminary drying is then succeeded by a more complete 
 drying process, for which purpose the frames are hung upon iron supports in specially 
 constructed drying rooms, constructed of fire-proof material, and heated by hot-water 
 pipes laid along the floor. The floor is strewed with sand to a depth of 4 or 5 inches, 
 so as to avoid the ignition of any matches that may have fallen on to the floor, should 
 one get trodden on. The sand serves further to extinguish any fire that may break 
 out. Each frame and its support is separated from its neighbour by a screen of 
 sheet iron, so as to localise the fire in case of ignition. 
 
 When the combustible mixture has thoroughly dried, the splints are removed from 
 the frames, and packed for exportation in paper, papier-mache boxes, or in boxes of 
 thin wood. 
 
 In order to prevent the matches from smouldering after the flame has been extin- 
 guished, Howse recommends soaking the splints, before dipping, in concentrated 
 saline solutions for about 48 hours, and then drying them rapidly. The salts proposed 
 are alum, sodium silicate, ammonium borate, ammonium sulphate, or ammonium 
 phosphate, sal ammoniac, and zinc sulphate. 
 
 The precautions necessary in match manufactories cannot be overrated. Tubs 
 filled with water ought to be placed in the rooms where phosphorus is handled, 
 so that in case of an accident happening to a workman by the spirting of phosphorus, 
 he may at once plunge the wound into cold water. Good ventilation also ought 
 especially to be provided, for that alone can protect the workmen from disease and 
 ill-health. 
 
 Matches without Sulphur. It has been already mentioned above that the unplea - 
 santness of sulphur matches may be avoided by dipping the splints in substances 
 like stearin, paraffin, etc. instead of sulphur. The preparation of stearin matches will 
 serve as an example of the process. The splints are fastened in the frames and their 
 ends scorched by pressing them against hot iron plates. They are then dipped in 
 shallow vessels lined with lead or tin, containing a layer of melted stearin ^ to ^ in. 
 deep, which is kept hot meanwhile. The stearin is absorbed by capillarity into the 
 pores of the wood, penetrating the entire lower extremity of the splints. The splints 
 are allowed to remain a short time in the melted stearin, and are then tipped with 
 combustible material in the usual way. 
 
 The ignition of the matches is faciliated by using a combustible composition con- 
 taining less glue or gum, and more of oxidising substances ; thus : 
 
 Phosphorus 3'0 
 
 Gum . 0'5 
 
 Water 3-0 
 
 Sand 2-0 
 
 Lead peroxide 2'0 
 
 Instead of lead peroxide, a somewhat larger quantity of red lead and 0'5 parts of 
 nitric acid may be substituted. 
 
 Wax or Vesta Matches. These are prepared in the following way. A number of 
 cotton wicks, from 100-200, wound round a large roller, are drawn through a bath of 
 melted wax, or a mixture of 2 parts stearin with 1 part wax, the individual wicks 
 being kept apart by a comb. Each wick is thus covered with a coating of wax, and 
 they are next passed through a perforated iron plate, the opening of which corresponds 
 with the thickness desired to bu given to the taper. The tapers are then cut by 
 machinery to the required length, packed in frames, and tipped in the usual way. 
 These matches require a very readily ignitable tipping, since they are too weak to bear 
 great pressure when rubbed. 
 
 The following composition of a mixture suitable for tipping wax matches is given 
 by Merckel : 
 
COMPOUNDS OF PHOSPHORUS. 161 
 
 Phosphorus 12 
 
 Gum .'...-.. 14 
 
 Antimonous sulphide .... 3 
 
 Bed lead .... 351 
 
 Nitric acid .' 2 i { Oxidised red lead -' 
 
 Cinnabar O'l 
 
 Zulzer has constructed a machine by means of which the tapers are cut, fastened in 
 frames, and then dipped, in one consecutive operation. The tapers are carried by 
 machinery to holes in a moveable vertical iron table, which is connected with a cutting 
 apparatus for dividing them into suitable lengths. The wicks when cut remain fast in 
 these holes, and are carried away, by a mechanical contrivance, to be dipped, while afresh 
 perforated iron table takes the place of the one already filled. 
 
 Fusees for lighting cigars, etc., are prepared from paper or other combustible 
 material which has been saturated with a solution of saltpetre, and thus rendered 
 capable of burning in the open air. 
 
 Amorphous Phosphorus Matches. In preparing these the splints are treated first of 
 all with sulphur or stearin in the usual way, after which they are dipped into a com- 
 bustible composition spread out upon a horizontal marble plate, to the depth of ^ to 
 in. To prepare the combustible composition, 40 parts of finely powdered potassium 
 chlorate are thrown into 60 parts of a thick solution of gum, to which is then added 40 
 parts of amorphous phosphorus and 20 parts of powdered glass. When glue is used in 
 the place of gum, it is softened by soaking in water for four or six hours, and then 
 dissolved by heating it for fifteen or twenty minutes in a water bath to 50 or 60. 
 To 75 parts of glue solution are then added 40 parts of potassium chlorate, 40 parts of 
 amorphous phosphorus, and 15 to 20 parts of powdered glass, the composition being 
 spread out upon a marble plate, heated by steam to a temperature of 35 or 40, and 
 the splints dipped in the mixture. The drying process is effected in the usual way. 
 
 In 1853 Lundstrom, in Sweden, took out a patent for non-poisonous matches, which 
 could only be ignited by rubbing them against a specially prepared surface. The splints 
 are either covered first of all with sulphur, or are impregnated with stearic acid, wax, 
 paraffin, etc., and are then dipped in the following composition : 
 
 Potassium chlorate 6 
 
 Antimonous sulphide 2-8 
 
 Glue 1 
 
 The surface against which the matches are rubbed is generally the side of the 
 box, or a piece of paper, painted over with the following composition : 
 
 Amorphous phosphorus 10 
 
 Manganese peroxide or antimonous sulphide .... 8 
 G-lue 3-6 
 
 Matches made in Paris, and known in the trade as androgynes, have their sulphured 
 end covered with a mixture consisting of 2 parts potassium chlorate, 1 part charcoal, 
 and 1 part umber, the composition being secured by glue, while their other end consists 
 of amorphous phosphorus, also attached by means of glue. When required for use, a 
 splint of the kind is broken in two, and the two opposite ends rubbed against one 
 another. 
 
 Compounds. Phosphorus forms a number of compounds with other elementary 
 substances, but only a few of them possess any industrial importance. These com- 
 pounds are generally termed phosphides, and they present considerable analogies 
 to the corresponding compounds of nitrogen, arsenic, and antimony. This is especially 
 evident in the gaseous compound of phosphorus and hydrogen PH 3 , known asphosphine 
 or phosphuretted hydrogen, which is closely analogous to ammonia, both in 
 constitution and many other respects. 
 
 There is another compound of phosphorus and hydrogen represented by the formula 
 PH 2 . Phosphorus combines with chlorine in two proportions, forming a trichloride 
 PC1 3 , in which it is trivalent, and a pentachloride PC1 5 , in which it is pentavalent. 
 The bromine compounds are similarly constituted, and there is a triodide PI S , as well 
 as a diiodide PI 2 , corresponding to the dihydride, but no pentiodide is known. The 
 compounds with fluorine and cyanogen correspond to the trichloride. Phosphorus 
 combines in several proportions with sulphur; it also combines with several of the 
 metals, but these substances are very little known ; they appear to be in some respects 
 analogous to the sulphides in their general characters. The presence of a very minute 
 proportion of phosphorus in some metals renders them hard and brittle (see ' Iron and 
 Copper'). 
 
 " les the above-mentioned compounds of phosphorus with elementary substances 
 
 M 
 
162 PHOSPHORUS. 
 
 a number of substances are known by the general name of phosphorus bases, which 
 are compounds of phosphorus with compound radicles or pseudo-elementary substances 
 such as ethyl C 2 H S . These substances are analogous in constitution to ammonia or 
 ammonium, and to the ammonia bases and other substances in which hydrocarbon 
 compounds act the part of pseudo-elementary substances (see ante, pp. 39 and 69). 
 
 The most important compounds of phosphorus are the oxides. Two of these are 
 known in the anhydrous state the trioxide or phosphorous oxide P 2 3 , and the 
 pentoxide P 2 5 , or phosphoric oxide; they both combine with water, forming 
 hydrates or the hydrogen salts known as phosphorous acid H 3 P0 8 and phosphoric 
 acid H 3 P0 4 , and with basic oxides, constituting the corresponding saline substances 
 known as phosphites and phosphates. A third oxide, P 2 0, is known only in the 
 state of combination either with basic oxides ashypophosphites, or with water, the 
 hydrate or hydrogen salt being hypophosphorous acid. 
 
 Hydrates 
 
 P 2 3H 2 = 2 H 3 P0 2 Hypophosphorous acid 
 
 Trioxide or phosphorous oxide P 2 S P 2 3 3H 2 = 2 H 3 P0 3 Phosphorous acid 
 Pentoxide or phosphoric oxide P 2 5 P 2 5 3H 2 = 2 H 3 P0 4 Phosphoric acid 
 
 These three acids, which may be regarded as forming a series of oxides of phosphine 
 PH 3 , differ in respect to the hydrogen replaceable by metals. In hypophosphorous acid 
 only one third of the hydrogen can be thus replaced, and the general formula of the 
 hypophosphites is MH 2 P0 2 . In phosphorous acid two thirds of the hydrogen can be 
 replaced by metals, and the general formula of the phosphites is M 2 HP0 3 ; but in the 
 acid corresponding to phosphoric oxide the whole of the hydrogen can be replaced by 
 metals, and according to the amount actually replaced in this way three series of salts 
 are formed, the composition of which, as compared with phosphoric acid, may be 
 represented by the following formulae : 
 
 Phosphoric acid . . . . .... . H S P0 4 
 
 Neutral sodium phosphate . . . . Na s P0 4 
 
 Acid sodium phosphates . . . . - -V v 
 
 Besides the ordinary phosphoric acid there are at least two other hydrates of phos- 
 phoric oxide which differ from it in many respects, and constitute essentially distinct 
 acids representing distinct series of salts. 
 
 Trihydrate P 2 5 3H 2 = H 6 P 2 8 or 2H S P0 4 orthophosphoric acid 
 Dihydrate P 2 5 2H 2 = H 4 P 2 7 pyrophosphoric acid 
 
 Monhydrate P 2 5 H 2 = H 2 P 2 6 or 2HP0 3 metaphosphoric acid 
 
 The metaphosphates containing one atomic proportion of a monovalent metal have 
 the general formula MP0 3 , those containing one atomic proportion of a divalent metal 
 have the formula M"P 2 6 , and those containing one atomic proportion of a trivalent 
 metal M'"P 3 9 . The metaphosphates are capable of combining with each other and 
 forming a great number of double salts or polymeric compounds. There are four 
 series of pyrophosphates which may be represented by the sodium salts : 
 
 Neutral sodium pyrophosphate ..... Na 4 P 2 7 
 
 ( Na 3 HP 2 7 
 Acid sodium pyrophosphates ..... J Na 2 H 2 P 2 0. 
 
 The neutral calcium salt is Ca" 2 P 2 7 , and the neutral aluminum salt Ar" 4 P e 2I . 
 The salts of the first three series may contain two or more different metals. 
 
 The characters of the three kinds of phosphoric acid and those of the correspond- 
 ing salts are totally distinct; thus, for instance, metaphosphoric acid coagulates albu- 
 men, and the acid as well as its salts give a white precipitate with silver nitrate, while 
 orthophosphoric acid does not coagulate albumen or give the same white precipitate 
 with silver nitrate, and its salts give a bright yellow precipitate with silver nitrate. 
 Pyrophosphoric acid does not coagulate albumen, and its salts give a white precipital e 
 with silver nitrate. Both metaphosphoric acid and pyrophosphoric acid are readilv 
 converted into orthophosphoric acid by boiling their solutions in water. The corre- 
 sponding salts are also converted into orthophosphates in the same way, or by fusion 
 with excess of alkali. 
 
CHLORINE. 
 
 SYMBOL 01. ATOMIC WEIGHT 35-5. 
 
 History. This substance was discovered in 1774, by Scheele, who regarded it, 
 according to the views then prevailing, as dephlogisticated hydrochloric acid. Ber- 
 thollet held chlorine to be a compound substance, containing oxygen for one of its 
 constituents and hydrochloric acid for the other. G-ay-Lussac and Thenard were of 
 the same ^opinion, or at least they did not consider chlorine to be an elementary sub- 
 stance. Sir H. Davy was the first to ascertain the real nature of chlorine, and it owes 
 its name to him. 
 
 Occurrence. Chlorine does not occur naturally in the free state ; it exists, 
 however, very abundantly in combination with other substances. Combined with 
 hydrogen as hydrochloric acid, it occurs in the water of some volcanic springs ; it 
 occurs in very large quantities combined with sodium, as rock salt or common salt, 
 either forming extensive beds, or in solution, as in sea- water and the water of springs. 
 In combination with potassium, chlorine occurs as sylvin at Stassfurt and at Kalucz 
 in Galicia ; combined with magnesium it occurs in sea water, and in combination with 
 potassium and magnesium, as carnallite, at Stassfurt and other places; in combina- 
 tion with ammonium or with calcium, chlorine also occurs in smaller quantities in 
 volcanic exhalations, and in certain mineral waters. 
 
 Chlorine also occurs naturally in combination with the heavy metals, such as 
 silver, lead, etc., but in comparatively small quantities. Chlorine is a never-failing 
 constituent of the juices, etc., of both plants and animals ; consequently it may be 
 reckoned as one of the most widely diffused elements. 
 
 Characters. Chlorine is at the ordinary temperature and pressure a greenish 
 yellow gas. This character induced Sir H. Davy to give to it the name chlorine, from 
 X.\(ap6s, greenish-yellow. It has an unpleasant smell and exerts a powerful suffocating 
 action, causing very dangerous irritation of the air passages, accompanied by violent 
 coughing, and even expectoration of blood. The density of chlorine gas relatively to 
 hydrogen is 35'5, and it has relatively to air a specific gravity of 2*442. At and 
 under a pressure of 6 atmospheres, it condenses, forming a liquid of dark greenish 
 yellow colour, having in relation to water a specific gravity of T38. Chlorine has not 
 yet been obtained in the solid condition. The solubility of chlorine gas in water varies 
 with the temperature very considerably. At water dissolves only 1'45 times its 
 volume, and at 8 as much as 3'04 times its volume; at 17, 2'37, at 35C. T60, and 
 at 50C. 1-09 times its volume. Upon conducting chlorine gas into water cooled below 
 8, there is formed a compound of chlorine with water, which has a composition 
 represented by the formula Cl 5H 2 ; it is a colourless crystalline substance, which 
 decomposes at the ordinary temperature into chlorine and water. A solution of 
 chlorine in water is decomposed by exposure to sunlight, yielding hydrochloric acid 
 and oxygen gas, which escapes. On this account a solution of chlorine which, when 
 freshly prepared, has a green colour, soon bleaches on exposure to light ; hence it is 
 necessary to keep solution of chlorine in a dark place. 
 
 The most ir 
 a large scale, 
 
 This bleaching actic 
 
 a constituent of nearly all organic substances. Chlorine accordingly deprives all such 
 organic substances of their hydrogen, producing indirectly oxidation, and thereby de- 
 composing them. It is, however, capable of acting both as an oxidising and bleaching 
 agent upon vegetable colouring matters by combining with the hydrogen of any water 
 that may be present, thus liberating oxygen, which combines with the colouring 
 matter. 
 
 Preparation. Chlorine is prepared on a small scale by gently heating concen- 
 trated hydrochloric acid with pieces of manganese peroxide broken up to about the siso 
 
164 CHLORINE. 
 
 of a nut, in a good-sized glass flask. The reaction that takes place is represented 
 by the equation 
 
 4HC1 + Mn0 2 = MnCL, + 2H 2 + 2C1 
 146 87 126 " 36 71 
 
 When chlorine ceases to be developed, the solution of manganese protochloride is 
 poured off and fresh hydrochloric acid poured into the generating flask. In order to 
 dry the gas, it is passed first through a Woulfe's bottle, contaning concentrated sul- 
 phuric acid, and then through one or two U tubes, filled either with pieces of calcium 
 chloride or pumice stone saturated with concentrated sulphuric acid. 
 
 In the above method of preparing chlorine, half of the chlorine remains in com- 
 bination with manganese. By acting upon common salt with sulphuric acid and 
 manganese peroxide, the entire amount of chlorine contained in it may be liberated, 
 according to the equation : 
 
 2NaCl -f Mn0 2 + 2H 2 S0 4 = MnS0 4 + Na 2 S0 4 + 2H 2 + 2C1 
 117 87 196 151 142 36 71 
 
 Practically three equivalents of sulphuric acid are taken, because sodium chloride is not 
 entirely decomposed by sulphuric acid, except at very high temperatures, unless sul- 
 phuric acid be present in quantity sufficient to cause the formation of acid sodium sul- 
 phate. On a large scale, it is seldom customary to employ common salt and sulphuric 
 acid, as the price of hydrochloric acid is now so very moderate. The use of mag- 
 nesium chloride, which is now extremely cheap, would offer many advantages over 
 the use of salt. 
 
 Several other methods of preparing chlorine have been proposed, of which the 
 following are examples : 
 
 Schlosing's method consists in acting upon manganese peroxide with a mixture of 
 hydrochloric and nitric acids, the concentration being so regulated that chlorine only 
 is evolved. The residue consisting of manganous nitrate, yielding upon calcination 
 manganese peroxide and nitrous gas, which by contact with water yields nitric acid. 
 
 Mallet oxidises cuprous chloride by the oxygen of the air. This, when treated with 
 hydrochloric acid, yields chlorine and cuprous chloride, which is again oxidised as 
 before. 
 
 Schank's method consists in treating calcium chromate with hydrochloric acid, so 
 as to produce chlorine, calcium chloride and chromium chloride, from which chromic 
 oxide is precipitated by treatment with calcium carbonate, and the precipitate again 
 converted into calcium chromate by igniting it with lime. 
 
 Dunlop's method consists in decomposing a mixture of common salt and sodium 
 nitrate with sulphuric acid. Chlorine and nitrogen oxides are given off, and by pass- 
 ing the gas through sulphuric acid the nitrous compounds are absorbed and separated 
 from the chlorine. 
 
 Deacon's method consists in decomposing hydrochloric acid by heating the gas in 
 contact with atmospheric oxygen so as to form water with liberation of the chlorine. 
 For this purpose a mixture of hydrochloric acid gas and air is passed through a 
 chamber filled with lumps of porous clay heated to redness. 
 
 However, none of these methods have superseded the decomposition of hydro- 
 chloric acid by manganese peroxide. 
 
 For the preparation of chlorine on a large scale the apparatus consists either of a 
 leaden still or, as shown from A to B in fig. 102, of several stoneware jars of 20 to 40 
 
 gallons capacity, fitted into cast-iron baths, which are either left empty or filled with 
 water, and are heated by a fire (rf). If a temperature a little above 100 C. is required, 
 common salt, calcium chloride, or magnesium chloride is dissolved in the water of the 
 
PREPARATION OF CHLORINE. 165 
 
 baths. The baths are sometimes heated by steam of high tension admitted through a 
 rose into the water of the baths. 
 
 The generators are connected with each other by the tube (e) of lead or earthen- 
 ware. For setting the process going, the generators are half filled with hydrochloric 
 acid, the small openings closed, and after connecting them with the rest of the appa- 
 ratus, perforated stoneware cylinders (M, fig. 103), con- 
 taining pieces of manganese peroxide, are inserted into 
 the neck of the generating vessels. These cylinders are 
 closed below, and have two wide holes at the upper 
 ends, which serve as a hold for the tongs (M, fig. 104), 
 by means of which the cylinders are placed in, or re- 
 moved from the generating vessels. As soon as the 
 cylinders have been fitted into the generating vessels, 
 the lids (N, fig. 103) are luted on, and the generators are 
 heated at first gently, the heat being increased towards 
 the end of the process. The gas evolved is conducted, 
 so as to cool it, through the leaden tube (e') into a 
 stoneware vessel, and through the tube (e") into another FIG. 103. FIG. 104. 
 
 similar vessel, whence it passes to its final destination. 
 
 In manufactories where very large quantities of chlorine are employed, the gene- 
 rating stills consist of large cubical vessels of sandstone, holding 200 gallons and up- 
 wards. These chlorine stills are sometimes hewn out of a single stone block, or they 
 are built of slabs and soaked with tar so as to enable them to resist the influence of 
 the acid and the chlorine. They are heated either by passing steam into them, or into 
 a jacket of the same material as that of which they are made. The generators are 
 generally fitted with a grating, upon which the pieces of manganese peroxide are 
 placed, or, as is sometimes the case, a number of perforated cylinders like that 
 shown in fig. 103 are suspended in them, and they are closed by slabs of sandstone 
 with manhole and delivery tubes. Since it is not possible to raise the temperature of 
 these sandstone generators sufficiently high ; the hydrochloric acid is not so completely 
 decomposed in them as in the vessels of stoneware. 
 
 The residues from the chlorine generators may be used for purposes of disinfection, 
 or the manganese may be precipitated with lime, and the precipitate calcined and used 
 as a flux in blast furnaces in smelting iron. 
 
 The chief disadvantage attending the use of manganese peroxide arises from the 
 difficulty of disposing of the residual liquor from the stills. This consists of a solu- 
 tion of manganous chloride, ferric chloride, and hydrochloric acid, and being of a 
 noxious and destructive nature, it cannot be run into water-courses. Many attempts 
 have therefore been made to convert the manganese it contains into peroxide that 
 would be again available for producing chlorine. 
 
 Dunlops Process. Consists in treating the liquor with calcium carbonate in the 
 cold, so as to precipitate the iron. After drawing off the liquor, the manganese is pre- 
 cipitated in the form of manganous carbonate by treatment with calcium carbonate 
 under a steam pressure of two atmospheres. The precipitated manganous carbonate 
 is washed, dried, and calcined in roasting furnaces, until carbonic acid is driven off, 
 and it is converted by oxidation into peroxide, which is again available for use in the 
 preparation of fresh quantities of chlorine. 
 
 Gatttfs Process Consists in evaporating the liquor to dryness with sodium nitrate 
 and strongly heating the residue ; by this means nitrous gases are evolved, which are 
 used in the preparation of sulphuric acid, while manganese peroxide and sodium 
 chloride remain behind. The sodium chloride is then either washed out from this 
 mixture, or the mixture is used direct for preparing chlorine. 
 
 Hofmann's Process Consists in precipitating the manganese with the liquor ob- 
 tained' by lixiviating soda waste; the precipitate, consisting of manganese sulphide, 
 sulphur, and a small quantity of manganous oxide, is then decanted off, dried ar 
 roasted. The sulphurous oxide formed in this operation is conducted into vitr 
 chambers ; the residue in the roasting ovens, consisting of manganous sulphate a 
 manganous oxide and peroxide, is mixed with Chili saltpetre and heated to 3 
 this means sodium sulphate and manganese peroxide are formed, and themtrc jenper 
 oxide given off is passed into vitriol chambers. The sodium sulphate is dissolved out 
 and treated for soda, and the residue is used again for preparing chlorine. 
 
 Weldoris Method Consists in precipitating the manganese as protoxide by me 
 of lime and oxidising it by passing air through the mixture ; a compound is tni 
 containing about 70 per cent, of manganese peroxide. The precipitate is allowed to 
 settle, and is used with hydrochloric acid for a further development of chlo 
 manganese peroxide as regenerated by Weldon's process has the advantage o^er 
 
166 CHLORINE. 
 
 natural manganese that it is more easily and completely attacked by hydrochloric 
 acid. 
 
 Weldon's method is now almost universally adopted in chemical works where 
 chlorine is prepared. The first step is to separate the iron present as ferric chloride 
 by adding te the hot liquor run off from the stills crushed limestone sufficient to 
 neutralise free hydrochloric acid and convert the iron salt into ferric oxide, by a 
 decomposition which takes place according to the following equation : 
 
 Fe 2 Cl 6 + 3CaC0 3 = Fe 2 3 + 3CaCl 2 + 3C0 2 . 
 
 After the precipitated ferric oxide has subsided, the clear liquor containing man- 
 ganous chloride MnCl 2 , together with the calcium chloride formed by the neutralisation 
 of the hydrochloric acid and the decomposition of ferric chloride, is run while still hot 
 into tall cylindrical vessels fitted with pipes, through which a current of air can be 
 forced into the liquor from a blowing engine. If the temperature of the liquor has 
 fallen below 60, steam is blown in to raise it to that degree ; air is then forced in, and 
 caustic lime mixed with water in a fine state of suspension rapidly added in quantity 
 equal to T63 times the weight of the manganese in the liquor, by which means the 
 manganous chloride is converted into a white precipitate of mangai:ous oxide, accord- 
 ing to the following equation : 
 
 MnCl 2 + CaO = MnO + CaCl 2 
 126 56 71 111 
 
 Kather more than one third of the lime added remains mixed with the precipitated 
 mauganous oxide or dissolved in the hot solution of calcium chloride and communica- 
 ting to the liquor a strong alkaline reaction. The precipitate gradually becomes 
 darker, and after air has been blown into the mixture for some time it acquires a black 
 colour, owing to the conversion of the manganous oxide into peroxide by the absorption 
 of oxygen from the air injected. Meanwhile the alkaline reaction of the liquor 
 diminishes, and at length entirely disappears when the absorption of oxygen ceases. 
 A little more of the liquor containing manganous chloride is then run in, and after 
 continuing the injection of air a few minutes longer, the contents of the vessel are run 
 into a settling tank, where the manganese peroxide is deposited as a black mud, from 
 which the clear solution of calcium chloride is drawn off. 
 
 The manganese peroxide thus obtained being in a very fine state of division, is 
 acted upon by hydrochloric acid much more readily than the native peroxide, which is 
 sometimes extremely compact and hard, and therefore, instead of adding hydrochloric 
 acid to a charge of the recovered manganese peroxide, the stills are charged with hydro- 
 chloric acid and the moist precipitate is gradually run into the acid through openings in 
 the covers of the stills. 
 
 The result obtained by this method differs in a very important particular from that 
 produced by the oxidation of manganous oxide by exposure to atmospheric air. In 
 the latter case the final product is not peroxide Mn0 2 , but manganic oxide Mn 2 3 , and 
 moreover the conversion takes place very much more slowly than in the operation just 
 described, the ultimate result being just the same as if only one half of the manganous 
 oxide operated upon were converted into Mn0 2 , inasmuch as Mn 2 3 = Mn0 2 + MnO. 
 Mr. Weldon considers that this is due to the fact that Mn0 2 acts the part of an acid 
 oxide like carbonic dioxide and combines with basic oxides, forming salts analogous to 
 the carbonates. Hence in the oxidation of manganous oxide, in the absence of other 
 basic oxides, the peroxide formed combines with an equivalent of manganous oxide, 
 forming Mn 2 3 and then the action stops. But when another basic oxide is present, 
 such as lime or potash, the manganese peroxide formed combines with this oxide, 
 forming CaMn0 3 , and the whole of the manganous oxide is converted into peroxide. 
 The presence of a basic oxide for the purpose appears therefore to be an essential con- 
 dition of success in this operation, and it is for this reason that the excess of lime is 
 added in precipitating the manganous oxide. The more intimate the mixture of the 
 manganous oxide with the basic oxide that serves this purpose, the more readily does 
 the absorption of oxygen take place. For this reason the effect is produced more 
 rapidly in the presence of soda or potash, on account of their solubility ; but fortunately 
 the solubility of lime, in the hot solution of calcium chloride with which the manganous 
 oxide is mixed in the precipitated liquor, is sufficient to ensure the practicability of this 
 method of preparing manganese peroxide. The rapidity of the process may be judged 
 of from Mr. Weldon's statement, that as much as two hundredweight of oxygen per 
 hour may be thus absorbed from atmospheric air, and solidified in the condition of 
 manganese peroxide. 
 
 In the product actually obtained on the large scale, water appears to some extent 
 to act the part of the base with which the manganese peroxide is combined, and the 
 action that takes place may be represented by the following equation : 
 
COMPOUNDS OF CHLORINE. 167 
 
 2MnO + H 2 + CaO + 20 = CaH 2 2Mn0 3 or CaMn0 3 + H 2 Mn0 3 
 and this product, in the dry state, would contain 70 per cent, manganese peroxide. 
 
 Uses. Chlorine is principally used for bleaching substances made from vegetable 
 fibres, such as cotton and linen, also in paper manufactories for removing the colour- 
 ing matters from dyed or stained stuffs; also in preparing potassium chlorate and the 
 double aluminum and sodium chloride, and in the manufacture of aluminum, in pre- 
 paring iodine, chloroform, red prussiate, for the extraction of gold, and for disinfecting 
 purposes. It is also much used as a reagent in chemical laboratories. Greater part 
 of the chlorine produced in chemical works is converted into a portable state by bring- 
 ing the gas in contact with hydrate of lime, which absorbs it in large amount, forming 
 what is termed bleaching powder. 
 
 In the same way that chlorine destroys organic colouring matters, so does it act 
 upon bad-smelling gases and miasmas, whence its use as a disinfectant. 
 
 Chlorine gas is very suitable for disinfecting large chambers, and for this purpose 
 it may be prepared on the spot by warming a mixture of manganese with concentrated 
 hydrochloric acid in an earthen pan. 
 
 Compounds. Chlorine combines with most other elementary substances, forming 
 substances which are termed chlorides. The chlorides of monatomic metals contain 
 equal atomic proportions of chlorine and metal, and correspond to hydrogen chloride 
 or hydrochloric acid. The chlorides of polyatomic elements contain two, three, 
 four, five, or more atomic proportions of chlorine, according to the atomicity of the 
 particular elementary substances with which it is combined. These are distinguished 
 in the same way as oxides by adding to the name of the elementary substance they 
 con tain in common the terminations ous and ic, as ferrous chloride and ferric chloride. 
 The formulse in the following table represent the composition of the moro important 
 chlorides of the elementary substances : 
 
 Hydrogen HC1 
 
 Sodium NaCl 
 
 Potassium KC1 
 
 Silver Ag 4 Cl 2 AgCl 
 
 Calcium CaCLj 
 
 Strontium SrCl 2 
 
 Barium BaCl 2 
 
 Magnesium MgCl 2 
 
 Zinc ZnCl 2 
 
 Copper Cu 2 Cl 2 CuCl 2 
 
 Mercury Hg^ Hg^ 
 
 Lead ' PbCl 2 
 
 Manganese MnCL, Mn 2 Cl 6 MnCl. 
 
 Iron FeCl 2 Fe 2 Cl 8 
 
 Nickel NiCLj 
 
 Cobalt CoCl 2 Co 2 Cl 6 
 
 Chromium CrCl 2 Cr 2 Cl 6 
 
 Uranium UC1 2 
 
 Aluminum Al 2 Cl t 
 
 Palladium PdCL, PdCl 4 
 
 Platinum PtCl 2 PtCl 4 
 
 Tin SnCl 2 SnCl 4 
 
 Bismuth BiCl 2 BiCl 3 
 
 Antimony SbCl 3 SbCl 5 
 
 Arsenic AsCl 3 
 
 Phosphorus PC1 3 Cl s 
 
 Nitrogen NC1 3 
 
 Boron BC1 3 
 
 Iodine IC1 3 IC1 4 
 
 wci. wa, 
 
 Molybdenum o MoCl 4 
 
 Tellurium 
 
 Sulphur S 2 C1 2 SC1 4 (?) 
 
 Titanium TiCl 4 Ti 2 Cl 6 
 
 Three oxides of chlorine are known ; the monoxide CLO or hypochlorous oxide, 
 
168 CHLORINE. 
 
 the trioxide C1 2 S or chlorous oxide, and the tetroxide C1 2 4) the first two forming 
 saline compounds with water and basic oxides, known as hypochlorites and 
 chlorites, the respective hydrogen salts being hypochlorous acid HC10 and 
 chlorous acid H010 2 . Two other oxides are known only in combination with 
 hydrogen and metals as chlorates and perchlorates, the hydrogen salts being 
 chloric acid HC10 3 and perchloric acid HC10 4 . The relations of these oxides 
 to each other and to their hydrogen salts are shown in the following table : 
 
 Hypochlorous oxide C1 2 + H 2 = 2HC10 Hypochlorous acid 
 
 Chlorous oxide C1 2 3 + H 2 = 2HC10 2 Chlorous acid 
 
 Chlorine tetroxide C1 2 4 
 
 Chloric oxide ? C1 2 5 + H 2 = 2HC10 3 Chloric acid 
 
 Perchloric oxide ? C1 2 7 + H 2 = 2HC10 4 Perchloric acid 
 
 The hypochlorites are soluble in water, and readily undergo decomposition, evolving 
 oxygen ; the solutions oxidise many substances, and have the power of bleaching ; when 
 solutions of hypochlorites are heated to boiling these salts are converted into chlorate 
 and chloride, according to the following equation : 
 
 3KC10 = KC10 3 + 2KC1. 
 
 These salts are the essential constituents of the bleaching preparations made by 
 saturating alkaline solutions or lime hydrate with chlorine. 
 
 The alkaline hypochlorites are only known in solution; any attempt to evaporate 
 these solutions causing decomposition. These solutions are colourless when pure, but 
 more generally they have a yellow colour, due to the presence of free hypochlorous 
 acid ; they evolve an odour of this acid, and are used for purposes of bleaching and 
 disinfecting. The solution of potassium hypochlorite is known under the name of 
 eau de Javelle; that of sodium hypochlorite under the name of eau de 
 Labarraque ; and the calcium compound, either combined or mixed with calcium 
 chloride, is known as chlorinated lime or bleaching powder (see ' Bleaching 
 Preparations '). 
 
 Hypochlorous acid is a yellowish volatile liquid, having an acrid taste and a sweetish 
 odour. In a concentrated state it decomposes rapidly, and even the dilute acid is 
 decomposed by heat into chloric acid, chlorine, oxygen and water ; it is a powerful 
 bleaching and oxidising agent. 
 
 Hypochlorous acid or an acidified solution of a hypochlorite reacts with chlorides 
 and liberates chlorine from both, according to the" equation : 
 
 KC10 + 2HC1 = KC1 + H 2 + 2C1. 
 
 The chlorites are soluble salts having bleaching properties, but they have no 
 industrial significance. 
 
 The chlorates are also soluble salts of greater stability than chlorates or hypo- 
 chlorites, but they have no bleaching power. At a high temperature chlorates are 
 decomposed, generally with evolution of oxygen and formation of perchlorate, some- 
 times also with evolution of chlorine ; they are therefore powerful oxidising agents, and 
 when mixed with carbonaceous substances, sulphur, etc., give rise to violent explosion 
 on the application of heat or even by rubbing the mixtures. Chloric acid is a colour- 
 less syrupy liquid, having a strong acid reaction, and when warm a pungent odour 
 resembling that of chlorine. It is a powerful oxidising and bleaching agent, and 
 decomposes when heated, with evolution of oxygen and chlorine and formation of per- 
 chloric acid. 
 
 The perchlorates are of little importance industrially ; they are mostly soluble in 
 water the potassium salt only sparingly and are more stable than any of the previously 
 mentioned salts of chlorine oxides. The acid is a colourless volatile liquid that oxidises 
 carbonaceous substances with violent explosion, but does not bleach ; it is very corrosive 
 and forms a crystallisable hydrate. 
 
 BLEACHING PREPARATIONS. 
 
 The power which chlorine possesses of destroying Vegetable colours was observed 
 by Berthollet very soon after the discovery of this substance by Scheele, and attempts 
 were made to apply it in bleaching linen. It was soon found that chlorine could be 
 most conveniently used for this purpose when dissolved in an alkaline solution ; and in 
 1799 the use of dry hydrate of lime in place of solution of potash or milk of lime was intro- 
 duced by Macintosh for preparing bleaching powder or chlorinated lime. The 
 exact chemical nature of this material is somewhat uncertain, but it may be regarded 
 as consisting essentially of a compound or a mixture of calcium hypochlorite with cal- 
 
BLEACHING POWDER. 169 
 
 eium chloride. It is formed by the action of chlorine upon lime, which, for this pur- 
 pose, must be employed either as solid hydrate or in the condition known as milk of 
 lime. The chemical change which takes place is represented by the following equation : 
 
 2CaH 2 2 + 401 = CaCl 2 + 2H 2 + CaCl 2 2 . 
 
 However, chlorinated lime has never a composition exactly like that shown in the 
 above equation, corresponding to 49 per cent, of chlorine, but always contains water 
 and an excess of hydrate of lime, which is necessary for preventing its too quick 
 decomposition. The actual amount of chlorine seldom exceeds 35 per cent. 
 
 The solutions of alkaline hypochlorites are prepared by passing chlorine gas from 
 generators of the form shown in fig. 103 into carboys containing a solution of sodium 
 carbonate or potassium carbonate in from 6 to 10 parts of water. The introduction of 
 chlorine is attended with evolution of carbonic acid gas, the reaction being represented 
 by the equation : 
 
 K 2 C0 3 + 201 = KC10 + KOI + C0 2 . 
 
 The operation should be stopped before all the carbonic acid has been driven off, 
 and it is necessary that at the end of the reaction about 5 per cent, of alkaline 
 carbonate should remain undecomposed, or rather in the state of acid carbonate. 
 
 The alkaline hypochlorites are sometimes prepared with bleaching powder, by 
 mixing solutions of 20 parts of crystallised soda, or 12 parts of potash, in 100 parts of 
 water, with a filtered solution of 10 parts of strong chlorinated lime. By the reaction 
 of calcium hypochlorite with the alkaline carbonates, insoluble calcium carbonate is 
 precipitated, and the alkaline hypochlorites remain in the solution which is then 
 decanted from the insoluble calcium carbonate. 
 
 Characters, Chlorinated lime or bleaching powder is a white and somewhat 
 moist powder, which, when left to itself, undergoes gradual decomposition. Properly 
 prepared, it ought not to lose more than 3 or 4 per cent, of chlorine in the course of 
 a year. When chlorinated lime is treated with acids, chlorine is evolved, as shown 
 by the following equations, and the decomposition takes place in two consecutive 
 stages, hypochlorous acid being formed in the first instance : 
 
 Ca01 2 2 + H 2 S0 4 = CaS0 4 + 2HC10, 
 
 and when sufficient excess of hydrochloric acid is present both substances are resolved 
 into water and chlorine, HC10 + HOI = H 2 + 201. The application of a strong heat to 
 chlorinated lime causes decomposition of the calcium hypochlorite into oxygen and 
 calcium chloride (Ca01 2 2 = CaCl 2 + 20) ; oxygen is also evolved from chlorinated lime 
 when a solution in water is mixed with hydrated oxides, such as hydrated ferric iron 
 or cupric oxide. Sunlight also exerts a decomposing influence upon bleaching powder, 
 and in manufactories where it is produced it is at once packed into casks. Even then 
 bleaching powder undergoes decomposition, and might give rise to dangerous explosions 
 if packed in a close vessel. 
 
 In preparing solid chlorinated lime the purest lime is chosen, and especial care is 
 taken that it does not contain iron, which would render the bleaching powder dirty in 
 colour, or magnesia, which would render it too hygroscopic, owing to the formation of 
 magnesium chloride. 
 
 Slaking of the Lime. This operation is performed either by spreading out pieces 
 of lime and sprinkling them with water until they have crumbled away into a fine 
 powder, or the pieces are held in a sieve in water until they show signs of energetic 
 combination taking place. The slaked mass is then spread out, sprinkled once or twice 
 with some water, and made up into a layer 1* in. in height, in which condition it 
 is allowed to lie for some days and then sifted. The product obtained by this operatic: 
 when properly prepared contains between 6 and 12 percent, of moisture. 
 
 Absorption of the Chlorine. The arrangement shown in fig. 1 02 from B to c is 
 very often used for this purpose. It consists of a rectangular chamber, about ] eet 
 long, 34- feet wide, 2 feet high. The sides are formed either of sandstone plates, or 
 iron plates covered with bitumen, sometimes of well-tarred wood or of slates, or 
 brickwork arched over. At the 
 entrance of the chamber is a 
 kind of gutter running in a 
 diagonal direction, serving to 
 collect and run off condensed 
 liquid products. At the opposite 
 
 end is a door (H), and on the p IG . 106. 
 
 roof of the chamber a safety f ,, 
 
 valve (/). Slaked lime in fine powder is strewn upon the *^ 
 which must be perfectly even, a layer being formed about 6 or 8 inches i 
 
170 CHLORINE. 
 
 The charging is effected either through holes at the sides of the chamber, that can be 
 hermetically closed, or by means of a small truck of sheet iron (fig. 105, K), holding 
 enough to cover an area of 3 feet, and fitted with a sliding bottom. This truck is 
 pushed in as far as the gutter at the end opposite to the door (H), and the bottom of 
 the truck is then drawn away, leaving the charge of 
 lime behind. The opening at H is then closed, the lid 
 fitted on air-tight, and chlorine is passed into the 
 chamber either through the five openings (e"', fig. 106), 
 or through a wide tube fitted into the cover of the 
 chamber. Chambers in which the lime is spread upon 
 FIG. 106. tables or hurdles have of late fallen into disuse, since it 
 
 has been found that the chlorine acts quite as well when the lime is simply spread 
 upon the floor. The dimensions of these chambers are sometimes much larger. 
 
 Method of Conducting the Process. Chlorine is passed into the chambers very 
 slowly during the first 18 or 20 hours, as the reaction causes a considerable rise of 
 temperature, and when the temperature rises above 90, the calcium hypochlorite is 
 decomposed into calcium chlorate and chloride. It is not usual to allow'the tempera- 
 ture to rise above 25. The completion of the process may be ascertained either by 
 examining the gas escaping from the valve (/), which must bleach blue litmus paper, 
 or from the amount of chlorine generated, which may be judged of by the quantity 
 of materials used. The longer the chlorine is allowed to react the more slowly 
 is it absorbed: but it is never passed in until no further absorption takes place, 
 for in that case the bleaching powder would be far too rich in chlorine, and very liable 
 to decomposition. The proper amount of chlorine in bleaching powder is from 33 to 
 35 per cent. 
 
 In an apparatus of the above kind it is possible, with a superficial area of about 
 44 square feet, to convert 300 Ibs. of lime in 24 hours into 440 Ibs. of chlorinated 
 lime ; so that a manufactory furnished with 20 separate sets of apparatus can produce 
 every 24 hours about 4 tons of bleaching powder. 
 
 In preparing liquid chlorinated lime, chlorine is passed into milk of lime contained 
 in sandstone tanks, closed above air-tight with boards so as to prevent the escape of 
 gas. The gas is simply passed to the surface of the liquid, which is continually 
 stirred by a special contrivance. 
 
 G-ay-Lussac's method of determining the percentage of chlorine in chloride of lime 
 depends first upon the oxidising action of chlorine in presence of water upon arsenous 
 acid, and the formation of arsenic acid according to the equation : 
 As 2 3 + 4C1 + 2H 2 = As 2 5 + 4HC1; 
 198 142 230 
 
 and, secondly, upon the fact that a mere trace of free chlorine suffices to decolorise tincture 
 of indig j. 
 
 From the above equation it will be seen that one molecule of arsenous acid 
 requires four atomic proportions of chlorine for its conversion into arsenic acid. 
 When therefore a solution containing a known quantity of arsenous acid is mixed 
 with a solution of bleaching powder, until all the arsenous acid is converted into 
 arsenic acid, the amount of active chlorine contained in the bleaching powder may be 
 calculated from the quantity of bleaching powder required. The point of complete 
 oxidation of the arsenous acid is ascertained by adding to the solution of arsenous 
 acid a small quantity of a solution of indigo, which is decolorised the moment all the 
 arsenous acid is oxidised. 
 
 The arsenous acid solution is prepared for this purpose by dissolving 13-94 grms. 
 of pure arsenous acid in a small quantity of caustic potash solution, acidulating the 
 solution with hydrochloric acid, and diluting with water to one litre. 1 c.c. of this 
 solution then contains 0-01394 grm. of arsenous acid, which corresponds to 0-01 grm. of 
 chlorine. 
 
 The operation is conducted as follows: 10 grms. of the sample are triturated in a 
 porcelain mortar with distilled water, the solution de- 
 canted off and the operation repeated with fresh quan- 
 tities of water several times. The decanted portions of 
 the liquid are then collected in a litre flask (A, fig. 107), 
 furnished with an accurately fitting stopper, the flask 
 filled up to the mark with water and its contents shaken 
 | up. The next step is to place 10 c.c. of the solution of 
 
 arsenous acid (corresponding to 0-1394 grm. of As 2 2 , or 
 
 T? ^ iA* i? me 0-1 grm. Cl) in a glass vessel (B, fig. 108). The arsenous 
 
 <IG - 1U8 - acid solution is kept in a bottle (c, fig. 1 10), fitted with a 
 
 pipette (D), by means of which it can be measured out. The arsenous acid solution in 
 
CHLOROMETRr. 171 
 
 the vessel (B) is diluted with ten times its volume of distilled water, and a single drop 
 
 of tincture of indigo added. The solution of bleaching powder prepared in the way 
 
 above described is again shaken up and a portion drawn 
 
 off into the burette (E, fig. 109), which holds from 50 
 
 100 c.c., and is divided into divisions of i c.c. This 
 
 solution of bleaching powder is then allowed to drop from 
 
 the burette into the solution of arsenous acid until the 
 
 indigo begins to decolorise, the operation being aided by 
 
 continual stirring with a glass rod. 
 
 Supposing that 30 c.c. of such a solution of bleaching 
 powder be required for the complete oxidation to arsenic 
 acid of the *1394 grm. of arsenous acid contained in 10 
 cubic centimetres of the arsenous acid solution ; this 
 quantity requires for its oxidation O'l grm. of chlorine ; 
 
 the 30 c.c. bleaching powder solution would represent ffjf FIG. 110. 
 
 0'30 grm. of solid chlorinated lime, and accordingly the ^* 
 amount of active chlorine would be 33*33 per cent. : 
 
 0-30 : 0-1 = 100 x; x = 33*33. 
 
 Penot and Mohr's method consists in treating a measured volume of the bleaching 
 powder solution with a known quantity of an alkaline solution of sodium arsenite in 
 excess ; the arsenous acid remaining unaltered is determined by adding to the liquid 
 a small quantity of starch-paste, and titrating with a solution of iodine of known 
 strength until the blue coloration of the starch by iodine takes place. This cannot 
 occur until the whole of the arsenous acid present has been converted into arsenic 
 acid. In carrying out this test the following liquids are required : 
 
 1. A solution of bleaching powder prepared in the way above described. 
 
 2. A solution of arsenous acid (sodium arsenite). In preparing this, 4'436 grms. 
 of very pure arsenous acid is dissolved in water containing 25 grms. of crystallised 
 sodium carbonate, and then diluted to the volume of 1 litre. 1 c.c. of this solution 
 contains 0-004436 grm. of arsenous acid and represents 1 c.c. of chlorine gas. This 
 solution of sodium arsenite requires to be kept in small, well-closed bottles, which 
 ought to be quite full, so as to prevent the formation of sodium arsenate by oxidation. 
 
 3. Iodine Solution. This is prepared by dissolving 11 -38 grms. of dry iodine in 
 as small a quantity as possible of potassium iodide, the solution being made up to a 
 litre with distilled water. Since iodine in the presence of water oxidises arsenous 
 acid just like chlorine, 4 atomic proportions of iodine correspond to 1 molecule of 
 arsenous acid, or, in other words, 4*436 grms. of arsenous acid corresponds to 11*38 
 grms. of iodine (198 : 508 = 4-436 : 11*38); or, 1 c.c. of the solution of sodium arsenite 
 corresponds to 1 c.c. of the solution of iodine. On testing the solution of iodine, 10 
 c.c. of the solution of sodium arsenite are measured into a beaker by means of a pipette, 
 mixed with some starch paste, then diluted with water, and solution of iodine added in 
 quantity sufficient to cause blue coloration. 10 c.c. of solution of iodine ought to be 
 required, and should this not be the case, the corresponding correction must be made 
 in the final calculation of results. 
 
 4. Starch Paste. This ought to be very dilute, and freshly prepared. 
 
 The re-agents being prepared in the way above described, the process of testing is 
 conducted in the following manner. 50 c.c. of the solution of bleaching powder are 
 drawn off from a pipette into a beaker glass ; an excess of sodium arsenite solution is 
 added, as well as a small quantity of starch paste, and solution of iodine is then dropped 
 into the mixture until a blue coloration sets in. The number of c.c. of iodine solution 
 used is then deducted from the number of c.c. of sodium arsenite taken, the difference 
 being the number of c.c. of sodium arsenite oxidised by the bleaching powder. Sup- 
 posing the difference found to be 45 c.c., this would correspond to 45 c.c. of chlorine, 
 since 1 c.c. of the solution of sodium arsenite corresponds to 1 c.c. of chlorine. The 
 50 c.c. of bleaching powder solution representing *5 grm. of solid chloride of lime, there- 
 fore, contains 45 c.c. of active chlorine. Accordingly 1000 grms. or 1 kilo of bleach- 
 ing powder contains 90,000 c.c. or 90 litres of chlorine gas ; i.e. the bleaching powder 
 shows a strength of 90, 
 
 The chlorometrical degrees represent the number of litres of chlorine contained in 
 1 kilo of bleaching powder. By multiplying the chlorometrical degrees by 3*178 (the 
 weight of 1 litre of chlorine gas in grammes) and dividing by 10, the per-centage by 
 weight is obtained. On the contrary, the chlorometrical degrees are obtained by divid- 
 ing the percentage by weight by 0'3178. 
 
 The manganese peroxide that is used in the production of chlorine 18 tested in a 
 similar manner. The relative value of a sample of it depends upon the amount of 
 
172 
 
 CHLORINE. 
 
 peroxide present, or, in other words, upon the extent to which the material is capable 
 of liberating chlorine by reaction with hydrochloric acid. Hence the valuation of the 
 manganese peroxide of commerce may be effected by determining according to either 
 of the foregoing meth ds the amount of chlorine obtained with a given weight of the 
 manganese. (See article ' Manganese.') 
 
 Uses. Chlorinated lime is used for the same purposes as chlorine, since it readily 
 evolves chlorine gas when treated with dilute acids, and from ite portability it is better 
 suited for some purposes than chlorine gas prepared directly. It is on this account 
 extensively employed in the bleaching of textile fabrics and in calico printing, etc. 
 
 Chlorinated lime is also much employed for disinfecting rooms, which are either 
 
 r'nkled with the powder, or the floors, walls, etc. are washed with a solution of this 
 nfectant. Pettehkofer is opposed to the disinfection of privies with chlorinated 
 lime 
 
 HYDROCHLORIC ACID. 
 
 FORMULA HC1. MOLECULAR WEIGHT 36'5. 
 
 History. Basil Valentine, who lived in the fifteenth century, first described the 
 preparation of pure aqueous hydrochloric acid. Before his time a mixture of hydro- 
 chloric acid with nitric acid had been known under the name of aqua regia, its pre- 
 paration having been described by the Arabian chemist Geber in the eighth century. 
 In former times the general name for this substance was spirit of salt, a name 
 which is not quite extinct at the present day. Later, it received the name of muri- 
 atic acid, and it is now generally called hydrochloric acid. After various hypotheses 
 had been setup as to its composition, its true composition was discovered by Davy in 
 1810. 
 
 Occurrence. Hydrochloric acid occurs naturally in the exhalations of volcanoes, 
 and thence it finds its way into streams in their neighbourhood. Besides this it is 
 always present in small quantities in the gastric juice of animals. 
 
 Composition. Hydrochloric acid is a compound of hydrogen with 35'5 times its 
 weight of chlorine. In the gaseous state it contains half its volume of hydrogen. 
 
 Characters. In the anhydrous state hydrochloric acid is a colourless gas of 
 very penetrating order, which forms a thick cloud when allowed to escape into the air. 
 The density of the gas relatively to hydrogen is 18'25, and relatively to air it has a 
 specific gravity of 1-255. Under a pressure of 30 to 40 atmospheres, or when cooled to 
 50, at the normal pressure, it condenses to a colourless liquid. It is one of the most 
 soluble of gases, water dissolving at 0, and under the normal atmospheric pressure 
 500 times its volume of the gas, and at 1 5 475 times its volume. When water saturated 
 with hydrochloric acid gas is heated to the boiling point, a large part of the hydro- 
 chloric acid escapes ; but part remains as a solution, containing 20 per cent, of acid, 
 which has a specific gravity of I'lO ; boils at 110, and distils over. The ordinary 
 liquid hydrochloric acid of commerce is a solution of the gas in water ; and since 
 the specific gravity of this solution increases in proportion to the amount of gas it 
 contains, a determination of the specific gravity of samples of commercial acid affords 
 an excellent means of ascertaining their strength. 
 
 The strength of hydrochloric acid is often expressed in degrees of Baume' s or 
 Twaddle's hydrometer. The following table serves for ascertaining the strength of 
 samples of acid from the degrees of either hydrometer : 
 
 Degrees 
 Baume 
 
 Degrees 
 Twaddle 
 
 Percentage of 
 Hydrochloric acid 
 
 Degrees 
 Baume 
 
 Degrees 
 Twaddle 
 
 Percentage of 
 Hydrochloric acid 
 
 26 
 
 42 
 
 42-85 
 
 14-5 
 
 20 
 
 20-20 
 
 25 
 
 40 
 
 40-80 
 
 12 
 
 18 
 
 18-18 
 
 24 
 
 38 
 
 38-88 
 
 11 
 
 16 
 
 16-16 
 
 23 
 
 36 
 
 36-36 
 
 10 
 
 14 
 
 14-14 
 
 22 
 
 34 
 
 34-34 
 
 9 
 
 12 
 
 12'12 
 
 21 
 
 32 
 
 32-32 
 
 8 
 
 10 
 
 10-10 
 
 20 
 
 30 
 
 30-30 
 
 6 
 
 8 
 
 8-08 
 
 19 
 
 28 
 
 28-28 
 
 6 
 
 6 
 
 6-06 
 
 18 
 
 26 
 
 26-26 
 
 3 
 
 4 
 
 4-04 
 
 17 
 
 24 
 
 24-24 
 
 2 
 
 2 
 
 2-02 
 
 15-5 
 
 22 
 
 22-22 
 
 
 
 
HYDROCHLORIC ACID. 
 
 173 
 
 The following table gives the contents in chlorine and hydrochloric acid gas of 
 aqueous solutions of hydrochloric acid. 
 
 Acid of 
 1-2 sp. gr 
 
 Specific 
 gravity 
 
 Chlorine 
 
 Hydro- 
 chloric acid 
 gas 
 
 Acid of 
 1-2 sp. gr. 
 
 Specific 
 gravity 
 
 Chlorine 
 
 Hydro- 
 chloric acid 
 gas 
 
 100 
 
 1-2000 
 
 39-675 
 
 40-777 
 
 50 . 
 
 1-1000 
 
 19-837 
 
 20-388 
 
 99 
 
 1-1982 
 
 39-278 
 
 40-369 
 
 49 
 
 1-0980 
 
 19-440 
 
 19980 
 
 98 
 
 1964 
 
 38-882 
 
 39-961 
 
 48 
 
 1-0960 
 
 19-044 
 
 19-572 
 
 97 
 
 1946 
 
 38-485 
 
 39-554 
 
 47 
 
 1-0939 
 
 18-647 
 
 19-165 
 
 96 
 
 1928 
 
 38-089 
 
 39-146 
 
 46 
 
 1-0919 
 
 18-250 
 
 18-787 
 
 95 
 
 1910 
 
 37-692 
 
 38-738 
 
 45 
 
 1-0899 
 
 17-854 
 
 18-359 
 
 94 
 
 1893 
 
 37'296 
 
 38-330 
 
 44 
 
 1-0879 
 
 17-457 
 
 17-941 
 
 93 
 
 1875 
 
 36-900 
 
 37-923 
 
 43 
 
 1-0859 
 
 17-060 
 
 17-534 
 
 92 
 
 1857 
 
 36-503 
 
 37-516 
 
 42 
 
 1-0838 
 
 16-664 
 
 17-126 
 
 91 
 
 1846 
 
 36-107 
 
 37-108 
 
 41 
 
 1-0818 
 
 16-267 
 
 16-718 
 
 90 
 
 1822 
 
 35707 
 
 36-700 
 
 40 
 
 1-0798 
 
 15-870 
 
 16-310 
 
 89 
 
 1802 
 
 35-310 
 
 36-292 
 
 39 
 
 1-0778 
 
 15-474 
 
 15-902 
 
 88 
 
 1782 
 
 34-913 
 
 35-884 
 
 38 
 
 1-0758 
 
 15-077 
 
 15-494 
 
 87 
 
 1762 
 
 34-517 
 
 35-476 
 
 37 
 
 1-0738 
 
 14-680 
 
 15-087 
 
 86 
 
 1741 
 
 34-121 
 
 35-068 
 
 36 
 
 1-0718 
 
 14-284 
 
 14-679 
 
 85 
 
 1721 
 
 33-724 
 
 34-660 
 
 35 
 
 1-0697 
 
 13-887 
 
 14-271 
 
 84 
 
 1701 
 
 33-328 
 
 34-252 
 
 34 
 
 1-0677 
 
 13-490 
 
 13-863 
 
 83 
 
 1681 
 
 32-931 
 
 33-845 
 
 33 
 
 1-0657 
 
 13-094 
 
 13-456 
 
 82 
 
 1661 
 
 32-535 
 
 33-437 
 
 32 
 
 1-0637 
 
 12-697 
 
 13-049 
 
 81 
 
 1641 
 
 32-136 
 
 33-029 
 
 31 
 
 1-0617 
 
 12-300 
 
 12-641 
 
 80 
 
 1620 
 
 31-746 
 
 32-621 
 
 30 
 
 1-0597 
 
 11-903 
 
 12-233 
 
 79 
 
 1599 
 
 31-343 
 
 32-213 
 
 29 
 
 1-0577 
 
 11-506 
 
 11-825 
 
 78 
 
 1578 
 
 30-946 
 
 31-805 
 
 28 
 
 1-0557 
 
 11-109 
 
 11-418 
 
 77 
 
 1557 
 
 30-550 
 
 31-398 
 
 27 
 
 1-0537 
 
 10-712 
 
 11-010 
 
 76 
 
 1536 
 
 30-153 
 
 30-990 
 
 26 
 
 1-0517 
 
 10-316 
 
 10-602 
 
 75 
 
 1515 
 
 29-757 
 
 30-582 
 
 25 
 
 1-0497 
 
 9-919 
 
 10-194 
 
 74 
 
 1494 
 
 29-361 
 
 30-174 
 
 24 
 
 1-0477 
 
 9-522 
 
 9-786 
 
 73 
 
 1473 
 
 28-964 
 
 29-767 
 
 23 
 
 1-0457 
 
 9-125 
 
 9-379 
 
 72 
 
 1452 
 
 28-567 
 
 29-359 
 
 22 
 
 1-0437 
 
 8-729 
 
 8-971 
 
 71 
 
 1431 
 
 28-471 
 
 28-951 
 
 21 
 
 1-0417 
 
 8-332 
 
 8-563 
 
 70 
 
 1410 
 
 27772 
 
 28-544 
 
 20 
 
 1-0397 
 
 7-935 
 
 8-155 
 
 69 
 
 1389 
 
 27-376 
 
 28-136 
 
 19 
 
 1-0377 
 
 7-538 
 
 7-747 
 
 68 
 
 1369 
 
 26-979 
 
 27728 
 
 18 
 
 1-0357 
 
 7-141 
 
 7-340 
 
 67 
 
 1349 
 
 26-583 
 
 27-321 
 
 17 
 
 1-0337 
 
 6-745 
 
 7-932 
 
 66 
 
 1328 
 
 26-186 
 
 26-913 
 
 16 
 
 1-0318 
 
 6-348 
 
 6-524 
 
 65 
 
 1308 
 
 25-789 
 
 26-505 
 
 15 
 
 1-0298 
 
 5-957 
 
 6-116 
 
 64 
 
 1287 
 
 25-392 
 
 26-098 
 
 14 
 
 1-0279 
 
 5-554 
 
 6709 
 
 63 
 
 1267 
 
 24-996 
 
 25-690 
 
 13 
 
 1-0259 
 
 5-158 
 
 5-301 
 
 62 
 
 1247 
 
 24-599 
 
 25-282 
 
 12 
 
 1-0239 
 
 4-762 
 
 5-893 
 
 61 
 
 1226 
 
 24-202 
 
 24-874 
 
 11 
 
 1-0220 
 
 4-365 
 
 4-486 
 
 60 
 
 1206 
 
 23-805 
 
 24-466 
 
 10 
 
 1-0200 
 
 3-968 
 
 4-078 
 
 59 
 
 1185 
 
 23-408 
 
 24-058 
 
 9 
 
 1-0180 
 
 3-571 
 
 3-670 
 
 58 
 
 1164 
 
 23-012 
 
 23-150 
 
 8 
 
 1-0160 
 
 3-174 
 
 3-262 
 
 57 
 
 1143 
 
 22-615 
 
 23-242 
 
 7 
 
 1-0140 
 
 2-778 
 
 3-854 
 
 56 
 
 1123 
 
 22-218 
 
 22-834 
 
 6 
 
 1-0120 
 
 2-381 
 
 3-447 
 
 55 
 
 1102 
 
 21-822 
 
 22-426 
 
 5 
 
 1-0100 
 
 1-984 
 
 2-039 
 
 54 
 
 1-1082 
 
 21-425 
 
 22-019 
 
 4 
 
 1-0080 
 
 1-588 
 
 2-631 
 
 53 
 
 MOW 
 
 21-028 
 
 21-611 
 
 3 
 
 1-0060 
 
 1-191 
 
 1-224 
 
 52 
 
 1-1041 
 
 20-632 
 
 21-203 
 
 2 
 
 1-0040 
 
 0-795 
 
 1-316 
 
 51 
 
 1-1020 
 
 20-235 
 
 20-796 
 
 1 
 
 1-0020 
 
 0-397 
 
 1-408 
 
 a yellow colour, owing to the presence ot iemc chloride, iiesu 
 purity, commercial hydrochloric acid often contains chlorine, sulphurous oxide, and 
 sulphuric acid, as well as sodium chloride and sulphate. When arsenical sulphuric 
 acid has been employed in the manufacture of hydrochloric acid, the arsenic passes 
 into the hydrochloric acid, and since large quantities of sulphuric acid are now manu- 
 
174 
 
 CHLORINE. 
 
 factured from pyrites, the presence of arsenic in common commercial hydrochloric acid 
 is a matter of frequent occurrence. Selenium compounds are also often found in com- 
 mercial hydrochloric acid. 
 
 Preparation. Hydrochloric acid is generally prepared by heating together 
 equivalent proportions of common salt and sulphuric acid^ the ultimate result of the 
 decomposition being represented by the following equation : 
 
 2NaCl + H 2 S0 4 = N a2 S0 4 + 2HC1 
 117 98 142 73 
 
 Therefore, in preparing hydrochloric acid, it would be necessary to take 117 parts 
 by weight of sodium chloride to every 98 parts by weight of concentrated sulphuric 
 acid ; but as sulphuric acid generally contains rather more than 1 molecule of water, 
 it is usual to take more of it than the quantity above indicated. 
 
 The reaction between these substances may be more correctly represented as taking 
 place in two stages, there being formed in the first instance acid sodium sulphate 
 and hydrochloric acid, according to the equation 
 
 NaCl + H 2 S0 4 = NaHS0 4 + HC1 
 58-5 98 120 36-5 
 
 and then the heat being increased towards the end of the process, the acid sodium 
 sulphate decomposes a further quantity of salt, according to the equation 
 
 NaCl + NaHS0 4 = Na 2 S0 4 + HC1 
 58-5 120 142 36-5 
 
 On the small scale hydrochloric acid is prepared by pouring 10 parts of sulphuric 
 acid, containing 1 part of water to 9 parts of acid, over 5 parts of common salt con- 
 tained in a glass flask, fitted with a caoutchouc cork and delivery tube ; the flask is 
 heated at first gently, and afterwards more strongly, and the gas evolved is passed 
 through a Woulfe's bottle containing a small quantity of water, so as to free it from 
 particles of sulphuric acid carried over, and then into a bottle containing the water 
 for the absorption of the gas for use. 
 
 When gaseous hydrochloric acid is required, it is prepared in the same way, but 
 the "Woulfe's bottle is charged with sulphuric acid instead of water, in order to dry 
 the gas. The gas is to be collected over mercury. 
 
 The apparatus in which the operation is carried out on the large scale is of various 
 construction, but glass retorts must be used when pure hydrochloric acid is required. 
 
 The most simple arrangement of the kind is that shown in fig. 111. It consists of 
 four or more glass retorts placed over a single furnace. Each retort (c') is connected 
 with a receiver containing a small quantity of water for the absorption of hydrochloric 
 acid. The retorts are charged by holding the neck in a vertical position and intro- 
 ducing the necessary quantity of 
 common salt; they are then 
 placed over the furnace, sulphuric 
 acid is introduced through the 
 bent funnel, and the neck of the re- 
 tort connected with the receiver. 
 The retorts are then heated so 
 long as hydrochloric acid passes 
 over. 
 
 An apparatus with better 
 arrangement for the absorption 
 of the hydrochloric acid gas is 
 shown in figs. 112 and 113. 
 The glass retorts (cc) contain 
 the mixture of salt and sulphuric 
 acid. From four to eight of them 
 are supported over a furnace (B). 
 whore they are heated by the hot 
 air of the furnace (A). The re- 
 torts stand in ti chamber made 
 of fire-bricks, the hot air passing 
 beneath and uround them from 
 the furnace flues (B' B, B, B). A 
 couple of furnaces of the kind, 
 FIG. 112. eacn holding 8 or 10 retorts, are 
 
 so connected with one another 
 that the firr gases escape through a common chimney, separated internally by a 
 
HYDROCHLORIC ACID. 
 
 175 
 
 partition about 3 feet high, so as to prevent the gases from entering the chimney in 
 opposite directions. The arrangement for condensation or absorption of the hydro- 
 chloric acid gas consists of doubly 
 tubulated balloons (D B), into one 
 tubuluB of which the neck of the 
 retort passes, the other being in 
 communication with a receiver 
 (E) below. The receivers are 
 also furnished with a second 
 tubulus for passing non-con- 
 densed vapours into a second or 
 third, etc., receiver of like con- 
 struction. The first receiver is 
 at starting empty, receiving the 
 raw hydrochloric acid as it drops 
 from D ; the other receivers con- 
 
 FIG. 113. 
 
 tain each a small quantity of 
 
 water for the effectual absorption 
 
 of the hydrochloric acid vapours. The aqueous hydrochloric acid of the latter receivers 
 
 is purer in quality, since the chief impurities remain in the first receiver. 
 
 The hydrochloric acid of commerce is to some extent prepared in the manner above 
 described ; but most of the hydrochloric acid used in chemical works is obtained in 
 making sodium sulphate from common salt, and its preparation will be treated of in 
 the chapter describing the manufacture of that substance. (See ' Soda Manufacture.') 
 
 The saturated solution of hydrochloric acid is drawn off into glass or stoneware 
 carboys provided with stoppers of the same material, which are either ground so that 
 they fit accurately, or are luted into the necks of the carboys, and then cbvered over 
 with a piece of strong linen. In filling the carboys for transport, it is necessary to 
 leave in each carboy an empty space of at least a pint capacity, so as to avoid risk of 
 breakage of the carboys in warm weathor by the expansion of the hydrochloric acid. 
 
 The purification of raw hydrochloric acid may be effected in two ways viz., 
 either the raw acid is distilled and the product of distillation passed into water for 
 absorption, or the raw acid is diluted till it has a specific gravity of 1'12, and then 
 distilled. In both cases it is necessary to reject the first portion of the distillate, as 
 it contains chlorine or sulphurous acid, or both, also to avoid distilling too far, in 
 which case ferric chloride would distil over. 
 
 Pure hydrochloric acid may also be obtained from the raw acid, according to P. W. 
 Hofmann, by filling a vessel furnished with doubly perforated clay plugs to one 
 third of its capacity with raw hydrochloric acid, and then pouring through a funnel, 
 admitting of being closed, sulphuric acid of specific gravity 1'848. This causes the 
 immediate evolution of hydrochloric acid gas, which is passed through a sort of 
 Woulfe's bottle containing water so as to wash it, and then collected in another 
 vessel containing distilled water. The evolution of hydrochloric acid gas in this 
 process is very regular, and not accompanied by any considerable rise of temperature. 
 It ceases when the sulphuric acid has reached a specific gravity of 1-566. The residual 
 sulphuric acid contains only 0'32 per cent, of hydrochloric acid, and may be either 
 concentrated or used for making sodium sulphate. 
 
 For the removal of arsenic from hydrochloric acid according to Bettendorfs 
 method, raw hydrochloric acid is mixed with a small quantity of fuming stannous 
 chloride, the precipitate thus produced is separated after 24 hours, and the hydro- 
 chloric acid distilled off. The first tenth part of the distillate is thrown away, and 
 the residue distilled almost to dryness. This operation serves at the same time to 
 deprive the hydrochloric acid of chlorine. 
 
 Uses. Hydrochloric acid is used in the preparation of the following substances : 
 aqua regia, which is used for dissolving gold, platinum, certain alloys, as well as 
 minerals, etc. ; stannous chloride and stannic chloride, antimonous chloride, and sal 
 ammoniac. It is used for decomposing the lime soap formed in the bucking of linen 
 or woollen fabrics impregnated with fat ; also in bleaching instead of sulphuric acid, 
 and for converting non-fermentable cane sugar into fermentable sugar in the manufac- 
 ture of molasses spirit. Pure hydrochloric acid is also used for purifying animal char- 
 coal ; for preparing carbonic acid in the manufacture of aerated waters and double 
 carbonates ; for purifying ferruginous sand in the manufacture of glass ; for removing 
 the fur in steam boilers ; in the preparation of blacking ; in the preparation of copper, 
 etc. in the wet way ; for removing phosphates from iron ores ; for cleansing zinc before 
 soldering ; for converting barium carbonate into chloride ; also in the recovery ol 
 phur from soda refuse, as well as in a number of chemical operations in the laboratory. 
 
176 
 
 CHLORINE. 
 
 The impure hydrochloric acid obtained as a by-product in the manufacture of soda 
 is generally used in the manufacture of chlorine and the hypochlorites, especially 
 bleaching powder and Javelle liquor (see p. 168). It is also used for making zinc 
 chloride. 
 
 SULPHUR CHLORIDE. 
 
 FORMULA S 2 C1 2 . MOLECULAR WEIGHT 135. 
 
 History. This substance was first obtained by Hageman in 1782, but its con- 
 stitution was not fully ascertained until it was studied by Davy and Bucholz in 1810. 
 
 Characters. Sulphur chloride is at the ordinary temperature a mobile reddish- 
 yellow liquid that fumes in contact with the air, and has a peculiar penetrating dis- 
 agreeable smell ; its specific gravity is 1*687, that of its vapour relatively to air 4'668 ; 
 it boils at 139. When brought into contact with water it gradually decomposes, and 
 sulphur is liberated, with formation of hydrochloric acid and thiosulphuric acid, which 
 is soon converted into sulphurous oxide and sulphur. Sulphur chloride dissolves 
 sulphur in large proportion. 
 
 Preparation. Sulphur chloride is prepared by passing dry chlorine gas over 
 melted sulphur and distilling off the chloride from the excess of sulphur. The 
 apparatus for conducting the operation is represented by fig. 114. The chlorine gas 
 
 FIG. 114. 
 
 generated in the flask (A) is first washed by passing it through water in the Woulfe's 
 bottle (B), then passed through the tubulated flask (c) and the drying tube (D), filled 
 with calcium chloride, into the retort (E) containing the sulphur, and kept sufficiently 
 hot by means of a spirit lamp. Combination takes place very readily, and the chloride 
 distills over into the condenser (F), kept cold by a stream of water. 
 
 Uses. Sulphur chloride is used as a solvent for sulphur in vulcanising caoutchouc. 
 
BROMINE 
 
 SYMBOL Br. ATOMIC WEIGHT 80. 
 
 History. This elementary substance was discovered in 1826 by Balard in the 
 mother liquor obtained in the manufacture of salt from sea water, and its most impor- 
 tant properties were ascertained by him. 
 
 Occurrence. Bromine does not occur naturally in the free state, but in the state 
 of combination with the alkaline metals and associated with the corresponding chlo- 
 rides it occurs in sea water, in the water of salt springs, in rock salt, marine plants and 
 animals, and also in coal. Bromides exist in considerable amount in the water of 
 some mineral springs ; for instance, that of the Adelheid spring in Upper Bavaria, in 
 the water of the brine springs at Kreuznach, also in the water of the Dead Sea, etc. 
 (see ante, p. 33). Silver bromide occurs as bromargyrite or green silver, a mineral 
 which forms the chief constituent of some silver ores occurring in Mexico and Brittany. 
 
 Characters. -Bromine is at the ordinary temperature a dark red liquid of a 
 penetrating and unpleasant odour. Hence its name, from jSpoytos, a stink. Bromine 
 in the liquid state has a specific gravity of 2'976 ; at a temperature of 7*3 it 
 solidifies as a grey mass of metallic lustre ; it boils at 63, and is converted 
 into a yellowish-red vapour, having a density of 80 as compared with hydrogen, and 
 relatively to air a specific gravity of 5'54. The tension of bromine at the ordinary 
 temperature is so considerable that, when exposed to the air, it readily volatilises and 
 gives off a red vapour resembling nitrogen peroxide in appearance. On this account 
 bromine requires to be kept in well-stoppered glass bottles, and it is convenient to 
 keep it covered with a layer of sulphuric acid, specific gravity 1-652, which dissolves 
 only mere traces of bromine and prevents volatilisation. Bromine is soluble in water 
 only to the extent of about 3 per cent, by volume, but communicates to it a reddish- 
 yellow colour. This water solution of bromine decolorises in the sunlight, owing to 
 the formation of hydrogen bromide by decomposition of water, oxygon being liberated. 
 ] romine combines with water cooled down to 0, forming a solid reddish-brown 
 hydrate which crystallises in octahedra, and is not decomposed at a temperature of 16 
 to 20. The best solvents for bromine are alcohol, ether, chloroform, aqueous solu- 
 tions of potassium bromide, etc. In its chemical characters bromine closely resembles 
 chlorine, but it has less chemical energy. Bromine does not readily combine with 
 oxygen, but very readily with hydrogen, and the bleaching of organic substances by 
 bromine is attributable to the facility with which it combines with hydrogen. Bromine 
 combines with most metals, forming bromides. Starch paste yields with free bromine 
 an orange-red compound. 
 
 Preparation. Formerly bromine was chiefly obtained from the mother liquor 
 of sea water, which was treated for potassium salts according to a method to be de- 
 scribed further on, By this process, after various salts have been crystallised out, a 
 compound of potassium chloride with magnesium chloride is obtained, in which vari- 
 able quantities of chlorine are replaced by bromine. After the separation of this salt 
 it is redissolved, and the solution evaporated to crystallisation. The greater part of 
 the potassium chloride and magnesium chloride crystallises out, leaving behind a 
 liquor rich in bromine, which is then mixed with manganese peroxide and sulphuric 
 acid, and distilled from large stoneware retorts. 
 
 According to another method, the liquor from which iodine has been previously 
 separated by chlorine is concentrated in leaden jars, chlorine haying been added in smal 
 portions at a time, so long as the violet vapour of iodine is evolved. Tbe^liquo] 
 is then mixed with manganese peroxide and sulphuric acid, and the bromine distilled 
 off; some water also passes over, and retains considerable quantities of bromine in 
 solution. On this account the water is separated from the bromine by rowans of 
 separating funnel or by decantation, treated with potassium carbonate, evaporated, and 
 
178 
 
 BROMINE. 
 
 calcined. The residue contains the whole of the bromine that was dissolved in the 
 water as potassium bromide, and it is distilled with manganese peroxide and sulphuric 
 acid. 
 
 The manufacture cf bromine at Stassfurt was started by Frank, in 1865, at a time 
 when bromine had become very dear. The result was that, in 1866, the price of bro- 
 mine was reduced one-half, in 1867 to one-fifth, and still further during the years 
 1868, 1869, and 1870. The production was at first 3,000 pounds per annum ; it soon 
 rose to 15,000 pounds, and has since then increased considerably. 
 
 The raw material employed by Frank in the preparation of bromine is the mother 
 liquor which remains after separating potassium chloride and the double potassium and 
 magnesium chloride from the solution of raw Stassfurt salt by crystallisation (vide Potas- 
 sium Salts). This liquor contains from 1 to 1-5 per cent, of potassium chloride, 30 to 
 33 per cent, of magnesium chloride, 1 to T5 per cent, of sodium chloride, 1 per cent, 
 calcium chloride, the remainder consisting of water. It also contains about 0'08 or 
 0'15 per cent, of bromine. The amount of bromine varies considerably, and the more 
 recent of the salt deposits, especially those containing tachhydrite, are richer in bro- 
 mine than the others. 
 
 The apparatus used in distilling bromine consists of a stoneware pan, set in brick- 
 work, having a capacity of about 80 to 100 cubic feet. It has essentially the same 
 construction as the chlorine generator, described on page 165, the only difference 
 being that it is heated with steam. For this purpose a leaden steam pipe passes 
 through the lid of the still to the bottom, so as to deliver jets of steam from several 
 
 FIG. 115. 
 
 places. The delivery tube of the still is connected with a condensing worm (BB, fig. 115) 
 of earthenware or lead, surrounded by cold water, and the end of the worm is connected 
 by means of a glass adapter (c) with a three-necked Woulfe's bottle (D) holding about 
 18 pints, and fitted with a safety funnel (m) and a siphon () for drawing off the 
 bromine. A leaden tube (r) connects D with a stone jar (E), filled with moist iron 
 filings. The end of the tube (r) terminates in a wide glass cylinder (f), to prevent 
 stoppage of the narrow leaden tube by the formation of ferrous bromide. The joints 
 are made with a lute of clay and oil bound round w:>,h parchment. 
 
 The apparatus is set going by charging the still with mother liquor, manganese 
 peroxide, and sulphuric acid, or hydrochloric acid, and heating the mixture as quickly 
 as possible to the boiling point by passing steam into the still. 
 
 The escaping vapour condenses in the worm, and passes through the adapter (c) 
 into the Woulfe's bottle (D), where two layers are formed, the lower layer consisting of 
 bromine, the upper one of a solution of bromine in water. The uncondensed vapour, 
 which is very offensive owing to the bromine it contains, passes into (E E), and is 
 there completely absorbed by the moist iron filings. At the beginning of the operation 
 
COMPOUNDS OF BROMINE. 179 
 
 tolerably pure bromine passes over, but towards the end of the distillation the evolu- 
 tion of chlorine increases, as may be seen by the green colour of the vapour in the 
 adapter (c). Directly this is the case the distillation is stopped and the generator 
 emptied. 
 
 Purification. The bromine which collects in the "Woulfe's bottle is contaminated 
 with chlorine, with brominated hydrocarbon compounds not as yet studied, as -well as 
 with lead bromide carried over from the leaden worm and the leaden delivery tube. It 
 is therefore drawn off by means of the siphon and submitted to a process of rectifica- 
 tion. The apparatus for the rectification consists of large tubulated glass retorts, the 
 necks of which are luted into receivers also of glass. The tubulus of each receiver is 
 furnished with a glass tube fitted tightly into it, through which the uncondensed 
 vapour passes for absorption into a Woulfe's bottle filled with potash or caustic soda 
 solution, then into an open pot containing the same absorbent, or moist iron filings 
 may be employed instead of caustic alkali. The retorts are heated in sand baths, 
 consisting of a single casting, and they have double sides between which steam is 
 passed. When the retorts have been arranged as above described, they are charged 
 with crude bromine and heat applied. The first portion of distillate consists of bromine 
 considerably contaminated with chlorine, which is collected separately, mixed with 
 other products of the same nature, and again rectified. If the first portion of distillate 
 happens to be pure bromine chloride, it is treated with water, which causes the de- 
 composition of the compound into bromine and hydrochloric acid. After the first 
 chlorinated portion of distillate has been removed, and pure bromine distils over, the 
 receivers are changed and the pure bromine collected. There remains in the retort, 
 when the distillation is over, a thick dark mass, consisting of various lead salts and 
 brominated hydrocarbon compounds. 
 
 Packing. The bromine is run off from the receivers into glass vessels furnished 
 near the bottom with glass cocks, through which the bromine is run into the bottles 
 for transportation, which hold from 4 to 5 pounds of bromine, and are closed with well- 
 ground glass stoppers, covered with resin, over which is a clay luting secured with 
 parchment paper ; four such bottles being packed in a box with four compartments. 
 
 For the transport of bromine by sea, Frank evaporates a solution of ferrous bro- 
 mide to dryness, and packs the thoroughly dried mass in bottles. When required for 
 use this mass is dissolved in water, and the bromine separated by passing chlorine 
 into the solution. This method avoids the danger of leakage from an ill-fitting 
 stopper or loss by the breaking of bottles. 
 
 The bromine obtained from Stassfurt has the advantage over all other kinds of 
 commercial bromine, that it is entirely free from iodine. 
 
 Uses. Bromine in the form of potassium bromide is used extensively in photography 
 and also in medicine. The use of bromine in the preparation of aniline colours, which 
 at one time seemed likely to be extensive, has nearly ceased. Bromine also enjoys 
 repute as a disinfectant. 
 
 Compounds. Bromine closely resembles chlorine in its chemical relations, and 
 the bromides or compounds it forms with other elementary substances have a 
 general analogy to the corresponding compounds of chlorine in constitution and cha- 
 racters. The hydrogen compound HBr, or hydrobromic acid, is a colourless gas 
 soluble in water ; it is decomposed by chlorine with liberation of bromine and forma- 
 tion of hydrochloric acid. The metallic bromides are in like manner decomposed by 
 chlorine and converted into chlorides with liberation of bromine ; they are also 
 decomposed by hydrochloric acid with formation of chlorides and hydrpbromic acid. 
 Bromine appears to combine with chlorine, forming a substance which is probably a 
 pentachloride, BrCl 5 . 
 
 The oxygen compounds of bromine correspond to hypochlorous oxide and cnl< 
 but they are known only in combination with water or basic oxides. These compounds 
 resemble the corresponding compounds of chlorine, and are formed in the same manner ; 
 thus hypobromites are formed by digesting bromine in cold solutions of the caus 
 alkalies or alkaline earths. B r o m a t e s are formed together with bromides either by 
 boiling a solution of hypobromite or by saturating hot alkaline solutions with bromine, 
 the reaction being precisely similar to that which takes place in the f< 
 chlorates : 
 
 6KHO + 6Br = 5KBr + KBrO, + 3H,0. 
 
 
IODINE. 
 
 SYMBOL I. ATOMIC WEIGHT 127. 
 
 History. This elementary substance was discovered in 1811 by Courtois in 
 varec soda, and it was immediately made the subject of research by Clement and by 
 Gay-Lussac, who was the first to express the opinion that iodine was to be regarded 
 as an element very nearly related to chlorine. Davy also studied iodine, and ascer- 
 tained that when it is acted upon by caustic potash solution, it is oxidised, with 
 formation of potassium iodate. The reaction of iodine with starch, which is recipro- 
 cally one of the most delicate tests for both iodine and starch, was discovered by Colin 
 and G-aultier de Claubry. 
 
 Occurrence. Iodine does not occur naturally in a free state, and in a state of 
 chemical combination it occurs chiefly as potassium iodide and sodium iodide in sea 
 water. The amount of iodine in sea water is, however, relatively so small, that its 
 presence can only be determined with difficulty. It occurs in larger proportion in 
 some kinds of fuci, algae, and other marine plants, which extract iodine from sea water 
 and store it up in their tissues. Iodine has also been found in marine animals, such 
 as sponges, star-fish, and the like. 
 
 Iodine exists, probably in the state of iodides, in the water of most brine springs, 
 but not generally in sufficient amount to admit of its presence being easily ascertained, 
 except in the mother liquor obtained by evaporating large quantities of water. 
 
 Iodine is found in relatively greater amount, also in combination with potassium 
 and sodium, in the water of some mineral springs, as, for instance, in the Adelheid 
 spring in Bavaria, and in the water of Hall, in Austria. Iodine has also been found 
 in a number of minerals, in some Silesian zinc ores, in a silver ore from Mexico, in the 
 phosphorite of Amberg, in turf, and in the coal of Mons, Anzin, Comentry, etc., 
 which is used in gas-making. Chili saltpetre also contains a considerable amount of 
 iodine, which is found in the mother liquor obtained in purifying this salt. 
 
 Characters. Iodine is at the ordinary temperature solid, either presenting the 
 appearance of a compact mass with crystalline fracture or well-defined crystals. It 
 has a metallic appearance, is opaque, and of a greyish black colour. Its specific 
 gravity is 4'950 at 15 ; it melts at 107, forming a black liquid, which boils at 
 180, yielding a beautiful violet coloured vapour, the specific gravity of which is 
 8716, as compared with air and its density 127 times that of hydrogen. The name 
 this element bears is in allusion to this character, being derived from luS-qs. violet- 
 like. 
 
 The tension of iodine at the ordinary temperature is great enough to cause the 
 volatilisation of small quantities of the substance, and its penetrating smell, as well as 
 the corrosion of cork or other organic substances used for securing bottles containing 
 iodine, are due to this fact. At a temperature of from 45 to 50 the evaporation of 
 iodine is so considerable, that the upper part of bottles partly containing iodine are 
 filled with the violet vapour. When water containing iodine in solution is boiled, 
 iodine passes over with the steam in considerable quantities. Dry iodine vapour 
 deposits crystals of ioJine upon cold surfaces. Very good crystals may also be 
 obtained from solutions of iodine in potassium iodide, carbon bisulphide, etc. Iodine 
 precipitated from its alcoholic solution, by the addition of water, is found, when ex- 
 amined under the microscope, to consist of a conglomerate of small crystals. Iodine 
 has an acrid taste, and it acts very energetically upon the animal organism. 
 
 Iodine is but slightly soluble in water, requiring for its solution 5,524 times its 
 weight of water ; -such a solution has a brownish colour. It is easily soluble in 
 aqueous solutions of hydn'odic acid, or potassium iodide, and, generally speaking, 
 iodine is far more soluble in water containing salts than in pure water. The best 
 solvents for iodine are carbon bisulphide, alcohol, ether, ethyl iodide, chloroform, etc. 
 Iodine is not very readily oxidisable, but combines much more readily with hydrogen ; 
 
PREPARATION OF IODINE. 181 
 
 though in this respect it is surpassed by chlorine as well as by bromine. Iodine 
 combines directly and readily with sulphur and phosphorus ; it combines also with 
 the metals to form metallic iodides. It dissolves in solutions of the caustic alkalies, 
 forming iodide as well as iodate of the metal. 
 
 Tests for Iodine. Pure, refined iodine ought to volatilise completely when heated 
 to 180 ; it should dissolve in alcohol without leaving a residue, and the solution 
 ought to be completely docolorised when treated with an excess of caustic soda or 
 potash solution. 
 
 Iodine in an uncombined condition produces an intensely blue colour with starch, 
 and in testing for the presence of iodine it is usual to employ either freshly prepared 
 starch paste, or papers smeared with such paste and dried. If the iodine be in com- 
 bination, this colour does not appear until a drop of some oxidising agent such as 
 chlorine water, fuming nitric acid, or potassium nitrite, has been added to set the 
 iodine free. 
 
 Another way of ascertaining the presence of iodine is by shaking up a liquid 
 containing free iodine with carbon bisulphide, which extracts the iodine and forms a 
 red liquid easily discernible at the bottom of the test tube, after allowing the mixture 
 a short time to settle. 
 
 Commercial iodine is often adulterated with coal, charcoal, or graphite; but these 
 adulterations are easily recognised by treating the iodine with alcohol, in which pure 
 iodine dissolves, while the admixtures remain unacted upon. 
 
 Preparation. Iodine is prepared chiefly from the mother liquors obtained after 
 separating potassium chloride and other salts from the ashes of seaweed, known in this 
 country as kelp, and in France by the name of varec. 
 
 According to Courtois' method, as improved by Wollaston, the alkaline iodides 
 contained in the mother liquor are decomposed by sulphuric acid and manganese 
 peroxide, care being taken that these materials are not added in very great excess, 
 since in such cases chlorine and iodine chloride are formed. The reaction which takes 
 place is represented by the following equation : 
 
 2KI + 2H 2 S0 4 + Mn0 2 = K 2 S0 4 + MnS0 4 + 2H 2 + 21. 
 
 The liquor is first mixed with sulphuric acid in large vessels, in such a way that 
 as little increase of temperature as possible takes place. By this means sulphates of 
 the alkalies are produced, together with hydriodic acid, hydrochloric acid, sulphuretted 
 hydrogen, and carbonic acid, while sulphur is separated in the free state, and is 
 removed with a perforated ladle. Of the 
 acids thus produced, only carbonic and 
 hydrosulphuric acids escape, while hy- 
 driodic and hydrochloric acids remain dis- 
 solved. The mixture is allowed to remain 
 at rest, until it ceases to smell of sulphu- 
 retted hydrogen ; it is then drawn off from 
 the precipitated sulphates, and placed in a 
 still with manganese peroxide. The ar- 
 rangement of the distilling apparatus is 
 represented by fig. 116; it consists of a 
 cylindrical leaden vessel (a) furnished with 
 a head, and placed in communication with 
 a number of glass or stoneware receivers (d). 
 The still is heated over a sand bath, the 
 temperature being gradually increased until 
 violet vapour of iodine is given off, which 
 condenses in the receivers, and is deposited 
 
 there in the form of a crystalline crust. > "" , . , fi 
 
 The stoppered neck (6) in the head of the 
 still serves for introducing the charge, and the smaller aperture (c) for ascertaining 
 the progress of the operation. 
 
 Mr. Paterson, in Glasgow, distils from hemispherical vessels of cast iron 4 feet wide, 
 and furnished with a leaden head. The latter is closed above with a round clay 
 plate, furnished with an opening for admitting the manganese peroxide, and two 
 openings for the escape of the iodine vapours into two rows of receivers. Ine man- 
 ganese peroxide is added in small portions at a time. Five sets of stills of this kind 
 are placed side by side, each being heated by a separate furnace. m 
 
 According to Barruel's method, the iodine is separated by means of chlorine. At 
 Cournerie's works, in Cherbourg, the liquor, saturated exactly with sulphuric acid, is 
 mixed with 10 per cent, of manganese peroxide and evaporated. In this way the 
 
182 
 
 IODINE. 
 
 sulphides and hyposulphites are oxidised to sulphates ; and the residue is heated 
 until iodine vapour appears. The completion of the oxidation may be ascertained by 
 mixing a small quantity of the mass with water in a test tube, and adding sulphuric 
 acid, which does not cause any evolution of sulphuretted hydrogen if the oxidation is 
 complete. The calcined mass prepared as above is then treated with water, and the 
 solution brought to a specific gravity of 1-333. After it has become clear by standing, 
 the clear portion is decanted off, diluted with water to specific gravity 1*197, and 
 accurately saturated with chlorine gas. This causes the decomposition of the alkaline 
 iodides into free iodine and chloride of the metal according to the equation : 
 
 KI + 01 = KC1 + I. 
 
 The chlorine is generated in the apparatus described on page 165, fig. 103. Care 
 must be taken that exactly the right proportion of chlorine is employed ; it ought 
 neither to be insufficient in quantity nor in excess. In the latter case iodic acid and 
 iodine chloride are apt to be formed ; while in the former case the iodine is not all 
 separated, and the undecomposed potassium iodide retains a further quantity of 
 iodine dissolved, so that in either case there is a loss of iodine. In order to ascertain 
 whether the proper quantity of chlorine has been introduced, two portions of the 
 liquor are tested respectively with chlorine water and with solution of potassium 
 iodide. In neither case ought a separation of free iodine to take place. When this 
 point has been attained, the liquor is allowed to settle, so that the iodine may deposit, 
 the supernatant liquor is decanted off, and the residual iodine washed with cold water 
 until nothing more is dissolved. The washed iodine is placed upon a sieve and 
 drained. In order to dry it as far as possible, it is either spread out upon filter paper 
 laid upon dry ashes, or it is laid upon plates of porous earthenware. The iodine is 
 sometimes dried by passing over it a current of air at a temperature of about 25. 
 Frequently, however, it is not dried at all ; and the adherent water is separated from 
 it in the process of sublimation. 
 
 A number of propositions have been made for the separation of iodine from kelp 
 liquor. "Wagner, for instance, suggests distilling the liquor, previously acidulated with 
 sulphuric acid, with ferric chloride, which gives rise to the following reaction : 
 
 2NaI 
 
 Fe. 2 Cl 6 = 21 + 2NaCl + 2FeCl 2 . 
 
 This method has the advantage that no formation of iodine chloride is possible. 
 Luchs recommends treating the liquor with sulphuric acid and potassium chromate. 
 Soubeiran obtained iodine from liquor poor in that substance by precipitation as 
 cuprous iodide, by adding ferrous sulphate and cupric sulphate, and then decomposing 
 the cuprous iodide with manganese peroxide and sulphuric acid to liberate the iodine. 
 Theroulde separates the iodine by means of nitrous acid. An analogous process is 
 that of Lauroy, in which the nitrous acid is converted into nitrogen peroxide by mixing 
 it with air before passing it into the liquor. 
 
 Sublimation of Iodine. Before iodine is sent into the market, it is refined by 
 sublimation, in order to free it from adherent moisture. The apparatus commonly 
 
 used is shown in fig. 117. It consists 
 of six stoneware retorts (A A), resting 
 upon a sand bath (B B), and surrounded 
 entirely by sand. The necks of the 
 retorts pass through the side of the 
 sand bath, and the ends of them fit accu- 
 rately into large stoneware receivers 
 (D D). The necks of the retorts must 
 be as short as possible, to avoid the 
 deposition of iodine within them. The 
 receivers are furnished with a tubulus 
 (/), into which is fitted a tube (g\ for 
 the escape of air. Each receiver has 
 a lid (e) above, for the removal of the 
 iodine ; and near the bottom is a per- 
 forated plate for the escape of condensed 
 water. The entire number of retorts are 
 heated by the fire (c). Each retort is 
 
 F. 117. 
 
 charged with about 40 pounds of iodine, and is heated so long as iodine vapour escapes 
 into the receivers. The iodine deposits in the receivers in crystalline laminae. In 
 Cournerie's iodine works the retorts are heated in a solution of salt instead of the 
 Band bath. 
 
 EXTRACTION OF IODINE FROM CHILI SALTPETRE. The mother liquor obtained in 
 
IODINE COMPOUNDS. 183 
 
 refining Chili saltpetre is so rich in iodine that it is now usual to treat it for iodine. 
 At Tarapaca, in Peru, the liquors containing iodine were formerly treated with sul- 
 phuric acid, by which iodic acid is reduced ; but this method gives rise to a number of 
 inconvenient by-products, such as sodium sulphate, which renders the saltpetre impure, 
 and hygroscopic substances which adhere to the iodine. Thiercelin has therefore 
 introduced a new method of reducing the iodic acid by means of nitrous acid, obtained 
 by heating to redness a mixture of 1 part charcoal and 5 parts of saltpetre, in a 
 manner similar to that adopted in the preparation of sodium carbonate. The iodine 
 is thus precipitated in a form which admits of its being easily washed and dried, and 
 the precipitate contains about 80 per cent, of iodine. 
 
 if'or the determination of the value of commercial iodine Hesse's method is the 
 best. For this purpose a solution of ammonium sulphite is made by saturating a 4 
 per cent, solution of ammonia with sulphurous acid. A weighed quantity of iodine 
 is dissolved in this ammonium sulphite solution, and thus converted into hydriodic 
 acid : 
 
 2NH 4 ,S0 3 + H.,0 + 21 = 2NH<,S0 4 + 2HI 
 116 18 254 132 256 
 
 The hydriodic acid is decomposed with silver nitrate, the precipitated silver iodide 
 filtered off, washed with water, dried and weighed. The amount of iodine is es- 
 timated from the weight of the silver iodide. When chlorine is present, silver 
 chloride is also precipitated, and hence the quantity of iodine found would be in excess 
 of the real amount. In order to remove this source of error, the precipitated silver 
 iodide, before being dried and weighed, is treated with concentrated aqueous ammonia, 
 which dissolves silver chloride, leaving the silver iodide intact. The silver chloride 
 held in solution by ammonia is then precipitated by adding nitric acid, its weight 
 determined, and from the latter the amount of chlorine and iodine chloride calculated. 
 By subtracting the amount of iodine which was present in the form of iodine chloride 
 from the total amount of iodine found, the weight of free iodine present is obtained. 
 
 Use. Iodine is used in considerable quantity in medicine; and in making a 
 number of pharmaceutical preparations, such as potassium iodide, raercurous iodide, and 
 mercuric iodide, etc. Mercuric iodide is further used as a red pigment. However, 
 the greatest consumption of iodine is in photography, in the form of potassium iodide. 
 Iodine is also used for producing certain aniline dyes. It is finally a very important 
 and necessary substance in many chemical analyses and other operations of the 
 laboratory. 
 
 Compounds. Iodine resembles chlorine and bromine in its chemical relations 
 and compounds. The hydrogen compound HI, or hydriodic acid, is a colourless 
 gas soluble in water ; it is decomposed by chlorine and by bromine with formation of 
 hydrochloric or hydrobromic acid and liberation of iodine. The iodides are decom- 
 posed in the same way, and by hydrochloric or hydrobromic acid, with formation of 
 hydriodic acid and chlorides or bromides. Some of the metallic iodides are remarkable 
 for their brilliant colours, but in most other respects they have a general analogy with 
 the chlorides and bromides. 
 
 Iodine combines with chlorine in two proportions, forming a monochloride Id, 
 and a terchloride ICL, ; it also forms with bromine a monobromide IBr, and another 
 compound, probably IBr 5 . 
 
 The oxygen compounds of iodine that are known are iodic oxide I 2 5 and I 2 7 , both 
 of which combine with water and basic oxides, forming saline compounds, respectively 
 termed iodates and periodates, the hydrogen salts being iodic acid HI0 3 , and 
 periodic acid HI0 4 . The iodates correspond generally with the chlorates and 
 bromates, aod are formed in the same manner. The periodates correspond with per- 
 chlorates. 
 
FLUORINE. 
 
 SYMBOL F. ATOMIC WEIGHT 19. 
 
 History. The analogy between hydrochloric acid and the acid obtained by de- 
 composing fluorspar with sulphuric acid was first suggested in 1810 by Ampere, who, 
 on this ground, assumed the existence of an elementary substance similar to chlorine, 
 and regarded the acid obtained from fluorspar as being a hydrogen compound. This 
 view was more fully established by Sir H. Davy, J. Davy, and Berzelius, between 1812 
 and 1823. 
 
 The name fluorine was applied to this substance as indicative of its being a con- 
 stituent of fluor spar, so called from the Latin word fluo, on account of its efficacy as 
 a flux in promoting the fusion of certain minerals, etc. 
 
 Occurrence. Fluorine occurs only in a state of combination, chiefly with calcium 
 as f 1 u o r s p a r ; also combined with aluminum and sodium as c r y o 1 i t e, with aluminum 
 and silicon in topaz, and with cerium and yttrium in fluocerite and yttrocerite. 
 In smaller amounts fluorine occurs as calcium fluoride in apatite, and in other forms 
 of combination in wavellite, wagnerite, and a number of other minerals. Bones 
 both fossil and recent contain traces of fluorine, and in very minute proportions it 
 occurs in the water of some mineral springs and rivers, as well as in certain plants. 
 
 Characters. Although the probability that this constituent of the mineral known 
 as fluor spar is an elementary substance is now tolerably beyond question, and 
 though its analogy in this respect with chlorine, bromine, and iodine has been for some 
 time established by the study of its various compounds by Davy and Berzelius, little 
 is yet known of the characters of fluorine in a free state ; for, on account of its powerful 
 action upon almost all materials ordinarily used for constructing chemical apparatus, 
 it is doubtful whether fluorine has ever been isolated, and certainly it has never been 
 obtained in such a condition that its characters could be determined. 
 
 Compounds. The substances consisting of fluorine in combination with some 
 other elementary substance are termed fluorides, and are analogous in constitution to 
 the chlorides, bromides and iodides. Most of these salts are solid substances, and are 
 not decomposed when heated in a dry state ; but many of the fluorides containing 
 metals are readily fusible and some of them are volatile ; the hydrogen compound HF, 
 known as hydro fluoric acid, is gaseous; the compounds of fluorine with silicon 
 SiF 4 and with boron BF 3 are also gaseous. 
 
 The alkaline fluorides are soluble in water and crystallisable ; those of the earthy 
 metals are almost insoluble ; but several of the metallic fluorides, for instance, the tin 
 and silver salts, are readily soluble in water, and hydrofluoric acid dissolves in about 
 twice its weight of water. 
 
 Many of the fluorides combine together, forming definite crystallisable double salts ; 
 thus potassium fluoride combines with hydrofluoric acid, forming a crystallisable salt 
 the composition of which is KF,HF. This capability is very characteristic of the 
 fluorides, and a number of similar salts are known, among which the sodium- 
 aluminum fluoride, 3NaF,AlF 3 , occurs naturally as cryolite. 
 
 Silicon fluoride combines with hydrofluoric acid or with metallic fluorides, forming 
 compounds called fluosilicatesor silicofluorides ; the composition of the hydrogou 
 compound, fluosilicic acid, is represented by the formula II 2 SiF 6 . The same sub- 
 stance is formed, together with silica, when silicon fluoride is decomposed by water, as 
 shown by the following equation : 
 
 3SiF 4 + 2H 2 = Si0 2 + 2H 2 SiF 6 . 
 
 Potassium fluoride also combines with silicon fluoride, forming potassium fluosilicate, 
 a salt corresponding to the hydrogen compound fluosilicic acid, and represented by the 
 formula 2KF,SiF 4 , or K 2 SiF 6 . These compounds correspond to ordinary silicates, six 
 
HYDROFLUORIC ACID. 185 
 
 atomic proportions of the monovalent element fluorine taking the place of three atomic 
 proportions of the divalent element oxygen. 
 
 Similar compounds are formed, together with water, when silica or silicates are 
 acted upon by hydrofluoric acid ; thus calcium silicate yields 
 
 CaSi0 3 + 6HF = CaSiF 6 + 3H 2 0. 
 
 The fluosilicates are mostly soluble in water, but the potassium and barium salts 
 are very sparingly soluble. 
 
 Boron fluoride BF 3 , stannic fluoride SnF 4 , and titanic fluoride TiF 4 , form with 
 hydrofluoric acid and with the metallic fluorides similar compounds, which are 
 called borofluorides or fluoborates, fluostannates, and fluotitanates, 
 salts corresponding to borates, stannates, and titanates in the same manner that the 
 fluosilicates are related to silicates, by containing fluorine in the place of oxygen. 
 
 HYDROFLUORIC ACID. 
 
 FORMULA HF. MOLECULAR WEIGHT 20. 
 
 History. The corrosive action exercised upon glass by a mixture of fluor spar 
 and sulphuric acid was known as long since as 1670, and it was probably turned to 
 practical account for etching glass in 1725 ; but nothing definite was then known of 
 the substance to which this effect was due ; and though Scheele suggested that it was a 
 peculiar acid existing in fluor spar in combination with lime, the corrosion of the vessels 
 used in preparing the acid prevented its true character from being recognised, until 
 Ampere suggested that the constitution of this acid was analogous to that of hydro- 
 chloric acid, and this view was soon afterwards confirmed by Davy and Berzelius. 
 
 Characters. Hydrofluoric acid is a colourless gas which forms dense irritating 
 fumes in contact with moist air, and is copiously absorbed by water. It condenses at 
 28 to a thin liquid, having a specific gravity of -988, and boiling at 19-4. When 
 quite dry it does not act upon glass or upon most metals ; but when moist it reacts 
 violently with potassium or sodium ; mixed with water, it evolves great heat and forms 
 a solution which has a specific gravity of 1-06 and is very caustic, producing painful 
 ulcers on the skin. It dissolves metals, forming fluorides, with evolution of hydrogen ; 
 it also dissolves silicon, forming silicon fluoride 
 SiF 4 , which combines with another portion of 
 the hydrofluoric acid, forming fluosilicic acid 
 H 2 SiF 6 . Silica and silicates are also readily 
 dissolved by hydrofluoric acid, forming silicon 
 fluoride, metallic fluorides, and water. 
 
 Preparation. Hydrofluoric acid is prepared 
 by gently heating a mixture of fluor spar and con- 
 centrated sulphuric acid. The reaction taking 
 place is represented by the following equation : 
 
 CaF 2 + H 2 SO 4 = CaS0 4 + 2HF. 
 
 A strong solution of the acid is now prepared FIG. 118. 
 
 for etching glass by distilling a mixture of 
 
 powdered fluor spar with twice its weight of concentrated sulphuric acid, in a leaden 
 retort constructed in the manner represented by fig. 118. The acid is condensed in the 
 leaden tube fitted to the beak of the retort and surrounded by a freezing mixture. 
 
 Uses Hydrofluoric acid is used for etching glass, and as a solvent in the analysis 
 
 of silicates. 
 
 In both cases the gaseous acid is often used, and the substance to be acted upon is 
 suspended in an atmosphere of the gas generated from a mixture of fluor spar and 
 sulphuric acid, in a suitable leaden chamber ; when silicates are decomposed m thjs 
 way for analysis, platinum vessels must be used. 
 
 In etching glass it is first coated with a thin layer of wax, and the design traced i 
 the wax so as to expose the glass where the action of the acid is required. 
 
BORON. 
 
 SYMBOL B. ATOMIC WEIGHT 11 
 
 History. This elementary substance was isolated by G-ay-Lussac and Thenard in 
 1808 and almost at the same time by Davy. 
 
 Occurrence. Boron does not occur naturally in the free state, but only in com- 
 bination with oxygen and hydrogen as sassoliri, or with oxygen and various basic 
 oxides in the form of borates, as in tincal, boracite, hydroboracite, and 
 datolite; in smaller amount it also occurs in tourmaline and some other minerals. 
 
 Characters. Boron is a solid substance capable of assuming two distinct modifica- 
 tions amorphous and crystalline. In the amorphous state it is a dark greenish 
 brown powder, destitute of taste or smell ; it is very slightly soluble in water, to which 
 it gives a slight colour, and it stains the skin brown. At the ordinary temperature it 
 does not oxidise by exposure to atmospheric air ; when heated it does not melt or 
 sublime, but at about 300 it takes fire when in contact with air and burns with a 
 reddish light, forming boric oxide B 2 S . 
 
 Crystalline boron presents the form of octahedrons of a yellow or reddish colour 
 with considerable lustre, hardness, and refractive power; the specific gravity is 2'63. 
 In this state boron is oxidised only at a very high temperature, and is not acted upon 
 by acids or solutions of caustic alkalies, but in the amorphous condition boron is 
 oxidised by nitric acid or sulphuric acid. 
 
 Compounds. Borou is a trivalent element, and its compounds with fluorine, 
 chlorine, bromine, oxygen, and sulphur have the formulae BF 3 , BC1 3 , BBr 3 , B 2 3 , B 2 S 3 . 
 The most important compounds of boron are the oxide B 2 3 , and the saline substances 
 it forms with basic oxides, which are known as borates, the compound with water 
 B 2 3 3H 2 0, or the hydrogen salt H 3 B0 3 , being termed boracic acid. 
 
 The borates corresponding in composition to boracic acid, and containing three 
 atomic proportions of a monovalent element or corresponding proportions of polyvalent 
 elements, to one atomic proportion of boron, are probably the normal or neutral salts ; 
 but many of the borates contain larger proportions of boric oxide, thus ordinary sodium 
 borate in the anhydrous state contains two molecules of boric oxide combined with one 
 molecule of soda, and is represented by the formula Na 2 0,2B 2 3 . 
 
 The borates containing boric oxide and oxides of monovalent or divalent metals in 
 equal molecular proportions are termed metaborates, and they are often represented 
 according to the formula MB0 2 ; thus the salt obtained by melting together sodium 
 carbonate and boric oxide in molecular proportions has in the anhydrous state a com- 
 position corresponding to the formula Na 2 0,B 2 3 = 2NaB0 2 ; in the hydrated state 
 this salt contains four molecules of water, and may be represented by the formula 
 
 NaB0 2 + 4H 2 0, or as J ^ I B0 8 + 3H 2 0. Borates containing excess of boric oxide 
 
 may be represented as compounds of a metaborate with boric oxide, and according to 
 this view ordinary sodium borate would be 2NaB0 2 -*- B 2 3 . 
 
 Boric oxide is formed when boron is burnt in oxygen gas, or when the hydrated 
 oitide, boracic acid, is heated to redness and its water separated. The melted boric 
 oxide solidifies on cooling to a brittle glassy mass, which has a slight bitter taste, 
 and dissolves slowly in water, forming boracic acid by combination with a portion of the 
 water ; it also dissolves in alcohol, and renders the flame of the alcohol green. Boric 
 oxide does not sensibly volatilise when heated ; melted with basic oxides, it unites with 
 them, forming borates; and at a high temperature it displaces other acid oxides from a 
 great number of salts, combining with the basic oxides to form borates. 
 
 Boric oxide occurs in a number of minerals in the form of borates: as boracite 
 (magnesium borate and magnesium chloride), as boronatrocalcite (sodium borate 
 with calcium borate), as hydroboracite (calcium and magnesium borate), as 
 lagonite (iron borate), as larderellite (ammonium borate). 
 
 Many of the compounds of boric oxide with basic oxides are but sparingly soluble 
 in water, but the alkaline borates dissolve readily in water, and though they are acid 
 
BORACIC ACID. 187 
 
 salts, the solutions colour litmus wine-red or even blue when they are dilute. The 
 most important of the borates is the acid sodium salt Na202B 2 3 + 10H 2 0, which 
 occurs naturally in the water of certain lakes in Persia, India, and other parts of Asia, 
 and is known under the name of tinea 1 and magnesium borate orboracite. 
 
 BORACZC ACID. 
 
 FORMULA H S B0 3 . MOLBCTJLAB WEIGHT 62. 
 
 History. The first mention of boracic acid is by Becher in 1674, who described 
 it as a ' volatile salt ' obtained by heating together oil of vitriol and borax. The 
 preparation of this substance was first described with accuracy in 1702 by Homberg. 
 Stahl and Lemery gave new methods of preparing boracic acid, and its composition 
 was determined by Gay-Lussac, Thenard, Davy, and Berzelius. 
 
 Formerly the only source of boracic acid known was the tincal coming from Asia ; 
 but in 1777 Hofer found it in the lagoons of Monte Rotondo in Tuscany, and in 1788 
 Westrumb determined its presence in bora cite. Boracic acid was not employed 
 industrially until 1776. 
 
 Occurrence. Boracic acid occurs naturally as sassolin in volcanic districts 
 together with sulphur. In the Lipari Islands and some parts of Tuscany, large quan- 
 tities of boracic acid are brought up to the surface of the earth, together with steam. 
 These vapour springs, called suffioni or fumaroles, form marshes and lakes, and 
 the boracic acid is held in solution by the condensed water. 
 
 The formation of boracic acid in the interior of the earth has been the subject of 
 much speculation. Dumas ascribes it to the action of *ea water upon boron sulphide, 
 sulphuretted hydrogen being formed at the same time. Bolley supposes it to be 
 produced by the action of ammonium chloride vapour upon borates ; E. Wagner and 
 Warington suggest that boracic acid may be formed together with ammonia by the 
 decomposition of boron nitride by water. Bischof considers that boracic acid is 
 liberated in the interior of the earth by the action of superheated steam upon minerals 
 containing the acid, especially turmalin. 
 
 The fumarole vapour contains, according to Pay en, finely divided solid substances 
 mechanically suspended, such as calcium, magnesium, ammonium and iron sulphates, 
 manganous sulphate, alumina, hydrochloric acid, organic substances, clay, sand, a 
 small quantity of boracic acid, and a peculiar volatile oil. The gaseous constituents 
 vary, as may be seen from the following table : 
 
 I. II. III. 
 
 Sulphuretted hydrogen .... 4'1 37? gc.j 
 
 Carbonic acid . . . *: . 91'6 907} 
 
 Oxygen % . . , 0' 0' 27 
 
 Nitrogen and combustible gases . . 4'3 5*6 12'2 
 
 ioo~ 100 100 
 
 The unabsorbable gas consists, according to Payen, of 
 
 Nitrogen . . v . - . , ;.;;-< '-.. JJ'JJ 
 Hydrogen . .. . ..'.-.., . .. 28'56 
 Marsh gas ,> v . . . ;, ' '/ 28 { 
 
 100 
 
 Leblanc and Deville found the fumarole vapour to contain 93'6 per cent, 
 carbonic acid and 6-4 per cent, sulphuretted hydrogen. 
 
 Characters The boracic acid of commerce forms white scaly, shining crystals, 
 
 which on heating give up the entire amount of water contained in them, melting to a 
 transparent mass, which solidifies on cooling to a colourless glass. -Boracic acid is 
 not very soluble in water, requiring for its solution 25'6 parts of water at Id , D 
 only 2-9 parts at 100. It is also soluble in alcohol and wood spirit and these solu- 
 tions burn with a green flame when ignited. The aqueous solution of boracic 
 only a very slight acid taste ; it colours blue litmus paper purple, and turmeric paper 
 reddish BwnT Although aqueous boracic acid is but a weak acid, boric ^hydnde 
 expels at a red heat nearly all other acids, even the strongest, from their. ^P? 
 Upon distilling an aqueous solution of boracic acid, considerable quantities c 
 acid pass over with the steam. 
 
188 
 
 BORON. 
 
 Preparation. Most of the boracic acid of commerce is obtained from the suffioni 
 or fumaroles of Tuscany. 
 
 To obtain the boracic acid the suffioni are surrounded with basins of rough 
 masonry, called lagoons, several of which are arranged in steps one above the other 
 (A, B, c, D, B, F, G, H,figs. 119 and 120). The contents of the first basin pass through the 
 tubes (a, b, c) into the basin next below it, and from thence into a still lower one, etc. 
 
 
 FIG. 119. 
 
 Fresh water Irom a neighbouring spring is conducted into the uppermost basin, while 
 gases and vapours from the fumaroles rise through this water from beneath, their 
 action being often violent enough to cause the ejection of the water contained in the 
 basins to a height of several feet. After the lapse of 24 hours the liquor in the first 
 basin is generally muddy and is then conducted through b into the second basin (c B), 
 the first basin being recharged with fresh water. After another lapse of 24 hours the 
 contents of the second basin (c D) are passed into the third basin (E F), the contents of 
 the first into the second, and so on, until the liquid has passed through four or five 
 basins. From the last lagoon (G H, fig. 120) the solution passes into the three rectangular 
 reservoirs (i J K, figs. 120 and 121), where it deposits solid earthy constituents. It is then 
 decanted and brought into the evaporating pans (L, M,N, o, p, Q, fig. 120), which are 
 placed in couples, one above the other. These pans are heated by the gases and vapours 
 of fumaroles that on account of their situation admit of no other utilisation. For this 
 purpose such fumaroles are enclosed with woodwork, and their vapours conducted in 
 brick flues under the evaporating pans. The condensed water collects at the bottom 
 of the flue, and the uncoudensed gas and vapour escape from beneath the upper- 
 most pan into the air. The evaporating pans are square, about a foot deep and 9 feet 
 square ; they are supported on wooden beams. The solution decanted from the last 
 reservoir (K.) is distributed in the first eight pans (L L, M M, N N, o o) and heated for 24 
 hours. When the solution has attained a density of T017 it is again decanted into 
 the pans(p P, QQ) in which it remains another 24 hours, and is concentrated to 1-034, 
 and is then finally evaporated in the last four pans to a sp. gr. of 1'070. The tempera- 
 ture of the solution gradually increases on its passage, being in the first pans 
 about 60-71 C., in the following pans about 75 C., and in the last pans the tempera- 
 ture is as high as 80 C. In all these pans a precipitation of gypsum takes place, 
 which requires to be removed from time to time. The solution contained in the last 
 four pans having a sp. gr. of 1*070, is run through the funnels (R B, figs. 120 and 121) 
 into the crystallising vats (s s, figs. 120, 121 and 122) consisting of wooden tubs lined with 
 lead. The crystallisation is complete at the end of 24 hours ; the mother liquor is then 
 
 FIG. 122. 
 
 FIG. 123. 
 
 decanted off and distributed through the four evaporating pans (p p, Q Q) a few hours oe- 
 fore the termination of a concentrating operation. The crystals are drained in the baskets 
 
BORACIC ACID. 
 
 189 
 
 (j j, fig. 122), and after 24 hours they are spread out upon the bottom of a large dry- 
 ing oven (c c, fig. 123). The heating of this oven is likewise effected by the vapour from 
 the fumaroles, which is led under the bottom of the oven in the direction from A to B 
 The layer of boracic acid, generally about two or three inches thick, is stirred at 
 intervals, so as to assist the drying, which is complete at the end of 24 hours. An 
 apparatus of the above kind yields at each operation about 200 Ibs. of boracic acid. 
 
 At the present time there are ten boracic acid works in operation, viz. at Monte 
 Cerboh, Larderello, San Fedengo, Castel Nuovo, Sarro, Monte Kotondo, Lustignano 
 Serranzano, Lago and San Eduardo. Each of these works has from 8 to 35 lagoons, 
 1 00 to 200 feet in diameter. 
 
 It may be mentioned here that the water of the large lake of Monte Kotondo, 
 which has a surface area of 18* acres, has recently been worked for boracic acid. 
 The water of this lake contained originally 1 part in 2000 of boracic acid, but has 
 been concentrated to 2 parts in 1000 by digging a ditch round the lake so as to keep off 
 the rain and surface water. 
 
 Of late artificial suffioni have been formed by boring a kind of artesian well and 
 surrounding it with a lagoon. According to Durval, artificial suffioni have been 
 bored to a depth of 160 to 200 feet in the vicinity of Monte Kotondo, and thus yield 
 an annual supply of over 200 tons of boracic acid. 
 
 FIG. 121. 
 
 A more modern and improved evaporating apparatus is represented in fjg.^124. After 
 the solution in the reservoirs (A B) has deposited all the suspended mud, it is decanted 
 into a pan (c) and thence run into a slightly inclined trough made of a sheet of lead 6 
 feet wide and 130 to 150 feet long, with the edges turned upwards- This trough has 
 an undulatory form; it rests upon wooden sleepers, and is heated by the fumarole 
 vapour. The solution of boracic acid in passing over this heated surface becomes so 
 
 FIG. 124. 
 
 concentrated that it is ready for crystallising as it runs off at the other end. It is 
 collected for this purpose in a vessel (F), and treated in the way above describe d 
 The fumarole vapour passes first of all under the reservoir (F), thence under the lowest 
 part of the inclined leaden trough, and ascends under the evaporating ] 
 
 The preparation of boracic acid from boracite was at one time attempt* 
 Stassfurt, but has been given up. The boracite occurring at Stassfurt is joW direct 
 the potteries. 
 
190 BORON. 
 
 Purification. The boracic acid obtained in the above manner from fumaroles is 
 not pure. The follo\ring analysis by Payen shows the varying composition of raw 
 boracic acid : 
 
 Crystallised boracic acid .... 74-0084-00 per cent. 
 = 41-5 47 anhydrous oxide. 
 
 Hygroscopical water 7 '00 5' 75 
 
 Ammonium sulphate and magnesium sulphate 14-00 8'00 
 Calcium sulphate, clay, sand, sulphur . . 2-40 1-25 
 
 Organic substance, volatile oil . ~\ 
 
 Ferrous chloride, ammonium chloride > 2-60 I'OO 
 
 Hydrochloric acid 
 
 100-00 100-00 
 The following table gives 'the results of two analyses by H. Vohl : 
 
 Crystallised boracic acid . . 80*0912 86-1924 
 
 Hygroscopic water 
 
 Sulphuric acid .... 
 
 Silica 
 
 Sand . 
 
 Zinc oxide . 
 Manganous oxide 
 Alumina 
 Lime . 
 
 4-5019 1-5240 
 
 9-6135 7-8161 
 
 0-8121 0-6861 
 
 0-2991 0-4154 
 
 0-1266 0-0431 
 
 0-0031 traces 
 
 0-5786 0-1736 
 
 0-0109 traces 
 
 Magnesia 0*6080 traces 
 
 Potash 0-1801 0-4134 
 
 Ammonia 2-9891 3-0899 
 
 Soda 7-0029 traces 
 
 Ammonium chloride 0'1012 0*0321 
 
 Organic substance, and loss . . . 0'0918 0-0449 
 
 An advantage would be gained by submitting the raw boracic acid to a process of 
 purification on the spot, inasmuch as a marketable product of constant composition 
 would then be obtained, and the removal of the impurities, amounting to about 2 1 per 
 cent., would lessen the cost of carriage. Payen proposed the following method of 
 purification. The liquor before being admitted into the crystallising vessel is very 
 carefully decanted, in order to remove sand and clay, and the crystals obtained from 
 the clear decanted liquid are submitted to a methodical washing. The wash water is col- 
 lected, and the boracic acid obtained from it is treated in other purifying operatiors. 
 The mother liquor might also be distilled with caustic lime, and the ammonia set free 
 collected in sulphuric acid of specific gravity 1-550. Besides this, Payen recommends 
 drying the purified acid at a temperature of 100, until it has given off one half of 
 its water of crystallisation. Since 100 pounds of acid purified and dried as above 
 correspond to 150 pounds of raw acid, the adoption of this plan on the spot would no 
 doubt well repay the labour involved in carrying it out. 
 
 Clouet proposes mixing the crude boracic acid with 4 per cent, of nitric acid, 
 the mixture being allowed to stand a short time, and then heated in a stove. Organic 
 substances are thus destroyed, and ammonia salts volatilised. 
 
 Boracic acid is generally purified by recrystallising it, and in some cases solutions 
 of the acid are treated with animal charcoal. 
 
 Uses. The chief use of boracic acid is in the preparation of borax. It is also 
 used for glazing porcelain ; a solution of 1 part of boracic acid in 100 parts of wate: 
 is used for soaking the wicks of stearine candles. Boracic acid is also used for etching- 
 iron and steel, for preparing flint glass, certain chrome greens, pigments, etc. It ha;; 
 been also proposed to use boracic acid for the preparation of nitric acid from Chili salt- 
 petre, so as to obtain borax as a by-product. Boracic acid is also used as a laboratory 
 reagent. 
 
SILICON. 
 
 SYMBOL Si. ATOMIC WEIGHT 28. 
 
 History. This elementary substance was first isolated by Berzelius in 1823, but 
 its probable existence as a constituent of silica had been suggested by Lavoisier some 
 years previously, and it had actually been obtained in an impure state by Davy and 
 Berzelius. 
 
 Occurrence. Silicon occurs only in the state of combination with oxygen as 
 silica, in a variety of forms, such as quartz, flint, chalcedony, opal, sandstone 
 and sand, also combined with various basic oxides as silicates, constituting a great 
 variety of minerals, rocks, etc. Next to oxygen it is probably the most abundant of all 
 the elementary substances. 
 
 Characters. Silicon is a solid substance capable of assuming three conditions , 
 in the amorphous form it is a dense brownish powder insoluble in water, nitric acid, 
 or hydrochloric acid, but readily dissolved by hydrofluoric acid and solution of caustic 
 alkalies. When heated out of contact with atmospheric air, it melts at a very high 
 temperature, and when heated in the air it burns and is converted into silica. In the 
 graphitic state silicon has the form of hexagonal crystals, and a density of 2-49 ; it con- 
 ducts electricity and is not dissolved by acids, but is slowly dissolved by solution of 
 caustic alkali. Silicon also crystallises and assumes the form of hexagonal prisms of 
 a dark steel-grey colour. 
 
 Compounds. Silicon is tetravalent, and in its chemical relations presents con- 
 siderable analogy to carbon. It combines with hydrogen, fluorine, chlorine, bromine, 
 sulphur, and oxygen, forming compounds represented by the formulae SiH 4 , SiF 4 , SiCl 4 , 
 SiBr 4 , SiS 2 , Si0 2 ; it also combines with several metals, forming silicides, but 
 these substances are little known, and they do not generally possess any industrial 
 interest. There is but one oxide known, which has a composition represented by 
 the formula Si0 2 , and is called silicic oxide or silica; it combines with basic 
 oxides, forming a numerous class of saline substances called silicates, which fre- 
 quently contain excess of silica, as well as two or more metals or basic oxides, and 
 many of them ave double salts. Consequently the composition of the silicates is often 
 very complex, and therefore it is convenient to represent these substances as com- 
 pounds of silica with basic oxides, rather than by formulae like those by which many 
 other saline substances are represented. The composition of neutral silicates contain- 
 ing respectively monovalent, divalent, and trivalent metals is represented, according 
 to both methods, by the following formulae : 
 
 M' 4 Si0 4 = 2M'. 0, Si0 2 
 
 M" 2 Si0 4 = 2M"~ 0, Si0 2 
 
 M"' 4 3Si0 4 2M'" 2 3 ,3Si0 2 
 
 A great number of silicates occur naturally in great abundance as minerals, such 
 as felspar, hornblende, augite, etc. : many of the products obtained in smelting 
 operations and known as slag, as well as the various kinds of glass and pottery ware, 
 also consist of silicates, and the characters of hydraulic mortar and cements are due to 
 substances of this nature. 
 
 Silicic oxide combines with water, forming several hydrates, none of which, how- 
 ever, have a composition corresponding to the neutral silicates ; they are readily 
 decomposed into anhydrous oxide and water, and may be regarded as consisting of 
 neutral hydrogen silicate, H 4 Si0 4 , or silicic acid combined with excess of silica. 
 The gelatinous precipitate formed on adding hydrochloric acid to a solution of alkaline 
 silicate consists of hydrated silicic oxide, which is insoluble, or only very sparingly 
 soluble in water or in acids. A soluble hydrate is obtained by adding a dilute solu- 
 tion of alkaline silicate to a large excess cf hydrochloric acid, and separating the 
 alkaline chloride from the liqujd by dialysis ; a solution may be thus obtained con- 
 taining about five per cent, of silica, and by carefully evaporating the water it maybe 
 concentrated till the amount ofWica in solution becomes as much as 1 1 per cent. 
 
192 SILICON. 
 
 The silicates of the alkaline metals are generally soluble in water, but the other 
 silicates are either quite insoluble or only very sparingly soluble in water. Many of 
 the silicates insoluble in water are decomposed by hydrochloric acid or sulphuric acid, 
 and the silica is either dissolved wholly or partially, or it is separated as a gelatinous 
 mass or in a pulverulent state. In any case, however, the silica thus separated becomes 
 insoluble when the liquid containing excess of acid is evaporated to dryness. Some 
 silicates resist the action of all acids but hydrofluoric acid, which decomposes all 
 silicates, converting both the silica and the basic oxides into fluorides. 
 
 Most silicates melt when sufficiently heated, and assume a peculiar structure which 
 is termed vitreous, but some silicates require a very high temperature for their 
 fusion. Those silicates are most fusible which contain the most fusible basic oxides 
 and the largest proportion of basic oxide ; hence silicates that are but difficultly fusible 
 may be easily melted when mixed with alkalies, or some readily fusible basic oxide, 
 such as litharge, in sufficient proportion to form fusible silicates. The fusibility of a 
 mixture of silicates is generally greater than the mean fusibility of the several silicates 
 in the mixture, and frequently such a mixture melts at a lower temperature than the 
 most fusible of the silicates present would require by itself. On account of this fact 
 it is of great importance that, in metallurgical operations, the addition of the materials 
 used as fluxes in smelting ores should be regulated so as to produce slag of suitable 
 character in regard to fusibility. 
 
 Potassium silicates and sodium silicates are very similar in their general 
 characters. They are colourless and, in the vitreous condition, transparent. The 
 compounds K 2 0,Si0 2 and Na 2 0,Si0 2 are easily fusible, and they are soluble in water, 
 forming an alkaline solution known as liquor silicum. The silicates containing four 
 molecules of silica and one molecule of potash or soda, K 2 0,4Si0 2 and Na 2 0,4Si0 2 , 
 are also soluble in water, and constitute the materials known as water glass. 
 Alkaline silicates containing larger amounts of silica are proportionately less fusible 
 and less soluble in water. As a rule the sodium silicates are more fusible than the 
 corresponding potassium silicates, and in the vitreous condition they have greater 
 brilliancy. The alkaline silicates, when melted in contact with other silicates, readily 
 unite with them in almost any proportions, forming double silicates, the fusibility, 
 colour, and other characters of which vary according to the nature and relative pro- 
 portions of the basic oxides they contain. The different kinds of glass, enamel, etc., 
 consist of double silicates containing alkaline silicates in considerable amount. The 
 alkaline silicates do not occur naturally, except in combination with other silicates, as 
 double salts, such as felspar, mica, etc. 
 
 Calcium silicates are far less fusible than the alkaline silicates; the most 
 fusible compound, represented by the formula CaO,Si0 2 , requiring a very high 
 temperature to melt it. This silicate occurs naturally as wollastonite. A 
 disilicate CaO,2Si0 2 ,2H 2 occurs as okenite, a sesquisilicate as gyrolite, 
 3(CaO,3Si0 2 )8H 2 0. Calcium silicates also occur in combination with potassium 
 silicate as apophyllite. with sodium silicate as pectolite, and with other silicates 
 in a great number of minerals. Many kinds of glass consist of calcium silicates com- 
 bined with alkaline silicates ; thus Bohemian hard glass has a composition approxi- 
 mating to the formula J2K a o'3SiC- 2 ' and ordinar y window glass has a composition 
 approximating to the formula j - A oSiO ' 
 
 The presence of calcium silicate in glass adds to its brilliancy and hardness. The 
 hardening or setting of hydraulic mortar and cements is due to the formation of 
 calcium silicate, and many of the slags obtained in smelting operations contain con- 
 siderable amounts of calcium silicates. Compounds of calcium silicates, with calcium 
 borates, also occur as datholite, CaO,2Si0 2 .CaO,B 2 3 , and in the hydrated state as 
 botry olite, CaO,2Si0 2 .CaO,B 2 3 2H 2 0. A similar compound of calcium silicate with 
 calcium titanate occurs as sphene, Ca0.3Si0 2 .2CaO,Ti0 2 . 
 
 Magnesium silicates are in general respects like the -calcium silicates. They 
 occur naturally as minerals, but some portion of the magnesia is generally replaced by 
 other basic oxides. Thus 2MgO,Si0 2 occurs as forsterite, chrysolite, and olivin ; 
 MgO,Si0 2 as augiteand hornblende; 3Mg0.2Si0 2 2H 2 as serpentin. Silica 
 and magnesia combined in various other proportions are also the essential constituents 
 of steatite or talc, meerschaum, chondrodite, etc. 
 
 Aluminum silicates are especially characterised by their very difficult fusibility. 
 The neutral silicate,- 2 Al 2 3 3Si0 2 , occurs naturally in combination with various pro- 
 portions of water as certain kinds of kaolin or porcelain clay, and a large number of 
 other compounds of silica with alumina occur either as argillaceous minerals or in the 
 crystallised state as andalusite, cyanite, sillimanite, etc. The different kinds 
 of porcelain, pottery ware, and bricks consist chiefly of aluminum silicates, partially 
 
SILICIC OXIDE. 193 
 
 nitrified by the direct action of heat and by the melting of small proportions of fusible 
 silicates diffused throughout the mass. Aluminum silicates also occur in combination 
 with other silicates constituting the various kinds of felspar, garn et, tourmaline 
 mica, chlorite, augite, hornblende, zeolites, serpentine, etc. Many of the 
 slags produced in smelting operations consist of double silicates of this kind. Alu- 
 minum silicates likewise occur in combination with sulphates as in hauyne, lapis 
 lazuli, etc., with carbonates as in cancrinite, and with fluorides as in lepidolite 
 topaz, chondrodite, mica, etc. 
 
 Ferrous silicates are much more easily fusible than those of calcium or mag- 
 nesium, especially the compound of silica and ferrous oxide in equal molecular 
 proportions. FeO,Si0 2 also occurs naturally as griinerite and in some augitic 
 minerals. The^silicate represented by the formula 2FeO,Si0 2 occurs naturally as the 
 mineral fay a lite, and several of the slags obtained in converting cast iron into 
 malleable iron, as well as in the refining of copper, approximate in composition to this 
 silicate. Ferrous silicates have a dark green colour. 
 
 Manganous silicates are analogous in general characters to ferrous silicates. 
 The compound MnO,Si0 2 occurs in some augitic minerals; another silicate having a 
 composition represented by the formula 2MnO,Si0 2 occurs as tephroite, and together 
 with silicates of iron and zinc in troostite and knebelite. 
 
 Lead silicates are very easily fusible; in the vitreous state they are transparent 
 and colourless, or when containing a large amount of lead oxide brilliant, highly re- 
 fractive, and slightly yellow ; these substances are also very soft. 
 
 Zinc silicates are analogous to those of lead in general characters. 2ZnO,Si0 2 
 occurs naturally as willemite and in the hydrated state as siliceous calamine. 
 Zinc silicate also occurs together with other silicates in troostite and in some augitic 
 minerals. 
 
 SILICIC OXIDE (SILICA). 
 
 MOLECULAR WEIGHT 60. 
 
 History. The existence of a peculiar earth in rock crystal, flint, and similar 
 minerals was not known until about the middle of the seventeenth century, although 
 the art of making glass and porcelain had long before been carried to a considerable 
 degree of perfection, and even then the true chemical nature of silica was not recognised 
 until Berzelius showed in 1814 that it combines with basic oxides in definite proportions, 
 and that the various minerals containing silica and basic oxides were to be regarded 
 as definite saline compounds. 
 
 Occurrence. Silica occurs crystallised in a pure state as rock crystal and 
 other kinds of quartz; also containing slight admixtures of various metallic oxides, 
 as amethyst, cairngorm, carnelian, chalcedon y, and agate. Many sand- 
 stone s consist almost entirely of coherent quartz granules. Flint consists of silica 
 in a compact state without crystalline structure. Jn the amorphous state and com- 
 bined with water, silica occurs as opal and in a variety of other forms. In combina- 
 tion with various basic oxides/ silica is a constituent of a very large number of 
 minerals, some of which are comparatively rare, while others are very abundant and 
 constitute the chief mass of entire mountain ranges. 
 
 Characters. In the crystalline state as rock crystal, silica" is colourless and 
 transparent; but as it occurs naturally it is often variously coloured, presenting shades 
 of yellow, red, brown, green, or blue, owing to the presence of metallic oxides in small 
 proportions. Sometimes it is quite black. Other kinds of quartz are often opaque, as 
 in the form of flint, and in proportion as the amount of admixtures increases the 
 characters cf pure silica are replaced by those of other substances. The density of 
 silica in the crystalline form ranges from 2'5 to 2'8 ; that of amorphous silica vanes 
 from 2-3 to 1-9. 
 
 Silica prepared artificially is a white earthy powder ; like natural silica, it is per- 
 fectly insoluble in water, or in any acid except hydrofluoric acid ; both kinds, however, 
 are dissolved gradually when heated with solutions of caustic alkalies, or even solutions 
 of alkaline carbonates. Silica melts only at a very high temperature, forming a trans- 
 parent vitreous mass ; when heated in contact with basic oxides, it combir 
 them, forming silicates which either melt very readily or form a coherent mass by th 
 softening of the particles. Alkaline carbonates are readily decomposed by si 
 sufficiently high temperature, the silica displacing carbonic dioxide and 
 with the alkali to form a silicate. 
 
POTASSIUM. 
 
 SYMBOL K. ATOMIC WEIGHT 39*1. 
 
 History. Potassium was discovered in 1807 by Sir H. Davy, and the demon- 
 stration of its metallic character served to show that potash, or the vegetable alkali, 
 as it was termed to distinguish it from soda or mineral alkali, was in the caustic state 
 the oxide of a metal, and that the salts of potash corresponded in composition with 
 the salts of other metals. 
 
 Occurrence. Potassium does not occur naturally in the metallic state, but only 
 in combination, chiefly with chlorine, bromine, or iodine, or with oxygen and acid 
 oxides, forming salts, which are widely distributed in all three natural kingdoms. 
 
 Potassium chloride occurs in large well-formed crystals as the mineral called 
 sylvin, and in the form of a double salt, with magnesium chloride, as carnallite 
 (KClMgCLj + 6H 2 0). Potassium sulphate occurs in- alum stone, kainite, 
 schonite,glaserite, etc. Potassium nitrate effloresces from many parts of the earth's 
 surface. Potassium silicate forms one of the essential constituents of a large number 
 of silicates, such as leucite, felspar, mica, glaukonite, phonolithe, etc. 
 Potassium sulphate and potassium chloride are contained in the water of many salt 
 springs, and in sea water, which, when treated for common salt, affords potassium 
 salts as a by-product. Potassium salts are also contained in small quantities in many 
 other kinds of natural water. 
 
 Potassium salts occur in plants as phosphates, sulphates, chlorides, and salts of 
 organic acids; the ash remaining when the plants are burnt consists of these salts or 
 carbonates formed by decomposition of the organic acids. Potassium silicate is also a 
 constituent of the ash of most plants. In animals potassium occurs chiefly in the form 
 of phosphates. 
 
 Formerly potassium salts were obtained almost entirely by the incineration of 
 plants, and considerable quantities of potash are still derived from this source, as 
 described under the head of ' Potassium Carbonate.' 
 
 From the very earliest times sea-weed has been collected on the Scotch and Irish 
 coasts, as well as on the coasts of Normandy and Brittany, either for use as manure or 
 for obtaining the ash by burning it. The process of incineration is carried out at the 
 present day in the following manner : The sea-weed is either washed on shore by the 
 sea drift weed or that growing on the sea coast is cut ; it is partly dried in the sun, 
 and then burnt in heaps, piled up over shallow pits until a half-fused ash remains, 
 which constitutes the material called kelporvarec. The composition of the various 
 sorts of kelp differs considerably, as may be seen from the following analyses. 
 
 Kelp, which is obtained on the coasts of Scotland and Ireland, as well as on the 
 shores of the Orkney Islands, by incinerating various fuci and other sea-weeds, has, 
 according to Brown, the following percentage composition. 
 
 4-527 
 3-600 
 0-279 
 0-924 
 0-784 
 0-220 
 0-540 
 5-306 
 1-651 
 26-491 
 19-334 
 0-229 
 0-316 
 traces 
 
 64-200 
 
 1. Insoluble Salts. 
 
 Calcium carbonate . 
 Phosphoric acid 
 Basic calcium sulphide . 
 Calcium silicate 
 Magnesium carbonate 
 Sand .... 
 
 2-591 
 10-556 
 1-093 
 3-824 
 6-554 
 1-575 
 1-142 
 
 2. Soluble Sa 
 
 Potassium sulphate 
 Sodium sulphate 
 Calcium sulphate . 
 Magnesium sulphate 
 Sodium sulphite 
 Sodium hyposulphite 
 Sodium phosphate . 
 
 Carbon . . ) Unburnfc 
 Hydrogen . I or ~ an : c 
 Nitrogen . 
 Oxygen . .. j 
 
 Water .... 
 
 / 0-920 
 I 0-144 
 10-152 
 ' { 0-658 
 
 29-209 
 6-800 
 
 Sodium carbonate . 
 Sodium sulphide 
 Potassium chloride . 
 Sodium chloride 
 Calcium chloride 
 Magnesium iodide . 
 Magnesium bromide 
 
OCCURRENCE OF POTASSIUM SALTS. 195 
 
 Varec is made on the coastsof Normandy and'Brittany by incinerating sea-weed. It 
 has the following composition : 
 
 
 Villette 
 
 Cherbourg 
 
 Potassium sulphate . 
 
 20-35 
 
 22-19 
 
 42-54 
 
 Potassium chloride . 
 
 10-53 
 
 16-00 
 
 19-64 
 
 Sodium chloride 
 
 54-11 
 
 4578 
 
 25-38 
 
 Sodium carbonate . 
 
 1376 
 
 9-53 
 
 371 
 
 Insoluble substance 
 
 
 
 1-50 
 
 073 
 
 Iodine compounds . 
 
 traces 
 
 traces 
 
 traces 
 
 Water 
 
 1-25 
 
 5-00 
 
 8-00 
 
 The method of extracting the potassium salts from kelp or varec is described under 
 the head of ' Potassium Chloride.' 
 
 One of the most important sources of potassium salts is the enormous salt deposit 
 of Stassfurt and Leopoldshall. The deposit of potassium salts lies upon a very deep 
 layer of rock salt, and is subdivided by Bischof into the following regions : 
 
 a. Polyhalite region, which lies immediately above the pure rock salt. This 
 deposit is about 200 feet deep, and consists essentially of impure rock salt, interlaced 
 with veins of polyhalite. 
 
 j8. Kieserite region, which lies above the polyhalite region. This deposit is about 
 180 feet deep, and like the above consists essentially of impure rock salt, interstratified 
 with layers of kieserite, sometimes many feet thick. 
 
 7. Carnallite region. This deposit is between 130and 160 feet deep, and consists of 
 a variable mixture of rock salt and salts of magnesium and potassium. Amongst 
 the latter carnallite prevails, which is the most important salt for the production of 
 potassium chloride. It is chiefly this latter region which contains the salts that are 
 now treated for potassium salts, but were formerly thrown on one side at the period 
 when the only object in view was to get at the deposit of rock salt lying beneath. 
 The most important minerals of the above three regions are the following : 
 
 a. In the polyhalite region. 
 
 Polyhalite, which has a composition represented by the formula 
 2CaS0 4 + MgS0 4 + K 2 S0 4 + 2H 2 0. 
 
 )8. In the kieserite region. 
 Kieserite, the composition of which may be represented by the formula 
 
 MgS0 4 + H 2 0. 
 7. In the carnallite region. 
 
 Carnallite, which has the following composition- 
 Ed + Mg01 2 + 6H 2 0. 
 
 It contains 24 to 27 per cent, potassium chloride, small quantities of sodium chloride 
 and calcium sulphate, as well as traces of ferric oxide, rubidium, caesium, thallium, and 
 bromine. It is colourless when pure, of a coarse crystalline structure, and deliquescent. 
 The carnallite found among the salts has generally a reddish tinge of more or less 
 depth, owing to the presence of iron mica. 
 
 b. Kainite(MgCl 2 + MgS0 4 + K 2 S0 4 + 6H 2 0). Part of the magnesium is 
 always replaced by calcium, and part of the potassium by sodium. 
 
 c. Syl vin (KC1). This is probably a secondary product, produced by the magne 
 sium chloride of carnallite having been dissolved out by water. 
 
 d. Schonite (K,S0 4 + MgS0 4 ). This mineral often forms a crust upon 
 surface of kainite. 
 
 Other salts found in the carnallite region are tachydnte (calcium and 
 sium chlorides), boracite or stassfurtite (magnesium borate and 
 chloride), and small quantities of iron mica. 
 
 CharactersPotassium is a solid substance possessing distinct 
 characters ; it has a bluish-white colour, with considerable lustre when 
 and its specific gravity is -865 as compared with water ; at ordinary ^P 61 ? 
 
 knife at it becomes brittle ; it mdte 
 
 so soft that it can be easily cut with a knife ; at it becomes 
 
 62, and volatilises at a red heat. Potassium combines very readily witb oxy er ^ and 
 
 on that account requires to be kept immersed in a liquid hydrocarbon, such as 
 
 it absorbs oxygen from atmospheric air at the ordinary temperature ; * 
 
 o2 
 
196 POTASSIUM. 
 
 contact with air, it takes fire, and burns with a violet- coloured flame ; it decomposes 
 water, and displaces half its hydrogen, forming potassium hydrate, H 2 + K = KHO + H, 
 and the hydrate dissolves in the water, forming a solution of caustic potash. 
 
 Preparation. Potassium is prepared by heating to a very high temperature a 
 mixture of potassium carbonate and charcoal, obtained by heating to redness acid 
 potassium tartrate, in a covered crucible, until it ceases to give off vapour. The 
 black porous residue is rapidly cooled, broken into small lumps, and put into a wrought- 
 iron mercury bottle (b), which is supported in a furnace as shown by fig. 125, and fitted 
 with a short iron tube (d), which serves to conduct the potassium vapour into a con- 
 denser (c), the construction of which is shown on a larger scale by fig. 126. This 
 condenser consists of two pieces of sheet iron, a and b, fitted together with clamps so as 
 to form a shallow box about a quarter of an inch deep ; it is open at both ends, and the 
 narrow end fits upon the iron tube of the mercury bottle. Upon heating the mercury 
 
 FIG. 125. FIG. 126. 
 
 bottle to a reddish-white heat, the potassium carbonate is decomposed by the charcoal, 
 and the potassium thus reduced escapes in vapour together with carbonic oxide gas, 
 and is condensed in the narrow sheet-iron box, which is kept cool by wet cloths. 
 
 Compounds. Potassium combines with oxygen in three proportions, forming a 
 monoxide K 2 0, which is a powerful basic oxide and combines with acid oxides forming 
 salts ; a dioxide, K 2 2 , which is analogous in its characters to hydric peroxide, and a 
 tetroxide, K 2 4 . The compounds of potassium with fluorine, chlorine, bromine, 
 iodine, sulphur, are saline substances that will be described separately. 
 
 POTASSIUM OXIDE. 
 
 FORMULA K 2 0. MOLECULAR WEIGHT 94-2. 
 
 This substance is formed when potassium, in thin slices, is exposed to air free from 
 moisture and carbonic dioxide, or by heating potassium hydrate with potassium ; it is 
 a white solid substance, very deliquescent and caustic ; it melts at a red heat and 
 volatilises at a higher temperature. 
 
 POTASSIUM HYDRATE. 
 
 FORMULA KHO. MOLECULAR WEIGHT 56-1. 
 
 The substance commonly called caustic potash may be obtained by dissolving 
 potassium oxide in water, or more conveniently by decomposing potassium carbonate 
 dissolved in water by means of caustic lime, which abstracts the carbonic dioxide, and 
 forms calcium carbonate, leaving potassium hydrate in solution, according to the 
 equation : 
 
 K 2 C0 3 + CaH 2 2 = CaCO s + 2KHO. 
 
 The operation is conducted in the same manner as the preparation of sodium 
 hydrate (vide that article). 
 
 Characters. Potassium hydrate is a white solid substance having a specific 
 gravity of 2'1. It melts below a red heat to an oily liquid and volatilises at n, higher 
 temperature. It rapidly absorbs moisture from the atmosphere and deliquesces; it 
 
POTASSIUM CHLORIDE. 
 
 197 
 
 also absorbs carbonic dioxide, and forms potassium carbonate. It dissolves in about 
 half its weight of water, evolving great heat, and is extremely caustic both in the 
 solid state and in solution. 
 
 POTASSIUM CHLORIDE. 
 
 FORMULA KC1. MOLECULAR WEIGHT 74-6. 
 
 Occurrence. Potassium chloride occurs naturally in a pure state as sylvin 
 round the fumaroles of Vesuvius, and in the salt deposits of Stassfurt and at Kalucz 
 in Hungary. It also occurs very abundantly in combination with magnesium chloride 
 as carnallite in the salt deposits of Stassfurt, which are extensively worked. 
 Potassium chloride also occurs in sea water, in kelp, or the ash of sea-weeds, in natural 
 brines, and in the water of some mineral springs. 
 
 Michels represents the salts excavated from the Stassfurt mine and delivered 
 to the potash works as having the following percentage composition : 
 
 Carnallite 50-55 per cent. 
 
 Eocksalt 25-30 
 
 Kieserite and kainite .... 10-15 
 
 Anhydrite, clay, sand, etc. . . . 15-0 
 
 This amount of carnallite represents from 13 to 14 per cent, of potassium chloride. 
 
 The salt obtained from the Leopoldshall mine contains on the average a larger 
 amount of carnallite than that from the Stassfurt mine, the amount of potassium 
 chloride ranging from 15 to 17 per cent. 
 
 Characters. Potassium chloride is readily soluble in water ; it crystallises in 
 cubes, and presents many resemblances to sodium chloride or common salt. It has, 
 however, a stronger taste, and cannot be taken into the system in such large quantities 
 as common salt without injury. Crystals of potassium chloride decrepitate when 
 heated, the salt then melts, and at a sufficiently high temperature it volatilises ; it is 
 much more easily volatilised thar sodium chloride. 
 
 The potassium chloride of commerce is generally impure, and contains only from 80 
 to 90 per cent, of pure chloride, the remainder consisting chiefly of sodium chloride, 
 sulphates in variable amount, some insoluble substance, and water. When potassium 
 chloride has been prepared from molasses residue, it is generally mixed with alkaline 
 carbonates. 
 
 Frank gives the composition of a good sample of potassium chloride as follows, 
 and the other analyses are by Tissandier. 
 
 
 Frank 
 
 
 Tissandier 
 
 
 Potassium chloride . . t '. 
 ,, sulphate . 
 carbonate . " . . 
 Sodium carbonate . . ..,'., 
 
 86-14 
 10-94 
 
 79-80 
 12-31 
 1-00 
 2-10 
 
 93-52 
 4-01 
 0-61 
 
 75-01 
 11-81 
 3-28 
 2-13 
 
 Magnesium sulphate . . . 
 Insoluble matter . . . / . . 
 Water . . . . 
 
 0-24 
 0-45 
 4-29 
 
 0-32 
 4-27 
 
 0-28 
 1-38 
 
 0-90 
 6-35 
 
 Preparation. The greater part of the potassium chloride of commerce is now 
 made from carnallite ; but considerable quantities are obtained as by-products of 
 various industrial operations, as in the preparation of salt from sea water, and the 
 preparation of iodine from kelp ; potassium chloride is also obtained from the residues 
 of beet sugar molasses. The preparation of potassium chloride from the sylvm foun< 
 at Kalucz in Hungary, which is mixed with a great quantity of clay, has not at present 
 obtained any great dimensions, although it will probably soon do so. Small quantiti 
 of pure potassium chloride are even now prepared from potashes. 
 
 WORKING OF STASSFURT SALTS. The methods of preparing potassium chloride 
 adopted in the works of Stassfurt and Leopoldshall are different. They are alike in this 
 respect, that carnallite is lixiviated, either with water or a lye poor in magnesium 
 chloride, the lixiviating liquor being employed hot. The magnesium chloride and 
 potassium chloride of the carnallite dissolve, but upon cooling the liquor, potassium 
 chloride alone crystallises out, since carnallite only crystallises from a liquor conl 
 a large excess of magnesium chloride. However, upon evaporating the mother hquo] 
 
198 POTASSIUM. 
 
 from the first crystallisation to a certain density, artificial carnallite crystallises out, 
 owing to the liquor having become proportionally richer in magnesium chloride by the 
 former crystallisation of potassium chloride. The artificial carnallite is separated from 
 the mother liquor and once more dissolved and the liquor crystallised, whereupon a 
 further crop of crystals of potassium chloride is obtained. 
 
 A method much in use at Stassfurt and Leopoldshall is the following : 
 
 Breaking up of the Salts. The carnallite as it comes from the mine is either 
 crushed to a coarse powder in a mill, or it is simply broken up with hammers into 
 pieces about the size of one's hand. 
 
 In order to reduce the salts to a powder, Frank has recently introduced an apparatus 
 which he calls a disintegrator ; but it appears that the mills formerly employed do 
 better work. 
 
 Solution of the Salts. The broken or powdered salt is lifted by a mechanical 
 arrangement into a higher story, where the dissolving operation is carried out. 
 
 The lixiviating vessels are made of iron plates riveted together. They are cylin- 
 drical in shape, and have a diameter of between 6 and 1 feet, and a depth of from 
 8 to 10 feet, being capable of holding 100-300 cwts. of carnallite, together with the 
 water required for the solution of the same. The vessels are furnished with perfo- 
 rated false bottoms about six inches from the bottom, for supporting the carnallite 
 during the process of lixiviation. The bottom of the pan slopes towards the centre, so 
 as to admit of the liquor being run off with facility through a tap at that point. A rod 
 by which the tap can be closed or opened, as desired, projects above the lixiviating pan. 
 Over the tap is a perforated iron cylinder, which extends above the surface of the 
 liquid for the purpose of holding back fragments of the undissolved salt. There is also 
 a manhole above the perforated false bottom, for removing the undissolved residue. 
 Heat is applied by blowing steam into the pan, through a pipe running round the pan 
 between the bottom and perforated shelf. Beneath the lixiviating pan are placed 
 several tanks of sheet iron, in which the liquors are allowed to settle ; and to prevent 
 them from cooling too rapidly, they are surrounded by brickwork, or some other non- 
 conducting material. 
 
 "When the carnallite is added to the liquor in the lixiviating pan, the temperature 
 must be kept up to the boiling point, the addition being continued until the 
 turbid solution has a specific gravity of T282, or the clear solution a specific gravity 
 of 1-277. The liquor is then run off into the settling tanks below. The operation 
 should be conducted as rapidly as possible, in order to reduce to a minimum the 
 solution of potassium sulphate, which dissolves jnore slowly than the chloride. Afcer 
 the solution has been run off, large masses of undissolved salts remain, containing a 
 considerable quantity of potassium chloride; and on this account the residue is treated 
 a second time with water or weak liquor from a previous operation, the whole heated 
 by blowing in steam, and the solution, run off into settling tanks, is afterwards used in 
 place of water for operating upon fresh carnallite. 
 
 The residue left after the second treatment of the salt with water amounts to 
 about 25 per cent, and consists of kieserite, rock salt, anhydrite, etc., with about 5 per 
 cent, potassium chloride. It is either thrown aside as waste or worked up for magnesium 
 sulphate. 
 
 To obtain the potassium chloride, the clear liquor is run while hot from the 
 settling tanks into crystallising pans made of sheet iron, about 2 feet deep. After the 
 lapse of 24 or 48 hours, the mother liquor is drawn off, and the salt deposited upon 
 the sides of the pans is removed to vessels fitted with perforated false bottoms, in 
 which it is washed with water so as to remove all adherent mother liquor. This 
 operation is repeated several times, according to the degree of purity the salt is 
 required to have, and the residue, containing from 80 to 90 per cent, of potassium 
 chloride, is finally dried and sifted. 
 
 The mother liquor from the crystallising pans is evaporated until it has a specific 
 gravity of T299, when it deposits sodium chloride and some potassium sulphate, 
 which is used either for manure or for salting cattle food. The clear liquor drawn 
 off from this salt contains a large amount of magnesium chloride, together with some 
 potassium chloride, and by concentration it deposits these salts as artificial carnallite, 
 which is worked as already described for the separation of potassium chloride. 
 
 The last mother liquor from the crystallisation of carnallite is sometimes used for 
 the first solution, of the crude carnallite salt, by which means tho impurities are 
 separated and the double potassium and magnesium chloride is obtained in such a 
 state that, on treatment with water, it yields at once very pure potassium chloride. In 
 other works the last mother liquor is either evaporated down to obtain magnesium 
 chloride, or worked for the extraction of the bromine it contains (see p. 1 78). 
 
 EXTRACTION FROM THE ASH OF SEA- WEED. The amount of potassium chloride in 
 
 
POTASSIUM CHLORIDE FROM KELP. 
 
 199 
 
 some kinds of sea- weed is sufficiently large to make the extraction of this salt 
 desirable, and it is carried out in connection with the manufacture of iodine. 
 
 Lixiviation of the Kelp or Varec. This operation is performed in the same way as 
 lixiviation of ball soda (vide this article). The fused semi-vitreous mass is first 
 broken into small pieces, and then lixiviated with water. The apparatus used for 
 this purpose varies considerably in form. In some places square iron vats with 
 double bottoms are used, the upper or false bottom being perforated. Upon this 
 perforated bottom the broken kelp is placed, and water is added in quantity sufficient 
 to cover the kelp. After a lapse of a few hours, the liquor is drawn off by means of 
 a cock fitted between the two bottoms, and let into a second vat of like construction 
 filled with kelp ; the partly lixiviated mass in the first vat being treated again, either 
 with water or with dilute liquor. About six lixiviating vats of this description are 
 placed in connection with one another, the process being so conducted that fresh 
 water flows first into that vat which contains the most exhausted material, and 
 from thence successively into those vats containing less exhausted material. When 
 the kelp in the first vat is completely exhausted, it is taken out and a fresh charge 
 put in, and fresh water is run into the second vat, and so on to the last vat ; and 
 finally into the first, because that will then contain the least exhausted material. 
 This method of lixiviation secures the greatest possible exhaustion of the kelp, with 
 the least possible quantity of water. 
 
 The lixiviation is sometimes carried out in the apparatus shown in fig. 127, 
 which consists of five iron vats (A to E), arranged at different levels. In each vat there 
 
 FIG. 127. 
 
 are perforated boxes (a to e) containing pieces of kelp, and supported by iron rods. The 
 highest vat (A) is twice as large as any of the others, and it has two pairs of perforated 
 boxes (e e e e). "Water let in from above extracts the soluble constituents in the first 
 series of boxes (c e e e), and when the liquid has reached the level of the discharge pipe 
 (d), it flows out from the bottom of the vat into the upper part of the second vat (B), 
 from thence in like manner into the third, fourth, and fifth vats successively. The 
 liquid discharged from the last vat (E) into the reservoir (F) will have a specific 
 gravity of 1-18 1-25. When the material in the first series of perforated boxes is 
 sufficiently exhausted, the boxes are hoisted out from the vat and placed to drain 
 upon the support (&). The boxes in the second vat (B) are then transferred to the 
 vat (A), those of the third vat to the second vat (B), etc., fresh pieces of kelp being 
 placed in the fifth vat (E). In this way also fresh water comes first of all into 
 contact with the most exhausted material, and thus effects as complete an exhaustion 
 as possible. At the works of Cournerie, in Cherbourg, the liquor is heated by steam, 
 in vats furnished with double sides. 
 
 The liquor is allowed to settle in the reservoirs (r F'), and then drawn off into a series 
 of iron pans (o), placed near the reservoirs, where it is evaporated. These pans are 
 arranged in steps one above 
 the other, so that the liquor of 
 the first pan (G) flows into 
 the second pan and from 
 thence into the pan (i, fig. 128), 
 etc., until it arrives at the last 
 pan (K). The pans are heated 
 by a single furnace (t), placed 
 under the lowest pan (K), 
 and the hot air is passed along 
 under the other pans. The pan 
 
 FIG. 128. 
 
 (G), which is furthest away from the furnace, is consequently not heated so much as the 
 
200 
 
 POTASSIUM. 
 
 FIG. 129. 
 
 others ; and the temperature of each pan increases with its proximity to the furnace. 
 In proportion as the liquor is heated, the water evaporates ; and a portion of the less 
 soluble salts, sucli as potassium sulphate and common salt, is often deposited in the pan 
 (i). In order to prevent the deposited salt from adhering 
 to the hot part of the pan immediately in contact with 
 the fire, the bottom of this pan has the shape shown in 
 section by fig. 129. The precipitated salt collects at the 
 sides (I l\ where the heat is not so great, and it is taken 
 out by means of a, perforated ladle. After a short time 
 the liquor is drawn off into crystallising pans, where 
 it deposits, upon cooling, chiefly potassium chloride, 
 together with small quantities of sodium and potassium 
 sulphates. The mother liquor is once more concentrated 
 in specially adapted pans, the salts which separate out meanwhile, such as sodium 
 chloride and sulphate, etc., are removed with a perforated ladle, and the liquor again 
 set to crystallise. Potassium chloride then crystallises out ; the liquor drawn off, 
 again evaporated, and allowed to crystallise, generally yields another crop of crystals 
 of impure potassium chloride. 
 
 The residues remaining in the perforated boxes are further lixiviated with water, 
 and the liquor obtained is evaporated in pans like the first. Sodium sulphate 
 separates in the evaporating pans, and the further operation of crystallising yields 
 potassium chloride. A repetition of these operations yields common salt in the 
 evaporating pans, and impure potassium chloride in the crystallising pans. 
 
 The last liquor obtained from the residues, having a specific gravity of between 
 1-000 and 1'070, is used instead of water for afresh operation. 
 
 The salts separated out either in the evaporating or crystallising pans such as 
 potassium chloride, common salt, potassium sulphate, Glauber's salt, and soda, are 
 separately collected, and, after being washed or recrystallised, are sent into the market, 
 Payen suggests the evaporation of the concentrated lye in a pan (B B'), having a 
 yr form like that shown in fig. 130, heated 
 
 by a fire (A). Directly the precipitation 
 of salts sets in, a sieve (c), supported by a 
 chain moving upon rollers (d'd 1 ), and ad- 
 mitting of being raised and lowered by 
 the weight (e), is lowered into the pan. 
 The sieve is furnished with three feet 
 which support it inside the evaporating 
 pan, and keep it at a distance of six inches 
 from the bottom. The salts as they pre- 
 cipitate are forced to the surface by the 
 boiling liquid, and in falling back are 
 caught in the sieve. As soon as the sieve 
 is full it is drawn up, allowed to drain for 
 a short time, and its contents emptied on 
 to a shelf; so that the mother liquor 
 adhering to the crystals may drain off 
 into the evaporating pan. 
 Treatment of the mother liquor. The mother liquor obtained by the opera- 
 tion^ above described still contains minute quantities of all the salts contained in the 
 original liquor, such as sodium chloride, potassium sulphate, sodium sulphate, and 
 carbonate and potassium nitrate, together with iodides, bromides, cyanides, sulphides, 
 and bisulphites of sodium and potassium, and small quantities of unburnt organic 
 substance. 
 
 Uses. Large quantities of potassium chloride are used for converting sodium 
 nitrate into potassium nitrate, also as manure, and in the manufacture of potassium 
 sulphate and other potassium salts. 
 
 FIG. 130. 
 
 POTASSIUM BROMIDE 
 
 FOBMULA KBr. MOLECULAR WEIGHT 119-1. 
 
 This salt is prepared either by dissolving bromine in solution of caustic potash, 
 evaporating to dryness, and heating the residue mixed with charcoal until it is 
 red hot, or better still, by treating iron immersed in water with bromine, and preci- 
 pitating the solution of ferrous bromide thus formed with potassium carbonate. 
 
POTASSIUM IODIDE. 201 
 
 Potassium bromide may also be obtained by passing sulphuretted hydrogen into water 
 containing a layer of bromine, saturating the hydrobromic acid thus produced with 
 barium carbonate (witherite), and decomposing the solution of barium bromide with 
 potassium carbonate. 
 
 According to Frank's method, bromine vapour, containing chlorine as it escapes 
 from the Woulfe's bottle (D, fig. 106). is conducted through -a leaden tube into a second 
 Woulfe's bottle, filled with m6ist iron filings, and from thence into an open pot also 
 containing iron filings. A mixture of iron chloride and bromide is formed in the Woulfe's 
 bottle at first, but towards the end of the operation, when the evolution of chlorine 
 gradually increases, the bromine is displaced by it from the bromide formed in the 
 Woulfe's bottle, and passing into the open pot, it forms pure ferrous bromide, the 
 whole of the chlorine remaining in the Woulfe's bottle. The ferrous bromide is then 
 decomposed with potassium carbonate. The iron and water may be replaced by a 
 solution of caustic potash, in which case there is first of all formed potassium chloride 
 and bromide, as well as potassium bromate and chlorate ; the bromine is, however, 
 eventually displaced by the excess of chlorine, and pure bromine distils over into the 
 caustic potash solution in the second vessel. The liquor thus obtained is then mixed 
 with charcoal, evaporated, and ignited to convert the bromate into potassium 
 bromide. 
 
 If opaque crystals of potassium bromide are required, the solution from which the 
 salt is crystallised must be slightly alkaline. Since the mother liquor obtained in this 
 way is very alkaline, it is neutralised as nearly as possible with hydrobromic acid, 
 and again evaporated for a new crop of crystals. 
 
 Transparent crystals of potassium bromide are always formed from perfectly 
 neutral solutions, also when the solution contains traces of lead or tin, etc. 
 
 ARTIFICIAL SEA SALT. This consists of common salt containing varying proportions 
 of bromine in the form of magnesium bromide, which is prepared by precipitating a 
 solution of ferrous bromide with caustic lime, decomposing the calcium bromide 
 with magnesium sulphate, separating the precipitated gypsum, and evaporating the 
 solution to dryness. The consumption of artificial bathing salt from Frank's manu- 
 factory alone amounted in 1871 to about 50 tons. 
 
 POTASSIUM IODIDE. 
 
 FORMULA KI. MOLECULAR WEIGHT 166'V. 
 
 Characters. Potassium iodide crystallises in cubes; it is soluble in water and in 
 alcohol, and may be prepared by the direct combination of potassium and iodine. For 
 its preparation, however, other methods are used. 
 
 Preparation. The most usual way of preparing potassium iodide is by actn 
 upon a solution of caustic potash with iodine. Iodine is added as long as it is dis- 
 solved without colouring the liquid, potassium iodide and iodate being formed, as 
 shown by the following equation : 
 
 61 + 6KHO = SKI -f KI0 3 + 3H 2 0. 
 
 The solution thus obtained is mixed with a small quantity of powdered charcoal, 
 and evaporated to dryness. The residue is slightly ignited, so as to secure the reduc- 
 tion of potassium iodate, which takes place, as shown by the following equatio: 
 KI0 3 + 30 = KI + 300. 
 
 The residue contains accordingly the entire quantity of iodine in the form of 
 potassium iodide. It is lixiviated with water, and the solution evaporated unti 
 a specific gravity of 1-867, and set aside to crystallise. The crystals are thrown upon 
 funnels, so^as to drain off the mother liquor and then dried by spreading them out 
 upon glazed iron plates, in a current of air of a temperature of 120-125 . 
 
 Instead of heating to redness with charcoal, the ^^jf&* ^.l 
 effected in the wet way by treating the solution containing iodate with red 
 stances, such as hydrated ferrous oxide, sulphurous acid, etc, 
 
 "~ ' ' iodide may also be prepared by treating iron 
 
 SiFn 
 
202 POTASSIUM. 
 
 tion is filtered off, treated with potassium carbonate or sulphate, to precipitate the 
 barium as carbonate or sulphate, which is separated by another filtration, and tne 
 clear liquid containing potassium iodide in solution is evaporated to crystallisation. 
 
 "Wagner recommends adding iodine to a mixture of milk of lime and calcium 
 sulphite with water, so as to form calcium iodide, and then to decompose the solution 
 of that salt with potassium carbonate, separate calcium carbonate by filtration, and 
 evaporate the filtrate containing potassium iodide to crystallisation. 
 
 POTASSIUM CHLORATE. 
 
 MOLECULAR WEIGHT 122-6. 
 
 History. This salt appears to have been known in the early part of the seven- 
 teenth century to Glauber, who described a kind of saltpetre prepared by means of 
 common salt. Higgins, in 1786, also pointed out that a kind of saltpetre was 
 produced by the action of chlorine upon alkalies, and about the same time it was 
 investigated by Berthollet, but the true composition of this salt was first determined 
 by Gay-Lussac in 1814. 
 
 Characters. Potassium chlorate is an anhydrous salt. It is sparingly soluble 
 in cold water, more readily soluble in hot water. The degree of solubility of potas- 
 sium chlorate in 100 parts of water at various temperatures is shown in the following 
 table : 
 
 At . 3-33 pts. At 35-02 
 
 13-32 . . 5-60 49-08 
 
 15-32 . . 6-03 74-89 
 
 24-43 8-44 , 10478 
 
 12-05 pts. 
 18-96 
 35-40 
 60-24 ,. 
 
 Potassium chlorate crystallises out from its aqueous solution in laminae of a pearly 
 lustre ; it has a cooling taste resembling nitre. When gently heated, potassium 
 chlorate melts without decomposition ; a stronger heat converts it first into potassium 
 chloride (KC1) and perchlorate (KC10 4 ), and at a still higher temperature the whole 
 of the oxygen is given off, potassium chloride remaining : 
 
 KC10 3 = KC1 + 30. 
 
 According to the above equation, therefore, potassium chlorate, when subjected to a 
 very strong heat, yields 39-16 percent, of free oxygen, and 60-84 per cent, of potassium 
 chloride. 
 
 One of the most important properties of potassium chlorate is its extremely 
 energetic oxidising action : when mixed with combustible substances, such as sulphur 
 charcoal, or phosphorous acid, explosions of a most violent nature may occur if the 
 mixture is slightly warmed or rubbed. On this account, it is necessary to be very 
 cautious in working with potassium chlorate, and on no account should it be tri- 
 turated or heated with easily combustible bodies. 
 
 Preparation. Potassium chlorate may be prepared by passing chlorine into a 
 concentrated solution of caustic potash or potassium carbonate. The following equa- 
 tion shows the reaction which takes place : 
 
 3K 2 C0 3 + 6C1 = 5KC1 + KC10 3 + 3C0 2 . 
 
 The apparatus used for this purpose consists of a chlorine generator (fig. 103, page 
 164), and the absorption vessels containing the solution of potash are arranged in a 
 manner similar to that shown and described for the absorption of sulphurous acid 
 (fig. 46, page 106). Between the absorption vessels and the generators is a washing 
 arrangement. At the beginning of the operation there is formed in the first carboy, 
 potassium hypochlorite and chloride, as well as acid carbonate, and if the generation 
 of chlorine is stopped at this point, and the carboy allowed to cool slightly, the greater 
 part of the'potassium chloride crystallises out, and may bo separated by decanting off the 
 solution. When chlorine is again passed into the decanted liquid, potassium chlorate 
 is formed. The liquid soon becomes saturated with the salt, which separates out in 
 a crystalline condition. Potassium chlorate thus prepared is washed with a small 
 quantity of cold water, to get rid of potassium chloride, and is then crystallised from 
 hot water. According to this method, as may be seen from the above equation, only 
 about one sixth of the potash used is converted into chlorate ; the remaining five-sixths, 
 though not absolutely lost, are converted into potassium chloride, which is a far less 
 valuable substance. 
 
USES OF POTASSIUM CHLORATE. 203 
 
 In order to convert the entire quantity of potash into potassium chlorate, part of 
 the potash is replaced by lime. The following reaction then takes place : 
 2KHO + 5CaH 2 2 +1201 = 5CaCl 2 + 2KC10 3 + 6H 2 0. 
 
 In this case the entire quantity of potash used is converted into potassium chlorate, 
 the mother liquor yielding calcium chloride instead of the corresponding salt of 
 potassium. 
 
 Instead of passing chlorine into a mixture of caustic potash and lime, it is some- 
 times convenient to pass the chlorine direct into milk of lime, and afterwards to de- 
 compose the calcium chlorate with potassium chloride. The apparatus used for the prepa- 
 ration of calcium chlorate consists of a chlorine generator and washing and absorption 
 vessels, the latter being lined with lead and furnished with stirrers, so as to bring the 
 lime into intimate contact with the chlorine. The milk of lime is prepared by mixing 
 lime with five parts water. Chlorine gas is passed into this as long as it is absorbed. 
 The temperature of the liquid rises very quickly upon the introduction of chlorine to 
 95; at which temperature the formation of calcium chloride and chlorate takes 
 place. The saturated lye is run from the absorption vessels into tall vessels, where 
 it is allowed to clarify. From the clarifiers the liquid is drawn off by means of siphons 
 into evaporating pans, where it is evaporated, and when it has attained a spec, 
 grav. of 1'180, it is mixed with potassium chloride. It is then further evaporated till 
 a spec. grav. of 1'280 has been reached, and at this point it is allowed to cool. The 
 crystals that form are separated and the mother liquor again evaporated to obtain 
 another crop of crystals. Sometimes a third crystallisation is attempted. The crystals 
 from the first crystallisation are recrystallised once from hot water, those of the 
 second crop generally twice, in order to get rid of the admixture of calcium chloride. 
 The mother liquors are evaporated to obtain the calcium chloride. 
 
 Properly prepared potassium chlorate ought not to decrepitate when heated ; i.e. 
 it ought not to contain any mother liquor mechanically enclosed. Dilute solutions 
 of the salt should give no reaction either with a solution of silver nitrate (chlorine) or 
 with a solution of barium nitrate (sulphuric acid). When strongly heated it ought to 
 decompose with quiet effervescence and the residue should not exceed 60 or 70 per 
 cent. Should the residue exceed this amount, the potassium chlorate is contaminated 
 either with potassium chloride or some other salt. 378 grammes of potassium chlo- 
 rate ought to yield 1 litre of oxygen gas at and under a pressure of 760 mm. of 
 mercury. 
 
 Uses. Attempts have been made to use potassium chlorate in the preparation of 
 gunpowder, but they did not succeed, the powder thus prepared having two dis- 
 advantages. (1.) It exploded upon the slightest friction and (2) its decomposition 
 was so sudden and violent that often the guns in which it was employed burst. It 
 was supposed that this difficulty might be got rid of by the addition of nitre, but the 
 explosion was still too violent. 
 
 Potassium chlorate is used in preparing percussion caps, fusees for cannon, etc. 
 The following gives the composition of two mixtures of the kind. 
 
 Potassium chlorate . . . . .'.-. 27'5 . 26 
 
 Fulminating mercury 12'3 . 13 
 
 Nitre . 307 . 30 
 
 Sulphur . . . . .' .-..'.. 16'3 . 17 
 Powdered glass . . .. . , . . 11'2 . 14 
 G-lue or gum . . . . .* , ? TO . 1 
 
 The charge for a copper percussion cap weighing 78 milligr. is 25 milligr. of the 
 above mixture, so that 1 kilo of the mixture serves for 40,000 such caps. The caps 
 for fowling-pieces contain only 15'20 milligr. of the explosive mixture. The mixture 
 is put into the caps in a moist state and left to dry in them. 
 
 Potassium chlorate is much used in pyrotechnics, and it has found extensiv 
 employment in the manufacture of the patent safety matches, which are free from 
 phosphorus. 
 
 At one time considerable quantities of potassium chlorate were used : 
 paration of the so-called chemical matches, which were ignited by dipping them ir 
 centrated sulphuric acid. The ignitable part of these matches consisted of a mixture 
 of equal parts of potassium chlorate and sulphur together with a small quantity of 
 lycopodium or resin, and cinnabar. The ends of the wood splinters for making t 
 matches were first of all dipped in sulphur, and then the above mixture was mad< 
 adhere to the sulphur by means of gum. Upon pressing the head of such a 
 against asbestos saturated with sulphuric acid, the match ignited and the sulpht 
 abled it to communicate the fire to the wooden portion of the match. These mat* 
 have bees, however, entirely replaced by phosphorus lucifer matches (vtde .fnospnc 
 
204 
 
 POTASSIUM. 
 
 Matches without Phosphorus. There are many recipes for preparing combustible 
 compositions without phosphorus in either of its forms. The following are given by 
 Canouil, and are said to ignite when rubbed against sand or glass paper : 
 
 Potassium chlorate 
 Crocus of antimony 
 Oxidised red lead . 
 Gum 
 Water . 
 
 5 
 
 0-5 
 
 II. 
 
 Potassium chlorate 
 
 Sulphur. 
 
 Lead cyanide 
 
 Gum 
 
 Water . 
 
 6 
 
 0-5 
 
 2 
 
 2 
 
 8 
 
 III. IV. 
 
 Potassium chlorate . 5 Potassium chlorate . 28'5 
 
 Glass .... 3 Glue . .5-4 
 
 Potass, bichrom. . . 2 Potass, bichrom. . 2*9 
 
 Gum . . 2 Lead nitrate . .27 
 
 Water .... 8 Powdered glass . 10'8 
 
 Sulphur . . 85'0 
 
 Canouil gives further a recipe for preparing matches to be struck on a specially 
 prepared surface, both match and friction surface being free from phosphorus. 
 
 Combustible Composition. 
 
 Potassium chlorate . 7 '3 
 Lead nitrate. . . 2'3 
 Acid potass, chromate. 2*3 
 Sulphur . . .1-3 
 Gum . . . .6-3 
 Water . 18'0 
 
 Friction Surface. 
 
 Potassium chlorate . 6 
 
 Iron scales. . . .1 
 Red lead . 1 
 
 Glue (in quantity sufficient 
 to cause the mass to ad- 
 here) 
 
 Wagner considers Wiederhold's composition the best. It has the following composi- 
 tion : 
 
 Potassium chlorate . 7'8 
 
 Lead hyposulphite . 2'6 
 
 Gum arabic . 1-0 
 
 The combustible composition ordered by the French Academy for making matches 
 used in barracks consists of 
 
 Potassium chlorate 90 parts 
 
 Acid potassium chromate 45 
 
 Lead peroxide 25 
 
 Bed lead . , 20 
 
 Crocus of antimony 
 
 Antimonous sulphide 
 
 Glass 
 
 Potassium ferrocyanide 
 
 Gum 
 
 Water 
 
 20 
 15 
 15 
 5 
 15 
 55 
 
 The composition requires somewhat strong friction for ignition, but lessens on that 
 account the danger of accidental ignition. 
 
 Jettel gives the following theoretical principles upon which the action of the non- 
 phosphorus matches depends: 1. The chi,pf active constituent is potassium chlorate, the 
 quantity of which varies between 40 and 92 per cent., but being generally over 60 per- 
 cent. 2. Most of these compositions contain from 10 to 40 per cent, of other oxidising 
 substances. 3. When sulphur is used, a quantity is taken equal to 25 per cent, of the 
 potassium chlorate employed. When metallic sulphides are used instead of sulphur, a 
 relatively greater quantity of them is required. 4. Powdered glass, sand, water, etc. 
 are added to moderate the force of the explosion. 5. The quantity of thickening 
 material employed is equal to about ^-^ of the amount of oxidising salts. If the 
 former be in too great excess, ignition is rendered difficult. 
 
 A not unimportant use of potassium chlorate is in calico-printing for producing 
 certain tints. For this purpose the dye is mixed with the required amount of potas- 
 sium chlorate, and laid -on the stuff, which latter is then exposed to a steam pressure of 
 3 or 4 atmospheres, so as to fix the colour. The potassium chlorate undergoes de- 
 composition in contact with the organic substances, and exercises an oxidising action 
 upon the colouring matter, so producing the desired changes. 
 
 Potassium chlorate is further very considerably used in chemical laboratories, in 
 
VARIETIES OF POTASH. 
 
 205 
 
 uio preparation of oxygen gas, for the oxidation of organic substances in toxicological 
 researches, and for oxidising metals, etc. 
 
 the prepat 
 researches 
 
 POTASSIUM CARBONATE (POTASH). 
 FORMULA K 2 C0 3 . MOLECULAR WEIGHT 138-2. 
 
 History. This substance was known and used in the earliest times in the form 
 of the ashes obtained by burning plants, and commonly called potash. The first 
 account of the preparation of potassium carbonate in a purer state is found in the 
 writings of Aristotle, who describes a salt, obtained in Umbria from the ashes of 
 reeds and rushes, which, from the properties ascribed to it, can have been nothing 
 else than potassium carbonate. Dioscorides also describes the alkaline properties of 
 the liquor obtained by lixiviating the ashes of plants with water, but he does not 
 mention the solid residue obtainable by evaporating the liquor. The same author 
 however describes the preparation and properties of potassium carbonate, obtained by 
 heating tartar to redness, but without indicating that it is identical with the substance 
 contained in the liquor obtained by lixiviating the ash of plants. The Komans used 
 potassium carbonate chiefly for medicinal purposes, and in preparing soap. At a later 
 period the Arabian chemist Geber, and also Albertus Magnus, Raymond Lully, 
 Glauber, and others, gave directions for preparing potash. Kunkel ascertained 
 that the salt obtained by lixiviating the ash of plants is identical with the salt 
 obtained by exposing tartar to a red heat ; before his time it was generally supposed 
 that the different materials yielded different alkalies. 
 
 Characters. Potassium carbonate is a colourless salt, very soluble in water; 
 it deliquesces upon exposure to the air, for which reason it requires to be kept in 
 well-closed vessels. It melts at a red heat. Potassium carbonate crystallises from its 
 aqueous solutions with 2 molecules of water. 
 
 Crude potash is generally contaminated with foreign ingredients, which vary in 
 nature and amount according to the materials from which it has been obtained, as may 
 be seen from the following table : 
 
 
 I. 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 VI. 
 
 VII. 
 
 VIII. 
 
 IX. 
 
 Potassium carbonate . 
 
 74-10 
 
 62.6 
 
 68-07 
 
 41-7 
 
 71-38 
 
 69-61 
 
 53-90 
 
 32-9 
 
 44-28 
 
 ,, hydrate . 
 
 
 
 
 
 
 
 49-6 
 
 
 
 
 
 
 
 
 
 
 
 Sodium carbonate 
 
 3-00 
 
 11-0 
 
 5-85 
 
 1-4 
 
 2-31 
 
 3-09 
 
 23-17 
 
 18-5 
 
 13-48 
 
 Potassium sulphate . 
 
 13-47 
 
 15-5 
 
 15-32 
 
 4-0 
 
 14-38 
 
 14-11 
 
 2.98 
 
 14-0 
 
 5-71 
 
 chloride . 
 
 0-95 
 
 4.0 
 
 8-15 
 
 2-0 
 
 3-64 
 
 2-09 
 
 19-69 
 
 16-0 
 
 18-86 
 
 Water . 
 Insoluble matters 
 
 7-28 
 1-20 
 
 "1 6-9 
 
 2-64 
 
 },3 
 
 4-56 
 2-73 
 
 8-82 
 2-28 
 
 0-26 
 
 1 18-6 
 
 4-00 
 13-50 
 
 I. and II. are potash, from Tuscany, analysed by Pesier. III. rock ash, from 
 America, analysed by Pesier. IV. pearl ash, analysed by F. Mayer. V. Russian 
 potash, by Pesier. VII. French potash, from molasses mud, analysed by Pesier. 
 VIII. potash from Magdeburg, analysed by Griineberg. IX. French potash (from 
 department de 1'Aisne), by Tissandier. 
 
 The following are the chief varieties of potash met with in commerce : 
 
 1. German Potash (Stassfurt). 1st quality, white, dry, and friable, dissolving 
 almost entirely in 4 parts of water, and containing about 90 per cent, of pure potas- 
 sium carbonate, with, at the most, 3 per cent, of soda. 
 
 2. The same, partially purified, almost colourless, crumbly, and friable, containing 
 at least 80 per cent, of potassium carbonate, and up to 6 per cent, of soda. 
 
 3. Elyrian Potash. White, dry, granular, containing at least 80 per cent, pure 
 potash and from 2-3 per cent, of soda. 
 
 4. American Potash. a. Pearlash, very fine quality, b. Rock ash, owing to its high 
 price less often met with than Nos. 1 and 2 ; contains about 74 per cent, pure poti 
 and almost always considerable quantities of caustic potash. 
 
 5. German and Moravian Beet Potash. Greyish white hard granules, leaving a 
 considerable residue when treated with 4 parts water ; contains from 70 to 75 percent, 
 of alkaline carbonate and caustic alkalies, of which from 12 to 18 per cent, is soda. 
 
 6. Russian Potash and Kasan ash. True wood ash. a. Granular powder of an un- 
 equal degree of hardness ; colour, partly greyish-white, partly dirty, sometimes green, 
 from the presence of potassium manganate, or reddish, from the presence of u 
 
 yields a considerable residue, even when treated with a large quantity of water. 
 
206 
 
 POTASSIUM. 
 
 quantity of -alkalies about 60 per cent. b. Sunflower ash, consists of granules and 
 powder of a greyish-white colour, more uniform than the previous sort ; leaves a con- 
 siderable residue when treated with water, and contains about 50 per cent, of 
 alkalies. 
 
 Preparation. Potassium carbonate is obtained from a number of very different 
 materials. The greatest quantity is still produced from wood and other plant ashes, as 
 well as from the residues of the molasses of beet sugar after distillation, wine, 
 lees, and various kinds of sea weed. It is also obtained from the suint of the wool 
 of sheep. Large quantities of potash have been recently prepared from potassium 
 sulphate by Leblanc's process; while, on the other hand, the preparation of potash from 
 feldspar and similar rocks has ceased to be of importance since the discovery of the 
 potash deposits at Stassfurt and Kalucz. Attempts have been made of late, but with- 
 out success, to prepare potassium carbonate direct from potassium chloride. 
 
 POTASH FROM WOOD ASHES. Plants contain potassium combined with different 
 acids, amongst which are a great number of vegetable acids that yield carbonic acid 
 when the plants are incinerated. Only a very insignificant portion of the potassium 
 carbonate found in the ashes of plants is contained in the plants as such before 
 incineration. 
 
 The amount of potassium carbonate yielded by the ashes of different plants varies 
 considerably. The following table by Hoss gives the total ash yielded by 1000 parts 
 of the undermentioned kinds of wood, and the corresponding amount of potassium 
 carbonate yielded by the ashes. 
 
 
 Ash. 
 
 Potash. 
 
 Pine 
 Beech 
 Ash 
 Oak . 
 
 3-4 
 5-8 
 12-2 
 13-5 
 
 0-45 
 1-27 
 0.74 
 1'50 
 
 Elm 
 
 25-5 
 
 3-90 
 
 Willow 
 Vine . ... . . * . V 
 
 28-0 
 34-0 
 
 2-85 
 5-50 
 
 Fern 
 
 36-4 
 
 97-4 
 
 4-25 
 73-00 
 
 Fumitory 
 
 219-0 
 
 79-00 
 
 The different parts of the same plant yield upon incineration an ash of different 
 quality, and consequently with a different percentage of potash. Thus Saussure ob- 
 tained from the ash from different parts of the oak the following relative proportions 
 of potash, the trunk wood being taken as unit : 
 
 Trunk wood 1 
 
 Leaves and bark 36 
 
 Bark 30 
 
 Branches freed from bark 29 
 
 Sap-wood 2 
 
 The ash of plants contains other salts besides potassium carbonate, especially 
 potassium sulphate and potassium silicate, together with considerable quantities of 
 carbonates, sulphates, phosphates, silicates, and chlorides of calcium and magnesium, as- 
 well as small quantities of the corresponding salts of sodium, and traces of ferric oxide 
 and manganese oxide ; also sand and clay, and a small quantity of unburnt organic 
 substance. 
 
 In preparing the ash, either entire trees or the leaves and twigs only are burnt, 
 according as the secondary object in view is to clear the land or to make use of the 
 wood. Woodashis obtained by burning the wood on the spot ; cinder ash is the 
 waste product obtained when wood is used as fuel. 
 
 Adulterations of the wood ashes with substances such as turf, brown coal, coal, etc., 
 are determined by the taste. The worth of an ash (in its potash contents) is generally 
 roughly determined by the taste. 
 
 Lixiviation of the Ash. The lixiviation of the ash has for its object the solution 
 of the potassium carbonates ; but a number of other substances are also dissolved 
 which render the potassium carbonate impure. Before the actual lixiviation, the ash 
 is either placed in steeping tubs, or spread upon a smooth floor sprinkled with water, 
 and stirred so as to secure an equal moistening of the whole. After this operation the 
 ash can be more tightly packed in the lixiviating vessels, and it is exposed for some 
 
MANUFACTURE OF POTASH. 
 
 207 
 
 time to the action of the atmosphere, by which means a portion of the dissolved 
 potassium silicate is converted into carbonate. 
 
 The lixiviating apparatus consists of three tubs, as represented by fig 131 with 
 perforated false bottoms (c) and outlet pipes (a). The perforated bottom is covered 
 with a layer of straw, upon which the moistened ash 
 is placed and stamped in; the space above the ash 
 (about one-third of the tub) is then filled with water. 
 The water, penetrating through the ash, dissolves out 
 the soluble constituents, and the solution flows out 
 through the outlet pipes below into settling tanks. 
 The ash is again treated with water, and the liquor 
 thus obtained is used for lixiviating fresh portions of 
 ash in the second tub. A third supply of water to the 
 first tub dissolves out the last traces of soluble con- 
 stituents, and the dilute liquor is used for the second 
 lixiviation of the second tub, then for the first lixivia- -p, 
 
 tion of a fresh quantity of ash in the third tub. After 
 three lixiviating operations the tubs are emptied and recharged with fresh ash. 
 
 Instead of tubs, square brickwork vessels may be used, perforated at the bottom, 
 three or four being placed together. 
 
 The undissolved residue in the lixiviating vessels consists essentially of calcium 
 carbonate, clay, and sand, together with considerable quantities of calcium phosphate 
 (according to Wolff about 11 per cent.), on account of which the residue forms a 
 valuable manure. 
 
 Boiling down the Liquor. This operation is carried out in a shallow cast-iron pan, 
 fresh liquor being constantly added in proportion as the water evaporates, until a drop 
 taken out and placed upon 
 a cool metal plate solidifies 
 to a crystalline mass ; the 
 fire is slackened, and the 
 gradually solidifying resi- 
 due in the pan is gently 
 heated to dryness. 
 
 In order to avoid the 
 adhesion of the potash to 
 the bottom of the pan 
 during the drying opera- 
 tion, the mass should be 
 well stirred. 
 
 In some works the 
 liquor is only evaporated 
 so far that, upon cooling, 
 potassium sulphate crystallises out, and then the mother liquor from the crystals is 
 evaporated to dryness. 
 
 The product obtained by the above operation is called raw or crude potash. It is 
 in most cases coloured brown by an admixture of organic substance, and it contains 
 about 20 per cent, of water. 
 
 Calcination of Crude Potash. The object of this operation is the removal of water 
 and organic substance. Care must, however, be taken to avoid heating the potash too 
 much, otherwise it may melt, and some of the organic substance become imbedded in the 
 mass so as to prevent its being burnt ; besides this, the melted potash would dissolve out 
 silicic acid from the hearth. The calcination is carried out in reverberatory furnaces 
 heated with wood, the flame passing over the potash from the furnaces (a a, fig. 132) 
 on both sides of the calcination hearth (c). At first the potash froths up owing to 
 escape of water ; it then becomes black from the separation of carbon, and finally, 
 when the organic substance is completely burnt, the potash assumes a white or 
 greyish-white colour. The mass is stirred at intervals during the operation so as to 
 secure uniform heating. 
 
 Formerly the calcination was carried out in iron pots, and on this account the 
 product was termed potash ; but with the present extensive consumption of potash 
 this plan would be too inconvenient. 
 
 EOCK ASH. This substance is imported from America, and in preparing it caustic 
 lime is added in the lixiviation of the ashes. In this way caustic potash is formed. 
 Owing to the facility with which caustic potash melts, the calcination of rock ash can- 
 not be carried out in reverberatory furnaces, and, therefore, the liquor is evaporated m 
 
 FIG. 132. 
 
208 POTASSIUM. 
 
 pans until a drop solidifies to a hard mass upon cooling, and then the concentrated 
 liquor is poured into iron boxes, where it solidifies. 
 
 PEARLASH. This substance, also imported from America, is prepared by lixiviating 
 ordinary crude potash with water, drawing off the liquor when clear, evaporating, 
 drying, and calcining. Since potash absorbs moisture from the air, it requires to be 
 packed in well-closed vessels. 
 
 POTASH FROM MOLASSES. Beet molasses contains a considerable amount of inorganic 
 salt, especially potash salts, which can be profitably extracted. The molasses is first 
 fermented, and its sugar converted into alcohol, which is distilled off. The residue, 
 after distillation, is then concentrated in the cooler part of a reverberatory furnace, 
 the hearth of which is. formed by an iron pan, and afterwards calcined in the hotter 
 part of the furnace. The mass thus obtained is of a dark colour, owing to the presence 
 of carbonised substance ; it contains about 25 per cent, of insoluble substance, and 75 
 per cent, of soluble salts, including 30 to 35 per cent, of potassium carbonate and 18 to 
 20 per cent, of potassium chloride. This mass is submitted to a methodical lixiviation, 
 and the liquor thus obtained is treated for potash either in the ordinary way by 
 evaporating, drying, and calcining, or by fractional evaporation and crystallisation, to 
 obtain potassium sulphate, a mixture of potassium sulphate and sodium carbonate, 
 besides potassium chloride, sodium carbonate, a double compound of soda and potash, 
 and lastly tolerably pure potash, by evaporating the mother liquor to dryness and 
 calcining. 
 
 At some places other methods are adopted for concentrating the residue from 
 distilled molasses ; thus, for instance, it is often heated by steam in wooden vessels, 
 or boiled down in iron pans, heated from below. 
 
 The molasses residue is often so strongly calcined that it has a white or greyish- 
 white appearance. The insoluble residue obtained after lixiviating the calcined mass 
 is used as manure. 
 
 POTASH FROM WINE LEES. The quantity of potash obtained from this source is very 
 insignificant. The residue obtained in preparing ' after wine ' (vide Wine) is dried, 
 calcined, and lixiviated, the lye thereby obtained being treated for potash in the 
 ordinary way. 
 
 POTASH FROM SEA- WEED. In treating sea-weed, for kelp or varec, salts are sepa- 
 rated which contain potassium carbonate. They only require lixiviation in order to 
 obtain from them a pure potash. 
 
 POTASH FROM SUINT. The greasy exudation from the skin of sheep contains a large 
 amount of potash salts, and the water used for washing wool is worth working for 
 potash salts. In localities where woollen manufactures are carried on, considerable 
 quantities of potassium sulphate and potassium carbonate are obtained from this 
 source. 
 
 For this purpose the wash water is evaporated to dryness, and the residue heated 
 in gas retorts ; the gas evolved is washed to separate ammonia, and is then used as 
 illuminating gas. The carbonaceous residue in the retorts is lixiviated, and the 
 liquor submitted to fractional evaporation and crystallisation, so as to obtain succes- 
 sively potassium sulphate, potassium chloride, and a mother liquor, which, when 
 evaporated to dryness and calcined, yields comparatively pure potash. 
 
 POTASH FROM POTASSIUM SULPHATE. The preparation of potassium carbonate in 
 this way is conducted in the same manner as the preparation of sodium carbonate by 
 Leblanc's method by heating it with carbon and chalk. The potassium sulphate is 
 first reduced to potassium sulphide, according to the equation : 
 
 K 2 S0 4 + 40 = K 2 S + 400. 
 
 The potassium sulphide then reacts upon the chalk, forming calcium sulphide, and 
 potassium carbonate, according to the equation : 
 
 KjS + CaC0 8 = CaS + K 2 C0 3 . 
 
 Owing to the volatility of potassium sulphide, its formation in this process in- 
 volves great loss of potash. 
 
 The insoluble residue left, after lixiviating the calcined mass, consists essentially 
 of calcium sulphide, from which the sulphur is recovered according to one of the 
 methods mentioned in a former chapter (vide page 100). 
 
 POTASH FROM SCHONITE. Schonite (K 2 S0 4 + MgS0 4 ) also admits of being treated 
 for potash according to Leblanc's method of preparing soda, and in all cases where 
 potassium sulphate is to be converted into potassium carbonate, the presence of some 
 schonite is advantageous, since the magnesia produced from the magnesium sulphide 
 renders the mass porous, and facilitates the lixiviation. 
 

 ACID POTASSIUM CARBONATE. 209 
 
 Many methods have been proposed for converting potassium chloride into car- 
 bonate ; but none of them have yet proved successful. 
 
 REFINING. One method of purifying crude potash consists in treating it with about 
 three-fourths of its weight of pure cold water. The more soluble constituents, such 
 as potassium carbonate and potassium hydrate, are thus dissolved, while the less 
 soluble, such as potassium sulphate, remain for the most part undissolved. The clear 
 solution drawn off and evaporated to dryness yields a residue consisting of tolerably 
 pure potassium carbonate, contaminated with small quantities only of potassium 
 chloride, silicate, and sulphate. 
 
 Another method consists in treating crude potash with two parts of water in an 
 iron cauldron, with the application of a gentle heat; then either filtering off or de- 
 canting the solution, and evaporating it until potassium sulphate crystallises on cooling. 
 The mother liquor is then decanted off and concentrated until potassium carbonate 
 separates in small crystals upon cooling. The mother liquor contains potassium 
 chloride and potassium silicate. This method affords a very pure potash. 
 
 In this country crude pearlash is refined for the preparation of flint glass by 
 mixing it with sawdust and calcining the mixturein a reverberatory furnace. The car- 
 bonic acid, formed by the combustion of the sawdust, converts the potassium hydrate 
 and potassium sulphide in the crude potash into potassium carbonate. The mass is 
 then lixiviated with cold water, the liquor left to settle, the residue drawn off, 
 again evaporated to dryness, and the residue calcined in a reverberatory furnace. The 
 calcined mass is again lixiviated, the liquor evaporated to dryness, and the residue 
 calcined as before. The calcined product of this operation is once more lixiviated, the 
 liquor concentrated by evaporation until potassium sulphate crystallises out; the 
 mother liquor is then further concentrated until fine crystals of potassium carbonate 
 separate on cooling. The crystals are removed from the mother liquor, and consist of 
 very pure potash. 
 
 The value of crude potash is dependent upon the amount of potassium carbonate 
 and caustic potash it contains. For certain purposes, however, the other constituents 
 of crude potash are not without value. Thus, for instance, in the manufacture of alum 
 both potassium chloride and potassium sulphate are used. 
 
 Uses. Although the use of potash for industrial purposes is in many cases 
 supplanted by the cheaper substance soda, it still finds extensive employment. 
 
 Potassium carbonate is used in the manufacture of potassium nitrate, Bohemian 
 glass, for preparing smalt, alum, potassium cyanide and chlorate, as well as other 
 potassium salts ; it is also used as a manure, and in dye and bleaching works, etc. 
 
 ACID POTASSIUM CARBONATE. 
 
 FORMULA KHC0 3 . MOLECULAR WEIGHT 100-1. 
 
 This salt, commonly called potassium bicarbonate, is a white crystalline substance 
 very much less soluble in water than the normal carbonate, as shown by the following 
 table by Poggiale : 
 
 100 parts of water at dissolve 19-61 parts of the salt. 
 10 23-33 
 50 37-92 
 70 45-24 
 
 The solution does not materially affect the colour of red litmus or turmeric paper. 
 The crystals are rhomboidal prisms. They are anhydrous ; by heat the salt is decom- 
 posed, giving off water and carbonic dioxide ; this decomposition taking place 
 extent even when a solution of the salt is boiled. t 
 
 Acid potassium carbonate is prepared by passing carbonic dioxide into a sc 
 of potassium carbonate in water ; it is used chiefly for medicinal purposes. 
 
 POTASSIUM SULPHATE. 
 
 FOBMULA K 2 S0 4 . MOLECULAB WEIGHT 174-2. 
 
 Characters.-Potassium sulphate crystallises in four-sided prisms or *"&** 
 sided pyramids belonging to the trimetric system. It is sparingly soluble ni cold water 
 rather more so in hot water, and it is quite insoluble in alcohol The 
 alcohol to an aqueous solution of potassium sulphate causes th 
 
210 POTASSIUM. 
 
 of the salt. Potassium sulphate is remarkable for the facility with which it combines 
 with other s\ilphates to form double salts. A few of these double sulphates occur naturally, 
 as, for instance, polyhalite, kainite, and schonit e, found at Stassfurt. Nearlyall 
 soluble sulphates form double salts with potassium sulphate. 
 
 Preparation. The conversion of potassium chloride into sulphate by means of 
 sulphuric acid has been largely carried out of late years. The process is similar to 
 Leblanc's soda process. Potassium chloride is placed in a sulphate furnace, and covered 
 with sulphuric acid, the escaping hydrochloric acid being condensed and collected. The 
 potassium sulphate is then generally converted into carbonate by Leblanc's method. 
 
 According to Griineberg's method of preparing potassium sulphate from potassium 
 chloride and artificial schonite, potassium chloride and kieserite are first dissolved 
 together in hot water ; the change that takes place is represented by the following 
 equation : 
 
 Kieserite Schonite Carnallite 
 
 3KC1 + 2MgS0 4 = MgS0 4 + K^SO, + (KC1 + MgCl 2 ). 
 
 The liquor is then submitted to a process of fractional crystallisation, so as to 
 separate the schonite from the carnallite. The schonite is then dissolved in hot water, 
 the solution brought to a concentration corresponding to sp.gr. 1-321, and poured over 
 finely sifted potassium chloride, with which it is allowed to remain in contact, until 
 the temperature has sunk to 40. At this point the greater part of the potassium 
 chloride is converted into sulphate, according to the equation : 
 
 Schonite Carnallite 
 
 3KC1 + MgS0 4 + K0 4 = 2K 2 S0 4 + (KC1 + MgCl 2 ). 
 
 The mother liquor poured off from the potassium sulphate yields a further crop of 
 this salt, when cooled to a lower temperature, and by concentration it yields first 
 schonite and then carnallite. The potassium sulphate thus obtained is freed from 
 mother liquor by means of a centrifugal machine, and is then very pure (95 per 
 cent.) 
 
 Griineberg also treats schonite with a cold solution of potassium chloride of sp. gr. 
 1-160, by pouring and re-pouring the cold solution over the schonite, until the potassium 
 chloride has been almost entirely converted into potassium sulphate. The liquor then 
 contains chiefly carnallite, schonite, and potassium chloride, which are extracted by 
 evaporation and fractional crystallisation. 
 
 Potassium sulphate is obtained in considerable quantities as a by-product in the 
 preparation of a number of salts, as in the treatment of the mother liquors obtained in 
 the preparation of common salt from sea water and brine springs (see Sodium Chloride) ; 
 in the preparation of iodine (page 181) ; in the preparation of potash from the ashes of 
 plants ; in the preparation of nitric acid from potassium nitrate and sulphuric acid 
 (page 45), etc. 
 
 Potassium sulphate has also of late been obtained from kainite, by treating it with 
 water, which decomposes it into magnesium chloride and schonite; the schonite 
 crystallises out, and is treated for potassium sulphate, according to one or other of the 
 methods above given. 
 
 Uses. Potassium sulphate is considerably used as a manure, also in alum and glass 
 works. A recent application of the salt consists in treating it for potash by Leblanc's 
 method. 
 
 ACID POTASSIUM SULPHATE. 
 
 FORMULA KHS0 4 . MOLECULAR WEIGHT 136-1. 
 
 This salt is commonly called potassium bisulphate, and is intermediate in compo- 
 sition between potassium sulphate and hydric sulphate; it melts at 197, dissolves in 
 twice its weight of cold water and in half its weight of water at 1 00 ; the crystals have 
 the form of flattened rhombic prisms and are anhydrous. At a high temperature water 
 is given off and then sulphuric oxide, leaving neutral potassium sulphate. Acid potas- 
 sium sulphate is often obtained as a by-product in chemical operations, and it is used 
 sometimes as a flux in cases where the action of an acid oxide at a high temperature 
 is required, as in the decomposition of some aluminous minerals for analytical 
 purposes. 
 
POTASSIUM TARTRATE AND OXALATE. 211 
 
 ACID POTASSIUM TARTRATE, 
 
 FORMULA KHC 4 H 4 6 . MOLECULAR WEIGHT 188-1. 
 
 This salt, which is known in the purified state as potassium bitartrate or cream 
 of tartar, occurs in commerce in an impure form as tartar or argol, the latter con- 
 sisting of the crystalline crust deposited from grape juice during its fermentation, upon 
 the sides of the vats or wells in which the process takes place, while the former is 
 produced from it by extraction with hot water and crystallisation. 
 
 Argol exhibits a wide range of composition, the amount of tartaric acid ranging, 
 according to Warington, from 40 to 70 per cent. Pure bitartrate contains 79*7 per 
 cent, tartaric acid. Argol often contains small particles of sulphur, which originate 
 from the sulphuring of the casks. 
 
 Tartar contains from 70 to 77 percent, of tartaric acid, and, according to Waring- 
 ton, from T5 to 44'5 of this exists in the state of calcium tartrate in the best kinds of 
 tartar, which come from Southern Italy and Messina. According to Scheurer-Kestner, 
 some kinds of French and Hungarian tartar contain calcium tartrate in much larger 
 amount, as much as 46 per cent. Tartar of inferior quality contains, besides potassium 
 bitartrate and calcium tartrate, small amounts of carbonates, sulphates, phosphates, 
 and silicates, together with organic substances. 
 
 The purified salt as usually met with forms colourless crystalline masses ; it is but 
 slightly soluble in water, requiring 240 times its weight of cold water and 15 parts of 
 boiling water for solution ; it is insoluble in alcohol, and its solubility in water is re- 
 
 : duced by the presence of a small amount of alcohol. It is on this account that the 
 salt is deposited from grape juice, as in the process of fermentation the sugar it contains 
 is converted into alcohol. 
 
 Uses. Potassium bitartrate is frequently used as a mordant in dyeing wool and 
 for preparing pure potassium carbonate ; when mixed with alum and chalk it forms a 
 
 | good powder for cleaning plate. Black flux, consisting of potassium carbonate 
 
 ! mixed with carbon, is prepared by heating the bitartrate to redness in a close crucible. 
 
 [ White flux, consisting of potassium carbonate, is obtained by igniting a mixture of 
 
 j the bitartrate and potassium nitrate. 
 
 .* .""'.I 'I-'; :' 
 
 ACID POTASSIUM: OXAI.ATE. 
 
 FORMULA KHC 2 4 . MOLECULAR WEIGHT 128'1. 
 
 This salt, which is commonly called Salt of Sorrel, occurs in the juice of various 
 species of Eumex and Oxalis ; it is obtained either by crystallisation from the clarified 
 juice of these plants, or by partially neutralising oxalic acid with potassium carbonate. 
 It forms transparent crystals containing one molecule of water of crystallisation ; it has 
 a sour taste, and is sparingly soluble in water, requiring 14 times its weight of cold 
 water and 4 parts of boiling water. 
 
 Acid potassium oxalate is used for scouring metals and for removing ink stains or 
 iron mould, its action in this case being due to the formation of a double potassium 
 and iron oxalate, which is soluble in water. 
 
 Another salt, containing a larger proportion of oxalic acid, is sometimes met with 
 in commerce as salt of sorrel ; it is a tctroxalate or quadroxalate, the composition of 
 which is represented by the formula KE 3 . 2C 2 4 . 2aq. 
 
 POTASSIUM NITRATE (SAX.TPETHE). 
 FOEMULA KN0 3 . MOLECULAR WEIGHT 101-1. 
 
 History. The salt which the Greeks and Eomans called ' nitrum ' was in all 
 probability potassium carbonate, and not potassium nitrate, as was at one time sup- 
 posed. The earliest accounts of saltpetre are of more recent date. In the eight 
 century mention is made by Geber of a salt, sal petrae ' which was probably ordmary 
 saltpetre, Magnus Grsecus, to whom we are indebted for the first account of the pre 
 paration of gunpowder, must also have been acquainted with this salt. It was men- 
 tioned later on in the thirteenth and fourteenth centuries, generally under the name 
 of nitrum, in the writings of Albertus Magnus, Roger Bacon and Raymond Lily 
 Boyle, in 1667, was the first to state that saltpetre contains fixed alkali 
 
 acid. 
 
 r 2 
 
212 
 
 POTASSIUM. 
 
 Occurrence. Saltpetre occurs naturally in considerable quantities. It is often 
 found as an efflorescence upon the surface of the ground, as in the neighbourhood of 
 the Ganges in India, in the island of Ceylon, in Peru, Chili, Egypt, Persia, Hungary, 
 etc. The :rust of salt, which is often as much as in. in thickness, is generally formed 
 after the rainy season is over. In other districts, saltpetre is found at some distance 
 below the surface of- the earth, in layers of varying thickness, mixed with clay and 
 other impurities. Saltpetre is also found in caves, as in Ceylon, in Kentucky, in 
 North America, in Apulia, in Naples, etc. Saltpetre occurs in small quantities in 
 Germany, in the red sandstone near Gottingen, in the Tuff kalk caves near Wiirzburg ; 
 it is found in France, in the chalk at Roche-Guyon, Angouleme, etc. ; in Portugal near 
 Lisbon ; and in Russia in the Ukraine. 
 
 Composition and Properties. The composition of potassium nitrate is repre- 
 sented by the formula - f 0. It is often called prismatic saltpetre or potash salt- 
 petre, to distinguish it from cubic or Chili saltpetre, which is sodium nitrate. Potas- 
 sium nitrate crystallises in long six-sided prisms belonging to the trimetric system. 
 The crystals often contain cavities filled with mother liquor, which renders the salt- 
 petre impure. Potassium nitrate possesses a strong saline and cooling taste. When 
 gently heated it melts to a mobile liquid, which solidifies on cooling. A stronger 
 heat causes decomposition ; oxygen is evolved, and potassium nitrite remains. The 
 application of a still stronger heat causes decomposition of the potassium nitrite, 
 nitrogen and oxygen escaping, while a mixture of potash and potassium peroxide 
 remains behind. Potassium nitrate is not very soluble in water at the ordinary 
 temperature ; but its solubility increases very rapidly with rise of temperature. 
 According to Gay-Lussac the solubility of this salt in 100 parts of water at different 
 temperatures is as follows : 
 
 At 13-32 parts 
 
 ll-67 22-23 
 
 24-94 38-40 
 
 45-10. ...... 74-66 
 
 65'45 125-42 
 
 97'66 236-45 
 
 The following table by Gerlach shows the relation between the percentage of 
 saltpetre in aqueous solutions of the salt, at a temperature of 15, and the specific 
 gravity of such solutions : 
 
 Specific Gravity 
 
 Percentage of Saltpetre 
 
 Specific Gravity 
 
 Percentage of Saltpetre 
 
 1-00641 
 
 1 
 
 1-07905 
 
 12 
 
 1-01283 
 
 2 
 
 1-08595 
 
 13 
 
 1-01924 
 
 3 
 
 1-09286 
 
 14 
 
 1-02566 
 
 4 
 
 1-09977 
 
 15 
 
 1-03207 
 
 5 
 
 1-10701 
 
 16 
 
 1-03870 
 
 6 
 
 1-11426 
 
 17 
 
 1-04534 
 
 7 
 
 1-12150 
 
 18 
 
 1-05197 
 
 8 
 
 1-12875 
 
 19 
 
 1-05861 
 
 9 
 
 1-13599 
 
 20 
 
 1-06524 
 
 10 
 
 1-14361 
 
 21 
 
 1-07215 
 
 11 
 
 1-14427 
 
 21-074 
 
 Heated with other bodies, saltpetre exerts upon them a powerful oxidising action ; 
 carbon is oxidised to carbonic acid, sulphur to sulphuric acid, and most of the metals 
 to their respective oxides, etc. 
 
 Preparation. Saltpetre is obtained in three ways : o, by lixiviation of thoenvth 
 containing naturally formed saltpetre ; /8, by means of nitre plantations; 7, by decom- 
 posing Chili saltpetre with potassium chloride. 
 
 NATURAL SALTPETRE. The method adopted for the treatment varies with the 
 district where it is found. In India the saltpetre earth is made up into large heaps, 
 where, under constant stirring of the mass, it is exposed for some time to the action of 
 the air, the heaps being protected by sheds during the rainy season. After the earth 
 has lain sufficiently long, it is brought into macerating vessels, where it is treated with 
 water, and after a few hours the lye is drawn off, allowed to clear in large basins, 
 and then evaporated in suitable pans until a crust of saltpetre forms on the surface. 
 
PREPARATION OF SALTPETRE. 213 
 
 The lye is then drawn off into shallow crystallising vessels, where it deposits crystals 
 of crude saltpetre. 
 
 The same method is adopted in Egypt, Persia, and South America. 
 
 Saltpetre occurs in Ceylon in caves situated in a rock consisting chiefly of dolomite 
 mixed with felspar, quartz, and mica. To obtain the saltpetre the rock is excavated 
 from the sides of the caves, broken up, and mixed with wood ashes, and the mixture 
 lixiviated. Crude saltpetre is then obtained by evaporating the lye thus obtained, 
 and allowing it to crystallise in earthen pots. The addition of wood ashes is intended 
 to convert the magnesium nitrate into potassium nitrate by means of the potassium 
 carbonate contained in them. 
 
 In Hungary, at Nagy-kallo, Nyiregyhaza, Debreczin, etc., the saltpetre earth ig 
 scraped together with a kind of spade, or by means of a peculiarly constructed plough, 
 the saltpetre being then obtained by lixiviation and evaporation of the lye. 
 
 The amount of saltpetre contained in the different saltpetre earths varies con- 
 siderably. Saltpetre earth from Tirhoot in Bengal contains from 8 to 9 per cent, of 
 potassium nitrate, and from 3 to 4 per cent, of calcium nitrate. The saltpetre rock of 
 Ceylon contains, according to J. Davy, 2'4 per cent, of potassium nitrate, and 07 per 
 cent, of magnesium nitrate. Ragsky's analyses of the saltpetre earths of Hungary 
 represent the latter as containing from \ to 2 per cent of potassium nitrate. 
 
 PLANTATIONS. This method of preparing saltpetre was formerly far more 
 general than at the present time, it having been found that the importation of 
 naturally formed saltpetre, as well as the manufacture of potassium nitrate by con- 
 version from Chili saltpetre, are cheaper sources. 
 
 Theory of the formation of Saltpetre. The formation of nitric acid takes place 
 when decaying animal substances are exposed to the action of moisture and atmo- 
 spheric air in contact with materials containing much potash or carbonate, of lime for 
 instance, marl, old building rubbish, road scrapings, etc., or vegetable substances con- 
 taining potash, such as the leaves and stems of the potato, beet, sunflower, nettles, 
 etc. By the decay of the animal substances, ammonia is first formed, and this is 
 gradually oxidised. In saltpetre plantations these materials are arranged in ridges 
 or heaps of a pyramidal shape, exposed in all directions to the action of atmo- 
 spheric air, the circulation of which is promoted by layers of straw. The heaps are pro- 
 tected from rain by roofs. The ground upon which these heaps are built is first 
 covered with clay well rammed down, so as to prevent nitrates from being washed 
 away by the penetration of water. The heap is watered at intervals with lant (stale 
 urine), which affords a supply of nitrogenous material as well as water. These heaps 
 are generally allowed to remain at rest for a period varying from one to three years. 
 Tests are made from time to time to ascertain the point of ripening, when the 
 formation of saltpetre is at an end, A cubic foot of the earth ought to yield about 
 2 ozs. of saltpetre. 
 
 Preparation of the Crude Lye. The ripe earth is broken up with mallets or hammers, 
 and after being sifted to separate lumps, the finely divided earth is lixiviated in 
 such a manner that dilute solutions obtained from portions of earth that have already 
 been once washed are used for lixiviating fresh portions of earth. The lixiviating 
 vessels are either tubs with perforated false bottoms upon which the earth is strewn, 
 or shallow wooden boxes widening towards their upper part, and furnished near the 
 bottom with lateral holes for running off the lye. The holes can be closed with plugs, 
 and to prevent their being stopped by pieces of earth, they are protected internally 
 with perforated boards. Two of these vessels are placed side by side, and when filled 
 with earth, water, in quantity equal to half the volume of earth, is poured in, so as 
 just to cover the earth. After about twenty-four hours the lye is drawn off by re- 
 moving the plugs, and the residue in the lixiviating vessel is treated with afresh 
 quantity of water, the lye from this second lixiviation (if it does not contain over 
 ten per cent, of saltpetre) being used for lixiviating fresh portions of earth. A third 
 lixiviation of a quantity of earth yields a lye which is also employed for the lixiviation 
 of frosh portions of earth. 
 
 Other kinds of lixiviating apparatus, such as those used in alkali works, may be 
 very conveniently used for the lixiviation of saltpetre. 
 
 Breaking the Raw Lye. Since in the construction of saltpetre plantations calcium 
 carbonate is nearly always the material used for supplying the base, the nitric acid in 
 the raw lye is to a great extent in combination with calcium. Besides calcium nitrate, the 
 lye contains magnesium and potassium nitrates, as well as small quantities of calcium, 
 magnesium and potassium chlorides, together with organic substances and salts 
 ammonia. The conversion of the calcium or magnesium nitrate into the correspond- 
 ing potassium salt is an operation termed technically breaking the lye. For this 
 purpose potassium carbonate or potash is added to the lye, which re-acts With the 
 
214 
 
 POTASSIUM. 
 
 calcium nitrate, forming insoluble calcium carbonate and potassium nitrate, according 
 to the following equation : 
 
 Ca2N0 3 + K 2 C0 3 = CaC0 3 + 2KN0 3 . 
 
 Magnesium nitrate is likewise decomposed in a similar manner, while the calcium 
 and magnesium chlorides of the crude lye yield, with potassium carbonate, potassium 
 chloride and the carbonates of calcium and magnesium respectively. 
 
 The operation is carried out as follows. A small quantity of potash is dissolved 
 in double the quantity of water, and a measured quantity of the raw lye is treated 
 with this solution until all the calcium and magnesium are precipitated. From the 
 quantity of potash solution required in this test, the quantity required for the whole 
 of the crude lye is calculated, and mixed with the lye in large wooden tubs. After 
 standing a short time the precipitate settles, and the clear lye above is drawn off by 
 taking out plugs at different heights along the sides of the tubs. 
 
 Other materials used in the place of potash for breaking the lye are potassium 
 sulphate, potassium chloride, and sodium sulphate. In this case, however, the mag- 
 nesium salts contained in the crude lye are decomposed before adding the potash salt, 
 by the addition of milk of lime, which throws down magnesia as a precipitate. The 
 calcium is then precipitated as sulphate. 
 
 In the next operation of boiling down, the lye is concentrated to such an extent that 
 the potassium and sodium chlorides separate for the most part from the hot solution, 
 while the crude saltpetre crystallises out on allowing the lye to cool. 
 
 Fig. 133 represents an apparatus for boiling down the crude lye. The lye is 
 
 brought into the hemispherical pan BB' 
 and heated to the boiling point by means 
 of a fire A. The hot air from the fire plays 
 first of all upon the bottom of the pan, 
 then passes round it and underneath 
 another pan, where the lye is heated, and 
 escapes eventually into a chimney. In 
 some places the flue gas is made to heat a 
 pan for drying the saltpetre. When the 
 crude lye begins to boil, the previously dis- 
 solved calcium carbonate or sulphate are 
 first separated, the particles suspended in 
 the liquid being carried upwards at the 
 sides by the boiling motion of the liquid, 
 and falling to the bottom in the middle of 
 the vessel. In order to prevent this pre- 
 cipitate from adhering to the bottom of the 
 pan, as well as for the convenience of re- 
 moving it, a cullender (c), supported by a chain (d) running over pulleys (d 1 d 1 '), is placed 
 at the bottom of the pan ; this catches the precipitate, and is occasionally drawn out 
 and emptied upon a strainer (//')> which allows the adherent lye to flow back into the 
 evaporating pan. The scum formed during the boiling down is due to organic sub- 
 stances; this is removed by means of a perforated ladle. Further boiling down 
 causes separation of the potassium and sodium chlorides that are collected apart. 
 In spite of the care taken in allowing the adherent mother liquor to drain back 
 into the pan from the first precipitates, they still retain considerable quantities of 
 saltpetre. They are therefore placed in baskets and immersed in boiling water, this 
 operation being repeated with fresh portions until a lye is obtained saturated with 
 saltpetre, from which saltpetre crystallises out upon cooling. In proportion as the 
 crude saltpetre lye evaporates, new portions of lye are run in, until the further forma- 
 tion of cubic crystals of the chlorides of potassium and sodium ceases, and a fine 
 crystalline film of saltpetre is formed. A portion of the lye tested at this point by 
 dropping it upon a cold surface, solidifies at once. 
 
 When this point is reached the lye is run off into large settling vats, where it is 
 allowed to remain about six hours, in order to deposit all suspended impurities. 
 When the temperature of the mass has cooled down to 60 the clear lye is drawn off 
 into crystallising vessels, where it cools in about a couple of days, and the crude salt- 
 petre crystallises out. The mother liquor, separated from the salt, is returned to the 
 evaporating pans, but eventually it becomes so concentrated and contains so large an 
 amount of foreign salts, and is so much coloured with organic substances, that it is 
 either thrown away or added to the saltpetre earth. 
 
 According to the purpose for which saltpetre is to be used it is crystallised in 
 large or small crystals. When required for the manufacture of nitric acid, it is m;ide 
 to crystallise in a very minute state of division, by continually stirring the hot lye 
 
 FIG. 133. 
 
REFINING OF SALTPETRE. 215 
 
 during crystallisation ; but when it is required for subsequent refining, crystallisation 
 is allowed to go on slowly, so that large crystals may be obtained. 
 
 Crude saltpetre may contain as much as twenty-five per cent, of impurities, amongst 
 which the potassium and sodium chlorides constitute an important part ; it also con- 
 tains small quantities of sodium, calcium, and magnesium sulphates, together with a 
 small quantity of organic matter. 
 
 Hefining of Crude Saltpetre. In order to separate impurities, the crude saltpetre 
 is placed in large iron or copper vessels, and dissolved with the application of a 
 moderate heat in about half its weight of water. This solution is made to boil, and 
 a further addition is then made of one-and-a-half times as much more raw saltpetre. 
 The water present suffices for the complete solution of all the potassium nitrate, but 
 leaves a considerable quantity of the comparatively less soluble potassium and sodium 
 chlorides undissolved, which is removed with perforated ladles, while at the same 
 time the organic scum is skimmed off. When calcium and magnesium salts are present, 
 they are got rid of by adding to the lye a sufficient quantity of potassium carbonate. 
 The complete removal of organic matter is effected by diluting the lye with about 
 half its volume of water, and adding a hot solution of glue. A fresh scum is thus 
 formed containing all the organic substance combined with gelatin, and this is skim- 
 med off. When the formation of scum has entirely ceased, the lye is left at rest for 
 about twenty-four hours, after which time it will have cooled down to about 90, 
 and become clear. It is then drawn off into shallow cast-iron crystallising 
 vessels, the bottoms of which slope towards the centre. The liquid is constantly 
 stirred while cooling, so that very small crystals may be formed (saltpetre flour), 
 which are purer than large crystals, since they do not contain enclosed mother liquor. 
 The saltpetre flour is raked out as soon as formed, and the mother liquor is 
 drawn off from the centre of the pans, and used for dissolving fresh portions of crude 
 saltpetre. 
 
 Washing the Saltpetre Flour. The object of this operation is to remove from the 
 crystals adhering mother liquor, as well as to effect the solution and removal of any 
 chlorides separated with the saltpetre. For this purpose wooden washing vats are 
 employed about 10 feet long and 3 feet wide, narrower at the bottom than at 
 the top. They are furnished with a perforated bottom upon which the saltpetre flour 
 is placed, and covered with a concentrated solution of pure saltpetre, with which it 
 is allowed to remain in contact for three hours. The liquor is then drawn off, and 
 the saltpetre washed with an equal quantity of water, the operation of washing with 
 a solution of pure saltpetre and then with water being repeated twice or more until 
 a portion of the wash liquor when tested ceases to give a perceptible precipitate with 
 silver nitrate. The first portions of wash liquor are used for dissolving fresh portions 
 of raw saltpetre, the last purer portions for treating fresh quantities ef saltpetre 
 flour. The saltpetre flour, after having been in this way rendered perfectly pure, is 
 allowed to remain a few days still in the washing tanks, after which it is taken out 
 and dried. 
 
 Drying the Saltpetre. The drying of the saltpetre is effected in various ways. It 
 is sometimes dried in pans at a moderate temperature, sometimes in a current of hot 
 air upon drying tables covered with linen. In some places the saltpetre is melted and 
 cast into sticks or blocks. Occasionally it is again dissolved in water and converted 
 into large crystals by a process of slow crystallisation. 
 
 The loss sustained by refining amounts to about 25 per cent, of the total quantity 
 of potassium nitrate contained in the raw saltpetre. 
 
 Hefining of Indian Saltpetre. The method of refining the crude saltpetre from 
 India is essentially the same as that just described ; the loss is, however, not more 
 than from 5 to 7 per cent., since the raw material is less impure. 
 
 PREPARATION OF POTASSIUM NITRATE FROM CHILI SALTPETRE. The conversion 
 of Chili saltpetre or sodium nitrate into the corresponding potassium salt depends 
 upon the fact that concentrated solutions of potassium chloride and sodium nitrs 
 mutually decompose when heated, forming sodium chloride and potassium nitrate 
 according to the equation : 
 
 KC1 + NaNO g = KN0 8 + NaCl. 
 
 The operation is carried out as follows: An aqueous solution of potassium chloride 
 is prepared of a specific gravity of 1'200 to 1-210 in a large cast-iron cauld 
 about 880 gallons, and mixed with an equivalent quantity of Chili saltpetre; the 
 whole being heated until the lye has a specific gravity of 1 '500. In e^ mating the 
 quantities of the respective salts, it must be remembered that commerc 
 petre does not contain more than from 90 to 96 per cent, of sodium nitrate, and that 
 
216 POTASSIUM. 
 
 commercial potassium chloride, according to the source from which it is obtained, con- 
 tains only from 60 to 96 per cent, of potassium chloride. The sodium chloride separated 
 during the boiling of the lye is removed either with rakes or cullenders and placed 
 to drain in a wooden strainer above the boiling pan. The crystals of sodium chloride 
 are washed with a small quantity of water, which is also allowed to run back into the 
 boiling pan. As soon as the lye shows a specific gravity of T500, it is allowed to 
 stand a short time to get clear, and is then run into shallow crystallising vessels, 
 where the crystallisation is generally complete in about twenty-four hours. During 
 the crystallisation the whole is stirred so as to obtain very small crystals. When the 
 crystallisation is complete the mother liquor is drawn off and the crystals placed in 
 wooden tanks furnished with perforated false bottoms, where they are just covered 
 with water and allowed to remain thus for about eight hours. The lye thereby formed, 
 containing the greater part of the impurities present in the saltpetre, such as sodium 
 chloride, sodium nitrate, potassium chloride, etc., is drawn off, this operation being 
 repeated once or twice, according to the degree of purity required for the saltpetre. 
 The mother and wash liquors are used for dissolving fresh portions of potassium 
 chloride. 
 
 Wollner's Method. According to this method Chili saltpetre is converted into 
 potassium nitrate by means of potassium carbonate. Solutions of Chili saltpetre and 
 potassium carbonate, each of a concentration of sp. gr. 1-380, are allowed to flow 
 in the requisite proportions into large metal pans, where the liquor is heated till it 
 has a specific gravity of 1'462 to 1'490. The sodium carbonate, which continually 
 separates, together with much sodium nitrate, during the heating, is removed and placed 
 in filtering boxes consisting of sheet-iron cylinders, with perforated false bottoms. 
 These cylinders admit of being hermetically closed, and they are furnished at the upper 
 part with cocks for admitting steam, while at the lower part there are taps for running 
 off the lye. Upon passing steam into the cylinders filled with sodium carbonate con- 
 taining sodium nitrate, both salts are dissolved, but the potassium nitrate solution 
 being specifically heavier than the solution of sodium carbonate, in the proportion of 
 sp. gr. T462 or 1*490 to sp. gr. 1/299, sinks to the bottom of the cylinder, and is 
 drawn off first, the soda lye afterwards. The lye, containing potassium nitrate, is 
 run back into the boiling pan, and this operation is continued until pure potassium 
 nitrate crystallises out upon cooling the lye, for which purpose it is drawn off into 
 crystallising vessels. 
 
 A modification of the above process consists in treating the sodium carbonate 
 resulting from the decomposition of sodium nitrate and potassium carbonate with 
 hydrate of calcium before the separation, whereby the soda is converted into caustic 
 soda, and the calcium carbonate thereby formed settles at the bottom of the vessel as 
 an insoluble precipitate. The lye is drawn off from the latter and evaporated, where- 
 upon saltpetre crystallises out, and caustic soda remains dissolved, which is then 
 obtained by further evaporation. 
 
 Chili saltpetre may be also converted into ordinary saltpetre by treating it with 
 caustic potash, whereby caustic soda is obtained as a by-product. Another method 
 consists in treating soda saltpetre with a solution of barium chloride, so as to form 
 barium nitrate, which is sparingly soluble, and is precipitated in a very pure state. 
 By treating the barium nitrate with potassium sulphate, insoluble barium sulphate is 
 formed, and the lye contains potassium nitrate. 
 
 TESTING OF POTASSIUM NITRATE. In testing commercial saltpetre the chief thing 
 to be ascertained is the percentage of pure potassium nitrate. The actual impurities 
 are determined in the ordinary analytical way. 
 
 Austrian Saltpetre Test. This test was introduced by Huss, and is based upon the 
 fact that a definite quantity of water, at different temperatures, dissolves a definite 
 quantity of potassium nitrate ; and, further, that the quantity dissolved is in no way 
 influenced by the presence of sodium or potassium chloride. Therefore, on dissolving 
 a known quantity of saltpetre in a known quantity of water, potassium nitrate will 
 crystallise out of the solution immediately the temperature is reduced below the 
 point at which the potassium nitrate contained in the saltpetre sample forms a satu- 
 rated solution with the water employed. 
 
 In making this test 40 parts of saltpetre are dissolved in 100 parts of water, at a 
 temperature of 57 the water evaporated during the process of dissolving being replaced ; 
 the solution is filtered off, and the vessel containing the filtrate is placed in cold water, 
 the temperature at 'which potassium nitrate begins to separate being ascertained by 
 ine;ins of a very delicate thermometer. 
 
 By reference to the following table constructed by Huss, the quantity of pure salt- 
 petre thnt is dissolved in 100 parts <>f water maybe rend off. or the percentage of 
 pure potassium nitrate contained in the sample of crude saltpetre tested. 
 
TESTING OF SALTPETRE. 
 
 217 
 
 Temperature at 
 which the crys- 
 tals begin to 
 form 
 
 Amount of Po- 
 tassium Nitrate 
 dissolved in 100 
 parts of water 
 
 Percentage of 
 Potassium 
 Nitrate in the 
 crude Saltpetre 
 
 Temperature at 
 which the crys- 
 tals begin to 
 form 
 
 Amount of Po- 
 tassium Nitrate 
 dissolved in 100 
 parts of water 
 
 Percentage of 
 Potassium 
 Nitrate in the 
 crude Saltpetre 
 
 io-oo 
 
 22-27 
 
 55-7 
 
 18-12 
 
 30-36 
 
 75-9 
 
 10-62 
 
 22-80 
 
 57'0 
 
 18-75 
 
 31-09 
 
 77-7 
 
 ll-25 
 
 23-36 
 
 58-4 
 
 19-37 
 
 31-83 
 
 79-6 
 
 1 1 -87 
 
 23'92 
 
 59-8 
 
 20-00 
 
 32-50 
 
 81-5 
 
 12-50 
 
 24-51 
 
 61-3 
 
 20-62 
 
 33-36 
 
 83-4 
 
 13-12 
 
 25-12 
 
 62-8 
 
 21-25 
 
 34-15 
 
 85-4 
 
 13-75 
 
 25-71 
 
 64-3 
 
 21-87 
 
 34-96 
 
 87-4 
 
 14-37 
 
 26-32 
 
 65-8 
 
 22'50 
 
 35-81 
 
 89-5 
 
 15-00 
 
 29-96 
 
 67-4 
 
 23-12 
 
 36-70 
 
 91-7 
 
 15-62 
 
 27-61 
 
 69-0 
 
 2375 
 
 37-61 
 
 94-0 
 
 16-25 
 
 28-27 
 
 70-7 
 
 24-37 
 
 38-55 
 
 96-2 
 
 16.87 
 
 28-95 
 
 72-4 
 
 25-00 
 
 39-51 
 
 98-8 
 
 17'50 
 
 29-65 
 
 74-1 
 
 
 
 
 Swedish Test. A small quantity of the saltpetre to be tested is melted in a ladle 
 and cast in moulds into pieces of about 1 inch thick. When cold these pieces, if pure, 
 show when broken a coarsely rayed fracture ; the greater the proportion of impurities 
 contained in the crude saltpetre, the less distinct is this crystalline fracture, and it 
 disappears altogether when 2^ per cent, only of sodium chloride is present. 
 
 Testing for Chili Saltpetre in samples of Crude Saltpetre. Wollner's Method. A 
 portion of the sample to be tested is moistened with a little water and allowed to stand 
 several hours. The sodium nitrate being most soluble, it dissolves completely, while 
 comparatively little of the less soluble potassium nitrate dissolves. When the sample 
 is placed in a small funnel and washed with a very small quantity of cold water, the 
 filtrate will contain almost the entire quantity of sodium nitrate and very little potas- 
 sium nitrate. The filtrate is then evaporated to dryness, and the residue treated as 
 above, repeating this operation several times until the soda saltpetre is obtained in 
 such a pure state that it may be recognised by its crystalline form (cubical rhombo- 
 hedra piled up one on another) and the amount roughly estimated. 
 
 Pdouee's Method. Pelouze determines the amount of saltpetre contained in crude 
 saltpetre in the following way. A weighed quantity of pure iron wire is dissolved 
 in sulphuric acid, the solution is mixed with a weighed quantity of saltpetre, and the 
 whole heated. The nitric acid of the saltpetre is thus set free and oxidises a part of 
 the ferrous sulphate formed by the action of the sulphuric acid upon the iron wire. 
 The liquid is then poured into a beaker glass, cold distilled water added, and the 
 quantity of iron present in the state of ferrous salt determined by titration with a 
 solution of permanganate, of potash. 
 
 Since it is easy to calculate the quantity of ferrous oxide obtained from the iron 
 token, the amount of ferrous oxide oxidised by the nitric acid of the saltpetre is ob- 
 tained by simple subtraction. Since ferrous oxide is oxidised by nitric acid accord- 
 ing to the equation : 
 
 6FeO + N 2 5 = 3Fe 2 3 + 2NO 
 
 six molecules of ferrous oxide correspond to one molecule of nitric acid ; hence from 
 the amount of oxidised ferrous oxide found may be reckoned the amount of nitric 
 acid required for its oxidation, or what is the same thing, the amount of saltpetre con- 
 tained in the sample. Seeing, however, that Chili or soda saltpetre would be equally 
 affected by this test, the test only holds good for ascertaining the amount of both 
 nitrates. 
 
 Gay-Lussac's Test. In this test a weighed quantity of saltpetre is mixed with 
 4 parts of sodium chloride and \ part of powdered wood charcoal, and the whole 
 heated to redness. The potassium nitrate and sodium nitrate are thereby convert 
 into carbonates, and the amount of the latter determined by an alkalimetncal process. 
 This test, like the above, gives the total quantity of nitrates present. 
 
 Uses. Saltpetre proper or potassium nitrate is chiefly used in the manufacture 
 of gunpowder. Of late Chili saltpetre has chiefly been used for preparing nitric 
 acid and English sulphuric acid, on account of its cheapness. Saltpetre is u> 
 an oxidising agent as well as a flux in metallurgical operations, tor this purpose a 
 mixture of cream of tartar and saltpetre is often employed; when this mixture is 
 heated, the cream of tartar is oxidised at the expense of the saltpetre. Wfett the 
 
218 POTASSIUM. 
 
 mixture consists of 2 parts cream of tartar and 1 part saltpetre, a residue is obtained, 
 consisting of potassium carbonate and an excess of carbon, and is called black flux. 
 When an excess of saltpetre is employed, a residue is left, which is known as white 
 flux ; it consists of a mixture of potassium carbonate with undecomposed saltpetre. 
 For most purposes, in the place of black flux, a mixture of potash and soda may be 
 used, and in the place of white flux a mixture of potash and a little saltpetre. Ful- 
 minating powder is an intimate mixture of 3 parts saltpetre, 2 parts dry potassium 
 carbonate, and 1 part sulphur ; when heated, it first of all melts, then explodes with 
 a violent report. Quick flux consists of a mixture of 3 parts saltpetre, 1 part sulphur, 
 and 1 part sawdust. Biicher's mixture for extinguishing fires consists of 60 to 66 parts of 
 saltpetre, 36 to 30 parts of sulphur, and 3^ to 4 parts of charcoal. Its effect in extinguish- 
 ing fires depends upon the sudden evolution of a large quantity of sulphurous oxide, 
 which suffocates the flames. Saltpetre is further used in pyrotechnics for preparing 
 different coloured fires, etc. 
 
 GUNPOWDER AND OTHER EXPLOSIVE MATERIALS. 
 
 History. The discovery of gunpowder was probably made in India long before 
 our historic era. The Chinese, who were acquainted with the substance in the earliest 
 times, according to most historians, obtained their knowledge of its preparation from 
 the Hindoos. It is, however, curious that neither in India nor China was gunpowder 
 used for throwing projectiles, but only for fireworks. Whether the Chinese at a later 
 period possessed arms suited for gunpowder is uncertain. According to Uffano, an 
 Italian writer, as well as others, arms of the kind were found in some parts of the 
 Chinese coast, in the first century after Christ ; but this is disputed by other writers. 
 The art of preparing gunpowder is said to have been conveyed to Europe by the 
 Saracens. 
 
 In what relation the art of preparing gunpowder stands to the Greek fire dis- 
 covered by the Saracens in the seventh century, and employed by them in the conquest 
 of Constantinople, is uncertain. According to some, the discovery of gunpowder was a 
 result of attempts to perfect the Greek fire, and they of course deny that the knowledge of 
 gunpowder was derived from Eastern Asia. According to others there is no relation 
 between Greek fire and gunpowder. The first clear directions for the preparation of 
 gunpowder dates from the eighth century, when Marcus Grsecus prepared it by mixing 
 together 1 part sulphur, 2 parts charcoal, and 6 parts saltpetre. After him Albertus 
 Magnus and Roger Bacon, in the thirteenth century, both give similar directions for 
 the preparation of gunpowder ; they were probably both of them acquainted with the 
 writings of Marcus Grsecus. It is, at any rate, certain that Berthold Schwartz was 
 not thediscoverer of gunpowder ; for long prior to his pretended discovery, methods were 
 known according to which gunpowder could be prepared, and it is most probable 
 that he prepared his gunpowder according to the directions given by Marcus Grsecus. 
 
 The common opinion is that gunpowder was first used in Europe at the battle of 
 Crecy in 1346; according to other accounts arms fired by gunpowder existed in 
 England as early as 1327. Whether the Arabs used gunpowder for purposes of war 
 in the thirteenth century in Spain, as some historians declare, is uncertain. The first 
 account of the use of gunpowder in Germany dates from the year 1360, in which 
 year the town hall in Liibeck was burnt down owing to the carelessness of certain 
 gunpowder manufacturers. Gunpowder was, however, known in Germany in 1354. 
 
 Composition. Gunpowder is approximately a mixture of 2 equivalents of salt- 
 petre, 1 equivalent of sulphur, and 3 equivalents of charcoal, and corresponds to the 
 following percentage composition : 
 
 Saltpetre 202 74-8 
 
 Sulphur 32 11-8 
 
 Charcoal 36 13-4 
 
 The explosive effect of this mixture upon ignition depe'nds upon the very sudden 
 and almost instantaneous development of permanent and difficultly condensible gases. 
 The chemical change which takes place may be represented by the equation : 
 
 2KN0 3 + S + 3C = K 2 S + N 2 + 3C0 2 . 
 
 Besides this chief process, a number of minor reactions take place when gunpowder 
 is exploded, giving rise to the formation of a number of other compounds ; thus, for 
 instance, nearly all the potassium sulphide is oxidised to sulphate. Moreover, the 
 composition of gunpowder is not exactly that given in the above equation, apart from 
 the fact that the charcoal used in preparing gunpowder is not pure carbon, but contains, 
 besides carbon, hydrogen, oxygen, and ash constituents. 
 
COMPOSITION OF GUNPOWDER. 219 
 
 The following tables give the results Weltzien obtained, by the analysis of dif- 
 ferent kinds of gunpowder : 
 
 Cannon Powder. ' 
 
 
 Baden 
 
 Prussian 
 
 Bavarian 
 
 French 
 
 Saltpetre 
 Sulphur 
 
 72-94 
 12-01 
 
 75-58 
 12-45 
 
 72-50 
 12-62 
 
 7374 
 13-60 
 
 rCarbon . 
 Charcoal < Hydrogen 
 
 10-65 
 0-49 
 
 10-12 
 0-83 
 
 11-73 
 0-73 
 
 10-29 
 3-58 
 
 I Oxygen . 
 
 1-66 
 
 1-33 
 
 1-35 
 
 
 Water .... 
 
 2-25 
 
 1-89 
 
 1-61 2-28 
 
 Sporting Powder. 
 
 
 English 
 
 German 
 
 Saltpetre k 
 Sulphur . 
 
 79-36 
 10-63 
 
 76-95 
 11*52 
 
 {Carbon . . . . -i 
 Hydrogen . . . 
 Oxygen 
 
 8-76 
 0-60 
 
 9-58 
 0-48 
 
 Water 
 
 0'90 
 
 3-60 
 
 
 
 
 Blasting powder varies very considerably in composition, as shown by the follow- 
 ing table : 
 
 
 I. 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 VI. 
 
 Saltpetre . , . 
 Sulphur . . 
 Charcoal . . 
 Water 
 
 66-36 
 20-95 
 11-75 
 0-93 
 
 63-87 
 16-24 
 18-52 
 1-35 
 
 68'83 
 15-83 
 15-83 
 
 65-5 
 15-0 
 19-5 
 
 61-96 
 17-96 
 2008 
 
 70-08 
 11-98 
 18-01 
 
 I. is blasting powder from Mansfeld, analysed by Strong ; II. from the Upper 
 Harz ; III. from Westphalia ; IV. and V. is French blasting powder, and VI. is 
 Italian blasting powder. 
 
 According to the researches of Bunsen and Schischkoff, the process of combustion 
 upon exploding gunpowder is very complicated, for not only are nitrogen and carbonic 
 acid produced, but also considerable quantities of carbonic oxide and small quantities 
 of other gases. Besides potassium sulphide, a large number of other solid products 
 are also formed, as shown by the following table : 
 
 The composition of the sporting powder employed in the researches was as follows : 
 
 Saltpetre.. ......... 78-99 
 
 Sulphur . . . . . . .... . 9-84 
 
 c Carbon . . . .-,.-.. . 7'69. 
 
 Charcoal { Hydrogen . . . . v . . 0-41 1 1M7 
 
 I Oxygen. . . . . ... * -. 3-07J 
 
 Water . . . ' . . iy '. - * '. traces 
 
 One gram of this powder yielded upon explosion the following products : 
 
 Grain 
 Potassium sulphate ...... : . ' 422 
 
 carbonate . '".'* ..... ....'...' T 
 
 hyposulphite ;'...". . . . .. . 0'03 
 
 sulphide . . ' ..... . - 0-021 
 
 sulphocyanide ..... ; .. -,. 
 
 nitrate . . . : 
 
 Carbon 
 
 Sulphur ..... 
 
 Ammonium sesquicarbouate ...... . 
 
 Total solid residue . .... * 0'680 
 
 ' 028 
 
220 POTASSIUM. 
 
 Gram C.C. 
 
 Nitrogen 0'099 = 79-40 
 
 Carbonic acid 0-201 - 101-71 
 
 oxide 0-009 = 7'49 
 
 Hydrogen 0-0002 = 2'34 
 
 Sulphuretted hydrogen 0*0018 = M6 
 
 Oxygen ....:... 0-0014 = I'OO 
 
 Total gaseous products . . . 0'314 = l93'10 
 
 According to Fedorow's researches, the products of combustion are influenced by 
 the pressure under which they are formed. The higher the pressure, the greater is 
 the proportion of potassium sulphide and carbonate in the residue, and the smaller is 
 the proportion of undecomposed powder. According to the same researches, the reac- 
 tions ensuing upon exploding gunpowder may be assumed to take place in the follow- 
 ing stages. The decomposing saltpetre first ignites the sulphur, and forms potassium 
 sulphate ; the excess of oxygen combines with a portion of the carbon, forming 
 carbonic acid, according to the equation : 
 
 2KN0 3 + S + C = K 2 S0 4 + N 2 + C0 2 . 
 
 Nitrogen and carbonic acid are liberated as gases, while the excess of carbon con- 
 verts the potassium sulphate into hyposulphite and carbonate : 
 
 2K 2 S0 4 + 20 = K 2 S 2 3 + K 2 C0 3 + C0 2 . 
 
 When the combustion takes place under pressure, the carbon exercises a further 
 reducing action, forming potassium sulphide: 
 
 2K 2 S,0 3 + 30 = 2K 2 S + 2S + 3C0 2 . 
 
 Finally it is possible for the sulphur to react upon the potassium carbonate accord- 
 ing to the equation : 
 
 4K 2 C0 3 + 4S = K 2 S0 4 + 3K 2 S + 4C0 2 . 
 
 Characters. Inflammability of Gunpowder. The readiness with which gun- 
 powder takes fire depends upon its composition, upon the size of the grains, the 
 density and relative moisture. The larger-grained gunpowder is the most difficult to 
 ignite. According to Violette, the following kinds of gunpowder require for their 
 ignition the following temperatures : 
 
 Temperature of Ignition 
 
 Blasting powder . . 270 
 
 Kifle powder 276 
 
 Fine sporting powder 280 
 
 Superfine sporting powder 320 
 
 The dust of powder of the same kind takes fire more readily than the corresponding 
 powder itself. 
 
 Gunpowder is most easily ignited by bringing it into contact with red-hot sub- 
 stances ; less easily by means of a direct flame. Thus, for instance, a jet of ignited 
 illuminating gas requires to be left some time in contact with gunpowder before it, 
 takes fire. Gunpowder may, however, be exploded by strong friction or percussion, 
 especially when compressed between metal surfaces. Slaking lime is said to be capable 
 of igniting gunpowder. 
 
 Rapidity of Combustion of Gunpowder. The rapidity with which gunpowder 
 burns is dependent upon the composition and upon the mechanical condition, especially 
 the density. The less dense varieties of gunpowder burn quickest. Highly compressed 
 gunpowder burns very slowly, especially when very fine grained, or when it is mixed 
 with a fine powder. For this reason powder ought never to be rammed very tight 
 into guns. 
 
 Three different kinds of density are distinguished in gunpowder: 
 
 I. Mass Density, or Gravimetric Density, which signifies the relative weight of 
 equal volumes of grain powder. The weight of 1 litre of powder generally varies 
 between 0'820 and 0;293 kilos. 
 
 II. Grain Density, which signifies the relative density of the individual grains. 
 This varies between T4 and T9, and is of course greater the more highly the gun- 
 powder is compressed in its manufacture. 
 
 III. Absolute Specific Gravity, which signifies the specific gravity of the solid mass 
 of the powder, exclusive of the air enclosed between the individual grains. It amounts 
 on the average to 2 % 0. 
 
 The following are the essential characters that good gunpowder should possess : 
 
MANUFACTURE OF GUNPOWDER. 221 
 
 1. It should have a slate-grey colour. A black colour indicates moisture, bluish 
 black too much charcoal. 
 
 2. It ought not to glisten strongly. Light specks indicate saltpetre that has 
 become separated. 
 
 3. The grains ought not to be very friable when rubbed between the fingers, and 
 they ought to crackle when crushed. They should not, however, be too hard, since 
 powder that is highly compressed burns too slowly. 
 
 4. The grains ought to be, as near as possible, of equal size. 
 
 5. Should sharp particles be felt upon crushing a sample of gunpowder between 
 the fingers, it indicates that the sulphur has not been sufficiently finely divided. 
 
 6. Upon placing a few grains of gunpowder upon a piece of white note paper, and 
 moving them about by shaking the paper, no coloration of the paper should take 
 place, as this would indicate the presence of moisture or powder dust. 
 
 7. A small quantity of gunpowder when burnt upon a piece of paper must burn 
 without leaving any residue, and without igniting the paper ; otherwise it is moist, or 
 the carbon particles are not sufficiently finely divided. Yellow streaks indicate an 
 imperfect distribution of sulphur. When the mixing has been imperfect, some grains 
 remain unburnt. 
 
 8. Gunpowder when burnt should not evolve a large quantity of poisonous gas, 
 especially carbonic oxide. This requirement is especially necessary in the case of 
 blasting powder, since workmen are often much exposed to the gaseous products of 
 combustion. 
 
 Preparation. -The preparation of gunpowder consists essentially of a sequence 
 of mechanical operations, by which the materials are first of all brought, either singly 
 or together, into the state of a fine powder, then intimately mixed together, and 
 the mixture thus obtained is finally condensed, granulated, polished, and dried. The 
 raw materials used in the manufacture of gunpowder must have a certain definite 
 chemical and physical constitution. The essential properties required of them are as 
 follows : 
 
 Saltpetre. Refined saltpetre only can be used ; it must above all things be free 
 from chlorine compounds and from sodium nitrate, since these compounds would 
 render the gunpowder moist. The refining of crude saltpetre (vide p. 215) for purposes 
 of gunpowder manufacture is carried out either at the powder mills or in special 
 saltpetre refineries. The saltpetre used must always be so pure that a small quantity 
 of it dissolved in water is not rendered perceptibly cloudy when treated with a solu- 
 tion of silver nitrate. 
 
 Sulphur. Of the different kinds of sulphur found in the market, roll sulphur 
 alone is used in the preparation of gunpowder. When sufficiently pure it is at once 
 used for making gunpowder ; should it, however, contain mechanical impurities, these 
 must first be got rid of by re-melting : the sand, clay, lime, etc. sink to the bottom of 
 the melted mass, and the pure sulphur can be drawn off. It is then made to cool slowly, 
 so as to render it highly crystalline and brittle, in which state it can be powdered more 
 readily. Flowers of sulphur is not suitable for the preparation of gunpowder, on account 
 of the sulphurous and sulphuric acid it contains. Milk of sulphur is equally unsuit- 
 able, because it leaves a fixed residue when burnt. 
 
 Charcoal. The quality of gunpowder is considerably affected by the sort of 
 charcoal used in its manufacture. The charcoal should be light, porous, and easily 
 inflammable ; when burnt, it should not give any sensible quantity of ash. A thoroughly 
 burnt charcoal should always be used, because charcoal imperfectly burnt contains so 
 much oxygen that its combustibility is considerably lessened. Charcoal that has been 
 imperfectly burnt is known as red charcoal. Since light kinds of wood yield light 
 charcoal, only light and soft varieties of wood are used in making charcoal intended 
 for the manufacture of gunpowder. In this country the lime, the willow, poplar, horse- 
 chestnut, vine, hazel, cherry, alder, and other kinds of light wood are used for the 
 purpose. In Germany, the wood of the black alder is extensively used. In Italy, 
 where the material is cheap, excellent charcoal for gunpowder is prepared from hemp 
 stalks previously deprived of bast. 
 
 According to De Saussure's researches, the trunk wood of the oak contains less ash 
 than any other part of the tree. Trunk wood being taken as unity, he gives the fol- 
 lowing proportion of ash in the different parts of the oak: 
 
 Trunk wood * 
 
 Branches deprived of bark 
 
 Bark itself . ; 3( 
 
 Bast . . v 3( 
 
 Leaves . 36 
 
222 POTASSIUM. 
 
 Hence it is obvious that, as charcoal for making gunpowder must be as free as possible 
 from ash, it is a matter of no slight importance which part of the tree the wood is 
 taken from. The only parts fit for this purpose are the trunk and thicker branches 
 of trees five to six years old. 
 
 The season of felling timber has great influence upon the amount of ash in wood. 
 The most suitable season is spring, because atthis period, although the wood is full of 
 sap, the sap is very much diluted with water, and it contains but very small quantities 
 of solid saline constituents. Wood for making charcoal intended for the manufacture 
 of gunpowder ought therefore to be felled in spring, or at latest in the early part of 
 September. 
 
 PREPARATION OF CHARCOAL FOR MAKING GUNPOWDER. The manner in which the 
 charcoal is prepared affects its characters, and the relative amount obtained, very con- 
 siderably. The lower the temperature at which the charcoal has been prepared, the 
 more inflammable it is ; but at the same time it is more hygroscopic, and contains 
 less carbon and more oxygen. The relative amount of charcoal obtained is also 
 greater the lower the temperature of carbonisation. Violette gives the following 
 estimate of the relative amount of charcoal obtained from dry wood at different tem- 
 peratures : 
 
 Temperature Percentage of Charcoal 
 
 250 .... 50 
 
 300 .... 33 
 
 400 .... 20 
 1500 .... 15 
 
 The lowest temperature at which wood can be carbonised is 250. 
 
 An essential necessity in preparing good charcoal for making gunpowder is that 
 the wood should be dry. The wood before being carbonised is stored up six or nine 
 years in well-ventilated chambers. It was formerly customary before drying the 
 wood, to expose it several years to the action of rain, so as to wash out the sap ; and 
 thus wood was obtained containing less ash constituents. The same object is now 
 effected by treating the wood with superheated steam. 
 
 Carbonisation in heaps is not adopted in preparing charcoal for gunpowder manu- 
 facture, because the carbonisation is unequal, and the charcoal is also mixed with 
 clay, sand, etc., materials used in covering the heaps. For the same reason the car- 
 bonisation in pits is also unsuitable. 
 
 Carbonisation in Pits. This method is still in use in some parts of France. Pits 
 about four feet deep and four feet wide are dug in the earth and filled with the wood 
 to be carbonised, a first small portion being introduced alight so as to commence the 
 process of carbonisation. During the entire operation the pit is covered with a metal 
 lid to keep out the air, which would otherwise cause the combustion of the top layers 
 of charcoal, the lid being provided with small holes for the escape of the gases 
 evolved. The yield is about 23 per cent, of charcoal, which however, is not quite 
 uniformly carbonised, the charcoal lying against the comparatively cooler sides of the 
 pit being less strongly carbonised than that in the interior. 
 
 Carbonisation of Wood in Cylinders. This is the most general method of preparing 
 charcoal intended for the manufacture of gunpowder. In the Prussian powder works 
 the cylinders are of cast iron, and are about 6^ feet long and 2 feet wide ; both ends 
 admit of being closed with a cast-iron lid. The front lid is furnished with a small 
 opening, admitting of being closed, for taking out tests ; the hinder lid is furnished 
 with a tube for taking off the gaseous products of carbonisation, which are passed 
 through a number of condensing tubes where the tar is deposited, and the more volatile 
 portion is passed into a kind of tower, after which it escapes into the air. 
 
 In some places, the products of carbonisation are passed into the fire and burnt. It 
 is in any case necessary to let these products escape freely, without being exposed to 
 pressure in the condensing and purifying apparatus, because it has been found that 
 otherwise the charcoal easily becomes covered with a slimy soot, which retards its 
 combustion. 
 
 The fire is so arranged that the flame plays round the cylinder on all sides. In 
 order to prevent the lower part of the cylinder from being heated more than the other 
 parts, it is coated at the bottom with fire clay. As a rule, a couple of cylinders are 
 placed over each fire, and wood is used as fuel. 
 
 A cylinder of the dimensions above given admits of being charged with 2 cwts. 
 of black alder wood. 'The wood is cut into billets about a foot long, and laid in the 
 cylinder in such a way as to leave only a very small air space. The cylinders are first 
 heated strongly for 3 or 4 hours, the temperature being afterwards somewhat reduced, 
 and the process of carbonisation is complete in about 12 hours. The charcoal is then 
 allowed to cool, and placed in air-tight sheet-iron vessels, where the cooling process 
 
MANUFACTURE OF GUNPOWDER. 
 
 223 
 
 is completed. The amount of charcoal obtained by this process is about 20 to 30 
 per cent. The amount obtained in the powder manufactory at Dresden is about 27-4 
 per cent., while in France a precisely similar process yields on the average 34 to 35 
 per cent. The amount of charcoal may, of course, be increased or lessened according 
 to the duration and the degree of the heating. 
 
 Carbonisation by Superheated Steam. Violette has constructed an apparatus of this 
 kind by which excellent charcoal is obtained for gunpowder manufacture. It consists 
 of an iron cylinder, one end of which is closed and the other open. This cylinder is 
 fitted inside a wider cylinder closed at both ends in such a way that a space is left 
 between the two cylinders. Beneath the cylinders is a fire, the hot air from which 
 first plays round a spiral wrought-iron steam tube, and then upon the outer cylinder. 
 Steam is passed from a boiler through the serpentine tube into the space between the 
 two cylinders. The charging of the inner cylinder with wood is effected by removing 
 a lid in the front of the outer cylinder, and pushing in the wood packed in a perforated 
 cylinder ; the lid is then closed and luted. An iron tube conveys the products of car- 
 bonisation from the inner cylinder direct into the air. 
 
 The tension of the steam is not more than 1 atmosphere. The time required for 
 carbonisation is only one and a half to two hours ; the charge is each time 50 to 70 Ibs. 
 of wood. The emptying of the apparatus is effected by removing the lid of the outer 
 cylinder, and drawing out the perforated cylinder containing the charcoal into a suit- 
 able close vessel, where it is allowed to cool. The cylinders are then immediately re- 
 charged. 
 
 The following table gives the results of analyses, by Kahl, of charcoal prepared in 
 the Dresden powder factory : 
 
 
 By simple 
 Carbonisation 
 
 By Carbonisation with Superheated Steam 
 
 At 350 
 
 At a higher temperature 
 
 Carbon 
 Hydrogen 
 Oxygen 
 
 Ash . . .-.;-. 
 
 87-9 
 2-6 
 7-8 
 1'6 
 
 75-0 
 4-1 
 19-5 
 1-4 
 
 79-6 
 3-8 
 15-0 
 1-6 
 
 85-0 
 3-3 
 10-1 
 1-6 
 
 The red charcoal prepared by Violette at a low temperature contains on the average 
 only about 70 per cent, of carbon. 
 
 According to the old method of making gunpowder, the pulverisation, mixing, 
 and condensation are carried out in a single operation. For this purpose the charcoal 
 or the charcoal and sulphur are powdered in a moist state, by a stamping machine, and 
 then the saltpetre is added, in a fine state of division. This operation can be equally 
 well performed by mill stones. But since it is difficult to effect a perfect pulverisation 
 of a moist mass, it is now usual to pulverise the three ingredients separately, then to 
 mix and compress them. 
 
 The PULVERISATION is performed either by stampers, mill stones, or revolving 
 drums. 
 
 Pulverisation in Stampers. The stampers are made of wood, the weight of each 
 being about 1 cwt. The stampers are fitted with a bronze shoe, and are alternately 
 lifted, by means of a wheel furnished with teeth, and allowed to fall into a bed. The 
 beds containing the material to be reduced to powder are arranged in numbers cor- 
 responding to the stampers, and set in a block of very hard wood. 
 
 Grinding by Mill stones. Two heavy vertical runners of stone or cast iron, similar 
 to those used for crushing linseed, revolve round a vertical axis on a fixed horizontal 
 bed. The material to be powdered is spread upon the bed and is crushed by the 
 runners. The mass is stirred, and brought equally under the revolving stones by 
 means of scrapers fixed behind each runner. 
 
 Pulverisation by Bevolving Drums. This method came into use during the Frencli 
 revolution, and consists in placing the substance to be pulverised, together with a 
 number of bronze balls, in a wooden drum turning upon a horizontal axis, and then 
 rotating the drum. The-drums are furnished internally with wooden ledges running 
 in the direction of the axis of the drum, and covered with leather. The materials are 
 placed in the drum through a little door at the periphery of the drum, and upon 
 setting the drums in motion are quickly reduced to powder. When the materials lu\v 
 been sufficiently powdered, the drum is turned so that the door is downwards, and on 
 
224 POTASSIUM. 
 
 opening it the powder falls out into a vessel placed beneath. The bronze balls are 
 prevented from falling out by a sieve attached to the opening. 
 
 MIXINO THE MATERIALS. This operation is carried out in drums of precisely the 
 same construction as those above described ; they are either made of wood, covered 
 internally with leather, or are made entirely of leather. The bronze balls are smaller, 
 and the sieve for letting out the powder is also proportionately finer than in the 
 pulverising process. 
 
 MOISTENING. The gunpowder is placed in wooden boxes, and sprinkled at intervals 
 with water, until it has taken up 8 or 10 per cent. The moistening process is some- 
 times performed in the drums. 
 
 PRESSING. The object of this operation is to give coherence to the powder and such 
 consistency that it can be granulated. It requires much care ; for if the gunpowder be 
 too highly compressed, it burns too slowly ; the heating of the gases is less sudden, 
 their expansive force consequently less. On the other hand, gunpowder that has not 
 been sufficiently compressed burns too quickly, and has an explosive effect. The 
 ordinary method of compressing gunpowder consists in passing the mixture through a 
 rolling mill, consisting of two rollers, the upper one of bronze, and the lower one of 
 wood ; by means 6f a lever arrangement they can be pressed against one another so 
 as to exert a pressure of twenty to twenty-five tons. The mixture is conveyed to the mill, 
 already set in slow motion, by means of an endless cloth, and is pressed between the 
 rollers to a cake of about in. thick. The caking may be also effected by means of 
 hydraulic pressure ; for which purpose the mixture is laid upon copper plates, and 
 pushed by jerks under the press. It has been already mentioned that the operation 
 of pulverising the materials by stampers may be combined with the caking or com- 
 pressing operation. Neimke suggests a method according to which the saltpetre is 
 dissolved in water, and the mixture of charcoal and sulphur added in a fine state of 
 division ; the mixture is stirred and heated until about 15 per cent, of water remains. 
 When cool, the mass is pressed between rollers or stampers. 
 
 GRANULATION. The object of this operation is to reduce the powder cake into grains 
 of a definite size, according to the purpose for which the powder is to be used, the 
 rapidity of the combustion of gunpowder depending upon the size of the grains. Gun- 
 powder dust and caked powder both burn very slowly, while granulated powder, 
 owing to the intermediate hollow spaces between the grains, burns much quicker. 
 
 Three or four sieves are generally used in the granulating process, through which 
 the powder is passed. These sieves are made of wood, parchment, or metal ; they are 
 round in shape and are placed above one another in such a way that the uppermost 
 sieve has the biggest holes, the holes in the ones beneath gradually decreasing in size ; 
 the holes in the last sieve are so fine that powder dust only can pass through them. 
 The sieves are all set in a frame, and the uppermost sieve is covered with a wooden 
 lid. Powder in the form of cake is placed in the uppermost sieve through a funnel 
 and linen tube attached to the lid, and a shaking motion communicated to the sieves, 
 by means of which a rubber of hard wood is set in motion and breaks up the powder 
 cake into pieces which are separated in succession by the sieves. The grains which 
 are too large to pass through the second sieve are carried off through an opening at 
 its side, and are again exposed to the action of the rubber in the first sieve. The 
 same plan is followed out in the third and fourth sieve, with the exception that the 
 grains which do not pass through the last sieve are not again put into the upper sieve, 
 but are separately collected. The uppermost sieve is termed the first sieve, the 
 lowest sieve the dust sieve, and the intermediate ones the corning sieves. By this 
 means different grained varieties of powder are obtained, and the dust passing through 
 the last sieve is separately collected. In Lefevre's corning machines eight or twelve 
 siich sieves are fitted in boxes hung upon a beam, and they are set in motion by a 
 special mechanical contrivance. 
 
 Congreve's Granulating Process. The powder cake is first of all forced through a 
 shot sieve and the broken mass granulated by passing it between three pairs of rollers 
 furnished with pyramidal teeth. The teeth of the first pair of rollers are larger 
 than those of the second, and the latter larger than those of the third pair. The 
 teeth are set so near one another that they are almost in contact. The powder cake is 
 brought into the rollers by means of an endless cloth. Beneath each pair of rollers 
 passes an endless sieve, upon which the powder falls, and the sufficiently fine grains 
 pass through the sieve', while the coarser mass is conveyed to the next pair of rollers. 
 At the lowest part of the granulating apparatus, a couple of endless sieves of unequal 
 fineness pass over one another to catch the powder passed through both the upper 
 sieves and the lowest pair of rollers, separating it into coarse and fine grained powder 
 and powder dust. 
 
MANUFACTURE OF GUNPOWDER. 225 
 
 Champy's Method. According to Champy's method the powder is granulated in 
 revolving drums, by injecting water in a fine stream from the axis of the drum. Each 
 drop of water upon falling upon the powder forms with it a small adhesive lump, 
 which is increased in size by the movement of the drum. The drums are made to revolve 
 until the grains have attained the required size. The mass is then taken out and 
 sorted through sieves, the grains that are too large being powdered again, and 
 replaced with the powder dust in the drums. 
 
 The granulated powder is then superficially dried upon pieces of cloth stretched 
 upon frames, the frames being placed in the drying house upon wooden supports and 
 exposed to a current of air. 
 
 POLISHING OF GTUNPOWDEB. This operation is not carried out in all countries with 
 every kind of powder, since powder thus treated does not so readily take fire as un- 
 polished powder. On the other hand, polished powder has the advantage that it does 
 not so readily absorb moisture, nor does it so readily discolour substances brought in 
 contact with it, and it is less friable. For polishing gunpowder, granulated powder is 
 brought into horizontally placed drums with a smooth internal surface, and the drums 
 are caused to rotate slowly for a few hours. The addition of graphite, so as to give 
 the powder grains a more shiny appearance, is not to be recommended, on account of 
 its rendering the powder less readily inflammable. 
 
 Instead of simple drums, in some manufactories rolling tubs are employed, which 
 are divided lengthways into several compartments, each compartment being furnished 
 with a special door for admitting the powder to be polished. 
 
 DRYING OF G-UNPOWDEE. Before gunpowder is dried it may be conveniently pressed 
 into pieces having the shape of cartridges. This operation may be effected by the 
 aid of a gentle heat without it being necessary to surround the powder with cases of 
 paper or metal. The so-called prismatic powder consists of six-sided columns of this 
 kind perforated lengthways with seven holes. 
 
 Grunpowder requires drying very carefully, a very slighi and gradual heating being 
 necessary at first ; for if this is neglected the grains are liable to crack, and an 
 efflorescence of saltpetre is apt to take place. The powder is either dried in the air 
 or in chambers artificially heated. 
 
 Drying in the Air. The powder is spread in layers to \ inch thick upon tables 
 covered with cloth, the mass being often turned until dry. In some places the drying 
 is assisted by allowing the rays of the sun to fall upon the powder, while in others the 
 sun is kept off by roofing-in the drying chamber. In the former case the powder dries 
 in about four hours, in the latter in about ten hours. Where the ground is moist the 
 floor must be covered with asphalte, to keep the moisture from the powder. 
 
 Drying in artificially heated Chambers. The powder is spread out upon hurdles 
 supported upon wooden frames fastened in the sides of the chambers, which are gene- 
 rally heated up to 40-50. An oven is placed in the middle of the chamber. In 
 large powder works the powder is dried by steam, for which purpose it is spread out 
 on pieces of linen stretched on frames, which lie above one another, the steam pipes 
 passing under the frames. Gunpowder is also sometimes dried by placing it in 
 drying boxes, and passing air previously heated in iron tubes into the boxes. In all 
 cases care is taken to avoid heating the drying chambers above 60. 
 
 EEMOVING THE DTJST. For this purpose the powder is passed through linen tubes 
 having a sloping position and kept in constant agitation ; the powder dust escapes 
 through the meshes of the linen, while the powder grains fall out at the lower ex- 
 tremities of the tubes and are collected for use. 
 
 G-UNPOWDEES OF DiFFEEENT COMPOSITION. Attempts have long been made, by 
 partial or entire replacement of the ordinary constituents of gunpowder by other 
 substances, to alter its composition so as to render it less dangerous, and at the same 
 time to increase its energy and render it cheaper. 
 
 Thus, for instance, attempts have been made to replace the saltpetre either 
 entirely or in part by potassium chlorate. It was however found that a powder thus 
 prepared was very liable to cause accidents, owing to its taking fire when struck, and 
 further that, from its developing when ignited too suddenly large volumes of gases, 
 fire arms burst, and were moreover mucli corroded by the action of free chlorine. Some 
 value may be however attached to Augendre's white powder, which, according to 
 Pohl, has the following percentage composition : 
 
 Potassium chlorate ^ 
 
 Cane sugar ; 
 
 Potassium ferrocyanide ~ 
 
 This powder is not easily ignited by a blow, but very easily by contact v.-ith flame 
 
226 POTASSIUM. 
 
 or a red-hot body. It is said to be more effective than gunpowder, 60 parts of 
 white powder yielding the same volume of gas as 100 parts of ordinary gunpowder. 
 It leaves when burnt only a very small residue ; it has a low temperature of ignition, 
 and does not readily absorb moisture. On the other hand, it is far more easily ignited 
 by a blow than gunpowder ; it attacks the barrels of fire arms, and is dearer than 
 gunpowder. ' 
 
 A great number of attempts have been made to replace saltpetre by Chili saltpetre, 
 which is much cheaper. The disadvantages, however, are that, when the latter is not 
 perfectly pure, a very hygroscopic gunpowder is obtained, and even when the salt is 
 pure the gunpowder made from it burns too slowly. 
 
 Wagner proposed using barium nitrate as a substitute for potassium nitrate. A 
 powder thus prepared, known as saxafragin, is certainly less inflammable than 
 gunpowder ; but it is, on the other hand, specifically heavier, and leaves when burnt 
 a considerable residue. According to Wynand, saxafragin has the following per- 
 centage composition : 
 
 Charcoal .'.... 22'0 
 
 Barium nitrate 76*0 
 
 Saltpetre 2-0 
 
 Nobel's Blasting Powder. This is a powder containing nitro-glycerine, and is com- 
 posed as follows : 
 
 I. II. 
 
 Charcoal 12 10 
 
 TUrium nitrate . 68 70 
 
 Nitro-glycerine 20 20 
 
 Still greater in number are the substitutes proposed for charcoal, the chief of 
 which are tannic acid, tan, sawdust, flour, starch, sugar, potassium ferrocyanide, 
 cream of tartar, etc. Ehrhardt's blasting powder consists of 
 
 Saltpetre 12-25 
 
 Charcoal 49-00 
 
 Tannic acid . . . 24-50 
 
 Potassium chlorate 14-25 
 
 In the above powder the sulphur itself is replaced, which is seldom the case. 
 
 Schultze's gunpowder consists of granulated nitrified wood, impregnated with 
 potassium nitrate ; 100 parts of nitrified wood are brought into a solution consisting 
 of 26 parts potassium nitrate and 220 parts water, and eventually dried at a tempera- 
 ture of 32 to 44. The saltpetre may be replaced in part by barium nitrate. 
 
 TESTS FOR GUNPOWDER. The effect of gunpowder depends upon its forming when 
 ignited hot gases, which occupy a very considerably larger volume than the powder 
 itself. G-unpowder is consequently the more effective the larger the volume of gases 
 evolved, and the higher the temperature produced by its combustion, for the volume 
 of a gas or mixture of gases increases, and the force of expansion is greater, the 
 higher the temperature under which it is formed. However, the evolution of gas 
 when gunpowder is burnt must not be too sudden, for in such case the ball would not 
 have time to leave the barrel before the force of expansion would be conveyed to the 
 sides of the barrel and burst the gun. On the other hand, the combustion must not be 
 too slow, as in such case the ball would leave the barrel before the combustion is com- 
 plete, and a part of the gases developed by the combustion would be without effect 
 upon the ball. 
 
 According to Bunsen and Schischkoff, the temperature produced by burning 
 gunpowder in a closed space is 3340 0. The volume of the gases produced, reduced 
 to 0, exceeds the volume of the solid powder 193'1 times. Accordingly at the 
 temperature of combustion (3340), the volume of gases is 2369 times that of the 
 solid powder. 
 
 Testing the effect of Gunpowder. A number of methods have been given for test- 
 ing the effect of gunpowder, which depend chiefly upon ascertaining either the 
 distance a ball is projected, the height to which a weight is lifted, or the pressure 
 exerted upon a lever by a known quantity of gunpowder. 
 
 Mortar Test. For this purpose a given weight of the powder is placed in a 
 bronze mortar furnished with a powder chamber just large enough to hold that 
 quantity. A heavy bronze ball of known weight is then placed upon the powder, the 
 mortar inclined to 1 an angle of 45, and the powder fired. The quality of the powder 
 is indicated by the distance to which the ball is projected. 
 
 Rod Test. This test, which is chiefly in use in Austria, is performed as follows. 
 A known quantity of powder is placed in a small mortar, into the mouth of which fits 
 
GUNCOTTON. 227 
 
 accurately a weight of 5 Ibs. The weight is moveable between a couple of verti- 
 cally placed rods, one of which is furnished with teeth, and a ratchet work prevents 
 the weight from falling back, retaining ifc therefore at the height it is projected by 
 the powder. 
 
 Lever Test. For this test a jointed lever is employed, to the one arm of which a 
 small mortar is attached in such a way that in burning a small quantity of powder 
 (2 ounces) the force of reaction causes it to turn a certain distance, so that the 
 other arm of the lever to which a weight is attached is raised proportionately. A 
 small ratchet, which is pushed, during the turning, along a toothed sector, prevents 
 the lever falling back into its former position ; so that, after the explosion of the 
 powder, the height to which the weight has been raised may be read off. 
 
 Regnier's Powder Test. A double-limbed steel spring, mounted so as to move freely, 
 is set with the one limb connected with the mouth, the other limb with the button of 
 a small cannon; so that upon firing the powder both limbs the one being pro- 
 pelled forwards by the powder, the other in a contrary direction by the rebounding 
 of the cannon approach one another. The extent to which they approach one 
 another gives a measurement of the force exerted by the powder. 
 
 Pistol Test. A graduated wheel, supported by a spring, executes a revolution 
 corresponding to the force of the powder. The rotatory motion is given to the wheel 
 by an arm attached to it, which terminates just before the nozzle of a pistol. 
 
 GUNCOTTON. 
 
 History. The substance known as guncotton, or pyroxilin, was discovered 
 in 1846 simultaneously by Schonbein, by Boettger, and bv Otto. It caused a great 
 deal of excitement at that time in scientific as well as in political circles, since it was 
 supposed to be a destructive agent of extraordinary power. It has, however, been 
 since ascertained that the essential feature of this discovery consisted in better 
 methods of preparing and applying materials that had been long known. In 1833 
 Braconnot had prepared an easily inflammable substance which he termed xyloidin, 
 from the same materials which are now employed in the preparation of guncotton. 
 In 1838 Pelouze gave this substance his attention, and found that it might be ex- 
 ploded by concussion ; shortly afterwards Dumas prepared the same substance, and 
 called it nitramidin. 
 
 Composition. Guncotton consists of cellulose, in which part of the hydrogen 
 is replaced by N0 2 ; it is obtained by treating any kind of cellulose with very con- 
 centrated nitric acid. The nitric acid is decomposed, and for every molecule of de- 
 composed nitric acid, one atom of hydrogen in the cellulose is replaced by the group 
 NO.,. The number of hydrogen atoms replaced in a molecule of cellulose is dependent 
 upon the concentration of the nitric acid employed. Consequently guncotton must 
 not be considered as a substance of constant composition, but on the contrary there are. 
 a number of different kinds of nitro-cellulose, and guncotton consists either of one of 
 these nitro-compounds or of a mixture of several. It is only in this way that we can 
 explain the difference in composition between samples of guncotton prepared in 
 different ways. 
 
 This may be best understood by considering cellulose as a polyacid alcohol, i.e. as 
 a sex-acid alcohol derived from the water type. 
 
 Water Type Cellulose 
 
 We have therefore in cellulose six typical atoms of hydrogen, which are capable of 
 being replaced by N0 2 . . . 
 
 Accordingly, by acting upon the molecule of cellulose with one molecule o 
 acid, mononitro-cellulose is produced: 
 
 Cellulose Nitric Acid Mononitro-cellulose Water 
 
 By the action of two molecules of nitric acid : 
 
 Dinitro-cellulose 
 
 Q2 
 
228 GUNCOTTON. 
 
 By the action of three molecules of nitric acid : 
 
 Trinitro-cellulose 
 
 These compounds have therefore a composition analogous to the compound ethers, 
 as is shown by their chemical characters. Thus, for instance, when heated with 
 potassium hydrate, they react like compound ethers. Ethyl nitrate, for instance, when 
 boiled with potash, is converted into ethyl alcohol and potassium nitrate : 
 Ethyl Nitrate Potash Ethyl Alcohol Pot. Nitrate 
 
 Trinitro-cellulose, treated in like manner, is converted into cellulose and potassium 
 nitrate : 
 
 Trinitro-cellulose Potash Cellulose Pot. Nitrate 
 
 With reducing agents such as alkaline solutions of hydrogen sulphide, ferrous 
 chloride, mercury and sulphuric acid, etc., guncotton reacts like the nitrates, cellulose 
 is reproduced, and the nitric acid is completely destroyed. This is a proof that in 
 these compounds the radical N0 2 takes the place of the typical hydrogen, and does not. 
 as some suppose, replace hydrogen in the radical ; for in such case a nitrogenous 
 compound would be produced by reducing agents in the same way that aniline is 
 obtained by treating nitrobenzyl with an alkaline solution of sulphuretted hydrogen, 
 or -with ferrous chloride. 
 
 Characters. Guncotton dried at the ordinary temperature ignites when heated 
 to 175-185, while guncotton which has been dried by the aid of artificial heat is 
 far more readily ignitable, exploding at the temperature of boiling water ; indeed in 
 many cases it has been found that guncotton thus prepared explodes without any 
 apparent cause. The products of combustion obtained when guncotton is burnt differ 
 in quantity and composition according to the difference in composition of the gun- 
 cotton. Thus one observer obtained from 1 gram of guncotton 483 cc. of gas 
 (reduced to a temperature of 0), while another obtained from the same quantity of 
 guncotton 588 cc. of gas. The gaseous products of combustion consist of nitrogen, 
 nitric oxide, cyanogen, carbonic dioxide, carbonic oxide, and steam. The explosive 
 force of guncotton in fire arms is from two to six times greater than that of an equal 
 weight of gunpowder. Guncotton, when properly prepared, care being taken to use 
 pure acid and pure cotton, leaves no residue when exploded, nor is any acid formed. 
 In these respects guncotton has an advantage over gunpowder ; but it has the dis- 
 advantage that, owing to the gases produced by the explosion being formed too 
 suddenly, fire arms are subjected to a greater shock. 
 
 When kept for a long time, guncotton gradually decomposes. Red vapours are 
 evolved, the mass becomes viscous in consistency, deliquescing eventually to a pyrup- 
 like liquid. Active decomposition is sometimes attended with explosion. 
 
 Guncotton prepared in the way above described is completely insoluble in alcohol 
 and water, difficultly soluble in ether and solutions of ether in alcohol, and slightly 
 soluble in ethyl acetate. In respect to solubility in ether, alcoholic ether, and ethyl 
 acetate, this kind of guncotton behaves very differently from another kind of gun- 
 cotton prepared by treating cotton with potassium nitrate and sulphuric acid (vide 
 Collodion). 
 
 Great precautions are required in the manufacture of guncotton on a large 
 scale. 
 
 The first necessity is that the acid mixture should be quite cold before the cotton 
 is added. Besides this, care must be taken that the quantity of acid mixture 
 employed is sufficient to completely cover the cotton ; and it is also necessary that 
 the cotton should be covered by the acid mixture as quickly as possible. Should a 
 part of the cotton protrude beyond the surface of the acid liquid, spontaneous heating 
 very quickly takes place, and decomposition sets in, accompanied by the evolution of 
 red vapours. This decomposing action, if not quickly stopped, is apt to cause the 
 ignition and explosion of the whole mass. 
 
 Preparation. For preparing guncotton, a mixture is made of 3 vols. con- 
 centrated nitric acid and 7 vols. concentrated sulphuric acid. When cool, a quantity 
 of well-purified cotton is placed in about twenty times its weight of the mixture. 
 After being left to stand for one hour, the guncotton is taken out and pressed be- 
 tween a couple of iron plates, so as to remove the excess of acids ; it is then thrown 
 
GUNCOTTON. 229 
 
 into water for complete washing. The acids, owing to their high concentration, do 
 not attack the iron plates. The removal of the acids is more easily effected by means 
 of a centrifugal machine, the drum of which retains the guncotton while the acid runs 
 off. The concentrated acid mixture is collected for further use. So soon as the 
 excess of acid has been got rid of, water is brought into the revolving drum, and is 
 driven by the centrifugal force against the guncotton, penetrating its mass and washing 
 out the acid. When the escaping water ceases to taste acid, a dilute solution of soda 
 (| per cent.) is passed into the drum to neutralise the last traces of acid, the guncotton 
 is again washed with water, and then finally dried as far as possible in the drum. 
 The final drying is effected by causing a strong current of air to pass over the gun- 
 cotton at the ordinary temperature, without the aid of artificial heat. 
 
 In a carefully conducted operation, the proportion of guncotton obtained from 
 cotton is about 332 parts by weight of guncotton for every 200 parts of cotton em- 
 ployed. 
 
 Explosive Paper. The preparation of this substance is essentially the same as that 
 of guncotton. Special care is however required to avoid tearing the sheets of paper 
 during the treatment with acid, and during the washing process. 
 
 Pyroxam, or Explosive Starch. The starch requires previous drying, which 
 according to Payen is best effected in vacuo at a temperatiire of 125. After cooling 
 in a closed vessel, the starch is brought into the acid mixture, the proportion of the 
 latter being equal to 15 times the weight of starch taken. After six hours, the 
 pyroxam is taken out, washed with water, and then dried in a current of air. Payen 
 recommends drying it in vacuo at the ordinary temperature. 
 
 All the above substances when prepared in the same manner have the same com- 
 position, although, as we have seen, the composition can be very different, affecting 
 the properties of the substance, especially its ignitability. It may be assumed in 
 general that the projectile force of the gases of decomposition is in direct proportion 
 to the temperature required for ignition, so that the greatest amount of projectile 
 force may be expected from a preparation which ignites spontaneously at a tempera- 
 ture of about 180, while on the other hand the least amount of projectile force would 
 be expected from a compound which ignites spontaneously at 100. The latter kinds 
 have also the disadvantage that amongst the products of their decomposition there is 
 nitrous acid, which acts most injuriously upon fire arms, and when such compounds are 
 used in blasting, the nitrous acid attacks the lungs of the workmen. 
 
 The difference in constitution shown by the different kinds of nitro-cellulose com- 
 pounds is not only due to the difference in the way of preparing them, but also to 
 differences in the constitution of the raw cellulose material, especially its density and 
 the cohesion among its particles. Cotton in which the individual tubes are thin 
 walled and delicate, and the cohesive force equal throughout, offers at the same time the 
 greatest surface to the action of the acid, and owing to its homogeneity spreads the 
 ignition quickly throughout its mass, and consequently when free from foreign ingre- 
 dients it yields the best preparations, and such only ought to be used in fire arms. 
 Preparations made from cotton, or linen rags, or paper, are extremely dangerous ; 
 owing to the different thickness and different characters of the individual fibres, they 
 ignite at a very low temperature. Preparations of this kind have been the cause of 
 accidents both by spontaneous ignition and the bursting of fire arms, the trajectile 
 force they communicate to the projectile being also slight and uncertain. 
 
 Pyroxam is very ignitable, igniting between 90 and 100; it is also a very un 
 stable product, decomposing at the ordinary temperature, either very quickly with 
 explosion, or gradually with evolution of red vapours and conversion into a syrupy 
 mass ; this decomposition is favoured by a moist atmosphere. 
 
 The spontaneous decomposition of all the nitro-celhilose compounds is promoted by 
 the presence of a trace of free acid ; the washing-out process therefore requires great 
 attention. The action of heat upon these compounds produces a further alteration. 
 Their spontaneous ignition takes place at a lower temperature when they have been 
 kept for some time at a temperature of from 50 to 60. Thus guncotton, which 
 does not ignite till heated to 180, will readily take fire at 108, when it has been 
 heated for twelve hours to a temperature of 50 or 60. 
 
 The difference in ignitability of these bodies may fee demonstrated in the following 
 way. Three strong glass tubes are filled respectively with pyroxam, badly washed 
 explosive paper, and good guncotton, and all three tubes heated in a saturated solu- 
 tion of salt. It will then be found that pyroxam is the first to explode ; after a short 
 time when the liquid has got hotter the explosive paper ignites, while 
 cotton does not ignite even upon boiling the solution of salt. 
 
 The point however, at which guncotton takes fire is considerably lower than t* 
 at which gunpowder explodes. This may be demonstrated by spreading a small 
 
230 GUNCOTTOISr. 
 
 quantity of gunpowder upon a sheet of paper, laying upon it a piece of guueotton, 
 and then holding the sheet of paper a short distance over a flame. After a short 
 time, the guncotton suddenly burns away with a flash, while the gunpowder remains 
 unchanged. 
 
 Uses. The application of guncotton in fire arms has shown that its projectile 
 force as compared to gunpowder is as 4 to 1. Cartridges for sporting guns holding 
 3*2 grams of powder cannot with safety be replaced by guncotton cartridges 
 charged with more than 0'8 gram of the latter. In like manner, military fire arms 
 which require 8 '9 grams of powder for propelling a bullet weighing 25 grams, 
 require only 2 grams of guncotton to produce the same effect. It appears, however, 
 that in the larger kinds of fire arms the difference between the effect exerted by gun- 
 powder and guncotton is relatively less. 
 
 The difference between the force exerted by guncotton and by gunpowder is not 
 proportionate to the amount of gaseous products developed in their combustion. A 
 kilogram of gunpowder when burnt yields 450 to 500 litres of gaseous products, 
 while an equal weight of guncotton yields 600 to 800 litres of gaseous products (both 
 reduced to a temperature of 0). The greater projectile force so often observed in the 
 case of guncotton can therefore only be explained by the assumption that the gas 
 formed upon burning guncotton acquires a higher temperature, and consequently 
 greater expansive force, than the gas formed by gunpowder. 
 
 Advantages of G-uncotton. Since a given weight of guncotton is more effective than 
 the same quantity of gunpowder, its transport is easier ; it is not altered by moisture, 
 or even by soaking in water ; it does not soil fire arms like gunpowder ; when used in 
 sporting guns the shot is less scattered than is the case when gunpowder is used. 
 
 This last fact may be understood by assuming that the complete decomposition of 
 guncotton takes place within a very small space in the gun, in consequence of which 
 the shot receives its entire velocity before leaving the gun. On the other hand the 
 complete explosion of powder requires a longer time, extending over the entire length 
 of the barrel, and even beyond it so as to cause a lateral deviation of some of the shot. 
 
 These advantages are somewhat modified by guncotton being dearer than gun- 
 powder ; the chief disadvantage however in the use of guncotton is its injurious effect 
 upon the fire arms. These considerations have checked its general application. 
 
 The property possessed by guncotton of exploding when struck has led to attempts 
 being made to use it in the place of percussion caps, but at present without any 
 successful result. 
 
 The effect exerted by explosive paper is irregular, and is exerted more upon the 
 barrel than upon the projectile. These inconveniences are greater in proportion to the 
 thickness of the paper. For this reason the use of explosive paper is now given up. 
 
 The last result attained by the use of guncotton in the place of gunpowder is its 
 application to blasting purposes, where its entire explosive force is brought to account 
 and where the disadvantages are too insignificant to be worth noticing. The general 
 application, however, of guncotton for blasting purposes is retarded by its high price, 
 which at present is not counterbalanced by its greater explosive effect. It may 
 however be expected that, by means of manufactories well arranged and conducted, 
 guncotton will become cheaper, especially as the greater part of the acid employed 
 admits of being turned to further account. The mixture of acids recovered by press- 
 ing, and with the centrifugal machine, amounting to about 70 per cent, of the entire 
 quantity, is not strong enough to be used again ; but it might either be sold to 
 sulphuric acid manufacturers or the nitric acid distilled off. 
 
 The explosive force of guncotton is considerably increased by mixing it with 
 potassium chlorate or potassium nitrate, which is effected by saturating it with 
 solutions of these salts and then drying it. 
 
 Testing of G-uncotton. The only possible adulterant capable of being used for 
 adulterating guncotton is ordinary cotton. Both substances are readily distinguish- 
 able under the microscope. By moistening a mixture of the kind with solution of 
 iodine, and adding a drop of sulphuric acid, the guncotton assumes a yellow colour, 
 while the cotton becomes blue. Besides this, ordinary cotton is transparent, and is 
 seen to consist of fine tube-like cells, while guncotton presents an entirely altered 
 appearance, the cell character being no longer recognisable. 
 
 It has often happened that violent explosions have occurred in magazines and j 
 manufactories of guncotton without any apparent cause being traceable, and in rooms 
 that had not been ontered for several days. The probable cause of such explosions is 
 the heat developed by gradual decomposition and the increase of surrounding tempe- 
 rature up to the point of ignition, owing to the non-conductive power of the mass. 
 The liability to explosion would of course be increased by the presence of more easily 
 ignitable nitro-substances. Paycn refers an explosion that occurred in Vincennes to - 
 
NITROGLYCERIN. 231 
 
 this cause. The guncotton there stored up was prepared from hemp, which according 
 to Malagutti contains starch, which would have been converted during the nitrifica- 
 tion into the easily ignitable and decomposable pyroxam. 
 
 Accidents have also occurred in filling rockets into which the guncotton was driven 
 with great force, and this is not astonishing, since it is a well-known fact that, a 
 simple blow suffices to explode guncotton. 
 
 NITKOGLYCEKIN. 
 
 During the last few years attempts have been made to replace guncotton by 
 the compound known as nitroglycerin, or Nobel's blasting oil, the explosive 
 properties of which exceed those of guncotton. Nitroglycerin has a composition 
 represented by the formula : 
 
 and is accordingly the nitric ether of glycerin. For preparing nitroglycerin, 500 
 parts by weight of glycerin are slowly poured into a cold mixture consisting of 2200 
 parts concentrated sulphuric acid and 1100 parts very concentrated nitric acid; the 
 whole is allowed to stand for ten minutes, and then poured into a quantity of cold 
 water equal to six times its volume, taking care to stir the mixture constantly the whole 
 time. Nitroglycerin then separates in the form of a heavy oil, which is freed from 
 acid by repeated washing with cold water. Nitroglycerin has all the explosive pro- 
 perties of guncotton in a greater degree ; rapid heating, or a blow, causes its imme- 
 diate explosion, and these circumstances have led to terrible accidents. A special 
 danger accompanying nitroglycerin consists in its tendency to crystallise at low 
 temperatures ; attempts to remelt these crystals too quickly often cause the entire 
 mass to explode. 
 
 For blasting purposes a quantity of nitroglycerin is poured into the bore hole, 
 covered up with sand and ignited with a fusee. The effect produced is most as- 
 tounding. 
 
 The material known under the name of dynamite is a preparation of nitro- 
 glycerin ; it is not so dangerous as nitroglycerin, owing to its only exploding when 
 ignited and not by a simple blow. 
 
 
SODIUM. 
 
 SYMBOL Na. ATOMIC WEIGHT 23. 
 
 History .--This elementary substance was discovered in 1807 by Sir H. Davy, 
 about the same time as potassium, and the result of the isolation of this metal was to 
 establish the analogy between soda salts and the salts of other metals, which had 
 been long suspected, and was more definitely suggested by Lavoisier in 1787. 
 
 Occurrence. Sodium does not occur naturally in the free state, but in combi- 
 nation with some other elementary substances it occurs very abundantly ; as chloride 
 it occurs in the solid form as rock salt, and in a state of solution in sea water and 
 the water of many mineral springs. Sodium also occurs, combined with oxygen and 
 various acid oxides, in the form of salts ; thus, for instance, the nitrate occurs abun- 
 dantly as cubic nitre, the sulphate as the nardite and in the hydrated state as 
 mirabilite ; the carbonate occurs as soda and trona, and the borate as tincal or 
 borax. In the oxidised state sodium also enters into the composition of a great 
 number of siliceous minerals, such as albite, labradorite,oligoclase, mesotype, 
 and other zeolites, nephelin, sodalite, achmite, lapis lazuli, etc. Sodium 
 also occurs combined with fluorine and aluminum fluoride as cryolite. In small 
 proportions sodium salts occur in coal, limestone, dolomite, and other minerals, as 
 well as in solution in the water of rivers and mineral springs. In plants sodium 
 occurs asysulphate, iodide, and chloride, and combined with vegetable acids, especially 
 in some kinds of sea-weed, and in certain plants which grow near the sea, such as 
 salicornia, salsola, and chenopodium, etc. ; in animals sodium occurs as chloride, 
 phosphate, carbonate, and sulphate, and combined with various organic acids. 
 
 Characters. Sodium is 'a solid substance possessing all the essential characters 
 of a metal ; it has a dull silver- white colour and considerable lustre when the surface 
 is clean, but it soon becomes dull by oxidation. The density of sodium is less than that of 
 water, its specific gravity being about 0'972. At the ordinary temperature sodium 
 is soft, and can be easily cut with a knife ; when cooled to it is ductile, and at 20 
 it becomes much harder ; it melts between 96 and 97, and is volatilisable at a higher 
 temperature. When exposed to the air, sodium gradually oxidises, and when heated 
 in contact with atmospheric air, it burns with a yellow flame, forming sodium 
 monoxide Na 2 0, and sodium peroxide Na 2 2 ; heated in oxygen gas the peroxide only 
 is formed. Sodium decomposes water with evolution of hydrogen gas and formation 
 of sodium hydrate NaHO, which dissolves in the excess of water. 
 
 Preparation. Sodium is obtained by exposing to a very high temperature a 
 mixture of dry sodium carbonate and charcoal or coal. The reaction that takes place 
 consists in the formation of carbonic oxide, with reduction of the sodium, as shown by 
 the following equation : 
 
 Na 2 C0 3 + 20 = 3CO + 2Na 
 106 24 84 46 
 
 Deville recommends adding to the mixture some porous material, such as chalk, 
 to prevent the separation of the melted sodium carbonate from the charcoal, and he 
 gives the following proportions : 
 
 Dry sodium carbonate . . . . 30 parts by weight. 
 
 Charcoal or coal 13 
 
 Chalk 3 
 
 According to Tissier, the addition of chalk is unnecessary when the proportion of 
 charcoal is properly adjusted. 
 
 The materials must be well dried, powdered, and thoroughly mixed in such a way 
 as to avoid absorption of moisture. In making sodium on a small scale a mercury 
 bottle may be used for heating the mixture, and fitted in a furnace, as shown in 
 fig. 134. 
 
PREPARATION OF SODIUM. 
 
 233 
 
 The end of the mercury bottle (A) is supported by a firebrick (B), and into the neck 
 of the bottle (c) is fitted a short iron tube, by which the sodium vapour is passed 
 into the condenser (D E). 
 
 In preparing sodium on the large 
 scale, the mixture is heated in wrought- 
 iron tubes about four feet long and 
 five inches wide, closed at both ends 
 with wrought-iron lids, in one of which 
 is a hole for screwing in the delivery 
 tube by which the sodium distills off. 
 The tubes are covered with clay and 
 laid in fire-clay cases in a reverber- 
 atory furnace with good draught, in 
 such a way that the ends slightly pro- 
 trude. The space between the iron 
 tube and the fire-clay cases is filled in 
 with powdered fire clay or some other 
 fire-resisting material. For setting the 
 process going, the iron tubes are first 
 made very slightly red hot, and then 
 the non-perforated lid is removed, and 
 the mixture, packed in paper cart- 
 ridges, is introduced, each tube hold- FIG. 134. 
 ing about ten pounds of the mixture. 
 
 A number of tubes of the kind are laid side by side in the furnace. The lids arc 
 then again screwed on to the tubes, smeared over with clay, and the tubes are heated 
 to bright redness. After the escape of some water vapour, combustible hydrocarbons 
 are given off with carbonic oxide, etc., and finally vapour of sodium, which may be 
 recognised by its forming a thick fume in contact with the air (sodium carbonate) and 
 burning with a yellow flame. Directly large quantities of sodium vapour are ob- 
 served to come off, the delivery tubes are screwed in and connected with a wide con- 
 denser, in which the sodium vapour condenses and drops in the form of metallic 
 sodium into vessels placed beneath, half filled with petroleum. The crude sodium is 
 then melted under petroleum, and cast into bars for the market. 
 
 The condensers, which contain considerable quantities of sodium, are cleaned by 
 holding them beneath petroleum, and scraping off the sodium with some sharp instru- 
 ment. The impure residues found in the receivers are purified by distilling them 
 from a mercury bottle. 
 
 A couple of tubes of the above dimensions, holding together 24 pounds of sodium 
 mixture, yield about 42 ozs. of raw sodium, from which 38 ozs. of pure product may 
 be obtained. 
 
 When upon protracted heating sodium vapour ceases to be given off, the receivers 
 are removed, the retorts or tubes opened, the residue removed, and the tubes re- 
 charged. 
 
 Owing to the fact that sodium rapidly oxidises in contact with air and moisture, 
 it requires keeping under petroleum. 
 
 SODIUM OXIDE. 
 
 FORMULA Ka 2 0. MOLECULAR WEIGHT 62. 
 
 This substance closely resembles the corresponding potassium compound, and it is 
 formed in the same manner. 
 
 SODIUM HYDRATE. 
 
 FORMULA NaHO. MOLECULAR WEIGHT 40. 
 
 Characters. Caustic soda as usually met with is a white translucent crystalline 
 mass, which rapidly attracts moisture from the air, and is readily soluble in water; 
 even at the highest temperatures no water can be driven off from the fused robst ice, 
 and it volatilises without decomposition. The solution of sodmm hydrate in wat< 
 accompanied by rise of temperature. After deliquescing caustic soda soon becomes 
 hard again from formation of sodium carbonate. Aqueous solutions of it when coo 
 
234 
 
 SODIUM. 
 
 to deposit a crystalline hydrate containing Na 2 0.8H 2 0. The amount of caustic 
 soda in aqueous solutions may be ascertained from their specific gravity, which in- 
 creases with the amount of caustic soda dissolved, as shown in the following table : 
 
 Spec. Grav. 
 
 Per Cent. 
 
 Spec. Grav. 
 
 Per Cent. 
 
 2-00 
 
 77-8 
 
 1-40 
 
 29-0 
 
 1-55 
 
 63'6 
 
 1-36 
 
 26-0 
 
 72 
 
 53-8 
 
 1-32 
 
 23-0 
 
 63 
 
 46-6 
 
 1-29 
 
 19-0 
 
 56 
 
 41-2 
 
 1-23 
 
 16-0 
 
 50 
 
 36-8 
 
 1-18 
 
 13-0 
 
 47 
 
 34-0 
 
 1-12 
 
 9-0 
 
 44 
 
 31-0 
 
 1-06 
 
 47 
 
 Pure caustic soda, when dissolved in water, forms a clear colourless liquid that has 
 a strong alkaline reaction and caustic taste ; it dissolves fats, and forms saline com- 
 pounds with the acids they contain a process technically termed saponification. 
 When exposed to the air caustic soda absorbs carbonic acid, and therefore solutions 
 of caustic soda require to be kept in well-stoppered bottles. Sodium hydrate is also 
 soluble in alcohol ; the solution when freshly prepared is colourless, but gradually 
 becomes brownish, and eventually black in colour, owing to the formation of a resinous 
 substance. 
 
 Preparation. Sodium hydrate, or caustic soda, may be prepared on the small 
 scale by dissolving crystallised soda (sodium carbonate) in four times its weight of 
 water, in an iron or silver vessel, and adding one-fourth its weight of lime mixed with 
 four times its weight of water. This- mixture is boiled until carbonic dioxide has been 
 entirely abstracted by the lime, and a small quantity of the liquid filtered from the 
 suspended calcium carbonate no longer effervesces when treated with a dilute acid. 
 This indicates that the whole amount of sodium carbonate has been converted into 
 hydrate, the reaction taking place according to the equation : 
 
 106 
 
 CaH 2 2 = 
 
 74 
 
 2NaHO 
 80 
 
 CaC0 3 
 100 
 
 The clear liquor in the pan is then filtered or decanted from the calcium car- 
 bonate, and either at once filled into well-stoppered bottles, or evaporated to dryness 
 in silver or iron dishes. This method was formerly employed for the preparation of 
 caustic soda on the large scale. 
 
 Caustic soda is now produced, together with sodium carbonate, by Leblanc's method, 
 the quantity of coal added to the mixture of sodium sulphate and chalk being increased 
 in order to obtain more of the soda in the caustic state. After the liquor obtained 
 by the lixiviation of the ball soda has cleared, it is at once concentrated to a specific 
 gravity of 1*5, the sodium carbonate which separates is removed, and the mother liquor 
 heated in iron vessels to about 150. Some Chili saltpetre (sodium nitrate), amount- 
 ing to from 3 to 4 per cent, of the caustic soda in the liquor, is then thrown in for the 
 oxidation of the sulphides, hyposulphites, and sulphites of sodium present in the liquor. 
 The nitrogen of the sodium nitrate escapes partly as ammonia and partly in the free 
 condition, according to the following equations : 
 
 5Na 2 S 
 
 + NaN0 3 + 2H 2 = Na 2 SO, 
 8NaN0 3 + 4H 2 = 
 
 NaHO + 
 - SNaHO 
 
 NH 3 . 
 
 + 8N. 
 
 The sodium nitrate causes further the decomposition of cyanogen compounds 
 (sodium ferrocyanide) and the conversion of ferrous sulphide into ferric oxide, which 
 collects at the bottom of the pans, together with other impurities. The clear liquor 
 is then drawn off, concentrated to a spec. grav. of 1*9, and run into cylindrical or 
 rectangular cast-iron moulds, in which it solidifies to a crystalline mass. 
 
 The use of atmospheric air as an oxidising agent in place of sodium nitrate is of 
 considerable importance. It is forced into the solution either by means of an air 
 pump or by steam. An arrangement of the kind much employed in this country con- 
 sists of a cylindrical boiler furnished with a perforated false bottom at a little distance 
 above its bottom. A tube at right angles to the axis of the cylinder, furnished with a 
 funnel at its upper extremity and fitted into the middle of the false bottom, serves for 
 charging the liquor with steam and air, which is effected by allowing steam to escape 
 from a tube just above the mouth of the funnel. Steam mixed with air is thus brought 
 beneath the false bottom, the mixture serving at the same time to heat the liquor and 
 
SODIUM CHLORIDE. 
 
 235 
 
 oxidise impurities. ^ The admission of steam and air is continued until the liquor no 
 longer yields a precipitate of lead sulphide when a portion of it is treated with a solu- 
 tion of lead acetate. 
 
 A great number of other methods have been proposed for the preparation of caustic 
 soda, among which the following may be mentioned. A process that has been several 
 times patented consists in decomposing an aqueous solution of sodium sulphate with 
 caustic Baryta. Another method consists in first decomposing common salt with 
 fluosilicic acid, the sodium silico-fluoride being then converted into caustic soda, by 
 treating it with caustic lime, either at once, or after heating it to redness. When the 
 sodium silico-fluoride is heated to redness, it is decomposed into sodium fluoride and 
 gaseous silicium fluoride, which is converted into fluosilicic acid by passing it into water. 
 Jean melts together fluor spar, calcium carbonate, G-lauber's salt and carbon, the product, 
 upon treatment with water yielding a solution of sodium fluoride, which is then converted 
 into caustic soda either by means of caustic lime or by superheated steam. Priickner 
 suggests heating sodium sulphate to redness with coal, lixiviating out the sodium 
 sulphide, and then decomposing it with copper scales. In this way caustic soda and 
 cupric sulphide are formed (vide p. 268). Bachet recommends treating a solution of 
 common salt with lead oxide, by which means insoluble lead oxychloride and sodium 
 hydrate are formed. The oxychloride is then reconverted into soluble lead oxide by 
 treating it with milk of lime. 
 
 Pure sodium hydrate is prepared by treating metallic sodium very carefully with a 
 small quantity of pure water in bright iron or silver vessels. The product consists of 
 a thick paste of sodium hydrate, which is dried and afterwards melted. 
 
 The percentage of sodium hydrate in commercial caustic soda varies considerably. 
 Common caustic soda is always found to contain a number of foreign admixtures, and 
 besides this the percentage of water contained in it varies with the degree to which 
 the caustic soda liquor has been evaporated. 
 
 The following analyses of commercial caustic soda are given by Tissandier: 
 
 Sodium hydrate . 
 ,, carbonate 
 sulphate 
 chloride 
 Water 
 
 English Caustic Soda. 
 
 French Caustic Soda. 
 
 I. 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 VI. 
 
 87-73 
 3-45 
 1-00 
 7'23 
 0-59 
 
 87-50 
 3-68 
 1-32 
 6-82 
 0-68 
 
 85-71 
 5-48 
 2-10 
 5-60 
 1-11 
 
 75-31 
 5-58 
 3-41 
 11-32 
 4-38 
 
 72-65 
 9-82 
 2-00 
 12-32 
 3-31 
 
 86-10 
 3-69 
 2-60 
 3-90 
 3-71 
 
 Besides the above substances, commercial caustic soda often contains small 
 quantities of sodium hyposulphite, calcium carbonate, and other impurities. 
 
 Uses. One of the chief uses of caustic soda is in soap making. It is also used in 
 the place of soda in dye works, for removing fatty and other impurities from the stuff. 
 Caustic soda is further used for purifying carbolic acid, petroleum, and coal oil products, 
 etc., in the manufacture of oxalic acid and soluble glass, as well as for many purposes 
 in the laboratory. 
 
 SODIUM CHLORIDE. 
 
 FORMULA NaCl. MOLECULAR WEIGHT 58*5. 
 
 History. This important substance, generally termed common salt, has been 
 known from the earliest times as being a necessary adjunct to the food of animals, 
 and it is mentioned in the writings of Moses and Homer. In a chemical point of 
 view it is interesting as constituting the type of a large class of substances now com- 
 prised under the generic term of salts. The Greek name of salt, a\s, denotes the 
 solid substance left when sea water is evaporated, and the several steps by which this 
 specific application of the term was extended show that the idea indicated by th 
 etymology of the word led to its application to other substances obtained in like 
 manner by the evaporation of watery liquids. Thus the residue left on evaporating 
 the lye of wood ashes was termed a salt by Aristotle, and several other substances 
 were designated by the same term with specific reference to their origin, as in the cases 
 of sal vegetabile (potash), sal ammoniac, sal pctra, etc. 
 
 Occurrence. Sodium chloride is one of the most widely distributed substance*. 
 It occurs in large and extensive beds in all parts of the earth, and in the most various 
 
236 
 
 SODIUM. 
 
 rock formations, being nearly always accompanied by clay and gypsum. Beds of rock 
 salt, of large dimensions, occur in the Muschelkalk strata in Austria, in Wiirtemberg, 
 Baden, Upper Bavaria, Hanover, etc. Rock salt is found in England in the red 
 sandstone in Derbyshire, Worcestershire, etc.; it is found among the tertiary strata 
 in the Carpathians, Hungary, and G-alicia ; also in Zeckstein, to which belongs the 
 extensive rock salt bed formation north of the Harz mountains at Stassfurt, and 
 south of the Harz at Erfurt, and other beds in Brandenburg, the Teutoburger 
 forest, and other places in Germany. Rock salt occurs also in the chalk, Keuper 
 and lias formations. 
 
 Sodium chloride occurs naturally as an efflorescence from the earth's surface, as 
 for instance in the vicinity of the Caspian Sea, the tableland of Thibet, etc. Sodium 
 chloride also occurs very abundantly in a state of solution in the water of a number 
 of springs (salines), ia the water of the sea, and in small quantities in all kinds of 
 natural water. 
 
 Characters. Sodium chloride, when pure, is a solid white substance, crystal- 
 lising in cubes, but without water of crystallisation. It is hygroscopic only when 
 it contains foreign ingredients, such as calcium chloride and magnesium chloride. 
 The crystals of common salt, obtained by evaporating its solutions, are proportionally 
 larger when the evaporation has been slow, appearing then as hollow quadrilateral 
 pyramids with terrace-like sides, which are found upon examination to consist of 
 aggregations of distinct cubes. Although the crystals of sodium chloride contain no 
 water of crystallisation, they generally contain small quantities of mother liquor 
 enclosed in them, and this causes the crystals to decrepitate when heated. Sodium 
 chloride when strongly heated melts to a transparent colourless liquid ; at a red heat 
 it volatilises, and does so more readily when a current of air is passed over the 
 heated mass. The solubility of sodium chloride in water does not vary much with the 
 temperature : 100 parts of water at 15 dissolve 3273 parts of sodium chloride ; at 
 35-52 parts; at 25 36-13 parts ; at 70 37'88 parts ; and at 100 39-61 parts. A con- 
 centrated solution of salt, cooled down to 15 deposits hydrated crystals, having a 
 composition represented by the formula NaCl + 2H 2 0, which however give up their 
 water of crystallisation when the temperature is raised to 10. Sodium chloride 
 is soluble in aqueous alcohol, in proportion to the amount of water it contains. It has 
 a spec, gravity of from 2'10 to 2-15 and its taste is saline and pleasant. 
 
 Preparation. ROCK SALT. The salt of the various rock salt deposits is seldom 
 chemically pure, but always contains some admixtures of other salts, as may be seen 
 from the following table of analyses : 
 
 
 
 o 
 
 
 i 
 
 
 
 3 
 
 . 
 
 
 
 
 
 o 
 
 S 
 
 1 
 
 1 
 
 1 
 
 % 
 2 
 
 I 
 
 I 
 
 1 
 
 
 
 g 
 
 a 
 
 
 
 i 
 
 -a 
 
 a 
 
 1 
 
 13 
 
 1 
 
 'O-S 
 
 
 1 
 
 a 
 
 i 
 
 i 
 
 1 
 
 1 
 
 
 C/2 
 
 
 
 o 
 
 H 
 
 
 I 
 
 H 
 
 i 
 
 } 
 
 1 
 
 I 
 
 1 
 
 1 
 
 i 
 
 s i 
 
 "Wieliczka . 
 Berchtesgaden . 
 
 100-00 
 99.85 
 
 
 
 traces 
 
 traces 
 0-15 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Hall, Tyrol 
 
 99-43 
 
 
 
 0-25 
 
 0-12 
 
 
 
 0'20 
 
 
 
 
 
 
 
 
 
 Schwab. Hall . 
 
 99-63 
 
 
 
 0-09 
 
 0-28 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Vic. Lothringen 
 
 99-30 
 
 
 
 
 
 
 
 
 
 0-50 
 
 
 
 
 
 
 
 0-20 
 
 Erfurt 
 
 98-04 
 
 traces 
 
 0-41 
 
 0-06 
 
 
 
 1-48 
 
 
 
 
 
 
 
 
 
 Cordona 
 
 98-55 
 
 
 
 0-99 
 
 o-oi 
 
 
 
 0-44 
 
 
 
 
 
 
 
 
 
 Djebel Melah (Arabia) 
 Vesuvius 1822 . 
 
 9700 
 83-10 
 
 13-90 
 
 I 
 
 I 
 
 1-60 
 
 3-00 
 0-70 
 
 
 
 I 
 
 z 
 
 
 
 1850 . 
 
 62-45 
 
 37-55 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1855 . . 
 
 94-30 
 
 
 
 
 
 
 
 0-20 
 
 0-70 
 
 0-40 1-00 
 
 0-60 
 
 
 
 It often happens that rock salt contains gases enclosed within it. Some specimens 
 of rock salt from Wieliczka, for instance, decrepitate when thrown into water, owing 
 to the escape of condensed gas, which has been found to consist of hydrogen, carbonic 
 oxide, and marsh gas, olefiant gas sometimes replacing the latter. In some places 
 rock salt is found together with petroleum. 
 
 Rock salt, according to its mode of occurrence, is either quarried or mined. In 
 places where the deposit lies deep and is of great extent, large cavities are formed by 
 
BRINE SPRINGS. 
 
 237 
 
 blasting, one over the other, which are supported by pillars and walls of the salt 
 itself, as is the case in the enormous salt mine at Wieliczka. 
 
 Rock salt as it comes from the mine varies in purity. It is sometimes so pure and 
 white that it requires no preparation but grinding to convert it into snow-white culi- 
 nary salt. The more impure sort is, however, often lixiviated in suitable boilers with 
 natural or artificial brine, and the solution evaporated to obtain the salt. 
 
 FROM NATURAL AND ARTIFICIAL BRINE SPRINGS. Natural brine springs contain a 
 sufficient amount of salt to render it profitable to boil the brine down at once. Springs 
 of this kind are however rare, owing to the infiltration of surface water, which dilutes 
 the brine. This dilution by surface water is prevented by means of water-tight 
 shafts, which reach down to the spring. The more general plan is to bore a hole 
 right into the bed of rock salt, and to pump from it a more saturated brine. 
 
 Artificial Brine Springs. These differ from one another according to their situa- 
 tion, but they are all formed either by treating salt deposits themselves, or salt that has 
 been already quarried, with fresh water, or with weak brine, which contains too little 
 salt for boiling down. Thus brines are formed by boring into deposits of rock salt, 
 and admitting water, generally surface water, the brine being then removed either with 
 buckets or by pumping. The brine thus obtained contains about 20 per cent, of salt. 
 Another method consists in lixiviating already quarried salt, the latter being generally 
 impure from admixtures of clay and gypsum. The lixiviation is generally carried out 
 at the surface, and seldom in the mine itself. The salt is treated in large boxes or 
 pans, either with fresh water or with a weak brine ; in some places sea water is used. 
 The amount of salt in the brine thus obtained varies between 20 and 25 per cent. 
 
 The composition of brine varies considerably. The chief constituent is sodium 
 chloride or common salt, but it always contains some other salts in solution, which 
 considerably affect the value of the brine. 
 
 In the following table is given the analyses of brine from a few natural springs. 
 
 
 Halle 
 
 Scttone- 
 beck. 
 
 Dttrrenberg 
 
 Kreuznach 
 
 Sodium chloride . . , 
 
 17718 
 
 9-623 
 
 6-599 
 
 1-415 
 
 Potassium chloride . , : ' * ^ , . 
 
 0-166 
 
 0-007 
 
 0-008 
 
 0-006 
 
 Sodium sulphate . . . . .,. 
 
 
 
 0-249 
 
 0-208 
 
 
 
 Potassium sulphate . , , , *. 
 
 
 
 0-014 
 
 0-004 
 
 
 
 Calcium chloride . . , . ,. ,,, 
 
 0-134 
 
 
 
 
 
 0-261 
 
 Magnesium chloride . ..... 
 
 0-406 
 
 0-083 
 
 0-092 
 
 0-023 
 
 Calcium sulphate . 
 
 0-466 
 
 0-339 
 
 0-250 
 
 
 
 Magnesium sulphate 
 
 
 
 0-012 
 
 
 
 
 
 Calcium carbonate . 
 
 
 
 0-026 
 
 0-058 
 
 0-003 
 
 Iron carbonate ..... 
 
 
 
 0-001 
 
 0-004 
 
 O'OOo 
 
 Magnesium carbonate . . . 
 
 
 
 
 
 
 
 o-ooi 
 
 Alluminum sulphate . . . . V 
 
 
 
 
 
 
 
 o-ooi 
 
 Silica . . . 
 
 , 
 
 
 
 
 
 0-013 
 
 Organic substance ., . 
 
 
 
 o-ooi 
 
 0-012 
 
 traces 
 
 The following table gives the composition of a few artificial brines, which are as a 
 rule richer in sodium chloride than the natural ones. 
 
 
 Friedrichshall 
 
 Boring at 
 Artern 
 
 Rappenau 
 
 Sodium chloride . . ., . . < * 
 
 25-563 
 
 23-652 
 
 25-850 
 
 Potassium chloride . * &:* 
 
 
 
 0-112 
 
 
 
 Potassium sulphate , . . .- 
 Calcium chloride 
 
 
 
 0-272 
 
 0-085 
 
 Magnesium chloride ..- ., > 
 
 Calcium sulphate . .. '- .- 
 
 0-006 
 0-437 
 
 0-395 
 0-375 
 
 0-042 
 0-413 
 
 Magnesium sulphate . - 
 Calcium carbonate . 
 
 0-022 
 
 o-oio 
 
 
 
 o-ooi 
 
 For determining the percentage of salt contained in brino, gauges are used which 
 indicate either the specific gravity of the brine, or the number of pounds of salt con- 
 tained in a cubic foot of the brine. For finding the percentage of salts from 
 specific gravity of the brine, the following table by Bischof is used. 
 are for a temperature of 1-5 
 
238 
 
 SODIUM. 
 
 Spec. Grav. 
 
 Per cent, of Sodium 
 Chloride. 
 
 Spec. Grav. 
 
 Per cent, of Sodium 
 Chloride 
 
 1-00712 
 
 1 
 
 10323 
 
 14 
 
 1-012472 
 
 2 
 
 11095 
 
 15 
 
 02146 
 
 3 
 
 11872 
 
 16 
 
 02868 
 
 4 
 
 12655 
 
 17 
 
 03594 
 
 5 
 
 13443 
 
 18 
 
 04324 
 
 6 
 
 14327 
 
 19 
 
 05058 
 
 7 
 
 15038 
 
 20 
 
 05796 
 
 8 
 
 15844 
 
 21 
 
 06539 
 
 9 
 
 16657 
 
 22 
 
 07286 
 
 10 
 
 17476 
 
 23 
 
 1-08038 
 
 11 
 
 18302 
 
 24 
 
 1-08795 
 
 12 
 
 19135 
 
 25 
 
 1-09556 
 
 13 
 
 1-19975 
 
 26 
 
 In using this table, however, regard must be had to the fact that the presence of 
 other salts than sodium chloride influences the specific gravity of the brine, and that 
 too in a way different to sodium chloride ; on which account the table can only be 
 used for brine containing small quantities of other salts. The table, when used 
 for brines containing large quantities of foreign salts, requires a correction, which varies 
 with the brine, but is constant for one and the same brine, since in the latter case the 
 relative amounts of the salts remain the same. 
 
 The strength of brine is sometimes expressed by the quantity of water which holds 
 in solution one part by weight of salt. The measuring of brine is effected in various ways : 
 in measuring boxes ; in the receivers and evaporating pans, the capacity of which is 
 known ; or by observing the length of time occupied by the flow of the brine from 
 tubes of known diameter. 
 
 Concentrating the Brine. A great number of brines contain too little common salt in 
 solution to enable them to be boiled down at once. Such brines are, therefore, sub- 
 jected to a process of concentration, or what is technically termed gradation. 
 
 Faggot Gradation. This operation, which is also known as drop gradation, is that 
 most often employed. The weak brine is caused to trickle down the sides of a grada- 
 tion house, which consists of a framework of timber fitted with faggots of the sloe 
 (Prunus spinosa). The weak brine is pumped into a water-tight tank placed above the 
 gradation house ; this tank is provided with a number of taps from which the brine 
 trickles into channels provided with holes to admit of its falling on the faggots. The 
 entire construction is built over a water-tight tank which receives the concentrated 
 brine. According to the way in which the gradation is conducted, the operation has re- 
 ceived different names : ]. Surf ace gradation, in which the brine trickles down that 
 side of the gradation house which is most exposed to the prevailing wind. 2. Cubical 
 gradation, in which the brine drops down both outer sides, as well as both inner sides 
 of the gradation house. 3. Combined cubicand trilateral gradation. Thiskindof 
 gradation is the most effectual. Two gradation walls are placed side by side at a slight 
 distance apart. The brine trickles down both the sides and the interior of that wall 
 which is exposed to the prevailing wind, as well as over the exterior of the other wall 
 which is placed near it. The brine, after having passed over the sides of the gradation 
 house, is again pumped up into the dropping tank above, until it has attained the neces- 
 sary concentration. It is, however, not customary to allow the brine to drop a second 
 time over the same part of the gradation house, which is divided into 1st gradation, 
 2nd gradation, 3rd gradation, etc. ; the first gradation receiving the fresh brine, the 
 second gradation brine which has undergone one concentration, and the third grada- 
 tion receiving brine which has been twice concentrated, etc. The brine is pumped up 
 either by the aid of steam, water, or wind. 
 
 Figs. 135 and 136 represent the gradation house at the salt works of Diirrenberg. 
 c c are the inner walls of thorn faggots, d d are the outer walls, both being 1 8 inches 
 thick. At the top of the thorn walls are the brine spouts (oo), with the dropping 
 spouts (pp) for distributing the brine over the walls by the spigots (ss), as shown on 
 a larger scale by fig. 137. The brine cistern (bb) over which the walls are built is 
 supported upon brick walls (a a). 
 
 The gradation process not only serves the purpose of concentration, but also that 
 of purifying the brine, as some of the foreign salts are deposited on the faggots. The 
 first gradation generally seems to separate calcium carbonate, owing to the escape of 
 
EXTRACTION OF SALT. 
 
 239 
 
 carbonic acid which retained that salt in solution as acid carbonate. The other gradations 
 cause chiefly a deposit of gypsum. The salts deposited are called by the Germans 
 
 
 FIG. 135. 
 
 FIG. 136. 
 
 thorn sto n e. The following table gives the composition of such thornstones from the 
 salines of Schonebeck and Diirrenberg. 
 
 
 Schonebeck 
 
 DUrrenberg 
 
 
 I. Grad. 
 
 II. Grad. 
 
 III. Grad. 
 
 I. Grad. 
 
 II. Grad. 
 
 Calcium carbonate 
 
 83-166 
 
 1-492 
 
 0-924 
 
 0-612 
 
 0-113 
 
 Calcium sulphate . 
 
 3-540 
 
 95-322 
 
 96-138 
 
 97-444 
 
 98-748 
 
 Sodium chloride . 
 
 2-957 
 
 1-669 
 
 1-350 
 
 0-155 
 
 0-438 
 
 Sodium sulphate . . - ' 
 
 2-286 
 
 0-087 
 
 0-346 
 
 0-197 
 
 
 
 Potassium sulphate 
 
 0-904 
 
 0-756 
 
 0-592 
 
 0-586 
 
 0-398 
 
 Magnesium carbonate . 
 
 1-745 
 
 0-275 
 
 0-204 
 
 0-125 
 
 0-084 
 
 Aluminum sulphate 
 
 
 
 
 
 
 
 0-555 
 
 
 
 Ferric oxide . . . 
 Alumina . . . " ." 
 
 2-104 \ 
 0-499 / 
 
 0-094 
 
 0-077 
 
 0-136 
 
 
 
 Silica . . . . " . : 
 
 2-499 
 
 0-300 
 
 0-324 
 
 0-190 
 
 0-219 
 
 In the course of a few years the deposit becomes so thick, that the faggots require 
 renewing, and the old ones are sometimes used as manure. 
 
 The gradation of the brine causes a considerable loss of salt, which is carried away 
 by the wind. 
 
 The concentrated brine which is left in pits or basins to settle, yields a further 
 precipitate consisting chiefly of calcium carbonate and sulphate. 
 
 The concentration of graduated brine varies at different works, and the amount of 
 salt is generally between 17 and 25 per cent., sometimes as high as 27 per cent. 
 
 The composition of the brine used for boiling down at the Schonebeck salines is 
 given in the following table : 
 
 
 I. Grad. 
 
 II. Grad. 
 
 III. Grad. 
 
 IV. Grad. 
 
 
 
 
 1 
 
 
 Sodium chloride . . . . ; . 
 
 15-48 
 
 19-09 ' 
 
 23-54 
 
 25-16 
 
 Potassium sulphate 
 Calcium sulphate >; = 
 Magnesium sulphate . 
 Magnesium chloride . . 
 
 0-23 
 0-49 
 
 0-11 
 
 0-14 
 
 0-28 
 0-46 
 0-23 
 0-15 
 
 0-36 
 0-38 
 0-23 
 0-19 
 
 0-55 
 0-17 
 0-61 
 0-63 
 
240 SODIUM. 
 
 There are also other methods of gradation, as already mentioned, but they are 
 little suited for working brine. 
 
 Gradation by Freezing. This method is practised on the coast of the sea of Okotsk 
 and at Irkutsk in Siberia. The water is allowed to freeze, and the ice removed, a 
 strong solution of salt remaining. 
 
 Solar Gradation. This method is chiefly used for concentrating sea water, seldom, 
 however, for preparing salt from brine. The water is allowed to evaporate in the sun 
 in shallow basins. 
 
 Table Gradation consists in causing the brine to flow slowly down a number of 
 steps formed of shallow boxes. Roof gradation is a similar process, the brine being 
 made to flow over inclined surfaces like the roof of a house. Rope gradation consists 
 in passing the brine over vertical ropes, upon which it forms a crystalline deposit that 
 is scraped off when sufficiently thick. 
 
 Boiling down. This process is carried out either in hemispherical or flat pans. 
 Those usually employed are formed of sheet-iron plates riveted together, and are in 
 shape round, hemispherical, or square. The most convenient size is between 600 and 
 1000 square feet area. The pans are heated by hot air made to circulate beneath 
 them from a furnace. A suitable chimney conducts the vapour into the air. 
 
 According to the purity of the brine, the boiling down is performed in one or two 
 operations. Brine containing large quantities of gypsum or sodium sulphate is first 
 of all concentrated in special pans until these impurities separate, together with some 
 ferric hydrate, silica, and sodium chloride in the form of mud. The heating is then 
 continued until a crust of salt has formed on the surface, indicating that the liquor is 
 saturated. The clear liquor is then drawn off into other pans and evaporated until the 
 salt crystallises out, the crystals being removed as formed and placed on a board near 
 the pan to drain. Each time a portion of crystallised salt is removed, a fresh quantity 
 of brine is let into the pan, the operation being continued until the mother liquor is too 
 impure to yield a further crop of sufficiently pure salt. The mother liquor is then 
 either thrown away or treated for other products. 
 
 Fine-grained salt is obtained at a temperature of 90-100, coarse-grained salt at 
 a temperature between 60 and 70. The salt separated decreases in purity during 
 the process of crystallising. At the beginning of the operation, salt is obtained con- 
 taining 95 or 96 per cent, of sodium chloride, and towards the end of the operation the 
 amount of salt is only 80 per cent. The quantity of salt separated in a given time is 
 greater in proportion to its coarseness, being for fine-grained salt 20 to 25 Ibs., and 
 for coarse-grained salt only 25 to 25 Ibs. per square foot in twenty-four hours. 
 
 The sheet-iron pans are replaced in many districts by cast-iron pans made in sec- 
 tions, the flanges of which are fixed together by bolts ; they are more durable and also 
 cheaper than sheet-iron pans. 
 
 Wooden evaporating pans are but seldom used ; they are made of fir planks and the 
 brine is heated by means of copper tubes through which superheated steam is passed. 
 
 Another kind of evaporating pan is made of brickwork, and the brine is evaporated 
 by passing hot air from a fire over its surface. It is necessary in this case that the 
 pan should be arched over, and this renders the operation so difficult that these pans 
 have not been much employed. 
 
 Drying of the Salt. The operation of drying the salt is effected either in the open 
 air or in specially constructed drying chambers that are kept at a temperature of 50- 
 60, either by means of the hot air from the evaporating pans, or by a separate heating 
 arrangement. ' The salt is laid out in the chambers either upon wooden shelves in 
 layers of 3 to 5 inches in depth, or in the perforated boxes or baskets in which it was 
 placed to drain. 
 
 Instead of drying chambers, drying hearths or pans are sometimes used, the bottom 
 of which is made of limestone slabs or sheet iron. They are heated from beneath by 
 the hot air or vapour of the boiling pans. 
 
 Box Drying. The salt is spread out upon hurdles contained in wooden boxes, hot 
 air being passed into the boxes from below. The air is heated in tubes lying in the 
 hearth of the boiling pans. 
 
 In some districts of Transylvania salt is dried over an open fire, the salt being for 
 this purpose moulded into forms like sugar cones. 
 
 In drying salt care must be taken to avoid too high a temperature, for if it is too 
 high gypsum loses its water and becomes insoluble, and, further, magnesium chloride 
 is partly converted into insoluble magnesia. 
 
 The composition of the salt obtained from different salines may be seen from tho 
 following table : 
 
EXTRACTION OF SALT. 
 
 241 
 
 
 Wimpfen 
 
 Schwab. 
 Hall 
 
 Halle 
 
 Neu 
 Salzwerk 
 
 Ischl 
 
 Sodium chloride . 
 
 99-45 
 
 98-90 
 
 98-36 
 
 91-35 
 
 87-39 
 
 Sodium sulphate . 
 
 0-05 
 
 0-005 
 
 
 
 1-00 
 
 1-25 
 
 Calcium chloride . 
 
 
 
 
 
 
 
 
 
 
 Magnesium chloride 
 
 
 
 
 
 0-28 
 
 0-39 
 
 2-06 
 
 Calcium sulphate . 
 
 028 
 
 0-49 
 
 1-33 
 
 0-57 
 
 0-35 
 
 Magnesium sulphate 
 
 
 
 
 
 
 
 
 0-43 
 
 Magnesium carbonate . 
 
 
 
 0-005 
 
 0-Ofc 
 
 
 
 
 
 Water 
 
 - 
 
 0-60 
 
 
 
 6-68 
 
 7-91 
 
 Organic matter 
 
 
 
 
 
 
 
 
 
 0-35 
 
 An impure salt containing a considerable amount of gypsum (l-4 per cent.) and 
 organic substance is used for cattle. 
 
 In some countries where salt is an article upon which an excise duty is levied, in 
 order that it may be employed duty free for certain industrial purposes, common salt 
 is often mixed with substances which render it unfit for culinary use, such as gypsum, 
 Glauber's salt, green vitriol, charcoal, ashes, etc.> and it is then termed denatura lis ed 
 salt. The substances added are selected according to the ultimate use of the salt 
 for cattle, for manure, or for industrial purposes. 
 
 The pan scale which adheres to the vessels in which salt is boiled down is espe- 
 cially rich in gypsum, but it also contains considerable quantities of common salt. 
 The pan scale of the Halle salines has the following percentage composition: 
 Sodium chloride ..... ... . 29'028 
 
 Potassium chloride ..... * .1-310 
 
 Calcium chloride ..... i,. . . 2-431 
 
 Magnesium chloride . . .. / * - 0'243 
 
 Calcium sulphate . . v . . .* . . 62-981 
 Calcium carbonate ... . . . . ." 1*265 
 
 Magnesium carbonate . .. . 'V . - ' 1'905 
 Ferric oxide and alumina . . . '.' . . 0-304 
 Silica . .;.;'.. . '- . , J V . v 0'533 
 
 Pan scale from other salines has been found to contain, besides the above ingre- 
 dients, sulphates of sodium, potassium, and magnesium. 
 
 Pan scale is either treated for common salt or used as manure, or in the manu- 
 facture of green glass. 
 
 The mother liquor of brine from which the sodium chloride has been extracted 
 varies considerably in composition, and is treated accordingly for various products, the 
 saline constituents being extracted by fractional crystallisation. When the mother 
 liquor contains bromine or iodine, it is often dried and used as bathing salt. 
 
 SALT FROM SEA WATER. The essential constituents of sea water do not differ in 
 any part of the world, and the difference in quantity is very small, as may be seen 
 from the following table : 
 
 
 German 
 
 Atlantic 
 
 Pacific 
 
 Mediterra- 
 
 Red Sea 
 
 
 Ocean 
 
 Ocean 
 
 Ocean 
 
 nean Sea 
 
 
 Sodium chloride . . .* 
 
 2-5513 
 
 2-7558 
 
 2-5877 
 
 2-9424 
 
 3-030 
 
 Potassium chloride . .... 
 
 
 
 
 
 
 
 0-0505 
 
 0-288 
 
 Sodium bromide 
 
 0-0373 
 
 00326 
 
 0-0401 
 
 0-0556 
 
 0-064 
 
 Potassium sulphate . 
 Calcium sulphate 
 Magnesium sulphate . --.'.. . .;. 
 Magnesium chloride . 
 Calcium carbonate and ferric oxide 
 
 0-1529 
 0-1622 
 0-0706 
 0-4641 
 
 0-1715 
 0-2046 
 0-0614 
 0-3260 
 
 0-1359 
 0-1622 
 0-1104 
 0-4345 
 
 0-1357 
 0-2477 
 0-3219 
 0-0117 
 
 0-295 
 0-179 
 0-274 
 0-404 
 
 The method of obtaining common salt from sea water varies according to the 
 
 The most important and also the most general method which is 
 South of France, Spain, Portugal, Southern Italy, Sicily, Istna, and V 
 sists in evaporating the sea water in a series of pits or basins calJ 
 The sea water is passed first of all into basins of large ^nacitv 
 where it is allowed to stand some time so as to deposit 
 
 R 
 
 a, etc con 
 
 im 
 
242 
 
 SODIUM. 
 
 clear water is then drawn off into a system of basins, each successive basin being 
 shallower and smaller than the one before it. The basins are excavated in the ground 
 and are separated from each other by thin clay walls. The sea water, after having 
 passed through the first set of basins, has a specific gravity of 1/152, and the water 
 in the last of the smaller basins has a gravity of 1-197. The following table gives the 
 amount and nature of the foreign substances precipitated from sea water during its 
 concentration in the basins from sp. gr. 1-034 to 1-197, at the different degrees of 
 concentration : 
 
 10,000 parts of sea water deposit at f Ferric hydrate . 0-031 parts, 
 a specific gravity of 1-049 of \Calcium carb. . . 0-672 
 
 [ Calcium carbonate, 
 1-122 ofJ with a little mag- 
 
 |_ nesium carbonate . 0-530 
 1-122 of gypsum . . . 5-600 
 1-156 ... 5-600 
 
 1-169 ... 1-800 
 
 1-197 ... 1-600 
 
 The liquor having attained a specific gravity of 1-19, is passed into still smaller 
 and shallower basins, and in proportion as the sodium chloride deposits, it is raked out 
 from time to time and laid in small heaps to drain ; when dry, it is packed in sacks 
 for the market. 
 
 Usiglio gives the following table for the deposition of sodium chloride and other 
 salts from sea water at different degrees of concentration between sp. gr. 1-197 and 
 1-245. 
 
 
 10,000 parts 
 
 There is separated out 
 
 Specific 
 gravity 
 
 of water 
 originally 
 taken are 
 reduced to 
 
 
 
 Gypsum 
 
 Sodium 
 chloride 
 
 Magnesium 
 sulphate 
 
 Magnesium 
 chloride 
 
 Sodium 
 bromide 
 
 
 parts parts 
 
 parts 
 
 parts 
 
 parts 
 
 parts 
 
 1-208 
 
 950 
 
 0-508 
 
 32-614 
 
 0-040 
 
 0-078 
 
 
 
 1-216 
 
 640 
 
 1-476 
 
 96-500 
 
 0-130 
 
 0-356 
 
 
 
 1-247 
 
 302 
 
 0-144 
 
 26-240" 
 
 0-174 
 
 > 0-150 
 
 0-358 
 
 1-271 
 
 230 
 
 
 
 22-720 
 
 0-254 
 
 
 
 0-518 
 
 Treahnent of the Mother Liquor. The mother liquor of sea water, after the chief 
 part of the sodium chloride has been removed, is in some places thrown into the sea. 
 while in other districts it is treated for various by-products. 
 
 In the South of France the mother liquor, having a specific gravity of 1-267, is con- 
 centrated to sp.gr. 1-299, so as to deposit in one or two crystallisations magnesium 
 sulphate and common salt in nearly equal parts. This mixture is dissolved in as little 
 water as possible, and the liquor passed alternately into day and night receivers. 
 During the day sodium chloride crystallises out, and during the night magnesium 
 sulphate, together with a double salt of potassium and magnesium sulphate containing - 
 6 molecules of water. The mother liquor that has been drawn off from the deposit of 
 sodium chloride and magnesium sulphate is then run into other vessels ; when evapo- 
 rated further it yields crystals of artificial carnallite (KClMgCl 2 + 6H 2 0), which are 
 then treated for potassium chloride by dissolving them in water and crystallising. 
 
 Porosity of the soil and change of weather are very unfavourable to the treatment 
 of mother liquor by the above process ; for when by concentration of the mother liquor it 
 has attained a specific grarity of 1-299, very slight alteration in the amount of water 
 or in the temperature during the night gives rise to the formation of very different 
 products. 
 
 Payen recommends treating the mother liquor according to the method introduced by 
 Merle in the salines of the island of Camargue and of Alais, by which the mother liquor, 
 concentrated only to 1-968 specific gravity, is cooled by Carre's apparatus and treated 
 for different products, as follows 
 
 Separation of Sodium Sulphate. The liquor is conducted from the reservoirs by 
 subterranean tubes in any required quantity into vessels fitted with the ammonia tubes 
 of Carry's freezing apparatus, water being added in quantity sufficient to prevent the 
 crystallisation of socfium chloride with the sodium sulphate. The liquor is cooled by 
 passing it through tubes lying in a liquor cooled to 18 in a previous operation, so that 
 it comes into the freezing vessel cooled to a temperature of 10, and it is then further 
 cooled by the tubes of Carre's machine to a temperature of 18. 
 
SALTS FROM SEA WATER. 
 
 243 
 
 The effect of this cooling is that about 85 percent, of the sodium sulphate present 
 separates in the crystalline condition, and is removed with cullenders attached to an 
 endless chain, the adherent water being separated in a centrifugal machine. The sodium 
 sulphate is finally calcined, the salt being generally used in this state. 
 
 Separation of the Residual Sodium Chloride. The mother liquor obtained in the 
 last operation is saturated with sodium chloride by filtration through raw sea salt, and 
 it is then boiled down for common salt in the usual way. The product thus obtained, 
 after being washed with a solution of sodium chloride to remove the magnesium 
 chloride, is very pure. 
 
 Preparation of Potassium Chloride. The mother liquor of the last operation, from 
 which the sodium chloride has been extracted, having a specific gravity of 1'288, is 
 run out into crystallising vessels, and after a short time crystals of artificial carnallite 
 (KClMgCl 2 + 6H 2 0) are deposited. From these crystals magnesium chloride is 
 extracted, either by the aid of cold water alone, or by heating them with a small 
 quantity of water, and then cooling the solution. The product thus obtained contains 
 on the average 90 per cent, of potassium chloride, the remainder sonsisting of water, 
 traces of magnesium chloride, and earthy admixtures. 
 
 Separation of Magnesium Chloride. The mother liquor, freed from artificial 
 carnallite and concentrated to sp. gr. T333, deposits upon cooling almost pure mag- 
 nesium chloride in a crystalline condition ; this salt is used for the preparation of 
 freezing mixtures, or of pure hydrochloric acid, as well- as for the prevention of dust 
 in streets sprinkled with it. The property of preventing dust is due to its hygro- 
 scopic nature. 
 
 Preparation of Bromine. The preparation of bromine from the final residues of 
 the mother liquor of sea water has been already treated of on page 177. 
 
 Common salt obtained from sea water varies in competition, as may be seen from 
 the following analyses : 
 
 
 Charente 
 Interieure 
 
 Languedoc 
 
 Trapani, 
 Sicily 
 
 St. Ubes, 
 Portugal 
 
 Sodium chloride ' . ' * . " V 
 
 96-42 
 
 95-11 
 
 96-35 
 
 95-19 
 
 Sodium sulphate . . . 
 Magnesium chloride . '-.' \' 
 Calcium sulphate . '.'.*. 
 
 0-20 
 1-95 
 
 0-23 
 0-91 
 
 0-51 
 0-50 
 0-45 
 
 0-56 
 
 Magnesium sulphate . j . 
 
 0-43 
 
 1-30 
 
 
 
 1-69 
 
 Insoluble matter . 'J-.it -. 
 
 TOO 
 
 o-io 
 
 007 
 
 
 
 Water . . ... . 
 
 
 
 2-35 
 
 2-12 
 
 2-45 
 
 
 
 
 
 
 Of the different kinds of salt obtained from sea water, that made in Portugal has 
 the best repute ; the salt of St. Ubes, especially, is very much sought after for pickling 
 meat, fish, and the, like. It was formerly supposed that this salt owed its character 
 to the large amount of magnesium sulphate ; but Payen considers that its physical con- 
 sistency, its white colour, and compactness are the cause of this salt being so much 
 liked. He remarks further that sea salt produced in France and England, when 
 properly prepared, is just as good as that obtained from St. Ubes. 
 
 Uses. Sodium chloride being a necessary ingredient of human and animal food, 
 finds one of its most important applications as a condiment, to mix with the food of man 
 and' of cattle. It is also used for several agricultural purposes. Large quantities 
 of salt are used in the preparation of soda by Leblanc's process, also in the prepara- 
 tion of hydrochloric acid, chlorine, sal ammoniac, corrosive sublimate, aluminum, 
 sodium etc. Salt is further used in the glazing of the coarser kinds of pottery and 
 earthenware, in tanning, in soap works, etc.; as a preservative for wood, meat, ftsn, 
 butter, etc. ; it is also employed to some considerable extent in the laboratory for pro 
 paring freezing mixtures, etc. 
 
 SODIUM SULPHIDES. 
 
 probably a constituent of ultramarine, and the mpnosulphide has been lately in 
 dueed into use in the preparation of hides for tanning. 
 
244 
 
 SODIUM. 
 
 ULTRAMARINE. 
 
 History. Kopp considers it probable that ultramarine or lapis lazuli is iden- 
 tical with the sapphire of the ancients. The word ' lazur,' meaning blue, is said to be 
 of Persian origin, and at any rate it is certain that the expression ' lazur ' was used 
 in the sixth century by Leontinus, a Greek author, as designating a blue pigment, and 
 from his time it became very frequent. The first mention of the preparation of a blue 
 pigment from lapis lazuli dates from the eleventh century ; and at a later period it 
 received the name of ultramarine, when the only source of the material was ' beyond 
 the sea.' 
 
 The first imitations of ultramarine consisted in preparing blue glass fluxes ; how- 
 ever, this product was far from being of sufficiently pure or deep colour. For a long 
 time it was generally supposed that the blue colour of ultramarine was due to copper ; 
 but this supposition was, however, disproved by Marggraff. 
 
 The art of preparing true artificial ultramarine dates from the beginning of the 
 present century, as a result of the researches of G-melin in Germany and Ghiimet in 
 France. The priority of the discovery is claimed by both chemists. It has, however, 
 been ascertained that Gmelin in 1827 informed G-ay-Lussac of his discovery, and was 
 induced by him to keep the discovery a secret. In 1828 Gay-Lussac gave an account 
 before the French Academy of Guimet's discovery of artificial ultramarine, but kept 
 secret his knowledge of Gmelin's previous researches. 
 
 Occurrence. Ultramarine occurs naturally in lapis lazuli, a mineral found 
 in different parts of China, Thibet, Siberia, etc. ; and it was this mineral, reduced by 
 mechanical means to a very fine powder, which was formerly brought into the market 
 as ultramarine. 
 
 Composition. The composition of natural ultramarine may be seen from the 
 following analysis by Varrentrap : 
 
 Ferric oxide . . 
 
 Sulphur .... 
 
 Chlorine .... 
 
 Water . . . . . . 072 
 
 Silica . 
 Sulphuric acid 
 
 . 45-50 
 . 5-89 
 . 3176 
 
 Soda . 
 
 . 9-09 
 , 3-52 
 
 0-86 
 0-95 
 0-42 
 
 Lapis lazuli is a very rare mineral, and for this reason the native ultramarine 
 formerly prepared, at a time when the secret of preparing artificial ultramarine was 
 unknown, was a very costly article. 
 
 Under the head of artificial ultramarine are distinguished two substances, green 
 and blue ultramarine. The former admits of being converted into the latter, and is 
 indeed usually nothing more than an intermediate product obtained in the preparation 
 of the blue pigment. 
 
 The following analyses will serve to show the composition of different kinds of 
 blue ultramarine: I. Meissner ultramarine (analysed by R. "Wagner). II. Nuremberg 
 ultramarine (analysed by Eisner). III. The same (Gentele). IV. and V. Blue ultra- 
 marine (analysed by Breunlein). VI. Ultramarine analysed by Wilkens. 
 
 
 I. 
 
 II. 
 
 III. 
 
 IV. 
 
 V. 
 
 VI. 
 
 Silica. 
 
 44-70 
 
 39-9 
 
 36-91 
 
 40-91 
 
 36-59 
 
 39-39 
 
 Alumina 
 
 25-62 
 
 30-0 
 
 29-17 
 
 24-19 
 
 25-05 
 
 26-40 
 
 Ferric oxide 
 
 0-53 
 
 0-9 
 
 1-01 
 
 0-50 
 
 0-91 
 
 
 
 Soda .... 
 
 21-65 
 
 25-5 
 
 21-25 
 
 16-28 
 
 17-20 
 
 21-52 
 
 Sodium 
 
 
 
 
 
 
 
 3-17 
 
 3-19 
 
 
 
 a. Sulphur * 
 b. Sulphur . 
 
 [ 7-24 
 
 4-6 
 
 j 5-90 
 ( 
 
 2-20 
 8-45 
 
 2-22 
 8-68 
 
 j 12-69 
 
 Sulphuretted hydrogen 
 Sulphuric acid . 
 
 3-62 
 
 0-4 
 
 0-93 
 2-52 
 
 1-31 
 
 1-99 
 
 
 
 Lime .... 
 
 0-17 
 
 
 
 0-60 
 
 0-82 
 
 1-02 
 
 
 
 Clay . . . ^ . 
 
 
 
 
 
 
 
 1-46 
 
 2-81 
 
 
 
 Green ultramarine has a composition as shown in the following analyses of Breunlein 
 (I.) and Gentele (II.) : 
 
 a. Sulphur which upon treating the ultramarine with sulphuric acid separates out as sulphuretted' 
 hydrogen. 6. Sulphur which, treated with the same reagent, separates as sulphur. 
 
ULTRAMARINE. 
 
 245 
 
 
 I. 
 
 II. 
 
 Silica 
 
 38*39 
 
 37.00 
 
 Alumina 
 
 27-38 
 0'63 
 
 29-39 
 1'40 
 
 Soda 
 
 16-93 
 
 25*31 
 
 
 5*29 
 
 
 a. Sulphur 
 b. Sulphur 
 Sulphuric acid . . . 
 Lime ........ 
 
 3-68 
 3-49 
 0-52 
 0*83 
 
 3*00 
 3*64 
 0*59 
 1*13 
 
 Clay 
 
 170 
 
 
 As to the mode in which the different substances of which ultramarine is composed 
 are combined, or the chemical constitution of this substance, the most diverse views 
 are held, and it is a matter of great difficulty to deduce from known facts any satis- 
 factory representation on this point. 
 
 Breunlein and Bockmann consider blue ultramarine as consisting of silicates of 
 sodium and aluminum with sodium pentasulphide. 
 
 Stein considers ultramarine as a mechanical mixture consisting essentially of alu- 
 minum sulphide and sodium silicate, the latter substance enveloping the particles of 
 aluminum sulphide and protecting it from the action of atmospheric air. 
 
 The same chemist holds that the blue colour of ultramarine is not peculiar to the 
 substance, but due to the optical relations of the ingredients it consists of. He con- 
 siders that in the same way as an intimate mixture of various black substances with 
 an opaque white matrix (such as finely divided lamp black and milk, or black paper 
 behind a sheet of opalescent white glass) gives rise to a blue colour, so the blue colour 
 of ultramarine is due to the molecular dispersion of black aluminum sulphide through- 
 out a white matrix, the latter consisting essentially of sodium silicate mixed with 
 small quantities of sodium sulphate and sodium sulphite, together with some unde- 
 composed clay and calcium salts. 
 
 That ultramarine dees not contain sodium hyposulphite was proved by Stein, by 
 boiling ultramarine blue with copper sulphate. Copper sulphide was produced, but 
 no sulphurous acid, which must have been a product of the reaction if the ultra- 
 marine had contained sodium hyposulphite. 
 
 The absence of polysulphides is also proved by the fact that the copper sulphide 
 precipitated upon boiling ultramarine with copper sulphate contains no sulphur ex- 
 tractable by carbon bisulphide, while we know that when copper sulphate is made to 
 act upon a polysulphide, the precipitate thus formed does contain sulphur extractable 
 by carbon bisulphide. 
 
 The absence of sodium monosulphide has also been inferred by Stein, because 
 when sodium monosulphide is fused together with sodium silicate a yellow colour is 
 produced, which is not the case with ultramarine. 
 
 Characters. Ultramarine when quite pure is a most beautiful impalpable blue 
 powder insoluble in water. It is easily decomposed and bleached by weak acids, the 
 decomposition being accompanied by an evolution of sulphuretted hydrogen. Salts 
 having an acid reaction such as alum, etc. behave like acids with ultramarine. 
 
 Green ultramarine likewise occurs in the market as a fine powder. It is a pigment 
 of comparatively little importance, the colour not being equal to that of copper salts. 
 
 The chief object in testing ultramarine is to ascertain its colouring power, i.e. the 
 quantity requisite to produce a given shade. By comparison of the relative quantities 
 of different samples of ultramarine required to produce a shade of a definite intensity, 
 it is found that the amount required differs according to the quality of ultramarine. 
 Of course the less the quantity of ultramarine required, the greater is its colouring 
 power and relative value. 
 
 BarreswiVs method. Of two sorts of ultramarine to be compared with one another, 
 a small quantity of each (0*5-1 gram) is accurately weighed in watch glasses. 
 Two porcelain mortars are then separately charged with 20 grams of precipitated 
 barium sulphate, and into one of them is thrown a portion of the ultramarine from 
 one of the watch glasses, the whole being rubbed together to a homogeneous mass. A 
 portion of the ultramarine in the other watch glass is then added to the barium sul- 
 phate in the second mortar, and rubbed with it until the whole mass has assumed a 
 shade equal in intensity to that in the first mortar. Upon re-weighing the residual 
 portions of ultramarine in the watch glasses, the relative quantity of ultramarine re- 
 quired to bring about the same intensity of colour is easily ascertained. 
 
246 
 
 SODIUM. 
 
 Bernheim's test. This test consists essentially in ascertaining the quantity of dilute 
 sulphuric acid of known strength required for decomposing and decolorising a definite 
 quantity of the ultramarine to be tested. For this purpose 30 grams of sulphuric 
 acid are diluted with 300 grams of water; two equal portions of the sample of ultra- 
 marine (g-f- grams) are then brought separately into two glass flasks, and the sulphuric 
 acid dropped in, the flask being shaken meanwhile until every trace of blue has dis- 
 appeared. The quantity of acid required to bring about the decolorisation of the 
 ultramarine is in direct proportion to its colouring power, and the greater the quantity 
 of acid required to bleach the ultramarine, the stronger is the colouring power of the 
 ultramarine. 
 
 Ultramarine of good quality should be in the state of an impalpable powder that 
 will mix with water to a fine mud, and upon stirring up with water must remain for 
 some time suspended in that liquid. The dry powder, spread upon a sheet of paper 
 with the finger, should give a continuous streak with even surface. 
 
 The value of ultramarine is also much influenced by the amount of fixing material 
 necessary for causing it to adhere properly to paper ; for since ultramarine loses in 
 beauty of colour when a large proportion of fixing material is used, it is of relatively 
 greater value when it requires least fixing material. 
 
 Another important requisite of ultramarine is that it should be ' alum proof ; ' for 
 since alum is often used in blueing paper, the greater or less capability of ultramarine 
 to resist the action of alum is of importance. Ultramarine may be rendered ' alum 
 proof by using a good deal of silicic acid in its preparation. 
 
 Preparation. It is a matter of the utmost importance in preparing ultramarine 
 that all the materials used should be as pure as possible ; these consist of clay, 
 G-lauber's salt or soda, sulphur, and carbon. 
 
 Clay. The best kind of clay for making ultramarine is kaolin or porcelain earth. 
 If it contains sand, this must be removed by a process of elutriation. In order to 
 render the clay sufficiently friable, it is first heated to redness and then reduced to a 
 very fine powder by grinding. The powder is then passed through sieves so as to 
 render it as impalpable as possible. Clay containing more than 1 per cent, of ferric 
 oxide, and large quantities of lime and magnesia, is not suitable for use in the prepa- 
 ration of ultramarine. 
 
 Sodium sulphate. This substance is used in the calcined state, and is met with 
 in commerce sufficiently pure for the purpose. The chief points to be looked to, are 
 that it does not contain either free acid, sodium chloride, ferric oxide, or lead sulphate. 
 The calcined Glauber's salt is first pressed between rollers and afterwards passed 
 through sieves, to bring it to a sufficiently fine state of division. 
 
 Soda. Soda is often used instead of Glauber's salt, and the same degree of purity 
 is required as in the case of the sulphate. It is also used in the calcined state, and 
 in the form of a very fine powder. 
 
 Sulphur. Roll sulphur is employed, which has been previously ground and passed 
 through fine sieves. 
 
 Carbon. Carbon is generally used in the form of soft wood charcoal ; coal free 
 from ash being sometimes, but comparatively seldom, employed. The charcoal is re- 
 duced to the desired state of division by passing it between rollers and then grinding 
 the powdered charcoal with water to a fine paste between millstones. The fine paste 
 or mud is then dried and passed through sieves. In some manufactories colophonium 
 and other resinous substances are employed. 
 
 The following recipes are given by Wagner as the normal relative proportions of 
 the ingredients used in preparing ultramarine : 
 
 
 I. 
 
 II. ' 
 
 Porcelain clay (anhydrous) 
 Calcined Glauber's salt 
 
 100 
 83-100 
 
 100 
 41 
 
 Calcined soda . 
 
 
 
 41 
 
 Charcoal .... 
 
 17 
 
 17 
 
 Sulphur .... 
 
 
 
 13 
 
 But generally there is considerable diversity in the relative proportions of ingre- 
 dients taken by different manufacturers. When ultramarine of a dark blue colour is 
 desired, sodium sulphate is alone employed ; soda yields ultramarine of a lighter and 
 finer colour with more body ; 100 parts of soda replacing about 80 of Glauber's salt. 
 
 Very frequently sodium sulphide, a by-product obtained in the manufacture, is 
 
ULTRAMARINE. 247 
 
 partly substituted for soda or Glauber's salt in making ultramarine, the proportion 
 being 60 parts sodium sulphide for 100 parts sodium sulphate. 
 
 Not only is it necessary that the materials used in preparing ultramarine should 
 be pure, but they must likewise be employed in a very fine state of division, and very 
 intimately mixed together. The mixing is often carried out in drums similar to those 
 employed in the manufacture of gunpowder. 
 
 After the ingredients have been thoroughly mixed in the proper proportions, the 
 mixture is submitted to the following operations, and the character of the product 
 depends very much upon the manner in which they are conducted. 
 
 Heating the ingredients. The ingredients are generally heated in fire-clay crucibles 
 12 or 18 inches deep and about 6 inches wide. The composition, in a state of fine 
 division and intimately mixed, is firmly rammed into the crucible, which is then 
 covered with a lid and placed in the furnace. The furnaces are mostly muffle-shaped, 
 and are often so built that the hot air from the furnace first passes under the sole of 
 the muffle and then through it. The crucibles are heated to bright redness or in- 
 cipient white heat, and this temperature is kept up for half a day. When they have 
 been heated sufficiently, the crucibles are allowed to cool down in the furnace, and are 
 then removed. It is essential to the success of the operation to prevent the access of 
 any large quantities of atmospheric air during the heating process. 
 
 The contents of the crucibles are then broken up into small pieces, lixiviated with 
 water, and eventually submitted to a process of elutriation. In this stage the material 
 is in the state of ultramarine green, and is either sent as such into the market or is 
 converted into ultramarine blue. 
 
 Burning of Ultramarine Blue. The blue burning of ultramarine consists essen- 
 tially of a roasting process, assisted or not, as the case may be, by the addition of 
 sulphur. By this process a part of the sodium is extracted, and by the following ope- 
 ration of washing with water it is removed in the form of sodium sulphate. 
 
 For blue burning of ultramarine retorts or hearth furnaces are employed, which 
 must, however, be so constructed that the mass may be stirred up without much air 
 coming into contact with it, and that no access of hot air from the furnace is possible. 
 So soon as the ultramarine green in the retort has attained a red heat, sulphur is 
 thrown in, the whole mass being well stirred up. When the first portion of sulphur 
 has burnt away, a second portion is added, and the operation is continued iintil a 
 portion, on being taken out, presents the proper blue tint. 
 
 Lixiviation. The next step is the lixiviation of the calcined mass in order to 
 remove the substances rendered soluble, sodium sulphate being the principal one. 
 The Ifkiviated mass is then ground between millstones, in what are called wet mills, 
 and afterwards, by a process of elutriation, it is separated into ultramarine of different 
 degrees of fineness. After some time has been given for the ultramarine to settle, it 
 is first partially dried in clay boxes or linen sacks, with the aid of pressure, and then 
 it is brought into a special drying room, and finally ground and passed through 
 sieves. 
 
 When soda alone is used in the composition of the ingredients of ultramarine, 
 larger masses are generally heated at a time in clay boxes, or the composition in form 
 of a large block is laid direct upon the hearth of a reverberatory furnace, the hot air 
 of the fire being made to pass under the hearth of the furnace, before it passes into 
 the furnace. When the mass is sufficiently burnt, the furnace is closed, and the mass 
 is allowed to cool down. 
 
 During the slow cooling a further roasting process takes place, by which the ultra- 
 marine is partly rendered blue. 
 
 Of late the proportions of ingredients used in preparing ultramarine when soda 
 forms a part have been selected in such a manner, and the heating so conducted, that 
 ultramarine is at once produced. 
 
 Uses. Next to indigo, ultramarine is undoubtedly the most generally used blue 
 pigment. It is used for painting lime-washed walls, plaster of Paris, cement and 
 stucco work, for preparing carpets and paper, in calico printing, etc. Since ultramarine 
 is not in itself adhesive for the above purposes, it requires to be mixed with some sub- 
 stance of an adhesive nature ; such as glue, which is used in preparing coloured paper, 
 while for calico printing albumen is used. 
 
 Considerable quantities of ultramarine are used for blueing such substances t 
 exhibit or have a tendency to exhibit a brownibh or yellowish colour, the real colour 
 of which, ought, howt ver, to be white ; such are linen, starch, sugar, paper, stearme, 
 paraffin, etc. 
 
248 SODIUM. 
 
 SODIUM THIOSULPHATE. 
 
 Na 2 S 2 3 . MOLBCTJLAR WEIGHT 158. 
 
 This salt was formerly called sodium hyposulphite, and is still generally known by 
 that name ; but it is quite different in composition and characters from the true hypo- 
 sulphite. 
 
 Cbaracters. Sodium thiosulphate forms large clear monoclinic crystals, which 
 contain five molecules of water, Na 2 S 2 3 + 5H 2 = 248, and are unchangeable in the 
 air. The salt is readily soluble in water, and has a bitter cooling taste. When care- 
 fully heated, it melts and gives off its water of crystallisation ; when more strongly 
 heated, it decomposes into sodium sulphide and sodium sulphate. The solution 
 cannot be preserved long unaltered, but deposits sulphur. An aqueous solution of 
 sodium thiosulphate treated with a mineral acid gives off thiosulphuric acid, which is 
 quickly decomposed into sulphurous acid and sulphur. The property possessed by 
 an aqueous solution of sodium thiosulphate of dissolving the iodides and chlorides 
 of silver is of use in photography ; the salt is readily oxidised by iodine and chlorine 
 in presence of water ; the hydrogen of the water unites with these haloid elements to 
 form hydrogen acids, and the liberated oxygen combines with the thiosulphuric acid. 
 
 Preparation. Sodium thiosulphate is formed by boiling a solution of sodium 
 sulphite with sulphur, according to the following equation : 
 
 Na 2 S0 3 + S = Na 2 S 2 3 ; 
 
 or by the oxidation of sodium pentasulphide, with precipitation of sulphur : 
 Na 2 S 5 + 3 = S 3 + Na 2 S 2 8 ; 
 
 or by boiling a solution of sodium hydrate with sulphur, pentasulphide of sodium 
 being formed at the same time : 
 
 GNaHO + 12S = 2Na 2 S 5 + 3H 2 + Na 2 S 2 3 ; 
 
 and by exposing the dark coloured solution to the air, the pentasulphide is oxidised 
 and converted into thiosulphate, with separation of sulphur, according to the previous 
 equation. 
 
 According to Liebig's method, a solution of sodium carbonate is saturated with 
 sulphurous oxide gas, the product neutralised with sodium carbonate, and the solution 
 of sodium sulphite is mixed with a solution of sodium pentasulphide, prepared by 
 boiling caustic soda with sulphur until saturated. The whole is then filtered, and 
 the filtrate evaporated to crystallisation. 
 
 By Walchner's method, a mixture of soda ash with one-third its weight of sulphur 
 is gradually heated to the melting point of sulphur, while constantly stirred. In 
 this way sodium sulphide is formed, which, when heated in the air, takes up oxygen, 
 and is converted into sodium sulphite. The mass upon cooling is lixiviated, and when 
 the clear solution is boiled with sulphur, the sodium sulphite takes up an additional 
 atomic proportion of sulphur and is "converted into sodium thiosulphate. 
 
 By exposing the waste of the soda manufacture containing calcium oxysulphide 
 to the action of the atmosphere in a moist state, the calcium sulphide is con- 
 verted into calcium thiosulphate. The oxidised waste is lixiviated, and the liquor 
 boiled with sodium carbonate, by which means calcium carbonate and sodium thio- 
 sulphate are formed ; the precipitated calcium carbonate is then separated, either by 
 decantation or filtration, and the solution evaporated to crystallisation. 
 
 By Kopp's method, soda waste is mixed with 10 or 15 per cent, of sulphur and the 
 mixture is boiled in an iron boiler with from 12 to 15 times its weight of water. Cal- 
 cium sulphide and thiosulphate are thus formed. The whole liquor is then trans- 
 ferred to close vessels provided with agitators, and sulphurous oxide, produced by 
 burning sulphur, is passed in until the mixture has an acid reaction. This liquor is 
 then drawn off, neutralised with sodium carbonate, allowed to settle, and decanted. 
 The calcium thiosulphate contained in this liquor is converted into the corresponding 
 sodium salt by means of sodium carbonate or sulphate. 
 
 Sodium thiosulphate may be obtained in like manner, from the lime used in puri- 
 fying illuminating gas, which contains calcium thiosulphate, as well as some calcium 
 sulphide. 
 
 Uses. Sodium thiosulphate is employed to a large extent asantichlor in paper 
 manufactories, for removing the last traces of chlorine employed in bleaching the rags. 
 Large quantities of sodium thiosulphate are also used for photographic purposes. Its 
 employment in this branch of industry is due to its capability of dissolving those 
 
SODIUM SULPHATE. 249 
 
 parts of photographic negatives that have not been acted upon by light. It is further 
 used in fehe preparation of silvering and gilding solutions; for extracting silver 
 chloride from silver ores, in the preparation of aniline green, and in cotton printing, etc. 
 
 SODIUM SULPHATE. 
 
 FOEMUIA Na 2 S0 4 . MOLECULAR WEIGHT 142. 
 
 History. This substance was discovered and described in 1658 by Glauber, who 
 prepared it from the residues left in the preparation of hydrochloric acid by the action of 
 sulphuric acid upon common salt. Glauber termed it sal mirabile, and subsequently 
 chemists gave it the name sal mirabile Glauberi, whence its present designation of 
 Glauber's salt. The first preparation of this salt on a large scale was at Friedrichs- 
 hall, whence in 1767 it found its way into the market. 
 
 Occurrence. Sodium sulphate occurs in the water of a number of saline springs. 
 The water of several inland seas, as well as sea water itself, also contains sodium 
 sulphate, which is found in the mother liquor obtained in the extraction of common 
 salt from these sources. The water of the lakes of the Araxes plain yields an efflore- 
 scence consisting of sodium sulphate, chloride, and carbonate. The salt forms a crust at 
 the edges of the lakes, and when detached it floats upon the surface of the water. 
 
 Pure anhydrous sodium sulphate occurs naturally as the mineral thenardite, and 
 in a hydrated condition as mirabilite, while Glauberite is a double compound 
 of sodium sulphate and calcium sulphate. Blodite is a double compound of mag- 
 nesium sulphate and sodium sulphate. Large quantities of hydrated sodium sulphate 
 are found, together with gypsum and clay, in the valley of the Ebro, in Spain. 
 
 Composition. In the crystallised condition this salt contains 55'9 per cent, of 
 water, and its composition is represented by the formula Na 2 S0 4 10H 2 0. 
 
 Characters. Sodium sulphate crystallises from aqueous solutions at ordinary 
 temperature in well-formed colourless prisms, which effloresce on exposure to the air 
 by giving off their water of crystallisation, becoming first of all opaque and finally 
 falling to powder. 1 00 parts of water at dissolve 12 parts of crystallised sodium 
 sulphate, at 25 100 parts, at 33 322 parts, at 40 291 parts, at. 50 only 262 parts. It 
 will be seen from this that, unlike the generality of salts, the solubility of Glauber's s;ilt 
 in water does not increase with the temperature of the water, but that its maximum 
 solubility is at a temperature of 33, the solubility then decreasing with rise of tem- 
 perature. A solution of Glauber's salt saturated at 33 therefore deposits some of the 
 salt in the solid state upon raising the temperature of the solution. 
 
 Preparation. Sodium sulphate is obtained as a by-product in a number of 
 chemical operations, but it is chiefly in the manufacture of sodium carbonate that this 
 salt is produced upon a large scale by heating sodium chloride with sulphuric acid, this 
 operation constituting the first step in the conversion of sodium chloride into sodium 
 carbonate or ordinary soda ; the product thus obtained is termed salt cake. 
 
 From Common Salt and Sulphuric Acid. This method is in principle the same as 
 that employed by the discoverer Glauber. The action of sulphuric acid upon sodium 
 chloride to form Glauber's salt may be represented as taking place in two 
 stages, the first stage consisting in the formation of acid sodium sulphate according to 
 
 NaCl + H 2 S0 4 = NaHS0 4 + HC1. 
 
 The acid sodium sulphate at a higher temperature then acts upon a further 
 molecule of sodium chloride forming sodium sulphate and hydrochloric acid, thus : 
 NaHS0 4 + NaCl = Na 2 S0 4 + HC1. 
 
 An apparatus for the preparation of sodium sulphate in cylinders is shown by figs. 
 138 and 139. Each furnace, of which from 5 to 25 and more are placed side by side 
 contains from 2 to 4 retorts (c c) of cast iron, each retort being 5 feet in length 
 2* feet in width, the retorts being heated by a furnace 6). The retortsare built in to 
 an arched chamber of fire bricks, and are heated on all sides by the hot air from th, 
 fire. The hot air and flame, after being reflected from the arch, pass throug h ^the ^flues 
 (m) and (i) into the common flue (m m\ whence they escape into the chimney (n) 
 The cast-iron cylinders are closed at both ends with a lid (*), luted on by a hit 
 clay. The interior of each retort is connected with the absorption vessels .by means 
 of The stoneware adapter (A) fitting air-tight into the retort **j&* 
 of clav The other extremity of the adapter passes into the tubulus ot a carbo 
 whicSn EZSSE53* by meam of the tube (/) with a ser.es of carboys 
 
250 
 
 SODIUM. 
 
 nected by means of similar tubes, and arranged in rows in connection with one another. 
 The gases escaping from the last row pass through a tube into the common chimney. 
 
 FIG. 138. 
 
 Fm. 139. 
 
 The opening (/) in the posterior lid of the retort (fig. 138) is for admitting a leaden 
 funnel, the opening being closed during the process with a plug. 
 
 Each cylinder receives a charge of about 3 cwt. of common salt, and then the 
 lid is luted on, and 2 cwts. of sulphuric acid of sp. gr. 1*727 poured in through the 
 opening (/). The funnel is then removed and the opening closed with a plug. The 
 cylinders are heated at first gently, the heat being gradually increased towards the 
 end of the process. The hydrochloric acid evolved passes first of all into the carboy 
 (t), which is empty, and serves to retain mechanical impurities carried over with the 
 stream of gas. The hydrochloric acid gas thus purified passes into the carboys of the 
 second row, which are about half filled with water ; from thence into those of the third 
 row, the non-absorbed gas escaping finally into the chimney. 
 
 The carboys are connected with one another in the way shown in fig. 140. Into 
 the tubulatures of the carboys (A B) aro fitted the wide connecting tubes (c D). Through 
 a funnel (G H) water is poured into the carboys ; the lower 
 extremity of the funnel dipping beneath the water in the 
 carboy. Caoutchouc tubes (BE' and FF') connect the 
 lower part of the carboys with one another. Water is 
 poured in through the funnel (o H), and passes through 
 (K K') into the second carboy (B), and from thence through 
 (FF') into the third carboy, and so on until the whole row 
 of carboys has been passed. The hydrochloric acid gas is 
 introduced at the other end of the row of carboys; passes 
 therefore in the direction from D to B, from thence through 
 c to A etc., and during its passage it comes into contact with water of a less degree of 
 saturation, while the water on its passage, coming into contact with vapour of hydro- 
 chloric acid of continually increasing strength, becomes saturated more and more. 
 
 Each cylinder yields on an average 440 to 460 Ibs. of aqueous hydrochloric acid of 
 sp. gr. 1-160 to 1-170. When the operation is over the saturated solution of 
 hydrochloric acid is let off through the cocks at the bottom of the carboys, and where 
 
 FIG. 140. 
 
MANUFACTURE OF SALT CAKE. 
 
 251 
 
 the above method is not adopted, the empty carboys of the first row are filled with 
 the partly saturated acid of the following rows. 
 
 The residue left in the retorts at the end of the operation, after the hydrochloric 
 acid has all been distilled off, consists of a hard compact mass of sodium sulphate, of 
 about 400 Ibs. in weight. This residue is drawn out and the retorts recharged anew 
 in the manner above described. 
 
 The materials used in the production of sodium sulphate for the manufacture of 
 soda are the same as those already described, and the only difference is that the 
 operation is conducted in reverberatory furnaces. 
 
 In the oldest forms of furnaces in which the action of sulphuric acid upon common 
 salt was effected, the mixture was heated by passing hot air and gas from the furnace 
 directly over it. The reaction between sulphuric acid and sodium chloride was thus very 
 thorough, but it was on the one hand difficult to secure a complete condensation of 
 the hydrochloric acid gas which escaped with the fire gas, and on the other hand the 
 solution of hydrochloric acid obtained was not of the strength required for the manu- 
 facture of chlorine, etc. For this reason the ordinary reverberatory furnace ceased 
 to be used in the preparation of sodium sulphate and the reaction of sulphuric acid 
 upon common salt is now carried out in two distinct stages. The first stage consists 
 in preparing acid sodium sulphate in vessels heated from outside, so that the hydro- 
 chloric acid escapes unmixed with fire gas. The second stage consists in the prepara- 
 tion of neutral sodium sulphate or Glauber's salt by heating the mixture of acid sodium 
 sulphate and undecomposed salt from the former operation in reverberatory furnaces ; 
 this operation is termed roasting the salt cake ; the hydrochloric acid thus evolved 
 with the fire gases is condensed either in a series of carboys or some other suitable 
 arrangement to a dilute aqueous solution. 
 
 A furnace of the latter kind is represented by figs. 141 and 142. A is the fireplace, 
 B the reverberatory furnace, ddd'd' are flues. The latter pass under the leaden pan 
 (E) supported upon an abut- 
 ment of fire bricks. The 
 fire gas mixed with the 
 hydrochloric acid gas pro- 
 duced in the roasting fur- 
 nace, after having been 
 made to circulate several 
 times underneath the leaden 
 pan (E), escapes at both 
 ends through the outlets 
 (d m d"', fig. 142) into a row 
 of carboys (i"i"), where the 
 hydrochloric acid is con- 
 densed. Two earthenware 
 tubes (g g) having an outlet 
 in the chamber contai 
 the leaden pan (E), termi- 
 nate respectively in two 
 rows of carboys (h h'J. A 
 furnace 13 feet in length 
 and 5 feet wide requires fo 
 
 the condensation of the -p 14.9 
 
 hydrochloric acid from 72 . ., , . 
 
 to 78 carboys in the first two rows (" i") and from 40 to 50 carboys in the last two 
 rows (A A'),each carboy having a capacity of about 44 gallons. K is an aperture 
 admitting the common salt ; (?) a damper for placing the roasting space in con 
 cation with the pan space. . -tr-of nf 
 
 The leaden pan (E) is charged with common salt in the following way :- 
 all salt is thrown in at K and spread over the pan ; then sulphuric acid, generally a 
 chamber acid of sp. gr. 1-520 to 1-550, is poured in through a funnel tube 
 right angles ; K is then shut and luted. Hot air is then passed under E the es cap,ng 
 vapour of hydrochloric acid being passed through gg into the carboys (* A ) 
 
 The complete formation of acid sodium sulphate in the leaden pa. i not. ed by 
 
 FIG. 141. 
 
 with the fire gas, underneath E, then t 
 
252 
 
 SODIUM. 
 
 in the calcining chambers is continually stirred, during the operation so as to secure an 
 equal roasting. When the operation is over, the Glauber's salt is in the state of a 
 coarse-grained powder. 
 
 The condensation of the hydrochloric acid gas escaping from the reverberatory 
 furnace is difficult, for the reason that it is mixed with the fire gas, which is in 
 itself non-condensible and consequently carries off mechanically large quantities of 
 hydrochloric acid. A further requirement of this method is a tall chimney to carry 
 off the non-condensed vapour of hydrochloric acid gas, so as to prevent its causing 
 a nuisance to the immediate vicinity. 
 
 The condensing system described on p. 250 (fig. 140), in which the lower parts of 
 the condensing carboys are connected with caoutchouc tubes, and where it is only 
 necessary to pour water into the last carboy of a whole row, is here too the most suit- 
 able system to adopt. 
 
 As soon as the decomposition in the calcining or reverberatory furnace is complete, 
 the iron lid (c) which had served during the operation to cover the arched vault (c) is 
 removed, the sodium sulphate raked out into the vault, and the furnace recharged. 
 
 Alterations in the Construction of the Furnaces. The chief propositions made as to 
 improvements in sodium sulphate furnaces aim at getting rid of the reverberatory 
 furnace used for heating the mixture of acid sodium sulphate and common salt as it 
 conies from the lead pan in the first stage of the process. For not only does a great 
 loss ensue by the impossibility of effectually absorbing vapour of hydrochloric acid 
 mixed with fire gas, but further it is very difficult, if not impossible, to prevent the 
 large quantities of hydrochloric acid which escape from injuring the surrounding 
 neighbourhood. 
 
 Figs. 143, 144 and 146 represent a furnace where the sulphate is calcined in a 
 muffle. Figs. 143 and 144 show the furnace in section, fig. 145 the ground plan as 
 high as the grate. A A are two fireplaces with grate 2 feet long and 1 feet wide. 
 
 FIG. 143. 
 
 The flame plays round the muffle in the di- 
 rection from A' to A" and then passes under- 
 neath the leaden pan (M), and from thence 
 through a flue (A'") underneath leaden pans 
 for concentrating chamber acid. The muffle 
 (c) is made of single plates of fire clay 
 cemented together perfectly air tight. The 
 bottom of the muffle is 13 feet long, and 
 about 8 feet wide. The arch above the 
 muffle is also built of fire brick. A couple 
 of tubes (DD) serve to conduct the hydro- 
 chloric acid developed in the muffle and pan 
 space into the condensing apparatus. A" is a 
 damper, by lifting which the muffle (c) and 
 the pan (M) are placed in communication. 
 The pan (M) has a round shape with a dia- 
 meter of 10 feet, and stands in a brickwork 
 
 Fra. 144. 
 
 FlG - 
 
 chamber. The opening (E) communicates with the hopper of the salt reservoir, and 
 perves for admitting salt into the muffle ; a similar opening (F) serves to admit the 
 sulphuric acid. J is an opening admitting of the mass in M being stirred for an 
 hour, after which it is brought into the muffle, i is an opening communicating with 
 the muffle (c). The operation is conducted in a way similar to that described in the 
 case of the previously mentioned furnace. Each charge consists of about 12 cwts. of 
 salt, and 13 cwts. of sulphuric acid of sp. gr. 1-652. Calculating 12 charges to 
 every 24 hours, 144 cwts. of common salt would be worked up by a single furnace 
 every 24 hours, or 36 tons would be worked up in this time in a factory provided with 
 gix sulph;ito furnaces, and with five of them working. 
 
 In this country the leaden pans are replaced by cast-iron pans weighing as much 
 as 5 tons. They are sometimes not set in arched brickwork, the latter being ro- 
 
MANUFACTURE OP SALT CAKE. 253 
 
 placed by domed covers of cast iron. The fire gases from the roasting furnace are 
 not used for heating the pans, which are heated by a separate fire. 
 
 Modifications in the Condensing Apparatus. -The various forms of condensing 
 bottles have been already mentioned. In places where it was found necessary to 
 absorb the last traces of hydrochloric acid, various absorbent* have been proposed b 
 the place of water Kuhlmann fills the last carboy with pieces of coke over which a 
 stream of milk of lime is made to trickle ; the large surface of alkaline liquid absorbs 
 the hydrochloric acid completely. In order to obtain barium chloride as a by-product 
 he replaces the milk of lime by witherite in a fine state of division. 
 
 Condensing Towers, Coke Towers.-In very large works, especially in this country 
 the condensing carboys are replaced by towers having an arrangement similar to the 
 Gay-Lussac's coke towers Described on p. 124. The towers, of which a couple are 
 placed together communicating with one another above, are built of sandstone 
 saturated with tar, and are filled either with coke, broken pieces of earthenware, or 
 flints, over which a stream of cold water is kept constantly flowing. The acid 
 vapour enters at the lower part of one of the towers, passing through a perforated 
 
 Fra. 146. 
 
 vault upon which the pieces of coke, etc. rest, and then through the moistened coke 
 into the upper part of the next tower, passing downwards through it into a chimney. 
 The aqueou? Hydrochloric acid thus formed is let off through pipes placed at the lowest 
 part of the cowers. The acid of the first tower is of course more concentrated than 
 that of the second one. An arrangement of this kind is represented by fig. 146. 
 
 Instead of two towers, in some places a single tower is employed, divided by a 
 partition into two chambers. The acid vapour passes, as in the other case, upwards 
 through the first chamber and downwards through the second, escaping from beneath 
 the latter into the chimney. 
 
 SODIUM SULPHATE FROM OTHER SOURCES. Considerable quantities of this salt are 
 obtained from the mother liquors of brine springs, sea water, and kelp, and as a by- 
 product in the manufacture of potash salts from the saline deposits at Stassfurt. 
 
 The preparation of sodium sulphate from the mother liquor of saline springs, or 
 sea water, depends upon the fact that the magnesium sulphate contained in the 
 mother liquor of brine, and of sea water, reacts upon the sodium chloride at a low tem- 
 perature, forming sodium sulphate and magnesium chloride, the former separating 
 in the crystalline condition, while magnesium chloride remains in solution. ( Vide 
 p. 200.) 
 
 The scales found in the pans in which concentrated brine has been boiled down 
 are scraped off and lixiviated with water, which dissolves the sodium sulphate, 
 leaving the gypsum undissolved. The liquor thus obtained is used for lixiviating 
 fresh pan scales until a liquor has been obtained having a spec. grav. of 1 '197 or 1-206. 
 This is either decanted or filtered from the gypsum and the sodium sulphate crystallised 
 out in the winter season. 
 
 Sodium sulphate is obtained from the residues of the Stassfurt potash works on a 
 large scale at the works of Messrs. Ziervogel and Tuchen at Stassfurt. The residues 
 from the lixiviation of raw carnallite, consisting chiefly of common salt and kieserite 
 (magnesium sulphate), are exposed to the action of the air for several weeks. In 
 course of time the insoluble kieserite is converted into soluble magnesium sulphate ; 
 
254 SODIUM. 
 
 the mass is then lixiviated in large tanks, and the solution exposed in shallow 
 wooden basins to a low temperature. A crystallisation of sodium sulphate is thus 
 obtained, which, after the mother liquor has been drawn off, is collected and dried. 
 The conversion of hydrated sodium sulphate into tho anhydrous condition is effected 
 at the above works by heating it over a water bath with constant stirring. 
 
 In preparing sodium sulphate from common salt and ammonium sulphate, a 
 solution of common salt, having a spec. grav. of T 160, is mixed with an equivalent 
 quantity of ammonium sulphate, and the mixture heated to the boiling point. A mutual 
 decomposition takes place, sodium sulphate and ammonium chloride (sal ammoniac) 
 being formed, the former separating in the solid state. Upon evaporating the 
 mother liquor a further crop of sodium sulphate is obtained. The mother liquor is 
 finally drawn off into suitable vessels, and yields upon cooling crystals of sal 
 ammoniac, which are either simply dried and sent into the market, or are first of all 
 submitted to a process of sublimation. 
 
 When a mixture of ferrous sulphate and sodium chloride is heated to redness in a 
 current of air, there are formed sodium sulphate, ferric oxide, and free chlorine. The 
 mother ' liquor from the preparation of ferrous sulphate, or mine water containing 
 this salt, may be employed for the purpose, common salt being dissolved in the solu- 
 tion, the mixture evaporated to dryness, and the residue heated to redness in a current 
 of air. The sodium sulphate is then extracted with water. Another plan consists in 
 freezing out sodium sulphate from a solution containing common salt and ferrous 
 sulphate. This operation is performed in winter. 
 
 Tilghman prepares Glauber's salt from gypsum and common salt by melting the 
 two salts, and passing a stream of superheated steam over the melted mass ; sodium 
 sulphate is thus formed and hydrochloric acid, which escapes. Anthon prepares a 
 mixture of equal parts salt, gypsum, and calcined magnesia, stirs the mixture up 
 with a quantity of water equal to double its weight, and passes carbonic acid into the 
 mixture. In this way magnesium carbonate is formed, which with gypsum yields 
 calcium carbonate and magnesium sulphate, and by evaporating the solution of this 
 salt, mixed with sodium chloride, they yield magnesium chloride, and sodium sulphate 
 which crystallises out. Other methods of preparing sodium sulphate, consisting in 
 roasting magnesium sulphate, copper vitriol or zinc vitriol, pyrites, etc., with common 
 salt, have been proposed, but none of them have received industrial application. 
 
 There is, however, another process recently introduced by Mr. Hargreaves, which 
 promises to bring about a considerable change in the manufacture of sodium sulphate. 
 This consists in subjecting salt to the action of a mixture of sulphurous oxide, obtained 
 by burning pyrites, with atmospheric air and steam, so as to convert the sulphurous 
 oxide into sulphuric acid, and the sodium chloride into sulphate, with liberation of 
 hydrochloric acid ; the reaction taking place is represented by the following equation : 
 
 2NaCl + H 2 + S0 2 + = Na 2 S0 4 + 2HC1. 
 
 For the purpose of preparing sodium sulphate in this way, several cylinders of 
 cast iron, arranged so that they can be heated externally, are filled with salt in a dry 
 porous condition, and when heated to a temperature of about 426, a mixture of 
 sulphurous oxide, air, and steam is passed in at the top of one of the cylinders, at 
 the bottom of which is a pipe communicating with the top of the next cylinder. 
 After a time, when the salt in the first cylinder is wholly converted into sulphate, the 
 gas is passed into the second cylinder, and after removing the sulphate from the first 
 one, it is connected with the last cylinder, and so on through the entire series. 
 
 PURIFICATION. Sodium sulphate is purified by dissolving the raw salt in boiling 
 water, allowing the solution to settle, decanting it off from the sediment, and crystal- 
 lising in wooden troughs lined with lead. As soon as the temperature of the solution 
 has sunk a few degrees below 33, crystallisation commences, and further cooling pro- 
 duces large well-formed, transparent prisms of sodium sulphate. 
 
 When it is desired to obtain sodium sulphate with the appearance of Epsom salts, 
 the solution is stirred during the cooling process, so that no large crystals can form. 
 
 Uses. The chief use made of Glauber's salt or sodium sulphate is in the prepara- 
 tion of soda by Leblanc's method. Besides this, large quantities of the salt are used 
 in glass manufacture. Another important application of sodium sulphate is in the 
 preparation of ultramarine. 
 
 Sodium sulphate is further used for separating calcium, as sulphate, from various 
 mother liquors, such as those of saltpetre, which contains calcium chloride, for pre- 
 paring sodium acetate by decomposing calcium acetate, obtained in the saturation of 
 raw wood vinegar. Sodium sulphate is sometimes heated to redness with charcoal, so 
 as to obtain sodium sulphide, which is used for odourless sulphur baths. Finally, 
 it. is used in dye works, and for the production of freezing mixtures. An excellent 
 
NATURAL SODA. 255 
 
 freezing mixture is obtained by mixing 4 parts of crystallised sodium sulphate with 
 3 parts of sulphuric acid of sp. gr. 1-360, or 8 parts of powdered sodium sulphate 
 with 5 parts of fuming hydrochloric acid. 
 
 SODIUM CARBONATE. 
 
 FORMULA. Na 2 C0 3 . MOLECULAR WEIGHT 106. 
 
 History. Mention is made in the Old Testament of a substance called neter 
 which possessed the property of effervescing with vinegar ; it was a natural product 
 obtained from certain lakes in Egypt, and was used for cleaning purposes in the same 
 way as wood ashes, and it cannot well have been anything else than soda. It was 
 this substance, and not nitre, as was at one time supposed, that was mentioned by 
 ancient Greek and Latin authors under the names virpov and nitrum, as representing 
 the Egyptian name. The terms natron and soda were first applied to this sub- 
 stance in the fifteenth century. For a long time no distinction was made between 
 potash and soda ; and even as late as the last century both substances were held to be 
 identical, or at most only modifications of one and the same substance. It was not 
 until Siahl in 1702, and Duhamel in 1736, had shown that common salt contained a 
 base differing from ordinary potash, that soda and potash were proved, chiefly by 
 MarggrafFs investigations, to be different substances. 
 
 Up to the beginning of the present century soda was obtained exclusively from the 
 ashes of land and marine plants ; but as early as the middle of the last century 
 attempts had been made to prepare soda from common salt. In 1 782, according to 
 Kir wan, attempts to obtain soda from common salt were made in England by applying 
 the reaction discovered by Scheele, and decomposing salt with litharge, filtering the 
 solution, and exposing it to the air for absorption of carbonic acid. This attempt, as 
 well as a number of others of a similar kind, did not attain the desired result, owing 
 to the fact that soda obtained from the ashes of plants was cheaper than that pro- 
 duced by any of those methods. 
 
 It was not until a decree came into force in France prohibiting the importation of 
 soda into that country, that the method of preparing soda from common salt devised 
 by Leblanc, Dize", and She was adopted. This method is now commonly employed. 
 
 Occurrence. Sodium carbonate occurs naturally under various conditions. In 
 the solid form it occurs as an efflorescence as well as in some minerals ; in a state of 
 solution it is present in many kinds of mineral water, as at Carlsbad, Aix la Chapelle, 
 Vichy, etc. Sodium sesquicarbonate is found in considerable quantities in the water 
 of the soda lakes of Egypt, Central Africa, South America, in the vicinity of the 
 Caspian Sea, in Arabia, Hungary, etc. From some of these sources soda is still pre- 
 pared industrially. There are two kinds of natural soda, known as Trona and Urao. 
 
 Trona is obtained from Egypt, and it consists essentially of a compound represented 
 by the formula Na 4 C 3 8 + 4H 2 0, together with some admixtures of sodium sulphate, 
 sodium chloride, and earthy impurities. The amount of anhydrous sodium sesqui- 
 carbonate is about 60 or 70 per cent. It occurs as an incrustation formed by the 
 evaporation of the water in pools or lakes, and sometimes separates from the water in 
 masses which float on the surface. 
 
 Urao is obtained from the water of Lake La Lagunilla, in Columbia, and it also con- 
 tains sodium sesqiii carbonate. During the hot season the urao is deposited from the 
 water of the lake, in consequence of evaporation, and is collected. It is a purer 
 material than trona, but the quantity produced is less. 
 
 Native soda is also obtained from some Hungarian lakes, but the annual amount 
 now produced is small, although the production was formerly more considerable. The 
 Hungarian soda contains less sodium sesquicarbonate than trona or urao. 
 
 The ashes of some marine plants, as well as the ashes of plants growing on the 
 sea coast, often contain, besides various other salts, a quantity of sodium carbonate. 
 The manner of preparing kelp or varec has been already treated of, on p. 194. The 
 composition of the ash of soda plants varies according to the kind of plant from which 
 the ash is obtained, and according to the locality where the plants grow. The ash of 
 such plants under the name of bar i 11 a formerly constituted one of the chief sources of 
 soda, and this alkali was also obtained to some extent from kelp. 
 
 Barilla comes chiefly from Alicante, Malaga, and Carthagena ; it is the best kind 
 of soda obtained from soda plants, and contains from 14 to 30 per cent, of sodium car- 
 bonate, together with sodium and potassium chlorides and potassium sulphate. 
 
 Blanquette comes from the coast between Aigues-Mortes and Frontignan, and con- 
 tains from 8 to 10 per cent, of sodium carbonate. Sali cor comes from Narbonne, and 
 contains from 14 to 15 per cent, of sodium carbonate. 
 
 The amount of sodium carbonate in kelp varies between 2$ and 5 per cent. 
 
256 
 
 SODIUM. 
 
 Characters. Sodium carbonate occurs in the market as calcined soda, or soda 
 ash, either entirely anhydroxis or containing but little water, and as crystals, which 
 contain 10 molecules of water of crystallisation. Crystallised soda forms large colour- 
 less crystals, belonging to the klinorhombic system. Exposed to the atmosphere the 
 crystals become opaque, owing to loss of water of crystallisation, and at last crumble 
 to a fine powder. Crystallised soda, heated to 34, melts in its water of crystallisa- 
 tion ; subjected to a still stronger heat, after parting with nine-tenths of its water 
 of crystallisation, it again becomes solid, then gives off the remaining water of crys- 
 tallisation, at last melting, and upon cooling it solidifies to a crystalline mass. 
 
 Sodium carbonate resembles Glauber's salt (sodium sulphate) in respect to its 
 solubility in water, and deviates from the general rule, inasmuch as the solubility of the 
 salt does not increase with the rise of temperature beyond a certain point. The greatest 
 solubility is at a temperature of 36 ; a further addition of heat to a solution of sodium 
 carbonate saturated at this temperature causes a deposition of some of the salt in the 
 solid state. The following table gives the solubility of anhydrous sodium carbonate in 
 100 parts of water at different temperatures : 
 
 Temp. Anhy. 
 
 Sod. Carb. 
 
 6-97 
 12-06 
 16-20 
 
 
 10 
 15 
 20 
 
 21-71 
 
 Temp. 
 
 25 
 30 
 38 
 104 
 
 Anhy. 
 Sod. Carb. 
 28-50 
 37-24 
 51-67 
 45-47 
 
 When a hot solution of sodium carbonate is allowed to cool without disturbance, it 
 becomes supersaturated i.e. the liquid retains more salt dissolved than Corresponds 
 to the low temperature of the solution. Upon agitating a solution of the salt in this state, 
 the excess of salt held in solution is suddenly separated in crystals containing often 
 7 instead of 10 molecules of water of crystallisation. 
 
 The percentage of anhydrous soda contained in aqueous solutions of the salt can be 
 ascertained from their specific gravity, as given in the following table by Gerlach, con- 
 structed for a temperature of 15 : 
 
 Spec. Grav. 
 
 Percentage of 
 Sodium Carbonate 
 
 Spec. Grav. 
 
 Percentage of 
 Sodium Carbonate 
 
 1-0105 
 
 1 
 
 1-0843 
 
 8 
 
 1-0210 
 
 2 
 
 1-0950 
 
 9 
 
 1-0315 
 
 3 
 
 1-1057 
 
 10 
 
 1-0420 
 
 4 
 
 1-1165 
 
 11 
 
 1-0525 
 
 5 
 
 1-1274 
 
 12 
 
 1-0631 
 
 6 
 
 1-1384 
 
 13 
 
 1-0737 
 
 7 
 
 1-1495 
 
 14 
 
 Preparation. The method by which sodium carbonate or soda is now chiefly 
 
 prepared dates from the year 1794, and was introduced by Leblanc; it involves three 
 distinct operations : 
 
 1. The conversion of sodium chloride, or common salt, into sodium sulphate, or 
 salt cake, by means of sulphuric acid. 
 
 2. The conversion of sodium sulphate into sodium carbonate, by heating salt cake 
 with calcium carbonate and carbon. 
 
 3. The extraction of sodium carbonate from the black ash obtained by the last 
 operation. 
 
 Several other methods of preparing sodium carbonate have been suggested at 
 various times, but none of them have yet superseded that of Leblanc. 
 
 FROM SODIUM SULPHATE. The production of sodium carbonate in this way con- 
 stitutes the second stage of the modern process of soda manufacture. Sodium sulphate 
 prepared from common salt by Leblanc's method, as already described on p. 251, is con- 
 verted into carbonate by heating it to redness with carbon and calcium carbonate, and 
 the product thus obtained is termed black ash or ball soda. 
 
 The process was formerly supposed to take place in three stages : 
 
 1. Reduction of sodium sulphate to sulphide by the action of charcoal: 
 
 Na 2 S0 4 + 4C = Na 2 S - + 4CO. 
 
 2. Mutual conversion of sodium sulphide and calcium carbonate at a red heat into 
 sodium carbonate and calcium sulphide: 
 
 Na,,S + CaC0 3 - Na,C0 3 + CaS. 
 
MANUFACTURE OF SODA. 
 
 257 
 
 3. Combination of calcium sulphide with lime to form insoluble calcium oxy- 
 sulphide : 
 
 2CaS + CaO = Ca 3 S 2 0. 
 
 Unger considers the process of soda formation from sodium sulphate to be of a 
 more complex nature than that above given. He represents the process as taking 
 place in the following stages : 
 
 1. Conversion of one-third of the sodium sulphate by reaction with calcium car- 
 bonate into sodium carbonate and calcium sulphate, without the agency of charcoal : 
 
 Na 2 S0 4 + CaC0 3 = Na 2 C0 3 + CaS0 4 . 
 
 2. Eeduction of the remaining two-thirds of the sodium sulphate by charcoal to 
 sodium sulphide : 
 
 Na 2 S0 4 + 2C = Na 2 S + 2C0 2 . 
 
 According to Unger, this reduction is effected not only by the carbon, but also by 
 nascent hydrogen produced by the action of carbon at a red heat upon water, and 
 by the carbonic oxide, produced by the action of carbon upon carbonic acid. 
 
 3. Mutual conversion of the sodium sulphide and calcium carbonate at a red he^t 
 into sodium carbonate and calcium sulphide : 
 
 Na 2 S + CaC0 3 = Na 2 C0 3 + CaS. 
 
 4. Formation of calcium oxysulphide by the action of steam upon calcium 
 sulphide, formed either by this reaction, or by the reduction of calcium sulphate by 
 carbon : 
 
 4CaS + H 2 = Ca 4 S 3 + H 2 S. 
 
 5. The sulphuretted hydrogen thus formed combines with caustic soda or sodium 
 carbonate to form sodium sulphide, which yields with calcium carbonate sodium 
 carbonate and calcium sulphide, etc. 
 
 Kynaston considers that ball soda does not contain calcium oxysulphide, but only 
 sodium carbonate, calcium sulphide, and lime ; and that upon dissolving the fused mass 
 these substances react upon each other in the following way : 
 
 1 . The lime and sodium carbonate yield calcium carbonate and caustic soda. 
 
 2. The caustic soda and calcium sulphide form sodium sulphide and hydrate of 
 lime. 
 
 Kolb likewise questions the formation of calcium oxysulphide in the soda process. 
 According to him the process is as follows : 
 
 1. The sodium sulphate is reduced by carbon at a red heat to sodium sulphide : 
 
 Na 2 S0 4 + 2C = Na 2 S + 2C0 2 . 
 
 2. Lime is formed by the action of carbon upon calcium carbonate : 
 
 CaC0 3 + C = CaO + 2CO. 
 
 3. Sodium sulphide, in contact with excess of lime and carbonic acid, yields soda 
 and sodium sulphide : 
 
 Na,S + CaO + C0 2 = Na 2 C0 3 + CaS. 
 
 According to Kolb, the calcium sulphide thus formed is so insoluble in water that 
 it is unnecessary, on account of the insolubility of the material, to assume the presence 
 of calcium oxvsulphide. 
 
 Sodium thiosulphate is always formed when the melted material has been a lon 
 time in contact with atmospheric air, and become disintegrated, the metallic sulphides 
 being thus oxidised to thiosulphates. . 
 
 The relative proportions in which the ingredients should be taken, as given by 
 Leblanc, are as follows : 
 
 Sodium sulphate 
 
 Calcium carbonate 
 
 Carbon " . 
 
 Generally there has been but little deviation from these proportions, as may be seen 
 from the following table given by Scheurer-Kestner, as representing tl 
 at ten different works. 
 
 1000 parts 
 1000 
 550 
 
 Sodium sulphate 
 Calcium carbonate 
 Carbon 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 
 
 100 
 107-7 
 73 
 
 100 
 110 
 50 
 
 100 
 103 
 61-7 
 
 100 
 97-5 
 55-6 
 
 100 
 115 
 35 
 
 100 
 121 
 46-6 
 
 100 
 115 
 
 68 
 
 100 
 93-6 
 40-4 
 
 100 
 100 
 40-3 
 
 100 
 90-2 
 42-1 
 
258 
 
 SODIUM. 
 
 The sodium sulphate is used in the anhydrous state, and it ought to be as free as 
 possible from sodium chloride, because this salt would render the soda impure. The 
 sodium sulphate ought also to be free from excess of sulphuric acid, and from ferric 
 oxide, which is apt to be produced when the sulphate has been too strongly heated, 
 and would render the fusion of the material more difficult. 
 
 The calcium carbonate employed may very conveniently be in the form of chalk, 
 or, where that is not obtainable, tufaceous limestone, muschelkalk, or ordinary lime- 
 stone may be taken. The chief point is to have the calcium carbonate as pure as 
 possible, and in all cases it is used in the state of a fine powder. Carbon is supplied 
 in the form of coal, with as little silica as possible in the ash, so as to avoid the forma- 
 tion of soluble sodium silicate which would pass into the soda undecomposed, and also 
 
 of insoluble silicates, containing 
 sodium, which would cause a loss 
 of sodium carbonate. The coal is 
 generally employed in coarse frag- 
 ments. 
 
 The 'balling' furnaces em- 
 ployed for conducting this opera- 
 tion in soda works are reverbera- 
 tory furnaces, the construction of 
 which is represented by figs. 147 
 and 148. In most balling fur- 
 naces the hearth or bed is divided 
 into two parts, and, as shown in 
 fig. 148, the hearth nearest the fire 
 is lower than the one furthest from 
 it. Sometimes these portions of 
 the hearth are separated from one 
 another by a bridge. In these 
 furnaces, the charge is first placed 
 upon the higher hearth furthest 
 from the fire and is heated by 
 the flame from the lower hearth. 
 After the lapse of about an hour 
 the mass is pushed off the upper 
 hearth on to the lower one where 
 the reaction begins, and it is con- 
 sequently only necessary to stir 
 the mass upon this part of the 
 hearth. A furnace of this kind 
 with about 100 square feet super- 
 ficial area, where the united charges of the two hearths amount to 5 cwt., and where 
 charging takes place every hour, yields 6 tons of raw soda per 24 hours. Formerly 
 small furnaces were employed which were succeeded by furnaces of larger dimensions, 
 which have again been replaced by small furnaces, for the reason that the mixture 
 was not equally heated in the larger furnaces. 
 
 A furnace of the kind used on the continent is represented by figs 149 and 150. a 
 is the ash hole, b fire-place with horizontal grate, c fire-bridge separating the fire-place 
 from the hearth (d d}. The hearth and the arch above it are built of fire brick ; the flues 
 (e e) conduct the hot air from the furnace, either direct into the chimney (/), or into a 
 horizontal flue beneath the hearth, from thence underneath evaporating pans, into 
 the general chimney. The four side doors (gggg}, and the door (h) opposite the 
 fire-place, serve as working holes through which a workman stirs or withdraws the 
 soda. The stirring operation is assisted by an iron roller (i i), before each door, upon 
 which an iron stirrer is laid. The arch is furnished with three openings (j jjj\ for 
 charging the furnace, but as they affect the solidity of the masonry of the arch, they 
 are often left out, and the charging is then effected with shovels. The other arrange- 
 ment has, however, this advantage, that the mixture is previously warmed by lying 
 over the furnace vaulting. 
 
 The furnace is strongly heated before charging, and the mixture is placed upon the 
 hearth m coarse lumps, the whole being strongly heated until it melts, and then the 
 liquid mass is frequently stirred with the stirrer (A). The termination of the opera- 
 tion is indicated by diminution of the flames of carbonic oxide, which at the beginning 
 of the process cover the surface of the entire mass. The ball soda is then raked out from 
 the furnace with the rake (B) into iron boxes mounted on wheels. The heating is not 
 kept up until the flames of carbonic oxide have entirely ceased, because in that case 
 oxidation would take place, and sodium sulphate would be formed. Too high a tem- 
 
 FIG. 148. 
 
BALLING FURNACES. 
 
 259 
 
 perature must also be avoided, especially towards the end of the operation, since, on 
 the one hand, it would cause considerable loss of soda by volatilisation, and would also 
 have the effect of making the ball soda impure by the decomposition of the fire clay 
 forming the hearth by sodium carbonate and the formation of silicates. 
 
 FIG. 149. 
 
 FIG. 150. 
 
 riG. lou. 
 
 Figs. 151, 152 and 153 represent a soda furnace of another construction. A the 
 furnace door, V ash pit, A" grate, B fire bridge ; c c hearth of the furnace, which 
 
 FIG. 152. 
 s 2 
 
260 
 
 SODIUM. 
 
 position enables a stirrer thrust in through one of the doors to reach the soda on the 
 other side. E E are openings in the arch of the furnace, furnished with cast-iron tubes 
 which serve for charging the furnace. FG are flues 
 through which the hot air from the furnace passes into 
 the horizontal flue (G'), and from thence either under 
 pans for evaporating or under the surface for drying com- 
 mon salt. H is a second hearth serving for heating the 
 mixture previous to its admission into the furnace. The 
 charging and mode of working of this furnace are 
 similar to that described in the one previously men- 
 tioned. A furnace of this kind yields every 24 hours, 
 during which time six operations are carried out, 
 
 FIG. 153. 
 
 nearly 9 tons of ball soda of 38 alkalimetrical degrees. 
 
 Some soda furnaces are built in such way that the hot air from the furnace after 
 passing the second hearth is conducted over pans filled with soda liquor for evapora- 
 tion. 
 
 Another kind of soda furnace is that with rotatory hearth invented by Elliot and 
 Eussel, and improved by Stephenson and Williamson, represented by fig. 1 54. This fur- 
 nace differs from all former soda furnaces in this respect, that the stirring of the materials 
 by manual labour is dispensed with, tne stirring operation being effected by machinery. A 
 is the rotatory hearth, consisting of a cylinder of cast iron lined internally with fire 
 clay. Ribs or rails (B) cast on the cylinder run on the wheels (c), receiving motion 
 from the driving wheel (o), and causing the cylindtr to rotate. The heated air of the 
 furnace (r>) flows through the opening (E) into the cylinder, and passing through (F), 
 reaches the arched compartment (G), and is carried off by the flue (F) into the chimney. 
 The cylinder is charged by allowing the materials to fall into it through an opening 
 (B') from a small iron truck (a) through the hoppers (H). The cylinder is also emptied 
 through B', for which purpose the cylinder must be so turned that the opening is below. 
 A cylinder of the kind is generally about 13 ft. long and 7 ft. in diameter. In 
 order to charge it, there is first of all thrown in about 3 cwt. of chalk and 1 cwt. of 
 coal or charcoal powder, the cylinder being thus caused to rotate slowly and heated 
 for an hour and a half. The rotation is then stopped, and 2| cwt. of sodium sulphate and 
 | cwt. of charcoal are added, and the cylinder again caused to rotate slowly, the heat 
 being gradually increased, until it is observed that the mass has begun to melt, when a 
 rotation is given to the cylinder of one revolution every three minutes. When the 
 operation is over the melted mass is run out at B' into iron trucks. 
 
 FIG. 154. 
 
 The use of these cylindrical furnaces effects a more complete and quicker decom- 
 position of the materials than can be obtained in the other kinds of soda furnaces. At 
 the same time the oxidising action of the atmospheric air is avoided which, in the 
 older forms of furnaces resulted from the access of air through the working holes. 
 Moreover the cylindrical furnaces yield three times as much product, and as the fire 
 bricks of the cylinder do not suffer from raking, as is the cnso in the hearths of other 
 kinds of furnaces, the cylindrical furnaces are more durable. Wagner states 
 that at the Jarrow -chemical works, where formerly only one rotatory soda furnace 
 was employed, several of them have recently been erected, which speaks well for their 
 utility. 
 
 In former times when no extensive use was made of the hydrochloric acid evolved 
 
MANUFACTURE OF SODA. 
 
 261 
 
 in the preparation of sodium sulphate from common salt, soda and sodium sulphate 
 furnaces were connected with one another, and this is the case even at the present day 
 in some places. Figs. 155 and 156 represent the construction of a furnace of the kind. 
 
 FIG. 155. 
 
 B is an ordinary soda furnace, c the sulphate furnace. The hot air from the furnace 
 (A) flows over the fire bridge into the chamber (B), causing the raw soda in it to melt, 
 and it then passes into the sulphate chamber (c) and through the flues (D D) into the 
 chimney (D'). The sulphate which is obtained from (c) in the calcined state is drawn 
 out, mixed with charcoal and calcined carbonate, and brought into the soda fur- 
 nace (B). 
 
 The hearth of the soda furnace (B) is 10 ft. 8 in. long, and 8| ft. wide; the 
 
 FIG. 156. 
 
 hearth of the sulphate furnace (c) is 9 ft. 6 in. long and 8 ft. 6 in. wide. The sulphate fur- 
 nace is charged three times within the space of 24 hours, making an entire charge of 
 3l cwt. of common salt and 40 cwt. of sulphuric acid, of specific gravity 1'535, the pro- 
 duce being about 37i cwt. of sodium sulphate. The latter quantity is operated upon 
 in the soda furnace in twelve operations with about 40 cwt. of calcium carbonate and 22 
 cwt. of coal or charcoal, the amount of ball soda produced being about 55 cwt. of 
 38-40 alkalimetrical degrees. 
 
 Combined soda and sulphate furnaces have been constructed with three divisions, 
 of which the one furthest from the fire is used for decomposing the salt with sulphuric 
 acid, the next one for calcining the sulphate, the last or partition nearest the fire 
 being the soda furnace? 
 
 Lixiviation and Purification of Sail Soda. The composition of ball soda varies 
 considerably, and it depends upon the proportions of the raw materials taken, and 
 the way in which the process of soda-making is carried out. 
 
 Apart from accidental admixtures, ball soda has, according to Wagner, the follow- 
 ing composition : 
 
 Sodium carbonate . - * ' . . . - * ,. 45 
 
 Calcium sulphide . , . \ * i * ; .30 
 
 Caustic lime . . ^ . .. . - * . - ; ' ^ 
 
 Calcium carbonate . . . .- ,.; . 5 
 
 Foreign substance . . . . . .. .10 
 
 The percentage of sodium carbonate in ball soda is, at any rate in most cases, 
 less than 45 per cent. ; but it fluctuates more than is indicated by the analyses, and is 
 sometimes less than 30 per cent. 
 
262 
 
 SODIUM. 
 
 The following table gives the results of three analyses by Stohmann of ball soda 
 from the Jarrow soda works : 
 
 
 Soda prepared in an ordinary 
 furnace 
 
 Soda prepared 
 in cylindrical 
 furnace 
 
 Sodium carbonate .... 
 
 44-41 
 
 38-45 
 
 43-27 
 
 , hydrated oxide 
 
 
 
 3-17 
 
 
 
 , sulphate .... 
 
 1-54 
 
 1-54 
 
 1-06 
 
 , chloride 
 
 1-42 
 
 1-75 
 
 1-48 
 
 Calcium carbonate .... 
 
 3-20 
 
 
 7-52 
 
 , oxysulphide .... 
 
 38-98 
 
 36-91 
 
 25-48 
 
 , sulphide .... 
 
 
 
 9-38 
 
 Lime 
 
 0-33 
 
 0-61 
 
 
 
 Magnesia 
 
 0-10 
 
 0-51 
 
 0-19 
 
 Alumina ...... 
 
 079 
 
 
 
 0-72 
 
 Ferric oxide ..... 
 
 1-75 
 
 2-40 
 
 1-48 
 
 Silica (soluble) 
 
 0-89 
 
 1-36 
 
 1-74 
 
 Sand 
 
 2-20 
 
 1-16 
 
 2-66 
 
 Carbon 
 
 5-32 
 
 5-43 
 
 5-28 
 
 Water 
 
 671 
 
 
 
 
 
 
 100-90 
 
 100-00 
 
 100-17 
 
 The object of the lixiviation of ball soda is the separation of the soluble consti- 
 tuents, chiefly sodium carbonate, from the insoluble constituents, such as calcium 
 sulphide or oxysulphide, lime, carbon, etc. 
 
 If the melted material, when removed from the furnace, were to be allowed to cool 
 in the air, a number of changes would take place, causing a loss of soda. It has been 
 proved, for instance, that by contact with atmospheric air the calcium sulphide is 
 rapidly oxidised to sulphate, which, in lixiviating the ball soda, reacts upon part of 
 the sodium carbonate, forming calcium carbonate and sodium sulphate. A further 
 loss of sodium carbonate is sustained, oven by allowing the cold material to lie 
 exposed to moist air, a part of the calcium sulphide being oxidised to thiosulphate, 
 which reacts upon sodium carbonate, forming calcium carbonate and sodium thio- 
 sulphate. 
 
 The only advantageous process of oxidation is the oxidation of sodium sulphide to 
 thiosulphate. But, besides this, exposure to the action of atmospheric air has a 
 favourable effect in causing disintegration of the mass, since the caustic lime absorbs 
 water, and is thus converted into hydrate of lime a process which is very favourable 
 to the following operation of lixiviation. However, since calcium sulphide oxidises in 
 contact with moist air, forming calcium thiosulphate, which causes loss of soda by 
 forming sodium thiosulphate, the material should not be exposed to the action of 
 the air for a longer time than is necessary for its disintegration. According to the 
 condition of the material and the atmospheric moisture, this requires from 3 to 6 days. 
 
 In addition to the precautions that are requisite as above mentioned in order to 
 prevent loss of sodium carbonate as a result of the oxidation of the calcium sulphide 
 in the ball soda, it is also necessary to prevent the access of air to the ball soda while 
 it is at a high temperature, for in that case calcium sulphate would be formed by 
 oxidation, and in the subsequent lixiviation of the ball soda a proportionate quantity 
 of sodium carbonate would be converted by reaction with it into sodium sulphate. On 
 this account it ig customary to draw the ball soda from the furnace into sheet-iron 
 boxes furnished with close-fitting covers and mounted on wheels. 
 
 Breaking up of the Ball Soda. This operation is sometimes effected by allowing 
 the material to disintegrate in contact with moist air, or by treating it with steam in 
 a closed chamber. However, these methods are not suitable for large quantities, and 
 in such case the ball soda is broken up into pieces about the size of the hand, and 
 then ground to a coarse powder between mill-stones, or else broken into pieces about 
 the size of small nuts, between grooved or spiked rollers. Another method consists 
 in stirring the melted black ash as it comes from the furnace into the crushed frag- 
 ments of a previous charge. 
 
 Lixiviation. In this operation the soluble substances must be dissolved out from 
 the crude soda with as little water as possible. The use of too much water would 
 involve unnecessary expenditure of time and fuel in the subsequent evaporation of the 
 
MANUFACTURE OF SODA. 
 
 263 
 
 solution. On this account, therefore, the liquid is repeatedly brought into contact 
 with fresh portions of material, so as to make it fully saturated. 
 
 Hard and difficultly soluble ball soda requires to be lixiviated with hot water 
 but the temperature should not exceed 35, otherwise calcium sulphide reacts upon 
 sodium carbonate to form sodium sulphide and calcium carbonate 
 
 A lixiviating apparatus is represented by fig. 157. It consists usually of from 12 
 to 14 rectangular iron tanks (A, B, c, D, E), placed in steps, one above the other. 
 
 FIG. 157. 
 
 The uppermost tank is of cast iron, and twice as large as any of the others. It is 
 connected with the next tank by a tube, the mouth of which terminates about 6 inches 
 above its bottom, and each of the other tanks has a similar communication with its 
 neighbour ; so that a liquid, poured in at A, passes out eventually from E into F. 
 
 The outflow pipes may be replaced by the contrivance represented in section and 
 plan by fig. 158; it consists of a channel, open above and below, and the upper end ter- 
 minating above the level of the liquid, the lower end 
 reaching to within 8 in. of the bottom of the 
 tank. The liquid of the tank (A) passes into the 
 channel at the lower end (A'), and flows out at the 
 upper end (A"), into the second tank (B), whence 
 it escapes through a similar channel (B' B") into 
 the following tank, and so on to the last one. 
 
 The lowest tank (E), fig. 157, communicates in 
 like manner with six wide sheet-iron tanks (F F'), 
 of which two only are shown in the drawing. 
 These tanks are called the clearing or settling 
 tanks. They are all at the same level, and they 
 communicate with each other by means of a tube 
 placed 4 inches below the upper rim. They are 
 emptied by means of a siphon. 
 
 The lixiviating operation is conducted as fol- 
 lows: Ball soda, broken into small pieces, js 
 placed in perforated metallic boxes (ec, dd, etc.), 
 and the vessels (A, B, c, n, E), having been previously filled with water, a couple of 
 these perforated boxes are hung in the first lixiviating tank (E) by a bar thrust 
 through their handles. After they have remained there for 25 or 30 minutes, they 
 are taken out and placed in the tank (D), a couple of fresh boxes being at the same 
 time suspended in E. This operation is continued at regular intervals ; so that in the 
 course of about 8 hours, when 14 lixiviating tanks are used, the first boxes (V, ee), 
 containing the raw or ball soda, are suspended in the large tank (A), having by this 
 time passed through all the other lixiviating tanks, while the boxes (//) are taken 
 out and placed upon an inclined board (K) to drain into the tank. After about half 
 an hour the residue is removed from these latter boxes, and placed in trucks for 
 removal from the works, while c' e' take the place of//, ee the place of e'e, etc., a 
 couple of fresh boxes being then suspended in K. Each time this is done, a quantity of 
 water, equal to double the volume of soda, is poured into the tank (A). The water displaces 
 the heavy liquor at the bottom, and causes it to flow into the following tank (B), and 
 displace the heavy liquor from it into the next tank (c), and so on until an almost 
 saturated solution is found in the settling vessel (FF / ). After the mechanical impuri- 
 ties are deposited in the settling tanks, the liquor is drawn off into the evaporating 
 pans (a, H, i, j, fig. 159, page 265). 
 
 Supposing each couple of sieve boxes to hold a charge of 2 cwt. of crude soda, and 
 
 FIG. 158. 
 
264 SODIUM. 
 
 they are freshly charged every half-hour, a lixiviating apparatus of 1 5 tanks would Tie 
 capable of lixivating 4f tons of raw soda in 24 hours. 
 
 Instead of this form of apparatus another is sometimes used, in which the lixivi- 
 ating tanks are twice as long, and divided in the middle by a double partition into 
 two equal parts, a couple of perforated boxes containing crude soda being placed in 
 each division. The liquid flows out of the first division of the first tank through an 
 aperture near the bottom of the first partition, rises in the space between it and the 
 second partition, and flows through an opening in the upper part of the second parti- 
 tion into the second division of the tank, from whence it passes into a second tank of 
 the same kind, etc. The liquor is heated by steam pipes passed between the double 
 partition. 
 
 Another method consists in placing the crude soda upon a perforated shelf, about 
 8 inches from the bottom of the tanks, instead of putting it into perforated boxes or 
 baskets. 
 
 Schank's lixiviating apparatus is especially suitable for lixiviation on a large 
 scale, and consists of a row of 4, 6, or 8 sheet-iron tanks, each having a depth of 8^ 
 ft. and a height of 6 ft. Near the bottom of each tank is a perforated shelf. 
 The first tank communicates with the second by means of a tube, bent at right angles, 
 one end of which terminates near the bottom of the first tank, while its other 
 extremity terminates in the upper part of the second tank. All the other tanks are 
 connected together in like manner. A cock, placed above each tank, supplies water, 
 while another cock, placed between the perforated shelf and the bottom of each tank, 
 serves for drawing off the liquor. A system of four lixiviating tanks is generally sc 
 arranged that, when the fourth tank is charged with fresh crude soda, the third tank 
 contains soda that has been once lixiviated, the second soda that has been twice lixi- 
 viated, and the first soda almost entirely lixiviated. Fresh water is run into the first 
 tank, passing from it into the second tank, and so on to the last tank. After having 
 been allowed to stand some hours, the liquor is drawn off from the last tank into the 
 settling tanks, and during this operation the communication between the first and last 
 tank is interrupted. So soon as the raw soda in the first tank is completely lixiviated, 
 the tank is emptied and charged afresh with raw soda. Fresh water is then run into 
 the second tank ; from there into the fourth and last tanks ; then into the first tank 
 containing the fresh crude soda, and then the highly concentrated liquor is drawn off 
 into the settling vessels, during which operation the communication between the first 
 and second tanks is interrupted. This method of proceeding secures a methodical 
 lixiviation of raw soda without it being necessary, as in the other forms of apparatus, 
 that the soda should be moved, thus saving considerable manual labour. Besides 
 this, the apparatus yields a clearer lye, and the cost of the apparatus, as well as the 
 wear and tear, are less than in the forms of apparatus formerly used. 
 
 The liquor obtained has a specific gravity varying between T178 and 1'225, 
 according as a hard or soft kind of raw soda has been lixiviated. 
 
 Concentration of the Liquor. This operation is carried out in iron pans, heated 
 either from beneath or by passing over them the hot air from a reverberatory furnace. 
 
 The liquor contains besides sodium carbonate varying amounts of common salt, 
 sodium sulphate, caustic soda, etc. Upon evaporation tolerably pure sodium carbonate 
 (Na 2 C0 3 + H 2 0) separates first, while that subsequently deposited is less pure. By 
 removing the first deposit, and continuing the evaporation while adding fresh liquor, 
 a deposit is obtained of nearly pure soda, containing 95 per cent, of sodium carbonate, 
 until the operation has been continued so long that the foreign substances are concen- 
 trated in the mother liquor to such an extent that they are deposited together with the 
 sodium carbonate. When this point has been reached, the mother liquor, containing 
 only very small quantities of sodium carbonate, is removed, and the pans are charged 
 again with fresh liquor. 
 
 An evaporating apparatus, in which the hot air from the furnace serves to heat 
 and partly evaporate the liquor, is represented by figs. 159 and 160. The pans 
 (a, H, i, J, K) are heated by the hot air escaping from the furnace (i). The soda 
 liquor passes from the settling tanks first of all into the pan (o) ; from thence into 
 (H, i, etc.), the temperature constantly increasing until concentrated liquor passes into 
 the pan (K), heated directly by the fire (i), where crystals of sodium carbonate are at 
 once deposited. The first portions of the deposited salt are somewhat impure, from 
 containing the insoluble constituents held in suspension in the liquor. The following 
 portions are pure, and are taken out from the pan as soon as deposited by means of 
 perforated ladles, and laid to drain upon a wooden strainer lined with lead. 
 
 The forms of the pans used in evaporating the lyes vary considerably. Sometimes 
 rectangular and oval pans with a flat bottom are employed, and sometimes oval pans 
 with a round bottom. The pans are heated either by a special fire, or by the hot air 
 escaping from the reverberatory soda furnaces. The liquor is passed directly from the 
 
MANUFACTURE OF SODA 2# 
 
 FIG. 159. 
 
 FIG. 160. 
 
 rakes, and either laid upon strainers or upon an inclined shelf, so that the mother 
 liquor drains back into the evaporating pan. A more useful kind of pan is furnished 
 with a groove round the side, where the temperature of the pan is not so great. The 
 deposited soda is raked by the workman into this groove, and when it is full the salt 
 5s drawn out with a perforated ladle having a form corresponding to the shape of the 
 groove, the deposit being, as before, laid on strainers to drain. 
 
 In proportion as the level of the liquor in the pan sinks, owing to the removal of 
 the salt, fresh liquor is run into the pan. 
 
 A very important method of evaporation is that in which the hot air from the black 
 ash or balling furnaces is made to pass over the surface of the liquor in the evaporat- 
 ing pans (vide p. 264). This method of evaporation admits of being adapted to 
 every soda furnace. The method adopted in the case of the ordinary furnace has 
 been described on p. 260 ; that adopted in the case of the cylindrical furnace on 
 p. 260, fig. 154, in which G is the pan space through which the hot air from tht> 
 cylinder is made to pass over the surface of the pan. This method of evaporating the 
 liquor has many advantages over those above described ; for without taking into 
 account the fact that fuel is spared, it is clear that the work and attention required 
 are less, inasmuch as, by heating from above, no danger is incurred of the soda burning 
 to the bottom of the pan, and consequently no stirring is required. Besides this, it is 
 not necessary to remove the deposited soda so often as is required in the case of pans 
 heated from beneath. 
 
 Direct heating of the Lye to dryness. This method of treating mother liquor yields 
 a product containing all the constituents of the black ash. The operation is carried out 
 in a reverberatory furnace (fig. 161), the hearth (s) of which is made of fire bricks, 
 
 FIG. 161. 
 
 over which a thick coating of sodium carbonate (T) is well rammed, so as to prevent 
 the liquor from coming into contact with the bricks. The fuel burnt in the furnace (u) 
 coke ; q as soon as the furnace has become thoroughly red hot the liquor is run out of 
 the pan (Q) through the cock (B) by a cast-iron tube passing through the arch of t he 
 furnace, on to the hearth (s). Upon the liquor coming ,n contact with the hot layer of 
 soda upon the hearth, a lively ebullition takes place, the mass froths up a 
 dries. Constant stirring is requisite, partly in order to accelerate the drying and 
 mrtlv to render the soda pulverulent. So soon as a large quantity of dry salt lias 
 llll ^produced* the flow of liquor is interrupted by closing the cock (R), the salt . 
 removed from the furnace, and the operation recommenced. 
 
 Z compositiorof soda ash thus evaporated to dryness var.es considerably; the 
 following table gives the result of two analyses of such soda by J. Brown. 
 
266 
 
 SODIUM. 
 
 
 I. 
 
 II. 
 
 ! 
 1 
 
 Sodium carbonate .... 
 
 68-907 
 
 65-513 
 
 
 Hydrate of soda (caustic soda) . 14-433 
 
 16-072 
 
 
 Sodium sulphate .... 
 
 7-018 
 
 7-812 
 
 
 sulphite .... 
 
 2-231 
 
 2-134 
 
 
 thiosulphate 
 sulphide .... 
 
 traces 
 1-314 
 
 traces 
 1-542 
 
 
 chloride .... 
 
 3-972 
 
 3-862 
 
 
 aluminate .... 
 
 1-016 
 
 1-232 
 
 
 silicate .... 1-030 
 
 0-800 
 
 
 Insoluble matter .... 
 
 0-814 
 
 0-974 
 
 
 
 100-735 
 
 99-941 
 
 The salt is next calcined in order to convert sodium sulphide into sulphate, and a 
 part of the caustic soda into sodium carbonate, as well as to secure the destruction of 
 organic matter, and to render the salt anhydrous. For this purpose it is heated i n 
 a reverberatory furnace fed with coal, care being taken to stir the mass constantly, so 
 as to renew the surface exposed to the hot air. The mass is heated until it begins to 
 cohere, but not until it melts, in which case it would attack the hearth of the furnace, 
 and be rendered impure by the formation of sodium silicate and aluminate. The fol- 
 lowing table gives the results of two analyses of calcined soda ash by J. Brown. 
 
 
 I. 
 
 II. 
 
 Sodium carbonate .... 
 
 71-614 
 
 70-461 
 
 Caustic soda 
 
 11-231 
 
 13-132 
 
 Sodium sulphate .... 
 
 10-202 
 
 9-149 
 
 sulphite .... 
 
 1-117 
 
 1-136 
 
 ,, chloride .... 
 
 3-051 
 
 4-279 
 
 aluiniuate .... 
 
 0-923 
 
 0-734 
 
 ,, silicate .... 
 
 1-042 
 
 0-986 
 
 Insoluble matter .... 
 
 0-316 
 
 0-464 
 
 
 99-496 
 
 100-341 
 
 In order to convert the caustic soda into sodium carbonate, the soda ash is mixed 
 before calcination with finely pulverised charcoal or with sawdust, and the carbonic 
 acid yielded by these substances during the calcination combines with the caustic soda 
 to form sodium carbonate; for this reason the operation is termed carbonating. 
 
 To obtain soda crystals, pure black ash is first of all prepared, as little charcoal pow- 
 der as possible being added in the balling operation, to secure as complete conver- 
 sion as possible of the caustic soda into sodium carbonate. The addition of rather 
 more chalk than usual is also advantageous for the more complete conversion of 
 sodium sulphate into carbonate. The ball soda obtained is lixiviated in the usual way, 
 and the black ash liquor, concentrated to sp. gr. 1-267, is then run into cry stalli sing 
 vessels, which are from three to six feet long, one and a half wide, and ten to thirteen 
 inches deep. 
 
 When the liquor has thoroughly cooled crystallisation commences, and it goes on 
 moro rapidly the cooler the surrounding atmosphere. On this account the preparation 
 of soda crystals is very conveniently performed in winter time. 
 
 "When the crystallisation is complete, the mother liquor is run off by drawing out a 
 plug fixed in the bottom of the crystallising vessel, and having a handle extending above 
 the level of the liquid. The crystals are then detached from the sides of the crystal- 
 lising vessels with the aid of a chisel, and are placed upon strainers to drain. They 
 are usually somewhat impure and discoloured, but answer for many purposes. When 
 pure soda crystals are required, the salt is again dissolved in hot water, mixed with 
 i^Soth part of its weight of lime, which forms calcium carbonate, and carries down with 
 it the mechanical impurities contained in the solution. After the liquor thus ob- 
 tained has become quite clear, it is run into crystallising vessels, placed in a cool posi- 
 tion, and as soon as the crystallisation is complete the crystals are taken out, drained in 
 perforated troughs lined with lead, and, after having been loft for a short time to dry 
 in the air, they are packed. If left too long exposed to the air, they effloresce or 
 become dull on the surface, owing to loss of water of crystallisation. 
 
SODA CRYSTALS. 
 
 267 
 
 Soda crystals are often prepared from soda ash that has been mixed with a small 
 quantity of finely pulverised charcoal and calcined for the purpose of converting the 
 caustic soda into sodium carbonate. The calcined mass is dissolved in boiling water 
 in large iron pans heated by passing steam into the liquid until a solution is obtained 
 having a specific gravity of 1-216 ; this is run into settling vessels, and when clear eva- 
 porated to a specific gravity of 1 '256 to 1-267, and then run into the crystallising vessels, 
 either cast-iron boxes or pans, preference being now generally given to the pans. 
 
 In order to remove organic substance the liquor is treated with bleaching powder, 
 before allowing it to crystallise, and during this operation it must not be allowed to 
 cool below 33, otherwise some sodium carbonate would be precipitated. 
 
 The troublesome work of detaching with a chisel the soda crystals lining vessels 
 may be avoided by placing the boxes from which the mother liquor has been run off 
 in a vessel that can be filled with boiling water, so that the crystals adhering to the 
 surfaces of the boxes are melted and thus detached. 
 
 Soda that is to be used in the manufacture of white glass is again calcined. The 
 following table gives the results of analyses by Brown of soda ash before and after 
 calcination : 
 
 Sodium carbonate 
 sulphate 
 chloride . . . . . 
 Water . . . . . . 
 
 Crystallised Soda 
 
 Cyrstallised Soda 
 after calcination 
 
 I. 
 
 II. 
 
 I. 
 
 II. 
 
 36-476 
 0-943 
 0-424 
 62-157 
 
 36-931 
 0-542 
 0-314 
 62-213 
 
 98-120 
 1-076 
 0-742 
 
 97-984 
 1-124 
 0-563 
 
 
 100-000 
 
 100-000 
 
 99-938 
 
 99-671 
 
 Soda crystals, being tolerably pure, may be conveniently used for preparing chemi- 
 cally pure sodium carbonate, for which purpose it is only necessary to dissolve the 
 crystals in hot water and allow the solution to crystallise in a cool place. The opera- 
 tion is repeated until the crystals produced, when dissolved in water made slightly acid 
 with nitric acid, cease to give a reaction with silver nitrate (chlorine) or with barium 
 nitrate (sulphuric acid). 
 
 Kopp's method of preparing sodium carbonate from sodium sulphate, and at the 
 same time recovering the sulphate, consists in heating the sulphate to redness in a re- 
 verberatory furnace together with ferric oxide and carbon, allowing the product thus 
 obtained to disintegrate in a moist atmosphere, rich in carbonic acid, lixiviating with 
 water, and reconverting the mndissolved residue of ferrous sulphide into ferric 
 oxide by roasting it, the sulphurous acid thus produced being used for preparing 
 sulphuric acid. Kopp assumes the following chemical changes to take place : 
 
 a. Sodium sulphate, ferric oxide, and carbon yield when heated to redness a double 
 sulphide of sodium and iron, as well as carbonic oxide and carbonic acid : 
 
 3Na 2 S0 4 + 2Fe 2 3 + 160 = Fe 4 Na 6 S 3 + 14CO + 2C0 2 . 
 
 0. The double sulphide of sodium and iron is converted by the action of oxygen, 
 water, and carbonic acid into sodium carbonate, and another double sulphide of iron 
 and sodium containing less sodium : 
 
 Fe 4 Na 6 S 3 + 20 + 2C0 2 = Fe 4 Na 2 S 3 + 2Na 2 C0 8 . 
 
 7. The compound Fe 4 Na 2 S 3 yields upon roasting ferric oxide, sodium sulphate, and 
 sulphurous acid : 
 
 Fe 4 Na 2 S 3 + 140 - 2Fe 2 8 + Na 2 S0 4 + 2S0 2 . 
 
 According to Kopp, 125 parts of sodium sulphate are mixed with 80 parts of ferric 
 oxide and 55 parts of charcoal powder, the mixture being heated m an ordinary balling 
 furnace until it has assumed the consistency of a thin dough. It is then taken out 
 and allowed to cool in well-closed iron boxes. The blocks when cold are placed c 
 grating in a chamber furnished with draught holes, into which chamber moii 
 carbonic acid sas is passed from beneath the bars of the grating. The carbonic acid 
 faWC5 *e, and before the gas reaches the bars of tbo grating sup- 
 porting the blocks it IB moistened by being passed through tubes wetted internally and 
 cooled from outside The effect of the moistened carbonic acid upon the blocks is to 
 ?&r5uH fall down between the bars of tfe ^> **3 
 acted upon by further portions of carbonic acid. The crumbling of the blocks and the 
 
2<58 SODIUM. 
 
 consequent separation of the disintegrated portions from the solid blocks is of great 
 importance, inasmuch as an ignition of the entire mass would otherwise be apt to 
 occur. The disintegrated mass is separated with sieves from the siliceous fragments 
 from the furnace, and lixiviated in the usual way. This process when properly con- 
 ducted yields, upon evaporation of the crude soda liquor, soda ash containing as much 
 as 95 per cent, of sodium carbonate. 
 
 The residue from the lixiviation consists chiefly of ferrous sulphide. It is either 
 dried and further operated upon in this state, or made into bricks by the aid of pressure. 
 In either case it is eventually roasted, and the sulphurous acid evolved conducted into 
 leaden chambers for making sulphuric acid, which is used for converting fresh 
 quantities of common salt into sodium sulphate. The residual ferric oxide from the 
 incineration of the ferrous sulphide is again used for converting sodium sulphate into 
 carbonate. Since the ferric oxide thus obtained is always contaminated with the 
 sulphates of sodium, calcium, and magnesium, it is best to wash it with water before 
 using it again for the conversion of sodium sulphate into carbonate, in order to extract 
 the sodium sulphate, and then with dilute hydrochloric acid, which removes the sulphates 
 of calcium and magnesium. Thus treated, the ferric oxide is available for use for a 
 very considerable length of time. 
 
 Pelletan's process consists in converting sodium sulphide dissolved in water into 
 carbonate by passing carbonic acid into the solution : 
 
 Na 2 S + C0 2 + H 2 = Na 2 C0 3 + H 2 S. 
 
 For this purpose sodium sulphate is reduced to sulphide by heating it with charcoal, 
 the product is lixiviated, and carbonic acid passed through the liquor obtained. The 
 sulphuretted hydrogen given off admits of being again treated for sulphuric acid by 
 passing it through ferric oxide. Ferrous sulphide is thus formed, which is then 
 roasted, and the sulphurous acid is conducted into lead chambers for conversion into 
 sulphuric acid. Klemm and Bohringer bring the sulphuretted hydrogen into contact 
 with sulphurous acid, by which means sulphur is deposited in the free state : 
 
 S0 2 + 2H 2 S = 3S -f 2H 2 0. 
 
 This method has this disadvantage, that in consequence of the formation of 
 polysulphides, which are difficultly decomposed by carbonic acid, the soda obtained is 
 contaminated with sulphur. 
 
 Wilson decomposes sodium sulphide liquor by boiling it with double sodium 
 carbonate ; Bower by digesting it with ammonium carbonate, in which process bicar- 
 bonate of sodium is obtained and ammonium sulphate as by-product. 
 
 Sodium sulphide may also be decomposed by boiling it with hydrate of alumina, 
 which is obtained as a by-product in the preparation of soda from cryolite. Sodium 
 aluminate is thus formed, and sulphuretted hydrogen, which is absorbed by ferric oxide 
 and used for preparing sulphuric acid. The sodium of the sodium aluminate is then 
 converted into carbonate by treating the liquor with carbonic acid. 
 
 Priickner decomposes sodium sulphide solution with cupric oxide, by which means 
 a precipitate is formed consisting of cupric sulphide, the residual liquor consisting of a 
 solution of caustic soda. The cupric sulphide is roasted to obtain sulphurous acid and 
 sulphuric acid, while the caustic soda is mixed with sawdust and the mixture 
 calcined, so as to convert the caustic soda into sodium carbonate. The cupric sul- 
 phate is again treated for cupric oxide. 
 
 A method proposed for converting sodium sulphate into carbonate by acting upon 
 it with barium carbonate failed on account of the difficulty experienced in effecting the 
 decomposition either in the moist or dry way. Another method proposed by Wagner 
 consisted in using barium bicarbonate, or a mixture of it and the simple carbonate, 
 obtained by passing carbonic acid into water containing barium carbonate in suspen- 
 sion. This also has proved unsuccessful. 
 
 Caustic baryta is at present too dear for the purpose of converting sodium sulphate 
 into carbonate, although the decomposition is very complete. 
 
 Ungerer describes a method of preparing soda in which caustic strontia is employed 
 for converting sodium sulphate into carbonate. This method is worth notice on account 
 of the fact that both the sulphuric acid of the Glauber's salt, as well as the caustic 
 strontia employed for the decomposition, admit of being again tised. A saturated 
 solution of ammonium sulphate is mixed with its equivalent of common salt and the 
 mixture boiled for a-short time. The hot solution deposits sodium sulphate, which is 
 removed, and the residual liquor when sufficiently cooled deposits sal ammoniac, which 
 is likewise removed. The mother liquor is then boiled down and yields a second crop 
 of sodium sulphate. The sodium sulphate is dissolved in water and treated with 
 caustic strontia ; strontium sulphate is thus precipitated, while caustic soda remains in 
 solution, and is treated with carbonic acid to form sodium carbonate. Ammonium chloride, 
 

 MANUFACTURE OP SODA. 269 
 
 obtained by decomposing ammonium sulphate with common salt, is then heated 
 to redness with calcium carbonate, and thus converted into ammonium carbonate, with 
 which the strontium sulphate suspended in water is heated for some time. By this 
 means strontium carbonate is formed and ammonium sulphate, which is again used 
 for converting sodium chloride into sulphate. The strontium carbonate is mixed with 
 carbon and heated to redness in a reverberatory furnace, while at the same time steam 
 is passed through the mixture, and by this means it is again converted into caustic 
 strontia, which is used for decomposing sodium sulphate. 
 
 A method suggested by Weldon consists in preparing sodium sulphate by treat- 
 ing common salt with magnesium sulphate, converting the sodium sulphate into sodium 
 fluoride and acid sodium sulphate by treating it with hydrofluoric acid. The two 
 salts are then separated by crystallisation, and the sodium fluoride converted into 
 caustic soda by acting upon it with caustic lime. The caustic lime may be replaced 
 by the magnesia, obtained, together with Glauber's salt and hydrochloric acid, as a by- 
 product in treating sodium chloride with magnesium sulphate. 
 
 Jean melts together sodium sulphate, fluorspar, calcium carbonate, and carbon, so 
 as to produce sodium fluoride, calcium sulphate, carbonic oxide, and caustic lime. The 
 sodium fluoride is dissolved out by water and treated with caustic lime. 
 
 Baader converts sodium sulphate into carbonate by melting it with silica (sand) 
 and carbon ; the sodium silicate formed is dissolved out with water, and decomposed by 
 carbonic acid. 
 
 Puissant' s method of preparing soda together with lead carbonate consists in pass- 
 ing carbonic acid through a boiling solution of sodium sulphate, containing barium car- 
 bonate in suspension. In this way barium sulphate and sodium carbonate are formed. 
 The sodium carbonate solution is decanted from the barium sulphate, treated with lead 
 sulphate, heated to the boiling point, and again treated with carbonic acid, when lead 
 carbonate and sodium sulphate are formed, the latter being again used for preparing 
 sodium carbonate, etc. 
 
 PREPARATION DIRECTLY FROM SODIUM CHLORIDE. The oldest method of preparing 
 soda artificially consisted in the direct conversion of common salt into caustic soda 
 by filtering it through litharge. The caustic soda was then converted into sodium 
 carbonate, by exposing it for some time to the air. This method, originated by Scheele, 
 has been often patented, but has not met with much success. 
 
 Blanc and Bazille's method consists in decomposing common salt by heating it to 
 redness with sand in a current of steam. A mixture of 280 parts common salt and 
 200 parts sand is heated to redness in a cast-iron retort, into which steam is passed 
 by means of a pipe with small holes. By this means the sodium' chloride is decom- 
 posed according to the equation : 
 
 2NaCl + Si0 2 + H 2 - Na 2 SiO s + 2HC1. 
 
 The hydrochloric acid, escaping with the steam and a small quantity of sodium 
 chloride, passes through a stoneware tube into a chamber where the sodium chloride 
 is condensed, and the hydrochloric acid is either condensed in ordinary condensing 
 bottles or in a stoneware trough, the bottom of which is covered with water. The 
 solid product left in the retort is so difficultly soluble in water that it requires to be 
 melted with f of its weight of soda ; a readily soluble basic sodium silicate is thus ob- 
 tained, and when dissolved in water, is converted into sodium carbonate by passing 
 carbonic acid through the solution. 
 
 Gossage's method consists in passing the hot air from a coal fire through a flue 
 where it is mixed with steam, and then over a surface of common salt into the upper 
 part of a shaft furnace contracted towards its lower extremity, and filled with pieces of 
 quartz. The sodium chloride volatilised with the hot air and steam, on coming into 
 contact with the red-hot quartz, is converted into sodium silicate and hydrochloric acid. 
 
 Tilghman's method consists in passing superheated steam through melted sodium 
 chloride, which causes volatilisation of the salt, together with the steam. ^ This mix- 
 ture of steam and salt vapour is then passed into an iron cylinder filled with pieces of 
 red-hot alumina. Sodium aluminate is thus formed, which is treated for soda with 
 carbonic acid. 
 
 Dyer. Grey, and Harrison's method consists in treating a saturated solution of 
 common salt with finely powdered ammonium sesquicarbonate, or, still better, with 
 the bicarbonate. In this way acid sodium carbonate is formed, which separates owin<. 
 to its sparing solubility in water, together with a small quantity of ammonium 
 carbonate, and ammonium chloride remains dissolved. The precipitate, deprived of 
 adhering mother liquor as much as possible by filtering and pressing, is then dm 
 and heated to redness, so as to volatilise the adherent ammonium carbonate, and con- 
 vert the double sodium carbonate into simple carbonate. The mother liquor, contain- 
 
270 SODIUM. 
 
 ing ammonium chloride, is evaporated to dryness ; and the residue heated to redness 
 with calcium carbonate to convert it into ammonium carbonate. 
 
 An excellent modification of the above method consists in using caustic ammonia 
 in the place of ammonium sesquicarbonate or bicarbonate. Caustic ammonia is 
 mixed with the solution of common salt, and carbonic acid forced into the mixture 
 under pressure. A precipitate of acid sodium carbonate is thus formed, and is sepa- 
 rated from the mother liquor by a centrifugal machine, purified by washing, and dried. 
 The mother liquor is mixed with slaked lime, and boiled as long as ammonia is 
 evolved. The ammonia is in its turn passed into a solution of common salt for the 
 decomposition of the latter, in the way already stated. 
 
 A number of other methods have been suggested for the direct conversion of 
 common salt into sodium carbonate, but none of them have as yet met with industrial 
 success. Among such methods may be mentioned Samuel's, which consists in precipi- 
 tating acid sodium oxalate from a solution of common salt, by the addition of oxalic 
 acid. The precipitate is then boiled with slaked lime, by which calcium oxalate and 
 caustic soda are formed. Spilsbury and Maugham precipitate the sodium contained in 
 common salt as sili co-fluoride, by treating a solution of common salt with fluosilicic 
 acid. The sodium silico-fluoride is then decomposed by the aid of heat into sodium 
 fluoride and silicon fluoride ; the former, boiled with slaked lime, forms calcium fluoride 
 and caustic soda. The fluosilicic acid is obtained either by heating to redness a mix- 
 ture of sand, clay, and fluorspar, or as a by-product when silicon fluoride is passed 
 into water. The calcium fluoride obtained by the decomposition of the sodium fluoride 
 with lime is also treated for fluosilicic acid. Kessler patented a method for the con- 
 version of common salt into sodium carbonate, which consisted in first of all forming 
 sodium chromato by heating common salt to redness with chromium oxide, and passing 
 steam over the mixture. The sodium chromate was then mixed with carbon, and the 
 mixture heated to redness, so as to form chromium oxide and sodium carbonate. The 
 product only required lixiviating to separate the soluble sodium carbonate from the 
 insoluble chromium oxide, which was then ready for decomposing a fresh quantity of 
 sodium chloride. 
 
 PREPARATION FROM CRYOLITE. The composition of cryolit e is represented by the 
 formula A1F 3 , 3NaF. It occurs in large deposits in Greenland, whence it is chiefly 
 exported to Germany and Denmark. 
 
 Thomsen decomposes cryolite into sodium illuminate, calcium fluoride, and carbonic 
 acid by -heating it with calcium carbonate : 
 
 A1F 3 + 3NaF + 3CaC0 3 = AlNa 3 3 + 3CaF 2 + 3C0 2 . 
 
 The sodium aluminate is dissolved out with water and decomposed with carbonic 
 acid, hydrate of alumina being separated : 
 
 2AlNa 3 3 -f 3C0 2 + 3H 2 = 3Na 2 C0 3 + 2A1H 3 3 . 
 
 The aluminum hydrate thus obtained is treated with sulphuric acid to form 
 aluminum sulphate (see page 308). 
 
 For this purpose ] 00 parts of cryolite reduced to a very fine powder, are mixed with 
 127 parts of equally finely powdered calcium carbonate. The mixture is heated on the 
 hearth of a reverberatory furnace, fired with coke, and continually stirred until the 
 mass begins to cake together. It is then removed from the furnace, reduced to powder, 
 and lixiviated with hot water. The liquor, while still hot, is run into closed cylinders, 
 placed in a horizontal position and furnished with a condensing arrangement, where it 
 is treated with carbonic acid obtained from the hot air escaping from the reverberatory 
 furnace. The contents of the absorption cylinders are emptied into clearing vessels 
 where the aluminum hydrate is deposited. The clear liquor is then drawn off and 
 treated either for crystallised or calcined sodium carbonate. The deposit of aluminum 
 hydrate is washed several times with fresh water, and then placed in a wooden vat 
 lined with lead, where it is saturated with warm sulphuric acid (80-90), specific 
 gravity 1'490. The clear solution is decanted off and evaporated in copper pans until 
 a product is obtained having a composition represented by the formula : 
 
 A1 2 S 3 6 -}- 18H 2 0. 
 
 It is not possible by washing to remove the last traces of soda from the aluminum 
 hydrate, and consequently the aluminum sulphate thus obtained invariably contains 
 some sodium sulphate. It is however entirely free from iron. 
 
 Sauerwein boils finely powdered cryolite with milk of lime so as to form sodium 
 aluminate and calcium fluoride : 
 
 (A1F 3 + 3NaF) + 3CaO = AlNa 3 3 + 3CaF,. 
 
 The clear liquor thus obtained is deprived of alumina by treating it with an excess 
 
SODA WASTE. 
 
 271 
 
 of finely powdered cryolite and continually stirring ; by this means aluminum hydrate 
 and sodium fluoride are formed : 
 
 AlNa 3 3 + (A1F, + 3NaF) + 3H 2 = 2A1H 3 0, + 6Nal?. 
 The aluminum hydrate is heated as above described with sulphuric acid for 
 aluminum sulphate, and the sodium fluoride is treated with caustic lime for caustic 
 soda. 
 
 Weber's method consists in treating cryolite with sulphuric acid, by which means 
 aluminum sulphate and sodium sulphate are formed according to the equation : 
 2(A1F 3 + 3NaF) + 6H 2 S0 4 = A1 2 3S0 4 + 3N a2 S0 4 + 12HF. 
 
 The evaporation of the liquor yields in the first instance crystals of sodium sulphate, 
 and the mother liquor is then treated for aluminum sulphate. 
 
 The mineral called ba uxite, consisting of from 60 to 75 per cent, of alumina and 
 12 to 25 per cent, of ferric oxide, together with some silica and water, is also used in 
 the manufacture of soda, although it yields neither soda nor carbonic acid. Balard 
 heats bauxite to redness with sodium sulphate, so as to form sodium aluminate and 
 aluminum hydrate. Another method consists in passing superheated steam over a 
 mixture of bauxite and common salt, by which means sodium aluminate and hydro- 
 chloric acid are produced. 
 
 Sodium nitrate, or Chili saltpetre, commonly used in the preparation of nitric acid, 
 furnishes sodium sulphate, which admits of direct conversion into carbonate by 
 Leblanc's method. 
 
 A number of attempts have also been made to obtain sodium carbonate from 
 sodium nitrate in a more direct and simple manner. 1 . By means of potassium carbonate, 
 so as to obtain potassium nitrate and sodium carbonate. 2. Walz suggests heating a 
 mixture of sodium nitrate and calcium carbonate to redness in a current, of steam. 
 Nitric acid escapes with the steam, and is condensed in suitable vessels; while the 
 residue in the retorts consists of a mixture of sodium and calcium carbonates. This 
 residue is lixiviated, yielding soda liquor. 3. Sodium nitrate may also be decomposed 
 by caustic potash, yielding caustic soda and potassium nitrate ; and (4) by igniting 
 sodium nitrate with carbonaceous materials. 
 
 Uses. Soda, or sodium carbonate, is an article of very extensive consumption. 
 Amongst the uses to which soda is put may be mentioned the manufacture of glass, 
 the washing of wool and silk, the preparation of aerated water, soap-making, etc. 
 Further, it is used in the preparation of sodium bicarbonate, and of a number of 
 sodium salts, as well as various carbonates, as an agent in the chemical laboratory 
 for various purposes, and as a medicine. 
 
 UTILISATION OF SODA WASTE. The residue from the lixiviation of ball soda, known 
 as soda waste, varies considerably in composition, as shown by the following table, giving 
 the results of analyses by Brown and Eichter. 
 
 
 
 Eichter's Analyses (from the Chemical 
 
 
 Brown's 
 
 Works at Sarau, in Silesia) 
 
 
 
 I. 
 
 II. 
 
 III. 
 
 Calcium carbonate 
 
 24-220 
 
 23-18 
 
 22-24 
 
 24-02 
 
 sulphide 
 
 8-527 
 
 37-62 
 
 38-04 
 
 39-10 
 
 oxysulphide . . 
 
 20-363 
 
 
 
 
 
 
 
 sulphate 
 hyposulphite . 
 sulphite 
 
 4-281 
 traces 
 
 1-68 
 2-69 
 0-74 
 
 1-01 
 3-02 
 0-31 
 
 1-38 
 235 
 0-63 
 
 disulphide 
 
 3-583 
 
 
 
 
 
 
 
 oxyhydrate . 
 
 3-583 
 
 
 
 
 
 " ' 
 
 Sodium carbonate 
 
 1-309 
 
 
 
 
 
 
 
 Soda ' 
 
 
 
 2-52 
 
 2-10 
 
 1-86 
 
 
 
 
 6-49 
 
 7-00 
 
 7-26 
 
 Magnesium carbonate . 
 Magnesia ... , , 
 Alumina 
 
 5-987 
 
 0-64 
 2-11 
 
 0-51 
 
 2-02 
 
 070 
 200 
 
 Ferric oxide .... 
 
 5-716 
 
 
 
 
 
 
 
 Ferrous sulphide .... 
 Carbon 
 
 12-709 
 
 1-88 
 5-41 
 
 175 
 6-00 
 
 2-01 
 6-39 
 
 Sand 
 
 5-746 
 
 774 
 
 6-82 
 
 1"1\ 
 
 Silica (in combination) 
 Water. ./ ... . . ;. .-...' v 
 
 2-100 
 
 4-24 
 2-32 
 
 4-03 
 3-29 
 
 4-62 
 1-51 
 
21T2 SODIUM. 
 
 When soda waste is allowed to lie exposed to the air, a portion of its calcium sul- 
 phide is converted into calcium carbonate and disulphide, which yield by further 
 oxidation calcium thiosulphate, and this decomposes rapidly into calcium sulphite 
 and free sulphur. Upon continuing the oxidation the calcium sulphite is converted 
 into sulphate. The sulphur liberated from calcium thiosulphate is either oxidised by 
 contact with atmospheric air, forming sulphurous acid, or else it combines with 
 calcium sulphide to form bisulphide, which yields a further quantity of calcium thio- 
 sulphate. The exposure of soda waste to the atmosphere also gives rise to the forma- 
 tion of sodium thiosulphate, partly by the oxidation of sodium sulphide, and partly 
 by the mutual decomposition of calcium thiosulphate and sodium carbonate to sodium 
 thiosulphate and calcium carbonate. The higher polysulphides of calcium and sodium 
 may also be produced by the action of free sulphur, liberated from calcium thio- 
 sulphate, upon the monosulphides of calcium and sodium. The heat produced by the 
 oxidation of soda waste in the atmosphere is frequently sufficient to cause an ignition 
 of the entire mass. 
 
 Soda waste is chiefly used for the recovery of the sulphur contained in it. The 
 most important methods by which this is done are those of Hofmanu, Buquet, 
 Schaffner, and Mond. 
 
 Schaffner's method involves the following operations : 
 
 1. Preparation of the liquor containing Sulphur. For this purpose soda waste is 
 exposed in lumps for several weeks to the action of the air, care being taken that the 
 oxidation does not go too far. It must be just sufficient to cause the conversion of 
 sulphides into polysulphides and thiosulphates without formation of calcium sulphate, 
 for any sulphur converted into that compound would be entirely lost. The requisite 
 degree of oxidation is recognised by the dark grey colour of the mass, which is then 
 lixiviated with water, and the residue again exposed to oxidation in the lixiviating tubs 
 by passing through it a stream of warm air. The lixiviation is repeated after each 
 oxidation. The salts dissolved out consist chiefly of polysulphides, and thiosulphates 
 of sodium and calcium, and it is easy to regulate the oxidation in such a way that 
 sulphides and thiosulphates are produced in equal proportion. 
 
 2. Separation of tJie Sulphur. This operation depends upon the facts that thio- 
 sulphates treated with hydrochloric acid are decomposed into free sulphur and sul- 
 phurous oxide : 
 
 CaS 2 3 + 2HC1 = CaCl 2 + H 2 + S + S0 2 . 
 
 The sulphurous oxide reacts upon the polysulphides, liberating another portion 
 of sulphur, while at the same time fresh quantities of thiosulphates are formed ; thus : 
 
 2CaS 3 + 3S0 2 = 2CaS 2 3 + 5S. 
 
 The decomposition of the liquor by means of hydrochloric acid is carried on in one 
 of two close cylinders of cast iron or stone, the gaseous products of decomposition 
 being passed alternately into one or other of the two vessels. Each vessel has four 
 openings above, one of which serves for the admission of hydrochloric acid, another 
 for the escape of gaseous products, while the other two effect the alternate transmission 
 of the gaseous products from one cylinder into the other. A continual exchange of 
 sulphurous acid from one cylinder into the other is thus kept up, and thus the entire 
 quantity of sulphur contained in the liquor is deposited. The deposited sulphur has a 
 fine granular structure and admits of easy filtration. 
 
 3. Purification of the Sulphur. The precipitate thus obtained contains adherent 
 calcium chloride and gypsum, and to remove these impurities it is mixed with water 
 in an iron cylinder, closed at both ends and slightly inclined, so that one end is lower 
 than the other. Steam at a pressure of If atmospheres is then admitted into the 
 cylinder to melt the sulphur, the heat required being about 110 115. In order to 
 saturate any free acid or to cause the solution of any arsenic that might be present, 
 some milk of lime is added. The molten sulphur collects in the bottom of the cylinder, 
 flowing towards the deepest part of the inclined cylinder, where it is tapped off into 
 moulds. 
 
 In places where hydrochloric acid is dear, the residue from the preparation of 
 chlorine is used instead of acid in the treatment of the liquor from soda waste. But 
 since this residue contains ferric chloride, which from its action upon sulphurous acid 
 would cause a loss of sulphur, the ferric chloride mus^first be got rid of by mixing 
 the chlorine residue with soda waste until all the ferric chloride has been converted 
 into ferrous chloride by the sulphuretted hydrogen of the waste. The liquor thus 
 prepared is then used for the decomposition of the soda waste liquor. 
 
 At the Aussig soda works, Schaffner recovers in this way as much as 60-65 per 
 cent, of the sulphur contained in soda waste. The sulphur thus recovered is used in 
 the preparation of sulphuric acid, which is used to make sodium sulphate, etc. 
 
SODIUM BICARBONATE. 
 
 273 
 
 Mond's method is very similar, and is extensively carried out in this country. The 
 oxidation of the soda waste is accelerated by forcing air through the mass by means 
 of a fan. The decomposition by hydrochloric acid is effected by mixing a definite 
 quantity of hydrochloric acid with an excess of the liquor containing sulphur, and 
 then adding hydrochloric acid sufficient for complete decomposition. More liquor is 
 then poured in, hydrochloric acid added, and so on until the vessel is filled. Hoffman 
 accelerates the oxidation of the soda waste by sprinkling the heaps with manganese 
 chloride ; the sulphur is then separated by the method already described. 
 
 In places where the recovery of sulphur from soda waste has not been introduced, 
 the soda waste is used for other purposes. It is employed, for instance, in some cases 
 as manure, for which purpose complete oxidation of the sulphides of calcium to sul- 
 phates is necessary, and consequently the soda waste requires longer exposure to the 
 atmosphere. Further uses made of soda waste consist in the preparation of hypo- 
 sulphites of calcium and sodium : it is also employed in the making of roads, walls, 
 bricks, a kind of Portland cement, etc. 
 
 ACID SODIUM CARBONATE (BICARBONATE). 
 
 FORMULA NaHC0 3 . MOLECULAR WEIGHT 84. 
 
 Characters. Sodium bicarbonate is a white crystalline powder possessing an 
 alkaline taste and turning red litmus paper blue. When exposed to a moist atmo- 
 sphere, it gradually gives up parts of its carbonic acid ; by heating the salt loses half 
 of its carbonic acid together with water and is converted into sodium monocarbonate. 
 Sodium bicarbonate is sparingly soluble in water, 100 parts of water at 10 dissolving 
 about 10 parts of the salt ; at 40, 13'35 parts ; and at 70, 1 6'69 parts. Upon heating 
 an aqueous solution of sodium bicarbonate a little above 70, part of the carbonic acid 
 of the salt escapes, sodium sesquicarbonate remaining in solution, and for this reason 
 an aqueous solution of sodium bicarbonate must not be boiled. 
 
 Sodium bicarbonate is an essential constituent of many kinds of mineral water. 
 
 Preparation. Sodium bicarbonate is prepared by acting upon sodium mono- 
 carbonate with carbonic acid, the carbonic acid required for this purpose being either 
 obtained from natural acidulous springs, or by acting upon chalk or marble with a 
 dilute mineral acid. In some cases it is found convenient to make use of the carbonic 
 acid escaping from lime kilns or produced in fermentation. 
 
 An apparatus for preparing sodium bicarbonate with the carbonic acid of acidulous 
 springs is shown in fig. 162. The escaping carbonic acid is caught in a kind of bell 
 jar (B), the water escaping through an outlet at the side. The carbonic acid passes 
 through the tube (<Z) into the gasometer (c), and is then conducted by means of the 
 
 FIG. 162. 
 
 tube () into the absorption chamber (D), which is built of brick and fitted internally 
 
 with a wooden rack supporting a number of frames over which pieces of woven 
 
 are stretched. Sodium monocarbonate is spread out upon these frames in a _ layer 
 
 about 2^ or 3 inches thick, which thus exposes a considerable surface to the a 
 
 the carbonic acid. In cases where crystallised sodium monocarbonate is employed, nin 
 
 equivalents of water are liberated during the formation of bicarbonate. On tl 
 
 account each frame is covered with a sloping roof, so that the water which trickles down 
 
 from the frames and contains considerable quantities of sodium carbonate in sc 
 
 is carried off by passing over the sides of the roofs, and is conducted e entually along 
 
 the bottom of the chamber into a tub (A) lined with lead. A number of chambers of 
 
274 SODIUM. 
 
 this kind are placed together, so that the unabsorbed carbonic acid escaping from the 
 first chamber is conducted into the second and third, etc., for complete absorption. The 
 charging and emptying of the chambers are effected through a lateral opening, which is 
 closed during the operation by a plate (g). 
 
 The salt is dried either by passing through the chambers a stream of carbonic acid 
 gas heated to 40, or by burning charcoal on braziers placed in the chambers. 
 
 The carbonic acid used for preparing sodium bicarbonate is more frequently ob- 
 tained by treating a carbonate with a mineral acid. 
 
 An apparatus for preparing sodium bicarbonate in this manner is represented by 
 fig. 163. It consists of an iron generator (A) lined with lead, a wash vessel (G), and 
 the wooden absorption vessels (j and L). The raw material from which carbonic acid 
 is to be generated is placed in the generator (A) and mixed with water, the mixture kept 
 
 Fio. 163. 
 
 constantly stirred by the agitator (B B), driven by a strap on the fast and loose pulleys 
 (c c'). By openingthe tap (D) sulphuric acid of specific gravity 1-495 to 1-551 is run into 
 the generator through the funnel (D'), and causes evolution of carbonic acid. The gas 
 passes through the tube (F) into a wash vessel (G) filled to about one half with water, 
 and from thence through the tube (H H H), entering the absorption vessel (j) through 
 the perforated bottom, upon which the sodium carbonate is placed. As in the apparatus 
 previously mentioned, a number of chambers of this kind are connected together so as to 
 secure as complete an absorption of the carbonic acid as possible. The wooden vats 
 are charged and emptied at (j). The water liberated when crystallised carbonate is 
 employed collects below and is drawn off by a cock (M). 
 
 The carbonate most commonly employed for generating carbonic acid is calcium 
 carbonate, in the form of chalk, marble, dolomite, etc., and it is decomposed either by 
 sulphuric or hydrochloric acid. The use of magnesite, which was formerly the chief 
 material employed for generating carbonic acid, has considerably decreased of late, 
 owing to the fact that the kieserite mud of the Stassfurt potash works is such an excellent 
 and cheap material for the preparation of magnesium sulphate (Epsom salts). Another 
 material sometimes used for generating carbonic acid is witherite (barium carbonate), 
 barium salts being then obtained as by-products. 
 
 Another acid sodium carbonate, commonly called sesquicar bo nate, is formed 
 under certain conditions, and it occurs naturally as a deposit from the water of lakes 
 containing sodium carbonate, the materials known as trona and urao consisting 
 chiefly of this salt. Its composition is represented by the formula Na 4 H 2 3C0 3 , and 
 it may be regarded either as a compound of two molecules of neutral sodium carbonate 
 with one molecule of carbonic acid 
 
 2Na 2 C0 3 +H 2 C0 3 , 
 
 or as a compound of one molecule of neutral carbonate with two molecules of acid car- 
 bonate 
 
 Na 2 C0 3 + 2NaHCO s . 
 
 This salt crystallises in rhombic prisms which contain two molecules of water ; it 
 is less soluble than the neutral carbonate and more soluble than the acid carbonate. 
 
 TESTS FOB SODIUM BICARBONATE. Qualitative Tests. The presence of sodium 
 monocarbonate in sodium bicarbonate is ascertained by treating a small portion of a 
 solution of the latter with a few drops of a solution of magnesium sulphate. A 
 cloudiness or precipitate indicates the presence of sodium monocarbonate. The presence 
 of chlorine is ascertained by adding a few drops of a solution of silver nitrate, together 
 with a drop of nitric acid, to a solution of sodium bicarbonate. A white precipitate 
 or cloudiness indicates the presence of chlorine. Sodium sulphate is found by testing 
 a solution of sodium bicarbonate, previously acidulated with hydrochloric acid, with 
 barium chloride, which, if sulphate is present, causes a white precipitate of barium 
 sulphate. 
 
SODIUM BICARBONATE. 
 
 275 
 
 Quantitative Tests. In order to determine the precise amount of pure sodium 
 bicarbonate in a sample of the latter, the salt is heated to expel as much as possible 
 of the carbonic acid, and the volume of 
 the carbonic acid carefully measured. 
 Fig. 1 64 shows an apparatus for a de- 
 termination of the above kind. A is a 
 glass tube sealed at one end, into which 
 is brought five grams of the salt to be 
 operated upon. To the other end of the 
 tube is attached a glass tube (ccc), 
 fitted accurately into the mouth of the 
 tube A. by means of a good cock, the tube 
 (ccc) being bent in the manner shown 
 in the drawing and opening beneath the 
 mouth of the graduated glass cylinder 
 (D) of 1 litre capacity, the latter being 
 filled with water and inserted in a ilG - 164 ' 
 
 vessel (B) likewise filled with water. A small quantity of oil is inserted into the gradua' 
 ted cylinder to prevent absorption of carbonic acid by the water. The sodium bicar' 
 bonate in A is now heated by the aid of a spirit or gas lamp, which causes an 
 expulsion of carbonic acid, the latter passing through ccc into the graduated cylin- 
 der (D). The application of heat is continued until gas ceases to be evolved, then the 
 graduated tube (D) is so placed that the level of the liquid in it is the same as that 
 in the outer vessel (B), and the volume of gas in (D) is read off. Supposing the sample 
 of salt operated on to have been pure sodium monocarbonate, then no gas would be 
 found in D ; sodium sesquicarbonate would yield 272 c.c., and pure sodium bicar- 
 bonate 657 c.c. Scheibler's apparatus for determining tho amount of carbonic acid is of 
 like construction. 
 
 Uses. Sodium bicarbonate is ussd in the preparation of pure sodium monocar- 
 bonate, for preparing alkaline baths of gold or platinum, from which these metals are de- 
 posited upon other metals in the form of a thin bright coating. A very considerable use 
 is made of sodium bicarbonate for preparing effervescing beverages. Seidlitz powders 
 consist of a mixture of five parts sodium bicarbonate and three parts tartaric acid. A 
 method of preparing soda water consists in placing a previously prepared mixture of 
 equal parts by weight sodium bicarbonate and tartaric acid in a strong bottle, filling 
 up the bottle to about with water, rapidly closing it, and shaking up its contents. 
 Since, by this method, sodium tartrate is dissolved in the soda water, which acts as a 
 purgative, and has at the same time an unpleasant taste, other kinds of apparatus 
 have been constructed by means of which carbonic acid alone is admitted into the 
 water to be aerated. An apparatus of the kind is represented by figs. 165 and 168. 
 
 FIG. 165. 
 
 FIQ. 166. FIG. 167. 
 
 Fin. 168. 
 
 A mixture of 10-8 grams of sodium bicarbonate and 15 grams of tartaric acid 
 are placed in a strong glass vessel (A), protected by a covering of ^^ EJ. iJJ! 
 mouth of the bottle is then closed by the tube with the lid (D) fig. IGj, vnow 
 ing then screwed upon a vessel (a) of 1 litre capacity, fig. 168, which 
 JtPi. l fho ***** inverted (fie. 165). Water passes through the tube (i>) into 
 
 water, and the apparatus inverted (fig. 165) 
 
 T 2 
 
276 SODIUM. 
 
 the lower vessel (A''), causing the sodium bicarbonate and tartaric acid to react upon 
 one another. Carbonic acid is thereby liberated, and passes through the finely per- 
 forated plate (D'), fig. 167, into the upper vessel (G'), dissolving in the water contained 
 in the latter. When soda water (or more properly aerated water) is required for use, 
 the cock placed at the lowest part of (G) is opened, and the effervescing liquid drawn 
 off. Of course all other liquids may be made effervescing in the above manner. 
 
 Other uses of sodium carbonate are for preserving milk, neutralising acid and beer, 
 and for preparing the carbonic acid used in making Liebig's patent aerated bread. 
 Sodium bicarbonate is also used in medicine, and for washing wool and silk, as well as 
 many purposes in the laboratory. 
 
 SODIUM NITRATE. 
 
 FORMULA NaN0 3 . MOLECULAR WEIGHT 85. 
 
 This salt, known as Chili saltpetre or cubic nitre, occurs abundantly in 
 South America, forming, in the district of Tarapaca in Northern Chili, beds several 
 feet thick, together with gypsum, common salt, sodium sulphate, etc. The crude salt 
 is called caliche. The following table gives the composition of several samples of 
 this material. 
 
 Hayes 
 
 Sodium nitrate 
 
 . 64-98 
 
 43-14 
 
 36-37 
 
 27-85 
 
 6-92 
 
 ,, sulphate . 
 
 3-00 
 
 26-30 
 
 11-67 
 
 43-20 
 
 0-68 
 
 chloride . 
 
 . 28-69 
 
 11-40 
 
 44-80 
 
 18-30 
 
 88-70 
 
 iodide . 
 
 . 0-63 
 
 
 
 
 
 
 
 
 
 Calcium sulphate 
 
 . 
 
 1-36 
 
 1-36 
 
 0-68 
 
 
 
 Magnesium 
 
 
 
 trace 
 
 trace 
 
 4-20 
 
 
 
 Insoluble substances 
 
 . 2-70 
 
 10-30 
 
 3-30 
 
 0-32 
 
 0-03 
 
 Moisture 
 
 
 
 7-05 
 
 2-50 
 
 6-00 
 
 3-50 
 
 100* 100- 100- 100-55 99-83 
 
 The sodium nitrate is extracted by a rough lixiviation with hot water, separating 
 impurities and allowing the clear concentrated solution to crystallise. 
 
 Characters. Sodium nitrate crystallises in oblique rhombohedrons closely re- 
 sembling cubes, and in this respect it differs from potassium nitrate which crystallises 
 in prisms. The salt is slightly deliquescent and readily soluble in water, requiring 
 little more than its own weight of cold water for solution ; it melts at about 310 and 
 forms a white mass on cooling. At a red heat it is decomposed in the same manner 
 and more readily than potassium nitrate. 
 
 Uses. Sodium nitrate is used chiefly for preparing nitric acid or for conversion 
 into potassium nitrate, and as a manure. 
 
 SODIUM PHOSPHATE. 
 
 FORMULA Na 2 HP0 4 . MOLECULAR WEIGHT 142. 
 
 This salt is frequently termed neutral sodium phosphate, but its constitution is 
 that of an acid salt ; it is met with in commerce in a crystallised form, containing 
 12 molecules of water of crystallisation (Na 2 HP0 4 12aq); it dissolves in 4 times its 
 weight of cold water, and in less than its weight of boiling water ; the solution has a 
 faintly alkaline reaction ; the crystals effloresce in contact with dry air ; the taste 
 of the salt is saline and cooling, and less unpleasant than that of sodium sulphate. 
 When moderately heated the whole of the water of crystallisation is given off; at a ; 
 red heat the basic hydrogen is given off in the form of water, and the salt is con- 
 verted into neutral sodium pyrophosphate : 
 
 2Na,HP0 4 - H 2 = Na 4 P 2 7 . 
 
 Sodium phosphate is generally prepared by adding a solution of sodium carbonate 
 to the acid calcium phosphate obtained by treating bones with sulphuric acid, as in 
 the preparation of phosphorus, separating the precipitated calcium carbonate, and 
 evaporating the clear solution sufficiently to obtain the salt in crystals. 
 
 There are two other sodium phosphates corresponding to ordinary tribasic phos- 
 phoric acid, but differing in the relative proportion of sodium and phosphorus 
 from the salt above described; one containing three atomic proportions of sodium 
 Na 3 P0 4 is called trisodic phosphate, and the other containing two atomic proportions 
 
BORAX. 277 
 
 of hydrogen with only one of sodium NaH 2 P0 4 is called monosodic phosphate. The 
 former is the neutral salt, inasmuch as the whole of the hydrogen of tribasic phosphoric 
 acid is replaced by sodium, and the latter as well as the disodic salt ordinarily met 
 with are acid salts. 
 
 When a solution of disodic phosphate is mixed with a solution of about half its 
 weight of ammonium phosphate and evaporated to crystallisation, a salt is obtained 
 which has a composition represented by the formula NaNH 4 HP0 4 4aq. and is termed 
 microcosmic salt ; it has a cooling taste, dissolves readily in water, melts when 
 heated, giving off water and ammonia, until nothing remains but sodium metaphos- 
 phate, which has in a melted state the property of dissolving many metallic oxides, 
 and thus forming characteristically coloured phosphates ; on this account microcosmis 
 salt is used as a flux in blowpipe experiments. 
 
 SODIUM BXBORATX: (BORAX). 
 
 FORMULA Na 2 02B 2 3 . MOLECULAR WEIGHT 164. 
 
 History. The first mention of borax is in the writings of the Arabian chemist 
 Geber, and the alchemists of the thirteenth and fourteenth centuries seem to have 
 been acquainted with the substance, but considered it a product of art. Its prepara- 
 tion and chemical constitution were not known until the middle of the eighteenth 
 century, when, in 1747, Baron published his researches upon the substance. 
 
 Occurrence. Borax occurs naturally in the water of certain inland seas, in 
 China, India, Persia, California, and South America. The water of these _ seas when 
 evaporated yields a crystalline residue, which has received the name of tincal, and 
 is imported into Europe chiefly from China and India. 
 
 A compound of boracic acid with calcium and sodium has been discovered in 
 Peru. It is a soft, light, whitish, scaly mass, and has the following composition : 
 
 Borocalcite Boronatro- 
 
 (Hayes). calcite 
 
 (Dick). 
 Boracic acid . 46'4 46-11 45'42 
 
 Water 
 
 Lime 
 
 Soda 
 
 Sodium chloride 
 
 Potash . 
 
 Chlorine . 
 
 Sulphuric acid 
 
 32-6 35-00 97'42 
 
 14-0 18-81 14-32 
 
 5-2 9-63 
 
 1-8 
 
 0-51 
 
 1-10 
 MO 
 
 100-0 
 
 The substance is evidently a mixture of borocalcite and boronatrocalcite, of which 
 Hayes and Dick have given the analyses as above. 
 
 Borax may be easily obtained from this compound by treating it with soda at 
 a temperature of 100 C. 
 
 Characters. Ordinary or prismatic borax is sodium biborate (Na 2 02B 2 3 + 
 
 10II 2 0). It forms colourless transparent crystals, belonging to the rhombic system, 
 the surface becoming Efflorescent upon exposure to the atmosphere. Its specific 
 gravity is 1705. It is soluble in water, to which it imparts a weakly alkaline reaction. 
 The solubility of borax in water increases with the temperature, as may be seen from 
 
 TO fi-kllrrtirt'nfir fnVtln 
 
 the following table : 
 
 Solubility of borax in 100 parts of water 
 
 At . . 4 . . 2-83 
 
 ,,10 ..... 4-65 
 
 20 ..... 7-83 
 
 30 
 
 At 40 .... 17-90 
 
 60 .... 40-43 
 
 80 .... 76-19 
 
 100 . 201-43 
 
 Prismatic borax, when heated, melts in its water of crystallisation which is given 
 off, leaving a spongy mass known as burnt borax. The application of a st 
 converts borax into a viscous glass borax glass. 
 
 When an aqueous solution of borax, of specific gravity 1-245, is a lowed to 
 tallise at a temperature of 79 to 56 C., regular octahedra are obtained, which < 
 only 5 equivalents of water. The octahedral borax differs from ordumn borax nc 
 only in its crystalline form, but by its remaining clear when exposed t 
 
278 SODIUM. 
 
 sphere, while ordinary borax effloresces superficially, owing to loss of water of crys- 
 tallisation. On the other hand, octahedral borax disintegrates on the surface when 
 exposed to a moist atmosphere, owing to its passing into the prismatic form ; while 
 ordinary borax, under the same conditions, remains pellucid. Octahedral borax is 
 also harder than the prismatic variety, and its specific gravity is T815. 
 
 Melted borax possesses the property of dissolving metallic oxides with facility, its 
 chief use being due to this property. Most metallic oxides impart to the borax glass 
 a tint which is characteristic for the particular oxide. Thus, for instance, chromium 
 oxide imparts a green tinge, cobalt oxide a blue colour, and manganous oxide an ame- 
 thyst hue, etc. This solvent action of borax upon metallic oxides is due no doubt to 
 the fact that a part of the boracic acid enters into combination with the metallic oxide, 
 which then combines with the neutral sodium borate to form the double compounds. 
 
 The use of borax in soldering is also due to a similar chemical combination. It is 
 necessary, in order to secure perfect soldering of two metals, that their surfaces should 
 be free from oxide. This is effected by spreading over their surface a film of melted 
 borax, which dissolves the metallic oxide and protects the naked surfaces of the two 
 metals during the soldering process from the oxidising action of the air. 
 
 The use of borax in smelting depends upon its property of dissolving metallic oxides 
 and converting them into a liquid slag. 
 
 Preparation. Formerly the entire quantity of borax sent to the market was 
 obtained from the water of certain lakes in Asia. The chief lake is the Teschu-Lunibu 
 Sea in Thibet, the water of which contains considerable quantities of borax. Borax is 
 now made from native calcium borate and from boracic acid. 
 
 FROM THE WATEK OF THE BORAX LAKES, The water of these lakes is simply eva- 
 porated by the summer heat, leaving behind a crystalline mass, containing earthy, fatty, 
 and other impurities, which is known in the market as tincal. This tincal or raw 
 borax was formerly submitted to a process of crystallisation at Venice, and came into 
 the market as Venetian borax. 
 
 California borax is obtained from the mud of a lake called Clear Lake, by drying 
 it in the air, lixiviating with water and evaporating the lye till it crystallises. 
 
 FROM NATIVE CALCITTM BORATE. Borax has been obtained of late from the boro- 
 calcite and boronatrocalcite found in Peru, by boiling the finely powdered minerals for 
 some time with a solution of soda, decanting the clear liquid from the insoluble 
 calcium carbonate, and setting to crystallise. 
 
 Lunge, in treating boronatrocalcite for borax, separates out the specifically heavier 
 gypsum by elutriation, treats with warm dilute hydrochloric acid, decants and 
 crystallises, whereupon nearly all the boracic acid crystallises out. 
 
 FROM BORACIC ACID. The greater part of the borax which comes into the market 
 at the present day is prepared from boracic acid obtained from Tuscany. This method 
 was introduced in 1818 by Payen and Cartier. 
 
 A large tub, lined with lead, is charged with about 200 gallons of water, heated 
 to 100 C. by means of a perforated steam coil lying at the bottom of the tub, and 20 
 cwt. of soda crystals. As soon as the soda is dissolved, 23 cwts. of boracic acid are 
 then added in small portions at a time. The addition of the boracic acid causes a 
 strong effervescence, which is more violent towards the end, owing to the double and 
 sesqnicarbonates of sodium formed at the beginning being decomposed by the excess 
 of boracic acid. On this account more caution is required in adding the last portions 
 of boracic acid. The frothing of the mass ceases a few moments before the addition 
 of the last portions of boracic acid, at which point the temperature of the liquid ought 
 to be 104 C., and it ought to show a specific gravity of 1-160 to T170. If it is more 
 concentrated than this, water is to be added. If, on the other hand, the concentration 
 is not sufficient, raw borax is thrown in until the right specific gravity is attained. The 
 lid of the tub, which is made of three pieces, is then put on, and the liquid, after hav- 
 ing been allowed to stand from 10 to 12 hours to get clear, is decanted off with a 
 siphon and run into the crystallising pans. These consist of large wooden vats lined 
 with lead, about 20 feet long, 5| feet wide, and I foot deep. A single vat of the kind 
 is capable of holding the entire contents of the dissolving tub in which the boracic 
 acid and soda are made to react. The mud which collects upon the bottom of the dis- 
 solving tub is let out by removing a plug at the bottom. This mud consists of sand, 
 clay, calcium carbonate, and magnesium carbonate, produced by the action of soda 
 upon gypsum and magnesium sulphate. The lye mechanically retained between the 
 mud particles is washed out with water, and the wash water is used instead of fresh 
 water for dissolving soda in a subsequent operation. The crystallisation of the borax 
 is complete, according to the surrounding temperature, in 36-72 hours. The mother 
 liquor is then drawn off by removing a plug at the bottom of the vessel, the handle of 
 which extends above the surface of the lye. The crystalline mass is removed, and 
 
BORAX. 279 
 
 placed upon an inclined plain, so as to drain off the mother liquor, which is collected 
 in a reservoir. From this reservoir the mother liquor is once more brought into the 
 dissolving tub, where it is mixed with the wash water from the muddy residue, and 
 soda and boracic acid are then added in quantities sufficient to bring the concentration 
 of the solution to sp. gr. 1-169. The whole is allowed to remain quiet for tenor 
 twelve hours, and then the clear liquor is decanted off and crystallised. After three or 
 four operations of this kind, according to the purity of the boracic acid employed, such 
 quantities of sodium sulphate collect in the mother liquor, that upon cooling the latter 
 down to 30-31C. this salt crystallises out. 
 
 On evaporating the mother liquor again in a cast-iron vessel, it yields a further 
 crop of crystals of boracic acid, and the mother liquor from these gives a further 
 crop of sodium sulphate. The mother liquor can be treated for common salt, and the 
 final mother liquor evaporated to dryness : the saline mass thus obtained contains borax 
 and may be used in the manufacture of glass. 
 
 The method employed in England consists in melting together in a muffle furnace 
 under constant stirring a mixture of crude boracic acid with half its weight of calcined 
 soda, the escaping vapours, which contain ammonium carbonate, being condensed in a 
 suitable chamber. The melted product is lixiviated with hot water in iron boilers, 
 the liquor allowed to clarify, then decanted and gradually cooled. The more gradual 
 the cooling, the better are the crystals obtained. The precipitation from the solution 
 of hydrated ferric oxide is effected by adding soda residue in the proportion of 1 pound 
 for every two tons of lye. The clear lye is then crystallised. 
 
 Attempts have recently been made in France to obtain borax together with fum- 
 ing sulphuric acid (vide page 113), by distilling together boracic acid and sodium 
 sulphate, and treating the residue for borax. 
 
 It has been proposed to prepare borax in a similar manner, together with nitric 
 acid, by heating to redness a mixture of Chili saltpetre and boracic acid. 
 
 PURIFICATION OF TINCAL. Tincal was formerly purified by a process of washing. 
 For this purpose it was placed in a cloth bag and agitated with a dilute solution of 
 caustic soda as long as the filtrate ran away coloured. The washed mass was then 
 dissolved in water containing a small quantity of soda, the liquor boiled up, then 
 filtered and evaporated to crystallisation. The washing with caustic soda served 
 to saponify and remove a fatty substance contained in the crude tincal. 
 
 Tincal may be purified by pouring over it, first of all, milk of lime, then boiling 
 water, filtering, adding to the filtrate calcium chloride, and evaporating this filtrate 
 to crystallisation. A calcium soap is thus formed, which remains behind upon filtering 
 the solution. 
 
 Clouet's method consists in calcining powdered tincal, previously mixed with 10 
 per cent, of Chili saltpetre, in cast-iron pans, so as to destroy the fatty substance. 
 The calcined mass is lixiviated and crystallised. 
 
 Tincal as well as- artificially prepared raw borax admits -of being purified in the 
 following way. About 1,250 gallons of water contained in a tub lined with lead are 
 brought to the boiling point by a steam-pipe immersed in the tub. In this water is 
 hung a basket of wicker or wire work containing the raw borax, mixed with five per 
 cent, of soda ; the basket is so placed that it is entirely immersed, and fresh quantities 
 of raw borax are dissolved in the water until the solution has a concentration corre- 
 sponding to sp. gr. 1-169. When this point has been,attained, the supply of steam is shut 
 off, the liquid allowed to settle for two hours, the clear liquor is drawn off by cocks 
 placed a little above the bottom of the tub into a crystallising vessel of lead surrounded 
 with wood, about eight feet long, of a like breadth, and 4f feet deep. This is filled to 
 within l to 1J in. of the brim, and is immediately covered with a wooden lid covered 
 over with sheet lead, which serves, by condensing water on its surface, to produce a 
 layer of water on the surface of the lye, and by this means to avoid the formation of 
 small crystals at the surface. After alapse of eighteen or twenty days, according to the 
 surrounding temperature, the crystallisation is complete, and the temperature of the 
 liquid reduced to 27 or 28 C. It is not advisable to wait longer than this, since 
 impurities would be liable to find their way into the crystalline mass. The mother 
 lye is drawn off, the last portions being rubbed off with a sponge, and the crystallising 
 vessel immediately closed, so as to prevent the crystals from cracking. After a lapse 
 of three hours the crystals are taken out and placed upon wooden tables to dry, anc 
 sorted and packed. 
 
 PREPARATION OF OCTAHEDRAL BORAX. This kind of borax is to be preferred in 
 nearly every respect to the ordinary borax. It is harder, contains less water, froths less 
 when heated, melts quicker, and adheres better to surfaces to be soldered together. 
 
 For preparing it, the apparatus used is that described for the preparation < 
 ordinary borax, the only difference consisting in the proportions of water and borax. 
 
280 SODIUM. 
 
 Borax is dissolved in the way above described, until the solution shows a spec. grav. 
 of 1*245. The liquor is then allowed to settle, drawn off when clear into crystallising 
 vessels, and left there for five or eight days. As soon as the temperature has fallen 
 to 79 C., the crystallisation begins, and is allowed to continue until the temperature 
 has sui k to 56 C. If the crystallisation be allowed to continue at a lower tempera- 
 ture than this, a crystallisation of ordinary borax round the octahedral variety 
 would take place. For this reason the lye is quickly drawn off by a' number of 
 siphons directly the temperature has sunk to 56 C. and the crystalline mass is re- 
 moved. The mass requires protection from a moist atmosphere so as to prevent its 
 attracting moisture and passing into ordinary borax. 
 
 Uses. Borax is used in large quantities for soldering copper, silver, gold, etc. ; in 
 the preparation of certain kinds of glass enamels ; in glass and porcelain paintings ; in 
 smelting works ; in the detection of metallic oxides, with the blowpipe, etc. Borax is 
 further used in hair washes; and in fixing of certain colours in calico-printing. 
 
 Besides borax there are some other borates which have been employed, such as those 
 of zinc and manganese, used as siccatives in the preparation of varnishes ; chromium 
 borate is used for preparing Ghiignet's green ; ammonium borate is used for rendering 
 ikbrics fire-proof, etc. 
 
 UTHZUM. 
 
 SYMBOL Li. ATOMIC WEIGHT 7. 
 
 This metal was discovered in the state of oxide by Asfvedson, in 1817, as a con- 
 stituent of petalite; it also occurs in spodumene, amblygonite, triphyline, 
 lepidolite and other minerals, in several kinds of mineral water, in sea-water, and 
 in some meteorites. It was first obtained in the metallic state by Bunsen. 
 
 Lithium has a slightly yellowish-white colour, is harder than sodium and has a specific 
 gravity of 0'578, being the lightest solid substance known ; it is less oxidisable than 
 the other alkaline metals, melts at 180, and takes fire at a higher temperature, burn- 
 ing with an intense white light; in contact with water it oxidises and displaces 
 hydrogen, but does not melt like sodium. 
 
 The compounds of lithium closely resemble in general characters those of the other 
 alkaline metals. The chloride crystallises in cubes, but is very deliquescent; the 
 hydrate LiHO is much less soluble in water than potassium or sodium hydrates, and 
 separates from the solution in small granular crystals, which melt readily below a red 
 heat, corroding platinum, and solidifying on cooling to a crystalline mass ; the carbonate 
 Li 2 C0 3 is only sparingly soluble in water ; the phosphate Li 3 P0 4 is also insoluble. 
 
 CJESIUAX AND RUBIDIUM, 
 
 Cs SYMBOL Eb 
 
 133 ATOMIC WEIGHT 85'4 
 
 These two metals were discovered by Bunsen and Kirchhoff in 1860 and 1861. 
 They are of frequent occurrence but always in very minute proportions, chiefly in 
 minerals containing lithium and in some kinds of mineral water. They closely resemble 
 potassium, both in their general physical and chemical characters. 
 
CALCIUM. 
 
 SYMBOL Ca. ATOMIC WEIGHT 40. 
 
 Although the discovery of the metals potassium and sodium, and tho analogy 
 between the alkalies and alkaline earths, suggested the probability that the latter 
 were also oxides of metals, calcium was not isolated in a pure state until some few 
 years since by Mathiessen ; it is a yellowish coloured metal that melts at a red heat, 
 is very malleable, oxidises readily when exposed to moist air, and decomposes in water. 
 Calcium is divalent and its compounds possess the characters of salts. 
 
 Occurrence. Calcium occurs very abundantly in various states of combination ; 
 the fluoride occurs as fin or spar, the carbonate in the several forms ofcalc spar, 
 arragonite, limestone, chalk, etc., and combined with magnesium carbonate as 
 dolomite. Several silicates occur as wollastonite, etc., as well as in combina- 
 tion with other silicates. Calcium also occurs combined with silicic acid in a great 
 number of minerals, and the hardening of cements and hydraulic lime is due to tho 
 presence of calcium silicate. 
 
 Other compounds of calcium that occur very frequently and abundantly are, gypsum, 
 CaS0 4 + 2H20; Anhydrite, CaS0 4 ; Apatite, Ca 3 P 2 5 + CaCl 2 or CaF 2 ; Cal- 
 cium nitrate, Ca2N0 3 ; Fluor spar, CaF 2 . 
 
 Compounds of calcium occur abundantly in both the vegetable and animal king- 
 dom ; the ashes of plants contain both the sulphate and the carbonate ; corals, oyster 
 shells, and eggs consist essentially of calcium carbonate, and bones consist of calcium 
 carbonate and calcium phosphate. 
 
 CALCIUM OXIDE (LIME). 
 
 FORMULA CaO. MOLECULAR WEIGHT 56. 
 
 Occurrence. Lime does not occur naturally ; but, in combination with carbonic 
 dioxide and other acid oxides, it forms a very large portion of the earth's crust. 
 
 Characters. Calcium oxide or ' quick ' lime is a white, hard, amorphous mass, 
 which has a specific gravity of 2-300. It cannot be melted even by the heat of the 
 oxyhydrogen flame, but becomes intensely luminous when thus heated. The Drum- 
 mond light used for signalling is produced in this way. 
 
 Lime combines readily with water, and when exposed to the air gradually absorbs 
 water and carbonic acid, and is thereby rendered useless, on which account it must 
 either be used shortly after burning, or must be preserved from contact with moisture 
 and the action of the air. 
 
 Preparation. Lime, or crude calcium oxide, is prepared by strongly heating 
 any of the various natural calcium carbonates, and the operation is technically termed 
 lime burning. Intense heat causes the decomposition of calcium carbonate into calcium 
 oxide, or lime, and carbonic acid which escapes in the gaseous condition: 
 CaCO, = CaO + C0 2 . 
 
 One hundred parts of calcium carbonate should yield 56 parts of lime ; but this 
 result is seldom obtained in preparing lime on a large scale, owing to the presence oi 
 foreign ingredients in crude limestone. 
 
 By calcining ordinary limestone, which is generally somewhat impure, lime 
 obtained containing small quantities of ferric oxide, magnesia, clay, etc., which weaken 
 its resistance to the action of fire as well as its capacity for combining with water. 
 
 The material selected for preparing lime should be of tolerable purity, and it 
 should not contain more than from 2 to 5 per cent, of impurities, since, as above men- 
 tioned, the quality of the lime depends very much upon the amount of foreign sub- 
 stances. Lime is also better in quality, the harder the limestone is from which it is 
 
282' 
 
 CALCIUM. 
 
 prepared, on which account marble is the substance most suited for preparing lime. 
 Marble is, however, as a rule too dear for the purpose, and the material generally 
 used is ordinary limestone ; calcareous marl, or shells, etc., being seldom employed. 
 Chalk is often used for preparing lime, and owing to its porous nature it decomposes 
 in burning far more easily than ordinary limestone. 
 
 The operation of lime burning is carried out in heaps, field kilns, pits, or in 
 specially constructed kilns. 
 
 BURNING IN HEAPS. The pieces of limestone arc cither arranged alternately between 
 layers of fuel, or the entire quantity of limestone is laid upon a thick bed of fuel and 
 the whole covered, as in preparing charcoal, with earth, clods, etc. The operation is 
 conducted throughout in a way similar to that adopted in making charcoal. 
 
 BURNING IN FIELD OVENS. In this plan the larger pieces of limestone are built 
 up so as to form a fire chamber, and the small pieces of limestone piled up over 
 them. 
 
 BURNING IN PITS. For this purpose pits dug in the ground are either filled with 
 alternate layers of limestone and fuel, or the limestone is arranged so as to form at: 
 arch under which the fuel is burnt. 
 
 BURNING IN KILNS. Lime kilns are of two kinds, those in which the burning is 
 interrupted, and those in which the burning is continuous. 
 
 Periodic Kilns. Kilns of this kind are much used and are convenient in places 
 where the consumption of lime is irregular, since, as we have seen, a lime that has 
 been long burnt is not so good as that which has been recently burnt. 
 
 The kilns are made of fire brick, and have either a cylindrical or an oval form, 
 being furnished below with a large heating hole. The kilns are charged by piling up 
 large pieces of limestone upon the hearth of the kiln so as to form an arch, which is 
 then covered over with small pieces of limestone until the kiln is full ; care being 
 always taken to secure a free space for the fire. Some easily combustible fuel is then 
 introduced through the stoke-hole beneatli the arch and ignited, by which means the 
 limestone is gradually heated. A gradual heating is necessary at first in order to 
 prevent the limestone forming the arch from crumbling and falling into the fire space. 
 The lighter kind of fuel is then replaced by fuel of a denser kind, and the heat in- 
 creased until the pieces of limestone at the mouth of the furnace are white hot ; the 
 burnt lime is allowed to cool a little, withdrawn, and the kiln recharged. 
 
 Kilns of a similar kind are employed in which the hearth is formed of a grate and 
 ash pit ; the pieces of limestone, as in the above case, are built up so as to form an 
 arch, the only difference being that the fuel rs burnt on the grate. 
 
 A very useful periodic kiln with grate is shown in fig. 169. The shaft (A) is lU 
 feet wide below, and 10 feet wide at its upper extremity; it has a height of 11 feet, 
 and is covered above with an arch (6) furnished with draught holes; dd are firing 
 holes each of which has a fire grate inclined towards the hearth of the furnace upon 
 which the fuel is laid; //'is an opening for admitting the limestone. The latter, as 
 well as the opening (h) for drawing out the lime, are walled in during the burning; 
 
 FIG. 169. 
 
 170. 
 
 c is an aperture in the hood covering the furnace through which the draught holes 
 may be observed, and the heat regulated or directed to any desired part of the furnace 
 by placing bricks over the draught holes. 
 
LIME BUKNIISTG. 
 
 283 
 
 For charging the furnace, a wooden pole is placed in a vertical position in the 
 middle of the hearth, and the pieces of limestone arranged round it. The wooden stake 
 or pole upon burning leaves a cylindrical hollow space which serves for the regulation 
 of the combustion. The pieces of limestone are so arranged that, before and above 
 each stoke hole, a free arched space is formed, where the fire gases collect .and are 
 distributed equally in all directions. During the first six hours a moderate fire only 
 is kept up, the heat being gradually increased until yellow lime flames are observed 
 at the upper opening of the furnace, and the contents of the kiln are uniformly heated 
 to a sufficient degree. The time occupied by the operation is seventy-two hours. 
 
 Fig. 170 represents a kiln of novel construction by Swann, in which 20 per cent, 
 less fuel is required than in ordinary kilns. A is a chamber of the kiln formed by the 
 arch (F F), B the fireplace, furnished with an endless iron grate (c c), revolving upon 
 the rollers (a, a). D is a funnel for admitting the coal, E a flue through which the hot 
 gases pass into the chimney ; b is a small truck for reception and removal of the ash 
 and coke falling from the hinder part of the moveable grate. 
 
 In working the kiln it is first charged with pieces of limestone (KB), and heated 
 with hot air from other kilns ; the fire then is ignited and fuel thrown in through the 
 hopper (D) ; by means of the travelling endless hearth (c) the fuel is passed along the 
 fire grate at such a rate that it is completely burnt by the time the part of the grate 
 it falls upon gets to the other end of the fire. The air draught and fuel supply are 
 regulated by means of sliding dampers in front of the furnace. 
 
 A number of kilns of this kind are placed together in such a way that the hot air 
 can be made to pass from one kiln to the otiier. Fig. 171 represents a horizontal 
 
 FIG. 171. 
 
 section of a system of the kind, where a number of Swann's furnaces are grouped 
 together; act, are the individual kilns communicating with one another by means of 
 the flues (cc), which open in the arch of one furnace, and terminate at the hearth of 
 the next one. These flues admit of being closed by a sliding damper, which remains 
 closed during the drying of the furnace, and is opened after that operation is over so 
 as to admit the hot air into the next furnace. During the preliminary heating or 
 drying process the hot gases escape through the flues (E E) into the chimney ; F is a 
 pipe in which hot air circulates and is conducted through the branch pipes (H H) into 
 the fire-places. The method of heating this air is the same as in the blast furnaces of 
 iron works. 
 
 Continuous Lime Kilns are variously constructed. Figs. 172 and 173 represent a 
 kiln of the kind. It is funnel shaped at the upper part (abed) and cylindrical 
 shaped at the lower part, below the line c D. Its greatest diameter at a b is 13 feet, 
 its least diameter at c d only 5 J feet ; its depth down to c d is about 1 3 feet. The arches 
 (D, D', D") give access to the interior of the kiln for drawing the burnt lime, and 
 they are at the lowest part 26 inches, and at the highest part about 8 feet high. 
 The apertures for drawing the lime are 20 inches high, 16 inches wide, and they 
 are divided by pillars into two equal halves. The hearth of the furnace is furnished 
 with a cone 32 inches high having at its base a diameter of 30 inches ; the fhie 
 (efghik) is for carrying off the gases evolved, so as to facilitate the working. Dry 
 coal or coke is used as fuel. The limestone is broken into pieces about l inches 
 thick and 3 to 5 inches in breadth and length. 
 
 In working this kiln a small quantity of dry wood is placed upon the he:irth, 
 with about 11 bushels of coal, and above that 8 bushels of broken limestone. 
 Alternate layers of 1 to H inches of coal, and of limestone, 6 inches thick, are 
 then put in until the kiln is quite full, and then the wood upon the hearth is set 
 fire to. In proportion as the fuel burns, the calcined lime sinks down and is drawn 
 out through the holes at the bottom of the kiln ; fresh limestone and fuel being at the 
 same time put in above. If, upon drawing out the lime, it should be insufficiently or 
 too much burnt, the proportion of fuel added in charging the kiln is increased or 
 
284 
 
 CALCIUM. 
 
 diminished. A kiln of this kind is capable of producing about 300 bushels of burnt 
 lime in twenty- four hours with 120 bushels of coal. 
 
 FIG. 172. 
 
 FIG. 173. 
 
 The working capability of this kiln is considerably increased by carrying it up in 
 cylindrical form to a height of 3 feet above a b, and to a height of 10 feet above 
 that, with a gradual contraction to an opening 10 feet wide. A kiln of this kind yields 
 2500 bushels of burnt lime daily. 
 
 Continuous Lime Kilns with Lateral Furnaces. These kilns have the advantage that 
 the lime is not contaminated with ash from the fuel. Fig. 174 represents a kiln of 
 the kind. The height of the shaft from the hearth to the mouth is 20 to 40 feet, its 
 greatest diameter 5 to 10 feet. A is the fireplace with inclined grate, upon which 
 wood, turf, or coal is burnt. The hot air from the fire passes through the flue (B) 
 into the flue (c'), extending horizontally round the kiln, and through three openings 
 (c) equidistant from one another, into the kiln. The height of these openings above 
 the hearth of the kiln is 5 to 6 feet. These kilns are sometimes furnished with 
 three fireplaces, and the same number of stoke-holes. D is an opening for drawing 
 out the lime, EE is a kind of hoed for regulating the draught, and G a door for 
 charging the kiln. In working this kiln it is first heated from below; the lateral 
 fires are not lighted until afterwards. 
 
 FIG. 174. 
 
 FIG. 175. 
 
 A kiln first used at Riidersdorf, near Berlin, and now extensively employed, is re- 
 presented by fig. 175. The lining (d) of the shaft consists of fire brick, and is surrounded 
 by a counter wall (), separated from the lining by ashes or some other bad conductor 
 
APPLICATIONS OF LIME. 
 
 285 
 
 of heat. The height of the kiln from the hearth to the mouth is about 38 feet its 
 greatest diameter 9 feet; the mouth is 6 feet wide, and the lower part 6i feet wide 
 About 12 foet above the hearth of the shaft are the furnaces (bb), by which the kiln 
 is heated, of which there are three in a kiln of the above dimensions, and four or five 
 in larger kilns. The opening (g) of the furnace is closed by a door, and air passes 
 under the grate at (h\ from the ash-pit (t), which is so placed that the ashes are 
 raked into the arched chamber (E). The kiln is enclosed by an outer wall (B B) and 
 the gases from the kiln pass through the flue (K) into the chamber (p). The burnt lime 
 is drawn out through a hole (a a) that can be closed by an iron door. This kiln like 
 the former, is first heated at the discharge aperture, and afterwards by means of the 
 furnaces (b b}. A kiln of the kind with three fireplaces yields a daily produce of 3 to 
 1 tons of burnt lime. 
 
 Lime Kilns heated by Gas have been only recently introduced. Steinmann has con- 
 structed a kiln of the kind in which the gas is generated in special generators beneath 
 the shaft of the kiln, and having been deprived of tar vapour in a suitable chamber 
 is at once passed into the kiln. This kind of kiln is said to be especiaUy adapted for 
 sugar works, since both lime and carbonic acid can be obtained 1 of great purity. 
 
 Lime is said to be dead burnt when it has been too strongly heated, and with 
 the silica, alumina, etc. it contains made to undergo a kind of partial fusion. When 
 insufficiently burnt the interior of the lumps still consists of carbonate. Both dead- 
 burnt and half-burnt lime are useless for the ordinary purposes to which lime is 
 applied. 
 
 The accompanying table gives the results of analyses of fat and meagre limestones, 
 as well as the burnt lime obtained from them : 
 
 
 Fat Limestone 
 
 
 
 
 
 
 
 
 Vffle- 
 
 
 
 
 
 
 Vichy 
 
 
 
 franche 
 
 
 Chateau 
 Landon 
 (S. et M ) 
 
 St.Jaques 
 (Jura) 
 
 Craie 
 de Paris 
 
 Lagueux 
 near 
 Lyons 
 
 (Allior) 
 
 
 (Avey- 
 ron) 
 
 Limestone employed : 
 
 
 
 
 
 
 
 
 Calcium carbonate . 
 
 97 
 
 96-5 
 
 98-5 
 
 94-5 
 
 87'2 
 
 74-5 
 
 607 
 
 Magnesium carbonate 
 
 2 
 
 2 
 
 
 
 1-6 
 
 10 
 
 24-3 
 
 30-3 
 
 Clay and iron oxide 
 
 1 
 
 1-5 
 
 1-5 
 
 3-9 
 
 2-8 
 
 1-2 
 
 3 
 
 Manganous carbonate 
 
 
 
 
 
 
 
 
 6 
 
 Burnt lime obtained : 
 
 
 
 
 
 
 
 
 Lime 
 
 96-4 
 
 95-4 
 
 97-2 
 
 91-6 
 
 86 
 
 78 
 
 60 
 
 Magnesia 
 
 1-8 
 
 1-8 
 
 
 1-5 
 
 9 
 
 20 
 
 26-2 
 
 Clay, iron oxide, and 
 
 
 
 
 
 
 
 
 manganese oxide . 
 
 1-8 
 
 2-8 
 
 2-8 
 
 6-9 
 
 5 
 
 2 
 
 13-8 
 
 Uses. The chief use of lime is for preparing mortar, by mixing 1 vol. slaked 
 lime (containing about 70 per cent, of water) and 2 vols. sand with water, until they 
 form a stiff paste. The hardening of mortar takes place in two ways first, a partial 
 drying and contraction without acquiring any great solidity, and then by the combina- 
 tion with carbonic acid and the conversion of caustic lime into calcium carbonate. 
 After a considerable lapse of time, calcium silicate may also be formed in some cases, 
 the silica being derived from the sand. 
 
 Lime is also used in the preparation of caustic alkalies and ammonia, in soap 
 boiling, for precipitating magnesia from brine liquors, in the preparation of bleaching 
 powder, potassium chlorate, certain disinfecting powders, for clearing solutions of 
 soda, for removing carbonic acid from mineral waters and precipitation of calcium 
 carbonate retained in solution by the carbonic acid. Considerable quantities of 
 lime are used in preparing hydraulic mortar, for purifying illuminating gas from car- 
 bonic acid and sulphuretted hydrogen, by Laming' s process. Lime is also used for 
 decomposing Glauber's salt in the manufacture of soda, for bleaching some kinds of 
 tissues, for purifying the air in pits, wells, cellars, etc. which contain dangerous gases, 
 such as carbonic acid, sulphuretted hydrogen, etc. ; in preparing indigo, in the 
 dressing of corn, and in the manufacture of sugar. Lime is further extensively 
 employed in the manufacture of glass, in treating raw pyroligneous acid for wood 
 spirit, and acetic acid, in the preparation of alum from cryolite, in the manufacture 
 of stearic acid, as an admixture for forming slag in blast furnaces and other metal- 
 lurgical processes, for removing hair from the skin in tanning, for producing the 
 
286 CALCIL M. 
 
 Drummond light, in the preparation of a large number of organic substances (citric, 
 tartaric acids, etc.); for purifying camphor, for preserving eggs, fruit, etc. ; in the pre- 
 paration of absolute alcohol, in the manufacture of a number of lutings, as paint ; for 
 removing mould and acids from fermenting vats, etc. 
 
 CAXiCXUXK HYDRATE. 
 
 FORMULA CaH 2 2 . MOLECULAR WEIGHT 74. 
 
 Calcium oxide combines with water at the ordinary temperature, forming the 
 hydrate, great heat being evolved in the combination. This process is technically 
 known as slaking. Upon mixing 2 parts of pure lime with 1 part water, the tem- 
 perature of the mixture rises to 300. The calcium hydrate or slaked lime thus 
 formed is a light, white powder, occupying about 3 times as great a volume as the 
 lime from which it was produced. Water dissolves at the ordinary temperature 14 
 per cent, of this calcium hydrate, while boiling water dissolves only about one- half 
 that quantity. Upon evaporating aqueous solutions of calcium hydrate (lime water), 
 the hydrate is obtained in the crystalline state. 
 
 Calcium hydrate rapidly absorbs carbonic dioxide from the atmosphere, forming 
 calcium carbonate. When a somewhat thick mixture of lime and water is exposed to 
 the air it gradually hardens, owing to the absorption of carbonic acid ; to this cause 
 is due the hardening of mortar. 
 
 CALCIUM CARBONATE. 
 
 FORMULA CaCO s . MOLECULAR WEIGHT 100. 
 
 Occurrence. Calcium carbonate occurs very abundantly in a great variety of 
 forms. In a pure state, as calc spar, it is a colourless transparent mineral, but is 
 often coloured, owing to the presence of iron manganese, etc. ; it forms crystals belong- 
 ing to the rhombohedral system. 
 
 Aragonite is another form of calcium carbonate, crystallising in rhombic prisms. 
 
 Calcium carbonate also occurs combined with magnesium carbonate as dolomite, 
 CaMg2C0 3 , crystallising in rhombohedra ; when pure it is colourless, but more fre- 
 quently it is of a yellow, grey, green, or brown colour, owing to the presence of iron, 
 etc. Entire mountain ranges consist of dolomite. 
 
 Marble, limestone, and chalk all consist of calcium carbonate, in a more or less 
 pure state ; they often constitute entire mountain ranges. Marble has a crystalline 
 structure, and when pure is perfectly white ; but it is often coloured by admixtures of 
 various metallic oxides, as well as organic substances. It occurs in layers in gneiss, 
 micaceous schist, clay slate, and other rocks. Marble of an especially beautiful kind 
 is found at Carrara and Serravezza in Italy. Chalk is a less pure calcium carbonate 
 than marble ; it occurs in England, North France, Denmark, etc., often constituting 
 extensive strata. Ordinary limestone is a hard, opaque mass, often crystalline; it 
 occurs as extensive beds. Its colour depends upon its mode of occurrence, either 
 smoky grey, yellow, brown, or black. It nearly always contains a small quantity of 
 magnesium carbonate and clay. Marly limestone is the name for a variety of lime- 
 stone very rich in clay, etc. The stone used for lithographic purposes is a kind 
 of schistous limestone occurring in Bavaria. Stalactites and stalagmites likewise 
 consist of calcium carbonate. They owe their formation to calcareous water impreg- 
 nated with carbonic acid dropping slowly from the roofs of caverns, and losing the 
 greater portion of its carbonic acid upon coming into contact with the air, which 
 causes a gradual deposition of calcium monocarbonate. Depositions of calcium mono- 
 carbonate are in like manner formed round springs, in water pipes, etc. 
 
 Characters. Calcium carbonate is a colourless tasteless substance very sparingly 
 soluble in water, requiring, according to Fresonius, 10,601 times its weight of cold 
 water; the solution has a slightly alkaline reaction upon tost paper. As prepared 
 artificially calcium carbonate has the form of a white powder, but the particles gene- 
 rally have the crystalline form of calc spar. Calcium carbonate is decomposed at a dull 
 red heat and readily gives off its carbonic dioxide, especially when heated in a current 
 of air, by which the disengaged carbonic dioxide is removed. 
 
 Uses. Calcium carbonate is used for a great number of purposes in chemical 
 operations as well as for preparing lime. 
 
GYPSUM AND PLASTER OF PARIS. 287 
 
 CAI.CXUM FLUORIDE. 
 
 FORMULA CaF 2 . MOLECULAR WEIGHT 78. 
 
 This substance occurs abundantly as fluor spar, and is chiefly important as a 
 tioliT ydr flu0ric acid< Jt is also used in some cases a s a flux in smelting opera- 
 
 CAICIUM SULPHATE. 
 
 FORMULA CaS0 4 . MOLECULAR WEIGHT 136. 
 
 Occurrence. Anhydrous calcium sulphate occurs as anhydrite, sometimes in 
 the state of crystals, but chiefly as a coarse compact mass. 
 
 In the hydrated condition calcium sulphate occurs as gypsum, in great abundance 
 especially accompanied by common salt. It is sometimes found in colourless crystals 
 belonging to the monoclinic system ; sometimes also in large crystals which consist 
 of very thin laminae, in which form it is known as selenite; it also occurs as a 
 granular, crystalline, and translucent mass known as alabaster; more often in coarse 
 crystalline masses as gypsum, either in the ordinary granular condition, or as fibrous 
 gypsum. The occurrence of calcium sulphate dissolved in water has already been 
 mentioned in treating of water. 
 
 Characters. Calcium sulphate is sparingly soluble in water, 100 parts of 
 water dissolving only 0-205 parts of gypsum at 0, 0-237 parts at 12, 0-254 parts at 
 35, 0-251 parts at 50, or 0-217 parts at 100. The solubility is therefore greatest 
 at a temperature of 35. 
 
 Calcium sulphate is more readily soluble in dilute nitric or hydrochloric acid, 
 and concentrated sulphuric acid dissolves considerable quantities. The solubility is 
 increased by solutions of sodium chloride, potassium chloride, sal ammoniac, etc. 
 
 Gypsum when heated to ]00 first of all gives up 15 per cent, of its water ; but in 
 order to drive off all the water, it must be heated to 170. Gypsum deprived of its 
 water by heatingis termed burnt gypsum, or Plaster of Paris ; and it possesses the 
 property of hardening when mixed with water, the process being accompanied by the 
 evolution of a considerable quantity of heat. Gypsum is said to be dead burnt when 
 it has been heated so much that it has become slagged afc the surface, and in this con- 
 dition it is destitute of the power of combining with water, like the natural anhydrous 
 calcium sulphate, anhydrite. 
 
 The hardening of burnt gypsum when treated with water is due to combination 
 with water; 1 molecule of burnt gypsum combining with 2 molecules of water; if an 
 excess of water be taken, it remains simply mechanically mixed in the crystals of 
 hydrated calcium sulphate. 
 
 The hardness of the hydrated mass after treatment with water depends in part 
 upon the proportion of water taken, and in part upon the constitution of the gypsum 
 before burning. The best plaster of Paris is yielded by gypsum consisting of indi- 
 vidual, dense, granular crystals, containing only a very small amount of calcium 
 carbonate, and but a trace of clay. 
 
 Good gypsum properly burnt absorbs about its own volume of water, and forms a 
 hard mass, the absorption being accompanied by a slight elevation of temperature. 
 Plaster of Paris prepared from compact, fibrous, or laminated gypsum, absorbs much 
 more water, but the product is less hard. The cause of this different behaviour is that 
 very finely divided burnt gypsum becomes hydrated throughout its entire mass, and 
 expands so that the particles are less closely aggregated, while the plaster of Paris 
 made from granular gypsum retains its structure after burning, and when treated with 
 water becomes hydrated only at the surface of the individual granules in the first 
 instance, further absorption of water taking place slowly afterwards and without so 
 much expansion of the mass. 
 
 When plaster of Paris that has been slaked and become hard is reduced to powder 
 and again mixed with water, it sets again after a short time, but the product is not so 
 hard as before. This operation may be repeated four or five times when the gypsum 
 is of good quality, and, indeed, it is a simple means of determining the quality of 
 plaster of Paris. A good sample may be treated in this way five times with an equal 
 volume of water without entirely losing the power of setting. 
 
 From the property possessed by plaster of Paris of absorbing water with great 
 ividity, it is obvious that it requires keeping out of contact with moist air. 
 
288 
 
 CALCIUM. 
 
 FIG. 176. 
 
 FIG. 177. 
 
 sufficiently 
 
 Preparation. The burning of ordinary gypsum was formerly carried out in kilns 
 having a construction represented by fig. 176, being formed of three walls covered with 
 
 a roof of wood or iron covered with tiles. Large 
 pieces of gypsum are piled up in this chamber so as 
 to form a series of arches, each arch having an aper- 
 ture of 12 to 18 inches, and the smaller pieces of 
 gypsum are heaped abovet he arches. 
 
 Dry wood is used as fuel, brushwood being the 
 best. The flame penetrates the spaces between the 
 pieces of gypsum, and after a time the heap is covered 
 over with more small pieces of gypsum. After ten 
 to twelve hours, if the gypsum be sufficiently burnt, 
 the supply of fuel is stopped and the mass covered 
 over with refuse gypsum dust, which becomes partly 
 burnt and thus increases the yield. After being 
 
 allowed to cool for about five or six hours, the arches are broken down, the lumps 
 broken into pieces, and packed in sacks for the market. 
 
 This method of burning gypsum is of course very imperfect, Upon examining 
 
 the lumps, it is found 
 that the surface is 
 dead burnt, while the 
 interior is hardly 
 sufficiently burnt. 
 Where these kilns 
 are used the chief 
 thing to be attended 
 to is that the propor- 
 tion of unburnt and 
 dead-burnt lumps is 
 relatively slight, so 
 that the total pro- 
 duct is 
 plastic. 
 
 Shaft 
 sometimes 
 
 burning gypsum. 
 They differ in con- 
 struction and yield 
 far better results 
 than the kilns above 
 mentioned. These 
 kilns are either 
 worked continuously 
 or intermittently. 
 
 The continuous 
 shaft kilns are com- 
 paratively seldom 
 used, owing to their 
 requiring consider- 
 able attention. They 
 may have a construc- 
 tion similar to the 
 lime kilns (figs. 172 
 and 173, p. 284). 
 
 The intermittent 
 FIG. 178. kilns are employed 
 
 in a number of dis- 
 tricts ; they have either a form such as shown in fig. 178, or are of a cubical form with 
 rounded edges, cylindrical, etc. They are charged by first of all building upon the 
 hearth largo pieces of gypsum, so as to form two fire channels serving the purpose of 
 igniting the kiln through the stoke holes, and then the kiln is filled by piling up alternate 
 layers of fuel and. stones. In some places, after being charged in the above way, the 
 heaping up of alternate layers of fuel and stones is continued until a stack 12 feet high 
 protrudes above the mouth of the furnace. The kilns are set 'going by making a fire 
 upon the grate, which is kept up for a day or a day and a half. By means of the 
 fire channels the combustion is propagated to the upper layers of fuel, and the 
 whole mass is thus ignited. When the burning is over, the fire channels are broken 
 down, and the whole allowed to cool, so as to fit it for removal. 
 
 kilns 
 used 
 
 are 
 for 
 
PLASTER OF PARIS. 
 
 280 
 
 Gypsum kilns are sometimes heated by the hot air from coke ovens, since gypsum 
 burning does not require a very high temperature, and advantage is taken in some 
 cases of the waste heat escaping from coke ovens. Figs. 177 and 178 represent an 
 arrangement of the kind. A A' A" are the coke ovens from which the hot air is con- 
 ducted into the common flue (c), whence it passes through (D) and the openings (/) 
 into the chambers (B B' B") under the grates of the gypsum kilns (B). The hot air 
 passes through the gypsum mass and is conducted together with the steam escaping 
 from the gypsum into flues above the ovens, escaping finally into the common chimney 
 (L). F is an opening for charging and emptying. 
 
 Dumesnil's gypsum kiln is shown in section in fig. 179. A brickwork foundation ; 
 B fireplace beneath the hearth ; b' channel for admitting the fuel ; b" opening for 
 draught and withdrawal of ash ; c c 6 to 8 channels for conducting the hot air from the 
 fireplace (B) into the combustion chamber (D). These channels terminate at the 
 hearth in a corresponding number of cast-iron mouth-pieces (*, figs. 180 and 181), 
 
 FIG. 179. 
 
 i 
 
 furnished with about twenty or thirty lateral slits, through which the hot air passes 
 into the combustion chamber ; /is an opening for admitting the first charge of stones 
 as well as for emptying the furnace ; /' is an opening through which the filling is 
 completed ; a a are small channels kept open at the beginning of the operation so as 
 to allow of the escape of the large quantities of steam evolved, but these openings are 
 finally closed towards the end of the operation, the chief chimney then serving for con- 
 ducting off the steam. . . 
 
 The pieces of gypsum having an average diameter of 4 or 5 inches are set up 
 vertically in the kiln ; the larger ones being placed at the bottom, and the smalle: 
 pieces piled upon them. . , 
 
 Gypsum prepared according to the methods above described is, however, not suited 
 for fine castings; a very white and plastic gypsum being required for such purpose 
 In preparing the better kinds of plaster of Paris, great care must be taken to secure 
 uniform burning of the gypsum, and the admixture of ash from the fuel employed 
 
 in burning gypsum required for artistic purposes, it is often reduced to a fine 
 powder and heated very carefully in metallic cauldrons, or in cast-n 
 
 ^Pl^tr of Paris of good quality is sometimes prepared by burning homogeneous 
 pieces of gypsum upon the heartli of an ordinary baking oven. Ihe oven is first p 
 all heated to redness, the fuel and ash then withdrawn, and the pieces of gypsu 
 
290 CALCIUM. 
 
 upon the hearth. The gypsum for this purpose ought to be of a granular crystalline 
 nature, and not of very dense structure. According to this method no dead-burnt 
 gypsum can be formed, since the oven is not too hot, and its temperature is much 
 reduced by the cold gypsum. The lumps are left in the oven until a portion upon 
 being taken out and tested is found to have been burnt through. 
 
 Hardening of Gypsum. Many kinds of gypsum, when burnt and slaked, yield a 
 very soft product, and even gypsum of the best quality may be easily scratched. It 
 is only recently that a method has been discovered for preparing a harder and at the 
 same time less soluble gypsum. The operation consists in burning pieces of gypsum 
 about the size of a fist in suitable kilns at a scarcely perceptible red heat. After 
 burning the gypsum it is placed in a solution of alum, containing 12 per cent, of the 
 salt, at a temperature of 35. After the lapse of two or three hours, the gypsum is 
 taken out, drained, and dried at a gentle heat, and again submitted to a burning pro- 
 cess, as before. The gypsum that has been thus twice biirnt is powdered and sifted. 
 When required for use, it is either mixed with water, or still better with a solution of 
 alum, containing 7 to 8 per cent, of the salt. To form a proper paste only 55 to 57 per 
 cent, of liquid is required, while ordinarily good plaster of Paris requires 67 to 100 per 
 cent, of water. But while the plaster containing alum requires fifty-five to sixty 
 minutes to harden, that without sets in about fifteen or seventeen minutes ; it has, 
 however, the great advantage over ordinary plaster of being very much harder ; indeed 
 it is almost as hard as marble, and may be struck moderately, with a hammer, with- 
 out being injured. The mass when struck gives a ringing sound. Alumed plaster is 
 further only very slightly soluble in water, so that casts made of it may be washed 
 without injury. 
 
 This effect of alum upon gypsum has not at present been explained ; it is, however, 
 probably due to the formation of a double salt of potassium and calcium sulphate. 
 
 The use of other salts in place of alum for hardening gypsum has been tried, 
 but without success such as borax, soluble potassium silicate, potassium carbonate, 
 seignette salt, etc. 
 
 For the superficial hardening of gypsum casts Knaur and Knop recommend wash- 
 ing them with a mixture of potash water-glass solution, and a solution of curdled 
 milk in caustic potash. Objects thus treated may be washed without danger. 
 
 Uses. G-ypsum is seldom employed in an unburnt condition, except as a build- 
 ing stone, which is of little durability, owing to the solubility of gypsum in water. 
 Alabaster is used for making vases, table slabs, etc. Gypsum powder is used for de- 
 composing ammonium carbonate in the preparation of ammonium sulphate. As a 
 manure, burnt gypsum is preferable, owing to the greater facility with which it can 
 be reduced to powder. Natural gypsum is further extensively used for mixing with 
 colours, etc. Anhydrite is used for making vases, mouldings, etc. 
 
 Plaster of Paris is very extensively used as a cement, and for making mouldings, 
 ceilings, and various ornaments, etc. No other substance can be so cheaply and 
 quickly used for casting and luting. Plates furnished with grooves and pins are cast 
 from gypsum ; they are used for dry partition walls, for which purpose old mortar, 
 coal ash, broken pieces of crockery, bricks, etc. may be added to the gypsum so as to 
 render the mass cheaper. Dumesnil prepares useful bricks in the following way : 7 
 parts by weight of alum are mixed with 6 parts of lime flour, and 1 part of yellow 
 ochre, the whole being stirred up with. 500 parts by weight of water and 1 part of 
 glue dissolved in five parts of warm water added. This mixture is then poured 
 over 900 parts of gypsum, 450 parts of river sand being added at the same time. 
 The paste obtained is cast into moulds and dried when set, In order to secure the 
 bricks against the solvent action of rain water, they are painted over three times with 
 a solution of potash water-glass of specific gravity T15 to 1-20. 
 
 A very common application of gypsum is for casting all kinds of medals, statues, 
 busts, etc. Gypsum moulds serve for casting in gypsum as well as in metal, also 
 for preparing galvanoplastic reliefs, and busts, etc., for which purpose the gypsum 
 mould is saturated with a mixture of resin and wax, and its surface rubbed over with 
 graphite or silver, so as to render it conductive. 
 
 G-ypsum marble, or stucco, used for walls, pillars, etc., is prepared by applying a 
 mixture of fine plaster with glue water upon a coarse gypsum ground, and when dry 
 the surface is polished with pumice stone. The pores still remaining in the substance 
 are filled up with a paste made by mixing gypsum with glue water, and after drying 
 the whole is painted over with a very thin paste of the same kind ; after the second 
 drying the work is polished with tripoli powder, rubbed over it with a linen cushion ; 
 it is then smeared with oil, and receives a final polish with tripoli and oil. Stucco is 
 coloured according to pleasure, by mixing the glue water with which the gypsum is 
 stirred up with red lead, indigo, amber, lamp black, etc. 
 
CALCIUM PHOSPHATES. 291 
 
 Plaster casts are prepared by heating them to about 88 and then dipping them 
 into melted stearin or paraffin. When cool polish is given by brushing. 
 
 Gypsum moulds, owing to their porosity, are often used for moulding objects in 
 porcelain, etc. _The moulds absorb water, and thus the porcelain mass is dried and 
 hardened. Owing to its absorbent nature gypsum is also used for drying colours 
 yeast, etc. Gypsum forms a good luting for glass bottles with glass stoppers For 
 joining broken busts or casts of gypsum, a cement is employed consisting of gypsum 
 stirred up with a solution of alum or gum. 
 
 Gypsum is very extensively used for agricultural purposes, and it exerts a very 
 beneficial effect upon leguminous, liliaceous, and other plants. Gypsum burnt and 
 slaked in the air, strewed upon the soil in wet weather, exerts a beneficial effect 
 partly by virtue of its own constituents, and partly by fixing ammonia and ammonium 
 salts from air and ram water, and also partly by its decomposing magnesium and 
 potassium salts. From 1 cwt. to 5 cwt. of gypsum are used for every acre of soil. 
 Gypsum is also used as a manure by mixing it with urine, in which case its effect is 
 due to the conversion of ammonia into non-volatile ammonium sulphate. 
 
 Light white wines are mixed with -2 or -3 per cent of gypsum, so as to retard fer- 
 mentation and prevent acidity. Gypsum is also used for rendering weak wines stronger 
 by absorbing some of the water, and thus increasing the relative amount of alcohol. 
 
 Hardened gypsum is also used for casts, busts, etc. It is more suited for painting 
 upon than ordinary gypsum, owing to its greater density and less absorbing power. 
 
 Two preparations are found in the market, the one known as pearl hardening, 
 the other under the name of annalin, both of which are used as an addition to paper 
 pulp in the manufacture of paper. Annalin consists essentially of gypsum, and is 
 obtained in this country as a by-product in the preparation of carbonic acid. The 
 calcium chloride residue obtained by the action of hydrochloric acid upon chalk is 
 precipitated with sulphuric acid, the gypsum filtered upon a woollen cloth, washed 
 with^dilute lime water, and then pressed in linen pressing cloths. The cakes thus 
 obtained are sent into the market ; they contain about 40 per cent, of water. 
 
 CALCIUM PHOSPHATE. 
 
 FORMULA Ca 3 P a O 8 . MOLECULAR WEIGHT 310. 
 
 The salt occurs in bones, and is therefore commonly called bone phosphate; it 
 also occurs naturally as osteolite, and, in combination with calcium chloride and 
 calcium fluoride as apatite. The excrements of carnivorous animals also contain 
 it, and the fossil remains known as coprolites, as well as other extensive mineral 
 deposits, contain a large amount of this phosphate. 
 
 Characters. Tricalcic phosphate is insoluble in water, but is slightly soluble in 
 solutions of sodium chloride, ammonium salts ; starch, gelatin, and other organic sub- 
 stances also determine its solution in water to some extent, and it dissolves in larger 
 proportion in water containing carbonic acid. It is readily dissolved by nitric acid 
 or hydrochloric acid, less readily by acetic acid or other organic acids, and it is com- 
 pletely decomposed by sulphuric acid. 
 
 The salt is obtained by mixing a solution of calcium chloride with a solution of 
 trisodic phosphate (see p. 276), or by gradually adding a solution of ordinary sodium 
 phosphate mixed with ammonia to solution of calcium chloride; it is a gelatinous pre- 
 cipitate which dries into a white earthy powder. It is not decomposed when heated 
 to redness, but when heated in contact with carbon and silica, carbonic dioxide and 
 phosphorus vapour are given off and calcium silicate is formed. 
 
 Uses. Calcium phosphate, as it occurs in bones, is used in the manufacture of 
 phosphorus (see p. 150) and as manure; the calcium phosphate occurring as apatite, 
 osteolite, coprolites, and in various other forms as minerals, is also largely em- 
 ployed in the preparation of manure, for which purpose it is converted into a more 
 soluble condition by treating the several materials with sulphuric acid so as to form 
 what 'is technically termed superphosphate, consisting of a mixture of calcium 
 sulphate with acid calcium phosphate, the composition of which approximates to the 
 formula CaH 4 P 2 8 . Pure tricalcic phosphate treated in this manner should yield a 
 product containing in the dry state acid calcium phosphate equivalent to 61 per cent, 
 of tricalcic phosphate; but since the phosphatic materials employed for the preparation 
 of superphosphate rarely contain more than from 30 to 60 per cent, of tricalcic phos- 
 phate, the amount of soluble phosphate in the superphosphate ordinarily met with 
 varies accordingly, and is seldom more than equivalent to 30 or 40 per cent, of tri- 
 calcic phosphate. 
 
 u2 
 
292 CALCIUM. 
 
 HYDRAULIC LIME. 
 
 The lime obtained by burning certain kinds of limestone possesses the peculiar 
 property when mixed with water of gradually hardening to a stony consistency. 
 This hardening takes place in like manner and to the same extent when lime of this 
 kind has been mixed with water and is entirely immersed under water, on which 
 account hydraulic lime is extensively used for parts of edifices built under water, 
 and it is therefore known as hydraulic lime or water lime. It is also sometimes 
 termed cement, which is, however, an improper designation. 
 
 Hydraulic limestones contain as an essential constituent, besides lime, at least 
 10 per cent, of silica soluble in dilute acids. This silica is either originally con- 
 tained in the limestones, or is formed during the burning of the limestone from silicates 
 it contains. For preparing hydraulic lime, a limestone is selected that is rich in clay 
 (aluminum silicate). The amount of clay varies considerably. Limestone containing 
 10 or 20 per cent, of clay yields a poor hydraulic Lime, while limestone containing 20 
 or 30 per cent, of clay affords a good hydraulic lime. 
 
 Ordinary hydraulic lime may be considered as consisting essentially of a mixture 
 of burnt lime with soluble aluminum silicate. Since silicates of the kind often occur 
 naturally in the form of trass, pozzolane, santorin earth, etc., hydraulic lime or cement 
 may be prepared by mixing them with the requisite quantity of burnt lime. Cement 
 is the term given to the substance added to burnt lime for the purpose of converting 
 it into hydraulic lime. It is either a material occurring naturally, such as trass, or is 
 artificially prepared, like certain clays which are converted into cements by simple 
 heating. 
 
 The hardening of hydraulic lime has been explained in several different ways. 
 Two chief points have, at any rate, been determined which are (1), the formation of 
 silicates and aluminates, and (2), the formation of hydrates, both of which may be re- 
 ferred to the action of water. When hydraulic lime comes into contact with water, 
 the burnt lime in it first of all forms a hydrate, and some of it dissolves in the water ; 
 the lime solution thus formed reacts upon the clay (cement), forming calcium silicate 
 and aluminate. Calcium silicate in its turn combines with water, forming a hydrated 
 silicate. 
 
 Besides clay, some other constituents of hydraulic lime also influence its quality. 
 Magnesia when present in certain proportions is beneficial to the hydraulic property 
 of the lime. Limestone containing magnesia, however, requires burning very carefully. 
 Magnesia upon hardening probably gives rise to the production of small quantities of 
 magnesium silicate and aluminate. Ferrous oxide, when present in moderate amount, 
 is also beneficial according to some authorities, but ferric oxide is injurious. Alkalies 
 act beneficially from their property of dissolving silicic acid and alumina, by which means 
 they effect the combination of these substances with lime. A large amount of silicic 
 acid, especially in the state of quartz sand, has an injurious effect, owing to its not being 
 rendered soluble except by a strong heat which produces other injurious changes. 
 
 Good hydraulic mortar should not take long in hardening. The first stage of 
 hardening or binding, in the case of good cement under fresh water, ought not to re- 
 quire more than from half an hour to an hour and a half. Cement does not harden 
 so quickly under sea water, requiring from two to three hours. There is also a differ- 
 ence in the heat given off by cement in hardening, some kinds giving off much heat, 
 and others very little. Good cement should not increase in volume during the harden- 
 ing process. A test for good cement in this respect is that, upon filling a phial with 
 it and immersing the whole for some time under water, the phial should not be burst 
 by the expansion of the cement. 
 
 Freshly burnt cement, or hydraulic mortar, hardens more slowly than cement that 
 has been kept for some time in well-closed casks, and it first contracts in volume and 
 then in about fourteen days the volume again increases. It is in the best condition 
 for setting after about two or three weeks. 
 
 Preparation. The methods of preparing hydraulic lime are of three kinds : 
 
 1. From natural hydraulic limestone (Roman cement). 
 
 2. From burnt lime and natural or artificial cements. 
 
 3. From mixture of unburnt lime and clay (Portland cement). 
 PREPARATION OF HYDRAULIC LIME FROM HYDRAULIC LIMESTONE (ROMAN CEMENT). 
 
 This kind of -cement was at one time exclusively made from a particular kind of 
 argillaceous limestone found in the Island of Sheppy, in the Isle of Wight, and in 
 the London basin. Modern research, has, however, shown that a number of other 
 marls occurring in various parts of the continent are equally well adapted for the 
 preparation of Roman cement. The properties of the burnt lime are chiefly dependent 
 upon the amount of clay in the limestone, If this be known, the quality of the cement 
 
ROMAN CEMENT. 
 
 it will yield may be estimated. Looking at the matter from this point of view, Vicat 
 divides the limestone used for preparing cement into different classes, according to 
 the percentage of clay and the quality of hydraulic lime yielded by them. 
 
 Calcium carbonate 
 Clay . . . 
 
 Meagre Hydraulic Lime 
 
 Hydraulic Lime 
 good quality 
 
 Artificial 
 Cements 
 
 Middling 
 
 Ordinary 
 
 o 
 
 Jjf 
 
 1 
 
 1 
 
 I 
 
 64 
 36 
 
 1 
 
 j 
 
 
 
 
 
 83 
 17 
 
 80 
 20 
 
 77 
 23 
 
 73 
 27 
 
 39 
 61 
 
 16 
 
 84 
 
 2 
 
 88 
 
 Since, however, the composition of the clay itself is of vital importance, in using 
 the above table due consideration must be given to this point. 
 
 The limestones used in preparing hydraulic lime vary considerably in composi- 
 tion, as may be seen from the following table. The substances soluble and insoluble 
 in hydrochloric acid are given separately : 
 
 
 Sheppy stone 
 
 Tamowitz 
 
 Hausbrger near 
 
 
 
 
 Minden 
 
 Soluble in HC1 
 
 
 
 
 Calcium carbonate 
 
 6699 
 
 49-06 
 
 76-82 
 
 Magnesium carbonate 
 Ferrous carbonate 
 
 1-67 
 6-69 
 
 29-32 
 16-83 
 
 2-81 
 3-21 
 
 Alumina . ... 
 
 0-39 
 
 
 0-89 
 
 Insoluble in HC1 
 
 
 
 
 Silica 
 
 16-89 
 
 3-35 
 
 11-03 
 
 Alumina . 
 
 4-32 
 
 0-86 
 
 2-86 
 
 Ferric oxide 
 
 1-72 
 
 0-43 
 
 1-86 
 
 Lime 
 
 traces 
 
 0-06 
 
 0-12 
 
 Magnesia . 
 
 0-37 
 
 0-01 
 
 0-05 
 
 
 
 
 \ 
 
 Burning Roman Cement. The way in which this operation is carried out is of 
 great influence upon the quality of the cement. Some kinds of stone require longer 
 burning and more gentle heat, others a shorter time but stronger heat. Very siliceous 
 kinds of stone must not be heated very strongly, since this causes the production of 
 large quantities of calcium silicate, and thus the mass may even be partially melted. 
 A mass of the kind whether melted or not is said to be dead burnt, and it is incapable 
 of absorbing water. The stone is therefore only so far burnt as may be necessary to 
 expel the carbonic acid and convert the silica to a state in which it will combine in 
 the wet way with lime. When the burning has been insufficient the cement absorbs 
 water, but does not harden. Limestones, the clay of which contains only a small pro- 
 portion of bases, are consequently difficult to burn. 
 
 When the clay contained in the limestone is plastic and free from sand, a strong 
 but short burning is needed for producing the requisite change in the clay without 
 producing calcium silicate. Should the clay contain admixtures of ferric and manga- 
 nese oxides or ferric salts, a strong heat is required in order to convert these sub- 
 stances into silicates. The heating may in this case be continued until a slag begins 
 to be formed, and the product thus acquires a grey or brown, and even black, colour. 
 Cement limestones rich in iron, when sufficiently burnt, furnish very good hydraulic 
 lime. 
 
 When the limestone contains alkalies, they .help to render the silicic acid soluble, 
 by combining with it during the burning. By suitably raising the temperature, fusible 
 double silicates of potassium and sodium, iron, and alumina a/e formed. These fusible 
 double silicates are essential constituents of good cement. Hydraulic lime prepared 
 from limestone of this kind, when ground, forms a compact powder consisting of minute 
 laminae, in which the lime particles are protected against the action of the air and 
 moisture by a coating of semi-fused material, for which reason cement of this kind 
 keeps better than ordinary hydraulic lime. 
 
294 CALCIUM. 
 
 The kilns used in burning hydraulic lime are generally shaft kilns, worked con- 
 tinuously. The pieces of limestone and. the fuel are introduced alternately, so that 
 the thickness of the layers of fuel are regulated according to the degree of heat 
 desired. 
 
 The composition of hydraulic lime prepared from marly limestone corresponds of 
 course to the sort of marl from which it is prepared. The following table gives the 
 composition of a number of kinds of Eoman cement : 
 
 
 Sheppy 
 
 Essex 
 
 Bavarian 
 
 Sol. in Hydrochloric acid 
 
 
 
 
 
 Lime 
 
 48-2 
 
 46-1 
 
 44-96 
 
 50-40 
 
 Magnesia . 
 
 2-7 
 
 3-7 
 
 1-52 
 
 1-24 
 
 Manganese oxide/ 
 Ferric oxide . 
 
 9-2 
 
 12-4 
 
 traces 
 5-83 
 
 traces 
 8-64 
 
 Alumina . 
 
 7-3 
 
 4-6 
 
 6-43 
 
 471 
 
 Potash 
 
 0-8 
 
 0-9 
 
 0-45 
 
 0-50 
 
 Soda. 
 
 0-2 
 
 o-i 
 
 0-65 
 
 0-73 
 
 Silica 
 
 19-4 
 
 17-4 
 
 
 
 
 
 Carbonic acid . 
 
 3-4 
 
 3-6 
 
 4-52 
 
 4-61 
 
 Phosphoric acid 
 
 
 
 
 
 
 
 0-52 
 
 Sulphuric acid . 
 
 
 
 
 
 1-20 
 
 1-10 
 
 Water 
 
 1-0 
 
 07 
 
 072 
 
 1-31 
 
 Insol. in Hydrochlor. acid 
 
 " 
 
 
 
 
 Ferric oxide . l 
 
 
 ( 
 
 0-40 
 
 traces 
 
 Manganese oxide > 
 Alumina . . 
 
 1-3 
 
 .,{ 
 
 074 
 
 070 
 
 Quartz 
 Silica 
 
 6-2 
 0-3 
 
 8-3 f 
 0-5 \ 
 
 32-60 
 
 25-29 
 
 HYDRAULIC LIMB PREPARED BY MIXING LIME -WITH NATURAL OR ARTIFICIAL 
 CEMENTS. Silicates are found in volcanic regions which contain both silicic acid and 
 alumina in the soluble condition. Such silicates probably originate from hydrated com- 
 pounds related to clay, which have been changed and dehydrated by volcanic heat. 
 The most important silicates of the kind are trass, puzzolano, and santorin earth. 
 
 Trass occurs in several of the valleys branching out from the right bank of the 
 Khine, where it is quarried and brought into the market either as a powder or in 
 pieces. 
 
 The following analyses show the constituents of trass : 
 
 
 Brohlthal 
 
 Holland 
 
 Soluble in HC1 : 
 Lime 
 Magnesia 
 Ferric oxide . . . 
 
 3-16 
 2-15 
 11-77 
 
 6-5 
 1-1 
 3-9 
 
 
 1770 
 
 6-1 
 
 Potash ... ... 
 
 0-29? 
 
 
 Soda 
 Silica ... ... 
 
 2-44 j 
 11-50 
 
 64 
 
 29-5 
 
 Insoluble in Hydrochloric acid : 
 
 2-25 
 
 1-2 
 
 Magnesia 
 
 0-27 
 0-57 
 
 
 
 1-25 
 
 5-0 
 
 Potash 
 
 0'08 
 
 
 Soda 
 
 1-12 
 
 
 Silica 
 
 37-44 
 
 28'0 
 
 Puzzolane is a volcanic tufa found in Italy, France, and Belgium. Its composi- 
 tion is as follows : 
 
PORTLAND CEMENT. 
 
 295 
 
 
 Italy 
 
 France (Auvergne) 
 
 Soluble in HC1 : 
 
 
 
 
 8*0 
 
 9'0 
 
 Magnesia 
 
 0-9 
 
 
 Ferric oxide 
 
 6-3 
 
 21-8 
 
 Alumina ....... 
 
 97 
 
 2-0 
 
 Potash and Soda 
 
 2-6 
 
 1-2 
 
 Silica 
 
 19-5 
 
 28-2 
 
 Insoluble in HC1 : 
 
 
 
 Lime 
 
 1-2 
 
 1-3 
 
 Alumina 
 
 8-1 
 
 67 
 
 Silica . . . . . 
 
 32-7 
 
 25-0 
 
 Loss at a red heat ..... 
 
 10-2 
 
 4-1 
 
 Santorin earth is likewise a substance which yields a very good hydraulic lime 
 when mixed with lime. It is found in the island of Santorin, in Algiers, etc. 
 
 The following analyses by Feichtinger show the composition of santorin earth 
 used in subaqueous structures in Venice and Fiume : 
 
 Calcium sulphate . 
 
 Soluble in Water. 
 
 . 0'05 | Sodium chloride 
 
 Soluble in Hydrochloric Acid. 
 
 Alumina 
 Ferric oxide 
 Lime 
 
 Silica . 
 Alumina 
 Ferric oxide 
 Lime 
 
 1-36 
 1-44 
 
 0-40 
 
 Silica 
 
 Insoluble in Hydrochloric Acid. 
 
 . 66-37 
 . 12-36 
 . 2-90 
 . 2-58 
 
 Magnesia 
 Potash 
 Soda. 
 Water 
 
 traces 
 
 0-23 
 
 traces. 
 
 1-06 
 2-83 
 4-22 
 4-06 
 
 For preparing hydraulic mortar, these cements are mixed in the powdered state 
 with burnt lime, or lime flour, to which sand is sometimes added, the mortar being 
 prepared in quantities just sufficient for immediate use. The proportion of lime re- 
 quired for a certain cement must be specially ascertained for each kind of cement. 
 For this purpose the cement is mixed in a powdered state with a quantity of lime paste 
 sufficient to form a stiff dough ; the mixture is then submerged in water, and must 
 harden within twenty-four hours. 
 
 Powdered trass requires according to the quality of the trass from 1 to 3 parts 
 of burnt lime. When sand is also employed less trass is taken. Puzzolane requires from 
 half its weight to an equal weight of lime. Additions are often made of sand and other 
 materials, such as pieces of broken pottery, smithy scale, etc. In preparing hydraulic 
 mortar with santorin earth, it is mixed with one third or one fourth of slaked Jime and 
 an equal proportion of broken stones. 
 
 Among artificial cements added to lime for the purpose of preparing hydraulic lime, 
 the artificial puzzolane manufactured in France is especially worth notice. This is 
 prepared by carefully burning plastic clay containing 2 per cent, of lime. Other 
 cements are made with brickdust, Dutch bricks being especially suitable for the pur- 
 pose. The slag of blast furnaces, the ash of coal and lignite, etc., also yield hydraulic 
 mortar when mixed with lime. 
 
 Regarding the slag of blast furnaces, Hack states that those kinds only are suitable 
 for the preparation of hydraulic lime which gelatinise upon treatment with hydrochloric 
 acid. He further recommends treating the powdered slag before burning with a 
 small quantity of hydrochloric acid, for the purpose of increasing the hydraulic property 
 of the lime. 
 
 HYDRAULIC LIME FROM UNBURNT LIME AND CLAY (PORTLAND CEMENT). This 
 kind of cement is prepared in different ways ; the raw materials, however, always con- 
 sist of chalk (or lime) and clay in a finely powdered condition. In order to obtain the 
 chalk in a very finely divided state, it may be with advantage submitted to a process 
 of clutriation. The clay used has a composition which, after burning, approximates 
 
296' 
 
 CALCIUM. 
 
 as closely as possible to that of natural cements of good quality, and it is either finely 
 powdered and dried, or sometimes the argillaceous mud of rivers and streams is used. 
 
 Pasley's method. A stiff dough is made by mixing together 10 parts of powdered 
 chalk and one-fortieth of its weight of water, the mixture being then made into balls 
 and kneaded up with 13| parts of fresh clay mud from the river Medway. The mass is 
 shaped into bricks and burnt in a continuous shaft furnace. After burning, the bricks 
 are ground up to a fine powder. 
 
 Bleibtreu's method. Chalk that has been elutriated is mixed in the wet plastic 
 condition with clay in the state of fine powder, previously dried, the proportions being 
 1 vol. clay powder to 2 vols. chalk paste. The whole is intimately kneaded together 
 in a pugmill, and made into bricks, which are dried by placing them upon porous 
 bricks and exposure to the air. The burning of the dry bricks is carried out in a 
 shaft furnace filled with alternate layers of bricks and fuel ; this is ignited from below 
 and allowed to burn itself out. When sufficiently cool the bricks are taken out and 
 reduced to powder. Chalk is in some districts replaced by ordinary lime, which is 
 for this purpose allowed to disintegrate and form a fine powder. 
 
 The following analyses show the composition of Portland cement : 
 
 
 From England 
 
 From Bavaria 
 
 Soluble in HC1 : 
 Lime ... ... 
 Magnesia . . ... 
 Manganese oxide . ... 
 Ferric oxide . . . ... 
 Alumina . . . . . - V. 
 
 54-10 
 0-75 
 traces 
 5-30 
 775 
 2-15 
 
 53-14 
 
 1-59 
 1-30 
 4-45 
 3-50 
 2-10 
 
 Phosphoric acid 
 
 Soluble in water : 
 Sulphuric acid 
 Potash 
 
 075 
 
 1-00 
 1-10 
 
 
 Soda 
 
 1-66 
 
 
 Water 
 
 1-00 
 
 
 Insoluble in HC1 : 
 
 
 5-59 
 
 
 
 3-38 
 
 Alumina 
 Silica 
 
 22-23 
 
 2-32 
 22-35 
 
 Clay, sand ...... 
 
 2-20 
 
 
 The proportion of water required in the preparation of hydraulic mortar from 
 Portland cement varies with the kind of cement employed, and requires to be deter- 
 mined by trial. 
 
 Experience has shown that ordinary hydraulic lime, which retains its firmness and 
 hardness in fresh water, gradually disintegrates when applied to submarine structures. 
 This effect is brought about by the action of the magnesium salts in sea water, and 
 the replacement of the lime in the mortar by magnesia, as may be seen from the 
 following analyses of hydraulic mortar before and after being exposed to the action of 
 sea water. 
 
 
 I. 
 
 II. 
 
 Before immersion : 
 Lime 
 
 Silica . . . 
 
 13-21 
 67-82 
 
 13-92 
 55-65 
 
 
 19-73 
 
 30-43 
 
 
 9'21 
 
 
 After immersion : - 
 Lime . . . 
 Calcium carbonate 
 
 0-25 
 3-45 
 3-29 
 
 2-23 
 3-38 
 7'42 
 
 Cement residue . , , 
 
 93-00 
 
 86-30 
 
HYDRAULIC MORTAR. 
 
 297 
 
 No. I. is hydraulic mortar prepared from fat lime and ferruginous artificial cement. 
 No. II. is hydraulic mortar prepared from fat lime and pure clay. 
 
 For preparing hydraulic lime to resist the action of sea water, Vicat recommends 
 mixing the finest Koman puzzolane intimately together with 15 per cent, of fat lime. 
 It is essential that the lime should be very fat and that no sand should be mixed with 
 the cement. If trass be used in the place of puzzolane, the mortar decomposes in the 
 course of from five to twelve years. It is also possible to prepare artificial puzzolane 
 which, when mixed with lime, furnishes mortar that resists the action of sea water quite 
 as efficiently as that prepared from Koman puzzolane. For this purpose clay is reduced 
 to a very fine state of division by elutriation, and the moist sediment is formed into 
 balls about 2 in. in diameter, which are dried and burnt in a continuous shaft furnace. 
 The termination of the burning process may be judged of by the reaction of the clay 
 with boiling sulphuric acid. Clay which in the unburnt condition yields 9 per cent. 
 of its mass to sulphuric acid, should, after burning, give up from 16 to 18 per cent. ; 
 but when too much burnt very little of it dissolves in sulphuric acid. 
 
 Sainte-Claire Deville observed that, when magnesia is immersed in water, a hydr 
 is formed which, after a time, causes the hardening of the entire mass. This hardeni 
 also takes place when the magnesia is mixed with powdered marble, chalk, or ordi- 
 nary lime. Dolomite calcined at 400 likewise yields, when powdered and made into 
 paste by stirring it with water, a mass which hardens under water. This hardness 
 is due to magnesia and not to lime ; for upon heating dolomite sufficiently to expel the 
 carbonic acid of the calcium carbonate, a product is obtained which hardens at once 
 when mixed with water. This property of dolomite has been taken advantage of for 
 industrial purposes. 
 
 The following table gives the composition of some varieties of dolomite : 
 
 drate 
 ening 
 
 
 I. 
 
 II. 
 
 m. 
 
 Magnesium carbonate . .".. ' '. : 
 
 61-15 
 
 55-23 
 
 15-86 
 
 Calcium carbonate .... 
 
 21-41 
 
 33-99 
 
 72-23 
 
 Ferrous carbonate (and oxide) . 
 
 8-76 
 
 3-85 
 
 3-21 
 
 Silica 
 
 5-58 
 
 5-58 
 
 I 2-70 
 
 Alumina .... "." 
 
 2-07 
 
 2-27 
 
 
 Water and organic matter . 
 
 1-10 
 
 3-40 
 
 6-00 
 
 No. I. yields the Carigeract cement ; No. II. the hydraulic mortar of Port Cynfor; 
 No. II f. the stucco of Hell's Mouth. 
 
 As already mentioned, the product loses its hydraulic property when the dolomite 
 has been so strongly heated that not only the magnesia, but the lime also loses car- 
 bonic acid. But if dolomite contain the constituents of cement, silica, alumina, 
 etc., then, upon burning, ordinary hydraulic lime may be formed, besides magnesia, in 
 which case the expulsion of the carbonic acid from the calcium carbonate is advan- 
 tageous rather than otherwise. 
 
 A magnesian cement termed a Ibolith is prepared by burning^ the magnesite of 
 Frankenstein in Silesia in large retorts something like those used in gas works ; the 
 product is ground, sifted, and mixed with amorphous silica.^ Mixed with magnesium 
 chloride, it yields a very hard plastic mass, applicable as paint. 
 
 STRONTIUM. 
 
 SYMHOL Sr. ATOMIC WEIGHT 87'5. 
 
 This elementary substance was discovered in the state of carbonate by Crawford 
 in 1787, as a mineral occurring at Strontian in Argyllshire; its distinct nature wa 
 established in 1792 by Hope, and in 1793 by Klaproth. The metal was first isolated 
 by Davy in 1808. 
 
 Strontium occurs also naturally in the state of sulphate as ccelestin in small 
 proportion in some kinds ofarragonite and brewsterite, as well as in some kinds 
 of mineral water and in sea water. 
 
 The metal has a yellow colour like calcium ; its specific gravity is 2'542 ; it 
 oxidises more readily than calcium, and generally resembles the other metals of the 
 alkaline earths ; its compounds are also analogous to those of calcium and barium, and 
 they are distinguished by communicating a red colour to the outer portion of the blow- 
 pipe flame when heated in the inner portion. Alcohol containing strontium chloride 
 in solution also burns with a red flame. 
 
BARIUM. 
 
 SYMBOL Ba. ATOMIC WEIGHT 127. 
 
 This metal was first recognised in the state of oxide by Scheele in 1774, and it 
 was first isolated in the metallic state by Davy in 1808. It occurs naturally in great 
 abundance in the form of sulphate as heavy spur, and in the form of carbonate as 
 witherite, and with calcium carbonate as baryto-calcite, also in some manganese 
 ores and in mineral water. The physical characters of the metal have not been very 
 accurately determined, but its compounds are closely analogous to those of calcium 
 and strontium. 
 
 BARIUM CHLORIDE. 
 
 FORMULA BaCL. MOLECULAR WEIGHT 198. 
 
 Composition. Crystallised barium chloride contains a molecule of water, its 
 composition being represented by the formula : 
 
 BaCl 2 + HjjO. 
 
 Characters. As usually met with barium chloride forms pellucid crystals be- 
 longing to the rhombic system ; it is soluble in both cold and hot water, but is very 
 slightly soluble in sulphuric acid, its solubility in the latter menstruum decreasing 
 with the concentration of the sulphuric acid. 
 
 When heated, crystallised barium chloride gives off its water of crystallisation, 
 passing over into anhydrous barium chloride, a white pulverulent mass, which melts 
 upon the heat being increased. 
 
 Preparation. The most common sources of barium chloride are witherite, or 
 native barium carbonate, BaC0 3 , which does not occur in very large quantities, and 
 heavy spar, which is more abundant. 
 
 To convert witherite into barium chloride it is dissolved in hydrochloric acid ; 
 carbonic acid is evolved, which may be used as a by-product, and barium chloride 
 remains in the solution, which is evaporated to crystallisation. 
 
 Barium chloride is also obtained as a by-product in soda works by conducting the 
 hydrochloric acid escaping from the sulphate furnaces through carboys containing 
 witherite suspended in water (vide p. 253). 
 
 The preparation of barium chloride from heavy spar, BaSOj, is more difficult than 
 its preparation from witherite. 
 
 At the time when the consumption of barium chloride was inconsiderable this 
 substance was prepared by heating to redness a mixture of powdered heavy spar and 
 charcoal, so as to reduce it to barium sulphide in the manner represented by the fol- 
 lowing equation: 
 
 BaS0 4 + 4C = BaS + 400. 
 
 By lixiviating the fused mass with water, the barium sulphide is dissolved out, 
 and it is converted, by addition of hydrochloric acid, into barium chloride, while sul- 
 phuretted hydrogen is evolved. The large quantity of sulphuretted hydrogen thus 
 produced renders this method generally inapplicable. 
 
 In order to secure intimate contact between the powdered charcoal and heavy spar, 
 these substances are mixed together with linseed meal and water into a paste, which 
 is kneaded up and moulded into cylinders 3 inches long and 1 inch thick. These 
 cylinders are piled up in layers alternating with layers of coal, in a furnace, and 
 heated to bright redness, care being taken to avoid access of air. Heating in closed 
 crucibles causes too great a consumption of fuel. After lixiviation and decomposing 
 the liquor with raw hydrochloric acid, a good deal of iron remains in solution ; the 
 liquid is therefore treated with just sufficient barium sulphide to produce a weak alk;i- 
 
BARYTA WHITE. 299 
 
 line reaction. By this means iron is precipitated as sulphide ; the precipitate is then 
 allowed to deposit, and the clear liquid drawn off and evaporated to the point of crystal- 
 lisation. 
 
 The method adopted byKuhlmann for decomposing barium sulphate is easier. An 
 intimate mixture of coal and heavy spar is placed in the hinder part of a double rever- 
 beratory furnace, and mixed with a quantity of solution of manganous chloride (by- 
 product in the preparation of chlorine, the free acid of which lias been neutralised by 
 lime, vide p. 165), and well stirred meanwhile, until, after evaporation of the water, 
 a stiff doughy mass is obtained. The mass thus formed is then brought into the 
 anterior part of the furnace nearest the fire, -where it is heated for an hour to redness. 
 The semi-liquid mass is then drawn out, allowed to weather in the air for a few 
 days, lixiviated, and the liquor crystallised. Should the liquor contain an excess of 
 barium sulphide it is decomposed by manganous chloride, and any excess of manganous 
 chloride is neutralised with barium sulphide. 
 
 The essential features of this method are the same as in the first-mentioned process : 
 the barium sulphate is reduced by carbon to barium sulphide, which, together with 
 manganous chloride, yields manganese sulphide and barium chloride. The presence 
 of ferric chloride is a matter of indifference in this process, since it behaves in a 
 manner exactly analogous to manganous chloride. 
 
 The process of reduction is quicker by this method because the mass melts, and 
 thus a more intimate contact of the ingredients is effected. This method has also the 
 advantage that the heating may be carried out in a.reverberatory furnace. 
 
 G-odin's method consists in heating together in a reverberatory furnace charcoal, 
 heavy spar, calcium chloride and limestone, lixiviating the mass with water, and 
 evaporating to crystallisation. The calcium sulphide thus formed, being insoluble, 
 remains undissolved. 
 
 The method of Asselin and Wagner consists in heating to redness a mixture of 
 heavy spar, charcoal, and tachydrite (CaCl 2 + 2MgCl 2 ). 
 
 Uses. The consumption of barium chloride has increased considerably of late, in 
 consequence of its use for softening water used in steam boilers. As already shown, 
 water containing gypsum is not suitable for boilers, owing to its forming a very hard 
 crust, and where only water of this kind is available for use, it is first of all treated 
 in large basins with barium chloride. The process which takes place consists in the 
 conversion of the gypsum and barium chloride into calcium chloride and barium sul- 
 phate, which settles to the bottom of the basins in the form of a fine sand, while the 
 calcium chloride remains in solution, but forms no hard crust or scale when the water 
 is used in the boiler. The addition of barium chloride to water containing gypsum 
 is equally effective if the salt be added before the water enters the boiler, and without 
 waiting for the barium sulphate to deposit. 
 
 Besides this application of barium chloride, the substance is used in the prepara- 
 tion ofbarytawhite (barium sulphate) and other preparations of the metal. Barium 
 chloride is used in dyeing with Saxon blue, owing to its forming a very fast colour 
 with indigo dissolved in sulphuric acid. 
 
 BARIUM SULPHATE. 
 
 FORMULA BaS0 4 . MOLECULAR WEIGHT 223. 
 
 Occurrence. Barium sulphate occurs naturally as heavy spar, inconsiderable 
 quantities. 
 
 Characters. Artificial barium sulphate, or baryta white, is a very finely 
 divided pulverulent substance of dazzling whiteness and great covering power. When 
 carefully prepared it resists all atmospheric influences. Baryta white has the advan- 
 tage over white lead of not being blackened by sulphuretted hydrogen ; it covers 
 better also than zinc white, and is cheaper than either. Baryta white cannot, howeA'er, 
 be used with oil, on account of its mixing but imperfectly with that medium and con- 
 sequently covering badly. 
 
 It is generally used stirred up with about 30 per cent, of water to a paste. 
 
 Preparation. Baryta white is prepared either directly or is obtained as a by- 
 product. 
 
 It is prepared by mixing an aqueous solution of barium chloride in the cold with 
 sulphuric acid of sp. gr. 1-262 as long as a precipitate is produced, allowing the pre- 
 cipitate to settle, and washing it with water until the wash water ceases to show an 
 acid reaction. The washed barium sulphate is then placed on a linen cloth to drain, 
 and is ready for the market. 
 
300 BARIUM. 
 
 If the barium sulphate were to be thoroughly dried it would lose in covering 
 power ; the same evil would be caused by precipitating the sulphate from a hot solu- 
 tion, owing to the formation of a coarse crystalline powder; when it is precipitated 
 cold, an impalpable amorphous powder is produced. 
 
 In preparing baryta white from barium chloride, the liquor resulting from the 
 preparation of barium chloride may be used, which must, however, be free from sul- 
 phide, otherwise sulphur would be precipitated along with the sulphate, and render it 
 impure. The presence of free sulphur in baryta white, and the formation of sulphuric 
 acid owing to oxidation of sulphur in the air would cause the destruction of other 
 colours mixed with it. 
 
 In order to obtain a barium chloride liquor pure enough for preparing baryta 
 white, the barium sulphide liquor (page 298) is decomposed with a slight excess of 
 hydrochloric acid, and boiled by passing steam into it until no further smell of sul- 
 phuretted hydrogen is noticeable. 
 
 In preparing baryta white from witherite, the mineral is either first com- 
 pletely converted into barium chloride (according to Hahn a 10 per cent, solution is 
 the best), and this is treated with sulphuric acid, or according to Pelouze's method 
 which is better the two reactions are conducted simultaneously by treating finely 
 powdered witherite with dilute sulphuric acid containing from 2 to 4 per cent, of 
 hydrochloric acid. The process consists in the conversion of the barium carbonate 
 into barium chloride by the hydrochloric acid, and in the conversion of the barium 
 chloride into sulphate by the sulphuric acid, while the hydrochloric acid is again 
 liberated ; so that a small quantity of hydrochloric acid is in time capable of dis- 
 solving a large quantity of barium carbonate. When witherite contains galena, as is 
 often the case, the method is not applicable on account of the galena not being decom- 
 posed, and colouring the product. 
 
 Baryta white is obtained as a by-product in a number of industrial operations. In 
 nearly every instance where calcium carbonate is used for neutralising sulphuric acid, 
 barium carbonate can be used in its place, so as to obtain barium sulphate instead of 
 calcium sulphate, as a by-product. Instances of the kind are the manufacture of 
 caustic soda and potash, tartaric acid, starch, sugar, etc. 
 
 Wagner suggests the use of baryta instead of lime for the saponification of fats 
 in the manufacture of stearic acid, by which means barium sulphate would be ob- 
 tained instead of gypsum. 
 
 Uses. As already mentioned, baryta white is not well adapted for use as an oil 
 colour, since the mixture has a very imperfect covering power as paint. A paint of 
 good covering power is, however, obtained by mixing together equal parts of baryta 
 white and zinc white. Large quantities of baryta white are employed in the prepara- 
 tion of wall papers, coloured papers, playing cards, etc. It seems to be especially 
 useful in preparing papers to which it is desired to give a satin lustre. Baryta white 
 is especially adapted for mixing with other colours on account of its neutral charac- 
 ters and the difficulty with which it is decomposed. It forms also a useful addition 
 to paper pulp ; paper thus prepared has a dazzling white appearance, and is almost 
 opaque. 
 
 Powdered heavy spar is chiefly employed as a diluent or an adulterant for other 
 white colours (white lead, zinc white, etc.) and as an admixture with colours like 
 ultramarine, chrome yellow, etc. It is used unmixed as a cheap paint, but on a com- 
 paratively small scale. It is also employed, but at present not to any great extent, in 
 the manufacture of glass. 
 
 Although heavy spar is chemically the same as the artificially prepared barium 
 sulphate called blanc fix, it cannot like the latter be used as a paint, on account of its 
 great density. 
 
ALUMINUM. 
 
 SYMBOL Al. ATOMIC WEIGHT 27'5. 
 
 History. It is probable that Oersted first obtained aluminum in the metallic 
 state, for in 1824 he decomposed moist aluminum chloride with sodium amalgam. 
 However the first definite account of aluminum was given in 1827 by Wo'hler, who 
 obtained it by heating aluminum chloride with potassium. Bunsen first used the 
 double aluminum and sodium chloride for preparing aluminum by decomposing it 
 electrolytically. The native aluminum and sodium fluoride known as cryolite was 
 first used in the preparation of aluminum by H. Eose. But the successful prepara- 
 tion of aluminum industrially is chiefly due to the efforts of H. Sainte-Claire Deville ; 
 for though he did not introduce any essentially new method of preparation, and the 
 means of carrying out his experiments were furnished by the French Academy, 
 his modifications of the old methods served to make them practicable for industrial 
 purposes. The use of sodium in the preparation of aluminum in the place of potas- 
 sium is due to him. 
 
 Occurrence. Aluminum does not occur naturally in the free state, but in com- 
 bination with oxygen it is one of the most abundant and widely distributed elements. 
 The oxide or alumina, however, is itself of comparatively rare occurrence in the dif- 
 ferent forms of corundum, known as the ruby, sapphire, and emery; and it 
 occurs for the most part in the form of saline compounds, especially silicates, as 
 andalusite, cyanite, sillimanite, clay, etc., in which state, and combined with 
 other silicates, aluminum exists in felspar, mica, hornblende, etc. In the form 
 of sulphate it occurs as alunite or alums tone; wavelliteis an aluminum phos- 
 phate, and aluminum fluoride is an essential constituent of cryolite and topaz. 
 Aluminum hydrates occur as gibbsite and dia spore. 
 
 Characters. Aluminum in a compact state is a greyish white metal of consider- 
 able lustre, and it gives a clear ringing sound when struck. Its specific gravity is 2'5, 
 and it admits of being beaten out into sheet, as well as of being drawn into wire ; its 
 tenacity is between zinc and tin ; it is not very flexible ; and it melts at 700. The 
 industrial value of aluminum is chiefly due to its resistance to the influence of oxi- 
 dising agents ; at the ordinary temperature of the air it is entirely unaltered, and it 
 may even be heated to redness without being much oxidised. Aluminum does not 
 decompose water even at a red heat, neither is the metal acted upon by sulphuretted 
 hydrogen, owing to the slight affinity between aluminum and sulphur. Upon melting 
 together a mixture of aluminum and silver sulphide, sulphur is liberated, and an 
 alloy of aluminum and silver is formed. Aluminum is very little acted upon by 
 dilute sulphuric acid, but it is very energetically attacked by dilute hydrochloric acid, 
 forming aluminum chloride and free hydrogen. Aluminum is not attacked by 
 dilute or concentrated nitric acid, and boiling sulphuric acid acts very slowly on the 
 metal. Caustic potash and soda dissolve aluminum, forming soluble aluminates, 
 with evolution of hydrogen. Ammonia exerts very little action upon the metal. 
 
 Commercial aluminum is always contaminated with silicon and iron. Kammels- 
 berg found in a sample between 2 and 10 percent, of silicon, and the amount of iron is 
 sometimes as much as 6 per cent, and upwards. 
 
 Preparation. Wohler's method of obtaining this metal consists in decompos- 
 ing aluminum chloride with potassium ; but at the present day it is prepared either 
 from the double aluminum and sodium chloride prepared artificially, or from 
 natural cryolite (aluminum and sodium fluoride). 
 
 From Aluminum and Sodium Chloride. The essential feature of this process con- 
 sists in mixing the aluminum and sodium chloride with sodium, common salt, and fluor 
 spar, and exposing the mixture to a temperature sufficient to cause the sodium to ab- 
 stract the chlorine from the aluminum chloride, and liberate aluminum The common 
 salt serves as a flux, and the addition of fluor spar serves to dissolve small quantities 
 
302 ALUMINUM. 
 
 of alumina produced by the action of moisture upon the aluminum chloride and it is 
 essential, not only because alumina is not reduced by sodium, but also because the 
 alumina formed covers the granules of aluminum produced and prevents their fus- 
 ing together to a homogeneous mass. 
 
 For preparing aluminum, Sainte-Claire Deville, Morin, and Debray recommend 
 the following mixture : 
 
 Aluminum and sodium chloride 400 parts 
 
 Sodium 75-80 
 
 Common salt 200 
 
 Fluor spar 200 ,, 
 
 The aluminum and sodium chloride is mixed with the salt and fluor spar, both 
 thoroughly dried, and finely powdered ; alternate layers of this mixture of sodium are 
 then placed in a crucible covered with a layer of common salt and gradually heated 
 in a reverberatory furnace until the crucible and its contents acquire a white heat, 
 the melted mass being continually stirred during the operation. Upon pouring the 
 contents of the crucible upon a cold stone floor, the greater part of the aluminum is 
 obtained as a compact lump ; the small granules which remain dispersed through the 
 slag are afterwards, as far as may be, collected separately. 
 
 Morin heats the mixture in a reverberatory furnace, instead of crucibles, the hearth 
 being constructed so that the aluminum collects in a hollow and there melts to a 
 compact mass. He recommends a mixture consisting of : 
 
 Aluminum and sodium chloride 100 parts 
 
 Sodium 20 
 
 Fluor spar 50 
 
 Cryolite may always be used with advantage in place of fluor spar. It acts both 
 as a solvent for alumina like fluor spar, and also increases the yield by furnishing 
 some aluminum. When cryolite is substituted for fluor spar, the following mixture 
 may be used : 
 
 Aluminum and sodium chloride . . . . 110 parts 
 
 Sodium 35 
 
 Cryolite 40 
 
 From Cryolite. When cryolite and sodium are melted together in the presence of 
 a flux, the fluorine of the cryolite combines with the sodium, and aluminum is 
 liberated in the metallic state. The mixture used in the Eouen aluminum manufac- 
 tory consists of : 
 
 H. Rose. Wbhler. 
 
 Cryolite 50 parts 16 parts 
 
 Sodium 20 12^-15^ 
 
 Potassium chloride 50 9 ,, 
 
 Sodium 7 
 
 The mixture of finely-powdered cryolite and potassium chloride or sodium chloride 
 is placed in alternate layers with slices of sodium in a crucible, which is then strongly 
 heated in a reverberatory furnace. When the reaction is complete, the melted mass 
 is poured into iron moulds, the aluminum detached from the slag, remelted and cast 
 into ingots. 
 
 Dumas gives the following as the results of analyses of commercial aluminum : 
 
 Aluminum 92'5 96'IG 
 
 Silicon 07 0'47 
 
 Iron 6-3 337 
 
 Uses. The chief use of aluminum is in the manufacture of fancy articles ; for 
 instance, jewellery for setting stones, bracelets, watch cases, brooches, seals, pen- 
 holders, studs, handles of knives and forks, spectacles, opera glasses, etc., etc., for 
 which purposes it is especially fitted, owing to its not being attacked by sulphuretted 
 hydrogen. Aluminum is very useful for articles in which comparative strength com- 
 bined with great lightness is required, such as tubes for optical instruments, small 
 weights, surgical instruments, etc., etc. Pens made of aluminum are more durable 
 and lighter than those made of steel. 
 
 Aluminum is not well suited for coinage, owing to its fluctuating value, and 
 further because it loses its value when dissolved ; it may be used in making medals, 
 counters, etc. 
 
 Compounds. Aluminum forms only one series, of compounds, and as com- 
 pared with hydrogen or chlorine it is trivalent ; but since these compounds appear to 
 contain two atomic proportions of aluminum united in the molecules, it is probably 
 
COMPOUNDS OF ALUMINUM. 303 
 
 tetravalent and only apparently trivalent. The compounds of aluminum present 
 close analogies with some of those of iron and chromium ; the composition of the 
 chloride is represented by^the formula ALC1 3 , that of the oxide by the formula A1 2 3 , 
 and the sulphate is A1 2 3S0 4 . Most aluminum compounds combine with correspond- 
 ing compounds of monovalent elements, forming double salts ; thus the chloride com- 
 bines with sodium chloride, the sulphate with potassium sulphate, and the oxide with 
 water forming double salts, as shown by the following equations : 
 
 A1 2 C1 4 + 2NaCl = 2AlNa01 4 sodic aluminum chloride. 
 A1 2 3S0 4 + K 2 S0 4 = 2(A1K2S0 4 ) potassic aluminum sulphate. 
 A1 2 3 + H 2 = 2A1H0 2 monohydrate. 
 
 Besides the hydrate represented by the last formula, there are two others, a tri- 
 hydrate A1H 3 3 , arid an intermediate dihydrate A1 2 H 4 5 , with other basic oxides. 
 The oxide also forms compounds of a similar nature, which are termed aluminates; 
 thus, for instance, a potassic compound analogous to the monohydrate has a composi- 
 tion represented by the formula A1K0 2 , and several compounds of the same kind 
 occur naturally; for instance, the zinc aluminate Al 2 Zn0 4 , as gahnite, and mag- 
 nesium aluminate Al. 2 Mg0 4 , as spinel. The sodium compound AlNa 3 3 is used 
 as mordant in calico-printing, and is produced artificially for that purpose. 
 
 The oxygenated compounds of aluminum and silicon are among the most impor- 
 tant of the natural substances containing aluminum. All the different kinds of clay 
 consist essentially of an aluminum silicate, but the relative proportions of their 
 constituents vary considerably. Aluminum silicates combine with other silicates to 
 form double salts, and a very large proportion of the minerals which constitute the 
 various crystalline rocks are substances of this nature. 
 
 The compounds of aluminum are generally colourless. Those which are soluble 
 in water have a sweetish astringent taste. Many of the saline compounds are quite 
 insoluble in water, but they are readily dissolved by hydrochloric acid or sulphuric 
 acid, unless they have been strongly heated. 
 
 The alloys of aluminum are of great interest and importance ; with tin it forms 
 a very hard alloy; with copper the well-known gold-coloured alloy known as 
 aluminum bronze. 
 
 This alloy of aluminum and copper is much used for making artificial jewellery, 
 etc. It possesses great lustre, hardness, and durability : the proportions are generally 
 10 per cent, of aluminum and 90 per cent, copper. The hardness of this alloy in the 
 cast state is between iron and steel ; when hammered its hardness approaches that 
 of steel. 
 
 Owing to the great hardness of aluminum bronze, it might be used with advan- 
 tage for plumber blocks if sufficiently cheap. Experiments made with this object 
 gave excellent results. 
 
 An alloy of 96 per cent, aluminum and 4 percent, silver has a white colour and 
 considerable lustre. It would answer well for table plate. 
 
 CHLORIDE. 
 
 FORMULA. A1 2 C1 6 . MOLECULAR WEIGHT 268. 
 
 This salt is a yellowish crystalline substance volatilisable at a moderate red heat. 
 It is deliquescent and very soluble in water ; when the solution is evaporated to dry- 
 ness, decomposition takes place and alumina is formed, together with hydrochloric 
 acid, which escapes. 
 
 Preparation. For preparing aluminum chloride on the small scale, either a 
 tubulated glass retort, coated with fire clay, or a porcelain retort, is filled with an in- 
 timate mixture of alumina and charcoal made into a paste with oil ; the retort is then 
 placed in a reverberatory furuace, with the neck protruding, and heated to redness, 
 while at the same time chlorine is passed into the retort. Aluminum chloride distils 
 over, condensing in the neck of the retort and receiver as a mass of laminar crystals. 
 
 For preparing this salt on a large scale Sainte-Claire Deyille recommends the use 
 of a fire-clay gas retort set upright, at the bottom of which is an opening that can be 
 closed by a close-fitting slide, while the upper end is fitted with a lateral delivery 
 tube, through which the vapour produced in the retort passes into a condensing 
 chamber. In working the apparatus the retort is filled with a mixture of alumina, 
 coal tar, and charcoal, heated to redness, and dry chlorine, passed into the retort at 
 the lower part of it, the mouth being closed directly vapour of aluminum chloride be- 
 gins to appear in large quantity. The heating and supply of chlorine are continued as 
 
804 ALUMINUM. 
 
 long as aluminum chloride is formed, and then the slide at the bottom of the retort 
 is opened, the residue drawn out, and the retort charged again. 
 
 ALUMINUM OXIDE 
 
 FORMULA A1 2 S . MOLECULAR WEIGHT 103. 
 
 History. This substance was first shown to be distinct from lime in 1754 by 
 MarggraflJ who pointed out that the earth obtainable from alum does not disengage 
 ammonia from sal ammoniac, and that its saline compounds are quite different from 
 those of lime ; he also showed that clay contained this earth in combination with 
 silica. Some years before this, however, Hellot had described the earth obtained 
 from clay by means of sulphuric acid and subsequent precipitation by fixed alkali, as 
 being almost insoluble in acids after it had been heated to redness. The solubility 
 of moist alumina in caustic alkalies was first observed by Klaproth in 1789. 
 
 Occurrence. Alumina occurs naturally as corundum or adamantine spar, 
 the purer crystalline 'varieties of this mineral constituting the ruby and sapphire: 
 the impurer variety, termed emery, contains a considerable amount of ferric oxide. 
 
 Characters. Crystallised alumina is next to the diamond the hardest substance 
 known ; its density is about 3*9 ; the purer natural varieties are transparent or trans- 
 lucent, and in the pure state it is colourless ; the colour varies from white or grey to 
 blue, red, yellow, and brown, owing to the presence of minute proportions of 
 metallic oxides ; the more impure varieties are opaque and dark-coloured. In the 
 crystalline condition alumina is quite infusible and insoluble in acids. This is also 
 the case with artificially prepared alumina, especially after it has been heated to red- 
 ness ; but by fusion with acid sulphate of potassium or with alkaline hydrates it is 
 rendered soluble. 
 
 Alumina combines with water in three proportions, forming hydrates ; the mono- 
 hydrate A1H0 2 occurs naturally as di as pore. 
 
 The trihydrate A1H 3 3 also occui's naturally as gibbsite; it is obtained as a 
 gelatinous precipitate by adding an alkali to the solution of an aluminum salt, and 
 when dried at a moderate heat it is a soft friable mass, soluble in acids and caustic 
 alkalies ; it adheres to the tongue, and forms a stiff paste with water, but is insoluble 
 in that liquid. At a red heat it gives up its water and contracts considerably. This 
 hydrate has a marked capacity of combining with some neutral organic substances, 
 and the pigments termed lakes ;iro of this nature. The fibres cf cotton impreg- 
 nated with alumina acquire the power of retaining colour substances, and on this 
 account aluminous salts are used as mordants for producing fast colours in dyeing and 
 calico-printing. 
 
 The dihydrate A1 2 H 4 5 is formed when a dilute solution of aluminum diacetate is 
 exposed for several days to a temperature of 1 00 in a close vessel ; the salt appears 
 to be decomposed, and acetic acid liberated, though the alumina is not precipitated 
 and it remains dissolved when the solution is boiled in an open vessel to drive off the 
 acetic acid. The solution is coagulated on the addition of mineral or vegetable acids, 
 and by decoctions of dye woods, but the alumina it contains does not act as a 
 mordant. On evaporation to dryness, the dihydrate remains in a condition insoluble 
 in strong acids, but soluble in acetic acid. By boiling with solution of potash it is 
 converted into the trihydrate. 
 
 Preparation. Alumina may be prepared by igniting aluminum sulphate or 
 ammonia alum, or by adding ammonium carbonate to a boiling solution of an alu- 
 minum salt, washing the precipitate, and drying it at a moderate heat or by ignition, 
 accordingly as the alumina is required to be in the state of hydrate or anhydrous. 
 
 ALUMINUM AND SODIUM CHLORIDE. 
 
 FORMULA AlNaCl 4 . MOLECULAR WEIGHT 192-5. 
 
 Preparation. This double salt may be prepared by heating up to 200 for 
 a short time a mixture of equal molecular proportions of aluminum chloride and 
 sodium chloride ; the combination takes place with considerable development of heat. 
 To obtain aluminum and sodium chloride directly, a retort coated with fire clay is 
 filled with a mixture of alumina, coal tar, charcoal, ami common salt, heated to 
 redness, and chlorine passed into it. The aluminum chloride thus formed, combines 
 with the sodium chloride, forming the double salt which distils over; but as it is less 
 
ALUMINUM SULPHATE. 
 
 305 
 
 volatile than aluminum chloride, a higher temperature is required. However, by 
 this direct method, an operation is saved, and it is generally adopted. 
 
 The alumina used in the preparation of aluminum chloride (or the double salt) is ob- 
 tained in different ways. Sainte-Claire Deville recommends the use of calcined ammonia 
 alum. Impure cryolite also yields a useful alumina, when boiled in fine powder with 
 milk of lime, by which it is converted into soluble sodium aluminate and calcium 
 fluoride, which remains undissolved. The clear solution is decanted off and carbonic acid 
 passed through it, by which means sodium carbonate is formed and remains in solution, 
 while aluminum hydrate is precipitated ; this is separated from the solution and dried, 
 the soda solution being evaporated to obtain soda for preparing metallic sodium. 
 
 Other porous kinds of alumina may be used in the preparation of aluminum, but 
 care must be taken that they are free from iron, otherwise the aluminum prepared 
 from them is apt to be contaminated with that metal. 
 
 ALUMINUM SULPHATE. 
 
 FOBMTJLA A1 2 3S0 4 + 18H 2 0. MOLECULAB WEIGHT 667. 
 
 This salt occurs in commerce under the name of alum cake, or concentrated 
 alum, and is now often used in the place of ordinary alum. 
 
 Characters. Aluminum sulphate dissolves in two parts of water, and upon eva- 
 porating the salt crystallises in pearly scales, which form a crystalline mass when 
 separated from the mother liquor and dried. The salt melts in its water of crystal- 
 lisation upon cooling. The amounts of salt in solutions of different density are indi- 
 cated in the following table : 
 
 Degrees 
 Baume 
 
 Specific 
 gravity 
 
 Aluminum 
 sulphate 
 
 Degrees 
 Baume 
 
 Specific 
 gravity 
 
 Aluminum 
 sulphate 
 
 1 
 
 1-007 
 
 8-64 
 
 17 
 
 1-123 
 
 156-7 
 
 2 
 
 1-013 
 
 17-29 
 
 18* 
 
 1-132 
 
 166-5 
 
 3 
 
 1-020 
 
 25-95 
 
 19 
 
 1-140 
 
 176-4 
 
 4 
 
 1-027 
 
 33-72 
 
 20 
 
 1-148 
 
 189-2 
 
 5 
 
 1-033 
 
 41-51 
 
 21 
 
 1-157 
 
 202-1 
 
 6 
 
 1-040 
 
 49-29 
 
 22 
 
 1-166 
 
 215-0 
 
 7 1-047 
 
 57-08 
 
 23 
 
 1-174 
 
 227-9 
 
 8 
 
 1-055 
 
 67-20 
 
 24 
 
 1-183 
 
 241-9 
 
 9 
 
 1-062 
 
 77-50 
 
 25 
 
 1-192 
 
 255-9 
 
 10 
 
 1-069 
 
 86-9 
 
 26 
 
 1-201 
 
 269-9 
 
 11 
 
 1-077 
 
 97-2 
 
 27 
 
 1-211 
 
 283-9 
 
 12 
 
 1-084 
 
 107-4 
 
 28 
 
 1-220 
 
 297-6 
 
 13 
 
 1-092 
 
 117-3 
 
 29 
 
 1-230 
 
 311-3 
 
 14 
 
 1-099 
 
 127-1 
 
 30 
 
 1-239 
 
 325-0 
 
 15 
 
 1-107 
 
 137'0 
 
 31 
 
 1-249 
 
 338-9 
 
 16 
 
 1-115 
 
 146-8 
 
 32 
 
 1-260 
 
 352-8 
 
 The following table gives the results of analyses of different kinds of aluminum 
 nlphate: 
 
 Locality . , . ... .,- . . 
 
 Plympton 
 
 Schwennsal 
 
 
 
 
 
 Analyst . . . .>-. :. ., ..... 
 
 Muspratt 
 
 Wegand 
 
 
 H. Fleck 
 
 
 Aluminum sulphate '"<' 
 Sodium sulphate '.-> 
 Free sulphuric acid ; 
 Ferric oxide . 
 
 51-00 
 
 5370 
 1-15 
 
 47-35 
 4-35 
 0-73 
 
 50-80 
 1-24 
 0-27 
 
 51-63 
 0-77 | 
 
 Potash 
 
 
 
 0-62 
 
 ~ 
 
 ~~ 
 
 
 Water . . ... 
 
 49-00 
 
 45-79 
 
 47-37 
 
 47-47 
 
 46-94 
 
306 ALUMINUM. 
 
 Preparation. Aluminum sulphate is prepared from various raw materials, 
 such as clay, cryolite, bauxite, etc. 
 
 From Clay and Sulphuric Add. For preparing aluminum sulphate from clay, the 
 purest kind of clay is selected, kaolin, or pipe clay, being the most suitable kind, 
 care being taken that the clay contains only traces of lime and iron. The clay is 
 first heated to redness in a reverberatory furnace, and thus loses its plastic consis- 
 tency, becoming porous and friable, while any ferrous oxide is converted into ferric 
 oxide, which is less easily attacked by sulphuric acid when it has been heated to redness. 
 
 The calcined clay is reduced to a fine powder and sifted to separate coarse pieces, 
 then heated with sulphuric acid of sp. gr. 1-462 to 1-490. The treatment with acid 
 may be carried out either by mixing the clay in a pan covered with a brick arch 
 with about two-fifths of its weight of sulphuric acid, and heating the whole to about 
 70 by making the flame of a reverberatory furnace pass under the arch, or a wooden 
 trough lined with lead may be used for mixing the clay and sulphuric acid, allowing 
 the mass to remain 24 hours at the ordinary temperature, and then slightly heating 
 it in leaden pans for a few hours. The action of sulphuric acid upon clay consists in 
 decomposing the aluminum silicate, with formation of aluminum sulphate and free 
 silicic acid. The process is considered complete when no free sulphuric acid remains 
 in the mixture, which may be ascertained by testing a filtered portion of the liquid 
 with a solution of sodium hyposulphite, when no precipitate or cloudiness should be 
 produced. Another test consists in plunging a strip of zinc into the liquid ; no escape 
 of hydrogen indicates the absence of free sulphuric acid. 
 
 The clay, after treatment with sulphuric acid, is placed in wooden lixiviating 
 vessels lined with lead, and stirred up with water to a thin paste. After a time the 
 silica and undissolved clay settle to the bottom, leaving a clear solution above. The 
 first and strongest solution, having a specific gravity of M09 to 1-134, is evaporated 
 in leaden pans by the waste heat of the calcining furnaces, and the weaker solutions 
 are used for lixiviating fresh quantities of crude sulphate. 
 
 The solution, after being evaporated to a specific gravity of about 1-152, is allowed 
 to settle in tanks, and the clear liquid evaporated till it has a specific gravity of 
 1-357 or 1-420, and forms when cold a hard mass; it is then fun into moulds made of 
 lead. When the solution contains iron, a small quantity of yellow potassium prus- 
 siate is added to it while in the settling tanks, which forms an insoluble precipitate 
 of Berlin blue, that settles out with the other insoluble impurities at the bottom. 
 
 From Cryolite. The preparation of aluminum sulphate from cryolite (A1F 3 + 
 3NaF) is always carried out in connection with the manufacture of soda or sodium 
 hydrate. (See p. 270.) 
 
 From Bauxite. This mineral, containing from 60 to 75 per cent, of alumina, is 
 mixed with calcined sodium carbonate and heated in a reverberatory furnace. The 
 mass then lixiviated yields a solution of sodium aluminate, which is decomposed by 
 carbonic acid and the alumina precipitated ; after washing the alumina, it is heated 
 with sulphuric acid in the usual way. 
 
 Bauxite may also be decomposed either by heating it to redness with sodium sul- 
 phate and charcoal, or by boiling it with caustic soda. In both cases sodium alumi- 
 nate is formed, which is treated in the manner above described. Sodium aluminate 
 is also formed by passing superheated steam over a mixture of bauxite and common salt. 
 
 The methods above described involve the consumption of a large quantity of 'fuel 
 for dissolving the aluminum hydrate in sulphuric acid ; and insoluble basic alu- 
 minum sulphate is liable to be formed. Pemberton has, therefore, introduced the 
 following method by which these inconveniences are got rid of. A quantity of 
 moist aluminum hydrate (containing 38 per cent, of aluminum hydrate) is mixed 
 with such a quantity of sulphuric acid that the whole corresponds to the composition 
 of the aluminum sulphate, inclusive of the 18 molecules of water. The rise of tem- 
 perature caused by the mixing is sufficient when large quantities are operated upon 
 to determine the solution of the alumina in the sulphuric acid, and upon cooling the 
 whole forms a hard mass. When bauxite is used for preparing aluminum sulphate, 
 soda and caustic soda are always produced at the same time. (See p. 271.) 
 
 From Blast Furnace Slag. Liirmann's process consists in heating the granulated 
 slag with hydrochloric acid in a vat covered with a lid, to dissolve the alumina, which 
 is then precipitated by adding finely powdered calcium carbonate. The precipitate, 
 after being washed, is dissolved with sulphuric acid, the clear liquid drawn off from 
 the undissolved silica, and evaporated. Owing to the fact that ferrous oxide is not 
 precipitated by calcium carbonate, aluminum sulphate thus prepared -is but little 
 contaminated with iron, provided the access of air is prevented, after adding the cal- 
 cium carbonate. 
 
POTASH ALUM. 307 
 
 Uses. Aluminum sulphate may be used in nearly all cases as a substitute for alum 
 and since the useful qualities of alum are essentially due to the alumina contained in 
 that salt, it is obvious that there is an advantage in using aluminum sulphate, instead 
 of ordinary alum, inasmuch as it is cheaper, and contains a larger amount of 
 alumina ; it is also more soluble than potash alum. Aluminum sulphate has, how- 
 
 ___ ----- ------ sulphate as free 
 
 from iron as ordinary alum. 
 
 POTASSIUM AND ALUMINUM SULPHATE 
 
 FOBMULA A1K,2S0 4 + 12H 2 0. MOLECULAJJ WEIGHT 474-6. 
 
 History. The history of this salt is rendered somewhat uncertain, not only by 
 the fact that in early times it had different names, but also because the term alum 
 ((rriTTTepia of the Greeks and alumen of the Romans) was applied to very different 
 substances. 
 
 The substance termed oi-tirrepfci was known before the fifth century. It was 
 mentioned by Herodotus in the first century of the Christian era, and Dioscorides 
 described it as being found in Egypt, upon Melos, in the Lipari Islands, in Sardinia, 
 Macedonia, Phrygia, Armenia, etc. Pliny, who is the first author that makes mention 
 of alumen, speaks of several kinds : white alum, used for dyeing wool bright colours, 
 and black alum, for giving a dark colour. The same author mentions that alum is 
 coloured black by galls. 
 
 Hence it follows that the ancients either had no true alum, or at least it must 
 have been considerably contaminated with iron, for pure alum is not coloured by 
 gall nuts. Most probably the o-TiirTepla of the Greeks and the alumen of the Romans 
 was a mixture containing alum and a large quantity of iron sulphate. 
 
 The Arabian chemist Geber, who lived in the eighth century, was certainly 
 acquainted with pure alum. In his day, large quantities of alum came into the 
 market from the East. The same chemist described the burning of alum. 
 
 At the time of the taking of Constantinople by the Arabians, the manufacture 
 of alum was introduced into Italy by De Castro, who learnt the method of preparing 
 it during his travels in the East ; and on returning to his native country, recognised, 
 near Tolfa, a plant which he had observed to be characteristic of the alum districts in 
 the East. Upon examining the soil it was found to contain alum, and the immediate 
 result was the foundation (in 1458) of alum-boiling works on the spot. Soon after- 
 wards the manufacture of alum was commenced in Germany. The alum works near 
 Diibein existed at the beginning of the sixteenth century. 
 
 The alum works of Li6ge were famous at the beginning of the present century. 
 In 1806 there were no less than 23 alum works in the neighbourhood, and even at an 
 earlier period South Germany was entirely supplied with alum from Li6ge. 
 
 Occurrence. Alum occurs naturally, but only in small quantities, chiefly in 
 volcanic districts, as an efflorescence on the surface of fissures in lava ; also in coal 
 districts, as at Saarbriicken, and upon alum shale. 
 
 The mineral known as alunite occurs in much larger quantities than alum itself 
 in volcanic districts, and its composition is similar to that of alum, being repre- 
 sented by the formula : 
 
 A1 2 3S0 4 + K 2 SO t + 2A1 2 3 ,12H 2 0. 
 
 Composition. Potash alum is a double salt containing aluminum sulphate and 
 potassium in the state of sulphate, combined with water of crystallisation. 
 
 Characters. Alum is a colourless transparent substance, crystallising in forms 
 belonging to the regular system, generally in octahedra. When heated to 60, alum 
 loses 18 molecules of water. At a still higher temperature it gives off the remainder 
 of its water of crystallisation, swells up considerably, and is converted into burnt 
 alum. It is soluble in water, more so in hot than in cold water. 
 
 The following table gives the proportion of alum dissolved by 100 parts of water 
 at different temperatures : 
 
 Temp. C. Amount of Alum dissolved 
 
 3-90 
 
 10 9-52 
 
 20 15-13 
 
 30 22-01 
 
 40 30-92 
 
 50 44-11 
 
 Temp. C. Amount of Alum dissolved 
 60 66-65 
 
 70 90-67 
 
 80 134-47 
 
 90 209-31 
 
 100 357-48 
 
308 
 
 ALUMINUM. 
 
 Upon adding ammonia in excess to an aqueous solution of alum, pure aluminum 
 hydrate is precipitated ; but basic aluminum sulphate is precipitated when the 
 ammonia added is not quite sufficient to decompose all the alum in solution. By 
 carefully adding to a solution of alum sodium carbonate, but not sufficient to cause a 
 permanent precipitate, a solution of basic aluminum sulphate is obtained, known as 
 neutral alum. By heating this solution, basic aluminum sulphate is precipitated, 
 and when the solution is allowed to evaporate slowly in the air, cubic crystals of 
 alum are obtained. This cubic alum occurs in Roman alum. A solution of neutral 
 alum may also be prepared by treating a solution of alum with freshly precipitated 
 aluminum hydrate, until it ceases to be dissolved. 
 
 Roman Alum differs from ordinary alum in containing rather more alumina, and in 
 being crystallised in cubes, instead of octahedra. It dissolves in water without change, 
 but upon heating the solution to 42 basic alum is deposited ; and the solution con- 
 tains ordinary alum, which crystallises in octahedra. Roman alum is characterised 
 by great purity, but it generally presents a slightly rubbed appearance, and is often 
 covered with a reddish earth. 
 
 The term alum is now applied to a number of salts having a composition analo- 
 gous to that of potash alum, but having either the aluminum or the potassium re- 
 placed by kindred metals. The following formulae represent the relations of some of 
 these salts : 
 
 Potash alum A1 2 3S0 4 + K 2 S0 4 --24H 2 = 
 
 Chrome alum Cr 2 3S0 4 + K 2 S0 4 + 24H 2 = 
 
 Soda alum Al 2 3S0 4 + Na 2 S0 4 + 24H 2 = 
 
 Ammonia alum A1 2 3S0 4 + 2NH 4 S0 4 + 24H 2 = 
 
 2(A1K 2S0 4 +12H 2 0) 
 2(CrK 2S0 4 +12H 2 0) 
 2(AlNa 2S0 4 +12H 2 0) 
 2(A1NH 4 2S0 4 +12H 2 0) 
 
 Since potassium salts are comparatively dear, and the action of alum is essentially 
 due to the alumina it contains, potash or ordinary alum has of late been considerably 
 replaced by ammonia alum. 
 
 Preparation. Alum is prepared from various raw materials. Small quantities 
 are extracted from certain kinds of lava, and Roman alum is prepared from alum 
 stone ; but the greater part of the alum of commerce is prepared from alum shale. 
 
 Preparation from Lava. The alum found in volcanic districts is no doubt formed 
 by the action of free sulphuric acid, originating by the oxidation of sulphur and sul- 
 phuretted hydrogen in moist air, upon lava containing alumina and potash. Alum is also 
 formed by the action of volcanic heat upon alum stone, in the Auvergne, in solfatara, 
 and in burning coal seams ; in each instance it occurs mostly as an efflorescence. 
 
 In solfatara the efflorescence of alum is promoted by increasing the surface ex- 
 posed to the air by breaking the lava into small pieces and stacking them up in walls ; 
 the alum is then extracted by lixiviation, and the solution evaporated by the natural 
 heat of the soil (about 40). This source of alum is however very unimportant. 
 
 Alum from Alum Stone. This mineral, known as al unite, occurs imbedded in 
 volcanic rocks, but only in small quantities. The most important source of alum stone 
 is at Tolfa, near Civita Vecchia, where there are large alum works. Alum stone also 
 occurs in the Duchy of Piombino, near Montioni in Tuscany, near Tokay in Hungary, 
 on Mont Dore in France, and in some of the islands in the Grecian Archipelago 
 (Milo, Nipoligonte). Alum stone also occurs at Zabreze, in Upper Silesia. The 
 composition of the alum stone of different localities is shown by the following table :- - 
 
 Locality . 
 
 To 
 
 Ifa 
 
 Hungary 
 
 Montioni 
 
 Mt. Dore 
 
 Analyst . 
 
 Vauquelin 
 
 Klaproth 
 
 Klaproth 
 
 Descotils 
 
 Cordier 
 
 Sulphuric acid 
 
 25-0 
 
 16-5 
 
 12-50 
 
 35-6 
 
 27-o 
 
 Alumina . 
 
 43-9 
 
 19-0 
 
 17-50 
 
 40-0 
 
 31-8 
 
 Potash . 
 
 3-1 
 
 4-0 
 
 1-00 
 
 13-8 
 
 5-5 
 
 Water 
 
 4-0 
 
 3-0 
 
 5-00 
 
 10-6 
 
 3-7 
 
 Silica 
 
 24-0 
 
 56-5 
 
 62-25 
 
 
 
 28-4 
 
 Ferric oxide 
 
 
 
 
 
 
 1-4 
 
 It is evident from this table that the composition of alum stone varies, and its 
 constitution has been represented by different formulae ; Cordier represents it as 
 
 2A1 2 3S0 4 
 
 Mitacherlich represents it as 
 A1 2 3S0 4 
 
 5A1 2 S + 15H 2 0. 
 
 K 2 S0 4 + 2A1 2 8 + 12H 2 0. 
 
MANUFACTURE OF ALUM. 
 
 309 
 
 Ordinary alum stone is for the most part amorphous and of a reddish colour ; the 
 purer kind is white and crystalline. It is insoluble in water. When strongly 
 heated it behaves like alum, but when heated only to a dull red heat, water dissolves 
 out from it ordinary alum, while alumina remains behind a result which may be 
 understood by a glance at the formulae representing the composition of alum stone. 
 Hence the preparation of alum from this mineral is very simple ; the alum stone 
 being merely burnt, the calcined mass lixiviated with water, and the solution evapo- 
 rated to crystallisation. 
 
 In burning alum stone great care must be taken that the heating is neither too 
 great nor too little. When alum stone is insufficiently burnt it is not fully disin- 
 tegrated, and if heated too much sulphuric acid is driven off, leaving an insoluble 
 basic compound. The burning operation is generally judged to be complete when 
 vapour containing sulphurous and sulphuric oxides begins to be given off. The opera- 
 tion is carried out either in reverberatory furnaces as at Tolfa where the alum stone 
 is spread upon the hearth of the furnace, or in heaps as at Civita Vecchia in which 
 case it is piled up in alternate layers with fuel, the heap being set fire to and the 
 combustion regulated by draught holes. 
 
 After the alum stone has been roasted, it is gradually mixed with water into a 
 paste, and lixiviated with hot water in large pans. The solution when sufficiently 
 clear is drawn off, evaporated at a temperature of about 50 and allowed to cool and 
 crystallise in vats, upon the sides of which alum deposits ; the mother liquors yield 
 by further evaporation cubic alum. The crystallisation is often carried out so that 
 some cubic alum is deposited with the ordinary octahedral alum. 
 
 Alum prepared in the above manner is known asEoman alum. 
 
 Alum from Alum Slate and Alum Earth. These alum ores consist chiefly of clay 
 slates permeated throughout with finely divided iron pyrites as well as bitumen and 
 carbonaceous substance. Some kinds of earthy brown ooal are also regarded as alum 
 ores. When materials of this kind are exposed for some time to the action of the at- 
 mosphere, a process of oxidation takes place by which the iron pyrites FeS 2 is con- 
 verted into ferrous sulphate, basic ferric oxide and free sulphuric acid. The slower 
 the oxidation the smaller is the amount of ferrous sulphate and the greater the amount 
 of basic ferric sulphate and free sulphuric acid. The free sulphuric acid formed in 
 this process acts upon the clay, forming aluminum sulphate and free silica. Upon 
 lixiviating alum earth that has been thus altered, alum may be precipitated out from 
 the solution by adding to it potassium sulphate, arid on evaporation of the filtrate 
 crystals of ferrous sulphate are obtained. According to the amount of aluminum 
 sulphate or of ferrous sulphate in the oxidised earth depends its value for preparing 
 alum or green vitriol. The following table gives the results of analyses of several 
 different kinds of alum slates and earths. 
 
 
 ALUM SLATE 
 
 ALUM EARTH 
 
 Locality 
 
 Goslar 
 
 Whitby 
 
 Garnsdorff 
 
 Bornstadt 
 
 Analyst . . . . . 
 
 Frick 
 
 Richardson 
 
 Erdmann 
 
 H. MUller 
 
 Silica . . . . '. . 
 
 60-03 
 
 52-25 
 
 50-13 
 
 33-34 
 
 14-02 
 
 Alumina . ..... . ' . 
 
 14-91 
 
 1875 
 
 1073 
 
 1873 
 
 9-65 
 
 Cupric oxide . ,-.>-i. :.*:':. 
 
 0-28 
 
 
 
 
 
 
 
 
 
 Ferric oxide . ' , ....'. 
 
 8-94 
 
 
 
 2-27 
 
 
 
 
 
 Ferrous oxide . . , . .] 
 
 
 
 8-49 
 
 
 
 2-53 
 
 5-22 
 
 Lime . . .. , ( . 
 
 2-08 
 
 1-25 
 
 0-40 
 
 1-16 
 
 0-74 
 
 Magnesia . . .;-.,< 
 
 4-22 
 
 0-91 
 
 1-00 
 
 1-08 
 
 1-02 
 
 Potash . . .''...' 
 
 3-87 
 
 0-13 
 
 
 
 1-78 
 
 I M4 
 
 Soda . . . . : " .' .; 
 
 
 
 0-20 
 
 
 
 0-19 
 
 i 
 
 Iron pyrites .... 
 
 
 
 4-20 
 
 7-53 
 
 2-75 
 
 19-27 
 
 Carbon . *'";'' "'. . ) 
 
 
 (4-97 
 
 22-83 
 
 ) 
 
 
 Hydrogen . , . , " . I 
 
 5'67 
 
 - 
 
 
 
 I 34-63 
 
 43-64 
 
 Nitrogen . ... . 
 
 
 I - 
 
 
 
 
 
 Water . . ) 
 
 
 I 2-68 
 
 2-21 
 
 / 
 
 
 Sulphuric acid .... 
 
 
 
 1-37 
 
 traces 
 
 
 
 0-27 
 2-65 
 traces 
 
 0-67 
 1-87 
 
 o-io 
 
 Chlorine 
 
 Alum slate is often found near coal seams as at Whitby, at Hurlet, and Campsie 
 in Scotland, at Saarbriicken, also in Saxony, Bohemia, Har 
 
 - - - - - ...... * 
 
 , , 
 
 Diisseldorf, and in the neighbourhood of Liege. 
 
 OF THE 
 
ALUMINUM. 
 
 Alum earth, contains more carbonaceous material than alum slate, and it is gener- 
 ally associated with brown coal seams as in Brandenburg, and especially in the lower 
 Oder district near Ereienwalde, Grleissen, Schermeissel, etc., and in the neighbourhood 
 of Muskau and the valley of the Mulde, where the alum works at Schwermsal, near 
 Diiben, are more than three centuries old. 
 
 The alum earth of Bornstadt, in the Mansfield district, lies under the brown coal. 
 Besides these sources, alum earth is found at Bonn, Neuwied, and in several parts 
 of France and Austria. 
 
 Roasting of Alum Ores. Various methods are adopted in roasting alum ore. Some 
 kinds are sufficiently oxidised when exposed for some time to the action of the atmo- 
 sphere ; more frequently, however, the application of heat is requisite in order for 
 complete oxidation. At Bornstadt both methods are combined ; the alum earth is piled 
 up upon large well-ventilated clay stages, in layers 6 or 7 feet in depth, and left for 
 three years, a process of lixiviation being carried out each year, the specific gravity of 
 the liquor after the first year being 1125, the second year T091 to T108, and the third 
 year T067 to 1'075. At the end of the third year the mass is piled up in heaps, which 
 in a short time take fire spontaneously, and the ore is thus roasted by the combus- 
 tion of its carbonaceous material, or if it does not contain a sufficient amount, some 
 small coal or brushwood is added. The combustion is prevented from becoming so 
 active at any part of the heap as to cause the formation of too much sulphurous acid, 
 by covering the heap with earth or lixiviated ore. 
 
 As a rule, alum slate contains too little combustible material for burning it, and 
 therefore in most places it is heaped up with alternate layers of fuel. The roasting 
 heaps are made by covering a layer of brushwood, 110 feet long and from 6 to 10 
 feet wide, with a layer of 2 feet of alum slate. The brushwood is set fire to in the 
 middle of the heap, and the combustion is promoted by small openings. When 
 the combustion has extended sufficiently throughout the mass, a fresh quantity of 
 brushwood is laid on, and upon it a layer of alum slate of the same proportions as 
 before ; these successive operations being continued until eight or ten layers of alum slate 
 have been piled up ; the last layer of alum slate requires to be very compact so as to 
 keep out rain from the heap. The combustion must be conducted so slowly that 
 some months elapse before it is complete. 
 
 According to Mohr's method, the roasting is carried out in shaft furnaces, and the 
 ore is drawn out below, while fresh supplies are thrown in above, so that the process 
 is continuous. 
 
 Laminne's method consists in passing through the roasting heap sulphurous oxide 
 mixed with air and steam, the sulphurous oxide being a by-product of the roasting of 
 metallic sulphides. By this method the yield of alum is said to be greatly in- 
 creased. 
 
 Lixiviation of the Roasted Shale. This operation is often conducted in vats or 
 tanks arranged at different levels as in the extraction of soda from soda ash, so that a 
 given quantity of water is made to act successively upon several portions of material. 
 The liquor thus obtained is sometimes concentrated by evaporation, by running it 
 over the surface of thorn faggots as in the preparation of salt. In any case, during 
 the lixiviation a continual oxidation of the ferrous sulphate present in solution takes 
 place, and insoluble ferric sulphate is deposited, The liquor, after having been left to 
 settle, then contains chiefly aluminum sulphate, ferrous sulphate, together with alka- 
 line sulphates and chlorides and free sulphuric acid. The concentration of the liquor 
 is generally carried to such a degree that it has adensity of from 1'09 to I'lo, but not 
 more, since the muddy deposit would in that case retain some aluminum sulphate. 
 
 Soiling of the Liquor. This is conducted differently according to the relative pro- 
 portions of aluminum sulphate and ferrous sulphate. When the former preponderates, 
 and the liquor containsbut little ferrous sulphate, it is boiled down until it has a specific 
 gravity of T357 to T41, and then by .adding potassium chloride or potassium sulphate 
 alum is precipitated from it. Sometimes the solution from which the alum has been 
 separated is evaporated to obtain ferrous sulphate. When this is to be done 
 the precipitation of alum must be effected by potassium sulphate, so as to avoid the 
 conversion of the iron salt into chloride. 
 
 When the liquor contains much ferrous sulphate and but little aluminum sulphate, 
 it is either evaporated until it has a, specific gravity of 1-262 to 1-383 and then cooled, 
 in order that the, ferrous sulphate may crystallise out, or it is evaporated with constant 
 addition of mother liquor from previous operations until it has a specific gravity of 
 1'357 to 1'383 and ferrous sulphate begins to be deposited in the boiling pans. In case 
 the shale operated upon contains a sensible amount of potassium salts, the liquor is in 
 the first instance evaporated just so far that alum crystallises out, and when this has 
 been separated the boiling down is continued until greater pait of the ferrous sulphate 
 
MANUFACTURE OF ALUM. 311 
 
 has been deposited siml the mother liquor can be treated with potassium sulphate for 
 the purpose of precipitating alum. 
 
 The evaporating pans are either stone cisterns or leaden pans, and in some places 
 the liquor is heated by passing flame and hot gas from a furnace over the surface, 
 while in their places the pans are open and heated from below. 
 
 Precipitation of Alum. The solution containing aluminum sulphate when suffi- 
 ciently concentrated is first run into settling vats, and thfti into coolers, where it is 
 mixed with a hot concentrated solution of potassium salt, the whole being well stirred 
 meanwhile, so as to make the alum separate in a pulverulent form. It is requisite to 
 avoid the formation of large crystals, because they would retain mother liquor, and be 
 on that account less pure than the finely divided precipitate. The use of potassium 
 chloride for precipitating the alum of course presupposes that the liquor cpntains 
 other sulphates besides aluminum sulphate, and an amount sufficient to convert it into 
 sulphate, for the formation of alum. The proportion of potassium salt to be used 
 must be ascertained by special trials with small quantities of the liquor or by analysis 
 and calculation. 
 
 The alum flour thus obtained is collected upon large wooden strainers, and 
 washed by stirring it with water saturated with alum, so as to remove from the alum 
 flour adhering ferrous sulphate. Centrifugal machines are also used for the purpose of 
 washing the alum flour. 
 
 In order to obtain alum in the form of crystals, the flour is dissolved in hot water 
 until the solution has a specific gravity of 1*498 to 1-530, and then it is run into tub- 
 shaped wooden crystallising vats, where upon cooling it becomes almost entirely solid. 
 When the crystallisation is complete the mother liquor is drawn off and the solid 
 blocks of alum are taken out by removing the sides of the crystallising vats. 
 
 Uses. Alum is used in dyeing and calico printing, as a mordant for fixing 
 colours, also in the preparation of 1 a k e s or compounds of alumina with pigments, which 
 are obtained by mixing extracts of dye stuffs with solution of alum and then precipi- 
 tating the alumina. Alum is useful as a disinfectant, and when added in very small 
 proportion to muddy water, it promotes the deposition of suspended material. It is 
 used together with gelatin or resin soap for sizing paper. Alum combines with 
 gelatin, and is therefore used in tanning leather. When added to melted lard or 
 other kinds of animal fat, it promotes the separation of cellular substances and clears 
 the fat : it is used in medicine as an astringent and caustic. Alum is also used for 
 hardening gypsum casts and for colouring articles made of gold alloys. 
 
 AMMONIA AX.UM. 
 
 FORMULA A1NH 4 2S0 4 + 12H 2 0. MOLECULAR WEIGHT 453 -5. 
 
 This salt is now largely employed in place of potassium alum ; it has exactly the 
 same appearance, the crystalline form is the same, and it has nearly the same solu- 
 bility in water. When the solution is heated with caustic soda or lime, ammonia is 
 disengaged. At a red heat the salt is decomposed, giving off water, ammonium sul- 
 phate, and sulphuric acid, while alumina remains. Poggiale gives the following 
 quantities as representing the solubility of the salt at different temperatures : 
 
 100 parts of water dissolve 
 
 5-22 parts x 0' 
 
 9-16 10 
 
 13-66 - 20 
 
 19-29 
 
 36-51 
 
 71-97 
 
 187-82 
 
 421-90 
 
 ' at a temperature of 
 
 70 
 
 90 
 
 100 
 
 Ammonia alum is prepared in the same manner as potassium alum, a concentrated 
 solution of ammonium sulphate being substituted for the solution of potassium sul- 
 phate in precipitating the alum flour from the liquor containing aluminum sulphate. 
 
 SODIUM AXiUM. 
 
 FORMULA AlNa,2SO, + 12H 2 0. MOLECULAR WEIGHT 45S'5. 
 
 This salt is much more soluble in water than potassium alum, and when its solu- 
 ion is boiled or heated for some length of time to a temperature above 60, it becomes 
 
312 GLASS. 
 
 uncrystallisable. It effloresces readily when exposed to the air. On account of itJS 
 greater solubility it is more difficult to obtain it free from iron than potassium alum, 
 and for this reason it is seldom used. 
 
 SODIUM AI.UMIKTATE, 
 FORMULA AlNa 3 3 . MOLECULAR WEIGHT 144-5. 
 
 This substance has a composition analogous to that of aluminum trihydrate, hy- 
 drogen being replaced by sodium, as shown in the above formula. It is freely soluble 
 in water, and is for many purposes a useful substitute for ordinary alum. 
 
 A solution of sodium aluminate, when mixed with a solution of aluminum chloride, 
 gives a precipitate consisting of aluminum hydrate, according to the following 
 equation : 
 
 2ALNa 3 3 + A1 2 C1 6 + 6H 2 = 4A1H 3 3 + 6NaCl. 
 
 Sodium aluminate is prepared by heating to redness- a mixture of the aluminous 
 mineral called bauxite and soda ash, until the sodium carbonate has been decomposed 
 and a portion mixed with acid no longer effervesces. The mass is then lixiviated 
 with water, the silica remaining undissolved separated by filtration, and the clear 
 liquid evaporated to dryness. This substance may also be prepared from cryolite by 
 the methods already described at page 270, and it is produced in the manufacture of 
 soda according to Balard's method from sodium sulphate, bauxite, and carbon (p. 271). 
 
 Sodium aluminate is used for many of the purposes to which alum is applied ; in 
 dyeing and calico printing, for the preparation of lakes, for hardening stone, and in the 
 saponification of fat in candle factories ; in this case an insoluble aluminous soap is 
 produced which is decomposed with acetic acid, yielding soluble aluminum acetate 
 and fatty acid ; it is also used in making an opalescent glass or kind of semi -porcelain. 
 
 Among the materials employed in the manufacture of utensils for culinary and other 
 domestic uses, there are two which, from a chemical point of view, present great 
 similarity, viz. clay and glass, inasmuch as they are both compounds of silica, chiefly 
 with earthy or alkaline bases. The principles involved in the manufacture of glass 
 and the various kinds of pottery ware are, likewise, so similar, that it is convenient 
 to treat of these two branches of industry together. 
 
 GLASS. 
 
 History. The discovery of glass is described by Pliny as having been the result 
 of an accidental observation of certain Phoenician merchants, while heating a cauldron 
 supported upon soda blocks on the sea-shore. According to this tradition, the melted 
 soda formed glass with the sand beneath ; but the story has little probability, and, 
 moreover, modern research has clearly proved that the manufacture of glass was known 
 at a period much earlier than that referred to by Pliny. Most probably glass was 
 first made by the Egyptians, for some of their oldest works of art are partly made 
 of glass, or ornamented with enamel. At a later epoch the trade in glass was almost 
 entirely in the hands of the Phoenicians, and this may have given rise to the above- 
 mentioned myth. 
 
 In early times the glass works at Thebes, Sidon, and Alexandria were very cele- 
 brated. The first among the Greeks who makes mention of glass is Aristophanes, in 
 the fifth century before Christ. It appears to have been introduced into Italy about 
 the time of Cicero ; and during the reign of Tiberius a company of glass-blowers 
 established themselves in Home, where glass was soon afterwards very extensively 
 in use. Fragments of glass have been found at Herculaneum that are very similar 
 to modern window glass. The first mention of window glass proper is found in the 
 works of Lactantius, written at the end of the third century. During the middle 
 ages, Venice became famous for its glass manufacture, and this branch of industry 
 exists there at the present day in the island of Moreno. From Venice, the secret of 
 glass-making found its way into Bohemia, France, [England, Sweden, and other coun- 
 tries. The exact date of the introduction of glass into Germany is not known, but it 
 is probable that glass was made there earlier than .in the neighbouring countries, 
 although it did not attain great dimensions, owing to its having been carried on in 
 small forest smelting houses, where the materials were cheap. 
 
 Coloured glass, the production of which admits of the use of less pure mate- 
 rials than colourless glas, was known at a much earlier period. According to Seneca, 
 
COMPOSITION OF GLASS. 
 
 313 
 
 the art of making artificial emeralds was discovered by Democritus of Abdera ; other 
 artificial precious stones were, however, known before the time of Democritus. The 
 manufacture of coloured glass attained a high degree of perfection in Rome, and still 
 more so in Venice, whence the art spread to other countries. In ancient times the 
 art of glass painting consisted in connecting together pieces of differently coloured 
 glass with strips of lead. At the present day the art is so perfected that it is possible 
 to give different colours to the same plate of glass. 
 
 Composition. Glass generally consists of a mixture of two or more silicates 
 that have been united by fusion into a homogeneous, hard and brittle mass. The 
 silicates which constitute ordinary glass are chiefly those of potassium, sodium, cal- 
 cium, and lead ; iron, zinc, manganese, barium, and aluminum silicates are also fre- 
 quently present in small proportions, and some kinds of glass also contain borates. 
 
 The following table gives the composition of different kinds of glass : 
 
 
 SiO a 
 
 K a O 
 
 Na 2 
 
 CaO 
 
 PbO 
 
 MnO 
 
 A1 2 3 
 
 Fe a O, 
 
 Analyst 
 
 Window glass, English . 
 
 69-00 
 
 
 
 11-K 
 
 12-50 
 
 
 
 ~ 
 
 7-40 
 
 
 
 ,, French . 
 
 70'00 
 
 
 
 15-00 
 
 13-40 
 
 
 
 
 
 1-50 
 
 o-io 
 
 
 
 Plate ... 
 
 76-90 
 
 
 
 17-50 
 
 3-80 
 
 
 
 
 
 2-80 
 
 
 Payen 
 
 Aix-la-Chapelle 
 
 78-75 
 
 
 
 13-00 
 
 6-50 
 
 
 
 
 
 1-75 
 
 
 
 Benrath 
 
 Bottle Bohemian 
 
 58-40 
 
 1-80 
 
 9-90 
 
 18-60 
 
 
 
 __ 
 
 2-10 
 
 8-90 
 
 Maumene 
 
 Bohemian 
 
 71-70 
 
 12-70 
 
 2-50 
 
 10-30 
 
 
 
 0-20 
 
 0-40 
 
 0-30 
 
 Berthier 
 
 ii ... 
 
 76-00 
 
 15-00 
 
 
 
 8-00 
 
 
 
 
 
 1-00 
 
 
 
 Peligot 
 
 Plate 
 
 67*70 
 
 21-10 
 
 
 
 9-90 
 
 
 
 
 
 1-40 
 
 . 
 
 
 Bottle Sevres . 
 
 53-55 
 
 5-48 
 
 
 
 29-22 
 
 
 
 
 
 6-01 
 
 5-74 
 
 Dumas 
 
 St. Etienne 
 
 60-00 
 
 3-10 
 
 
 
 23-30 
 
 
 
 1-20 
 
 8-00 
 
 4-00 
 
 Berthier 
 
 Optical German . 
 
 62-80 
 
 22-10 
 
 
 
 12-5C 
 
 
 
 
 
 2-60 
 
 
 Dumas 
 
 Crystal French . 
 
 58-00 
 
 8-90 
 
 
 
 2-60 
 
 32-50 
 
 
 
 
 
 
 
 Payen 
 
 English . 
 
 59-20 
 
 9-00 
 
 
 
 
 
 28-20 
 
 
 
 
 
 0-40 
 
 Berthier 
 
 j> 
 
 51-90 
 
 13-70 
 
 
 
 
 
 33-30 
 
 
 
 
 
 
 
 Faraday 
 
 Optical Guinand's 
 
 i2-50 
 
 11-70 
 
 
 
 0-50 
 
 43-50 
 
 1-00 
 
 1-80 
 
 
 
 Dumas 
 
 Characters. Glass as ordinarily met with is a homogeneous mass possessing the 
 peculiar texture characteristic of the alkaline silicates after they have been melted ; it 
 has also a peculiar lustre, and is usually transparent as well as colourless, unless it 
 contains a large amount of metallic oxides which communicate to it colour and opacity. 
 At ordinary temperatures it is hard and brittle ; the fracture is conchoidal ; in thin 
 sheets or threads glass has some degree of flexibility ; when heated to a sufficiently 
 high temperature it becomes plastic and ductile. The characters of glass vary accord- 
 ing to the particular nature as well as the relative proportions of the silicates it con- 
 tains. The greater the amount of silica in glass, the less fusible it is ; the greater 
 the amount of alkali, the more fusible is the glass. The presence of a considerable 
 amount of calcium silicate renders glass less readily fusible. 
 
 The specific gravity of different kinds of glass differs slightly, as shown in the 
 following table by Dumas : 
 
 Bohemian glass . 
 Crown glass 
 Mirror glass 
 "Window glass 
 Bottle glass 
 Crystal or flint glass 
 Optical flint glass 
 
 2-396 
 2-487 
 
 2-488 to 2-506 
 2-642 
 2-732 
 
 2-900 to 3-255 
 3-300 to 3-600 
 
 
 When hot glass is rapidly cooled it becomes very brittle ; this is especially the 
 case when the pieces are thick, as the cooling then takes place very unequally, the 
 outer parts cooling much more quickly than the interior. Glass in this condition is 
 readily affected by change of weather, slight vibrations, etc., and is more apt to crack 
 the more rapidly it has been cooled. When a drop of red-hot glass is allowed to fall 
 into cold water, the surface cools very quickly, and becomes hard while the inner por- 
 tion is still very hot, and consequently expanded. When the interior also cools, it 
 cannot contract owing to the solidity of the outer surface. Glass drops thus prepared 
 are known as Eupert'sdrops or devil's tears; they terminate in a fine thread, 
 upon breaking which the entire drop explodes, and is converted into a fine powder. 
 When the experiment is conducted in a glass vessel filled with water, and having a 
 narrow mouth, the force of the explosion of the glass drop is sufficient to break the 
 
314 GLASS. 
 
 glass vessel. This pulverisation is due to the unnatural and constrained arrangement 
 of the glass particles, consequent upon the rapid cooling, and only a slight vibration 
 is sufficient to effect their mutual repulsion. The so-called Bolognese flasks have 
 a similar construction. These are small flasks with very thick sides that have been 
 very rapidly cooled in the air ; a grain of sand allowed to fall into one of these flasks 
 is sufficient to cause it to crack with a slight report. 
 
 In order to render glass proof against rapid change of temperature, such as takes 
 place when hot water is poured into a glass vessel, as well as the external influences, 
 it must undergo a process of very slow cooling, which is called annealing. 
 
 A remarkable change in glass, through which it becomes dull, opaque, and porce- 
 lainlike, is termed devitrification. It takes place when glass is kept for a long 
 time at a temperature near to its melting point, or when it is very slowly cooled ; 
 also on heating glass in the flame of a blowpipe, which is not sufficiently hot to 
 melt the glass. This devitrification is probably due to the more fusible alkaline 
 silicates melting at a temperature insufficient to fuse the more refractory silicates, 
 which are consequently separated in a crystalline condition. The old theory that de- 
 vitrification is due to the volatilisation of alkali has been refuted by the results of a 
 number of researches. 
 
 A very curious phenomenon is that of the coloration by sunlight of certain 
 kinds of glass ; they acquire first a yellowish colour, which gradually changes to violet. 
 This coloration is probably due to the presence in the glass of ferrous and manganous 
 oxides, the first reaction consisting in the higher oxidation of the ferrous oxide, pro- 
 ducing a yellow colour in the glass ; the protracted action of light and air then 
 oxidises the manganous oxide, the delicate violet colour of which blends with the 
 yellow of the iron oxide, colouring the glass red ; when still more manganese is pre- 
 sent, the glass assumes a violet colour. 
 
 Hydrofluoric acid attacks all kinds of glass, decomposing the silicates of which 
 it consists, and forming silicon fluoride, water, and fluorides of the metals contained in 
 the glass. This property of hydrofluoric acid is taken advantage of industrially for 
 glass engraving. 
 
 The resistance of glass to atmospheric and other influences decreases as the amount 
 of alkali increases ; glass containing a large amount of alkali readily loses its 
 lustre and becomes cloudy ; and it is more easily acted upon both by hot and cold 
 water than glass which is rich in silica. 
 
 Atmospheric moisture is especially injurious to glass, the effect being in propor- 
 tion to the greater amount of bases in the glass. This is often seen in window panes 
 made of bad glass, which after a short time become dull, the effect being due to the 
 separation of a very thin film of silica upon the surface of the glass, by the simul- 
 taneous action of atmospheric moisture and carbonic acid upon the silicate of which 
 the glass consists, and it occurs with greater rapidity in proportion to the degree of 
 moisture and heat to which the window is exposed ; hence the windows of stables and 
 hot-houses very quickly become dull. The action of water upon glass is manifested 
 in an especially unpleasant manner in optical glasses containing a large amount of 
 alkali. "When glass of this kind, owing to its slightly hygroscopic nature, becomes 
 coated with moisture, the water gradually decomposes the glass, rendering it dull, 
 and, in course of time, useless. 
 
 The behaviour of glass towards boiling water, different acids and saline solutions, 
 has been investigated by Emmerling. He found that the action of boiling solutions 
 and boiling water upon glass is, within certain limits, proportional to the time. With 
 new vessels it is somewhat greater at first (during the first hour) and diminishes with 
 longer use. The action is also proportional to the amount of glass surface exposed to 
 the boiling liquid. 
 
 The action of boiling liquids upon glass during a given time is independent of the 
 amount of liquid evaporated. The action decreases with the decrease of temperature 
 of the liquid. Glass is attacked by even small quantities of alkalies. 
 
 The action of most acids, especially in a dilute state, upon glass, is even less than 
 that of water, but sulphuric acid is an exception to this rule, as it, attacks glass more 
 powerfully than water. Glass is acted upon, more powerfully than by water, by solu- 
 tions of salts whose acids form insoluble calcium salts, such as sulphates, phosphates, 
 carbonates, and oxalates, the action increasing with the concentration of the 
 solutions. On the other hand, solutions of salts whose acids form soluble calcium 
 salts, such as chlorides, or nitrates, etc., attack glass less strongly than water, the 
 action decreasing with the concentration of the solutions. 
 
 Varieties of glass differing only slightly in their percentage composition have 
 nearly an equal power of resistance. The Bohemian glass (potash glass) resists reagents, 
 especially acids, better than soda glass. The constituents of glass dissolve in about 
 the same ratio as they are contained in the glass. 
 
GLASS MAKING. 315 
 
 The following table shows the quantity per hour of glass dissolved from flasks 
 having a capacity of 600-700 c.c. by 400 c.c. of different solutions of salts, being the 
 average of from 1 to 30 hours boiling. The glass taken for the experiment was from 
 glass works near Great Rhuden in Hanover, and had the following percentage com- 
 position : 
 
 Silica .... 
 
 
 73-79 
 
 
 
 0-58 
 
 Zinc oxide 
 
 
 0-68 
 
 Manganous oxide . 
 
 
 0-32 
 
 Lime .... 
 
 
 8'61 
 
 Magnesia 
 
 1 
 
 0-12 
 
 Soda .... 
 
 
 13-94 
 
 Potash .... 
 
 
 0-60 
 
 Solvent 
 
 Per cent. 
 
 Quantity of glass dissolved per hour 
 
 Water .... 
 Dilute hydrochloric acid 
 
 11 
 
 0-0021-0-0022 gram 
 . 0-00044-0-00029 
 
 Aqueous ammonia . 
 
 9 
 
 0-0029-0-0033 
 
 
 Sulphuric acid 
 
 2-5 
 
 . ,,,'j 0-0038 
 
 
 jj 
 
 5 
 
 p .... . 0-0044 
 
 
 l> 5> 
 
 2-5 . 
 
 ' . . , ; ..,. 0-0036 
 
 
 Sodium carbonate . 
 
 1 
 
 .' *,; . . 0-0329-0-0355 
 
 
 
 
 0-25 
 
 . . . 0-0171-0-0189 
 
 
 Caustic potash 
 
 0-25 
 
 . . . . ' 0-0115 
 
 
 Potassium chloride . 
 
 10 
 
 0-0014-0-0017 
 
 Sodium sulphate 
 
 2 
 
 . . ^ . ;>"., o-ooeo 
 
 Preparation. Glass is made by melting together various materials containing 
 silica and the requisite basic oxides so as to form silicates, and while the mass is in 
 a melted state it is worked into the different shapes requisite for the purposes to 
 which it is to be applied. The materials used in making glass are the following: 
 
 Siliceous Materials. The most convenient material to use as a source of silica for 
 glass manufacture is sand, owing to the fine state of division in which it occurs. 
 In the manufacture of ordinary glass any convenient river cr sea sand may be used ; 
 but in the preparation of white glass only the purest sand can be used, such as is found 
 in the Isle of Wight, near Lemgo in Germany, and at Fontainebleau in France. Such 
 sand is, however, previous to use, freed from mechanical admixtures of clay, etc., by 
 washing. 
 
 Both quartz and flint occur abundantly in certain districts in a sufficiently 
 pure state for making glass ; before being used, they require to be reduced to a fine 
 state of division, an operation which is very tedious, owing to their hardness. It is 
 effected by heating the materials to redness, and then cooling them in water. This 
 gives rise to a number of small fissures, and by stamping and grinding the previously 
 hard mass can then easily be reduced to a fine powder. 
 
 Infusorial earth, consisting of the siliceous remains of infusoria, is on accountof 
 its fine state of division and great purity very suitable for glass manufacture. 
 
 Benrath recommends the use of granite as the siliceous material for making 
 glass. "Experiments made by him with granite from quarries in Finnland, which 
 contained 75 to 78 per cent, of silicic acid, 10 to 12 per cent, of alumina, and 4 to 6 per 
 cent, of potash, yielded very good results. 
 
 Basic Materials. In the manufacture of ordinary glass, crude potash is em- 
 ployed as the potassium constituent ; but for the better kinds of glass, refined potash 
 must be used. For the commonest, sort of glass, wood ashes may be used. 
 
 Formerly, the soda used in the manufacture of glass was obtained by the in- 
 cineration of land and marine plants, and known as kelp or varec. Afterwards 
 the purer soda obtained by Leblanc's process was employed ; it is used in the calcined 
 state, and, according to the quality of glass required, more or less pure. 
 
 Since the beginning of the present century, sodium carbonate has been almost en- 
 tirely replaced by sodium sulphate, or Glauber's salt, used in the calcined state. To 
 this is added about 5 per cent, of powdered charcoal, which facilitates the volatilisa- 
 tion of the sulphuric acid, the reaction consisting in the reduction of sulphuric acid to 
 sulphurous oxide, which escapes as gas. The formation of glass is accelerated by 
 this process. In some places common salt is employed ; in the manufacture of glass, 
 but its decomposition is very slow and difficult. A better material js found in pan 
 scales, or the scaly mass adhering to the cauldrons in which brine is evaporated. 
 
SI6 GLASS. 
 
 It consists essentially of a mixture of gypsum, sodium chloride, and sodium sulphate. 
 The best material for supplying calcium is chalk, which is used in the powdered 
 condition. In the manufacture of common kinds of glass, the selection of the chalk is 
 unimportant, but for glass of better quality, chalk free from ferrous carbonate must 
 be used. In districts where chalk is scarce, ordinary limestone is used, either 
 merely powdered, or, as in France, previously burnt and then reduced to a fine powder 
 by exposure to the air. The limeashes from soap works, consisting of calcium 
 hydrate, calcium carbonate and potassium carbonate, or sodium carbonate, form a mate- 
 rial very suitable for use in the manufacture of glass. 
 
 Calcium fluoride, a by-product obtained in the preparation of soda from 
 cryolite, is from its ready fusibility very suitable for use in glass-making. 
 
 In French glass works, heavy spar is used in the state of powder. It is said to 
 exert a very solvent action upon the sand, and yields a very homogeneous and easily 
 fusible glass, which admits of being easily worked. Strontia has also been pro- 
 posed as a constituent of glass. 
 
 In the preparation of crystal or flint glass and other kinds which contain lead as 
 an essential constituent, red lead (Pb 3 4 ) is used. It is decomposed upon melt- 
 ing into lead oxide and oxygen ; the liberation of oxygen ensures the oxidation of 
 any organic substances present, and thus prevents the reduction of the lead oxide to 
 metallic lead. Litharge is less frequently used, since metallic lead is apt to be pro- 
 duced. 
 
 Zinc oxide is used in Belgian glass works. Wagner recommends the use of 
 blende, and gives the following recipe for making zinc glass : 
 
 Glauber's salt 213 parts 
 
 Blende 48'6 
 
 Sand . 205-1 
 
 Manganese peroxide is used in glass-making to neutralise the green colour 
 caused by the presence of iron ; it is therefore obvious that the manganese peroxide 
 must .be itself free from iron. Another purpose served by manganese peroxide is the 
 oxidation of organic substance, thus preventing discoloration of the glass by carbon. 
 
 Felspar and other easily fusible silicates are but seldom used in the manu- 
 facture of glass, and only for glass of inferior quality; the same may be said of basalt 
 and blast furnace slag, which are sometimes used in making bottle glass. In 
 many places arse nous acid is used for oxidising organic substance by its decom- 
 position into free oxygen 'and metallic arsenic which escapes as vapour. 
 
 The several raw materials used in making glass are now nearly always employed 
 in a fine state of division. When necessary they are first of all stamped, then ground 
 and passed through sieves ; afterwards they are mixed together upon a smooth floor 
 with shovels. The mixing is completed in an apparatus introduced by Chance, which 
 consists of a wooden box with a round bottom, in which a roller furnished with stout 
 projections is made to revolve. The mixture is introduced through a wooden hopper 
 in the lid, and the thoroughly mixed powder is withdrawn through a trap at the bottom 
 of the mixing box. 
 
 BOTTLE GLASS. The materials used in the manufacture of bottle glass differ very 
 much. For green, yellow, brown and other coloured varieties, impure raw materials 
 may be used, provided that the silica and the basic oxides are taken in correct pro- 
 portions. If bottle glass contains too much alkali, it may be acted upon by acid 
 liquids; if it contains too much silica, it is difficult to melt. To produce white bottle 
 glass the materials must be very carefully selected. If perfectly colourless glass is 
 required, potash must be used in place of soda, because soda glass always has a bluish- 
 green tinge. 
 
 The following table shows the composition of mixtures for different kinds of bottle 
 
 100 100 40 
 35 
 165 
 35 
 6 
 
 8 
 
 10 8 
 
 80 
 50 
 
 80 
 100 
 
 Green Bottle Glass. 
 
 Yellow sand . 
 
 100 
 
 100 
 
 Fresh wood ashes . 
 
 60-70 
 
 50 
 
 Exhausted ashes 
 
 . 160-170 
 
 
 
 Varec soda . 
 
 30-40 
 
 200 
 
 Common salt 
 
 
 
 
 
 Glauber's salt 
 
 
 
 
 
 Chalk . ' . 
 
 . 
 
 
 
 Clay loam 
 
 80-100 
 
 80-100 
 
 Iron slag 
 
 
 
 
 
 Iron spar 
 
 . 
 
 
 
 Cullet (broken glats) 
 
 100 
 
 100 
 
GLASS MAKING. 317 
 
 Pale Coloured Bottle Glass. White Bottle Glass. 
 
 Sand . . 100 100 . 100 100 100 
 
 Potash . . . 50-60 30-35 . 50-60 41 '5 54 
 
 Lime . . . 10-12 17 . 10-12 17'5 15 
 
 Ashes . . . 110-120 . 
 
 Manganese . . 0-5 0'25-0'5 . 0'5 (?) 1 
 
 Cullet . . . 60-66 . 100 
 
 Very frequently, however, in the mixture for white glass, and especially for pale 
 coloured glass, the potash is partly or entirely replaced by soda. 
 
 CRYSTAL OB FLINT GLASS is a potash and lead glass, that may be considered as 
 a double silicate of potassium and lead. Pure lead silicate has a yellowish colour, 
 which disappears when melted with a sufficient quantity of potassium silicate. Bis- 
 muth might be substituted for lead, if it were not too costly. Eecently, however, zinc 
 has been brought into use in the place of lead. 
 
 Pure crystal glass is absolutely colourless, and refracts light more strongly than 
 ordinary kinds of glass. Its specific gravity is between 2'900 and 3-255. 
 
 The materials used in the manufacture of crystal glass must be of the greatest 
 purity. The silica must be perfectly free from ferric oxide and manganic oxide. It 
 is, therefore, advisable in some instances to wash the sand with dilute hydrochloric 
 acid before using it, then to remove the acid by means of water, and dry the sand at 
 a red heat. Sometimes the sand is cleansed by washing several times with pure 
 water, by which means the particles of clay are suspended and removed. 
 
 Usually, the potash undergoes purification by treating the crude potash with a 
 small quantity of water, so that only the potassium carbonate is dissolved, whilst 
 the potassium sulphate and other impurities remain undissolved ; by evaporation 
 of the water and calcination, the potash is again perfectly dried. 
 
 The lead oxide of commerce is scarcely ever sufficiently pure, as it contains cupric 
 oxide, ferric oxide, and manganic oxide, which would impart colour to glass prepared 
 with it. Generally, therefore, the lead oxide is prepared in the crystal glass factory 
 itself by heating pure lead in a reverberatory furnace at a moderate temperature, and 
 thus converting it into red lead (Pb 3 4 ). The use of red lead has the great advan- 
 tage that the oxygen liberated from it upon heating, oxidises any organic substance 
 that may be present in the raw material of the glass mixture. This is so far essen- 
 tial that, by the removal of oxygen from lead oxide by organic matter, it would be 
 reduced to metallic lead, and thus cause cloudiness in the glass. With the same 
 object, the oxidation is in some manufactories effected by an addition of saltpetre. 
 
 The composition of the glass mixtures used in different crystal glass manufactories 
 varies very much. In the following table some of them are placed side by side : 
 
 Sand 300 300 300 300 100 100 
 
 Eed lead 200 200 215 180 70 60 
 
 Potash 100 90-95 110 120 30 20 
 
 Saltpetre 10 
 
 Borax 10 
 
 Glass cullet 300 100-200 300 
 
 To these mixtures is often added - 45 of manganese peroxide or 0'60 of arsenous 
 acid. Occasionally borax also is added ; boracic acid, as before mentioned, increas- 
 ing the brilliancy of the glass considerably. 
 
 WINDOW AND SHEET GLASS. Window glass, in respect to its composition, is of 
 two kinds, potash glass and soda glass. The first, of which the manufacture was 
 formerly general, contains potash as the basis of the glass mixture ; the latter, soda. 
 In countries where wood abounds, such as Bohemia, a considerable quantity of potash 
 glass is still manufactured ; but almost everywhere else soda glass is made. 
 
 Glass Mixtures for the Manufacture of Bohemian (Potash) Glass. 
 Powdered quartz ... 100 110 120 100 
 
 Purified potash 60 64 60 54 
 
 Chalk ' 20 24 15 
 
 Manganese 
 
 Saltpetre 
 
 Arsenous acid 0-5' 0'5 0-5 
 
 To these materials is always added about as much broken glass (cullet) as the 
 weight of powdered quartz, sometimes more, sometimes less. 
 
318 GLASS. 
 
 Glass Mixtures for Soda Glass. 
 
 Sand 
 
 Powdered quartz 
 
 Chalk 
 
 Soda 
 
 Sodium sulphate 
 
 Arsenous acid . 
 Charcoal 
 
 
 Payen 
 
 
 Escautpont 
 
 Muspratt 
 
 100 
 
 100 
 
 100 
 
 50 
 
 560 
 
 
 
 
 
 
 
 50 
 
 
 
 35 
 
 40 
 
 13 
 
 30 
 
 154 
 
 28 
 
 35 
 
 
 
 
 
 119 
 
 
 
 
 
 58 
 
 40 
 
 63 
 
 0-25 
 
 0-25 
 
 
 
 1-5 
 
 
 
 0-20 
 
 0-20 
 
 
 
 
 
 2 
 
 __ 
 
 
 
 4-5 
 
 2-5 
 
 
 
 60 
 
 180 
 
 25 
 
 variable 
 
 448 
 
 It will be seen from the foregoing instances that the preparation of glass mixtures 
 is exceedingly variable both as regards the ingredients and their proportions. Accord- 
 ing to the Keport of the International Exhibition in London in the year 1862, the 
 following glass mixtures are used in different countries : 
 
 England Prussia Bohemia France 
 
 Sand . . . . 100 100 100 100 100 
 Limestone . . .38 
 
 Chalk ... 37 30 35 
 
 Sodium sulphate . 28 34 36 
 
 Potash ... 20 
 
 Soda .... 5 24 
 
 Common salt . . 
 
 Powdered coke . . 1-3 2-25 175 
 
 Arsenous acid . . 1 1 1 I '25 
 
 Willow or elm ashes . 40 
 
 Smalt ... 0-1 
 
 PLATE GLASS. In making the thick sheets of glass used for mirrors and of late 
 years also for windows and various other purposes, the materials are mixed in such 
 proportions as to form a somewhat more fusible glass than that used' in making ordi- 
 nary sheet or window glass. 
 
 The thickness of the plate glass necessitates a very colourless material, and for 
 this reason potash glass would be preferable, because of its greater freedom from 
 colour. But soda glass is used, since it is more fusible and, therefore, better adapted 
 for clearing and casting, great care being taken in the selection of the raw materials. 
 In making very thick plates, for mirrors especially, great care must be exercised to 
 produce the whitest glass possible, because any colour in the glass becomes more 
 manifest with the increased thickness of the plate. Plates of a medium size are - 
 made from one sixth to one half an inch in thickness, but very large plates are made 
 thicker still. 
 
 The thickness of the larger plates especially increases the danger of the occur- 
 rence of waves, knots, clouds, etc. in the glass. These flaws only become apparent 
 when the manufacture is advanced comparatively far, and considerable cost has been 
 incurred ; all that can be done then is to cut the better portions into smaller plates. 
 It is particularly for the avoidance of such flaws that soda glass, as an easily fusible 
 glass, is used ; and as the fusibility augments with the amount of soda, this is carried 
 as far as possible, without rendering the glass hygroscopic, and consequently liable 
 in the course of time to become dull on the surface. 
 
 Ordinary soda is used for the most part, but in many cases sodium sulphate 
 or Glauber's salt and charcoal are also added. 
 
 For Mirror Glass. 
 
 I. ii. in. 
 
 Sand 300 100 100 
 
 Soda 100 33 
 
 Glauber's salt 3D 
 
 Lime (pulverised in the air) ... 43 14 
 
 Limestone 39 
 
 Manganese peroxide .... 0-f> 
 
 Arsenic 0*4 
 
 Wood charcoal 2 -ft 
 
 Broken glass 300 100 
 
 OPTICAL GLASS. This is a finer kind of lead glass, which is principally used for 
 
GLASS MAKING. 319 
 
 optical purposes. It should therefore be as as colourless possible, and free from waves, 
 cloudiness, or air-bubbles. Its specific gravity is from 3'3 to 3*6. 
 
 Flint glass in moderately large pieces, free from flaw, and suitable for optical 
 purposes, was for a long time a desideratum. It was first obtained by Guinand, and 
 the manufacture was considerably improved by his successor Bontemps. 
 
 The glass mixture used by Bontemps gives a glass having a specifi gravity of 
 3 - 6, and has the following composition : 
 
 Sand 300 
 
 Eedlead . 300 
 
 Potash . : .'.. 90 
 
 Guinand added to the foregoing mixture : 
 
 Borax 5.5 
 
 Saltpetre . 4 
 
 Arsenous acid ... 1 
 
 Manganese peroxide 1 
 
 The lenses of telescopes and other optical instruments consist of a combination of 
 two kinds of glass. Flint glass is highly refractive, but as the different rays are 
 variously refracted, the resulting image is coloured at the edges. For the removal of 
 this dispersion, crown glass is combined with flint glass and an image is thus obtained 
 with sharp uncoloured edges. 
 
 The manufacture of optical crown glass is conducted essentially in the same way 
 as that of flint glass ; but on account of the greater heat required, it is still more 
 difficult. The mixture used by Bontemps consisted of 
 
 Sand 120 parts 
 
 Potash ; - . . 35 
 
 Soda fl . . - . . . 20 
 
 Chalk . .' . 15 
 
 Arsenous acid . . . , . .' ^. ' 1 
 
 COLOURED GLASS. Glass is coloured for different purposes, as, for instance, the 
 preparation of artificial precious stones, coloured sheet glass, bottle glass, etc. In 
 making artificial gems an extra pure glass, called s trass, is prepared with powdered 
 rock crystal, and pure potassium carbonate or caustic potash, and red lead that is 
 perfectly free from copper, iron, or manganese. Borax is also usually added in the 
 preparation of strass, but it must previously be purified by repeated recrystallisations. 
 The following is a mixture f^r the production of strass : 
 
 Eock crystal 
 Bed lead . 
 Caustic potash 
 Borax 
 Arsenous acid 
 
 300 
 
 470-460 
 
 163-168 
 
 22-18 
 
 1-0-5 
 
 The materials are finely powdered, thoroughly mixed, and melted in porcelain, 
 or Hessian crucibles. 
 
 Amethyst is obtained by the addition of a small quantity of manganic oxide, 
 cobalt oxide, and purple of Cassius. 
 
 Emerald by the addition of a little cupric oxide and chromic oxide. 
 
 Kuby by the addition of manganic oxide. 
 
 Topaz by the addition of antimony glass and a very little purple of Cassius. 
 
 Sapphire by the addition of smalt. 
 
 These materials, as well as the strass, are very finely powdered, thoroughly 
 mixed and melted together. 
 
 The production of variously coloured sheet and bottle glass is carried out accord- 
 ing to different methods. The glass is either coloured throughout the entire mass when 
 it is made, or in working the glass by the usual methods a thin layer of coloured glass 
 is extended over one surface by an operation that is called flashing and caseing. 
 "When the glass is coloured throughout, the colouring materials are melted together 
 with the glass in the ordinary manner. 
 
 Bed glass can be prepared by adding cuprous oxide to the glass metal ^generally 
 copper scale is used, a small quantity of soot or iron filings being added to reduce any 
 cupric oxide present, the green colour of which would injure the red colour of the 
 glass. Cuprous oxide glass is mostly used as a coating, because it would be too dark 
 and opaque in a mass. The finest red, however, is obtained by the use of a gold 
 solution, or the purple of Cassius; a solution of gold in aqua regia, or gold chloride 
 can also bo used. 
 
320 GLASS. 
 
 The following mixture is given by Muspratt and Stohmann : 
 
 Sand 20 
 
 Kedlead 16 
 
 Hungarian potash 2 
 
 Saltpetre- 2'5 
 
 Of this mixture 20 parts are mixed and melted with 
 
 Borax 1'56 
 
 Tin oxide '12 
 
 Antimony oxide '12 
 
 Gold solution .... sufficient to produce the colour required. 
 
 Yellow glass is obtained by adding charcoal to the glass mixture, and a finer 
 colour by means of glass of antimony. But the finest yellow is produced by covering 
 the glass to be coloured with a mixture of clay and silver chloride, and heating it in 
 a muffle. A fine greenish-yeljow coloured glass is obtained by the addition of 
 uranium oxide to the metal. 
 
 Blue glass is obtained by adding cobalt oxide, in the shape of smalt, 
 
 G-reen glass is made by adding chromic oxide or cupric oxide ; a less beautiful 
 colour is produced by ferrous salts. The colour of bottle glass is due to the latter. 
 
 Violet glass is obtained by manganic oxide; with a blue shade by manganic 
 oxide and a little smalt. 
 
 Black glass is only known in the opaque condition; it is produced by the 
 addition of ferrous oxide, or cuprous oxide and smalt. 
 
 Opaque white glass is obtained by the addition of bone ash to colourless glass. 
 The lime phosphate is not dissolved, but remains suspended in the metal, rendering 
 the glass opaque. 
 
 Alabaster glass is prepared with a very small addition of bone ash. It differs 
 from ordinary opaque white glass in containing an excess of silica. 
 
 In American, Bohemian, and Silesian manufactories, cryolite glass has been 
 prepared for some years. Benrath uses for this purpose a glass mixture of 1 pai t of 
 cryolite and 2 parts of sand. 
 
 GLASS PAINTING. Formerly coloured glass windows were made by setting pieces 
 of differently coloured glass in the manner of mosaic-work by means of lead, the 
 shading being effected with colour on the back. Afterwards uncoloured glass was 
 painted as in ordinary painting. The colours used are metallic oxides, cobalt oxide, 
 chromic oxide, etc., which are mixed with an easily fusible glass, painted with tur- 
 pentine upon the glass surface, and then melted by heat, or fired. Of eouise, as 
 the under layer should not be softened, the flux should melt before this happens, and 
 consequently it must be more easily fusible. 
 
 A glass having the following composition can be used as a flux: 
 
 Powdered quartz . 20 
 
 Lead oxide 25 
 
 Bismuth oxide 10 
 
 Should the colours be attacked by the lead or bismuth oxide, the following mix- 
 ture may be used : 
 
 Powdered quartz 20 
 
 Borax 15 
 
 Saltpetre . . . 2-5 
 
 Calcium carbonate 2'5 
 
 In melting glass mixture a certain proportion of broken pieces of glass, or cull et, 
 is added to it. This glass refuse is always at hand in glass works. The glass which 
 has run out of the furnace from broken crucibles is also used in like manner as a flux. 
 By this means the refuse glass is not only turned to account, but its addition to the 
 glass composition facilitates vitrification, since this glass melts at a lower temperature 
 than the composition and thus exerts a solvent action upon it. 
 
 The melting pots used for making glass are large crucibles, made of the most 
 difficultly fusible fire clay, which must not contain more than mere traces of iron or 
 lime ; one of the best- kinds of clay for the purpose is Stourbridge clay. In making 
 glass pots, the clay is always mixed with a quantity of pieces of broken melting pots 
 in a fine state of division, and kneaded up into a paste with water, and moulded with 
 the hands into the desired shape. Before new melting pots are used, chips of broken 
 glass are melted in them, so as to form on the surface a difficultly fusible glaze, techni- 
 
GLASS POTS AND FURNACES. 
 
 321 
 
 cally termed lining, which helps to prevent the clay from being afterwards acted 
 upon by the glass mixture. 
 
 The size of the melting pots depends upon the size of the furnace. In this 
 country they are larger than in Germany. They differ also in shape, the section being 
 round or elliptical ; in this country they are wider above than 
 beneath (4 to 5 feet above, and at the most 3 feet below). 
 They are generally open above ; but those used for lead 
 glass are covered with an arched top, as shown in fig. 182, and 
 for charging and taking out the glass they are furnished with 
 a muffle-shaped opening (A) at the side. The arched cover 
 serves to protect the lead oxide from the reducing influence of 
 the hot air of the furnace. 
 
 Figs. 183, 184, and 185, represent Siemens' glass melting 
 pots, in the construction of which advantage is taken of the 
 fact that, as the glass mixture approaches complete fusion, it 
 becomes specifically heavier. To provide for the separation of 
 the metal in different stages of the melting, these pots, of -p 182 
 
 which figs. 183 and 185 show the vertical section, and fig. 
 
 184 the horizontal section, consist of three compartments communicating with each 
 other. A is the melting compartment, B the space where the settling takes place, and 
 c the working space, from which portions of the melted glass are taken out through 
 
 j- 
 
 FIG. 183. 
 
 FIG. 184. 
 
 FIG. 185. 
 
 the opening (c) for working. The compartment (A) is filled with the glass mixture, 
 and as this fuses and the molten mass increases in density, it sinks to the bottom, 
 and passes through the opening (a) into the second compartment (B), where again the 
 heaviest portion, corresponding with that nearest to complete fusion, sinks to the 
 bottom, and passes through the opening (b) into the working space (c). 
 
 The furnace in which the glass pots are heated is in all cases a capacious vaulted 
 chamber substantially constructed of refractory stone or fire bricks upon a solid 
 foundation and over an arched passage called the cave, which is beneath the floor 
 level and, extending from side to side of the furnace, serves to receive the ashes from 
 the fireplaces as well as any portions of melted glass that escape from cracked glass 
 pots. The fire grates are placed at the level of the floor over the cave as shown in 
 fig. 187, and at the sides of the furnace are several arches by which access to the 
 interior of the furnace can be obtained for setting the melting pots and when repairs 
 are needed. The furnace is generally placed in the centre of a building called the 
 glass house, in which the various operations of working up the glass are carried 
 out, and the hot gas and smoke from the fire escapes either through flues at the side 
 of the furnace, as shown in figs. 189 and 192, or into a conical tower built up round 
 the furnace to a sufficient height to cause a draught. 
 
 The hot gas from the melting furnace is sometimes drawn off through side open- 
 ings and conducted by flues to adjoining chambers which serve for fritting, calcining, 
 drying and annealing, or for drying the glass pots. 
 
 Glass furnaces are sometimes made large enough to contain eight or ten melting 
 pots and sometimes they have only four pots. In various other respects also the con- 
 struction of glass furnaces presents minor differences according to the nature of the 
 work to be done. 
 
 The furnaces employed in making glass require to be very carefully built, 
 both in order to produce the necessary temperature and to resist its influence for a 
 considerable length of time. In their construction fire brick alone is _ employed. 
 The bricks are laid with a very thin layer of fire-clay paste between the joints. In 
 spite of all precautions, however, the sides of the furnaces are so much acted upon oy 
 the heat and the volatilised alkalies, that they are worn out and require rebuilding 
 within 12 months, or sometimes within 6 months. Furnaces in which the more easily 
 fusible lead glass is melted last proportionately longer than those in which the more 
 
GLASS. 
 
 refractory kinds of glass are prepared. When the composition of the fire brick is 
 defective the furnace has to be put out of use immediately, otherwise drops of melted 
 silicates fall into the glass pots, where they either dissolve and colour the metal, or 
 remain undissolved and form knots. 
 
 The interior or melting space of a glass furnace is either round, square, or ellip- 
 tical, and it is heated either by a fireplace in the centre, or, according to the size of the 
 space to be heated, by fireplaces at both ends or at one side only. Figs. 186 and 187 
 represent the elevation and horizontal section of a furnace for making crown-glass. 
 On both sides of the melting space or all round it is an elevation, technically termed 
 the bank, upon which the melting pots (1, 2, 3, 4, 5, 6, fig. 187) are placed, 4, 6, or 
 10 of these being placed in the furnace at one time. The melting space is arched 
 above so as to concentrate the heat upon the melting pots. Above each pot is an aper- 
 ture (1, 2, 3) in the side of the furnace for charging the pots as well as for withdrawing 
 the glass when melted, and 4, 5, 6, 7 are pipe holes for warming the pipes before 
 beginning to work the glass. Beneath the working holes are small tunnels (8, 9, 10), 
 through which the melting pots can be removed when worn out, and replaced by 
 fresh ones ; these tunnels are built up when the furnace is in use. 
 
 FIG. 186. 
 
 dft 
 
 FIG. 187. 
 
 In consequence of the high temperature requisite for melting the materials in 
 making glass about 12,000 and the necessity of maintaining the furnace at a high 
 temperature while the glass is being worked, the consumption of fuel is very consider- ' 
 able, and there is in this case, as in all others where very high temperatures are 
 necessary, a large quantity of heat carried off in the gaseous products of combustion 
 which escape from glass furnaces. This heat is sometimes turned to account for heat- 
 ing the kilns or ovens in which the glass is annealed after it has been shaped, and 
 several other plans have been devised for economising the heat produced in the glass 
 furnaces and reducing the consumption of fuel. Among these may be mentioned the 
 application of Siemens' regenerative furnace, which is furnished with two masses of 
 brickwork arranged in such a manner that, while the hot gas from the furnace passes 
 through one compartment, the supply of air to the furnace passes through the other 
 compartment. By this means much of the heat in the waste gas is absorbed by the 
 brickwork, and when this has become red hot the direction of the current is change^ 
 
GLASS MAKING. 
 
 323 
 
 by shutting and opening valves, so that the supply of air to the furnace is made to 
 pass through the heated brickwork and acquire a high temperature before entering 
 the furnace, while the other compartment is being heated by the waste products of 
 combustion. The heat which would otherwise be wasted is thus to some extent again 
 made useful for maintaining the temperature of the furnace, and there is a propor- 
 tionate reduction in the amount of fuel consumed. 
 
 In Belford's furnace, represented by fig. 188, the fuel is used in the state of gas 
 on each side of the melting space where the glass pots(c c c c) stand upon the bank (a) 
 are the chambers (D D) in which the coal is subjected to the action of a blast forced in 
 through the tube (F) and the branch tubes (F' F'), so that the coal is made to furnish 
 combustible gas, partly by distillation, and partly by the formation of carbonic oxide 
 This gas flows through the openings (dd) into the melting space, and burns there on 
 coming into contact with air supplied by the blast through the tubes (H H) and heated 
 by passing through the chambers (j j), into which the heated air of the melting space 
 passes through the openings (gg}. The supply of this air is regulated by valves (jj). 
 One advantage presented by this furnace is that the glass metal is not contaminated 
 by the floating ashes, etc. from the fires. 
 
 FIG. 188. 
 
 The reactions which take place in the melting of the glass materials are very 
 simple. When silica is melted with alkaline or earthy carbonates, the silica displaces 
 carbonic acid and combines with the basic oxides, forming silicates. A similar change 
 takes place when red lead is mixed with the alkali, lead silicates being also formed 
 by the decomposition of the red lead. During this process a considerable evolution 
 of gas takes place, which is the cause of the bubbles so often observed in glass vessels. 
 These bubbles may be expelled by heating the melted mass until it passes into a 
 mobile liquid condition. Veins and streaks in glass are caused by the density of the 
 melted mass not being homogeneous throughout. 
 
 A source of great inconvenience in the manufacture of glass is the volatilisation of 
 alkali, which takes place before vitrification, i.e. before the alkalies have combined 
 with the silica. When impure alkali or alkaline salts are used, a higher temperature 
 is requisite and greater volatilisation takes place. The presence of chlorides, and 
 especially of sulphates, gives rise to opaque threads and knots in the glass, which are 
 caused by the melting of these salts in various parts of the mass without mixing with 
 it. The volatilised alkalies condense upon the vault of the furnace, forming with the 
 stonework impure silicates which melt and drop into the crucibles beneath, rendering 
 the glass impure. 
 
 A further inconvenience attending the use of pots in making glass consists in the 
 solvent action exerted upon the material of the pots by the melting alkalies, which 
 not only renders the glass impure by dissolving alumina and iron, but is also very 
 destructive to the pots. 
 
 Both the volatilisation of alkali and the solvent action exerted by the alkalies 
 upon the melting pots must be taken into account in the mixing of the glass materials, 
 and a corresponding extra quantity of alkali added. 
 
 The separate constituents of the glass having been calcined, the proper quan- 
 tites are weighed out, and thoroughly mixed together. Sometimes only a portion 
 
 Y2 
 
GLASS. 
 
 of the silica, with an excess of the bases, is melted with the broken glass, in 
 order to fix the bases quickly ; otherwise these being the first to melt, they would be 
 volatilised in greater quantity, and afterwards the remainder of the materials, contain- 
 ing relatively less bases, is added. In any case, considerable loss of alkali cannot be 
 avoided; amounting, with potash, ordinarily to 16 or 17 per cent., but frequently ex- 
 ceeding 25 per cent. The mixed materials are heated, generally in side ovens, seldom 
 in special furnaces, to a red heat, or sometimes even until they commence to act upon 
 each other, and the mass becomes pasty or fritted. Meanwhile new melting pots 
 that have been previously heated to a red heat are introduced into the melting fur- 
 nace through the crucible holes, which are then bricked up. The heat is then in- 
 creased, and the glass material is introduced, in several portions? into the melting pots 
 through the working holes. The heat is again increased to the utmost, in order to 
 thoroughly melt and combine the silica with the basic oxides, the carbon dioxide and 
 other acid oxides, previously in combination with them, being displaced and driven 
 off. Foreign salts, such as potassium chloride and sulphate, which are decomposed 
 very slowly or not at all, collect at the surface as scum or gall, and those that are not 
 volatilised at the high temperature are skimmed off. The formation of glass gallis 
 therefore due to impurities in the soda or potash. The temperature is now reduced 
 until by the disappearance of the gas bubbles arid the deposit of other impurities the 
 metal has become completely clear. This clear melted glass is called metal, but being 
 too thin to be worked, the temperature of the furnace is still further reduced. The glass 
 when ready for working should be perfectly clear and transparent, and contain no air 
 bubbles, or portions of the salts, grains of sand, etc. 
 
 In working glass into various shapes advantage is taken of the plastic condition 
 it acquires when sufficiently heated, and in most instances this is done by forcing air 
 into a lump of the glass sufficiently large to make the article required, so as to form 
 a hollow globe which is afterwards shaped by various devices. This operation is 
 termed glass-bio wing, and the principal instrument used in carrying it out is an 
 iron tube about an inch in diameter, and four or five feet long called the pipe. At 
 one end there is a knob which serves as a mouth-pipe for blowing through the pipe, 
 at the other end is a knob upon which the soft metal is taken up out of the glass 
 pot, and part of the tube is sometimes cased with wood or other non-conducting 
 material, so as to enable the workman to handle it more conveniently. When the 
 lump of metal has been taken up on the pipe it is kept in a globular shape by rotating 
 the pipe and rolling the metal upon the marver, which is either a smooth iron plate 
 or a moistened block of wood which has several concavities in which the ball of metal 
 is rolled to bring it into shape. At the same time the workman blows gently into the 
 pipe and slightly distends the glass, the object being to obtain uniform distribution of 
 -the metal round the axis of the pipe before it cools so far as to require reheating. The 
 further shaping of the glass globe after it has been heated at one of the working holes 
 of the furnace is effected either entirely by blowing, or in part also by moulding the 
 glass externally while air is forced in through the pipe. 
 
 This method of working glass is adopted not only for making bottles and various 
 
 domestic utensils, but also for 
 making sheet glass for windows, etc. 
 The thicker kinds of sheet glass 
 are, however, mostly made by cast- 
 ing and rolling the soft metal be- 
 tween a heated metal plate and 
 a roller. Some articles are also cast 
 or pressed into moulds. 
 
 BLOWN GLASS. Bottles, drink- 
 ing glasses, and other small articles 
 are always blown, and the glass 
 used for the purpose is either lime 
 glass or flint glass. The arrange- 
 ment of a glass house for making 
 bottles, etc. is represented by fig. 
 189. 
 
 In the manufacture of bottles 
 the pipe is the principal tool. 
 Having taken out a sufficient quan- 
 tity of glass fora bottle, the blower 
 first works it to the front of his 
 pipe, with a flat iron, blowing into 
 
 Fro. 189. 
 
 it occasionally, and then rolling it in one of the depressions of the marver, so ,is to 
 
BOTTLE AND FLINT GLASS, 325 
 
 form it into a slightly elongated globe. This is again heated in the furnace and 
 lengthened by swinging the pipe backwards and forwards, after which it is put into 
 a cylindrical mould, and blown out so that, whilst the colder neck is drawn out with- 
 out being dilated, the body acquires the right diameter and height. The bottom of 
 the bottle is then warmed, and pressed inwards with an iron rod in the direction of 
 the axis, in order to produce the usual cavity, and an even edge upon which to stand 
 the bottle. A second iron called the ponty is then attached by means of a 
 piece of^lass to the cavity in the bottom, the neck is separated from the pipe, and 
 tke bottle is held at the furnace mouth in order to melt the sharp edges, and to lay 
 some threads of molten glass round the mouth to strengthen it. The neck is then 
 levelled on the outside and enlarged cylindrically from the inside, with a pair of shears. 
 The bottle joined to the iron is now carried by a boy to the annealing oven, where 
 by a slight blow it is separated from the iron. Sometimes a complete mould in several 
 parts is used, in which the bottles are rapidly blown, and thus a uniformity of size and 
 shape is obtained that is otherwise only approximated to, notwithstanding the skill of 
 the workman. 
 
 The annealing ovens for blown glass ware are either at the side of the melting 
 furnaces and heated by the hot gas passing off from the melting furnace, or there are 
 special annealing kilns heated by separate fires, as shown in fig. 189, and the bottles are 
 allowed to remain there until they acquire the temperature of the oven. In England 
 a continuously acting annealing oven is used. It consists of a long arched chamber, 
 heated by a separate furnace. Wheeled trays run on rails from end to end. These 
 trays are packed with the bottles to be cooled and slowly pushed from the hotter 
 end of the chamber to the cooler end, by which time the bottles become sufficiently 
 cool to be taken out. Instead of the trays an endless chain passing through the oven 
 may be used, and the articles to be cooled are placed on the chain in boxes or trays. 
 
 Good bottles must not only withstand ordinary changes of temperature, but fre- 
 quently, as in the case of champagne and soda-water bottles, they must be strong 
 enough to sustain a considerable pressure from the inside ; and to ensure this the 
 glass must be of equal thickness throughout, and well annealed. In order to avoid 
 loss by the bursting of champagne bottles, each bottle is proved separately before 
 being filled, by pumping water into it under a pressure of twelve atmospheres. 
 
 In blowing very large round bottles, such as sulphuric acid carboys, the blower 
 with his mouth spirts some water into the partly blown sphere of glass through the 
 pipe, which he then closes with his thumb, and the vaporisation of the water serves to 
 blow out the glass. 
 
 In making the finer kinds of blown glass articles lead glass is generally used, and 
 in order to avoid the reduction of the lead oxide in the preparation of the metal, 
 the glass pots are always closed above, so that reducing gases and coal dust are pre- 
 vented from coming into contact with the molten metal, and they have also a kind of 
 muffle-fehaped opening at the side which fits into the working hole of the furnace. 
 
 After the raw materials have been thoroughly mixed, successive small portions are 
 thrown into the glass pots and brought to the melting point as quickly as possible. 
 Whilst the melting is going on the openings in the glass pots are closed. About 14 
 hours are required for the complete fusion of the metal, and about the same time for 
 working up the metal of a pot nontaining about 6 cwts. 
 
 Crystal glass being more easily fusible than ordinary glass, it is more easily worked 
 and can be more frequently reheated without becoming devitrified, provided that the 
 flame does not exercise a reducing action upon it. It is worked into shape by means 
 of the blowpipe, like ordinary glass ; or by blowing it into metal moulds, for bottles 
 and similar articles ; or, lastly, by pressing it into metal moulds, for dishes, plates, etc. 
 The glass obtained by blowing or pressing into moulds resembles cut glass and is 
 much cheaper, but from the rapid cooling of the metal it is not sufficiently fluid to fill 
 the mould perfectly, and therefore has not the sharp edges and angles of cut glass. 
 
 The softness, great density, and strong refracting power of crystal glass render it 
 especially suitable for cutting. This is effected by pressing it against acute or obtuse- 
 angled wheels driven rapidly by means of a belt. The glass-cutter's work may there- 
 fore best be compared with that of the turner inverted. The wheels as well ^as the 
 grinding powders are changed at different stages of the cutting. The glass is first 
 roughly ground with an iron wheel and sand and water ; then follows a fine grinding 
 with a sandstone wheel. The glass is then polished by means of a wooden wheel and 
 pumice stone, and lastly by a cork wheel an^^in oxide. 
 
 In the manufacture of coated glass the workman takes a small quantity of the 
 coloured glass metal on his pipe, blows it MJRtly, and then dips the pipe in the pot 
 containing the colourless metal, gathers as much as is necessary, and then blows it, etc. 
 In this manner a hollow glass, coloured on the inside, is obtained, specially suited for 
 cutting, since the grinding being carried out on the colourless exterior, the coloured 
 
326 
 
 GLASS. 
 
 inner layer remains of equal thickness and depth of colour. If the glass is not to be 
 ground the operation may be reversed, first the white and then the coloured metal 
 being gathered with the pipe. 
 
 In this country a covering of coloured glass is first blown ; this is opened at the 
 top and colourless metal introduced on the pipe through the opening, and carefully 
 blown so as to form a uniform layer on the interior. 
 
 In Bohemia small pieces of coloured glass are heated almost to melting on an iron 
 rod in the working spaces, then laid on some colourless glass attached to a pip^^rpread 
 out evenly by means of the iron rod, and finally the whole is blown. 
 
 CROWN OR MOON GLASS. The manufacture of this kind of glass is extremely 
 difficult, and is attended with considerable loss. The workman, having by repeated 
 dippings of his pipe into the glass pot gathered a sufficient quantity 
 of the metal, first forms it by blowing and rolling it on the 
 marver ; till it takes the forms i, K, L, fig. 190. This is again heated 
 at the circular opening in the furnace, and the pipe is rapidly 
 rotated, so that the bottom of the ball is flattened and forms a 
 circular disc, as shown at M. To the middle of this disc, the ponty 
 is soldered by means of a small quantity of glass, and the bulb is 
 -37 then separated from the pipe by breaking the neck across with a 
 cold iron. The opening thus made is heated, by holding the bulb 
 opposite the circular opening in the furnace, the ponty meanwhile 
 being continually rotated, and the hole slightly widened by a wooden 
 stick so that the bulb acquires the form shown at N. It is then 
 Ssm^ carried to the flashing furnace, fig. 191, and heated opposite 
 -p qn the opening (A) from which the flame issues and comes in contact 
 .IG. 19U. ^..^ ^ bulb. The ponty is then rested horizontally on an iron 
 bar, so as to expose the mouth of the bulb to the flame issuing from the round aper- 
 ture (A), and very rapidly rotated. Through the influence of centrifugal force the edges 
 of the hole widen, as shown at o, and presently a disk 
 is formed, which is thick in the middle, where the 
 ponty is attached, but elsewhere is tolerably uniform. 
 This operation is called flashing, and the mode in 
 which it is conducted is represented by fig. 192. 
 When the disk has been formed and become suffi- 
 ciently cool, it is laid upon a bed of hot ashes, sepa- 
 rated from the ponty, and then removed by means 
 of a fork-shaped iron into the annealing oven at the 
 side of the flashing furnace, where it is placed on 
 edge. The disk being cut, in order to remove the 
 thicker part from the centre, two half-moon-shaped 
 
 FIG. 191, 
 
 portions are obtained ; hence, its German name of moon glass. It is evident that in 
 the cutting u*p of these disks into regular panes of glass there must be considerable 
 
 waste ; it is on that account much more 
 costly than the sheet glass made from 
 cylinders. 
 
 CYLINDER OR SHEET GLASS. At the 
 present time window glass is almost uni- 
 versally prepared from cylinders, obtained 
 by manipulation of the metal with the 
 blow-pipe. When the glass has cleared 
 and been skimmed, the workman, having 
 heated his pipe, gathers with it some glass 
 from the pot and then turns it so that 
 the metal congeals without running off; 
 the pipe is then dipped in again, and the 
 operation repeated until a sufficient quan- 
 tity of metal is gathered on the end of 
 , the pipe, proportionate to the size and 
 thickness of the cylinder to be made. 
 When sufficient metal is attached to the 
 pipe, the workman blows into it through 
 pipe, again heats it at the working 
 ^^pioie, and while holding the lump of glass 
 in the moistened cavity of a wooden block 
 blows more air into it until the glass gradually takes the form of a pear-shaped 
 bulb (A, B, c, D, fig. 193). He then holds the pipe vertically with the glass under- 
 
SHEET GLASS. 327 
 
 neath, and swings it to and fro like a pendulum in a pit at the side of the working 
 space, called the swinging pit, still blowing into the pipe from time to time. The 
 glass thus gradually assumes the form of a cylinder (E F, fig. 193). It is necessary 
 during this operation to keep the soft glass continually in motion or 
 it would become unequally distributed. When the glass has been 
 blown out to the required size, the workman supports his pipe upon 
 a portable rest, and puts the cylinder into the working space of the 
 furnace, so that the lower closed end of it may become heated. 
 He then closes the pipe with his thumb, and the expansion of the 
 enclosed air by the heat causes the softened bottom of the cylinder 
 to swell out and finally burst. By rapidly turning the pipe back- 
 wards and forwards, this opening is widened ; the cylinder is then 
 taken out, and revolved, and swung to and fro until the opening has 
 the full width of the cylinder (G, fig. 193). When the glass is so far 
 cooled as to retain its shape without being swung, the cylinder is laid 
 upon a rest, and a drop of water is applied with an iron to the upper 
 end, where it is attached to the pipe ; and then upon striking the pipe 
 about the centre with an iron bar the cylinder separates. If the I 
 cylinder be of thick glass, it is cooled very slowly in proper cooling 
 ovens ; but with very thin glass this operation is superfluous. 
 
 The next step is to break off the conical end of the cylinder (the 
 neck or cap), as shown at H, which is effected by encircling it at the 
 place where it is to be separated with a red-hot thread of glass, or I 
 
 holding against it a red-hot circular iron called the springing iron,' 
 
 and afterwards touching the heated place with the moistened finger, ,-, 
 
 or throwing a few drops of water upon it. The detached cylinder is G * 
 
 then opened or slit lengthways, and for this purpose the workman draws the sharp 
 
 edge of the iron in a straight line to and fro along the inner side of the cylinder, and 
 
 then, by merely scratching with a pointed stone along the line thus heated, the cylinder 
 
 cracks from one end to the other, the result being shown at H, fig. 193. 
 
 The flattening of the opened cylinder is carried out in an oven which consists 
 of two parts, the flattening oven and the cooling or annealing oven. Within the 
 oven is the flattening bed, which is a perfectly level surface made of fire clay and 
 cement. In order to prevent the glass adhering to this surface some lime or ground 
 gypsum is thrown into the furnace, so that the flame carries the powder forward into 
 the oven and deposits it in a fine layer upon the flattening surface. The flattening 
 oven is connected by an opening with the cooling oven, which contains a similar flat 
 surface. When a cylinder is to be flattened, it is passed with the openings upwards, 
 through the passage into the flattening oven, and gradually pushed forward towards 
 the flatting space. As the cylinder advances into the oven it becomes heated by 
 the hot gas from the fire, and it arrives at the flatting plate in a softened condition. 
 The cylinder is then spread out by the workman by means of the flattening iron, 
 with which he presses the glass outwards at each side of the crack until it forms a flat 
 sheet ; the polisher is then passed over it to render it perfectly even, and it is pushed 
 forward by means of the flattening iron through the opening into the cooling oven, 
 where it soon becomes sufficiently cooled to allow of its being set up on edge against 
 iron rods. This operation is repeated upon fresh cylinders until the cooling oven is 
 full, when it is closed in order. to allow the cooling of the plates of glass to take place 
 gradually. 
 
 Corrugated sheet glass is obtained by blowing out the cylinder in a ribbed 
 bronze mould, the corrugations remaining even after the flattening. 
 
 In order to avoid loss in the transfer of the sheets of glass from the flatting 
 stone to the cooling oven, Kirn has suggested a contrivance that presents decided 
 advantages. It consists of two very thin flatting stones, arranged one over the 
 other, which can be passed alternately from the flattening oven into the cooling oven. 
 The glass cylinder having been flattened on one of the plates in the flattening oven, 
 is carried forward on it into the cooling oven, allowed to cool and set upon edge. 
 Meanwhile, another cylinder is being spread out on the second flatting stone in the 
 flattening oven. 
 
 The flattening oven of Chance is constructed on a new principle. It consists of 
 two domed chambers, standing side by side, and communicating through an opening. 
 The hearth of each oven has a circular basis, and can be moved in a rotary direction 
 by special machinery. Each oven is divided by radiating partitions into eight com- 
 partments, each compartment in the flatting oven containing a flatting stone. The 
 opened cylinder of glass, after passing the heating flues, is pushed forward into the 
 first of the eight compartments of the flatting oven, and passes from there with the 
 entire portion of hearth into the second compartment, under which the firing is 
 
328 
 
 GLASS. 
 
 placed, and in which the flatting and smoothing is carried out. From this it passes 
 into the third compartment and so on, until the seventh, from which it is pushed out 
 for further cooling through the passage of communication, into the annealing' oven. 
 Under the eighth compartment is placed a second fire, by which the hearth is re- 
 heated for another revolution. The annealing oven is constructed upon the same 
 principle as the flatting oven, except that, instead of lying upon a flatting stone, the 
 sheet of glass there lies upon wires. After one revolution in this oven the sheets of 
 glass are sufficiently cooled to allow of their being taken out. The sheets of glass, as 
 they come from the flatting oven, have a length of from 40 to 50 inches, and a 
 breadth of from 20 to 30 inches ; these dimensions, however, are frequently ex- 
 ceeded. 
 
 The finer sorts of sheet glass are afterwards polished, as described at p. 329. 
 
 PLATE GIASS. Formerly plate glass was generally prepared according to the 
 method adopted in the cylinder glass manufacture. Perfectly smooth plates, however, 
 were never obtained in this way ; but being like window glass clouded and impure, 
 they consequently gave distorted images. It was not until after Stewart, in the year 
 1691, introduced the casting of mirrors that perfectly even plates could be prepared. 
 Since that time casting has gradually supplanted the cylinder method for making 
 mirror glass. 
 
 The plate-glass furnace usually contains ten or twelve glass pots ; they are round 
 or oval, and open above. Besides these pots for melting the glass, square vessels made 
 
 of clay and called cis- 
 terns or cuvettes are 
 used for the melted glass 
 to settle in and become 
 clear. Each cistern is 
 capable of holding as 
 much glass as is required 
 for a single plate ; they are 
 therefore of three sizes, 
 small, medium, and large. 
 The cisterns are sur- 
 rounded by a groove about 
 inch broad and 1\ 
 'inches deep, in order to 
 furnish a hold for the 
 tongs (T, fig. 194) by which 
 they are held and sus- 
 FIG. 194. pended from a crane in 
 
 casting the plates. 
 
 The carefully mixed glass materials are put into the glass pots in three successive 
 portions, each addition being made when the former portion has melted. The pro- 
 cess of heating is divided into three periods the fusing, the clearing, and the red 
 heat. If the process of melting does not advance equally in the different pots in a 
 furnace, the progress of those that are behind is hastened by the addition of glass 
 cullet. 'The fusing period lasts about seven hours and the clearing period about six. 
 After these two periods t-he fire is moderated and the metal is brought to the proper 
 consistence for casting. The time required for casting 12 plates is about an hour. 
 After the metal has been for some time in a state of fusion, a previously cleaned cistern 
 is placed in the furnace and the opening is closed and plastered up. When the 
 cistern has acquired the temperature of the furnace, the liquid glass is removed by 
 means of a copper ladle from the glass pots into the cistern, care being taken not to 
 disturb the impurities that have settled to the bottom. After every third dip the 
 copper ladle is cooled by dipping it in water, or it would melt. 
 
 The furnace being again completely closed, the metal is allowed to settle and become 
 clear in the cistern for several hours. In order to ascertain whether the glass is ready 
 for casting, a sample is withdrawn by dipping the end of a pipe into the molten metal, 
 and judging from the dependent portion, which takes the form of a pear or tear of 
 glass, whether it has the correct consistence and no longer contains any air bubbles. 
 When the right condition is attained the cistern is removed from the furnace and the 
 metal is poured out upon the casting surface, the construction of which is represented 
 by fig. 194. Only' occasionally, in the production of very large plates, are two cisterns 
 of metal used for one plate ; but then thai is a risk that it will be of two different 
 shades. 
 
 Whilst the metal is clearing in the cisterns, the casting table and annealing 
 oven are heated. Formerly the casting tables or plates were made of bronze, but 
 recently they have been made of cast iron ; usually they have a thickness of about 
 
PLATE GLASS. 329 
 
 8 inches. Experiments have been made with casting tables only 2 inches thick ; but 
 the result has been to show that they are only useful for casting small plates contain- 
 ing a small quantity of metal. The other dimensions of the casting tables vary very 
 much, according to the size of the glass plate required. In the larger manufactories 
 the casting table is from 16 to 20 feet long and from 10 to 12 feet wide, the weight 
 sometimes exceeding 35 tons. It is evident that the casting surface must be perfectly 
 even. It is supported upon a strong frame, the feet of which are furnished with iron 
 wheels to facilitate the removal of the table to the annealing oven. 
 
 The thickness of the plate of glass is regulated by means of bronze or iron bars 
 (tt, fig. 194) corresponding in thickness with the plate to be cast and as long as the 
 table. The distance at which they are set apart from each other regulates the dia- 
 meter of the plate. In order to spread out the metal equally when poured upon the 
 table, a bronze or cast-iron cylinder (ED) is used, 16 to 24 inches thick, weighing from 
 a ton to a ton and a half, and supported by and rolling upon the side bars (t t). It is 
 very essential that this cylinder should be perfectly roiind and free from air holes or 
 other flaws upon its surface. The cylinder is worked by means of two handles which 
 are fixed to its axis. 
 
 When the cistern is taken out of the furnace it is placed upon a waggon and 
 wheeled quickly to the casting table ; there it is seized by the tongs (T, fig. 194) and 
 suspended to the chain of a crane, by which the cistern is raised, and after being 
 carefully cleaned on every side is swung at a distance of about a foot above the 
 casting table and then tilted so as to pour the metal upon the table. The cylinder 
 being immediately set in motion distributes the metal equally and skims off any sur- 
 plus glass into a trough of water. The weight of the cylinder is sufficient to carry all 
 surplus glass before it, and there is thus formed between the cylinder, table, and side 
 bars, a perfectly even plate of the thickness of the bars. At the conclusion of the 
 operation the cylinder and bars are removed and the plate of glass is pushed forward 
 into an annealing oven. In the meanwhile another cistern of metal is being prepared 
 for a fresh casting; but in order to avoid overheating the casting table not more than 
 six plates are cast without intermission upon the same table. If a plate of glass be 
 still soft when it is removed into the annealing oven, its surface easily becomes rough, 
 and this has to be removed by the subsequent polishing. 
 
 The annealing oven is sufficiently large to hold six plates. It has usually several 
 openings for the introduction of the plates, and a perfectly level sole covered with fine 
 sand. When the plates are put in the oven it should be of a dull red heat. As soon 
 as it is filled with plates the openings are closed up and kept so for several days until 
 the oven has so far cooled that the glass plates can be taken out without danger. 
 Latterly the annealing ovens have been improved so that the cooling is effected in four 
 days, which renders a smaller number necessary. 
 
 The plates, when taken from the annealing oven, are rough and opaque, and before 
 they can be used they require to be ground and polished until they appear perfectly 
 smooth and transparent. Previously to this, however, the plates are examined closely; 
 those without flaws are trimmed at the edges with a diamond, whilst those that have 
 flaws are cut so as to yield the largest pieces possible with the least loss. 
 
 The grinding of glass was formerly done by hand, but now machinery is used. 
 A large plate is set in plaster of Paris upon a firm bench, and a smaller plate to be 
 used as a grinding plate is set in a similar manner on. a large stone and made fast in 
 an iron frame. Between the two plates, coarse sand or crushed fire clay and water 
 are placed, each successive quantity of sand or powder being finer than the preceding, 
 and the grinding plate is then set in motion upon the underlying plate. The motion 
 is partly rotatory and partly reciprocating, so that the opposing parts of the plates 
 undergo a continual change. After the operation of grinding with sand is finished, 
 the sand is rinsed off with water and emery is placed between the plates. The plates 
 having been ground perfectly smooth on one side they are reversed, and the other 
 sides are ground in a similar manner. 
 
 According to Newton's method, the glass plate to be ground is so fastened by means 
 of a frame upon a rotating round iron plate that the centre of the glass plate lies out- 
 side the centre of the iron plate. The iron plate being rotated, the glass plate, which 
 can also revolve in its frame, is set in motion, and a very rapid and complete polishing 
 is effected. In this case also the different powders are used with water. 
 
 The polishing of ground, but still dull, glass plates is also carried out by machinery. 
 The polishing machine consists of a flat board, covered on the under side with thick 
 felt. The felt is impregnated with colcothar or ferric oxide. For this purpose the 
 ferric oxide from the Nordhausen acid manufactories is sometimes used after being 
 purified and reduced to a fine powder. 
 
 The glass plate is polished until it has a perfectly brilliant surface ; it is then re- 
 
330 
 
 GLASS. 
 
 moved and washed with very dilute hydrochloric acid, to remove any adhering gypsum 
 or polishing powder. 
 
 OPTICAL GLASS. The preparation of glass for optical purposes requires to be 
 conducted with the greatest care in order to obtain the requisite homogeneity and free- 
 dom from colour. The furnace used by Bontemps for the purpose is represented, in 
 vertical and horizontal sections, by figs. 195 and 196. A is the bank, with furnaces 
 
 on each side ; B the covered crucible, the 
 mouth of which is opposite the working 
 space; c a stirring iron fastened into a 
 difficultly-fusible clay cylinder (d) ; / is a 
 trestle carrying a roller upon which the 
 stirrer works to and fro. 
 
 The melting pot is first made red hot, 
 then placed in the previously heated melt- 
 ing furnace, and its opening closed with a 
 double lid. The furnace is then brought to 
 the highest possible temperature for three 
 hours, and when the required heat has been 
 obtained the lid is taken from the opening 
 of the melting pot and about 20 Ibs. of the 
 
 Fia 195. 
 
 FIG. 196. 
 
 flint glass mixture (p. 319) introduced. After an hour a further quantity of 40 Ibs. 
 is added ; two hours afterwards 80 Ibs. more, and this is continued until, in from 8 to 
 10 hours, the entire charge has been put into the crucible. After 4 hours further 
 heating of the closed crucible, the stirrer, previously brought to a red heat, is intro- 
 duced, and worked about so as to produce a uniform mixture of the metal and 
 promote the escape of all air bubbles. After 3 minutes the stirrer is taken out, the 
 fire-clay cylinder being left at the side of the pot ; the opening of the melting pot is 
 again closed and the fire increased. Five hours afterwards the metal is again stirred, 
 and after that it is stirred every hour. A layer of coal about a foot thick is then put 
 upon the fire, and the temperature being thus somewhat reduced, thecrucible is loft 
 for the next two hours to allow bubbles to escape. By the end of this time the heat 
 again rises, and it is then got up as high as possible for about 5 hours, until the 
 metal attains its maximum fluidity. The supply of air to the furnace is then checked, 
 and the metal is continually stirred until it thickens and the stirring begins to 
 become difficult. The stirrer and the clay cylinder are then withdrawn, the furnace 
 perfectly closed, and left to cool gradually for about 8 days, after which time the 
 crucible is taken out. 
 
 The glass generally forms one mass, which is polished at opposite ends in order to 
 ascertain the portions that are uniform and free from flaws. The pure portions aj-e 
 cut out, and the irregular-shaped pieces which are cut as large as possibleare then 
 heated in a furnace or under a muffle until they become so soft that they can be 
 pressed into bronze moulds ; the finished lenses are afterwards placed in an annealing 
 oven. 
 
 The crown glass used for optical purposes (p. 319) is made in the same manner as 
 the flint glass, but as it is less fusible it requires a higher temperature, and is to that 
 extent more difficult to make. 
 
 The crucible is placed in the furnace as in the preparation of flint glass, and after 
 being brought to a white heat the mixture is put in so as to complete the charge in 
 8 hours. After 4 or 5 hours the stirrer is used, and this is done again every 2 hours ; 
 the heat is then allowed to go down for 2 hours, afterwards increased as much as 
 possible for 7 hours, the metal again stirred, and after closing the openings of the 
 furnace completely it is allowed to cool gradually. The remainder of the treatment if 
 the same as with flint glass. 
 
ENAMEL. 331 
 
 ENAMEL. This name is applied to the vitreous preparations used for coating 
 metallic surfaces, either to protect them from oxidation or for decorative purposes. 
 Enamel is generally rendered opaque by the addition of stannic oxide, and sometimes 
 it is coloured with various other oxides. It is applied to metallic surfaces in the state 
 of powder and is then melted by exposing the articles to a suitable heat in a muffle or 
 kiln. 
 
 In the production of ordinary white enamel, crystal glass is thoroughly incor- 
 porated with a mixture of zinc oxide and lead oxide by carefully melting them to- 
 gether. The oxides are prepared by mixing an alloy of tin and lead in proportions 
 varying between 15 and 40 parts of tin to 85 and 60 parts of lead in contact with air 
 until it is completely oxidised. The whiter and more opaque the enamel is required 
 to be the larger is the proportion of tin that must be used. As however a large propor- 
 tion of tin oxide affects the fusibility of the enamel, a smaller amount of sand is used 
 in such case. 
 
 The most diverse mixtures are used as the basis of coloured enamels. The 
 principal requisites are that it should be perfectly colourless and more easily 
 fusible than the white enamel upon which it is to be laid. The following are two 
 mixtures used for the purpose : 
 
 Parts by weight. 
 
 Sand 3 
 
 Crystal glass .3 
 
 Calcined borax 1 3 
 
 Chalk . ' - 1 
 
 Cubic nitre .- . . . 
 
 Antimonic oxide 1 . 
 
 The materials used for colouring enamel are in general the same as those already 
 mentioned as being used for colouring glass. 
 
 The enamelling of gold articles is effected by making the surface to be 
 enamelled as rough as possible, spreading the enamel upon it, and then heating in a 
 muffle furnace until the enamel melts. The enamel then remains closely adherent 
 to the roughened surface. 
 
 In enamelling dial plates the enamel powder is mixed with water and is 
 spread upon both sides of thin sheets of copper, which are then heated in a muffle fur- 
 face until melted. The figures are afterwards burnt on in black enamel. 
 
 The enamelling of kettles, pipes, and other utensils is carried out according 
 to different methods. One consists in first etching the smooth metallic surface of the 
 object to be enamelled with dilute sulphuric acid ; this is washed completely off, and 
 after the article is dried, its surface is smeared with a solution of gum arabic and 
 sprinkled with the enamel powder, and it is heated in a muffle furnace to about 100 
 or 120. It is next removed to another muffle furnace and there heated so strongly 
 as to melt the enamel, the operation being watched through a hole in the muffle. 
 Lastly it is slowly cooled in an annealing oven. Should the enamel si;rface be imper- 
 fect the article is again coated and reburnt. The mixture used by Paris consists 
 of: 
 
 Flint glass /** *-,,v : '*--* 130 
 
 Sodium carbonate . .*.,' 20'5 
 
 Boracic acid . . . . . ' 12 
 
 These ingredients are carefully melted together in a crucible, the enamel poured 
 out, and after cooling crushed and ground to a fine powder. 
 
 According to a second method the iron surface is first covered with a ground 
 coating and then with an outer coating of the actual enamel. The object of the 
 ground coating, which must possess a certain degree of pliability, is to prevent the 
 separation of the actual enamel through unequal expansion caused by heating. 
 
 The following are the ingredients for the ground coating, according to Heeren : 
 
 I. II- 
 
 Quartz powder ...'..*. 30 30 
 
 Borax . . . . , 16'5 25 
 
 White lead . ' 3 
 
 Powdered feldspa 
 
 30 
 
 These ingredients are all brought into as fine a powder as possible, and melted to- 
 gether in a large Hessian crucible placed in a reverberatory furnace. At the bottom 
 of the crucible is a hole, which, until the complete melting of the mixture, is stopped 
 with a plug of quartz powder. As soon as the fusion is accomplished the plug is 
 driven in by an iron implement, and the melted mass run into a vessel placed beneath, 
 and filled with cold water. It thua becomes divided into small pieces and is more 
 
332 GLASS. 
 
 easily ground. To the product obtained from mixture I is added the following mix- 
 ture la, or to mixture II the mixture Ha : 
 
 In. Ila. 
 
 Quartz powder 9 
 
 Pipeclay 8f lOf 
 
 Feldspar 6 
 
 Magnesia alba 3-5 If 
 
 The following are two mixtures used for the outer coating, the essential difference 
 between them being that the first contains no lead : 
 
 Quartz powder 37 37i 
 
 Borax 27 24 
 
 Tin oxide 30 25 
 
 White lead 15 
 
 Sodium carbonate 15 11| 
 
 Saltpetre 10 10 
 
 . 5 5 
 
 The mixture is melted and broken up in the same manner as that for the ground 
 coating, and is then ground to a fine powder with the following addition : 
 
 Quartz powder 6 
 
 Tin oxide 3| 
 
 Sodium carbonate ' . . . . f 
 
 Magnesia alba f 
 
 In the application of the enamel the articles are first treated with dilute sulphuric 
 acid, and afterwards scoured bright with sand, washed and dried. The powder for 
 the ground coating is then made into a thin paste with water and laid on, dried in a 
 furnace, and afterwards fired in the usual way in a muffle. Upon this basis the outer 
 coat is laid and dried in the same manner. 
 
 SOLUBLE GLASS OB WATER GLASS. 
 
 This material is an alkaline silicate containing relatively to silica a larger propor- 
 tion of alkali than ordinary glass. 
 
 Composition. There are two kinds of water glass : potash water glass, which 
 consists of potassium silicate, and soda water glass, consisting of sodium silicate. 
 
 Soda water glass contains from 72 to 75 per cent, of silica, and potash water glass 
 from 64 to 69 per cent. 
 
 Characters. Water glass when pure is colourless and transparent, but is more 
 generally of a yellowish or brown colour, which is due to impurities. It is soluble in 
 water, and the solution when evaporated leaves the silicate in the form of a glassy 
 film upon the surface to which it has been applied. 
 
 Preparation. Fuchs recommended for the preparation of water glass the 
 following proportions of ingredients, which are melted together in a crucible : 
 
 Potash Soda 
 
 water glass water glass 
 
 Quartz 45 4o 100 
 
 Potash 30 
 
 Calcined soda 23 
 
 Sodium sulphate - 60 
 
 Wood charcoal 3 3 20 
 
 On exposing the melted mass for a short time to the action of the air, the salts 
 that have not been converted into silicate effloresce and may be washed away. When 
 required for use water glass is dissolved in hot water. 
 
 Schur gives the following recipe for preparing water glass : 
 
 Soda Potash 
 
 water glass water glass 
 
 White sand (containing 90 per cent. Si0 2 ). . .180 180 
 White Jarrow soda (52 per cent.) . . . .100 
 
 Ordinary potash (90 per cent.) - 125 
 
 Powdered wood charcoal 3 8 
 
 Water glass may also be prepared in the wet way, by dissolving siliceous infusorial 
 earth in a boiling solution of caustic soda, having a specific gravity of T15. In order 
 
POTTERY WARE. 333 
 
 to separate from the solution organic substance derived from the infusorial earth, a 
 small quantity of lime water should be added to it. The solution is then allowed to 
 settle, is afterwards decanted, the clear liquid evaporated to a syrupy consistency, and 
 the solid residue dried in the air. 
 
 Kuhlman prepares water glass by heating together caustic soda, or potash and 
 broken flints, in a suitable digester, under a pressure of 7 atmospheres, until the 
 liquid is saturated with silica. 
 
 Uses Water glass is used for painting over plastered walls, both in the interior 
 and exterior of buildings. Three coats are generally given. 
 
 For this purpose pigments are often mixed with the water glass, such as chalk, 
 ochre, green earth, etc. A light blue colour is given by the addition of ultramarine 
 and chalk or heavy spar. By penetrating into the porous surface of the plaster, and 
 drying in it, or perhaps combining chemically with the lime, the water glass gives a 
 shiny appearance to the surface, which not only serves to keep it clean, but admits of 
 its being washed even with soap and water. In choosing pigments for mixing with 
 water glass, care must be taken to avoid using any that would cause decomposition, 
 like zinc white, white lead, chrome yellow, Prussian blue, mineral blues, Schwein- 
 furt green, etc. 
 
 "Water glass is also used for painting over limestone that is liable to disintegrate. 
 Chalk as well as porous limestone is rendered very hard and weather proof by water 
 glass, and the surface becomes smooth, but at the same time of an undesirable yellow 
 colour. 
 
 For coating wood, the solution of water glass should be applied only as a thin solu- 
 tion in quantity sufficient to penetrate the wood ; otherwise it is very liable to peel off, 
 owing to the slight adhesion between wood and water glass. Wood thus treated with 
 water glass becomes darker in colour ; it does not ignite readily when exposed to the 
 action of flame, although, when thrown into a fire, the inner portion becomes entirely 
 carbonised. 
 
 Water glass adheres very readily to iron and other metals, protecting them from 
 rust, and even from oxidation at a high temperature, on which account it is useful for 
 painting iron stoves and stove pipes. When mixed with pigments, it is also used for 
 painting glass. 
 
 Water glass is useful for cementing glass, porcelain, and similar substances. For 
 this purpose the pieces to be united are heated up to the temperature of boiling water, 
 the edges of the pieces to be united are then moistened with a hot concentrated solu- 
 tion of water glass, pressed together, and bound round with string. When the water 
 glass has thoroughly dried, which in the case of small objects takes a few days, and 
 with pieces about an inch thick about fourteen days, the cement attains such hardness 
 that the objects repaired may be used as before. 
 
 In calico printing water glass is used for fixing ultramarine. 
 
 POTTERY OR EARTHENWARE; PORCELAIN, ETC. 
 
 The art of making vessels of clay is one of the most ancient branches of industry, 
 and although very great improvements have been made at various times in matters of 
 detail, the manufacture of earthenware is still conducted essentially in the same 
 manner that it was originally. The fundamental facts upon which this manufacture 
 is based are to be found in two of the characters of the aluminous silicate which 
 occurs naturally as clay, viz., the hardening it undergoes when heated to a sufficiently 
 high temperature and the plasticity it possesses when mixed with water. In these 
 and other respects the various kinds of clay differ very considerably on account of 
 differences in their chemical composition, and consequently it is necessary to make 
 suitable allowance for such differences, either by modifying certain operations or by 
 adding to the clay other materials ; but in all cases the manufacture of earthenware 
 consists in preparing an argillaceous dough or paste of such a consistence that it can 
 be wrought into, and retain the various shapes required, and then subjecting the 
 articles made from it to such a degree of heat as will give them the desired hardness 
 and coherence. In all cases the selection of a suitable description of clay is a most 
 important point, both as regards the nature of the articles to be made, and the par- 
 ticular treatment to be adopted in the manufacture. 
 
 The purer varieties of clay, consisting almost entirely of aluminum silicate, are 
 either white or of a slight greyish tint, and they are extremely refractory even at the 
 highest temperatures. Many varieties of clay, however, contain besides aluminum 
 silicate other silicates or oxides, etc., which make the clay more susceptible to the 
 influence of heat, and sometimes even fusible, while at the same time these substances 
 
334 
 
 CLAY. 
 
 often communicate colour to the clay. The commoner kinds are generally of a brown, 
 red, or yellow colour. The composition varies considerably, as shown by the follow- 
 ing table. 
 
 
 Common 
 Clay 
 
 Poole 
 Clay 
 
 Sandy 
 Clay 
 
 Yellow 
 Clay 
 
 Pipe 
 
 Clay 
 
 Fire 
 Clay 
 
 Fuller's 
 Earth 
 
 China Clay 
 
 Locality . 
 
 - 
 
 - . 
 
 - 
 
 - 
 
 - 
 
 - 
 
 - 
 
 Corn- 
 wall 
 
 Halle 
 
 Analyst . 
 
 - 
 
 "Weston 
 
 - 
 
 Brown 
 
 - 
 
 Tookey 
 
 - 
 
 - 
 
 - 
 
 Silica . 
 
 49-44 
 
 48-99 
 
 66-68 
 
 58-07 
 
 53-66 
 
 65-10 
 
 53-10 
 
 46-32 
 
 39-62 
 
 Alumina 
 
 34-26 
 
 32-11 
 
 26-08 
 
 27-38 
 
 32-00 
 
 22-22 
 
 10-00 
 
 39-74 
 
 45-00 
 
 Lime 
 
 1-48 
 
 0-43 
 
 0-84 
 
 0-50 
 
 0-40 
 
 0-14 
 
 0-50 
 
 0-36 
 
 0-07 
 
 Magnesia 
 
 5-14 
 
 0-22 
 
 trace 
 
 trace 
 
 trace 
 
 0-18 
 
 1-25 
 
 0-44 
 
 3-32 
 
 Ferric oxide . 
 
 774 
 
 
 
 
 
 
 
 
 
 
 
 9-75 
 
 
 
 
 
 Ferrous 
 
 
 
 2-34 
 
 1-26 
 
 3-30 
 
 1-35 
 
 1-92 
 
 
 
 0-27 
 
 
 
 Alkaline bases 
 
 
 
 3-31 
 
 
 
 
 
 
 
 18 
 
 trace 
 
 r -i o. (>* 
 
 
 
 Water . 
 
 1-94 
 
 11-96 
 
 5-14 
 
 10-30 
 
 12-08 
 
 9-28 
 
 24- 
 
 ) 
 
 10-00 
 
 
 100- 
 
 99-36 
 
 100- 
 
 99-55 
 
 99-49 
 
 99-02 
 
 98-60 
 
 
 
 
 
 The effect of heat upon clay differs according to the amount of lime and ferric 
 oxide or ferrous oxide it contains ; those kinds containing but very little of these sub- 
 stances are known as fire clay, on account of their capability of bearing very high 
 degrees of heat without melting, and they are used for making crucibles, glass pots, 
 and the bricks for building furnaces, etc. Iron is a frequent constituent of clay, 
 either in the state of silicate or as oxides, and it is to one or other of these substances 
 that the red, blue, or yellow colours of many kinds of clay is due. When clay of this 
 kind is subjected to action of heat, and especially when it is brought into contact 
 with carbonaceous vapour from the fuel used, there is a possibility of its melting 
 in consequence of the formation of a comparatively fusible ferrous silicate. The 
 presence of lime as silicate or carbonate has a similar influence, though in a less 
 degree. Clay containing so much iron as the Fuller's earth in the above table would 
 be too readily fusible to use for pottery ware, and even when the amount is less 
 care must be taken in firing the articles made with such clay that the temperature is 
 not raised too high. For this reason it is only the? purer kinds of clay, such as that 
 occurring at Poole and other parts of Dorsetshire and Devonshire, that are suitable for 
 the manufacture of the better kinds of earthenware, while in the manufacture of 
 porcelain only the finest kind of clay, known as kaolin or china clay, can be used. 
 
 Clay frequently contains calcium carbonate or magnesium carbonate, and is then 
 termed marl, which is distinguished as aluminous or calcareous, according as the 
 clay or the carbonate preponderates. These materials are often used in the manu- 
 facture of earthenware, bricks, etc. The mixture of clay with sand, gravel, etc., 
 which frequently occurs in the more recent geological formations, and is known by the 
 name of loam, is used chiefly for brick-making. 
 
 The colour of clay as it occurs naturally is sometimes due wholly or in part to the 
 presence of organic substances, and in such cases the clay frequently burns white, un- 
 less it contains iron in addition. 
 
 When clay consisting only of pure aluminum silicate is, in technical language, 
 burnt, or exposed to the influence of a temperature sufficiently high to give it the 
 maximum degree of coherence ; it contracts and the mass becomes much denser. Since 
 this shrinking of clay in burning would have the effect of distorting vessels made 
 of it or causing them to crack when fired, it is necessary to counteract the contrac- 
 tion of the clay by mixing with it a sufficient proportion of some other material which 
 is not susceptible of contraction when intensely heated. Silica is the substance used 
 for this purpose either in the state of sand for the coarser descriptions of clay ware, or 
 for the better kinds of ware as finely divided flint or quartz. The clay used in the 
 manufacture of porcelain, and known by the name of china clay, generally contains, 
 besides aluminum silicate, a considerable amount of finely divided silica. In order to 
 prevent the shrinking it is also customary in preparing the clay for moulding to mix 
 with it a quantity of broken fragments of the same kind of ware that is to be made or 
 some previously burnt clay, etc. 
 
 Although, by the operation of b ur ni n g, clay is rendered permanently coherent, ami 
 its texture is thus so far altered that it is no longer susceptible of disintegration or 
 becoming soft when in contact with water, it is still so porous that it is capable of 
 
VARIETIES OF POTTERY WARE. 
 
 335 
 
 absorbing water or other liquids, and even allows liquids to percolate through its mass. 
 For many of the purposes to which vessels of clay ware are applied this character 
 would be very objectionable ; consequently, it is necessary to render the surfaces of the 
 articles impermeable, and this is done by coating them with a thin layer of siliceous 
 material that is much more readily fusible than the clay of which the ware is made. 
 This coating is generally applied after the ware has been partially burnt, and when it 
 is fired again the fusible coating melts, forming upon the surface of the articles a 
 smooth vitreous film called the glaze. 
 
 Another method of rendering earthenware articles impervious is to mix intimately 
 with the clay another substance which is much more fusible, and at the temperature 
 to which the ware is exposed in firing it, this admixture becomes sufficiently soft to 
 permeate the particles of clay, so as to cement them together and render the mass 
 semi-vitreous or even translucent in the case of the finer kinds of ware, such as 
 porcelain. 
 
 Pottery ware presents very great differences of character according to the nature 
 of the raw material used in the manufacture and the treatment to which it has been 
 submitted, and while the difference between some kinds is considerable, it is in other 
 cases so slight that no essential distinction can be recognised. There is, however, one 
 feature in regard to which all varieties of pottery ware may be distinguished as be- 
 longing to one or other of two classes. 
 
 1. Those kinds of ware in which the texture of the body is similar to that of burnt 
 clay, and, independently of the glaze by which the surface is rendered impervious, the 
 body remains porous after burning. This class comprises the commoner kinds of 
 earthenware or. terra cotta, common roofing tiles, bricks, etc. 
 
 2. Those kinds of ware in which the texture of the body is throughout stony or 
 partially vitreous, in consequence of the more intimate aggregation of its particles by 
 the softening of the mass during the burning. This class comprises, besides porcelain, 
 several of the finer kinds of earthenware nominaHy distinguished as stone china, 
 Wedgwood ware, stoneware, etc., and some of the better kinds of bricks, tiles, etc. 
 present characters of a similar nature. 
 
 Under the general name of earthenware several varieties of pottery are comprised, 
 in all of which the body has an earthy texture and is porous and opaque. Delft and 
 majolica wares are of this kind. In the finer kinds of earthenware the body is denser 
 and harder, besides being to some extent vitrified. The best kind .is called iron stone 
 china, and the wares belonging to this class present almost innumerable differences of 
 degree. The fine stoneware commonly called Wedgwood is a still closer approxima- 
 tion to porcelain, and common stoneware is of the same character essentially, but is 
 made of coarser material and is less carefully prepared. 
 
 The following table of analyses of different kinds of pottery ware will serve to 
 show the differences that exist between them in regard to composition : 
 
 
 Si0 2 
 
 A1 2 3 
 
 CaO 
 
 MgO 
 
 Fe 2 s 
 
 Calcium 
 phosphate 
 
 C0 a 
 
 Alkali 
 
 Earthenware, Delft 
 
 49-07 
 
 16-19 
 
 18-01 
 
 0-82 
 
 2-82 
 
 
 
 13-09 
 
 
 Majolica . 
 
 48-00 
 
 17-50 
 
 20-12 
 
 1-17 
 
 3-75 
 
 
 
 9-46 
 
 
 Italian . . 
 
 49-65 
 
 15-50 
 
 22-40 
 
 0-17 
 
 3-70 
 
 
 
 8-58 
 
 
 
 Spanish . 
 
 46-04 
 
 18-45 
 
 17-64 
 
 0-87 
 
 3-04 
 
 
 
 13-96 
 
 
 
 {Paris . 
 
 61-50 
 
 12-99 
 
 16-24 
 
 0-15 
 
 3-01 
 
 
 
 6-10 
 
 
 
 Kouen . 
 
 47-96 
 
 15-02 
 
 20-24 
 
 0-44 
 
 4-07 
 
 
 
 12-27 
 
 
 
 Nevers. 
 
 56-49 
 
 19-22 
 
 14-96 
 
 071 
 
 2-12 
 
 
 
 6-50 
 
 
 
 Common English ware . 
 
 68-55 
 
 29-13 
 
 1-24 
 
 
 
 
 
 
 
 
 
 
 
 Chinese porcelain, inferior . 
 
 68-96 
 
 29-24 
 
 1-60 
 
 
 
 
 
 
 
 
 
 
 
 ,, , superior . 
 
 71-04 
 
 22-46 
 
 3-82 
 
 
 
 
 
 
 
 
 
 2-68 
 
 Berlin 1 
 
 72-96 
 
 24-78 
 
 1-04 
 
 trace 
 
 __ 
 
 
 
 
 
 1-22 
 
 English No. 1 
 
 39-88 
 
 21-48 
 
 10-06 
 
 
 
 
 
 26-44 
 
 
 
 2-14 
 
 No. 2 
 
 40-60 
 
 24-15 
 
 14-22 
 
 0-43 
 
 
 
 15-32 
 
 
 
 5-28 
 
 No. 3 
 
 39-68 
 
 24-65 
 
 14-18 
 
 0-31 
 
 
 
 15-39 
 
 
 
 5-79 
 
 Stoneware Vauxhall 
 
 74-00 
 
 27-04 
 
 0-60 
 
 0-17 
 
 2-00 
 
 
 
 
 
 1-06 
 
 Frechen 
 
 64-01 
 
 24-50 
 
 0-56 
 
 0-92 
 
 8-50 
 
 
 
 
 
 1-42 
 
 ,, Wedgwood . 
 
 66-49 
 
 26-00 
 
 1-04 
 
 0-15 
 
 6-12 
 
 
 
 
 
 0-20 
 
 The analyses at the top of the table show that the several kinds of ware which 
 they represent are essentially different from true porcelain, such as that of China or 
 Germany ; and the presence of undecomposed carbonate shows that they were fired at 
 a moderate heat. Ordinary English earthenware is intermediate between this kind 
 of ware and true porcelain, and this differs from stoneware chiefly by reason of the 
 
336 
 
 POTTERY WARE. 
 
 purity of the material it is made from. English porcelain is peculiar in containing!; 
 calcium phosphate as an essential constituent. 
 
 COMMON POTTERY WARE. The clay used for making articles of this description is 
 carefully selected and prepared, chiefly by mechanical means, in such a manner as to 
 have a very uniform texture and considerable plasticity. The shaping of the articles 
 is performed upon the potter's lathe, the construction of which is represented by fig. 197. 
 
 FIG. 197. 
 
 It consists of an upright shaft a b, the lower end of which runs in a step fixed to 
 the frame of the table (c), through which the head of the shaft projects into a block 
 () called the head of the lathe. The upright shaft is fitted with a pulley (d) having 
 several grooves for receiving the driving cord passing over the guide pulley (/) and 
 the wheel (e\ to which motion is communicated by the winch (r) and the head of the 
 lathe (a) is thus made to revolve rapidly. The workman sits upon the bench (&) and 
 placing a lump of prepared clay upon the head of the lathe while it is revolving, 
 moulds it with his hands into the desired form. This operation is termed throwing. 
 In large works the lathes used for shaping clay ware are of improved construction, 
 and are often driven by steam power ; but in principle they do not essentially 
 differ from the most primitive form of potter's wheel represented above, which has 
 been in use from the remotest period. After the vessels have been moulded, they are 
 thoroughly dried in covered sheds to which the air has free access, and sometimes 
 the sheds are warmed by flues under the floor. 
 
 On account of the fusibility of the clay used in making the coarser kinds of pottery 
 they are burnt at a comparatively low temperature. The kilns used for the firing 
 are often very rudely constructed brick chambers heated by a fire at the side ; some- 
 times long horizontal reverberatory furnaces are used, the construction of which is 
 represented by fig. 198. The chamber (A) in which the articles to be burnt are 
 
 Fia. 198. 
 
 placed is heated by the hot gas passing from the fireplace (B) through the perfor- 
 ated wall (a a) which separates the fire from this chamber. The fire gr;ite slopes from 
 the furnace door (c) down towards the kiln to fucilitatu the firing ;md stoking, and 
 
GLAZIISTG AND DECOBATIOK 337 
 
 the door can be raised by means of the weight (o) attached to a chain passing over the 
 pulleys (n n). The chimney is furnished with a damper (D) for the purpose of regulat- 
 ing the draught. The hollow space (p) beneath the firing chamber serves to keep the 
 brickwork dry, and at the side of the chamber there are several smaller flues for the 
 same purpose. The firing chamber is charged and emptied through the archway (6), 
 which is bricked up when the kiln is in use. 
 
 In many instances common pottery is used without being glazed. When it is re- 
 quired to^be impervious the glaze is produced either by dusting the moulded articles 
 while moist with a finely powdered material consisting of clay, sand, and litharge in 
 such proportions as to form a very fusible lead and alumina silicate when the ware is 
 fired. A coloured glaze is produced by adding to the mixture various metallic oxides. 
 The glaze applied to such ware as is known by the terms fayence, majolica, delft, etc., 
 is often more of the nature of enamel, and is made opaque to conceal the dark colour 
 of the body. Stannic oxide is used for this purpose in preparing the glazing material, 
 together with some lead oxide to give the requisite fusibility. The two metals are 
 generally alloyed together in the proportion of three parts lead to one of tin, and then 
 converted by roasting into the state of oxide, which is mixed with various proportions 
 of sand, soda ash, or common salt, and sometimes the decomposed felspar known as 
 Cornish stone, and the mixture is heated in a reverberatory furnace until it begins to 
 melt and becomes pasty or fritted, as it is termed. The agglutinated material is 
 then thrown into water and finely ground to make it fit for applying to the ware. 
 
 Sometimes the glazing material is made into a paste with water and is applied to the 
 surface of the moulded vessels in that condition, or it is mixed with sufficient water 
 to form a thin sludge into which the partially fired articles, termed biscuit ware, 
 are dipped. This latter plan of applying the glazing material is the best, but it is 
 also the most expensive, since it involves the necessity of firing the ware twice, and is 
 therefore seldom adopted, except in making superior kinds of earthenware. 
 
 The better varieties of glazed pottery with a porous body, which are somewhat 
 vaguely termed earthen ware, are generally made either with a mixture of clay, marl 
 and sand, or with a paste composed of plastic cla}' and powdered quartz or flint. In 
 the former case the ware when fired is soft, and contains so much undecomposed earthy 
 carbonate that it effervesces with acids ; in the latter case the ware is much harder and 
 more compact. The temperature requisite for firing the body of fine earthenware is 
 higher than that requisite for common ware, and it is much higher than the glaze will 
 bear ; consequently articles of this kind are always fired twice, in the first instance to 
 render the body sufficiently hard and compact, and afterwards, when the glazing 
 material has been applied, sufficiently to melt the glaze uniformly over the entire 
 surface of the articles. In firing these- kinds of earthenware the articles are never ex- 
 posed to the direct action of the flame, but are enclosed in cylindrical envelopes called 
 saggers, made of refractory material, and these are piled up one upon the other in the 
 kiln. Slabs of clay are sometimes used instead of saggers for common wares, and they 
 are arranged round the articles to be fired so as to protect them from contact with the 
 flame. The articles require also to be separated from each other by means of trian- 
 gular bars of hard burnt clay, so as to prevent them from sticking together in conse- 
 quence of softening. This precaution is necessary even in the first firing in the biscuit 
 kiln, and it is still more so in the second firing when the glaze is burnt on. The 
 material used for producing the glaze is a mixture of felspar or Cornish stone with 
 alkalies, borax and lead oxides. The glaze is either colourless and transparent, or 
 when the body of the ware is dark coloured, it is made opaque by the addition of 
 stannic oxide, and is sometimes coloured with other metallic oxides. 
 
 The decoration of the ordinary varieties of earthenware is generally effected by 
 transferring to the surface of the biscuit ware an impression of the intended design 
 that has been printed upon thin paper, with ink composed of suitable pigments and 
 linseed oil varnish. The paper is then washed off, leaving the design attached to the 
 surface of the ware, and it is burnt in by a special firing operation. The chemical, 
 characters of the pigments used for this purpose must be such that they will resist not 
 only the influence of heat in burning them in, but also that of the glaze material 
 which is generally applied to the ware afterwards. For blue, cobalt oxide is used, and 
 various shades are produced by mixing with it zinc oxide ; for green, chromous oxide 
 or cupric oxide is used; for yellow, uranium oxide, lead chromate, ferric oxide, or 
 potassium antimonate ; for red, cuprous oxide or ferric oxide ; for violet and rose- 
 colour, purple of cassius ; for pink, chromium stannate and calcium stannate. Some- 
 times the designs are printed upon the glaze after coating it with a layer of varnish. 
 
 Ordinary earthenware is not often decorated otherwise than by printing, and it is 
 only the superior kinds that have designs painted by hand in the manner that fine 
 pottery ware like porcelain is ornamented. Brilliant metallic films called lustres 
 are sometimes produced on the surface of ordinary earthenware by applying dilute 
 
 Z 
 
338 
 
 POTTERY WARE. 
 
 solutions of metallic salts and afterwards exposing the articles to the reducing action 
 of hot air containing smoke, which has the effect of reducing the metal. 
 
 The kiln used for firing this kind of pottery is represented by figs. 199, 200, 201, 
 202. The body of the kiln is a cylindrical domed chamber (D), the interior of which 
 
 FIG. 200. 
 
 FIG. 199. 
 
 FIG. 201. 
 
 (I) communicates with the fireplaces (/) of the furnaces (a a) by the vertical and 
 horizontal flues (y g}, shown on a larger scale in fig. 202. The kiln is surrounded by 
 a conical tower (TT) called the ho well, into which the 
 hot gas escapes from the kiln through the small apertures 
 (ccc) in the dome and is discharged from the throat (o) 
 or lunette of the howell. Fig. 200 is a horizontal plan of 
 the kiln (at the line d d), showing the arrangement of the 
 radiating and circular horizontal flues (g, fig. 199) and the 
 fireplaces (/). Fig. 201 represents on one side (c) a plan 
 of the kiln at the line (ee), showing the disposition of the 
 fireplaces (/), the upper mouths (6) of the furnaces, as 
 well as the vertical flues (y), and the horizontal peep- 
 holes or registers (x] which pass into the vertical flues, and 
 are also shown on a larger scale in the vertical section of 
 
 JIG. 202. 
 
 one of the furnaces (fig. 202). The other half (D) of fig. 201 
 
 is a bird's-eye view of the top of the kiln dome (s) and the disposition of the vent 
 holes (cc). The register slits (v) and (v r ), fig. 199, are for regulating the heat in the 
 kiln and the door (p) is for charging and emptying the kiln. The draught passes iu_^ 
 a downward direction through the upper mouths of the furnace (b), and the flame isT* 
 divided into two parts on entering the kiln, one part passing horizontally into the 
 flues (g\ under the sole (/c) of the kiln, and converging towards the centre, enters t he-- 
 interior of the kiln at that point, while the other part passes up through the low flues 
 or bags (y} into the body of the kiln. 
 
 The saggers containing the articles to be burnt are piled up in the space between 
 the furnaces in such a way that the top of one sagger is closed by the bottom of the 
 one above it, and they are built up in stacks until the kiln is full. The door (p) of the 
 kiln is then bricked up, the fires lighted, and the heat maintained for two or three 
 days at a proper degree. During the firing the lower furnace mouths (b') are kept 
 closed, fuel is supplied through the upper furnace, mouth (b), and the heat is regulated 
 by the tiles (z). By means of small cups made of the same clay as the ware tint is 
 being burnt, which are taken out and examined at intervals, the progress of the 
 operation is judged of, and when it is completed the kiln is allowed to cool very 
 slowly until the temperature has fallen low enough to take out the saggers. As the 
 
PORCELAIK 
 
 339 
 
 biscuit ware is taken out of the saggers, it is dipped into the glazing material, dried, 
 and then submitted to a second firing in the glaze kiln. 
 
 PORCELAIN. The materials used in the manufacture of this kind of clayware are 
 chiefly the white clay called kaolin, quartz, or some other kind of pure silica, and 
 felspar. These materials are very intimately mixed in such a manner that, while the 
 infusible kaolin gives plasticity to the mass that admits of its being shaped, the other 
 ingredients constitute a fusible mixture or flux which undergoes partial fusion, when 
 the ware is exposed to a high temperature, and thus forms a kind of cement by 
 which the particles of kaolin are permeated and held together. The mass conse- 
 quently acquires a considerable degree of translucency which is characteristic of this 
 ware. 
 
 The preparation of the materials involves a number of operations, chiefly of a 
 mechanical nature, having for their object the production of extreme uniformity in 
 the paste or mass of which porcelain articles are made. The clay is in the first in- 
 stance worked with water to separate undecomposed felspar and sand, then submitted 
 to a process of elutriation so as to obtain it in a state of very minute subdivision. 
 The felspar and other ingredients, such as gypsum, chalk, and fragments of broken 
 porcelain, are ground to an equally fine powder in mills having the construction re- 
 presented by fig. 203. 
 
 These mills consist of two stones (B B'), the lower one being fixed upon a solid bed 
 (b), while the upper one can be made to revolve by the shaft (M"), and gearing (M M). 
 Both stones are enclosed in a vat (c) hooped with 
 iron. The siliceous or felspathic materials are 
 ground in these mills with water, and when 
 reduced to a state of sufficiently fine subdivision 
 the sludge is run out through the spigot hole (c'). 
 
 The vat (c) extends above the upper move- 
 able millstone (B), and the lower stone (B 7 )is sur- 
 rounded with a strong wooden ring which is 
 funnel-shaped at the top (c) in order to throw 
 back any fragments forced upwards by the 
 motion of the stone. The millstone (B) is not 
 perfectly round, but has a portion cut away on 
 two sides so as to guide the materials under the 
 grinding surface, which is also grooved, as 
 shown at deg, in order that the materials being 
 ground may be retained between the surfaces of 
 the stones. 
 
 When the grinding of the siliceous or fel- 
 epathic material is nearly completed, the mass 
 aggregates together at the bottom of the vat as a 
 tenacious pasty magma, and when the mill is not 
 kept running at sufficient speed it is liable to be 
 set fast. 
 
 In mixing the ingredients, great care is re- 
 quired to secure the proper proportions ; and as * IG * " 
 
 this is an essential condition of the production of a suitable paste, regard must be 
 had to the composition of the raw materials used. At the porcelain works at Sevres 
 it is usual to make the paste so that it has the following composition percentage : 
 
 58-0 
 
 Alumina 
 34-5 
 
 Lime 
 4-5 
 
 The finely divided materials are mixed by long-continued stirring in the state 
 of thick sludge in large wooden vats, and the excess of water is then removed, either 
 by drawing off the mud into boxes fitted with plates of plaster of Paris at the 
 bottoms which absorb the water or by pressure in bags. When the mass is thus 
 reduced to a pasty consistence, it is kneaded and worked together into lumps by the 
 hands and feet of workmen until it becomes sufficiently plastic. The lumps of paste 
 ire then placed in layers in a moist place, and left for some length of time, to un- 
 iergo a process termed mouldering, in the course of which the paste acquires a dark 
 ?rey colour, and evolves sulphuretted hydrogen, while at the same time it becomes 
 more plastic. 
 
 Porcelain articles are either shaped upon a potter's wheel or by pressing sheets of 
 ,he paste between moulds made of gypsum, and sufficiently porous to absorb water 
 Tom the paste while it is being moulded, and render it so stiff that it cau be re- 
 "noved "without bending. 
 
 z2 
 
340 
 
 POTTERY WARE. 
 
 Plaster moulds are also used for casting some articles by pouring into them a liquid 
 mixture of the paste with water. By the absorption of the water into the mould, the 
 paste forms a crust upon the surface of the mould, and when this is thick enough, the 
 superfluous liquid is poured out. 
 
 The articles moulded by any one of these methods are afterwards submitted to 
 several further operations to finish them ; and then they are thoroughly dried in the 
 
 air and fired in saggers in the por- 
 celain kiln, which is constructed 
 as shown by fig. 204. It has 
 three compartments (LL'L") in 
 which different degrees of heat 
 are produced ; the upper com- 
 partment serves for drying sag- 
 gers or baking biscuit ware, 
 while the two lower compart- 
 ments are used for the subsequent 
 firing of the finished ware. The 
 kiln is heated by four furnaces 
 (A A) arranged round the kiln, 
 and the fuel is thrown in through 
 the mouths (b'b 1 ) so as to fill the 
 space (/). The draught passes 
 downwards through the mouth 
 (b') of the furnace and the flame 
 enters the kiln through the flue 
 (p), which is divided by a kind 
 of grating to disperse the flame 
 in the chamber (L). The ash pit 
 (b} is kept closed as well as the 
 small aperture (o). The arches 
 (D E) serve for placing the articles 
 to be burnt in the several com- 
 partments and removing them 
 when burnt. The draught is 
 produced by an opening (c) at the 
 top of the kiln, the flame and 
 hot gas passing upwards through 
 apertures (1 1 1) in the arch of 
 each compartment. 
 
 Since a very intense heat is 
 required for firing porcelain, the 
 
 kiln is massively built of refractory bricks, and strongly bound with iron hoops. Such 
 kilns are generally about 20 feet in diameter. 
 
 The glaze used for porcelain is a mixture either of kaolin, gypsum, and broken 
 porcelain, or of quartz and felspar very finely ground and made into a thin sludge or 
 slip with water. On dipping the biscuit ware into this mixture, a sufficient quantity 
 adheres to the surface, and after drying the articles they are again fired at a higher 
 temperature than in the first instance. 
 
 Another kind of ware, called tender porcelain, is made of a mixture of pure plastic 
 clay, kaolin, Cornish stone or partially decomposed granite, burnt bones, and flint. 
 These ingredients are ground and made with water into a homogeneous paste, which is 
 moulded on the potter's wheel, yielding, when fired, a highly vitrified porcelain. The 
 glaze consists of a mixture of felspathic stone, chalk, soda, and borax. 
 
 A kind of semi-porcelain, known by the name of fine stoneware, is extensively 
 made in England from plastic clay mixed with a felspathic material, which acts as a 
 flux, and gives the ware a close texture as a result of partial fusion in the firing. 
 In glazing this kind of ware the interior of the sagger is smeared with a mixture of 
 sodium chloride, potash, and lead oxide, which is vaporised during the firing sufficiently 
 to coat the articles and produce a glaze. The characters of stoneware depend very 
 much upon the quality of the clay used in making it, and there are several varieties of 
 it. The commoner kind, such as jars and bottles are made of, is glazed by exposing 
 it while in the kiln to the action of sodium chloride vapour, which penetrates the sub- 
 stance of the ware, and acts upon the siliceous material so as to form a fusible alkaline 
 silicate. This operation is called salt glazing. 
 
 BRICKS. The ordinary bricks used for building purposes are made of common 
 plastic clay, mixed with sufficient sand to produce a mass that will dry without crack - 
 
 FIG. 204. 
 
BRICKS AND ARTIFICIAL STONE. 341 
 
 ing, and bear firing without too much contraction. The temperature at which bricks 
 are burnt must be regulated according to the composition of the clay employed, so as 
 to avoid the melting of the bricks, which might readily occur when the clay contains 
 much iron. 
 
 Both loam and marl frequently occur of such a character as to be applicable at 
 once to making bricks, but clay generally requires to be mixed with a certain propor- 
 tion of sand, and sometimes chalk has to be added when the material used is too 
 sandy. In all cases, it is especially important to render the earth used for making 
 bricks as homogeneous as possible, to make it uniform in consistence, and to separate 
 from it any stones, shells, or remains of plants. This is effected either by kneading 
 the brick earth, or by passing it through a pug mill. To facilitate this operation, the 
 clay is generally exposed to the influence of frost, which causes its disintegration, and 
 sometimes it is mixed with sufficient water to form a sludge, which is run through 
 sieves to separate the coarser particles, and then left to settle in pits until the water 
 can be drawn off. Cinders are often mixed with brick earth for the purpose of pre- 
 venting the bricks from contracting too much when burnt, and in the neighbourhood of 
 London the siftings of dust heaps are used for this purpose under the name of breeze, 
 
 The operation of moulding is performed either by hand or by machinery, and the 
 bricks are then piled up in contact with the air, so that they may dry sufficiently to 
 be fired either in kilns, or in clamps constructed of alternate layers of green 
 bricks and breeze, with flues running throughout in communication with the fireplaces, 
 so that, by the combustion of the fuel thus distributed, the entire pile can be heated 
 to a sufficiently high temperature. 
 
 The characters of bricks depend upon the composition of the earth from which 
 they are made. When the amount of ferric oxide is considerable, the bricks often 
 have a dark red colour after burning ; but in some cas*s a portion of the oxide is 
 reduced, and by combining with silica, produces a fusible ferrous silicate which has a 
 dark colour and forms a vitreous glaze upon the surface of the bricks. When the 
 brick earth contains little or no iron, the bricks are white or pale coloured. 
 
 Tiles for roofing and drain pipes are made of clay mixed with a smaller proportion 
 of sand than is used in making bricks. 
 
 ARTIFICIAL STONE. Calcium salts and alkaline silicates react upon each other in 
 the presence of water, giving rise to alkaline carbonate and calcium silicate which is 
 a substance of sufficient durability to serve for building purposes. A method of pre- 
 paring artificial stone in this manner was introduced some years ago by Mr. Kansome.- 
 In the first instance he made this stone chiefly of sand, which was kneaded into a firm 
 dough with water glass, and, after being moulded into the shape required, was then 
 saturated with a solution of calcium chloride so as to convert the alkaline silicate in 
 the mass into calcium silicate, which acted the part of a cement and bound the grains 
 of sand into a solid coherent mass that was not susceptible of being disintegrated or 
 acted upon by water. 
 
 After the blocks had been submitted to the action of the calcium chloride solution 
 they were washed with water to extract the sodium chloride resulting from the decom- 
 position that had taken place between the alkaline silicate and the calcium chloride, 
 and then were finally baked in a kiln. It was found, however, that the complete re- 
 moval of the salt was difficult, and that the blocks of stone^ could not well be acted 
 upon throughout unless hydraulic power was applied for forcing the solution into the 
 mass of sand and alkaline silicate. 
 
 An improved application of this idea of making artificial stone consists in using, 
 instead of sand, calcareous materials and silica in the soluble condition for preparing 
 the paste with soluble alkaline silicate, A mixture of limestone, soluble silica, and 
 caustic lime made into a paste with alkaline silicate soon becomes hard, in consequence 
 of the formation of calcium silicate by the action of the lime upon the alkaline silicate. 
 If requisite, it can be still further hardened by treatment with a solution of calcium 
 chloride. 
 
MAGNESIUM. 
 
 SYMBOL Mg. ATOMIC WEIGHT 24. 
 
 History. This metal was first/ isolated by Davy in 1808. The distinction 
 between its compounds and those of calcium was not recognised until the middle of 
 the eighteenth century, when Black pointed out the characters which distinguish 
 magnesia from lime. Bergman subsequently gave a more complete description of the 
 chemical characters of the magnesium compounds. 
 
 Occurrence. Magnesium occurs very abundantly in several states of combina- 
 tion, especially in the form of carbonate as magnesite, and combined with calcium 
 carbonate as dolomite; in the state of hydrate it occurs as hydrophyllite, the 
 oxide as periclas, the sulphate as bittersalt, the borateas boracite, thearsenate 
 as a variety of pharmacolite, the phosphate in combination with magnesium fluo- 
 ride as wagnerite. The silicates occur as agreat variety of minerals, such as talc, 
 steatite, meerschaum, serpentine, etc.; also in combination with other silicates, 
 as in hornblende, augite, etc. The chloride and sulphate occur in sea water and 
 many kinds of mineral water. Magnesium also occurs in plant and animal organisms, 
 chiefly in the forms of carbonate and phosphate 3 or in combination with organic acids. 
 
 Characters. Magnesium is a bluish-white dull-looking metal, moderately hard 
 and malleable, but having very little ductility ; its specific gravity is T750, it melts 
 at a moderate red heat, and volatilises at about the same temperature as zinc. In a 
 dry atmosphere it does not oxidise, but in contact with moist air it soon becomes 
 covered with a film of magnesium hydrate ; when heated to redness in atmospheric 
 air or in oxygen gas it takes fire and burns with a very intense light ; it decomposes 
 water slowly, but is rapidly dissolved by dilute acids. 
 
 Preparation. Magnesium is prepared on a large scale by melting in an iron 
 crucible a mixture of magnesium chloride, sodium chloride, and calcium fluoride, with 
 sufficient sodium to separate the metal from the magnesium chloride. The reduced 
 metal sinks to the bottom of the crucible and is protected from oxidation by the layer 
 of melted salt above it. The magnesium is thus obtained free from nitrogen ; but as 
 it contains impurities and is too brittle to be worked, it is distilled from a close iron 
 vessel furnished with a discharge tube, by which the vapour is made to pass from the 
 top of the vessel downwards into another closed iron vessel placed underneath, where 
 it is condensed into blocks which are washed and broken up into small pieces. To 
 convert the metal into wire the pieces are packed into a cylinder with a perforated 
 bottom, and when made just hot enough to render the metal soft, pressure is applied 
 by means of the ram of an hydraulic press placed in the cylinder, until the metal oozes 
 out through the perforations in the bottom of the cylinder in the form of wire. By 
 passing the wire through warmed rollers it is converted into a flat ribbon, in which 
 form it is generally used. 
 
 Uses. Magnesium is used for burning, as a source of light for producing photo- 
 graphs, for which purpose it is well adapted, since the light evolved is rich in the rays 
 exercising chemical action ; it is also used in preparing fireworks. 
 
 Compounds. Magnesium is divalent and its compounds present considerable 
 analogy to those of zinc ; it combines directly with chlorine, bromine, iodine, sulphur, 
 and nitrogen, forming compounds which are represented by the formulae MgCl 2 , 
 MgBr 2 , MgS and Mg 3 N 2 . 
 
 The oxide MgO, known as magnesia, is the only known compound of magnesium 
 and oxygen. It is formed when the metal burns in atmospheric air or oxygen, as a 
 finely divided powder diffused through the remaining gas as a dense smoke. As 
 ordinarily obtained by heating the carbonate to redness, it is a bulky white powder 
 which bears a very high temperature without melting. Its specific gravity is from 
 3'070 to 3*200, and by strong ignition it is increased to 3'610. Magnesia has neither 
 smell nor taste ; it is but very slightly soluble in water, and has an alkaline reaction 
 

 MAGNESIUM COMPOUNDS. 343 
 
 upon test paper, but is not caustic. Magnesia is a strong base which combines with 
 acid oxides, forming salts. 
 
 Magnesium hydrate, MgH 2 2 , is a white pulverulent substance formed on 
 adding solution of potash, soda or baryta to the solution of a magnesium salt. It oc- 
 curs naturally as brucite in rhombohedral crystals. Magnesium carbonate, 
 MgC0 3 , is very sparingly soluble in water; it occurs naturally as magnesite, and 
 can be prepared by heating magnesium sulphate and sodium carbonate to 160C. 
 under pressure. It combines readily with ca,rbonic acid, forming a solution which 
 has a bitter taste and alkaline reaction ; but the acid carbonate, MgH 2 2C0 3 , has not 
 been obtained in a solid state. It also combines with other carbonates, forming 
 double salts, and on this account ammonium carbonate does not produce a precipitate 
 in solution of magnesium salts. The precipitate produced by fixed alkaline carbonates 
 is a compound or mixture of carbonate and hydrate. Magnesium chloride, 
 MgCl 2 , is a white translucent substance which melts at a red heat, bu^ is decomposed 
 when heated in contact with water, yielding hydrochloric acid and magnesia. It has 
 a sharp bitter taste, and is very soluble in water. A hot saturated solution deposits 
 crystals containing 6 molecules of water, MgC^GH^O. This salt forms double salts 
 with alkaline chlorides. It occurs naturally in sea water and in the water of many 
 springs. Magnesium bromide, MgBr 2 , which also occurs in sea water, in the 
 water of salt springs, and of mineral springs, is likewise a very soluble salt. 
 
 MAGNESIUM CARBONATE. 
 
 FORMULA MgC0 3 . MOLECULAR WEIGHT 84. 
 
 This substance has been known since the early part <rf the eighteenth century under 
 the name of magfiesia alba, but the distinction between it and calcium carbonate 
 was first recognised by Black in 1755. 
 
 Occurrence. Magnesium carbonate occurs naturally as magnesite, and in 
 combination with calcium carbonate very abundantly as dolomite ; it also occurs less 
 frequently in combination with ferrous carbonate, as spherosiderite, and with 
 manganous carbonate as dialogite. 
 
 Characters. Magnesium carbonate, as prepared artificially, almost always con- 
 tains water, and its composition is represented by the formula MgC0 3 3aq. The pre- 
 cipitate obtained by mixing solutions of sodium carbonate and magnesium sulphate is 
 a compound of magnesium carbonate with magnesium hydrate, and the pharmaceutical 
 preparation known as magnesia alba is of this nature, the relative proportions of 
 carbonate and hydrate depending upon the strength of the solutions used, their tem- 
 perature, and other conditions. It is a white earthy powder, very sparingly soluble 
 in water. When prepared with cold dilute solutions it is extremely light and bulky, 
 but when prepared with strong hot solutions it is much denser. At a red heat it gives 
 off water and carbonic dioxide, leaving magnesium oxide or magnesia. 
 
 MAGNESIUM SULPHATE. 
 
 FORMULA MgS0 4 . MOLECULAR WEIGHT 120. 
 
 This salt is commonly known as Epsom Salt, having been at one time obtained 
 chiefly from the water of mineral springs in the neighbourhood of Epsom. It occurs 
 abundantly in sea water and in the water of many mineral springs. It also occurs in 
 a hydrated state as kieserite in the salt beds of Stassfurt and several other localities. 
 
 Characters. Magnesium sulphate, as usually met with, is in the form of pris- 
 matic crystals containing 7 molecules of water of crystallisation ; it dissolves in its 
 own weight of cold water and in larger proportion in boiling water ; it has a bitter 
 unpleasant taste, and is highly purgative. When heated, 6 molecules of water are 
 readily given off, but 1 molecule is retained even at 200. At a red heat it becomes 
 anhydrous, and is only partially decomposed at a very high temperature. 
 
 Preparation Magnesium sulphate is largely prepared by acting upon magne- 
 sian limestone with sulphuric acid, separating the sparingly soluble calcium sulphate 
 by filtration, and evaporating the filtered liquid to crystallisation. It is also obtained 
 as a by-product in the treatment of sea water for alkaline salts, and from the kieserite 
 of Stassfurt. 
 
ZINC. 
 
 SYMBOL Zn. ATOMIC WEIGHT 65. 
 
 History. This metal was known to the ancients only in the form of an alloy 
 with copper, as brass ; and although the existence of a peculiar metal in the ores used 
 together with copper ores for obtaining this alloy was suspected by Basil Valentin 
 and others, it was not generally recognised until the early part of the eighteenth 
 century. The production of this metal on the large scale appears to have been carried 
 out in England as early as 1730. 
 
 Occurrence. Zinc seldom occurs naturally in the metallic state, but chiefly in 
 a state of combination. It occurs in considerable abundance in the state of carbonate 
 as calamine, and in the state of silicate as siliceous calamine; the sulphide 
 also occurs very abundantly as blende; the oxide to some extent as red zinc ore, 
 and combined with alumina and ferrous oxide as gahnite; the arsenate, phosphate 
 and sulphate are also met with as minerals. 
 
 Characters. Zinc is a bluish-white metal of considerable lustre when freshly 
 polished, but readily becoming dull by oxidation when exposed to the air. It is brittle, 
 and the fracture presents a crystalline texture. The density of zinc is 6'862, and by 
 hammering it is increased to 7'210. Its malleability is increased by heating to 120 
 or 150, sufficiently to admit of the metal being rolled into sheets, in which form it is 
 used for a great number of purposes. At 210 it again becomes so brittle that it can 
 readily be reduced to powder. 
 
 Zinc melts at 412, and at a bright red heat it volatilises ; it boils at 1040 and 
 gives off vapour which in contact with air takes fire and burns with a very luminous 
 flame, tinged with green and blue, forming a cloud of zinc oxide in the pulverulent 
 form known as flowers of zinc. Zinc is not very subject to oxidation under atmospheric 
 influences, and after the first film of oxide has been formed it seems to protect the 
 metal from further alteration either by air or water, except when it is in contact with 
 another metal and thus forms a galvanic circuit. Zinc dissolves readily in dilute acids, 
 hydrogen being eliminated and salts of zinc formed which remain dissolved; it is also 
 dissolved by alkaline solutions with evolution of hydrogen, and the zinc oxide thus 
 formed combines with the alkali, forming a compound which is soluble in water. 
 
 Commercial zinc, commonly known as spelter, always contains small amounts 
 of lead and iron, together with very minute quantities of carbon, tin, cadmium, 
 copper and arsenic, which render the metal brittle and more difficult to roll into sheets 
 than pure zinc. According to Karsten's experiments, lead is the most objectionable 
 impurity, and even when it amounts to less than 1 per cent, it reduces the tenacity of 
 the metal. Iron does not appear to affect the tenacity of zinc so much as lead, but 
 it increases the hardness of the metal, and renders it more readily soluble by acids. 
 
 Preparation. Zinc is obtained on the large scale by reducing the oxide with 
 charcoal and distilling off the metal into suitable condensers. The ore used for this 
 was formerly one of the two kinds of calamine, but more recently blende has been 
 extensively worked as a source of zinc. It is first roasted to get rid of the sulphur 
 and to convert the metal into the state of oxide ; sometimes this roasting is conducted 
 in such a way as to admit of the sulphurous oxide produced being used either for 
 making sulphuric acid or some other purpose. 
 
 Roasting Ores. Calamine is sometimes roasted in kilns, but more frequently rever- 
 beratory furnaces are used in roasting both calamine and blende. In the case of siliceous 
 Cidamine the operation of roastingis chiefly useful in disintegrating the ore,but in the case 
 of calamine consisting of zinc carbonate it has the further advantage of separating car- 
 bonic dioxide and water, which would other wise interfere with thesmelting operation by 
 lowering tbe temperature, and thus retarding the reduction of the oxide. Blende requires 
 to be crushed to a fine powder, and spread in a layer about 4 inches thick over the bed of 
 the furnace, which is generally about 36 feet long by 9 feet wide, and is divided into 
 
 
ZINC SMELTING. 
 
 345 
 
 three parts, differing a few inches in height, the lowest portion being next to the fire 
 bridge. When the furnace is sufficiently hot a charge of crushed ore is placed in the 
 highest compartment of the bed and 
 stirred from time to time so as to expose 
 fresh surfaces to contact with the 
 air, and thus facilitate the oxidation. 
 After some hours this charge is raked 
 down into the next compartment of the 
 bed, and replaced by a fresh quantity 
 of ore. After another interval the par- 
 tially roasted ore is transferred to the 
 lowest compartment of the hearth, and 
 in this way successive charges of ore are 
 worked through the roasting furnace. 
 
 Seduction. The roasted ore is 
 mixed with half its weight of powdered 
 charcoal or coal dust, placed in cruci- 
 bles, retorts, or muffles, and heated 
 sufficiently to effect the reduction and 
 vaporisation of the metal. According 
 to the English system, cast-iron cruci- 
 bles are used in a circular furnace repre- 
 sented by figs. 205 and 206. Thecruci- 
 bles (h A) are closed above and have 
 tubes passing through the bottom for the 
 escape of the zinc vapour downwards. 
 The sole (ii) of the furnace is per- 
 forated where the crucibles stand, to 
 allow of the tubes being connected with 
 sheet-iron pipes (kk) dipping into pots (II) for receiving the condensed zinc. This 
 operation is called distillation per desccnsutn. 
 
 According to the Belgian system of smelting zinc, retorts are used for the reduction 
 
 of the oxide. They are made of fire clay, as shown in fig. 207, and are 3 feet 
 
 I 
 
 -p 2QR 
 
 FIG. 207. 
 
 6 inches long from b to d, 7 inches in diameter ; short conical pipes of fire clay (dc) 
 are fitted into the necks, and to these are fitted conical tubes of thin sheet iron (fe). 
 
 FIG. 208. FIG. 209. 
 
 The furnace in which the retorts are heated is represented by figs. 208 and 209. ^ F 
 is the fireplace and A the chamber in which the retorts (a c, b d) are placed in a sloping 
 position with the conical tubes (rr) adjusted to the mouths of the retorts. 
 
 When the retorts have been heated to a proper temperature they are charged with 
 a mixture of calcined ore and carbonaceous material by means of a scoop, which fits 
 
346 
 
 ZINC. 
 
 into the retorts, and the conical tubes are then fitted to the retorts with fire-clay luting. 
 Carbonic oxide soon begins to escape and burn at the mouth of the conical tubes, and 
 when the flame assumes a greenish-white colour, giving off white fumes, the sheet- 
 iron cones are fitted on for the condensation of the zinc vapour. After some time the 
 cones become filled with zinc oxide ; they are then removed to clear out the oxide, 
 and replaced as often as may be necessary. When a sufficient quantity of metallic 
 zinc has collected in the conical clay tubes, it is scraped out into an iron ladle held 
 under the mouths of the tubes and poured into moulds, this operation being repeated at 
 intervals until all the zinc has been distilled off. The residue in the retorts is then 
 drawn out and a fresh charge put in. 
 
 In the Silesian zinc works muffles made of baked clay (M, figs. 210 and 211) are used 
 for the reduction ; they are about 3 feet long and 20 inches high. At the front are 
 
 FIG. 210. 
 
 FIG. 211. 
 
 two holes, a and d ; the lower one is intended for the removal of the residue left after 
 each operation, and can be closed by a cover of fire clay while the distillation is going 
 on. Into the upper hole is fitted a rectangular tube made of fire clay, which is open 
 at the end (c) and has an aperture at b through which the muffle can be charged by 
 means of a proper scoop. The furnace in which the muffles are heated is represented 
 
 FIG. 213. 
 
 by figs. 21 2 and 213. Six or ten of these muffles arc arranged in the apertures M M M 
 and heated by the furnace o. The zinc vapour escnpes through the rectangular pipes 
 (E B) and passes into cavities (o o 0), where it is condensed in iron pans. 
 
 The Sflesian method of smelting zinc has been introduced in this country in place 
 of the system formerly adopted, which was expensive on account of the largo consump- 
 tion of fuel it involved. 
 
 The zinc thus obtained is remelted in iron pots holding about half a ton each, the 
 oxide collecting on the surface is skimmed off, and the metal cast into ingots for the 
 market. Sometimes this operation is conducted in a reverberafcoiy furnace, the hearth 
 
 i 
 
COMPOUNDS OF ZINC. 347 
 
 of which is inclined to one side, where at the lowest point there is a hemispherical 
 reservoir in which the liquid metal collects, the ingots of zinc to be melted being piled 
 up on the highest part of the hearth near the fire bridge. The melted zinc is ladled 
 out of the reservoir, and poured into moulds which have the form of slabs if the 
 metal is required for rolling into sheets. 
 
 Uses, Zinc is largely used in the form of sheet for purposes of construction, such 
 as roofing, etc. ; it is also much used for coating iron and producing what is termed 
 galvanised iron. In order to coat iron with zinc the surface of the metal is first 
 cleansed by immersing the sheets, or other articles to be galvanised, in a bath of dilute 
 sulphuric or hydrochloric acid, and when perfectly free from oxide they are dipped 
 into a bath of melted zinc on the surface of which is a layer of fat to prevent oxidation. 
 The zinc then combines with the iron at the surface, forming an alloy which serves to 
 protect the iron from oxidation and render it more durable. 
 
 Compounds. Zinc is a divalent metal forming only one series of compounds. 
 The oxide ZnO is a strong base, and the saline compounds it forms with acid oxides 
 are isomorphous with magnesium salts ; the chloride ZnCl 2 is a translucent fusible 
 and volatilisable substance, very soluble in water, deliquescent and poisonous. A 
 solution of this substance is used as a disinfectant under the name of Burnett's Fluid. 
 Zinc chloride mixed with ammonium chloride is often used to clean metallic surfaces 
 in soldering. Zinc sulphide, ZnS, is a white or yellowish-white substance insoluble 
 in water ; it is slowly acted upon by acids, with evolution of sulphuretted hydrogen, 
 and is slowly oxidised when heated in contact with atmospheric air. It occurs natu- 
 rally in the form of blende or black jack, is crystalline, of a dark yellow, brown, 
 or black colour, and is one of the most important ores of zinc. 
 
 Zinc readily unites with other metals, forming alloys, most of which are hard and 
 some of them brittle. Zinc and bismuth melted together do not form an alloy, but 
 separate into two layers, the zinc containing about 2'5 per cent, of bismuth, and the 
 bismuth from 8 '5 to 15 per cent, of zinc. Alloys of zinc, tin, and copper constitute 
 several kinds of bronze which, on account of their hardness, are well adapted for the 
 journals and other parts of machinery. Some kinds of bronze contain lead as well as 
 copper, tin, and zinc, such as British bell metal and the biddery ware of India. 
 
 The most important alloy of zinc is brass, which consists of zinc and copper in 
 various proportions. The amount of zinc in brass ranges from 20 to 67 per cent. 
 Muntz's yellow metal, or patent sheathing, is an alloy of this kind, consisting of 40 
 per cent, zinc and 60 per cent, copper. The alloy called smilior contains a larger 
 proportion of copper and white button metal more zinc. 
 
 zxxrc OXIDE. 
 
 FORMULA ZnO. MOLECULAR WEIGHT 81. 
 
 History. Zinc oxide was first proposed as a substitute for white lead by 
 Courtois in 1780; in 1783 Gayton Horveau described- its preparation, and showed 
 the advantages it had over -white lead ; three years afterwards Courtois commenced 
 preparing zinc white on a large scale. In 1796 Atkinson took out a patent in this 
 country for the preparation of zinc white ; but here as in France these earlier attempts 
 to introduce the manufacture were not successful. 
 
 In 1849 the manufacture of zinc white was started again by Leclaire, and its 
 establishment is due to him. 
 
 Occurrence. Zinc oxide occurs naturally as zin cite and franklinite, both 
 of which contain also manganese oxides, and the latter ferric oxide and ferrous oxide 
 in considerable amount. Franklinite occurs abundantly in New Jersey, and unsuccess- 
 ful attempts have been made to work this ore for zinc. It is also smelted for iron, and 
 it is said that the zinc contained in the iron thus obtained has the effect of giving 
 greater tenacity to the metal. 
 
 Characters. Zinc oxide obtained by burning zinc or igniting the carbonate is 
 an amorphous flocculent substance which is largely used as a paint under the name of 
 zinc white and for pharmaceutical purposes ; it is insoluble in water ; has a specific 
 gravity of about 5'6 ; is very refractory in the fire, but is said to volatilise to some 
 extent when very intensely heated. While hot it has a yellow colour, but becomes 
 white again on cooling. Zinc oxide is very easily reduced by charcoal at a moderately 
 high temperature, less readily by hydrogen or carbonic oxide. Heated with sulphur 
 it forms zinc sulphide and sulphurous oxide. Chlorine displaces the oxygen at a red 
 heat, forming zinc chloride and free oxygen. Zinc oxide is a strong base combining 
 
348 
 
 ZltfC. 
 
 readily with acid oxides and forming salts. It also combines with sesquioxides, such 
 as alumina, chromic hydrate, and ferric oxide, and several of these compounds occur 
 naturally. 
 
 By adding ammonia or fixed caustic alkali to the solution of a zinc salt this oxide 
 is obtained in the state of hydrate, ZnH 2 2 , as a gelatinous precipitate soluble in 
 excess of the precipitant. When dried and heated it readily gives up its water. It 
 can be obtained in a crystalline state from the ammoniacal solution of zinc oxide, and 
 a dihydrate, ZnH 4 3 , is deposited slowly from a saturated solution of the oxide in 
 caustic soda. 
 
 Preparation. Zinc oxide is sometimes prepared by igniting the carbonate 
 sufficiently to drive off the carbonic dioxide. 
 
 Attempts to prepare zinc oxide in the wet way have not as yet been commercially 
 successful. Its manufacture on a large scale consists essentially in burning zinc 
 vapour in contact with atmospheric air, and collecting the zinc oxide thus formed, in 
 condensing tubes or chambers. 
 
 The furnace used in preparing zinc white is represented in vertical and horizontal 
 sections by figs. 214, 215, and 217- 
 
 FIG. 214. 
 
 FIG. 216. 
 
 FIG. 215. 
 
 The metal is heated in fire-clay retorts (a a), 8 
 or 10 of which are placed together in the furnace 
 (fig. 214). The shape of these retorts is shown 
 by fig. 216. The length is 27 inches, the width 
 10 inches, height 6 inches, thickness of the walls 
 l inch, height of the opening (b b b, figs. 214 
 and 215) 2 inches, width 4 inches. 
 
 The retorts are heated by the furnace (c, figs. 
 215 and 217), the flame playing round the retorts 
 
PREPARATION OF ZINC WHITE. 349 
 
 S^9fi2S*3!3f^ 
 
 c, which melts, and the 
 
 apertures (b b), coming into 
 contact with air at a tem- 
 perature of 300 C., trans- 
 mitted from the channels 
 (ss, fig. 214) towards (5), 
 burns to zinc oxide, which 
 is carried by the draught 
 through the tubes (KK/) 
 into a series of condensing 
 chambers, where it is pre- 
 cipitated. The arrange- 
 ment of the condensing 
 chambers is shown by 
 figs. 218 and 219. A is 
 the retort furnace, H com- 
 mon chimney, B B tubes 
 leading into the chambers. 
 Each pair of tubes termi- 
 nate in a system of four 
 chambers. The inlet into 
 
 the first chamber is above, FIG. 217. 
 
 and the outlet below ; in the second chamber this is reversed. The outlet (M) of the 
 
 hist chamber is covered with a piece of wire gauze, to keep back as much as possible 
 
 le zinc white. After leaving this chamber, the gas passes through a long flue (o) 
 
 FIG. 218- 
 
 FIG. 219. 
 
 into the chimney (H). Wire-gauze partitions are often placed in the flue (a) to retain 
 the zinc oxide. Most of the zinc white collects in the funnel-shaped parts of the con- 
 densing chambers, and is drawn out at intervals into the sacks or casks. 
 
 The zinc white deposited in the chamber is pure white, and only that portion 
 deposited in the receiver (o) under the mouths of the retorts is a little grey, owing 
 to the presence of a small quantity of metallic zinc. This greyish product, however, 
 after being washed yields a product applicable for ordinary purposes. 
 
 Since zinc white is of a very loose and light nature, and consequently occupies a 
 proportionately large space, it requires to be pressed into the barrels in which it is 
 packed. 
 
 Figs. 220 and 221 represent another kind of retort for preparing zinc white. The 
 
350 
 
 ZINC. 
 
 inner space is 3^ feet long, 1 foot wide, and 4 inches high ; the walls of the retorts are 
 l inch thick a"t the bottom, and above f inch. The opening (a) for putting in 
 the zinc and for the escape of zinc vapour is 10 inches wide, and l inch high. 
 
 FIG. 220. 
 
 FIG. 221. 
 
 Two retorts of this kind are placed one above the other, as shown at (a a, fig. 222), 
 with their mouths towards a common receiver, with a 
 little bridge (&) at the side, which serves the purpose of 
 separating the pure zinc white from that which is con- 
 taminated with particles of metallic zinc. This is de- 
 posited in front of the bridge (b) and falls down into 
 the receivers (b'b 1 ), while the pure product deposited in 
 the conical tubes (d d) falls down through the space 
 between b and c into the receivers (c c). Opposite the 
 mouths of the retorts is a large iron door, which serves 
 for removing damaged retorts and replacing them with 
 new ones. This iron door is also furnished with 
 smaller doors, opposite the mouth of each retort, 
 through which the metallic zinc is thrown in. 
 
 The retorts are placed in rows of 5 pairs together, or 
 10 in all over a common furnace ; each retort of the 
 lower row is charged with about f cwt. of zinc, the 
 retorts of the upper row each receiving half as much 
 
 FIG. 222. 
 
 more. A single retort is capable of burning from 6 to 7 cwts, of zinc in the course of 
 24 hours. The coal required for this purpose is estimated at about 40-45 per cent, of 
 the weight of the zinc used. 
 
 FIG. 223, 
 
PREPARATION OF ZINC WHITE. 
 
 351 
 
 Fig. 223 represents in section a furnace with the retorts above described. The 
 condensing chambers are shown in projection. (A A) ash pit, over which is a grate about 
 10 feet long, fed with coal through the fire doors (bb). The flame passes into the 
 niches (c c c), in each of which are placed a couple of retorts, one above the other, as 
 shown at the left hand of the drawing. The hot air, after having played round the 
 retorts, passes through flues into the chimney (B). The burnt zinc vapour from each 
 pair of retorts passes through the conical tubes (d' d') to a flue (d d) of sheet iron, and 
 then through upright tubes into a system of tubes shown in fig. 224, where A represents 
 the ash pit, B the chimney for two series of furnaces, B' the retort furnaces, c' c' the 
 tubes through which the heavy zinc white falls into the receivers beneath, while the 
 lighter sort passes into the tube (d). The hot air with the suspended particles of zinc 
 white then passes through the siphon-shaped metal tubes (d" d'"d* d 5 ), which terminate 
 at their lower extremities in the receivers (e e' e" e'" e*). These receivers have funnel- 
 shaped bottoms, in which the zinc white deposited in the tubes collects, and falls 
 into sacks placed beneath. These siphon-shaped tubes (d" d'") may be arranged in 
 pairs side by side, and carried round the whole of the building. Considerable quanti- 
 ties of zinc white are deposited in these tubes, and the hot air from them is passed 
 into the chambers on the side of the building opposite to the furnaces, in order to 
 collect the last particles of zinc white. The arrangement of the condensing chambers 
 is represented in vertical section lengthways by fig. 225, six of them being placed 
 together, 3 to each furnace, as shown in fig. 226. The gas cooled to 50 in the tubes, 
 passes from the receiver (/') into the first chamber (gg 1 ), lined with plush linen, 
 
 FIG. 224. 
 
 and divided into two parts (g g') by a partition, reaching not quite to the top. From 
 the first chamber the gas passes from below into the first division (# 2 ) of the second 
 chamber, then over the partition into the second division (g 3 ), then into the third 
 chamber (<7 i # 5 ), and so on until it reaches the eighth. It then passes into a second 
 series of 8 chambers, afterwards into a third similar series of chambers, and from 
 the eighth chamber of this series it escapes through a curtain of wire gauze into 
 the chimney (# 15 ). Each chamber terminates below in a funnel, where the zinc white 
 collects and is drawn off into c:isks. 
 
352 
 
 ZINC. 
 
 Beckoning together the tubes and chambers, the products of combustion of each 
 furnace with ten retorts travel a distance of nearly 1000 yards. In the 40 retorts 
 of a furnace with four sets of retorts, the quantity of zinc burnt in 24 hours may be 
 reckoned at about 12 tons ; 3000 tons in the year of 250 working days. 
 
 FIG. 225. 
 
 Fig.. 226 represents a horizontal section of the retort furnaces, condensing tubes 
 and chambers. A A four series of retort furnaces, b b receivers, dd'd" . . . d 6 funnel- 
 shaped receivers for the siphon-shaped condensing tubes, out of which the gas passes 
 into the chamber system opposite to the retort furnaces. 
 
 10. 226. 
 
 The products of this apparatus are: 1. Zinc dust, consisting of a mixture of 
 zinc white and finely-divided metallic zinc, which is purified by a special washing 
 process. 2. Zinc white, which is removed from the receivers every morning. The 
 
 
PREPARATION OF ZINC WHITE. 
 
 353 
 
 227 
 
 FIG 228 
 
 products deposited in the different receivers vary in tint. In order to render the 
 zinc white uniform, the contents of the different receivers are well mixed together 
 in some suitable vessel before being packed into casks for transport. 
 
 At G-renelle a different method is adopted, and the zinc is burnt in fire-clay cru- 
 cibles (B, figs. 227 and 228), instead of retorts. A is the support for the crucibles in 
 the furnace, c the lid with an opening D, 2 inches in diameter, for 
 throwing in the zinc aucl for the escape of zinc vapour. Figs. 229 and 
 230 represent a crucible furnace with 7 crucibles. The ashpit beneath 
 the grate is closed at pleasure by the door (/). When closed, hot air 
 passes through the flue (/') under the grate. The flame plays round the 
 7 crucibles (h K), and escapes through the flue () to the chimney. Above 
 each crucible is an opening large enough for removing 
 broken crucibles and replacing them with new ones ; the 
 opening is generally closed by the lid (/&). At the part of 
 the furnace (b c) shown in projection in fig. 229 there are 
 iron doors (' i), and small openings (jj), which serve to 
 admit and regulate the supply of air required for the com- 
 bustion of the zinc vapour. Opposite the mouth of each 
 crucible is an opening (m\ through which the gas passes, together with zinc white, 
 into the tube (q r), then into the condensing chambers. Between the opening (m) 
 and the tube (q) are two cavi- 
 
 ties (o and p\ in the first of 6 
 
 which is deposited zinc dust, 
 and in the second impure 
 zinc white. Beneath the tube 
 (qr) is a sliding damper for 
 drawing off the zinc white 
 deposited at q into a vessel (v). 
 
 PREPARATION FROM ZINC 
 ORES. The preparation of 
 zinc white from calamine, red 
 zinc ore, or blende, has not at present attained any importance, since the product thus 
 obtained is deficient in whiteness. The ores most suitable for conversion into zinc 
 white are those which contain zinc oxide, such 
 as calamine, red zinc ore, and franklinite ; 
 blende is less suitable. The essential feature 
 of the process consists in heating the ore to 
 redness with coal in muffle-shaped furnaces, 
 the zinc vapour thus produced being burnt to 
 zinc white. 
 
 The zinc white deposited in the first re- 
 ceivers of the furnaces has a greyish tint, owing 
 to an admixture of finely-divided metallic zinc. 
 In order to separate this, the product is sub- 
 mitted to a process of elutriation, in an appa- 
 nitus represented by fig. 231. a is a water tank from which the flow of water into 
 the box (<?) is regulated by the cock (6). The impure zinc white is placed in the 
 
 FIG. 129. 
 
 FIG. 230. 
 
 FIG. 231. 
 
 box (c) and stirred with a rake (d), while water flows in from the tank (o). The 
 water, retaining zinc white in suspension, flows over a partition through a han 
 
 A A 
 
354 
 
 ZINC. 
 
 (c') into the trough (e), then under the partition (e r ) over the next partition (e"), and 
 so on to the partition (e 4 ), etc., till it reaches the partition (e 6 ), and passes through a 
 channel into the large basin (i), where the zinc white still retained in suspension is de- 
 posited after some time. From c 6 the liquid flows into the long settling trough (/#), the 
 bottom of which has a number of perforations closed with wooden plugs. Beneath these 
 openings are placed a corresponding number of vats (h h! h" h'"} into which the zinc 
 white deposited in the trough is let out. After remaining here for eight days, 
 
 the supernatant water is drawn off. 
 and the pasty zinc white, as well as that 
 in the boxes (e e" e* e 6 ) removed to 
 filters consisting of linen bags (a a a, 
 fig. 232), supported upon wooden frames. 
 After the water has drained off, the 
 stiff pasty zinc white remaining in the 
 
 ^ 9q9 filter must be dried as quickly as possi- 
 
 ble by the application of heat. When 
 slowly dried the mass becomes so hard that it is difficult to break up. 
 
 The drying apparatus is represented by figs. 233 and 234, and consists of a cast- 
 iron pan (b) about 50 feet long and 8 inches deep, supported upon a thin bed of bricks 
 
 FIG. 233. 
 
 FIG. 234. 
 
 beneath which pass two flues from the furnace (A). The metal lids (c c), turning on 
 hinges, are for the purpose of observing the progress of the drying as well as for stir- 
 ring the mass. The water condensing on the lids runs off by the channel (d). The 
 pasty zinc white is spread out upon the pan (A), 3 or 4 inches deep, and kept there 
 until completely dry. Instead of applying direct heat, the hot air from a zinc white 
 furnace may be made to pass under the drying pans. The dried zinc white is broken 
 up, pressed through a fine sieve, and packed. 
 
 Latry in Grenelle separates the metallic zinc from zinc white by boiling the zinc 
 dust in a cauldron with water, by which means the zinc white is brought into sus- 
 pension, and carried with the water through a side opening into settling tanks, while 
 the metallic zinc settles to the bottom even in the boiling water and remains in the 
 cauldron. 
 
 SICCATIVE FOB ZINC WHITE. White lead paint is rendered drying by mixing it 
 with linseed oil that has been boiled with litharge. This plan does not answer in the 
 case of zinc white, because the chief advantage of zinc white, of not blackening in an 
 atmosphere of sulphuretted hydrogen, would then be lose. Leclaire prepares a drying 
 oil to be used with zinc white by boiling linseed oil with manganese peroxide. 100 
 parts of well-boiled and purified linseed oil and 5 parts of well-ground manganese 
 peroxide are heated with frequent stirring nearly to boiling. Instead of mixing the 
 manganese peroxide with the oil, it may be suspended in a bag in the heated oil. The 
 manganese peroxide remaining, as the case may be, either in the bag or at the bottom 
 of the boiling vessel, when exposed to the air, acquires the property of rendering 
 oil drying in a greater degree, so that the same manganese peroxide serves for any 
 number of operations. 
 
 According to Sirel, a very good dryer for zinc white is obtained by intimately mix- 
 ing manganese subchloride completely freed from iron by means of potassium ferro- 
 cyanide with 19 parts of zinc oxide or barium sulphate; and 2 percent, of this 
 mixture, added to zinc white, is sufficient to make the oil paint thus prepared dry in 
 36 hours. 
 . The Vielle Montagne Company employs the following dryers : 
 
 Zinc white . . . 980 parts I Manganous acetate . 6*66 parts 
 Manganous sulphate . 6'66 Zinc sulphate . . 6'66 
 
 The*o materials in a fine state of division are intimately mixed, and 2 per cent, of 
 the mixture added to the zinc white in making paint. 
 
APPLICATIONS OF ZINC WHITE. 355 
 
 Barruel's dryer consists of zinc white and 5 to 6 per cent, of manganous borate. 
 Kochaz's dryer is made of 20 parts zinc white, 6 parts pine resin, 2 parts turpentine, 
 and 1 part boiled linseed oil ; or, 20 parts zinc white, 3 parts Burgundy pitch, and 
 1 part boiled linseed oil. 
 
 PREPARATION or ZINC WHITE OIL COLOURS. For preparing zinc white paste, 
 the dry zinc white is mixed with 4'8 per cent, of dryer and 48 per cent, linseed oil. 
 Paint ready for use is made by mixing together zinc white with 76 per cent, linseed 
 oil, 4-8 per cent dryer, and 8 per cent, of turpentine. 
 
 When the surface to be covered has a strong tendency to absorb, as is the case with 
 plaster of Paris walls, etc., the quantity of oil used in the first coating is increased 
 threefold. The use of much turpentine is to be avoided, not only on account of the 
 slow rate of evaporation, the unpleasant smell, and the formation of a resinous coating. 
 but also because it leaves the zinc white in such a loose condition that it adheres very 
 badly. Benzin may be used instead of turpentine when desired. 
 
 Zinc white admits, like white lead, of being made into an oil colour while in a 
 moist condition ; the oil displaces the water, which may be easily drawn off. 
 
 The following table gives the percentage amounts by weight of different pigments 
 requisite for producing different tints with zinc white : 
 
 Azure blue 1 part indigo 
 
 Pearl blue 1 charcoal 
 
 Slate blue 100 parts zinc dust 
 
 Straw yellow . . . . 2-5 zinc or lead chromate 
 Chamois . . . . . 3 ,, yellow ochre and 3 parts 
 
 cinnabar 
 Lemon yellow . . . . 2'5 ,, chrome yellow and 2 parts 
 
 Prussian blue 
 
 Gold colour 10 chrome yellow 
 
 Water green . . . . 8 Prussian blue 
 
 Grass green * *;'' 100 ,, chrome yellow and 8 parts 
 
 Prussian blue 
 
 Olive green 50 yellow ochre and 1 2 pts black 
 
 Bronze green .... chrome yellow, 6 parts Prus- 
 
 sian blue and 6 parts black 
 
 The black employed is either ivory black, bone black, lamp black, or manganese 
 peroxide, etc. 
 
 Uses. Zinc white admits of being substituted in all cases for white lead, and its 
 use is advantageous in all cases where the atmosphere is liable to contain sulphuretted 
 hydrogen. Besides the use of zinc white in the preparation of printed goods, writing 
 paper, wall paper, cards, wood, stone, and gypsum painting, etc., it has of late been 
 used for stopping teeth when mixed with zinc chloride; it is used for polishing optical 
 glasses, for decolorising glass, for preparing artificial meerschaum, for printing " 
 fabrics so as to give them the appearance of lace or embroidery work. 
 
 ZINC SULPHIDE. 
 
 FORMULA ZnS. MOLECULAR WEIGHT 97. 
 
 History. This substance occurring naturally as blende, was first shown to be 
 an ore of zinc in 1735 by Brandt ; prior to that time it had been regarded as a useless 
 lead ore, galena inanis. It is now one of the chief sources of metallic zinc. 
 
 Occurrence. Zinc sulphide occurs very abundantly in various geological form- 
 ations, frequently associated with galena, heavy spar, copper pyrites, spathic iron, and 
 silver ores. 
 
 Zinc sulphide is a constituent of several metallurgical products, as, for instance, 
 copper regulus ; it gives rise to the formation of accretions in the furnaces where lead 
 or copper ore is smelted. 
 
 It also occurs, combined with various other sulphides, in some of the varieties of 
 fahl-ore. 
 
 Characters. Zinc sulphide when pure is colourless, and in the crystalline state 
 transparent or translucent ; the sulphide obtained by precipitation is white and pul- 
 verulent. As it occurs naturally it has more frequently a yellow, brown, or black 
 colour, owing to the presence of impurities ; and the mass has either a scaly crystalline 
 texture or is granular and compact. Blende often contains a large amount of iron in 
 
 AA2 
 
356 
 
 ZINC. 
 
 the state of sulphide, and has then a black colour, on which account it is termed 
 black jack. 
 
 
 New Jersey 
 
 Clausthal 
 
 Carinthia 
 
 New Hamp- 
 shire 
 
 Tuscany 
 
 
 Henry 
 
 Kuhlemann 
 
 Kersten 
 
 Jackson 
 
 Beccui 
 
 Sulphur . 
 
 32-22 
 
 33-04 
 
 32-10 
 
 32-6 
 
 33-65 
 
 Zinc 
 
 67-46 
 
 65-39 
 
 64-22 
 
 52-0 
 
 48-11 
 
 Cadmium 
 
 
 
 0-79 
 
 trace 
 
 3-2 
 
 
 
 Iron 
 
 
 
 1-18 
 
 1-32 
 
 11-3 
 
 16-23 
 
 S" : : : 
 
 
 
 0-13 
 
 0-72 
 0-80 
 
 
 
 z 
 
 Antimony 
 
 
 
 0-63 
 
 
 
 
 
 
 
 
 99-68 
 
 101-16 
 
 99-16 
 
 99-1 
 
 97-99 
 
 Zinc sulphide in the form of blende requires a very high temperature for melting, 
 and it volatilises at a white heat ; it oxidises but slowly when heated in contact with 
 atmospheric air, and less readily than most other sulphides. Sulphurous oxide is 
 given off, and there is formed a mixture of zinc oxide with zinc sulphate, from which 
 greater part of the sulphuric oxide is given off at a higher temperature. Part of the 
 zinc sulphide always remains unoxidised. By fusion with nitre zinc sulphide is easily 
 and completely converted into sulphate; it is decomposed slowly by acids with evolu- 
 tion of sulphuretted hydrogen. The amorphous hydrated sulphide obtained by pre- 
 cipitation, ZnS.H 2 0, oxidises very rapidly on exposure to the air, and is dissolved very 
 readily by acids even when dilute. 
 
 ZINC SULPHATE. 
 
 FORMULA ZnS0 4 . MOLECULAR WEIGHT 161. 
 
 History. This salt, commonly known as white vitriol or white copperas, 
 was certainly manufactured as an article of commerce at Groslar in the Hartz about 
 the middle of the sixteenth century ; but it was mentioned at an earlier date by Basil 
 Valentin, and was probably known long before that time. The relation of white 
 vitriol to zinc and calamine was partially recognised by Geoffroy in 1713, but its com- 
 
 C'tion was not established until 1735, when Lemery pointed out that it was different 
 a green vitriol or ferrous sulphate, and Hellot prepared it by dissolving zinc 
 with sulphuric acid. Shortly afterwards Brandt demonstrated that this salt contained 
 zinc, both by preparing it from the metal and by making brass by melting the calcined 
 salt with charcoal and copper. 
 
 Occurrence. Zinc sulphate occurs naturally as goslarite at several places, 
 together with blende, and is probably a product of the oxidation of this mineral. A 
 considerable quantity of zinc sulphate is now obtained as a secondary product. 
 
 Cbaracters. Zinc sulphate is colourless, has an astringent metallic taste, and 
 is a powerful irritant poison ; it is readily soluble in water and usually crystallises 
 with 7 molecules of water in right rhombic prisms, which effloresce in dry air, give off 
 37'6 percent, or 6 molecules of water at about 100, but retain 1 molecule until heated 
 up to 260. At a full red heat the dry salt is decomposed, giving off sulphuric oxide, 
 which is partially converted into sulphurous oxide, and yielding zinc oxide, which 
 remains as a white powder. The crystalline salt dissolves in less than its weight of 
 boiling water and rather more than twice its weight of cold water ; it is quite in- 
 soluble in alcohol. 
 
 Preparation. Zinc sulphate may be prepared by dissolving either zinc or the 
 oxide or carbonate in dilute sulphuric acid, and it is made on the large scale by roast- 
 ing the native sulphide or blende until it is converted into sulphate by oxidation, then 
 dissolving out the salt with water, and evaporating the solution to dryuess. Since 
 the blende used for this purpose generally contains other minerals, the salt obtained 
 in this way is impure, containing iron, copper, lead, etc. : it is therefore slightly cal- 
 cined to oxidise ferrous sulphate, redissolved in water, and the solution left in contact 
 with plates of metallic zinc until the foreign metals are precipitated; the clear colour- 
 
ZINC CARBONATE. 
 
 357 
 
 less solution is then evaporated down to a small bulk, and on cooling the zinc sulphate 
 separates in small crystals as an opaque white granular mass. 
 
 Uses. Zinc sulphate is used in medicine, as a mordant in dyeing, in calico- 
 printing, and in the preparation of drying oil for painting. 
 
 ZINTC CHLORIDE. 
 
 FORMULA ZnCl 2 . MOLECULAR WEIGHT 136. 
 
 This salt is a white translucent solid, fusible without decomposition when anhy- 
 drous, and volatile at a red heat. It is very soluble in water and deliquesces when 
 exposed to moist air ; it is also soluble in alcohol. The specific gravity is 2753. 
 
 Zinc chloride may be prepared by dissolving zinc in hydrochloric acid and evapo- 
 rating the solution to dryness, or by heating the metal in an atmosphere of chlorine 
 gas. _ 
 
 Zinc chloride combines with ammonium chloride and other chlorides, forming 
 double salts ; and with albumen or gelatin it forms sparingly soluble compounds. A 
 solution of zinc ammonium chloride is much used in soldering for the purpose of re- 
 moving oxide from the surface of the metals. Zinc chloride in the solid state has a 
 powerful corrosive action on the skin and is used as a caustic ; in solution it is used 
 for preserving wood, and as a disinfectant, the action in both cases being due to the 
 combination of the salt with albuminous and gelatinous substances. Burnett's Disin- 
 fecting Fluid is a strong solution of zinc chloride ; it is highly poisonous. 
 
 ZIMTC CARBONATE. 
 
 FORMULA ZnC0 3 . MOLECULAR WEIGHT 125. 
 
 History. This substance as it occurs naturally was probably known at a very 
 early period, under the name of calami ne, as the earth by which copper was coloured 
 yellow in the production of brass. The term calamirie, however, was applied not only 
 to the carbonate but also to the silicate of zinc ; and for a long time these two minerals 
 compounded together were the only source from which metallic zinc was obtained. 
 
 Occurrence. Zinc carbonate occurs naturally both crystallised and as granular 
 or earthy masses ; when pure it is colourless, transparent, or translucent, but is more 
 frequently coloured by the presence of iron, manganese, copper, etc. 
 
 
 Somerset- 
 shire 
 
 
 Aix-la-Chapelle 
 
 Mexico 
 
 
 
 Kobell 
 
 
 
 
 Smithson 
 
 
 Monheim 
 
 Genth 
 
 Zinc oxide . , 
 Carbonic dioxide 
 
 64-8 1 
 35-2 i 
 
 96-00 
 
 60-35 55-89 
 
 1 
 
 34-92 
 
 74-42 
 
 93-74 
 
 Ferrous carbonate . 
 
 
 
 2-03 
 
 32-31 | 36-46 
 
 1-58 
 
 3-20 
 
 
 
 Lead 
 
 
 
 1-12 
 
 | 
 
 
 
 
 
 
 
 Manganous ,, 
 
 
 
 
 
 4-02 
 
 3-47 
 
 6-80 
 
 14-98 
 
 1-50 
 
 Calcium 
 
 
 
 
 
 1-90 
 
 2-27 
 
 1-58 
 
 1-68 
 
 1-48 
 
 Magnesium 
 
 
 
 
 
 0-14 
 
 
 
 2-84 
 
 3-88 
 
 0-29 
 
 Cupric 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3-42 
 
 i Zinc silicate 
 
 
 
 
 
 2-49 
 
 0-41 
 
 1-85 
 
 
 
 
 
 Silica 
 
 
 
 __ 
 
 
 
 
 
 
 
 0-20 
 
 
 
 1 Water . 
 
 
 
 
 
 
 
 
 
 
 
 0-56 
 
 
 
 
 100-00 
 
 99-15 
 
 101-21 
 
 98-50 
 
 99-57 98-92 
 
 100-43 
 
 Characters. Zinc carbonate is colourless and insoluble in water, it is decomposed 
 slowly at 300, and readily by a red heat, and giving^off carbonic dioxide is con- 
 verted into zinc oxide. As usually obtained, by grinding and washing native cala- 
 mine, it presents the appearance of a pale flesh-coloured powder ; the colour, however, 
 is merely due to the presence of accidental impurity, generally iron or manganese. 
 
 Preparation. The precipitate obtained by mixing solutions of zinc salts and 
 fixed alkaline carbonates is not zinc carbonate, but a mixture or compound of the car- 
 
858 ZItfC. 
 
 bonate with zinc hydrate, and the only method of preparing neutral zinc carbonate is 
 to dissolve the precipitate by charging the liquid with carbonic dioxide, and to evaporate 
 the solution in an atmosphere of the gas. 
 
 The substances precipitated from solution of zinc salts by alkaline carbonates differ 
 in composition according to the nature, strength, and temperature of the solutions 
 used. Cold concentrated solutions yield a precipitate containing less carbonic acid 
 than that formed in very dilute cold solutions or in boiling solutions. 
 
 A similar hydrocarbonate occurs naturally as zinc bloom, and in combination 
 with copper compounds as aurichalcite and buratite. 
 
 All these hydrocarbonates give off water and carbonic dioxide at 200, yielding zinc 
 oxide ZnO. The precipitate produced by a fixed alkaline carbonate dissolves in solu- 
 tion of ammonic carbonate and yields, on evaporation, crystals of a double salt. 
 Similar double salts containing potassium and sodium can be obtained. 
 
 The native zinc silicate, which is so often confounded with the carbonate, occurs 
 both crystallised and compact, frequently associated with the native carbonate. ' It is 
 white when pure, but generally coloured in consequence of the presence of ferric oxide 
 or other impurities. A specimen analysed by Eammelsberg had a composition corre- 
 sponding to the formula 2ZnO.Si0 2 + H 2 0. Part of the zinc is sometimes replaced 
 by iron or lead. 
 
 Anhydrous zinc silicate often occurs as wi lie mite in deposits of zinc ores, and 
 very abundantly in New Jersey; a variety called troos tit e occurs associated with 
 franklinite in the same locality. 
 
 ZINC ACETATE. 
 
 FORMULA Zn2(C 2 H 3 2 ). MOLECULAR WEIGHT 183. 
 
 The salt dissolves in three times its weight of cold water and half its weight of 
 boiling water, crystallises with 3 molecules of water, melts at 100, and gives off its 
 water with partial decomposition. It is used by dyers as a mordant, and is often pre- 
 pared for that purpose by mixing solutions of zinc sulphate and of lead acetate, which 
 decompose each other according to the following equation : 
 
 ZnS0 4 + Pb2(C 2 H 3 2 ) = PbS0 4 + Zn2(0 2 H 3 2 ). 
 
 The clear liquid drawn off from the precipitated lead sulphate is then evaporated 
 until sufficiently concentrated to crystallise on cooling. 
 
 CADMIUM. 
 
 SYMBOL Cd. ATOMIC WEIGHT 112. 
 
 This metal was discovered by Stromeyer in 1817, and about the same time by 
 Hermann. It occurs either as sulphide, carbonate, or silicate, associated with zinc ores 
 in small amounts, and its name is derived from the term cadmia fossilis by which 
 calamine was formerly known. 
 
 Cadmium is a white metal resembling tin in appearance ; its density is 8'604, and 
 after hammering 8'694 ; it is very malleable, melts at a red heat, and is very volatile. 
 Like zinc, it is divalent, and forms but one series of compounds ; the oxide CdO has a 
 pale brown colour, is infusible, and absorbs carbonic dioxide, forming carbonate. The 
 chloride, bromide, and iodide are soluble salts. The sulphide CdS is a bright yellow 
 crystalline powder, that is used as a pigment on account of its fine colour. It occurs 
 naturally as greenockite. The other salts and compounds of cadmium present con- 
 siderable analogy with those of zinc in character and composition. 
 

 LEAD. 
 
 SYMBOL Pb. ATOMIC WEIGHT 207. 
 
 History. The earliest definite mention of this metal is to be found in the works 
 of Pliny, who called it plumbum nigrum, and thus distinguished it from another 
 metal called plumbum candidum or album, which was probably either tin or an alloy 
 containing tin ; but, prior to that time, the two metals appear to have been frequently 
 confounded together under the name fj.6\if$os. Lead was used by the Eomans for 
 making water pipes, and its ores were worked by them both in Spain and in this 
 country. 
 
 Occurrence. Lead does not occur naturally in the metallic state to any great ex- 
 tent, but the compound with sulphur occurs abundantly as galena, and combined 
 in several proportions with antimonous sulphide, aszinkenite, plagionite, jame- 
 sonite, feather ore, boulangerite, geokronite, kilbrikenite; with anti- 
 monous sulphide and. cuprous sulphide as bournonite; with cuprous sulphide and 
 bismuth sulphide as needle ore, and with some other sulphides. Lead also occurs 
 in the oxidised state as minium, as peroxide and litharge; the sulphate as lead 
 vitriol, the carbonate as white lead ore, and in combination with the sulphate as 
 leadhillite and sulphato-carbonate, the tungstate as scheeletine, the molyb- 
 date as wulfenite, the chromate as melanochroite, the aluminate as lead gum. 
 Lead also occurs in combination with chlorine as cott unite, and the. chloride 
 occurs combined with the phosphate and arsenate as pyromorphite, combined with 
 the carbonate as horn lead, and combined with the oxide as mendipite. 
 
 The most abundant ore of lead is galena, and it almost invariably contains silver, 
 the amount varying from mere traces up to such proportions that this ore is an im- 
 portant source of silver. 
 
 Characters. Lead has a bluish-grey colour and "considerable lustre when free 
 from the thin film of oxide which is readily formed by contact with atmospheric air. 
 The metal is so soft that it can be easily scratched or cut with a knife ; it is very 
 malleable and ductile when pure, and can be rolled into very thin sheets or drawn 
 into wire ; but these characters are considerably modified by the presence of very small 
 proportions of other metals or of lead oxide. The tenacity of lead is but slight, and 
 a wire i inch diameter will not support a weight of 20 pounds. The specific gravity 
 is about 11-35 or 11-44. 
 
 Lead melts at 325 to 335, and at a red heat it volatilises ; its specific heat is 
 0-0314, and it has a low conductive power for heat and electricity. When exposed to 
 dry air or to water free from air it is not altered, but in contact with moist air it is 
 rapidly covered with a film of oxide ; and in water containing air and carbonic acid it 
 soon becomes covered with a white coating of carbonate and hydrate, which is par- 
 tially dissolved by the water. 
 
 Heated in contact with air lead assumes at the surface an iridescent appearance 
 as a result of oxidation, and it is soon covered with a yellowish coating of oxide. 
 When the temperature is sufficiently high to melt the oxide, it is absorbed by the un- 
 oxidised metal, which then becomes dull and brittle. 
 
 Acids which do not readily yield oxygen do not act upon lead except when it is 
 also in contact with air; moderately dilute nitric acid dissolves lead very readily, 
 forming a nitrate. Strong sulphuric acid converts it into sulphate when heated to the 
 boiling point, but when the acid is dilute it has little action upon lead ; hydrochloric 
 acid has but little action upon lead. Weak acids like acetic acid exert a considerable 
 solvent action upon lead, especially when it is in contact with atmospheric air ; and 
 on this account leaden vessels are not fit to be used in the preparation or preservation 
 of articles of food containing acids. 
 
 The action of water upon lead is of great importance in a sanitary point of view, 
 since this metal is extensively used for cisterns and water pipes. Water containing 
 dy a small amount of saline substances, such as sulphates, carbonates, or phosphates, 
 
360 LEAD. 
 
 does not dissolve the lead oxide formed on the surface of the metal, and water contain- 
 ing acid calcium carbonate does not act upon lead to any appreciable extent after a 
 film of lead carbonate has been formed on its surface. With water free from saline 
 .impregnation, but containing carbonic acid, like rain water, the case is very different ; 
 since lead carbonate is dissolved by the carbonic acid sufficiently to cause a dangerous 
 contamination of the water. 
 
 Preparation. Since galena is the most abundant ore of lead and the most im- 
 portant source of this metal, the various operations of lead smelting are chiefly regu- 
 lated in accordance with the chemical characters of lead sulphide. The ores consist- 
 ing either wholly or in part of carbonate, sulphate, phosphate, or other oxy-salts of 
 lead require somewhat modified treatment ; but such ores do not furnish more than 
 one-tenth part of the material used in the production of lead. 
 
 Lead ores, however, frequently contain admixtures of other minerals, some of which 
 like fluor spar, quartz, calc spar, or barium sulphate do not yield metal in the pro- 
 cess of smelting and are comprised under the general term gangue ; while others, 
 like pyrites of different kinds, blende, etc., contain metals which are reduced together 
 with the lead and remain alloyed with it. In many instances such a result would not 
 be desirable, and therefore such lead ores are submitted to mechanical operations of 
 picking and sorting before being smelted, in order to separate as far as possible the 
 admixtures from the galena. Very often, however, the foreign minerals are intimately 
 mixed with the galena, or even combined with it, so that their separation by mechanical 
 means is impracticable ; and in such cases the operations of smelting are modified in 
 certain details with the view of effecting the separation of the lead from the other 
 reducible metals associated with it. Sometimes the subsidiary operations carried out 
 for this object are extremely complicated. 
 
 As regards the extraction of lead from galena, the operation of smelting, as most 
 frequently carried out, is based upon the behaviour of lead sulphide when heated to- 
 gether with lead oxide ; mutual decomposition takes place, the sulphur combining with 
 the oxygen of the lead oxide to form sulphurous oxide gas, while the lead of both 
 substances is separated in the metallic state, according to the following equation : 
 
 PbS + 2PbO = 3Pb + S0 2 
 239 446 621 64 
 
 A precisely similar reaction takes place when lead sulphide is heated together 
 with lead sulphate ; and in this case also the products of the chemical change are 
 sulphurous oxide and metallic lead, according to the following equation : 
 PbS + PbS0 4 = 2Pb + 2S0 2 
 239 303 414 128 
 
 When lead sulphide is heated in contact with atmospheric air, it is gradually 
 oxidised, sulphurous oxide is given off, and the lead eventually remains partly in the 
 state of oxide and partly as sulphate, as shown in the following equation : 
 
 2PbS + 70 = S0 2 + PbO + PbS0 4 
 478 112 64 223 303 
 
 Consequently, the substances requisite for effecting the separation of sulphur from 
 galena so as to obtain the lead in the metallic state may be produced by operating 
 upon the ore in such a manner as to effect the oxidation of part of the lead sulphide 
 and the formation of lead oxide and lead sulphate sufficient to decompose the lead 
 sulphide that remains unoxidised. The smelting of rich load ores consisting of 
 galena is, in most instances, effected in this way, and sometimes the operation is 
 carried out in two distinct stages, in the first of which, termed the calcination, the 
 finely powdered ore is exposed to the action of atmospheric air at a moderate heat, and 
 constantly stirred about meanwhile, until the sulphide has been oxidised to a 
 sufficient extent. The true smelting of the ore, or the reduction of the metal it con- 
 tains, is effected in the second stage of the operation, and it requires a much higher 
 temperature than the calcination. 
 
 It is obvious that, in order to obtain the whole amount of lead contained in the 
 ore operated upon, the proportion of lead sulphide oxidised should bear exactly the 
 relation to the unoxidised portion that is indicated by the equations given above. 
 Practically it would be impossible to obtain such a result even with ore consisting of 
 pure galena; and in all cases some portion of the lead remains, either in the state of 
 sulphide, or as oxide, sulphate, etc. Besides, lead ores always contain, together with 
 galena, other substances which must be separated in the smelting, either as slag or 
 otherwise; and the conditions under which this result is brought about also determine 
 the formation of lead compounds, which escape reduction ;tncl remain in the slag or 
 other by-products. In this way it happens that in smelting lead ore there are obtained, 
 
BOASTING OF LEAD ORES. 
 
 3G1 
 
 besides metallic lead, various other products containing an amount of the metal 
 sufficient to be worth extracting by further treatment. 
 
 Another method of smelting lead ores is based upon the action of metallic iron 
 upon lead sulphide at a high temperature, as shown in the following equation : 
 
 PbS + Fe = FeS + Pb 
 239 56 88 207 
 
 A portion of the lead sulphide combines with the ferrous sulphide formed, pro- 
 ducing a regulus approximating to the composition FeS + PbS. 
 
 Ferrous silicate, in the form of slag from iron-refining or from copper-smelting 
 works, is sometimes substituted with advantage for metallic iron for the reduction of 
 lead from galena, by smelting a mixture of the ores and slag in contact with coke in a 
 blast furnace. 
 
 The coarser kinds of ore containing, besides galena, admixtures of iron pyrites or 
 other sulphides in considerable amount, yield, when smelted with scrap iron, only a 
 small proportion of metallic lead, together with a large quantity of regulus rich in 
 lead. To render such ores more suitable for smelting they are often submitted to a 
 preliminary roasting, either in open heaps, stalls, or reverberatory furnaces, by means 
 of which the sulphur, arsenic, antimony, zinc, etc., are partially volatilised, and the 
 other sulphides are partially converted into oxides, which can be dissolved by melting 
 the roasted ore with siliceous slag in contact with reducing agents, while the more 
 easily reduced lead oxide yields metallic lead. A certain proportion of lead regulus 
 is generally formed at the same time by the reduction of the sulphates into which the 
 sulphides are partly converted in the roasting operation. 
 
 At Freiberg the lead ore is roasted in a finely divided state in reverberatory fur- 
 naces until the amount of sulphur remaining does not exceed 5 per cent. ; and the 
 following analysis by Mrazek represents its composition after roasting : 
 
 Silica, . 17-4 
 
 Alumina . . . . *. . . . 1*8 
 
 Lime . . . . . . . v T\ 2-0 
 
 Magnesia . 0'5 
 
 Ferrosoferric oxide . . . .. . 33'3 
 
 Zinc oxide . . . . .... . 16*0 
 
 Manganous oxide . trace 
 
 Lead oxide . ... > . . .'...' . 22-0 
 
 Cupric oxide . 0*3 
 
 Antimonic oxide ... . . trace 
 
 Arsenic oxide ... ./.. .;.. I'l 
 
 Sulphuric acid . ';.'.., . . . . trace 
 
 Sulphur in sulphides . ... . .-, N . - 3*62 
 
 Silver . . .<:, i .' V '' .' ' . .' 0-13 
 
 9.8'io 
 
 sented 
 
 The arrangement of the roasting heap in the Lower Hartz and in Sweden is repie- 
 ted in vertical section by fig. 235. A thick rectangular bed of pine wood (a a) is 
 
 FIG. 235. 
 
 kid down, as shown upon a larger scale in fig. 
 236, which represents only one fourth the area 
 of the bed, in such a way as to form channels 
 for the access of air beneath the heap, and a 
 wooden shaft (c) is built up in the centre; the 
 larger lumps of ore are then spread upon the 
 wood above the opening (c) in the form of a FIG. 236. 
 
 conical heap (dd), up to the level of the central 
 
 shaft, and covered over with layers (//) of the dust or smaller fragments of ore, 
 stamped down to prevent access of air. The wood is set fire to below, and the com- 
 bustion regulated by closing or opening the air channels beneath the wood. A heap 
 
362 
 
 LEAD. 
 
 Fio. 237. 
 
 of this kind contains from 100 to 200 tons of ore and remains burning for 20 or 30 
 weeks. A number of cavities (s s s s) are formed at the top of the heap which servo 
 for the collection of the sulphur given off from the ore in sufficient amount to cover 
 the cost of roasting. This operation is sometimes repeated once or twice until the 
 ore has been sufficiently oxidised. Ore containing much blende is sometimes lixivi- 
 ated after the first roasting in order to dissolve out the zinc sulphate formed by the 
 oxidation of that substance. 
 
 The smelting of lead ores is conducted either in low furnaces called hearths, in 
 shaft furnaces, or in reverberatory furnaces. 
 
 SMELTING IN HEARTHS. By heating lumps of galena in contact with burning fuel 
 part of the lead is reduced to the metallic state and part remains in the state of sul- 
 phate. Such a method of smelting could only be applied to very pure ore, and 
 moreover it would involve a very considerable waste ; it is, however, practised to 
 some extent, and the rudest form of lead smelting is carried out in this way in the 
 back-woods hearth, represented by fig. 237, and consisting simply of a square 
 
 chamber in which the ore is 
 heated with wood or other fuel. 
 The metal, reduced partly by 
 the two reactions above de- 
 scribed and partly by the action 
 of the carbonaceous substance of 
 the fuel upon the lead sulphate, 
 runs out through the arched 
 opening on one side of the 
 chamber into a pit made for its 
 reception, and through the 
 same opening atmospheric air is 
 supplied for the combustion of 
 the fuel. The ancient British 
 smelting furnaces used in Derby- 
 shire were probably of this 
 nature, and prior to the intro- 
 duction of bellows worked by water power, they were placed in such a position as 
 to be exposed to the prevailing wind. At the present day an artificial blast of air is 
 always used. 
 
 The simplest form of blast furnace is that known by the name of the ore hearth, 
 in which the ore is reduced by heating it in contact with fuel. One form of this fur- 
 nace, called the Scotch ore hearth, is much used in Scotland and the northern parts of 
 the country ; a somewhat similar furnace is used in America. 
 
 The Scotch ore hearth is represented in vertical section by fig. 238. It consists of 
 a rectangular chamber (c) about 22 inches square and 2 feet high, built of refractory 
 
 material or lined with cast-iron 
 plates. At the front of the fur- 
 nace is the sloping work stone 
 (M), over which the reduced lead 
 flows out of the furnace, and be- 
 yond it is a cast-iron pot (p) to 
 receive the metal. The bellows' 
 pipe is placed in a cavity at the 
 back of the hearth, about 6 inches 
 above the level of the work stone. 
 The ore can be worked in the 
 hearth either raw or calcined, but 
 it is now usual to calcine it pre- 
 viously; it is placed upon the surface of the burning fuel in the hearth bottom, 
 and when submitted to the action of the blast for about five minutes it melts and is 
 reduced, running down between the fuel into the hearth bottom. Fresh portions of 
 ore are added in this way at intervals until the hearth becomes filled with lead upon 
 which floats a mass of burning fuel mixed with partially melted and reduced ore, 
 which is termed browse. From time to time a poker is thrust into the hearth so as 
 to raise up and open the mass as well as to bring some portion forward upon the work 
 stone to make room for fresh supplies of ore. The browse thus brought forward is 
 then examined, any lumps that have been formed are broken up, and those which have 
 become vitrified or hardened by the heat arc picked out for working by another method. 
 Such lumps are called ' grey slag.' A little slaked lime is then sprinkled over on the 
 work stone ; if it has a pasty appearance fresh fuel is added, and the browse pushed 
 back into the hearth is covered with a further quantity of fresh ore. 
 
 Fio. 238. 
 
LEAD SMELTING IN HEALTHS. 
 
 363 
 
 Either peat or wood is used as fuel in this operation, and as it proceeds the re- 
 duced lead sinks down into the hearth bottom until it flows over the work stone into 
 the iron pot (p), from which it is transferred by ladles into moulds. 
 
 In working the ore hearth the regulation of the blast is an important point. Too 
 weak a blast would not produce sufficient heat for the reduction of the ore, and too 
 strong a blast would cause the production of slag containing lead. The nature of the 
 ore operated upon also requires to be considered. 
 
 The ore hearth, when constructed in the manner above described, allows lead 
 fumes to escape ; and besides the loss thus occasioned there is a possibility of detri- 
 ment to the workpeople. In order to obviate this objection the modification repre- 
 sented by fig. 239 has been introduced, the hearth being covered with a brickwork 
 
 hood (a), at the back of which there is an opening into the flue, and the area of this 
 opening can be regulated by means of a damper movable from outside at b. The open- 
 ing in front can also be adjusted by the movable iron plate (c), which can be raised 
 or lowered as requisite. The brickwork hood is securely bound with iron bands (d d), 
 through which bolts pass from side to side of the hood. The opening (e) under the 
 arch (/) admits of access to the tuyere at the back of the hearth for the regulation 
 of the blast, and the opening (g} at the side is for introducing the charges of ore and 
 fuel. 
 
 The American ore hearth represented by fig. 240 is constructed with a hollow cast- 
 iron casing (d) round the upper part of the hearth (a), which serves for heating the 
 
 FIG. 240. 
 
 air by which the blast is produced, inasmuch as it is forced into the pipe (c) and 
 after traversing the hollow casing (d) escapes into the hearth through the tuyere (g). 
 
364 
 
 LEAD. 
 
 The work stone (b) is made of cast iron, with a gutter for the molted lead to flow into 
 the iron pot (c). The form of the ore hearth is used in Carinthia, and it is worked 
 essentially in the same manner as the Scotch hearth. 
 
 In smelting lead ore in these hearths, waste products containing partially reduced 
 lead ores accumulate in course of time under the name of hearth ends, which are 
 generally washed, roasted, and smelted in the same way as fresh ore. The vitrified 
 product known as grey slag contains lead chiefly in an oxidised condition, and it is 
 smelted in the slag hearth described below. 
 
 The slag produced in working the ore hearth has been analysed by Plattner and 
 found to have the following composition 
 
 Silica 5-260 
 
 Lead oxide 37*710 
 
 Sulphuric acid 5-038 
 
 Ferric oxide 19-500 
 
 Zinc oxide . . . . . . . 19*200 
 
 Lime 8'856 
 
 Magnesia and manganous oxide . . . 1*417 
 
 Alumina, cupric oxide, and alkalies . . . 1'760 
 
 Molybdicacid -460 
 
 99-201 
 
 The rich slags resulting from the smelting of lead ore either in hearths or rever- 
 beratory furnaces, and containing lead in an oxidised condition, are smelted by a pro- 
 cess of reduction ; either in contact with the fuel used for producing the requisite 
 temperature, in blast furnaces, or, with the addition of carbonaceous materials, in re- 
 verberatory furnaces. Lead sulphate, which is a frequent constituent of the rich slags 
 from lead smelting, is reduced at a red heat by carbon, with formation of carbonic 
 dioxide and lead sulphide : 
 
 PbS0 4 + 20 = 2C0 2 + PbS; 
 
 and when lead sulphide is heated to a sufficiently high temperature with lead sulphate, 
 both substances are decomposed in the manner already mentioned, with production of 
 sulphurous oxide and metallic lead. The smelting of slags containing lead silicate 
 would be facilitated by the addition of ferrous silicate. 
 
 The slag hearth (known in Germany as the Krummofen, and in France as 
 the fourneau a manche), represented by figs. 241 and 242, is a small rectangular 
 blast furnace somewhat similar to the ore hearth. The sole (a) is a cast-iron plate 
 -p 241 sloping towards the fore hearth (b\ into which the melted 
 
 material is discharged. On each side of the sole plate 
 there are strong cast-iron beams (cc), called bearers, 
 which support the side walls, and the cast-iron plate (d) 
 called the fore stone, which carries the front wall of 
 the shaft, leaving an open space above the sole plate 
 | about 7 inches high. The back of the hearth is lined 
 l -i with an iron plate reaching up to the tuyere, which is 
 
 , about 20 inches above the sole plate. The cistern (c) in 
 
 front of the fore hearth is kept full of water, so that the 
 melted slag flowing off from the surface of the lead in the 
 fore hearth is suddenly cooled and granulated, and thus ad- 
 mits of the more easy separation of the lead mechanically 
 mixed with it. The lead runs off from the fore hearth into 
 an iron pot (/) which is kept hot by a fire. 
 
 In working the slag hearth the bottom is filled with coke 
 or cinders up to within 4 or 5 inches of the tuyere, and when 
 the fire has been got up the slag to be smelted is thrown on, the alternate addition of 
 fuel and the material to be smelted being repeated at intervals. The process is one 
 of reduction, effected chiefly by the carbonaceous portion of the fuel, with production 
 of metallic lead and a fusible slag nearly free from lead. 
 
 The loss of lead in smelting by the slag hearth is very great in all cases, but very 
 much depends upon the manner in which the operation is conducted. In all cases the 
 hearth should be covered, not only to protect the workmen from the effects of the 
 fume, but also to reduce the loss of lead by volatilisation, by making the furnace gas 
 p;iss into a long flue, where the lead is condensed and deposited. 
 
 Though the slag hearth, as its name indicates, is specially intended for working 
 up by products which contain too much lead to be thrown away, a modification of it 
 is sometimes used for smelting ores containing only a small amount of lead, which is 
 
 Fio. 242. 
 
LEAD SMELTING IN HEARTHS. 365 
 
 chiefly in an oxidised state. In Spain, for instance, ores occur very abundantly con- 
 sisting of earthy carbonates mixed with lead carbonate, and containing from 5 to 15 
 per cent, of lead, together with silver amounting to about 15 or 20 ounces per ton, 
 and the smelting of these ores is conducted in furnaces similar to the slag hearth. 
 
 The Spanish slag hearth represented by figs. 243, 244, and 245, has been intro- 
 duced into this country, and is much used for smelting poor and easily fusible slags 
 
 FIG. 243. 
 
 FIG. 244. 
 
 containing lead. It consists of a hollow shaft 
 of fire brick, the upper part of which is sup- 
 ported upon four cast-iron pillars (////), to 
 admit of the body of the furnace being renewed 
 when requisite without interfering with the 
 upper part. The hearth (g} is dish-shaped and 
 made of a mixture of coke dust and fire clay. 
 The breast of the furnace is made of a semi- 
 circular plate of cast iron, with a lip to carry off 
 the slag and a slot furnished with a clay plug, 
 by withdrawing which the lead accumulating in 
 the hearth is let off into a pot (h) at the side of 
 the furnace. There are generally several tuyeres 
 a short distance above the level of the breast 
 plate. 
 
 In working this furnace it is charged up to 
 the level of the door (6), and the lead fume 
 passes off through the aperture (d) into a flue. 
 
 The lead in the materials smelted exists chiefly in the oxidised state as silicate, etc., 
 and the reducing agent is either metallic iron or slags containing ferrous silicates. 
 Fluor spar is often used as a flux, and when the materials contain barium sulphate it 
 is especially useful. The slag is either allowed to run into the breast pan (i) contain- 
 ing water, or into cast-iron waggons, and turned out in blocks when it has solidified. 
 
 In Spain a furnace is used for lead smelting, the working part of which resembles 
 the slag hearth in its construction, but the ore is worked without a blast, the draught 
 being produced by a chimney instead, as shown by figs. 246, 247, and 248. The body 
 of the furnace is about 8 feet high, and 4 feet wide. Six openings (GU) are left in 
 the walls for the admission of air and for drawing off the slag. ' 
 
 FIG. 245. 
 
 The furnace is con- 
 
3*36 LEAD. 
 
 nected with the chimney (A) by the flue (c), supported on the arch (K). The chimney 
 (A) is about 50 feet high, and has an area large enough to work two furnaces. The 
 
 FIG. 246. ' 
 
 air holes (GO) are 12 inches high and 15 inches wide outside, tapering inwards to 
 smaller dimensions, as shown in figs. 247 and 248. Above them are other holes (FF), which 
 
 FIG. 247. 
 are generally bricked up, but can be opened if requisite. The inclined plane (H) serves 
 
 lor raking out the slag, and the door (D) for charging the furnace. In the sectional 
 view of this furnace, fig. 247, the shape of the sole (P) is shown. It is made of a 
 refractory argillaceous material, ground to fine powder with one third its weight of 
 coke, moistened with water, and stamped down into a compact mass. The crucible (K) 
 is then cut out, and in working the furnace the reduced lead collecting in it is run off 
 into a metal pot (T, fig. 248). 
 
 FIG. 248. 
 

 LEAD SMELTING IN SHAFT FURNACES. 367 
 
 SMELTING IN SHAFT FURNACES. Lead ores containing earthy admixtures in con- 
 siderable amount are advantageously smelted in shaft furnaces, together with materials 
 suitable for acting as fluxes upon the foreign substances in the ore, and converting 
 them into a sufficiently fusible slag. The decomposition of the sulphide or other 
 lead compounds may be in this case effected by metallic scrap iron added to the 
 charge, or by ferruginous materials which are capable of yielding iron when heated in 
 contact with carbon. The ferrous sulphide formed in this way by the combination of 
 the reduced iron with the sulphur of the galena does not mix with the metallic lead 
 separated, neither is it dissolved by the slag, and when the melted contents of the 
 furnace are run out, it separates as a distinct layer between the reduced metal and the 
 slag, forming what is termed regulns or matt. In smelting lead ores by means of iron, 
 part of the lead contained in the ore is almost always retained in the regulus by the 
 combination of the ferrous sulphide with some of the lead sulphide, and consequently 
 further operations are necessary for obtaining the whole of the lead, or there is a log's 
 of this metal proportionate to the amount of regulus produced. 
 
 The proportion of lead retained in the regulus is to a great extent dependent upon 
 the temperature. The higher the temperature the more completely is the lead sul- 
 phide decomposed, and hence, so far as the yield of lead is concerned, the use of coke 
 as fuel has given better results than wood. However, this method of smelting has 
 not been found advantageous when the ores worked are rich in galena, and do not 
 contain copper ; in which case it is desirable to avoid the production of regulus. 
 
 One of the chief advantages resulting from the use of iron in smelting poor sul- 
 phuretted lead ores consists in the separation of any copper they may contain ; since 
 the sulphide of this metal is less readily decomposed by iron than the lead sulphide 
 associated with it, and as it combines more readily with ferrous sulphide, the greater 
 part of the copper in the ore is retained in the regulus formed. In the case of 
 argentiferous lead ore, the greater part of the silver is obtained in the metallic lead 
 and a smaller proportion is retained in the regulus ; but, in order to secure this result 
 with the greatest advantage, it is requisite that the proportion of silver to lead in the 
 charge should not be too great, and since silver sulphide combines readily with ferrous 
 sulphide, it is often necessary in smelting ores rich in silver to limit the amount of 
 silver in the regulus, by smelting the ore in such a manner that a large proportion of 
 the lead remains in the regulus. In some cases it is even necessary to add metallic 
 lead to the materials smelted in order to prevent the retention of too much silver in 
 the regulus. 
 
 Among the other minerals associated with galena in mix.ed ores blende is to some 
 extent dissolved in the slag ; part of it is decomposed by metallic iron, and the zinc 
 volatilised gives rise to the formation of deposits in the upper part of the furnace, 
 where it comes into contact with atmospheric air. The sulphur compounds of arsenic 
 and antimony are also decomposed by iron, and the metals are either volatilised, or 
 they combine with iron, copper, nickel, and cobalt, forming the product known as 
 sp e i s e. Some portions of the zinc, antimony, and arsenic are retained by th lead and 
 by the regulus, and part of the antimony in an oxidised state is- taken up by the slag. 
 
 The substitution of slags consisting of ferrous silicate in the place of metallic iron 
 for smelting sulphuretted lead ores is no doubt, to some extent, an economical plan of 
 supplying iron for the decomposition of the lead sulphide in the ore ; but it is also 
 probable that there is a more direct reaction between the lead sulphide and part of 
 the ferrous oxide of the silicate, resulting in the formation of ferrous sulphide and 
 lead oxide, which again reacts with a further portion of the lead sulphide, forming sul- 
 phurous oxide and metallic lead. The final effect of these reactions may be repre- 
 sented by the following equation : 
 
 2(2FeO,SiOo) -f 5PbS = 3Pb + 2(FeS,PbS) + 2(FeO,Si0 2 ) + S0 2 
 408 1195 621 654 264 64 
 
 Ores containing a large proportion of pyrites or other sulphides besides galena 
 would yield a large quantity of regulus when smelted with iron, and in order to avoid 
 this result, as well as to economise iron, and to obtain lead free from arsenic OP 
 antimony, such ores are roasted sufficiently to oxidise the excess of sulphides, and to 
 volatilise some of the impurities. These ores are sometimes roasted to such an extent 
 as to oxidise the lead as well as the other metals, and then smelted in shaft furnaces 
 with slag capable of dissolving the metallic oxides, which are not so readily reduced 
 as the lead oxide by contact with carbonaceous gases at a high temperature. Even in 
 this case a certain amount of regulus is always formed, since the sulphates produced to 
 some extent by roasting lead ores containing sulphides are deoxidised in the smelting, 
 and again converted into sulphides. In smelting according to this plan^ some lead 
 is also reduced by the reaction of oxygenated compounds with lead sulphide. 
 
 Very poor lead ores containing argentiferous minerals and small quantities of 
 
368 
 
 LEAD, 
 
 copper pyrites, etc. are sometimes smelted together with fluxes and iron pyrites 
 sufficient to separate the whole of the lead, silver, and copper in the regulus, which is 
 afterwards roasted and smelted in the same manner as a roasted lead ore. 
 
 The furnaces employed in smelting lead ores by these methods differ from the 
 slag hearths chiefly in having the lateral walls carried up to a much greater height, 
 so that they contain a considerable quantity of the material to be smelted, as a 
 column extending several feet above the level of the tuyere. The charge is therefore 
 subjected for some length of time to the action of reducing gases in the upper part of 
 the shaft, and is gradually heated to a temperature at which the various substances 
 contained in it are decomposed by heat, or by the action of reducing gases, or by re- 
 acting upon each other. Owing to the solubility of lead and its sulphide there is 
 always a considerable portion of the metal carried off in the current of gas escaping 
 from the throat of the furnace, and on this account it is generally connected with a 
 long flue or a series of chambers in which the volatilised lead is gradually deposited. 
 In Silesia a furnace is used of the form represented by fig. 249. It consists of a 
 brick shaft (a a) about 18 feet high, and for some distance above the tuyere (t) the 
 
 section is rectangular, above that height it 
 is circular. The exterior wall (c c) is built 
 of ordinary bricks, and the lining (a a) is 
 built of fire brick. At the level of the 
 charging door (/) is a floor (E), upon which 
 the ore and flux are mixed before being 
 thrown into the furnace; and the fumo 
 passes off from the top of the furnace into 
 condensing chambers. 
 
 In working this furnace it is charged 
 with lead ore or slag, cast iron, and forge 
 slag. The melted products, consisting of 
 metallic lead, regulus and slag, sink down 
 into the hearth and are either run off at 
 the breast (c) or by tapping a channel that 
 passes to the bottom of the hearth. The 
 regulus sometimes contains in addition to 
 ferrous sulphide 7 or 8 per cent, of lead in 
 the state of sulphide, and then it is roasted 
 and worked again, but otherwise is thrown 
 on the waste heap. The slag consists chiefly 
 of ferrous silicate, but sometimes it contains 
 sufficient lead to be worked again, 
 
 The regulus obtained in this operation 
 at some other works contains as much as 
 30 per cent, of lead, together with a con- 
 siderable amount of copper and some silver, 
 and it is worked in various ways according 
 to its composition. For the complete ex- 
 traction of the lead several smelting opera- 
 tions are sometimes necessary, and the regu- 
 lus ultimately obtained, containing greater 
 part of the copper, is rich enough in 
 this metal to be worked for copper. 
 Kegulus poor in lead is sometimes roasted 
 
 FIG. 249. an( i lixiviated to extract the soluble sul- 
 
 phates of copper or zinc, and the copper 
 
 obtained by precipitation with iron. When the amount of iron in the roasted regulus 
 is large, it is again used as a flux in smelting ore. 
 
 The lead ores smelted by the iron method in the Upper Hartz contain galena 
 mixed with some copper pyrites, fahl-ore, bournonite and blende. The amount of 
 silver varies considerably, and in some instances the argentiferous galena is accom- 
 panied by true silver ores, as well as minerals containing large amounts of copper, 
 nickel, antimony and arsenic. The principal gangue substances are quartz, calcspar 
 and heavy spar. 
 
 These ores are smelted both in the state of lumps and as a coarse powder, and 
 they are mixed, according to the nature of the substances constituting the gangue, in 
 such a manner as to give rise to the production of a fusible slag, and so as to contain 
 on the average about 55 or 63 per cent, of lead, in proportion to the amount of silver 
 in the material smelted. Materials containing lead oxide are also added, partly for 
 the sake of extracting the lead they contain and partly to facilitate the extraction 
 of silver from the ore smelted. The separation of the quartz is effected by means of 
 
SMELTING IN SHAFT FURNACES. 
 
 369 
 
 an addition of slag containing a sufficiently large proportion of ferrous oxide to dissolve 
 the quartz and form a fusible slag, while at the same time it prevents the formation 
 of lead silicate. In some cases the ore contains a considerable amount of blende, and 
 then it is necessary to increase the proportion of basic slag. The slag produced in 
 the smelting of regulus (p. 371) is used for this purpose, as it always contains some 
 lead which augments the yield from the ore. 
 
 The shaft furnace used at Clausthal in 
 the Harz, represented by figs. 250 and 251, is 
 about 24 feet in height from the breast to 
 the charging door (T), and the upper part 
 communicates with a series of condensation 
 chambers (c c). The tuyere is 18 inches 
 above the sole; and the hearth, projecting 
 beyond the breast (b) of the furnace, slopes 
 at the bottom from the back to the front. 
 The slag flows out at the breast, and as it 
 solidifies it is drawn down the incline (p). 
 At the side is an iron pot () to receive the 
 melted lead when the tap hole leading to 
 the bottom of the hearth is opened. 
 
 The hearth is formed of refractory 
 sandstone, and is lined with a mixture of 
 clay and charcoal stamped down to form 
 a hollow space or crucible, in which the 
 melted products of the operation collect 
 and separate in layers before escaping from 
 the furnace. 
 
 In charging this furnace the ore is always 
 thrown towards the back against the tuyere 
 and the fuel towards the breast of the 
 furnace ; by this means a channel or nose 
 of solidified slag, about 8 or 10 inches long, 
 is formed opposite the tuyere, and the 
 successful working of the furnace depends 
 very much upon the way this is managed. 
 
 As a result of this method of charging, the mixture of ore, slag, etc. to be smelted 
 forms a vertical layer above the nose of 
 the tuyere, and the blast passing through 
 the nose impinges directly upon the 
 fuel, which forms a similar layer against 
 the front of the furnace. The highest 
 temperature is therefore at the centre 
 of the furnace, near the level of the 
 tuyere. When coke is used as fuel, 
 there is greater difficulty in regulating 
 the operation, as the furnace is liable 
 to become too hot ; but it has neverthe- 
 less been substituted almost entirely 
 for charcoal. The throat of the furnace 
 is not allowed to become red hot, in 
 order to prevent the oxidation of the 
 iron, and to limit as much as possible 
 the loss of lead as fume and dust. 
 
 The charge, consisting of finely- 
 divided ore, old hearth bottoms, or 
 other materials containing lead oxide, 
 together with granulated cast iron, and 
 a quantity of slag from previous opera- 
 tions, is gradually heated in the upper 
 part of the shaft, and the lead oxide 
 contained in it is probably to some ex- 
 tent reduced by the ascending current 
 of gas ; but the reaction between the 
 iron and lead sulphide does not take 
 place until the materials of the charge 
 have sunk down to a point near the 
 tuyere, and before reaching the level 
 
 B B 
 
 FIG. 251. 
 
370 
 
 LEAD. 
 
 of the tuyere this reaction should be complete. It is at this part of the shaft 
 also that the combination of silica and other gangue constituents with the ferruginous 
 slag takes place, and the melted products of these reactions, sinking into the hearth, 
 separate according to their density, but do not undergo much further change. The 
 higher the temperature of the furnace at the point where the reaction of the iron and 
 lead sulphide takes place, the more complete is the decomposition of the lead sulphide, 
 and the smaller the proportion of lead retained by the regulus produced ; -but at the 
 same time there is a greater risk of loss from volatilisation of lead, unless the furnace 
 be provided with ample means of condensation. Since the greater part of the lead 
 in the materials smelted is in the state of sulphide, there is less risk of loss by the 
 formation of lead silicate and the production of slag containing lead than there is in 
 smelting roasted ores. 
 
 The products of the operation consist of metallic lead containing silver, regulus, or a 
 mixture of ferrous sulphide with lead sulphide and cuprous sulphide, also containing 
 some silver, and a black glassy slag consisting chiefly of ferrous silicate, the com- 
 position of which approximates to the formula FeO,Si0 2 , as shown by the following 
 analyses : 
 
 
 Bodemann 
 
 Rammelsberg 
 
 Silica ... 
 
 48-80 
 
 45-00 
 
 Alumina 
 
 4-62 
 
 4-62 
 
 Ferrous oxide 
 
 36-00 
 
 35-83 
 
 Lime ... 
 
 3-26 
 
 6-31 
 
 Magnesia . 
 
 1-24 
 
 0-75 
 
 Lead oxide 
 
 5-30 
 
 7-80 
 
 Antimouous oxide 
 
 
 
 0-50 
 
 
 99-22 
 
 100-81 
 
 The lead obtained contains from 0*1 to 0*2 per cent, of silver, from 0'4 to 0'76 per 
 cent, of copper, 0*2 to 3*46 per cent, of antimony, sometimes with traces of iron, zinc, 
 and sulphur. 
 
 This lead matt or regulus is frequently crystalline ; it has a bluish grey colour 
 somewhat like that of lead and iron, and soon becomes tarnished by superficial oxida- 
 tion of the ferrous sulphide, and then it presents the colour of magnetic pyrites ; it 
 contains a considerable amount of metallic lead disseminated through it in a very 
 minute state of division, and has a very variable composition, as shown by the follow- 
 ing table : 
 
 
 Briiel j Bodemann 
 
 Joy 
 
 Sulphur 
 
 15-34 
 
 16-40 
 
 17-27 
 
 18-92 
 
 19-33 
 
 16-12 
 
 Lead 
 
 73-35 
 
 60-69 
 
 65-78 
 
 59-33 
 
 53-31 
 
 52-27 
 
 Iron . 
 
 9-90 
 
 20-55 
 
 13-15 
 
 19-79 
 
 21-77 
 
 28-32 
 
 Copper 
 
 0-39 
 
 0-49 
 
 1-15 
 
 MO 
 
 0-23 
 
 1-42 
 
 Zinc . 
 
 20 
 
 0-55 
 
 0-67 
 
 0-17 
 
 2-25 
 
 1-56 
 
 Antimony 
 
 40 
 
 36 0-18 
 
 0-13 
 
 0-38 
 
 0-31 
 
 Silver 
 
 12 
 
 11 
 
 
 
 
 
 
 
 
 
 
 99-70 
 
 99-15 
 
 98-20 
 
 99-44 
 
 97-27 
 
 100-00 
 
 On account partly of the presence of metallic lead in this regulus, the relative 
 proportions of sulphur lead and iron deviate from that of the double iron and lead 
 sulphide, FeS + PbS, which contains 19-57 per cent, of sulphur, 63-33 per cent, of lead, 
 and 17' 10 per cent, of iron. However, it is probable that this compound constitutes 
 the greater part of the regulus, together with varying amounts of copper, antimony , 
 zinc, silver, etc., in the state of sulphides. 
 
 In order to extract the lead retained in the regulus or matt, it is first roasted so 
 as to separate the greater part of the sulphur as sulphurous oxide and ultimately convert 
 the metals into the state of oxides. A considerable portion of the lend sulphide is left 
 in the state of sulphate, when the amount of lead in the regulus is large. 
 
 The roasting of this regulus is conducted in heaps under sheds, and it gradually 
 becomes bluish-grey, earthy, and friable. It is then smelted with cast-iron, materials- 
 containing lead oxide and some silicious slag from previous operations in a slag hearth, 
 the construction of which is represented by figs. 252, 253, and 254. The shaft (A B" 
 is about 4 feet 6 inches high, and wider above than below. 
 
SMELTING IN SHAFT FURNACES. 
 
 371 
 
 Coke is used as fuel; and during the melting, part of the iron in the oxidised 
 regulus combines with the silica of the slag, forming a more fusible silicate, and the 
 lead sulphide is reduced either by the oxidised materials or by the metallic iron yield- 
 ing metallic lead and another regulus. The carbon of the fuel also helps the reduction 
 of lead. In this way, by repeating the operations of roasting and smelting several 
 times, the amount of lead in the regulus is reduced; and in the last melting when 
 the addition of materials containing lead oxide is omitted, a regulus is obtained with 
 very little lead, but almost all the copper that was contained in the original ore 
 
 FIG. 254. 
 
 FIG. 253. 
 
 The furnace is worked with a 
 single tuyere (T) placed at the back ; 
 the sole slopes sharply downwards 
 from the level of the tuyere, and the 
 lowest point extends beyond the 
 breast of the furnace, forming a cru- 
 cible (E) in which the melted materials 
 collect and are drawn off at intervals 
 by tapping into the receptacle (F) 
 outside, fig. 254 representing a hori- 
 zontal section at the level of the 
 tuyere, and fig. 253 a vertical section ; 
 
 from x to Y show the mode in which the sole and crucible are formed, charcoal 
 and clay stamped down upon the slabs of stone (a, b, c) at the bottom of the furnace. 
 The composition of the slag obtained in smelting the lead regulus is shown by 
 the following analyses : 
 
 
 Eammelsberg 
 
 Bodemann 
 
 K 
 
 erl 
 
 Silica 
 
 39-79 
 
 32-34 
 
 29-90 
 
 3779 
 
 Ferrous oxide . 
 
 46-44 
 
 43-90 
 
 33-60 
 
 46-44 
 
 Lead oxide 
 
 9-17 
 
 10-01 
 
 2-34 
 
 21-56 
 
 Lime 
 
 2-12 
 
 2-07 
 
 2-07 
 
 13-63 
 
 Alumina . 
 
 traces 
 
 5-06 
 
 3-12 
 
 9-98 
 
 Ferrous sulphide 
 
 
 3-50 
 
 
 
 
 
 Manganous oxide 
 
 _._ 
 
 1-20 
 
 
 
 
 
 Cupric oxide 
 
 
 
 05 
 
 
 
 
 
 Potash 
 
 
 
 05 
 
 
 
 
 
 
 97-52 
 
 98-18 
 
 
 
 
 
 The last two columns of the table give the maximum and minimum amounts of 
 the several constituents of the slag obtained in smelting the lead regulus. A comparison 
 with the table at p. 370 will show that this slag is much more basic than that pro- 
 
 BB 2 
 
372 
 
 LEAD. 
 
 duced in smelting the ores, in consequence of its having dissolved part of the ferrous 
 oxide formed in the smelting of the roasted regulus. 
 
 The lead obtained by smelting regulus contains a larger amount of copper and 
 antimony than that obtained in smelting the original ore, but at the same time the 
 greater part of the copper in the materials operated upon is retained in the regulus 
 that is obtained in each successive smelting together with metallic lead, unless the 
 roasting of the regulus has been carried too far, and too much iron has been used in 
 smelting it, in which case some copper would pass into the slag, and the lead obtained 
 would also contain too much copper. 
 
 The following analyses show the effect of the operation in augmenting the relative 
 proportions of copper to lead in the regulus, until at last it presents the compositioi] 
 of a copper regulus : 
 
 
 No. 3 regulus 
 Brttel 
 
 No. 4 regulus 
 Bodemann 
 
 Sulphur . . 
 
 17-12 
 
 15-55 
 
 Lead . ... 
 
 43-07 
 
 32-07 
 
 Iron . ... 
 
 8.03 
 
 13-15 
 
 Copper . ... 
 Antimony . ... 
 
 30-46 
 0-74 
 
 34-01 
 2-67 
 
 Silver . ... 
 
 0-12 
 
 0-07 
 
 
 99-54 
 
 97-51 
 
 The further treatment of such regulus for the extraction of the copper will be de- 
 scribed under the head of ' Copper Smelting.' 
 
 Lead ores containing arsenic, antimony, nickel, and cobalt, yield in smelting a 
 peculiar product called s p e i s e, which separates as a distinct layer in the hearth, between 
 the metallic lead and the regulus : it has a steel-grey colour generally, but is some- 
 times almost as white as silver. The fracture has a metallic lustre, and is granular OT 
 laminated, like specular pig iron ; it is brittle, magnetic, and has a specific gravity oi 
 7 '381. The composition is shown by the following analyses : 
 
 
 Jordan 
 
 Ahrend 
 
 Kammelsbei-g 
 
 Sulphur 
 
 Arsenic . v *-" . 
 Antimony 
 Iron 
 
 7-82 
 5-05 
 3-35 
 68-03 
 5-68 
 
 2-86 
 12-98 
 5-21 ( 
 5-54 
 44-56 
 
 2-04 
 29-13 
 
 51-74 
 3-55 
 
 Nickel . ' '.*-' 
 Cobalt 
 Lead 
 Silver . 
 
 6-52 
 1-67 
 0-60 
 003 
 
 0-71 
 1-63 
 26-11 
 13 
 
 8-85 
 2-89 
 trace 
 
 
 98-723 
 
 99-73 
 
 98-20 
 
 These products consist essentially of arsenides and antimonides mixed with sul- 
 phides. Speise of this kind is always produced to some extent at the Lower Hartz 
 lead works. 
 
 Formerly the lead speise was repeatedly roasted and melted, in order to concentrate 
 the cobalt. More recently, it has been the practice to melt it with wood under a blast, 
 BO as to obtain black copper containing cobalt and nickel, together with a greenish- 
 black slag, which finally becomes red, and contains about 2 per cent, cobalt with 
 twice as much nickel. (See Nickel and Cobalt.) 
 
 The lead ores smelted in the neighbourhood of Goslar in the Lower Hartz contain 
 only a small amount of galena together with iron pyrites, copper pyrites, blende, 
 arsenical pyrites, and antimonial compounds. The gangue substance consists of heavy 
 spar, calc spar, quartz, and schist, so that the amount of lead in the ore is not more 
 than from 4 to 10 per cent. On account of the large proportion of foreign admix- 
 tures these ores are roasted before being smelted, and by this means the arsenic, 
 antimony, zinc; and sulphur are partly volatilised. Sulphates are at the same time 
 formed, and by the reduction they undergo in the smelting of the ore there is always 
 a considerable production of regulus. The amount of lead in the regulus is sometimes 
 as much as 20 per cent. The large proportion of zinc in these ores gives rise to the 
 
SMELTING IN SHAFT FURNACES. 
 
 373 
 
 formation of deposits in the upper part of the furnace, and it is sometimes so consider- 
 able that metallic zinc is obtained as a by-product of the smelting operation. Ores 
 containing a very large amount of zinc are sometimes lixiviated after the first roasting 
 to remove the zinc sulphate. 
 
 On account of the large amount of metallic oxides in the roasted ores it is neces- 
 sary in the smelting to use silicious fluxes, in order to dissolve the basic oxides and 
 prevent the formation of deposits in the hearth, in consequence of the reduction of 
 iron and copper. Another reason for adding a sufficient proportion of silica is that 
 slag containing too much basic oxide solidifies rapidly and is so dense that it does not 
 separate readily from the regulus, thus causing considerable loss. Too large a pro- 
 portion of silica, on the contrary, is disadvantageous, since it promotes the formation 
 of lead silicate, -which dissolves in the slag and causes loss of lead. 
 
 In the lead works near G-oslar the silicious ore slags produced in the Upper 
 Hartz district (p. 370) are used as fluxes, together with waste materials containing 
 lead oxide. 
 
 In smelting lead ores by this method lead is produced partly by the reaction of 
 oxidised materials and lead sulphide, partly also by the action of metallic iron upon 
 lead sulphide. The regulus obtained amounts to as much or even more than the lead. 
 It is roasted and smelted again several times in succession, until the lead is sufficiently 
 separated from the copper, and the copper regulus finally obtained is then worked in 
 the same manner as the copper regulus above referred to. 
 
 The slags produced in copper smelting, and consisting of ferrous silicate with traces 
 of copper and silver, have recently been employed as the source of iron for the de- 
 composition of lead ores containing galena. The furnace used for this purpose is 
 elliptical, with six tuyeres on each side and a tap hole at each end. It bears the 
 name of the inventor Kachette. The copper slag used in ore smelting has the follow- 
 ing composition : 
 
 
 Streng 
 
 Silica 
 
 17-17 
 
 16-95 
 
 Alumina 
 
 2-73 
 
 3-69 
 
 Ferrous oxide . 
 
 69-84 
 
 70-27 
 
 
 3-27 
 
 3-37 
 
 Magnesia . . . . 
 
 0-83 
 
 1-30 
 
 Cupric oxide .... 
 Manganous oxide .... 
 
 1-77 
 0-54 
 
 1-90 
 0-07 
 
 Zinc oxide ..... 
 Cobalt oxide .... 
 
 | 1-54 
 
 0-98 
 
 
 1-58 
 
 1-73 
 
 
 
 
 
 90-27 
 
 100-26 
 
 This furnace has been tried for some time at the Harz lead works, both by using 
 the cast iron obtained by smelting the copper slags separately and by smelting the 
 lead ore with the copper slags. The lead obtained in this was not more impure than 
 that from the ordinary shaft furnaces, and both the regulus and the slag produced at 
 the same time contained very much less lead than those from the old form of furnace, 
 as will be seen by the following analyses : 
 
 
 Regiilus 
 
 
 Slag 
 
 
 Hilgenberg 
 
 Ey 
 
 
 Kerl 
 
 Hilgenberg 
 
 Sulphur 
 Iron , . 
 
 24-43 
 40-69 
 
 26-67 
 55-90 
 
 Silica 
 Alumina . 
 
 4510 
 8-40 
 
 41-06 
 7-28 
 
 Lead 
 
 29-15 
 
 10-88 
 
 Ferrous oxide 
 
 33-40 
 
 38-37 
 
 Copper . 
 Zinc ) 
 
 3-71 
 
 3-33 
 
 Lead oxide 
 Lime 
 
 1-02 
 7-80 
 
 0-88 
 7-58 
 
 Manganese \ ' 
 Antimony ) , 
 Arsenic J 
 
 1-41 
 0-13 
 
 1-13 
 0-27 
 
 Magnesia . 
 Zinc oxide ) 
 Manganous oxide > 
 Copper and antimony 
 
 90 
 3-40 
 traces 
 
 93 
 1-60 
 traces 
 
 
 99-52 
 
 98-18 
 
 
 100-02 
 
 97-70 
 
374 
 
 LEAD. 
 
 At Pontgibaud in France the lead ore smelted is a highly argentiferous galena con- 
 taining admixtures of blende, pyrites, quartz, heavy spar, and felspar. The average 
 amount of lead in the ore is from 25 to 36 per cent. The ore is thoroughly roasted 
 on the upper hearth (a) of a reverberatory furnace, figs. 255 and 257, and when coin- 
 
 FIG. 257. 
 
 pletely oxidised it is transferred through the flue (d) to the lower hearth (<?), where it 
 is sufficiently heated to make the mass melt before it is drawn out. This lower 
 hearth is concave, as shown in fig. 256, which represents a transverse section on the 
 line A B of figs. 255 and 257. Part of the sulphates formed in the roasting are thus 
 decomposed, and the sulphuric oxide driven off passes, together with gaseous products 
 of combustion, through the outlet (ii) at the end of the hearth into the condensation 
 chamber (&). This chamber is connected with the chimney (I) and with a flue (n), 
 through which the gas can be passed for the condensation of fume if requisite. In 
 this state the material contains about one-third its weight of gangue substance, 
 consisting chiefly of quartz, felspar, and heavy spar, with about 35 to 40 per cent, of 
 lead, partly in the state of silicate, sulphate, and oxide, with not more than 1-5 per 
 cent, of lead sulphide. 
 
 The smelting of the roasted ore is carried out in low shaft furnaces, about 5 feet 
 high, withthe addition of metallic iron, fluor spar, limestone, materials containing lead 
 oxide, and slags from previous operations. The products obtained are metallic lead, 
 containing from 0'35 to 0*5 per cent, of silver, and a slag which does not contain more 
 than 3 per cent, of lead when the furnace works well. Sometimes a regulus is pro- 
 duced which contains a large amount of lead, but this is due to defective working ; its 
 composition is shown in the following table : 
 
 
 Rivot 
 
 Berthier 
 
 Sulphur ' ' 
 
 2-3 
 
 4-0 
 
 23-6 
 
 Lead 
 
 79-5 
 
 670 
 
 5' 
 
 Iron , ' ; ' 
 
 12-2 
 
 22-4 
 
 64-6 
 
 Zinc 
 
 1-1 
 
 1-1 
 
 
 
 Arsenic 
 Antimony 
 
 j 
 
 4-5 
 
 166 
 
 
 99-3 
 
 99- 
 
 99-8 
 
SMELTING IN SHAFT FURNACES. 
 
 375 
 
 The reduction of lead in this case is chiefly due to the action of metallic iron and 
 carbon upon the lead silicate, and the ferrous oxide thus produced combines with the 
 silica, forming a fusible slag. The lead sulphate is probably reduced by reaction with 
 lead oxide, rather than by the iron, when the operation is well conducted, and owing 
 to the small amount of sulphides in the material smelted very little regulus is then 
 produced. 
 
 The following analyses of the slags formerly produced at these works will show 
 that the operation was very defective : 
 
 
 Berthier 
 
 
 Rivot 
 
 
 Silica . 
 
 27- 
 
 39- 
 
 40- 
 
 38- 
 
 Alumina 
 
 7'6 
 
 1-5 
 
 17 
 
 1-4 
 
 Ferrous oxide 
 
 32- 
 
 21-2 
 
 187 
 
 19-2 
 
 Lime . 
 
 13- 
 
 11- 
 
 15- 
 
 24-1 
 
 Baryta 
 
 
 
 26- 
 
 3-2 
 
 3-3 
 
 Magnesia 
 
 
 
 2-1 
 
 3-2 
 
 2-9 
 
 Lead oxide . 
 
 18-6 
 
 18-2 
 
 13-1 
 
 6-0 
 
 Zinc oxide . 
 
 
 
 1-7 
 
 1-5 
 
 1-6 
 
 Sulphuric acid 
 
 
 
 1-0 
 
 2-3 
 
 2-1 
 
 
 
 
 
 
 987 
 
 98-6 
 
 At Freiberg lead ores consisting of argentiferous galena, and containing from 20 to 
 30 per cent, of lead, are smelted with the twofold object of obtaining the lead from 
 them and of making it serve at the same time to extract silver from other ores 
 which contain little or no lead, but consist chiefly of quartz containing argentiferous 
 iron pyrites, copper pyrites, and blende. For this purpose the several ores are mixed 
 so that the average amount of lead is from 20 to 35 per cent, and roasted in order to 
 oxidise the pyritic minerals, as well as to volatilise arsenic, antimony, and zinc. Some 
 of the Freiberg ores which contain too little lead to be worth smelting for this metal 
 alone, but contain a considerable amount of silver and some copper, are smelted to- 
 gether with slags produced in smelting lead ores, so as to obtain the metallic sulphides 
 they contain in the state of a regulus, which is roasted and mixed with the lead ores 
 when they are smelted, with the object of furnishing in the furnace ferrous oxide to 
 combine with the silica of the ores and form a fusible slag. Formerly such poor 
 pyritic ores were smelted in shaft furnaces, but recently these have been superseded 
 by reverberatory furnaces, and the ores are worked together with lead slags containing a 
 small amount of lead, which is by this means extracted, and passes into the regulus to- 
 gether with the silver, lead and copper of the ores. The composition of the regulus is 
 given in the following table : 
 
 Sulphur . .-.'. 
 Lead. . ...-. . J,. f i: " , V 
 Iron . . , . , . .-. f . t 
 Copper . . .-, . . 
 Zinc . . . . , . . 
 
 Plattner 
 
 Richter 
 
 26-49 
 8-86 
 57-33 
 3-27 
 1-38 
 15 
 51 
 19 
 1-24 
 
 23-43 
 7'35 
 53-81 
 387 
 7-65 
 
 Jo-84 
 2-11 
 
 21-81 
 5-69 
 51-33 
 11-33 
 2-14 
 
 0-73 
 6-97 
 
 Silver . . . , ' . 
 
 Nickel . ... .. . ;> .- 
 
 Arsenic . -' t , . , .': 
 Silica . . . . .'''' 
 
 Oxygen slags . . . *-Jj"tv 
 
 99-42 
 
 90-06 
 
 100- 
 
 Owing to the large amount of pyrites in these poor ores and to the circumstance 
 of their being smelted in the raw state, no metallic lead is obtained, and the effect of 
 the operation consists chiefly in the concentration of such small amounts of lead and 
 copper as the ore contains, while, at the same time, the lead regulus left in the slag 
 produced in smelting the richer ore is extracted. 
 
 The slag produced at the same time consists chiefly of ferrous silicate containing 
 about 1 per cent, of lead, 0'24 per cent, copper, and a trace of silver : it is cast into 
 blocks, which are either used at once for building purposes or thrown tnvay. 
 
376 
 
 LEAD. 
 
 The richer lead ores are smelted in a shaft furnace of the kind represented by 
 figs. 258 to 261. It is constructed of substantial stone walls (dcg} lined with fire brick 
 (/) and upon a solid foundation (c) under which there are drains (a b) to carry off water. 
 Below the hearth there is a bed of slag (0) covered by a layer of loam ( p). The shaft 
 
 
 FIG. 258. FIG. 259. 
 
 is separated by a partition into two 
 parts, and is triangular in section, as 
 shown by fig. 260. The hearth (i) 
 projects beyond the breast (w) under 
 which the slag flows off into the gutter 
 (m) and it is formed of a layer of coke 
 dust and fire clay (q) supported in front 
 by the dam plate (n). There are two 
 tuyeres (kk) set at an angle, and in- 
 clined downwards. The charge is 
 thrown in through the doors (z z) ; the 
 holes (ar) are for removing any obstruc- 
 tion while the furnace is in operation. 
 
 In smelting the roasted lead ore it 
 is mixed with roasted regulus from 
 previous operations, fluor spar, lime, 
 and silicious slag. Coke is used as 
 fuel, and the smelting operation is con- 
 ducted so that a nose is formed before 
 
 ~~* * * * ' z; ' the tuyere and without flame at the 
 
 tunnel head of the furnace. 
 
 The products are metallic lead, regulus, and slag ; sometimes, also, a epeise con- 
 
SMELTING IN SHAFT FURNACES. 377 
 
 sisting principally of iron and arsenic. The lead thus obtained contains about '5 per 
 
 PIG. 261. 
 
 cent, silver, together with some copper, antimony, arsenic, and iron, amounting in all 
 to about 3 per cent, of the metal obtained. 
 
 The slag produced has the composition given in the following table : 
 
 
 Plattner 
 
 Richter 
 
 Silica . . . 
 
 35-16 
 
 43-26 
 
 28-14 
 
 2705 
 
 Alumina 
 
 1-06 
 
 3-20 
 
 5-78 
 
 685 
 
 Ferrous oxide .... 
 
 38-25 
 
 33-15 
 
 37-23 
 
 41-21 
 
 lame 
 
 5-96 
 
 5-41 
 
 7-68 
 
 8-84 
 
 Baryta 
 
 
 
 
 
 3-87 
 
 
 
 Magnesia 
 
 
 
 0-71 
 
 0-63 
 
 0-90 
 
 Lead oxide , t ; ,- 
 
 7-11 
 
 5-64 
 
 7-35 
 
 3-90 
 
 Zinc oxide . . . ... 
 
 8-06 
 
 7-83 
 
 7-60 
 
 8-62 
 
 Cupric oxide . . . '< . . . 
 
 0-73 
 
 0-61 
 
 0-50 
 
 1-00 
 
 Sulphur . . . .,..., , . 
 
 3-30 
 
 0-32 
 
 2-47 
 
 3-63 
 
 
 99-63 
 
 100-13 
 
 101-25 
 
 101-90 
 
 The slag as usual contains some regulus mechanically disseminated through the 
 mass, and about 5 or 6 per cent, of lead, with 0-02 per cent, of silver. It is therefore 
 Bmelted together with the poor ores above mentioned in the reverberatory furnace, 
 
378 
 
 LEAD. 
 
 and while the ferrous oxide it contains serves as a flux for the silicious ingredients of 
 those ores, the lead and silver it contains are extracted and obtained in the regulus. 
 
 The regulus produced in smelting the lead ore in the shaft furnace amounts to 
 about half the weight of the lead obtained with it, and on the average it contains 20 
 per cent, of lead, 20 per cent, of copper, and 0-2 per cent, of silver. 
 
 The regulus from the blast furnace, after having been roasted, is submitted to a 
 second smelting with slag and various by-products containing lead, by which a further 
 quantity of metallic lead is obtained from it, together with a smaller quantity of 
 regulus containing some of the lead, the composition of which is shown by the follow- 
 ing analyses, 2, 3, 4, as compared with the composition of the first regulus 1 : 
 
 
 I 
 
 
 Plattner 
 
 
 
 
 2 
 
 3 
 
 4 
 
 Sulphur 
 Lead 
 
 19-53 
 25-13 
 33-12 
 
 21-31 
 20-25 
 27-05 
 
 19-85 
 23-29 
 36-02 
 
 22-85 
 21-82 
 37-20 
 
 Copper 
 Nickel . . . . 
 Zinc 
 
 12-10 
 
 27-61 
 1-01 
 0-23 
 
 15-28 
 2-33 
 0-14 
 
 12-94 
 54 
 1-44 
 
 Silver 
 Arsenic 
 Antimony 
 Carbon 
 
 20 
 2-45 
 4-75 
 
 0-12 
 0-65 
 1-00 
 
 0-12 
 1-25 
 0-85 
 
 o-io 
 
 0-73 
 72 
 
 
 
 
 99-23 
 
 99-13 
 
 98-34 
 
 It is probable that part of the lead in this regulus is in the metallic state, being dis- 
 solved by the melted ferrous sulphide of which it chiefly consists. From the foregoing 
 figures it will be seen that in the regulus from the ore smelting the proportion of 
 copper to iron and lead is much smaller than it is in the regulus obtained by the sub- 
 sequent operation of smelting the first regulus from the shaft furnace with materials 
 containing lead oxide. The effect of this operation is in fact not only to separate lead 
 in the metallic state, but also to concentrate the copper in the regulus. 
 
 The subsequent treatment of the regulus is intended to effect a further separation 
 of the lead and silver from the copper ; for this purpose the regulus is slightly roasted 
 in kilns so as to convert the greater part of the iron and lead into the state of oxides, 
 while leaving the copper as sulphide. It is then smelted together with blast-furnace 
 slag, which is sufficiently silicious to dissolve the oxidised iron. The products of this 
 operation are metallic lead containing most of the silver and some copper, together 
 with copper regulus, containing lead and some silver, in the proportions shown by the 
 following analysis, and a slag consisting of ferrous silicate : 
 
 Copper Regulus Slag. 
 
 Sulphur ..... 21-00 
 
 Copper ..... 36-20 
 
 Lead ..... 24-80 
 
 Silver ..... 0'16 
 
 Arsenic . . . . . 
 
 Iron . . . . . 15-20 
 
 Zinc 
 
 100-00 
 
 Silica 
 Ferrous oxide . 
 Alumina . 
 
 Brooks 
 . 28-05 
 . 61-08 
 . 4-33 
 . . 3-02 
 
 Magnesia . . . 
 Lead oxide 
 Cupric oxide 
 
 . 0-85 
 2-67 
 . '*'& . trace 
 
 
 100-00 
 
 The slag from this operation is used as a flux in smelting silicious ores, or in 
 smelting regulus, and according to the amounts of lead and silver in the copper regulus 
 it is either roasted and smelted again with materials containing lead oxide, until a 
 regulus is obtained containing 50 or 60 per cent, of copper with about 10 per cent, of 
 copper, or treated at once for copper. (See Copper Smelting). 
 
 SMELTING IN REVERBERATORY FURNACES. In the extraction of lead from galena 
 by this method, the ore is in the first instance partially roasted, so as to convert some 
 of the sulphide into lead sulphate and lead oxide (see p. 360) ; the heat is then raised 
 to such a degree that these substances react upon the unaltered portion of sulphide, 
 yielding in both cases metallic lead and sulphuric oxide, according to the following 
 equations: PbS + PSO< = 2Pb + 2SO., and PS + 2PbO = 3Pb + SO 
 
LEAD SMELTING IN REVERBERATORY FURNACES. 379 
 
 In order to obtain this result in the most advantageous manner, it is evident that 
 the roasting operation must be regulated so as to furnish lead oxide and sulphate in 
 such proportion relatively to the unaltered sulphide as is indicated by the foregoing 
 equations. An essential condition of this method of smelting sulphuretted lead ores 
 is that they should consist chiefly, if not entirely, of galena. Ores containing ad- 
 mixtures of other sulphides, oxides, etc., are not so advantageously worked by this 
 method (see p. 384), and the presence of silica or silicates is very prejudicial on 
 account of the liability to the formation of fusible lead silicate which does not react 
 with lead sulphide in the sfeme manner as the sulphate does, and mixing with the slag 
 causes very great loss. The lead ore is therefore carefully prepared so as to separate 
 quartz and other substances from the galena, but since the purification of the galena 
 by such preparatory operations is never complete, the slag produced in smelting lead 
 by this method always contains some lead, and very frequently sufficient to admit of 
 being worked by other methods for the extraction of the metal. Even when pure 
 galena is operated upon in the reverberatory furnace, a certain amount of the lead 
 remains in the slag. 
 
 The reverberatory furnace employed in lead smelting is somewhat differently con 
 structed in different localities, and the hearth is either cup-shaped with the lowest 
 point at the centre, or it is uniformly inclined towards the end of the furnace, and is 
 slightly hollowed in the same direction at the slope. The former mode of construction 
 is designed for melting down the charge in one mass, and retaining it in a melted con- 
 dition long enough to allow the separation of the reduced metal from the slag, and 
 furnaces of this kind are chiefly used in England, Brittany, and Savoy. The furnaces 
 with sloping hearth are used in Carinthia, Grermany, Spain, and they are intended to 
 admit of the gradual separation of the lead from the roasted ore without melting 
 down the charge, but merely heating it to such a degree that the reactions between 
 lead sulphide and the sulphate or oxide may take place. The temperature requisite to 
 produce this result is above the melting point of lead, and consequently the metal 
 flows away from the heated mass along the sloping hearth to the point where it escapes 
 into a receptacle placed outside the furnace. 
 
 The Flintshire furnace is represented by fig. 262 in vertical section, and in hori- 
 zontal section by fig. 263. 
 
 On each side of the smelting 
 chamber of the furnace there are 
 three doors (///) by which the 
 workmen have access to the charge 
 for the purpose of stirring. The 
 fireplace (a) is separated from the 
 smelting chamber by the fire bridge 
 (c). The hopper (h) in the arched 
 roof (d) of the furnace serves for 
 introducing the charge of ore. The 
 
 hearth is nearly square, and it slopes down from the fire bridge and from the opposite 
 end of the smelting chamber towards the centre, where it is about two feet deeper 
 
 than the sill of the middle furnace " *Tf7 N >~ ? T~'VT~ ~1 
 
 door(/); the tap hole (e, fig. 262), h" \^\^^-\ 
 
 is at a level with the bottom of the / \ 
 
 hearth, and through it both the | _<? (' 
 
 reduced lead and the slag are run off 
 
 into the cast-iron pan (i). The hearth 
 
 of the furnace is formed of slag 
 
 obtained in previous operations ; this 
 
 is heated until it assumes a pasty 
 
 condition, and then spread into the 
 
 required shape by means of paddles. 
 
 The flues (gg} carry off the gaseous 
 
 products from the fuel as well as those 
 
 evolved by the treatment of the charge. 
 
 and since there is a considerable 
 
 quantity of lead carried off in the - 
 
 state of vapour, or as an extremely 
 
 fine dust, the flues of the smelting furnaces are often connected with condensing 
 
 chambers which serve no less for the recovery of lead that would otherwise be 
 
 wasted, than for preventing injury to vegetation and animal life by its discharge into 
 
 the air. In such instances several furnaces are connected together as shown in 
 
 fig. 264, and the waste gas from all the furnaces (a a a) is led into a common flue 
 
 (c c c) communicating with the condensing chamber (e) and the chimney (K). 
 
 FIG. 262. 
 
380 
 
 LEAD. 
 
 The ordinary charge of ore in these furnaces is about 20 cwt. : after being shot in 
 through the hopper (h), it is spread uniformly over the upper part of the hearth and 
 
 moderately heated during the space of two hours, 
 while the furnace doors are closed and the 
 draught checked by lowering the dampers of the 
 flues. During this stage of the operation, termed 
 the first fire, the ore is oxidised, and when 
 this process has been carried far enough, the 
 dampers are partly raised, fresh fuel added, and 
 the heat increased to bright redness for running 
 down the charge by the second fire, which is 
 kept up for 25 minutes, during which time a 
 considerable quantity of reduced lead is melted, 
 and collects at the bottom of the hearth. 
 
 FIG. 264. 
 
 The furnace doors are then opened and the workmen throw some lime over the 
 surface of the slag, which renders it sufficiently pasty to allow of being pushed back 
 from the melted metal to the higher parts of the hearth. Meanwhile the furnace cools 
 down a little, and the slag and ore upon the upper parts of the hearth are stirred 
 with rakes, and after about three hours fresh fuel is added for the third fire, the 
 dampers fully opened and the furnace doors kept closed for nearly an hour. This 
 alternate heating and cooling of the furnace, and the manipulation of the slag and ore 
 have the effect of facilitating the separation of the lead, and the addition of lime pro- 
 tects the melted metal from oxidation, besides rendering the slags less liquid, or as it 
 is termed dry. After giving a fourth fire the doors are opened and the tap 
 hole (e, fig. 262) is pierced so as to let the melted lead flow from the hearth into the 
 pot (). Some more lime is then added, and then the dried slag is pushed back and 
 raked out of the doors at the back of the furnace. 
 
 The whole operation termed a smelting shift occupies about four hours and a 
 half from the time of charging the furnace. In the north of England smaller charges 
 are worked, varying from 12 to 14 cwt., and in Cornwall the charge is as much as 
 30 cwt. or even 3 tons. 
 
 Sometimes the operations of roasting and smelting are conducted in separate 
 furnaces which are connected together, as shown by fig. 265, which represents the front 
 or tapping side of the furnace. 
 
 Fi. 265. 
 
 This plan is followed in Cornwall, and the two operations of roasting and smelting 
 are termed the calcination and the flowing. The calcining furnace has holes in 
 the bed through which the roasted ore is raked down into an arched vault beneath. 
 The flowing furnace is similar to that used in Wales, and the operation is conducted 
 essentially in the same manner as the second stage of the treatment just described. 
 
 After tapping off the reduced lead which has melted and run down into the lowest 
 part of the hearth, the melted slag is mixed with lime and coal dust, and when thus 
 
LEAD SMELTING IN REVERBERATORY FURNACES. 381 
 
 rendered pasty or dried up as it is termed, it is spread upon the higher part of the 
 hearth. Some scrap iron is generally added, which helps the reduction of lead sul- 
 phide, and fluor spar is added as a flux. The furnace doors are then closed and the 
 charge melted down again. The lead oxide in the slag is decomposed partly by the 
 carbon added in the shape of coal dust, and by the action of the iron upon lead sul- 
 phide, a further quantity of lead is produced, together with ferrous sulphide, that 
 forms a regulus and retains greater part of the copper. In tapping the furnace, this 
 regulus is separated and subjected to further treatment for separating any lead it 
 may contain. 
 
 The reverberatory furnace employed at Bleiberg in Garinthia for lead smelting is 
 represented by figs. 266 to 269. The hearth (b) is long and narrow, with a consider- 
 able inclination from one end to the other, and hollowed out so as to form a gutter- 
 like channel as shown in the transverse section, fig. 269. The fireplace (a) is at the 
 side of the hearth, and separated from it by a fire bridge, and the fire gas after passing 
 through the working chamber of the furnace, escapes through the flue () into the 
 chimney. 
 
 J Ik 
 
 a, 
 
 
 2 
 
 '" 
 
 : 
 | 
 
 * 
 
 FIG. 266. 
 
 FIG. 268. 
 
 FIG. 269. 
 
 The hearth is formed of two layers, as shown in figs. 267 and 269, the lower one 
 consisting of clay and the upper one of slag, rammed down and hardened by heat. 
 These furnaces are generally built in pairs with a common chimney, as shown in fig. 
 266, which represents a front elevation. The sloping hearth is intended to afford an 
 opportunity for the lead resulting from the reaction between lead sulphide and lead 
 oxide or sulphate to flow out at once into the receptacle (d) placed outside the work- 
 ing door of the furnace. The quantity of ore worked does not amount to more than 
 3 or 4 hundredweight at each charge. 
 
 In working this furnace, the roasting operation is carried out very gradually, and 
 when sufficiently far advanced, the heat is raised to bring about the reaction between 
 the oxidised portion and the lead sulphide. The separation of the metal is promoted 
 by vigorously stirring the mass, and increasing the temperature until the whole of 
 the lead sulphide is decomposed and no more lead flows out into the receptacle (d). 
 The lead which separates at first when the temperature is lowest is the most pure, 
 and that obtained after raising the heat is less pure. When the pasty mass from 
 which lead has ceased to run out begins to melt, it is mixed with coal dust and again 
 heated strongly ; the lead oxide it contains is thus reduced, and a further separation 
 of lead takes place, until at last when the furnace has attained a full red heat, the slag 
 remaining contains but very little lead. 
 
 This method of smelting is expensive on account of the time and labour it requires. 
 
LEAD. 
 
 With pure ore rich in lead it yields lead of very good quality, but it would not be ap- 
 plicable in the case of ore containing admixtures of other minerals. 
 
 The reverberatory furnace employed for lead smelting in France is represented by 
 figs. 270 to 272, the first being a longitudinal section on the line A B, fig. 271, the 
 second a horizontal section on the line c D, fig. 270, and the third a transverse section 
 on the line E F, fig. 270. The working doors, three in number, are placed on one side 
 of the furnace, and the pot (i) for receiving the lead is opposite the middle door. 
 
 FIG. 271. 
 
 The fireplace is separated from the smelting chamber by the bridge (h), and the hearth 
 (#), besides being slightly hollowed from end to end, as shown in fig. 270, slopes 
 from one side of the furnace to the other, as shown in fig. 272, the lowest side 
 being next to the receptacle (i). 
 
 In working this furnace a 
 charge of about one ton of ore is 
 heated very gradually until a 
 thick crust of lead sulphate has 
 formed on the surface. The tem- 
 perature is then reduced, and the 
 charge stirred until at the end of 
 about four hours it begins to 
 soften, and globules of lead appear 
 as the result of the reaction be- 
 tween lead sulphate and lead 
 sulphide. At this stage a quantity 
 of wood or small coal is thrown 
 upon the mass, and it is actively 
 stirred, while metallic lead runs 
 into the well of the hearth, from 
 whence it is tapped off into the 
 FIG. 272. pot (i). A second roasting then 
 
 follows, and some coal or wood is thrown upon the charge in order to reduce the lead 
 oxide, followed by further stirring to separate the reduced lead. 
 
LEAD SMELTING IN REVERBERATORY FURNACES. 383 
 
 The chief point in which the French method differs from that practised in 
 Carinthia consists in roasting the ore so that a much larger proportion of the lead 
 sulphide is converted into sulphate, before the temperature is raised to the point at 
 which the reaction between lead sulphate and lead sulphide takes place. Consequently 
 there is only a small quantity of lead produced in this way, and the product of the re- 
 action is chiefly lead oxide, as shown in the following equation : 
 
 PbS + 3PbS0 4 = 4PbO + 4S0 2 . 
 
 The lead oxide thus formed is readily decomposed by carbon, the products being 
 metallic lead and carbonic oxide, according to the following equation : 
 
 4PbO + 4C 4Pb + 400. 
 
 Any lead sulphate that remains in the charge is partly converted by the carbon of 
 the wood into sulphide, with formation of carbonic dioxide, and then by reaction with 
 another portion of the sulphate, yields lead oxide and sulphurous oxide : 
 3PbS0 4 + PbS = 4PbO + 4S0 2 . 
 
 A rude form of reverberatory furnace has long been used in Spain under the name 
 of boliche for the smelting of lead ore. It consists of two arched chambers, only 
 one of which is used for the treatment of the ore, and the other probably serves the 
 purpose of regulating the draught. The hearth of the boliche is sloping, and at one 
 extremity there is a well connected with a receptacle outside the furnace, into which 
 the reduced lead runs out by tapping. 
 
 The slag produced in smelting lead ores in reverberatory furnaces is always rich 
 in lead ; but as will be seen from the following table of analyses, it varies in composi- 
 tion according to the nature of the gangue substance in the ore. 
 
 
 Flintshire 
 
 
 Poullaouen 
 
 
 
 Derbyshire 
 
 
 
 Tookey 
 
 
 Berthier 
 
 Silica . 
 
 13-52 
 
 
 
 
 
 
 
 
 
 24- 
 
 Alumina . *" . : 
 
 3-01 
 
 
 
 
 
 
 
 
 
 ^_ 
 
 Ferric oxide 
 
 2-86 
 
 15-4 
 
 5-6 
 
 I A.* 
 
 2-0 
 
 14- 
 
 Zinc oxide . ."" 
 
 7-52 
 
 7'2 
 
 8-0 
 
 \ * 5 
 
 2-0 
 
 27' 
 
 Lime . . . "s 
 
 12-68 
 
 16-0 
 
 14-7 
 
 8-0 
 
 8-0 
 
 __ 
 
 Lead oxide. 
 
 48-87 
 
 
 
 
 
 
 
 
 
 26-5 
 
 Lead sulphate . 
 
 9-85 
 
 12-0 
 
 30-0 
 
 22-0 
 
 9-0 
 
 3-0 
 
 Barium sulphate. 
 
 
 
 22-0 
 
 24-4 
 
 25' 
 
 30-0 
 
 
 
 Calcium sulphate 
 
 
 
 1-6 
 
 5'6 
 
 22-5 
 
 33-0 
 
 
 
 Calcium fluoride . 
 
 
 
 7-2 
 
 8-5 
 
 16- 
 
 13-6 
 
 
 
 Lead sulphide 
 
 0-90 
 
 17-0 
 
 2- 
 
 
 
 
 
 5-0 
 
 
 99-66 
 
 98-4 
 
 98-7 
 
 98-0 
 
 97-6 
 
 
 
 As already mentioned, the ores of lead always contain other earthy and metallic 
 compounds which interfere with the reactions by which lead is reduced, and thus in 
 various ways the result obtained in smelting such impure ores is different from that 
 obtained when pure galena is operated upon in the reverberatory furnace. 
 
 Ores containing only small amounts of calcium carbonate can be worked without 
 inconvenience, and even when there is from 10 to 12 per cent, of this substance, 
 it facilitates the decomposition of the lead sulphide, besides preventing the charge from 
 becoming too liquid. 
 
 Barium sulphate is quite inert during the smelting operation, and it is objection- 
 able only as mechanically hindering the reaction of the lead sulphate or oxide with 
 the unoxidised sulphide. When the ore contains 15 per cent, of this substance, it is 
 not suitable for smelting in a reverberatory furnace^ 
 
 Fluor spar acts much in the same way as calcium carbonate, but it is beneficial 
 when associated with barium sulphate, since it acts as a flux upon that substance. 
 
 Quartz and silicates are very injurious even when amounting to only 5 or 6 per cent, 
 of the ore, and when they amount to 12 per cent, no metal can be obtained by heating 
 lead ore in the reverberatory furnace. During the operation of roasting these sub- 
 stances do not react upon the lead compounds, but when the temperature is raised in 
 the smelting operation, silica combines with lead oxide before this reacts with lead 
 sulphide, forming lead silicate, which melts and renders the whole charge so liquid that 
 it cannot be worked. 
 
384 LEAD. 
 
 Zinc sulphide in the form of blende is often associated with lead ore, and when 
 the amount does not exceed 10 or 15 per cent., its presence does not much interfere 
 with the working of the reverberatory furnace; it is objectionable chiefly by its con- 
 version into oxide and sulphate, which prevent the intimate mixture of the lead com- 
 pounds. The blende which escapes oxidation during the first stage of the operation 
 reacts afterwards upon the lead oxide, producing metallic lead, zinc oxide and sul 
 phurous oxide. When carbonaceous materials are added in the smelting, the zinc 
 oxide is reduced together with lead oxide, and, the zinc being volatilised, a consider- 
 able quantity of lead is carried away by the zinc vapour. 
 
 The presence of a small amount of iron pyrites does not seriously interfere with 
 the smelting in reverberatory furnaces. In roasting, the pyrites is oxidised more 
 rapidly than galena ; the portion that escapes oxidation is afterwards useful in reduc- 
 ing lead oxide, but in the subsequent stage the ferric oxide disseminated through the 
 mass interferes with the melting of the lead compounds. A large amount of pyrites 
 is very prejudicial, since the unoxidised portion would form a very fusible compound 
 with the lead sulphide and prevent its decomposition. Arsenical pyrites is still more 
 objectionable, because the lead obtained is contaminated with arsenic and the presence 
 of this substance in lead augments the loss both of lead and silver in cupellation. 
 
 Antimonous sulphide is always very injurious even when there is only 2 or 3 per 
 cent. It undergoes the same changes as lead sulphide, a portion of the antimony is 
 reduced and alloyed with the lead, rendering the metal hard besides causing loss of lead 
 and of silver in cupellation. Moreover the compounds of antimony form very fusible 
 compounds with lead, which cannot be reduced, and owing to the great volatility of 
 antimony as well as of its oxide and sulphide, the loss of lead and silver is very much 
 augmented. 
 
 The presence of copper pyrites renders lead ores unfit for treatment in reverbera- 
 tory furnaces ; even when the amount is so small that the reactions proper to this 
 method are not interfered with, the lead obtained retains some copper, and is on that 
 account less valuable. 
 
 Ferrous ^ carbonate acts only as a mechanical obstacle to the working in the 
 furnace, as it is gradually converted into ferric oxide : in the latter stage of the 
 operation this interferes with the melting of the slag and retards the reactions until 
 almost all of the lead sulphide is oxidised; in small amount ferrous carbonate is rather 
 advantageous than otherwise. 
 
 Besides the ores containing lead in the state of sulphide some others occur in 
 various localities which contain either lead carbonate or lead sulphate. Generally 
 they occur together with ores containing galena and are worked with them, but in a 
 few instances these oxidised ores are sufficiently abundant to be smelted separately. At 
 the Kussian lead works in the Altai mountains large quantities of ore are smelted 
 which contain from 8 to 20 per cent, of lead in the state of carbonate associated with 
 cupreous minerals, quartz, heavy spar, and slate. Shaft furnaces are used and the ore 
 is smelted with limestone, common salt, and slag from previous operations. 
 
 Ores containing lead carbonate are also worked to some considerable extent in 
 Spain, either in the Castilian blast furnace (p. 365) or the furnace in which a draft is 
 produced by means of a chimney (p. 366). 
 
 Lead sulphate occurs even less frequently than lead carbonate in such quantity as 
 to be worked separately ; but a large quantity of lead sulphate is produced in calico 
 works. Several methods have been proposed for treating this substance. That of 
 Kivot and Phillips consists in roasting the lead sulphate until sulphuric acid is no 
 longer given off, then adding about 20 per cent, of quartz and some coal dust, and 
 heating the mass until it melts and ceases to give off sulphurous and sulphuric oxides. 
 In this way the lead is for the most part converted into silicate, which can be smelted 
 with the addition of scrap iron or with lime and coke in a shaft furnace. In both cases 
 the yield of lead falls short of the quantity that should be obtained and the cost of 
 the operation is considerable. By smelting the silicate with iron pyrites less lead is 
 retained by the slag, but a regulus is produced unless the pyrites is very intimately 
 mixed with the silicate. The iron pyrites is then decomposed in the smelting, sulphur 
 being driven off, and the ferrous sulphide reacts with the lead silicate, producing lead 
 sulphurous oxide and ferrous silicate. 
 
 Most lead ores contain some silver, and since this metal is always reduced in 
 smelting argentiferous lead ores, the lead thus obtained is often of great value as a 
 source of silver. The methods of cupellati on and crystallisation by which the two 
 metals are separated will be described in detail under the head of ' Silver.' 
 
 In the separation of these metals by one method the lead is entirely converted into 
 lead oxide or litharge, and in order to obtain metallic lead this oxide has to be 
 reduced by an operation analogous to the smelting of oxidised lead ores either in 
 reverlieratory furnaces or shaft furnaces. On the continent litharge is frequently 
 
REDUCTION- OF LITHARGE. 385 
 
 smelted in shaft furnaces, since the reduction is rapidly effected and less labour is 
 required, but the lead thus obtained still contains some copper and antimony and is 
 inferior in quality to that reduced in reverberatory furnaces. 
 
 The shaft furnaces employed for the reduction of litharge are similar to those in 
 which lead ore is smelted, but generally they are not so high and they are worked 
 with flame issuing from the throat. To prevent loss of lead, lumps of coke are piled 
 up above the throat of the furnace, so as to be heated by the flame sufficiently to reduce 
 the lead oxide carried up by the ascending gas. 
 
 The reduction of lead oxide is in this country generally effected in a reverberatory 
 furnace of the kind represented by figs. 273 and 274. A is the fireplace, B the ash pit 
 c the fire bridge, D the hearth, E the working door, F the iron gutter by which the 
 lead is run off into the pot a. 
 
 FIG. 274. 
 
 The oxide is mixed with about 10 per cent, of coal dust and placed on the hearth 
 near the fire bridge where it is soon reduced, and the metal flows down to the lower 
 part of the hearth. To prevent the action of the lead oxide upon the material of 
 which the sole is made, a layer of small coal is spread upon it before the charge is 
 put in. 
 
 Condensation of lead fume. Owing to the volatilisation of lead sulphide and 
 metallic lead which always takes place in smelting lead ores either in shaft furnaces or 
 reverberatory furnaces, the gas escaping from the smelting furnaces carries away a 
 large quantity of lead, for the collection of which very efficient means of condensation 
 are required. In some cases the condensation is effected by making the gas pass 
 through flues of great length, where the vaporised lead is gradually deposited together 
 with that held in suspension in the state of finely divided particles. The quantity of 
 
 CC 
 
386 
 
 LEAD. 
 
 lead volatilised in smelting lead ores is very much influenced by the presence of other 
 volatilisable substances in the ore, such as zinc, antimony, and arsenic, and these 
 substances are found chiefly in an oxidised condition together with the lead in the 
 deposit formed in the flues, which is commonly known by the name of lead fume. 
 This frequently contains lead in the metallic state, also lead oxide as well as sulphate, 
 carbonate, and sulphide. Some of these compounds are probably formed by the action 
 of atmospheric air upon the vaporised lead, or by the action of sulphurous oxide and 
 sulphuretted hydrogen within the flues. Since the lead in this deposit amounts to 
 from 1 to 10 per cent, of the total amount in the ore smelted it is evident that the 
 fume is worth collecting independently of the deleterious effect that would result 
 from its being allowed to escape into the atmosphere. The following table gives the 
 composition of the fume from several lead works, where the ores are smelted in shaft 
 furnaces and reverberatory furnaces. 
 
 
 Pontgibauct 
 
 Alston 
 moor 
 
 Redruth 
 
 I 
 
 
 Rivot 
 
 Berthier 
 
 1 
 
 Lead 
 
 
 
 55-4 
 
 
 
 
 Lead oxide . 
 
 
 
 66-5 
 
 3-7 
 
 10-20 
 
 71-21 
 
 27-9 
 
 Lead carbonate 
 
 35-0 
 
 
 
 
 
 
 
 
 
 
 Lead sulphate 
 
 39-0 
 
 
 
 13-0 
 
 65-60 
 
 
 
 13-0 
 
 Lead sulphide 
 
 4-5 
 
 
 
 
 
 1-40 
 
 
 
 
 
 Zinc oxide . 
 
 2-7 
 
 12-0 
 
 3-1 
 
 13-80 
 
 
 
 49-5 
 
 Zinc sulphate 
 
 2-3 
 
 
 
 
 
 
 
 
 Arsenous acid 
 
 1-5 
 
 1-1 
 
 1-5 
 
 
 
 
 
 2-1 
 
 Cupric oxide 
 
 
 
 
 
 
 
 
 
 0-2 
 
 
 
 Ferric oxide . 
 
 
 
 3-0 
 
 13-0 
 
 3-40 
 
 trace 
 
 
 
 Sulphur 
 
 
 
 
 
 8-9 
 
 
 
 
 
 
 
 Sulphuric acid 
 
 
 
 17'0 
 
 
 
 
 
 
 
 
 Carbonic dioxide 
 
 
 
 
 . 
 
 
 
 
 
 7-0 
 
 Substance insoluble in acids 
 
 13-2 
 
 
 
 
 
 5-60 
 
 21-8 
 
 
 
 98-2 
 
 99-6 
 
 98-2 
 
 
 
 
 
 
 
 One of the arrangements for condensing lead fume by mechanical means, known 
 as Stokoe's condenser, is represented by fig. 275. At the top of the flue (A) which 
 receives the gas discharged from the smelting furnaces is a fan, capable of being 
 driven at a high speed, by means of which the gas is drawn out of the flue and forced 
 into a chamber (F F, F F) containing water at the bottom, and separated by partitions 
 into six or more compartments ; so that the gas is made to travel up and down in the 
 direction of the arrows and come several times in contact with the water in the 
 chamber. In its passage through the chamber to the outlet (H) the gas has also to 
 pass several times through the horizontal perforated shelves (A A), covered with layers 
 of pebbles or other fitting material, and at the same time it is exposed to the action of 
 a shower of water falling from the cistern (M) at the top of the chamber. In Stagg's 
 condenser the gas is drawn out of the furnaces by a powerful double-acting air-pump, 
 which also forces it through water. 
 
 Fio. 275. 
 
 Before the lead obtained from certain kinds of poor ores, or by smelting in blast fur- 
 naces, can be operated upon for the extraction of the silver it contains (p. 38 4 ), a prelimi- 
 nary purification is requisite for the purpose of separating any antimony, tin, or 
 
REPINING OF LEAD. 
 
 387 
 
 copper it may contain, together with other impurities, which render the metal hard and 
 unfit for the process of desilverising. The following table shows the composition of 
 different kinds of hard lead, and the nature of the impurities it contains : 
 
 
 English 
 
 Spanish 
 
 Ha 
 
 rtz 
 
 Pontgibaud 
 
 Freiberg 
 
 
 Richai-dson 
 
 - 
 
 Streng an 
 
 d Overbeck 
 
 - 
 
 Karsten 
 
 Lead 
 
 99-27 
 
 95-81 
 
 83-65 
 
 7775 
 
 91-4 
 
 91-51 
 
 Antimony . 
 
 0-57 
 
 3-36 
 
 16-00 
 
 21-27 
 
 8-2 
 
 5-32 
 
 Arsenic 
 
 
 
 
 
 
 
 
 
 0-4 
 
 1-02 
 
 Copper 
 
 0-12 
 
 0-32 
 
 0-13 
 
 0.16 
 
 
 
 0-90 
 
 Iron .) 
 
 Zinc ./ 
 
 0-04 
 
 0-21 
 
 0-30 
 
 0-49 
 
 
 
 0-62 
 
 Sulphur 
 
 
 
 
 
 
 
 
 
 
 
 0'20 
 
 Some kinds of lead are so hard that they are unfit for many of the ordinary pur- 
 poses to which this metal is applied, and for this reason also the softening operation is 
 essentially necessary. It consists in exposing the melted metal to the oxidising action 
 of the air for a length of time which depends upon the nature and amount of the im- 
 purities to be removed. 
 
 The furnace employed for this operation of calcining or improving is repre- 
 sented by figs. 276 to 278. It is a reverberatory furnace, the hearth (D) of which 
 
 Fio. 276. 
 
 m 
 
 E 
 
 FIG. 277. 
 
 consists of a cast-iron pan, separated by the 
 bridge (c) from the fireplace (A). Below the 
 bed are several channels (p r r) for the escape 
 of moisture, and at the side there is a working 
 door (G), as well as an opening (H), by which 
 the softened lead can be run off when the 
 operation is at an end. 
 
 The charge varies from nine to ten tons, and 
 as soon as the furnace is at a working heat, the 
 surface of the melted metal becomes covered 
 with a scum or dross, consisting of metallic 
 oxides, which is skimmed off and removed 
 through the working door (o). When the lead 
 
 FIG. 278. 
 
 is very impure, this scum often floats in a semi- 
 
 liquid state on the surface of the lead, and then it requires the addition of some hme, 
 hich renders it dry and capable of being removed. 
 
 As the 
 ladle, run 
 
 ers ry an c . . 
 
 operation progresses, a small quantity of the lead is dipped oat with a 
 into a mould, and examined when cold, to ascertain whether it issuffidently 
 
 c c 2 
 
388 
 
 LEAD. 
 
 purified. If it presents at the surface a flaky, crystalline appearance, and is soft, the 
 charge is ready to be run off. The spout (H) of the iron pan is then opened, and the 
 metal run into moulds. 
 
 An improved form of furnace for softening lead by calcination is represented by 
 figs. 279 and 280. The hard lead is melted in the pot (a), heated by a fire at 6, and 
 
 FIG. 280. 
 
 the calcining pan (c) is fed with melted lead by raising the plug (d). When the 
 softening is completed, the metal is run into the pot (e), and then cast in moulds. 
 
 The amount of soft lead thus obtained from different kinds of hard lead varies 
 from 76 to 93 per cent. 
 
 The use of a mixture of sodium nitrate, soda ash, and lime, has been proposed with 
 the object of shortening the time requisite for softening lead by oxidation ; but it is 
 doubtful whether any real advantage is gained in this way, especially if it be the case 
 that the antimony in lead collects as an alloy at the surface in consequence of its 
 lower specific gravity, and is therefore readily acted upon by atmospheric oxygen. 
 
 The dross obtained in the softening contains a considerable amount of antimony, 
 together with some copper, iron, and a certain proportion of lead, yielding when re- 
 duced by heating it with carbonaceous material, an alloy that has the following com- 
 position : 
 
 Lead 
 Antimony 
 Copper . 
 Iron 
 
 Without 
 alkaline 
 flux 
 
 Reduced 
 with addi- 
 tion of 
 soda ash 
 
 Alloy from dross of 
 first calcination 
 
 Alloy from dross of 
 second calcination 
 
 English 
 
 Spanish 
 
 English 
 
 Spanish 
 
 82-88 
 16-09 
 68 
 35 
 
 58-70 
 40-66 
 32 
 32 
 
 86-53 
 11-29 
 traces 
 0-34 
 
 64-98 
 29-84 
 5-90 
 0-20 
 
 52-84 
 47-16 
 trace 
 trace 
 
 56-60 
 43-40 
 traces 
 traces 
 
 100-00 
 
 100-00 
 
 98-16 
 
 100-92 
 
 100-00 
 
 100-00 
 
 The addition of a little soda ash as a flux facilitates the reduction, but the metal 
 obtained is too hard to be used for many purposes. By calcination, the impurities 
 may be separated from the lead, and the dross from this operation gives, on reduction, 
 an alloy containing a still greater proportion of antimony, which can only be used for 
 making type metal or as bullets. 
 
LEAD COMPOUNDS. 389 
 
 Richardson proposed to act upon the dross of the second calcination with acetic 
 acid, so as to dissolve the lead and obtain sugar of lead. The residue was then 
 reduced in the same way as antimony ores. The same process serves for the separa- 
 tion of tin. In some cases, the dross may be turned to account for preparing lead 
 antimonate, which is used as a pigment under the name of Naples Yellow. 
 
 Uses. Lead is one of the most useful metals, and it is applied to a great many 
 purposes, such as the lining of cisterns, roofing, etc. ; in the form of pipe it is used for 
 the supply of water to houses and factories ; very thin sheets of lead are used for pack- 
 ing articles requiring to be kept dry, and in chemical works lead is employed for a 
 number of purposes, such for instance as the construction of sulphuric acid chambers. 
 Many of the alloys of lead with other metals have an equally wide range of utility. 
 
 Compounds. Lead is divalent in most of its compounds. There are three 
 definite oxides ; a suboxide Pb 2 which is of little importance, the protoxide PbO is a 
 powerful base, forming saline compounds with acid oxides, some of which are iso- 
 morphous with the corresponding salts of barium and strontium, and the dioxide Pb0 2 
 which has to some extent the character of an acid oxide. There is but one sulphide 
 PbS, corresponding to the protoxide. With chlorine, bromine, iodine, and fluorine, 
 lead forms compounds represented by the formulae Pb01 2 , PbBr 2 , PbI 2 , PF 2 . Many 
 lead salts are insoluble in water, as, for instance, the sulphate, phosphate, arsenate and 
 carbonate ; those which are soluble have a slight-acid reaction even when neutral, and a 
 peculiar sweet taste ; all lead salts are poisonous. 
 
 Melted lead mixes readily in all proportions with other metals the melting points 
 of which are lower than that of lead or not much above it, and with some of them it 
 forms definite alloys, the melting points of which differ from those of the constituent 
 metals. Lead also unites with metals of much higher melting point, but in many in- 
 stances the lead can be separated from such mixtures by heating them to the tempera- 
 ture at which leads melts. This process is termed liquation, and is taken advan- 
 tage of in metallurgy. Several of the alloys of lead are of great importance for various 
 practical applications ; thus the alloy of lead with about one third its weight of anti- 
 mony constitutes typemetal. Pewter is an alloy of lead with one fourth its weight 
 of tin ; the different kinds of s ol der are alloys of lead and tin in various proportions. 
 Lead also enters into the composition of the alloys known as Britanniametal, 
 Queen's metal, etc., and some kinds of bronze contain lead. The alloy of lead with 
 about one-fiftieth of its weight of arsenic is used for making shot. 
 
 Lead and zinc may be mixed together in any proportions when melted, and the 
 alloy is harder than lead, takes a high polish and is very malleable. At a high tem- 
 perature the zinc is volatilised together with some of the lead. The presence of a 
 small proportion of zinc in lead renders the metal less capable of being rolled into 
 sheets. 
 
 The other alloys of lead will be described under the heads of the different metals. 
 
 XiEAD OXIDE. 
 
 FORMULA PbO. MOLECULAR WEIGHT 223. 
 
 History. This substance, commonly called litharge or massicot, was known 
 at a very remote period under the names of \iOdpyvpos and ffuwpta (j.o\i>P$ov, plumbum 
 ustum, etc. 
 
 Occurrence. Lead oxide occurs naturally as lead ochre in volcanic districts 
 and associated with lead ores, but not to any great extent. It is obtained by oxidation 
 of ,lead as a by-product of the cupellation method of extracting silver from argenti- 
 ferous lead. 
 
 Characters. Lead oxide when pure is a lemon-yellow substance, but is met 
 with in several different forms which depend upon the conditions under which it is 
 produced. When in the crystallised state, in which it is obtained by the solidification 
 of the melted substance, it has a pale reddish-yellow or buff colour, the particular 
 shade varying according to the state of aggregation. In this state it is called 
 litharge. When formed by the oxidation of lead at a temperature below the melting 
 point of the oxide, it forms a dull yellow amorphous powder known as massicot. 
 The specific gravity varies from 9'2 to 9'5. Lead oxide melts at a red heat, forming a 
 dark red transparent liquid. It is stated by Fournet to be volatilised at a white heat, 
 but less readily than metallic lead. 
 
 Lead oxide is decomposed when heated to redness with carbon or carbonaceous 
 substances, and in some cases at lower temperatures, metallic lead being produced 
 
390 LEAD. 
 
 together with carbonic dioxide ; it is also decomposed when heated with iron, zinc, 
 copper, etc., to a sufficiently high temperature, and is on this account frequently useful 
 as an oxidising agent in some metallurgical operations. Melted lead oxide also dis- 
 solves a number of other oxides which cannot be melted themselves or only at very 
 high temperatures. "With silica or silicates it readily combines, forming a very 
 fusible glass which is colourless unless it contains a very large amount of lead. Lead 
 silicate is a constituent of several kinds of glass, and especially that known as flint 
 glass or crystal. 
 
 Lead oxide combines readily with most oxyacids forming salts, many of which are 
 soluble in -water ; the oxide also dissolves in solutions of caustic potash, soda, baryta, 
 or lime ; it is also soluble to some extent in water, but requires from 7,000 to 12,000 
 parts of water for solution. 
 
 Lead hydrate PbH 2 2 is a white pulverulent substance which loses water when 
 heated above 100, and is converted into anhydrous oxide. When metallic lead is 
 immersed in pure water lead hydrate is formed, and to some extent dissolved. The 
 hydrate readily absorbs carbonic dioxide, and is converted into carbonate ; it also 
 absorbs ammonia and retains it in combination. 
 
 Preparation. Lead oxide is prepared on the large scale by the oxidation of 
 melted lead, and it is obtained as a product of the operation by which silver is sepa- 
 rated from lead. (See Silver.) 
 
 Uses. In the forms of litharge and massicot,' lead oxide is used for preparing dry- 
 ing oil, by boiling linseed oil with a small quantity of the oxide. It is also used in 
 the preparation of a cement for repairing the stone work of buildings by mixing with 
 8 or 10 times its weight of brick dust, and sufficient linseed oil to form a stiff paste. 
 This preparation is called Dhilmastic; it rapidly hardens by exposure to the air. 
 Lead oxide is also used as a flux in assaying, and for several pharmaceutical prepara- 
 tions. 
 
 FORMULA Pb0 2 . MOLECULAR WEIGHT 239. 
 
 This substance occurs naturally as plattnerite in brilliant prismatic crystals, 
 and is formed when chlorine is brought into contact with lead oxide suspended in 
 water, or when the oxide is acted upon by melted potassium chlorate. A more ready 
 way of obtaining the peroxide is to digest red lead with weak nitric acid. As pre- 
 pared artificially it is a brown powder insoluble in water and dilute acids ; it is decom- 
 posed by strong hydrochloric acid and converted into lead chloride with evolution of 
 chlorine Pb0 2 + 4HC1 = PbCl 2 + 2H 2 + 2C1. It reacts violently with sulphurous oxide, 
 absorbing the gas and forming lead sulphate Pb0 2 + S0 2 + PbS0 4 , with nitrous acid 
 it forms lead nitrate. A mixture of the oxide with one-sixth its weight of sulphur 
 takes fire when rubbed. Lead peroxide when heated gives off half its oxygen, and it 
 acts as an oxidising agent towards many organic substances. 
 
 Lead peroxide combines with bases, forming a series of compounds called plum- 
 bates, in which it acts the part of an acid. It has also to a slight extent the power 
 of forming salts with acids. 
 
 EED LEAD. This substance is a compound of lead oxide with the peroxide, gener- 
 ally in proportions approximating to the formula Pb0 2 2PbO. It occurs naturally as 
 minium together with ores of lead, and is formed when lead oxide is exposed for some 
 length of time to the action of atmospheric air at a dull red heat insufficient to melt 
 the oxide. 
 
 Characters. Red lead is a scarlet crystalline powder. The specific gravity 
 varies from 8'62 to 9'08. When heated the colour becomes temporarily darker, and 
 gradually passes into violet, becoming red again on cooling : at a red heat, oxygen is 
 given off and lead oxide remains. Red lead is also reduced by many oxidisable sub- 
 stances such as sulphurous oxide, sugar, and other organic substance's; when mixed 
 with hydrochloric acid it is converted either into lead chloride, peroxide and water, 
 
 Pb0 2 1- 2PbO + 4HC1 = 2PbCl 2 + 2H 2 O + Pb0 2 , 
 or into lead chloride, water and chlorine according to the proportion of acid, 
 Pb6 2 + 2PbO + 8HC1 = 3PbCl 2 + 4H 2 + 201. 
 
 When red lead is digested with glacial acetic acid, or cold concentrated solutions 
 of phosphoric acid, or arsenic acid, it dissolves, forming solutions containing salts of 
 
LEAD SULPHIDE. 
 
 39; 
 
 the peroxide which are readily decomposed. Strong acids decompose red lead ; sul- 
 phuric acid converting it into sulphate with evolution of oxygen ; nitric acid dissolves 
 the lead oxide and leaves the peroxide as a brown powder. 
 
 Preparation. Eed lead is prepared on a large scale by oxidising lead HI a re- 
 verberatory furnace, at a temperature insufficient to melt the lead oxide formed. By 
 this means the lead oxide is obtained in the state of massi cot, which is then ground to 
 a fine powder, again placed in a reverberatory furnace, and exposed for two clays to a 
 carefully regulated temperature until it has absorbed sufficient oxygen and a portion 
 taken out has a bright red colour when cold. The furnace is then closed and allowed 
 to cool slowly. 
 
 X.EAD SULPHIDE. 
 
 FOKMULA PbS. MOLECULAR WEIGHT 239. 
 
 This substance occurs very abundantly as galena, and the most important ores 
 of lead consist chiefly of this mineral. 
 
 The following table gives the composition of galena from different localities : 
 
 Lead .... 
 Silver 
 Iron .... 
 Zinc .... 
 Sulphur > . 
 
 
 England Hanover 
 
 Bohemia ! Schemnitz 
 
 Thomson 
 
 "Westrumb 
 
 Lerch 
 
 Beudant 
 
 86-61 
 13-39 
 
 85-13 
 0-50 
 13-02 
 
 83-00 
 08 
 
 16-41 
 
 81-80 
 
 3-59 
 14-41 
 
 83-61 
 
 2-18 
 14-18 
 
 79-60 
 7-00 
 
 13-40 
 
 100-00 
 
 98-65 
 
 99-49 
 
 99-80 
 
 99-97 
 
 100-00 
 
 The amount of silver in galena generally ranges between O'pl and 0-03 per cent., 
 but sometimes is as nmch as 0'5 or even 1 per cent. Argentiferous galena almost 
 always contains a recognisable amount of gold. 
 
 Lead sulphide has in the crystalline state a dark grey colour and high metallic 
 lustre; the specific gravity is from 7'25 to 7'7. The sulphide formed by melting 
 together lead and sulphur, and by melting the precipitate obtained by treating solu- 
 tions of lead salts with sulphuretted hydrogen, has a specific gravity of 7'505. 
 
 Lead sulphide melts at a full red heat, above the melting point of lead ; it vola- 
 tilises at a higher temperature, and if kept out of contact with air sublimes without 
 decomposition. Hence it is often found in this state in smelting furnaces in which 
 ores containing lead have been smelted. 
 
 When moderately ignited in contact with atmospheric air lead sulphide is gradually 
 oxidised, and gives off part of its sulphur as sulphurous oxide, with production of 
 lead oxide and some lead sulphate. 
 
 The following analyses of roasted galena show the nature of the material operated 
 upon in different localities : 
 
 
 Pezey 
 
 Holzapfel 
 
 Pontgibaud 
 
 Lead oxide 
 
 18 
 
 35 
 
 31-0 
 
 52-6 
 
 16-9 
 
 62-9 
 
 sulphate . 
 
 86 
 
 19 
 
 8-0 
 
 8-0 
 
 12-1 
 
 
 
 sulphide 
 
 10 
 
 4 
 
 11-8 
 
 
 
 
 
 
 
 Ferric oxide 
 
 
 6 
 
 9-0 
 
 13-0 
 
 21-3 
 
 4-9 
 
 Zinc oxide 
 
 
 27 
 
 30-2 
 
 9-0 
 
 21-6 
 
 3-7 
 
 Manganous oxide 
 
 
 
 2 
 
 
 
 
 
 
 
 
 
 Arsenic oxide 
 
 
 
 
 
 
 
 0-4 
 
 1-0 
 
 
 
 Barium sulphate 
 Silica . . . 
 
 
 
 7 
 
 10-0 
 
 14-0 
 3-0 
 
 19-8 
 6-2 
 
 0-7 
 23-9 
 
 Lime 
 
 
 
 
 
 
 
 
 
 
 
 3-1 
 
 
 114 
 
 100 
 
 100-0 
 
 100-0 
 
 98-9 
 
 99-2 
 
392 LEAD. 
 
 Lead sulphide is insoluble in most dilute acids; when boiled with dilute nitric 
 acid, it is converted into nitrate with separation of sulphur. Strong hydrochloric acid 
 converts it, with the aid of heat, into chloride, with evolution of sulphuretted hydrogen ; 
 fuming nitric acid converts it into lead sulphate.. When lead sulphide is heated with 
 lead oxide in the proportion of 2 molecules to 1 of sulphide, the whole of the lead is 
 reduced and sulphurous oxide given off: 
 
 PbS + 2PbO = 3Pb + S0 2 ; 
 
 melted with alkaline carbonates, part of the lead is reduced to the metallic state. 
 
 Lead sulphide is decomposed when heated to a full red heat with metallic iron, 
 according to the equation : 
 
 PbS + Fe = FeS + Pb. 
 239 56 88 207 
 
 The temperature must be sufficient to melt the ferrous sulphide; and unless excess of 
 iron is present, part of the lead sulphide combines with the ferrous sulphide formed, 
 producing a regulus in which the proportion of lead to iron varies according to cir- 
 cumstances. In smelting ores containing galena, the decomposition of lead sulphide 
 is sometimes effected by means of metallic iron ; and in such cases there is generally 
 obtained, together with metallic lead, a regulus containing lead which requires to be 
 subjected to further treatment for extracting the lead. Lead sulphide is partially 
 decomposed in a similar manner when melted together with ferrous silicate, and 
 ferrous sulphide is formed which combines with the undecomposed lead sulphide, 
 forming a regulus. Both these methods of decomposing lead sulphide are employed 
 in the smelting of lead ores. 
 
 Lead sulphide combines readily with ferrous sulphide when the two substances are 
 brought into contact at a high temperature in the melted state. The product thus 
 obtained is of variable composition and is termed regulus. In smelting poor lead 
 ores the production of such a mixture of sulphides is often practised with the object 
 of separating the lead from the earthy constituents of the ore and obtaining it in a 
 more concentrated condition. If the ore does not naturally contain sufficient ferrous 
 sulphide, it is mixed with iron pyrites before smelting. 
 
 LEAD SULPHATE. 
 
 FORMULA PbS0 4 . MOLECULAR WEIGHT 303. 
 
 This substance occurs naturally both in a crystallised state, as anglesite and 
 in amorphous masses together with galena. Some lead ores contain a considerable 
 amount of lead sulphate. It is also produced in considerable quantity as a secondary 
 result of the preparation of aluminic acetate for calico printing works. 
 
 Lead sulphate is almost insoluble in water, but it dissolves slightly in nitric acid, 
 and freely in solutions of ammoniacal salts, especially ammonium acetate. It is dis- 
 solved also by concentrated sulphuric acid to some extent. Hydrochloric acid dissolves 
 it with decomposition, and the hot solution deposits crystals of lead chloride. It 
 bears a high temperature without decomposition, but when heated together with 
 carbon it is reduced, and, according to the proportion of carbon, the lead is separated 
 either in the state of metal, as sulphide or as oxide. 
 
 I.EAD CARBONATE. 
 
 FORMULA PbC0 3 . MOLECULAR WEIGHT 257. 
 
 History. The preparation of white lead, which consists chiefly of this sub- 
 stance, was described by Dioscorides in the fourth century before Christ, and at a later 
 period by Theophrastus, Pliny, and Vitruvius. The Arabians prepared white lead. 
 Geber writing in the eighth century recommended for its preparation exposing lead to 
 the vapour of vinegar. The art was afterwards introduced into Venice, Holland, 
 England, Germany, and France. 
 
 Occurrence. Lead carbonate occurs naturally in a well-crystallised condition, 
 but in comparatively small quantity, as cerusite, a mineral found in Scotland, 
 Germany, France-, etc. 
 
 Composition. The native carbonate is a neutral anhydrous salt having the 
 composition represented by the formula given above ; but the precipitate formed on 
 adding a solution of alkaline carbonate to solutions of lead salts is a compound of the 
 carbonate with lead hydrate, and the composition varies according to the conditions of 
 
WHITE LEAD. 
 
 392 
 
 temperature and concentration under which it is produced. The artificially prepared 
 lead carbonate, commonly called white lead, is also a basic salt, which may be re- 
 garded as a combination of neutral lead carbonate with hydrated lead oxide in various 
 proportions approximating to one or other of the following formulae : 
 
 2PbC0 3 .PbH 2 2 , 3PbC0 3 .PbH,0 2 , 5PbC0 3 .3PbH 2 2 . 
 
 Phillips found one sample to have a composition represented by the formula 
 5PbC0 3 .PbH 2 2 . 
 
 Characters. In the crystallised state, as it sometimes occurs naturally, lead 
 carbonate is a transparent, colourless, brittle substance. It frequently forms fibrous 
 or compact opaque masses ; it has a specific gravity varying from 5'5 to 6'4. 
 
 The artificially prepared hydrocarbonate is a brilliant white pulverulent substance 
 insoluble in pure water, but soluble in water containing carbonic acid, as well as in 
 solutions of caustic potash or soda ; it is also easily soluble in nitric acid or acetic 
 acid, the solution being attended by effervescence. It is poisonous ; is decomposed 
 by sulphuretted hydrogen and ammonium sulphide, black lead sulphide being formed, 
 aiid on this account it cannot be employed as paint in the vicinity of places where the 
 atmosphere is contaminated with sulphuretted hydrogen gas, zinc white or baryta 
 white being invariably used in such cases, since neither of these latter is blackened 
 by sulphuretted hydrogen. Heated to dull redness, white lead loses carbonic acid 
 and water, and is converted into lead oxide, which absorbs oxygen when heated to red- 
 ness in the air, yielding very pure red lead. 
 
 Preparation. Several methods are in use for preparing white lead, known 
 respectively as the Dutch, French, and English methods, in each of which lead car- 
 bonate is formed by the decomposition of a basic compound of lead oxide with acetic 
 acid. In order to obtain white lead of good quality it is desirable that the lead em- 
 ployed should be free from copper. 
 
 DUTCH METHOD. Metallic lead is converted into basic lead carbonate by the joint 
 action of acetic acid, carbonic acid and atmospheric oxygen. This method is the 
 oldest, and is still the one most practised. Metallic lead is melted in a cast-iron 
 cauldron (A), over which is a sheet-iron hood (A'), through which the lead vapour is 
 carried into the chamber (A"). The hood can be closed by a couple of sliding doors (B), 
 an arrangement that is very necessary in melting down old lead, which gives off a 
 good deal of dust. As soon as the lead is melted, it is ladled out, and cast in 
 moulds into thin plates 16 inches long, 4 inches wide, and from -gg to | in. thick. These 
 plates thus obtain a rough surface which facilitates the ensuing process of oxidation 
 of the metal under the influence of acetic acid vapour. When plates 
 of this kind are used, they are rolled up into loose coils. In order 
 to secure the exposure of a considerable surface, Besangon recom- 
 mended the use of moulds with rectangular furrows, so that the 
 lead castings have the form as shown on a larger scale in fig. 282, 
 and in the manufacture of white lead this plan is now generally 
 adopted. The advantage of using the lead in this form of grates 
 is that more surface is exposed, and the circulation of the vapour 
 through the stacks is facilitated. The casting of the grates is 
 accelerated by placing the moulds upon a rotatory disc (c) fig. 281, 
 which the caster turns round directly a mould has been filled, and a 
 second workman empties the moulds that have been filled. 
 
 FIG. 281. FIG. 282. 
 
 The next operation consists in exposing the lead castings to the simultaneous 
 action of moist air, carbonic acid, and acetic acid vapour at a temperature of 35 to 60. 
 
 The carbonic acid requisite for this purpose is often produced by the fermentation 
 of horse dung mixed with straw, and large quantities of the lead castings are piled 
 up with alternate layers of such materials in pits or brick chambers, where they are 
 left for several weeks. The heat evolved by the fermenting material and by the oxi- 
 dation of the lead is sufficient to keep up the temperature of the stack to the requisite 
 degree. 
 
394 
 
 LEAD. 
 
 The dung baths (fig. 283, a a) consist of rectangular chambers about 20 feet high 
 
 and 13 feet square. Two rows of 6 or 8 
 chambers are built together back to Lack. 
 Charging the Chambers. The bottom 
 of each chamber is first covered with a 
 layer of stable litter, upon which are 
 placed a number of glazed earthen pots each 
 containing about half-a-pint of vinegar. 
 Five or six layers of lead gratings are 
 laid above the pots, then several pieces of 
 wood, and a layer of planks above. Upon 
 this layer (No. 1, fig. 283) some more 
 horse dung is spread with a similar layer 
 of pots and lead gratings above it, and 
 in this way a stack is built to the top 
 of the chamber, a thick layer of horse 
 dung being spread over the whole. In 
 order to promote the circulation of air 
 through the stacks, a space is left between 
 one end of each layer and the wall of 
 the chamber alternately at opposite sides, 
 as shown in the vertical section, fig. 283. 
 In the place of horse dung, which 
 must contain a sufficient quantity of 
 straw, spent tan may be used, the action 
 in both cases being due to the development of heat and carbonic acid by the de- 
 composing organic substances. The heat causes evaporation of vinegar and water, 
 which convert the lead in contact with atmospheric oxygen into basic lead acetate, and 
 this salt is converted by the carbonic acid in the air into basic lead carbonate, or 
 white lead, the neutral lead acetate formed at the same time being also converted by 
 the moist and warm carbonic acid into carbonate, with liberation of acetic acid. The 
 range of temperature best suited for this process is from 40 to 50. In the centre 
 of the stacks, especially at the beginning, when the fermentation is very active, the 
 temperature rises as high as 90 or 100, but near the sides of the chamber the tem- 
 perature may be lower than 40. 
 
 The stacks are opened after the lapse of 30 or 35 days when horse dung is used, 
 or after 6 or 7 weeks when spent tan is employed. Since a favourable result depends 
 very much upon the maintenance of a uniform temperature, this is provided for by 
 means of double walls and other arrangements, or even by warming the stacks, as in 
 Carinthia and Styria, where there are very extensive white lead and litharge works. 
 The bent leaden plates are there hung upon lathes, in well-pitched wooden boxes, at 
 the bottom of which the vinegar is placed and mixed with the decomposing materials, 
 such as wine lees, fruit, etc., so that the lead plates do not come into contact with them. 
 After packing, the boxes are closed with lids. A number of boxes of this kind are 
 placed together in chambers which are well closed, and furnished with double walls, 
 the space between which is filled in with some bad conductor of heat, and the 
 chambers are gradually warmed by hot-air pipes, so that after the first week the 
 temperature is not more than 25, after the second week 37, after the third week 44, 
 and after the fourth or sixth week 50. Then, after a few days, air is admitted to 
 the chambers, and the corroded lead is removed. The process which takes place in 
 these chambers is exactly the same as in the stack method above described. 
 
 The white lead thus produced is in an extremely minute state of division, and free 
 from crystalline particles, and in this respect it differs from the substance obtained 
 from solutions of lead salts by precipitation with carbonic acid. This precipitate is 
 generally crystalline in structure, and when used as paint it does not cover the surface 
 to which it is applied so well as the white lead prepared by the Dutch method. The 
 opaque character of this material, technically expressed by the term body, is mainly 
 due to its amorphous structure and the very fine state of subdivision. 
 
 The lead plates when taken out are covered with a coating of crude white lead, 
 but are seldom entirely converted into white lead ; when this is the case, the product 
 is sold as flake white. To separate the white lead from the unaltered metal, the 
 plates are tapped with the hand, an operation which is very injurious to the health 
 of the workmen ; for which reason, this is done immediately upon the removal of the 
 plates from the chambers, while they are still moist, and in all cases with very great 
 precaution. 
 
 In some works more regard is paid to the health of the workmen, and mechanical 
 contrivances are used for removing the white lead. An arrangement of the kind is 
 
WHITE LEAD. 
 
 395 
 
 FIG. 284. 
 
 represented by fig. 284. be is a pulley by means of which the corroded lead plates 
 are hauled up in baskets into an upper chamber, where a workman spreads them 
 upon an endless cloth (df), which passes them between a couple of pairs of flanged 
 bronze cylinders (//'), by which means 
 the white lead is rubbed off and falls over 
 the sloping shelf (i) into a vessel (j) filled 
 with water, while the unaltered lead falls 
 into the box (h). 
 
 Before white lead is fit for use it re- 
 quires to be ground to a homogeneous im- 
 palpable powder. On account of the 
 poisonous nature of the substance, and the 
 danger of injury to the workmen that 
 would arise from grinding it in a dry state, 
 water is always mixed with the white lead 
 in this operation. The mills used for the 
 purpose consist of flat stones running 
 horizontally, and several of them are placed 
 side by side, as shown in fig. 286, which re- 
 presents a series of nine mills. 
 
 Fig. 285 represents a mill of the kind 
 in section; a is the shaft with driving 
 
 FIG. 286. 
 
 FIG. 285. 
 
 gear (d), bb the runner, cc the 
 bed stone. The white lead mixed 
 with water is placed in the cistern 
 (k), and then raised by the ele- 
 vator (&') into the first of the 9 
 grinding mills (II, fig. 286), from 
 which it is discharged into the 
 receivers (m m), and then trans- 
 ferred to the remaining mills 
 successively. After having passed 
 through 7 mills (2 mills being always out of use for cleaning), the white lead is re- 
 duced to a very fine paste, and when it has settled it is transferred to unglazed 
 conically shaped pots, having a capacity of 1 to 6 pints, which are first set to dry 
 upon the stand (n, fig. 286) in the open air, and afterwards put in a drying chamber. 
 During the drying the temperature must be gradually raised, and care must be taken 
 to avoid sudden change of temperature, since this is apt to make the lumps of white 
 lead split. 
 
 White lead is sometimes mixed with a little indigo to increase its whiteness, and 
 after the grinding, gum or dextrin is sometimes added to give it greater density. 
 Hardness is given by the addition of 8 or 10 per cent, of dissolved sugar of lead (lead 
 acetate). It is chiefly the better sorts of white lead that are treated in this way. 
 
 White lead is often met with in commerce in the form of cones, weighing from 2 
 to 3^ Ibs. each. If this particular form is not in request, both space and time 
 may be spared by drying the white lead in cakes. 
 
 Instead of obtaining the carbonic acid required in making white lead by the fer- 
 mentation of dung or tan, it may be prepared by combustion of some carbonaceous 
 material, and passed, together with acetic acid vapour and air, into the chambers con- 
 
LEAD. 
 
 taining the lead plates. Brammer recommends the use of chambers 24 feet long, 
 12 feet wide, and 8 feet high, furnished internally with 3 tiers of frames, upon which 
 strips of lead 30 to 40 inches long and 4 inches wide are hung. On the floor is 
 hung a vinegar pot or cauldron, furnished with a steam-jacket for heating it. Car- 
 bonic acid is obtained by burning charcoal, and is forced by means of an air-pump 
 through purifiers, to separate dust ; into a reservoir, from which it is passed through 
 tubes into the bottom of the white lead chambers, near the vinegar pot. A separate 
 furnace for producing carbonic acid is required for every 4 or 6 chambers. The 
 supply of vinegar vapour is regulated by the steam passed into the jacket, and the 
 supply of carbonic acid by means of stopcocks. 
 
 Each of the chambers above described is usually worked in the way described 
 3 times a day, for an hour, and at intervals of 3 or 4 hours, the complete conversion 
 of the lead into white lead requiring about 30 days. 
 
 FRENCH METHOD. This consists in passing carbonic acid into a clear solution of 
 basic lead acetate, so as to precipitate basic lead carbonate, and leave neutral lead 
 acetate in solution, which is again converted into basic lead acetate by treating it with 
 lead oxide. This process was suggested by Thenard, and practically carried out by 
 Board. 
 
 The solution of basic lead acetate is prepared by dissolving litharge in wood 
 vinegar and evaporating the solution to 18 B. The carbonic acid required may be 
 obtained either by lime-burning or fermentation, by the action of hydrochloric acid 
 upon limestone, magnesite, etc., or by burning charcoal. 
 
 An apparatus for preparing white lead according to the French process is repre- 
 sented by fig. 287. The vat (A), of about 4,500 gallons capacity, serves for dissolving 
 
 Fia. 287. 
 
 the litharge in acetic acid, the solution of the litharge being facilitated by the stirrer 
 (e c) ; the prepared liquid having a specific gravity of 1*1 3"4 is run through the cock (d) 
 into the reservoir (E), 5 feet deep, made of tinned copper, where the insoluble sub- 
 stances, such as metallic lead, copper, iron, and sometimes traces of silver chloride, 
 are allowed to deposit, and the clear liquid is then run into a second tank having at 
 a depth of 2 feet a capacity of nearly 2,000 gallons. 
 
 This tank is covered with a close-fitting lid secured by clamps. Into the lid are 
 soldered 800 tubes which dip 12 inches into the liquid and are connected with 20 
 tubes above the lid which branch out from a main (g g). Chalk or limestone is burnt 
 with coke (2| parts limestone to 1 part coke) in a small limekiln (D D), 6 feet high 
 and 27 inches in diameter at the widest part, which is charged six times daily. The 
 carbonic acid is drawn out through the tube (&) by an archimedean screw, then forced 
 into the main (g g) and through the 800 branch tubes into the solution of lead acetate. 
 After carbonic acid has been passed in for about 12 or 14 hours the precipitation of 
 the white lead is complete ; it is then allowed a few minutes to settle, the clear super- 
 natant liquid which has then a density of only o B. is drawn off into the tank (m\ 
 and pumped back through the pipe (p) into the solution vat (A) to prepare a fresh 
 quantity of basic lead acetate solution. 
 
 The precipitated white lead is then stirred with water, run off from the large tank 
 into the tank (0), and after settling there the supernatant liquid is transferred into 
 the vat (A), together with the first solution. The precipitated white lead is washed 
 twice with fresh water and filled into the ordinary moulds to dry. 
 
 Instead of dissolving the litharge by stirring it with the sugar of lead solution, 
 it is a simpler plan to filter the solution through litharge contained in tinned copper 
 cylinders. 
 
 White lead prepared according to the French method has essentially the same 
 composition as that prepared by the Dutch method, provided excess of carbonic acid 
 
WHITE LEAD. 397 
 
 is avoided in the precipitation, which would give rise to the formation of some neutral 
 lead carbonate. 
 
 French white lead is superior in whiteness to the Dutch, which generally contains 
 some lead sulphide ; it does not cover so well, on which account Dutch white lead is 
 preferred. The difference in covering power of these two sorts of white lead is pro- 
 bably due to the fact that the French variety is crystalline by reason of its formation 
 from solutions at the ordinary temperature, while the Dutch white lead, prepared in 
 the dry way and at a higher temperature, is amorphous. In point of fact, it has been 
 ascertained that, by precipitating a hot solution of basic lead acetate, white lead is ob- 
 tained of better covering power than the ordinary white lead. 
 
 ENGLISH METHOD. Pure litharge, prepared by oxidising lead free from copper in 
 a reverberatory furnace in a state of fine powder and moistened with a 1 per cent, 
 solution of sugar of lead, is exposed to a stream of carbonic acid. The gas is easily 
 absorbed, and in order to facilitate the action the mass is either stirred about with 
 rakes or is placed in barrels turning upon a hollow axis, through which the carbonic 
 acid is passed into them. In this way basic lead acetate is formed which is decom- 
 posed by the carbonic acid, while a further quantity of basic lead salt is formed with 
 the unchanged litharge, and so on. 
 
 Several other methods of preparing white lead have been proposed with the object 
 of reducing the time requisite for the operation ; but none of them have been suffi- 
 ciently successful to supersede the Dutch method, which is chiefly practised in the 
 manufacture of white lead. 
 
 A compound of lead chloride with the oxide PbCl 2 + PbO was introduced by 
 Pattinson as a substitute for lead carbonate, and prepared by grinding powdered 
 galena with strong hydrochloric acid, and thus converting it into lead chloride, which 
 is dissolved in boiling water for the purpose of separating particles of gangue, unde- 
 composed galena, etc. ; the solution is then mixed with lime sufficient to decompose 
 one half of the lead chloride and a precipitate is thus obtained consisting of oxy chloride. 
 A similar compound is obtained by decomposing lead chloride with ammonia, or by 
 precipitating basic lead acetate with sodium chloride, its composition being probably 
 represented by the formula Pb 4 H 2 Cl 2 4 = PbCl 2 + 3PbO + H 2 0. 
 
 WHITE LEAD FROM LEAD SULPHATE. Payen suggested that white lead might be 
 readily prepared from lead sulphate an abundant and almost worthless by-product 
 of calico printing by treating it with a solution of ammonium carbonate or sodium 
 carbonate, and grinding the two salts together. When the salts are sufficiently sub- 
 divided and mixed, the decomposition takes place almost immediately, soluble ammo- 
 nium sulphate or sodium sulphate being formed, together with lead carbonate. 
 
 In order to render white lead cheaper it is often mixed with lead sulphate, heavy 
 spar, chalk, clay, gypsum, and other substances, which are sometimes added to such 
 an extent that the material does not contain more than 10 per cent, of real white lead. 
 
 A recent procedure in preparing white lead consists in kneading the moist 
 white lead as it comes from the wet mills (p. 395) with oil. The oil displaces the 
 water and unites with the white lead, settling to the bottom, while the water swims 
 above, and only requires to be drawn off. By this method of preparing white lead, 
 the injurious effects of lead dust upon the health of the workmen are avoided. 
 
 Mixtures of this kind are often met with in commerce under various names, such as 
 Venetian white, Hamburg white, Dutch white, etc., and the relative 
 qualities of these articles as pigments correspond to the proportion of foreign sub- 
 stances mixed with the lead carbonate. 
 
 These admixtures admit of ready detection by simply treating the white lead with 
 dilute acetic or nitric acid, heavy spar, lead sulphate, clay, and gypsum remaining 
 undissolved ; the solution may contain besides lead nitrate or acetate (dissolved 
 white lead), a salt of lime, and by treating such a solution with excess of caustic 
 potash the lime is precipitated. Another method of testing white lead consists in pre- 
 cipitating the acid solution of the salt with sulphuretted hydrogen and filtering off 
 the lead sulphate, when the filtrate ought not to leave any considerable residue upon 
 evaporation. Small traces of residue, however, may be due to the use of spring water 
 in washing out the white lead. 
 
 Uses. White lead is used almost exclusively as paint, for which purpose it is 
 
 ground up with linseed or poppy oil. The denser its nature, the less oil is it capable 
 of absorbing. In order to secure intimate mixture, the white lead requires to be in 
 a very finely divided state. 
 
 White lead paint dries easily in the air, pure white lead facilitating the drying of 
 the oil. Exposed to air and light, the whiteness of the colour becomes intensified ; 
 but when mixed with heavy spar, it assumes a greyish hue. In dark places white 
 lead turns yellow ; the Dutch white load more readily than the French ; exposed to the 
 
398 LEAD. 
 
 light a bleaching takes place and the white colour is restored. This yellow colora- 
 tion of white lead paint may be due to the lighter oil coming to the surface during 
 drying, especially when a dense kind of white lead is used ; upon exposure to light 
 the oil is bleached and the white colour of the paint restored. 
 
 In places exposed to the action of ammonium sulphide or sulphuretted hydrogen, 
 lead colour turns black, owing to the formation of lead sulphide. The darkening of 
 pictures is said to be in part due to this cause. 
 
 White lead is sometimes used as a flux, in making glass and enamel colours ; it is 
 also used in the preparation of glazed paper, cards, etc. 
 
 KEAD ACETATE. 
 
 FOEMULA Pb 2(C 2 H 3 2 ). MOLECULA.R WEIGHT 325. 
 
 History. This salt was known as early as the thirteenth century as sugar of 
 lead, by which name it is still commonly designated. The basic acetate was known 
 at a still earlier period and is described by Geber ; in 1760 a solution of this salt was 
 specially recommended for medical use by a French physician, and hence it has been 
 termed Goulard's extract. 
 
 Characters. Lead acetate is a colourless salt, having a peculiar sweet taste. 
 As usually met with, it resembles sugar in appearance ; hence, the popular name 
 which it bears. It is soluble in rather more than its weight of cold water, and 
 crystallises with three molecules of water. It is also soluble in alcohol. The crystals 
 effloresce in a dry atmosphere, and by absorbing carbonic dioxide are partially converted 
 into lead carbonate ; when gently heated they melt and give off water. The dry salt 
 melts at a higher temperature, and is then decomposed with formation of acetone and 
 other empyreumatic products, leaving a finely divided mixture of metallic lead and 
 carbon, which takes fire on contact with atmospheric air. 
 
 When lead oxide in the form of finely powdered litharge is digested with a warm 
 solution of lead acetate, it is dissolved and basic acetates are formed. This solution 
 constitutes the Goulard extract or lead vinegar of pharmacy. It has an alka- 
 line reaction, and readily absorbs carbonic dioxide from the air, becoming turbid by the 
 formation of carbonate ; when mixed with solutions containing gum or mucilage, an 
 insoluble compound of these substances with lead oxide is formed. There are two 
 distinct basic acetates containing acetic acid and lead oxide in the proportions indi- 
 cated by the following formulae : 
 
 Pb2(C 2 H 3 O 2 )PbO 
 Pb 2(C 2 H 3 2 ) 2PbO. 
 
 Preparation. Lead acetate is made by gradually dissolving litharge in acetic 
 acid until the liquid is but slightly acid ; it is then evaporated until it has a density 
 of about 1-500, and run into crystallising vats. The vessels used for the purpose are 
 made either of lead or copper. 
 
 Uses. Lead acetate is largely used in calico printing. It is also sometimes 
 employed in the preparation of other compounds, such as white lead according to the 
 French method, aluminum acetate, and ferric acetate. Both the neutral and the 
 basic lead acetates are used in medicine, and in the laboratory. 
 
399 
 
 COPPER. 
 
 SYMBOL Cu. ATOMIC WEIGHT 63*4. 
 
 History. This metal has been known from the earliest times, and it appears to 
 have been used for making weapons, tools, and agricultural implements long before 
 iron was applied to these purposes. It was termed CBS cyprium by the Eomans, who 
 obtained it from the island of Cyprus ; and this name was ultimately corrupted to 
 cuprum. The Greeks obtained copper from Chalcis in Euboea, and hence called it 
 Xa\i<6s, but both this name and the Koman CBS appear to have been applied indif- 
 ferently to copper, bronze, and brass. 
 
 Occurrence. Copper occurs naturally in the metallic state, sometimes in con- 
 siderable masses ; but it is much more abundant in various states of combination, 
 chiefly with sulphur, in the form of cuprous sulphide, Cu 2 S, as redruthite or copper 
 glance, and in the form of cupric sulphide, CuS, as covellite or indigo copper. 
 These sulphides also occur combined with other sulphides, as in copper pyrites ; the 
 composition of which approximates to the formula CujS.Fe 2 S 3 or CuS.FeS. Another 
 compound of cuprous sulphide with ferric sulphide, varying in composition, occurs as 
 purple or variegated copper, SCuJS.FeoSg, and a number of other minerals, such 
 as the varieties of fahl-ore, contain cuprous sulphide associated with sulphides of 
 other metals. Cuprous oxide, Cu 2 0, occurs naturally as red copper ore; cupric 
 oxide, CuO, asmelaconite orb lack copper; and in combination with manganous 
 oxide as cuprous manganese, with zinc oxide as aurichalcite, and with lead 
 sulphate as 1 i n a r i t e; the carbonate combined with cupric hydrate occurs as malachite 
 and azurite. 
 
 Cupric silicate occurs as dioptase, CuO,Si0 2 .H 2 0, and with a larger proportion 
 of water as chrysocolla. Cupric chloride occurs combined with cupric oxide and 
 water as atacamite. Cupric phosphates and arsenates also occur nuturally. 
 
 The sulphur compounds of copper which constitute the principal ores of this metal 
 occur as veins or lodes in the older rocks, frequently associated with other minerals in 
 such large proportions that the mass contains only a small amount of copper. Besides 
 the copper ores occurring in this way, rocks occur in some localities so highly impreg- 
 nated with copper as to be available for the extraction of the metal. The copper in 
 these rocks is sometimes in the state of oxide, carbonate, or sulphide; but it is probably 
 always of secondary origin and derived from sulphuretted minerals by a series of slow 
 chemical changes, the first being the formation of cupric sulphate as a result of the 
 oxidising action of the atmosphere upon cuprous sulphides, in consequence of which 
 the water in copper mines is often highly impregnated with cupric sulphate. This 
 salt being soluble in water is dissolved by rain, and the solution filtering through 
 beds of limestone or other rocks containing carbonates, is decomposed with production 
 of cupric carbonate, which is deposited in the rocks where the decomposition takes 
 place. At a high temperature the product of decomposition in such cases might be 
 cupric oxide, and if the strata permeated by the copper solution contained organic 
 substance, the cupric sulphate might be deoxidised and cupric or cuprous sulphide 
 formed as a result of the chemical action. Probably the copper pyrites in the 
 bituminous slate of the Mansfeld district in Saxony has originated in this way. 
 
 Copper also occurs very frequently in minute proportions in some meteorites, in 
 iron ores, soils, and mineral water. It has also been detected in sea-weeds, in the 
 red pigment of the wing feathers of the Turaco, and in the blood of some animals. 
 
 Characters. Copper has a characteristic yellowish-red colour ; its density varies 
 
 from 8-910 to 8'950. It is very hard, malleable, and ductile ; by hammering or draw- 
 ing into wire the hardness is increased and the metal becomes brittle, but it can be 
 softened again by heating it to redness and allowing it to cool slowly. The fracture 
 is granular after melting, but after the metal has been hammered it breaks with a 
 fibrous fracture. At a red heat it is so brittle that it can be crushed to powder. 
 
 Copper melts at a bright red heat somewhat higher than the melting point of 
 
400 COPPER. 
 
 silver and below the melting point of gold. At the ordinary temperature it does not 
 readily oxidise in dry air, but in contact with a moist atmosphere it gradually becomes 
 coated with a green incrustation consisting partly of cupric carbonate ; when heated 
 to redness in atmospheric air, copper readily oxidises and becomes covered with a 
 black scale consisting of cupric oxide. It is scarcely affected by hydrochloric acid or 
 sulphuric acid when dilute, but it dissolves readily in concentrated sulphuric acid 
 with evolution of sulphurous oxide ; nitric acid dissolves it readily, even when diluted, 
 nitrous fumes being evolved ; and moderately strong acid acts violently upon the metal, 
 but very strong nitric acid does not act upon it at all. 
 
 The oxidation of copper is promoted very much by contact with acids when it is 
 exposed to the air, and under these conditions the metal is rapidly corroded and con- 
 verted into a salt. It is in this way that a green incrustation is formed upon culinary 
 vessels that are not thoroughly cleansed from fat, etc., or in which liquids are allowed 
 to remain exposed to the air. 
 
 The presence of very small proportions of arsenic, antimony, bismuth, zinc, or iron 
 in copper renders this metal inferior in malleability and tenacity. The toughness of 
 copper is also very much reduced by the presence of cuprous oxide, which is dissolved 
 by the melted metal generally to the extent of more than 4 per cent. (See Blister 
 Copper.) Melted copper is capable of dissolving as much as 19 per cent, of cuprous 
 oxide. 
 
 Preparation. Though metallic copper occurs naturally in North America and 
 some other localities, comparatively very little of it is turned to account. The ores 
 containing copper in the state of oxide and carbonate are in some instances smelted by 
 themselves, and then the production of metallic copper from them consists chiefly in 
 the reduction of the oxide by smelting with coal and suitable fluxes for the separa- 
 tion of the earthy ingredients of the ore, These ores, however, generally contain some 
 admixture of sulphuretted minerals, and some of the copper in them is not reduced 
 by this treatment to the metallic state, but is obtained as a regulus consisting of 
 cuprous sulphide and ferrous sulphide. Sometimes an addition of iron pyrites is found 
 desirable in order to prevent the slag from retaining copper in the state of silicate. 
 
 In most instances the ores consisting either of copper pyrites or some other sulphur 
 compound of copper constitute the chief sources from which copper is obtained. The 
 extraction of the metal from these ores is effected by a series of operations based 
 upon the characters of cuprous sulphide, and upon the fact that copper combines with 
 oxygen less readily than iron does. These operations consist in first separating sulphur 
 from the iron pyrites in the ore by oxidation, and at the same time converting greater 
 part of the iron into the state of oxide ; then melting the roasted ore with silicious 
 material so as to convert the oxidised iron into the state of a liquid slag, from which 
 the heavier cuprous sulphide separates by subsidence ; lastly, decomposing the cuprous 
 sulphide partly by direct oxidation, and partly by the reaction of the cupric oxide 
 thus formed with the unoxidised sulphide, according to the following equation : 
 Cu,S + 2CuO = 4Cu + S0 2 . 
 
 It is chiefly in this way that copper is reduced when the operation of smelting is 
 carried out in reverberatory furnaces. 
 
 When copper pyrites is roasted at a low red heat, sulphurous oxide is given off, 
 and after some time the mass is eventually converted into a reddish-coloured pulve- 
 rulent mixture of ferric oxide and cupric oxide. At the commencement some ferrous 
 sulphate and cupric sulphate are formed, but these salts are decomposed at a high 
 temperature. 
 
 When a mixture of this kind is smelted in contact with carbonaceous substances 
 and silica, the ferric oxide is reduced to ferrous oxide, which combines with the silica, 
 forming a fusible slag, and the cupric oxide is reduced to the metallic state chiefly by 
 the action of carbonic oxide : 
 
 CuO + CO = Cu + C0 2 . 
 
 It is in this way that copper is reduced when the operation of smelting is conducted 
 in shaft furnaces, and in the case of rich copper ores containing little impurity the 
 roasted ore might be at once subjected to this treatment. 
 
 Copper ores, however, generally contain, in addition to cuprous sulphide and iron 
 pyrites, admixtures of other minerals containing arsenic, antimony, silver, and other 
 substances, which have to be separated either to ensure the purity of the copper, or 
 on account of their intrinsic value, and the treatment to which the ore is subjected 
 varies in each case according to the nature and amount of those substances. 
 
 Thus, for instance, in the first operation of roasting the ore by which some of the 
 sulphur is separated and the iron converted into ferric oxide, arsenic and antimony 
 are to some extent driven off as vapour by the direct action of the heat or by oxidation. 
 
COPPER SMELTING. 401 
 
 But at the same time arsenates and antimonates are formed, which remain in the 
 roasted material, and would in the subsequent smelting operation either give rise to 
 the production of speise, which is an alloy of arsenic and antimony with copper 
 and other metals, or render the copper so impure that it would be unfit for use. For 
 this reason it is not found advantageous to roast copper ore to such an extent that 
 it will yield in the first smelting metallic copper, but only so far that in the first 
 instance the copper is obtained in the state of cuprous sulphide, together with some 
 ferrous sulphide and other sulphides, constituting what is termed coarse metal or 
 crude regulus. 
 
 After the ore has been sufficiently roasted, it is melted, together with silicious 
 fluxes, limestone, fluor spar, etc., in contact either with the reducing gases produced in 
 a reverberatory furnace, or with the fuel itself in shaft furnaces. The ferric oxide is 
 thus reduced to ferrous oxide, and combining with the silica of the flux, forms a fusible 
 slag, from which the copper separates in the state of regulus, consisting of cuprous 
 sulphide, ferrous sulphide, and other sulphides. So long as the material operated upon 
 in this way contains more sulphur than is sufficient to form cuprous sulphide with the 
 copper, none of this metal is dissolved by the slag, and even though some copper 
 may have been oxidised in the roasting of the ore, it will be converted into cuprous 
 sulphide by the reaction with ferrous sulphide, which takes place very readily accord- 
 ing to the following equation : Cu 2 + FeS = FeO + CugS. 
 
 The ore regulus or coarse metal, obtained by smelting the roasted ore, is roasted 
 in the same manner as the ore, for the purpose of effecting a further separation of sul- 
 phur, arsenic and antimony, as well as the conversion of the iron into ferric oxide. 
 The extent to which this roasting is carried depends upon the character of the ore 
 worked. If it be free from any considerable amount of impurities, the coarse metal 
 may be roasted so far that when smelted it will yield at once metallic copper and only 
 a small proportion of copper regulus. More frequently however, when poor ores are 
 worked, the copper thus obtained would be very impure, and it is requisite to roast 
 the coarse metal only to such an extent that in smelting it the whole of the copper 
 is obtained in the state of cuprous sulphide as a regulus differing from the coarse 
 metal only in containing a larger amount of copper and a smaller amount of arsenic, 
 antimony, or other impurities. In some instances these alternate operations of roast- 
 ing and smelting are repeated several times before the regulus is obtained in such a 
 condition of purity and concentration that it can be worked for metallic copper. 
 
 The water collecting in copper mines and pumped out of them in the course of the 
 working often contains a considerable amount of copper in the state of sulphate, to- 
 gether with ferrous sulphate, these salts being formed by the oxidation of copper 
 pyrites, and in some places this copper is extracted by bringing the water into con- 
 tact with metallic iron, which precipitates the copper in the form of a finely divided 
 spongy mass. This process is termed cementation. 
 
 The extraction of copper from poor ores is also practised in a similar manner by 
 first converting the copper into a soluble salt, and separating it from the earthy and 
 other ingredients of the ore by lixiviation, after which the copper is precipitated by 
 metallic iron. When the copper is in the state of oxide it can be dissolved by dilute 
 acids, provided the other constituents of the ore are not also acted upon by acid ; but 
 when the copper is combined with sulphur, it must be rendered soluble either by oxi- 
 dation and conversion into cupric sulphate, by exposure to the air, or by roaating. 
 The ferrous sulphate formed at the same time by oxidation of ferrous sulphide is 
 readily converted by exposure to the air into a basic ferric sulphate which is insoluble. 
 It is also more readily decomposed by heat than cupric sulphate, and is thus converted 
 into basic ferric salt or ferric oxide. 
 
 The copper in ores of this kind is often rendered soluble by converting it into 
 cupric chloride, either by roasting the ore with sodium chloride or by digesting the 
 roasted ore with a solution of ferric chloride. 
 
 The roasting of copper ores is sometimes carried out either in heaps constructed in 
 the manner already described at p. 362, or in stalls of the kind represented by fig. 
 288, where the ore is laid upon layers of 
 brushwood between the walls. Arrange- 
 ments are sometimes made for condens- 
 ing the sulphur volatilised in roasting 
 copper ores in this way. If necessary, 
 also, the stalls are covered with a roof 
 to protect the roasting ore from rain or 
 from being too much cooled by the 
 access of atmospheric air. Stalls are 
 often made very much larger than those Fia - 288 - 
 
 shown in fig. 288, and capable of containing large quantities of ore, and then they 
 
 D D 
 
402 
 
 COPPER. 
 
 are surrounded on all sides by walls in which flues are constructed for the purpose 
 of condensing the sulphur volatilised, as shown in the accompanying drawings (figs. 
 289, 290, and 291), which represent the stalls used at Agordo, in the Venetian Alps. 
 
 FIG. 290. 
 
 The floor of the stall is constructed so as to form ridges (b b), communicating at 
 the lowest point with channels (d d d) through the walls 
 by which the melted sulphur separated from the ore 
 runs away into receptacles (eee) outside, and the 
 sulphur vapour escapes through the channels (g gg] 
 which communicate with the flues (//) where the 
 vapour is condensed. The air requisite for oxidation 
 is admitted through the apertures (c c c c) at the lower 
 part of the walls. 
 
 Kilns similar to those used for burning lime are also 
 FIG. 291. used for roasting copper ores. In all these cases the 
 
 ore can be roasted in lumps, and as the sulphides, when 
 
 once sufficiently heated, continue to burn and evolve heat, very little fuel is required. 
 When the ore is in the state of fine powder, it is roasted in a reverberatory furnace. 
 
 Ores containing arsenic and antimony in considerable amount require to bo 
 thoroughly roasted, and it is often necessary to repeat the operation several times if 
 these substances are to be got rid of in this stage of the treatment. After the ore has 
 been once roasted it is in the subsequent roasting mixed with some fuel to reduce the 
 arsenites and antimonates formed by oxidation. But in any case the ore must not be 
 deprived of the- whole of its sulphur, or if there is a deficiency of sulphur in the 
 roasted material some pyrites must be mixed with it when the subsequent operation of 
 smelting is carried out. 
 
 In roasting ores containing blende an admixture of coal is requisite for the pur- 
 pose of decomposing the zinc sulphates formed by oxidation. In smelting a roasted 
 ore containing zinc sulphate this salt would be reduced to sulphide, which is liable to 
 be taken up by the slag. When this is the case, the slag is rendered less fluid, and as 
 it does not readily separate from the regulus, considerable loss of copper is the result. 
 Ores containing only a very small proportion of copper in the state of sulphide, 
 together with much ferrous sulphide, undergo a remarkable alteration in roasting, the 
 result of which is that the copper accumulates at some point in the interior of the 
 lumps of ore, and while the outer portion of the lumps consists almost entirely of ferric 
 oxide containing only a trace of copper, the core or nucleus consists chiefly of copper 
 combined with sulphur. Advantage is sometimes taken of this fact to concentrate 
 the copper in poor ores by roasting them until the greater part of the ferrous sulphide 
 has been oxidised and the cuprous sulphide has collected in this way at the interior. 
 
COPPER SMELTING. 
 
 403 
 
 The outer part of the lumps is then broken off and the cores are separated, This opera- 
 tion is termed core roasting. It is probable that this concentration of the copper 
 is due to the circumstance that cuprous sulphide is oxidised less readily than ferrous 
 sulphide, so that while a crust of ferric oxide is formed at the outside of the lump of 
 ore, the cuprous sulphide, merely melted by the heat, combines with the unoxidised 
 sulphides at the interior of the lump, and thus gradually accumulates there. 
 
 Large quantities of iron pyrites containing about two per cent, of copper are now 
 roasted chiefly for the sake of obtaining the sulphur in the form of sulphurous oxide 
 for the manufacture of sulphuric acid ; and since the residue thus obtained, known as 
 burnt pyrites, is afterwards treated for the extraction of the copper it contains, 
 this operation may be regarded as an instance of the roasting of a copper ore. 
 
 Spence's furnace for this purpose, already mentioned under the head of Sulphuric 
 Acid (see p. 122), is represented in longitudinal and transverse sections by figs 292 and 
 294. 
 
 j 
 
 FIG. 292. 
 
 It consists of a long bed (c cc) constructed of fire brick, in such a manner that it is 
 heated by the flame and hot gas passing from the fireplace (a) through the flues (b b b\ 
 the ends (i) of which communicate with a chimney. The finely divided ore is spread 
 upon the bed (c) at the end furthest from the fireplace, and when it has become suffi- 
 ciently hot, it is pushed forwards towards the fireplace by rakes introduced through the 
 doors (' * to e n , fig. 293) at the side of the furnace. 
 
 FIG. 293. 
 
 The bed (c) of the furnace is covered with 
 i a brickwork arch so as to form a chamber 
 ! (d), into which atmospheric air gains access 
 
 through the aperture (/) in the brickwork 
 I at the end of the furnace* and becomes heated 
 
 sufficiently in its passage through the cham- 
 ' ber (d) to oxidise the sulphides on the bed of 
 
 the furnace. 
 
 G-erstenhofer's kiln, already described at 
 
 p. 123, is a similar contrivance which is also 
 
 ^^ ^ FIG. 294. 
 
 used for roasting copper ore when it is intended to make use of the sulphurous oxide 
 for the manufacture of sulphuric acid. 
 
 In England all the operations involved in copper smelting are conducted in rever- 
 beratory furnaces ; but on the continent shaft furnaces are very generally employed 
 for the melting and reduction of the ore, the oxidation of the regulus being carried 
 out either in stalls, like those used in roasting the ore, or in reverberatory furnaces, and 
 the term roasting is applied to both of these operations. In this country, however, it 
 is customary to restrict the term roasting to that operation by which metallic copper 
 is obtained from the regulus, which consists chiefly of cuprous sulphide, and is calle 
 white metal, and the several operations by which the ore and the regulus are 
 oxidised are termed calcination. In both cases, however, the chemical change pro- 
 
 DD 2 
 

 404 
 
 COPPER. 
 
 duced consists in the oxidation of the sulphides in the material operated upon, by 
 atmospheric oxygen, and the only peculiarity of the operation termed roast-ing in this 
 country is, that part of the cuprous sulphide is decomposed by reacting with the 
 cuprous oxide formed at the outset. 
 
 SMELTINO IN REVEBBERATOBY FUBNACES. The several operations by which copper 
 is extracted from its ores in this way are conducted in the following manner at the 
 smelting works in Wales and Lancashire. 
 
 Calcination. The object of this operation is to effect a partial separation of sulphur 
 from the ore, consisting essentially of a mixture of copper sulphides with iron sulphides; 
 it is conducted in a reverberatory furnace of the kind represented by figs. 295 and 
 296, in vertical and horizontal sections on the lines XY and z v. 
 
 FIG. 295. 
 
 The bed or hearth of the furnace is about sixteen or twenty feet long, and is formed 
 of fire brick supported on a solid mass of brickwork over the vault u, with which there 
 is a communication through the apertures (rrrr) ; the roof of the calcining chamber 
 slopes downwards from the fireplace (?) so as to make the flame and gaseous products of 
 combustion come into contact with the charge of ore as they pass towards the smoke flue 
 (BB) leading to a chimney, and at the sides of the furnace are doors (pppp) which 
 admit of the ore being stirred from time to time by means of rabbles. The charge of ore 
 
 FIG. 296. 
 
 is introduced into the furnace by the hoppers (T T), made of cast iron, and then spread 
 evenly over the hearth ; and during the calcination the apertures communicating with 
 the vault u are closed by iron plates. A mixture of anthracite and bituminous coal is 
 used as fuel, and a considerable mass of coal is kept upon the fireplace, so that carbonic 
 oxide is at first produced by the combustion, and coming into contact with atmospheric 
 air admitted through the opening (o, fig. 296) near the fire bridge, this gas burns with 
 a large flame extending throughout the entire length of the calcination chamber. The 
 ore upon the hearth is thus kept in contact with a highly heated atmosphere of oxi- 
 dising gas, and a considerable part of the sulphur in the ore is thus converted into 
 sulphurous oxide, which passes away to the chimney, while the greater part of the 
 iron and some of the copper in the ore are at the same time oxidised. 
 
COPPER SMELTING. ; 405 
 
 The calcination is generally continued from 12 to 24 hours, the ore being frequently 
 stirred meanwhile so as to expose fresh surfaces to the action of the oxidising gas, and 
 the heat is regulated so as to prevent the ore from caking together during the earlier 
 stage of the operation. When the calcination is completed, the iron plates covering 
 the apertures (rr) are removed, and the calcined ore is raked down into the vault (u) 
 and allowed to cool. A fresh charge of ore is then introduced as before by opening 
 the sliding dampers at the bottom of the hoppers, and the operation continued. 
 
 The nature of the change which takes place in the calcination of the ore may be 
 seen by the comparison of the figures in the following tabular statement based on the 
 analyses made by Le Play : 
 
 Saw Ore. Calcined Ore. 
 
 Cuprous oxide, Cu 2 
 
 Copper pyrites . 
 
 Iron pyrites 
 
 Various sulphides 
 
 Ferric oxide 
 
 Various oxides . 
 
 Silica 
 
 Earthy ashes . 
 
 Water and carbonic dioxide 
 
 0-4 5-4 
 
 22-7 11-2 
 
 22-4 Ferrous sulphide . . 11-2 
 
 I'O 0-6 
 
 0-6 117 
 
 0-3 '0'6 
 
 34-3 34-3 
 
 2'0 2-0 
 
 0-5 .... i-i 
 
 84-2 78-1 
 
 Atmospheric oxygen consumed . 15-8 Water and C0 2 . . 0-5 
 
 Sulphurous oxide . . 21 -4 
 
 100-0 100-0 
 
 The loss of weight of the ore by calcination amounts in this operation to about 7' 5 
 per cent., and about 51 per cent, of the total sulphur in the ore is removed. The actual 
 quantity of sulphur thus volatilised chiefly in the state of sulphurous oxide amounts 
 to about 13 per cent, of the weight of ore operated upon, and in the South Wales 
 district several thousand tons of sulphur are thus discharged into the atmosphere in 
 the course of the year. With the object of turning this large quantity of sulphur to 
 account for making sulphuric acid, the kilns already described (pp. 403 and 123) 
 have been introduced in some works for the calcination of copper ores. 
 
 It will be seen from the foregoing table that in the roasted ore there is still a con- 
 siderable proportion of the sulphides left unoxidised, since the object of the subsequent 
 operation of smelting is to obtain the copper not in the metallic state but in combina- 
 tion with sulphur as a regulus, containing a smaller proportion of ferrous sulphide 
 than that originally present in the ore. The sulphur of the ferrous sulphide in the 
 roasted ore is also useful in the smelting as an agent for the reduction of the ferric 
 oxide and converting it into ferrous oxide by the reaction which takes place at a high 
 temperature according to the following equation : 
 
 3Fe 2 3 + FeS - 7FeO + S0 2 
 480 88 504 64 
 
 In this way a further separation of sulphur is effected by the formation of sul- 
 phurous oxide, and since the ferrous oxide thus produced is capable of combining 
 with silica to form a fusible slag, a considerable portion of the iron may also be sepa- 
 rated by adding suitable silicious fluxes to the roasted ore when it is being melted. 
 
 If the roasting of the ore be carried too far, part of the copper may be reduced to 
 the metallic state in the smelting by a similar reaction between cuprous sulphide and 
 ferric oxide ; but in the presence of a sufficient proportion of ferrous sulphide this 
 does not take place. Under this condition also the presence of some portion of the 
 copper in the roasted ore in the oxidised state, as cuprous oxide or cupric oxide, is not 
 attended with loss of copper in the smelting by the formation of silicate, because the 
 ferrous sulphide in the regulus reacts upon the slag and converts any copper it con- 
 tains into cuprous sulphide. 
 
 If, on the other hand, the ore is insufficiently roasted, the regulus obtained by 
 smelting will contain too large a proportion of ferrous sulphide ; consequently the ex- 
 tent to which any particular ore is roasted must be regulated according to the amount 
 of copper it contains. In order to economise fuel in the roasting, the ore should not 
 contain less than 9 per cent, of copper, and to prevent loss of copper in the slag it 
 should not contain more than 14 per cent. Ores of different character in this respect 
 are therefore mixed so that the average amount of copper is about 13 per cent. 
 
406 
 
 COPPER. 
 
 Melting the Calcined Ore. This operation is also conducted in a reverberatory 
 furnace called the ore furnace, which is represented by figs. 297 and 298. The 
 
 FIG. 297. 
 
 bed of this furnace is formed of sand with a hollow at B in which the melted material 
 may collect. The charge consists of a mixture of roasted ore with slag obtained in 
 another operation (see p. 408), and some fluor spar as a flux. It is introduced into the 
 furnace through the hopper (T) and, in melting, the ferric oxide reacts upon the sulphides 
 so as to produce sulphurous oxide, which escapes to the chimney (c), and ferrous 
 oxide, which combines with the silica, forming a fusible slag. At the same time there 
 is obtained a regulus containing the greater part of the copper in the state of sulphide, 
 together with some ferrous sulphide. This regulus collects as it melts in the cavity 
 
 Fio. 298. 
 
 of the hearth, and the liquid slag lying over it is drawn oit by a rabble through the 
 door (p) into the pits (uu) formed in abed of sand outside the furnace, while the coarse 
 metal is run out through the trough (b) into a reservoir (B) containing water so as to 
 reduce it to a granulated condition. The melting operation lasts about 4 or 5 hours. 
 
 The regulus obtained by this operation is called coarse metal ; it is of a bronze 
 colour, brittle, and easily powdered, and the fracture is granular or vesicular ; it 
 generally contains about 33 per cent, of copper, in the state of cuprous sulphide, to- 
 gether with ferrous sulphide, and it has a composition approximating to the formula 
 Cu 2 S,2FeS, as shown by the following analyses : 
 
COPPER SMELTING. 
 
 407 
 
 
 Le Play 
 
 Napier 
 
 Cu 3 S,2FeS 
 
 Copper 
 
 33-7 
 
 21-1 
 
 39-5 
 
 38-0 
 
 Iron .... 
 
 33-6 
 
 33-2 
 
 36-4 
 
 33-4 
 
 Nickel, cobalt, manganese 
 
 1-0 
 
 
 
 
 
 
 Tin .... 
 
 07 
 
 
 
 
 
 . 
 
 Arsenic 
 
 0-3 
 
 , 
 
 
 
 
 
 Sulphur 
 
 29-2 
 
 45-5 
 
 25-0 
 
 28-6 
 
 Slag .... 
 
 1-1 
 
 
 
 
 
 
 
 
 99-6 
 
 99-8 
 
 100-9 
 
 100-0 
 
 The slag produced in this operation is a hard vesicular black glass, with fragments 
 of quartz imbedded in the mass ; it consists chiefly of ferrous silicate, the composition 
 of which, as shown below, approximates to the formula FeOSi0 2 , and tho effect of the 
 melting is therefore to separate part of the iron as well as a further portion of the 
 sulphur 
 
 
 LePlay 
 
 FeOSiO, 
 
 Silica 
 
 30'0 
 
 23-75 
 
 45-46 
 
 Ferrous oxide .... 
 
 28-5 
 
 28-50 
 
 54-54 
 
 Alumina 
 
 2-9 
 
 
 
 
 
 Lime 
 
 2-0 
 
 
 
 
 
 Magnesia 
 
 0-6 
 
 
 
 
 
 Various oxides (Sn, Mn, Ni, Co) 
 
 1-4 
 
 
 
 
 
 Fluorine 
 
 1-0 ) 01 
 
 
 
 Calcium 
 
 1-1 [ 2<1 
 
 
 
 
 
 Copper 
 
 0-5) 
 
 
 
 Iron . 
 
 0.9 \ 2-0 
 
 
 
 
 
 Sulphur 
 
 0-6) 
 
 
 
 Quartz fragments . 
 
 30-5 
 
 
 
 
 
 100 
 
 42-25 
 
 100- 
 
 The amount of copper in the slag is very small, and it is chiefly in the state of 
 minutely disseminated particles of the regains. Any copper that may be dissolved in 
 the slag as silicate is converted into sulphide by contact with the ferrous sulphide 
 present in the slag; and to ensure this result iron pyrites is sometimes added in smelt- 
 ing oxidised copper ores. 
 
 Calcination of Coarse Metal. This operation is conducted in a furnace very similar 
 to that in which the crude ore is calcined ; free access of air is admitted, and the 
 charge is frequently stirred during the calcination, which lasts from 24 to 36 hours ; 
 towards the end of the operation, the temperature is raised to a higher degree than in 
 ore roasting, but not sufficiently to melt the material. Under the influence of atmo- 
 spheric air, the sulphides are oxidised ; part of the sulphur being removed in the form 
 of sulphurous oxide and sulphuric oxide, so that the amount of sulphur in the coarse 
 metal is thus reduced from about 29 to 16 per cent., while oxygen is substituted 
 for it, and both the copper and iron are partly in the state of oxides. 
 
 The calcined product amounts to about 97'5 per cent, of the coarse metal operated 
 upon, and the oxidised material is altered in appearance to a brownish-black pulveru- 
 lent mass, but it is mixed with many hard unaltered granules of coarse metal. 
 
 Melting of Calcined Coarse Metal with Oxygenated Materials. The object of this 
 operation is to separate the iron oxidised in the calcination of the coarse metal as 
 well as that still remaining as sulphide in the roasted material ; it is effected partly 
 in the way already described (p. 401), and partly by means of the reaction that takes 
 place between ferrous sulphide and cuprous oxide, ferrous oxide being formed, which 
 is converted into slag, and cuprous sulphide, which separates in the regulus, as repre- 
 sented by the following equation : 
 
 FeS + Cu 2 = Cu 2 S + FeO. 
 
 The materials added to the calcined coarse metal for this purpose ^ in melting _ it 
 are almost entirely free from ferrous sulphide, and they should contain, in addition 
 to cupric or cuprous oxides and silicious substances, only cuprous sulphide. Ve-y 
 
408 
 
 COPPER. 
 
 little sulphurous oxide is given off, and by mixing these materials together in suitable 
 proportions, the product thus obtained may consist almost entirely of cuprous sulphide. 
 Practically, this is seldom the case, and it has been found preferable to leave a certain 
 amount of ferrous sulphide in the regulus as well as a considerable amount of copper 
 in the oxidised condition in the slag, since slag of this kind is useful in other opera- 
 tions which have for their object the preparation of pure copper. 
 
 The regulus obtained in this operation is called fine metal or white metal; 
 when quite free from iron it has a greyish-white colour, and crystalline radiated fracture ; 
 its specific gravity is 5*7, and it is quite free from metallic copper. But generally it 
 contains from 4 to 8 per cent, of iron, the colour being darker and bluish, specific 
 gravity 5'3, and particles of metallic copper can be detected in cavities of the mass. 
 In this state it is called blue metal. The composition of the two kinds of regulus 
 is represented by the following figures : 
 
 Copper .... 
 Sulphur . . . . 
 
 White Metal 
 . 77-4 
 . 21-0 
 07 
 
 B 
 
 rush-white M 
 64-8 
 22-6 
 9-0 
 0-5 
 0-7 
 1-8 
 
 "etal 
 
 Blue Metal 
 567 
 23.0 
 16.3 
 1-6 
 1-2 
 0-5 
 
 Nickel, cobalt, manganese 
 Tin and arsenic 
 Slag and sand 
 
 traces 
 0-1 
 0-3 
 
 99-5 
 
 99-4 
 
 99-3 
 
 Cuprous sulphide contains nearly 80 per cent, of copper. 
 
 The presence of metallic copper in the blue metal is characteristic of it, and the 
 reduction appears to take place by the reaction of cuprous sulphide with cuprous oxide. 
 When the materials used in this operation contain an excess of copper in an oxidised 
 state, some copper is reduced in this way, and the regulus presents warty excrescences 
 at the surface, on which account it is called pimple metal. 
 
 The slag produced in this operation is called metalslag; it is compact, homo- 
 geneous, of a dark brownish-green colour, and has a crystalline fracture : the com- 
 position varies according as the regulus is free from iron or not. 
 
 Slag from Slag from 
 
 Bluish- white Metal Blue Metal 
 
 
 Slag from 
 White Metal 
 
 Silica 
 
 . 33-0 
 
 Ferrous oxide 
 
 . 55-0 
 
 Cuprous oxide . 
 
 . 27 
 
 Other oxides 
 
 . 2-0 
 
 Alumina . 
 
 . 1-6 
 
 Lime . 
 
 1-4 
 
 Magnesia . 
 
 . 0-3 
 
 
 .2-9 
 
 Iron . 
 
 . 0-3 
 
 Sulphur 
 
 .0-8 
 
 100- 
 
 33-8 
 56-0 
 0-9 
 2-1 
 1-5 
 1-4 
 0-3 
 2-9 
 0-3 
 0-8 
 
 100- 
 
 36-0 
 54-4 
 07 
 2-5 
 0-8 
 1-2 
 0-2 
 
 100- 
 
 On account of the basic character of this slag, it is used as a flux in smeltii 
 silicious ores. 
 
 Roasting of White Metal. The object of this operation is to separate sulphur fror 
 the regulus, consisting chiefly of cuprous sulphide, and to obtain the copper in th< 
 metallic state. This is effected by exposing the white metal at a temperature near it 
 melting point to the oxidising influence of heated atmospheric air. Part of tl 
 cuprous sulphide is thus oxidised, yielding sulphurous oxide, which escapes, anc 
 cuprous oxide, which reacts upon the remaining cuprous sulphide, producing metalli 
 copper and sulphurous oxide. At the same time other metals present in small prop( 
 tions in the white metal are oxidised, and either volatilised or converted into slag 
 combination with silicious substances. 
 
 This operation is conducted in a reverberatory furnace similar to that already d< 
 scribed, but furnished with a door at the side through which the pigs of white metf 
 are put into the working chamber, and with openings near the fire bridge foradmittin 
 air as it may be required for the oxidation of the cuprous sulphide. While the whil 
 metal is being heated sulphurous oxide is given off, as a result of the direct oxida 
 tion of cuprous sulphide, and when the charge begins to melt and run down upon th 
 hearth, the cuprous oxide formed by the oxidation reacts with the cuprous sulphide 
 and the melted mass appears to boil in consequence of the evolution of sulphtiror 
 oxide. After several hours, when the whole charge has been melted down, the 
 
COPPER SMELTING. 
 
 400 
 
 collecting meanwhile on the surface is skimmed off, and the furnace is allowed to cool 
 down until the melted mass becomes pasty at the surface, and is thrown up in the 
 form of craters by the sulphurous oxide produced within it. During this stage a con- 
 siderable quantity of cuprous oxide is formed by the oxidation of the partially solidi- 
 fied mass thrown up by the escaping gas and exposed to the air. 
 
 After some time the heat is again raised sufficiently to melt the entire charge, and 
 make the cuprous oxide react upon any remaining sulphide. Sometimes materials 
 containing copper in an oxidised state are added with the same object. The slag is 
 then again skimmed off and the metallic copper is run out into moulds. 
 
 The blister copper obtained by this treatment of the white metal is not per- 
 fectly compact, but has numerous cavities throughout its mass, formed by the evolu- 
 tion of gas, the surfaces of the pigs presenting corresponding blister-shaped 
 protuberances ; and the fractured surfaces of a pig broken crossways present numer- 
 ous tubular cavities extending from the bottom to the top of the pig. In this state 
 it has the following composition : 
 
 
 LePlay 
 
 
 Napier 
 
 
 Copper ... 
 Iron .... 
 Nickel, cobalt, manganese 
 Tin and arsenic . 
 Sulphur ... 
 
 98-4 
 07 
 0-3 
 0-4 
 
 0-2 
 
 97'5 
 07 
 1-0 
 0-2 
 0-6 
 
 98-0 
 0-5 
 07 
 0'3 
 0-5 
 
 98-5 
 0-8 
 
 0-1 
 0-6 
 
 
 100- 
 
 100- 
 
 100- 
 
 100- 
 
 The slag obtained at the same time, and termed roasterslag, is a dark reddish- 
 brown porous mass, consisting chiefly of ferrous silicate together with cuprous oxide, 
 partly in the state of silicate, and metallic copper, as shown by the following analysis : 
 
 
 Le Play 
 
 FeO, 2SiO a 
 72 120 
 
 Silica .... '' ; -i '' , . . 
 
 47-5 
 
 46-6 
 
 Alumina . . . ..-..... 
 
 3-0 
 
 16-9 
 
 
 Ferrous oxide .- 
 Nickel, cobalt, and manganous oxides ;; " . 
 
 28-0 
 0-9 
 0-3 
 
 28- 
 
 Lime and magnesia . . '. ... 
 
 traces 
 2-0 
 
 
 
 
 
 
 
 98-6 
 
 
 
 
 On account of the large amount of copper in this slag, it is used as an adjunct in 
 the melting of the calcined coarse metal as already described, and the copper is extracted 
 by the reaction between the cuprous oxide of the slag and the ferrous sulphide re- 
 maining unoxidised in the calcined coarse metal. 
 
 Blister copper is never in such a condition as to be fit for use until it has under- 
 gone further treatment for the purpose of separating impurities and converting the 
 metal into a marketable condition. This is effected partly by the operation of 
 refining (seep. 418) in which the foreign metals are oxidised, and partly by the 
 operation of toughening, in which the cuprous oxide mixed with the metallic copper 
 is reduced, and the metal is made to assume the requisite texture. 
 
 It has already been mentioned that in smelting copper ores containing arsenic, an- 
 timony, tin, lead, etc., in any considerable proportion, it is usual to repeat the alter- 
 nate calcination and melting of the material several times in order to separate these 
 substances either by volatilisation or in the state of slag, before the copper is reduced 
 to the metallic state. In some cases, however, a different plan is adopted, and advan- 
 tage is taken of the fact that when the copper regulus is calcined so far that in the 
 subsequent melting only a portion of the copper is reduced to the metallic state, almost 
 the whole of the impurities present in the regulus will be concentrated in this reduced 
 copper, while the remaining regulus will by further treatment yield copper of better 
 quality. This operation is termed selecting, and it is adopted in producing that 
 kind of copper known as best selected copper. The melted material, consisting of 
 a mixture of metallic copper alloyed with the foreign metals and purified regulus, 
 is run into a series of moulds where the copper sinks to the bottom, while the regulus 
 
410 
 
 COPPER. 
 
 forms a distinct layer above it. The regulus so purified is termed closeregulus 
 and the metallic copper is termed bottoms. The composition of these products is 
 shown by the following analyses by W. T. Grent and J. A. Phillips. 
 
 
 Close regulus 
 
 Bottoms 
 
 75-55 
 19-50 
 2-05 
 trace 
 trace 
 0-35 
 1-44 
 0-66 
 trace 
 trace 
 0-29 
 
 75-62 
 19-60 
 2-01 
 0-06 
 trace 
 0-28 
 1-39 
 0-48 
 trace 
 trace 
 0-25 
 
 89-63 
 1-07 
 4-75 
 1-54 
 trace 
 1-62 
 0-30 
 0-76 
 trace 
 
 89-80 
 0-96 
 4-60 
 1-73 
 trace 
 1-57 
 0-31 
 0-94 
 trace 
 
 Sulphur 
 Lead 
 
 Tin . ' 
 Antimony 
 Arsenic 
 Iron 
 Nickel 
 Manganese . , 
 Alumina . . . . 
 Silica 
 
 99-84 
 
 99-69 
 
 99--67 
 
 99-91 
 
 SMELTING IN SHAFT FURNACES. In order to effect in this way the separation of 
 copper in the state of cuprous sulphide from the silicious ingredients of the ore 'and 
 the ferric oxide formed by roasting, it is important to regulate not only the propor- 
 tion of sulphur to copper in the material operated upon, but also the proportions of 
 silica and ferric oxide, so that a slag may be formed sufficiently fusible to admit of 
 the easy separation of the regulus. 
 
 A deficiency of silica has the disadvantage of giving opportunity for the reduction 
 of some iron to the metallic state, and the formation of deposits, consisting chiefly of 
 iron, in the hearth of the furnace. At the same time the regulus produced tinder 
 these conditions contains too small a proportion of copper and too much iron. 
 
 An excess of silica is equally disadvantageous, since it is attended with the forma- 
 tion of slags containing copper as well as iron in the state of silicate, and owing to 
 the more difficult fusibility of the silicates containing a large amount of silica, the 
 smelting operation proceeds but slowly. It is therefore necessary either to mix ores 
 of different composition, or to add suitable fluxes in order that the slag produced in 
 smelting may be sufficiently liquid. In most instances the slags produced in smelting 
 copper ores consist chiefly of ferrous silicate approximating to the formula FeO, Si0 2 ; 
 but when the ore contains much lime or alumina, the slag must contain a large pro- 
 portion of silica, and then is probably a mixture of Silicates having that composition 
 with others corresponding to Fe02Si0 2 . In some cases the addition of fluor spar is 
 very useful in smelting ores containing earthy ingredients. 
 
 The reduction of the ferrous oxide in smelting roasted copper ore in a shaft furnace 
 is effected almost entirely by the carbonic oxide derived from the fuel. The height of 
 the shaft has considerable influence in this respect, and very ferruginous ores are apt 
 to have some of the iron reduced to the metallic state in furnaces of considerable 
 height, especially when the shaft is constructed without boshes, and the heat generated 
 by combustion produces a much higher temperature in the upper part of the shaft 
 than it does when the width of the shaft is much greater at the part just above the 
 tuyere level than it is either above or below that point. In furnaces constructed 
 with boshes of sufficient width, the heat is more concentrated in the neighbourhood of 
 the tuyeres, and there is less tendency to the production of deposits consisting of iron 
 reduced to the metallic state which solidifies in the hearth. 
 
 The shaft furnaces employed in smelting copper ores are generally constructed 
 with an open breast, and the hearth in which the melted products accumulate projects 
 beyond the breast. This form of furnace affords greater opportunity of removing 
 deposits from the hearth than that in which the bottom of the furnace is closed, with 
 the exception of two small holes through which the melted products run off continu- 
 ously into basin-shaped cavities outside the furnace. In certain cases, however, the 
 closed furnaces have advantages, since they work easier and more rapidly than furnaces 
 with open breast. 
 
 In addition to the normal products of slag and regulus, it sometimes happens that 
 in smelting copper ores in shaft furnaces other by-products are obtained, such as the 
 ferruginous deposits already mentioned, and in the case of ores containing much 
 antimony, arsenic, nickel and cobalt, the product termed speise, which is an alloy of 
 arsenic or antimony, with varying proportions of iron, nickel, cobalt, copper, and 
 lead : it is less dense than the copper regulus, but denser than the slag, and conse- 
 
COPPEE SMELTING. 
 
 411 
 
 quently forms an intermediate layer between them. This product has always a highly 
 crystalline texture, is very brittle and easily fusible. The composition of several 
 samples of the speise obtained in smelting copper ores is given in the following table : 
 
 
 
 Hungary 
 
 
 Oeblarn 
 
 
 
 Hauch 
 
 
 Schenzl 
 
 Copper 
 Iron ...... 
 
 12-99 
 12-63 
 
 16-52 
 75*74 
 
 41-18 
 35-41 
 
 48'10 
 1*20 
 
 Nickel 
 Cobalt 
 Antimony 
 
 1-40 
 0-09 
 60-00 
 7-42 
 
 7'36 
 2-63 
 
 0-09 
 0-04 
 1079 
 6-10 
 
 0-32 
 
 21-56 
 0'76 
 
 Sulphur . 
 Lead 
 Bismuth 
 Silver 
 Gold 
 
 2-04 
 0'09 
 1-26 
 0-36 
 0-06 
 
 trace 
 0-03 
 
 2.60 
 0-69 
 
 0-03 
 
 1-88 
 20-69 
 2-04 
 trace 
 
 Speise is sometimes worked for the production of black copper by subjecting to 
 oxidation in a melted state and volatilising the antimony in the state of oxide, but is 
 more frequently concentrated for the production of nickel and cobalt, and ^hen it 
 contains a sufficient amount of silver, this metal is extracted. 
 
 The reduction of iron to the metallic state is frequently a source of considerable 
 inconvenience in the smelting of copper ores in shaft furnaces, especially when the 
 temperature is high in the upper part of the shaft and the charge contains too large 
 a proportion of silica. The reduced iron combines with phosphorus, molybdenum, sill 
 con, etc., and is then deposited in the hearth of the furnace, forming a granular mass 
 which gradually blocks it up, and has to be removed from time to time. 
 
 The composition of some of the ferruginous products called bears is given in the 
 following table : 
 
 
 Mansfeld 
 
 Fahlun 
 
 Freiberg 
 
 Perm 
 
 
 Stromeyer 
 
 Sefstrom 
 
 I'lattner 
 
 Cmbine 
 
 Iron 
 
 76-77 
 
 64-82 
 
 88-51 
 
 76-30 
 
 Copper . . . . I 
 
 3-40 
 
 32-88 
 
 
 
 19-90 
 
 Nickel . . . 
 
 1-15 
 
 
 
 
 
 
 
 Cobalt ..... 
 
 3-25 
 
 
 
 
 
 
 
 Manganese 
 
 0-02 
 
 
 
 
 
 
 
 Zinc 
 
 
 
 0-02 
 
 
 
 
 
 Bismuth 
 
 
 
 
 
 0-85 
 
 
 
 Vanadium . 
 
 
 
 
 
 
 
 0-12 
 
 Molybdenum .... 
 
 9-97 
 
 
 
 
 
 
 
 Arsenic 
 
 1-40 
 
 
 
 
 
 
 
 Sulphur 
 
 2-06 
 
 1-20 
 
 1-24 
 
 trace 
 
 Phosphorus .... 
 
 1-25 
 0-35 
 
 
 
 9-03 
 
 0-83 
 
 Carbon 
 
 0-38 
 
 
 
 
 073 
 
 Alumina . . .' . . 
 
 
 
 0'72 
 
 
 
 
 
 Silica ; j ~. -" ' . " ; : : . 
 
 __ 
 
 1-58 
 
 
 
 0-43 
 
 Slag 
 
 
 
 
 
 
 
 3-33 
 
 
 
 
 
 
 These products are sometimes smelted with sulphur or iron pyrites, so as to con- 
 vert them into regulus, from which the copper and other metals can be extracted by 
 the methods adopted with copper regulus. They are also used in smelting lead ores 
 for the decomposition of lead sulphide. 
 
 In smelting copper ores in shaft furnaces, other deposits are also formed, consisting 
 of zinc oxide or zinc sulphide, as well as lead sulphide and cuprous sulphide. 
 
 The regulus obtained by smelting copper ores in shaft furnaces is roasted either 
 in heaps or stalls, in the same manner as the ore, or, when silver is to be extracted, 
 the roasting of the regulus is conducted in reveberatory furnaces. Regulus contain- 
 ing little antimony or arsenic and a sufficient amount of copper is at once roasted to 
 such an extent that most of the sulphur is oxidised and separated as sulphurous 
 
412 
 
 COPPER. 
 
 oxide, and the roasted material, consisting chiefly of oxides, is then ready for the 
 reduction of the copper. When the amount of copper in the regulus is small, and it 
 is associated with considerable proportions of antimony, arsenic, etc., the roasting is 
 only carried so far that on smelting the roasted mass the copper is again obtained in 
 the state of a regulus containing a larger amount of copper. According to the amount 
 of arsenic or antimony present, this operation of concentrating the copper by alternate 
 roasting and smelting, and getting rid at the same time of those impurities, may have 
 to be performed several times in succession. In every case it is desirable to leave a 
 small amount of sulphur in the roasted material that is to be smelted for the reduction 
 of copper, in order to prevent the formation of cuprous silicate that would be retained 
 by the slag. 
 
 When the regulus obtained from the smelting contains as much as 60 per cent, 
 and upwards of copper, it will, after roasting, be fit for smelting, but otherwise the 
 concentration treatments must be repeated until this proportion of copper has been 
 reached and the impurities are sufficiently separated. The chief point to be observed 
 is that the roasting should not be carried so far in any case as to admit of copper 
 being reduced to the metallic state in smelting the roasted material. The slag 
 formed in the concentration of regulus consists chiefly of ferrous silicate, together 
 with small quantities of other silicates, and it should not contain more than from one 
 to three per cent, of copper. 
 
 The shaft furnaces employed in Sweden for smelting copper ores are of the kind 
 represented by the vertical sections (figs. 299 and 300) taken at right angles to each 
 
 FIG. 299. 
 
 FIG. 300. 
 
 FIG. 301. 
 
 other. The internal wall (h Ji) is constructed of refrac- 
 , tory material, and it is surrounded by a rough wall (f) 
 with a space (g) between them. The hearth (a a) is 
 formed of a mixture of clay and coal dust, beaten down 
 so as to form a cavity extending beyond the breast (>) 
 of the furnace. The horizontal section (fig. 301) at 
 the level of the tuyeres (cc) shows the shape of the 
 hearth (a a) and the position of the tapping hole (c) by 
 b which the melted contents of the hearth are run off at 
 intervals. In some of the Swedish furnaces the hearth 
 is made of much greater capacity than that shown in 
 the figures, in order to allow of the accumulation of a 
 large quantity of the melted products and give time for 
 
 the separation of the regulus from the slag, 
 
 The copper ore smelted at Fahlun in Sweden consists of copper pyrites accom- 
 panied by iron pyrites and quartz, together with some galena, blende, arsenical pyrites, 
 
COPPER SMELTING. 
 
 413 
 
 and calc spar. The amount of copper in this ore varies from 0-5 to 30 per cent., but 
 averages from 2 to 3 per cent. 
 
 After the ore has been roasted it is smelted in a shaft furnace about 18 feet high 
 with an admixture of black copper slag, produced in another stage of the opera- 
 tion, and containing a large amount of ferrous silicate. The proportions of the charge 
 are so adjusted that the slag produced may approximate to the formula FeOSi0 2 and 
 contain sufficient silica to prevent the walls of the furnace from being corroded, while 
 at the same time it is liquid enough to facilitate the separation of the regulus. The 
 following table gives analyses of this slag : 
 
 
 Bredberg 
 
 Starbok 
 
 Olsen 
 
 
 4472 
 
 4.5-35 
 
 45.53 
 
 
 4*39 
 
 Q./jO 
 
 4.00 
 
 Ferrous oxide . . . . 
 
 44-88 
 3-50 
 
 43-58 
 
 45-61 
 
 
 1*20 
 
 7-23 
 
 3-50 
 
 
 
 
 
 
 98-69 
 
 9974 
 
 98-86 
 
 The regulus obtained in smelting the ore contains about 10 per cent, of copper and 
 has the composition shown in the following table : 
 
 Sulphur 
 Copper 
 
 Bergsten 
 
 Winkler 
 
 Johnson 
 
 26-35 
 8-32 
 62-26 
 1-23 
 
 0-07 
 0-44 
 
 26-07 
 8-85 
 60-29 
 1-09 
 traces 
 1-78 
 0-61 
 
 26-70 
 9-81 
 58-14 
 1-44 
 0-58 
 1-95 
 
 24-62 
 12-00 
 55-86 
 2-92 
 3-96 
 0-20 
 
 
 Lead 
 
 Silica 
 
 Magnesia . 
 
 98-67 
 
 98-69 
 
 98-62 
 
 99-55 
 
 The smelting of copper ore is conducted in a similar manner at Nafvequarn, 
 Garpenberg, Atvidaberg, Ko'raas, and other places in Sweden and Norway ; the ore 
 smelted contains a larger amount of copper than that smelted at Fahlun, but as the 
 proportion of blende in the Atvidaberg ore is also much larger, amounting on the 
 average to one third, very careful roasting is necessary in order to convert the zinc 
 sulphide first formed into oxide. In the smelting operation a richer regulus is 
 obtained with from 25 to 30 per cent, of copper. 
 
 The regulus is thoroughly roasted in stalls several times in succession, and then 
 smelted, together with quartz or silicious ore, in a shaft furnace of much smaller di- 
 mensions than that in which the ore is smelted. The products of this operation are 
 black copper, together with one-fourth as much, or less, of a regulus which is called 
 thin regulus or copper regulus, and a slag consisting of ferrous silicate contain- 
 ing, according to Winkler : 
 
 Silica . . . ,* . . . . * . 32-79 
 
 Ferrous oxide . * , 66-12 
 
 Magnesia. . .-..'; 1'58 
 
 Copper . ...... . . . . traces 
 
 100-49 
 
 This slag is used as a flux in smelting the copper ore. 
 
 The thin regulus, produced together with black copper, contains, according to 
 Johnsen : 
 
 Sulphur . . .'..'. 24-50 
 
 Copper 5778 
 
 Iron . . . J 7'23 
 
 Zinc , , ' - - 0-7* 
 
 100-25 
 It is roasted several times and then smelted, together with the roasted ore regulus. 
 
414 COPPER. 
 
 The black copper contains from 70 to 90 per cent, of copper. A sample from tho 
 Atvidaberg works contained 
 
 Copper 94-39 
 
 Iron r 2-04 
 
 Zinc 1-55 
 
 Cobalt and nickel 0*63 
 
 Tin . . . . . . 0-07 
 
 Lead . 0'19 
 
 Silver O'll 
 
 Sulphur 0'80 
 
 Arsenic . traces 
 
 09-78 
 
 It is then refined in order to effect the separation of the impurities and the con- 
 version of the metal into a marketable condition. (See p. 418.) 
 
 In several parts of Hungary copper ores containing from 0'75 to 13 per cent, of 
 copper are smelted in a manner very similar to that practised in Sweden and Norway. 
 The regulus obtained by smelting the poor ores is roasted and smelted for the purpose 
 of concentrating the copper. The richer ores are smelted at Schmolnitz without being 
 roasted, and a regulus is obtained containing about 20 per cent, of copper. 
 
 Ores containing lead and copper, together with silver and gold, such as those in 
 the Naygbanya district in Hungary, are smelted together with lead in order to extract 
 the silver and gold, and as a final product of the operation copper regulus is obtained, 
 which is then either roasted and worked for copper in the usual manner, or smelted 
 with materials containing lead, for the purpose of effecting a further separation of 
 silver, and obtaining a regulus containing a large amount of copper as in the smelting of 
 lead ores (see p. 367). This regulus or the copper regulus obtained as a by-product in 
 smelting cuprous lead ores is roasted and granulated and then treated for extracting 
 the silver, and the desilverised material is smelted for black copper. 
 
 At Agordo in the Venetian Alps ores containing on the average 2 per cent, of 
 copper are worked. The poorer ores are submitted to the operation of core roasting, 
 and the ferruginous crust of the roasted lumps is lixiviated to extract any remaining 
 copper. The cores are smelted for regulus in the usual manner. 
 
 In the Upper Hartz, and in Silesia, Nassau, and Saxony, copper ores are generally 
 smelted in shaft furnaces, closed at the breast, and furnished with two small apertures 
 at the bottom of the shaft, through which the melted products run out continuously 
 into receptacles outside the furnace. 
 
 The ores of the Upper Hartz contain a large amount of antimony, and consequently 
 several alternate roastings and smeltings of the regulus are requisite. The Silesian 
 ores frequently contain a considerable proportion of silver, in which case the regulus 
 is submitted to special treatment for the extraction of this metal. 
 
 The cuprous slate smelted at Reich elsdorf and Friedrischshiitte in the Grand Duchy 
 of Hesse contains besides sulphuretted and oxygenated compounds of copper, blende, 
 galena, compounds of cobalt, nickel, and other minerals. The amount of copper in 
 the ore is from 3 to 4 per cent, on the average, and it is smelted in shaft furnaces 
 worked with hot blast, the gaseous product being collected at the throat of the furnace 
 and used as fuel for heating the air. 
 
 The ore smelted at Mansfeld and the other works in that district is a bituminous 
 shale containing copper pyrites and other sulphuretted minerals, disseminated 
 throughout the mass. The amount of copper varies, and is barely more than 6 per 
 cent., and some of the shale does not contain more than 1*5 per cent., but in some 
 cases there is a considerable amount of silver. The composition of this shale is as 
 follows, according to Berthier : 
 
 Silica 
 
 Alumina 
 
 Ferric oxide , 
 
 Calcium carbonate 
 
 Magnesium carbonate 
 
 Copper pyrites , 
 
 Potash 
 
 Water and bitumen . 
 
 The shale is first roasted in heaps with layers of brushwood beneath them, and 
 the bitumen it contains servos in part as fuel. r lphur is driven off as sulphurous 
 
COPPER SMELTING. 
 
 415 
 
 oxide, and some of the iron in the pyrites is oxidised. The burnt shale has a greyish 
 white colour, and has the following composition, according to Berthier : 
 
 50-6 
 23-4- 
 
 Silica 
 
 Alumina > 
 Magnesia i 
 
 Lime 7-3 
 
 Cupric oxide . . . . . . . . 2'8 
 
 Ferric oxide .9-0 
 
 Sulphur 4-0 
 
 Loss by ignition .... Q-8 
 
 43-8 
 
 98-4 97-1 
 
 The roasted ore is mixed with a suitable proportion of fluor spar and smelted to- 
 
 FIG. 302. 
 
 gether with slags from previous operations in 
 shaft furnaces of the kind represented by figs. 
 302, 303 and 304. These furnaces are from 16 to 
 21 feet high and are furnished with two tuyeres 
 (t t), and at the bottom of the hearth are two holes 
 (00) through which the melted products are alter- 
 nately run off into the fore hearths (c c) from which 
 the regulus is taken in cakes as it cools at the 
 surface. Eecently, hot blast and much larger 
 furnaces have been used in smelting this slate, 
 and the regulus is run into water for the purpose 
 of obtaining it in a granulated condition. 
 
 A largo quantity of slag is produced, which 
 has the following composition : 
 
 FIG. 303. 
 
 FIG. 304. 
 
 
 Berthier 
 
 Hoffmann 
 
 Ebbing- 
 
 1 KlUS 
 
 Heine 
 
 Silica . . 
 
 49-8 
 
 48-22 
 
 50-00 
 
 54-13 
 
 53-83 
 
 57-43 
 
 Alumina .... 
 
 12-2 
 
 16-35 
 
 15-67 
 
 10-53 
 
 4-43 
 
 7-83 
 
 Lime 
 
 19-2 
 
 19-29 
 
 20-29 
 
 19-41 
 
 33-10 
 
 23-40 
 
 Magnesia .... 
 
 2-4 
 
 3-23 
 
 4-37 
 
 1-79 
 
 1-67 
 
 0-87 
 
 Ferrous oxide 
 
 13-2 
 
 10-75 
 
 8-73 
 
 10-83 
 
 4-37 
 
 7'47 
 
 Cuprous oxide . . 
 
 
 
 075 
 
 0-67 
 
 2-03 
 
 0-25 
 
 0-30 
 
 Zinc oxide .... 
 
 
 
 1-26 
 
 MI 
 
 
 
 
 
 
 
 Fluorine . . . . 
 
 1-1 
 
 
 
 
 
 
 
 2-09 
 
 1-97 
 
 
 97-9 
 
 99-85 
 
 100-84 
 
 98-72 
 
 99-74 
 
 99-27 
 
416 
 
 COPPER. 
 
 The regulus consisting of the metallic contents of the ore in the state of sulphides 
 varies in the amount of copper it contains, as shown in the following table : 
 
 
 Bamm 
 
 elsberg 
 
 
 Heine 
 
 
 Soutzos 
 
 Sulphur 
 
 2676 
 
 28-70 
 
 26-44 
 
 24-58 
 
 27-80 
 
 32-00 
 
 Copper 
 
 47'27 
 
 43-62 
 
 52-44 
 
 48-25 
 
 31-70 
 
 23-58 
 
 Iron 
 
 19-69 
 
 23-35 
 
 20-49 
 
 17-35 
 
 28-75 
 
 38-42 
 
 Zinc . } 
 Nickel . 
 Cobalt . 
 
 4-09 
 
 I 3-45 
 
 __ 
 
 2-90 
 | 0-80 
 
 4-35 
 1-25 
 
 | 5-67 
 
 Lead . 
 
 __ 
 
 
 
 0-41 
 
 1-05 
 
 0-65 
 
 __ 
 
 Silver 
 
 
 
 0-13 
 
 0-30 
 
 0-16 
 
 
 Silica 
 
 
 
 
 
 
 1-55 
 
 1-65 
 
 
 
 
 97-81 
 
 100- 
 
 99-91 
 
 96-78 
 
 96-31 
 
 99-67 
 
 The regulus which does not contain more than 20 or 30 per cent, of copper 
 was formerly roasted and smelted again in shaft furnaces to obtain a regulue 
 richer in copper and the black copper afterwards obtained by smelting the concentrated 
 regulus was submitted to a process of liquation for extracting the silver it contained. 
 (See p. 431.) This plan has been superseded and the concentration of the poor 
 regulus is now performed in a reverberatory furnace represented by figs. 305, 306, 
 and 307. 
 
 FIG. 305. 
 
 FIG. 306. 
 
EXTRACTION" OF COPPER. 
 
 417 
 
 The regulusis roasted in muffle furnaces 
 and melted on the hearth (d) of thereverbe- 
 ratory furnace mixed with sand or silicious 
 slag, by means of which the ferrous oxide is 
 dissolved and the amount of copper in the 
 regulus increased to about 70 per cent. The 
 slag is then drawn off and the concentrated 
 regulus granulated by running it into water. 
 
 Before treating the regulus further for 
 the production of black copper, it is ground 
 to a fine powder and roasted so as to con- 
 vert the copper into the state of oxide and 
 leave the silver in the state of sulphate. 
 In this condition it is desilverised by 
 Ziervogel's method (see p. 444). FIG. 307. 
 
 The residue from the desilvering of the roasted regulus is then smelted in a shaft 
 furnace to obtain black copper. For this purpose it is mixed with a small quantity 
 of rich regulus to prevent oxide of copper from being taken up by the slag, made 
 into balls with wet clay, dried, and smelted with coke. 
 
 In this way the greater part of the copper is obtained in the state of black copper, 
 together with a small quantity of rich regulus, and a slag containing a small quantity 
 of copper, which is used as a flux in smelting ore. 
 
 EXTEACTION OF COFFEE IN THE WET WAY. The precipitation of copper from 
 mine water by metallic iron has long been carried out at the copper mines in Wicklow 
 and in the Isle of Anglesea ; on the continent mine water is worked in the same 
 manner, at the Eio Tinto mines in Spain, and at Schmollnitz in Hungary, Eammels- 
 berg in the Hartz, etc. 
 
 The treatment of poor cupreous materials with the object of converting the copper 
 into a salt that can be dissolved out by water, is also extensively practised, not only in 
 places where such materials occur naturally, but also in connection with the use of 
 pyrites as a source of sulphur for sulphuric acid factories. 
 
 The material operated upon at some places where this method is carried out is a 
 sandstone impregnated with cupric carbonate, and containing on the average about 2 
 per cent, of copper. The crushed sandstone is mixed with dilute hydrochloric acid in 
 large vats fitted with agitators ; the solution of cupric chloride thus obtained is 
 drawn off and the copper precipitated from it by metallic iron. 
 
 At Alderly Edge, in Cheshire, a similar plan has been adopted for extracting 
 copper from sandstone. 
 
 Sulphuric acid is sometimes used in the same way, for the purpose of extracting 
 copper from poor ores when it exists in an oxidised state : but in either case it is es- 
 sential to tbe success of this method that the ore to be operated upon should not con- 
 tain any large proportion of carbonates which would be decomposed, by the acid used 
 and thus consume a large amount of acid. It is also essential that the ore should not 
 contain other substances that would be dissolved by the acid used. 
 
 In the case of poor copper ores which contain copper in combination with sulphur, 
 the copper is sometimes converted into sulphate by oxidation, by roasting the ores in 
 heaps and then dissolving out the cupric sulphate by lixiviation with water. This 
 plan has been worked in a rude way at the mines of Eio Tinto and Tharsis in Spain, 
 and other places. In a more perfect manner this plan was applied by Bankart for 
 the treatment of ores, containing a considerable amount of copper, which were roasted 
 in the state of fine powder in reverberatory furnaces.^ The chief difficulty attending 
 this method of treatment consists in regulating it so that greater part of the 
 ferrous sulphate formed may be decomposed with formation of ferric oxide, and at the 
 same time preventing the decomposition of some of the cupric sulphate formed, and 
 the production of cupric oxide, which is insoluble in water. 
 
 The plan that has been found most advantageous for converting the copper into 
 the state of a soluble salt is that of roasting the ore together with sodium chloride. 
 This method of treating copper ores was applied by Longmaid in 1842, and has since 
 been practised with various modifications by others. It is now chiefly adopted for 
 the extraction of copper from the residue left in burning pyrites for the manufacture 
 of sulphuric acid. This material is mixed with from 12 to 15 per cent, of common 
 salt, and if the residual sulphur in the burnt pyrites does not amount to rather more 
 than the quantity of copper in it, sufficient iron pyrites is added to make up the de- 
 ficiency. The mixture is then roasted in a reverberatory furnace with a long bed. 
 The sulphur of the pyrites is thus oxidised and the sulphuric oxide produced by the 
 decomposition of the ferrous sulphate converts the sodium chloride into sulphate and 
 
 E Ei 
 
418 
 
 COPPER. 
 
 hydrochloric acid, which combines with the copper, forming cupric chloride. The for- 
 mation of cuprous chloride must be avoided by carefully regulating the temperature 
 in the roasting, since the sparing solubility of this substance in water would cause 
 considerable loss of copper. 
 
 The roasted mass is then lixiviated with water and a little dilute hydrochloric 
 acid in a series of tanks, and when the solution contains a sufficient amount of copper, 
 it is run into tanks containing a quantity of scrap iron, where the precipitation of the 
 copper is facilitated by heating the liquid. The finely divided copper thus obtained 
 is then washed and melted into ingots. 
 
 EEFINING AND TOUGHENING. The metallic copper obtained by precipitation by 
 iron is always very pure and possesses great malleability and ductility ; but that 
 obtained by smelting copper ores either in reverberatory or in shaft furnaces is never 
 in a condition to be used, but contains a variety of impurities, the nature of which 
 depends partly on the kind of ores from which the metal has been produced ; among 
 these impurities a small amount of sulphur and some cuprous oxide are always present. 
 The following table gives the composition of some samples of blister copper and black 
 copper : 
 
 
 Swansea 
 
 Mansfeld 
 
 Reichelsdorf 
 
 Freiberg 
 
 Altenau 
 
 Le Play 
 
 Napier 
 
 Ebbinghaus 
 
 Willie 
 
 Lampadius 
 
 Hahn 
 
 Copper 
 
 98-4 
 
 97'5 
 
 92-83 
 
 71-0 
 
 69-5 
 
 _ 
 
 Iron . 
 
 07 
 
 0-7 
 
 1-38 
 
 11-0 
 
 6-7 
 
 0-04 
 
 Arsenic . ) 
 Tin . i 
 
 0-4 v 
 
 
 
 
 
 
 
 
 0-45 
 
 Antimony 
 
 | 
 
 ro 
 
 
 
 
 
 
 
 
 Lead 
 
 
 
 
 
 2-79 
 
 
 
 6-0 
 
 6-84 
 
 Bismuth . 
 
 
 
 
 
 
 
 
 
 1-0 
 
 
 
 Silver 
 
 
 
 
 
 0-26 
 
 
 
 0-5 
 
 
 
 Zinc . 
 
 
 
 
 
 
 2-0 
 
 
 
 Nickel . / 
 Cobalt . f 
 
 0-3 
 
 
 1-05 
 
 10-0 
 
 8-3 
 1-3 
 
 0-99 
 004 
 
 Sulphur . 
 
 0-2 
 
 0-2 
 
 1-07 
 
 7-o 
 
 trace 
 
 
 
 Oxygen . 
 
 
 
 0-6 
 
 
 
 
 
 
 
 
 
 100- 
 
 100- 
 
 
 
 
 
 
 
 
 
 The refining of blister copper is carried out in this country in reverberatory 
 furnaces similar in construction to the smelting furnaces, but without any opening in 
 the roof. The hearth slopes from all sides, and the lowest part is near the door at 
 one end. About six or eight tons of copper are placed upon the hearth, and when 
 melted the metal is exposed for several hours to the oxidising action of the atmospheric 
 air entering the furnace. The superficial oxidation of the cakes of metal while melt- 
 ing furnishes material for the formation of slag by combination of the oxide with the 
 sand adhering to the copper and with the silicious material of the hearth. Arsenic, tin, 
 and other metals which are oxidised more readily than copper are separated by the 
 action of the slag upon them and the remaining sulphur in the metal is separated as 
 sulphurous oxide. To facilitate this action the contents of the furnace are several 
 times stirred, and when the purification of the metal is sufficiently advanced the slag 
 is skimmed off the surface. 
 
 The slag formed in the refining of blister copper contains a large amount of 
 copper as well as those metals which the operation is intended to remove, as shown 
 by the following analysis : 
 
 Silica .... 
 
 Alumina 
 
 Cuprous oxide 
 
 Ferrous oxide . 
 
 Nickel and manganous oxide 
 
 Stannous oxide 
 
 Lime . ' . 
 
 Magnesia . . . 
 
 Metallic copper 
 
 47-4 
 2-0 
 
 36-2 
 3-1 
 0-4 
 0-2 
 1-0 
 0-2 
 9-0 
 
 99-5 
 
REFINING COPPER. 
 
 419 
 
 This slag is called re finery slag, and it is worked up iu the melting of calcined 
 coarse metal as already mentioned. 
 
 The copper is then in the state of dry copper and contains cuprous oxide dis- 
 solved in it, -which renders it deficient in toughness and malleability. The separation 
 of this oxide is effected by throwing upon the surface a quantity of coal and after 
 some time stirring the metal with a pole of green wood, which becomes charred by the 
 hot metal and gives off carburetted gases which reduce the cuprous oxide and in 
 escaping cause the metal to boil up. A sample of the metal is then taken out and 
 tested to ascertain whether it is of good quality, or, as it is termed, tough pitch, 
 and when this is the case the surface is skimmed and the metal is ladled out into 
 moulds. 
 
 The reverberatory furnace commonly used in Germany for refining copper is repre- 
 sented by figs. 308, 309, and 310. The hearth is made of a mixture of clay and charcoal, 
 
 FIG. 309. 
 
 FIG. 308. 
 
 and at one side there are two basins (&) also 
 lined in the same way, into which the refined 
 metal can be run from the hearth. Fig. 310 
 is an elevation on the line I K of the horizontal 
 section, showing the fireplace (y\ the tuyere 
 holes (nn), the door (#) by which the slag 
 floating on the melted metal is raked out, and 
 the tapping holes (v v} which are opened when 
 the refined metal is run out. Fig. 309 is a ver- 
 tical section on the line i. M through one of the 
 FIG. 310. tuyere holes, and showing the charging door (q). 
 
 In some parts of the continent the refining of black copper is carried out in a 
 hearth of the kind represented by figs. 311 and 312. It consists of an hemispherical- 
 shaped cavity (c), formed by compressing a mixture of clay and sand into the space 
 left for it in the brickwork of the hearth, whieh is constructed so as to leave on one 
 
 
 FIG. 311. 
 
 Fro. 312. 
 
 side an opening (A), which can be closed by the iron door (s). The small channel (i t) 
 serves to let the slag run off on to the iron slab (B) with which part of the brickwork 
 is covered. The blast tuyere (T) passes through an aperture (c) in the back wall of 
 the hearth. 
 
 In working this hearth the copper is placed on the top of some ignited charcoal 
 and melted down with the aid of the blast. In this way iron, lead, and other foreign 
 
 EK2 
 
420 
 
 COPPER. 
 
 metals are oxidised as the copper melts, and the oxides combine with the ashes of the 
 charcoal, and the silicious material of the hearth, forming a fusible black slag. Some 
 copper is also oxidised, and the cuprous oxide dissolving in the melted copper, is 
 again reduced by the cuprous sulphide and by the foreign metals it contains. When 
 these have been almost entirely separated, some of the cuprous oxide remains dis- 
 solved in the melted copper, and some of it is dissolved by the slag, communicating 
 to it a reddish colour. 
 
 The progress of the operation is tested from time to time by plunging an iron 
 rod into the melted copper so as to withdraw a portion ; this is cooled in water and 
 the copper examined as to its flexibility. When the requisite degree of purity has 
 been attained the blast is stopped, the slag and fuel drawn off the surface of the melted 
 metal, and some water thrown upon it sufficient to solidify the upper portion, which is 
 then removed in the form of a thin disc called a rosette. This is continued till nearly 
 all the copper is removed from the hearth. 
 
 When copper is refined in hearths it is obtained in the dry state, which is caused 
 by the presence of cuprous oxide, and the toughening of the rosette copper is carried 
 out in a separate operation by melting the metal under charcoal in a hearth like that 
 already described. 
 
 At the copper works of Hettestadt a gas reverberatory furnace is used for refining 
 copper, the construction of which is represented by figs. 313 and 314. The combus- 
 tible gas is generated in the chamber () which is supplied with fuel through the 
 shaft (c) closed by a lid (d) at the top. The gas passes into the working chamber 
 over the fire bridge (/) in which there is an opening (g) for cooling it. Air for com- 
 
 Fio. 313. 
 
 bustion is supplied through the flues (e e), and if requisite also through the openings 
 (h h) ; the air for the oxidation of the copper is supplied through the openings (i i). 
 The door (I) at the side of the working chamber serves to introduce the charge, and 
 the working door (m) is at the end where the flue (n) communicates with a high chimney 
 (o) adjoining the furnace. The bed () of the working chamber is formed of slag and 
 crushed quartz, and the sides (p) are lined with a refractory mixture of quartz and 
 loam in order to protect the outer wall (q q) of the furnace. 
 
 This furnace is capable of working five tons of copper at once. 
 
 The slag produced in refining black copper consists partly of silicates and partly 
 of metallic oxides, as shown by the following analyses : 
 
KEFLNING COPPER. 
 
 421 
 
 FIG. 314. 
 
 
 Karsten 
 
 Plattner 
 
 Gcnth 
 
 Silica. . . 
 
 22'9 
 
 4*27 
 
 7-88 
 
 32'23 
 
 Lead oxide 
 
 62-1 
 
 37'83 
 
 f OO 
 
 
 Cuprous oxide . 
 
 10-4 
 
 13-13 
 
 1-26 
 
 4-79 
 
 Ferrous oxide . ' - -, ',. 
 
 1-1 
 
 2-30 
 
 82-49 
 
 2072 
 
 Manganous oxide 
 
 
 
 0-17 
 
 
 
 Nickel oxide . . ; 
 
 
 
 31-53 
 
 3-59 
 
 34-16 
 
 Arsenic oxide . . -..-^* 
 
 
 
 5-43 
 
 
 
 Antimony oxide . 
 
 
 
 4-37 
 
 
 
 
 
 Alumina . 
 
 3-4 
 
 0-93 
 
 0-81 
 
 5-60 
 
 Sulphuric acid . ' ... 
 
 
 
 20 
 
 
 
 
 
 Molybdous oxide 
 
 
 
 
 
 2-36 
 
 0-87 
 
 Lime, potash and soda 
 
 
 
 
 
 2-26 
 
 1-66 
 
 
 99-9 
 
 100-16 
 
 100-65 
 
 100-03 
 
 Uses. Copper is one of those metals which are of very general applicability in 
 the arts ; for the construction of pans, stills, tubes, etc. ; for sheathing ships, and for 
 culinary vessels ; in the state of alloys with other metals it is also applied to a great 
 number of purposes. Some of the saline compounds of copper are used as pigments ; 
 for the preservation of wood, and in medicine. 
 
 Compounds. Copper forms two series of compounds, and it is bivalent in the 
 compounds of one series, but apparently univalent in the other?. These compounds 
 are termed respectively cupric and cuprous. There are two oxides, cupric oxide 
 CuO, which is a strong base forming stable saline compounds with acid oxides, and 
 cuprous oxide Cu 2 0, which is a feeble base, forming only with a few acid oxides saline 
 compounds which are readily converted by oxidation into cupric salts. The chlorides 
 CuCl 2 and Cu 2 Cl 2 , as well as the sulphides CuS and Cu 2 S, correspond to the oxides. 
 
 Cupric salts have generally a green or blue colour, but some of them are colourless 
 in the anhydrous state ; many of them are soluble in water ; they have a disagreeable 
 metallic taste and are very poisonous. 
 
 The nitrate is a very deliquescent salt, crystallising in blue rhomboidal prisms, 
 the composition of which is represented by the formula Cu2N0 3 .6H 2 ; it is soluble 
 
422 
 
 COPPER. 
 
 in alcohol, and is decomposed when moderately heated, yielding a basic salt of a green 
 colour, which gives off the whole of its acid at a higher temperature, leaving pure 
 cupric oxide as a black powder. The carbonates occurring naturally as malachite 
 and azurite, or prepared artificially by mixing solutions of fixed alkaline carbonate 
 with the solution of a cupric salt, are all basic salts ; the precipitate obtained from 
 a hot solution has a green colour, and is known as mineral green or green 
 verditer. The arsenite CuHAs0 3 is a brilliant green substance, largely used as 
 a pigment under the name of Scheele's green. 
 
 Cupric chloride forms green hydrated crystals, the composition of which is repre- 
 sented by the formula CuCl 2 .2H 2 ; this salt is freely soluble in water and alcohol ; 
 when heated it loses water and becomes brown ; at a higher temperature the salt 
 gives off half its chlorine and is converted into cuprous chloride. 
 
 Cupric acetate Cu2C 2 H 3 2 + H 2 forms dark green crystals soluble in 14 parts of 
 cold water and 5 parts of boiling water ; the salt is also soluble in alcohol ; it is used 
 asapigment under the name of distilled verdigris. A basic acetate of a bluish- 
 green colour obtained by exposing plates of copper in contact with the husks oi 
 grapes to the action of the atmosphere is used as a pigment under the name oi 
 verdigris. 
 
 Cuprous salts are generally insoluble in water, and they are very unstable, 
 absorbing oxygen readily, and passing into cupric salts. 
 
 Copper unites readily with other metals, and several of the alloys of this metal 
 are important in their practical applications. 
 
 Zinc and copper can be mixed together in the melted state in almost any propor- 
 tions, forming a number of alloys known by the names of br a s s, Muntz's metal, etc., 
 the composition and characters of which are given in the following table : 
 
 
 Copper 
 
 Zinc 
 
 Specific 
 gravity 
 
 Colour 
 
 
 9072 
 
 9-28 
 
 8-605 
 
 reddish yellow 
 
 
 89-80 
 
 10-20 
 
 8-607 
 
 
 Similor 
 
 88-60 
 
 11-40 
 
 8-633 
 
 > 
 
 
 81-30 
 
 12-70 
 
 8-587 
 
 9, 
 
 
 85-40 
 
 14-60 
 
 8-591 
 
 yellowish red 
 
 Bath metal . 
 
 83-02 
 
 16-98 
 
 8-451 
 
 u 
 
 Dutch brass 
 
 79-65 
 
 20-35 
 
 8-448 
 
 
 Kolled sheet brass 
 
 74-58 
 
 2542 
 
 8-397 
 
 pale yellow 
 
 Ordinary brass . 
 
 71-43 
 
 28-57 
 
 
 
 }> 
 
 British brass 
 
 66-18 
 
 33-82 
 
 8-299 
 
 full yellow 
 
 Muntz's sheathing 
 
 60-00 
 
 40-00 
 
 8-200 
 
 
 German brass 
 
 49-47 
 
 50-53 
 
 8-230 
 
 ' 
 
 for watchmakers 
 
 32-85 
 31-52 
 
 67-15 
 68-48 
 
 8-283 
 7721 
 
 deep yellow 
 silver white 
 
 
 30-30 
 
 69-70 
 
 7-836 
 
 it 
 
 
 29-17 
 28-12 
 
 70-83 
 71-88 
 
 8-019 
 7-603 
 
 silver grey 
 
 
 27-10 
 
 79-90 
 
 8-058 
 
 
 
 26-24 
 
 73-76 
 
 7-882 
 
 
 
 25-39 
 
 74-61 
 
 7-443 
 
 
 
 24-50 
 
 75-50 
 
 7-449 
 
 
 White button metal . 
 
 19-65 
 
 80-36 
 
 7-371 
 
 
 
 16-36 
 
 83-64 
 
 6-605 
 
 
 The characters which are of most importance in brass are the colour, hardness, 
 and capability of forming sharp castings. The malleability of brass depends partly on 
 the temperature at which it is worked, and it is inversely proportionate to the amount 
 of zinc in the alloy. 
 
 Muntz's metal is used for coating ships, and is said to keep cleaner than copper, 
 besides being less costly. 
 
 Copper, alloyed with a small proportion of zinc, has a paler red colour than pure 
 copper ; with a larger proportion of zinc the alloy is yellow. The alloy consisting of 
 equal parts of the metals has the brightest colour. With a still larger proportion of 
 zinc the alloy is white. The ductility of the alloys of copper and zinc is in many 
 cases greater than that of copper, those containing 15'5 and 28'5 per cent, of zinc 
 being the most ductile. Alloys of copper and zinc become hard and brittle when 
 hammered, and consequently require to be annealed frequently in working them. 
 
COPPER OXIDES. 423 
 
 Lead mixes with melted copper, but the mass readily separates into two layers, 
 the lower one consisting of lead containing some copper, the upper one of copper con- 
 taining some lead. Even when the melted mass is rapidly cooled, the greater part of 
 the lead may be separated by heating the alloy to the melting point of lead. The mode 
 of separating lead from copper is sometimes practised under the name of liquation 
 (see p. 431). 
 
 The ductility of copper is reduced by the presence of a small amount of lead. 
 Copper containing O'l per cent, of lead may be used for ordinary purposes, but can- 
 not be rolled into thin sheets or drawn into thin wire. A small proportion of lead 
 renders brass more capable of being worked in the lathe and in some other respects ; 
 but when the brass is to be drawn into wire, the presence of lead is injurious. 
 
 The alloys of copper with tin, and sometimes other metals, are known as bronze, 
 gun metal, bell metal, speculum metal, etc. The alloy of copper and nickel 
 is known as German silver; these and other alloys of copper will be described 
 under the heads of the several metals which they contain. 
 
 CUPROUS OXIDE. 
 
 FORMULA Cu 2 0. MOLECULAR WEIGHT 142-8. 
 
 History. The existence of this substance as a distinct compound of copper and 
 oxygen was first ascertained in 1801 by Proust, who described its characters and the 
 mode of preparing it. In the following year Chenevix showed that red copper ore 
 consisted of this oxide. 
 
 Occurrence. Cuprous oxide occurs naturally asredcopperore and as chal- 
 cotrichite or copper bloom, and in some cases it is sufficiently abundant to be 
 worked as an ore. 
 
 Characters. In the crystallised state, cuprous oxide forms octahedrons or 
 cubes, slightly translucent, of a fine red colour, sometimes crimson, and considerable 
 lustre. The specific gravity is from 5'85 to 6'15. The artificially prepared oxide is 
 generally pulverulent and the more finely it is divided the brighter is the colour. 
 Cuprous oxide is readily reduced when heated with carbon or in an atmosphere of 
 hydrogen, carbonic oxide, or other reducing gas. 
 
 Cuprous oxide is dissolved by hydrochloric acid, forming cuprous chloride, and it 
 is converted into cupric nitrate by nitric acid, but is decomposed by most other acids, 
 with separation of metallic copper and formation of the corresponding cupric salt. 
 
 Cuprous oxide in the hydrated state, obtained by adding caustic soda or potash to 
 a solution of cuprous chloride, or by boiling freshly precipitated cupric hydrate with 
 solution of milk sugar, is an orange yellow pulverulent substance, which is readily 
 converted into cupric oxide by exposure to the air. It is rendered anhydrous by a 
 temperature of 360, but does not assume the red colour till it is heated to a much 
 higher temperature. 
 
 CUPRIC OXIDE. 
 
 FORMULA CuO. MOLECULAR WEIGHT 79-4. 
 
 History. The oxidised copper mentioned by Dioscorides and Pliny under the 
 names of avBos xaAwoO andflos aeris were probably mixtures of cupric oxide with some 
 cuprous oxide, as the substances are described as being reddish when powdered, and 
 beyond the opinion that copper might undergo different degrees of calcination, no 
 distinction appears to have been made between the two oxides until the year 1800. 
 
 Occurrence. Cupric oxide occurs abundantly near Lake Superior, and in 
 smaller quantities it is frequently associated with copper ores. 
 
 Characters. The native cupric oxide is sometimes crystalline, and of a dark 
 steel grey colour, the specific gravity varying from 5'952 to 6*25. More frequently it 
 is in compact masses or, like the artificially prepared oxide, a brownish black powder. 
 Crystals consisting of cupric oxide are sometimes found in the furnaces of copper works. 
 
 Cupric oxide melts at a full red heat, and in cooling the mass assumes a crystal- 
 line texture. It is not decomposed by heat alone, but is easily reduced to the metallic 
 state when heated in contact with carbon, hydrogen, carbonic oxide, or other reducing 
 gases ; it dissolves in melted silicates, communicating to the mass a fine green colour ; 
 it is also dissolved by melted lead oxide. When cupric oxide is melted with metallic 
 lead it is reduced to cuprous oxide, which dissolves in the lead oxide formed, and 
 when the proportion of lead is large some of the copper isseparated in the metallic state. 
 
424 COPPER. 
 
 Cuprie oxide is readily dissolved by acids, with which it forms soluble salts ; when 
 heated with fatty substances it is also dissolved to some extent, and on this account 
 copper vessels used for cooking purposes require to be kept bright and free from oxide 
 by frequent scouring. 
 
 Cuprie hydrate, CuH 2 2 , is a greenish-blue pulverulent substance which is con- 
 verted into anhydrous cupric oxide at a temperature a little above 100 and by boiling 
 with a solution of caustic alkali. The blueverditerof commerce consists chiefly of 
 this substance. Cupric hydrate is readily soluble in solution of ammonia, forming a 
 deep blue liquid which has the property of dissolving cellulose. 
 
 Preparation. Cupric oxide may be prepared in the form of copper scale, by 
 exposing red-hot copper for some time to the action of atmospheric air, or by 
 moderately igniting the carbonate or nitrate. The hydrate is obtained by mixing 
 the solution of a cupric salt with caustic alkali, quickly washing the blue precipitate 
 with cold water and drying it at the ordinary temperature. 
 
 CUPROUS SULPHIDE. 
 
 FORMULA Cu 2 S. MOLECULAR WEIGHT 158'8. 
 
 History. The art of extracting copper from copper pyrites appears to have been 
 known at a very remote epoch ; Dioscorides describes TrupiTTjs as a kind of stone, from 
 which copper was obtained ; but it appears to have been confounded with iron pyrites, 
 and Agricola described copper pyrites and iron pyrites as varieties of the same 
 mineral. The existence of cuprous sulphide as a distinct substance was first estab- 
 lished by Proust in 1801. 
 
 Occurrence. Cuprous sulphide occurs naturally as redruthite or copper 
 glance, associated with other minerals containing copper. It also occurs in combina- 
 tion with ferric sulphide very abundantly as copperpyrites, Cu 2 S,Fe 2 S 3 , and as 
 purple copper ore, 3Cu 2 S,Fe 2 S 3 . 
 
 Cuban is another ferruginous compound of cuprous sulphide that occurs naturally. 
 The regulus obtained in smelting copper ores and in the separation of copper from 
 lead ores is a similar compound of cuprous sulphide with ferrous sulphide. Cuprous 
 sulphide also occurs combined with bismuthous sulphide as tannenite, combined 
 with antimonous sulphide as wolfsbergite or antimonial copper ore, Cu 2 S, 
 Sb 2 S 3 , combined with antimonous sulphide and arsenous sulphide as fa hi ore or 
 grey copper, of which there are several varieties, containing also silver, zinc, copper, 
 iron, and mercury, as sulphides in variable proportions. A similar compound of 
 cuprous sulphide and lead sulphide with antimonous sulphide occurs asbournonite, 
 Cu 2 S,Sb 2 S 3 ,2PbS,Sb 2 S3. 
 
 Characters. Cuprous sulphide, as it occurs naturally, is sometimes in the form 
 of six-sided prismatic crystals, sometimes compact and granular ; it has a grey colour, 
 metallic lustre, and the specific gravity is from 5'5 to 5'8. Artificially prepared 
 it has a density of 5'98, a dark lead grey colour, and it melts more readily than copper. 
 It is not decomposed when heated out of contact with air ; heated in the presence of 
 air it is oxidised, sulphurous oxide is given off, and cuprous oxide is at first formed, 
 together with some cupric sulphate which is decomposed by further heating. The 
 cuprous oxide is converted into cupric oxide, partly by the sulphuric oxide given off, 
 and partly by atmospheric oxygen. If the oxidation be interrupted before the whole 
 of the cuprous sulphide is oxidised, and the mass be heated sufficiently to melt it, a re- 
 action takes place between the cupric oxide and the remaining sulphide, which results 
 in the production of metallic copper and sulphurous oxide, according to the following 
 equation : 
 
 2CuO + Cu = 4Cu + S0 2 . 
 
 The same reaction takes place when the mass containing cupric sulphate is melted 
 together with carbon, the cupric sulphate being thus reduced to cuprous sulphide. It 
 is upon this reaction that the production of copper depends in copper smelting. If 
 the proportion of cupric oxide be large, cuprous oxide is produced in place of metallic 
 copper, as shown by the following equation : 
 
 6CuO + Cu 2 S = 4Cu 2 + S0 2 ; 
 
 and it is in this way that it sometimes happens that cuprous oxide is produced instead 
 of copper in the smelting operation. 
 
 Cuprous sulphide is not decomposed when melted with metallic lead, but if 
 argentic sulphide be also mixed with the cuprous sulphide, the silver is extracted to a 
 great extent by the lead and lead sulphide is formed. Cuprous sulphide mixes readily 
 with lead oxide when they are melted together, sulphurous oxide is given off, some lead 
 
CUPKIC SULPHATE. 425 
 
 is reduced, and a reddish coloured vitreous mass formed, consisting of lead oxide and 
 cuprous oxide, as shown by the following equation : 
 
 Cu 2 S + 3PbO = 3Pb + Cu 2 + S0 2 
 158-8 669 621 142-8 64 
 
 But unless the lead oxide amounts to 25 times as much as the cuprous sulphide, a 
 portion of the latter remains undecomposed. If the cuprous sulphide be mixed with 
 argentic sulphide, the silver is taken up by the reduced lead. 
 
 Cuprous sulphide is decomposed by metallic iron, yielding a regulus consisting of 
 ferrous sulphide and cuprous sulphide, with brittle copper containing some iron ; part 
 of the copper is taken up by the excess of iron. 
 
 CUPRXC SULPHIDE. 
 
 FORMULA CuS. MOLECULAR WEIGHT 95'4. 
 
 Occurrence. This substance occurs naturally ascovelliteor blue copper ore 
 and associated with other minerals containing copper, but it is comparatively rare. 
 
 Characters. The crystallised cupric sulphide is in the form of soft flexible laminae, 
 but it occurs more frequently in compact masses, or in some instances as a sooty incrusta- 
 tion ; it has a bluish-black colour and a slight resinous lustre ; its specific gravity is 3*8. 
 Artificially prepared by precipitation with sulphuretted hydrogen from solutions of 
 cupric salts, it has a brown colour while moist, but becomes almost black with a 
 greenish tinge when dried ; it oxidises readily when exposed to the air, and in the 
 moist state is converted into cupric sulphate. By ignition, half the sulphur is driven 
 off, and it is converted into cuprous sulphide ; it is dissolved by hot nitric acid, the 
 copper being converted into nitrate, part of the sulphur separated, and part converted 
 into sulphuric acid ; heated with concentrated hydrochloric acid, it is slowly converted 
 into cupric chloride with evolution of sulphuretted hydrogen and separation of 
 sulphur. It is slightly soluble in solution of ammonium sulphide but not in sodium 
 sulphide. 
 
 CUPRZC SULPHATE. 
 
 FORMULA CuS0 4 . MOLECULAR WEIGHT 159*4. 
 
 History. It was probably this substance, commonly known as blue vitriol, 
 that Dioscorides described under the name x^ Ka>v ov > Dut n P to a comparatively 
 recent time it was frequently confounded with ferrous sulphate or green vitriol and 
 even with verdigris. 
 
 Occurrence. Cupric sulphate frequently occurs in solution in the water that 
 has penetrated into copper mines, and sometimes crystals of the salt occur where such 
 a solution has evaporated. 
 
 Characters. In the crystallised state, this salt contains 5 molecules of water, 
 and forms large transparent prisms of a deep blue colour. The specific gravity is 
 2-274. It dissolves in 3'5 times its weight of cold water, and in a smaller proportion 
 of hot water, as shown in the following table by Poggiale : 
 
 Anhydrous 
 20'9 
 23-5 
 30-3 
 53-1 
 75-3 
 
 Cupric sulphate is insoluble in anhydrous alcohol, but is slightly soluble in dilute 
 alcohol. The crystals effloresce and turn white at the surface in a dry atmosphere, 
 and at 100 they give off 4 molecules of water, forming a white powder. A tempera 
 ture of 200 is necessary for separating the fifth molecule of water. The anhydrous 
 salt has a powerful attraction for water, and rapidly absorbs it from the air, reassuming 
 the blue colour ; on this account it is used as a dehydrating material in preparing 
 absolute alcohol ; it is decomposed at a bright red heat, sulphurous oxide and oxygen 
 being given off, while cupric oxide remains. 
 
 Cupric sulphate dissolves in hydrochloric acid, forming a green liquid from which 
 cupric chloride crystallises on evaporation. Both the anhydrous salt and the 
 powdered crystals, absorb hydrochloric acid gas rapidly and with evolution of heat, 
 
 Ten 
 100 parts of water at 
 
 iperatnre 
 10 
 20 
 40 dissolve 
 80 
 100 
 
 Crystallised 
 36-9 
 42-3 
 56-9 
 118-0 
 203-3 
 
426 COPPEE. 
 
 forming a deliquescent mass. The anhydrous salt absorbs gaseous ammonia rapidly, 
 forming a blue powder. A solution of cupric sulphate mixed with ammonia in excess 
 forms a deep blue liquid which, by evaporation or the addition of alcohol, yields 
 .crystals of a salt having the formula CuS0 4 4NH 3 ,H 2 0. 
 
 Cupric sulphate combines with ammonium sulphate and the alkaline sulphates, 
 forming definite double salts, the composition of which is represented by the following 
 formulae : 
 
 Cu2NH 4 .2S0 4 6H 2 
 
 CuMgS0 4 14H 2 
 
 CuNa 2 2S0 4 2H 2 0. 
 
 A solution of cupric sulphate mixed with ferrous sulphate, or the corresponding 
 salts of zinc, magnesium, or nickel, yields crystals consisting of the different sulphates 
 in proportions varying according to the relative amounts in the solutions. The form 
 of these crystals is that of the salt present in largest proportion, and the amount of 
 water of crystallisation in them varies in the same manner. 
 
 The salt prepared at Buxweiler under the name of Salzburg vitriol is of 
 this nature and contains ferrous sulphate. At other places salts are produced which 
 consist of mixtures in various proportions of the two sulphates. The salt called 
 Cyprian vitriol, prepared at Chessy near Lyons, is a similar mixture of cupric 
 sulphate with zinc sulphate. 
 
SILVER. 
 
 SYMBOL Ag. ATOMIC WEIGHT 108. 
 
 History. This metal has been known from the earliest times, and the names 
 given to it in various languages refer to the colour; thus, for instance, the Greek name 
 &pyvpos is derived from apy6s white. The extraction of silver from its ores by means 
 of lead was known at a very remote period, and was the only method employed until 
 amalgamation was adopted in Mexico about the year 1557 by Bartholomy von Medina. 
 
 Occurrence. Silver occurs naturally together with silver ores and sometimes in 
 considerable quantities, but it occurs more frequently in combination with sulphur as 
 argentite; the sulphide also occurs combined with cuprous sulphide as stromeye- 
 rite, with antimonous sulphide, arsenous sulphide, and other sulphides as the different 
 varieties of fa hi ore and other minerals. Silver also occurs combined with selenium 
 as naumanite, with tellurium as hessite, with chlorine as horn silver, with 
 bromine as bromargyrite, with iodine as iodargyrite, with antimony as discra- 
 site, with mercury as silver amalgam. Galena almost always contains silver, 
 probably in the state of sulphide and in varying proportions, and several other 
 minerals, such as blende, iron pyrites, and some kinds of copper ore, often contain small 
 amounts of silver. 
 
 Characters. This metal is remarkable for its whiteness ; it is harder than gold 
 but softer than copper, and when polished it has a lustre almost equal to steel. With 
 the single exception of gold it is the most malleable of the heavy metals, and admits of 
 being beaten out into extremely thin sheets of silver leaf, which are not more than 
 Too'oot) f an i ncn thick. Silver is also very ductile, and can be drawn into wire so thin 
 that 400 feet of it weighs only one grain. By hammering and drawing into wire it 
 readily becomes brittle and requires to be frequently annealed during the operation. 
 
 Silver has considerable tenacity, and a wire having the diameter of only two 
 millimetres (0-0787 inch) is capable of supporting a strain of nearly 87 kilogrammes 
 (187 Ibs.) which is the breaking weight. The specific gravity of silver is 10 - 5 after 
 being melted ; by the operation of coining it is increased to 10'57. The finely divided 
 metal obtained by precipitation from the solution of a silver salt has a specific gravity 
 of 10*62. Silver crystallises in forms belonging to the regular system, generally cubes, 
 but the crystals sometimes present octahedral faces. 
 
 Silver is the best known conductor of heat and electricity ; the conductivity is 
 reduced by increase of temperature. The specific heat of silver is 0'05701, the latent 
 heat of fusion is 21-07 ; it melts at a white heat, and the melted metal gives off some 
 vapour at very high temperatures ; in the presence of vapour of arsenic, lead or zinc, 
 etc., silver is more readily volatilised. 
 
 Silver does not combine with oxygen at the ordinary temperature, or when heated 
 in contact with atmospheric air, but it is oxidised under the influence of the electric 
 discharge, and when in a finely divided condition it is converted into peroxide by 
 ozone. When the metal is heated upon charcoal under a jet of oxygen, it burns with a 
 bluish flame and vapour of silver oxide is given off: when melted in contact with 
 alkaline or earthy silicates, it is oxidised to some extent, and the oxide is dissolved by 
 the silicate; it is also oxidised when heated in a finely divided state with cupric oxide, 
 arsenic, or antimony. Silver is not acted upon when heated in contact with caustic 
 alkalies or alkaline nitrates, and on this account silver crucibles are used in chemical 
 operations with these substances. 
 
 Melted silver exposed for some time to contact with atmospheric air absorbs 
 oxygen and holds it in solution until the metal has cooled to near the solidifying 
 point. The gas is then suddenly disengaged, producing a kind of effervescence by 
 which particles of the metal are thrown out of the crucible. Melted silver is capable 
 of absorbing in this way twenty-two times its volume of oxygen gas. The presence 
 of a very small proportion of copper in the melted metal prevents this absorption of 
 Oxygen. 
 
428 SILVER. 
 
 Silver combines readily with sulphur and decomposes sulphuretted hydrogen, even 
 at the ordinary temperature becoming covered with a brown or black film of silver 
 sulphide ; it also combines readily with selenium, phosphorus and arsenic. With 
 chlorine, bromine, or iodine, silver combines even at the ordinary temperature. Hydro- 
 chloric acid has but little action upon the metal, unless it be heated to the boiling 
 point with very finely divided silver; but gaseous hydrochloric acid is decomposed by 
 silver at a red heat with formation of silver chloride ; vapours of other chlorides are 
 also decomposed by silver in the same way. Finely divided silver is almost entirely 
 converted into chloride when heated to redness with sodium chloride ; but when 
 the metal is in lumps, silver chloride is formed only at the surface of them, unless 
 the sodium chloride be melted so as to dissolve the silver chloride and expose fresh 
 surfaces. When sodium carbonate is mixed with the sodium chloride, the for- 
 mation of silver chloride is prevented. Aqueous solutions of alkaline chlorides act 
 upon silver and gradually convert it into chloride, which dissolves in the solution, 
 forming a double chloride. Solutions of cupric chloride and other chlorides also convert 
 silver into chloride. 
 
 Dilute sulphuric acid does not act upon silver, but strong sulphuric acid is decom- 
 posed when heated with the metal, yielding silver sulphate and sulphurous oxide. 
 Nitric acid acts violently upon silver, even at the ordinary temperature, forming silver 
 nitrate, with evolution of nitrous fumes. 
 
 Preparation. Minerals containing a large amount of silver are in most in- 
 stances so intimately associated with the ores of other metals, that they do not admit 
 of being mechanically separated, and consequently in smelting such ores the silver 
 they contain is extracted in the form of an alloy. The ores of lead, as already men- 
 tioned, almost invariably contain some silver, and this is often the case with copper 
 ores. The metallic lead or copper or the copper regulus obtained in smelting these 
 ores contains the whole or greater part of silver, and when the amount of silver is 
 not too small, these products are submitted to special operations for the purpose of 
 extracting the silver. 
 
 Ores containing a large amount of silver are sometimes smelted together with me- 
 tallic lead, litharge, or galena, so as to obtain argentiferous lead, which is then operated 
 upon for the separation of the silver. Argentiferous copper ores, or the regulus ob- 
 tained by smelting them in the usual way, are also smelted with lead or galena, so as 
 to obtain lead containing greater part of the silver, and a regulus containing most of 
 the copper. 
 
 Argentiferous iron pyrites is sometimes smelted, so as obtain a regulus consisting 
 chiefly of ferrous sulphide and containing the silver in the state of sulphide. This is 
 roasted and smelted again to concentrate the silver, until a regulus is obtained, from 
 which the silver can be extracted by melting it with lead. 
 
 The extraction of silver from its ores, and from other argentiferous materials pro- 
 duced in metallurgical operations, is also effected by a method termed amalgama- 
 tion, which is based upon the solubility of silver in mercury. This method is prac- 
 tised largely in America, where the cost of fuel is too great to admit of the ores being 
 smelted. The precise nature of the chemical changes that take place in treating 
 silver ores by this method are not thoroughly understood, and some difference of 
 opinion prevails as to the necessity of converting the silver sulphide into chloride. 
 According to the European system of working silver ores by amalgamation, this is 
 done by roasting the ore together with sodium chloride, and then the silver chloride is 
 decomposed by metallic iron in the presence of mercury, which acts merely as a sol- 
 vent, the reaction taking place in the following equation: 
 
 2AgCl + Fe + Hg = FeCl 2 + 2AgHg 
 287 56 137 216 
 
 According to the Mexican system, the ore is treated with a solution of cupric 
 chloride and sodium chloride, and it is the opinion of some that the silver sulphide in 
 the ore is in this way converted into chloride, which is decomposed by the mercury 
 with separation of metallic silver, which is dissolved by the excess of mercury, while 
 part of the mercury is converted into mercurous chloride, as shown by the following 
 equation : * 
 
 2AgCl + 2Hg = Hg 2 Cl 2 + 2Ag 
 287 400 471 216 
 
 In this case, therefore, the quantity of mercury required would be much larger, 
 since in addition to that necessary for dissolving the silver, a further quantity would 
 be consumed in decomposing the silver chloride. 
 
 When silver sulphide is digested with solution of cupric chloride no reaction 
 takes place, but, according to Boussiugault, in the presence of sodium chloride the 
 
AMALGAMATION OF SILVER ORES. 429 
 
 silver sulphide is slowly decomposed and cuprous chloride is formed, which is dissolved 
 by the excess of sodium chloride ; the other products are cupric sulphide and silver 
 chloride, probably according to the following equation : 
 
 3Ag 2 S + 4CuCl 2 = 6AgCl + 2CuCl + 2CuS + S. 
 
 By a further reaction between the cuprous chloride thus formed and a further 
 quantity of silver sulphide, more silver chloride would be produced together with 
 cuprous sulphide : 
 
 Ag 2 S + 2CuCl = 2AgCl 4- Cu 2 S. 
 
 This view of the change that takes place in the Mexican amalgamation has been 
 disputed, and the formation of silver chloride has been questioned, since ores contain- 
 ing this substance are said to be especially difficult to work by the amalgamation 
 method. The decomposition of silver sulphide is also considered to take place as a 
 result of the reaction with cupric oxychloride, giving rise to cuprous chloride, sul- 
 phuric acid, and metallic silver, according to the following equation: 
 Ag 2 S + 3Cu 2 Cl 2 = GCuCl + S0 3 + 2Ag. 
 
 The ores worked by the amalgamation method in Mexico contain some silver in a 
 metallic state together with sulphide and chloride ; they sometimes contain antimony 
 and arsenic, and the gangue substance consists chiefly of quartz, iron pyrites, ferric 
 oxide, and earthy carbonates. After being crushed, the ore is ground very fine with 
 water, in a roughly constructed mill, resembling a porcelain mill. The sludgy mass 
 of ground ore is afterwards placed upon a stone pavement, surrounded with" a low 
 circular wall, and allowed to dry until it has the consistence of thin mud ; it is then 
 mixed with about 5 per cent, of common salt and well stirred together. Some days 
 afterwards it is mixed with about 1 per cent, of a material called magistral, con- 
 taining cupric and ferrous sulphates, which is prepared by roasting copper pyrites 
 in a reverberatory furnace ; the mass is again well mixed, and some mercury is added, 
 the whole being again thoroughly mixed. Chemical action then commences, and the 
 stirring is repeated every day for two to six weeks. Meanwhile samples of the mass 
 are examined by washing with water, so as to separate the mercury. If this is bril- 
 liant and liquid, more magistral must be added, but if it presents a very grey colour, 
 the quantity added has been t90 large and some lime is added. 
 
 When the mercury is found to have dissolved the silver contained in the ore, the 
 mass is washed in small portions with water, and the sludge run into settling tanks 
 where the mercury collects at the bottom and the earthy material is run off. This is 
 continued until the whole mass of ore has been washed, and the amalgam is then col- 
 lected, pressed in sacks to separate the excess of mercury, and then distilled in iron 
 retorts, by which means the silver is obtained in the form of a porous mass, which is 
 melted and cast into ingots. 
 
 The consumption of mercury in treating ores by this method is very considerable, 
 and the loss is said to amount to as much as twice the weight of silver obtained. 
 The extraction of the silver is also incomplete. 
 
 In working rich ores, the amalgamation is sometimes effected by grinding them in 
 copper pans with successive additions of magistral, salt and mercury. 
 
 The silver ores of the Nevada district are amalgamated by grinding in iron pans 
 with mercury, and sometimes common salt and cupric sulphate. The amalgam is 
 then separated by washing with water and distilled. 
 
 Some of the silver ores of this district contain intimate admixtures of galena. 
 Arsenical and antimonial minerals cannot be treated in this way, but are roasted with 
 common salt and treated with mercury by the German method. 
 
 The treatment of silver ores by amalgamation according to the European system 
 was formerly practised on a large scale at Freiberg. The ores there worked contain 
 silver sulphide together with arsenous and antimonious sulphides, iron pyrites, blende, 
 etc. They are mixed so that when smelted a regulus is obtained amounting to about 
 30 per cent. The finely ground ore is then mixed with about 10 per cent, of common 
 salt, and roasted in a reverberatory furnace. The charge is put into the furnace moist, 
 heated gently until it is dry, and stirred to prevent the formation of lumps. As the 
 temperature is raised, vapour is given off containing arsenic and antimony. The oxi- 
 dation of the iron pyrites then commences, and as heat is thus generated little fuel is 
 required at this stage, which lasts about two hours. After the formation of sulphurous 
 oxide has ceased, the heat is again raised in order to decompose the sulphates that 
 have been formed. During this stage the mass swells up, vapour of chlorides and hy- 
 drochloric acid are given off, together with some chlorine, and the silver is converted 
 into chloride. After about half an hour the charge is drawn. It then contains, 
 besides various oxides and the earthy ingredients of the ore, silver chloride, cupric 
 
430 SILVER. 
 
 and ferric chlorides, sodium sulphate, together with other sulphates and unaltered sul- 
 phides. 
 
 During the roasting some silver is carried off by the vapour, and therefore the 
 furnace is connected with condensing flues. The presence of antimony in the ore in- 
 creases the loss of silver in this way. 
 
 The roasted ore is screened to separate lumps, which are ground, and again roasted 
 with salt. The fine powder is ground in a mill, and reduced to a state of very fine 
 division. It is then put into wooden casks with some water and metallic iron or 
 copper, and by means of machinery fitted to the casks they are made to revolve. In 
 this way the silver chloride is gradually decomposed, and metallic silver separated. 
 After this has been done a quantity of mercury equal to half the weight of the roasted 
 ore is added to the contents of each cask, and the stirring is continued for about 
 twenty hours. Meanwhile the contents of the casks are examined to ascertain 
 whether the proper proportions have been used. The casks are then filled with water, 
 and made to revolve slowly for about two hours, after which time the greater part of 
 the mercury will have separated from the sludgy mass and collected together so that it 
 can be drawn from the casks. It is filtered through bags to separate the excess of mer- 
 cury, and the amalgam left in the bags is distilled in iron retorts. 
 
 The pressed amalgam contains about 85 per cent, of mercury and 10 or 12 per cent, 
 of silver, with varying amounts of copper, lead, antimony, etc. The strained mercury 
 contains about 1 ounce of silver to the hundredweight. 
 
 The sludgy mass from which the greater part of the mercury has been separated 
 still contains particles of amalgam and mercury disseminated through it, which are 
 separated by washing off the lighter portion of the mass with water, and treating the 
 heavier portion with some more mercury. 
 
 The loss of silver and mercury in this operation is very variable, but it is less than 
 in the Mexican amalgamation. Only a small portion of the mercury is converted into 
 mercurous chloride, and the waste arises chiefly from the mechanical mixture with the 
 finely divided material. The presence of arsenic, lead, and other metals which are 
 easily reduced and amalgamated, augments the waste of mercury very much. Still 
 the loss of silver is much less than when the ores are smelted : the operations are very 
 simple, and very little fuel is required. The amalgamation method, however, is not 
 applicable to ore containing lead or copper. Although lead unites readily with mer- 
 cury, only a small portion of this metal is amalgamated when ore containing lead is 
 operated upon. This is probably due to the circumstance that the greater part of the 
 lead remains in the state of chloride or sulphate, neither of which are decomposed un- 
 less a very large excess of iron is used. Copper is to some extent amalgamated, but 
 the greater part remains in the waste and is lost. Consequently ores containing more 
 than 7 per cent, of lead or 1 per cent, of copper are not suited for treatment by this 
 method. 
 
 Auriferous ores cannot be advantageously worked by this method, because the 
 greater part of the gold remains in the waste after amalgamation. The cause of this 
 is that, though gold unites readily with mercury, it is less readily acted upon than 
 the very finely divided silver precipitated by the iron from a solution of silver chloride 
 in sodium chloride. 
 
 The nature of the earthy ingredients of the ore has likewise some influence in the 
 working : argillaceous substances render the mass tenacious, heavy spar makes it dense ; 
 calcareous substances reduce the consumption of iron and of mercury by decomposing 
 the chlorides, but they also reduce the yield of silver. When copper is used for de- 
 composing the silver chloride a purer amalgam is obtained than when iron is used ; 
 but copper acts more slowly than iron, and even when used in large proportion is less 
 effective in extracting the silver. 
 
 At Poullaouen in Brittany some of the ores from the Huelgoat mines, consisting 
 of metallic silver, antimonial silver, and silver chloride disseminated through quartz, 
 ochre, and clay, are treated in a manner which combines both the Mexican and Euro- 
 pean methods. After the mechanical preparation of the ore, it is mixed with about 
 10 per cent, of a material consisting chiefly of sodium chloride with some ferrous sul- 
 phate, alum, and a very small proportion of cupric siilphate. The mixture is left for 
 several days in tubs to allow the chemical action to take place, and then it is treated 
 with mercury in the manner already described. 
 
 The amalgamation method is now largely practised in California and Nevada in 
 working silver ores, and great improvements have been made in the mode of operat- 
 ing. Large iron pans are used for grinding the ore with the mercury in place of tubs, 
 and by this means the silver or its compounds are more effectively brought into con- 
 tact with the mercury. The application of heat in the operation has also been found 
 advantageous in some instances. 
 
 The cupric oxychloride is supposed to result from the oxidation of cuprous 
 
SEPARATION OF SILVER FROM COPPER. 
 
 431 
 
 chloride, formed in the first instance, together with mercurous chloride, by the action 
 of mercury upon cupric chloride: 2CuCl 2 + 2Hg = Hg 2 Cl 2 + 2CuCl, and then 
 converted into cupric oxychloride by absorbing oxygen from the atmosphere : 2CuCl 
 + = Cu 2 Cl 2 0. According to this view, the action of sodium chloride in the amal- 
 gamation of silver ores would probably consist chiefly in dissolving the cupric oxy- 
 chloride and thus facilitating its action upon the silver sulphide. 
 
 The solubility of silver chloride in a strong solution of sodium chloride has also 
 been taken advantage of for the purpose of extracting silver from argentiferous 
 materials. For this purpose the silver is converted into chloride by roasting the 
 material with sodium chloride, and the roasted material is then digested with a solu- 
 tion of salt in wooden vats until the silver chloride is dissolved. The solution is then 
 drawn off and passed through a series of vats containing precipitated copper, which 
 precipitates the silver and is itself dissolved. 
 
 A still more simple and inexpensive method of extracting silver from argenti- 
 ferous copper regulus is based upon the solubility of silver sulphate in water, 
 and the circumstance that this salt requires a higher temperature for decomposition 
 than the other sulphates soluble in water which are produced in roasting copper 
 regulus or argentiferous iron pyrites. The success of this method depends mainly 
 upon the proper roasting of the material from which silver has to be extracted, so 
 that the whole of the silver may be converted into sulphate, while the cupric sulphate 
 and ferrous sulphate produced in the earlier stage of the oxidation are decomposed or 
 converted into an insoluble state. These methods are applicable in the case of silver 
 ores, provided they do not contain much lead, zinc, antimony, or arsenic. 
 
 It has already been mentioned that in smelting argentiferous lead ores the silver 
 they contain is taken up by the metallic lead, and the amount of silver in the lead 
 obtained by smelting such ores is frequently sufficient to admit of its being profitably 
 extracted. Argentiferous copper ores, when smelted in the usual way, yield a regulus 
 containing silver, and in some instances the silver is separated from the copper by 
 melting the regulus with metallic lead, or with materials containing lead, much in the 
 same manner that lead ores containing copper are smelted. By this means argen- 
 tiferous lead is obtained, and a copper regulus containing less silver ; but the separa- 
 tion of the silver from the copper regulus is seldom effected completely unless the 
 operation is performed several times, and then there is always considerable loss, as 
 well as great consumption of fuel. 
 
 If the argentiferous copper regulus is subjected to the usual treatment for the pro- 
 duction of metallic copper, the black copper thus obtained contains the silver, and 
 formerly it was the practice to extract the silver by melting the black copper together 
 with lead, casting the alloy into round cakes, and subjecting them to a heat sufficient 
 to melt lead. This process is termed liquation, and the separation of the silver is 
 due to the circumstance that in cooling the triple alloy of lead, copper, and silver, it 
 separates into two alloys, one consisting of copper and lead, the other of lead and 
 silver. On heating this mechanical mixture, the argentiferous lead separates, in the 
 liquid state, from the less fusible alloy of copper and lead. 
 
 The heating of the cakes of alloy was carried out in a kind of hearth, the construc- 
 tion of which is represented by figs 315, 316, and 317. 
 
 FIG. 315. 
 
 FIG. 316. 
 
 FIG. 317. 
 
 It consists of two low walls on the top of which are placed cast-iron plates upon 
 which the cakes of alloy are set on edge with charcoal between them, and a fire is 
 made in the arched space between the walls. The melted argentiferous lead running 
 
 lis 
 a 
 considerable loss of the metal. 
 
 mae n e arce space eween e w. 
 
 into the receptacle placed in front of the hearth, is then ladled into moulds. In thi 
 
 way the greater part of the silver is separated from the copper, but there is always 
 
432 
 
 SILVER. 
 
 The spongy mass remaining still contains lead, and for its separation a higher 
 degree of heat requires to be applied to it, in a furnace of somewhat similar construc- 
 tion, which is termed a sweating furnace. This method of extracting silver from 
 copper was formerly practised on a large scale in Germany, but has now been very 
 generally superseded, and the regulus obtained by smelting argentiferous copper ores 
 is desilverised before the copper is reduced to the metallic state. (See pp. 417, 444.) 
 
 The argentiferous lead obtained by the operation of liquation was treated in the 
 same manner as that produced in smelting argentiferous lead ores. 
 
 The extraction of silver from argentiferous lead is effected by exposing the melted 
 metal to the oxidising action of heated air ; lead oxide is thus formed, which melts 
 and is run off, but the silver is not oxidised to any considerable extent, and ultimately 
 the greater part of it remains in the metallic state. This operation is termed cup el - 
 lation, and is conducted in a reverberatory furnace with a bed (D, figs. 318 to 320), 
 
 FIG. 319. 
 
 FIG. 320. 
 
SEPARATION OF SILVER FROM LEAD. 433 
 
 formed of bone ash beaten down into a moveable iron framework, represented in the 
 vertical section, fig. 318, by the thick lines, and on a larger scale by fig 321 
 
 The moveable bed of the English cupellation furnace is called a test. It consists 
 of an oval iron ring (a a, fig. 321) with strong iron bars (bb) bolted to it, forming 
 the bottom. A mixture of finely 
 ground bone ash, moistened with a 
 very weak solution of potassium 
 carbonate, is beaten down into a 
 compact mass in the cavity of this 
 frame, and then scooped out so as to 
 form a basin (<?) and leave a lining 
 (ddd) which covers the whole of 
 the iron work. The apparatus used 
 in lining the test frame is repre- 
 sented by fig. 322. 
 
 At the wider end of the test a 
 portion of the lining is sometimes 
 cut away so as to leave a space be- 
 tween the lining and the ring, 
 through which the melted lead 
 oxide may flow away ; but it is now 
 more usual to bore some holes through the lining, and cut a channel in the upper edge 
 of the lining to such a depth as is required. 
 
 FIG. 322. 
 
 The working chamber of the furnace is separated from the fireplace (A) by a wide fire 
 bridge (c), and the hot gas passes over the test (D) through the flues (EE) into the chimney. 
 Opposite the narrow end of the test there is an aperture (F) in the wall of the furnace 
 through which a blast tuyere is inserted, and at the other end of the test a channel is 
 cut in the bone-ash lining of the test, or holes are bored in it, through which the 
 melted lead oxide runs oif. The lead from which silver is to be extracted is run 
 into the test from a pot outside the furnace, and while heating up to the requisite 
 temperature, the surface becomes covered with a greyish crust of dross. As soon as 
 the lead oxide melts and the metal becomes visible, the blast of air is turned on to 
 accelerate the oxidation, and the melted litharge is driven oif the surface of the metal 
 by the current of air towards the gate or outlet at the opposite end of the test, where 
 it runs out into an iron vessel mounted on wheels. As the metal in the test is reduced 
 in this way, fresh lead is supplied at intervals, either in a melted state or by slipping 
 in pigs of lead through apertures (a a) in the sides of the furnace, so as to keep the 
 test full. 
 
 When the operation has been continued so long that the metal in the test is suffi- 
 ciently rich and contains about 8 per cent, of silver, the furnace is either allowed to 
 cool, and the test removed with its contents, or the metal is run off by drilling a hole 
 in the bottom of the test and running it into moulds. 
 
 The further separation of the lead is effected in the same manner upon a fresh 
 test, and the operation is continued until the metal remaining is nearly pure silver. 
 This point is indicated by the brightening of the surface of the metal. The blast is 
 then turned off and the mass of silver, after being allowed to solidify, is removed 
 together with the test. 
 
 The proper regulation of the temperature in this operation is of considerable in- 
 
 F F 
 
434 
 
 SILVER. 
 
 fluence upon the loss of silver and lead. When the heat is too great much lead is 
 volatilised, and when it is too low the melted litharge is viscid and carries off some 
 silver. During the latter stage of the operation the litharge formed contains a 
 larger proportion of silver, and on this account it is kept apart. 
 
 The extraction of silver from lead by cupellation is conducted much in the same 
 manner in Germany, but the furnaces employed differ in having the bed fixed, and in 
 
 FIG. 323. 
 
 FIG. 324. 
 
 being fitted with a movable sheet- 
 iron roof or dome, as shown by 
 figs. 323 to 326. 
 
 The hearth (6) of this furnace 
 was formerly made of washed 
 wood ashes mixed with some lime, 
 but is now generally made of cal- 
 careous marl beaten down upon 
 the bricks (5), set so as to form a 
 hemispherical cavity : beneath 
 them is a layer of slag (4), and the 
 whole is supported upon a solid 
 foundation (1) with channels (2) 
 
 FIG. 325. 
 
 for the escape of moisture. The back and front elevations, (figs. 323 and 324) show 
 the position of the working door (q) by which the lead is put in while working, and of 
 
 the bellows (s), the arrangement 
 by which the dome (&) is taken 
 off; the furnace door (y) and the 
 opening (#) through which the 
 litharge is drawn off into recep- 
 tacles placed over the pan (0), 
 which serves to collect anything 
 that may be spilt. 
 
 In working this furnace the 
 charge consists of from 3 to 5 
 tons of argentiferous lead. 
 When this is melted down upon 
 the hearth, a pasty dark- 
 coloured scum collects upon the 
 surface, consisting of a mixture 
 
 FIG. 326. 
 
 of lead with metallic oxides, 
 sulphides, arsenides and anti- 
 monides, together with some particles of marl from the hearth. After this scum is 
 raked off, the blast is turned on, and the heat increased, a further quantity of frothy 
 scum is removed, and when the lead oxide formed is sufficiently free from impurities, a 
 notch is cut in the edge of the hearth opposite the door (x), deep enough to allow the 
 liquid litharge to run out. If the lead contains much antimony, the heat must be 
 raised very gradually to ensure the oxidation of the antimony, which is then separated 
 after the removal of the dark frothy scum in the state of lead antimoniate, presenting 
 a greenish-brown colour. 
 
 During the operation, the melted litharge should form a ring about fifteen inches- 
 wide round this metal, and this is regulated by cutting the notch deeper as the lea,d is 
 oxidised. The blast should be directed upon the. surface of the metal by adjusting 
 the tuyeres (nn) so as to cause a slight undulation, and drive the melted litharge to- 
 wards the edges of the hearth. Towards the end of the operation, when but little 
 
CUPELLATION. 
 
 435 
 
 lead remains unoxidised, the temperature requires to be increased in order to prevent 
 the metal from solidifying. 
 
 The material of which the hearth is made absorbs a large quantity of lead oxide, 
 and often contains from 58 to 65 per cent, of lead with some silver ; it is therefore 
 smelted together with lead ores. The actual loss of lead, chiefly by volatilisation, 
 amounts to about 8 per cent., and the loss of silver is about 0'5 to 075 per cent, of 
 the quantity in the lead operated upon. 
 
 The loss of silver experienced in extracting this metal from argentiferous lead by 
 cupellation is chiefly due to the retention of some silver by the lead oxide. The 
 extent to which this takes place depends very much upon the temperature at which 
 the operation is conducted, and likewise upon the rate at which the melted lead oxide 
 is allowed to flow away. The higher the temperature and the more rapidly the opera- 
 tion is carried on the greater is the proportion of silver carried off in the lead oxide ; 
 but the longer the lead oxide remains in contact with the metal the smaller is the loss 
 of silver in this way. 
 
 The silver thus obtained is called brightened silver; it usually contains 
 about 6 per cent, of impurities, chiefly consisting of lead, copper, bismuth, arsenic and 
 other metals, and the separation of these is effected either by exposing it in a melted 
 state for some length of time to the action of an oxidising atmosphere, or by melting 
 the silver in crucibles with an oxidising flux. 
 
 Much of the lead obtained on the continent by smelting in shaft furnaces is very 
 impure, containing copper, zinc, iron, antimony, and arsenic, in considerable propor- 
 tions, and it is by the oxidation of these metals at the commencement of the cupella- 
 tion that the dark-coloured scum is produced. In extracting silver from lead of this 
 kind, the entire quantity of lead treated in one operation should be placed on the 
 hearth at once if it be desired to obtain pure litharge as a product, for if the lead 
 were added in successive portions, the impurities it contains would be to a great ex- 
 tent mixed with the whole of the litharge. 
 
 The following table gives the composition of the scum formed during the earlier 
 stage of the cupellation. 
 
 
 Pontgibaud 
 
 Poul- 
 laouen 
 
 Katzen- 
 thal 
 
 Freiberg 
 
 VUlefort 
 
 Lead . . . 
 
 23-0 
 
 
 
 63-6 
 
 _ 
 
 _ 
 
 _ 
 
 Lead oxide . 
 
 53-1 
 
 89-5 
 
 
 
 67-6 
 
 955 
 
 82-0 
 
 Cupric oxide 
 
 1-1 
 
 0-2 
 
 7-0 
 
 0-4 
 
 0-5 
 
 
 
 Zinc oxide .... 
 
 4-6 
 
 1-5 
 
 
 
 0-2 
 
 1-1 
 
 
 
 Ferric oxide . . 
 
 5-4 
 
 2-6 
 
 28-6 
 
 4-4 
 
 0-3 
 
 
 
 Antimonic oxide . 
 
 
 
 
 
 
 
 
 
 
 
 17-6 
 
 Antimony teroxide 
 
 0-5 
 
 
 
 
 
 
 
 
 
 
 
 Arsenic oxide . . 
 
 3-0 
 
 07 
 
 
 
 19-2 
 
 2-2 
 
 
 
 Sulphur . 
 
 
 
 
 
 
 
 0-3 
 
 
 
 0-4 
 
 Carbon ..... 
 
 5'6 
 
 
 
 
 
 
 
 
 
 
 
 Silica, alumina, etc. 
 
 
 
 
 
 1-6 
 
 7-6 
 
 
 
 
 
 
 96-3 
 
 94-5 
 
 100-8 
 
 997 
 
 99-6 
 
 100-0 
 
 It is evident from the composition of the products comprised in the above table, 
 that in extracting silver from lead by cupellation there is at the same time a very 
 considerable separation of the foreign metals with which it is associated. The result 
 is due in some cases to the solvent action of the lead oxide formed during the opera- 
 tion upon the oxides of other metals such as copper, zinc, tin, antimony, etc. 
 
 In order to extract silver from argentiferous lead by this method, the lead should 
 not contain less than about 8 ounces of silver in the ton, otherwise the value of the 
 metal obtained is not sufficient to cover the cost of the operation and of the subsequent 
 reduction of the lead oxide produced. A very large proportion, however, of the lead 
 produced contains a much smaller amount of silver, varying from mere traces to 3 or 
 4 ounces in the ton, and formerly the silver in such poor argentiferous lead was not 
 obtainable, until early in the present century another method was accidentally dis- 
 covered by Mr. Pattinson, which admitted of much smaller quantities than 8 ounces 
 in the ton of lead being profitably extracted. 
 
 When argentiferous lead is melted and allowed to cool gradually, crystals are 
 formed which sink to the bottom and contain much less silver than the metal which 
 remains liquid. Advantage was taken of this fact by Mr. H. L. Pattinson as a means 
 for effecting the separation of silver from lead, and it had the merit of being applica- 
 ble to lead containing only such amounts of silver as cannot be profitably extracted by 
 
 FF2 
 
436 
 
 SILVER. 
 
 the cupellation method. This method is now extensively employed, and a considerable 
 quantity of silver is thus obtained which -would otherwise be unavailable. 
 
 The operation is conducted in a series of hemispherical cast-iron pans, each capable 
 of holding 6 or 8 tons of lead, and arranged in the manner represented by figs. 327 
 
 SECTION AT.C.H. 
 
 SECTION AT. I.K 
 
 HORIZONTAL AT.L.M. 
 
 OS- 
 
 . 327. 
 
 to 332. Beneath each of these pans is a fireplace, and between each pair of pans is a 
 smaller-sized pan filled with melted lead for the purpose of warming the tool used for 
 dipping out the lead crystals. A quantity of lead is melted in one of the pans at the 
 centre of the series, and the dross collecting at the surface of the liquid metal skimmed 
 off. The fire is then withdrawn, and while the melted lead is cooling it is stirred with an 
 iron rod to promote crystallisation. As soon as a sufficient quantity of crystals have 
 been formed, they are dipped out by means of a perforated iron ladle (fig. 329), and 
 transferred to the pot on the right hand of the workman, care being taken to drain 
 away from the crystals as much as possible of the liquid metal adhering to them. 
 This operation is continued until three-fourths or more of the metal has been removed 
 from the pan, and then the liquid portion is transferred to the adjoining pan on the 
 left-hand side. In this way the metal is separated into two portions, one containing 
 double or more than double the amount of silver originally in the lead, and the other 
 considerably less. The precise extent to which the metal is allowed to crystallise and 
 then removed from the liquid portion depends upon the amount of silver in the lead 
 operated upon. "With very poor lead a larger proportion is taken out of the pan in 
 the form of crystals, and with lead containing much silver a smaller proportion is sepa- 
 rated in the crystallised state. In the former case as much as seven-eighths of the 
 metal is separated in the crystallised state, and this method of working is technically 
 termed the low system; with lead richer in silver as little as two-thirds of the 
 metal is dipped out in the crystallised state, and this is termed the high system; 
 the whole of the lead under treatment being then kept in the pans, of which ten or 
 fifteen are required. In the low system of working a smaller number of pans are 
 used, and a considerable part of the crystals separated are laid aside and kept until 
 there is a sufficient quantity for the full charge of the pots. 
 
 The same operation is carried out with the metal in the other pans right and left 
 of the one in which the first portion of lead is crystallised; and by this mode of work- 
 ing, the metal finally transferred to the last pan to the right of the series, is almost 
 free from silver, while that in the last pan to the left will contain as much as 07 to 
 1 per cent, of silver, or between 200 and 300 Troy ounces per ton. This appears to 
 be about the extent to which the concentration of the silver can be carried with prac- 
 tical advantage by the application of Pattinson's process to argentiferous lead. In 
 regard to this point C. Reich has shown that when the lead operated upon contains 
 1-442 per cent, of silver the crystallised portion contains 0'682 percent, and the liquid 
 portion 1-922 per cent., but when the silver in the lead operated upon amounts to 2-09 per 
 cent, the crystallised portion contains 2-011 per cent, and the liquid portion contains 
 2'260 per cent. Moreover, the separation of the liquid metal from the crystals becomes 
 more difficult as the amount of silver increases, and when it is as much as 2-3 per 
 cent, there is a tendency to the solidification of the whole mass of metal at once. 
 
 The separation of silver from lead by Pattinson's method depends upon the cir- 
 cumstance that the melting point of an alloy consisting of lead with only a small 
 proportion of silver is less than that of lead itself, and consequently this alloy remains 
 liqui '., while the lead solidifies in the form of granular crystals. 
 
 The extent to which silver can be thus extracted from lead does not in any case go 
 beyond the limit of half an ounce per ton, and the lead operated upon in this way 
 
SEPARATION OF SILVER FROM LEAD. 437 
 
 should never retain more than that amount of silver ; but, taking into account the cost 
 of the operation and the loss of metal attending it, as well as the production of dross 
 by oxidation, it is but rarely that lead with so small an amount of silver as 2 ounces 
 per ton can be profitably worked in this way, so far as separation of the silver alone 
 
 PLAN AT TOP. 
 
 FIG. 328. 
 
 is concerned. When the silver amounts to 3 ounces per ton, its extraction by the 
 Pattinson method is practicable, and consequently this method can be worked in many 
 instances where the cupellation of lead would not be applicable. (See p. 435.) A 
 further advantage of the Pattinson method is the purification of the lead by the 
 oxidising action of the atmosphere upon the melted metal ; at the same time the loss 
 of lead is very much less than it is in cupellation. 
 
 The extent to which oxidation takes place during the treatment of lead by Pattin- 
 son's method varies according to the amount of silver and other metals in the lead; 
 on the average, it is sufficient to produce a quantity of dross amounting to from one- 
 fifth to one-third the weight of the lead operated upon. This dross is skimmed off and 
 put aside for reduction in the same manner as litharge or the pot dross obtained in 
 refining lead. The oxidation that takes place during the desilvering operation lias the 
 effect of purifying the metal. 
 
 Fio. 329. 
 
 The arrangement of a series of ten pans is shown at different levels by the hori- 
 zontal plan (figs. 327 and 328) ; fig. 330 represents a portion of the range of pans in 
 vertical section longitudinally, showing the mode in which the pans are heated, by flues 
 running round them, and figs. 331 and 332 show, in transverse sections, the flues lead- 
 ing from the sides of the pans into the main flue communicating with the chimney. 
 The last pot on the right hand is called the market pot, since it is the final recep- 
 tacle of the desilverized lead, which is ladled from it and cast into pigs. The pots on 
 the left hand of this one are called working pots. 
 
 , SECTION AT A. B. 
 
 FIG. 330. 
 
 >Kcnox AT c. v. 
 
 SECTION AT K. F. 
 
 FIG. 331. 
 
 FIG. 332. 
 
 The following table of analyses by Streng of lead desilverised by this method will 
 serve to show the proportions of other metals it contains : 
 
438 
 
 SILVER. 
 
 
 English 
 
 Stolberg 
 
 Billach 
 
 Esch\veiler 
 
 Pirach 
 
 Altena 
 
 Lead. 
 
 99-983 
 
 99-935 
 
 99-975 
 
 99-907 
 
 99-892 
 
 99-957 
 
 Antimony . 
 
 0-015 
 
 0-007 
 
 0-012 
 
 0-053 
 
 0-061 
 
 0021 
 
 Copper 
 
 trace 
 
 0-050 
 
 007 
 
 0-026 
 
 0-041 
 
 0-016 
 
 Iron .... 
 
 0-008 
 
 006 
 
 006 
 
 0-003 
 
 004 
 
 0-006 
 
 Zinc .... 
 
 0-004 
 
 001 
 
 trace 
 
 0-011 
 
 002 
 
 trace 
 
 
 100-010 
 
 99-999 
 
 100-000 
 
 100-000 
 
 100-000 
 
 100-000 
 
 Besides the separation of some of the impurities in lead by the oxidation that takes 
 place in working Pattinson's process, there is a concentration of some of these sub- 
 stances in the portion of metal remaining liquid. Baker has investigated this subject, 
 and finds that copper is in this way separated from the lead crystallising out. In one 
 case the original lead contained : 
 
 Silver Copper Iron Sulphur 
 
 1. . . ' . 0-0046 0-0066 0'0065 trace 
 
 2. ... 0-0052 0-0154 0-0068 trace 
 The various products obtained in the operation contained : 
 
 
 
 Silver 
 
 Copper 
 
 Iron 
 
 Eich pot : 
 
 
 
 
 
 Before crystallising 
 
 
 
 0-0108 
 
 0-0344 
 
 0-0312 
 
 Crystals . 
 
 25 parts 
 
 0-0052 
 
 0-0152 
 
 0-0086 
 
 Liquid portion 
 
 85 
 
 0-0140 
 
 0-0476 
 
 0-0122 
 
 Second pot : 
 
 
 
 
 
 Before crystallising 
 
 
 
 0-0052 
 
 0-0154 
 
 0-0068 
 
 Crystals .... 
 
 95 
 
 0-0020 
 
 0-0066 
 
 0-0118 
 
 Liqiiid portion 
 
 25 
 
 0-0126 
 
 0-0286 
 
 0-0146 
 
 Third pot : 
 
 
 
 
 
 Before crystallising 
 
 
 
 0-0020 
 
 0-0102 
 
 0-0118 
 
 Crystals .... 
 
 70 
 
 o-ooio 
 
 0-0038 
 
 0-0198 
 
 Liquid portion 
 
 25 
 
 o-oioo 
 
 0-0240 
 
 00082 
 
 Fourth pot : 
 
 
 
 
 
 Eefinedlead .... 
 
 
 
 C-0014 
 
 0-0054 
 
 0-0112 
 
 From these results it was inferred that there is an alloy of lead with copper which 
 has a low melting point, like the alloy of lead with a small proportion of silver 
 that remains liquid in the Pattinson operation, and that in this way copper is separated 
 from the lead as well as silver. 
 
 Nickel appears to be in like manner concentrated in the metal that remains liquid, 
 and Baker found in operating upon lead containing from 0'0023 to - 0057 per cent, of 
 nickel, that this metal is not separated by oxidation, but that the liquid lead contains 
 as much as 0'0043 and 0*0072 per cent. 
 
 In proportion as the amount of silver in the alloy increases, the difference between 
 the melting point of the alloy and the melting point of lead decreases, and consequently 
 the separate crystallisation of the lead is either prevented, or, when it does take place, 
 there is much greater difficulty in draining away from the lead crystals the argenti- 
 ferous alloy. Reich has investigated this subject, and the results arrived at by him 
 are given in the following table : 
 
 Amount of Silver in the 
 melted Lead before 
 crystallising 
 
 Amount of Silver in the 
 drained crystals 
 
 Amount of Silver in the 
 residual liquid 
 metal 
 
 Per cent. 
 
 Per cent. 
 
 Per cent. 
 
 0-704 
 
 0-390 to 0-466 
 
 1-025 
 
 0-732 
 
 0-318 0-374 
 
 1-076 
 
 0-966 
 
 0-410 0-680 1 1-450 
 
 0-988 
 
 0-390 0-624 
 
 1-530 
 
 1-442' 
 
 0-682 
 
 1-922 
 
 2-090 
 
 2-011 
 
 2-260 
 
 2-116 
 
 1-728 2-216 
 
 2-248 
 
 2-206 
 
 2-212 
 
 2 '264 
 
SEPARATION OF SILVER FROM LEAD. 489 
 
 The removal of the lead crystals, besides being a laborious operation, is one that 
 causes considerable wear and tear of the pans, and several attempts have been made 
 to economise labour by adapting machinery for this purpose and for the, stirring of 
 the lead while it is cooling. The apparatus represented by fig. 333 has been intro- 
 duced with this object. It consists of a windlass and crane (ab) so placed that a 
 
 FIG. 333. 
 
 chain attached to the shank of the ladle is wound up on the windlass, and the ladle 
 drawn up filled with crystals out of the pans. The workmen guide the handle of the 
 ladle and place it under the catch (<?) while the crystals are draining, and then by turn- 
 ing the crane the ladle is readily moved until it comes over the adjoining pan, into 
 which the crystals are to be transferred. "Worsley's apparatus for stirring the metal 
 consists of a vertical shaft running in a step at the bottom of the pan and furnished 
 with radiating arms. The lead was melted in a separate pan and then run into the 
 crystallising vessel, and when the crystallisation had gone far enough the enriched 
 liquid metal was drawn off into moulds through tapping holes at the sides of the 
 crystallising vessel. This mode of working has not as yet proved successful. 
 
 When lead and zinc are melted and stirrrd together and then slowly cooled, the 
 two metals separate almost completely ; the zinc being specifically lighter than lead, it 
 collects at the surface of the lead, and having a higher melting point it solidifies first. 
 Mr. Parkes observed that by treating argentiferous lead in this way the silver was 
 separated from the lead and retained by the zinc. 
 
 In operating upon lead by this method two cast-iron pans are used ; one, capable 
 of holding several tons of lead, for melting the lead, and the other one, of much smaller 
 dimensions, for melting the zinc. The temperature of the melted lead is raised to the 
 melting point of zinc, and then about a twentieth of its weight of melted zinc is ladled 
 out of the small pot, mixed with the lead, the whole well stirred, and then allowed to 
 cool gradually. When the zinc has solidified at the surface it is skimmed off with a 
 perforated ladle, and the lead remaining in the liquid state contains about half an 
 ounce of silver per ton. 
 
 The metal skimmed off retains some lead, and to separate this it is heated to a 
 temperature above the melting point of lead, but not so high as the melting point of 
 zinc, in a cast-iron retort set over a furnace and inclined so that the lead separating 
 by liquation runs into a cast-iron pan placed at the end of the retort, and is set aside 
 for further treatment with zinc. When the alloy of zinc and silver has been in this 
 
SILVER. 
 
 way drained of lead, it is distilled with lime and charcoal in a retort so as to distil 
 off the zinc from the silver, which is much less volatile. The chief difficulty en- 
 countered in working this process is in the separation of zinc from the desilverised 
 lead. The use of superheated steam as an oxidising agent, introduced for this pur- 
 pose by Cordurie in 1866, has been found effectual; and lead containing 0'75 per cent, 
 of zinc has been purified in this way so as to retain only mere traces of zinc. 
 
 The extraction of silver from black copper by the method of liquation, which was 
 formerly the only way of effecting the separation of these metals on a large scale, is 
 now very rarely practised, and the method of amalgamation by which it was super- 
 seded has likewise been to a great extent discontinued in favour of methods of treat- 
 ment which are more economical. In most instances the desilverising treatment is 
 carried out with the copper regulus, consisting chiefly of cuprous sulphide, and con- 
 taining the silver in the state of sulphide. 
 
 In order to extract silver as silver chloride from argentiferous copper regulus, it 
 is first ground to a fine powder and roasted in a reverberatory furnace, until all the 
 silver is converted into sulphate, and the other metals are in the state of oxides or 
 insoluble basic sulphates. On treating a portion of the roasted material with water, 
 it should yield an almost colourless solution that gives a precipitate of silver chloride 
 on adding a few drops of hydrochloric acid. The mass is then removed from the 
 furnace mixed with from 1 to 6 per cent, of sodium chloride, and again roasted at a 
 temperature barely approaching redness, in order to avoid loss of silver by volatilisa- 
 tion as well as the melting of the chloride. If the copper regulus operated upon be 
 free from lead, zinc, antimony and arsenic, and the first roasting has been properly 
 conducted, the product of the second roasting will contain but little iron and copper 
 in the state of chlorides, but the whole of the silver will be in that state. It is then 
 lixiviated, while hot, with a concentrated solution of sodium chloride in tubs fur- 
 nished with false bottoms covered with filters of linen cloth. These tubs (a a, fig. 
 334) are placed on a truck (d) mounted on wheels and running upon rails (cc?) so that 
 
 FIG. 334. 
 
 they can be transferred to a gallery (bb) underneath a trough (e) by which the sodium 
 chloride solution is run in from a cistern (x). This solution is heated by steam, and 
 in filtering through the roasted material in the tubs dissolves the silver chloride. 
 After escaping from the lower end of the tubs it passes by the trough (g) into a 
 tank (k, fig. 335) situated at such a level as to supply the tubs (iiii} in which the 
 silver is precipitated by copper. The liquid is then run off into the tubs (III) also 
 containing finely divided copper; afterwards passing through two more rows of 
 tubs (m and ), containing scrap iron to precipitate the copper, into the tank (0), 
 which also contains some scrap iron, and it is then pumped up into the reservoir (p). 
 
 When the material in the tubs has been extracted, it is washed with water, and 
 for this purpose the tubs are transferred to the tram road (z) beside the cisterns 
 (qr s), the last of which contains clean water, while the others contain water that has 
 been used once or more for washing the contents of the tubs. Each tub is first filled 
 from the cistern (q) and the liquid allowed to run into the trough (g), then from the 
 cistern (r), and the liquid run into the tank (t) is pumped up into the cistern (q), then 
 from the cistern () and the liquid run into the tank () is pumped up into the cistern 
 (r). The tubs are then carried forward and tipped over, so as to discharge their 
 contents upon the table (to) through the opening (te). 
 
 The extracted residue should not contain more than 0'03 per cent, of silver, and 
 when the amount is greater it is again roasted and lixiviated, otherwise it is treated 
 for the extraction of copper, as already described. The precipitated silver collecting 
 in the tubs (4 and I) is in the form of a fine crystalline powder. It is removed 
 
SEPARATION OF SILVER FROM COPPER. 441 
 
 every week and washed with dilute hydrochloric acid, then pressed, dried, and refined. 
 The washing of the silver is carried on in the space (y). 
 
 
 
 FIG. 335. 
 
 The precipitated copper in the tubs (m n) is again used for precipitating silver, 
 and the liquid containing sodium sulphate which is transferred to the tank (p) is 
 sometimes evaporated for the sake of obtaining that salt. 
 
 Black copper is sometimes treated by this method tor the purpose of extracting 
 the silver it contains ; the metal, which should not contain more than about 10 per 
 cent, of lead or antimony, is crushed to a fine powder and roasted with sodium chloride 
 for several hours, with constant stirring meanwhile. During the latter stage of the 
 roasting the heat is increased for the purpose of decomposing antimonial compounds. 
 The roasted material is then finely powdered and lixiviated with sodium chloride 
 solution in the manner already described. 
 
 The treatment of argentiferous speise is more difficult on account of the antimony 
 and arsenic which this produ.-t often contains, and long continued roasting is requisite 
 in preparing the material for lixiviation. 
 
 Sodium thiosulphate is sometimes used instead of sodium chloride for dissolving 
 silver in the state of chloride, and this method of treatment has been found advan- 
 tageous in working the rich silver ores, containing cobalt and nickel, which occur in 
 the neighbourhood of Joachimstbal in Bohemia. The ores are coarsely powdered and 
 roasted in reverberatory furnaces for several hours in contact with steam. The 
 roasted material is then ground up with from 4 to 10 per cent, of sodium chloride, 
 and if requisite some ferrous sulphate is mixed with it. After roasting this mixture 
 again in contact with steam, the silver should be almost entirely extracted by solu- 
 tion of sodium thiosulphate. The mass is then sifted, moistened with water, and left for 
 a time, in order that the silver may be more completely converted into chloride; it is 
 then washed with hot water to remove salts of iron, cobalt, nickel, zinc, copper, and 
 lead ; a small quantity of silver is also extracted at the same time. The washed 
 material is then mixed with a cold dilute solution of sodium thiosnlphate which dis- 
 solves the silver chloride, and after separating this solution from the residue, the silver 
 is precipitated as sulphide by adding a solution of sodium sulphide ; the silver sul 
 phide is collec-ted, washed, and dried, and then melted with iron, to separate the silver 
 in the metallic state. 
 
 The use of sodium thiosulphate as a solvent of silver chloride in the treatment 
 of argentiferous copper regulus is more advantageous than that of sodium chloride, 
 since it dissolves the silver chloride in much larger proportion ; consequently the 
 volume of liquid to be dealt with is relatively much smaller, and the operation 
 requires less time. 
 
 In precipitating the silver as sulphide, by adding solution of sodium sulphate, 
 the thiosulphate is left in solution, and can be used again in subsequent operations on 
 fresh quantities of roasted regulus. 
 
 In both these methods the result of the first roasting of the copper regulus is to 
 convert the silver into the state of sulphate, which is a salt sufficiently soluble to be 
 extracted with water alone. 
 
 When the silver is extracted by dissolving it in the state of sulphate, the 
 copper regulus is roasted in double reverberatory furnaces of the kind represented by 
 
442 
 
 SILVER. 
 
 figs. 336 to 339. The lower hearth (a) is formed of fire brick bedded upon a layer 
 of loam, and above the arch which forms the working chamber is the upper hearth (0), 
 also covered with an arch and communicating with the lower hearth by the channel 
 (n), which is closed by a lid at the upper end, as shown in figs, 337 and 338. 
 
 Fro. 337. c 
 
 The lower -working chamber also communicates by means of the flue (i) wit 
 the condensation chamber (ddd}, and this flue is provided with a damper (c} by 
 which it can be closed. The upper working chamber communicates with the con- 
 densing chamber by the flue (<?). The working doors (m and p} of the lower 
 
SEPARATION OF SILVER FROM COPPER. 443 
 
 and upper hearths are provided with supports for tools. The ash pit (?) com- 
 municates by the opening (a?) with the tunnel (I), running beneath several of these 
 furnaces, and the opening (x) can be closed by a lid (i) worked by the rod (h) to 
 regulate the admission of air beneath the fire-grate. The ashes are removed occftsion- 
 
 FIG. 338. 
 
 FIG. 339. 
 
 ally through the door (*). The condensation chamber (dddd} communicates by the 
 vertical flue (e, figs. 338 and 339) with the horizontal flues (fff), which are covered 
 witli iron plates and serve for drying the desilverised material. 
 
 The roasted material when cold is lixiviated with water at a temperature of 70 
 
444 
 
 SILVER. 
 
 in tubs (A, fig. 340) fitted with false bottoms, several of them being placed in a row 
 so that water or dilute sulphuric acid can be run into them from the leaden pipes 
 (b and a). The solution of silver sulphate running out from the bottom of these tubs 
 passes into a settling tank divided into two parts (B and c) by a vertical partition, 
 then through a row of tubs corresponding to , containing precipitated copper for 
 the precipitation of the silver. The liquid discharged from these tubs does not con- 
 tain much silver, but it is again brought into contact with sheets of copper in the 
 
 long tank (E), and in the tubs of the row corresponding to (F), from which it is run 
 off through the trough (g} into a reservoir, and pumped up again for further use. 
 
 The copper regulus operated upon should contain about 80 per cent, of cuprous 
 sulphide ; it is ground very fine and then spread over the upper hearth of the furnace, 
 which has been previously heated. When quite dry it is mixed with about 5 per 
 cent, of coal, and well stirred for some time to prevent the formation of lumps of 
 basic ferric sulphate. 
 
 A certain amount of ferrous sulphide .is requisite to facilitate the formation of 
 cupric sulphate, but when the material operated upon contains much more than 1 1 
 per cent, of ferrous sulphide, and but little cuprous sulphide, the silver cannot be so 
 completely converted into sulphate. The presence of lead sulphide or antimonous 
 sulphide in the regulus interferes with the formation of silver sulphate by causing the 
 material to cake in roasting. Metallic zinc, antimony, or arsenic, also cause loss of 
 silver, either by volatilisation in the roasting, or by the formation of silver antimonate 
 and silver arsenate, which are not readily decomposed by sulphuric acid. For these 
 reasons the extraction of silver as sulphate is not applicable to ores or other materials 
 which do not contain copper combined with sulphur, or even to copper ores containing 
 arsenic, antimony, zinc, or lead. 
 
 Silver is sometimes separated from copper regulus by means of hot dilute sul- 
 phuric acid. The regulus to be treated in this way should not contain much iron ; 
 it is roasted in the state of powder, and then mixed with the acid in wooden tubs into 
 which steam is forced, to heat the liquid. The cupric oxide in the roasted material 
 is thus dissolved as sulphate, while the silver is almost entirely left in the residue, 
 together with ferric oxide, antimonates, and any gold that may be present. The solu- 
 tion of cupric sulphate is drawn off and crystallised, and the argentiferous residue is 
 either melted with lead, or the silver is extracted in the wet way. 
 
 Argentiferous black copper is also treated in a similar manner with dilute sulphuric 
 acid in order to separate the silver it contains. 
 
 The cuprous iron pyrites employed as a source of sulphur in the manufacture of 
 sulphuric acid often contains a small proportion of silver, and in treating the burnt 
 pyrites for the extraction of copper (p. 417) the silver it contains is now separated by 
 a method introduced by Mr. Claudet. In roasting the burnt pyrites with sodium 
 chloride the silver is converted into chloride, and sufficient sodium chloride remains 
 undecomposed to dissolve the silver chloride when the roasted material is extracted 
 with water. The liquor obtained by lixiviation, containing about three grains of silver 
 in the gallon, is mixed with a sufficient quantity of a soluble iodide to convert the 
 silver into iodide, and when left to settle a precipitate is deposited, consisting of silver 
 
REFINING OP SILVER. 
 
 445 
 
 iodide, lead chloride, lead sulphate, and cuprous salts. The clear liquid is then run 
 off, and the precipitate, after being washed with dilute hydrochloric acid to remove 
 copper, is decomposed with metallic zinc. By this means zinc iodide is formed -which 
 can be used for treating fresh quantities of liquor, and the silver is separated in the 
 metallic state, together with some lead, by the decomposition of lead chloride by the 
 zinc. 
 
 KEFININQ OF SILVER. - -The silver obtained by cupellation of argentiferous lead 
 generally retains a certain amount of impurity, for the separation of which it is some- 
 times subjected to further treatment in a reverberatory furnace with a fixed concave 
 hearth formed of a layer of marl with a layer of clay and broken bricks beneath it. 
 The charge consisting of about a ton of silver is placed on this hearth, covered with 
 some coal dust or charcoal, and slowly melted down ; the melted metal is then stirred, 
 the dross skimmed off, and some bone ash thrown upon the surface ; sometimes a blast 
 of air is applied to facilitate the oxidation of the impurities, and when the silver has 
 been kept in this state for several hours, it is ladled out into ingot moulds. 
 
 The precipitated silver obtained by the decomposition of silver sulphate (p. 444) is 
 refined by melting it down in a furnace of this kind, and skimming off the slag and 
 dross formed by the oxidation of the copper present in the precipitate, together with 
 calcium sulphate and other substances. 
 
 Smaller furnaces which have moveable hearths formed of bone ash are also employed 
 for refining silver, and the operation is carried out almost exactly in the same manner 
 as the cupellation, but as the proportion of lead oxide formed is much smaller, it is 
 chiefly absorbed by the porous material of which the test is constructed. The loss of 
 silver by volatilisation is, however, sometimes considerable ; and it is largest when a 
 blast of air is used and the silver operated upon contains much antimony or other 
 volatilisable metal. 
 
 The construction of the refining furnace with moveable hearth is represented by 
 figs. 341 and 342. Except in dimen- 
 sions this furnace closely resembles 
 the cupellation furnace (p. 432). The 
 test (d) consists of a thick layer of 
 bone ash pressed into the iron frame 
 which rests upon the iron bars (ee) 
 and can be drawn out when the opera- 
 tion is completed. The flame from 
 the furnace (b~) passes over the surface 
 of the test and escapes by the flue (/) 
 into a chimney. 
 
 The quantity of metal operated 
 upon at once varies from 1 to 5 
 hundredweight, and the operation 
 lasts about six hours. By this treat- 
 ment silver may be refined to such an 
 extent as to contain only one tenth 
 per cent, of impurity, or even less. 
 
 A still higher degree of purity may be 
 attained by melting the metal in crucibles 
 with nitre, or some oxidising flux. 
 
 It frequently happens that in the ores 
 from which silver is obtained there is a 
 minute proportion of gold which becomes 
 concentrated in the silver, and is then worth 
 separating. When this is the case, the 
 refining of silver is carried out in the wet 
 way, by treating it with sulphuric acid. Fio. 342. 
 
 This plan is also adopted for refining 
 
 silver containing copper. The metal is first melted in large crucibles, heated to 
 bright redness in furnaces fed with coke, the hot air from these furnaces being made 
 to heat the bars of alloy that are afterwards to be melted. About 2 or 3 per cent, of 
 nitre is thrown into the crucibles containing the fused metal, to remove any oxidisable 
 metals by converting them into slag, which floats together with the melted nitre upon 
 the surface of the melted silver, and is removed with a perforated cast-iron ladle. 
 
 As soon as this skimming is over, the melted metal is granulated, by pouring it 
 in a thin stream, from some height, into cold water, contained in an iron vessel. 
 This granulated metal is placed in a hemispherical pan (fig. 343), about 3 feet in dia- 
 meter, the sides of which are about 1 inch thick, and treated with sulphuric acid of 
 specific gravity 1'84. A head (c), provided with a door (p), fits air-tight upon the flange 
 
446 
 
 SILVER. 
 
 of the pan, and is connected with a bent leaden pipe (T T), passing through a trough 
 (B) kept cool by a current of water flowing in by the funnel at the side, while the 
 hot water is escaping through a tube in the upper part of the opposite side. The sul- 
 phurous oxide escaping from the pipe (T) is conducted into a lead chamber for con- 
 version to sulphuric acid, or is otherwise disposed of. 
 
 FIG. 343. 
 
 The pan is set in the furnace so that in case it should leak at any time the escap- 
 ing liquid must flow into a hollow beneath and finally escape into a vessel placed 
 under the tube (o). On this account the pan is heated from the side, the furnace (G) 
 being separated from the hollow underneath the pan by a low wall. 
 
 By the action of the heated sulphuric acid, the granulated metal is dissolved, 
 silver sulphate and cupric sulphate being formed, together with sulphurous oxide 
 gas. Fresh quantities of sulphuric acid are added at intervals until all the metal 
 is dissolved, the operation lasting about three hours. 
 
 When the alloy contains from 90 to 95 per cent, of silver, it dissolves entirely, 
 yielding a clear liquid which is drawn off with a platinum siphon ; but when the alloy 
 contains less than 90 per cent, of silver, the solution remains turbid, and is then run 
 into a leaden vessel, fitted with a cock about 2 inches above the bottom, mixed with 
 nearly an equal volume of cupric sulphate solution, of spec. grav. 1-288 to T310, 
 obtained from a previous operation, and steam is passed into the liquid through a 
 leaden tube. By this means the suspended substance is almost entirely dissolved ; the 
 leaden vessel is then covered, and the liquid, after being kept hot for about two hours, 
 during which it is allowed to settle, is drawn off by the cock into a thick leaden pan, 
 where the silver is precipitated by adding copper turnings. The process is accelerated 
 by frequent stirring, so as to detach the precipitated metallic silver from the surfaces 
 of the pieces of copper. The reaction is complete when the dark blue solution ceases 
 to yield a precipitate (silver chloride) with a solution of sodium chloride. When 
 this point has been attained, the liquid is drawn off into another leaden pan. where 
 any suspended portions of silver are allowed to settle. The vessol used for this pur- 
 pose is generally that in which the turbid solution from the retorts is heated with 
 so'ution of cupric sulphate. The clear blue liquid is finally evaporated and crystallised. 
 
 The precipitated silver is thoroughly washed, by placing it in a trough lined with 
 lead and furnished with a fine sieve bottom. A leaden tube with a number of very 
 fine perforations extends round the inner sides of the trough, and discharges a fine 
 stream of warm water, which washes the silver, and then escapes through the sieve 
 bottom. The water curries with it some particles of silver, which are allowed to 
 settle in another trough below, and are afterwards collected and placed again in the 
 washing trough. The water in the lower trough is let off at intervals through a cock 
 placed at no great distance from the bottom. The silver precipitate is then removed, 
 pressed, and melted. 
 
 Uses. Silver has long been very generally employed for coining money, and for 
 
SILVER COMPOUNDS. 447 
 
 this purpose it is alloyed with a small proportion of copper, which gives the requisite 
 degree of hardness ; the same alloy is also largely used for making articles for domes- 
 tic use and for ornamental purposes. On account of the great power of silver to 
 reflect light, it is used in making the reflectors used in lighthouses. Various articles 
 of copper are coated with silver by uniting the two metals by heat, and rolling or 
 hammering the mass into the required shape, so that when finished it presents a 
 uniform layer of silver at the surface. The coating of articles with silver is now very 
 largely effected by depositing the silver electrolytically, and in some instances the 
 coating of silver is applied by rubbing the surface of the articles with an amalgam 
 of silver and mercury, then driving off the mercury by heat and polishing. 
 
 The coating of glass with silver is effected by means of the reducing action of 
 certain organic substances upon silver salts in the presence of ammonia, and this 
 method has been applied not only to the silvering of mirrors for telescopes, but also 
 to the making of large mirrors, and for various purposes of decoration. Liebig re- 
 commended the use of milk sugar with a solution of silver nitrate mixed with just 
 enough ammonia to redissolve the precipitate first formed, and some caustic soda. The 
 glass to be silvered is suspended so that the surface touches the liquid, and after some 
 time it is coated with a deposit of silver. 
 
 Compounds. Silver is monovalent in most of its compounds which are of im- 
 portance industrially. The chloride, bromide, and iodide have the formulae AgCl. AgBr. 
 Agl. ; the oxide Ag 2 corresponding to these compounds is a powerful base forming 
 well-defined saline compounds with acid oxides, some of which are isomorphous 
 with the corresponding salts of the alkali metals ; and the sulphide Ag 2 S is also a 
 powerful basic substance which combines with acid sulphides forming a large number 
 of sulphur salts, several of which occur naturally as minerals. The peroxide Ag 2 2 , 
 corresponding in composition to the peroxides of hydrogen, potassium, etc., resembles 
 these compounds in their general chemical relations. A compound of silver with 
 nitrogen is formed when freshly precipitated silver oxide is treated with ammonia ; 
 it is easily decomposed when rubbed and explodes with great violence. 
 
 Silver unites with most other metals when melted with them, forming alloys which 
 are sometimes nearly as white and ductile as silver, but are always harder than the 
 pure metal ; a very small proportion of copper has this effect of increasing the hard- 
 ness of silver, and the presence of only a small amount of zinc, antimony, arsenic, bis- 
 muth, or tin, renders silver brittle, and liable to crack when rolled. 
 
 The alloys of silver and aluminum are harder than aluminum, and when the 
 silver does not exceed 30 per cent, they are even more fusible than aluminum, and 
 can be used for soldering this metal. The alloy containing 3 per cent, of silver is 
 not acted upon by sulphuretted hydrogen ; that containing 5 per cent, of silver has a 
 fine white colour, takes a good polish, is tolerably malleable, and has about the same 
 hardness as British standard silver. The alloy consisting of equal parts of aluminum 
 and silver is brittle. 
 
 The alloys of silver with zinc are of a bluish-white colour. Doppler's reflector 
 metal consists of silver with one-fourth its weight of zinc. 
 
 Silver mixes in all proportions with lead when the two metals are melted together ; 
 but when the melted mass is gradually cooled some separation takes place, and the 
 interior contains a much larger proportion of silver than the outer parts. 
 
 Silver and copper may be melted together in any proportions ; the alloys are 
 almost as ductile as silver, they are much harder, more elastic, and take a higher 
 polish than pure silver. When the silver amounts to more than 50 per cent., the 
 colour of the alloy is white. The most important alloys of copper and silver are 
 those used under the name of standard silver for coinage and for making utensils 
 and ornaments. The alloy used for this purpose in the United Kingdom contains 
 7'5 per cent, of copper ; its specific gravity is 10'20. In France three alloys are 
 used, one containing 95 per cent, of silver for medals and plate, another containing 
 90 per cent, of silver for silver coin, and the third containing 80 per cent, of silver for 
 jewelry work. 
 
 Silver solder is an alloy of silver with about half its weight of zinc and copper. 
 
 Alloys of silver and copper when solidified very gradually do not remain homo- 
 geneous throughout ; but, according to the amount of silver they contain, the inner or 
 outer portions of the mass contain a larger proportion of silver than the remainder. 
 The alloy consisting of 71 '9 per cent, silver and 28' 1 copper does not separate in 
 this way. 
 
 Although the alloys of silver with copper are white even when containing a large 
 amount of copper, the colour is not so fine as that of pure silver, and in order to give 
 articles made of such alloys an appearance more closely resembling pure silver, they 
 are submitted to an operation termed whitening, by which the copper at the surface 
 is oxidised and dissolved, leaving the silver almost pure. 
 
448 SILVER. 
 
 SILVER OXIDE. 
 
 FORMULA Ag 2 0. MOLECULAR WEIGHT 232. 
 
 Characters- This substance is a dark brown powder sparingly soluble in water ; 
 its specific gravity is 7'14 to 7'25 ; it is readily decomposed by heat into metallic 
 silver and oxygen, and when exposed to sunlight it is gradually decomposed; it is 
 readily reduced by oxidisable substances, such as solution of sulphurous oxide, or by 
 contact in the moist state with copper, zinc, or tin. Strong aqueous ammonia converts 
 it into a fulminating compound which explodes with great violence when rubbed, 
 especially in the dry state. 
 
 Preparation. When a solution of a silver salt is mixed with caustic alkali out 
 of contact with atmospheric air, silver oxide is precipitated, and after washing several 
 times with boiled water it is dried at a moderate heat. The oxide may also be pre- 
 pared by pouring a mixture of freshly-precipitated silver chloride and water into a 
 boiling solution of caustic potash about 1*3 specific gravity. The chloride should be 
 added very gradually, and the liquid kept boiling all the time. 
 
 SILVER CHLORIDE. 
 
 FOBMULA AgCl. MOLECULAR WEIGHT 143-5. 
 
 History. Silver chloride was certainly known to the older chemists in so far as 
 it must have been a product of many of their operations, but the accounts given of 
 this substance prior to 1595 are very vague ; in that year Libavius clearly described 
 the precipitate produced in solutions of silver by sodium chloride, and gave it the 
 name of lac argenti. In 1608 Croll gave to the melted substance the name of luna 
 cornea, and in the following century most of the characters of this substance became 
 known. 
 
 Occurrence. This substance occurs naturally as horn silver, accompanying 
 ores of silver in various localities ; it is most abundant in Peru, Chili, and Mexico ; 
 an eartny variety called buttermilk ore occurs at Andreasberg in the Hartz. 
 
 Characters. Silver chloride as it occurs naturally is sometimes crystalline, 
 forming octahedrons and cubes ; its specific gravity is about 5 '4, and it has a pearl 
 grey or greenish colour, turns brown on exposure and is slightly translucent. The 
 precipitated chloride is a white powder quite insoluble in water, but readily soluble 
 in ammonia ; it is also dissolved by solution of alkaline chlorides, forming double salts 
 which are crystallisable, but are decomposed by water. Silver chloride is also dis- 
 solved by solutions of alkaline sulphites and thiosulphates. 
 
 At a temperature of about 260 silver chloride melts, forming a transparent yellow 
 liquid, which on cooling solidifies to a horny translucent mass. At a high tempera- 
 ture it is slightly volatilisable, especially when mixed with other volatile substances. 
 It is not decomposed when heated with charcoal, but is readily reduced by hydrogen at 
 a high temperature, or when heated with alkaline carbonates. By contact with zinc, 
 iron, or other easily oxidisable metals in the moist state it is soon reduced, especially 
 if the water be acidulated with sulphuric acid, and the silver remains as a spongy 
 mass. Weak alkaline solutions do not act upon silver chloride, but when boiled with 
 a strong solution of caustic potash the chloride is converted into oxide. When boiled 
 with solution of sodium carbonate and glucose, the chloride is decomposed and 
 metallic silver separated. 
 
 By exposure to light silver chloride acquires a dark violet colour, the change being 
 probably due to the formation of subchloride. Paper charged with silver chloride is 
 very sensitive to light, and is used for taking photographs ; the unaltered silver 
 chloride being afterwards removed by means of a solution of sodium thiosulphate. 
 
 Preparation. For the purposes of photography silver chloride is prepared upon 
 the surface of the paper used for printing positives, by first saturating it with an 
 alkaline chloride, and then floating the paper upon the surface of a solution of silver 
 nitrate. The production of silver chloride is also an important point in the treat- 
 ment of silver ores and other argentiferous materials for the extracting of silver ; it 
 is effected chiefly by the reaction which takes place between silver sulphate and 
 alkaline chlorides, or the hydrochloric acid given oft 7 when mixtures of ferrous sulphate 
 arid sodium chloride are heated together, as in the roasting of copper regulus with 
 sodium chloride. (See p. 440.) 
 
SILVER SULPHIDE AND SULPHATE. 449 
 
 SILVER SULPHIDE. 
 
 FORMULA Ag 2 S. MOLECULAR WEIGHT 248. 
 
 Occurrence. This substance occurs naturally as argyrose, or silver glance, 
 and as acanthite ; also in combination with other sulphides with cuprous sulphide 
 as stromeyerite AgCuS, with antimonous sulphide as miargyrite Ag 2 S. Sb 2 S, 
 pyrargyrite 3Ag 2 S. Sb 2 S 3 , freibergite 4Ag 2 S. Sb 2 S 8 , stephanite 6Ag 2 S. Sb 2 S s , 
 polybasite 9Ag 2 S. Sb 2 S 3 , with antimonous sulphide and lead sulphide as brogni- 
 ardite PbS,Ag 2 S, Sb 2 S 3 , and freieslebenite 2Ag 2 S,3PbS, 2Sb 2 S,, with arsenous 
 sulphide as proustite 3Ag 2 S. As 2 S 3 , and xanthoconite ; with ferrous and ferric 
 sulphides/as sternbergite (Ag 2 S. 2FeS). 3Fe 2 S 8 . Silver sulphide also occurs, very 
 frequently, associated with the sulphides of lead, copper, and zinc in varying propor- 
 tions, as argentiferous galena, fahl-ore, and blende, and in some kinds of iron pyrites. 
 
 Characters. Silver sulphide in the crystalline state generally presents forms 
 of the regular system ; the crystals are irregularly developed in dendritic and filiform 
 masses ; it has a dark grey colour and metallic lustre. The density is from 7' 196 to 
 7'36o. The artificially prepared sulphide has a density of 6*85. 
 
 Silver sulphide is not decomposed when heated out of contact with air, and it is 
 but slowly oxidised when heated in the air, sulphurous oxide being given off while 
 metallic silver remains ; part of the sulphide is converted into silver sulphate, which 
 requires a very high temperature for its decomposition, yielding then sulphurous 
 oxide, oxygen, and metallic silver. The sulphide is decomposed by ignition in hydrogen 
 gas, and the melted sulphide is decomposed by iron, but in the presence of cuprous 
 sulphide or lead sulphide some of the silver sulphide remains unaltered. Both lead 
 and copper decompose only part of the sulphide. Silver sulphide rubbed with 
 mercury yields mercuric sulphide and silver, the latter forming an amalgam with the 
 excess of mercury ; chlorine gas acts upon the sulphide only when heated, and then 
 slowly, but converts the silver entirely into chloride. When the sulphide is heated 
 with sodium chloride it is but slightly acted upon and mere traces of silver chloride 
 formed. When the sulphide is heated in contact with water vapour to a temperature 
 insufficient for fusion, it is decomposed, and the reduced metal presents the same 
 filiform appearance as the silver occurring naturally. 
 
 Silver sulphide is but little acted upon when digested with solution of ferric 
 chloride or cupric chloride, but in the presence of sodium chloride it is partly con- 
 verted into silver chloride, and sulphur is separated, while the solution contains a 
 compound of cuprous chloride with sodium chloride. The formation of silver chloride 
 takes place more readily when silver sulphide is digested with a solution of cuprous 
 chloride in sodium chloride. It is possible that in the amalgamation of silver ores 
 by the Mexican method, cuprous chloride may be formed by the action of metallic 
 silver in the ore upon the cupric chloride used in the operation, or this effect may be 
 in part produced also by the action of the mercury upon the cupric chloride, mercurous 
 chloride being formed at the same time. 
 
 When silver sulphide is heated with a solution of cupric oxychloride, the sulphur 
 is oxidised to sulphuric acid, the silver being separated in the metallic state, and 
 cuprous chloride formed. 
 
 When silver sulphide is heated together with a considerable proportion of cupric 
 sulphate to a temperature sufficiently high to decompose the cupric salt, the silver 
 sulphide is converted into sulphate, and one of the methods of extracting silver from 
 argentiferous copper regulus is based upon this fact. 
 
 SILVER SULPHATE, 
 
 FORMULA Ag 2 S0 4 . MOLECULAR WEIGHT 312. 
 
 Characters. Silver sulphate is a colourless salt soluble in _ about 200 parts of 
 cold water and 88 parts of boiling water. It separates as a white pulverulent pre- 
 cipitate on adding sodium sulphate to a solution of silver nitrate, but is cry stalli sable 
 in anhydrous needles belonging to the trimetric system, and isomorphous with an- 
 hydrous sodium sulphate. When exposed to light it gradually turns green. The 
 salt melts at a moderate heat, and at a high temperature is decomposed, leaving 
 metallic silver ; but it requires a higher temperature for decomposition than either 
 cupric sulphate or ferrous sulphate, a circumstance which is of importance in the 
 roasting of argentiferous copper regulus, since it admits of the ferrous sulphate and 
 
450 SILVER. 
 
 cupric sulphate formed in the first stage of that operation being converted into basic 
 ferric sulphate and cupric oxide, while the silver sulphate remains unaltered and 
 capable of being extracted from the roasted material by lixiviation with water, and 
 thus separated from the preponderating mass of insoluble copper and iron compounds 
 with which it is associated. (See p. 444.) 
 
 Preparation. It is chiefly in the extraction of silver from copper regulus that 
 the production of silver sulphate is carried out, and then this salt is formed partly by 
 the oxidation of the sulphide by atmospheric air, but chiefly by the action of 
 sulphuric acid vapour upon the ulphide. (See p. 442.) 
 
 FORMULA AgN0 3 . MOLECULAR WEIGHT 170. 
 
 Characters. This salt forms colourless anhydrous crystals belonging to the 
 trimetric system; it dissolves in its own weight of cold water, and in half its weight 
 of hot water ; it is also soluble in four parts of boiling alcohol. The salt melts at 
 219, and when cast into small sticks is used as a caustic in surgery under the name 
 of lunar caustic. When applied to the flesh of animals it instantly destroys the 
 vitality of the part touched. It is decomposed by exposure to light. In contact with 
 organic substances the silver is reduced either to the metallic state or to oxide. On 
 this account it is employed in the preparation of hair dye, and of ink for marking 
 linen, etc. 
 
 Preparation. Silver nitrate is easily prepared by dissolving the metal in nitric 
 acid, and evaporating the solution until sufficiently concentrated to deposit crystals on 
 cooling. 
 
MERCURY. 
 
 SYMBOL Hg. ATOMIC WEIGHT 200. 
 
 History. The knowledge of this metal does not appear to have dated back so 
 far as that of gold, silver, copper, iron, etc. ; and the first mention of it is found in the 
 works of Theophrastus about 300 B.C., where liquid silver XUT^I/ &pyvpov is spoken of 
 as being obtainable by rubbing cinnabar and vinegar together in a copper vessel with 
 a copper pestle. Discorides described this metal under the name of vSpdpyvpos, from 
 vtiap water and Hpyvpos silver, and gives the method of preparing it by distillation. 
 The metal occurring naturally was described by Pliny as argentum vivum, and that 
 obtained by cinnabar as hydrargyrum. Mercury was considered by the alchemists 
 a constituent of all metals, and it was not until the time of Lavoisier that it was 
 classed among the elementary substances. 
 
 Occurrence. Mercury occurs naturally in the metallic state to some extent, but 
 more frequently in combination, with either gold or silver, as amalgams, which are 
 sometimes crystallised. It also occurs combined with chlorine, as horn quick- 
 silver, Hg 2 Cl 2 , and more rarely as selenide and iodide. It occurs most abundantly 
 in combination with sulphur as cinnabar HgS, which is the source from which 
 mercury is chiefly obtained. 
 
 Some kinds of fahl-ore contain mercury in the state of sulphide. Ores of this 
 kind occur in various parts of Hungary, and have the composition given in the fol- 
 lowing table : 
 
 Copper . - . 
 
 36-39 
 7-11 
 
 34-23 
 9-46 
 
 30-58 
 1-46 
 
 32-80 
 5-85 
 
 39-40 
 7-38 
 
 Mercury ..... 
 Silver 
 Antimony ..... 
 Arsenic . . . . . 
 Sulphur . . ... 
 
 3-07 
 0-11 
 2670 
 trace 
 25-90 
 
 3-57 
 
 o-io 
 
 33-33 
 
 trace 
 19-38 
 
 16-69 
 0-09 
 25-48 
 trace 
 24-37 
 
 5-57 
 0-07 
 30-18 
 trace 
 24-89 
 
 0-52 
 0-12 
 31-56 
 trace 
 22-00 
 
 The chief localities in which mercury ores occur are Spain, Carniola in Southern 
 Austria, California, Mexico, Peru, China and Japan. They are also met with on a 
 smaller scale in France, Tuscany, and some parts of Germany. 
 
 Characters. Mercury at the ordinary temperature is a very mobile but coherent 
 liquid, of a bluish-white colour and metallic lustre. At a very low temperature it 
 solidifies as a soft ductile mass. Its density in the liquid state is 13*559 ; it boils at 
 360, and is converted into a colourless vapour, the density of which is 6-97 as 
 compared with that of atmospheric air, and 100 as compared with hydrogen. 
 
 Mercury is not readily oxidised when exposed to atmospheric air at the ordinary 
 temperature, unless it is in contact with greasy substances, but when heated in con- 
 tact with atmospheric air it is gradually oxidised and converted into mercuric oxide. 
 It combines readily with chlorine or bromine, and with sulphur or iodine, when 
 rubbed with those substances ; it also unites with many of the metals at the ordinary 
 temperature. It is not acted upon by hydrochloric acid even when heated with it, 
 but sulphuretted hydrogen or hydriodic acid is slowly decomposed when in contact 
 with mercury. Strong sulphuric acid has no action upon mercury, unless heated 
 together with it, and then, if the acid be in excess, mercuric sulphate is formed, and 
 sulphurous oxide given off; but if mercury be in excess, mercurous sulphate is formed. 
 Nitric acid dissolves mercury rapidly at the ordinary temperature, with evolution of 
 nitrous fumes, forming mercuric nitrate if the acid is in excess, and when nitric acid 
 is warmed with excess of mercury, basic mercurous nitrate is formed; dilute nitric 
 icid dissolves mercury slowly, forming neutral mercurous nitrate. 
 
 Q G 2 
 
452 
 
 MERCURY. 
 
 Preparation. The ores from which mercury is principally extracted contain the 
 metal in the state of mercuric sulphide, associated with various argillaceous and earthy 
 substances. The mercury is separated either by heating the ore in contact with at- 
 mospheric air, so as to oxidise the sulphur and form sulphurous oxide while the 
 mercury is volatilised,- - 
 
 HgS + 20 = S0 2 + Hg 
 232 32 64 200 
 
 or by heating a mixture of the ore with lime or some other substance capable of com- 
 bining with the sulphur and separating the mercury in the metallic state. With lime 
 the reaction which takes place is as follows : 
 
 4HgS J- 4CaO = 3CaS + CaS0 4 + 4Hg 
 928 800 
 
 In both cases the mercury is volatilised and the vapour condensed by passing the 
 gaseous products through a series of clay tubes or large chambers built of brick. 
 
 The mercurial fahl-ores which occur in Hungary are worked in a very rude way 
 by roasting them in heaps surrounded by walls in which flues are formed, and the 
 mercury is obtained as a by-product, much in the same manner that sulphur is ob- 
 tained in roasting copper ores (see p. 401); in fact, the roasting of these ores is carried 
 out mainly as a necessary preparation for smelting them as copper ores in the usual 
 way. Part of the mercury is condensed in the upper layer of finely divided ore with 
 which the heaps are covered, and when the operation of roasting is ended this is care- 
 fully removed and washed with water so as to separate the metallic mercury dis- 
 tributed amongst it. 
 
 The apparatus used for heating the ore sometimes consists of a number of close 
 iron vessels, like retorts, heated in a galley furnace ; reverberatory furnaces or kilns are 
 also used in some cases. 
 
 The treatment of mercury ores in closed vessels admits of a more ready and com- 
 plete condensation of metal than is the case when atmospheric air is mixed with the 
 vapour, but it is more costly. 
 
 In Germany, sandstone containing a very small amount 
 of cinnabar, varying from -005 to '01 per cent., is worked 
 by distilling it in cast-iron vessels of the form shown in the 
 accompanying drawing. The ore is broken into small 
 fragments and about fifty or sixty pounds placed in each 
 of the vessels together with some quick-lime. A number 
 of these vessels are then arranged in rows in a galley fur- 
 nace of the kind represented in plan, section and elevation 
 by figs. 344, 345, and 346. The necks of the iron vessels 
 (a a and bb} project beyond the side walls of the furnace, so 
 that stoneware receivers containing some water can be 
 adapted to them for the condensation of the mercury 
 vapour. The iron vessels are then gradually heated to 
 redness by making a fire upon the grate (c) extending from 
 end to end, with an ash pit (d) beneath. In the arch 
 covering the iron vessels openings (e e) are made by which 
 the draught of the furnace is regulated. 
 
 When the distillation is completed, the contents of the 
 receivers are poured into a wooden bowl, where the metallic 
 mercury sinks to the bottom, and the black substance sus- 
 pended in the water is washed into a vat placed under- 
 neath. This black substance, containing mercury in the state 
 of sulphide and oxide, is allowed to deposit, then dried and 
 distilled with lime in the same manner as the ore. 
 
 A similar method of working mercury ore is practised in 
 Transylvania, but stoneware retorts are used for the heat- 
 ing of the ores, and the operation is conducted in a very 
 crude manner. 
 
 An improved form of apparatus for heating mercury 
 ores is represented in vertical section lengthways by fig. 
 347. It consists of a series of cast-iron retorts (a.) open at 
 one end and each fitted with a lid by which the retorts can 
 be completely closed and their contents kept from contact 
 with atmospheric air. At the opposite end of each retort 
 is a delivery tube (b) through which the mercury vapour 
 escapes when the mixture of ore and lime in the retort la 
 
 .FiG. 346. 
 
EXTRACTION OF MERCURY FROM ITS ORES. 453 
 
 heated. The delivery tubes (b) are connected with a tubular vessel (c) containing 
 water and arranged much in the same manner as the hydraulic main used in gas 
 works, the ends of the delivery tubes 
 dipping just below the surface of the water. 
 The retort is heated by the fireplace (i), and 
 as the delivery tube dips under water a 
 fresh charge of ore and lime can be intro- 
 duced immediately after the contents have 
 been worked off and drawn out. 
 
 These retorts are arranged in sets oi 
 three within an arch placed over each 
 furnace, as shown in the transverse section 
 fig. 348, where three of these sets of retorts 
 are placed side by side, and fig. 349 repre- 
 sents an elevation of the ends of the retorts 
 to which the delivery tubes are attached, 
 together with a longitudinal section of the 
 cylindrical tube (c c) into which the ends 
 of the delivery tubes (b b b) of the retorts 
 are fitted. At one end of the hydraulic 
 main there is a water valve (g} which 
 serves to counteract the effects of unequal F IQ - 347. 
 
 pressures caused by sudden expansion or contraction in the hydraulic main. The 
 
 FIG. 348. 
 
 FIG. 349. 
 
 hydraulic main condenser is placed in a square trough made of wood, as shown in the 
 section fig. 347, and water is made to flow through it by which the contents of the 
 condenser are cooled. The condensed mercury collects at the bottom of the hydraulic 
 main, which has a slight inclination, and the mercury flows towards the lower end (A) 
 and falls through the tube (D) into the iron receiver (), which is secured by a padlock 
 (H) and is furnished with a graduated iron gauge rod (), by which the quantity of 
 mercury collected in the reservoir may be ascertained. 
 
 One of the forms of apparatus employed in Idria for the extraction oi mercury 
 
 
454 
 
 MERCURY. 
 
 from its ores is represented by figs. 350 to 353. It consists of a kiln in which the 
 
 mercury ore is heated in contact with 
 
 tl 
 
 atmospheric air and connected on 
 each side with a series of chambers 
 
 FIG 350 
 
 where the mercury vapour is con- 
 densed as it passes through them. 
 Fig. 350 gives a general view of the 
 apparatus in vertical section. In the 
 furnace (b) fuel is burnt to heat the 
 ore and the fire is regulated by the 
 ^ oor ( a )' Above the fireplace are 
 several arches indicated by the 
 
 numbers 1 " to 7, upon which the ore is placed through the opening (d) at the 
 upper part of the kiln. The products of combustion, mixed with mercury vapour, 
 
 pass ont of the kiln through the brick flues (e e) on each side, into the condensing 
 
 chambers 
 
 which are shown on a 
 
 -p, 
 
 larger scale in the horizontal plan, fig. 
 351. It will be seen that the condens- 
 ing chambers communicate with each 
 other by openings placed alternately at 
 the upper and lower parts of the 
 chambers, so that the smoke and vapour 
 pass up and down through the chambers 
 until the chimney (II) on each side is 
 reached. During the passage of the gas 
 and vapour, condensation takes place and 
 the mercury collecting at the bottom of 
 the successive chambers flows out into 
 
 the basins (mm) placed opposite the doors of the condensing 
 chambers which are shown in figs. 351 and 352. The condensed 
 mercury collecting in these basins flows then into the trough 
 (n n) and runs into a common reservoir in the direction of the 
 arrows. The arched passages (p p) shown in figs. 350, 351, and 
 352, admit of access to the sides of the furnace and the arches 
 (qq) figs. 350, 352 communicate with the flues (ee). The ele- 
 vation of one half of the apparatus fig. 352 shows the position 
 of the doors (sstt) by which access can be gained to the con- 
 densing chambers (/&), fig. 350, and the doors (uu) of the kiln 
 in which the mercury ore is heated. 
 
 Fig. 353 represents the floors (xyz} corresponding to the 
 doors (u w) of the kiln, and these floors are reached by stairs in 
 different parts of the building. This section also shows the 
 position of the fireplace (b) and of the arches (1 to 7) above 
 it ; (d) is the opening at the top of the kiln, and just below it 
 are the brick flues (e e) by which the smoke and vapour escape 
 into the condensing chambers. 
 In charging these kilns large blocks of the ore which is poorest in mercury are 
 placed upon the lower arches above the fireplace, above this the smaller fragments of 
 ore are placed, and on the middle arches the small ore containing a larger amount of 
 metal is placed in small pots. Upon the upper arches the more finely divided portion 
 of the ore is placed also in pots. All the doors are then closed and the fire being 
 lighted, it is kept up until the whole furnace has acquired a cherry red heat. The 
 distillation lasts from ten to twelve hours, and the kiln is then allowed to cool during 
 several days, after which the exhausted residues are drawn and a fresh charge put in. 
 At Almaden in Spain the mercury ore is heated in contact with atmospheric air in 
 
 FIG. 353. 
 
EXTRACTION OF MERCURY FROM ITS ORES. 455 
 
 brick kilns, and the mercury vapour is condensed in earthen pipes called aludels, a 
 
 number of which are fitted together so 
 
 as to form long channels for the pro- 
 
 ducts of combustion to pass through. 
 
 The general arrangement f this appa- 
 
 ratus is represented by figs. 354 and 
 
 355. The kiln (d) in which the ore is 
 
 placed is separated from the fireplace 
 
 \b) by a perforated brick arch on 
 
 which the mercury ore rests. The 
 
 fuel is introduced through the arch (a) 
 and below the fireplace is the ash pit 
 (c). In fig. 355 the same parts are 
 shown in plan. At the top of the kiln 
 (d) there are at one side a number of 
 openings (/) which communicate with 
 the rows of aludels placed on the slop- 
 ing terrace, at the lowest point of 
 which there is a gutter (g} into which 
 the condensed mercury runs out of a 
 hole in the last aludel, and then passes 
 through the wooden pipes (h h) into cis- 
 terns filled with water. 
 
 The uncondensed mercury vapour 
 passes on into the aludels on the oppo- 
 site sloping terrace and then through an 
 opening (/') into a chamber (&), where it 
 is made to pass to the bottom by the 
 partition (1), and is then condensed and 
 
 FIG. 354. 
 
 p 
 ' IG> 
 
 deposited in the cistern (). At the top of this chamber is an arch (ri) with an opening 
 through which the uncondensable gas escapes into another small chamber (&'). 
 
 FIG. 356 
 
 FIG. 357. 
 
 356 and 
 
 The arrangement of the series of aludels is shown more distinctly by figs. 
 357, as well as the connection between them on one side with the kiln and on the 
 other with the condensing tower (&). 
 
 The loss of mercury in working ores in this kiln is very considerable, since the 
 aludels are readily broken and the connections cannot be kept perfectly tight. In 
 addition to this disadvantage, the escape of mercury vapour has a prejudicial effect 
 upon the workmen, and as the operation has to be stopped when each charge of ore 
 has been exhausted, much time is lost in this way while the kiln cools sufficiently to 
 be opened for removing the residues. 
 
 The furnaces constructed by Hahner in Idria are intended to admit of continuous 
 
456 
 
 MERCURY. 
 
 working. They are represented by figs. 358 and 359. The mercury ore is heated in 
 the shaft (a) by means of a fire made on- the grate (c) ; this shaft is closed at the top 
 and the ore is fed in through a hopper (b), In the flue (/) which connects the shaft 
 with the first of a series of condensation chambers (g g g) there is a sliding damper (e), 
 which is closed while the exhausted ore is being drawn from the shaft and replaced by 
 a fresh charge. The condensing chambers (g g g) are constructed of brick, and are 
 
 FIG. 368. 
 
 FIG 359. 
 
 covered on the top with iron plates (i i, fig. 359), over which a stream of cold water is 
 made to run. These chambers are six in number, communicating by the openings (&) 
 at the bottom, and the last of the series communicates in the same way with the 
 chimney (A). The floor or sole (I) of each condensing chamber is made of loam beaten 
 down upon a bed of brick, to form a hollow in which the condensed mercury collects. 
 
 In charging this kiln some bricks are placed upon the sloping grate (c") and upon 
 them a quantity of brushwood or coal ; alternate layers of ore and coal are then thrown 
 in until the shaft is filled to the requisite height, and after setting light to the brush- 
 wood the fire is made to burn gradually for several hours. After the end of the 
 second day the fire should become visible at the top of the materials in the shaft, and 
 then the regular charging of fresh ore and fuel is commenced, about seven hundred- 
 weight of ore, together with 3 or 4 per cent, of fuel, being thrown in through the 
 hopper (6) at intervals of an hour or rather less, while, at the same time, the exhausted 
 residue of the ore is drawn out from the bottom of the shaft into waggons running 
 upon a tramway under the kiln. 
 
 Even in the kilns constructed on this plan there is a great waste of mercury, 
 amounting to about one-third of the contents of the ore ; but these kilns do away 
 with the necessity for interrupting the operation, and they are, in this respect, an 
 improvement upon those previously described. In some places the soles of the con- 
 densation chambers are constructed of cast iron, with a tube through which the 
 mercury collecting upon them runs out into a receiver outside, 
 
EXTRACTION OF MERCURY FROM ITS ORES. 457 
 
 Reverberatory furnaces are also used for extracting mercury from its ores. Those 
 employed in Idria are represented together with the condensing arrangements by figs. 
 360 to 362. 
 
 FIG. 361. 
 
 The furnace () is fed through the hopper (b) and closed by the sliding door 
 (m). Between the hearth and the fire bridge is a space (c) for receiving the roasted 
 ore. The mercury vapour passes from the furnace first into the chambers (d d), and 
 then through long cast-iron pipes (//// ) kept cool by water dropping on them from 
 the gutter (e e}. The uncondensed vapour escaping from these pipes passes into the 
 two chambers (ffff), from thence into other two chambers (cf tf) above, and then into 
 another set of cast-iron pipes (h h) also kept cool by water supplied from the gutters 
 (ee), and lastly the uncondensable gas escapes through 
 the brick chamber (d') into the chimney (&), which 
 is divided into compartments as shown in the transverse 
 section fig. 362, by two vertical walls ('*) that make 
 the gas pass up and down before escaping into the 
 air through the openings (I I) at the top of the chimney. 
 
 In working this furnace the ore is spread upon the 
 hearths (a a), the working doors (m) closed securely, and 
 the ends of the hearths nearest to the door are heated to 
 redness ; the fire is then let nearly out, the ore stirred 
 for a few minutes, then heated again to redness, and 
 lastly raked down through the opening (c). The hot ore 
 on the middle of the hearth is then drawn forward, and 
 that at the further end of the hearth placed in the middle, 
 while a fresh charge of ore is introduced through the 
 hopper (b), and then the heating of the ore to redness is 
 carried out again as before. In this way the fresh ore is 
 gradually heated while a part of the charge is being roasted. 
 The mercury collects chiefly in the lower tubes (//) 
 and the chambers (g g) and part of it runs out from them 
 into the vessels (n n\ The deposit in the chambers 
 (g g' d' d'} and that in the iron tubes contains about fifty 
 per cent, of mercury ; it is first dried, and after the mer- 
 cury has been drained off the residue is distilled. 
 
 FIG. 362. 
 
458 MEECURY. 
 
 Uses. Mercury is employed for a great number of purposes. On account of its 
 great density and uniform expansion it is used in the construction of thermometers, 
 barometers, and other kinds of experimental apparatus. A considerable quantity is 
 used in the extraction of silver and gold from their ores ; it is also used in various 
 forms of combination for medicinal purposes, and several of the compounds of mercury 
 with other metals are employed under the name of amalgams for various technical 
 purposes. 
 
 Compounds. Mercury forms two well-defined series of compounds, mercuric 
 compounds, in which it is divalent, and mercurous compounds, in which it is 
 apparently monovalent. The compounds of the latter series correspond in constitu- 
 tion to the cuprous compounds, and are readily converted into mercuric compounds by 
 oxidising agents ; but they are generally much more stable substances than the 
 cuprous compounds. Both mercuric oxide HgO, and mercurous oxide Hg 2 0, are 
 basic, and combine with acid oxides, forming saline compounds. There is but one 
 compound of mercury with sulphur, mercuric sulphide HgS, and the precipitate ob- 
 tained on adding sulphuretted hydrogen to solutions of mercurous salts is a mixture 
 of this sulphide with metallic mercury. The chlorides, bromides, and iodides are 
 represented by the formulae HgCl 2 , HgBr 2 HgI 2 , and Hg 2 Cl 2 , Hg 2 Br 2 , Hg 2 I 2 . 
 
 Many of the mercuric compounds combine with corresponding compounds, forming 
 a great k number of double salts, in which the mercury compounds act the part of 
 acid ; thus, for instance, mercuric oxide combines with potassium iodide, forming 
 potassio-mercuric iodide KI, HgI 2 , or, as it is sometimes called, potassium iodo-hydrar- 
 gyrate. 
 
 Mercurial compounds of both series combine with ammonia, forming a great 
 variety of substances, in which the mercury takes the place of part of the hydrogen in 
 ammonium. The substance known as white precipitate is of this nature, and its 
 composition is represented by the formula (NH 2 Hg)Cl. Hahnemann's soluble 
 mercury is another compound of this kind, the constitution of which is represented by 
 the formula (Hg 3 HN)N0 3 H 2 0, corresponding to ammonium nitrate, in which three- 
 fourths of the hydrogen of the ammonium is replaced by mercury. 
 
 Mercury also forms compounds with alcohol radicles. 
 
 The alloys of mercury with other metals are called amalgams, and those of de- 
 finite composition are solid, while the liquid amalgams are probably solutions of those 
 substances in mercury ; in many cases the excess of mercury can be separated from 
 the solid amalgam by pressure. 
 
 Mercury unites with the alkali metals with very considerable evolution of heat ; 
 the alloy of potassium with 70 parts of mercury is solid ; that with 30 parts of 
 mercury is hard and brittle. The alloy of sodium with 30 parts of mercury is hard 
 and crystalline ; that with 60 parts of mercury becomes pasty when slightly warmed. 
 
 The amalgams of barium, calcium, etc., are analogous to those of the alkali metals, 
 and they may be obtained by decomposing saturated solutions of the respective salts 
 by means of sodium amalgam. 
 
 Aluminum, according to Deville, does not unite with mercury to form an amalgam. 
 
 Magnesium forms with mercury a solid amalgam when the metals are heated to- 
 gether. Zinc unites with mercury slowly at the ordinary temperature, but readily 
 with the aid of heat. The alloy of zinc with one-eighth its weight of mercury is very 
 brittle ; that with one-sixth of mercury melts at the boiling point of olive oil. The 
 alloy containing 80 per cent, of mercury is brittle and pulverulent ; it is used for 
 coating the rubbers of electrical machines. 
 
 When sheet zinc moistened with a dilute acid is rubbed with mercury, hydrogen is 
 disengaged and the surface of the zinc is amalgamated ; the zinc plates of galvanic 
 batteries are prepared in this way. 
 
 Lead unites readily with mercury, forming an amalgam which is liquid even when 
 containing one-third its weight of lead. The metals contract considerably in uniting 
 and the amalgam has a higher specific gravity than either of them. The presence of 
 a very small proportion of lead about 0'02 per cent. in mercury renders this metal 
 more suitable for barometers and thermometers, since it is then less disposed to form 
 globules that adhere to the glass. 
 
 Copper does not unite very readily with mercury except in the presence of an acid 
 or when one or other of the metals are in the state of a salt, as when mercury is rubbed 
 together with verdigris, or copper foil is immersed in a solution of a mercury salt. 
 When mercury is covered with a solution of cupric sulphate and placed in contact 
 with the negative pole of a voltaic battery while the positive pole is connected with a 
 wire dipping into the cuprie sulphate solution, it becomes saturated with copper. 
 
 The alloy of copper and mercury containing about 30 per cent, of copper is crys- 
 talline and harder than zinc ; it has the property of becoming soft and plastic when 
 rubbed in a warm mortar, and then of becoming hard again when kept ; on this account 
 
MERCURY OXIDES. 459 
 
 it is sometimes used by dentists for stopping decayed teeth. This alloy is prepared 
 by mixing mercurous sulphate and finely divided metallic copper under warm -water. 
 After rubbing them together for several minutes the water is poured off and replaced 
 by fresh, this being continued so long as the water has any blue colour. 
 
 Silver unites with mercury but slowly at the ordinary temperature, and rapidly 
 when the finely divided metal is heated and brought into contact with the mercury. 
 Amalgams of silver and mercury in various proportions occur naturally ; that called 
 arquerite is crystalline and has a composition represented by the formula AgHg 3 ; 
 other varieties approximate to the formulae AgHg and Ag 2 Hg s . 
 
 The artificially prepared silver amalgam is sometimes soft and granular and some- 
 times crystalline. The union of the metals is attended with considerable contraction. 
 
 The other amalgams will be described under the heads of the several metals. 
 
 1VIERCUROUS OXIDE. 
 
 FORMULA Hg 2 0. MOLECULAR WEIGHT 416. 
 
 History. The existence of this compound was ascertained by the study of the 
 difference between the solution obtained by dissolving mercury in nitric acid with and 
 without the aid of heat. In 1775 Bergman showed that these solutions gave different 
 precipitates with reagents, but it was not until a later period that this difference was 
 ascribed to the different degrees of oxidation of the mercury. 
 
 Characters. Mercurous oxide is a dark brown pulverulent substance insoluble 
 in water ; it is decomposed slowly by exposure to light, and readily when rubbed or 
 warmed, into mercuric oxide and metallic mercury. As obtained by the action of 
 caustic alkali upon calomel, it has a specific gravity of 8*95. 
 
 Mercurous oxide forms with acids a number of saline compounds in which the 
 metal appears to be monovalent ; the composition of the nitrate is represented by 
 the formula Hg 2 2NO s , that of the sulphate by the formula Hg 2 S0 4 . There are also a 
 number of basic salts. 
 
 1VXERCTJRIC OXIDE. 
 
 FORMULA HgO. MOLECULAR WEIQHT 216. 
 
 History. This substance was known to Greber, and it was prepared by him by 
 heating mercury in contact with atmospheric air. Raymond Lully obtained it by 
 heating mercuric nitrate ; in 1774 Bayen observed that by mere heating it was con- 
 verted into metallic mercury and a gas, and that the mercury thus obtained weighed 
 less than the oxide operated upon. The discovery of o-xygen by Priestley and the pub- 
 lication of Lavoisier's views on the nature of metallic oxides took place immediately 
 after these important facts were made known. 
 
 Characters. Mercuric oxide is either a bright red crystalline powder, or when 
 prepared by precipitation from a mercuric salt, a pale orange yellow powder. Its 
 specific gravity is 11*136. When heated its colour becomes darker and almost black, 
 but on cooling it resumes its original tint. When more strongly heated it is decom- 
 posed into metallic mercury and oxygen gas ; it is also decomposed to some extent 
 when exposed to sunlight. The oxide obtained by precipitation is more readily de- 
 composed than that obtained by heating the nitrate or by the oxidation of mercury, 
 probably owing to the different states of aggregation. 
 
 Mercuric oxide is very sparingly soluble in water, and the solution has a strong 
 metallic taste. Chlorine converts it into mercuric chloride with evolution of oxygen, 
 at a high temperature, and at lower temperatures hypochlorous acid is also formed. 
 Mercuric oxide combines with lime and baryta, forming soluble crystalline substances ; 
 it also combines with caustic alkalies and with ammonia. With acid oxides it forms 
 saline compounds, many of which are crystallisable, but are decomposed by water un- 
 less there is excess of acid present. The composition of the sulphate is represented 
 by the formula HgS0 4 , that of the nitrate by the formula Hg2NO s . There are also a 
 number of basic salts. 
 
 Preparation. Mercuric oxide maybe prepared by adding caustic potash or 
 soda, to a solution of mercuric chloride, or by gradually heating mercuric nitrate until 
 nitrous vapour is no longer given off, and when thus prepared it is known as red 
 precipitate. It is also formed by direct combination when mercury is kept for some 
 
460 MERCURY. 
 
 time at a temperature near the boiling point in contact with amospheric air until the 
 whole of the metal is oxidised. 
 
 MERCUROUS CHLORIDE. 
 
 FORMULA Hg 2 Cl 2 . MOLECTJLAB WEIGHT 471. 
 
 History. This substance was known under the name of mercurius dulcis at the 
 early part of the seventeenth century, and had been previously obtained mixed in various 
 proportions with mercuric chloride. Under the name of calomel (from Ka\bs and 
 jueAas) it was used medicinally, and it is said that this designation had reference to 
 its efficacy in bilious disorders. The nature of the difference between this substance 
 and mercuric chloride was not clearly ascertained until the time of H. Davy. 
 
 Occurrence. Mercurous chloride occurs naturally as hornquicksilver, 
 associated with cinnabar, but it is generally prepared artificially. 
 
 Characters. Mercurous chloride in the form of horn quicksilver is either in 
 prismatic crystals or granular masses of a dirty white colour. As prepared by sub- 
 limation, it is also crystalline or in fibrous masses ; its density is 7'14. As obtained 
 by precipitation from a solution of a mercurous salt, it is a heavy white powder with 
 a slight tinge of yellow, tasteless, inodorous, and quite insoluble in water. When 
 heated it does not melt, but at a red heat it volatilises without decomposition ; by ex- 
 posure to light it gradually acquires a grey colour. 
 
 Mercurous chloride is dissolved by nitric acid with evolution of nitrous vapour, 
 and the solution contains mercuric chloride and nitrate. Sulphuric acid does not act 
 upon it unless heated. By boiling with hydrochloric acid mercurous chloride is gra- 
 dually converted into mercuric chloride and metallic mercury ; the same change is 
 more readily produced by solutions of the alkaline chlorides, and it takes place to a 
 slight extent when mercurous chloride is boiled with water. Solutions of caustic 
 alkali convert mercurous chloride into black mercurous oxide, and solution of ammonia 
 also converts it into a black substance which is the chloride of dimercurosammonium 
 NH 2 Hg 2 ei. 
 
 A similar compound NH 3 HgCl is formed when precipitated mercurous chloride is 
 exposed to the action of dry ammonia at ordinary temperatures ; the gas is absorbed, 
 and the black powder formed gives off ammonia, when exposed to the air, leaving 
 white mercurous chloride. 
 
 Preparation. Mercurous chloride may be obtained by mixing a solution of 
 sodium chloride with a warm dilute solution of mercurous nitrate ; the chloride solu- 
 tion must be added in excess, and the precipitate well washed with boiling water. It 
 is however generally prepared by sublimation ; for this purpose mercuric chloride 
 is rubbed with three-fourths of its weight of metallic mercury and some water and 
 alcohol, until the globules of mercury entirely disappear and the mercuric chloride 
 has been to a great extent converted into mercurous chloride : 
 
 HgCL, + Hg = Hg 2 CL, 
 275 200 475 
 
 The mixture is then sublimed in a glass vessel. 
 
 It may also be prepared by heating an intimate mixture of mercurous sulphate 
 and sodium chloride until the mercurous chloride sublimes : 
 
 Hg 2 S0 4 + 2NaCl = Na^SO, + Hg 2 Cl 2 
 496 , 117 142 471 
 
 The mercurous sulphate is prepared for this purpose by rubbing mercuric sulphate 
 with sufficient mercury to produce the alteration : 
 
 HgS0 4 + Hg = Hg 2 S0 4 
 296 200 496 
 
 The mercurous chloride obtained by sublimation in the form of a dense fibrous 
 mass is powdered and thoroughly washed. Sometimes, in order to obtain the substance 
 in a very fine powder, steam is injected into the vessel receiving the vapour of mer- 
 curous chloride, or the vapour is condensed in a large brick chamber. In both cases 
 it is necessary to wash the product obtained in order to remove any mercuric chloride 
 that may be mixed with it. 
 
 Use. Mercurous chloride is used largely in medicine. 
 
MERCURIC SULPHIDE. 461 
 
 TOERCURIC CHLORIDE. 
 
 FORMULA HgCl 2 . MOLECULAR WEIGHT 271. 
 
 History This substance, commonly called corrosive sublimate, was well 
 known to Geber and Albertus Magnus, and in the time of Basil Valentin it was an 
 article of commerce under the name of mercurius sublimatus. 
 
 Characters. Mercuric chloride is a colourless crystallisable substance. The 
 specific gravity is 5*42. It melts at 265, and boils at 295, volatilising more readily 
 than mercurous chloride. It has an acrid metallic taste and is very poisonous. It 
 dissolves in water in the following proportions according to Poggiale: 
 
 Temperature. Quantity of Salt. 
 
 , 573 
 
 20 7-39 
 
 100 parts of water at $ *<>lve 62 
 
 80 24-32 
 
 V100 58-96 
 
 Mercuric chloride also dissolves in 2 - 5 times the weight of alcohol at the ordinary 
 temperature, and in rather more than its own weight of boiling alcohol. Ether 
 dissolves it almost in the same porportions. 
 
 Boiling hydrochloric acid dissolves mercuric chloride and appears to combine with 
 it, forming a double salt 2HgCl 2 . IIC1, which is decomposed by exposure to the air. 
 Mercuric chloride combines with other chlorides in a similar manner. The compound 
 with ammonium chloride HgCl 2 , 2NH 4 Cl.H a O has long been known under the name 
 of sal alembroth. 
 
 Mercuric chloride dissolves readily in nitric acia without alteration. It is not 
 acted upon by sulphuric acid. When intimately mixed with metallic mercury, it is 
 almost entirely converted into mercurous chloride ; caustic alkalies precipitate mercuric 
 oxide from a solution of mercuric chloride ; solution of ammonia abstracts half the 
 chlorine, and produces the substance known as white precipitate NH 2 HgCl, 
 according to the following equation : 
 
 HgCl 2 -i- 2NH 3 = NH 2 HgCl + NH 4 C1. 
 
 The dry salt absorbs gaseous ammonia rapidly, and forms a substance having the 
 composition HgCl 2 NH 3 which can be distilled without separation of ammonia, but is 
 decomposed by water. 
 
 Mercuric chloride combines with albumin, forming an insoluble white substance 
 which does not putrefy when kept. 
 
 Preparation. Mercuric chloride is formed by the direct combination of mercury 
 and chlorine ; by dissolving mercury with nitro-hydrochloric acid, containing a sufficient 
 amount of hydrochloric acid, or by dissolving mercuric oxide in hydrochloric acid. 
 
 It is prepared on the large scale by sublimation from a mixture of mercuric 
 sulphate and sodium chloride : 
 
 HgS0 4 + 2NaCl Na^SO, + HgCl 2 . 
 296 117 142 271 
 
 MERCURIC SUX.PRXDE. 
 
 FORMULA HgS. MOLECULAB WEIGHT 232. 
 
 History. This substance in its natural form has been known from a very 
 
 remote time, and was described under the name of Ktvi-dfiapi by Theophrastus, who 
 also speaks of its being made artificially, but it was often confounded with minium 
 or red lead, and with the resin called dragons' blood. The production of this sub- 
 stance by combining sulphur with mercury was, however, distinctly described by 
 Albertus Magnus, and in the time of Agricola cinnabar was made in this way at 
 Venice. The~black substance obtained by rubbing hot mercury with melted sulphur 
 was first described by Turquet de Mayerne at the commencement of the seventeenth 
 century, and in 1689 Harris prepared it by rubbing mercury with powdered sulphur. Its 
 reparation from a solution of mercury by means of an alkaline sulphide was described 
 y Jacobi in 1757, and under the name of pulvis hypnoticus it was used in medicine, 
 "he production of cinnabar by shaking mercury with a solution of sulphur in ammonia 
 described by Schulz in 1687, and in 1797 Kirchhoff discovered a method of 
 
462 MERCURY. 
 
 preparing it in this way. T?p to a comparatively recent period, however, it was con- 
 sidered that the composition of the black substance was different from that of 
 cinnabar, until Fuchs showed that the difference in colour was due to the state of 
 
 Occurrence. Mercuric sulphide occurs naturally as cinnabar, associated with 
 metallic mercury and amalgam, disseminated throughout slaty or calcareous rocks 
 which are not unfrequently bituminous : it constitutes the principal ore of mercury. 
 
 Characters. Mercuric sulphide as it occurs naturally is either in the form of 
 hexagonal prisms or fibrous compact masses. It has a dark red colour and consider- 
 able lustre. The specific gravity is 8'0 to 8'99. The powder has a fine scarlet 
 colour. The artificially prepared substance known as vermilion is a very finely 
 divided crystalline powder. 
 
 The amorphous sulphide obtained by precipitation is a black powder, and when 
 heated in a close vessel it volatilises without melting, forming a crystalline sublimate. 
 
 The black amorphous sulphide obtained by precipitation is converted by contact 
 with alkaline persulphides into the crystalline red sulphide. This change takes 
 place slowly at the ordinary temperature and more rapidly by the aid of heat. 
 
 The crystalline sulphide acquires a dark colour when heated, but resumes the red 
 colour on cooling,. if the heat has not been sufficient to cause volatilisation. 
 
 When heated in contact with atmospheric air, mercuric sulphide is decomposed, 
 the sulphur being converted into sulphurous oxide, and the mercury volatilised. 
 Heated with caustic alkalis, alkaline earths, or alkaline carbonates, it is also decom- 
 posed, mercury being set free, as shown by the following equation : 
 
 4HgS + 4CaO = 4Hg + 3CaS + CaS0 4 . 
 
 Mercuric sulphide is decomposed by strong nitric acid with separation of sulphur ; 
 it is readily dissolved by nitro-hydroehloric acid, but is scarcely at all acted upon by 
 dilute nitric acid ; the amorphous substance is dissolved by potassium sulphide which 
 combines with it, forming a crystallisable substance HgSKS. 5H 2 0, which is decomposed 
 by water. Mercuric sulphide is decomposed when heated and rubbed with finely 
 divided copper or iron. 
 
 Preparation. The amorphous sulphide is formed when sulphuretted hydrogen 
 is passed through a solution of a mercuric salt, or when mercury and sulphur are 
 rubbed together for a considerable time ; the product thus obtained was formerly 
 known by the name of Aethiops mineralis, and it is entirely soluble in boiling caustic 
 potash. 
 
 The crystalline sulphide, or vermilion, is prepared by subliming an intimate mix- 
 ture of mercury or mercuric oxide and sulphur. When melted sulphur is mixed with 
 5 or 6 times its weight of mercury, and the mixture heated with constant stirring, 
 till the sulphur begins to become thick, combination takes place suddenly with a 
 crackling noise and evolution of heat and light. The substance thus obtained has a 
 blackish-red colour, and consists partly of cinnabar with some amorphous sulphide, 
 uncombined mercury and sulphur ; when powdered and gradually heated to redness 
 in a close vessel a sublimate of pure cinnabar is obtained. 
 
 The subliming vessels used for making cinnabar are earthen cylinders about 4 feet 
 long, closed at one end and glazed inside ; these are set vertically in a furnace so that 
 the bottom can be heated to redness ; the mixture of mercury and sulphur is thrown 
 into each, and when the excess of sulphur has been driven off, the open ends of the 
 cylinders are closed with cast-iron plates, upon which the sublimed cinnabar con- 
 denses. 
 
 Uses. Mercuric sulphide is chiefly used in the form of vermilion as a pigment. 
 
 MERCUROUS SULPHATE. 
 
 FORMULA Hg 2 S0 4 . MdLKCULAR WEIGHT 496. 
 
 This salt is prepared by heating sulphuric acid with excess of mercury until the 
 whole is converted into a white powder, care being taken that the heat is not allowed 
 to rise to the boiling point of the acid ; the residue is then washed to remove free 
 acid. 
 
 Mercurous sulphate is sparingly soluble in water, requiring 500 parts of cold 
 water, and 300 parts of hot water for solution. It crystallises from the hot solution 
 in rhombic prisms. 
 
 
MERCURY NITRATES. 463 
 
 MERCURIC SULPHATE. 
 
 FOBMULA HgS0 4 . MOLECULAR WEIGHT 296, 
 
 This salt is prepared by heating mercury with rather more than its weight of 
 sulphuric acid, until sulphurous oxide is no longer given off and a dry saline mass is 
 formed : 
 
 Hg + 2H 2 S0 4 = HgS0 4 + S0 2 + 2H 2 0. 
 
 200 196 296 64 36 
 
 Mercuric sulphate melts at a red heat, but is partially decomposed when volatilised ; 
 it is decomposed by water into an acid salt which dissolves, and an insoluble basic 
 salt of a lemon -yellow colour, formerly known as turpeth mineral: 
 
 4HgS0 4 = HgS0 4 2S0 3 + HgS0 4 2HgO. 
 
 MERCUROUS NITRATE. 
 
 FORMULA Hg 2 2N0 3 . MOLECULAR WEIGHT 524. 
 
 This salt is formed when moderately strong nitric acid is digested with an excess 
 of mercury in the cold, and it is deposited in the form of crystals containing one 
 molecule of water, which may be dissolved in a small proportion of water, but are 
 decomposed by a larger proportion, forming an insoluble yellow precipitate of basic 
 mercurous nitrate Hg 2 2N0 3 .Hg 2 0,H 2 ; there are several other basic mercurous 
 nitrates, some of which are soluble and are deposited in crystals from a hot solution 
 of the neutral salt in contact with metallic mercury. 
 
 Mercurous nitrate forms double salts with barium, strontium, and lead nitrates, 
 and the solution is decomposed by ammonia, yielding a black precipitate called 
 Hahnemann's soluble mercury, the composition of which varies according to 
 the conditions under which it is produced. (See p. 458.) 
 
 MERCURIC NITRATE. 
 
 FORMULA Hg2N0 3 . MOLECULAR WEIGHT 324. 
 
 This salt is formed when mercuric oxide is dissolved in excess of nitric acid ; by 
 evaporating the solution at a gentle heat, a syrupy liquid is obtained, containing the 
 salt in a hydrated state, and by exposing this liquid over sulphuric acid, it deposits 
 crystals having the composition represented by the formula 2(Hg2N0 3 )H 2 0. 
 
 Mercuric nitrate is readily decomposed by water with formation of a white pre- 
 cipitate consisting of a basic salt insoluble in water, and convertible into red mercuric 
 oxide, by washing with large quantities of water. Another basic nitrate is formed 
 when mercury is dissolved in boiling nitric acid, and it is deposited as the solution 
 cools in needle-shaped crystals, consisting of Hg2N0 3 ,HgO. A solution of mercuric 
 nitrate digested with excess of mercury yields mercurous nitrate. ^ 
 
 Mercuric nitrate combines with mercuric cyanide, mercuric iodide, and argentic 
 iodide, forming double salts which are crystallisable ; also with mercuric phosphide 
 and mercuric sulphide. 
 
TIN. 
 
 SYMBOL Sn. ATOMIC WEIGHT 118. 
 
 History. It is at least tolerably certain that in the first century of our epoch 
 this metal was indicated by the term Kafffflrepos, and that it was the plumbum 
 candidum or album mentioned by Pliny. Whatever may have been known of this 
 metal prior to that time, it probably was not regarded as being essentially different 
 from lead, which was termed by the Romans plumbum nigrum. The name stannum 
 was used by Pliny to denote an alloy of lead, and it is only since the fourth century 
 that this term has been used as the equivalent of Kairfflrepos to denote tin. In Pliny's 
 time the art of coating copper vessels with tin was known ; the tinning of iron is 
 mentioned by Agricola, but it appears to have been little known at that time, and 
 it is commonly stated to have been discovered in Bohemia about the year 1620 ; a 
 hundred years afterwards it was practised in England and somewhat later in France. 
 
 Occurrence. Tin does not occur naturally in the metallic state, but chiefly in 
 combination with oxygen, as cassiterite Sn0 2 , which is the principal source of this 
 metal. It also occurs to some extent combined with sulphur, cuprous sulphide, and 
 ferrous sulphide, or zinc sulphide, asstannine, or tin pyrites Cu 2 S,FeS,SnS 2 . 
 
 Characters. Tin is a white metal closely resembling silver in appearance ; its 
 specific gravity is 7'29. When rubbed it has a peculiar smell. It is harder than 
 lead, takes a high polish, and is very malleable ; when bent it gives a crackling sound. 
 It is sufficiently ductile to be drawn into wire when slightly warmed, but its tenacity 
 is not much greater than that of lead. 
 
 Tin melts at from 222 to 237 without sensible volatilisation, but it boils at a 
 white heat. When exposed to the atmosphere at the ordinary temperature it does 
 not oxidise, but is soon tarnished by impure air, probably owing to the formation of 
 sulphide on the surface. When heated and exposed to moist air, a film of oxide is 
 formed on the surface. At a red heat it decomposes steam and is oxidised, while 
 hydrogen is liberated. When melted in contact with atmospheric air the metal is 
 oxidised, and at a full white heat it burns with a bright flame, stannic oxide being 
 formed. 
 
 Tin is dissolved slowly by dilute hydrochloric acid, and rapidly by the strong acid 
 with the aid of heat, stannous chloride being formed and hydrogen evolved ; it is 
 but little acted upon by dilute sulphuric acid, even when heat is applied, but the 
 concentrated acid acts upon the metal and sulphurous oxide is produced. Strong 
 nitric acid has no action upon tin, but dilute nitric acid acts violently and converts 
 the metal into the insoluble form of stannic acid. Melted caustic alkalies oxidise and 
 dissolve tin, melted alkaline nitrates have the same action. Tin combines readily 
 wilh chlorine, bromine, sulphur, or phosphorus, when heated with these substances. 
 
 The tin of commerce is seldom quite pure, but generally contains either arsenic, 
 lead, iron, or copper, in small proportions, sometimes antimony, zinc, bismuth, manga- 
 nese, tungsten, molybdenum and gold. 
 
 Tin has a remarkable tendency to crystallise, and on washing the surface of the 
 metal with warm dilute nitro-hydrochloric acid, the crystalline structure becomes 
 apparent, owing to the unequal reflection of light from the faces of the crystals exposed 
 by the action of the acid. 
 
 Preparation. The only ore from which tin is extracted is cassiterite, or native 
 stannic oxide, and as this mineral is generally associated with sulphuretted and 
 arsenical compounds, the ore is subjected to several operations to purify it, from these 
 admixtures before the oxide is reduced. To a great extent these preliminary opera- 
 tions are mechanical, and consist in first washing the finely divided ore with water so 
 as to separate those impurities which are less dense than stannic oxide, and by reason 
 of the great density of this substance its concentration and purification by this means 
 can be carried to a considerable extent. The denser impurities which remain mixed 
 with the stannic oxide after washing consist of metallic arsenides and sulphides, for 
 
ROASTING OF TIN ORB. 
 
 465 
 
 the separation of which the washed material is next roasted in contact with atmo- 
 spheric air, by which means sulphur and arsenic are oxidised and separated, while the 
 metals combined with these substances are converted into oxides or soluble sul- 
 phates ; the roasted material is then washed again with water to dissolve out the 
 soluble salts and separate the insoluble oxides, which are inferior in density to stannic 
 oxide. The residue left after this treatment of the ore is called black tin. 
 
 The smelting of tin ore thus prepared is effected either in reverberatory furnaces 
 or shaft furnaces, by heating the oxide with coal or charcoal and lime, and the 
 chemical change involved in this operation consists chiefly in the reduction of the 
 stannic oxide by the carbonaceous material used as fuel. The temperature requisite 
 for this reduction is very high, and sufficient to effect the reduction of other metallic 
 oxides present in the ore, as well as to determine the combination of stannic oxide 
 with silica ; so that while the reduced metal thus obtained is impure, and requires re- 
 fining, the slag or scoria produced still contains some tin, and is again smelted in a 
 similar manner. 
 
 Since tin ore frequently contains a considerable amount of arsenic, the operation 
 of roasting is a necessary part of the preliminary treatment. In Cornwall it is con- 
 ducted in furnaces of the kind represented in vertical section and plan by figs. 363 
 and 364. 
 
 FIG. 363. 
 
 FIG. 364. 
 
 In working this furnace the bed is supplied with fresh ore through an opening 
 in the arch by which it is covered, and the ore lying upon the top of the arch is 
 dried by the waste heat. Close to the working door, which is at the end of the bed 
 opposite to the fire, there is an ascending flue by which the arsenical vapour passes 
 away into an arched tunnel of considerable length where the arsenous oxide is 
 condensed and deposited. While this operation is going on the finely divided ore on 
 the bed of the furnace requires to be frequently stirred in order to facilitate the 
 oxidation of the arsenical and sulphur compounds, by exposing fresh surfaces; and 
 mechanical arrangements have been devised for the purpose of effecting this. 
 
 11 11 
 
466 
 
 TIN. 
 
 One of these contrivances which has been extensively used is known as Bruuton s 
 Calciner, and its construction is represented by fig. 365. 
 
 FIG. 365. 
 
 It consists of a circular table constructed of fire bricks set in an iron frame 
 attached to a vertical shaft, the lower end of which rests on a step, and by means 
 of toothed wheels the table is made to revolve slowly. Above the table is a flat 
 arch or dome communicating with two furnaces, and the flame from them passes over 
 the surface of the table. At the centre of the dome is a hopper through which the 
 finely divided ore is fed on to the table, and to the top of the dome are attached cast- 
 iron frames fitted with blades, which stir up the ore as it is carried round on the 
 table, so that by the time the ore has passed from the centre of the table to the 
 circumference it has been sufficiently roasted, and then it falls down through an 
 aperture in the brick-work into a vault beneath. 
 
 Another kind of calciner is that of Messrs. Oxland and Hocking, in which the ore 
 is exposed to the action of flame and hot air from a furnace, in a long iron tube 
 supported in an inclined position and made to revolve on its axis by toothed wheels. 
 The lower end of this tube communicates with a furnace, and likewise with a 
 
TIN SMELTING. 
 
 467 
 
 chamber into which the roasted ore falls after having slowly travelled down the 
 entire length of the tube. The upper end of the tube is connected with condensing 
 chambers into which the products of combustion from the furnace pass, together with 
 the arsenical and sulphurous vapour given off from the ore in roasting. The interior 
 of the iron tube is lined with fire brick in such a manner as to form projecting 
 ridges parallel with the axis of the tube ; in this way the ore is raised as the tube 
 revolves, and is then shot off the ridges in a shower. 
 
 Tin ore sometimes contains a considerable amount of the mineral called wolfram, 
 which consists of ferrous tungstate and manganous tungstate, and it is desirable to 
 separate this substance before smelting the ore ; this cannot be done by washing, 
 since wolfram has nearly the same density as stannic oxide, and the ordinary calcina- 
 tion also has little effect upon it. Oxland has devised a method of separation which 
 consists in converting the tungstic oxide of the wolfram into sodium tungstate, which 
 is soluble in water and can be washed out, while the iron and manganese oxides 
 separated can be got rid of by washing. For this purpose the ore is mixed with 
 rather more soda ash than is sufficient to form sodium tungstate by acting upon the 
 wolfram present. This mixture is then heated upon the bed of a reverberatory 
 furnace until it becomes red hot and has a semi-liquid appearance. Meanwhile the 
 mass is well stirred, and after two or three hours it is drawn from the furnace : when 
 cold it is lixiviated with water until the soluble portion is extracted. The residue is 
 then washed with water so as to float off the oxides resulting from the decomposition 
 of the wolfram, and leave the heavier stannic oxide ready for reduction. 
 
 SMELTING IN KEVERBERATORT FURNACES. This plan is now generally adopted 
 in Cornwall, and the furnaces used for the purpose are represented by figs. 366 and 
 367. The bed (/) is slightly hollowed, 
 and the fire bridge (c) by which it is 
 separated from the fireplace (6) is 
 provided with an air channel (i) ex- 
 tending also under the bed of the 
 working chamber to prevent injury 
 by too great heating. The charging 
 door (d) is placed on one side of the 
 bed, and at the opposite side is a 
 tapping hole (</), by which the reduced 
 metal can be drawn off into the basins 
 (k k). The working door (e) is placed 
 at the end of the bed, and the gaseous 
 products pass off through the flue (I) 
 into a chimney (m) at the side. 
 
 The material to be smelted, which 
 should contain from 60 to 65 per cent, 
 of tin, is well mixed with about one 
 fifth its weight of small coal, some 
 slaked lime and fluor spar, sometimes 
 also with a little sodium chloride ; the 
 mixture is slightly damped with water 
 before it is charged into the furnace, 
 and after about five hours, when the 
 heat has been raised to a sufficient de- 
 gree, the mass is well stirred with a 
 rabble to facilitate the separation of the 
 reduced metal from the slag which is 
 drawn out through the door (e). The 
 metal and some liquid vitreous slag are 
 then run off through the tap hole (g*) into one of the basins (k k} where the melted 
 elag is skimmed off. 
 
 The metallic tin thus obtained is still impure, and it is refined by gradually heat- 
 ing it in a reverberatory furnace of the same construction as fig. 366 until the tin 
 melts and runs down upon the hearth, leaving a less fusible mixture of tin, iron, 
 arsenic, etc. By opening the tap hole the melted metal is drawn into one of the 
 basins (k Jc), under which there is a fire kept up sufficient to retain the metal in the 
 liquid state ; it is stirred with a piece of green wood for several hours, and the dross 
 formed meanwhile is skimmed off the surface. 
 
 Another mode of refining the tin is to lift the liquid metal in ladles and pour it 
 back from a considerable height into the pot. In either case, when the formation of 
 dross has ceased, the metal is ladled out into moulds. 
 
 H H 2 
 
468 
 
 TIN. 
 
 SMELTING IN SHAFT FURNACES. This method was formerly adopted in Cornwall, 
 but has now been 'superseded by the use of reverberatory furnaces ; it is however, 
 still followed in Saxony and Bohemia. The furnaces used at Altenberg are represented 
 by figs. 368 and 369. They are constructed of rough masonry (a a) lined with refractory 
 materials (b b b\ and the front wall (c) is supported upon a bar of iron, so as to leave 
 
 an opening (K) called the eye, 
 through which the melted con- 
 tents of the furnace are run out 
 into the fore hearth (i), formed 
 of stone blocks (&) with a lining 
 of loam (I), and kept in position 
 by the iron plate (p) ; the chan- 
 nel (m) connects the fore hearth 
 with another hemispherical re- 
 ceptacle (ri) made of cast iron 
 or stone, lined with loam and 
 furnished with a fireplace for 
 keeping the contents melted. 
 At one side of the fore hearth 
 provision is made for running 
 the slag over the wall (5) on to 
 a sloping iron plate (o), and 
 then into the tank (r) contain- 
 ing water. The sole (/) of the 
 furnace slopes from the back 
 to the upper level of the fore 
 hearth (i) and the melted pro- 
 ducts flow through the eye (h) 
 into the fore hearth. The blast 
 
 FIG. 368. 
 
 tuyere is inserted through the 
 opening (#). 
 
 FIG. 369. 
 
 The height of the furnace shaft depends very much on the amou:it of iron in the 
 ore, varying from seven to ten feet, the lower shaft being used in the smelting of 
 highly ferruginous ores. Such ores frequently give rise to the production of deposits 
 of the following composition : 
 
 Iron . . . 61-52 62-60 
 
 Tin 30-50 31-43 
 
 Arsenic T45 
 
 Tungsten 0'90 1'60 
 
 Carbon, Silica, and Alumina . . . 4-41 2'40 
 
 9878 98-03 
 
 The tin ores worked in shaft furnaces in Saxony and Bohemia are generally impure, 
 and according to the nature of the substances they contain different materials must 
 
TIN SMELTING. 
 
 469 
 
 be used as fluxes. Ores containing much ferric oxide are mixed with quartz, or other 
 silicious substances, while silicious ores are mixed with lime, and ores containing 
 wolfram are also mixed with lime. The proportion of lime should not 'be more than 
 sufficient to render the slag moderately fusible, since an excess would cause loss of 
 tin by the formation of calcium stannate. 
 
 The slag formed in smelting tin ore consists chiefly of ferrous silicate, together 
 with some stannous silicate, and that portion which is drawn out before running off 
 the melted products consists of a mixture of unburnt coal and other substances with 
 metallic tin : this is crushed, washed, and again smelted. 
 
 The composition of the slag produced in reverberatory furnaces at Poullaouen is 
 as follows, according to Berthier : 
 
 Silica 41-30 40'00 
 
 Ferrous oxide 20-50 20'30 
 
 Manganous oxide 11-40 11-10 
 
 Alumina 12-80 9 -60 
 
 Lime 3-90 3'60 
 
 Magnesia 0'80 1-00 
 
 Stannous oxide 9'00 8-40 
 
 99-70 
 
 94-00 
 
 The slag produced in smelting tin ore in shaft furnaces has the following com 
 position : 
 
 
 Wallach 
 
 Berthier 
 
 Lampadins 
 
 Silica. . ... 
 
 24-06 
 
 16-0 
 
 27-5 
 
 5-81 
 
 Alumina 
 
 9-00 
 
 2-4 
 
 8-5 
 
 18-14 
 
 Ferric oxide .... 
 
 20-75 
 
 41-5 
 
 48-2 
 
 39-51 
 
 Manganous oxide 
 
 5-64 
 
 1-7 
 
 1-5 
 
 1-34 
 
 Lime ...... 
 
 3-58 
 
 3-7 
 
 3-4 
 
 - 
 
 Magnesia 
 
 0-37 
 
 1-7 
 
 1-6 
 
 
 
 Stannic oxide . . . 
 
 10-41 
 
 
 
 
 
 12-13 
 
 Stannous oxide . 
 
 
 
 32-0 
 
 6-3 
 
 
 
 Tungstic oxide .... 
 
 24-33 
 
 1-0 
 
 3-0 
 
 
 
 Tin 
 
 __ L _ 
 
 
 
 
 
 21-20 
 
 
 
 
 
 
 98-14 
 
 100- 
 
 100- 
 
 98-13 
 
 The residue left in the refining of the metal obtained in the first smelting has 
 the following composition : 
 
 I Berthier Phillips 
 
 Iron 55-6 62-50 
 
 Tin .... 36-2 17'25 
 
 Cobalt 
 
 Arsenic 
 
 Sulphur 
 
 4-0 
 4-2 
 
 100-0 
 
 19-02 
 1-26 
 
 100-03 
 
 Uses. Tin is employed for making various kinds of vessels for domestic use and 
 other purposes, and is often alloyed with some lead in order to render it less brittle. 
 It is also used in the form of very thin sheets, called tin foil, for wrapping articles 
 of food, etc. ; looking-glasses also are coated with tin foil, which is then converted 
 into an amalgam with mercury, and thus made to adhere to the glass and present a 
 very brilliant reflecting surface. Tin is also extensively employed for coating sheet 
 iron and rendering it more suitable for use in the form of domestic vessels, etc., by 
 protecting the iron from atmospheric oxidation. Sheet iron so coated is commonly 
 called tinplate; it is prepared by dipping sheets of iron, well cleansed at the surface 
 by means of acid, into melted tin until the surface is sufficiently coated with tin. 
 
 Compounds. Tin forms two well-defined series of compounds ; it is tetravalent 
 in the stannic compounds, and divalent in the stannous compounds. In 
 many respects the compounds of tin present considerable analogy with those of silicon 
 and titanium. Stannous oxide SnO is a moderately strong base, forming definite 
 saline compounds with acid oxides ; stannic oxide Sn0 2 is an acid oxide which forms 
 saline compounds with water and basic oxides ; the hydrogen salt H 2 Sn0 3 is called 
 stannic acid. The oxide Sn 2 s is probably a compound of this kind in which 
 
470 
 
 TIN. 
 
 stannous oxide is the base combined with stannic oxide. There are in the same -way 
 three compounds, of tin with chlorine, the dichloride SnCl 2 corresponding to stannous 
 oxide, the tetrachloride SnCl 4 corresponding to stannic oxide, and a sesquichloride 
 Sn 2 Gl 6 , which is probably a compound of stannic chloride with stannous chloride, 
 analogous to the salts formed by the combination of stannic chloride with potassium 
 chloride, etc., called chlorostannates, in which stannic chloride acts the part of an 
 acid. The compounds of tin with fluorine, with bromine, and with iodine correspond 
 to stannous and stannic chlorides ; stannic fluoride, however, has not been obtained in 
 a separate state, but only in combination with other fluorides corresponding to 
 potassium fluoride, in the form of fluostannates, which are analogous in constitu- 
 tion to the stannates, but contain fluorine in the place of oxygen ; the composition 
 of the barium salt is represented by the formula BaF 2 SnF 4 = BaSnF 6 . These com- 
 pounds are analogous to the fluosilicates, fluotitanates, and fluoborates (see p. 184). 
 The compounds of tin with sulphur correspond to the oxides, and stannic sulphide 
 SnS 2 combines with basic sulphides, forming a series of compounds called sulpho- 
 stannatesin which stannic sulphide acts the part of an acid. These salts are also 
 analogous to stannates, but contain sulphur in place of oxygen. 
 
 Tin also forms a number of compounds with alcohol radicles. 
 
 Tin unites with most other metals when melted with them, forming alloys which 
 are generally hard and ductile. In some instances a very small proportion of tin 
 modifies the characters of other metals very considerably. 
 
 The alloys of tin with zinc are harder than tin but softer than zinc ; they are also 
 less malleable than tin ; that containing one-twelfth part of tin is used for making 
 foil that is employed as a substitute for silver leaf. The alloy containing 6 molecular 
 proportions of tin to one of zinc solidifies at 204, and the alloys of these metals in 
 different proportions separate, when gradually cooled, into this alloy and another 
 which solidifies at a higher temperature. 
 
 The alloys of lead with tin are harder than tin, rather darker in colour, and when 
 bent they do not give the crackling sound characteristic of tin. The solder used for 
 various purposes consists of lead and tin in the following proportions : 
 
 Fine solder 
 Common solder 
 Coarse solder 
 Sealed solder 
 
 Tin 
 2 
 1 
 
 1 
 
 Lead 
 1 
 
 1 
 
 Melting point 
 340 
 370 
 
 441 
 
 Pewter generally consists of tin alloyed with one-fourth its weight of lead, but 
 zinc or other metals are sometimes added, and the better kind contains a larger pro- 
 portion of tin. This alloy is remarkable in not being acted upon by acid liquids in 
 the same way that lead is, and on this account it can be used for domestic utensils 
 when the proportion of tin is not less than 82 per cent. Alloys of tin and lead in 
 various proportions differ considerably in the melting point, as shown in the following 
 table, and they are used as baths, for tempering articles made of steel : 
 
 Lead 
 
 Tin 
 
 Melting 
 point 
 
 1 
 
 14 
 
 8 
 
 213'4 
 
 used for tempering lancets 
 
 15 
 
 8 
 
 221 
 
 surgical instruments 
 
 16 
 
 8 
 
 225 
 
 razors 
 
 17 
 
 8 
 
 240 
 
 penknives 
 
 28 
 
 8 
 
 257 
 
 shears 
 
 38 
 
 8 
 
 262 
 
 hatchets, planes, etc. 
 
 60 
 
 8 
 
 275 
 
 table knives, scissors, etc. 
 
 96 
 
 8 
 
 284 
 
 swords and watch springs 
 
 100 
 
 8 
 
 289 
 
 , augurs, saws, and strong springs 
 
 The alloys of tin and lead are remarkable for the readiness with which they 
 undergo oxidation when heated in contact with atmospheric air. The alloy contain- 
 ing 20 or 25 per cent, of tin burns like charcoal at a red heat. This oxidation ap- 
 pears to be promoted by the combination of the stannic oxide with the lead oxide. 
 (See Enamel, p. 331.) 
 
 The alloys known by the names of bronze, gun metal, bell metal, consist 
 either entirely or chiefly of tin and copper, and their characters vary according to the 
 relative proportions of the two metals, as shown in the following table by Mallet : 
 
STANNOUS OXIDE. 
 
 
 Copper 
 
 Tin 
 
 Specific 
 gravity 
 
 Colour 
 
 Tenacity 
 
 Hardness 
 
 1 
 
 100- 
 
 
 
 8-60? 
 
 
 
 24-6 
 
 10 
 
 2 
 3 
 
 84-29 
 82-81 
 
 15-71 
 17-19 
 
 8-561 
 8-462 
 
 reddish yellow 
 
 16-1 
 15-2 
 
 8 
 5 
 
 4 
 5 
 
 81-10 
 78-97 
 
 18-90 
 21-03 
 
 8-459 
 8-728 
 
 yellowish red 
 
 177 
 13-6 
 
 4 
 3 
 
 6 
 
 7 
 
 76-29 
 72-80 
 
 23-71 
 27-20 
 
 8-750 
 8-575 
 
 pale red 
 
 9-7 
 4-9 
 
 2 
 1 
 
 8 
 
 68-21 
 
 31-79 
 
 8-400 
 
 ash grey 
 
 0-7 
 
 6 
 
 9 
 
 61-69 
 
 38-31 
 
 8-539 
 
 dark grey 
 
 0-5 
 
 7 
 
 10 
 11 
 
 51-75 
 34-92 
 
 48-25 
 65-08 
 
 8-416 
 8-056 I 
 
 greyish white 
 
 1-7 
 1-4 
 
 9 
 11 
 
 12 
 
 21-15 
 
 78-85 
 
 7-389 ' 
 
 
 3-9 
 
 12 
 
 13 
 
 15-17 
 
 84-83 
 
 7.447 
 
 nrliif A 
 
 3-1 
 
 13 
 
 14 
 
 11-82 
 
 88-18 
 
 7-472 
 
 WlJlLc 
 
 3-1 
 
 14 
 
 15 
 
 9-68 
 
 90-32 
 
 7-442 , 
 
 
 2-5 
 
 15 
 
 16 
 
 o- 
 
 100- 
 
 7-291 
 
 
 
 2-7 
 
 16 
 
 The alloy containing only a small proportion of tin is much harder than copper, 
 and when hammered it becomes still harder and brittle ; it is however softened by 
 heating to redness and sudden cooling ; when slowly cooled it becomes hard. The 
 alloy used as gun metal and for castings contains from 8 to 19 per cent, of tin ; when 
 the tin amounts to-21 per cent, the alloy is very hard and suitable for the bearings of 
 machinery ; the alloys with somewhat larger amounts of tin are used for casting 
 bells, and some zinc and lead are often mixed with the alloy. In proportion as the 
 amount of tin is augmented the alloys become whiter and more brilliant ; that used 
 for the mirrors of reflecting telescopes, under the names of speculum metal, con- 
 tains about 33 per cent, of tin ; it is very hard, of a steel colour, and takes a high 
 polish. 
 
 The alloys of tin with silver are nearly as white as silver. They are brittle and 
 generally hard, that containing 20 per cent, of tin being as hard as bronze. 
 
 Tin unites readily with mercury, even at the ordinary temperature, forming a 
 brittle granular amalgam if the proportion of mercury is not too large. The metallic 
 reflecting surface on plate-glass mirrors consists of an amalgam of tin. 
 
 The other alloys of tin will be described under the heads of the several metals. 
 
 STAWTMOUS OXIDE. 
 FORMULA SnO. MOLECULAR WEIGHT 134. 
 
 History. The distinction between the oxides of tin was not recognised until the 
 latter end of the last century. 
 
 Characters. Stannous oxide is either black, greenish brown, or red, according to 
 the way in which it is prepared. At the ordinary temperature it is not oxidised by 
 contact with atmospheric air, but when heated it is rapidly converted into stannic 
 oxide. It is reduced by hydrogen or carbon at a red heat. Chlorine converts it into 
 stannic chloride and stannic oxide ; when heated with sulphur it yields stannic sul- 
 phide and sulphurous oxide ; by boiling caustic alkali it is converted into alkaline 
 stannate, with separation of metallic tin ; it is dissolved by acids, forming stannous 
 salts. 
 
 Stannous hydrate Sn 2 H 2 3 , as obtained by mixing a solution of a stannous 
 salt with an alkaline carbonate, is a white precipitate readily soluble in acids and 
 fixed alkalies, but insoluble in solution of ammonia. When boiled with water it is 
 converted into anhydrous stannous oxide, and by exposure to the air it is oxidised and 
 converted into stannic hydrate. 
 
 Preparation. Stannous oxide may be prepared either by drying the hydrate 
 out of contact with air at a temperature not exceeding 80 or by boiling the hydrate 
 with some caustic potash or soda insufficient to dissolve it. It may also be prepared 
 by heating stannous oxalate out of contact with air. The red modification is prepared 
 by evaporating a dilute solution of ammonium chloride in which stannous hydrate 
 oxide is suspended. As soon as the chloride crystallises, the hydrate is converted 
 into anhydrous oxide in the form of a cinnabar red powder. 
 
472 TIN. 
 
 STANNIC OXIDE. 
 
 FORMULA Sn0 2 . MOLECULAR WEIGHT 150. 
 
 History. The true composition of this substance was not determined until the 
 early part of the present century, and it was shown by Berzelius that the product 
 obtained by oxidising tin with nitric acid had the same composition as that precipi- 
 tated from stannic chloride by an alkali. 
 
 Occurrence. Stannic oxide occurs naturally as cassiterite or tin stone, 
 either as crystals and lumps imbedded in granite and other crystalline rocks, or in the 
 form of pebbles in alluvial deposits. 
 
 Characters. Stannic oxide in the crystalline state, as it occurs naturally, forms 
 quadratic prisms which are colourless when pure, but are more frequently yellove, 
 grey, brown, or black, owing to the presence of other substances. In the amorphous 
 state, stannic oxide is a white or yellowish-white powder, which acquires a slight brown 
 tinge when heated, but becomes white again on cooling. The specific gravity is 
 from 6'6 to 6'9. It is extremely hard, melts only at a very high temperature, and is 
 not acted upon even by concentrated acids ; when melted with acid potassium sulphate 
 it is dissolved, but separates completely on treating the melted mass with water ; it is 
 not dissolved when melted with alkaline carbonates, but when melted with caustic 
 alkali it is converted into a soluble stannate ; by ignition in contact with chlorine it is 
 converted into stannic chloride; heated to redness with hydrogen, carbonic oxide, 
 carbon, or carburetted gases, it is reduced to the metallic state. 
 
 Stannic oxide forms two compounds with water Sn0 2 H 2 and Sn 5 Oi 5H 2 0, which 
 represent two series of salts called respectively stannates and metastannates, 
 the stannic hydrates being the hydrogen salts of those two series, or stannic acid 
 H 2 Sn0 3 and metastannicacid H 10 Sn 5 Oj 5 . The whole of the hydrogen in stannic 
 acid can be replaced by metals, but only one-fifth of the hydrogen in metastannic acid 
 can be thus replaced. 
 
 Stannic acid, as obtained by drying the precipitate formed on adding an acid to 
 the solution of an alkaline stannate, has the form of translucent lumps like gum, and 
 it reddens litmus paper; it is dissolved by hydrochloric acid, forming stannic 
 chloride, and by oxyacids, forming stannic salts, which are very unstable. The sulphate 
 Sn2S0 4 is an uncrystallisable syrupy liquid having a strong acid reaction ; it is de- 
 composed by water. 
 
 Potassium stannate K 2 SnO s is a very soluble salt, crystallising in rhombic 
 prisms containing 3 or 4 molecules of water ; it is insoluble in alcohol, but dissolves 
 in less than its weight of cold water ; the solution has a specific gravity of 1'627. 
 
 Sodium stann ate Na 2 Sn0 3 is less soluble than the potassium salt, requiring 
 rather more than one and a half times its weight of water for solution. It crystal- 
 lises in hexagonal plates containing 3 molecules of water. It is less soluble in warm 
 water than in cold water. 
 
 The calcium, barium, and strontium stannates are obtained by boiling the corre- 
 sponding hydrates or carbonates with a solution of sodium stannate, or by heating a 
 mixture of natural stannic oxide and the respective nitrates to a high temperature in 
 a reverberatory furnace. 
 
 Cupric stannate CuSn0 3 is an insoluble substance of a green colour obtained 
 by mixing a solution of tin in nitro-hydrochloric acid with cupric sulphate and adding 
 excess of caustic soda. It is used as a pigment. 
 
 Metastannic acid H 10 Sn 5 Oi 5 is a white crystalline powder insoluble in water 
 and in nitric acid ; it unites with hydrochloric acid and with sulphuric acid, but with- 
 out dissolving ; the compound with hydrochloric acid dissolves in pure water, but is 
 again precipitated on the addition of strong hydrochloric acid ; the compound with 
 sulphuric acid is decomposed by water and all the sulphuric acid is extracted. When 
 metastannic acid is heated with hydrochloric acid it is gradually converted into 
 stannic chloride, and when melted with caustic alkali it is converted into stannic acid. 
 
 Metastannic acid dissolves slowly in solution of caustic alkalies, and when the 
 solution is exposed to the air, it is again precipitated as carbonic dioxide is absorbed 
 or on the addition of an acid. The precipitate thus produced is insoluble in nitric 
 acid, but soluble in ammonia, while the acid formed by the action of nitric acid upon 
 tin is insoluble in ammonia. 
 
 Potassiummeta stannate K 2 H 8 Sn s Oj 5 is a gummy uncrystallisable substance 
 with a strong alkaline reaction ; it is soluble in water. 
 
 Sodium metastannate Na 2 H 8 Sn s O, 5 is a crystalline substance soluble in 
 water, but decomposed when the solution is heated, and on boiling the whole of the 
 metastannic acid is deposited. 
 
STANNOUS CHLORIDE. 473 
 
 Stannousmetastannate SnH 8 Sn 5 15 is a yellow substance insoluble in water 
 formed by placing metastannic acid in contact with stannous chloride. When heated 
 it gives off water and becomes brown at 140. By contact with atmospheric air and 
 by the action of nitric acid it is converted into metastanuic acid. 
 
 Preparation. Stannic oxide is prepared by heating metallic tin for some time 
 in contact with atmospheric air. The stannates are prepared by dissolving stannic 
 hydrate in alkaline solutions ; by melting stannic oxide together with basic oxides, or by 
 boiling the solution of a soluble stannate with basic oxides. The sodium salt is pre- 
 pared on the large scale by melting tin ore with sodium hydrate, nitrate, chloride, or 
 sulphide ; also by boiling the ore with caustic soda or by melting metallic tin with a 
 mixture of sodium carbonate and sodium nitrate. Tin containing lead can be used for 
 this purpose, or waste cuttings of tinned iron instead of pure tin. 
 
 Uses. Stannic oxide is used in a finely divided state, under the name of putty 
 powder, for polishing metals ; it is also used in the production of enamel and opaque 
 glass. In the state of sodium stannate it is used in calico printing as a mordant or 
 preparingsalt; when the dilute solution of this salt is brought into contact with the 
 fibres of the fabric to be dyed, stannic hydrate is deposited upon them. 
 
 STAN-NOUS CBZiORZBE. 
 
 FOEMTTLA SnCl 2 . MOLECULAB "WEIGHT 189. 
 
 History. The difference between the solution of tin in hydrochloric acid and 
 that obtained by dissolving tin in nitro-hydrochloric acid was first ascertained by 
 Pelletier in 1792. 
 
 Characters. Stannous chloride is a translucent, almost colourless substance 
 having a fatty lustre ; it melts at 250, boils near a red heat, and can be distilled ; 
 when heated in contact with atmospheric air it is decomposed, giving off stannic 
 chloride, while stannic oxide is formed. It absorbs dry ammonia, and when heated 
 with it forms the compound SnCl 2 NH 3 . Stannous chloride combines with water, 
 forming a hydrate which is soluble in water and crystallises in large prisms, con- 
 taining 2 molecules of water, commonly known as tin salt. This substance when 
 heated gives off water and hydrochloric acid, and is converted into stannous chloride 
 and stannous oxide. The crystallised salt dissolves completely in a small proportion 
 of water free from atmospheric air, but a large proportion of water causes decomposi- 
 tion of some portion, and hydrated stannous oxychloride SnOSnCl 2 2H 2 is deposited 
 as a white precipitate, while hydrochloric acid is formed : 
 
 2SnCl 2 + H 2 = SnOSnCl 2 -r 2HC1. 
 
 The clear solution becomes turbid when exposed to the air, oxychloride being 
 deposited and stannic chloride formed by oxidation : 
 
 3SnCl 2 + = SnOSnCl 2 + SnCl 4 . 
 
 The decomposition may be prevented in either case by adding some hydrochloric 
 acid, tartaric acid or ammonium chloride to the solution. The crystals decompose in 
 the same manner when exposed to the air ; they are also decomposed by cold sulphuric 
 acid, and when heated with sulphuric acid some hydrochloric acid is given off with 
 sulphurous acid and sulphuretted hydrogen, while stannic sulphate is formed. 
 
 Stannous chloride combines with several other chlorides, forming saline compounds 
 called chlorostannites, in which the stannous chloride acts the part of an acid. 
 The ammonium salt 2NH 4 C1. SnCl 2 is soluble in water and forms crystals which are 
 sometimes anhydrous and sometimes contain two molecules of water. The solution 
 becomes cloudy on boiling, but is not altered by exposure to the air. The composition 
 of the barium and strontium salts is represented by the formulae BaCl 2 SnCl 2 4H 2 and 
 SrCl 2 Sn01 2 4H 2 0. 
 
 Stannous chloride is readily converted into stannic chloride, either in the dry state 
 by direct combination with chlorine, or in solution when mixed with any substance 
 capable of giving up chlorine or oxygen, such as hypochlorous acid, nitric acid, 
 chromic acid, and arsenic acid, or ferric, manganic, and cupric salts. 
 
 Preparation. The anhydrous salt is prepared by heating tin in hydrochloric 
 acid gas, or by heating the hydrated salt gradually until the water has been driven 
 off; and then raising the heat sufficiently to distil off the chloride. 
 
 The hydrated salt is prepared by dissolving tin in hydrochloric acid. Copper 
 vessels are used for the purpose, and they are not acted upon so long as some of the 
 
474 TEST. 
 
 tin remains undissolved. When the acid is fully saturated with tin the liquid is eva- 
 porated and left to crystallise. 
 
 Uses. Stannous chloride is extensively used as a mordant in dyeing and calico 
 printing; also as an antichlor and as a reagent in volumetric analysis. 
 
 STANNIC CHLORIDE. 
 
 FORMULA SnCl 4 . MOLECTTLAK WEIGHT 260. 
 
 History. This substance was formerly known in the anhydrous state as the 
 spiritus fumans of Libavius. In 1770 Demachy observed that when mixed with a 
 small quantity of water it solidified to a soft crystalline fusible mass called butter 
 of tin. 
 
 The solution obtained by dissolving tin with nitro-hydrochloric acid has been 
 known since 1630, when Drebbel discovered its use for dyeing. 
 
 Characters. Stannic chloride is a colourless mobile liquid ; its specific gravity 
 is 2'234 ; it gives off dense white fumes when exposed to the air and is very caustic ; 
 it boils at 115, and distils without alteration. When heated with a small quantity 
 of water in a sealed tube it is decomposed and converted into stannic oxide. It 
 absorbs water from the air and combines with it, forming a crystalline hydrate 
 SnCl 4 3H 2 which dissolves in water, and the solution when evaporated yields crystals 
 containing 5 molecules of water. Stannic chloride is decomposed when the solution 
 is largely diluted with water, and stannic acid, or metastannic acid, is precipitated. 
 The solution of stannic chloride is decomposed when mixed with a solution of alkaline 
 sulphate, and stannic hydrate is precipitated, while alkaline chloride and acid sulphate 
 remain in solution. 
 
 The solution of stannic chloride dissolves stannous oxide, forming stannous 
 chloride, which crystallises with 4 molecules of water when the solution is evaporated, 
 and the liquid contains stannic hydrate dissolved in stannic chloride : 
 
 2SnCl 4 + 2SnO + H.,0 _ 2SnCl 2 + H 2 Sn0 3 + Sn01 4 . 
 
 With a larger proportion of stannous oxide, stannic oxide separates in the hydrated 
 state, and the liquid contains stannous chloride : 
 
 SnCl 4 + 2SnO = Sn0 2 + 2SnCl 2 . 
 
 Stannic chloride dissolves crystalline sulphur, but not amorphous sulphur ; from 
 the hot saturated solution sulphur crystallises in rhombic prisms. It also dissolves 
 phosphorus and iodine ; it mixes in all proportions with bromine and carbon bisul- 
 phide. It absorbs ammonia and forms the compound SnCl 4 2NH 3 which sublimes 
 without decomposition and after sublimation is soluble in water. Vapour of sul- 
 phuric oxide is also absorbed by stannic chloride, forming a solid mass. 
 
 Sulphuretted hydrogen is absorbed by stannic chloride, and some hydrochloric 
 acid is given off, while stannic sulphide is formed, which combines with part of the 
 stannic chloride forming a reddish-yellow liquid : 
 
 3SnCl 4 + 2H 2 S = SnS 2 2SnCl 4 + 4HC1. 
 
 Stannic chloride combines with sulphur tetrachloride, forming a yellow crystalline 
 substance SnCl 4 2SCl 4 ; with phosphorus pentachloride, forming a white crystalline 
 substance SnCl 4 PCl 5 ; with phosphorus oxychloride, forming a volatile cry stalli sable 
 substance SnCl 4 POCl 3 , and with phosphuretted hydrogen 3SnCl 4 2PH 3 . 
 
 Stannic chloride combines with alkaline chlorides, forming saline compounds 
 called chlorostannates, which correspond to the stannates, but contain chlorine 
 in place of oxygen, and the stannic chloride acts the part of an acid. The ammonium 
 salt 2NH 4 C1. SnCl 4 is a crystalline powder, soluble in three times its weight of water. 
 The concentrated solution is not decomposed by boiling, but a dilute solution deposits 
 stannic hydrate. This salt is used as a mordant in calico-printing under the name 
 of pink salt, since the stannic hydrate separated by heating a dilute solution readily 
 combines with colouring substances, and renders them insoluble ; it is prepared by 
 mixing concentrated solutions of the two chlorides in proper proportions. The potas- 
 sium salt 2K 2 C1. SnCl 4 is soluble in water, crystallisable, and permanent in the air. 
 The sodium, calcium, magnesium, barium, and strontium salts are analogous. 
 
 Preparation. The anhydrous substance is prepared by heating metallic tin or 
 stannous chloride in contact with dry chlorine, or by distilling a mixture of tin filings 
 
TIN SULPHIDES. 475 
 
 with four times the weight of mercuric chloride. The hydrated salt known as butter 
 of tin is obtained by mixing anhydrous stannic chloride with one third its weight of 
 water; by dissolving this substance in water and crystallising, the pentahydrate 
 SnCl 4 5H 2 is obtained. 
 
 An impure stannic chloride, known asnitromuriatepftin, is prepared by dis- 
 solving tin in nitrohydrochloric acid or a mixture of nitric acid and ammonium 
 chloride. 
 
 Uses. Stannic chloride is used chiefly by dyers, either in solution or in the form 
 of pink salt, for brightening and fixing red colours. 
 
 STANNOUS SULPHIDE. 
 
 FORMULA SnS. MOLECULAR WEIGHT 150. 
 
 History. The compound obtained by melting tin with sulphur is mentioned by 
 Kunkel, but so very vaguely that it is uncertain whether he was really acquainted 
 with this substance. 
 
 Characters. Stannous sulphide is either a dark lead-coloured crystalline mass, 
 or a brownish black amorphous powder. The specific gravity is from 4'8 to 5'2. It 
 melts less readily than tin, and in the compact state is tough and difficult to powder. 
 It is soluble in melted tin ; when boiled with hydrochloric acid it is decomposed and 
 sulphuretted hydrogen is given off; it is slowly oxidised when heated with nitric 
 acid ; chlorine gas converts it into stannic chloride and the compound of that sub- 
 stance with sulphur tetrachloride ; when heated in contact with hydrogen the tin is 
 slowly reduced to the metallic state, and when melted with potassium cyanide, tin is 
 reduced, while potassium sulphocyanate is formed. 
 
 Stannous sulphide is but slightly dissolved by ammonium sulphide solution, but 
 solutions of alkaline polysulphides dissolve it readily and convert it into stannic 
 sulphide. 
 
 STANNIC SULPHIDE. 
 
 FORMULA SnS 2 . MOLECULAR WEIGHT 182. 
 
 History. This substance was known in the eighteenth century as aurummusivum, 
 or mosaic gold, and its preparation was described in 1771 by Peter Woulf ; but its 
 composition was not correctly ascertained until 1812, when Davy and Berzelius showed 
 that it did not contain oxygen. 
 
 Occurrence. Stannic sulphide occurs 'naturally in combination with cuprous 
 sulphide, ferrous sulphide and zinc sulphide, as .stannine or tin pyrites, a mineral 
 which is sometimes associated with tin ore. 
 
 Characters. Stannic sulphide is a yellowish substance which in the crystalline 
 state forms soft golden yellow laminae, having a metallic lustre, and resembling bronze 
 powder ; in the amorphous state it is a yellowish brown powder. The specific gravity 
 varies from 4'4 to 4- 6. Stannic sulphide sublimes when heated in a close vessel, but 
 is partly decomposed into sulphur and stannous sulphide. Heated in contact with 
 atmospheric air it is oxidised, yielding stannic oxide and sulphurous oxide. In 
 contact with chlorine it forms a brown liquid, from which crystals of the compound 
 SnCl 4 2SCl 4 separate after some time. Heated with iodine it yields a dark yellow 
 volatilisable substance SnSI 2 SI 2 , and the same substance is formed by boiling the 
 amorphous sulphide with alcoholic solution of iodine. 
 
 Stannic sulphide in the crystalline state is not decomposed by hydrochloric acid, but 
 the amorphous substance is slowly dissolved with evolution of sulphuretted hydrogen ; 
 hot nitric acid oxidises the amorphous sulphide, but not the crystalline substance ; 
 nitrohydrochloric acid oxidises it in both states, forming stannic oxide and sulphuric 
 acid. When melted with litharge, stannic sulphide is decomposed, yielding metallic 
 lead, sulphurous oxide and a yellow glass, or mixtures of both metals in the state of 
 oxide and sulphide according to the proportions of the two substances. 
 
 Stannic sulphide combines with metallic sulphides forming a series of saline 
 compounds called sulphostannates, in which it acts the part of an acid, and 
 these salts correspond to the stannates, but contain sulphur in place of oxygen. The 
 hydrogen salt H 2 SnS 3 or H.,S.SnS 2 is a yellow precipitate formed on adding an 
 
476 TITANIUM. 
 
 acid to the solution of an alkaline sulphostannate. The ammoniumsalt 2NH 4 .SnS 3 
 is soluble; the potassium salt K 2 SnS 3 is a heavy dark brown oily liquid; the 
 sodium salt forms crystals containing water Na 2 SnS 3 2H 2 0, and it combines with 
 sodium sulphide, forming a colourless crystallisable salt resembling gypsum, the 
 composition of which is represented by the formula Na 2 SNa 2 SnS 3 12H 2 0. The cor- 
 responding barium, calcium and strontium salts are sparingly soluble in water. The 
 compound of tin and sulphur, called sesquisulphide Sn 2 S 3 , intermediate between 
 stannous sulphide and stannic sulphide, is probably a stannic sulphostannate SnSnS 3 ; 
 it is a greyish yellow substance with metallic lustre, or a liver-coloured powder when 
 obtained by digesting stannic sulphide with a saturated solution of sulphostannate. 
 
 Preparation. Stannic sulphide may be prepared by heating a mixture of tin 
 filings, sulphur, and ammonium chloride or mercuric chloride. So much heat is 
 evolved by the combination of the tin and sulphur, that the sulphide would be decom- 
 posed unless this heat were absorbed by volatilisation of the ammonium chloride. 
 There is, however, a chemical action between the tin and the ammonium chloride, 
 according to the following equation : 
 
 2Sn + 4NH 4 Cl = 2NH 4 Cl.SnCL, + 2H + 2NH 8 . 
 
 The ammonium chlorostannate thus formed is again decomposed by reaction with 
 sulphur, yielding stannic sulphide and ammonium chlorostannate, according to the fol- 
 lowing equation : 
 
 2(2NH 4 Cl.SnCl 2 ) + 2S = SnS 2 4- 2NH 4 Cl.SnCl 4 + 2NH 4 C1. 
 
 Stannous oxide, stannous sulphide, or stannous chloride may be substituted for the 
 metallic tin in preparing stannic sulphide. The mixture is heated in a glass retort or 
 flask until the excess of sulphur is driven off from the stannic sulphide. 
 
 Stannic sulphide is obtained in the amorphous form by passing sulphuretted 
 hydrogen into a solution of stannic chloride. 
 
 Uses. The crystalline variety of stannic sulphide is used under the name of 
 mosaic gold for coating objects in imitation of bronze. Sometimes also it is used 
 in place of the amalgam of tin and zinc, for coating the rubbers of electrical machines. 
 
 SYMBOL Ti. ATOMIC WEIGHT 50. 
 
 This elementary substance was discovered in 1789 by Gregor as a constituent of a 
 Cornish mineral called menaccanite, and in 1795 Klaproth discovered the same 
 substance in rutile : in 1802 Vauquelin showed that anatase consisted essentially 
 of a compound of this substance with oxygen, and in 1822 "Wollaston ascertained the 
 presence of a compound of titanium and nitrogen among the products of iron 
 smelting furnaces. 
 
 Titanium does not occur naturally in the free state, but is most frequently met 
 with in combination with oxygen either as rutile, anatase, and brookite, or com- 
 bined with lime as perow skit e, with ferrous oxide as ilmenite and several ana- 
 logous minerals, among which are the various kinds of titaniferous iron ore. The 
 compound of titanic oxide and lime also occurs combined with calcium silicate as 
 spheneortitanite; titanium occurs likewise in a number of rare minerals con- 
 taining cerium, yttrium, tantalum, and niobium ; some iron ores contain titanium in 
 small amount. 
 
 Titanium, as usually obtained by the reduction of the oxide, or by heating the 
 double titanium and potassium fluoride with metallic potassium, is in the form of a 
 dark greenish-coloured amorphous powder, but it may be obtained in prismatic 
 crystals by heating sodium in the vapour of titanium chloride : heated in atmospheric 
 air, in oxygen, or in chlorine, it burns with great brillianc}'' ; it does not decompose 
 water until the temperature is raised to 100. Titanium is dissolved by hydrochloric 
 acid, and it has a great disposition to combine with nitrogen at a high temperature. 
 
 There are at least two series of titanium compounds, in one of which that sub- 
 stance is quadrivalent, while in the other it is apparently trivalent, as in the oxides 
 
TITANIUM COMPOUNDS. 477 
 
 Ti0 2 and Ti 2 3 , or in the chlorides TiCl 4 and Ti-^Cl,;. There is probably another 
 series of titanium compounds corresponding to an oxide having the formula TiO. 
 
 Titanium unites with aluminum, forming a yellowish-brown crystalline alloy : it 
 is also found in some kinds of pig iron, and its presence in iron is said to be advan- 
 tageous, but it is still doubtful whether the titanium in iron exists as an alloy, or 
 merely disseminated through the mass. 
 
 Titanous oxide Ti 2 3 is a black pulverulent substance obtained by heating ti- 
 tanic oxide to redness in contact with hydrogen. In this state it is not dissolved by 
 nitric acid or hydrochloric acid, but sulphuric acid dissolves it, forming a violet-coloured 
 solution, from which a crystalline deliquescent salt having the formula Ti 2 3 3S0 3 
 may be obtained by evaporation over sulphuric acid. 
 
 The hydrated titanous oxide obtained by adding ammonia to a solution of titanous 
 chloride is a dark brown substance, insoluble in water but soluble in acids, and appa- 
 rently forming salts, though the sulphate is the only one that has been obtained in a 
 solid state. Titanous hydrate gradually oxidises, turning black, blue, and eventually 
 white, while hydrogen is evolved ; the blue colour is probably due to the formation of 
 a titanous titanate. 
 
 Titan ic oxide Ti0 2 is a reddish- coloured substance fusible only at a very high 
 temperature, insoluble in water and all acids except strong sulphuric acid ; as it 
 occurs naturally it Is crystalline, and crystals of it may be obtained by decomposing 
 the vapour of titanic chloride by steam in a red-hot tube. 
 
 Titanic oxide forms saline compounds with basic oxides, the hydrate 2H 2 Ti0 2 , or 
 hydrogen salt, called titanic acid, and corresponding to stannic acid, being the repre- 
 sentative of the compounds called titanate s. 
 
 There is also another hydrate analogous to metastannic acid, which is called meta- 
 titanic acid, and there is a corresponding series ofmetatitanates. 
 
 Titanic acid is obtained by adding ammonia to solution of titanic chloride, as a 
 white pulverulent substance which acquires a yellowish colour when heated, and 
 becomes white again on cooling. At a high temperature it loses water, and is converted 
 into titanic oxide, with vivid incandescence. Titanic acid is dissolved readily by 
 hydrochloric, nitric, and sulphuric acids, even when they are dilute, and when the 
 dilute solutions are boiled, metatitanic acid is deposited as a white powder, insoluble 
 in all acids but strong sulphuric acid. Titanic acid is also converted into metati- 
 tanic acid by washing with hot water and by drying it at a high temperature. 
 
 The other saline compounds in which titanic oxide acts the part of an acid oxide 
 present a general analogy with the stannates and silicates. The potassium salt K 2 Ti0 3 
 obtained by fusing titanic oxide with potassium carbonate is a yellowish fusible mass 
 decomposable by water into an insoluble acid salt, and a soluble salt containing a 
 larger proportion of basic oxide. The sodium salt is similar. Calcium titanate 
 CaTi0 3 occurs naturally as perowskite, and in combination with calcium silicate 
 as sphene or titanite CaTi0 3 Ca Si0 3 . Ferrous titanate Fe 2 Ti0 4 is a constituent of 
 i 1 m e n i t e and the varieties of that mineral comprised under the name of titaniferous 
 iron ore. 
 
 Titanic oxide also presents the character of a feeble base, and it forms saline 
 compounds with some acid oxides ; the sulphate Ti0 2 S0 3 is formed when titanic oxide 
 is dissolved in strong sulphuric acid ; the solution gelatinises on cooling, and when 
 part of the sulphuric acid is evaporated, a white powder is obtained, the composition 
 of which corresponds with the above formula ; it is soluble in hydrochloric acid, and 
 when ignited gives off all the sulphuric acid. The nitrate obtained by dissolving 
 titanic hydrate in nitric acid forms crystalline laminae imperfectly soluble in water ; 
 the phosphate is formed on adding ammonium phosphate to a solution of titanic hydrate 
 in hydrochloric acid, as a white gelatinous precipitate ; and the oxalate is a curdy 
 mass obtained on boiling the aqueous solution of a titanic salt with oxalic acid. 
 
 Titanic oxide does not dissolve in solution of caustic alkali ; but it may be rendered 
 soluble by fusion with acid potassium sulphate, and in this particular it differs from silica. 
 
 Titanous chloride, Ti 2 Cl 6 , presents the form of violet-coloured scales soluble 
 in water ; it is volatilisable, deliquescent, and readily oxidised. 
 
 Titanic chloride, TiCl 4 , is a colourless volatile liquid ; its specific gravity is 
 T76 at 0, and it boils at 135 ; it is obtained by passing chlorine over an ignited 
 mixture of titanic oxide and carbon ; when exposed to the air it absorbs moisture and 
 forms a crystalline hydrate, but is decomposed when mixed with a large proportion 
 of water ; it forms double salts with ammonium chloride, and combines with ammonia, 
 cyanogen, hydrocyanic acid, phosphine, and sulphur tetrachloride. When heated in 
 contact with hydrogen, it is converted into titanous chloride. 
 
 Titanic sulphide, TiS 2 , which is the only known compound of titanium and 
 sulphur, resembles the corresponding tin compound. 
 
 The nitrides TiN 2 , Ti 5 N 6 , and Ti 6 N 8 are violet or copper- coloured substances. The 
 
478 TUNGSTEN. 
 
 compound of titanic cyanide, TiCy 2 , with another nitride, Ti 3 N 2 , is sometimes found, 
 in the form of copper- coloured crystals, among the products of iron-smelting furnaces, 
 and it was for a long time supposed to be metallic titanium. The composition of this 
 substance is represented by the formula TiCy 2 3Ti s N 2 . Its production is probably 
 connected with the formation of potassium cyanide, which is frequently observed in 
 iron furnaces. 
 
 Titanic fluoride, TiF 4 , is a colourless volatile liquid; it combines with hydro- 
 fluoric acid and other fluorides, forming a series of crystalline salts called fluoti ta- 
 na tes, which are isomorphous with the fluosilicates, fluostannates and fluozirconates. 
 
 TUNGSTEN. 
 
 SYMBOL W. ATOMIC WEIGHT 184. 
 
 This elementary substance was first isolated by the brothers D'Elhujar in 1783, 
 and shortly before both Scheele and Bergman had come to the conclusion that the 
 mineral wolfram contained a peculiar metallic oxide combined with iron in an 
 oxidised state. Tungsten occurs only in the oxidised state, either as wolframite, or 
 combined with ferrous oxide and manganous oxide as wolfram, or with lime as 
 scheelite, and with lead oxide as scheeletine. 
 
 As prepared by reduction of the oxide, tungsten is a steel-grey powder which ac- 
 quires a metallic lustre by burnishing ; the specific gravity is about 17'6; it melts 
 only at a very high temperature. When heated in contact with atmospheric air in a 
 pulverulent state, tungsten is oxidised and converted into tungstic oxide ; but when 
 heated in a compact state it undergoes no change ; aqua regia, or nitric acid, converts 
 it into tungstic acid, and by fusion with caustic or carbonated alkalies, or by boiling 
 with solutions of those substances, it is converted into a soluble alkaline tungstate. 
 Tungsten may be prepared from the oxide or nitride by heating either of them to 
 redness in a stream of hydrogen, or by submitting a mixture of tungstic oxide and car- 
 bon to an intense heat in a crucible lined with charcoal. 
 
 Tungsten forms compounds in which it is respectively quadrivalent and sexivalent, 
 as in the chlorides WC1 4 and WC1 6 , or the oxides W0 2 , W0 3 . Neither of the 
 oxides forms saline compounds with acid oxides, but tungstous oxide, W0 2 , combines 
 with soda, forming sodium tungstite Na 2 02W0 2 , and tungstic oxide combines with 
 bases to form the tungstates. 
 
 There is an intermediate series of compounds represented by the chloride W 2 C1, 
 and the oxide W 2 5 , which are probably compounds of tungstous chloride or tungstous 
 oxide with tungstic chloride and tungstic oxide. 
 
 The bromides, fluorides, sulphides, and phosphides are represented by the formulae 
 WBr 4 , W 2 Bri , WF 6 , WS 2 , WS 3 , W 3 P 4 , W 2 P. Tungsten has been alloyed with several 
 other metals ; it forms with steel an extraordinarily hard alloy, containing 9 to 10 per 
 cent, of tungsten : wootz, or Indian steel, contains tungsten. The presence of tungsten 
 in steel is said to increase its power of retaining magnetism. 
 
 Tungstic oxide W0 3 occurs naturally as wolframite or as wolfraraochre, 
 accompanying other minerals containing tungsten. It is a yellow powder insoluble 
 in water and in acids, but soluble in alkalies, and may be obtained in a crystallised 
 condition. When heated the yellow colour changes to green without any chemical 
 alteration, and on cooling the yellow colour returns. Keducing agents convert it into 
 the brown tungstous oxide, and when heated to redness on charcoal it is reduced to the 
 metallic state. Tungstic oxide combines with basic oxides, forming the salts called 
 tungstates, and the hydrate W0 3 H 2 or tungstic acid is obtained, as a yellow pre- 
 cipitate, when a hot solution of an alkaline tungstate is mixed with hydrochloric acid. 
 Another hydrate W0 8 2H 2 is formed, as a white gelatinous precipitate, when a cold 
 dilute solution of alkaline tungstate is mixed with an acid, or when tungstic chloride 
 is mixed with a large proportion of water. Tungstic acid is insoluble in water and in 
 most acids, but there is a modification of it corresponding to metastannic acid and 
 metatitanic acid, which is very soluble in water, forming a syrupy liquid of sour and 
 bitter taste. It is obtained in form of a salt by boiling an ordinary alkaline tungstato 
 with excess of tungstic hydrate. 
 
MOLYBDENUM. 479 
 
 The salts corresponding to tungstic acid and metatungstic acid are somewhat com- 
 plex in character. The alkaline tungstates and magnesic tungstate only are soluble in 
 water, whilst nearly all the metatungstates are soluble. The alkaline tungstates are 
 obtained from wolfram by fusion with alkaline carbonates, the sodium salt, from which 
 most of the other salts are prepared, being represented by the formula Na^OWO,,. 
 
 Sodium tungstate has been used as a mordant in dyeing and in calico printing, 
 and more particularly to render cotton fabrics uninflammable. 
 
 Metatungstic acid is said to be a delicate test for detecting organic bases when 
 occurring in solution, excelling in that respect phosphomolybdic acid. 
 
 Tungstic chloride WC1 6 forms dark violet scales, which by sublimation can 
 be obtained in needles having a metallic appearance. It may be prepared by heating 
 tungsten or its sulphide in chlorine gas ; also by passing chlorine over an ignited 
 mixture of tungstic oxide and charcoal. It melts at 183 to a black liquid : its vapour 
 density is 11*86. Heated in contact with air, tungstic chloride is converted into the 
 red monoxychloride WC1 4 0, and tungstic hydrate W0 3 2H ? 0. Alkalies dissolve it 
 with the formation of tungstates. Two compounds of tungstic chloride with tungstic 
 oxide are known ; the dioxychloride WC1 6 , 2W0 3 is a yellow solid, volatilising at about 
 265, which is formed when tungstic dioxide is heated in chlorine ; the red monoxy- 
 chloride 2WC1 6 W0 8 is produced by the action of heat on the dioxychloride. 
 
 MOLYBDENUM. 
 
 SYMBOL Mo. ATOMIC WEIGHT 96. 
 
 The existence of this elementary substance as a peculiar constituent of the mineral 
 molybdenite was first indicated in 1778 by Scbsele, who established the distinc- 
 tion between that mineral and graphite, with which it had previously been confounded. 
 The terms ju<5\u)88os, plumbago, were vaguely applied by Dioscorides and Pliny to 
 litharge, galena, and other substances containing lead, and at a later period antimonous 
 sulphide, graphite, and native manganese peroxide were regarded as being closely 
 related, if not identical with molybdenite, until Pott proved, in 1740, that it did not 
 contain lead. In 1781 Bergman suggested that the substance produced by oxidising 
 molybdenite might be a metallic oxide, and in 1782 he announced that it had been 
 reduced by Hjelm. In 1797 Klaproth showed that wulfenite was a lead molybdate. 
 
 Molybdenum occurs only in combination, either with sulphur as molybdenite, 
 or in the oxidised state combined with lead oxide as wulfenite. It is a white and 
 brittle metallic substance, with a specific gravity of 8*6. At the ordinary temperature 
 it is unoxidisable in the air, but it burns when heated, forming a trioxide. Nitric acid 
 oxidises it first to molybdic dioxide, then to the trioxide ; sulphuric acid converts it 
 into molybdic dioxide, then Into the blue oxide, or molybdic molybdate Mo0 2 , 4M0 3 . 
 
 Molybdenum may be prepared by reducing the oxides with hydrogen or by expos- 
 ing them to a white heat in a crucible lined with charcoal. It forms compounds in 
 which it is respectively bivalent, quadrivalent, and sexivalent ; as in the oxides MoO, 
 Mo0 2 , Mo0 3 , or the chlorides MoCl 2 and MoCl 4 , and the fluoride MoF 6 . Both 
 molybdous . oxide MoO and molybdic oxide Mo0 2 combine with acid oxides forming 
 salts, and molybdenum trioxide combines with basic oxides forming the molyb dates. 
 
 Molybdenum unites with most metals, rendering themless fusible but more brittle. 
 
 The alloy of molybdenum and iron is sometimes formed in smelting copper ore. 
 and constitutes the deposits known as ' bears ' which are found in the furnaces. 
 
 Molybdous oxide MoO is black in ordinary daylight ; it combines with acid 
 oxides, forming molybdous salts, and is obtained in the hydrated state as a black 
 precipitate by adding ammonia to the dark-coloured solution of molybdous chloride 
 formed when one of the higher oxides is brought into contact with hydrochloric acid 
 and zinc, or one of the metals which decompose water. The anhydrous oxide is 
 obtained by drying the hydrate in a vacuum ; it is insoluble in acids and oxidises 
 when exposed to the air. The hydrate is dissolved by acids, forming molybdous 
 salts, the solutions of which are black or purple and nearly opaque, except when 
 largely diluted, when they have a greenish-brown colour ; these salts have an 
 astringent taste, and -vrhen exposed to the air they undergo oxidation. 
 
480 VANADIUM. 
 
 Molybdic oxide Mo0 2 has a reddish-brown colour, and combines with acid oxides 
 forming molybdic salts; as obtained by reducing molybdic trioxide with hydrogen ; 
 it is insoluble in acids and in caustic alkalies, but is oxidised by ignition in contact 
 with atmospheric air and by nitric acid. In the hydrated state it is obtained as a 
 reddish-brown precipitate by adding ammonia to a solution of molybdic chloride or 
 some other molybdic salt. The hydrate is sparingly soluble in water, and is dissolved 
 by acids, forming dark red solutions of molybdic salts ; it is insoluble in caustic 
 alkalies, but dissolves in solutions of ammonium carbonate or potassium carbonate, and 
 more readily in solution of acid carbonate ; on boiling these solutions molybdic 
 oxide is precipitated of a yellowish colour. 
 
 Molybdenum trioxide Mo0 3 , or permolybdic oxide, occurs naturally as 
 molybdic ochre, sometimes in rhombic prisms ; as prepared artificially, it is white 
 and porous, having a specific gravity of 3'49. It melts at a red heat, then sublimes in 
 laminae, but when heated out of contact with air it does not volatilise. Hydrogen, 
 charcoal, and sodium, with the aid of heat, reduce it to the metallic state. It is very 
 sparingly soluble in water. Molybdenum trioxide may be prepared by heating native 
 molybdic sulphide in a current of air in an open glass tube, when the trioxide sublimes 
 in a pure state. 
 
 Molybdenum trioxide forms with bases well-characterised neutral and acid salts 
 called molybdates; the neutral salts may be represented by the formula of the 
 ammonia salt 2NH 4 Mo0 4 . The neutral alkaline molybdates formed by digesting the 
 trioxide with alkalies are very soluble in water ; the other molybdates are insoluble 
 and are obtained by precipitation. Lead molybdate PbMo0 4 occurs naturally as 
 wulfenite. 
 
 "With some acids molybdenum trioxide also forms compounds ; permolybdic phos- 
 phate is a yellow insoluble salt, sometimes called phosphomolybdicacid; it is obtained 
 by digesting the trioxide in aqueous phosphoric acid. A fine yellow precipitate of 
 unascertained composition is produced by the addition of ammonic molybdate to a 
 solution containing phosphoric acid, and this reaction is employed to detect phosphoric 
 acid. 
 
 Molybdic sulphide MoS 2 occurs naturally as molybdenite in veins of iron 
 and tin ores. It is of a lead-grey colour, with metallic lustre ; sp. gr. about 4'4. It 
 undergoes no change when heated out of contact with air ; but in contact with air it 
 is converted into molybdenum trioxide, with evolution of S0 2 . At a red heat it 
 decomposes water vapour. It is dissolved by aqua regia, forming molybdic acid and 
 sulphuric acid ; and is oxidised by nitric acid. It may be prepared artificially by 
 heating molybdenum trioxide with sulphur. 
 
 Molybdenum forms two other sulphides, the trisulphide MoS 3 and the tetrasulphide 
 MoS 4 , both of which combine with basic sulphides, forming sulpho-salts namely, the 
 sulphomolybdates and the persulphomolybdates represented by the formulae K 2 SMoS 3 
 or K 2 MoS 4 andK 2 SMoS 4 or 
 
 VANADIUM. 
 
 SYMBOL V. ATOMIC WEIGHT 61 '2. 
 
 This elementary substance was discovered in 1830 by Seftstrom as a constituent 
 of the iron ore of Taberg in Sweden, and in a previous investigation of a lead ore from 
 Zimapan in Mexico, Del Rio had detected it as a peculiar metal, to which he gave the 
 name oferythronium. The chemical relations of vanadium were more fully studied 
 by Berzelius, and in 1830 Wohler showed that the Mexican mineral examined by Del 
 Rio was lead vanadate. More recently, Roscoe has shown that the substance regarded 
 by Berzelius as vanadium was really an oxide. 
 
 Vanadium occurs chiefly in the oxidised state and in combination with lead oxide 
 as dechenite and descloizite; also combined with lead chloride as vana- 
 dinite ; it has been also found in some iron ores and in the cupriferous sandstone of 
 Cheshire. 
 
 As prepared from the chloride by the action of hydrogen at a red heat, vanadium 
 is crystalline, and of a silver-white lustre ; it does not change when in contact with 
 the air at the ordinary temperature, or at 100 ; but when ignited in contact with at- 
 
VANADIUM. 481 
 
 mospheric air it gradually absorbs oxygen, becomes brown, possibly in consequence 
 of the formation of the monoxide V 2 0, and is eventually converted into the pentoxide. 
 V 2 5 ; it combines directly with oxygen, chlorine, and nitrogen, forming respec- 
 tively the pentoxide, tetraehloride, and vanadic mononitride. It is insoluble in either 
 hot or cold hydrochloric acid, but soluble in sulphuric acid, nitric acid, and in hydro- 
 fluoric acid, with evolution of hydrogen. 
 
 Vanadium may be prepared in the pure state by reducing one of the vanadic 
 chlorides in a stream of Tiydrogen. 
 
 In its compounds it is, according to Eoscoe, analogous to arsenic and phosphorus, 
 in being pentavalent, as in vanadic oxide V 2 5 , in sodium orthovanadate 3Na 2 0. V 2 5 
 = 2Na 3 V0 4 , sodium pyrovanadate 2Na 2 O.V 2 5 = Na 4 V 2 Oj, vanadic oxytrichloride 
 VOC1 3 , and it resembles nitrogen in its oxides," V 2 0, V 2 2 , V 2 3 , V 2 4 , V 2 5 . 
 
 The three chlorides VC1 2 , VC1 3 , and VC1 4 have been obtained, the first two from 
 the decomposition of the tetrachloride, which is a reddish-brown liquid of 1'85 sp. 
 gr. at 0, produced when the metal or its nitride is heated in a current of chlorine. 
 The oxychlorides and oxybromides are represented by the formulae VOC1 3 , VOC1 2 , VOC1, 
 V 2 2 C1, and the tribromide by the formula VBr 3 . 
 
 Vanadic pentoxide V 2 5 is a reddish-yellow solid with an acid reaction, and 
 requiring 1,000 parts of water to dissolve it. It is unalterable by heat. The stronger 
 acids dissolve it, forming crystalline vanadic salts, but it also combines with basic 
 oxides, and by fusion with alkaline carbonates it yields the saline compounds called 
 vanadates. 
 
 It may be prepared from ammonic vanadate by heating that salt to a temperature 
 below redness. 
 
 Vanadic anhydride forms compounds with bases much more readily than with 
 acids. The vanadates resemble the phosphates in composition, but differ from them 
 in being stable in a reverse order, the metavanadates being more stable and the ortho- 
 vanadates being the less stable compounds. 
 
 The metavanadates, of which the composition may be represented by the formulae 
 of the ammonium salt NH 4 V0 3 , and the barium salt Ba2V0 3 , are yellow, and some 
 of them change into colourless isomeric compounds when heated. 
 
 Plumbic and argentic orthovanadates Pb 3 2V0 4 , Ag 3 V0 4 , with the argentic pyro- 
 vanadates Ag 4 V 2 9 , which may be taken as types of these compounds, are obtained 
 by adding a soluble metallic salt such as argentic nitrate to the corresponding sodium 
 vanadate. 
 
 Vanadic dioxide V 2 2 , which was regarded by Berzelius as va; adiuni, the tri- 
 oxide V 2 3 , and the tetroxide V 2 4 , may all be prepared by reduction of the pent- 
 oxide ; the dioxide prepared by reducing a solution of the pentoxide in sulphuric acid, 
 after passing from blue to lavender, finally exists as a hypovanadous salt, which is 
 remarkable for being equal to chlorine in its bleaching action. 
 
 The tetroxide forms insoluble salts with nearly all bases ; it also dissolves in 
 acids, giving blue solutions of a vanadous salt. These vanadites in the presence of 
 water become green vanadites. 
 
 Vanadic pentasulphide can only be prepared in the wet way. It is obtained as a 
 brown precipitate by adding hydrochloric acid to a solution of the pentoxide or 
 alkaline vanadate in an alkaline sulphide. It is decomposed when heated out of 
 contact with air, into snlphur and the tetrasulphide ; heated in air it is oxidised to 
 vanadic pentoxide and sulphurous anhydride. 
 
 With metallic sulphides it combines to form a class of sulphur salts namely, the 
 sulphovanadates. 
 
 There is also a tetrasulphide V 2 S 4 , analogous to the tetroxide, from which it 
 is obtained by ignition in a stream of sulphuretted hydrogen. Vanadic tetrasulphide 
 forms the sulphovanadites by combination with basic metallic sulphides. 
 
 II 
 
482 NIOBIUM AND TANTALUM. 
 
 NIOBIUM. 
 
 SYMBOL Nb. ATOMIC WEIGHT 94. 
 
 This elementary substance was discovered in 1801 by Hatchett in an American 
 mineral called columbite, and hence it was termed colnmbium. In 1809 Wollaston 
 pronounced it to be identical with the tantalum found by Ekeberg in Swedish 
 tantalite, and this idea prevailed until 1846, when Kose showed that it was incor- 
 rect, and that the two metals were distinct. He found that the American mineral 
 contained an acid metallic oxide which he named niobic oxide, and to the metal he 
 gave the name niobium. 
 
 Niobium occurs in columbite as niobic oxide, combined with the ferrous oxide 
 and manganous oxide; it is also associated with yttrium, uranium, iron, etc., in^a 
 number of Siberian minerals, and in a variety of pitchblende from Satersdalen in 
 Norway. 
 
 The metal is obtained by heating the fluoride with metallic sodium in a covered 
 iron crucible, and washing out the soluble part of the fused mass with water. Thus 
 obtained, it is a black powder with a sp. gr. 6'27-6'67, which oxidises with incan- 
 descence when strongly heated in the air. When strongly heated in chlorine gas it 
 yields niobic chloride ; it dissolves in boiling dilute hydrochloric acid and in hot hydro- 
 fluoric acid, with evolution of hydrogen, but is not dissolved by nitric acid, and only 
 slowly by nitrohydrochloric acid. 
 
 Niobium is pentavalent in its compounds. The chloride NbCl 5 is a volatile, 
 fusible substance, obtained by the action of chlorine at a red heat upon the corre- 
 sponding oxide mixed with charcoal ; a corresponding fluoride is also known, as well 
 as an oxychloride, and an oxyfluoride NbOCl 3 and NbOF s . 
 
 Two bromides are also known, a nitride, a sulphide, and a number of double 
 fluorides which have been investigated by De Marignac. 
 
 Elaborate investigations of the natural niobates have also been recently published 
 by Kammelsberg. 
 
 TAWTALUIVT. 
 
 SYMBOL Ta. ATOMIC WEIGHT 182. 
 
 This elementary substance was discovered in 1802 by Ekeberg, as a constituent of 
 the Swedish minerals tantalite and yttrotantalite. 
 
 It occurs only in the oxidised state, combined with yttria, ferrous oxide, and other 
 basic oxides ; it is often associated with niobium in the various natural niobates and 
 tantalates which Eammelsberg has shown to be represented by the formulae KNb 2 0, 
 E 2 Nb 2 7 , and E 3 Nb 2 8 , corresponding to the phosphates and arsenates. Tantalum 
 also occurs as a constituent of some varieties of wolfram. 
 
 Tantalum, as obtained by heating potassium fluotantalate with metallic sodium in 
 a covered iron crucible, is a black powder which conducts electricity well, and after 
 ignition in hydrogen has a specific gravity 10'78. When heated in the air, it burns 
 with a bright light, and is oxidised. It dissolves readily in hydrofluoric acid, with 
 evolution of hydrogen, but is not attacked by other acids. 
 
 Tantalum forms two series of compounds corresponding to the dioxide Ta0 2 and to 
 tantalic oxide Ta 2 6 , which latter oxide unites with bases and forms salts. In most of 
 its compounds it is pentavalent. 
 
 By passing chlorine over tantalic oxide heated to redness with charcoal, a volatile 
 pentachloride is formed (TaCl 5 ), and a corresponding bromide is known less well. 
 
 A similar fluoride is known, a nitride, and a sulphide. 
 
 Both tantalum and niobium appear to resemble vanadium in being more inti- 
 mately related to the phosphorus group than to silicon. 
 
THALLIUM. 483 
 
 THALLIUM. 
 
 SYMBOL Tl. ATOMIC WEIGHT 203-6. 
 
 This metal was discovered by Crookes in 1862, during the spectroscopic examina- 
 tion of a seleniferous deposit from a sulphuric acid works. The green line which it 
 exhibits in the spectrum suggested to him the name which he gave to the metal. 
 
 Soon after Crookes had announced his discovery, Lamy obtained it more abundantly 
 from a like source. 
 
 Thallium is but sparingly distributed in nature. Nordenskiold found from 16 to 
 1 9 per cent, thallium in a selenide of copper and silver from Skrikerum in Sweden, 
 to which he gave the name crook esite. Hitherto the metal has been principally 
 obtained from the Spanish, Belgian, and Bolivian pyrites. It is a soft, heavy, dia- 
 magnetic metal, of a lustre resembling that of cadmium, but tarnishing on exposure. 
 
 Eegnault has assigned to it a specific heat of 0'03355, while Lamy found 0'0325. 
 It is a crystalline metal, which crackles like tin when bent ; but from its soft nature it 
 admits of hammering out into foil or drawing into wire, although its tenacity is small. 
 According to Crookes it melts at 293-9 C. (290 C. Lamy), undergoes atmospheric 
 oxidation, and if heated to 315 C. in oxygen, takes fire and burns with a green light. 
 The metal is volatile, and boils below a white heat ; it may be distilled in a current 
 of hydrogen. 
 
 It combines directly with chlorine, bromine, iodine, sulphur, and phosphorus ; and 
 most of the acids attack it readily with evolution of hydrogen ; the chloride being 
 insoluble, hydrochloric acid does not exercise a powerful action upon the metal. 
 
 The thalliferous dust deposited in the flues of sulphuric acid works is the best 
 source of the metal, which may be obtained by extracting the dust with dilute sul- 
 phuric acid, and precipitating the solution with hydrochloric acid. By suspending 
 the impure thallic chloride thus obtained in a solution of carbonate of sodium, 
 and passing a current of chlorine through the mixture, insoluble thallium peroxide is 
 obtained, which after washing may be resolved into sulphate by suspending it in water 
 and submitting it to the action of sulphurous anhydride. On evaporation the sul- 
 phate is obtained in a crystalline form. From its solution the metal may be precipi- 
 tated by the action of metallic zinc or by electrolysis. It can be obtained in the 
 dense metallic state by fusion out of contact with oxygen, as secured by covering it 
 with potassic cyanide, etc. 
 
 Thallium forms two series of compounds corresponding to the oxides T1 2 and 
 T1 2 3 . Thallous oxideT! 2 is a very soluble substance. Its aqueous caustic solution 
 absorbs carbonic anhydride readily from the air. By evaporation in vacuo the hydrate 
 TIHO is obtained in crystals. Like silver compounds this gradually blackens by con- 
 tact with the air, and fuses at 315 C. into a brown liquid. A solution of thallous 
 oxide precipitates many metals as oxides from their solutions. 
 
 Thallic oxide T1 2 3 is formed during the electrolysis of thallous sulphate as 
 a brown powder at the positive electrode. It may also be obtained by the action 
 of hydric peroxide on the metal, or by the action of chlorine upon the chloride held in 
 suspension in a solution of sodic carbonate. It is also formed by the action of ozone 
 or peroxide of hydrogen upon paper impregnated with a thallous salt ; hence this paper 
 is really no absolute test for ozone, since hydric peroxide is known to behave like it. 
 
 Thallous chloride T1C1, molecular weight = 239'1, is a yellowish-white salt, sparingly 
 soluble in water or ammonia. With ferric chloride it furnishes a double salt, 6T1CJ, 
 Fe.,Cl 6 , of a cinnabar-red colour, and crystallising in prisms. Water decomposes this 
 compound into the respective chlorides. It also forms double salts with the chlorides 
 of gold and platinum. Lamy has described three other chlorides of the composition 
 T1 2 C1 3 , T1C1 2 , and T1C1 3 . Thallous iodide and bromide are yellow and but sparingly 
 soluble. There are also a number of double chlorides, iodides, and bromides, which 
 may be illustrated by the following examples : 3KC1,T1C1,,2H 2 ; 3KBr 2TlBr 3 , 3H 2 ; 
 3KI 2T1I 3 ,3H 2 0, etc. Besides the normal salt there is also known an acid sulphate. 
 
 The nitrate T1N0 3 crystallises in anhydrous prismatic needles, which melt easily, 
 and are insoluble in alcohol. It is obtained by dissolving the metal in nitric acid, 
 and is isomorphous with the nitrates of potassium, sodium, etc. The carbonate 
 T1C0 3 is also crystalline, as is the perchlorate T1C10 4 and the various phosphates. 
 
 Thallium may be easily alloyed with most of the metals, and several of these 
 alloys have been studied by Carstanjen. Excepting the compound with tin, they all 
 tarnish in the air, and all are more or less attacked by dilute sulphuric acid, with the 
 evolution of hydrogen. 
 
 u2 
 
484 CERIUM, DIDYMIUM, AND LANTHANUM. 
 
 CERIUM. 
 
 SYMBOL Ce. ATOMIC WEIGHT 138. 
 
 Cerium was discovered in 1803 by Klaproth and by Hisinger and Berzelius, who 
 obtained it as oxide from cerite. It is a rare metal which has been found in but 
 few minerals. It occurs in cerite, a hydrated basic eerie silicate, and also in 
 churchite, which is a hydrous phosphate of cerium. 
 
 In cerite it is accompanied by lanthanum and didymium. As extracted from its 
 chloride, it is a dark red or chocolate-coloured powder, assuming a metallic lustre on 
 friction ; it is infusible, and does not conduct electricity well. 
 
 Wohler has given a method for extracting it from the oxide, by fusing it with 
 mixed potassium and ammonium chlorides ; on reduction of the fuse by metallic sodium 
 at a high temperature metallic cerium is obtained. 
 
 Cerium oxalate CeC 2 0,j, 3H 2 is one of the best known salts ; it furnishes the 
 oxide on ignition. 
 
 Two oxides are known ; cerons oxide Ce 2 3 , and eerie oxide Ce0 2 , a body which 
 is obtained in colourless transparent crystals with a density of 6*94. The cerous- 
 potassic sulphate and cerous chloride, 2CeCl 3 , 9H 2 0, which forms colourless crystals, 
 are both well-defined salts. 
 
 Marignac has obtained the sulphate Ce(S0 4 ) 3 3H 2 0, and a number of other com- 
 binations are also known. 
 
 Ceric sulphate crystallises in a yellow indistinct form, Ce(S0 4 ) 2 4Aq. 
 
 DIDYMIUM. 
 
 SYMBOL Di. ATOMIC WEIGHT 144-75. 
 
 This metal was discovered by Mosander in 1841, and its compounds have since been 
 studied by him, also by Watts, Marignac, Hermann, Bunsen, and others. 
 
 It occurs associated with cerium and lanthanum in cerate, all an it e, orthite, 
 and allied minerals, but not in the free state ; in fact, it is scarcely known in the 
 metallic form. 
 
 It is said that the metal may be prepared by heating the chloride strongly with 
 potassium, and washing out the soluble chlorides by water. It is thus obtained partly 
 as a grey powder and partly in globules. The powder decomposes water at normal 
 temperatures, and the metal in any form dissolves easily in dilute acids with evolution 
 of hydrogen. 
 
 But few of its compounds are known. One oxide (Di 2 3 ) is known, but it is pro- 
 bable that others exist, notably a peroxide. 
 
 The oxide (Di 2 3 ) is obtained in the anhydrous state by ignition of the nitrate or 
 the hydrate in a covered crucible ; the anhydrous oxide becomes hydrated on immer- 
 sion in water, dissolves easily in acids, and expels ammonia from solution of its salts 
 when boiled with them. 
 
 Didymium gives a white oxalate, and forms double sulphates of a rose-red colour 
 with potassium, sodium, and ammonium. 
 
 Chloride of didymium forms rose-coloured crystals of the' composition DiCl 3 , 
 4H 2 0. When a solution of it is evaporated, hydrochloric acid is evolved, and an 
 oxide is left behind, thus behaving similarly to the chloride of magnesium. 
 
 Most of the salts of didymium are pink or violet-coloured, and are not precipitable 
 by sulphide e f ammonia ; they possess also spectroscopic properties which are 
 characteristic. 
 
 LANTHANUM. 
 
 SYMBOL La. ATOMIC WEIGHT 139. 
 
 This metal was discovered by Mosander in 1841, and occurs along with didymium 
 cerium iu cerite, and along with didymium in lanthanite as carbonate. 
 It forms two oxides, but the peroxide requires more pi'ecise study. The pro- 
 
 and cerium iu cerite, and along with didymium in lanthanite as carbonate. 
 s two oxides, but the peroxide requires more pi'ecise study. Th 
 toxide La 2 3 is a buff-coloured substance obtained by ignition of the hydrate, car- 
 
 bonate, or oxalate, first in contact with the air, and afterwards in the reducing gases 
 of the flame. 
 
 The peroxide dissolves in acids with evolution of oxygen. 
 
INDIUM. 485 
 
 Lanthanum forms colourless, astringent salts whose solutions give white precipi- 
 tates with the soluble oxalates. 
 
 Sulphide of lanthanum is obtained by igniting the metal in the vapour of carbon 
 disulphide ; it is a yellow powder. 
 
 The chloride LaCl 3 is obtained in the anhydrous state by igniting the oxide in 
 hydrochloric acid gas, or by dissolving the oxide in the acid, etc. 
 
 A hydrated chloride LaCl 3 2H 2 which is crystalline and some other combinations 
 are also known, such as the sulphate La 2 (S0 4 ) 3 9H 2 and the double salt LaK s (S0 4 ) s . 
 
 SYMBOL In. ATOMIC WEIGHT 113*4. 
 
 This metal was discovered in 18"63 by Reich and Eichterin the zinc blende of Frei- 
 berg, by means of its peculiar spectrum, which consists of two bright lines in the blue 
 and indigo, one very bright, and the other fainter. It has been since found by Bottger in 
 the flue-dust of the zinc furnaces of the Julius works at Goslarin the Hartz; by 
 Winkler in the black blende (christophite) of Saxony, and by others in wolfram and 
 steatite. 
 
 It has also been detected in certain zinc blendes from New Hampshire (U.S.) by 
 H. B. Cornwall. Bayer suggested a process for the extraction of indium, which is as 
 follows. Freiberg zinc is heated with a quantity of hydrochloric acid insufficient to 
 entirely dissolve it, when, in the course of several days, the indium is precipitated 
 upon the surface of the residual metal. The metallic mud is isolated, heated with a 
 little dilute sulphuric acid to dissolve any oxychloride of zinc that may be .present, 
 and then thoroughly washed with hot water. The product is then .heated with nitric 
 acid, sulphuric acid added and the mixture evaporated to dryness ; tin and lead are 
 thus separated as oxide and sulphate. The residue is extracted with water at 100C. 
 and the solution after filtration precipitated by excess of ammonia, thus throwing 
 down the indium and iron, and leaving copper, zinc, and cadmium in solution. The 
 precipitate is washed, dissolved in the minimum amount of hydrochloric acid, and 
 sodic-hyd-ric sulphite added in excess. On boiling, the indium is obtained as sulphite, 
 and by re-solution in sulphurous acid and re-precipitation by boiling the salt is obtained 
 pure, of the composition 2In 2 3 S0 2 8H 2 0. This substance, treated with other acids, 
 furnishes the various salts of indium. There are several other processes for extracting 
 the metal from its ores. 
 
 The metal may be obtained from its oxide by reduction with hydrogen or sodium, 
 or it may be precipitated from its solution by zinc and fused with potassic cyanide, 
 giving a button of the metal. 
 
 Indium is a silver-white, soft, ductile, compact metal, destitute of crystalline 
 structure, and having a sp. gr. 7'421 and a melting point of 176. At higher 
 temperatures suboxide is formed, if melted in the air. At a strong red heat the metal 
 burns in air with a violet flame, and forms the same yellow oxide. In dilute sulphuric 
 or hydrochloric acid it dissolves slowly, giving off hydrogen ; nitric acid oxidises it. 
 The chloride In 2 Cl c is formed by heating the metal in chlorine, when it burns with 
 a greenish light and the chloride sublimes in white laminae ; it forms double chlorides 
 with those of the alkali metals. The bromide In 2 Br 6 and Iodide In 2 I 6 are both crys- 
 talline bodies, which may be prepared by heating the metal with bromine or iodine 
 in an atmosphere of carbonic anhydride. Several oxides are known. 
 
 The yellow oxide In 2 3 may be obtained by igniting the hydrate which is thrown down 
 from the solutions of indium by ammonia, In 2 H 6 6 . Indie oxide (In 2 3 ) is readily soluble 
 in acids and furnishes three other oxides by ignition in hydrogen ; at 180C. the green 
 substance In 7 9 is produced ; at 220 C. the grey oxide In 4 5 is formed ; and at 
 300 C. a black compound, perhaps InO. These substances, however, have not been 
 well examined. By fusing metallic indium with sulphur, indie sulphide In,jS 3 is 
 obtained in shining scales resembling mosaic gold (Winkler). From a neutral or 
 acetic acid solution of indium sulphuretted hydrogen precipitates yellow sulphide 
 which dries to a brown colour and is decomposed by acids. 
 
 Indie sulphate is known, as also is the nitrate In 2 (N0 3 ) 6 , 9H 2 as a crystalline 
 substance which loses 6H 2 at 100C. 
 
 The carbonate is a white gelatinous body as obtained by precipitation, it is soluble 
 in ammonic carbonate, and is re precipitated on boiling. 
 
 Neither the metal nor its salts are used in the arts. 
 
486 ZIRCONIUM. 
 
 Closely associated in many respects with indium is the new metal GALLIOM 
 (symbol Ga ; atomic weight 68) recently discovered by Lecoq de Boisbandrau in zinc 
 blende from the mine of Pierrefitte. Gallium gives an oxide Ga 2 3 , and a chloride 
 GraCl s , and forms also an ammonium alum. 
 
 The specific gravity of the metal is 5'9 and its melting point 30'1. 
 
 ZIRCONIUM. 
 
 SYMBOL Zr. ATOMIC WEIGHT 89'6. 
 
 The oxide of this element was first obtained from zircon, and was recognised as a 
 peculiar body by Klaproth in 1789. 
 
 It is found as oxide in eudialyte, polymignite, cerstedite, fergusonite, and cata- 
 pleiite. The zircon, like the hyacinth, is a silicate of the composition Zr0 2 Si0 2 , and 
 is found in the Eadau valley near Harzburg. 
 
 Zirconium is generally regarded as a tetratomic element, and may be obtained like 
 silicium in three states amorphous, crystalline, and graphitoidal. Indeed, in its pro- 
 perties and compounds it ranges between silicium on the one hand and aluminum on 
 the other hand. 
 
 Berzelius was the first (in 1824) to obtain the metal in its amorphous form ; this 
 he did by heating together potassio-zirconic fluoride 2KF,ZrF 4 with metallic potassium. 
 
 Troost prepared it by passing the vapour of zirconic chloride over melted sodium 
 at a red heat, or by heating the sodio-zirconic chloride with either metallic sodium or 
 magnesium in a crucible. 
 
 The amorphous metal passes under the burnisher into a lustrous, graphitic-looking 
 mass, which conducts an electric current but feebly. Heated in the air it takes fire 
 below redness, and burns with a bright light, forming zirconia. It is attacked very 
 little by acids, even by hydrochloric acid ; but hydrofluoric acid dissolves it with evo- 
 lution of hydrogen. 
 
 The crystalline variety is prepared by heating a mixture of 1 part potassio-zirconic 
 fluoride with 1 parts of aluminum in a plumbago crucible, to a temperature equal to 
 that of melted iron. From the product the residual aluminum is dissolved out by 
 hydrochloric acid, leaving nearly pure zirconium behind. Thus obtained, it resembles 
 antimony in appearance, and has a specific gravity 4'15. It is very infusible, and 
 burns only in the oxyhydrogen flame. 
 
 Fused caustic potash oxidises it, with evolution of hydrogen ; nitrohydrochloric 
 acid dissolves it when hot, with ease ; but other acids act feebly on it. 
 
 Graphitoidal zirconium is formed under conditions less well determined. Troost, 
 in attempting to decompose zirconate of sodium with iron, obtained light scales of it, 
 having a steel-grey colour. 
 
 Zirconium is closely allied to titanium. It forms but one oxide, Zr0 2 ; a tetra- 
 chloride ZrCl 4 , and a corresponding tetrafluoride ; also a bromide, nitride, and a number 
 of fluozirconates, or double fluorides of zirconium and other metals. 
 
 Oxide of zirconium Zr0 2 is prepared by fusing a mixture of finely 
 powdered zircon with caustic soda or potash, and saturating with hydrochloric acid ; 
 the mixture is evaporated nearly to dryness, and the zirconic chloride dissolved by 
 water, leaving the silica behind. From the solution the zirconium is precipitated as 
 thiosulphate (hyposulphite), and this on ignition gives pure zirconia. 
 
 Thus prepared, it is insoluble in acids, excepting concentrated sulphuric acid. 
 
 The hydrated oxide is a gelatinous white precipitate, insoluble in caustic alkalies. 
 
 ZIRCONIC CHLORIDE ZrCl 4 crystallises in needles which are soluble both 
 in water and alcohol ; when exposed to the air they lose water and hydrochloric acid 
 and give a soluble oxychloride(Zrd 4 , Zr0 2 , 18H 2 0). 
 
 It may be prepared by heating the metal in chlorine gas, or by heating the oxide 
 with charcoal in a current of dry chlorine. It is a volatile body, with a vapour 
 density of 8-1 5 (Deville and Troost). 
 
GLUCINUM AND THORIUM. 487 
 
 GLUCIWUM. 
 
 SYMBOL G or Be. ATOMIC WEIGHT 9'4. 
 
 The oxide of this metal, sometimes termed berylium, was discovered by Vauquelin 
 in 1798; but the metal itself was first obtained by Wohler and Bussy in 1828, by 
 fusing the chloride with potassium. It may be extracted from the emerald or the 
 beryl, which consists in great measure of silicate of aluminum and glucinum 3GO, 
 A1 2 3 , 6Si0 2 . It occurs also as a silicate in the mineral phenacite ; with other sili- 
 cates it is found in various other minerals, and as aluminate it occurs in chrysoberyl 
 or cymophane. 
 
 Gi-lucinum is a white, malleable metal, more fusible than silver, and combines 
 readily with chlorine, iodine, and silicon. It is easily dissolved by dilute hydrochloric 
 or sulphuric acid, but is not vigorously attacked even by strong nitric acid. In potash 
 it dissolves with the evolution of hydrogen. 
 
 Debray regards glucinum as monatomic in character; but there appears ta be some 
 doubt regarding its atomicity. 
 
 Beyond the method given above for the preparation of the metal, the following one 
 by Debray may be adopted for extracting it in a compact state. Chloride of glucinum 
 is first introduced into a combustion tube, and the air then expelled by a current of 
 hydrogen, after which metallic sodium is introduced and heat applied. The chloride 
 of glucinum volatilises, and thus coming into contact with the melted sodium, it is 
 reduced, forming a black mass with the salt, from which the globules of metal are 
 obtained on treating the fuse with water. Thus obtained, it has a specific gravity 
 2-1, and may be forged and rolled into sheets like gold. 
 
 Only one oxide of the metal is known, and, as yet, the formula has not been 
 thoroughly established ; by some it is regarded as a protoxide (GO) and by others as a 
 sesquioxide (G- 2 3 ). It may be obtained from the beryl, which contains 10'6 per cent, 
 of this substance. The silicon is first of all removed as silicic fluoride by heating 
 the mineral with fluospar and sulphuric acid ; the residue is ignited to redness, dis- 
 solved in dilute sulphuric acid, and sulphate of ammonium added. By a process of 
 crystallisation the aluminum is removed as alum, and any which remains behind is 
 deposited as basic sulphate on digesting the mother liquor with metallic zinc. The 
 zinc has then to be removed by addition of sodic acetate, and precipitation by sul- 
 phuretted hydrogen, after which glucina is obtained on adding excess of ammonia. 
 
 Several sulphates of the metal are known, the principal one being GS0 4 , 4H 2 0, 
 which crystallises in octohedra. 
 
 A great number of phosphates are also known. Heated in bromine vapour, the 
 metal takes fire, and forms a bromide GBr 2 , which sublimes in colourless prismatic 
 crystals ; it is a fusible volatile body. 
 
 Chloride of glucinum GC1 2 is formed by heating the metal in chlorine gas or 
 hydrochloric acid. The anhydrous salt is obtained by passing chlorine over an 
 ignited mixture of glucina and charcoal ; the hydrated salt crystallises with one 
 molecule of water, GC1 2 , H 2 0. 
 
 From many of its characters it appears to be a member of that group of metals 
 characterised by aluminum. 
 
 Very little is known about the alloys of glucinum. According to Stromeyer, by 
 heating the oxide to whiteness, with iron and charcoal, an alloy with iron is obtained. 
 H. Dairy also obtained an alloy with iron, by decomposing glucina in an atmosphere of 
 hydrogen, by a powerful voltaic current, having the negative pole of the battery 
 formed of an iron wire which is fused'lby the current. 
 
 THORIUM. 
 
 SYMBOL Th. ATOMIC WEIGHT 231-5. 
 
 This metal was discovered in 1829 by Berzelius, in a rare black mineral thorite, 
 which occurs in a syenitic rock in Norway. Since then it has been found in 
 pyrochlore by Wohler, in monazite by Karsten, in euxenite, gadolinite, 
 orthite, etc. 
 
 As prepared from its chloride by heating with potassium or sodium it is a grey 
 metallic powder of sp. gr. 7'6 to 7'8, closely resembling zirconium ; it burns in the 
 air with brilliancy and forms oxide. 
 
488 YTTRIUM AND ERBIUM. 
 
 Thoria (sp. gr. 9'402) is probably a dioxide, which is precipitated as a hydrate 
 from the sulphata.or chloride by ammonia, and this on ignition gives the anhydrous 
 oxide (Th0 2 ) which is insoluble in acids, excepting strong sulphuric. 
 
 Thorium chloride ThCl 4 is prepared by heating an intimate mixture of thoria 
 and charcoal in dry chlorine, when the salt, which is not very volatile, sublimes as a 
 white crystalline mass. 
 
 By dissolving the hydrated oxide in hydrochloric acid, and concentrating the 
 solution, the chloride is obtained as a deliquescent crystalline saline mass, 
 
 Ammonio-thoric chloride 4NH 4 Cl,ThCl 4 , 4H 2 0, is known, and also the corre- 
 sponding potassic salt. 
 
 Fluoride of thorium has the composition ThF 4 , while the hydrated fluoride is 
 ThF 4 , 2H 2 ; there are known also a bromide and an iodide, an acetate, phosphide, 
 sulphide, and a number of other compounds. 
 
 Thoric sulphate is deposited from its boiling solutions, and is redissolved on 
 cooling. 
 
 The oxalate of thorium is white and insoluble. 
 
 SYMBOL Y. ATOMIC WEIGHT 92. 
 
 Gradolin in 1794 obtained from the ytterite or gadolinite of Ytterby in 
 Sweden, a peculiar oxide resembling lime and alumina. In 1797 Ekeberg confirmed 
 these results and named the earth yttria. 
 
 A number of chemists studied this substance and others accompanying it, and in 
 1843 Mosander, after a careful study of crude yttria, concluded that it contained 
 three earths of different basicity ; to the more abundant of these he gave the name 
 yttria, and the others he named erbia and terbia. It is doubtful, however, whether 
 terbia exists. 
 
 This metal, which belongs to the class known as earth metals, exists only in a few 
 rare minerals. 
 
 Metallic yttrium is obtained by igniting its chloride with metallic potassium, and 
 as thus prepared it is a blackish-grey powder, which acquires some lustre under the 
 burnisher. Yttrium as thus obtained by Berzelius was, however, contaminated by 
 erbium. It is of tritomic character, and forms only one series of compounds. 
 
 The oxide Y 2 3 = 232 occurs naturally in gadolinite and in yttrotantalite. 
 It is a white earthy powder of sp. gr. 4'842, insoluble in caustic alkalies, but dissolved 
 by their carbonates. It may be obtained by ignition of the oxalate, and as thus 
 prepared it differs from erbia, by yielding a spectrum without bright bands. 
 
 The chloride is a non-volatile salt obtained by heating the metal in a current of 
 chlorine ; the bromide is obtained by dissolving the oxide in hydrobromic acid ; so, 
 also, the iodide may be prepared in a corresponding way by using hydriodic 
 acid. 
 
 Besides a selenide and a sulphide, which are known, there exists also a basic 
 nitrate Y(N0 3 ) S Y 2 3 , 3H 2 which crystallises in needles. 
 
 The sulphate 3"Yo(S0 4 ) 3 8H 2 forms also well-defined crystals. 
 
 ERBIUM. 
 
 SYMBOL Eb. ATOMIC WEIGHT 168-9. 
 
 Very little, indeed, is known about this metal or its compounds. It was discovered 
 by Mosander in 1843, and is found as oxide associated with the oxide of yttrium in 
 gadolinite. Erbia is a weaker base than yttria, and, as obtained by ignition of the 
 precipitated hydrate, it has a deep yellow colour with a formula Eb 2 3 , and a doubt- 
 ful molecular weight of 385'8. Its salts have a rose-red colour and astringent taste. 
 
URANIUM. 
 
 SYMBOL U. ATOMIC WEIGHT 240. 
 
 History. Uranium was discovered by Klaproth in 1786, in the mineral named 
 pechblende or pitchblende, -which had hitherto been regarded as a zinc ore. He 
 assigned to the new metal the name of uranium, in honour of Herschel, who about 
 the same time discovered the planet of that name. 
 
 Occurrence. Uranium is a metal whose compounds are sparingly distributed 
 in nature ; the principal ore is pitchblende, a brownish-black mineral which is essen- 
 tially uranoso-uranic oxide U0 2 .2U0 3 , of which it generally contains from 40 to 90 per 
 cent. With this green oxide there are associated varying quantities of copper, lead, 
 iron, arsenic, and sometimes nickel and cobalt. 
 
 Pitchblende is found in veins with lead and silver ores in Saxony, and with tin 
 in Cornwall. 
 
 Uranite, a mineral of a micaceous character, and rarely met with, occurs in 
 France, and is also found in a beautiful form near Redruth in Cornwall. It consists 
 of a hydrated calcic diuranic diphosphate Ca"2(U 2 2 ) "2P0 4 , 8H 2 0. 
 
 Chalcolite is a corresponding mineral in which the calcium is replaced by copper. 
 
 Samarskite and uranotantalite, which contain oxide of uranium, together 
 
 with yttria and niobic acid, are forms of minerals which are met with here and there ; 
 
 so also johannite (sulphate of uranium); zippeite (sulphate of uranium ses- 
 
 quioxide), and uranochre (an impure yellow oxide). 
 
 Beyond these a number of arsenites are found in the White Hart mine in Saxony, 
 and according to Winkler contain from 50 to 63 per cent, of uranium oxide. His 
 analyses lead to the following formulae : 
 
 Specific gravity. 
 
 Trogenite . . . 3U0 3 . As 2 5 + 12H 2 3'23 
 
 Walpurgite . . 5Bi0 2 . As 3 5 + 3U0 3 , A 2 5 + 10H 2 5'64 
 Zeunerite . . . CuO. 2U0 3 . As 2 5 + 8H 2 3'53 
 
 Uranospinite . . CaO. 2U0 3 . As 2 5 + 8H 2 3-45 
 
 Uranosphserite . . Bi 2 3 . U0 3 + H 2 6'36 
 
 Characters. Uranium when in the metallic state constitutes a black coherent 
 powder or is of a steel-white colour, according to the state of aggregation. Under 
 ordinary atmospheric conditions it does not oxidise, but it burns brilliantly when heated 
 in contact with the air. It combines with chlorine and sulphur with considerable 
 violence, and is dissolved by sulphuric and hydrochloric acids with evolution of 
 hydrogen. Chemically, it is allied in many respects to iron and manganese ; but it 
 possesses some characters which are not common to them. Thus it has a high specific 
 gravity (18-4) and forms a volatile chloride (UC1 4 ); uranic oxide does not form salts 
 similar to ferric chloride, and, while it is less easily reducible than iron, its oxides 
 are weak bases compared to the oxides of iron. From these and other considerations 
 Mendelejeff doubles the atomic weight ordinarily assigned to uranium, and makes it 
 240, regarding it as a hexad analogous to chromium. 
 
 Uranium forms three oxides uranous or protoxide U0 2 ; uranoso-uranic oxide 
 U0 2 .2U0 3 ; and uranic oxide U0 3 . 
 
 Peligot further admits the existence of two other combinations of the metal 
 with oxygen. 
 
 Uranium is used for enamel painting and glass staining ; the dioxide gives a 
 fine black colour, not unlikely by absorbing oxygen and becoming black oxide. The 
 sesquioxide gives a fine yellow colour. 
 
 Preparation. The isolation of metallic uranium is due to Peligot, who showed 
 that the substance originally regarded as such was uranous oxide. 
 
 The following method, which is the device of Valenciennes, is described by 
 Peligot : 
 
 A mixture, consisting of 75 grms. uranous chloride, 150 grms. potassic chloride, 
 
490 URANIUM. 
 
 and 50 grms. of metallic sodium cut into small pieces, is covered by potassic chloride 
 in a crucible, which is Enclosed in a second one, and the space between the two is packed 
 with charcoal. The mixture is first exposed to a red heat, when the reaction occurs ; 
 after which the fire is strongly urged so as to meit the metal without volatilising the 
 flux. The metal may be obtained by afterwards dissolving out the flux. To ensure 
 success it is essential to carefully exclude all moisture ; otherwise the chloride of 
 uranium is converted into irreducible uranic oxide. As thus obtained, the specific 
 gravity of the metal is 18'33. 
 
 To extract the metal from pitchblende, this mineral is heated to redness, and pul- 
 verised by throwing it whilst hot into water. The powder so obtained is washed with 
 dilute hydrochloric acid, heated with charcoal, and then digested in stronger acid. In 
 this way most of the iron, arsenic, and sulphur is removed together with the earthy 
 matters. The washed product is roasted, then treated with nitric acid, and the result- 
 ing solution evaporated nearly to dryness to expel the acid. Water is then added, ferric 
 arsenate is thrown down, and on passing sulphuretted hydrogen through the clear 
 solution, copper, lead, and arsenic are precipitated as sulphides. After this treatment 
 the solution is evaporated till crystals of uranic nitrate begin to form. The nitrate is 
 next decomposed at a red heat, giving the oxide (U 3 ? ), which is mixed with charcoal, 
 and heated in a current of dry chlorine ; carbonic oxide and carbonic anhydride are 
 given off, and uranous chloride sublimes. On now heating this chloride with metallic 
 potassium, intense heat is evolved, potassic chloride is formed, and metallic uranium 
 results. 
 
 To obtain the metal in fused globules it is best to place layers of sodium, potassic 
 chloride, and mixed potassic and uranous chlorides in a porcelain crucible enclosed in 
 an earthen one lined with charcoal ; on heating in a blast furnace the fused metal is 
 obtained. 
 
 Compounds. Uranium forms two chlorides, UCL and UCL, and an oxychloride 
 U0 2 C1 2 . 
 
 The tetrachloride (UC1 4 ) is prepared as above described, and is a volatile deliques- 
 cent salt, which crystallises in dark green octahedra of a metallic lustre. 
 
 Uranous chloride is decomposed by boiling water ; it is also decomposed by dry 
 hydrogen, giving the sub-salt UC1 3 , which is a crystalline body of dark brown colour, 
 forming with water a purple solution. Ammonia precipitates from this latter a brown 
 suboxide, which speedily absorbs oxygen on exposure to the air. 
 
 The oxychloride was made by Peligot, and is formed by the passage of chlorine 
 over uranous oxide ; it is a deliquescent substance, giving a yellow aqueous solution, 
 and forming double salts. Thus, with potassic chloride, it gives 2KC1,U0 2 C1 2 , 2H 2 
 in rhombic plates of a greenish-yellow colour. 
 
 Uranium also forms bromides, corresponding apparently to the chlorides-. 
 
 Uranic nitrate, like most of the salts, is yellow, and forms striated prisms of the 
 composition expressed by the formula U0 2 "2NO S , 6H 2 0. 
 
 Uranium has a capacity for forming double salts ; thus besides the double chloride 
 above alluded to there is known a uranic potassic sulphate K 2 (U0 2 )"2SO 4 , 2H 2 0. 
 
 When the salts of uranic oxide (U0 3 ) are heated with alkalies, the oxide is not 
 obtained, but a yellow precipitate, which in the case of potassic hydrate has the 
 formula K 2 0,2U0 3 ,3H 2 0, that is. uranate of potassium. 
 
 The commercial yellow oxide, or uranium yellow, is a hydrate retaining about 2 
 per cent, of ammonia ; on heating, water and ammonia are liberated and the uranic 
 oxide is converted into the black or green oxide. 
 
 Thallous oxide gives with uranium solutions a yellow precipitate of thallium 
 uranate, analogous to the potassic salt described above. Normal uranic sulphate 
 (U0 2 )"S0 4 crystallises in yellow non-fluorescent crystals. When its solution in con- 
 centrated sulphuric acid is evaporated in an open dish at 200, an acid sulphate 
 H 2 (U0 2 ) 2S0 4 forms. 
 
 Uranic nitrate, heated with solution of tetrethylammonium hydroxide, gives a 
 yellow precipitate of tetrethylammonium uranate 4C 2 H 5 .NOUO S + 3H 2 0. 
 
 Roscoe has recently studied the pentachloride of uranium UC1 5 which is obtained 
 along with the tetrachloride or uranous chloride (UC1 4 ), by passing dry chlorine over 
 a moderately heated mixture of any oxide of uranium, or the oxychloride and charcoal. 
 
 Uranic oxide forms no chloride, bromide, or iodide, nor are there normal 
 uranic oxysalts ; all the uranic salts contain the group U0 2 or uranyl, which plays the 
 part of a bivalent radicle for instance, in the following compounds: 
 
 Uranyl oxide, or uranic oxide (U0 2 )0 
 Uranyl chloride, or uranic oxychloride (U0 2 )C1 2 
 Uranyl nitrate, or uranic nitrate (U0 2 ) 2N0 3 
 Uranyl sulphate, or uranic sulphate (U0 2 ) (S0 4 ). 
 
URANIUM OXIDES. 491 
 
 URANOUS OXIDE. 
 
 MOLECULAR WEIGHT 272. 
 
 This oxide may be obtained in several ways, as by ignition of the oxalate in a 
 closed crucible, or the potassio-uranic chloride in hydrogen. The anhydrous oxide is 
 not attacked by dilute acids. 
 
 The hydrated oxide is produced by adding ammonia to a solution of uranous 
 chloride UC1 4 and this reddish-brown precipitate is readily soluble in acids. 
 
 This oxide forms green salts of a crystallisable nature, exhibiting a tendency to 
 absorb oxygen. On igniting the protoxide to redness, and suddenly cooling it, the 
 black oxide U 2 5 is obtained ; it is also obtained by ignition of the nitrate and finds 
 a high price in the arts for its uses in colouring porcelain. 
 
 When the black oxide is heated moderately in air or oxygen, it is converted 
 into the oxide, forming the essential constituent of a pitchblende, that is, the green, 
 or uranoso-uranic oxide U 3 8 or U0 2 .2U0 3 . On stronger ignition the black oxide is 
 reformed. This oxide does not form salts. 
 
 OXIDE. 
 
 FORMULA UO S . MOLECULAR WEIGHT 288. 
 
 This oxide partakes, as we have already seen, of the characters of both an acid 
 and a base. 
 
 According to Ebelmen, a hydrate of it, U0 3 3H 2 0, is obtained by exposing a 
 strong solution of uranic oxalate to the sun's rays, when a brownish-violet powder 
 forms consisting of the green oxide in a hydrated state, U 3 8 , 3H 2 0, while carbonic 
 anhydride is evolved. On further exposure to the air, this substance takes up 
 oxygen and becomes transformed into a greenish-yellow mass of U0 3 , 3H 2 0. From 
 this the anhydrous oxide is obtained by heating it to a temperature of 300 C. 
 
 The salts of uranic oxide are of a bright yellow colour. 
 
 The compounds of this oxide with the earths are capable of withstanding a strong 
 heat without decomposition ; hence they are employed to give a fluorescent yellow 
 colour to glass. 
 
 Uranates. As already shown, uranic oxide possesses not only basic, but also acid 
 powers of combination. The combinations with the alkali metals may be obtained 
 by precipitation of a uranic salt with an alkali. 
 
 The potassic salt has the formula K 2 0.2U0 3 ,3H 2 0, while the sodic salt which is 
 prepared as a commercial article for staining glass is represented by Na 2 02U0 3 6Aq. 
 To prepare it, pitchblende is roasted with lime in a reverberatory furnace, and the 
 resulting product, which contains calcic uranate, is decomposed by dilute sulphuric 
 acid, giving uranic and calcic sulphates. On now heating the solution when drawn off 
 from the calcic sulphate with sodic carbonate, sodic uranate is precipitated in an 
 impure form ; it is redissolved by excess of the alkali, and reprecipitated by dilute 
 sulphuric acid, giving pure hydrated sodium uranate (Na 2 0.2U0 3 ,6H 2 0). 
 
 Of the ammonium salt, or ' uranium yellow ' as it is termed, we have already 
 spoken. 
 
 The uranates of the earth metals and heavy metals are prepared by adding 
 ammonia to a mixture of a uranic salt and a salt of the metal desired. The double 
 carbonates and acetates of uranium and other metals yield uranates on ignition. 
 
ARSENIC. 
 
 SYMBOL As. ATOMIC WEIGHT 75. 
 
 History. Though this elementary substance was known at a very remote period, 
 it was first accurately investigated in 1733, and its relation to white arsenic pointed 
 out by Brandt. In 1775 arsenic acid and arsenuretted hydrogen were discovered by 
 Scheele, and the general chemical relations of arsenical compounds were afterwards 
 more thoroughly investigated by Berzelius. 
 
 Occurrence. Arsenic occurs naturally to some extent among the mineral 
 deposits in the older rocks, but it is much more frequently met with in a state of com- 
 bination; either with sulphur as realgar and orpiment, with antimony as alle- 
 montite, with iron as arsenic pyrites Fe 2 As 3 and arsenosiderite FeAs 2 , 
 with cobalt as smaltine and tesseral pyrites, with nickel as white nickel 
 pyrites, copper nickel, and plaeodin; also in combination with various other 
 metals and their sulphides, as in mispickelFeAs 2 FeS 2 , grey copper, etc.; combined 
 with oxygen as arsenolite, and with oxygen and metallic oxides in the state of 
 arsenates as pyromorphite, skorodite, cube ore, etc. In smaller amount and in 
 various states of combination, arsenic also occurs in a very large number of minerals, 
 as well as in the water of some mineral springs and in the ferruginous deposits from 
 such water. 
 
 Characters. Arsenic is a solid substance of a steel-grey colour and metallic 
 lustre ; it is crystalline and very brittle ; its specific gravity varies from 57 to 5*9. 
 When heated it does not melt, but volatilises, and in contact with atmospheric air is 
 readily oxidised. The vapour is very poisonous, and has a characteristic odour re- 
 sembling garlic. It exhibits a vapour density of 150, which is twice its atomic weight, 
 so that its gaseous molecule like that of phosphorus occupies only one half the volume 
 of a molecule of hydrogen. Arsenic is capable of assuming at least two distinct allo- 
 tropic conditions, and its physical characters vary according to the manner in which 
 it is sublimed. Thus, if it be strongly heated, or made to condense upon plates at a 
 temperature slightly below that at which arsenic volatilises, so that the deposition 
 takes place in an arsenical vapour, it takes the form of a nearly white mass, with a 
 powerful metallic lustre. This form of arsenic, even when in the state of powder, 
 scarcely oxidises in the air or at a temperature of 80 C. It is this form of the 
 metal which is produced by heating arsenical pyrites. 
 
 On the other hand, the arsenic obtained by reduction of arsenous acid with charcoal 
 takes the form of a dark grey crystalline powder of less density than the compact 
 form o arsenic. Arsenic assumes this condition when obtained in any way in which, 
 before condensation, its vapour is mixed with other gases. This form of arsenic 
 oxidises readily in the air, especially at higher than normal temperatures. Arsenic 
 combines readily with chlorine, bromine, iodine, or sulphur, especially when heated ; 
 it is oxidised by nitric acid, but is little affected by hydrochloric acid. 
 
 Native arsenic, which is sometimes definitely cr} 7 stalline (indistinct rhombohedral 
 crystals), resembles in its general characters the artificial preparation. 
 
 Preparation. Arsenic is obtained by subjecting either the native iron arsenides 
 FeAs 2 and Fe 2 As s , ormispickel FeAs 2 FeS 2 , mixed with scrap iron and lime, to the 
 action of heat in tubular earthen retorts, by which means these substances are decom- 
 posed, and the arsenic liberated is sublimed into suitable condensers, leaving a residue 
 of metallic iron or of ferrous sulphide. It is also prepared from the crude arsenous 
 oxide obtained as a sublimate in roasting arsenical ores, by reducing this product with 
 charcoal, and distilling off the arsenic from tubular retorts into condensers made of 
 thin sheet iron rolled into the form of tubes, and connected with the mouths of the 
 retorts with a luting of fire clay. 
 
 The furnaces employed at Ribas in Spain for extracting arsenic from mispickel are 
 represented by figs. 370 and 371. The ore is heated in a number of horizontal tubes 
 (a a) arranged on each side of the arched chamber heated by a fire on the grate (d). 
 
AESENICAL COMPOUNDS. 
 
 493 
 
 The products of combustion pass off through the flues (c c) into a chimney. To the 
 ends of the tubes projecting beyond the side of the furnace are attached the receivers 
 (b b) in which the arsenic is condensed. 
 
 FIG. 370. 
 
 FIG 371. 
 
 At Eeichenstein in Silesia similar furnaces are employed in working mispickel and 
 arsenical pyrites, which frequently contain some gold. 
 
 D'ses. Arsenic is used principally to form an alloy with lead for making shot, 
 as it renders the metal harder and prevents the globules from losing their spherical 
 shape. 
 
 Compounds. The constitution of arsenical compounds is in many instances 
 closely analogous to that of phosphorous compounds, and in some instances to that of 
 nitrogen compounds. With hydrogen it forms a gaseous substance AsH 3 , called 
 arsine or arsenetted hydrogen, and corresponding to ammonia and phosphine 
 in its chemical relations. "With chlorine it forms a trichloride AsCl 3 ; it also forms 
 similar compounds with bromine, iodine, and fluorine. Besides the trivalent character 
 which it presents in these compounds in common with nitrogen, phosphorus, antimony, 
 and bismuth, arsenic has like them a pentavalent character in some of its compounds. 
 For instance, there are two oxides arsenous oxide As 2 3 , and arsenic oxide As 2 5 , 
 the compounds corresponding to these two substances being distinguished as arsenous 
 compounds and arsenic compounds. Both the oxides combine with water and basic 
 oxides, forming two series of salts termed respectively arsenites and arsenates, 
 corresponding to the phosphites and phosphates ; of the two hydrogen salts of these 
 oxides, constituting arsenous acid H 3 As0 3 , and arsenic acid H 3 As0 4 , the latter 
 only is known. The normal constitution of the neutral arsenites is represented by the 
 formula M 3 As0 3 , but they are readily converted into basic or acid salts and the com- 
 position of them is only imperfectly known. The neutral arsenites of the alkalies and 
 alkaline earths are soluble in water; most of the others are insoluble. The neutral 
 arsenates correspond to the formula M 3 As0 4 , and they are much more stable substances 
 than the arsenites ; the neutral arsenates of the alkalies are soluble in water and all 
 the others insoluble in water, but several of them are dissolved by arsenic acid, form- 
 ing monometallic acid salts which dissolve in water. The dimetallic arsenates of the 
 
494 ARSENIC. 
 
 alkaline earths are also dissolved by solutions of ammoniacal salts, owing to the form- 
 ation of double arsenates which are soluble in water. 
 
 Arsenic combines with sulphur in three proportions, forming a disulphide As 2 S 2 , 
 which occurs naturally as realgar; a trisulphide As 2 S 3 , which occurs as orpiment, 
 and a pentasulphide As 2 S 5 . The two latter correspond to arsenous oxide and arsenic 
 oxide, and they both combine with basic sulphides, forming two series of saline com- 
 pounds termed sulpharsenites and sulpharsenates, many of which correspond 
 in constitution with the oxygen salts, sulphur taking the place of oxygen. Only the 
 disulphide and the trisulphide or arsenous sulphide are known in the uncombined state. 
 
 Arsenic unites readily with many metals when melted with them, forming alloys 
 which are generally brittle and very fusible ; it also forms definite compounds with 
 metals, which are termed arsenides, and many of these substances occur naturally 
 either as distinct minerals, such as smaltine CoA 2 , tesseral pyrites CoAs 3 , 
 w hite nickel pyrites NiAs 2 , copper nickel NiAs, placodin Ni 2 As, arseno- 
 siderite Fe 2 As 3 , arsenic pyrites FeAs 2 ; or associated with sulphides, as in 
 cobaltine CoAs 2 CoS 2 , nickel glance NiAs 2 NiS 2 , mispickel FeAs 2 FeS 2 , and the 
 various kinds of fahl ore and arseniferous pyrites, etc. 
 
 ARSEKTOTTS OXIDE. 
 
 FOBMTTLA AS 2 3 . MOLECULAR WEIGHT 198. 
 
 History. This substance was first distinctly mentioned by Geber, as the product 
 obtained by oxidation of arsenous sulphide, and subsequently by Avicenna and Basil 
 Valentin, as arsenicum album. It was long considered to contain sulphur, and this 
 opinion was first disputed by Kinkel in 1677; but it was not recognised to bean 
 oxide until the year 1787, and in 1800 Fourcroy gave it the name of arsenous acid. 
 
 Occurrence. Arsenous oxide occurs naturally to some extent as arsenite, to- 
 gether with ores of nickel and cobalt, but it is chiefly obtained as an accessory product 
 in the treatment of ores containing arsenical compounds. 
 
 Characters. Arsenous oxide is a solid white substance which crystallises in two 
 distinct forms, and is also capable of assuming an amorphous or vitreous condition. 
 Octahedral arsenous oxide has a specific gravity of 2'695, and is the most stable form 
 of this substance ; the prismatic variety is converted into the octahedral form by sub- 
 limation and by solution in water ; the vitreous oxide has a specific gravity of 3 '74 ; 
 it gradually passes into the octahedral form. 
 
 Arsenous oxide volatilises at about 218, forming a dense colourless vapour the 
 specific gravity of which is 13'85 as compared with atmospheric air. The vapour has 
 no smell. The crystalline oxide sublimes without melting, but the vitreous oxide 
 melts before volatilising to any great extent. Arsenous oxide dissolves sparingly in 
 water, requiring 10 or 12 times its weight of hot water and about 30 parts of cold 
 water ; the vitreous oxide dissolves more readily than the crystalline variety. The 
 solution reddens litmus paper slightly. Dilute acids dissolve arsenous oxide more 
 copiously than water with aid of heat, but greater part of the oxide crystallises out as 
 the solution cools. 
 
 Arsenous oxide readily gives up its oxygen to oxidisable substances, and is de- 
 composed in this way when heated with carbon, sulphur, phosphorus, sodium, or zinc, 
 with liberation of arsenic. The vapour brought into contact with red-hot lime is 
 decomposed, and arsenic liberated, while calcium arsenate is formed ; at a lower tem- 
 perature part of the arsenous oxide combines with the lime, forming calcium arsenite. 
 A similar result is produced by heating arsenous oxide with potassium carbonate. 
 
 Arsenous oxide is converted into arsenic oxide by nitric acid, chromic acid, hypo- 
 chlorous acid and other substances capable of giving up oxygen ; it is, therefore, a 
 powerful reducing agent. 
 
 Arsenous oxide combines with basic oxides, forming a series of saline compounds 
 called arsonites, in which it acts the part of an acid. The hydrate or hydrogen 
 salt is not known, but it is probably tribasic, and most of the salts have the following 
 formulae : 
 
 Trimetallic salts M 3 As0 3 or M" 8 2As0 8 
 
 Bimetallic salts M 2 HAs0 3 or M"HAsO s 
 
 Monometallic salts MH 2 As0 3 or M''H 4 2As0 8 
 
 Some of the arsenites have a composition represented by the formula 2M 2 O.As 2 3 , or 
 MjAsA, and acid salts M 2 0.2As 2 3 and 2M 2 0.3As 2 8 . 
 
 Ammonium arsenite NH 4 As0 3 is crystalline and sparingly soluble; it is very 
 readily decomposed by contact with atmospheric air. 
 
ARSENOUS OXIDE. 
 
 495 
 
 Potassium arsenites. The monopotassic salt 2KH 2 As0 3 .As 2 3 obtained by 
 digesting arsenous oxide with potassium carbonate solution at 100 forms prismatic 
 crystals which give off water at 100, and are converted into a compound of pyro- 
 arsenite with arsenous oxide K 2 H 2 As 2 5 .As 2 3 ; this when heated more strongly gives 
 off water, melts to a yellow liquid which solidifies on cooling, and consists of metar- 
 senite combined with arsenous oxide 2KAs0 2 .As 2 3 or K 2 02As 2 3 . 
 
 Sodium arsenites are formed by the reaction of arsenous oxide with sodium 
 carbonate in the same manner as the potassium salts, but their composition has not 
 been so fully determined. 
 
 Preparation. Arsenous oxide is prepared in some places by roasting either 
 mispickel or arsenical pyrites in a kind of muffle furnace, so that the powdered ore is 
 exposed at a high temperature to the oxidising action of atmospheric air, without 
 coming in contact with the products of combustion furnished by the fuel used. At 
 Altenberg in Saxony and Reichstein in Silesia this operation is carried out on a large 
 scale, and the vapour of arsenous oxide is condensed in spacious chambers connected 
 with the muffles. The furnaces used for this purpose are represented in transverse 
 and longitudinal sections by figs. 372 and 373. The muffle (a) is inclined upwards 
 
 FIG. 372 
 
 from the mouth of the furnace (b) and is heated by flues (c c c) passing round it and 
 communicating with the smoke flue (e) and with the fireplace (A). The arsenous 
 oxide vapour passes off through two flues (//) shown in the ground plan, fig. 375, into 
 two other flues (g g~), both terminating in the flue (&) which conducts the vapour into 
 the vault (B) ; it then passes through the opening (i} into the chamber (&) and 
 through the opening (I) into the lower chambers (mri) of a condensation tower re- 
 presented in vertical section by fig. 374. This is divided into several compartments 
 
 FIG. 374. 
 
 FIG. 375. 
 
 (mnopqr); here the arsenous oxide is deposited in the state of a fine powder and 
 the uncondensable gas passes away through the chimney (s). When the operation is 
 completed the covers (t t) on the floor of the chambers are removed for the purpose of 
 transferring the arsenous oxide into the lower chambers of the tower. The residue 
 left in the muffle contains ferric arsenate, together with the silicious portion of the ore, 
 and it is either thrown away, or in some instances treated for the extraction of gold and 
 silver. 
 
496 
 
 ARSENIC. 
 
 Very frequently arsenous oxide is obtained as a by-product in the roasting of 
 various ores containing arsenical minerals, and then it is condensed from the gaseous 
 products by passing them through a series of flues connected with the roasting 
 furnaces. 
 
 Fia. 376. 
 
 The furnaces used in this case are sometimes constructed so that the flame can be 
 admitted into the roasting chamber, or excluded at will. Fig. 376 represents a furnace 
 
 of this kind used at Eibas in Spain, for 
 roasting arsenical pyrites. The hearth 
 (a) is supported on cross walls (6) 
 between which the flame from the fire 
 grate (&) plays against the lower sur- 
 face. The opening (c) at the end of 
 the hearth can be closed by a sliding 
 damper (d) and the flame is then made 
 to pass into the chimney (/) through 
 the flue (e). If it be desired to admit 
 the flame into the roasting chamber, 
 the flue (e) is closed by a damper (g} 
 and the draught then passes across the 
 hearth to the flue (i). Above the 
 mouth of the furnace is a vertical flue 
 (1} through which any arsenical vapour 
 escaping from the chamber passes off. 
 The pulverulent arsenous oxide 
 obtained in either case, requires to be 
 refined and converted into a market 
 able condition ; for this purpose it 
 is sublimed in cast-iron pots sur- 
 mounted by cylinders of the same 
 material. The general arrangement 
 of the apparatus is represented by figs. 
 377 and 378. The iron pots (e e) for 
 heating the. arsenous oxide are set 
 over separate fireplaces (d d} fitted 
 
 Fia. 377. 
 
 FIG. 378. 
 
 with doors (c c) and having flues (//) 
 leading to a common chimney (g). 
 Above the pots are the iron cylinders 
 (h K) covered with the caps (i i\ and 
 pipes (kJc) leading to the chamber (/) ; 
 at the lower part of these pipes there 
 are openings (m m) for introducing an 
 iron rod. 
 
 According to the temperature at 
 which the operation is conducted, the 
 sublimed arsenous oxide is obtained 
 in the state of a loose friable mass or 
 as a hard vitreous cake. 
 
ARSENIC OXIDE. 
 
 497 
 
 The following table gives the composition of arsenous oxides obtained from the 
 roasting of tin ores at Altenberg. 
 
 Arsenous oxide 
 Arsenous sulphide 
 Bismuth 
 
 90-10 
 2-05 
 
 95-95 
 0-32 
 
 94-31 
 1-03 
 0-25 
 
 98-20 
 
 Sulphur . 
 Antimonous oxide 
 Ore 
 
 0-13 
 6-55 
 
 071 
 279 
 
 0-50 
 3-21 
 
 1-68 
 
 ARSENIC OXIDE. 
 
 FORMULA As 2 5 . MOLECULAR WEIGHT 230. 
 
 History. This substance was first prepared by Scheele in 1775 ; but some of its 
 compounds were known long before that time, and the preparation used in medicine 
 by Paracelsus under the name of arsenicum fixum was potassium arsenate obtained by 
 heating arsenous oxide with nitre. Macquer also in 1744 found that the residue left 
 in preparing nitric acid according to Glauber's method by distilling nitre with 
 arsenous oxide, contained a crystallisable salt, and in 1798 by heating white arsenic 
 with sulphuric acid he obtained a fixed Titreous substance which was probably the 
 hydrate of arsenic oxide ; prior to 1764 Cavendish had studied this substance, to 
 which he gave the name of arsenical acid. 
 
 Occurrence. Arsenic oxide does not occur naturally in the free state ; but it often 
 occurs in combination with lime as pharmacolite 2CaHAs0 4 + 5H 2 and as haid- 
 ingerite 2CaHAs0 4 + H 2 0, with ferric oxide as iron cinder 2Fe 2 3 .As 2 O s + 12H 2 0, 
 asscorodite Fe 2 3 As 2 5 + 4H 2 0, as pittizite 2Fe 2 3 .As 2 5 + 12H 2 0, and with 
 ferrous and ferric oxides as cub core FeO.Fe 2 3 . As 2 5 + 6H 2 ; with lead oxide 
 and lead chloride as pyromorphite 3PbO.As 2 5 .PbCl 2 , with lime and magnesia as 
 picropharmacolite CaHAs0 4 .MgHAs0 4 + 2CaMg 3 As0 4 + 5H 2 0, with cobaltous 
 oxide as cobalt bloom Co 3 As0 4 4H 2 0, and with cupric oxide as olivinite 
 4CaOAs 2 5 + H 2 0, as well as in various other minerals. 
 
 Characters. Arsenic oxide is a white substance nearly insoluble in water, but it 
 gradually combines with water, forming a soluble hydrate ; it is decomposed at a full 
 red heat into arsenous oxide and oxygen ; it is also decomposed when heated to redness 
 with carbon, metals, potassium cyanide, etc., yielding metallic arsenic. 
 
 The compound of arsenic oxide with water As 2 5 3H 2 = 2H 3 As0 4 is called 
 arsenic acid, and is the representative of a series of saline compounds called 
 arsenate s, consisting of arsenic oxide combined with various basic oxides. The 
 normal or neutral arsenates contain three atomic proportions of monovalent metals to 
 one atomic proportion of arsenic, or three of divalent metals to two of arsenic, and 
 their composition is represented by formulae corresponding to that of arsenic acid 
 B 3 As0 4 ; thus, for instance, potassium arsenate is K 3 As0 4 , calcium arsenate is Ca 3 2As0 4 
 and ferric arsenate FeAs0 4 . There are also two series of acid arsenates in which 
 only part of the hydrogen of arsenic acid is replaced by a metal; the acid sodium 
 arsenates have the formulae Na 2 HAs0 4 and NaH 2 As0 4 ; the corresponding barium salts 
 are BaHAs0 4 and BaH 4 2As0 4 . The arsenates are isomorphous with the corresponding 
 phosphates. 
 
 Arsenic acid H 3 As0 4 is a crystallisable substance readily soluble in water. It 
 may be prepared by heating arsenous oxide with nitric acid of 1-35. specific gravity 
 in sufficient quantity to oxidise the arsenous oxide ; a syrupy liquid is thus obtained 
 which by standing deposits crystals containing two molecules of the acid and one 
 molecule of water of crystallisation 2H 3 As0 4 + H 2 ; these crystals are very deli- 
 quescent, and when heated to 100 they melt, lose the water of crystallisation, and 
 are converted into a crystalline powder consisting of H 3 As0 4 . This substance may 
 also be obtained in large crystals by exposing a concentrated solution of arsenic acid 
 to a very low temperature. Another hydrate of arsenic oxide As 2 5 2H 2 = H 4 As 2 7 
 is obtained by heating the hydrated crystals of arsenic acid to a temperature ranging 
 from 140 to 160 ; it separates in hard shining crystals which dissolve in water with 
 great increase of temperature. By heating these crystals to 200 for some time, and 
 then raising the temperature to 206, water is given off, the mass suddenly becomes 
 pasty, and is converted into a white flaky monohydrate HAs0 3 which dissolves slowly 
 in cold water. These hydrates of arsenic oxide correspond to the hydrates of phos- 
 
 K K 
 
498 ARSENIC. 
 
 phoric oxide, but differ from them in being at once converted into the ordinary trihy- 
 drate when dissolved in water. 
 
 Ammonium arsenate 3NH 4 .As0 4 is a soluble pulverulent substance obtained 
 by saturating strong ammonia solution with arsenic acid ; it is decomposed by heat 
 and converted into the acid salt 2NH 4 .HAs0 4 , which crystallises in prisms that 
 effloresce in the air, giving off half their ammonia ; this salt when heated is decomposed, 
 yielding ammonia, water, metallic arsenic, and nitrogen. The salt NH 4 H 2 As0 4 is very 
 soluble in water and has a strong acid reaction ; it crystallises in octahedra, is very 
 deliquescent, and is decomposed by heat like the last mentioned salt. 
 
 Barium arsenate Ba 3 2As0 4 is insoluble in water; the acid salt BaH 4 2As0 4 is 
 soluble in water and crystallisable, and the intermediate salt BaHAs0 4 obtained as a 
 precipitate by adding solution of disodic arsenate to barium chloride is readily con- 
 vertible into the two salts first mentioned ; it combines with ammonia, forming a cry- 
 stalline precipitate having the composition represented by the formula Ba.NH 4 As0 4 . 
 
 Calcium ar senates correspond in composition and characters with the barium 
 salts, and some of them occur naturally. 
 
 Cobaltous arsenate Co 3 2As0 4 occurs naturally in a hydrated state, as cobalt 
 bloom, in red crystals, and as prepared by precipitating cobalt salts with sodium 
 arsenate it is a reddish powder. 
 
 A basic cobaltous arsenate known by the name of chaux metallique is used as a pig 
 ment ; it is prepared either by adding potassium carbonate to a solution of cobalt 
 glance in nitric acid as long as ferric arsenate is precipitated, and then precipitating 
 the cobaltous arsenate from the filtered solution ; or by melting cobalt glance with 
 twice its weight of potash and some sand, extracting the cold mass with water, and 
 again melting the insoluble portion with potash ; by this means a blue slag is ob- 
 tained together with cobalt arsenide, which can be converted into the basic arsenate by 
 careful roasting. 
 
 Cupric arsenate Cu 3 2As0 4 is a green powder, soluble when freshly precipitated 
 in ammonia, forming upon evaporation of the liquid crystals which are decomposed by 
 exposure to light ; they have a composition represented by the formula Cu4NH 4 2As0 4 
 + 2(NH 4 HO). Several basic cupric arsenates occur naturally. 
 
 Ferrous arsenateFe 8 2As0 4 is a white pulverulent substance which acquires a 
 greenish colour when exposed to the air. 
 
 Ferricarsenate FeAs0 4 occurs naturally in the hydrated state as scorodite, 
 cube ore, and in other minerals. The precipitate formed by adding disodic arsenate 
 to ferric chloride solution dissolves in ammonia, and on evaporating the solution gives 
 a ruby red mass consisting of ammonio-ferric arsenate. 
 
 Lead arsenate Pb 3 2As0 4 is a white insoluble powder that turns yellow and 
 cakes together when heated, but does not melt. This salt occurs in sgme varieties of 
 pyromorphite in the place of lead phosphate. 
 
 Magnesium arsenates correspond in composition and characters with the cal- 
 cium salts ; the acid salt MgH 4 2As0 4 is readily soluble and forms a gummy mass in 
 the dry state. Ammonio-magnesic arsenate MgNH 4 As0 4 + 6H 2 is formed as a cry- 
 stalline precipitate on adding an ammoniaeal solution of arsenic acid to the solution of 
 a magnesium salt mixed with ammonium chloride ; it is almost insoluble in water, 
 containing ammonia like the corresponding ammonio-phosphate. Double salts con- 
 sisting ofimagnesium arsenates and calcium arsenates occur naturally as picropharma- 
 colite, and corresponding salts containing potassium or sodium arsenates may be formed 
 artificially. 
 
 Nickelarsenate Ni 3 2As0 4 occurs naturally asnickelbloom; artificially pre 
 pared it is a pale green powder soluble in strong acids and in ammonia. 
 
 Potassium arsenate K 3 As0 4 is a very soluble salt, crystallisable in small 
 needles which deliquesce rapidly on exposure. Of the acid arsenates the salt 
 K 2 HAs0 4 is a deliquescent non-crystalline mass, and the salt KH 2 As0 4 forms crystals 
 permanent in the air ; it dissolves in about 6 parts of cold water and a smaller propor- 
 tion of hot water, but is insoluble in alcohol. 
 
 Silverarsenate Ag 3 As0 4 is formed by mixing soluble arsenates with a solu- 
 tion of silver nitrate as a dark brown precipitate which melts when heated, is converted 
 into chloride by hydrochloric acid, and is soluble in acetic acid or ammonia. This salt 
 dissolves in solution of arsenic acid, and on evaporation of the solution the monargentic 
 salt AgH 2 As0 4 is deposited. 
 
 Sodiumarsenate Na 3 As0 4 is soluble in water, and crystallises with 12 molecules 
 of water in rhombic prisms which are permanent in the air and melt at 86. The disodic 
 salt Na 2 HAs0 4 is also soluble, and forms crystals with 12 molecules of water, which 
 effloresce and are isomorphous with ordinary sodium phosphate. A more concentrated 
 solution kept at a temperarure of 20 gives crystals containing 14 molecules of water, 
 which are not efflorescent. 
 
 
ARSENOUS SULPHIDE. 499 
 
 The monosodic salt NaH. 2 As0 4 is more soluble than the disodic salt, and forms 
 large crystals isomorphous with the corresponding phosphate. 
 
 The double sodic andammonic arsenate NaNH 4 HAs0 4 + 4H 2 0, obtained by mixing 
 solutions of the disodic and diammonic salts, forms crystals resembling those of the 
 corresponding phosphate known as microcosmic salt. 
 
 Zinc arsenate Zn 3 2As0 4 occurs naturally combined with 8 molecules of water 
 askottigite; on adding a solution of sodic arsenate to zinc acetate this salt is 
 obtained as a white precipitate which dissolves in excess of arsenic acid, and on evapo- 
 rating the solution crystals of an acid salt are deposited. 
 
 ARSENIC BISULPHIDE. 
 
 FORMULA As 2 S 2 . MOLECULAR WEIGHT 21 4. 
 
 History. This substance, commonly called realgar, was known at a very 
 remote period, and was mentioned by Aristotle, Theophrastus, and Dioscorides under 
 the name aavSopctarj, by Latin writers as sandaraca. 
 
 Occurrence. Arsenic disulphide occurs naturally in the form of oblique rhombic 
 prisms of an orange yellow or reddish colour, accompanying ores of lead and silver. 
 
 Characters. As prepared artificially by melting metallic arsenic with sulphur 
 the disulphide is of a ruby colour, transparent, easily fusible, and it solidifies to a 
 crystalline mass. It burns in the air with a blue flame, yielding sulphurous oxide 
 and arsenous oxide. 
 
 Arsenic disulphide combines with basic sulphides, forming saline compounds called 
 hyposulpharsenites, which are sparingly soluble in water. 
 
 ARSENOUS SULPHIDE. 
 
 FORMULA A.s 3 . MOLECULAR WEIGHT 246. 
 
 History. The term apffevucbv was probably first used by Dioscorides to indicate 
 this substance as distinguished from the red sulphide, and though at a later period the 
 difference in external characters between these substances was recognised, they were 
 often regarded as being in common with white arsenic merely modifications. It was 
 not until 1801 that Proust showed that orpiment, or the yellow sulphide, did not 
 contain oxygen. 
 
 Occurrence. Arsenous sulphide occurs naturally as orpiment, and in com- 
 bination with basic sulphides it is a constituent of a great number of minerals. 
 
 Characters. Arsenous sulphide has a fine yellow colour, is insoluble in water 
 and dilute acids, melts at a moderate heat and is volatilisable. The crystalline 
 form of the native sulphide is the rhombic prism. The specific gravity is 3'48. 
 When heated in contact with atmospheric air it burns and by oxidation is converted 
 into arsenous oxide and sulphurous oxide. Chlorine converts it into a brown liquid 
 consisting of arsenic sulphochloride ; nitric acid or nitromuriatic dissolves it with oxi- 
 dation ; by fusion with acid potassium sulphate it is converted into potassium awenite 
 and sulphurous oxide is given off: 
 
 12KHS0 4 + As 2 S 3 = 3K,,S0 4 i 12S0 2 + 6H 2 + 2K 3 As0 3 
 
 When the vapour is brought into contact with red-hot lime, calcium arsenate is formed, 
 together with calcium sulphide : 
 
 As 2 S s + 6CaO = 3CaS + Ca 8 As 2 6 , 
 
 and is attended by the conversion of the arsenate into arsenite and arsenic is gives off : 
 5Ca 3 As 2 6 = 3Ca 3 As 2 8 + 6CaO + 4As. 
 
 Arsenous sulphide combines with basic sulphides forming the saline compounds 
 called sulpharsenites, of which there are three series represented by the potassium 
 salts 3K 2 S.As 2 S 3 or K 3 AsS 3 , 2K 2 S.As 2 S 3 or K 4 As 2 S 5 , and K 2 S.As 2 S s or KAsS 2 . The 
 alkaline salts are soluble in water, but the solutions are decomposed by evaporation. 
 
 KK2 
 
ANTIMONY. 
 
 SYMBOL Sb. ATOMIC WEIGHT 122. 
 
 History. This elementary substance was first definitely described by Basil 
 Valentin towards the end of the fifteenth century, but it was probably known at an 
 earlier period. It was at first regarded as a variety of lead, and likewise as contain- 
 ing iron, or as being in some way subject to planetary influences in its production. 
 
 Occurrence. Antimony occurs to some extent naturally in the metallic state 
 and in the form of alloys with other metals; in various states of combination it occurs 
 more frequently the sulphide as grey antimony or stibnite, the oxides as 
 antimony bloom, valentinite or senarmontite, and as antimony ochre or 
 cervantite. The sulphide also occurs in combination with several other sulphides, 
 as berthierite, zinkenite, miargyrite, bournonite, pyrargirite, grey 
 copper, etc., and in combination with antimonous oxide as red antimony or 
 kermesite. 
 
 Characters. Antimony is a bluish-white metal of high lustre and very crystal- 
 line structure ; it is very brittle, and the density varies from 6'702 to 6'860 ; it melts 
 at 450, and volatilises at a higher temperature. Antimony is not sensibly oxidised 
 by exposure to atmospheric air at ordinary temperatures, but it oxidises readily when 
 melted. At a red heat it takes fire and burns with a white flame, giving rise to white 
 fumes of antimonous oxide. 
 
 Antimony is oxidised by nitric acid, but is not dissolved ; by moderately dilute acid 
 it is converted chiefly into antimonous oxide, and only a small proportion of antimonic 
 oxide is formed, but with strong nitric acid the product is chiefly antimonic oxide. 
 Antimony is not acted upon by dilute sulphuric acid, but when heated with strong 
 sulphuric acid it is oxidised, sulphurous oxide is given off, and antimonous sulphate 
 is formed. In the compact state antimony is not dissolved by hydrochloric acid, but 
 when the powder is heated with hydrochloric acid, it is dissolved with evolution of 
 hydrogen. 
 
 When in the form of powder antimony is dissolved by a solution of an alkaline 
 polysulphide, while the metals usually associated with it are left undisturbed. 
 
 When certain solutions of antimony are subjected to electrolysis, the metal is 
 deposited in an amorphous form with properties differing according to the nature of 
 the solution employed and the mode of deposition. A deposit having an explosive 
 property is obtained by using weak currents of constant strength and concentrated 
 acid solutions. When deposited from the chloride, the amorphous antimony has a 
 density of 5'8 ; if heated to 77 and up to 99 sudden evolution of heat occurs with 
 violence. The metal deposited from the bromide has a sp. gr. of 5'44, and at 121, 
 if touched with a red-hot wire, it gives out heat with explosive violence. The variety 
 deposited from the iodide has a sp. gr. of 5'25, and gives out less heat than the other 
 forms. 
 
 Preparation. Antimony is obtained entirely from the sulphide, either by con- 
 verting it into oxide by roasting, and then reducing the oxide by heating with 
 carbonaceous materials, or by melting the sulphide with metallic iron or charcoal and 
 alkalies. When iron is used for the purpose of extracting antimony from the sulphide, 
 it should be either in the spongy state or in the form of filings. The operation is con- 
 ducted either in crucibles or in reverberatory furnaces. The reduction by metallic 
 iron takes place according to the following equation : Sb 2 S 3 + 3Fe = 2Sb + 3FeS. 
 The whole of the sulphur is separated from antimonous sulphide by iron at a 
 moderate heat, but a higher temperature is requisite for melting the ferrous sulphide 
 so as to enable the antimony to separate from it and form a distinct layer ; at this 
 high temperature the antimony is liable to oxidation, and to prevent this, the mass 
 must either be covered with charcoal or some sodium carbonate must be added to the 
 materials, and the double sulphide of iron and sodium thus formed melts more 
 readily. These two methods of extraction may be briefly described as follows : 
 
ANTIMONY. 
 
 501 
 
 In the first the sulphide is roasted in a reverberatory furnace until the sulphur 
 is expelled, and a grey mass consisting mainly of teroxide of antimony results : 
 Sb.jS 3 + 90 = Sb ? 3 -t- 3S0 2 . During this operation the charge of stibnite 
 requires constant raking or stirring, to bring every part in contact with the oxygen 
 of the air, which mixed with the flame plays over its surface. Meanwhile care 
 must be taken that the temperature shall not rise above a given extent ; otherwise 
 sulphide of antimony volatilises and causes a serious loss in the process. 
 
 The product obtained in this way is now mixed with one tenth its weight of crude 
 tartar and the mixture reduced in large earthen crucibles placed in a wind furnace. 
 The following equation represents the change which here takes place : 
 
 Sb 2 3 + 2KC 4 H 5 6 = 2Sb + K 2 C0 3 + 7CO + 5H a O. 
 
 Sometimes however this reduction is effected by mixing the crude oxide of antimony 
 with one sixth of its weight of charcoal, and making the whole into a paste with a 
 strong solution of potassic carbonate. In either case the metal collects at the bottom 
 of the crucibles, and above it there forms a scoria which consists chiefly of antimonic, 
 sodic, or potassic sulphide, which is known in the arts as crocus of antimony. 
 Sometimes the metal is re-washed with the scoria. In the process it is estimated that 
 three sevenths of the total amount of antimony is lost. The metal obtained in this way 
 is not pure, but is nevertheless ready for the market ; its principal impurity is iron. 
 
 Figs. 379 and 380 illustrate the construction of a furnace which was used at Linz, 
 in Germany, for reducing the sulphide by one operation. The bed is concave, and 
 is formed of sand and clay ; through the pipe (a) the fused metal flows out as soon 
 as it is produced ; (b) is an air channel in the bridge (d). The charge is introduced 
 
 FIG. 379. 
 
 FIG. 380. 
 
 through the door (c), and through the same opening the residuary slag is removed ; 
 the fire is shown at (/) ; (e) is the grate, and (g) the chimney. 
 
 In the English process of obtaining metallic antimony there are three distinct 
 operations, termed singling, doubling, and melting for star metal. 
 
 1. Singling.^ About 40 Ibs. of the ore, broke up into lumps, are introduced into 
 a red-hot crucible with a quantity of slag produced from the doubling operation. 
 Above this mixture there is placed a mass of iron which generally takes the form of 
 a cone, consisting of old tin plate, 20 or 22 Ibs. of which constitute a charge. When 
 the charge of ore and slag has melted, the iron is pressed down into the mass and 
 reduction thus effected. Each fusion requires about l hours, and at its termination 
 the molten mass is poured into a conical mould ; when sufficiently cold, the antimony 
 is separated from the ferruginous mass covering it. 
 
 Doubling. The impure metal from the first operation is next fused in a similar 
 crucible with the addition of a little sulphate of sodium and a small quantity of 
 slag from the third operation, 80 Ibs. of crude metal, and 2 of salt cake being the 
 proportions employed. The fusion lasts nearly 10 hours and gives bowl metal. 
 
 Refining, Wrenching, or Melting for Star Metal.. About 60 Ibs. of bowl metal are 
 broken into fragments and mixed with 2 Ibs. of pearl ash or American potash and 5 Ibs. 
 of slag obtained from a previous similar operation. The mass is melted in less than 
 an hour, and the refined metal is cast into rectangular ingots, care being taken to 
 cover each one with slag. In this way the metal crystallises, owing, as Matthieson has 
 shown, to the presence of some little impurity. 
 
 Uses. Antimony is too brittle to be of much value when used alone, but its 
 alloys are widely employed ; such are type metal, Britannia metal, plate pewter, etc. 
 Antimony is also used for hardening bullets and shots, etc. 
 
 Compounds.- Antimony forms two series of compounds in which it is respect- 
 ively trivalent and pentavalent, as in the chlorides SbCl 3 and SbCl 5 , or the oxides 
 Sb 2 3 and Sb.,0 s . There are some compounds intermediate between these, as, for 
 instance, the oxide Sb(X, which may be regarded as containing antimonic oxide 
 
502 ANTIMONY. 
 
 combined with antimonous oxide Sb 2 3 + Sb 2 s = 4Sb0 2 . Both the oxides combine 
 with water and basic oxides, forming two series of salts, termed respectively ant i- 
 monites and antimonates; the former are very unstable, but the latter are in 
 many instances well-defined salts. Antimonous oxide also acts the part of a feeble 
 base, forming compounds with sulphuric, nitric, and tartaric acids. 
 
 The salts formed from antimonous oxide when in solution, and largely diluted 
 with water, give a milky deposit of basic compounds, which are, however, soluble in 
 tartaric acid. 
 
 Antimony unites with most other metals when melted with them, forming alloys 
 which are hard and brittle ; some of these compounds occur naturally, as for instance 
 dicrasite or antimonial silver Ag,Sb and Ag 6 Sb in the form of six-sided 
 prisms of a silver- white colour. Nickel antimonide Ni 2 Sb occurs naturally as breit- 
 hauptite in thin hexagonal plates. A compound of antimony with arsenic occurs 
 naturally as allemontite. Antimony and lead unite readily in all proportions, the 
 hardness and other characters of the alloys varying according to the relative propor- 
 tions of the metals. The alloy, consisting of equal proportions of lead and antimony, 
 is brittle and sonorous; when the antimony amounts to only one twelfth the weight of 
 the lead, the alloy is malleable and somewhat harder than lead. Type metal is an 
 alloy of lead containing from 17 to 20 per cent, of antimony. One sort of type metal 
 consists of tea lead 75 parts, antimony 20 parts, block tin 5 parts ; another kind is 
 composed of tea lead 70 parts, antimony 25 parts, block tin 5 parts. 
 
 Stereotype metal consists of 6 parts of lead, 1 part of antimony, and sometimes a 
 little block tin is added. 
 
 Of Britannia metal there are various varieties, the best being composed as fol- 
 lows: tin 150 Ibs., antimony 10 Ibs., copper 3 Ibs. Bismuth and zinc are sometimes 
 added in small proportions. Alloys of antimony with tin, or with tin and lead or 
 copper, are used in place of zinc metal for the bearings of machinery. 
 
 ANTXMON-OUS SULPHIDE. 
 
 FORMULA Sb 2 S 3 . MOLECULAR WEIGHT 340. 
 
 History. This substance was known at a very early period under the name of 
 stibium, and subsequently among German alchemists as spiess glass, on account of 
 its acicular crystalline structure, and of its furnishing a glassy product when partially 
 roasted and exposed to a strong heat. It was also termed antimonium, and it has 
 been fancifully supposed that this name was adopted to indicate the poisonous effects 
 produced by it and its preparations upon the monks to whom Basil Valentine admin- 
 istered it medicinally. 
 
 Occurrence. Antimonous sulphide occurs naturally in large quantities as stib- 
 nite or antimony glance in the older rock formations, and it is the principal ore 
 of antimony. It occurs sometimes combined with antimonous oxide as red anti- 
 mony ore and with ferrous sulphide as berthierite. It also occurs in combina- 
 tion with various other sulphides such as lead sulphide, cuprous sulphide, silver 
 sulphide, etc., constituting sulphantimonites, which are frequent ingredients of 
 the ores of lead, silver, and copper. 
 
 Characters. Native antimonous sulphide is a steel-grey crystalline substance 
 that is readily fusible and volatilisable at a very high temperature. Its sp. gr. is 4-62. 
 
 It is this substance which constitutes the crude antimony of commerce. When 
 heated in contact with atmospheric air it burns with a blue flame, sulphurous oxide 
 and antimonous oxide being formed : 
 
 Sb 2 S 8 + 90 * 3S0 2 + Sb 2 s . 
 
 Antimonous sulphide prepared by precipitation with acids from solution of alkaline 
 sulphantimonites is a brownish-red pulverulent substance, having a sp. gr. of 4-15. A 
 mixture of the amorphous sulphide with antimonous oxide, known by the name of 
 mineral kermes, is prepared in a variety of ways for medicinal purposes. When 
 melted, the amorphous sulphide becomes black ; and, if slowly cooled, it assumes a 
 crystalline condition. Antimonous sulphide is obtained in the hydrated state by 
 passing sulphuretted hydrogen through an acid solution of antimonous chloride ; it 
 nas a fine orange colour, which becomes darker when the precipitate is dried and 
 moderately heated. 
 
 When kermes' mineral is digested for soifle time with tartaric acid, any anti- 
 monous oxide or potassium salt which may be present is dissolved, and the pure 
 tersulphide remains. 
 
ANTIMOSTIC SULPHIDE. 
 
 503 
 
 FIG. 381. 
 
 This sulphide may also be obtained in crystals, by melting antimonous oxide and 
 sulphur together, 2Sb 2 3 + 9S = 2Sb 2 S 8 + 3S0 2 . 
 
 Antimonous sulphide combines with basic sulphides forming a series of saline 
 compounds called sulphantimonites; the most important of those which are pre- 
 pared artificially are the alkaline salts called liver of antimony which are obtained 
 by melting mixtures of antimonous sulphide with alkaline carbonates, or alkaline 
 sulphates and charcoal ; or by melting metallic antimony with alkaline sulphates. In 
 the melted state these substances are black or dark brown and crystalline. They dis- 
 solve in water, but when the solutions are mixed with a very large proportion of water 
 the sulphantimonite is deposited in a gelatinous state. 
 
 Preparation. Antimonous sulphide is obtained by heating the native ore suffi- 
 ciently to melt the sulphide and separate it from the gangues with which it is asso- 
 ciated in the native state. This operation is carried out either in crucibles or 
 closed cylindrical vessels heated externally. One of the simplest forms of apparatus 
 for this purpose is represented by fig. 381. The large 
 crucible (b) is filled with the ore from which the sulphide 
 is to be extracted ; holes are pierced in the bottom so that 
 the melted sulphide runs out into a smaller crucible (c) 
 placed beneath. A number of these crucibles are arranged 
 in this way side by side between two walls (a a), and a fire 
 is made in the intervening space at e e. 
 
 The liquation of crude antimony is effected at Malbosc, 
 in the department of the Ardeche, in an apparatus of 
 which the figure (382) represents a vertical section. 
 
 The mineral is placed in large earthen 
 pots (R) of which four are set in one 
 furnace. At the bottom of each an aper- 
 ture is left, and this corrresponds with 
 one in the tile upon which each pot rests. 
 Beneath these in the chambers (c) are 
 placed earthen pots (p) into which the 
 melted sulphide flows as it descends from 
 the cylinders. 
 
 Owing to the fusible nature of sulphide 
 of antimony, this process of liquation is 
 one which is easily conducted, and gives 
 little trouble. 
 
 Fir wood constitutes the fuel employed. 
 
 In England a reverberatory furnac'e 
 has sometimes been employed instead of 
 the plant described above. 
 
 Uses. The artificial sulphide is 
 used to some extent as a red pigment 
 which is sold under the name of antimony 
 vermilion. It is prepared by pouring 
 solution of antimonous chloride in hydrochloric acid into one of calcic thiosulphate 
 (hyposulphite) ; on heating to 60 C. the antimony vermilion is deposited. 
 
 Kermes' mineral is still largely used as a medicine in England, particularly for 
 veterinary purposes. It may be prepared in many ways, the oldest and one of the 
 best being as follows. The powdered sulphide is boiled with a solution of potassic 
 carbonate or caustic potash, when it dissolves, and on cooling the filtered liquid, 
 Kermes is deposited as a reddish-brown substance. 
 
 FIG. 382. 
 
 ANTIIVTOBTIC SULPHIDE. 
 
 FOEMTOLA Sb-jSg. MOLECTJIAR WEIGHT 404. 
 
 This body, known sometimes as sulphantimonic acid, maybe obtained by 
 passing sulphuretted hydrogen through an acid solution of antimonic pentachloride. 
 It forms an anhydrous, orange-yellow precipitate, and has a remarkable facility of 
 inter- combination with the sulphides of the alkali metals, forming a series of saline 
 compounds called sulphantimonates. The composition of these salts may be repre- 
 sented by that of trisodic sulphantimonate 3Na 2 S,Sb 2 S 5 = 2Na 3 SbS 4 . This compound 
 may be obtained as a crystalline salt with 9 molecules of water. 
 
 The medicinal effects of this sulphide are more active than those of kermes, 
 and it is used as an alternative in chronic diseases of a rheumatic and cutaneous 
 nature, as well as in liver complaints. 
 
504 ANTIMONY. 
 
 AirTiMoxrous OXIDE. 
 
 FOBMTTLA Sb 2 s . MOLECTJLAB WEIGHT 292. 
 
 As previously stated, this substance is found to some extent as a mineral (valentin- 
 tite or antimony bloom). It was well known to Basil Valentine, who named itflores 
 antimonii. 
 
 It may be prepared in several ways, the best of which is by boiling powdered 
 metallic antimony mixed with excess of strong sulphuric acid to dryness ; there is 
 thus/formed an insoluble sulphate, while sulphurous anhydride is evolved. The last 
 traces of acid are removed by washing first with water, and then with dilute sodic 
 carbonate, when the oxide remains behind as a white powder. 
 
 On heating, it assumes a yellow colour, but becomes again white on cooling. It 
 may be melted in closed vessels, and is volatile at a high temperature ; the vapour 
 which thus forms condenses in brilliant needles similar to those obtained in the 
 same way from arsenous oxide. 
 
 On burning it in the air, it forms antimony tetroxide. It is freely soluble in 
 hydrochloric and tartaric acid, but is oxidised to a higher form by nitric acid. It is 
 also soluble in acid tartrate of potassium, forming tartar emetic. 
 
 ANTIIVIONIC OXZDE. 
 
 FOBMTJLA Sb 2 5 . MOLECTJLAE WEIGHT 324. 
 
 Antimonic oxide may be obtained by oxidising the metal with nitric acid, and 
 expelling the acid at a temperature below red heat. It is pale yellow in colour, and 
 insoluble in water. If subjected to a strong heat it loses oxygen and forms antimony 
 tetroxide Sb 2 4 , and this on treatment with hydric potassic tartrate (cream of tartar) 
 forms tartar emetic, and antimonic anhydride is left undissolved : 
 
 2Sb 2 4 = Sb 2 3 + Sb 2 s . 
 
 Antimonic acid forms definite compounds with the alkali metals. Thus, on boil- 
 ing it with potash, it dissolves, and on the addition of an acid, hydrated antimonic 
 acid is deposited as a white powder, Sb 2 5 , 4H 2 0. 
 
 The normal potassic salt is K 2 Sb 3 O a , SH-jO. 
 
 CHLORIDE. 
 
 MOLECULAB WEIGHT 228-5. 
 
 This substance, formerly known as butter of antimony, owing to its fusible 
 nature, may be obtained in the anhydrous condition by distilling a mixture of eight parts 
 corrosive sublimate with three of powdered antimony, when a reaction indicated by 
 the following equation results : Sb 4 + 4HgCl 2 = 2SbCl s + Sb 2 Hg 2 + Hg 2 Cl 2 , that 
 is to say, terchloride of antimony distils over, while an alloy of antimony and mer- 
 cury and calomel remain behind. Or the chloride may be prepared by distilling a 
 mixture of antimonous sulphate with twice its weight of common salt. 
 
 Trichloride of antimony is a volatile, fusible, crystallisable body of a deliquescent 
 nature, and of corrosive properties. It is soluble in hydrochloric acid and in water, 
 but much water will cause a precipitate of an insoluble oxychloride, SbCl s , Sb 2 3 , when 
 added to its solutions. 
 
 Antimonous chloride is used in the bronzing of gun barrels, so as to prevent them 
 from rusting. 
 
 ANTIIVKONIC CHLORIDE. 
 
 FOBMULA SbCl 5 . MOLBCULAB WEIGHT 299 '5. 
 
 This compound is produced when a current of dry chlorine is passed over or 
 through antimonous chloride, gently heated in a retort. It is a very volatile, 
 slightly yellowish liquid, which emits dense white fumes on exposure to the air, and 
 is decomposed on distillation. 
 
 When treated with much water the following reaction occurs : 2SbCL + 7ILO 
 = H 4 Sb 2 7 + 10HC1. 
 
 With sulphuretted hydrogen, antimonic chloride produces a white crystalline sub- 
 stance of the formula SbCl s S. It also forms interesting compounds with the higher 
 chlorides of phosphorus, selenium, sulphur, etc. 
 
 In studies upon so-called organic compounds it is often used as a chlorinating body. 
 
BISMUTH. 
 
 SYMBOL Bi. ATOMIC WEIGHT 210. 
 
 History. The first distinct mention of this metal is to be found in the last tes- 
 tament of Basil Valentin (fifteenth century), but it is very uncertain whether the term 
 marcasite then applied to this metal, as it occurred naturally, was also at an earlier 
 period used in that sense by Arnold Villanova, Roger Bacon, Albert Magnus, and 
 others, or merely as a designation of any kind of bright mineral. However, bismuth 
 was included by Paracelsus among the semi-metals ; Agricola mentioned it as bisemutum 
 and plumbum cinereum. It was confounded with antimony by Libavius, and with 
 zinc by N. Lemery, and it was not until the year 1739 that the specific characters of 
 this metal were made known by Pott, and afterwards by Bergman. 
 
 Occurrence. -Bismuth occurs naturally in the metallic state associated with 
 ores of silver, lead, zinc, nickel, cobalt, etc. ; it also occurs, combined with sulphur, as 
 bismuth glance Bi 2 S 3 ; with tellurium as tetrady mite Bi 2 Te 3 ; the sulphide 
 also occurs combined with cuprous sulphide as tannenite Cu 2 S.Bi 2 S 3 , and 
 wittichenite 3Cu 2 S.Bi 2 S 3 ; with cuprous sulphide and lead sulphide as needle 
 ore Cu 2 S2PbS.Bi 2 S 3 , and with nickel sulphide in several minerals ; the oxide Bi 2 3 
 occurs as bismuth ochre, a silicate as bismuth blende, and the carbonate as 
 bismuthite. The principal source of bismuth is the native metal that occurs in 
 Saxony and Bohemia. 
 
 Characters. Bismuth is a grey coloured metal with a distinct rose tint. It is 
 very brittle and readily crystallisable, and is probably dimorphous, crystallising in 
 forms belonging to both the cubic and hexagonal system. Its density is 9'830 in the 
 solid state, and greater in the liquid state ; after being exposed to great pressure, the 
 density of bismuth is reduced to 9'556. Bismuth melts at about 260, and expands 
 in solidifying ; at a higher temperature it volatilises and burns with a bluish-coloured 
 flame, but under ordinary conditions the metal is not readily oxidised by the air. It 
 exhibits the phenomena of diamagnetism in a higher degree than any other substance. 
 
 Preparation. Bismuth is obtained chiefly from the ores containing it in a 
 metallic state, and the method by which it is extracted consists simply in heating the 
 ore sufficiently to melt the metal, so that it separates from the earthy substances and 
 minerals with which it is associated. This process is termed liquation. Some- 
 times the ore is merely mixed with a little charcoal upon a layer of wood, and after 
 setting fire to the heap at the top, it is allowed to burn downwards ; the metal is then 
 picked out of the ashes and remelted, and cast into ingots. A better mode of con- 
 ducting this operation is to heat 
 the ore in iron tubes fixed in a 
 sloping position in a furnace, as 
 shown in fig. 383. The liqua- 
 tion tubes (b d) are about 8 or 
 12 inches in diameter ; the 
 upper ends (d) can be closed 
 with sheet-iron covers, and to 
 the lower ends (b} are fixed clay 
 or iron plates with small aper- 
 tures (00), through which the 
 liquid metal runs into the pots 
 (a a\ which are heated by a 
 small fire at (K) sufficiently to 
 keep the metal liquid, and ad- 
 mit of its being ladled out into 
 
 FIG. 383. 
 
 moulds. The ore is put into the red-hot tubes at the higher ends (d\ and after about half 
 an hour, when the metal has run off, the residue is raked out from the higher ends of 
 
506 BISMUTH. 
 
 the tubes into the water tank beneath. The bismuth thus obtained is impure, contain- 
 ing arsenic, sulphur, lead, copper, etc. ; it may be purified by melting it with 10 per 
 cent, of nitre. 
 
 The extraction of bismuth from ores of cobalt and nickel is practised in this way 
 at Schneeberg in Saxony, and the residual material is often smelted to obtain the cobalt 
 and nickel in the form of speise, which yields a further quantity of bismuth by liqua- 
 tion. (See COBAXT and NICKEL). 
 
 Bismuth is also extracted by melting the ore with soda, lime, and fluor spar in 
 crucibles. When the ore contains bismuthous sulphide or arsenical compounds of 
 nickel or cobalt, some metallic iron is added, which combines with the sulphur and 
 arsenic, preventing the formation of speise containing much bismuth; by this means 
 the bismuth is separated from the nickel and cobalt which are obtained as speise, 
 which should not retain more than 2 per cent, of bismuth. 
 
 The ores from which nickel and cobalt are extracted at Joachimsthal generally 
 contain some bismuth, and it may be advantageously extracted in this way when it 
 does not amount to more than 2 per cent., provided the ore does not also contain lead, 
 which would be reduced and mixed with the bismuth. 
 
 Bismuth is obtained also to some extent as a by-product in the treatment of 
 cobalt ores. 
 
 Compounds. Bismuth forms three series of compounds, in which the metal is 
 respectively divalent, as in the dichloride BiCl 2 ; trivalent, as in bismuthous oxide 
 j3i 2 3 ; and pentavalent, as in bismuthic oxide Bi 2 s . The compounds in which the 
 metal is trivalent are the most stable. 
 
 Bismuthous oxide Bi 2 3 is formed when the metal is heated in contact with 
 atmospheric air, or it may be obtained by heating the basic nitrate to dull redness. 
 It is a pale yellow pulverulent substance that melts at a full red heat and combines 
 readily with silica. It dissolves in strong acids, forming saline compounds. This 
 oxide occurs naturally as bismuth ochre. 
 
 Bismuthous hydrate Bi 2 3 .H 2 or BiH0 2 is obtained in the form of a white 
 precipitate when a solution of a bismuthous salt is decomposed by an alkali. When 
 heated with excess of potash, the hydrate is converted into bismuthous oxide, which 
 presents the appearance of a yellow crystalline powder. 
 
 Bismuthic oxide Bi 2 5 is a bright red pulverulent substance, obtained by pass- 
 ing chlorine into a concentrated solution of potash containing bismuthous hydrate in 
 suspension, and treating the red-coloured product thus produced with dilute nitric 
 acid. Bismuthic oxide, when heated above 100, loses part of its oxygen, and thus 
 yields a substance represented by the formula Bi 2 4 , which may be regarded as a saline 
 compound of bismuthic oxide with bismuthous oxide Bi 2 5 + Bi 2 3 = 2Bi 2 4 . Bis- 
 muthic oxide combines with other basic oxides, forming similar compounds, which are 
 called bismuthates. 
 
 Bismuth forms two compounds with sulphur : disulphide BiS, a dull black powder 
 obtained in a hydrated state by treating and mixing alkaline solutions of bismuthous 
 oxide and stannous oxide with sulphuretted hydrogen. The trisulphide Bi 2 S 3 occurs 
 naturally as bismuth glance ; it may beobtained by heating a mixture of powdered 
 bismuth with one-third its weight of sulphur until it melts. This substance expands 
 considerably in solidifying. It is formed also as a brownish-black precipitate by the 
 action of sulphuretted hydrogen on solutions of bismuthous salts. 
 
 Bismuthous chloride Bi01 3 is a white fusible substance which may be ob- 
 tained by heating the metal in an atmosphere of chlorine gas ; it is very hygroscopic 
 and combines with water, forming a crystalli sable hydrate, but is decomposed by a 
 larger proportion of water, forming an oxychloride BiCl 3 .Bi 2 3 or BiCIO and hydro- 
 chloric acid Bid, + H 2 = BiCIO + 2HC1. 
 
 The same substance is formed by mixing solutions of bismuthous nitrate and 
 sodium chloride. Bismuthous chloride combines with the alkaline chlorides, forming 
 crystallisable double salts. 
 
 Bismuth dichloride BiCl 2 is a brown crystalline substance easily fusible and 
 decomposed by water ; it is formed by heating the trichloride with metallic bismuth. 
 At a high temperature it is converted into trichloride and metallic bismuth. 
 
 The bromide BiBr s is a steel grey substance fusible at 200 and resembling fused 
 iodine. 
 
 The iodide BiI 3 is a grey crystalline vaporisable substance ; when heated in con- 
 tact with atmospheric air, it forms an oxyiodide BilO, crystallising in copper-coloured 
 rhombic laminae. 
 
 Bismuth unites readily with other metals, forming alloys which are more easily 
 fusible than bismuth itself. An arsenide containing 3 per cent, of bismuth occurs 
 naturally. Bismuth unites in all proportions with antimony, forming brittle alloys 
 
BISMUTH NITRATE. 507 
 
 which expand considerably in solidifying. With tin and lead it forms an alloy known 
 in England as fusible metal, and called in France after its alleged discoverer, 
 metal fusiblede d' A r c e t. In preparing fusible metal the three constituents are used 
 in varying proportions according to the purpose for which the alloy is required. 
 An alloy consisting of 1 part of bismuth, 2 of tin, and 1 of lead, is sometimes used as 
 a soft solder by pewterers, and in making moulds for toilet soaps. An alloy of 5 
 parts of bismuth, 2 of tin, and 3 of lead, melts at 93, and is used for stereotype 
 cliches. Another of 8 parts of bismuth, 5 of lead, and 3 of tin, melts at 94 0< 5, and 
 the alloy, consisting of 2 bismuth, 1 lead, and 1 tin, melts at 94 : all of these are 
 suitable for taking casts of anatomical preparations. A small addition of mercury 
 is said to increase the fusibility. Bismuth and lead in equal parts form a brittle 
 alloy of the same colour as bismuth, and having a density (10709) greater than 
 the mean of its constituents. "With tin bismuth forms an alloy more elastic and 
 sonorous than tin itself, a property sometimes utilised by pewterers. About 4 per 
 cent, of bismuth gives an alloy that is slightly malleable, but with a larger proportion 
 of bismuth to the tin the alloy is brittle. An alloy of tin, bismuth, nickel, and 
 silver is said to prevent iron from rusting. 
 
 Uses. Besides its use alloyed with other metals, as above mentioned, bismuth 
 finds employment in various ways. The property that the pure metal has of regular 
 expansion when heated is utilised in the adjustment of the scale of high-ranged ther- 
 mometers. The oxide, carbonate, and subnitrate are used in medicine, The sub- 
 nitrate is known as pearl powder, and is used as a flux for enamels, as a vehicle 
 for the colours of other metallic oxides, and, mixed with fifteen times its weight of 
 gold, in gilding porcelain ; it is also used as a cosmetic. A subchloride, too, is used 
 as pearl powder. The nitrate, mixed with a solution of tin and tartar, has been 
 employed as a mordant in calico printing. 
 
 FOBMTJLA Bi3NO s . MOLECULAR WEIGHT 396. 
 
 This salt is obtained by dissolving bismuth in hot nitric acid and evaporating the 
 solution until it crystallises. The crystals are colourless, very deliquescent, and con- 
 tain five molecules of water. The salt dissolves in dilute nitric acid, but is decomposed 
 by water and converted into a basic salt which forms a white precipitate, and was 
 formerly known as magistery of bismuth. The composition of this precipitate 
 appears to vary according to the extent to which it is washed with water, but approxi- 
 mates to the formula Bi3N0 3 .Bi 2 3 3H 2 0. 
 
NICKEL. 
 
 SYMBOL Ni. ATOMIC WEIGHT 59. 
 
 History. The distinction between this metal and copper was first pointed out in 
 1754 by Cronstedt, who showed that kupfernickel, the mineral formerly supposed to 
 be a copper ore, and to which the name nickel was derisively applied on account of the 
 failure of all attempts to obtain copper from it, was in reality a compound of a pecu- 
 liar metal differing in many of its characters from copper. 
 
 Occurrence. Nickel occurs most abundantly as kupfernickel (arsenide or 
 nickel), from which it is extracted, as also from speise, a material which is pro- 
 duced as described, during the manufacture of ' smalt.' Speise may be said to be 
 an impure arsenio-sulphide of nickel. 
 
 Kupfernickel is of a pale copper colour, and is found in masses of metallic lustre ; 
 it is very brittle and has a specific gravity of 7 '3 7*5. Its formula is NiAs, and it is 
 composed of 44 per cent, nickel and 56 per cent, arsenic. Although it is principally 
 obtained from the mines in Saxony, where it occurs associated with the ores of copper, 
 silver and cobalt, considerable quantities have been raised in Great Britian, particu- 
 larly at Pengelly and St. Austell Consols mines in Cornwall, and at the Bathgate 
 silver mine in Scotland, 
 
 An analysis of a foreign kupfernickel made by Eammelsberg shows it to be 
 nearly identical with the English product. Arsenic 48'80 per cent. ; nickel 39*94 per 
 cent. ; cobalt 0'16 per cent. ; antimony 8'00 per cent. ; silica 2*00 per cent. 
 
 There are various other nickel-bearing minerals, but none of them have any im- 
 portant commercial value, owing to their scarcity. Among these are white nickel 
 (NiAs 2 ) which is found at Eeichelsdorf in Hesse Cassel and at Schneeberg in Saxony. 
 Nickel glance (NiAsS) is found in Sweden, in theHartz, and some parts of Austria; 
 it contains from 20 to 38 per cent, nickel. Antimonial nickel (NiSb) is found at 
 Andreasberg and contains about 29 per cent, nickel. Millerite (sulphide of nickel) 
 occurs in Saxony, Bohemia, Cornwall and South Wales ; it contains 64 percent, nickel. 
 Nickel-linnseite, or siegenite, a mineral containing about 30 per cent, nickel, 
 has been found at La Motte in Missouri. Zaratite, a hydrated carbonate of nickel, 
 also occurs there. Pentlandite (Fe 2 NiS 3 ) is obtained from South Norway, and 
 contains from 18 to 21 per cent, nickel. 
 
 The greatest consumption of nickel, as of cobalt, is in England, but for our supplies 
 we are almost entirely dependent upon Norway, the Netherlands, and Northern Ger- 
 many. 
 
 Characters. Nickel is remarkable for having an atomic weight apparently 
 almost identical with that of cobalt, but it must be admitted that there exists some 
 small doubt about the correctness of the determinations. 
 
 Eathoff determined the atomic weight as 59*08 ; Dumas by the same plan 
 arrived at 59'02 ; Kussell by another method found 58*738 ; Winkler also by a dis- 
 tinct process found 59'06 ; E. H. Lee by a study of some organic salts has determined 
 the atomic weight of nickel at 58*00. 
 
 Nickel is a bright silver-white, hard but ductile metal, slightly more fusible than 
 iron, which, according to Deville, it surpasses in tenacity. Like cobalt, it is associated 
 with iron in meteorites, and also admits of magnetisation, but it loses this property at 
 a temperature of 330 C. When containing carbon, the metal is more fusible than 
 otherwise. The metal has a sp. gr. of 8*279, but by forging this may be raised to 
 8-666. 
 
 Nickel oxidises in a current of air at a high temperature, and if previously heated 
 will burn in oxygen like iron ; the pulverulent metal which results from the reduction 
 by hydrogen of oxide of nickel is, like cobalt when similarly obtained, of a pyrophoric 
 nature. 
 
 When suspended in water it is readily attacked by chlorine and bromine, and it is 
 also easily dissolved by nitric acid or aqua regia, but is less soluble in dilute acids. 
 
USES OF NICKEL. 509 
 
 The oxide of nickel, when strongly heated with charcoal, gives a fusible carbide of 
 the metal. 
 
 Preparation. The principal works in this country for the extraction of nickel 
 are situated near Birmingham, but endeavours are made to maintain the utmost 
 gecresy as regards the various processes employed. According to Louyet the method 
 is somewhat as follows : 
 
 The speise or native ore, or a mixture of both, is fluxed with chalk and fluorspar 
 in a re verberatory furnace ; the slags are thrown away, and the resulting matt is 
 reduced to powder and roasted for twelve hours to free it from arsenic. 
 
 The product is next dissolved in hydrochloric acid, and the solution, after separa- 
 tion from what little remains insoluble, is diluted with water ; a little bleaching powder 
 is added to peroxidise the iron, and the iron and arsenic are precipitated by neutralisa- 
 tion with milk of lime and boiling. The clear liquor and washings of the precipitate 
 retain all the cobalt and nickel in solution, together with copper, bismuth, and lead. 
 These last three substances are precipitated by means of sulphuretted hydrogen, and 
 the supernatant liquors boiled afterwards to expel the excess of the gas. After this they 
 are again neutralised 'by milk of lime and more bleaching powder added. Sesqui- 
 oxide of cobalt is thus obtained, which is washed and ignited, and is then ready for the 
 market, while the nickel still remains behind in the mother liquors, and is obtained 
 therefrom as hydrated protoxide by adding excess of milk of lime. 
 
 From the oxide the metal is frequently obtained by a process of cementation. A 
 number of cylinders made of clay are set vertically in a furnace, so that the flame 
 may play on all sides of them. These cylinders are open at the top, and terminate in 
 truncated cones which project beneath the fire bars. 
 
 Oxide of nickel, either in lumps or in small cubes, and intimately mixed with 
 charcoal, is introduced at the top, and on the application of a strong heat the metal 
 is reduced, but retains the form of the oxide, and is withdrawn through orifices in the 
 bottoms of the cylinders. As the nickel is withdrawn from below fresh charges of 
 oxide and charcoal are introduced at the top, and so the cylinders are worked on the 
 principle of lime kilns, the process being therefore in a sense continuous. 
 
 Sometimes the wet hydrated oxide of nickel is worked into a paste with a small 
 quantity of flour and syrup, giving a mass of a dough-like consistency, which may 
 then be cut up into cubes about |- of an inch square, and reduced by intense ignition 
 either in crucibles or in tubes, where they are surrounded by charcoal dust. 
 
 There are various methods of obtaining the metal in a pure state on the small 
 scale, but as they are nearly all based upon the same principles the description of one 
 will serve to illustrate all. 
 
 The roasted ore is dissolved in aqua regia containing an excess of nitric acid, so as 
 to get the iron in a ferric state ; excess of ammonia is then added ; the ferric oxide is 
 separated by filtration, and caustic potash is added to the blue liquid until the colour 
 has nearly disappeared. In this way a pale green precipitate consisting of hydrated 
 nickel oxide and potash is obtained. On washing with hot water the potash is re- 
 moved, and the residual precipitate after drying gives, by reduction at a high 
 temperature in a stream of hydrogen, metallic nickel of a pyrophoric nature. On 
 heating in contact with charcoal at a forge a well-fused button of carbide of nickel 
 is obtained. 
 
 Nickel oxalate also gives the metal on decomposition by heat, and it may likewise 
 be obtained in laminae by the electrolysis of a solution of ammonio-nickel sulphate 
 NiS04(NH 4 ) 2 S0 4 , 6H 2 0. This method is now often employed where it is desired to 
 deposit nickel in dense layers capable of receiving a good polish. 
 
 Uses. As nickel is now so largely used for coating surfaces of wrought or cast 
 iron, steel, copper, brass, zinc, etc., it is of interest to note the following process 
 which, according to F. Stolba, is very effectual. 
 
 A mixture is made of one part of concentrated solution of zinc chloride and two of 
 water, and raised to the boiling point, any turbidity that may exist being corrected by 
 the careful addition of hydrochloric acid. The objects to be nickel-plated are now 
 cleansed and immersed in the zinc solution, and on adding to the latter a little pow- 
 dered zinc they become lightly coated with it, and to this the nickel will attach itself. 
 Nickel sulphate, or the double salt of potassium and nickel, is now added, either 
 in the dry state or as a solution, until the boiling mixture exhibits a green colour, 
 when a few zinc cuttings are added and the boiling continued. Provided that the 
 liquor remains clear, a closely adhering yellowish nickel deposit occurs, shining or 
 dull, according as the surface on which it is deposited be polished or rough. 
 
 The chief use of nickel in the arts is for the preparation of the white alloy known 
 as German silver, more than 600 tons of which are produced annually with a largely 
 increased demand. 
 
510 
 
 NICKEL. 
 
 Compounds. Nickel forms two oxides ; a protoxide NiO and sesquioxide Ni 2 8 ; 
 the latter does not form salts. 
 
 The oxide is ot'an ash grey colour and may be obtained from nickel salts, as the 
 sulphate or chloride, by precipitation with an alkali. 
 
 The sesquioxide, which is black, maybe obtained by gentle ignition of the 
 nitrate, or by treating the hydrated protoxide with a solution of sodic hypochlorite, 
 when it is precipitated as a hydrate Ni 2 H 6 6 . On strong ignition it loses part of its 
 oxygen, and on heating it with acid it forms proto-salts. 
 
 Nickelous chloride NiCl is obtained by dissolving the oxide in hydrochloric 
 acid ; the resulting solution, on evaporation, yields crystals of a green hydrated cha- 
 racter, containing 9H 2 0. 
 
 In the anhydrous state (obtained on heating) it forms a yellowish-brown mass 
 which volatilises at higher temperatures in crystalline scales that are but slowly 
 soluble in water. 
 
 When heated in a current of air some oxide is found. Three sulphides of nickel 
 are known, of the formulae Ni-jS, NiS, and NiS 2 . 
 
 The protosulphide (NiS) occurs, as we have already seen, in a native state 
 (miller it e) in grey or yellowish crystals soluble in nitric acid. These may be 
 artificially produced by fusing sulphur with nickel. When a salt of nickel in solution 
 is precipitated by ammonic hydric sulphide, a black hydrate of this sulphide is pro- 
 duced. 
 
 The subsulphide (Ni^) is yielded by heating nickel sulphate in contact with 
 charcoal or hydrogen. 
 
 The disulphide (NiS 2 ) is obtained as a steel grey powder, when a mixture of 
 carbonate of nickel, potassic carbonate and sulphur is heated to redness and treated 
 with water. 
 
 Several double sulphates of nickel and other metals are known, the most important 
 of which is the compound potassic salt NiS0 4 ,K 2 S0 4 ,6H 2 0, which may be obtained 
 in a crystallised form. Nitrate of nickel Ni2N0 3 , 6H 2 crystallises in emerald green 
 prisms which are readily soluble in water ; the solution on heating yields a basic 
 salt. 
 
 Several carbonates are known, all of which have a green colour. On pouring the 
 nitrate of nickel into an excess of solution of sodic bicarbonate, the normal carbo- 
 nate of nickel is thrown down as a crystalline powder. 
 
 All salts of nickel give in the oxidising flame of the blowpipe, with borax, a 
 reddish-yellow glass which pales as it cools. 
 
 Various alloys of nickel are known. Argentane, or German silver, consists 
 ordinarily of 8 parts of copper, 2 of nickel, and 3 of zinc, but owing to its yellow tint 
 it is not employed for the better purposes. White argentane or plate has one part 
 more nickel than German silver, and is a very fine alloy. Slectrum has yet one 
 more part nickel than argentane plate and resists oxidation almost perfectly. 
 
 If the proportion of nickel be increased much beyond that in which it exists in 
 electrum, the alloy is hard and difficult to work. 
 
 Packfong is also a compound of zinc, nickel, and copper, in which the propor- 
 tions of the constituent metals may vary considerably. According to Miller, a good 
 alloy is obtained by using 51 parts of copper, 30'6 of zinc and 18 '4 of nickel. 
 
 Futenangis the Chinese name for a similar alloy, composed of 8 parts of copper, 
 6 of zinc, and 3 of nickel. In consideration of the increased price of nickel experienced 
 during the last few years, it is reasonable to expect that before long processes will 
 be devised for extracting the 3 or 4 per cent, of nickel contained in the nickeliferous 
 pyrites that occur in Italy and elsewhere. These pyrites might first of all be em- 
 ployed in the manufacture of sulphuric acid and then submitted to processes for 
 extracting nickel, just as now the silver is extracted from the burnt residuum. 
 
 The following analyses of various alloys are by A. Eopler : 
 
 
 White 
 Copper 
 
 Paris 
 Alloy 
 
 Chinese Packfong 
 
 Used for 
 knife 
 handles 
 
 Used for 
 forks 
 
 Copper . . . 
 
 88-00 
 
 65-9 
 
 43'8 
 
 40-4 
 
 55-0 
 
 50-0 
 
 Nickel 
 
 875 
 
 16-8 
 
 15-6 
 
 31-6 
 
 20-0 
 
 25-0 
 
 Zinc .... 
 
 
 
 13-0 
 
 40-6 
 
 25-4 
 
 25-0 
 
 25-0 
 
 Iron . :..'.,,, 
 
 175 
 
 3-4 
 
 
 
 2-6 
 
 
 
 
 
NICKEL SULPHATE. 511 
 
 NICKEL OXIDE. 
 
 FORMULA NiO. MOLECULAR WKIGHT 75. 
 
 This substance has a specific gravity of 5 - 75, and is obtained in the anhydrous 
 form by ignition of the nitrate or carbonate in a covered crucible. As precipitated 
 from its salts by alkalies it is a light green bulky hydrate (NiH ? 2 ?) and may be 
 obtained in a crystalline form by decomposing the solution of nickel carbonate in 
 ammonia by ebullition. 
 
 This oxide of nickel has a curious power of combination with potash or soda, 
 yielding insoluble compounds which require very great and continued washing with 
 hot water to entirely decompose them. The potash or soda may be replaced by 
 other bases, as baryta, strontia, etc. 
 
 SULPHATE. 
 
 FORMULA NiS0 4 . MOLECULAR WEIGHT 155. 
 
 This salt crystallises in rhombic prisms of a green colour, containing seven 
 molecules of water, and requiring three parts of cold water for solution ; it is in- 
 soluble in alcohol. It may be obtained by dissolving the metal, or its oxide or car- 
 bonate, in sulphuric acid. By crystallisation at a temperature of 15 25 C. 
 octahedra are obtained containing only 6H 2 (sp. gr. = 2*037). 
 
COBALT. 
 
 SYMBOL Co. ATOMIC WEIGHT 59*8. 
 
 History The elemental character of cobalt was originally recognised by Brandt, 
 in 1733, although it. had been known for some considerable time previous that the 
 mineral named kobalt was capable of imparting a blue tint to glass. 
 
 This mineral was well known to the Bohemian and Saxon miners of the fourteenth 
 century, but at that time was without use. 
 
 Brandt first detected the metal in certain ores of a bismuthic character, and since 
 his investigation other chemists have studied this metal and its compounds ; among 
 them Bergman, Tassaert, Thenard, and Proust. 
 
 Occurrence. Excepting traces of the metal which occur in meteoric iron, cobalt 
 is not found in the native state. It occurs in nature usually in association with ar- 
 senic as speis-cobalt(CoAs 2 ) and occasionally with arsenic and sulphur as cobalt 
 glance (CoSAs). Its ores are as a rule very complicated, and contain -nickel, iron, 
 bismuth, copper, and sometimes manganese. 
 
 Smalt ine (arsenical cobalt or tin-white cobalt) occurs largely at Schneeberg in 
 Saxony, at Joachimsthal in Bohemia, and at Wittichen, Siegen, Saalfeld, and at Mans- 
 feld. It is also found in various parts of Cornwall. This mineral contains from 20 to 
 23 per cent, of cobalt, but some of this is replaced in some samples by varying quantities 
 of iron, nickel, and copper. 
 
 It is, however, from cobalt glance or cobaltine that most of the cobalt preparations 
 are made. It is found largely in Sweden and Norway, sometimes occurring in very 
 definite crystals of the cubic system. From its yellowish- white colour tinged with 
 red this mineral is sometimes known as bright white cobalt; it contains from 33 
 to 44 per cent, cobalt, 43 to 55 per cent, arsenic, ^ to 20 per cent, sulphur, together 
 with a varying percentage of iron. The black oxide has been met with in the Western 
 States of America associated with the sulphide and other oxides. Cobalt also occurs 
 as erythrite or cobalt bloom Co 3 ls 2 8 ,8H 2 0, often found side by side with 
 cobaltine. Pyrolusite and mispickel sometimes contain as much as 5 per cent, cobalt, 
 and it also enters into the composition of skutt erudite (Co 2 As 3 ). 
 
 The ores of cobalt are found chiefly in the primitive rocks, either as imbedded 
 crystals or finely dispersed, and from this fact and the varying nature of the other 
 associated matters the value of the ores varies extremely. 
 
 Characters. Cobalt is nearly as infusible as iron, and cannot be reduced from 
 its oxides by carbon without assimilating some of the latter into its constitution, thus 
 giving a product not unlike cast iron. The metal has a dull -grey colour shaded by 
 red. Its specific gravity is, according to Berzelius, 8'513; but Lampadius has 
 assigned to it the specific gravity 8'7 and Turner 7'834. It possesses a specific heat 
 0'10696 (Regnault). The purest metal is obtained by ignition of the oxalate (CoC 2 0,), 
 when carbonic anhydride is evolved ; thus CoC 2 4 = Co + 2C0 2 . The metal may 
 also be obtained from its oxide by reduction with hydrogen ; but as obtained in this 
 manner it takes fire on exposure to the air, producing cobaltoso-cobaltic oxide. Like 
 iron, it is attracted by the magnet, but loses this property by gentle heating. When 
 the metal is heated to redness it absorbs oxygen, forming first of all a blue oxide, 
 which, if time be allowed, peroxidises into black Co 2 3 or Co 3 4 according to the 
 temperature employed. The mineral acids dissolve it slowly, even when aided by 
 heat, hydrogen being evolved, and the respective salts resulting. These latter impart 
 to their solutions a fine red colour. 
 
 Preparation. As cobalt is never used in the arts, its metallurgy is confined to 
 laboratory processes which all start with the oxide obtained as hereafter to be de- 
 scribed. The oxide is dissolved in nitric acid, the resulting solution is then neutralised, 
 and nitrite of potassium added, when a yellow precipitate is formed. This is washed, 
 dissolved in acid, and the cobalt precipitated either as oxide by means of an alkali, or 
 as oxalate by ammonic oxalate. In either case the product is dried, mixed with oil, and 
 
SMALT. 
 
 513 
 
 strongly heated in a well-luted charcoal-liiied crucible, when a button of the carbide 
 of cobalt is obtained. 
 
 To obtain chemically pure cobalt, it is best to employ purpureo-cobaltic chloride 
 (a compound ammonium salt), which on ignition gives cobaltic chloride, a substance 
 admitting of easy reduction by hydrogen at a red heat. 
 
 Uses. Although metallic cobalt is not used in the arts, a blue pigment containing 
 it and known as smalt is largely consumed, and is prepared by fusing properly 
 prepared cobalt ore with certain materials to form a suitable glass. 
 
 Manufacture of Smalt. The arsenical cobalt ores which are mainly used in pre- 
 paring smalt first undergo a process of sorting, powdering, and washing. If bismuth 
 be present, it has to be removed before the stamping operation by a process of liquation 
 in iron tubes. The ores are next roasted in a current of air, the object being to 
 oxidise the cobalt, whilst the nickel, copper, and iron remain in combination with arsenic 
 and sulphur. Some of the arsenic is converted in this way into arsenious acid, and 
 proper arrangements are made for condensing this substance in a chamber known as 
 the poison gallery. This roasting process is not carried to perfection, otherwise all 
 the metals would be oxidised, and by entering into the composition of the smalt 
 would impair the colour, and thus exercise a depreciative influence on its value. 
 
 From 4 to 5 parts of the roasted product or schlich, as it is called, are next 
 mixed with 10 parts of ground calcined quartz and 4 parts of potassic carbonate, 
 together with white arsenic as obtained in the poison galleries above alluded to. 
 This mixture is then submitted to fusion in pots arranged in a furnace like that in an 
 ordinary glass-making factory. The pots are a little conical, being about 18 inches in 
 diameter at the top, and 14 at the bottom, with a thickness of 2 inches. Each pot 
 holds about 84 Ibs. of the mixture and its normal period of duration is about seven or 
 eight months. In this fusion operation the oxide of cobalt combines with the fused 
 potassic silicate, forming a deep blue glass, while the mixed metallic arsenides and 
 sulphides fuse and collect at the bottom of the pots, forming when cold a brittle mass 
 of metallic appearance and termed speise. It is cast into ingots, and is used in the 
 manufacture of nickel. The blue glass is from time to time ladled out and poured into 
 cold water, by which operation it is reduced to innumerable fragments, and these are 
 afterwards powdered and then ground between granite stones so constructed that the 
 grinding takes place under water, which carries off with it the smalt thus obtained in 
 a finely divided state. The washings so obtained are made to pass through a number of 
 tanks arranged so that the liquor overflows from one to the other successively, and in 
 this way a number of deposits are obtained, of which the earlier ones are the coarsest 
 in grain, and the later ones the finest in division. The greater the degree of sub- 
 division, the less intense is the colour. 
 
 After drying, the azure is broken up by mallets, and is then reduced again to fine 
 powder by falling from a hopper upon two wooden cylinders turning horizontally. In 
 the next stage of its manufacture it is further dried upon shelves at a temperature of 
 about 105 to 112 F., after which it is returned to the braying machine. Finally 
 it is sifted and packed. The yield of marketable blue as produced from the blue glass 
 is about 3 tons of azure for 5 tons of glass. The two following analyses of smalt are 
 by Ludwig : 
 
 
 
 Gennar 
 
 i Smalt 
 
 
 Norwegian 
 
 High Eschel 
 
 Coarse Eschel 
 
 Silica .... 
 
 70-86 
 
 66-20 
 
 72-11 
 
 Oxide of cobalt 
 Potash and soda 
 
 6-49 
 21-41 
 43 
 
 6-75 
 16-31 
 8-64 
 
 1-95 
 20-04 
 1-80 
 
 Ferric oxide . 
 
 24 
 
 1-36 
 
 1-40 
 
 Smalt is chiefly manufactured in Saxony, but it is also made in Norway, Silesia, 
 and Hesse. The furnaces employed are built universally upon the same principles, 
 but in certain details there is a difference according as the fuel employed is wood or 
 coal, etc. 
 
 Smalt is employed in fresco-painting, and in the manufacture of porcelain pottery, 
 stained glass, etc. 
 
 The paper manufacturers used it for a purpose similar to that which leads 
 to its use in washing namely, to correct the yellow colour which often exists in 
 animal- sized papers. The important feature regarding smalt is that only those 
 
 L L 
 
COBALT. 
 
 reagents which attack glass have any action upon it ; hence it constitutes a more 
 stable colour than most blues. 
 
 Zaffre of commerce is a very crude oxide of cobalt, prepared by roasting cobalt 
 ore and mixing the product with several times its weight of silicious sand. 
 
 Thenard's blue is another valuable pigment containing cobalt in the state of 
 oxide, and it may be said to consist of alumina coloured by oxide or phosphate of 
 cobalt. There are several modes of preparation, the most approved of which is as 
 follows : Cobaltous nitrate is precipitated by hydric disodic phosphate and the pre- 
 cipitate so obtained is mixed whilst moist with hydrated alumina produced by adding 
 carbonate of soda to a solution of alum free from iron. The moisture is dried and ig- 
 nited in a well-covered crucible, but notwithstanding this care, the gases produced by 
 the fuel exercise an injurious influence on the colour, to correct which a little oxide of 
 mercury is usually added to the mass, so that it is constantly in contact with an oxi- 
 dising atmosphere, by reason of the oxygen thus generated. The mercury which is 
 formed simultaneously volatilises and so does no harm. 
 
 In another process a mixed solution of cobalt sulphate and ammonia alum is eva- 
 porated to dryness, and the residue subjected to intense ignition in a furnace. 
 
 Cseruleum is the name of a blue pigment made by Messrs. Rowney and Co. It 
 has the following composition: binoxide of tin, 49'66 per cent. ; oxide of cobalt, 18'66 
 per cent. ; silica and lime sulphate, 3T68 per cent. 
 
 This pigment like Thenard's blue is used both as an oil and water colour. 
 
 Rinman's green consists of oxide of zinc coloured with oxide of cobalt, and is 
 prepared by precipitating a mixture of zinc sulphate and cobalt sulphate with sodic 
 carbonate and igniting the precipitate after due washing. Or it may be made from 
 the two nitrates, or from nitrate of cobalt and oxide of zinc mixed, by simple evapora- 
 tion and ignition. ' 
 
 Printer's blue is used for printing patterns on china, and is made by fritting 
 silicate of cobalt with nitre, after the addition of a little basic sulphate. To use it, 
 it must be mixed with oil, printed on paper and transferred to the biscuit ware ; it is 
 during the process of glazing that the colour is developed. 
 
 Other colours are prepared from cobalt, but they do not call for special mention. 
 
 Compounds. Cobalt is divalent, and forms two classes of salts corresponding 
 to the two classes of iron salts, ferrous and ferric. 
 
 The cobaltous salts are the more stable, the more numerous, and the most 
 important. They all are red in a state of solution, but are blue when anhydrous, and 
 all are decomposed at a moderate red heat, with the exception of the sulphate. - 
 
 The similarity between the oxides and salts of cobalt and those of iron is seen 
 from the following formulae : 
 
 Cobaltous oxide 
 
 Ferrous 
 
 Cobaltous chloride 
 nitrate 
 ,, sulphate 
 
 CoO 
 
 FeO 
 
 CoCl 2 
 
 Co2N0 3 
 
 CoSO, 
 
 Cobaltic oxide 
 
 Ferric 
 
 Cobaltic chloride 
 ., nitrate 
 sulphate 
 
 Co 2 3 
 Fe 2 3 
 Co,Cl 6 
 
 Co 2 6N0 3 
 Co 2 3S0 4 
 
 The salts derived from cobaltous oxide may be prepared by disolving the oxide in 
 the respective acids. 
 
 The chloride is also prepared by passing chlorine over metallic cobalt ; at a high 
 temperature it volatilises. It may be obtained by crystallisation in a ruby red form 
 containing 6H 2 0, and its aqueous solution, when mixed with excess of hydrochloric 
 acid, gives a blue solution, becoming pink on dilution. This solution in a dilute state 
 may be used as a sympathetic ink ; the characters formed by writing it are invisible 
 when cold, but become blue on warming, owing probably to the production of the 
 anhydrous salt, because the colour gradually disappears again when the paper 
 is exposed to hygroscopic moisture. The colour can, moreover, be modified at 
 desire ; the addition of a small amount of an iron or nickel salt gives the writing a 
 green colour ; a salt of zinc produces in like manner a red colour, and one of copper 
 gives a yellow tint. 
 
 Three sulphides of cobalt are known viz. protosulphide CoS ; sesquisulphide Co 2 S 3 ; 
 and a disulphide CoS 2 . The first of these is the most important, and is obtained in 
 a hydrated condition by precipitating cobaltous acetate with sulphuretted hydrogen. 
 Cobaltous sulphide quickly oxidises and passes into sulphate. 
 
 There are known also a number of ammoniacal compounds of cobalt of scientific 
 interest only. 
 
 All compounds of cobalt are easily -recognisable by reason of the intense blue 
 colour which they impart to a bead of borax before the blow-pipe. 
 
 The alloys of cobalt are unimportant. The metal unites by fusion with antimony 
 
COBALT OXIDES. 515 
 
 and arsenic, and the formation of the alloy is attended by incandescence ; the resulting 
 alloys have an iron grey colour and are very brittle. 
 
 COBAX.TOUS OXIDE. 
 
 FORMULA CoO. MOLECULAR WEIGHT 75 - 8. 
 
 In order to prepare oxide of cobalt from the speise or matt which forms in the 
 roasting of arsenical ores of cobalt, it is dissolved in strong hydrochloric acid, and 
 iron and arsenic are precipitated by the addition of milk of lime. The supernatant 
 liquors are run off after settling, and submitted to a current of sulphuretted hydrogen 
 so long as metallic sulphides are formed. The clear liquor resulting after settling is 
 again drawn off, and now on adding a solution of bleaching powder, cobaltous oxide 
 is precipitated in a hydrated condition, and the product, on being heated to redness, 
 gives the blue oxide of commerce; when heated further to whiteness, there is 
 obtained the prepared oxide of commerce. 
 
 The manufacture of these oxides is carried on by the nickel refiners at Birmingham ; 
 the products are used in the potteries and by glass makers and enamellers, either 
 alone or with various fluxes, for giving a blue colour to their wares. 
 
 Pure protoxide of cobalt when dried at a low temperature is greenish grey, and 
 on ignition to dull redness in a current of air it gives an oxide Co 3 4 , corresponding 
 to the magnetic oxide of iron Fe s 4 . 
 
 COBALTZC OXIDE. 
 
 FORMULA Co 2 3 . MOLECULAR WEIGHT 166. 
 
 This substance may be prepared in several ways, one of the best methods being as 
 follows. The hydrated protoxide of cobalt is suspended in water and submitted to 
 a current of chlorine ; in this way cobaltous chloride is formed and dissolved, whilst 
 black hydrated cobaltic oxide is precipitated; thus: 
 
 3CoH 2 2 + C1 2 = Co 2 H 6 6 -f CoCl 2 . 
 
 If, in this reaction, an alkaline solution be substituted for the water, then all the 
 cobalt is obtained as peroxide. 
 
 A gentle heat renders this oxide anhydrous ; at higher temperatures it is converted 
 into a black oxide Co 3 4 . This cobaltoso-cobaltic oxide, as it is called, corresponds to 
 the compounds termed manganites which are obtained by blowing air through protoxide 
 of manganese held in suspension, in the presence of lime. In this way, in fact, in 
 Weldon's process of manganese regeneration, there is obtained, among other bodies, 
 one whose presumable formula is MnO, Mn0 2 that is, a manganite of manganese, in 
 which the protoxide seems to exist as a basic radicle and towards which the per- 
 oxide acts as a combining acid radicle. 
 
 Cobaltoso-cobaltic oxide CoO, Co 2 3 , would appear to be a similar substance, and 
 may be obtained in steel-grey octahedra by boiling a solution of roseo-cobaltic chloride. 
 This last named substance is one of the ammonium combinations of cobalt previously 
 referred to, and has the composition (Co 2 Cl 6 , 1 ONH 3 . H 2 0). Cobaltic oxide Co 2 3 has 
 feeble basic powers ; in its hydrated form it is soluble in cold acids, but the salts so 
 produced become quickly reduced into those of the protoxide, even at normal tem- 
 peratures ; the acetate is the most stable salt. 
 
 COBALTOUS NITRATE. 
 
 FORMULA Co2NO s . MOLECULAR WEIGHT 183-8. 
 
 This salt crystallises with 6 molecules of water, and is perhaps the most impor- 
 tant salt of cobalt. It is made by dissolving cobaltous oxide in nitric acid, and as a 
 salt is of a deliquescent character. 
 
 When a concentrated solution of this salt is acidified with nitric or acetic acid, 
 and mixed with one of potassic nitrite, a beautiful yellow salt is precipitated in a 
 crystalline form. It contains 13'6 per cent, of cobalt, and has the formula Co 2 3 , 
 2N 2 3 , 6KN0 3 , 2H 2 (A. Stromeyer). 
 
 LL2 
 
MANGANESE. 
 
 SYMBOL Mn. ATOMIC WEIGHT />5. 
 
 History. This metal was first isolated by G-ahn in 1774, and although the black 
 oxide or dioxide occurring naturally had long been known and used for decolorising 
 glass, the existence in it of a peculiar metal -was not recognised. Originally the 
 mineral known as brownstone and consisting essentially of manganese dioxide was 
 regarded as an iron ore ; but various researches about the years 1770 to 1774 proved 
 that the metal contained in this mineral is distinct from iron. 
 
 Occurrence. Manganese exists somewhat abundantly in nature, chiefly occurring 
 in an oxidised state. The dioxide occurs as pyrolusite or grey manganese ore, 
 which has a metallic lustre, and a specific gravity of 4'85 ; this is the most abundant 
 ore and, from its uses in various manufactures, the most important. It is largely con- 
 sumed for the generation of chlorine in the manufacture of bleaching powder, of which 
 more than 100,000 tons are made annually in Great Britain. Pyrolusite contains 
 about 63'3 per cent, manganese and 367 per cent, oxygen. Large quantities are 
 found in Spain, Devonshire, and Cornwall. Braunite is the native form of the 
 sesquioxide, and contains 69*68 per cent, manganese -and 30*32 per cent, oxygen. 
 Hausmannite, which is a rarer ore, consists of a mixture of protoxide and sesqui- 
 oxide. Manganite is a hydrated sesquioxide, and manganese b 1 e n d e consists 
 of manganous sulphide. As carbonate manganese occurs in diallogite, and as 
 hydrosilicate in rhodonite. "Wad or bog manganese, which is a hydrated 
 peroxide, occurs largely in Cornwall, Devonshire, the Hartz, and Piedmont. When 
 mixed with linseed oil it forms a mass which is liable to inflame spontaneously. 
 
 The ores used in commerce contain from 60 to 75 per cent, of peroxide of manganese, 
 and are chiefly derived from Spain, Germany, France, Belgium, and Holland. 
 
 Characters. Manganese is of a greyish-white colour and is brittle ; when 
 obtained by Brunner's process it is hard enough to scratch steel, but it has been ques- 
 tioned whether this property is not due to the presence of silicon derived from the 
 materials employed. Manganese is feebly magnetic, and oxidises on exposure to the 
 atmosphere. It decomposes water at normal temperatures, and to preserve it, it is 
 necessary to place it in sealed tubes or under naphtha. When the metal is strongly 
 heated in contact with carbon and silicon, it combines with these substances ; a sili- 
 ciuretted carbide is thus produced. 
 
 Preparation. The metal is extracted from its compounds only with considerable 
 difficulty. One of the best methods is to mix the carbonate into a paste with oil and 
 sugar or oil and lampblack, and to expose the mixture, contained in a crucible lined 
 with charcoal and provided with a cover luted on, to the heat of a smith's forge. In 
 this way after about two hours a metallic button results, which contains however 
 a little carbon. 
 
 The metal may also be obtained, according to Brunner, by imitating the process 
 of Deville for the reduction of aluminum. The chloride or fluoride treated with 
 metallic sodium under these conditions gives metallic manganese. 
 
 When a solution of chloride of manganese is subjected to electrolysis plates of the 
 reduced metal are obtained. 
 
 It may be obtained in a pulverulent form by heating its amalgam in a tube which 
 is filled with the vapour of rock oil (Giles). 
 
 Uses. The metal has no uses in the arts in a pure state, but an alloy of manga- 
 nese with iron is largely used in the manufacture of steel and Bessemer metal. 
 
 Compounds. Manganese, like many other metals, cannot well be classed 
 according to its atomicity or quantivalence, because this power is a fluctuating quantity 
 which varies with the compounds, in some of which it is divalent, in others trivalent 
 or heptavalent. 
 
 With oxygen it forms a number of compounds, four of which are well defined ; the 
 
MANGANESE OXIDES. 517 
 
 other two have an existence known only in combination. The protoxide MnO is a 
 powerful base ; the sesquioxide Mn 2 3 has feebly basic powers ; the red oxide Mn 3 4 
 and the black dioxide Mn0 2 have no basic characters. 
 
 The potassium salts of the two higher oxides are potassic manganate K^MnO^, 
 supposed to contain Mn0 3 , and potassic permanganate B^Mn.^, supposed to contain 
 Mn 2 7 . 
 
 The dioxide would seem to possess powers of combination of an acid character, 
 according to Mr. Weldon's interpretation of the results he has obtained in the peroxi- 
 dation of manganous oxide by air in the presence of an excess of lime. He claims 
 to have demonstrated the existence of various compounds, which he terms manganites 
 and sesquimanganites ; thus CaOMn0 2 and Ca02Mn0 2 are obtained, a small portion 
 of the CaO being usually replaced by an equivalent amount of MnO. 
 
 Of the chlorides, manganous chloride MnCl 2 is the most important ; a trichloride 
 Mn 2 Cl 6 or manganic chloride is also known. Besides these, it is said a tetrachloride 
 MnCl 4 and yet another chloride MnCl 7 also exist. Manganic chloride is obtained when 
 the sesquioxide is treated with cold hydrochloric acid; heat converts it into manganous 
 chloride and free chlorine. The tetrachloride is obtained in ethereal solution by passing 
 hydrochloric acid gas into a properly cooled mixture of manganese dioxide and ether ; 
 it imparts to the ether a fine green colour. The heptachloride MnCl 7 is said to be 
 formed when potassic permanganate is dissolved in strong sulphuric acid and fused 
 sodic chloride is gradually added ; under these conditions a greenish-yellow gas is 
 obtained which condenses to a liquid at 0. Water decomposes it into permanganic 
 acid and hydrochloric acid ; and Dumas regards it as a heptachloride. H. Eose, how- 
 ever, believes it to be an oxychloride MnCl 2 2 analogous to chromic oxychloride. It is 
 said that fluorides corresponding to the above described chlorides have been formed. 
 
 Manganese forms two sulphates, viz., manganous sulphate MnS0 4 5H 2 and man- 
 ganic sulphate, which is a deep green powder that combines with potassic sulphate, 
 giving a double salt crystallising in octahedra of the composition K 2 Mn 2 ''4S0 4 . 
 
 Sulphide of manganese is obtained in a hydrated state as a reddish-yellow precipi- 
 tate MnS + H 2 0, when a manganous salt is precipitated by sulphydrate of ammonium. 
 
 The carbonate MnC0 3 frequently accompanies spathic iron ; as a white hydrate 
 2MnC0 3 .H 2 0, it is formed by precipitating a salt of manganese by an alkaline carbon- 
 ate. The carbonate is decomposed on heating, leaving an oxide. 
 
 An arsenide and a bromide are also known. 
 
 Manganese yields several alloys, none of which however are of much importance. 
 They are difficult to prepare, because it is difficult to reduce metallic manganese. Mr. 
 F. F. Allen directs as follows for preparing the copper alloy : a mixture of dioxide or 
 carbonate of manganese is fused with cupric oxide and charcoal in a plumbago crucible 
 at the highest attainable temperature. Alloys with tin, lead, etc., have also been 
 prepared. Manganese in combination with iron gives a harder and mose elastic metal 
 than is iron alone. 
 
 mA.NGA.NOVS OXIDE. 
 
 FORMULA MnO. MOLECULAR WEIGHT 71. 
 
 In an anhydrous condition this oxide is obtained by ignition of the carbonate or any 
 higher oxide in a current of hydrogen. It is a green coloured powder liable to oxidise 
 in the air, and when ignited in contact with air combustion takes place and a brown 
 oxide results. 
 
 This oxide is soluble in acids, and forms the corresponding salts from whose solu- 
 tions alkalies reprecipitate the oxide as a pinkish hydrate MnILj0 2 , which rapidly 
 absorbs oxygen from the air or oxygen gas and passes into the sesquioxide Mn 2 s . 
 
 MANGANIC OXIDE. 
 
 FOBMULA Mn 2 3 . MOLECULAR WEIGHT 158. 
 
 Occurs naturally as braunite and as a hydrate in manganite Mn 2 3 ,H 2 0. It 
 may be prepared as stated above from the protoxide or from the carbonate by suspen- 
 sion in water and passing chlorine gas through the mixture. If excess of chlorine 
 be used the dioxide results. It forms also the principal part of the residue left behind 
 when the dioxide is heated for the purpose of making oxygen. 
 
 This oxide has a brown colour, and is resolved by strong nitric acid into monoxide 
 and dioxide, the former of which alone dissolves. Heated with strong sulphuric acids, 
 oxygen is liberated, and manganous sulphate results. With hydrochloric acid it forms 
 
518 MANGANESE. 
 
 chlorine gas. On strong ignition it loses one-eighth of its oxygen, and leaves the red 
 oxide Mn 3 4 . 
 
 The colour of the amethyst is supposed to be due to the presence of this oxide. 
 
 MANGANOSO-MANGAttTC OXIDE. 
 
 FORMULA Mn s 4 . MOLECULAR WEIGHT 229. 
 
 This oxide corresponds to the magnetic oxide of iron. It occurs naturally as 
 hausmannite, and is obtained when any one of the other oxides is heated strongly 
 in the air. It is incapable of forming definite salts, although it is dissolved both by 
 phosphoric and sulphuric acids. 
 
 BUNTOXIDE OF 1VTABTGANESE. 
 
 FORMULA Mn0 2 . MOLECULAR WEIGHT 87. 
 
 The native forms of this oxide are found both massive and crystallised. It is a 
 good conductor of electricity, being strongly electro-negative in the voltaic circuit. 
 
 It may be prepared by precipitating a salt of manganese by a solution of bleaching 
 powder, or by gentle ignition of nitrate of manganese. 
 
 It is black in colour, and does not form corresponding salts with acids. 
 
 On ignition it yields one-third of its oxygen, and leaves the red oxide 
 3Mn0 2 = Mn 3 4 + 2 . Treated with sulphuric acid the following reaction occurs : 
 
 2Mn0 2 + 2H 2 S0 4 = 2MnS0 4 + 2H 2 + 2 . 
 With hydrochloric acid it gives rise to chlorine : 
 
 Mn0 2 + 4HC1 = Mn01 2 + 2H 2 + C1 2 . 
 
 It is by this process that chlorine is manufactured for the preparation of bleaching 
 powder ; the chloride of manganese which results is precipitated by an excess of milk 
 of lime, and air is then blown through the mixture. 
 
 In this way (Weldon's process) the manganese is again peroxidised, giving rise to 
 the compounds treated of above, and these on treatment with fresh hydrochloric acid 
 yield a further supply of chlorine, while the manganese may be continually 
 regenerated. 
 
 When manganate or permanganate of potassium is decomposed by an acid, 
 hydrated dioxide is precipitated, Mn0 2 H 2 0, as a reddish-brown body. 
 
 Another hydrate, 4MnO.,H 2 0, is obtained on heating the red oxide of manganese 
 with nitric acid. 
 
 According to Fremy, manganic dioxide not only acts as an acid, but also as a base, 
 forming definite salts with acids for example, a sulphate of the formula MnO a S0 3 . 
 
 The manganese of commerce is never pure manganese peroxide, but always con- 
 tains, besides lower oxides of manganese, a number of other admixtures which reduce 
 its value. Since it is the peroxide of manganese which yields chlorine with hydro- 
 chloric acid, the value of commercial manganese to the chlorine producer depends upon 
 the percentage of manganese peroxide it contains. In order to determine the amount 
 of peroxide in a sample of manganese, a weighed quantity of the manganese is treated 
 with an excess of hydrochloric acid, so as to liberate all the chlorine it is capable of 
 yielding. This chlorine is absorbed in a dilute solution of caustic soda, and then de- 
 termined by titration. 
 
 For this purpose 4'35 grms. of finely powdered commercial manganese is weighed and 
 placed in a glass flask, with from 15 to 20 c.c. of concentrated hydrochloric acid. 
 The flask is then closed as quickly as possible with an india-rubber cork, in order to 
 avoid escape of chlorine, a glass tube bent at an angle of 45 passing through a 
 perforation in the cork. The end of this glass tube is fastened into the neck of an 
 inverted retort reaching as far as the bulb of the retort. The retort is filled to about 
 four-fifths with a solution of caustic soda, so that no air is contained in the bulb itself. 
 The glass flask containing the manganese and hydrochloric acid is then gently heated, 
 the chlorine evolved being immediately absorbed by the caustic soda in the retort. The 
 temperature is eventually raised to the boiling point and kept at this point until 
 chlorine ceases to be evolved, which is ascertained from the peculiar noise caused by 
 the condensation of pure hydrochloric acid. All chlorine having been driven out of 
 the glass flask, this is disconnected from the retort, and the contents of the retort are 
 poured into a litre flask, the retort being washed with water and the washings added 
 to the contents of the litre flask, which is then filled with water up to the mark. The 
 
BINOXIDE OF MANGANESE. 519 
 
 litre flask is then shaken up and the chlorine contents of the liquid (10 c.c. being 
 taken at a time) determined by titration, either according to the method of Gray Lussac 
 or Penot and Mohr. 
 
 Since the equivalent weight of peroxide of manganese is 87, and 4'35 grms. of 
 manganese is taken, a pure sample ought to yield 3'5 grms. of chlorine, and accordingly 
 10 c.c. of the Gay Lussac arsenious acid solution ought to be saturated by 10 cc. of 
 the chlorine solution prepared as above. If, however, less chlorine has been evolved, 
 more of the chlorine solution is required. If, for instance, 14 c.c. be required to com- 
 pletely oxidise 10 c.c. of the Gay Lussac arsenious acid solution, the amount of man- 
 ganese peroxide contained in the sample of commercial manganese would be according 
 to the proportion : 
 
 14 : 10 = 100 : x 
 
 x = 71-43 
 
 The manganese sample would therefore accordingly contain 71'43 per cent, of 
 active manganese peroxide. 
 
 Instead of absorbing the chlorine by means of a dilute solution of caustic soda, it 
 may be passed into a weighed quantity of Penot's solution of sodium arsenite, the non- 
 oxidised arsenious acid being titrated back by means of iodine and starch paste. 
 
 Determination of the quantity of hydrochloric acid required for the complete decom- 
 position of a given quantity of manganese. The value of manganese is not alone 
 dependent upon the quantity of chlorine it is capable of yielding with hydrochloric 
 acid, but also upon the quantity of hydrochloric acid required for its complete decom- 
 position. Pure manganese peroxide liberates half the chlorine contained in a given 
 quantity of hydrochloric acid ; but commercial manganese contains, besides manganese 
 peroxide, compounds which decompose hydrochloric acid, setting very little, if any, 
 chlorine free. Manganese oxide, for instance, decomposes hydrochloric acid according 
 to the equation: 
 
 Mn 2 3 + 6HC1 = 2MnCl 2 + SBLX) + 2C1. 
 
 Thus it liberates only one -third of the chlorine contained in hydrochloric acid. 
 Manganous oxide yields no chlorine when treated with hydrochlori acid 
 
 MnO + 2HC1 = Mn C1 2 + H 2 0, 
 
 thus using up hydrochloric acid in a manner no way suitable to the chlorine manu- 
 facturer. Besides these oxides, commercial manganese may contain substances which 
 consume hydrochloric acid without evolving chlorine, as, for instance, iron oxides, etc. 
 
 But the most objectionable admixtures in commercial manganese are the carbonates, 
 such as calcium and barium carbonates, which consume hydrochloric acid and liberate 
 carbonic acid instead of chlorine. This carbonic acid is a great nuisance in the 
 chlorine chambers where bleaching powder is being prepared, as it combines with part 
 of the lime to form calcium carbonate, which resists the action of chlorine. This 
 causes not only a loss of hydrochloric acid, but also waste of lime at the same time. 
 
 According to Fresenius the quantity of hydrochloric acid required for the complete 
 decomposition of a definite quantity of manganese may be determined in the following 
 way. 
 
 The amount of acid in a strong solution of hydrochloric acid (spec. grav. I'lO) is 
 determined by titration either with ammoniacal copper oxide or with normal potash 
 solution. 10 c.c. of this acid is placed in a small flask containing the manganese 
 to be examined, which must be in a finely powdered state. The flask is then closed 
 with a perforated caoutchouc cork fitted with a glass tube 3 feet long, then gradually 
 heated until all the chlorine has been expelled. The flask and its contents are allowed 
 to cool, diluted with water, and the quantity of free acid again determined either by 
 titration with ammoniacal copper oxide or with normal potash solution. 
 
 When an oxide of manganese is fused with caustic potash, oxygen is absorbed 
 from the air, and a dark green mass results containing manganate of potassium 
 K 2 Mn0 4 . Potassic nitrate or chlorate, if added during the fusion, assists the oxida- 
 tion. If soda be used instead of potash, the sodium salt is obtained, and a solution 
 of either yields crystals by evaporation in a vacuum. This is necessary because the 
 salts readily absorb more oxygen passing into permanganate. 
 
 Barium manganate BaMn0 4 may be similarly prepared. 
 
520 MANGANESE. 
 
 PERMANGANATES. 
 
 Permanganates are obtained when maraganates are dissolved in much water ; man- 
 ganese dioxide is precipitated in a hydrated state, and the solution becomes purple 
 from the formation of a permanganate : 
 
 3K 2 Mn0 4 + 2H 2 = Mn0 2 4 K 2 Mn 2 8 + 4KHO. 
 
 This effect is accelerated by heat, but retarded by the presence of much free alkali. 
 Potassic permanganate may be readily made by heating to dull redness a mixture 
 prepared by drying a solution of five parts caustic potash containing in mixture 3 
 parts of potassic chlorate and 4 parts of finely divided manganese dioxide. After an 
 hour's heating, the mays is cooled, powdered, neutralised with sulphuric acid, filtered, 
 and evaporated. On cooling, beautiful acicular crystals of potassic permanganate 
 result. 
 
 Or the salt may be obtained by passing a current of carbonic anhydride through 
 potassic manganate in solution : 
 
 3K 2 Mn0 4 + 2C0 2 = K 2 Mn 2 8 + 21^003 + Mn0 2 ; 
 
 or chlorine may be used insteadthus: 
 
 2K2Mn0 4 + C1 2 = K 2 Mn 2 8 + 2KC1 
 
 Other permanganates are well known, such for instance as the argentic salt, which 
 is also crystalline. 
 
 Both the manganates and the permanganates are powerful oxidising agents. 
 
 Permanganic acid H 2 Mn 2 8 is prepared by dissolving the potassium salt in sul- 
 phuric acid diluted with one molecule of water and distilling the mixture at 60-70. 
 The acid then passes over in violet vapours, which condense to a greenish-black 
 liquid which has a powerful attraction for water, and is so powerful in its oxidising 
 effects as to instantly set fire to paper or alcohol. . 
 
 CHLORIDE. 
 
 FORMULA MaCl 2 . MOLECULAR WEIGHT 126. 
 
 As already explained, this salt is obtained on a large scale in the manufacture of 
 chlorine. It crystallises in plates of a delicate pink colour containing 4 molecules of 
 water. These when heated yield the anhydrous salt which is soluble in alcohol, 
 and forms a double combination which may be obtained in a crystalline form ; it 
 has the formula MnCl 2 ,40 2 H 6 0. 
 
 IVCANGANOTJS SULPHATE. 
 
 FORMULA MnS0 4 . MOLECULAR WEIGHT 151. 
 
 This salt is used to some extent by calico-printers. It is a very soluble rose- 
 coloured salt, isomorphous with magnesium sulphate. On the large scale it is prepared 
 by heating manganese dioxide and coal in a closed vessel, and dissolving the crude prot- 
 oxide thus obtained in sulphuric acid, with addition of a little hydrochloric acid. The so- 
 lution is then evaporated to dryness and the residue exposed to a red heat, by which 
 any ferric sulphate which is present is decomposed. From the product so resulting 
 water dissolves out pure sulphate of manganese. It is used by the printers by 
 steeping the cloths in it, and then passing them through a solution of bleaching 
 powder which precipitates the insoluble hydrated dioxide within the fibres of the 
 articles, thus producing a permanent brown. Sulphate of manganese crystallises either 
 with 7 or 5 molecules of water, and forms double salts with the sulphates of the 
 alkali metals ; thus the potassium double salt is MnS0 4 ,K,S0 4 , 6H 2 0. 
 
 When sulphate of manganese is crystallised from boiling sulphuric acid, it forms. 
 an acid salt of the formula MnH 2 2S0 4 . 
 
CHROMIUM. 
 
 SYMBOL Or. ATOMIC WEIGHT 52 - 5. 
 
 History. Chromium was discovered in 1797 by Vauquelin, in a mineral having 
 the composition of plumbic chromate PbCr0 4 . This, however, occurs but rarely in 
 nature. 
 
 Occurrence. Chromium is not found very abundantly in nature, and it never 
 occurs in the metallic state. The only ore which is found in any abundance is 
 chrome iron ore, a compound of oxides of chromium and oxides of iron, corre- 
 sponding to magnetic oxide of iron (FeO, Cr 2 3 or FeCr 2 4 ). Chrome iron ore occurs 
 chiefly in serpentine, which is found in Saxony, Silesia, Bohemia, Transylvania, in 
 Norway, the Ural and various parts of North' America. It is found in a massive 
 state in the Shetland Isles, while the chief supply is derived from Sweden and North 
 America. Chromium is also found as sesquioxide (chrome ochre), and as already 
 mentioned in the form of chromate of lead, a crystalline mineral of great beauty. 
 
 Characters. In the hard crystalline state the metal resists the action of strong 
 acids, even nitro-hydrochloric acid ; otherwise it is readily attacked by dilute hydro- 
 chloric acid, less so by dilute sulphuric acid, and even less by strong nitric acid. 
 
 When heated to redness in the air, it tarnishes, and is gradually covered with a 
 thin film of green oxide. When thrown into a flame fed with oxygen, it scintillates 
 like iron, and when melted with potassic chlorate it burns very brightly. It also 
 exhibits a brilliant incandescence when heated in chlorine gas ; it also combines with 
 bromine, iodine, fluorine, cyanogen, nitrogen, oxygen, phosphorus, and sulphur. When 
 absolutely pure, it is less fusible than platinum. 
 
 Preparation. There are several processes for the preparation of metallic 
 chromium. Deville obtained it by reducing chromium sesquioxide in a lime crucible, 
 by means of charcoal at a high temperature ; it is thus obtained as a porous mass con- 
 sisting of grains as hard as corundum and of specific gravity 5'9. Wo'hler prepared 
 metallic chromium by reducing the sesquichloride by means of zinc at a red heat. The 
 regulus of zinc obtained in this way is heated with dilute nitric acid, which dis- 
 solves the zinc and leaves the chromium as a grey powder. Peligot obtained it in a 
 similar form by the use of potassium in the place of zinc, and Fremy, by employing 
 the vapour of sodium along with a current of hydrogen, produced metallic chromium 
 in hard shining crystals. 
 
 Chromium is also obtained in brittle laminae when a solution of the sesquioxide is 
 submitted to electrolysis (Bunsen). 
 
 Compounds. Chromium forms two classes of salts, viz. the chromous and 
 chromic compounds. In the first of these the chromium is bivalent like iron in 
 ferrous chloride ; as for instance in the chloride CrCl 2 or the oxide CrO, etc. In the 
 chromic compounds the metal behaves as a triad or tetrad, and the salts are com- 
 parable to those of ferric iron, as the oxide Cr 2 3 and the chloride Cr 2 Cl 6 , etc. There 
 is a third oxide Cr0 3 which combines with water and basic oxides forming a series of 
 compounds called chromate s. The hydrate or hydrogen salt is chromic acid 
 H 2 Cr0 4 ; this acid is analogous to sulphuric acid. 
 
 Chromous oxide CrO is known only in the hydrated state, and is obtained when 
 chromous chloride CrCl 2 is precipitated by caustic potash ; in this state it is brown 
 and absorbs oxygen rapidly ; it even decomposes water with avidity, setting free 
 hydrogen, and forming an intermediate oxide of chromium CrO,Cr 2 3 ,H 2 0. 
 Chromous oxide forms salts which are of a pale blue colour and have a great affinity 
 for oxygen ; it forms a double sulphate with potassic sulphate Cr"K 2 2S0 4 . The ses- 
 quioxide Cr 2 3 corresponds to ferric oxide. The dioxide (Cr0 2 ) is obtained as a 
 brown substance by digesting chromic oxide with excess of chromic acid, or by partial 
 reduction of chromic acid ; it may be a chromic chromate Cr 2 3 ,CrCv 
 
 Perchromic acid is the name given to the blue solution obtained when chromic 
 acid or a solution of potassic di chromate acidulated with sulphuric acid is treated 
 
522 CHROMIUM. 
 
 with dilute peroxide of hydrogen ; it has been suggested that the colouring principle 
 may have the formula H 2 Cr 2 8 , containing an oxide Cr 2 7 analogous to permanganic 
 acid. 
 
 Chromium forms two chlorides, Cr01 2 and Cr 2 Cl a ; the latter of these will be de- 
 scribed more fully hereafter. Chromous chloride may be obtained by reduction of 
 chromic chloride at a red heat in a current of hydrogen ; the white product dissolves 
 easily in water, giving a blue solution liable to undergo atmospheric oxidation and 
 capable of absorbing nitric oxide just as ferrous chloride does. By atmospheric oxida- 
 tion a solution of chromous chloride turns green and yields chromic oxy chloride 
 Cr 2 01 6 ,Cr 2 3 . 
 
 With ammonic sulphide, chromous chloride gives a black precipitate of chromous 
 sulphide. 
 
 Two fluorides of chromium are well known, the trifluoride Cr 2 F 6 and the hexfluoride 
 CrF 6 . The former of these is obtained by treating dry sesquioxide of chromium 
 with hydrofluoric acid, and strongly heating the dried mass. The trifluoride, which is 
 dark green, sublimes at a high temperature and crystallises in regular octahedra. The 
 hexfluoride is produced on distillation of a mixture of 4 parts plumbic chromate with 
 3 of powdered fluor spar and 8 of concentrated sulphuric acid : 
 
 PbCr0 4 + 3CaF 2 + iH^ = PbS0 4 + 3CaS0 4 + 4H 2 + CrF 6 . 
 
 The deep red vapours of hexfluoride which pass over may be condensed to a red 
 liquid by use of a very low temperature. On contact with water the substance is 
 decomposed, yielding hydrofluoric acid and chromic acid : 
 
 CrF 6 + 3H 2 = Cr0 3 + 6HF. 
 
 It is said an intermediate fluoride between these two which have been described 
 can be obtained by the action of hydrofluoric acid on the brown dioxide of chromium. 
 
 Chromium also unites with bromine, iodine, cyanogen, phosphorus, and sulphur ; 
 besides the chromous sulphide above referred to, there is a chromic sulphide Cr 2 S 3 , 
 which may be obtained in black scales when the vapour of carbon bisulphide is passed 
 over strongly heated chromic oxide contained in a porcelain tube. By addition of 
 sulphide of ammonium to the solution of a chromic salt, hydrated sesquioxide is 
 precipitated and sulphuretted hydrogen set free. 
 
 A nitride of chromium Cr 3 N 4 ? has been described by Schrotter. 
 
 Chromic nitrate Cr 2 6N0 3 is a soluble salt of a green colour ; on gentle ignition 
 it yields brown dioxide of chromium Cr0 2 or Cr 2 3 ,Cr0 3 . 
 
 Chromic oxalate forms two well-defined series of double salts of the general 
 formula : M 6 'Cr 2 '"6C 2 4 and M 2 'Cr 2 " 4C 2 4 . 
 
 Little is known of the alloys of chromium ; it combines with aluminum and iron, 
 and also forms an amalgam which is obtained on treating a solution of chromic 
 chloride with sodium amalgam ; the product, when heated in a current of hydrogen, 
 leaves metallic chromium as a pulverulent sponge. 
 
 CHROMIC OXIDE. 
 
 FORMULA Cr 2 s . MOLECULAR WEIGHT 153. 
 
 This oxide in an anhydrous condition may be variously prepared. 
 (a) In dark green crystals when the vapour of chromic oxydichloride is passed 
 through a red-hot porcelain tube 4CrCl 2 2 = 2Cr 2 3 + 4C1 2 + O 2 . 
 (6) By heating ammonic or potassic dichromate. 
 When required for industrial purposes it is obtained : 
 
 (c) By mixing solutions of mercurous nitrate and potassium chromate or di- 
 chromate, and exposing the precipitated mercurous chromate to a red heat. The 
 sesquioxide so obtained as a residue is of a fine green colour, and, like alumina which 
 has been strongly heated, is insoluble in acids. 
 
 (d) Another good method of preparation consists in strongly igniting in a covered 
 crucible a mixture of 4 parts of potassic chromate in powder with 1 part of starch ; 
 potassic carbonate is thus formed, and may be dissolved out from the residue, and the 
 chromic oxide remaining only requires a second calcination to obtain it in a clear 
 bright green form. 
 
 Chromic oxide is not decomposed by heat, and it is therefore used in enamel 
 painting. 
 
 The pink colour used on earthenware is prepared by heating to redness a mixture 
 of 30 parts of stannic oxide, 10 of chalk, and 1 of potassic chromate : the product is 
 finely powdered and washed with weak hydrochloric acid. A beautiful rose tint is 
 thus obtained (Miller). 
 
CHROMIUM TRIOXIDB. 523 
 
 The crystalline sesquioxide is used in the preparation of razor strops. 
 
 The hydrated oxide may be obtained by boiling potassic dichromate in the presence 
 of alcohol or sulphurous anhydride, when potassic chromate is formed ; and on addition 
 of ammonia, the sesquioxide is thrown down as a greyish-green hydrate. This bulky 
 form of the hydrated oxide retains alkali with pertinacity ; it dissolves readily in acids, 
 and forms salts of a green colour, which do not crystallise. 
 
 Chromic oxide forms another set of salts having a violet colour which admit of 
 crystallisation, and the oxide which ammonia precipitates from their solutions is of a 
 bluish-green coloiir. 
 
 Berzelius accounted for these results by admitting the existence of two distinct 
 hydrates of chromic oxide. Through the researches of Fremy and Siewert these 
 hydrates have been more particularly made known. According to the conditions 
 of preparation and drying, the amount of water associated with the oxide is deter- 
 mined. The following combinations exist : 
 
 Cr 2 3 , 9H 2 0; Cr 2 3 , 7H 2 0; Cr 2 3 , 6H 2 0; Cr 2 3 , 4H 2 0; and Cr 2 s , H 2 0. 
 
 The hydrated sesquioxide parts with its water below redness, and if heated beyond 
 this point it becomes incandescent, shrinks, and is then insoluble in acids. Chromic 
 oxide is a weak base, resembling ferric oxide and alumina ; its salts are green or 
 purple. 
 
 CHROMIUM TRIOXIHE. 
 
 FORMULA CrO s . MOLECULAR WEIGHT 100*5. 
 
 This compound may be readily obtained by mixing 4 measures of concentrated 
 cold solution of potassic dichromate with 5 of oil of vitriol ; on cooling, the chromic 
 trioxide crystallises out in beautiful crimson needles. Chromic anhydride is very 
 soluble in water ; but, although soluble in dilute and even more concentrated acid 
 than that of 1'55 sp. gr., it is not soluble except to a slight extent in acid of that 
 particular strength. 
 
 To rid the crystals of sulphuric acid, they should be first drained on a tile, then 
 dissolved in water and precipitated by an equivalent amount of acid barium 
 chromate, BaH 2 2Cr0 4 , calculated upon the sulphuric acid present. On evaporation 
 of the resulting solution in vacuo, the chromic anhydride is obtained pure. 
 
 Chromic trioxide may be also obtained by decomposing chromium hexafluoride 
 with a little water. It is deliquescent and easily freed from water by drying at a 
 gentle heat. It is black when hot, but regains its dark red colour on cooling; it 
 fuses at 200C, and at a higher temperature evolves oxygen while the sesquioxide is 
 left behind. When heated with hydrochloric acid, chlorine is liberated according to 
 the following reaction : 
 
 2CrO s + 12HC1 = Cr 2 Cl 6 + 6H 2 + 3CL,. 
 
 Chromic trioxide combines with sulphuric acid to form several crystalline com- 
 pounds, which are all decomposable by water. 
 
 When in contact with water, for which the trioxide of chromium exhibits a strong 
 affinity, it exists as chromic acid, H 2 Cr0 4 , which is bibasic, and corresponds to sul- 
 phuric acid. 
 
 Chromic acid forms three classes of salts, namely, basic, normal, and acid; the 
 normal salts have a yellow, and the acid salts an orange colour. 
 
 Potassium, chromate, K 2 Cr0 4 , is made by calcination of chrome iron ore with nitre or 
 with potassium carbonate, or with caustic potash. 
 
 This operation is ordinarily conducted in a reverberatory furnace, using the chrome 
 iron ore in a powdered condition. The furnace product is lixiviated with water, and 
 the solution on evaporation yields crystals of the chromate in an anhydrous condition. 
 
 Potassium dichromate, K 2 Cr 2 7 , is obtained by heating chrome iron ore to redness 
 and plunging it into cold water, by which means it is rendered friable. It is finely 
 powdered and heated to bright redness with a mixture of chalk and potassium car- 
 bonate in a reverberatory furnace with frequent stirring in a current of air. Any 
 calcium chromate that may have formed is afterwards decomposed by lixiviating the 
 product with water, and addition if necessary of potassium carbonate. In any case the 
 yellow solution is drawn off, supersaturated with nitric acid, and, after separation by 
 filtration of any silica that may thus be precipitated, evaporated, when crystals of 
 potassium dichromate are obtained, and may be purified by recrystallisation. The chalk 
 is used in the furnace operation to keep the mass in a porous state, which is one 
 favourable to the oxidation. 
 
524 CHROMIUM. 
 
 This salt may also be obtained by treating the neutral salt with a calculated 
 quantity of sulphuric acid. 
 
 Potassium dichromate melts when heated, and is soluble in 10 parts of water. 
 
 By treating potassium dichromate with an equivalent of such bases as lime or mag- 
 nesia several double salts may be obtained. Thus we have magnesio-potassium 
 chromate, K 2 Mg2Cr0 4 .2H 2 0, which crystallises in oblique rhombic prisms. 
 
 Mitscherlich obtained a trichromate of potassium, K 2 Cr 3 10 , by acting on the 
 dichromate with excess of nitric acid ; and Siewert, by evaporating a solution of this 
 compound in nitric acid, obtained a tetrachromate K 2 Cr 4 18 . 
 
 Sodium chromate may be similarly prepared, using soda in the place of potash ; 
 it crystallises with 10H 2 0. An acid sodium chromate, 2NaHCr0 4 .H 2 0, can also be 
 obtained in ruby coloured crystals. 
 
 Argentic chromate, Ag 2 Cr0 4 , is precipitated when solutions of silver nitrate and 
 potassic chromate are mixed ; it is a reddish-brown powder, soluble in hot dilute 
 nitric acid, and crystallising therefrom on cooling in ruby-red crystals. 
 
 Chromate of calcium is soluble, while the chromates of barium, zinc, and mercury 
 are insoluble. 
 
 Plumbic chromate is the only other compound that calls for notice here ; it is largely 
 used in organic analysis by reason of the facility with which it yields oxygen to 
 organic matter heated in contact with it, while it fixes any such bodies as chlorine or 
 iodine which may be present in the substance to be analysed or ' burned.' 
 
 Plumbic chromate is the basis of the pigment known as chrome yellow, -and is 
 obtained by precipitating a solution of acetate of lead with one of potassium chromate 
 or dichromate. 
 
 At 200-250 C C it becomes brown, and at a much higher temperature it fuses and 
 evolves about 4 per cent, of oxygen, basic plumbic chromate being formed. 
 
 8PbCr0 4 = 4PbCr0 4 PbO + 2Cr 2 3 + 30 2 . 
 
 A dibasic plumbic chromate is also known of the formula (2PbO,Cr0 8 ) ; it is used 
 to impart a permanent orange to calico, and may be obtained by fusing one part of the 
 normal plumbic chromate with 5 parts of nitre. Potassium chromate and the dibasic 
 plumbic chromate are thus produced, while the potassium salt may be dissolved out 
 from the product by means of water. 
 
 CHROMIC SULPHATE. 
 
 FORMULA Cr 2 3S0 4 . MOLECULAR WEIGHT 393. 
 
 This salt is obtained by dissolving the hydrated sesquioxide in dilute sulphuric 
 acid. It forms with the sulphates of the alkalies double combinations which are 
 highly crystalline ; important among these is the ammonium compound : 
 
 CrNH 4 2S0 4 12H 2 0. 
 There are three varieties of chromic sulphate, represented as follows : 
 
 Bed insoluble sulphate . . . . Cr 2 3S0 4 
 
 Green soluble sulphate . . . . Cr 2 3SO., 5H 2 
 
 Violet .... Cr 2 3S0 4 , 15H 2 0,. 
 
 CHROMIC CHLORIDE. 
 
 FORMULA Cr 2 Cl 6 . MOLECULAR WEIGHT 318. 
 
 This compound may be obtained in the anhydrous condition by passing a current 
 of dry chlorine gas over an intimate mixture of chromium sesquioxide and charcoal 
 heated to redness in a porcelain tube. The chloride which forms sublimes and deposits 
 in the cool part of the tube in crystalline plates of a violet colour. 
 
 The crystals are quite insoluble in cold water ; but, when boiled, a green solution 
 is formed containing a trace of the dichloride. This change from the violet insoluble 
 condition to the green soluble variety is attended with evolution of heat. 
 
 The crystals of chloride above described are also not attacked by sulphuric, hydro- 
 chloric, or even nitro-hydrochloric acid. 
 
 The green hydrated chromic chloride is readily formed by dissolving chromic 
 hydrate in hydrochloric acid, or by boiling the chromates of lead or silver, or chromic 
 acid with hydrochloric acid in the presence of a reducing agent such as alcohol or 
 sulphurous acid. 
 
 2CrO, + 12HC1 = Cr 2 Cl 8 + 6H 2 + C1 8 . 
 
CHLOROCHROMIC OXIDE. 
 
 525 
 
 On evaporation of the solution a green syrup results ; and this, heated to 100C. 
 in a current of dry air, yields a mass containing Cr 2 Cl 6 ,9H 2 ; in a vacuum the solu- 
 tion yields Cr 2 Cl 6 ,H 2 0. 
 
 A compound of chromic chloride and chromic oxide known as chlorochromic oxide 
 Cr0 2 Cl 2 is formed when equal parts of potassium dichromate and common salt are dis- 
 tilled with one and a half times their combined weight of sulphuric acid ; this com- 
 pound passes over as a dark red vapour which condenses into a liquid like bromine. 
 Or 10 parts of common salt may be previously fused with 17 parts of potassic 
 chromate ; the mass is then broken into small fragments and heated in a retort, with 
 30 parts of oil of vitriol. 
 
 Water decomposes chlorochromic oxide into hydrochloric and chromic acids, just 
 as it similarly decomposes chloromolybdic, chlorotungstic, and chlorosulphuric oxides. 
 
 When chlorochromic oxide is dropped into strong ammonia it solidifies with in- 
 candescence, and it sets fire to alcohol, owing to the intense heat evolved in the reaction. 
 
 If heated to 180-190 C., it is resolved into a dark -coloured, deliquescent 
 powder, trichromyl dichloride, Cr 3 Cl 2 6 or 3Cr0 2 Cl 2 , which takes fire when gently 
 heated in hydrogen gas, being resolved into chromium sesquioxide, hydrochloric acid, 
 and water. 
 
 2Cr 3 Cl 2 6 + 10H = 3Cr 2 3 + 4HC1 + 3H 2 0. 
 
GOLD. 
 
 SYMBOL ATT. ATOMIC WEIGHT 197. 
 
 History. Gold has been known from the earliest times on record, and has 
 always been regarded as the king of metals by reason of the properties which qualify 
 it for the uses to which it is applied. The estimation in which the alchemists regarded 
 this metal is shown by the continuous vain endeavours they made to transform the 
 baser metals into gold. 
 
 Occurrence. Gold is most widely distributed in nature, and occurs chiefly in 
 the metallic state, sometimes crystallised in cubes, associated with quartz, iron oxide, 
 etc. It occurs in the crystalline rocks, the trachytic and trap rocks, and alluvial 
 deposits. The larger masses of filiform, arborescent shapes are known as pepitas or 
 nuggets. The gold dust of commerce is obtained from the sands of various rivers, 
 and is separated by a simple process of washing. Although gold occurs in many 
 parts of the world, being found for instance in small quantity in the pyritic forma- 
 tions of Wicklow in Ireland and in Cornwall, also in Hungary and Transylvania, in 
 Piedmont, Spain, China, Japan and other countries, yet the large supplies are now 
 derived from California and Australia, while the new gold field of British Columbia 
 is also very productive. Formerly Brazil, Hungary, and the Ural mountains furnished 
 the chief supply. 
 
 Native gold is generally associated with silver in a greater or less degree, and 
 the percentage of gold contained in the native alloy, although sometimes as low as 28 
 per cent., is usually from 88 to 98 per cent. Thus Californian gold averages from 
 87*5 to 88'5 per cent., and Australian from 96 to 96-6 per cent. gold. In certain kinds 
 of iron pyrites the amount of gold is but a few dwts. per ton, nevertheless processes 
 have been devised for the profitable extraction of even these small quantities. 
 
 Eecently, E. Sonstadt has demonstrated the presence of minute traces of gold in 
 sea water. 
 
 Characters. Gold is of a fine yellow colour and metallic lustre; it is sofb and 
 surpasses all other heavy metals in malleability, the thinnest gold leaf being of no 
 greater thickness than aMooo of an incn - In ductility it ranks next to silver and 
 admits of drawing into wire. 
 
 The density of the metal is 19'5, and it fuses according to Becquerel at 1037C. 
 
 Gold is one of the best conductors of heat and electricity, and suffers no change 
 by exposure to the air and water ; neither is it attacked by the unmixed acids, but it 
 dissolves readily in aqua regia. 
 
 Extraction. Gold is obtained by two distinct processes termed placer mining 
 and vein mining, both of which consist essentially in the separation of the metal by 
 mechanical means from the earthy substances with which it is associated. 
 
 Placer mining. This process is applied to the metal found in strata of clay, sand 
 and gravel ; it is as follows. Into a pan made of stiff tin plate or sheet iron, having 
 a flat bottom of about 12 in. in diameter, and whose sides are from 5 to 6 in. high, 
 eloping outwards at an angle of 45, is charged the ' pay dirt,' as it is termed, so as to 
 three fourths fill the pan. The pan is then immersed in about a foot depth of water, 
 and the miner by working the contents with his hands and shaking from time to time 
 removes the clay as a kind of thin mud ; the light sand follows the clay, while the 
 stones and pebbles rest on the top of the finer and denser gold sand, and are removed 
 by the hands. Finally there remains only gold dust and a certain small quantity of 
 black magnetic iron-sand, to get rid of which the dust is dried and then placed in a 
 'blower' or shallow tin scoop open atone end; into this the miner blows, shaking 
 the scoop from time to time, and he thus removes the black iron-sand which is carried 
 away in the current of air. The ' cradle,' ' torn ' and ' puddling box' are the names 
 which have been given to other pieces of apparatus designed and used for the same 
 purposes as the pan just described. The ' sluice ' is the form of washing apparatus 
 now usually employed in California, and consists virtually of a long wooden trough, 
 
GOLD COMPOUNDS. 527 
 
 through which a stream of water constantly flows; it is further provided with 
 suitable arrangements for preventing the gold dust from being carried away mechani- 
 cally. The gold remains behind in the apparatus employed, or it is caught and 
 amalgamated with mercury. 
 
 Vein mining. The quartz bearing gold is finely powdered and is then placed on 
 the rough surface of blankets or skins, over which a current of water flows ; the gold 
 is caught in this way, or it is amalgamated with mercury. The most usual method 
 of arresting very fine gold is to amalgamate the surface of a copper plate, and to allow 
 the water containing gold dust to flow over it. 
 
 From the amalgamated gold the excess of mercury is removed by filtration through 
 a prepared skin, and what remains in the skin is then subjected to distillation in a 
 cast-iron retort. The gold so obtained is usually submitted to fusion, for the purpose 
 of being cast into ingots. Dr. Wurtz and Mr. Crookes have both patented the use of 
 a little metallic sodium with the mercury used for amalgamation processes, and it is 
 said to be beneficial in some cases, especially where the gold is at all of a greasy 
 nature. 
 
 In the case of poor ores of gold, containing sulphide of copper and iron, etc., these 
 are first allowed to disintegrate and oxidise by atmospheric influences or are washed, 
 before they are submitted to the amalgamation process. Gold which has been treated 
 by amalgamation ordinarily contains nothing but silver, which may be removed by 
 nitric acid, if the proportion of silver be about 66 per cent, of the alloy ; if it be 
 below this, by being protected by the gold it fails to dissolve in the nitric acid. In 
 such cases, therefore, the gold must first be alloyed into the necessary amount of 
 silver, a process known as quartation. 
 
 Gold containing silver and copper may also be refined by boiling repeatedly with 
 concentrated sulphuric acid ; sulphates of silver and copper are thus formed, and 
 sulphurous anhydride generated. From the sulphuric acid solution, the silver may 
 be regained by precipitation with copper. 
 
 Refining of Alloys containing little Gold. The alloy is melted, granulated, and 
 treated with sulphuric acid in the way above described; the residual gold, still contain- 
 ing silver and some copper, is melted and treated in the manner described above for 
 alloys containing a large amount of gold. 
 
 From the solutions of silver sulphate obtained in refining operations, silver is pre- 
 cipitated by hanging strips of copper in the warm diluted solution, the silver powder 
 being finally melted together. 
 
 PARTING BY QTTARTATION. This method consists in forming an alloy of 1 part gold 
 and 2 parts silver, granulating it, treating and boiling the granulated alloy with pure 
 nitric acid of sp. gr.1'345 for five hours, in stoneware pots placed in a water bath, 
 the whole being frequently stirred. The undissolved gold is allowed to settle during the 
 night, the liquid is drawn off, and the treatment with nitric acid repeated in the same 
 way as before. The liquid from the second operation contains very little silver, and 
 is used for a further quantity of the alloy. The liquid from the first treatment is 
 treated with sodium chloride, to separate the silver as chloride. The gold, after being 
 washed, is pressed, dried and melted. 
 
 The separation of gold and silver by means of aqua regia is very seldom practised. 
 It depends upon the fact that, when alloys of the two metals are treated with aqua 
 regia, both are converted into chlorides, and the gold chloride being soluble in water, 
 can be readily separated from the insoluble silver chloride. 
 
 It is, however, only with alloys containing very little silver that this method can 
 be adopted, because the silver chloride forms a coating upon the pieces of alloy, and 
 prevents the further action of aqua regia. 
 
 Pure gold may be obtained from any alloy containing it, by solution in nitro-hydro- 
 chloric acid ; separation of any chloride of silver by filtration ; evaporation till all 
 acid is expelled ; solution of the residue in water acidulated with hydrochloric acid 
 and precipitation with ferrous sulphate : 
 
 6FeS0 4 + 2AuCl s = 2(Fe 2 (S0 4 ) 3 ) + Fe 2 Cl 6 4- Au 2 
 
 Metallic gold is thus obtained as a fine brown powder, which when suspended in 
 water and viewed by transmitted light is of a purple colour. Silver and some other 
 metals when present may be removed from gold by a process introduced by F. B. 
 Miller, and now used in the Eoyal Mint. This consists in forcing a current of chlorine 
 gas through the melted metal ; argentic chloride thus forms and collects upon the 
 surface, whilst any chlorides of arsenic, antimony, bismuth and zinc that may result 
 from the presence of these metals, are volatilised. 
 
 Compounds. Gold forms two series of compounds, termed respectively the 
 aurous and auric ; in the first of these it is univalent, and in the latter it is trivalent. 
 
528 GOLD. 
 
 Gold forms two oxides Au 2 and Au 2 3 , and two chlorides AuCl and AuCl 3 ; 
 auric bromide AuBr s is also known, and two iodides corresponding to the chlorides. 
 There are also two sulphides Au 4 S 4 and Au 2 S 3 . Hydrated auric oxide combines with 
 the alkalies forming salts termed aurates. 
 
 When dilute gold solutions are treated with stannous chloride a brownish purple 
 precipitate known as ' purple of Cassius ' is formed. It is this compound which is 
 employed to colour the red glass of Bohemia, and for enamel painting. The composi- 
 tion of the precipitate is not exactly known, but after ignition it consists of a mixture 
 of stannic oxide and metallic gold. Oxalic acid slowly reduces gold solutions to the 
 metallic state. 
 
 The alloys of gold are interesting and numerous. The most useful one is that 
 which it forms with copper ; it is of a redder colour than pure gold, harder, and more 
 fusible, but not so ductile nor so malleable. 
 
 British standard gold contains 8-33 per cent, of copper, and has a specific gravity 
 of 17' 157. The standard gold of France and the United States contains 10 per cent, 
 of copper. 
 
 Silver unites with gold in all proportions ; giving an alloy which is nearly white 
 when the two medals are in equal proportions. 
 
 Palladium communicates also a white colour to gold, but renders it brittle. 
 
 The electrum mentioned by Pliny was an alloy of gold and silver, containing, 
 according to Klaproth, 667 per cent, gold or 2 gold to 1 silver. A native amalgam 
 of gold Au 2 Hg 3 is found in small yellowish crystals, having a specific gravity of 15*47, 
 in the native mercury of Mauposa in California. 
 
 T. H. Henry obtained also a solid amalgam which crystallised in shining four- 
 sided prisms of great lustre, and which was not decomposed by boiling nitric acid ; 
 its formula proved to be Au 8 Hg. 
 
 Uses. In its finely divided state, gold is used for gilding porcelain articles. 
 These are first painted with an adhesive varnish, and after partially drying are 
 brushed over with a mixture of the powdered metal with some fusible enamel. The 
 articles are next fired and the gilt portions subsequently burnished. 
 
 The fine ruby colour possessed by Bohemian red glass is due to the presence of 
 gold. Of course the great use of gold is in the coinage of the world, while it is also 
 largely used in the fabrication of ornamental articles. 
 
 Gilding upon wood-work, etc., is effected by the use of gold-leaf, while the gilding 
 of metals is brought about by the use of aurous potassic cyanide AuCyKCy, or of 
 aurous potassic sulphide AuKS, as in the operations of electro-silvering. 
 
 Gilding on copper may be performed by immersion of the articles in a solution of 
 mercuric nitrate, and then shaking them with a soft lump of gold amalgamated with 
 mercury ; in this way the articles are covered with a film of the amalgam from which 
 the mercury may be expelled by heating. 
 
 AUROUS OXIDE. 
 
 FOBMULA Au 2 0. MOLECULAR WEIGHT 409-2. 
 
 This compound is obtained as a dark green powder by adding a dilute solution of 
 potash to one of aurous chloride. It is slightly soluble in excess of the alkali ; while 
 digestion with ammonia transforms it into fulminating gold. Hydrochloric acid con- 
 verts aurous oxide into metallic gold and auric chloride. 
 
 AURIC OXIDE. 
 
 FOBMITLA AUj0 8 . MOLECULAB WEIGHT 44 T2. 
 
 This oxide is best prepared, by adding magnesia to a solution of auric chloride, 
 which gives sparingly soluble aurate of magnesium ; or digesting this with nitric 
 acid, magnesia is removed and the teroxide of gold is left as an insoluble reddish- 
 yellow powder. If the nitric acid employed be weak, the yellow hydrate Au 2 3 , 
 3H 2 is obtained, but if strong acid be taken then the anhydrous brown powder 
 results. It is reduced both by heat and by exposure to light ; at 245C it is resolved 
 into gold and free oxygen. Although soluble in nitric, sulphuric, and hydrofluoric 
 acids, no true salts are formed, because on dilution with water the teroxide is re- 
 precipitated. It is also soluble in hydrochloric, hydrobromic, and hydriodic acids, 
 forming auric trichloride, tribromide, and triodide. 
 
 Hydrated auric oxide is soluble in the alkalies, forming salts which are termed 
 
AURIC CHLORIDE. 529 
 
 au rates, the solutions of which are yellow, and maybe used for electro-gilding 
 purposes. 
 
 Potassic aurate (KAu0 2 , 3H 2 0) crystallises in yellow needles, and a compound of 
 this with acid sulphite of potassium, or potassium aurosulphite, is also known, 
 2(KAu0 2 , 4KHS0 3 ).H 2 0. Both sodio-aurous thiosulphite and bario-aurous thiosul- 
 phite are known salts (Na 3 Au(S 2 3 ) 2 .2H 2 0) and Ba 3 Au 2 (S 2 3 ) 4 . 
 
 AUROUS CHLORIDE. 
 
 FORMULA AuCl. MOLECULAR WEIGHT 232-1. 
 
 Aurous chloride is obtained as a yellowish white mass insoluble in water, when 
 the trichloride is kept for some time at a temperature of about 1750 ; under these 
 conditions free chlorine is generated. 
 
 Even in the cold, and more quickly when hot, water decomposes this substance 
 into the trichloride and metallic gold. At about 200C aurous chloride gives up its 
 chlorine. 
 
 AURIC CHLORIDE. 
 
 .FORMULA Au01 3 . MOLECULAR WEIGHT 303-1. 
 
 This is by far the most important compound of gold, and is formed, as already 
 stated, when gold is dissolved in nitro-hydrochloric acid. By evaporating the solution 
 at a low temperature, the chloride is obtained as a dark red deliquescent mass. It 
 is also formed as a sublimate when gold leaf is heated to 300C in a current of chlorine. 
 
 Auric chloride is soluble in water, alcohol, and ether, and combines with a 
 number of metallic chlorides, forming double salts termed chloro-aurates. 
 
 Thus, there are known the following salts among others ; the sodium salt NaCt, 
 AuCl 3 , 2H 2 ; the potassium salt 2(KC1, AuCl 3 ), 5H 2 ; and the ammonium salt 
 NH 4 C1, And,, H 2 0. 
 
 Like platinic chloride, it also combines with the chlorides of organic bases and 
 alkaloids, but from the ease with which auric chloride is reduced, its use cannot be 
 recommended so strongly for these purposes. 
 
 M M 
 
PLATINUM. 
 
 SYMBOL Pt. ATOMIC WEIGHT 197*1. 
 
 History. Platinum was first recognised as a distinct metal, by an assayer in 
 Jamaica, named Wood, who pointed out its characteristics in 1741. 
 
 According to another account, the metal was discovered in the auriferous sand of 
 the river Pinto in the district of Choco in South America, by a Spanish traveller 
 named Ulloa ; it derives its name from the Spanish word ' Platina ' (meaning ' little 
 silver ' ). 
 
 Occurrence. Platinum always occurs in the native state in rounded or flattened 
 grains of a metallic lustre, which contain, besides platinum, the following other metals: 
 palladium, rhodium, ruthenium, and iridium. 
 
 More rarely it occurs in nodules alloyed with gold, and traces of silver, and with 
 copper, iron and lead. 
 
 The deposits of platinum are met with chiefly in valleys traversing serpentine, and 
 everywhere it is associated with the debris of the earlier volcanic formations. It is 
 rarely that the grains of native ore exceed the size of peas, but now and then masses 
 are found weighing sometimes as much as twenty pounds. 
 
 Platinum is found chiefly in Mexico, Brazil, and the Ural Mountains, besides 
 which sources it has been met with in California and Australia. 
 
 The largest quantity of platinum at present produced comes from the Ural 
 districts, and is worked from the auriferous sands of Kuschwa, Nischne, Tagilsk, and 
 Goroblagodat. 
 
 Thirty-five cwts. of the metal are annually afforded by Eussia, and this is said to 
 be five times the total amount given by Brazil, Borneo, St. Domingo, and the States of 
 Columbia. 
 
 The native grains have usually a grey colour, like that of tarnished steel, the 
 cavities being filled with earthy or ferruginous material, and sometimes grains of the 
 magnetic oxide of iron. The specific gravity of these native grains varies from 15 
 to 18'94, which latter figure relates to the larger specimen of M. Humboldt which 
 weighed more than 2 ounces avoirdupois. 
 
 The native ore contains from 73 to about 86 per cent, of platinum ; the following 
 analyses are by Deville and Debray. 
 
 
 Columbia 
 
 California 
 
 Russia 
 
 Oregon 
 
 Platinum . - ' .. , 
 
 86.20 
 
 76-82 
 
 85-50 
 
 76-50 
 
 77-50 
 
 51-45 
 
 Indium . . * 
 
 0-85 
 
 1.18 
 
 1-05 
 
 0-85 
 
 1-45 
 
 0-40 
 
 Ehodium . * . 
 
 1-40 
 
 1-22 
 
 1-00 
 
 1-95 
 
 2-80 
 
 0-65 
 
 Palladium . 
 
 0-50 
 
 1-14 
 
 0-60 
 
 1-30 
 
 0-85 
 
 0-15 
 
 Gold . . . 
 
 1-00 
 
 1-22 
 
 0-80 
 
 1-20 
 
 Little 
 
 0-85 
 
 Copper . ... 
 
 0-60 
 
 0-83 
 
 1-40 
 
 1-25 
 
 2-15 
 
 2-15 
 
 Iron .... 
 
 7-80 
 
 7-43 
 
 6-75 
 
 6-10 
 
 9-60 
 
 4-30 
 
 Osmiridium . 
 
 0-95 
 
 7'98 
 
 MO 
 
 7-55 
 
 2-35 
 
 37-30 
 
 Sand .... 
 
 0-95 
 
 2-41 
 
 2-95 
 
 1-50 
 
 1-00 
 
 3-00 
 
 Lead . . . '. 
 
 
 
 
 
 
 
 0-55 
 
 
 
 
 
 Osmium and loss . 
 
 
 
 
 
 - 
 
 1-25 
 
 2-30 
 
 
 
 
 100-25 
 
 100-28 
 
 101-15 
 
 100-00 
 
 100-00 
 
 100-25 
 
 Platinum has only been known in Europe since 1748, and was at first introduced 
 into the market as ' white gold.' 
 
 Characters. Platinum is a very white metal of great ductility and malleability, 
 besides which it is the heaviest metal known, having a density of about 21*50; in 
 hardness it is about equal to copper. 
 
PURIFICATION OF PLATINUM. 531 
 
 Deville and Debray state that platinum, like "silver, has the power of absorbing 
 oxygen when melted, and, if in considerable masses, spits on rapidly cooling. 
 
 In the state of very fine wire the metal may be melted in an ordinary blowpipe 
 flame ; otherwise the heat of the oxyhydrogen flame is required to fuse it. 
 
 Among the acids aqua regia alone attacks it, while the alkalies and their carbonates 
 have an action upon it only at elevated temperatures, 
 
 Under the influence of heat it expands very little, and is inferior to gold, and 
 ranks very near to iron, in its conductivity of heat and electricity. 
 
 When heated with phosphorus, the two elements readily combine ; sulphur has very 
 much less attraction for it, and chlorine no action upon it. 
 
 Platinum has a remarkable capacity of inducing combination of gases which may 
 be presented to it ; this power is exhibited in a faint degree by bright surfaces of the 
 metal, but much more strongly by spongy platinum, which is obtained on strong 
 ignition of ammonio-platinic chloride. Platinum black has a still greater power 
 of the same kind. It may be variously prepared ; as, for instance, by reduction of 
 platinic chloride solution by sodic carbonate and suar on boiling, or by dissolving 
 platinum chloride in hot caustic potash and adding alcohol gradually to the mixture. 
 
 Platinum in this state is like lamp black in appearance, and readily absorbs oxygen. 
 The power of finely divided platinum to cause the combination of hydrogen and 
 oxygen has been ascribed to the power of the metal to absorb and condense into 
 more intimate contact the respective gases. 
 
 Finely divided platinum is also useful in effecting the decomposition of hydro- 
 chloric acid by air or oxygen, when these gases are passed over it at a red heat, thus 
 obtaining water and chlorine. 
 
 Preparation. When gold is present in sufficient quantity, the platinum is first 
 subjected to a process of amalgamation in order to remove it, after which the ore is 
 generally treated by a method devised by Wollaston. 
 
 The method may be described as follows : 
 
 After removing the gold, the ore is extracted first with nitric acid, and afterwards 
 with hydrochloric acid in order to free it from the more oxidisable metals. It is then 
 placed in carboys or stoneware vessels heated on a sand bath, and connected with 
 suitable means for condensing the acid vapours generated in the next stage of the 
 extraction. This consists in extracting the ore with aqua regia, always keeping the 
 hydrochloric acid in excess. When the solution of the ore is completed, the liquors 
 are run off from the insoluble osmiridium, and foreign earthy matters allowed to 
 settle, and the supernatant solution fully precipitated with solution of sal-ammoniac, 
 NH 4 C1. This operation requires about 41 parts of the salt to 100 of ore, and the 
 salt for use is dissolved in 5 times its weight of water. The precipitate obtained in 
 this way is the double salt 2NH 4 C1, PtCl 4 , which is but sparingly soluble. 
 
 The mother liquors, yet containing a considerable amount of platinum, are pre- 
 cipitated by bars of zinc or iron ; this operation gives a black deposit containing 
 platinum, and this, on re-solution in aqua regia and precipitation with ammonic. 
 chloride, gives a further quantity of the double salt. 
 
 The compound chloride is then heated to redness in black-lead crucibles, by which 
 means the ammonia and chlorine are expelled and metallic platinum left. 
 
 The spongy platinum is then rubbed between the hands and mixed with water 
 intimately, and by a process of levigation, the lighter non-metallic impurities are 
 carried away ; the metal then remaining usually retains a little iridium. While in 
 the form of a dense mud, it is poured into a gun metal or brass cylinder somewhat 
 conical in form and well fitted with a steel piston, and, after ramming with a wooden 
 piston, the' whole mass is subjected to strong pressure by means of the steel piston. 
 
 The discs of metal obtained in this way, and having a specific gravity of about 
 10, are next exposed to a strong white heat in a wind furn?ce, and the ingot forged by 
 hammering until rendered homogeneous, and the specific gravity is about 2T5. 
 
 When a metal of greater purity is required, a modification of the process just 
 described is employed. 
 
 When the aqua regia solution is boiled, chlorine is evolved, and the palladium 
 tetrachloride is reduced to dichloride, which remains in solution; platinum is then 
 precipitated, not by ammonium chloride, but by chloride of potassium. The precipitate 
 so obtained is yellow, when pure, but red if iridium , be present. After washing 
 it with dilute solution of potassic chloride, it is ignited with twice its weight of 
 potassic carbonate, thus obtaining metallic platinum, while at least a part of the 
 iridium is left as teroxide insoluble in the aqua regia, which is afterwards used to dis- 
 solve the platinum freed from the fused mass by water. 
 
 The complete removal of iridium sometimes necessitates the repetition of these 
 processes several times, after which the aqua regia solution of platinum is precipitated 
 
 M M 2 
 
532 
 
 PLATINUM. 
 
 by chloride of ammonium, and the spongy platinum, obtained on ignition, treated as 
 already stated. 
 
 Even this product contains small quantities of osmium and silicon, to free it from 
 which Deville and Debray recommend the fusion of the platinum by means of the 
 oxyhydrogen blowpipe, in a cavity formed in a mass of lime. The silicon then 
 combines with the lime as a slag and the osmium is volatilised as tetroxide. 
 
 The apparatus employed for this purpose is represented by fig. 884. The iron 
 frame (b) is lined with well-burned lime in such a manner that a cavity is left for the 
 metal and an opening (d) for running out the melted charge. To the upper part of 
 the apparatus are attached two copper tubes (e e) fitted with platinum nozzles, 
 
 FIG. 384. 
 
 through which a .mixture of oxygen gas and hydrogen or carburetted hydrogen is 
 supplied for combustion by opening the cocks (ff and 1 1) in the supply tubes (gg and 
 h h). The oxygen gas is supplied through the tubes (h h) and by means of the stuffing 
 boxes (mm) they can be moved up or down as required. The handle (c] serves for 
 tilting over the apparatus when the melted contents are run out through the opening 
 (d) into moulds. 
 
 These same chemists also purify platinum by fusing the ore with galena in a 
 reverberatory furnace. The lead forms an alloy with the platinum, from which the 
 lead may be removed by cupellation. 
 
 Uses. Platinum finds extensive use in chemical laboratories, where material is 
 often required capable of withstanding a high temperature and the influence of strong 
 re-agents. 
 
 The metal is also strongly employed for constructing stills used in the concentra- 
 tion of oil of vitriol. Sometimes these alembics are strongly gilt on the inside ; for, 
 unless protected in this way, the platinum made by Wollaston's process slowly 
 becomes porous and admits of the transudation of the acid. 
 
 There are thirty-nine platinum alembics in use at twenty-six sulphuric works in 
 France, and in Germany they are also much used ; but they are not used to the same 
 extent in England. 
 
 Scheurer-Kestner has proved that platinum is slowly dissolved by hot concen- 
 trated sulphuric acid ; and, if traces of nitrous compounds are present, this action 
 becomes more serious. 
 
 Platinum containing a little iridium is not nearly so subject to the action of sul- 
 phuric acid as the pure metal, but such impure metal is far harder to work. 
 
 Some years ago an attempt was made to introduce a platinum coinage into Eussia, 
 but the experiment was abandoned after a few years. 
 
PLATINUM COMPOUNDS. 533 
 
 Compounds. Platinum forms two series of compounds ; the platinous or bi- 
 valent compounds and the platinic or quadrivalent combinations. 
 
 There are two oxides, PtO and Pt0 2 ; two chlorides, PtCl 2 and PtCl 4 , and double 
 combinations of these with the chlorides of the alkali metals, as for instance 
 2KCl.PtCl 2 ; 2KCl.Pt01 4 ; 2NaCl.PtCl 4 6H 2 ; and 2NH 4 Cl.PtCl 4 . 
 
 The bromides and iodides are analogous to the chlorides in composition. 
 
 There are also two sulphides, PtS and PtS 2 , which correspond to the two oxides. 
 
 Sulphate and nitrate of platinum are also known, as well as sulphite PtS0 3 . 
 
 Fulminating platinum (Pt lT H 2 N 2 , 4H 2 ?), as it is called, is an insoluble black 
 powder obtained by dissolving ammonic platinic chloride in caustic soda, and addii _ 
 excess of acetic acid, or by precipitating the sulphate with ammonia. At 200 C. 
 this compound suddenly explodes. 
 
 Besides the foregoing compounds, a large number of ammoniacal platinum com- 
 pounds are known, which cannot be more than mentioned here. 
 
 Thus taking K to indicate a univalent radical, series of combinations are known 
 representable by the formulae 
 
 2NH,.Pt% ' 4NH s .Pt"K 4 
 
 4NH 3 .Pt"K 2 8NH 3 .Pt *K 6 0" 
 
 2NH s .Pt*K 4 
 
 Platinum may easily be alloyed with many other metals, the combinations being 
 usually accompanied by evolution of light and heat. 
 
 The alloy, with 10 or 12 parts of silver to one of platinum, is completely soluble 
 in nitric acid. 
 
 Copper and platinum in certain proportions form a brilliant alloy, while the alloy 
 with iron is malleable and lustrous. 
 
 None of these alloys are used in the arts. 
 
 PLATINOITS OXIDE. 
 
 FORMULA PtO. MOLECULAR WEIGHT 213-1. 
 
 This substance is obtained on digesting platinous chloride in a solution of potash, 
 and precipitation of the dark green solution by neutralisation with sulphuric acid ; it 
 is thus thrown down as a black hydrated powder. 
 
 This oxide is also formed when the dioxide is heated with a solution of oxalic 
 acid; this gives a dark blue solution, which deposits fine copper-red needles of 
 platinous oxide. The protoxide is soluble in acids and alkalies. 
 
 Platinous sulphite forms several double salts with the sulphites of the alkali 
 metals, and among them the following is one of the most important 3K.SO.. 
 PtS0 3 3H 2 0. 
 
 PLATINIC OXIDE. 
 
 FORMULA Pt0 2 . MOLECULAR WEIGHT 229'1. 
 
 This oxide has a curious tendency to combine with alkaline bases. It may be pre- 
 pared in several ways ; best, perhaps, by precipitating a solution of platinic nitrate 
 with half the quantity of sodic carbonate necessary for complete precipitation. Thus 
 obtained, platinic oxide is a voluminous brown hydrate (Pt0 2 , 2H 2 0) ; on heating, the 
 water is expelled, and on ignition, it parts with its oxygen, also leaving metallic platinum. 
 
 The solutions obtained by dissolving the dioxide in caustic alkalies give on 
 crystallisation definite compounds; among them there is NajjO.SPtOjjGHjO. 
 
 By dissolving this oxide in acids the various platinic salts may be obtained ; they 
 axe of a reddish-yellow brown colour. 
 
 PLATINOUS CHLORIDE. 
 
 FORMULA PtCl 2 . MOLECULAR WEIGHT 268-1. 
 
 Is obtained by gentle ignition of the tetrachloride at 235 C., when chlorine is 
 expelled ; the residue is of an olive colour and is insoluble in water, but dissolves in 
 warm hydrochloric acid, and readily in caustic potash, 
 
534 PLATINUM. 
 
 It may also be prepared by passing a current of sulphurous anhydride into a 
 solution of platinic chloride, until the latter no longer gives a precipitate -with 
 ammonic chloride. When its hydrochloric acid solution is mixed with potassic 
 chloride, there is deposited a red crystalline crop of 2KC1, Pt01 2 . 
 
 Such compounds as the latter, of which there are a great -number known, are 
 termed chloro-platinites or platinoso-chlorides. 
 
 PXiATXirXC CHLORIDE. 
 
 FORMULA PtCl 4 . MOLECULAR WEIGHT 339'1. 
 
 This chloride is obtained as described upon the preparation of the metal ; it is a 
 deliquescent salt which crystallises in prisms. It is readily soluble in water, alcohol, 
 and ether, and its solutions have a characteristic orange colour. 
 
 On evaporating its hydrochloric acid solution over lime and sulphuric acid, there 
 are obtained crystals of the compound 2HC1, PtCl 4 , 6H 2 0. 
 
 Platinic chloride unites with a great number of metallic chlorides, forming platino- 
 chlorides or chloro-platinates. Thus beyond the ammoniacal double saLt and the 
 potassium salt, there are known also compounds with the chlorides of magnesium, 
 manganese, zinc, iron, nickel, cobalt, cadmium, copper, etc. 
 
 Platinic chloride forms definite compounds with many alkaloidal bases, and with 
 them and hydrochloric acid double salts of the hydrochlorides of the bases are obtained. 
 
 When the respective chlorides of platinum are submitted to the action of hydric 
 sulphide, or the sulphydrate of an alkali metal, the corresponding sulphides are pro- 
 duced. 
 
 On ignition in a close vessel platinic sulphide PtS 2 loses half its sulphur, and 
 becomes platinous sulphide PtS. 
 
 PAX.X.ADXU1MC. 
 
 SYMBOL Pd. ATOMIC WEIGHT 106'5. 
 
 Palladium was discovered in 1803 by Wollaston, and obtained from platinum ore. 
 It constitutes about 1 per cent, of the Columbian ore and from \ to 1 per cent, the 
 Uralian ore of platinum, occurring in loose grains of a steel-grey colour and of sp. gr. 
 11-8 to 12-14. 
 
 It also occurs in Brazil as an alloy with gold, in many varieties of which it is 
 found. 
 
 To extract the metal from the ore of platinum, this is dissolved in nitrohydro- 
 chloric acid, and the platinum removed by means of chloride of ammonium as de- 
 scribed under that metal. The mother liquor is then precipitated by cyanide of 
 mercury, when the palladium cyanide is precipitated as a pale yellow cyanide, which 
 yields the metal on ignition ; or the cyanide may be roasted with sulphur ; this gives 
 sulphide of palladium, which loses its sulphur on continued roasting, and furnishes the 
 metal. 
 
 The metal may be also obtained from the gold alloy above referred to by the 
 following process. The alloy is melted with 2 or 3 parts of silver, granulated and 
 digested in nitric acid of I 1 3 sp. gr. ; the gold does not dissolve, while the palladium 
 silver goes into solution, and this on treatment with salt gives a precipitate of argentic 
 chloride. 
 
 The filtrate is concentrated after neutralisation by ammonia and yields a rose- 
 coloured salt of ammonio-chloride of palladium in long silky crystals. These yield 
 40 per cent, of metal on ignition. 
 
 Instead of the foregoing proceeding, after precipitation of the silver as chloride, 
 the following modification may be used. 
 
 Bars of zinc are introduced into the solution containing palladium, copper, lead 
 and iron, when these metals are precipitated as a black powder upon the zinc. The 
 precipitate is next dissolved in nitric acid, and supersaturated with ammonia, by 
 which means the copper and palladium oxides are kept in solution, while the others 
 
PALLADIUM COMPOUNDS. 535 
 
 are precipitated. The clear mother liquor is now supersaturated with hydrochloric 
 acid which throws down the sparingly soluble yellow double chloride, PdH e N 2 Cl 2 . 
 This on ignition gives metallic palladium. 
 
 Palladium is a very hard metal, white, ductile, and tenacious ; more fusible 
 than platinum, and more oxidi sable than silver, tarnishing in the air at ordinary 
 temperatures. According to Deville and Debray, it absorbs oxygen like silver does 
 when melted, and spits on cooling. If heated on lime before the oxyhydrogen flame, 
 it is dissipated in green vapours. 
 
 The metal is soluble in nitric or nitro-hydrochloric acids, but is not attacked to 
 any great degree by other acids. 
 
 Palladium exhibits a curious power of absorption of hydrogen, which it gives out 
 again in a high temperature. 
 
 It forms a carbide by holding the foil in a smoky flame. 
 
 It forms apparently three oxides ; a suboxide Pd 2 corresponding to cuprous 
 oxide, and like it forming a series of salts. It may be prepared by ignition of the 
 hydrated protoxide. 
 
 The protoxide or palladous oxide PdO is a black powder obtained by igniting the 
 nitrate ; as a hydrate it is furnished by precipitating the solution of a palladous salt 
 by an alkaline carbonate. This hydrated oxide is brown in colour and loses its water 
 on heating. 
 
 The dioxide Pd0 2 is obtained by adding caustic potash to the double palladic- 
 potassic chloride (2KC1, PdCl 4 ); it forms a yellowish-brown hydrate. 
 
 Palladous chloride is obtained on evaporating to dryness a solution of the 
 metal in aqua regia. It forms brown hydrated crystals which lose their water on 
 heating and become black ; on stronger ignition the metal is obtained. It forms 
 double salts with the soluble chlorides and a series of ammonium compounds like 
 those of platinum. Thus palladamine PdH 6 N 2 is obtained from the salts 
 PdH 6 N 2 Cl 2 , and is a powerfully alkaline base forming definite salts. 
 
 Palladia chloride (PdCl 4 ) cannot be obtained in crystals, but it forms double 
 salts which are crystalline. The compound 2KC1, PdCl 4 consists of ruby red prisms. 
 
 The iodide PdI 2 may be obtained as a black powder by double decomposition ; it is 
 insoluble in water, but dissolves in ammonia. 
 
 A cyanide PdCy 2 , a fluoride PdF 2 , and a bromide are also known. 
 
 There appear to exist also three sulphides palladous sulphide PdS; palladic 
 disulphide PdS 2 (crystalline), and a subsulphide Pd 2 S. 
 
 The protosulphide is prepared by heating the metal with sulphur, or by precipi- 
 tating a salt of palladium with sulphuretted hydrogen. 
 
 The disulphide is obtained on fusing the monosulphide with potassic carbonate 
 and sulphur. 
 
 Palladous sulphate PdS0 4 is obtained by dissolving the oxide in sulphuric 
 acid or decomposition of the nitrate thereby. 
 
 The nitrate is yielded by dissolving the metal in nitric acid, and may be obtained 
 in rhombic prisms. 
 
 All the ordinary salts cf palladium when in the state of solution are red or 
 brown. 
 
 The alloys of palladium. Palladium forms alloys with antimony, arsenic, barium, 
 copper, bismuth, gold, iron, lead, nickel, tin and platinum, etc. 
 
 The alloy with gold has a remarkably whitened appearance when the palladium 
 amounts to 20 per cent. The native alloy from Porpez contains gold 85'98 per 
 cent. ; palladium 9'85 per cent. ; silver 4*17 per cent. (Berzelius). 
 
 With eight times its weight of tin at a red heat palladium forms an alloy (Pd 3 Sn 2 ) 
 which is obtained in brilliant laminae on digesting the mass in cold hydrochloric 
 acid. 
 
 An alloy of palladium and silver is sometimes employed for making surgical in- 
 struments, as it does not tarnish in the air. 
 
 Sometimes also the metal is used in the construction of astronomical instruments 
 and accurate balances, on account of the whiteness, hardness, and unalterability of 
 palladium in the air. 
 
 Faraday and Stodart recommended an alloy of 1 part palladium with 100 parts of 
 steel as one well adapted for cutting instruments. 
 
 The Wollaston medal of the Geological Society was formerly made of palladium. 
 
KM Itlini) I CM. 
 
 RHODIUM. 
 
 SYMBOL( Ro. ATOMIC WKIQIIT 1043. 
 
 This metal was discovered by Wollaston in 1803 in the ore of platinum. Tho 
 platinum ore of Antioquia in Columbia contains about 3 per cent. Rhodium 
 also occurs in tho Ural ore and in tho gold alloy of Mexico. 
 
 Under l he head of palladium has been described tin- method by which that metal 
 
 is extracted from platinum ores at cyanide; in the mother liquor there is contained 
 rhodium, \\hi.-h may be i follows. Hydrochloric acid is .-elded ;, m | tin- 
 
 whole evaporated to drvness. In this way the cyanogen is expelled and tho metallic 
 salts converted into chlorides. The dr\ m a--s is powdered and extracted \\ith alco- 
 hol of 0-837 sp. gr., in which operation the double chlorides of sodium with platinum, 
 indium, copper and mercury are dissolved, while that with rhodium is left behind as 
 a fine dark red powder. 'This on i-nition givc-s the metal, or the latter may bo 
 obtained from tho double chloride by treating it gently in a glass tube in a stream of 
 hydrogen ; on then washing out the residual sodic chloride the metal is left behind. 
 
 !NI >re recently Devilleand Debray have described another process f,,r t he ext tac 
 tion of rhodium. 
 
 The platinum residues are fused with an equal weight of lead and twice their weight 
 of litharge. In this way a button of lead is obtained containing all the metitls less 
 oxidisablo than load, and this is heated with nitric acid (I : 1), which removes, 
 besides the lead, the copper and palladium. The insoluble powder is mixed with live 
 times its weight of peroxide of barium, and heated to redness for several hours in a 
 day crucible. The mass is then heated with water, and afterwards with aqua ro^ia 
 to remove the arsenic acid. Sulphuric acid is next added to exactly precipitate the 
 barium, the liquid boiled, filtered, and evaporated first with a little nitric acid and 
 afterwards with much ammonic chloride. The mass, dry at 100C., is extracted with 
 a concentrated solution of chloride of ammonium, which dissolves the rhodium, and from 
 tho solution the chloride of ammonium is expelled by evaporation. Finally nitno 
 acid is added and the evaporation is completed in a porcelain crucible. The mass is 
 now moistened with sulphide of ammonia mixed with sulphur, and ignited for some 
 time, when metallic rhodium is obtained. 
 
 Rhodium is lossfusiblo than platinum, butoxidises like palladium. In appearance 
 it resembles aluminum, and when pure is ductile and malleable after fusion. Its 
 density is then 12'1. Rhodium is oxidised by fusion with a mixture of nitre and 
 potassic carbonate. It is also oxidised by acid potassium sulphate, giving a double 
 sulphate K Ivo'JSO,,, while sulphurous anhydride escapes. 
 
 Heated in contact with salt, in a stream of chlorine, a double chloride results, 
 
 3NaCl, Rod,. 
 
 Berzelius and others have contended for the existence of three chlorides, but 
 according to Olaus. there is but one definite chloride, vi/. the one with tho composi- 
 tion RoCl 8 . It may be obtained anhydrous, by igniting the powdered metal in chlorine, 
 and as thus prepared it is insoluble. By decomposing potassic rhodic chloride by silico- 
 fluoric acid, potassic fluosilicate is formed, and may be filtered off, while a solution 
 results which, on evaporation, gives the chloride of rhodium as a red-brown mass of 
 composition Ro01 8 , 4H 2 0. If to a solution of rhodic chloride excess of ammonia 
 be added, and the mixture boiled, a yellow compound is precipitated which may be 
 purified by re-crystallisation ; it has the formula RoCl 8 , 5NH 8 . When ignited tho 
 compound yields pure rhodium. 
 
 Rhodic oxide Ro 2 8 is the only oxide which gives rise to salts. It is produced 
 by the oxidation of the metal by a fused mixture of nitre and potassic carbonate. 
 
 A hydrate Ro 2 8 6H 2 is also known and three other oxides viz. a green-coloured 
 hydrate of the oxide Ro0 2 ; a trioxide Ro0 8 which is blue, and a protoxide RoO. 
 
 Rhodium when heated in the vapour of sulphur gives protosulphide RoS. 
 
 The sesquisulphide Ro 2 S 8 is prepared as a brown hydrate by decomposing a hot 
 solution of sodio-rhodic chloride with potassic or sodic sulphide. 
 
 The acetate is an amorphous orange-yellow body, whilst the nitrate and sulphate 
 are both crystalline. Several phosphates and a cyanide are known. The salts of 
 rhodic oxide are chiefly of a rose-red colour and are decomposed by iron or zinc with 
 the production of metallic rhodium. 
 
 The alloys of rhodium, so far as they have been studied, appear to be true chemical 
 compounds, as evidenced by the heat, evolved in combination. The /inc. alloy resists 
 the action of hydrochloric acid. Tho alloy with tin is crystalline, black, and fusible 
 only at a, very hi:',h temperature. 
 
RUTHENIUM COMPOUNDS. 537 
 
 A native alloy of gold and rhodium found in Mexico contain* from 34 to 43 per 
 cent, rhodium. 
 
 An alloy made from 1 part of rhodium and 1 part of steel has a specific gravity 
 of 9-1 76, and is of fine colour, and does not tarnish in the air. 
 
 RUTHENIUM. 
 
 SYMBOL Bo. ATOMIC WEIOHT 104*2. 
 
 This metal was first shown to exist by Glaus, who discovered it in an ore of 
 platinum. Since then the metal and its compounds hare been carefully examined by 
 Fremy and Deville and Debray. 
 
 It is found chiefly in osmiridium, which contains from 3 to 6 per cent., but it 
 is not found in that part of the platinum ore soluble in aqua regia. 
 
 From this last-mentioned source the metal may be extracted after the method of 
 Fremy. After exhausting the ore with aqua regia, the residue containing osmium, 
 indium, ruthenium, and rhodium, together sometimes with titaniferons and chrome 
 iron, is roasted in a current of dry air in a porcelain or platinum tube. The tube is 
 connected with some glass flasks, and where the tube projects from the furnace it is 
 plugged with some fragments of porcelain, 
 
 During the oxidation the osmium is converted into tetroxide, which, owing to its 
 superior volatility, is carried over and condensed in needles in the glass flasks, while 
 the ruthenium becomes dioxide, and this being less volatile deposits in regular square 
 prisms upon the broken porcelain. By heating this oxide in a current of hydrogen, 
 the metal is obtained as a dark grey powder. 
 
 Bnthenium is a very hard, brittle metal, which is difficultly fusible even in the 
 oxybydrogen blowpipe. Deville and Debray have assigned a sp. gr. of 11 '0 to 11 '4 
 to the melted metal. By fusion with nitre and cafcitic potash, the metal gives an 
 orange-coloured soluble rnthenate, and on saturating a solution of this salt with 
 chlorine, there is obtained hvper-rnthenic acid Ku0 4 , the analogue of osmic acid OsO 4 ; 
 hyper-ruthenic acid is volatile, and condenses in golden crystals or globules. 
 
 Deville and Debray in their later researches have employed this body as the source 
 of t.h';ir purest metaL A solution of hyper-rnthenic acid in potash gives with 
 alcohol oxide of ruthenium BuOj, and this, on reduction with coal gas at an elevated 
 temperature, yields the pure metal. When obtained from one of its ammoniacal 
 chlorides by calcination it is a white (spongy mass. 
 
 Ruthenium forms five oxides with the formula, BuO, Bt^O, , BnO* BuO ( , Bn0 4 . 
 The higher oxide has already been described ; it is incapable of combination with 
 bases. When dropped into potash it is dissolved slowly, oxygen is evolved, and a 
 green salt crystallises out which has the formula KBu^O,. 
 
 The oxide BuO, (ruthenic anhydride or rnthenic acid) is insoluble in water; it 
 may be obtained on fusing any of the other oxides with nitre. The sesquioxide is 
 the most stable basic oxide of ruthenium, and is prepared by igniting the metal in a 
 current of air ; it is of a deep blue colour and insoluble in acids. As a hydrated oxide 
 K>: 2 0, : :ii IS), it u pftdpitoted from tha trichloride *>.. bulky bladdsh-brown p^v/dor 
 which forms salts with acids. 
 
 The dioxide Bu0 2 is formed by roasting the disulphide, or by strongly igniting the 
 sulphate Bu28O 4 . 
 
 The protoxide is prepared by calcining the dichloride with carbonate of sodium in 
 a current of carbonic anhydride and dissolving out the soluble part of the product 
 by water. This oxide is of a dark grey colour and metallic lustre, and is not acted 
 upon by acids. 
 
 Three chlorides of ruthenium are known viz. Bud* BuCl* and BuCl 4 , 
 
 The most important is the trichloride, which may be obtained by dissolving the 
 hydrated sesquioxide in hydrochloric acid ; on evaporation there results a yellowish 
 crystalline mass of the salt which is soluble in alcohol. Not only does this chloride 
 form double salts with the chlorides of potassium and sodium, but also a number of 
 ammoniacal basic salts corresponding to those obtainable from platinic chloride. 
 
 Two sulphides of ruthenium are known, sesqnisnlphide BujS r and a disulphide 
 1 ti r The first of these is obtained by conducting sulphuretted hydrogen into the 
 
538 IRIDIUM. 
 
 blue solution of the protochloride. When the same gas is passed for a long time into 
 a solution of the trichloride, the disulphide is formed as a brown yellow precipitate. 
 
 Two alloys of ruthenium are well known ; one with zinc which crystallises in 
 regular hexagonal prisms which take fire when heated in the air and burn with 
 deflagration. 
 
 The alloy of tin and ruthenium RuSn 2 is obtained by heating ruthenium to redness 
 with about ten times its weight of tin, in a graphite crucible, and dissolving out the 
 excess of tin from the product with hydrochloric acid. The alloy is thus obtained in 
 fine cubic crystals, resembling those of melted bismuth. 
 
 SYMBOL Ir. ATOMIC WEIGHT 198. 
 
 History and Occurrence. Iridium was discovered simultaneously with 
 osmium by Smithson Tennant in 1804 in the black scales which remain undissolved 
 when platinum ore is extracted with nitro-hydrochloric acid. The same alloy, which 
 is known as iridosmine, occurs also in flat metallic grains in native platinum. 
 
 Characters. Iridium is a hard, white, brittle metal, which requires the heat of 
 the oxyhydrogen blowpipe or that of a strong voltaic current to melt it. After fusion 
 it has a density of 21 -15. When heated in a finely divided state in the air, it 
 absorbs oxygen, but is not oxidised when in the massive state. Alone it is not acted 
 upon bv acids or even by nitro-hydrochloric acid, but when alloyed with platinum 
 aqua regia readily dissolves it. 
 
 By fusion with nitre or caustic alkalies the metal is oxidised. By decomposing 
 a solution of the sulphate with alcohol, iridium may be obtained as a black powder, 
 possessing characters corresponding to those of platinum black. 
 
 Preparation. Iridium may be prepared most easily by reducing the native alloy 
 to powder, mixing it with common salt, and heating the mixture to redness in a glass 
 tube, through which a stream of moist chlorine gas is transmitted ; to the extreme 
 end of the tube a receiver containing ammonia is attached. In this way the respective 
 chlorides of osmium and iridium are formed, and the former of these being volatile 
 is carried over by the chlorine into the alkaline solution by which it is decomposed, 
 forming osmic acid and hydrochloric acid, which then combine with the ammonia. 
 The chloride of iridium remains behind in the tube, and is dissolved out together with 
 sodic chloride by water; the solution thus obtained is evaporated with sodium 
 carbonate to dryness, and the mixture then ignited. After this the mass is extracted 
 with water, dried, and the residue of ferric oxide and oxide of iridium, in combination 
 with soda, is reduced by hydrogen at a high temperature. By extracting the residue 
 with water and strong hydrochloric acid the iron and alkali are removed, and there 
 remains metallic iridium. Or the metal may be prepared by precipitating ammonic 
 iridic chloride from the solution of mixed chlorides above described, and igniting the 
 precipitate. But the metal so obtained is liable to be contaminated with ruthenium. 
 
 Compounds. Iridium forms three series of compounds related to the three 
 oxides as follows. Monoxide or hypoiridious oxide, IrO ; iridious or sesquioxide, Ir 3 ; 
 and iridic oxide, Ir0 2 . There is a fourth or periridic oxide, Ir0 3 , which is not known 
 in the free stats. 
 
 The monoxide (IrO) is formed when an alkaline hypochloriridite is decomposed by 
 caustic alkali in an atmosphere of carbonic anhydride. It quickly oxidises in the air. 
 
 The sesquioxide (Ir 2 3 ) is formed when the metal is oxidised by fusion with nitre 
 or caustic alkali, or when it is heated in a pulverulent state in the air. 
 
 According to Glaus, a hydrate of the dioxide (Ir0 2 , 2H 2 0) is formed on boiling a 
 solution of iridic trichloride with caustic potash, when the substance is precipitated 
 as an indigo-coloured powder. On ignition it becomes anhydrous, 
 
 There are three chlorides of iridium of the formulae IrCl 2 , IrCl 3 , and IrCl 4 ; all 
 these form double salts with the chlorides of the alkali metals. 
 
 On heating the double salt of trichloride of iridium (3KC1, IrCl s . 3H 2 0) with 
 hydric potassic sulphite in solution, until the green colour passes into red, and 
 
OSMIUM. 539 
 
 evaporating the solution, the dichloride of iridium is obtained as a double salt in red 
 crystals 4KC1. Ir01 2 , 2K 2 S0 3 , IrS0 3 , 12H 2 0. 
 
 The trichloride is the most stable of the three chlorides, and is obtained as a black 
 sublimate on heating the metal in a current of chlorine. It is known to form a com- 
 pound of the composition 2IrCl 3 . 3Hg 2 Cl 2 . 
 
 The tetrachloride (IrCl 4 ) is prepared by dissolving the metal or any of its oxides 
 in aqua regia. 
 
 An iridic tribromide (IrBr 3 , 4H20) may be obtained in olive brown crystals, and 
 three iodides are known, viz., IrI 2 , IrI 3 , and IrI 4 . 
 
 Corresponding to the three principal oxides there are three sulphides which may 
 be obtained by decomposing the respective chlorides with sulphuretted hydrogen. 
 
 The alloys of iridium are very interesting, and a number of them have been studied, 
 such as those with gold, copper, lead, mercury, osmium, platinum, silver, tin, and 
 zinc. 
 
 The native alloy of osmium and iridium is used, by reason of its hardness, to point 
 metallic pens. 
 
 OSMIUM, 
 
 SYMBOL Os. ATOMIC WEIGHT 199-2. 
 
 History and Occurrence. Osmium, as stated elsewhere, was discovered in 
 the ore of platinum in 1803 by Tennant. Its most plentiful source is the native 
 osmiridium. 
 
 Preparation. The metal may be extracted from osmiridium or platinum 
 residues, resulting after extraction of the ore by aqua regia, by several methods which 
 have undergone simplification at the hands of Fremy. Perhaps the simplest process 
 consists in preparing the tetroxide of osmium as described under ' Iridium,' and treating 
 this with hydrochloric acid and mercury at 140 0., in a closed vessel, when the 
 following reaction results : 
 
 Os0 4 + 8Hg + 8HC1 = Os + 4Hg 2 01 2 + 4H 2 0. 
 
 On evaporation the water and excess of acid are expelled, and by distilling the 
 residue in a retort the mercury and calomel pass over, leaving pure metallic osmium 
 in a pulverulent form behind. 
 
 The metal may also be obtained by igniting ammonium chloro-osmite with sal- 
 ammoniac. 
 
 Characters. The properties of osmium differ somewhat according to the mode of 
 preparation. When in the jpulverulent state it is black and only acquires a metallic 
 lustre by burnishing. When exposed to a damp atmosphere it emits an odour of the 
 tetroxide, and, when set on fire in the air, it burns away entirely into the same volatile 
 body. Osmium which has been once heated to the melting point of rhodium will not 
 burn in the air, until heated above the melting point of zinc. Deville and Debray 
 obtained the metal in a compact state by reduction of the sulphide with gas coke in a 
 closed retort at about the melting point of nickel. Obtained thus it is brittle, and 
 has a blue cast of colour like that of metallic zinc. 
 
 In the pulverulent state the metal has a density of 10, but after heating to the 
 melting point of palladium its density becomes 21 '4. Osmium is the least fusible of 
 all metals, and possesses characters approaching those possessed by arsenic and 
 antimony. 
 
 Combinations. Five oxides of osmium are known of the formulae here given : 
 OsO, Os 2 3 , Os0 2 , Os0 3 , and Os0 4 . 
 
 The protoxide is obtained by heating hypo-osmious sulphite in carbonic anhydride; 
 it is a dark greenish powder almost insoluble in acids ; its hydrate is bluish-black 
 and dissolves in hydrochloric acid forming an indigo-coloured solution of the di- 
 chloride OsCl 2 . 
 
 The sesqui oxide (Os 2 3 ) is unknown in the free state, although it is said to be 
 obtained by heating either of the double salts of the trichloride with sodium carbonate 
 in a stream of carbonic anhydride. 
 
 The dioxide is a black powder obtained by heating a mixture of potassic osmio- 
 
540 OSMIUM. 
 
 chloride with sodic carbonate in carbonic anhydride. As a hydrate (Os0 2 , 2H 2 0)it is 
 formed on precipitating potassic osmiochloride with potash. 
 
 The trioxide is only known in combination with alkalies as osmites ; the potassium 
 salt is K 2 O.Os0 3 .2H 2 and it> a rose-coloured crystalline powder. This salt is readily 
 obtained on heating a solution of the tetroxide in potash with a little alcohol. On 
 digesting the salt so obtained in ammonic chloride, a yellow salt is obtained of the 
 composition (2NH 4 C1, OsO^ N 2 H 4 ), and this on ignition in hydrogen gives pure 
 osmium. 
 
 The tetroxide forms colourless acicular transparent crystals which melt below 
 100 and boil at a temperature somewhat higher. The vapour of this oxide is 
 irritating and excessively poisonous. It is a powerful oxidising agent, and gives a 
 characteristic blue precipitate when its solutions are mixed with tincture of galls. It 
 does not form salts. 
 
 Three chlorides of osmium are known, corresponding to those of iridium and 
 ruthenium. Osmious chloride (OsCl 2 ) is the product of the action of chlorine gas upon 
 the metal ; it dissolves in water to a violet colour, and gives double salts of a green 
 colour. 
 
 The tetrachloride (OsCl 4 ^ is produced in the same way as the dichloride, using 
 excess of chlorine ; it is a volatile, red, crystalline, fusible powder which is soluble in 
 water, and is then decomposed into tetroxide and hydrochloric acid, a decomposition 
 which is also accompanied by the deposition of some dioxide. 
 
 A double salt of the formula 2KC1. OsCL is known, and also one represented by 
 (2AgCl. OsCl 4 ). 
 
 The trichloride (OsCl s ) and the hexachloride (OsCl 6 ) are only known in combination 
 as double salts. 
 
 Osmium gives with ammonium salts a number of interesting combinations ; thus 
 when the tetroxide is heated with much ammonia, there is obtained N 2 H 6 Os0 2 H 2 0, 
 and if potash be present we get K 2 N 2 Os 2 5 , or potassic osmiamate as it is called. This 
 is a yellow crystalline body of a detonating character. 
 
 A tetrasulphide of osmium appears to be the best known sulphide ; there are said 
 to be others corresponding to the various oxides, and obtained by decomposition of the 
 chlorides with sulphuretted hydrogen. 
 
 Osmium also combines with phosphorus, etc. 
 
 The native alloy, osmium-iridium or irodosmine, gave by analysis the following 
 percentages (Berzelius) : iridium 4677 ; osmium 49*35 ; iron 0'74 ; rhodium 3-15. 
 
 
IRON. 
 
 SYMBOL Fe. ATOMIC WEIGHT 56. 
 
 History. This metal was known at a very remote period, and many of the 
 references to it in ancient writings are of a mythical character. The Greek and 
 Eoman names xd\vty and chalybs are considered to have been derived from the 
 name of a tribe of people that lived on the shores of the Black Sea. and were especially 
 skilled in the art of working iron, or that form of the metal which is now called 
 steel. 
 
 Occurrence. Iron occurs naturally to some extent in the metallic state, consti- 
 tuting the chief mass of some meteorites, while in others it is disseminated throughout 
 an earthy matrix. Metallic iron also occurs associated with platinum in some ferru- 
 ginous deposits, and disseminated through the mass of basaltic rocks. Meteoric iron 
 always contains nickel, sometimes also cobalt, copper, chromium, and tin, as shown 
 by the following tabular statement of analyses : 
 
 
 Berzelius 
 
 Trehole 
 
 Jack- 
 
 Morren 
 
 Sillman 
 
 Stro- 
 
 and 
 
 
 
 
 son 
 
 
 Hunt 
 
 meyer 
 
 Iron .... 
 
 9378 
 
 88-04 
 
 89-78 
 
 85-61 
 
 66-56 
 
 83-57 
 
 92-58 
 
 81-8 
 
 Nickel 
 
 3-81 
 
 1073 
 
 8-89 
 
 12-27 
 
 24-71 
 
 12-67 
 
 5-71 
 
 11-9 
 
 Cobalt . 
 
 21 
 
 46 
 
 67 
 
 89 
 
 
 
 
 
 
 1-0 
 
 Copper 
 
 
 
 07 
 
 
 
 
 
 
 
 
 
 
 Manganese 
 
 
 
 13 
 
 
 
 
 
 3-24 
 
 
 
 
 
 2 
 
 Chromium >;.! , 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Tin . . . . 
 
 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Magnesium 
 
 
 
 05 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Arsenic 
 
 
 
 
 
 
 
 
 
 
 
 
 
 trace 
 
 
 
 Sulphur . . 
 
 
 
 trace 
 
 
 
 
 
 4-0 
 
 
 
 
 
 5-1 
 
 Ferrous sulphide 
 
 
 
 
 
 
 
 
 
 
 
 2-30 
 
 
 
 
 
 Carbon . . 
 
 
 
 04 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Chlorine . . . 
 
 
 
 
 
 
 
 
 
 1-48 
 
 91 
 
 
 
 
 
 Insoluble . . . 
 
 2-20 
 
 48 
 
 
 
 
 
 
 
 
 
 1-40 
 
 
 
 
 lOO'O 
 
 lOO'O 
 
 99-34 
 
 98-77 
 
 99-99 
 
 99-45 
 
 99-69 
 
 100-0 
 
 Iron occurs, however, far more frequently and in much greater abundance in various 
 states of combination with oxygen as magnetite, hematite, or specular iron. 
 
 Compounds of ferrous oxide or ferric oxide with various acid oxides also occur 
 abundantly : the carbonate asspathiciron; the phosphates asvivianite, dufre- 
 nite, and in several other minerals; the arsenates as shorodite and cube ore, etc. ; 
 the silicates as fayalite, and in a great number of other minerals; the titanate as 
 iserine, ilmenite, and the various kinds of titaniferous iron ore; the chromate as 
 chrome- iron ore ; the tantalate as columbite; the tungstate as wolfram. Iron 
 also occurs in various states of combination with sulphur as pyrites, and with 
 arsenic as arsenosiderite. Iron in various states of combination is likewise very 
 widely distributed, and there are few natural bodies in which this metal is not present 
 to some extent. It exists in the ashes of most plants, and appears to be an essential 
 constituent of the blood pf animals. 
 
 Characters. Iron is a moderately soft metal, resembling silver in whiteness ; 
 it is capable of acquiring a very high lustre when polished, and is extremely tenacious. 
 The specific gravity varies from 7'6 to 8-14, according to the mode in which the 
 metal has been worked. The crystalline form of iron is either the cube, octahedron, 
 or some other form belonging to the regular system. 
 
542 IRON. 
 
 Though iron is the most abundant of the heavy metals, and is most largely 
 employed in the arts, it is very rarely met with in a state of absolute chemical purity. 
 Owing to the fact that it readily combines with or retains in a state of admixture 
 various other elementary substances, such as carbon, oxygen, phosphorus, sulphur, 
 silicon, etc., the metallic iron ordinarily used contains some one or more of those 
 substances in varying amount, and the physical characters of the metal are very 
 materially influenced by the nature as well as the proportion pf the admixtures it 
 contains. It is to this circumstance that the differences between the three forms of iron 
 known as malleable iron, pig iron, and steel, are referrible; and it appears 
 to be chiefly the amount of carbon in iron which determines, those remarkable differ- 
 ences in virtue of which iron has such a wide range of applicability to a great variety 
 of purposes. 
 
 The distinction between the three kinds of iron is not by any means absolute, but 
 is marked rather by the extent to which particular characters are developed in asso- 
 ciation with others. Iron containing a large proportion of carbon melts at a tempera- 
 ture comparatively much lower than that required for melting the pure metal ; but 
 at the same time its malleability is so much inferior to that of iron containing only a 
 very small proportion of carbon, that it cannot be wrought under the hammer. Iron 
 which contains but little carbon, and is malleable, has also a much higher degree of 
 toughness or tenacity than pig iron, which on the other hand, is very much harder. 
 On account of these differences iron which approaches nearest to a state of purity 
 is termed malleable iron, while that which is highly carburetted and capable of 
 being wrought by smelting is termed cast iron. Intermediate between these two 
 kinds of iron is steel, which combines some of the peculiarities of malleable iron and 
 cast iron, since it can be melted as well as forged and rendered hard or soft at will ; 
 or, as it is technically termed, tempered, by cooling it suddenly or gradually. 
 
 Leaving out of consideration for the present all other substances met with in iron 
 except carbon, it appears that the greater or less approximation to the character of 
 pure iron is so uniformly accompanied by very slight differences in the amount of 
 carbon in the metal, that these two circumstances must be regarded as having a very 
 intimate causal connection. 
 
 Compounds. Iron forms two classes of compounds namely, the ferrous com- 
 binations in which it behaves as a dyad, as in ferrous oxide, or the corresponding 
 sulphate and chloride ; and the ferric compounds in which iron is trivalent for ex- 
 ample, ferric chloride (Fe-jClg). 
 
 The vapour density of this last named substance, as determined by Deville, would 
 seem to indicate that in ferric chloride the metal is tetratomic ; the compound would 
 therefore have a rational formula as follows : 
 
 Cl 8 Fe FeCl s . 
 
 The three oxides have the formulae FeO Fe 2 3 and Fe 3 4 , and the sulphides are 
 represented by Fe 2 S, FeS, FeS 2 F 2 S 3 . Iron forms apparently two other sulphides with 
 the formulae Fe 7 S 8 and Fe 3 S 4 . The former of these, both of which are termed mag- 
 netic sulphides, is often formed together with ferrous sulphide when sulphur and iron 
 are heated together ; it is soluble in hydrochloric acid. 
 
 There are two chlorides (FeCl 2 and Fe 2 Cl 6 ) and corresponding bromides, iodides, 
 apd fluorides ; two sulphates, nitrates, and phosphates. Ferrous carbonate (FeC0 3 ) is 
 a well-defined body, and beyond these there are a number of compounds of less import- 
 ance. 
 
 Ferrous oxalate, 2FeC 2 4 . 3H 2 0, is occasionally met with in the native state, 
 as humboldite or iron-resin, which is formed in the brown-coal strata. It may 
 be prepared by double decomposition or by exposing ferric oxalate in presence of free 
 oxalic acid to sunlight; carbonic anhydride is then evolved, and ferrous oxalate is 
 precipitated in a crystalline form with two molecules of water. 
 
 Ferric oxalate, which is a yellow salt, nearly insoluble in water, may also 
 be prepared by double decomposition. 
 
 Ferrous hydric phosphate, Fe"HP0 3 , is precipitated as a white powder, 
 when a solution of trisodic phosphate is added to one of a ferrous salt. 
 
 The native blue phosphate or vivianite has been already spoken of. 
 
 A ferric phosphate, Fe 2 "P 2 8 4H 2 0, is obtained as a white powder by precipi- 
 tating ferric chloride by an alkaline orthophosphate. 
 
 Several silicates of iron exist, notably ferrous orthosilicate 2FeO. Si0 2 , which con- 
 stitutes for the most part ' finery slag.' 
 
 Ferrous nitrate, Fe2N0 3 , results from the action of cold dilute nitric acid 
 upon the protosulphide of iron. When its aqueous solution is evaporated in a 
 vacuum, it forms pale green crystals Fe2N0 3 ,6H 2 0, which are liable to change. 
 
 Ferric nitrate, Fe3N0 3 , is produced by the action of tolerably strong nitric 
 
FERROUS OXIDE. 543 
 
 acid upon the metal ; it is of a deep red colour, and its solution is used as a mordant 
 in dyeing. 
 
 Several basic nitrates also exist. 
 
 Di ferrous phosphide, Fe 2 P, is produced when the phosphate is reduced with 
 charcoal. 
 
 A silicide of the formula Fe 2 Si also is known, and it is probable that the compound 
 FeSi exists. 
 
 A nitride of the composition N 2 Fe 4 was obtained by Stahlschmidt. 
 
 The alloys of iron are not of great importance, although such combinations with 
 most of the metals are known. When iron contains more than traces of silver, 
 copper, arsenic, or antimony, it is rendered what is termed red short, which 
 quality is considered defective. 
 
 Galvanised iron is used largely for roofing, etc., and is prepared by immersing 
 clean sheet iron in a bath of molten zinc ; if the iron be first coated with a thin 
 film of tin by means of voltaic deposition, it furnishes a superior kind of galvanised 
 iron. The zinc protects the iron from oxidation. 
 
 Deville and Caron obtained an alloy of the formula Fe 2 Sn, and another of the 
 composition FeSn is also known. 
 
 Among many other alloys of iron, one of the formula Fe 4 K has been also de- 
 scribed. 
 
 FERROUS OXIDE. 
 
 FORMULA FeO. MOLECULAR WEIGHT 72. 
 
 This oxide constitutes the base of the ferrous salts, and is isomorphous with mag- 
 nesia, etc. 
 
 It is obtained as a hydrate when a ferrous salt is precipitated by an alkali ; in 
 this form it is nearly white, but on boiling the mixture water is given off, and the 
 precipitate turns black. Ferrous oxide, from its affinity for oxygen, is an unstable 
 body ; on exposure it turns reddish-brown from formation of ferric oxide Fe 2 3 . This 
 tendency to oxidation is also exhibited by all ferrous solutions, which pass on expo- 
 sure to the air into a higher state of oxidation a change which is often accompanied 
 by the formation of insoluble basic salts. Ferrous acetate seems to admit most, 
 readily of atmospheric oxidation. Ferric acetate is ^f a blood-red colour. 
 
 FERRIC OXIDE. 
 
 MOLECULAR WEIGHT 160. 
 
 History. The compounds of iron with oxygen, though known and used at a very 
 remote period, were not fully distinguished from each other as regards their chemical 
 composition until the end of the eighteenth century. Iron rust was used by ^Esculapius 
 medicinally, and forge scale, er/cwpta tnS^pou, was described by Dioscorides as a similar 
 but less effective remedy. Bloodstone, or alfji.ariT-r)s, was also mentioned by this 
 author, and it was regarded by Pliny as a variety of sideritis, or magnetic iron ore. 
 In Geber's works red oxide of iron is termed crocus martis, while Basil Valentin gave 
 it the name of colcothar, and in 1735 the black oxide was known by the name of 
 cethiops martis. Scheele was the first to indicate, in 1777, the fact that in these sub- 
 stances iron was combined with oxygen in different proportions ; this view was 
 further developed in 1782 by Lavoisier, and finally brought to its present position by 
 Berzelius. 
 
 Occurrence. Ferric oxide occurs very abundantly in a variety of forms; it. 
 occurs beautifully crystallised as specular iron ore in Elba and other places. As 
 red hematite or bloodstone it occurs incompact and amorphous masses, and 
 constitutes an important iron ore. There are several native hydrates of this compound 
 known as brown hematite, gothite, and bog iron ore. 
 
 Characters. Ferric oxide is not so powerful a base as ferrous oxide ; it may 
 be prepared by precipitation of a ferric salt in solution by an alkali, as a reddish- 
 brown bulky hydrate which loses its water on ignition. When in fine powder this 
 oxide has a fine red colour which renders it available for use as a pigment, and it is 
 prepared on a large scale for this purpose by calcination of ferrous sulphate. 
 
 The hydrated oxide is readily soluble in acids ; the anhydrous oxide is not so 
 readily dissolved, and the salts formed have a tendency to produce basic compounds. 
 A number of hydrates of this oxide are known. 
 
544 IRON. 
 
 Mixed with sawdust, hydrated ferric oxide is used in Hill's process for separa- 
 tion of sulphuretted hydrogen from coal gas. There is thus produced ferrous sul- 
 phide and free sulphur, as shown by the following equation : 
 
 Fe 2 3 + 3H 2 S = 2FeS + S + 3H 2 0, 
 
 and when the product is exposed to the air (or ' rarefied ') ferric oxide is reproduced, 
 and more sulphur therefore set free ; in this way the oxide may be constantly renewed. 
 Ferric oxide plays towards some bases the part of a feeble acid. Thus Pelouze has 
 described a compound he obtained of the formula 
 
 4CaO,Fe 2 3 . 
 
 FERROSO-FERRIC or MAGNETIC OXIDE. 
 
 FORMULA Fe 3 4 . MOLECULAR WEIGHT 232. 
 
 This compound, known also as loadstone and black oxide, is supposed to acquire 
 its magnetic character from the inductive influence of the earth. In its various 
 native forms occurring in beds and constituting even mountains, sometimes found in 
 Sweden, America, etc., it constitutes one of the most valuable ores of iron. 
 
 It may be formed artificially by mixing due proportions of ferrous and ferric salts, 
 and adding to the mixed solution an excess of alkali ; on boiling the two hydrates 
 combine and form minute crystals of magnetic oxide. 
 
 If recently precipitated hydrated ferric oxide be boiled with water and iron turn- 
 ings in excess added, then hydrogen is evolved and magnetic oxide is produced. It 
 is also produced when metallic iron is exposed at an elevated temperature to the 
 presence of steam ; in this way at 500F. or 1000F. the iron becomes coated with 
 magnetic oxide as a continuous compact layer on the surface not liable to change by 
 atmospheric influences or even by dilute acids ; and Professor Barff has recently pro- 
 posed the application of this process to iron goods, such as rails, cooking utensils, 
 lamp-posts, gas-pipes, etc., in order to avoid the rusting to which such articles are 
 ordinarily subject when exposed to a damp atmosphere. 
 
 Magnetic oxide is soluble in acids ; it does not form specific salts, but yields a 
 mixture of ferrous and ferric salts, thus 
 
 Fe 8 4 + 4H 2 S0 4 = FeS0 4 + Fe 2 3S0 4 + 4H 2 0. 
 
 FERRIC ACID. 
 
 FORMULA H 2 Fe0 4 . MOLECULAR WEIGHT 122. 
 
 Although this compound has not been prepared in the free state, its barium, 
 strontium, and calcium salts may be obtained by mixing solutions of the earths 
 with potassium ferrate, which is obtained as follows : 
 
 A mixture of ferric oxide with four times its weight of nitre, is heated to redness 
 during an hour in a covered crucible, and the resulting brown deliquescent mass is 
 treated with ice-cold water which gives a violet-coloured solution from which the 
 potassic ferrate may be precipitated by a strong alkali. 
 
 It may also be made by suspending recently precipitated hydrated ferric oxide 
 in a strong solution of potash, and submitting the mixture to a current of chlorine 
 gas ; it is then deposited as an amorphous black powder which can be drained upon 
 a tile. 
 
 Pota&sic fen-ate is an unstable salt readily decomposed by organic matter, or by 
 exposure to a temperature of 100C ; acids resolve it into free oxygen and ferric 
 oxide. 
 
 FERROUS CHLORIDE. 
 
 FORM OLA FeCl 2 . MOLECULAR WEIGHT 127. 
 
 This salt may be obtained in the anhydrous state by passing hydrochloric acid 
 gas over red-hob 'iron, hydrogen being evolved Fe + 2HC1 = FeCl 2 + H 2 ; the white 
 salt which forms sublimes at a temperature of melting glass. 
 
 Ferrous chloride may also be obtained by dissolving iron in hydrochloric acid ; 
 the concentrated solution yields crystals of the composition FeCl 2 , 4H 2 0, and of a 
 green colour. 
 
 Ferrous chloride is also formed when ferric chloride is heated in a current of 
 
FERROUS SULPHIDE. 545 
 
 hydrogen. It is a deliquescent salt, soluble in water and alcohol, and liable to 
 undergo atmospheric oxidation. When heated in the open air, it loses chlorine and 
 forms ferric oxide. 
 
 Ferrous chloride forms a double salt with ammonic chloride. 
 
 FERRIC CHLORIDE. 
 
 FORMULA Fe 2 Cl 6 . MOLECULAR WEIGHT 325. 
 
 This salt may be prepared by dissolving ferric oxide in hydrochloric acid ; on 
 evaporation of the solution to a low bulk, red hydrated crystals Fe 2 Cl 6 , 6H 2 are 
 deposited, which are exceedingly soluble in water and alcohol. It may be prepared 
 in the dry state by passing chlorine over iron heated to redness. The salt sublimes 
 in lustrous scales; it also crystallises with 10H 2 and 12H 2 0. With ammonic 
 chloride it furnishes a double salt which crystallises in cubes, and with other chlorides 
 other double salts are obtained. 
 
 FERROUS IODIDE. 
 
 FORMULA FeI 2 . MOLECULAR WEIGHT 310. 
 
 This preparation, which is used in medicine, is made by digesting one part of iron 
 wire in water containing four parts by weight of iodine. The iodide thus produced 
 gives to the solution a pale green colour, and on evaporation in vacuo crystals of the 
 composition FeI 2 4H 2 are obtained. The salt may be rendered anhydrous by heating, 
 and is then fusible. By atmospheric oxidation it is resolved into iodine and hydrated 
 ferric oxy iodide. 
 
 FERROUS SULPHIDE. 
 
 FORMULA FeS. MOLECULAR WEIGHT 88. 
 
 Occurrence. This substance does not occur naturally in a separate state, except 
 in some meteorites; but it occurs combined with ferric sulphide, as pyrrhotin or 
 magnetic pyrites, 5FeS, Fe 2 S 3 ; with nickel sulphide, NiS2FeS; with antimonous 
 sulphide in several proportions, as berthierite and haidingerite; with zinc 
 sulphide in some kinds of blende and in some kinds of fahl-ore. Ferrous sulphide 
 is a constituent of the different kinds of regulus obtained in smelting ores of lead and 
 copper. 
 
 Characters. Ferrous sulphide, prepared in the compact state, by melting to- 
 gether iron and sulphur, is a heavy substance of a yellowish colour and metallic lustre. 
 As obtained by mixing a solution of a ferrous salt with alkaline sulphide, it is black, 
 amorphous, pulverulent and is probably hydrated, sometimes presenting a distinct 
 green tinge when very finely divided. Ferrous sulphide melts at a full red heat and 
 is not decomposed when heated to whiteness out of contact, with air ; but, when heated 
 moderately in contact with atmospheric air, it is gradually oxidised and converted 
 into ferrous sulphate. In the compact state it is but little altered by exposure to the 
 air at the ordinary temperature ; but, as obtained by precipitation from the solution of 
 ferrous salts by alkaline sulphides, it oxidises rapidly when exposed to the air, arid 
 is converted into ferrous sulphate which by further oxidation is converted into basic 
 ferric sulphate. 
 
 Ferrous sulphide is readily decomposed by acids, generally with evolution of sul- 
 phuretted hydrogen and formation of a ferrous salt; nitric acid converts part of the 
 sulphur into sulphuric acid with evolution of nitrous vapours, and part of the sulphur 
 is precipitated. Heated to redness in contact with water vapour it is decomposed ; 
 hydrogen and sulphuretted hydrogen are given off, and the iron remains in the state 
 of ferroso-ferric oxide, which retains a portion of the sulphur. Ferrous sulphide is 
 not affected by chlorine at the ordinary temperature, but when heated in contact with 
 the gas it is converted into sulphur chloride and ferric chloride. When melted with 
 alkalies, alkaline carbonates, or alkaline earths, it is partly decomposed and some 
 alkaline or earthy sulphide is formed ; melted with a large proportion of lead oxide 
 the whole of the sulphur is oxidised to sulphurous oxide, metallic lead is separated 
 and ferrous oxide formed, which remains mixed with the undecomposed lead oxide. 
 
 The black mud deposited at the bottom of drains, cesspools, ponds, etc., where 
 ferruginous substances are in contact with decomposing organic materials, contains 
 
546 IRON. 
 
 ferrous sulphide, and its formation is probably due in part to the deoxidation of 
 sulphates by the putrefying substances. On exposure to the atmosphere this mud 
 often evolves sulphuretted hydrogen. 
 
 Preparation. Ferrous sulphide may be prepared by melting together sulphur 
 and some excess of iron filings, or by holding a stick of sulphur against a red-hot bar 
 of iron. "When a mixture of iron filings and sulphur is moistened with water, and 
 warmed, combination takes place suddenly with considerable evolution of heat. 
 Ferrous sulphide is also produced when dry ferrous sulphate is ignit ed with charcoal 
 out of contact with air, when ferrous sulphate is in contact with decomposing organic 
 substances, when magnetic pyrites, ferric sulphide, or iron pyrites are heated to 
 bright redness in contact with hydrogen, or with metallic iron out of contact with air, 
 and by precipitation from ferrous salts by alkaline sulphides. 
 
 FERRIC SULPHIDE. 
 
 FORMULA Fe 2 S s . MOLECULAR WEIGHT 208. 
 
 This substance is probably a constituent of magnetic pyrites, copper pyrites and 
 some other minerals, but it does not otherwise occur naturally. It may be prepared 
 by heating iron or ferric oxide with excess of sulphur ; when ferric oxide is used, the 
 operation requires to be repeated several times in order to decompose the whole of 
 the ferric oxide. 
 
 Ferric sulphide is also formed by the action of sulphuretted hydrogen upon ferric 
 axide at 100, or upon ferric hydrate at the ordinary temperature, and by dropping 
 o solution of neutral ferric sulphate into excess of ammonium sulphydrate. When 
 dried out of contact with air, it is a yellowish-grey substance; it is not magnetic when 
 moist, and oxidises very rapidly on exposure ; acids decompose it with formation of the 
 corresponding ferrous salt, disengaging sulphuretted hydrogen and precipitating 
 sulphur. When heated to redness in a close vessel sulphur is given off, and the 
 residue consists of magnetic pyrites. Heated in contact with atmospheric air it is 
 oxidised and converted into ferric oxide, while the sulphur is chiefly given off as 
 sulphurous oxide. When very gradually heated some ferrous sulphide is formed, 
 the residue having a composition represented by the formula 5FeS, Fe 2 S 3 . Ferric 
 sulphide combines with alkaline sulphides, forming substances which are represented 
 by the formulae K 2 S, Fe 2 S 3 and Na 2 S, Fe 2 S 8 ; they may be prepared by melting a mix- 
 ture of iron filings, sulphur and alkaline carbonate, and afterwards extracting the mass 
 with water. 
 
 FERROSO-FERRXC SULPHIDE. 
 
 FORMULA FeS, Fe 2 S 3 . MOLECULAR WEIGHT 296. 
 
 This substance occurs naturally as one of the varieties of pyrrhotin or magnetic 
 pyrites, or hepatic pyrites, which more frequently however has a composition corre- 
 
 rding with the formula Fe 7 S 8 = 5FeS. Fe^. It is this latter substance which is 
 ined by heating the disulphide or ferric sulphide out of contact with air, and by 
 heating iron filings with a slight excess of sulphur till the mass melts. Magnetic 
 pyrites when crystalline presents a form belonging to the hexagonal system, but it 
 is frequently compact, granular, or amorphous. The colour varies from bronze yellow 
 to copper red ; as prepared artificially it has a brownish-yellow colour. The specific 
 gravity varies from 4*51 to 4'64. It is attracted by the magnet. When heated in 
 a close vessel it is not altered ; but in contact with atmospheric air it is oxidised, gives 
 off sulphurous oxide, and is converted into ferric oxide. Heated in contact with 
 hydrogen it yields sulphuretted hydrogen, and is converted into ferrous sulphide. 
 It is dissolved by dilute acids with separation of sulphur, and sulphuretted hydrogen 
 is given off. 
 
 IRON 1 BISULPHIDE. 
 
 History. The various kinds of pyrites occurring naturally were often confounded 
 together by the ancients ; and, even so late as the time of Agricola, copper pyrites 
 and iron pyrites were regarded as being merely varieties of the same mineral. 
 
 Occurrence. Iron disulphide occurs very abundantly as iron pyrites, of wiiich 
 
IRON PYRITES. 
 
 547 
 
 there are two distinct kinds differing in colour and crystalline form. Mundic or 
 yellow iron pyrites crystallises in cubes or some other form belonging to the regular 
 system ; it also occurs in compact granular or fibrous masses ; it is opaque, has a 
 metallic lustre and a bronze yellow colour : the specific gravity varies from 4'98 
 to 5-1. 
 
 Marcasite or white iron pyrites crystallises in rhombic prisms, but occurs also 
 in compact or granular masses ; it has a pale yellowish grey colour and metallic lustre : 
 the specific gravity varies from 4'65 to 4-85. 
 
 The following table gives the composition of several kinds of iron pyrites from 
 different localities : 
 
 
 
 Pattinson 
 
 
 Clap- 
 ham 
 
 
 FeS 2 
 
 Spain 
 
 Bel- 
 gium 
 
 West- 
 phalia 
 
 Norway 
 
 Ireland 
 
 Coal- 
 brasses 
 
 Wales 
 
 Corn- 
 wall 
 
 Iron . 
 Sulphur . 
 
 46-63 
 53-33 
 
 38-70 
 44-60 
 
 41-41 
 49-30 
 
 39-68 
 45-01 
 
 38-22 
 45-60 
 
 39-22 
 45-50 
 
 40-52 
 44-20 
 
 31-44 
 38-10 
 
 1 49-72 
 
 32-20 
 34-34 
 
 Copper 
 
 
 
 3-80 
 
 5-81 
 
 
 
 
 
 1-80 
 
 0-90 
 
 trace 
 
 
 
 0-80 
 
 Lead. 
 
 
 
 0-58 
 
 0-66 
 
 0-37 
 
 0-64 
 
 
 
 1-50 
 
 
 
 
 
 0-40 
 
 Zinc . 
 
 
 
 0-30 
 
 trace 
 
 1-80 
 
 6-00 
 
 1-18 
 
 3-51 
 
 
 
 
 
 1-32 
 
 Thallium . 
 
 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 
 Ferrous oxide 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 11-01 
 
 
 
 Lime . . 
 
 
 
 0-14 
 
 0-14 
 
 0-25 
 
 0-11 
 
 2-10 
 
 0-24 
 
 4-96 
 
 7-95 
 
 
 
 Magnesia . 
 Carbonic acid . 
 
 
 
 trace 
 
 trace 
 
 
 
 
 
 o-oi 
 
 1-65 
 
 
 
 0-33 
 5-11 
 
 5-74 
 19-29 
 
 
 
 Arsenic 
 
 
 
 0-26 
 
 0-31 
 
 trace 
 
 trace 
 
 
 
 0-33 
 
 trace 
 
 
 
 0-91 
 
 Oxygen 
 
 
 
 0-23 
 
 0-25 
 
 0-42 
 
 0-37 
 
 0-45 
 
 0-25 
 
 0-31 
 
 
 
 
 
 Coaly substance . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 14-45 
 
 6-10 
 
 
 
 Gangue 
 
 
 
 11-10 
 
 2-00 
 
 12-23 
 
 8-70 
 
 9-08 
 
 8-80 
 
 1-40 
 
 . 
 
 29-0 
 
 Moisture . 
 
 
 
 0-17 
 
 0-05 
 
 0-25 
 
 0-36 
 
 0-17 
 
 0-90 
 
 0-90 
 
 
 
 
 
 
 
 99-88 
 
 99-93 
 
 100-01 
 
 100-00 
 
 101-16 
 
 101-15 
 
 97-00 
 
 99-81 
 
 98-97 
 
 Iron disulphide is decomposed when heated to redness in a close vessel, and by 
 giving off' three sevenths of its sulphur is converted into ferroso-ferric sulphide Fe 7 S 8 
 according to the equation : 
 
 7FeS 2 -6S = Fe 7 S 8 or 5FeS, Fe 2 S 3 . 
 
 "When heated in contact with atmospheric air it burns with the blue flame of sul- 
 phur, and is gradually converted into ferric oxide, while sulphurous oxide is given off. 
 
 Yellow iron pyrites in a crystalline or compact state does not undergo alteration 
 when exposed to the air, and the artificially prepared disulphide when compact is but 
 slowly oxidised in the presence of moisture ; but white iron pyrites is rapidly oxidised, 
 and when the yellow variety is in a finely divided condition it is also oxidised by 
 exposure to the air at ordinary temperatures with considerable evolution of heat. It 
 is in this way that coal is sometimes ignited by the oxidation of iron pyrites, finely 
 disseminated throughout its mass. The same alteration of iron pyrites by atmospheric 
 oxygen takes place in the aluminous shale from which alum is made, and the pyrites 
 is gradually converted into ferrous sulphate ; sulphuric acid is also formed, which acts 
 upon the aluminous silicate and forms aluminum sulphate (see p. 309). When 
 iron pyrites is ignited with carbonaceous substances carbon bisulphide is formed ; 
 when mixed with 10 per cent, of charcoal and exposed to the action of superheated 
 steam mixed with atmospheric air, the whole of the sulphur is said to be given off 
 partly as sulphuretted hydrogen and sulphurous oxide, and partly in the free state, 
 while the iron remains either in the metallic state or as ferric oxide. 
 
 FERROUS SULPHATE. 
 
 FORMULA FeS0 4 7H 2 0. MOLECULAR WEIGHT 278. 
 
 Characters. Ferrous sulphate forms pale bluish -green crystals, easily soluble 
 in water ; it has a ferruginous, astringent taste, and absorbs oxygen very radily, 
 both in the dry state and in solution, with formation of basic ferric sulphate. The 
 colour of commercial green vitriol is often dark green or greenish brown, owing to 
 the presence of ferric salt. 
 
 N N 2 
 
548 
 
 For many purposes it is more advantageous to employ the pure salt, especially 
 when other substances are to be reduced by it, as, for instance, in the reduction and 
 solution of indigo, in the indigo vat. For other purposes, as in the preparation of a 
 number of pigments, an impure salt containing basic ferric oxide is preferable. 
 
 On heating ferrous sulphate most of the water of crystallisation is expelled, but 
 one molecule remains even at 260C. At a higher temperature, it is decomposed as 
 follows: 2FeS0 4 = Fe 2 3 + S0 2 +S0 3 ; but this reaction generally takes place in the 
 presence of a little water, so that the distillate consists of a thick oily liquid, known 
 as ' Nordhausen acid.' This name was derived from Nordhausen, at which place the 
 sulphuric acid of commerce was made by the same method, long before the present 
 mode of manufacture was introduced. The ferric oxide which remains after the 
 distillation is sold under the name of colcothar, rouge or crocus of Mars, and 
 is largely used for glass polishing and as a pigment. 
 
 Ferrous sulphate forms double combinations with the sulphates of the alkali 
 metals, the potassium compound being FeS0 4 K 2 S0 4 6H 2 0, and has the power of 
 absorbing nitric oxide in common with other ferrous salts. 
 
 Preparation. For preparing pure ferrous sulphate, iron is dissolved in dilute 
 sulphuric acid, an excess of iron being necessary to prevent oxidation ; the solution is 
 then filtered quickly, rendered slightly acid by the addition of sulphuric acid, and 
 evaporated to crystallisation. The addition of sulphuric acid to the filtered solution, 
 before evaporating, is made for the purpose of dissolving up any basic ferric sulphate 
 that may be formed by the action of the air upon ferrous sulphate during the evapo- 
 ration. Crystals of ferrous sulphate, in order to keep well, must be perfectly dry, 
 but the drying must be effected without the application of heat, owing to the readi- 
 ness with which ferrous sulphate oxidises at a slightly elevated temperature. The 
 best method of drying the crystals is to place them on a filter and wash them with 
 alcohol. Ferrous sulphate thus prepared keeps much better than that prepared in 
 the ordinary way. The reason is that the ferric sulphate is very soluble in alcohol, 
 which dissolves out any trace of that salt ; crystals that are free from ferric sulphate 
 keep well, but the presence of a mere trace of ferric salt is sufficient to cause the 
 whole mass to pass into the higher oxidised state. 
 
 Ferrous sulphate may be prepared in a very pure and finely divided state by pre- 
 cipitating a concentrated aqueous solution of the salt with alcohol, filtering and 
 washing the precipitate with alcohol. Thus prepared the salt keeps well. 
 
 Ferrous sulphate is also prepared on a large scale by dissolving scrap iron with 
 warm sulphuric acid, specific gravity of 1-150, in vessels lined with lead, and evapo- 
 rating the neutral solution until a portion rapidly cooled deposits a sufficient quantity 
 of solid salt. When this point has been attained the evaporation is stopped, the liquid 
 left to settle, drawn off from the sediment into large tanks, where it is left for 24 
 hours to clear, and then the liquid is run into the crystallising vessels. In order 
 to facilitate the formation of good crystals, pieces of string or straws are supported 
 from pieces of wood laid across the crystallising vessels, so as to dip into the liquid, 
 and crystals are deposited upon them. Sometimes pieces of wood are used in the 
 place of string. When the crystallisation is complete, the mother liquor is drawn off, 
 the crystals removed, washed with a small quantity of water, and dried. The crystals 
 deposited on the sides of the vessels are separated from those formed in the midst of 
 the solution, which are purer. 
 
 Large quantities of green vitriol are prepared from iron pyrites, partly as a by- 
 product of the alum manufacture, and partly in the manufacture of sulphur -by dis- 
 tillation from iron pyrites ; it is ' also formed by partly roasting iron pyrites, and 
 then exposing it to the action of the atmosphere. 
 
 When the iron pyrites contained in alum slate is oxidised by roasting or weather- 
 ing, ferrous sulphate is formed, together with sulphuric acid and sometimes also 
 sulphurous acid. Upon lixiviating the oxidised mass, ferrous sulphate is dissolved, 
 and separated either before precipitation of the alum, or afterwards by crystallisation 
 from the mother liquor. 
 
 In some districts sulphur is obtained by distillation from iron pyrites, the disul- 
 phide of iron being converted into sulphur and ferrous sulphide, which remains in the 
 retort. 
 
 This residue, termed sulphur waste,, is taken out and laid upon shelves slightly 
 inclined, where it is allowed to remain for some time in contact with the air, and by 
 oxidation is converted into ferrous sulphate : 
 
 FeS + 40 = FeS0 4 . 
 
 Upon lixiviating the weathered mass at intervals, the ferrous sulphate dissolves 
 out and is obtained in the crystalline form by evaporating the solution. In somo 
 
WRITING INK. 549 
 
 districts the lixiviation is effected by rain, the solution thus formed being collected in 
 a large reservoir placed beneath the heap. 
 
 Ferrous sulphate is also obtained by the weathering and lixiviation of the pyrites 
 often found in large quantities in both brown coal and ordinary coal. 
 
 At Fahlun ferrous sulphate is obtained as a by-product of the extraction of 
 copper from mine water containing cupric sulphate, copper being precipitated in the 
 metallic state by means of iron, while ferrous sulphate is formed, and can be obtained 
 by evaporating the liquid. 
 
 Ferrous sulphate is also obtained as a by-product in the preparation of sulphu- 
 retted hydrogen, which is used in large quantities in some sulphuric acid works for 
 precipitating arsenic (vide page 137) : 
 
 FeS + H 2 S0 4 =. FeS0 4 . + H 2 S. 
 
 The solution thus obtained, containing ferrous sulphate, is evaporated to a specific 
 gravity of 1'357, and then left to crystallise. 
 
 Uses. One of the chief uses of ferrous sulphate is in dyeing textile tissues, 
 leather, wood, etc., for various black, grey, lilac, and brown shades. These colours, as 
 well as the preparation of ordinary writing-ink, are due to the formation of com- 
 pounds of the iron and salt with organic substances. Ferrous sulphate is also used 
 as a mordant for producing Prussian blue in calico printing. After conversion into 
 basic ferric salt, by oxidation, it is used in the preparation of Nordhausen sulphuric for 
 dissolving indigo. A weak aqueous solution of ferrous sulphate is said to be useful 
 in preventing the chlorosis of plants. Mixed with excremental matter, ferrous sulphate 
 converts the bad smelling volatile substances into non- volatile compounds, and thus 
 serves as a deodoriser ; besides which, it retains volatile ammonium compounds, such 
 as ammonium carbonate and ammonium sulphide, by converting them into ammonium 
 sulphate. 
 
 PREPARATION OF INK. By mixing a ferric salt with a solution containing 
 tannin, such as a decoction of nutgalls, oak bark, or similar substances, a black 
 liquid is produced, which results from the formation of ferric tannate, that is sus- 
 pended in the water in a very fine state of division, and is only gradually deposited 
 as a black precipitate. "When a solution of ferrous sulphate is used, the black colora- 
 tion is gradually produced in proportion as air is allowed to mix with the solution and 
 oxidise the ferrous sulphate. 
 
 When a liquid prepared as above is mixed with some mucilaginous substance such 
 as gum arabic, the ferric tannate remains for the greater part permanently' sus- 
 pended, and ordinary writing ink is a liquid of this kind. 
 
 Kecipes for preparing ink are numerous enough. The best ferruginous inks are 
 prepared with nutgalls; the following recipe may serve as an illustration : 
 
 Broken nutgalls 2 parts by weight. 
 
 Ferrous sulphate 1 part 
 
 Logwood chips . . 0'15,, 
 
 Gum arabic . . . ' . . . , . 1-2 
 
 Kiver water . ... . . . 22 parts 
 
 Oil of lavender ....... a few drops. 
 
 The galls and logwood chips are macerated for 24 or 36 hours in 10 or 51 
 parts of water, and then boiled for 2 hours, water being added in proportion as it 
 evaporates ; the decoction is then strained through a cloth and mixed with the gum 
 arabic and ferrous sulphate, each previously dissolved in 2 or 3 litres of water. The 
 mixture is then exposed in shallow vessels for 2 or 3 days to the action of the atmo- 
 sphere, with frequent stirring, so as to oxidise the ferrous salt as completely as pos- 
 sible ; lastly, the oil of lavender is added, and the ink preserved for use in well-closed 
 bottles. 
 
 Ink is generally pale at first, and darkens upon drying on the paper in proportion 
 as ferric salt is formed. When a ferric salt is employed in the preparation, the .ink 
 does not flow readily from the pen. Ink of this kind when dry is insoluble in water, 
 but easily soluble in dilute hydrochloric or sulphuric acid. Chlorine at once destroys 
 its colour. 
 
 A still better ink is said to be obtained as follows : 4 parts by weight of nut- 
 galls are covered with 22 parts by weight of water, and allowed to remain 2 days 
 under frequent stirring ; the nutgalls are then pressed, and the liquid exposed in 
 summer for two months to the action of the atmosphere. To the mass, which is then 
 covered with mould, is added 2 parts of ferrous sulphate and 1 part of gum arable, 
 both in a state of solution, so that the entire quantity of ink amounts to 22 parts. 
 Ink thus prepared contains ferrous gallotannate, which is black, but does not deposit ; 
 another excellent feature of this ink is that it does not become mouldy. 
 
550 IRON. 
 
 A very cheap kind of ink, which does not attack steel pens, flows well from the 
 pen, writes at once -black, does not become mouldy, and is not dissolved by dilute 
 acids like ordinary ink, may be prepared by boiling 125 parts of logwood in suffi- 
 cient water to form a decoction of 1,000 parts, and adding when cold 1 part of yellow 
 potassium chromate. The ink thus obtained is bluish black, forms no deposit, flows 
 well from the pen without any addition of gum, and has the great advantage of being 
 extremely cheap. 
 
 1 Sulphate of copper may also be substituted with advantage for sulphate of iron in 
 logwood inks. The following is the formula for such an ink, given in proportions for 
 a manufacturing scale : 20 parts by weight of extract of logwood are dissolved in 
 200 parts of water, and the liquor clarified by subsidence and decantation. A 
 yellowish-brown. liquid is thus obtained. In another vessel 10 parts of ammonia-alum 
 are dissolved in 20 parts of boiling water. The two solutions are mixed, - 2 part by 
 weight of sulphuric acid is added, and finally 1*5 part of sulphate of copper. The 
 ink should be exposed to the air for a few days to acquire a good colour, after which 
 it should be stored in well-corked bottles. 
 
 Alizarin Ink. This ink flows well from the pen, and does not form any deposit. 
 Winternitz describes its preparation as follows: 100 parts of nutgalls are digested 
 with 1,200 parts crude wood vinegar for several days, the liquid filtered off and the 
 nutgalls washed upon the filter with a quantity of wood vinegar sufficient to make 
 up 1,200 parts. In this liquid is then dissolved 12 parts ferrous sulphate and 50 
 parts gum arabic, indigo carmine being added until the entire quantity of liquid amounts 
 to 1,500 parts. 
 
 Leonhardi's recipe recommends, for preparing alizarin ink, extracting 42 parts nut- 
 galls and 3 parts madder with hot water, sufficient to form 120 parts of solution; filtering 
 and adding 12 part of indigo solution. This ink admits of being dried and trans- 
 ported in the dry state, 1 part of the dry ink requiring for solution 6 parts of water. 
 
 Copying Ink. This consists in most cases of ordinary ink to which a considerable 
 quantity of sugar or gum has been added. 
 
 Red Ink. Boothe's method of preparing red ink consists in boiling together 2 
 ounces of brazil-wood chips with A drachm salt of tin, and 1 drachm gum arabic with 
 32 ounces of water. The whole is boiled until the net weight amounts to 16 ounces ; 
 the red liquor is then filtered off. 
 
 Other kinds of red ink are prepared from cochineal, or carmine, generally dis- 
 solved by the aid of a solution of ammonia. 
 
 Blue Ink. Normandy's is made by triturating together 1 drachm salt of sorrel, 
 3 drachms Prussian blue, 7 ounces of water, and 1 drachm gum arabic. Nearly all 
 kinds of blue ink owe their colour to Prussian blue. 
 
 FERRIC SULPHATE. 
 
 FORMULA Fe 2 3S0 4 . MOLECULAR WEIGHT 400. 
 
 This salt is found native in considerable quantities in Chili as coquimbite, as a 
 white silky mineral or as powder FegSSO^B^O. It is best prepared artificially by 
 mixing ferrous sulphate with sulphuric acid in the proportions so as to bring up the 
 relation of the one to the other to that form in which they exist in ferric sulphate ; 
 the mixture is then boiled and peroxidised by the addition of nitric acid. When the 
 solution obtained in this way is evaporated sufficiently, a buff coloured mass is ob- 
 tained, which is not very soluble in water ; at a gentle heat the salt is rendered 
 anhydrous. 
 
 With the sulphates of potassium and ammonium, ferric sulphate forms compounds 
 of the form and constitution of alums ; thus we have 
 
 K 2 Fe 2 4S0 4 24H 2 0, and 2NH 4 .Fe 2 4S0 4 24H 2 0. 
 Several basic sulphates of iron are known. 
 
 FERROUS CARBONATE. 
 
 FORMULA FeC0 8 . MOLECULAR WEIGHT 116. 
 
 This substance occurs in nature as spathose iron ore or iron spar in immense 
 quantities, forming a most valuable ore of iron ; in its less usual condition it exists 
 in a highly crystalline form isomorphous with calc spar. Clay iron ore is another 
 impure form of ferrous carbonate. 
 
IROlSr SMELTING. 551 
 
 Ferrous carbonate exists in many mineral waters, being held in solution by the 
 excess of carbonic anhydride ; such waters deposit ferric oxide on exposure and 
 standing. 
 
 When ferrous carbonate is strongly heated in a closed vessel, carbonic anhydride 
 and carbonic oxide are evolved, and magnetic oxide remains behind. 
 
 3FeC0 3 = Fe 3 4 + 2C0 2 + CO. 
 
 Ferrous carbonate may be produced by precipitating ferrous salts with an alkaline 
 carbonate, and in this state it constitutes a whitish-green precipitate which rapidly 
 undergoes atmospheric oxidation, losing carbonic anhydride and becoming hydrated 
 ferric oxide. 
 
 METALLURGY OF IRON. 
 
 Iron is always obtained in the metallic state by the reduction of one of the oxides, 
 by heating either in contact with hydrogen gas, carbon, carbonic oxide, or some 
 other substance capable of combining with oxygen. When this reaction takes place 
 at a moderate temperature the metal is obtained in a finely divided pulverulent con- 
 dition ; in this state it is pyrophoric and takes fire on contact with atmospheric air, 
 being converted into ferric oxide or magnetic oxide. When the reduction is effected 
 at a full red heat, the metal is obtained in a partially coherent state, forming a porous 
 spongy mass which is less readily oxidised. 
 
 Owing to the high melting point of pure iron, it is difficult to obtain the metal in a 
 compact state ; but when metallic iron is intensely heated in contact with carbon or carbu- 
 retted gases, it combines with the carbon, and is then fusible at a much lower tempe- 
 rature than pure iron. Since carbon is the reducing agent employed in smelting iron 
 ores, the metal obtained in this operation always contains some carbon, and from its 
 consequent greater fusibility in that state this circumstance is an important means 
 of facilitating the manipulation of the metal. As already mentioned, the degree of 
 fusibility of carburetted iron depends upon the proportion of carbon in the metal, 
 and when this amounts to from 3 to 6 per cent., the metal is sufficiently fusible- to be 
 run out from the smelting furnace in a liquid state and cast in moulds. In the ex- 
 traction of iron from such of its ores as are suitable for metallurgic purposes, and as 
 that operation is now chiefly carried out in iron-producing countries, the metal is 
 always obtained in the first instance in the carburetted state, commonly known 
 as crude iron or pig iron, on account of its being run out from the smelting furnace 
 into ingot-shaped masses. 
 
 The processes comprised in the smelting of iron ores by this method are : 
 
 1. The separation of water, carbonic acid, sulphur, and other volatilisable sub- 
 stances by the action of the heat upon the ore, so as to bring it as nearly as pos- 
 sible to the condition of ferric oxide or magnetic oxide. 
 
 2. The reduction of the oxide thus prepared to the metallic state by the action of 
 carbonic oxide under the influence of heat. 
 
 3. The separation of the earthy substances commonly present in iron ores, from 
 the reduced metal, by the formation of compounds of those substances which are 
 fusible at a high temperature, as slag. 
 
 4. The carburation and melting of the reduced metal. 
 
 The operations by which iron ores are brought to a condition fit for being smelted 
 vary according to the nature of the ore worked. In most instances the preparation 
 of the ore is effected by roasting, and sometimes this treatment is preceded by 
 a mechanical operation of washing. The only ferruginous minerals that are suitable 
 for the extraction of iron are the several oxides and the carbonate, all of which 
 occur naturally in great abundance, but associated with varying proportions of 
 silicious or earthy minerals and other admixtures in smaller amount. 
 
 The most important varieties of iron ore are the following : 
 
 Magnetic Iron Ore. This mineral consists essentially of magnetic oxide of iron 
 and is known by the name of magnetite ; when pure it is the richest of all the iron 
 ores, containing upwards of 72 per cent, of iron. It is black and generally has 
 a metallic lustre, occurring both crystalline or granular and compact, or even earthy, as 
 well as in the state of sand. In many localities it forms beds or veins, and some- 
 times enters mountain masses associated with volcanic or schistose rocks, chiefly in 
 Norway, Sweden, Siberia and North America, to some extent also in the west of 
 England, and at Eosedale, in Yorkshire. This ore is sometimes largely mixed with 
 pyrites and other sulphuretted minerals. The mineral known as Franklinite 
 appears to be a variety of magnetic iron ore in which ferrous oxide is replaced by 
 zinc oxide. 
 
552 
 
 IBON. 
 
 Analyses of Magnetic Iron Ore. 
 
 
 
 Dartmoor 
 
 Cornwall 
 
 Eosedale 
 
 Danne- 
 mora 
 
 Frank- 
 lin ite 
 
 
 Riley 
 
 Noad 
 
 North- 
 cutt 
 
 Fattin- 
 son 
 
 Karsten 
 
 Rammels- 
 berg 
 
 Ferric oxide . 
 
 62-20 
 
 44-40 
 
 66-50 
 
 12-22 
 
 32-67 
 
 70-23 
 
 64-51 
 
 Ferrous oxide . 
 
 17'32 
 
 20-00 
 
 13-00 
 
 35-25 
 
 33-85 
 
 29-65 
 
 . . 
 
 Manganous oxide 
 
 14 
 
 16 
 
 56 
 
 
 
 69 
 
 
 
 13-51 
 
 Zinc oxide 
 
 
 
 
 
 
 
 
 
 
 
 
 
 2530 
 
 Alumina .... 
 
 3-81 
 
 5-20 
 
 > 3'60 
 
 14-10 
 
 3-15 
 
 
 
 
 
 Lime .... 
 
 5-52 
 
 60 
 
 56 
 
 2-38 
 
 2-86 
 
 
 
 
 
 Magnesia .... 
 
 1-82 
 
 1-00 
 
 1-52 
 
 3-95 
 
 1-59 
 
 
 
 
 
 Potash and soda 
 
 10 
 
 
 
 
 
 
 
 trace 
 
 
 
 
 
 Silica .... 
 
 9-66 
 
 
 
 
 
 9-65 
 
 6-95 
 
 
 
 
 
 Carbonic acid . 
 
 
 
 
 
 
 
 16-25 
 
 10-36 
 
 
 
 
 
 Phosphoric acid 
 
 10 
 
 50 
 
 57 
 
 
 
 1-41 
 
 
 
 
 
 Sulphuric acid . 
 
 
 
 04 
 
 04 
 
 trace 
 
 trace 
 
 
 
 
 
 Iron pyrites 
 
 07 
 
 
 
 
 
 trace 
 
 03 
 
 
 
 
 
 Water j combined 
 \ hygroscopic 
 Insoluble in acid 
 
 -28 ) 
 34 J 
 
 2-50 
 24-20 
 
 3-20 
 9-40 
 
 4-80 
 
 3-76 
 84 
 
 
 
 
 
 
 101-36 
 
 98-60 
 
 98-95 
 
 98-60 
 
 98-16 
 
 99-88 
 
 103-32 
 
 Percentage of iron . 
 
 57-01 
 
 - 
 
 
 
 35-98 
 
 49-17 
 
 71-68 
 
 45-16 
 
 Hematite, or red iron ore. This mineral consists essentially of ferric oxide and in 
 the purest state contains 70 per cent, of iron. It occurs in various states, crystalline, 
 massive, compact and earthy ; very often the lumps of ore have a radiating, fibrous 
 structure and smooth nodular surface; in this form it is known as kidney ore. 
 Hematite also forms large veins or beds associated with quartz, calcspar and heavy 
 spar. Some kinds of the ore are hard, others soft and friable, and it generally con- 
 tains a varying amount of earthy admixtures. The principal deposits of hematite 
 in Great Britain are in Cumberland, Lancashire, the Isle of Man, Devonshire and 
 Cornwall. On the Continent it occurs chiefly in the Hartz, Silesia, Austria and 
 Norway. A peculiar oolitic hematite occurs in the neighbourhood of Lie'ge. Ked 
 ochre is an earthy variety of ferric oxide containing a large proportion of clay. 
 
 Analyses of Bed Iron Ore. 
 
 
 Whitehaven 
 
 Ulverstone 
 
 Cleator 
 
 Ulverstone 
 
 Whitchnrclx 
 
 
 Dick 
 
 Spiller 
 
 Smith 
 
 Dick 
 
 RatclifEe 
 
 Ferric oxide 
 
 98-71 
 
 95-16 
 
 94-23 
 
 90-94 
 
 90-55 
 
 86-5 
 
 66-55 
 
 Ferrous oxide . 
 
 
 
 
 
 
 
 
 
 
 
 
 1-13 
 
 Manganous oxide 
 
 trace 
 
 24 
 
 23 
 
 25 
 
 10 
 
 21 
 
 1-13 
 
 Alumina . 
 
 
 
 06 
 
 63 
 
 trace 
 
 1-43 
 
 30 
 
 2-79 
 
 Lime 
 
 trace 
 
 07 
 
 05 
 
 99 
 
 71 
 
 2-77 
 
 9-40 
 
 Magnesia 
 
 
 
 
 
 trace 
 
 trace 
 
 06 
 
 1-46 
 
 1-39 
 
 Potash . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 42 
 
 Soda 
 
 
 
 
 
 
 
 
 
 ' 
 
 
 
 15 
 
 Silica 
 
 1-00 
 
 5-66 
 
 4-90 
 
 6-68 
 
 7-05 
 
 6-18 
 
 8-90 
 
 Carbonic acid . 
 
 
 
 
 
 
 
 78 
 
 
 
 2-96 
 
 573 
 
 Phosphoric acid 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 1-02 
 
 Sulphuric acid 
 
 
 
 trace 
 
 
 
 24 
 
 trace 
 
 11 
 
 1-31 
 
 Iron pyrites 
 
 
 
 trace 
 
 09 
 
 
 
 
 
 
 
 
 
 Water combined 
 
 
 
 
 
 03 
 
 
 
 
 
 
 
 
 
 hygroscopic 
 
 
 
 
 
 17 
 
 
 
 
 
 
 
 2-12 
 
 Organic substance 
 
 
 
 
 
 39 
 
 
 
 
 
 
 
 38 
 
 
 99-71 
 
 101-19 
 
 100-72 
 
 99-88 
 
 99-90 
 
 100-49 
 
 102-42 
 
 Percentage of iron 
 
 69-10 
 
 66-60 
 
 65-98 
 
 63-66 
 
 63-25 
 
 6-55 
 
 47-47 
 
BROWN IRON ORE. 
 
 553 
 
 Specular iron ore also consists of anhydrous ferric oxide in a crystallised state. 
 Its colour varies from iron grey to black. Specific gravity 4'8 to 5'3. The crystals 
 of this mineral belong to the hexagonal system. Specular iron ore occurs chiefly in 
 schistose rocks, in Norway, the Erzgebirge, Bussia, and several parts of the south of 
 Europe, the most extensive deposit being in the island of Elba, where it has been 
 worked for upwards of 3,000 years. This mineral often contains titanic oxide, either 
 in the form of rutile, or combined with the ferric oxide constituting ilmenite. The 
 presence of this substance was formerly considered prejudicial to the ore, but more 
 recently it has been stated that the presence of titanium in iron ores contributes, in 
 some way not yet understood, to the production of good iron. 
 
 Brown iron ore consists essentially of hydrated ferric oxide, and is sometimes called 
 brown hematite. In the pure state it contains 59'89 per cent, of iron and 14*44 
 per cent, of combined water. It is sometimes indistinctly crystalline or fibrous ; but 
 more generally compact or earthy, and of various shades of colour from blackish-brown 
 to yellowish-brown. This ore frequently contains a considerable amount of man- 
 ganese oxides, together with a varying proportion of earthy admixtures. It occurs 
 abundantly in the Forest of Dean in Gloucestershire, in several parts of Devonshire, 
 Northamptonshire and Lincolnshire, as well as in "Weardale, Durham, where it has 
 originated chiefly by the alteration of spathic iron ore. On the Continent it is very 
 abundant, and it is one of the principal ores smelted in France. A very large deposit 
 of this ore occurs in the carboniferous limestone in the neighbourhood of Bilbao in 
 Spain. The mine of Somorrostro is very extensively worked, and is said to yield as 
 much as 1,000 tons of ore daily. At the Graldames mine there is a mountain, con- 
 sisting entirely of iron ore, 1,200 yards long, and rising about 170 yards high above the 
 river. The quantity of ore actually in sight is estimated at from sixty to seventy 
 million tons, and it is believed that there is three or four times that quantity of ore 
 to be obtained at this place. 
 
 Brown hematite also occurs in lias, oolite, and greensand rocks of more recent date 
 than the coal measures, but then it is often less pure than the ore found in older rocks, 
 which is frequently a product of the oxidation of ferrous carbonate. 
 
 A variety of brown iron ore known under the name of b o g i r o n o re occurs in many 
 places, and it has probably been formed by deposition from ferruginous water under 
 the influence of living organisms. Some kinds of this ore furnish very good iron, as 
 for instance the lake ores of Sweden and Lower Canada, but generally the amount of 
 phosphates in bog iron ore is so large as to render it useless for the production of 
 malleable iron. 
 
 Yellow ochre is an argillaceous variety of hydrated ferric oxide, containing more 
 combined water than brown iron ore, together with basic ferric sulphate and sometimes 
 also silicate, phosphate, or arsenate. 
 
 Analyses of Brown Iron Ore. 
 
 
 Dean Forest 
 
 Devon- 
 shire 
 
 Northampton- 
 shire 
 
 Weardale 
 
 
 Price 
 
 Dick 
 
 - 
 
 Dick 
 
 - 
 
 - 
 
 Tookey 
 
 Spiller 
 
 Ferric oxide . ' , 
 
 89-28 
 
 90-05 
 
 89-80 
 
 89-39 
 
 76-00 
 
 74-32 
 
 72-08 
 
 49-57 
 
 Ferrous oxide . . 
 
 
 
 
 
 
 
 
 
 trace 
 
 
 
 
 10-77 
 
 Manganous oxide 
 
 
 
 88 
 
 04 
 
 33 
 
 40 
 
 57 
 
 6-60 
 
 3-06 
 
 Alumina . . . j. 
 
 
 
 14 
 
 98 
 
 52 
 
 2-30 
 
 2-91 
 
 40 
 
 84 
 
 Lime . . . ' ' \ 
 
 . 
 
 06 
 
 51 
 
 33 
 
 41 
 
 76 
 
 56 
 
 5-69 
 
 Magnesia . 
 
 
 
 20 
 
 40 
 
 20 
 
 11 
 
 18 
 
 1-90 
 
 1-21 
 
 Potash . .* "*- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 05 
 
 Silica . . : .'. 
 
 -98 
 
 ' -92 
 
 2-14 
 
 1-42 
 
 5-33 
 
 603 
 
 4-09 
 
 6-64 
 
 Carbonic acid . 
 
 
 
 
 
 
 
 
 
 
 
 57 
 
 . -13 
 
 14-49 
 
 Phosphoric oxide 
 
 trace 
 
 09 
 
 -13 
 
 13 
 
 1-03 
 
 3-17 
 
 22 
 
 01 
 
 Sulphuric oxide . \ 
 
 
 
 trace 
 
 trace 
 
 trace 
 
 
 
 trace 
 
 
 
 trace 
 
 Iron pyrites 
 
 
 
 trace 
 
 
 
 trace 
 
 
 
 06 
 
 
 
 03 
 
 .r,,. , (combined } 
 Water |hygroscopi4 ' 
 
 9-74 
 
 9-22 
 
 7-05 
 
 | 8-83 
 
 12-40 
 1-80 
 
 11-89 
 
 } 12-40 
 
 6-63 
 1-81 
 
 Organic substance 
 
 
 
 
 
 
 
 
 
 
 
 trace 
 
 
 
 trace 
 
 
 100- 
 
 101-56 
 
 101-05 
 
 101-15 
 
 99-78 
 
 100-46 
 
 99-38 
 
 100-80 
 
 Percentage of iron 
 
 62-57 
 
 63-04 
 
 62-86 
 
 62-60 
 
 53-20 
 
 52-05 
 
 49-78 
 
 43-02 
 
554 
 
 IROK 
 
 Analyses of Brown Iron Ore continued. 
 
 
 North- 
 
 Wales : 
 
 Lincoln- 
 
 North- 
 
 
 Wilt- 
 
 North- 
 
 Corn- 
 
 
 ampton- 
 shire 
 
 Llan- 
 trissant 
 
 shire : 
 Brigg 
 
 ampton- 
 shire 
 
 Dorset- 
 shire 
 
 shire: 
 Seend 
 
 ampton- 
 shire 
 
 wall: St. 
 Austell 
 
 
 Price 
 
 
 
 
 
 
 
 
 
 ana Ni- 
 
 Riley 
 
 Tookey 
 
 Percy 
 
 Tookey 
 
 Biley 
 
 Spiller 
 
 Riley 
 
 
 cholson 
 
 
 
 
 
 
 
 
 Ferric oxide 
 
 68-58 
 
 59-05 
 
 58-10 
 
 56-20 
 
 55-21 
 
 53-48 
 
 52-86 
 
 51-87 
 
 Ferrous oxide . 
 
 
 
 
 
 
 
 trace 
 
 
 
 
 
 trace 
 
 
 
 Manganous oxide 
 
 0-36 
 
 0-09 
 
 0-88 
 
 0-20 
 
 0-95 
 
 1-60 
 
 0-51 
 
 0-43 
 
 Alumina . 
 
 3-27 
 
 trace 
 
 4-95 
 
 2-43 
 
 7-70 
 
 4-38 
 
 7-39 
 
 4-01 
 
 Lime . 
 
 0-66 
 
 0-25 
 
 4-15 
 
 0-49 
 
 0-70 
 
 0-84 
 
 7-46 
 
 0-52 
 
 Magnesia . 
 
 
 
 0-28 
 
 0-96 
 
 0-17 
 
 1-16 
 
 0-72 
 
 0-68 
 
 0-17 
 
 Silica 
 
 11-63 
 
 34-40 
 
 11-70 
 
 29-07 
 
 19-65 
 
 26-23 
 
 13-16 
 
 36-03 
 
 Carbonic acid . 
 
 
 
 
 
 1-08 
 
 
 
 
 
 trace 
 
 4-92 
 
 
 
 Phosphoric acid . 
 
 0-97 
 
 0-14 
 
 1-40 
 
 0-84 
 
 0-42 
 
 0-87 
 
 1-26 
 
 0-49 
 
 Sulphuric acid . 
 
 0-18 
 
 
 
 
 
 
 
 0-16 
 
 
 
 
 
 
 
 Iron pyrites 
 
 
 
 0-09 
 
 
 
 
 
 
 
 trace 
 
 0-03 
 
 0-03 
 
 Water ^ h y grOSC pic f 
 Water } combined \ ' 
 
 11-56 
 
 0-24 
 6-14 
 
 J 16-46 
 
 / 1-16 
 19-74 
 
 J13-11 
 
 13-61 
 
 jll-37 
 
 0-80 
 5-80 
 
 Organic substance 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 97-21 
 
 100-68 
 
 99-68 
 
 100-30 
 
 99-05 
 
 101-73 
 
 99-64 
 
 100-15 
 
 Percentage of iron 
 
 48-00 
 
 41-34 
 
 40-67 
 
 39-34 
 
 38-65 
 
 37-44 
 
 37-00 
 
 36-31 
 
 
 North- 
 ampton- 
 shire 
 
 Oxford- 
 shire : 
 Wood- 
 stock 
 
 Dean 
 Forest 
 
 Staf- 
 ford- 
 shire: 
 Frog- 
 hall 
 
 North- 
 ampton- 
 shire 
 
 Dean 
 Forest 
 
 Belfast 
 
 North- 
 ampton- 
 shire 
 
 
 Dick 
 
 Tookey 
 
 Dick 
 
 Eiley 
 
 Dick 
 
 Tookey 
 
 Eiley 
 
 Ferric oxide . ^ . 
 
 38-04 
 
 44-67 
 
 32-76 
 
 52-83 
 
 50-53 
 
 48-99 
 
 35-91 
 
 34-41 
 
 Ferrous oxide . 
 
 10-54 
 
 0-86 
 
 
 
 
 
 trace 
 
 0-24 
 
 6-57 
 
 trace 
 
 Manganous oxide 
 
 0-69 
 
 0-44 
 
 trace 
 
 0-81 
 
 0-51 
 
 0-16 
 
 0-05 
 
 0-27 
 
 Alumina . 
 
 13-02 
 
 9-10 
 
 0-05 
 
 
 
 7-52 
 
 0-17 
 
 27-95 
 
 6-40 
 
 Lime .... 
 
 trace 
 
 9-29 
 
 0-25 
 
 14-61 
 
 11-92 
 
 14-07 
 
 0-60 
 
 25-72 
 
 Magnesia . 
 
 4-35 
 
 0-66 
 
 0-25 
 
 5-70 
 
 0-62 
 
 10-21 
 
 0-20 
 
 0-87 
 
 Potash 
 
 0-38 
 
 
 
 
 
 
 
 0-11 
 
 
 
 0-49 
 
 
 
 Silica 
 
 23-24 
 
 12-34 
 
 63-52 
 
 trace 
 
 8-80 
 
 0-79 
 
 9-75 
 
 6-69 
 
 Carbonic acid . 
 
 0-16 
 
 6-11 
 
 
 
 18-14 
 
 7-98 
 
 20-75 
 
 
 
 18-45 
 
 Phosphoric acid 
 
 0-26 
 
 0-55 
 
 0-09 
 
 0-32 
 
 1-28 
 
 0-06 
 
 
 
 1-47 
 
 Sulphuric acid . . " 
 
 trace 
 
 
 1 t 
 
 0-28 
 
 
 trace 
 
 
 
 0-07 
 
 Iron pyrites 
 
 0-13 
 
 trace 
 
 / 
 
 
 
 0-17 
 
 
 
 
 
 0-30 
 
 Wat( , r J hygroscopic) 
 /e {combined J ' 
 
 6-92 
 
 J16-31 
 
 { 3-55 
 
 4-75 
 
 jll-00 
 
 [ 5-18 
 
 1 18-60 
 
 6-97 
 
 Organic substance 
 
 0-19 
 
 
 
 
 
 1-30 
 
 
 
 
 
 
 
 
 
 
 97-92 
 
 100-33 
 
 100-47 
 
 9874 
 
 100-44 
 
 100-62 
 
 100-12 
 
 101-62 
 
 Percentage of iron 
 
 34-83 
 
 31-94 
 
 22-93 
 
 36-98 
 
 35-37 
 
 34-46 
 
 30-25 
 
 24-09 
 
 Spathic iron ore consists essentially of ferrous carbonate, and in its purest state it 
 contains 48*27 per cent, of iron. It is generally crystalline, sometimes presenting dis- 
 tinct crystals ; it also occurs in the form of fibrous nodular masses known by the name 
 ofsphserosiderite. It varies in colour from white to yellow or brown, and is very 
 often found to have undergone partial conversion into hydrated ferric oxide. Spathic 
 iron ore occurs as veins or beds in the older rocks and associated with limestone 
 strata ; it frequently contains manganous carbonate, calcic carbonate, or magnesic car- 
 bonate, and is sometimes associated with lead or copper ore, quartz, fluor spar, calc spar, 
 heavy spar, etc. It is worked in this country chiefly in Durham and Somersetshire ; 
 
SPATHIC IRON ORB. 
 
 555 
 
 on the Continent it occurs more frequently and in great abundance, the chief localities 
 being Styria and Westphalia, where it constitutes entire mountains, and has long been 
 renowned under the name of steel ore for yielding very fine qualities of iron and 
 steel. 
 
 Analyses of Spathic Iron Ore. 
 
 
 West- 
 phalia : 
 
 Miisen 
 
 Durl 
 
 Eipsey 
 vein 
 
 lann 
 Wear- 
 dale 
 
 Somersetshire : 
 Brandon 
 
 Siegen 
 
 Saxony 
 
 Devon : 
 Ex- 
 moor 
 
 
 Peters 
 
 Dick 
 
 Tookey 
 
 SpiUer 
 
 Price 
 and Ni- 
 cholson 
 
 Schna- 
 bel 
 
 Magnus 
 
 Spiller 
 
 Ferric oxide 
 
 2-75 
 
 
 
 0-81 
 
 0-81 
 
 
 
 
 
 
 
 0-07 
 
 Ferrous oxide . 
 
 48-13 
 
 49-47 
 
 49-77 
 
 43-84 
 
 43-94 
 
 43-59 
 
 36-81 
 
 17-91 
 
 Manganous oxide 
 
 0'83 
 
 2-42 
 
 1-93 
 
 12-64 
 
 12-88 
 
 17-87 
 
 25-31 
 
 7-64 
 
 Zinc oxide. 
 
 0-04 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Alumina . 
 
 1-63 
 
 0-06 
 
 
 
 o-oi 
 
 
 
 
 
 
 
 
 
 Lime. 
 
 1-75 
 
 3-47 
 
 3-96 
 
 0-28 
 
 
 
 0-88 
 
 
 
 24-80 
 
 Magnesia . 
 
 2-29 
 
 3-15 
 
 2-83 
 
 3-63 
 
 4-00 
 
 0-24 
 
 
 
 6-17 
 
 Silica 
 
 1-62 
 
 4-93 
 
 3-12 
 
 0-07 
 
 
 
 
 
 
 
 
 
 Carbonic acid . 
 
 39-92 
 
 3771 
 
 37-20 
 
 38-86 
 
 39-18 
 
 38-22 
 
 38-35 
 
 41-75 
 
 Phosphoric acid. 
 
 0-54 
 
 trace 
 
 trace 
 
 
 
 
 
 
 
 
 
 trace 
 
 Sulphuric acid . 
 
 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Iron pyrites 
 
 0-22 
 
 
 
 0-04 
 
 
 
 
 
 
 
 
 
 0-11 
 
 Water ! h yg rosc P ic ( 
 
 
 
 
 
 0-30 
 
 0-18 
 
 
 
 
 
 
 
 0-38 
 
 \ combined {' 
 
 0-45 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Organic substance 
 
 0-39 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 100-55 
 
 101-21 
 
 99-96 
 
 100-32 
 
 100-00 
 
 100-20 
 
 100-47 
 
 98-83 
 
 Percentage of iron 
 
 42-59 
 
 38-56 
 
 38-95 
 
 34-67 
 
 34-18 
 
 33-90 
 
 28-03 
 
 13-98 
 
 Ferrous carbonate mixed with clay often occurs with beds of coal in sedimentary 
 rocks, and is then known under the name ofclayironoreor argillaceous sphse- 
 rosiderite. This ore occurs in lenticular masses or nodules ; it is compact and earthy, 
 
 Analyses of Clay Iron Ore from the Coal Measures. 
 
 
 Low- 
 moor 
 
 Parkgate 
 
 Butter- 
 ley 
 
 Stanton 
 
 Staveley 
 
 Staffordshire 
 
 
 SpiUer 
 
 Dick 
 
 Ferric oxide 
 
 1-45 
 
 1-69 
 
 2-39 
 
 1-49 
 
 3-49 
 
 1-42 
 
 0-12 
 
 0-05 
 
 Ferrous oxide . 
 
 36-14 
 
 39-38 
 
 41-77 
 
 37'99 
 
 39-55 
 
 28-27 
 
 51-07 
 
 46-53 
 
 Manganous oxide 
 
 1-38 
 
 0-95 
 
 1-13 
 
 1-51 
 
 1-50 
 
 1-02 
 
 2-36 
 
 2-54 
 
 Alumina . . ' ',; 
 
 6-74 
 
 6-42 
 
 4-79 
 
 5-57 
 
 5-45 
 
 2-21 
 
 2-47 
 
 1-22 
 
 Lime. . . , \,\\ 
 
 2-70 
 
 2-26 
 
 2-55 
 
 4-59 
 
 3-38 
 
 13-94 
 
 1-74 
 
 2-44 
 
 Magnesia . . j. 
 
 2-17 
 
 3-89 
 
 3-85 
 
 3-37 
 
 2-88 
 
 9-27 
 
 1-10 
 
 1-39 
 
 Potash . " '*>: 
 
 0-65 
 
 0-37 
 
 0-43 
 
 0-55 
 
 0-48 
 
 0-16 
 
 0-28 0-20 
 
 Silica 
 
 17-37 
 
 12-16 
 
 8-93 
 
 10-04 
 
 10-22 
 
 3-55 
 
 3-02 
 
 1-93 
 
 Carbonic acid . 
 
 26-57 
 
 29-38 
 
 31-39 
 
 29-92 
 
 28-63 
 
 37-61 
 
 33-63 
 
 30-77 
 
 Phosphoric acid . 
 
 0-34 
 
 0-47 
 
 0-75 
 
 0-80 
 
 1-12 
 
 0-74 
 
 1-12 
 
 0-69 
 
 Sulphuric acid . fc 
 
 trace 
 
 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 0-04 
 
 Iron pyrites . , . 
 
 o-io 
 
 trace 
 
 
 
 0-06 
 
 0-05 
 
 0-04 
 
 0-17 
 
 0-34 
 
 (hygroscopic . 
 
 0-61 
 
 0-68 
 
 0-55 
 
 0-74 
 
 0-51 
 
 0-18 
 
 > ft-QQ 
 
 1 '4-7 
 
 (combined 
 
 1-16 
 
 1-41 
 
 1-15 
 
 1-47 
 
 1-24 
 
 0-73 
 
 ' I/ */!/ 
 
 j. */ 
 
 Organic substance 
 
 2-40 
 
 0-54 
 
 0-86 
 
 1-42 
 
 1-14 
 
 0-92 
 
 1-24 
 
 10-46 
 
 
 99-78 
 
 99-60 
 
 100-54 
 
 99-52 
 
 99-64 
 
 100-06 
 
 99-01 
 
 100-07 
 
 Percentage of iron 
 
 29-12 
 
 31-82 
 
 34-16 
 
 30-60 
 
 33-20 
 
 22-98 
 
 39-88 
 
 36-39 
 
 of various shades of grey or brown, and sometimes it is quite black, owing to the admix- 
 ture of carbonaceous material. Clay iron ore is generally very abundant in the coal 
 
556 
 
 IRON. 
 
 measures, but in some instances it is almost wholly wanting in those rocks ; as, for 
 instance, in the co.al fields of Northumberland, Durham, Lancashire and Belgium. The 
 principal localities where it is worked in this country are the coal fields of Scotland, 
 Staffordshire, Shropshire and Wales. Clay iron ore is found abundantly in America, 
 and also to some extent in Franco and Germany. 
 
 
 Pins 
 
 Grains 
 
 Gubbin 
 
 White- 
 stone 
 
 Binds 
 
 Balls 
 
 White- 
 stone 
 
 Gubbin 
 
 
 
 Dick 
 
 Spiller 
 
 Dick 
 
 Tookey 
 
 Ferric oxide . 
 
 0-54 
 
 0-13 
 
 0-40 
 
 0-04 
 
 1-15 
 
 0-43 
 
 3-17 
 
 3-82 
 
 Ferrous oxide . 
 
 45-35 
 
 46-30 
 
 45-86 
 
 48-63 
 
 30-96 
 
 52-04 
 
 33-92 
 
 49-40 
 
 Manganous oxide 
 
 0-56 
 
 1-44 
 
 0-96 
 
 1-29 
 
 0-73 
 
 0-92 
 
 0-77 
 
 0-86 
 
 Alumina . 
 
 5-70 
 
 4-80 
 
 5-86 
 
 3-64 
 
 9-58 
 
 4-98 
 
 6-44 
 
 3-05 
 
 Lime. 
 
 2-60 
 
 0-76 
 
 1-37 
 
 445 
 
 1-84 
 
 0-53 
 
 2-65 
 
 0-86 
 
 Magnesia . 
 
 1-26 
 
 0-94 
 
 1-85 
 
 0-80 
 
 3-11 
 
 1-18 
 
 4-43 
 
 0-52 
 
 Potash 
 
 0-36 
 
 
 
 
 
 0-11 
 
 0-74 
 
 0-32 
 
 0-74 
 
 0-30 
 
 Silica 
 
 10-63 
 
 10-29 
 
 10-88 
 
 6-21 
 
 26-50 
 
 6-63 
 
 18-23 
 
 6-22 
 
 Carbonic acid . 
 
 30-21 
 
 30-44 
 
 31-02 
 
 32-16 
 
 22-13 
 
 32-31 
 
 26-89 
 
 32-05 
 
 Phosphoric acid 
 
 0-46 
 
 0-74 
 
 0-21 
 
 0-31 
 
 0-26 
 
 0-21 
 
 0-35 
 
 0-23 
 
 Sulphuric acid . 
 
 trace 
 
 trace 
 
 trace 
 
 0-06 
 
 trace 
 
 trace 
 
 
 
 
 
 Zinc sulphide . 
 Iron pyrites 
 
 0-20 
 
 0-07 
 
 o-io 
 
 0-16 
 
 0-12 
 
 0-13 
 
 0-15 
 
 1-27 
 0-13 
 
 {SSSf}- 
 
 1-64 
 
 1-38 
 
 1-08 
 
 I 0-32 
 I 1-23 
 
 0-56 
 1-83 
 
 0-46 
 
 0-42 
 0-98 
 
 0-37 
 0-29 
 
 Organic substance 
 
 1-59 
 
 1-14 
 
 0-90 
 
 0-28 
 
 o-io 
 
 0-51 
 
 0-47 
 
 0-54 
 
 
 101-10 
 
 98-43 
 
 100-09 
 
 99-69 
 
 99-61 
 
 100-65 
 
 99-61 
 
 99-91 
 
 Percentage of iron 
 
 3574 
 
 36-14 
 
 35-99 
 
 37-45 
 
 24-88 
 
 40-84 
 
 28-87 
 
 41-60 
 
 
 Ponty- 
 pool 
 
 Blae- 
 navon 
 
 Car- 
 narvon 
 
 Aberdare 
 
 Aber- 
 carn 
 
 Llanelly 
 
 
 Balls 
 
 Black 
 pin 
 
 Sul- 
 phury 
 mine 
 
 Coal brass 
 
 Blackband 
 
 
 Biley 
 
 Dick 
 
 Price and 
 Nicholson 
 
 Rat- 
 cliffle 
 
 Price 
 
 Ferric oxide 
 
 0-50 
 
 0-45 
 
 0-34 
 
 
 
 
 
 4-10 
 
 raw 
 
 calcined 
 80-00 
 
 Ferrous oxide . ' . " 
 
 44-50 
 
 41-22 
 
 40-30 
 
 37-07 
 
 42-64 
 
 43-37 
 
 43-30 
 
 
 
 Manganous oxide 
 Manganic oxide . 
 
 0-73 
 
 1-07 
 
 1-03 
 
 0-23 
 
 0-26 
 
 | 1-50 
 
 | 1-08 
 
 | 1-80 
 
 Alumina . 
 
 5-95 
 
 4-88 
 
 7-90 
 
 
 
 
 
 6-50 
 
 
 
 
 
 Lime. . . . 
 
 2-05 
 
 2-89 
 
 1-44 
 
 6-61 
 
 5-24 
 
 3-00 
 
 1-26 
 
 2-10 
 
 Magnesia . 
 
 3-26 
 
 3-68 
 
 2-94 
 
 7-40 
 
 5-26 
 
 0-25 
 
 2-67 
 
 4-45 
 
 Soda . . . ' . 
 
 0-13 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Potash 
 
 
 
 0-48 
 
 0-82 
 
 
 
 
 
 0-32 
 
 
 
 
 
 Silica . . . 
 
 10-81 
 
 11-60 
 
 14-43 
 
 
 
 
 
 0-80 
 
 7-20 
 
 10-61 
 
 Carbonic acid . 
 
 30-92 
 
 30-07 
 
 28-23 
 
 37-14 
 
 36-89 
 
 30-50 
 
 28-46 
 
 
 
 Phosphoric acid . . 
 
 0-23 
 
 0-76 
 
 
 
 0-23 
 
 0-17 
 
 trace 
 
 0-67 
 
 1-03 
 
 Sulphuric acid . 
 
 
 
 trace 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 
 Sulphur 
 
 
 
 
 
 
 
 
 
 
 
 1-56 
 
 0-26 
 
 
 
 Iron pyrites 
 
 O'll 
 
 0-15 
 
 0-09 
 
 trace 
 
 0-22 
 
 
 
 
 
 
 
 Clay. . . . 
 
 
 
 
 
 
 
 2-70 
 
 
 
 
 
 
 
 
 
 Water J hyg 800 ? 10 
 )r j combined 
 
 076 
 
 1-21 
 
 0-74 
 
 
 
 
 
 0-27 
 0-31 
 
 
 
 
 
 Organic substance 
 
 0-21 
 
 0-82 
 
 0-29 
 
 9-80 
 
 8-87 
 
 6-25 
 
 15-10 
 
 
 
 
 100-16 
 
 99-28 
 
 98-55 
 
 101-18 
 
 99-55 
 
 98-73 
 
 100-00 
 
 99-99 
 
 Percentage of iron 
 
 34-96 
 
 32-44 
 
 31-63 
 
 28-88 
 
 33-17 
 
 36-4 
 
 33-68 
 
 56-00 
 
ARGILLACEOUS IRON ORB. 
 
 557 
 
 A variety of clay iron ore known as black band, and containing from 10 to 15 or 
 20 per cent, of coaly substance, occurs as thin layers in the coal measures of Scotland 
 and some parts of England and Wales. 
 
 
 Scotch Blackband 
 
 
 Colquhoun 
 
 Ferric oxide 
 
 
 
 0-33 
 
 1-16 
 
 0-23 
 
 0-47 
 
 1-16 
 
 0-23 
 
 272 
 
 Ferrous oxide . 
 
 45-84 
 
 38-80 
 
 35-22 
 
 53-03 
 
 43-73 
 
 35-22 
 
 53-82 
 
 40-77 
 
 Manganous oxide 
 
 0-20 
 
 0-07 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Alumina 
 
 2-53 
 
 6-20 
 
 5-34 
 
 0-63 
 
 5-13 
 
 5-34 
 
 
 
 
 
 Lime. 
 
 1-90 
 
 5-30 
 
 8-62 
 
 3-38 
 
 2-10 
 
 8-62 
 
 1-51 
 
 0-90 
 
 Magnesia . 
 
 5-90 
 
 6-70 
 
 5-19 
 
 1-77 
 
 2-77 
 
 5-19 
 
 0-28 
 
 d-72 
 
 Silica 
 
 7-83 
 
 10-87 
 
 9-56 
 
 1-40 
 
 9-70 
 
 9-56 
 
 2-00 
 
 10-10 
 
 Carbonic acid . 
 
 33-63 
 
 30-76 
 
 32-53 
 
 35-17 
 
 32-24 
 
 3253 
 
 34-39 
 
 26-41 
 
 Sulphur . . 
 
 
 
 0-16 
 
 0-62 
 
 
 
 0-20 
 
 0-62 
 
 
 
 
 
 Water j hygroscopic . 
 (combined 
 
 z 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1-00 
 
 Organic substance 
 
 1-86 
 
 1-87 
 
 2-13 
 
 3-63 
 
 1-50 
 
 2-13 
 
 7-70 
 
 17-38 
 
 
 99-29 
 
 99-26 
 
 100-37 
 
 
 
 97-84 
 
 100-37 
 
 100-03 
 
 100-00 
 
 Percentage of iron 
 
 28-40 
 
 30-00 
 
 28-40 
 
 40-90 
 
 34-00 
 
 28-40 
 
 41-60 
 
 34-60 
 
 Clay iron ore also occurs abundantly in strata belonging to the Lias series, as well 
 as the oolitic and tertiary series of rocks ; sometimes it is partially or wholly converted 
 into brown iron ore by atmospheric oxidation. This kind of ore is now worked on a 
 large scale in the Cleveland district in Yorkshire. 
 
 
 Middles- 
 boro' 
 
 Hutton 
 Low 
 Cross 
 
 Eston 
 Nab 
 
 Up- 
 leatham 
 
 Belmont 
 
 Gros- 
 mont 
 
 Nor- 
 manby 
 
 North- 
 ampton- 
 shire 
 
 
 Percy 
 
 Crowder 
 
 Percy 
 
 - 
 
 Pattin- 
 son 
 
 Dick 
 
 Ferric oxide 
 
 2-86 
 
 4-25 
 
 1-20 
 
 5-80 
 
 3-50 
 
 
 
 2-60 
 
 3-31 
 
 Ferrous oxide 
 
 43-02 
 
 40-86 
 
 40-35 
 
 38-25 
 
 39-00 
 
 40-77 
 
 3806 
 
 33-29 
 
 Manganous oxide 
 
 0-40 
 
 
 
 
 
 
 
 1-30 
 
 0-67 
 
 074 
 
 1-11 
 
 Alumina . 
 
 5-87 
 
 3-44 
 
 9-88 
 
 12-20 
 
 7-46 
 
 1-32 
 
 5-92 
 
 7'89 
 
 Zinc oxide. " j ' 
 
 5-14 
 
 3-80 
 
 0-58 
 
 5-00 
 
 7-44 
 
 4-08 
 
 7-77 
 
 0-50 
 
 Magnesia . 
 
 5-21 
 
 3-70 
 
 5-35 
 
 2-40 
 
 3-82 
 
 5-34 
 
 4-16 
 
 11-77 
 
 Potash 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 0-20 
 
 Silica 
 
 7-17 
 
 7-20 
 
 7-65 
 
 7-45 
 
 9-46 
 
 8-80 
 
 10-36 
 
 19-49 
 
 Carbonic acid 
 
 25-50 
 
 32-50 
 
 22-96 
 
 25-40 
 
 23-06 
 
 31-80 
 
 22-00 
 
 24-79 
 
 Phosphoric acid. 
 
 1-81 
 
 0-96 
 
 3-87 
 
 0-50 
 
 1-60 
 
 0-06 
 
 1-07 
 
 0-22 
 
 Sulphuric acid . 
 
 
 
 0-30 
 
 
 
 trace 
 
 
 
 
 
 trace 
 
 trace 
 
 Iron pyrites 
 
 
 
 1-60 
 
 0-09 
 
 trace 
 
 
 
 
 
 0-14 
 
 013 
 
 tir i (hygroscopic 
 Waters J& , . f 
 (.combined 
 
 0-34 
 3-14 
 
 J 1-45 
 
 5-07 
 
 3-00 
 
 3-66 
 
 2-70 
 
 4-45 
 
 {-5, 
 
 Organic substance 
 
 0-15 
 
 
 
 
 
 
 
 
 
 
 
 
 
 0-08 
 
 
 100-61 
 
 100-06 
 
 100-00 
 
 100-00 
 
 100-30 
 
 95-54 
 
 97-27 
 
 103-32 
 
 Percentage of iron 
 
 35-46 
 
 34-75 
 
 34-54 
 
 38-81 
 
 32-78 
 
 31-71 
 
 31-42 
 
 18-28 
 
 The various kinds of argillaceous iron ore are frequently accompanied by other 
 minerals, either metalliferous, sulphuretted, arsenical, or phosphatic, and the proportion 
 of such admixtures is sometimes so large as to detract from the value of the ore for 
 iron smelting ; but, generally speaking, argillaceous iron ore is sufficiently pure to 
 furnish iron of good quality. 
 
 The mechanical treatment to which iron ore is subjected before being smelted is 
 generally more simple than in the case with other ores. In this country it is rarely 
 
558 IRON 
 
 requisite to do more than break the masses of ore into lumps of tolerably uniform siz- 
 in order to secure .the regular working of the smelting furnaces. 
 
 With poor argillaceous brown iron ore, such as is used in many Continental 
 districts for iron smelting, it is necessary to separate the adhering sand and clay by 
 a preliminary operation of crushing and washing. A simple washing arrangement 
 is to allow a current of water to pass through the ore, which is kept agitated in a 
 cylindrical trough by means of a revolving horizontal shaft provided with paddles. 
 In this way the clean ore is deposited, whilst the lighter earthy material is carried 
 away in a fine state of division suspended in the water that runs off. 
 
 With some kinds of iron ore it is found often advantageous to expose them to the 
 action of atmospheric air, by which they undergo oxidation and other changes. This 
 .is termed weathering, and in this way the shale adhering to such ores as the argilla- 
 ceous ores of the coal measures becomes disintegrated and easily detached ; in like 
 manner the sulphuretted minerals e.g. copper, iron, and magnetic pyrites are oxidised 
 and give rise to soluble sulphates which can be removed by washing with water. In 
 addition to the removal of the sulphur, the iron becomes peroxidised and the mass is 
 rendered much more porous. It is important when weathering ores to stop the action 
 when it has advanced far enough for the object desired, so as to avoid unnecessary 
 disintegration. 
 
 Iron ore is seldom smelted in a raw state, but is generally roasted beforehand. The 
 chemical changes effected by calcination over and above the disintegration of the ore 
 consist chiefly in the separation of water, carbonic acid, and bituminous material when 
 the ore is carbonaceous. In this case the ferric oxide may undergo partial reduction 
 to magnetic oxide or ferrous oxide ; but more generally the effect of calcination is to 
 bring the iron into the state of ferric oxide, if it be not already in that condition. 
 Another important effect of calcination is the removal of sulphur, which is in most 
 instances present in the state of pyrites. By the action of heat this is decomposed, 
 losing half of its sulphur, and the residual ferrous sulphide is then converted by oxida- 
 tion into sulphate which may be decomposed if the heat applied in roasting the ore be 
 sufficient. However, the entire separation of sulphur in this way is rarely practi- 
 cable. 
 
 The following analyses of Cleveland iron ore in the raw state and after calcina- 
 tion will serve to illustrate the nature of the change produced by roasting : 
 
 Eaw Calcined 
 
 Ferrous oxide . . . '''. , y . 38'06 
 
 Ferric oxide . ... . . . . 2'60 66'25 
 
 Manganous oxide ^ . . ., ' . . -74 
 
 Mn 8 4 . . . . . . . -65 
 
 Alumina . . .''*,. . . 5'92 772 
 
 Lime . . . . : . . , . 777 6-46 
 
 Magnesia . . . ... . 4'16 478 
 
 Potash . . . ,.. ., .,, . . trace '02 
 
 Carbonic dioxide . . . . ' . 22-00 
 
 Silica, 10-36 11-87 
 
 Phosphoric oxide 1'07 1*13 
 
 Sulphuric oxide ...*.,. -90 
 
 Sulphur ': ... -14 
 
 Water ! 4'45 
 
 97-27 99-58 
 
 By reference to the foregoing analyses of different kinds of iron ore, it will be seen 
 that in the case of the richer varieties of ore, calcination or roasting is seldom requisite 
 as a preliminary operation for the purpose of separating volatilisable substances; but 
 this treatment is nevertheless generally advantageous, inasmuch as it has the effect 
 of disintegrating the ore and rendering it more susceptible of reduction in the smelting 
 furnace. 
 
 The calcination of iron ore is carried out by heating it to dull redness in contact 
 with air, either in heaps formed of alternate layers of ore and coal, or in kilns built 
 of brick or stone, from which the roasted ore can be drawn out at the bottom. Care- 
 ful regulation of the temperature to which the ore is heated is essential to the success 
 of the operation, so as to ensure on the one hand the separation of all volatilisable 
 substances and the proper disintegration of the ore without causing the formation of 
 fusible silicates in the case of silicious ore, or the reduction of iron to the metallic state 
 in the case of carbonaceous ore. 
 
 The method of calcination in heaps is cheapest as regards labour, and it offers full 
 
BOASTING OF IRON ORE. 
 
 559 
 
 opportunity for oxidation, but the consumption of fuel is large and the effect produced 
 by the heat is irregular. Fig. 385 represents the construction of an ore heap consisting 
 of alternate layers of ore (bbb) and of fuel (ace), the whole being placed on a bed of 
 large lumps of ore (dd). Sometimes the ore heap is made rectangular and several feet 
 long. 
 
 Fro. 385. 
 
 The Welsh method is to form in the open air a pile of about 5 ft. high having 
 alternate layers of ore and coal, each coal layer being a few inches thick, and the 
 ore layer about a foot in depth. When once lighted the pile burns so long as coal 
 remains, and when the operation is properly carried on so as to prevent the ore fusing, 
 there is a loss in weight of about 30 per cent, on the weight of ore taken. Black 
 band ores of themselves contain sufficient carbonaceous material to continue the roasting 
 when the pile has been ignited. 
 
 Boasting in kilns is, however, generally preferable to open-air roasting, on account 
 of the saving in fuel and the more uniform condition of the residuary mass. The 
 alternate layers of coal and ore are piled in a manner similar to open-air roasting. 
 The kiln is kept charged by withdrawing the bottom layer of calcined ore, and 
 running in a fresh charge at the throat. 
 
 The kilns used for the purpose are variously constructed, sometimes with a fire 
 grate and sometimes without. Fig. 386 represents the circular kilns used at Middles- 
 borough, which are made of cast-iron plates lined with fire brick, and supported upon 
 hollow cast-iron pillars so that a space is left below f >r drawing out the calcined ore. 
 Each kiln has a central cone of cast iron which spreads the ore outwards as it descends 
 towards the openings from which it is drawn out. Bound the lower part of the kiln 
 are a number of holes for admitting air. 
 
 The consumption of fuel in roasting iron ore in these kilns amounts to about five 
 per cent, of the weight of calcined ore. 
 
 The height of these kilns is sometimes upwards of 30 feet, and the diameter 
 24 feet. A kiln having a capacity of 8,000 cubic feet is capable of calcining about 
 800 tons of ore per week. 
 
 The kilns used in Wales have a rectangular form ; they are 18 feet high, 20 feet 
 long, and are wider at the upper part than at the bottom : air is admitted on one side 
 through apertures in the wall above the opening through which the roasted ore is 
 drawn out. These kilns are built in ranges, with a tramway running along the top of 
 them. The capacity of each kiln is such as to hold about 70 tons of ore, and the 
 quantity of ore roasted amounts to about 146 tons per week. 
 
560 
 
 IROK. 
 
 FIG. 387. 
 
 The waste gas discharged from smelting furnaces is sometimes used as fuel for the 
 calcination of iron ore, and the gas is burnt for this purpose in a kiln constructed in 
 the manner represented in vertical and horizontal sections by figs. 387 and 387A. 
 
 The body of the kiln is in the form of a cylindrical shaft (a) from 6 to 10 feet 
 diameter, at the upper end of which is a lateral opening (b) fitted with a sliding door, 
 through which the iron ore is shot into the kiln, and when this is not being used the 
 
 door is kept closed. As the iron ore falls into the 
 kiln it is distributed by the hopper (c). The open- 
 ing (d) admits of the examination of the kiln to 
 ascertain whether it is sufficiently filled. At the 
 bottom of the shaft () are several arched open- 
 ings (Hi, figs. 387 and 387 A) through which the 
 roasted ore is drawn out. The openings (I ra) 
 serve for inserting iron bars by which the mass of 
 ore can be loosened, if requisite, when it is being 
 drawn. The openings (ooo) at different heights 
 serve as sight holes for regulating the temperature, 
 and at the tipper end of the shaft is a tall chimney 
 (n) the mouth of which can be closed by a damper 
 for regulating the operation. The combustible 
 gas is led into the kiln from a pipe (<?) passing 
 round it, and enters through the channel (g) and 
 the passages (&) in the brickwork, of which there 
 are several, as shown in the horizontal section. 
 The air requisite for combustion is supplied 
 through the pipe (K) into a hollow ring extending 
 round the kiln, and it escapes through several 
 openings in this ring. 
 
 The chief disadvantage of this kiln is that the 
 flame does not always penetrate to the centre of 
 the mass of ore in the shaft, but passes up along 
 the wall. This tendency can be counteracted by 
 making the gas tube pass across the kiln under a 
 strong cast-iron ridge extending from side to side, 
 over which the roasted ore can slide down when it 
 is drawn out. 
 
 Economy of fuel may in some cases be ensured 
 by making the calcination of the ore the first stage 
 in the series of changes that take place in the 
 blast furnace, where the heat necessary for the 
 I purpose is obtained from the ascending current 
 L of gases. This process might probably be made 
 more effectual by so increasing the height of the 
 N shaft that it might serve as a substitute for the 
 _ calcining kiln, as in the Cleveland district, where 
 blast furnaces 75 ft. high have been erected with 
 this object ; it is, however, doubtful whether the 
 saving of fuel compensates for the disadvantages 
 arising from the liability of some kinds of fuel 
 and ore to be crushed by the weight of the column 
 of materials in the shaft, and from the reduction 
 in the calorific power of the discharged gases 
 which can be advantageously used as fuel. 
 
 Formerly the coal used as fuel in smelting iron 
 
 FIG. 387 A. 
 
 -C ore was always previously charred, so as to sepa- 
 rate the volatilisable portion. This procedure 
 involves a considerable waste of heating power, 
 amounting to something like 39 per cent., but in 
 some cases it is unavoidable, on account of the 
 character of the coal employed. Thus, for instance, 
 if highly bituminous caking coal were used in the 
 raw state, there would be considerable risk of 
 
 agglomerating the contents of the smelting furnace and disturbing the operation. 
 
 With coal of a friable nature, there would be a danger of stopping up the furnace. 
 
 However, when the coal is sufficiently hard, and does not cake when heated, it is now 
 
 often used in the raw state. 
 
 B 
 
PRODUCTION OF PIG IRON. 561 
 
 In smelting iron ore for the production of pig iron, the reduction of the ferruginous 
 oxide in the ore is effected chiefly, if not entirely, by means of carbonic oxide, the re- 
 action in the case of ferric oxide being represented by the following equation : 
 
 Fe 2 3 + SCO = 3C0 2 + 2Fe 
 160 84 132 112 
 
 according to which the iron thus produced amounts to rather more than three times 
 the weight of the carbon consumed in the state of carbon oxide. 
 
 The supply of carbonic oxide requisite for this reduction is furnished by the com- 
 bustion of the fuel used in the operation, and most likely the whole of the carbon it 
 contains is burnt in such a manner as to yield only carbonic oxide in the first instance. 
 The reaction by which ferric oxide is reduced may be regarded as the completion of 
 the combustion of that portion of the fuel which takes part in it. Carbon in the state 
 of carbonic oxide is in this way capable of reducing nearly four and a half times its 
 weight of ferric oxide, and since the percentage amount of ferric oxide in iron ore 
 generally ranges from 40 to 90 per cent., while the fuel used in smelting maybe taken 
 as containing on the average 90 per cent, of carbon, the fuel consumed in this part of 
 the iron smelting process varies from about one-tenth the weight of the ore up to 
 rather less than one-fourth in the case of very rich ores. 
 
 The conversion of the carbon supplied as solid fuel to the smelting furnace into a 
 gaseous state by combination with oxygen is doubtless a circumstance of great im- 
 portance as regards the reduction of the ferruginous oxide in the ore, for though ferric 
 oxide is readily reduced when heated in con tact with carbon, this condition would not be 
 so easily attained in operating upon the large scale. By the formation of carbonic 
 oxide however, and by the absorption of this gas by the porous lumps of ore, reduction 
 is soon brought about by the reaction above referred to. 
 
 This reaction takes place at a temperature ranging between 140 and 400, but 
 most readily at a red heat. The extent to which it takes place when ferric oxide is 
 heated with carbonic oxide is limited, and the complete reduction of ferric oxide 
 cannot be effected by the proportion of carbonic oxide indicated in the above equa- 
 tion, since carbonic dioxide, which is one of the products of the reaction, is capable of 
 giving up part of its oxygen to metallic iron when brought into contact with it at a 
 temperature above 400. Consequently the reduction of ferric oxide by carbonic oxide 
 at a moderate red heat does not continue after the resulting carbonic dioxide has attained 
 a proportion to the unaltered carbonic oxide of about one half its volume. To ensure 
 complete reduction therefore the ferric oxide must be exposed to the action of a current 
 of the reducing gas, so that the carbonic dioxide formed may be constantly swept away 
 out of contact with the reduced iron. 
 
 Besides the reduction of the ferruginous oxide, it is essential to the production of 
 pig iron that the reduced metal should combine with carbon and form a readily fusible 
 carburet. The precise mode in which this takes place in smelting iron ore is not 
 thoroughly understood, but it is highly probable that it is a result of the decomposi- 
 tion of carbonic oxide according to the following equation : 
 
 2CO = C0 2 + C. 
 
 Except in the case of very unusually rich iron ore, the reduction of the ferruginous 
 oxides requires to be accompanied by the formation of a readily fusible compound ot 
 the earthy admixtures with which most kinds of iron ore are associated. These sub- 
 stances generally consist for the most part of silica, various silicates, clay, calcium car- 
 bonate, or some analogous minerals, as will be seen by reference to the tabulated 
 analyses of the different varieties of iron ore, and as they are not only intimately 
 mixed with the ferruginous oxide of the ore, but are also infusible at the temperature 
 produced in iron smelting, their presence in such an infusible condition would offer a 
 mechanical obstacle to the fusion of the reduced iron. In order to effect the separation 
 of these admixtures, it is therefore necessary to convert them into readily fusible com- 
 pounds. The double silicates containing two or more bases are substances whose 
 fusibility and general characters correspond to the requirements of the case, and con- 
 sequently in smelting iron the separation of the earthy admixtures in the ore is 
 effected by the formation of a vitreous silicate capable of being readily melted so as 
 to separate from the metal in the form of a s 1 ag. 
 
 The fusibility of the silicates varies considerably, not only according to the nature 
 of the basic oxide they contain, but also according to the relative proportions of silica 
 and basic oxide. Those containing only one basic oxide are moreover generally less 
 fusible than the silicates containing two or more basic oxides, and the degree of 
 fusibility is still further influenced by the relative proportion of the basic oxides, as will 
 be seen from the following table of Plattner's results : 
 
 
 
562 
 
 IRON. 
 
 Melting Points of Silicates. 
 
 Temperature of 
 formation 
 
 Melting 
 point 
 
 SiO a 
 
 BaO 
 
 CaO 
 
 MgO 
 
 Al a 3 
 
 FeO 
 
 MnO ! 
 
 PbO 
 
 Ratio of 
 oxygen in 
 bases to 
 oxygen in 
 silica 
 
 2400 
 
 
 
 64-3 
 
 
 
 i 
 
 35-7 
 
 
 
 
 
 
 
 i : 2-0 
 
 2400 
 
 
 
 73-0 
 
 
 
 
 
 27-0 
 
 
 
 
 
 
 
 i : 3-2 
 
 2250 
 
 
 
 59-8 
 
 
 
 
 
 _ 
 
 
 
 
 
 
 
 i : 2-0 
 
 2200 
 
 
 
 69-0 
 
 
 
 40-2 
 
 
 
 
 
 
 
 
 
 i : 2-8 
 
 2200 
 
 
 
 29-1 
 
 70-9 
 
 31-0 
 
 
 
 
 
 
 
 
 
 i : 2-1 
 
 2150 
 
 
 
 52-0 
 
 
 
 48-0 
 
 
 
 
 
 
 
 
 
 i : 2-0 
 
 2100 
 
 
 
 61-8 
 
 
 
 38-2 
 
 
 
 
 
 
 
 
 
 
 
 i : 3-0 
 
 2100 
 
 
 
 37'6 
 
 62-4 
 
 
 
 
 
 
 
 
 
 
 
 i : 3-o 
 
 2100 
 
 
 
 48-6 
 
 10-0 
 
 41-4 
 
 
 
 
 
 
 
 
 
 i : 2-0 
 
 2100 
 
 
 
 45-0 
 
 20-0 
 
 35-0 
 
 
 
 
 
 
 
 
 
 i : 2-0 
 
 2050 
 
 
 
 54-0 
 
 20-0 
 
 
 
 
 
 26-0 
 
 
 
 
 
 
 
 i : 2-0 
 
 2000 
 
 
 
 55-5 
 
 
 
 25-8 
 
 18-7 
 
 
 
 
 
 
 
 
 
 i : 2-0 
 
 1950 
 
 
 
 57-5 
 
 
 
 26-5 
 
 16-0 
 
 
 
 
 
 
 
 
 
 1 : 2-0 
 
 1918 
 
 
 
 40-5 
 
 
 
 37-2 
 
 
 
 22-3 
 
 
 
 
 
 
 
 1 : 1-0 
 
 1832 
 
 
 
 47-0 
 
 
 
 
 
 
 
 
 
 53-0 
 
 
 
 
 
 1 : 2-0 
 
 1789 
 
 
 
 30-5 
 
 
 
 
 
 
 
 69-5 
 
 
 
 
 
 1 : 1-0 
 
 Iron furnace slag 
 
 1445 
 
 58-0 
 
 _ 
 
 22-0 lO'O 
 
 6-0 
 
 2-0 
 
 2-0 
 
 
 
 1 : 2-2 
 
 1876 
 
 1431 
 
 50-0 
 
 
 
 30-0 
 
 
 
 17-0 
 
 3-0 
 
 
 
 
 
 1 : 1-g 
 
 Freiberg copper 
 
 
 
 
 
 
 
 
 
 
 
 slags 
 
 
 
 
 
 
 
 
 
 
 1730 
 
 1360 
 
 50-0 
 
 1-5 
 
 3-0 1-5 
 
 6-0 
 
 38-0 
 
 
 
 
 
 1 : 2-0 
 
 1690 
 
 1331 
 
 48-0 
 
 
 
 4*5 1-5 
 
 9-0 
 
 37-0 
 
 
 
 
 
 1 : 1-75 
 
 1546 
 
 1345 
 
 32-7 
 
 
 
 
 
 
 
 7-0 
 
 60-3 
 
 
 
 
 
 1 : 1-0 
 
 Freiberg lead 
 
 
 
 
 
 
 
 
 
 
 
 slag 
 
 
 
 
 
 
 
 
 
 
 1460 
 
 1 
 
 1317 
 
 36-5 
 
 
 
 4-0 3-0 
 
 8-5 
 
 40-5 
 
 
 
 7-5 
 
 I : 1-25 
 
 The temperatures given as those at which the several silicates are formed and 
 melted refer to the following melting points adopted by Plattner as standards of com- 
 parison : 
 
 Platinum . . . . ' . .... 2534 
 
 Gold , i . . . . 1102 
 
 Silver 1023 
 
 Lead 334 
 
 It seldom happens that the foreign substances associated with iron ore are of such 
 a nature or present in such relative proportions as to produce under the influence of 
 heat a silicate that would be suitable for the purposes of iron smelting. Hence it is 
 necessary to mix with the ore some substance that will contribute to the formation of 
 a fusible slag, by combining with the admixtures in the ore. The substance added 
 with this object is termed flux, and its nature as well as the proportion in which it is 
 used will of course depend upon the composition of the ore to be smelted. 
 
 When the ore contains calcareous substances a silicious material such as forge cinder 
 or the roasted slag from the puddling furnace is added as a flux, or the ore may be 
 mixed in suitable proportions with one containing silica or clay. In the more frequent 
 case of ore containing silica, clay, or other silicates the material used as a flux is lime- 
 stone or burnt lime, in order to effect the formation of a double silicate containing 
 alumina and lime as its basic constituent. 
 
 The published analyses of iron slags are very numerous, and the general characters 
 of them are indicated by the accompanying table. 
 
 The character generally considered to be indicative of the formation of a suitable 
 slag consists in its being sufficiently liquid to separate perfectly from the metal, though 
 as it flows from the surface it is generally somewhat viscous. When solidified the 
 slag should not be vesicular, but compact and homogeneous, without being either very 
 vitreous or stony. The colour of the slag from iron smelting furnaces varies very 
 much, butitdoes not afford much indication of its character. When charcoal is used as 
 fuel, the slag is lighter coloured than that from furnaces in which coke or coal is used. 
 
IRON FURNACE SLAGS. 
 
 563 
 
 Analyses of Slags from Blast Furnaces worked wilh Charcoal. 
 
 
 Ullgren 
 
 Karsten 
 
 Rammels- 
 berg 
 
 Ferrous oxide . 
 
 0-95 
 
 1-45 
 
 0-2 
 
 ' 
 
 2-44 
 
 21-5 
 
 0-06 
 
 1-27 
 
 Manganous oxide 
 
 1-86 
 
 1-40 
 
 11-6 
 
 4-30 
 
 2-20 
 
 292 
 
 33-96 
 
 3-16 
 
 Alumina . 
 
 4-30 
 
 6-25 
 
 6-7 
 
 12-60 
 
 13-04 
 
 2-1 
 
 6-63 
 
 5-71 
 
 Lime 
 
 38-64 
 
 19-71 
 
 26-9 
 
 42-85 
 
 25-67 
 
 
 
 
 
 27-60 
 
 Magnesia 
 
 7-40 
 
 0-70 
 
 
 
 
 
 0-57 
 
 8-6 
 
 10-22 
 
 7-01 
 
 Potash . 
 
 0-30 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Soda 
 
 1-38 
 
 
 
 
 
 
 
 
 
 . , 
 
 
 
 
 
 Silica 
 
 46-37 
 
 70-12 
 
 54-1 
 
 39-60 
 
 53-79 
 
 37-8 
 
 48-39 
 
 55-25 
 
 Phosphoric acid 
 
 trace 
 
 
 
 
 
 
 
 . 
 
 
 
 
 
 
 
 Sulphur . 
 
 0-03 
 
 0-37 
 
 0-5 
 
 0-65 
 
 - 
 
 0-8 
 
 
 
 
 
 
 101-23 
 
 100-00 
 
 10000 
 
 100-00 
 
 97-71 
 
 100-0 
 
 99-26 
 
 100-00 
 
 Percentage of iron . 
 
 0-740 
 
 1-130 
 
 0-160 
 
 
 
 1-900 
 
 16-72 
 
 
 
 0-990 
 
 Ferrous oxide . 
 Manganous oxide 
 Alumina . 
 Limo. 
 Magnesia . 
 Silica 
 Sulphur 
 
 Percentage of iron 
 
 Hartz 
 
 Styria 
 
 Sweden 
 
 Eammelsberg 
 
 Bromeis 
 
 Wehrle 
 
 Oengren 
 
 Sjogren 
 
 Follm 
 
 4-03 
 25-04 
 5-88 
 20-56 
 2-41 
 39-99 
 
 0-44 
 24-85 
 4-96 
 2666 
 1-10 
 41-49 
 
 3-25 
 24-53 
 11-27 
 21-55 
 0-82 
 38-58 
 
 5-83 
 22-18 
 5-12 
 20-00 
 2-18 
 43-58 
 1-11 
 
 1-4 
 28-6 
 2-6 
 10-4 
 1-3 
 54-d 
 1-1 
 
 1-68 
 2-81 
 6-62 
 19-35 
 10-46 
 58-60 
 
 3-29 
 263 
 5-38 
 19-81 
 7-12 
 61-06 
 
 1-0 
 4-1 
 5-1 
 18-0 
 13-3 
 58-1 
 
 97-91 
 
 99-50 
 
 100-00 
 
 100-00 
 
 100-00 
 
 99-52 
 
 99-29 
 
 99-6 | 
 
 3-130 
 
 0-340 
 
 2-420 
 
 4-560 
 
 1-090 
 
 1-310 
 
 2-460 
 
 0-780 j 
 
 Analyses of Slags from Blast Furnaces worked, with Coal. 
 
 
 
 Dowlais 
 
 Dudley 
 
 Russell's 
 Hall 
 
 Belgium 
 
 Russell's 
 Hall 
 
 Cwm- 
 Celyn 
 
 
 Riley 
 
 Percy 
 
 Forbes 
 
 Percy 
 
 Dick 
 
 Noad 
 
 Ferrous oxide . 
 
 3-08 
 
 6-91 
 
 0-76 
 
 1-27 
 
 0-93 
 
 4-94 
 
 1-00 
 
 19-80 
 
 Manganous oxide 
 
 1-02 
 
 1-67 
 
 1-62 
 
 0-40 
 
 2-79 
 
 2-26 
 
 2-20 
 
 1-53 
 
 Alumina . . , . 
 
 11-55 
 
 15-51 
 
 15-13 
 
 14-11 
 
 13-01 
 
 13-05 
 
 12-91 
 
 20-20 
 
 Lime . , \ 
 
 32-09 
 
 23-81 
 
 32-82 
 
 3570 
 
 31-43 
 
 32-53 
 
 29-92 
 
 10-19 
 
 Magnesia . . -\ . 
 
 3-78 
 
 4-38 
 
 7-44 
 
 7-61 
 
 7-27 
 
 1-06 
 
 4-79 
 
 2-90 
 
 Potash . ...'..; 
 
 1-53 
 
 l-'98 
 
 1 92 
 
 1-85 
 
 2-60 
 
 2-69 
 
 0-87 
 
 1-10 
 
 Silica 
 
 45-23 
 
 44-88 
 
 38-48 
 
 38-05 
 
 37-91 
 
 42-06 
 
 47-08 
 
 42-96 ! 
 
 Phosphoric acid . ; 
 
 
 
 0-43 
 
 0-15 
 
 
 
 
 
 0-19 
 
 0-05 
 
 
 
 Calcium 
 Sulphur 
 
 1-04 
 0-83 
 
 0-59 
 0-47 
 
 1-23 
 0-99 
 
 0-82 
 
 365 
 
 1-03 
 
 1-78 
 
 1-32 
 
 
 100-15 
 
 100-63 
 
 100-54 
 
 99-81 
 
 99-56 
 
 99-81 
 
 100-60 
 
 100-00 
 
 Percentage of iron 
 
 2-39 
 
 5-37 
 
 0-60 
 
 0-99 
 
 0-62 
 
 3-84 
 
 0-80 
 
 15-40 
 
 
 1 
 
 
 
 
 
 
 I 
 
 In smelting iron ore with charcoal the temperature of the furnace is generally lower 
 than when coke or coal is used, and on that account the slag requires to be more fusible 
 than in the latter case ; on the other hand, when coke or coal is used as fuel the fusi- 
 bility of the slag requires to be reduced by increasing the proportion of lime relatively 
 
 o o 2 
 
564 
 
 IRON. 
 
 to silica and alumina to such an extent that the fusion of the slag may not take place 
 until after the reduction of the iron has been completed. This is requisite in order 
 to prevent the materials constituting the charge from becoming agglutinated, and to 
 admit of their remaining porous while passing through that portion of the smelting 
 furnace where reduction takes place. This is especially necessary when hot blast is 
 used. 
 
 In smelting silicious iron ore there is a further necessity for the addition of lime, 
 which is even more important than that relating to the production of a suitable fusible 
 slag. This arises from the circumstance that the double silicate containing ferrous 
 oxide and alumina is very fusible, and owing to the tendency to the formation of this 
 silicate in smelting a silicious or argillaceous ore, the result would be that a con- 
 siderable portion of the iron would escape reduction and be lost, besides the production 
 of other serious inconveniences. The presence of a sufficient proportion of lime pre- 
 vents the combination of ferrous oxide with the aluminous silicate in the ore, and in 
 order to prevent it as much as possible the quantity of lime mixed with the ore is such 
 as to form a silicate in which the oxygen of the basic oxides is equal to that of the 
 silica. In some kinds of iron ore the relation existing between the silica and alumina 
 is very different from that generally obtaining in the clay iron ore of the coal-measures, 
 as will be seen from the following table and by reference to the analyses of ores : 
 
 
 Low Moor 
 
 Brierley 
 
 Stanton 
 
 Butterley 
 
 Parkgate 
 
 Cleveland 
 
 Alumina 
 
 23 
 
 24 
 
 20 
 
 26 
 
 24 
 
 25 
 
 Lime .... 
 
 9 
 
 9 
 
 13 
 
 11 
 
 13 
 
 27 
 
 Magnesia . 
 
 8 
 
 7 
 
 17 
 
 9 
 
 19 
 
 14 
 
 Silica .... 
 
 60 
 
 60 
 
 50 
 
 54 
 
 44 
 
 34 
 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 100 
 
 In consequence of this difference, and the greater proportion of alumina in the ores 
 of the Cleveland district, the slags produced in smelting them are much more stony 
 and less vitreous than those produced in smelting other kinds of ore. The relative 
 deficiency of silica as compared with alumina probably renders the slag much less 
 fusible, and may serve to account for the apparent necessity for a very high tempera- 
 ture in smelting the Cleveland ore. 
 
 Analyses of Slags from Cleveland Ores. 
 
 
 Crowder 
 
 Clarence Laboratory 
 
 Ferric oxide 
 
 
 
 _ 
 
 _ 
 
 _ 
 
 8-20 
 
 Ferrous oxide . 
 
 072 
 
 3-64 
 
 0-61 
 
 032 
 
 
 
 Manganoue oxide 
 
 0-35 
 
 1-02 
 
 trace 
 
 0-80 
 
 
 
 Zinc oxide 
 
 
 
 
 
 
 
 
 
 460 
 
 Alumina . 
 
 24-69 
 
 20-72 
 
 22-28 
 
 21-70 
 
 16-00 
 
 Lime 
 
 40-00 
 
 36-88 
 
 40-45 
 
 38-72 
 
 12-15 
 
 Magnesia . 
 
 3-55 
 
 4-25 
 
 7-21 
 
 6-10 
 
 0-57 
 
 Potash 
 
 0-46 
 
 0-50 
 
 
 
 
 
 0-40 
 
 Soda 
 
 0-99 
 
 
 
 
 
 
 
 6-85 
 
 Silica . . ' < 
 
 27-65 
 
 30-40 
 
 27-80 
 
 29-92 
 
 34-82 
 
 Phosphorus 
 
 0-26 
 
 
 
 
 
 0-07 
 
 
 
 Sulphur . 
 
 1-95 
 
 1-34 
 
 2-00 
 
 1-61 
 
 8-80 
 
 Chlorine . 
 
 
 
 
 
 
 
 
 
 1-56 
 
 Water 
 
 
 
 
 
 
 
 
 
 5-60 
 
 
 100-62 
 
 98-75 
 
 100-35 
 
 99-24 
 
 99-55 
 
 Percentage of iron . 
 
 0-560 
 
 2-830 
 
 0-470 
 
 0-250 
 
 
 
 As already mentioned, the conditions under which fuel is burnt in smelting iron oro 
 for the production of pig iron are such that greater part of the carbon is converted 
 into carbonic oxide, and with the exception of those portions which are converted into 
 carbonic dioxide in the reduction of ferric oxide and the carburation of the reduced 
 iron, the whole of the carbonic oxide is discharged from the smelting furnace, together 
 
CHARACTERS OF PIG IRON. 
 
 565 
 
 with the nitrogen of the air consumed in supporting combustion, the carbonic dioxide 
 separated from the limestone used as flux, and the hydrogen or hydrocarbon vapour de- 
 rived from the fuel. The following table gives the percentage composition by volume 
 of the gas discharged from iron smelting furnaces in several different localities : 
 
 Composition of Furnace Gas. 
 
 
 Cleve- 
 land 
 
 Vecker- 
 hagen 
 
 Barum 
 
 Audin- 
 court 
 
 Clerval 
 
 Seraing 
 
 Alfreton 
 
 
 
 
 Langberg 
 
 
 Bunsen 
 
 
 Bell 
 
 Bunsen 
 
 and 
 
 Ebelmen 
 
 and 
 
 
 
 
 Scheerer 
 
 
 Playfair 
 
 Carbonic oxide . 
 
 26-7 
 
 24-20 
 
 8-04 
 
 25-24 
 
 24-65 
 
 28-93 
 
 25-97 
 
 Carbonic dioxide 
 
 11-7 
 
 8-77 
 
 22-20 
 
 12-59 
 
 12-01 
 
 11-39 
 
 777 
 
 Nitrogen . 
 
 60-9 
 
 62-34 
 
 64-43 
 
 55-62 
 
 57-22 
 
 56-64 
 
 55-35 
 
 Marsh gas 
 
 
 
 3-36 
 
 3-87 
 
 
 
 93 
 
 
 
 3-75 
 
 Olefiant gas 
 
 
 
 
 
 
 
 
 
 
 
 
 
 43 
 
 Hydrogen . 
 
 7 
 
 1-33 
 
 1-46 
 
 6-55 
 
 5-19 
 
 3-04 
 
 6-73 
 
 
 100-0 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-00 
 
 lOO'OO 
 
 Since the gas contains almost the whole of the carbon in the fuel consumed, and it 
 is chiefly in the state of carbonic oxide, the gas is combustible, and admits of being 
 usefully employed as fuel for various purposes connected with the smelting operation, 
 so as to effect a considerable economy of fuel. 
 
 Pig iron or cast iron. There are two distinctly different kinds of carburetted iron; 
 one in which the carbon is entirely combined with the iron, and another in which 
 the greater part of the carbon is not in a state of combination, but is disseminated 
 throughout the mass in the form of minute crystalline laminae. 
 
 White cast iron varies in colour from tin white to pale grey. It is very hard 
 and brittle, has a crystalline lamellar texture, and is sometimes vesicular. The frac- 
 ture is bright, and it varies from lamellar to compact and conchoidal, in proportion 
 as the colour is tin- white or grey. The most characteristic variety is called 
 specular iron. The amount of carbon varies from 3 - 5 to 5'24 or 5*75 per cent. 
 
 Grey cast iron varies in colour from pale grey to dark grey. It has generally 
 some slight degree of malleability, but is much harder and more brittle than malleable 
 iron. Its texture is granular, sometimes very fine grained, sometimes coarse grained 
 at the fracture, with minute particles of graphite visible throughout the mass. The 
 amount of carbon varies from 2 to 4'65 per cent. 
 
 The specific gravity of white cast iron is on the average 7"5, that of grey cast iron 
 is about 7*1. 
 
 Grey cast iron melts at about 1600, and more easily in proportion as the amount 
 of carbon is greater. White cast iron melts at a lower temperature, but it does not 
 become so liquid when melted as grey cast iron, which passes suddenly from the solid 
 to the liquid state, while white cast iron remains for some time in a pasty condition. 
 White cast iron when cooled very gradually from the melted state is conver' od into 
 grey cast iron. On the contrary, grey cast iron, when slowly cooled from the melted 
 state, is not altered, except in becoming softer and more malleable ; but when cooled 
 rapidly, it is converted into white cast iron more completely in proportion as the 
 amount of carbon it contains is large. On this account the outer surface of a casting 
 has a hard crust or s k i n in consequence of the more rapid cooling and solidification 
 of that portion of the melted metal which comes into contact with the sides of the 
 mould, and its conversion into white cast iron. This effect is often augmented in prac- 
 tice by lining the mould with iron plates so as to faciliate the solidification of the 
 outer portions of the casting, and form a layer of white cast iron from to \ of an inch 
 thick, while the interior retains the condition of grey cast iron, thus combining the 
 particular advantages of white cast iron as regards hardness and of grey cast iron as 
 regards strength. Melted cast iron dissolves malleable iron and is thus rendered tougher 
 and stronger. 
 
 It has been observed that in large masses of cast iron there is an inequality in 
 the amount of carbon contained in the metal at the exterior and interior portions. 
 There is also a further difference as to the condition in which the carbon exists. At 
 the centre the relative proportion of graphitic carbon as compared with combined 
 carbon is greater than it is at the exterior portions. This difference is more marked 
 
566 
 
 IRON. 
 
 in proportion as the melted metal is more rapidly solidified at the surface, 
 stance referred to ]>y Karsten the following relations obtained : 
 
 In 
 
 Cast iron before melting 
 Outer white portion of casting 
 Inner grey portion of casting 
 
 Total Carbon 
 4-0281 
 5-0929 
 3-8047 
 
 Combined Carbon 
 
 7812 
 
 5-0929 
 
 6106 
 
 Graphite 
 3-2469 
 
 3-1941 
 
 Between the two extremes of white and grey cast iron there are a number of 
 intermediate states in which the white and grey varieties are mixed together in 
 different proportions, constituting what is termedmottled c ast iron. The hardness 
 and strength of these varieties of cast iron differ considerably ; as a rule, the grey 
 iron is stronger than white iron, while this is harder than the grey. White cast iron 
 is however too brittle to be used for structural purposes, except for the purpose of 
 coating the surface of castings with a hard skin or crust by chill casting, as already 
 described. 
 
 The tenacity of cast iron is very much less than that of malleable iron, but its 
 capability of resisting crushing force is very much greater. 
 
 
 Direct tenacity 
 
 Kemstance 
 to direct 
 crushing 
 
 Modulus of 
 rupture of 
 square bars 
 
 Modulus of 
 elasticity 
 
 
 In pounds per square inch 
 
 Cold blast cast iron . 
 
 (from 12,694 
 Ito 18,855 
 
 56,455 
 102,408 
 
 36,693 
 39,609 
 
 14,000,000 
 17,036,000 
 
 Hot blast cast iron . 
 
 (from 13,434 
 Ito 23,468 
 
 72,193 
 
 104,881 
 
 29,889 
 43,497 
 
 11,539,000 
 22,733,000 
 
 Toughened cast iron . 
 
 1 from 23,461 
 Ito 25,764 
 
 129,876 
 119,457 
 
 
 
 
 
 The strength of cast iron is increased by remelting, but reduced when the melting 
 is repeated several times. At very low temperatures it becomes more brittle and 
 weaker. 
 
 The specific heat of specular iron is 0-12983, that of ordinary white cast iron is 
 0-12728. 
 
 The linear expansion of cast iron is greater than that of malleable iron, amounting 
 to gfo between 20 and 560 (red heat) and ^ between 20 and a white heat. 
 
 Pieces of cold cast iron thrown into the melted metal sink to the bottom, but when 
 they have a temperature near the melting point they float on the surface of the melted 
 metal. Hence it would appear that some contraction takes place in the passage from 
 the solid to the liquid state. This character is important as regards the application 
 of cast iron to casting, for the increment of bulk attending solidification ensures the 
 perfect filling of the moulds at that moment, and the production of sharp, well-defined 
 castings. But the greatest amount of expansion or contraction takes place just below 
 the melting point. On account of this contraction between a temperature near the 
 melting point and the ordinary atmospheric temperature, it is necessary to make the 
 mould for castings proportionately larger than the castings are required to be. The 
 contraction for grey cast iron amounts to about one per cent., that of white cast iron 
 is from 2 to 2'5 per cent, of the linear dimensions. The allowance generally made for 
 this shrinkage in casting is ~ or one-eighth of an inch to the foot. Cast iron also 
 undergoes a permanent increase of bulk under the long continued influence of heat. 
 
 White cast iron exposed to an oxidising atmosphere at the ordinary temperature 
 rusts much more slowly than grey cast iron, and this again, provided it does not 
 contain much sulphur or other readily oxidisable substances, rusts more slowly than 
 malleable iron. Specular iron is but very little liable to oxidation under ordinary 
 atmospheric conditions. 
 
 At an elevated temperature grey cast iron becomes coloured by oxidation sooner 
 than malleable iron; white cast iron, on the contrary, becomes coloured even sooner 
 than steel. When cast iron is heated to redness in contact with atmospheric air, the 
 carbon it contains is first oxidised and the metal is rendered somewhat malleable ; 
 then a crust of ferroso-ferric oxide is formed at the surface, which gradually increases 
 in thickness. 
 
 Grey cast iron is most slowly oxidised in this way, and after the removal of its 
 carbon it becomes porous and friable. White cast iron is decarburised more rapidly, 
 and it acquires a malleable steely character. Upon this fact is based the manufacture 
 
CHARACTERS OP PIG IRON. 567 
 
 of malleable cast iron, which consists in heating to redness small castings imbedded in 
 powdered charcoal, chalk, or ferric oxide, so as to be partially protected from the 
 oxidising influence of the air. 
 
 Cast iron melted in contact with atmospheric air becomes covered with a crust of 
 oxide, and by continually removing this crust as it is formed, the whole mass may be 
 converted into oxide ; if the crust of oxide be allowed to remain in contact with the 
 melted metal, this gradually becomes decarburised, steely, and less readily fusible. 
 White cast iron heated in contact with atmospheric air till it assumes a pasty 
 condition is decarburised much more rapidly than by mere heating to redness, and it 
 passes from the steely condition to that of pure iron, without so great a degree of oxida- 
 tion as takes place when the metal is melted. The most important method of 
 manufacturing malleable iron is based upon this fact. 
 
 Cast iron melted under alkaline or earthy carbonates is gradually decarburised and 
 may be wholly converted into malleable iron, if the heat be sufficiently raised, as the 
 iron becomes less fusible. 
 
 Atmospheric air forced into melted cast iron oxidises the carbon and silicon, as 
 well as part of the iron, and converts the remainder into malleable iron. The tem- 
 perature produced in this way is sufficiently high to determine the fusion of the 
 wholly decarburised iron. 
 
 White cast iron heated with concentrated hydrochloric acid is entirely dissolved ; 
 but grey cast iron heated in the same way leaves a residuum of graphite. In both 
 cases the combined carbon of the cast iron enters into combination with a portion of 
 the nascent hydrogen eliminated by the solution of the iron, forming volatile oily 
 hydrocarbons, the vapour of which communicates a peculiar smell to the gas evolved. 
 The oily substance, which appears to be of a nature analogous to petroleum, also collects 
 as a thin film on the surface of the liquid. 
 
 The action of dilute hydrochloric acid upon cast iron is somewhat different. 
 Specular iron is acted upon very slowly at the ordinary temperature ; but, with the 
 aid of heat, both it and grey cast iron are readily dissolved. The hydrogen gas 
 evolved has the characteristic smell, but the amount of hydrocarbon formed appears 
 to be less than when concentrated acid is employed. White cast iron leaves a bulky dark 
 brown carbonaceous residue which is soluble in potash, and when washed and dried is 
 very readily combustible, leaving a black residue containing silica. Grey cast iron leaves 
 a residue consisting partly of graphite, partly of a carbonaceous substance similar to 
 that obtained from white cast iron, and partly of another black carbonaceous substance 
 that is magnetic, taking fire on contact with the air, and leaving a residue of ferric 
 oxide when burnt. 
 
 Cast iron is slowly acted upon by sea water. Cannon balls that had been lying in 
 the sea off the coast of Normandy since 1692 were found to have lost two-thirds of 
 their original weight, and had been converted into a substance that could be cut with 
 a knife, the metallic iron having entirely disappeared. Cannon balls taken from vessels 
 that had been sunk fifty years before near Carlscrona were found to be partly converted 
 into a grey porous graphitic substance, which after exposure to the air for a quarter of 
 an hour in a moist condition became so heated that the adherent water was converted 
 into steam. The substance remaining after the action of sea water upon cast iron 
 appears to be very similar to that remaining, mixed with graphite and the bulky 
 carboniferous substance, after dissolving grey carbon by dilute hydrochloric acid. 
 Karsten considered it to be a compound of iron with three atomic proportions of 
 carbon. Berzelius ascribed the solution of cast iron by sea water to the conjoint 
 action of carbonic acid and oxygen ; wherever cast iron is exposed to the combined 
 influence of fresh water and sea water by tides, this solvent action takes place more 
 rapidly than in sea water. 
 
 Cast iron generally contains besides iron and carbon some other substances, 
 especially manganese,- silicon, phosphorus, sulphur, arsenic, copper, etc., the amounts 
 varying considerably, as shown in the accompanying analyses ( see p. 568), and some 
 of these substances appear to exercise considerable influence in modifying the cha- 
 racters of the metal. 
 
 Silicon is almost always present in pig iron to some extent. It originates from 
 the deoxidation of silica in the process of smelting and the amount varies very much. 
 In white cast iron it generally ranges from O'l to 0'5 per cent. ; in grey cast iron the 
 amount is larger, being seldom less than 0'5, and sometimes exceeding 3 per cent. 
 Karsten found 3 '45 to be the maximum amount of silicon in pig iron. The greater 
 amount of silicon in grey cast iron is considered to be due to the circumstance that it 
 is produced at a higher temperature than white pig iron. Iron produced with hot 
 blast also contains more silicon than that smelted with cold blast. 
 
 It is generally considered that within the ordinary limits of from 0'5 to 3 per cent, 
 the presence of silicon in cast iron does not exercise any prejudicial influence upon the 
 
568 
 
 IRON. 
 
 quality of the metal ; but since it is very detrimental to malleable iron, and reduces 
 its tenacity, it is essential that in the conversion of cast iron into malleable iron the 
 silicon should be separated as much as possible. The greater the amount of silicon 
 in pig iron, the greater also is the waste of metal incurred in its conversion into 
 malleable iron by the puddling operation. 
 
 Locality. Kind of pig 
 
 Fe 
 
 Mn 
 
 c 
 
 Si 
 
 8 
 
 P 
 
 Analyst 
 
 
 
 Com- 
 bined 
 
 Gra- 
 phitic 
 
 
 
 
 Styria (specular iron) . 
 
 94-68 
 
 98 
 
 3-88 
 
 
 
 41 
 
 02 
 
 04 
 
 Widtermann 
 
 Miisen , 
 
 82-86 
 
 10-707 
 
 4-323 
 
 
 
 997 
 
 014 
 
 059 
 
 Fresenius 
 
 Bohemia , 
 
 
 
 22-183 
 
 2-311 
 
 
 
 2-732 
 
 
 
 
 Richter 
 
 Damemora , 
 
 92-906 
 
 1-987 
 
 4-809 
 
 
 
 176 
 
 trace 
 
 122 
 
 Henry 
 
 > 
 
 95-57 
 
 10 
 
 4-2 
 
 
 
 08 
 
 }f 
 
 05 
 
 }i 
 
 New Jersey , 
 
 81-363 
 
 11-50 
 
 6-9 
 
 
 
 10 
 
 137 
 
 
 
 
 
 Tow Law 
 Clyde (white pig iron) . 
 
 92-24 
 
 2-37 
 2-60 
 
 4-1 
 3 
 
 1-52 
 
 23 
 
 1-79 
 
 03 
 
 60 
 
 073 
 95 
 
 Tookey 
 3erthier 
 
 Dowlais 
 
 95-10 
 
 14 
 
 2-84 
 
 1-21 
 
 46 
 
 64 
 
 Riley 
 
 Blaenavon (forge pig) . 
 
 
 
 22 
 
 2-37 
 
 1-09 
 
 73 
 
 76 
 
 W.A. 
 
 Whitehaven (No. 4) 
 
 
 
 07 
 
 35 
 
 1-86 
 
 2-63 
 
 10 
 
 03 
 
 3erthier 
 
 Kussell's Hall (No. 4) . 
 
 92-82 
 
 72 
 
 19 
 
 2-45 
 
 2-07 
 
 32 
 
 1-43 
 
 lenry 
 
 Clyde (foundry) . 
 
 94-63 
 
 50 
 
 1-20 
 
 1-40 
 
 1-53 
 
 35 
 
 39 
 
 Berthier 
 
 
 
 92-30 
 
 
 
 40 
 
 1-80 
 
 2-80 
 
 1-40 
 
 1-30 
 
 n 
 
 Dowlais (No. 3) . 
 
 94-36 
 
 50 
 
 04 
 
 3-10 
 
 2-16 
 
 11 
 
 63 
 
 Riley 
 
 Park End (No. 1) . 
 
 
 
 23 
 
 
 
 3-26 
 
 2-34 
 
 04 
 
 14 
 
 W.A. 
 
 (grey forge) . 
 
 
 
 14 
 
 
 
 3-08 
 
 2-18 
 
 06 
 
 14 
 
 
 
 Pontypool (grey pig) . 
 
 
 
 42 
 
 
 
 2-53 
 
 1-23 
 
 08 
 
 46 
 
 
 
 Blaenavon (No. 3) . 
 
 
 
 66 
 
 
 
 2-64 
 
 1-68 
 
 08 
 
 27 
 
 
 
 (No. 1). . 
 
 
 
 28 
 
 
 
 3-40 
 
 1-36 
 
 07 
 
 29 
 
 H 
 
 Tow Law (No. 1) . 
 
 90-584 
 
 1-837 
 
 
 
 2-795 
 
 4-414 
 
 039 
 
 099 
 
 Riley 
 
 Weardale (No. 1) . 
 
 
 
 1-45 
 
 
 
 3-24 
 
 1-80 
 
 04 
 
 19 
 
 W.A. 
 
 (No. 2) . 
 
 
 
 1-04 
 
 
 
 2-26 
 
 4-25 
 
 06 
 
 07 
 
 
 
 (No. 3) . . 
 
 
 
 trace 
 
 
 
 2-15 
 
 1-18 
 
 12 
 
 19 
 
 
 Stockton-on-Tees (No. 3) 
 
 
 
 06 
 
 
 
 3-31 
 
 1-43 
 
 03 
 
 1-36 
 
 n 
 
 South Bank (No. 2) 
 
 
 
 38 
 
 
 
 3-04 
 
 2-73 
 
 04 
 
 1-30 
 
 ' 
 
 Whitehaven (No. 1) . 
 
 
 
 11 
 
 
 
 3-22 
 
 3-02 
 
 
 
 06 
 
 t 
 
 (No. 2) . 
 
 
 
 07 
 
 
 
 2-24 
 
 2-77 
 
 01 
 
 05 
 
 
 Newland . 
 
 
 
 
 
 
 
 2-83 
 
 59 
 
 03 
 
 10 
 
 
 Beeston (No. 3) . 
 
 
 
 1-00 
 
 __ 
 
 2-83 
 
 2-17 
 
 05 
 
 55 
 
 t 
 
 ,. (No. 4) . . 
 
 
 
 61 
 
 
 
 2-76 
 
 1-80 
 
 84 
 
 55 
 
 : 
 
 Bowling (No. 1) . 
 
 
 
 
 
 
 
 2-90 
 
 1-94 
 
 04 
 
 57 
 
 
 (No. 3) . 
 
 . 
 
 
 
 
 
 2-80 
 
 1-51 
 
 06 
 
 44 
 
 
 Butterley (No. 2) . 
 
 
 
 1-06 
 
 
 
 2-74 
 
 2-36 
 
 02 
 
 1-21 
 
 J 
 
 (No. 4) . 
 
 
 
 40 
 
 
 
 2-60 
 
 1-34 
 
 11 
 
 75 
 
 
 West Hallam (forge pig) 
 
 
 
 94 
 
 
 
 2-57 
 
 1-53 
 
 05 
 
 70 
 
 t 
 
 ,. (foundry . 
 
 
 
 60 
 
 
 
 2-40 
 
 1-50 
 
 06 
 
 34 
 
 
 Wellingbro' (No. 1 grey) 
 
 
 
 24 
 
 
 
 2-85 
 
 1-92 
 
 10 
 
 1 19 
 
 ' 
 
 (mottled) . 
 
 ' 
 
 08 
 
 
 
 2-10 
 
 2-11 
 
 13 
 
 1-07 
 
 
 G-oldendale . 
 
 
 
 98 
 
 
 
 2-54 
 
 2-71 
 
 04 
 
 1-07 
 
 
 Netherton (forge pig) . 
 
 
 
 13 
 
 
 
 2-81 
 
 57 
 
 06 
 
 29 
 
 
 Dudley (grey pig) . 
 
 
 
 49 
 
 
 
 2-61 
 
 1-40 
 
 04 
 
 72 
 
 f 
 
 !> ' 
 
 
 
 06 
 
 
 
 2-56 
 
 1-75 
 
 05 
 
 63 
 
 t 
 
 it ' ' 
 
 
 
 
 
 
 
 3-21 
 
 1-54 
 
 07 
 
 23 
 
 
 
 > 
 
 
 
 
 
 
 
 3-34 
 
 1-18 
 
 07 
 
 55 
 
 t 
 
 
 
 
 
 
 
 
 
 2-87 
 
 1-16 
 
 08 
 
 
 
 > 
 
 India 
 
 
 
 14 
 
 
 
 3-38 
 
 44 
 
 04 
 
 27 
 
 
 Nova Scotia (No. 1 grey) 
 
 94-85 
 
 44 
 
 
 
 350 
 
 84 
 
 02 
 
 19 
 
 Tookey 
 
 Sulphur is almost always present in cast iron, but sometimes the amount is so 
 very small that it can scarcely be determined. In good cast iron the sulphur pro- 
 bably never reaches 0'5 per cent. Pig iron smelted with mineral fuel always con- 
 tains more sulphur than that smelted with charcoal, in consequence of the sulphur 
 present in the coal or coke being transferred to the iron. The presence of sulphur in 
 cast iron renders the metal more fusible, but also more liable to solidify sooner when 
 slightly cooled below the melting point, so as to become quite viscid while still red 
 hot. When specular iron is melted with sulphur, carbon is separated, and it collects 
 
COMPOSITION OF PIG IRON. 
 
 569 
 
 upon the surface of the melted metal in the form of graphite, which differs from 
 ordinary graphite in having no lustre. Grey cast iron melted with sulphur is con- 
 verted into white cast iron, containing a larger amount of carbon than the original 
 grey iron, as shown by the following results obtained by Karsten : 
 
 Combined carbon 
 Graphite . 
 Sulphur . 
 
 The grey cast iron contained 
 
 in 100 parts. 
 . 0-6253 
 . 3-3119 
 . 0-0286 
 
 The resulting white iron 
 contained in 100 parts. 
 . 5-4878 
 
 ] 0-4464 
 
 Hence it appears that while sulphur displaces carbon existing in combination, still 
 up to a certain point the carbon so displaced from combination with one portion of 
 iron is taken up by another portion, until no more can be taken up. The presence 
 of sulphur in cast iron appears, therefore, to determine the existence of the carbon in 
 a state of combination with the iron, and thus to conduce to the production of white 
 cast iron. 
 
 Phosphorus is frequently present in cast iron, sometimes to the extent of one 
 or two per cent. "When amounting to more than 0*5 per cent., it renders the metal 
 brittle but more fusible, very liquid when melted, and capable of remaining much 
 longer in the liquid state. Within certain limits, therefore, the presence of phos- 
 phorus in iron intended for casting is advantageous rather than otherwise. 
 
 Manganese is frequently present in cast iron, and it appears to have some 
 influence in determining a high degree of carburation of the iron, as well as the 
 existence of the carbon in a state of combination with the iron, so that its presence in 
 the materials used in smelting tends to bring about the production of white cast iron. 
 
 Nitrogen is frequently present in very small proportion in pig iron, and it 
 appears to have a considerable influence on the character of the metal. Schafhautl 
 estimated the amount of nitrogen in several kinds of cast iron as follows : 
 
 White cast iron 
 Grey cast iron 
 Specular iron 
 
 0-764 per cent. 
 0-720 
 1-200 
 
 Marchand's experiments led him to doubt the existence of nitrogen in cast iron, 
 and to infer that, if it were present, it never amounted to 0'02 per cent. Bouis, on the 
 contrary, considered that nitrogen is often present in cast iron, and he has stated 
 that very hard cast iron containing much manganese will contain 0'15 per cent, 
 of nitrogen. 
 
 Arsenic. There is much difference of opinion as to the influence of arsenic upon 
 iron, and as to the frequency of its presence ; but there are some well-established 
 instances of cast iron containing a considerable amount of arsenic. Wohler found it 
 in four samples of pig iron, and Schafhautl has stated that the pig iron made at 
 Alais from an arsenical ore contained from 2-5 to 4 per cent, of arsenic. According 
 to Berthier's analyses of some iron shells and shot from Algiers, the metal contained 
 from 9'8 to 27 per cent, of arsenic, constituting a true alloy ; and more recently a 
 wrought-iron shot from Sinope has been found by Wood to contain 16-2 per cent, of 
 arsenic. Karsten however never detected arsenic in pig iron. 
 
 The presence of small amounts of arsenic in cast iron is considered to have the 
 effect, like phosphorus, of rendering the metal more fusible, brittle, and weaker. 
 
 Titanium appears to be frequently present in some kinds of cast iron, and it has 
 been supposed to improve the quality of the metal. The following analyses of 
 titaniferous pig iron by Eiley show the extent to which it is present : 
 
 Iron .... 
 
 93-47 
 
 92-79 
 
 92-04 
 
 87-90 
 
 86-88 
 
 84-26 
 
 Carbon . . { 
 
 3-31 
 
 3-18 
 
 3-11 
 
 31 
 3-12 
 
 1-02 
 3-01 
 
 07 
 2-61 
 
 Silicon . . ' . 
 
 1-86 
 
 3-28 
 
 3-55 
 
 2-59 
 
 2-55 
 
 3-32 
 
 Titanium . . . 
 
 1-15 
 
 71 
 
 47 
 
 79 
 
 1-15 
 
 1-63 
 
 Sulphur 
 
 06 
 
 06 
 
 11 
 
 03 
 
 03 
 
 02 
 
 Phosphorus 
 
 08 
 
 06 
 
 09 
 
 15 
 
 15 
 
 20 
 
 Manganese . 
 
 05 
 
 48 
 
 1-09 
 
 5-85 
 
 6-37 
 
 8-09 
 
 Nickel and cobalt 
 
 
 
 
 
 
 
 06 
 
 O'll 
 
 
 
 Copper and antimony . 
 
 
 
 
 
 
 
 06 
 
 04 
 
 06 
 
 
 100-437 
 
 100-56 
 
 106-46 
 
 100-85 
 
 100-31 
 
 100-27 
 
570 
 
 IROK 
 
 Vanadium has also been found in the pig iron made from the ores of Taberg 
 in Sweden, and in pig iron made from the Seend ore of Wiltshire. 
 
 Chromium has been found in some kinds of pig iron, but there is no evidence to 
 show whether it has any influence on the character of the metal. 
 
 Copper is not unfrequently present in pig iron. When exceeding 0'2 per cent., 
 it is said to render the metal harder, tougher, and stronger. 
 
 Zinc is sometimes present in pig iron smelted from ores containing zinc, and 
 Karsten found cast iron containing traces of zinc to be very soft, but rotten and brittle. 
 
 Aluminum, magnesium, calcium, and potassium are sometimes indicated 
 by analyses as existing in very minute proportion in some kinds of pig iron, but 
 scarcely anything is known of their influence on the characters of the metal. 
 
 The furnace used in the smelting of iron ores consists of a cylindrical chamber, 
 the lower portion of which forms a hearth where the melting of the reduced ore and 
 flux takes place, while the upper portion of the chamber, termed the shaft, serves as 
 a receptacle for the charge while it is undergoing the chemical changes produced by 
 the heated gases resulting from the combustion of the fuel. This takes place at the 
 lower part or hearth of the furnace, and is promoted by a powerful blast of air, the 
 term blast furnace being on that account generally applied to iron-smelting 
 furnaces. According to the kind of fuel used, the nature of the ore to be smelted, 
 
 FIG. 389. 
 
 FIG. 390. 
 
 FIG. 388. 
 
 and a number of other circumstances, the form and dimensions of the blast furnace 
 vary considerably, as shewn by the accompanying sections of the Norwegian charcoal 
 furnace (fig. 388), and the blastfurnace formerly used in this country (fig. 389). 
 
 One of the most approved modern forms of blast furnace is represented in vertical 
 section by fig. 390. The shaft is cylindrical, and is gradually contracted towards the 
 hearth, differing considerably in this respect from the older form of smelting furnace, 
 the interior sectional contour of which is represented by the dotted outline shown in 
 the figure, the shaft (b' b'') having a conical form, the hearth being much more con- 
 tracted, while the side of the furnace between the upper part of the hearth at b and 
 the lower extremity of the shaft at b' is considerably inclined, forming a decided 
 angle at its junction with the shaft and with the hearth. 
 
 At one side of the hearth (h) there is an opening formed by an arch (), called the 
 tymp, and below this arch the hearth is prolonged some distance beyond the piano of 
 
IRON SMELTING. 
 
 571 
 
 the tymp, as far as the block of stone (d) called the dam, which servos to retain the 
 melted iron in the hearth, while the melted clay, floating on the surface of the iron, 
 flows away through a depression in the upper surface of the dam called the cinder 
 notch, along an inclined plane called the cinder fall (s). Through the bottom of one 
 side of the dam there is a channel called the tapping hole, communicating with the 
 hearth, to admit of the melted metal accumulating in the hearth being run out at 
 intervals. This channel is stopped up with sand or clay while the smelting operation 
 is going on, and until the hearth is filled with metal. The side of the furnace at 
 which the dam is situated is called the front, and the opposite side is called the 
 back. At the side of the furnace there is an arched opening called the tuyere hole, 
 and in many instances there are similar openings at the other two sides. 
 
 Air is supplied to the furnace through pipes connected with a powerful blowing 
 engine, and furnished with conical tubes called tuyeres, extending into the furnace 
 as far as the inner surface of the hearth wall. Each tuyere is surrounded with a 
 hollow conical sheath, through which a stream of water is passed to prevent thetuyero 
 from melting. In many cases the air supplied to the furnace in smelting iron ore is 
 previously heated by making it pass through a series of cast-iron pipes which are 
 heated externally. By this means the air is sent into the smelting furnace with a 
 
 Fro. 392. 
 
 temperature varying from 100 to 400, or even 700. Within the last few years, 
 great improvements have been made in the arrangements for heating the blast by the 
 regenerative system introduced by Siemens. One of the stoves used for this purpose 
 is represented by figs. 391 to 394. It consists of a series of parallel walls of fire- 
 brick enclosed in a brickwork chamber, the spaces between the walls being separated 
 by partitions, so as to form a number of rectangular channels, which are alternately 
 heated by the combustion of the gas discharged from the top of the smelting furnace, 
 and cooled by passing through them the air supplied to the furnace. The gas from 
 the furnace is admitted through the valve (/) and, after being burnt in the oven, it 
 escapes through the valve (c) to the chimney. After the mass of brickwork has been 
 sufficiently heated, cold air is admitted through the valve (n) and passes through the 
 oven, escaping from the valve (A) to the smelting furnace. The doors (E, F) at the 
 
572 
 
 IRON. 
 
 Fio. 395. 
 
 top and bottom of the oven are for cleaning out the dust which accumulates in the 
 brickwork channels. .The apertures (a, b) are to admit air for the combustion of the gas. 
 
 Of late years the capacity of iron smelting fur- 
 naces has been very considerably increased, and in 
 some localities furnaces of 30,000 or 40,000 cubic 
 feet capacity, and from 80 to 100 feet high, have 
 been constructed. The chief alteration of shape 
 has consisted in approximation to the cylindrical 
 shaft, but it has been proposed to facilitate the 
 uniform descent of the charge by using a furnace 
 with an enlarged mouth, as shown by fig. 395. 
 With the object of ensuring uniform distribution 
 of the blast and equal temperature in the hearth, a 
 furnace of similar section, but with a long narrow 
 hearth, has been introduced by Eachette. The 
 general arrangement of this furnace is represented 
 by figs. 396 and 397. On each side of the hearth 
 (a a), are a number of tuyeres (b b). 
 
 In working the blast furnace the shaft is kept 
 nearly full, the iron ore, flux, and fuel constituting 
 the charge being shot in at intervals through the 
 throat, as the contents of the shaft sink down. 
 Meanwhile, a continuous supply of air is forced into 
 the lower end of the furnace through the tuyeres, 
 under a pressure of from half a pound to two pounds per square inch in charcoal 
 furnaces, and from two pounds to five pounds per square inch in furnaces worked with 
 coal or coke. The supply of air must be proportionate to the size of the furnace and 
 
 FIG. 396. 
 
 its rate of working, so as to maintain a rapid combustion of the fuel at that part of 
 the furnace immediately above the level of the tuyeres. 
 
 The upper extremity of the furnace shaft is generally contracted, so as to form an 
 aperture nearly one half the diameter of the shaft, which is termed the throat, and 
 it is generally surrounded by a low wall or chimney called the tunnel head, having 
 arched openings at the side for introducing the materials of the charge into the 
 furnace. Iron smelting furnaces are sometimes worked with the throat open, but 
 sometimes the gaseous products given off are collected ; the throat of the furnace is 
 then fitted with a hopper, which can be closed by a movable cone as shown in fig. 390, 
 and the gas is led away through a tube to the furnace, where it is used as fuel. 
 
 In consequence of the different physical conditions of the several products result- 
 
IRON SMELTING. 
 
 573 
 
 ing from the changes that take place in the materials used in smelting iron ore, those 
 products are continuously discharged from the smelting furnace in a manner exactly 
 the reverse of that in which the raw materials are supplied, the melted iron and slag 
 flowing out at the bottom, while the gaseous products of combustion escape from the 
 throat of the furnace. 
 
 FIG. 397. 
 
 -D 
 
 The kind of fuel employed in smelting iron ore has a great influence upon the 
 mode of working. "With porous bulky fuel such as charcoal, combustion takes place 
 more readily than when the more compact and denser kinds of mineral fuel, are used, 
 and, owing to the greater liability of charcoal to crumble under pressure, the furnaces 
 in which it is used are generally much smaller than those worked with coal or coke. 
 Owing to the relatively small amount of earthy substances in charcoal, and its entire 
 freedom from sulphur and phosphorus, the iron melted with charcoal is always much 
 purer than that smelted with mineral fuel, which is often prejudicial to the quality of 
 iron. 
 
 Though the weight of the solid materials constituting the charge amounts to from 
 four to five tons per ton of pig iron made, according to the kind of ore, flux, and fuel 
 used, or even to seven tons and upwards when the materials are used in the raw 
 state, by far the greater quantity of the total material supplied to a blast furnace in 
 smelting iron consists of the atmospheric air by which combustion is supported. 
 Taking carbonic oxide to be the ultimate product, the quantity of air needed to supply 
 sufficient oxygen for combustion would amount to at least five times the weight of the 
 fuel burnt. Consequently the total quantity of air supplied to a blast-furnace per ton 
 of pig iron made according to the consumption of fuel will be as follows : 
 
 
 Tons Cwt. 
 
 Tons 
 
 Tons 
 
 Fuel consumed . . . . * 
 
 1 3 
 
 2 
 
 3 
 
 Quantity of air . .- . . . , 
 
 5 15 
 
 10 
 
 15 
 
 The greater part of the oxygen in this air is consumed in burning that portion of 
 the fuel exclusively concerned in the production of a temperature high enough for 
 effecting fusion of the slag and the reduced iron, and that part of the oxygen which is 
 consumed in producing the carbonic oxitle requisite for the reduction of the ore does 
 not amount to quite half the weight of the iron obtained. 
 
 The temperature of the gas produced by the combustion of the fuel in smelting iron 
 ore, and discharged from the throat of a blast-furnace, differs according to the kind of 
 materials used in the smelting operation, the height of the furnace shaft, and the 
 mode of working. In the case of charcoal furnaces, the escaping gas has generally a 
 temperature ranging from 300 to 400, while that from furnaces worked with coal or 
 
574 IRON. 
 
 coke is much hotter, usually ranging from 500 to 600 and upwards, according to 
 circumstances. Tha whole of the heat corresponding to the temperature of the dis- 
 charged gas is waste heat, except in so far as it has served at an earlier stage of the 
 operation to produce the high temperature requisite for the fusion of the reduced 
 metal and slag at the lower part of the furnace ; and it is only by applying that heat 
 toother purposes for which it may be available that it is possible to realise the full 
 economical efficiency of the fuel consumed in the smelting of iron ore. 
 
 The extent to which the heat generated in smeltiug iron ore is thus dissipated, 
 
 without producing the full useful effect of which it is capable, may be judged of from 
 
 ' the fact that the weight of the gas discharged from a blast furnace exceeds the joint 
 
 weight of the air and fuel consumed, amounting to from eight to seventeen times the 
 
 weight of the pig iron produced. 
 
 But besides the waste of heat due to the high temperature of the discharged gas, 
 there is a further and even more considerable waste of heat resulting from the 
 circumstance that the product of combustion is carbonic oxide. Consequently the gas 
 discharged from the furnace contains a very large proportion of carbonic oxide, 
 together with some hydrocarbon vapour and hydrogen, and in all ordinary cases, at 
 the temperature at which it escapes from the furnace, it is sufficiently inflammable to 
 take fire on coming in contact with atmospheric air. 
 
 The consumption of fuel in iron smelting is one of the most important points con- 
 nected with the economical production of this metal, and it is exceedingly desirable 
 to reduce it to the lowest possible limit. The amount of fuel consumed per ton of pig 
 iron made varies considerably, not only according to the kind of fuel, its calorific power, 
 combustibility, texture, &c., but also according to the kind of ore operated upon and 
 numerous other circumstances. Among these the shape of the furnace has an influence, 
 in so far as it admits of the easy and uniform descent of the charge in the shaft. 
 Another most important difference in the consumption of fuel is that resulting from 
 the use of air at the ordinary atmospheric temperature, or air previously heated to a 
 temperature considerably higher. 
 
 So great is the influence exercised by the use of heated air, that in charcoal 
 furnaces the consumption per ton of pig iron made varies from half a ton to two tons 
 and upwards, according as hot or cold air is used. In smelting with coal or coke the 
 consumption usually amounts to from two to three tons and upwards with cold blast, 
 and with hot blast it is from 23 cwt. to two tons. 
 
 This economy in the consumption of fuel is to a great extent effected by utilising 
 as fuel the combustible gas which is discharged from the throat of the smelting fur- 
 nace, and thus turning to account the heat that would otherwise be wasted. Some- 
 times also the air-blast is heated by fuel of a cheaper kind than that used in the 
 smelting furnace. 
 
 In either case, since the temperature of the air is raised to from 327 to 700 
 and upwards, a considerable quantity of heat is thus conveyed into the smelting 
 furnace, and proportionately less fuel requires to be burnt in the furnace. Moreover 
 the carbon of the fuel burnt in the smelting furnace is for the most part only con- 
 verted into carbonic oxide, while in the case of the fuel burnt in heating the blast it 
 is converted into carbonic dioxide, and thus produces more than three times as much 
 heat as when burnt in the smelting furnace. The full advantage of this difference in 
 heat production is not indeed realised in the smelting furnace, since a portion of the 
 heat developed is carried off in the product of combustion from the hot air stoves, and 
 a further portion is lost by radiation. A further advantage attending the use of heated 
 air, arises from the larger proportion of iron ore to fuel in the charge, and the con- 
 sequent greater power of the contents of furnace to absorb heat from the ascending gas. 
 
 The heat generated when carbon is burnt to carbonic dioxide amounts to 8,000 
 heat units ; but when carbonic oxide is produced the amount of heat generated is not 
 quite one third, or 2,400 heat units, so that as regards heat-producing power the effect 
 is the same as if only one third of the carbon in the fuel consumed had been converted 
 into carbonic dioxide. 
 
 Taking the consumption of fuel in smelting iron ore to be equivalent to a quantity 
 of carbon twice as great as that of the pig iron produced, the quantity of carbon that 
 is converted into carbonic dioxide by the reduction of ferric oxide will amount to only 
 one sixth of the whole. The heating effect produced by the remaining five sixths of 
 the fuel consumed will be less than one third of that which it would produce if the 
 product of combustion were carbonic dioxide. In other words, the only portion of the 
 fuel consumed so as not to be further available as a source of heat is that equivalent 
 to the reduction of the iron in the ore, supposing also the metiil to be in the state of 
 ferric oxide, the carbon thus consumed would be only about one third the weight of 
 the pig iron obtained, and when the consumption of fuel is at the rate of two tons for 
 the ton of pig iron, it will amount to only 16 per cent, of the fuel consumed. 
 
IRON SMELTING. 
 
 575 
 
 Of the heat actually evolved in the smelting operation, a portion is absorbed in 
 raising the temperature of the materials constituting the charge, and a further portion 
 is rendered latent by the fusion of the slag and reduced iron, as well as by some of 
 the chemical changes which take place ; further portions are dissipated as sensible by 
 conduction and radiation, by the heating of the tuyere water and heat carried off by 
 the gas discharged from the furnace throat. 
 
 The rate at which the mixture of carbonic oxide and nitrogen ascends through the 
 column of materials in the shaft of the furnace is determined by the rapidity of com- 
 bustion and fusion at the tuyeres. As the gas comes in contact with the iron ore, 
 reduction will take place, and a portion of the carbonic oxide will be converted into 
 carbonic dioxide. There is, however, a considerable difference in the susceptibility of 
 different ores to reduction. Consequently the reducing effect produced under con- 
 ditions otherwise similar may be very much less in some cases than in others ; and 
 since the oxygen in the ore is a tolerably constant quantity per ton of pig iron, the 
 way to ensure its separation from a difficultly reducible ore is to make the current of 
 gas more rapid, or to increase the temperature of the region in which the reduction of 
 iron ore takes place. The adoption of the former alternative involves the consumption 
 of more fuel, and a proportionate increase in the amount of carbonic oxide in the gas 
 discharged from the furnace. The latter alternative involves a possibility of the re- 
 conversion of carbonic dioxide into carbonic oxide by reaction with carbon of the 
 heated fuel, a change which is attended not only with absorption of heat, but also 
 with an excessive waste of carbon. 
 
 Most probably the reduction of the ferric oxide in the iron ore by reaction with 
 the carbonic oxide in the ascending gas takes place progressively, and since it does not 
 require a very high temperature it may extend for a considerable range in the de- 
 scending column of materials, in proportion to the temperature prevailing and the amount 
 of carbonic oxide in the gas. 
 
 When the iron ore smelted has not been previously calcined, and it contains carbonic 
 acid or water, these substances will be separated during the descent of the charge in 
 the shaft, and will mix: with gaseous products of combustion. This will also' be the 
 case with the carbonic acid of the limestone used as a flux, and if coal be used as fuel 
 its volatilisable portion will likewise be expelled and mix with the ascending gas. 
 In proportion as the extent of this admixture is greater, the gas discharged from the 
 throat of the furnace will have lower heating power when burnt, and therefore it is 
 desirable to reduce the amount of carbonic acid and water vapour in the gas by 
 previous calcination of the ore and limestone whenever the gas is to be used as fuel. 
 
 In all cases the essential conditions for securing economy of fuel are to reduce as 
 far as possible the temperature of the gas before it is discharged, and to convert as 
 much as possible of the carbon into the state of carbonic dioxide. By augmenting 
 the capacity of the blast furnace and the height of the shaft, these effects have been 
 produced to such an extent that the discharged gas has sometimes a temperature of 
 only 190, instead of 600 and upwards, as is the case in some furnaces. At the 
 same time the calorific power of the fuel consumed has been realised to such an extent 
 that the carbonic dioxide in the discharged gas amounts to nearly one-half the volume 
 of the carbonic oxide associated with it, as shown in the following table : 
 
 Locality 
 
 Height of shaft 
 
 Capacity of furnace 
 
 Relative i 
 CO 
 
 rolume of 
 CO' 
 
 
 feet 
 
 c. feet 
 
 
 
 Ferryhill 
 
 80 
 
 16,000 
 
 100 
 
 33-6 
 
 55 
 
 103i 
 
 33,000 
 
 100 
 
 34-9 
 
 Ormesby 
 
 76 
 
 20,640 
 
 100 
 
 34-6 
 
 Consett . 
 
 55 
 
 11,400 
 
 100 
 
 31-9 
 
 
 
 55 
 
 10,300 
 
 100 
 
 40 
 
 Clarence . 
 
 80 
 
 11,500 
 
 100 
 
 44-14 
 
 55 
 
 80 
 
 25,500 
 
 100 
 
 40-3 
 
 55 
 
 
 
 11,500 
 
 100 
 
 39-64 
 
 
 
 
 
 15,500 
 
 100 
 
 35-4 
 
 The advantage of a large furnace with a high shaft may, according to Mr. Bell, 
 be regarded as consisting in the removal of the region at which reduction of ferric 
 oxide and carbon deposition takes place so far from the tuyeres that it never acquires 
 a temperature high enough to induce the conversion of carbonic dioxide into carbonic 
 oxide by combination with carbon. When that is done the furnace has reached the 
 
576 IRON. 
 
 dimensions necessary for working with the maximum of carbonic dioxide in the dis- 
 charged gas, the least loss of sensible heat, and as a consequence with the minimum 
 amount of fuel. 
 
 If these dimensions are exceeded, the result, so far as reduction and carbon im- 
 pregnation are concerned, is the establishment of a region of neutral character in the 
 furnace, which may probably be advantageous in securing regularity of action, but is of 
 no value in altering the power of the gas to hold only a certain amount of carbonic 
 dioxide. 
 
 If the operation can be carried on so that the whole of the carbonic dioxide arising 
 from deoxidation of iron ore and carburation of the reduced iron escapes in the gas 
 discharged from the furnace at a temperature of about 275, the air does not require 
 to be heated beyond 297 to ensure the greatest economy of fuel. 
 
 The use of hot blast also admits of a change in the relation between the solid and 
 gaseous contents of the furnace that has the effect of accelerating the distribution 
 of heat from the gas through the solid materials which are thus heated more rapidly 
 while the gas is more fully saturated with oxygen in consequence of its longer reten- 
 tion in the furnace. Supposing, for instance, a furnace of 6,000 cubic feet capacity 
 has supplied to it by means of hot air a quantity of heat equal to 6 cwts. of carbon 
 over and above what it would receive if the air were driven in at the atmospheric 
 temperature, the proportion of fuel in the charge could be reduced to that extent, and 
 the result would be a reduction of the volume of gas flowing upwards through the 
 contents of the shaft, equal to nearly ten per cent, of the volume the gas would have 
 when cold blast is used and the consumption of fuel amounts to 60 cwts. per ton of 
 pig iron. The carbonic oxide would therefore be retained one-tenth longer in the 
 furnace, and it would have a greater opportunity of heating the solid contents of the 
 shaft and absorbing oxygen from the iron ore. 
 
 As a general result of the experimental investigation carried out by Mr. Bell, it is 
 inferred that the value of hot blast is in no way dependent on the increase of intensity 
 of heat in the furnace, but that the differences in the amounts of fuel requisite for 
 smelting different kinds of iron ore are due to the fact that the rate of reduction must 
 be almost as rapid as the rate of fusion. The means by which economy of fuel is to 
 be effected in accordance with this principle, are to increase the capacity of the furnace 
 sufficiently to ensure the most perfect combustion of the fuel inside the smelting 
 furnace, instead of having carbonic oxide outside the furnace and returning to it the 
 heat so generated in the hot-air apparatus. The improvement on the consumption of 
 fuel in certain cases by the use of hot blast, is therefore not so much due to the 
 additional heat conveyed into the hearth of the smelting furnace as to the increase in 
 the reducing energy of the furnace gas consequent upon the increased temperature to 
 which the ore is raised in the upper portions of the shaft. 
 
 The following tabular statement of the result of analyses of gas taken from different 
 heights in the shafts of blast furnaces will serve in some degree to illustrate the 
 nature of the changes resulting from the chemical reaction taking place between the 
 gaseous products of combustion and the solid materials contained in the shaft. The 
 formation of carbonic oxide is probably one of the most important features of the 
 smelting operation, since there is every reastin to believe that the reduction of the 
 iron ore is effected mainly, if not entirely, by this gas, aided perhaps in some instances 
 by hydrocarbon vapour and gas produced from the fuel by the action of heat. In the 
 immediate neighbourhood of the tuyeres, the oxygen of the air-blast becomes saturated 
 with carbon immediately it comes into contact with the fuel at that part of the 
 furnace. It is at this point that, while the fuel is being consumed, the reduced metal 
 and the earthy substances mixed with it are melted, and, falling down into the hearth, 
 make room for a fresh quantity of the material in the shaft of the furnace to sink 
 down and undergo the same change, while the gaseous mixture of carbonic oxide and 
 nitrogen ascends and communicates its heat to the materials in the upper part of the 
 shaft. 
 
 The volume of the carbonic oxide, formed by the conversion of oxygen into carbonic 
 oxide, is twice that of the oxygen consumed, and when carbon is burnt in this manner 
 by atmospheric air, containing 21 per cent, of oxygen by volume, the gas produced 
 will have the following percentage composition by volume : 
 
 Carbonic oxide .... 34'71 
 Nitrogen 65*29 
 
 100- 
 
 The ratio of oxygen to nitrogen in this mixture is 2658'!, the same as in atmo- 
 spheric air. On reference to the table giving the composition of the gas in the smelting 
 
COMPOSITION OF GAS IN SMELTING FURNACES. 577 
 
 
 Depth be- 
 
 Percentage composition by volume 
 
 Ratio 
 foxy- 
 
 Name of work, etc. 
 
 low the 
 
 
 en to 
 
 
 mouth. 
 
 TSf 
 
 CO 
 
 co a 
 
 H 
 
 3A 
 
 JI 4 
 
 ON 
 
 nitro- 
 gen 
 
 
 feet 
 
 
 
 
 
 
 
 
 
 r 
 
 5 
 
 55-35 
 
 25-97 
 
 7-77 
 
 6-73 
 
 3-75 
 
 0-43 
 
 
 
 0-374 
 
 
 8 
 
 54-77 
 
 20-24 
 
 9-42 
 
 6-49 
 
 8-23 
 
 85 
 
 
 
 375 
 
 ALFBETON ; 
 
 11 
 
 52-57 
 
 23-16 
 
 9-41 
 
 9-33 
 
 4-58 
 
 95 
 
 
 
 418 
 
 Derbyshire. 
 
 14 
 
 50-95 
 
 19-32 
 
 9-10 
 
 12-42 
 
 6'64 
 
 T57 
 
 
 
 368 
 
 Fuel, coal. 
 
 17 
 
 55-49 
 
 18-77 
 
 12-43 
 
 7-62 
 
 4-31 
 
 1-38 
 
 
 
 375 
 
 Hot blast 390. 
 
 20 
 
 60-46 
 
 19-48 
 
 10-82 
 
 4-83 
 
 4-40 
 
 
 
 
 
 340 
 
 Bunsen and Playfair. 
 
 23 
 
 58-28 
 
 26-97 
 
 8-19 
 
 4-92 
 
 1-64 
 
 
 
 
 
 371 
 
 
 24 
 
 56-75 
 
 25-19 
 
 10-08 
 
 5-65 
 
 2-33 
 
 
 
 
 
 381 
 
 
 34 
 
 68-05 
 
 37-43 
 
 
 
 3-18 
 
 
 
 
 1-34 
 
 0-322 
 
 
 i ! 
 
 57-06 
 
 28-61 
 
 11-39 
 
 2-74 
 
 0-20 
 
 
 
 
 
 0-450 
 
 
 
 56-64 
 
 28-93 
 
 11-39 
 
 3-04 
 
 
 
 
 
 
 
 
 
 SEBAINQ ; 
 
 4 
 
 59-64 
 
 28-06 
 
 9-85 
 
 0-97 
 
 1-48 
 
 
 
 __ 
 
 
 
 Belgium. 
 
 9 
 
 62-46 
 
 33-88 
 
 1-54 
 
 0-69 
 
 1-43 
 
 
 
 
 
 
 
 Fuel, coke. 
 
 Q5 
 
 61-67 
 
 35-20 
 
 1-08 
 
 1-72 
 
 0-33 
 
 
 
 
 
 0-301 
 
 Hot blast 100. 
 
 "s 
 
 61-15 
 
 35-35 
 
 1-13 
 
 2-08 
 
 0-29 
 
 
 
 
 
 
 
 112. 
 
 61-34 
 
 36-30 
 
 o-io 
 
 2-01 
 
 0-25 
 
 t ___ 
 
 
 
 
 
 . 
 
 45 
 
 54-63 
 
 45-08 
 
 
 
 0-25 
 
 0-07 
 
 
 
 
 
 0-412 
 
 
 3 
 
 62-34 
 
 24-20 
 
 8-77 
 
 1-33 
 
 3-36 
 
 
 
 
 
 0-334 
 
 VECKERHAGEN ; 
 Hesse- Cassel. 
 Fuel, charcoal. 
 Bunsen. 
 
 4-5 
 6 
 7-6 
 9 
 12 
 
 62-25 
 66-29 
 62-47 
 63-89 
 61-45 
 
 22-24 
 25-77 
 30-08 
 29-27 
 26-99 
 
 3-32 
 3-44 
 3-60 
 7-57 
 
 1-27 
 0-58 
 1-77 
 2-17 
 0-15 
 
 3-10 
 4-04 
 2-24 
 1-07 
 3-84 
 
 
 
 
 
 0-295 
 0-285 
 
 
 15 
 
 64-58 
 
 26-51 
 
 5-97 
 
 1-06 
 
 1-88 
 
 
 
 
 
 0-296 
 
 1 
 
 9 
 
 64-43 
 
 8-04 
 
 22-20 
 
 1-4 
 
 3-87 
 
 
 
 
 
 
 
 BA.BTJM ; 
 
 12 
 
 62-65 
 
 15-33 
 
 18-2 
 
 2-5 
 
 1-28 
 
 
 
 
 
 0-413 
 
 Norway. 
 
 14 
 
 63-20 
 
 18-57 
 
 12-4 
 
 4-5 
 
 1-27 
 
 
 
 
 
 
 Fuel, charcoal. 
 
 17 
 
 64-28 
 
 29-17 
 
 4-2 
 
 1-05 
 
 1-23 
 
 
 
 
 
 0-293 
 
 Scheerer. 
 
 19 
 
 66-12 
 
 20-28 
 
 8-5 
 
 3-29 
 
 1-18 
 
 
 
 
 
 
 
 
 22 
 
 64-97 
 
 26-38 
 
 5-6 
 
 296 
 
 
 
 
 
 
 0-290 
 
 
 throat 
 
 57-79 
 
 23-5 
 
 12-8 
 
 5-82 
 
 
 
 
 
 
 
 
 
 CLERVAL ; 
 
 3 
 
 57-8 
 
 22-24 
 
 13-9 
 
 6-00 
 
 
 
 
 
 
 
 0-434 
 
 France. 
 
 8 
 
 58-1 
 
 22-65 
 
 13-7 
 
 5-44 
 
 
 
 
 
 
 
 
 Fuel, charcoal. -1 < 
 
 12 
 
 59-1 
 
 28-1 
 
 8-8 
 
 382 
 
 
 
 
 
 
 
 0-387 
 
 Hot blast 175 to 190. 
 
 16 
 
 60-5 
 
 33-64 
 
 2-2 
 
 3-59 
 
 
 
 
 
 
 
 
 Ebelmen. 
 
 IT* 
 
 63-0 
 
 35-0 
 
 
 
 1-92 
 
 
 
 
 
 
 
 0-279 
 
 
 tuyere 
 
 56-0 
 
 41-5 
 
 0-3 
 
 T42 
 
 
 
 
 
 
 
 
 
 Ql 
 
 57-2 
 
 24-6 
 
 12-0 
 
 5-19 
 
 0-9 
 
 
 
 " 
 
 0-424 
 
 
 *4 
 
 58-5 
 
 23-8 
 
 11-9 
 
 4-31 
 
 1-3 
 
 
 
 
 
 
 CLEBVAI* ; 
 
 Ql 
 
 60-9 
 
 31-5 
 
 4-1 
 
 3-04 
 
 0-3 
 
 
 
 
 
 0-327 
 
 France. 
 
 8 
 
 608 
 
 31-3 
 
 4-2 
 
 2-77 
 
 0-7 
 
 
 
 
 
 
 Fuel, charcoal. 
 
 1Q2. 
 
 63-0 
 
 35-0 
 
 0-4 
 
 1-06 
 
 0-3 
 
 
 
 
 
 0-206 
 
 Cold blast. 
 
 1 3 
 
 63-0 
 
 35-4 
 
 00 
 
 1-09 
 
 0-3 
 
 
 
 
 
 
 
 
 275 
 
 61-2 
 
 37-5 
 
 
 
 1-13 
 
 o-i 
 
 
 
 
 
 
 
 
 *! 
 
 58-1 
 
 39-8 
 
 0-9 
 
 0-79 
 
 0-2 
 
 
 
 
 
 0-359 
 
 
 throa 
 
 55-6 
 
 25-2 
 
 12-5 
 
 6-25 
 
 
 
 
 
 
 0-453 
 
 AUDINCOTJBT J 
 
 11* 
 
 54-3 
 
 23-6 
 
 14-4 
 
 7'53 
 
 
 
 
 
 
 
 France. 
 
 14f 
 
 56-0 
 
 28-8 
 
 9-5 
 
 5-56 
 
 
 
 
 
 
 
 
 Fuel, charcoal. 
 
 18 
 
 57-8 
 
 30-0 
 
 7-5 
 
 4-59 
 
 
 
 
 
 
 0-391 
 
 Hot blast 250. 
 
 81* 
 
 57-8 
 
 34-2 
 
 3-8 
 
 4-04 
 
 
 __ 
 
 
 
 
 
 26| 
 
 61-6 
 
 36-3 
 
 0-2 
 
 1-79 
 
 
 
 
 
 
 0-298 
 
 "WBBNA ; 
 
 11 
 
 70-5 
 
 13-1 
 
 16-3 
 
 
 
 
 
 
 
 
 
 0-325 
 
 Styria. 
 
 17 
 
 71-3 
 
 10-8 
 
 17-8 
 
 
 
 
 
 
 
 
 
 
 Fuel, charcoal. * 
 
 23 
 
 68-8 
 
 21-5 
 
 9-6 
 
 
 
 
 
 
 
 
 
 0-296 
 
 Hot blast 200. 
 
 27 
 
 66-6 
 
 30-6 
 
 2-6 
 
 
 
 
 
 
 
 
 
 0-270 
 
 Tunner. 
 
 34 
 
 66-3 
 
 20-0 
 
 11-6 
 
 
 
 
 
 
 
 
 
 0-327 
 
 pp 
 
578 
 
 IRON. 
 
 furnace, it will seem that even in the gas at the bottom of the furnace the oxygen it 
 contains almost invariably exceeds this proportion. Mr. Bell is of opinion that this 
 excess of oxygen in the gas at and near the level of the tuyeres is due partly to the 
 formation of cyanogen and the reduction of alkalies accompanying the formation of 
 alkaline cyanides, partly, also, to the reduction of silica, sulphuric oxide, phosphoric 
 oxide, and probably lime : he also considers that a further addition of oxygen to the 
 gas results from the presence of some oxygen in a state of combination with the 
 spongy metal, which cannot be removed by the action of carbonic oxide, but only when 
 the metal is* undergoing fusion and the finely divided carbon mixed with the spongy 
 metal reacts with the oxidised portion. The following tabular statement of the relative 
 quantities of carbon, oxygen, and nitrogen in the gas at different levels of the smelting 
 furnace, as deduced from the foregoing analysis, will show clearly the extent to which 
 there is a variation in the ratio of oxygen to nitrogen by volume. 
 
 throat 
 3 feet 
 8 
 12 
 
 16 
 
 above tuyere 
 
 3 feet 
 
 9f 
 
 19f 
 
 28 
 
 at tymp 
 
 11 feet 
 
 17 
 23 
 
 27 
 at tuyeres 
 
 1 
 
 4 
 
 9 
 
 10 
 
 111 
 
 near tuyeres 
 
 Clerval. 
 
 N 
 
 5779 
 
 57-80 
 58-15 
 59-14 
 60-54 
 63-07 
 56-08 
 
 Clerval. 
 57-22 
 60-92 
 63-04 
 61-22 
 58-17 
 
 Wrbna. 
 70-50 
 71-36 
 68-81 
 66-66 
 66-34 
 
 Seraing. 
 57-06 
 59-64 
 62-46 
 61-67 
 61-34 
 54-63 
 
 O 
 
 24-63 
 25-08 
 25-08 
 22-95 
 19-05 
 17-50 
 21-10 
 
 24-33 
 19-92 
 18-01 
 18-77 
 20-86 
 
 22-94 
 23-24 
 20-39 
 18-01 
 22-63 
 
 25-69 
 23-88 
 18-48 
 18-68 
 18-25 
 22-52 
 
 C 
 
 36-39 
 36-30 
 36-41 
 37-04 
 35-87 
 35-01 
 41-90 
 
 36'66 
 35-70 
 35-54 
 37-55 
 40-79 
 
 29-50 
 28-69 
 31-19 
 33-34 
 
 40-00 
 37-91 
 35-42 
 36-28 
 36-40 
 45-05 
 
 It is also evident from these data that at some distance above the level of the 
 tuyeres the amount of carbon in the gas is less in proportion to the nitrogen than it 
 is at a lower level. This reduction in the amount of carbon is probably due to deposi- 
 tion of carbon by the decomposition of carbonic oxide, which takes place simultaneously 
 with the reduction of ferric oxide, and appears to be a very important feature of the 
 action taking place in the smelting furnace. The temperature at which the elimina- 
 tion of carbon takes place is, according to Mr. Bell, between 399 and 455, and it 
 accompanies the reduction of ferric oxide by carbonic oxide. The carbon thus 
 eliminated appears to be diffused throughout the mass of the iron ore undergoing 
 reduction, and this absorption of the carbon is attended with a considerable disin- 
 tegration of the iron ore, to such an extent that it is often converted into a black 
 pulverulent mass. 
 
 Manufacture of Malleable Iron. There are two methods by which iron maybe pro- 
 duced in such a state as to be capable of being wrought by hammering or rolling. 
 According to the one method, which was formerly the only one adopted, the metal is 
 obtained by heating a suitable iron ore in contact with charcoal burning under the 
 influence of a blast of air, as in a smith's forge. The reduction of the iron in this 
 case is probably effected entirely by carbonic oxide, and since the temperature is not 
 high enough to determine thecarbur.ition of the metal to such an extent as is requisite 
 for the formation of cast iron, the reduced iron is obtained in the state of a coherent 
 spongy mass, termed a bloom, which is then rendered compact by hammering it while 
 red hot so as to weld or unite together the particles into one mass. Only the richer 
 kinds of iron ore can be worked in this way, and even with such ore the production of 
 
THE CATALAN FORGE. 
 
 579 
 
 malleable iron by the direct method is always attended with very considerable waste, 
 since a large portion of the metal escapes complete reduction and, in the state of 
 ferrous oxide, combines with the silicious and earthy portions of the ore, giving rise to 
 the production of a readily fusible slag consisting chiefly of ferrous silicate. 
 
 The other method, by which malleable iron is now chiefly produced, consists in 
 operating upon fusible carburetted pig iron in such a way as to deprive it of the 
 greater part of the carbon and silicon it contains. This is in all cases effected by a 
 partial oxidation of the pig iron, the excess of carbon being burnt together with the 
 silicon, while a portion of the iron is at the same time oxidised. A fusible slag consist- 
 ing of ferrous silicate is thus formed, which reacts upon the remaining carburetted iron, 
 oxidising and separating a further portion of the carbon, as well as other substances 
 which are frequently present in pig iron and would be prejudicial to the quality of 
 malleable iron. 
 
 The production of malleable iron by the direct method is chiefly practised accord- 
 ing to what is termed the Catalan method, which consists in heating the roasted ore 
 in a charcoal fire urged by a blast in a 
 manner very similar in its general cha- 
 racter to that adopted in working a smith's 
 forge. The most important part of the 
 arrangement for this operation is the 
 hearth, which is a nearly cubical cham- 
 ber built of stone and lined with slabs of 
 iron (sstt, fig. 398) at the back and front. 
 The hearth is placed against a wall (N N) 
 through which the tuyere (T) of the blow- 
 ing machine projects into the hearth. The 
 ore to be reduced is broken into pieces 
 the size of a nut and placed against the 
 front of the hearth (s s), while the remain- 
 ing space (M) is filled with charcoal, and 
 when the hearth is filled in this way the 
 upper part of the heap of ore forms a 
 ridge (dfg) the surface (fg] being covered 
 with a layer of closely packed charcoal 
 dust. The fire is then urged by the blast 
 and the ore becomes gradually deoxidised, 
 while the gangue, or earthy substance 
 contained in the ore, combines with a 
 portion of ferrous oxide, forming a fusible 
 silicious slag which runs down to the 
 bottom of the hearth. Fresh charcoal and finely divided ore are constantly supplied 
 to the fire meanwhile, and eventually the deoxidised metal sinks down in a pasty con- 
 dition to the bottom of the hearth where the fragments are worked together by a 
 workman into a spongy mass, which is taken from the fire and rendered solid by 
 hammering while still red hot, so as to crush the metallic particles ; it is then drawn 
 out into bars under a forge hammer. 
 
 In the reduction of iron ore by this method the consumption of fuel is very con- 
 siderable, and, as charcoal must be employed, it can only be practised in districts 
 where wood is very abundant and cheap. This mode of making malleable iron is now 
 almost entirely abandoned in Europe, but in some parts of America it is still adopted, 
 though less extensively than it was at one time. 
 
 A variety of other methods of producing malleable iron direct from iron ore have 
 been proposed from time to time ; thus, for instance, Chenot subjected a mixture of 
 brown hematite or other rich ore with charcoal to a high temperature in close chambers 
 
 FIG. 398 
 
 heated externally, and thus obtained 
 
 spongy metallic iron which was afterwards 
 Gurlt endeavoured to effect the reduction of 
 
 welded together into a compact mass. 
 
 iron ore by heating it in an atmosphere of carbonic oxide, and afterwards to obtain 
 
 the metal in a compact state by welding. 
 
 At a later period Siemens endeavoured to produce malleable iron direct from the 
 ore by dissolving the spongy metal in melted pig iron. In the first instance the iron 
 ore was reduced by heating it with charcoal in vertical cylinders heated externally, 
 but as the expenditure of fuel was too large, a rotating chamber was tried in the in- 
 terior of which the mixture of charcoal and iron ore was heated by the flame of 
 gaseous fuel, and the spongy metal was delivered into a bath of melted pig iron until 
 so much of it had been dissolved as to produce malleable iron. It was, however, found 
 that as the spongy metallic iron absorbed sulphur, the production of good iron by 
 this mode of working could not be accomplished. 
 
 PP2 
 
580 
 
 IRON. 
 
 A further improvement consisted in first melting the iron ore with suitable fluxes 
 and then stirring up the liquid mass with sufficient carbonaceous material to pre- 
 cipitate metallic iron in a compact state while the earthy constituents of the ore 
 formed a fusible slag. It was found that the reduction of iron in this way could be 
 accomplished only at a very intense heat far exceeding the welding heat of iron, but tha 
 iron so produced was very pure, even when there were considerable amounts of sul 
 phur and phosphorus in the ore and the fuel used. 
 
 The operation is carried out in a rotating cylindrical chamber lined with a very 
 refractory material made of bauxite mixed with some fire clay. This cylindrical 
 chamber is mounted on friction wheels and fitted with wheel gearing, so that it can 
 be made to revolve about once in a minute, and thus mix the ingredients of the charge 
 operated upon. At the same time a mixture of gaseous fuel and air is supplied to 
 the chamber to keep up a sufficiently high temperature, and when the reduced iron 
 assumes the form of balls, it is taken out and shingled in the usual manner. 
 
 The production of malleable iron by the indirect method is conducted in three 
 different ways, either by heating pig iron in an open hearth or forge, termed a finery, 
 or in a reverberatory furnace, and, while it is in a partially fused pasty condition, ad- 
 mitting sufficient access of atmospheric air to effect the requisite degree of oxidation ; 
 or b*y submitting melted pig iron to the action of a current of atmospheric air, forced 
 through it until a sufficient degree of decarburisation is effected. When the open 
 hearth is employed the fuel used is generally charcoal, and this method of producing 
 malleable iron is therefore termed the charcoalfinery. When the reverberatory 
 furnace is used, the operation is termed puddling, and the third method of forcing 
 air into melted pig iron, recently introduced by Bessemer, is termed converting. 
 
 The main distinction between the treatment of pig iron in the charcoal finery and 
 in reverberatory furnaces is that in the former case charcoal is employed as fuel, and 
 in contact with the pig iron operated upon, while in the latter case the iron is acted 
 upon in a separate chamber without actual contact with the fuel, so as to admit of 
 coal being used. 
 
 For the production of malleable iron in this way white pig iron containing but a 
 small amount of carbon is most suitable, because in melting it does not become so 
 liquid as grey pig iron, but acquires a viscous condition which admits of its being 
 stirred about so as to present a greater extent of surface to the oxidising influence 
 of the air. Moreover, the carbon existing in a state of chemical combination in white 
 pig iron is oxidised much more readily than the graphitic carbon in grey pig iron. 
 
 The production of malleable iron in the charcoal finery is carried out in different 
 localities with a great variety of modification in the details of manipulation, some of 
 which are determined by special peculiarities in the nature of the material operated 
 upon, while others depend upon less important circumstances. 
 
 The hearth and its accessories are generally constructed in the manner represented 
 by figs. 399 and 400. The vertical section fig. 399 shows the hearth (D) lined with iron 
 
 FIG. 399. 
 
 Fio. 400. 
 
 slabs two or three inches thick, the bottom plate having a cavity (m) beneath it into 
 which water can be run through the tube (I), when it is desirable to cool the contents of 
 the hearth, and hasten the solidification of the iron. The blast of air is furnished by 
 means of bellows (a b) as in a smith's forge, and they are often worked by a water- 
 wheel (c) driving a shaft carrying canes (d, f, e g). At the back of the hearth there is 
 an arched opening'(r) in the wall supporting the hood, and through that opening the 
 
FINERY SLAGS. 
 
 581 
 
 tuyeres of the bellows are fitted so as to deliver the air at a suitable angle into the 
 hearth. 
 
 The pig iron is melted above the tuyere, so that it may not be exposed to the 
 action of the blast until it is melted, and it is then kept in a proper state of fusion by 
 regulating the blast. At intervals the blast is stopped, and after the slag has been 
 run out of the hearth, the mass of metal is lifted up from the bottom and a fresh 
 supply of charcoal placed beneath it. When the consistency of the metal indicates 
 that the decarburation has been carried far enough, the mass is again raised up, 
 covtrred over with charcoal, and subjected to a strong welding heat by which the ad- 
 hering slag is melted and detached, while the iron is brought to such a temperature 
 that it can be hammered into a compact lump or bloom. 
 
 During the first stage of the operation, a slag is produced which is readily fusible 
 and very liquid, but solidifies rapidly, forming a blackish-grey crystalline mass of 
 metallic lustre and frequently iridescent. Notwithstanding the crystalline structure 
 of this slag, it is sometimes porous. Chemically it presents some analogy to olivinenot 
 only in its composition, as shown by the following analyses, but also in its general 
 characters and the crystalline form it sometimes presents. 
 
 Analyses of Poor Slags from the Charcoal Finery. 
 
 
 Mitscher- 
 lich 
 
 Eammels- 
 berg 
 
 Walchner 
 
 Wiegand 
 
 Dugendt 
 
 2FeO.SiO, 
 
 Ferric oxide 
 
 
 
 2-25 
 
 
 
 
 
 074 
 
 
 
 Ferrous oxide 
 
 67-24 
 
 63-51 
 
 62-04 
 
 57-3 
 
 65-83 
 
 70-59 
 
 Manganous oxide 
 
 
 
 
 
 2-64 
 
 4-5 
 
 
 
 
 
 Magnesia . 
 
 0-65 
 
 
 
 1-40 
 
 
 
 
 
 
 
 Lime .... 
 
 
 
 
 
 
 
 2-8 
 
 
 
 
 
 Alumina 
 
 
 
 
 
 
 
 3-0 
 
 
 
 
 
 Potash 
 
 
 
 
 
 0-28 
 
 
 
 
 
 
 
 Silica .... 
 
 31-16 
 
 34-38 
 
 32-34 
 
 32-4 
 
 33-47 
 
 29-41 
 
 
 99-05 
 
 100-14 ' 
 
 98-70 
 
 100-0 
 
 
 
 
 
 Percentage of iron 
 
 52-30 
 
 50-69 
 
 48-25 
 
 44-95 
 
 
 
 
 
 The slag formed towards the end of the operation is less liquid than that just 
 described ; but it does not solidify so rapidly, and forms an agglutinated mass of iron- 
 grey colour, considerable density and compact fracture. The composition of this slag 
 varies very much, as shown by the analyses given in the following table, and the 
 later the period at which it is formed the higher is the amount of iron it contains. In 
 some instances this slag may contain a compound of ferric oxide with ferrous oxide, 
 together with a basic silicate 3FeO.Si0 2 , the percentage composition of which is 78-26 
 ferrous oxide and 21-74 silica. 
 
 Analyses of Rich Slag from the Charcoal Finery, 
 
 
 Winckler 
 
 Sefstrom 
 
 Lam- 
 padius 
 
 Berthier 
 
 Str'dm 
 
 Karsten 
 
 Hoff- 
 mann 
 
 Ferric oxide . 
 
 
 
 
 
 
 
 
 
 _ 
 
 _ 
 
 6-00 
 
 Ferrous oxide . 
 
 82-9 
 
 82-1 
 
 77-00 
 
 74-0 
 
 71-3 
 
 61-2 
 
 71-15 
 
 Manganous oxide 
 
 
 
 6-8 
 
 3-00 
 
 3-6 
 
 
 6-7 
 
 
 Magnesia . 
 
 (3-2 
 
 2-8 
 
 
 
 
 
 2-7 
 
 2-4 
 
 0-46 
 
 Lime . . 
 
 
 
 
 1-75 
 
 1-8 
 
 
 0-9 
 
 1-26 
 
 Alumina . . . . ; , 
 
 
 
 
 3-00 
 
 1-2 
 
 
 
 0-2 
 
 
 Potash . 
 
 
 
 
 
 
 
 
 
 
 
 
 Silica . . ' Y 
 
 13-9 
 
 7-6 
 
 10-25 
 
 19-8 
 
 21-4 
 
 18-1 
 
 21-01 
 
 Phosphoric acid . 
 
 
 
 
 1-75 
 
 
 
 3-7 
 
 
 
 
 100-0 
 
 99-3 
 
 96-75 
 
 100-4 
 
 99-1 
 
 89-5 
 
 99-88 
 
 Percentage of iron . 
 
 64-48 
 
 63-86 
 
 59-89 
 
 57-56 
 
 55-46 
 
 47-6 
 
 59-50 
 
 i 
 
 
 
 
 
 
 
 In addition to the two kinds of slag produced in making malleable iron by the 
 charcoal finery method, a further portion of the metal is converted by oxidation into 
 magnetic oxide which, in the form of forge scale, coats the blooms while they are 
 
582 
 
 IRON. 
 
 being taken from the hearth and welded together or hammered out. In order to 
 reduce the waste of metal, this scale is added to the charge in subsequent operations, 
 and it serves to promote the decarburation of the pig iron. 
 
 In the production of malleable iron by this process, the separation of carbon, 
 silicon, phosphorus and manganese from the pig iron is effected by the oxidation of 
 these substances, partly by the direct action of atmospheric air and partly by the 
 ferric oxide and ferrous oxide in the slag formed towards the end of the operation. 
 When carburetted iron is heated in contact with ferric oxide or magnetic oxide of iron 
 they yield carbonic oxide gas and metallic iron. Under the same conditions silicide 
 of iron yields normal ferrous silicate which forms slag, but this substance is not de- 
 composed when heated to redness in contact with carburetted iron or with carbon, 
 and it is only at a very high temperature that any reaction takes place resulting in 
 reduction of the iron. However, the basic ferrous silicate contained in the slag formed 
 at a later stage of the operation is decomposed even at a red heat by carburetted iron, 
 and while the excess of ferrous oxide in the slag is reduced to the metallic state, carbon 
 is abstracted from the pig iron. 
 
 When the pig iron is first melted down in the hearth, normal ferrous silicate is 
 formed, partly by the oxidation of silicide of iron in the pig, and partly also by the 
 combination of ferrous oxide with silica derived from the ashes of the fuel and from 
 sand adhering to the metal. The slag thus produced takes up the ferrous oxide con- 
 tinually formed by the oxidation of the metal, gradually becoming richer in iron, and in 
 this state it acts as an oxidising agent upon the carbon of the pig iron, at the same time 
 any manganese or phosphorus present in the pig iron is also oxidised and taken up 
 by the slag as manganous oxide and phosphoric acid. 
 
 The conversion of pig iron into malleable iron by this method must not be carried 
 on too rapidly, or the oxidation of the silicon, phosphorus, etc. will not be complete, 
 and consequently the decarburised iron will be impure. This is especially the case 
 with the less pure varieties of pig iron. But it is equally important that the opera- 
 tion should not be protracted so far as to cause unnecessary waste of iron by oxidation. 
 In all cases this waste is considerable, since much more iron is oxidised than is re- 
 quisite for effecting the chemical changes that take place and the malleable iron 
 obtained does not on the average amount to more than from 70 to 75 per cent, of the 
 pig iron operated upon. The waste is less in working white pig iron than in working 
 grey pig iron, which is more liquid when melted, and less readily decarburised. 
 
 The charcoal finery employed in South Wales for the production of a superior kind 
 of iron suitable for the manufacture of tin plate is represented by fig. 401. It consists of 
 
 a rectangular hearth formed of cast- 
 iron slabs, set in brickwork. The 
 bottom slab is cast hollow in order 
 that it may be kept cool by the circu- 
 lation of a current of air through it 
 while the hearth is being worked. 
 The hearth is enclosed within bri^k 
 walls, and the waste gas from the 
 fire is carried off by a chimney. 
 Sometimes the pig iron is heated by 
 this gas, or even melted in a separate 
 furnace before it is introduced into 
 the finery, the object being to econo- 
 mise fuel and to expedite the opera- 
 tion. The charcoal finery is now 
 constructed of larger dimensions 
 than formerly, and the pig iron is 
 first run down under coke so as to 
 obtain it in the state of white pig 
 iron, which is decarburised by heat- 
 ing it with charcoal in the finery 
 hearth. When the charge of metal 
 becomes sufficiently malleable, it is 
 worked under a hammer into a slab- 
 shaped mass called a stamp, which is then broken into pieces, and a number of them 
 piled upon a kind of shovel are raised to a welding heat in the centre of a mass of 
 ignited charcoal; the pile is then again hammered into slabs, which are reheated, 
 cut up, and rolled, first into bars and then into sheets of the size and thickness required. 
 The fuel employed in producing malleable iron from pig iron in this way is almost 
 always charcoal, and the operation is essentially of the same nature as that already 
 described as being carried out in various parts of the continent, the superior character 
 
 FIG. 401. 
 
LANCASHIRE CHARCOAL FINERY. 
 
 583 
 
 of the metal produced and known as charcoal iron being in all cases chiefly due to 
 the purity of the fuel employed. 
 
 The Lancashire hearth or charcoal finery is represented by figs. 402 and 403. The 
 hearth is a shallow quadrangular space iormed of cast-iron plates (a bee, fig. 403). 
 
 FIG. 402. 
 
 Under the hearth is an open shallow cast-iron box having a gutter (/) on one side, 
 and a round hole in the centre, the sides of which are raised so that water may be 
 kept in the box when the furnace is working. Hot blast is used in the operation, 
 and the pipes (k' k") for heating the air are arranged in the flue by which the product 
 of combustion, escaping through the opening (I) is carried off into the chimney (o). 
 
 By means of the pipe () attached to the tuyere 
 box a current of water is made to circulate within 
 the box so as to protect it from the influence of 
 the heat where it projects into the hearth. 
 
 FIG. 403. 
 
 The cast-iron plate (m) is for heating the blooms, and a cast-iron platform (K) is fixed 
 in front of the hearth. The opening (n) serves for the introduction of an iron bar for 
 cleaning the flue. 
 
584 
 
 IRON. 
 
 The substitution of a reverberatory furnace for the open hearth in the production 
 of malleable iron from pig iron was attempted with the object of using coal in the 
 operation, and the introduction of this system by Cort in 1784 was one of the most 
 important epochs in the history of the iron trade. The chief point in which this 
 method of puddling differs from that of the charcoal finery is the decarburation of 
 the pig iron in a chamber separated by- a wall or fire bridge from the furnace in which 
 the fuel is burnt. The metal is thus kept out of contact with the fuel, and is acted 
 upon only by the flame and hot gaseous product of combustion, passing over the fire 
 bridge into the chamber containing the iron. By this arrangement the contamination 
 of the iron with the impurities always present in coal is prevented. 
 
 The construction of a puddling furnace is represented by figs. 404, 405, and 406, in 
 elevation, vertical and horizontal sections. It is built of brick and cased with strong 
 plates of cast iron held together by iron bars. 
 The fire place (bb) is shown in the sections, and 
 at one side of it is the firing hole (a) ; it is 
 separated by the fire bridge (c) from the bed 
 of the working chamber (/), and the arched roof 
 of this chamber dips down at the end next to 
 the chimney (i) so as to bring the flame from 
 the fire place into contact with the pig iron. The 
 bed or hearth (dd) of the working chamber is 
 constructed of cast-iron plates covered with a 
 
 FIQ. 404. 
 
 layer of red iron ore, or some other material consisting chiefly of ferric oxide. 
 The working door by which the opening (g} is closed has a small hole at the bottom 
 through which an iron tool is passed for the purpose of stirring the melted metal. 
 
 Just below the door and level with the surface of the hearth is a small hole called 
 the fl o s s or tap hole, that can be closed with a plug, and through which the slag 
 formed on the hearth is run out at intervals. Sometimes the slag is allowed to run 
 
REFINING PIG IRON. 
 
 585 
 
 away through a hole (&) below the chimney. The door (h) serves for introducing 
 a fresh charge of pig iron into the puddling chamber. The chimney (i) is generally 
 from 30 to 50 feet high, and it is furnished with a damper at the top for regulating 
 the draught, as shown by fig. 404. 
 
 The chemical changes that take place in the production of malleable iron by puddling 
 are essentially the same as those already described under the head of the charcoal finery, 
 the decarburation being effected by the joint action of the atmospheric air passing 
 through the working chamber, and of materials capable of yielding oxygen, such as basic 
 ferrous silicate, forge scale, ferric oxide, etc. 
 
 In the production of malleable iron by puddling, oxidation takes place by the direct 
 action of atmospheric air more readily than in the charcoal finery, since the melted 
 pig iron on the bed of the puddling chamber exposes a larger surface, and it is more 
 readily stirred about than in a hearth ; but the reaction of basic ferrous silicate and 
 other ferruginous materials capable of yielding oxygen to the pig iron is also of con- 
 siderable importance, and in order to promote this reaction, it is requisite to maintain 
 a constant intermixture of the pasty iron with the liquid slag. By the addition of 
 hammer scale or powdered hematite at intervals, the slag is rendered more basic and 
 of a' pasty consistency, and on subsequently raising the heat, the evolution of blue 
 flames of carbonic oxide indicates the progress of the decarburation. 
 
 Under the influence of the free oxygen in the atmosphere of the puddling chamber, 
 a portion of the iron is oxidised, and at the same time the carbon, silicon, sulphur, 
 phosphorus and manganese present in the pig iron are gradually oxidised, either by 
 the direct action of atmospheric oxygen or by reaction with the ferruginous oxides 
 added to the pig iron and formed during the operation. As a result of this oxidation 
 a slag is produced consisting of ferrous and manganous silicates, together with mag- 
 netic oxide of iron and the various earthy impurities present in the pig iron operated 
 upon, as well as part of the sulphur and phosphorus it contained, the one probably in 
 the state of sulphide and the other as phosphate. 
 
 Another mode of conducting this operation is sometimes practised under the name 
 of pig boiling, the distinctive characteristic of which is that the decarburation of 
 the pig metal is effected more by the action of a slag consisting of basic ferrous and 
 manganous silicates than by the direct action of atmospheric oxygen. In this case 
 the bed of the working chamber is made deeper, so that the pasty mass of pig iron is 
 immersed in a bath of the liquid slag, and considerable quantities of materials con- 
 taining ferruginous oxides are added, together with some roasted slag from a previous 
 operation. 
 
 In that modification of the method of producing malleable iron known as p i g 
 boiling, the pig iron does not undergo any preliminary treatment, and the furnace is 
 sometimes charged with liquid metal run in direct from the smelting furnace so as to 
 save the fuel requisite for remelting it. But in puddling the practice is generally to 
 submit the pig iron beforehand to an operation known as refining, which consists in 
 melting the pig iron in contact with coke and with the aid of a blast, in a hearth some 
 what similar to a charcoal finery, but of larger dimensions, and termed arefiningor 
 running out fire. This operation has the effect of partially decarburising the iron 
 and removing from it the greater part of the silicon, corresponding in fact to the first 
 melting of the pig iron under the blast in the charcoal finery operation. 
 
 At the same time grey pig iron is brought into the condition of white pig iron, 
 which is more suitable for conversion into malleable iron by puddling. This change 
 is facilitated by suddenly cooling the metal with water as it runs from the hearth of 
 the refinery. 
 
 The following analyses of refined iron, technically termed metal, serve to show 
 its composition as well as the changes effected by this treatment. 
 
 
 Dick 
 
 Abel 
 
 Noad 
 
 Regnault 
 
 
 
 pig iron 
 
 refined 
 
 pig iron 
 
 refined 
 
 pig iron 
 
 refined 
 
 Iron . 
 
 95-14 
 
 
 
 
 
 
 
 
 
 97'8 
 
 92-3 
 
 p , ( combined 
 
 3-07 
 
 
 
 
 
 
 
 0-30 
 
 1-7 
 
 3-0 
 
 n I graphitic 
 
 
 
 
 
 
 
 2-40 
 
 
 
 
 
 
 
 Silicon 
 
 0-63 
 
 4-66 
 
 0-62 
 
 2-68 
 
 0-32 
 
 0-5 
 
 4-5 
 
 Sulphur . 
 
 0-16 
 
 0-04 
 
 0-30 
 
 0-22 
 
 0-18 
 
 
 
 
 
 Phosphorus 
 
 0-73 
 
 0-56 
 
 0-50 
 
 0-13 
 
 0-09 
 
 
 
 0-2 
 
 Manganese 
 
 trace 
 
 
 
 
 
 0-86 
 
 0-24 
 
 
 
 
 
 iioo- 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-00 
 
 100-0 
 
 100-0 
 
586 
 
 IRON. 
 
 The construction of a refinery or running out fire is represented by figs. 407 and 408. 
 It consists of a rectangular hearth (H) about 2 ft. deep, formed of cast-iron plates set 
 upon a stone bed and arranged in such a way as to make a hollow space for water to cir- 
 culate round the interior, as shown IP the vertical section, fig. 407. The chimney (c) is 
 
 FIG. 407. 
 
 supported upon cast-iron columns, and the spaces between them are closed with cast- 
 iron plates. On each side of the hearth are three blast tuyeres (ttt} connected with a 
 blowing apparatus. At one end of the hearth is a tapping hole, through which the 
 
 FIG. 408. 
 
 contents can be let out as desired into the square mould (B), where the refined metal 
 solidifies in the shape of slabs. 
 
 When the pig iron is not run into the hearth of the refinery direct from the smelt- 
 ing furnace, it is piled up in the hearth upon a bed of ignited coke, and after being 
 covered with more coke, the blast is turned on to accelerate the combustion until the 
 whole of the pig iron has melted and run down upon the hearth. Under the oxidising 
 influence of the blast the carbon and silicon in the pig iron are separated, and a slag 
 consisting of ferrous silicate is produced which floats upon the surface of the liquid 
 metal. Fresh fuel is then added and the heat is maintained until the purification of 
 the metal has been carried far enough. The tap hole at the end of the hearth is then 
 opened and the refined metal is run into the mould (B), where water is thrown upon it 
 until it solidifies and the slag can be detached from the surface of the mass. 
 
 In addition to the partial decarburation of pig iron, and the separation of its 
 silicon by the operation of refining, the sudden solidification of the metal has the effect 
 of preventing the carbon from separating in the graphitic state, and the whole of it 
 remains in combination. The product is therefore in the state of white cast iron, and 
 
SLAG FROM REFINING. 
 
 587 
 
 there is a considerable advantage in this for the puddling treatment, since the com- 
 bined carbon is more readily oxidised than when it is in the graphitic state. 
 
 The slag produced in the operation of refining is vitreous and dark coloured. It 
 consists essentially of ferrous silicate, and generally contains greater part of the man- 
 ganese present in the pig iron operated, as well as some of the phosphorus and sulphur, 
 together with the ash of the coke used as fuel. The composition is shown by the 
 following analyses : 
 
 
 Stourbridge 
 
 Dowlais 
 
 Bromford 
 
 
 Rammelsberg 
 
 Riley 
 
 Forbes 
 
 Ferric oxide 
 
 13-09 
 
 
 
 
 
 
 
 Ferrous oxide 
 
 73-22 
 
 65-52 
 
 54-94 
 
 61-28 
 
 Manganous oxide . 
 
 
 
 1-57 
 
 2-71 
 
 3-58 
 
 Alumina 
 
 
 
 3-60 
 
 5-75 
 
 7'30 
 
 Lime .... 
 
 
 
 0-45 
 
 1-19 
 
 3-41 
 
 Magnesia 
 
 
 
 1-28 
 
 0-60 
 
 0-76 
 
 Silica .... 
 
 13-69 
 
 25-77 
 
 33-33 
 
 22-76 
 
 Sulphur 
 
 
 
 0-23 
 
 
 
 0-46 
 
 Ferrous sulphide . 
 
 
 
 
 
 0-17 
 
 
 
 Phosphorus . 
 
 
 
 1-37 
 
 0-99 
 
 
 
 Copper 
 
 
 
 
 
 trace 
 
 
 
 
 100-00 
 
 99-79 
 
 99-68 
 
 99-55 
 
 Percentage of iron 
 
 66-11 
 
 50-96 
 
 42-84 
 
 47-66 
 
 In working the puddling process, the pig iron to be decarburised is piled up on the 
 hearth of the working chamber, and when it begins to melt some oxidised material in 
 the shape of hammer scale is added. The pasty metal is then broken up and stirred with 
 an iron rabble worked through the small hole in the door ((7, fig. 404). This operation 
 is continued until the whole mass is reduced to a kind of sandy half-melted condition. 
 The heat is then increased, and soon after the whole of the metal is melted, it begins 
 to swell and heave as if boiling, while jets of blue flame issue from all parts of the 
 mass. These are due to the combustion of the carbonic oxide produced by the re- 
 action of the carburetted pig iron with the ferruginous oxides present. As this reac- 
 tion progresses the metal becomes pasty, and in consequence of the oxidation of silicon 
 in the pig iron, and the formation of ferrous silicate, a liquid slag separates from it, and 
 collects upon the hearth. 
 
 The following analyses of slag from puddling furnaces will give an idea of the 
 general composition of this product, which is commonly known by the name of tap 
 cinder. It will be evident from these analyses that in the operation of puddling, 
 phosphorus is removed to a considerable extent. 
 
 
 Chilling- 
 ton 
 
 Dowlais 
 
 Broms- 
 grove 
 
 Bromford 
 
 Wales 
 
 
 - 
 
 Riley 
 
 Percy 
 
 Noad 
 
 Ferric oxide . . * 
 
 16-42 
 
 13-53 
 
 8-27 
 
 17-00 
 
 23-75 
 
 17-11 
 
 
 
 Ferrous oxide . . 
 
 60-14 
 
 57-67 
 
 66-32 
 
 58-67 
 
 39-83 
 
 48-43 
 
 70-48 
 
 Manganous oxide 
 
 2-29 
 
 0-78 
 
 1-29 
 
 0-57 
 
 6-17 
 
 1-13 
 
 12-80 
 
 Alumina . . .- : . 
 
 trace 
 
 1-88 
 
 1-63 
 
 2-84 
 
 0-91 
 
 1-28 
 
 
 
 Lime . . ; . 
 
 0-70 
 
 4-70 
 
 3-91 
 
 2-88 
 
 0-28 
 
 0-47 
 
 
 
 Magnesia . ... 
 
 0-42 
 
 0-26 
 
 0-34 
 
 0-29 
 
 0-24 
 
 0-35 
 
 
 
 Silica . . .. 
 
 15-30 
 
 8-32 
 
 7-71 
 
 11-76 
 
 23-86 
 
 29-60 
 
 8-24 
 
 Iron sulphide . 
 
 
 
 7-07 
 
 
 
 3-11 
 
 0-62 
 
 1-61 
 
 
 
 Sulphur . 
 
 trace 
 
 
 
 1-78 
 
 
 
 
 
 
 
 0-53 
 
 Phosphoric acid 
 
 4-66 
 
 7-29 
 
 8-07 
 
 4-27 
 
 6-42 
 
 1-34 
 
 7-66 
 
 Copper . . - , 
 
 
 
 trace 
 
 trace 
 
 
 
 
 
 
 
 
 
 
 99-93 
 
 101-50 
 
 99-32 
 
 101-39 
 
 102-08 
 
 101-32 
 
 99-71 
 
 i Percentage of iron . 
 
 58-26 
 
 58-04 
 
 57-37 
 
 47-61 
 
 47-60 
 
 44-22 
 
 54-81 
 
588 IRON. 
 
 When the separation of carbon from the metal has advanced to some considerable 
 extent, the oxidising action of the atmosphere in the working chamber is lessened by 
 lowering the damper at the top of the chimney and keeping the iron surrounded by 
 highly carbonised or smoky gas. After this condition has been maintained some time, 
 and the iron has become malleable, or as it is termed ' come to nature,' the fragments 
 are gathered together by means of an iron bar and worked into lumps, which are lifted 
 out of the puddling chamber and consolidated by hammering. 
 
 The elimination of sulphur or phosphorus from pig iron appears to be always 
 necessarily attended with oxidation of the metal in a degree proportionate to the 
 quantity of those substances separated. Consequently it is essential that the amount 
 of those substances in the pig iron operated upon should not be large, in order that 
 the waste of metal thus incurred in producing malleable iron of good quality may not 
 exceed such a limit as would be tolerable in practice. The smaller the amount of 
 phosphorus and sulphur in pig iron, the more readily is it convertible into good malleable 
 iron ; .and so far as the separation of those substances is concerned, the smaller is the 
 necessary waste incurred in the operation. 
 
 The presence of sulphur in pig iron retards the conversion into malleable iron, and 
 in the case of pig iron that is very liquid when melted, there is greater difficulty in 
 bringing the metal into the plastic condition requisite for puddling than when it has 
 a viscid consistency in the melted state, like good white pig metal containing a small 
 amount of carbon and but little sulphur. 
 
 The manganese frequently present in pig iron is generally separated almost en- 
 tirely in the manufacture of malleable iron by puddling. A certain proportion of 
 manganese in the pig iron appears to exercise a beneficial influence upon the quality of 
 the malleable iron produced from it by the operation of puddling, but the precise 
 nature of this influence and the mode in which the manganese acts are still imperfectly 
 understood. Caron's experiments led him to the conclusion that the presence of man- 
 ganese promoted the separation of sulphur during the decarburation, but that it was 
 not similarly effectual in causing separation of phosphorus. By melting sulphuretted 
 pig iron, containing 1*15 per cent, of sulphur, three times without any admixture, the 
 amount of sulphur was reduced to 0-96 per cent. ; by adding to the pig iron 6 per cent, 
 of metallic manganese, and then melting the alloy three times with access of air, the 
 amount of sulphur was reduced to - 8 per cent. The same pig iron melted with 10 
 per cent, of ferric oxide showed a reduction in the amount of sulphur from 1-15 to 1'08 
 per cent., and by melting the alloy of pig iron containing 6 per cent, of metallic man- 
 ganese with 10 per cent, of ferric oxide, the sulphur was reduced to 0'07 per cent. 
 
 The separation of silicon from pig iron takes place very readily in puddling, as in 
 other modes of producing malleable iron, under the influence of oxidation, the result 
 being formation of a readily fusible ferrous silicate. The chief importance attaching 
 to the presence of this substance in the pig iron employed for conversion into malleable 
 iron relates more to the amount of malleable iron obtainable than to any special diffi- 
 culty in the elimination of silicon. In the ferrous silicate constituting the slag of the 
 puddling furnace there is three and a half times as much iron as silicon, so that if 
 both the silica and the ferrous oxide of the slag originate from the oxidation of the 
 pig iron operated upon, the waste of iron in this way will be considerable if the 
 amount of silicon in the pig iron be large. Assuming that the slag is derived entirely 
 from the pig iron by oxidation, the presence of 5 per cent, of silicon would be attended 
 with a loss of 17'5 per cent, of iron due to that cause alone, independently of the loss 
 resulting from the separation of carbon, silicon, and other substances. Hence it is very 
 desirable that the amount of silicon in pig iron intended for conversion into malleable 
 iron should not be very large. 
 
 The proportion of slag produced in puddling depends very much upon the kind of 
 pig iren operated upon. Grey cast iron and unrefined pig iron containing a con- 
 siderable amount of carbon furnish more slag than refined metal, the slag from which 
 is relatively richer in ferrous oxide, and being consequently less fusible than the slag 
 formed from grey cast iron it accumulates upon the bottom of the hearth in a thick 
 layer and may sometimes contain an admixture of ferric oxide formed by the oxida- 
 tion of the basic ferrous silicate or of the ferrous oxide produced in excess of that 
 requisite to combine with the silica and form ferrous silicate. 
 
 The temperature to which iron requires to be heated in the operation of puddling 
 may be expressed as corresponding to 1650C., and assuming that the specific heat of 
 cast iron augments above 350C. in the same ratio that it does up to that temperature, 
 it would be about 0*26 at 1650, so that in this case the quantity of heat requisite to 
 raise the temperature of a pound of iron to that extent above 16 the average atmo- 
 spheric temperature would be 424-84 heat units. 
 
 1650- 16 x 0-26 = 424-84. 
 
GASEOUS FUEL. 589 
 
 A further quantity of heat is consumed in melting the pig iron, which may be 
 assumed as equal to 30 heat units, making the total heat requisite to raise the tem- 
 perature of the iron up to 1650 and to melt it, equal to 454 - S4 heat units, and the 
 quantity requisite for one ton of pig iron 1,018,841 heat units. 
 
 Taking the average calorific power of coal to be 7,778 heat units, it appears there- 
 fore that the quantity of heat actually communicated to the ton of iron in the operation 
 of puddling is not more than that capable of being generated by 131 pounds of coal 
 131 x 7,778 = 1,018,918. 
 
 The consumption of coal in puddling iron may, however, be taken as equal to the 
 weight of pig iron worked, so that out of every ton of coal consumed in the puddling 
 furnace, only 131 pounds, or not more than one-sixteenth part, is really effective in 
 heating the iron. But though the quantity of heat actually communicated to the 
 iron bears only this small proportion to the whole quantity generated by the combus- 
 tion of the fuel used, it must be remembered that under existing circumstances, this 
 large consumption of fuel is unavoidable, since it is indispensable that during the 
 whole of the operation the temperature should be maintained sufficiently high to keep 
 the iron melted or in a pasty condition. For this purpose the rate of combustion 
 must be rapid, and the intensely heated product of combustion must pass rapidly 
 through the working chamber of the furnace. The quantity of heat thus carried 
 away in the gas passing off to the chimney is very large. It has been estimated that 
 in the ordinary puddling furnace, when the consumption of coal is at the rate of 240 
 pounds per hour, the volume of heated gas passing through the working chamber 
 amounts to upwards of 72 cubic feet per second, or sufficient to fill the working chamber 
 twice in that time, and this rapid flow of gas is requisite in order to counteract the 
 influence of conduction and radiation in reducing the temperature of the working 
 chamber. 
 
 It is in consequence of the necessity for maintaining an extremely high temperature 
 in the working chamber of the puddling furnace that only so small a fraction of the 
 heat generated by combustion of the fuel consumed is really effective in heating the 
 iron, inasmuch as it is only the heat corresponding to the difference existing at any 
 moment between the temperature of the iron and the higher temperature of the 
 atmosphere in the working chamber of the furnace that is available for maintaining 
 or raising the temperature of the iron. So long, therefore, as the temperature of the 
 iron in a puddling furnace requires to be 1650, the gas passing into the chimney 
 must be at a temperature not less than that, and the whole of the heat corresponding 
 to the quantity of gas discharged at that temperature into the chimney will be without 
 other useful effect. A variety of arrangements have been devised for turning this 
 waste heat to account in raising steam for driving the machinery of iron works, and 
 one of the simplest plans is to connect the working chambers of the puddling furnaces 
 with a main flue for leading the gas under a steam boiler. 
 
 A still more effectual mode of utilising the waste heat of the gas from puddling 
 furnaces is to transfer this surplus heat to the air used for supporting combustion, 
 and, if the fuel is also used in a gaseous state, this plan of working can be still more 
 advantageously practised. By this means the heat in the gas discharged from the 
 puddling chamber is transferred to the combustible gas used as fuel, and to the air 
 required for its combustion, so that as they both enter the working chamber at a very 
 elevated temperature, the result produced by burning the gas is so much greater than 
 it would be if the gas and air were at the normal atmospheric temperature, and a 
 very considerable portion of the heat which would otherwise pass away and be wasted 
 is turned to account. By thus gradually accumulating, within the working chamber, 
 the heat passing off in the gaseous product of combustion, a very much higher tem- 
 perature may be attained than is possible with ordinary furnaces. 
 
 The use of fuel in the form of combustible gas has long been practised in Germany 
 and other parts of the continent where coal is scarce, and the materials used for the 
 purpose have been either peat, as in Hanover, or wood and lignite, as in Carinthia 
 and Styria, and it is only by such a contrivance that these inferior kinds of fuel could 
 be made available for the puddling of iron and many other purposes. The use of 
 gaseous fuel in this country has been adopted chiefly in connection with the above- 
 mentioned regenerative system introduced by Mr. Siemens, and it has been applied 
 not only in the furnaces used in glass making, etc., but also in puddling furnaces, 
 reheating furnaces, etc. with very great advantage. 
 
 The composition of the gas produced from coal by burning it with an insufficient 
 supply of air for converting the carbon into carbonic dioxide depends somewhat upon 
 the kind of coal and the arrangement of the apparatus used, but the following analyses 
 of the gas obtained at the St. Gobain glass works will serve to illustrate its general 
 character : 
 
590 
 
 IRON. 
 
 Carbonic oxide . 
 Hydrogen . 
 Carburetted hydrogen 
 Carbonic dioxide 
 Nitrogen . 
 Oxygen 
 
 Volume 
 
 237 
 
 8- 
 
 2-2 
 
 4-1 
 61-5 
 
 0-4 
 
 99-9 
 
 24-2) 
 8-2V34-6 
 2-2J 
 
 4-2 
 61-2 
 
 100- 
 
 65'4 
 
 The fuel used by Mr. Siemens for the production of combustible gas is coal of the 
 kind that does not cake when heated. The gas producer employed for the purpose is 
 represented in vertical section by fig. 409 ; it consists of a rectangular brick chamber 
 having one of its sides (B) inclined at an angle of from 45 to 60, and fitted with a 
 grate (c) at the lower end. At the top the chamber has an opening (A) capable of 
 being closed by a tight-fitting lid, and through this opening the coal in small fragments 
 is supplied to the chamber so as to fall upon the inclined plane (B) and slide down 
 until it forms a thick layer above the grate (c). By means of an arch above the 
 inclined plane some of the coal is kept in the position shown in the drawing. Com- 
 bustion takes place immediately above the grate (c), and carbonic oxide is produced 
 either in consequence of the large excess of carbon presented to the air entering 
 between the bars of the grate or by the action of the ignited coal upon any carbonic 
 dioxide that may be formed. At the same time the coal overlying the ignited mass 
 is subjected to destructive distillation, and thus the mixture of carbonic oxide and 
 nitrogen passing up through it becomes mixed with hydrocarbon gases and vapours. 
 The combustible gas thus produced passes out through the flue (H) at a rate regulated 
 by the damper (D) and is then led through an underground conduit to the pipe (j) 
 which is connected with the furnaces where the gas is to be burnt. 
 
 Fm. 409. 
 
 Siemens has applied the regenerative principle of economising heat to the con- 
 struction of puddling furnaces, using gaseous fuel obtained by burning coal so as to 
 produce carbonic oxide, and burning this in the puddling chamber. The general 
 arrangement of this furnace is shown by figs 410, 411, and 412. 
 
 The bed of the puddling chamber (DP) is shown in section in fig. 411. It is 
 formed of cast-iron plates, lined with a layer of ferric oxide and fitted with water 
 bridges at the ends. Beneath the bed of the puddling chamber is a tank, into which the 
 overflow from the water bridges escapes, and the evaporation from this tank keeps the 
 iron plates of the bottom from becoming too hot. The steam passes away through the 
 ventilating shafts (K K, fig. 412). On each side of the bed there are heating chambers 
 (H H) in which the charge of pig iron is heated to redness before it is put into the 
 puddling chamber. 
 
 The front elevation, fig. 410, shows the valve (B) through which the gas is passed 
 into the flue (M) and then into the bottom of the chamber (c, fig. 411). Air is ut the 
 
GAS PUDDLING FURNACES. 
 
 591 
 
 same time passed into the chamber (E, fig. 411) through the flue (N, fig. 410). The gas 
 and air, after passing through these chambers, rise through the flues (G G and F F F, fig. 
 
 FIG. 412. 
 
 41 2) and combustion takes place when they meet in the puddling chamber. The pro- 
 duct of combustion passes away through a corresponding series of flues at the opposite 
 end of the furnace into the chambers (c' B') which become heated before the gas passts 
 
592 
 
 IRON. 
 
 away through the flues (M' N') into the chimney flue (o). When the furnace has worked 
 for some time in this way, and the chambers (c E') are sufficiently heated, the valve (B ) 
 is reversed by means of the lever (p), so that the currents of air and gas are made to 
 pass through the chambers (c' E'), where they become heated, and thus produce, on com- 
 bustion, a proportionately higher temperature. The product of combustion then escapes 
 through the flues (GF)and the chambers (MN)into the chimney flue (o). By thus 
 alternately changing the direction of the currents of gas and air, the waste heat of the 
 product of combustion is arrested in the brick chambers and transferred to the fresh 
 supply of gas and air. The supply of gas and air in suitable proportions is regulated 
 by valves worked by the levers (Q K s, fig. 410). 
 
 The necessity of keeping the pasty mass of iron constantly stirred while decarbu- 
 ration is effected by puddling, makes the work of the puddler so extremely laborious 
 
 FIG. 413. 
 
 that various attempts have been made to carry out this part of the operation by 
 machinery. It is, however, only within the last few years that any of these attempts 
 have been successful in almost entirely doing away with the need for hand labour, 
 at the same time shortening the operation, and economising the fuel as well as iron. 
 The accompanying drawing, fig. 413, represents the arrangement of a mechanical 
 puddler designed by Mr. Eastwood. It is fixed to the outside of the puddling furnace, 
 and when the shaft is driven by the chain, the crank at its extremity raises the rabble 
 by means of the bent lever and makes it move from back to front of the puddling 
 chamber : at the same time the rabble is made to shift from side to side by the rod 
 connecting the gib with the horizontal wheel driven by a worm pinion on the shaft. 
 Every turn of the wheel alters the position of the gib upon which the rabble is sup- 
 ported, and thus the rabble is made to move over every part of the puddling bed 
 This arrangement is one of the simplest forms of mechanical stirrer, but it shares 
 with others the disadvantage of being useless for balling the puddled iron, which 
 is the most laborious part of the operation. 
 
 The idea of making the motion of the puddling chamber itself do the work of 
 stirring the pasty iron has been practically carried out by Danks and Siemens with 
 considerable success. The general arrangement of Banks' puddler is represented by 
 figs. 414 and 415. The puddling chamber is cylindrical in shape and formed of cast- 
 iron segments bolted together. Internally it is lined with fire brick and fettling, 
 while on the outside there is a toothed wheel extending round the whole circumference 
 of the iron casing. The chamber is supported on friction rollers, mounted on pillar 
 blocks (BB), fixed to a bed plate (c, fig. 414), and is made to rotate by the pinion 
 carried by the standard (A). Fig. 415 represents, on a smaller scale, a sectional 
 elevation of the furnace (E, fig. 414)by which the puddling chamber (K) is heated, and 
 the mode in which they are connected together by the flue (H). The ashpit of the 
 furnace is closed and air is supplied partly by a fan through the pipe (G), partly also 
 by the pipe (A), fitted with branches (c) by which the air is delivered in jets above the 
 fuel burning upon the fire grate (F). The iron plate forming the fire bridge between 
 
ROTATORY PUDDLING FURNACES. 
 
 593 
 
 the back of the furnace and the puddling chamber has a coil of pipe cast in it 
 through which water is made to circulate to keep it cool. At the opposite end of the 
 
 FIG. 415. 
 
 puddling chamber is a cover fitted in such a manner as to be moveable and to admit 
 of the ball of malleable iron being taken out. At this end of the puddler there is a 
 fixed flue by which it is connected with the chimney. 
 
 QQ 
 
594 
 
 IEON. 
 
 In working this puddler too much time would be lost by melting the pig iron in it ; 
 an ordinary cupqla is used for the purpose, or the metal is run in directly from the 
 smelting furnace. 
 
 The decarburised iron obtained by puddling is removed from the working chamber 
 of the furnace in lumps termed puddleballs, which consist of intensely heated 
 metallic iron in a spongy state, intermixed with melted slag and oxidised iron. In 
 order to separate these admixtures and reduce the metallic iron to a compact and uni- 
 form mass, the puddle balls are either hammered or pressed while at a welding heat. 
 This operation is termed blooming or shingling. The hammers employed for 
 the purpose are termed forge hammers; they are very powerful and are constructed 
 of cast iron, as represented by fig. 416. 
 
 XIXIXIXIXCx 
 
 xtxnxixi^ix 
 
 FIG. 416. 
 
 The massive beam (c) is 8 or 10 ft. long, and one end is supported on a fulcrum 
 (/) upon which the beam is moveable, while the other end is fitted with a shaped head 
 (d), and is lifted by the wipers (bbb) of the cam wheel (a), by the revolution of which 
 the hammer head of the beam is made to fall at the rate of 70 or 80 strokes a minute 
 upon the anvil (e) where the puddle ball is placed. A steam hammer is often used 
 for this purpose, consisting of a block of iron weighing several tons, attached to the 
 piston of a steam engine fixed above it, so that the block can be lifted vertically in 
 guides fitted to the framework and let fall upon the puddle ball placed on an anvil. 
 
 The machines employed for compressing puddle balls are of various forms, and 
 are termed squeezers. One of the most usual kinds represented by fig. 417 con- 
 
 FIG. 417. 
 
TREATMENT OF PUDDLE BALLS. 
 
 595 
 
 sists of a lever worked upon a fulcrum at the centre, by a crank connected to one end, 
 so that the jaws are alternately brought at the rate of 60 or more strokes a minute 
 nearer to the corresponding anvil faces of the stationary portion of the machine upon 
 which the puddle balls are placed to receive the pressure. 
 
 Squeezers of this kind are now employed more generally than hammers for con- 
 solidating the puddle ball and converting it into a bloom. Sometimes the squeezer is 
 of a different construction and consists of a strong cylindrical casting furnished at 
 the inner surface with blunt triangular teeth, and within which a small rotating 
 cylinder having similar teeth on the outer surface is fitted excentrically in such a 
 manner that as it revolves the distance between the two cylinders gradually diminishes, 
 and when the puddle ball is placed between them at the widest part it is gradually 
 submitted to increasing pressure as it is carried forward by the rotating cylinder 
 until it reaches the narrowest part, and is then ready for the rolling mill. 
 
 The puddle ball produced by Banks' rotatory puddler is very much larger than 
 those produced by hand labour, and it often weighs five or six hundredweight. The 
 ordinary form of squeezer is therefore 
 insufficient for the purpose of working 
 these large balls, and a specially con- 
 structed machine is necessary. It con- 
 sists of two corrugated rollers (DD, fig. 
 418) about 4 feet long and 18 inches 
 diameter, mounted side by side on axes 
 turning in journals in the strong frame 
 (B), and having at one end geared wheels, 
 as shown in fig. 419, by which they can 
 both be made to revolve in the same 
 direction at the rate of fifteen or twenty 
 revolutions per minute. Above these 
 rollers, and mounted in the same frame, 
 is a large excentric cam (A), which re- 
 volves in the same direction as the two 
 rollers (D D). The periphery of this ex- 
 centric revolves at the same rate as the 
 circumference of the two rollers, and the 
 puddle ball in passing between the ex- 
 centric and the rollers is submitted to a 
 gradually increasing pressure. In order J 
 to consolidate the mass of iron while U! 
 passing between the rollers, there is fitted 
 on one side of the squeezer a horizontal 
 
 steam hammer, as shown in fig. 419, the F IG . 418. 
 
 ram (H) of which strikes the end of the 
 ball as it is being squeezed. The head of this ram is seen at c, in fig. 418. 
 
 FIG. 419. 
 
 When the puddle ball has passed between the cam and rollers twice, it is removed 
 and lifted by a crane to the reheating furnace before being taken to the rolls. 
 
 Hydraulic power is sometimes employed with advantage for compressing and con- 
 solidating large masses of decarburised iron, since intense pressure can be produced 
 
 QQ2 
 
596 
 
 IRON. 
 
 without concussion, and the massive foundations requisite for steam hammers can be 
 dispensed with. , An hydraulic machine of this kind constructed by Haswell of Vienna 
 consists of a long vertical hydraulic press the ram of which acts downwards against a 
 table serving as an anvil. This ram is lifted by a smaller hydraulic press with which 
 it is connected, and as the ram rises the water expelled from the larger cylinder is 
 returned to an accumulator containing a piston, upon the surface of which steam can 
 be admitted when it is desired to move the ram rapidly. When the full power of the 
 machine is required, the connection between the press and the accumulator is cut off, 
 and the press is connected with a pair of hydraulic pumps driven by a direct-acting 
 steam engine. 
 
 The hammering or squeezing of the puddle balls occupies only a few seconds, and 
 when it has been somewhat consolidated in this way, it is termed abloom; it is then 
 rapidly passed several times between grooved rollers while still red hot and is thufa 
 drawn out into a bar. The rollers used for this purpose, constituting what is termed 
 a forge train, consist of two pairs of rollers (JR F) fitted in frames and driven b/ 
 machinery. The pair of rollers (B), called roughing rolls, have corresponding V-- 
 shaped grooves round the surfaces. The other pair of rollers, termed finishingrolls, 
 
 FIG. 420. 
 
 have flat grooves, and in both cases the grooves gradiially decrease in size from one end 
 of the roller to the other, so that by passing the blooms successively through several 
 pairs of grooves they are reduced to bars, measuring from 7 to 3 inches in width, by 
 from 1| to 5 an inch in thickness. In this condition the iron is termed pu ddle bars 
 or No. 1 iron. 
 
 The iron after leaving the rolls in the state of puddle bars, and while still hot, is 
 tut up into short lengths, by means of powerful shears, and the pieces are tfed together 
 
 with strong wire in bundles 
 termed piles, which are then 
 brought to a welding heat in a 
 reverberatory furnace, called 
 the reheating furnace or 
 mill furnace, constructed 
 somewhat like a puddling fur- 
 nace, as shown in fig. 421, in 
 vertical section. The hearth (a) 
 of this furnace on which the iron 
 piles are placed is made of sand 
 and it slopes down towards the 
 chimney flue, so that any slag 
 that is formed may run down 
 FIG. 421. and escape through the hole (6), 
 
 leaving the hearth quite dry. 
 
 The piles are raised as rapidly as possible to a full welding heat in the mill fur- 
 nace, and are then removed from the hearth with tongs to mill rolls of a similar kind 
 to those already described, but more highly finished, and they are again drawn out 
 into bars, which are a second time cut into short lengths, piled and submitted to the 
 same operations of heating and rolling several times according to the required quality 
 of the iron. After the first rolling of the iron into puddle bars, hammering is some- 
 times substituted in the place of drawing out between rollers. It is in this series of 
 operations that the iron acquires texture, and that close uniform and continuous fibre 
 upon which the strength and general good quality of malleable iron is considered to be 
 chiefly dependent. The mode in which the pieces of iron are arranged in the piles is 
 considered to be of great importance as regards the result obtained. 
 
CHARACTERS OF MALLEABLE IRON. 
 
 597 
 
 During the reheating of the piles in the mill furnace a certain proportion of slag 
 is produced which has a composition very similar to that of the slag from the puddling 
 furnace ; but the silica it contains is mainly derived from the sand forming the hearth 
 of the furnace. 
 
 Analyses of Mill-furnace Slag. 
 
 
 Dowlaia 
 
 Wasseralfingen 
 
 {Sweden 
 
 - 
 
 
 Riley 
 
 Rammelsberg 
 
 Dugent 
 
 Noad 
 
 Ferric oxide . 
 
 
 
 8-49 
 
 
 
 5-00 
 
 Ferrous oxide 
 
 66-01 
 
 55-36 
 
 65-83 
 
 62-50 
 
 Manganous oxide . 
 
 0-19 
 
 
 
 0-74 
 
 
 
 Alumina 
 
 2-47 
 
 
 
 
 
 9-60 
 
 Lime .... 
 
 0-81 
 
 0'36 
 
 __ 
 
 
 
 Magnesia 
 
 0-27 
 
 trace 
 
 
 
 
 
 Silica .... 
 
 2871 
 
 34-00 
 
 33-47 
 
 32-00 
 
 Sulphur . 
 
 0-11 
 
 
 
 
 
 
 
 Ferrous sulphide . 
 
 
 
 
 
 
 
 1-95 
 
 Phosphoric acid 
 
 1-22 
 
 
 
 
 
 0-25 
 
 Copper .... 
 
 trace 
 
 
 
 
 
 
 
 
 99-79 
 
 98-21 
 
 100-04 
 
 101-30 
 
 Percentage of iron 
 
 51-34 
 
 49-0 
 
 51-20 
 
 45-34 
 
 When all these successive operations have been completed, the iron is in the con- 
 dition known as merchant iron, and the different degrees of quality are indicated 
 as No. 2, No. 3, etc., or as ' common,' ' best,' and ' best best,' as well as by particular 
 brands. 
 
 Besides the waste of iron resulting from the formation of slag in refining, puddling, 
 etc., there is always a further waste due to the oxidation of hot iron while passing 
 through the operations of shingling, hammering, and rolling to which it is subjected. 
 The product of this oxidation consists chiefly of magnetic oxide, which forms a crust 
 on the surface of the hot iron and falls off in scales, constituting what is known as 
 hammer scale or mill scale. 
 
 The total waste of iron in the conversion of pig iron into malleable iron varies 
 according to the kind of pig iron operated upon, and the amount of impurities to be 
 got rid of; to some extent also it depends upon the skill of the workmen. The greater 
 part of the waste of iron takes place in the refining, and on the average it amounts to 
 about 10 per cent, of the pig iron. In puddling refined iron the waste does not amount 
 to more than from 4 to 7 per cent. In the mill furnace the waste is much less, vary- 
 ing from 5 to 6 per cent, according to the number of times the piles are reheated, and 
 the size to which the iron is rolled. 
 
 The consumption of fuel in the various stages of the conversion of pig iron into 
 malleable iron varies according to the skill of the workmen, as well as the kind of fuel 
 and pig iron used. 
 
 In refining from 6|- to 8 cwt. of coke is used for each ton of metal produced when 
 the pig iron has to be melted, and when the charge is run into the refinery direct from 
 the smelting furnace from 4 to 5 cwt of coke per ton of metal is sufficient. 
 
 In pig boiling the consumption of coal varies from 18 to 22 cwt. per ton of bar iron 
 made, according as the coal is more or less bituminous and capable of burning with 
 flame. 
 
 In puddling refined metal the consumption of fuel is about 10 or 14 cwt.. of bitu- 
 minous coal, and from 17 to 18 cwt. of anthracitic coal, per ton of iron made. 
 
 In heating the piles the consumption of fuel ranges from 7 cwt to 13 cwt. per ton 
 of merchant bars, according as they are large or small. 
 
 Ordinary malleable iron has a grey colour, which varies in its shade according to 
 the character of the iron, and has sometimes a bluish or blackish tinge. The specific 
 gravity ranges between 7'3 and- 7'9, that of the better kinds approximating to the 
 mean of these two limits. The specific gravity is to some extent affected by the 
 alteration of mechanical texture produced mechanically. Thus a bar, 4 inches wide 
 and 1 inch thick, having a specific gravity of 7'801, acquired a specific gravity of 
 7'8621 when rolled out to a very thin sheet, and iron of 7'7938 specific gravity 
 acquired a specific gravity of 7'8425 when drawn into very thin wire 
 
598 
 
 IRON. 
 
 The specific heat of ordinary malleable iron is (H 13795; it is somewhat higher 
 when the amount of carbon in the metal is large. The conductivity for heat is 374-3 
 as compared with gold = 1000. The linear and cubic expansion by heat is less than 
 that of 'most other metals. The linear expansion for each degree between 100 and 
 300 is eiioo- AM iron bar expands ^ when raised from a red heat to a white heat, 
 and 550 when heated from 20 to whiteness. 
 
 The melting point of malleable iron has not been determined with any degree of 
 accuracy. It is between the melting point of cast iron and that of platinum ; it is 
 estimated at 1550 by Pouillet, and at 2000 by Scheerer, and there is no doubt it is 
 higher in proportion as the metal contains less carbon. 
 
 Pure iron is attracted by the magnet more powerfully than iron containing carbon ; 
 but it does not retain the magnetic condition so long as the iron containing some carbon. 
 Ordinary malleable iron is also more strongly attracted than steel, and it is more 
 easily rendered magnetic, but it loses the polar condition much sooner than steel does. 
 It appears, therefore, that the presence of a certain amount of carbon is in some way 
 necessary for the retention of the magnetic condition by iron. Bars of iron placed 
 vertically, or nearly so, become, in course of time, magnetic. The magnetic condition 
 of iron is very nearly destroyed by a red heat, and entirely so by exposure to a white 
 heat. 
 
 The electric conductivity of malleable iron is much less than that of copper. 
 Taking this as 100, that of iron is 20 according to Harris, 17 '74 according to Lenz, 
 and 15 '8 according to Becquerel. Matthiessen considered the conductivity of pure 
 electro-deposited iron to be much higher than that of ordinary malleable iron. 
 
 The hardness of malleable iron varies considerably; it is influenced by the presence 
 of foreign substances and reduced by increase of temperature. It is but very slightly 
 increased by sudden cooling of the red-hot metal, and less so in proportion as the 
 amount of carbon in the metal is smaller. The hardness of malleable iron seems to 
 be essentially dependent upon the presence of a certain amount of carbon in the metal. 
 Absolutely pure iron is so soft that it offers but little resistance to friction. 
 
 The tenacity of malleable iron also varies very much, and is influenced by the 
 nature of the foreign admixtures in the metal, by their amount, and by the internal 
 texture of the metal, by temperature, and other conditions. Up to a temperature of 
 146 the tenacity of boiler plate is not sensibly diminished ; but at a red heat it is 
 reduced one-fourth. According to Fairbairn, the tenacity of good rivet iron at 190 
 is one-third greater than at the ordinary temperature, but at a red heat it is reduced 
 to nearly one-half. 
 
 Tenacity or Tensile Strength of Malleable Iron. 
 
 Kind of iron 
 
 Lengthwise 
 in pounds per sc 
 
 Crosswise 
 luare inch 
 
 Ultimate 
 extension 
 
 Authority. 
 
 Lowmore iron wire . 
 
 64,200 
 
 52,490 
 
 
 
 Fairbairn 
 
 Staffordshire bar iron . { 
 
 from 62,231 
 to 56,715 
 
 I 
 
 302 
 186 
 
 Kerkaldy 
 
 Swedish bar iron . . { 
 
 from 48,232 
 to 47,855 
 
 { 
 
 264 
 
 278 
 
 Napier. 
 
 The malleability of iron containing from 0*25 to 0*5 per cent, of carbon is very 
 considerable, though less than that of silver or gold. It is influenced by the presence 
 of the foreign substances which modify the hardness and tenacity of the metal ; the 
 degree of malleability being apparently determined chiefly by the relative hardness 
 and tenacity, but to some extent also by the internal texture, of the metal. The 
 malleability of iron is increased in proportion as the temperature is raised, and iron 
 becomes very much softer without its tenacity being proportionately lessened. At a 
 red heat the metal is sufficiently soft to be brought into any required shape by 
 hammering or rolling, and at a white heat it becomes quite pasty, so that separate 
 pieces may be, as it were, kneaded together into one mass, or, as it is termed, welded. 
 This capability of being forged and welded, so important as regards the working of 
 iron for various useful purposes, is partly referable to the wide interval between the 
 temperature at which the metal presents its ordinary degree of hardness, and that at 
 which it becomes liquid : partly, also, to the fact that at temperatures far below 
 the melting point iron acquires a soft plastic condition which is retained in some 
 degree through a considerable range of temperature. 
 
 Among the foreign substances influencing prejudicially the malleability of iron, the 
 chief are sulphur, phosphorus, and silicon. The first communicates to iron the cha- 
 racter of being brittle while hot, or, as it is called, red short in forging. Phosphorus 
 
CHARACTERS OF MALLEABLE IRON. 599 
 
 renders malleable iron cold short, or brittle and weak, at the ordinary temperature. 
 Silicon has a similar influence in a higher degree. Manganese seems to be beneficial 
 rather than otherwise as regards the malleability of iron. When red-hot iron is 
 immersed in cold water the malleability is considerably reduced. The same effect is 
 produced by long hammering or rolling, but the malleability is again restored by 
 heating the metal to redness and allowing it to cool gradually. 
 
 The texture or molecular structure of iron varies considerably according to the 
 treatment the metal has been subjected to. After fusion, iron is decidedly crystalline 
 or granular, and the fractured surface presents distinct indications of that condition. 
 By hammering or rolling the metal while hot, it acquires a fibrous texture, becomes 
 more tenacious, less susceptible of true fracture, and capable only of being torn 
 asunder. In the usual method of producing malleable iron the metal is not melted but 
 wrought mechanically while in a kind of doughy condition, and the uniform close 
 fibrous texture which determines the quality of the metal depends very much upon 
 the nature of this treatment and the extent to which it is carried. 
 
 By hammering fibrous iron while cold it is rendered harder and brittle ; when 
 afterwards broken the metal presents a granular or crystalline fracture, but opinions 
 differ as to whether this crystalline condition is really a result of the hammering. 
 This is also the case in regard to the influence of long-continued pressure, vibration, 
 or concussive action, etc. in affecting the texture of malleable iron, some maintaining 
 that under these conditions the fibrous texture of the metal is gradually destroyed, 
 and its strength reduced. 
 
 Malleable iron undergoes no change in dry air, or in water free from air ; but in 
 moist air, or in water containing air, it gradually becomes oxidised or rusted at the 
 surface, and, after exposure for a sufficient length of time, the entire mass may be 
 eventually converted into oxide. The carbonic acid present in atmospheric air appears 
 to contribute largely to the production of this change. The presence of saline sub- 
 stances in water also facilitates the oxidation of iron, while alkalies and oily or resinous 
 substances retard the oxidation. Contact with more highly electro-positive metals, 
 such as zinc, also hinders the oxidation of iron within a certain distance around the 
 point of contact. 
 
 At a temperature of about 230, iron becomes capable of combining directly with 
 atmospheric oxygen, and the polished surface of the metal at first becomes covered 
 with an extremely thin film of magnetic oxide, presenting a yellow colour which 
 gradually passes into a red, blue, and grey. At a red neat this film of oxide becomes 
 thicker and forms a crust, which separates as the metal cools, constituting what is 
 commonly known as forge scale, and when the iron is kept hot for some considerable 
 time the outer surface of the crust is converted, by further oxidation, into ferric oxide. 
 At a white heat iron burns in the air with production of magnetic oxide, and this 
 combustion may be sustained for some time by directing a blast of air upon the heated 
 metal. 
 
 At a temperature of about 390, malleable iron decomposes water vapour, forming 
 magnetic oxide and liberating hydrogen. It is dissolved completely by strong hydro- 
 chloric acid ; but with dilute acid a carbonaceous residue is left undissolved. In both 
 cases the hydrogen evolved carries with it a carburetted vapour or gas which com- 
 municates to the hydrogen a peculiar smell. 
 
 Malleable iron generally contains from 0'25 to 0'5 per cent, of carbon, but some- 
 times the amount of carbon is much less, and in a few instances it is higher. The 
 smaller the amount of carbon, the softer is the iron, and the larger the amount of 
 carbon within these limits, the nearer does the metal approximate to the character of 
 steel. The only ordinary iron that is probably quite free from carbon is that technically 
 known as burnt iron, which cannot be soundly welded. Hence it has been supposed 
 that the capability of being welded is determined by the presence of some carbon in 
 the metal. It is more probable, however, that the peculiarity of burnt iron in this 
 respect is only indirectly determined by the absence of carbon, and that it is due to 
 the presence of a minute quantity of oxide in the metal, which could not have been 
 introduced so long as any carbon remained in it. 
 
 Among the foreign substances other than carbon, which are often present in 
 malleable iron, the most important are sulphur, phosphorus, and silicon, existing 
 probably in combination with equivalent proportions of the metal as sulphide, phosphide 
 and silicide. 
 
 Sulphur is generally present to some extent in most kinds of malleable iron, and 
 even when amounting to only 0-034 per cent, it has the effect of rendering the metal 
 red short, and liable to crack at the edges in forging. It has been considered that 
 O'Ol per cent, of sulphur is the highest amount consistent with the usefulness of 
 malleable iron. 
 
 Phosphorus is also frequently present, and when amounting to 0'75 per cent, it 
 
600 
 
 IKON. 
 
 renders the metal very weak and brittle at the ordinary temperature, or, as it is 
 called, cold short. In smaller amounts it is, however, considered to be serviceable 
 in rendering the metal more capable of being welded. 
 
 Silicon renders malleable iron harder and lessens its tenacity, making it what is 
 termed rotten in working, even when present only to the extent of 0*37 per cent,. 
 
 Manganese is considered to render malleable iron harder, but not to make it steely. 
 
 Copper is considered to render malleable iron red short, and to reduce the capability 
 of being welded, without, however, affecting the tenacity of the metal. 
 
 The following table gives the composition of several kinds of malleable iron which 
 illustrate the extent to which the above-mentioned substances are present. 
 
 Kind of iron 
 
 Fe 
 
 C 
 
 Si 
 
 S 
 
 P 
 
 Mn 
 
 As 
 
 Analyt 
 
 Swedish 
 
 99-863 
 
 054 
 
 028 
 
 055 
 
 trace 
 
 trace 
 
 . 
 
 Henry 
 
 
 
 99-22 
 
 087 
 
 056 
 
 063 
 
 005 
 
 
 
 trace 
 
 n 
 
 . . 
 
 99-544 
 
 087 
 
 115 
 
 220 
 
 034 
 
 
 
 trace 
 
 
 > 
 
 9973 
 
 24 
 
 03 
 
 
 
 trace 
 
 trace 
 
 
 
 .Karsten 
 
 Silesian 
 
 99-873 
 
 09 
 
 03 
 
 007 
 
 
 
 
 
 
 
 >: 
 
 Russian 
 
 99-412 
 
 272 
 
 062 
 
 234 
 
 
 
 02 
 
 trace 
 
 Henry 
 
 f 
 
 99-594 
 
 34 
 
 trace 
 
 066 
 
 
 
 trace 
 
 
 
 M 
 
 Welsh 
 
 97-72 
 
 
 
 26 
 
 21 
 
 71 
 
 
 
 
 
 Riley 
 
 > 
 
 98-54 
 
 
 
 13 
 
 05 
 
 42 
 
 
 
 
 
 J} 
 
 Shropshire . 
 
 
 
 
 
 18 
 
 06 
 
 37 
 
 
 
 
 
 Price 
 
 
 
 
 
 
 
 18 
 
 03 
 
 30 
 
 
 
 
 
 ?> 
 
 Lowmoor 
 
 99-372 
 
 016 
 
 122 
 
 104 
 
 106 
 
 28 
 
 
 
 Tookey 
 
 "Weardale 
 
 
 
 17 
 
 11 
 
 058 
 
 089 
 
 33 
 
 
 
 Percy 
 
 Russell's Hall . 
 
 99-361 
 
 19 
 
 144 
 
 165 
 
 14 
 
 
 
 
 
 Henry 
 
 Manufacture of Steel. By smelting very rich iron with charcoal in a bloomery 
 much in the same way that malleable iron is produced directly (see p. 579) the metal 
 may be obtained in the state of steel, and possessing the character of acquiring con- 
 siderable hardness when suddenly cooled. This method of manufacture was formerly 
 much practised ; but it is now almost entirely superseded and steel is generally pro- 
 duced either by the carburation of malleable iron or by the decarburation of pig iron. 
 The steel made by the former method is termed cement steel and that made by 
 decarburising pig iron in a charcoal finery is termed natural steel. Pig iron is also 
 converted into steel by puddling and by the action of atmospheric oxygen on the 
 melted metal according to the method of Bessemer. 
 
 In addition to these indirect methods of manufacture, attempts have lately been 
 made to produce steel directly from iron ore by methods more easily manageable than 
 smelting in the bloomery ; among these the application of the regenerative furnace by 
 Siemens is most worthy of consideration. The arrangement adopted is shown by 
 fig. 422. The furnace is similar in construction to the gas puddling furnace already 
 described, but above the combustion chamber (F F) there are two cylindrical hoppers 
 (A A) formed of cast iron, in which the iron ore is subjected to the action of reducing gas, 
 which is passed into the hoppers through wrought-iron pipes (G G) connected with the 
 supply main (B). The lower extremities of these hoppers projecting into the com- 
 bustion chamber (F F) are made of fire clay in order to resist the high temperature. 
 The upper part of each hopper is surrounded by a flue (s s s s) into which the flame 
 from the furnace ascends and keeps the contents of the hoppers at a proper tem- 
 perature. 
 
 In starting the operation in this furnace some pig iron is placed on the hearth, 
 together with sufficient charcoal to support the iron ore in the hoppers (A A). The 
 gas is then turned on and ignited in the usual way, and by the time the pig iron has 
 melted, the ore in the lower ends of the coppers will have been reduced to a metallic 
 sponge, which sinks down and is gradually dissolved in the melted pig iron, while fresh 
 portions of the ore are reduced in the same way. This is continued until the amount 
 of carbon in the liquid metal upon the hearth corresponds with the kind of steel re- 
 quired and then the charge is run off into ingot moulds. ' 
 
 Since the reduction of the iron ore in this way takes place but slowly, this part of the 
 operation has since been carried out in a rotatory chamber, consisting of a cylindrical 
 iron tube lined with fire brick. This chamber is mounted on friction rollers and fitted 
 with a toothed wheel by which it is made to revolve slowly while the contents are 
 subjected to the action of heat produced by the combustion of gas supplied together 
 with air at a high temperature from a series of regenerators. 
 
MANUFACTURE OF STEEL. 
 
 601 
 
 In carrying out the manufacture of steel by this method, an unanticipated difficulty 
 was encountered in the absorption of sulphur by the spongy metal, and consequently 
 recourse was had to the plan of melting the iron ore with fluxes and then precipi- 
 tating the iron from the liquid mass by mixing it with carbon in the form of coal. 
 
 For this purpose the ore is mixed with sufficient lime to prevent the combination 
 of much ferrous oxide with the silica present, and a charge of about a ton is put into 
 
 the rotating furnace previously heated to bright redness. Sometimes aluminous iron ore is 
 added when the iron ore contains much silica, and the addition of materials containing 
 manganese is also advantageous. After the cylinder has been made to revolve slowly 
 for about 40 minutes and, under the influence of the flame, the contents have acquired 
 a bright red heat, about 5 or 6 cwts. of small coal is added, and the cylinder made to ro- 
 tate more rapidly to effect a thorough intermixture. By the reaction of the carbon and 
 ferric oxide, magnetic oxide is first formed, which melts, and at the same time metallic 
 iron begins to be deposited, while the remaining ingredients of the iron ore and the 
 flux form a silicious slag. During the continuance of this reaction carbonic oxide is 
 evolved in such abundance that the supply of gas to the cylinder can be almost 
 entirely shut off, and only air requires to be supplied to burn the carbonic oxide 
 evolved by the reaction. 
 
 When the reduction of the iron ore is nearly completed, the rotation of the cylinder 
 is stopped and the liquid slag is drawn off. Then by rotating the cylinder again the 
 loose lumps of metal are united into balls, which are transferred to a steel melting 
 furnace containing some melted pig iron where they are run down, and the resulting 
 melted steel is then cast into ingots. 
 
 Carburation method : cementation. This method of producing steel is based upon 
 the circumstance that when malleable iron is heated to a temperature somewhat 
 below its melting point, in contact with charcoal or some other carbonaceous substance 
 and without access of air, carbon is absorbed by the metal. 
 
 The malleable iron used for producing steel in this way must be of the best 
 quality and free from the impurities which affect the character of steel. The 
 carburising material or cement used in the operation is coarsely powdered char- 
 coal, and sometimes this is mixed with horn shavings, ferrocyanides, and similar 
 substances containing carbon. 
 
 The furnaces in which the operation is conducted somewhat resemble glass-house 
 furnaces in their general arrangement, as shown by figs. 423 and 424. They 
 are constructed so that a uniform temperature may be kept up in them for several 
 
602 
 
 IRON. 
 
 days, the hot air from the furnace (A B) passing through the horizontal and vertical 
 flues d d round the Chambers (cc), which are constructed of fire bricks and serve to 
 
 FIG. 423. FIG. 424. 
 
 receive the bars of iron which are 
 to be converted into steel. In 
 charging these chambers or pots 
 the bars of iron are imbedded in 
 finely ground charcoal, and when 
 the chambers are filled the surfaces 
 are covered with a layer of loam. 
 The doorway (P) is then bricked 
 up, and the furnace is gradually 
 heated up to the requisite tempe- 
 rature, which is kept up uniformly 
 for several days until the conver- 
 sion of the iron into steel is com- 
 plete. The precise nature of the 
 process by which iron is thus con- 
 verted into steel is not thoroughly 
 FIG. 425. understood ; but it is probable that 
 
 gaseous carbon compounds, such 
 
 as carbonic oxide or hydrocarbons, are concerned in the change, either by a reaction 
 similar to that which takes place in the production of pig iron, or by the absorption 
 of carbon from hydrocarbons, which takes place when malleable iron is heated in 
 contact with marsh gas or olefiant gas. 
 
 When the conversion of the iron into steel is complete, the furnace is allowed to 
 cool gradually and the bars are taken out. A remarkable characteristic of the steel 
 produced in this way is the presence of numerous small blisters on the surface of the 
 bars, for which reason it is called blister steel. The uniform size and distribution 
 of the blisters over the surfaces of the bars are considered to indicate the good quality 
 of the steel, while, on the contrary, if the blisters are large and unequally distributed 
 the steel is probably deficient in homogeneity. 
 
 Iron, when converted into steel by the cementation method, increases in weight 
 from 0*5 to 075 per cent., and the fuel consumed in the operation amounts to 75 or 
 90 per cent, of the steel produced. 
 
 The bars of blister steel obtained by the cementation method are never uniform 
 throughout in texture and composition, the exterior portions being more highly car- 
 burised than the interior, and the difference is not always the same in all parts of the 
 bars. To render steel made in this way homogeneous, the bars are heated and drawn 
 out while hot under hammers into thin bars, which are laid together in a faggot, 
 heated to a welding heat, and then hammered or rolled so as to weld them together 
 into one mass. This operation is repeated several times, until the metal has acquired 
 the requisite degree of homogeneity, and the steel is then termed shear steel. 
 
 The physical characters of the metal are also considerably changed during the ce- 
 mentation, and the surfaces of fracture present a crystalline or granular texture very 
 different from that of malleable iron ; the colour also is reddish white, somewhat like 
 bismuth. 
 
 Another method of producing steel by carburetting malleable iron consists in 
 melting scrap iron with sufficient pig iron to furnish the requisite amount of carbon. 
 
BESSEMER METHOD. 
 
 COS 
 
 The practical success of this method is principally due to the application of furnaces 
 in which gaseous fuel is burnt upon the regenerative system introduced by Mr. Siemens. 
 The furnace employed for the purpose is similar to that represented by fig. 410, the beds 
 upon which the pig iron is melted being formed of refractory sand, and at the side O A 
 it is an ordinary reverberatory furnace in which the malleable iron is heated to redness 
 before being added to the bath of liquid pig iron in which it is dissolved, until metal 
 of the required character has been produced. A prominent advantage of this method 
 is that of obtaining considerable masses of steel in a liquid state, which facilitates the 
 production of homogeneous steel. 
 
 Decarburation methods. The production of steel from pig iron by abstracting a 
 portion of its carbon is in all cases effected chiefly by means of the oxidising action of 
 atmospheric oxygen, and to some extent also by reaction with slag containing 
 ferrous silicate, much the same as in the production of ordinary malleable iron ; but 
 the nature of the metal produced is very much determined by the extent to which the 
 docarburation is carried. 
 
 When the operation is conducted in a finery hearth with charcoal, the metal pro- 
 duced is termed natural steel. The material operated upon is either white pig iron or 
 easily fusible grey pig iron obtained by smelting spathic or magnetic iron ore with 
 charcoal. The decarburising operation was formerly conducted in this manner with 
 a great variety of modifications in minor details, determined chiefly by the particular 
 nature of the pig iron to be worked or by other local circumstances. In Westphalia, 
 Silesia, Styria, Carinthia, Sweden, and some other places, steel was largely produced in 
 this way, but of late years other methods have been to a great extent substituted for 
 the decarburation in the finery hearth. 
 
 Among the more recent methods of producing steel, that of p u d d 1 i n.g is conducted 
 essentially in the same manner as in the production of ordinary malleable iron, except 
 in so far that the decarburation is not carried to the same extent, and the pig iron 
 operated upon requires to be free from substances prejudicial to steel. 
 
 The greatest advance in the manufacture of steel has been effected by the intro- 
 duction of Bessemer's method of decarburising. pig iron, by blowing atmospheric air 
 into the melted metal. Under these conditions the carbon is oxidised more readily 
 than the iron, and converted into carbonic oxide with considerable evolution of heat, 
 so that the temperature of the metal is kept above the melting point of steel, and 
 when the decarburation has been carried far enough, the liquid steel can be run into 
 moulds. 
 
 The apparatus employed in Sweden in the production of steel according to Bessemer's 
 method consists of an upright cylindrical chamber constructed of fire brick strongly 
 cased with sheet iron. At one side of the chamber 
 is an opening through which melted pig iron can 
 be run in, and the top is closed by a moveable 
 cover of similar construction, having an open 
 neck through which the gas evolved during the 
 operation can escape. At the bottom of the 
 chamber is a tapping hole that can be closed 
 with a plug, and a gutter for running out the 
 decarburised metal. Round the bottom also are 
 a number of concentric tuyeres connected with a 
 main through which air can be forced through 
 the contents of the chamber. The melted pig 
 iron is either run into the converting chamber 
 direct from the smelting furnace where it is 
 made, or it is first run into a large ladle and 
 weighed. This plan has the advantage of saving 
 the fuel requisite for melting the pig iron, and it 
 is well suited for cases where the ore smelted 
 yields pure pig iron of uniform quality. 
 
 The converter used in this country is re- 
 presented by fig. 426 : it is an egg-shaped vessel 
 made of stout sheet iron, and lined with fire 
 brick or some other refractory silicious material. 
 
 At the bottom of the converter are a number 
 of air tuyeres communicating with a lateral tube, 
 by which air can be forced into the interior 
 under a high pressure, and the upper end of the 
 converter is furnished with a contracted neck, 
 which is left open. The converter is mounted 
 upon trunnions in such a manner that it can be turned over into any required position 
 
604 
 
 IRON. 
 
 by means of machinery connected with it, The general arrangement of these vessels 
 in pairs is shown by fig. 427. 
 
 The converters (A A) are placed on opposite sides of a deep cylindrical pit, in the 
 centre of which is a water-pressure engine with a vertical cylinder and a solid piston 
 (G), having at the upper end a strong crosshead (D), formed of two strong parallel 
 girders braced together, and arranged in such a manner as to hold at one end the 
 ladle (c), while at the other end there is a counterpoise weight (E) which can be 
 shifted to and from the centre of the erosshead according as the ladle (c) is full or 
 empty. The ladle can be moved round the circumference of the pit opposite to either 
 of the converters to be filled, or over any of the ingot moulds which are placed round 
 the periphery of the pit. For this purpose the crosshead is raised up by the water- 
 pressure engine at the centre of the pit, sufficiently high to clear the moulds ; and by 
 means of a hole at the bottom of the ladle fitted with a plug, the contents can be run 
 into the ingot moulds in succession. The hydraulic engines (In) are used for tipping 
 the converters to discharge their contents into the ladle. 
 
 sMet. 
 
 FIG. 427. 
 
 In working this apparatus, the charge of pig iron, varying from one and a half to 
 five tons, is first melted in a cupola or reverberatory furnace, and run into the con- 
 verter, previously heated o redness by burning a quantity of coke inside it. While 
 the melted pig iron is being run in, the converter is placed so that the bottom and 
 the neck are level with the central axis, and while it is being brought back to the 
 vertical position the blast is turned on. A reddish-yellow faintly luminous flame then 
 issues from the neck of the converter for a few minutes ; after a while it becomes 
 more brilliant, the liquid metal becomes violently agitated, and a shower of sparks 
 appears, consisting of fragments of burning iron together with particles of slag, which 
 are thrown out by the rapid disengagement of carbonic oxide. After some minutes 
 the discharge of sparks ceases, the action becomes less violent, and the flame presents 
 the bluish violet characteristic of carbonic oxide, until, when the whole of the carbon 
 is oxidised, it is replaced by a stream of intensely heated gas, consisting chiefly of 
 nitrogen resulting from the oxidation of iron by the air. At this period the converter 
 is turned round to the horizontal position, and about 10 per cent, of manganiferous 
 pig iron is run in or a sufficient quantity to give the requisite amount of carbon in 
 the metal. The contents of the converter are then run out into a ladle and trans- 
 ferred to ingot moulds. 
 
 The chemical changes that take place in the converter are indicated by the following 
 table showing the composition of the gas evolved at different stages of the Bessemer 
 operation : 
 
 
 Two 
 minutes 
 
 Pour 
 minutes 
 
 Six 
 minutes 
 
 Ten 
 
 minutes 
 
 Twelve 
 minutes 
 
 Fourteen 
 minutes 
 
 Carbonic oxide . 
 
 
 
 3-95 
 
 4-52 
 
 19-59 
 
 29-30 
 
 31-11 
 
 Carbonic dioxide . 
 
 10-71 
 
 8-57 
 
 8-20 
 
 3-58 
 
 2-30 
 
 1-34 
 
 Oxygen 
 
 92 
 
 
 
 
 
 
 
 
 
 
 
 Hydrogen . 
 Nitrogen 
 
 8 8-37 
 
 88 
 86-58 
 
 2-00 
 85-28 
 
 2-00 
 74-83 
 
 2-16 
 66-24 
 
 2-00 
 65-55 
 
 The corresponding alteration in the composition of the metal is shown by the fol- 
 lowing analyses by Snelus of portions taken out of the converter during the different 
 stages of the operation : 
 
BESSEMER STEEL. 
 
 605 
 
 
 Grey pig 
 
 Composition of metal after 
 blowing 
 
 Steel 
 
 
 operated 
 
 
 
 
 upon 
 
 Six 
 minutes 
 
 Nine 
 minutes 
 
 Thirteen 
 minutes 
 
 Ingot 
 
 Rail 
 
 (graphitic 
 
 2-070 
 
 
 
 _ 
 
 _ 
 
 
 i 
 i 
 
 011 1 combined 
 
 1-200 
 
 2-170 
 
 1-550 
 
 097 
 
 566 
 
 519 
 
 Silicon 
 
 1-952 
 
 795 
 
 635 
 
 020 
 
 030 
 
 030 
 
 Sulphur 
 
 014 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 trace 
 
 Phosphorus 
 
 048 -051 
 
 064 
 
 067 
 
 053 
 
 053 
 
 Manganese . 
 
 086 trace 
 
 trace 
 
 trace 
 
 309 
 
 309 
 
 Copper 
 
 
 
 . 
 
 
 
 039 
 
 039 
 
 It will be seen that the sulphur present in the pig iron is almost entirely eliminated ; 
 the greater part of the silicon is also separated, together with the carbon, and almost 
 in the same proportion ; but the phosphorus is not removed, and, owing to the oxidation 
 of some iron, the amount is actually greater in the finished steel than in the pig iron. 
 The copper and manganese present in the steel are due to the manganiferous pig iron 
 added at the end of the operation. The following analyses of the metal in different 
 stages represent the results obtained at the Neuberg works in Styria, which are 
 essentially of the same nature as those obtained at Dowlais. The copper and manga- 
 nese in this case are chiefly derived from the pig iron operated upon, and the copper 
 is due to the presence of pyrites in the spathic iron ore from which the pig is made. 
 
 Silicon . . . 
 Sulphur . 
 Phosphorus 
 Manganese . 
 Copper . . . 
 
 Grey pig 
 operated upon 
 
 Composition of metal 
 
 After 
 scorification 
 
 Towards end 
 of boiling 
 
 Before adding 
 manga- 
 niferous pig 
 iron 
 
 Ingot 
 
 3-180 
 750 
 1-960 
 018 
 040 
 3-460 
 085 
 
 2-465 
 443 
 trace 
 040 
 1-645 
 091 
 
 949 
 ""112 
 trace 
 045 
 429 
 095 
 
 087 
 028 
 trace 
 045 
 113 
 120 
 
 234 
 033 
 trace 
 044 
 139 
 105 
 
 The composition of the slag taken from the converter at the same time as the dif- 
 ferent portions of iron is shown in the following table : 
 
 
 Smelting fur- 
 nace slag 
 
 After 
 scorification 
 
 Towards end 
 of boiling 
 
 Before adding 
 pig iron 
 
 While 
 casting 
 
 Ferrous oxide . 
 
 0-60 
 
 6-78 
 
 5-50 
 
 16-86 
 
 15-43 
 
 Manganous oxide 
 
 2-18 
 
 37-00 
 
 37'90 
 
 32-23 
 
 31-89 
 
 Lime 
 
 30-35 
 
 2-98 
 
 1-76 
 
 1-19 
 
 1-23 
 
 Magnesia . 
 
 16-32 
 
 1-53 
 
 0-45 
 
 52 
 
 61 
 
 Potash 
 
 18 
 
 trace 
 
 
 
 
 
 
 
 Soda 
 
 14 
 
 
 
 ^_ 
 
 
 
 
 
 Silica . 
 
 40-95 
 
 46-78 
 
 51-75 
 
 46-75 
 
 47-25 
 
 Alumina . 
 
 8-70 
 
 4-65 
 
 2-98 
 
 2-80 
 
 3-45 
 
 Sulphur . 
 
 34 
 
 04 
 
 trace 
 
 trace 
 
 tracr 
 
 Phosphorus 
 
 01 
 
 03 
 
 02 
 
 01 
 
 01 
 
 
 9977 
 
 99-79 
 
 100-36 
 
 100-36 
 
 99-87 
 
 It is evident from these analyses and from those showing the composition of the 
 metal and of the gas given off, that the heat generated in the decarburation of pig 
 iron by the Bessemer method is in great measure due to the oxidation of silicon, since 
 the carbon is chiefly separated as carbonic oxide, and consequently it appears that the 
 pig iron to be converted into steel by that method should contain a considerable 
 amount of silicon; at the same time the amount of silicon should not exceed the 
 quantity capable of being oxidised by the time the carbon is burnt off and the end of 
 
606 IRON. 
 
 the operation is indicated by the cessation of the flame, otherwise the steel produced 
 may* retain sufficient silicon to render it weak and brittle, or the excess of silicon will 
 give rise to the formation of a large amount of slag, and consequent waste of iron by 
 oxidation and the production of ferrous silicate. The oxidation of iron or manganese 
 in the formation of slag is also a further source of heat. 
 
 The uniformity of composition and texture essential to steel of good quality may 
 be to a great extent ensured by subjecting blistered steel or puddled steel to repeated 
 welding and forging or rolling. But this method is laborious, while it has the further 
 disadvantage that in carrying it out the amount of carbon in the metal is reduced by 
 oxidation and the metal is thus rendered softer. By melting the steel in crucibles, 
 however, it is possible to exclude air, and thus to obtain under the name of cast steal 
 a more perfectly homogeneous metal. This method of treating cement steel has been 
 practised since 1740, when it was introduced by Huntsman at Handsworth, near 
 Sheffield. The more recent methods of Bessemer and Siemens have furnished steel in 
 a melted condition, and have thus to some extent superseded the necessity for subjecting 
 cement steel, etc., to this operation, but it is still practised on a considerable scale. 
 
 The material used for the production of cast steel of high quality, whether it be 
 cement steel or puddled steel, must be free from impurities, and, according to the 
 amount of carbon in the metal operated upon, as well as the kind of steel required, 
 various substances are used as admixtures such as charcoal, manganese, and manga- 
 uiferous pig iron. 
 
 The metal is melted in crucibles so as to exclude access of air, and as it is impor- 
 tant that the fusion should take place rapidly, Siemens' regenerative furnaces have 
 been employed for this purpose with great advantage. The melted metal is run into 
 ingots, which are generally of unequal texture, and to render them compact and 
 uniform, they are heated and drawn out under powerful hammers until the metal 
 acquires the requisite characters. 
 
 The characters of steel are to some extent intermediate between those of cast iron 
 and ordinary malleable iron, but steel is distinguished from both by the capability cf 
 acquiring considerable hardness when suddenly cooled. The greater the reduction of 
 temperature and the more rapidly it takes place, the greater i& the degree of hardness 
 thus produced. Steel raised to a white heat and then immersed in cold mercury ac- 
 quires a degree of hardness nearly equal to that of the hardest white cast iron or even 
 of the diamond : it is then also extremely brittle. By heating such hardened steel 
 and allowing it to cool gradually, it again becomes soft and less brittle. It is in 
 virtue of this capability, which is one of the most distinctive characteristics of steel, 
 that various degrees of hardness can be communicated to it, by regulating the tem- 
 perature to which the hardened metal is heated before being allowed to cool gradually, 
 or to which the soft metal is heated before being suddenly cooled. Steel tools and in- 
 struments are made and finished while the metal is in the soft state and the requisite 
 degree of hardness is given to them as above described. This operation is termed 
 tempering. The temperatures to which the metal requires to be heated in order to 
 acquire, in this way, particular degrees of hardness are indicated by the yellow or 
 bluish colours which the metal assumes by the formation of an extremely thin film 
 of oxide on the surface. 
 
 By cooling the heated metal slowly these colours appear in the reverse order, and 
 as soon as the required colour appears, the article to be hardened is plunged into the 
 liquid in which it is to be cooled. This is generally water, but sometimes saline 
 solutions are used, as well as oil, melted tallow, wax, etc. 
 
 The distinction between steel and cast iron or malleable iron is not by any means 
 absolute ; it consists rather in the degree to which considerable hardness or the 
 capability of acquiring that character is associated with tenacity and malleability. 
 Accordingly there are numerous varieties of steel approximating in various degrees 
 to malleable iron or to cast iron. Together with such gradational differences in the 
 characters of the metal, there are corresponding differences in the amount of carbon 
 it contains ; the closer the approximation to malleable iron, the smaller is the amount 
 of carbon in the metal ; the closer the approximation to cast iron, the larger is the 
 amount of carbon. When the amount of carbon is less than about 0'65 per cent., 
 the capability of being tempered is either wanting or very slight ; when the carbon 
 amounts to I 1 75 per cent., the metal is capable of being made very hard, but its 
 tenacity is much reduced. The capability of being hardened and tempered is asso- 
 ciated with the maximum of tenacity when the carbon amounts to about 1*5 per 
 cent. The opinion has long been entertained that these characters of steel are inti- 
 mately connected with the amount of carbon it contains, but it is still unknown in 
 what manner these facts are related. Cement steel contains from '496 to 1*87 per 
 cent, carbon, natural steel from '985 to 2*44 per cent., soft steel -95 per cent., the 
 softest Bessemer metal '08 per cent., and cast steel from '86 to T94 per cent. In 
 
CHARACTERS OF STEEL. 607 
 
 Sweden several qualities of Bessemer metal are made, differing in the amount of car- 
 bon they contain, and distinguished by numbers as follows : 
 
 No. 1. No. 2. No. 3. No. 4. No. 5. 
 
 Amount of carbon . 2'0 T5 ! "5 '05 
 
 The metal No. 1 can be forged, though with some difficulty, but it does not weld. On 
 the contrary, No. 5 welds perfectly, but cannot be tempered. 
 
 The presence of silicon in steel is considered by some authorities to be advantageous 
 so far as regards the capability of being hardened ; but others are of opinion that it 
 increases the tenacity of the metal at the ordinary temperature, and makes it difficult 
 to weld, though a small amount of silicon renders steel soft. The best kinds of steel 
 often contain only minute traces of silicon, and few contain more than '02 or '03 per cent. 
 
 Among the various substances which are frequently present in malleable iron and 
 in cast iron, those which are most prejudicial to the Duality of steel are sulphur, 
 phosphorus, and copper. The amount of sulphur in steel of the best quality rarely 
 exceeds '012 ; within the limit of '1 per cent, it is considered to render the metal more 
 capable of being welded at a moderate heat, but to make it red short. Phosphorus 
 also renders steel more capable of being welded and at the same time makes it cold 
 short when it amounts to '1 per cent. The best steel rarely contains so much. Copper 
 renders steel decidedly red short when present in very small amount, and for this 
 reason iron smelted from ores containing copper pyrites is not suitable for making 
 steel. 
 
 The fact that certain kinds of iron ore containing manganese are especially suitable 
 for the production of steel has given rise to the opinion that this metal is a necessary 
 constituent of good steel ; but it is in fact rarely the case that steel contains much 
 manganese, and whatever beneficial influence the presence of that metal may exercise 
 in the manufacture of steel would appear therefore to be of a totally different nature. 
 
 The presence of chromium, nickel or rhodium in steel is said to improve its quality, 
 but the data on which the opinion rests are somewhat insufficient. 
 
 The results of the observations on the influence of silver upon steel are discordant. 
 Tungsten and titanium have been stated to improve the quality of steel, but further 
 experience is requisite in regard to this point. The steel of which the celebrated 
 Damascus sword blades are made contains from '05 to '1 per cent, of tungsten, and 
 it has been asserted that the presence of this metal increases the tenacity of steel and 
 renders it especially suitable for cutting instruments. Four samples of tungsten 
 steel analysed by Sievert contained from '9 to 4*75 percent. 
 
 The presence in steel of a minute amount of nitrogen as a necessary constituent 
 has been alleged by Fremy ; but Marchand, Kammelsberg, and Boussingault have 
 failed to detect by their analyses any greater indications of nitrogen in steel than 
 might fairly be ascribed to accidental sources. Caron infers from his observations 
 that if steel contains nitrogen, it is not as an essential constituent, and similar results 
 have been obtained by Baker and Stuart. 
 
 The colour of steel is greyish-white, sometimes almost pure white, and the 
 hardened metal is sometimes whiter than the soft metal. The lustre of steel is not 
 remarkably different from that of malleable iron. The surface of fracture presents a 
 very fine granular texture, very uniform and without any of the fibre characteristic of 
 good malleable iron. The fracture of hardened steel presents a remarkably close 
 fine grained texture. Steel is always harder than malleable iron ; but it is never so 
 hard as that kind of white cast iron known as specular iron. The tenacity of steel 
 is greater than that of either cast iron, malleable iron, or any other metal. According 
 to the experiments of Muschenbrock and Eennie, it is at least twice as great as that 
 of malleable iron ; it is slightly reduced by hardening, but by annealing the metal 
 the tenacity is rendered even greater than that of the unhardened steel. 
 
 The malleability of soft steel at the ordinary atmospheric temperature is even 
 less than that of hard cast iron. Hardened steel is very brittle, and it will not bear 
 working with the hammer. The malleability of steel is, however, considerably in- 
 creased when the metal is heated. 
 
 The specific gravity of soft steel varies between 7'6224 and 7'8131. It is some- 
 what reduced by hardening the metal, viz. from 7'75 to 7'55 or from 7'79 to 7'67. 
 
 The specific heat of steel is (H1848 ; its linear expansion when heated from to 
 100 is scarcely greater than that of ordinary malleable iron, but it is less than that 
 of cast iron. By heating from 30 to a red heat, a steel bar lengthens about ^ ; the 
 elongation of a bar of malleable iron within the same range of temperature is , and 
 that of cast-iron is g| 5 ; by heating steel to whiteness, it lengthens ^, and the corre- 
 sponding expansion for malleable iron is ^fg, that for cast-iron ^. 
 
 When steel is heated to whiteness it becomes soft like ordinary malleable iron 
 under the same conditions, and it is then capable of being wrought and welded, not 
 
608 
 
 IRON. 
 
 oiily to steel but also to ordinary malleable iron ; steel welds, however, at a lower 
 temperature than malleable iron does. 
 
 The melting point of steel is between that of cast iron and that of malleable iron ; 
 probably about 1800, but the fusibility is influenced by the amount of carbon con- 
 tained in the metal. 
 
 Steel is less susceptible of magnetic induction than pure iron, but it far exceeds 
 iron in the capability of becoming permanently magnetic, for which reason it is 
 generally used for making magnets. 
 
 Steel is oxidised much less readily than malleable iron by exposure to the atmo- 
 sphere at the ordinary temperature, especially when it is polished and clean. When 
 gradually heated in contact with atmospheric air, steel acquires as the temperature 
 rises a succession of colours at the surface, from faint yellow to blackish blue. At 
 360 all colour disappears, but if the heat be raised still further, the colours reappear 
 in the same order as before, but more faintly. The coloration is due to oxidation, and 
 the change of colour is caused by the increasing thickness of the film of oxide, just as 
 the succession of colours in Newton's rings is caused by the unequal thickness of a 
 layer of air. 
 
 Hardened steel is dissolved by acids less readily than soft steel. With dilute 
 hydrochloric acid or sulphuric acid, soft steel gives a larger amount of the black 
 graphitic substance which is attracted by the magnet than malleable iron does. By 
 the continued action of the acid, this substance is converted into a carbonaceous mass 
 which burns without leaving any residue, as in the case of malleable iron and cast 
 iron. With dilute nitric acid this graphitic substance is not separated from soft steel. 
 Concentrated hydrochloric acid dissolves soft steel completely without residue. 
 
 The following table gives the composition of several kinds of steel : 
 
 Kind of steel 
 
 Locality 
 
 Fe 
 
 Mn 
 
 Cu 
 
 Carbon 
 
 Si 
 
 s 
 
 p 
 
 Authority 
 
 Com- 
 bined 
 
 Gra- 
 phi- 
 tic 
 
 Natural steel . 
 
 Siegen 
 
 _ 
 
 _ 
 
 379 
 
 1-698 
 
 _ 
 
 038 
 
 _ 
 
 _ 
 
 Karsten 
 
 
 
 Solingen . 
 
 
 
 
 
 
 
 1-570 
 
 
 
 020 
 
 
 
 
 Lampadius 
 
 Puddled steel . 
 
 Hartz 
 
 
 
 012 
 
 
 
 1-380 
 
 
 
 006 
 
 (Al -12) 
 
 trace 
 
 Brauns 
 
 Cement steel . 
 
 English . 
 
 
 
 
 
 
 
 1-807 
 
 
 
 100 
 
 
 
 
 
 Berthier 
 
 i 
 
 German . 
 
 
 
 
 
 
 
 416 
 
 080 
 
 
 
 
 
 __ 
 
 Bromeis 
 
 Cast steel 
 
 Sheffield . 
 
 
 
 
 
 
 
 950 
 
 220 
 
 
 
 
 
 
 
 ?j 
 
 
 
 
 
 
 
 
 
 
 
 1-758 
 
 
 
 
 
 
 
 Karsten 
 
 > 
 
 French 
 
 
 
 
 
 
 
 65 
 
 040 
 
 
 
 
 
 
 
 Sword steel 
 
 Damascus . 
 
 
 
 070 
 
 
 
 1-089 
 
 
 
 (Ni -07 Wo -1) 
 
 
 
 H 
 
 
 
 
 
 trace 
 
 
 
 775 
 
 
 
 (Ni -21 Co trace 
 
 
 
 
 
 
 
 
 
 
 
 Wo trace) 
 
 
 Wootz . 
 
 Indian 
 
 
 
 , 
 
 
 
 1-500 
 
 600 
 
 
 
 
 
 
 
 t ''" 
 
 51 
 
 98-092 
 
 __. 
 
 
 
 1-3331-312 
 
 045 
 
 (As -037) 
 
 
 
 Henry 
 
 Cast steel 
 
 G-erman 
 
 _. 
 
 trace 
 
 300 
 
 1-180 
 
 330 
 
 (Ni -12) 
 
 020 
 
 
 
 J5 
 
 English 
 
 
 
 024 
 
 066 
 
 1-275 
 
 213 
 
 (Ai -007) 
 
 
 
 . 
 
 Bessemer metal 
 
 Dowlais . 
 
 
 
 576 
 
 025 
 
 490 
 
 009 
 
 033 
 
 036 
 
 
 
 
 Sweden 
 
 
 
 trace 
 
 
 
 085 
 
 008 
 
 trace 
 
 025 
 
 Brusewitz 
 
 
 
 
 
 
 179 
 
 
 
 300 
 
 044 
 
 > 
 
 033 
 
 M 
 
 
 
 
 
 
 2,56 
 
 
 
 700 
 
 032 
 
 M 
 
 
 
 M 
 
 
 
 
 
 
 464 
 
 
 
 950 
 
 047 
 
 n 
 
 032 
 
 . 
 
 
 
 
 
 
 355 
 
 
 
 1-050 
 
 067 
 
 jj 
 
 
 
 j} 
 
 Wired " . 
 
 Barrow-in- 
 
 
 
 
 
 
 
 
 
 
 
 Furness . 
 
 
 
 214 
 
 
 
 200 
 
 179 
 
 030 
 
 026 
 
 , 
 
 Kail heads 
 
 German 
 
 
 
 386 
 
 
 
 138 
 
 306 
 
 040 
 
 034 
 
 
 Eails . 
 
 
 
 
 
 264 
 
 
 
 150 
 
 091 
 
 025 
 
 032 
 
 
 
 
 
 
 
 
 638 
 
 
 
 046 
 
 634 
 
 045 
 
 093 
 
 j) 
 
 Boiler plate . 
 
 
 
 
 
 136 
 
 
 
 250 
 
 016 
 
 010 
 
 
 
 
 
 
 ~~ 
 
 
 273 
 
 ~~ 
 
 300 
 
 056 
 
 040 
 
 041 
 
 " 
 
ORGANIC CHEMISTRY. 
 
 STTBSTAWCES DERIVED FROM PLANTS AND AWIMAI.S. 
 
 The material of which plants and animals consist comprises a great variety of 
 distinct substances, some of which are constant constituents of all plants or animals, 
 while others are peculiar to certain species or to particular organs of plants and 
 animals (ante, p. 67). Apart from the phenomena of reproduction, growth and 
 development by which plants and animals differ from minerals, the substances of 
 which they consist differ in their general character very widely from those treated of 
 in the preceding part of this work. These substances are also remarkable from a 
 chemical point of view on account of the general similarity of their composition, 
 since they all consist either of carbon, hydrogen and oxygen, or of these elements 
 together with nitrogen, sulphur, or phosphorus, while some consist simply of carbon 
 and hydrogen. Many of them contain exactly the same elements combined in the 
 same proportions, but are nevertheless totally different substances. 
 
 Under ordinary conditions the formation of these substances is incidental to the 
 performance of those functions of plants and animals which collectively constitute 
 the phenomenon of life, and on account of this peculiarity the substances formed in 
 the organisms of plants and animals are termed organic substances, while those 
 which do not originate in this way are distinguished from them as inorganic 
 substances. (See p. 15, and Carbon Compounds, pp. 67, 69.) 
 
 Until recently it was supposed, not only that the constitution of organic sub- 
 stances was essentially different from that of inorganic substances, but also that their 
 formation was the result of special influences, of a nature altogether distinct from 
 those to which ordinary chemical action is due. These suppositions are now 
 abandoned, and the substances produced by plants and animals are regarded as being 
 in no way essentially distinct, as regards their origin and constitution, from those 
 commonly termed inorganic substances, 
 
 It is in the plant organism chiefly that the formation of organic substances takes 
 place, and the chemical activity of the animal organism is characterised rather by the 
 transformation of substances derived from plants. 
 
 All the organs of plants are formed by the aggregation of numerous elementary 
 parts differing in form, characters, and composition. These elementary parts are called 
 cells ; the combination of cells is termed tissue. 
 
 Cells in their simplest form are minute vesicles closed on all sides, consisting 
 of various organic substances partly nitrogenous and partly non-nitrogenous ; they 
 also contain mineral constituents, and so long as they exercise the functions of life 
 they are charged with water. 
 
 The young organs of vegetation, such as the germ, the embryo, the young rootlet, 
 and the cotyledons, consist of cells with extremely delicate walls, which enclose chiefly, 
 and in greater proportion than the other tissues of plants organic compounds consist- 
 ing of carbon, hydrogen, oxygen, nitrogen, and sulphur. These substances are very 
 similar in composition and properties to those forming the principal part of theanimal 
 body. They are classed together under the term albuminoids. The young organs 
 of plants, besides being very rich in albuminous substances, also contain a very large 
 proportion of mineral constituents which remain as ash when the organic portion is 
 burnt. 
 
 The albuminoids of the vegetable cell are saturated with water, presenting the 
 appearance of a viscid material insoluble in water and mixed with granular concretions. 
 This material constitutes the protoplasm of the cells, and it is the seat of the chemical 
 changes, such as the formation of cellulose or the substance of which the cell-mem- 
 brane consists. 
 
 RE 
 
610 
 
 COMPOSITION OF PLANTS. 
 
 The cells are formed in the midst of the juices which permeate the plant, and as 
 they are successively developed become agglutinated together with the cells previously 
 produced. The original spherical form of the cells often becomes modified in con- 
 sequence of the pressure attending this agglutination ; and sometimes they form in 
 this way elongated tubes communicating at their contracted extremities, as shown in 
 the longitudinal section of the asparagus (fig. 428 ; fig. 429 being a transverse sec- 
 tion) : they then form what is called vascular tissue, other illustrations of which are 
 to be found in hemp and cotton fibres. 
 
 As growth proceeds, the cells contained in the seed alter their form and arrange- 
 ment in the most diverse manner. They change into cells of other kinds, elongated 
 cells unite by fusion of their outer surfaces into tubes and vessels ; in many cases the 
 extremely delicate cell membrane thickens considerably by the deposition and accumu- 
 lation of various substances. But whatever change of form may take place, whatever 
 shape or size the vessels or tubes may assume, the material forming their envelope 
 
 FIG. 428. 
 
 FIG. 429. 
 
 remains always the same. This is cellulose, or, as it is sometimes called, lignin, 
 an organic substance consisting of carbon, hydrogen, and oxygen. The relative 
 proportions of the elements in this substance are such that the hydrogen and oxygen 
 bear the same ratio to each other as in water ; hence cellulose and bodies of similar 
 composition are classed together under the term carbo-hydrates. 
 
 The epidermis or external envelope of plants consists of cells the walls of which 
 have become very much thickened, and the cellulose partly changed and partly im- 
 pregnated with various substances, such as fat, albumin, salts of calcium, and silica. 
 When the epidermis is detached or injured, the underlying tissues acquire the charac- 
 ter of the epidermis cells, and by absorption of those substances become changed into 
 cork tissue. 
 
 The thin elongated cells which constitute cotton and are the seed hairs of the 
 cotton plant, as well as the cells thickened by concentric layers in the fibres of hemp, 
 flax, Pkormium tenax, Agave americana, Urtica nivea, etc., consist of nearly pure 
 cellulose. In the cells and vessels of woody tissue the cell membrane, originally con- 
 sisting of cellulose, is thickened by the gradual deposition and alteration of repeated 
 layers of cellulose ; it is thus converted into woody fibre, and is, moreover, impreg- 
 nated with colouring matters, resin, etc. In algae and lichens the cellulose is pene- 
 trated with 1 i c h e n i n. In some cases the membranes of individual cells are cemented 
 togetherwithpectose, pectin, pec tic acid, or the calcium, potassium, or sodium salts 
 of this acid ; as, for instance, in the epidermis tissue of the Cactacees, in the vascular 
 tissue of hemp and flax, as well as in the parenchyma of the succulent roots, tubers, 
 or rhizomes of carrots, sugar beets, potatoes, and some fruits. 
 
 By suitable treatment these foreign substances can be separated from cellulose. 
 For this purpose it is sufficient to macerate thin slices of the roots, etc., for about a 
 fortnight in hydrochloric acid diluted with ten times its volume of water, then to wash 
 them with water, afterwards with dilute ammonia, and finally again with water. The 
 cellulose can thus be almost entirely deprived of most foreign ingredients. 
 
 The woody fibres which constitute the greater part of the pith and sap wood of 
 trees are not cemented together with pectin substances. 
 
 The substance, which permeates the cellulose in wood and is called by Payen in- 
 crusting material, is an amorphous, hard, brittle substance of complex composition, richer 
 
COMPOSITION OF PLANTS. 
 
 611 
 
 in carbon than cellulose ; the proportion of hydrogen to oxygen is greater than in water 
 and in the carbo-hydrates. It occurs in the hard masses of the bark of trees, in 
 certain hard concretions of fruits especially pears in the shells of nuts, and in the 
 stones of fruits. The amount of this substance in the different kinds of wood varies. 
 
 The hardness, weight, and brittleness of wood are due to incrusting materials. 
 The greater amount of carbon and hydrogen in wood, as compared with cellulose, is 
 likewise due to their presence. These substances are accompanied by colouring matters 
 and by albuminoids, which are the remains of the protoplasm of the young cell. The 
 younger the wood the less incrusting materials it contains, and the richer it is in 
 unaltered cellulose and albuminoids. 
 
 Each fibre of woody tissue is enveloped with a solid albuminous material which, 
 when moistened with iodine solution, gives no reaction with sulphuric acid ; and on 
 this account woody tissue does not give the cellulose reaction, or but indistinctly, 
 until the foreign substances have been got rid of. 
 
 The mineral substances present in plants are not accidental, they are found partly 
 in the cell membrane, partly in the juices of the cell, partly deposited in certain parts 
 of plants, such as the epidermis or in the interior of the tissues.* 
 
 Thus calcareous secretions are often found in the leaves of the Urticacea, in the 
 spongy cell membranes of the seeds of various sorts of Celtis, in some of the Characees, 
 and in the incrusted tissues of Coralllna. 
 
 Crystalline concretions occurring free in the cell are term edraphides. Such con- 
 cretions of calcium oxalate are very frequent in phanerogamous plants, especially in 
 the leaves round the bundles of vessels forming the veins of the leaf. They also occur 
 in the branches, and are very plentiful under the layers of epidermis in the cellulose 
 tissue of the CactacecB. 
 
 The presence of calcium carbonate in such concretions was shown by Payen in 
 1845. Before that time it was thought that the earthy carbonates always found in 
 the ash of plants were produced by the decomposition of salts of organic acids. 
 Although the greater part of the carbonates in the ash is undoubtedly thus produced 
 during combustion, the existence of calcium carbonate in the plant has been con- 
 firmed by others. Some parts of plants are so rich in carbonates that their presence 
 is easily recognised. If ten or twelve seeds of Celtis orientalis are placed in a test tube 
 and covered with diluted hydrochloric acid, brisk effervescence takes place owing to 
 the escape of carbonic acid ; which, if the test tube be closed with a soft cork, is 
 strong enough to drive out the cork after a short time. According to Payen, these 
 seeds contain as much as 40 per cent, of calcium carbonate. 
 
 The accumulation of considerable masses of mineral substances to form such con- 
 cretions is, however, to be regarded as exceptional, but all parts of plants contain 
 mineral constituents to some extent ; indeed, no cells can be formed without a sufficient 
 supply of mineral substances. 
 
 Seeds, spores, fungi, and the germs and buds of the more highly organised plants, 
 contain, besides cellulose or one of the substances analogous to it such as starch, 
 dextrin, inulin, gum, sugar, mannite other substances, such as albuminoids, 
 fat, earthy phosphates, alkalies, silica, and water, which are all necessary for their 
 development and for the exercise of their vital functions. Precisely the same condi- 
 tions prevail in the egg of an animal and in milk, which is the first food of the young 
 mammal ; both in the egg and in milk, as in the case of plants, there are albuminoids, 
 saccharine substances, fat, and mineral constituents. These are the food upon which 
 'both animals and plants subsist during the first period of development or of 
 germination. 
 
 The following table gives the composition of a few plants when dried : 
 
 
 Morels 
 
 Mush- 
 rooms 
 
 Beer 
 Yeast 
 
 Traffics 
 
 Cauli- 
 flower 
 
 Albumin ..... 
 
 44-0 
 
 52-0 
 
 3T36 
 
 62-7 
 
 66-0 
 
 Fat . . . . . 
 
 5-6 
 
 4-4 
 
 2-00 
 
 2-1 
 
 4-5 
 
 Mannite, dextrin, cellulose, etc. 
 
 36-8 
 
 38-4 
 
 59-25 
 
 29'4 
 
 18-3 
 
 Earthy phosphates, alkaline 
 chlorides, silica, etc. . \ 
 
 13'6 
 
 5-2 
 
 7-39 
 
 5-8 
 
 11-2 
 
 Amount of water in the fresh/ 
 
 90-0 
 
 91-0 
 
 90-00 
 
 72-0 
 
 907 
 
 state . . . i 
 
 
 
 
 
 
 * The amount of carbon in most parts of plants varies from 48 to 54 per cent., while 
 cellulose, as already mentioned, contains only 44-4 per cent. This excess in the amount 
 
 EK 2 
 
612 GROWTH OF PLANTS. 
 
 of carbon in plants as compared with cellulose is caused by the deposition of substances 
 richer in carbon than cellulose, such as resin, albumen, fat, etc. These substances 
 are not only richer in carbon than cellulose, but they also contain proportionally more 
 hydrogen ; and therefore in plants there is always an excess of hydrogen relatively to 
 oxygen, the conditions in regard to the amount of elementary constituents being the 
 same in the entire plant as they are in the cells. 
 
 The elemental substances which always occur in all plants are carbon, hydrogen, 
 oxygen, nitrogen, sulphur, potassium, sodium, calcium, magnesium, iron, phosphorus, 
 silicon, and chlorine. Besides these, which must be considered as essential con- 
 stituents of plants, there have been found in certain plants rubidium, caesium, lithium, 
 barium, aluminum, manganese, zinc, bromine, iodine, and fluorine, which may be 
 regarded as incidental. The former must be supplied to the plant if new vegetable 
 substance is to be formed, whilst most plants are able to attain their full growth with- 
 out the presence of the latter ; therefore, the elements of the first-mentioned group in 
 various states of combination form the food of plants. 
 
 As regards assimilation of nourishment plants vary. The lower kinds, as well as 
 the most highly organised, during the period of germination require, as already men- 
 tioned, ready-formed organic material for their nutrition. Fungi obtain this from the 
 substratum upon which they live ; the germinating embryo of the seed and the sprouting 
 buds of the tree, however, obtain this organic material from a store laid up during the 
 previous period of vegetation in the tissues surrounding or accompanying the embryo 
 or the bud. 
 
 But it is quite another thing in the plants provided with green organs or in 
 the young shoot as soon as it has developed green leaves. When this is the case, the 
 most simple compounds of the requisite elementary substances serve as food, as in 
 the case of every plant provided with foliage. These food elements consist of car- 
 bonic dioxide, water, nitric acid, ammonia, sulphuric acid, phosphoric acid, potash, 
 sodium chloride, lime, magnesia, oxides of iron, and silica. 
 
 On examining the cells of the leaves of the higher organised plants there are found, 
 close under the epidermis, numerous cells, in the protoplasm of which is a granular 
 green substance called chlorophyll, to which the leaves owe their colour. 
 
 This substance possesses the property, by the aid of light and warmth, and when 
 the other materials of plant food are present, of decomposing carbonic acid and water, 
 with disengagement of oxygen, and converting these inorganic substances into organic 
 material. 
 
 Green plants produce organic substances out of inorganic substances, while plants 
 that do not contain chlorophyll use organic material to build up their structure. 
 There is, however, a further difference : plants that do not contain chlorophyll not 
 only use organic substance for the building up of their own body, but they also de- 
 compose a part of that substance and convert it into carbonic dioxide, while green 
 plants decompose carbonic dioxide and produce organic substances. The greater part 
 of the dry substance of plants consists of carbon, and therefore above all other forms 
 of food carbonic dioxide must be supplied to plants in the largest quantity. The 
 atmosphere affords a constant supply of this gas, and from that source plants obtain 
 all that they require of this material. The relative amount of carbonic acid in the 
 atmosphere as compared with its other constituents is certainly small, but the absolute 
 quantity is so considerable that it would suffice for sustaining vegetation many years 
 if the whole surface of the earth, not only our gardens and fields but also all sterile 
 places, and the entire surface of the sea, were covered with the most luxurious vegeta- 
 tion. 
 
 Those plants or parts of plants which serve as food for man and animals are, for 
 the most part, burnt in the animal system, and their carbon again converted into 
 carbonic dioxide ; whatever portion does not undergo this change passes after some 
 time into decay. When either plants or animals die the same kind of decomposition 
 lakes place, and all the carbon of the organic substance is converted into carbonic 
 dioxide. Vegetable materials, either of modern growth or those belonging to a former 
 age, when burnt as fuel also give back their carbon as carbonic dioxide to the atmo- 
 sphere. 
 
 Thus plant life and animal life maintain a constant balance. Animals require for 
 their existence oxygen, and they discharge carbonic dioxide into the air. Plants 
 abstract carbonic dioxide from the atmosphere, and maintain the latter in a state 
 respirable by animals by returning to it oxygen. 
 
 All the green parts of plants possess the power of assimilating carbonic dioxide. 
 Plants which live immersed in water behave just in the same manner as those that 
 groir on land. They derive their carbon from carbonic dioxide, which the water 
 animals expire, and they thus render the water habitable by animals. 
 
 Hydrogen and water are abundantly furnished to plants by rain and the water 
 
GROWTH OF PLANTS. 613 
 
 vapour present in the atmosphere. Nitrogen, although it exists abundantly in the 
 free state in the atmosphere, is not thus assimilated by plants. Besides free nitrogen, 
 however, atmospheric air contains two compounds of nitrogen, viz. ammonia and 
 nitric acid. From both these substances plants obtain the nitrogen from which they 
 produce albuminoids and their other nitrogenous constituents. Kain and dew collect 
 the ammonia and nitric acid contained in the air and carry them into the soil, from 
 whence the roots of plants absorb them. The remains of human and animal food are 
 supplied to the earth as manure, and all dead bodies of animals are returned to it. 
 By the process of decomposition and decay nitrogenous organic compounds are trans- 
 formed into ammonia and nitric acid, just in the same way as carbon is converted into 
 carbonic dioxide. By thus returning to the soil all materials capable of decomposition, 
 the soil is supplied with substances which serve again for a new generation of vege- 
 table life. Thus, destruction and reproduction go hand-in-hand. Material existence 
 is in a constantly uninterrupted cycle of change from life to death and from death 
 back again to life. 
 
 In consequence of the source from which carbonic dioxide, water, ammonia, and 
 nitric acid are chiefly derived, these substances are termed the atmospheric food 
 materials of plants. 
 
 All other essential ingredients of plant food are derived from the soil. That soil 
 only can be fertile in which all the nutritive substances are contained ; its productive 
 capacity is determined by the amount and state of combination of the food materials 
 it contains It is not sufficient that the elements above-mentioned are present in the 
 .soil, but they must also be present in such a condition that plants can easily absorb 
 them. The substances present in rocks acquire that condition by the process of 
 weathering under the disintegrating influences of the atmosphere and water, which not 
 only break up their state of aggregation, but also alter their chemical composition, so 
 that their constituents can be absorbed by the roots of plants. As a consequence of 
 this weathering some of the constituents of the soil are rendered soluble in water, or 
 in water containing carbonic acid, while others remain insoluble. 
 
 All the materials of plant food are equally important, although it is true that in 
 all kinds of plants the quantity of constituents derived from the soil is less, and fre- 
 quently much less, than the other part of them ; still it is not possible for any plant, 
 or even the smallest organ of a plant, to be formed when they are wanting ; even when 
 a single constituent fails the remainder are worthless. Therefore vegetation is only 
 possible when all are present together, and the productive capacity of land is deter- 
 mined by that food material which it contains in the least quantity. It is thus clear 
 that, in virtue of the weathering process continuing from year to year, the fertility of 
 land could be maintained by returning to it all the constituents of the plants grown 
 upon it. This, however, does not generally happen. Each year a great quantity of 
 plant material is produfcd in the form of corn, milk, meat, etc., which is consumed in 
 large towns ; and, instead of being returned to the land again, the products contaminate 
 the soil and the atmosphere of the towns, as well as the rivers into which the drainage 
 of the towns is discharged. Not only in this respect do injurious results follow, but 
 the continual drain upon the land where those materials were grown causes it to 
 become poorer in the food materials which are necessary for the growth of plants. 
 This impoverishment of the soil can be prevented either by returning to the land the 
 refuse of towns, or by giving back to it in another form the food materials of plants. 
 
 The proximate organic constituents of plants, in the free state or chemically com- 
 bined, generally occur in various amounts in the individual organs, while some are 
 found especially in particular tissues. Thus the albuminoids, together with some 
 other nitrogenous and mineral substances, preponderate in the young growing organs ; 
 cellulose preponderates in the cell membranes, which are more delicate the younger 
 the tissues and the greater the vegetative activity in them. 
 
 Sugar exists as an aqueous solution in the parenchyma of the cells, deposited 
 round the fibro- vascular bundles, as in the sugar cane or sugar beet. 
 
 Starch is found in similar tissues, as in the potato. 
 
 Lignin penetrates and thickens especially the cell membranes of woody tissue, which 
 in the early state consist of pure cellulose. 
 
 Various ethereal oils, resins, and balsams are secreted in the glands, reservoirs, 
 and ducts of the plant. 
 
 In the ice plant (Mesembryanthemum crystallinum) oxalates of sodium and potas- 
 sium in alkaline solution fill numerous glands of the leaves and branches. 
 
 One or two rows of cells situated immediately below the epidermis of the seeds of 
 the Graminece are filled with drops of oil or albumin. The cotyledon of the same 
 seed exhibits a large number of cells, the contents of which consist of oil aud 
 albumin. 
 
 The cotyledons of the seeds of the so-called oil fruits are especially rich in cells 
 
614 GROUPS OF ORGANIC SUBSTANCES. 
 
 containing oil and albumin. Seeds generally are rich in albuminoids, and these are 
 always accompanied by fat, or starch, and the mineral food of the plants. 
 
 Those branches of industry embracing the manufacture of organic substances aim 
 generally at the extraction of the constituents of plants and animals (textile fibres, 
 starch, sugar, fats and oils, alkaloids, organic acids and dye stuffs, albumin, gelatin, 
 etc.), or at the conversion of vegetable and animal substances into other products 
 (dextrin, grape sugar, bread, wine, beer, alcohol, and vinegar, soap, leather, etc.). 
 
 Between the various groups of organic substances certain broad distinctions and 
 relations exist, and thus a sort of classification is possible. 
 
 First in order, from their simplicity of composition, come the essential oils ; these 
 consist for the most part of liquid hydrocarbons having the same composition as 
 turpentine Ci H 16 , but including several allotropic modifications. Other oils are com- 
 posed in part of a mixture of these or one of them, with polymeric modifications of the 
 composition C 15 H 24 , while a few contain also C 20 H 3 ,>. Most essential oils also contain 
 oxidised substances, which generally partake of the nature of camphors C 10 H 16 0, and 
 associated with these are still more highly oxidised bodies, as gums and resins. 
 The fixed oils and fats come next in order of simplicity of composition ; they genera lly 
 contain oleic acid C 18 H 34 2 and allied compounds, while the fatty acids CnH 2n -0 2 
 sometimes occur in the free state. More often, however, the fatty acids are in com- 
 bination as glycerides or ordinary fats, such as stearin C 3 H 5 (C 18 H 35 2 ) 3 . 
 
 The different' kinds of sugar and starch are also made up of carbon, hydrogen, and 
 oxygen, the two latter elements being present in the same proportions as in water ; 
 hence these substances are termed carbon-hydrates. Thus, cane-sugar is C 6 H, 2 G , 
 and potato starch is C 6 H, 05. Cellulose and such substances are allied to starch. 
 
 The organic acids constitute another group of substances, presenting no features 
 of composition in common, beyond their nature as acids, as in the case of tartaric 
 acid C 4 H 6 6 ; malic acid C 4 H 6 5 ; citric acid C 6 H 8 7 ; meconic acid G 7 H 4 7 ; gallic 
 acid C.H 6 5 , etc. Allied to gallic acid is tannic acid, and this latter substance is 
 closely related to tannin, which in its natural state is said to be a glucoside. Grlucosides 
 are met with widely in organic nature, and may be split up into glucose and acids or 
 other substances, just as fats split up into glycerine and acids. 
 
 The colouring matters or dye stuffs are partly oxidised compounds, such as alizarin 
 C 10 H 6 3 ; while yet others are also nitrogenous in nature, as indigo blue (C 8 H 5 NO). 
 
 Again, the alkaloids are nitrogencais compounds, as for instance quinine 0201124^202, 
 and morphine C 17 H 19 N0 3 . 
 
 More complex in constitution are the substances allied to albumin, which occur in 
 both plants and animals. All of them contain nitrogen and a few contain sulphur, 
 but they possess in common a distinct relationship to one original form which has a 
 formula C 72 H, 12 N 18 S0 23 . 
 
 Another group of organic substances occurring less widely than the albuminous 
 principles, but possessed of equal complexity of constitution, contain another element, 
 viz. phosphorus, but no sulphur. These substances occur in the nervous tissues of 
 animals, and resemble in general structure the fats, but differ in being nitrogenous 
 and phbsphorised. An instance of this kind is presented by lecithine C 42 H 84 NP0 8 , 
 which occurs in the yelk of eggs and in the brain. Such substances as those just 
 described are found in combination with salts, a feature due to their partly alkaloidal 
 nature. 
 
615 
 
 CELLULOSE. 
 
 The substance of which the solid framework of plants consists has received this 
 name from its origin in the form of cells. The physical properties of cellulose vary 
 according to the internal arrangement of the particles. In Iceland moss they are so 
 loosely aggregated, and moreover their cohesive power is so weakened by the deposi- 
 tion of inulin between them, that upon simply boiling the moss with water the cells 
 swell up and disintegrate, forming a liquid which gelatinises on cooling. The cellu- 
 lose in this gelatinous mass is coloured blue by iodine, a reaction which is also 
 exhibited by a few other lichens, by the tissues of a number of fungi, and by the very 
 thick membranes of the leaf cells of several Aurantiacese. 
 
 This coloration by iodine has given rise to the assumption that, in such cases, the 
 substance is different from ordinary cellulose, and it has been called lichen-in, and 
 it was further assumed that this substance was converted into a gum-like substance 
 by boiling it with water. The liquid contains, however, no gum, since it does not 
 yield mucic acid when treated with nitric acid. There is indeed no sufficient reason 
 for assuming that the substance called lichenin is specifically distinct from cellulose, 
 rather than one of the numerous modifications of cellulose, all of which differ merely 
 in the arrangement of the cellulose molecules. 
 
 The substance of the cells in other plants has a very different character. The 
 inner shell of the cocoanut, and the fruit of Phytelephas macrocarpa (vegetable ivory), 
 have cells with thick walls of an almost stony consistency. To this property vege- 
 table ivory owes its name, and its application to articles of turned and carved work. 
 
 The woody fibre of trees, as above mentioned, consists in part only of cellulose, 
 and, according to the age of the cells, is more or less incrusted with other substances, 
 
 FIG. 430. 
 
 as shown in fig. 430, which represents a section of oak wood. The dark spaces (a ad) 
 are large sap-conducting vessels. 
 
 Composition. Cellulose has the same percentage composition as starch, dextrin, 
 inulin, etc., containing : 
 
 Carbon . . - . . . . . . 44-44 
 
 Hydrogen . . . '.V 6'18 
 
 Oxygen . . ' 49*88 
 
 100-00 
 
616 CELLULOSE. 
 
 It is, therefore, isomeric with those substances. Its composition is always the same 
 from whatever plant, or part of a plant, it is obtained, and it is represented by the 
 formula C 12 H 20 0, . 
 
 Characters. Cellulose when pure is a white translucent substance, insoluble in 
 water, alcohol, ether, fats, or ethereal oils. Its specific gravity is about T5. 
 
 Dilute aqueous solutions of caustic alkalies and dilute acids do not affect moder- 
 ately compact cellulose even by protracted boiling. Concentrated sulphuric or phos- 
 phoric acid decomposes cellulose even in the cold, converting it first into a substance 
 resembling starch, then into dextrin, and finally into grape sugar. Very strong nitric 
 acid converts cellulose into pyroxylin, or gun cotton. (See p. 227.) 
 
 Strong oxidising agents, such as chlorine and the hypochlorites. effect the oxidation 
 of cellulose even in the presence of water. When paper pulp, or filter paper torn to 
 shreds, is digested with a saturated aqueous solution of bleaching powder, and the 
 mixture slightly heated, a very violent reaction takes place, which continues even after 
 the source of heat has been removed. The cellulose is disintegrated and oxidised, 
 carbonic acid being copiously evolved. The destruction of linen and other organic 
 tissues in bleaching, by the inconsiderate use of bleaching powder, is due to this cause. 
 
 Pure cellulose is not altered by exposure to atmospheric air, but, as it occurs in 
 wood and the ligneous tissues of plants associated with albuminous and resinous 
 substances, it undergoes gradual alteration, and is converted, probably by oxidation, 
 into a friable substance of a yellow or brown colour called touchwood. 
 
 Cellulose shows a characteristic behaviour when treated with iodine and sulphuric 
 acid. If cotton, paper, or any vegetable tissue consisting of pure cellulose be 
 moistened with an aqueous solution of iodine, and a drop of concentrated sulphuric 
 acid be then added, a blue coloration is instantly produced. This reaction is also 
 characteristic of starch, therefore it may be assumed that, in the case of cellulose, the 
 reaction is due to the conversion of cellulose into a substance allied to starch by the 
 action of the sulphuric acid. However, some other substances beside starch show the 
 same reaction when treated with iodine and sulphuric acid. 
 
 The facility with which cellulose may be prepared in a state of purity depends 
 upon the raw material operated upon. The easiest method of obtaining pure cellulose 
 is to separate it from white cotton, unsized white paper, or old linen. For this pur- 
 pose the material is boiled for an hour with a dilute aqueous solution of potash or 
 soda (containing about 5 per cent, of alkali), it is then washed with water, and boiled 
 with an equally dilute solution of sulphuric acid, again washed with water, and finally 
 washed with alcohol and ether. The cellulose obtained by this means is contaminated 
 only with traces of silica. 
 
 It is far more difficult to obtain pure cellulose from wood, or the woody tissues of 
 plants. It is necessary to boil the wood first with a solution of bleaching powder, 
 then to wash it with water, boil it with a strong solution of potash, and evaporate the 
 liquid to dryness ; the undissolved portion is again treated with bleaching powder, 
 these operations being repeated successively until the substances incrusting the wood, 
 such as lignin, nitrogenous matters, colouring matters, fats, etc., have been removed. 
 This method, however, causes considerable loss of material, owing to the action of 
 chlorine and potash upon the cellulose. 
 
 According to Fr. Schultze very pure cellulose may be obtained as follows. The 
 raw material is digested in the cold for a length of time, varying from a fortnight to 
 three weeks, with a mixture of 8-10ths of its weight of potassium chlorate, and 12 
 parts of nitric acid of specific gravity TIOO. The mixture, in order to avoid explosion, 
 should not be heated. A bleached mass is thus obtained, which is washed first with 
 cold water, and then continuously with boiling water, afterwards digested with dilute 
 ammonia, again washed with water, and finally washed with alcohol and ether. 
 Though the cellulose remains intact by this process, it is not always possible to de- 
 compose all the lignin. 
 
 Cellulose may be also obtained from the solid excrements of animals, especially 
 the ruminants. The individual tissues are in this case destroyed by mastication, and 
 a number of foreign substances are extracted by the process of digestion. The finer 
 and more loosely aggregated particles of cellulose are dissolved by the digesting 
 process, and absorbed by the body of the animal, while the more solid portions, the 
 layers of epidermis, the vascular bundles, and the woody tissue, pass into the 
 excrements. 
 
 Cellulose is dissolved by an ammoniacal solution of oxide of copper. A solution 
 of this kind may be prepared in different ways. Peligot prepares it by oxidising 
 copper turnings in contact with ammonia ; a glass tube open at both ends is filled 
 with copper turnings that have been oxidised on the surface by heating to redness and 
 then f educed in a stream of hydrogen, and a very strong solution of ammonia gradually 
 
TEXTILE FIBRES. 617 
 
 dropped upon the copper turnings. The blue solution thus formed is passed once or 
 twice more over the copper turnings so as to complete its saturation. 
 
 Cellulose, as it is contained in unsized paper, swells up and very soon dissolves. 
 A solution of ammonium cuprate, containing from 3 to 4 per cent, of cellulose dissolved 
 in it, has a viscous consistency. In order to separate undissolved substance, and ob- 
 tain a clear solution of cellulose in ammonium cuprate, an asbestos filter must be 
 employed for filtering it. 
 
 By the addition of dilute hydrochloric acid to the clear solution of cellulose in 
 ammonium cuprate, the cellulose is precipitated in a pure state. 
 
 Cellulose thus prepared, when examined under the microscope, exhibits granular 
 flakes of an indefinite form. In spite of the extraordinarily fine state of division of 
 cellulose thus prepared, it is not converted into the starch-like modification; it is 
 chemically unaltered, and is not coloured blue by iodine until first acted upon by sul- 
 phuric acid. 
 
 If cellulose held in solution by ammonium cuprate is in a state of chemical com- 
 bination, the combination is certainly of a very unstable nature, for a solution of this 
 kind merely requires diluting with water to cause the separation of cellulose. Or 
 further, if to a moderately diluted solution hydrochloric acid be added, drop by drop, 
 so as to partly neutralise the great excess of ammonia, cellulose is likewise pre- 
 cipitated. When thus precipitated cellulose, according to Payen's researches, is not 
 pure, but alwaj^s contains copper. 
 
 When vegetable tissues are treated with a solution of ammonium cuprate the 
 parenchyma cells and the cell nu*clei easily dissolve, while the epidermis, the 
 cuticle, and the woody fibres, are not affected, on account of the presence of incrusting 
 substances. 
 
 Different substances behave differently when treated with a solution of ammonium 
 cuprate, which may be seen from the following resume : 
 
 The pure cellulose of textile fibres dissolves, and is precipitated upon saturating 
 the solution with acids. 
 
 Mucilage, a body isomeric with cellulose, behaves like cellulose. 
 
 Gluten dissolves completely. 
 
 Fibrin swells up, dissolves completely after standing 36 hours ; upon saturating the 
 solution with an acid 93 per cent, of the fibrin is precipitated, a part being decomposed. 
 
 Albumen coagulated white of egg swells up, dissolves completely in 3 days; upon 
 saturating with acid only 53 per cent, is precipitated. 
 
 Gelatin, softened in water, is dissolved in a few seconds, and no precipitate is 
 formed on addition of acid to the solution. 
 
 Wool swells up, disintegrates, is mostly dissolved after a space of 6 days ; upon 
 saturating the solution with an acid only 16 per cent, separates out. 
 
 Hair behaves like wool. 
 
 Horse hair dissolves to the extent of 94 per cent., of which 38 per cent, is pre- 
 cipitated upon saturating the solution with an acid. 
 
 Horn dissolves completely, 1 6 per cent, being precipitable by acids. 
 
 According to Schlossberger cotton, dissolved in ammonium cuprate and treated 
 with a concentrated solution of common salt, becomes, after a time, insoluble, and 
 after washing and drying is coloured blue by iodine. Not only do acids effect the 
 precipitation of cotton dissolved in ammonium cuprate, but gum, dextrin, grape sugar, 
 etc., also precipitate cotton from such solutions. 
 
 Amorphous cellulose is more easily converted into dextrin and sugar than the un 
 altered cellulose of cotton. 
 
 This different deportment of cellulose under different conditions serves to show 
 what entirely different properties the same substance may assume, according to its 
 organised structure and the state of molecular aggregation. 
 
 Cellulose can also be distinguished by chemical means from other constituents of 
 textile fibres. A solution of nickel oxide in ammonia dissolves silk but not cellulose ; 
 therefore, in mixed tissues, cotton, linen, and hemp remain unaltered by this reagent. 
 
 Uses. The cellulose of cells with delicate walls, since it is digested by animals, 
 must be considered as an article of nourishment playing the same part as starch in the 
 animal economy ; but it is not known what secretion of the animal system effects 
 the digestion of cellulose. 
 
 Cellulose in the form of long-extended cells forms the chief constituent of the 
 textile fibres known as flax, hemp, cotton, and the fibres of Agave americana, 
 Phormium tenax, banana, Bb'hemeria utilis, Urtica nivea, etc., which are used in the 
 manufacture of string, ropes, textile fabrics, paper, pasteboard, etc. 
 
 Another application of cellulose is in the preparation of oxalic acid. For making 
 this acid sawdust is evaporated with a very strong solution of potash, and the re- 
 sidue then strongly heated. The mass contains potassium oxalate. 
 
618 CELLULOSE. 
 
 ANIMAL CELLULOSE (Tuiacm). While the epidermis of all the higher organised 
 animals, as well as all their tissues, consists of very nitrogenous material, the epi- 
 dermis of low organised animals is proportionately poor in nitrogen, and a non- 
 nitrogenous substance having the composition of cellulose can be separated from it. 
 This substance was discovered by C. Schmidt, whose observations were confirmed by 
 Loewig and Kollicker. The brown mantle of the Tunicata, the covering of PhaUusia 
 manillaris, the cartilaginous covering of the Ascidice, the mantle of Cynthia, all yield, 
 when treated in succession with hot water, alkalies, acids, alcohol, and ether, a white 
 substance which retains the shape of the material employed. This substance is animal 
 cellulose, or tunicin. Although its composition is the same as that of cellulose obtained 
 from plants, and although both have many properties in common, it is still questionable 
 whether they are identical, and tunicin certainly possesses properties which distinguish 
 it from vegetable cellulose. According to Berthelot it is coloured yellow by iodine, 
 and it is difficultly soluble in ammonium cuprate; again, vegetable cellulose is carbon- 
 ised by boron fluoride, while tunicin is not attacked by that reagent. 
 
 Animal fibres are distinguishable from vegetable fibres by their more complex 
 chemical composition. Thus, wool is an albuminous substance, and contains a large 
 amount of nitrogen and some sulphur ; silk contains no sulphur. Animal fibres dis- 
 solve easily when boiled in a solution containing from 5 to 10 per cent, of potash, 
 while the more compact cellulose of the vegetable fibres is unaltered. In order there- 
 fore to determine whether a fabric consists of wool or silk alone, or mixed with cotton, 
 flax, or hemp, it is only necessary to boil a small piece for a short time in a weak 
 solution of potash. If the fabric consists of pure'silk or wool it is completely dissolved ; 
 if it contains other fibres they remain undissolved. In order to determine the pro- 
 portion between these fibres it is best to cut out from the fabric a piece of a definite 
 size, and to count the individual fibres. The piece is then boiled with the solution of 
 potash, and when the animal fibres are dissolved it is washed and dried, and the fibres 
 left intact are counted. The difference between the number of fibres before and after 
 boiling gives the amount of wool and silk fibres, the remainder the number of the 
 vegetable fibres. In undyed materials the percentage by weight of both kinds of fibres 
 may be determined by drying and weighing the piece of fabric in question in a closed 
 vessel before boiling with potash, and again weighing it after washing and drying. 
 
 Wool and silk, when occurring together, may be distinguished by treating the 
 fabric containing them with a solution of potassium plumbate, prepared by dissolving 
 10 parts of potash in 100 parts of water and boiling it with 15 parts of litharge ; the 
 piece of fabric is plunged into the cold solution of potassic plumbate. All substances 
 containing sulphur, such as wool, horn, hair, skin, nails, muscles, albumin, etc., assume 
 a brown colour, while substances that do not contain sulphur, such as silk, bones, glue, 
 chitin a substance contained in the wing-cases of beetles and in the carapace of crabs 
 ivory, gelatin, etc., are not coloured by this reagent. 
 
 For detecting cotton, wool' and silk, in mixed tissues, they are boiled with concen- 
 trated hydrochloric acid. Cotton is completely destroyed, being partly dissolved and 
 partly rendered so brittle that it can be separated as dust from the remaining mass 
 after washing and drying. This residue is then placed in cold strong nitric acid, which 
 dissolves the silk in a few minutes, while the wool remains comparatively unaltered. 
 
 The fibres of New Zealand flax (Phormium tenax) and of jute (Conchorus capsu- 
 laris), when occurring in the same fabric together with hemp and flax, may be recog- 
 nised by the curious behaviour of the nitrogenous constituents of the former. The 
 piece of fabric to be examined is plunged for a moment into red fuming nitric acid, of 
 a specific gravity of 36 B. ; New Zealand flax (provided it was not before completely 
 bleached) is at once reddened. The following reaction is still more characteristic. 
 Pieces of the yarns or fabrics to be tested are dipped in a saturated solution of chlorine. 
 In the case of fabrics, warp and woof ought to be isolated by drawing out a few fibres 
 from the edges of the piece in order to liberate the two crossing threads. After the 
 pieces have remained a minute in the chlorine water they are taken out, placed upon 
 a flat plate, and covered with ammonia, which produces characteristic colorations. 
 The fibres of jute and Phormium tenax assume a red colour which rapidly darkens, 
 and in about a minute passes into brown ; cotton and linen assume, according as the 
 flax has been more or less steeped, a yellow, orange, or brownish hue, which cannot 
 be mistaken for the coloration assumed by the New Zealand flax. Of course these 
 reactions can only take place when the fibres have not been previously fully bleached, 
 for the pure cellulose of these fibres does not behave in this way either with chlorine 
 and ammonia or with nitric acid ; the reaction is entirely due to the foreign substances 
 present in the fibres. 
 
 The fibres of plants as already stated are connected together with pectates and 
 albuminoids, and always contain some remains of protoplasm. To destroy these and 
 to set the fibres free is the object of steeping or retting. This operation is 
 
PREPARATION OF FLAX. 619 
 
 attended with various evils, such as the contamination of streams and the destruction 
 of fish, the charging of the air -with disgusting smells, etc. A new method discovered 
 in America by Schenk obviates all these nuisances, and seems likely with a few im- 
 provements to give a new direction to the preparation of flax and hemp. 
 
 The flax is grown upon a dry if necessary, drained and manured soil, and is 
 with advantage drilled in rows. The crop must not be got in too late, the seeds must 
 still be soft, the stalks yellow below, but from the middle upwards still green. After 
 plucking, the plants are laid in rows in an inclined position against one another, m 
 order to ripen. The seed perfects itself at the expense of the sap still contained in 
 the plant, the fibre obtains great firmness, and a slow drying of the plant takes place 
 from below upwards. Passing showers do the plant no harm. 
 
 The flax bound in bundles is then carried to the dressing-house, where it is stored 
 up in barns or sheds for further treatment. 
 
 There the first operation is the collection of the seeds. For this purpose the stems 
 are grasped in the hand, and placed, with the lower end foremost, between a pair of 
 revolving rollers. In passing through these rollers the fragile seed capsules are 
 crushed and the seed falls into a chaff machine, where it is freed from the remains of 
 the capsules. The rollers employed are of cast iron and hollow, having each a dia- 
 meter of 6 to 8 inches ; they are set one above the other, and the lower one alone re- 
 ceives a rotatory motion, while the upper one acts by its weight alone. 
 
 After separation of the seeds, the next thing is to separate the stems from the 
 roots. For this purpose the bundles, just as they come from the rollers, are beaten 
 between the hands upon a table, so as to get them in an upright position ; in this 
 position the lower portions are held in a kind of chaff-cutting machine, which sepa- 
 rates the stems from the roots. There then follows an accurate sorting out ; the 
 bundles are loosely strewed upon a table, and the too short or too thick stems are 
 removed. Three sortings can be made with advantage, each of which is afterwards 
 worked up for itself. 
 
 The retting process is carried out in a water tank with a false bottom. The stems, 
 once more arranged together in bundles, are placed upright upon the false bottom ; 
 when the rat is nearly full up to the margin with the stems, a wooden trellis or 
 grating is laid over them, and the vat is completely filled with water, having a tem- 
 perature of 36 C., so that not only the stems but also the wood grating is covered. 
 The temperature of the water sinks by this operation to 25. After a short time 
 fermentation sets in, gases are evolved, and the liquid smells slightly of sulphuretted 
 hydrogen. When this is observed, the water is renewed by opening the cock of a 
 water-pipe underneath the false bottom. From this pipe branches another, opening 
 just at the surface of the liquid, which serves to drive the scum collecting on the 
 surface into an outlet pipe placed opposite it. In this way a stream of lukewarm 
 water is made to flow regularly through the vat, regulating the fermentation, and at 
 the same time carrying away all soluble substances and those rendered soluble during 
 fermentation. After a period of from 72 to 96 hours, according as soft or hard water 
 has been used, the retting is complete, which is easily seen when upon crushing the 
 stem the bast separates from the woody tissue beneath. 
 
 The vat is then emptied by means of an outlet pipe at the bottom, and the wet 
 flax placed in a machine, consisting of two pairs of rollers, in order to press out from 
 it the remainder of the retting water. When the flax has passed the first pair of 
 rollers, it is washed with water to remove impurities, and it is then passed through 
 the second pair of rollers which squeeze out the greater part of the absorbed water. 
 
 When the weather is suitable, the drying of the flax is carried out in the open air, 
 the stems being fastened between wooden clasps and hung up in an airy shed. In 
 winter time and during damp weather drying sheds, specially heated and ventilated, 
 are necessary. After drying, the flax is stored up from two to three months, and the 
 straw passed through a crushing machine consisting of five pairs of rollers, each 
 crushing finer than the last, whereby the brittle and woody covering of the stems is 
 broken, and this is then removed by a scutching machine. The flax now only 
 requires passing through a heckling machine in order to fit it for the market. 
 
 This method of preparing flax avoids all the evils attending the ordinary process, 
 and, besides this, the process admits of being watched and regulated, so that a product 
 is obtained of better quality than that got by the old retting method. 
 
 WOOD. 
 
 The tissue of the different kinds of wood employed in the arts and industries consists 
 essentially of cellulose impregnated with incrusting matters, such as resin and 
 similar substances, and contains also various nitrogenous and non-nitrogenous 
 substances, various fats, oils, colouring substances, and ash constituents. 
 
620 WOOD. 
 
 The substances penetrating and incrusting the cell membranes of the tissues are 
 hard and brittle ; their amount varies in the individual kinds of wood, being more 
 abundant in heart than in sap wood, and in the hard and heavy kinds of wood than 
 in the soft and light varieties. They are richer in carbon than cellulose. The greater 
 percentage of carbon and hydrogen in wood as compared with cellulose depends upon 
 the presence in it of the incrusting substance. According to Payen's researches, 
 however, it is not a simple substance, but a mixture of different substances, which 
 penetrate the cellulose in different proportions according to the variety of wood and 
 the rapidity of its growth. 
 
 Upon the proportion of incrusting material in wood depends its density, hardness 
 and capacity for receiving a polish. Incrusting material increases the value of wood 
 as fuel by reason of the hydrogen it contains. The richer the various kinds of wood 
 are in incrusting material, the more acetic acid do they yield upon dry distillation. 
 Thus Payen operating under nearly the same conditions obtained from different 
 materials the following amounts of pure acetic acid : 
 
 Oak wood 4-0 per cent. 
 
 Poplar wood . . . 3-6 
 
 Cotton 27 
 
 Starch 2-3 
 
 Wood containing 25 per cent, of water, when submitted to dry distillation, yields on 
 the average 28 per cent, of carbon, 23 per cent, of pyroligneous acid and tar, and 39 
 per cent, of gaseous products. The maximum quantity of pure acetic acid obtained 
 is 5 per cent., but the yield seldom exceeds 3 per cent. 
 
 In determining the density of the different kinds of wood it is important to 
 distinguish between the real and apparent specific gravity. In a dry state, all the 
 tissues of wood as well as the inner parts of the cells are filled with air. If therefore 
 a given volume of wood be weighed in air or in water without previously expelling 
 the air from the tissues and cells, an apparent or false specific gravity is obtained. 
 Kumford found that the actual specific gravity of wood is always greater than that 
 of water, and that the difference in specific gravity between the different kinds of 
 wood is very slight, being generally between 1-462 and 1-534. For ordinary purposes, 
 however, the knowledge of the actual specific gravity of wood is of but slight moment ; 
 the apparent specific gravity or the weight of a definite volume of dry wood 
 weighed in the air is far more important. But, even in regard to this character, 
 only approximate data can be obtained, and the same kind of wood has a different 
 density according to the nature of the soil upon which it is grown, the conditions of 
 culture, climate, etc. ; as will be seen from the following table : 
 
 Kind of wood Specific gravity 
 
 Ebony . . 1-300-1-400 
 
 Oak (60 years old, heart wood) . . --'," * 1'170 
 
 Nut (heart) . . . ... . . I'OOO 
 
 Eo e wood ......... 0-800 
 
 Oak (Quercus pedunculata) heart .... 0-850-0-800 
 
 sap .... 0-700-0-640 
 
 Oak (heart) . . . . ,. . '.' . . 0-790 
 
 (sap) 0-600 
 
 Acacia . ">. 0700-0-720 
 
 Beech and larch 0-750-0-800 
 
 Scotch fir . . 0-600-0-650 
 
 Small beech 0720-0-750 
 
 Fir \ . ..' . 0-490-0-495 
 
 Willow .', . . 0-492 
 
 Poplar . 0-400-0-550 
 
 Paulownia imperialis 0'380 
 
 A cubic centimetre of the dry wood of 60 years' old oak weighs therefore 1-170 
 grams, a cubic decimetre T170 kilos, and a cubic metre 1170 kilos. 
 
 Composition. Trunk wood when burnt yields 0-5-0*9 per cent, of its weight 
 of ash ; the bark-and twigs are far richer in ash, sometimes yielding 2'5 to 3 - per 
 cent. The nitrogenous constituents of trunk wood seldom exceed 0-5 to 1 per cent. 
 The amounts of carbon, hydrogen and oxygen in a few different kinds of wood, as 
 compared with pure cellulose, after deduction of the ash and nitrogenous constituents, 
 are given in the following table. The fourth column of the table contains the excess 
 of hydrogen, i.e. the amount of hydrogen which remains as difference if the total 
 amount of the oxygen present be considered as combined with hydrogen in the form 
 
COMPOSITION OF WOOD. 
 
 621 
 
 of water. The last column of the table gives the carbon equivalents of wood ; these 
 data are calculated under the assumption that the excess of hydrogen has three times as 
 great heating value as an equal quantity of carbon ; they are thus found by multiplying 
 the excess of hydrogen by three, and adding the result to the actual percentage of 
 carbon. 
 
 
 Carbon 
 
 Hydrogen 
 
 Oxygen 
 
 Excess of 
 Hydrogen 
 
 Carbon 
 Equivalents 
 
 Prunus Mahaleb wood . 
 
 53-20 
 
 6-07 
 
 41-03 
 
 0-950 
 
 55-15 
 
 Ebony wood .... 
 
 52-87 
 
 6-00 
 
 41-15 
 
 0886 
 
 55-43 
 
 Fir wood .... 
 
 51-79 
 
 6-28 
 
 41-93 
 
 1-038 
 
 54-90 
 
 Oak wood .... 
 
 50-00 
 
 6-20 
 
 43-80 
 
 0-630 
 
 51-39 
 
 Beech wood .... 
 
 49-25 
 
 6-40 
 
 44-65 
 
 0-720 
 
 5V41 
 
 Poplar wood 
 
 48-00 
 
 6-00 
 
 46-00 
 
 0-025 
 
 58-75 
 
 Cellulose .... 
 
 44-44 
 
 6-17 
 
 49-39 
 
 o-ooo 
 
 44-44 
 
 By treating wood successively with the following solvents dilute hydrochloric 
 acid, dilute and concentrated ammonia, alcohol, carbon bisulphide, concentrated acetic 
 acid, and ammonium cuprate a number of different substances are extracted, the 
 nature and properties of which are still little known. 
 
 Ammonium cuprate dissolves, together with cellulose, a number of compounds 
 which are not precipitated upon neutralising the solution with an acid, and a residue 
 finally remains which resists all the above solvents. 
 
 The results of a few researches of this kind made with different kinds of wood 
 are given HI the following table, from which it may be seen that the individual con- 
 stituents of wood occur in very different amount in the different kinds of wood : 
 
 
 Oa 
 
 k 
 
 Nettle 
 
 
 
 
 
 Tree 
 
 Willow 
 
 
 
 
 (Celtis 
 
 
 
 ffeartwood 
 
 Sap wood 
 
 Australis) 
 
 
 Water escaping at 100 ... . 
 
 9'87 
 
 9-80 
 
 10-60 
 
 9-26 
 
 Water chemically combined . . ,. 
 
 10-60 
 
 4-29 
 
 7-85 
 
 4-39 
 
 Substances soluble in the following mens- 
 
 
 
 
 
 
 
 
 
 
 In hydrochloric acid ] per cent. . " ..> 
 
 4-55 
 
 5-53 
 
 475 
 
 5-71 
 
 In ammonia 5 per cent. 
 
 5-20 
 
 5-20 
 
 5-84 
 
 6-32 
 
 In a saturated solution of ammonia 
 
 8-72 
 
 6-00 
 
 6-38 
 
 622 
 
 In alcohol ...... 
 
 0-50 
 
 0-45 
 
 1-76 
 
 0-35 
 
 In carbon bisulphide .... 
 
 0-65 
 
 0-38 
 
 0-95 
 
 0-07 
 
 In glacial acetic acid .... 
 
 3-90 
 
 3-28 
 
 2-67 
 
 3-68 
 
 In ammonium cuprate .... 
 
 25-52 
 
 37-00 
 
 36-65 
 
 34-80 
 
 Insoluble substances .... 
 
 23-15 
 
 28-00 
 
 14-15 
 
 22-50 
 
 Substances dissolved by ammonium cu- } 
 prate and not reprecipitable by acids [ 
 
 7-34 
 
 7-98 
 
 570 
 
 8-40 
 
 Loss j 
 
 
 
 
 
 
 
 
 
 
 
 100 
 
 100 
 
 100 
 
 100 
 
 The insoluble residue contains some of the incrusting material of the cellulose, 
 together with various other substances, most of which dissolve in hot potash. Hence 
 woody fibre is far from being a simple organic substance, but is on the contrary a 
 mixture of a number of different substances. 
 
 Payen found in the incrusting material four substances, which, according to their 
 solubility, he termed respectively lignose, iignin, lignon, and lignireose. The behaviour 
 of these substances towards different solvents is as follows : 
 
 
 Menstrua in which the substances 
 
 Menstrua in which the substances 
 
 
 are soluble. 
 
 are insoluble 
 
 Lignose 
 Lignon 
 Lignin 
 
 potash 
 potash 
 potash 
 
 soda 
 soda 
 soda 
 
 ammonia 
 ammonia 
 
 alcohol 
 
 water 
 water 
 water 
 
 alcohol 
 alcohol 
 
 ether 
 ether 
 ether 
 
 ammonia 
 
 Lignireose 
 
 potash 
 
 soda 
 
 ammonia 
 
 alcohol 
 and ether 
 
 water 
 
 
 
 
 
 
 
 Cellulose . 
 
 
 
 
 
 
 
 
 
 water 
 
 alcohol 
 
 ether 
 
 ammonia 
 
622 
 
 WOOD. 
 
 Of these five substances, at present cellulose alone has been obtained in a pure 
 state; concerning % the nature and properties of the other four bodies scarcely any- 
 thing is known. These substances have been submitted to elementary analysis, the 
 results of which, however, are of no importance, since the analysed bodies may have 
 been mixtures. 
 
 Payen examined well-w r ashed beech wood, and found it to have the following 
 proximate percentage composition : 
 
 Cellulose 40 
 
 Incrusting material . .60 
 
 According to Payen the incrusting material consisted of: 
 
 Lignose 25'2 
 
 Lignon 10'8 
 
 Lignin 21'6 
 
 Lignireose . . 2'4 
 
 The percentage composition of these several constituents was : 
 
 
 Carbon 
 
 Hydrogen 
 
 Oxygen 
 
 
 50*00 
 
 6-19 
 
 43-31 
 
 cellulose 
 incrusting matter ..... 
 
 44-44 
 54-73 
 56-10 
 
 6-18 
 6-20 
 6-09 
 
 40-38 
 40-06 
 47-81 
 
 
 50'10 
 
 5-93 
 
 44-08 
 
 
 62-25 
 
 5-93 
 
 31-82 
 
 lignireose 
 
 67-91 
 
 6-89 
 
 25-20 
 
 Uses. The applications of the different kinds of wood depend upon special 
 qualities, according to which they admit of being arranged in five groups: 1. white 
 soft wood; 2. heavy and hard wood; 3. half hard wood; 4. coloured wood; 5. 
 resinous and scented wood. 
 
 Poplar wood, one of the lightest of all the varieties of wood, is cut into boards for 
 making boxes, casks, etc., and the chief result aimed at is to increase the weight of 
 the articles packed in them as little as possible. Many manufacturers prepare from 
 poplar wood the little boxes for packing lucifer matches. Poplar wood torn into 
 libres is also mixed with rag pulp in the manufacture of paper. For use as fuel 
 poplar is one of the worst kinds of wood, since a given volume of it develops very 
 much less heat than a corresponding volume of any other kind. The wood of the birch 
 is much more valuable as fuel ; it has a far denser tissue, and it contains in the 
 epidermal layers of the bark a white resinous substance which protects bark and 
 wood, and gives the wood a great heating power. The epidermal layers of the birch 
 bark are used for making snuff-boxes and band-boxes ; they resist friction and moisture 
 better than the same material from poplar. In Canada canoes and boats are built 
 of birch bark. Besides these applications, birch bark yields upon distillation an oil 
 known as birch tar oil, which is used for imparting to Russian leather its agreeable 
 smell. The lighter kinds of wood, poplar, alder, willow, lime, etc., yield upon car- 
 bonisation the charcoal for gunpowder manufactories. A recent use of poplar and 
 fir woods is in the manufacture of spirit and paper. 
 
 The hard woods which are used as fuel and for other industrial purposes are very 
 numerous ; among those growing in this country, oak, beech, elm, ash, and chestnut 
 are the chief. The wood of the acacia is very much prized ; it is remarkable for its 
 great hardness and tenacity, which is the result of the cells of the woody fibre being 
 closely packed; the cell membranes are little penetrated with incrusting matter. 
 Owing to the rapid growth of the tree, the wood is comparatively cheap to produce, 
 at least, cheaper than other kinds of wood. In acacia, the sap wood is not very thick ; 
 the amount of heart wood is on the other hand very considerable. Acacia wood, owing 
 to its hardness and capacity of resistance, is used with advantage in the construction 
 of various parts of machinery, i.e. for the teeth of mill wheels, for spinning machines, 
 wheel spokes, and many other purposes. It has proved especially suitable for plank- 
 ing corridors and galleries in mines ; it has been found to be from two to three times 
 as durable as oak, and from four to six times as durable as other kinds of wood. 
 
 The innumerable applications of the different kinds of wood are too well known 
 to need recapitulation here. 
 
 PRESERVATION OF WOOD.- -The preservation of wood is unquestionably one of the 
 most important problems of applied chemistry. Owing to the enormous development 
 
PRESERVATION OF WOOD. 623 
 
 of industry, and the extension of railways, the consumption of wood increases from 
 year to year, while its production not only does not increase, but is in many countries 
 absolutely on the decline. 
 
 In 1791, the forests in France belonging to the State and private individuals, 
 covered a space of 23,497,800 acres, while in 1851 they covered only 21,894,000 acres, 
 thus showing a decrease of 1,603,800 acres during the 60 years. The condition of 
 forests in 1851 was shown to be as follows : 
 
 14,231,100 acres private property 
 4,633,325 public forests 
 3,029,395 state forests. 
 
 Of late the replanting of barren tracts has been extensively carried out, in the 
 Gascoigne especially, large districts have been planted with useful trees. 
 
 From an industrial point of view, as well as a matter of national economy, it is 
 therefore of great importance to render timber more durable and less susceptible of 
 decay. Formerly, only oak wood could be used for the sleepers of railways, while 
 now, by means of an artificial hardening process, many other kinds of wood can be 
 used for this purpose. 
 
 The chief cause of the destruction of wood is rotting or decay, which is brought 
 about by the presence of nitrogenous substances, from which no kind of wood is 
 altogether free. Under the influence of moisture and oxygen these substances decom- 
 pose, and induce the decomposition of the more difficultly decomposable non-nitro- 
 genous bodies, such as cellulose, etc. Moreover, the nitrogenous constituents of wood 
 nourish fungi of all kinds, which by penetrating further into the substance of the 
 wood promote its destruction. The greater the amounts of nitrogenous substances 
 in wood, the more perishable it is. For this reason, wood to be durable should be 
 felled in late autumn or in winter, but never in spring, when it is filled with ascend- 
 ing sap. 
 
 Many substances, very different in their nature, preserve the nitrogenous con- 
 stituents of plants and animals. Among them are tannin, creasote, arsenic, pyroligne- 
 ous acid, lime, salt, blue vitriol, iron dissolved in pyroligneous acid, corrosive subli- 
 mate, etc. Tannin has been employed for ages to preserve the nitrogenous matter of 
 skins, resins and oils for embalming corpses, impregnating wood, etc. ; creasote for 
 rapidly curing meat, etc. ; and salt for the same purpose. Timber impregnated with 
 salt in the salt works of Hallein before the Christian era, has been preserved up to 
 the present time. Aqueous or alcoholic solutions of corrosive sublimate are used for 
 preserving anatomical and botanical specimens. All such substances as are suited 
 for the preservation of animal products may also be used wilh equal efficiency for 
 preserving those of vegetable origin. 
 
 The only difficulty met with in preserving wood by impregnation is that it is not 
 easy to force the antiseptic solutions into the individual cells, tissues and vessels of 
 the wood ; the desired effect can only then be expected when the protective reagents 
 actually come into contact with the substances they are to preserve. Many endeavours 
 have been made, and with varying success, to overcome these difficulties. 
 
 Besides those methods of preservation, which are founded upon the impregnation 
 of wood with antiseptics, it is also possible by various other means to protect wood 
 from rotting, as by charring, baking, or smoking. 
 
 One of the oldest attempts to preserve wood is that carried out by Champy in the 
 year 1813. The object was to preserve from rot the inner woodwork of a very 
 moist powder magazine, the walls of which were to be covered with lead. For this 
 purpose, the wood was soaked for several hours in a tallow bath at a temperature of 
 from 120 to 130. The water contained in the wood was thus expelled as steam, 
 the melted fat taking its place. The wood took up about one fifth'part of its weight 
 of fat. 
 
 Many liquids, the boiling point of which is higher than that of water, can in like 
 manner be employed for impregnating wood such are oil, resins, tar, etc. By such 
 treatment the softer kinds of wood, such as pine, Scotch fir, poplar, etc., or even 
 denser kinds like beech, etc., can be easily impregnated with these substances. By 
 raising the temperature to 180, Payen succeeded in giving soft kinds of wood such 
 durability, that they could be used in the construction of chemical manufactories, 
 where they were exposed, not only to the action of air and moisture, but also to the 
 influence of acid vapours and gases. It was proved that such wood suffered less 
 than the most durable kinds of wood in a natural condition. 
 
 When timber is merely immersed for some time in the antiseptic liquid, the 
 results produced are not very satisfactory, because the penetration of the liquid is 
 prevented by the air in the tissues. Better results are obtained by plunging the wood 
 entirely into the liquid in a vertical position, so that, owing to the capillary attraction 
 
624 WOOD. 
 
 of the hollow spaces in the tissues, and partly also to atmospheric pressure, the 
 liquid is forced into the pores and expels the air, which escapes at the upper end of 
 the vessels. 
 
 Kyan employed in this way a solution of corrosive sublimate of 1 per cent, 
 strength ; the penetration of the liquid was assisted by having the trunks cut into 
 boards, and after they had remained 14 days in the liquid, they were again fastened 
 together by means of bolts. 
 
 Breant constructed an apparatus by means of which he exposed the immersed wood 
 to a pressure of 10 atmospheres; and the consequent compression of the air permitted 
 the penetration of the liquid. His process was rendered still more effective by first 
 creating a vacuum in his apparatus, so that the air contained in the tissues of the 
 wood escaped, and it was then easy under a pressure of 10 atmospheres to force the 
 antiseptic liquid into all the cavities of the wood. 
 
 The first industrial application of this method of Breant's was made by Bethel, 
 whose apparatus consists of a cylinder of sheet iron, closed in at one end like an 
 ordinary steam boiler, and at the other end furnished with an air-tight cover secured 
 by means of bolts. The wood to be impregnated is laid upon small trucks which are 
 run into the cylinder upon rails laid upon the inside. According to the length of the 
 pieces of timber, 2, 3, or 6 trucks are pushed in, the cylinder is then closed in front, 
 and steam passed into it to expel the air ; the cylinder is then cooled by allowing cold 
 water to flow over it. The condensation of the steam causes a partial vacuum which 
 facilitates the expulsion of the air from the tissues of the wood. After a short time a 
 cock is opened through which the antiseptic liquid is sucked into the cylinder, then a 
 force pump is set in action which completely fills the cylinder with the liquid, and 
 the pump is kept going until a pressure of 1 atmospheres is attained. After several 
 hours, according to the kinds of wood, the penetration is complete, often to the inner- 
 most core of the wood. The liquid is then run off, and the trucks containing the 
 wood are drawn out of the cylinder, which is then ready for a second charge. 
 
 The antiseptic employed by Bethel is a mixture of hydrocarbons obtained by the 
 distillation of coal tar. This oil of tar, wrongly termed creasote, is very suitable for 
 impregnating railway sleepers, but is not applicable for the preservation of wood 
 for other purposes, owing to its unpleasant smell and its inflammability. In Moll's 
 process the wood is exposed first of all to steam in a closed chamber, then creasote 
 vapour is admitted, which penetrates the wood, and condenses in it upon cooling. A 
 solution of cupric sulphate is sometimes used in place of creasote. 
 
 The injecting cylinder used in this case is made of copper plates strong enough to 
 resist a pressure of 12 or 15 atmospheres. The steam does not, as in the old 
 method, serve to create a vacuum, but to heat the wood, enlarge its pores and destroy 
 the ferments present in it. The copper solution is heated up to 70 before being 
 admitted into the cylinder, in order to avoid condensation of the steam either in the 
 cylinder or in the pores of the wood, and also the contraction of the pores that had 
 been previously expanded by the action of the steam. The excess of steam after it 
 has effected the expansion of the pores of the wood in the cylinder is passed through a 
 serpentine tube and serves to heat the solution of cupric sulphate ; the condensed 
 water serves to feed the boiler and to prepare the copper sulphate solution. The 
 rarefaction of the air within the cylinder is effected by means of a special condenser, 
 in which the vapours are condensed ; in this way it is possible not only to get rid of 
 the steam, but of the greater portion of the air and non-condensible gases, without any 
 serious cooling of the wood taking place, so that a condensation of the steam in the 
 pores of the wood is prevented. The vacuum is kept up by means of air pumps 
 which continually remove the condensed water, and work so that a barometer 
 connected with the cylinder only shows a column of mercury 5 or 10 c.m. Finally 
 the impregnating liquid is forced into the cylinder by the aid of special pumps, and 
 according to the kind and size of the logs of wood a pressure of 12 or 15 atmo- 
 spheres is produced. 
 
 This process is now so perfected that each apparatus is capable of receiving 10 or 
 12 charges per diem ; and has been very extensively used in the impregnation of 
 the sleepers of the Paris, Lyons and Mediterranean railway. 
 
 The exterior view of the entire apparatus is shown in fig. 431. The cylinder 
 consists of copper sheets rivetted together. The lid E is ri vetted on the cylinder, and 
 the opposite lid B' turns on an iron hinge. This lid is furnished with a wide rim 
 that rests against a corresponding rim round the cylinder, to which it is screwed with 
 bolts. A special adjusting screw regulates the lid in such a way that the perforations 
 of both rims exactly fit together, and by its means the lid may be brought into 
 the proper position, should it get displaced by any accident. A couple of levers fur- 
 nished with balance weights (F r, figs. 432 and 433) are attached to the moveable axis of 
 
PRESERVATION OF WOOD. 625 
 
 the lid to facilitate the opening and shutting, so that the operation may be performed 
 by a single man. 
 
 The closing of the cylinder is secured by laying a broad piece of rope saturated 
 with fat upon each of the protruding rims, which upon screwing in the bolts are so 
 pressed together that a close joint is secured. The details of this arrangement are re- 
 presented by figs. 432, 433, and 434. 
 
 Besides the water and pressure gauges and safety valves, the cylinder is furnished 
 with a number of different cocks with their connecting pipes ; these are the air cock; a 
 cock (H) in the pipe for conveying steam ; a delivery pipe for the impregnating liquid ; 
 another communicating with the condenser of the air pump ; and a valve (K) for ad- 
 mitting the liquid into the exhausted cylinder. 
 
 The copper coil H' corresponds with the steam outlet cock ; it lies within the basin 
 and serves for heating the copper solution. The non-condensed steam and water of 
 
 FIG. 431. 
 
 condensation are conducted into a vessel in which is contained the water for feeding 
 the boiler, and both may be passed by means of the vertical tube H", bent at its upper 
 end, into the dissolving basin. The entire apparatus, with the exception of the 
 reservoir for the copper solution, is supported upon a strong railway truck, so that it 
 admits of being moved at pleasure. The method of carrying out the operation is as 
 follows. 
 
 The trucks, laden with the sleepers and other pieces of timber to be impregnated, 
 which are made fast to the trucks by means of a couple of bronze bands turning on 
 hinges, are pushed into the cylinder. The lid which swings readily on its axis is let 
 down and screwed on the cylinder. Directly this is done the cock, which connects the 
 cylinder with the steam boiler by means of the tube H, is opened, the steam expels the 
 air from the cylinder through a special cock and fills the cylinder completely, the 
 excess of steam escaping as soon as the air cock is shut through the serpentine 
 tube, or, provided the copper solution is hot enough, into a reservoir for feeding the 
 boilers. 
 
 The steam pressure is generally kept up for 15 minutes ; but, according to the size 
 and kind of wood, it is often necessary to keep up the action of the steam longer, until 
 
 S S 
 
626 
 
 WOOD. 
 
 the innermost parts of the wood have attained a temperature of 65 or 70. The steam 
 is then shut off and the cylinder connected with the condenser, into which a jet of cold 
 water is immediately pumped. At the same time the air pump is set in motion 
 in order to remove the water pumped in, the non-condensed steam and the air 
 escaping from the pores of the wood. Owing to the continual evaporation of water from 
 the pores of the wood, it is not possible to obtain a perfect vacuum ; the air pump is 
 therefore kept going until the barometric column stands at 6 c.m., and the vacuum is 
 kept up generally 15 minutes, or iu the case of dense kinds of wood 25 minutes. 
 
 The large cock (K) is then opened, which places the cylinder in communication with 
 the basin containing the copper solution. The solution has a concentration of 2 per 
 cent, and is in the meantime heated by the escaping steam to 70. The atmospheric 
 pressure forces the liquid into the cylinder which tills itself nine-tenths full. The 
 pressure pumps are then set going, to fill the cylinder entirely with the warm copper 
 solution, and are kept going until a pressure is obtained in the cylinder of 12 atmo- 
 spheres, which is maintained from 20 to 30 minutes. 
 
 The comparatively small quantity of air left in the pores of the wood after steam 
 and vacuum have done their work is by this latter operation reduced to a very small 
 
 FIGK 432. 
 
 FIG. 433. 
 
 volume. The copper solution occupies the space previously occupied by air, penetrates 
 the wood, and fills up all its pores. 
 
 When the full pressure has been attained, and it has been kept up long enough, 
 the large outlet cock is opened and the excess of impregnating liquid is run off into 
 the reservoir. The cylinder is now opened, and both the cars are run on to a truck 
 placed at the mouth of the cylinder to receive them. The cylinder is then charged 
 with two fresh cars laden with timber. Each car holds 32 railway sleepers or a corre- 
 sponding quantity of other timber ; therefore 64 sleepers are impregnated in a single 
 operation ; and since 8 operations are carried out every 12 hours, it is possible, by 
 working a double apparatus, to impregnate 1,024 sleepers daily. 
 
 The relative volume of preservative liquid which penetrates the wood differs 
 according to the constitution of the wood, inasmuch as light spongy wood absorbs more 
 liquid than dense and hard kinds of wood ; and in preserving timber by this means 
 attention mast be paid to this fact. The action of the impregnating liquid is regulated 
 accordingly, being allowed to operate for a longer or shorter time, and its strength is 
 also modified according to the kind of wood. Dense heavy kinds of wood require a 
 liquid of 2 per cent, strength, while for lighter sorts of wood a liquid of 1 per cent, 
 strength suffices. Long experience has shown that wood is sufficiently impregnated 
 when 1 cubic yard has absorbed 9 Ibs. 5 oz. to 9 Ibs. 10 oz. of copper sulphate. 
 
 The results of some experiments conducted by MM. Hennezel and Vetillard showed 
 that a copper sulphate solution of 2 per cent original strength, after removal from tlio 
 
PRESERVATION OF WOOD. 
 
 627 
 
 cylinder, had still a concentration of 1728 per cent; and the amount of liquid absorbed 
 by different kinds of wood was as follows : 
 
 j Original weight 
 1 per cubic yard 
 
 Liquid absorbed 
 per cubic yard 
 
 Copper Sulphate 
 absorbed per 
 cubic yard 
 
 Oak : sleepers, square and half) 
 round, planks . . . J 
 
 11 cwt. 25 Ibs. 
 
 6 cwt. 51 Ibs. 
 
 14^ Ibs. 
 
 Deal : half round sleepers, sound ) 
 
 
 
 
 timber, 6 months felled 
 
 8 95 
 
 6 104 ! 15 
 
 Small beech-tree wood : planks, 
 
 
 i 
 
 pith wood, 8-10 years felled 
 
 11 !> 8 ,, 
 
 9 13^ 1 20^ 
 
 Poplar : sleepers, sound timber, } 
 6 months felled . . . \ 
 
 8 " ^ " 
 
 10 41 i ! 20J 
 
 
 Seven different experiments with oak wood showed that it took up more liquid in 
 proportion to the length of time that had elapsed since felling; for wood between 4 
 months and 5 years old i.e., from the time of felling the amount of liquid absorbed 
 per cubic yard varied between 4| cwts. and 8i cwts. It is therefore evident that the 
 age, texture, and general condition of timber have a great influence upon the amount 
 of impregnating liquid it is capable of absorbing. 
 
 The steaming and rarefication have the effect of altering the volume of the timber, 
 which increases in sectional area in the proportion of 100 to 104 ; no increase in length, 
 however, takes place. 
 
 The penetration of cupric sulphate into the wood may be tested by making a section 
 of one of the pieces and dropping upon it a solution of potassium ferrocyanide ; the 
 quantity of copper salt in any particular part of the wood is then approximately indi- 
 cated by the degree of brown coloration. By applying this test it has been found that 
 sap wood is the most easily impregnable, especially wheu the wood has been previously 
 heated by storing ; heart wood absorbs less, but sufficient for the preservation of the 
 wood, especially as in dense kiqds of wood the most decomposable parts are the most 
 easily penetrated by the impregnating liquid. 
 
 In Germany, railway companies have employed a similar method for impregnating 
 their sleepers, with the difference that, instead of cupric sulphate, zinc chloride is used, 
 which is not only as effective, but considerably cheaper, and does not require the ex- 
 pensive copper apparatus. 
 
 Another method has been introduced by Boucherie. It consists essentially in 
 replacing by means of hydrostatic pressure the sap of freshly-felled wood by an 
 antiseptic liquid, which is in most cases cupric sulphate. 
 
 The time required for perfect penetration differs considerably, and is dependent 
 upon the density of the wood, the kind of wood treated, the amount of sap in the wood, 
 and the length and thickness of the pieces. In oak the sap wood only is penetrated, 
 the vessels being wider than in heart wood ; sap wood is, however, the part most liable 
 to decomposition. Beech, birch, plane, elm, fir, and Scotch fir are the kinds of wood 
 chiefly employed, as being cheap and easily impregnated ; they replace oak for many 
 purposes. The different kinds of poplar absorb the liquid, with the exception of a 
 small portion round their axis ; the trunks are often used as poles, being cut length- 
 ways into four parts, and the part which refuses to absorb the impregnating liquid 
 cut away with the axe. 
 
 In all kinds of wood the circulation is easier and more complete in proportion to 
 the nearness of the operation to the time of felling. In order to avoid as far as possible 
 loss of sap in felling, all the branches and twigs are immediately chopped off. When 
 the felling takes place before the budding of the trees between January and April, the 
 trunks are most fitted for impregnation in the course of a couple of months, at which 
 time a disc about 4 inches thick is chopped off from the end of each trunk on account 
 of these portions being too dry. In summer the impregnation ought either to be 
 carried out at once, or at the latest within 8 or 12 days from the time of felling. 
 
 The impregnation process is also easier in proportion to the shortness of the trunks 
 and the pressure of the liquid. The diameter is also of importance ; for while a trunk 
 9 feet long and 15 inches in diameter is completely impregnated in 24 hours, 100 
 hours are required for the perfect impregnation of a trunk having the same length but 
 a diameter of 2 feet ; and besides this it is necessary to pass through it a quantity of 
 impregnating liquid equal to six or seven times its volume. Indeed, in the case of such 
 thick trunks, it is advisable, after the outer parts have been sufficiently impregnated, 
 to give the interior parts a special treatment by screwing on to the trunk a board of 
 
 s s 2 
 
628 WOOD. 
 
 sufficient size, and exposing the harder parts of the tissue once more to the pressure 
 of the liquid. The complete penetration of the harder parts is often secured by in- 
 verting the block and passing the copper solution in at the outflow end. 
 
 Above all things it is absolutely necessary that the cupric sulphate employed 
 should be as pure as possible, and free from excess of acid ; it is especially necessary 
 that it should contain no ferrous sulphate, since this salt exerts an oxidising action 
 upon the fibres. The absence of ferrous sulphate may be proved by a solution of 
 cupric sulphate yielding with ammonia a blue and quite clear liquid. In order to 
 avoid rendering the solution of cupric sulphate impure, all the vessels employed in 
 the impregnating process are made of wood, bronze, or brass. 
 
 Cupric sulphate preserves wood by fixing itself upon the cellulose, lignin, and 
 nitrogenous substances present in the wood. It is poisonous enough to prevent insects 
 from lodging themselves in the tissues of the wood; besides which, owing to the dis- 
 placement of the sap, a number of the most easily decomposable constituents are re- 
 moved from the wood. 
 
 Eecent experience has shown that a slight variation may be made with advantage 
 in the above method of proceeding. This may be easily done by allowing the liquid 
 to run away until the greater part of the sap has escaped ; the process causes the loss 
 of a small quantity of cupric sulphate, but a liquid of a purer quality is passed into 
 the wood. 
 
 A method a little different to the above, and proposed by Renard-Perrin, consists 
 in forcing the impregnation liquid into the wood by atmospheric pressure. For this 
 purpose the logs placed in an upright position have their lower extremities connected 
 with an iron vessel in which a vacuum has been made by burning in it balls of tow 
 soaked in alcohol. Directly the flame has burnt out the iron vessel is closed, and 
 upon cooling down a partial vacuum is produced within it. The impregnating liquid, 
 which is poured upon the upper end of the wooden block, is then forced downwards 
 through the wood by the pressure of the atmosphere. This operation several times 
 repeated suffices for the impregnation of the wood. Perrin's method is, however, more 
 used for preparing coloured wood than for preserving wood by antiseptic liquids. 
 
 For colouring wood in the above way a number of colours and mordants are em- 
 ployed, which are likewise used for dyeing cloth ; thus the different shades of red and 
 violet are obtained by using madder, alkanet, orchil, logwood, and Brazil wood ; blue 
 is got by using litmus, indigo, logwood ; green by cupric acetate, or verdigris ; black 
 by using extract of oak galls, ferrous sulphate, etc. Other kinds of wood are bleached 
 by a similar process ; thus the wood of the dwarf beech is bleached by treating it with 
 a very dilute solution of soda ( per cent.), then with water, chloride of lime, dilute 
 hydrochloric acid, and finally again with water. Wood thus bleached is used instead 
 of ivory in mosaic work. 
 
 Timber or wood that has been impregnated is not only useful for the purposes for 
 which up to the present it has been almost exclusively employed, such as railway 
 works, etc. ; but it may be also employed with great advantage for a number of other 
 purposes : such as carpentry work which is exposed to the action of atmospheric air 
 and moisture, the timbering of galleries in mines, for posts and stakes of all kinds, 
 such as telegraph posts, and for many parts of ships, etc. 
 
 Tannin or tannic acid must be reckoned amongst the best preservatiA^e agents ; it 
 enters into combination as well with the nitrogenous constituents of wood, forming 
 with them insoluble and difficultly decomposable products, as with the nitrogenous 
 constituents of animal tissues, as in leather. The durability of oak wood is ascribed 
 to the large percentage of tannin it contains, but it is very probably due still more 
 to the great density of the tissues. Fishermen are in the habit of dipping their nets 
 and sails from time to time in liquids containing tannin which gives them greater 
 durability. 
 
 From the most remote times, wood tar has been used for preserving the 
 timbers in ships, and its application at the present day for the same purpose is a 
 sufficient proof of its usefulness as a preservative agent. The active preservative 
 principle in wood tar is creasote ; in coal tar a kindred substance is found, which is 
 called carbolic acid. 
 
 Carbolic acid, even when present in the smallest quantity, possesses the property 
 of checking processes of fermentation and decay, and of destroying lower organisms 
 both vegetable and animal. Carbolic acid is obtained in large quantities as a by- 
 product of the manufacture of gas and of paraffin oil, and being very cheap it might 
 be used with advantage for preserving timber. 
 
 When wood is treated with oils, fats, wax, and resins in the melted state, its 
 pores are filled with them, and it is rendered impervious to air and moisture ; how- 
 ever, all these bodies are too dear to admit of general application in the preservation 
 of wood. 
 

 PRESERVATION OF WOOD. 629 
 
 Salt preserves wood just in the same way as it does meat, fish, and similar 
 materials ; in moderately moist situations, as in certain mines, timber impregnated 
 with salt resists decomposition for a considerable length of time. Salt cannot, how- 
 ever, be used for this purpose in very wet places, since it would be dissolved .out, nor 
 can it be used in places where it would at one time have opportunity to absorb water, 
 and then again to become dry, as this would cause a crystallisation of the salt between 
 the fibres of the wood and be detrimental to its durability. 
 
 A number of iron salts have been used for preserving wood. The most useful of 
 these is unquestionably iron acetate, obtained by dissolving iron in the impure acetic 
 acid, called pyroligneous acid, or the aqueous liquid obtained by distilling wood, which 
 contains besides acetic acid a number of other substances, such as creasote, etc. The 
 value of iron salts for preserving wood seems, however, very problematic. Watteau 
 has introduced a method of treating wood with ferrous sulphate, but it is not probable 
 that much good will be obtained from it. The timber is first impregnated with a 
 solution of barium sulphide (5 per cent.) under a pressure of 10 atmospheres, and then 
 in like manner with a solution of ferrous sulphate of 5 per cent. According to M. 
 Watteau, the sulphuric acid is precipitated within the wood as barium sulphate, and 
 ferrous sulphide is produced, an excess of barium sulphide remaining, which is 
 poisonous to insects, cryptogams, and ferments. Barium sulphide, however, is readily 
 decomposed, and would be converted by the air into insoluble or inactive barium 
 carbonate, and then the ferrous sulphide would be converted by the air into sulphate, 
 which is most of all detrimental. 
 
 Cupric sulphate and zinc sulphate act as antiseptics without exerting the in- 
 jurious effects produced by the corresponding ferrous salt. 
 
 Basic lead acetate forms with the most easily decomposable constituents of wood 
 insoluble stable compounds. It penetrates wood easily, and may be used with ad- 
 vantage when it can be obtained cheaply. 
 
 Mercuric chloride or corrosive sublimate has long been used for preserving 
 anatomical and botanical preparations, and as well as arsenious acid is sometimes used 
 for preserving wood. The use of both these substances, however, on account of their 
 poisonous nature, has been now for the most part given up, since both by the impregna- 
 tion as well as in the further working up of timber thus treated the danger to the 
 workmen is very considerable. Wood impregnated with corrosive sublimate, and 
 used in the building of greenhouses, was found to be injurious not only to creepers 
 trained to the wood itself, but also to the entire vegetation in such houses. 
 
 Zinc chloride is an excellent preservative for timber, and is much employed for 
 curing railway sleepers ; but care must be taken that it contains no free hydrochloric 
 acid. 
 
 Calcium chloride is in its action similar to common salt ; it is used with advantage 
 for the hoops of casks deposited in dry places, since owing to its hygroscopic nature, 
 it gives the casks a certain degree of moisture and prevents their shrinking. 
 
 It has been already mentioned that the perishable nature of wood is due to the 
 constituents of the sap, which are in themselves of a decomposable nature and impart 
 this property to the wood itself. This tendency to decomposition is favoured by the 
 fact that certain constitutents of the sap possess the property of absorbing moisture 
 even from moist air. Neither fermentation nor decomposition can take place in the 
 absence of water, and hence many methods are employed either to alter the nature of 
 the constitutents of the sap, and render them less hygroscopic by baking, surface 
 charring, or smoking, or the sap constitutents are expelled as far as possible by steam- 
 ing the wood. 
 
 In baking wood care must be taken to dry it well before submitting it to the 
 baking process, otherwise the wood would crack and split. Well-dried wood is placed 
 in a brick chamber, into which a stream of hot air is forced by means of a blast 
 The air is heated by forcing it through a fire, the gaseous products of combustion 
 being then passed into the drying chamber, so that the effect of smoking is connected 
 with that of baking. Care has to be taken by means of proper regulation of the heat 
 and by ventilation that the temperature of the wood is raised very gradually, other- 
 wise it is certain to crack, and that no sparks from the fire are carried into the drying 
 chamber. 
 
 Baking causes wood to shrink, the tissues become denser, the juices are altered in 
 composition, and the wood is rendered more durable. To obtain good results, the 
 temperature must be finally raised so high that the surface of the wood appears of a 
 yellow or brownish hue. 
 
 The steaming of wood is carried out in the way already mentioned in treating of 
 the impregnation of wood ; when however steaming is the only preservative employed, 
 it requires to be continued for a longer time. Steam either under high or ordinary 
 pressure is made to act upon the wood until the condensed water runs off colourless, 
 
630 WOOD. 
 
 or until it ceases to extract colouring matters. According to Prechtl it is well to 
 cause vapour of l^ar to act upon the wood together with steam, which is effected by 
 placing a small quantity of tar in the boiler as soon as the condensed water from the 
 wood runs off colourless ; the tar vapour passing over with the steam penetrating tho 
 wood and giving it greater durability. Steamed wood dries well without distortion or 
 cracking ; before drying it is soft and pliable, and may be bent into any desired shape. 
 This property of steamed wood is taken advantage of in bending the staves of casks 
 and the fellies of wheels, etc. After cooling and drying, such wood assumes its 
 original hardress. 
 
 According to a process introduced by Chemall6, wooden bolts and wedges are 
 rendered very hard and durable by steaming and smoking. They are first steamed 
 and then soaked in a bath of hot oil or coal tar ; while still hot they are submitted to 
 strong pressure in a specially constructed machine, and thus reduced 20 per cent, in 
 volume. A machine of the kind made by Ransome and May in Ipswich produces 
 18,000 finished bolts every 10 hours. 
 
 Surface charring has been long employed for preserving wood. Posts that are to 
 be placed in the earth are previously burnt at their lower extremities, by which means 
 the essential aim of baking is attained. A century ago a trial of this method was 
 made for preserving the keels of ships ; the result was favourable, but the process was 
 not further carried out, probably on account of fire risks. 
 
 A gas flame is made to play upon the part of the ship to be charred. The gas is 
 contained in wrought-iron cylinders filled at the gasworks under a pressure of 11 
 atmospheres. Under the ordinary pressure of the atmosphere each cylinder holds 
 26*487 cubic feet of gas. The cylinders are brought from the gasworks to the ship 
 yards on cars, and are there connected with a regulator, which admits of the gas 
 escaping from them under a pressure of about one inch of water. The gas is con 
 ducted by means of india-rubber tubes from the cylinders to the burners, which are 
 connected with a blast, by which a large and hot flame is forced against the part of 
 the ship that is to be charred. One square yard of surface requires 5'88 cubic feet 
 of gas. 
 
 The same process has been employed with success by Lapparent for disinfecting 
 the interior of ships. The methods formerly considered sufficient, such as thorough 
 washing and disinfection with chlorine, or painting over with chloride of liine, have all 
 been found to be comparatively inefficient. 
 
 The charring of the interior of ships causes a quick evaporation of the absorbed 
 moisture, when a torrification of decomposable substances or spores and germs of 
 plants and animals, and finally a partial dry distillation of the wood, by which it 
 becomes charged with pyroligneous acid, creasote, hydrocarbons and other antiseptic 
 substances. 
 
 The apparatus employed is the same as that used in charring the exterior of ships. 
 A couple of workmen are required, the one to regulate the flame and the other the 
 blast ; they can easily char 12 sq. yards in 10 hours, using 5'88 cubic feet of gas per 
 square yard. Not only are the wooden parts of ships thus treated, but the iron heads 
 and bolts and other iron portions of the vessels are also submitted to the same opera- 
 tion, the rusted surface of which is especially suited for harbouring spores and 
 germs. The unequal expansion of the metal and of the rust attached to it causes the 
 latter to fall off in large pieces. 
 
 Iron ships are also treated in like manner ; the greater capacity of the metal for 
 conducting heat requires, however, a stronger blast and greater consumption of g;>s 
 than is required in treating wooden vessels. Experiments made at Woolwich showed 
 that iron ships require a consumption of gas equal to 7 '3 5 cubic feet per squaro 
 yard. 
 
 Since the use of illuminating gas would for many purpose- be too expensive, it has 
 been replaced by oils, the heavy hydrocarbons obtained from coal tar; common kinds 
 of fuel, coal, and even coke, is burnt in a specially constructed apparatus in such a way 
 that a lengthened flame is obtained. This kind of apparatus is used for the surface 
 charring of railway sleepers, telegraph posts, etc. 
 
 The heavy hydrocarbons have been employed by Lapparent. These oils can be 
 used with advantage for charring wood, since the smoke they produce does not interfere 
 with their application, and by means of suitable apparatus the smoke may also be 
 burnt and used as fuel. 
 
 For this purpose Lapparent constructed a lamp of peculiar construction, the chief 
 feature of which is a large cylindrical hollow wire, through \vhich air is passed by 
 means of a concentric tube and a blast. The oxygen of the air effects the complete 
 combustion of the carbon of the hydrocarbons, so that a large and almost smokeless 
 flame of a very high temperature is produced which is made to play upon the surface 
 to be charred. When stakes and such articles are treated, the lower ends are placed 
 
PRESERVATION OF WOOD. 
 
 631 
 
 directly in the flame a little further than they require to be buried in the earth ; larger 
 objects, such as rafters, sleepers, etc. are supported upon bearers, so that they can easily 
 be turned. Comparatively rough timber work can be thus treated, and even finished 
 carpentry work admits of being rendered hard and durable by this means ; if such work 
 requires painting, all that is necessary is to scrape off the charred surface. 
 
 The combustion of the oil of tar is facilitated and rendered more equal by mixing 
 it with an equal volume of heavy petroleum, which does not ignite spontaneously upon 
 dipping into it a burning splint. 
 
 An apparatus for charring railway sleepers, etc. constructed by Hugon, is repre- 
 sented in front view by fig. 435, and in end view by fig. 436. 
 
 It consists of a cast-iron cylinder (A), furnished above with a tube (A'), which 
 serves for the introduction of the fuel. At the other end of the cylinder is an open- 
 ing shown in the figure closed with a lid and screw for drawing out the ash. The 
 flame and combustible gas escape at the mouth of a tube 2 inches wide, at the upper 
 part of the cylinder ; opposite the ash door there is a horizontal tube connected with 
 a blowing machine by means of a caoutchouc tube. A small tube (/) is inserted into 
 
 FIG. 435. 
 
 FIG. 436. 
 
 this blast tube and serves for injecting a fine stream of water into the red-hot fuel. 
 This is effected by causing the lever which moves the blast to press upon a piston in 
 the water tank (E), so that in proportion to the action of the blast the required 
 quantity of water is injected into the fire. The furnace (A) is supported by the cylin- 
 der (B), moveable upon its axis, by the means of the lever (p) and the weight (Q), so as 
 to admit of the entire furnace being raised or lowered to give the flame any desired 
 direction. The blowing apparatus (D) is furnished with air chambers by means of 
 which a uniform blast may be produced. 
 
 To set this apparatus going, small pieces of wood are thrown into the furnace (A) 
 through the ash hole; this is ignited and the furnace is half filled through the opening 
 (A'); all the openings remain open, the draught then effecting combustion ; both open- 
 ings are then closed and the blast set going. The air passing over the ignited fuel 
 accelerates the combustion and causes a strong flame to issue from the exit tube. 
 When the volatile portions of the coal are destroyed, the residue remaining in the cylin- 
 der consists of coke, which burns almost without flame. At this point the piston of 
 the water tank is connected with the connecting rod of the blast, and the cock (F) 
 opened so as to inject a fine stream of water upon the coke. The water is at once 
 converted into vapour and decomposed by the red-hot coke into hydrogen and car- 
 bonic dioxide, which in contact with the red-hot coke takes up carbon and forms car- 
 bonic oxide. A combustible gas is thus obtained which issues from the exit tube and 
 burns with a long and intense flame. It is true that the conversion of carbon into 
 carbonic oxide does not effect the most economical use of combustion heat of coke, 
 but the object in view is attained, viz. the production of a flame large enough to 
 cover the surface to be charred. The sleepers (H) to be charred rest upon metal 
 rollers (i) supported by the frame (o). The rollers are set at a distance of 6 inches 
 
632 
 
 WOOD. 
 
 from the burner of the furnace. The sleepers are exposed to the action long enough 
 to char the surface as required, by pushing them slowly or quickly along the rollers, 
 By raising or lowering the furnace the workman is able to guide the flame directly 
 upon the wood, so as to economise the heat. 
 
 In charring cylindrical stakes, such as telegraph posts, the apparatus represented 
 by fig. 437 may be conveniently employed. It is fastened at c to the support (G 
 fig. 435), and consists of an iron pillar turning upon the 
 pdint (o), the upper part of which is furnished with a piece 
 of sheet iron bent so as to form a gutter. The portion of 
 the stake or part to be charred is laid in this gutter, the 
 flame made to play upon it and the gutter moved slowly 
 forwards. The flame bends itself in the shape of the 
 gutter, thus playing completely round the stake or post, 
 charring it equally, without it being necessary to give it a 
 rotatory motion. The end of the post which is to be 
 placed in the earth requires more complete charring, for 
 which purpose it is again exposed to the action of the 
 flame after the whole post has been charred ; this is done 
 by turning the whole apparatus at a right angle round o, 
 by means of the lever (N). so that the entire end of the 
 post is exposed to the full action of the flame. 
 
 ^_ ^___ MK . In mining and excavations for railway works, etc., 
 
 _ rocks are often met with which are so hard that boring is 
 
 *'* very expensive, and blasting effects only the loosening of 
 
 small pieces. In such cases the cohesion of the rock may be considerably loosened 
 by means of heat. This fact was known and employed ages ago, but has been almost 
 neglected on account of the imperfectness of the old method. More recently the appli- 
 catien for this purpose of an apparatus similar to that described for charring timber 
 has been employed with great success. 
 
 The apparatus is represented by fig. 438. It consists of a furnace (A), the fore part 
 of which is turned towards the pnrt of the rock to be heated, and in front of the open- 
 
 
 FIG. 438. 
 
 ing is placed a cross bar to prevent the coal falling out. The furnace itself runs on 
 four wheels upon a tramway. A lever (E) at the hinder part of the furnace serves 
 for giving it an inclined position, so as to direct the flame upwards if necessary. The 
 hinder part is also furnished with a blast nozzle connected by means of tubing with a 
 blowing apparatus. 
 
 Dry wood is ignited in the furnace, air being allowed to enter very slowly, and 
 coal is then thrown in through the opening (B) ; when the first portions of coal are 
 ignited, fresh coal is added until the furnace is completely full. After about 15 or 
 20 minutes, when the coal is quite red hot, the mouth of the furnace is placed against 
 the rock to be loosened, and air is forced in. The air, as in the apparatus above 
 described, conducts water to the fire, which drops through the cock (F) into the blast 
 nozzle ; this causes a large flame to issue from the mouth of the furnace, and play 
 over the surface of the rock, heating it so considerably that, in consequence of unequal 
 expansion, in the course of a short time pieces of rock loosen and fall away. When the 
 
PAPER. 633 
 
 rock is very hard, it often happens that pieces of rock are ejected with sufficient 
 violence to cause injury to the workmen. 
 
 So soon as the work begins to split and show cracks, the furnace is removed to 
 another spot and the flame made to play upon new portions of rock. The heated 
 rock is then chilled with cold water, and can be easily removed. 
 
 For loosening rocks which offer difficulties in blasting, this apparatus is three or four 
 times as effective as blasting powder. It is only necessary to adapt the dimension 
 of the furnace to the hardness of the rock, the size of the surface to be loosened, etc. 
 In experiments made at Echallange, with quartz rock containing galena, there was 
 excavated in a gallery during 54 working hours a space 5 ft. high, 4J ft. wide, and 
 6^ ft. long. 
 
 A new industry started by Latry in Grenelle has recently attained a certain 
 importance. It consists in condensing the sawdust from rosewood, and using it 
 for imitations of carvings in ebony, mosaic work, dice, etc. The sawdust is for this 
 purpose carefully sifted and mixed with \ to ^ of its volume of blood, previously so 
 far diluted with water as to admit of the entire mass of sawdust being completely 
 moistened by it. The mixture is spread out upon hurdles, and dried in a kind of 
 oven in a current of air of a temperature of 45. 
 
 After cooling, a friable mass is obtained which is then worked up. For this 
 purpose strong cast-iron boxes are employed, the bottom of which is furnished with 
 the matrix of the object to be moulded. The matrix is then covered with the 
 powdered mass and this stamped in under a pressure of 500 tons ; the space left 
 after removal of the pressure is filled in with more powder and then again pressed, 
 the operation of filling and pressing being continued until the matrix is quite full. 
 The compressed mass is then heated to 175, by placing red-hot bolts 2 in. thick in 
 special apertures of the iron moulds, which communicate their temperature to the 
 pressed powder. The high temperature and pressure is kept up, according to the 
 size of the object to be moulded, from half an hour to an hour. The condensation is 
 so considerable that the moulded objects acquire an apparent specific gravity of 
 1-300, while rosewood has a specific gravity of O'SOO ; their hardness is so great that 
 they admit of being cut and polished like ebony. Wood thus prepared is extensively 
 employed for different articles of elegant cabinet work. 
 
 The union of the wood particles is effected by the blood fibrin, softening at a 
 temperature of 175 and hardening to a solid mass upon cooling ; besides this, there 
 is no doubt that a resinous substance which is present in large quantities has also an 
 influence. Pay en extracted from rosewood by means of alcohol 35 per cent, of a 
 resinous substance. 
 
 PAPER. 
 
 History. In the earliest periods of civilisation, paper was perfectly unknown. 
 The oldest writings were not traced upon paper, but upon stone and tiles; after- 
 wards wood, barks, leaves, and also bones, skins, metal plates, etc., were 
 used. In the time of Alexander the Great, papyrus, prepared principally in 
 Alexandria from a plant growing on the banks of the Nile, came into use. Accord- 
 ing to Pliny a layer of fibres was placed side by side and close together upon a board ; 
 another layer was then placed transversely over these ; the whole was then moistened 
 with water, or with a solution of sugar containing vinegar, and so pressed together 
 by rubbing with a burnisher or beating with a hammer as to become united into one 
 sheet. Such was the composition of the paper upon which the works of Cicero and 
 Virgil were written. 
 
 Parchment also was in early times and is still used for writing upon. It is 
 said to have been discovered in the third century B.C. by Eumenes, King of Pergamos. 
 It was prepared from the skins of asses, sheep, pigs, goats, and other animals, a 
 material that had been used before, but in a less prepared condition. 
 
 The discovery of the preparation of paper from vegetable fibre and tissue must 
 he attributed to the Chinese, who have practised the art for two thousand years, and 
 at the present time produce the finest varieties of paper. Their method is still 
 nearly the same as at first, and as imperfect as that which is still current in many 
 of our paper mills in the preparation of the so-called hand-made paper. The Chinese 
 method of making paper was known in Persia A.D. 650, and it was introduced from 
 there into Arabia about A.D. 700. The Arabians transplanted it into Spain, from 
 whence it spread into France, Germany, and England. The first paper manufactories 
 in France were established at the commencement of the fourteenth century at Troyes 
 and Essones. In Germany, manufactories were established at Ravensburg in 1290, 
 
634 PAPER. 
 
 Kauffbeuren in 1312, Nuremberg in 1319, and Augsburg in 1320. The English 
 paper manufactories had their origin later, in the fifteenth or sixteenth century. In 
 Holland the manufacture was very much perfected at a comparatively early period, 
 and an apparatus called a holla nder was invented for tearing the rags by means 
 of cylinders having sharp ridges, instead of the previous very tedious way of disinte- 
 grating them by mallets. Paper was first dried by means of cylinders heated by 
 steam at Crompton. 
 
 A considerable advance in the paper manufacture resulted from the discovery of 
 the artificial preparation of soda, as well as the artificial bleaching materials, chlorine 
 and the hypochlorites. The latest revolution in the art of paper making has been in 
 the use of substitutes for rags, especially of wood and straw. 
 
 Composition and Properties. Paper is to be considered as a felt-like coherent 
 mass of fine vegetable fibres. The vegetable fibre, or its tissue as it occurs in nature, 
 is submitted to a thorough purification to free it from foreign constituents ; it is then 
 brought to a state of fine division and stirred up with water to a paste, which is 
 spread out over an even surface, where, upon the removal of the water, the intertwined 
 fibres remain united into a uniformly thick solid mass. Paper made from vegetable 
 fibre consists consequently of the purest possible cellulose. 
 
 The most essential properties of paper, by which its quality is estimated, are its 
 firmness, smoothness and glossiness of surface, its colour, transparency and durability. 
 Paper should offer a certain amount of resistance to tearing. For some purposes it 
 must possess a rough surface and be opaque ; for others a smooth and transparent 
 paper is required. It is very essential for writing-paper that it should retain its 
 colour and firmness as long as possible. 
 
 Preparation, Materials. In the manufacture of paper, vegetable fibres are 
 almost exclusively used, as they possess in a much higher degree than do animal 
 fibres the property of being worked up into a closely felted sheet. These fibres occur 
 either as the refuse of worn out tissue, as rags, or they are prepared specially for the 
 paper manufacture, and are then called surrogate. In rags two kinds of fibre- 
 tissue have to be dealt with, linen and cotton. 
 
 The fibres of linen are round tubes with thick walls, formed of concentric layers 
 of cellulose. The density of these tubes increases from within, or the newer forma- 
 tion, to the outer or older parts. Each separate fibre is pointed at both ends, has a 
 smooth surface, is flexible, and is so firm that it will undergo considerable pressure 
 without being crushed or pressed flat. 
 
 Cotton fibres also are formed of small tubes, the walls of which are much thinner 
 than those of linen. Consequently these fibres possess much less firmness, and by a 
 slight pressure are pressed together into a sort of band. Whilst, too, the linen fibre 
 is pointed at both ends, the cotton fibre is pointed only at one end. These two condi- 
 tions cause the felting of cotton fibres to be more difficult and less close, and therefore 
 cotton rags are not so suitable to the paper manufacture as linen rags ; the lattei 
 yielding a closer and smoother paper. 
 
 Woollen and silk stuffs are not suitable for the paper manufacture. Their fibres 
 are not hollow; they are consequently too rigid and hard. They are only used for 
 making packing papers. In recent years the substitutes for rags have become of 
 greater importance to the paper manufacture, and especially among these wood and 
 straw. 
 
 The kinds of wood especially suited for the paper manufacture are those which 
 are least compact in structure, so that they can easily be brought into a finely divided 
 condition. They are principally light woods, such as the fir, pine, poplar, birch, 
 lime, hornbeam, etc. 
 
 In the preparation of wood for the manufacture of paper, the individual fibres 
 have to be isolated as much as possible, and freed from incrusting material, such as 
 resin, albumen, tannin, oil, etc. This is effected either by mechanical or chemical 
 methods, or by the aid of both. 
 
 PREPARATION OF SURROGATE BY MECHANICAL TREATMENT. The most remark- 
 able mechanical method of preparing wood was introduced by Woelter, of whose 
 machines a great number are in use in Germany, Belgium and France. By this 
 method the wood is ground under a continuous jet of water, the wood being pressed 
 against the grindstone parallel to the fibres or the axis of the tree. The apparatus 
 consists of three principal parts : the defibrator, which is a grindstone of sandstone, 
 having a surface sufficiently rough to tear and disintegrate the fibre of the wood 
 pressed against it ; the purifier, or sorting apparatus, a series of drums provided with 
 metal sieves of various sized meshes, through which the fibres suspended in the water 
 are deposited in different heaps; and the refiner, by which the inferior and coarser 
 woody fragments are converted into a fine paste. 
 
PREPARATION OF PULP. C35 
 
 The defibrator consists of a grindstone, 4 ft. in diameter and 16 in. thick. Its 
 axis lies horizontally in two cast-iron sockets. It makes 150 revolutions a minute, 
 for which a driving force equal to 45 to 55 horse-power is required. A machine 
 of 50 horse-power only yields about half a ton of marketable wood fibre daily. This 
 considerable consumption of force in comparison with the yield limits the use of the 
 machine to districts where there is an abundance of water power and wood. Over 
 the grindstone are, according to its size, five or more iron chests. The wood to be 
 disintegrated, sawn into pieces about 14 in. long, is laid in these chests with its 
 fibres parallel to the axis of the grindstone, against which whilst rotating it is pressed 
 by a spiral arrangement that pushes the wood forward at the rate of from 1 to 3 ft. 
 per hour. Above the grindstone are also two cocks through which water is allowed 
 to run in sufficient quantity to keep the rubbing surface always wet. The wood paste 
 flows away into a reservoir placed underneath the stone. 
 
 The epurateur or sorting apparatus consists of a series of troughs each 
 provided with a drum sieve with its axis fixed horizontally. These drums are 1 foot 
 in diameter, 3| ft. in length, and are completely covered with wire gauze, each drum 
 in succession having finer gauze than its predecessor. The wood paste from the 
 reservoir is run through a coarse sieve, which retains the largest pieces, and then 
 allowed to stand a short time in a settling tank, during which time especially any 
 sand that may have been derived from the grindstone is deposited. The paste passes 
 from here through the drum sieve of the first sorting trough. A portion of the 
 woody fibre remains behind, but the finer fibre passes through the gauze and the 
 hollow axis of the drum into the second trough, where another portion is retained. 
 This is repeated until the last drum of the series is reached, through which only water 
 should pass, the meshes being sufficiently fine to retain the finest fibre. The rate 
 of rotation of the drums varies: the first makes 30 to 36, the second 15 to 18, the 
 third and fourth 18 to 20, and the fifth 15 revolutions per minute. The wood fibre 
 accumulating on the exterior is scraped off by means of a small cylinder, and thrown 
 into a collecting vessel. 
 
 The raff incur consists of two mill-stones, the lower of which is stationary, the 
 upper rotating upon it. Into this apparatus are placed the portions of fibre retained 
 by the first, or first and second drums, and ground into a fine paste, which is brought 
 again into the sorting apparatus. The loss of wood by Woelter's method amounts 
 to 50 per cent. 
 
 The greatest difficulty in the preparation of ground wood stuff is the impossibility 
 of bleaching it with chlorine or chloride of lime, which would colour the wood fibre 
 yellow or brown. If on the other hand an unbleached wood fibre, perfectly white in 
 appearance, be used, the paper prepared from it darkens very rapidly when exposed 
 to the light. A good bleaching material for ground wood fibre has yet to be dis- 
 covered. Sulphurous acid imparts to it a light yellow colour ; oxalic acid, which has 
 been recommended in several quarters, has scarcely any action. 
 
 Falkenhayn has patented in Bavaria a wood disintegrating machine, in which the 
 wood is rasped by pressure against a cast-iron cylinder set with steel saw-like teeth. 
 The mass, in the condition in which it comes from the cylinder, can be used as an 
 addition to ordinary paper paste. In order to make it available for finer paper, it is 
 passed between two spirally channelled cast-iron cylinders. By this machine half a 
 ton of pine-wood can be disintegrated in twenty-four hours. Similar wood disin- 
 tegrating machines are still constructed in great number. One that is highly spoken 
 of was exhibited by Decker and Co. at the Paris exhibition of 1867. 
 
 The rasped wood stuff is inferior in quality to the ground, the separate fibres 
 being so much broken up that their capability of felting is ranch diminished, and the 
 paper is not so strong. 
 
 PREPARATION OF SURROGATE BY CHEMICAL TREATMENT. For a long time 
 chemical agents have been used to free the cellulose of wood, straw and many other 
 vegetable tissues from the incrusting materials, and to prepare it in a pure condition. 
 These methods can in some measure be made useful in the preparation of wood for 
 the paper manufacture. 
 
 In the manufactory at Pontcharra, Messrs. Orioli, Neyret, and Fredet treat slices of 
 wood one-fifth of an inch thick, or wood shavings, at a warm temperature with a kind of 
 aqua regia, then in a closed double-sided vessel with ammonia or soda, and thus free the 
 wood from the incrusting material. A subsequent bleaching process with chloride of 
 lime, and washing, suffice to produce a beautiful white and pure wood stuff, which 
 forms an excellent substitute for rags. The proportions for the aqua regia, according 
 to Orioli, are one part of nitric acid to four parts of hydrochloric acid. If more 
 hydrochloric acid be used the wood is turned brown. 
 
 In the method of treating with aqua regia in the cold, the well-dried slips of 
 wood, one-fifth of an inch thick, are placed in a mixture of 94 parts of strong 
 
636 PAPER. 
 
 hydrochloric acid (sp. gr. 1-160) and 6 parts of nitric acid, contained in an earthen- 
 ware vessel capable of holding about 200 gallons, and left in contact with the aqua 
 regia during six' to twelve hours. The wood absorbs about 50 per cent, of its 
 weight of the acid ; the excess of acid is mixed with fresh aqua regia and used in a 
 subsequent operation. A portion of the colouring substances is changed into picric 
 acid ; the incrusting material is partly dissolved and partly converted into a soluble 
 condition ; whilst the fibrous cell substance, with careful treatment, is not attacked. 
 
 The method of treatment with hot aqua regia is to be preferred to the foregoing, 
 because by it the cellulose is more preserved, whilst the foreign substances are more 
 strongly attacked. For 100 parts of wood about 260 parts of aqua regia, or sufficient 
 to dip the whole of the wood slips in at once, are taken. The liquor consists of 6 
 parts of strong hydrochloric acid, 4 parts of nitric acid, and 250 parts of water. The 
 entire operation is carried out in a wooden trough, the bottom of which consists of a 
 granite slab cemented to the edge of the wooden trough with caoutchouc. As soon 
 as the trough is prepared with the aqua regia and wood, steam is passed in through 
 a wooden pipe, at the end of which is a valve to prevent the aqua regia from flowing 
 into it. 
 
 After treatment with either cold or hot aqua regia the excess of acid is poured 
 off, and the woody mass is washed in the same vessel several times with fresh water. 
 The washed slips of wood are then crushed into a brown mass by means of vertically 
 placed granite mill-stones, again washed with cold water, and finally, in order to 
 remove the last trace of acid, treated with a small quantity of milk of lime. 
 
 In the washing with alkaline liquor there is used in the manufactory at Pontcharra 
 an apparatus invented by Neyret, Oriolo, and Fredet. It consists of a strong rotating 
 iron cylinder, 13 ft. 4 in. long and 6 ft. in diameter, resting on its axis in a strong 
 iron frame. The rags or wood stuff, as well as the alkaline wash liquor, are introduced 
 through a manhole. The cylinder is surrounded by a jacket, leaving a space into 
 which steam can be introduced. The steam enters through the hollow axis, and a 
 stuffing box into this space ; the condensation water flows back into the steam chest 
 through the stea'm pipe. In this manner the inner cylinder is heated over its entire 
 surface. A too great loss of heat is prevented by a wooden shell covering the outside 
 cylinder, and over this again is a thin tarred sheet-iron case. During the working 
 the manhole of the inner cylinder is closed air-tight. A cock above is available for 
 the recovery by distillation of ammonia when it is used ; whilst a cock at the bottom 
 of the cylinder is used for drawing off the liquor freed from ammonia, or the soda 
 ley when soda is used. 
 
 As the operation is effected in a closed vessel, this apparatus is especially suitable 
 for the use of ammonia water, because the vapour of this liquor, by heating, produces 
 double the pressure of water vapour. When heated with water vapour up to 145 or 
 152, the pressure in the inner cylinder produced by the ammonia vapour corresponds 
 to eight to ten atmospheres. The revolutions number l to 2 per minute; the 
 contents of the inner cylinder amount to 2,000 gallons. 
 
 When wood stuff is to undergo treatment with alkalies in this apparatus, a 
 quantity of about 2 cwts. is placed in the inner cylinder, 600 or 700 gallons of 
 solution of ammonia added, to which a further addition of 50 or 60 Ibs. of caustic 
 soda, to preserve the ammonia in the caustic state, is an improvement ; the manhole 
 is closed air-tight ; a tap communicating with the space between the two cylinders 
 through which air can escape is opened ; steam at 150 is admitted to the inter-space, 
 and the apparatus is set in motion. After 5 or 6 hours the process is ended. The 
 ammonia is then distilled off, the liquor is allowed to run away, and the apparatus 
 is turned so that the manhole is underneath ; upon the removal of the lid the wood 
 stuff then falls out. Instead of ammonia a corresponding quantity of soda ley can 
 be used. This is prepared direct for use by dissolving 7 parts of soda in six times its 
 weight of water, and rendering it caustic with lime water containing 5 parts of burnt 
 lime. The turbid liquor is allowed to stand, and the clear ley afterwards drawn off* 
 
 The bleaching of the wood stuff after treatment with alkali is effected with 
 chloride of lime. The greatest care must, however, be used that the cell substance 
 itself is not burnt by it. Ordinarily for 100 parts of wood paste, 50 parts of chloride 
 of lime are taken. The total loss amounts to 60 per cent, of the weight of the wood. 
 
 The difficulty in the above-described methods consists, according to Orioli, in the 
 large vessels used for the action of the acid mixture upon the wood. Sandstone 
 vessels always let the acid through, and finally show cracks that cannot be sufficiently 
 stopped up with wax. Besides, the workmen are exposed to the vapour of nitric acid, 
 so that latterly the chemical method has been abandoned, notwitli standing that by it 
 a very fine and useful wood stuff may be obtained. 
 
 Bachet and Machard's method of treating wood has a double object : the bringing 
 of the wood into a fine fibrous arid easily felted mass, and the conversion of the 
 
PREPARATION OF PULP. 637 
 
 incrusting materials into sugar. A portion of the cell fibre also is always converted 
 into sugar, but it is exactly that portion that is most recently formed and least tough. 
 This condition therefore is so far favourable, that the remaining fibres are tough and 
 more easily felted. Experiments carried out in Payen's laboratory, in one of which 
 14 oz., and in two others 18 oz. of deal slips, ^ in. thick, were treated for ten hours 
 with a boiling mixture consisting of 3 pints of water, and ^ pint of strong hydrochloric 
 acid, gave on the average 21-13 parts of sugar from 100 parts of wood. 
 
 In some paper manufactories the saccharification is carried out in the following 
 manner. About a couple of tons of deal shavings are placed in a large vessel con- 
 taining about 1,760 gallons of water and 16 cwt. of crude hydrochloric acid, and the 
 whole is kept at the boiling temperature for 1 3 hours by means of a current of steam. 
 The acid liquor is then drawn off, and 99 per cent, of the free acid is neutralised with 
 carbonate of lime, free carbonic acid being formed, and calcium chloride, which does 
 not interfere with the operation of fermenting. Fermentation is set up by the addition 
 of yeast, the temperature of the liquor being kept at 22 to 25C. In the subsequent 
 distillation a quantity of alcohol is obtained corresponding to the sugar previously 
 formed. 
 
 The residual wood stuff is submitted to a methodical washing, then crushed under 
 a mill-stone, again washed, freed from mechanical impurities, drained and pressed. 
 In this way a brown wood stuff is obtained, that is very suitable for the manufacture 
 of packing paper. 
 
 A better and lighter paper is obtained when the wood paste is submitted to strong 
 pressure in a hydraulic press, so as to form cakes about ^ in. thick, which still contain 
 60 per cent, of water. These are formed into cylindrical rolls, and in this condition 
 are bleached for 36 to 48 hours in a chlorine chamber. A reddish wood stuff is thus 
 obtained which can be used directly for the manufacture of ordinary paper. 
 
 For the production of a white stuff, the wood mass, after its removal from the 
 chlorine chamber, has to be thrice macerated in lime water, each 100 parts of which 
 has been treated with 10 parts of soda at 80 to 90C. Lastly, the paste is thoroughly 
 washed in a vessel provided with a sieve bottom. At the same time tne mass is 
 perfectly bleached by chloride of lime mechanically distributed through it, which 
 leads to a loss of 30 per cent. 
 
 The considerable loss of cellular substance during the preparation of wood for the 
 paper manufacture is dependent on the use of chlorine gas or chloride of lime, it 
 being difficult to limit the action of these substances to the colouring and incrusting 
 matters of the wood. If the quantity of these agents be rather too large, or the 
 temperature be too high, a portion of the cellulose is burnt to carbonic acid and 
 water. In some measure this may be prevented by using less chlorine or chloride of 
 lime, and allowing them to act at a lower temperature but for a longer time. 
 
 The cost of paper stuff, prepared according to the chemical method from wood, is 
 much less than that of rag stuff, to which it can be added to the extent of 80 per 
 cent., but only 20 per cent, of the mechanically prepared wood stuff can be so added. 
 The price of the latter however is so much the lower, that at present it is more 
 extensively used than the chemically prepared. 
 
 G-. Fry treats the wood in fine shavings with water and high pressure steam only, 
 and works the liquor running off and pressed from the shavings for alcohol. 
 
 Straw, by proper treatment, yields a paper stuff which is preferred to that pre- 
 pared from wood, and in many manufactories in Germany and other countries a very 
 large quantity is now made from straw. The fibres obtained from straw by suitable 
 treatment are thin and smooth, easily felted, and yield a close, firm paper, but which, 
 when it consists only of straw, is brittle. The straw stuff is therefore also used to- 
 gether with rag stuff, to which it can be added to the extent of 80 per cent, without 
 the paper becoming too brittle for ordinary use. For instance, the paper on which 
 some newspapers are printed consists of two parts of straw and only one of rags. 
 
 The preparation of the straw is partly mechanical and partly chemical, and on the 
 whole is rather troublesome. In a large manufactory at Krollwitz, near Halle, it is 
 carried on according to the following method originally introduced by Keferstein, but 
 known as Lahousse's method. 
 
 The chopped straw is placed in a large vertical sheet-iron cylinder, which revolves 
 round a hollow axis ; the apparatus is then completely filled with a solution of caustic 
 soda, prepared with lime from the very best soda. The manhole is closed, and 
 during four or five hours the cylinder containing the cold ley is rotated. After this 
 the caustic soda is drawn off from the chopped straw and pumped into the ley reser- 
 voir ready for a new operation. 
 
 During this treatment with cold caustic soda, the greater part of the incrusting 
 material of the straw, principally gum and protein stuff, is washed off; the silica, of 
 which the straw contains as much as 5 per cent., is not attacked. 
 
638 PAPER. 
 
 After the soda ley has been drained off from the straw as much as possible, the 
 drum is turned so that the straw falls out through the open manhole into the steamer, 
 which usually is arranged similarly to the revolving rag boiler. When the steamer is 
 filled with straw superheated steam at 150 is admitted through the hollow axis. As 
 soon as the entire mass has acquired the temperature of the steam, hot water is run 
 in, which causes the steamer to rotate. After a time the wash water is run off and 
 steam at 150 is again admitted, and this treatment is repeated six or seven times. 
 At the commencement of the process, the pores of the straw are still full of absorbed 
 ley. When the steam is admitted this forms a hot ley, by which the silica, unattacked 
 by the cold ley, is converted into soluble sodium silicate. By the succeeding treatment 
 with warm water this is dissolved and washed out. As the disengagement of the 
 silica, however, is only effected slowly, the operation, as before stated, has to be 
 several times repeated. 
 
 It is very essential that the silica should be removed as completely as possible, 
 because otherwise the paper manufactured from straw stuff is transparent. 
 
 The bleaching and crushing of the straw mass, which operations follow next, are 
 carried out simultaneously. The steamed and washed straw is removed from the 
 steamer and put with chloride of lime into a large bleaching and pulping vessel, about 
 10 or 15 pounds of the chloride being added for each hundredweight of straw origin- 
 ally used. After the entire mass has been reduced to a pulp, it is brought into tubs 
 standing on a lower stage, in which the straw is prevented from settling by the 
 motion of a stirrer. It is then raised by a pump and run through a trough between 
 two ordinary millstones, by which means all the knots, ears, etc., are crushed, and 
 made accessible to the action of the chlorine. Decomposition of the chloride of lime 
 by the addition of an acid is not necessary, as decomposition is sufficiently effected by 
 the heat of the friction generated in passing between the millstones. 
 
 If it is intended to send the material into the market, the bleached mass is 
 pressed. If, on the other hand, it is to be worked up at once into paper of the 
 ordinary sort, it is run directly into the tubs over the paper machine. But if it is to 
 be used for finer paper, it is previously allowed to stand upon porous stone, by which 
 the greater part of the lime liquor is absorbed. 
 
 According to Keferstein, the yield of fibre by this method amounts to 55 per cent, 
 of the straw used. If the straw be at first treated with hot instead of cold soda ley, 
 the yield diminishes to 40 per cent. Wood in the rasped condition can also be pre- 
 pared for paper stuff by this method. 
 
 Straw can also be treated according to the method before described, as followed at 
 the Pontcharra works, in the preparation of wood stuff (p. 635). The straw is 
 chopped into pieces ^ in. to 1 in. long, and then treated in the same way as the wood 
 with hot or cold aqua regia, washed, crushed, again washed and bleached. By Berges 
 and Zuber, and Kieder, the straw is cut in a machine, freed from knots in a kind of 
 powder mill, crushed and ground by a cylinder, and washed for ten or twelve hours in 
 a rotatory apparatus ; 25 to 30 parts of 90 soda dissolved in 200 parts of water being 
 used for each 100 parts of chopped straw. The wash liquor is drawn off, and united 
 with that obtained by strong pressure of the straw between cylinders, concentrated by 
 hot air drawn from the flue of a reverberatory furnace, and finally brought to dryness 
 and calcined in the furnace itself. A salt mass is thus obtained which, after lixiviation 
 and treatment with lime, yields a caustic ley that can be again used for the washing 
 of straw. The washed straw mass is pressed, dipped in warm water, then washed in 
 cold water, the fibres being at the same time again separated. The bleaching is done 
 in the same vessel as the washing, by means of chloride of lime. 
 
 PRELIMINARY TREATMENT OF THE RAGS. When rags are used for the manufacture 
 of paper, the operations commence with the sorting of the rags, which is not done 
 with sufficient care by the rag collectors. The work is usually done in the basement 
 of the factory by women and girls, and with it was formerly combined the cutting up 
 of the rags. The workers stand before a kind of table with a wire net surface, upon 
 which the rags to be sorted are spread out, and the rags are cut by a perpendicularly 
 fixed knife ; the new rags into pieces 2 in. wide by 5 in. long, and the old rags into 
 pieces 4 in. wide by 6 in. long. At the same time all the hooks, buttons, seams, and 
 especially all hard parts of the rags are removed ; the rags being thrown according to 
 their quality into various receptacles. During this operation a large quantity 
 of dirt from the rags falls through the wire surface into a receptacle underneath. At 
 the present time the cutting up of the rags is sometimes done by a special machine. 
 
 The degree to which the sorting is carried out differs in various manufactories. 
 In some the rags are sorted only according to the material from which they are woven, 
 into linen, cotton, silk, and woollen; more generally the sorting is carried further, and 
 extends to the colour and the form in which the fibre occurs in the rag. This more 
 
PREPARATION OF PULP. 639 
 
 thorough sorting, however, applies only to the linen and cotton rags, because only 
 t hose are used for the better sorts of paper. 
 
 The principal object of the sorting is to bring together as nearly as possible rags 
 of the same quality, so that in the succeeding operations of washing, bleaching, and 
 pulping, a material as nearly equal as possible in colour and texture may be used. If 
 dirty rags be washed with clean, or coloured rags bleached with white, the latter are 
 under treatment much longer than is necessary. The same holds good for the pulping 
 in the hollander, which is worked much more rapidly for open texture than for close. 
 
 The apparatus used for cutting the rags is of various construction. The simplest 
 and oldest is in principle the same as a straw cutter. The rags are pushed under a 
 fixed horizontal band, in front of which, and just in contact with the edge, a sharp 
 knife passes up and down in a vertical direction. Sometimes instead of a vertical the 
 knives have a rotary motion. 
 
 Fox's rag-cutter consists of two horizontal cylinders, surrounded by sharp steel 
 edges at intervals corresponding with the size to which the rags are to "be cut. The 
 cylinders are placed so that, when they revolve, the knife edges of one fit exactly over 
 those of the other, and the rags are passed between them, the machine being fed 
 through a funnel. 
 
 The purification of the rags is divided into a dry and a wet cleansing. The first is 
 partially effected in the sorting and cutting, during which a considerable quantity of 
 dirt falls through the wire gauze. After leaving the cutting machine, the rags are 
 passed into a sifter, consisting of a large cylinder covered with wire gauze, and revolv- 
 ing round a wooden shaft. Upon the cylinder being set in motion the rags are tossed 
 about, and the dirt falls through the wire gauze into a surrounding wooden frame, 
 from which the dust is carried forward by a current of air. The length of the cy- 
 linder is from 7 to 10 feet and the diameter about 32 inches. Instead of the revolving 
 cylinder, a stationary one is sometimes used. In this the rags are beaten by wooden 
 arms set spirally round a revolving shaft and reaching almost to the periphery 
 of the cylinder; the shaft makes 150 to 200 revolutions per minute. 
 
 The loss during this operation (independent of loss of weight representing mois- 
 ture) amounts with fine clean rags to from 1-1*5 per cent.; for hems and seams, to 
 2 - 5 3'6 per cent. ; for coarse rags, packing cloth, rope, and string, which have to be 
 very thoroughly shaken, to 4-5'5 per cent. 
 
 In order to avoid the inconvenience of stopping the machinery for the emptying 
 and filling the cylinder, a continuous apparatus has been introduced. It consists of a 
 stationary conical sieve cylinder, having a shaft passing through it to which are 
 fastened wooden or iron beating arms. The rags are introduced at the narrow end of 
 the cylinder, fall towards the opposite side, and are thrown out purified at the wide 
 end. 
 
 In most manufactories the rags are not washed in water alone, but are carried 
 directly from the sifter to the boiler. When they are so washed, the washing is done 
 in a horizontal wire gauze cylinder, revolving on its axis in a trough of water, like a 
 beet-washing cylinder (see SUGAR). 
 
 In order to remove greasy dirt, and to destroy many colours preparatory to the 
 bleaching process, the purified rags are boiled in a caustic ley. For the finer rags, 
 soda potash or caustic soda are used ; for the coarser, caustic lime, sometimes with 
 the addition of some soda. In the older paper manufactories, 10 to 20 parts of 
 caustic soda are taken for each 1,000 parts of rags, according to their quality. When 
 the rags have not been previously washed with water, they are first moistened with 
 warm water, then thrown on the heap, and afterwards brought into the boiler, which 
 may consist of an open or closed stationary or revolving vessel. 
 
 Payen gives the following proportions of lime and soda for 100 parts of different 
 kinds of rags : 
 
 Lime. Soda. 
 
 Hard and dirty rags 15 6 
 
 Strongly coloured rags 12 3 
 
 White rags 5-10 
 
 E. Hoyer gives the following proportions : 
 
 Lime. Soda. 
 Fine white well-worn rags . . . .... 5 
 
 Fine, less worn 15 1 
 
 Half fine, not quite white '. 20 1 
 
 Coarse unbleached 25 
 
 Fine coloured . 15 15 
 
 Coarse coloured . . . .20 
 
 According to Hoyer, the finer rags are best treated witn soda only, whilst for the 
 coarser he recommends an addition of caustic lime, or the lime alone. The lime is 
 
640 PAPER. 
 
 converted into a fine milk and mixed with the dissolved soda before adding to the 
 rags. 
 
 The stationary boiler is a large vessel heated by steam. It is provided with a 
 perforated false bottom, situated a short distance above the real bottom, and upon 
 which the rags are placed. The boiler being then partly filled with the ley, the 
 steam is admitted into the interspace between the two bottoms, passing either directly 
 into the ley or first through a spiral. The ley is thus heated, and is driven upwards 
 through a vertical copper pipe, which opens towards the top of the boiler ; from 
 thence the ley falls on to the rags, and permeating through them, drains through the 
 perforated bottom into the interspace, where it is again heated and driven upwards 
 through the copper pipe. The operation lasts from four to six hours, after which the 
 liquor is run off through a tap placed below the perforated bottom, and the rags are 
 again boiled with water. 
 
 The boiling is carried out much more effectively and quickly in a vessel having a 
 rotatory movement, the rags being thus brought more perfectly into contact with the 
 ,ley. The apparatus of Bryan Donkin consists of a spherical boiler, about 8 feet in 
 diameter, supported at the two ends of its hollow axis upon a strong cast-iron frame. 
 The boiler makes two revolutions in four or five minutes. Through one end of the 
 hollow axis water can be run into the boiler from a reservoir placed at a higher level, 
 or by means of a pipe fixed in it the liquor can be pumped out of the boiler. Through 
 the other end steammay be admitted from a steam chest situated below the boiler and ley 
 from a reservoir above. The steam passes from the hollow axis through a pipe into 
 a kind of cylinder sieve, fixed in the middle of the boiler, and constructed of twelve 
 perforated sheet-iron plates, the holes being % in. in diameter, and 1| in. apart. This 
 cylinder, which is about 4 feet wide, guards the end of the steam pipe from becoming 
 stopped up by the fragments of rag, and also distributes the steam over a large sur- 
 face. Over the surface of the cylinder, at intervals of about 2 feet, are teeth, by 
 which the rags are beaten up during the rotation of the vessel. The filling and 
 emptying of the boiler with rags are effected through a round manhole, and the dirty 
 liquor is drawn off through a tap. The spherical vessel will hold a ton of rags at one 
 time, and only requires one-sixth of a horse-power to set it in motion. Its efficiency 
 may be increased by fixing pegs on the inner surface, which set up a brisker agitation 
 of the rags ; also by increasing the pressure of steam to 3 to 5 atmospheres, thus 
 raising the temperature of the contents to J33 to 152. The height of the liquor is 
 observed through a small tap fixed in the side of the vessel ; at the commencement 
 of the operation it should not exceed one half the height of the boiler, and at the 
 finish not exceed two-thirds. 
 
 Li filling the apparatus the manhole is brought directly under a shoot through 
 which the rags fall ; the rags are pressed together with a lever or by treading them 
 down, and when a sufficient quantity is admitted, the manhole is closed. The milk 
 of lime or other caustic liquor is then run in through a tap until its level reaches 
 half-way up the vessel, and afterwards the steam is admitted through one tap, 
 another being opened to allow the excess to escape. After three or four hours' boiling, 
 both taps are shut off, but the rotation is continued three hours longer, and then the 
 caustic liquor and condensed steam are run off, and a stream of fresh water is allowed 
 to pass through the rags for two hours. The average time required for the entire 
 washing is twelve hours. The height of the liquor is never allowed to be increased 
 by the condensed steam beyond two-thirds, the excess being run off through a tap. 
 When the boiling is finished, the lid is taken off the manhole and a half turn given so 
 as to bring the opening underneath ; water is let in and the rags are washed out and 
 fall into a receiver beneath, which is provided with a sieve bottom, through which 
 the water can drain away. 
 
 An apparatus for boiling with ammonia has been before described (p. 636) in the 
 preparation of wood paper stuff, and can be used with advantage in the boiling of rags. 
 
 PULPING OF THE WASHED AND BOILED RAGS. Before bleaching, in order to pre- 
 sent the largest possible surface to the action of the bleaching agent, the rags require 
 to be disintegrated. This, however, must not be carried too far at once, as the wash- 
 ing of a finely-divided mass would be ver}' difficult. The preparation of the paper 
 pulp is therefore divided into two stages : (1) partial disintegration before bleaching; 
 (2) complete disintegration after bleaching. The product is called half stuff or 
 whole stuff, according as it has gone through both, or only one stage. 
 
 Formerly the disintegration of the rags was effected, according to the German 
 method, by stampers ; but at the present time only the Dutch method is followed. 
 The apparatus in which the rags are reduced to a pulp by the Dutch method 
 is called a hollander, and, according as it is used in the preparation of half 
 stuff or whole stuff it is called a half hollander or a whole hollander. 
 
PAPER MAKING. 
 
 641 
 
 At the same time as the rags are reduced to pulp in the hollander they are also 
 thoroughly washed. 
 
 The hollander (figs. 439 and 440) consists of a large shallow trough, about 10 ft. 
 long, 5 ft. wide, and 20 to 25 inches deep. It is divided into two equal portions by an 
 upright partition (A A) running lengthways, the ends of which do not reach the ends 
 of the trough, a free space being left equal at each end through which the rags and 
 the liquid can circulate round the partition. The trough is generally made of wood, 
 lined with sheeh copper or lead. Kecently, however, cast-iron hollanders have been 
 coming more into use ; these do good service, but they cannot be used for the bleach- 
 ing of the paper stuff with chloride of lime and acids, unless they are first coated 
 with cement, because the iron would be attacked. Stone troughs, and troughs made 
 of pieces of stone and cement, are also used, and, especially the latter, are much ap- 
 proved. 
 
 On one side of the apparatus are the pulping cylinders (c c), the axes of which are 
 supported at one end by the side of the trough and at the other by the partition in 
 
 FIG. 439. 
 
 FIG. 440. 
 
 the middle called the midfeather (A A) ; they then extend through the other side of the 
 machine, where they are driven by pulleys fitted on to the projecting ends of the shafts 
 (B B). The cylinders are fitted in the direction of the axis with cutters, which are 
 generally made of steel, but where bleaching with chlorine is carried on in the 
 hollander they are made of bronze (85 per cent, of copper and 15 per cent, of zinc). 
 The number of knives in the cylinder of a half hollander varies from 30 to 50 ; in a 
 whole hollander it varies from 65 to 75. Below the cylinders are frames (D D), gene- 
 rally of cast iron, set with sharp knives at a slight angle with those of the cylinder, 
 so that, upon the cylinder being rotated, a cutting action is set up between the two 
 sets. The knives are fastened in their respective places by wooden plugs. 
 
 The rags being in comparatively large pieces when first put into the hollander, 
 the space between the knives in the cylinder and those beneath has at first to be 
 wider than it is afterwards, and for this purpose there is an arrangement by 
 which the axis of the cylinder can be raised or lowered as required. 
 
 The rags being put into the hollander, together with a quantity of water, and 
 the cylinder set in motion, a circulation is established, the rags being carried by the 
 current of water between the cylinder and the fixed cutters and thus disintegrated. 
 
 T T 
 
642 PAPER. 
 
 The cylinder makes 180 to 220, or even 240 revolutions in a minute ; it is worked 
 less rapidly in the half hollander than in the whole hollander. 
 
 At the same time as the disintegration of the rags takes place a further cleansing 
 is effected, dirt being removed from between the tissues which the previous washing 
 and boiling could not touch. For this purpose a constant flow of water is kept up. 
 The soiled water escapes through wire-gauze screens, fixed behind and before the 
 cylinder. By the action of the cylinder, the rags and water are flung against 
 these screens ; the water passes through and runs away through the outflow pipe, 
 and the rags remain partly adherent to the screen and part fall back into the trough. 
 When the mass has been sufficiently washed, the wire screens are covered over, and 
 the supply of fresh water is stopped ; the pulping process is then continued alone. 
 
 A more convenient contrivance is the washing cylinder, the circumference of 
 which is formed of wire gauze. The water passing through this into the cylinder is 
 carried by spirally arranged pipes into the hollow axis from which it passes into an 
 outflow pipe. The washing cylinder makes about twenty revolutions per minute ; 
 it is at first set in motion by special machinery, but afterwards the motion is kept 
 up by the current of the liquid in the hollander. 
 
 In order to separate any sand present, there is a trough running across the bottom 
 of the hollander, covered with wire gauze, through which the sand falls into the de - 
 pression beneath. 
 
 Each hollander is charged with 1 to 2 cwt. of rags, the water required being from 250 
 to 450 gallons. The entire operation lasts from two to four hours. The emptying is 
 effected through an opening at the bottom of the hollander. 
 
 In most paper manufactories this first pulping work is carried out in a half 
 hollander, and for white rags, which are easily washed and pulped, it is sufficient. 
 But for coarse, hard rags, as well as seams, cord, etc., which are very difficult to 
 pulp, Planche recommends the use of two hollanders, which should be so fixed that 
 the pulp can flow from one into the other. In the first the operation is chiefly 
 directed to washing the rags ; in the second the pulping is carried on. The cylinder 
 of the first hollander is set with 36 knives and there are 6 or 8 fixed knives ; these are 
 sufficient for the beginning of the pulping process ; it makes 150 revolutions per 
 minute. There are besides in this hollander a washing cylinder, washing screens, 
 and two sand-catching troughs. The cylinder of the second hollander is set with 54 
 knives and there are 10 or 12 fixed knives ; these knives are also thinner. The revolu- 
 tions amount to 1 80 in the minute. The wire gauze of the washing cylinder is finer than 
 in the first hollander ; the washing screens are not used. The operation lasts four 
 hours. The loss varies, for good rags, between 7 and 14 per cent., and for inferior 
 rags, seams, rope, etc., between 18 and 35 per cent. 
 
 The paper stuff from the second hollander is allowed to run into a vat, the bottom 
 of which is made of wire gauze. After it has drained, it is conveyed, in many 
 factories, upon an endless cloth between a pair of gutta-percha or hardened caoutchouc 
 cylinders, and the adhering water expressed as much as possible. A cake of paper 
 stuff is thus obtained about a quarter of an inch thick, containing 60 per cent, of 
 water and 40 per cent, of dry stuff. Kecently Kieder has recommended the removal 
 of water from half stuff by submitting it to the action of a centrifugal apparatus 
 making 1,200 to 1,300 revolutions per minute. 
 
 BLEACHING. The bleaching of paper stuff has for its object the destruction of 
 colouring matter, and the conversion of the stuff into as white a mass as possible. 
 The operation is carried out with chlorine gas or chloride of lime. 
 
 In bleaching with chlorine gas, the chlorine preparedfrom manganese and 
 hydrochloric acid, according to one of the methods described on p. 163, passes through 
 leaden pipes into the upper part of the bleaching chamber. The half stuff having 
 been sufficiently freed from water, and, if it has been pressed, again separated by the 
 action of the wolf, a shaft armed with teeth and revolving in a trough is spread out 
 upon wooden shelves in the chamber. The chlorine entering at the top, makes its 
 way by virtue of its greater specific gravity towards the bottom, passing through the 
 stuff on the upper stages to that on the lower, the excess of chlorine escaping through 
 an opening at the bottom into an adjoining bleaching chamber. 
 
 The chambers may be replaced by several bleaching chests, about 3 feet high, and 
 filled with paper stuff. The chlorine is introduced into these chests also at the top, 
 and the bleaching is completed in ten or twelve hours. 
 
 Instead of tearing up the stuff which has been pressed between rollers, the cakes 
 may be rolled up loosely and the rolls stood side by side in a receptacle about 16 
 feet long, 5 feet wide, and 4 feet 2 in. deep, constructed of brickwork, the inside of 
 which is coated with tar and lined with wooden planks, whilst the outside is 
 coated with either wood or stone, all crevices being well stopped up. The washed and 
 
PAPER MAKING. 643 
 
 cooled chlorine is admitted at one end into the upper part and makes its way towards 
 the opposite end, displacing the air. Each receptacle of the dimensions given will 
 contain two tons of dry paper stuff. In working a system of 13 receptacles, 3 are 
 being charged, 3 are being emptied, 6 are in action, and one is under repair. 
 
 If the temperature be too high during the bleaching process, the action of the 
 chlorine upon the paper stuff is too energetic; it attacks the cellulose and in this way 
 a loss of much fibre substance may result. The temperature must therefore be kept 
 as moderate as possible, and the chlorine should only be admitted in small quantities 
 at a time. But at too low a temperature the bleaching goes on slowly, and then the 
 temperature has to be raised by the admission of a little steam. 
 
 After the paper stuff has been bleached with chlorine gas, it is placed for further 
 draining in boxes, where it lies for 24 to 48 hours, during which time it undergoes 
 an after bleaching from the still adhering chlorine. 
 
 In order to wash and pulp the bleached mass at the same time it is put into a 
 hollander, the knives in which are of bronze, as steel knives would be too strongly 
 attacked by the chlorine. 
 
 Bleaching with chloride of lime. Latterly chloride of lime has been 
 used for bleaching in by far the most paper manufactories. The chloride of lime, or 
 bleaching lime, contains the active constituent calcium hypochlorite, which upon the 
 addition of hydrochloric acid is decomposed into calcium chloride, water, and chlorine. 
 Instead of hydrochloric acid, sulphuric acid may be used, because this decomposes 
 any calcium chloride present in the chloride of lime, with formation of calcium sul- 
 phate and hydrochloric acid, the hydrochloric acid then reacting upon the calcium 
 hypochlorite and liberating chlorine. 
 
 For the purpose of bleaching with chloride of lime, a clear solution of it is pre- 
 pared and added, together with hydrochloric or sulphuric acid, to the paper stuff. 
 The mixing is effected in a hollander which has usually double the capacity of those 
 previously used. This hollander is constructed of wood, cement, etc., or even occasion- 
 ally of cast iron ; in the latter case, the interior must be coated with cement or the 
 iron would colour the paper mass. Instead of steel knives, the cylinder and the 
 frame below are best provided with wooden cutters. Washing screens are not used, 
 but sometimes a sand-catcher, and here and there a couple of washing wheels. In 
 the place of the cylinder furnished with wooden bands, there is in many hollanders 
 only an axis upon which between two wooden disks are six or eight wooden shovels ; 
 these should be covered with sheet lead to protect the wood from splintering. The 
 rotation of these shovel wheels must be sufficiently rapid to communicate to the 
 liquid the same rate of motion as in the ordinary hollander. 
 
 In order to accelerate the washing and bleaching, Blanche uses instead of the 
 shovel wheel one set with bronze bands, and beneath it a frame furnished with 
 three similar bands. He also recommends a simple arrangement for supplying the 
 bleaching liquid or water. It consists in providing the hollander with a perforated 
 double bottom made of bronze plates and having the holes one-twelfth of an inch in 
 diameter. At the side is a smaller tank of wood communicating through the bottom 
 with the space below the false bottom of the hollander. At a higher elevation are 
 fixed three vessels, one containing fresh chloride of lime solution, one a weaker 
 liquor that has been already used once, and the other water, and from each of 
 these a pipe having a tap at the end passes into the small wooden tank. Upon a tap 
 being opened, the liquor runs from the respective vessel first into the small tank, and 
 then from it through the false bottom into the hollander. 
 
 Frequently, especially in large factories, bleaching with chlorine gas and with 
 chloride of lime are combined, the rags or half stuff undergoing a first bleaching with 
 chlorine gas in bleaching closets or boxes, and an after bleaching with chloride of 
 lime solution in the hollander. More often, however, both bleachings are effected 
 with chloride of lime, but in this case the after bleaching is carried out on the whole 
 stuff. 
 
 The quantity of bleaching material required varies according to the nature of the 
 paper stuff to be bleached, as well as with the strength of the bleaching material. 
 In bleaching with chlorine gas there is required, on the average, for 100 parts by 
 weight of dry stuff, 4 parts of manganese and a corresponding quantity of crude 
 hydrochloric acid. When chloride of lime is used, the quantity required for 100 
 parts of stuff varies, according to its strength, between 1 and 8 parts and part of 
 sulphuric acid. The sulphuric acid is diluted with twenty times as much water, and 
 added to the chloride of lime solution, a small quantity at a time. 
 
 It is very important that before further working the bleached half stuff it should 
 be perfectly washed. With this object there is in the bleaching hollander a washing 
 cylinder, by means of which, after the bleaching is completed, the half stuff is 
 thoroughly washed. When the greater part of the chlorine has been removed by the 
 
 T T 2 
 
644 PAPER. 
 
 water, a small quantity of sodium hyposulphite (antichlor) dissolved in water is 
 added ; this is oxidised to sodium sulphate by the bleaching material still adhering 
 to the stuff, and the whole can then te easily removed with water. 
 
 The bleached and washed half stuff is now brought to as fine a pulp as possible 
 in the whole hollander, and is then called whole stuff. The difference between the 
 whole hollander and half hollander, as before explained, consists chiefly in the pulp- 
 ing cylinder and frame of the former being provided with more and finer knives, so 
 as to effect a more complete disintegration, and the absence of the washing screens. 
 The pulping of the paper is carried on in the whole hollander in the same manner as 
 in the half hollander, but it requires more care, as the disintegration may easily go 
 too far, a result that is called dead pulping. The time required for this stage is 
 about the same as that taken up in the preparation of the half stuff. 
 
 Planche distributes the work of the whole hollander between two Hollanders, one 
 of which stands at a higher elevation than the other, so as to allow its contents to 
 pass from the upper one into the lower. In the first the half stuff coming from the 
 bleaching hollander is thoroughly washed with water. As soon as this is accom- 
 plished the supply of water is stopped, but a part of the water is still allowed to run 
 off through the washing cylinder, so that a denser mass remains. Meanwhile the 
 pulping cylinder is lowered into the hollander, and a pulping process is commenced, 
 which, after the stuff has upon the opening of a valve passed through into the second 
 hollander, is there completed. By this arrangement the pulping of the whole stuff is 
 effected in two or three hours. 
 
 The mixing of the various kinds of stuff to form a paper stuff of certain quality 
 is carried out in the whole hollander, and the greatest care has to be used in the 
 selection and proportions of the sorts mixed. For instance, a stuff from coarse rags 
 must not be mixed with one from fine rags, as the resulting paper would be rough and 
 unequal, and the finer stuff would be so far wasted. In order to obtain a fine paper, 
 only stuffs as nearly as possible of similar character should be mixed together, the 
 fine-fibred with the fine-fibred, and the coarse-fibred with the coarse. 
 
 Lately, a considerable proportion of wood stuff or straw stuff has been added to 
 that from rags in the preparation of the better kinds of paper. Thus, in the factory 
 at Krollwitz near Halle, 66'6 parts of rag stuff and 33'3 parts of straw stuff are used 
 in the making of fine letter paper, and 33*3 parts of rag stuff and 66'6 parts of straw 
 stuff in the making of good writing or printing paper. "Wood stuff cannot be added 
 in so large a proportion. According to C. Hoyer, 15 to 30 per cent, may be used for 
 a medium-fine writing and printing paper ; 30 to 50 per cent, for ordinary writing and 
 printing paper ; 50 to 80 per cent, for ordinary paper-hangings, bottle and packing 
 paper ; millboard and pasteboard may be made entirely from wood stuff. 
 
 Tinting. In order to give to the paper a greater whiteness, as well as to increase 
 its weight, the so-called dressing is sometimes added to the whole stuff. This coats 
 the separate fibres and fills up the interspaces of the felted mass. Only a finely- 
 powdered beautifully white material can be used for this purpose, such as baryta 
 white, heavy spar powder, gypsum, washed chalk, or perfectly white kaolin powder ; 
 lead sulphate and lead white are also used. The ' pearl-hardening ' that is imported 
 from America is an artificially prepared silicate of lime. The chalk and fine white 
 clay in the form of kaolin, or some other preparation of clay, are to be preferred, 
 because the paper has a more uniform appearance than when the specifically heavier 
 and consequently more difficultly distributed baryta or lead compounds are used. The 
 quantity of dressing added amounts to from 10 to 20 per cent, of the weight of dry 
 stuff. Too much should not, however, be used, or the weight of the paper would be 
 increased at the cost of its quality. 
 
 As it is generally desired that a paper should have a somewhat bluish tint, whilst 
 the bleached stuff always still retains a trace of yellow, it is usual to add some blue 
 colouring material to stuffs intended for fine papers whilst still in the hollander. 
 Ultramarine is most frequently used for this purpose, about 1 per cent, of the weight of 
 stuff being added, more or less according to the shade required. Instead of ultramarine, 
 smalt, indigo, or prussian blue may be used : but the first has the advantage that it 
 can always be obtained in commerce, already reduced to a sufficiently fine powder. 
 
 Sizing. In consequence of the felt-like texture of unsized paper, it absorbs like a 
 sponge any liquid with which it comes into contact ; it is therefore quite unsuited for 
 writing upon. In the preparation of writing papers the interstices between the fibres 
 have to be stopped up by some glutinous material such as size. 
 
 The operation of sizing can be carried out in different ways. Formerly only the 
 finished sheet of paper was sized, but now the size is generally added to the paper 
 stuff whilst in the tubs or in the hollander. The first method is called sheet- 
 sizing, the second tub-sizing. 
 
 The sheet-sizing is usually done with ordinary animal size only, but it is neces- 
 
PAPER MAKING. 645 
 
 8ary that this should be as colourless as possible in order not to injure the colour 
 of the paper. The size used for the purpose is prepared from the skins of hares 
 and rabbits, the hoofs of sheep and goats, parchment refuse, eel skins, etc. These 
 materials are washed, then steeped in lime water, and afterwards perfectly cleansed 
 from it by washing in acidulated and then in pure water. It is next gently boiled 
 in 8 or 10 times its weight of water for six hours, during which time it is sprinkled 
 with a small quantity of very finely powdered lime, in order to convert the fat into 
 nn insoluble lime soap. As soon as a drop of the liquor placed upon a cold porce- 
 lain plate solidifies to a jelly, the boiling is completed. To 100 parts of this jelly is 
 added 2 or 3 parts of alum previously dissolved in water, by which the size is coagu- 
 lated and rendered insoluble, and consequently is in a more suitable form for the 
 sizing of paper. The same quantity of jelly is required, whether added to the stuff 
 in the vat or to an equal quantity of paper. Practically the ready-made size of com- 
 merce is used. This is steeped for two or three hours in water and then dissolved 
 in boiling water; 13 to 18 Ibs. of size mixed with 4 to 6 Ibs. of alum, dissolved in 
 22 gallons of water, is sufficient for the sizing of a whole vatful of paper. 
 
 The solution of size is brought to a temperature of 25, and then about 100 
 sheets of paper are dipped into it at one time, and so moved about that each 
 sheet becomes coated with size on both sides ; they are next pressed so as to dis- 
 tribute the size in the interior of the separate sheets, and afterwards separated and 
 hung to dry on lines in a drying room. The greatest caution has to be exercised in the 
 drying ; it must in general go on slowly, without however lasting sufficiently long 
 to allow .of decomposition of the moist size to take place. This decomposition is in- 
 duced sometimes during thunderstorms in summer ; the size is covered with mould, 
 becomes liquefied, and loses its glutinous properties. If the paper be too rapidly 
 dried the size remains distributed throughout the whole mass ; whilst during a slow 
 drying the size is drawn, together with the moisture, to the surface, and there forms 
 an impermeable layer. For this reason a paper sized in sheets will blot if written 
 upon where the sized surface has been scraped off. 
 
 In tub-sizing the size is added to the stuff in the tubs or in the hollander ; 
 the paper prepared from it is therefore uniformly sized throughout the whole thick- 
 ness. Ordinary animal size is seldom used for this operation ; but much more gener- 
 ally a resin soap and alum, or aluminum sulphate, or resin soap, aluminum sulphate 
 and starch together, are used. The respective quantities of these substances used 
 are generally a secret in each manufactory. In the following description the quanti- 
 ties recommended by Planche are stated. 
 
 In order not to injure the whiteness of the paper, upon which much of its value 
 depends, it is necessary that the purest and whitest resin and starch be used. Of 
 the different kinds of resin the French and American have the preference. They are 
 the residues obtained in distilling turpentine with steam in the preparation of oil of 
 turpentine, and are usually known as colophony. This resin is either only slightly 
 yellowish or quite colourless. 
 
 For the paper manufacture a specially white and pure starch is made. It con- 
 tains at the most not more than 18 per cent, of water, which is tested by the loss 
 of weight of a weighed quantity at 110. The ash should not amount to more than 
 3 to 4 parts per 1 ,000 ; a larger quantity would indicate a fraudulent admixture. 
 
 The alum, or aluminum sulphate, used for breaking up the resin soap must be 
 perfectly free from iron ; this may be tested by dissolving it in water, and adding 
 potassium ferrocyanide, which should not produce a blue precipitate even upon the 
 addition of some drops of chlorine water. Alum has the advantage over aluminum 
 sulphate that in consequence of its power of crystallisation it can more easily be 
 obtained pure. On the other hand, the aluminum sulphate is lower priced, and if it 
 can be obtained free from iron it is more profitable. 
 
 In the preparation of the resin soap 22 Ibs. of caustic soda are dissolved in a 
 boiler in about 160 gallons of water, and brought to the boiling point by the introduc- 
 tion of steam. To this 220 Ibs. of powdered and sifted resin are added gradually, 
 and the boiling of the liquid is continued until the resin is completely dissolved ; it 
 is then allowed to stand quietly for two days in a settling vessel to deposit sus- 
 pended matter. On the other hand, 1,100 Ibs. of aluminum sulphate are dissolved 
 by heating with steam in 110 gallons of water. This quantity is sufficient for 
 the sizing of the paper stuff from 166 Hollanders, reckoning 10 pints of solution 
 for each, corresponding to about 6^ Ibs. of aluminum sulphate. In a special 
 vessel 22 Ibs. of starch are stirred up in 11 gallons of water, and this is poured into 
 about 160 gallons of the resin soap liquor, where it is heated by steam to 100, 
 and then added to the paper stuff in the hollander whilst in operation. After the 
 soap has become thoroughly distributed amongst the pulp 10 pints of the aluminum 
 sulphate solution are added, which fixes the size in the fibre of the paper. 
 
646 PAPER. 
 
 The results obtained by the above operation are briefly as follows. By the intro- 
 duction of the resin into the boiling soda ley, soluble compounds of the soda with the 
 acids of which the resin consists (abietic acid, etc.) are formed. The soda-resin soap 
 is therefore a compound of sodium resinate soluble in water. "When this solution is 
 mixed with a solution of aluminum sulphate a double decomposition takes place, 
 sodium sulphate and aluminum resinate being formed. The former dissolves in the 
 water ; the latter is the size, which, being insoluble in water, separates out as a 
 jelly-like substance. When the mixing of the solutions is effected in the hollander 
 the size is precipitated as an extremely fine coating of the paper fibres. 
 
 Frequently, however, the mixed size is adopted. In this case a mixture of 
 resin soap containing about 4^ Ibs. of resin, 8| Ibs. of starch, and 4| Ibs. of size pre- 
 viously dissolved in water is put into the hollander, and solution of aluminum 
 sulphate is added until the liquid gives quite a weakly acid reaction. 
 
 In general it may be stated that in the sizing for writing paper of 100 Ibs. of 
 paper stuff (dry) there is used 1 to 1 Ibs. of soda, 10 to 12 Ibs. of resin, 20 to 30 
 of starch and 5 to 6 Ibs. of aluminum sulphate. 
 
 In the sizing of ordinary paper, a cheaper tallow or oil soap is used in place of 
 the fine resin soap. According to Hoyer 100 Ibs. of stuff take 3 Ibs. of soap and 
 3 Ibs. of alum. For very fine paper on the other hand a wax soap is used, made by 
 dissolving 40 Ibs. of wax in a potash ley, containing 10 Ibs. of potash and 5 Ibs. of 
 caustic lime. This soap is added to the stuff in the proportion of 2 Ibs. of wax to 
 100 Ibs. of stuff, and to this is added 3 Ibs. of alum or 1 Ibs. of aluminum sul- 
 phate. 
 
 PAPER MAKING. According to the older methods, the conversion of paper stuff 
 into paper was effected by hand labour, paper machines being of comparatively recent 
 introduction. L. Eobert, of Esonne, France, was the first to construct, in 1798, a 
 small machine, and bring it into use. In Germany the first paper machine was set 
 up at Weida, in 1819, by A. Keferstein. 
 
 Hand Paper. The manufacture of hand paper is at the present time only of 
 secondary importance ; it requires too much time and skilled labour for it to compete 
 with machine-made paper. Only paper for special purposes, such as filtering paper, 
 is now made by hand. 
 
 The contents of several Hollanders are united in one large vat, and diluted with 
 water to form a thin milky paste. Across the top of the vat is a perforated plank 
 called the great bridge. During the operation the pulp in the vat is kept continually 
 stirred to prevent the fibre from settling to the bottom, and it is also kept warm 
 either by the admission of steam or by a special furnace. The formation of the 
 paper is accomplished in the so-called mould which is a rectangular wooden frame, 
 spanned with fine wire gauze, and corresponding to the size of the sheet of paper re- 
 quired. This mould is dipped by a workman into the paper pulp and lifted out 
 again in a horizontal position, so that it remains filled with pulp to the height of the 
 movable sides or deckel of the frame of the mould. The water drops through the 
 meshes of the gauze, leaving the fibre upon the wires to form the sheet of paper, a 
 process which is hastened by shaking the frame. The water falls back into the 
 vat, but in order to prevent the pulp from becoming thus too much diluted, fresh 
 stuff is added from time to time. The thickness of the paper therefore is depen- 
 dent upon the consistency of the pulp and the height of the side or deckel of the 
 mould. 
 
 After the greater part of the water has run through, the mould is placed for 
 further draining on the bridge. A second workman then reverses the mould, so as 
 to bring the paper underneath, upon a sheet of felt, an operation that is termed 
 couching. Upon the removal of the mould the paper is left upon the felt. On 
 this is placed another sheet of felt, then another of paper, and this is repeated until a 
 post is formed, consisting of sheets of paper and felt alternately. The post is al- 
 lowed to stand some time that the felt may absorb the water, and then it is placed 
 in the press and pressure applied so long as any water runs away. The sheets of 
 paper and felt are then separated, and paper of good quality is submitted to the 
 same operation once or twice more, but ordinary paper is at once dried after the first 
 pressing. In order to prevent mould, the felts require to be occasionally dried. 
 The paper is dried by hanging it on lines ir. a suitable drying room. 
 
 Machine Paper. In the manufacture of machine paper, the paper stuff from 
 at least six hollanders is brought into a large common reservoir, where it is diluted 
 with water according to the thickness of the paper to be made ; for thick paper only 
 a small quantity of water being added, and for thin paper more. A stirrer is kept 
 continually in action to prevent the fibre sinking to the bottom. From the reservoir 
 
PAPER MAKING. 647 
 
 the pulp passes into the vat, a special mechanical arrangement being used to regulate 
 the flow. From the vat it passes to the paper machine, but before doing so it is fre- 
 quently subjected to an operation for the removal of any sand or lumps present. The 
 objects sought to be attained in the paper machine are to remove the greater part of 
 the water from the pulp, to effect the felting of the fibres, to form the sheet of 
 paper, and finally to dry the latter. The pulp flows first on to an endless band of 
 wire gauze, which is carried forward on a number of small rollers, by which arrange- 
 ment the web is kept in an exactly horizontal position. On each side of the wire 
 gauze, and travelling at the same rate, is an india-rubber band, forming the sides or 
 deckel. The draining off of the water and the felting of the fibres is hastened by a 
 jogging sideways motion. As the pulp is carried forward on the gauze band, the 
 principal part of the water falls through the meshes, whilst the fibres remain and 
 become more and more compacted into a sheet of paper. The water collects below, 
 and is raised by a turbine arrangement again to the reservoir, where it is used for 
 the thinning of a fresh quantity of stuff from the hollanders. A further portion of 
 the water is removed by passing the gauze band over a series of open chambers 
 where the pulp is subjected to the action of an aspirator. Kaufmann's apparatus, 
 which has recently been introduced for this purpose, is shown in vertical section in 
 *. 441. It consists of a wooden chamber divided into parts, over which the endless 
 
 band passes. The width of the band does not however correspond with the length 
 of the chamber, but the edges of the cloth run over the partitions (E E) leaving on 
 either side a free space (G G). Into the latter from the pipes (E E) through the funnels 
 (T T) a continual stream of water runs, so as to continually overflow the chambers 
 (G G), and thus form an air-tight water barrier between the gauze band and the trans- 
 verse divisions (BE), which is essential to prevent outside air gaining admission to 
 the aspiration chamber. A second bottom (o) runs from end to end of the chamber ; 
 in the centre of it, is a round opening (H) establishing a communication between the 
 upper and lower divisions. From the lower division a pipe (s) runs perpendicularly 
 into a vessel standing about 4 feet lower, and filled with water, below the surface of 
 which the end of the pipe dips. To set the aspirator in action, the lower space is 
 filled with water up to the false bottom (o), the wire-gauze band supporting the 
 paper is brought over the chamber, and the cock (x) is opened. As soon as the 
 water runs off through the pipe (s), a partial vacuum is established in the upper 
 division of the chamber, and this exercises a compressing and absorbing action upon 
 the paper mass. 
 
 After the paper has passed the absorption apparatus it is carried, still very moist 
 and soft, between two cylinders covered with felt, where it undergoes pressure. 
 From these cylinders the sheet of paper is carried on an endless band of felt to 
 another pair, constructed of cast iron, hollow, and very smooth, between which it is 
 strongly pressed. It then passes on to a second, but dry, band of felt, and is carried 
 between a third pair of cylinders, but this time the paper is reversed so that the 
 side which had in the previous pressing lain next to the felt is now next to the 
 cylinder. The paper next passes to the drying apparatus, consisting of three hollow 
 iron cylinders heated by steam admitted through their hollow axes ; it is carried 
 round these three cylinders in succession^ being pressed against the hot surface by an 
 endless band of felt. The second and third drying cylinders have each in connection 
 with them a smooth iron pressing cylinder, by which a final pressing and glazing is 
 imparted to the paper. In some of the newer machines, however, the paper passes 
 between two more pair of polished iron pressing cylinders, by which means a satiny 
 surface is imparted to it. Otherwise it passes from the drying cylinders to the 
 
648 PAPER. 
 
 cutting machine, where it is first slit into strips lengthwise, and then cut trans- 
 versely into sheets. After the cutting, the sheets are sorted, and defective sheets 
 thrown out, and the finer kinds are submitted to further glazing operations by 
 pressure between polished metal cylinders or between metal plates in a hydraulic 
 
 Where no size has been added to the paper stuff, or in the case of papers which 
 are required to have a well-sized surface, and therefore have to undergo an a f t e r 
 sizing, an arrangement for sizing is sometimes woi'ked in connection with the paper 
 making machine. The size is contained in a wooden trough lined with sheet copper, 
 and heated by a jet of steam opening at the bottom of the trough. The paper com- 
 ing from the drying cylinders is carried round the under surface of a wooden cylinder 
 which dips below the level of the sizing liquid in the trough, then between copper 
 cylinders by which any excess of size is removed, the quantity remaining being regu- 
 lated by approximation or separation of the cylinders. 
 
 COLOURED PAPERS. Puip coloured papers are prepared by adding the colouring 
 materials to the paper stuff whilst in the hollander. 
 
 Yellow paper is made by adding zinc oxide, ferrous sulphate, decoctions of 
 Campeachy or Pernambuco wood, or umber ; but lead chromate is principally used. 
 Payen recommends for 500 parts by weight of dry paper stuff 25 parts of basic lead 
 acetate and 4^ parts of potassium bichromate. 
 
 Blue. For ordinary papers Berlin blue is used, and ultramarine for the finer. 
 Indigo is but little used. A decoction of Campeachy wood with ferrous sulphate 
 and potassium ferrocyanide produces a dark blue paper. Payen gives for 50 parts of 
 paper stuff 2^ parts of ferrous sulphate and 1 ^ parts of potassium ferrocyanide. 
 But as paper stuff has usually a yellowish tone, which with the blue would give a 
 green shade, to prevent this a little red is added. 
 
 G-reen is almost always prepared by mixing yellow and blue, because the 
 cheaper greens cannot be used on account of their poisonous properties. Lead chro- 
 mate is used together with Berlin blue or ultramarine. According to Payen 50 parts 
 of paper stuff require 1^ of his yellow, and 3 parts of his blue. 
 
 .Red is usually coloured with Pernambuco wood, chiefly with an addition of alum, 
 aluminum sulphate, zinc chloride, etc. A more beautiful red is yielded by safflower 
 or carmine, though both these colouring materials are too dear. 
 
 Violet is prepared by mixing blue and red, or with extract of logwood. 
 
 Eose is prepared by adding 6 parts of extract of Lima wood to 50 parts of dry 
 paper stuff. 
 
 Brown is yielded by ochre, umber, or a mixture of chrome yellow and green 
 vitriol, with Pernambuco wood, Berlin blue, etc. 
 
 Chamois is obtained, according to Payen, by using 3 parts of double ferrous and 
 cupric sulphate and 3 parts of chloride of lime with 50 parts of paper stuff. 
 
 Grey and black are produced by means ot ferrous sulphate and extract of galls, 
 as well as by mixture of different colouring stuffs in certain proportions ; decoction 
 of Campeachy wood with ferric nitrate ; also Orleans umber, Berlin blue, lamp 
 black, etc. 
 
 In the preparation of ordinary packing papers the coloured rags are some- 
 times assorted and worked up into paper without bleaching, blue paper being ob- 
 tained from blue rags, brown from brown, etc. Papers made according to this 
 method are called nature-coloured or nature papers. But the colours never 
 being very fine, they are seldom made. 
 
 Surface-coloured paper differs from pulp-coloured paper in not being coloured 
 throughout the body of the paper, but only on the surface, on one or both sides. 
 For this purpose the most insoluble colouring materials, or body colours are used, 
 such as ultramarine, Berlin blue, chrome yellow, ochre, etc. The colour is retained 
 upon the surface of the paper by means of a kind of cement, for which purpose 
 ordinary size dissolved in water, or the so-called alum size (alum, 1 part; size, 2 
 parts ; water, 10 parts) is generally used. In the preparation of a specially durable 
 surface-paper a second coating of lime and alum is given. Instead of ordinary size 
 gum may be used, but not starch paste, as that would allow the colour to be easily 
 effaced. 
 
 The colouring is done either by hand with a brush, or by a colouring machine. 
 In the latter case the paper passes in a long band over a colour cylinder which takes 
 up the colour from the trough beneath, next over an endless gum cloth, and then 
 through several smoothing cylinders provided with brushes, some working longi- 
 tudinally, and others transversely, by which means the colour is spread equally over 
 the paper. The coloured paper then goes to the drying cylinders, which are heated 
 with steam, and is finally wound on a roller. 
 
 Amongst surface papers must also be included marble paper, rainbow 
 
PAPER MAKING. 649 
 
 paper, and paper hangings, each of these being again subdivided according to 
 the pattern. 
 
 In the preparation of marble or Turkish paper a very thick mucilage of 
 tragacanth, with a little alum added, is placed in a shallow trough, which at the top 
 is of rather larger dimensions than the sheet of paper to be marbled. Upon this 
 mucilage the marble pattern is formed by sprinkling on it finely triturated colouring 
 materials with a brush. The colours diffuse through the mucilage, running into each 
 other. Into this liquid the paper is carefully laid so as to bring the whole of the 
 surface into contact with it, and then taken out and dried. Granite paper is 
 prepared by sprinkling the different colours one upon another upon the paper by 
 means of brushes. Mottledpaper is prepared by sprinkling drops of a dark colour 
 on paper to which the ground colour has been already given. Before the sprinkling 
 the paper is moistened on the reverse side and spread out upon a smooth board ; 
 after the sprinkling the board is sloped so as to cause the spots to run. 
 
 Eainbow paper is made by using a brush as wide as the paper, and formed of 
 as many separate brushes as the number of bands to be produced. This is dipped 
 carefully into a colour box, which is divided into compartments corresponding with 
 the brush and filled with different coloured pigments, and then passed over the paper 
 so as to produce a number of parallel lines ; these are afterwards blended into one 
 another with a second brush. Sometimes the stripes are printed on by means of a 
 mould. 
 
 Paper hangings are printed by means of blocks on which the pattern stands in 
 relief. The operation resembles ordinary calico printing. 
 
 Grold and silver papers are prepared by laying gold or silver leaf respectively 
 upon paper to which a ground colour, which is reddish-yellow for gold and white for 
 silver, is rubbed up with gum solution ; the leaf is either laid upon it whilst it is 
 still moist, or, if it has become perfectly dry, is brushed over with A^arnish, to which 
 the leaf adheres. After the metal leaf has been laid on, which has to be done care- 
 fully to prevent unevenness or flaws, it is pressed down with cotton wool, and the 
 sheet is then glazed and dried. 
 
 Usually, in order to impart a shining surface to these papers, they are glazed, satined, 
 or varnished. The glazing is effected by means of a polished stone moving to and fro 
 under the pressure of a spring or a weight. The satining is done by scattering upon 
 the surface fragments of French chalk, and working it with a brush : lastly, a 
 solution of gelatine or of isinglass is used. 
 
 OTHER KI-NBS OF PAPER. Morocco paper is prepared by passing the paper 
 between a bronze cylinder, in which the pattern is engraved, and a cylinder covered 
 with paper. After the embossing is effected a coat of copal or mastic varnish is 
 given to the paper. Da mask, shagreen, and other papers are prepared in a similar 
 manner. 
 
 Kep cr filagree paper can be prepared on the paper machine, by means of a 
 cylinder surrounded by a brass wire work, which is called a dandy roller, 
 placed over the endless band between the absorption chambers and the first pressing 
 cylinders. ' . 
 
 The brass wires are separated to correspond with the width of rep required, 
 which is produced in the still soft paper pulp by the pressure of the cylinder. 
 
 The water mark can also be given by a similar arrangement, but in this case 
 the cylinder is covered with wire cloth, the design of the water mark (name of the 
 maker, coat of arms, etc.) being worked in relief in fine copper wire. In the produc- 
 tion of the water mark in bank notes, paper money, and other valuable papers, where 
 the greatest regularity is required, another method is adopted. The design is worked 
 in brass wire on the inner side of the wire cloth of a hand paper mould. By the 
 settling of the paper stuff there is formed over the raised design a thinner layer of 
 paper fibre than elsewhere, so that the paper at that spot is thinner and more trans- 
 parent. The difference between the two methods consists in the paper produced by 
 the former being equal throughout as to fibre : the part covered by the design being only 
 compressed together, whilst the transparent water mark in the latter is the result of 
 a thinner layer of paper fibre. 
 
 .Filter paper has to be made from very carefully purified fibres, which are also 
 specially suited to yield a paper of sufficient strength to sustain in the filter form the 
 pressure of the liquor to be filtered without bursting. With this object linen rags 
 well washed and treated with ley are first submitted to a careful pulping, and then 
 to a not too energetic treatment with chlorine gas ; or, better still, chloride of lime. 
 The pulp thus obtained is perfectly freed from adhering lime by means of dilute 
 hydrochloric acid, and afterwards thoroughly washed with very pure water ; it is then 
 ready for working into paper. 
 
650 PAPER. 
 
 A grey filter paper, of more spongy properties and filtering more rapidly than 
 the preceding, is obtained by using a mixture of cotton rags and linen. In order to 
 save the fibre it fe not specially treated with ley or bleached, bnt passes from the 
 hollander to the paper mould. Notwithstanding the most careful washing the filter 
 obtained from this stuff generally imparts a marked smell to liquids filtered 
 gh.it. 
 
 Berxelius's or Swedish filter paper is characterised by the greatest purity, 
 and is used for especially delicate analysis in chemical laboratories. As a raw material 
 new linen is used, which has been first bleached according to the old method of ex- 
 posing it kept constantly wet on the ground in the open air. The moist stuff is 
 placed in a reservoir where it undergoes a kind of fermentation, during which a 
 number of pectous and glutinous substances pass into the soluble form; but the pro- 
 cess must be carefully watched, as the cellulose itself may easily be attacked. The 
 stuff thus prepared is treated with a strong ley, pulped in the hollander, washed with 
 dilute hydrochloric acid (1 of acid to 10 of water), and finally washed with wateruntil 
 the last trace of acid disappears. It is then worked into paper by hand, and dried 
 without sizing. Most of the fibres of this paper have a length of from to of an 
 inch. 
 
 Parchment paper or vegetable parchment is prepared by steeping un- 
 sized paper (filter or blotting paper) in slightly diluted sulphuric acid (8 parts of 
 English acid to 1 part of water). The thicker the paper the longer the acid must be 
 allowed to act. Ordinary paper should not lie more than twenty seconds in the 
 acid, because it otherwise becomes brittle. It is then washed with water, next with 
 ammonia, and again with water, to remove the sulphuric acid. A machine for the 
 manufacture of parchment paper has been constructed, in which a band of paper is 
 passed first through sulphuric acid, then through ammonia, twice, and afterwards 
 drawn over felt and drying cylinders. 
 
 Mrr.T.BOABT> AND PASTKBOABD. In the manufacture of millboard, rags that are not 
 suited for ordinary paper, wood stuff, straw stuff, potato skins, beet pressings, and 
 paper refuse, may be used as raw material. The rags are converted in the ordinary 
 hollander into a coarse stuff. In the preliminary preparation of potato skins 
 and. beet pressings they are treated with dilute hydrochloric acid at 48 to 50, 
 then washed again with water and mixed with 1 to 2 per cent, of *mmnnJ5>_ 
 A pectinate of ammonia is thus formed, which gives to the mass a glutinous pro- 
 perty. To give it the requisite firmness there is mixed with it 10 per cent, of 
 ordinary paper stuff from rags. Old paper and paper refuse are soaked in water, and 
 allowed to undergo fermentation during fifteen to thirty days, after which they are 
 ground, still wet* between millstones. Generally there is added to stuff to be used 
 for millboard, before moulding, about one-fourth of its weight of clay, chalk, or simi- 
 
 The ordinary paper moulds are generally used in the same way as for hand paper, 
 the sides of the frame of the mould being, however, higher to hold the necessary 
 thickness of stuff, The couching and pressing between felt is the same as in hand- 
 made paper, after which the boards are dried separately. Ordinary millboard may 
 also be made with a machine, consisting of a cylinder covered with wire gauze, which 
 moves in a trough supplied with pulp. The cylinder becomes coated with a layer of 
 pulp, from which the greater part of the water is removed by a couching cylinder 
 pressing against it ; the pulp thus acquires a degree of firmness, and can then be 
 carried on an endless band of felt between the pressing cylinders, after which it is 
 dried, wound, and cut. 
 
 A finer fabric, the couched millboard, is made by pressing together freshly 
 drained, but still moist, sheets of paper. It has the advantage over the preceding of 
 being uniform in tJrirknm, it not being possible, in dealing with the quantity of pulp 
 required for a sheet of millboard, to deposit it equally in the mould. Moreover, 
 better materials are used for the couched millboard, such as coarse linen rags, 
 'cum, rope, etc,; straw and wood stuff can also be added. 
 
 Pasteboard is made by fixing sheets of finished paper one upon another by 
 means of paste. In this way the finest cardboard, used for playing-cards, etc., is 
 made. 
 
 Glazed boards and similar hard substances may be made by the couching 
 method. In this case the stuff must be sized in the vat, and upon the inner side of 
 the mould is laid a sheet of paper made from a long-fibred stuff; also great can if 
 used in the subsequent pressings. 
 
 Papier msehe is made by starring up waste paper or paper refuse to a paste 
 with water and sand, clay, or chalk, removing the greater part of the water by pres- 
 sure, sizing the mass thus obtained with bone size or paste, and then pressing it into 
 ofledmoulds. The moulded object is dried, soaked in linseed oil, and baked. A kind 
 
PAPER MAKING. 6ol 
 
 of papier mache is also made by pasting separate sheets of paper upon each other 
 in a wooden mould, and subsequently turning the surface in a lathe. 
 
 TBOTECO. Paper which has been sized with animal size can be distinguished 
 from that sized with resin size, as the latter always contains starch, which gives an 
 intensely blue colour when brought into contact with dilute solution or vapour of iodine. 
 The resin may be extracted by treating the paper first with a dilute acid, and then, 
 after drying, with alcohol, which dissolves out the resin set free by the acid; upon 
 ration of the alcohol the resin is left as a residue. The amount of animal size 
 might be estimated by an elementary analysis for nitrogen; the quantity of 
 nitrogen corresponds to about one-fifth of the size. But it is here assumed that the 
 paper consists of vegetable fibre. In unsized paper the quantity of wool or silk 
 fibre present may be juwrtamed by a nitrogen estimation. 
 
 spar, lead sulphate, etc. which has for its object to increase the weight of the 
 paper, but diminishes its firmness can easily be recognised. If the paper is pore, 
 it should leave only * to 1 per cent of ash; a larger proportion of ash, provided that 
 the water used in the iiBUiiifartiire was not very hard, would indicate an admiilnre. 
 An admixture of lead sulphate, which may act injuriously if the paper be used for 
 wrapping food in, may be detected by ammoniom sulphide, which will give a dark 
 brown spot where the paper is touched with it. 
 
 Miter paper should be tested for the amount of ash, that being the best which 
 thesma 
 
 The material used for the blue colouring of a paper may be recognised s* follows. 
 Berlin blue is not attacked by acids, whilst it is decoloarised by alkalies. Ultrama- 
 rine is decolourised by adds, with evolution of sulphuretted hydrogen. Cobalt 
 blue is decolourised by either acids or *lV*jifs ; its presence may be confirmed by in- 
 cinerating the paper, and fusing the ash with borax under the blowpipe flame, when 
 cobalt forms a blue glass. Copper may be detected by treating the paper ash with 
 hot hydrochloric acid, and supersaturating the clear filtered solution with ammonia, 
 when if copper be present, * blue colour is produced. 
 
 
PECTOUS SUBSTANCES. 
 
 The substances comprised under this name are generally characterised by the 
 formation of a gelatinous mass or viscous solution when acted upon by heat and dilute 
 acids. The change that takes place in the ripening of fruit is to a great extent due 
 to the modification of -which these substances are susceptible. 
 
 Pectous substances occur in the intercellular spaces of different plants, and serve 
 the purpose of cementing together parenchymatous cells. In order to see this, it is 
 only necessary to cut a thin slice from the potato, parsnip, beet root, or the epidermal 
 tissues of the cactus. The slices are washed with distilled water so long as the latter 
 takes up soluble matter from them, they are then digested from a fortnight to a month 
 with dilute solution of hydrochloric acid, the whole being kept at a temperature be- 
 tween 15 and 40, and finally the slices are taken out and washed with pure water. 
 The tissue remains after this treatment quite intact, the individual cells remaining 
 connected together, and connected with the bundle of vessels which cover them, as well 
 as with the epidermal layer. If a little ammonia be added to the water, in a very short 
 time the pectic acid which has been separated from its calcium salt by the action of 
 the hydrochloric acid, dissolves, and the parenchyma cells separate from one another 
 on the slightest touch, while the cuticle and epidermis, as well a.s the starch-bearing 
 cells, remain entirely unaltered. This experiment proves that the pectous substances 
 occur as intercellular masses. 
 
 PECTASE. Together with the peeious substances plants contain a neutral non- 
 crystallisable substance, which resembles diastase in its properties, and has conse- 
 quently received the name of pectase. It possesses the property of converting a sub- 
 stance, pectose, presently to be described, into pectic and pectosic acids. Pectase 
 occurs in a soluble and insoluble form. 
 
 Pectase is dissolved in the juice of turnips, carrots, and other roots, ibr this juice 
 possesses the property of converting pectin into pectic acid. The flesh of unripe 
 apples contains pectase in the insoluble form, and when reduced to a pulp, and washed 
 with water to remove all the juice, the washed residue is capable of converting pectin 
 into gelatinous pectic acid and pectosic acid. 
 
 Soluble pectase is precipitated and rendered insoluble by alcohol. The washed 
 precipitate coagulates pectin, while the supernatant liquid exhibits an indiffereni 
 deportment. Aqueous solutions of pectase decompose easily, a mould rapidly forms 
 upon them, and they lose the property of acting upon pectin ; their activity is also 
 destroyed by boiling. 
 
 Pectous substances are noncrystalli sable ; many of them, such as pectic acid and 
 pectosic acid, gelatinise and retain in this condition a very large amount of water. 
 This property of gelatinising was the cause of attention being drawn towards these 
 substances ; it is also presented by a few other substances, such as gelose and dialose, 
 which in this respect resemble pectous substances. 
 
 PECTOSE. This substance has not as yet been isolated, but its existence is inferred 
 from the origin of the other pectous compounds pectin, pectic acid, and pectosic acid 
 which are supposed to be formed from it. 
 
 Pectose occurs in certain roots, such as carrots, turnips, etc., and in most unripe 
 fruits. Under the joint influence of acids and heat it is changed into pectin. In the 
 cold not even concentrated sulphuric acid has any effect upon pectose, a mixture of 
 sulphuric acid and pectose not producing pectin even after standing many days ; on 
 the other hand, when pectose is boiled for a short time with water slightly acidulated 
 the change takes place at once. The hardness of unripe fruit is due to pectose, and the 
 softening of fruit when it ripens, or when it is boiled, is owing to the conversion of 
 pectose into pectin. 
 
 PECTIN. This substance does not occur in unripe fruit, but is formed when the fruit 
 is boiled, by the action of malic and citric acids upon pectose, also when turnip pulp is 
 boiled with slightly acidulated water. Pectin is most easily prepared from fully ripe 
 fruit, such as juicy pears which are grated, an 1 the juice pressed out and filtered. 
 
PECTIC ACID. 653 
 
 The calcium compounds contained in the juice are got rid of by treating the juice with 
 oxalic acid, and the albumin is separated by means of tannin. The clear liquid is 
 then mixed with alcohol, which precipitates pectin as a stringy, doughy mass, which 
 is washed with alcohol, again dissolved in water, and once more precipitated with 
 alcohol, these operations being repeated four or five times, until the liquid when tested 
 ceases to give indications of sugar. 
 
 Pectin can be easily obtained from unripe fruit and from roots. The pulp is 
 washed with_ water, pressed out, stirred up with dilute hydrochloric acid, and the 
 whole then digested for a few days in the cold. Pectin is then precipitated from the 
 expressed liquid by adding alcohol. 
 
 The composition of pure pectin may be represented by the formula, C 32 H 40 28 .4H 0. 
 It is a colourless noncrystallisable body, soluble in water, and is precipitated "by 
 alcohol from its concentrated solutions, in the form of doughy threads, from dilute 
 solutions as a gelatinous mass. Lead acetate gives a precipitate only with parapectin ; 
 tribasic lead acetate precipitates pectin completely. The alkaline bases, lime and 
 magnesia, combine with pectin, forming pectates, which are decomposed by acids 
 yielding gelatinous pectic acid. Pectin does not influence a ray of polarised light. 
 When heated with acids pectin is changed into metapectic acid. By the action of 
 pectase it is converted into pectic acid and pectosic acid. 
 
 PAKAPECTIN. Pectin when boiled with water, loses its doughy consistency, and is 
 changed into parapectin. The new compound is not crystallisable ; it is neutral, and 
 is precipitated from its solutions by alcohol in the form of a transparent jelly. Para- 
 pectin may be distinguished from pectin by being precipitated from its solutions by 
 lead acetate. Parapectin dried at a temperature of 100 has the same composition as 
 pectin ; at 140 it loses water, and may be represented by the formula, C 32 H 46 31 ; it 
 has then the same composition as in the lead oxide compound. Parapectin when 
 boiled with acids is changed into an acid parapectic acid, which is precipitable by 
 alcohol, and unites with alkaline bases, forming compounds which are isomeric with 
 the compounds of pectin and parapectin. but are distinguishable from them by yield- 
 ing a precipitate with barium chloride. 
 
 PECTOSIC ACID. This acid is insoluble in the presence of acids, and is but slightly 
 soluble in pure cold water ; it dissolves, however, in boiling water, and forms a jelly 
 upon cooling. Boiling water converts pectosic acid quickly into pectic acid, the same 
 effect being produced in the cold by pectase, and an excess of alkaline bases. 
 
 Pectosic acid is formed by acting upon pectin with cold solutions of potash, soda, 
 or their carbonates, or ammonium carbonate ; gelatinous pectosates are thus produced, 
 which yield gelatinous pectosic acids when decomposed with acids. Pectosic acid is 
 also formed when pectase reacts upon a solution of pectin. Pectosic acid is dibasic ; 
 its composition may be represented by the formula C 32 H 46 31 . 
 
 PECTIC ACID. This acid occurs abundantly in plants, as a calcium salt forming the 
 intercellular substance of a number of tissues, as in the pith of Aralia papyri/era. 
 Pectic acid is also produced by the action of soluble or insoluble pectase upon aqueous 
 solutions of pectin at a temperature of 30. 
 
 Gelatinous pectic acid is insoluble in cold water, and but slightly soluble in boil- 
 ing water. If it be boiled for a long time, replacing the water that evaporates, it is 
 changed into metapectic acid, a deliquescent and non-gelatinous substance. An excess 
 of caustic alkalies, or their carbonates, transforms pectic acid into the very soluble 
 metapectic acid. The alkaline pectates when treated with acids yield a precipitate of 
 gelatinous pectic acid ; when treated with calcium chloride they yield calcium 
 pectate. 
 
 Pectic acid is obtained by boiling crushed carrots with a very dilute solution of 
 alkaline carbonate. The pectic acid is in this case formed by the reaction of the 
 alkalies upon pectose. Aqueous solutions of the pectates are precipitated by calcium 
 chloride, and the calcium pectate formed, washed with water, decomposed with hydro- 
 chloric acid, yields pectic acid. 
 
 Pectic acid, when boiled with alkalies, soon becomes converted into easily soluble 
 metapectic acid. 
 
 Pectic acid may be prepared with greater facility as follows : Cactus tissues, that 
 have been previously washed with water, are treated for a few days with dilute 
 hydrochloric acid (1 part acid, 9 parts water). The calcium pectate of the inter- 
 cellular substance is thus decomposed, and the pure pectic acid remaining may then be 
 washed out from the tissues completely with water without injuring them in the least, 
 and it is only necessary to add to the water 2 or 3 per cent, of ammonia in order to 
 dissolve the pectic acid. The filtered solution decomposed with acid yields pure 
 pectic acid. 
 
 Pectic acid is dibasic, and its composition is represented by the formula C 32 H 4 ,,0 40 . 
 
654 PECTOUS SUBSTANCES. 
 
 It is dissolved by several salts of the alkalies, forming double salts having an acid 
 reaction, which when dissolved in boiling water gelatinise upon cooling. 
 
 PABAPECTIC ACID. This acid is soluble in water ; it is not crystallisable. It is 
 formed by prolonged action of boiling water upon pectic acid. The soluble and in- 
 soluble pectates are in like manner converted by protracted boiling with water into 
 parapectates. 
 
 Parapectic acid has a very acid reaction; it combines with the alkaline bases, 
 forming soluble salts ; it is precipitated from its aqueous solutions by excess of baryta ; 
 it is dibasic, and is represented by the formula C 24 H 34 23 . 
 
 METAPECTIC ACID. This acid, as well as its salts, is easily soluble in water; it is a 
 non-crystallisable acid, precipitable from its solutions by basic lead acetate in presence 
 of ammonia. The metapectates are coloured yellow by an excess of bases ; they yield 
 with silver nitrate a white precipitate, which assumes a deep brown colour when boiled 
 with water. 
 
 Metapectic acid is formed under several different conditions : 1 . Spontaneously 
 in a solution of pectin in the course of a few days ; more easily in presence of pectase, 
 the solution becoming sour and then no longer precipitable by alcohol. 2. By the reaction 
 oi concentrated acids upon pectin, or by boiling pectin with hydrochloric acid. 3. By 
 the action of potash or soda upon pectin. 4. From pectic acid when suspended in water 
 and left to stand two or three months. 5. Aqueous solutions of parapectic acid pass 
 rapidly into metapectic acid. 6. The pectose of the intercellular substance of various 
 fruits and roots is changed by the action of lime into metapectic acid. 
 
 Metapectic acid is also dibasic, and has a constitution represented by the formula 
 
 Scheibler prepares metapectic acid by heating mangold-wurzel pulp with milk of 
 lime on a water bath, decomposing the soluble calcium salt with ammonia, and pre- 
 cipitating the solution of the ammonia salt which must be alkaline with basic lead 
 acetate. The lead metapectate is then decomposed by sulphuretted hydrogen, the 
 free acid filtered from the lead sulphide, and decolorised by treating it with animal 
 charcoal. 
 
 Metapectic acid thus obtained is a colourless liquid with very acid reaction; it decom- 
 poses carbonates. Solutions of alkaline metapectates are not precipitated by solu- 
 tions of lime, baryta, strontia, or copper salts. The acid does not taste sour, although 
 it has a very acid reaction. Metapectic acid, when strongly concentrated, assumes a 
 viscous, almost doughy consistency. Solutions of the acid have the same specific 
 gravity as sugar solutions of the same concentration; Metapectic acid rotates the 
 plane of polarised light more strongly than cane sugar, so that when dextro-rotatory 
 cane sugar and metapectic acid occur together, as is the case in the sugar juice of the 
 factory, 1'6 parts of the cane sugar becomes optically inactive. The rotatory power 
 of neutral or alkaline solutions of metapectates is equal to that of the acid, but alters 
 at once if the acid be heated for a short time with strong inorganic or organic acids. 
 The Isevo-rotatory power then diminishes rapidly to zero and passes into the dextro- 
 rotation, which is at its maximum when nearly equal to the original Isevo-rotation. 
 Metapectic acid, when treated with acids, undergoes a complete change and then causes 
 a considerable reduction of alkaline solutions of copper. Acids convert metapectic acid 
 into a new organic acid and into a new dextro-rotatory sugar, called pectin sugar. 
 Metapectic acid belongs accordingly to the glucosides. 
 
 PECTIN SUGAR OB PECTINOSE. This sugar is obtained from metapectic acid that 
 has been altered by heating for some time over the water bath in contact with sul- 
 phuric acid. After neutralising with barium carbonate, the barium sulphate is filtered 
 off and the filtrate concentrated by evaporation to a thin syrup, which is then treated 
 with three times its volume of 90 per cent, alcohol, which precipitates the barium salt of 
 the new acid in a flocky condition, while the sugar remains dissolved, but upon evapora- 
 ting the liquid to a thin syrup soon crystallises out. Pectinose is easily prepared 
 direct from lead metapectate by decomposing this salt with dilute sulphuric acid instead 
 of with sulphuretted hydrogen ; after filtration of the lead sulphate a small quantity 
 of sulphuric acid is added, and the whole gently heated over the water bath. The 
 liquid is then treated as above. The first crop of brownish crystals of the sugar are 
 crushed in the mother liquor and spread upon dry bricks. The further purification 
 by recrystallising is much facilitated by this treatment. 
 
 Pectin sugar crystallises in long colourless shining prisms. 
 
 The crystals are very brittle ; they have a pleasant taste, but are not so sweet as 
 cane sugar. Boiling water dissolves large quantities of pectinose, the greater part of 
 which crystallises out upon cooling. Pectinose melts at a gentle heat, but decomposes 
 when the temperature is raised ; yielding, like most other kinds of sugar, a very diffi- 
 cultly combustible charcoal. Upon heating with nitric acid pectinose is converted into 
 
GELOSE. 655 
 
 oxalic acid without the production of mucic acid. Pectinose dissolves alkaline earths, 
 forming a mucilaginous liquid which becomes yellow upon standing ; this liquid is 
 speedily decomposed by heat, behaving in this respect like grape sugar. Its com- 
 position is the same as that of grape sugar, C 12 H 24 Oi 2 ; in its other properties, however, 
 it is entirely different from grape sugar. 
 
 Pectinose does not ferment in contact with yeast. 
 
 Pectin, which occurs in much abundance in the juice of ripe fruit, is probably 
 formed during the ripening of fruit by the action of the acids of the fruit upon the 
 pectose existing in unripe fruit ; for if the pulp of such unripe fruit be exhausted 
 with water to get rid of all acids, no pectin is produced upon boiling it ; pectin is, 
 however, at once formed upon the addition of an acid. 
 
 A number of fruit juices after boiling gelatinise upon cooling. These jellies may 
 be formed: 1. By the reaction of pectase upon pectin ; pectic acid and pectosic acid 
 being formed. 2. By the solubility of pectic acid in the salts of the alkalies contained 
 in the juice. 3. By a possible decomposition of the pectates by the free acids of the 
 juice. The action of pectase upon pectin may be seen by mixing the juice of currants, 
 which is poor in pectase, with the juice of raspberries, which is especially rich in 
 pectase, and thus produces a jelly with the currant juice. 
 
 "When imperfectly ripened pears, apples, plums, etc., are slowly heated, different 
 changes take place ; the acids of the juice (malic and citric acids) convert the pectose 
 into mucilaginous pectin, part of which is changed by the action of pectase into pectic 
 acid and pectosic acid. Pectase would not be able to effect this change if it were pre- 
 viously coagulated and rendered inactive by rapid heating up to the boiling point. 
 The change of the pectous substances does not extend to the cellulose forming the 
 cell walls ; this remains entirely unaltered. 
 
 During the early period of growth, in the green state, fruit behaves just like the 
 other green parts of plants, decomposing carbonic dioxide and forming new organic 
 material (tannin, acids, sugar, pectin, and gum). During the second period of actual 
 ripening it behaves in an exactly opposite manner ; it no longer assimilates carbonic 
 acid from the air, but on the contrary assimilates oxygen, decomposes a portion of 
 its organic substance, forms carbonic acid, and changes the compounds contained in 
 it in the most various manner. Sugar resists this decomposition the longest. 
 
 G-ELOSE. In the beginning of the year 1856 a Frenchman of the name of 
 De Montravel brought back from his travels a substance consisting of thin white 
 sheets called Chinese moss, and much used by the natives in China in the preparation 
 of edible jellies. This Chinese moss, according to his account, was prepared from 
 lichens growing on certain trees in South China and the Philippines. Payen submitted 
 this substance to examination, and found it to contain 6 per cent, of organic substance 
 soluble in water, as well as a small quantity (0'7 per cent.) of a body soluble in 
 alcohol. The greater part of the insoluble substance swells up in water, forming 
 right-angled prisms. The gelatinous mass dissolves in acetic acid, leaving a nitro- 
 genous residue. When heated with water the gelatinous substance dissolves, leaving 
 the nitrogenous substance and traces of other foreign substances; this solution 
 solidifies upon cooling to a colourless jelly, which contains a quantity of water, equal 
 to about 500 times the weight of the original substance. The gelatinising property 
 of Chinese moss is therefore about ten times as great as that of the best animal gela- 
 tine. The jelly when again dried consists of a peculiar body insoluble in dilute 
 alkalies, dilute acids, water, alcohol, ether, and ammonium cuprate. It dissolves 
 in a very small quantity of concentrated sulphuric acid, or hydrochloric acid, assuming 
 a brown colour ; the solution solidifies after a time to a mass insoluble in water and 
 alkalies. 
 
 Gelose has the following percentage composition : 
 
 Carbon 42770 
 
 Hydrogen . ; ' . .' 5775 
 
 Oxygen ......... 51 '455 
 
 Up to the present time no compound of gelose has been prepared from which the 
 chemical constitution of gelose might be ascertained. According to recent reports of 
 Champion, the riband-like strips of the substance are prepared by pouring the jelly 
 forming liquid into a shallow vessel, allowing it to solidify, and then cutting it into 
 even prisms, which upon drying shrink up considerably, forming a riband-like mass. 
 The same traveller brought with him specimens of the plant from which the moss is 
 prepared. According to Decaisne, it is an alga, Grrateloupia filidna. 
 
 Grelose has a general importance, inasmuch as it can be used with advantage in the 
 preparation of edible jellies. It has this advantage over ordinary gelatine and 
 isinglass, that it is entirely odourless and very durable. 
 
 Attempts made to prepare gelose from different kinds of lichens have been hitherto 
 
656 PECTOUS SUBSTANCES. 
 
 unsuccessful. Payen, however, succeeded in proving the presence of gelose in largo 
 quantities in two marine algse, Gelidium corneum from Java, and Plocaria lichenoides 
 from the Mauritius. 
 
 Gelidium corneum was treated successively with cold dilute hydrochloric acid (2 
 per cent.), water, and ammonia ; and again washed, owing to the extraction of different 
 salts and organic substances, it lost 53 per cent, in weight. After boiling the residue 
 with water, all the tissues appeared unaltered, and it yielded a liquid which upon 
 solidifying formed a colourless transparent jelly, which was proved to be identical 
 with gelose. 
 
 CUBILOSE, DIALOSE, APIIN. To substances possessing the property of gelatinising, 
 and therefore resembling those just described, belong the three bodies, cubilose, 
 dialose, and apiin. The first, cubilose, is the chief constituent of the East India birds' 
 nests. Many opinions have been expressed concerning its origin, some considering it 
 to be a product of vegetable, others one of animal origin. According to the latest 
 researches of Payen, it appears to be a kind of slime excreted by certain birds during 
 .the pairing period. 
 
 Dialose has been found by Payen in the fruit of a species of Dialium, which is used 
 in China for washing instead of soap. Apiin is a gelatinous substance, discovered by 
 Braconnot, and obtained by extraction of parsley (Apium petroselinum), its composition 
 being represented by the formula C 24 H U 13 . 
 
ALBUMINOUS SUBSTANCES. 
 
 The various substances which resemble the albumin of eggs and blood occur both 
 in plants and animals ; they all contain nitrogen, and from a chemical point of view 
 present analogies which indicate that their constitution is referable to a common 
 type. In the natural state albuminous substances are always combined with water 
 in a colloid condition, which cannot be separated by squeezing, but only under condi- 
 tions similar to those by which hydrated crystals lose water. 
 
 In its best known form albumin occurs as white of egg, and as the chief consti- 
 tuent of the serum of blood. Other forms of albumin occur in the juices of plants. 
 
 Fibrin forms the mass of muscular tissue, and gluten or vegetable fibrin occurs 
 in the grain of wheat. Fibroin is an analogous substance, constituting about 16 per 
 cent, of raw silk. Casein occurs in milk. Leguminis the name given to the albu- 
 minous substance found in the seeds of leguminous plants, such as beans, peas, and lentils. 
 
 Globulin or crystallin is an albuminous principle occurring in the crystal- 
 line lens, while vitellin is the designation of the albuminoid constituent of egg- 
 yelks. 
 
 Syntoninisan albuminous substance derived from muscle-fibrin by treatment with 
 dilute hydrochloric acid and precipitation of the solution with ammonia. 
 
 Gelatin and chondrinare substances obtained from bone, cartilage and cer- 
 tain other animal tissues; sericin is an analogous constituent of raw silk. 
 
 The composition of various albuminoid substances is shown by the following 
 table : 
 
 
 Albumin 
 
 Mucin 
 
 Gelatin 
 
 Chondrin 
 
 Fibrin 
 
 Syntonin 
 
 Lardacein 
 
 
 Mulder 
 
 - 
 
 - 
 
 Mulder 
 
 Mulder 
 
 - 
 
 - 
 
 c. 
 
 53-5 
 
 52-4 
 
 50-16 
 
 49-97 
 
 52-7 
 
 54-1 
 
 53-6 
 
 H. 
 
 7-0 
 
 7-0 
 
 6-60 
 
 6-63 
 
 6'9 
 
 7-2 
 
 7-0 
 
 N. 
 
 15-5 
 
 12-8 
 
 18-30 
 
 14-44 
 
 15-4 
 
 16-1 
 
 15-0 
 
 S. 
 
 1-6 
 
 Nil 
 
 0-14 
 
 38 
 
 1-2 
 
 1-1 
 
 1-3 
 
 0. 
 
 22-0 
 
 27-8 
 
 24-80 
 
 28-58 
 
 23-5 
 
 21-5 
 
 23-1 
 
 
 Protein 
 
 Casein 
 
 Globulin 
 
 Vitellin 
 
 Legumin 
 
 
 Mulder 
 
 Mulder 
 
 Mulder 
 
 Gobley 
 
 Dumas and 
 Cahours 
 
 C. 
 
 537 
 
 53-85 
 
 54-5 
 
 52-26 
 
 18-1 
 
 H. 
 
 7-0 
 
 7-15 
 
 6-9 
 
 7-25 
 
 6-91 
 
 N. 
 
 14-2 
 
 15-65 
 
 16.5 
 
 15-06 
 
 50-53 
 
 S. 
 O. 
 
 1-6 
 23-5 
 
 0-85 
 22-52 
 
 I 22-1 
 
 1-17 
 23-24 
 
 | 24-41 
 
 P. 
 
 
 
 
 
 ' 
 
 1-02 
 
 
 
 It will be seen that Gobley found a small percentage of phosphorus in vitellin, 
 and other observers have testified to the presence of phosphorus in other substances 
 considered to be albuminous ; nevertheless, phosphorus is no. a normal constituent of 
 any form of albumin, and where it has been found it is to be regarded solely as an 
 impurity derived from the association of a trace of some phosphorised substance 
 such as lecithin. Thus the yelk of egg contains a great deal of lecithin, and the sub- 
 stance of brain, as shown by Thudichum and others, is largely composed of this and 
 allied phosphorised principles, whose constitution is now well established. Sulphur 
 
658 ALBUMINOUS SUBSTANCES. 
 
 is not a constant constituent, and, indeed, there is some little doubt whether it really 
 forms part of the albumin molecule, or whether it is only present by accident. How- 
 ever this may be, it admits of removal in many cases, as, for instance, by digestion 
 with alkalies. The compound thus formed, termed a 1 k al i-a 1 b u m i n a te, is free from 
 sulphur. Albumin has a very high molecular weight, which has been approximately 
 determined as 1612 by two methods, namely, by analyses of the potassic and platino- 
 hydrocyanic combinations. 
 
 Eegarding sulphur as an essential constituent of albuminoids, Lieberkuhn pro- 
 posed for them the formula C 72 H 112 N 18 S0 22 ; this formula, however, must only be 
 accepted provisionally. 
 
 All albuminous substances give up their sulphur to alkalies, forming sulphide 
 and hyposulphite and soluble alkali-albuminate, which, on neutralisation with an acid, 
 yields a substance which Mulder termed protein, and regarded as the base of all 
 albuminous substances. It has, however, been shown since then, that protein still 
 contains sulphur in some instances, in a form not removable by alkalies. 
 
 Liebig viewed albuminoid substances as being isomeric, while Sterry-Hunt con- 
 sidered them to be amides or nitrites of cellulose, dextrin, gum, or sugar. This latter 
 theory is not consistent with facts to be stated hereafter. 
 
 Berthelot viewed the substances under description as complex amides. 
 
 Strecker viewed them as composed of a great number of radicles, most of which 
 are common to all forms, while a few are peculiar to each form; he thus accounted 
 for the differences to be observed in the properties of albumin in its various states. 
 
 Thus, for instance, Thudichum and Kingzett have recently shown that all the various 
 phosphorised substances derived from the brain, from yelk of eggs, or from blood- 
 corpuscles, etc., are constructed on a common type. When decomposed by boiling 
 with baryta water, dilute acids, or other hydrating agents, the phosphorus they con- 
 tain is invariably yielded as phosphoglyceric acid (C 3 H 9 P0 6 ) ; the nitrogen is always 
 yielded in the form of neurine, oxyneurine, or choline (C 5 H, 5 N0 2 ). The only other 
 products of decomposition are various fatty acids, and the sums of the decomposition 
 products give the same formulae as those obtained by analysis of various compounds 
 of these principles themselves. The constitution of these bodies appears therefore 
 to be representable by a common formula, which is that of glycerine having two 
 hydroxyls replaced by fat acid radicles, and the third by phosphoryl ; one of the 
 hydroxyls of the phosphoryl is in its turn replaced by the nitrogenised nucleus. Thus, 
 the formula for lecithin is 
 
 (C 18 H 33 2 
 C S H 5 C 16 H 31 2 
 
 t(HO) OPO (C 5 H 15 N0 2 ) = C 42 H 85 NP0 9 . 
 
 The general structure of all similar bodies is exhibited by glycerophosphoric acid 
 as a type : 
 
 (HO 
 C 3 H 5 HO 
 
 (HO (OPO) (HO). 
 
 As albumin occurs in nature it is generally associated with mineral salts; and 
 from the difficulty experienced in ridding it entirely of these, and from other con- 
 siderations, it is not improbable that the molecule of albumin has a feeble power of 
 combination with salts, just as alkaloids have. In fact, the products of decomposi- 
 tion of albuminous substances support this view. In the blood and all serous liquids, 
 and in the juices of vegetables and plants, the albumin exists in a liquid state, and 
 on boiling the albuminous liquids the albumin is precipitated in a coagulated state. 
 It is necessary in such cases to have the solution as nearly as possible neutral, or 
 coagulation does not invariably occur. 
 
 Albumin exists in two states, namely soluble and insoluble, and the second of 
 these may be readily produced from the first named, although the immediate causes 
 underlying the transformation are unknown. If the serum of blood be evaporated 
 below 40 C. the product is soluble in water, but if a higher temperature be applied, 
 the product is insoluble in water. Again, if a dilute solution of white of egg be boiled, 
 the albumin is thrown down in an insoluble condition ; or if serum of blood be sub- 
 mitted to a current of air in the presence of turpentine at normal temperatures, 
 peroxide of hydrogen is formed, and this bleaches the solution, which then yields on 
 evaporation at a gentle temperature insoluble albumin. 
 
 Albuminous solutions are precipitated by nitric acid, strong alcohol, corrosive 
 sublimate, phenol, tannic acid, etc. 
 
 Coagulated albumin, like fibrin, dissolves in concentrated hydrochloric acid, 
 especially with the aid of heat, forming a blue or violet solution, which examined 
 spectroscopically shows an absorption band in the yellow-green. Coagulated albumin 
 
COMPOUNDS OF ALBUMIN. 659 
 
 also dissolves in strong nitric acid, giving a yellow solution, and when a small quantity 
 of mercurous nitrate is added and the mixture boiled, a crimson precipitate is 
 produced. 
 
 Albumin solutions grow opalescent at 66 C., and at 80 C. they coagulate. 
 
 Fibrin may be obtained by whipping blood, during which operation it adheres to 
 the twigs used, in the form of threads. When placed in peroxide of hydrogen, it 
 causes the evolution of oxygen. 
 
 Albumin derived from white of egg is designated ovalbumin; and that from 
 serum of blood is termed seralbumin. 
 
 White of egg when heated in a sealed tube at 150 to 200 C., passes first into an 
 opaque coagulum, which is afterwards transformed into a reddish transparent jelly, 
 and finally into a reddish liquid, behaving with reagents like ordinary solutions of 
 albumin, but not coagulable by heat. When white of egg is placed in a dialyser over 
 solutions of acids, there are formed upon the dialyser what Gr. S. Johnson regards as 
 compounds of albumin. The figures he obtained from a determination of the acid 
 contained in the presumed compounds, lead to the following formulae for them, if 
 Lieberkuhn's formula for albumin be accepted : 
 
 C 72 H I12 N 18 S0 22 -2HN0 3 
 
 C 72 H n2 N ]8 S0 22 -H 2 S0 4 
 
 2(C 72 H m N 18 S0 22 )-3H 3 P0 4 
 
 C 72 H, 12 N 18 S0 22 -HP0 3 
 
 C 72 H 112 N 18 S0 22 -2H 3 C 6 H 5 7 
 
 C 72 H 112 N 18 S0 22 -H 2 C 2 4 
 
 C 72 H 112 N 18 S0 22 -2H 2 C 4 6 
 
 C 72 H 112 N 18 S0 22 -HC 2 H 3 2 . 
 
 Although the existence of such definite compounds had been long before rendered 
 almost certain by the investigations of Lieberkuhn and others, further investigation 
 and the ultimate analyses of the substances are to be desired, before the formulae 
 assigned to them can be accepted. 
 
 In addition to these acid compounds, a number of albuminates have been described, 
 although the folio wing formulae assigned to them are to a certain extent hypothetical : 
 Albuminate of Barium, C 72 H no BalS' 18 S0 22 + H 2 (?) 
 Copper, C 72 H, 10 CuN, 8 S0 2 o + H 2 (?) 
 Potassium, C 72 H 110 K 2 N 18 S0 ., + H 2 (?) 
 Sodium, C 72 H 110 Na 2 N 18 S0 22 (?) 
 
 + H 9 
 
 Silver, C 72 H 110 Ag 2 N 18 S0 22 + H 2 (?) 
 Zinc, C 72 H 110 Zn 2 N 18 S0 22 + H 2 (?) 
 
 besides the albuminates of lead and mercury. 
 
 When albuminoid substances are submitted to the gradual oxidising action of a 
 mixture of potassic dichromate and sulphuric acid, or a mixture of manganic dioxide 
 and sulphuric acid, various products are obtained. Guckelberger and Schlieper have 
 both found, among the products of oxidation, the following : 
 
 Formic acid Acetic aldehyde Benzoic acid. 
 
 Acetic , Propionic Benzoyl hydride. 
 
 Propionic 
 Butyric 
 
 Butyric Hydrocyanic acid. 
 
 Valeronitrite. 
 
 Valeric 
 Caproic 
 
 Bechamp, during the oxidation of albumin by means of potassic permanganate, 
 observed the presence of a small quantity of urea, a matter of extreme importance 
 when considered in the light of the more recent researches of Schiitzenberger. 
 
 In 1820, Braconnot obtained glycocine or sugar of gelatin (amido-acetic acid) by 
 boiling gelatin with dilute sulphuric acid, and when muscle was heated in a similar 
 manner he obtained leucine C 6 H, 3 N0 2 (amido-caproic acid). Liebig demonstrated the 
 formation of an accompanying crystalline body, namely, tyrosine C 9 H M N0 3 (oxyphenyl- 
 amido-propionic acid). Erlenmeyer and Schaeffer continued these researches and ob- 
 tained for 100 parts of dry substance 
 
 Leucine Tyrosine 
 
 Fibrin 14 0'8 
 
 Albumin. . . : 10 1-0 
 
 Syntonin. . . , 18 I'O 
 
 Eitthausen obtained from products formed by the action of boiling dilute sulphuric 
 acid on vegetable nitrogenous substances, two cry stalli sable acids: glucamic acid 
 C 5 HgN0 4 from coaglutin, and legumic acid C 8 Hi 4 N 2 6 from legumin. 
 
 u u 2 
 
660 ALBUMINOUS SUBSTANCES. 
 
 Schiitzenberger commenced his researches with the idea that the urea group 
 exists in albumin, and although he has not succeeded in isolating this substance, he 
 has at least obtained evidence of its existence. His method consists in boiling 
 albumin during a number of hours with a solution of caustic baryta, a process which 
 of course destroys any urea that might be formed. Nevertheless, he has obtained 
 carbonic acid and ammonia in the exact proportions which urea would yield, and he 
 concludes that out of the eighteen atoms of nitrogen in the molecule of albumin, four 
 belong to the urea group. 
 
 Besides urea and tyrosine, traces of sulphurous acid and sulphuretted hydrogen 
 are formed, and oxalic and acetic acids. These substances are accompanied by the 
 amido-acids of the series C n H 2n+ iN0 2 , corresponding to the fat acids CJzLjnOg, 
 from amido-oenanthylic acid C 7 H 15 N0 2 , to amido-propionic acid ; leucine C 6 H 13 N0 2 ; 
 butalinine C 5 H U N0 2 ; and amido-butyric acid C 4 H 9 N0 2 . Besides these, one or two 
 acids allied to aspartic acid C 5 H 9 N0 4 , and glutamic acid C 4 H 7 N0 4 , are produced, and 
 one or two analogous to legumic acid C 8 H, 4 N 2 6 . Schiitzenberger also obtained by 
 decomposition of albumen with baryta, a small quantity of a dextrin-like body which 
 was resolved by boiling in acids into a substance like sugar. From his researches 
 he regards the albuminoids as urea and amido-acid combinations. 
 
 It should be observed that when albumin is subjected to the influence of caustic 
 alkalies melted in their water of crystallisation there are obtained just those products 
 which might be expected from a further action upon the substances yielded by the 
 baryta process. 
 
 Thudichum obtained several alkaloids from the baryta decomposition of albumin, 
 and among them one of the formula C 3 H<;N0 5 . 
 
 The importance of the results here briefly described will be seen when it is 
 considered that the putrefaction of albuminoid substances gives rise to the production 
 of leucine, tyrosine, and a number of volatile fat acids of the series C n H 2n 2 , ammonia, 
 and a number of compound ammonias, carbonic dioxide, sulphuretted hydrogen, 
 hydrogen and nitrogen. 
 
 It is known that in the presence of putrefied fibrin, leucine is resolved into am- 
 monia and valerianic acid, and from all that is known the products observed during 
 putrefaction are those of hydratation modified according to circumstances, especially 
 by contact with special ferments or by the presence of air. 
 
 By the further prosecution of such investigations as those described, it may be 
 possible to hope for something like a true explanation of the action of antiseptics 
 and disinfectants ; for the power of an antiseptic is undoubtedly one which confers upon 
 the molecule of albumin increased stability, thus rendering the attacks of so-called 
 germs or ferments of less avail in splitting up the molecule, and therefore rendering 
 them powerless to reproduce themselves and cause simultaneously putrefaction and 
 
 Uses of Albumin. Albumin occurs in commerce in several forms, differing in 
 purity and whiteness. 
 
 "White of egg contains 12 per cent, of albumin, and for commercial purposes this 
 is dissolved in water and evaporated in thin films at a gentle temperature (40 C.), 
 thus forming white scales, which before use have to be dissolved in water again. Egg 
 albumin is used by calico printers for fixing the better and lighter sorts of colours ; 
 it is also used for photographic purposes on account of its whiteness compared with 
 seralbiimin. Blood contains about 7 per cent, of albumin, and it is from this source 
 that most of the albumin used in the arts is made. The blood of slaughtered animals 
 is allowed to stand in shallow vessels until the fibrin has coagulated ; during this 
 spontaneous process most of the colouring matter of the blood is enveloped in the 
 fibrinous clot, and the serum is drawn off and evaporated down at a gentle tempera- 
 ture. 
 
 An inferior sort of blood albumin is prepared by beating or shaking blood in 
 vessels provided with staves ; in this way the fibrin is coagulated, but most of the 
 blood corpuscles remain in the serum ; hence albumin prepared by this process is 
 not so good, and can only be used for fixing the darker colours on calico, etc. 
 
 Albumin in a state of solution is also used for clarifying vinous and syrupy 
 liquids, inasmuch as when boiled with thorn it coagulates and envelopes the substances 
 which it is desired to remove. Thus it is used to a considerable extent in sugar refining. 
 
 For the better purposes, as already stated, it is necessary to use egg albu- 
 min, and this is not only scarce, but its use withdraws a large amount of food 
 from the market. Moreover on account of the liability of albuminous solutions to 
 decomposition, albumin is only met with in commerce in the dry state. Thus, there 
 is the trouble of redissolving the albumin for use, and, since the whole does not 
 redissolve, there is always somo loss. 
 
GELATIN, ETC. 661 
 
 Haying regard to these facts Messrs. Kingzett and Zingler have recently intro- 
 duced a method which consists in subjecting serum for several hours to a current of 
 air at about 30-40 C. in the presence of about 10 per cent, turpentine. In this way 
 peroxide of hydrogen and camphoric acid are produced by the oxidation of the turpen- 
 tine. The former of these substances, by its oxidising action, bleaches the serum at 
 once, while the camphoric acid exercises an antiseptic action, so that the albumin 
 may be kept indefinitely in the state of solution. Albumin thus prepared admits of 
 the fix-ing of some colours which could not before be made fast. As thus prepared 
 the albumin solution contains about 17 oz. to the gallon. 
 
 GELATIN, ISINGLASS, GLUE, AND SIZE. 
 
 Gelatin is a nitrogenous substance of the albuminous class, and is obtained 
 from white fibrous tissue, cellular tissue, skin, serous membranes, bones and other 
 animal tissues. 
 
 It may be prepared by various methods, of which the following will serve as 
 illustrations. 
 
 According to Nelson's patent method, the parings, etc. of skins, are washed, 
 their surfaces scored, and then digested in a dilute caustic ley (soda) during about 
 10 days. After this they are removed to an air-tight fat lined with cement, and kept 
 at a temperature of 21, after which they are exposed to a current of sulphurous 
 oxide in a wooden chamber. The moisture is next expelled by pressure, and the pro- 
 duct heated with fresh water in earthen vessels provided with a steam jacket. In 
 this way soluble gelatin is prepared and may be purified by straining it at a tenipe- 
 rature of 38 to 49. 
 
 From bones this substance is prepared by the combined action of steam and a 
 current of water which is allowed to trickle over the broken fragments in a suitable 
 apparatus. Calf s-foot jelly is an alimentary article consisting of gelatin, while 
 isinglass contains from 86 to 93 per cent, of gelatin, and is prepared from the inner 
 membrane of the floating bladder of sturgeons and other fish. 
 
 By another process the phosphates of calcium contained in bones are dissolved 
 out by dilute hydrochloric acid or sulphuric acid, and the gelatinous residue, on boiling 
 with water under pressure, furnishes a kind of soup which is said to be nutritious and 
 has been used in foreign hospitals, etc. 
 
 Prom time to time a number of modifications have been introduced into the 
 preparation of commercial gelatin with the view of improving its hardness and sizing 
 qualities. 
 
 This manufacture of gelatin from the skins of animals gives rise to another 
 branch of industry of some importance, namely, the manufacture of glue and size. 
 Glue, in fact, is the crude solid form of gelatin, whilst size is a semi-liquid state of 
 the same substance. 
 
 The strongest glue is furnished by the parings of ox hides ; the ears and refuse 
 trimmings of thick hides yield on an average 45 to 50 per cent. glue. 
 
 The process to which these clippings are subjected may be briefly described as 
 follows. 
 
 They are first steeped in lime water, to remove the air and blood, and after 
 washing in cold water, are exposed in layers to the air, so that whatever lime is left 
 in the tissues may be converted into carbonate. After this, the dippings are boiled 
 in water contained in a large copper, sometimes being first enclosed in a coarse cloth 
 to prevent the adhesion and consequent burning of any gelatin upon the bottom of 
 the vessel. It is, however, preferred to boil the mixture under moderate pressure, 
 and this operation is continued until it is found that the liquor contains so much dis- 
 solved substance that it gelatinises on cooling, when it is run into a deep vessel and 
 maintained in a warm state to allow of the deposition of impurities, etc. Any 
 animal substance left undissolved gives, on a second boiling, an inferior kind of glue, 
 and if there be any third quantity it constitutes a sort of size ; the ultimate residue 
 is useful as manure. The solution after settling is run into wooden boxes, where it 
 cools, and gelatinises, and the solid mass is cut up into blocks, and finally into slices, 
 which are dried by exposing them to a free current of air upon nets placed in a 
 wooden frame. Much of the success of this operation depends upon atmospheric 
 conditions ; if the weather be hot, there is a danger of the whole liquefying ; in foggy 
 weather the glue is apt to turn mouldy, and frost has a tendency to make it crack 
 into fragments. Spring and autumn are therefore the most favourable seasons for 
 the performance of the drying operation. Artificial drying now commonly resorted 
 to, and this obviates the difficulties above enumerated. 
 
662 ALBUMINOUS SUBSTANCES. 
 
 Properly-made glue is a hard, brittle, pale-brown, glassy-looking substance, which 
 swells tip, but does'not dissolve in cold water. 
 
 Size is usually made from the thinner kinds of skins and is chiefly used in the 
 gelatinous condition. 
 
 THE MANUFACTURE OF LEATHER. 
 
 Ox. hides are imported from the plains of South America and the Cape of Good 
 Hope, and the leather prepared from them is chiefly used for making soles of boots 
 and shoes, for harness, and articles in which strength and durability are the requisite 
 qualities. 
 
 Calves' and seals' skins furnish leather for the uppers of boots and shoes, while 
 for book-binding and more general articles, sheep skins constitute the chief material 
 used. 
 
 Some hides are immensely thick ; for instance, that of the hippopotamus is often as 
 much as two inches in thickness. 
 
 They may be used either as they come from the animals, or after being preserved, 
 an operation which is necessary when the hides come from abroad. This preservation 
 is generally carried out by soaking the skins in a strong solution of salt, but various 
 agents are now employed for the same purpose. 
 
 In all cases where it is intended to make leather, the first thing necessary is to 
 cleanse the skins thoroughly from any preservative agent that may have been used, 
 blood, and other matters. This is done by washing or immersion in pits containing 
 frequently renewed water. To expedite this operation the hides are often sent to the 
 fulling mills, where they are beaten with heavy hammers shod with iron, and in this 
 way they are also rendered supple. After trimming, the hides are then freed from 
 fatty matters and the hair loosened by means of lime water or a weak solution of 
 caustic soda. In other places the hides are exposed in a warm room until putrefac- 
 tion begins, and in this way the hair becomes loosened just as readily as lime or soda 
 effects it. 
 
 To remove the hair, the hides are next placed upon tables termed ' beams,' and 
 while stretched out, the operator shaves the skin by means of a two-handled knife 
 which is worked over the surface. 
 
 Rinsing is then resorted to, after which the hides are immersed for a number of 
 hours in a very dilute bath of sulphuric acid ; this removes the lime or soda, makes 
 the skins swell, and indeed fits them for the tanning process, which is of an extremely 
 slow nature. 
 
 During a period of about six weeks the hides are passed through a series of wooden- 
 lined pits containing an infusion of oak-bark termed ooze, of gradually increasing 
 strength, and are finally placed in other pits in an extended state, one above the other, 
 with layers of powdered oak bark between each ; these pits are then filled up with 
 water, and in this state the hides stay for three months. This last operation is 
 usually repeated a second time or even a third time, until the whole texture is 
 tanned throughout ; this is evidenced by the uniform brown colour which obtains. 
 This tanning is effected by the combination of the vegetable astringent principles of 
 the oak bark with the skins, and when completed the hides are dried in lofts fed 
 with a good current of air, and generally warmed by steam pipes ; after this the hides 
 have to be beaten and rolled. 
 
 In the tanning process above described, it is the tannic acid of the oak bark 
 which by its combination with the gelatinous tissue of the hides, produces the sub- 
 stance called leather. Other substances are often used, but generally in combination 
 with oak- bark. Thus sumach from the bark of Rhus cotinus, or Rhus coriaria ; catechu 
 or Terra Japonica which is furnished by various species of acacia ; dividwi, the crushed 
 pods of Caesalpinia coriaria; mimosa from the bark and pods of several kinds of 
 Erosopis ; valonia, the acorn of the prickly- cupped oak (Quercus JEgelops) ; and nut- 
 galls, are all used. 
 
 In the process called Tawing, which is only applied to the thinner kinds of hides, 
 such as those of sheep, goats, and calves, alum and common salt are used, and are 
 worked with some oily matter into the skins. The process termed Shamoying consists 
 essentially in combining with the softer part of the hides of the goat, doe, or" chamois, 
 some suitable fatty matter. 
 
 Light kinds of parchment are prepared from calf or sheep skins, by the use of 
 lime, while the stronger kinds are made from the skins of asses and pigs. 
 
 Altogether, the processes used in the preparation of leather differ according to the 
 nature of the skin, and the kind of leather it is proposed to make, and tho description 
 here given is but an outline of some of the most important methods in use. 
 
FAT AND OIL. 
 
 Both fat and oil occur as constituents of animals as well as of plants. Substances 
 of this class are found in all parts of plants, especially in seeds and in many kinds of 
 fruit ; whilst in animals they are often deposited in large quantities in particular tissues. 
 
 Characters. The various kinds of fat occurring in vegetables and animals are 
 distinguished as well by their physical as by their chemical characters. The state 
 of aggregation is at once a distinctive feature, and many kinds of fat may be thus 
 distinguished. Such as are liquid at the ordinary temperature are termed fat oils; 
 whilst those which have a soft consistency at the ordinary temperature and melt at 
 about 30 are classified with butter or lard. Those kinds of fat which melt at 
 higher temperatures and are solid at the normal temperature are termed tallow. 
 Most kinds of fat are liquid at the ordinary temperature, or a little above it. In 
 a fresh condition they are white or colourless, or sometimes faintly yellow; they 
 possess but a slight smell, and have an average specific gravity of 0'9. They are 
 insoluble in water, but form with it or with mucilage an emulsion ; they dissolve with 
 difficulty in alcohol, freely in ether, in carbon bisulphide, in turpentine and in other 
 volatile oils. Most of them leave a greasy stain upon linen and paper, thus present- 
 ing a marked distinction from ethereal oils, which volatilise completely ; but some 
 fat oils dry up in the air (by absorption of oxygen) to such an extent that no greasy 
 stain is left upon the paper. These latter are termed drying oils. 
 
 Heated to 250 or 300, the fats are decomposed, yielding free volatile acids and 
 products of disagreeable odour, viz., acrolein, allylic alcohol, water, etc., leaving 
 a carbonaceous residue ; when heated in sealed vessels to a red heat they are converted 
 almost entirely, with separation of carbon, into combustible gas consisting of marsh 
 gas, olefiant gas, acetylene, carbonic oxide and carbonic anhydride. Most fats absorb 
 oxygen from the atmosphere, becoming viscid and acquiring a sharp rancid smell. 
 As oxygen is absorbed, heat is generated, and if this takes place rapidly the mass 
 may take fire, especially when porous bodies like wool, cotton, etc., saturated with 
 the fatty oils are exposed in such a manner as to present a large surface to the air, 
 thus giving rise to the danger of spontaneous combustion ; great care, therefore, is 
 required where such material accumulates, as in turkey-red dye works or in storing 
 greasy rags from machinery use. 
 
 Composition. The different kinds of fat must be regarded as acid ethers of the 
 tri-atomic alcohol, glycerin, the composition of which is represented by the formula 
 
 TT ?3- By replacing the typical hydrogen with acid radicles, glycerides or fats 
 -tla) 
 
 p| TT \ 
 
 are formed. Stearin consequently is represented by the formula 3 ^ -^ Q [ O s , or 
 
 glyceryl stearate. The term fatty acids is applied to the great number of like acids 
 forming fats with glycerin. 
 
 P TT O ) 
 Stearic Acid ^^ n ^ JO forms a chief constituent of hard fats. In a pure state 
 
 it is white and crystalline, insoluble in hot and in cold water, but soluble in alcohol. 
 It melts at 69'9 and forms salts with bases. The alkaline stearates are soluble in 
 water, the ammonium salt particularly so. The potash or soda salts are separated 
 from their solutions by an excess of alkali, or by sodic chloride. On this latter 
 property depends the separation of soap chiefly an alkaline stearate by mixing 
 the soap ley with common salt (sodic chloride). When a concentrated solution of 
 an alkaline stearate is mixed with much, water, a turbidity ensues, due to the pre- 
 cipitation of a stearic acid compound with but little alkali ; the rest of the alkali 
 and a small quantity of stearic acid remain dissolved. The stearates of the alkaline 
 earths (lime, baryta, strontia, magnesia), are insoluble in water, consequently when 
 lime or baryta water is added to a soap solution, a calcium or barium salt of the 
 fatty acid is precipitated. It is for this reason that hard waters, or waters rich in 
 
664 FAT AND OIL. 
 
 lime salts, are not suitable for washing purposes ; the stearates of the heavy metals 
 are also insoluble in water. 
 
 Palmitic Acid 16 31 jj?0- This acid resembles stearic acid in its chemical 
 
 properties. At ordinary temperatures it is hard and crystalline, insoluble in water 
 but soluble in alcohol ; with bases it forms soluble and insoluble salts. It occurs 
 in nearly all fats, but in less quantity than stearic acid ; margaric acid Ci 7 H 34 2 , 
 whose existence has been disputed, theoretically ranks between stearic and palmitic 
 acids. 
 
 Oleic Acid C 8 H ssO JQ ig liquid at or( ji nar y temperatures, solidifies at +4, and 
 
 then melts at + 14. It is insoluble in water, but easily soluble in alcohol, in ether, 
 and in carbon bisulphide. The solid acid undergoes no change when exposed to the 
 air, the liquid acid is assumed to absorb oxygen rapidly, and to be transformed into 
 several oxidised products. The acid so changed remains liquid even below 0, and 
 possesses a rancid odour and taste. By distillation, the acid is decomposed into 
 several gaseous and liquid products, amongst which is sebacic acid, whilst charcoal 
 remains behind. 
 
 Nitric acid converts oleic acid into suberic acid, pimelic acid, etc., with a great 
 number of very volatile acids including acetic, butyric, valeric, caproic, and capric 
 acids. In general the oleates resemble the stearates and palmitates. Potassic 
 oleate is soft, attracts water readily, dissolves in 2 or 3 parts of water, but is less 
 easily decomposed by water than the corresponding stearate and palmitate. Sodic and 
 potassic chloride, and other soluble salts separate alkaline oleates from their aqueous 
 solutions. Sodic oleate is harder than the potassium salt, less deliquescent, and more 
 difficultly soluble. The remaining salts are insoluble in water, soluble in alcohol, and 
 in oils, and fusible by gentle heat. Plumbic oleate is the basis of the ordinary lead 
 plaster. Nitrous acid in the cold transforms oleic acid into a solid isomer, elaidic 
 acid, which crystallises from alcohol in splendid white laminae, having the same com- 
 position as oleic acid, but with a melting point of 45. 
 
 The various fats comprise a great number of acids belonging to the same homo- 
 logous series as stearic acid, differing only in their composition by the group CH 2 or 
 a multiple thereof. Although the series of this group is incomplete, yet very many, 
 as butyric, valeric, caproic, and cenanthylic acids are found in the various kinds of 
 fats, and this series, beginning with formic acid (CH 2 2 ) and ending with melissic 
 acid CgoHgoOg, forms the so-called ' fat acid ' series. 
 
 Behaviour of Fats towards Basic Substances. When fats are heated with strong 
 bases such as potash, soda, baryta, lime, etc., in the presence of water, they are de- 
 composed, yielding glycerin and soaps or combinations of the fatty acids with the 
 base. The term saponification or plastering, originally used to express the process 
 of soap and plaster making, is now extended to these reactions. The following 
 equation expresses the saponification of glyceryl oleate or olein with caustic potash, 
 and serves to illustrate the saponification of fats generally : 
 
 Sulphuric acid decomposes fatty bodies in such a manner that by the addition of 
 water they split up into the respectiye fat acid and glycerin : it is evident, therefore, 
 that the action of the acid differs but slightly from the change produced by saponifica- 
 tion. A recent process, wherein fat is decomposed by superheated steam into glycerin 
 and fat acid, is being largely used in the manufacture of stearic acid. The change 
 is thus expressed : 
 
 + 30H * = 
 
 ("* TT ) 
 
 Stearin or Glyceryl Stearate ^ fa Q > O 3 is found in animal fat generally, but 
 
 chiefly in beef and mutton fat : the presence of stearin increases their consistency. 
 To prepare it pure, melted tallow is recrystallised several times from ether or turpen- 
 time. So prepared it is white and crystalline, insoluble in water, difficultly soluble in 
 hot alcohol, but easily soluble in ether. From the fact that the melting point ranges 
 from 56 to 71 G., its permanent point (as deduced by the observations of Heintz), 
 there appear to exist several modifications of stearin, and Duffy has confirmed this 
 presumption by the description of a modification which melts at 63. 
 
 P TT ) 
 
 Palmitin, ^ fa Q J 8 is found in most fats and can be obtained from palm oil 
 
 by strong pressure ; then by treating the residue with boiling alcohol and rocrystal- 
 
PURIFICATION OF TALLOW. 665 
 
 Using it several times from ether, it is obtained white and crystalline, soluble with 
 difficulty in boiling alcohol, but easily soluble in ether. Its melting point is 60 and 
 solidifying point 46. 
 
 f TT ) 
 
 Olein 3 ^, |j Q J0 3 is the chief constituent of the liquid non-drying oils, but is 
 
 also found in many fats of the animal and vegetable kingdoms, as for instance mutton 
 and beef fats and palm oil. In order to separate it from the other fats, the mixture 
 is gently warmed with concentrated potash ley, whereby only stearin, etc., becomes 
 saponified, allowing the olein which floats on the alkaline liquid to be mechanically 
 separated. It is colourless, liquid below ; and it is less easily saponified than the 
 other glycerides, but oxidises much more quickly in the air. By acting on olein with 
 nitric acid, elai'din is produced. All the glycerides can be artificially prepared. 
 
 Tallow. Tallow consists chiefly of stearin mixed with palmitin and olein. It 
 is solid at 12 to 15, but its degree of solidity depends upon several conditions, 
 such as the kind of animal it is obtained from, upon the feed of the animal, etc. 
 It is also to be noticed that fat produced in summer is softer than winter fat. ' The 
 fat occurs enveloped in very thin cellular tissues composed of nitrogenous compounds, 
 and in fresh marrow the globular cells can be easily separated and distinctly recog- 
 nised under the microscope. In consequence of moist membrane and other easily 
 decomposed substances being mingled with the fat, it readily undergoes change in the 
 air, therefore it is necessary, especially in summer, either to keep it in a cool and airy 
 place, or at once to separate it from the membranes by melting. 
 
 Tallow melting. The tallow is first cut up and hacked into pieces by knives, 
 in order to facilitate the melting out of the fat from the cells. The finely-divided 
 tallow is placed in a copper or brass vessel, and is heated, either over an open fire, 
 or by means of steam, which is better. By gentle stirring, the mass is melted with 
 very little heat, which causes the membrane to contract, and the albuminous portions 
 to shrivel up, at the same time allowing the tallow to flow out. The mass is 
 allowed to settle and is afterwards drawn off by a tap. Having been strained, it is 
 mixed with from four to five parts of alum per thousand, which easily and com- 
 pletely separates the remaining impurities. After six to seven hours' standing, the 
 clarified fat is racked off into conical wooden casks, where it is allowed to cool. The 
 residue or refuse left in the copper vessel is scooped out and placed in a screw press, 
 to extract more of the fat; and the pressed cake, consisting of the animal membrane, 
 the fat tissues, muscle, blood corpuscles, particles of bone, and other impurities, 
 together with 1 or 1 5 per cent, of unexpressed fat, is used under the name of greaves 
 for manure and as dog-feed. 
 
 Treatment of Tallow with Acid. Darcet has proposed the use of sulphuric acid 
 to facilitate the extraction from the raw material. On the large scale a copper 
 vessel, which can be heated with steam, and of about 1,200 litres capacity, is em- 
 ployed, 50 kilograms of the muddy acid liquors from a previous operation are 
 added, together with four successive portions of 250 kilograms each of chopped fat, 
 and 5 kilograms of sulphuric acid (T846 sp. gr.)in 150 litres of water. The vessel is 
 covered and heated for 2 hours at 105 to 110C. At this temperature the sul- 
 phuric acid acts on the skin, allowing the fat to. melt out freely, and when this process 
 is used an unimportant amount of fat is left in the refuse. The liquid fat is now run 
 off and mixed with a solution of 1| to 2 kilograms of alum in 20 litres of water. 
 The mass is allowed to settle during 8 to 10 hours, and afterwards the fat, now 
 floating in a clear condition on the surface, is placed in casks. By the acid treatment 
 83 to 85 per cent, of tallow is obtained, whilst by the ordinary method it is 
 only possible to get 80 to 82 per cent. On the other hand, the last method yields, as 
 above mentioned, a refuse having a market value of 12 to 15 francs per 100 kilo- 
 grams. The tallow prepared with acid is in winter hard and white, but in summer 
 a liquid fat settles out, whilst the other kind of tallow is more uniform. At this 
 period of the year the candle makers prefer to use the tallow which has been puri- 
 fied without acid. It appears that the acid separates some of the olein from the 
 stearin, and causes the formation of a certain amount of free fatty acid, which sepa- 
 rates out by the slow cooling of the fat (a process necessary in the hot seasons of the 
 year), and renders the product less homogeneous than otherwise. 
 
 The method adopted by Evrard at Douai is as follows : 
 
 The crude fat, in the same condition as taken from the animal, without having 
 been cut up or freed from flesh, etc., is treated with a dilute solution of caustic soda. 
 The soda ley by penetrating the membrane, inflates and dissolves it, allowing the fat 
 easily to flow from its skin envelope. In addition to fixing the offensive smelling 
 fatty acids by their combination with the alkali, it has the advantage over any 
 other method of producing after once washing with water a very white inodorous 
 
666 
 
 FAT AND OIL. 
 
 fat; and as the temperature of 100 is never exceeded, there is no possibility of over- 
 heating. 800 kilograms of tallow can be melted per day by the following arrange- 
 ment: 10 sheet-iron cylinders, each of 1 metre in diameter, and 1 metre 25 centimetres 
 deep, and furnished, 17 centimetres above the ground, with a false bottom, having 
 perforations of 3 millimetres each in diameter, are placed side by side. Steam can 
 be conducted under the false bottom by means of a perforated steam pipe. Three 
 hectolitres of soda ley, of specific gravity 1-25, are mixed in each vessel with 400 
 kilograms of fat and heated with a jet of steam; and that the fat may be quite im- 
 mersed in the alkali, a second perforated plate is placed on the top of the mixture. 
 This works upon vertical rods, in such a way that it falls of its own weight, or it 
 may be pressed down by the hand. The fat rises above the perforated plate as soon 
 as the alkaline solution has penetrated and dissolved the membrane. After about 
 three hours' boiling the two plates almost touch each other, leaving but a modicum of fat 
 with the skin refuse between the two plates. The steam is then turned off, and the 
 soda liquor drawn off by a lower tap, and clean water having been run in for a short 
 time, the vessel is again heated with steam. After the contents of the cylinder have 
 been allowed to settle, the fat is run off from the aqueous solution into copper 
 vessels 1 metre in length with a diameter of 75 centimetres, and two of these are 
 required for each of the larger vessels. These twenty cylinders are heated in one 
 large water bath. After standing twelve hours the tallow is siphoned into a copper 
 cooler, and afterwards placed in casks to give it the commercial form ; or it is at once 
 worked up into candles. The alkaline and aqueous liquids are poured into sheet-iron 
 vessels worked on the Florentine principle, in which the exit tube from the bottom of 
 the first leads into the upper part of the second vessel, and so on throughout the 
 series, and in this manner the fat collects on the surface, allowing the liquid under- 
 neath to flow out. The alkaline liquid that separates, still containing the odorous 
 fatty acids which have been dissolved by the soda, is decomposed in wooden vats with 
 dilute sulphuric acid, and the fatty acid rising to the surface is separated from the 
 saline solution in the way just described. 
 
 The fatty mixture so obtained, consisting of offensive-smelling and coloured 
 fatty acids with to 1 per cent, by weight of pure fat, is used in the manufacture 
 of common soap. 
 
 Many plans have been suggested to prevent the offensive odours always arising 
 in tallow melting. Amongst those plans in which the melting pots are provided 
 with covers through which the gases are conducted into a flue or are previously burnt, 
 the following is almost the only one which answers successfully. Fig. 442 represents 
 
 FIG. 442. 
 
 H. Vohl's covered apparatus for tallow melting. A is a cast-iron vessel, lined with 
 sheet lead, with a riddled bottom d d ; a is a tap to draw off the aqueous liquid ; b is 
 the tap through which the fat is drawn, p is the fire-grate. B is a cast-iron ring with 
 door T for filling the pot, c the cover, with a mica plate s s. In the door T is also 
 an aperture covered with mica for the purpose of seeing into the interior ; D is the 
 vessel into which the gases given off in the melting process are passed by 
 the tube w ; y is a cover with sand joints r r ; powdered lime is placed in the 
 
VARIOUS KINDS OF OIL, ETC. 667 
 
 inside of D on oblique shelves to retain the offensive smelling products. The eondensed 
 liquid flows off through the pipe (h), and the gases and steam pass through into the 
 condenser (E), which contains coke moistened with sulphuric acid. The liquid which 
 is here condensed, passes through the pipes (z and K), whilst the gas passes from g 
 along the tube F into the ash pit (G) under the furnace, o is enclosed by an iron door, 
 through which a powerful draught of air can be sent, carrying with it all the gas 
 from the apparatus into the furnace. The waste gas from the furnace passes out at o. 
 In the manufactory of Arlot and Co. at La Villette, the fat is melted in pear-shaped 
 and perpendicular cauldrons placed directly over the fire. The manhole is closely 
 fastened during the working, and the gases force their way through another opening 
 to a channel which is common to 1 6 cauldrons. The mixed gases before reaching 
 the large furnace are carried over the grate of a second or auxiliary furnace which is 
 kept in a red-hot state by a separate fire, so that the gases may be completely con- 
 sumed before passing into the chimney. It has not been found satisfactory to lead the 
 vapours direct to the cauldron furnace, in consequence of the draught being so 
 diminished as to be insufficient to support the heat necessary for the melting opera- 
 tion. A better combustion of the gases ensues if they are carried over the hottest 
 part of the furnace. 
 
 Stein has proposed to absorb the noxious vapours and to render them innocuous, 
 before allowing them to escape into the atmosphere, by a layer of wood charcoal and 
 lime placed to the depth of 3 to 4 inches on a perforated plate over each cauldron. 
 
 In addition to the disadvantage arising from the necessity of using a fresh layer 
 of deodorising material at every melting, the cauldron must be fitted with special 
 contrivances (such as a false bottom, steam heat, etc.) made necessary by the stirring 
 required during the melting operation. 
 
 The different kinds of fat and oil derived from plants are generally extracted by 
 a simple mechanical operation of pressing the seeds and other parts of the plants 
 which contain these substances in large proportion. Heat is sometimes applied to 
 facilitate the extraction of the oil; but the product thus obtained is almost invari- 
 ably inferior to that extracted without heat, or as it is termed cold drawn. Oil 
 .is extracted from the livers and other parts of fish in the same manner, as well as 
 from various marine animals, such as the whale, seals, etc. 
 
 Of the Principal Kinds of Oil that are Liquid at the ordinary Temperature. 01 i ve 
 oil is obtained by pressing the fruit of the olive tree (Olea europcea), a native of 
 Asia, growing luxuriantly in the south of Europe. Oil of almonds is the fixed 
 oil obtained by expression from the fruit of the almond tree (Amygdalus communis). 
 Rape or colza oil is expressed from the seeds of various species of Srasicca, and 
 nut oil from the fruit of the ground nut (Arachis hypogcea). Linseed oil is ex- 
 pressed from the seeds of the common flax (Linum usitatissimum), and cotton seed 
 oil from the seeds of the cotton plant (G-ossypium barbadense, and other species): 
 these two oils have siccative properties. Train oil is obtained by boiling the blubber 
 of various species of whales, especially Balcena mysticetus, but the sperm whale 
 (Physeta macrocephalus) yields sperm oil. Cod liver oil is obtained principally from 
 livers of the common cod (Gadus Morrhud), the best quality being extracted without 
 heat and the commoner kinds by heat and pressure ; seal oil is obtained similarly 
 from the fat of different species of seals. Lard oil is the Liquid oil that separates 
 when pig's fat is subjected to pressure. 
 
 Of the Principal Solid Fats. Palm oil is obtained by bruising and boiling with 
 water the fruit of a palm (Elais guianensis) growing in Western Africa. Cocoa nut 
 oil is obtained by pressing or boiling the kernel of the fruit of the cocoa nut palm 
 (Cocos nucifera). Cacao butter is obtained by expression from the seeds of the 
 Theobroma Cacao. Butter is the fat separated by churning from cow's milk. Lard 
 is prepared by melting the fat of pigs, and separated from the membranes by 
 straining. 
 
 Purification of Fish Oil. For some time past Payen has recommended the purifica- 
 tion of fish oil by warming it in deep copper vessels, placed in a water bath ; and 
 then in the same vessels, allowing the oil to cool very slowly to a temperature of 12 
 to 15. A viscid but somewhat firm fat remains at the bottom, whilst the oil can be 
 separated by decantation. The residue is mixed with others of a like nature in a 
 copper vessel, where, after some time, a further decantation of oil is possible, and it can 
 thus be very completely separated. The further clearing of both products is carried out 
 in the following manner: the firm fat, about 5 to 10 per cent, of the whole, is melted 
 in a wooden vat by allowing steam to enter freely. At the temperature of ] 00, 1 to 
 2 per cent, of muriatic acid or tartaric acid is added. The mass having been well 
 stirred is allowed to cool as slowly as possible, which is attained by wrapping a non- 
 conducting material round the melting tub. The fat will now be found to be much 
 
668 FAT AND OIL. 
 
 firmer and whiter, as a considerable quantity of the impurity has been either 
 destroyed or retained by the acid. The liquid oil thus separated is heated to 100, then 
 violently stirred after mixing with it 1 per cent, by volume of a saturated solution of 
 caustic potash (1 '453 sp. gr.), which saponifies the noxious part of the oil, whilst the oil 
 itself is left clear and colourless. As a final operation the oil is filtered through woollen 
 bags. The soap residue is dissolved in water, and the fatty acids precipitated from 
 their potash compounds. In the purification of the much darker oil obtained from 
 some kinds of fish it is preferable to use 1 per cent, by volume of soda ley. 
 
 MANUFACTUEE OF SOAP. 
 
 It has been already explained that when fatty acids or the neutral fats are heated 
 with alkaline or other bases, combination or decomposition occurs, and that salts of 
 the fatty acids are formed. The commercial production of these salts, or ' soaps,' as 
 they are termed, constitutes an immense industry, the consumption of soap as a 
 cleansing agent increasing with advance in civilisation. Chemically speaking, any salt of 
 a fatty acid is a soap; industrially, the term soap signifies an alkaline salt of a fatty 
 acid. On treatment with water, these salts liberate alkali, and it is the alkali thus 
 liberated which, by its action upon fatty and other impurities, renders them soluble in 
 water, and thus produces the cleansing effect. The liberation of free alkali from soaps 
 by water is due to the fact of their being split up into free alkali, and a more acid 
 combination than the original soap. Thus, when ordinary hard soap is used in 
 washing, the water decomposes it, resolving it into soluble free soda and curds ; 
 these curds or insoluble flocks, which float on the surface of the water, consist of the 
 sodium salt of a fatty acid ; but it is a combination of an acid character, in which the 
 fatty acid is not combined with soda to its fullest possible extent. It is not unlikely 
 that in the future fatty acids will be replaced in the manufacture of soap by other 
 cheaper acids such as silica, a substance capable of forming soluble salts with 
 alkaline bases, which is, indeed, already largely employed in the production of what 
 is termed silicated soap. 
 
 "Without repeating what has been described in another place (see p. 664) regarding 
 saponification, it is sufficient here to point out that fats and fatty acids give rise to 
 soaps when acted upon by alkalies, as represented by the two following equations: 
 
 C 18 H 36 2 + NaHO = C 18 H 35 Na0 2 + H 2 0. 
 C 3 H 6 3C 18 H 85 2 + SNaHO = ^JO, + 3C I8 H M NaO,. 
 
 The latter equation serves to represent the manner in which all fats or glycerides 
 decompose when saponified with basic oxides. Ordinary fats (including fixed oils) 
 are constituted of glycerin a triatomic alcohol (C 3 H S 3HO), in which three 
 hydroxyls are substituted by the residues of fatty acids. Thus, in the instance re- 
 presented above, tri-stearin or glyceryl tri-stearate is taken. Other combinations 
 however are known, and, indeed, a few are actually used in soap making, which differ 
 somewhat from ordinary neutral fats. This will be seen in a better way by writing 
 the typical formulae of glycerin and an ordinary fat side by side : 
 
 Glycerine. Tri-stearine. 
 
 (HO /C 18 H 35 2 
 
 C 3 H 6 HO C 3 H 5 C 18 H 35 2 
 
 ( HO tc i8 H 35 2 
 
 It is possible to substitute one hydroxyl in glycerin by a radical, not of a fatty 
 acid nature, for instance phosphoryl. which would yield glycerophosphoric acid : 
 
 ,HO 
 C 3 H 5 ]HO 
 
 IHO(OPO)HO or C 3 H 9 P0 6 
 
 From this substance others of a more complex nature may be obtained, and many are 
 known, being mainly of animal origin. Thus the two residual hydroxyls may be re- 
 placed by two molecules of the same fatty acid, or by two distinct acids ; thus with 
 palmitic and stearic acids, the following compound would result: 
 
 C 18 H 95 0, 
 C 3 H 5 C 16 H 31 2 
 
 OH(OPO)OH 
 
 Still greater variations may be effected, and still more complex bodies result. For 
 instance, one of the subsidiary hydroxyls in the group, phosphoryl, maybe substituted 
 
SOAP MAKING. 669 
 
 by the residue of any amine, and, in fact, compounds are obtained from the brain and 
 bile which have this constitution : 
 
 (C 18 H 33 2 
 G 3 H 5 C 16 H 32 2 2 
 
 lOH(OPO)C 5 H 13 NO 
 
 Many such substances have been described by Strecker, Thudichum, and Kingzett, 
 and they are saponifiable by alkalies in the same kind of way as ordinary fats. Thus 
 the body above represented has a total formula of C 42 H 84 NP0 8 , and decomposes by 
 boiling with alkaline bases into oleate, palmitate, and glycerophosphate of the base 
 employed, and the nitrogenous compound C 15 H 13 NO. 
 
 The yelk of eggs, formerly used in soap making, being obtained from the print 
 works where only the albumin is used, contains a compound similar to that just de- 
 scribed, and, indeed, its soap-making qualities are divided between this substance 
 and the neutral tri-olein also contained in it. 
 
 The different kinds of soap in common use are classified as hard, soft, and silicated. 
 
 Hard soap is made with soda, and its hardness depends in a great degree 
 upon the amount of stearic and palmitic acids contained in the fat which is 
 employed ; the combination of these acids with bases being firmer in consistency than 
 the corresponding oleates. 
 
 The kinds of fat usually employed in making hard soaps are tallow, palm oil, 
 cocoa-nut oil, etc. ; in southern countries, coarse olive oil is also employed. Ordinary 
 resin is often used in addition to these fats. The use of resin in soap making, in the 
 proportion of about one fourth of the tallow employed, modifies the hardness of the 
 soap, and increases its solubility. The use of resin in making both hard and soft 
 soaps may be at once explained ; it consists of pinic, sylvic, and colophonic acids, or 
 oxidised products of turpentine, considerable quantities of which are obtained in the 
 distillation of crude turpentine, etc. The resin is first purified and freed from colour 
 by distillation in steam, after which it may be used for making soap either alone or in 
 mixture with fat. The acids of resin are strong enough to decompose sodic carbonate, 
 and their combinations with fixed alkaline bases are soaps, in the sense that on treat- 
 ment with water they liberate alkali. 
 
 The pans, or coppers as they are termed, used in soap making are of various sizes, 
 the larger ones being about 15 feet in diameter and as many feet in depth, and con- 
 structed of wrought-iron plates rivetted together. Such coppers can turn out from 25 
 to 30 tons of soap in one operation. Heat may be applied in several ways ; in some 
 instances the contents of the coppers are heated by a steam pipe passing into them ; 
 in other cases a steam jacket is used, while yet other manufacturers heat their pans by 
 fire. These pans are first charged by the fat or oil, and resin (if it be desired to use 
 it), and then to the mass is added a weak caustic soda ley of TOS specific gravity, and 
 the whole boiled and stirred ; saponification gradually ensues, or if it does not take 
 place properly, the evil is remedied by tie further addition of soda ley. From time 
 to time stronger leys are run in, but these never exceed a gravity of about 1'09. 
 When the alkali is in excess, a further quantity of fat or oil is added, then more soda, 
 then fat again, and so on, finally adjusting and completing the saponification in the 
 pans by the time they are nearly filled. A precaution which is always observed is 
 that finally there is no considerable excess of alkali present. 
 
 The soap thus produced has next to be separated in a solid form from its solution, 
 and this is effected by the addition of common salt to the mixture ; soaps being 
 insoluble in a strong solution of salt. About 10 Ibs of salt are used to every 100 Ibs. 
 of fatty material employed. The soap thus precipitated floats in the state of a 
 granular mass or curd, from which the spent ley containing the glycerin is run off, and 
 the soap itself is boiled again with fresh weak ley, until a ' close ' state or homogeneous 
 mixture is obtained. The details of further operations now depend upon the kind of 
 soap it is desired to turn out, but these are of a simple kind and need not be entered 
 into particularly. The soap curd is allowed to remain quiescent for some hours, or 
 a period ranging up to two days : in this way the ley subsides and the soap may be 
 ladled from the top and transferred to cast-iron frames, where by cooling it solidifies. 
 The final operation consists in cutting up the soap into slabs or bars by means of wires. 
 Soft soap is made for the most part from whale, seal, and linseed oils, tallow 
 and resin in this country ; hemp, linseed, and poppy, and other drying oils, as well as 
 rape and train oils, are also used on the Continent. The manufacture resembles in all 
 important points that of hard soap, with the difference that potash ley is used in- 
 stead of soda. The potash solution (of from 9 to 110 B., specific gravity from 1*06 
 to 1-08), is made from pearlashes and American potashes. The boiling of the oil or 
 fatty material with the weaker ley is continued, until the mixture becomes of a streaky 
 appearance, when the stronger alkali is added to effect clarification, and the boiling 
 
670 FAT AND OIL. 
 
 continued with continual stirring. After a time the soap begins to ' talk,' as the 
 soap makers term^the noise of the bursting bubbles, and when this happens, the heat- 
 ing is discontinued, and the soap is ready to pack in casks on cooling. 
 
 Mottled soap is often produced by the addition to the nearly finished soap of 
 crude soda liquor, containing in solution the double sulphide of iron and sodium. As 
 it falls through the soap, the iron is precipitated as oxide in veins, thus giving rise to 
 the appearance of marble. At times other reagents, such as prussian blue, are used 
 with the same object. Mottling is merely a trade practice, and serves no useful 
 purpose. 
 
 Hard soap differs in composition, and contains from 20 to 30 per cent, water, 70 to 
 60 per cent, of fatty acids, and 8 to 10 per cent, alkaline base ; while soft soap contains 
 from 40 to 50 per cent, water, with 50 to 40 per cent, fatty acid, and from 10 to 12 
 per cent, potash. 
 
 Toilet soap is produced by dissolving ordinary curd soap, and incorporating with it 
 perfumes or particular substances, the addition of which determines the name and 
 character of the soap to be produced. 
 
 Silicated soap is now produced on a large scale, in particular by Messrs. W. Gossage 
 and Sons, and it represents the most recent advance in soap making. 
 
 Silicated soap is a mixture of ordinary soap and soluble glass or alkaline silicates, 
 which latter substances are possessed of detergent power, from the fact that by treat- 
 ment with water they liberate alkali. Silicated soap is cheaper than ordinary soap, 
 and besides its domestic employment, it admits, therefore, of use in certain manufac- 
 turing processes : such as the fulling of woollen goods when operations of cleansing 
 are involved. 
 
 The soluble glass is first made by melting 9 parts of soda ash (of 50 per cent, 
 caustic soda) with 11 parts of clean sand; while when soft soaps are required, equal 
 weights of carbonate of potash and sand are taken. The melted glass is ground, then 
 dissolved by boiling in water rendered alkaline, and the solution thus obtained is 
 mixed with the ordinary soap by a mechanical stirring apparatus. 
 
 In 1852 Great Britain produced 83,200 tons, about one-half of which was made in 
 Lancashire. In 1870 Lancashire alone produced as much as the whole of Great Britain 
 had produced in 1852. 
 
 AETIFICIAL LIGHT AND LIGHTING MATEEIALS. 
 
 One of the most important applications of fat and oil is that of burning for the 
 production of light. Towards the end of the eighteenth century animal fat, such as 
 tallow and several kinds of oil obtained from fish, were the only materials used in this 
 way, the former being used as candles, the latter for burning in lamps. Since that 
 time other kinds of oil derived from plants have been introduced into use for this 
 purpose, and considerable improvements have been made in the preparation of the 
 material for candles. Combustible substances of mineral origin have also been brought 
 into extensive use as light-producing materials. In burning any of these substances 
 either in a lamp or in the form of a candle, they undergo decomposition of. such a 
 nature as to produce combustible gas, and in both cases it is the combustion of this 
 gas, as it is formed, that gives rise to the luminous flame. The special production of 
 gas suitable for burning in this way, and capable of being stored up for use when re- 
 quired or transported to considerable distances, is another improvement in the art of 
 artificial lighting, beside which all others sink into comparative insignificance. The 
 material employed for this purpose is coal, and the process by which combustible gas is 
 obtained from it is essentially the same as that taking place in the flame of a candle or 
 a lamp, except that the gas produced is not immediately consumed as in these cases, 
 but is first conveyed in pipes to the place where it is to be burnt. 
 
 The industrial operations connected with the preparation of materials for artificial 
 lighting may therefore be treated of under three heads viz., the treatment of natural 
 oil and fat, so as to render them suitable for burning in lamps, and for the manufac- 
 ture of candles ; the extraction of liquid and solid materials from petroleum as well as 
 the production of analogous materials from bituminous minerals by destructive dis- 
 tillation ; and, lastly, the production of gas from coal. 
 
 PBEPABATION OF OIL OB FAT FOB BUBNING. The kinds of oil now chiefly used 
 for burning in lamps are sperm oil and rape or colza oil, and the preparation they 
 undergo for the purpose is intended only to separate admixtures of mucus and other 
 substances, which would give rise to incrustation of the wick with carbon. 
 
 The treatment to which tallow and other kinds of solid fat are subjected, in order 
 to prepare them for making candles, is intended chiefly to increase the consistency of 
 the various materials and reduce their fusibility. These objects are, to some extent, 
 
ARTIFICIAL LIGHTING. 671 
 
 attained by pressing the fat, so as to separate the olein or liquid portion from the 
 solid constituents, stearin and palmitin. But the most effectual method is to decom- 
 pose the fats by saponification, and then, after removing the glycerin, to separate the 
 fatty acids by pressure. By this means also a candle material is obtained which is not 
 liable to become rancid like natural fat. The separation of the fatty acids can be carried 
 out in several ways : e.g. 1. By saponifying the fat with lime and decomposing the 
 lime salt with acid. 2. Bythe^iise of very little lime simultaneously with high- 
 pressure steam. 3. By decomposition with sulphuric acid. 4. By means of superheated 
 steam. Beef and mutton tallow, and latterly also palm oil, chiefly serve as the raw 
 material for the preparation of stearic acid. Mutton tallow contains the most stearic 
 acid, but the other fats, palm oil especially, are generally much cheaper, and these are 
 now being more largely employed for this purpose. 
 
 Saponification with Lime. The lime used must be as pure as possible. It is 
 mixed with 10 times its weight of water, and then passed through a fine wire sieve. 
 1000 kilograms of tallow are mixed with 1,600 kilograms of water, in a wide wooden 
 vat lined with sheet lead, of 4,000 litres capacity. This vessel is heated by means of 
 steam so as to melt the fat, and milk of lime containing 140 kilograms of burnt lime 
 is added. In order to facilitate the action of the lime the mixture must be kept 
 stirred either by manual or by mechanical appliances. A hard insoluble lime soap is 
 formed, and the water holdst he glycerin dissolved. The whole of the fat is saponified 
 after 6 to 8 hours heating, and the aqueous solution is separated. In many 
 manufactories, in order to save time, the still warm and consequently soft soap is 
 mixed in the same vat with sulphuric acid. In other works, on the contrary, the cold 
 soap is pulverised and sifted, then decomposed with sulphuric acid in a fresh vessel 
 of the same form and capacity as the first. Ordinary chamber acid or concentrated 
 acid of T846 sp. gr. will decompose the lime soap, although it is preferable to use acid 
 of T2J sp. gr. 140 parts by weight of lime theoretically require 245 parts of sulphuric 
 acid, but to ensure a successful operation it is usual to employ 274 parts of sulphuric 
 acid for every 140 parts of lime used. About three hours are occupied to effect the 
 decomposition, which results in the formation of stearic acid and sulphate of lime. 
 At the termination of the operation the sulphate of lime is deposited at the bottom 
 of the vat, whilst the fatty acids swim as an oily layer on the top of the acid liquid. 
 
 Washing the fatty acid. The fatty acids are brought into a vessel of the same 
 shape and arrangement as the one used in decomposing the soap, and then to 
 remove the last traces of lime it is warmed with sulpltoric aeid of 1/091 sp. gr. As a 
 final operation to remove the excess of acid it is once washed into water. The washing 
 processes are conducted at a temperature of 100. The yield of fatty acids of course 
 varies with the kind and the purity of the fat employed. According to K. Wagner, 
 tallow gives 94'4 per cent, of fatty acids, which contain about 46 per cent, of solid 
 acid as stearic acid and palmitic acid. 
 
 Crystallisation. The washed fatty acids are placed in moulds made of tin plate 
 somewhat wide and of a capacity of 3 litres each : here by cooling the mass solidifies 
 to slightly coloured cakes, each of which weighs about 2 kilograms. To separate the 
 impure and coloured oleic acid the solid cakes are pressed first cold and finally hot. 
 
 Cold pressure. Each cake of fatty acids is wrapped in woollen cloths and placed 
 under an ordinary hydraulic press in alternate layers of press bags and zinc plates, 
 to the height of one metre, and in this way subjected to a gradual and increasing 
 pressure for from 5 to 6 hours. By this means the greater part of the oleic acid is 
 expressed, but by cold pressure it is impossible to get rid of the last portions ; it has 
 therefore to be subjected to hot pressure at about 40. 
 
 Hot pressing. The cakes to be pressed are wrapped in horse-hair cloths, and 
 placed between hot iron plates in an hydraulic press arranged so that the whole can 
 be heated by steam. The expressed oleic acid is run off into a reservoir where, by slow 
 cooling, more solid acid separates and is recovered by cold pressing, and afterwards 
 added to a large batch for hot pressing. 
 
 The solid cakes of fatty acids after hot pressure have once more to be refined in 
 order to eliminate the last portions of lime. For this purpose they are melted with hot 
 dilute sulphuric acid of T022 sp. gr., in a large vat : the mass washed with hot water, 
 then clarified with albumin. In this way stearic acid is completely purified, and is ready 
 for the market, either as cakes or in candles. To prevent the loss of sulphuric 
 acid in the form of gypsum, it has been proposed to use baryta, or alumina in the form 
 of sodic aluminate, instead of lime for the saponification ; these would, by the after 
 process with acid, become respectively sulphate of baryta and sulphates of soda and 
 alumina. But neither method has been much used, partly on account of the heavy 
 mass of baryta required, but also because lately in large manufactories quite a diffe- 
 rent process has been carried on. 
 
672 FAT AND OIL. 
 
 Saponification with very little Lime, with the simultaneous employment of High-pres- 
 sure Steam. De Milly has found that the decomposition of the tallow can be com- 
 pleted by using 3 per cent, of lime instead of 14 per cent, by weight, but increasing 
 the temperature in an enclosed vessel by means of high-pressure steam to 172, which 
 answers to eight atmospheres. The chief advantage presented by this process is of 
 course in using less lime, thereby preventing expenditure of sulphuric acid. The 
 reason of so little lime doing the work lies in the fact that high-pressure steam by 
 itself, as fully described before (p. 664), splits up the fatty bodies into glycerin and 
 fatty acids. The small quantity of lime serves a subordinate part, by preventing 
 the re-formation of glycerides by the action of the free acids and glycerin on one 
 another. The starting of the process is also due to the lime. 
 
 The apparatus devised by De Milly consists of a vertical vessel of strong copper 
 or iron sheeting lined with lead, of two metres in height and one metre in diameter. 
 The melted tallow is poured from a reservoir into the vessel through a narrow tube, 
 and a second tube serves as an exit passage for the vapours. There is also a third 
 pipe passing through the middle and reaching almost to the bottom, which serves for 
 emptying the vessel ; the cylinder is provided in addition with a man-hole at the side 
 for the introduction of the lime, and with a thermometer, a manometer, and with a 
 safety valve to resist a pressure of ten atmospheres. 
 
 2,300 parts by weight of tallow are placed in the melting pot and mixed with 
 2,000 parts of milk of lime (containing 69 parts of lime) having been previously made 
 hot by steam. Steam under a pressure of 10 atmospheres is then allowed to enter 
 by the steam cock, from the lower part of the vessel, and exerts a pressure of about 8 
 atmospheres, which is equivalent to a temperature of 172. High-pressure steam cor- 
 responds to the following temperatures : 
 
 5 atmospheres 152 
 
 '-..- . . . . 160 
 
 7 
 
 8 
 
 9 
 
 10 
 
 166 
 172 
 177 
 182 
 
 The decomposition is accomplished in 7 hours ; the steam cock is then closed and 
 the temperature lowered to 130 for 30 to 40 minutes. The aqueous liquid con- 
 taining the glycerin is drawn off, and can be used at the next operation instead of 
 water. In this way the glycerin is incidentally concentrated. The mixture of the 
 fatty acids and soap floating on the surface having been separated from the lower 
 liquids is decomposed in a vat lined with lead, by means of sulphuric acid, in a 
 manner similar to that explained above for the old process. As here, however, the 
 chief part of the fatty body consists of free acid with only a small quantity of lime 
 soap, just sufficient sulphuric acid and no more is used for the decomposition 
 (namely 133 parts), nor is it necessary to pulverise the soap as it lies finely divided 
 in the fatty acids. All the principal operations of washing, etc., to be carried out 
 with the fatty acids are the same as in the old method. 
 
 Decomposition of the Fatty Bodies by Sulphuric Acid with subsequent Distillation. 
 According to the observations of Fremy, fatty bodies are split up by concentrated 
 sulphuric acid into sulpho-gly eerie acid and the sulpho-fatty acids. These com- 
 pounds are decomposed by treatment with boiling water into free glycerine and sul- 
 phuric acid, which are dissolved, and into the insoluble fatty acids. On this reaction 
 is based a new method of separation, which is specially adapted for impure fatty 
 bodies such as kitchen refuse, butcher's offal, and the like, but more particularly for 
 palm oil, as the fat acid separated in this way is afterwards subjected to distillation. 
 
 There is a great variation observed in factories working the methods of Grwyne, 
 Wilson, and Coley Jones, in the strength of the sulphuric acid, in the temperature em- 
 ployed, and in the time occupied for the operation. Usually 12 to 16 per cent, by 
 weight of concentrated sulphuric acid serves for tallow, 10 to 13 per cent, for fat refuse, 
 and 8 to 9 per cent, for palm oil. The temperature is raised or the time of opera- 
 ing is lengthened as the proportion of sulphuric acid is lowered. Fatty refuse 
 requires a special process of purification. Soap waste, from the washing of fleeces 
 for wool spinning, is treated with sulphuric acid, and the floating fatty layer having 
 been skimmed off by wooden spoons, is melted down on the water bath and clarified. 
 The oil which here separates is decanted 0$ and the solid dirty sediment is placed in 
 linen bags and pressed. If the soap waste is largely contaminated with extraneous 
 substances, such as wool cuttings, earth, etc., it must first be cold pressed to remove 
 the water, and afterwards hot pressed for the fat, which is then further operated 
 with in the manner above described. In order to extract the lust portion of fat in the 
 
PREPARATION OF FATTY ACIDS. 
 
 673 
 
 woolly material, it is (after the hot pressing in which the major part has been ex- 
 tracted) mixed with boiling water, and then again pressed. 
 
 The crude residues are re-melted with dilute sulphuric acid in large lead-lined 
 vats heated by steam, whereby some of the impure organic substances are dissolved, 
 and the soap residues become decomposed. The separation of the water from the 
 crude fat is carried out in reservoirs fitted on the Florentine system. 
 
 Bogaert's method consists in decomposing the soap water with muriatie acid, then 
 pressing the fatty mass and heating to the boiling point by means of steam ; after 
 cooling, nitric acid is added. 
 
 The decomposition of the fatty bodies by means of sulphuric acid is carried on in 
 the boiler A (fig. 443), which is made of strong iron or copper plates lined with lead. 
 The steam used to heat it is 
 led from D into the jacket c, 
 and the surplus steam along 
 with the condensed water 
 passes out through E. Over 
 the vessel is fitted a cylindri- 
 cal body (B), of sheet iron lined 
 with lead, and provided with 
 a cover F having two windows 
 for observation and a man- 
 hole. GGG is a large pipe 
 which discharges from the 
 apparatus the exceedingly 
 foul gases, consisting of sul- 
 phurous acid, acrolein, etc., 
 together with suspended par- 
 ticles of fat, over the cast-iron ,, 
 basin i into the ash pit H. 
 
 A L is a stirrer ending in a perforated disk and moved 
 backwards and forwards by means of the eccentric J L. 
 
 As already stated above, the quantity of sulphuric acid taken varies with the 
 kind of fat that is to be refined. The temperature of the mixture is raised from 
 100 to 115 and the operation is continued for twelve to eighteen hours. Ironi 
 time to time a sample is taken from the melting pot,- and when this solidifies to a 
 hard cake, and the violet colour which appears at the commencement of the opera- 
 tion has disappeared, the action is completed. 
 
 Washing the crude fatty acids. When the decomposition is sufficiently advanced, 
 the mass is allowed to cool for two or three hours, and while still liquid is drawn oi 
 by syphons into the large 
 reservoir A, fig. 444, which 
 is half filled with water. 
 Through the pipe a, steam is 
 conducted from the boiler by 
 the connecting pipe G H. The 
 temperature being raised to 
 100, the decomposition of 
 sulpho-glyceric acid and the 
 sulpho-fatty acids into glyce- 
 rin, sulphuric acid, and the p IG 444, 
 
 fatty acids commences. The . ,^0-0 *>, 
 
 liquid then passes under the dividing wall into a second reservoir B, where thj 
 temperature is also kept at 100 by the steam coming in through b. third 
 
 reservoir c serves the same purpose, steam entering at c. Uro 
 liquid flows under a third dividing wall into the canal D, and 
 or three more similar receptacles. . . . ,, Q fr.a 
 
 In this washing apparatus the fatty acids remain behind in the separators, 
 the specifically heavier watery liquid flows under the partitions. 
 
 The sulphuric acid treatment and the subsequent washing affect the melting 
 oints of the fatty bodies in the following manner : 
 
 Bone fat 
 Palm oil 
 
 Melting points 
 
 In normal 
 residue 
 
 After treatment with 
 sulphuric acid 
 
 After washing 
 at 100 
 
 24 
 30 
 
 ' 36 
 68 
 
 33 
 44 
 
674 
 
 FAT AND OIL. 
 
 The washed fatty acids in the first reservoir A are drawn off above the water level 
 through the cock a', and are placed in the general receiver ready for the distilling 
 apparatus. The fatty acids of the second and third receptacles B and c are poured 
 back into the first and washed with a fresh portion. After every washing operation, 
 there is taken from the bottom of the reservoir (A) a black deposit of a resinous consis- 
 tency, amounting to about 4 to 10 per cent, of the original material. The applica- 
 tion of this residue is described in detail afterwards. 
 
 Instead of sulphuric acid, latterly, chloride of zinc has been recommended for the 
 decomposition of the fat, but it has not been approved of in practice. 
 
 The plan of Knab differs essentially from the one just described, inasmuch as the 
 fat previously heated is mixed with hot acid, and the mixture after being allowed to 
 act for a short time is poured into water. The decomposition thereby proceeds 
 quicker, and in consequence of the short digestion with sulphuric acid much fewer 
 products of decomposition are formed, and the yield of fatty acids is increased accord- 
 ingly. 
 
 The fat is heated with concentrated sulphuric acid in a horizontal iron cylinder, 
 and kept continually agitated. The mixture flows through the apparatus with suffi- 
 cient rapidity to pass in about two minutes from one end to the other. It is then 
 run into a vat which is three-quarter parts filled with boiling water, and the fatty 
 acids floating on the surface can be separated. 
 
 The acid residue is so pure that there is no need to distil, but merely to melt it 
 in the ordinary manner, and then subject it to coM and hot pressing. The quantity 
 of acid used in Knab's process ranges in different manufactories from 4 to 15 per 
 cent., the smaller the proportion of acid the higher must the temperature be raised. 
 It is possible to obtain by this method about 90 to 95 per cent, of acids, whilst the 
 older process will only yield 87 per cent. 
 
 Distillation. As the fatty acids become contaminated during the sulphuric acid 
 treatment with the black resinous substance before mentioned, they must be sub- 
 mitted to distillation ; as the temperature required is very high, it is necessary to use 
 high-pressure steam to prevent decomposition and an impure distillate. By the use 
 of steam, the distillation will proceed between 170 and 230, but in practice a higher 
 temperature is generally used. 
 
 The fatty acids are placed in a vessel and heated by an arrangement of water 
 bath in which the water flows back to the steam generator and keeps the tempera- 
 ture round the crude acids at about 45 to 50. At this gentle heat the rest of the 
 water and a few other impurities are separated by decantation. The liquid is after- 
 wards heated in a square pan, D, fig. 445, having sides 6| feet in length ; over the 
 
 FIG. 445 
 
 pan is a vaulted cover from which the condensed water trickles round and forms a 
 luting to the cover. The heat is obtained from a fire which passes from the furnace 
 J into the flues h and i, containing steam worms into which steam is introduced 
 by the tube g from the steam boiler, and can be heated to 300. In the distilling 
 operation this steam is led by the cock K into the retort A. 
 
 The retort is of sheet-copper, about 3| feet in diameter and 6 feet in height ; 
 the top B is rivetted on so as to be air-tight. The fatty acids are admitted through 
 the tubes e, by opening the cocks d'. The retort is heated by means of a sand bath 
 of cast iron placed at an interval of about an inch, and reaching up to about f of the 
 height of the retort. On the cover B is the man-hole, and above all is the cover plate 
 B' B' of sheet iron filled in with ashes to keep in the heat. As soon as the tempera- 
 
PREPARATION OF FATTY ACIDS. 
 
 675 
 
 ture of 250 is reached, known by means of thermometers placed in the retort, the 
 steam cock K is opened, and steam led in at the temperature of about 250 to 300. 
 The steam tube ends in a circle f, from which the steam issuing from a great number 
 of small holes is strongly forced into the liquid fatty acids. The temperature of the 
 steam is observed from a thermometer placed near the steam cock K. 
 
 The steam carries over the fatty acids by the connecting tube r, through the 
 middle vessel M, into the double worm o o. The receiver M serves to arrest the first 
 distillate, which consists of impurities, and can be drawn off at once. The fatty acids 
 flow into the worm o o, thence by the pipe p into the receiver Q, arranged on the 
 Florentine system. 
 
 The lighter fatty acids swim on the surface of the water in the first division of 
 the receiver, and the water forces itself under the partition into the second division. 
 The fatty acids are drawn off at R and the water at s. The composition of the acids 
 successively distilled depends on the time occupied in the distilling process as well 
 as on the quality of the raw material. 
 
 The following table shows the melting points of the distillates : 
 
 Kitchen and Bone Fat Palm Oil 
 
 1st product ... 40 .... 54'5 
 
 2nd 
 3rd 
 
 4th 
 5th 
 6th 
 
 7th 
 
 41 
 
 41 
 
 42-5 
 
 44 
 
 45 
 
 41 
 
 52 
 48 
 46 
 44 
 41 
 39-5 
 
 The quantity .of acids usually submitted to distillation in an apparatus of the 
 size above described is about one ton, and the time occupied in distilling this quantity 
 is about twelve to fifteen hours. The residue left in the retort is of a brown tarry 
 nature, and is run off by opening the valve T, through the tube a?, into a receiver, 
 where, on cooling, it solidifies to an asphalte- or bituminous-like body, equal in amount 
 to about 6 or 7 per cent, of the crude bone fat employed. 
 
 100 parts palm oil of the consistency of butter give 75 to 80 parts of distilled 
 fatty acids a yield equal to 50 to 52 parts of pressed acids. 
 
 Apparatus for Continuous Distillation. An engraving of such an apparatus is 
 shown in figs. 446 and 447- It consists of an horizontal cylinder B, which is heated 
 by a lead bath G G. An ordinary man-hole permits access to the interior of the 
 cylinder. The fatty acids, in a melted condition, flow in a thin continuous stream 
 through the funnel c from a tap above it, the quantity being regulated by a float, in 
 connection with the tap, shutting or opening it by its rise and fall, according to the 
 level in the cylinder B. As soon as the fatty acids in the cylinder reach the tempera- 
 ture of 300 a stream of steam is sent in through D D. The mixture of acids and 
 steam passes out through the discharge pipe (F) into the condenser. The intervening 
 vessel E serves to retain the water condensing in the conduit tube from the ingressing 
 steam. 
 
 IMG. 446. l r io. -M7. 
 
 Instead of employing steam at the normal temperature, which is barely 100, 
 latterly superheated steam at 250 has been used, and the steam pipe D has also been 
 placed horizontally on the bottom of B and furnished with many small holes for the 
 steam to pass upwards through the melted mass. After three to four days' working 
 a residue will have collected in great quantity in B, and must be drawn off by an ar- 
 rangement similar to that of T (fig. 445). 
 
 xx2 
 
676 . FAT AND OIL. 
 
 There has also been a still constructed in which the fatty acids are heated without 
 the intervention of a bath, by means of hot air from the furnace used for the pro- 
 duction of the steam necessary in the distillation. Masse and Tribouillet have intro- 
 duced a still of this description into their manufactory at Neuilly. 
 
 Pressing and Purification. The distilled products are separated according to their 
 different degrees of purity. The first distillate with a melting point of between 54'5 
 and 56 can at once be used for candle making, but the after distillates, containing 
 liquid and coloured acids, must be first cold pressed and then hot pressed. 
 
 The pressed cakes are melted in large tubs with water, which has had the lime 
 previously precipitated with oxalic acid. 
 
 The following table gives the quantity obtainable from the raw material by the 
 sulphuric acid treatment : 
 
 Soap suds obtained by wool washing from Eheims . . 50-55 per cent. 
 
 from Tourcoing . 47-50 
 
 Thick olive oil . . 55-60 
 
 Palm oil 75-80 
 
 Fat from slaughter houses 60-66 
 
 Oleic acid from stearin works 25-30 
 
 Decomposition of Fat by Superheated Steam. After Tilghmann had found that 
 fatty bodies could be decomposed by superheated steam, various pieces of apparatus were 
 devised wherein this action was technically employed. Tilghmann subjects a mixture 
 of the fatty body and water, circulating in a system of tubes, to a heat of from 330 
 to 350. The decomposed liquid is then passed through a spiral cooler, where it is 
 cooled to 1 00 ; thence it passes to a receiver in which the two layers aqueous and 
 fatty can be separated. 
 
 Wilson and Gwyne heat the fatty bodies in retorts to 290 to 315 and then 
 pass, for twenty-four to thirty hours, steam heated to 315. The escaping vapours 
 are condensed in a worm. This method is used in England and in Eussia. 
 
 One hundred pounds of tallow should give sixty-six pounds of stearic acid, against 
 45 to 50 per cent, by the older process. 
 
 Manufacture of Candles. The operations merely consist in melting and shaping the 
 material of which the candles are to be made, and at the same time inserting a cotton 
 wick in the centre of the candle. Besides tallow and the fats prepared in the manner 
 already described, several other materials are used for making candles, such as wax, 
 spermaceti, paraffin, etc. 
 
 Dipped Candles. 15 to 20 wicks suspended from a thin stick of light wood are 
 dipped all together into tallow which is just at the point of solidification. The wicks 
 with adhering tallow are brought out and cooled and the operation of redipping and 
 cooling is successively performed until each candle is considered to be of sufficient 
 thickness and of the required weight. Dipped candles are conical in shape, and 
 are thinner at the top than at the bottom. They are cheap and in some places still 
 preferred. 
 
 Moulded Candles. A very gentle heat is sufficient to melt the tallow which is used 
 for this purpose. The moulds are prepared, slightly conical in form, from an alloy of 
 one part tin and two parts lead. Through each mould passes a wick of twisted 
 cotton thread, which, in order to keep it in position, is fastened to a cross bar above 
 and below to a plug, which at the same time serves as a stopper to the aperture. 
 The moulds are suspended in great numbers from a frame, and the tallow, in not too 
 hot a condition, is run in through a funnel at the top. The tallow having cooled, 
 the candle is removed from the mould and the funnel-shaped head is cut off. The 
 candles are now ready to be packed, and in such a way that from 6 to 12 equal a 
 pound. The weight of cotton used is in the proportion of 1 part of cotton to 100 
 parts of tallow. 
 
 Stearin Candles. The wicks used in these candles are generally made of twisted 
 or plaited cotton threads, but sometimes, though seldom, of flax or hemp. The 
 twisted wick is merely a screw-like thread, but in the plaited wick the separate 
 threads twine through each other. Cambaceres devised a method in which the wick 
 was thin and so strongly plaited, that the tip of the wick turned to the outside of the 
 flame and was consumed as the candle burnt down, so that it was not necessary to 
 cut off the wick from time to time, as is required with the old twisted wicks, to 
 prevent the obscuration of the flame by the deposition of soot. That the wicks may 
 burn quickly and completely, they are dipped in an oxidising material such as salt- 
 petre, chlorate of potash, etc.; also to prevent the inflation of the carbonised wicks, 
 they are treated with such substances as boric acid, borax, sal ammoniac, phosphate 
 and borate of ammonia, which melt with the ashes and fall aside from time to time. 
 
CANDLE MAKING. 
 
 .677 
 
 It is essential that the thickness of the wick should be in the right proportion to 
 the thickness of the candle. If it be too thin, a higher rim of unmelted tallow is 
 formed round the candle : if it be too thick, no rim is formed at all, but the tallow 
 continually gutters. 
 
 For candle making the stearic acid is melted on the water bath, and mixed with 
 1 to 5 per cent, of wax, or with paraffin in quantities up to 20 per cent. The further 
 addition of such poisonous compounds as arsenious acid a plan formerly adopted 
 has now been abandoned. The object of adding wax and paraffin is to destroy the 
 crystalline structure of the stearic acid, and thus to render the candles less brittle and 
 capable of burning more evenly. The stearic acid before being cast into the moulds 
 is brought into a semi-solid condition which prevents in some degree a crystalline 
 solidification of the mass. 
 
 The moulds (fig. 449) with the exception of having a larger funnel are similar to 
 those used for tallow candles ; a new form of mould recently in use has one funnel for 
 thirty candles (figs. 450 and 451). In the upper part of each mould is a small disk, a a! 
 (fig. 448), with a centre hole through which the wick is drawn and fastened there by 
 being tied in a knot ; at the bottom the wick is kept in its place by a small peg ; 
 instead of using the perforated plate at the top, the wick is sometimes 
 FIG. 448. fastened to a small holdfast. In order to obtain well-made candles, it 
 <-^ is essential that the wicks should be held accurately in the axes of the 
 fc|) moulds while they are being filled with the melted fat, so that after its 
 solidification the wicks of the candles are in the centre throughout the 
 whole length. 
 
 FIG. 449. 
 
 FIG. 450. 
 
 FIG. 451. 
 
 Before fixing the wicks, it is necessary to steep them in the solutions which shall 
 serve the object of causing a steady combustion ; and of the substances previously 
 mentioned as serving this purpose, it is the custom to use boric acid. 
 
 The moulds with the wicks fastened in them are placed in a cast-iron vessel which 
 can be so arranged as to be heated to 100 with water or with steam from the outside. 
 To this end a great number of such vessels are placed air tight in a large wooden vat 
 in which steam can play round the cast-iron vessel (c c, figs. 450 and 451). The fatty 
 acids are run in as soon as the air bath is at 45. The tap r allows the air to escape, 
 and / the condensation water. 
 
 Instead of using steam in this way, the moulds may be heated in a water bath or 
 in an air bath heated by hot pipes. 
 
 After being cooled the pegs are taken from the bottom of the moulds, and the wicks 
 cut off underneath the disk a a. The waste cuttings, etc., are melted with tartaric 
 acid either in a silver-plated or in a porcelain vessel and utilised at the next moulding. 
 Should the candles adhere to the moulds, hot water must be applied externally. 
 
 The very short thick candles called night lights are made by ruiming melted 
 fat into metal moulds, or into paper cases of the requisite size, and, after the fat has 
 solidified, the wicks, previously soaked in wax, are passed through the centre. 
 
 Moulding machines are now generally in use in stearin candle factories. One 
 of this kind, the machine of Cahouet and Morgane, is shown in fig. 452. A A is the 
 mould frame for 200 candles, having one filling funnel for every 20 moulds. The 
 separate moulds are fixed between the plates a a and b b. At the bottom of the 
 machine are reels for unwinding wicks, which are fastened above the plate a a by 
 means of two rails pressed together, and capable of being drawn upwards by the 
 lever arrangement h h on the stand K, which can be set in operation by the rack and 
 pinion i. In the filling operation, the wicks are held and stretched above the moulds 
 by the iron rails. By opening the cocks//, steam passes from the main pipe e into 
 
678 
 
 FAT AND OIL. 
 
 
 the moulds. The steam is first passed in to warm the moulds, then, after turning 
 it off, the stearic acid is run into the moulds. Cold air is passed through from 
 the ventilator g in order more quickly to cool the moulds. After complete solidifica- 
 
 tion, the wicks are drawn up by means of the above-mentioned apparatus h h, 
 and with them the candles from the moulds ; while simultaneously the necessary 
 wicks for the next casting are drawn through. There only remains the final opera- 
 tion of cutting off the wicks above the rails and the tops of the candles. 
 
 Of the many other machines for this purpose it will suffice here to mention the 
 American moulding machine of Francis Saase. The essential parts are the same as 
 in the machine previously described, except that the finished candle is not removed 
 
CANDLE MAKING. 
 
 679 
 
 from the mould by the wick, but is pushed out by a peculiar contrivance, worked 
 from below, consisting of a short metal barrel that also serves to conduct the wick 
 from the reel to the mould, and having on the upper end a tin cone which exactly 
 fits the mould and forms the bottom. After the solidification of the stearic acid the 
 metal pipe is pushed upwards by a mechanical movement carrying with it the moulded 
 candle now ready for removal. With the machine of Cahouet and Morgane, two 
 persons are required, and can turn out 600 candles per hour, whilst one man can 
 work four machines of Saase's and mould 1,200 candles per hour. 
 
 The candles are sometimes bleached by exposure to air and light, but this is an 
 operation not always carried out. 
 
 Fig. 453 represents a machine for cutting and polishing. The candles having 
 been placed in parallel layers in the box A, fall one after another into the gutter of 
 the cylinder B, immediately under the circular saw c, which cuts off the ends : they 
 then fall upon the woollen cloth drawn over the rollers a a G G and H H. The three 
 large cylinders D D' D", also covered with woollen cloths, revolve in an opposite direction 
 to G, at the same time moving quickly backwards and forwards in the direction of 
 
 FIG. 453. 
 
 their longitudinal axes. In this way the candles passing between two friction cloths 
 and being rubbed lengthways by the roller G, now fall quite polished and ready for 
 packing into the box I. 
 
 The Various Kinds of Candles. Coloured Candles. The dyeing material is placed 
 in the melted fatty body before the moulding process. According to Vohl, the follow- 
 ing compounds are the pigments used. For red, cinnabar, minium dragons blood, 
 and alkanet root ; for rose colour, madder lake and madder ; for yellow, chromate of 
 lead sulphide of arsenic, chromate of zinc and turmeric ; for green, Schwemfurt 
 green stearate of copper, verdigris, and a mixture of Berlin blue and chrome yellow ; 
 for blue, ultramarine. Amongst those named are some poisonous compounds, such 
 as cinnabar, sulphide of arsenic, Schweinfurt green, and the use of them should be 
 
 V ThV names ' Star,' ' Milly ' and ' Apollo,' applied to stearin candles, have been 
 derived from the Barriere d'Etoile, Paris, where De Milly started the first stearin 
 candle works, and from the ' Apollo Company,' Vienna. 
 
 Palm candles are made of the fat acids prepared from palm oil. 
 
 The English composite candle is made from a mixture of stearic acid and cocoa- 
 nut stearin ; it has the lowest melting point of any kind of stearin candle. 
 
 Plated Tallow Candles. These are not moulded but dipped, as in the ordinary 
 dippin^ process, successively in three mixtures wherein the proportion of tallow de- 
 creases^ the stearic acid increases, by which means a core of easily melting material 
 is coated by a less fusible substance. Composition of the three mixtures : 
 
 Stearic acid . 
 Tallow . . 
 Dammara resin 
 White resin . 
 White wax . 
 Camphor . 
 
 1 
 
 50 
 44 
 
 2 
 70 
 
 3 
 
680 FAT AND OIL. 
 
 Another method consists in filling moulds with stearic acid and allowing it to 
 remain there sufficiently long to form a hard coating ; then the unsolidified portion 
 is turned out and its place filled with melted tallow. 
 
 Treatment of the Undistilled Residues. The brown tarry retort residues obtained 
 in the distillation after the sulphuric acid treatment can be used for the manufacture 
 of illuminating gas ; for this purpose, according to Payen, it is mixed with sawdust 
 impregnated with the residue from the purification of rape oil. The residue without 
 doubt could be used in the manufacture of common soap or as a japan for leather. 
 If the dried residue be mixed with sawdust, and then extracted with carbon bisul- 
 phide, an appreciable quantity of fatty acids is obtained after distilling off the 
 carbon bisulphide at 48 or 50 ; the fatty acids can be then easily distilled by super- 
 heated steam. 
 
 The liquid oil obtained by cold pressure from crude fatty acids consists essentially 
 of oleic acid, and can be used, partly as burning oil, partly for soap making. It is 
 worthy of remark that for these purposes the oil obtained by the lime process is 
 preferable to that which is prepared by the decomposition of the fatty body with 
 sulphuric acid. 
 
 Estimation of Paraffin in Stearin Candles. As it is now the custom to a very 
 large extent to mix paraffin with stearic acid, it is important to have the means of 
 qualitatively and quantitatively estimating both. E. Wagner has a qualitative 
 method, in which the mixed bodies are dissolved in alcohol, heated to boiling, and 
 mixed with an alcoholic solution of neutral acetate of lead. The presence of stearic 
 acid is indicated by a flocculent precipitate, whilst pure paraffin gives no precipitate. 
 Unfortunately, as a practical method, this is of but little use, as it is much more 
 requisite to detect the presence of paraffin in stearin than of stearin in paraffin. 
 
 Hock gives the following method (Wagner's Jahresber. 1871, p. 858) for the 
 qualitative and quantitative determination of paraffin in stearin. 5 grams of the 
 mixture are saponified by potash ley of tolerable strength ; the soap and the paraffin 
 are precipitated by a concentrated solution of common salt, filtered, and the residue 
 washed with cold water or with very dilute alcohol. The common salt and the soap 
 are in solution whilst the paraffin remains behind on the filter. It is dried at 30 
 to 40, and then dissolved in ether, filtered, and the ether evaporated in a porcelain 
 capsule. The weight of the residue expresses the quantity of paraffin in 5 grams 
 of the substance ; the amount of stearic acid is obtained by difference. 
 
 Wax Candles. The kinds of wax occurring in commerce are of various origin and 
 differ in their composition as well as in their physical and chemical properties. The 
 most important are the following : 
 
 Sees' Wax. This is formed in the plant from which it is collected by the bees 
 and stored in the honeycomb. From the comb the wax is separated by a simple 
 melting operation. Native wax, especially that produced by young bees, is of a light 
 yellow colour, but the foreign sort is of a darker hue. It is brittle and granular; it 
 begins to soften at 30 and melts at 62 to 63. In ether, carbon bisulphide, benzol, 
 fatty oils and in fats it is easily soluble ; alcohol dissolves only a part, viz., cerotic 
 
 C* TT O ) 
 acid, 27 "TT [ 0, formerly called cerin, with some palmitic acid ; the insoluble part 
 
 consists essentially of myricylic palmitate, O. There is a third constituent 
 
 existing to a small extent, but of a composition still less understood. The varying 
 quantity of the different constituents in wax of course affects the melting point. The 
 best European bees' wax comes from Turkey and the Danube (Moldavia, Wallachia, 
 Hungary, etc.) North Germany produces very good wax, but that from South Ger- 
 many, Spain, and from France is very little valued. America, Asia Minor, Egypt, 
 Morocco, and Barbary also supply very good wax. 
 
 Chinese Wax, or, Pe La wax, is collected by the wax insect (Coccus ceriferus), and 
 deposited upon certain trees (Ehus succedanea). It is white in colour, hard and 
 crystalline in fracture, and melts at 82 ; it is soluble in ether. It essentially consists 
 
 of cerotylic cerotate, jg 0. 
 
 Japanese Wax (also called American) occurs in round disks ; it is white and brittle, 
 soluble in boiling alcohol, and melts at 42. It is probably a glyceride (glycerilic 
 palmitate ?) Another kind of vegetable wax is obtained from the rind of the fruit 
 kernels of various trees, called by the Japanese lacquer trees. Sometimes the rind 
 is removed from the kernels and steamed and pressed separately ; sometimes the 
 whole kernel is so treated. The wax separates as a bluish-green mass, which is 
 purified by boiling it with alkali and then pouring it into cold water, when the wax 
 separates from the impurities and floats on the top of the water. It is then bleached 
 
WAX CANDLES, ETC. 681 
 
 by exposure to the sun, and the resulting white powder is melted to form a homo- 
 geneous mass. 
 
 Carnauba^ and Ociiba Wax both come from Brazil. The first forms a coating on the 
 leaves of a kind of palm (Corypha cerifera). In consequence of its high melting point 
 (83'5) it is used to raise the fusibility of a low-melting wax. 
 
 Ocuba wax occurs in the nut of a shrub growing on the banks of the Amazon in 
 the province of Para ; it is green in colour and melts at 36 to 48. 
 
 Myrtle Wax is extracted by boiling, from the berry of Myrica cerifera occurring in 
 the Southern States of North America. Its melting point is 46. 
 
 Palm Wax is scraped from the bark of a palm (Ceroxylon andlcola) found growing 
 on the Cordilleras. It melts at 83 to 86. 
 
 Andaquies Wax somewhat resembles bees' wax ; it is produced by an insect met 
 with on the banks of the rivers Orinoco, Amazon and Magdalene. Its melting point 
 is about 77, and it therefore offers a very good candle-making material. 
 
 Wax Refining. The object to attain is the separation of mechanical impurities. 
 For this purpose the wax is melted in hot water, to which is added per cent, of alum 
 or tartar, and occasionally sulphuric acid. The mixture is allowed to settle, when the 
 impurities fall to the bottom and the wax floats on the surface ; after cooling it may 
 either be rernelted or at once bleached. 
 
 Wax Bleaching. The primitive method of sun -bleaching is still in use by prefer- 
 ence over any artificial process. 
 
 In order that a large surface may be exposed to the sun, it is usual to roll the 
 wax in thin sheets, and for this purpose the melted wax is poured through a vessel 
 having fine slits in the bottom on to a moistened roller on which it immediately solidifies 
 in the form of bands, and thence falls into a vessel of water placed underneath. In 
 this form the wax is exposed on linen sheets to the sun, and once daily sprinkled with 
 water. As only the surface exposed to the sun is bleached, it is necessary to re-melt 
 the wax, and go once or twice through the operation. In 20 to 40 days, according to 
 the weather, the bleaching is completed. The wax is then melted, passed through a 
 hair sieve, and cast into the required form. The loss in refining and bleaching by 
 the process described varies from 2 to 10 per cent. 
 
 Many ways have been suggested for artificial bleaching, but as yet they have not 
 been able to supersede the old method. Chlorine, bleaching powder, etc. cannot be 
 employed, as they all tend to the decomposition of the wax. The best method, how- 
 ever, is by means of hydrogen peroxide, which is developed by melting the wax with 
 oil of turpentine, rolling as before, and then exposing to the air. Other processes, 
 such as the use of sulphuric acid and bichromate of potash or permanganate of potash, 
 give but unsatisfactory results. 
 
 Wax Candles can be prepared by (1) pouring the wax on the wicks, (2) by 
 drawing the wicks through the wax, (3) by moulding, (4) by pressing the wax 
 through a mould. 
 
 The P o u r i n g-o n P r o c e s s. The wicks are suspended by hooks from a revolving 
 ring, and the melted wax is poured on by a ladle from the- top and allowed to solidify 
 on the wicks. To ensure the uniform thickness of the candles the wicks are turned 
 and the pouring on commenced again, until the candle is sufficiently thick. Fre- 
 quently to save time and labour the wax is poured on at one operation, but great skill 
 is necessary to do this. That the wicks may remain free at the ' burning-end,' they 
 are fixed in small tin-plate caps. The still warm candle is now rolled until smooth 
 between woollen cloths on a marble slab table by means of smooth boards. Having 
 been so polished they are then bleached by exposure to air and light. 
 
 The drawingprocessis used for the most part for wax tapers and festival candles, 
 and for these purposes the wax is almost always mixed with resin and turpentine, 
 or with tallow. The wick is wound from a roller through melted wax contained in a 
 heated copper vessel, thence through the hole of a horse-shoe-shaped drawing-plate, 
 containing larger holes, on to another cylinder placed on the opposite side to the first. 
 From the drawing-plate it again passes through the wax bath, and a larger hole of the 
 horse-shoe on the first cylinder, and so on until the end of the operation. 
 
 The moulding of wax candles, an operation similar to that described for tallow 
 and stearine candles (p. 677) is accompanied by the disadvantage of the wax 
 shrinking; in consequence, hollow places are liable to form near the wick, and the wax 
 clings to the mould. This .can be prevented to some extent by first dipping the 
 wicks in wax and also by using glass moulds. 
 
 The method of enwrapping the wick with bands of wax is still generally em- 
 ployed for the manufacture of large candles. Soft wax is made in long strips on 
 which the wick is placed lengthways ; the wick, having been covered with wax, the 
 mass is then rolled on the marble-topped table until it has acquired the cylindrical 
 
682 FAT AND OIL. 
 
 form. Another method is to take the cylinder of wax and to make a hole through 
 the middle, then pass the wick through and fill in with melted wax. 
 
 Wax Candle Pressing. The machine devised by Kiess for this purpose is shown in 
 fig. 454. It consists of a jacketed chamber (H), with a bent tube (T) for carrying the 
 wicks ; L, the tube for passing steam to the jacket (j) of the press cylinder ; M is the 
 pipe for efflux of condensation water ; j, is the mould. The kneaded wax is poured 
 from the side into the press chamber H, where it is made hot by the surrounding steam 
 
 and pressed by means of a piston through 
 the conical end of the pressing chamber. 
 Simultaneously with the wax the wick is 
 drawn through T into the mould (j y ), and en- 
 veloped by the wax from T by a concentric ; 
 the strongly pressed candle roll is then 
 passed over a roller, through cold water, to 
 cool it. Other sized mouthpieces can be 
 screwed on at T in order to vary the make 
 of candles. This apparatus is specially 
 adapted for the manufacture of wax 
 tapers, and surpasses the older process 
 above described, by the production of four 
 to six times as many during the same time. 
 The colouring materials used for wax aro 
 the same as for stearin. 
 
 Wax is frequently adulterated with 
 cheap materials, as rosin, paraffin, tallow, 
 FIG. 454. stearic acid, Japanese wax, etc. For the 
 
 detection of paraffin, Landolthas proposed 
 
 a plan based on the decomposition of wax by fuming sulphuric acid, and on the 
 paraffin being unaltered by this treatment ; the plan is only a qualitative test for the 
 detection of a large quantity of paraffin. 
 
 Donath recommends the following method for the detection of impurities in wax. 
 A piece of the wax, about the size of a nut, is boiled for five minutes with a concen- 
 trated solution of carbonate of soda. Thereupon one of two things may occur : either 
 (A) an emulsion is formed remaining when cooled, and giving evidence of the presence 
 of rosin, tallow, stearic acid, or Japanese wax ; or (B) the wax swims completely as 
 a fatty layer on the surface of the liquid, which is only somewhat yellow in colour, 
 showing the wax to be pure or adulterated only with paraffin. 
 
 To determine the point (A) the suspected wax is boiled for a minute or so, with. 
 moderately strong potash ley, afterwards adding common salt. If a complete iloc- 
 culent separation of soap (a) is produced, it is shown that all the substances under CA) 
 excepting Japanese wax may be present; (6) a fine granular magma shows the pre- 
 sence of Japanese wax. (B) the detection of paraffin is best determined according to 
 E. Wagner, by taking the specific gravity of the wax. If it be so low as 0'96, it can 
 be assumed, in conjunction with the evidence given by the carbonate of soda treatment; 
 that paraffin is present, and in such a case a-n estimate of the quantity of paraffin can 
 be formed. On this principle K. Wagner has tabulated results of such admixtures 
 deduced from the specific gravity. 
 
 Spermaceti Candles. Spermaceti occurs in the bone cavities in the head of the 
 whale, under its skin from the head to the tail, and in the flesh and blubber. Ir, 
 remains dissolved in the oil by the natural heat of the whale, but separates out when 
 life is extinct. The crude solid spermaceti is purified by pressing away the oil and 
 treating the residue with soda or potash ley, which saponifies any remaining oil. It 
 is then washed with water, and the now purified spermaceti solidifies on cooling. 
 About five tons of oil are obtained from one whale, and this yields 30 to 40 cwt. of 
 solid spermaceti. 
 
 Pure spermaceti is white and crystallises in laminae, having a mother-of-pearl ap- 
 pearance with a fatty feel. It melts at 48 and distils almost unchanged at 360; 
 it is soluble in alcohol. In its chemical composition it is cetylic palmitate, having 
 
 P TT O ) 
 
 the formula ^ IV [ 0, but it also contains a small quantity of another fat acid 
 
 ss 
 other, with more carbon atoms. 
 
 Moulding Spermaceti Candles. The operation is somewhat similar to that followed 
 with stearine candles, except in this case it is necessary to afterwards run in spermaceti 
 in the cavities round the wick, in consequence of the great contraction of spermaceti. 
 The candles are taken from the moulds and polished by hand friction. It is 
 customary to mix about 3 per cent, of wax or stearic acid with the spermaceti, to 
 
PETROLEUM ; PARAFFIN, ETC. 683 
 
 destroy its crystalline texture. Spermaceti candles are very dear, but surpass all others 
 by their alabaster appearance. They are used in large quantities, especially in 
 England, by the wealthy classes. 
 
 Paraffin Candles. The material known in commerce by the name of paraffin, 
 and used for making candles on account of its similarity to wax and spermaceti in 
 physical characters, consists of carbon and hydrogen combined in nearly the same pro- 
 portions as in olefiant gas ; but it is probably a mixture of several distinct hydrocar- 
 bons belonging to the marsh gas series, differing from the liquid and gaseous members 
 of that series only in state of aggregation, and in the number of atomic proportions of 
 carbon and hydrogen in the molecules, after the manner of homologous substances gener- 
 ally. The term ' paraffin ' is therefore now employed by chemists as a generic designation 
 of all the substances belonging to the marsh gas series, and it is only in regard to the 
 technical application of those which are solid within the ordinary range of temperature, 
 as candle material, that the name has a limited significance ; in the same manner, 
 since some of the liquid paraffins are used for burning in lamps, or for lubricating 
 machinery, etc., they are also called paraffin oil. 
 
 Solid paraffins occur naturally as the minerals ozokerite or earth wax, and 
 associated with liquid paraffins, as constituents of the various kinds of petroleum, 
 and probably also as constituents of the volatile oils obtained from some plants. 
 These substances also exist among the products obtained by the action of heat upon 
 substances of organic origin, such as wood, and consequently they are present together 
 with liquid paraffins, etc., in the tar resulting from the destructive distillation of 
 peat, coal, bituminous shale, etc. The crude solid paraffin obtained from any of these 
 sources often varies considerably in hardness and fusibility ; and for making candles it 
 requires to have the softer and more fusible portions separated. Its preparation forms 
 a part of the hydrocarbon oil manufacture described below. 
 
 Candle paraffin is a colourless or bluish-white translucent substance, destitute of 
 smell or taste ; when warmed it softens and then melts, at temperatures ranging from 
 30 to 60 according to the source from which it has been obtained and the extent to 
 which the more fusible portions have been separated. The specific gravity varies from 
 870 to -912. Paraffin is insoluble in water, and but sparingly soluble in cold 
 alcohol, but it is copiously soluble in ether, turpentine, carbon disulphide, and hot 
 alcohol. At ordinary temperatures it is not acted upon by concentrated acids or alka- 
 lies ; it boils at a temperature above 300, and is partially decomposed when distilled. 
 
 HYDROCARBON OILS ; PARAFFIN," ETC. Materials of this kind, obtained either by 
 the rectification of natural petroleum, or by the destructive distillation of wood, peat, or 
 bituminous minerals, are now largely used as substitutes for candles, and for the differ- 
 ent kinds of fat oils which were formerly the only source of artificial light. 
 
 The first impulse was given to this industry by Eeichenbach, who, in 1830, pre- 
 pared from beech wood tar both solid paraffin and an oil that could be burnt in 
 suitably constructed lamps. But, owing to the small amounts in which these products 
 were obtainable from tar or from the bituminous minerals then known, the various 
 attempts made to bring them into practical application proved unsuccessful, until 
 materials capable of yielding a larger amount of oily products were discovered. 
 Among these the principal were a remarkable bituminous mineral, occurring in the 
 coal measures at Boghead, in Scotland, and the tertiary coal or lignite occurring in 
 several parts of Germany. 
 
 Not long after the industrial production of these hydrocarbon oils, etc., from bitumi- 
 nous minerals had become established, a further source of supply was furnished by 
 the discovery of the vast deposits of petroleum in America, and at the present time, 
 the liquid hydrocarbons analogous to- paraffin, and associated with it in petroleum, as 
 well as in the products of distillation, are very largely used for burning in lamps. 
 
 Petroleum or mineral oil occurs in many parts of the earth as a dark-coloured in- 
 flammable liquid, possessing a bituminous smell and various degrees of density, from 
 0*7 to I'l. Some kinds that are thin and but slightly coloured, are known by the name 
 of n aphtha, while other kinds that are viscid and almost black are termed mineral 
 tar. These different kinds of mineral oil occur chiefly in North America, Persia, the 
 Caucasus, Georgia, Burmah, the Carpathians, Italy, some parts of Germany, and 
 Switzerland, as well as in France and England to some extent. 
 
 The petroleum of Pennsylvania is a dark brownish-coloured mobile liquid having a 
 specific gravity varying from '782 to '820, and a peculiar greenish fluorescence. Some 
 of the petroleum occurring in America has a greater density ; for instance, that known 
 as Mecca oil, which is a thick viscid liquid having a specific gravity of from -860 to 
 910, and some of the Californian petroleum has a specific gravity of '927. The 
 petroleum of Canada has a very offensive odour, owing to the presence of sulphuretted 
 compounds which render its purification difficult. 
 
 In America petroleum is obtained by boring deep wells, constructed in the same 
 
684 
 
 ARTIFICIAL LIGHTING MATERIALS. 
 
 manner as artesian wells, until a deposit of petroleum is tapped, and then it either 
 rises to the surface and flows out in intermittent gushes, constituting what is termed 
 a flowing well, or the petroleum has to be raised to the surface by means of a pump. 
 The quantity obtained from these wells is sometimes very large. One of the great 
 flowing wells at Enniskillen yielded as much as 600,000 gallons when first opened, 
 but it was soon exhausted, and the greater number of wells yield only from 400 to 
 800 gallons daily, though some few have yielded as much as 4000 gallons a day. 
 
 In Wallachia petroleum is obtained from strata about thirty feet below the surface, 
 and the wells are made by sinking square shafts lined with timber like rude water 
 wells, and fitted with a windlass above, by means of which the petroleum gradually 
 oozing into the well from the adjoining strata is from time to time taken out by 
 buckets attached to a rope wound upon the windlass. Petroleum is also obtained in 
 this way in Moldavia and Galicia along the entire range of the Carpathians. That 
 best suited for refining has a specific gravity of about -803, but some kinds are thick 
 and much denser, and they are used chiefly for greasing cart-wheels, etc. 
 
 Chemically, the materials known as naphtha, petroleum, etc., are all very closely 
 allied, inasmuch as they consist for the most part of homologous liquid and solid 
 hydrocarbons, differing chiefly in density and volatility. The petroleum of America, 
 as well as that of the Carpathians, consists chiefly of substances homologous with 
 marsh gas, and those which have been isolated present the following characters : 
 
 Formula 
 
 Specific gravity 
 
 Boiling point 
 
 Yapour density 
 
 Authority 
 
 Marsh gas CH 4 
 C 2 H 6 
 
 gaseous. 
 
 
 
 E( 
 
 Eonalds. 
 
 CH 8 
 
 0-600 
 
 0-4 
 
 2-lloJ 
 
 
 C H 12 
 
 628 
 
 30 
 
 2-5381 
 
 
 
 C 6 H 14 
 
 669 
 
 68 
 
 3-050 
 
 
 
 
 699 
 
 92-94 
 
 3-616 
 
 
 
 C 8 H 8 
 
 726 
 
 116-118 
 
 4-009 
 
 
 
 C 9 H 20 
 
 741 
 
 136-138 
 
 4-541 
 
 
 Pelouze 
 
 C 10 H 22 
 
 757 
 
 160-] 62 
 
 5-040 
 
 
 and 
 
 C n H 24 
 
 766 
 
 180-184 
 
 5-458 
 
 
 Cahours. 
 
 C 12 H 26 
 
 776 
 
 196-200 
 
 5-972 
 
 
 
 
 792 
 
 216-218 
 
 6-569 
 
 
 
 C 14 H 30 
 
 
 
 236"240 
 
 7-019 
 
 
 
 C 15 H 32 
 
 
 
 255-260 
 
 7-523J 
 
 
 The various kinds of petroleum also contain other liquid substances of higher 
 boiling point, and of a specific gravity sometimes exceeding -900. They likewise 
 contain in most instances solid* hydrocarbons, varying in amount from 2 to 10 per 
 cent, and upwards, together with pitchy and resinous substances. 
 
 The dark coloured oily product obtained by the destructive distillation of wood, 
 peat, or coal and other bituminous minerals and commonly called tar, contains sub- 
 stances identical with those existing in petroleum, together with resinous and pitchy 
 substances, carbolic acid, creasote, nitrogenous bases, etc., the nature and relative 
 proportion of these constituents varying with the kind of material submitted to 
 distillation, and the temperature at which this operation is carried out. The amount 
 of tar obtainable by destructive distillation depends largely upon the amount of 
 hydrogen in the material operated upon, the relative proportion it bears to the carbon, 
 and the amount of oxygen present. The larger the proportion of hydrogen to carbon 
 and the smaller the amount of oxygen, the greater as a rule is the yield of tar, and 
 distillation at a moderate heat only just sufficient for decomposition gives a larger 
 amount of tar than is obtained at a higher temperature, which has the effect of de- 
 composing the oily products to some extent and converting them into permanent gas, 
 "while at the same time furnishing tar of a very different character. Thus in the 
 manufacture of illuminating gas by distilling coal at a very high temperature so as to 
 obtain the largest possible amount of gas, the tar obtained is of a totally different 
 nature from that produced at a lower heat, and at the same time a very much 
 smaller amount is obtained. 
 
 In the manufacture of hydrocarbon oils, etc., from petroleum, this material is at 
 once submitted to distillation for the purpose of separating the most volatile and the 
 least volatile portions of the petroleum from that portion of the oil which is suitable 
 for burning in lamps ; but in manufacturing these products from bituminous minerals 
 it is first necessary to submit the material to destructive distillation and then to 
 operate upon the oily tar thus obtained. 
 
 ; 
 
OIL FROM COAL, SHALE, ETC. 685 
 
 It is of course essential that the materials employed for producing the t ar or crude 
 oil should be capable of yielding it in sufficient amount. The most productive minerals 
 are cannel coal, and some kinds of bituminous shale and lignite. Peat has 
 also been used for the purpose, but generally speaking it yields too little to be worth 
 working. The tar obtained by distilling wood is not suitable for the manufacture of 
 hydrocarbon oils, etc., for though it contains these substances together with solid 
 paraffin, they are associated with a very large proportion of resinous impurities that 
 are difficult to separate. 
 
 Several varieties of Scotch cannel coal yield a fair amount of crude oil by distilla- 
 tion, but it is chiefly in North Wales that cannel coal has been used for this purpose. 
 That occurring in Flintshire is of three kinds : the curly cannel, which yields about 
 30 per cent, of crude oil, having a specific gravity ranging from -875 to '890, smooth 
 cannel, and bastard cannel, which is more of the nature of shale. The second yields 
 about 16 per cent, of crude oil, of a specific gravity from -925 to -940, and the third, 
 which is now most used for distillation, yields from 12 to 15 per cent, of crude oil, 
 having a specific gravity of about '900, In Scotland extensive beds of bituminous 
 shale occur, associated with coal, and this mineral is largely used for the production 
 of crude oil. The Boghead coal or Torbanehill mineral formerly used for this purpose 
 is now worked out. 
 
 These minerals appear to differ from coal chiefly in regard to the proportion of 
 earthy material according to which the applicability of bituminous minerals as fuel is 
 mainly determined. 
 
 Lignite or brown coal often yields a considerable amount of tar or crude oil by 
 distillation, especially those kinds in which the ligneous tissues of the plants they 
 originated from have been very considerably altered. On the contrary, those kinds 
 of lignite which have undergone but little alteration yield on distillation products 
 analogous to those obtained from wood. 
 
 The lignite, or brown coal, most suitable for the production of oil tar by distilla- 
 tion, occurs in Saxony, and beds varying from half a fathom to four fathoms in thick- 
 ness extend from the neighbourhood of Weissenfels as far as Zatz. Inferior varieties 
 of the same mineral are obtained also in some other localities. 
 
 As regards the chemical composition of this mineral, it is distinguished by the 
 high percentage of hydrogen it contains, amounting sometimes to 1 1 per cent., while 
 ordinary brown coal does not contain above 6 per cent. The finest kind, which is 
 termed pyro pis site, is characterised by a smeary consistence and pale yellow 
 colour ; in the fresh state it contains as much as 70 per cent, of water, and when 
 dried it is almost white, earthy, and of light density. This material melts at 150 or 
 200 to a black vesicular mass ; it readily takes fire, and burns with a white smoky 
 flame, emitting a slightly empyreumatic odour ; on distillation it yields from 18 to 26 
 per cent, of an almost colourless oil, that can easily be worked up into marketable 
 products. Generally, the material submitted to distillation for producing oil is less 
 productive, yielding only from 9 to 18 per cent, of oily tar, which contains resinous 
 substances, carbolic acid, creasote, etc. 
 
 Peat has been used in several places as a material for the production of hydro- 
 carbon oils and paraffin by destructive distillation, but generally the amount of oil tar 
 obtainable is so small that the working of this material can only be carried on under 
 excepfionally favourable circumstances. The best kinds of dense peat, which approxi- 
 mate in composition to lignite, will yield from 5 to 8 or even 10 per cent, of tar when 
 carefully distilled ; but those kinds which are light and spongy, and in which the 
 woodv tissue of the mosses they consist of has undergone but little alteration, yield 
 very much less tar by distillation. 
 
 Ozokerite or earth wax occurs in various places, associated with coal, but generally 
 in small quantity. In Galicia and in Moldavia there are extensive deposits that are 
 worked as raw material for the manufacture of paraffin and hydrocarbon oils. The 
 colour and other external characters of the mineral vary somewhat, but it is generally 
 brown and compact, less frequently yellow or quite black, and sometimes it has a 
 fibrous or laminated texture. The melting point ranges from 60 to 80. Another 
 kind is of buttery consistence, and has a greenish brown colour. 
 
 Preparation of the Tar or Crude Oil. This is the most important operation in the 
 manufacture of mineral oil and paraffin from coal, shale, peat, or similar materials, 
 and though the process of destructive distillation appears to be very simple, it is in 
 reality a matter of some considerable difficulty to conduct it in such a manner as to 
 prevent the overheating and decomposition of the oil vapour. A great number of 
 different forms of apparatus have been devised for this purpose. 
 
 The construction and arrangement of the horizontal retorts are represented by 
 figs. 455 and 456. The retorts are made of cast iron, they are about 8 or 10 feet 
 long, from 28 to 34 inches wide, and from 9 to 14 inches deep. At the end where 
 
686 
 
 ARTIFICIAL LIGHTING MATERIALS. 
 
 the charge is introduced and the charred residue removed there is a cover (b b, fig. 
 455) fitted so as be closed air-tight while the distillation is going on. At the 
 
 FIG. 455. 
 
 other end is a pipe (c) for carrying off the product of distillation to a larger pipe (d) 
 communicating -with the condenser. 
 
 A number of these retorts are set together in a row, as shown on a smaller scale 
 in fig. 456, with a furnace (e) at one end, and flues (g gg) extending beneath the 
 retorts, while the upper parts of the retorts are covered with brickwork (h h h), to 
 prevent the oil vapour from being decomposed by the heat of the waste furnace gas 
 passing to the chimney through the flue above the retorts. 
 
 The mixture of oil vapour and uncondensable gas discharged from the retorts into 
 the pipe (d, fig. 455), passes through a number of iron pipes exposed to the air, or 
 cooled by means of a stream of water running over them, so as to condense the oil 
 which then runs into a reservoir while the uncondensed gas is discharged through an 
 outlet in the system of condensing pipes. In some works this gas is used as fuel, 
 or burnt for producing light. 
 
 The retorts are charged through the opening (b b), and the material to be distilled 
 is spread over the bottom of each retort in a layer about two inches thick. "While the 
 retorts are being charged care must be taken to prevent explosions from taking 
 place, in consequence of the mixture of atmospheric air with the combustible gas 
 and vapour given off. Steam is sometimes driven into the retorts while the distilla- 
 tion is going on, and this practice has the advantage of driving the oil vapour more 
 quickly out of the retorts into the condenser, but it is doubtful if the expense 
 attending the use of steam is not out of proportion to the benefit realised. 
 
 The vertical retorts are formed of cast-iron cylinders, set upright in brickwork, as 
 shown in fig. 457. They are from 12 to 16 feet high, and from 3 to 6 feet wide. In 
 some cases these retorts are fitted inside with a system of rings (a a a), arranged in 
 such a manner that the coal or other material to be distilled is made to fall down 
 between the edges of these rings and the inside of the cylinder forming the retort, 
 which is heated by the flues (e e ee] extending round it and communicating with the 
 furnace (E). At the lower end of the cylinder it is connected with a conical fitting (B n) 
 into which the exhausted coal falls down from the rings (a ft). The bottom of this 
 cone is connected with the cylindrical box (D), having a damper both at the top and 
 bottom, so that the exhausted coal can be let down into the box and, after closing 
 the damper at c, discharged from the box by opening the lower damper, The vapour 
 
OIL FROM COAL, SHALE, ETC. 
 
 687 
 
 given off by the material distilled escapes through the tubes (F G) into a main (H) 
 connected with the condenser. 
 
 Fia. 457. 
 
 The crude oil or tar obtained from bituminous shale or cannel coal is a dark-coloured 
 thick liquid of disagreeable smoky odour, and having a specific gravity ranging from 
 840 to '940 ; that best suited for refining has a gravity of about -890. 
 
 The tar from brown coal is yellowish brown, having the consistence of butter at 
 the ordinary temperature, and melting at from 25 to 40 into a brown liquid, which 
 
688 ARTIFICIAL LIGHTING MATERIALS. 
 
 has a dark greenish fluorescence^ The specific gravity varies from '820 to '870 and 
 upwards, but when it exceeds '900 the tar is not suitable for the preparation of burning 
 oil. The proportions of the several products obtained from it vary as follows : 
 
 Burning oil 28 to 35 per cent. 
 
 Heavy oil 10 to 15 
 
 Paraffin 15 to 17 
 
 The tar obtained from peat is almost black, and has a pungent disagreeable smell ; 
 at the ordinary temperature it is solid, and has a buttery consistence owing to the 
 large amount of solid paraffin it contains. 
 
 The character of the tar or crude oil produced by destructive distillation depends 
 not only upon the nature of the material from which it is obtained, but also to some 
 extent upon the mode in which the distillation is conducted. It is therefore necessary 
 to adapt the retorts to the kind of material to be worked accordingly. The amount 
 furnished by any given material is greater when the distillation is conducted slowly 
 at a low temperature than when the same material is exposed to a higher temperature. 
 The tar produced in vertical cylinders from which the air is excluded is lighter, 
 cleaner, and generally of better quality than that made in horizontal retorts, though 
 a larger yield is obtained with horizontal retorts, and the amount of paraffin in the 
 tar is larger. 
 
 For the purpose of preparing oil suitable for burning, etc., the natural petroleum, 
 or the tar or crude oil obtained by distillation of coal, lignite, shale, or other 
 materials, is first submitted to distillation, which has the effect of separating to a 
 great extent the pitchy and resinous substances that give to the materials in their crude 
 state a dark colour, thick consistence, and offensive smell. 
 
 At the same time the oil submitted to distillation may be separated into fractions, ac- 
 cording to the degrees of volatility and density that the refined products are required 
 to have, and the distillate is run into suitable receivers until only a very small residue 
 remains in the still, which is run out and used for making waggon grease. It is 
 undesirable to continue the distillation until the residue in the still becomes charred, 
 since that causes injury to the still bottom, and trouble in removing the coke formed. 
 
 The relative density of the several substances present in petroleum or shale oil, 
 etc., generally bears an inverse proportion to their volatility, those of least density 
 being the most volatile. This relation varies somewhat for different kinds of material, 
 but since in all cases the specific gravity of each successive portion of the oil distilling 
 over is greater as the operation advances, this character affords a means of ascertaining 
 the points at which the distillate should be collected apart from that whichhas already 
 passed over. 
 
 The oil subjected to distillation is thus separated into portions differing in degree 
 of volatility, density, etc., and on this account the operation is termed fractional dis- 
 tillation. The "most volatile constituents pass over at the commencement, and 
 since their presence in the burning oil would render it too readily inflammable for 
 burning in lamps with safety, this portion of the distillate is rejected until it pre- 
 sents a degree of density such as corresponds with the particular point at which the 
 collection of the oil for burning in lamps may be commenced. This is regulated ac- 
 cording to the nature of the material worked and the kind of product required. The 
 oil distilling over after this point has been passed is then run into another receiver, 
 and the distillation is continued until the gradually increasing density of the distillate 
 has again reached a point which indicates that all the oil which can be used for 
 burning in lamps has passed over. What then remains in the still is in many cases 
 drawn off into tanks and distilled separately, but sometimes the distillation is con- 
 tinued until the solidification of the distillate, on cooling, furnishes another indication 
 for collecting the remainder in a separate receiver. When the distillate begins to 
 show eigns of solidifying, the water in the condenser tank is allowed to become warm, 
 or, if necessary, it is heated by a jet of steam sufficiently to keep the distillate liquid 
 and prevent the stopping up of the worm, which might give rise to the bursting of 
 the still. 
 
 In this way the distilled oil is usually separated into four portions, viz. : 
 
 1. The light volatile oil or spirit known by the name ofbenzoline, etc. 
 
 2. Oil suitable for burning in lamps. 
 
 3. Oil having a specific gravity above *850, which is used for lubricating 
 machinery, etc. 
 
 4. Oil containing a considerable admixture of solid paraffin, which crystallises when 
 the oil is cooled, either at once or after some time. 
 
 The distillation of crude petroleum or shale oil is carried out in large vessels made 
 of cast iron or wrought iron, and in some cases superheated steam is forced into the 
 still during the operation. In America cylindrical wrought-iron stills holding 1,600 
 gallons and upwards are used for distilling petroleum. 
 
RECTIFICATION OF CRUDE OIL. 
 
 689 
 
 The retorts used for distilling shale tar or crude oil are often constructed of large 
 cast-iron flanged pans (A, fig. 458), each capable of holding from li to 3 tons of the 
 oil and forming the body of the retort. The pan is set in brickwork, with flues (ii) 
 running round the upper portion, and beneath it is a perforated dome of brickwork 
 through which the flame and hot gas from the furnace (c) pass up round the bottom 
 of the pan (A) before entering the flues (i i) by which the upper portion of the pan 
 
 is heated. To the flange of the pan is fitted a flanged cover, having at one side a 
 discharge pipe (b) through which the vapour is passed to the worm (ddd} of the con- 
 denser (B B). In the centre of the cover is a manhole (c). 
 
 The oil condensed in the worm is discharged through the pipe (eg) into a receiver 
 (D), and the uncondensable gas escapes through the ascending pipe (A). 
 
 The several portions of oil obtained by distilling either petroleum or the oily tar 
 
 YY 
 
690 , ARTIFICIAL LIGHTING MATERIALS. 
 
 furnished by coal, bituminous shale, or lignite, etc., are generally somewhat coloured, 
 and contain impurities which require to be separated. Thus, for instance, the oil 
 derived from most kinds of tar made by destructive distillation, contains carbolic acid, 
 creasote, and similar substances, for the removal of which the oil is agitated with a 
 strong solution of caustic soda. The products from petroleum rarely require this 
 treatment. When the soda solution used is sufficiently strong the compounds of soda 
 with creasote and carbolic acid, etc., separate as a thick black layer between the layer 
 of oil and the excess of caustic soda solution. After the mixture has been left to 
 settle, the oil is drawn off, washed with water to remove adhering alkali, and then 
 mixed with strong sulphuric acid in the proportion of from two to four per cent. 
 This operation is carried out in large cylindrical vessels furnished with paddles, by 
 means of which the acid can be thoroughly mixed with the oil. By the action of the 
 sulphuric acid the oil acquires a dark brown colour and a considerable quantity of 
 sulphurous oxide is given off. When the mixture is left to settle, a thick tarry liquid 
 of a very dark brown colour is deposited, and the oil, after being drawn off from this 
 depositof acid tar, is well washed with water, or if necessary with lime water or caustic 
 alkali. With some kinds of oil it is necessary to repeat these operations alternately 
 several times, and sometimes the oil is distilled afterwards. By each treatment of 
 the oil, its colour and smell are gradually removed and, if desirable, it may be ren- 
 dered quite colourless and almost free from smell. When the oil intended for burning 
 in lamps is distilled a second time, a further quantity of solid paraffin is frequently ob- 
 tained by collecting the last portions of distillate and leavingthem in tanks to crystallise. 
 
 The more volatile portion of the distillate from the crude oil is treated in a similar 
 manner with sulphuric acid and alkali, and, if requisite, it is rectified by distillation. 
 It is used for burning in sponge lamps, as a substitute for turpentine and, when highly 
 purified, for removing grease spots from clothes, etc. 
 
 The denser portion of the distillate which comes over after the burning oil is 
 seldom sufficiently thick for use as a lubricant for machinery, and it is therefore re- 
 distilled and fractionated, the first runnings being added to the bulk of the burning 
 oil before it is treated with chemicals, and the intermediate portion set apart as 
 lubricating oil, while the last portion, containing most of the paraffin dissolved in the 
 oil operated upon, is kept in a cold place until the paraffin crystallises in scales, or it 
 is mixed with the fourth portion of the distillate from the crude oil after that has been 
 treated with acid. 
 
 To extract the paraffin from this mixture of heavy oil and paraffin crystals, filter 
 bags are employed in some factories ; in others centrifugal machines are used. The 
 scale paraffin thus separated from the greater part of the adhering oil is then wrapped 
 in horsehair cloths and pressed, if necessary with the aid of heat. The pressed mass 
 is then mixed with a quantity of the most volatile oil or spirit and again pressed, this 
 treatment being repeated several times until the paraffin is sufficiently free from 
 colour and smell, and has the requisite melting point. 
 
 The refined oil used for burning in lamps varies somewhat in colour, smell, specific 
 gravity, and other physical characters, according to the source from which it has 
 been derived", as well as the care with which it has been prepared, and it is known 
 under a great variety of designations, such as photogen, solar oil, kerosene, 
 paraffin oil, besides other more fanciful names, indicative of a particular make 
 rather than of any essential peculiarity in the oil. 
 
 The applicability of these products for burning in lamps is dependent upon the 
 temperatures at which they take fire or give off inflammable vapoxir. The tempera- 
 ture at which the vapour given off by a sample of oil takes fire by contact with a 
 flame, or the flashing point of the oil, lies a few degrees lower than that at which 
 the oil itself takes fire and continues to burn. In an oil of good quality the flashing 
 point should be above any temperature which the oil will attain during use. Accord- 
 ing to Chandler, petroleum, during its consumption in glass lamps with a surrounding 
 temperature of 28-29, becomes heated after some hours to 30 or 33 ; and with a 
 surrounding temperature of 32 or 331 it becomes heated to 33 or 36. In lamps 
 with metal vessels the oil becomes heated to 54 ; therefore such lamps are not to be 
 recommended. According to the standard adopted in Great Britain and the United 
 States, the flashing point of oil of good quality should be above 37'6. Most of the 
 burning oil made from petroleum complies with this requirement, but when it is 
 mixed with oil boiling at a lower temperature it will flash at a much lower tempera- 
 ture, as is the case with inferior kinds of oil met with in commerce containing an 
 admixture of naphtha. An oil flashing at 45 would, according to Chandler, by the 
 addition of 1 per cent, of naphtha, have its flashing point lowered to 39 ; by 5 per 
 cent, of naphtha it would be lowered to 28, and by 20 per cent, to 4. 
 
 Van der Weyde gives the following methods of testing oil for the amount of hydro- 
 carbons having a low boiling point contained in it. A graduated glass tube closed at 
 
ILLUMINATING GAS. 691 
 
 one end is filled with the oil to be tested, the open end is closed with the finger and 
 the tube is placed mouth downwards in a vessel of water that is heated to 43-14. 
 The vapour from the portion volatilised at this temperature then collects in the upper 
 part of the tube and expels a corresponding quantity of oil. 
 
 In this country petroleum is defined by Act of Parliament as being any oil which 
 gives off an inflammable vapour at a temperature of less than 37'6 ; the method, 
 however, at present in use for determining this point is very imperfect and gives 
 results that cannot be depended upon. 
 
 The oil prepared from petroleum is almost colourless, but has a slight bluish 
 fluorescence ; it has a specific gravity of about -810, and when of good quality only a 
 slight and rather aromatic odour. It is now entirely manufactured in America, and is 
 exported thence in very large quantities. 
 
 The oil obtained from bituminous shale or from coal is generally of higher specific 
 gravity ; it has more colour and a less agreeable smell. 
 
 The oil obtained from brown coal tar, and known by the name of solar oil, is 
 almost colourless, with a slight yellowish green or blue fluorescence ; its specific gravity 
 is from -825 to '835 ; the lighter and more volatile portion of the oil obtained from 
 this source, and called photogen, has a specific gravity of '810 or -825. The tem- 
 perature at which either of these kinds of oil take fire varies in proportion to the 
 specific gravity as follows : 
 
 Specific gravity. Temperature. 
 
 Photogen 800 33 
 
 805 37 
 
 808 45 
 
 Solar oil 824 60 
 
 827 68 
 
 830 76 
 
 835 77 
 
 845 92 
 
 ILLUMINATING GAS. The issue of columns of inflammable vapour from the soil in 
 various parts of the world was known to man many centuries since : at first the 
 phenomenon was the object of fear and superstition, but eventually it was turned to 
 account by practical individuals. In the Middle Ages, the Mahomedans in the district 
 of Baku, south-west of the Caspian Sea, where there was much bituminous oil, col- 
 lected the vapours streaming from the soil and used them for lighting, brick burning and 
 cooking. Similarly the Chinese of the province of Ou Tong Kias are said to have turned 
 the vapour there exuding through the soil to practical account from the earliest times. 
 The history of the artificial production and application of coal gas for illuminating 
 and heating purposes is much more modern. Nevertheless, long before coal gas 
 was thus used, much was known regarding its properties. As early as 1667 an 
 Englishman, Mr. Thomas Shirley, published in the Philosophical Transactions a 
 communication in which it was stated that the explanation of a burning well at Wigan 
 in Lancashire was to be found not in the water, but in the gas mixed with it, the 
 origin of which gas was attributed to the coal strata lying below. This paper attracted 
 much attention from the scientific world, and gave rise to many attempts to produce 
 combustible gas artificially. In 1685, Professor J. J. Becher published at Frankfort 
 the results of some experiments on the dry distillation of coal, in which he obtained 
 coke, tar, and a luminous combustible gas. Dr. Stephen Hales, in 1726, estimated 
 the amount of gas obtainable from a given weight of Newcastle coal. In 1739, Dr. 
 Clayton, in a paper communicated to the Koyal Society, showed that coal gas admitted 
 of storing in bladders, and in 1767 Dr. "Watson proved that it retained its inflammable 
 character after passing through water. In 1786 the gas produced by distilling coal 
 at the works of Lord Dundonald, Culross Abbey, was used for lighting. 
 
 In 1792, William Murdoch (a Scotchman) experimented, at Kedruth in Cornwall, 
 upon the quantities and qualities of the gases furnished by the destructive distillation 
 of various vegetable and animal substances. Subsequently he produced coal gas by 
 heating coal in iron retorts, and used the gas, which was conveyed by pipes, to 
 illuminate his house and offices. The only method of gas purification employed by 
 Murdoch consisted in its passage through water ; the use of lime was introduced by 
 Dr. Henry and Dr. Clegg. 
 
 In 1798 Murdoch illuminated part of Messrs. Boulton and Watt's foundry in Soho, 
 near Birmingham, with gas; and in 1802 the whole premises were supplied in this 
 way and a number of mills and shops also. 
 
 While Murdoch was thus striving to introduce the use of coal gas into England, 
 Lebon was endeavouring to do the same thing for France, although he was anticipated 
 by Murdoch by seven years. 
 
 Y Y 2 
 
692 ARTIFICIAL LIGHTING MATERIALS. 
 
 In 1799 Lebon illuminated his house in Paris witR coal gas, and caused much 
 astonishment by tlje proceeding. Mr. Winsor, who was staying at Brunswick at this 
 time, happened to read Lebon's report to the French Institute, and on his return to 
 England did all in his power to introduce the use of coal gas for universal illumin- 
 ating purposes, but it was a long time before the public prejudice against this innova- 
 tion could be overcome. Gradually, however, various establishments were lighted by 
 coal gas, and in 1803 the Lyceum Theatre was thus illuminated. 
 
 In 1810 Mr. Wiusor succeeded in obtaining an Act of Incorporation for the Gas 
 Light and Coke Company, and in the course of a few years a number of other rival 
 companies were started, while the use of coal gas steadily progressed and increased 
 until in fact it became universal. 
 
 Paris was first partially lighted with coal gas in 1820 ; and it was introduced into 
 Germany a few years later. At the present time more than 2,000,000 tons of coal are 
 consumed in gas making for the metropolis, with the production of 14,000,000,000 
 cubic feet of gas annually. The total consumption of coal in the gas and water 
 works of the United Kingdom amounts annually to more than 7,000,000 tons. 
 
 The Chemistry of Gas Manufacture. When coal is burned in the open air, most of 
 the carbon and hydrogen are burned off as carbonic anhydride and water, while small 
 quantities of ammonia and sulphurous anhydride are produced, being derived from the 
 nitrogenous constituents and the pyrites contained in the coal. 
 
 But when coal is strongly heated in closed vessels, in other words when it is sub- 
 mitted to destructive distillation, the decomposition which is effected is quite of a 
 different order. A large amount of permanent or uncondensable gas is formed, and a 
 certain amount of heavier vapour which afterwards, on cooling to normal tempera- 
 tures, condenses to the liquid or solid state, while a large amount of combustible matter 
 or coke is left behind in the retorts. This gas coke constitutes the bulk of the carbon, 
 and contains, of course, the ash. 
 
 The products obtained from cannel coal yielding about 11,000 feet of gas per ton 
 of the density 0*600, are on the average for every 100 Ibs. subjected to distillation, 
 about : 
 
 Gas =22-25 Ibs. 
 
 Tar = 8-50 
 
 Ammonia water = 9 '50 ,, 
 
 Coke =59-75 
 
 100-00 
 
 The gas so produced contains the following constituents ; the volume per cent, of 
 each is represented by some determination by the late Dr. Letheby: 
 
 Formulae. Volume per cent. 
 
 Hydrogen 2550 
 
 Light carburetted hydrogen . . . CH 4 35 52 
 
 Olefiant gas C 2 H 4 1 
 
 Propylene C 3 H 6 V 320 
 
 Butylene C 4 H 8 J 
 
 Acetylene C 2 H a ? 
 
 Carbonic oxide CO 5 9 
 
 Carbon disulphide . . . . " . CS 2 -004 -04 
 
 Carbonic anhydride . . . . CO., 2 
 
 Ammonia . . . . . . NH 3 -00 -06 
 
 Aqueous vapour H 2 -6 2 '5 
 
 Oxygen -0 '1 
 
 Nitrogen N -0 8'0 
 
 Benzene and derivatives . . . C 6 H ? 
 
 Naphthalin C 10 H 8 ? 
 
 Dr. Letheby assigned to London gas an average composition as follows : 
 
 Common gas =32 candles. Cannel =20. 
 
 Hydrogen 46'0 277 
 
 Light carburetted hydrogen . . . 39'5 50-0 
 
 Condensible hydrocarbons ... 3'8 13 - 
 
 Carbonic oxide 7'5 6*8 
 
 anhydride .... 0'6 0-1 
 
 Aqueous vapour 2-0 2'0 
 
 Oxygen 0-1 O'O 
 
 Nitrogen 0-5 0'4 
 
 It is now known that, although the illuminating power of gas depends upon the amount 
 
COMPOSITION OF COAL GAS. 693 
 
 of hydrocarbons it contains, yet it bears more relation to the nature of these constitu- 
 ents than to any relation between the carbon and hydrogen. By long storing or 
 passage through cold pipes, gas loses in illuminating power, owing, no doubt, to the 
 condensation of naphthalin and benzene, and allied or derived substances. Moreover, 
 as olefiant gas is soluble in water, this constituent, which is very serviceable for 
 lighting purposes, is also diminished by storing the gas. 
 
 The liquid products furnished by the destructive distillation of coal contain : 
 
 Water . H 2 
 
 Carbon di sulphide CS 2 
 
 Benzol C 6 H 6 
 
 Toluol C 7 H 8 
 
 Cumol C 9 H 12 
 
 Cymol C 10 H U 
 
 Aniline C 6 H 7 N 
 
 Picoline CgH^N 
 
 Leucoline C 9 H 8 N 
 
 Carbolic acid C 6 H 6 
 
 together with other hydrocarbons of the general formulae C n H 2n ; C n H 2IH _ 2 ; and C n H 2 n_ 
 The following substances, which maybe obtained in the solid state by refrigeratioi 
 are also among the products of coal distillation : 
 
 Ammonium carbonate 2NH 4 .C0 3 
 
 sulphydrate NH 4 HS 
 
 sulphite 2NH 4 .S0 8 
 
 chloride NH 4 C1 
 
 Paraffin .... . . C 20 H 42 
 
 Naphthalin .... 
 
 Anthracene .... 
 
 Pvrene . 
 
 6' 
 
 ion. 
 
 Chrysene 
 
 I54 
 
 As a matter of fact, the products of the distillation of coal do not range themselves 
 sharply into these three groups. It will be seen that the gas itself generally contains 
 some of the liquid and solid products, while the liquid distillate invariably contains 
 in solution some of the gaseous products. 
 
 The relative proportions of permanent gas and condensable solids and liquids, as 
 well as the chemical nature of these products, depend upon the temperature employed 
 in the retorts and the length of time the materials are exposed to the action of heat ; 
 the lower the temperature and the more quickly the operation is carried out, the 
 greater is the proportion of solid and liquid products, and vice versa. The reason for 
 this is, that more complex substances generally split up into simpler ones on exposure 
 to a high temperature, and the higher this is, the simpler the products. Thus olefiant 
 gas splits up when passed slowly through a red-hot tube into light carburetted 
 hydrogen, hydrogen, and carbon, with loss of illuminating power ; and so with other 
 bodies. Therefore, although it is the object of the distillation to get a large yield of 
 permanent gas, it is equally necessary that the illuminating value of the gas should 
 not be destroyed by using too high a temperature or by too slow distillation. 
 
 From what has been said, it will be evident that the substances entering into the 
 composition of coal gas may be classed under three headings illuminants, diluents, 
 and impurities : 
 
 Illuminants. Diluents. Impurities. 
 
 Olefiant gas. Hydrogen. Sulphuretted hydrogen. 
 
 Acetylene. Light carburetted hydrogen. Ammonic hydrosulphide. 
 
 Propylene. Carbonic oxide. ,, carbonate. 
 
 Butylene. Carbonic anhydride. 
 
 Hydrocarbons of disulphide. 
 
 the C n H 2n "1 Nitrogen. 
 
 C n H 2n . 6 Ueries Oxygen. 
 
 C n H 2n ..,J Aqueous vapour. 
 
 Of the illuminants, taking olefiant gas as a standard, the order in which they 
 stand is directly proportionate to the amount of carbon contained in an equal volume 
 of each, so that naphthalin, the highest, has five times the lighting power of olefiant gas. 
 
 The denser members of the group of illuminants are the most readily condensed. 
 From this cause the gas mains frequently become blocked with naphthalin, which 
 has been gradually deposited, owing to the gas having left the holder at a higher 
 temperature than that of the pipes conveying it. 
 
694 
 
 ARTIFICIAL LIGHTING MATERIALS. 
 
 The diluents burn at best with a bluish flame which emits no light ; they therefore 
 serve merely to swell the bulk of the gas. 
 
 The impurities are not merely useless, but are also noxious or injurious, and 
 require to be removed. Sulphuretted hydrogen rarely occurs in coal gas ; but sulphy- 
 drate of ammonium and carbon disulphide when present give rise during combustion 
 to sulphurous anhydride ; this combining with water and oxygen forms sulphuric 
 acid, which exercises a most deleterious influence upon books and paintings, etc. It is 
 therefore desirable to remove these substances so far as is practicable from coal gas 
 before it is supplied to the consumers. 
 
 Carbonic anhydride does not support combustion ; it should therefore be removed 
 from coal gas intended for purposes of illumination, inasmuch as 1 per cent, of it- 
 depreciates the illuminating power of the gas to the extent of about 6 per cent. The 
 nitrogen present in coal gas is chiefly derived, as is also the oxygen, from the leakage of 
 atmospheric air into the retorts during distillation ; since they both reduce the lighting 
 power of gas, it is desirable to avoid their presence as far as possible. 
 
 Coal gas being stored over water, becomes necessarily saturated with aqueous 
 vapour, and although the actual amount present is not large, it is objectionable on the 
 same ground as oxygen and nitrogen ; moreover, if the gas be used for heating pur- 
 poses, it is still more objectionable, because it absorbs a certain amount of heat in 
 passing into a more highly attenuated state. 
 
 Different kinds of coal used in gas making. The value of coal for gas making 
 depends upon the amount and nature of the volatile products furnished by heating it, 
 and as bituminous coal excels in these respects, it is the best sort to use for the pur- 
 pose. Bituminous coal includes the varieties called caking coal, and parrot or cannel 
 coal. Anthracite, which is almost wholly carbon, is quite useless for gas production, 
 and ' steam coal ' is unsuitable also in a less degree. The coal used should contain 
 only a small amount of ash, in order that the residual coke may be serviceable as fuel. 
 The absence of sulphur (as pyrites) is also desirable, since the carbon disulphide 
 formed from it in the process of manufacture has afterwards to be removed from 
 the gas produced. The freer coal is from oxygen, the better it is for gas making, 
 since it is only the excess of hydrogen (among other available constituents of coal 
 gas) over the quantity requisite to form water with the oxygen of the coal which is 
 available for lighting purposes. 
 
 The Scotch cannel coal yields the largest and richest quantity of illuminating gas, 
 and English cannel ranks next. Newcastle coal is, however, largely used, although its 
 light-producing capacity is only represented by 10, compared with the best Durham 
 at 15, Lesmahago at 25, and Boghead at 40. 
 
 The following table illustrates the yield of gas and other products from varjus 
 coals : 
 
 , 
 
 
 
 Con- 
 
 
 
 Produce of one ton of coal 
 
 Equivalent 
 
 sump- 
 tion per 
 
 Value of 
 
 
 
 of one 
 
 hour to 
 
 the gas 
 
 Name of coal 
 
 
 cubic foot 
 of gas in 
 
 give a 
 light 
 
 from one 
 ton of coals 
 
 
 
 
 
 
 Cubic feet 
 
 Lbs. of 
 
 Lbs. of 
 
 Lbs. of 
 ammo- 
 
 grains 
 sperm 
 
 equal to 
 
 twelve 
 
 in pounds 
 of sperm 
 
 
 of gas 
 
 coke 
 
 tar 
 
 niacal 
 
 
 standard 
 
 
 
 
 
 
 liquor 
 
 
 candles 
 
 
 Boghead Cannel . 
 
 13,334 
 
 715 
 
 733-3 
 
 none 
 
 1109 
 
 1-3 
 
 2057 
 
 Newcastle 
 
 9,883 
 
 1,426 
 
 98-3 
 
 60 
 
 606 
 
 2-37 
 
 851 
 
 Wigan . 
 Lochgelly . 
 
 10,850 
 8,331 
 
 1,332 
 1,245 
 
 218-3 
 225 
 
 161-6 
 340 
 
 465-8 
 439 
 
 3-09 
 3-28 
 
 718 
 522 
 
 Mixture of f Loch-^ 
 
 
 
 
 
 
 
 
 gelly and Bog- 1 
 head Cannel . j 
 
 9,005 
 
 1,200 
 
 400 
 
 170 
 
 695 
 
 2-07 
 
 899 
 
 ^ Lochgelly and ^ 
 Boghead Cannel 
 
 9,050 
 
 1,205 
 
 335 
 
 290 
 
 600 
 
 2-4 
 
 774 
 
 ii Lochgelly and ^ 
 Boghead Cannel 
 
 9,750 
 
 1,240 
 
 227 
 
 270 
 
 443 
 
 3-25 
 
 617 
 
 Pelton Main 
 
 9,500 
 
 1,540 
 
 112-5 
 
 112-5 
 
 311 
 
 4-7 
 
 422 
 
 Mixture of f Pelton ) 
 
 
 
 
 
 
 
 
 and J Boghead V 
 
 12,800 
 
 1,366 
 
 116-6 
 
 116-6 
 
 553 
 
 2-6 
 
 1009 
 
 Cannel. . J 
 
 
 
 
 
 
 
 
 The data here given are derived from experiments made by Mr. Barlow, who is 
 
GAS RETORTS. 
 
 695 
 
 of opinion that coal containing above 30 per cent, of volatile matter requires a higher 
 temperature for distillation. 
 
 Newcastle coal gives from 8,000 to 12,500 cubic feet of gas per ton, having a 
 specific gravity ranging between '398 and '521. 
 
 Parrot or cannel coal gives from 9,000 to 15,000 cubic feet of gas per ton, having 
 a specific gravity ranging between -460 and '752. 
 
 The coal of Derbyshire, "Wales, and Staffordshire, more or less approaches to the 
 Newcastle coal. 
 
 The various kinds of coal, especially those of a bituminous nature and intended 
 for gas making, should be protected as far as may be from atmospheric influences. 
 Exposure to rain and sunshine alternately is liable to cause spontaneous combustion ; 
 in any case it sets up a rapid oxidation of matter which would otherwise be available 
 for producing gas. This is more especially liable to occur when the coal contains 
 much ferrous sulphide, as this readily takes up oxygen from the air and passes into 
 ferrous sulphate ; this oxidation sets up a like action in the coal which is intensified 
 by the heat liberated. A coal may thus in the course of three months lose from 
 these causes as much as 10 per cent, of its productive power. 
 
 The following analyses will suffice to show the average composition of coals : 
 
 Per cent. C. Per cent. H. Per cent. 0. 
 
 Boghead cannel .... 80'35 11-21 671 
 
 Wigan cannel .... 85'95 5'71 8'14 
 
 Gas coal 88*15 5-26 5'41 
 
 Manufacture. When coal is distilled in close vessels, the elements of which it 
 is composed rearrange themselves, forming a series of bodies the nature of which 
 depends upon a variety of conditions. An excessive temperature splits up the pro- 
 ducts first formed into more simple ones, such as hydrogen, light carburetted 
 hydrogen, etc., which are valueless for illuminating purposes ; on the other hand, if 
 deficient heat be employed, tar results. As it is impossible to keep the contents of 
 the retorts at a uniform temperature throughout, complicated conditions arise, and 
 therefore, besides coal gas, a quantity of tar and ammoniacal compounds pass over, 
 leaving behind in the retorts a highly porous coke. Ordinarily the retorts are charged 
 with from 2 to 4 cwts. of coal, and are maintained as far as possible at a cherry-red 
 heat ; at some works, on the introduction of fresh charges of coal, the furnaces are 
 made white hot or nearly so. This operation of distillation takes about four or six 
 hours, during which time the coal yields up all its gas and leaves a saleable coke. 
 
 The retorts constitute a most important portion of 
 the apparatus, since upon their construction and arrange- 
 ment the quality of the gas is largely dependent. They have 
 been the subject of many modifications and improvements, 
 varying most widely in the material of which they are con- 
 structed, their form, and their arrangement in the furnace. 
 During the first twenty years iron retorts were always used, 
 but at the present time clay retorts have almost displaced them. 
 A disadvantage attending the use of a retort having a cir- 
 cular transverse section was found to be that the contents 
 were unequally heated, and that in order to reach the central 
 portions of the charge the temperature required to be so 
 high or long continued that it acted injuriously on the gas 
 produced from the coal lying nearer to the circumference. 
 This led to the adoption of the ear-shaped and rectangular 
 retorts (figs. 459 and 460), and afterwards of the Q shaped 
 retorts (figs. 461 and 462). The more rapid decomposition 
 of the coal lying in the angles of these retorts left still 
 much to be desired, and to avoid this inconvenience, the oval 
 retort (fig. 463) is now much used, especially in North 
 Germany. The length of the clay retorts varies ordinarily 
 between 6 ft. and 10 ft. ; their breadth and height average, 
 when of the shape of fig. 460, 19 in. by 12 in.; fig. 461, 
 32 in. by 6* in. ; fig. 462, from 15 in. by 12 in. to 25 in. by 
 15 in. ; fig. 463, from 17 in. by 12 in. to 23 in. by 39 in. 
 
 In the construction of the clay retorts, a mixture of burnt 
 clay with fresh plastic clay is used. The clay must not 
 contain much iron or lime ; it nrnst be very plastic and cap- 
 able of resisting the action of fire, and it should not be too 
 liable to crack or shrink when fired. 
 
 The retorts are made with one end closed, and to the other end is fitted a tubular 
 cast-iron mouth piece having tb same size and sectional form as the retort, so as to 
 
 FIG. 463. 
 
696 
 
 ARTIFICIAL LIGHTING. 
 
 form a prolongation of it, as shown in fig. 464. This mouth piece (a) is connected 
 with the fire-clay retort by means of cement, and is held in its place by screw bolts 
 passing through tfie flange (d) of the mouth piece, and screwed into nuts (c) imbedded 
 in the neck of the fire-clay retort. The length of this mouth piece does not require to 
 
 FIG. 464. 
 
 FIG. 465. 
 
 FIG. 466. 
 
 FIG. 467. 
 
 be more than enough for attaching the exit pipe (e) for the escape of the gas, and 
 that is either cast upon the mouth piece, as shown in 
 fig. 464, or it is fitted on by means of a flange with 
 bolts and nuts. The mouth piece is 'closed by a lid 
 made of thick iron plate, which fits accurately against 
 the flange (#), and, as shown in fig. 465, is furnished 
 with ears or projections (gg) at the sides. These ears 
 rest upon two stout iron bars (h k, fig. 466), fitted with 
 sockets (ii) on the corresponding sides of the mouth 
 piece and held fast by wedges at k k. The front ends 
 of these bars have each a slit, into which is inserted 
 the cross bar (I), having at the centre a strong screw (m) 
 fitted with a handle, and by this means the lid can be 
 pressed tightly against the flange (y) of the mouth 
 piece, which is previously smeared with a cement con- 
 sisting of a mixture of lime and water. A simpler and more convenient arrange- 
 ment for closing the lid of the retort consists of an eccentric lever attached to a cross 
 bar, as represented by fig. 467. 
 
 The Retort Furnace is ordinarily an enclosed arched chamber constructed of fire 
 
 bricks, in which the retorts are 
 now almost universally ar- 
 ranged in a horizontal position. 
 When iron retorts were used, it 
 was usual to surround them 
 with a casing of fire clay, or to 
 divide them by a closed arch, 
 into which the fire gases passed 
 from behind in order to pre- 
 serve them from the violent 
 action of the flame from the 
 furnace. Since the general in- 
 troduction of clay retorts, how- 
 ever, this arrangement has been 
 abandoned. The number of 
 retorts laid in one furnace 
 varies from one to fifteen, ac- 
 cording to the size of the estab- 
 lishment. 
 
 Fig. 468 represents a small 
 furnace in which two retorts 
 (a a) lie side by side about 3 
 feet above the ground, and be- 
 neath a flattened arch of about 
 feet span, so as to enclose the 
 retorts as nearly as possible^ 
 The fire passes from the hearth 
 FIG. 468. right and left of the retorts, 
 
 and, meeting again above them, 
 is drawn towards the front wall of the furnace, where it descends, and passes along 
 
GAS RETORT FURNACES. 
 
 697 
 
 a horizontal canal, the sides of which are formed by the two retorts ; at the back of 
 the furnace the fire gases enter a perpendicular flue controlled by a damper, and 
 through it pass into the chimney. 
 
 The bed and interior part of the furnace exposed to the action of the fire are con- 
 structed of infusible fire bricks. The outer walls are usually double, and are 
 strengthened by iron stays connecting them with each other and the retort benches. 
 By this means not only is additional solidity of the building secured, but the exterior 
 walls assist in retaining the heat and preventing undue loss by radiation. When 
 coke is used for fuel, the fireplace is made comparatively deep ; the air entering from 
 beneath has then to pass through a considerable depth of fuel, a condition which 
 favours the formation of carbonic oxide and the consequent production of a flame of 
 great heating power. An ash pan beneath the fire grate is kept partly filled with 
 water, in which the hot ashes falling are extinguished, whilst the resulting steam 
 tends to lower the temperature of the furnace bars, and passing upwards through the 
 incandescent fuel is decomposed with the formation of carbonic oxide and hydrogen. 
 
 Notwithstanding all precautions taken for the equal heating of the retorts, some of 
 them are always exposed to a greater heat than the others ; consequently they are 
 
 FIG. 469. 
 
 destroyed more quickly, and require to be thrown out of action until the re-setting of 
 the entire bench. Those retorts that are exposed to the greatest heat also require to 
 be re-charged more frequently than the others, to prevent the contamination of the 
 gas with sulphur to a greater extent than is the case when the coal is not heated 
 strongly for a long time ; when the distillation is not carried too far much of the 
 sulphur is left in the residual coke. In charging the retorts, the coals are placed as 
 far back in the retort as possible, by means of a sheet-iron scoop. At the same time 
 the mouth of the exit pipe is closed to prevent either gas flowing back into the retort, 
 or atmospheric air, carbonic dioxide, etc., being drawn into the pipe from the furnace. 
 Fig. 469 shows the arrangement in a furnace containing six retorts capable of 
 producing with retorts of the ordinary dimensions 50,000 cubic feet of g'as in twenty- 
 four hours. An important point to be considered is that there should be perfect 
 combustion of the fuel in the furnace. The retorts are therefore arranged in the 
 form of an arch around the hearth. At the grate (a) the fire hearth is about 1 foot 
 wide ; at a distance of 1 foot higher it widens to 2 feet ; it then rises about l feet, 
 and is closed in by a brick arch (b). The fuel, usually coke produced in previous 
 operations, is introduced through the furnace door (c) ; this and the ash pit door (e) 
 are set in a cast-iron frame (d), securely bolted into the front wall of the furnace. 
 The flame rising from the hearth is hindered from passing between the retorts (g h i), 
 by barriers of brick (k I). It therefore rises between the arch (b) and the top retorts 
 (J ' g) to the crown of the vault, then spreads right and left, and descends between the 
 
698 
 
 ARTIFICIAL LIGHTING. 
 
 outer side of the retorts and the wall of the vault to the level of the bottom of the 
 lowest retorts (i i); 'the fire gases here enter a passage (m) running under the entire 
 length of these retorts, which acts as a draught, through which they are drawn at a 
 velocity regulated by a damper into the chimney. 
 
 The same advantages are said to be afforded by a furnace containing seven retorts, 
 
 ' FIG. 470. 
 
 the same proportions being maintained. The arrangement is represented in figs. 470, 
 471, and 472; fig. 470 being a front view, fig. 471 a horizontal section at the line 
 A B, and fig. 472 a vertical section at the line E D. 
 
 FIG. 471. 
 
 ^ The seventh retort (r) is here laid over the furnace formed by the fire bricks (a /<?) ; 
 d is a plate which supports the middle retort, and at the same time protects it from' 
 the play of the fire ; o is the opening for the introduction of fuel ; p the opening for 
 
GAS RETORT FURNACES. 
 
 699 
 
 the ash pit ; g g the corresponding doors. Under the grate is a cast-iron water tank 
 (q), where water is always kept, in which falling pieces of coke are extinguished and 
 at the same time steam is produced that exercises a cooling action on the fire bars. 
 The fire plays round the middle retort (r), and being prevented by the fire-brick par- 
 titions (k s) from passing out sideways, rises as in the six retort furnace, between the 
 top retorts (t u\ descends in- 
 to the flues (a and K), and 
 through them into the chim- 
 ney ; v and w are the stays 
 of the retorts against the 
 sides of the furnace ; b and e 
 brickwork supports for retort 
 u ; I a swing flap for observ- 
 ing the heat of the oven. 
 Besides the interior supports, 
 the retorts rest at either end 
 in the front and back walls 
 of the furnace. The front 
 wall is built of fire bricks, 
 9 inches thick ; the back wall 
 is double (x y\ being sepa- 
 rated by a stratum of air 
 that acts as a non-conductor 
 of the heat. The entire fur- 
 nace is enclosed above by 
 five arches, the three inner 
 ones lying close on one 
 another, being built with 
 fire bricks ; the other two, 
 separated from them by a 
 small interval, being built 
 with ordinary bricks. A- 
 bove the outermost arch 
 there are frequently two 
 layers of plaster to retard 
 the radiation of heat. In 
 fig. 472 is shown the mouth 
 of the retort (A.), which pro- 
 jects beyond the front wall, 
 and is fitted with a vertical 
 cast-iron pipe (B), through 
 which the whole products of 
 
 FIG. 472. 
 
 the distillation ascend to the hydraulic main (F). When the coal has been intro- 
 duced into the retort, the mouth is closed with a lid luted with fire clay, or some other 
 suitable material, and fastened with a screw or lever as already described. 
 
 The hydraulic main (fig. 472, F), into which the gas passes from the ascension 
 pipes (B c), is a horizontal iron trough that is at first half filled with water, into 
 which the continuations (D E) of the ascension pipes dip. The gas bubbles through, 
 but a part of the tar and ammoniacal liquor is condensed, and this soon displaces the 
 water, and in its turn, when it has reached a certain level, flows over into the tar 
 well. The hydraulic main acts therefore as a water joint, and effects a partial con- 
 densation and purification. 
 
 Eetorts are usually set in groups of three, five, seven, eight, or nine to a bench, 
 each setting being heated by a separate fire regulated by independent dampers, but 
 connected with a common flue. They are either single, when they are about 8 
 feet long, and closed at one end, the other being fitted with the mouth piece ; or they 
 are double, in which case they are 18 or 20 feet long, and have a mouth piece at 
 each end. Single clay retorts are usually in one piece, and to strengthen them they are 
 set in a casing of fire bricks ; but the double retorts may be either built in sections 
 or constructed entirely of fire bricks. After a time the retorts become coated with a 
 very hard deposit of carbon, and require to be scurf ed. This is done by removing 
 the deposit with a hammer and chisel, or when it has become very thick and hard, by 
 admitting atmospheric air to the retort and allowing the carbon to burn away until 
 the crust is sufficiently thin to be easily removed. 
 
 The quantity of fuel consumed varies greatly, and depends especially upon the 
 quality of the coke ; usually it is calculated to use one third of the coke drawn from 
 the retorts in feeding the fire. This quantity, however, can be reduced if air pre- 
 
700 
 
 ARTIFICIAL LIGHTING. 
 
 viously heated be introduced under the fire grate. This passes to and fro through 
 narrow channels along the length of the flue, and increases by its heat the effect of the 
 combustion. Thus 'the seven retort furnace represented in fig. 470 would require on 
 the average 236 parts of coke for the distillation of 1,000 parts of coal ; whilst a 
 furnace with nine retorts and double fires, as represented in fig. 473, in which this 
 plan is adopted, would only require 213 parts of coke to do the same amount of work. 
 
 FIG. 473. 
 From the hydraulic main the gas passes to the condenser, which it enters at a 
 
 temperature of about 70 C 
 
 at which it still retains a considerable quantity of tarry 
 and aqueous vapour. In the smaller gasworks, the con- 
 denser used for the separation of these impurities consists 
 of a series of pipes kept cool by exposure to the air. Such 
 an arrangement is shown in fig. 474, a ground plan in fig. 
 47o. The pipes are supported upon and open into a cham- 
 ber (a a) for the reception of the condensation products, 
 the chamber being divided into several compartments by a 
 series of partitions reaching not quite to the bottom. The 
 gas entering at s into the first compartment (1) rises 
 through the pipe opening into it (b), passes through the 
 cross-pipe (e), and descends by the opposite pipe (c) into 
 the second compartment (2), then rises through the third 
 pipe (3), and passes through another cross pipe correspond- 
 ing to e, and so on through the whole series of pipes, and 
 escapes through the outlet (A). The condensation products 
 
 1 
 
 10. 
 
 FIG. 474. 
 
 FIG. 475. 
 
 escape through an overflow pipe (g\ arranged so as to maintain a constant level 
 within the chamber above the communication between the several compartments. 
 
CONDENSATION OF TAR, ETC. 
 
 701 
 
 In large gas works, where it would be difficult to obtain a sufficient condensation 
 by the action of atmospheric air alone, cold water is also used; the arrangement is 
 shown in fig. 476. In this condenser the gas passes through three upright tubes (A B c) 
 about 3 feet in diameter and 16 feet in height, each containing seven iron 1\ inch 
 pipes (eee), arranged as shown in (CB), in which water circulates in a contrary 
 direction to the gas. The gas enters at a, passes through the tubes (ABC) and the 
 connecting pipes (b c) successively, to the exit valve (d). The cold water enters through 
 a pipe (/), at a point below the third tube (c), ascends through it and passes through 
 the connecting pipe (g\ then descends through the second tube (fi)and the connecting 
 pipe (B), and finally rises through the first tube (A), escaping at the top. The tem- 
 perature is shown by a thermometer in each tube (i i i), and the flow of water is so 
 regulated that the gas leaves the condenser at about 15. The condensation products 
 run from A through b, and then pass with those from e into a 2 inch pipe (&), onward 
 to the tar reservoir (I). Should any defect occur in the apparatus, the valves at the 
 entry () and exit (d) are closed, and the gas passes directly from the supply pipe 
 through a branch (a 8) communicating directly with the discharge pipe, the valve con 
 trolling it (/8) being opened. 
 
 FIG. 476. 
 
 The object of the condenser is to effect the cooling of the gas to the atmospheric 
 temperature, and at the same time the separation of suspended water and tar. In 
 many cases this result can be produced by making the gas pass up and down through 
 a few pairs of upright pipes of the kind above described, but several improved arrange- 
 ments have been introduced with the object of offering a greater surface of contact 
 between the gas and the cooling medium. In Kirkham and Wright's condensers this 
 has been done by making the gas traverse an annular space formed by two concentric 
 cylinders, and the gas passing through this annular space was thus cooled both from 
 
702 
 
 ARTIFICIAL LIGHTING. 
 
 within and from without by the cold air passing up through the inner cylinder as well 
 as over the surface of the outer cylinder. These annular condenser tubes are connected 
 by smaller pipes, which convey the gas from the bottom of one condensing cylinder 
 to the top of the adjoining one, so that in all cases the gas passes from the top to the 
 bottom of the condensing cylinders in a direction contrary to that of the current of air 
 by which it is cooled. An area of six to ten square feet of condensing surface is con- 
 sidered to be necessary for each thousand cubic feet of gas made during twenty-four 
 hours. 
 
 Passing from the condenser the gas reaches the exhauster, an apparatus having 
 for its object the withdrawal of the gas from the retorts as soon as it is produced, and 
 its propulsion through the various purifying materials to the gas holder. The reason 
 for drawing off the gas from the retorts as quickly as possible is to avoid its being 
 subjected to pressure, which if it be at all considerable at a given temperature exer- 
 cises upon the gas the same effect as a much higher temperature without pressure, 
 namely, the splitting up of condensable hydrocarbons into non-illuminants, which has 
 the effect of not only reducing the amount of gas obtained, but also of lessening 
 the illuminating power of the gas, and causing a deposition of carbon upon the interior 
 surface of the retorts. 
 
 A rotary exhauster is shown in figs. 477 and 478. This consists of a cylindrical 
 case (A) in which a smaller cylinder (B) is rotated eccentrically by a driving shaft 
 
 making 60 to 100 revolutions a 
 minute. At a right angle with the 
 shaft are two sliding plates working 
 in a groove upon one another in such 
 a manner that whatever the position 
 of the inner cylinder the space of 
 the outer frame is divided into two 
 parts. In the position shown in 
 the sketch the entrance and exit 
 are closed, and the upper space is 
 filled with gas. When the cylinder 
 is rotated in the direction of the 
 arrows, the left-hand slide is pushed 
 in, whilst the right-hand one slides 
 forward so as to remain in contact 
 with the side of the frame. At the 
 same time the opening of the exit 
 pipe becomes uncovered, and the 
 gas in the upper part of the frame 
 is by the eccentric action of the 
 inner cylinder driven forward by 
 FIG. 477. the right-hand slide into the pipes. 
 
 When the revolution is half com- 
 pleted, the inlet pipe in its turn becomes uncovered, and a fresh quantity of gas enters 
 
 FIG. 478. 
 
 the chamber. In this manner, exhaustion on the one side and pressure on the othc, 
 are constantly kept up. 
 
CONDENSATION OF TAR, ETC. 
 
 703 
 
 A machine of this kind about four feet in diameter is capable of passing through 
 it about 150,000 cubic feet of gas per hour, according to the rate at which it is driven. 
 
 A piston exhauster is represented in fig. 479, which resembles a steam engine in 
 its action. The gas entering at the inlet pipe (A) passes according to the position of 
 the slide (c) in the slide chamber 
 (B B), into a vertical cylinder through 
 either of two channels, one (D) above 
 the piston (a), the other (E) below 
 it. When the piston (a) is at the 
 bottom of the cylinder, the slide (c) 
 is in the position represented in the 
 figure, and the inlet pipe (A) and the 
 two channels (D and E) are shut off 
 from each other. Directly the 
 movement of the piston is reversed 
 the slide slips downwards, and com- 
 munication is established between 
 the inlet pipe (A) and the lower 
 channel (E), and between the upper 
 channel (D) and the slide chamber 
 (B), so that the ascending piston 
 drives the gas contained in the 
 upper part of the cylinder forward 
 through the upper channel (D) and 
 the chamber (B), whilst a fresh 
 quantity of gas is drawn in from 
 the inlet pipe (A) through the lower 
 channel (E) to fill the vacuum 
 created. When the piston reaches 
 the top of the cylinder, communica- 
 tion is again shut off, and when it 
 descends the conditions are reversed, 
 the gas being drawn in through the 
 upper channel and expelled through 
 the lower one. 
 
 In order to avoid the danger of 
 explosion that would result from the 
 inflow of air in consequence of the 
 quantity of gas produced in the re- 
 torts being sometimes unequal to the 
 action of the exhauster, the supply FIG. 479. 
 
 of gas is controlled by a regulator. 
 
 The construction of the regulator used for this purpose is represented by fig. 480. 
 The cylindrical vessel (A) is partly filled with tar, and the cylindrical bell (B), fur- 
 nished with a hollow ring (c) internally, dips into the tar contained in the vessel (A), 
 and is kept down to the required level by weights 
 (p) slipped on to a pin attached to the top. 
 Beneath this bell are fixed two concentric pipes 
 (s s and D) ; the external wider tube (s) branches 
 from the main through which the gas is 
 sucked from the scrubber ; the inner tube (B) 
 branches from the main through which the gas 
 drawn out by the exhausters is forced into the 
 purifiers. In the former there is consequently 
 pressure, and in the latter rarefaction, of the 
 gas. The exhauster and regulator are some- 
 times placed immediately after the hydraulic 
 main or after the condenser, but in that case the 
 separation of tar and ammoniacal water causes 
 destruction of the metal or hinders the action 
 of the regulator. When the dip pipes of the 
 retort are immersed about an inch, it is neces- 
 sary that the exhauster should be driven in 
 such a way as to produce a rarefaction equal to 
 nearly half an inch in the suction tube. This 
 is the normal condition of the regulator, which 
 is adjusted in such a way that a conical valve (F) 
 attached to the cover of the bell closes the outlet of the tube (i>). So soon as the 
 
 FIG. 480. 
 
704 
 
 ARTIFICIAL LIGHTING. 
 
 rarefaction becomes greater the regulator begins to act, and by sinking opens the 
 conical valve (F), admitting gas into the bell and reducing the rarefaction. As this con- 
 dition recurs at frequent intervals, a trembling motion of the bell is produced, which 
 admits of the action of the apparatus being observed. "When the speed of the 
 exhauster is too great for the rate at which the gas is being produced, the gas 
 which has already been exhausted and driven to the purifiers escapes again into the 
 suction tube. 
 
 In some works the gas is next made to bubble up through water in the washers ; 
 in others it passes directly to the scrubber. This is constructed on the same 
 principle as Gossage's towers for the condensation of hydrochloric acid gas, and 
 is represented in figs. 481 and 482. It consists of one or more cast-iron cylinders or 
 square chambers (D n), the interior of which is separated into two parts by a partition 
 reaching from the top almost to the bottom. These compartments are filled almost 
 to the lids with a porous material, usually coke, the extensive surface of which with- 
 draws from the gas a considerable portion of the ammoniacal compounds, and nearly 
 
 FIG. 481. 
 
 FIG. 482. 
 
 all the remaining tar. This effect is increased by keeping the coke moistened with 
 dilute ammonia liquor from the hydraulic main, which absorbs sulphuretted hydro- 
 gen, and the resulting ammonium sulphydrate combines with carbon disulphide. 
 The coke saturated with tar is afterwards used for heating the retorts. The gas 
 enters the right-hand compartment through a pipe (A B c), passes through the coke to 
 the bottom, rises through that in the left-hand compartment and escapes through 
 another pipe (FG). In cases where particles of tar adhere very pertinaciously to the 
 gas, or where it is important to remove the last traces of it, the scrubber is combined 
 with shallow cast-iron chambers (K) having a large horizontal area, in which lie 
 wooden hurdles covered with a loose layer of coke refuse, broken clay retorts, etc. 
 The last traces of tar condense here, and the gas entering from H and j, after passing 
 through three layers of hurdles in the boxes (K), leaves through the pipe (r.) for the 
 purifiers, absolutely free from tar. 
 
PURIFICATION OF GAS. 
 
 705 
 
 The gas should leave the condenser at a low temperature, for the cooler the gas 
 as it enters the scrubbers, the greater is the purification they effect. At this stage all 
 the remaining ammonia, mainly in combination with carbonic acid and sulphuretted 
 hydrogen, is removed, and the solution thus obtained is used for the manufacture of 
 ammoniacal salts. The average amount of ammoniacal liquor thus obtained from the 
 scrubbers and condensers is estimated at about 20 to 25 gallons of 10 oz. liquor per 
 ton of coal. 
 
 Besides these constituents of gas liquor, there are many others, including sul- 
 phurous acid, sulphuric acid, cyanic acid, sulphocyanic acid, and hyposulphurous acid, 
 and a small quantity of free ammonia. 
 
 Up to this point, with the partial exception of the scrubber, the purification of the 
 gas has been mechanical. Thus the gas before reaching the condenser deposits in the 
 hydraulic main some of the heavier tarry matter and water containing ammonia in 
 solution. The amount of liquid tar deposited in the condenser is greater, and the am- 
 monia liquor amounts to about 9 gallons of 6 or 7 oz. strength to the ton of coal ; 
 this represents about one fourth of the total ammonia present in unpurified gas. 
 
 Sometimes dilute sulphuric acid is employed in the washers to fix the ammonia, 
 but this plan is only used in certain small works ; it has the advantage of pro- 
 ducing sulphate of ammonia direct, but the product requires purification by recrys- 
 tallisation before it is ready for the market. 
 
 Here and there sulphate of iron is employed in the purifiers for the removal of 
 ammonia and sulphuretted hydrogen ; its use is based upon the following reactions : 
 
 (1) FeS0 4 + 2NH 4 HO = 2NH 4 .S0 4 + FeO + H 2 
 (2) FeO + H 2 S = FeS + H 2 
 
 Ordinarily, however, the ammonia is removed from coal gas by the process first 
 described. Its removal from coal gas is desirable not only because of the value of 
 ammonia, but also on sanitary grounds. During combustion of the gas any ammonia 
 present is liable to conversion by oxidation into nitrous compounds, and these are not 
 only deleterious to health, but act injuriously on brass and other metal fittings. 
 
 FIG. 483. 
 
 FIG. 484. 
 
 The impurities still requiring to be removed from the gas before it is fit for use 
 are carbonic dioxide and sulphuretted hydrogen. 
 
 To remove the carbonic acid from gas nothing is more efficient than lime, which 
 also absorbs the sulphuretted hydrogen when used either in the state of milk of 
 lime or simply slaked. 
 
 Although wet lime is more effectual as a purifier than dry lime, its use is open to 
 many objections, so that now, if lime is used at all, it is almost invariably used in the 
 dry state. 
 
 Cubic feet of Cubic feet of 
 Sulphuretted hydrogen Carbonic acid 
 
 lib. of quick lime in the dry state absorbs 678 and 3;39 
 lib. of wet 6-78 and* Q'^8 
 
 The vessels in which the gas is submitted to the action of dry lime consist of 
 sheet-iron boxes fitted with a water 
 
 joint, into which the cover dips and J^ ^ 
 
 prevents escape of gas, as shown in 
 figs. 483, 484 and 485, which repre- 
 sent an elevation, and two sections 
 of one of these purifiers. The gas 
 enters at the bottom, and passes 
 up through the purifying material 
 spread upon the shelves on one side 
 of the central partition, and then 
 down through the shelves on the 
 opposite side to an exit pipe at the 
 bottom (fig. 483). 
 
 B 
 
 FIG. 485. 
 
706 ARTIFICIAL LIGHTING. 
 
 Several of these chambers are connected together, and the gas is made to pass 
 through them successively. A usual arrangement is represented by fig. 486, 
 where four chambers (B i. to R iv.) are connected together in such a manner that, 
 
 FIG. 486. 
 
 while any three of them are being used the gas is shut off from the fourth, in order to 
 remove the exhausted purifying material and replace it with a fresh supply. The 
 gas is admitted to these chambers from the main through which the unpurified gas 
 passes by opening the valves (EJ to E 4 ) in the connecting pipes. The valves (v t to u 2 , 
 etc.) are for connecting the several chambers with each other as may be required, and 
 the valves (AJ to A 4 ) are for letting out the purified gas. If the chamber (B n.) is to be 
 cleared out and charged with fresh material, the gas enters the chamber (B in.) 
 through the valve (E 3 ), passes through r s to the chamber B rv., through u 4 to the 
 chamber B I} and then through the valve A, to the main for purified gas. 
 
 Another material used for purifying gas is hydrated ferric oxide, which absorbs 
 the sulphuretted hydrogen very effectually. 
 
 In the gas purifiers oxide of iron is sometimes used alone ; but this plan, while it 
 effectually removes the sulphuretted hydrogen and admits of constant regeneration 
 of the purifying material and utilisation of the sulphur, has the disadvantage of allowing 
 the carbonic anhydride present in the gas to escape removal. On the other hand, 
 slaked or moist lime absorbs both impurities, but the sulphur cannot be utilised. 
 
 A mixture of slaked lime and peroxide of iron is still largely used, although more 
 generally peroxide of iron is used without lime, but mixed with sawdust to give it 
 porosity. Peroxide of iron occurs in a hydrated state naturally as bog iron ochre, and 
 this constitutes the material usually employed in gas purification. The credit of 
 having brought this process to perfection is due to Mr. Hills. To carry it into effect, 
 the gas to be purified is passed through the mixture of ferric oxide and sawdust for 
 a period of 18 hours, and by the reaction of the ferric oxide with the sulphuretted 
 hydrogen ferrous sulphide and water are formed, while sulphur is liberated : 
 
 Fe 2 0, + 3H 2 S = 2FeS + S + 3H 2 0, 
 
 after which the mixture is subjected to a current of air produced by a fanner daring 
 a period of three hours. In this way the ferrous sulphide formed by the action of the 
 sulphuretted hydrogen upon the oxide of iron undergoes oxidation, giving once more 
 ferric oxide and free sulphur, thus : 
 
 2FeS + 3 = Fe 2 s + S 2 
 
 These processes are repeated and continued until the product contains as much as 
 40 per cent, of sulphur, and 1 ton of this mixture is said to yield, when burnt for sul- 
 phuric acid making, 1 tons of hydrated sulphuric acid. About once a month a certain 
 amount of the oxide of iron has to be replaced, owing to the bottom layer becoming 
 clogged with tar ; but the loss thus occasioned is not very great. 
 
 In addition to sulphuretted hydrogen and carbonic anhydride, there are other im- 
 purities which it is desirable to remove from coal gas, notably carbon disulphide 
 and sulphuretted hydrocarbons ; all of which when burnt in the air form sulphurous 
 
COMPOSITION OF GAS. 
 
 707 
 
 acid. Mr. Wright has ascertained that if a moderate temperature be employed in 
 distilling the coal used for gas-producing, the amount of these substances is reduced 
 very considerably, but this is a remedy not likely to be adopted to any great extent. 
 It is therefore important to find other means of obviating this evil. 
 
 Mr. Harcourt has attempted to meet it by a process which consists in passing the 
 gas through heated tubes containing lime or other substance, when sulphuretted hy- 
 drogen is produced by decomposition of the bisulphide of carbon. This action is not 
 peculiar to lime ; almost any material will act like it ; hence it appears to result from 
 physical rather than chemical causes. When the process was used on a large scale, 
 however, it was found that after a time the catalytic substance became inactive, and 
 the difficulty thus experienced has not yet been surmounted. If it could be, it would 
 be easy to apply this process to coal gas before it passes to the purifiers which 
 remove the sulphuretted hydrogen ; the problem of removing the bisulphide of carbon 
 from coal gas must therefore still be regarded as unsolved. 
 
 The following table, representing the composition of the gas taken from different 
 parts of the apparatus, will serve to show the effect produced by different stages of 
 the purification : 
 
 Hydrogen 
 Marsh gas 
 Carbonic oxide 
 Heavy hydrocarbons 
 Nitrogen . 
 Oxygen . . 
 Carbonic dioxide 
 Sulphuretted hydrogen 
 Ammonia . 
 
 From 
 condenser 
 
 From 
 scrubber 
 
 From 
 
 washer 
 
 From 
 purifiers 
 
 37-97 
 39-78 
 7-31 
 4-19 
 4-81 
 0-31 
 3-72 
 1-06 
 0-95 
 
 37-97 
 38-81 
 7-15 
 4-66 
 4-99 
 0-47 
 3-87 
 1-47 
 0-54 
 
 37-97 
 38-48 
 7-11 
 4-46 
 6-89 
 0-15 
 3-39 
 0-56 
 
 37-97 
 40-29 
 3-93 
 4-66 
 7-86 
 0-48 
 3-33 
 0-36 
 
 37-97 
 39-37 
 3-97 
 4-29 i 
 9-99 
 0-61 
 0-41 
 
 These quantities, in parts by measure in 1,000 cubic feet, are as follow : 
 
 
 
 
 1 
 
 
 From 
 
 From 
 
 From 
 
 From 
 
 
 condenser 
 
 scrubber 
 
 washer 
 
 purifiers 
 
 Hydrogen ..... 
 Marsh gas 
 
 380 
 390 
 
 380 
 388 
 
 380 
 384 
 
 380 
 403 
 
 380 
 394 
 
 Carbonic oxide .... 
 
 72 
 
 71 
 
 71 , 
 
 39 
 
 30 
 
 Heavy hydrocarbons . 
 
 42 
 
 48 
 3 
 40 
 
 46 
 50 
 5 
 39 
 
 45 
 69 
 2 
 34 
 
 46 
 79 
 5 
 33 
 
 43 
 100 
 6 
 4 
 
 Oxygen . . . . 
 Carbonic dioxide 
 
 Sulphuretted hydrogen 
 
 15 
 
 15 
 
 5 
 
 3 
 
 
 
 Ammonia .... 
 
 10 
 
 5 
 
 
 
 ~~ 
 
 
 
 1000 
 
 999 
 
 990 
 
 988 
 
 966 
 
 After leaving the purifiers, the preparation of the gas is complete, and it only has 
 to pass through the station meter where the daily make is registered, from whence it 
 passes on to the gas holder, where it is stored. 
 
 As supplied to consumers, coal gas has a composition shown by the following table, 
 giving the average composition of coal gas supplied by the companies named: 
 
 
 Great Central 
 
 Imperial 
 
 Chartered 
 
 Illuminating hydrocarbons . . 
 
 3-56 
 35-28 
 
 3-67 
 40-66 
 
 3-53 
 35-26 
 
 Hydrogen . . . . 
 Carbonic oxide . . . 
 Carbonic acid . . . . "''." 
 
 51-24 
 
 7-40 
 0-28 
 1-80 
 
 41-15 
 8-02 
 0-29 
 5-01 
 
 51-80 
 8-95 
 
 0-38 
 
 Oxygen . . 
 
 0-44 
 
 1-20 
 
 0-08 
 
 i 
 
 100-00 
 
 100-00 
 
 100-00 
 
708 
 
 ARTIFICIAL LIGHTING. 
 
 After being measured by passing through the station meter, the gas reaches the 
 gas holder, where, it is stored up until required. The gas holder consists essentially 
 
 of a cylindrical vessel made of sheet iron, covered at the top and open at the bottom. 
 
 This is placed in a sunk pit, lined with masonry (c c c), 
 of a somewhat greater diameter than the cylinders, 
 and capable of being filled with water. Such a gas 
 holder is represented in fig. 487. Into this basin 
 project several inches above the level of the water, 
 and supported by a wall (E), the inlet and outlet 
 pipes (D). As there is a liability of condensed 
 water, tar, etc., collecting in the lower part of these 
 pipes, they slope slightly to the outside of the basin, 
 where the accumulated substances can be removed 
 by a hand-pump. 
 
 The passage of the gas in either of the tubes 
 can be stopped by a valve of 'the kind represented in 
 fig. 488. This valve consists of a bell-shaped cover 
 fitting over the end of the inlet pipe (A), and 
 dipping into tar or water retained round the end of 
 the pipe by an outer casing, to the side of which the 
 outlet pipe (B) is attached. While this bell-shaped 
 cover is in the position shown in the drawing, the 
 valve is closed, but when it is raised by means of 
 the connecting rod and windlass above, communica- 
 tion is established between the inlet and outlet 
 pipes. 
 
 The upper and lower edges of the gas holder are 
 strengthened by wrought iron rings (FFF, fig. 487), 
 and the sides are strengthened by vertical ribs (o G) 
 of angle iron. The cylinder is capable of being 
 raised as it becomes filled with gas, and the rollers 
 (j j) attached to the upper ring, run upon guide bars 
 FIG. 488. attached to the pillars (KK). 
 
 The Meter. Before the gas is delivered for consumption, it is requisite it should 
 be measured. The metres employed for this purpose are distinguished as wet meters 
 and dry meters, and they are fixed to the supply pipe in each house. The construction 
 
GAS METERS. 709 
 
 of a wet meter is represented by fig. 489. The gas enters through the pipe (a) into 
 the upper part (6) of the chamber (A A), and passes through the hole (e) into the lower 
 
 .v, 
 
 FIG. 489. 
 
 space (d), containing water at the lower end. From 
 this chamber it passes through the tube (e) and 
 through the lateral tube (/) into the large cylin- 
 drical chamber (B B), and then rises through the 
 tube (g) into the front space (Ji) of the drum (c). 
 This drum is closed at the back (), and rests upon 
 an axis (i) in the back (I) on one side, and at the 
 other on a prolongation of the tube (/). The interior 
 surface is not parallel to the axis, but separated by 
 four partitions placed at an incline from one side of 
 the drum to the other, so as to form four separate 
 chambers. The back (&) has four slits and thus 
 forms the wings (m, n o p, fig. 490), situated at right 
 angles with the partitions. The gas by its pressure 
 turns the drum, and as the fissure belonging to each IG - 49 - 
 
 chamber is raised above the water level, the gas escapes into the space (q), from which 
 it passes through the tube (r) to the burners. By increase of temperature the gas 
 takes up water, and lowers the level of water in the meter. When this takes place, 
 the hollow ball (t) sinks, and the plate () closes the aperture (e), so as to shut off the 
 supply of gas, thus indicating that the meter is deficient in water. In order to prevent 
 too much water being put in, so as to fill the tubes (efg), the tube (e) has a prolonga- 
 tion (v), which dips into a small reservoir (ar), filled with water up to the level of the 
 screw (w). In supplying the meter with water this screw is removed, and when water 
 begins to run out of the hole, the meter has been filled to the proper level. The screw 
 (to) is placed at such a height from the bottom of the reservoir (ar), that the column of 
 water is equal to a pressure of somewhat less than four inches, and thus gas is pre- 
 vented from escaping through the hole into which the screw (w) fits. 
 
 The wet meter, when well constructed, measures very accurately, and requires 
 only a. slight pressure of gas to work it ; but it is liable to derangement by alteration 
 
710 
 
 ARTIFICIAL LIGHTING. 
 
 of temperature. It has therefore to a great extent been superseded by the dry meter, 
 which consists of chambers of definite capacity, and capable of being expanded ancj 
 contracted. In both cases the quantity of gas passing through the meter is indicated 
 by a clockwork arrangement. 
 
 FlG 4gi The Eegulator. The varying 
 
 pressure of the gas in the mains 
 depends upon the distance between 
 the gas works and the place where 
 the gas is consumed, and for this 
 reason it is desirable to have regu- 
 lators connected with the gas 
 supply of each house, in order to 
 maintain a constant pressure. One 
 kind of regulator used for this pur- 
 pose consists of a small metal bell, 
 so arranged in an outer casing, par- 
 tially filled with water, that it is 
 raised by increasing pressure of the 
 gas, and entirely closes a conical 
 valve connected with it through 
 which the gas passes ; while, on 
 the contrary, with decreasing pres- 
 sure the bell sinks and opens the 
 valve wider. A regulator of this 
 construction is represented by figs. 
 491 and 492. At the centre is the 
 valve (c) through which the gas 
 passes attached by a chain to the 
 bell (D), and when it is in the posi- 
 tion shown in the drawing, the gas 
 is entirely shut off. When the valve 
 (c) is lowered to the position 
 marked (F) the gas entering through 
 the pipe (K) has free access in the 
 bell (n), out of which it passes 
 through the pipes (L i) to the 
 burners. The pressure of the gas 
 on the bell (D) is regulated by add- 
 ing or removing cast-iron disks 
 through the opening (G) at the top 
 of the casing (E), within which the 
 bell is fitted. To the top of this 
 casing is fixed a tube (H) which is 
 open to the air and carries at the 
 end a small light metal disk, so 
 that when through any accident 
 the water level in the casing (E) 
 falls too low, or from any other 
 reason gas escapes, it is discharged 
 outside the building. In order to 
 maintain a constant level of liquid in 
 the casing (E), glycerine of 1*143 sp. 
 gr. is used instead of water. 
 
 The membrane regulators are 
 preferable to those just described. 
 The construction of one form of 
 this apparatus is represented by 
 tig. 493. The gas enters by the 
 supply pipe (A) and is discharged 
 through the pipe B, after passing 
 through the chamber (c) which is 
 covered at the top with an imper- 
 vious flexible membrane (E), to the 
 centre of which is attached a rod 
 (F), carrying at one end a conical 
 plug (H) by which the opening of the 
 FIG. 493. lower portion of the chamber (c) 
 
 FIG. 492. 
 
IMPROVEMENTS IN GAS MAKING. 
 
 711 
 
 can be closed when the membrane is pressed upwards. The tension requisite for 
 effecting this may be regulated by suitably loading the lever (j) to which the upper 
 end of the rod (F) is attached, and for this purpose the lever carries a sliding 
 weight (x) which can be fixed at any part of the lever by means of a screw. The 
 influx of the gas is therefore regulated by adjusting the weight (K), and the gas escapes 
 regularly through the pipe (B) at the pressure required. 
 
 The gas consumed in street lamps is not measured, but the quantity burnt within 
 a given time is regulated by a tap, set to allow the gas to pass under a definite pres- 
 sure at a certain rate. The plan, how- 
 ever, is open to objection, and in some 
 places membrane regulators are fixed to 
 the burners in the manner represented by 
 fig. 494. The gas in passing from the 
 pipes (c and n) to the burner is made to 
 pass through the vessel (A A) fitted with a 
 membrane diaphragm (B B), to the centre 
 of which is attached a rod (z) carrying a 
 valve (r). The chamber (A A) is divided 
 by the membrane into two parts, so that 
 when the gas passes into it under in- 
 creased pressure, the membrane is forced 
 upwards into the upper part, and the 
 valve (r) being thus raised, it contracts 
 the aperture by which the gas enters from 
 the supply pipe (c) below. 
 
 A great number of proposed improve- 
 ments in gas production have been sug- 
 gested. According to one, the coal is dis- 
 tilled at a much lower temperature than 
 usual, and hence it takes about double 
 the ordinary time. The gas thus pro- 
 duced has a high illuminating power, and 
 a quantity of oily tar is obtained, which 
 is afterwards submitted also to destructive 
 distillation, thus furnishing a further 
 quantity of permanent gas. Practically, 
 the two distillations are conducted simul- 
 taneously, the combined result being that 
 a larger yield of gas is obtained, of some- 
 what higher illuminating power than usual, 
 and, owing to the lower temperature of 
 distillation, containing less sulphur com- 
 pounds than the gas made by the ordinary 
 process. A special apparatus is required 
 for the distillation of the oil and the ad- 
 ditional plant, labour, and fuel required 
 outbalance the favourable results. 
 
 Another system aimed at continuous 
 working, and constant and regular re- 
 moval of the gas produced. It was 
 sought to effect this by introducing the 
 coal into vertical retorts, through a 
 hopper, whence it was carried by the 
 action of a revolving screw down through 
 the length of the retort, reaching the bottom in the form of coke. The resistance 
 offered by the coal to the free revolution of the screw proved an insuperable difficulty 
 in the process, which otherwise promised to yield satisfactory results. 
 
 There have also been a number of processes proposed for producing gas suitable 
 for heating purposes from steam, and when further treated for the purposes of illu- 
 mination. These consist in admitting steam into retorts charged with coal or coke, 
 at a high temperature. The steam is thus decomposed and the hydrogen set free ; 
 the oxygen by oxidation of the coke is partly converted into carbonic anhydride, and 
 this by reduction with more red-hot coke becomes partially transformed into carbonic 
 oxide ; so that the ultimate result is a non-illuminating gas which consists of hydrogen, 
 carbonic oxide, and carbonic anhydride. To give it illuminating power it is passed 
 through petroleum spirit, and thus saturated witli that vapour, or the petroleum is 
 decomposed and the vapour mixed with the gases. 
 
 Various other processes have been suggested for making gaseous mixtures of car 
 
712 ARTIFICIAL LIGHTING. 
 
 bonic oxide and hydrogen, or carbonic oxide alone, for use as fuel, but, with the 
 exception of the method already described at page 589, and the application of the 
 combustible gas from iron smelting furnaces, none of them demand special attention, 
 since none have so far achieved commercial success. 
 
 The gas evolved in the distillation of coal, bituminous shale, or other similar 
 materials, for the production of hydrocarbon oil, has generally a high illuminating 
 power, since it contains in large proportion the vapour of the more volatile hydro- 
 carbons produced in the operation. In large works this gas is produced in such 
 quantity, that it is very much in excess of the requirements of lighting the buildings 
 belonging to the works, and it is generally turned to account by burning it under the 
 retorts in which the coal or shale is distilled. Attempts have also been made to 
 convey the gas, thus produced in oil works, throiigh pipes to the neighbouring 
 towns, and there to utilise it for purposes of illumination. It is, however, probable 
 that in this case the illuminating power of the gas would be too much reduced by 
 the condensation of the hydrocarbon vapours if the places to which the gas had to be 
 carried were situated at a very considerable distance from the works where it was 
 produced. 
 
 Carburetting Gas. Various plans of causing any kind of gas to become saturated 
 with coal tar, naphtha, or petroleum vapour, have been proposed with the object of 
 augmenting the illuminating power. 
 
 Air saturated with the vapour of volatile hydrocarbons has frequently been pro- 
 posed as a substitute for coal gas, and if used at once, the mixture serves very well for 
 the purposes of illumination ; but when it is attempted to conduct the air gas through 
 any length of pipes, the deposition of the hydrocarbon vapour reduces the quality of 
 the gas. 
 
 The extent to which the illuminating power of such gas, prepared with petroleum 
 spirit, depends upon the temperature, is illustrated by the following table, showing 
 the percentage of vapour present in the air gas at different temperatures, when petro- 
 leum spirit of 0*650 sp. gr. is used : 
 
 Temperature Percentage 
 
 10 = 14 F 57 
 
 = 32 107 
 
 10 = 50 17'5 
 
 Temperature Percentage 
 15 = 60 22-0 
 
 20 = 68 27-0 
 
 40 = 104 39-0 
 
 These quantities correspond with the tension of this vapour at the several tem- 
 peratures, which varies as follows , 
 
 Temperature Vapour tension 
 
 10 = 14 F 43-5 mm. 
 
 = 32 81-0 ,. 
 
 10 = 50 132-0 , 
 
 Temperature Vapour Tension 
 15 = 60 167-0 mm. 
 
 20 = 68 203-0 
 40 = 104 301-0 ' 
 
 One of the chief difficulties attending the production of this gas consists in ob- 
 taining a supply of suitable volatile hydrocarbon. Benzol, or the more volatile portion 
 of gas-tar naphtha, being much in demand for other purposes, bears too high a price to 
 be used for making air gas, or for carburetting. The more volatile portion of petro- 
 leum has been therefore chiefly employed, and, as will be seen from the following 
 table, the substances present in oil that does not exceed the specific gravity of 0'660 
 have a high degree of volatility : 
 
 Specific gravity Boiling point Specific gravity Boiling point 
 
 0-600 4 C 
 
 0-628 30 
 
 0-669 68 
 
 0-699 92 
 
 0726 118 C 
 
 0-741 136 C 
 
 0-757 160 C 
 
 This portion of the distillate obtained in refining petroleum or shale oil is un suited 
 for burning in lamps, and tinder certain conditions, such as the lighting of country 
 houses and remote villages, its conversion into atmospheric gas may be conveniently 
 carried out ; but the supply of a sufficiently volatile portion of petroleum or shale oil 
 is too small to admit of competition with ordinary coal gas. The gas obtained in this 
 way from the volatile petroleum spirit has a density of 1-2 as compared with air, and 
 it consists of about 70 per cent, of atmospheric air, with about 30 per cent, of 
 hydrocarbon vapour. When burnt at the rate of 3 cubic feet an hour in one of Sugg's 
 argand burners, such gas will give a light equal to about 18 candles. 
 
 Fat, resin, and the tarry residue left in distilling petroleum or shale oil some- 
 times serve as materials for making gas, and although in general they are too costly 
 for ordinary use, they are sometimes preferable to coal, and when the" subsidiary pro- 
 ducts of petroleum or paraffin oil refineries are used, the gas produced requires but 
 little purification. 
 
OIL GAS. 
 
 713 
 
 Eia.495. 
 
 The retorts used are sometimes horizontal, and arranged in much the same manner 
 as those used in making coal gas. The oil is supplied in a continuous stream, and as 
 it volatilises tho vapour passes through a discharge tube into another retort of nar- 
 rower dimensions, which is kept at a bright red heat, where the oil vapour, coming into 
 contact with the sides of the red-hot retort, is decomposed and converted into gas. 
 
 From the hydraulic main the gas passes to a series of vertical condenser pipes, where 
 any remaining suspended particles of oil are separated ; then into a washing apparatus 
 and purifiers charged with slacked lime, which extract traces of sulphuretted hydrogen, 
 as well as the carbonic dioxide, before the gas is sent into the gas holder. 
 
 In making oil gas the use of an exhauster does not seem desirable, since in this 
 case the prolonged contact of the oil vapour with the sides of the red-hot retorts 
 under a pressure of 3 or 4 inches is requisite for the production of the gas in such a 
 condition that it will burn without producing smoke. 
 
 With retorts of the kind above described, about 38 Ibs. of paraffin oil can be de- 
 composed per hour, and' the yield of gas obtained amounts to about 1000 cubic feet 
 per cwt. The success of the operation depends largely upon the adaptation of the oil 
 supply and the maintenance of the sides of the retorts at a uniform red heat ; both 
 conditions being difficult to secure, the result is that the yield of gas is often much 
 below the average, and there is a proportionate increase in the amount of the liquid 
 products. 
 
 These difficulties are to a great extent obviated by the use of a retort introduced by 
 Hubner, the general arrangement of which is represented in vertical and horizontal sec- 
 tions by figs. 495 and 496. The body of 
 the retort is formed by a slightly coni- 
 cal cast-iron tube (a a) closed above 
 and below, and protected by a fire-clay 
 casing at the lower end. This retort 
 is heated by a flue winding round it 
 and communicating with the furnace 
 at the side. The oil is supplied to the 
 retort through several funnel tubes (b) 
 fitted into the upper end of the retort 
 in such a manner, that the oil runs 
 down the heated sides and is there 
 converted into gas, which escapes 
 through the central tube (e) into the 
 pipe (m), connected with the hy- 
 draulic main (). The tubes (e and 
 m) are furnished with an arrange- 
 ment (/), by which deposits of carbon 
 in the shape of coke or soot can be 
 removed. At the bottom of the 
 retort is a movable mouth piece, 
 which can be removed by loosening the 
 screw (d), and the soot or other ac- 
 cumulations can then be drawn out 
 by the rod (c). The flue running 
 round the sides of the retort is fur- 
 nished with several apertures (k k k k} 
 by which soot and ashes can be re- 
 moved. 
 
 The heat produced with this ar- 
 rangement is very high and uniform, 
 so that from 50 to 80 pounds of oil 
 can be converted into gas hourly, and 
 the yield of gas amounts to 1100 cubic 
 feet per cwt., the illuminating power 
 of which is fully three times as 
 great as that of the ordinary coal gas. 
 The consumption of fuel as well as the 
 labour required are less than with the horizontal retorts, and owing to the uniform 
 temperature obtainable, as well as the small deposition of carbon taking place, the 
 retorts last a long time. . , 
 
 Oil gas has a specific gravity of about 07 ranging to 0'6 when the heat applied 
 in decomposing the oil is great, and when it is too low the specific gravity of the gas 
 is sometimes as high as 0'9 ; its composition is very different from that of coal gas, 
 as shown by the following analyses : 
 
714 
 
 ARTIFICIAL LIGHTING. 
 
 Olefiant gas and homologues 
 Marsh gas 
 Hydrogen 
 Carbonic oxide 
 Nitrogen 
 
 Oil gas 
 
 Gas from 
 
 petroleum residues 
 
 22-5 
 50-3 
 77 
 15-5 
 4-0 
 
 17-4 
 58-3 
 24-3 
 
 Gas burners may be constructed on one of two principles, according to the use for 
 which they are intended. If it be required to use the burner for purposes of illumina- 
 tion, its construction differs materially from that adopted when the burner is in- 
 tended for heating purposes. It has already been explained (p. 23) that flame is 
 merely gas heated to, and maintained by its own combustion at such a temperature, 
 that it emits light as well as heat. But the illuminating power of coal gas is essenti- 
 ally due to the presence in it of dense hydrocarbons such as defiant gas, and not to 
 the light carburetted hydrogen or the hydrogen which burns with scarcely any light. 
 The production of light in this case has been attributed to the fact that these dense 
 hydrocarbons split up at a high temperature into free carbon, and gases containing 
 less carbon ; and although in any case the ultimate products of their combustion are 
 carbonic anhydride and water, yet the evolution of light is to some extent referable 
 to the intensely heated condition of the particles of carbon liberated in the flame, as a 
 result of that decomposition. A mixture of coal gas, with a sufficient quantity of air 
 to effect rapid combustion, burns with a faint blue non-luminous flame, and no 
 carbon is deposited upon a cold plate held in the flame. 
 
 It has however been ascertained that the luminosity of flame is not altogether due 
 to the presence of solid particles, and Frankland has shown that marsh gas may be 
 made to give a luminous flame, by heating to redness the gas and the air in which it 
 is burnt. He has also shown that the luminosity of flame is augmented by increase 
 in the density of the air in which gas is burnt, so that the evolution of light attending 
 combustion is a complicated phenomenon influenced by a variety of conditions. 
 
 In the combustion of gas for illuminating purposes, the form of the flame depends 
 upon the nature of the aperture from which the gas issues. The batwing burner is 
 formed by a narrow slit across the end of a closed tube, and the flamo has the shape 
 of a fan. The fish-tail burner has in the place of the slit two converging round holes 
 inclined towards each other at an angle of 60. The two jets of gas striking against 
 each other produce a flattened flame. 
 
 The Argand burner consists of an annular chamber, the upper surface of which is 
 perforated with a number of holes from which the gas issues in small jets, and is thus 
 brought into sufficient contact with atmospheric air to insure complete combustion. 
 One of the best forms of Argand burner is that introduced by Sugg under the name 
 of the London burner, the construction of which is represented by fig. 497. 
 
 In this burner the joint area of the apertures (/) through which the gas escapes 
 is much greater than that of the apertures (g\ by which the gas passes into the an- 
 nular space (c), and thus the pressure with which 
 the gas escapes from the burner is considerably 
 reduced. There is consequently less tendency to 
 mechanical mixture of gas and air at the surfaces 
 of contact, and the flame is very luminous. At 
 the neck (A) of the burner is fixed a conical plug, 
 which fits into the contracted part (/>) of the 
 tube (c), when the neck of the burner is screwed 
 close down upon the tube (c), but by inserting 
 thin paper washers between this tube and the 
 neck of the burner, the size of the aperture left 
 between the tube (b) and the conical plug may 
 be regulated so as to suit the nature of the gas 
 used, and the pressure under which it is supplied 
 to the burner. 
 
 When gas is used as a source of heat, it may 
 bo burnt cither in the form of very small jets, 
 formed by the discharge of the gas through 
 
 Fio. 497. 
 
 a number of minute apertures in a metal pipe, bent into the form of a ring, or it may 
 be previously mixed with about half its volume of air, and burnt in this state, in 
 what is termed an atmospheric burner. The gas then burns with a blue flame, and 
 does not deposit soot. The several parts of a burner of this kind are represented by 
 
GAS BURNERS. 
 
 715 
 
 fig. 498. When the piece (6) is inserted into the foot (a) as shown in the drawing, 
 the gas passes from the supply pipe (e) through the channel (/), and mixes with air 
 passing in through g g into the hollow space (i i). By turning the plug (a) communi- 
 cation between e and / may be shut off as far as required. 
 
 Another arrangement of atmospheric burner is represented by fig. 499. It consists 
 of a hollow sheet-iron cone (6), partially closed at the bottom, and covered at the top 
 with wire gauze. The gas is supplied to the interior of the cone through the tube (a), 
 
 and the mixture of gas and air burns above 
 the surface of the wire gauze, which is suffi- 
 ciently fine to prevent the flame from being 
 communicated to the gas beneath it. 
 
 FIG. 498. 
 
 Owing to the high illuminating power of oil 
 gas, the consumption is not more than one-third 
 or one-fourth as great as when coal gas is used. 
 The apertures of the burners are therefore ad- 
 justed, so that under a pressure of about 1 inch, 
 the quantity of gas burnt per hour is about f 
 foot. 
 
 When this gas is used mixed with air for 
 producing a heating flame, the ordinary Bunsen 
 burner gives a smoky flame, and acetylene is pro- 
 duced, which causes a bad smell. These incon- 
 veniences are prevented by using a burner of the 
 construction represented by fig. 500. The inner 
 tube (a) has a screw thread upon which a ring 
 with three arms works up or down, and the 
 conical part of the chimney (b) is soldered to 
 the arms of this ring. The lower edge (c) of 
 this chimney is ground even so as to fit closely 
 upon the surface of the foot (d) of the burner. 
 The first mixture of the gas with air takes place 
 in the tube.(a), the air being drawn in through 
 the holes (/) by the gas flowing through the tube 
 (e), and escaping from the aperture (g}. A 
 further admixture of the gas with air takes 
 place in the tube (6), so that by properly adjust- 
 ing the height of the chimney a clear blue flame 
 is produced. 
 
 FIG. 499. 
 
 FIG. 500. 
 
716 
 
 ARTIFICIAL LIGHTING. 
 
 Tessie du Motay has introduced a method of burning highly carburetted gas with 
 oxygen, in specially constructed burners of the kind represented by fig. 501, and has 
 
 succeeded in producing a very much greater 
 luminous effect. 
 
 The carbonaceous residue or coke left in 
 the retorts in making illuminating gas from 
 coal is an important subsidiary product 
 amounting to from 60 to 75 per cent, by 
 weight of the coal worked. Gas coke is 
 generally much more bulky than the coal 
 from which it is produced, and in some 
 cases it forms a very convenient fuel ; its 
 value in this respect depends however 
 upon the amount of ash which it contains. 
 Some kinds of cannel coal which yield a 
 large amount of gas contain so much in- 
 combustible material that the coke they 
 yield is not applicable as fuel. 
 
 Ammoniacal gas liquor is another im- 
 portant subsidiary product which is largely 
 used for the manufacture of sulphate of 
 ammonia by boiling the liquor with lime in 
 an iron retort and passing the ammonia gas 
 thus liberated into leaden vats containing 
 sulphuric acid (see pp. 49, 52, et seq.) ; as 
 J?IG. 501. ^ e ac j b ecomes neutralised, and therefore 
 
 concentrated, the sulphate of ammonium crystallises out and is then baled out and 
 laid upon racks to drain and dry. This manufacture is often conducted on the pre- 
 mises of the gas works, especially in .the north of England. 
 
 The tar produced in gas making is also a valuable product, and has within the last 
 few years furnished not only a number of products useful in particular manufactures, 
 as for instance, naphtha in caoutchouc working, creasote for preserving wood, and 
 pitch for asphalt paving, etc v but also the raw material of several new branches of 
 industry, especially the benzol naphtha from which aniline dyes are made, and anthra- 
 cene which is now the source of artificial madder. Carbolic acid also, which is so 
 largely used as a disinfectant and for the production of colours, is obtained chiefly 
 from coal tar. 
 
 Gas tar is a thick black liquid having a density from 1*120 to 1'150. It contains 
 a large variety of substances, including ammonia, aniline, picoline, quinoline, pyridine, 
 acetic acid, phenic acid, rosolic and brunolic acids ; also benzene, toluene, cumene, 
 cymene, naphthalene, anthracene, chrysene, and pyrene. 
 
 When properly distilled it yields a light volatile oil called coal tar naphtha, a 
 heavy oil of high boiling point called dead oil, and a residue of pitch ; the relative 
 proportions of these products varying according to the kind of coals from which the tar 
 is obtained. 
 
 
 Naphtha 
 
 Dead oil 
 
 Pitch 
 
 Common coal tar . . . . . * 
 
 3 
 
 62 
 
 35 
 
 Ordinary cannel tar 
 
 9 
 
 60 
 
 31 
 
 Boghead cannel tar . . .... 
 
 15 
 
 67 
 
 18 
 
 The naphtha so obtained is largely used for dissolving caoutchouc. 
 
 The dead oil is extensively used as a lubricator for machinery. The black residue 
 left in the retorts on distillation of coal tar, and called pitch, is very much used for 
 making certain kinds of asphalt. 
 
 The distillation of coal tar is conducted on an extensive scale, as a distinct in- 
 dustry, the operation being performed upon quantities of several hundred gallons at a 
 time in large iron retorts. At first water, ammonia, and some permanent gases pre- 
 viously held in solution by the tar are evolved, after which, as the temperature in- 
 creases, a light fetid brown oil passes over ; this constitutes the light oil, and amounts 
 to about 5 or 10 per cent, of the tar. It is purified by mixing with a little oil of 
 vitriol, which destroys the brown oxidised compounds to which the colour of the crude 
 oil is due, and forms with them a tarry deposit that is easily separated. On rectifi- 
 cation the purified oil furnishes coal-tar naphtha, which admits of further purification 
 and fractionation. Dead oil is the heavier yellow oil which comes over after the 
 
GAS TESTING. 
 
 717 
 
 naphtha in the distillation of tar, and it generally amounts to about 25 or 30 per cent, of 
 the tar. 
 
 Towards the end of the operation, the distillate becomes thicker and contains 
 anthracene. At a still more advanced stage, chrysene and pyrene pass over as 
 orange-coloured vapours, which condense readily on cooling. When the distillation is 
 completed, the pitch remaining in the retorts is run out into a pit underground to 
 cool. 
 
 Heavy coal tar oil or dead oil contains carbolic acid, aniline, quinoline, and a 
 mixture of hydrocarbons boiling between 390 and 570, and containing in solution a 
 quantity of anthracene. Dead oil is largely used for the preservation of railway 
 sleepers ; it is also used for feeding common lamps, but mainly for burning into lamp 
 black. 
 
 The Examination of Coal Gas. The gas manufacturer often relies upon specific 
 gravity as an indication of the quality of gas. The photometric method most com- 
 monly employed consists in a comparison of the intensity of the light transmitted 
 through a semi-transparent disc of a paper screen, as compared with reflected light 
 striking on an opaque portion of the screen. When the screen is so adjusted that the 
 light reflected and that transmitted are equal, their intensities are to each other in the 
 ratio of the squares of their distance from the disc. The standard ordinarily em- 
 ployed is the light of a spermaceti candle, burning at the rate of 120 grain* of sper- 
 maceti per hour, and the intensity of the light emitted by a gas flame, consuming in a 
 given time a known quantity of gas, is expressed as being equal to so many candles. 
 
 The jet photometer, represented by figs. 502 and 503, is much used in gas 
 works. It is constructed upon the principle that the luminous intensity of different 
 is inversely proportionate to the pressure requisite to obtain flames of equal 
 
 Fig. 502. 
 
 FIG. 503. 
 
 height. The flame (a) is surrounded by a graduated glass cylinder (6), and by means 
 of an adjustment at e, the pressure of the gas is measured and registered upon the 
 scale (d) by the index (e). The index (<?), is attached to the hollow cylinder (/), which 
 is fixed at i in a horizontal position, and can be turned on its axis. The weight of 
 this cylinder gives it a specific gravity equal to 0'5. It is immersed up to its point of 
 suspension in water, contained in the vessel (#), the bottom of which communicates 
 with the chamber (h). Any pressure exerted at the tube (c) forces water from the 
 
718 
 
 ARTIFICIAL LIGHTING. 
 
 vessel (A) into the vessel (g), but it does not rise in this vessel when its volume is 
 less than or only equal to that of the float (/). But this float is raised by the water, 
 and thus the pressure is registered by the index on the scale. The instrument there- 
 fore shows the quantities of water that must be displaced in proportion to the differ- 
 ences of pressure. 
 
 A rough chemical test often used by the practical gas maker consists in introducing 
 into a known volume of coal gas a bubble of chlorine or a trace of bromine, and 
 observing the contraction in volume resulting from the combination of the haloid 
 with the hydrocarbons to which gas principally owes its luminiferous quality. 
 
 There are many exact methods of coal gas analysis, one of the most appropriate of 
 which may be briefly described as follows : 
 
 A fragment of coke saturated with Nordhausen sulphuric acid is introduced into 
 a measured quantity of the gas over mercury. In the course of a few hours the lumi- 
 niferous constituents are condensed. The sulphurous anhydride thus formed is re- 
 moved by means of a pellet of peroxide of manganese ; the aqueous vapour and car- 
 bonic acid may be then separated by a ball of caustic potash. The difference in the 
 reading of the gas volume then and the original quantity is the expression of the 
 volume of luminiferous hydrocarbons, and as the value of these is ordinarily accepted 
 to stand in relation to the amount of carbon they contain, it may be ascertained by 
 exploding known quantities of the gas both before and after removal of the lumini- 
 ferous constituents, with excess of oxygen and comparison of the relative amounts of 
 carbonic anhydride produced. 
 
 The power of strong sulphuric acid to absorb the luminiferous hydrocarbons was 
 taken advantage of by the Kev. W. K. Bowditch to determine them, by a com- 
 parison of the intensity of the red colour which these heavy hydrocarbons impart to 
 woody fibre, moistened with the strong acid. The results obtained by this method 
 are only approximate. 
 
 Bisulphide of carbon and sulphuretted hydrogen may be estimated by the use of a 
 simple apparatus devised by Wright, in which a known volume of gas is caused to 
 burn in the presence of excess of air ; the amount of sulphuric acid thus produced is 
 an indication of the amount of sulphurous impurity. 
 
ESSENTIAL OIL, CAMPHOR, 
 RESIN, ETC. 
 
 A great number of plants contain oily substances which differ from ordinary fat 
 oil in being volatile and having a strong smell, and the characteristic odours of plants 
 or particular parts of plants are in many instances due to their presence. These 
 substances consist either of hydrocarbons, as in the case of turpentine oil, lemon 
 oil, etc. ; or of oxygenated compounds, as in the case of winter-green oil, which is 
 methyl salicylate, C 8 H 8 3 ,rueoil, which consists chiefly of euodic aldehyde, C,,H 22 O, 
 cinnamon oil and cassia oil, consisting chiefly of cinnamic aldehyde, C^O, and 
 anise oil, consisting of anethol, C 10 H 12 ; while other volatile oils consist of mixtures of 
 hydrocarbons with various oxygenated compounds, as in the case of cumin oil, which 
 containscymene, C 10 H 14 , together with cumic aldehyde, C 10 H 12 0, and thyme oil, which 
 contains thymene, C 10 H, 6 , cymene, C 10 H, 4 , and cymophenol, Ci H 14 0. 
 
 The hydrocarbons occurring naturally in plants have sometimes a composition 
 corresponding with that of cymene, C 10 H 14 , but more frequently their composition 
 corresponds with that of terpene, C 10 H 16 , which is the chief constituent of turpentine 
 oil. and since the hydrocarbons contained in some other varieties of essential oil are 
 either isomeric with it, like bergamot oil and neroli oil, or polymeric with it, like 
 copaiba oil and cubeb oil, C 20 H 32 , the term terpene is applied to them as a generic 
 designation. The chemical constitution of many of these substances is still imper- 
 fectly known. 
 
 The various kinds of essential or volatile oil occurring in plants often contain 
 solid hydrocarbons, which separate when the oil is exposed to a low temperature, and 
 this solid portion of the oil is called stearoptene, while the liquid portion is called 
 elaeopteno. 
 
 Two remarkable solid hydrocarbons, known as caoutchouc and guttapercha, 
 which have a composition analogous to some varieties of essential oil, but differ from 
 those substances in not being volatile without decomposition, occur in the milky juice of 
 various species of Ficus, Euphorbia, Hevea, etc., and in the milky juice of Isonandra 
 gutta. 
 
 The substances known under the name of camphor are in many respects analogous 
 to the various kinds of essential oil, and they not only occur together with terpenes, 
 etc., but are from a chemical point of view closely related to those substances. 
 Although the term camphor is especially applied to the two substances obtained from 
 Laurus camphora and Dryobalanops campkora, there are several other plants, such as 
 feverfew (Pyrethrum parthenium), rosemary, lavender, sage, marjoram, hops, cajeput, 
 peppermint, coriander and patchouli, etc., which contain substances analogous to 
 these more ordinary forms of camphor. 
 
 The substances to which the generic name resin is applied often present marked 
 indications of relationship to the several kinds of volatile oil, both in their chemical 
 nature and in their natural association with them. They are generally solid, yellow 
 and translucent bodies of a specific gravity ranging from 0'92 to 1'2 ; some are hard 
 and friable, but they often occur mixed with volatile oil, forming soft and adhesive 
 or semi-liquid masses, as in the case of pine resin, turpentine, Canada balsam, copaiba 
 balsam, etc. They mostly melt without decomposition, but are not volatile, and at 
 higher temperatures burn with a thick white smoke which is inflammable. When 
 heated in closed vessels most of them yield volatile hydrocarbons ; others oxidised 
 volatile products. They are insoluble in water, but soluble in alcohol and ether ; 
 those which fail to dissolve in alcohol are usually found to dissolve in ether ; they 
 are also dissolved by essential oils, etc. Some few may be obtained in a crystalline 
 form by evaporation of their solutions. 
 
 The substances named resins which occur naturally are compounds of carbon, 
 hydrogen and oxygen, and are generally derived by oxidation from hydrocarbons or 
 bodies containing originally less oxygen than themselves. But, as in the case of the 
 
720 RESIN, ETC. 
 
 essential oils and the camphors, comparatively little is known of the composition and 
 chemical relations of these substances. 
 
 In no case is a resin a simple substance, but it is generally a mixture of several, 
 the various constituent members being referable to as many distinct bodies from 
 which by natural oxidation they are produced. 
 
 A considerable number of resins are of an acid character, and in such cases they 
 are competent to produce soaps by combination with alkalies ; the soaps thus formed 
 are not insoluble in a solution of salt ; nevertheless, ordinary colophony is largely 
 used in soap-making. 
 
 The resins are insulators of electricity, and become negatively electric by friction. 
 
 The process of extraction of resins from the plants which yield them varies with 
 the circumstances and plant. Many of them are obtained by spontaneous exudation 
 from the growing trees ; in other cases incisions are made in the trunk of the tree, 
 and the exuded matter caught in appropriate vessels. In other cases the resins are 
 extracted from plants by means of solvents, such as alcohol, aided by heat. 
 
 The best known resins are those produced in the pine and other trees which secrete 
 essential oils. These oils are mixtures of hydrocarbons, often consisting of allotropic 
 modfications and polymers of the body C 10 H lfl . Thus several varieties of the terpene 
 C 10 H 16 may co-exist, together with the polymeric substances C 15 H 24 and C 20 H 32 ; from all 
 of these resins are produced by oxidation. So that the resins as they occur naturally 
 are necessarily mixtures and may be very complicated. The act of oxidation may 
 consist in mere addition ; or it may be an act of substitution of part of the hydrogen, 
 or part of the carbon may be oxidised as carbonic acid. Any or all of these changes 
 may take place and the nature of the resin produced is determined accordingly. 
 
 Besides the resins already mentioned, there is another class termed fossil resins, 
 including amber, asphalt, resins from lignite, and a number of others all of vegetable 
 origin, but scarcely entitled to be considered properly as resins. 
 
 In many cases the resin existing in plants is accompanied by and intimately mixed 
 with other substances, such as volatile oil or gum, benzoic acid, etc. These mixed 
 products are known by the names of oleores ins, balsams,gumresins, etc. Thus, 
 for instance, the exudations from some plants are semi-liquid or soft and viscous, and 
 contain a large amount of essential oil; these oleoresins are termed balsams, as, for 
 instance, Canada balsam and copaiba balsam, etc., but this term is more correctly 
 applied to materials containing benzoic acid or cinnamic acid together with resin, such 
 as Peru balsam, American liquid storax, Oriental liquid storax, solid storax, tolu 
 balsam, and Mecca balsam, which are among those containing benzoic acid. 
 
 In other cases the resin is accompanied by a considerable amount of gum, as in 
 gamboge, olibanum, ammoniacum, and other kinds of gum resin. Sometimes the products 
 belonging to this class also contain essential oil, which gives them an agreeable 
 odour, as for instance, myrrh. 
 
 A mixture of volatile oil and resin, constituting the oleoresin known by the name of 
 turpentine, exudes spontaneously from several kinds of pine and fir trees, and is 
 obtained more abundantly by making incisions through the bark of the trees ; it is a 
 yellowish white transparent or translucent sticky viscid liquid, having an acid reaction 
 and strong smell. Several kinds of turpentine are distinguished according to the 
 sources from which they are obtained, and they differ in consistency according to the 
 amount of turpentine oil, which varies between 12 and 32 per cent. When the tur- 
 pentine exudes spontaneously and remains a long time exposed to the air upon the 
 stem of the trees, it hardens and forms what is called pine resin, from which 
 Burgundy pitch is made by melting in water and separating a further portion of 
 the turpentine oil. The resin left as a residue when turpentine is distilled, in order to 
 obtain the volatile oil, is called colophony (see p. 725). 
 
 Another kind of oleoresin, called Canada balsam, is obtained from Abies balsa- 
 mea. It is either colourless or pale yellow, has an aromatic odour, is partially soluble 
 in alcohol, and has a right-handed rotation. By distillation with water it yields 
 about 17 per cent, of an aromatic terpene, and a resin of which about one-third is 
 soluble in alcohol, another is soluble in ether, and the remainder is insoluble in both 
 liquids. This variety of turpentine is chiefly employed in cementing optical lenses 
 and microscopic glasses. 
 
 Gurgun balsam, an oleoresin obtained from several varieties of East Indian 
 Dipterocarpus, resembles capivi balsam in odour and taste, but is heavier. It is 
 readily soluble in alcohol, ether, benzol, and carbon bisulphide. It consists of a 
 crystalline acid, gurgunic acid, C 22 H 84 4 , and a hydrocarbon, C 20 H 32 , that boils at 235 
 and has a specific gravity of -9044. 
 
 Copaiba balsam is an oleoresin obtained from varioiis species of Copaifera. It 
 is a pale yellow thick liquid, of a disagreeable aromatic smell and sharp bitter taste. 
 Its specific gravity varies between (V91 and 0'99. It is perfectly miscible with absolute 
 
TURPENTINE OIL. 721 
 
 alcohol, bisulphide of carbon, and volatile and fat oils, and readily soluble in ether 
 and acetic ether. It contains a terpene,C 20 H 32 , of aromatic odour, sp. gr. 0'88 to 0-91, 
 boiling between 245 and 260, partially crystallisable at 26, and Isevo-rotatory ; 
 copaivic acid, a crystallisable substance insoluble in water, soluble in ether and 
 alcohol, C 20 H 30 2 ; sometimes also oxy-copaivic acid, C 20 H 2S 3 ; and an amorphous 
 neutral resin partly soluble and partly insoluble in alcohol. Some remarkably liquid 
 varieties of Para balsam contain no crystallisable acid, but besides volatile oil only 
 the neutral resin, and the Maracaibo balsam, from Columbia, contains only traces of 
 metacopaivic acid, C 22 H 34 4 . 
 
 Turpentine oil is the volatile oil obtained by distillation of turpentine, or the 
 oleoresin contained in all parts of the different species of Pinus, Picea, Abies, and 
 Larix. According to the particular source from which the oleoresin is obtained, this 
 volatile oil presents variations, chiefly in its physical characters. Four chief varieties 
 of turpentine oil are in this way to be distinguished : 
 
 German turpentine oil, obtained from the turpentine of Pinus sylvestris, 
 Pinus Abies, or Picea vulgaris, Pinus Picea, and Pinus rotundata. 
 
 French turpentine oil, from the turpentine of Pinus maritima. 
 
 English or American turpentine oil, from the turpentine of Pinus Taeda 
 and Pinus australis. 
 
 Venetian turpentine oil, from the turpentine of Pinus Larix. 
 
 In addition to these, some scarcely different varieties of volatile oil are obtained by 
 distilling the cones of Pinus Pumilio, the fruit of Pinus Begince-Amalia, the needles 
 and branches of Pinus sylvestris and Pinuf Abies. 
 
 The crude turpentine oil of commerce contains formic acid, acetic acid, etc., and 
 resinous acids, from which it is separated by re-distillation with water, to which some 
 caustic alkali is added. In a pure state it is a colourless thin liquid, with a peculiar 
 unpleasant smell and burning taste. Its specific gravity varies from 0'S6 to 0*87 ; 
 the boiling point from 152 to 160. The G-erman, French, and Venetian varieties of 
 oil rotate the plane of polarised light to the left, but in different degrees. The 
 English variety has a right-handed rotation. Turpentine oil is misciblewith absolute 
 alcohol, wood spirit, ether, chloroform, benzol, and carbon bisulphide. It dissolves in 
 four times its volume of alcohol of 0'830 sp. gr., and in twelve times its volume 
 of alcohol of 0*860 sp. gr. The varieties of turpentine oil consist chiefly of 
 terpenes or camphenes, together with small proportions of polymeric hydrocarbons. 
 All these substances are susceptible of molecular alteration, especially under the joint 
 influence of heat and pressure, accompanied with alteration of the specific gravity, the 
 boiling point, and especially the rotatory power. When exposed to the air, turpentine 
 oil absorbs oxygen and becomes resinified, while at the same time hydrogen peroxide 
 is formed, together with formic acid, carbonic acid, etc. When water is present, a 
 crystalline hydrated oxide, C 10 H 16 + H 2 0, is formed, which has a camphoraceous smell 
 and is soluble in water, alcohol, and ether. By contact with dilute nitric acid a cry- 
 stalline hydrate is formed, having a composition represented by the formula C 10 H 20 0.; 
 + 2H 2 0, called terpin, and sometimes a liquid hydrate is formed having the formula 
 C, H 18 0. Turpentine oil absorbs dry hydrochloric acid gas with evolution of heat, 
 and when the liquid is kept cold and saturated with the gas, a white crystalline cam- 
 phoraceous substance is separated after some time, which is insoluble in water, soluble 
 in alcohol and ether, melts at 115, and has a composition represented by the formula 
 C, H, 6 HC1. The liquid portion has the same composition as the crystals, and essenti- 
 ally the same characters. Both the liquid and the solid portions have the rotatory 
 powers of the turpentine from which they have been prepared. Another compound of 
 terpene and hydrochloric acid, C 10 H )6 2HC1, which is formed by longer continued 
 action of hydrochloric acid gas upon turpentine oil, crystallises in long thin pearly 
 laminae that melt between 48 and 50. 
 
 Juniper oil, obtained by distilling the unripe berries of Juniperus communis, 
 has a sp. gr. of 0'86 to 0'88, distils between 155 and 280, has a left-handed rotation, 
 is sparingly soluble in alcohol of 0'850 sp. gr., soluble in half its volume of absolute 
 alcohol, and miscible in all proportions with ether. By exposure to the air it is 
 oxidised and deposits a crystalline camphor. 
 
 Savin oil, obtained from the leaves, branches, and berries of Juniperus Sabina, 
 has a specific gravity of 0'89 to 0*94, boils at 159 to 161, and dissolves in two parts 
 of alcohol of 0*85 sp. gr. 
 
 Cedar oil, obtained from the wood of Juniperus Virginiana, is colourless, of a 
 buttery consistence, and consists of cedar camphor, Ci 5 H 26 6, and cedrene, Ci 5 H 24 . 
 
 Sandal wood oil, obtained from Santalum album, is a thick yellowish liquid, of 
 powerful odour, having a spec. gr. of 0'963, and distilling between 214 and 255. 
 
 Thuja oil, obtained from the leaves and young shoots of Thuja occidentalis, has 
 a camphoraceous odour, and is said to be a mixture of two oxygenated oils 
 
 3 A 
 
722 RESIN, ETC. 
 
 Cubeb oil, obtained by distilling the fruit of Piper Cubcba, consists of a light 
 hydrocarbon, boiling at 220, having a sp. gr. of 0-915, and strong refractive power; 
 and a thick hydrocarbon, having asp. gr. of 0-937, and boiling at 250. Both are Isevo- 
 rotatory, have a faint aromatic odour and a burning camphoraceous taste. They are 
 miscible in all proportions with ether, benzol, carbon bisulphide, chloroform, and 
 volatile and fat oils, and are soluble in 27 parts of ordinary alcohol, and 18 parts of 
 absolute alcohol. The composition of both is represented by the formula C 15 H 24 . 
 The oil from old cubebs, when cooled to 12 or 20, deposits a camphor, C, 5 IL; 6 0. 
 
 Pepper oil, obtained from the unripe fruit of Piper nigrum ; matico oil, from 
 the leaves of Piper angustifolium ; and the oil of long pepper (Chavica officinarum) 
 are sometimes used in medicine. 
 
 East Indian grass oil, obtained from Andropogon Ivarancusa, is an oxy- 
 genated oil. It boils between 107 and 160, and has a penetrating aromatic odour 
 and a sharp taste. 
 
 Citronella oil is an oxygenated oil, obtained from Andropogon ScJwnanthus. 
 It has a specific gravity of 0-874, and boils at 200. This is sometimes called 
 geranium oil or palma rosaoil. The volatile oil obtained from Andwpogon 
 Nardus, in Ceylon, is scarcely to be distinguished from the last mentioned. 
 
 Lemon grass oil, obtained from Andropogon citratus, is sometimes called ver- 
 bena oil. 
 
 Birch oil, obtained from the leaves of Betula alba, consists of a hydrocarbon, 
 boiling at 171, closely analogous to cymol, and another hydrocarbon, boiling at a 
 higher temperature, which has the peculiar smell of Eussian leather. 
 
 Hop oil, obtained by distilling the strobiles of Lupulus humulus with water, has a 
 sp. gr. of 0-91, boils between 125 and 235, and consists of a terpene and an oxy- 
 genated oil having the formula C 1? Hi 8 0. 
 
 Hemp oil is obtained by distilling the flowering plant of Cannabis sativa. 
 
 Cassia oil is obtained from the liber of Ginnamomum aromaticum, and probably 
 also from the undeveloped flowers of Ginnamomum Loureirii. It is a yellowish or 
 brownish thick liquid, of an agreeable aromatic odour and sweetish burning taste. 
 Its specific gravity is from 1-03 to 1'09 ; it boils at about 225. It is highly refractive, 
 but has no rotatory power. It is readily soluble in alcohol, and consists principally 
 of cinnamic aldehyde C 9 H 8 0, some cinnamic acid, resin (C 30 H, 5 4 ), soluble in al- 
 cohol, and a resin (C 12 H 5 0) insoluble in alcohol. When long kept it deposits a cry- 
 stalline stearoptine having a formula C^H^O-jo. This oil is called Chinese, or ordi- 
 nary cinnamon oil. The Ceylon cinn amon oil, obtained from the bark of Ginna- 
 momum Zeylanicum, closely resembles the foregoing. The oil obtained from the 
 flowers of this plant resembles clove oil and pimento oil. It is brown, has a penetrat- 
 ing aromatic odour, biting taste, acid reaction, and sp. gr. T053. It contains eugenic 
 acid, benzoic acid, and a hydrocarbon resembling cymol, which has a sp. gr. 0'862, 
 and boils between 160 and 165. Another oil obtained from the bark of Persea 
 caryophyllacea, is pale yellow, heavier than water, and similar in smell and taste to 
 clove oil. Massoy oil, obtained in Java from the bark of Cinnamomum Kiamis, is 
 separable by water into a light almost colourless oil of aromatic odour, and a thick 
 heavy oil of less odour : both are readily soluble in alcohol. The oil from the bark of 
 Cinnamomum Culilawan is colourless, heavier than water, and smells like cajeput 
 oil and clove oil. 
 
 The volatile oil obtained from the fruit of Laurus nobilis has a bitter taste, 
 sp. gr. 0'88, and solidifies when cool. It consists of a terpene and eugenic acid. 
 
 Nutmegoil, ormaceoil, is obtained from the arillus of the seed kernels of 
 Myristica moschata; it consists of a terpene, an oxygenated oil, and a camphor, 
 C|gHj 6 5 . 
 
 Sassafras oil, obtained from the wood and root bark of Laurus Sassafras, is 
 reddish yellow, has a sharp smell, and sp. gr. 1'08. It dissolves in 25 parts of 
 alcohol of sp. gr. 0-850. It consists of a terpene, boiling between 155 and 157, an 
 oxygenated oil, C, H 10 2 , boiling between 221 and 233, and a cry stall i sable camphor, 
 C, H 10 2 . It melts between 5 and 17. Another kind of sassafras oil is obtained in 
 Brazil from Nectdndra Cymbarum. 
 
 Japan camphor oil, said to be obtained from Laurus Camphora, has a sp. gr. 
 0'94, and deposits camphor at 10. The most volatile portion has a composition 
 corresponding to the formula C 10 Hi 6 0, and is converted by nitric acid into ordinary 
 camphor. 
 
 Borneo camphor oil, occurs, together with a solid camphor, in the stem of 
 D'ryabalanops camphora, especially in the younger trees. It has a sp. gr. of 0'945. It 
 consists principally of a terpene, some camphor which is deposited on cooling, and a 
 resinous substance. 
 
 Valerian oil, obtained from the roots of Valeriana officinalis, has a specific 
 
ESSENTIAL OILS. 723 
 
 gravity from - 90 to 0'96 ; it begins to boil at 200, and the temperature rises to 
 400 before the whole distils over. It consists of a mixture of terpene, Talerianic 
 acid, and a cry stalli sable camphor, C 12 H 20 0, together with some resin. 
 
 Chamomile oil, obtained from the flowers of Matricaria camomilla, is a 
 dark blue thick liquid, which solidifies at 12 and has a sp. gr. from 0*92 to 0'94. 
 It boils between 240 and 300. Its composition is represented by the formula 
 oC 10 H, 6 .3H 2 0. Its blue colour is due to coerulin. Eoman chamomile oil, ob- 
 tained from the flowers of Anthemis nobilis, is said to be a mixture of angelic acid, 
 C 5 H 8 2 , angelic anhydride, C IO H 14 3 , together with valerianic acid, or a valerianic 
 ether, and a terpene boiling at 175. 
 
 Wormwood oil, obtained from the flowering plant Artemisia Absinthium, has a 
 dark green colour, a burning taste, sp. gr. 0'92 to 0*97, and boils between 180 to 205 ; 
 it is dextro-rotatory and very soluble in alcohol. It consists of a hydrocarbon, an oil 
 corresponding to the formula C 10 H, 6 0, and ccerulin. Wormwood oil is used in medi- 
 cine, and in the preparation of a liqueur. 
 
 The volatile oil obtained from Artemisia Cina is a brownish yellow thick liquid, 
 of disagreeable smell and burning taste. 
 
 Wintergreen oil, obtained from the flowers of Gaultheria procumbens, is a 
 mixture of methyl salicylate and a terpene. 
 
 Thyme oil, obtained from the flowering heads of Thymus vulgaris, has a sp. gr. 
 0'87 to 0'90, and is Isevo-rotatory. It consists of a terpene, thymene, together with 
 cymol and thymol, C, H, 4 0. 
 
 Peppermint oil, obtained from the plant of Mentha piperita, very abundantly 
 in North America, is a mixture of a hydrocarbon and a camphor, menthol, C IO H 20 0, 
 which separates at to 8, plentifully from the American and Japanese oil. It is 
 chiefly used in medicine. Several other species of Mentha yield analogous oils. 
 
 Lavender oil, obtained from the flowers of Lavendula vera, contains several 
 terpene hydrates and a stearoptene. The oil obtained from the leaves and flowers of 
 Lavendula spica, called spike oil, has a less agreeable smell, and is more analogous to 
 turpentine. 
 
 Kosemaryoil, obtained from the flowers and leaves of Eosmarinus officinalis, is 
 used in medicine. 
 
 Patchouli o i 1 , obtained from Pogostemon Patchouli, consists chiefly of a cam- 
 phor, Ci 5 H 28 0, and a hydrocarbon. 
 
 Many of the other plants belonging to the Labiates yiftld similar kinds of volatile 
 oil. 
 
 Kosewood oil, obtained from the root and stem of Convolvulus scoparius, con- 
 sists chiefly of a terpene boiling at 249. 
 
 Anise oil, obtained from Pimpinella Anisum, consists of solid and liquid anethol, 
 C 10 H I2 0. Fennel oil, obtained from Anethum foeniculum, has a similar composition. 
 
 Cumin oil, obtained from the fruit of Cuminum Cyminum, is a mixture of 
 cuminol, C ]0 H ]2 0, and cymene, C 10 H 14 . 
 
 Caraway oil, obtained from the fruit of Carvum Carui, consists of a terpene 
 boiling at 173, and carvol, Ci H, 4 0, boiling above 250. Many other species of 
 Umbellifera yield similar kinds of oil. 
 
 The volatile oil of meadow sweet consists of salicylic aldehyde, C 7 H 6 2 , a 
 neutral hydrocarbon, and a cry stalli sable stearoptene. 
 
 Ottoof roses, obtained from the flowers of Rosa centifolia, E. damascena, 
 E. moschata, and some other varieties, has a sp. gr. 0'815 to 0'888. It solidifies be- 
 tween 15 and 30, is sparingly soluble in water, not very readily dissolved by alcohol 
 in the cold, but copiously soluble in hot alcohol. It consists of a liquid oxygenated 
 dextro-rotatory elseoptene, boiling at 210, and a crystallisable stearoptene, C 8 Hi 6 , 
 which melts at 35, boils between 280 and 300, and sublimes without decom- 
 position. 
 
 Lemon oil, obtained from the fruit rind of Citrus medica and C. Limonum, is 
 limpid, greenish or yellow, has a sp. gr. of 0'84 to 0'86, boils at 160 to 175, and is 
 dextro-rotatory. It is miscible in all proportions with absolute alcohol, dissolves in 
 10 parts of alcohol of 0'85 sp. gr., and readily in ether as well as volatile and fat oils. 
 It is a mixture of two terpenes, citrene and citrilene, and a crystallisable camphor, 
 C 10 H 18 5 . It is closely analogous to the terpene of turpentine oil in its chemical 
 characters. It is chiefly used in medicine and the manufacture of perfumes. Closely 
 analogous to this are three kinds of orange oil, obtained from the fruit of Citrus 
 aurantium, C. Bigarardia, and C. Bigarardia sinensis; also lime oil, from the fruit 
 rind of Citrus Limetta. Bergamot oil, obtained from the fruit rind of Citrus 
 Berqamia, is yellowish or pale green, has an agreeable odour, bitter taste and gene- 
 rally acid reaction; it boils between 183 and 195, has a sp. gr. of 0'85 to 0'88, is 
 dextro-rotatory, miscible in all proportions with absolute alcohol, and readily soluble 
 
 3 A 2 
 
724 RESIN, ETC. 
 
 in ether and fat oils. It is a mixture of one or two terpenes with a terpene hydrate 
 and a product of oxidation. By keeping the oil deposits a camphor, C 9 H 6 3 . By 
 contact with water it forms a crystallisable hydrate identical with terpin, and forms a 
 crystallisable compound with hydrochloric acid gas. It is used in medicine, and in 
 the manufacture of perfumery. Nerolioil, ororangefloweroil, obtained from 
 the flowers of Citrus Bigarardia, has an agreeable odour, a sp. gr. of - 85 to 0*90, and 
 is dextro-rotatory. It contains a camphene boiling at 173, an oxygenated oil of 
 higher boiling point, and by keeping it deposits neroli camphor (auradine). 
 
 Kue oil, obtained from the leaves and flowers of Ruta graveolens, has a sp. gr. of 
 0-83 or '0-84, solidifies at 1 or 2 in brilliant laminae, and consists of a hydro- 
 carbon boiling at 200, and an oxygenated oil of 0-826 sp. gr., boiling between 225 
 and 226, probably methyl caprinol or methyl pelargonyl ketone, C n H 22 0. 
 
 Cajeputoil, obtained from Melaleuca minor, M. Ccy'&puti, and M. leucadendron, 
 which are natives of the Molucca and Sunda islands. It has a pale green colour, 
 partly due to the presence of a green resin and partly due to copper. Its specific 
 gravity varies from 0'91 to 0*97- It is readily soluble in alcohol, and consists chiefly 
 of a terpene hydrate, C, H 18 0. It is chiefly used in medicine. 
 
 Clove oil, obtained from the flower buds and flower stalks of Caryophyllus 
 aromaticus, has a sp. gr. of 1-04 to T06, and is laevo-rotatory. It consists of eugenol, 
 C, H, 2 2 , and a hydrocarbon, probably C ]5 H 21 , having a sp. gr. 0'90 to 0'92, and boil- 
 ing at 142 or 143. It is used in medicine. 
 
 Pimento oil, obtained from the unripe fruit of Myrtus Pimento,, has a sp. gr. of 
 1'03, and is separable by water into a heavy and a light oil. It has the same com- 
 position as clove oil, and is separable by caustic potash into eugenol, C 10 H 12 O a , and a 
 hydrocarbon, C, 5 H 24 . 
 
 Eucalyptus oil, obtained from the flowers of Eucalyptus globulus, consists of 
 eucalyptol, C 12 H 20 0, boiling at 175, dextro-rotatory, and readily soluble in alcohol. 
 The oil of Eucalyptus resinifera contains a hydrocarbon resembling the terpene of 
 turpentine oil. The oil of E. oleosa resembles cajeput oil. According to some 
 authorities, eucalyptus oil contains a terpene, cymene, C 1() H 14 , and an oxygenated oil, 
 C 10 H 12 0. 
 
 Jasmine oil is obtained from the flowers of Philadelphus coronaria. 
 Bitter almond oil, obtained from the fruit kernels of a variety of Amygdalus 
 communis, Amygdalus Persica, Prunus Lauro-cerasus, P. domestica, P.padus, and from 
 the barks, leaves, and flowers of the last-mentioned plants, as well as from other parts 
 of several plants belonging to the Amygdalacese. The volatile oil, consisting of 
 benzoic aldehyde, C 7 H 6 O, with some hydrocyanic acid, benzoic acid, etc., does not 
 exist in the plants, but is formed by the decomposition of the amygdalin, C 20 H 27 NO U , 
 which they contain. 
 
 The volatile oil of Cochlearia officinalis contains sulphur, and is homologous with 
 allyl sulphocyanide, having the formula C 5 H 9 "N"S. The oil of Cochlearia Armoracia 
 (horse radish) is almost identical with mustard oil, as are also several other oils 
 from various species of Cruciferce. 
 
 The oil of Allium sativum (garlic) also consists of allyl sulphide, C ti H, S, and that 
 of Allium cepa (the onion), is essentially identical. 
 
 Mustard oil, obtained from the seeds of Sinapis nigra, does not exist in them, 
 but is formed by the decomposition of myronic acid, C, H,<,NS 2 10 , when the seeds 
 are distilled with water. The oil consists chiefly of sulphocyanide of allyl, C 4 H 5 NS, 
 sometimes mixed with allyl cyanide. 
 
 The substances known under the name of camphor are in many respects analo- 
 gous to the various kinds of volatile oil ; they often occur together with terpenes, and 
 are closely related to the substances of that group. The principal varieties of cam- 
 phor are camphol or common camphor, C, H 16 0, obtained from Laurus camphora, and 
 borneol, C 10 H I8 0, obtained from Dryobalanops camphora. Substances analogous to 
 the former are obtainable from several other plants, such as feverfew (Pyrethrum 
 parthenium), rosemary, marjoram, lavender, sage, etc., while others analogous to the 
 latter occur in hops, cajeput, peppermint, coriander, and patchouli. 
 
 Laurel camphor is a colourless translucent tough mass, having a crystalline tex- 
 ture, a specific gravity of 0'985, and a peculiar strong odour. It melts at 175, and 
 distils at 204, but is slowly volatilized even at the ordinary atmospheric tempera- 
 ture. It is sparingly soluble in water, copiously soluble in alcohol, ether, acetic acid, 
 and hydrocarbons or volatile oils. 
 
 Distilled with chloride of zinc, this camphor is converted into cymene, C IO H H , and 
 water, other products being formed at the same time. When the vapour is passed 
 over heated soda lime, campholic acid, C ]0 H 1H 0. 2 , is formed. By treatment with nitric 
 acid, camphor is oxidised, yielding camphoric acid, C, H, 6 4 , camphoronic acid, 
 C 9 H 12 6 , and oxycamphoronic acid, C 8 H, 2 6 . This camphor also forms an oily com- 
 
COPAL. 725 
 
 pound with nitric acid, 2C, H )6 O.N 2 5 . This kind of camphor is obtained from 
 Japan and the island of Formosa. 
 
 Borneo camphor comes from Borneo, Sumatra, and Labuan. It has a smell some- 
 what resembling pepper. It melts at 19'8, and boils at 212. When heated with 
 nitric acid it is first converted into ordinary camphor, and then into the acids above 
 mentioned. When heated with phosphoric anhydride, it yields water and borneene, 
 C, H I6 , which is probably identical with the terpene contained in ordinary camphor 
 oil. 
 
 Borneol is an alcohol, forming with the fatty acids ethers containing the radicle 
 camphyl, C 10 H, 7 . 
 
 Menthol, Ci H 20 0, is a camphor occurring in peppermint oil. It melts at 36, 
 boils at 213, and is laevo-rotatory. 
 
 Both laurel camphor and Borneo camphor are dextro-rotatory, but other kinds of 
 camphor are Isevo-rotatory. 
 
 Colophony is the resin obtained by the distillation of crude turpentine, which 
 often yields a much as 75 or 90 per cent. Two varieties are found in the 
 market, one of which is white and obtained from the Pinus maritima ; the brown 
 variety is obtained from the Pinus Abies. 
 
 The brown resin, according to Laurent, consists of two isomeric acids, viz. pinic 
 and sylvic acids, C 20 H 30 2 . The pinic acid may be extracted by cold alcohol, and 
 from the residue the sylvic acid is dissolved out by means of hot alcohol, from which 
 it is deposited in colourless prisms or plates that fuse at 127 C. Sylvic acid 
 gives also a crystalline lead salt. 
 
 The white resin, or galipot, consists of pimaric acid, which is also isomeric with 
 the acids of the brown resin, and may be obtained in a semi-crystalline state. It is 
 best dissolved by a mixture of 6 parts alcohol and 1 part ether, and may be recrystal- 
 lised from alcohol ; it is freely soluble in ether. 
 
 The acids of colophony yield terebic acid C 7 H 10 4 , on oxidation with nitric acid. 
 
 When common resin is submitted to distillation in a closed vessel, it yields turpen- 
 tine C 10 H 16 , colophene C 20 H 32 , resinein C 20 H 28 0, toluol C 7 H 8 , cumol C 9 Hj 2 , a substance 
 having a composition corresponding with the formula C 16 Hi 6 , naphthalin C, H 8 , and 
 what is termed metanaphthalin C 20 H 16 . From this it is seen that common resin does 
 not entirely consist of oxidised compounds, but probably also contains the polymer of 
 turpentine C 20 H 32 , in a form rendered solid by the true resin. 
 
 Copal is obtained from trees of the genera Hymenaa, Trachylobium, Foapa, 
 Guibourtia, BhuK, Icica, Elceocarpus, and Dammara. It is excreted partly in tears 
 between the bark and wood, and partly collects in large masses about the roots. It 
 has generally a yellowish or brownish, and, less frequently, a reddish colour, is rough 
 and dark at the surface, internally clear and transparent, and is tolerably hard and 
 brittle ,the fracture being conchoidal and splintery. It is without odour, and has a specific 
 gravity varying between 1-045 and P139 ; the melting point is between 180 and 340. 
 Dilute alcohol does not dissolve copal, absolute alcohol dissolves it only sparingly, 
 but the solubility of copal is increased by the addition of camphor or by long-continued 
 melting, or by long exposure of the powdered resin to the air, under which conditions 
 oxidation takes place. In contact with ether the resin becomes gelatinous, and is then 
 soluble in alcohol. Chloroform dissolves it abundantly, benzol slowly ; volatile oils 
 and carbon bisulphide dissolve it only partially. The best solvents of copal are the 
 oil obtained by the destructive distillation of caoutchouc and the empyreumatic oil 
 obtained by heating copal to a high temperature. In contact with ammonia solution 
 copal swells up, and when warmed with strong caustic potash it forms a clear solution. 
 The African as well as East Indian varieties of copal consist of five different resins. 
 Copal is chiefly used for making varnishes, and combined with asbestos as a cement 
 for stopping teeth. 
 
 Anime, obtained from the West Indian Hymen&a Courbaril and sometimes 
 termed copal, has the form of pale yellow translucent fragments, having a sp. gr. 
 1'028 to T03, and a vitreous fracture. It softens in the hand, and smells agreeably 
 aromatic when warmed. It is perfectly soluble in turpentine oil and benzol, and in 
 warm ammonia solution. Cold alcohol dissolves out a volatile and a portion of resin ; 
 the residue being crystallisable in boiling alcohol in delicate needles, having the 
 formula C 40 H SS 0. 
 
 Sandarac is the resin that exudes from Thuja articulata, a native of Barbary. 
 It forms pale yellow transparent granules, having a specific gravity T05, a faint odour, 
 and of somewhat bitter taste. It is easily fusible, brittle, and the surface of the fracture 
 has a vitreous lustre. Sandarac is used for incense and the preparation of varnish. 
 
 Dammar. Two kinds of this resin occur in commerce; the East Indian, 
 obtained from Pinus Dammara, forms large transparent and colourless or yellowish 
 Jumps. It is friable, odourless, and has a resinous taste. Its specific gravity varies from 
 
726 RESIN, ETC. 
 
 1-04 to 1-12. At 100 it becomes partially liquid, and it melts at 150. It is almost 
 entirely soluble in. cold ether and in boiling absolute alcohol, and dissolves in fat and 
 volatile oils. It consists of an acid resin, dammarylie acid, C 45 H 37 4 , soluble in dilute 
 alcohol ; dammarylic anhydride C 45 H 36 3 , soluble in absolute alcohol ; a solid hydro- 
 carbon, dammaryl, C 40 H 32 ; and a resin, dammaryl hydrate, 4C 40 H 32 2HO(?), insoluble in 
 alcohol and ether. 
 
 The Australian dammar resin, or kaurie copal, is obtained from Dammara 
 australis, a native of New Zealand. It forms large amber-yellow slightly opalescent 
 lumps, is readily fusible, and perfectly soluble in absolute alcohol. It consists of a 
 crystallisable acid resin, dammaric acid, C 40 H 30 7 , and a neutral resin, dammaran, 
 C 40 H 30 6 . 
 
 Another resin, obtained from Shorea robusta, is sometimes mixed with East Indian 
 dammar. These resins are largely used in making varnish. 
 
 Elemi, obtained from species of Idea and Amyris, generally forms yellowish or 
 greenish opaque masses of fatty lustre, which soften between the fingers, are readily 
 fusible, and have a specific gravity of 1-02 to T08. It is only partially soluble in 
 cold alcohol, completely soluble in boiling alcohol, and readily soluble in ether and 
 turpentine oil. It consists of about 13 per cent, of a Isevo-rotatory camphene, boiling 
 between 166 and 174, and having a specific gravity of 0'85, a brown amorphous 
 resin, and a crystallisable substance identical with amyrin. Elemi is used chiefly for 
 preparing varnishes and in medicine. 
 
 Mastic, obtained from a particular variety of Pistachio lentiscus, has the form of 
 tears of a yellowish or greenish colour, covered with a whitish dust, and sometimes 
 having a fissured surface. It is tolerably hard, has a vitreous fracture, and a faint 
 balsamic odour. It softens at 80, and melts between 105 and 180 with partial 
 decomposition. Its specific gravity is about 1 '07. It is readily soluble in benzol and 
 volatile oils ; ordinary alcohol dissolves about four-fifths of a resin, the composition of 
 which corresponds to the formula C 40 H 32 4 , and a soft resin, masticin, C 40 H 30 2 , 
 remains undissolved. It is used in medicine, as incense, for dental cement, etc. 
 
 Lac resin, obtained from the branches of Croton lacciferum, and probably also 
 from some East Indian species of Ficus, Acacia, ZAzyphus, Aleurites laccifera, Croton 
 aromaticus, Butea frondosa, Ficus religiosa, &n&Zizyphus jugrita. The female insect, 
 Coccus lacca, makes the puncture through which the resin exudes and coats the 
 young shoots, enclosing at the same time the body of the insect. These shoots con- 
 stitute stick lac. It consists chiefly of a brilliant, brittle, translucent resin, soluble in 
 alcohol and wood spirit, a small proportion of wax, a difficultly soluble resin, and 
 about 10 percent, of a scarlet pigment known as lac dye. The resin is used for 
 making sealing wax, French polish, and varnish. When the resin is separated from 
 the wood, the pigment is extracted with carbonate of sodium, and the insoluble residue 
 forms seed lac, which, by melting, straining, and pressing, gives shell lac. 
 
 Shell lac contains a number of substances, including, according to Unverdorben, 
 oleic and margaric acids. Lac is soluble in a solution of borax, a property which 
 enables it to be distinguished from more common resins with which it is frequently 
 adulterated. 
 
 Podophyllin is a resin obtained from 'PodopTvyllum peltatum. It is soluble in 
 alcohol, partially soluble in ether, and is chiefly used in medicine. 
 
 Botany Bay resin, obtained from the stem of Xanthorrhwa australis, is reddish- 
 brown, and has a faint benzoic smell. An analogous resin from Xanthorrhcea 
 Jiastilis, has a stronger smell and a bright yellow colour. Both kinds are readily 
 soluble in alcohol and ether, and when treated with water yield gum, cinnamic acid, 
 and benzoic acid. When melted with potash they yield paraoxybenzoic acid, proto- 
 catechuic acid, pyrocatechin, and resorcin. They are used for colouring varnishes, and 
 the yellow kind" is used in medicine. 
 
 Dragon's blood. Three kinds are met with in commerce. East Indian dra- 
 gon's blood, obtained as an exudation from the cortical scales of the fruit of an East 
 Indian palm, Calamus Draco. Canary dragon'sblood, obtained as an exudation 
 from incisions in the stem of Draccena Draco. American dragon's blood, ob- 
 tained in a similar manner from Pterocarpus Draco. 
 
 The first-named is the most frequently met with. It is reddish-brown, opaque, 
 and bitter, without taste or odour; its specific gravity is 1-196. When melted it 
 gives off an odour of benzoic acid. It is readily soluble in alcohol, less so in ether; 
 also soluble in acetic acid, amylic alcohol, volatile and fat oils. It dissolves in alkaline 
 solutions partially, and acids throw down a yellow precipitate from the solution. 
 The resin purified by solution in alcohol and ether has a composition represented by 
 the formula C 40 H 20 8 . When dragon's blood is melted with caustic potash much 
 benzoic acid is obtained, which probably existed ready formed ; also protocatechuic 
 acid, paraoxybenzoic acid, and phloroglucin. By dry distillation it yields gaseous 
 
GUAIACUM. 727 
 
 products, and a reddish-black oil containing toluol, styrol and benzoic acid. Dragon's 
 blood is used in medicine, and for colouring varnishes. 
 
 Guaiacum. This resin, obtained from Guaiacum officinale, a native of the West 
 Indies, has the form of irregular fragments of a greenish colour, which appear opaque 
 externally, but internally are yellow or reddish-brown. It is hard, very brittle, has 
 a conchoidal, vitreous, splintery fracture, and gives .a greyish-white powder. The 
 smell is slight, agreeable, and increased by warming. The taste is at first sweetish 
 bitter, and then sharp and irritating. It melts very readily. Its specific gravity is 
 about 1-2. It is readily and perfectly soluble in alcohol, partially and with difficulty 
 in ether or turpentine oil. It contains about 10 per cent, of guaiaretic acid, C 20 H 26 4 ; 
 70 per cent, of guaiaconic acid, C 19 H 20 5 ; and a small proportion of guaiacic acid, 
 C 6 H 8 3 , which is soluble in water, and crystallises according to Deville from its 
 alcoholic solution in needles ; about 10 per cent, of a neutral resin, C 40 H 20 12 , in- 
 soluble in ether ; a crystallisable pigment, guaiacum yellow ; some gum, ash consti- 
 tuents, and mechanical admixtures. Guaiacum resin readily melts, and when distilled 
 yields, at a temperature of about 320 C., among other products, the following: a 
 light volatile oil, guaiacene C 5 H 8 (b. p. 118 C.), and a substance which sublimes in 
 crystals, pyroguaiacin C 19 H 22 3 ; also guaiacol C 7 H 8 2 , a liquid probably homologous 
 with creasote, and boiling at 210 C. This resin is remarkable for its susceptibility 
 to oxidation, and a consequent blue or green colouration. Eeducing agents restore 
 the yellow colour. By exposure to the air the change of colour takes place but 
 slowly ; most rapidly in violet light ; while in red light it becomes yellow. Chlorine 
 and other oxidising agents cause a rapid blue colouration. By dry distillation 
 guaiacum resin yields a thick reddish -brown tar, containing guaiacol, pyroguaiacin, 
 guaiacene, C 5 H 8 0, and creosol, C 8 H 10 2 . Melted with caustic potash it yields proto- 
 catechuic acid. It is chiefly used in medicine. 
 
 Myrrh, obtained from Balsamodendron Myrrha and B. Ehrenbergianum, has the 
 form of irregular yellow, reddish, or reddish-brown fragments. It has a balsamic 
 odour, and pungent bitter taste. Its specific gravity is from 1*12 to 1*28. It contains 
 about 2 per cent, of volatile oil, myrrhol, C 10 H 14 0, 30 or 40 per cent, of resin soluble 
 in alcohol, which melts at 90 to 95, is perfectly soluble in ether and acetic acid, but 
 only partially soluble in caustic potash, and 40 or 50 per cent, of gum. When 
 melted with caustic potash it yields protocatechuic acid and pyrocatechin. It is chiefly 
 used in medicine. 
 
 1 i b a n u m, obtained in Africa from Boswcllia floribtunda and in Asia from Boswellia 
 serrata, has the form of pale yellow, sometimes reddish, translucent or opaque brittle 
 fragments, having a mealy surface and a splintery fracture. Its specific gravity is 
 T22. It has a faint balsamic odour and a sharp bitter taste. It melts imperfectly, 
 giving off a pleasant odour. It consists of about 4 or 5 per cent, of a volatile oil, 56 
 per cent, of a resinous acid, 30 to 36 per cent, of gum, and 6 percent, of bassorin. 
 It is chiefly used as incense, and to some extent as medicine. 
 
 Ammoniacum is obtained from Dorema Aucheri and Ferula tingitana. The 
 Persian variety forms milk-white or yellowish granules and brownish masses. At 
 the ordinary temperature it is hard and brittle. It softens when moderately heated, 
 but does not thoroughly melt. It has an offensive smell, and a slightly bitter acrid 
 taste. It consists of a resin, 0400.2509, soluble in alcohol, a strong smelling volatile oil, 
 and some gum. African ammoniacum has the form of light brown or yellowish-white 
 masses, and gives off a benzoic odour when warmed. 
 
 Galbanumis obtained from Ferula erubescens and several other varieties of Ferula. 
 It has the form of yellowish or brown granules or masses. It is brittle in the 
 cold, but becomes soft and sticky when warmed. The odour is not disagreeable ; the 
 taste is sharp and bitter. It contains a resin, C 26 H 38 5 , and a volatile oil isomeric 
 with turpentine oil. By dry distillation the resin yields a thick blue volatile oil, 
 C 20 H 30 0, and crystals of umbelliferon, C 6 H 4 2 . When melted with potash it yields 
 resorcin, C 6 H 5 2 , oxalic acid, and volatile fat acids. 
 
 Assafoetida, also obtained from several species of Ferula, natives of Persia, 
 occurs as granules, more frequently in large masses. The fresh surface of fracture is 
 white, but soon acquires a reddish violet or yellowish-brown colour. It is readily 
 fusible, has a very disagreeable garlic odour, and a sharp bitter taste. It consists of 
 a sulphuretted volatile oil, 2C 6 H 11 S,C 6 H 10 S, ferulic acid, C, H 10 4 , together with resin, 
 gum, inorganic salts, and admixtures of wood and sand. The resin yields, when 
 melted with potash, resorcin, protocatechuic acid, and volatile fat acids. 
 
 Sagapenum, obtained from Ferula szowitziana, occurs as brownish-yellow or 
 reddish-brown granules and masses. It softens when warmed, but does not melt at a 
 higher temperature. It has a garlic odour, a sharp bitter taste, and is only partially 
 soluble in alcohol. It contains a volatile oil, several kinds of resin, gum, ash consti- 
 tuents, and mechanical admixtures. 
 
728 RESIN, ETC. 
 
 Op op an ax, obtained from the roots of Opopanax Chironium, has the form of 
 granules and lumps of reddish yellow or brown colour and waxy fracture, yielding a 
 yellow powder. The smell is strong and peculiar, somewhat resembling garlic ; the 
 taste is bitter. It is only partially soluble in alcohol. It contains a little volatile 
 oil, a resin that melts at 100, gum, organic and inorganic salts, and mechanical 
 admixtures. 
 
 Bdellium, obtained from Balsamodendron africanum in Senegambia, and B. 
 Mukal in India, has the form of yellow or reddish-brown fragments. It softens between 
 the fingers, smells like myrrh, and tastes bitter. Carana resin, obtained from 
 Bursera acuminata in the Antilles, is soluble in alcohol, ether, and alkalies. Gomart 
 resin, obtained from Bursera gummifera, in the West Indies and South America, is 
 colourless, crystalline, has an odour resembling turpentine and elemi, and yields 
 about 5 per cent, of volatile oil. Mecca balsam, obtained from Balsamodendron 
 gileadense, is a pale yellow thin liquid, readily soluble in alcohol and ether. 
 
 Tacamahac, obtained from Amyris tomcntosa, has the form of yellow or yellowish- 
 brown translucent fragments of sp. gr. 1-46, readily fusible, and soluble in alcohol and 
 potash. It is used as incense. 
 
 Icica resin, obtained from species of Idea in Cayenne, has the form of yellowish- 
 white fragments or transparent granules of pleasant odour, and is soluble in alcohol and 
 turpentine oil. It consists of two cry stalli sable resins, brean and icican, and an 
 amorphous resin, colophan, all of which are insoluble in potash. 
 
 Euphorbium, obtained from various species of Euphorbia, indigenous in Africa 
 and the Canary Islands, has the form of yellowish or brownish-yellow opaque brittle 
 fragments, internally whitish, without smell, but producing irritation to the nose in 
 the form of powder. It is partially soluble in alcohol and in water. It contains 
 about 22 per cent, of a resin, euphorbon, C J3 H 22 0, soluble in alcohol ; 38 per cent, of 
 an amorphous .acrid resin, Ci 3 H 22 2 ; 18 per cent, of gum, 12 per cent, of malates, 
 and 10 per cent, of inorganic salts. It is used to some extent in medicine. 
 
 Ladanum, obtained from Cistus creticus, is dark brown, soft, has a sp. gr. 1'86, 
 an agreeable odour and bitter taste. It consists of a resin soluble in alcohol, and 
 another insoluble in alcohol. 
 
 Gamboge, obtained chiefly from Garcinia morella, a native of Ceylon and Siam, 
 and to some extent from G-arcinia cochinchinensis and Gr. pictoria, occurring through 
 a greater part of India. It has the form of cylindrical sticks or flat cakes, and has 
 externally a dirty greenish -yellow colour ; the fracture is a brilliant brownish -yellow, 
 and the powder bright yellow. In thin fragments it is translucent. It has no smell, 
 but a sharp irritating taste. It softens when warmed without melting, gives off a 
 peculiar odour, and is partly decomposed. It forms an emulsion in water, is par- 
 tially dissolved by alcohol and more readily by ether, and contains about 72 per cent, 
 of an acid resin, C 20 H 24 4 , 23 per cent, of gum, sometimes with admixtures of starch and 
 woody fibre. It is used in medicine, as a water colour, and for colouring varnishes. 
 
 Storax. The liquid variety is obtained from the bark of Liquidambar orientals. 
 It has a greenish -brown colour, and a smell resembling vanilla and benzoin. It contains 
 styrol, C 8 H 8 , styracin, C, 8 Hi 6 2 , cinnamic acid, benzoic acid, and a resin that is said to 
 be metastyrol. The solid variety is obtained from the same tree, as an exudation that 
 has dried upon the bark in the form of yellowish or brown transparent granules of 
 aromatic odour ; it is readily fusible and soluble in alcohol. Both kinds are used in 
 perfumery and medicine. 
 
 B e n z o i n is obtained from Styrax Benzoin. It forms roundish reddish-white frag- 
 ments, internally of a white colour, and reddish-brown masses, or a conglomerate of 
 the two kinds. It has an agreeable odour, and a sweetish pungent taste. When 
 heated it melts and gives off benzoic acid. It is completely soluble in warm alcohol, 
 and partially soluble in ether, and contains three or four kinds of resin, together with 
 benzoic acid, and sometimes cinnamic acid. It is used in medicine, and as incense. 
 
 Peru balsam, obtained from Myroxylon Sonsonatense, by bruising the bark of 
 the trees and heating it with torches, has the form of a dark brown thick liquid of 
 agreeable odour, sharp irritating taste and acid reaction. Its specific gravity varies 
 from 1-14 to 1*15. It is miscible in all proportions with absolute alcohol; ether 
 leaves a brown smeary residue ; hot turpentine oil or almond oil dissolves only about 
 one half. Caustic potash digested with the balsam separates as an upper layer, an 
 oil consisting chiefly of benzyl cinnamate or cinnamein, C 16 Hi 4 2 , benzyl alcohol, 
 C 7 H 8 0, benzyl benzoate, C 14 H 12 2 , and styracin or cinnyl cinnamate, C 18 H 16 2 . The 
 alkaline liquor contains cinnamic acid, benzoic acid, a resin soluble in alcohol, 
 and another insoluble in alcohol. Peru balsam is used in medicine, and in making 
 perfumery, chocolate, and for similar purposes. Another kind of Peru balsam, de- 
 rived from the same source, is obtained by pressing the fruit ; it is a thick pale 
 
CAOUTCHOUC. 729 
 
 yellow liquid, with a smell resembling vanilla. When kept for some time it deposits 
 crystals of myroxocarpin, C 24 H 34 3 . 
 
 Tolu balsam, obtained from Myroxylon toluiferum, is, in the fresh state, a 
 yellowish transparent thick liquid. By keeping it becomes reddish-brown and viscid, 
 ultimately drying up to a crystalline brittle resinous mass. It has an agreeable 
 aromatic odour, and a sweetish pungent taste. The solid balsam softens at 30, and 
 melts between 60 and 65. It is perfectly soluble in alcohol and chloroform, and 
 partially soluble in ether ; it is almost entirely insoluble in ethereal oils and carbon 
 bisulphide. With caustic potash of sp. gr. 1-17 it forms a clear solution, and concen- 
 trated sulphuric acid dissolves it with a red colouration. It consists of tolene, C, 2 H 1S , 
 cinnamic acid, benzoic acid, a resin readily soluble in alcohol, and another sparingly 
 soluble in alcohol. It is used in medicine, and in the manufacture of perfumery. 
 
 Amber is so well known that its general description is almost unnecessary. Its 
 sp. gr. is slightly greater than water, and it becomes electric on friction. It is found 
 in the beds of brown coal, but is mainly gathered on the coasts of the Baltic, between 
 Konigsberg and Memel, after storms. About 13 per cent, of amber dissolves in alcohol 
 and about 10 per cent, in ether. Succinic acid is a product of its dry distillation, and 
 is accompanied by an empyreumatic oil, consisting of mixed hydrocarbons, almost 
 identical in combination with turpentine. According to Schrotter it is that portion of 
 the resin soluble in ether which yields the succinic acid, whereas the oil is supposed 
 to be yielded by the part insoluble both in alcohol and ether. 
 
 When amber is boiled with nitric acid, camphor passes over, and succinic acid is 
 formed in the solution. 
 
 Applications of Resins. Amber is mainly used for ornamental purposes ; thus it 
 is employed in making bracelets, necklaces, mouthpieces of pipes, etc. 
 
 Lac is used in the stiffening of hats, and in the manufacture of the better forms 
 of sealing wax. Lowig gives the following proportions for a good red wax 48 parts 
 of shell lac, 12 of Venetian turpentine, 1 part of balsam of Peru ; these are melted 
 together at a gentle heat, and incorporated with 36 parts of vermilion. 
 
 Bronzing lacquer is a varnish formed by mixing lac with about half its weight of 
 sandarach, and a little Venice turpentine, and dissolving the whole in 10 or 12 parts 
 of alcohol. 
 
 Varnishes. The principal resins used for making varnishes are copal, anime, 
 mastic, and sandarach. The solubility of copal is increased by powdering and expos- 
 ing it to the air, when it absorbs oxygen. 
 
 Spirit varnishes, which dry rapidly, are made by dissolving the resins in turpentine, 
 wood naphtha, alcohol, or a mixture of two or all of these solvents. 
 
 Oil varnishes are made similarly, but a certain amount of drying oil, such as that 
 of linseed or poppy, is incorporated with the varnish. Such varnishes dry more slowly 
 and furnish hard and durable coatings. 
 
 Camphor is often used in varnish-making, and of late years a number of other 
 carbon compounds have been used in making patented preparations. Crystal varnish 
 for maps, etc., is made by dissolving Canada balsam in refined oil of turpentine. 
 Varnishes are used, as 5s well known, for coating the surfaces of wood and metal, and 
 forming hard, glossy crusts which protect the articles from atmospheric influences of 
 a destructive nature. 
 
 CA.OTJTCHOTTC. This substance, which is commonly known by the name of Indian 
 Eubber, occurs in the milky juice of several plants, but only a few, all occurring within 
 the isotherms of 70 F., yield it in quantities sufficient for industrial purposes. It 
 occurs abundantly in various species of Hevca, especially in H. brasiliensis, Mull 
 (Siphonia brasiliensis, Willd.), and H. guyanensis, Aubl. (Siphonia elastic, Pers.), the 
 juice of which constitutes as much as 0*3 of the entire plant. These plants are operated 
 upon for the extraction of caoutchouc chiefly in Brazil, Guiana, and central America. 
 The product is of good quality, and is generally known as Para rubber. Other 
 American -varieties of caoutchouc are yielded by species of Castilloa. 
 
 In India, especially in Assam and in Java, caoutchouc is for the greater part ob- 
 tained from Ficus elastica (Artocarpese). In the islands of the Indian Archipelago, 
 caoutchouc is obtained from Urceola elastica (Apocynese), the juice of which is so rich 
 in caoutchouc, that a single specimen of this gigantic tree yields annually fifty or sixty 
 pounds of that substance. 
 
 Caoutchouc is further obtained from the following plants : Camararia latifolia 
 (Apocyneae), growing in South America ; Valea gummifera, growing in Madagascar ; 
 species of Landolphia in Eastern and Western Africa ; Taberncemontana utilis, grow- 
 ing in the equatorial regions of America ; and from Willoughbeia fdulis, and Melodinus 
 mnnogynus (Melodineae), growing in India. 
 
 Caoutchouc consists of carbon and hydrogen, in the proportions represented by the 
 
730 RESIN, ETC. 
 
 formula C 4 H 7 . This formula, however, does not probably represent its molecular 
 constitution, which must be at least C 8 H, 4 , in which case caoutchouc might be con- 
 sidered as a higher homologxie of acetylene. Caoutchouc in a state of purity is a 
 white, transparent substance, a delicate section of it when placed under the microscope 
 exhibiting a number of small pores, which are, like those of sponge, continuous 
 throughout its mass. The specific gravity of caoutchouc is 0'925. It is a very elastic 
 body, but loses this property when cooled down below 0, not regaining it until its tem- 
 perature is raised to about 35 or 40. On this account, when an expanded piece of 
 caoutchouc is cooled down to a few degrees below 0, it retains its elongated form, and 
 does not return to its original shape until considerably warmed. Pure caoutchouc is 
 very adhesive, freshly cut surfaces of it adhering well and firmly, when simply pressed 
 together. 
 
 Some of the hydrocarbons obtained by the distillation of coal tar cause caoutchouc 
 to swell up, and partially dissolve it. Oil of turpentine that has been dried by distilla- 
 tion over quick lime acts in a similar manner; but better solvents than these substances 
 are found in pure oil of lavender and carbon bisulphide. The fatty oils dissolve only 
 very minute quantities of caoutchouc. Pay en has shown that water and alcohol are 
 not entirely without effect upon caoutchouc. 
 
 Caoutchouc is hardly attacked by chlorine, and resists almost entirely the action 
 of hydrochloric acid, and all weak acids. In like manner, most gases, and also solu- 
 tions of potash and soda, are almost without effect upon it. On the other hand, 
 caoutchouc is very strongly attacked by concentrated nitric acid or sulphuric acid, 
 and more especially by a mixture of the two. Caoutchouc yields with sulphuric acid 
 sulphurous acid and a carbonaceous residue ; with nitric acid it yields beside a fat-like 
 substance, oxalic acid and camphresinic acid(C, H 14 7 ). Steam exerts a softening effect 
 upon caoutchouc, lessening its tenacity very considerably. Caoutchouc heated alone 
 up to 120 gradually loses its consistency, becoming very sticky; at a tempera- 
 ture of from 145 to 155 it is so sticky at the surface, that it adheres readily to dry 
 solid bodies. At a temperature of about 180-200 it begins to melt, and apparently 
 passes into another modification, for caoutchouc that has been exposed to such a tem- 
 perature remains sticky when cold, although its analysis shows it to have the same 
 percentage composition (C 9 H 14 ) as before. At a temperature of from 200 to 230, caout- 
 chouc assumes an oily consistency and becomes darker in colour. 
 
 If caoutchouc be ignited, it burns with a bright, somewhat reddish, and very 
 smoky flame, evolving an unpleasant penetrating smell. 
 
 When submitted to destructive distillation, caoutchouc yields tar-like products, 
 from which, by means of fractional distillation, hydrocarbons are obtained, belonging 
 probably in part to the olefine series, and partly to the terpene group. The most 
 important of these hydrocarbons are butylene (C 4 H 8 ), caoutchene (C 10 H, 6 ), isoprene 
 (C 5 H, ), and heveene. The boiling points of the products obtained by the fractional 
 distillation of caoutchouc tar are very different, a part boiling at 14, and others at 
 33, 171, 215, etc. Most of the substances thus separated from the crude product 
 of distillation are good solvents for caoutchouc. 
 
 Among the different sorts of raw caoutchouc imported from various districts of 
 Asia, Africa, and America, the following may be distinguished: 1. Light, opaque 
 caoutchouc, occurring in large irregular pieces; 2. Yellowish, semi-transparent caout- 
 chouc, occurring in irregular plates; 3. A light brown variety, occurring in the form of 
 pear-shaped bottles, spheroidal lumps, or in twisted and woven bands ; 4. Another 
 brown variety, having an irregular cubical shape and rounded corners and edges. 
 
 The light colour and opacity of the first kind depend upon its containing a con- 
 siderable quantity of water, more or less of which every sort of caoutchouc is liable to 
 contain. The brown colour of most of those sorts of raw caoutchouc occurring in the 
 market is due to admixture, pure caoutchouc, as already observed, being colourless. 
 
 If caoutchouc be allowed to remain thirty days in water, its pores get filled with 
 water, a consequence of which is that its weight increases from 187 to 26*4 per cent., 
 and its volume about 15 or 16 per cent., while on the other hand its tenacity and ad- 
 hesiveness decrease. 
 
 When thick pieces of caoutchouc have become permeated with water, it is ex- 
 tremely difficult to deprive them again of the entire quantity absorbed, as upon dry- 
 ing the caoutchouc, the water escapes first of all from the surface pores, and these 
 then contracting, prevent the escape of water from the interior of the pieces. On 
 this account, the lighter coloured kinds of caoutchouc, containing absorbed water, are 
 of less value, not only because their weight is thus increased, but also because, in 
 order to expel such water by drying, the pieces have to be cut into thin bands. 
 
 When treated with boiling water, many kinds of caoutchouc yield a resinous 
 substance. 
 
 Absolute alcohol, especially when heated, penetrates caoutchouc quicker than 
 

 CAOUTCHOUC. 731 
 
 water, producing, like the latter substance, a lighter coloration of the caoutchouc. 
 Caoutchouc that has been steeped in absolute alcohol for a space of eight days, the 
 alcohol being heated at intervals, becomes more opaque and adhesive, its volume in- 
 creases about 9'4 per cent., and its weight about 18 per cent., while the alcohol dissolves 
 out of it about 2 per cent, of a yellow fatty oil. After the evaporation of the alcohol 
 absorbed the caoutchouc is not so tenacious as it was before, while on the other hand 
 it is more transparent and adhesive. 
 
 Ether, benzol, oil of turpentine, carbon bisulphide, etc., or mixtures of them, 
 penetrate caoutchouc very quickly, cause it to swell up and appear to dissolve it com- 
 pletely. The solution is however only a partial one, nearly the whole of the solution 
 remaining in the expanded insoluble portion, as in a sponge, the entire piece retaining 
 the original shape, only much enlarged. The non-soluble portion contains the brown 
 colouring matter, while the soluble portion, upon evaporation of the solvent, exhibits 
 a slightly tinged, soft, and flexible mass, which is but slightly tenacious or elastic. 
 
 Caoutchouc repeatedly treated with anhydrous ether gives up to this solvent 66 
 per cent, of an almost colourless substance, and 34 per cent, of residue remains having 
 a colour varying from yellow to brown. 
 
 Pure anhydrous oil of turpentine dissolves out from caoutchouc 49 per cent., leaving 
 51 per cent, of residue. The soluble portion is left, upon evaporation of the solvent, as 
 a light brown mass, the insoluble residue being darker coloured. But if the oil of 
 turpentine contain a mere trace of any resinous body, the soluble as well as the 
 insoluble portion assumes a sticky consistency, dries difficultly, and decomposes 
 readily when exposed to the air. 
 
 Caoutchouc that has been exposed for a long time to the action of the sun's rays 
 in a warm atmosphere undergoes a peculiar change which has been termed solarisa- 
 tion, its surface becoming less elastic ; anhydrous benzol then extracts from it a 
 substance which, upon the evaporation of the solvent, does not possess the elasticity . 
 and tenacity of ordinary caoutchouc, but is friable and brittle. 
 
 That this decomposition is owing to a process of oxidation may be seen from the 
 following results of 'an analysis by Spiller of some solarised caoutchouc : 
 
 Carbon 63'00 
 
 Hydrogen 8-50 
 
 Oxygen 27'50 
 
 Pure caoutchouc, as already observed, contains only traces of oxygen. Gutta 
 percha, under the same conditions, undergoes a similar decomposition. 
 
 A very peculiar behaviour is exhibited by caoutchouc in respect to sulphur. 
 When these two substances are melted together, caoutchouc absorbs indefinite 
 quantities of sulphur, but when only a comparatively small quantity has been absorbed, 
 the caoutchouc does not present any alteration of its chief physical properties. This 
 product of the action of sulphur upon caoutchouc is termed vulcanised caout- 
 chouc. When caoutchouc has been made to absorb much sulphur, a solid mass is 
 obtained having a hornlike consistency, and called vulcanite. 
 
 Caoutchouc is prepared by inspissating the milky juice of the plants yielding it. 
 The juice, not containing it in solution but suspended in it in a very fine state of 
 division, is generally obtained by cutting the bark of the tree so as to rupture the 
 laticiferous vessels, situated principally in the middle layer of bark, or mesophlceum ; 
 care should be always taken not to cut sufficiently deep to injure the cambium layer 
 underneath. The cuts are sometimes made in a spiral form, and sometimes as two 
 series of diagonal incisions running into a common channel cut perpendicularly in the 
 trunk. The juice flows into hollows made at the bottom of the tree. The plants do 
 not yield any juice from the trunk during the flowering period, and the tapping 
 operation should not be performed at that time, nor during the wet season, as the 
 juice then contains a larger proportion of water. 
 
 The inspissation has to be performed as rapidly as possible, as the juice 
 easily decomposes and becomes sour, especially in the sun. It is sometimes heated 
 over a fire in clay moulds of various forms. A thick mass of caoutchouc being difficult 
 to dry throughout, only small quantities of juice are treated at a time, to which other 
 portions are added successively, lumps of caoutchouc of any desired thickness being 
 thus obtained. The caoutchouc thus dried together with the clay mould is then 
 placed in water, and the softened clay removed ; the product thus obtained is known 
 as raw caoutchouc. In other places the juice is often dried with the smoke of a fire 
 in wooden moulds. In the East Indies it is often dried directly in the air in the 
 hollows at the foot of the trees, protected however from direct sunlight. 
 
 Anthoine exhibited at Paris in 1855 caoutchouc separated from the juice by the 
 addition of from 2 to 3 per cent, of spirits of wine. The juice thus treated forms 
 two layers, the upper containing the coagulated caoutchouc, which is removed 
 
732 RESIN, ETC. 
 
 and thrown upon a piece of linen stretched upon a frame and lying upon sand ; tlie 
 water then filters into the sand and the caoutchouc is dried in the air. A method 
 somewhat similar to the above is employed in St. Salvador, where the fresh juice is 
 mixed with double its volume of water, and allowed to stand twenty-four hours, when, 
 as in the former case, the caoutchouc forms a layer upon the .surface of the water. It 
 is -washed several times with water, a small quantity of a solution of alum is added, 
 the caoutchouc separated from the water, and dried. In Nicaragua the coagulation 
 of the juice is effected by the addition of the juice of other plants, one of which has 
 been identified as the Ipomcea bona-nox. 
 
 Caoutchouc, as already observed, occurs in the market in various forms. A very 
 excellent and pure caoutchouc is that imported from Para (Brazil). It is more 
 valuable than other sorts of caoutchouc, and occurs in the form of pear or bullet 
 shaped bottles, having an exterior diameter of about 5 inches, with sides 2 inches 
 thick, or in the form of round disks, 2 inches thick and 8 inches in diameter, or in the 
 form of plates of the same thickness as the disks. 
 
 From Java a brown, very elastic kind of caoutchouc is imported, containing how- 
 ever 10, and sometimes 15 percent, of foreign admixtures. It occurs in the market in 
 the form of cubical-shaped pieces, from 8 to 10 inches in length, which are formed from 
 plates and bands pressed together. 
 
 From Valparaiso (Chili) is imported a darker brown sort of caoutchouc, more 
 elastic than the above, and occurring in thick plates. 
 
 The caoutchouc imported from Gabon, in Africa, is of a lighter colour, containing 
 water; it is elastic, but more easily decomposed under the action of light and air than 
 that from Valparaiso. It occurs in broad thick ribands. 
 
 From Carthagena (New Granada) caoutchouc is imported in the form of brown, 
 fibrous plates, that are tolerably elastic. 
 
 The caoutchouc imported from Buenos- Ayres occurs in thick shapeless pieces, white, 
 and containing water. 
 
 From Assam (Asia) caoutchouc is imported in irregular blocks, formed of light and 
 dark kinds kneaded together ; it often contains foreign substances, as well as a con- 
 siderable amount of water ; it has good elastic properties, but decomposes gradually 
 on exposure to light and air. 
 
 Vizagapatam exports a peculiar kind of caoutchouc, which at present has not 
 found much employment. It occurs in the market in the form of hard, unelastic 
 plates, from f to inch thick, which become soft and sticky when heated, resuming 
 their original properties upon cooling. 
 
 A great quantity of caoutchouc comes to Europe which has got damaged by 
 fermentation, produced by the watery sap enclosed in it. 
 
 Caoutchouc has been known and used in South America and India for a very 
 long time. It found its way into Europe at the beginning of the 18th century, 
 having been introduced by M. de la Condamine, who sent specimens of the substance 
 from Peru to Paris, and at the same time made known the fact that it was obtained 
 by drying the milky juice of certain plants. In 1751 MM. Fresnau and Macquer 
 discovered the caoutchouc tree in Cayenne, and shortly afterwards communicated 
 details as to the method of obtaining caoutchouc. 
 
 For a long time the only employment made of caoutchouc was for rubbing out 
 from paper the marks of a lead pencil, and hence its name Indian rubber; in 1790, it 
 was used for making gum balls, elastic bands, valve springs, and for rendering coarse 
 tissues impervious ; in 1791 M. Grassart made tubes of it. In 1820 M. Nadler suc- 
 ceeded in cutting caoutchouc into threads fine enough for preparing various objects, 
 and especially elastic tissues. A few years later Mr. Mackintosh perfected the manu- 
 facture of caoutchouc tissues, rendered them impervious to water by employing a mix- 
 ture of oil of turpentine and caoutchouc, and made waterproof mantles of this article. 
 It was not, however, until the discovery of the method of vulcanising caoutchouc 
 that caoutchouc found the extensive employment it now enjoys. 
 
 The first patent for a method of sulphurating caoutchouc was taken out in 1839, 
 by Mr. Goodyear in the United States, but he gave at that time neither the amount 
 of sulphur nor the temperature necessary for its combination. He made, however, 
 in 1844 a more complete report upon the properties and advantages of sulphurated 
 caoutchouc, and the process being so akin to the attributes of the Vulcan of Mythology, 
 was termed by Mr. Brockedon, vulcanisation, which name it has retained. 
 
 In the same year Mr. Hancock produced vulcanised caoutchouc by using 
 a bath of molten sulphur. In 1846 Mr. Parkes described the process of vul- 
 canising caoutchouc by means of a mixture of carbon bisulphide and sulphur 
 chloride. 
 
 Caoutchouc juice is not simply an emulsion of caoutchouc in water, as it contains 
 Other constituents. 
 
CAOUTCHOUC. 733 
 
 Faraday analysed a specimen of caoutchouc juice imported from America, which 
 upon drying yielded 45 per cent, of caoutchouc. He found it to contain 
 
 Caoutchouc 37-70 per cent. 
 
 Vegetable albumin 1-90 
 
 A bitter nitrogenous substance, soluble in alcohol and 
 
 in water. t t 7-13 f> >f 
 
 A substance insoluble in alcohol 2*90 * 
 
 Water | 56 -47 
 
 Adriani gives the following results of an analysis of the sap of Ficus elastica 
 obtained upon making an incision in a terminal bud : 
 
 Caoutchouc 9.57 per cent. 
 
 A substance soluble in alcohol, but insoluble in ether . 1'58 
 An organic acid in combination with magnesium . 0'36 
 
 A substance insoluble in water 2'18 
 
 Salts of sodium and potassium traces 
 
 Water 82'30 
 
 It follows from the above analyses that the caoutchouc of commerce is not pure 
 caoutchouc, for when prepared by simply drying the sap it contains, besides caoutchouc, 
 all the other constituents of the sap, such as albumin, resinous substances, salts, etc. 
 When caoutchouc is prepared by separating it from the sap and washing with water 
 it is certainly purer, being then free from substances soluble in water, but it still 
 contains substances insoluble in that menstruum. 
 
 It has been attempted to import caoutchouc juice in the fresh state. It retains its 
 quality without becoming acid, when mixed with a small percentage of ammonia 
 water (5 to 7 per cent.), and kept in vessels hermetically closed. 
 
 Vulcanisation of Caoutchouc. Before the discovery of the process of vulcanising 
 caoutchouc had nothing like the extensive employment which it now enjoys, for its 
 property of becoming soft at a temperature of from 30 to 50, and of becoming very 
 nard at temperatures below 0, rendered its employment in either very hot or very 
 cold climates impossible. 
 
 These inconvenient properties of caoutchouc are got rid of by combining it with 
 sulphur ; when thus combined it retains its elasticity and flexibility at temperatures 
 varying from 20 to 180. Its adhesive property is however entirely lost, and on this 
 account it is not possible to combine pieces of vulcanised caoutchouc by simple pres- 
 sure. 
 
 If a plate of caoutchouc, from p to inch thick, be plunged into melted sulphur 
 having a temperature of from 115 to 120, and kept in it for two or three hours, the 
 caoutchouc absorbs from 1 5 to 20 per cent, of its weight of sulphur, without its phy- 
 sical properties becoming materially altered. It is as elastic as before, and pieces of 
 it can be united by the aid of pressure. Just as little change takes place when caout- 
 chouc is either brought into contact with sulphur dissolved in carbon bisulphide, or 
 kneaded with sulphur at a temperature of from 25 to 40, but its porosity is dimin- 
 ished by its pores having become filled with sulphur. 
 
 If caoutchouc, thus penetrated with sulphur, be heated up to 132 or 140, an im 
 portant change takes place in a few minutes ; long exposure to this high temperature 
 deprives it of its flexibility ; it becomes hard " and unelastic. It is then capable of 
 taking up enough sulphur to constitute 48 per cent, of the entire vulcanised product ; 
 this would remain even after treatment with potash or soda, which are unable to dis- 
 solve out the sulphur thus chemically combined. 
 
 By the action of sulphur upon caoutchouc, some sulphuretted hydrogen is produced 
 and the melted sulphur is capable of absorbing a quantity equal to its own volume. This 
 gives rise to the following curious phenomenon. If a piece of caoutchouc be dipped 
 in a sulphur bath, and the bath then allowed to cool, at the moment of crystallisation 
 of the sulphur, the sulphuretted hydrogen that had been retained in the liquid sulphur 
 escapes, and being then mechanically imprisoned between the crystals of sulphur, 
 causes a rising of the whole mass. 
 
 In a compound of caoutchouc and sulphur containing only 1 or 2 per cent, of the 
 latter, the relation between the carbon and hydrogen of the caoutchouc is not percep- 
 tibly altered. Caoutchouc, when sufficiently vulcanised, does not contain more than 
 1 or 2 per cent, of sulphur in a state of chemical combination; the rest, which often 
 amounts to from 5 to 15 per cent., may be extracted by treatment with caustic potash 
 or soda. Sulphur which has been simply mechanically retained in vulcanised caout- 
 chouc, if not removed by the agency of solutions of soda or potash, escapes in course 
 of time through the pores of the caoutchouc in the form of a fine powder. This 
 
734 RESIN, ETC. 
 
 efflorescence also occurs when caoutchouc plates, into which an excess of sulphur has 
 been kneaded, are allowed to remain at rest for a long time. 
 
 Carbon bisulphide, benzol, and oil of turpentine, also cause vulcanised caoutchouc 
 to swell up, its volume increasing ninefold upon long contact with these liquids. 
 Sulphur not chemically combined is then dissolved, and can be extracted by this 
 means. 
 
 The several sorts of caoutchouc differ considerably in their capacity for absorbing 
 water. Payen conducted comparative experiments with: 1. Non- vulcanised, or fresh 
 caoutchouc ; 2. With vulcanised caoutchouc ; 3. With desulphurised caoutchouc ; 
 and found that the first absorbed from 20 to 26 per cent, of water, the second 4'2 per 
 cent., and the third 6 '4 per cent. 
 
 Further, a bottle with sides ^ inch thick, filled with water under pressure in such 
 a manner that its diameter becomes doubled, loses by evaporation in twenty-four 
 hours and at a temperature of 16 C., for every square yard of surface, about 280 
 grains of water when made of common non-vulcanised caoutchouc, and only about 
 50 grains when made of vulcanised caoutchouc. Balloons of this kind filled with air 
 under a similar pressure, and at the same temperature, do not suffer any noticeable 
 loss. 
 
 The Vulcanising Process. There are various methods now in use for vulcanising 
 caoutchouc. The first English patent was taken out by Mr. Hancock. It consists in 
 dipping the caoutchouc into sulphur melted in an iron vessel, at a temperature of from 
 115 to 120, and allowing it to remain until it has absorbed equally throughout its 
 mass about 15 per cent, of sulphur. After the caoutchouc has been taken out of the 
 sulphur and got cool, its exterior adherent coating of sulphur is scratched off, and it 
 is then heated to between 132 and 140; an operation technically termed burning 
 the caoutchouc, as it is when this temperature has been attained that the sulphur 
 combines chemically with the caoutchouc, and produces in it that marvellous change 
 which distinguishes vulcanised caoutchouc from common caoutchouc. 
 
 According to Mr. Goodyear's method, powdered sulphur is kneaded with caout- 
 chouc, ina-machine constructed for the purpose, until it has taken up from 10 to 15 per 
 cent, of sulphur; it is then heated up to and kept at a temperature of from 132 to 
 140, until it has chemically combined with about 2 per cent, of sulphur. 
 
 Mr. Parkes, of Birmingham, introduced the use of carbon bisulphide in the sul- 
 phuration of caoutchouc. According to his process, pieces of caoutchouc are dipped, 
 for a length of time varying with their thickness, into a mixture of 100 parts of 
 carbon bisulphide, and 2^- parts of sulphur chloride. The liquid penetrates the caout- 
 chouc, causing it to swell up, a part of its hydrogen being replaced by sulphur derived 
 from the sulphur chloride. When taken out, the pieces are rapidly dried in a current 
 of dry air. In the case of thick pieces, it is necessary to dip them often, so as to 
 insure their thorough penetration by the liquid. 
 
 This method of Parkes was improved by Gerard, who suggested dipping the 
 pieces of impregnated caoutchouc into lukewarm water immediately after their re- 
 moval from the bath, so as to avoid the reaction of the sulphur chloride upon the sur- 
 face of the caoutchouc during the drying ; the sulphur chloride becoming decomposed 
 upon contact with the water. 
 
 Another method is also due to Mr. Parkes, according to which the caoutchouc is 
 kneaded together in a kneading machine, with from 10 to 13 per cent, of a solid mix- 
 ture of sulphur and sulphur chloride, until a complete mixture has taken place. 
 
 Gerard introduced a method of vulcanising caoutchouc, which consists in heating 
 the caoutchouc for three or four hours with a solution of calcium pentasulphide, having 
 a specific gravity of from T200 to T245, at a temperature of 143 C., and under a 
 pressure of four atmospheres. The liquid penetrates pieces of caoutchouc, which are 
 not too thick, completely, affording them the necessary quantity of sulphur with 
 which they combine. After removal from the bath, they only require to be washed 
 with water and dried. 
 
 Gerard's ' alkaline caoutchouc,' which is said to resist most reagents well, is pre- 
 pared in the following way. The caoutchouc (100 parts) cut into ribands is covered 
 with a mixture consisting of 6 parts of powdered sulphur, and from 6 to 10 parts of 
 powdered calcium hydrate, and kneaded together with this .powder by means of 
 hollow cylinders, heated internally by steam to 40 or 50, until a combination of the 
 powder with the caoutchouc has taken place. The next operation is to heat the 
 caoutchouc thus treated, for one and a half or three hours in hermetically closed 
 vessels, either in steam or water according to the thickness of the pieces. This 
 causes a combination of sulphur with the caoutchouc, a part of the sulphur and lime 
 being dissolved out as calcium sulphide and hyposulphite. This method yields a vul- 
 canised rubber more sulphuretted internally than externally, so that its surface is less 
 friable and brittle. 
 
CAOUTCHOUC. 735 
 
 Propositions were made in the first instance by Mr. Hancock, and afterwards by 
 others, to replace sulphur by other substances for vulcanising purposes. Of the sub- 
 stances proposed may be mentioned artificially prepared antimonous sulphide, mixtures 
 of zinc white and sulphur, of pipe clay and sulphur, lead hyposulphite and sulphide, 
 and lead sulphide and bismuth sulphide. 
 
 Decomposition of Vulcanised Caoutchouc. If vulcanised rubber be heated for any 
 length of time to 130 C. in contact with metals, a double reaction takes place ; on 
 the one side free sulphur combines with the caoutchouc rendering it too strongly sul- 
 phurated, and at the same time a sulphide of the metal is produced. 
 
 Vulcanised caoutchouc when exposed to light and air also undergoes oxidation, 
 which renders it brittle. According to Gerard, this objectionable property may be 
 overcome by mixing the caoutchouc before vulcanisation with some anhydrous coal 
 tar. 
 
 Vulcanised caoiitchouc does not swell up so much in benzol as non-vulcanised 
 caoutchouc. Ether or carbon bisulphide dissolve out from it about 4 or 5 per cent, 
 of caoutchouc, as well as the chemically uncombined sulphur. Vulcanised caoutchouc, 
 when immersed for two months in a mixture consisting of 10 parts of carbon bisul 
 phide and 4 parts of absolute alcohol, yields to this menstruum 25 per cent, of caout- 
 chouc and 10 per cent, of sulphur, 65 per cent, remaining behind. That vulcanised 
 caoutchouc is less easily penetrated by liquids than ordinary caoutchouc has already 
 been mentioned. 
 
 Desulphuration of Vulcanised Caoutchouc. An excess of sulphur in vulcanised 
 rubber may act very injuriously ; methods have therefore been devised for getting rid 
 of the chemically uncombined sulphur. This is generally effected by boiling the vul- 
 canised caoutchouc in a solution of caustic soda or potash, until the excess of sulphur 
 is dissolved. 
 
 Vulcanised caoutchouc, thus desulphurated, is quite as durable as that which has 
 not been so treated ; it has however this inconvenience, that tubes made from it 
 become after a time stiff, and when packed together for any length of time, stick to 
 one another. They soon regain perfectly their former ductility and elasticity, when 
 stretched strongly a few times. 
 
 To prepare Threads of Eaw Caoutchouc. The most regularly shaped and least 
 vesicular bottles of Para caoutchouc are softened in hot water, cut in two, and 
 pressed into disks between strong metal plates at a temperature of 100, and they 
 retain the discoid form upon cooling. These disks are then fastened to a rotatory 
 apparatus with their centre opposite a circular knife in rapid motion, upon contact 
 with which the entire disk is cut up into a band having a spiral form. Adhesion of 
 the caoutchouc to the knife is prevented by keeping the knife constantly wet with 
 water. The bands are next passed through circular slitters, by which they are cut into 
 long threads. Such threads are of the most elastic and durable kind, but possess the 
 inconvenient property of becoming hard at a temperature a little below 0, and soft 
 a little above 30. For weaving purposes they are cooled below 0., and the fabric 
 afterwards rendered elastic by raising its temperature to 45. 
 
 Purification of Eaw Caoutchouc. Caoutchouc, as it is found in the market, gene- 
 rally contains a number of impurities, consisting partly of mechanically enclosed 
 woody particles, leaves, etc., and partly of normal constituents of the caoutchouc sap ; 
 it has therefore in most cases to undergo a process of purification before it can be 
 made use of for industrial purposes. For this purpose it is first softened in warm 
 water, then cut by means of a circular knife into pieces of inch to 2 inches in thick- 
 ness, and finally squeezed between a couple of rollers over which a continuous gentle 
 stream of water is permitted to flow. These rollers are either equal in diameter 
 (about 16 inches), and one rotates more slowly than the other, or they have unequal 
 diameters and similar rates of rotation. The pieces of caoutchouc are thus pressed 
 and torn into the form of broad shreds, so that they offer the largest possible amount 
 of surface for being washed in a solution, consisting of warm dilute caustic soda into 
 which they are next plunged. In some places a rag machine, similar to that used in 
 paper manufactories, is employed, instead of the mill used for tearing the pieces of 
 caoutchouc. In this case, however, the caoutchouc must have been already torn to 
 shreds. The raw caoutchouc imported from Brazil is purer than that from India, and 
 clops not need this energetic cleansing process ; it only requiring a single laceration 
 and simple washing with water. 
 
 Reunion of washed Caoutchouc is effected by kneading the pieces in an apparatus 
 t-rmed the wolf (figs. 504 and 505). This consists of a strong cylinder of sheet iron 
 divided into two parts, the lower part (BB) being fixed, while the upper part(cc) 
 moves on an hinge (o), and can be opened by aid of a handle (M). A strong iron 
 roller (A) furnished with teeth rotates in the interior of the cylinder, making from 60 
 
736 
 
 RESIN, ETC. 
 
 to 100 revolutions per minute. The other half of the cylinder is surrounded below 
 with an iron jacket (E E), so as to allow of its being heated by steam. About 30 
 
 T, L 
 
 FIG. 504. 
 
 FIG. 505. 
 
 Ibs. of well washed and dried caoutchouc shreds are thrown into the cylinder's B, the 
 cylinder is then firmly closed, and the roller A set in motion. The pieces of caout- 
 chouc are kneaded and squeezed together in the comparatively narrow space between 
 the interior sides of the cylinder and the roller, until they become united into a single 
 lump. 
 
 For the first ten or fifteen minutes in all seasons, and for the whole time during the 
 winter, the union of the pieces is facilitated by heating the cylinder to 45C. by letting 
 steam into E E through the cock (G). The extent of conglomeration is observed by 
 means of an aperture at d. 
 
 The caoutchouc lump, being under considerable pressure in the cylinder, alters in 
 shape very much when taken out. After a lapse of about ten minutes it assumes the 
 
 form depicted in figs. 506 and 507, 
 
 A A having a diameter of about 7 or 8 
 
 inches, and being about 16 inches in 
 length, while the surface of the 
 roller is only about 2^- inches apart 
 from the interior of the sides of the 
 cylinder, and the ends of the 
 FIG. 506. FIG. 507. cylinder only about 14 inches apart 
 
 from each other. 
 
 The force required for the revolution of the roller is as much as 5 or 6 horse 
 power, as the caoutchouc mass, rendered sticky by the heat produced by friction, etc., 
 adheres fast to the sides of the cylinder and has to be torn away by the roller; the 
 roller making from 80 to 100 revolutions in a minute, and the caoutchouc lump only 
 3 or 4. This apparatus has undergone several improvements. Guibal employed a 
 fluted roller in the place of the toothed one ; Aubert and Gerard line the bottom of 
 the cylinder also with quadrilateral teeth. 
 
 Boiling mills have been much used recently instead of the wolf, being more simple 
 and not requiring the application of so much force. 
 
 Mr. Goodyear' s rolling mill consists of two strong hollow rollers of wrought iron, 
 placed either against or over each other, and set within or inch of one another. 
 The rollers are heated by steam, and the dried and washed pieces of caoutchouc are 
 pressed between them until they appear homogeneous throughout. Sometimes one of 
 the rollers is fluted parallel to its axis, and rotates 1^ times more frequently than the 
 other. The rollers generally lie perpendicularly one above the other, and have a 
 length of 2 feet and a diameter of 13 inches, being capable of working up at one 
 operation upwards of 40 Ibs. of caoutchouc. 
 
 When regularly formed blocks are desired, the raw shapeless pieces are cut into 
 disks, and being placed one above the other are squeezed together under a powerful 
 hydraulic press at a temperature of 45, either alone or in an iron mould. A block 
 thus formed, being allowed after cooling to remain six or eight days under pressure, 
 retains the shape given to it when removed. The blocks are then stored up for use 
 in a cellar. 
 
 Plates of any desired thickness may be cut from blocks by fixing the block with 
 caoutchouc cement upon a movable slide placed in a horizontal position, and pressing 
 against it a thin very sharp knife oscillating 800 or 900 times in a minute. The 
 thickness of the plates is regulated by a screw arrangement, which raises the level of 
 the slide holding the block. Adhesion between the knife and the caoutchouc is pre- 
 vented by a stream of water which keeps the knife continually wet. By this means 
 
CAOUTCHOUC. 737 
 
 plates may be cut of any thickness from i of an inch upwards. These serve for the 
 manufacture of light balloons, tubing, elastic garters, and various chemical and 
 chirurgical instruments and utensils. All such objects, however, require vulcanising, 
 for reasons already given. 
 
 Guibal prepares cylindrical blocks directly from the irregular lumps (figs. 506 and 
 507) as they are turned out from the kneading apparatus. A block is pressed with 
 great force while still warm into a strong cylindrically-shaped iron mould, placed 
 vertically, by means of a ram fitting into the mould, and moved by an hydraulic press ; 
 it is allowed to remain 24 hours or longer under pressure. 
 
 These cylindrical blocks are generally cut into long bands, the width of which 
 corresponds to the height of the cylinder, by means of a circular knife pressed against 
 it in a direction parallel to the axis of the cylinder. 
 
 Bands are easily united, the ends being laid over one another, and either 
 squeezed together in a press or welded together with a hammer upon an anvil like 
 pieces of iron. In this operation it is necessary to work in a room having a tempera- 
 ture of 25, the caoutchouc having been previously brought to this temperature. 
 Should the bands or plates of caoutchouc have cooled to below 0, they must be heated 
 to 40 or 44 in order to give them their former elasticity and adhesive properties. 
 The various objects manufactured from these caoutchouc sheets, such as tubes, 
 overshoes, balloons, bottles, etc., have then to be vulcanised in one of the ways already 
 described. 
 
 Threads. For preparing threads from purified rubber, plates j or 1 inch thick are 
 either punched or cut into disks 6 or 8 inches in diameter. These disks are then cut 
 into spiral bands, and finally into threads, by being passed through circular slitters. 
 Another method is to cut the disks direct from cylindrical blocks, and then into 
 threads. 
 
 Another method differing considerably from either of the above, consists in stretch- 
 ing a piece of India rubber tubing over a roller having a screw arrangement, and 
 placed against a sharp knife in such a way that upon moving the roller in the direc- 
 tion of the screw line, the caoutchouc tube is cut into one long thread, the breadth of 
 which throughout is the same as the width of the grooves in the screw. 
 
 A machine constructed by M. G-erard is capable of cutting from 150 to 250 
 threads in a single operation. Bands of the best Para caoutchouc are drawn out 
 between warm rollers and kneaded up with 6 per cent, of sulphur. Upon coming 
 from the rollers, the bands are strewn on either side with powdered talc, and wound 
 round other rollers together with strips of linen. The length of an individual band is 
 about 66 yards, its width about 26 inches, its thickness varying from to inch, 
 according to the thickness of the threads to be made from it. The rolled up bands, 
 together with the rollers, are placed in a strong vertical iron cylinder, and heated for 
 a couple of hours by means of superheated steam to a temperature of 1 40. In order 
 that the bands may have perfectly parallel sides, their edges are cut when cool, and 
 the bands are then divided lengthways by three parallel incisions into four parts. 
 The ribbons thus formed are then drawn over a roller composed of 150 or 250 
 sharpened steel disks, having a diameter of 2| inches, and a thickness of ^ inch, ^and 
 separated from one another by disks of brass 2 inch in diameter, and ^ to | inch 
 thick, according to the thickness of the threads to be produced. These disks are at- 
 tached to an axle, and pressed firmly together by means of a screw adjustment. The 
 whole forms a roller, the entire surface of which is covered by circular knives project- 
 ing about I inch. This is set in rapid motion (about 1,500 revolutions in a minute), 
 and the prepared caoutchouc ribbon is drawn under it by means of a smaller roller 
 placed parallel to the first, which makes only 8 or 10 revolutions in a minute, and 
 being pressed at the same time against the cutting roller by means of a caoutchouc 
 band, is thereby cut into threads. Adhesion of the threads is prevented as in other 
 instances, by a stream of water kept flowing over them. The cutter is at first 
 slightly raised, and then lowered on the ribbon, in such a manner that an end piece 
 remains uncut. As the cut ribbon leaves the cutter, the individual incisions are 
 seized by a comb, the teeth of which correspond with the circular knives of the roller. 
 The incisions are so fine, that ribbons cut in this manner, upon coming from the 
 cutter, look just like uncut ones. The slightest touch, however, is sufficient to show 
 the division in 150 to 200 threads. In order to render the surface of the threads 
 more pliable, they are wound into skeins upon reels, drawn from thence through a 
 heated solution of potash, then washed with water and afterwards dried in the air. 
 Finally, to prevent them sticking together, they are wound round vertically placed 
 frames, furnished with copper teeth, and then either packed at once, or worked in the 
 loom. 
 
 According to Payen, this machine yields from ten to fifteen times as great a quan- 
 tity of caoutchouc thread as the ordinary machines employed. 
 
 3 B 
 
738 RESIN, ETC. 
 
 Round Caoutchouc Threads. The manufacture of round threads of caoutchouc is 
 also due to MM. Aubert and Gerard ; it consists in pressing caoutchouc that has 
 been rendered plastic by some solvent, through round holes, and carefully drying the 
 thread. Caoutchouc, cut into small pieces, is placed in hermetically closed tin boxes, 
 with an equal weight of 5 per cent, alcohol, and allowed to remain some time. The 
 caoutchouc swells up without dissolving, and forms, after standing twelve hours, a 
 pasty mass. As it generally contains mechanical impurities which would be disad- 
 vantageous for the next operation, the pasty mass is forced through a sieve in which 
 the impurities remain behind. The caoutchouc is then passed into a strong iron 
 cylinder, the bottom of which is furnished with round holes having tin points, which 
 give it the required form. The caoutchouc paste is pressed through these holes by a 
 piston that exactly fits into the cylinder. The threads upon issuing from the holes 
 are very soft, and require careful drying. To effect this, they are wound over an 
 endless cloth of cotton velvet, passing over two rollers set at a distance of 1 3 feet 
 from each other. The threads are wound from this cloth on to an endless wire sieve, 
 likewise turning upon two rollers set apart at a distance of about 40 inches, and are 
 here dusted with powdered talc to prevent adhesion. Finally, the threads are drawn 
 over five endless linen bands, each of which passes over two rollers set apart at a dis- 
 tance of 52 feet. The threads, upon leaving the linen bands, are completely dry, the 
 whole process of drying occupying only ten minutes. 
 
 The thickness of the threads is of course dependent upon the size of the holes at 
 the bottom of the cylinder through which the caoutchouc is pressed, but, as the thickness 
 diminishes considerably during the drying, threads passed through a hole of ~ inch 
 in diameter, have when dry a diameter of only ^ inch. 
 
 The packing of the threads is performed by passing them directly from the linen 
 bands through a runnel into a tin box, revolving on its axis, by which means they 
 get laid together in the box in regular convolutions. 
 
 Very thin threads of caoutchouc are prepared by stretching thicker ones until these 
 have attained the required thinness, when they are submitted for some time to a tem- 
 perature of 115; after cooling the threads retain the elongated form, but are not 
 further altered by the operation. 
 
 Solid Balls of Caoutchouc. These are generally made from the caoutchouc blocks 
 (figs. 506 and 507), as they are turned out of the wolf. The blocks are pressed with 
 some force against rollers, the surface of which is furnished with saw blades running 
 parallel to the axis of the roller, so that the points project beyond the roller, like the 
 rasps of the roller employed in sugar manufactories. These rollers, which make from 
 500 to 600 revolutions in a minute, tear the caoutchouc into shreds, and at the same 
 time heat it sufficiently to cause it to form a soft sticky mass, which is then made with 
 the hand into rough sorts of balls, that are afterwards pressed in moulds. These 
 moulds consist of two movable halves, fitting over one another, and the soft caout- 
 chouc getting into the groove between them, the balls exhibit a distinct ring when 
 cool. This ring can bo got rid of by changing the position of the balls in the moulds 
 after the first pressing, and squeezing them again. The balls are cooled down in the 
 moulds for about twelve hours, before being taken out. They are rendered again , f 
 elastic by being heated to 50 in a heated room or in hot water. 
 
 A cloth-like covering is sometimes given to these balls by smearing them with I 
 caoutchouc cement, and rolling them in fine wool. The wool sticks to their surface, ' 
 forming, after the balls" have been dried in a warm room, a very durable covering. 
 
 When a permanent elasticity is to be attained by vulcanising the caoutchouc, ' 
 about 6 or 8 per cent, of sulphur is added to the caoutchouc in the wolf, and the balls \ 
 made from such vulcanised rubber are brought, while still in the moulds, into a > 
 cylinder heated to 140. 
 
 Boiled Caoutchouc Plates. These are made by rolling thick and large pieces ofi 
 caoutchouc previously heated to 40 or 50, then rolled out between warmed rollers \ 
 which are brought gradually nearer together, the operation being repeated until the ! 
 desired thickness is attained. The rollers are heated to 80 or 100. either by bars |, 
 of red-hot iron let into them, or preferably by steam. 
 
 As the sheets of caoutchouc leave the rolling machine in a very warm and half 
 sticky condition, they are passed through cold water rendered slightly alkaline, or 
 covered with talc powder before being folded up. 
 
 Coloured Caoutchouc Plates are prepared by mixing up with the caoutchouc some 
 non-transparent colouring powder. White plates are obtained by the addition of zinc 
 white, red ones by adding cinnabar, yellow or orange by adding different ochres, blue 
 ones by adding ultramarine, and black ones by adding ivory black or lamp black, etc. 
 
 Caoutchouc Foot Rugs have recently come much into vogue. They generally have 
 a raised pattern, and those having a dimension of about 6 feet by 3 are made from a 
 
CAOUTCHOUC. 739 
 
 single thick caoutchouc plate in a single pressing. The caoutchouc plate, in which 
 sulphur has been kneaded, is pressed strongly between two hollow iron plates upon 
 which some design is engraved, and heated by steam conducted through the hollow 
 iron plates first of all for a short time up to 115, and finally to 145 C. so as to vul- 
 canise the caoutchouc. As it is easy to conduct several pressings together upon a 
 long strip, Aubert and Gerard prepare pieces of caoutchouc carpet for galleries, etc., 
 upwards of 100 yards in length. 
 
 A mixture suitable for the purpose has the following composition : 
 
 Caoutchouc 50 parts 
 
 Teazed linen 15 
 
 Zinc oxide 25 
 
 Sulphur 4 
 
 Slaked lime . 5 
 
 Chalk 6 
 
 M. Guibal prepares network door mats from the following mixture : 
 
 Caoutchouc 40 parts 
 
 Chippings of vulcanised rubber . . . . . . 10 
 
 Other caoutchouc chippings 5 
 
 Litharge 35 
 
 Chalk ' 8 
 
 Sulphur 2 
 
 India Rubber Tubes are generally prepared from strips of sulphurated but unburnt 
 caoutchouc, the width of which corresponds to the diameter of the tube. The caout- 
 chouc strip is folded together, and the sides clipped off in the 
 manner represented in section by fig. 508. The cut surface A xio. 508. 
 
 forms with the lower surface on one side an angle of 45, and on the 
 other an angle of 135, so that both surfaces fit exactly together 
 when laid over one another. The operation of laying over is 
 assisted by a mandrel made of iron tube or wire, as shown by fig. 
 509, and the surfaces are united by strong pressure. Another way 
 consists in winding the caoutchouc slip round the mandrel and 
 uniting the edges. 
 
 The burning (i.e. the completion of the vulcanisation) is the 
 next process, which is performed by binding the tubes and man- 
 drels round with linen strips, and heating them in iron cylinders 
 by means of steam to a temperature of 132 or 140 for between p IGi 599. 
 
 1| and 2 hours. The mandrel, the thickness of which must corre- 
 spond to the bore of the tube, is drawn out after the burning. Should it adhere to the 
 tube at any part, it may be liberated by means of a little cold water. 
 
 Tubes that are required to resist strong internal pressure are prepared in the 
 following way. A linen band previously dipped in caoutchouc varnish is wound in a 
 spiral manner round a tube of sulphurated but unburnt caoutchouc ; the whole is then 
 surrounded by a second caoutchouc tube, and burnt in the manner above described. 
 Tubes of still greater durability are made by using iron wire instead of linen. 
 
 India rubber tubes may be also prepared by using a press like that described in 
 the manufacture of round threads, mandrels being fixed in the moulding holes. 
 
 A mixture recommended by Payen for the preparation of India rubber tubes has 
 the following composition : 
 
 Caoutchouc . ..... '. ' . r;>- . . . 59 parts 
 
 Zinc oxide . . . . ; . .. ' . . . . 35 ' 
 
 Sulphur ; . 'i.'V . . 5 
 
 Lime ..,.. . . . . . . . 1 
 
 Waterproof fabrics, and very thin Plates of Caoutchouc. Two distinct methods are 
 followed in the manufacture of waterproof fabrics : 
 
 (1) Thin caoutchouc plates are pressed into or upon the stuff; 
 
 (2) The caoutchouc is spread upon the stuff in the form of varnish. 
 
 In order to prepare waterproof materials from thin plates of caoutchouc, the 
 'plates in anon-vulcanised, still adhesive state are placed between two pieces of cloth 
 and then passed several times between heated rollers. By this method, waterproof 
 fabrics are obtained which are rather heavy, but are free from the unpleasant smell 
 which clings to other waterproof stuffs when solvents are used. The method was in- 
 vented by Mr. Macintosh, who employed it in the preparation of the first waterproof 
 fabrics. 
 
 Lighter waterproof stuffs are obtained by rolling together a single piece of cloth 
 
 3u2 
 
740 RESIN, ETC. 
 
 with a single piece of caoutchouc. The fabric obtained is thus covered on one side 
 only with caoutchouc. 
 
 The second method for preparing waterproof fabrics, which consists in covering 
 the cloth with caoutchouc varnish, has been recently much employed. Strips of puri- 
 fied caoutchouc are thoroughly dried by leaving them in a drying room for twenty -four 
 hours, and are then softened by immersion for from twenty-four to forty-eight hours 
 in three times their weight of rectified oil of turpentine in wooden boxes lined with 
 sheet iron, each box holding about 110 gallons. The expanded caoutchouc mass is 
 distributed in eight metal cylinders with perforated bottoms, so as to form a layer of 
 2| inches in height in each cylinder. These eight cylinders are then placed in a 
 column apparatus, similar to that used in distilleries, closed hermetically with a lid, 
 the whole being fitted over a still filled with rectified oil of turpentine. The turpentine 
 is made to boil ; its vapour, passing through the perforated bottoms of the cylinders, 
 raises the temperature of the caoutchouc to about 150, and permeates it more com- 
 pletely than is the case in a simple process of kneading. The turpentine vapour 
 passes out through a tube at the top of the apparatus into a serpentine condenser, the 
 condensed product being again used as rectified oil of turpentine. 
 
 At the end of two hours the operation is stopped, the cylinders taken out of the 
 column apparatus, and the caoutchouc thrown into a kind of vermicelli press furnished 
 with 3 or 4 fine metallic wire nets attached to perforated sheet iron. A piston fitting 
 accurately into the press is then set in motion by means of a screw, and the caout- 
 chouc mass is pressed by it through the wire sieves, which retain mechanical 
 impurities. The soft caoutchouc mass is then strongly rubbed and kneaded between 
 rollers ; and, when a colour is desired, the colouring material to the amount of 5 per 
 cent, is thrown in. Blue is obtained by adding ultramarine, yellow by the addition oi 
 orpiment, white is produced by zinc white, red by powdered cinnabar, and black by 
 lamp black, etc. When vulcanisation of the caoutchouc is required, from 3 to 4 per 
 cent, of sulphur is added. The apparatus represented by fig. 512, p. 744, may be used for 
 these operations. Should the caoutchouc paste not be soft enough, from 5 to 4 parts 
 of oil of turpentine are added to 1 part of caoutchouc. 
 
 The oil of turpentine employed in the preparation of this caoutchouc paste should 
 be pure rectified oil, raw non-rectified turpentine containing always considerable 
 quantities of resinous substance. 
 
 M. Guibal employs benzol in the place of oil of turpentine, the articles manu- 
 factured from caoutchouc paste prepared with benzol having the advantage that they 
 are not injured by the action of the air, like those manufactured from varnish or paste 
 prepared with oil of turpentine. The cause of the latter being affected by the air 
 seems to be owing to a decomposition, caused by a small quantity of oil of turpentine 
 retained by the caoutchouc. 
 
 The caoutchouc paste or varnish is spread upon the cloth in a well- ventilated room 
 protected as far as possible from dust, the cloth being placed on an endless band re- 
 volving round two horizontal cylinders, set apart at a distance of about 30 yards. 
 Across this band, and perpendicular to it, is fixed a wooden scraper edged with 
 iron, and having adjusting screws by which the thickness of the caoutchouc layer can 
 be regulated. 
 
 As soon as the cloth is in movement, the caoutchouc paste is laid upon it with a 
 trowel in front of the scraper, under which it passes in a more or less thin layer, ac- 
 cording as the scraper is set. The speed is about 11 yards a minute, so that a web 
 64 yards long makes a single revolution every seven minutes. An interval of two 
 hours is allowed between the application of each layer of paste, so as to insure the 
 evaporation of the greater part of the oil of turpentine; a coating of 14 layers 
 would therefore require from twenty-eight to thirty hours. This inconvenient delay, 
 caused by the time required for the evaporation cf the oil of turpentine, has been 
 avoided by Messrs. Guibal and Cuminge, who have constructed an apparatus in which 
 the web is passed over heated boxes ; evaporation of the oil of turpentine or benzol is 
 by this means so accelerated that the whole operation may be completed in two hours. 
 In order to recover the turpentine thus evaporated, Messrs. Guibal and Cuminge have 
 constructed a condensing apparatus just over the spot where the chief quantity of oil 
 of turpentine or benzol evaporates. It consists of a couple of pieces of sheet metal 
 laid together to form a kind of roof, and kept cold on the outside by a current of water. 
 
 If the caoutchouc has been previously kneaded with sulphur with the object of 
 eventual vulcanisation, it is now heated for an hour to 132 or 140 in an iron cy- 
 linder with double sides, between which steam is passed. For the most part linen 
 stuffs only are vulcanised, stuffs of silk or wool being very apt to crinkle and pucker 
 at the high temperature required for vulcanisation. 
 
 Double textures, or textures which consist of a layer of caoutchouc between two 
 layers of web, may be also prepared by the aid of this apparatus. For this purpose two 
 
CAOUTCHOUC. 741 
 
 lengths of coated web are laid together with the caoutchouc sides against one another 
 and pressed firmly together into one piece by passing them between rollers. 
 
 Instead of the scraper arrangement for regulating the thickness of the caoutchouc 
 layers, two rollers are sometimes employed, through which the coated webs are passed. 
 The upper roller is stationary, the distance between it and the lower one being 
 regulated either by adjustment screws or a lever arrangement. The lower roller re- 
 volves in the direction of the cloth. 
 
 Various recipes have been given for preparing the caoutchouc paste. 
 
 Gruibal recommends the following mixture as forming a cheap and durable caout- 
 chouc paste, void of disagreeable smell : 
 
 Purified caoutchouc 33 
 
 Powdered litharge 
 
 Chalk ! ! '. 10 
 
 Lamp black .... 
 
 Sulphur 5 
 
 100 
 Benzol 100 
 
 Payen recommends the following mixture : 
 
 Caoutchouc 80 parts 
 
 Powdered litharge 50 
 
 Chalk 10 " 
 
 Lamp black 2 
 
 Sulphur . . 4-5 
 
 A method of softening and partly dissolving caoutchouc with carbon bisulphide in 
 the cold, and kneading the mass to a homogeneous paste or dough, is employed in 
 preparing the caoutchouc for the double textures already alluded to. 
 
 Stuffs of the kind have this advantage, that carbon bisulphide volatilises more 
 quickly than oil of turpentine. Indeed it sometimes evaporates too quickly, and in 
 order to prevent a too rapid volatilisation a small quantity of benzol is added. 
 
 When carbon bisulphide is employed, the process must be conducted in a well- 
 ventilated room, so as to prevent the workmen suffering from the stupefying and 
 poisonous vapours of that substance. 
 
 Mr. Norris suggested a direct application of raw caoutchouc sap to webs to be coated 
 with caoutchouc. Mr. G-oodyear recommends the addition of oil of tar, and more sulphur 
 than is usual. M. Chevalier has recommended boiling caoutchouc that has been 
 previously softened by oil of turpentine, with a mixture of linseed oil and litharge, etc. 
 An interesting patent for preparing caoutchouc paste was taken out by Mr. Fry, which 
 consists in submitting to distillation a mixture of two parts of rectified oil of turpen- 
 tine with from three to four parts of caoutchouc, using the distillate as a solvent for 
 caoutchouc. 
 
 The apparatus for the manufacture of waterproof fabrics above described may 
 be advantageously used in the preparation of very thin sheets of caoutchouc, and the 
 caoutchouc used may be either pure or after it has been treated with colouring, litharge, 
 sulphur, etc. 
 
 In this case, the linen cloth which runs over the two rollers receives a coat- 
 ing, consisting of equal parts of treacle and gelatine. This gelatine covering is on 
 the one hand dry enough to prevent substances adhering to it, and on the other 
 hand, owing to the hygroscopic properties of treacle, moist enough to retain its flexi- 
 bility for a long time. The caoutchouc paste is spread upon the gelatine coating and 
 the cloth passed under the scraper; 40 very thin coatings being applied for the 
 preparation of a sheet ^ inch thick. The spreading of each layer occupies about 10 
 minutes, the drying itself an hour, so that a sheet of 40 coatings requires 40 hours 
 for its preparation. The sheets are easily removed from the gelatine coating, are 
 then covered with finely-powdered talc, and wound up on rollers. 
 
 These very thin sheets of caoutchouc are well adapted for the production of a 
 number of objects, which, when the caoutchouc has been previously kneaded up with 
 sulphur, may be vulcanised by simply heating them. 
 
 In order to give the sheets a smooth surface, they are boiled for about an hour 
 with a solution of caustic soda or potash ; they are rendered still smoother by drawing 
 them through a solution of potassium hypochlorite heated to 60 (Jayelle water). 
 
 Hollow Balls are prepared from caoutchouc plates | to \ inch in thickness, and 
 occur in the market in sizes varying from 2 to 5 inches in diameter. The plates 
 themselves are prepared either by cutting up blocks of caoutchouc with the oscillating 
 knife, or are rolled out ; the caoutchouc mass is generally previously mixed with 5 or 
 
742 
 
 RESIN, ETC. 
 
 6 per cent, of sulphur, so as to admit of eventual vulcanisation. The plates are cut 
 into spherical segments upon a model, and in such a way that the cut surfaces have an 
 oblique direction, which renders their union more easy. Four such segments are 
 taken for a single ball, and their edges united either by simply pressing them to- 
 gether with the hand, or sometimes with the aid of a cement consisting of caoutchouc, 
 sulphur, carbon bisulphide, and benzol, care being taken that as much air as possible 
 remains in the ball. The balls are then placed in spherical moulds, something like 
 those employed in bullet-casting, and heated in iron cylinders to over 130, partly in 
 order to vulcanise them, and partly to expand the air contained in them. The furrows 
 exhibited by the balls before undergoing this process, get filled out, the sides of the 
 balls are pressed strongly against the interior of the moulds, and retain upon cooling 
 the form assumed during vulcanisation. As it is difficult during the union of 
 the segments to retain sufficient air in the balls to completely expand them during 
 the vulcanising process before the balls are completely closed, a small quantity of 
 water or ammonium carbonate is poured in, which substances exert considerable pres- 
 sure in the interior of the balls when heated. 
 
 Balls, thus prepared, are naturally not very elastic. When very elastic hollow 
 balls are required, they are prepared in the above way, but stronger caoutchouc plates 
 are taken, and they are finally expanded by means of compressed air. In order to 
 effect this, a fine perforation is made in each ball immediately after its removal from 
 the mould, air is forced into the aperture by means of a force pump, and the opening 
 is then closed as quickly as possible with caoutchouc cement. Such balls are often 
 painted of different colours. 
 
 Light Gas Balloons require to be made of very thin caoutchouc sheets so that they 
 may rise in the air readily when filled with hydrogen gas under moderate pressure. 
 In order to be effective the weight of the caoutchouc envelope, plus the weight of the 
 enclosed hydrogen gas, must be less than the weight of an equal volume of air. Thus, 
 for instance, supposing the volume of air replaced by the balloon to be 1 gallon, this 
 weighs oz. at the ordinary temperature and pressure, an equal volume of hydrogen 
 under the same conditions weighing only ^ oz., so that when the weight of the 
 caoutchouc envelope is less than the difference between the weight of the air and hydro- 
 gen gas (in the above instance ^ oz.) the balloon rises. Eeferring to the figures just 
 given, if the caoutchouc envelope of the balloon weighs oz., the balloon will be 
 impelled upwards with a force equal to ^ oz. 
 
 The thinnest plates of caoutchouc are selected for preparing these balloons, plates 
 of 2 J g inch thickness, and of the best Para caoutchouc. These plates are cut with 
 the oscillating knife into segments of a form represented by 
 fig. 510. Each segment has an elongation b a at one end 
 about f in. in length and | in. wide. Four segments of the 
 kind are joined together to form a single balloon in the 
 following way. They are heated up to 45 or 50 C. and their 
 edges united by beating them together on an anvil with a 
 hammer in a room having a temperature of 25 or 28 C. The 
 elongation of the segments then forms a tube f of an inch 
 long and about | in. in diameter, which serves for the filling 
 of the balloons with hydrogen gas. 
 
 The balloons are vulcanised by immersing them for two 
 seconds in a mixture of carbon bisulphide and sulphur 
 chloride containing from 4 to 5 per cent, of the latter sub- 
 stance, and then allowing the carbon bisulphide to evaporate 
 in the air. The balloons are generally coloured by dipping 
 them into a solution of some colouring material dissolved in 
 carbon bisulphide. 
 
 These balloons are filled with hydrogen by attaching their 
 contracted ends to an apparatus from which the gas is being 
 evolved, filling them with it under a pressure of 40 inches of 
 water, and then binding the ends securely with thread. 
 
 Strong Caoutchouc Rings for the Bitffers of Railway 
 Carriages, etc. Messrs. Aubertand Gerard prepare these rings 
 ^^^^^^ from a mixture consisting of 100 parts of purified caoutchouc 
 
 shreds, 5 or 6 parts of sulphur and 5 parts of slaked lime, the materials being combined 
 either in the wolf or by passing them between heated rollers. This product is then 
 rolled out to a strip | or f of an inch in thickness between a couple of rollers having each 
 a diameter of 20 inches revolving slowly (about 1 revolution per minute) in opposite 
 directions. Immediately upon its departure from the rolling mill, this strip is bound 
 round a hollow roller of sheet iron, the thickness of the rings being dependent upon 
 the number of times the piece is wound round this iron roller. Kings are prepared in 
 
 FIG. 510. 
 
CAOUTCHOUC. 
 
 743 
 
 this way, having an outer thickness of as much as 2 inches, which are used for connect- 
 ing engines and tenders, and also for the buffers of railway carriages, by cutting them 
 with the circular knife. For these purposes especially the best Brazil caoutchouc is 
 to be preferred to the caoutchouc from India or Africa. The vulcanisation of these 
 rings is effected in the usual way either by heating them in iron cylinders by means 
 of steam, or for one or two hours in hermetically closed vessels with water to a 
 temperature of 135. If the rings are not required to be vulcanised, they are heated 
 for a short time to a temperature not exceeding 100 in order to unite the layers, but 
 this is comparatively seldom the case. 
 
 When a heavy caoutchouc mass is required, specifically heavy substances are added 
 in a finely powdered condition, such as heavy spar, lead sulphate, red or yellow ochre, 
 zinc oxide, etc. A greater firmness and tenacity, but less elasticity, is obtained by 
 adding to the caoutchouc heated to 50 or 60 C. from i to ^ of its weight of teazed 
 linen rags. 
 
 Driving Belts. These articles are prepared with purified caoutchouc, kneaded up 
 with 5 per cent, of its weight of sulphur between rollers heated 
 to from 50 to 60, which is pressed into strong linen tissue with 
 such force as to penetrate nearly all the meshes. The machine, 
 called a spreader, is represented by fig. 511. It consists of 
 three hollow rollers (A B c) made of cast-iron, which admit of 
 being heated internally by steam. Each roller has a diameter 
 of 14 inches, and has a toothed wheel attached to one of its 
 extremities. The middle wheel (D) is 9 inches in diameter, 
 the outer wheels (E E') are 19 inches in diameter, so that as 
 motion is given to the whole by (D), the wheels (E E') make 
 only half the number of revolutions executed by (D). The 
 linen strip which is very strong, about 40 inches in width, and 
 from 10 to 50 yards long, is passed together with the caoutchouc 
 between the rollers, which are set very near one another, and 
 it is pressed together by them with such force that the caout- 
 chouc penetrates all the meshes of the linen, causing a very in- 
 timate union of the two substances. These impregnated linen 
 pieces are then laid one over another in layers of from 3 to 10, 
 pressed between heated rollers, and cut by a suitable cutting 
 instrument into straps or bands of the required length and 
 breadth. In order to prevent their fraying, as well as to pro- 
 tect their exterior, the bands are covered with linen. In 
 vulcanising these driving belts, they are laid in moulds consist- 
 ing of a kind of iron gutter with right-angled grooves pre- 
 viously soaped, from which the belts extend at both ends, and G- "** 
 
 into which an iron lid exactly fits, but is about to ^ inch higher than the mould. A 
 number of such moulds are laid together upon a press, the plates of which are hollow 
 and admit of being heated with steam. The press is first of all drawn together, and 
 then steam at a temperature of 140 is let into the press plates. Since iron is a good 
 conductor of heat the belts soon become heated, the operation being complete in an 
 hour. The press is then drawn up, the lids of the moulds removed, and new non- 
 vulcanised portions of the belts are laid in the moulds and treated in the same 
 manner, the operations being continued until the entire lengths of the belts are vul- 
 canised. These bands are very durable, and in respect of price compare favourably 
 with those made from leather. 
 
 Goloshes are made from purified caoutchouc mixed with sulphur and lamp black, 
 and rolled out to a light and somewhat elastic fabric, which is stamped out in patterns 
 and moulded over iron shapes. A shining surface is given to them by covering them 
 with asphalt lac, and they are finally vulcanised while still on the moulds. 
 
 A kind of golosh which formerly found its way into the market from America was 
 made by covering moulds with several layers of caoutchouc juice until the necessary 
 thickness had been attained. 
 
 Pressing Rollers for dye works are obtained by stretching a strong caoutchouc tube 
 mixed with sulphur over a roller engraved with the required design, and compressing 
 it firmly by linen bands. This is next burnt in an iron cylinder, and finally, when 
 cool, detached, turned inside out and fastened to an even roller. 
 
 Elastic Tissues are prepared by weaving thin caoutchouc threads upon looms. Fine 
 caoutchouc threads, the manufacture of which has been already treated of, are softened 
 in warm water, and when very much extended are wound upon bobbins, and exposed 
 for some time to a low temperature. Before weaving, they are generally wound .on to 
 other bobbins. The fabric, when complete, consists of very expanded inelastic threads, 
 
744 RESIN, ETC. 
 
 and must be heated to 100 to render it elastic, whereupon it contracts just in the 
 same way as a separate thread. 
 
 Elastic tissues, are also prepared from vulcanised caoutchouc threads. These 
 require considerable stretching when woven. 
 
 The industrial applications of caoutchouc are so numerous that it is impossible to 
 detail them all here. The following list gives some of the most important articles 
 made of this substance : 
 
 Ordinary or non-vulcanised caoutchouc is used for making cut sheets for surgical 
 apparatus, and for very thin balloons ; cut or rolled sheets for preparing tubes, bands, 
 threads, discs, shoes, balls, etc. ; very thin sheets rolled out from heated caoutchouc 
 for preparing waterproof fabrics, cements, varnishes, solvents and plaster ; cements 
 and varnishes for joining wood, and for mixing with wool in the manufacture of 
 carpets, and also for book-binding ; solid purified elastic blocks for elastic balls, and 
 pieces of india rubber for rubbing out pencil marks. Further, non- vulcanised caout- 
 chouc is used when mixed with linseed oil in the proportion of 2 parts of caoutchouc 
 to 98 parts of oil, for preparing oil for lubricating machinery, and for marine glue, etc. 
 
 Vulcanised caoutchouc is used in the manufacture of waterproof fabrics, goloshes, 
 buffers of railway carriages, surgical bandages, garters, straps for binding manuscripts, 
 cravats, etc. ; driving belts, air cushions for chairs, sofas, beds, carriages, etc. ; water 
 beds for invalids, springs for doors, locks, bells, physical and chemical apparatus, etc. ; 
 connecting links of engines and tenders ; also for the padding of the sides of billiard 
 tables, for air lids, traps, and for making elastic threads for knitting and weaving. It 
 is further used in the manufacture of rollers employed in dye and printing works, non- 
 corrosive bottles, stoppers, gas and water tubes, solid and hollow balls, etc. ; it is also 
 employed for fastening artificial teeth, and for preparing vulcanite, etc. 
 
 A very curious application of vulcanised caoutchouc is for the reproduction of en- 
 larged or diminished copies of drawings, etc. This is effected by stretching a plate of 
 vulcanised caoutchouc upon a four-cornered frame, and pressing the drawing upon it. 
 The frame is so arranged that its sides admit of being altered by adjusting screws. 
 Thus, for instance, if it be desired to produce a copy of a picture enlarged four times, 
 the sides of the frame are stretched to double their length. The drawing thus en- 
 larged is then copied upon stone and printed off in the usual way. For preparing 
 diminished copies of a drawing, the frame is expanded, the drawing impressed upon 
 it, and then the frame is drawn together again until the drawing has assumed the 
 required dimensions. 
 
 Dialysis of Gases. Graham and others have shown that all gases do not pass with 
 equal rapidity through the pores of a very thin caoutchouc membrane, that carbonic 
 acid for instance passes through a membrane of the kind with greater rapidity than 
 hydrogen, that oxygen passes through quicker than nitrogen, etc. If a caoutchouc 
 balloon having very thin sides be filled with sawdust, and after the air has been 
 pumped out by means of an air-pump, it be allowed to remain for some time in contact 
 with atmospheric air, it becomes gradually filled with air which contains so large a 
 proportion of oxygen that a glowing match bursts into flame when plunged into it. 
 This air is found upon examination to contain 4T6 per cent, of oxygen, while atmo- 
 spheric air contains only 21 per cent. 
 
 This is a proof that oxygen passes through caoutchouc pores more easily and 
 quickly than nitrogen does. Graham assumed that, upon passing through caoutchouc 
 pores, even permanent gases become liquid, reassuming the gaseous condition upon 
 escaping from the caoutchouc. 
 
 Caoutchouc Varnishes and Cements. For the preparation of caoutchouc varnish or 
 cement, very thin caoutchouc plates are the most suitable. These are cut into small 
 pieces, and placed in closed boxes with from one and a half to two or three times their 
 weight of some liquid which dissolves the caoutchouc either entirely or in part. The 
 
 Fia. 512. 
 
 solvents generally employed are oil of turpentine or benzol. Caoutchouc, when im- 
 mersed in either of these liquids for a length of time varying from twenty-four to 
 
CAOUTCHOUC. 745 
 
 forty- eight hours, becomes entirely soft and swells tip very considerably ; it may be 
 then kneaded in a kneadiug machine to a perfectly homogeneous mass. A machine of 
 the kind is represented by fig. 512. The rollers (A A) have each a diameter of 
 4 inches, and a length of 16 inches ; they revolve in the semicircular troughs (b b) in 
 the direction of the arrows. The troughs are fixed over a wide iron casing (c c) into 
 which steam may be conducted. The softened caoutchouc mass is thrown in at (d), 
 seized by the roller and thoroughly squeezed ; after passing through it is freed from 
 the roller, liberated by a knife blade (g) on the opposite side, and falling down is taken 
 up by the next roller, and so on until it finds its way from the knife of the last roller 
 on to the inclined plane (e), and into a vessel (/) placed beneath it. 
 
 Caoutchouc cement or varnish thus prepared has a more or less viscous consistency, 
 and is used for various purposes ; for instance, for connecting india-rubber plates, in the 
 preparation of waterproof fabrics, for covering wainscot work on the side next the 
 wall, for gluing dry pieces of wood in joinery, in the manufacture of musical instru- 
 ments, and in bookbinding, etc. 
 
 Mastic Cement is prepared by heating 2 parts by weight of caoutchouc to 220, 
 and mixing it when liquid with 1 part by weight of slaked lime. This yields a soft 
 mastic which remains plastic for a long time, and is very suitable for hermetically 
 sealing bottles or other vessels. This method of hermetically closing bottles, etc., was 
 introduced by M. Maissiat, and by its means bottles may be kept hermetically sealed 
 for years. If equal parts of caoutchouc and lime be taken, the result is a solid, but 
 still plastic cement, and if a mastic be required which shall be externally dry and 
 solid, 2 parts of caoutchouc, 1 of lime, and 1 part of litharge are taken. 
 
 Machine Grease from Caoutchouc. An oil is obtained by putting from If to 2 per 
 cent, of caoutchouc into rape seed oil heated to 120 or 130. The mixture is kept at 
 this temperature for 5 or 6 hours, forming at the end of the operation a dark brown, 
 sticky liquid, which is well adapted for smearing parts of machinery. 
 
 Caoutchouc Plaster is prepared by heating caoutchouc to 220. It forms a sticky, 
 adhesive mass, which has been used successfully to protect wounds from the air. 
 
 Manufacture of Vulcanite. Mr. Groodyear started this branch of industry in 
 America in 1848, and two years afterwards it was introduced into Europe. It has 
 already been mentioned that an excess of sulphur renders caoutchouc hard and less 
 elastic. This fact is taken advantage of in the manufacture of vulcanite. The 
 materials employed in this manufacture are raw caoutchouc from India or Java, and 
 powdered roll sulphur. The raw caoutchouc is submitted to the following process of 
 purification before being mixed with the sulphur. 
 
 The raw caoutchouc is softened by immersion for thirty-six to forty-eight hours in 
 water heated to 45 or 50 C., and when sufficiently soft is cut with a knife into long 
 bands weighing each about 2 Ibs., and having a thickness of 2 or 4 inches. These are 
 pressed and torn between moistened rollers, which revolve in opposite directions, 
 one making one, the other two revolutions in a minute. The bands thus torn are 
 next further lacerated in a hollander (see p. 641), impurities being at the same time 
 removed by the action of the water. The caoutchouc shreds are now taken out and 
 spread out to dry upon linen frames in a current of warm dry air. Care must be 
 taken that the air is not too warm, or some of the shreds might stick together, re- 
 taining water between their interstices. 
 
 The dried caoutchouc is pressed and kneaded between rollers heated to 50 or 60 C., 
 so as to form a doughy mass, with which sulphur readily mixes. The proportions 
 used are 100 parts of caoutchouc to 50 parts of very finely powdered and sifted 
 sulphur. When the caoutchouc and sulphur are thoroughly mixed, the two rollers 
 arc set apart at a distance corresponding to the thickness of the plate required. The 
 sheets upon coming from the rolling mill are cut into pieces about 16 inches in 
 breadth and 24 inches in length, which are immersed in water at a temperature 
 of about 28 C., in order to give them a certain amount of hardness. They are then 
 again dried and laid upon plates of tin plate or glass smeared with lard. A roller 
 having a horizontal motion is then passed over the pieces of caoutchouc in order to 
 press them against these plates, the caoutchouc being covered with powdered talc to 
 prevent adhesion. 
 
 After having been allowed to remain twenty-four hours in a horizontal position, 
 the plates are laid upon iron frames which are placed on supports in such a way that 
 they have an incline of 45, which serves on the one hand to prevent the caoutchouc 
 plates from slipping when heated, and on the other hand to drain off the condensed 
 water in the next operation. The supports set upon rollers are pushed upon a tram- 
 way into a large cylinder of sheet iron, 40 inches in diameter and 20 feet long. This 
 cylinder is closed hermetically by means of a caoutchouc ring fitting in between the 
 edge of the cylinder and a lid of sheet iron, the lid being pressed against the caout- 
 
746 RESIN, ETC. 
 
 chouc ring by means of clinches or screws. When the cylinder is closed, superheated 
 steam is conducted into it through a perforated pipe lying along its bottom, and its 
 contents are thereby raised gradually within two or three hours to a temperature of 
 135 C., which temperature is then kept up for seven hours. When the thicker caout- 
 chouc plates are operated upon, such as are | inch thick, the temperature must be 
 raised still more gradually, requiring four hours, and the temperature of 135 C. is 
 kept up for a space of eight hours. The whole is then allowed to cool, and air is 
 admitted into the cylinder, the lid is removed, the supports taken out, and the plates 
 removed from them. The caoutchouc should now be very hard, but still retain a 
 certain amount of elasticity. 
 
 When either too great a temperature has been employed, or too much sulphur 
 has been added, the caoutchouc is hard, but it is at the same time brittle and friable. 
 Payen has shown that caoutchouc heated with an excess of sulphur is capable of 
 absorbing as much as 48 per cent, of that substance. A good hard vulcanite, however, 
 should not contain more than 33 per cent, of sulphur. 
 
 During the process of heating in the cylinder water is constantly condensing upon 
 the upper part of the cylinder, and drops down upon the caoutchouc plates if these are 
 not properly protected. This is liable to exert an injurious effect on the caoutchouc, 
 owing to particles of rust being carried down along with the water, rendering the 
 surface of the caoutchouc coarse and impure. This may be prevented either by pack- 
 ing the caoutchouc plates between two pieces of sheet iron, and setting them perpen- 
 dicularly on the supports, or by covering the plates as they lie inclined on the sup- 
 ports with a metal roof which carries away the condensed water. 
 
 Plates of vulcanite thus prepared are principally used for making combs. For this 
 purpose after the required shapes are drawn upon them with a piece of pointed steel, 
 they are cut into smaller pieces with a saw. These pieces are then planed on one side, 
 and afterwards rendered smooth by grinding them on tables of slate. The teeth are 
 cut with a circular saw, and polished with pumice powder and tallow. Bent combs 
 are prepared by dipping straight ones into hot water, and giving them the bent form 
 while in the water ; they are then dipped as quickly as possible in cold water, and 
 retain afterwards the bent form. 
 
 Besides sulphur a number of other substances are employed for hardening 
 caoutchouc, the use of which depends upon the purposes the caoutchouc is afterwards 
 to serve. Thus, for instance, zinc white, white lead, chalk, powdered heavy spar, etc., 
 are sometimes mixed with caoutchouc. For the manufacture of spindles and shuttles, 
 an addition of shellac is made. 
 
 Uses of Vulcanite. The chief use of vulcanite is in the manufacture of combs ; 
 combs made of this material having the advantage that they are not injured either by 
 lukewarm or cold water, and do not fray out like horn combs, those made of buffalo 
 horn not excepted, all being of a fibrous nature. 
 
 Vulcanite is also used for the disks of electric machines, for furniture, various 
 ornaments, book covers, fans, for corsettes instead of whalebone, for very smooth 
 shuttles, measures, kandles of knives, etc. ; further for the small silver baths of pho- 
 tographers, for the supports of galvanic batteries, etc. 
 
 These articles are coloured either by simply painting them, or the colour is 
 kneaded in with the caoutchouc before vulcanisation. 
 
 Manufacture of Artificial Grindstones. This branch of industry was founded about 
 twelve years ago by M. Deplanque, and since then it has been so much improved that 
 it has now attained considerable importance. The stones are prepared from a composi- 
 tion consisting of quartz sand, powdered flint, emery powd.er, and caoutchouc dissolved 
 in some cheap oil of tar. This mixture is kneaded together, and yields a product of 
 such durability that it may be used for a very long time without showing much sign 
 of wear. Such stones are well adapted for polishing various implements of wrought 
 iron, steel, cast steel, etc. 
 
 The apparatus in which these grindstones are prepared is shown in figs. 513 and 
 514. A is a boiler (fig. 513) heated from below, the heating of which admits of being 
 easily regulated. About 84 Ibs. of caoutchouc clippings are heated in this boiler to 
 220 or 230 C. In order to facilitate the distribution of heat and the melting of the 
 caoutchouc, 7 Ibs. more of heavy oil of tar are added after a lapse of two hours. The 
 caoutchouc gradually melts, and after a lapse of another two hours, another 7 Ibs. of 
 oil are added, and this is again repeated in two hours more, so that about 21 Ibs. are 
 added in six hours. 
 
 The greater portion of this oil of tar evaporates and passes through the iron head 
 B into the tube c, which terminates in a chimney about 100 feet high, so as to carry 
 off the unpleasant-smelling vapour. 
 
 When the mixture has become liquid, it is let out through a tuba into the receiver 
 E. As vapour escapes here also, the receiver is covered with a capacious head, E', 
 
ARTIFICIAL GRINDSTONES. 
 
 747 
 
 through which the vapour escapes into the tube c, and finally into the flue. At M is 
 a valve, serving to interrupt the communication between E', the tube c, and the flue. 
 
 FIG. 513. 
 
 The products of combustion from the fireplace pass also through D into c, and into the 
 flue. 
 
 The receiver is brought to G (fig. 514), and 28 Ibs. of sulphur are stirred up with the 
 caoutchouc mass in it. In order to prevent vesiculation by the formation of sulphuretted 
 hydrogen, 5 Ibs. of lime or 10 Ibs. of powdered litharge are added to the mixture. 10 or 
 1 2 cwts. of powdered quartz, flint, emery, etc., are next added, and a stiff dough is thus ob- 
 tained, which is then kneaded between the rollers (F) in order to render it homogeneous 
 throughout. The rollers revolve in opposite directions, and the one makes two, the 
 other six revolutions per minute. They have each a diameter of 24 inches, and are 
 heated internally by means of steam to 50 or 60 C. As oil of tar escapes during this 
 process, causing an unpleasant smell, the rollers are covered with a sort of mantle of 
 sheet iron, which conducts the vapours through the tube (F') into the common flue. The 
 caoutchouc mass thus prepared is rolled out to plates of | to 3 inches thick, between 
 two rollers of a similar kind, but having equal rates of revolution (one revolution per 
 minute). These plates are laid on a table strewn with talc powder, and the upper 
 surface of the. plates is also covered with the same. By means of a cylindrical cutting 
 machine, fig. 515, disks are cut from these plates, which are covered on their entire 
 surface with powdered talc, and being placed in round moulds under a powerful 
 
 FIG. 515 
 
 FIG. 516. 
 
 FIG. 517. 
 
 hydraulic press, fig. 516, are submitted to a pressure of from 150 to 200 tons. The 
 caoutchouc plates are then forced out of the moulds by means of a screw press (fig. 517), 
 laid again on the table (fig. 515), the irregular edges cut off by the aid of the cutting 
 machine, and a hole is made in the centre of each plate. The disks or plates are 
 next burnt in a cylinder, so as to give the necessary degree of hardness. 
 
 The burning is carried out in an apparatus represented by figs. 518 and 519, which 
 consists of a cylinder with a double jacket between which steam is passed through c' 
 under a pressure of 5 atmospheres, and at a temperature of 153 C., so that the tem- 
 perature of the interior of the cylinder rises to 100 G ; the condensed water escapes 
 ate The interior walls of the cylinder are furnished with supports b, b, b, upon 
 which are placed the iron plates for holding the grinding stones. When the cylinder 
 is fully charged, the lid e is screwed up, steam is passed into the double jacket, and 
 
748 RESIN, ETC. 
 
 the cylinder kept for seven or eight hours at the temperature of 100. During the 
 entire course of the operation, an escape of sulphuretted hydrogen takes place together 
 
 FIG. 518. FIG. 519. 
 
 with small quantities of vapours of oil of tar, both of which are carried off by a 
 gentle current of air, that enters by a hole in the lid of the cylinder and escapes 
 through a tube at the opposite end. When the burning process is over, the whole is 
 allowed to cool down, and the stones are taken out. As a cylinder of this kind holds 
 on an average half a ton of stones, a ton may be easily burnt in two hours, or in the 
 course of two operations. 
 
 The stones thus prepared are fastened upon axes, and are capable of sustaining a 
 rate of rotation of 1,500 or 2,000 revolutions per minute. The largest stones are 2 feet 
 in diameter and 3 inches thick ; they weigh about 1^ cwt. each; the smallest are about 
 1 foot in diameter and inch thick. For sharpening large saws, stones are employed 
 of a thickness varying between and f inch. For this latter purpose especially the 
 stones seem to be well adapted, and they have a double advantage over files, in saving 
 manual work and being more durable. Besides this application, the stones are much 
 used for grinding and polishing a variety of objects made of wrought and cast iron 
 and steel. 
 
 GUTTA PERCHA. This substance is a product of trees indigenous to Southern Asia, the 
 East Indies, and the Indian Archipelago. It has been long known to the inhabitants 
 of those regions, but its utilisation on a large scale dates from its importation into 
 Europe. 
 
 The first notice of it appears to have been in 1842 by Dr. Montgomery, Physician in 
 the Presidency at Singapore, in a letter to the Calcutta Medical Board, and soon after- 
 wards to the East Indian Company, to whom he sent specimens of gutta percha, at the 
 same time alluding to its valuable properties. Dr. Montgomery's priority of dis- 
 covery, however, was disputed by Dr. Joze D' Almeida, who had also resided for some 
 time in the same locality, and who, on his return to England in 1843, laid specimens 
 of the substance before the Asiatic Society of London, and received an honorary re- 
 cognition for his services. 
 
 Europe had not long discovered the valuable properties of gutta percha before an 
 enormous demand was made for the substance, especially in this country ; so great, in- 
 deed, that while in 1844 only 4 cwts. were sent over to this country as samples, in the 
 next year as much as 9 tons were imported, and the imports have since risen to 
 thousands of tons. 
 
 According to M. Bleekrod's report, there were exported from the Indian Archi- 
 pelago in 1851 13 tons, while in 1855 the export from those islands rose to 314 tons. 
 
 One consequence of this enormous and sudden increase in the consumption of gutta 
 percha was that every available means was taken to produce great quantities of it as 
 quickly as possible, which eventually led to a complete devastation of the trees yield- 
 ing it. Collectors of the gutta percha juice appeared on the coast of Sumatra, Java, 
 Borneo, and all the islands of the Indian Archipelago where the trees grow; and, not 
 contented with simply drawing off the sap, cut down whole trees. In this way entire 
 forests were destroyed in the first few years, and it was not until the ' Gutta Percha 
 Trading Society ' took the matter in hand, that a simple tapping of the trees was sub- 
 stituted for the former process of felling. 
 
 Gutta percha is the chief constituent of the milky juice of the Isonandra gutta, 
 Hooker, a tree belonging to the family Sapotacese. This tree flourishes in the 
 island of Singapore and in the small neighbouring islands, in Sumatra, on the south 
 east and west coasts of Borneo and Java, and other islands, being found all up the 
 Malayan Peninsula. According to Oxley, the tree grows to a height of 40 to 70 feet, 
 the diameter of the trunk reaching 6 feet. Payen describes the trees as having a 
 height of 65 feet and a diameter of upwards of 3 feet. A tree entirely felled is capable 
 
GUTTA PERCHA. 749 
 
 of yielding as much as from 33 to 40 Ibs. of solid gutta percha. The wood of the 
 gutta-percha tree is too soft for use except as fuel. 
 
 The milky juice containing the gutta percha circulates in dark-coloured vessels 
 along the stem between the bark and woody pith ; in this the gutta percha occurs in 
 the form of globules suspended, but not dissolved, in a watery sap. These globules 
 readily cohere together to form a solid mass. 
 
 It appears from an interesting treatise by M. Bleekrod, upon the gutta percha of 
 Surinam, that the price of this article varies considerably according to its quality. 
 The cheapest kind was sold in the Amsterdam market at Z\d. per lb., while the 
 dearest cost Is. kd. per lb., sold from the 4,615 cvvts. that year imported from the 
 Dutch possessions in the East Indies. M. Bleekrod further showed that the gutta- 
 percha plants admit of being cultivated with advantage in Dutch Guiana, and also that 
 the export from the Dutch Colonies was on the increase, while the exports from Singa- 
 pore were on the decline owing to the early irrational treatment of the trees. 
 
 M. Bleekrod also mentions the production of a substance identical with gutta 
 percha from the Sapota Miilleri, a tree also belonging to the Sapotaceous family. 
 He states that the sap is obtained in the same way as from the gutta-percha trees, 
 but that the trees suffer by the process. This substance has now become an article of 
 commerce. 
 
 From the researches of M. Payen and others, it appears that ordinary gutta 
 percha consists essentially of three substances, their relative proportions to one 
 another in gutta percha determining its quality. These substances have been termed 
 gutta, alban, and fluavil ; and the average composition of gutta percha is : 
 
 Gutta 78 to 82 per cent. 
 
 Alban 16 to 14 
 
 Fluavil 6 to 4 
 
 According to M. Payen, these three substances may be separated as follows 
 Gutta percha is boiled with absolute alcohol as long as the alcohol dissolves any- 
 thing, when the residue is pure gutta. The alcoholic liquid contains alban and 
 fluavil ; alban is precipitated upon cooling and can be removed by filtration, and the 
 fluavil can be obtained by evaporating the remaining alcoholic liquid. 
 
 Pure gutta is insoluble in alcohol, and also in cold ether, but soluble in chloroform 
 and in carbon bisulphide. It is a white substance, melting at 100, at which tem- 
 perature thin plates of it are transparent. When cold, such plates are not transparent. 
 Thin strips of gutta percha at a temperature of from 10 to 30 C. are tenacious but 
 not elastic. 
 
 In this condition gutta possesses a peculiar property which is taken advan- 
 tage of in preparing straps, ropes, ribbons, etc. of gutta percha. When, for instance, 
 gutta at the above temperature is stretched out to double its length, it retains upon 
 cooling nearly its extended form. Its structure however becomes essentially altered, 
 passing from a porous into a fibrous condition, while its transparency increases. 
 Gutta percha of the finest quality shows a like behaviour. A band of the latter, 
 i inch thick, 1 inch wide, and 8 inches long, when stretched to 17 inches by attach- 
 ing to it a weight of 38 oz., does not retain the extended form when the weight is 
 removed, nor even when extended to 25^ inches by a weight of 70 oz., but an elonga- 
 tion of the band f inch more by a weight of 75 oz. causes a permanent extension of 
 the band If inches upon removal of the weight, while at the same time the condition 
 of the gutta percha itself is altered. This experiment was made at a surrounding 
 temperature of 19. 
 
 Pure gutta begins to soften at 50; thin strips of it become thicker at this tem- 
 perature, but decrease in length and width. When heated further gutta becomes 
 sticky, assuming between 100 and 110 a doughy consistency, and becoming more 
 transparent. It melts at a temperature of 130. A still further application of 
 heat causes it to boil, and it yields, as products of destructive distillation, an empy- 
 reumatic oil and some gaseous hydrocarbons. 
 
 All the three constituents of gutta percha become electrical upon being rubbed, 
 and they are bad conductors of heat. When first thrown into water gutta floats, but it 
 soon becomes specifically heavier by its pores getting filled with water, and then sinks. 
 
 As already mentioned, gutta is insoluble in alcohol, and in ether when it has been 
 previously treated with alcohol. It is also very slightly soluble in either benzol or 
 oil of turpentine at a temperature of 0, but its solubility in these substances in- 
 creases with the rise of temperature. Carbon bisulphide and chloroform dissolve 
 pure gutta as well as gutta percha at the ordinary temperature. 
 
 Pure gutta is not attacked either by the caustic alkalies or by dilute acids ; con- 
 centrated sulphuric acid or nitric acid, however, exerts a powerful action upon it. Con- 
 
750 RESIN, ETC. 
 
 centrated hydrochloric acid acts upon gutta very slowly, colouring white gutta brown, 
 the colour increasing, gradually in intensity. 
 
 Alb an, as already mentioned, separates out from a hot alcoholic extract of gutta 
 percha upon cooling. It forms a white crystalline powder, or sometimes small wart- 
 like lumps. It may be easily obtained in the latter form by allowing its alcoholic 
 solution to evaporate in the air. Examined under the microscope the crystals are seen 
 to be transparent or translucent and in radiating groups. Alban may be heated up to 
 100 without undergoing any change ; it begins to melt at 160 0. and is entirely liquid 
 and transparent at 175 to 180. When again cooled it contracts considerably, forming 
 a solid transparent mass specifically heavier than water. 
 
 Hydrochloric acid, and dilute acids, as well as alkaline liquids, exert no action upon 
 alban, but like gutta it is violently attacked by concentrated nitric acid or sulphuric 
 acid. Alban is soluble in benzol, oil of turpentine, carbon bisulphide, ether, and 
 chloroform. It may be obtained in a crystalline condition from its solutions in the 
 last two solvents, as well as from absolute alcohol. 
 
 Fluavil. This substance is resinous and of a yellow colour, a little heavier 
 than water, and hard and brittle at a temperature of 0. At higher temperatures 
 it is soft ; at 60 it assumes a doughy consistency, melting completely when heated to 
 100 or 1 10. When exposed to a still higher temperature it boils, at the same time 
 undergoing decomposition, the products of its distillation consisting of acid vapours 
 and a number of different hydrocarbons. Fluavil is soluble in hot and cold alcohol, 
 also in ether, oil of turpentine, carbon bisulphide, and chloroform. When its solutions 
 in these solvents are evaporated, fluavil is deposited in the amorphous condition only. 
 As obtained by evaporation from an alcoholic solution it retains very energetically the 
 last portions of the solvent, from which it can be separated only by protracted heating 
 at 100C. Fluavil is not attacked either by dilute acids or solutions of caustic 
 alkalies, but is attacked energetically by concentrated nitric acid or sulphuric acid. 
 
 Grutta percha being a mixture of the three substances gutta, alban, and fluavil, 
 its properties may be deduced from a consideration of those of these three bodies. 
 Grutta percha is not attacked either by alkaline liquids or by dilute acids, a fact of 
 considerable importance for the industrial applications of this substance, since it 
 follows that most liquids such as wine, beer, vinegar, soda ley, etc, are without action 
 upon it. G-utta percha is, however, energetically attacked by concentrated nitric acid, 
 yielding upon protracted boiling with this reagent nitric oxide, nitrous acid, camph- 
 resinic acid, and other products of oxidation. Concentrated sulphuric acid causes 
 gutta percha to swell, and converts it into a mucilaginous mass. Although concen- 
 trated hydrochloric acid attacks gutta percha only slightly, still the gutta percha 
 syphons employed in manufactories of this acid suffer considerably in course of 
 time. 
 
 One of the most valuable properties of gutta percha is that of becoming soft and 
 plastic when moderately heated. At the ordinary temperature it is tenacious and 
 stiff, but becomes pliant when heated to 25, begins to soften at 48, and is so plastic 
 between 55 and 60 that it may be moulded into any desired form. 
 
 Results, differing in many respects from those of M. Payen, have been obtained by 
 M. Baumhauer. He has come to the conclusion that the chief constituent of gutta 
 percha is a hydrocarbon having a composition represented by the formula C 10 H, 6 , 
 besides various products of its oxidation, two of which he has determined with cer- 
 tainty and represents by the formulae C 20 H 32 and C 20 H 32 2 . The opinion of 
 M. Baumhauer is that only the first of these three substances, C JO H 16 , is contained in 
 the fresh gutta-percha sap, and that this is identical with the gutta of M. Payen. 
 The other two oxygen compounds which occur in gutta percha, together with small 
 quantities of a number of other similar products, he considers to be the results of the 
 oxidising influence of the air upon the pure sap. 
 
 M. Baumhauer prepares pure gutta by treating gutta percha first with water and 
 hydrochloric acid respectively, and then with boiling ether. The ether dissolves 
 everything except a brownish-black substance, which is quickly filtered off, the gutta 
 separating from the filtrate upon cooling in the form of a white powder. This powder 
 is then recrystallised from ether until, upon cooling, nothing more remains dissolved. 
 
 When exposed to the air, gutta percha undergoes a peculiar change, which is es- 
 pecially noticeable when the air has a temperature of 25 or 30, and the gutta percha 
 is in the form of thin plates, ribbons, or threads. The gutta percha emits a peculiar 
 smell, which is accompanied by the evolution of acid vapours, while the substance 
 assumes a yellowish colour. This change is very injurious, for it is accompanied by a 
 loss of tenacity, hardness, and pliancy in the gutta percha itself, the gutta grad ually 
 disappearing, a fact which may be verified by treating such altered gutta percha with 
 cold absolute alcohol, in which it dissolves after a lapse of some time. On this account 
 many attempts have been made to protect gutta percha from this destructive influence 
 
GUTTA PERCHA. 751 
 
 of the air. It may be conveniently preserved under water in vessels of wrought or 
 cast iron, probably because the iron deprives the water of the oxygen dissolved in it. 
 Ozonised air exerts a strongly oxidising effect upon gutta percha. Grutta percha is 
 especially quickly oxidised when exposed to a moist atmosphere under the influence of 
 the sun's rays. 
 
 The method of obtaining the sap of gutta-percha trees formerly employed, con- 
 sisted in felling the trees, making incisions in the bark at distances of from 1 to l 
 feet from each other, and then collecting the juice in vessels placed beneath such in- 
 cisions. The method now employed is simply to make incisions in the stems of living 
 trees and to collect the juice in hollows at the foot of the trees. The juice coagulates 
 in a short time, and is then kneaded with the hands, formed into various shaped 
 blocks, and sent to Europe, packed in coarse wrappers. 
 
 The raw gutta percha of commerce contains a number of mechanical impurities, 
 such as pieces of woody fibre, earthy mixtures, etc., which have to be got rid of be- 
 fore the gutta percha can be worked. The process of purification is executed by the 
 aid of a specially constructed apparatus. The gutta percha is first of all cut into 
 shreds by a machine consisting of a large disk, fitted with three straight or curved planing 
 irons in such a way that upon turning the disk the pieces of gutta percha lying upon 
 the inclined surface, and slightly pressed against the revolving disk, are planed into 
 delicate shreds. The planing irons are kept wet with water during the operation. 
 The gutta percha passes from this cutting machine on to a shelf, when it is pressed 
 by means of two rollers against a drum furnished with saw teeth similar to that used 
 in cutting beet roots in sugar manufactories (see SUGAR), and cut into still finer pieces. 
 From this shelf the pieces of gutta percha fall into a basin filled with cold water, 
 where the ligneous particles, absorbing water and becoming heavier, fall to the bot- 
 tom, the other impurities are dissolved out by the water, while the gutta percha itself 
 floats on the surface. Here it is caught by an endless cloth, stretched upon two 
 rollers, pressed upon a second drum, passed into a second water basin, and then to the 
 third cutting machine, which may either have the form of the two former ones, or it 
 may consist of a hollander (see p. 641). The gutta percha after this finds its way 
 into a large basin filled with water at a temperature of 80, then is brought by the agency 
 of an endless cloth under a drum, furnished with knife blades, and between it and 
 its breasting, also armed with knife blades, it is once more submitted to a cutting and 
 tearing process. 
 
 This last tearing and the action of the hot water serve to aggregate the pieces of 
 gutta percha, admitting of its formation into blocks. For this purpose it is carried 
 upon an endless cloth between five pair of rollers, which are so set that the lower 
 one of each pair revolves underneath water, and the upper one just on the surface. 
 The rate of revolution of the rollers increases towards the last pair. The gutta 
 percha is converted into a long band, and passes from the bath upon the endless cloth, 
 between another pair of rollers, which press out adherent water from it. The gutta 
 percha is then either rolled out directly into plates by a rolling mill, or into round or 
 angular threads, bands, etc., by means of a grooved mill, the rollers being set in equal 
 but opposite motion. 
 
 In Mr. Hancock's manufactory, the gutta percha is purified by placing the shreds 
 in water heated to 100, and violently agitated. The shreds become sticky, and are 
 then pressed into balls. These balls are placed in a cylindrical vessel in which re- 
 volves a toothed roller which again tears it into very fine pieces. The pieces are washed 
 with water to separate the impurities which fall to the bottom. 
 
 Upon leaving the washing apparatus, the gutta percha is rolled out into plates, 
 which, when required for moulding, are softened by gentle heating. This heating is 
 effected by placing the gutta-percha plates in a semi-globular vessel of iron with 
 double sides, between which steam is passed at a temperature of 153, and under a 
 pressure of 5 atmospheres, and this serves to heat the gutta percha to 112 or 115. 
 The gutta percha is thus not only rendered soft and plastic, but adherent water is 
 driven off, and a material is obtained which is more durable, and admits of being 
 more easily and firmly united. 
 
 M. Payen proposed the use of spirit of wine, where it can be had cheaply, for 
 purifying gutta percha, injurious substances such as alban and fluavil being dissolved 
 out by the spirit. To prevent loss of alcohol he recommended further the use of the 
 apparatus referred to in the description of the extraction of fatty oils by carbon bi- 
 sulphide (see p. 144). 
 
 The following alterations and improvements in the method of purifying gutta 
 percha have been introduced by M. Leverd. 
 
 The complete division of the gutta percha is effected by a machine depicted in 
 figs. 520 and 521. Blocks of gutta porcha are cut with a circular saw into irregular 
 prisms, and then pressed against a tearing drum upon a table (D). The drum has a 
 
752 
 
 RESIN, ETC. 
 
 width of 6 inches, and a diameter of 12 inches, and is covered on its exterior surface 
 with rows of strong v sharp steel teeth in such a way that the teeth of one row face 
 
 FIG. 621. 
 
 the divisions between the teeth of the second row, etc., as shown in fig. 520. The 
 tearing operation is assisted by a stream of water flowing over the drum which is 
 kept slowly revolving. 
 
 The torn shreds of gutta percha are next washed in three vessels, communi- 
 cating with one another either by syphons or straight tubes. The wash water passes 
 from the third tub or basin into the second, and from the second into the first, from 
 whence it is then run off, so that in this way the washed gutta percha comes into con- 
 tact with water increasing in purity. 
 
 FIG. 522. 
 
 FIG. 523. 
 
 The washed gutta-percha mass is then spread out upon an inclined floor for the 
 water to run off. It is further dried by passing it through a rolling mill, the rollers 
 of which are heated internally by steam. The gutta percha issues from between the 
 rollers in very thin plates, which are at once seized by workmen, who stretch them 
 out to double their width ; any particles of ligneous fibre that they may still contain 
 are in this thin condition of the plates easily detected and picked out. The sheets or 
 plates are then spread out in the air for a short time to effect a further drying. 
 
 The last traces of moisture are removed by heating in an apparatus represented 
 by fig. 522, consisting of a flat vessel A with double sides B, into which steam is passed 
 through the cock c, and the contents of the vessel thus heated up to 110 or 115 C. 
 The condensed water escapes through D back again into the boiler. The shallow 
 vessel A is fitted with a lid consisting of three movable pieces, which arrangement ad- 
 mits of an easier filling and emptying of the vessel than if the latter were made of a 
 single piece. When the gutta-percha mass has been so long heated in this apparatus 
 that, no more moisture is driven off, it is next passed into the kneading machine 
 (fig. 523), which consists of an elongated vessel A (shown in the fig. in section). In 
 this vessel rotate two grooved rollers c and D, the grooves of which fit into each 
 other. The rollers revolve in opposite directions, as shown by the arrows, and effect 
 a thorough kneading of the mass, which latter is kept of a doughy consistency by 
 steam passed through the cock c, into the jacket of the kneading vessel, the con- 
 densed water returning to the boiler by the pipe /. 
 
 The kneading of the gutta percha to a homogeneous mass in this apparatus is 
 generally effected in the course of an hour, and it is then passed into a rolling mill, 
 which rolls it out into bands, straps, ropes, threads, etc. 
 
GUTTA PERCHA. 753 
 
 The gutta-percha dough obtained by the aid of this apparatus is especially 
 suitable for the preparation of round ropes or tubes with the vermicelli press. 
 
 In the manufacturing of ropes and tubes of gutta percha, a jacketed cylinder, 
 heated with steam to 100, is charged with gutta-percha dough. By means of a 
 closely fitting piston entering at one end of the cylinder, the dough is pressed out 
 through a conical mouthpiece at the other end, and thus receives the desired form. 
 The tubes first pressed out are put on one side, as they are vesiculated by the air 
 originally contained in the apparatus. The tubes pass from the aperture into a 
 trough filled with cold water, by which they are sufficiently hardened to retain their 
 form. 
 
 Firmer and more compact tubes are obtained by moulding the gutta-percha mass 
 first into wide tubes, and stretching these out to twice their length. To avoid the 
 loss of time in the frequent filling of the apparatus, and the disadvantage of introduc- 
 ing air into the cylinder with each supply of material, causing a vesiculation of the 
 tubes, Messrs. Nichols and Selby use, instead of a piston, a pair of rollers moving in 
 opposite directions and pressing upon the gutta-percha mass in the cylinder. The 
 dough is supplied through the rollers in quantities exactly corresponding to that 
 passing out at the aperture in the form of tubes, etc. The action is thus continuous, 
 and tubes of any required length may be made. 
 
 Eound threads of gutta percha are prepared by a method exactly corresponding to 
 that employed in the manufacture of round threads of caoutchouc. 
 
 Plates of gutta percha are also prepared by a process similar to that employed in 
 the manufacture of the same articles in caoutchouc, the only difference being that 
 plastic gutta percha heated to 100 or 115 is used. 
 
 Kibbons and angular threads are prepared from gutta-percha plates by cutting 
 them lengthways with sharp-pointed knifes set against the drawing rollers. The 
 width of the ribbons or threads depends upon the distance the knives are set apart from 
 each other. The still soft ribbons or threads are passed over an endless cloth so as 
 to cool them. 
 
 Gutta-percha mouldings, impressions of medals, etc., are obtained by pressing the 
 plastic gutta percha into moulds or upon the surfaces to be copied, and allowing it to 
 cool. 
 
 Vulcanisation of Gutta Percha. As gutta percha becomes so soft at a temperature 
 of 45 to 60 that it cannot be used for machines in warm rooms, or for reins, etc., 
 attempts have been made to vulcanise it, and it has been found that gutta percha, like 
 india rubber, undergoes a peculiar change when heated with sulphur. 
 
 For vulcanising gutta percha the hyposulphites of lead or zinc are more suitable 
 than sulphur itself. A mixture of 100 parts of gutta percha with 15 parts of the hy- 
 posulphite is kneaded at a temperature of 100, and the moulded object made from 
 this is afterwards heated to 140. 
 
 A number of other substances have also been proposed for mixing with gutta percha 
 so as to modify its properties. Mr. Hancock recommends an addition of caoutchouc for 
 preparing ribbons, straps, etc. Mr. JForster recommends an addition of 1 part oi bone 
 black to 4 parts of gutta percha for making a varnish for clothes, leather, etc. He 
 also recommends for pressed manufactures the following mixture : 
 
 Gutta percha " '. < . .4 parts 
 
 Bone black 2 
 
 Arsenious acid ;-..'. ^ 
 
 A very hard mass is yielded by 
 
 Gutta percha ..... 3 parts 
 
 Powdered bones . . . . . , . . . 1 ,, 
 
 Pipe clay . . . . . -. ,. . rt , . i 
 
 Insulation of Telegraph Wires with Gutta Percha. Siemens was the first to employ 
 gutta percha for the insulation of telegraph wires, but his method has not been found 
 efficient for subterranean lines, owing to the insulating material being eaten by animals. 
 This kind of insulation has been found very serviceable, however, for submarine 
 telegraphs, and it is that adopted, among other instances, in the submarine telegraphs 
 between Europe and America. 
 
 The copper wire is covered by means of an apparatus similar in construction to 
 that already described for pressing gutta-percha tubes, a perforated block through which 
 the wire is drawn being setagainst the moulding aperture, and as the wire passes through 
 it is covered with gutta percha. The wire is in this case drawn out by the fric- 
 tion of the gutta percha itself. When several wires have to be covered at the same 
 time a block is employed, having the required number of perforations, through which 
 the wires are drawn. 
 
 ac 
 
754 RESIN, ETC. 
 
 The Atlantic cable laid in 1858 consists of a nucleus of 7 copper wires, 6 lying 
 round a middle one. This nucleus of wires is surrounded by a threefold covering of 
 gutta percha ; this again by a stuffing of hemp soaked in tar, and round this is finally 
 wound spirally 18 strands of soft iron wire. 
 
 The cable of 1866 consists also of a nucleus of 7 copper wires, surrounded by 
 Chatterton's compound ; over these are wound 4 coats of gutta percha, alternating with 
 4 coats of Chatterton's compound, and finally 10 strands of galvanised iron wire, each 
 being surrounded with jute yarn saturated with tar. The Atlantic cable of 1865 is 
 of similar construction. 
 
 The insulation of the French Atlantic cable is nearly the same as the above, con- 
 sisting of 4 coats of gutta percha with intermediate layers of Chatterton's compound. 
 The nucleus also of 7 strands of copper wire is, however, thicker than in the previously 
 mentioned cables. The external coating consists of galvanised wires of Bessemer steel 
 covered with yarn. 
 
GUM. 
 
 Gum is the general name for a number of allied carbohydrates which frequently 
 occur in plants, especially various species of acacia, and exude from the trees in the 
 form of transparent tears. Various fruit trees, such as the plum and cherry, furnish 
 a similar product. The seeds of various plants also contain a kind of gum, which 
 differs from the gum arabic, gam Senegal, cherry tree or native gum, gum of Bassora, 
 and gum tragacanth, by being insoluble even in boiling water, only swelling up into a 
 gelatinous mass. The various kinds of gum form a thick glutinous solution with water, 
 and are insoluble in alcohol. By oxidation with nitric acid, they are converted into 
 oxalic and mucic acids. 
 
 Until the year 1860, when Fremy published the results of his investigations, gum 
 was looked upon as a neutral substance, analogous to dextrin, but intermixed with 
 some organic matters. Fremy, however, came to the conclusion that the different 
 kinds of gum are compounds of bases with modifications of a gelatinous substance, 
 comparable to the pectic compounds derived from pectose. The following are the 
 principal grounds upon which he based his conclusions. 
 
 When a solution of gum arabic is treated with oxalic acid and lime eliminated, 
 there remains in solution an organic substance which Fremy considered to be a 
 weak acid, and he named it gummic acid. 
 
 When a very thick aqueous solution of gum arabic is left for several hours in 
 contact with concentrated sulphuric acid, so as not to mix, the previously soluble gum 
 becomes transformed into a kind of membrane which is insoluble even in boiling 
 water. This is an isomeric modification of the previously mentioned ' gummic acid,' 
 and has been named metagummic acid. This change does not take place when 
 dilute sulphuric acid or simply powdered gum is used. 
 
 Upon heating the insoluble metagummic acid with traces of an alkali, it is imme- 
 diately dissolved, and is no longer precipitated by an acid ; the metagummic acid 
 having been reconverted into gummic acid, which remains in combination with the 
 alkali used. -When lime is employed, the product presents all the"" characters of gum 
 arabic. On the other hand, when the gummic acid set free by oxalic acid is heated, 
 it is converted into metagummic acid, and when this in its turn is treated with lime, 
 gum arabic is regenerated. 
 
 Gelis had observed that, under the influence of a temperature of 150 C. maintained 
 for several hours, gum arabic becomes insoluble in water, and that after boiling it for 
 several hours in water it again becomes soluble. This is explained by supposing that, 
 under the influence of heat, insoluble metagummate of lime is formed, the lime re- 
 maining in combination, and that, under the influence of boiling water, soluble gum 
 (gummate of lime) is regenerated. 
 
 Cherry tree gum contains a substance soluble in water, and identical with gum 
 arabic, together with another insoluble in water, called cerasin, identical with 
 G-elis's metagummate of lime, obtained by heating gum arabic, and like it becoming 
 soluble after prolonged boiling in water. From the fact that cerasin is occasionally 
 met with ready formed in some kinds of fruit, and from other considerations, Fremy 
 considered it probable that the insoluble body is first formed naturally, and that the 
 soluble modification is the result of the subsequent influence of vegetation. 
 
 Bassora gum is almost entirely insoluble, a portion consisting of a gelatinous 
 substance presenting many analogies with metag\immic acid, but not identical with 
 it. When treated with alkalies or alkaline earths, it yields true gum soluble in water, 
 insipid, uncrystallisable, and insoluble in alcohol, but differing from gum arabic in 
 being precipitated by neutral acetate of lead. 
 
 Fremy suggests that the facility with which the conversion of soluble gum into an 
 insoluble condition takes place may allow of the use of gum as a substitute for 
 albumin in fixing colours. 
 
 Gum Arabic exudes from several kinds of acacia, such as A. vera and A. arabica of 
 Eerypt and Arabia. The tears are either white or slightly yellow or brown, and 
 
 3 c 2 
 
756 GUM. 
 
 crack on exposure to the air. If this gum be dissolved in water, acidulated with 
 hydrochloric acid, and mixed with alcohol, white flakes of arabin or arabic acid, 
 2C 6 H 10 5 .H 2 0, or C 12 H 22 O n (the gummic acid of Fremy), are deposited. 
 
 Gum arabic consists of soluble calcium, magnesium, and potassium gummates. 
 Gummic acid dried at 127 C. becomes C 12 H 20 10 by loss of H 2 0. Gum arabic has 
 a specific gravity of 1-355, and contains 70*40 per cent, arabin and 17*60 per 
 cent, water; the remaining 12 per cent, is made up of combined bases, acid calcic 
 malate, etc. A solution of the gum produces left-handed rotation of a polarised ray, 
 and is not susceptible of alcoholic fermentation by means of yeast, but if digested 
 with cheese and chalk, it may be made to furnish 12 per cent, or more of alcohol ; 
 calcic lactate is simultaneously formed. Dilute sulphuric acid changes gum arabin 
 into dextrin, and this on boiling becomes dextro-rotatory sugar capable of being 
 fermented. A sulpho-gummic acid is produced by the action of strong sulphuric acid 
 upon gum arabic. When oxidised with nitric acid it yields not only oxalic acid and 
 mucic acid, but also saccharic and tartaric acids ; with fuming acid, substitution com- 
 pounds are produced. 
 
 Gum arabic is much used in medicine for the preparation of emollient pastes and 
 syrups ; it is also used in the preparation of inks to sustain the suspension of the 
 tannate of iron. For thickening colours, etc., it is also largely employed. 
 
 Gum Senegal from A. Senegal shows a specific gravity of 1'436, and contains 
 81-10 per cent, arabin, 16-10 per cent, water, and 2 or 3 per cent, saline matters. It 
 is mainly used by calico printers for thickening colours and mordants. 
 
 Cherry-tree Gum exudes from trees of the amygdalaceous order. It is only partially 
 soluble in water, and consists of 52 1 per cent, arabin, 34*9 per cent, cerasin (a meta- 
 gummate of lime), 12 per cent, water, and 1 per cent, saline matters. 
 
 Bassora Gum appears to be furnished by a cactus. The soluble part constitutes 
 about 1 per cent, of the gum ; the insoluble bassorin dissolves in weak alkalies and 
 acids by means of heat. 
 
 Gum Tragacanth exudes from the Astragal'us verus of Armenia and Persia. Its 
 sp gr. is 1*384, and about 50 per cent, dissolves in cold water ; the insoluble part swells 
 up and has been shown to contain starch. Warm dilute acids effect the entire solution 
 of gum tragacanth, and boiling water dissolves it almost entirely. 
 
 The soluble portion of tragacanth, although closely resembling the arabin of gum 
 arabic, differs from it in not giving any reaction with silicate of potash or perchloride 
 of iron, and in the appearance of the precipitate produced by alcohol. For this reason it 
 has been sometimes distinguished from the arabin of gum arabic as tragacanthin. 
 The insoluble portion has generally been described as bassorin, but some 'recent re- 
 searches of Giraud appear to indicate that it consists largely of an insoluble pectic 
 principle, probably pectose. When digested with fifty times its weight of water for 
 several hours in a water bath, it becomes partially soluble, and loses its property of 
 swelling after drying. Submitted to the action of acidulated water (1 per cent.), it 
 becomes entirely soluble. The new product is principally pectin, combining with al- 
 kalies to form pectates and metapectates that are precipitated by alcohol. By treat- 
 ment of the barium compound with hydrochloric or acetic acid, pectic acid is set free. 
 According to Giraud, the composition of gum tragacanth is : 
 
 Water ... . ... . y , . . . 20 percent. 
 
 Pectic compound . ... . . . 60 
 
 Soluble gum ....".... 8-10 
 
 Cellulose . . ". . . . -.'.. .3 
 
 Starch . . . . . . :<; i . . 2-3 
 
 Inorganic matter ....... 3 
 
 Nitrogenous bodies . . . . . . traces 
 
 It is used in medicine and calico printing, and also by shoemakers. 
 
 Mucilage, or the gum of seeds and roots, appears to be an almost universal con- 
 stituent of plants. It is extracted by steeping the seeds and roots in hot water, when 
 a jelly is formed consisting of swollen cells containing mucilage in solution. Dilute 
 acids at 100 furnish from this product glucose. 
 
 Gum from Sugar. According to Eeichardt, a gum is produced and accompanies 
 gummic acid when glucose is oxidised by cupric salts. The formula C 12 H 26 13 has 
 been assigned to it. 
 
 Artificial gum, known as British gum and dextrin, is produced by the torrefaction 
 of starch. 
 
STARCH. 
 
 Occurrence. Starch is a substance closely related to cellulose, having the same 
 percentage composition and similar properties. It does not occur in such large quan- 
 tities as cellulose, but quite as frequently ; and probably all phanerogamous plants 
 contain starch at some period of their growth. 
 
 Starch occurs in relatively larger quantities in many of the organs of propagation, 
 such as tubers and rhizomes ; in potatoes, the seeds of cereals, the fruit of chestnuts, etc., 
 and it serves as food for the young plant in the first stages of its growth, being dis- 
 solved and assimilated until leaves have been developed, and the plant becomes 
 capable of taking its nourishment from the air and soil. 
 
 Starch also occurs in many other parts, as in the pith of trees and shrubs, in woodj 
 and parenchyiuatous tissues, etc. Its occurrence in these parts is not, however, con- 
 stant and equal, the same tissues being at certain seasons fully charged with starch, 
 and at others almost entirely devoid of it. During the period of active growth plants 
 produce from inorganic substances organised material in greater quantity than they 
 require. Part of this material assumes the form of starch, and is stored up for use 
 when, at a future time, in the formation of new substance, the plant can no longer 
 obtain food from external sources. Other substances similar to starch, such as sugar, 
 inulin, etc., serve the same purpose in the plant. 
 
 Characters. Starch in its earliest condition, as it originates in plant cells, always 
 forms hard round granules which exhibit a peculiar process of growth ; dissolved sub- 
 stances formed by the chemical agency of the protoplasm being absorbed, converted 
 into starch, and deposited in such a way that these substances are uniformly dis- 
 tributed in all directions throughout the entire mass of the granule. The growth of a 
 starch granule is not, as was at one time supposed, similar to the growth of a crystal, 
 in which the new substance arranges itself symmetrically around a nucleus, neither 
 are new layers deposited in the interior of the original granule, or by apposition, but 
 in the way described, by intussusception. 
 
 As the growth increases, a peculiar alteration takes place in the substance. The 
 original nucleus appears under the miscroscope as a homogeneous mass ; but the grow- 
 ing granule becomes stratified, owing to layers arranging themselves concentrically or 
 excentrically round a nucleus. Every granule contains one or more nuclei, each of 
 which is surrounded by a number of layers. This stratification depends upon the 
 degree of density of the material, and the density varies with the different amount of 
 water in each layer, the result being that a layer rich in water always alternates with 
 one poor in water. The external layer is always dense, containing but a small quantity of 
 water ; next to this is a layer richer in water and less dense, and so on until the nucleus 
 itself is reached, which always contains a proportionately large quantity of water. 
 
 The nuclei of starch granules are surrounded on all sides by layers, but this 
 stratification is not equally perceptible in all kinds of starch ; it is easily seen in the 
 large starch grains of the potato tuber, 
 and those obtained from the fruit of the 
 potato are still better for demonstrating 
 this appearance. Fig. 524 represents starch 
 grains that have been crushed by pressure. 
 A similar appearance is presented by 
 starch grains that have been heated to a 
 temperature of 200 or 210 and then 
 moistened with water. Fig. 526 re- 
 presents starch grains that have been 
 thus treated, and the stratification may 
 be easily seen. Fl - 524 ' Fl *' 526 ' 
 
 The growth of starch granules is not alike in all plants, one plant yielding larger 
 granules than another; in some plants the granules are round, in others they are len- 
 ticular ; some are irregularly round ; many are polyhedral, being partly flattened by 
 
758 
 
 STARCH. 
 
 the pressure of other granules ; others are club-shaped. The origin of most starches 
 can be determined by their form, and some of the principal varieties of starch met 
 with in commerce are represented by the following illustrations taken from Hassall's 
 tvork on ' Food.' 
 
 Potato starch, represented by fig. 526, as magnified 200 diameters, has the form 
 of ovate or oyster-shaped granules, exhibiting distinct concentric rings. The hilum is 
 well defined, but small, and is situated at the narrow end of the granule. 
 
 Maranta starch, or West India arrowroot, obtained from the rhizomes of 
 Maranta arundinacea, is represented by fig. 527, as magnified 240 diameters. The 
 
 Fia. 526. 
 
 FIG. 527. 
 
 granules are generally oblong or ovate, sometimes mussel shaped, or even to some ex- 
 tent triangular. The size of the granules varies considerably. They present distinct 
 concentric lines and the hilum is well defined, in most cases as a distinct transverse 
 line, which is specially characteristic of this kind of starch, less frequently as a 
 circular spot. 
 
 The starch obtained from Canna edzdis,&ndi commonly known astous-les-mois 
 arrowroot, is represented by fig. 528, as magnified 225 diameters. The granules are 
 
 FIG. 528. 
 
 FIG. 529. 
 
 very large, ovate, flat and broad, and sometimes pointed at the narrow end. They 
 exhibit distinct concentric rings, which are very fine, regular, and close together. The 
 granules vary considerably in size, but they are generally much larger than those of 
 potato starch, and the hilum is less distinctly marked. 
 
 The starch known by the name of sago is obtained from the pith of several kinds 
 of palm, growing in the islands of the Indian Archipelago, Madagascar, and New 
 Guinea, Sagus Eumphii, 8. farinifera, 8. raphia, 8. lavis, and 8. genuina ; also from 
 Cycas circinalis and C. revoluta, growing in China and Japan. The granules of this 
 starch are represented by fig. 529, as magnified 225 diameters. They vary in size, 
 are elongated, rounded at one end, and truncated at the other. The hilum is some- 
 times circular, but often presents the appearance of a transverse slit or star. The 
 concentric rings are generally indistinct, and sometimes the granules have a somewhat 
 corrugated appearance. 
 
 Tacca or Tahiti arrowroot consists of the starch obtained from the tubers 
 
ARROWROOT. 
 
 759 
 
 of Facca oceanica, a native of the South Sea Islands. The granules of this starch are 
 represented by fig. 530, as magnified 220 diameters. They somewhat resemble those 
 of sago starch, having similar rounded and truncated ends, but are generally 
 very much smaller and less elongated. The concentric rings are very indistinct. The 
 hilum is generally circular, but sometimes presents the stellate form observed in sago 
 starch. 
 
 The starch obtained from the tubers of Curcuma angustifolia, and commonly 
 known as East India arrowroot, is represented by fig. 531, as magnified 240 dia- 
 meters. The granules are fiat, elongated, and irregularly shaped, usually with one 
 
 FIG. 530. 
 
 FIG. 531. 
 
 end pointed and the other obtuse. The hilum, situated at the pointed extremity, is 
 very indistinct and sometimes not recognisable. The concentric lines are frequently 
 interrupted. The granules are generally larger than those of West Indian arrowroot, 
 and in several other respects these two kinds of starch are easily distinguishable. 
 
 The starch obtained from Manihot utllissima, M. Aipi, and M. Janipha, known as 
 Brazilian arrowroot and tapioca, is represented by fig. 532, as magnified 225 
 
 FIG. 532. 
 
 FIG. 533. 
 
 diameters. The granules are small, and sometimes two or more are united together. 
 They frequently present truncated surfaces. The hilum is distinct, generally circular, 
 but sometimes stellate. 
 
 The starch obtained from the tubers of Arum maculatum, and commonly known as 
 Portland arrowroot, is represented by fig. 533, as magnified 240 diameters. The 
 granules present considerable resemblance in configuration to those of tacca arrowroot, 
 having the truncated surfaces, the fissured or stellate hilum and indistinct rings, but 
 are very much smaller, and are thus easily distinguishable from them. 
 
 The starch obtained from the different sources above mentioned, with the excep- 
 tion of potato starch, is met with in commerce under the name of arrowroot, of 
 which there are several kinds, pretenting slight differences in their characters, and in 
 the facility with which they are converted into paste by hot water, on which account 
 they have a higher value than potato starch. Potato starch, rice starch, and maize 
 starch are also commonly met with, but they are generally inferior to those kinds 
 known as arrow root. For illustrations of the granules of these and some other kinds 
 of starch, see article ' BKEAD, 
 
T 60 
 
 STARCH. 
 
 It has been established by the researches of Nageli, confirmed by many others, 
 that starch granules consist of two substances chemically different, but having a like 
 composition. 
 
 If certain solvents, such as saliva at a temperature of 40 to 47, dilute extract of 
 malt, or very dilute acids, be allowed to act on starch for some time, the greater part 
 of it is dissolved. The undissolved residue is a little reduced in volume, but other- 
 wise apparently unaltered, the stratification being more distinct than before. The 
 residue when treated with a solution of iodine shows a different deportment from that 
 of the original granules ; these ara at once coloured intensely blue by iodine, while the 
 residue does not show that reaction provided the solvents have been allowed to act 
 long enough. The coloration, however, takes place immediately if the residue be 
 first treated with a drop of concentrated sulphuric acid. Starch, therefore, consists of 
 an easily soluble substance, coloured blue by iodine, and an insoluble substance, which 
 is only coloured blue by iodine after the addition of sulphuric acid, behaving in this 
 respect like cellulose. Nageli accordingly distinguishes these two constituents as 
 starch cellulose and starch granulose. The granulose is present in relatively greater 
 quantity, and to it the unaltered starch owes the property of becoming blue with 
 iodine. Both substances are distributed throughout the entire mass of the starch 
 granule, and are not separated in layers. 
 
 Unaltered starch granules are at the ordinary temperature and pressure insoluble 
 in water. But starch absorbs water in different proportions, and retains it so per- 
 sistently that Payen was on this account led to assume the existence of different 
 chemical compounds of starch with water. Starch dried in a vacuum at a tempera- 
 ture of 120- 140 is anhydrous. In this condition Payen represents the composition 
 of starch as : 
 
 C 12 H 18 9 .H 2 or 2C 6 H 10 5 , 
 
 in which the molecule of water is considered as water of combination replaceable by 
 bases. Anhydrous starch is a very mobile powder, of exceedingly hygroscopic nature. 
 It absorbs moisture with great rapidity from the air, passing into the first hydrate, 
 which, besides the water of combination, also contains a further two molecules of 
 water according to the formula : 
 
 C 12 H 18 9 .H 2 -i- 2H 2 or C 6 H 10 5 H 2 0. 
 
 This compound is also obtained when starch is dried in a vacuum at a temperature of 
 10 to 15. 
 
 When exposed for a longer time to the action of the atmosphere, starch takes up 
 two more molecules of water, in which condition it contains 18 per cent, of water. 
 This is the amount present in ordinary commercial starch. In an atmosphere saturated 
 with moisture the absorption extends to 10 molecules of water, the resulting com- 
 pound containing 35 per cent, of water. In this condition the granules stick together, 
 and can be made into balls by simply kneading with the hands. A still further com- 
 pound of starch with water, called green starch, contains 45 per cent, of water. It 
 is obtained by absorbing the excess of water from starch paste by placing the 
 paste on a plate of gypsum. Upon throwing this green starch, in small quantities at 
 a time, upon plates heated to 140 or 150, the granules suddenly swell up and 
 agglutinate. This property of starch is taken advantage of industrially in preparing 
 from potato starch imitations of certain exotic kinds of starch, known in the market 
 astapioca. 
 
 The following table gives the composition of the different hydrates of starch : 
 
 Anhydrous only in combination . 
 Dried in vacuum at 150 . 
 Dried in vacuum at 15 
 Air dried ..... 
 Kept in moist atmosphere . 
 Green starch .... 
 
 Formula 
 
 Percentage Composition 
 
 Anhydrous 
 
 Starch 
 
 Water 
 
 C I2 H 18 9 
 C 12 H 18 9 .H 2 
 C 12 H 18 9 .H 2 + 2H 2 
 C 12 H 18 9 .H 2 + 4H..O 
 C 12 H 18 9 .H 2 + 10H 2 
 C 12 H 18 9 .H 2 + 15H 2 
 
 100 
 90 
 81-82 
 64-39 
 54-55 
 
 | 
 
 10 
 18-18 
 35-71 
 45-45 
 
 - 
 
 I 
 
 It appears very doubtful whether these hydrated starch compounds can be 
 properly considered as chemical compounds, since the water is so loosely, combined that 
 the slightest change of temperature, indeed every change in the atmospheric moisture, 
 causes an expulsion of part of their water or vice versd. Payen's dry starch may be 
 considered as a constant compound, having a composition represented by the formula 
 
CHARACTERS OF STARCH. 
 
 761 
 
 C 12 H 20 10 . This substance is hygroscopic, retaining with more or less energy the 
 absorbed water just like wool, silk, and many vegetable substances. It is possible 
 that a part of the water is held by simple surface attraction, while the other part is 
 held by the power of absorption of the less dense layers of the granules. 
 
 For the determination of the amount of water in a sample of starch Scheibler has 
 given a method which may easily be employed. It is based upon the fact that starch 
 which contains more than 11 -4 per cent, of water readily parts with the excess when 
 treated with alcohol of -8339 specific gravity, while starch containing less water takes 
 up from alcohol of the above strength water sufficient to bring the amount up to 11 '4 
 per cent. The increase or diminution of the proportion of water in the alcohol em- 
 ployed is ascertained from its specific gravity, which becomes, therefore, a measure of 
 the aqueous contents of the starch operated upon. The test is carried out in the 
 following way : Starch is covered with double its weight of alcohol, having at the 
 normal temperature a density of '8339 ; the mixture is frequently shaken during an 
 hour, and the alcohol then filtered off and its specific gravity determined. For 
 simplification the alcohol may be measured instead of weighed. For every 100 c.c. of 
 alcohol ( = 83*39 grams) 41'7 grams of starch must then be weighed off. The change 
 effected in the specific gravity of alcohol by the different starch hydrates has been 
 exactly determined by a number of experiments, and the following table has been con- 
 structed in which the resulting specific gravity of the alcohol is given, together with the 
 corresponding percentage of water in starch : 
 
 Aqueous con- 
 tents of Starch 
 per cent. 
 
 Specific 
 gravity of 
 Alcohol 
 
 Aqueous con- 
 tents of Starch 
 per cent. 
 
 Specific 
 gravity of 
 Alcohol 
 
 Aqueous con- 
 tents of Starch 
 percent. 
 
 Specific 
 gravity of 
 Alcohol 
 
 
 
 0-8226 
 
 22 
 
 0-8455 
 
 44 
 
 0-8643 
 
 1 
 
 0-8234 
 
 23 
 
 0-8465 
 
 45 
 
 0-8651 
 
 2 
 
 0-8243 
 
 24 
 
 0-8474 
 
 46 
 
 0-8657 
 
 3 
 
 0-8253 
 
 25 
 
 0-8484 
 
 47 
 
 0-8665 
 
 4 
 
 0-8262 
 
 26 
 
 0-8493 
 
 48 
 
 0-8673 
 
 5 
 
 0-8271 
 
 27 
 
 0-8502 
 
 49 
 
 0-8680 
 
 6 
 
 0-8281 
 
 28 
 
 0-8511 
 
 50 
 
 0-8688 
 
 7 
 
 0-8291 
 
 29 
 
 0-8520 
 
 51 
 
 0-8695 
 
 8 
 
 0-8300 
 
 30 
 
 0-8529 
 
 52 
 
 08703 
 
 9 
 
 0-8311 
 
 31 
 
 0-8538 
 
 53 
 
 0-8710 
 
 10 
 
 0-8323 
 
 32 
 
 0-8547 
 
 54 
 
 0-8716 
 
 11 
 
 0-8335 
 
 33 
 
 0-8555 
 
 55 
 
 0-8723 
 
 12 
 
 0-8346 
 
 34 
 
 0-8563 
 
 56 
 
 0-8731 
 
 13 
 
 0-8358 
 
 35 
 
 0-8571 
 
 57 
 
 0-8738 
 
 14 
 
 0-8370 
 
 36 
 
 0-8579 
 
 58 
 
 0-8745 
 
 15 
 
 0-8382 
 
 37 
 
 0-8587 
 
 59 
 
 0-8753 
 
 16 
 
 0-8394 
 
 38 
 
 0-8595 
 
 60 
 
 0-8760 
 
 17 
 
 0-8405 
 
 39 
 
 0-8603 
 
 61 
 
 0-8762 
 
 18 
 
 0-8416 
 
 40 
 
 0-8612 
 
 62 
 
 0-8775 
 
 19 
 
 0-8426 
 
 41 
 
 0-8620 
 
 63 
 
 0-8783 
 
 20 
 
 0-8436 
 
 42 
 
 0-8627 
 
 64 
 
 0-8791 
 
 21 
 
 0-8446 
 
 43 
 
 0-8635 
 
 65 
 
 0-8798 
 
 Perfectly anhydrous starch maybe heated to 160 without undergoing any change : 
 at a temperature of 200 it assumes a brownish-yellow colour, and is converted with- 
 out any alteration in weight into a substance having the same composition and called 
 dextrin, which is soluble in cold water. Starch containing about 18 or 20 percent, 
 of water is converted into dextrin at a temperature of 160, especially if the heating 
 be effected in closed vessels, so as to prevent evaporation of the water. 
 
 When starch is boiled with 200 times its weight of water it swells up to such an 
 extent that it is apparently dissolved, and the liquid so obtained passes almost clear 
 through a filter. This is due, however, less to actual solution than to an extraordinary 
 expansion, as the apparently dissolved starch is again deposited from the liquid in a 
 flocculent form upon alternately freezing and thawing the filtrate. In like manner 
 the separation of water from apparently dissolved starch can be effected by bringing 
 the roots of growing plants into the liquid ; the plants take up only the water, the 
 starch accumulating in flocks about the roots. 
 
 A mixture of starch with 12 to 15 parts of water may be heated to 55 without 
 any change being effected in the starch ; at a temperature of 57 the youngest gra- 
 nules begin to swell up, and in proportion as the heat increases the remaining granules 
 
762 STARCH. 
 
 likewise swell up. At a temperature of 72 the liquid first becomes viscous, and when 
 at the boiling point it is converted into paste. 
 
 The starch granules in swelling up may expand to twenty -fire times their volume, and 
 upon this depends the consistency of paste, which is thicker the less space the starch gra- 
 nules have in the liquid for expansion ; the granules press against one another and 
 form eventually an adherent shapeless mass. Upon cooling, the paste contracts and 
 becomes harder, and when very thick it cracks. This contraction reaches its maximum 
 when the paste is frozen, a separation of the water and starch taking place by the water 
 crystallising out. Upon melting the frozen paste the water and starch do not again 
 combine, but the water drains away, and the disorganised starch remains as a kind of 
 felty mass, which when dry has the appearance of mother-of-pearl. 
 
 Solutions of potash or soda change starch into paste, even in the cold ; treated 
 with a solution containing 2 per cent, of caustic soda, potato starch swells to 75 times 
 its original volume. This property is taken advantage of in testing flour. 
 
 Ammonia does not convert starch into paste. If a trace of starch be added to a 
 solution of salt of ammonia and then solution of caustic soda drop by drop, the starch 
 remains unchanged until the whole of the ammonia salt has been decomposed ; but 
 the least excess of soda causes immediately an expansion of the starch granules. The 
 dilatation of starch in the cold is also caused by several acids in the diluted state, 
 such as sulphuric, hydrochloric, nitric, and others. Concentrated solutions of various 
 salts have a similar effect upon starch ; thus, cold saturated or half saturated solu- 
 tions of potassium bromide or sodium bromide convert starch into paste, but other 
 salts, such as potassium chloride, have no such effect upon it. 
 
 The further action of acids upon starch differs widely according to the concentra- 
 tion of the acid and the temperature. "When starch is heated to boiling with very 
 dilute acids (1 to 2 per cent.), no formation of paste takes place ; after a short time 
 a complete solution is formed, containing at first a modified soluble starch, which 
 passes into dextrin, and this is converted gradually into grape sugar, so that even- 
 tually the whole of the starch is changed into this form of sugar. 
 
 The same change as is produced by dilute acids at a high temperature is also 
 effected by a number of other substances, the exact nature of which, however, is not 
 known. Thus it is brought about by a substance called diastase, which is formed 
 during the germination of cereals ; also by a peculiar body found in the saliva and 
 gastric juice of animals. The saliva and the gastric juice by their action upon starch 
 render it digestible. The action of diastase is applied industrially in brandy distilla- 
 tion and in brewing. 
 
 Starch triturated with concentrated sulphuric acid is changed into starch sul- 
 phuric acid, a mucilaginous substance soluble in water. Upon neutralising the 
 aqueous solution with bases uncrystallisable salts are formed. When the mixture of 
 starch and sulphuric acid is diluted with alcohol it is decomposed, and deposits a greasy 
 mass, which may be kneaded. If this be treated with water the greater part is dis- 
 solved, and upon filtering and adding alcohol to the clear filtrate white flocks are 
 deposited, which are soluble in cold water but insoluble in alcohol. This flocculent 
 substance is a modification of starch, having the same composition as starch, but differ- 
 ing from it by being soluble in cold water and not forming a paste. This soluble 
 starch is formed under different conditions, as by the action in the cold upon starch of 
 very concentrated or glacial acetic acid, and during the change effected in starch by 
 dilute acids, etc. The fact, that when starch is triturated for a long time with a small 
 quantity of water a small quantity of the starch passes into solution, is possibly 
 due to the formation of this soluble modification through the heat generated by the 
 friction. 
 
 Concentrated nitric acid (sp. gr. 1-52) dissolves starch even in the cold. Upon 
 diluting such a solution with water a white powder is precipitated, which when dry 
 explodes upon being struck. This substance is called xyloidin, and has the same 
 composition as the corresponding compound of cellulose. Very dilute nitric acid 
 behaves with starch in the same way as other acids. When starch is boiled with 
 moderately concentrated nitric acid it is converted completely into oxalic acid. 
 
 Iodine in solution in water, potassium iodide, or dilute alcohol, when brought into 
 contact with unchanged starch, starch paste, or soluble starch, immediately colours it 
 blue, the coloration produced varying from light blue to almost black, according to 
 tho proportions between the starch and iodine. Solution of iodine in absolute alcohol 
 does not produce the blue colour with starch, but the colour is immediately produced 
 upaa the addition of water. This reaction serves for the detection of starch and for 
 distinguishing it from other substances, especially in microscopical researches. 
 
 Liquids containing only a very small quantity of starch (1 per cent.) are coloured 
 blue by the addition of iodine, the starch iodide appearing to be completely dissolved; 
 but upon dissolving salts in such liquids insoluble starch iodide is precipitated as the 
 concentration increases. 
 
CHARACTERS OF STARCH. 763 
 
 Starch iodide suspended in water is bleached by the sunlight, owing to the con- 
 version of the iodine into hydriodic acid; but the colour is restored by ozone and other 
 oxidising agents. All alkalies by combination with the iodine of starch iodide, de- 
 colorise it, but the addition of acids causes the colour to reappear. 
 
 Starch iodide suspended in water loses its colour also when heated to 6t>, the 
 coloration reappearing upon cooling. This experiment may be performed with the 
 same portion of starch iodide several times, but the blue colour gradually disappears, 
 owing to the volatilisation of the iodine; the addition of a fresh quantity of iodine 
 immediately restores the colour. 
 
 The reaction between iodine and starch only takes place when both are present in 
 the free state ; thus, potassium iodide gives no coloration with starch. The charac- 
 teristic blue colour appears in this case only when some of the iodine in the potassium 
 iodide has been set free by such reagents as chlorine, ozone, nitrous acid, etc. ; iodine 
 is not liberated in the free state by hydrochloric, sulphuric, and nitric acids, but con- 
 verted into hydriodic acid. A mixture of potassium iodide and starch is therefore a 
 useful reagent for the detection of chlorine, ozone, peroxide of hydrogen, nitrous acid, etc. 
 
 The different behaviour of starch, dextrin, and sugar towards iodine makes it pos- 
 sible to follow the changes effected in starch by dilute acids, diastase, saliva, etc. So 
 long as unchanged or modified starch is present the addition of iodine produces a blue 
 coloration; when the starch is almost completely changed, into dextrin, a characteristic 
 red colour appears ; finally, when nothing but sugar is present, no colour at all is pro- 
 duced by iodine. This test requires that the liquids should be cold, on account of the 
 decoloration of starch iodide at a slightly-elevated temperature. 
 
 Starch possesses the property of combining with bases. Upon mixing together a 
 solution of caustic soda (6 parts soda to 200 parts water) and water containing starch 
 suspended in it (25 parts starch to 100 parts water), a transparent colourless jelly is 
 formed after a short time, which is a compound of sodium hydrate and starch. If this 
 jelly is mixed with a 7 per cent, aqueous solution of calcium chloride a double decom- 
 position takes place, and a thick white insoluble mass is formed which is a compound 
 of starch with lime, sodium chloride being in solution. A series of compounds of 
 starch with other bases may be similarly formed in which the starch cannot be de- 
 tected by means of iodine. The starch in such compounds is immediately sot free 
 upon the addition of acids. 
 
 Starch exhibits a characteristic reaction with ammoniacal copper solution 
 (Schweitzer's cellulose test). If 40 times its volume of ammonium cuprate be 
 poured over starch and allowed to stand six hours, the starch swells up to ten times 
 its original volume ; examined under the microscope the granules appear translucent 
 and of a bluish colour. The substance when washed with ammonia gives up copper 
 oxide, and, if the washing be continued until the entire quantity of copper oxide is 
 dissolved out, the residual starch likewise dissolves in aqueous ammonia. Starch is by 
 this process converted into its soluble modification. If water be used for removing 
 the excess of copper solution the starch dissolves, and a greenish compound remains 
 behind, being a compound of starch with from 12 to 13 per cent, of copper oxide. 
 This compound may also be obtained direct by pouring very thin starch paste into an 
 ammoniacal copper solution. 
 
 When this compound is treated with hydrochloric acid it is immediately decom- 
 posed, and, according to the amount of water present, is either converted into a jelly 
 or is completely dissolved. The addition of alcohol to the jelly or the solution 
 causes the separation of the starch, which then gives a blue colour with iodine. No 
 conversion of starch into dextrin is effected by this treatment. 
 
 All the substances belonging to the starch group are closely related to sugar. 
 Thus, every kind of starch when boiled or heated under pressure with dilute sulphuric 
 acid, 'undergoes alteration and is converted into a substance known as dextrin, having 
 the same composition as starch, but like the substance occurring in British gum (see 
 p. 800), being very soluble in water and causing the rotation of a polarised ray from left 
 to right ; if the boiling or heating be continued, dextrose sugar is formed by the fixation 
 of a molecule of water. It was formerly supposed that, by the action of dilute acids, starch 
 is converted wholly into dextrin by mere alteration of its physical structure, and that 
 by continuing the treatment dextrin combines with the elements of water, giving rise 
 to the formation of glucose. But recent experiments by Musculus appear to indicate 
 that both dextrin and glucose are produced simultaneously by the action of dilute 
 acids upon starch, and that the substances thus produced bear the proportion of 1 
 molecule of glucose to 2 molecules of dextrin, according to which result, the moleculb 
 of starch may be regarded as having a composition represented by the formula 
 C 18 H 30 15 , and its decomposition by dilute acids may be represented by the following 
 
 equation: Cj8 H 80 15 + H.O = C 6 H 12 6 + 2C 6 H 10 5 . 
 
764 STARCH. 
 
 Again, during germination the diastase of seeds converts starch into a soluble 
 mixture of dextrin and dextrose, or maltose (see p. 803) in various proportions, ac- 
 cording to the temperature and other conditions under which the action takes place. 
 Although starch cannot be induced to undergo fermentation by means of yeast, yet 
 Berthelot has shown that chalk and cheese at 38 C. cause the fermentation of starch, 
 with the production of a considerable amount of alcohol ; doubtless sugar is produced 
 as an intermediate principle. Starch, like sugar, also yields oxalic acid on oxidation 
 with nitric acid. 
 
 Inulin (C 6 H I0 5 ) is found in quantity in the roots of Inula Helenium, Helianthus 
 tuberosus, and Dahlia, and may be prepared by merely rasping them and levigating 
 with water ; inulin deposits from the washings, on standing, and may be readily puri- 
 fied by solution in hot water and precipitation by alcohol. It is a white amorphous 
 tasteless substance, nearly insoluble in cold water, but freely soluble in hot water. 
 Iodine produces a brown coloration. It has the same percentage composition as 
 ordinary starch, and when boiled with dilute acids is completely converted into Isevu- 
 lose. 
 
 Grlycogen is the name given to a kind of starch or amylaceous principle produced 
 by the livers of most animals, and it is supposed to constitute the intermediate 
 product in the formation of sugar in the animal organism. It is a white amorphous 
 substance, without taste or smell, insoluble in alcohol, and yielding with water an 
 opalescent solution. When boiled with dilute acids it is converted into glucose. 
 
 No kind of starch exists as such in the brain, notwithstanding the numerous state- 
 ments which have been made to this effect. The reactions, which have probably led 
 to this statement being made, are referable to a substance named cerebrine, and to 
 others allied to it, all of which yield dextrose on boiling or heating under pressure 
 with dilute sulphuric acid. This reaction would indicate the existence in these 
 substances of a starch-like molecule, in spite of their nitrogenous nature. 
 
 In the chapter on CELLULOSE (see p. 615) it will be seen how very much its properties 
 assimilate to starch, and indeed it has a like composition. That there is a very distinct 
 difference between the various members of the starch group is shown by many facts, 
 notably because inulin for instance yields laevulose, whilst ordinary starch yields 
 dextrose on boiling with dilute acids. 
 
 As a whole, the starches seem to be constituted on the type of a complex ether, 
 under which light the sugars may be regarded as polyatomic alcohols derived from 
 them ; but the true constitution of no one kind of starch or sugar has so far been 
 determined. 
 
 The alcoholic nature of sugar derives considerable support from the researches of 
 Berthelot, who has shown that when fatty acids and various sorts of sugar are heated 
 together under certain conditions, water is eliminated, and saccharides are formed 
 which on boiling with dilute acids yield again sugar and fatty acids. 
 
 Starch is known to form a colligated acid with strong sulphuric acid, and recently 
 Kingzett and Hake have shown that certain kinds of sugar and various benzene deri- 
 vatives may enter into coloured combinations under the influence of strong sulphuric 
 acid possibly by the abstraction of water. Such compounds have several characters 
 in common with the better known and simple combinations of the alcohols with sul- 
 phuric acid. (See ETHERS.) 
 
 Preparation. The method of extracting starch from the amylaceous parts of 
 plants consists in reducing the material to pulp, either by grinding or rasping and 
 mixing with water, then washing the pulp with a stream of water so as to float the 
 starch granules away from the disintegrated cellular tissue. 
 
 The materials from which starch is chiefly prepared are potatoes, wheat, rice, 
 maize, and the grain of other cereals. Several other varieties of starch, commonly 
 known as arrow-root, are obtained from the tubers of Maranta arundinacea, etc. 
 
 MANUFACTURE OF STARCH FROM POTATOES. This includes the following operations : 
 Steeping, washing, separation of stones, rasping, straining, settling, removal of the 
 starch, purification, second straining, washing, draining, and drying in the air or in a 
 centrifugal machine, drying in an oven, packing. 
 
 Steeping. Potatoes grown in tough clay or loam are covered with adherent earth, 
 etc., which clings so tenaciously as not to be removed by simple washing. They are 
 therefore allowed to soak for several hours in a large vat containing water. 
 
 Washing. In the washing an apparatus called the washing drum is used, con- 
 sisting of a hollow revolving cylinder, the case of which is formed of wood or iron 
 bands \ to l i ncn broad, and fastened at intervals of about J of an inch. The 
 cylinder is slightly inclined, and dips to half of its diameter in water placed in a 
 capacious vat. It makes about fifteen revolutions per minute, by which means the 
 
MANUFACTURE OF STARCH. 
 
 765 
 
 potatoes are kept in continual motion, rubbing against and being rubbed by the case 
 of the cylinder. The heavier portion, the sand and small stones, sink to the bottom and 
 fall through the intervals between the bands. The potatoes are introduced at the 
 upper end of the cylinder, and by the action of a spiral arrangement revolving on its 
 axis are thrown out at the opposite end; where, falling upon the edge of the vat, they 
 roll along a sloping latticed surface to the stone catcher. 
 
 Payen proposes a more energetic purification by the use of a large circular brush, 
 with a revolving cylinder also furnished with brushes, the interval between the 
 central brush and those of cylinder being only sufficient to allow of the passage of a 
 medium-sized potato. The larger and smaller potatoes being previously separated, 
 are to be washed in a specially wider or narrower cylinder. A sufficient rigidity could 
 be given to the brushes to remove at the same time the epidermis and the substances 
 adhering to it, and so obtain a material free from skin. On the other hand, the great 
 wear and cost of renewing the brushes must be considered. 
 
 Separation of the Stones. In the French manufactories this is effected by the 
 stone catcher of Joly (fig. 534). This apparatus consists of a semi -cylindrical 
 
 FIG. 534. 
 
 sloping trough, filled with water to the level AB In the trough is a shaft (c D) fur- 
 nished with arms placed spirally, which, through the cogwheel, is rotated by the driving 
 wheel (F). The shape of the arms 
 is shown by figs. 535 and 536. The 
 potatoes being thrown in at A, are 
 rubbed upon one another by the 
 arms and repeatedly dipped in the 
 water, so that the remainder of the 
 dirt and all stones and sand is 
 washed off, and the heavier par- 
 ticles sinking to the bottom are re- 
 moved from time to time through 
 an opening. The potatoes are carried -p, 
 
 forward by the action of the spiral 
 until they reach the upper end of the trough, over which they fall into the hopper of 
 the rasping machine. 
 
 It appears to be preferable to remove the stones and the greater part of the sand 
 by the first washing, as is done in the German factories. With this object the vat in 
 which the washing drum is placed is separated into. two unequal divisions, the larger 
 for the washing drum and the smaller for the stone catcher. The potatoes are placed 
 in the water in the smaller division, and are drawn forward and kept in incessant 
 motion by six or eight large arms arranged spirally on a prolongation of the shaft of 
 the washing drum. The potatoes thus reach the washing drum previously washed 
 and freed from stones. 
 
 Too much care cannot be taken in the complete removal of all stones, as these would 
 have a most injurious effect upon the machinery used in the subsequent operations. 
 
 Fio. 536 
 
STARCH. 
 
 Hasping. The rasper, represented by figs. 537 and 538, consists of a cylinder 
 (a a) armed with steel saw blades, which are fastened by iron bands at intervals of 
 
 about an inch, and project about 
 an inch from the cylinder. The 
 washed potatoes are passed into the 
 machine through the spout (b 6), and 
 being seized by the cylinder making 
 800 revolutions per minute are 
 pressed against the casing enclosing 
 it ; the teeth of the saw blades tear 
 through the potatoes and reduce them 
 to pulp, which falls through the hop- 
 per (d). 
 
 The rasper has been altered and 
 improved by Champonnois, and in its 
 modified form yields a more uniform 
 and finer paste. This consequently 
 admits of a larger product being ob- 
 tained, since it is only the starch from 
 the cells actually ruptured that can 
 be obtained, whilst all that remains 
 in closed cells is lost to the manu- 
 facturer. 
 
 Champonnois' rasper, which, is 
 
 FIG. 537. 
 
 FIG. 538. 
 
 represented by figs. 539 to 542, like the other, consists of a cylinder furnished with 
 saw blades ; but the essential peculiarity is, that instead of the blades being on the 
 
 FIG. 539. 
 
 FIG. 540. 
 
 FIG. 541. 
 
 FIG. 542. 
 
 surface of a solid cylinder, they are arranged on the inner surface of a hollow cylinder, 
 and instead of the cylinder rasping against the potatoes, the potatoes are rubbed against 
 the cylinder. The case of the cylinder is shown in fig. 540 (A), with the peculiar rasper 
 inside. The r.isper is so arranged that from one to four saw blades lie between thin 
 steel bands, and between each group is a space through which the paste formed can 
 flow. In the machines first constructed there was an interval of ^th of an inch between 
 each saw blade, but in those of recent construction there is an interval between each 
 four saw blades which is reduced to from J^th to ^th of an inch; by this arrangement 
 a finer paste is produced and the probability of clogging diminished. Figs. 541 and 542 
 show the arrangement with an interval between every blade. In the axis of the rasping 
 cylinder is a shaft (B B) making 800 to 1,000 revolutions per minute, by power applied 
 to the wheels (E B) and regulated by a fly wheel ; at the other end of the shaft within 
 
MANUFACTURE OF STARCH. 
 
 767 
 
 the drum is a strong fork-shaped scoop. The potatoes falling through a side opening 
 are seized by the scoop and pressed forcibly against the saw blades in the cylinder (c). 
 Water being admitted into the interior is driven by centrifugal force against the sides 
 of the cylinder, and makes its way through the interstices, carrying with it the potato 
 paste formed, which passes away through a pipe underneath. The teeth of the saw 
 blades are very short, projecting ^th of an inch from the drum. They require reversing 
 twice a day, and after two days' use need to be refiled. As much as 1 3 tons of potatoes 
 can be rasped by this machine in ten working hours, whilst the yield of starch from a 
 given quantity of potatoes is considerably increased. 
 
 Straining. The paste thus obtained is a mixture of starch and potato fibre. To 
 separate them the paste is washed with water upon brass- wire sieves of different 
 degrees of fineness, which allow the starch granules to pass through with the liquid, 
 and retain the coarser portions of the fibre. The pulp is made to pass over the sieves 
 by means of an endless band, and various arrangements are in use for this purpose. 
 
 As the washed pulp always retains a portion of the starch, and more in proportion 
 as the rasping is imperfectly performed, different plans have been proposed for its 
 recovery. Huck subjects the pulp to a second rasping, but the benefit from this is 
 very doubtful. Fiska passes the pulp between two cylinders, one revolving more 
 rapidly than the other. The membranes of cells that escape the action of the grater 
 are in this way ruptured, and as much as 3 per cent, more starch is thus set free. 
 
 Settling. The starch liquid as it comes from the sieves generally contains some 
 sand which was not separated during the washing of the potatoes and was too fine to be 
 retained by the sieves. It is therefore run into a large vat and vigorously stirred so as 
 to bring all the starch into suspension. Before the starch has had time to settle, but 
 after the sand through its greater specific gravity has fallen to the bottom, the liquid 
 is run off by means of a wide syphon, or through a cock placed near the bottom of 
 the vat, into another capacious vat, where it is allowed to stand for four hours, by which 
 time the starch settles to the bottom. The supernatant liquid containing the sap 
 constituents of the potato is then removed. 
 
 Purification. The lower part of the sediment deposited in the vats consists of pure 
 starch, but this is covered by a greyish layer consisting of fine fibres that have passed 
 through the sieves. This impure mass is scraped off with a special instrument and 
 undergoes another operation to remove from it the starch it contains. 
 
 The purified starch is again suspended in water by the action of a stirrer, then 
 passed through a silk or wire strainer (90 meshes to the inch) and again allowed to 
 settle. The starch is then placed in a slightly sloping flat-sided trough (figs, 543 and 
 544, A B c), about 22 feet long, 3 feet wide. Below this is a second trough (D E), in- 
 
 FIG. 543. 
 
 Clined in the contrary direction, and a third (o r) inclined like the first. A spray of 
 water from a very fine rose (s) controlled by a cock (B), falls upon the starch which .w 
 placed beneath it, and at the same time stirred with a spatula. The water gradually 
 washes all forward with it, but while flowing slowly along the ouhsthe rcbM 
 deposited and only the ligh 
 very little starch through the _ 
 posited is added to that purified in 
 
768 
 
 STARCH. 
 
 The residual washed pulp is generally used as fodder, either in the fresh condition, 
 when it has had a portion of its water removed by pressure, or after it has undergone 
 fermentation in pits. The pressure is applied by passing it through a pair of cylinders 
 between two endless bands of cloth, by which half the water is removed. When not 
 used in the fresh state it is stamped into pits, covered with straw, and then with a 
 layer of earth. It there undergoes acetic fermentation, by which, however, its food 
 value is not deteriorated. When using the pulp as fodder it must be borne in mind 
 that it consists almost exclusively of non-nitrogenous materials, and that it is neces- 
 sary to supply albuminoid constituents by the addition of oil cake, bran, etc. 
 
 When dried the pulp is easily ground to powder, and in this form is sometimes 
 added to wheaten-flour in bread-making. But this can scarcely be done profitably, as 
 it is very questionable whether cellulose, which is easily digested by beasts, is digestible 
 by man, especially after being dried. But it can be used in the place of flour for 
 dusting the hearth of the oven to prevent the paste adhering. Lastly, the pulp is 
 also used in the glucose, beer and brandy manufacture. 
 
 The moist but drained pulp contains about 12 per cent, of solids, about 7 per 
 cent, of which is starch, a proportion however which is correspondingly lessened by the 
 arrangement for crushing and good rasping. 
 
 Several other forms of apparatus have 
 been constructed for carrying out these ope- 
 rations, especially for washing and strain- 
 ing. A longitudinal section, of that of Huck 
 and Stoltz, is shown in fig. 545. It consists 
 of three cylinders, the case of the first (A) 
 being formed of a wire sieve, 25 meshes to 
 the inch. The paste from the rasper is in- 
 troduced through the funnel (a). Within 
 this cylinder is another formed of per- 
 forated metal plate into which water flows 
 through the pipe ("), and is distributed uni- 
 formly through the perforations upon the 
 potato pulp in A. This gradually moves 
 forward, and comes, after parting with 
 the greater part of its starch, into the 
 second cylinder (B), which is covered with 
 sheet copper. The pulp is here agitated 
 with a fresh jet of water, coming through 
 the perforated pipe (d) supplied from a'", 
 and carried forward into the third cylinder 
 (c) covered with wire tissue, 35 meshes to 
 the inch. Whilst in the cylinders the 
 paste undergoes a continual working, in A 
 and c with brushes and in B with a T-- 
 shaped iron, both fastened to the shaft 
 (DD'), which is rotated by the driving- 
 wheel (G) in an opposite direction to the 
 cylinder. The liquid flowing from A and c 
 collects in the trough (K) below and from 
 thence runs into another sieve cylinder (HH') 
 covered with wire gauze, 50 meshes to the 
 inch. The fibrous pulp which has. passed 
 through the other sieves is here retained, 
 the liquid then running off along the 
 trough (L) into the settling vats. The 
 coarse pulp is pushed out of the cylinders 
 and falls into the receivers (MM') under- 
 neath. 
 
 In order to prevent the clogging of the 
 sieves a fine stream of water is thrown 
 upon them during revolution from pipes 
 running parallel with their axis. 
 
 In most manufactories the wash water is 
 allowed to flow into the nearest ditch or 
 watercourse. It contains all the soluble 
 constituents of the potato, including 
 nearly all the albumin and other substances 
 that are highly putrescible and these 
 
MANUFACTURE OF STARCH. 
 
 769 
 
 afford favourable conditions for the development of numerous algae, oscillaria, beggiotoa, 
 vibrios, etc. These increase so rapidly that frequently in a short time the bed of the 
 watercourse is filled with them. Many of the algae have the property of decomposing 
 sulphates dissolved in the water with evolution of sulphuretted hydrogen, contami- 
 nating the air and rendering the water unfit for man, beasts, or fishes. The waste 
 water from sugar manufactories behaves similarly but in a higher degree. Many 
 attempts have been made to remedy these inconveniences, which give rise to numerous 
 actions against the manufacturers by the inhabitants and regulations by the govern- 
 ment. Payen recommends that the water should be allowed to clear in several 
 cisterns. In the first it deposits principally starch, and in the latter albuminous 
 substances, after which the water itself may be used for irrigation. The deposit in 
 the cisterns can be used as manure. The quantity of manure which can be utilised in 
 this way during the operations of a three months' season is considerable, and Payen 
 estimates that it is obtainable at one-fifth of its market value. If there is sufficient 
 land in the neighbourhood of the manufactory, a system of direct irrigation is the best 
 and simplest method, experience having shown that the effluent water is n^t injurious. 
 When this is not the case, the disinfection of the water with a milk of lime to which 
 magnesium chloride has been added is recommended. Part of the lime and magnesium 
 forms with the different organic substances insoluble compounds which are mechanically 
 carried down by the remainder, so that a comparatively pure water flows off from the 
 first settling basin. 
 
 According to Fesca, a large proportion of the albuminous bodies can be recovered 
 and used as food for cattle by boiling the fresh wash water, when the albumen is 
 coagulated and deposits as a flocculent mass. 
 
 FIG. 516. 
 
 Figs. 546, 547, and 548 show a modification by which considerably less water is re- 
 quired. The paste coming from the 
 rasper (A, fig. 548, enlarged) is raised 
 by the centrifugal pump (D) into 
 the first cylinder (B, fig. 546), where 
 it gives up by far the greater part 
 of its starch. The strained liquor 
 
 from this cylinder is not joined with p . - 7 
 
 that from the other cylinders, but run 
 off into the purification vessel. The liquor from the mixing cylinder (c) and the other 
 
 FIG. 548. 
 
 sieve cylinder (D) which contains but little starch is carried by the pipe (o o') back 
 to the rasper, where it is used for the first thinning of the paste. 
 
 3 D 
 
770 
 
 STARCH. 
 
 By the further modifications shown in fig. 549 a second working of the pulp is 
 effected and a larger yield of pulp secured. The pulp thinned with water falls from 
 
 the rasper driven by the wheel (A) 
 into a small cistern, from which it is 
 raised by the pump (B) through the 
 pipe (B') into the sieve and mixing 
 cylinders (DD'D"), and in the latter 
 washed by a stream of water ('). 
 The pulp rejected from D" falls into 
 the hopper of a second rasper, where 
 it is rubbed between two cylinders 
 (F) rotating in different directions. 
 It then flows into the sieve (o), 
 where it meets with more water 
 from A" and A'", and being washed 
 falls into a trough, along which it is 
 pushed by an archimedean screw. 
 The starch liquid from D falls into 
 the trough (E), that from G into E', 
 and both united flow into the first 
 purifier (K. L) ; the purified product 
 flows through the trough (j) into the 
 cistern (M), from whence it is raised 
 ,,by the pump (N) to the second puri- 
 fication apparatus (o), where the last 
 portions of fibre are left, and the 
 liquid passes through the trough 
 (p P) to the settling vats or the in- 
 clined plane, by which in the larger 
 factories the settling vats are now 
 completely supplanted. For the 
 working of twenty tons of potatoes 
 per day a trough is required about 
 90 yards long and 3^ feet wide, with 
 a fall of 1 to l per 1,000 (see fig. 
 550). 
 
 The starch from the troughs is 
 sufficiently pure to be sent at once 
 into the market; but as it is still 
 contaminated by the potato sap, it is 
 advisable again to wash it with 
 water in the settling vats. When 
 the inclined plane has been used 
 this last purification is much more 
 easy, the greater part of the impurity 
 having been already separated. 
 
 Drying. The starch is left 
 behind in the settling vats as a very- 
 thick paste, from which the water is 
 removed by centrifugal action, by 
 drying in the air or in ovens. 
 
 In drying starch by centrifugal 
 action the same apparatus is used 
 as in draining the syrup from the 
 raw sxigar crystals in the sugar 
 manufacture (see SUGAR). It needs 
 now only to be mentioned that it 
 consists of a shallow cylindrical 
 drum, the case of which is made of 
 wire gauze. The drum being very 
 rapidly rotated, the water is forced 
 out by centrifugal force, whilst the 
 starch is retained by the wire gauze. The starch as it comes from the settling vats 
 or the inclined plane is unfitted for the centrifugal machine, being too thick to 
 become so equally distributed as is necessary to the proper working of the machine. 
 It is therefore stirred with sufficient water to bring it to the condition of a liquid 
 paste that will flow into the apparatus while it is in motion, when it is immediately 
 
MANUFACTURE OF WHEAT STARCH. 771 
 
 flung against the circumference, the water flies off, and the starch lies as a compact 
 round cake upon the case of the cylinder. 
 
 A fresh process of purification may easily be combined with the use of the centri- 
 
 FIG. 550. 
 
 fugal machine. The densest and most heavy portion is driven off most rapidly and 
 furthest by the centrifugal force, the lighter portion less rapidly; the largest and 
 purest granules therefore lie closest to the sieve. The fibrous portion remains longer 
 suspended, and is at length deposited as a layer upon the surface of the pure starch, 
 from which it is easily removed. A suitable purifying centrifugal machine has been 
 constructed by Fesca of Berlin. 
 
 For different purposes, such as the manufacture of dextrin and starch sugar, the 
 starch as it comes from the centrifugal machine is perfectly suitable. It contains 
 35 to 40 per cent, of water, and is known in commerce as green starch. 
 
 Where a centrifugal machine is not used the water is removed as much as possible 
 from the starch before proceeding with the drying. The paste is therefore laid in 
 shallow receptacles made of clean smooth slate slabs, then covered with clean linen 
 cloths, and on the top are laid dried porous stones. The stones absorb the moisture, 
 and after a short time green starch rema'ins. This is next removed to the drying 
 floor, where it remains freely exposed to the air until sufficiently dried. During this 
 time, which varies in length with the period of the year, the starch is exposed to many 
 accidents, especially to becoming dusty. This should be considered in the construction 
 of the drying floor, which should be as far removed as possible from dusty places. 
 Another disadvantage is the freezing of the moist starch, as paste made from once 
 frozen starch is, in the opinion of experts, deficient in cohesive power. 
 
 Both these defects may be avoided by drying the starch in ovens. According to 
 this method, a current of warm air is circulated through closed chambers, and a 
 methodical evaporation of the water is thus effected. The temperature is so regulated 
 that the green starch is heated to 60, not too rapidly or beyond, otherwise the starch 
 swells and becomes pasty ; but when the greater part of the water has been removed, 
 the temperature can be raised considerably. 
 
 During the drying of potato starch, the larger proportion of it crumbles sponta- 
 neously to powder ; differing in this respect from wheat starch, the granules of which 
 remain pressed together. The powder is sifted, the retained firmer granules passed 
 under a roller, and the whole then well mixed. The dried starch is now ready, and 
 is packed in paper-lined vessels and sent to market. 
 
 MANUFACTURE OF WHEAT STARCH. The process of obtaining starch from wheat 
 is somewhat different from that before described for its manufacture from potatoes. 
 Whilst the potatoes are only treated so as to rupture the separate cells in order that 
 the starch stored up in the sap may be washed out, in the case of wheat a separation 
 has to be effected of the starch from the surrounding gluten and the removal of the 
 husk and remaining constituents of the grain. This can be carried out by two essen- 
 tially different methods. 
 
 3 D 2 . 
 
772 
 
 STARCH. 
 
 (1.) By utilising the plastic property of the gluten, which allows the starch to be 
 washed out from the dough, the pure gluten remaining. 
 
 (2.) By destroying the gluten through a process of fermentation and decay, by 
 which a part is rendered soluble and a part loses its coherence, and can then be sepa- 
 rated from the unaltered starch. 
 
 The latter method has long been used, and at the present day it is met with in by 
 far the greater number of manufactories. But it has many inconveniences: a large 
 quantity of gluten, which could be used as fodder or as human food, is lost ; the yield 
 of starch does not correspond to the amount in the grain ; the waste discharge from 
 the manufactory, laden with putrefying and fermenting material, is dangerous to the 
 health of the neighbourhood, spoiling the water in the streams into which it flows 
 and diffusing a most disgusting smell. 
 
 Production of Starch and Gluten from Wheat Flour. According to this method, 
 introduced by Martin, a dough is first prepared, exactly as for bread making, 100 
 parts of flour and 40 to 50 parts of water being mixed together. The dough is 
 kneaded, either by hand labour or in a machine, until perfectly uniform, and then, in 
 order to allow the dough to become saturated with moisture before washing, it is 
 allowed to stand in summer 25 minutes and in winter one nour. 
 
 For the washing out of the starch a semi-cylindrical trough is used, at different 
 parts of the circumference of which are slits covered with wire-gauze, to allow of the 
 discharge of the water holding the starch in suspension. At the bottom of the trough 
 is a slightly channelled cylinder, to which a mechanical arrangement imparts a 
 swinging motion to and fro. The dough, formed into small balls, is placed in the 
 trough, and whilst a fine jet of water plays upon it incessantly from a water pipe, it is 
 continually moved to and fro by the cylinder. The starch is thus washed free, and 
 flows together with the water through the openings covered with wire to the receiver ; 
 whilst the gluten gradually becoming more compacted together, is left finally as a 
 tenacious elastic mass, possessing the characteristic properties of that substance. 
 In such an apparatus, with a trough 6| feet long and 4 feet wide, the dough from 
 2 cwt. of flour can be worked hourly with an expenditure of about 100 gallons of water. 
 
 In apparatus of more recent construction two washing troughs are placed next to 
 each other, the working power being thus doubled. Fig. 551 shows a section of the 
 
 FIG. 551. 
 
 FIG. 652. 
 
 apparatus ; fig. 552 gives a view from above ; and fig. 553 an end view. The letters 
 designate the same parts in each. FF are the wooden troughs. In fig. 553 at cis 
 shown one of the openings covered with wire-gauze. The longer sides are provided 
 with two wide gutters (D D), in which, by means of a movable outflow arrangement, 
 
MANUFACTURE OF WHEATEN STARCH. 773 
 
 the liquid is so retained that in both the gutters and the trough it reaches to half the 
 height of the wire-gauze, the excess of starch-laden water flowing off, through a pipe 
 (d, fig. 551) that can be raised or lowered at 
 pleasure, into the receiver (G). Over the par- 
 tition common to the two troughs is placed an 
 arched plate for the purpose of breaking the 
 waves of the liquor when set in motion and pre- 
 veiiting it from running from one trough into 
 the other. A A' are two iron shafts resting in 
 sockets on the sides of the trough. At each 
 end of these shafts are iron arms having forked 
 extremities which span the ends of the corru- 
 gated wooden cylinders (B B'), so that the latter 
 can turn freely in the fork. By means of the F IQ . 553. 
 
 handles (a a) connected with the shaft (A A') 
 
 an oscillatory movement is imparted to the cylinders (B B') at the bottom of the 
 trough. At first the turning of the handle requires the exercise of considerable force, 
 but after about ten minutes the volume of the dough is much reduced, and the work 
 becomes lighter. The water is brought to both troughs through copper pipes pierced 
 with fine holes, through which it falls during the whole operation in fine jets upon the 
 moving dough underneath. 
 
 The operation with this apparatus is carried out in the following manner. A 
 sack of flour is made into dough with about half its weight of water, which requires 
 in summer 20 to 30 minutes or in winter an hour. This dough is worked into balls 
 of about two pounds in weight, and distributed equally in both troughs, where being 
 partly covered with water it is rolled to and fro by the cylinders. If the dough 
 becomes adherent in larger lumps, it is at once again divided up by the workman in 
 charge. Care has also to be taken that the wire-gauze does not become stopped up by 
 small pieces of gluten ; this is prevented by applying with one hand a brush to the 
 outside whilst the portions of gluten are removed from the inside by the other. The 
 washing of the dough lasts about an hour, after which time the water scarcely 
 carries off any more starch. The outlet pipe (d) is then entirely withdrawn from the 
 gutter (D), which allows the fluid contents of the gutter and trough to flow away into 
 the receiver (G). The gluten which is left behind is freed from excess of water by 
 five minutes' kneading and removed, and the apparatus is then ready for a fresh 
 operation. 
 
 On the average there is obtained from a sack of flour about 110 Ibs. of moist gluten 
 and a liquid containing equal to about 220 Ibs. of dry starch. The most suitable kinds 
 of wheat for this method of manufacture are the half-soft wheats ; neither from the 
 hard horny nor from the soft mealy wheats is the production of starch and gluten to 
 be effected with equal results. 
 
 Martin's method also allows of the use of bruised wheat. The operation is exactly 
 the same as just described ; though the products differ in so far that, with a pure 
 starch, there is obtained a gluten mixed with corn husks, which cannot be used for 
 human food, though suitable for fodder. 
 
 The purification of the starch is essentially the same as described under POTATO 
 STARCH. Upon running off from the trough the liquor first passes through a fine wire 
 sieve, 100 meshes to the inch, which retains some membrane and small particles of 
 gluten carried off by the water. From the first receiver the liquor is raised by a 
 pump to a higher reservoir, from which it flows on to the inclined surfaces de- 
 scribed. The pure starch is deposited and soon forms a thick uniform layer, whilst 
 the lighter and impure portion is carried forward to the end of the inclined surface, 
 and finally collects in the reservoir underneath. There it is allowed to remain at 
 rest for twenty-four hours, during which the starch settles at the bottom and the 
 liquor becomes clear. This liquor contains more or less albuminous matter, dextrin, 
 grape sugar, and salts, and can be used either as a drink for cattle and horses, or in 
 the preparation of beer or brandy. After the separation of the clear liquor the 
 impure starch obtained is subjected to a further purification by stirring it with water, 
 passing it through a fine sieve, and then running it in a very thin layer upon the in- 
 clined surface. Pure starch is again deposited, whilst from the water flowing off there 
 is a further settlement after standing forty-eight hours of a small quantity of very 
 inferior starch, which is drained in a linen filter, pressed and dried. 
 
 By a still more recent method of Martin's, the impure starch can be readily freed 
 from foreign admixture and a better product obtained' than is possible through simple 
 washing. It consists in treating the starch, after the first deposit has been collected 
 up-'H the inclined surface, not simply with water, but also with a weak solution of 
 caustic soda, by which the gluten is dissolved before th starch is attacked. After the 
 
774 STARCH. 
 
 settling and removal of the supernatant liquor, the deposit is stirred with water and 
 solution of caustic soda, specific gravity 1-013, added until the liquor blues red litmus 
 paper. The liquor is allowed to act for two hours ; then a considerable quantity of 
 water is added, and the whole is thrown on a No. 200 sieve, which retains the swollen 
 gluten and allows the starch to pass through. After standing a short time, during 
 which a small quantity of sand settles, the starch milk is poured on to the inclined 
 surface. Almost the whole of the starch is thus obtained as first product, whilst with 
 simple washing about 25 per cent, is produced in an impure unmarketable form. 
 
 The pure starch deposited upon the inclined surface is once more stirred up with 
 water, then passed through a fine sieve, and allowed to settle during twenty-four 
 hours. After the removal of the supernatant liquor, some impurities are found in 
 the top layer, which is removed and submitted to further operations. 
 
 In order to dry the starch it is first spread out evenly in a flat stone receptacle, 
 covered with clean linen cloths, and overlaid with some porous material that will 
 absorb moisture, such as burnt porous limestone, gypsum, purified ashes, etc. After 
 a short time the starch loses so much water, that it can be cut up in the form of large 
 blocks as green starch. These blocks are then dried upon hollow stands, situated in 
 airy places. As the water evaporates from the surface of the mass, moisture is drawn 
 from the interior, carrying with it a small quantity of impurities still present, and a 
 fungoid growth commonly takes place on the yet moist surface, which causes the 
 appearance of yellow spots. The impurities and vegetation give to the cake an 
 unseemly appearance ; as soon therefore as the drying is so far advanced that no 
 farther development of vegetable organisms is possible, the outer surface is carefully 
 scraped off with a knife. This refuse is known as starch scrapings. 
 
 The purified cakes are broken up into smaller pieces, Schafchen, and perfectly 
 dried, in summer in the open air, and in winter in heated rooms. 
 
 Wheaten starch differs essentially in its appearance from potato starch. Whilst 
 the latter, upon drying, crumbles more or less into a fine powder, the granules of 
 wheaten starch lie close together and assume a rod-like structure, so that a broken 
 cake or the surface of a mass appears to consist of prisms lying nearly regularly one 
 upon another. 
 
 Production of Starch by Decomposition of the Gluten. In this process either whole 
 or crushed grain is used, but whole corn is most frequently used. The wheat is 
 placed with water in a large receptacle, and left in contact for about three days, or 
 until it has become so uniformly penetrated by moisture and softened that, by 
 moderate pressure between the fingers, the outer husk separates from the grain and 
 the latter is crushed into a milky mealy mass. It is very advantageous to the quality 
 of the product if a washing of the grain is effected, together with the soaking, in order 
 to remove dust and adhering impurities. This can be done by changing the water 
 every twenty-four hours until it remains clear and colourless. 
 
 The swelled corn is crushed either between two wooden cylinders revolving in 
 opposite directions and fed through a hopper, or by one or two cylinders revolving 
 upon a horizontal stone having a rim. The husks of the softened corn are thus easily 
 separated. 
 
 After the crushing follows the fermentation. This is effected in large stone 
 vessels, into which the swelled corn is passed direct from the crushing mill, and then 
 stirred up with some water. In order to induce the fermentation, some liquor, or 
 sour water, derived from a previous operation is added. During this fermentation 
 various processes go on simultaneously. A constant evolution of gas takes place, 
 resulting from alcoholic fermentation ; the alcohol formed is converted by further 
 fermentation into vinegar ; besides these, lactic fermentation takes place, and other 
 fermentations the products of which have not yet been studied. Actual putrefaction, 
 understanding by this term the fermentative processes which evolve stinking gases, 
 must be avoided ; the fermenting mass should always have an agreeable vinous smell. 
 The duration of the fermentative process differs with the temperature of the surround- 
 ing atmosphere ; usually it has progressed sufficiently in three or four weeks. The 
 liquor in which the pulpy mass is contained, the sour water, has then acquired a light 
 yellow colour, and has a peculiar sticky feeling, the starch separates readily from the 
 husk, whilst part of the gluten is dissolved and the other part is softened, and has 
 completely lost its adherent elastic properties. 
 
 The separation of the starch from the fermented mass takes place in the washing 
 wheel or washing drum. This consists of a shallow cylinder, which is rotated 
 vertically by a shaft passing through it. The surface of the cylinder is either made 
 of wooden staves pierced with fine holes or from perforated sheet copper. At the 
 extremities are strong wooden covers, having an opening that can be closed, for the 
 purpose of filling and emptying the cylinder. On one side water flows in through a 
 pipe opening in the shaft. The lower half of the wheel is surrounded by a wooden 
 
MANUFACTURE OF STARCH FROM BEAISTS, ETC. 775 
 
 vessel, in which the escaping starch milk is collected, and from which it passes into 
 the clearing vessel. The fermented mass is introduced into the washing wheel, which 
 is slowly set in motion by the continual flow of water ; the starch is thus washed out, 
 and separated from the residue containing more or less gluten that is left in the wheel. 
 The operation is ended when the escaping water no longer has a milky appearance. 
 
 The further purification of the starch is essentially the same as that described for 
 potato starch. After passing through a fine sieve, it is run into the clearing vessel, 
 where the pure starch is deposited at the bottom, the slimy or glutinous starch forms 
 a layer upon it, and the dilute sour water becomes gradually clear. The sour water 
 is then drawn off through taps, and the impure starch which contains particles of 
 gluten, and of the finer membranes of the grain, embryo, etc., is purified by stirring 
 with water, straining and passing over the inclined surface. The purer starch, after 
 removal of the impure layer, is further purified by submitting it several times to 
 stirring with water and settling. 
 
 According to Payen, the starch manufacture in Alsace is carried on in a similar 
 way, but without the fermentation, the swelled corn being crushed, and the starch 
 immediately washed out with water. The starch milk so obtained is strained with 
 difficulty, in consequence of the relatively large quantity of unaltered gluten mixed 
 with it ; the further purification is effected by settling, and the inclined surface. It 
 is difficult by this method to carry out the purification perfectly, and the yield of 
 starch of the first quality is small, whilst about one third of the whole product is 
 almost worthless. 
 
 Yield of Starch. The following yield of starch is obtained by the respective 
 processes from 100 parts of wheat of equal quality, used either whole or crushed : 
 
 By the Fermentation Process : 42 parts of the finest starch, and 6 to 8 parts of 
 second product ; the greater part of the gluten is lost. 
 
 By the Alsace Method : 34 parts of fine starch and 18 parts of second product of 
 little value ; the greater part of the gluten is lost ; the husks, not being altered by 
 fermentation, are of more value as fodder than the fermented, and about 45 parts are 
 obtained in the moist condition. 
 
 By Martin's Method : 52 parts of fine starch, 6 parts of second product, and 
 residue, which contains the whole of the gluten, husk, etc., and forms a very nourishing 
 fodder. 
 
 Martin's method is therefore distinguished as well by the yield of valuable product 
 as by the complete utilisation of the remaining constituents of the corn. By carrying 
 on the manufacture in connection with agriculture, it is possible to sell only the starch 
 of the harvested corn, and to retain the remaining constituents on the farm. 
 
 MANUFACTURE OF STARCH FROM BEANS. In preparing starch from this material the 
 beans are soaked during 24 to 30 hours in water, and then crushed between cylinders 
 under a flow of water. The crushed mass is washed in a cylindrical sieve, such as is 
 figured on p. 768, the starch being carried through with the water and the husks re- 
 maining. The starch milk is poured upon the inclined surface, where the larger starch 
 granules form a layer, whilst the smaller, together with other matters suspended in 
 the liquor, are deposited in large clearing vessels. This deposit is rich in nitrogenous 
 food material and the whole of the finest starch granules. After the separation of the 
 water it can be made into fodder with the husks retained in the cylindrical sieve; or, 
 with very careful treatment, this substance can be used for human food. Separation 
 of the albuminous matters by means of an alkaline solution is not in this case possible, 
 as bean starch has the property of swelling when in contact with very dilute alkaline 
 solutions ; a solution of soda, which would not act upon wheaten starch, converts the 
 bean starch into a paste. 
 
 Bean starch is distinguished from wheaten starch by its greater capability of form- 
 ing a paste, the same effect being obtained with two parts of bean starch as with three 
 of wheaten starch. Linen starched with bean starch remains pliable, and has not the 
 stiffness of that treated with wheaten starch. 
 
 MANUFACTURE OF STARCH FROM MAIZE. The grain of maize is rich in starch and 
 generally richer than wheat. It differs from wheat grain in the individual cells being 
 denser and harder. In order to obtain the starch, therefore, the grain, whole or 
 crushed, must undergo a prolonged swelling in water. The manufacture is then 
 essentially the same as that of bean starch. After washing in the cylindrical sieve 
 the milk is run on to the inclined surface, and the matter suspended in the water is 
 purified by repeated settlings and strainings. 
 
 MANUFACTURE OF STARCH FROM EICE. The preparation of starch from rice is carried 
 on principally in English manufactories. The product is much esteemed by laundresses, 
 and preferred to wheaten starch. No other raw material is so rich in starch as rice ; 
 but the cells and the starch granules contained in them are so closely cemented 
 
776 STARCH. 
 
 together that their separation cannot be effected by a simple washing and crushing, 
 and an alkaline solution is always used. The rice is allowed to stand in a ^ per cent, 
 solution of caustic soda until it is perfectly softened. The liquor is then drawn off 
 and the softened rice crushed, and afterwards stirred during 24 hours in fresh alkaline 
 solution of similar strength. By this means the other substances are sufficiently 
 swelled to allow of the starch being washed out, which is effected in the cylindrical 
 sieve. The starch milk generally contains granules still cemented together, and in 
 order to remove these the liquor is allowed to stand a short time until the heavier 
 particles have sunk to the bottom, whilst the lighter particles still remain suspended 
 in the water. The milk is then passed on to the inclined surface, and the larger par- 
 ticles are again treated with soda solution. 
 
 Uses. The best kinds of potato starch are used in the sizing of paper, especially 
 those of finer qualities, the preparation of white glucose syrups, the dressing of fine 
 fabrics, the manufacture of white dextrin, and in the preparation of light pastry. The 
 inferior kinds are used for similar purposes, but in cases where the quality is not of so 
 much importance, such as the dressing of cloth, the thickening of mordants and colours 
 in calico printing, the manufacture of vermicelli, as a low priced addition to bread, in 
 the imitation of tapioca, sago, etc. Starch has also formed a very important applica- 
 tion in the dusting of moulds in metal foundries. Formerly powdered charcoal ex- 
 clusively was used for that purpose ; but it was very prejudicial to the health of the 
 workmen, the fine splinters of which- charcoal consists acting injuriously upon the 
 respiratory organs. The relative softness of starch, the roundness of its granules, 
 and the readiness with which it is acted upon by different liquids in the human body 
 render it free from these hurtful properties. It was introduced into the metal industry 
 by Rouy, the merit of the inventor being recognised by the Academy of Sciences in the 
 award of the Montyon prize. 
 
 Potato starch has the disadvantage compared with other starches of possessing a 
 peculiar smell and taste which is due to the presence of a volatile oil. This smell 
 and taste are to many persons not perceptible, but to others they are so objectionable 
 as to render food prepared from such starch unpalatable. According to Martin, this 
 oil can be separated by first treating the starch with a solution of 2 parts of sodium 
 carbonate in 100 parts of water, and then washing it perfectly with water. 
 
 BREAD AND FLOUR. 
 
 The origin of the art of bread making may be said to be hidden in the mists of 
 antiquity, for although bread is not the form of food that might be supposed to have 
 presented itself most obviously to the human race, it may be inferred that some one 
 or more varieties of it were in use by all the races of men referred to in the earliest 
 records extant. It appears probable that the first approach to bread making was 
 made by steeping grain of some kind in water, pressing it and then drying the mass 
 by natural or artificial heat. Indeed, Pliny asserts that the art of making cakes was 
 not known until long after the process of reducing grain to flour had been discovered. 
 He also alleges that barley was the only grain at first used for food ; but Herodotus, 
 on the other hand, says that the Egyptians ate neither barley nor wheat, but a 
 peculiar kind of corn. Although this point cannot now be decided, there is little 
 doubt that all the earlier forms of bread were unleavened, and that the cakes of the 
 patriarch Abraham bore a considerable resemblance to the damper of the modern 
 Australian settler, the corn bread of North America, or even to the oatmeal bannocks 
 and the scones of Scotland. This view is confirmed by illustrations on early Egyptian 
 monuments, where the loaves depicted are of the shape of modern biscuits and have 
 evidently not undergone fermentation. 
 
 It would appear, however, that by the time of the exodus, the preparation of un- 
 leavened bread in Egypt had become sufficiently common to need special instructions 
 to be given for the preparation of this article of food. Indeed the practice of the art of 
 baking, as a distinct calling, appears to have been carried on by the Jews and two or 
 three neighbouring nations, the Phoenicians, Cappadocians, and Lydians, long before 
 it was introduced into Europe. The Greeks then became also expert in the art, and 
 after the conquest of Macedonia, some of the Greek artizans being carried to Rome, 
 the trade grew into such favour there, that in the time of Augustus, there were up- 
 wards of three hundred public bakehouses in that city, almost all of which were in the 
 hands of Greeks. It is stated, however, that even so late as the sixteenth century, 
 unleavened cakes constituted the only bread known in Sweden and Norway. 
 
 At the present day, the French and Viennese excel in bread making, and a large 
 number of varieties of fancy bread are made by them besides the coarser kind. In 
 England several kinds of fancy bread, known as bricks, coburgs, cottage loaves and 
 
COMPOSITION OF CORN. 777 
 
 French rolls, are usually made of the finest flour, and they differ from ordinary bread 
 chiefly in this respect and in the shape of the loaves. In Germany, Kussia, and other 
 parts of the continent, bread is commonly made of rye, or a mixture of rye and 
 wheat. Maize is also used in some countries, especially in America and in the East 
 of Europe. 
 
 For the preparation of bread according to modern methods, the corn is subjected 
 to a preliminary operation of grinding, and the meal thus obtained is then sifted in 
 order to separate the coarser husky portions from the farinaceous part which con- 
 stitutes flour. 
 
 Under the term flour or meal are generally included all those products that are 
 obtained by grinding and sifting from different kinds of seed, and especially the seed 
 of cereals. By these operations a separation is effected between the different parts of 
 the grain ; the greater portion of the interior being converted into flour, whilst the 
 outer layers, the epidermis, etc., together with the adherent portions, are removed by 
 the sieve as bran. 
 
 The flour of cereals contains the following constituents in varying proportions: 
 Nitrogenous, neutral, organic substances : gluten, albumen, casein, glucin. 
 Non-nitrogenous organic substances (the so-called carbohydrates) : starch, sugar, 
 cellulose, fats, and volatile oils. 
 
 Mineral substances : magnesium, potassium, and calcium phosphates ; other potas- 
 sium and sodium salts, and silica. 
 
 Bran does not differ in the nature of its constituents from flour, but contains them 
 in different proportions ; it being richer in albuminous, fatty, and mineral substances 
 than the internal portion of the grain. In the preparation of flour, therefore, for 
 human consumption, a quantity of most important alimentary material is removed ; 
 a more nourishing bread would be obtained if this were allowed to remain in the 
 flour, and if only the most exterior portion about 4 or 5 per cent, of the whole grain, 
 consisting of the indigestible woody fibres of the pericarp were removed. 
 
 There are a number of different species of wheat ; these again have their varieties. 
 For instance, there are 
 
 I. True wheat : the ears growing upon a tough stalk, and the grain separating 
 easily from the grain chaff. 
 
 1. Common wheat : Triticum vulgar e. 
 
 (a) Beardless wheat : Triticum vulgare vnuticum, with awnless ears. 
 (6) Bearded wheat : Triticum vulgare aristatum, differing from the pre- 
 ceding in having awned ears. 
 
 2. English wheat : Triticum turgidum. 
 
 3. Horny wheat : Triticum durum. 
 
 4. Polish wheat : Triticum polonicum. 
 
 II. Speltwheat: with a more brittle, easily broken seed-stalk, the grain being 
 shut in close by the chaff, so that it is not easily separated. 
 
 1. The typical Spelt : Triticum spelta. 
 
 2. Starch corn : Triticum amylum. 
 
 3. One-grained wheat, Lesser Spelt : Triticum monococcum. 
 
 This is n'ot the place to enumerate the large number of separate varieties, 
 Technically they are divided into three groups according to the properties of the 
 grain, as follows : viz. 
 
 (1.) Hard or horny wheat, with hard, dense, somewhat translucent reddish grain, 
 the least hygroscopic giving little bran when ground, and a tolerably white flour, rich 
 in albumen, fat and salts. 
 
 (2.) Soft or white wheat, with soft white non-translucent grain, rich in flour, 
 but poorer in gluten, fat and salts than the foregoing, and easily ground to a fine white 
 flour. 
 
 (3.) Half-hard white, intermediate in its characters between the two foregoing, 
 without in any decided degree having the properties of either. This group is specially 
 valued for the preparation of flour, because the separation of the bran is easily effected 
 and the groats by grinding yield a very fine white flour. 
 
 Structure of the Wheat Grain. The ripe wheat grain is of a cylindrical form, 
 rounded at both ends, furrowed longitudinally on one side. The exterior of the grain, 
 especially at one end, is clothed with fine hairs. These hairs present most favourable 
 opportunities for the adhesion of spores and fungi which come into contact with them, 
 and thus indirectly lead to the destruction of the grain. 
 
 In a cross section of a grain of wheat the unaided "eye can distinguish three 
 essential parts ; the husk, the mealy portion, and the embryo. The membrane forming 
 the husk or testa envelopes the grain uniformly; it consists of considerably elongated, 
 thickened, and dried cells, as represented in fig. 554. It is too indigestible for human 
 
778 
 
 BREAD. FLOUR. ETC. 
 
 food, in consequence of the amount of cellulose it contains, but it is rich in nitro- 
 genous substances, fat, and salts. Immediately under the husk is a series of tolerably 
 large closely packed thick-walled cells (6), which surround the whole grain and form 
 the gluten layer. These cells are devoid of starch, and are entirely filled with albumi- 
 
 Fio. 554. 
 
 nous matters and oil globules ; upon treatment with iodine they are coloured yellow. 
 The gluten layer forms the outer circumference of the mealy portion of the grain, the 
 remainder consisting of thin-walled cells filled with starch. Finally at one end of 
 the grain, surrounded by the gluten layer of the mealy portion, is the embryo, from 
 
 Fw. 555. 
 
 which by germination the young plant is developed. Fig. 555 represents a vertical 
 section of the grain of wheat. 
 
 Constituents of Corn. Besides the cellulose which forms the membrane of the 
 separate cells, and which in the seed husk is more or less altered, all kinds of corn 
 contain starch, albuminous substances, fats, sugar, etc., and mineral substances. 
 
COMPOSITION OF CORN. 
 
 779 
 
 The form, composition, and properties of starch are described in another section 
 (see p. 757). 
 
 The albuminous matter in wheat is known as gluten ; it can be separated from most 
 of the other constituents by kneading under a flow of water. As left by the water, the 
 gluten is greyish white, tough, elastic, very ductile, in its unaltered condition and 
 having a faint smell. From damaged grain or flour the gluten is separated with 
 difficulty, being washed away in the flow of water. 
 
 Gluten is not a simple substance ; as obtained by kneading wheaten flour in water, 
 it always contains the larger proportion of the fat and mineral constituents, the latter 
 being principally phosphates. By treatment with boiling alcohol three different 
 bodies can be separated vegetable fibrin, casein or mucin, and glutin all of them 
 belonging to the group of albumenoids. The fibrin is insoluble in boiling alcohol 
 and is therefore left behind when the gluten is boiled. The alcoholic solution being 
 concentrated deposits upon cooling a slimy mass of impure casein. This is removed 
 and again treated with absolute alcohol, which removes all fat, etc., and dries up the 
 insoluble casein to a white earth-like mass. The solution, upon further evaporation, 
 after the separation of the crude casein, yields the gluten, which is soluble in 
 boiling and cold dilute alcohol, but insoluble in ether and absolute alcohol. 
 
 In its composition and properties gluten is exceedingly similar to the animal albu- 
 menoids, as they occur in flesh, muscle, etc. As a food material therefore it can re- 
 place flesh, and for this reason food materials prepared from the varieties of corn have 
 a higher food value in proportion as they are rich in gluten. Notwithstanding its 
 great nutritive value too little importance has been attached to gluten. In order to 
 obtain as white a bread as possible, parts of the grain richest in gluten are allowed to 
 go into the bran. In the starch manufacture the gluten is sometimes intentionally 
 destroyed in order to facilitate the separation of the starch. A more perfect method 
 of separating the starch is described on p. 772, by which the gluten is obtained un- 
 altered. The individual constituents are distributed in very unequal proportions in 
 different kinds of corn, and even in the same kind a great difference may occur, 
 according to the influence of climate, weather, soil, manuring, or harvesting. Thus, 
 the hard wheats are always richer in gluten than the soft, and therefore correspond- 
 ingly poorer in starch. The grain richest in starch, and therefore the poorest in al- 
 bumenoids, is rice ; and the richest in fat are maize and oats. In the following table 
 some analyses of different kinds of grain are brought together, though these only 
 approximate to a representation of the average composition, because considerable 
 Variations may be induced by the influence of the conditions of growth. Besides the 
 constituents represented, corn in the air-dried condition always contains from 12 to 
 lf> per cent, of moisture. 
 
 Composition of Different Kinds of Grain. 
 
 
 Starch 
 
 Albumen 
 (Gluten) 
 
 Dextrin, Sugar 
 and similar 
 bodies 
 
 Fat 
 
 Cellu- 
 lose 
 
 Ash 
 
 Hard Venezuela Wheat . 
 
 58-12 
 
 22-75 
 
 9-50 
 
 2-01 
 
 4-00 
 
 3-02 
 
 Hard African Wheat 
 
 64-57 
 
 19-50 
 
 7'60 
 
 2-12 
 
 3-50 
 
 2-71 
 
 Hard Taganrog Wheat . 
 
 63-30 
 
 20-00 
 
 8-00 
 
 2-25 
 
 3-60 
 
 2-85 
 
 Half-hard French Wheat 
 
 68-65 
 
 16-25 
 
 7-00 
 
 1-95 
 
 3-40 
 
 2-75 
 
 Soft Wheat . 
 
 75-31 
 
 11-65 
 
 6-05 
 
 1-87 
 
 3-00 
 
 2-12 
 
 Rye .... 
 
 65-65 
 
 13-50 
 
 12-00 
 
 2-15 
 
 4-10 
 
 2-60 
 
 Barley .... 
 
 65-43 
 
 13-96 
 
 10-00 
 
 2-76 
 
 4-75 
 
 3-10 
 
 Oats . . ... 
 
 60-59 
 
 14-39 
 
 9-25 
 
 5-50 
 
 7-06 
 
 3-25 
 
 Maize .... 
 
 67-55 
 
 12-50 
 
 4-00 
 
 8-80 
 
 5-90 
 
 1-25 
 
 Rice .... 
 
 89-15 
 
 7-05 
 
 1-00 
 
 0-80 
 
 1-10 
 
 0-90 
 
 The flour of cereals is white, bordering upon a yellowish colour ; it has an agree- 
 able smell, and is soft to the touch. With half its weight of water it can be kneaded 
 into an elastic homogeneous dough, in which no hard lumps, bran, or sand, should bo 
 recognisable by the touch, From this dough the principal constituents of the flour 
 can be separated without difficulty. If a continual stream of water be allowed to flow 
 upon the dough during the kneading the starch is washed out, and can be recovered 
 by allowing the liquid to settle ; the gluten finally remains free from starch. 
 
 Flour contains from 12 to 18 per cent, of hygroscopic moisture; this is driven off 
 completely by heating the flour to 100, but moisture is taken up again upon exposure 
 to the air. A high degree of moisture is one of the principal causes of the spoiling 
 of flour, causing it to agglutinate together and become converted into a hard mass ; 
 
780 
 
 BREAD, FLOUR, ETC. 
 
 fermentation also sets in, and through the decomposition of a portion of the gluten 
 the flour then loses its property of making a light, white, palatable bread. Moisture 
 also favours the development of mould, the flour acquiring an impleasant peculiar 
 smell, and becoming more or less injurious to health. 
 
 The finest kind of flour is obtained from several varieties of wheat (Triticum 
 vulgare), and it is the kind chiefly used for making bread. The flour of other kinds 
 of grain, such as rye, oats, maize, barley, etc., are also used to some extent for the 
 same purpose. One of the chief characteristics of the flour obtained from these dif- 
 ferent kinds of cereals is the configuration of the starch granules proper to the 
 several kinds of grain, by means of which it is possible to distinguish one kind of 
 flour from others, and to detect admixtures. 
 
 The flour of cereals is subject to many adulterations, such as admixtures of potato 
 flour, pea flour, the flour of maize and buckwheat flour. Bean flour added in considerable 
 quantity imparts to it a greyish-yellow colour, and the bread prepared from such 
 mixed flour has an unpleasant taste and smell. Moreover, the gluten is also acted 
 upon, so that the bread does not rise. An addition of 4 per cent, of bean flour is quite 
 manifest by the heaviness of the bread. 
 
 The starch granules of wheat are generally round, disc-shaped, and without any 
 recognisable hilum or distinct annular lines, while others are much smaller, frequently 
 
 truncated at one end, and present at the 
 rounded end a tolerably distinct hilum 
 with concentric marks, as shown in 
 fig. 556, representing wheat flour as 
 magnified 420 diameters. To the right 
 hand of the drawing is shown the ap- 
 pearance of the cells containing the starch 
 granules. 
 
 The starch granules of the bean 
 (Faba sp.), represented by fig. 557 as 
 magnified 420 diameters, are characterised 
 by their uniform or oval shape. The 
 hilum appears very distinctly as a simple 
 or multiple longitudinal fissure, and in 
 bean flour the thickness of the walls of 
 the cells containing the starch granules 
 FIG. 556. is considerable, as shown at the lower 
 
 part of the drawing. 
 
 Bean flour is sometimes used to adulterate wheat flour, but palatable bread can 
 be prepared from mixtures containing up to one-third part of bean flour, by adding a 
 larger quantity of salt than is ordinarily used during the preparation of dough. 
 
 FIG. 557. 
 
 Fm. 558. 
 
 The starch granules of the oat (Avena sativa) are smaller than those of wheat 
 and tolerably uniform in size, truncated on several sides, and thus often presenting a 
 polygonal figure (a a, fig. 558, which represents oat flour magnified 420 diameters) It 
 is without a recognisable hilum or rings. A characteristic feature of this starch is 
 the aggregation of a number of granules forming rounded masses (b b). The tissue (c) 
 of the cells is very delicate, presenting a filiform appearance. 
 
 The starch granules of barley (Hordeum distichon) are partly large and partly 
 much smaller, as shown in fig. 559, representing barley flour magnified 140 diameters*. 
 
CHARACTERS OF FLOUR. 
 
 781 
 
 The larger granules sometimes present distinct rings, and many of them a longitudinal 
 furrow. The tissue of the cells is delicate and filiform. 
 
 FIG. 559. 
 
 FIG. 560. 
 
 The starch granules of rye (Secale cereale) are partly large and partly much 
 smaller, the larger granules presenting a very distinctly marked stellate hilum. The 
 tissue of the cells presents some resemblance to that of wheat flour, as shown in 
 fig, 560, representing rye flour as magnified 420 diameters. 
 
 The starch granules of Indian corn or maize (Zea Mays) are rounded or indis- 
 tinctly polygonal, often presenting a stellate hilum, as shown in fig. 561, which repre- 
 sents Indian corn flour magnified 420 diameters. 
 
 FIG. 561. 
 
 FIG. 562. 
 
 The starch granules of rice (Oryza sativa) are small and generally angular, with 
 well-marked central depressions, as shown in fig. 562, representing rice flour magni- 
 fied 420 diameters. The granules are very similar to those of the oat, but are smaller, 
 while the cells in which they are enclosed are angular and separate readily from each 
 other. 
 
 Other methods of testing samples of flour and bread have been given by Donny. 
 
 (1.) Adulteration with Potato Starch. A thin layer of the suspected flour is 
 moistened with a 2 per cent, solution of potash and examined under a strong magni- 
 fying glass or a microscope. The wheat starch undergoes no change, whilst the potato 
 starch swells considerably, retaining the contour of the granule. The change may be 
 rendered more distinct by treating the partially dried mass with solution of iodine. 
 
 The presence of potato meal in bread may be detected in a similar manner. If a 
 little of the bread crumb be moistened with potash solution and covered with a glass, 
 the large granules of potato starch, greatly swollen and intensely coloured by the 
 iodine, can, if present, be easily recognised by the aid of a magnifying glass. 
 
 (2.) Adulteration with Rice or Maize Flour. The suspected flour is kneaded under 
 a jet of water and the liquid passed through a fine sieve. The starch is collected, 
 washed, and examined, under a microscope. If the sophistication has occurred, the 
 angular granules, which are formed in rice and maize through the excessively filled 
 cells pressing against one another and adhering together, can be easily found. The 
 single granules of maize and rice adhere so closely together that they do rot fall 
 asunder, but ordinarily retain the form of the surrounding cells or their fragments. 
 
782 BREAD, FLOUR, ETC. 
 
 (3.) Adulteration of Eye Flour or Bread with Linseed Meal If linseed meal 
 be moistened with a 10 per cent, potash solution, a large number of very characteristic 
 small bodies become manifest, which are of smaller dimensions than potato starch, 
 have a glassy appearance, and are mostly red in colour, and square or oblong in 
 shape. These are fragments of seed husks, and are so characteristic that they can 
 with certainty be found if the rye flour contains only 1 per cent, of linseed meal. In 
 examining the bread or flour for this adulteration a little should be moistened with the 
 potash solution on the object-glass of a microscope. The adulteration of rye flour 
 with oatmeal cake was very prevalent in Belgium and the North of France in the 
 years 1846 and 1847. 
 
 (4.) Adulteration with Buck-wheat Flour. This adulteration may be detected with 
 a glass by proceeding in the same way as in testing for maize and rice flour. Buck- 
 wheat flour yields polyhedric masses of starch resembling that of maize ; but from this 
 it can be distinguished by the agglomeration of the simple cells. 
 
 (5.) Adulteration of Corn Flour with Leguminous Meal. The meal of leguminous 
 plants (beans, peas, vetches, lentils, etc.) always contains the cellular tissue of the seed 
 from which it is prepared, and its characteristic form renders its detection possible. 
 The flour is spread out upon the object-glass and moistened with a 10 per cent, potash 
 solution. The starch of the cereals is dissolved and disappears, whilst the form of 
 the leguminous cellular tissue is made more clear and can be recognised with a glass. 
 An admixture of the meal of beans and vetches can also be detected through the 
 peculiar reaction when treated successively with nitric acid and ammonia. Bean meal 
 and vetch meal are coloured red, whilst the flours of different kinds of corn acquire a 
 yellow colour. In mixtures containing these kinds of meal red spots are produced in 
 number corresponding with the amount of foreign admixture. The best method of 
 applying this test is to spread out the flour round the sides of a white porcelain vessel ; 
 place inside this a smaller vessel containing concentrated nitric acid, cover the whole 
 with a glass plate, and then gently warm them in order to bring the acid vapour in 
 contact with the flour. As soon as part of the flour has become yellow, the small dish 
 containing the acid is replaced by one containing ammonia, the vapour of which is 
 allowed to act for some time. If leguminous meal be present, it soon assumes a red 
 colour perceptible to the naked eye and appearing under the glass in red spots. With 
 pure corn flour only a yellow colour and yellow spots are observed. 
 
 For the detection of bean meal and vetch meal in bread an aqueous extract is 
 prepared, which would contain the matters that are coloured red by the action of nitric 
 acid and ammonia. A portion of the crumb mixed with cold water is heated to boiling 
 and thrown on a sieve. After a time the clear liquid is poured off from the sediment, 
 evaporated in a water bath to a thick extract, treated with alcohol, and the alcoholic 
 solution evaporated. There is then left upon the sides of the capsule a layer of the 
 extracted substance, which can be submitted to the successive action of the vapours 
 of nitric acid and ammonia. 
 
 (6.) Detection of Wheaten Flour in Rye Flour. There are many places where a 
 tax is levied upon, all food introduced, such as flesh, bread, flour, etc. As a rule the 
 kinds of flour principally used by the poorer classes are less highly taxed than others 
 which yield a finer bread suited for the consumption of the more wealthy inhabitants. 
 This renders possible attempts, by representing wheaten flour or mixtures of the two 
 as rye flour, to escape with paying the lower tax. Doubtful cases not unfrequently 
 arise where the taxing officer confiscates a suspected flour, and the expert has to give 
 an opinion on oath whether a sample submitted to him has been prepared from wheat 
 or rye, or whether it only contains an admixture of wheat. The only possibility of a 
 determination depends upon a difference which ordinarily is manifest between the 
 gluten of wheat and the gluten of rye. Whilst the gluten of wheat forms, as a rule, 
 when kneaded, a plastic, elastic mass, the gluten of rye is iisually wanting in this 
 property. If a dough be kneaded from rye flour and washed in a stream of water, the 
 dough has a tendency to dissolve and the gluten to be washed away with the starch ; 
 whilst that from wheat remains behind as a plastic mass. This is the only difference 
 between normal wheaten flour and normal rye flour. It has already been mentioned 
 that the smallest alteration in the flour, through sprouting of the grain or fermentation 
 of the finished product, is at once shown in the changed properties of the gluten, which 
 loses its toughness and elasticity. The wheat gluten then behaves exactly as rye 
 gluten, and is washed away by a stream of water. 
 
 The tenacious character of wheat gluten can, however, be restored by various 
 agents. If flour from sprouted wheat, or fermented flour, be kneaded with common 
 salt, lime water, or alum, the gluten recovers its original toughness and elasticity. 
 Eye flour behaves in a similar manner. If a dough be made of rye flour with the 
 addition of a small quantity of lime water, and washed, the gluten obtained has all 
 the properties of wheat gluten, or at most is a little less elastic. 
 
PRESERVATION OF CORN. 783 
 
 As therefore the two kinds of gluten differ so little that wheat gluten can be 
 changed by moisture or fermentation so as no longer to be distinguishable from that 
 of rye, whilst rye gluten may be altered by a small quantity of lime acquired from 
 the soil in which the plant grows, the small differences between them cannot be 
 sufficiently characteristic to furnish scientific evidence for a court of justice. The light 
 spongy property of well-made bread is dependent upon certain qualities of the gluten. 
 When obtained from good flour this is elastic, soft, pliable, and ductile ; upon rapidly 
 heating it to 200 it swells up considerably. These properties are met with princi- 
 pally in wh eaten flour ; from other kinds of meal an adherent gluten cannot, as a 
 rule, be separated. Every change in flour induces a change in the properties of the 
 gluten present in it, so that from fermented flour light bread cannot be prepared. 
 These changes may commence as early as the harvest, through continued wet, sprout- 
 ing, etc. 
 
 The properties of the gluten in various kinds of flour may also be turned to account, 
 in comparing the value of different kinds of flour and detecting adulteration. 
 
 Potato Flour. For a long time it was sought to bring the potato by desiccation 
 into such a form that it would be preserved from spoiling, and to prepare from it a 
 concentrated food that could be transported for long distances such as sea voyages 
 without ihe necessity of carrying 75 per cent, of water with the 25 per cent, of food 
 material. No great success was attained in this direction until Chollet invented a 
 method by which a faultless material could be prepared at a comparatively low cost. 
 
 Potato meal is not very liable to spoil, and will keep for a considerable time in 
 dry places. A considerable quantity of this article is imported from France into 
 England, and is used specially in the provisioning of emigrant ships. 
 
 Hollands Test for Wheaten Flour. 25 grams of flour are kneaded into a dough 
 with 12 or 13 grams of water ; the mass is then allowed to stand some time in order 
 to allow the gluten to swell completely, which in warm weather requires about half 
 an hour and in winter 1 hour. The dough is then kneaded under a gentle stream of 
 water until the water flows off colourless, and the moist gluten is well drained. 
 From this 5 grams are weighed off, rolled into a ball, and allowed to drop on to the 
 bottom of a small brass cylinder, the interior of which is slightly smeared with oil. 
 The cylinder is then placed in an oil bath, previously heated to 210, in order to heat 
 the gluten rapidly. The vaporisation of the enclosed water causes the elastic mass 
 of gluten to puff up and lift a light piston to a distance corresponding with the increase 
 in volume. This increase is proportional to the quality of the flour, and amounts to 
 from 2 to 6 times the original volume of the gluten. The experiment can be con- 
 trolled by taking out the gluten remaining in the cylinder, drying it completely at 
 100, and taking its weight. 
 
 If it is desired to estimate the quantity of starch also, the wash water from the 
 gluten is poured upon a fine sieve in order to retain any detached gluten and traces 
 of bran, and the starch is allowed to settle. After clearing, the water is decanted off, 
 the starch is washed once with pure water, dried, and weighed. 
 
 With the estimation of the starch a test for adulteration with potato-starch flour 
 can be easily combined. For this purpose the starch is washed with a small quantity 
 of water into a conical glass, and allowed to settle. The larger and heavier granules 
 of potato starch sink to the bottom most rapidly, and are found at the extreme point 
 of the cone formed by the settling of the starch. The upper portion is removed with 
 a spatula, and the lower layers are submitted to a microscopical examination, when 
 the potato starch can be at once recognised by its form and size. 
 
 Preservation of Corn. In countries where agriculture constitutes the chief occupa- 
 tion of the people, and where a relatively small number of inhabitants cultivate a 
 large area of land, considerably more corn is produced than is consumed, except 
 in years when the crop fails. In more thickly populated countries also there are 
 sometimes years of plenty when the produce exceeds the demand. Under such con- 
 ditions the storing of corn and its protection from decay become of great impor- 
 
 Care for the preservation of corn needs to commence as Dearly as the harvest ; for 
 frequently the basis of after decomposition is laid at that time, and a large propor- 
 tion of grain becomes injured through negligent treatment. By exposure to moisture 
 the corn begins to sprout in the ear, and its value is diminished ; or_it is attacked^by 
 fungi and becomes mouldy and rotten. One method of preventing rain from damaging 
 corn consists in standing a number of sheaves upright together, and inverting above 
 them another sheaf, in such a manner that the downward hanging ears form to some 
 degree a roof for the others. Sometimes four or more sheaves are placed upright close 
 together, or one is placed in the middle, and the others are packed around, and se- 
 
784 BREAD, FLOUR, ETC. 
 
 cured closely together at the top by a band (fig. 563), and then covered with another 
 sheaf (fig. 564). The grain is thus perfectly protected from wet, as the rain flows off 
 
 FIG. 563. FIG. 564. 
 
 rapidly from the downward hanging straw of the covering without penetrating. The 
 sheaf further presents the great advantage of favouring the full maturity of the corn, 
 the sap constituents contained in the stalk becoming concentrated in the grain, and a 
 better product yielded. On the other hand, more labour and time are required by this 
 method than by the ordinary ones, and the scarcity of labour at harvest time prevents 
 it being generally adopted, notwithstanding its acknowledged advantages. 
 
 Equal protection is afforded by the stacking of corn, if the stacks are protected in 
 a similar manner. Hei'e the sheaves are not arranged in a circle, but in two rows 
 leaning against each other, with the ear upwards ; above these is placed a covering 
 of sheaves with the ear downwards. The rain is thus kept off, whilst free ventilation 
 is secured. By this method also the corn can be harvested before it is perfectly ripe, 
 and the quantity and quality of the grain augmented. 
 
 Not only during the harvest, but in the granary also, corn is exposed to many 
 causes of decay, which require to be combated by the greatest care and by different 
 methods of preservation. Notwithstanding the ordinary precautions, frequently 
 upwards of 12 per cent, of the harvested corn is lost in a single year. 
 
 The greatest injury to corn is caused by insects ; moisture also induces fermenta- 
 tion and putrefaction ; and further damage is done by rats, mice, and similar animals. 
 
 The principal destroyers of corn are the black corn worm or corn weevil 
 (Curculio granarius, L. ; Calandra granaria, Fab. ; Sitophilus granarius, Schcen.), and 
 the white corn worm, or corn moth, or wolf ( Tinea granella, L. ; Alucita aranella, 
 Fab.) 
 
 The black corn worm, or corn weevil, belongs to the tribe Rkyncophus. It is 
 about a twelfth of an inch long ; when young it is light brown, but it gradually be- 
 comes darker, and at last almost black. During the winter the weevil remains in 
 chinks and crevices of the rafters and boards ; but at the beginning of the warm 
 weather it comes forth and the female lays 100 to 150 eggs, each one in a separate 
 grain just under the husk. From these eggs shortly afterwards escape worms pro- 
 vided with strong mandibles, which using the contents of the grain for food and the 
 hull for a domicile, pass there their pupa existence. Six weeks after the laying of the 
 eggs the perfect insects are formed, and other similar augmentations take place. It 
 has been calculated that a dozen pair of these pests will bring forth during the warm 
 weather 75,000 individuals. Should this dozen pair nestle in five or six bushels of 
 wheat and each of their progeny destroy only three grains, the loss would amount to 
 at least 12 per cent. The destruction caused, however, appears somewhat to depend 
 upon the insect being left undisturbed, and to be diminished by frequent shovelling 
 and sifting of the corn. The insect, moreover, can with difficulty withstand strong 
 currents of air, especially in the winter ; a thorough ventilation of the granary there- 
 fore is one of the most certain preventives against its ravages. 
 
 The white corn worm, or corn moth, is a small moth with front wings of a light 
 yellow colour spotted with black, and dark grey hinder wings. It makes its appear- 
 ance with the beginning of warm weather ; during two weeks the female lays eggs, 
 depositing them either singly or two together in a grain of corn, showing a prefer- 
 ence for rye. After a short time from each egg is hatched a yellow worm, which 
 
PRESERVATION OF CORN. 
 
 785 
 
 dovours the grain, then passes to another, and so on until the end of the summer. It 
 passes the winter as a caterpillar, enters the pupa state in the spring, and is trans- 
 formed at the commencement of summer into the perfect moth. Turning and sifting 
 of the corn is only an imperfect remedy against these troublesome insects, as only a 
 portion of them are destroyed by the operation. 
 
 Besides injury by insects, the grain is affected by fermentation and decay. If it is 
 too fresh when threshed and brought damp into the granary, it easily becomes 
 heated; mould accumulates, setting up different kinds of fermentation, which 
 generally end in putrefaction. Different methods have been suggested for the pre- 
 servation of corn, and carried out with more or less satisfactory results. They aim 
 at: 
 
 (1) Thorough airing or vent : lation of the corn by continued motion. 
 
 (2^ Perfect drying by means of heated air. 
 
 (3; The preservation of the grain in grain pits dug in dry soil. This method is 
 adopted in southern countries Southern France -and Spain and Africa with satis- 
 factory results, but it is only suited for localities possessing a sufficient dryness of 
 soil. 
 
 For these different methods the following forms of apparatus have been con- 
 structed : 
 
 Vallcry's Apparatus (grenier mobile) consists of a large wooden cylinder (d d d d, 
 fig. 565, transverse section; fig. 566, longitudinal section), the frame being made of 
 strong staves bound together with iron hoops. Within this is a much smaller 
 cylinder (M M), bound to it by strong cast-iron end plates, which at the same time 
 close the ends. Round the circumference of both cylinders are a large number of 
 oblong openings (o o'), covered with wire gauze. The space between the two cylin- 
 ders is partitioned off into eight equal divisions (A, B, c, etc.) for the reception of the 
 corn, and each of these is again divided by three cross partitions into four small com- 
 partments, making thirty-two in all. The cylinder rests upon a strong wooden 
 frame (g), and can be easily rotated upon its axis by means of a cogwheel (b), 
 working a toothed wheel (a) at one end. At the same time as the cylinder is slowly 
 revolving the shafts of the ventilator (/) are set in motion very rapidly by the 
 driving straps (i e). The ventilator being in communication with the interior of the 
 smaller cylinder (M), air is thus drawn through the openings (o <?) in the outer cylin- 
 der, through the corn, and finally through the inner cylinder to the ventilator. The 
 strong current of air dries the corn perfectly ; whilst the motion destroys the worms 
 and rubs off the adhering eggs which fall through the meshes. For filling and 
 emptying the apparatus some of the wire-gauze coverings in each compartment are 
 fixed in sliding frames. The cylinder is about 30 feet long and 15 feet in diameter. 
 
 FIG. 565. FIG. 566. 
 
 The inner space will- hold about 3.850 bushels, but in order to allow of the movement 
 of the grain only about 2,750 bushels are used. 
 
 ConincKs Apparatus is based upon the same principle of agitation and ventila- 
 tion, but is differently constructed. It is a square brickwork shaft, having walls 
 each about -10 feet wide and 50 feet high, and holding nearly 3.4CO bushels. The 
 shaft is divided by seven horizontal layers of beams which act as supports for strong 
 plates of zinc. Two of these, contracting funnel-wise and not far apart, are placed in 
 each interval between the joists, so that the floor -thus formed is broken by long 
 slits, the slits being wider in the lower than in the upper floors. When all the com- 
 partments are full of corn, if a small portion, about ten per cent, of the whole, be 
 
 3E 
 
786 BREAD, FLOUR, ETC. 
 
 allowed to run out rapidly at the bottom, the entire mass is set in motion. But 
 through the unequal width of the interstices this movement is not uniform, the corn 
 passing out from each compartment more rapidly than it is replaced from the one 
 above, and this causes a current of air to be drawn in through side openings covered 
 with wire- gauze. The corn which runs out from the lowest compartment is raised to 
 the top by a chain-pump arrangement. 
 
 Huarfs Apparatus. An apparatus has been introduced into the military depart- 
 ment in Paris very similar to the preceding, but having sheet-iron sides instead of 
 walls. Each shaft is divided by 24 to 28 lattice-work screens made of iron rods. The 
 corn is set in motion by the opening of a door in the lowest compartment. 
 
 Devaux's Apparatus is also an iron shaft 32 feet high and 4 feet in diameter, but 
 it differs from the preceding in having its sides perforated with small holes. A pipe 
 to | inch in diameter, closed at the top and finely perforated over its whole sur- 
 face, passes through the shaft, and ventilation is effected by forcing through it a 
 strong current of air. 
 
 Preservation in Pits (Silos). Earth pits or silos are only suitable for keeping 
 corn in hot countries. Brickwork silos, that can be closed air tight, or large metal 
 receptacles, have also been recommended. In order to protect corn placed in them 
 from decay several methods have been described. Persoz and Petitot recommend the 
 introduction of quick lime in baskets covered with" wire gauze ; the lime absorbs 
 moisture, so that even sprouted corn can be thus preserved. An experiment made by 
 Petitot with wheat harvested in wet weather showed that at the end of five years it 
 was perfectly sound and fit for making into bread. 
 
 According to Doyere and G-arreau the most certain means of extirpating the corn 
 worm in such silos is by using a small quantity of bisulphide of carbon. About 1 
 part by weight to 50,000 of the corn is sufficient to destroy all insects, and even the 
 eggs in five or six days. About 5 parts to 100,000 will have the same effect in 
 twenty-four hours. 
 
 Production and Preservation of Potatoes. The potato is unquestionably one of the 
 most useful crops in agricultural economy, inasmuch as it leaves the ground upon 
 which it is cultivated in capital order for the next crop in rotation, and in regard to 
 yield is excelled by no other crop. A comparison of the yield of different crops 
 shows that the potato takes the first place, as may be seen from the following table : 
 
 
 Average Production 
 per Acre in Tons 
 
 Total Dry Matter 
 in Cwts. 
 
 Potatoes . . . . . . J . 
 
 21 to 28 
 
 54- to 6A 
 
 Jerusalem artichoke . . , 
 
 19 23f 
 30 40 
 
 3f 4f 
 4i 5 
 
 Swedish turnips . . . ,., 
 Wheat 
 
 18 22 
 
 H 1* 
 
 l| If 
 
 1 , 4 
 
 The potato crop and the quality of the potatoes depend upon the soil and the state of 
 the weather, the amount of starch yielded by potatoes varying so considerably that it is 
 hardly possible to make an estimate of the yield of any sort of potato. According to 
 some experiments of Payen, the yield of starch from various kinds of potatoes grown 
 in France varied from 3 to 5 tons per acre. The Eohan potato is still more pro- 
 ductive, in starch, but its tubers are very watery, and on this account it is not much 
 liked by the manufacturer. Scotch shaws, a very favourite early potato, is for the 
 most part used as food; it is, however, much prized by starch manufacturers, as its 
 early maturity enables them to begin work early in the year. 
 
 The starch contents of gathered potatoes does not remain constant, but decreases 
 continually, owing to the growth of the tubers. Potatoes laid in heaps generate heat, 
 and begin to germinate, producing rootlets and young shoots. All these processes 
 depend upon the formation of new cells, the material for which is supplied by the 
 starch in the potato, it being converted into the cellulose constituting the membrane 
 of the cells. Hence it happens that potatoes which immediately after harvesting 
 yield 17 to 18 per cent, of starch, yHd in January and February only 15 per cent., and 
 in March and April not more than 13 per cent. The starch manufacturer, therefore, 
 endeavours by suitable storing to suppress germination in the potatoes as completely 
 as possible, and also so to conduct his operations as to finish the starch manufac- 
 ture within four months of the harvest. 
 
 In order to protect the potatoes as far as is possible from spontaneous changes 
 they are stored in dry chambers, the temperature of which is low without sinking to 
 zero, and which are protected as completely as possible against changes of tempera- 
 
COMPOSITION OF POTATOES. 787 
 
 tore. Cellars and pits in the earth are used for this purpose. It is necessary in 
 storing the potatoes to keep out diseased and rotten tubers, as these would affect the 
 sound ones. The construction of the earth pits depends upon the soil ; where this is 
 moist the pits are made shallow, ditches are dug round them, and the potatoes are 
 piled up partly above the mouth of the pit, and covered with the earth taken from the 
 ditches. Where the soil is dry the pits are made deeper. The pits are generally 
 about 5 feet wide at the bottom, and at the mouth 6 feet. The walls or sides of the 
 pits being sloped. The depth of the pits is about 3 feet ; the length varies between 
 60 and 320 feet. 
 
 In some manufactories, potatoes are stored in brickwork pits, and covered either 
 with earth or straw. Dailly employs pits of this kind, sunk 5 to 6 feet deep in the 
 earth, 160 to 200 feet long, 25 feet wide, and 8 to 10 feet high, a slate or thatched 
 roof protecting them from rain and moisture. The pits are filled and emptied through 
 openings in the walls, which are closed in winter with straw to keep out the cold. 
 Although the first cost of such pits is considerable, the expense of the yearly construc- 
 tion of the simple pits is saved. 
 
 Brickwork pits are especially serviceable where the soil is moist. They are, how- 
 ever, little used in Germany, the agricultural system in that country seldom allowing 
 sufficient time during the harvest for conveying the potatoes to the manufactory from 
 distant parts of the farm ; the potatoes are simply buried in the earth, and in winter 
 when the weather permits are transported to the manufactory in quantities sufficient 
 for a few days. 
 
 In burying potatoes special care must be taken that they are sufficiently protected 
 from frost, which may be secured by sufficient warm covering, and careful reclosing 
 of such pits as have been opened but not emptied. Should any potatoes be frozen, 
 however, for the manufacture of starch it is better to use them in the frozen state 
 than to thaw them, as this renders the cells soft, and the membranes, which were 
 before impenetrable by the sap, allow the sap to escape freely through them. Such 
 potatoes are but incompletely torn in the rasping machine, and since starch only 
 escapes from open cells a loss of material is occasioned. When frozen potatoes are 
 worked up, the teeth of the rasping machine may, perhaps, suffer a little, but the 
 proper quantity of starch is extracted. 
 
 Composition of Potatoes. It has been already mentioned that the starch contents 
 of potatoes is influenced by a number of circumstances ; t,he same may be said of the 
 other constituents of the potato. For this reason approximate figures only can be 
 given for their percentage composition. The following is the average percentage 
 composition of good potatoes : 
 
 Water 74'00 
 
 Starch 20'00 
 
 Epidermis, cellulose, pectose, and colouring substances . . 1'65 
 Albumen and other nitrogenous substances .... 2'12 
 
 Fat 0-11 
 
 Sugar, resin, volatile oil -. 1'06 
 
 Salts and ash constituents . . . . ' . . . 1'06 
 
 
 100-00 
 
 The amount of starch in different sorts of potatoes grown under equal conditions 
 varies between 12 and 14 per cent.; although the fluctuation is not so great in 
 potatoes of the same kind it is liable to considerable variations. For this reason, 
 therefore, it is important that the starch manufacturer should examine the potatoes 
 to be used, so as to ascertain their quality. 
 
 The testing of the starch contents of potatoes is based upon the fact that starch 
 has a considerably higher specific gravity than water; the richer, therefore, the 
 potatoes are in starch, the greater is their specific gravity . A table has been Con- 
 structed, showing the percentage of starch in potatoes of different specific gravities. 
 The determination of the specific gravity is accurately accomplished with a very 
 simple apparatus. It consists of a glass cylinder, having a capacity of about 5 pints, 
 the upper rim of which is ground ; the cylinder itself is supported upon a wooden 
 foot. The foot is furnished with 'three screws for bringing the cylinder into an 
 exactly upright position. The volume of the cylinder up to a certain point is deter- 
 mined once for all by measuring with water. This point corresponds with the length 
 of a finely pointed brass rod, which is fastened vertically upon a small brass plate. 
 The cylinder is brought into a perfectly upright position by means of the screws at the 
 foot, so that the bubble in a water-level laid on its edge shall rest exactly in the middle. 
 From a measure graduated to cubic centimetres so much water is then poured in as to 
 nearly but not quite reach the point corresponding with the length of the brass rod, 
 which should be previously scratched on the side of the cylinder. The brass rod is 
 
 3 E 2 
 
788 
 
 BREAD, FLOUR,, ETC. 
 
 then suspended in the cylinder, and water is carefully added drop by drop until the 
 point of the rod exactly touches its image reflected on the surface of the water. As 
 the brass rod marks an invariable length, the expansion through changes of tempe- 
 rature being too inconsiderable to be taken into consideration, a point can thus be 
 fixed, the volume of the cylinder up to which could be determined by measurement 
 once for all. 
 
 In making the test, about five pounds of potatoes are selected which fairly repre- 
 sent the average of the bulk. These are washed perfectly clean, a brush being used 
 if necessary, then dried with a clean cloth, and the weight taken in grams. They are 
 then placed in the empty cylinder, previously brought perfectly upright, and water 
 added until the surface comes exactly into contact with the point of the rod. The 
 quantity of water used will be less in proportion to the larger volume of the potatoes. 
 In a case where the volume of the cylinder up to a fixed point was 3,185 cubic centi- 
 metres, and the sample of potatoes used weighed 2,960 grams, if 514 cubic centimetres 
 of water were used the volume of the potatoes used would be 3,185 514 = 2,671. 
 
 The specific gravity of the potatoes could then be easily calculated : 
 
 2960 
 2671 
 
 1-108. 
 
 According to the following table, which is based on numerous experiments, a specific 
 gravity of 1-108 would correspond with 20'61 per cent, of starch contents : 
 
 Table of the Average Contents of Potatoes in Starch according to their 
 Specific Chravity. 
 
 Specific 
 Gravity 
 
 Contents in 
 Starch per cent. 
 
 Specific 
 Gravity 
 
 Contents in 
 Starch per cent. 
 
 Specific 
 Gravity 
 
 Contents in 
 Starch per cent. 
 
 1-072 
 
 12-22 
 
 1-089 
 
 16-11 
 
 1-106 
 
 20-13 
 
 1-073 
 
 12-45 
 
 1-090 
 
 16-35 
 
 1-107 
 
 20-37 
 
 1-074 
 
 12-67 
 
 1-091 
 
 16-58 
 
 108 
 
 20-61 
 
 1-075 
 
 12-90 
 
 1-092 
 
 16-81 
 
 109 
 
 20-85 
 
 1-076 
 
 13-12 
 
 1-093 
 
 17-05 
 
 110 . 
 
 21-09 
 
 1-077 
 
 13-35 
 
 1-094 
 
 17-28 
 
 Ill 
 
 21-33 
 
 1-078 
 
 13-58 
 
 1-095 
 
 17-52 
 
 112 
 
 21-57 
 
 1-079 
 
 1381 
 
 1-096 
 
 17-76 
 
 113 
 
 21-81 
 
 1-080 
 
 14-04 
 
 1-097 
 
 17-99 
 
 114 
 
 22-05 
 
 1-081 
 
 14-27 
 
 1-098 
 
 18-23 
 
 115 
 
 22-30 
 
 1-082 
 
 14-50 
 
 1-099 
 
 18-46 
 
 116 
 
 22-54 
 
 1-083 
 
 14-73 
 
 1-100 
 
 18-70 
 
 117 
 
 22-78 
 
 1-084 
 
 14-96 
 
 1-101 
 
 18-93 
 
 118 
 
 23-03 
 
 1-085 
 
 15-19 
 
 1-102 
 
 19-17 
 
 119 
 
 23-27 
 
 1-086 
 
 15-42 
 
 1-103 
 
 19-41 
 
 120 
 
 23-52 
 
 1-087 
 
 15-65 
 
 1-104 
 
 19-65 
 
 121 
 
 23-76 
 
 1-088 
 
 15-88 
 
 1-105 
 
 19-89 
 
 122 
 
 24-01 
 
 Potato Disease. The special malady of the potato, known as the potato disease, 
 first broke out in the United States in 1843 ; two years later it made its appearance 
 in Europe, and rapidly spread over the various countries. The disease is due to the 
 penetration and growth of a fungoid parasite, Perenospora infestans (the Botrytis 
 wfestans of Montagne). The mycelia of this fungus penetrate either through the 
 fissures in the plant or directly through the membrane of the outer cells, and spread 
 with extraordinary rapidity in the tissue, where they fructify and throw off myriads 
 of new spores. From the leaves the fungus spreads over the stalk to the tuber, 
 where it impoverishes the cells by dissolving the starch, and absorbing the remaining 
 mineral and organic substances. In this condition the fungus may lie dormant in 
 the tuber during the winter, and in the spring set? up a fresh growth. But ordinarily 
 the destruction commenced by the fungus is accompanied by a putrefaction which 
 destroys the entire tuber and very frequently the fungus with it. 
 
 If a potato only just attacked be cut, brown spots can be seen which spread from 
 the stalk, where they are most developed, to the extremity. These discolorations 
 are due to the parasitic vegetation which fills the tissues, mnking it more resistant 
 and less transparent. If sucli a potato be boiled for four hours in water, the parts 
 that have not been attacked by the fungus appear mealy and soft, as is usual with a 
 sound potato ; but the spotted parts, the colour of which is intensified by the boiling, 
 become firmer, and can no longer be crumbled between the fingers. 
 
 By the action of the fungus the starch is dissolved and converted into carbonic 
 acid and water, whilst the albumen, fat, etc. are used in the formation of tissue. The 
 disappearance of the starch can be recognised by the naked eye in a very thin section, 
 
BREAD MAKING. 789 
 
 but it can be made more evident by boiling such a section in water, and treating it 
 with an aqueous solution of iodine. The parts yet unattacked are coloured intensely 
 blue, whilst the parts in which the fungus occurs is not coloured. If the brown 
 portion of the boiled tuber be removed and treated for several hours with boiling 
 water acidified with sulphuric acid, the residue remaining after drying has the 
 same composition as has been observed in other fungi, containing 8'75 per cent, of 
 nitrogen. 
 
 The disease can easily be communicated by contact with a diseased potato, especi- 
 ally to freshly cut surfaces. During the preservation it readily spreads in the pits ; 
 the greatest care is therefore taken not to bury potatoes visibly diseased with the 
 sound ones. Should the disease break out in the pit, the only method to limit the 
 injury is to work the potatoes up as rapidly as possible, as the loss increases from 
 day to day. Many of the starch granules become hollowed out by the fungus, and 
 set up a fermentation in the liquid. This fermentation can be controlled by adding 
 O'l per cent, of sulphurous acid to the liquid, which stops the agitation in the liquor, 
 and facilitates the settling of the starch. Such potatoes can be used in the prepara- 
 tion of spirit. 
 
 The pulp remaining from the working up of diseased potatoes may be used with- 
 out danger as fodder, and it can be preserved in pits without decomposing. 
 
 The Preparation of Bread is in general extremely simple ; but it involves certain 
 difficulties if the object be to obtain a spongy, light, well-flavoured bread. The 
 ancient art of bread-making, which in many localities is still practised exactly in the 
 same manner as it was a thousand years ago, has undergone successive improvements, 
 and already in some places has taken rank as a large industry, being carried on with 
 improved machinery. It is not possible to give here an exact description of bread- 
 making, since many modifications depend upon the habits of the consumer, the raw 
 materials, and the products to be obtained. Only the essential points in the manu- 
 facture will therefore be noticed, and especially some of the numerous improvements in 
 the machinery used. 
 
 The separate stages of the operation by which flour is converted into bread are 
 the making of the dough, kneading, fermentation, and baking. 
 
 The making of the dough consists in a uniform saturation of the flour with water. 
 The soluble portions of the flour, i.e. the sugar and dextrin the proportion of which 
 is increased by the action of a peculiar principle (diastase) on a portion of the starch 
 the albumen, and the casein, are dissolved, and the gluten, by the absorption of water, 
 commences to swell. Dough kneaded with water only would yield a close, heavy, dry 
 bread. But, by the addition of yeast, fermentation is induced, which converts the 
 sugar into alcohol and carbonic dioxide. The gas evolved increases the volume of the 
 dough and induces the ri si ng ; for since the escape of the gas is hindered by the tough- 
 ness of the gluten, it forms small bubbles wherever it is evolved throughout the dough, 
 and so produces the sponginess of the finished bread. 
 
 The fermentation of the dough is set up by an alcoholic ferment, beer yeast or 
 pressed yeast. Beer yeast is, however, only used exceptionally on the Continent, 
 because, by the addition of hops, it acquires a bitterness which it communicates to the 
 bread. A more suitable yeast is prepared artificially from an infusion of malt in 
 which fermentation is set up by the addition of pure yeast. The preparation of such 
 artificial yeast is subsequently described under 'Spirit Manufacture.' In the prepara- 
 tion of bread yeast is not always added ; but a portion of the dough in which 
 fermentation has commenced is reserved for the following operation. This sour 
 dough is then added to the fresh dough, and being rich in ferment induces fermenta- 
 tion in the whole mass. 
 
 If sour dough, however, be allowed to stand too long, not only alcoholic but lactic 
 acid fermentation is set up, and it would then induce the same process in the bulk of 
 the dough to which it might be added. In order to confine this secondary fermenta- 
 tion within the requisite limit, care must be taken that in the sour dough the con- 
 ditions most favourable to the alcoholic fermentation are always present. This is 
 effected by continually adding, at short intervals, fresh material in the shape of flour 
 to the dough, an operation which is known, as reviving the sour dough. 
 
 The sour dcugh from previous bakings is kept in a moderately warm place, at as 
 uniform a temperature as possible. It is allowed to stand for seven or eight hours, 
 during which time it gradually increases in size, and gives off a faint alcoholic odour. 
 The first reviving is then effected by kneading with it sufficient flour and water to 
 bring the dough to double its former volume; but no more water is used than 
 necessary, in order to leave as stiff a dough as possible. After about six hours the 
 volume of the dough is again doubled by a second reviving, and a somewhat larger 
 quantity of water is added to soften the dough. Finally it undergoes a third reviving. 
 The additions of flour are so regulated that in winter the sour dough contains one 
 half and in summer one third of the entire quantity of flour to b used. 
 
790 BUEAD, FLOUR, ETC. 
 
 When bread is made in this way the sour dough is stirred up with the whole 
 amount of water to be used in the baking, and kneaded until no more lumps are 
 perceptible in the mass. Flour is then added in small portions, and continually and 
 vigorously kneaded, until the whole of the flour is uniformly distributed throughout 
 the sour dough. The dough gradually becomes more stiff and dry, and it requires 
 considerable power and skill to make the mixture uniform. Nowhere in the mass 
 must any dry spots remain, since they would be found as lumps of flour in the 
 finished bread ; whilst, above all, the sour dough must be thoroughly distributed, as it 
 is only by actual contact with the remaining dough that fermentation takes place. 
 Another object is attained during kneading in the introduction of as much air as 
 possible into the dough ; this air upon being heated expands and contributes to the 
 sponginess of the bread. During the kneading salt is added. This is either strewed 
 in the dry state, or more suitably, in order to secure a better distribution, dissolved 
 in the water used in the first working of the sour dough. The quantity of salt used 
 varies according to the taste of the consumer. The Parisian bakers use about 1 part 
 of salt to 300 parts of flour. 
 
 By the addition of salt, the quality of bread made from flour of which the gluten 
 has lost some of its plasticity, is considerably improved. Bread prepared from sprouted 
 corn with but little salt added is close and heavy. But by using 3 parts of salt to 
 every 100 parts of such flour, the gluten recovers its original elasticity and the bread 
 is spongy and light. A sound, nourishing and well-flavoured bread can be prepared 
 from a mixture containing rye flour and bean meal, if 2 or 3 parts per 100 of salt 
 be added. 
 
 The dough being prepared, it is divided into portions corresponding with the size 
 of the loaf. On an average 1 15 or 116 parts of dough yield 100 parts of bread ; large 
 loaves, however, require somewhat less, as they lose proportionally little moisture in 
 baking, and small loaves more. The separate loaves are then lightly powdered with 
 flour, and placed in the neighbourhood of the oven, the warmth of which favours the 
 fermentation. The fermentation is not continued longer than is required for the 
 rising of the bread, but is arrested as soon as the requisite point is reached by placing 
 the dough in the oven. If the dough were allowed to stand longer, the carbonic acid 
 formed would gradually escape, and the dough would sink together; further, the 
 alcoholic fermentation would be followed by the acetic fermentation, and a badly 
 flavoured bread would result. 
 
 During the baking various changes take place in the dough. The enclosed gases, 
 carbonic acid and air, are increased in volume very considerably by becoming 
 heated, and as the tough dongh mass does not allow them to escape, it is puffed up 
 and increased in size ; so that the sponginess of the bread induced by the fermentation 
 is still further increased by the baking. The alcohol formed during the fermentation 
 behaves in a similar manner, being converted into vapour at the temperature of the 
 oven. The starch swells in contact with water and combines with it at a high tem- 
 perature, and the previously soft moist dough becomes firm and dry. By the strong 
 radiated heat a portion of the starch is converted into dextrin ; this dissolves in 
 the moisture, and upon the evaporation of the latter it remains as a close shining 
 crust upon the top layer of the bread. Lastly, a portion of the dextrin or of the 
 starch is changed into yellow or brown substances, which impart to the crust its 
 characteristic colour. 
 
 According to Mege Mouries, the internal part of the perisperm of the grain, and 
 consequently the bran, contains a peculiar nitrogenous principle capable of acting as a 
 ferment, which he has named cerealine. Like diastase, cerealine has the property of 
 liquefying starch, which is converted into glucose and dextrin, the glucose in its 
 turn being transformed into lactic, acetic, butyric, and formic acids, which partly dis- 
 solve the gluten. To this action Mege Mouries attributes the inferior cohesion of the 
 crumb of bread made from meal containing bran, and its colour. In order therefore 
 to utilise the whole of the farinaceous substance of wheat in the preparation of white 
 bread, he proposes to remove the cerealine before sufficient time has elapsed for it to 
 have been converted, by exposure to the air or otherwise, into a ferment. At first he 
 effected this by submitting about 20 per cent, of the groats, after the removal of about 
 70 per cent, of fine flour, to vinous fermentation, by which the ceroaline was destroyed. 
 More recently he has adopted the plan of diluting the last 8 or 10 per cent, of groats 
 with five or six times its weight in water, and precipitating the cerealine with a solu- 
 tion of common salt. 
 
 Although the rising of the dough and the resulting sponginess of the bread 
 is, as a rule, produced in the above manner, various plans have been sug- 
 gested for attaining the same end without submitting the dough to the process 
 of fermentation. The incorporation with the dough of a solution of bicarbonate 
 of ammonia, which is subsequently completely converted into vapour by the heat of 
 
BREAD MAKING. 
 
 791 
 
 the oven, yields a bread that is very porous, in consequence of the expansion of the 
 gas, but which is not spongy. Moreover there is generally a trace of the ammonia 
 retained in the bread. The production of an evolution of carbonic anhydride by the 
 admixture with the dough materials of a certain quantity of hydrochloric or tartaric 
 acid and bicarbonate of soda has also been recommended. But bread made in this 
 way without fermentation is heavy and clammy, and differs in many respects from 
 fermented bread. The use of tartaric acid, with the resulting formation of tartrate of 
 soda in the bread, is open to obvious objections. 
 
 One method of preparing an unfermented bread, invented by Dauglish, has how- 
 ever met with a certain amount of acceptation in this country. It consists in 
 kneading the flour and salt in water charged with carbonic anhydride under a pres- 
 sure of ten or twelve atmospheres in a closed vessel kept at the same pressure. 
 When this kneading has been carried far enough to impart to the dough the requi- 
 site tenacity, the pressure is removed ; the gas at once seeks to recover its normal 
 volume, and in doing so raises the dough. In consequence of the low temperature at 
 which dough thus prepared is placed in the oven, and the fact that after the first 
 sudden expansion it undergoes a slow springing during heating, until it reaches the 
 boiling point, it has been found necessary to construct a special oven for its baking. 
 This oven is heated through the bottom, and is furnished with the means of regulating 
 the heat at the top. The bread is cooked through the bottom, and when this is 
 nearly completed the top heat is applied and the crust formed. 
 
 Baking ovens are constructed in the most diverse manner and for different kinds 
 of fuel. The simplest form, which has obtained from the most ancient times, and is 
 still very much used, consists of an elliptical hearth, either horizontal or sloping in 
 front, and spanned by a flat arch, the front opening being used both as a fire door 
 and smoke draught. The oven is heated by kindling a fire of wood or coals upon the 
 hearth, fresh additions of fuel being made until the required temperature is attained. 
 The fuel is then withdrawn, and the oven being purified from the ashes, it is 
 ready for the reception of the bread. 
 
 The oven ordinarily used by bakers in London is shown in figs. 567 (longitudinal 
 
 FIG. 567. 
 
 FIG. 568. 
 
 section), 568 (plan), and 569 (front view), a, is the body of the oven ; b, the door, 
 c, the fire grate and furnace ; d, the smoke flue ; e, the flue above the door to carrv 
 off the steam and hot air when withdrawing the bread ; /, recess below the door, for re"- 
 ceiving the dust ; g, damper plate, to shut off the 
 steam flue ; h, damper plate to shut off the smoke 
 flue ; i, small iron pan over the fireplace for heat- 
 ing water ; 7c, ashpit. The flame and hot air from 
 the fire (<?) sweep along the right-hand side of 
 the oven to the back, by which they are reflected 
 to the left-hand side and thence escape into the 
 flue (d). When the oven is sufficiently heated, 
 the fire is withdrawn, the flues closed by the 
 damper plate, and the dough introduced. 
 
 In recent times many improvements have 
 been made ; the dough is kneaded by machinery 
 instead of by hand labour, and the old oven has 
 been altered in many ways. All these improve- 
 ments, however, have hitherto been bub little 
 used. Some of the more important alterations in the apparatus for kneading and 
 baking are the following : 
 
 Fio. 569. 
 
792 
 
 BREAD, FLOUR, ETC. 
 
 Moret's kneading machine is represented in figs. 570 and 571. It consists of a 
 strong iron cylinder (A B, fig. 570), divided into portions by a partition. Inside the 
 
 , ' cylinder is an iron 
 
 <ia - 570 ' shaft (a, fig. 571), pro- 
 
 vided with iron arms, 
 (a, b). The sides of 
 the cylinder are also 
 furnished with similar 
 arms (d d'), which are 
 so arranged that when 
 the cylinder is set in 
 motion they pass be- 
 tween the arms of the 
 shaft. The cylinder 
 can be closed by a 
 hinged cover. Sour 
 dough, flour and water 
 are placed in both the 
 compartments (A B), 
 and the cylinder is 
 caused to make four 
 revolutions per min- 
 ute during eighteen 
 minutes, by the end 
 of which time the 
 kneading is completed. 
 An automatic mecha- 
 nism registers the 
 number of revolutions, 
 and upon the comple- 
 
 FIQ. 571. 
 
 tion of each thirty-six revolutions gives a signal on the bell (c). The cylinder is set 
 in motion by turning the handle (F), which is fastened to an axis upon which are 
 also a flywheel (a) and a pinion (i). The pinion works in a large cogwheel, which 
 being connected with the cylinder causes its revolution upon the shaft (a). When 
 steam power is available it is applied by means of the driving-wheels (H). When the 
 kneading is completed the cover of the cylinder is raised by means of two cords, 
 which are wound on two drums (M M') connected with a shaft (L) that is set in motion 
 by a handle (j). 
 
 A similar machine, in which the arms do not stand opposite to the .axis, but are 
 bent spirally, has been constructed by Boland. It requires the application of some- 
 what more power than the preceding, but yields a dough more closely resembling that 
 kneaded by hand. 
 
 Machine-made dough has the disadvantage of requiring a longer time to ferment 
 than that kneaded by hand, but this may be overcome by the addition of a little more 
 fresh or yeast, or increasing the quantity of sour dough. As a rule only half the finished 
 dough is used in a baking, the other half being retained as ferment for the following batch. 
 
 FIG. 572. 
 
 FIG. 573. 
 
 Holland's kneading machine differs from the foregoing, as the trough is stationary 
 whilst the kneading mechanism rotates. It is represented in horizontal section by 
 fig. 572, and in vertical section by fig. 573. The trough (M M o) is semi-cylindrical, 
 tvhe side towards which the turning takes place being higher than the other, the trough 
 
BAKING OVENS. 
 
 793 
 
 not being closed. The two end pieces (M M) are straight, and support the shaft (B) of 
 the kneading machinery. This consists of an iron plate bent into the shape of an S 
 (def}, and several times divided, giving rise to a number of alternately long and 
 short arms by which the kneading of the dough is effected. The apparatus is set in 
 motion by the large cogwheel (c) working in a small one on the shaft (B), the power 
 being applied through the handle (A') and regulated by the flywheel. 
 
 Clayton's kneading trough, shown in section in fig. 574, consists of a cylinder (a a) 
 into which the ingredients are put. It is mounted in a frame (b) with hollow axles 
 
 Fia. 674. 
 
 (c d), that turn in bearings at e. A revolving frame (/ ) supported in the interior 
 of the cylinder by axles (g h). The ends of this revolving frame are braced together 
 by oblique cutters or braces (i i i) that act upon the dough -when the machine is put in 
 motion, and effect the operation of kneading. The cylinder may be made to rotate 
 without the internal frame, or the frame without the cylinder, or both may be made 
 to revolve at the same time but in opposite directions ; the respective motions being 
 obtained through the gear work (klm). 
 
 An American kneading machine consists essentially of a spiral arrangement, re- 
 sembling a large corkscrew, working in a cylinder, by which the dough is worked up 
 and finally pushed out well kneaded. 
 
 Perkins's hot-water oven is heated by means of pipes full of water, hermetically 
 closed, but with sufficient space for expansion of the water within the pipes. The 
 outer part is built of brickwork made very thick in order to retain the heat. The 
 
 FIG. 575. 
 
 internal surface of the oven (E) is lined with wrought-iron pipes of 1 inch external 
 and fth of an inch internal diameter, which are connected by the flow pipe (c c) with 
 a coil of pipe (B) in the furnace (A) ; the coil has such a relative proportion of surface 
 to that of the pipes in the oven as to allow of the temperature being raised to 288 
 and no higher. The temperature is maintained exactly constant by the expansion or 
 contraction of a pipe (D) which acts upon three levers contained in the regulating 
 box (j j), supported by the iron bar (i). The temperature is regulated by the adjust- 
 ment of a movable nut (K) at the botlom of the expanding pipe. The least variation 
 
794 
 
 BREAD, FLOUR, ETC. 
 
 in the temperature of the water in the pipes is sufficient to expand or contract the 
 pipe (D), which at once acts upon the levers, and these raise or depress the straight 
 rod (L) and open or close the damper (M) of the furnace. F is the return hot- water 
 pipe; G, door of the oven; H, flue for the escape of vapour from the oven; N, un index 
 of the temperature in the pipes. 
 
 FIG. 576. 
 
 G-rouvelle and Mouchot's oven. This oven, which was originally constructed 
 by Lemarre and Jamtel, but improved by Q-rouvelle and Mouchot, is shown in 
 longitudinal and transverse section, by figs. 576 and 577. Coke or coal can be used 
 
 FIG. 577. 
 
 for the heating of this oven, and it is burnt in a fire grate (A) separate from the hearth. 
 The oven is heated both by radiated heat and by currents of hot air. The baking 
 hearth, with its arch, is shown at FF. The fire space (A) is divided in the middle by 
 bars, .so that the under portion (j ) forms an ash-pit. The products of combustion 
 
BAKING OVENS. 
 
 795 
 
 circulate in a series of flues (c c\ imparting their heat to the sole of the oven, and 
 finally passing into the chimney. During the baking the oveu is entirely closed in 
 order to keep up a regular circulation of the air. In proportion as the air in the oven 
 becomes cooler, by parting with its heat, and specifically heavier, it sinks through a 
 number of pipes (b b} into a system of arches (BB) distributed round the fire. After 
 passing through these arches and becoming reheated, it passes upwards through a a 
 and enters the flues (B E) immediately over the fire, where it is raised to the highest 
 temperature, and then passes into the oven. The circulation is kept up continually, 
 so that an incessant current of hot air flows into the oven. This oven presents the 
 advantage of great cleanliness, as it yields a bread the crust of which is never con- 
 taminated by ash or cinders; it allows of the use of coal, which is cheaper than wood; 
 finally, the operations can be carried on continuously, as the heat of the oven can be 
 kept constant. 
 
 FIG. 578. 
 
 Fig. 578 represents a ground plan of a bakehouse in which such ovens are used : 
 the ovens (b 6) are separated by a space (e) common to the two ovens, into which the 
 hot air passes. The kneading machine (c) is driven by machinery in the chamber (/). 
 
 Lespinasse's oven resembles the ordinary oven in which the heating material 
 is burnt upon the hearth of the oven itself; but differs from it in the air draught not 
 entering through the mouth of the oven, but through a flue lying under the hearth, so 
 that only air already considerably heated enters the oven. The smoke also, instead 
 of escaping through the mouth of the oven, passes into a chimney through a flue 
 situated over the arch. This oven is usually heated with beech or poplar wood, or 
 some other wood burning with a strong clear flame; oak and deal have, however, 
 been used with advantage. About one-third of the cost of the combustibles can be 
 recovered in the value of the charcoal produced. As soon as the oven has reached a 
 temperature of about 200 this is withdrawn into closed vessels, where it is allowed 
 to cool. The hearth is then cleansed, and the dough introduced. 
 
 Holland's Oven. The principle of this oven is essentially different from that of all 
 others. The baking hearth is formed of iron plates supported upon an iron frame- 
 work, and is covered with glazed tiles. It is not stationary, but can be revolved 
 horizontally. In order to set the hearth in motion it is connected with a revolving 
 shaft about 6 feet long, passing under the oven and having at its end a small conical 
 cogwheel working in a spur wheel ; the shaft is rotated by means of a handle. The 
 shaft, and with it the hearth of the oven, can be raised or lowered at pleasure, the 
 socket in which it rests being prolonged beneath into a screw worked by means of a 
 lever. The heating is effected by passing the combustion products of a furnace into 
 iron heating pipes situated under the movable hearth, and resting upon a bed of brick- 
 work sloping slightly upwards from the furnace. The heating pipes open into vertical 
 flues from which the hot air from the furnace is conducted into a compartment con- 
 structed of iron plates and situated above the baking space. The upper surface of this 
 is covered with a layer of non-conducting materials, such as ashes ; whilst from the 
 under surfn.ce the heat radiates freelv into the oven. The oven has therefore essen- 
 
796 
 
 BREAD, FLOUR, ETC. 
 
 tially the construction of a muffle, all connection between the inner space and the 
 heating space .and the products of combustion being cut off. 
 
 The oven can be heated either with coal or wood. In the first case there is the 
 fire space with its grate, and under this a roomy ash-pit. When wood is used the 
 falling charcoal is caught in a charcoal extinguisher (B) placed under the fire space 
 (fig. 579). 
 
 As the charcoal crumbles off from the burning wood it falls through the widely- 
 placed bars of the grate into a shallow hopper (D), and from thence into the funnel- 
 shaped head (c) of the extinguisher (B). This head is closed by a trap springing from 
 
 FIG. 579. 
 
 the inside and balanced by a weight. As soon as sufficient charcoal has collected in 
 the head to overbalance this weight, the trap opens, allows the charcoal to fall into the 
 extinguisher, and then closes again immediately, so that the glowing embers are pre- 
 served from contact with the air. 
 
 The introduction of the dough to be baked into the oven is easily effected. The 
 portion of the hearth opposite the mouth of the oven (fig. 580) is first covered with 
 loaves, and then by means of the handle (a) the hearth is rotated until the space 
 opposite the mouth is again clear ; this is in its turn covered with bread, and the 
 operation is repeated until the hearth is full (fig. 581). The oven is emptied in a 
 
 FIG. 580. 
 
 FIG. 581. 
 
 similar manner, the portion of the hearth first covered being, after the complete revo- 
 lution, again opposite the mouth of the oven, so that the bread first put in presents 
 itself first for removal. During the operation the progress of the baking can be 
 observed through an opening covered with glass, the oven being lighted up with gas 
 or otherwise ; in the event of any irregularity of temperature becoming manifest, it 
 can be overcome by rotation of the hearth. 
 
MACARONI, ETC. 
 
 797 
 
 Manufacture of Macaroni and Vermicelli. The flour paste which comes into 
 commerce under various forms and names is prepared from wheaten flour very rich in 
 gluten by kneading it with comparatively little hot water, and pressing the stiff dough 
 into shapes. The best vermicelli is made in Italy, from a hard wheat which is not 
 ground to a fine flour, but worked as grit. 34 parts of grit are kneaded with 10 to 
 12 parts of boiling water into a perfectly homogeneous dough, and then pressed, the 
 yield being about 30 parts of dry vermicelli. 
 
 In the manufacture of vermicelli, the gluten from the starch manufacture can be 
 used with great advantage by adding it to flour poor in gluten. A product not inferior 
 to the best Italian manufacture can be obtained by using 30 parts of ordinary flour, 
 10 parts of fresh gluten, and 5 to 6 parts of boiling water, the yield being about 30 
 parts. The vermicelli thus prepared is nourishing, and when boiled softens without 
 dissolving. 
 
 In order to prepare a really white vermicelli, some manufacturers replace a portion 
 of the flour by potato starch ; but the improvement is only in the outer appearance, 
 since, on account of the deficiency in gluten, the product is less nourishing and has 
 the disadvantage of losing its consistency when boiled. By the addition of a corre- 
 sponding quantity of wheat gluten, however, a good vermicelli can be prepared with 
 potato flour. 
 
 According to Martin a good vermicelli can also be prepared from rice flour by the 
 addition of wheat gluten ; 50 parts of fresh gluten and 100 parts of rice flour being 
 worked into a dough with 1 parts of boiling water. 
 
 In consequence of the necessary stiffness of the dough, the working of it cannot 
 well be effected by hand or with the ordinary kneading machines. A special kneading 
 stick is used, one end of which is fastened by a ring to the wall. With this kneading 
 stick, which is shaped like a knife at one end for the purpose of cutting the dough 
 and rounded at the other, the dough, after being prepared as far as possible by the 
 hand, is worked until no further traces of flour are visible. 
 
 A machine for the working of this stiff dough is represented by fig. 582. It con- 
 sists of a corrugated metal cylinder (A), which is rotated at the same time on its own 
 
 FIG. 582. 
 
 axis, and in a circular direction by the shaft (c), thus working up the dough (D) in the 
 trough (B). It is useful to connect with the shaft (c) a shovel or plough, which follows 
 the cylinder (A), and turns the dough after it has been pressed together, i is a front 
 view of a segment of the cylinder, showing the corrugation. In the manufactory at 
 Grenelle about 170 Ibs. of flour and 5 gallons of water are mixed at each operation, 
 and kneaded by such a machine into dough in 20 or 25 minutes. 
 
798 
 
 BREAD, FLOUR, ETC. 
 
 The dough is shaped by means of presses shown in figs. 583 and 584, being intro- 
 duced, still as hot as possible, into the bronze cylinder (D). It is then covered by a 
 
 FIG. 583. 
 
 FIG. 584. 
 
 metal lid (B), and pressed out in the proper shape through the holes at the bottom, 
 the pressure being applied by the piston (c) in connection with the hydraulic press 
 (AB). To fill the pressing cylinder (D) the pump cylinder (B) is raised after the 
 emptying of the pump by means of pulleys and balance weights (c c), the piston (c) 
 is removed, and the dough introduced. The lower part of the pressing cylinder is 
 surrounded by a jacket in which steam circulates in order to keep the dough hot 
 during the pressing. The threads of vermicelli issuing from the cylinder are rapidly 
 cooled on the surface by a powerful current of air issuing from the ventilator (E), 
 which prevents them from adhering together. When they reach a length of about 
 3 feet they are cut off, laid upon screens, and carried into the drying room, where 
 women cut the large pieces into smaller ones, roll them together, and place them on 
 screens covered with paper in the drying oven. 
 
 For the preparation of macaroni the bottom plate is replaced by one having large 
 circular openings provided with a mandril, which gives to the dough passing through 
 the shape of a hollow pipe. The pipes are then hung on round rods and dried. In 
 the preparation of macaroni, therefore, care must be taken to use a flour that will yield 
 a dough sufficiently tenacious to bear this treatment, or the pipes will be broken through 
 their own weight. These bottom plates are shown in figs. 586 and 587- 
 
 In the preparation of vermicelli moulded into different shapes such as stars, 
 crosses, wheels, rings, etc. a similar press is used, but differing in being horizontal 
 instead of upright. As shown in fig. 585 A is the pressing shaft, B the cylindrical 
 hydraulic pump by which the shaft, supported by the roller (fl), is driven forward into 
 the filled pressing cylinder. In the bottom plate are openings corresponding to tho 
 
MACARONI, ETC. 799 
 
 shape required. The thickness of the cake is regulated by a revolving knife which 
 cuts the dough as it issues from the cylinder, the cakes being thicker or thinner 
 according as the revolution of the knife is fast or slow. The cakes fall into a tray 
 underneath, to which a movement to and fro is imparted in order to prevent the cakes 
 from falling in one place and sticking together. 
 
 FIG. 585. 
 
 FIG 586. FIG. 587. 
 
 A yellow colour is frequently given to the dough by mixing with it a small quan- 
 tity of a decoction of turmeric or of saffron. 
 
 Granulated Gluten. In some manufactories the greater part of the gluten from 
 the starch manufacture is worked up into a kind of vermicelli, which comes into com- 
 merce under the name of granulated gluten. The fresh gluten, broken into small 
 pieces, is kneaded into a stiff dough with double its weight of floar. The granulation 
 of the dough is effected in a revolving cylinder, the inner surface of which is covered 
 with iron spikes. Inside the cylinder is a stirrer, also provided with spikes, which 
 revolves in the opposite direction. Both the cylinder and the stirrer make about fifty 
 revolutions per minute. The granules thus obtained are dried in an oven and sepa- 
 rated into different sizes by means of sieves of various degrees of fineness. 
 
 When prepared with the necessary care granulated gluten is preferable to the best 
 vermicelli. It is more nourishing, being richer in gluten, has a pleasanter taste, does 
 not boil down, but after about 5 minutes boiling becomes perfectly soft. Granulated 
 gluten is particularly adapted for travellers in tropical countries and for use at sea ; 
 when properly packed it remains unaltered, whilst it is more nourishing than an equal 
 volume or weight of flour or ship biscuit. 
 
 Alterations in Bread. After keeping some time bread is subject to change through 
 the formation of mould, the spores of which are brought into contact with it by the 
 air. These develope with extraordinary rapidity into the well-known green and white 
 mould spots, which quickly spread through the interior of the loaf and impart to it a 
 disagreeable smell and taste. The development of this mould is more favoured in 
 proportion to the moisture in the kneaded dough, and it takes place especially when the 
 corn or flour has already suffered during production. Whether, as has been affirmed, 
 the spores of the mould occur in the bread, having escaped the higli temperature of 
 the oven, appears doubtful; it is much more probable that bread prepared from altered 
 flour presents a specially fa vourable soil for the development of mould; and that bread 
 prepared from good flour does not favour the germination of the falling spores to the 
 same extent. The best protection against mould is to avoid an excess of water in the 
 bread crumb and to use a larger addition of salt ; but especially a rapid consumption. 
 Less frequently, a red fungus, the Oidium aurantiacum, makes its appearance in 
 bread, to which it imparts all the injurious properties of the ordinary mould. 
 
DEXTRIN. 
 
 Occurrence. Dextrin is widely distributed in the sap of various plants. 
 
 Characters. Dextrin is soluble in water and dilute alcohol, but insoluble in 
 strong alcohol. It has the same percentage composition as starch and cellulose. 
 When quite pure dextrin is not coloured by iodine, and the brownish red coloration, 
 sometimes observed upon treating solutions of dextrin with iodine, is due according 
 to Payen to the presence of unaltered starch. Dextrin resembles in many respects 
 gum ; consequently it can be employed for many purposes in the place of gum, and 
 this fact has led to its production on a large scale. Dextrin and gum are, however, 
 chemically different ; the former does not yield mucic acid by oxidation with nitric 
 acid. 
 
 Preparation. Chemically pure dextrin is prepared by heating starch 
 with dilute hydrochloric acid, until the liquid when treated with a solution of 
 iod : ne assumes a claret colour. The cooled liquid is then treated with strong alcohol 
 until a flocculent precipitate begins to be deposited. This flocculent precipitate contains 
 the unchanged starch, which is not soluble in alcohol and is filtered off. To the clear 
 filtrate alcohol is again added until the precipitate formed ceases to increase upon 
 further addition of alcohol. The precipitated dextrin is then filtered off and washed 
 with alcohol upon a filter to remove grape sugar. Dextrin thus prepared is, however, 
 still not quite pure ; it requires to be again dissolved in water, precipitated and 
 washed with alcohol, this operation being repeated several times until a product is 
 obtained which does not reduce an alkaline solution of cupric oxide. On the large 
 scale dextrin is generally obtained either by heating starch or by treating it with 
 dilute acids. As obtained by the former method, dextrin is always yellow or brown 
 in colour, while it may be obtained almost colourless by the latter method. 
 
 In preparing dextrin by roasting starch, an oven is employed capable of being 
 heated by hot air. The dry starch is exposed to heat in thin layers in trays. The 
 air is heated by passing through flues before entering the oven. The starch gradu- 
 ally becomes yellowish brown, and is converted into dextrin, which is for the most 
 part soluble in water. 
 
 The regulation of the temperature in this operation is somewhat difficult, and 
 therefore some manufactories employ a copper cylinder placed in an oil bath, which 
 is kept at a constant temperature of 210. The starch is placed in the cylinder, 
 which is furnished with a stirrer, so as to continually bring fresh portions of starch 
 in contact with the heated surface. By this means starch is converted more com- 
 pletely and rapidly into dextrin than in the oven above described. 
 
 By treating starch with a very small quantity of acid, nitric acid being best for 
 the purpose, its conversion into dextrin is effected much more easily at a low tem- 
 perature, a white, friable, and very soluble product being obtained. For this purpose 
 Payen recommends the following procedure : 2 Ibs. of nitric acid, sp. gr. 1-310 to T360, 
 are mixed with 300lbs. of water and 1,000 Ibs. of starch, the whole being carefully mixed 
 and dried in the open air. As soon as the mass is dry enough to admit of being broken 
 in pieces, it is beaten into cakes, from 4 to 5 inches thick, with a flat instrument, and 
 heated in the shallow brass boxes above described. The conversion of the starch into 
 dextrin takes place at a temperature between 110 and 120 within 2 hours. When 
 the temperature of the oven does not exceed 100, 4 hours are necessary; at a tem- 
 perature of 130 the conversion is complete in 30 or 40 minutes. 
 
 When the conversion of the starch is complete, the boxes are emptied into shallow 
 brickwork vessels, where the dextrin cools and is then ready for the market. It is 
 packed in well-dried casks, secured with iron bands, and lined internally with paper 
 saturated with turpentine so as to keep out dust. 
 
 Dextrin prepared by treating starch with acid is pulverulent and has the appear- 
 ance of starch ; it is almost as white when the temperature has not been high. A still 
 better and whiter product is obtained by using hydrochloric instead of nitric acid. 
 For this purpose 500 Ibs. of starch are moistened with a mixture of 1 Ib. hydrochloric 
 
MANUFACTURE Ob 1 DEXTRIN. 801 
 
 acid and 125 Ibs. of water. The mixture is kept in an oven at a temperature between 
 55 and 60 for 48 hours, in order to dry it completely ; and then it is heated for 4 
 hours to a temperature of 1 10 or 120. In this case zinc boxes are used. 
 
 White dextrin is also obtained by using sulphuric acid. The acid is diluted with 
 water in the same proportions as above, and is most conveniently mixed with the starch 
 in a kneading machine. In using sulphuric acid the temperature need not exceed 
 45 or 50. The boxes in which the mixture is placed in the oven may in this case be 
 made of iron. The conversion of the starch and the solubility of the product obtained 
 :s in proportion to the amount of acid employed. 
 
 Dextrin may be obtained in the wet way by using diastase or malt extract ; the 
 product thus obtained always contains some sugar. For many purposes dextrin con- 
 taining sugar is preferable. 
 
 To prepare dextrin by means of diastase, an infusion of malt is heated to 75 and 
 mixed with starch as long as this is dissolved, the temperature of the mixture being 
 maintained meanwhile by passing into it a sufficient quantity of steam. The 
 point of complete change of the starch is ascertained by means of iodine, for which 
 purpose a small quantity of the liquid is treated with a drop of aqueous solution 
 of iodine. So long as a blue coloration is observed, unaltered starch is present ; but 
 when the liquid assumes a claret colour the further action of diastase must be stopped. 
 This is done by blowing steam into the liquid, and bringing it quickly to the boiling 
 point. Prolonged action of diastase would give rise to the production of a material 
 too rich in sugar. Directly the liquid begins to boil the further action of the diastase 
 stops, and the boiling liquid is run off through a filter into a reservoir and concen- 
 trated until it assumes a viscous consistency. This kind of dextrin is used in some 
 breweries. This dextrin syrup is stated by Payen to contain 5271 per cent, of 
 grape sugar and 47'29 per cent, of dextrin. 
 
 Dextrin syrup may be also prepared by acting upon starch with dilute acids, such 
 as sulphuric acid. The acid liquid obtained is saturated with chalk, the precipitate 
 of gypsum filtered off, and the filtrate concentrated. The greater part of the gypsum 
 which still remains in fine suspension separates during the concentration, and the 
 filtered liquid is concentrated to the proper strength. 
 
 The syrup thus obtained is colourless, but has the disadvantage that it contains 
 calcium sulphate. For this reason brewers prefer dextrin syrup prepared with malt 
 to that prepared with sulphuric acid. 
 
 The methods described for the preparation of dextrin yield products pure enough 
 for industrial purposes, although the dextrin prepared in the dry way always contains 
 a certain amount of unchanged starch, and that prepared in the wet way always contains 
 grape sugar. 
 
 Uses. Dextrin is used in confectionery, as weaver's dressing, for making muci- 
 laginous drinks, in the manufacture of beer, fruit wines, brandy, liqueurs, court plaster, 
 etc. In the form of British gum, either alone or together with starch, it is used for 
 finishing bobbin-net and fine fabrics, and as weaver's dressing, in which case it is some- 
 times mixed with glycerin ; it is also UvSed for thickening mordants in dyeing and 
 calico printing, and for rendering envelopes, postage stamps, etc., adhesive. Dextrin 
 in the form of powder has been used by Velpeau with great success in the place of 
 paste bandages for fractured limbs. For this purpose it is stirred with some cam- 
 phorated spirit, and the whole mixed with 40 per cent, of lukewarm water. The 
 dextrin absorbs the water and speedily dissolves to a thick liquid, which is then spread 
 upon linen. The bandages are at once laid upon the part to be protected, and when 
 dry they afford a complete protection against dislocation of the fracture. 
 
 3F 
 
SUGAR. 
 
 Under the name sugar are included a number of substances characterised by sweet 
 taste, and presenting several other features of analogy physically as well as chemi- 
 cally. An intimate relation exists between various kinds of sugar and starch, cane 
 sugar being to a certain extent intermediate between starch and grape sugar, containing 
 more water than starch, and less than grape sugar, as shown by the following com- 
 parison : 
 
 Starch 2C 6 H 10 5 - C 12 H 20 10 
 
 Cane sugar C, 2 H 22 O n 
 
 Grape sugar 2C 6 H 12 6 = C 12 H 24 12 
 
 Starch is readily convertible into grape sugar with the assimilation of water, and 
 cane sugar is convertible into grape sugar, also with the assimilation of the ele- 
 ments of water. By the action of diastase upon starch a variety of sugar called 
 maltose is produced, which has a composition the same as that of lactose. 
 
 Occurrence. The different kinds of sugar are very widely distributed in the 
 vegetable kingdom ; and probably there is no plant which does not contain one or 
 other kind of sugar. A particular kind of sugar occurs in milk, and under special 
 conditions sugar occurs in other animal secretions. The kinds of sugar most fre- 
 quently occurring are: glucose, C 6 Hi 2 6 , comprising grape sugar and fruit 
 sugar ; saccharose, or cane sugar, Ci 2 H 22 On ; and lactose, or milk sugar, 
 Cj2H.220jj.H20. These kinds of sugar are compounds of carbon with hydrogen and 
 oxygen in the same proportions as in water. They may be regarded as derivatives 
 of a .hexatomic alcohol, C 6 Hj 4 6 . Among other kinds of sugar of similar composition 
 are inosite, C 6 H 12 6 , occurring in the unripe fruit of Phaseolus mtlgaris, in other 
 plants, and in the animal organism ; s or bin, having the same composition, occurs in 
 the berries of the mountain ash, Sorbus Aucuparia; melitose, having the same 
 composition as cane sugar, occurs in various species of Eucalyptus. In addition to 
 these, some other kinds of sugar occur, having a somewhat different composition. For 
 example, mannite, C 6 Hj 4 6 , the chief constituent of manna, an exudation from 
 Fraxinus owws, occurs also in other plants, in seaweed, and in mushrooms. Substances 
 closely analogous to the last named occur in Melampyrum nemorosum, in the berries 
 of the mountain ash, and in a Californian pine, Pinus Lambcrtiana. 
 
 Glucose. This variety of sugar is present in most sweet- tasting fruit?, and in 
 many other parts of plants in various proportions, as follows : 
 
 Strawberry (Princess Eoyal) . . . . '. . . 5*86 per cent. 
 
 Cherry . . . 10- 
 
 Fresh grapes from Fontaiiu'bleau .... 9'42 
 
 Preserved grapes . ... . . . 16 ! 5 
 
 Hot-house grapes . . . .-. .,' . 18-37 
 
 Green grapes .' *,-' . . /. . 1-60 
 
 White currant . . . ... . . 6'40 
 
 Green figs . . ....... . . . 11-55 
 
 But there are at least two different kinds of glucose, distinguishable chiefly by 
 their relation to polarised light. One kind is crystallisable, and on account of the 
 large amount contained in grape juice, it is often called grape sugar. It turns the 
 plane of polarisation to the right, and is for that reason termed dextrose. This 
 kind of sugar sometimes occurs also in animals, and in the disease termed diabetes, 
 large quantities of it are excreted in the urine. The other kind is uncrystallisable, 
 and as it turns the plane of polarisation to the left, it is called laevulose; hony 
 consists chiefly of this sugar. According to the source from which these kinds of 
 sugar are obtained, a numbers of distinctions were formerly made which are now no 
 longer recognised. 
 
 Glucose also occurs very frequently in a state of combination, constituting a 
 variety of substances known as glucosides which are decomposed by boiling with 
 
CHARACTERS OF GRAPE SUGAR. 
 
 803 
 
 dilute acids or alkalies and by the action of ferments, yielding glucose and other sub- 
 stances. Amongst the more important of the substances of this class are amygdalin 
 (C 20 H, 7 NO U ), salicin (C 13 H J8 7 ), sesculin (C 21 H 24 13 ), glycyrrhizin (C 24 H 3(i 9 ), and 
 arbutin (C 12 H 16 O 7 ). 
 
 Saccharose or cane sugar occurs in the juice of the Saccharutn officinarum or 
 sugar cane; it also occurs abundantly in the sugar grass (Sorghum saccharatum\ 
 in maize, beetroot, melons, the cocoa nut, in pine apples, in chestnuts, 
 in the juice of palms, in the sugar maple, and in the bulbs of many liliaceous 
 plants. At one time it was supposed that the parts of plants, the juice of which had 
 an acid reaction, contained no cane sugar, since this substance is easily converted by 
 the action of acid into a mixture of grape sugar and fruit sugar. However, the re- 
 searches of Payen and Buignet have shown that even the most acid fruits may contain 
 abundance of cane sugar. 
 
 Payon showed that the juice of oranges and of lemons contains cane sugar ; and 
 Buignet found in various fruits the following amounts of cane sugar and other kinds 
 of sugar : 
 
 
 Cane Sugar 
 
 Total Sugar 1 
 
 Pineapple (Montserrat) 
 Strawberry (Collina. d'Ehrhardt) .... 
 
 per cent. 
 11-33 
 6-33 
 6-04 
 
 per cent. 
 13-30 
 11-31 
 
 8-78 
 
 
 5'28 
 
 14-00 
 
 preserved . . .' . .: 
 English . 
 
 Calville, preserved . . . . . ' V 
 
 3-20 
 2-19 
 0-43 
 5-24 
 
 15-83 
 7'65 
 6-25 
 8-67 
 
 
 1-23 
 
 5-55 
 
 
 4-22 
 
 8-58 
 
 Lemon ......... 
 
 0-41 
 2-01 
 
 1-47 
 7-23 
 
 
 0-92 
 
 1-99 
 
 
 0-36 
 
 8-78 
 
 Pear . . . . . . . . 
 
 0-68 
 
 7-84 
 
 Characters. Of those kinds of sugar which are frequently met with, cane sugar 
 is the most easily crystallisable ; grape sugar crystallises only with difficulty, and 
 fruit sugar not at all. 
 
 Glucose or grape sugar is considerably less sweet than cane sugar, three times as 
 much being necessary to produce the sweetness due to a given quantity of cane 
 sugar. Glucose crystallises from its aqueous solutions, taking up a molecule of water, 
 in which state its composition may be represented by the formula : 
 
 C 6 H 12 6 + H 2 0. 
 
 When heated up to 100 it melts, giving up its water of crystallisation, differing 
 in this respect from cane sugar, which contains no water of crystallisation. Anhy- 
 drous <rrape sugar exposed to a moist atmosphere slowly absorbs water of crystallisa- 
 tion Grape sugar is more soluble in alcohol than cane sugar: 100 parts of boiling 
 alcohol dissolve 1-66 parts of grape sugar; alcohol of 83 per cent, dissolves 18 parts of 
 grape sugar. At a high temperature grape sugar is converted into glucosan, caramel, 
 and other brown substances. 
 
 The alkalies and alkaline earths combine with grape sugar. These compounds are, 
 however very unstable even at the ordinary temperature, and the solutions are instantly 
 decomposed xipon heating ; they begin to colour at 70, and when heated to boiling in 
 contact with atmospheric air they become at once black. By the action of alkalies upon 
 grape sugar a body called glucinic acid, C 12 H 18 9 , is formed, besides other substances. 
 The deportment of alkalies towards grape sugar admits of its presence being detected 
 even in small proportion when mixed with cane sugar. Since cane sugar is not 
 affected in the same manner by alkalies no colouration is obtained by boiling solutions 
 of pure cane sugar with alkalies. 
 
 Concentrated sulphuric acid dissolves grape sugar, forming with it gluco-sul- 
 phuric acid, which yields soluble barium and calcium salts. Protracted boiling 
 with dilute sulphuric or hydrochloric acids renders grape sugar unfermentable, it is 
 then gradually changed into dark coloured substances, caramel, etc. Cupric oxide in 
 alkaline solution is reduced by grape sugar to cuprous oxide. Solutions of grape 
 
 3 F 2 
 
804 SUGAR. 
 
 sugar are decomposed by yeast, yielding alcohol and carbonic dioxide besides other 
 products, the formation of alcohol taking place according to the following equation : 
 
 C 6 H 12 6 = 2C0 2 + 2C 2 H 6 0. 
 (See FERMENTATION.) 
 
 Grjipe sugar turns the plane of a polarised ray of light to the right, fruit sugar turns 
 it to tHe left 
 
 The behaviour exhibited by grape sugar towards alkaline solutions of cuprie 
 oxide is taken advantage of in determining grape sugar quantitatively. For this pur- 
 pose it is only necessary to knovv how much of a saccharine liquid is required for the 
 complete precipitation of the copper in a solution of cupric oxide of known strength ; 
 1 molecule of grape sugar reduces 10 molecules of the cupric salt to cuprous oxide, 
 or in other words 5 grammes of grape sugar decompose 34'64: grammes of crys- 
 tallised cupric sulphate. The cupric oxide solution is prepared in these proportions by 
 dissolving 34-64 grammes of pure cupric sulphate in 150 or 160 c.c. of water ; adding 
 150 grammes of crystallised potassium tartrate dissolved in 600 or 700 c.c. of a solu- 
 tion of sodium hydrate. At first there is formed a voluminous light blue pre- 
 cipitate which dissolves upon shaking, forming a dark blue liquid, which is then 
 diluted -with water to the volume of 1,000 c.c. The solution thus prepared is pre- 
 served for use in a dark place. 
 
 In applying the test 1 gramme of the saccharine substance is placed in a flask 
 holding 100 c.c. dissolved in water and the solution diluted exactly to 100 c.c. A 
 measured quantity (20 c.c.) of the solution of cupric oxide is then diluted with twice 
 or thrice its volume of water and heated to boiling in a porcelain dish. The blue 
 liquid must remain perfectly clear during this operation. Should the liquid have 
 been kept so long that cuprous oxide is precipitated upon simply boiling, it is then 
 worthless and a fresh solution must be prepared. Some of the sugar solution is then 
 dropped from a burette into the hot liquid in the porcelain dish, observing after each 
 addition whether the copper solution still appears there ; so soon as this ceases to be 
 the case it is a sign that all the cupric oxide is reduced and the experiment is com- 
 plete. It is advisable to repeat the experiment, the second time adding approximately 
 as much sugar solution as in the first experiment, and then to proceed very carefully 
 with the conclusion of the operation. Thus, for instance, should the copper solution in 
 the first experiment remain palpably blue after adding 1 1 c.c. of sugar solution, but 
 become colourless upon the addition of another cubic centimetre, then in performing 
 the operation a second time, 1 1 c.c. of sugar solution may be at once added. 
 
 Since 1,000 c.c. of copper solution contain exactly as much cupric oxide as 5 
 grammes of pure grape sugar are capable of reducing, it follows that the 20 c.c. would in 
 the testing represent exactly O'lOO gramme of grape sugar. If, therefore, the liquid to 
 be tested has been diluted to 100 c.c., and 11 '6 c.c. taken for the test, the percentage 
 of grape sugar in it is found by the simple proportion 
 
 11-6 : O'lOO = 100 : x; x = 0'862. 
 
 Saccharose or cane sugar crystallises in rhomboidal prisms. When deposited 
 from a hot concentrated solution, quickly cooled, the crystals are small and adhere 
 together, forming a granular mass ; by allowing the warm solution to evaporate very 
 slowly, very large crystals are formed (sugar candy). 
 
 Cane sugar has a specific gravity of 1-606. When rubbed or struck in the dark, 
 it emits a phosphorescent light ; by long continued trituration, cane sugar undergoes 
 alteration and acquires a peculiar smell. 
 
 Cane sugar is very soluble in water, one-third of its weight of water being suffi- 
 cient to dissolve it in the cold, and in boiling water it is soluble in almost any pro*- 
 portion. The boiling point of a solution of sugar varies with the amount of sugar 
 present, rising in proportion as the syrup contains less water. If the heat be con-" 
 tinned, the sugar remaining after evaporation melts at a temperature only a little above 
 the boiling point of the saturated solution. When the boiling point of a cane sugar 
 solution is lowered very considerably by evaporating under reduced pressure, a very 
 copious crystallisation of the sugar takes place in the boiling solution. 
 
 Solution of cane sugar possesses the property of rotating the plane of polarisation 
 of a ray of light to the right, the specific capacity of rotation being: D = 73'8. 
 Cane sugar is insoluble in cold absolute alcohol, but boiling absolute alcohol dissolves 
 1-25 per cent, of cane sugar, which is again almost completely deposited upon cooling; 
 alcohol of 83 per cent, dissolves 25 per cent, of cane sugar. When a cold saturated 
 solution of cane sugar in 90 per cent, alcohol is mixed with double its volume of ether, 
 the sugar is precipitated in the form of minute crystals on the sides of the vessel con- 
 taining the solution. This reaction may be used for determining the presence of cane 
 sugar in different parts of plants ; the juice or an aqueous extract of the plant is 
 evaporated to dryness at a low temperature, then treated with alcohol, the insoluble 
 
CANE SUGAR. 
 
 805 
 
 portion separated by filtration, and the solution mixed with ether ; any cane sugar 
 present crystallises out after a short time. 
 
 Cane sugar combines with a number of bases, such as lime, baryta, lead oxide, 
 potash and soda. These compounds have been carefully studied by Peligot and 
 Soubeiran. A large quantity of calcium hydrate is dissolved when heated with a 
 solution of cane sugar. The solution prepared in the cold, provided the concentration 
 of the liquid does not exceed a certain limit, is a compound of 1 molecule of sugar 
 with 1 molecule of calcium oxide : 
 
 In concentrated solution of sugar, lime is dissolved in greater proportion. If such a 
 solution be heated to boiling it becomes cloudy, and a bulky precipitate is formed 
 which may be separated by filtering the hot liquid, and purified by washing with 
 boiling water. This insoluble compound consists of 1 molecule of cane sugar and 3 
 molecules of lime : 
 
 It is formed by the decomposition of 3 molecules of the first mentioned compound, 
 1 molecule of the tribasic compound being produced, while 2 molecules of sugar are 
 set free : 
 
 3(C 12 H 22 O n CaO) = C 12 H 22 O n .3CaO + 2(C I2 H 22 O n ). 
 
 If the precipitate be suffered to cool in the liquid from which it was formed, it re- 
 dissolves and the first compound is again produced. The monobasic compound may be 
 prepared in a pure state by digesting lime with a tolerably concentrated solution of 
 sugar until no more lime is dissolved ; the liquid is then filtered, mixed with a small 
 quantity of sugar in order to convert all the sugar lime into a monobasic compound, 
 and alcohol added ; a dirty white precipitate is formed which is insoluble in 
 alcohol, and after the removal of the liquid forms an amorphous brittle mass. The 
 substance thus prepared behaves exactly like a solution of lime in sugar : it is com- 
 pletely soluble in water, and is decomposed when heated, etc. 
 
 Upon mixing a solution of the monobasic lime compound with a second molecule 
 of sugar, and then with hydrated cupric oxide, the latter is dissolved. The same liquid 
 in contact with metallic coppper and atmospheric oxygen causes oxidation of the 
 metal, and the cupric oxide is dissolved. The proportion of lime taken up by a 
 solution of sugar varies very much according to the concentration of the sugar solution. 
 Very concentrated solutions of sugar take up as much as 2 molecules of lime to every 
 molecule of sugar, while dilute solutions take up less than 1 molecule. 
 
 The following table by Peligot shows the relative proportions of sugar and lime in 
 solutions of different degrees of concentration, and also the specific gravity of the 
 solutions ; for the sake of comparison the proportions of sugar and lime in the com- 
 pounds, containing respectively 1 and 2 molecules of lime, are given ; the latter com- 
 pound however is not known in the pure state. 
 
 Percentage of 
 sugar 
 
 Specific 
 of sugar solution 
 
 gravity 
 
 of sugar solution 
 saturated with 
 lime 
 
 100 parts of sug 
 Lime 
 
 ar lime contain 
 Sugar 
 
 C 12 H 22 O n .CaO 
 
 
 
 
 
 14-1 
 
 85-9 
 
 Cj.,H 2 O n .2CaO 
 
 
 
 
 
 24-7 
 
 75-3 
 
 40-0 
 
 1-122 
 
 1-179 
 
 21-0 
 
 79-0 
 
 37-5 
 
 1-116 
 
 1-175 
 
 20-8 
 
 79-2 
 
 35-0 
 
 1-110 
 
 1-166 
 
 20-5 
 
 79-5 
 
 32-5 
 
 1-103 
 
 1-159 
 
 20-3 
 
 79-7 
 
 30-0 
 
 1-096 
 
 1-148 
 
 20-1 
 
 79-9 
 
 27-5 
 
 1-089 
 
 1-139 
 
 19-9 
 
 80-1 
 
 25-0 
 
 1-082 1-128 
 
 19-8 
 
 80-2 
 
 22-5 
 
 1-075 1-116 
 
 19-3 
 
 807 
 
 20-0 
 
 1-068 ' -.- 1-104 
 
 18-8 
 
 81-2 
 
 17-5 
 
 1-060 1-092 
 
 18-7 
 
 81-3 
 
 15-0 
 
 1-052 1-080 
 
 18-5 
 
 81-5 
 
 12-5 
 
 1-044 1-067 
 
 18-3 
 
 81-7 
 
 10-0 
 
 1-036 1'053 
 
 18-1 
 
 81-9 
 
 7-5 
 
 1-027 1-040 
 
 169 
 
 83-1 
 
 5-0 
 
 1-018 
 
 1-026 
 
 15-3 
 
 84-7 
 
 2-5 
 
 1-009 
 
 1-014 
 
 13-8 
 
 86-2 
 
806 
 
 SUGAR. 
 
 The solubility of lime in dilute solution of sugar was studied by Berthelot. 
 
 The following table gives the results of his researches. Columns I. and II. show 
 the percentage amounts of sugar and lime in the solution. Column III. shows the 
 ratio of sugar to lime ; but since the ratio is somewhat obscured in dilute solutions 
 because pure water dissolves some lime, Column IV. gives the ratio of sugar to lime 
 after making allowance for the lime dissolved in water alone. The numbers show that 
 the monobasic compound was only formed in the first experiment, while in every other 
 case, owing to the small amount of sugar, the proportion of lime dissolved was less 
 than 1 molecule of lime for each molecule of sugar. 
 
 I. 
 Sugar 
 
 II. 
 Lime 
 
 u 
 
 Lime 
 
 I. 
 Sugar 
 
 I 
 Lime 
 
 v. 
 
 Sugar 
 
 4-850 
 
 1-301 
 
 17-5 
 
 82-5 
 
 15-4 
 
 84-6 
 
 2-401 
 
 0-484 
 
 16-8 
 
 83-2 
 
 12-3 
 
 87-7 
 
 2-000 
 
 0-433 
 
 17'8 
 
 82-2 
 
 12-5 
 
 87-5 
 
 . 1-660 
 
 0-364 
 
 18-0 
 
 82-0 
 
 11-5 
 
 B8'5 
 
 1-386 
 
 0-326 
 
 19-0 
 
 81-0 
 
 11*4 
 
 88-6 
 
 1-200 
 
 0-316 
 
 20-8 
 
 79-2 
 
 12-2 
 
 87-8 
 
 1-058 
 
 0-281 
 
 21-0 
 
 79-0 
 
 11-2 
 
 88-8 
 
 0-960 
 
 0-264 
 
 21-6 
 
 78-4 
 
 10-8 
 
 89-2 
 
 0-400 
 
 0-194 
 
 32-7 
 
 67-3 
 
 10-3 
 
 89-7 
 
 0-191 
 
 0-172 
 
 47-4 
 
 52-6 
 
 11-2 
 
 88-8 
 
 0-096 
 
 0-154 
 
 61-6 
 
 38-4 
 
 
 
 Not only in respect to the solubility of the lime, but also when heated, the liquids 
 behave differently, according to their strength. Coagulable sugar lime is obtained by 
 mixing a solution of 25 parts of sugar in 50 parts water with 51 parts dry lime 
 suspended in 50 parts of water, stirring the mixture for about ten minutes, then adding 3 
 parts more lime, again stirring, and finally filtering, after having allowed the mixture 
 to stand for half an hour. The clear filtrate coagulates when it is slowly heated to 
 boiling, and becomes clear again upon cooling. When, however, it is heated very 
 quickly to boiling and a lively ebullition is kept up, no coagulation takes place. 
 Upon diluting the liquid with 2, 3, and 4 times its bulk of water, a milky cloudiness 
 is produced upon boiling, and the liquid is no longer transparent or translucent, but 
 it does not coagulate. A solution which does not coagulate when heated to boiling 
 is obtained by using less water. Upon mixing lime and sugar in the above propor- 
 tions with only one half the quantity of water, the solution may be heated slowly or 
 quickly without coagulating. Protracted contact with the air causes the formation 
 of an opaque pellicle of calcium carbonate upon the surface of the liquid. 
 
 Sugar lime is easily decomposed by all acids, even carbonic acid. Upon 
 mixing concentrated solutions of caustic baryta and cane sugar, a crystalline paste is 
 formed, and the same compound is formed upon boiling dilute solutions. It has a 
 composition analogous to that of the monobasic lime compound, Ci 2 H., 2 O n .BaO. 
 Upon mixing an alcoholic solution of cane sugar with potash or soda, a sticky pre- 
 cipitate is formed, which hardens in alcohol ; the potassium compound is represented 
 by the formula: C^H^On.KjO. 
 
 Another compound is obtained by treating sugar lime with lead acetate, or 
 by mixing concentrated solutions of sugar with an ammoniacal solution of lead 
 acetate. A gelatinous precipitate is formed, which dissolves in boiling water, and 
 after a while deposits acicular crystals. The composition of this substance differs 
 from that of the other compounds, the lead oxide replacing 2 molecules of water, as 
 shown in the following formula : C J2 H 18 Pb 2 p n or C 12 Hi ? 9 .2PbO. 
 
 Cane sugar differs from grape sugar in its behaviour towards alkaline bases. 
 Grape sugar when treated with alkalies or alkaline earths decomposes slowly at the 
 ordinary temperature, but immediately upon boiling, with the formation of brown or 
 black products ; while cane sugar combines with these reagents without decomposi- 
 tion. Use is made of this different behaviour of these two sugars in distinguishing 
 them in analytical chemistry. Besides entering into combination with bases, cane 
 sugar also forms compounds with certain salts for instance, with sodium chloride or 
 common salt. The composition of the compound is represented by the formula: 
 C 12 H 22 O n .NaCl ; or according to other analyses : C^H^On + C 12 H 20 1? .2NaCl. 
 
 The compound of sugar with sodium chloride is even more soluble in water than 
 pure sugar ; upon evaporating solutions of sugar containing sodium chloride, this 
 compound remains dissolved after the excess of sugar has crystallised out. For this 
 
CANE SUGAR. 807 
 
 reason the presence of sodium chloride in the juice of sugar cane or beet root is very dis- 
 advantageous, since a part of the sugar is thus rendered uncrystallisable and retained 
 in the molasses. From the formula of the compound it will be seen that the sodium 
 chloride is combined with nearly six times its weight of sugar, and that hence the 
 production of sugar from beet grown on a salt soil would be attended with great dis- 
 advantage and loss. ^ A sugar factory established near Naples was ruined from this 
 cause ; the beets having been grown on a soil situated near the sea, were impregnated 
 with salt, and they contained so much sodium chloride that the juice yielded no crystal- 
 lisable sugar at all. The chlorides of ammonium and potassium enter into similar 
 combination with sugar. 
 
 Cane sugar melts at 160, and upon cooling solidifies to a transparent amorphous 
 mass called barley sugar, which gradually becomes opaque and crystalline. Upon 
 heating cane sugar for some time at a temperature of 170-180, according to Gelis it 
 is converted into a mixture of equal molecules of grape sugar and of a substance 
 having the same "constitution as starch and cellulose, which he called sac char id or 
 glucosan. This change may be considered as consisting in the removal of a molecule 
 of water from one molecule of cane sugar, and its transfer to another to form grape sugar : 
 2Cj 2 H 22 O u = 2C 6 H 12 6 + 2C 6 H 10 5 . 
 
 An aqueous solution of melted cane sugar treated with yeast yields only half the 
 quantity of alcohol and carbonic acid obtainable from ordinary cane sugar. The solution 
 of melted sugar reduces alkaline solutions of cupric oxide, but it yields only one half as 
 much cuprous oxide as is obtained when cane sugar has been converted by an acid 
 into grape sugar and fruit sugar. This shows that by melting cane sugar one half of 
 it is converted into a fermentable substance, capable of reducing cupric oxide (grape 
 sugar), while the other half is converted into a non-fermentable substance which does 
 not reduce cupric oxide (saccharid). 
 
 By protracted heating at a temperature of 180-200 cane sugar assumes a yellow 
 colour which passes into different shades of brown, and finally, with evolution of 
 water and inflammable products, the sugar is converted into a mixture of sub- 
 stances known under the name of caramel. According to Gelis, caramel consists of 
 three distinct substances, the relative proportions of which depend upon the tempera- 
 ture and the duration of the heating. The first product formed appears to be 
 caramelan Ci 2 H 18 9 , which under evolution of water passes into caramelene and cara- 
 melin. All three substances combine with bases. Caramel is soluble in water and 
 in alcohol, and under the name of couleuris used fo* colouring liqueurs and for 
 various culinary purposes. 
 
 When strongly heated cane sugar swells up, gives off a number of inflammable 
 products, and finally yields a voluminous and difficultly combustible charcoal. 
 
 Aqueous solutions of cane sugar are changed by protracted boiling, a part of the 
 sugar becoming uncrystallisable. 
 
 Cane sugar is not itself fermentable, but in contact with yeast it undergoes altera- 
 tion ; and taking up the elements of water, it is converted into a mixture of equal 
 molecules of grape sugar and fruit sugar, which are both fermentable. This change 
 may be represented by the following equation : 
 
 ,, + H 2 = C 6 H 12 6 + C 6 H 12 6 
 
 Cane sugar Grape sugar Fruit i 
 
 The same change takes place when a solution of cane sugar is heated for a short time 
 with a trace of free acid. The mixture of the two kinds of sugar turns the plane of 
 polarised light to the left, for which reason sugar that has been altered by acids is 
 called inverted sugar. Si nee the formation of i nverted sugar reduces the quan tity of 
 crystallisable sugar, the sugar manufacturer takes care to keep the juice operated upon 
 continually alkaline with small quantities of sugar lime during the entire operation. 
 
 Concentrated acids decompose cane sugar ; treatment with hydrochloric or sul- 
 phuric acid, and the application of a gentle heat, produce humus substances, which 
 become continually richer in carbon as the reaction proceeds. Concentrated nitric 
 acid changes cane sugar into nitro-saccharose, a substance resembling gun cotton in 
 its properties. When sugar is heated for a short time with nitric acid of specific 
 gravity 1-310, a deliquescent acid saccharic acid is produced; and, by protracted 
 boiling with nitric acid, oxalic acid is formed. 
 
 Lactose, or milk sugar (C 12 K 22 O ll -H 2 0) is much less soluble than either grape or 
 cane sugar, requiring five or six times its weight of cold water for solution. It is 
 not so sweet as grape sugar and is dextro-rotatory. It crystallises in hard white, trans- 
 lucent, four-sided prisms. Lactose combines with bases, forming compounds that 
 have an alkaline reaction, and by the action of dilute acids it is converted into galac- 
 tose (C 6 H, 2 6 ), a readily crystallisable dextro-rotatory glucose, distinguished by yielding 
 mucic acid (C 6 H| 8 ), when oxidised by the action of nitric acid, instead of saccharic 
 acid (C 8 H 10 8 ). 
 
808 SUGAB. 
 
 Milk sugar does not readily undergo alcoholic fermentation. When decomposing 
 gluten or casein is used as the ferment, milk sugar is chiefly converted into lactic acid 
 (C 3 H 6 3 ), but sonle alcohol is formed at the same time. 
 
 Preparation. The kind of glucose commonly known as grape sugar or dex- 
 trose is produced by the protracted action of dilute acids or diastase upon starch, 
 and also by the decomposition of a number of organic substances termed glucosides; 
 thus, for instance, amygdalin can be decomposed into grape sugar, oil of bitter al- 
 monds, and hydrocyanic acid : 
 
 + 2^0 = C 7 H 6 + CNH + 20 8 H 1!8 6 . 
 
 The glucose obtained from these sources sometimes presents peculiarities and 
 differs in the facility with which it undergoes alcoholic fermentation. Cellulose is 
 also convertible into ordinary glucose by the action of dilute acids. 
 
 G-rape sugar is artificially prepared from starch, which is converted into grape 
 sugar by addition of the elements of two molecules of water. It may also be prepared 
 from cane sugar, and is met with in commerce in three different conditions, as hard 
 sugar, granular sugar, and as syrup. 
 
 The manufacture of grape sugar from starch is carried out by heating a mixture 
 of starch with dilute sulphuric acid, by forcing steam into the liquid contained in large 
 wooden vats in which about 1,000 gallons of water and 84 Ibs. of sulphuric acid are 
 first mixed, and heated to boiling. Meanwhile about 2 cwts. of starch are mixed with 
 30 gallons of lukewarm water in a smaller vat. The liquid in the large vat is kept 
 boiling, and the mixture of starch and water is run in until about 4,000 Ibs. of 
 starch and 600 gallons of water have been added. After adding the last portion 
 of starch and water the liquid in the vat is kept boiling about 40 minutes, and then 
 a few drops are taken out and tested with a drop of iodine solution, which ought not 
 to produce any blue coloration ; if it does, the boiling is continued and the liquid 
 tested with iodine solution from time to time until no coloration is produced. 
 When this point has been reached, the steam is shut off and the "liquid neutralised 
 with chalk, previously powdered and stirred up with water to a thin pap, which 
 is added in small quantities at a time until no effervescence is observed upon the 
 addition of a fresh portion, or, what is still better, until a drop of the liquid ceases 
 to colour blue litmus paper red. A large excess of chalk is avoided, owing to its 
 rendering somewhat difficult the final clarification of the liquid. 
 
 When the neutralisation is complete the muddy liquor is run off into a reservoir, 
 where it is allowed to remain ten or twelve hours to deposit the calcium sulphate. The 
 clear liquid is filtered through granulated animal charcoal. The filtered sugar 
 solution is then evaporated by steam heat until the hot liquid has a sp. gr. of T231, 
 and when cold a sp. gr. of 1' 29 6. 
 
 The syrup thus obtained stands a couple of days, during which the greater part of ] 
 the calcium sulphate still remaining dissolved in the liquid separates. The clear liquid 
 is then drawn off and sold in this state to brewers and confectioners. For finer kinds 
 of confectionery and for liqueurs a syrup is required as free as possible from colour, 
 and it is again passed through animal charcoal. 
 
 When hard sugar is required instead of syrup a little more acid is used in the 
 saccharification, 55 or 60 Ibs. being taken to every 2,000 Ibs. of starch, and the 
 liquid is evaporated till it has a specific gravity of 1-309 in the hot state, or T370 
 upon cooling. The syrup is then run into a large vessel and when it begins to crys- 
 tallise it is run into tubs or moulds to solidify. 
 
 For the manufacture of sweetmeats, preserves, and fruit syrups, a glucose syrup is 
 prepared containing some dextrin still unaltered. For this purpose only 14 or 15 Ibs. 
 of sulphuric acid are used for 2,000 Ibs. of starch, and the syrup is evaporated until 
 while hot it has a sp. gr. of 1-32, when it is passed boiling through a charcoal filter 
 heated by a steam jacket. 
 
 The manufacture of the three products is essentially of the same nature, the only 
 difference being that, in preparing the solid sugar, the saccharification of the starch is 
 carried as far as possible, so as not to leave any dextrin unconverted, since the 
 presence of that substance would hinder the crystallisation. The syrup used for 
 liqueurs, etc. is required to be quite free from crystallisation, and at the same time it 
 must have a high degree of concentration. On this account a considerable quantity of 
 dextrin is left unconverted, and by this means there is obtained a dense viscid liquid 
 that is readily soluble in water, but is not at all liable to crystallise. In ordinary 
 starch sugar syrup the saccharification is almost complete, but the product is not con- 
 centrated to such a degree that it is capable of crystallising. The syrup used for 
 liqueurs, and called by the French sirop imponderable, contains about 11 per 
 cent, of water, and the dry substance it contains consists of 42 per cent, of sugar and 
 68 per cent, of dextrin. The starch sugar syrup of 1'296 sp. gr. contains 30 per cont, 
 
MANUFACTURE OF GLUCOSE. 809 
 
 of water, and in the dry substance it contains there is from 85 to 90 per cent, of 
 sugar. The solid glucose contains from 10 to 12 per cent, of water, and the dry sub- 
 stance from 95 to 98 per cent, of sugar. The quantity of calcium sulphate in the 
 solid sugar amounts to \ per cent, and in the liqueur syrup to ^ per cent. 
 
 The manufacture of granular grape sugar was introduced by Fou chard in Neuilly. 
 The saccharification is carried out in the way just described, care being taken to 
 secure as perfect a conversion as possible of the starch, since large quantities of dex- 
 trin would retard the crystallisation. So soon as the saccharification is complete the 
 liquid is neutralised, carefully filtered and evaporated in summer till it shows while 
 hot a density of T262, and in winter in the same state a density of T242. The cal- 
 cium sulphate is allowed to deposit in large clearing vessels situated in a cool place 
 or cooled by means of serpentine tubes through which cold water is passed to prevent 
 fermentation. After 24 or 30 hours the syrup is cold and clear; it is then brought to 
 crystallisation in vertical tubs open above, furnished with a perforated bottom, the 
 apertures of which are closed with little wooden plugs during the crystallisation. The 
 tubs are placed upon a stand over a gutter lined with lead. After 10 or 12 days 
 crystallisation commences. As soon as the liquid is charged to about two-thirds with 
 crystals, the little plugs at the bottom of the tubs are drawn out and the syrup allowed 
 to run out. The syrup is again boiled with sulphuric acid to convert the unchanged 
 dextrin contained in it into sugar. 
 
 The drained crystals are placed upon gypsum plates in a drying oven and exposed 
 to a current of air at a temperature of 22 or 25. If the temperature were higher 
 the crystals would melt in the adhering syrup and stick together. The formation of 
 lumps is unavoidable even with the utmost care, and the dry sugar is therefore sifted 
 and the pieces left on the sieve are broken between rollers. 
 
 Grlucose or starch sugar, either in the solid form or in the state of syrup, is used 
 for a variety of purposes : in brewing as a substitute for malt (see BEEB) ; and in the 
 manufacture of spirit. It is also used in the production of wine (see WINE). The 
 dense syrup is chiefly used for preserving fruit, and in the preparation of liqueurs. 
 
 CANE' SUGAR is chiefly prepared from the sugar cane and the sugar beet. Smaller 
 quantities are prepared in Canada and the United States from the sugar maple (Acer 
 sacckarinum), in China from Sorghum saccharatum; and in India from the juice of the 
 palm. 
 
 In North America, where the maple is indigenous-find very abundant, the produc- 
 tion of sugar from this source is a regular branch of industry. The process of manu- 
 facture is very crude : about the month of February or March, holes are bored in the 
 trees to the depth of about half an inch into the white bark or splint of the stem, 
 and the juice which slowly flows out is collected in troughs, from which it is trans- 
 ferred to the boiling pans, where it is rapidly evaporated, and skimmed meanwhile, 
 until it is sufficiently concentrated to be filtered through woollen cloths. The syrup 
 thus obtained is further boiled down and allowed to crystallise in moulds. 
 
 Culture of the Sugar Cane. The sugar cane (Saccharum officinarwri) is richer 
 in sugar and contains less non-saccharine matter than any other sugar-bearing plant. 
 When ripe it contains 90 per cent, of juice, having a saccharometer density of 15 to 
 20, varying in the amount of sugar it contains from 12 to 22 per cent., but averaging 
 about 18 per cent, The manufacture of sugar from the sugar cane has been known 
 from the most ancient times. The methods of manufacture have in some colonies 
 undergone many improvements in recent years ; but in many places it is still so im- 
 perfectly carried on that a yield of 5 or 6 per cent, is with difficulty obtained. 
 
 The sugar cane comes from India and China. The inhabitants of those countries 
 first used the juice of the plant as a sweet drink, and then prepared from it a syrup 
 and crystallised sugar. The, sugar cane flourishes only in countries with a tropical 
 climate ; in northern countries the product, and especially the amount of sugar, is 
 much smaller. Different varieties are cultivated ; the best of them are known as 
 Otaheite and Batavia cane, and violet and striped violet canes from Java. 
 
 The cultivation of the sugar cane requires a generous rich soil, as free as possible 
 from soluble salts and artificial manuring. A too large amount of salt in the soil, as 
 it often occurs in the neighbourhood of the sea, is injurious to the quality of the cane, 
 the salt passing into the juice and promoting the formation of molasses. In the 
 absence of a sufficiency of stable manure, guano and fish refuse, and phosphates, flesh 
 and blood manure, and bone black from Europe are used. During the last few years 
 a considerable quantity of potash salts from Stassfurt, and of superphosphates, have 
 been sent to the colonies. The manuring with blood in the colonies has given rise to 
 a peculiar result ; the rats allured by the smell seek out this manure, and eat not only 
 it but the root stocks of the cane also, thus doing considerable damage. It is said 
 that this can be avoided by mixing charcoal dust and soot with the blood. 
 
810 
 
 Fia. 590. 
 
 FIG. 591. 
 
THE SUGAR CANE. 
 
 811 
 
 The sugar cane can be raised from seed ; this is done however only exceptionally, 
 generally it is multiplied by cuttings. These cuttings are placed obliquely, at an 
 angle of 45, in small furrows 20 inches long, 1 inches wide, and 7 inches deep, and 
 covered with moist earth. Fig. 588 represents a slip which has already thrown up 
 several rooting shoots. The first development of the young plant is shown in fig. 589. 
 The slender stalk shoots upward, forming numerous knots, and throwing off first the 
 lower and then the following leaves. Eig. 59 1 shows a plant two-thirds or three-fourths 
 grown. The stalks are from 6 to 12 feet high, with a diameter at the centre of lto 2 
 inches. The largest leaves are 3 to 4 feet long, and 1 to 2 inches broad. The leaves 
 are longitudinally veined, and have very stout whitish nerves ; the colour of the re- 
 mainder of the leaf is green to yellowish green ; the surface is smooth and the edges 
 rough. After from twelve to fifteen months, according to the soil and the climate, the 
 plant begins to flower ; the upper part increases considerably in length (fig. 590), and 
 there is formed a panicle of silvery white flowers. 
 
 Frequently it happens that the cane does not flower, and consequently it cannot 
 then bear seed. The ripeness of the stalk is then recognised by its becoming yellow 
 
 FIG. 595. 
 
 FIG. 596. 
 
 FIG. 592, 
 
 FIG. 593. 
 
 coloured, beginning from below. Figs. 592, 593, and 594 show sections of the cane in 
 the ripe condition. The knots are separated from each other by a distance of 3 to 5 
 inches The tissue at the knots is much harder and denser than that between them, 
 and the sap there also is poorer in sugar ; the further therefore the knots are from one 
 another and the longer the internodes, the more advantageous is the cane for working. 
 
 Fiff '593 shows the longitudinal section of a cane that has been split, in which 
 appear a number of strong parallel fibres, packed closely upon each other near the 
 Sterior, but in the middle wider apart. Figs. 595 and 596 (on a larger scale) show 
 these more clearlv They are the vascular bundles, formed of tubes and vessels im- 
 bedded in the parenchyma of the medulla, and are dispersed through the entire plant. 
 
 The sap contains various nitrogenous and non-nitrogenous substances, phosphates, 
 alkaline salts, silica, and a very small quantity of an essential oil having an agreeable 
 odour Through this oil sugar prepared from the cane can be easily distinguished 
 from beet sugar. The agreeable smell of sugar from the cane, as well as the molasses, 
 allows of its immediate consumption; but an essential oil occurring in the beet imparts 
 to beet suga*so disagreeable an odour that it cannot be eaten without previous refining. 
 
812 
 
 SUGAR. 
 
 FIG. 597- 
 
 Structure and Composition of Sugar Cane A longitudinal section of the sugar 
 cane in the ripe condition, when it has acquired a yellow colour and most of the 
 leaves have fallen off, if examined proceeding from the exterior to the centre, presents 
 the following points : 
 
 1. A fine layer (g g, fig. 597), lying upon the cuticle, and consisting of a kind 
 of wax, which Dumas examined and described as cerosin. 
 
 2. The cuticular layer (h) with square prominences, lying 
 close upon the intercellular spaces of the tissue beneath. 
 
 3. Thick walls (jj, figs. 597 and 598) of long epidermis 
 cells (i ). The separate cells lie close to one another, though 
 a line of demarcation between them is perceptible. The 
 cell cavities are in communication with each other through 
 a delicate membrane by ducts in the cell walls. 
 
 4. A thin- walled cellular tissue (m m) under the epidermis 
 (II, fig. 597). 
 
 5. A somewhat thick-walled cell tissue, the membranes of 
 which are traversed by pitted canals. 
 
 6. Two series of bundles of woody vessels, parallel with 
 the surface, and surrounding a space fillod with vessels. 
 In the first series these vessels lie close to one another, in 
 the second they are further apart. Similar bundles, but with 
 fewer woody vessels, separated more widely from each other 
 and lying in the midst of larger cells, occur as far as the 
 centre of the axis of the cane. 
 
 The layers of cells between the epidermis and the first two 
 series of woody bundles are free" from sugar. The sugar is 
 contained in the thin- walled cells which surround the vascular 
 bundles in the middle of the stem. 
 
 In the ripe condition, all the tissues after washing with 
 water are coloured yellow by iodine ; an addition of sulphuric 
 acid makes the colour more intense. The cuticle (h, fig. 597) 
 is coloured orange. Upon treating the tissues with caustic 
 soda, the albuminous substances situated in the cell mem- 
 branes are dissolved and washed out. The membranes of 
 the small pitted vessels and those of the sugar-bearing cells 
 then give the cellulose reaction, being coloured blue when 
 treated with iodine and sulphuric acid. The outer cell layers 
 withstand the action of caustic soda ; they become swollen 
 and distorted, and are broken up into separate cellular por- 
 tions, but they still continue to give the yellow colour when 
 treated with iodine and sulphuric acid. 
 
 The younger the cane is, the more easily is the cellulose reaction produced. In 
 young canes the sacchariferous cells, upon treatment with iodine and sulphuric acid, 
 take at first a yellow colour ; this is soon changed to green, and finally to blue. When 
 a quite young shoot, 7 or 8 inches long, and still surrounded by the germinal leaves, 
 is treated with aqueous solution of iodine the entire tissue, with the exception of the 
 small pitted vessels, is coloured yellow. A drop of sulphuric acid produces in this 
 a most beautiful microscopic appearance. The tissue of the knots, the cuticle, and all 
 the inner parts of which are yellow, become violet through the entire thickness of 
 their swollen walls ; the cuticle and epidermis take a deep orange yellow 
 colour, and the entire thickness of the cells of the underlying cellular 
 tissue becomes blue. The small pitted vessels are also coloured blue, and 
 form a blue cylindrical bundle, which is surrounded by a yellow portion, 
 consisting of the large pitted vessels with their numerous pits, the 
 circular vessels, and the woody vessels. In the middle of the latter can 
 be seen the inner swollen layer, consisting of purer cellulose, which is 
 coloured blue. 
 
 Throughout the young stalks and shoots occur also numerous spiral 
 vessels (fig. 599) ; but these disappear afterwards, and are not detected in 
 the ripe cane. 
 
 In the young stalks and newly formed leaves numerous starch 
 granules occur; the stalks especially contain them in the tissue lying 
 directly under the epidermis, and in the sugar-bearing cells surrounding 
 the vascular bundles. They are also found in the cells surrounding the 
 vascular bundles in the young leaves. In the ripe stalks these deposits 
 
 
 
 of starch no longer occur, or at most in the upper and younger internodes. The 
 richness of the sap in sugar is in proportion to the ripeness of the cane ; in 
 
CONSTITUENTS OF THE SUGAR CANE. 813 
 
 the unripe condition it contains, besides starch, many other foreign bodies that 
 exercise an injurious influence upon the crystallisation of the sugar. For this 
 reason the tops and root shoots are removed at the harvest, and are used as cuttings 
 for the next 'crop, as fodder, or as fuel. This occurrence of starch in the young parts of 
 the plant, and its disappearance in the ripe parts, explains how it is that many analysts 
 have found the juice of the sugar cane rich in starch, whilst others have not met with it. 
 The following table shows the composition of the sugar cane when ripe, and also 
 in the first third of its development : 
 
 Perfectly Ripe. 
 
 Water ' . 71-04 
 
 Cane sugar 18-00 
 
 Cellulose, lignin, pectin, pectic acid 9-56 
 
 Albumin and three other nitrogenous bodies . . . . 0'55 
 Cerosin, chlorophyll, yellow, brown, and red colouring matters, 
 
 fat, resin, essential oil, and an aromatic soluble substance . 0'37 
 Insoluble salts 0"12; soluble salts 0'16; calcium and magnesium 
 phosphates, alumina, calcium sulphate, oxalate, acetate, and 
 malate, soda, potassium sulphate and chloride, and sodium 
 
 chloride 0'28 
 
 Silica 0-20 
 
 100-00 
 
 First Third of Development. 
 
 Water . . . .... . . . . 7970 
 
 Cane sugar and grape sugar 9'06 
 
 Cellulose and incrusting matters . . . ... 7 '03 
 
 Albumin and three other nitrogenous bodies . . . .1-17 
 
 Starch, cerosin, chlorophyll, and yellow, brown and red colour- 
 ing matters . ,..,' . . 1*09 
 
 Fat and aromatic bodies, hygroscopic substances, essential oil, 
 
 soluble and insoluble salts, alumina, and silica . . . T95 
 
 100-00 
 
 According to Casaseca, the sugar is distributed in the Havanna cane in the 
 following proportions : 
 
 Entire Cane Peeled Cane Bind 
 
 Water , . ~. . . . . 77 77'8 69'5 
 
 Sugar, etc. . ... . . 12 16'2 11-5 
 
 Ligneous substances . .' . . 11 6 19 
 
 The amount of water in the sugar cane increases towards the top of the stalks, 
 and the greatest amount of sugar is found in the lower third of the cane, much less 
 in the upper third , 
 
 The average composition of the juice of the sugar cane is : 
 
 Water . . ... . -. . .' . . 81-00 
 
 Sugar 18-20 
 
 Organic substances precipitated by lead salts . '.'.' . '45 
 
 Saline substances . . .'' -. . V ; ". , . '35 
 
 100-00 
 
 Although it may be assumed that in the ripe cane, only cane sugar, but no grape 
 or fruit sugar, occurs, it may happen, through decomposition produced by mechanical 
 injuries received during the gathering of the cane, that the juice to be manufactured 
 will contain small quantities of both these kinds of sugar. 
 
 The quantity of cellulose, lignin, etc., is dependent upon the greater or less dis- 
 tance between the knots, as the tissues of the nodes are much more dense than those 
 of the internodes. The pectic acid is also combined with bases. 
 
 The aromatic soluble substance is soluble in cold 95 per cent, alcohol ; it is preci- 
 pitated by tannin, and at the temperature of boiling is coloured red brown. Accord- 
 ing to Plagne and Hervy, this substance has the property of converting the sugar 
 info a visc.oiis, tasteless substance, and of preventing the alcoholic fermentation. It 
 can be removed by filtration of the cold juice through animal charcoal. 
 
 According to Payen's observations cane juice contains acid calcium and magnesium 
 
814 SUGAR. 
 
 phosphate. The addition of a slight excess of ammonia produces a crystalline preci- 
 pitate of ammonio-magnesian phosphate (0'09 per cent.), besides a flocculent pre- 
 cipitate, which, collected and treated with sulphuric acid, yields calcium sulphate 
 and acid phosphate. Under the influence of air and ammonia the juice is coloured 
 brown. 
 
 From the foregoing figures it appears that the unripe cane contains only about 
 half as much sugar as the ripe cane and about a third less tissue-forming material ; on 
 the other hand, it contains three times as much foreign or non-saccharine substances. 
 These differences make it evident that in districts where, through climatic influences, 
 the cane does not come to perfect maturity, either a very insufficient yield of sugar 
 is obtained or only syrup can be produced ; whilst in hot countries where the plant 
 attains its normal maturity, it yields a cane containing but little non-saccharine material. 
 The knots of the cane are formed of a dense tissue, in which woody vessels with 
 thick walls predominate. The membranes of all the cells are here much thicker than 
 in other parts ; and the sugar-bearing cells are smaller and less numerous. The pro- 
 portion of sugar is consequently hardly half as high as in the internodes. As the 
 cells not filled with sugar contain other constituents, the sap in the nodes is propor- 
 tionally inferior. 
 
 The ripe canes are cut down close to the base, and carried to a warehouse near the 
 boiling house. The flowering stalk and the leaves are removed ; and the four or five 
 upper knots, containing less sugar, are cut off, and used as cuttings, fodder, or fuel. 
 Further, all the canes that have sustained mechanical injury those broken by the 
 wind or gnawed by the rats must be carefully separated, as these readily commence 
 to putrefy, and the fermentation may spread through the whole contents of the ware- 
 house. The juice from these injured stalks is mixed with molasses, and used in the 
 manufacture of rum. 
 
 The harvest of canes varies very much in the different colonies according to 
 climate. The following quantities are said to represent the average yield per acre for 
 the fifteen months period of growth : Martinique, 20 cwts. ; Guadeloupe, 24 cwts. ; 
 Eeunion, 40 cwts. ; Brazil, 60 cwts. 
 
 Culture of the Sugar Beet. Although the manufacture of beet sugar dates 
 back but a few decades, its development during this period has progressed more 
 rapidly than that of the old methods of preparing sugar from the sugar cane. 
 
 It is now one of the most important of agricultural industries. It can be carried 
 on profitably and well only when the producer of the raw material the beet root 
 is at the same time interested in its manufacture into sugar. When this is not the 
 case, there is a possibility that the producer of the raw material, looking after his own 
 interests only, will endeavour to raise as many roots as possible upon his land irre- 
 spective of their quality. But the cultivator who is at the same time a sugar manu- 
 facturer directs his attention to raising sugar-producing beet roots, in order that he 
 may bring to the factory a superior raw material. 
 
 Properly carried on, the cultivation of the sugar beet is greatly beneficial to other 
 agriculture. The deep and careful cultivation which the beet requires greatly im- 
 proves the land, the soil becoming thereby considerably deepened, and the disintegra- 
 tion and solution of the mineral constituents greatly accelerated. 
 
 The tap-root of the beet, which is 3 to 6 feet in length, descends to a great depth, 
 loosening the subsoil, and drawing the greater part of its nourishment from a depth 
 of soil which most other plants fail to reach. The nourishment thus obtained passes 
 partly into the leaves, and is left with them upon the ground, after the gathering in of 
 the crop. When the sugar manufacture is carried on in connection with the beet cul- 
 tivation, all the constituents of the beet, with the exception of the carbon obtained 
 from the atmosphere, can be returned to the land, since the refuse of the factory the 
 heads of the beets, pressings, lixiviated residue, molasses, etc. is consumed by farm 
 stock and becomes converted into manure, while the residuary products and 
 the bone black used, etc. are, either immediately or after preparation, incorporated 
 with the soil. By such a method, in which only raw sugar, an organic substance 
 almost free from nitrogen or ash, is withdrawn from the soil, it is not exhausted. 
 
 In very few sugar factories, however, is the molasses used for fodder, but it is sold, 
 and with it many important constituents of the soil potash salts in particular. 
 Nevertheless, commercial manures are quite capable of supplying the deficiency occa- 
 sioned by the sale of molasses. 
 
 On the other hand, the culture of the beet, improperly carried on, with no provi- 
 sion made to return to the land the constituents taken away, is most exhausting. The 
 consequences are, that the beot roots first deteriorate in quality, producing a less 
 amount of sugar, then fall off in quantity, and at last become stunted and liable to 
 disease. Rcots that appear sound when gathered, become in a short time decayed 
 and afterwards completely rotten. 
 
THE SUGAR BEET, 815 
 
 Further, when beets are raised too often upon the same ground, the crops suffer 
 much from various parasites, animal as well as vegetable, which increase in the 
 beet fields, in the most surprising manner. Among the enemies of the beets, the 
 cockchafer or May bug is especially prominent, the larvae remaining for a number of 
 years in the ground and making great havoc among the young plants. 
 
 The mole cricket or fen cricket (Gryllotalpa vulgaris, Latr.) is another insect 
 which has lately shown itself exceedingly destructive to the beet, as it feeds upon the 
 roots of the beets which stand about its nest. Another enemy is the beet worm. 
 Of vegetable parasites there are the beet killer (Rhizoctonia violacea, Tul.), a fungus 
 which appears in reddish-brown spots upon the surface of the roots, and passing in- 
 wards, causes rottenness and complete "destruction of the beet, and the beet blight 
 ( Uromyces bette, Tul.) which attacks the leaves. 
 
 For the cultivation of the beet, a dry, or at least well-drained, generous deep clay 
 soil, containing some lime, should be selected. This should be broken up, as soon as 
 the preceding crop has been got in, in order to destroy the weeds ; after a little time 
 it should be ploughed as deeply as possible, and then left lying during the winter in 
 great furrows. As a thorough preparation of the soil is essential to the success of the 
 beet culture, in many sugar-producing districts the steam plough is profitably em- 
 ployed, no other implement being able to do the work so regularly and thoroughly. 
 Except levelling and a slight loosening of the heavy soils, or compacting the lighter 
 ones by means of rolling, little should be left to be done in the spring, as disturbance 
 of the soil at this season is disadvantageous to the proper growth of the beet. 
 
 Fresh stable manure should never be used for beets, although it may be profitably 
 used for the preceding crop. Liquid manures are valuable, but should only be em- 
 ployed in autumn. In beet culture extensive use is made of commercial manures, 
 such as guano, superphosphate, and potash salts. The use of the latter should never be 
 neglected, unless the soil itself be especially rich in potash, as it is potash in particular 
 which is needed by the beets, and it ' is also removed in great quantities in the 
 molasses. In using the potassium salts from the Stassfurt factories, they should be 
 brought upon the ground in autumn, and carefully distributed in the soil. By this 
 means, the foreign salts contained in this fertiliser become dissolved by moisture, and 
 partly washed away, while the potash in contact with the soil becomes absorbed and 
 retained in an insoluble form. Guano and superphosphate are spread upon the 
 ground immediately before planting, and are incorporated with the soil by means of 
 the harrow. These fertilisers may be most profitably used incorporated with qne 
 another, in the proportion of one part of guano to two or three of superphosphate. 
 It often happens that manuring with guano alone, or the use of large quantities of it, so 
 greatly accelerates the growth of the beets, that they pass through the whole course of 
 their development the first year, and shoot up into seed, instead of producing roots 
 containing sugar. This is avoided by using a moderate amount of guano mixed with 
 superphosphate. 
 
 The work of planting should be done as early as possible, so as to afford the plants 
 a long growing season, and yet enable the factory operations to be begun early in 
 autumn. It is necessary to wait until the close of the spring, as the land should 
 no longer be wet, but thoroughly warmed by the sun, so that the young plants may 
 soon spring up. For the early growth, warm weather and a moderate amount of 
 rain are most favourable. 
 
 The interval between the plants should not be too great, or else, though the growth 
 goes on rapidly, and the crop is large, there is little sugar yielded. Other circum- 
 stances being equal, the roots are rich in sugar in proportion as they remain of small 
 size, and stand near together. Yet as this implies a considerable diminution in the crop, 
 the question is to get a satisfactory quantity of roots, and yet such as are rich in 
 sugar. The extreme distance between individual plants found advisable is IJfeet 
 each way ; but the interval is frequently less. Boots are thus obtained of medium 
 size, averaging in weight from 1 Ibs. to If Ibs. 
 
 The plants usually reach maturity some time in September, according to the time 
 of sowing, and the condition of the weather during the period of growth. The root 
 no longer increases in volume, and the leaves begin to wither, commencing at the 
 outer circle. Warm rains followed by warm weather at this period are especially 
 damaging, causing the beet to begin a new growth, and to send out new leaves from 
 the middle of the plant. The ingredients of the sap stored in the root are used in 
 the formation of these new leaves, and the consequence is a root containing but little 
 sugar. The most favourable beet crop is obtained when the withering of the leaves 
 is accompanied by rather dry and cool weather. 
 
 The roots are gathered one by one, being raised out of the ground by means of a 
 spade ; the leaves are removed, and the roots are buried in pits until required for use 
 iu the factor^'. To remove the loaves the usual custom is to cut off the upper part 
 
816 
 
 SUGAR. 
 
 of the beet with the leaves attached, but sometimes they are wrenched off with the 
 hand, leaving the root entire, by which method the inner part of the root is less 
 exposed to the action of the air and remains sounder. The leaves should never be 
 removed before the beets are gathered. The pits used for storing the roots are 
 usually dug in the field itself as near as possible to the road, so as to admit of the 
 beets being easily carted away. The pits are prepared in a way similar to those used 
 for storing potatoes (see p. 787). Some manufacturers prefer large pits, others again 
 select pits of smaller dimensions ; some cover in their pits deeply at once, others 
 prefer to wait until cold weather sets in ; in every case the chief object in view is 
 to keep the pits dry and preserve them against a change of temperature. The pits 
 should be well protected against the winter frosts, and against a sudden occurrence of 
 warm weather in the spring. The frosts of winter are hardly more damaging than 
 warm weather in the spring, which causes the beets to sprout in the pit, and lose a 
 considerable part of their sugar. Loss of sugar goes on during the whole of the time 
 the beets are kept, so that even the best contain considerably less sugar in February 
 than in October, and in March and April the loss increases. The storing time should 
 therefore be reduced as far as possible by working up the beets quickly. 
 
 The choice of seed has great influence upon the quality of the beet crop. There 
 are many varieties of beet, all of which have proceeded from the white sugar beet 
 originally cultivated in Silesia. Where plants of good quality are at hand, it is well 
 to raise the seed from them, provided the field where they are grown is sufficiently 
 distant from other fields of seed beet ; if this precaution be not taken, it is impossible 
 to guard against hybridising. To the proper culture of the beet seed, the German 
 manufacturers are greatly indebted for the high position which the sugar industry 
 has reached among them, they being in this, respect far beyond their French com- 
 petitors. Generally it may be stated that in the German factories 9 per cent, of 
 crystallised sugar is obtained from the roots, while the French do not get more than 
 6 to 7 per cent. 
 
 Anatomical Structure of the Sugar Beet. If a sugar beet be cut, its cross-section 
 exhibits a number of concentric rings. At the exterior are seen five or six courses of 
 cells which form the epidermis. These cells consist of much thickened membranes, 
 and con-tain albumin, oil, salts of calcium and silicic acid. Frequently the 
 epidermis is bruised or injured during growth, and when this occurs the underlying 
 cells become converted into epidermis by thickening of their membranes, thus making 
 compensation for the injury, and securing the protection of the tissues underneath. 
 This, however, is not a peculiarity of the epidermis of the sugar beet, for the same 
 phenomenon is observed in all plants provided with an epidermis. 
 
 Immediately under the epidermis lies a layer 
 of cells rich in protoplasm, which, when the 
 plants are exposed to the light, form chlorophyll ; 
 to this is due the green colour of that part of the 
 beet which is not covered by the earth. The 
 whole of the remainder of the beet consists of 
 parenchyma, in which vascular bundles are sym- 
 metrically disposed in concentric circles. The 
 parenchyma consists of small cylindrical roundish 
 or polyhedral cells, and is recognisable in the 
 beet by its white colour and its structure. The 
 circularly disposed vascular bundles may be seen 
 with the naked eye, and are easily distinguished 
 from the parenchyma. The parenchyma cells 
 are filled with the sugar sap, and in good beets 
 this kind of tissue is present in considerably 
 greater quantity than in beets of inferior 
 quality a fact which allows the value of dif- 
 ferent kinds of beets to be approximatejy esti- 
 mated. 
 
 The anatomical structure of the sugar beet 
 is shown in fig. 600 which represents a longi- 
 tudinal section of the sugar beet, showing the 
 spindle shape, and the long tap root reaching from 
 3 to 6 feet. In digging, the root is usually torn 
 off at the point N, and remains in the ground, 
 producing by its decomposition and decay a 
 mellow condition of the soil, its constituent 
 elements becoming available for future crops. 
 
 FIG. 600. 
 
STRUCTURE OF THE BEET ROOT. 
 
 817 
 
 The head of the beet (b c), which protrudes from the ground, assumes a green colour 
 upon exposure to the light ; it contains little sugar, but more foreign matter than the 
 remainder of the beet. Hence those varieties are preferred of which the largest por- 
 tion possible grows under the earth. The disadvantage would be very great if the 
 part above ground extended as far as is shown by the letters (a d). Upon the top of 
 the beet (B) is a pithy spot containing much water and salts, and but little sugar. 
 The tissue which forms this pith easily undergoes change during the ripening of the 
 plant, cavities being produced through degeneration of the cells. At a later period 
 this decomposition readily extends to the other parts of the beet. 
 
 The white zones (A B c D E) in this section 
 show the sugar-bearing tissues which surround 
 the vascular bundles. The part of the beet be- 
 tween these rings either contains very little sugar 
 or none at all. 
 
 Pig. 601 shows a cross- section of the same 
 variety of beet, in which the position of the con- 
 centric layers is very noticeable. In the middle, 
 round the axis of the root, may be seen the 
 vascular bundles surrounded by the sugar- 
 bearing tissues, which gives to this part the ap- 
 pearance of a ringed surface (A). Another circle 
 (B) similarly shows the vascular bundles sur- 
 rounded by sugar-bearing tissues in this region. 
 The remaining concentric circles (c B E F) cor- 
 respond to the same parts. -^ ia - 601. 
 
 Fig. 602 is a representation of a cross-section as it appears under the microscope 
 and shows the details more clearly. The zones of vascular bundles are shown at 
 (A B c D) with the sap-bearing vessels (a a, a) in the midst of these zones, and beneath 
 
 FIG. 602. 
 
 is a longitudinal section of such a zone, the sap-bearing vessels being here also shown 
 at a. The letter b in both sections marks the cambium portion of the vascular bundles, 
 the cells of which are considerably elongated. The parenchyma lying between the 
 vascular bundles, which contains the sugar, is shown at c. The parenchyma cells 
 become more approximated to each other towards the surface of the beet. In the 
 outside ring are dark semi-transparent cells (e e) around an isolated vessel, the dark 
 cells being again surrounded by sugar-bearing cells. The dark cells (e e) contain 
 small crystals of crystalline agglomerate of calcium oxalate, and they are found in the 
 greatest quantity near the head of the beet. 
 
 Fig. 602 shows also the epidermis tissue (d d), consisting of four or five layers of 
 cells, the membranes of which are impregnated with silicic acid, calcium salts, and 
 fattv and nitrogenous substances. Under the epidermis is a layer of cells rich in 
 protoplasm, and in the red varieties, containing the red colouring matter which forms 
 
 3 G 
 
818 SUGAR. 
 
 chlorophyll upon exposure to light. At df is shown a lesion of the epidermis, where 
 the cell layers lying under it have become changed into epidermis. 
 
 Composition of the Beet. By far the greater part of the sugar beet consists of 
 water and substances dissolved in water. If the beet be reduced by attrition upon a 
 rasp, or pulper, so that the cellular membranes are thoroughly broken up, a pulp is 
 obtained from which, by treatment with water, all that is soluble may be removed, 
 leaving the cell membranes and the insoluble constituents of the tissue. When dried 
 this residuum is equal, upon an average, to 4 per cent, of the weight of the beet. The 
 variation in the amount of residuum is never very great, being never below 3 or exceed- 
 ing 5 per cent. It can therefore be assumed that the beet consists of : pith or residue 
 4 per cent., sap 96 per cent. 
 
 The composition of the sap is influenced greatly by the quality of the beet, the 
 nature of the soil, the manuring, and the character of the weather. Even if beets be 
 grown throughout under similar conditions, they will exhibit the greatest diversity of 
 composition in individual specimens. In an examination of about one hundred 
 specimens of beets grown under like conditions upon the same field, it was found that 
 the dry substance varied between 13'37 and 2T52 per cent., the mean of all the ob- 
 servations being 18' 19. If the amount of insoluble residue be estimated at 4 per cent., 
 the following will be the result : 
 
 Maximum Minimum Mean 
 
 Sap ingredients 17'52 9'37 14-19 
 
 Water 78'48 86*63 81-81 
 
 Insoluble residue .... 4-00 4'00 4-00 
 
 By far the largest part of the sap ingredients is sugar (cane sugar), but the pro- 
 portion varies within wide limits, dependent upon a variety of circumstances. 
 
 1. The quality of the Seed. There are so-called sugar beets, the proportion of 
 sugar in which, under even the most favourable circumstances, does not amount to 
 more than 8 or 9 per cent., while other choice seeds produce beets containing 17 per 
 cent, and upwards of sugar. 
 
 2. The nature of the Soil. A soil unsuited to beet culture, even if the seed be of 
 the best, will not 'yield beets containing so much sugar as is secured from beet 
 grown in more suitable soil. If a great amount of stable manure is used also, the 
 crop of beets will be large, but will leave much to be desired as to quality. Eepeated 
 experiments have shown that beets manured in autumn with potassium salts are much 
 richer in sugar than those not thus manured. 
 
 3. The size of the Beets. Usually the larger the beet, the poorer it is in sugar; 
 the greater the circumference, the greater the amount of water and foreign elements 
 contained in the sap. 
 
 4. The Weather. The weather has the greatest influence upon the beet at the 
 close of its growth, when the plant is maturing. If, in consequence of rain followed 
 by warm weather, the ripe beets commence a second growth, the quantity of sugar 
 diminishes daily, it being used up for the nourishment of the new leaves. 
 
 5. Other causes which cannot be explained co-operate with those mentioned, and the 
 result is that beets grown under similar conditions, raised from the same seed, upon 
 the same ground, and in the same year, are never found to contain precisely the same 
 percentage of sugar and other constituents. 
 
 Experiments made upon about one hundred specimens of sugar beets gave the 
 following percentage composition of the juice : 
 
 Maximum Minimum Mean 
 
 Sugar 17*68 9*56 13-93 
 
 Other substances . * . . 3-51 -38 1'73 
 
 Water 81-20 87*65 84-45 
 
 There being so great a diversity as to the quantity of sugar in individual specimens, 
 it is plain that no correct estimate can be formed of the amount of sugar contained in 
 a large quantity of beets, even if they have been grown in the same field. It is im- 
 portant to bear in mind the great liability to error, in drawing conclusions from the 
 results of single experiments as to the amount of profit to be derived from the manu- 
 facture of considerable quantities. In order to get tolerably correct data for deter- 
 mining the amount of sugar in quantities of beets, ihe juice from twenty, thirty, or 
 even fifty specimens should be well mixed and then examined. Of the remaining 
 ingredients of the juice, the following may be mentioned: 
 
 Grape Sugar and Fruit Sugar. In beets of good quality, mere traces or none 
 at all of those kinds of sugar are found ; they result from the transformation of cane 
 sugar through the rotting or germination of the beet. Their presence is disadvan- 
 tageous, owing to the fact that, in the process of refining the juice, they remain in the 
 
CONSTITUENTS OF THE BEET ROOT. 819 
 
 alkaline solution, and quickly decompose upon contact with the air, imparting a dark 
 colour to the juice, that requires a considerable expenditure of bone black for its 
 removal. 
 
 Organic Acids. Oxalic, tartaric, citric, malic, and some other acids, combined 
 with potassium, sodium, calcium, magnesium, and other bases, sometimes as neutral, 
 and sometimes as acid salts. In the refining of the juice the acid salts are neutralised 
 by the addition of lime, and the acids previously combined with alkalies become 
 for the most part converted into calcium salts. The calcium salts occurring in the 
 sap of the beets combined with organic acids are usually insoluble in water ; they 
 are therefore removed in the process of clarifying. But their removal by this process 
 is not complete, owing to the fact that the salts insoluble in pure water are slightly 
 soluble in water containing sugar in solution. Consequently a portion of the calcium 
 salts remains in the juice, and is afterwards removed by means of animal charcoal. 
 
 Grum, Starch, and Fatty Substances. These substances occur only in very 
 small quantities, and are easily removed in the first process of clarifying, and by the 
 treatment with animal charcoal. 
 
 Colouring Matter. In the undamaged beet the juice is colourless, but as soon 
 as it comes into contact with air, it becomes coloured, first, of an indefinite grey colour, 
 then reddish, and frequently a rather deep brownish red ; after long exposure to the 
 air it becomes almost black. The composition and properties of this colouring matter 
 which thus decomposes upon exposure to the air are not known. It is easily removed 
 from the juice by treatment with lime or basic lead acetate. The red varieties of 
 beet contain also a red colouring matter in the sap. The part of the otherwise 
 colourless beet which grows above the ground always contains chlorophyll in the outer 
 cell layers. 
 
 Albumenoids. Among the different albumenoid compounds in the beet is albu- 
 min itself. Upon heating the sap, this curdles into flakes insoluble in water and 
 separates out as a scum. Upon treatment with alkalies the albumin, which is otherwise 
 insoluble in the boiling liquid, becomes decomposed and goes partly into solution. 
 The removal of this dissolved albumin is extremely difficult, a part of it always 
 remaining in the juice and in a modified form in the syrup. Albumin being itself 
 incapable of crystallising, prevents the crystallisation of sugar also. The smaller, 
 therefore, the proportion of albumin contained in a beat juice, the better it is fitted 
 for the operations of the factory, and methods of obtaining the juice must be estimated 
 according to the relative amount of albumin in the juice they yield. 
 
 A spar agin. A nitrogenous organic substance, widely distributed in the veget- 
 able kingdom, which may be considered as an amide of malic acid. Upon boiling 
 with alkaline fluids in the clarifying process, asparagin is decomposed into aspartic 
 acid and ammonia, the latter escaping with the steam. 
 
 Betaine. A nitrogenous organic base discovered by Scheibler in beet juice, the 
 composition of which is represented by the formula Cj 5 H 83 N 3 6 . It is very soluble 
 in water, and is not removed from the juice during the manufacture, but passes into 
 the molasses in the crystallising process. 
 
 Ammonia and Nitric Acid. The first is combined with different acids, the 
 latter chiefly with potassium. The ammonium salts are decomposed in the clarifying 
 process, the ammonia escaping during the boiling of the juice, giving rise, together 
 with that from the decomposition of asparagin and albumenoids, to the penetrating 
 smell of ammonia which is present in a sugar factory, especially in the neighbourhood 
 of the clarifying vessels. The amount of ammonia escaping is sufficiently considerable 
 to render its recovery desirable. According to some experiments of Reiset, juice 
 from different kinds of beets yielded 0-441 to 0'775, or on an average 0'634 parts per 
 1,000 of ammonia. In a daily consumption of 50 tons of beets, this would represent 
 about 66 Ibs. of ammonia, or for the whole season of five months about 4 tons, which 
 would represent a large sum could it be utilised in manure. The proportion of 
 nitrates varies from the merest traces to considerable quantities, the amount being 
 dependent upon the richness in these compounds of the soil in which the beets are 
 grown. Potassium nitrate being very soluble in water, it is not removed during the 
 manufacture, but crystallises out with the sugar. Raw sugars have come into the 
 market, especially from Russia, which have contained a very large proportion of 
 potassium nitrate. 
 
 Other Inorganic Substances. Potash, soda, lime, magnesia, ferric oxide, 
 phosphoric acid, sulphuric acid, and chlorine, are never-failing constituents of plants, 
 and are therefore always found in beet juice. They are partially removed during the 
 manufacture, and part passes into the sugar, but the largest proportion is found in 
 
 3 a 2 
 
820 SUGAR, 
 
 the molasses. Many other substances occur in the beet juice, concerning the nature 
 and properties of \yhich nothing is yet known. They are the substances called ex- 
 tractives, which require to be further studied. 
 
 The constituents of the juice, other than cane sugar and water, are all in- 
 cluded under the name of non-saccharine matters. The relative behaviour of the 
 individual members of this group varies greatly ; some may be very easily removed 
 from the juice, others require a considerable expenditure of clarifying material ; 
 others again cannot be got rid of at all, while some so greatly hinder the crystallisa- 
 tion that a portion of the sugar is consequently lost. Hence, the value of a beet for 
 sugar manufacturing is not dependent alone upon the amount of sugar it contains, 
 but the amount of non-saccharine matter is also very important. Two varieties of 
 beet containing the same quantity of sugar may yield widely varying amounts of 
 crystallised sugar. For example, a beet which contains 14 per cent, of sugar and 2 per 
 cent, of non-saccharine matter will give very satisfactory results, while another also 
 containing 14 per cent, of sugar, but with 4 per cent, of non -saccharine matter, will 
 hardly pay for working up. 
 
 In estimating the value of a specimen of beet, therefore, the relative proportions of 
 sugar and non-saccharine matter should be accurately determined. As every con- 
 stituent which is neither sugar nor water is non-saccharine, it is sufficient to deter- 
 mine the amount of dry substance and of sugar in the juice. The amount of sugar is 
 determined either by an hydrometer or by polarisation (see p. ) the dry 
 substance by evaporating a previously weighed or measured quantity of the juice, and 
 weighing the residuum. The difference between the percentage of dry substance and of 
 sugar gives the amount of non-saccharine matter. The determination of the dry sub- 
 stance in the juice is not easy, some aptitude in chemical manipulation, and the expendi- 
 ture of considerable time while the evaporation is going on, being necessary. Results suf- 
 ficiently accurate for most purposes may be obtained by means ofthesaccharometer. 
 The saccharometer made by Brix and others is a hydrometer, the tube of which is 
 graduated in such a manner that each division represents 1 per cent, by weight of 
 sugar, in a liquid containing sugar in solution. If, for instance, the instrument sinks 
 in a solution of sugar to the 15 of its scale, the solution contains 15 parts of sugar in 
 every 100 parts of the mixture. If the solution contains, besides sugar, another sub- 
 stance having precisely the same specific gravity, the reading of the saccharometer 
 gives the percentage weight of sugar and the foreign substance together. If, however, 
 the specific gravity of the substance in solution with the sugar differs from that of 
 sugar, the saccharometer no longer gives the precise amount of dry residue. For 
 example, in a solution containing 14 per cent, of sugar and 2 per cent, of some sub- 
 stance having a specific gravity higher than that of sugar, the saccharometer will 
 register more than 16. If, however, the specific gravity of the second body be less 
 than that of sugar, the saccharometer will indicate an insufficient proportion of dry 
 residue. 
 
 As, however, sugar forms in all cases the principal constituent of beet juice, 
 whilst non-saccharine substances occur in relatively small quantities, and as moreover 
 these non-saccharine matters consist of a mixture of substances of different specific 
 gravities, many being of the same specific gravity as the sugar, some greater and some 
 less the saccharometer always gives results which are sufficiently exact for most 
 purposes. In practice, therefore, it is generally used for determining the amount of 
 dry residue, the difference between the results of the saccharometer and the polariser 
 being taken as indicating non-saccharine matter. 
 
 For example, the saccharometer shows 16 or 16 per cent., and by polarisation 
 14 per cent, of sugar is found; the juice then contains 16 14 = 2 per cent, of non- 
 saccharine matter, or ^|=0'875 of sugar. This fraction, which thus shows the pro- 
 portion both of dry residue and sugar, is called the sugar quotient or sugar factor, 
 and indicates that in 100 parts of dry substance in the juice examined, 87'5 parts are 
 sugar, and 12'5 are non-saccharine. 
 
 Similarly a non-saccharine factor can be obtained showing the relation of sugar to 
 non-saccharine matter. In the example given, the fraction is ^ = 0*143, the non- 
 sugar quotient, which indicates that, for every 100 parts of sugar in the juice, there 
 are 14*3 of non-saccharine constituents. 
 
 Besides the constituents of the juice, those of the pith have also to be considered. 
 When the pith is completely deprived of sap, it consists essentially of the membranes 
 of the parenchyma cells, and of the more or less woody portions of the vascular bundles, 
 the whole cemented together by pectous substances. Neither the pure cellulose nor 
 that which is partly converted into wood is of significance in the sugar manufacture; 
 for should some of it pass into the juice, it simply causes a mechanical turbidity 
 which is very easily removed. With the pectous substances it is however entirely 
 different. They become converted into metapectic acid, upon being subjected to the 
 
MANUFACTURE OF CANE SUGAE. 821 
 
 action of alkaline liquids. This acid, combining with the lime during the clarification, 
 becomes converted into non-cry stallisable calcium metapectate. Since all non-cryBtal- 
 lisable bodies impede the crystallisation of the sugar, the presence of this calcium 
 metapectate is a hindrance to the proper working up the juice. For this reason the 
 mixture of any pith with the juice should be carefully avoided. 
 
 The Operations of the Sugar Factory. The production of sugar consists essentially 
 of a number of operations, partly mechanical, and partly of a chemical nature, carried on 
 in various ways, and by the aid of apparatus of various construction. They consist in 
 
 1. The extraction of the saccharine juice. 
 
 2. The treatment of the juice with the object of separating dissolved and suspended 
 impurities. 
 
 3. The evaporation of the clear juice. 
 
 4. The crystallisation of the sugar. 
 
 According as the material from which sugar is to be obtained is sugar cane or beet 
 root, the several operations carried out differ somewhat in detail, though they are 
 essentially of the same nature. 
 
 Expression and Preparation of the Juice. The working of sugar cane is carried out 
 in various ways. Many factories have still the simplest and most imperfect arrange- 
 ments ; others are provided with all the improved apparatus used for similar purposes 
 in the beet-sugar manufactories. 
 
 In the older factories, the juice is obtained by simply crushing the cane between 
 channelled stone cylinders ; in many factories iron cylinders are used. The motive 
 power is variously water, wind, horses, or cattle, and sometimes steam. 
 
 The juice runs from the cylinders through a trough into a collecting vessel, where 
 it stands for an hour to allow fragments of crushed cane, sand, etc., to deposit. This 
 delay before the defecation is however highly injurious, as it may allow of the com- 
 mencement of fermentation. 
 
 An essential improvement has been obtained in the colonial manufactories by the 
 introduction of more perfect presses. "Whilst the old presses scarcely squeezed out 
 half the juice, the newer presses at first gave 60 to 65, and afterwards by further im- 
 provement 70 to 72 parts of juice from 1 00 parts of cane. 
 
 These presses consist of three hollow cast-iron cylinders, mounted horizontally in 
 a strong iron frame. By means of pressure screws, which move the bearings in which 
 the individual cylinders revolve, they may be brought riftarer to or removed further 
 from each other. One of the cylinders is set in motion by spur wheel and pinion, and 
 toothed wheels on the axes of the other cylinders work in one another so as to commu- 
 nicate the motion to them. The cane to be pressed is carried upon an endless band 
 to an inclined staging, and passed between the first pair of cylinders, where it is 
 pressed flat, and is then pressed a second time between other cylinders. As the in- 
 terval between the first pair of cylinders differs from that between the second pair, the 
 pressure on the cane varies. At first it is only crushed. 
 
 In order to allow the juice time to flow away, the motion of the cylinders has to 
 be a very slow one. From 70 to 75 parts of juice are obtained in Cuba and Keunion 
 from 100 parts of cane. 
 
 This satisfactory result is due to the great solidity of the presses and their mount- 
 ings, and also to the slow motion given to the cylinders, which make only one revolu- 
 tion in two minutes. In order to increase the production, this slowness of motion is 
 compensated by large dimensions, the cylinders constructed having sometimes a 
 diameter of 3| feet, and a length of nearly 7 feet. They yield daily from 70,000 to 
 90,000 gallons of juice, and are driven by 90 horse power. 
 
 The more perfect removal of the juice causes however a scarcity of fuel. When 
 only half of the juice is pressed from the cane, the trash from 100 parts of cane still 
 contains 10 parts of fibre and 10 parts of sugar, corresponding in heating value to 
 20 parts of wood. When 70 parts of juice are obtained, there remains in the trash 
 only 4 parts of sugar together with 10 parts of fibre, representing only 14 parts of 
 combustible material analogous to wood, or nearly one third less than before. But 
 with this smaller quantity of fuel, there is two fifths more juice to evaporate. The 
 improvement in the presses therefore necessitates an improvement in the evaporating 
 apparatus. 
 
 It often happens that several knots in the cane come simultaneously between the 
 cylinders, or that a foreign body may enter, and cause so great a resistance, as to en- 
 danger breaking a necessary part of the apparatus. In order to prevent this, one of the 
 least important, because easily replaced, parts of the machine, the shaft which com- 
 municates the movement to the pinion of the larger wheel, is made comparatively 
 weaker. If therefore a stoppage takes place, the probability is that this shaft will 
 give way. A reserve of shafts is therefore provided, so that the broken one can be 
 replaced, and the working proceed without loss of time. Another more suitable 
 
822 SUGAR. 
 
 method consists in connecting one of the wheels with the principal shaft by a friction 
 coupling ; if the resistance should then be too great, the wheel remains stationary, 
 the shaft overcoming the friction of the coupling. 
 
 The yield of juice may be still further improved by heating the cylinder of the 
 press with steam. The heat causes the cane to lose part of its elasticity, and allow 
 the juice to flow out more freely, whilst the cane also expands less upon the removal 
 of the pressure, and therefore sucks up less juice. 
 
 In the manufacture of sugar from beet roots the extraction of the juice requires to be 
 preceded by a cleansing operation by which they are first freed from earth, sand, stones, 
 grit, etc , so as to avoid injury to the machinery in w r hich they are afterwards worked up. 
 For this purpose a washing cylinder is used, such as is described on p. 764. It consists 
 essentially of a long cylindrical body, made either of wooden laths, or of perforated 
 iron surrounding a revolving axis, which with its barrel is supported in a large trough 
 corresponding in size and filled with water. At one end of the cylinder is an opening 
 for the introduction of the beets, and at the other is a self-acting arrangement by 
 means of which the beets are removed from the wash. By means of suitable cog- 
 wheels, the cylinder is rotated ten or fifteen times per minute ; the beets are thus set 
 in rapid motion in the water, so that the earth clinging to them is loosened and rubbed 
 away. Sand and stones at once sink, and fall through the openings of the cylinder 
 to the bottom of the vat, from which they are from time to time removed. The 
 lighter portion of earth remains incorporated with the water, and is removed either 
 by renewing the water from time to time, or by a constant stream of water running 
 through the vat. By slightly raising the temperature of the water, the removal of 
 tough clay is greatly facilitated. This is effected by means of a steam pipe laid 
 along the floor of the vat ; but it is only necessary when the beets are very clayey or 
 have been frozen while buried. In the last case the frozen earth should at once be 
 thawed away in warm water. 
 
 The more carefully the washing is performed, the less will be the damage to 
 the machinery in the subsequent operations. But a thorough washing can only be 
 effected by allowing the beets to. remain a long time in the cylinder. It cannot be 
 done by violent action, which has the further disadvantage that it injures the beets, 
 destroying the small roots that contain relatively most sugar. 
 
 Different modes of carriage are used to carry the beets from the place of storage to 
 the washing cylinder. One arrangement is shown in fig. 603 ; figs. 604 to 606 repre- 
 sent parts of the washing cylinder. 
 
 to 
 
 ' FIG. 603. 
 
 The beets are thrown upon an endless band (A, fig. 603) formed of iron rods united 
 each other by means of joints. This band, supported by rollers, revolves round 
 
PREPARATION OF BEET ROOTS. 
 
 823 
 
 cylinders, and the beets are thus carried forward to the chain-pump work (B), by 
 which they are raised, and allowed to drop into the hopper (c) of the washing cylinder 
 The construction of this cylinder as well as the chain arrangement is shown in figs. 
 604, 605 and 606, where the washing cylinder is united with a rinsing apparatus. By 
 means of the trap arrangement, the beets are thrown into a second vessel (B), contain- 
 
 15* 
 
 FIG. 604. 
 
 FIG. 605. 
 
 FIG. 606. 
 
 ing water in which is a stirrer with screw-shaped arms (B). The beets being freed 
 from all coarse dirt, are placed in the rinsing apparatus, which contains clean water, 
 and are there cleansed from any dirt that may remain. They are then thrown upon 
 the sloping surface (F), and are carried away for further operations. 
 
 If possible, it is well to have the washing apparatus in a low situation, such as in 
 the cellars of the factory; but of course this is only practicable where the nature of 
 the ground will allow the dirty water to flow away. The beets may then be brought 
 immediately from their place of storage to the wash-hopper upon the inclined plane, 
 the washed beets being afterwards raised to. the ground level by means of a chain- 
 pump or other arrangement. 
 
 The next operation is to remove by means of a knife the fine rootlets growing 
 from the side of the beet, also the green coloured upper part of the beet called the 
 beet head, which grew above the ground, and lastly the rotten specks. In this process 
 every single beet is subjected to a close inspection. To expedite this work, various 
 kinds of machinery have been constructed. For removing the beet tops a knife is 
 used, one end of which is fastened to a block by means of a hinge, while the rotten 
 portions are removed by a rotating bent blade ending in a point. Some manufacturers, 
 however, altogether dispense with this machinery, for although time may be gained by it, 
 the work is never so well done as by hand. There is, however, a very useful arrangement 
 called the beet round-about used for bringing the beets in the best manner to the 
 workmen who are to trim them. It consists of a perforated iron plate surrounded by 
 a rim, and revolving in a horizontal direction. The beets upon coming from the wash, 
 fall upon the conical case surrounding the vertical shaft, and slide toward the rim of 
 the plate. The labourers are posted around, and are able to seize the beets in the 
 most convenient position for trimming. Frequently another washing takes place upon 
 the round-about, a fine spray of water being brought to play upon the beets by means of a 
 strainer-like arrangement ; the dirt is carried off through the perforations in the plate. 
 
 In Germany, the trimmed roots are next thrown into a box-shaped, sheet-iron 
 weighing machine, having a perforated bottom, and again rinsed ; when the water has 
 drained off, they are weighed by the customs officer. 
 
 The reduction of the beets is effected either by grating them to a fine pulp or 
 cutting them into thin slices, according to the method by which it is intended to 
 obtain the juice. As the juice is contained in closed cells, which while closed 
 either yield no juice at all, or only yield it under strong pressure, it is requisite to 
 burst these cells by rupturing the membranes. This tearing is done by means of 
 graters which correspond essentially in their construction to those used in the manu- 
 facture of starch (vide STARCH). 
 
 The beet grater was invented by Thierry, and consisted originally of a cylinder, 
 the frame of which was formed of saw blades placed at a little distance from each other. 
 This cylinder is still used almost unaltered in the latest improved machines. Like 
 the potato crusher it is surrounded by a fixed case, with an opening for the hopper, 
 through winch the beets are carried to the teeth of the quickly revolving drum ; the 
 irregular form of the beets often leads to a choking of the hopper, and sometimes 
 they are so smooth that they glide upon the teeth of the drums without being reduced, 
 unless some pressure is applied. In the old machines in connection with the hopper, 
 which was situated on the side of the grater, there was a broad tube horizontally 
 placed, into which the beets fell one by one from the hopper. In this tube was a 
 
824 SUGAR. 
 
 wooden lever, with which the workman pressed the beets upon the grater. Eecent 
 improvements in the crusher consist in the proper adjustment of this pressing ar- 
 rangement. It is now made of metal instead of wood, and instead of being worked by 
 hand, its action is now effected by machinery. One 'form of the machine used in the 
 French factories is shown in fig. 607. A is the cylinder, the case of which is re- 
 moved in order to show the teeth of the grater. It consists of a great number of saw 
 
 Fro. 607. 
 
 blades, each of which lies between and is held fast by two iron bands, the teeth of 
 the grater being about ^ inch above the bands. The cylinder has a diameter 
 of about 2 feet, and a length of 4 feet, and has a motion communicated by the strap 
 of about 1000 revolutions per minute. Above the cylinder, and inside of the case, there 
 is a tube T, through an opening in which water is constantly sprinkled upon the 
 cylinder in order to keep the teeth of the grater free, and to thin the pulp. The beets 
 are thrown upon the inclined plane c, and carried to the body of the hopper D, where 
 they are caught in the opening of the pressing apparatus and carried to the grater. 
 The presser B, which in the cut is shown at one limit of its action, has a backward and 
 forward motion caused by a double-armed shaft turning upon the point E in the 
 following manner. The excentric o, turning upon its axis, at a certain point strikes 
 the upper part of the shaft, and drives it as far forward as the position shown in the 
 cut, and at the same time the presser, which is united with it, is driven to the one 
 limit of its action. The excentric continuing its revolution ceases to be in contact 
 with the shaft, and then the weight r attached to the other end of the shaft becomes 
 operative, and causes it to turn in the opposite direction. This motion brings the 
 presser back to the position indicated by B', the lower opening of the hopper becomes 
 free, and another quantity of beets are brought upon the presser. The excentric still 
 in motion, again meets the upper arm of the shaft, drives it forward, and forces upon 
 the grater the beets which are in front of the presser. The track of the presser is 
 about 1 ft. 2 in. in length, and the excentric makes seven revolutions in one minute. 
 The more rapid the movement of the cylinder and the slower that of the presser, the 
 finer is the resulting pulp. At the lower edge of the box in which the presser 
 works is an adjustable bar which connects the box with the grater. It is so placed 
 that it almost touches the teeth of the grater, and the nearer it comes to the grater, 
 the finer is the pulp, as it prevents coarse pieces which have been torn off and the 
 outer rind from passing into the pulp. The fine pulp is thrown upon this bar, and 
 falls at G into a suitable receptacle, under the grator. Each grater has four pressers 
 about 10 in. in breadth, and these dimensions are sufficient for working up 250 tons of 
 beets daily. 
 
 The graters of the German sugar manufactories differ from those of the French 
 in being smaller, on which account they are more easily managed and more durable. 
 The drum or cylinder of the G-erman grater is only about half the diameter, usually 
 24 or 26 inches, and each is double, corresponding to two pressers. The drum consists 
 of an iron frame formed of two disks and a shaft passing through the axis ; the shaft 
 has a driving strap wheel at each end, and a third upon the shaft between the disks, 
 
EXTRACTION OF JUICE FROM BEET ROOTS. 825 
 
 dividing them into two courses. Two rings are cast upon each of these wheels, form- 
 ing a groove. In fastening the teeth a clamp of seasoned wood is placed in the 
 circular depression thus formed ; then a saw blade is placed in position, and other 
 clamps and saw blades are placed alternately until the whole case of the drum is 
 fitted. The wooden clamps swell through absorption of moisture, and thus keep the 
 saw blades secure in their position. 
 
 Sometimes the teeth become bent by the strong pressure, and unfitted to furnish a 
 good pulp. The cylinder is then lifted from its position, and reversed so that it 
 revolves in the opposite direction ; the teeth then take hold of the beets and furnish a 
 good pulp. The turning may be repeated until the teeth have been almost com- 
 pletely worn away, when a reserve drum is placed in the grater, the other being 
 taken apart, and the teeth sharpened. 
 
 Champonnois' beet grater has been lately introduced into many of the French 
 factories. The advantage which it possesses over the ordinary grater is that it 
 furnishes a uniform pulp, entirely free from irregular pieces. The apparatus is very 
 similar to the potato grater described on page 766, the only difference being that it is 
 adapted to the larger size of the beets, and to the different quality of pulp required. 
 If the pulp of the beets is too fine, it is not so easily pressed and partially passes 
 through the pores of the pressing cloth. The dimensions found most effective for both 
 purposes are as follows : 
 
 Champonnois' 
 
 Beet grater Potato grater 
 
 Interior diameter of the cylinder . . . 1 5 in. 1 2 in. 
 
 Length of the saw blades . 
 
 Number of revolutions of the shaft per minute 
 
 7| in. 
 900-1000 
 
 Length of the teeth . 
 
 Width of the opening between the saw blades 
 
 Length of these openings .... 
 
 A grater of these dimensions, having the speed above given, works up 62 to 65 
 tons of beets in twenty-four hours. 
 
 In using Champonnois' grater or crusher, it has been found that very hard incrus- 
 tations form in a short time about the perforations through which the pulp escapes. 
 These perforations are only about inch in width, and become completely stopped up 
 in six or seven days. Payen found that these incrustations consisted partly of 
 crystals of calcium oxalate and partly of cell residue*. They may be easily removed 
 by introducing a small brazier, containing a few glowing coals, into the hollow of the 
 grater. The heat causes the concretions to shrivel up, and they may then be brushed 
 away or removed with a fine steel knife. 
 
 In this way a fresh grater is run for five days. During the succeeding three days 
 the cylinder has to be reversed every twelve hours, so that the teeth which are now 
 becoming shorter may meet the beets from the opposite direction. During the 
 following two days, the cylinder has to be reversed every six hours, after which the 
 cylinder must be removed and replaced by a freshly sharpened one. The reversal of 
 cylinders takes up about ten or twelve minutes. 
 
 The reduction of beets is considerably facilitated by the constant flow of a stream 
 of water through the hollow shaft. The pulp thus thinned with about 15 to 18 per 
 cent, of water, passes far more readily through the perforations of the cylinder, whilst 
 the water added sets up an osmotic action with the unruptured cells, and thus a por- 
 tion of the juice is secured which would otherwise be lost. 
 
 The dilution of the pulp is of great advantage in obtaining the whole of the juice, 
 as will hereafter appear. For this reason, frequently much more water is used than 
 stated above. But as the evaporation of the water added involves expense, it must be 
 considered how far this expense is covered by the increase in sugar. Besides the cost 
 of the fuel, the relative value of the raw material affects the practice on this point. 
 If the French manufacturer fails in securing a portion of his sugar, although he thus 
 loses a part of his raw material, the residue has more value as fodder. The German 
 manufacturer working with raw material made more expensive by a heavy tax en- 
 deavours to obtain the greatest possible amount of sugar, and uses with 100 parts of 
 beets 30 or even 50 parts of water. 
 
 Obtaining the Juice by Pressure. In the separation of the juice from the pulp by 
 pressure, the hydraulic press is generally used. This consists of a pump by which 
 water is driven into a closed vessel, containing a movable piston or shaft that bears 
 the table of the press. In proportion as water is driven into the vessel, this piston is 
 raised. Opposite the movable table is a stationary one, and the substance to be 
 pressed is placed between the two; the whole pressure exerted upon the water of the 
 vessel by means of the pump can thus be transferred to the matter to be pressed. 
 Fluids which are incompressible transmit a pressure exerted upon them equally in 
 
826 SUGAR. 
 
 every direction. The pressure exerted by the press bears the same relation to the 
 power employed as the area of the cross-section of the press cylinder bears to the area 
 of the cross-section of the pump piston. The power remaining the same, the effect 
 will be greater the smaller the area of the pump piston, and the greater that of the 
 press shaft. 
 
 Whilst the pulp is rich in juice, it flows away rapidly under a slight pressure. At 
 this point of the work therefore but little force is needed, and a pump with a piston 
 of proportionately greater section is used to drive water into the vessel. When how- 
 ever a certain quantity of the juice has been removed, the force available by means 
 of this pump is no longer suitable, for upon increasing the power applied to it, the re- 
 sulting pressure is so sudden, that the elasticity of the pulp would burst the cover- 
 ing in which it is being pressed before the juice could flow out. To avoid this, 
 another pump with a considerably smaller piston is used. The action of this is 
 slower, but all the more powerful. Thus, if the areas of the two pump pistons are to 
 each other as 100 : 1, the area of the press piston and the working power remaining the 
 same, the force exerted by the smaller pump will be one hundred times greater than 
 that of the larger. 
 
 These pumps are so arranged that at first both work together; but as soon as the 
 maximum effect for which it was designed is attained, the larger one ceases working 
 and the smaller alone remains operative. This is allowed to work until the water in 
 the tub of the press is under a pressure equal to 200 to 250 atmospheres. This 
 pressure is continued as long as the pulp yields any juice, and then the water is run 
 off from the press to the reservoir, the press piston with the table attached sinking in 
 proportion as the press is emptied. The machine may then "be emptied and freshly 
 filled. 
 
 In order to press the pulp as produced by the grater, it is necessary to surround 
 it with a covering that will allow the juice to flow freely through and retain the marc. 
 Square cloths of very strong woollen texture are generally used for this purpose. 
 Formerly several thicknesses of sacking were employed, but this material has now 
 quite gone out of use. It had no advantage over the cloth, but the disadvantage of 
 being more difficult to clean. The cloths are filled with the pulp upon the packing 
 table at the press. This table is made of sheet iron, and has a rim round it ; on one 
 side of it there is a channel which allows such juice to run off as collects during the 
 packing process. Upon this packing table is laid first a metallic plate of the same 
 size as the pressing table ; above this is placed a sheet-iron frame or shape, about 
 | inch in height, and the whole is covered with the press cloth. With a scoop about 
 five or six pounds of the pulp is then thrown into the depression formed in the sheet- 
 iron frame, then levelled, and the edges of the cloth thrown over it. Upon this is 
 laid a second plate, and another cloth is filled in the same manner, so that at last 
 there is a series of layers of pulp enclosed in cloths, and separated from each other 
 by metallic plates. A portion of the juice now flows away in consequence of the 
 pressure exerted by the mere weight of the metallic plates. The pile of alternating 
 metallic sheets and layers of pulp is next placed upon the table of the press, and 
 when the press is filled the pumps are set in operation. As the pressure is applied, 
 the juice flows over the metallic borders, and along the surface of the pressing table, 
 which is surrounded by a rim, and provided with an outlet pipe connected with a 
 tube through which the juice is conducted to a proper receptacle. 
 
 The pulp possesses considerable elasticity, and offers so strong a resistance to the 
 pressure, that, if too great quantities of pulp were to be operated upon at one time, the 
 cloths would burst before the whole of the juice was separated. The layers of pulp 
 are therefore made thin and metallic plates placed between them, so that the pressure 
 may be uniform throughout the entire mass. 
 
 When the juice ceases to flow, the pressing table is lowered and the press is 
 emptied. The cloths are found to contain beet fibres pressed into a very compact 
 form, but still holding juice. The residue is therefore taken out of the cloths and 
 either immediately used for fodder, or subjected to a second pressure to obtain the re- 
 maining juice, after having been again converted into pulp by the addition of water. 
 
 Various machines have been constructed for the purpose of reconverting the press 
 residue into pulp. The so-called mashing machine of Fesca consists of a horizontal 
 iron trough in which is a shaft furnished with a great number of knives arranged 
 spirally. The knives cut up the press residue, and water being added, knead it into 
 a stiff paste. This machine does not seem to be much used. Schlickeysen's machine, 
 which is constructed after the pattern of the well-known clay pugmill, has met with 
 much approval. It consists of an upright iron cylinder in which is a shaft furnished 
 with strong arms inclining downwards ; at the bottom of the cylinder is an opening 
 for the escape of the pulp. The press residue is thrown from above through a funnel 
 into the cylinder ; at the same time water is poured on ; the material being caught 
 
EXTRACTION OF JUICE FROM BEET ROOTS. 827 
 
 by the moving arms of the shaft, becomes reduced, and escapes as pulp ready for a 
 second pressing. 
 
 Beet juice is a tenacious sticky liquid in proportion as it is rich in sugar. Owing 
 to its viscidity, it is impossible to extract more than a certain portion of the juice, 
 the rest remaining in the residue, notwithstanding the strongest pressure. The better 
 the quality of the juice, the greater is the proportion of juice -which remains behind. 
 When, by the addition of water, the juice ~is rendered thinner, it is less tenaciously 
 held, and may be more completely separated from the press residues by pressure. 
 Good beets with the strongest pressure yield about 80 per cent, of juice, and 20 per 
 cent, of press residues, the latter containing 4 per cent, of pith and 16 per cent, 
 juice ; one fifth of the entire quantity of juice would therefore remain in the press 
 residues. By the addition of water this loss is much diminished, because it can be 
 more completely pressed ; so that, instead of 20 per cent, only about 1 7 per cent, of 
 press residue is left ; further, the juice left in the residue is no longer a concentrated 
 but a diluted juice, and consequently not only less in quantity but poorer in sugar. 
 
 The effect of thinning the juice may be shown by a few simple examples. Take, for 
 instance, the case where beets of the following composition are used : 
 
 Sugar 13 per cent. 
 
 Eefuse 4 
 
 Water and non-saccharine matter 83 
 
 If these beets be subjected to pressure without the addition of water, until 20 per 
 cent, of press residue is left, the residue will be composed of refuse and of 16 parts of 
 juice in which sugar and water are present in the same proportions as in the beets 
 themselves, thus: 
 
 Sugar 2-2 parts by weight 
 
 Eefuse ......... 4*0 
 
 Water, etc 13'8 
 
 Since therefore 100 parts of beet contain 13 parts of sugar, and 20 parts of such press 
 
 residue would contain 2*2 parts of sugar, there would be in this case a loss of 17 per 
 
 cent, of the whole of the sugar. 
 
 If 20 parts by weight of water be added to every 100 parts of beets, this will 
 
 produce 120 parts of pulp of which the composition will be as follows : 
 
 Sugar 13 parts by weight 
 
 Eefuse 4 
 
 Water 103 
 
 This thin pulp may be easily pressed until not more than 18 parts of residue remain 
 
 from every 100 parts of beet. But the relative proportions of sugar and water are no 
 
 longer the same in this residue as in the beets, but are the same as in the diluted pulp. 
 The composition therefore of the 18 parts of the residue will be as follows: 
 
 Sugar 1-6 parts by weight 
 
 Eefuse *' " 
 
 Water, etc 1*4 
 
 The loss in sugar is therefore reduced to 12 per cent, of the whole. 
 
 Still further dilution is attended by a corresponding gain in sugar. If, for 
 
 example, 50 parts of water be added to every 100 parts of weight of beets, this will 
 
 give 150 parts by weight of pulp, which will consist of: 
 
 Sugar 13 P arts b 7 wig nt - 
 
 Eefuse .... 
 
 Water, etc. . "'' , . 133 
 
 As the process of obtaining the juice is easy in proportion as the pulp is thin, the 
 pressing may be conveniently carried on until 100 parts of beets leave only 17 parts 
 of residue, which will consist of: 
 
 Sugar 1-2 parts by weight. 
 
 Eefuse 4 
 
 Water, etc 11*8 
 
 Thus the loss in sugar in a single pressing would be reduced 9 per cent, upon the 
 
 Tiie yield of sugar is still more favourable when the residuum from the first 
 pressure is thinned with water and pressed a second time. If a pulp obtained withoiit 
 any water being poured upon the grater, be subjected to a first pressing, and this 
 pressing be only sufficient to yield 70 parts of juice and 30 parts residue from every 
 100 parts of beets, the residue would then contain : 
 
828 SUGAR. 
 
 Sugar . 3'5 parts by weight. 
 
 Kefuse 4' 
 
 Water, etc 22'5 
 
 If now to these 30 parts of residue, 30 parts of water be added, the resulting 60 
 parts of pulp may be pressed without difficulty, so as to obtain 27 parts of juice and 
 17 parts of residuum, the composition of this, residue will be as follows: 
 
 Sugar 0'8 parts by weight. 
 
 Befuse 4- 
 
 Water, etc . 12-2 
 
 This would be a loss of only 6 per cent, upon the whole of the sugar. By proper 
 management this loss in sugar can be still further reduced. If, for instance, in 
 reducing another lot of beets the 43 parts by weight of thinned juice, which had been 
 obtained by a second pressure, be caused to flow upon the grater instead of water, the 
 product will be a pulp which is thinned by means of diluted juice. Thus the pressing 
 of this new pulp would be facilitated, there would be a less amount of residuum than 
 before, and this would contain a smaller quantity of sugar. If this residue be a 
 second time subjected to pressure, nearly all the sugar is obtained. 
 
 In these calculations it has been assumed that when water is applied it is com- 
 pletely incorporated with the juice ; this takes place more perfectly if, in the grating 
 process, the individual cells have been thoroughly ruptured, as it is only from the 
 cells that have been actually torn open that the juice can issue freely and mix with 
 the water. When unruptured cells come into contact with the water, there is of 
 course an interchange of the constituents of the juice with the water by diffusion, but 
 this process is a slow one. Although it may not be possible to attain a complete 
 mixture of the juice and water in the short time which intervenes between the ap- 
 plication of water and the pressing, yet the effect of the dilution is always consider- 
 able, especially if the pulp be pressed a second time. 
 
 As soon as the juice leaves the cells it is liable to many prejudicial changes. 
 Fermentation occurs in consequence of the action of the ferments contained in the air; 
 acids are formed and a considerable formation of mucus takes place, which is dis- 
 tinctly observable when fresh juice is exposed for a short time to the action of th> 
 air. This formation of mucus may take place to such an extent that the whole of 
 the juice is changed to a jelly-like mass. To prevent this the greatest expediti 
 should be used in working up the juice, but especially the greatest cleanliness should 
 be everywhere observed. If the apparatus is left unused even for a short time t 
 should be thoroughly washed -with water, as the standing juice is not only subject to 
 chemical changes, but it is a focus of fermentation of every kind. On this account 
 the press cloths must be thoroughly cleansed after they have been used only a very 
 short time. The cloths become covered with mucus every few hours, and no^longer 
 allow the juice to flow freely through. They must then be at once removed and 
 washed, clean ones being employed in their place. 
 
 The press cloths are subject to a good deal of wear and tear, and are soon 
 destroyed; hence attempts have been made at different times to construct an apparatus 
 which should render their use unnecessary. It has been proposed to place the pulp 
 between two endless wire tissues, and to press these together between rollers. This 
 plan, however, has not yet met with much acceptance. 
 
 The juice as it leaves the press is not quite clear, but is more or less contaminated 
 with fibrous matter that has been forced through the pores of the press cloths. 
 Formerly no notice was taken of this, biit it has now been discovered that the pectic 
 substances upon treatment with lime become changed into metapectic acid, which 
 hinders the crystallisation of the sugar. These fibrous constituents are therefore 
 removed by filtration of the juice ; for this purpose long rather narrow linen sacks are 
 used, which hang freely ; into these the juice is poured, and it leaves the sacks a clear 
 liquid, the fibrous matter remaining. 
 
 Obtaining the Juice, by Centrifugal Force. The beet pulp is prepared in the 
 ordinary way by rasping, and is placed in a centrifugal machine like that used for 
 raw sugar, but of larger dimensions and having the rotating machinery underneath 
 the drum. The paste falls from the rasper into an iron funnel, suspended from a pair 
 of iron rails, and having a capacity exactly corresponding to that of the drum. Im- 
 mediately underneath the rails stand the centrifugal machines in a row; the funnel 
 when filled is pushed forward until it is exactly over the already revolving drum, a 
 slide at the lower end is opened and the paste falls into the drum. Here it is imme- 
 diately flung against the periphery; the mark is retained whilst the juice flows 
 through. ' As, however, the pressure is not so great by far as that exerted by the 
 hydraulic press, the mark retains after this treatment much more juice, and con- 
 sequently sugar, than when the press is used. In order to recover this sugar, water 
 
EXTRACTION OF JUICE FROM BEET ROOTS. 829 
 
 is allowed to play upon the partially exhausted paste in the drum from a very fine 
 rose. Under the influence of the centrifugal force, the water percolates through the 
 paste driving the juice before it. 
 
 Obtaining Juice by Maceration. The apparatus introduced by Schutzenbach con- 
 sists of twelve shallow cylindrical vessels placed terrace-like, and communicating 
 with each other by a pipe, similar to the apparatus used for lixiviating crude soda 
 (see p. 263). A pipe that can be closed by a valve passes from the bottom of the upper 
 vessel and opens over the vessel next underneath. Each vessel has besides a tap at 
 the bottom through which the entire liquid contents can be run off into a trough. 
 Each vessel is provided with a false bottom, consisting of a fine wire sieve, through 
 which none of the paste can pass. In the upper part of the vessel is a second false 
 bottom of perforated sheet iron. The entire capacity of the vessel is about 36 cubic 
 feet ; the space from the true bottom to rather over the upper false bottom will hold 
 94 gallons of water and 66 gallons of paste. The paste is placed between the two false 
 bottoms, where by means of a stirrer it is intimately mixed with the incoming water. 
 
 The stirring machinery consists first of an iron bar directly underneath and resting 
 against the upper bottom ; from this bar numerous iron teeth, 6 inches long, project 
 downwards. Through a circular opening in the middle of this bar passes a vertical 
 shaft that revolves in a socket at the bottom of the vessel, and is connected above 
 with the driving power common to all the shafts. Between the two false bottoms this 
 shaft supports a horizontal iron bar, almost as long as the diameter of the vessel. To 
 this are fastened vertical bars, arranged so that the upward directed half passes 
 between the before mentioned teeth, whilst the half directed downwards reaches to 
 within an inch of the lower bottom. The shaft also supports above each of the two 
 bottoms an arm set with briishes, the upper one serving to break up the scum and the 
 under one to purify the sieve bottom. All twelve vessels are arranged in a similar 
 way, and can easily be connected with or disconnected from the motive machinery. 
 
 The upper vessel is first two thirds filled with cold water, into which sixty-six 
 gallons of paste have been thrown, the upper false bottom is put on, the stirrer is put 
 in motion, and just so much water is added as will exactly cover the upper bottom. 
 After the paste has been five minutes in contact with the water the valve of the pipe 
 that connects the first vessel with the second is opened, and water is allowed to flow 
 upon the upper stage of the first vessel which drives the juice out and forward into 
 the second vessel. The flow of water is kept up until the juice in the second vessel 
 equals the quantity of water present in the first vessel at the commencement of the 
 operation ; the stirrer is then set going, sixty-six gallons of fresh paste are added, the 
 false bottom is put on, and the paste and juice are left in contact five minutes. The 
 third vessel is then filled by opening the overflow pipe connecting it with the second 
 vessel, and allowing more water to run into the first vessel ; this drives the thin juice 
 in the second vessel, which has already been in contact with two separate quantities 
 of paste, forward into the third vessel. This operation is repeated until eight vessels 
 have been filled. 
 
 By this time the juice has attained nearly the same concentration it has in the 
 paste ; it is therefore run off through a cock at the bottom into a trough that conducts 
 it to the montejus, by which it is raised to the juice reservoir. The paste in the first 
 vessel being now exhausted, fresh water is allowed to flow into the second vessel, 
 which then becomes the first of the series, whilst the ninth being fitted with fresh 
 paste after five minutes yields a second portion of finished juice. Thus, after the 
 operation has once been started, a vessel full of juice is obtained and a portion of 
 paste is exhausted every five minutes. When saturated juice has been drawn off from 
 the twelfth vessel at the foot of the terrace, the next quantity of juice passing into 
 it is run off through a trough into a small cistern, from whence it is pumped into 
 a reservoir standing higher than the first vessel, which has meanwhile been filled 
 with fresh paste, and into which it can then be run. A complete circle is thus set 
 up, eight vessels being always at work, the four intervening ones being meanwhile 
 emptied and cleaned, the water being run off through the cock at the bottom, and the 
 mark withdrawn through an opening just above it, and submitted to slight pressure 
 to free it from the large quantity of absorbed water. 
 
 Before the clarification, the juice always requires to be filtered, as it is impossible 
 completely to prevent the passage of fibre through the sieve bottom. 
 
 Obtaining the Juice by Diffusion. When a living cell or a number of uninjured 
 cells are placed in water an interchange of the cell contents with the water is always 
 set up : water passes through the cell membrane and protoplasm, and the matters 
 dissolved in the cell juice pass through into the water. This interchange continues 
 until the oppositely attracting influences are balanced, and the liquids inside and out- 
 side the cell have an equal concentration. The protoplasm and cell membrane 
 present a certain resistance which varies very much accordin^t^-tfaff'Ch^^al compo- 
 
830 SUGAR. 
 
 sition and physical properties of the body. Many bodies pass readily from the cell 
 into the water, others slowly, and some not at all. All bodies that are capable of 
 taking the crystalline form pass easily through the cell membrane, whilst those that 
 are not remain in the cell. Thus when a cell containing juice rich in sugar, which is 
 crystallisable, is laid in water, sugar passes out into the water and water enters into 
 the cell, until the concentration of the cell juice and that of the liquid outside the cell 
 are equal. This is known as the process of diffusion; sugar is a diffusible or 
 crystalloid body. On the other hand, with a cell the juice of which contains al- 
 bumen in solution, under otherwise equal conditions, the albumen does not pass out 
 from the cell into the surrounding water. The albumen is not diffusible, not having 
 the power of crystallisation; it is a colloid. Finally, from a cell enclosing juice 
 containing sugar and albumen only the diffusible sugar passes into the water whilst 
 the albumen is retained. The power of diffusion therefore can be used to separate 
 these bodies from one another, and to effect a clarification even in the cell. 
 
 The diffusion takes place very unequally, according to the conditions of the cells. 
 In the living cell the process goes on slowly, the diffusible matters being held so 
 closely during the life of the cell that they cannot penetrate the protoplasm and mem- 
 brane. But as soon as the life of the cell is destroyed through frost and a rapid thaw, 
 or heating to 40 or 50, the diffusion goes on rapidly. 
 
 Upon these facts the method introduced by Dombasle, and afterwards improved 
 by Eobert, is based. By suitable arrangements, this method effects a complete re- 
 moval of the sugar, and the juice is moreover obtained almost of the same concentra- 
 tion as that in which it exists in the beet. 
 
 If 100 parts of beet, containing 96 parts of juice with 14 parts of sugar, be 
 brought together with 60 parts of water, the result after diffusion is 156 parts of juice, 
 containing 14 parts of sugar, or a 9 per cent, juice. If from this juice be taken as much 
 as the quantity of water used, i.e. 60 parts, and this be placed with 100 parts of fresh 
 beet, as the added juice already contains 5'4 parts of sugar, there will be after dif- 
 fusion 166 parts of juice, with 19'4 parts of sugar, or a 12'5 per cent, juice. 60 parts 
 of this juice containing 75 parts of sugar placed with another 100 parts of beet will 
 give 156 parts of juice with 2T5 parts of sugar, or a 13'8 per cent, juice ; this would 
 consequently be equal to that in the juice. 
 
 If the beet from which the first juice was withdrawn, which still contains 
 14 5'4 = 8 P 6 parts of sugar, be again treated with 60 parts of water, 156 parts of 
 juice are obtained with 8'6 parts, or 5'5 per cent, of sugar. If 60 parts of this juice 
 be again replaced by 60 parts of water, the resulting juice will still contain 5'3 parts, 
 or 3 '4 per cent, of sugar. It will be evident that by continuing this treatment a 
 point is reached when the sugar of the beet cells is almost completely replaced by 
 water. The result of the last treatment, being almost pure water, is used with the 
 beets still containing 1 per cent, of sugar, and the yield from this is used with beet 
 containing double that quantity, and this is repeated until the most concentrated juice 
 is obtained. 
 
 The apparatus used by this method consists of a small dividing machine and the 
 diffusers. In this case the beets are not reduced to a paste, but by means of a special 
 machine they are cut into small very thin uniform slices. The thinner these are, so 
 that the cells may come into immediate contact with the water, the more uniform will 
 be the diffusion and the more completely will the juice be obtained. 
 
 The diffusers are tall iron cylinders, eight or ten of which are combined together 
 to form a battery. Above and below at the side, they are provided with a large man- 
 hole for the introduction and removal of the slices. They are connected with each 
 other by pipes, that pass from underneath one into the upper part of another into 
 which they discharge through a rose. A second series of pipes connects each separate 
 cylinder with an elevated water reservoir. A third series of pipes passes from the 
 bottom of the cylinders to a warming apparatus situated between the reservoir and 
 the cylinder, and containing a pan that can be heated by steam. This pan is suffi- 
 ciently large to hold the quantity of liquid water or juice required for the filling of 
 the cylinder. In working with a battery of eight diffusers, it is usual to use 60 parts 
 of water or juice to each 100 parts of beet; with a larger number, less liquid will 
 suffice. 
 
 In commencing operations, the pan is filled with water which is heated to boiling. 
 The hot water is allowed to flow slowly into the first cylinder, and at the same time 
 the slices of beet are thrown in, until the cylinder is completely filled with beet slices 
 and liquor ; the cover of the man-hole is then closed, and the whole is allowed to 
 stand for twenty minutes. The temperature should reach 50 in order to kill the 
 cells and thus allow the diffusion to go on rapidly. The temperature of the water in 
 the pan must therefore be regulated according to the temperature of the beet, and the 
 proportion of water used. After twenty minutes, the valve which connects the first 
 
EXTRACTION OF JUICE FROM BEET ROOTS. 831 
 
 cylinder with the water reservoir and the heating pan is opened. As the water 
 reservoir stands at a considerably higher elevation than the other portions of the ap- 
 paratus the water flowing in drives the juice through the pipe commencing at the 
 lowest part of the cylinder into the heating pan. "When this is filled with juice, the 
 valve is closed and the juice is heated, whilst the first cylinder filled with water is 
 allowed to stand under the pressure of the column of water. From the heating pan 
 the juice is run into the second cylinder, which is also filled with slices ; when full 
 the second cylinder is closed and allowed to stand twenty minutes. The connection 
 between the first and second cylinders and the water reservoirs being then opened, 
 fresh water enters the first cylinder and drives the juice there forward into the second 
 cylinder and the juice from the second cylinder into the heating pan. When the pan 
 is full, the connection is closed and the first and second cylinders remain under 
 water pressure. The hot juice from the second cylinder is then run into the third, 
 where it is used as before, for heating a fresh quantity of slices of beet. After being 
 in contact with three portions of fresh beet the juice is sufficiently concentrated. It 
 is then passed through a special pipe into the defecation pans, which are of a capacity 
 corresponding with that of the cylinders. 
 
 After the juice has been run off, the connection between the second and third 
 cylinders is opened. Water again flows into the first cylinder, and drives the thin 
 juice into the second, and the contents of the second into the third cylinder. After 
 twenty minutes the third cylinder is connected with the heating pan, and for the fourth 
 time fresh water is let into the first cylinder, which drives the contents of each 
 cylinder successively into the next. The juice from the heating pan meets with fresh 
 beet in the fourth cylinder ; it there becomes sufficiently concentrated and is drawn 
 off, the cylinder being again filled from the third. In the same way the other 
 cylinders are filled, until all are in connection. By the time the contents of the 
 seventh cylinder are passed into the eighth the beet slices in the first cylinder are 
 perfectly exhausted of sugar. The second cylinder is then connected with the water 
 reservoir, the valve between the first and second cylinders is closed, and the fluid 
 contents of the first, consisting only of pure water, are run off, and the exhausted 
 slices are removed. The eighth cylinder is then connected with the first, and the first 
 is filled with fresh slices of beet and juice from the eighth. Meanwhile the second 
 cylinder has become exhausted ; the water pressure is therefore applied to the third ; 
 the second is connected with the first, and so on. 
 
 In working with a battery of twelve cylinders the method is essentially the same. 
 Either a larger quantity of beet, or the same quantity with less water, can be ex- 
 hausted in the same time ; but the usual plan is to have two batteries of eight diffusers 
 each, and to manage so that whilst one is under pressure the other is being freshly 
 filled. 
 
 Of all the methods of obtaining the juice, diffusion is undoubtedly the most to be 
 recommended. The apparatus is the simplest, least costly, and undergoes scarcely 
 any wear ; the building not having to sustain the violent shaking of the raspers can 
 be more simply constructed ; the batteries do not take so much room as the presses ; 
 press bags are not required ; the juice is of at least equal concentration, and can even 
 be obtained less dilute than by other methods ; whilst the loss of sugar is not greater 
 than when presses or the centrifugal apparatus is used. 
 
 It has been sought to simplify this method by using instead of the batteries a 
 single apparatus, in which by a mechanical arrangement a stream of water and slices 
 of beet are carried forward in opposite directions. Thus at one end the fresh slices 
 are introduced, and the concentrated juice flows out, while at the other end the ex- 
 hausted slices are thrown out. 
 
 Only one difficulty stands in the way of the diffusion method, the condition of the 
 residue, or exhausted slices. The residue from the hydraulic press is comparatively 
 free from water, containing 30 to 33 per cent, of dry substance. From the ruptured 
 cells the juice can be expressed, but not so from the undestroyed cells after diffusion. 
 These are filled with water, and contain at most 8 per cent, of dry substance, or much 
 too little to allow advantageously of its use as fodder. The adherent water can be 
 separated by simple pressure, but that in the cells is expelled with difficulty. Several 
 presses have already been constructed with this object. 
 
 Obtaining the Juice from dried Beets. Attempts have long been made to work the 
 beets in the dry instead of the fresh condition, the advantage being the more easy 
 transport of the beets, and the extension of the working season through the entire 
 year. On the other hand, it has its disadvantages. The sugar must still be exhausted 
 from the dried beets with water, and the quantity of liquid to be evaporated is great. 
 Moreover the roots in drying are subject to many injuries. If they are overheated a 
 portion of the sugar is destroyed ; whilst if they are imperfectly dried, they form a 
 favourable basis for fungoid vegetation, by which also sugar is decomposed. These 
 
832 SUGAR. 
 
 disadvantages appear to outweigh the advantages, and but few manufacturers have 
 adopted this method. 
 
 After gathering the beet roots they are washed and cut by machinery into long 
 rectangular pieces, and dried in a kiln. The dried pieces contain about 3 to 5 per 
 cent, of moisture, and with care can be preserved in a perfectly dry room for a long 
 time. For obtaining the juice an apparatus similar to that used in diffusion is used. 
 Fourteen cylinders are connected with one another by pipes to form a battery. The 
 pieces of beet are placed in the cylinder, covered with half per cent, of their weight 
 of calcium hydrate, and then boiling water is poured over them. The juice passes 
 from one cylinder to another, and acquires a concentration of 36 to 40 of the 
 saccharometer ; it is then run into the defecation pan, where it is heated only to 90. 
 The further working is the same as in the other processes. 
 
 The difficulty of transporting the beet root has given rise in one or two places 
 in France to the separation of the processes, the juice being obtained on the spot 
 where the beets are grown, and then conducted by pipes to a central manufactory 
 to be worked up. The juice is mixed with 1 per cent, of lime to preserve it, and 
 is then driven by powerful pumps through the pipes into a large reservoir in the 
 central manufactory. The pipes are laid about three feet below the surface of the 
 earth, the juice being thus protected from freezing. 
 
 Clarification of the Juice. The process of defecation or the clarifying of the juice 
 has for its object the removal of such constituents as are coagulated by heat or pre- 
 cipitable by lime. Lime enters into combination with any free acids that may exist 
 in the juice, saturates the acid salt, and combines with gum, albumin and casein, 
 forming an insoluble precipitate. It also converts the fatty substances into insoluble 
 lime soap, and precipitates the colouring matter. Magnesia, ferric oxide, and 
 phosphoric acid are separated in an insoluble form. The salts of the organic acids 
 are decomposed, and the bases with which they were combined, such as ammonia, 
 potash and soda, are liberated, while the excess of lime combining with sugar 
 forms sugar- lime. If the juice contains grape or fruit sugar, this also enters into 
 combination with lime, but the compound quickly decomposes, colouring the juice 
 yellow or brown, according to the quantity present. Thus the lime affects the most 
 diverse constituents of the juice, and the non-saccharine constituents could be almost 
 completely separated by its use, if all the reactions took place in this simple way. 
 Various secondary processes, however, hinder the clarification from being as com- 
 plete as might be expected. The albumen contained in the juice becomes so much 
 changed by the action of the alkalies set free, that a part of it is dissolved, and 
 cannot be removed. The lime salts too, which are insoluble in pure water, are dis- 
 solved by water containing sugar, and the liberated alkalies partly replace the lime in 
 the lime salts of the organic acids, forming the same salts which had been previously 
 decomposed by the lime. The object of further operations is to remove these sub- 
 stances. 
 
 The defecation and evaporation of cane juice were formerly carried out in a very 
 rough manner in a series of cauldrons standing side by side, and heated by a common 
 fire. The cauldron furthest removed from the fire was the defecation pan and in this a 
 small quantity of milk of lime (0'2 to 0'3 per cent.) was added to the juice. The im- 
 purities rose to the top as scum which was removed with a ladle. 
 
 By precipitating juice having a specific gravity of T060, or 15sacchar, with cold 
 lime water, Avequin obtained per 1,000 parts 38'36 parts of dried scum, which con- 
 tained : 
 
 Cerosin 7'15 
 
 Green colouring matter 1'50 
 
 Albumin and traces of cellulose 5*56 
 
 Calcium and magnesium phosphate . ' 15 '70 
 
 Calcium carbonate 2-30 
 
 Silica 6*15 
 
 Ferric and manganic oxide traces 
 
 The juice from a cane grown in new land gave 40 to 70 parts per 1,000 of dry 
 scum ; that from a quite ripe cane grown upon land that has been longer in culture 
 yielded a smaller amount of scum. 
 
 After the removal of the scum, the juice is transferred by means of a ladle into 
 the second vessel. Here during evaporation, a fresh scum is formed that is continu- 
 ally skimmed off and returned to the first vessel, which has been meanwhile filled 
 with fresh juice. After becoming clear, the juice passes into the third vessel. Here 
 the colour and condition of the juice are noted, and, if necessary, a small quantity more 
 lime added, and it is then skimmed until all the impurities have been removed. In 
 the fourth vessel it is brought to the consistence of a syrup, and finally in the fifth 
 
CLARIFICATION OP THE JUICE. 833 
 
 the boiling is finished when the boiling juice throws up bubbles that burst with a 
 crackling noise. 
 
 The original cast-iron hemispherical vessels have been replaced by flat pans having 
 perpendicular sides, arranged terrace-like one above another, but still heated by one 
 fire. The pans are therefore not set firmly, but so that each can be raised at one end, 
 and its contents emptied into the next lower pan. Pans of this kind are termed swing 
 pans. The combustion products passing from under the last pan are conducted into 
 a tubular boiler and the steam is used for heating the apparatus in which the final 
 concentration takes place. 
 
 Whatever form of apparatus may be used, however, the boiler over a bare fire is 
 always extremely imperfect. The juice undergoes change by the long contact with 
 atmospheric air, and by overheating a larger quantity of the sugar is converted into 
 a non-crystallisable coloured product, called caramel, so that a disproportionately 
 large quantity of syrup and but little crystallisable sugar is obtained. In order to 
 avoid this, apparatus heated by steam is being more and more used. By large capi- 
 talists the steam apparatus of Eillieux is used ; while those of smaller means use 
 apparatus in which, though not provided with the aarangement for producing a 
 vacuum, the heating of the concentrated syrup is effected by steam. The kinds of 
 apparatus used in the French colonies are in principle similar to those used in the 
 concentration of dextrin solutions. Two kinds of apparatus, Wetzel's and Bour's, are 
 especially in use. 
 
 "Wetzel's apparatus consists of a half cylinder having double sides. It has a 
 stirring arrangement formed of a hollow shaft, which is fitted with two lenticular 
 shaped bodies, connected one with the other, by numerous pipes. Steam is passed 
 into the space between the inner side of the cylinder and the jacket, as well as into 
 the hollow shaft of the stirrer. The agitator is set in motion, and throxigh the con- 
 siderable surface it presents, the heat is rapidly communicated to the liquor and the 
 evaporation rapidly effected. 
 
 The apparatus of Bour has a similar arrangement ; it is shown in figs. 608 and 609. 
 B is the juice-holder, having a semi-cylindrical bottom, and surrounded by a steam- 
 jacket (c). The steam enters through the pipe (a), and passes off through d, into the 
 
 
 FIG. 608. FIG. 609. 
 
 steam collector. The stirrer (A) consists of a hollow shaft (D), upon which are fast- 
 ened four hollow bodies (//). The steam goes in the direction of the arrows, but on 
 its way must pass through the four bodies (//). Each of these bear two cups, which 
 dip into the juice, carry with them a portion, and upon becoming reversed, pour it 
 out over the space filled with steam. The shaft is driven by means of pullies or a 
 handle. 
 
 Durino- the evaporation of the juice, there is formed on the side of the pan or 
 cauldron a deposit, called in the colonies cal. It consists of almost pure calcium 
 phosphate. According to an analysis by Avequin, it contains : 
 
 Calcium phosphate 92'43 per cent, 
 
 Cupric phosphate - . 1'42 
 
 Calcium carbonate . . . 1'35 
 
 Silica 4> 7 
 
 The composition of the cal naturally varies according to the purity of the lime 
 used in the defecation. The amount of copper salt depends upon the use of copper 
 vessels in the evaporation. In order to remove it, the pans are heated after the re- 
 moval of the juice to dryness ; the adherent mass is thus rendered friable and can 
 easily be removed with a chisel. In Killieux's apparatus the deposit is not so dense, 
 and can be easily removed with dilute hydrochloric acid. 
 
 3 H 
 
834 SUGAR. 
 
 The clarification of beet -root juice is carried on by very different methods. The 
 older method and that which is stili very much in use is as follows : The clear juice 
 is run into the clarifying pan, placed so that the juice can be conducted to it from the 
 press or filters by means of inclined channels ; or if this arrangement is not possible, 
 the clarifying pan may be placed in the upper story of the building, so that the juice 
 may flow from it to any other position required. To raise the juice, which must 
 be done either now or at some other stage of the work, an apparatus called the 
 monte-jus is generally used. This consists of a closed cylindrical iron vessel in 
 the upper part of which terminate two pipes furnished with stopcocks. One of 
 these cocks is used for filling the vessel with juice, and the other opening at the 
 highest point of the arched lid is in direct communication with the steam chest of the 
 boiler ; a third pipe passes through the bottom of the apparatus, and is used for 
 running off the juice to the clarifying pan or any other receptacle. The steam 
 tube being closed the monte-jus is filled with juice. The juice tube is then closed 
 and the cock of the steam tube opened. The steam admitted presses with the whole 
 of its expansive force upon the surface of the sap and drives it through the pipe 
 opening at the bottom of the apparatus into the clarifying pan or other vessel ap- 
 pointed for its reception. When the monte-jus is emptied the juice cock is again 
 opened and the steam cock shut and the operation is repeated. 
 
 The clarifying pan is a circular boiler made of copper, the bottom of which is 
 round, generally hemispherical. It is surrounded by a steam jacket, furnished with 
 a pipe for the inlet of the steam, and another for carrying away superfluous steam 
 and the water which has become condensed. For the purpose of heating the juice, 
 steam is used either directly from a boiler, or more advantageously steam which has 
 already been employed in driving the engine. The jacket must be strong enough to 
 bear the pressure of steam of high tension, as the liquid in the pan has to be brought 
 to boiling. 
 
 As soon as the pan is filled with juice, steam is let into the jacket, and the tem- 
 perature raised as quickly as possible to 80. The first effect is the separation of 
 albumin, which coagulates at a temperature of 65. When the thermometer indicates 
 a temperature of 80 or 85 at the most, the flow of steam is lessened so that further 
 increase of temperature may take place gradually. Lime mixed with water to a thin 
 paste is then added, and well stirred up with the juice so as to cause a thorough 
 mixture. 
 
 Directly the lime comes into contact with the juice, a considerable quantity of 
 flocculent precipitate separates. The temperature is then gradually raised, causing 
 the formation of more precipitate, which does not sink to the bottom, but floats as a 
 scum of gradually increasing thickness upon the surface of the liquid ; for this reason 
 the process is known as the upward clarification process. The liquid is just 
 allowed to enter into ebullition, and the steam is then shut off. If the operation has 
 been properly conducted all the scum will now be found upon the surface and beneath 
 will be a completely clear liquid. The scum contains almost all the colouring matter, 
 and the previously dark coloured juice is now a clear yellow. If the liquid remains 
 turbid after the boiling, or if the juice is not separated from the scum, the result 
 indicates that not enough lime has been used, and in the next clarification the quantity 
 of lime must be increased. 
 
 Two different arrangements of the pan are in use for separating the clear fluid 
 from the scum ; one consists of a tube passing through the bottom of the pan and 
 jacket, which is closed by means of a valve during the process of clarification, and 
 then carefully opened. The clear liquid is allowed to flow away, but as soon as it 
 begins to be clouded by admixture of scum the A r alve is closed, and the scum is run 
 off to the filter press, where it is completely freed from juice. 
 
 The other arrangement for the separation of the juice from the scum consists in a 
 siphon which passes through the wall of the pan and enters the liquid below its 
 surface, the short arm terminating at the bottom. The long arm opens outside the 
 pan over a funnel connected with the juice reservoir, and governed by a stopcock. 
 As the highest point of the siphon is below the surface of the liquid, the stopcock 
 need only be opened to set it in motion ; the clear liquid is allowed to run off, but 
 the scum, the consistency of which will not permit it to escape, remains behind and 
 is ladled out afterwards. 
 
 With reference to the quantity of lime which is requisite in clarification, nothing 
 definite can be stated, because the amount of matter required to be removed varies 
 greatly. Some kinds of beet contain much more non-saccharine matter than others. 
 Those that have been -well preserved too contain a less amount than those which become 
 rotted in the pits, and the same beets contain less immediately after they are gathered 
 than in the spring. All these considerations affect the use of lime, so that reliance 
 must be placed entirely upon observation of the appearance of the juice, and sufficient 
 
CLARIFICATION OF THE JUICE. 835 
 
 lime be used for the juice to be clear after boiling and no longer dark coloured. In 
 general, however, it may be assumed that for 100 parts of beets by weight, half to 
 three-quarter parts of lime will be required. The variation will generally be within 
 these limits. 
 
 The clarified juice has a very alkaline reaction in consequence of the liberation of 
 the bases, potash, soda, and ammonia (which escape in the boiling), and by the for- 
 mation of sugar-lime. Since lime is only difficultly soluble in hot solutions of sugar, 
 the formation of sugar-lime never exceeds a certain limit, even should an excess of 
 lime be used, which should however be avoided. The alkalimetrical strength of 
 ordinary refined juice represents an average contents of about 0'2 per cent, of lime. 
 The alkalinity of the juice is of great importance for its preservation ; fermentation 
 and formation of mucus occurs only in acid or neutral juice, whilst an alkaline juico 
 remains free from these changes. On this account the sap is never, even in the later 
 processes, completely freed from dissolved sugar-lime. 
 
 Saturation. Although a certain quantity of sugar-lime in the juice is requisite 
 for its preservation, the amount present after clarification is too considerable to be 
 profitably allowed to remain. It is true the lime would certainly be removed in the 
 subsequent filtration through animal charcoal ; but this would be at the expense of the 
 quality of the charcoal, for when the charcoal is saturated with lime it is no longer 
 capable of absorbing the substance for the removal of which it is chiefly employed. 
 
 As carbonic acid readily decomposes sugar-lime, it is now generally used for 
 saturating the juice. The apparatus used for this purpose was invented by Kindler. 
 It consists of an iron cylinder which is higher than it is wide. Some factories employ 
 wooden vats, the sides of which are furnished with a spiral steam tube for heating 
 the juice. At the bottom is a second tube or coil perforated along its surface for the 
 purpose of admitting the carbonic acid. The large quantities of steam formed escape 
 from the saturator through a funnel-shaped head-piece, prolonged so as to extend 
 above the roof. In this head-piece a trap is fixed, through which the progress of the 
 juice may be easily watched. 
 
 Carbonic acid decomposes not only the sugar-lime, but also a number of other 
 sugar constituents precipitated from the juice by the lime ; care must therefore be 
 taken that only the clearest juice is saturated, and that all the scum remains in the 
 clarifying pan. For this reason the first and last portions of juice, which are always 
 contaminated with scum, are separated and added to the bulk of the scum that they 
 may be filtered before being saturated. 
 
 The saturator being filled with hot clarified juice, steam is admitted into the 
 heating coil, and the liquid heated to ebullition ; carbonic acid is then introduced into 
 the boiling juice by means of a force-pump. The boiling liquid has a great tendency to 
 form a froth, and would be partly lost if the frothing were not prevented. This is 
 effected by the addition of small quantities of fat, tallow, butter, or paraffin, which 
 melt and form a thin layer upon the surface of the liquid, causing the bubbles of the 
 steam to burst. 
 
 Production of the Carbonic Acid. The carbonic acid used for saturating the juice 
 need not be chemically pure. An admixture of other gases presents no further disad- 
 vantage than that a greater volume must be used, and that the carbonic acid thus 
 diluted is not so readily absorbed as that which is pure. Pure carbonic acid produced 
 by decomposition of carbonates with stronger acids would be much more expensive 
 than a larger quantity of carbonic acid mixed with other gases. 
 
 A number of different kinds of apparatus are used in the preparation of carbonic 
 acid gas, amongst which Handler's furnace still enjoys considerable reputation. It 
 consists of a small shaft furnace, at the grate of which a fire is kindled. As soon as 
 this is in a lively flame, the entire shaft is filled gradually with fuel, generally coke, 
 as free from sulphur as possible. The upper opening of the furnace is then completely 
 closed, and a strong draught maintained by an air-pump, which drives the air through 
 the grate, bringing it into contact with the red-hot fuel, the oxygen of the air com- 
 bining with the carbon to form carbonic acid. The product of combustion containing 
 nitrogen and steam is at once drawn off from the side of the furnace near the fireplace, 
 in order to avoid the carbonic acid remaining too long in contact with the red-hot coke, 
 which would cause the reduction of the carbonic acid to carbonic oxide, and consequent 
 waste. The hot gas is then cooled by drawing it first through a chamber filled 
 with pieces of limestone and pans of water, and then through a reservoir filled with 
 water. The high temperature of the gas serves to expel a portion of the carboiric 
 acid from the limestone, and any sulphurous oxide present, originating in the combustion 
 of sulphur compounds in the coke, is retained. In passing through the water, the 
 accompanying dust, ashes, etc., are removed. After the gas leaves this water tank, 
 it passes into a suction and force-pump, and is by it forced either into a reser- 
 voir or gasometer, or, as is customarily the case, immediately into the saturation vessel. 
 
 3 u2 
 
836 
 
 SUGAE. 
 
 FIG. 610. 
 
 In many factories at the present time, the production of carbonic acid and of 
 lime are combined, and the furnace made use of is that shown in the figs. 610 to 612. 
 
 Fig. 611 is a vertical section ; 
 fig. 612 is a horizontal section 
 made on the line CD, at a 
 height of about 2 feet above 
 the grate. Fig. 610 is a hori- 
 zontal section through the 
 line A B at the top of the 
 flue. 
 
 The furnace forms a cone, 
 the greatest diameter of 
 which upon the ground is 
 about 11 feet, and the least 
 diameter at the top is about 
 3 feet. A little way above 
 the ground at the side of the. 
 shaft are two fireplaces, the 
 grates of which are about 
 3 feet long, 2 feet 8 inches 
 wide. These are provided 
 with doors, by means of 
 which the draught may be 
 regulated. The flame does 
 not enter the furnace im 
 mediately, but is broken by 
 a fire bridge, as shown in 
 fig. 612, and enters the fur 
 nace in two currents. A re- 
 gular distribution of heat 
 throughout the shaft is thus 
 attained, the four openings 
 of the two fireplaces being 
 situated at an equal distance 
 from each other. Around 
 the furnace are five tiers of 
 openings, each tier contain- 
 ing three, which are situated 
 at an eqxial distance each 
 from the other. These shut 
 hermetically, but are used to 
 observe the state of the fur- 
 nace, and also for allowing 
 air to enter if required ; any 
 choking of the furnace is re- 
 moved through these open 
 ings with an iron bar. 
 Above is the shaft, and the 
 whole furnace is covered by 
 a strong cast-iron plate, 
 composed of three different 
 parts. Beneath this plate 
 at a distance of l feet, 
 there is a circular channel 
 
 running roiind the whole of 
 
 the upper part of the shaft 
 (B), and this is in connection 
 with the interior by means 
 of fire linnet holes. This 
 channel receives the whole of 
 the product furnished by the 
 combustion as well as the 
 carbonic acid driven out of 
 the limestone, and carries it 
 Fio. 612 away by means of the cast- 
 
 iron pipe (j 1 ). The draught 
 is supplied by a large force pump, which first collects the air, then the products of com- 
 
 - I) 
 
 FIG. 611, 
 
CLARIFICATION" OF THE JUICE. 
 
 837 
 
 bustion from the furnace, and afterwards drives these products to the place where 
 they are required. 
 
 Such a furnace yields in twenty-four hours 6 tons of burned lime which requires 
 upwards of 10^ tons of pure carbonate of lime in the limestone used. The limestone 
 is broken into pieces about 10 cubic inches in size, and after the furnace has been set 
 going, small quantities of these are thrown in at intervals of an hour, through three 
 round holes in the upper plate, each 8 inches in diameter. As soon as the limestone 
 is thrown in, the holes are closed by means of three large hollow balls (B, fig. 611), 
 provided with handles. The holes are charged alternately so that the limestone may 
 be placed as uniformly as possible in the furnace. About 3 cwt. of limestone is 
 thrown into the furnace at a time, and with this limestone is mixed about 15 Ibs. 
 of coke. Beside this, about 30 cwt. of coke is used in the two fireplaces, making in 
 all about 2 tons in the twenty-four hours. The 6 tons of pure lime in the limestone 
 is combined with about 5 tons of carbonic acid, and the 2 tons of coke, if it were pure 
 carbon, would produce nearly 7 J tons of carbonic acid in the combustion. Theoreti- 
 cally, then, the capacity of the furnace would be equal to the production of about 
 12 tons of carbonic acid in twenty-four hours. But the limestone is not pure calcium 
 carbonate, neither is the coke pure carbon, so that the actual amount obtained will 
 fall considerably below this estimate. 
 
 The burnt lime is drawn out at the hearth of the furnace through the opening 
 (gg) closed by iron doors. The carbonic acid drawn off by the pump is cooled by 
 passing through a wide iron tube, 
 which conducts it from the top of 
 the furnace to a washing apparatus. 
 This is shown in fig. 613, and con- 
 sists of a cast-iron cylinder about 
 5 ft. in diameter and 7f ft. in 
 height. The interior part of- the 
 cylinder is divided into four cham- 
 bers (L M N o), by means of three 
 perforated disks (bed efg). K is 
 the tube for conducting the car- 
 bonic acid from the furnace. At 
 its entrance into the washing ap- 
 paratus it is bent at right angles 
 and closed at the end. The lower 
 half of that part of the pipe which 
 is in the washing apparatus is per- 
 forated by numerous holes, the 
 diameter of which is at least equal 
 to that of the tube. The carbonic 
 acid enters through these orifices, 
 then passes through the perfora- 
 tions of the three disks, and also 
 through the layers of water upon 
 the plates. The perforations of 
 these plates are about \ in. in 
 diameter, and are arranged so that 
 the whole surface occupied by them 
 is equal to the diameter of the 
 main pipe or a little more. The 
 wash water enters through a small tube at b, and falls into a dish placed on the top 
 disk where it overflows and covers the disk. Owing to the pressure of the gas, the 
 water cannot pass through the perforations but remains over them until it reaches 
 the height of the escape tube above, the gas all the while passing through it. The 
 freshly admitted water falls through the outlet pipe into a similar dish upon the 
 second disk, flowing over and covering this also ; it then falls through a second outlet 
 pipe on to the third disk, from whence it escapes into the lower chamber, where it 
 collects until the openings of the main pipe are covered. The bent tube (H) now 
 keeps the water at a constant level, and allows the superfluous water to escape. The 
 water and the gas thus flow in opposite directions, and the gas which enters below is 
 forced to make its way through the four layers of water. In no way can it make its 
 escape, because the escape tubes are kept closed by the water flowing over from the 
 dishes. The water meets the gas from above, and the arrangement is such that the 
 same water is used four times. This is a systematic method of cooling and purifying 
 at the least possible expenditure of material. Having reached the top, the gas is 
 drawn off by the pump through the tube (OP) to a dry purifier, find afterwards con- 
 ducted to the saturator. 
 
 FIG. 613. 
 
838 
 
 SUGAR. 
 
 Fig. 614 represents in one view all the apparatus for the production and use of the 
 gas. To the left hand is the lime furnace described. The limestone and coke are 
 mixed in the given proportions upon the plate (a). 
 
 The hourly charging of the furnace is effected tnrougn the openings in the plate 
 by the three balls (u). The burnt lime is withdrawn every hour through the 
 
CLARIFICATION OF THE JUICE. 839 
 
 openings (g g} below. The carbonic acid rises to the top of the furnace through the 
 spiral channel, and is then conducted to the first washing apparatus by the pipe F F' ; 
 it then rises through the apertures in the extension of this pipe (h), passes into the 
 chambers (L M N o) through the perforations of the disks, and is washed by the water 
 entering at b'. The washed gas then passes through the tube o into a dry purifier (R), 
 which is advantageously filled with coarse pieces of limestone, and here any water 
 mechanically carried over with the gas is deposited and runs off through a bent tube 
 (B!), s is a horizontal air-pump which draws the gas to this point and then forces it 
 on through the tube (T) into the receptacle (u), where it is under a pressure of from 
 6 1 to 10 ft. of water, causing it to flow into the saturator upon the opening of the 
 cocks which govern it. v is one of the saturators, and x is the clarifying vessel in 
 which -the saturated juice deposits its precipitate. For the purpose of separating the 
 clear liquid from the precipitate on the bottom there is a simple arrangement. To 
 the escape cock upon the inside of the clarifying vessel, a wide caoutchouc tube is 
 attached, upon the end of which is a float, keeping the open end constantly on a level 
 with the liquor. When the turbidity is deposited the stopcock is opened, the clear 
 liquid runs off through the tube into the receptacle (Y), and afterwards the precipitate 
 is withdrawn through a valve at the bottom of the vessel, and is conveyed by a monte- 
 jus (not represented in the cut) to the filtering presses. From the receptacle (Y), the 
 clear juice either flows immediately into the charcoal filters, if the apparatus for 
 saturation and clarification are above them, or if not, it is raised to the filters by a 
 monte-jus. 
 
 Various other methods, having for their object the production of concentrated 
 carbonic acid, however, are not practically available, because the extra expense of 
 producing it is by no means proportionate to the advantage gained. It has been pro- 
 posed, for instance, to heat lime in closed iron retorts by a stream of superheated 
 steam. Another plan consists in passing carbonic acid from lime kilns into a solution 
 of neutral sodium carbonate ; the carbonic acid being absorbed and acid sodium 
 carbonate formed, whilst the nitrogen of the air entering the furnace and the carbonic 
 oxide gas produced pass off through the liquid. The solution of acid sodium carbonate 
 is then heated to boiling, causing the evolution of the absorbed carbonic acid, neutral 
 sodium carbonate remaining, which can be used in a fresh operation. 
 
 The first effect of the carbonic acid is to produce a cloudiness of the juice, due 
 to the precipitation of calcium carbonate. After a short time the precipitate gathers 
 in large flocks and settles to the bottom. The liquid is examined from time to time 
 during the saturation, by removing a small portion with a little iron spoon. The 
 progress of saturation is shown by the appearance of the liquid, an insufficiency of 
 carbonic acid being indicated as long as it remains cloudy, but when large flakes 
 appear and quickly settle to the bottom of the spoon, leaving the juice above clear, 
 the saturation is complete. 
 
 The supply of carbonic acid is then stopped, the liquid is once more brought to 
 ebullition, and then immediately drawn off into a clarifying vessel standing directly 
 under the saturator, where in a very short time the precipitate subsides. The fluid is 
 now filtered and the precipitate expressed together with the scum. 
 
 The precipitate formed in the process of saturation is not pure calcium carbonate, 
 but is mixed with various nitrogenous and non -nitrogenous organic substances. 
 Whether this further precipitation takes place because the substances in combination 
 with the lime were dissolved in the juice previous to its saturation, and were then 
 thrown out of solution, or whether they are mechanically carried down by the calcium 
 carbonate, is not known. 
 
 The treatment with carbonic acid is never carried so far that all the lime is re- 
 moved from the sap. A small quantity of it is always allowed to remain, because it 
 has been observed that in the subsequent decolorisation by animal charcoal, a much 
 more complete result is obtained if the juice still contains some lime ; for although 
 juice free from lime can be perfectly decolourised, it readily turns dark afterwards. 
 It appears therefore that after the clarification, the juice contains a substance colour- 
 less in itself, but which undergoes change and becomes coloured, and that this sub- 
 stance in combination with lime is absorbed by charcoal, while it is not absorbed in a 
 free condition. 
 
 Rousseau's Method of Clarification. According to this method the juice is clarified 
 in pans sucli as have been described, but six times the ordinary quantity of lime is 
 used, or sufficient to combine with not only the non-saccharine matters organic 
 acids, etc. but also with the whole of the sugar. On an average 4 Ibs. of lime are 
 used to 100 gallons of juice, varying according to the quality of the beets. The lime 
 is mixed with 5 or 6 times its volume of hot water and added to the juice at a tem- 
 perature of 60 to 65. The mixture is then heated to 90 or 95, but should not be 
 made to boil. The liquor is separated from the precipitate and passed through a 
 
840 
 
 SUGAR. 
 
 small filter to remove suspended particles of lime scum. This filter consists of a box 
 having a strainer at the bottom, over which a cloth is spread, and this is covered with 
 a layer of granular animal charcoal 10 inches thick. 
 
 The clear juice is saturated in the apparatus represented in fig. 615. It consists of 
 a double-action air pump (A) worked by machinery, by which air is drawn in through 
 the pipes (a a) and driven through the pipes (b b) into an iron furnace (B), on the base 
 of which is a mixture of charcoal and coke. "When the carbonic acid produced by the 
 combustion is not used it escapes through the valve (s). When this is closed, the 
 combustion products go through the pipe (c (/) into the washing vessel (D), supplied 
 with water, where suspended ash is deposited ; the dirty water can be run off through 
 the cock (d 1 ). From the wash vessel the carbonic acid passes through a pipe (F), 
 common to all the saturators, and the branch pipe (G H) into the saturator (i). The 
 saturator has the same construction as the ordinary defecation pan. It is a boiler 
 with an arched bottom, under which is a steam jacket ; this is supplied with steam 
 through one pipe (N), whilst another pipe (o) conducts the condensed water and excess 
 of steam into a steam chest. 
 
 FIG. 615. 
 
 The vessel (i) is filled with clear juice, which is then heated to boiling and treated 
 with carbonic acid. The gas enters through a rose at the end of the pipe (G H), by 
 which means it is driven in separate bubbles through the liquid. The completion of 
 the saturation is recognised by the liquid becoming less viscous, and allowing the 
 precipitate of calcium carbonate formed to sink readily to the bottom. A valve at 
 the bottom is then opened by turning the rod (j K), and the juice runs through the 
 trough (L) into the settling vessel, or through a box filter into a reservoir, ready to 
 be passed through the principal filter. It is evident that by this method a large 
 quantity of scum is produced, and for this reason it has not met with favour in the 
 German works. Recently special apparatus has been constructed facilitating the 
 working of the scum, but at the same time the methods of defecation have been 
 improved. 
 
 Perner Possoz-JehneK s Methods of Defecation. The peculiarities of these methods 
 are usually united in working. The cold juice is mixed with milk of lime heated 
 and saturated ; after the resulting defecation milk of lime is added a second time, 
 and it is again saturated. The milk of lime used contains 20 per cent, of lime. 
 It is made by mixing 480 Ibs. of burnt lime with about 130 gallons of water or 
 defecated juice, and afterwards diluting this paste with 650 gallons more liquor ; the 
 milk is passed through a coarse sieve to remove stones and sand. It will then contain 
 nearly 20 per cent, of lime, but in order to bring it to its right strength 10 c. c. are 
 removed with a pipette and diluted with 200 c. c. of water, in which 50 grams of 
 pure sugar is dissolved, and thus all the lime is obtained in solution as sugar-lime. 
 The solution is then coloured blue with litmus, and titrated with normal sulphuric 
 acid. After the amount of lime has been thus ascertained, it is easy to reckon how 
 much water has yet to be added to bring the solution to the right strength. 
 
 In the first treatment with lime, when the liquor is kept alkaline, the greater part 
 of the foreign substances is separated. In the second treatment with lime, when a 
 very much smaller proportion is used, the remaining impurities are got rid of. The 
 saturation with carbonic acid is then carried so far that all the compounds of sugar with 
 alkalies and lime are decomposed. At the same time the excess of carbonic acid 
 causes a small portion of the impurity to pass into solution again, and in order to get 
 rid of this a small quantity of lime is added, insufficient to produce any detrimental effect 
 upon the subsequent boiling. 
 
 The clear juice is mixed with the milk of lime in such proportions that 15 to 30 
 parts of pure lime are added to each 1,000 parts of juice. Usually 20 parts are suffi- 
 cient, but the quantity must be regulated by the quality of the beet. The mixture is 
 
CLARIFICATION OF THE JUIOE. 
 
 841 
 
 brought by means of a monte jus into the apparatus for defecation and saturation, vertical 
 and horizontal sections of 
 which are shown in figs. 
 61 6 and 6 17. It consists 
 of a square cistern 6 feet 
 8 inches long and 4 feet 
 deep. At the bottom 
 lies a pipe (a) 4 inches 
 in diameter, united by 
 four kneepieces, and 
 forming a square parallel 
 to the walls of the 
 cistern. This pipe is 
 perforated over its en- 
 tire surface with fine 
 holes, in order to dis- 
 tribute through the 
 liquid the carbonic acid, 
 which is carried to it 
 by a vertical pipe with 
 a cock (u). A 3^-inch 
 spirally bent steam pipe 
 (<?), the three coils of 
 which are about 6 inches 
 apart, obtains direct 
 steam from the pipe (b) ; 
 the condensed and un- 
 condensed steam passing 
 off through/ into a steam 
 chest. A 5-inch valve 
 pipe (d) is used for 
 emptying. When the 
 cistern is full of the 
 mixture of juice and 
 lime, steam is let into 
 the spiral, and carbonic 
 acid is admitted at the 
 same time. A layer of 
 froth of considerable 
 consistence immediately 
 begins to form, for the 
 dispersion of which an 
 addition of fat is always 
 requisite. A simple ar- 
 rangement for the pre- 
 vention of the froth hus 
 been introduced by 
 Evrard. Two 2 -in hori- 
 zontal pipes are placed at a distance of 40 inches from each other, 6 inches below the 
 edge and 20 inches from the sides of the box. Both pipes communicate with the 
 steam, and on two sides they are perforated with fine holes. When steam is let in it 
 is driven horizontally in a fine stream through these openings, makes its way through 
 the frothy mass, and causes the bubbles to burst. By the aid of these froth breakers 
 e'mousseurs the work can be carried on rapidly without fear of boiling over. 
 
 Under the continued inflow of the carbonic acid the temperature of the juice rises 
 from 60 to 80, and it is retained at this temperature until the precipitate sinks 
 readily in great flocks to the bottom, and the liquor only contains 1 to 3 parts per 
 1,000 of dissolved lime ; the temperature is then raised to 90 or 95. The juice thus 
 treated separates easily from the precipitate, which does not rise as in the ordinary de- 
 fecation to the surface, but collects at the bottom. As soon as the defecation is com- 
 pleted, the valve at the bottom of the cistern is opened, and the juice and sediment rue 
 out into a clearing vessel. After a short time two-thirds of the juice can be separated 
 clear from deposit ; the remainder with the sediment is passed into the filter press, 
 where the sediment is completely retained, and the juice is obtained clear. 
 
 The whole of the juice is then brought back to the saturator, when an amount of 
 milk of lime corresponding to 5 Ibs. of pure lime to each 100 gallons of juice is added 
 
 FIG. 617. 
 
842 SUGAR. 
 
 and the whole is boiled for five minutes. The steam is then shut off, and carbonic 
 acid is let in until all lime and alkali is completely neutralised, turmeric paper not 
 being coloured brown, or red litmus paper blue, by a few drops of the juice. Excess 
 of carbonic acid, by which some of the precipitated impurities are redissolved, is then 
 removed by boiling, and a slight alkalinity is restored to the liquid by the addition of 
 Ib. to 1 Ib. of lime to each 100 gallons. After settling, the clear juice goes to the 
 filter, and is then boiled in the usual way. 
 
 The advantage of this method is that the cold beet juice dissolves a much larger 
 quantity of lime than at a higher temperature, and consequently the precipitation of 
 the matters forming insoluble compounds with lime can be more easily effected. 
 The large excess of sugar lime is at once again decomposed through the saturation, 
 calcium carbonate being precipitated, carrying down with it foreign matters. The result- 
 ing precipitate is dense and compact, and can be more easily freed from juice than 
 the voluminous slime of the ordinary defecation. 
 
 Filtration of the Juice. After the defecation of cane juice it is allowed to run 
 through a small preliminary filter into the filter which has already been used, for 
 the filtration of thick juice (see p. 847). The filtered juice has a specific gravity of 
 about 1*063 (17 sacch.) ; it is then concentrated to about sp. gr. 1-118 (30 sacch.) 
 The juice flowing from thence is collected in a reservoir, from which it is drawn as 
 required into the evaporating body of a vacuum apparatus (p. 849). The thick juice 
 is then at once boiled to the thread proof or granulation. 
 
 The advantages of the improved arrangements in colonial sugar factories consist in 
 an increased yield of 33 per cent, from the cane, and the product commands about 10 
 per cent, higher price than that prepared by the old method. The rapid evaporation 
 in the vacuum pans allows of a larger quantity of cane being worked in the same 
 factory. A large central factory can therefore be erected in the midst of several 
 plantations, in which the cane produced in the different places can be worked, and a 
 separation thus effected between the strictly agricultural and the manufacturing works. 
 A large manufactory of this kind exists in Havanna ; it unites the work of four old 
 boiling houses St. Thomas, St. Susanna, St. Martin, and Zuluetta and produces 
 125 tons of sugar daily. Another central manufactory, erected by Gail and Souques, 
 at Point-a Pitre, Guadeloupe, receives by water the cane harvest of the entire coast ; a 
 canal bears the ships to a railway that has its terminus at the manufactory. This 
 central manufactory is erected for the working of 1,000 tons of cane daily, with a 
 yield of 100 tons of sugar. 
 
 By the clarification and saturation, a great many non-saccharine constituents are 
 removed from the juice ; but others still remain, which would hinder the crystalli- 
 sation of the sugar, especially in the case of beet juice. To remove these, animal charcoal 
 is employed. Animal charcoal is obtained by heating bones to redness out of contact 
 with the air, and has the property of attracting to its surface and rendering insoluble 
 most diverse substances contained in solution. Its power of absorbing colouring 
 matter has been long known ; but it also absorbs various organic substances, such as 
 salts of organic acids, calcium citrate, for example (which, according to the researches 
 of Kunze and Reichardt, is completely withdrawn from solution by filtration through 
 animal charcoal), calcium succinate, and others. Inorganic substances are also re- 
 moved, such as salts of the alkalies and alkaline earths, calcium sulphate, free 
 alkalies, and caustic lime ; in fact, animal charcoal effects transformations of the 
 most diverse kinds. According to Kunze and Reichardt, upon filtering solutions of 
 calcium chloride through animal charcoal, 26 per cent, of the dissolved salt is 
 absorbed ; and from a solution of sodium citrate 35 per cent. But if a solution con- 
 taining both calcium chloride and sodium citrate is similarly filtered, 98 per cent, of 
 the citric acid, 65 per cent, of lime, 8 per cent, of the chlorine, and 3 '4 per cent, of 
 the soda, are absorbed, so that evidently the animal charcoal decomposes the sodium 
 citrate and calcium chloride into calcium citrate and sodium chloride, the first of 
 which is readily absorbed, and the second only in small quantities. The absorbing 
 power of animal charcoal for lime is so great, that before the process of saturation 
 was known the whole of the lime was removed from the juice by this means. Of 
 course, as the absorbing capacity of the charcoal is limited, a very great quantity was 
 requisite, and hence it is a great gain to the manufacturer that this part of the work 
 can now be effected in an easier and less expensive manner. Under all conditions 
 the amount of non-saccharine matters is always considerably reduced, and the propor- 
 tion of sugar is improved, by the use of animal charcoal. 
 
 The condition of the chare ;al has a great influence upon the filtration. As it 
 absorbs by surface attraction, that charcoal will be the most effective which has the 
 greatest surface, and contains most pores. The best charcoal is prepared from hard 
 bones, and is of a dull black colour. Brown charcoal which is not burned sufficiently 
 is worthless, and may even spoil the juice. A shining black sort of animal charcoal is 
 
FILTRATION OP THE JUICE. 
 
 843 
 
 equally unserviceable, not being porous enough, its pores being closed with layers of 
 dense charcoal. 
 
 Formerly, animal charcoal was used in the form of a fine powder. But as this is 
 only separated from the juice with difficulty and loss, it is now universally used in 
 pieces about the size of a bean. The juice passes easily through such pieces of bone 
 black, and becomes in the process quite pure and clear, whilst the charcoal remains in 
 the filtering apparatus. 
 
 The filters of modern construction are always completely closed. A considerable 
 number of them are always placed alongside of each other, and are united by 
 means of tubes in such a way that 
 they are capable of being worked sepa- 
 rately or together, the sap passing 
 through the first filter and afterwards 
 through the others. Filters united in 
 this way are called a filtering battery. 
 
 One of the filters belonging to a 
 battery is shown in fig. 618. It consists 
 of an iron cylinder (A), closed above 
 and below, 2 feet in diameter, 10 to 16 
 feet high. Close to the bottom is a 
 perforated iron plate (B), covered with a 
 cloth. Upon this the charcoal is thrown 
 in such quantities that the cylinder is 
 almost entirely filled. The manhole 
 (H) serves for admitting the charcoal, 
 and a second manhole (F) is used for 
 removing the charcoal that has become 
 
 exhausted. Both are tightly closed 
 
 while the work of filtration is going 
 
 on, by means of screws. The liquid 
 
 to be filtered is admitted through a 
 
 perpendicular pipe (B), which is in con- 
 nection with four other pipes fixed in a 
 
 horizontal position (i J K L), that run the 
 
 whole length of the battery. One of these 
 
 pipes is shown on a larger scale by fig. 619. 
 
 If, for instance, the first filter be in action, 
 
 the object being to filter juice from the 
 
 pipe (i), the cocks (j K L) are closed, 
 
 and the liquid will then pass through (i) 
 
 into the perpendicular pipe (R), and 
 
 flow into the filter. If the second filter 
 
 is to be filled with the juice from L, in 
 
 this case the cocks UK will be closed, 
 
 and L left open. The juice being ad- 
 mitted from above, passes through the 
 
 layer of charcoal, and appears again 
 
 below; there it enters the pipe (CD), 
 
 bent upwards perpendicularly, and is 
 
 conducted by it to one of four channels 
 
 (m n o p), which it enters through a 
 
 funnel, and is carried off. By means of 
 
 the cock at (K), the juice is completely 
 
 removed from the cylinder. p m> gig. 
 
 If two filters are to work together, 
 
 another arrangement is requisite which is now in general use. The vertical tube (c D) 
 
 in such case extends above the head of the filter, where it fork-; into two tubes, each 
 
 of which is shut by a cock. One of these allows 
 
 the juice to escape immediately into the channels, 
 
 which are now placed somewhat higher than 
 
 before, and the other inclines upward and opens 
 
 into the perpendicular pipe of the next filter, 
 
 uniting thus the first and the second. In a 
 
 similar way the second may be united with the 
 
 third, this with the fourth, and the last joined 
 
 again to the first. If juice be admitted into the first filter, the cock of its escape pipe 
 
 being closed, and the pipe opened which connects the first filter with the second, the 
 
 FIG. 619. 
 
844 SUGAR. 
 
 juice must necessarily, after it has passed through the first, go on to the second, and 
 be then filtered a second time. Thus, the same juice could be passed successively 
 into all the filters, but two filters worked together are sufficient. In filling the filter, 
 the perforated bottom, covered with linen cloth, is put in its proper position through 
 the opening (F), and a layer of coarse charcoal is spread evenly over it. The lower 
 manhole is then closed, and the cylinder filled about half full of water by opening 
 the cock (L). The object of the water is, that the charcoal introduced at the upper 
 manhole may be disposed in regular and uniform layers. The cylinder is then filled 
 up to the point G with charcoal, when the manhole (H) is closed, an air cock situated 
 at the top of the vertical pipe (it') is opened, and the water is allowed to flow away by 
 opening the cock (E). The air cock is then closed, and the steam cock (K) is opened. 
 The water is thus driven off and the whole filter warmed. Steam is allowed to enter 
 until it ceases to condense, and escapes in large quantities at E. E and K are now 
 closed and j opened. This admits the thick juice which at once drives out the water 
 remaining in the pores of the charcoal through the pipe D ; after which the pure juice 
 itself flows away. 
 
 If the filter has just been filled with the charcoal, the first juice which escapes is 
 sufficiently pure, and is conducted through D at once into the channel intended for it. 
 After a time "the juice is no longer sufficiently pure and colourless. The escape is 
 then cut off and the juice is carried to a second filter, which has in the meantime been 
 freshly filled. 
 
 When juice of the requisite purity is no longer yielded by this second filter, the 
 first filter is not used for the thick juice. The cock at j is now closed, and the one 
 at i opened, through which thin sap is admitted. This is first allowed only to flow 
 through the first filter, while the second still receives thick juice for a while through 
 its perpendicular pipe. If the thin juice is not rendered colourless by one filtration, 
 then the thick juice is shut off from the second filter, and the thin juice is passed over 
 from the first into the second. 
 
 In this way the absorbing power of the charcoal is exhausted as much as possible. 
 The thick juice being much purer than the thin, gives up comparatively little to the 
 charcoal, which therefore does not become greatly saturated with impurity, and is still 
 able to remove a considerable quantity from the thin juice. 
 
 When the charcoal becomes so greatly vitiated by the thin juice that it is no longer 
 effective, the water cock is opened and water is permitted to flow in until all the thin 
 juice still remaining with the charcoal is driven over through the connecting pipe 
 into the second cylinder. The water is then run off through the cock (E), the charcoal 
 is removed through the manhole (F) and the filter freshly filled. 
 
 During the filtration the filter is kept constantly filled with the juice, which is 
 effected by regulating the height of the escape pipe (CD). Care is also taken to keep 
 the juice as hot as possible while in the filter, as the action of the charcoal is greatly 
 promoted by heat. A current of steam is therefore directed through the filter 
 immediately after it has been filled with fresh charcoal, whilst the juice is brought 
 hot to the filter without any delay after the process of clarification by saturation. 
 To prevent cooling during the filtration, the cylinder is placed in a warm situation, 
 and sometimes is surrounded by bad conductors of heat. 
 
 Revivification of the Animal Charcoal. The animal charcoal, after becoming clogged 
 up, is not worthless, but can be used again and again after the absorbed substances 
 have been removed from it. This process of removing the absorbed substances is 
 called revivification. The animal charcoal is taken from the cylinder and thrown 
 into large vats, where it is flooded with water, to which a small quantity of hydro- 
 chloric acid has been added. The hydrochloric acid dissolves the lime which has 
 been absorbed ; but an excess of acid must be avoided, since this would dissolve the 
 calcium phosphate to which the charcoal owes its density, and the charcoal would be 
 injured. An active fermentation commences which destroys the organic substances 
 and renders others soluble. When the fermentation ceases the water is run off, and 
 the charcoal washed with fresh water. It is then dried and heated to redness, when 
 it is again ready for use. 
 
 Evaporation of the Juice. The juice as it flows from the filter is not more con- 
 centrated than when it comes from the crusher ; for although in the processes of 
 clarification and saturation it is heated, yet the amount of concentration is not worth 
 mentioning, because in the lime clarification, at least as much water is added as is 
 removed by evaporation, and the further evaporation during the process of saturation 
 is counterbalanced by the water used in washing and cleaning the filter. It may be 
 assumed that the juice when ready for evaporation marks on an average 7 or 8 on the 
 scale of the saccharometer, and that the liquor has to be reduced by evaporation to one- 
 fifteenth or one-sixteenth of its volume to effect the crystallisation of the sugar. 
 
 The evaporation consists of two operations. In the first the thi n j u i ce is brought 
 
EVAPORATION OF THE JUICE. 
 
 845 
 
 
 to a specific gravity of about 1-490. This process yields thick juice, and may be 
 designated the evaporation. The thick juice is subjected to another operation called 
 boiling, by which it is brought to the point of crystallisation. 
 
 The evaporation may be performed by 
 
 (1.) Heating directly over a fire. 
 
 (2.) Heating by means of steam. 
 
 (3.) Heating by means of steam in a partial vacuum. 
 
 The first method may be regarded as obsolete, as it is not now employed in good 
 sugar factories. The disadvantages are the following : the juice is exposed to injurious 
 changes ; it requires the utmost attention to prevent the juice from burning, and 
 lastly the constant action of the air causes a coloration of the juice. 
 
 To avoid these disadvantages, heating by steam has taken the place of heating 
 directly by fire. The apparatus used is various. Pecqueur's apparatus (fig. 620) con- 
 sists of an evaporation pan (A), 
 made of sheet copper, and having 
 the form of a long horseshoe. 
 The bottom is flat and the sides 
 are vertical. It is supported by 
 iron feet (D E). At one end are 
 pivots which can be turned upon 
 two beds in the foot (E), and a 
 pressure upon the bar (B) is suffi- 
 cient to give an inclined position 
 to the whole pan, as is indicated 
 by the dotted lines. The object 
 of this turning arrangement is 
 that the pan may be more easily 
 emptied. When the process of evaporation is finished, the juice is run off through 
 the cock (c), which takes place readily with the pan in a level condition when it con- 
 tains a quantity of juice, but for the purpose of removing the bottom portion the 
 inclined position is .given. Heat is applied by means of six tubes in the shape of a 
 horseshoe, all united together (fig. 621). 
 These six tubes lie in a horizontal plane, 
 and their ends are fastened to two sup- 
 porting pipes which do not directly com- 
 municate with each other. The steam 
 is admitted at K directly into one of the 
 supporting pipes, and passes through the 
 whole length of the six tubes, and into 
 the second supporter, from which it es- 
 capes into a collector, the object of which 
 is to remove the condensed water as well 
 as sustain the tension of the steam. The 
 ends of the pipe supporter (R) pass 
 through the pivots upon which the appa- 
 ratus is turned, and these pivots thus serve as stuffing boxes for the pipe supporters. 
 The heating tubes can be easily removed from the floor of the pan and every part of 
 them reached, so that they can be frequently washed. This is a very necessary opera- 
 tion, as in the process of evaporation of the thin sap a part of the impurity contained 
 in it lime salts, for example is deposited upon the bottom of the pan and on the 
 surface of the tubes, forming a layer which hinders the passage of the heat and impairs 
 the process of evaporation. To clean the apparatus, very dilute hydrochloric acid is 
 poured upon the bottom until this, as well as the coating upon the tubes, is covered. 
 After the acid has acted a short time, it is run off. The tubes are then raised into a 
 perpendicular position and all dirt removed with brushes, etc. 
 
 The rapidity with which' the evaporation of the juice goes on depends upon the 
 difference between its boiling point and the temperature of the heating surface. 
 Therefore steam of very high tension is used (about five atmospheres), which brings 
 the temperature of the tubes up to 152 C. This great heat is of no disadvantage 
 Because the juice cannot be heated above its boiling point as long as it surrounds the 
 steam pipes on all sides. The pan must therefore be kept filled during the process of 
 evaporation, or at any rate, the level of the liquid must not be allowed to sink so that 
 any part of the pipes is left uncovered, for in such case the juice at that point would 
 be burned. 
 
 Steam of a tension of 5 atmospheres effects the evaporation of about 120 Ibs. of 
 water per hour from every 10 square feet of heating surface. 
 
 Another very suitable apparatus for the evaporation of juice is that which was 
 introduced by Claes de Lembeck of Brussels. It consists essentially of a some- 
 
 Fio. 621. 
 
846 SUGAR. 
 
 what coined cylinder about 16 feet in height. The jacket is filled with steam 
 under a pressure of 4 or 5 atmospheres. The whole surface of the cylinder inside as 
 well as out is kept constantly covered with a thin layer of the juice to be evaporated. 
 The juice is supplied from a reservoir above, and as it flows over the heated surfaces 
 of the cylinder it is rapidly evaporated. 
 
 The danger of overheating the juice is even greater with this apparatus than with 
 Pecqueur's pan, and consequently it is little used. 
 
 A third method of effecting the evaporation by steam heat is to connect the vessel 
 in which the thick juice is boiled with a, serpentine pipe communicating at the other 
 end with an air pump, and in this way to boil down the thick juice under reduced 
 barometric pressure, at the same time making the thin juice flow over the surface 
 of the serpentine pipe, heated by the steam given off by the thick juice. 
 
 It is evident that such a method of evaporation must be very imperfect. The 
 quantity of the thick juice boiled down bears no sort of relation to the thin juice to 
 be evaporated by the steam it furnishes. Further, in consequence of the rarefaction, 
 this steam enters the heating pipes at a temperature much below the boiling point 
 of the juice. The arrangement may serve the purpose of condensing the steam, 
 but can never effect the required concentration of the juice, which must be completed 
 in a boiling apparatus specially designed for this purpose. This apparatus may be 
 profitably employed for the purpose of warming the juice, or for economising the 
 water used in condensation in places where fuel is expensive or where water is scarce, 
 as, for example, in the sugar cane plantations. But in the manufacture of beet sugar 
 it is never used. This apparatus has the further disadvantage, in common with the 
 Lembeck apparatus, that the juice is exposed to the air in thin layers, and is thus 
 acted upon by the air. which always damages it by producing colour. 
 
 In ail the better factories these forms of apparatus have been abandoned and the 
 juice is evaporated in vacua. The apparatus for this purpose was first introduced 
 in the manufacture of sugar in America by Eillieux. It was then brought into the 
 German factories at Magdeburg by Tischbein. It was afterwards essentially im- 
 proved by Kobert of Selowitz. Many changes in the apparatus have since taken 
 place, but these affect only the details. The general principles upon which its con- 
 struction rests have not been changed. 
 
 The arrangement of the apparatus depends essentially upon the following prin- 
 ciples : 
 
 The evaporation of water from a liquid is rapid in proportion to the difference 
 between the boiling point of the liquid and the temperature of the heating surface. 
 
 Steam of a low temperature may cause rapid evaporation of a liquid if the boiling 
 point of the liquid is below the temperature of the steam. 
 
 The boiling point of any liquid depends upon the pressure to which it is subjected. 
 By diminishing the pressure, the boiling point of a liquid may be lowered. 
 
 The steam from any liquid has the same temperature as the liquid in which it was 
 generated. 
 
 By increasing the heating surface the same result may be obtained with steam of 
 a low temperature as with steam of a high temperature and less heating surface. 
 
 If, for instance, in a Pecqueur's pan there were, instead of six, as many as eighteen 
 to twenty-four pipes of the same size, it would not be necessary to use steam at 150 
 to evaporate the amount of water indicated ; the same result would be obtained by 
 the use of steam of a much lower temperature. Instead of steam with a pressure of 
 five atmospheres, the work might be done by steam under a pressure of one and a half 
 atmospheres at a temperature of 112. Such steam is constantly at disposal in great 
 quantities in a sugar factory. The steam that has already been used for driving the 
 machinery, instead of being allowed to escape into the air, can be led into a steam 
 collector without materially interfering with the steam engine. The steam, too, which 
 escapes from the jacket of the clarifying pan, and that which has been used to heat the 
 liquid in the saturation vat, may also be led into a common collector, and after having 
 been used for their special work, can still be used for the purpose of evaporating thin 
 juice contained in an apparatus having a large heating surface. 
 
 Again, if the pan of Pecqueur were transformed into a large closed vessel, and the 
 steam generated in it, which would have the temperature of the boiling juice, or 
 about 100, were to be conducted into the extended pipe system of a second Pecqueur 
 pan, also closed, and from which air and steam were exhausted by an air pump and 
 a condensing arrangement, such a diminution of 'pressure could be attained that the 
 juice in this pan would boil at 85. There would thus be a difference of 15 between 
 the boiling point and the temperature of the heating surface, which would be quite 
 sufficient to effect active evaporation. 
 
 Further, this second pan might in the same way be connected with a third, in 
 which the boiling point of the juice through exhaustion of the air could be reduced to 
 
EVAPORATION OF THE JUICE. 847 
 
 70.^ The steam formed in the second pan could then be used for the evaporation of 
 the juice in the third pan. 
 
 Instead of the shape of the Pecqueur's pan, Killieux adopted the form of the 
 tubular boiler, conducting the waste steam from the manufactory through the tubes, 
 and filling the boiler with the juice to be evaporated. The steam thus generated was led 
 into the heating pipes of the second vessel, and from those into the pipes of the third 
 vessel ; after passing this it was completely condensed by contact with cold water. At 
 the same time the second and third vessels were partially exhausted by an air 
 pump. Eobert's modification consists in the pipes not being used for the reception 
 of the steam, but for the fluid to be evaporated, the space between the pipes being 
 filled with steam. Eobert also abandoned the horizontal position of the pipes, and 
 placed them in a vertical position. This arrangement of Kobert's has many advan- 
 tages, although after all these alterations there is a tendency to return to the original 
 machinery introduced by Billieux and Tischbein. 
 
 In practice it has been found that there is some difficulty in carrying on the work 
 with three vessels. Generally, therefore, only two are united together, or the three 
 vessels are so arranged that either of them can, at will, be shut off from the others. 
 In case there is an insufficiency of waste steam, arrangements are introduced to make 
 use of direct steam. 
 
 The three evaporation vessels are technically known as the three bodies of the 
 apparatus. 
 
 The evaporation in each of the bodies is regulated by bringing the juice in the first 
 body to 20 of the saccharometer, in the second to 30, and in the third to 50. 
 
 In 1000 parts of thin juice at 8 there will be 80 parts of solid constituents, 
 sugar, etc., and 920 of water. This is evaporated to 20 in the first body, and then 
 contains 80 parts of sugar and only 320 parts of water ; so that in the first body 
 920 - 320 = 600 parts of water are evaporated. This juice of 20 is evaporated in the 
 second body to 30 and then contains 80 parts of sugar, etc., and 187 parts of water ; 
 consequently in the second body 320 187 = 133 parts of water are evaporated by means 
 of the 600 parts of steam from the first body. Lastly, in the third body the juice is 
 brought to 50, and then contains 80 parts of sugar and 80 parts of water ; so that in 
 order to attain this degree of concentration 187 80 = 107 parts of water are evapor- 
 ated by means of the steam from the second body. 
 
 Consequently, in the first body, 600 parts of water are evaporated. 
 second 133 
 third 107 
 
 In all 840 parts of water. 
 
 There remain 160 parts of thick juice of 50 to be subjected to further processes. 
 
 The progress of the evaporation is ascertained by removing a small portion of the 
 boiling liquid as a test, either by means of a gauge, after shutting off the communica- 
 tion between it and the inner space, or by means of a small apparatus, consisting 
 of a glass tube connected with the vacuum chamber and fitted with cocks, so that a 
 quantity of the juice can be drawn out as required, without disarranging the action of 
 the pan. 
 
 During the evaporation, the non-saccharine constituents which were not removed 
 by the first filtration are concentrated in the juice. A portion of them is precipitated 
 in an insoluble form, in the body, covering the boiling tubes and the surface of the 
 juice chambers with an incrustation of calcium compounds, especially calcium oxalate 
 and lime soaps, the latter being formed by the action of dissolved lime upon the fat 
 added. In course of time these incrustations impede the evaporation, as the 
 heat from the steam no longer passes so readily through the walls of the tubes. 
 Hence, from time to time, a thorough cleaning of the apparatus is necessary. For 
 this purpose all the bodies are filled with water to which some hydrochloric acid 
 has been added for the purpose of dissolving the lime salts ; this is allowed to remain 
 some time, the manholes being open. Lastly, the acidulated water is run off below, 
 the apparatus steamed out, and after every tube has been scoured out with suitable 
 cylindrical brushes, the apparatus is again rinsed out with water. As the hydro- 
 chloric acid employed, as well as the acids liberated from the lime salts, attack the 
 iron, the apparatus should not be subjected to the action of acid longer than is abso- 
 lutely necessary. Further, through the action of the acids upon the iron, hydrogen 
 is liberated, which, mixing with the air, forms a very explosive compound. Hence, 
 the apparatus should be allowed to stand for some time after the acidulated water has 
 been removed, or what is still better, it should be thoroughly steamed out before ap- 
 proaching it with a naked light. Otto records an instance of a great disaster which 
 occurred in a factory from neglect of this precaution. 
 
948 SUGAR. 
 
 In order to remove the impurities still remaining in the thick juice, it is again 
 filtered through animal charcoal. It has already been mentioned that the freshly 
 filled filters are always used at first for the thick juice. This is done as long as the 
 filter has sufficient power of decolorisation. The filtered thick juice should be quite 
 clear, and almost colourless. 
 
 Boiling down the Thick Juice. In the operations previously described, the object 
 has been, besides the concentration of the juice, the removal of foreign elements by 
 the action of lime, carbonic acid, and animal charcoal, and consequently to attain a 
 better proportion of sugar to non-saccharine matters. It is not possible to improve 
 this proportion any further, and the next step is to obtain the sugar dissolved in the 
 juice, which after the second filtration is designated technically clear liquor, in the 
 solid form. It is therefore brought to crystallisation, so that the crystallisable sugar 
 may be separated from the non-crystallisable or difficultly crystallisable bodies which 
 remain in the mother liquor or treacle. 
 
 The following points are of importance to be noted : 
 
 1. Cane sugar requires for its solution a certain amount of water. 
 
 2. A solution which contains sugar and water in such proportions that it will dis 
 solve no more sugar is called a saturated solution. 
 
 3. A dilute solution is converted into a saturated solution by evaporation. 
 
 4. A saturated solution, if further concentrated, must deposit sugar, and this 
 deposition takes place in the crystalline form as long as any solution remains. 
 
 5. A solution which is saturated at a low temperature will still dissolve sugar if 
 :he temperature be raised. 
 
 6. A boiling saturated solution upon a lowering of the temperature deposits a 
 corresponding portion of its sugar, the result being a saturated solution corresponding 
 to the temperature. If water be removed from this by evaporation, it yields when 
 cooling a second crystallisation of sugar, and the mother liquor will yield upon further 
 concentration a third crystallisation. 
 
 7. A saturated solution of sugar is still capable of dissolving other non-saccharine 
 substances. 
 
 8. A boiling saturated solution containing non-saccharine matters will yield upon 
 cooling almost pure crystals of sugar, while the non-saccharine bodies in the mother 
 liquor and syrup become concentrated. 
 
 9. The non-saccharine matters impede the crystallisation of sugar. 
 
 10. When the amount of non-saccharine matter in a solution exceeds a certain 
 quantity, such a liquid, although rich in sugar, will no longer crystallise, even if very 
 greatly concentrated. 
 
 11. Saturated solutions of sugar boil under ordinary atmospheric pressure, at 
 115-120 ; under reduced pressure, the boiling point may be reduced to 50-60. 
 
 12. Concentrated solutions of sugar undergo change during protracted boiling in 
 contact with air. They assume a colour varying from yellow to dark brown, part of 
 the sugar being decomposed, and rendered uncrystallisable. If the boiling take 
 place at a temperature oi; 50-60 these changes do not occur. 
 
 The method of boiling the thick juice or clear liquor is essentially as follows : The 
 juice on coming from the filter is evaporated in vacuo at the lowest possible tempera- 
 ture. The operation is carried on as rapidly as possible, until such a degree of con- 
 centration is reached that crystals form upon cooling (clear boiling), or while the 
 liquid is hot (boiling to granulation). The crystals obtained in either way are 
 removed from the mother liquor or syrup, and freed as completely as possible from 
 adhering syrup. This crystallisation is called the first product. The syrup 
 from this is further concentrated by clear boiling, and yields a second crop of crystals 
 upon cooling. This second product is never so pure as the first; it is more coloured, 
 and contains more foreign constituents; but the proportion of sugar to other sub- 
 stances is always more favourable than in the thick juice before the first crystallisation. 
 The syrup from the second product upon being further evaporated yields a crystallisa- 
 tion of the third product. From the syrup of this third product a fourth crystal- 
 lisation may be obtained if the beets have been of a good quality, and the juice has 
 been well clarified in the different processes ; otherwise the syrup will no longer yield 
 crystals, and is now called molasses. 
 
 The first product is always a marketable article. The following crystallisations 
 together with the after product go to the refinery, where each is subjected to further 
 processes according to its quality. 
 
 If the second product is uncoloured and the crystals are well formed, the grain 
 being sharp, it is often mixed with the first product. If the quality, however, is in- 
 ferior, it would find a somewhat lower price in the market, as would also the sub- 
 sequent products. In many cases, however, it is more profitable to convert the after 
 
VACUUM PANS. 849 
 
 products into first product, and leave only a small quantity of after product. In the 
 second product, as before mentioned, the proportion of sugar to non-saccharine matters 
 is always better than in the thick juice. By the separation of the syrup from the 
 after products, which can be easily effected with the improved machinery of the 
 factories, a similar proportion between the sugar and non-saccharine matters is at- 
 tained in them. Thus, if such after products be dissolved in the thick juice, not only 
 is its quality not impaired, but it is even improved, because the relation of the con- 
 stituents of the thick juice is improved, and more of the first product can be obtained 
 from a similar amount of the thick juice, and almost all the after products can be 
 converted into the more valuable article. 
 
 This operation is called the incorporation. In carrying it out the juice is not 
 evaporated to the degree of concentration given above, but is removed earlier. 
 Enough after product is then dissolved in the juice to make the solution indicate 
 50 on the saccharometer, and it is then subjected to the second filtration. The char- 
 coal by this method removes non-saccharine matters not only from the juice, but also 
 from the added after products, and the effect is a more complete clarification. 
 
 The boiling apparatus used in the operation is essentially the same as the last 
 body of the Eillieux apparatus for evaporation ; but as the amount of the clear liquor 
 to be reduced by boiling is always much less than that of the thin juice, the apparatus 
 is not so large, and instead of being cylindrical, it is either round, or the upper part 
 is spherical and the lower part flat. 
 
 Howard's evaporating pan, as represented by fig. 622, consists of a copper pan 
 (B B), fitted with a jacket (A A) and a dome (c c). Internally is fitted a coil of pipes 
 (D D D) through which steam can be passed, entering through the valve (F), traversing 
 the copper coil (D), and filling the steam jacket. To the top of the dome is fitted a 
 
 FIG. 622. 
 
 cylindrical steam chest (B), connected by means of a pipe (N) with the receiver (M), in 
 which any particles of the juice carried over by the steam are collected. The vapour 
 given off is condensed by jets of cold water, and by means of a powerful air pump a 
 reduced barometric pressure is maintained within the pan during the whole operation. 
 The liquor to be evaporated is supplied from the measure cistern (L), through the tap 
 (b) In the dome of the pan are fitted a thermometer (i), a vacuum gauge (*), and an 
 V 31 
 
850 
 
 SUGAR. 
 
 apparatus called a proof stick (H), by means of which a sample of the contents may 
 bo removed without allowing air to enter. When the operation is completed, the con- 
 tents of the pan are let out through the discharge cock (p). 
 
 A modified construction of the vacuum pan is represented by figs. 623 and 624. 
 The form here used is that of a short vertical cylinder, the bottom as well as the top 
 
 FIG. 623. 
 
 FIG. 624. 
 
 being arched. The heating is not effected by means of a jacket, but through three spiral 
 pipes inside the vessel, each coil being connected at one end with the steam boiler and 
 at the other end with a vessel into which the condensed steam runs off. 
 
 The operation of boiling differs somewhat according as the juice is to be merely 
 concentrated or boiled to granulation. The first method, boiling blank, is practicable 
 with all kinds of juice without exception, the second only with very pure juice. 
 
 For the blank boiling the valve in connection with the juice reservoir is opened, and 
 the air pump being set in operation the juice is drawn in ; when the apparatus is two- 
 thirds full the valve is closed. The condition of the liquid can always be observed 
 through glasses fixed to the side. Steam being introduced, and the flow of water to 
 the condenser and the action of the air pump increased, the juice soon begins to boil 
 and evaporates very rapidly. From time to time fresh juice is introduced in order to 
 keep the apparatus as full as possible, so that at last, notwithstanding the diminution 
 of volume caused by evaporation, the entire apparatus becomes filled with finished 
 juice. The juice being now too thick to permit the use of the saccharometer, to 
 ascertain the finish of the boiling, what is called the thread or string test is used. 
 This is done by trying a drop of the juice between the thumb and fingers ; the correct 
 consistency is reached when the liquor is so viscous that it forms a thread, which 
 breaks upon the separation of the thumb and finger to a certain distance; if insuffi- 
 ciently concentrated no thread is formed ; if too much so, the thread stretches to a 
 longer distance. 
 
 For taking out some of the juice to test the apparatus cannot be opened, as this 
 would destroy the vacuum, neither can it be obtained through a tap, which would 
 admit air but would not give passage to any juice. A special implement, called the 
 proofstick, is therefore used. It consists of a bronze tube, running obliquely down- 
 wards, so that the lower end reaches almost the middle of the boiling space, whilst 
 the other end opens on the upper side of the pan. The tube is closed at its lower end, 
 but has in its side a circular opening in. in diameter. Within the tube is a capsule 
 that can be rotated, which is closed below, open above, and has in its side a similar 
 circular opening. When the capsule is turned so that its opening corresponds with 
 that of the tube it is in communication with the interior of the apparatus ; in any 
 other position all communication is cut off, so that air cannot penetrate in this way. 
 In order to take a proof, a solid piston having a cavity corresponding with openings 
 in the tube and capsule is thrust into the capsule and turned, so that its cavity and 
 the openings in the capsule and tube are in accord ; a small quantity of juice flows 
 into the cavity, the piston and capsule are turned so as to shut off the communication. 
 and the piston is withdrawn containing the juice for testing. As soon as the string 
 test shows the boiling to be finished, the action of the air pump and condenser is 
 stopped, air is admitted by opening the air cock, the steam is shut off. tho finished 
 
EVAPORATION OF THE JUICE. 851 
 
 syrup is then run off through the out-flow valve, and the apparatus is ready for a 
 fresh operation. 
 
 During the boiling of the juice certain contingencies may arise that exert an 
 injurious influence on the operation. With inferior or imperfectly clarified juice it 
 may happen that it does not boil regularly, but froths strongly and threatens continu- 
 ally to boil over. Loss can then be prevented only by very careful regulation of the 
 temperature, not admitting too much steam, and boiling more slowly under rather 
 more pressure. A sudden ebullition can be rendered harmless by some fat, as the 
 steam bubbles burst more rapidly under a layer of fat ; also by the admission of air 
 through careful momentary opening of the air cock. 
 
 The reverse happens when the juice contains an excess of lime or other alkali. 
 The alkali can only be in the juice in combination with the sugar, and these alkaline 
 sugar compounds have the property at a certain point of the concentration of the 
 juice to arrest the boiling and the rapid evaporation, and at the same time to decom- 
 pose a portion of the sugar with the formation of coloured products. It is not known 
 how the alkaline sugar compounds so influence the boiling. Under such conditions 
 the boiling cannot be carried successfully to a termination, and nothing remains but 
 to remove the syrup from the apparatus, dilute it to the consistence of thick juice, 
 and filter it afresh. 
 
 In most cases the lime and alkali are removed in sufficient quantity by the action 
 of fresh charcoal ; but if simple filtration be insufficient, dilute sulphuric acid is added, 
 which sets free the sugar and combines with the lime and alkali to form salts that do 
 not interfere with the boiling. This neutralisation with acid must, however, be 
 effected cautiously, and the greatest care taken to avoid any excess, since the smallest 
 quantity of free acid would, upon heating, make the whole of the sugar uncrystalli- 
 sable. Only so much acid must be added as to leave the juice still with a faintly 
 alkaline reaction sufficient to colour turmeric paper brown or red litmus paper bine. 
 With such juices as are known by experience to boil badly, the neutralisation of the 
 alkali is regularly effected previous to the last filtration. Phosphoric acid, instead 
 of sulphuric, is chiefly used for this purpose, as it forms with the lime an insoluble 
 salt, which can be separated in a small preliminary filter. 
 
 In the blank boiling, the finished juice becomes a saturated solution at the tem- 
 perature at which the boiling is carried out; the deposit of the sugar in crystals only 
 takes place upon cooling. In the boiling to granulation the concentration is carried 
 much further, and a syrup is obtained in the vacuum, that no longer holds in solution 
 all the sugar it contains even at the boiling point, but in which a large portion of the 
 sugar already exists as crystals. By boiling to granulation, therefore, there is finally 
 obtained after the cooling much finished product and little syrup ; whilst by blank 
 boiling, the quantity of syrup is much more considerable. By boiling an impure 
 juice to granulation, a crystallisation would be obtained, so enclosed in the mother 
 liquor or syrup containing the impurities that it could not be perfectly separated. 
 
 In a manufactory daily working up 250 tons of beets, two vacuum pans of the 
 form shown in figs. 623 and 624 are used. They are 7 ft. 8 in. in diameter, 8J ft. 
 from top to bottom, and hold each upwards of 1,300 gallons of juice. 
 
 In boiling to granulation the air is first driven out from the boiling space by a 
 jet of steam ; the condenser and air pump are then brought into action, and the 
 clarified juice is drawn into the pan, the height being observed through^four glasses 
 in the side. When the juice reaches the level of the lowest glass the juice valve is 
 closed, and steam is admitted by the opening of the cock (b) into the lower spiral. 
 By means of the condenser and the air pump a rarefaction is attained corresponding 
 to 4 or 4'5 inches on the barometer ; the pressure of steam in the spiral reaches 
 five atmospheres, corresponding to a temperature of about 150. Under the 
 reduced pressure the juice boils at 60 ; there is, therefore, a very considerable 
 difference between the temperature of the heating surface and the boiling point, and 
 the evaporation goes on rapidly. Juice is continually introduced in such quantity as 
 to maintain the surface of the liquor nearly constant, until a concentration of about 
 70 to 72 of the saccharometer is obtained. The evaporation is then somewhat 
 slackened by allowing the pressure in the interior to reach 10 inches of the barometer, and 
 reducing the steam pressure in the spiral to two atmospheres, or 122. Small quantities 
 of fresh juice are successively drawn in so that the concentration is kept near the above 
 point. As the surface of the liquor rises, the two other spirals are successively 
 brought into operation. When the liquor covers the topmost observation glass, the 
 juice valve is closed, and the whole is boiled to strong proof. When this point is 
 reached, the temperature of the syrup is reduced to 50-55, with an atmospheric 
 pressure of 2 to 3 inches, the steam in the spirals being under a pressure of two atmo- 
 spheres, or about 122. At this lower temperature a formation of sugar crystals 
 
 3i2 
 
852 SUGAR. 
 
 commences immediately, which can be recognised by the pasty appearance of the mass 
 as seen through the glasses. As the evaporation proceeds small quantities of juice 
 are admitted, until at last the whole apparatus is full of a pasty mass of sugar 
 throughout which numberless crystals are distributed. 
 
 After seven or eight hours the boiling is completed, the air pump is disconnected, 
 the air cock is opened, and the syrup is allowed to run oft 1 through a valve at the bot- 
 tom and a trough into the crystallisation vessel, which must be sufficiently spacious 
 to receive the entire product of an operation, or above 8^ tons. 
 
 Seyfert proposes to improve the syrup during the boiling, by adding to it an 
 aqueous solution of sulphurous acid, which bleaches a portion of the colouring matters 
 and also decomposes the compounds of sugar with lime and alkali. The sugar crystals 
 thus obtained are very light coloured, well crystallised, and free from foreign taste or 
 smell. It appears, however, that sugar so treated is not so easily refined as that to 
 which no sulphurous acid has been added ; for should sulphite of lime so formed ac- 
 company the crystals it oxidises in the air, and acts very injuriously upon the char- 
 coal filter. In some refineries, however, no such influence has been noticed. 
 
 In making sugar from the sugarcane the finished boiled juice was formerly brought 
 into a reservoir, and allowed to cool to 45 or 50 ; the mass of crystals and syrup 
 was then put into a vessel with a perforated bottom, and the syrup allowed to drain 
 away. At the present time, this imperfect method is almost completely abandoned. 
 In most boiling houses the thick syrup passes into large shallow receptacles, where 
 it is allowed to cool, and the crystallisation to proceed for twenty-four hours. The 
 finishing of the crystallisation takes place in moulds, from which the syrup is run off 
 through an opening at the end. Many sugar boilers have already introduced the centri- 
 fugal apparatus for the removal of the syrup, using a solution of sugar for the purpose. 
 
 The yield of 1,000 parts of sugar cane by the methods described does not exceed 
 55 to 65 parts of cane sugar ; but the amount of sugar present in the cane originally 
 may be taken as 160 to 190 parts. A part of the difference goes into the syrup, and 
 part remains in the imperfectly pressed cane, the sugar being distributed in the fol- 
 lowing proportions : 
 
 Sugar obtained in crystals . . . . . 55 to 65 parts 
 
 Sugar in the syrup . 25 to 20 
 
 Sugar remaining in the crushed cane . . . . 80 to 75 ,, 
 
 This considerable loss, amounting on the average to 56 per cent., is therefore prin- 
 cipally due to the imperfect 'method of obtaining the juice. As an improvement, it 
 has been recently recommended to disintegrate the cane similarly to the way in which 
 the beet is treated, and to press the paste' in hydraulic presses, adding per cent, of 
 the weight of cane of sodium sulphite, in order to prevent change in the juice. The 
 use of sodium sulphite in Louisiana, where in consequence of the cooler climate, the 
 cane is poorer in sugar and richer in foreign matters than in the West Indies, is said 
 to have given good results. By a complete extraction of the juice, especially if the 
 press residue be mixed with 15 or 20 per cent, of water and again pressed, a consider- 
 ably higher yield is obtained ; but it must be borne in mind that the crushed cane, 
 the bagasse, or cane trash, is generally the only available fuel, and that probably 
 this could only be very imperfectly replaced by the disintegrated press residue. 
 When coal can be purchased, Kobert's diffusion process is, on account of its sim- 
 plicity, undoubtedly best adapted for obtaining an improved yield of juice. 
 
 Another essential improvement consists in boiling the sugar to granulation in the 
 vacuum pan, by which means the formation of crystals of the largest size is promoted. 
 After the crystallisation is finished, the crystalline sugar is brought into the centri- 
 fugal apparatus, and treated first with pure syrup and then with steam. A product 
 is thus obtained which is fit for consumption without refining. 
 
 A new method of defecating cane juice has been introduced by Perrier, Possoz, and 
 Oail. It depends upon the use of neutral sodium sulphite. The dried salt is dis- 
 solved in three times its weight of cold water, and the solution is added to the juice 
 in the defecation pan, in such proportion that to 1 part of the dry salt is mixed 
 with 1,000 parts of juice. If the juice is not thus sufficiently clarified, a little milk 
 of lime is used ; but only enough lime is used to render the juice exactly neutral, 
 without being alkaline. During the consequent defecation, the juice is boiled a short 
 time and the scum is carefully removed. The further evaporation can be carried on 
 either in open vessels or in vessels partially exhausted of air. This method has 
 found acceptance in several colonies, and a large quantity of the salt is exported from 
 France for the purpose. 
 
 Crystallisation and Working up of the After Products. According to the quality of 
 the juice, or the arrangements of the factory, the crystallisation yields either lump 
 sugar (melis) or raw sugar. The former is only yielded by juice of good quality 
 
CRYSTALLISATION OF THE SUGAR 853 
 
 carefully treated ; the latter by any juice. Lump sugar always forms a hard mass of 
 definite shape, resulting from numberless more or less well defined crystals, growing 
 closely upon, and combined with one another. The raw sugar consists of separate, 
 generally larger and better formed crystals, that do not grow upon one another. By 
 a special operation, the syrup is completely removed from the lump sugar, which is 
 not necessary to the same degree with the raw sugar. 
 
 Lump sugar can be prepared either from juice boiled blank or to granulation, but 
 the latter is the one generally used. The juice boiled to granulation is to be con- 
 sidered as an intimate mixture of sugar crystals with blank boiled juice that crystal- 
 lises upon cooling between already existing sugar crystals ; it thus yields a denser 
 mass of sugar than blank boiled juice, in which only so many crystals can form as may 
 correspond with the degree of concentration. 
 
 In order to obtain lump sugar from juice boiled to granulation, the product of a 
 boiling is allowed to flow from the vacuum pan into a spacious receiver, consisting of 
 a large shallow copper dish with double sides. It is there heated by steam to 90 
 and passed into the crystallisation vessels, the well-known conically shaped moulds 
 made of lacquered sheet iron. This reheating of the liquor has for its object to re- 
 dissolve a portion of the crystals. All the crystals, however, do not dissolve equally ; 
 the smaller crystals presenting the largest proportional surface are chiefly dissolved, 
 the larger remaining and forming the gr a i n of the sugar. Upon cooling, the dissolved 
 portion again crystallises between the existing crystals and thus forms a hard dense loaf. 
 In order to obtain this hardness with blank boiled juice, the formation of large 
 crystals is prevented by stirring the mass from the commencement of the crystallisa- 
 tion. When intended for the preparation of lump sugar, it is boiled to a somewhat 
 stiffer consistence. It is run into a large receiver, similar to that just described, but 
 called the cooler, as in this case the liquor is not reheated, but left to crystallise, 
 being meanwhile vigorously stirred with a wooden spatula and after some time it is 
 run into the moulds. 
 
 The further treatment of the lump sugar in the moulds is the same as in the ope- 
 ration of refining, which is described on p. 863. 
 
 In the preparation of raw cane sugar various crystallising vessels are used, either of 
 the same conical shape as for lump sugar, but three or four times as large, or large 
 rectangular or pentangular chests, or a large vessel capable of receiving a third of the 
 entire boiling. These stand in a room heated to 28 or 32. The size and sharpness 
 of the crystals are dependent upon their forming very slowly, and having time to grow, 
 and this can only be accomplished by a very gradual cooling. The more rapidly the 
 liquor is cooled the smaller are the crystals, and the presence of non-crystallisable 
 matters has a similar effect. From a specially good juice comparatively large 
 crystals are obtained even with rapid cooling, whilst an inferior juice under similar 
 conditions only hardens to a pasty mass. The size of the crystallising vessel has also 
 an influence upon the crystallisation, small moulds being used for good juice, and 
 large ones for inferior juice. The time required for the completion of the crystallisation 
 depends on circumstances ; with good juice in small moulds it is finished in six to eight 
 hours, the larger ones take twenty-four to thirty-six hours. 
 
 The mother liquor or syriip is drained off from the crystals in the cones, by re- 
 moving a plug from the apex ; the chests are inclined so that the syrup can run off 
 over the brim ; and the larger vessels are provided at the bottom with an opening. 
 The syrup flows off gradually, but more quickly the higher the temperature of the 
 room and the purer the juice ; several days are, however, always required. Even 
 after the draining is ended the sugar is never quite free from syrup, the separate 
 crystals retaining some by surface attraction and capillary action. This is removed 
 by liquoring, or by centrifugal action. The liquoring, which is confined to the 
 cone-shaped vessels, is carried out by pouring upon the sugar in the broad upper por- 
 tion of the mould either pure water or a solution of purer sugar. The water dissolves 
 a portion of the sugar, and becoming saturated, percolates through the mass of 
 crystals, driving before it the adhering syrup. The operation is repeated a second or 
 third time, until the remaining sugar is sufficiently pure. It is immaterial whether 
 pure water or sugar solution is used for the liquoring ; in the former case the solution 
 being formed at the cost of the sugar operated upon. This operation is best carried 
 out in the conical moulds, as the liquid has there to traverse the greatest distance. 
 After the last liquor has completely run off, the moulds are removed from their 
 frames and emptied, by reversing them and striking their broad ends once or twice 
 on the floor, by which the more or less adhering mass of sugar is jerked out. It is 
 then broken up with a mallet, and passed between toothed rollers, after which it is 
 ready for the market. 
 
 The liquoring of the sugar in moulds takes a very long time, as the syrup drains 
 slowly, necessitating the use of a great many crystallising vessels and the occupation 
 
 
854 
 
 SUGAR. 
 
 of much space. This difficulty is completely overcome by the use of the centrifugal 
 machine, which has now been introduced into most sugar manufactories. In many 
 
 FIG. 625 
 
 Km. 626. 
 
 FIG. 627- 
 
 places its use is confined to the after products, but in others it is applied to the first 
 product. A section of the centrifugal machine is shown in fig. 626 ; its external appear- 
 ance in fig. 625 ; as , 
 seen from above in 
 fig. 627 ; and some 
 of the details in 
 fig. 628. It consists 
 of two concentric 
 hollow vessels : the 
 outer one (A), which 
 is made of cast 
 iron, is intended to 
 receive the syrup and 
 has an opening (o) 
 through which it can 
 be run off ; the inner 
 one (L L) which holds 
 the sugar mass, is 
 made of strong per- 
 forate' 7 heet iron or 
 
 copper, and is covered inside with a fine wire sieve. This inner 
 vessel, the drum, is driven by means of the cone (K) and the 
 vertical shaft (D) with which it is connected. The shaft passes 
 through a stuffing box into the hollow bearing (c) below, and 
 its extremity rests upon a ground steel plate ; to diminish the 
 friction the hollow bearing is filled with oil. On the edge of the 
 outer vessel, or jacket, is fastened a strong iron arch (GO) 
 which supports the driving mechanism. The shaft passes through p IQ ^23 
 a bush in this arch, and has at its upper end a friction cone (E), 
 formed of a disk of leather closely pressed together; upon this acts a conical 
 friction wheel (F), fitted on a horizontal shaft (H i), and pressed by a spring (H H) against 
 the cone, the degree of pressure being regulated by screws in the springs. Over the 
 pulley (.T), which runs loose upon the shaft (H i), is the driving strap (H, figs. 627, 
 628), which when the machine is to be set in motion is pushed by an arrangement, 
 shown in fig. 627 (enlarged in fig. 628), upon the strap wheel (j''), which is fastened to 
 the shaft. A bar (a b, fig. 627 ; A B, fig. 628) lies parallel over the shaft (i H), and 
 supports near its ends two forks, between which the driving strap runs. This bar 
 being fitted in a female screw, when turned by a handle (E) slides to or fro in a hori- 
 zontal direction; the driving strap is thus pushed off or on to the loose pulley (.T), aru 
 
SEPARATION OF SYRUP. 855 
 
 the drum is made to revolve or stopped at will. A modification of this apparatus 
 has been made very generally in the placing of the driving machinery beneath the 
 drum instead of above it ; this gives greater convenience in filling and emptying. 
 The drum has a diameter of 32 inches and is 13 inches deep; it makes about 1,200 
 revolutions per minute. 
 
 Alter the crystallisation of the sugar has ended, the entire contents of the chest, 
 without first removing the syrup, is emptied into the crushing machine, a horizontal iron 
 trough, in which numerous blunt knives revolve in a vertical direction. These break 
 up the sugar mass, and mix it with the syrup. The result should be a uniform 
 moderately fluid paste ; should the syrup present be insufficient to give it the desired 
 liquidity, sufficient from another operation is added. This paste is ladled into the 
 drum whilst in full rotation ; it is at once flung by the centrifugal force against the 
 side, where the sugar is retained by the sieve, whilst the syrup flows through into the 
 jacket. In a few minutes the sugar is freed from all but a small quantity of the 
 syrup, which is separated by a liquoring operation. A small quantity of clear syrup 
 is thrown into the drum ; this penetrates at once through the sugar mass, and is 
 driven off by the centrifugal force. After a second similar liquoring, the sugar is 
 usually pure white. The syrup that flows off from the second liquoring can be used 
 in the next operation for the first liquoring. The entire operation including two or 
 three liquorings is finished in eight or ten minutes. When the ordinary moulds are 
 used, and the syrup allowed to drain, the operation takes several weeks, according to 
 the quality of the product. 
 
 The syrup that runs off from the first product is still a saturated sugar solution, 
 of course rendered impure by the nons accharine matter that was previously contained 
 in the whole of the juice. In order to -obtain this sugar, it is again boiled in a 
 vacuum to string proof and left to crystallise. The product is purified in the centri- 
 fugal machine, and the syrup driven off is again boiled, and yields a third product. 
 The syrup from this still contains about half its weight of crystallisable sugar, but 
 the non-saccharine matters have now become so concentrated that no more crystals 
 can be obtained by a fresh boiling. It is therefore collected in large cisterns, when 
 after standing for months some crystals gather at the bottom. The supernatant 
 liquor, or molasses, is removed as far as possible by skimming, and ultimately 
 the crystals are placed in the centrifugal machine and yield a last product. The 
 molasses still always contains about 45 per cent, of sugar, and some methods will be 
 described having for their object the obtaining of this sugary generally, however, the 
 molasses is not worked further, but used in the manufacture of spirit. 
 
 Working up of By-Products. The by-products of the manufacture of sugar from 
 the sugar cane consist of the scum, the pressed cane (bagasse or trash), and the syrup. 
 The scum, which is produced only in small quantity, is used as manure. The trash is 
 used as fuel for heating the evaporating pans ; the ash which it yields is unusually rich 
 in potash, and could be used in the glass- manufacture ; but it is preferable to restore 
 it to the soil in order to provide nourishment for the succeeding crop. The syrup 
 goes partially into the market, and being free from the disagreeable smell of beet 
 syrup, and containing a smaller amount of salts, is fit for direct consumption. The 
 larger portion is worked in the West Indies, after fermentation, for the preparation of 
 rum and alcohol. Generally it is allowed to ferment with the juice of the damaged 
 canes, and a rum is thus obtained which is especially liked for its fine aroma 
 
 The following represents the plant of a sugar-boiling house capable of working 
 10,500 gallons of juice daily, or nearly 1,600,000 gallons in a season of 150 days, pro- 
 ducing about 1,200 tons of sugar. 
 
 The steam power is equal to about 92 horse power, of which 16 horse power is 
 used for driving the machinery, and 76 horse power for the evaporation. For the 
 defecation six pans, 4J feet in diameter, are provided ; each holds about 220 gallons of 
 juice, and makes eight operations daily, or altogether 48 operations. From 5 to 10 
 ounces of lime are used for each defecation. The filtration requires eleven filters, 
 each containing 1 tons of animal charcoal, or altogether 13| tons. Six of the filters 
 filter about 88 gallons of thin juice hourly, or in the twenty-four hours, including four 
 hours' rest, between 10,000 and 11,000 gallons. Five filters used for thick juice yield 
 about 4,400 gallons daily. Every twenty-four hours two filters are freshly filled. 
 The charcoal from each filter retains about 12 cwts of thick juice ; this is first dis- 
 placed with thin juice, and then the thin juice is washed out with water until the 
 liquor flowing away is of sp. gr. T013. The washing of the filter lasts three hours. 
 The evaporation is effected first in three systems of condensation pipes, and then in 
 two vacuum pans ; the first of them exhausted to 12'5 inches and the second to 6'5 
 or 7 inches. In the crystallisation the syrup is heated to 80, and yields then 160 
 moulds each containing about 150 Ibs. of mass ; after draining there remains about 
 110 Ibs. of sugar in each mould. The daily product of sugar would therefore be 
 nearly 8 tons. 
 
856 
 
 SUGAR. 
 
 Working of the Scum. The different scums produced in the defecation and satura- 
 tion are permeated by a large quantity of juice, in proportion to the voluminousness of 
 the precipitate. Formerly, to recover this juice the scum was filled into linen bags, 
 the juice allowed to drain as much as possible, and the bags then placed in the 
 hydraulic press. This was the most disagreeable and uncleanly operation of the 
 whole manufacture. The larger quantity of lime scum produced by the modern 
 methods of defecation has rendered this method impracticable, and a great advance 
 in the sugar manufacture was made by the introduction of the filter press used by 
 Needham, for the removal of water from clay in the porcelain manufacture. This he 
 
 afterwards adapted to the requirements of the sugar manufacture, and at the Ex- 
 hibition in London in 1862 he produced the sugar scum press. Since that time it has 
 
MOLASSES. 857 
 
 been several times modified and improved by Danek of Prague, Trinks of Helmstadt, 
 and Eiedel and Kemnitz in Halle. 
 
 The filter press may be described as consisting of very narrow, tall, and broad 
 chambers, the two tall and broad sides of which are formed of willow rods laid per- 
 pendicularly and covered with linen. In the upper narrow end is an opening, into 
 which is set a very tall pipe. When a slimy liquid is poured into this pipe, the water 
 at first passes easily through the linen covering the sides, and no other way being open 
 it follows the direction of the rods. The sides soon become covered with a dense layer 
 of ecum, which would prevent the flow of the liquid were it not for the pressure 
 exerted by the column of liquid in the long pipe, which drives out the water until the 
 chamber is full of dense scum from which the water has been driven out. A filter 
 press consists of eighteen or more of these chambers, the four closed sides of which are 
 formed by planed iron frames. The wicker work is now imitated by two thin iron 
 plates, perforated by long slits, which are so arranged that when the plates are placed 
 against one another there is a communication between all the openings. The plates 
 are covered with linen, and the chambers thus formed by the frames and plates being 
 filled with scum, the liquid runs through into the connected slits, and escapes between 
 each pair of frames, leaving the scum in the chamber. The long pipe is filled by a 
 monte-jus which is in connection with all the chambers. One modification of the 
 filter press is shown in figs. 629 to 631. Fig. 630 is a vertical section through a 
 chamber showing the iron plates forming the sides with the longitudinal openings. 
 In the middle and near the upper edge is a circular opening. Each pair of plates is 
 covered with linen, and between each pair is an iron frame (A') with a circular 
 opening exactly corresponding with the circular opening in the plates, so that when 
 pairs of plates and frames are placed alternately, a corresponding number of chambers 
 are formed, which are connected by a common channel formed by the circular openings 
 in the plates and frames. The sides of the opening in each frame are perforated several 
 times in an oblique direction, so that the channel is thus placed in communication 
 with the interior of each chamber. This is shown in fig. 629, which represents a 
 section at right angles with that in fig. 631. The frames are suspended on a strong 
 iron frame, each being provided with two projections (G), that rest upon an iron balk. 
 The eighteen frames are pressed closely together by means of a strong screw (F, fig. 
 631) until they are watertight. The complete press is shown in fig. 631. The pipe 
 (A) leading from the monte-jus is connected with the end of the press ; its prolongation 
 (A') is formed by the circular openings in the frames and plates, and at the opposite 
 end it is closed by a screw (E). The frames and plates are secured by the pressure 
 of the screw (F) upon the end piece of the press. The filtered liquid runs through the 
 openings in the plates into the trough (B), and thence into the iron reservoir (c), 
 from which it is run off at (D). 
 
 The scum to be filtered is worked up into a uniform mass, then run into a monte- 
 jus and driven under steam pressure into the filter press. The removal of the liquid 
 takes place very quickly, and the press remains filled with a dry cake of scum. To 
 empty the press the screw (F) is loosened and the end piece withdrawn ; the frames 
 and plates are then lifted out successively, and the intervening scum cake removed, 
 until the press is emptied. The plates are covered with clean cloths, and returned 
 with the frames to the press ; the screw is applied, and the press is ready for a fresh 
 operation. 
 
 The suggested modifications of this apparatus have been very numerous, but the 
 principle remains the same in all. 
 
 Working of the Molasses. The liquor from the last crystallisations, known under 
 the name of molasses, is a solution of crystallisable sugar, in which however 
 crystallisation is prevented by the pi'esence of a large proportion of foreign matters. 
 Its composition evidently varies with the quality of the juice, but on an average 
 molasses contains 50 per cent, of crystallisable sugar, 30 per cent, of non-saccharine 
 bodies and 20 per cent, of water. Upon incineration the non -saccharine matter yields 
 3 parts of ash. To separate this large quantity of crystallisable sugar different 
 methods have been proposed. Some of these are based upon the fact that sugar will 
 form insoluble compounds with the alkaline earths, which can then be separated from 
 the soluble non-saccharine matters ; another method depends upon the osmotic 
 behaviour of molasses. 
 
 Dubrunfaut has introduced a method based upon the insolubility of sugar baryta. 
 The molasses is diluted with boiling water, and whilst hot mixed with so much solu- 
 tion of barium hydrate as contains one molecule of baryta for each molecule of sugar. 
 A flocculent precipitate of sugar baryta is immediately thrown down, whilst the re- 
 maining matters, or at least the greater part, remain in solution. The sugar baryta 
 is washed with hot water until all other matters are removed, an operation in which 
 the filter press may be used with advantage, and it is then suspended in water and satu- 
 
858 SUGAR. 
 
 rated -with carbonic acid. The carbonic acid decomposes the sugar baryta, forming 
 insoluble barium carbonate, whilst the sugar is set free. The precipitated barium 
 carbonate is freed from sugar in a filter press, and by ignition with charcoal it can be 
 again converted into barium hydrate, so that the same quantity of baryta can be re- 
 peatedly used. The saturation must be effected at the temperature of boiling, to 
 avoid the formation of acid barium carbonate. Even when this is accomplished, some 
 baryta always remains in solution. As barium acts poisonously upon the system, 
 this must be completely removed ; the juice is therefore filtered through animal char- 
 coal, upon which is placed 2 parts of calcium sulphate or gypsum, or an equivalent 
 quantity of sulphuric acid (sp. gr. T49), for every 1 ,000 parts of the prepared molasses. 
 The latter treatment, however, does no good to the animal charcoal. 
 
 Another method, in which baryta with its disadvantages is replaced by lime, has 
 been invented by Scheibler. Each 100 Ibs. of molasses is thoroughly mixed with 
 about 27 gallons of 82 to 85 per cent, spirit and 37 or 38 Ibs. of lime. A sugar lime 
 compound is produced that is completely insoluble in spirit, whilst the non-saccharine 
 matters remain dissolved. The alcoholic solution is separated from the sugar lime in 
 the filter press, and the sugar lime is washed with alcohol ; the alcoholic solution and 
 washings being afterwards submitted to distillation to recover the alcohol. The 
 sugar lime still saturated with alcohol is placed in a saturator connected with a dis- 
 tillatory apparatus, and heated with water to boiling, while at the same time carbonic 
 acid is introduced. The alcohol distils off from the boiling liquid, whilst the sugar 
 lime yields calcium carbonate and crystallisable sugar. 
 
 The osmotic treatment of the molasses is essentially the same as the diffusion 
 method of separating sugar from beet previously described, but in this case the 
 natural diffusion organ, the membrane of the vegetable cell, is replaced by an artificial 
 one of parchment paper. The parchment paper is stretched over the edges of shallow 
 frames, a number of which, filled alternately with water and molasses, are fastened 
 together, and diffusion then goes on between the water on the one side, and the 
 molasses on the other. The constituents of the molasses are diffusible in very dif- 
 ferent degrees; the sugar, although a crystalloid, diffusing more slowly than the 
 salts and some of the other organic substances. The greater part of the salts can 
 therefore be obtained in the outflowing water, but also with a loss of a certain quan- 
 tity of sugar, the amount depending upon the way in which the operation is carried 
 out. When the water diffuses rapidly, little sugar is taken up ; but when it is long 
 in contact with the molasses, a proportionately larger quantity of sugar is carried 
 through. An absolute separation of sugar and salts by this method is not possible, 
 the most that can be done is to reduce the proportion of salts. But as it has not 
 been shown that the presence of the salts hinders the crystallisation of the sugar, and 
 it is much more probable that this is dependent on the presence of non-saccharine 
 matters, it is not likely that all the sugar can be obtained in a crystalline form in this 
 way. Practically, only about 15 per cent, of a very impure dark-coloured sugar is 
 obtained from molasses containing 50 per cent. 
 
 It has been recommended by Champonnois, and afterwards by Payen, that the 
 syrup from the first product should be mixed with fresh beet pulp in such proportions 
 that the pulp produced in a day should be used up with the syrup made the previous 
 day. The syrup is first diluted with water to the concentration of the normal juice, 
 heated to 70, added to the pulp brought to the same temperature, defecated by the 
 Perrier-Possoz method, and afterwards worked in the ordinary way. A coagulation 
 of the albumin and a considerable absorption of the salts by the substance of the 
 pulp is said to take place ; consequently the constituents of the beet, with the ex- 
 ception of the sugar, would be retained in the pressed pulp and the juice would be 
 considerably purified. All working of the after product would be done away with, as 
 only first product and no molasses would be produced. It has yet to be proved that 
 this method can be practically carried out, but experiments by Bodenbender have 
 shown it to be very improbable that the beet pulp has such an absorbent action upon 
 non-saccharine matters. 
 
 The whole of the by-products and refuse of the beet-sugar manufacture find useful 
 application as fodder, manure, or in other ways. They consist of the beet leaves and 
 tops, the pressings, residues from the centrifugal maceration or diffusion operations, 
 the washing, defecation, and saturation scum, the refuse from the washing of the 
 charcoal, and lastly the molasses. 
 
 The beet leaves are generally used with least advantage, being simply thrown 
 upon the land and there allowed to rot. Sometimes they are used as fodder, and 
 during the beet harvest the yoke oxen are fed exclusively upon them. This is almost 
 equally irrational, for though on account of their richness in albuminoids, they form 
 good fodder when given in suitable quantities, in large quantities they produce 
 purging and weaken the beasts. 
 
WASTE PRODUCTS. 
 
 859 
 
 The leaves are also used after being buried in pits, and there allowed to ferment. 
 Immediately after the harvest, the leaves are stamped into brick or simple earth pits, 
 so as to lie close and enclose but little air and are then covered with earth. Fermenta- 
 tion commences almost immediately and continues for a long time. The leaves are 
 kept in this condition till the following spring or summer. The parts round the edges 
 and the top layer are usually overgrown with mould and have to be separated. As 
 soon as the principal fermentation is over the leaves may be used for fodder ; the 
 peculiar smell that the leaves acquire is at first distasteful to the beasts, but after a 
 short time they become habituated to it and take the fodder willingly. The value of 
 the leaves is dependent upon their remaining green at the time they are gathered. 
 
 The beet tops are always worked up into fodder with the pressings and other resi- 
 dues from the juice winning operations. They are placed in alternate layers in large 
 brick pits, pressed down, and then treated in the same way as the leaves. They 
 immediately commence to ferment and acquire an agreeable faintly acid smell, and 
 the beasts eat them greedily. If the jiiice has been imperfectly removed, and much 
 sufifar is left, a considerable quantity of free acetic and lactic acid is formed during 
 the fermentation. In this case there is not only loss of sugar, but the consumption of 
 such sour pressings in any quantity affects the beasts injuriously. The fermented 
 pressings should only have a faintly sour taste and slightly redden blue litmus paper. 
 
 The residues from the juice extraction form a poor fodder compared with al- 
 buminoid substances, but rich compared with easily digestible non-nitrogenous 
 matters. Mixed with substances rich in albumin, such as oil-cake or beans, they 
 form a good fattening food for cattle and sheep. 
 
 The residue yielded by the various methods of obtaining the juice differs consider- 
 ably in composition, especially in the amount of water it contains. That from the 
 hydraulic presses contains most dry substance, about 30 per cent. ; that from the 
 centrifugal machine contains only half as much ; that from maceration by Schutzen- 
 bach's method usually 16 to 20 per cent., but more or less according as it is pressed. 
 Finally, the diffusion residue only contains about 8 per cent., and sometimes only 4 
 per cent, of dry residue ; in the latter case the water is allowed to drain off until the 
 dry substance reaches about 8 per cent, before burying it in the pits. 
 
 The following analyses of the residues of different factories will show the composi- 
 tion of the pressings and diffusion residues : 
 
 Pressings (StohmannX 
 
 Albumin . 
 
 Fibre .... 
 
 Fat 
 
 Non -nitrogenous extract . 
 
 Mineral matters 
 
 Water .... 
 
 2-36 
 6-86 
 0'38> 
 
 17-30$ 
 3-05 
 
 70-05 
 
 2-41 
 5-72 
 
 20-03 
 
 3-40 
 68-44 
 
 1-43 
 
 4-15 
 
 < 0-13 
 
 j 14-60 
 
 4-36 
 
 76-33 
 
 2-11 
 4-90 
 0-19 
 
 18-42 
 2-51 
 
 71-87 
 
 Diffusion Eesidue. 
 Stohmann 
 
 Fresh from 
 diffuser. 
 
 0-74 
 
 1 46 
 
 0-06 
 
 4-20 
 
 1-64 
 91-9C 
 
 From the 
 pits. 
 0-60 
 2-24 
 0-03 
 5-22 
 1-74 
 
 90-17 
 
 Von Wicke. 
 
 , * N 
 
 Pressed by 
 Schottler's press. 
 
 1-29 
 3-06 
 0-16 
 5-72 
 3-53 
 86-24 
 
 0-76 
 2-18 
 0-15 
 6-90 
 2-90 
 87-H 
 
 Albumin . . . 
 
 Fibre . . . 
 
 Fat . . .... 
 
 Non -nitrogenous extract . 
 
 Mineral matters 
 
 Water . ... 
 The wash residue from the beets, the refuse beets, and the scum from the filtration, 
 defecation and saturation, the latter containing much lime, can be made into a good 
 compost. The defecation scum is usually overrated as a manure, the organic sub- 
 stances in it containing on an average only 0'5 per cent, of nitrogen ; of other plant 
 foods, with the exception of lime, it contains only about 1 per cent, of phosphoric 
 acid. But on soils poor in lime and heavy clayey soils the beneficial action of the 
 compost on account of the lime it contains cannot be denied. 
 
 The refuse of the charcoal washings is carefully collected in settling basins ; at 
 the end of the season the charcoal slime is either converted into superphosphate or 
 sold to the manure makers. 
 
 The molasses is used in the spirit manufacture, or when the market price is low it 
 may be used for feeding cattle if given with a proper proportion of albuminous fodder. 
 The latter method has the advantage that the greater part of the mineral constituents 
 of the beet is returned to the soil in the dung. 
 
860 SUGAR. 
 
 The Effluent Water. In all parts of the manufactory foul water is produced, laden 
 with more or less organic and fermentable substances. When this is allowed to run into 
 the streams and ditches it supports the growth of a large quantity of slimy algae. 
 One of these, the Begfyiatoa alba, has tho property of decomposing the sulphates, which 
 are present in all waters, with the liberation of sulphuretted hydrogen, killing the fish 
 nnd giving rise to foul smells. If there be meadow land in the neighbourhood of tho 
 manufactory, the injury to tho streams may be avoided by using the effluent water for 
 the irrigation of the land, and thus purifying it before it flows into the watercourses. 
 Where there are no meadows an artificial disinfection has to be effected. 
 
 Suvern's disinfectant consists of milk of lime prepared by slaking 1 00 parts of 
 lime with water, and during the effervescence adding 1\ parts of coal tar and 15 to 
 20 parts of magnesium chloride. This milky mass is allowed to flow in a thin stream 
 into a narrow canal through which the whole of the foul water from tho factory flows. 
 When the turbid water and milk of lime meet, aflocculent precipitate is formed. Tho 
 water passes through a canal 100 to 150 ft. long', and through two large basins suc- 
 cessively ; in the second basin the deposit of the precipitate is completed, and the 
 water flows from thence clear. The addition of the milk of lime must be so regulated 
 that the effluent water has a distinctly alkaline reaction. Through the addition of tho 
 lime dissolved matters are precipitated in an insoluble form, the precipitate carries 
 down mechanically all suspended matters, together with organic germs, whilst the 
 alkalinity of the water destroys all vegetation of the lower organisms. The water is 
 thus at a small cost sufficiently purified to be allowed to run into the streams without 
 injuring them. Whether the coal tar and magnesium chloride are necessary is very 
 questionable ; probably pure lime is sufficient. The -precipitate obtained by this 
 method in three different factories in Saxony had the following composition (Stoh- 
 mann) : 
 
 Phosphoric acid 0'37 0'18 0-20 
 
 Nitrogen 0'12 0-16 0-09 
 
 Potash 0-23 0'21 0-06 
 
 Lime 6-23 9'17 6'56 
 
 Alumina and ferric oxide .... 2-64 2'40 1-37 
 
 Sand and earth 26*05 24-29 10-64 
 
 Water 56-98 55-15 75'69 
 
 Magnesia, carbonic dioxide, chlorine, etc. . 7*38 8'44 5'39 
 
 The disinfection scum may be advantageously incorporated with the compost 
 previously described, the quality of whicli should be improved by the lime it contains. 
 
 SUGAR KBFINING. Neither the cane sugar from tho plantations nor that pre- 
 pared from beet comes in any considerable quantity directly into consumption ; by 
 far the greater portion is worked up again in special establishments, the Kefineries, 
 and converted into a purer white product. 
 
 The object of the refining is to remove from the sugar mechanical impurities, such 
 as sand, earth, splinters from the casks and chests in which the sugar was parked, 
 particles of crushed cane, colouring materials, uncrystallisable sugar, and albumin; 
 different salts, such as potassium chloride and nitrate, sodium chloride, calcium carbo- 
 nate, phosphate and malate, and magnesium phosphate. In sugar from the tropics, 
 free acids are present, such as malic acid, pectic acid, acetic acid, and lactic acid, the 
 two latter being products of fermentation, which easily takes place in these kinds of 
 sugar in the stores or on board ship, a,nd these acids give rise to the formation of 
 grape and fruit sugar. In beet sugar those changes do not take place, if the. juice he. 
 kept alkaline during the working; on the other hand, there is always then a residue 
 of sugar lime. 
 
 In establishing a refinery, it is necessary to secure a sufficient supply of the purest 
 possible soft water; it should also bo within reach of good and cheap fuel. 
 
 Formerly the value of cane sugar was judged exclusively by external characters : 
 the form of the crystal, tho grain, tho colour, and the smell. This however no longer 
 suffices, and the amount of pure sugar is now accurately determined by the saceharo- 
 meter, as well as the amount of moisture and non-crystallisable sugar. Only with a 
 knowledge of the sugar contents, and of the proportion between the crystallisablo and 
 non-crystallisable sugar, is it possible to make an accurate estimate of tho yield to bo 
 expected. 
 
 The better qualities of cane sugar have well formed, distinct crystals, and a close 
 grain ; they are white or of light yellow colour, and fool hard and dry (soft whito sui;ir> 
 are imperfectly frocd from syrup). They should not have an acid reaction, for that 
 indicates partial decomposition ; on the other hand, a strong alkaline reaction is not 
 desirable, as it would be due to a great excess of sugar lime. 
 
 Generally the colonial sugar, prepared from juico containing grape sugar, and defe- 
 
SUGAR REPINING. 861 
 
 cated without an excess of limo, is more or less altered during transport, imd it feels 
 sticky to the touch; it has then less ^r.-iiii, lbrmin- snuillor crystals lhan U-ot sugar. 
 
 Beet sugar, if well i>roparod, if not over boiled, or loo rapidly crystallised, aud con- 
 sequently containing too much syrup, is easily refined, and givesa high yield of white 
 en no sugar. It is therefore preferred to the colonial sugar, except that of the best 
 qualities, notwithstanding that the syrup obtained as a by-product from the latter is 
 more easily disposed of. 
 
 As the sugar refiner is compelled, in order to meet his requirements, to purchase 
 sugar of the most diverse qualities, care has to be taken to assort it immediately upon 
 its reception, so that afterwards it may be worked up either with sugar of the same 
 quality only, or with a suitable mixture of different qualities. Thus colonial sugar is 
 sometimes mixed with beet sugar, in order to neutralise the alkalinity and the dis- 
 agreeable smell of the latter with the acidity and better aroma of the former. 
 
 The whiter kinds of colonial sugars are usually reserved, in order to use their solu- 
 tion for liquoring the refined sugar ; they are seldom refined, being sought for, for the 
 preparation of the finer products. On the other hand, they are often used for the pre- 
 paration of fruit syrups, confectionery, etc. The finest beet sugar, containing 98 pr>r 
 cent, of sugar, is also used for the finishing of the syrup. 
 
 The refining includes the following operations : the storing of the cane sugar, the 
 emptying of the casks or running of the sugar, the solution or melting and clearing, 
 the filtration, the boiling, the crystallisation, the draining of the syrup and claying, 
 the drying, and finally the treatment of the syrup. 
 
 Storage. The sugar is brought at once into an airy, dry room, the well-boarded or 
 cemented floor of which slopes to one side, so that the syrup draining from the sacks 
 or casks flows off into a reservoir. The casks are piled upon one another according to 
 their size, care being taken that the best and strongest casks are underneath. 
 
 At the commencement of the refining the casks are emptied near to the solution 
 apparatus, the thick hard pieces which always occur being picked out and broken up 
 by themselves. A certain quantity of sugar always remains adherent to the side of the 
 cask, and this is best recovered by solution in condensed steam. For this purpose a 
 hollow brickwork chamber corresponding to the size of the cask is provided, which is 
 lined with copper, and has a steam pipe in the centre. The cask is placed bottom 
 upwards over the steam pipe, and an iron bell hanging from a pulley is then let 
 down over the cask. Upon opening the steam pipe, the cask is filled with steam. 
 which condenses upon the cold sides ; the water dissolves out the sugar, and the syrup 
 collects at the bottom of the chamber. The wood of the cask is softened by the 
 steaming out, and after the removal of the bell, it is in a suitable state for repairing, 
 re-hooping, etc. 
 
 The sugar emptied from the casks is thrown upon a sieve, and the lumps that do 
 not pass through are broken up between a pair of toothed cylinders, or a suitable mill. 
 
 Melting and Clarification. The clarification or separation of all mechanical im- 
 purities and a portion of the dissolved foreign matters from the syrup obtained by 
 dissolving the sugar, is effected by means of finely powdered animal charcoal and a 
 solution of albumin. The albumin being added to the syrup at a low temperature 
 is distributed through it equally ; upon heating the syrup, the albumin coagulates 
 in flocks, which enclose within them the foreign matters and the mechanical im- 
 purities. as well as the animal charcoal that has been added. When a sour colonial 
 sugar is being worked, sufficient milk of lime is added at the same time to give it a 
 very faint alkalinity. But this is avoided when possible, and it is preferred to work 
 a mixture of colonial and beet sugars, so as to neutralise the acidity of the one with 
 the alkalinity of the other. 
 
 Generally the albuminous liquor used is the blood of cattle and sheep, from which 
 the fibrin has been separated by beating it with rods immediately after the slaughter 
 of the beasts. It is preserved in sulphured vessels, or with an addition of sulphurous 
 acid or sodium sulphite. In consequence of the rapidity with which blood commences 
 to putrefy, and the unbearable stink thus produced, its use is very offensive, but the 
 uae of a small quantity of sulphurous acid retards the process of decomposition con- 
 siderably. Kobierre and Dureau recommend that the blood should be mixed with 
 double its weight of animal charcoal and dried at a low temperature, preferably in a 
 current of air heated to not above 55. In this dried condition the blood can be 
 preserved, and its action is equal to that of the fresh. Blood dried without the addi- 
 tion of charcoal is at present a commercial article, but its use in this form would pro- 
 bably be too expensive. 
 
 In many refineries the use of blood has been either entirely given up or limited to 
 the! working of specially slimy sugars. The clarification is then replaced by a propor- 
 tionally more careful treatment of the filters. 
 
862 SUGAR. 
 
 The clarifying pans have generally the same construction as the defecation pans of 
 the beet-sugar manufacture. They are placed sufficiently high to allow the syrup to 
 run from them directly into the filters. The water for effecting the solution, about 
 50 parts of water to 100 parts of sugar, is run into the clarifying pan and heated. 
 The sugar is then shovelled in, and the first melting is effected with continual 
 stirring; powdered animal charcoal is added in the proportion of 5 parts to 100 
 parts of sugar, and by vigorous agitation distributed throughout the entire liquid. To 
 the lukewarm juice is then added 1 to 2 parts of blood that has previously been mixed 
 with five or six times its volume of water ; the whole is again well stirred and then 
 boiled. When the black coating of scum is broken through by white bubbles it is an 
 indication that the clarification is effected. The liquor is next cleaned from scum by 
 a first filtration, the turbid portion first flowing off being returned to the filter, and 
 the clear liquid passes to the charcoal filter. 
 
 Filtration. As preliminary filters the old Taylor's filters are generally used. 
 They consist of strong wooden copper-lined chests, 3 to 6 feet square and 20 inches 
 high. The front side is formed of a door. Over this is a still larger chest, also of 
 wood and copper lined, but only 6 inches high. In the bottom of this 24 copper pipes 
 are fitted into as many holes, about 2 inches in diameter. The pipes are sufficiently 
 long to project an inch or two into the under chest. At the lower end is a rim, and 
 above this a ring opening with a hinge and tightened by a screw ; -by means of these 
 rings the filtering bags are fastened to the pipes. The filtering bags are made of linen, 
 and are 40 inches long and 20 inches in diameter ; each of these is enclosed in a 
 second bag 8 inches in diameter, but of loose texture. By thus putting a broad into 
 a narrow bag numerous folds are formed, and the filtering surface correspondingly 
 increased. 
 
 The juice with the scum flows from the clarifying pan into the upper chest, and 
 from this through the short pipes into the bags fastened to them, in which the scum 
 is retained ; from these it passes through a pipe fixed in the bottom of the lower chest, 
 into a trough by which it is conducted away. As the removal of the slime from the 
 filter is a rather difficult operation, the filtration in many refineries is reversed ; in- 
 stead of filtering from the inside to the outside, the filtration is effected from the out- 
 side to the interior, so that the slime is retained in the spaces between the filters. 
 
 Another method is to use a rectangular copper-lined wooden chest, open above, 40 
 inches wide, 52 inches long, and 80 inches deep. The chest is provided with a false 
 bottom, in which are a series of wide openings having copper pipes as in Taylor's 
 filter, but in the reverse direction, so that they project upwards. Below the false 
 bottom is the proper one, from which the filtered liquid is run off by means of a tap. 
 The filtering bags are fastened to the copper bags with their mouths opening down- 
 wards, a strong bent wire being previously placed iu them to keep their sides apart. 
 The separate bags are supported by cross pieces fastened to the sides of the chest. 
 The syrup to be filtered is run into. the chest, when the slime remains between the 
 separate bags, whilst the clear liquor enters them and flows off through the pipes. 
 The slime can then be easily removed from between the bags, especially if the pipes 
 are unscrewed and the bags lifted out. In continual working this is only necessary 
 when the entire chest is filled with slime. The residue is stirred up with water and 
 boiled ; the liquor is afterwards allowed to settle, and when clear is drawn off and 
 replaced by fresh water, and this is repeated until it no longer takes up much sugar. 
 The wash water containing sugar in solution is used instead of water to dissolve a 
 fresh quantity of sugar. The slime is finally pressed and sent to the manure factory, 
 where by treatment with sulphuric acid it yields a nitrogenous superphosphate. 
 
 The preliminary filtration has for its object to save the charcoal filters, and to 
 separate the matters mechanically retained in the coagulated albumin. The hot syrup 
 flows directly from the preliminary filter on to the real filter, which is arranged exactly 
 as described under the beet-sugar manufacture. Generally two filters are used to- 
 gether, the syrup passing from one to the other, and a filter being used as long as the 
 syrup passes from it perfectly colourless. 
 
 When foul the filter is cleansed with boiling water ; the first liquor, so long as it 
 is sufficiently concentrated, being added to the other syrup, and the more dilute liquor 
 is used like the wash water from the preliminary filter for dissolving fresh sugar. As 
 the charcoal of the refinery takes up far less foreign matters, its revivification is much 
 more simple. When the water flows from the filter pure, the charcoal is steamed in 
 the filter itself, dried, and then brought to a red heat. After a time, a considerable 
 quantity of lime salts accumulates, and a treatment with acid is necessary. 
 
 Boiling. In the boiling of the syrup, vacuum apparatus similar in construction to 
 those used in the boiling of the thick juice in the cane-sugar manufacture are now 
 used probably without exception. As in sugar refineries they have to do with nearly 
 pure sugar solution, it is boiled until it commences to grain, and the cry.stallisn.HoT] ir. 
 
 
SUGAR REFINING. 863 
 
 allowed to begin in the vacuum pan. The finished syrup is then brought into 
 the heater, and is there heated to 80, in order to melt the greater part of 
 the small crystals, the sugar from which runs between the larger crystals and 
 forms a combination between them. The heater is usually sufficiently large to unite 
 in it several fillings of the vacuum pan, and by their mixing these yield a large 
 quantity of uniform products. After sufficient heating the steam is turned off in order 
 to allow the crystallisation to proceed. By repeated stirring the formation of a con- 
 glomeration of crystals is prevented, and the granulation made uniform. 
 
 The Filling. Usually the heater stands in the filling room, for convenience in 
 filling the forms. A spacious trough runs through the wall of the filling room from 
 the vacuum pan to the heater, and the syrup flows immediately from one to the 
 other. The filling room is a large chamber, with a well-boarded level floor, so that 
 any sugar spilt may be easily collected, and that the moulds may stand up regularly. 
 
 The following utensils are here used : 
 
 Filling basins, for the removal of the syrup from the heater to the forms. These 
 are round or oval copper flat-bottomed basins with wide spouts, provided with iron 
 handles for convenient transport. 
 
 Large copper hemispherical ladles, 10 inches in diameter, provided with long 
 handles These are used for the removal of the syrup from the heater into the filling 
 basins. Spatulas or stirring knives, for stirring the syrup in the forms. These are 
 of beech- wood, 4 feet long, the upper third forming the round handle ; the spatula 
 itself is knife-shaped, sharpened on both sides, 1J inches wide, and f inch thick. 
 
 The moulds have the well-known conical shape of the sugar loaf. Formerly the 
 moulds were generally made of burnt unglazed earth, protected from breaking by 
 wooden hoops ; at the present time these have been entirely replaced by moulds made 
 of sheet iron. At the apex of the mould there is a small opening through which the 
 syrup can drain away. To protect them from rusting, the moulds are coated with oil 
 colour and varnished with a good siccative. As soon as the coat becomes injured 
 at any part it must be renewed, as otherwise the sugar would be injured by rust, and 
 moreover it would adhere to the mould. 
 
 The size of the moulds varies exceedingly, being influenced by the custom of the 
 consumer and the quality of the product. For the finer kinds of refined sugar the 
 smaller are used ; for those prepared from the after products the larger ones are 
 taken. 
 
 Before the filling of the moulds the opening in the head is stopped up with a plug 
 of linen rag, and the inner surface is wiped with a dimp sponge, the moisture remain- 
 ing from which prevents the close adherence of the crystals to the side. The moulds 
 are then placed upright, with the wide end upwards, side by, side and resting against 
 each other, the outside now being prevented from falling by an equal number of heavy 
 cast-iron moulds standing on their broad bases. 
 
 During the filling of the moulds the syrup is carefully stirred with a large spatula 
 in order to distribute equally the large crystals that may have sunk to the bottom. 
 The filling basin is placed on an iron stand close by the side of the heater, so that its 
 upper brim is on a level with the brim of the heater, and filled with the ladle ; it is 
 then carried to the mould and emptied, so that at first the moulds are only half filled. 
 When this is completed they are filled in the same order to within inch of the brim. 
 This filling is carefully performed in two, or frequently three, operations, in order to 
 distribute uniformly through the whole of the moulds the crystals, which continue 
 to form in the heater during its emptying ; otherwise the moulds would contain sugar 
 6f different grains. 
 
 A short time after the filling the mass becomes covered with a crust of crystals. 
 This is the time chosen for the first stirring, the object being to raise the large crystals 
 that have sunk through the still soft mass into the head of the mould and distribute 
 them equally. This is done by thrusting the spatula into the sugar with its flat side 
 against the side of the mould, and then drawing it rapidly in a perpendicular position 
 upwards towards the centre. This is repeated several times, taking care to stir the 
 sugar in a different place each time, in order to carry into the middle the crystals that 
 are deposited by more rapid cooling on the sides. The right time for stirring must be 
 carefully judged, as if it takes place whilst the mass is still too hot the grains again 
 sink down through the thin liquor; whilst if it be effected too late a striped loaf is 
 the resultthrough the unequal distribution of the granules. A short time after the first 
 stirring the spatula is again drawn through the mass twice. 
 
 The temperature of the filling room should be kept as uniform as possible between 
 30 and 35, so as to avoid too rapid cooling of the forms. Above all strong draughts 
 must be prevented, as these cause an unequal cooling, and consequently an unequal 
 crystallisfition. 
 
864 SUGAR. 
 
 The further operations are carried on in the sugar floors, which occupy the upper 
 part of a refinery. They are large rooms, not more than 6 feet high, in order to 
 economize space and heating material, and well floored and well lighted. The necessary 
 heating is effected by steam circulating through iron or copper pipes, arranged round 
 the walls. Direct heating by ovens is no longer adopted in well-arranged refineries. 
 
 Formerly, each mould was placed to drain separately on the floor in a pot, but 
 this inconvenient arrangement has been substituted by placing them on a shelf, per- 
 forated with holes of sufficient diameter to receive the points of the moulds, the upper 
 part being supported by a frame. Below the perforated shelf is a zinc-lined funnel, 
 from which the syrup runs off through a pipe into a trough, and is conducted away. 
 The trough is movable, so that, according to the quality of the syrup, it can be con- 
 nected with special piping communicating with different reservoirs. Each stand 
 holds two or three rows of moulds, so that they can easily be reached, and between 
 each stand is a gangway sufficiently wide for a man to pass. A still better arrange- 
 ment is for the holes in the shelves to be larger, so that the moulds hang by their 
 broader ends; the head of the moulds and the draining of the syrup can then be more 
 conveniently watched. 
 
 The filled moulds remain in the filling room eight to twelve hours, and are then 
 removed to the floor, being raised in a frame by means of a lift. Arrived at the floor, 
 the plug is removed from the head of the mould, and a small hole is bored in the head 
 of the loaf with an awl, to facilitate the running off of the syrup. The temperature 
 of the floor is maintained at 25 to 28. 
 
 The still fluid portion of the sugar, the syrup, drains slowly from the opened 
 mould, and in about twelve hours the upper layer of the sugar appears white and dry. 
 The draining lasts six or seven days longer, during which time 8 to 11 Ibs. of green 
 syrup will drain from a large sugar loaf, weighing 33 to 36 Ibs. The temperature 
 of the floor is then moderated to 20, and the liquoring, or displacement of the syrup 
 with pure sugar solution commenced. 
 
 By means of a scraper the top layer of sugar is first removed, in order to give to 
 the loaf a smooth base, it having become uneven through the stirring and unequal 
 solidification. 
 
 The scraped sugar is then made quite level on the surface, and a further covering 
 of pure ground sugar or white well-clayed colonial sugar given to it : this is beaten 
 close by means of a wooden hammer. 
 
 The liquoring or claying is carried out in different ways. The oldest method, 
 and that from which it derived its name, claying, is by means of clay. A paste of 
 clay and water is spread upon the levelled base of the loaf covered with loose sugar ; 
 the water gradually drains from the clay, and forms with the loose sugar a saturated 
 solution that passes through the loaf displacing the impure syrup ; the pure sugar is 
 left undissolved, the sugar solution being a completely saturated one before it enters 
 the loaf itself. 
 
 The clay used must possess a certain capability of taking up water, and be neither 
 too fat nor too lean. In the former case it would retain the water too long and thus 
 protract the operation, whilst in the latter the water would drain away too rapidly. 
 Usually a white pipe clay is used, but the colour is quite immaterial, and a yellow or 
 blue clay answers as well. One thing is essential however; it should not contain any 
 soluble iron salts, pyrites, or soluble organic matters, as these would colour the sugar, 
 the pyrites would become partly oxidised during the claying, and the sugar would be 
 percolated by a syrup containing sulphuric acid and ferric sulphate. The raw clay is 
 first dried, the lumps broken up, suspended in water and washed. The mud is passed 
 through a fine sieve to remove sand ; it is then allowed to settle and the supernatant 
 water separated. The paste is again stirred up with fresh water several times, the 
 liquor being separated each time. The prepared paste should form a mud of tolerable 
 consistency ; the exact consistency is recognised by an empirical sign. A portion is 
 taken from the mass upon a trowel, and thrown back by a vigorous movement upon 
 the mass, into which it ought not to sink directly but form on it a slight prominence. 
 Enough of this paste is placed on the levelled base of the loaf to form a layer about 
 1 inch thick. As before mentioned, this paste parts with its water, which passes 
 through the sugar, and after a time the clay remains as an almost dry covering on the 
 sugar. Should the syrup not drain off from the sugar sufficiently rapidly, and the 
 clay consequently not remain moist sufficiently long, the operation can be hastened by 
 boring a larger hole in the apex of the loaf. Ordinarily for the medium-sized loaf 
 seven or eight days are required. According to the quality of the product desired the 
 claying is repeated two or three times, the dried layer of clay being removed and re- 
 placed by a fresh one. The syrups draining off are known as first, second, and third 
 syrups. With good sugars, as a rule, two layers are sufficient. In order to ascertain 
 this, some moulds are emptied by standing the loaves upon their broad bases, and 
 
SUGAR REFINING. 865 
 
 knocking them gently upon the floor ; the mould seiarates and it can be lifted 
 off. Should the loaf prove to be unequal in colour, the apex being still yellow, it is a 
 sign that it still retains syrup, and it is subjected to another claying. 
 
 About the fourth day after the claying, a knife is passed between the side of the 
 form and the clay in order to prevent adherence ; otherwise, since the clay shrinks in 
 drying, it would split and form an imperfect cover. Too sudden changes of tempera- 
 ture and especially draughts are to be avoided, as these also are likely to cause the 
 splitting of the clay. After the green syrup has drained off, the temperature of the 
 floor is moderated in order to dissolve as little sugar as possible. 
 
 After the claying is finished, the loaf is laid in a horizontal position and the clay 
 removed by a lathe, which cleans and levels the broad end of the loaf. At the same 
 time the loaf is loosened, but is still left in the mould while a little more syrup runs 
 away. When no more syrup can be removed, in order to distribute any remaining 
 equally through the loaf, it is reversed and allowed to stand on its base still 
 covered with the mould, for twenty-four hcurs. It is then restored to its original 
 position, and in two or three days again reversed. After twenty-four hours the 
 mould is lifted off, and the loaf is dried, first during a day in the open air, and then 
 in the drying oven, being previously covered with sheets of paper to protect it from 
 dusts and smuts. 
 
 Although clay, on account of the gradual and uniform way in which it gives up its 
 water, forms the best cover, it is not now used on account of the time required, and a 
 solution of pure sugar is substituted in its place. This is prepared by making a saturated 
 solution of sugar of the same quality as that required, at the temperature of the room. 
 For this the scrapings and broken loaves are mostly used, or the white colonial sugar. 
 When these latter are used the syrup is first passed through the charcoal filter, to 
 remove any impurities present. In the preparation of the syrup, the quality of the 
 product and the stage of its manufacture have to be considered. It would be wasteful 
 to use the finest syrup for an ordinary product ; as it would also be for a fine loaf 
 which had only been drained of the green syrup. For the first liquoring the syrup 
 from the second liquoring of another loaf is used, and for the second liquoring syrup 
 from a third is used, the fresh syrup being used for the third liquoring. Before pour- 
 ing on the clear syrup the base of the loaf is levelled, sufficient loose sugar being added 
 to make it eren. About a quart of syrup is used for each form ; after a short time this 
 is absorbed and the operation is repeated till the syrup drains away as clear as water. 
 
 For ordinary goods three liquorings are usually sufficient; for the finer five or six 
 are required, the successive liquorings being effected with increasingly clear syrup. 
 The last draining takes the longest time, five or six days being required. The further 
 treatment is then the same as when clay is used. 
 
 The methods differ essentially from each other in that when clay is used the 
 syrup is first formed during the operation by the solution of the loose sugar on the 
 base of the loaf, whilst by the other method the syrup is specially prepared. The 
 liquoring presents the advantage that the operation is finished in seven or eight days 
 whilst the claying requires about twenty-four days. Even the shorter method is now 
 abbreviated by the use of apparatus which removes the syrup from the sugar. 
 
 One method is to remove the syrup by centrifugal power. The apparatus 
 used for this purpose is shown in fig. 632. The revolving* drum is formed of two 
 strong iron cylinders (a b). These are perforated by 
 three rows of 12 holes each, the holes in the outer 
 cylinder being of a diameter to fit and support 
 the tops of the forms, and those in the inner cylinder 
 their broad ends. The outer of the two cylinders is 
 about -i feet in diameter, and the outer case (c c) cor- 
 respondingly wider. The drum being caused to make 
 about 400 revolutions per minute, the syrup is pro- 
 jected from the tops of the loaves, and runs off from 
 the outer case through the spout (D). The draining 
 of the syrup, which by the old method took five or 
 six days, is thus effected in an hour and a half. 
 Larger machines carry 72 moulds and work up 700 or 
 800 loaves daily. The centrifugal machine however 
 presents no advantage over the extractor apparatus ; it 
 requires more driving power, wears out more rapidly, and for an equal capability of 
 production is more expensive in its first cost. 
 
 The apparatus known as the extractor consists of a system of horizontal iron 
 pipes connected with each other and with a hermetically closed reservoir. Upon 
 these, at intervals corresponding with the breadth of the moulds, are set short vertical 
 pipes, each provided with a tap and supporting a email funnel coated with caoutchouc, 
 
866 SUGAR. 
 
 the angle of which corresponds with the shape of the mould. As soon as the syrup 
 ceases to flow off quickly, the moulds are placed with the apex in the funnel of the 
 apparatus, the corresponding tap is opened, and a vacuum set up in the common 
 reservoir and the connected piping by means of an air pump. The air then takes the 
 place of the syrup used ; the claying penetrating into the spaces between the crystals 
 and driving the syrup before it into the piping, and thence into the reservoir. This 
 method allows of a much more perfect freeing of the loaves from green syrup with less 
 claying ; a small quantity of syrup always remains in this case also, which is dispersed 
 equally by repeated reversals as before described. 
 
 The drying oven, or stove, is a space 12 to 16 feet wide, 20 to 28 feet long, and 
 of the same height as the sugar floor. It is surrounded by thick walls, in order to 
 retain the heat and prevent variations in the temperature. The heating is effected 
 by steam pipes, and the inlet of fresh air and the outlet of damp air is regulated by 
 means of openings in the floor and at the top. The frames for supporting the loaves 
 of sugar are so arranged as to admit the greatest possible number of loaves into the 
 oven at one time. Each stove usually accommodates from 2,000 to 4,000 loaves, and 
 the drying must be very carefully watched. At first the temperature is raised only 
 slightly above that of the room from which the loaves have been removed, and the 
 heat is afterwards gradually increased. Were the heat to be applied too rapidly, the 
 relatively large quantity of syrup still present would become saturated with sugar at 
 the higher temperature, and might melt the loaf. The stronger heat should be first 
 applied when the greater part of the water of the syrup has evaporated, and only a 
 little syrup is left. Finally, the temperature is raised to 50 or 60, to remove the 
 last traces of water from the sugar. 
 
 The temperature is regulated by the opening or closing of the steam cocks. The 
 condition of the sugar is ascertained by entering the oven, and inspecting the separate 
 loaves. The drying is completed when the loaves give a clear clang upon being 
 struck. During the drying, all sudden variations of temperature have to be avoided ; 
 the current of air caused by the rapid opening of a door might cause the splitting of 
 a loaf. For the same reason the cooling of the oven should 'be gradual, the door 
 being allowed to stand open at last, in order to allow the temperature of the oven to 
 become assimilated to that of the sugar floor. 
 
 The sugar now needs a little cleaning externally, spots of dirt being removed with 
 a scraper, and dust with a brush. The finished loaf is then encased in paper, and is 
 ready for the market. 
 
 AFTER PBODUCTS OF SUGAR EEFIKING. The different syrups of the refinery are 
 collectively still capable of crystallisation, and yield upon further boiling products 
 which, although not such fine sugar, are still almost white ; these are brought into 
 commerce under the names of crystallised and flour sugar. Not only the syrups are 
 thus worked up, but the ordinary raw sugar, the droppings and the sweepings of the 
 sugar floor, etc. These are placed with some added water in the clarifying pan, boiled 
 with inferior charcoal, and filtered. The boiling of old syrups must be carefully 
 conducted, as generally they are in slight fermentation ; they therefore contain car- 
 bonic dioxide, which is driven off by the heat, and may easily cause a frothing over of 
 the hot syrup. In such case the froth is broken by carefully spirting water into it. 
 The improved machinery yields syrups that are not so old ; the stronger fermentation 
 therefore does not take place, and the frothing over is avoided. 
 
 According to the^quality which it is desired to give to the after products, the fil- 
 tration is more or less carefully carried out. For this purpose the filters are used 
 through which the syrup has already passed in the first refining. The finer syrups 
 are boiled to granulation, the inferior are boiled blank. The moulds for the after 
 products are larger than for the refined ; the crystallisation takes a longer time, ar.d 
 the draining of the more impure syrup takes place more slowly. The sugar is again 
 well clayed, in order to have the loaf as equal in colour as possible. The loaves are 
 sometimes yellow or brown at the top. These tops are usually broken off, and the 
 whiter remaining portion broken up into large pieces or lumps. The more coloured 
 loaves are ground after drying, and the powder sold as flour sugar. With the better 
 secondary products, the artifice is frequently practised of boiling them with a little 
 ultramarine, by which the sugar acquires a faint blue colour that covers and is more 
 acceptable than its natural yellow tinge. 
 
 The last syrup collected in a large receptacle still yields a further crystallisa- 
 tion, which, after being submitted to the centrifugal action, is used as raw sugar, or 
 after liquoring in the centrifugal machine is mixed with flour sugar. 
 
 The molasses finally remaining in the refinery is always far superior to that of 
 the sugar manufactory. It can be directly consumed, or is sold for making sweet 
 pastry ; it is sometimes added to beer worts. 
 
 Description of a large Paris Befinery. Fig. 633 shows the general arrangements 
 
SUGAR REFINING. 
 
 867 
 
 for dissolving, raising, clarifying, and filtering the syrup. The pan (A) is used for 
 melting the sugar; it is 10 feet in diameter and 10 feet deep. It stands on the 
 ground floor of the building. The sloping bank (B) is used for the raising of the raw 
 sugar to the pan. Into the pan is first brought ,about 380 gallons of water, or a 
 corresponding quantity of thin syrup obtained by washing the filters. During the 
 throwing in of the sugar steam is let into the spiral to raise the temperature of the 
 liquor to 50, at the same time the stirrer (D) is set in motion by the driving wheel 
 
 FIG. 633. 
 
 (c). When about 5 tons of sugar have been thrown in and melted, if the syrup has a 
 slightly acid reaction enough lime is added to render it neutral or faintly alkaline, 
 and afterwards about 2 cwts. of ground animal charcoal and 12 gallons of blood. 
 After being thoroughly mixed by the stirrer, the valve (E) is opened, and the mixture 
 runs through the funnel, provided with a tap (F), into the monte-jus (H), until it is 
 three-fourths full. The tap (F) being then closed, steam under a pressure of five 
 atmospheres is admitted through the pipe (G). The pressure of the steam and of the 
 expansion of the air resulting from the heat drives the mixture through the pipes (i i) 
 into the clarifying pan (B), placed at a height of 50 feet. This is entirely closed and 
 
 3 K2 
 
868 
 
 SUGAR. 
 
 provided with a condenser. When it is three parts fillou with a mixture of syrup, 
 charcoal, and blood, the cock of a steam pipe (j), terminating in a rose in the interior 
 of the boiling space, and just over the surface of the mixture, is opesed, and steam 
 admitted until all the air ha= been expelled through the open air cock and the space 
 is completely filled ; the steam and air cocks are then closed. By the condensation of 
 the steam a partial vacuum is rapidly produced over the mixture, which is maintained 
 by the action of the condenser. In other factories the vacuum is produced by an 
 air pump ; steam is then admitted into the spiral, and the mixture heated to vigorous 
 ebullition, in order to effect the most intimate mixture possible of the ingredients. 
 The air cock is then opened, destroying the vacuum, and the temperature rapidly 
 raised to the boiling point under ordinary pressure, which with this concentrated 
 solution is 105. The temperature is taken with a thermometer, the bulb of which 
 is in the liquor, whilst the scale is outside the apparatus. A manometer shows the 
 internal pressure ; the progress in the boiler can be watched through lunettes (xxx), 
 which are lightej} by a lamp shining through a similar lunette on the opposite side. 
 As soon as the mixture boils, the valve (L) is opened by pressure upon the lever (K), 
 the fulcrum of which is at M ; the mixture then runs out into the preliminary filter 
 (N). This is arranged for filtration from outside to inside as described at p. 862. 
 The clarified syrup runs from thence through' a trough on to the charcoal filter. 
 
 The melting of the sugar in the pan (A) takes about 50 minutes, so that in twenty- 
 four hours about twenty-five operations can be effected, equal to about 130 tons of 
 sugar. Each preliminary filter is 7 feet 4 inches long, 5 feet 10 inches wide, and 4 
 feet 10 inches deep. Twelve of these filters stand side by side, and are xised 
 simultaneously. 
 
 The charcoal filter (o), 4 feet in diameter and about 36 feet in height, is provided 
 with a manhole (R), an emptying tap (Q), and au ascending pipe (p), 13 feet high. 
 Each filter contains nearly 300 bushels of animal charcoal, and 25 filters are used. 
 Every twenty-four hours four of these filters are emptied, so that nearly 1,200 bushels 
 j>f charcoal require to be revivified daily. 
 
 The filtered syrup, the whiteness of which is carefully watched, is conducted into 
 the reservoir of the vacuum apparatus. The boiling apparatus (A, fig. 634) is 
 arranged as shown in figs. 623 and 624, and described on p. 850. It is connected above 
 at B with a condenser and an air pump. The boiling is conducted so as to obtain 
 the crystals larger or smaller according to the product required. It is quickly ac- 
 complished, as the syrup comes into the apparatus with a previous concentration of 
 
 FIG. 634. 
 
 55 to 58 S. (sp. gr. 1-245). The apparatus is 10 feet in diameter and 16 feet 
 high, and its capacity corresponds to the syrupy mixture containing 13 tons of siigar. 
 As ten or twelve operations can be carried out daily, one apparatus is sufficient for 
 the entire quantity. The steam spirals of the apparatus have a heating surface of 
 about 320 square feet; the steam enters under a pressure of five atmospheres, or at a 
 temperature of about 150. 
 
 After sufficient concentration the emptying is effected by means of the valve (c), 
 
SUGAR REFINING. 869 
 
 which is opened inwards by pressure on the lever (D). The syrup then flows into 
 double-bottomed heaters (G), each of which has a diameter of 10 feet and a depth of 
 6 feet. The subsequent operation in the filling room and the sugar floor is carried 
 out as before described. 
 
 The apparatus for drawing off the syrup consists of three horizontal pipes, upon 
 which 1,500 moulds find room simultaneously; the drawing off of the syrup lasts 
 1 hours. The air pump of this apparatus is worked by a 70 horse power engine. 
 
 Each floor has its stove, and each stove holds in three rows, standing one above 
 another, 1,500 to 3,000 loaves weighing 22 Ibs. to 26 Ibs. each. The heating is effected 
 by waste steam passing through four pipes, 6 to 8 inches in diameter, arranged one 
 above another on one of the walls. 
 
 The boiling of the clayed syrups is carried out in a special vacuum apparatus 
 (A', fig. 634), 8 feet in diameter and about 17 feet high This is heated like Eobert's 
 apparatus, by a system of 2|-in. pipes, 40 inches long, fitted between the two bottoms, 
 and having a heating surface of nearly 1,000 square feet. The steam enters at the 
 side through a pipe (B), circulates between the pipes, and passes then with the con- 
 densation water into the steam chest. These syrups are boiled to thread proof, 
 consequently blank boiled; the granulation is carried out in coolers standing by the 
 side of the heater (G). 
 
 After the first granules form the crystallisation is finished in from twenty-four to 
 forty-eight hours, in a cast-iron vessel holding about 1 1 gallons. The syrup from 
 this product is boiled in the same apparatus, and then crystallised in an iron vessel 
 of upwards of 100 gallons capacity, the crystallisation lasting five or six days. The 
 third, fourth, and fifth crystallisations yield flour, which is swung in the centrifugal 
 apparatus and then liquored. The crystallisations take place in vessels of constantly 
 increasing size, respectively containing 200, 400, or 800 gallons ; the time, likewise, 
 required for the crystallisation continues to increase, the last crystallisation requiring 
 four to eight months, during which the vessel is kept at a temperature of 35 to 40. 
 The syrup of the last crystallisation constitutes molasses, which still contains 50 to 
 55 per cent, of crystallisable sugar. 
 
 The proceeds of the final crystallisations are well drained and methodically liquored 
 in the centrifugal apparatus, using purer syrup at each liquoring, and finally a jet of 
 steam is allowed to play upon the rotating mass in the drum from a finely perforated 
 pipe at a distance of 2 or 3 inches. The steam condenses in the sugar and forms 
 syrup which rapidly permeates the sugar loaf, carrying before it the impurer portion. 
 All the unclayed sugars undergo the same purification. Sugar that has been 
 already clayed, and is suitable, is treated once with steam, and then, after solution and 
 filtration thi'ough charcoal, used for clear liquor. Sugar, of which the grain is coo 
 fine to bring it into the centrifugal apparatus, is first granulated,, by melting, clarifying, 
 filtering, and allowing it to crystallise in large vessels ; it is then swung. It will be 
 seen that in this manufactory only sugars almost free from syrup are used ; the 
 inferior cane sugars are first recrystallised, in order to obtain the purest possible 
 material for the refinery. The advantage is that. the crystallisations are easily effected, 
 and the refinery syrups can be worked up almost to the last drop. For the claying 
 there are forty centrifugal apparatus 32 inches in diameter, each of which is filled 
 with about 100 Ibs. of syrup; the rotation required is about 1,200 revolutions per 
 minute. 
 
 Manufacture of Sugar Candy. The name of candy is applied to well-formed 
 crystals of sugars of different colours. The principal shades met with in commerce 
 are white, straw-coloured, and brown. The consumption of candy is comparatively 
 limited and localised in certain districts; thus East Friesland, Holland, and Belgium 
 consume large quantities of candy, whilst in other countries its use is almost un- 
 known'. The manufacture is carried on either in refineries or in special candy-boiling 
 houses. 
 
 In the preparation of white candy, the finer refined or quite white tropical sugars 
 are used ; clayed beet root sugar cannot be used for the purpose, as the large crystals 
 always contain some enclosed syrup, which would communicate to the candy an after- 
 taste and smell. This after-taste makes such candy perfectly unfit for the manu- 
 facture of sparkling wines, in which it finds its principal use, whilst the peculiar 
 aroma of the colonial sugar is a desideratum. Through the great purity of the raw 
 material the crystallisation may easily take place too rapidly, and instead of large 
 crystals, small indefinitely formed ones are obtained. According to Payen, this may 
 be avoided by adding to the syrup, when placed for crystallisation, 1 part in 1,000 of 
 tartaric acid. 
 
 The straw-coloured candy is prepared either from beet sugar, or from a mixture of 
 Havunnah and Indian sugars. The brown is especially prepared from Brazil sugar. 
 The first operations of the candy manufacture are similar to those of refining. 
 
870 
 
 SUGAR. 
 
 The sugar is melted in water in a pan (A, fig. 635), and clarified by the addition of 
 animal charcoal and albumin ; the syrup is then passed through the preliminary filter (B), 
 and is brought to the right degree of decolorisation in the charcoal filter (c). From 
 
 Fia. 635. 
 
 thence it flows through a tap (D) along a trough into the reservoir (E), from which it 
 is drawn through the pipe (F) into the vacuum pan (H). In the place of the vacuum 
 pan, there is still found in many candy factories copper swinging pans heated over an 
 open fire. When the vacuum pan is used, the evaporation is only carried on to slight 
 stringiness, and then the syrup is allowed to run off through the valve (i) into the 
 heater (j), where the boiling is finished. The evaporation is conducted differently 
 according to the quality of the syrup. With the most easily crystallising white candy, 
 it is carried farther than with the darker sorts. Generally the finish of the evapora- 
 tion is recognised by empirical tests, such as the bubbles, or the boiling mass is tested 
 with an areometer. With white candy the evaporation should be carried to a specific 
 gravity of 1*357, the straw-coloured to 1-363, and the brown to 1'369. 
 
 As soon as this stage is reached, the hot mass is removed by means of the filling 
 bowl (L, fig. 636), into the crystallising vessels or candy pots, which are erected in the 
 
 candy room, a strongly heated 
 space, similar to the sugar stoves 
 (figs. 636 and 637). The candy 
 pots are round copper bowls, 
 with flat bottoms and sloping 
 sides. In the sides are fine 
 holes, through which, before the 
 filling, fine threads are drawn 
 for the crystals to form upon. 
 After the introduction of the 
 threads, the holes are plastered 
 over with paper on the outside. 
 The candy rooms differ from the 
 sugar stores by being ventilated 
 as little ;is possible, consequently 
 no steam draught, is used. The 
 frames upon which the pots 
 stand are separated about 14 or 
 16 inches from each other. By 
 means of an externally heated 
 oven, or better still by steam 
 pipes, a temperature of 60 is 
 maintained for sevent-two to 
 
 Fia. 036. 
 
 hours 
 
 then 
 and 
 
 the 
 the 
 
 topped, 
 s kept closed for nine 
 
 FIG. 637. 
 
 seventy-six 
 heating is 
 room i 
 
 days. By the twelfth day the 
 temperature has sunk to 35 to 
 38. In all cases, sudden varia- 
 tions of temperature, shaking of 
 the vessels, or draughts, are 
 avoided, as causing a proper 
 tionate irregularity in the cry 
 
 
SACCHAEIMETRY. 871 
 
 stals. The temperature is observed upon a thermometer placed inside the room 
 against a window in the door. 
 
 In medium-sized vessels, the crystallisation proceeds far enough by the twelfth 
 day ; with small vessels and white syrup, the crystallisation is ended earlier ; with 
 the grosser and more impure syrups, especially if very large crystals are required, it 
 lasts longer. The crystallising vessel is then taken out, a hole broken in the crystal- 
 line crust that forms on the surface, and the greater part of the syrup poured off, 
 and the rest left to drain by placing the bowl in an inclined position over a trough. 
 The last adhering syrup is washed off with lukewarm water and this is again left to 
 drain over a trough. During the draining, the surface of the candy becomes dried, 
 and the threads are then cut from the outside and the candy lifted from the pots. 
 Lastly, it is dried at a temperature of 36 for twenty-four hours, and, either whole 
 or broken into pieces, is sent to market. 
 
 In the factory from which the foregoing description is taken there are six candy 
 rooms side by side. Each has three doors (F o H) placed one over another, corre- 
 sponding with as many stages fitted with frames. Opposite the doors, pullies (K K.') 
 are placed for the convenient raising of the filling bowl (i/) and the removal of 
 the crystallising pots (L). Each oven is 18^ feet high, 13 feet long, and 10 feet wide, 
 and contains ten stages one over another, each supporting thirty pots, so that the 
 entire room holds 300 pots. The pots are 24 inches in diameter and 13 inches deep, 
 and hold when full 110 Ibs. of syrup, which yields 55 Ibs. of candy. The emptying of 
 the oven is effected through doors at the back of the oven. 
 
 The syrup drained from candy is boiled for loaf sugar. 
 
 SACCHAEIMETRY. The determination of the amounts of sugar in various materials 
 is effected by one or other of the following methods : 
 
 1 . Chemical methods, based upon the known capability of some kinds of sugar to 
 reduce metallic oxides either to a lower state of oxidation or to the metallic state. 
 
 2. Areometric methods, based upon the observed relation between the specific 
 gravity of a sugar solution and the amount of sugar it contains. 
 
 3. Optical methods, based upon the power of cane sugar to turn the plane of 
 polarisation of a ray of light to a certain extent to the left hand. 
 
 Chemical Methods. Of these, the first to be mentioned is Fehling's. It is founded 
 on the fact that glucose, or the mixture of grape and fruit sugar obtained when a solu- 
 tion of cane sugar is boiled with a little hydrochloric, sulphuric, or oxalic acid, reduces 
 cupric oxide in alkaline solution to cuprous oxide. 
 
 Pure cane sugar has no such reducing action. Essentially, the method has been 
 described before on p. 804. 1 gram of the substance to be examined, a sample of cane 
 sugar, for instance, is dissolved in about 50 c.c. of water, in a flask holding exactly 
 100 c.c. up to a mark in the neck, a few drops of a concentrated solution of oxalic acid 
 are added, and the solution boiled in order to convert the cane sugar into the mixture 
 of two kinds of sugar known as inverted sugar. After the liquid is cool the free acid 
 is neutralised with sodium carbonate, the solution diluted to exactly 100 c.c., and 
 titrated according to the method described on p. 804. An amount of grape sugar is 
 thus found corresponding to the amount of cane sugar originally present. As the 
 quantities of grape sugar and cane sugar concerned in this reaction are in the proportion 
 of 360 to 342, the quantity of cane sugar corresponding to the grape sugar is easily 
 calculated. 
 
 The same method admits of the estimation of the two kinds of sugar cane sugar 
 and grape sugar when they occur together. The solution can be titrated at once, to 
 determine the amount of grape sugar present, and again after boiling with acid. The 
 difference between the amounts of grape sugar found in the two operations represents 
 the amount of cane sugar. 
 
 This method is not without disadvantage. It is especially difficult to determine 
 the exact point at which all the cupric oxide is reduced, and not to add sugar in ex- 
 cess. In proportion as the greater portion of the copper is reduced, the previously 
 intensely blue liquid loses its colour, until at last it is very doubtful whether it has 
 still a blue shade or not. In effecting the perfect reduction of the cupric oxide, it 
 becomes uncertain whether or not too much sugar has been added. In order to avoid 
 this uncertainty, an excess of copper solution is used, and the quantity of oxide reduced 
 by it is estimated. 60 c.c. of Fehling's solution of the strength previously given is 
 diluted with two or three times its volume of water, heated to boiling, and so much of 
 the solution to be examined added as shall contain not more than 0-250 gram of 
 sugar. As the quantity of copper solution would require 0*300 gram of sugar to 
 reduce it perfectly, an excess remains. After a short boiling the liquor is allowed to 
 stand ; the heavy intensely red coloured precipitate of cuprous oxide settles rapidly 
 to the bottom, and the clear blue supernatant liquor can be decanted off. Boiling 
 
872 SUGAR. 
 
 water is then poured over the precipitate, and it is again left to settle ; afterwards it 
 is thrown upon a small filter and washed as quickly as possible. The filter is then 
 dried, and the precipitate, after the combustion of the filter, is kept at a red heat for 
 some time in contact with air to convert the cuprous oxide into cupric oxide. To en- 
 sure that no trace of cuprous oxide remains, it is moistened with a drop of nitric acid, 
 carefully dried, and again brought to a red heat. From the weight of cupric oxide 
 found, the amount of sugar can then be calculated. 
 
 One molecule of cane sugar, or 342 parts by weight, after being changed into 
 inverted sugar, reduces ten molecules, or 794 parts by weight of cupric oxide; the 
 same quantity of cupric oxide is reduced by two molecules, or 360 parts by weight of 
 grape sugar. But as the cupric oxide found is produced from the reduced cuprous 
 oxide, the statement is : 
 
 x : 1 - 342 : 794 
 x I 1 = 360 : 794 
 
 the unit of weight of cupric oxide corresponding to : 
 0'4307 cane sugar, and 
 0*4534 grape sugar (inverted sugar). 
 
 A large number of estimations carried out by Scheibler with chemically pure 
 sugar showed that the sugar quantities calculated from the cupric oxide obtained 
 are a little too high, and that a more exact result is arrived at when the cupric oxide 
 obtained is multiplied bj : 
 
 0*43 for cane sugar, and by 
 0*45 for invert sugar. 
 
 Other methods have been recommended for the estimation of the precipitated 
 cuprous oxide. One is to dissolve the cuprous oxide in hydrochloric acid, with the 
 addition of sodium chloride, and to convert the cuprous chloride thus formed into 
 cupric chloride, with a titrated solution of potassium permanganate. Or the cuprous 
 chloride may be treated with ferric chloride, a corresponding quantity of ferric chloride 
 being converted into ferrous chloride ; the ferrous chloride can then be estimated with 
 potassium permanganate or chromate. These methods do not present any advantage 
 over the method above described. 
 
 Another easily worked method is based upon the fact that invert sugar completely 
 reduces mercury from an alkaline solution of mercuric cyanide ; according to the ob- 
 servations of K. Knapp, 100 parts of grape sugar being required to reduce 400 parts 
 of mercuric cyanide. A titrated solution is used consisting of 10 grams of pure cry- 
 stallised mercuric cyanide dissolved with 100 c.c. of solution of caustic soda (sp. gr. 
 1-145), to make 1,000 c.c. 40 c.c. of this liquor, representing O'lOO gram of grape 
 sugar, is boiled and then allowed to act upon the sugar solution until the whole of 
 the mercury is precipitated to the bottom of the vessel in small globules. A drop of 
 the boiling liquid placed on a fine filter paper, and held over a vessel containing con- 
 centrated ammonium sulphide, will undergo a brown coloration, owing to the forma- 
 tion of mercuric sulphide, so long as any mercuric cyanide remains unchanged ; but 
 the moistened spot remains colourless when mercury is no longer in solution. In 
 estimating by this method, the process followed is the same as described on p. 804. 
 A gram of sugar is dissolved in the case of cane sugar, after being inverted by the 
 addition of acid and heating and made up to 100 c.c. In the first estimation, the 
 point is approximately sought at which to stop the addition of sugar, and this is 
 determined exactly by a repetition. 
 
 The areometric method of determining the amount of sugar gives exact results 
 only with solutions of pure sugar, but when other substances are present they affect 
 the specific gravity of the liquid. Nevertheless this method is very generally used 
 for some purposes. The accompanying table gives the results of Gerlach, which corre- 
 spond very closely with those of other observers. 
 
 When the specific gravity has been taken the sugar contents can be easily ascer- 
 tained from this table. But, in order to avoid this trouble also, Brix and others have 
 constructed special areometers, or saccharometers, upon the scales of which the 
 percentage of sugar is directly indicated. Of the various saccharometers, that of 
 Brix is the most generally used. In using these instruments it must be borne in 
 miudthat, since all liquids become lighter by expansion, the same liquid, for instance, 
 will give a different saccharometer figure at a temperature of 10 to what it does at 
 15. It is therefore necessary to make all observations at the particular temperature 
 for which the instrument is constructed, usually 17'5 C. ; colder solutions have 
 therefore to be heated and warmer solutions cooled to this point. On the other hand, 
 the indications of the saccharometer can be reduced by means of the table to the cor- 
 responding specific gravities. 
 
 The saccharometer used in Great Britain is that constructed by Bate. The stem 
 bears a scale of divisions numbered downwards to 30. Each of these divisions indi- 
 cates a one-thousandth part of the specific gravity of water. 
 
SACCHABIMETBY. 
 
 873 
 
 Sugar. 
 Contents of 
 solution. 
 Weight 
 
 Specific gravity 
 at 17-5 
 
 Sugar. 
 Contents of 
 solution. 
 Weight 
 
 Specific gravity 
 at 17-5 
 
 Sugar. 
 Contents of 
 solution. 
 Weight 
 
 Specific gravity 
 at 17-5 
 
 per cent. 
 
 
 per cent. 
 
 
 per cent. 
 
 
 1 
 
 .1-003880 
 
 26 
 
 1-110646 
 
 51 
 
 1-238293 
 
 2 
 
 1-007788 
 
 27 
 
 1-115330 
 
 52 
 
 1-243877 
 
 3 
 
 1-011725 
 
 28 
 
 1-120048 
 
 53 
 
 1-249500 
 
 4 
 
 1-015691 
 
 29 
 
 1-124800 
 
 54 
 
 1-255161 
 
 5 
 
 0-019686 
 
 30 
 
 1-129586 
 
 55 
 
 1-260861 
 
 6 
 
 1-023710 
 
 31 
 
 1-134406 
 
 56 
 
 1-266600 
 
 7 
 
 1-027765 
 
 32 
 
 1-139261 
 
 57 
 
 1-272379 
 
 8 
 
 1-031848 
 
 33 
 
 1-144150 
 
 58 
 
 1-278197 
 
 9 
 
 1-035961 
 
 34 
 
 1-149073 
 
 59 
 
 1-284054 
 
 10 
 
 1-040104 
 
 35 
 
 1-154032 
 
 60 
 
 1-289952 
 
 11 
 
 1-044278 
 
 36 
 
 1-159026 
 
 61 
 
 1-295890 
 
 12 
 
 1-048482 
 
 37 
 
 1-164056 
 
 62 
 
 1-301868 
 
 13 
 
 1-052716 
 
 38 
 
 1-169121 
 
 63 
 
 1-307887 
 
 14 
 
 1-056982 
 
 39 
 
 1-174222 
 
 64 
 
 1-313946 
 
 15 
 
 1-061278 
 
 40 
 
 1-179358 
 
 65 
 
 1-320046 
 
 16 
 
 1-065606 
 
 41 
 
 1-184531 
 
 66 
 
 1-326188 
 
 17 
 
 1-069965 
 
 42 
 
 1-189740 
 
 67 
 
 1-332370 
 
 18 
 
 1-074356 
 
 43 
 
 1-194986 
 
 68 
 
 1-338594 
 
 19 
 
 1-078779 
 
 44 
 
 1-200269 
 
 69 
 
 1-344860 
 
 20 
 
 1-083234 
 
 45 
 
 1-205289 
 
 70 
 
 1-351168 
 
 21 
 
 087721 
 
 46 
 
 1-210945 
 
 71 
 
 1-357518 
 
 22 
 
 092240 
 
 47 
 
 1-216339 
 
 72 
 
 1-363910 
 
 23 
 
 096792 
 
 48 
 
 1-221771 
 
 73 
 
 1-370345 
 
 24 
 
 101377 
 
 49 
 
 1-227241 
 
 74 
 
 1-376822 
 
 25 
 
 105995 
 
 50 
 
 1-232748 
 
 75 
 
 1-383342 
 
 The optical method of ascertaining the amount of sugar in different solutions is 
 based upon the fact that a fixed quantity of sugar in solution rotates the rays of a 
 beam of polarised light exposed to its action to a known extent right or left. 
 
 The apparatus of Mitscherlich consists of two Nicol calc spar prisms, which in the 
 normal arrangement of the instrument are so placed opposite to one another that the 
 rays of light passing through the first prism are completely absorbed by the second. 
 If a liquid capable of deviating the plane of the beam of light be brought between 
 the two prisms, the absorption by light of the second prism no longer takes place; it 
 appears much more illuminated, and, according to the extent of the deviation, of a 
 red, yellow, green, blue, or violet colour. In order to measure the amount of devia- 
 tion, the second prism is rotated until the field of sight appears half blue and half 
 violet coloured, the distance being shown by a pointer connected with the second 
 prism and moving round a circle divided into 360 parts. 
 
 A column of liquid 200 mm. long, consisting of sugar solution containing exactly 
 30 grams of chemically pure cane sugar in 100 c.c., rotates the beam of polarised 
 light exactly 40. With columns of liquid of the same length, but containing an 
 unknown amount of sugar in solution, each degree which the second prism has to be 
 rotated indicates 0'75 gram of sugar in each 100 c.c. 
 
 Soleil's apparatus has the Nicol prisms the same as that of Mitscherlich, but 
 between them is inserted a further arrangement, which facilitates the observation 
 considerably. The ray of light polarised by its passage through the first prism passes 
 then through a plate of quartz cut perpendicularly to the axis of the crystal. It is 
 divided through the middle of the field of vision, so as to form a disc consisting of two 
 halves, one half rotating to the right and the other half to the left. With a thick- 
 ness of one-eighth of an inch, these plates appear when viewed through the second 
 Nicol prism of one colour, quite faint and between green and red. The least rotation 
 of the polarised ray at once produces a change of colour, towards green on the one 
 side and red on the other. The ray of light then passes through another quartz 
 plate cut perpendicularly to its axis, and then through two wedge-shaped quartz 
 plates, having both equal but opposite rotating powers like the plates above mentioned. 
 The two wedge-shaped plates with their settings are connected with mechanism by 
 
874 
 
 SUGAR. 
 
 which they can be pushed over one another so as to form one plate of variable thick- 
 ness. On the frame of one of these plates is a scale and on the other an index. The 
 zero of the scale is so -placed that it coincides with the index when the thickness of 
 the two wedges equal the thickness of the plate p". In this position the effects of 
 both are completely neutralised, and on looking through the second prism the above- 
 mentioned faint colour is again seen, whilst in any other position of the wedge-shaped 
 plates the red and green colours appear. The further divisions of the scale are so 
 made that at the point 100 the thickness of the plate formed by shifting the two 
 wedges is exactly 1 millimeter, or one twenty-fifth of an inch. Finally the ray of 
 light passes to the second prism. 
 
 The apparatus is represented by figs. 638 and 639. Between the tubular ends TT' 
 and T" T"' is a space to receive the tube containing the liquid to be examined. The 
 
 FIG. 638. 
 
 Nicol prism is placed at q and the quartz plates at p and p . The quartz wedges 
 (I and I') are represented on a larger scale in fig. 639. They are made to slide back- 
 wards and forwards by turning the milled head (B', fig. 638). 
 
 FIG. 639. 
 
 When a sugar solution is brought between the two quartz plates p and p", its 
 rotative power enhances the rotation of the polarised ray by the one half of the double 
 plate p', and weakens the action of the other half. Both halves thus acquire a 
 different colour ; the uniformity of colour is again restored when the wedge-shaped 
 quartz plates are shifted, until the thickness of the plate formed corresponds with the 
 rotative power of the interposed sugar solution. 
 
SACCHARIMETBY. 875 
 
 The rotating power of a quartz plate ^ in. or 1 mm. in thickness equals that of 
 a column of liquid 200 mm. long, containing 16*350 grams of chemically pure cane 
 sugar in each 100 c.c. If, therefore, a tube, exactly 200 mm. long, filled with sugar 
 solution of unknown strength, be placed between the quartz plates p' and p", and the 
 two wedge-shaped quartz plates be shifted until the uniform colour is again produced 
 on both sides, each degree of the scale will correspond to a sugar contents of 0'1635 
 gram in each 100 c.c. of the solution. 
 
 Ventzke's apparatus is a modification of Soleil's. It is so arranged that a layer of 
 sugar solution 200 mm. deep, of sp. gr. MOO, requires exactly 100 shifting of the 
 scale. Such a solution contains in 100 c.c. 26-048 grams of sugar ; each degree of the 
 scale corresponds therefore to 0*26048 gram of fine sugar in 100 c.c. of the solution. 
 
 In using the polarisation apparatus its correctness has first to be ascertained, as 
 regards the placing of the zero point, the thickness of the quartz wedges, the division 
 of the scale, and the length of the observation tube. In order to ensure a correct 
 placing of the zero point, an empty tube, or one filled with pure water, is placed 
 between the two prisms of Mitscherlich's apparatus, or between the two quartzes of a 
 Soleil or Ventzke's apparatus ; the light of a clear burning lamp is allowed to fall on 
 the apparatus, and an observation is made after the index has been placed exactly 
 upon the zero point. In Mitscherlich's apparatus the light should be absorbed and 
 the field of vision become darkened. In the other two forms of apparatus, upon 
 looking through the eye-piece in front of the second prism, a very small bright disk, 
 divided through the middle by a sharp streak, and uniformly coloured on both sides, 
 should be observed. In this case the apparatus is in order in respect to its zero 
 point ; but if the disk is not darkened in the Mitscherlich's apparatus the prism is 
 turned until complete obscuration takes place, and then the index is placed exactly 
 over the zero point. In the Soleil and Ventzke's apparatus the disk may appear 
 uniformly coloured, but of an intensely red or blue colour. This is induced by the 
 position of a third prism, not previously mentioned in this description, which in 
 Soleil's apparatus is situated immediately in front of the eyeglass, and in Ventzke's 
 before the first prism. This prism is therefore arranged so that the intense colour 
 disappears and the illuminated field is as free from colour as possible. If both halves 
 of the disk are then uniformly coloured the zero point is correct ; but if one half has 
 a green tint and the other a red tint the quartz wedges are to be shifted until perfect 
 uniformity of colour is produced. If the instrument is furnished with an arrange- 
 ment for the adjustment of the quartz wedges they should be arranged so that the 
 index coincides exactly with the zero point. If this cannot be done the correct point 
 is noted, and a corresponding correction is to be made after the observations. The 
 correct position of the zero point should be ascertained previous to each use of the 
 instrument. In order to test the apparatus further a solution of pure cane sugar is 
 prepared by dissolving 163'5 grams in water and diluting to exactly one litre. For this 
 purpose pure white sugar candy is finely powdered, and, after being washed with some ice- 
 cold water, drained, and washed with very strong alcohol, the powder is pressed between 
 filtering paper, dried in the air and afterwards at 100. When this solution is put 
 into a tube 200 mm. long, the quartz plates require to be shifted until the index 
 stands exactly over 100, in order to produce uniformity of colour. Of the same 
 solution, 10, 20, 30, 40, 50, 60, 70, 80, and 90 c.c. are mixed with 90, 80, 70, 60, 50, 40, 
 30, 20, and 10 c.c. of water respectively, and these solutions being observed in the ap- 
 paratus, always in a column 200 mm. long, in order to produce with them uniformity 
 of colour the index should require to stand at 10, 20, 30, etc. Mitscherlich's 
 apparatus is tested in a similar manner, but of course using a different amount of 
 sugar. If it should happen that the figures do not correspond, but that the differences 
 are proportional ; if, for instance, with the concentrated solution the index stands at 
 102 instead of at 100, when diluted with half water at 51, and when tenfold diluted 
 at 10 0< 2, this would be an indication that the quartz wedges are somewhat too thin, but 
 quite evenly ground, or that the tube is a little too long. A correction would then be 
 made that would always show the value of a single degree : 
 102 : 16-35 = 1 : x ; x = 0-1603. 
 
 Each degree of the scale would consequently in this case represent 0-1603 gram 
 in 100 c.c. of solution. If on the other hand the variation is not proportional, this 
 may be the result of the scale being incorrectly divided, or the quartz wedges not being 
 equally ground ; either of these conditions renders the instrument perfectly worthless. 
 
 Some modifications of the operation have to be made according as crystallised 
 sugar, intermediate products, or crude products have to be examined. 
 
 (a.) Crystallised sugar. In this case the cane sugar, moisture, ash, and 
 glucose have to be estimated. In most kinds of continental sugar there is either no 
 glucose, or it is present in such small traces as not to be worth notice, and this cir- 
 cumstance greatly simplifies the experiment. For the estimation of the amount of 
 
876 SUGAR. 
 
 sugar, when Soleil's apparatus is used, 16' 35 grams of a well -mixed sample are 
 thoroughly dissolved first in 50 c.c. of water, and then sufficient added to measure 
 exactly 100 c.c., and filtered. The filtration is absolutely necessary, as the smallest 
 quantity of suspended substance in the liquid renders the observation very difficult. 
 Kefined white crystallised cane sugar yields a colourless solution, but the raw sugar gives 
 a coloured liquid, the colour of which can in most cases be removed by the addition 
 of a few drops of basic lead acetate solution before the dilution. Many kinds of sugar 
 however that are thus decolorised do not give a clear solution and pass turbid through 
 the filter. Such solutions, according to Scheibler, can be cleared by the addition of a 
 small quantity of aluminum hydrate suspended in water. It is necessary that the 
 solution should be quite clear after filtration. The observation tube, 200 mm. long, 
 carefully purified and dried, is then filled with the solution, and the observation made 
 as previously described. The estimation of sugar in molasses is made in a similar way, 
 but the precipitation of the foreign matters in it requires a larger addition of lead acetate. 
 
 The amount of moisture is determined by drying a weighed quantity of the sugar 
 in a small shallow dish until it no longer loses weight. The amount of ash is ascer- 
 tained by incineration, but the sugar carbon does not burn readily, and is so enveloped 
 in the fused salts, that either some of the salt is driven off by the heat or some of the 
 carbon remains unburnt. This difficulty is overcome by a method introduced by 
 Scheibler. 1 to 2 grams of the sugar are weighed in a small shallow dish, moistened 
 with rather concentrated sulphuric acid, and at first carefully heated. After the 
 greater part of the organic matter has been destroyed the dish is placed in a small 
 muffle, formed of two sheets of platinum bent together, and heated to redness, when 
 the remainder of the carbon is easily burnt. The white ash consists of sulphates, and 
 the half of its weight is taken as the amount of ash. This method is allowable with 
 crystallised sugar, where the amount of ash is always small ; in the examination of 
 molasses, beet juice, etc., another method has to be adopted. 
 
 When glucose and cane sugar are associated together, the polarisation apparatus 
 can be used, but the chemical method is then preferable. A weighed quantity dissolved 
 in water is mixed with cnpric oxide solution, and heated for ten minutes in a water 
 bath at a temperature of 75 ; all the glucose is thus decomposed. A second quantity 
 is treated as described on p. 871. The first experiment gives the quantity of glucose 
 present ; the second the quantity of inverted sugar originating from the cane sugar 
 plus the glucose. The difference represents the amount of inverted sugar formed from 
 the cane sugar present. 
 
 (ft.) Molasses. In erder to estimate the amount of water present in molassss, 
 it is advisable to distribute it over a large surface by mixing it with some anhydrous 
 substance, because otherwise, in drying, it forms a dense layer from which the complete 
 removal of the water is very difficult. A crucible is half filled with sand and heated to 
 redness ; then allowed to cool completely, and weighed. A cavity is made in the 
 sand with a platinum spoon, into which a small quantity of molasses is poured, and 
 it is again weighed. Upon heating, the molasses is liquefied and permeates the sand, 
 and can then be easily dried at a temperature of 100. 
 
 The sugar is estimated as before described. On account of the large quantity of 
 foreign constituents a considerable precipitate is produced on the addition of lead 
 acetate. As the volume of this precipitate would influence the volume of the liquid 
 to be examined it is better to dilute the solution to a greater degree. 1 6 grams of 
 molasses are dissolved in about 200 c.c. of water in a flask of 250 c.c. capacity ; lead 
 acetate is then added and the liquor brought to the correct volume. If the filtered 
 solution is not sufficiently colourless for polarisation, a second sample is prepared with 
 a larger addition of lead acetate. When this does not give a satisfactory result the 
 liquid may be shaken with some animal charcoal previously dried at ] 00. But the 
 use of the charcoal is to be avoided as much as possible, because it absorbs a portion 
 of the sugar as well as the colouring matters. 
 
 As molasses may contain, besides sugar, other bodies influencing polarisation, the 
 estimation should be controlled by a second experiment made according to the chemical 
 method. In estimating the ash about 10 grams of molasses are heated, at first very 
 gently, in a platinum dish of at least 200 grams capacity. Gradually, as it ceases to 
 froth strongly, the heat is increased until finally the entire mass is carbonised and no 
 more empyreumatic vapours are given off. The voluminous charcoal is broken up, 
 boiled with water, thrown upon a filter, and washed until the washings cease to give 
 an alkaline reaction. The charcoal is then dried, and with the filter incinerated at a 
 bright red heat. The aqueous solution is poured over the resulting white ash, eva- 
 porated to dryness, and heated until the whole of the water is driven off. If the 
 charcoal were incinerated without lixiviation, the potash and sodium salts might be 
 volatilised at the high temperature required, and a considerable proportion of the ash 
 constituents lost ; moreover the ash would not be obtained free from carbon. 
 
SACCHARIMETRY. 877 
 
 (c.) Slime from the Filter Presses. In order to control the operations of 
 the sugar manufacture it is necessary that the slime from the filter presses should be 
 examined periodically. Several cakes produced on different days are taken and brayed 
 in a porcelain mortar. About 150 grams are placed in a flask, with about 500 c.c. o* 
 boiling water, and carbonic acid passed into the liquor, kept hot, until all the lime is 
 converted into carbonate. This treatment with carbonic acid has for its object the de- 
 composition of the insoluble sugar lime. The liquor is filtered into a capacious flask, 
 and the precipitate well washed with hot water. The flask is then connected with the 
 exhaust pipe of an air pump and the atmospheric pressure being reduced the liquid 
 can be rapidly evaporated in a water bath without causing the decomposition of the 
 sugar. When the volume is reduced to about 50 c.c., the liquor is poured into a bottle 
 of 100 c.c. capacity, the flask washed with a small quantity of water several times, 
 and the solution cleared with lead acetate. It is then made up to 100 c.c., filtered, 
 and examined in the polarisation apparatus. 
 
 (d.) Pressings, and Maceration and Diffusion Besidues. Care being 
 taken to obtain an average sample, the substance is divided as finely as possible, the 
 pressings by tearing apart, and the diffusion residues by cutting. A quantity of not 
 less than 100 grams is taken, treated with cold water, and lime water or milk of lime 
 added until it has a weak alkaline reaction. After two hours, the solution is poured 
 off and replaced by fresh water. After this has also been poured off, the insoluble 
 portion is collected on a piece of linen and well pressed. The united liquors are 
 filtered through paper and evaporated as above ; the residue from the evaporation is 
 saturated with carbonic acid at boiling temperature, filtered to separate carbonate of 
 lime ; lead acetate is added and the clear liquor polarised. 
 
 (<?.) Sugar Beets. The beets are converted into a paste with an ordinary hand 
 rasper, the paste enclosed in a linen bag and pressed in a hand press. The residue is 
 taken out and again pressed as sharply as possible, as the juice from the different 
 degrees of pressure has not the same composition ; a juice richer in sugar flowing 
 from the slight pressure than from the stronger. Usually only the sugar and non- 
 saccharine matters in the juice are estimated. Immediately after pressing, the juice 
 is tested at the normal temperature with a Brix's saccharometer ; the saccharometer 
 should sink to 16-6. If the saccharometer does not indicate higher than 17, 100 c.c. 
 of the juice are removed with a pipette and mixed with 10 c.c. basic lead acetate solution. 
 "With a higher indication the 100 c.c. of juice is diluted with 100 c.c. of water, and 
 20 c.c. of lead solution added. After well shaking it is filtered through paper and 
 the clear liquor is placed in the polarisation apparatus. It has to be borne in mind 
 that the volume of juice has been increased one-tenth by the acetate of lead solution, 
 and a correction must be made accordingly. Supposing a juice undiluted with water 
 to give a polarisation of 82'5, in order to find the quantity of sugar in the juice un- 
 mixed with lead acetate, the observation has to be increased one-tenth. The polarisa- 
 tion corresponding to the amount of sugar would therefore be 82'5 + 8'25 = 90'75. 
 As in a correctly adjusted instrument each degree of polarisation shows a sugar con- 
 tents of 0-1635 gram in each 100 c.c., such a juice would contain 90'75 x 0'1635 = 
 14'84 grams of sugar in 100 c.c. When the juice has been diluted with 100 c.c. of 
 water, and 20 c.c. of lead acetate solution, the calculation must be made in the same 
 way, but doubling either the final result or the degree of polarisation indicated. 
 
 In calculating the weight per cent, the method used is as follows. The saccharo- 
 meter indication in the previous example was 16'6. Keference to the table on p. 873 
 shows that this corresponds with a specific gravity of 1'068, 100 c.c. of the juice 
 weigh 106'8 grams and contain 14' 84 grams of sugar. Consequently it contains 
 
 14-84 x lOO^jg.Q p er centi by weight of sugar. The difference between the original 
 
 106'8 
 
 saccharometer indication and the amount of sugar represents the amount of non- 
 saccharine matters ; in this case it is 16'6 13'9 = 2'7 per cent. The sugar quotient 
 
 1 q.q 
 
 of this juice (see p. 820) would be i = 837. 
 
 lo'o 
 
 It has been already stated that this difference only gives the amount of non- 
 saccharine matter approximately, but sufficiently near for practical purposes. For an 
 exact estimation the amount of dry substance must be determined. For this pur- 
 pose a weighed quantity of juice (say 100 grams) is diluted with an equal weight of 
 water, and filtered to remove suspended matter, the thick juice being difficult to filter 
 About 20 c.c. are weighed off and evaporated to dryness in a water bath, and the 
 residue afterwards dried at 100 until the weight remains constant. The best way 
 is to stand the dish in a larger one filled with sand heated to 100, and place them 
 both under the bell of an air pump. The percentage weight of dried substance found 
 has to be doubled in consequence of the dilution. The ash is estimated by the method 
 described for molasses, a larger quantity of juice being taken. 
 
878 
 
 SUGAB. 
 
 The amount of albuminous substances is determined by evaporating a weighed 
 quantity of the juice to dryness, mixing soda lime with the dry residue, igniting in a 
 combustion tube, and collecting the ammonia formed in titrated sulphuric acid. As 
 albuminous substances contain on the average 16 per cent, of nitrogen, the quantity 
 of nitrogen found is multiplied by 6 - 5, in order to reduce it to albumin. It being very 
 difficult to remove the dried juice from the sides of the vessel, very small thin glass 
 dishes are used for the evaporation ; they have a capacity of 25 c.c. and weigh scarcely 
 0'5 gram, and are pounded up with the dried residue in a mortar, in order to mix the 
 whole with soda lime without any loss. 
 
 KEVIVIFICATION OF THE CHARCOAL. The kilns used for the ignition of the animal 
 charcoal, after being submitted to the treatment described on p. 844, are of various con- 
 struction. A continuously acting calcining kiln is represented by figs. 640 and 641. In 
 the centre of the brickwork (H H) is a fireplace (B), covered in by an arch, in which 
 
 FIG. 640. 
 
 are fixed the square chambers (D and c' D'), the upper ends of which communicate 
 with a shallow tray of sheet iron (i j), extending over the whole area of the kiln. The 
 
 Fio. 641. 
 
 flame passes from the furnace through eighteen flues, constructed, in the intervals 
 between the calcining tubes, into an open space under the sheet-iron tray. The 
 lower ends of the calcining tubes are connected with bent tubes, each containing a 
 siding damper (/), and with sheet-iron boxes (A A' B B') sufficiently large to receive the 
 whole contents of the ignition cylinders. The charcoal is spread 'out upon the drying 
 surface (u), and when sufficiently dried is fed into the tubes (c D). The heat is then 
 -aised to redness, and when the tubes have been maintained at this temperature for 
 
CHARCOAL KILKS. 
 
 879 
 
 about half an hour the dampers (/) are drawn out, and the calcined charcoal is 
 allowed to fall into the boxes (A A' and B B'). The dampers are then closed, the tubes 
 again filled, and the operation is repeated every half hour. 
 
 A calcining furnace, introduced by Gail, is represented by figs. 642 to 645. On 
 each side of the fireplace (G) are series of flues, through which the hot gas passes from 
 
 FIG. 643. 
 
 FIG. 644. 
 
 the fire to the calcining tubes (I I), and then escapes through the flues (L L), under the 
 drying surface (c c), into the chimney (o). Each of 
 the calcining tubes consists of three pieces communi- 
 cating at one end with the drying floor (c), as shown 
 in the large drawing (fig. 644). The ten tubes on each 
 side of the fireplace can be separated by two dampers 
 (p q) into two parts, the lower of which is about one- 
 fifth of the total capacity of the tubes. When the cal- 
 cining process is commenced the tubes are made red 
 hot, and the sliding damper (p) being closed by means 
 of the lever (I), the upper parts of the tubes are about 
 half or two-thirds filled with charcoal that has been 
 partially ignited, and then filled up to the top with 
 merely dried charcoal, which is also heaped up 
 above the opening of the tubes upon the drying 
 floor, so that on discharging the charcoal from the 
 lower parts of the tubes the heaps above sink into 
 them. After the lapse of half an hour the sliding 
 damper (q) is closed by means of the lever (I'), and 
 the damper (p) is opened to allow the space 
 between p and g to become filled with ignited char- 
 coal. The damper (p) is again closed, and after the 
 lapse of half an hour the damper (q) is opened so as to allow the cooled charcoal to 
 fall into the brick chamber below. The damper (q) is then again closed, more 
 
 FIG. 645. 
 
880 
 
 SUGAR. 
 
 ignited charcoal is let down by opening the damper (p), this being repeated ever* 
 half hour. The horizontal section of the calcining tubes is oval, measuring about 10 
 inches by 3 inches, and the distance between the two dampers is about 16 inches. 
 
 Another common form of charcoal 
 kiln is represented in vertical longi- 
 tudinal section by fig. 646. The fire- 
 place (A), with its grate (r) and fire 
 door (h\ is so placed that the hot gases 
 from the fire pass through the perforated 
 brickwork (//) into the chamber (D) 
 where the calcining cylinders (c c) are 
 fixed. These cylinders are most strongly 
 heated at the upper portion of the 
 lower half, and are not at all heated at 
 the lower ends, but are at this part 
 freely exposed to the air so as to be- 
 come cooled. The hot gas from the fire 
 escapes under the drying floor (F) 
 through the flue (z) into the chimney. 
 The charcoal is fed into the cylinders 
 at their upper ends, where it is gra 
 dually heated until it reaches that 
 portion of the cylinders where it is 
 fully ignited. About every twenty 
 minutes the dampers (s s) by which the 
 lower ends of the tubes are closed are 
 FIG. 646. opened so as to allow about one-fourth 
 
 of the contents of the cylinders to fall 
 
 into sheet-iron boxes placed beneath, while a further equivalent quantity is fed 
 into the cylinders at their upper ends. In this way the charcoal is gradually heated 
 up to a sufficiently high temperature and then cooled in the lower ends of the cylin- 
 ders before being discharged. 
 
ALCOHOL. 
 
 The term alcohol was formerly restricted to a substance which is the characteristic 
 constituent of wine, beer, and similar fermented beverages ; it is now, however, employed 
 not only in this special sense but also as a generic designation of a number of sub- 
 stances analogous to that existing in wine, etc. These substances have all a similar 
 constitution, and may be regarded as the hydrates of organic radicles resembling 
 metals in their chemical relations, or as derivations of hydrocarbons by the replace- 
 ment of one or more hydrogen atoms by hydroxyl. Thus, for instance, the alcohol of 
 wine may be represented by the formulae : 
 
 or C 2 H 5 (OH). 
 
 Wine alcohol is ordinarily the product of an alteration of sugar under the in- 
 fluence of organised bodies of a low order, called yeast, the change being one 
 instance of that class of phenomena known under the name of fermentation, and 
 the formation of alcohol from sugar takes place according to the following equation : 
 
 C 8 H 12 6 -> 2C0 2 + 20^0. 
 
 Fermentation is a chemical change which takes place in certain organic substances 
 when they are in contact with other nitrogenous organic or organised bodies, called 
 ferments, and by some it is considered that this change is effected without these 
 latter taking any material part in the process. Hence fermentation has been 
 considered to belong to those processes which depend upon so-called contact action. 
 
 As to the way in which the yeast ferment acts upon sugar a number of hypotheses 
 have been set up. This much is certain, that the yeast ferment and the sugar must 
 come into contact in order to secure fermentation. On the other hand, it is uncertain 
 whether the products of fermentation are so far due to the vital action of the ferment 
 cells that the sugar is taken up as food into their organism, and there decomposed 
 into alcohol and carbonic acid, etc., or whether the ferment cells contain a substance 
 capable of decomposing sugar, with which the sugar solution comes into contact, possibly 
 by diffusion through the cell membranes. This last hypothesis seems, according to the 
 most recent researches on the subject, to be the true one. 
 
 The decomposition in question may be an analytical process, as is the case in alco- 
 holic fermentation (where sugar breaks up into alcohol and carbonic acid) or in the lactic 
 acid fermentation (where sugar breaks up into two molecules of lactic acid). The process 
 may also be synthetical, as in the formation of sugar from starch by means of diastase ; 
 finally analysis and synthesis may go on simultaneously, as in the acetic fermentation 
 in which hydrogen is liberated and oxygen absorbed. 
 
 As regards the nature of the substances exciting fermentation two kinds may be 
 distinguished. 
 
 1. Where the ferment is a nitrogenous organic (non-organised) substance, as for 
 instance protein substances in a state of decomposition, saliva, etc. 
 
 2. Where the ferment is an organised body, some low vegetable organism or in- 
 fusorium, as in the alcoholic, the lactic, and butyric fermentation, etc. 
 
 It is probable the way in which the two kinds of ferments act is identical, and 
 that the ferments of the second class, by virtue of their vitality, produce a substance of 
 the nature of the first class, which then itself causes the phenomenon of fermentation 
 either with or without the ferment itself. 
 
 In each class of ferments may be further distinguished a number of individual 
 ferments, which differ from one another in their individual nature as well as in their 
 manner of action. Thus diastase converts starch into sugar, decaying cheese converts 
 milk sugar into lactic acid, the protein substances convert sugar into mannite, yeast 
 converts sugar into alcohol and carbonic acid, and mother of vinegar converts alcohol 
 into acetic acid. 
 
 Yeast belongs to the organised ferments ; it is a kind of fungus consisting of a 
 number of cells linked together like a chain, and differing in form and size. The 
 
 3L 
 
882 
 
 ALCOHOL. 
 
 individual cells are round or oval, their diameter varies between 0-025 and O'Ol 
 millimetres. 
 
 The composition of yeast is shown by the following analyses : 
 
 
 Schlos 
 
 sberger 
 
 
 r^r 
 
 
 50'1 
 
 47'9 
 
 45'5 
 
 52-5 
 
 Hydrogen 
 Nitrogen 
 
 6-5 
 11-18 
 
 6-2 
 9-8 
 
 6-2 
 9-4 
 
 7'2 
 9-7 
 
 Oxygen and sulphur . 
 
 31-6 
 
 35-9 
 
 38-9 
 
 30-6 
 
 The ferment cells break up into the characteristic cell substance and the cell con- 
 tents. The cell substance has the composition of ordinary cellulose ; the cell con- 
 tents consist of a portion which can be dissolved out by means of acetic acid or dilute 
 solution of potash, leaving the cell substance as a residue. Upon the neutralisation 
 of the solvent, the dissolved substance is precipitated, with the loss however of its 
 sulphur. Its composition appears from the following analyses by 
 
 Carbon 
 Hydrogen 
 
 Nitrogen . .... ... 
 Oxygen . .- J '\\ , r ' 
 
 From Acetic Acid 
 Mulder 
 
 From Potash Solution 
 Schlossberger 
 
 53-3 
 7-0 
 16-0 
 237 
 
 55-0 
 
 13-9 
 23-6 
 
 The ash of yeast consists essentially of phosphoric acid and potash, with small 
 quantities of magnesia and lime. It amounts to about 7 7 per cent, of the -weight of 
 the yeast. 
 
 Formation of Yeast. The formation of yeast is assumed to depend upon the 
 presence of germs and spores suspended in the air, which begin to develop when they 
 fall into liquids suitable in containing the nutriment necessary to their propagation. 
 
 The presence in the air of germs necessary for bringing about the propagation of 
 yeast has been inferred by the following experiment by M. Pasteur: 
 
 A solution of sugar containing the necessary food for yeast germs is boiled in a 
 glass flask long enough to secure the destruction of all germs and spores previously 
 contained in the liquid, as well as to drive out the air in the neck of the flask and 
 replace it by steam, whereupon the neck of the flask is sealed. A flask thus prepared 
 may be left for weeks at the temperature (30 to 33) most suitable for the propaga- 
 tion of yeast without any formation of ferment or fermentation ; on the other hand, 
 both formation of ferment and fermentation begin directly the flask is opened and ex- 
 posed to the air, especially when a little dust is thrown into the flask. 
 
 The food of the yeast plant consists of carbonaceous and nitrogenous substances, 
 as well as of those inorganic substances found in the ash of yeast, which are chiefly 
 potash and phosphoric acid. Sugar serves as the carbonaceous constituent ; the nitro- 
 genous and inorganic substances are contained in the juice of most plants or extracts 
 prepared from them, the first in the form of albuminoids, the latter in the form of 
 various salts. 
 
 A liquid capable of supporting yeast vegetation may be artificial!}' prepared by 
 dissolving sugar and ammonium tartrate in water, adding a small quantity of 
 potassium carbonate and glacial phosphoric acid, then saturating the liquid with 
 carbonic acid, and finally adding a very small quantity of calcium carbonate and of 
 magnesium carbonate. 
 
 The growth of yeast is stopped by the addition of strong mineral acids or large 
 quantities of organic acids, also by salt, sulphur, and a number of other reagents ; 
 small quantities of organic acids are however not prejudicial. 
 
 All kinds of sugar are not capable of undergoing alcoholic fermentation. The 
 kinds of sugar usually employed in carrying on fermentation industrially, namely 
 grape and fruit sugar, are capable of direct fermentation. On the other hand, cane 
 sugar and milk sugar have not the power of direct fermentation, but may easily be 
 converted into fermentable sugar. This transformation may be effected either by 
 treatment with acids or by prolonged contact with large quantities of yeast. The 
 conversion of cane sugar into fermentable sugar is designated inversion, and is a 
 change analogous to fermentation. 
 
 The process of fermentation is unequally rapid in proportion to tho quantity of 
 
FERMENTATION. 883 
 
 sugar in solution, the most favourable proportion of sugar in a solution being 12 per 
 cent. ; more sugar hinders the fermentation. 
 
 Not only an excess of sugar but an excess of alcohol also retards the progress of 
 fermentation, so that in a solution containing much sugar, after a certain quantity of 
 alcohol is formed by fermentation, the remaining sugar ceases to ferment, because the 
 further fermentation is hindered by the alcohol. 
 
 The relative proportions of sugar and yeast also influence the duration of the 
 fermentation. In practice, in order to secure quick fermentation, the proportions used 
 are 5 parts of sugar to 1 of yeast, although the same quantity of yeast is capable of 
 fermenting a much greater quantity of sugar. 
 
 The phenomena of fermentation also differ with the temperatures at which it is 
 allowed to take place. Up to a certain point the rapidity of the fermentation increases 
 with the temperature, but when a temperature of 33 is reached, the fermentation 
 becomes slower, and a further rise stops it altogether. 
 
 When fermentation is conducted at a low temperature the yeast employed remains 
 at the bottom of the fermenting liquor, and this fermentation is known as sedimentary 
 fermentation. This kind is considerably employed industrially ; the most suitable 
 temperature for conducting it being between 5 and 10. 9 
 
 The other kind of fermentation, which is conducted at a temperature of between 
 10 and 24, is more rapid, and is known as surface fermentation, owing to the fact 
 that the yeast cells rise to the surface in consequence of the strong development of 
 carbonic acid. 
 
 The products of the fermentation of sugar with yeast alcoholic fermentation are 
 chiefly alcohol and carbonic acid. 
 
 About 5-6 per cent, of the sugar is, however, decomposed into glycerin, succinic 
 acid, and carbonic acid, yielding at the same time material for the formation of the 
 yeast cells. The quantities in which the latter substances are produced are, according 
 to Pasteur, as follow : 
 
 Succinic acid . . ' . . . . . 0'6-0*7 per cent. 
 
 Glycerin 3'2-3'6 
 
 Carbonic acid 0'6-0'7 ,, 
 
 Cellulose and fatty substances .... 1-2-1-5 
 
 Pressed Yeast. For purposes of storing, yeast is deprived of the greater part of 
 its water and other impurities, by a process of washing and pressing, the product 
 being known as pressed yeast. Surface yeast is most suited for this purpose. 
 
 The yeast is pressed through linen or a hair sieve, so as to remove particles of 
 hops and other impurities ; the filtered liquid is then allowed to stand whilst the yeast 
 settles to the bottom. The supernatant liquid is then decanted off; the yeast treated 
 with a fresh quantity of cold water, and the whole thoroughly stirred up. These 
 operations of decanting and washing are repeated until the wash water ceases to give 
 an acid reaction. The thoroughly washed yeast is finally mixed with 15 to 30 per 
 cent, its weight of starch, filled into sacks and pressed. This pressed yeast comes 
 into the market in lumps of a pound in weight, whence it is sometimes called pound 
 yeast. 
 
 Artificial Yeast. The consumption of yeast is so great that frequently it is manu- 
 factured by itself. For this purpose thin mash, or still better, clear wort, is employed 
 to which, in order to secure the formation of yeast cells, as much as possible of the 
 nitrogenous compound of malt is added; a small quantity of sulphuric acid about 
 -1 per cent, of the weight of groats is employed previously diluted with water, 
 being added to the solution of gluten. Artificial yeast is much used in distilleries ; a 
 more detailed account of its preparation will therefore be given under that head. 
 
 In what has preceded, the results attending the vinous fermentation have been 
 detailed, but fermentation is a process in nowise limited to carbohydrates of the 
 class of grape sugar, neither is it dependent upon one particular ferment. For 
 instance, ordinary yeast does not consist only of the cells of Torula cerevisia, but also 
 contains some of Penicillium glaucum ; these last may be separated in some measure 
 by shaking up yeast with water and filtering ; the Torula cells, being the larger, are 
 retained by the filter, and when added to a sugar solution, they cause the alcoholic fer- 
 mentation, but tie filtrate containing the cells of Penicillium, if added to a sugar solution, 
 causes the lactic fermentation to set in. 
 
 Again, an aqueous extract of yeast rapidly converts cane sugar into dextrose and 
 laevulose, but cannot further influence it. 
 
 This last process is suggestive of that form of fermentation which i s supposed by Bernard 
 and others to cause the transformation of liver glycogen or dextrine into glucose in itself 
 merely a process of hydration. But Pasteur and his disciples consider this act due to 
 the influence of a special ferment in the bl,ood, which, while it causes this change, 
 reproduces itself from a part of the material influenced by it. 
 
884 ALCOHOL. 
 
 Not so, however, did Liebig regard such processes of fermentation ; it was suffici- 
 ent for him that the conditions necessary for starch to take up a molecule of water 
 were present ; he did not perceive the necessity of believing the result due to a form 
 of life, all that was required being the presence, and the contact of a substance itself in 
 process of change. Thus he compared such processes to the decomposition of argen- 
 tic oxide caused by its contact with peroxide of hydrogen. The latter body being 
 unstable and slowly undergoing .decomposition, influences the oxide of silver in a simi- 
 lar manner, and the contact action is therefore expressed by the equation H 2 2 + Ag.,0 
 
 Here it is that Pasteur and Liebig differed. Pasteur regards all processes of fer- 
 mentation as essentially ' correlative phenomena of a vital act ; beginning and ending 
 with it ; ' so that wherever there is fermentation, there is also organisation, develop- 
 ment, and multiplication of the globules of the living ferment. Liebig never ad- 
 mitted the necessity of the living element. But after all, the difference between these two 
 views is but slight ; in both the direct cause is something in change ; whether that 
 change be essentially connected with the function of life possessed by cells and spores 
 is a matter not even yet decided. 
 
 4 It is not possible nor desirable here to enter into a further consideration of the life 
 processes of yeast. It is sufficient to remember that in a large measiire the conditions 
 upon which the life, health, and disease of cells depend have been established, and it 
 has even been demonstrated by Pasteur that yeast, like higher forms of life, breathes. 
 
 There are many other media in which yeast excites a process of decomposition, 
 but, so far as observed, malic acid is the only plant acid which admits of the multi- 
 plication of the yeast cell. When a mixture of calcic malate with water and yeast is 
 set aside in a warm place, the acid is split up into succinic, acetic, and carbonic acid 
 and water, thus : 
 
 3C 4 H 6 5 = 2C 4 H 6 4 + C 2 H 4 2 + 2C0 2 + H 2 0. 
 
 If the temperature rises beyond a certain point, hydrogen is evolved and butyric 
 acid is formed. Again, if a solution of cane sugar or milk sugar be mixed with stale 
 cheese or milk, and chalk, and kept at 30-35, the sugar is gradually converted into 
 lactic acid, and the process is termed the lactic fermentation, C 6 H 12 6 = 2C 3 H 6 3 ; the 
 chalk merely serves to neutralise the acid as it forms, otherwise its presence would 
 stop the fermentation. When this change is completed, the calcic lactate gradually 
 disappears, and butyrate is formed, while hydrogen is evolved ; other products also 
 accompany the butyrate of lime. 
 
 Another form of fermentation and one well known is the acetous, which consists in 
 the transformation of alcohol into acetic acid, by the agency of the ferment Myco- 
 derma aceti. This change is one of oxidation only, and it appears that the ferment 
 acts like spongy platinum, viz. as a carrier of oxygen. 
 
 There are many other processes of fermentation, among which that termed 
 mucous fermentation is induced in sugar by some nitrogenous substances, and ter- 
 minates in the production of mannite, lactic acid, and hydrogen, together with carbonic 
 anhydride. 
 
 Emulsin (a nitrogenous constituent of bitter almonds) also splits up amygdalin 
 into benzoic aldehyde, glucose, and hydrocyanic acid. The ptyaline of saliva converts 
 starch into glucose ; the pepsine of the gastric juice renders soluble the albuminous 
 constituents of food, with some slight change. All these may be regarded as fermen- 
 tative changes, just in the same way also as putrefaction is of the same nature. 
 When albuminous substances are allowed to putrefy by contact with the air, in the 
 presence of moisture, the albumin is decomposed, yielding a number of products which 
 are identical with those obtained from the same substance, by a combined chemical 
 process of oxidation and hydration. That is to say, the changes induced by fermenta- 
 tion are of an ordinary chemical type, and it is only by chemical means that it 
 can be decided whether such changes are primarily due to the presence of living 
 organisms, or whether that is merely a coincident circumstance. 
 
 In the case of albumin, for instance, a knowledge of its composition and of its 
 decomposition products, as well as the total products induced by what is termed 
 fermentation or putrefaction, may make it possible to decide upon the measure of 
 the influence exerted by cell life in the process. Albumin is a complex substance 
 liable to change ; exposed to the air and moisture it is speedily contaminated with 
 germs and spores ; in their nutrition the albumin is finally quite destroyed by oxida- 
 tion and hydration. 
 
 A word may here be said appropriately concerning antiseptics. Albumin in a 
 combined state is not nearly so prone to change as when in a free state, so that if it 
 be possible to effect such combination, or if it be possible to shroud the albumin from 
 oxygen in any way; as, for instance, by enveloping it with a medium of an agent not 
 
CHARACTERS OF ALCOHOL. 885 
 
 penetrable by oxygen, or having a greater affinity for oxygen than albumin has, then 
 the albumin may be preserved from change, and in so far the agent employed for this 
 purpose becomes an antiseptic. 
 
 Cbaracters. Alcohol is a colourless liquid, having a peculiar agreeable odour 
 and a burning taste. In the raw state, as it is obtained by distillation of fermented 
 liquors, the smell and taste are modified by the presence of other substances, which 
 are formed at the same time with alcohol in the process of fermentation, and are col- 
 lectively designated fusel oil. In a diluted state, alcohol has an agreeable taste. 
 Mixtures of about equal parts of alcohol and water, with various flavouring substances 
 in small proportion, constitute the different kinds of spirits used for drinking. In 
 this state, alcohol exerts a peculiar stimulating influence upon the nervous system, 
 and in large doses it produces intoxication and stupor. The action of all alcoholic 
 beverages is due to the alcohol they contain. In a concentrated state, alcohol acts as 
 a poison. 
 
 The specific gravity of alcohol at a temperature of 15 is 0*7947, and at it is 
 8064 ; its specific heat is 0*6 1 5, as compared with that of water taken as unity, according 
 to Kopp ; and the latent heat of vaporisation is 208'92, while that of water is 536*5. 
 Alcohol boils at 78*4 under a barometric pressure equal to 0*760. This low boil- 
 ing point of alcohol admits of the separation of alcohol from water by distillation, 
 and by reason of the low specific heat, as well as the low latent heat, it is possible to 
 increase the strength of a mixture of alcohol vapour and water by abstracting part of 
 its heat, the effect being the condensation of water vapour chiefly, while the alcohol 
 remains uncondensed. Alcohol vaporises to some extent, at all temperatures, and on 
 this account there is liability to loss when alcoholic liquids are kept. 
 
 The vapour of alcohol is inflammable even when mixed with air, and therefore 
 care must be taken to avoid bringing a light near to it ; neglect of this precaution 
 has often given rise to serious accidents. Alcohol is also readily inflammable in the 
 liquid state, and it burns with a bluish flame, emitting but little light. The presence 
 of foreign substances communicates to the flame of alcohol characteristic colours ; 
 sodium salts produce a yellow colour, strontium salts a purple red colour, calcium 
 salts a yellowish red, and copper salts a green colour. 
 
 Alcohol is miscible with water in all proportions, and in the pure state it has such 
 an attraction for water, that it absorbs it from the atmosphere. On mixing alcohol 
 with water heat is evolved, and after cooling there is a considerable contraction of 
 volume, so that the bulk of the mixture is always less than the joint bulk of the sepa- 
 rate liquids. This contraction is greatest when 537 parts by measure of alcohol are 
 mixed with 49'8 parts of water, and the volume of the mixture is 100 parts instead of 
 103'5. By reason of this contraction, the specific gravity of mixtures of alcohol and 
 water does not correspond with the proportions of the two liquids. The relations 
 between the specific gravities of such mixtures, and the relative amounts of water and 
 alcohol, have been studied by Gilpin and Gay-Lussac, and tables have been constructed 
 by which these data can be ascertained, those of Tralles referring to a temperature of 
 15ij (60 F.), while those of Gay-Lussac refer to a temperature of 15. In order to ob- 
 viate the use of specific gravity determinations and tables indicating the correspond- 
 ing amounts of alcohol and water, aerometers have been constructed, by means of 
 which the amount of alcohol may be directly ascertained. In France, Gray-Lussac's 
 alcoholometer is employed, and in Germany that of Tralles. Both indicate differences 
 of specific gravity which are in excess of those that may result from temperature 
 within the ordinary range of variation, but Tralles' alcoholometer is most to be de- 
 pended upon for accuracy. Besides the alcoholometer of Gay-Lussac, there is another 
 instrument used in France, that of Carlier, which is constructed upon a purely empirical 
 basis. The scale is divided into 44 parts or degrees, and immersion to 10 represents 
 the specific gravity of water, while 44 represents the specific gravity of absolute 
 alcohol. A further difference between this instrument and others consists in the ob- 
 servation of gravities being conducted at a temperature of 12*5. 
 
 Sykes's hydrometer is the one officially employed in this country ; it is made of 
 metal, and has a four-sided stem divided into eleven equal parts, which fits into 
 a hollow brass ball, while at the opposite side of the ball there is another stem 
 of sufficient weight to make the instrument float upright in a liquid, and shaped 
 in such a manner that the weights for loading the stem can be slipped upon it. 
 The instrument is adjusted to float with the zero of the scale, in spirit of specific 
 gravity 0*825 at 60 F. (15*6), coinciding with the surface of the liquid. The mixture 
 of alcohol and water having this density contains 89 per cent, by weight of absolute 
 alcohol, and it is the standard alcohol of the Excise. In weaker spirit the in- 
 strument does not sink so low, and if the density of the liquid be much greater, it is 
 necessary to hang one of the weights upon the lower stem, in order to cause the im- 
 mersion of the bulb. 
 
886 ALCOHOL. 
 
 In France the strength or alcoholic contents of liquids is expressed as follows : 
 
 Cartier Gay-Lussac 
 
 Anhydrous or absolute alcohol . . .44 . .100 
 
 Kectified spirit 39 . 94-1 
 
 36 . 89-6 
 
 Wine spirit 33 . 84'4 
 
 22 . 587 
 
 21-6 . . 58- 
 
 Brandy (Cognac) 20 . . 52'5 
 
 Ordinary spirit 19 . 49'1 
 
 Weak 18 . 45'5 
 
 In Germany the value of alcoholic liquids is indicated by the amount of pure 
 alcohol ; spirit of 80 per cent, for instance is a mixture of alcohol and water, contain- 
 ing 80 per cent, by volume of anhydrous alcohol measured at a temperature of 15| 
 ( = 12f Ror60F.) 
 
 Strong alcohol is a powerful solvent of many substances ; it dissolves the hydrates 
 and the sulphides of the alkali metals, and many salts, especially those which are deli- 
 quescent, such as calcium chloride, magnesium chloride, strontium chloride, calcium 
 nitrate, and magnesium nitrate, but strontium nitrate is insoluble in alcohol. 
 
 Mercuric chloride is dissolved by alcohol more readily than by water ; mercuric 
 bromide and mercuric iodide are likewise soluble in alcohol. Many other salts 
 which are soluble in water do not dissolve in alcohol ; and this character is often 
 taken advantage of in analysis for effecting the separation of substances, as well as in 
 the purification of some preparations. Substances that are soluble in water but in- 
 soluble in alcohol may sometimes be precipitated from their aqueous solutions by the 
 addition of alcohol. The solubility of calcium nitrate in alcohol is applied technically 
 for separating this salt from strontium nitrate. Ferrous sulphate is insoluble in al- 
 cohol, and in order to prepare this salt in a pure state it is precipitated from the 
 aqueous solution by adding alcohol. Many organic substances which are insoluble in 
 water dissolve readily in alcohol, as, for instance, ethereal oils, most resins, and vege- 
 table alkaloids, the fat acids, some fat oils, hydrocarbons, paraffin, camphor, soap, etc. 
 
 The alcoholic solutions of ethereal oils are used in preparing the solutions of 
 resins, in varnishes ; the solubility of vegetable alkaloids is taken advantage of in the 
 preparation of these substances, and by the evaporation of an alcoholic solution of 
 soap the material known as transparent soap is obtained. 
 
 Concentrated alcoholic solutions of some salts deposit, on cooling, crystals which 
 contain alcohol as a constituent, in the same manner that water is sometimes a con- 
 stituent of crystallised salt. Compounds of this kind were termed by Graham 
 alcoholates. 
 
 The chemical action of substances upon each other is sometimes modified by 
 alcohol, according to the solubility or insolubility of the substances to which they are 
 capable of giving rise. Thus when carbon dioxide is passed into an alcoholic solution 
 of potassium acetate, potassium bicarbonate is precipitated, and acetic acid is produced. 
 In aqueous solutions, however, all carbonates are readily decomposed by acetic acid. 
 
 Under the influence of atmospheric oxygen, alcohol undergoes a gradual decom- 
 position, and is converted into acetic acid ; but this change takes place only to a slight 
 extent when the alcohol is not very much diluted with water. Very dilute alcoholic 
 liquids when distributed, throughout porous substances, so as to expose an extended 
 surface of contact with the atmosphere, rapidly absorb oxygen, and the alcohol they 
 contain is thus converted into acetic acid. The preparation of vinegar by what is 
 termed the quick process depends upon this fact. 
 
 By the mutual reaction of concentrated sulphuric acid and alcohol at the ordinary 
 temperature, there is formed ethyl-sulphuricacid, and when this substance is heated 
 with an excess of sulphuric acid to a temperature of 140, while a stream of alcohol is 
 allowed to flow slowly into the mixture, decomposition takes place, ether and water 
 being formed which distill over together ; and by suitably regulating the supply of 
 alcohol, as well as the temperature of the mixture, the sulphuric acid is but very 
 slightly altered. When the temperature is raised above the point mentioned, a 
 further decomposition takes place, and the alcohol is converted into olefiantgas. 
 
 Preparation. In order to obtain pure absolute alcohol, the spirit resulting from 
 the distillation of any fermented liquors must be first subjected to various operations 
 for the purpose of purifying and concentrating it. The product thus obtained con- 
 stitutes the rectified spirit of commerce, which should be free from other alcohol, 
 and contain no more than from five to eight per cent, of water. This amount of 
 water cannot be separated from alcohol by mere distillation, and the complete dehy- 
 dration can only be effected by bringing the alcohol into contact with substances 
 
PREPARATION OF ALCOHOL. 887 
 
 which combine chemically with water, and form compounds that are not again decom- 
 posed at the temperature of boiling alcohol. Thus, for instance, when alcohol contain- 
 ing water is mixed with quicklime, the water is abstracted by reason of the formation 
 of calcium hydrate, from which the alcohol may then be separated by distillation. 
 Another plan of abstracting the water from dilute alcohol consists in mixing it with 
 cupric sulphate, from which the water of crystallisation has been separated by heating 
 the salt. After some time, the water in the alcohol is taken up by the cupric sulphate. 
 Calcium chloride in a dry state acts in the same manner. Alcohol may be to a great 
 extent deprived of water by these substances ; but when quicklime is used for the pur- 
 pose, the product often has a disagreeable smell and taste, which may be due to the 
 action of the lime upon some foreign substance in the spirit, or to a slight decomposi- 
 tion of the alcohol itself. 
 
 In preparing absolute alcohol on a small scale, cupric sulphate may be con- 
 veniently used. For this purpose, the coarsely powdered salt is heated in an iron pan 
 until its blue colour disappears, and it is converted into an almost white powder, con- 
 sisting of anhydrous cupric sulphate. A quantity of this powder is placed in a flask 
 and covered with rectified spirit, the flask closed with a cork, and the mixture left to 
 digest for about twenty-four hours with occasional agitation. According to the 
 amount of water in the rectified spirit, the cupric sulphate combines with it more or 
 less rapidly, and again acquires the blue colour of the hydrated salt. When this has 
 taken place, the flask is connected with a condenser heated in a water bath, and the 
 alcohol distilled off. 
 
 Paw Materials. Any material may be used for obtaining alcohol which contains 
 alcohol ready formed, or fermentable sugar, or even sugar and other substances that 
 are not susceptible of fermentation, provided they are capable of being converted into 
 fermentable sugar. Thus wine, beer, cider, etc., may be used on account of the spirit 
 they contain ; the various kinds of fruit may be used on account of the grape sugar 
 and fruit sugar they contain ; beet root and molasses as containing cane sugar ; milk 
 also as containing lactose ; potatoes, the grain of cereals, and many other kinds of seed, 
 on account of the starch they contain ; and even wood may be used for this purpose, 
 inasmuch as the cellulose it contains can be converted into grape sugar. 
 
 Various considerations, however, have to be taken into account in selecting a 
 material for the production of alcohol. In general, that material wquld be preferable 
 which under given conditions would furnish the largest amount of alcohol with the 
 least expense. But, on the other hand, certain objects for which the spirit is to be 
 used must be considered. If a drinkable product is to be produced, only such raw 
 materials can be used as are capable of satisfying this requirement ; hence, wine is 
 used to prepare brandy, and cherries to prepare a similar spirit known as Kirsch- 
 wasser, the higher value of the product making up for the cost of the raw material. 
 Besides these circumstances, there may also be others of a more artificial nature 
 which preclude the possibility of using certain materials. Thus the duty levied upon 
 spirit in many countries renders it impracticable to use other materials for producing 
 alcoholic products than those which yield a considerable amount of alcohol in propor- 
 tion to their bulk. 
 
 The method of procedure followed in the manufacture of spirit varies according to 
 the nature of the raw material operated upon. 
 
 Treatment of Alcoholic Liquors. In this case all that is necessary is to separate 
 the alcohol already existing in the liquids from the other substances mixed with it, 
 partly volatile and partly fixed, and then to obtain the alcohol in a concentrated con- 
 dition. This is effected by distillation. Alcohol, as already mentioned, has a lower 
 boiling point and a lower latent heat of vaporisation than water has. When, there- 
 fore, a liquid containing but a small amount of alcohol is heated and kept for some 
 time at the boiling point, a mixture of alcohol vapour and water vapour is lormed, 
 which is under all conditions proportionately richer in alcohol than the original 
 liquid, and after some time the liquid remaining is free from alcohol. If the vapour 
 be condensed, a liquid is thus obtained which is free from non-volatile substances, and 
 contains alcohol and water in varying proportions, according to the time the distilla- 
 tion has been carried on. It may be assumed in general that, in order to obtain 
 all the alcohol from fermented liquors by distillation, about one-third of the volume 
 of the liquid must be vaporised. The residue thus freed from alcohol is termed 
 spentwash. The distillate obtained is termed 1 o w w i n e, and unless the distilla- 
 tion has been stopped at an early stage, as is sometimes requisite, it contains alcohol 
 and water in such proportions that the amount of alcohol is not sufficient to admit of 
 the product being used at once as a beverage ; it contains moreover substances which, 
 though possessing in a pure state a boiling point much higher than that of alcohol, 
 have the property of distilling over to some extent together with water vapour. These 
 
888 ALCOHOL. 
 
 substances are comprised under the general term fusel oil. The one among them 
 that is best known is amyl alcohol, which is produced especially in the fermenta- 
 tion of amylaceous substances. The constituents of fusel oil have generally an ex- 
 tremely disagreeable smell and taste, and their presence deteriorates the quality of 
 spirituous liquors. Some of these substances, on the contrary, are distinguished by 
 their great aroma, and therefore their preservation is requisite for giving a high 
 quality to the spirit. When this is the case, the distillation is conducted in such a 
 manner that the collection of the distillate is stopped as soon as it begins to be diluted 
 by the condensation of water vapour to a greater degree than corresponds to the strength 
 of the spirituous liquor required. Loss of alcohol would thus be entailed, unless the 
 alcohol still remaining in the liquid undergoing distillation were distilled off; this 
 is therefore collected in a separate receiver under the name of after wine, and is 
 added to the liquid to be distilled in the subsequent operation. 
 
 In most cases, it is necessary to submit the product of the first distillation to 
 further concentration and purification. Besides the fusel oil above mentioned, it con- 
 tains some substances the boiling points of which are lower than that of alcohol ; such 
 as aldehyd, various ethers, etc., formed by the alteration of alcohol. These substances 
 communicate to the spirit a fiery taste, and consequently they must be removed. 
 The purification of the low wine is effected by distillation, which is termed rectifi- 
 cation. In this operation heat is at first applied gradually, in order to remove the 
 most volatile of the foreign substances from the spirit, and to concentrate them in the 
 first portion of the distillate. As soon as the spirit distilling over is free from 
 objectionable odour, the receiver is changed, and the spirit is then collected as 
 long as it is of sufficient strength. The receiver is then changed again, and the re- 
 mainder of the alcohol collected apart as weak spirit, which always contains much 
 fusel oil. The first and last runnings are mixed together and again distilled with a 
 fresh charge. 
 
 When strong spirit is required, the rectification is sometimes repeated several times, 
 and the first and last portion of each distillate are collected apart. This method of 
 operation involves considerable expenditure of fuel and labour, as well as much loss of 
 alcohol ; and as methods are now known by which these disadvantages may be avoided, 
 the direct production of spirit is practised only when it is desirable to preserve the 
 peculiar aroma of the fermented liquors, as in the manufacture of brandy, or when 
 the operation is carried out on such a small scale that the erection of costly plant is 
 not practicable. In far the great number of cases, it is customary with the improved 
 forms of apparatus to produce, at the outset, spirit containing but little fusel oil, and 
 of a strength equal to at least 80 per cent, alcohol : this is further purified and con- 
 centrated by rectification, and then reduced by admixture of water to the strength 
 required for use. 
 
 The principle upon which the apparatus used for this purpose is constructed is 
 the following. In a mixture of alcohol vapour and water vapour, there are two sub- 
 stances which differ considerably in regard to the amount of heat they require for 
 maintaining the condition of vapour. The latent heat of water is much higher than 
 that of alcohol. When such a mixture is cooled and part of the heat abstracted from 
 it, part of the vapour is condensed to the liquid state. But since alcohol requires 
 much less heat in order to maintain the form of vapour than water does, it is evident 
 that, by the abstraction of heat, that portion of the mixed vapour must be first con- 
 densed which requires the greatest amount of heat for its maintenance; in other words, 
 the water is first condensed, and in consequence of this the mixed vapour is rendered 
 poorer in water and richer in alcohol. If this process is repeated often enough, the 
 condensation of the water and the concentration of the alcohol continue until a point 
 is reached at which the mixture consists chiefly of alcohol vapour, and only contains 
 a small proportion of water vapour, and the condensation of the whole remaining 
 vapour then furnishes strong spirit. 
 
 A large variety of variously constructed distillatory apparatus are based iipon this 
 behaviour of the mixed vapour, and though they present very different external 
 deviations of arrangement, their operation is essentially referable to the same prin- 
 ciple. In all cases, the liquid to be distilled in such forms of apparatus is heated 
 either by direct fire, or by high-pressure steam, or by injection of steam. The mix- 
 ture of water vapour with a small proportion of alcohol vapour thus produced is 
 passed into a second vessel with the liquid to be distilled, either cold, or already heated 
 to a certain degree. According to the temperature of the vapour and that of the 
 liquid, in the second vessel a certain portion of the vapour is condensed, but that part 
 of the vapour which requires the greatest amount of heat is always condensed in the 
 largest proportion. The mixed vapours subsequently passed into the second vessel 
 have then sufficient heat to convert into vapour not only the alcohol, at first con- 
 densed together with water, but also the alcohol originally contained in the liquid, in 
 
SPIRIT STILLS. . 889 
 
 the second vessel. The vapour thus produced, and containing a large amount of 
 alcohol, is passed in a similar manner into a third, fourth, and fifth vessel, each of 
 which is charged with the liquid to be distilled, and the result is that there is a pro- 
 gressive condensation of water vapour, and a simultaneous increase in the proportion 
 of alcohol vapour. The operation may also be conducted in such a way that the 
 vaporisation of fresh quantities of alcohol is not attempted/ but the mixed vapour is 
 rendered richer in alcohol by abstracting water from it by condensation, until at last 
 it is conducted into an empty vessel surrounded by a liquid, at a temperature between 
 the boiling point of alcohol and that of water. By this means the vapour is so far 
 cooled, that a large proportion of water is condensed with only a small proportion of 
 alcohol, and if this is repeated often enough, the vapour ultimately remaining uncon- 
 densed will have almost any desired amount of alcohol. 
 
 APPARATUS USED IN DISTILLATION. The oldest apparatus, which was widely used 
 until within the last thirty or forty years, consisted of a retort-shaped vessel, heated 
 by an open fire, and connected with a coil of pipes lying in a wooden vat, surrounded 
 by cold water. Such an apparatus could only be worked in the production of low 
 wine, the distillation of the low wine to weak spirit, and the rectification of the 
 spirit. The first improvements were made by the French manufacturers, who were 
 soon followed by the Germans. Each had to keep in view the material of their respec- 
 tive countries, in the one case wine, and in the other a material far more difficult to 
 work, the thick mash from grain and potatoes with their skins and refuse. 
 
 The first improvement appears to have been originated by Argand. He placed a 
 coil of pipe immediately over the retort or still in a vessel filled with wine, so that the 
 vapour passing from the still into the lower part of this pipe was there partially con- 
 densed, and the condensed portion, consisting principally of water, flowed back into 
 the still, whilst the more alcoholic vapour passed upwards, heating the wine in the 
 cooling vessel, and then, entering another worm surrounded by cold water, being there 
 perfectly condensed. In this way strong spirit was obtained in one operation. The 
 heated wine was then run into the retort and used for the next distillation. 
 
 The same principle was adopted by Dora, with the difference, however, that the dis- 
 tillate condensed in the first cooling pipe did not flow back into the still, but was col- 
 lected in a special receiver where it underwent rectification by fresh vapour, so that a 
 
 FIG. 647. 
 
 liquid nearly free from alcohol had to be worked up with the already heated mash in 
 the next distillation. 
 
 This arrangement is represented by fig. 647. The body (A) of the still is surmounted 
 by a capacious head (B), from which the vapour is conveyed by the neck (r) to the 
 worm in the vessel (c i>), separated by a partition into two compartments, the upper 
 one serving as a heater for the wash, while the lower one acts as a rectifier. The 
 compartment (c) when filled to the level of the tap (m) contains the quantity of wash 
 for charging the still. The vapour passing from the still is at first condensed in 
 passing through the worm (g\ and flows into the compartment (D). When the 
 contents of the compartment (c) have become so hot that no more condensation occurs 
 in the worm (g), the vapour bubbles through the liquid in the compartment (D), and 
 heating it to the boiling point drives off alcohol vapour, which is then condensed in the 
 worm of the condenser (E). By means of the pipe (/) connected with the small rcfri- 
 
890 
 
 ALCOHOL. 
 
 gerator, the strength of the distillate passing from the still can be tested from time to 
 time. 
 
 Edward Adam made the following modification. The still was connected with a 
 series of ovoid metal vessels by a pipe that ended in a rose almost at the bottom of 
 the first vessel. Another pipe connected the upper part of the first vessel with the 
 lower part of the second, and the other vessels were similarly connected. From the 
 last the vapour, which by this time had become very rich in alcohol, passed into the 
 cooling worm. Through the radiation of heat from the surface of the ovoid vessels, 
 causing a corresponding condensation, a part of the mixed vapour was withdrawn, but 
 the succeeding vapour, passing through this liquid, took up and carried forward a part 
 of the alcohol. At the close of the distillation, each condensing vessel contained an 
 alcoholic liquid of higher concentration in proportion as it was further from the still. 
 In order to improve this the contents of the first vessel were emptied into the retort ; 
 the second into the first, and so on, so that in the next distillation the previously con- 
 densed liquid underwent further rectification. 
 
 Cellier-Blumenthal introduced the continuous apparatus, in which the condensation 
 is effected exclusively by the wine to be distilled ; the essential novelty being that 
 there is a continual inflow of wine at one end, whilst the spent liquid is discharged 
 from the apparatus underneath in a continual stream. It is a disadvantage of this 
 apparatus that the effluent spent liquor is not quite free from alcohol ; but this has 
 been overcome by Derosne's arrangement, in which the outflow is made intermittent 
 whilst the inflow is continual. 
 
 Simultaneously, Pistorius introduced into Germany an apparatus consisting of two 
 connected stills, placed one under the other, and provided with a preliminary warmer. 
 Adams's series of condensing vessels was adopted, but instead of being ovoid they were 
 in the form of shallow basins ; the condensed liquid too, instead of being collected, 
 flowed back directly into the distilling apparatus. Pistorius's apparatus, with 
 numerous modifications, is now found in almost all German distilleries; but it has 
 lately come into strong competition with one made upon the Cellier-Blumenthal and 
 Derosne principle, and arranged for the working of thick mash. 
 
 The heating of distillatory apparatus by steam was introduced in 1 829 by Gall. 
 
 One of the simplest arrangements admitting of a continuous supply of the liquid 
 to be distilled and an intermittent discharge of the spent wash is that of Laugier, 
 
 Kir 
 
 FIG. 648. 
 

 
 LAUGIER'S STILL. 891 
 
 represented by fig. 648. It consists of two stills (A c), a dephlegmator (E), and a con- 
 denser (G). The still (A) is set over a furnace (B), the flue of which (c d e) is continued 
 under and round the second still (E). The two stills are connected together by the 
 tube (;') fitted with a valve by which the communication can be opened or shut at 
 pleasure. They are also connected together by the pipe (i i), by which the steam 
 generated in the still (A) is passed into the liquid contained in the still (c). The still 
 (c) is connected with the worm of the dephlegmator (E), by the pipe (m), and the 
 liquid condensed in each of the coils (/to/ 7 ) is run off through a small pipe attached 
 to the lowest part of the coil into a common discharge-pipe (n), which is connected with 
 the still (c), so that the condensed liquor is discharged into it. The vapour that is not 
 condensed passes from one coil to the other through the upright connecting pieces until 
 it reaches the tube (o o) connected with the worm of the condenser (o), and being 
 there condensed is delivered through the outlet pipe (q) into the receiver (r) in which 
 an alcoholometer (s) floats, and flows away to the store vessels. The liquid to be dis- 
 tilled travels in the opposite direction. It is supplied from the reservoir (v) through 
 the tap (u) into the funnel tube (t) of the condenser (a), and being delivered into this 
 vessel at the bottom displaces its contents through the pipe (L), serving to condense 
 the alcohol vapour passing through the worm of the condenser, and thus becomes heated 
 itself before it escapes through the pipe (L) into the dephlegmator (E), where it is 
 delivered at the bottom, and after filling this vessel escapes in a heated condition 
 through the overflow pipe (I) connected with the still (c), into which the heated liquor 
 to be distilled is thus supplied. From this still the liquor can be discharged as required 
 into the still (A) by opening the valve in the pipe (j). By means of the tap (/) the 
 spent wash can be discharged from the still (A). Both stills are fitted with glass 
 gauges (g g K) to indicate the level of the liquid contained in them. The liquor in the 
 dephlegmator (E) is sufficiently hot to give off alcohol vapour, which is conveyed by a pipe 
 (pj into the pipe (o) connected with the worm of the condenser. The working of this 
 apparatus is very simple. On opening the tap (u) of the reservoir the liquid to be dis- 
 tilled flows into the condenser (G), and, when that is full, into the dephlegmator (E), 
 and from thence into the still (c). As soon as the liquor in the still reaches the level 
 of the steam pipe (i), indicated by a mark on the gauge glass (g), the tap (u) of the 
 reservoir is closed, and the still (A) is filled to three-fourths of its capacity with the 
 liquid to be distilled, which is then heated to boiling. The heating is continued until 
 about two-thirds or three-fourths of the liquid is distilled off, according to its alcoholic 
 contents. During this distillation the greater part of the vapour is condensed in the 
 still (c) and in the dephlegmator, but very little alcobol passes over through the worm 
 of the condenser, because the contents of the still (c), as well as the liquid in the 
 dephlegmator, are not sufficiently heated. When the contents of the still (A) are ex- 
 hausted of alcohol, the tap (/) is opened and the spent wash run off 5 the valve (j) is 
 then opened, and the contents of the still (c) run into the still (A). After closing the 
 valve ^'), the fire is increased so as to bring the hot liquid rapidly to boiling. The 
 tap (u) of the reservoir is then opened, and the liquor to be distilled is allowed to run 
 in a slow continuous stream into the apparatus, displacing the slightly warmed liquid 
 in the condenser into the dephlegmator, and driving the still more heated contents of 
 the latter into the still (c), which also receives the hot liquid from the tubes (/, to/ 7 ). 
 The supply of liquid to be distilled is so regulated that the still (c) is filled by the 
 time the liquid in the still (A) has been completely deprived of alcohol. This requires 
 about three-quarters of an hour to an hour. The spent wash is then run off, and the 
 contents of the still (c) transferred to the still (A) as before. In this way the operation 
 once started goes on continuously. The liquor to be distilled, flowing continuously 
 into the still (c), is finally deprived of its alcohol in the still (A) and discharged as 
 spent wash. 
 
 The strength of the alcohol obtained can be regulated at will. With a strong firing 
 and rapid ebullition in the still (A) the contents of the dephlegmator are heated 
 rapidly and so much that little condensation is effected in it, and only weak alcohol is 
 then obtained. By firing moderately and conducting the distillation more slowly 
 stronger alcohol is obtained ; or the same result may be secured by increasing the 
 number of coils in the dephlegmator and increasing its dimensions. 
 
 In working this apparatus care has to be taken that the spent wash is not run off 
 until the whole of the alcohol has been extracted. This may be ascertained best by 
 attaching to the still (A) a small ascending worm, connected with a second small de- 
 scending worm. By opening a cock a small quantity of distillate may be drawn off 
 and tested. 
 
 Laugier's apparatus is well adapted for working wine, or other material of a 
 similar nature, which is tolerably uniform in strength, and for producing a spirit of 
 moderate and uniform strength ; but it is not well suited for producing strong alcohol, 
 in which case an arrangement of the kind introduced by Cellier-Blumenthal is more 
 
892 
 
 ALCOHOL. 
 
 convenient, and can be worked so as to yield spirit having any strength that may be 
 
 Derosne's modification of 
 this apparatus is represented 
 by fig. 649. It consists of 
 two stills, arranged in the 
 bame manner as in Laugier's, 
 and the alcoholic vapour es- 
 caping from the still (B) rises 
 through the column (c), 
 which contains a series of 
 lenticular discs over which 
 the heated wash flows down 
 from the heater (E) through 
 the pipe (II). Within the 
 column (c) water is condensed 
 from the vapour, and alcohol 
 vaporised from the heated 
 wash, and the vapour passing 
 upwards through the recti- 
 fying column (D), and a coil 
 of pipe in the heater (E) is 
 further deprived of water by 
 partial condensation. The 
 extent to which the dehydra- 
 tion of alcohol can be carried 
 in an apparatus of this kind, 
 depends upon the extent of 
 surface exposed in the 
 columns and the other parts. 
 
 The apparatus of Cellier- 
 Blumenthal, as improved by 
 Derosne and Dubrunfaut, is 
 used in many of the best 
 spirit works in France. It 
 is represented by fig. 650, and 
 consists of two stills (A B), 
 furnished with steam jackets. 
 The still (A) has a draw-off 
 tap (a). To the upper part 
 of the still is fitted a tube 
 (a") by which the vapour 
 
 FIG. 649.. 
 
 is led into the second still (B), which performs the same function as the second still in 
 Laugier's apparatus. The. still (B) is furnished with an air-cock (>''), and it is con- 
 nected with the still (A) by the tube (b\ fitted with a valve. At the top is another 
 tube (V), by which the vapour is led into the bottom of the column (c c), which con- 
 sists of ten compartments with distillation plates, to be described presently. The 
 tube (D) extending from the dome of the column conducts the vapour into the worm 
 (B'') of the first heater. To the lower end of this worm is connected the receiver (F), 
 in which the uncondensed vapour is separated from the liquid condensed in the worm 
 a pipe being attached to the bottom through which the condensed liquid from the worm, 
 is conveyed into the cooling tube(K'), while the vapour escapes from the upper part of 
 the receiver (F) through a tube (G') connecting it with the worm (H) of the second 
 heater, where the alcohol is condensed and flows, together with any remaining vapour, 
 through the tube (i) to the condenser (K K). The vapour produced in the first heater 
 also passes through the bent tube (t) into the tube (i) and into the condenser (K K), 
 where the whole of the distillate is united. The condenser is supplied with cold water 
 from the reservoir (TT) through the pipe (v v), and the heated water is discharged 
 through the pipe (x). The worm of the condenser is connected by the pipe (L) with 
 the alcoholometer vessel (M), the overflow of which is immediately above the funnel of 
 the reservoir (N), which is in communication with the storehouse where the spirit is 
 run off into the casks (o o o). 
 
 In working the apparatus the condenser (K K) is first filled with cold water, and 
 the tap (v) is closed until distillation commences. By opening the cock (p 3 ) both the 
 heaters (Q H and B 2 n s ) are filled, as well as all the diaphragms of the column (c). 
 During this time the air cocks (a 1 6 2 ) are opened. As soon as the still (A) has been 
 two-thirds filled, the air cock (a") is closed, and steam, of from three to five atmo- 
 
 
SPIRIT STILLS. 
 
 893 
 
 spheres' tension, is blown into the jacket of this still. The liquid is thus rapidly made 
 to boil, and the<vapour passes through the tube (a 2 ) into the second still (B), heating 
 the liquid it contains, and driving off a great part of the alcohol in the state of vapour, 
 which passes through the tube (&') into the column (c), and there traverses the 
 layers of liquid upon the diaphragms. The liquor to be distilled flowing downwards 
 
 FIG. 650. 
 
 in an opposite direction to the vapour is thus gradually deprived of its alcohol as it 
 approaches the lower diaphragms ; while, on the contrary, the vapour becomes more 
 alcoholic ; since, in proportion as alcohol is vapourised in the diaphragms, there is a 
 corresponding condensation of watervapour. 
 
 During the time requisite for filling the still (B) two-thirds full, the liquid in the 
 
894 
 
 ALCOHOL. 
 
 FIG 651. 
 
 still (A) is completely deprived of alcohol. The spent wash is then run off, and by 
 opening the tap (b) the contents of the still (B) are transferred to the still (A), the 
 operation as above described being again repeated. By the action of the column the 
 alcohol is sufficiently concentrated to have a strength suitable for ordinary purposes. 
 A greater concentration may, if necessary, be obtained by making the first heater act 
 as a dephlegmator ; and, instead of uniting all the condensed alcoholic liquids, making 
 the portion condensed in the first heater flow on to the upper plate of the column and 
 undergo a further rectification. When the working of this apparatus is to be stopped, the 
 whole of the liquor to be distilled is run out of the reservoir (p) ; this is then filled with 
 water, and the alcoholic liquor is thus displaced from the several parts of the apparatus. 
 The liquor to be distilled travels in a contrary direction to the vapour. It is sup- 
 plied from the reservoir (p) into which it is pumped through the tube (p') until it 
 overflows through the pipe (P"). The pump represented by 
 fig. 651, consists of a solid plunger working in the barrel (A B) and 
 a pair of ball valves (c D) so arranged that the upward stroke of the 
 plunger raises the liquor through the valve (c), while the down 
 stroke forces it through the valve (D), and the ascending pipe (E) 
 into the reservoir (P) above. 
 
 The tap through which the liquor to be distilled escapes from 
 the reservoir (P) is furnished with an arrangement (p"'p 4 ) by which 
 it can be opened and closed as required to regulate the flow of 
 liquid into the funnel pipe (Q Q) into the second heater, and from 
 there through the pipe (E E) through the first heater, and then through 
 the pipe (s) into the upper part (c') of the column, where, having 
 become considerably heated in its passage, it is discharged upon the 
 uppermost of the eighteen diaphragms, which have the construc- 
 tion represented in vertical sections by figs. 652 and 653, and in plan by 
 fig. 654. Each of these diaphragms consists of a plate fitted to the sides of the 
 column, and carrying nine hemispherical caps, of which five ^efghi) are shown in the 
 
 section fig. 652. Beneath these caps 
 are as many holes in the plate having 
 raised collars fitted into them, and 
 projecting upwards into the caps, as 
 shown in the cap (i}, about half an 
 inch above the level of the edge of 
 the cap. By this arrangement liquid 
 is retained upon the plate to the 
 height of the collars ; and, since the 
 edges of the caps dip into this liquid 
 the vapour rising upwards through 
 the holes in the diaphragm into the 
 caps is made to pass through the 
 liquid lying upon the plate. 
 
 The level of the liquid upon the 
 plates is kept constant at such, a 
 height that it is midway between 
 the upper edges of the raised collars 
 of the tubes and the lower edges of 
 the caps above them. To insure this 
 there is fixed near the centre of the 
 plate a tube (d), the upper edge of 
 which is about half an inch lower 
 than the upper edges of the raised 
 collars, and about half an inch 
 higher than the lower edges of the 
 caps. The tube (d) extends down- 
 wards through the plate, as shown 
 in the drawing, and terminates about 
 three-quarters of an inch above the 
 next following plate (.;' Jc, fig. 652) 
 beneath. By this arrangement the 
 liquid upon the plate is maintained 
 at the level indicated by the line 
 (a b\ Anything in excess of this 
 quantity runs away to the plate 
 
 FIG. 654. underneath, while at the same time 
 
 the openings of the caps are sealed by 
 
 1 
 
 FIG. 653. 
 
SPIRIT STILLS. 
 
 895 
 
 the liquid. The ascending vapour can escape only through the raised collars and 
 under the caps, but not through the tube (d), because its lower end is closed by the . 
 liquid on the plate below. The entire column is made up of ten such diaphragms, 
 fixed one above the other. 
 
 In order to keep up a circulation of the liquid upon the several plates, the ar- 
 rangement represented in the horizontal section (fig. 654) is adopted. To the 
 straight diaphragm (A r) is fitted the curved diaphragm (r s t on one side, and r u v on 
 the other). When liquid flows down from the upper plate through the wide tube at 
 a, it takes the course indicated by the arrows in order to reach the tube (J) and flows 
 down through it upon the plate below, where similar diaphragms are fixed, and the 
 liquid is made to circulate in a similar manner in the opposite direction. 
 
 
 FIG. 656. 
 
 Champonnois' Distilling Apparatus. The apparatus introduced by Champonnbis is 
 essentially a simplification of the Cellier-Blumenthal apparatus, described before. It 
 consists of a still, arranged for an open fire, a column, and a cooling apparatus, and is 
 represented in fig. 656. The still (A) is set over a furnace ; it has its bottom bent in- 
 wards, in order to present the largest surface possible to the heat of the fire, and at 
 the same time to prevent any deposit, which might form a layer at the bottom were it 
 exposed to the action of the fire. 
 
896 
 
 ALCOHOL. 
 
 The column consists of cylindrical rings, the outer edge of each of which has a 
 trough-like depression, in which is laid a caoutchouc ring, and by this means the 
 ioints between each ring are closed without screws. The top and bottom rings being 
 provided with flanges (B B'), can be made tight by means of nuts screwed upon the 
 ends of long rods passing through them. 
 
 Each ring has a diaphragm with a wide central vapour pipe, covered by a cap, the lower 
 edge of which is toothed so as to distribute the vapour. There is also inserted in each 
 diaphragm a discharge pipe, the upper end of which is one-third of an inch below the 
 vapour pipe, whilst the lower end extends nearly to the next diaphragm. 
 
 The peculiarity of this apparatus is the introduction into the top part of the 
 column of a dephlegmator, in which a portion of the vapour is condensed, in order that 
 
 -p o 
 
 it may be again rectified in the upper portion of the 
 column. This dephlegmator is shown in fig. 656 at D, 
 and is represented on a larger scale in figs. 657 and 
 658. It consists of a shallow spiral reservoir with 
 double sides, standing in a vessel filled with the liquid 
 to be distilled. The vapour coming from the top- 
 most division of the column enters the reservoir at c, and 
 after circulating in it, passes through a pipe (D) opening 
 above the surface of the liquid, and through e to the 
 condenser, whilst the liquor condensed in the dephleg- 
 mator, flows through a narrow pipe, bent TJ-shape at the 
 bottom, into the top division of the column. 
 
 Instead of the ordinary worm, there is in the condenser 
 a double walled cylinder (g g, fig. 656), the walls of 
 which are a small distance apart, so that they form a cy- 
 lindrical ring surrounded on all sides by the cooling 
 liquid. The alcoholic vapour enters at the upper part of 
 the condenser, is there condensed, and flows off through 
 the aleohometer (i). 
 
 In working, the fermented liquor is run from the 
 upper reservoir through the funnel pipe (j) into the outer 
 space of the condenser at /. When the liquor has filled 
 this space it rises, the lid being hermetically closed, 
 through the pipe (K), and passes into the liquor space of 
 the dephlegmator at e'. When this is filled also, the 
 liquor, driven forward by that freshly arriving, falls 
 through a pipe bent first downwards and then upwards 
 . 658. ( m m ') upon the plate of the fourth division of the 
 
 column, runs through its outflow pipe into the next division, and finally into the still. 
 The liquor is allowed to run until the still (A) is sufficiently full, which is shown by 
 the juice running out through the pipe a. The contents of the still are then heated to 
 boiling. The vapour rises into the separate divisions, heating them to the boiling 
 temperature, passes into the dephlegmator, where at first it is completely and after- 
 wards partially condensed, and finally reaches the condenser. 
 
 When, by the continued boiling, the contents of the still have been exhausted, 
 a fresh supply of fermented liquor is allowed to flow in at j. This drives the liquid 
 that has become heated in the condenser into the cooling space of the dephlegmator, 
 and from thence into the column, etc. The flow of liquor is then allowed to go on 
 uninterruptedly, and in proportion as this takes place, a corresponding part of the con- 
 tents of the still (A) runs off through the pipe (a), so that the operation is continuous. 
 The firing and the inflow of the fermented liquor have therefore to be so regulated 
 that on the one side a completely exhausted wash is always running off at a, and on 
 the other a sufficiently cooled spirit at i. 
 
 Stills constructed after the same principle are in the present day coming into 
 more general use in the potato spirit manufacture in Germany. Champonnois' appa- 
 ratus is so far modified, that the outflow is not continuous, but intermittent, there 
 being two stills heated by steam fixed one above the other, as in the Cellier-Blumen- 
 thal apparatus. The fermented mash flows in above, in an uninterrupted stream 
 until the second still is full ; the first, which has been meanwhile worked up, is 
 then emptied, and the contents of the second are, by the opening of a valve, trans- 
 ferred into the first. The thicker, character of the mash further makes it requisite 
 that the outflow pipes of the different divisions should be proportionally wider, in 
 order to avoid their stopping up. Lastly, the upper rectifying division of the column 
 is considerably increased, and the surface of the dephlegmator enlarged, so as to 
 augment the separation of water by fractional condensation and thus obtain the 
 strongest and purest spirit possible. 
 
 
SPIRIT STILLS. 
 
 897 
 
 Belgian Apparatus. In the Belgian distilleries, where a comparatively thin corn mash 
 is worked up, as described on p. 924, the apparatus represented in fig. 659 is used. It 
 consists, like Laugier's apparatus, of two retorts (A B), one placed a little higher than the 
 other, which can be heated either over an open fire, or preferably by steam. In the latter 
 case the vapour passes through the pipe (z) into the first still, either directly into the 
 liquid, or when steam under pressure is used by circulating through a heating coil. 
 The still has also an exit cock (#), an indicator of the height of the liquid (x), an air- 
 cock (v), and a safety valve (d). The steam from the first still (A) passes through the 
 bent pipe (b) into the second still (B), and goes from thence into the column (c D), 
 the ten divisions of which are provided with steam pipes covered with caps and with 
 wide discharge pipes. The vapour formed here is carried through the pipe (i>') into 
 the rectifier (E F). B is a comparatively small still in the bottom of which the pipe 
 (D') ends ; it supports a column (F) having a perforated bottom. From thence the 
 vapour passes through another pipe (G) into the dephlegmator (H), the action of 
 which is effected by a coil of pipes provided with a discharge cock at each opening, 
 upon the principle described on p. 902. The liquid here condensed runs back into 
 the column (F). The vapour not condensed in the dephlegmator passes through a 
 pipe (fff) into the condenser (s), kept cold by a continuous stream of water, and then 
 through the alcoholometer (u) into the spirit reservoir. 
 
 Fia. 659. 
 
 The fermented mash is raised by a pump (R) through a pipe (u') into the mash 
 reservoir (o) in which is a stirrer, worked by a handle (p) and pinion (p") to prevent the 
 husks from settling. From thence the mash flows through a^pipe (Q) entering at the 
 bottom of the dephlegmator, where it is kept thoroughly agitated by the stirrer (M) 
 worked by a pinion (p') ; it thus becomes heated, and then passes through a pipe (d c) into 
 the top division of the column (ED), and thence from one plate to another, and come?, 
 almost exhausted of spirit, into the second still. The heating is so regulated that the 
 contents of the first still is vapour! sed in the time required to fill the second. When 
 the first is emptied the contents of the second are run into it. The object of the in- 
 terposition of the third still (K) with its column (F) is the further rectification of the 
 vapour ; at the same time the value of the wash is thereby considerably increased. 
 From this still no back flow of condensed liquid takes place ; all the fusel oil, there- 
 fore, which was vapourised in the first two stills and ia the column (ED) is retained 
 here, and the wash in the first and second stills is thus freed from that constituent, 
 besides being made more concentrated by the retention of w^ter in E. 
 
 Savallc's distillatory apparatus (fig. 6GO) is constructed upon the same principle ae 
 
 3M 
 
898 
 
 ALCOHOL. 
 
 his rectifying apparatus. It consists of a still (A), which supports the column (B), 
 formed of numerous perforated plates. In this case the liquid to be distilled enters 
 from above, and flows down from one plate to another, meeting the steam that passes 
 upwards through the perforations ; it is thus heated and, by undergoing distillation, 
 becomes poorer in alcohol as itdescends. The vapour escaping at c passes into the pre- 
 liminary chamber (D), where any liquid carried forward separates and is carried back 
 
 FIG. 660. 
 
 oy a bent pipe into one of the upper divisions of the column. The vapour goes on 
 through another pipe (/) into the condenser (E), and the distillate flows off at F into 
 the alcoholometer vessel, and from thence into the spirit reservoir. The condensation 
 is effected by the fermented liquor, which enters through the pipe ( j) at the bottom of 
 the condenser, and as it becomes gradually heated, rises and flows off at the highest 
 point through a bent pipe (n) to the top plate of the column. B is the regulator ; 
 o the connection with the steam boiler ; p the pipe admitting the steam to the heating 
 coil ; x the pipe connecting the regulator with the upper part of the still. 
 
 ENGLISH DISTILLATORY APPARATUS. As a consequence of the revenue laws exist- 
 ing in this country, the spirit manufacture is limited to a few colossal establishments. 
 
COFFEY'S STILL. 
 
 .899 
 
 In these the apparatus invented by Coffey is used for the distillation of fermented 
 worts. This apparatus, shown in figs. 661 and 662, consists of two columns, the first 
 [c) being used for distillation and the second (B) for rectification. It is further pro- 
 vided with a dephlegmator (D) and two condensers (E F). The two columns of equal 
 deight are constructed of strong cast-iron plates, held together by iron rivets. They 
 are 42 feet high, and rise through four stories of the manufactory. The first column 
 'c) contains thirty-eight copper perforated plates, which are fastened to the sides of 
 ihe column. The columns are quadrangular, about 20 feet broad by 13| feet deep. 
 The perforated plates are 4 inches less in width than the interior of the column, leav- 
 ng a corresponding free space for the overflow of the wort from one plate to another. 
 The plates are fastened alternately to one and then to the other side of the column ; 
 >y this arrangement part of the wort is caused to traverse the surface of the plate 
 upon which it falls and pours off on the opposite side, and part falls through the per- 
 
 FIG. 661. 
 
 FIG. 662. 
 
 forations in a finely divided shower. Between each two plates in the side of the 
 column are manholes which can be shut close, and are used for the purification of the 
 interior of the apparatus. 
 
 At the bottom of the first column, the orifice of a steam pipe opens into the liquid. 
 At the top of it is an escape pipe through which the vapour passes into the second 
 column. Tnis is arranged similarly to the column in Savalle's apparatus, but differs 
 from it in that the wort does not flow freely over the plates, but through a capacious 
 .pipe, about 6 inches in diameter, bent to and fro (a a), the bends of which, in order to 
 facilitate their purification, are carried through the column to the exterior of the 
 apparatus. The wort, coming from the reservoir (A), fills this pipe, flowing down 
 through its windings until it reaches the lowest division of column B. Here it is sur- 
 rounded by the whole of the vapour coming from the other column (c). This streams 
 from division to division in an opposite direction to the wort, so that the fermented 
 liquor by the time it reaches the bottom becomes strongly heated, whilst the alcoholic 
 vapour as it rises upward from division to division becomes gradually cooled, and by 
 condensation of the aqueous portion continually richer in alcohol. 
 
 The heated wort rises from the foot of the second column (B), and after circulating 
 through the chambers of the preliminary vessel (D D'), flows on to the topmost plate of 
 the first column (c). The object of the preliminary vessel is to separate the most 
 volatile portion of the fermented liquid, which has already been converted into vapour 
 by the heat in the second column, and thus to obtain a purer distillate. It is there- 
 fore connected by a pipe with a special condenser. 
 
 The aqueous liquor condensed from the vapour in the divisions of the second 
 column flows into a small reservoir (H), from whence it is lifted by a pump (j) kept 
 continually going during the distillation, to the top plate of the first column (c). 
 
 From the upper end of the second column (B) the vapour, now rich in alcohol, 
 
 3 M 2 
 
900 ALCOHOL. 
 
 passes into the tubular condenser (F, shown in section in F'). The condenser is con- 
 structed similarly to a locomotive boiler. The vapour enters a first chamber, then 
 into a system of three hundred pipes, each l in. in diameter, surrounded by a continually 
 renewed stream of cold water, and then flows off perfectly cooled from the last division 
 of the condenser through the alcoholometer stand into the reservoir. 
 
 One such apparatus will yield hourly 480 gallons of 58 spirit, or a quantity 
 equivalent to nearly 6,000 gallons of 80 spirit in twenty-four hours. 
 
 BECTIFICATION OF SPIRIT. The alcoholic liquid obtained with the foregoing ap- 
 paratus contains, besides varying quantities of alcohol and water, various, mostly 
 badly 'smelling, admixtures of other alcohols, ethers, etc. These are separated from 
 the alcohol, and the proportion of water is at the same time reduced, by submitting 
 the liquid to rectification in a suitable apparatus. But since these oils have the 
 property of volatilising readily with the vapour of alcohol, the liquid to be distilled is 
 considerably diluted with water, so that at first a vapour is generated contain- 
 ing proportionately little alcohol and much water, the water being condensed by 
 further running in the apparatus, and the alcohol becoming concentrated. But even 
 with such distillation a fine product is only obtained when the several parts of the 
 distillate are recovered separately ; firstly, the portion containing the most volatile 
 constituents being separated, and then that passing over last as after-running. But 
 it is advisable to discontinue the distillation before this after-running comes over, 
 and transfer it to a special vessel, in order to prevent the oils, which distil over in 
 larger quantities towards the end of the operation, from contaminating the sides and 
 interior part of the rectification apparatus ; as these bodies collecting there would 
 injure the quality of the following distillate. 
 
 The liquor remaining after the rectification, especially when spirit from potatoes, 
 corn, molasses, or grape husks is worked, contains a large quantity of these oils, 
 which having been held in solution by the alcohol, separate from the liquor after the 
 removal of the alcohol in an oily layer, and can then be recovered for use. 
 
 Besides glycerin and succinic acid, which occur in all fermented liquors, all kinds 
 of wine contain small quantities of different oils which can be recovered in the 
 rectification. They can also be separated by distillation from the fermented juices of 
 apples, pears, cherries, sugar cane, etc. Only a few of these oils have at present been 
 closely studied. 
 
 The best known is the so-called fusel oil, or amylic alcohol, C 5 Hi 2 0, which 
 occurs most abundantly in raw potato spirit, but also in wine and other fermented 
 liquors. In the pure condition, amylic alcohol is an oily liquid, having a specific 
 gravity of 0'818 ; at a temperature below 23 it solidifies in the crystalline form ; it 
 boils at 132, and has a vapour density of 3'12. 
 
 The spirit obtained from wine and wine residues yields during rectification an 
 oily liquid, which consists chiefly of the ethyl ether of cenanthic acid. The free acid 
 corresponds in composition to the formula : 
 
 The ethyl compound has the formula : 
 
 Both the acid and the ether are, in the pure condition, oily liquids, solidifying at low 
 temperatures, and characterised by a most disagreeable smell. They are insoluble in 
 water, but very soluble in alcohol. The acid boils at 212, but is then partly decom- 
 posed ; the ether has a still higher boiling point. Both are lighter than water. 
 
 It is not to these compounds that different wines, brandy, rum, or cherry water 
 owe their peculiarly pleasant flavour and aroma ; neither is it amylic alcohol alone 
 that gives to potato, beet, and corn spirits their characteristic odour. The bouquet 
 of wines, and the peculiar taste and smell of every fermented liquid, are dependent 
 upon various volatile compounds, many of which are soluble in water, and may be 
 obtained from the vegetable substance yielding the fermented liquid. 
 
 The possibility of the separation of all these bodies from the spirit depends upon 
 the varying degrees of heat which are required to convert them into vapour. Alcohol 
 boils at 78, water at 100, most of the oils at 130, 150, or still higher temperatures ; 
 whilst the boiling point of some of the compounds lies far below that of alcohol. 
 
 Apparatus for Rectification. The apparatus at present in use for rectification 
 resembles the Cellier-Blumenthal distillatory apparatus. Such an apparatus is repre- 
 sented in fig. 663. The still (A) has a capacity of from 600 to 1200 gallons and the 
 larger capacity is most advantageous for working. The steam is forced into the still 
 through the pipe (c) terminating either in a rose or a coil of pipe. The tap (d) serves 
 
RECTIFICATION OF SPIRIT. 
 
 901 
 
 to draw off the spent wash. The pipe (a) is for the supply of weak spirit. The 
 tap (') serves either as an air cock, or for testing whether the vapour produced still 
 contains alcohol, and the gauge glass (b) shows the level of the liquid. The alcoholic 
 vapour passes from the still through the tube (e) into the bottom of the column (B), 
 while the liquid condensed in the column flows back nto the still through the pipe (f). 
 
 FIG. 663. 
 
 The column (B B') consists of ten compartments, with eighteen diaphragms, similar 
 to those described at p. 893. The alcoholic vapour escaping from the uppermost 
 compartment of the column passes througli the tube (cc') to the double dephlegmator, 
 
902 
 
 ALCOHOL. 
 
 consisting of two worms contained in a cylindrical vessel. The upper worm (c") 
 terminates in the receiver (D), to the bottom of which is fitted the bent tube (D'), by 
 which the whole of the liquid condensed in the worm (c") is delivered into one of the 
 upper compartments of the column, where it undergoes further rectification. The 
 upper part of the receiver (D) is connected by the pipe (D'') with the lower worm (E) 
 of the dephlegmator, and thus the whole of the vapour escaping from the upper worm 
 is passed into the lower worm (E), which terminates in a second receiver (E'), where 
 the condensed liquid is run off as before through the tube (//) into the upper compart- 
 ment of the column, while the alcohol vapour passes through the tube (E ''E") into the 
 worm (F) of the condenser. In this way the liquids condensed in the different parts 
 of the dephlegmator are returned to different parts of the column according to their 
 alcoholic strength. The lower end of the condenser worm is connected by means of 
 the pipe (G o) with the alcoholometer stand (H), from the overflow of which the 
 distillate runs into the funnel tubes (h h' ti' h"'} and into the reservoirs (H H"H"). 
 
 If it be desired to carry the concentration further, the upper part of the worm in 
 the condenser can be made to act as a dephlegmator. by adopting the arrangement 
 shown in figs. 664 and 665. By means of pipes (BE) fixed at the lowest part of each 
 coil of the worm (D D), the liquor there condensed can be run off through a common pipe 
 (i / ). By more or less opening the cocks (F) governing the pipes (EE), it is possible to 
 obtain the spirit of any desired degree of strength. The condensed liquid is then 
 carried back through the pipe (F) into the upper part of the column, in order to undergo 
 a fresh rectification. Cold water is supplied from the pipe (B'), and cock (B"), and passes 
 
 FIG. 664. 
 
 down through the pipe (B) into the lower part of the condenser, while the warm water 
 flows off from the pipe (c). 
 
 The separation and collection of the first runnings, the spirit, and the after run- 
 nings are effected by a suitable combination of alcoholometer vessels with a system of 
 pipes, as shown in fig. 666. The lower end of the worm coming from the condenser 
 is provided with a small pipe (A A), through which the air in the apparatus as well as 
 the most volatile and incondensible products are conducted to another pipe opening 
 outside, whilst the liquid runs into the inner cylinder, in which the alcoholometer 
 floats. The distillate rises to the edge of the inner cylinder, raising the alcoholometer 
 more or less according to the amount of alcohol, and thus indicating the nature of 
 the distillate passing at the moment, and it flows over into the outer cylinder (B). 
 This has a discharge pipe, connected with a movable bent copper pipe that can 
 be brought opposite the mouth of any one of the pipes, b', b", or //", by which the 
 liquid is carried into a special reservoir. In a similar manner several rectifying 
 stills can be connected by the same system of pipes with their corresponding reservoirs, 
 
RECTIFICATION OF SPIRIT. 
 
 . 903 
 
 as shown in figs 667 and 668. The three pipes (A A) lying side by side belong to 
 as many rectifiers, and the air from all escapes into the common pipe (A'). Each 
 pipe passes into a separate alco- 
 holometer vessel (B, c, D). In 
 front of these are the pipes (b, 
 c', $} by which the preliminary 
 runnings can be carried away; 
 (b", c", d") which communicate 
 with the pure spirit reservoir, 
 and (&'", c'", d'"} for carrying 
 away the after runnings. When 
 distillation commences in the 
 first still, the alcoholometer vessel 
 of which is at B, the end of the bent 
 portion of the overflow pipe is 
 brought over the opening (b^ for 
 carrying off the preliminary run- 
 nings. As soon as the alcohol- 
 ometer shows that pure spirit is 
 passing over, a slight movement 
 of the pipe brings it over the 
 opening (b"). If the second still 
 yields pure spirit at the same 
 time, its alcoholometer vessel (c) 
 is. in a similar way connected 
 with the corresponding opening 
 (<?"), and afterwards, when the 
 after runnings begin to flow, with 
 the opening (c'"). In whatever 
 stage therefore the distillation 
 in each still may happen to be, 
 each separate distillate, according 
 to the indications of the alcohol- 
 ometer, may easily and without the least loss be conducted to the proper reservoir. 
 In each spirit reservoir is placed a float, the counterpoise of which moves on a 
 scale in the immediate neighbour- 
 hood of the alcoholometer vessels, 
 so that at any time the heights 
 of the liquid in the separate reser- 
 voirs can be easily observed. 
 
 In carrying out the rectifica- 
 tion the retort is filled with dilute 
 spirit of 49 to 50, and steam is 
 admitted, the condenser and the 
 dephlegmator being filled with 
 cold water. At first all the vapour 
 condenses in the column and the 
 dephlegmator, and thus fills the 
 separate compartments of the 
 column, the whole of the most 
 volatile constituents, forming the 
 preliminary runnings, collecting 
 in the upper compartments. 
 
 Gradually the water in the 
 dephlegmator becomes warm, the 
 vapour is no longer completely 
 condensed there, and distillation 
 commences. At the same time 
 the cock through which the con- 
 denser is supplied with cold 
 water is opened, and the flow is 
 regulated so that the temperature 
 in the upper part of the dephleg- 
 mator shall be 50. This tem- 
 perature is 28 below the boiling 
 point of alcohol ; an almost com- 
 plete condensation would there 
 fore be effected here were the 
 
 FIG. C66. 
 
 FIG. 667. 
 
 Fiu. 668. 
 
904 ALCOHOL. 
 
 alcohol vapour to remain long in contact with the sides of the dephlegmator. But the 
 admission of steam into the still is so regulated that alcohol vapour is abundantly 
 produced, and even after a large quantity has been condensed in the column, it always 
 passes with some rapidity through the dephlegmator, so that although the tem- 
 perature is lowered it never sinks so far as to cause complete condensation. By the 
 admission of the steam into the still, and of cold water into the dephlegmator, the 
 strength of the spirit can be regulated. In well-arranged distilleries, the steam valves 
 and the water cock are always in the neighbourhood of the alcoholometer vessels, so 
 that by observing the alcoholometers the supply of steam and of water can be suit- 
 ably regulated. 
 
 After the preliminary runnings at the commencement of the distillation have been 
 separated, pure spirit of 96 is first distilled. The spirit is allowed to run off into the 
 proper reservoir until its strength falls to about 90, or until it no longer possesses the 
 pleasant odour required in fine spirit. Then the after runnings, containing some fusel 
 oil, are kept apart. Frequently this is also divided into two portions, the first, contain- 
 ing the least fusel oil, being used in the manufacture of a common spirit, while the 
 second is again rectified. The operation is ended when a sample of the vapour passed 
 off through a cock into a small worm no longer contains alcohol. The still is then 
 emptied. 
 
 In the rectification a certain portion of fusel oil is always vapourised ; but the 
 greater part of it is at once condensed in the lower divisions of the column, and flows 
 
 continuously back into the still, becoming 
 again and again vapourised as long as the 
 rectification lasts. In order to separate this 
 portion of the fusel oil the arrangement 
 shown in fig. 669 has been introduced, by 
 which the liquid coming from the column 
 can be made to flow either back into the 
 still or to the outside, The pipe (DE) 
 coming from the last plate of the column 
 does not open immediately into the still (A), 
 but is first carried through the side of the 
 still to the exterior. Here it branches out 
 into three pipes, which can be closed by the 
 cocks (F G H). One of the branches turns 
 back into the still, so that when the cocks G 
 and H are closed, and F is opened, the liquid 
 coming from the column passes into the 
 still. When F and G are closed and H 
 opened it passes into a reservoir (i) sur- 
 FIG. 669. rounded with cold water, and then by pres- 
 
 sure is driven up through the ascending pipe 
 
 (j). When F and H are closed and G open, everything can be brought directly to the 
 exterior, as, for instance, when it is desired to purify the apparatus, from time to time, 
 or to effect any necessary repairs. 
 
 Savalle's apparatus for rectifying, represented by fig. 670, consists of the following 
 parts : A double still (A B), with steam coils ; a column (B) formed of a large number 
 of sieve-like perforated plates, upon which the condensed liquid collects, whilst steam 
 rising from below passes through the perforations and through the liquid lying -above 
 them, the level of the liquid upon the plates being regulated by escape pipes (/), each 
 of which ends in a depression (g] on the perforated plate underneath ; a cylindrical 
 dephlegmator (E) ; a cylindrical, condenser (F) ; a cold water reservoir (H) ; and alco- 
 holometer vessel (i). 
 
 In working the apparatus the lower part of the still (A) is filled with dilute raw 
 spirit, and steam is then admitted to the coil of pipes so as to bring the spirit rapidly 
 to the boiling paint. The alcoholic vapour rises through a pipe (b) into the upper 
 division of the still (B), fills this, and then passes on through another pipe (e) into the 
 column. The cock of the water pipe (b) is then opened in order to fill the dephlegmator ; 
 the vapour rising from the column is there condensed, and flows through the pipe (Jfc) 
 back into the column, where it collects upon the perforated plates until they become 
 gradually filled. When this is effected, the inflow of water is regulated by partially 
 closing the cock so that only about two-thirds of the vapour that reaches the 
 dephlegmator is condensed there, and this liquid passing back into the column flows 
 over the perforated plates, continually giving up alcohol to' the steam passing through, 
 until when it reaches the bottom of the column it contains little alcohol but much 
 fusel oil. It then either passes through the pipes (d c) into the upper division of the 
 still, or is run off from the apparatus altogether. The vapour not condensed in the 
 
SAVALLE'S APPARATUS. 
 
 905 
 
 dephlegmator goes first into a small chamber where a further small quantity of liquid 
 is separated, and goes into the column together with that from the dephlegmator ; the 
 vapour then passes into the condenser (F), where it is completely cooled. 
 
 A peculiarity in this apparatus is the automatic regulator (o), by which the ad- 
 mission of steam into the heating coils can be exactly controlled. The construction 
 of the column requires a certain pressure to prevail in the apparatus, which must be 
 
 FIG. 670. 
 
 obtained before the distillation will proceed. This pressure exercised by the alcoholic 
 vapour is naturally dependent upon the quantity of steam admitted to the heating 
 coils in the still. 
 
 In the construction of this regulator Savalle utilises the pressure prevailing in 
 the apparatus to control the admission of the steam. Besides the principal valve in 
 the steam pipe, a second one is inserted, the body of which (fig. 672) is of sufficient 
 width to allow the quantity of steam normally required to pass through when the 
 
906 
 
 ALCOHOL. 
 
 FIG. 672. 
 
 FIG. 671. 
 
 piston (fig. 673) is raised to half its maximum height. It is upon this 
 piston that the regulator (fig. 671) acts. The lower chamber of the 
 regulator (A), partially filled with water, communicates by the pipe (F) 
 with the interior of the second division of the still (fig. 670), so that 
 the pressure prevailing in the interior of the still is communicated to 
 the lower chamber (A) of the regulator, driving a corresponding quantity of 
 water up through an ascending pipe (B) into the upper chamber (B). In this 
 space is a large float (c), which rises and falls with the level of the 
 water in the chamber. At its highest part this float supports a vertical 
 rod, which is fastened to the long arm of a lever (D), whilst the short 
 arm of the lever is connected by means of a screw with the piston of the 
 valve (E). 
 
 The action of the regulator is therefore evident. At the commence- 
 ment of the distillation the piston of the regulating valve is raised to 
 its highest point, and the admission of steam is regulated by the prin- 
 cipal valve. As soon as the pressure in the apparatus attains the proper 
 degree, the piston of the regulating valve is connected with the short 
 p arm of the lever at such a height as to only half close the opening of the 
 
 IG - b7<J< valve. If from any ca,use the pressure in the apparatus afterwards in- 
 creases, more water is driven from the lower chamber (A) of the regulator to the upper 
 
PURIFICATION OF SPIRIT. - 907 
 
 one (B), raising the float and with it the long arm of the lever, and depressing the short 
 arm ; the supply of steam is thus diminished or brought to a standstill for a time 
 until the normal pressure in the apparatus is restored. If, on the contrary, the pres- 
 sure in the apparatus is reduced through too great condensation of the vapour, the 
 pressure in the chamber A becomes insufficient to support an equal column of water in 
 the chamber B ; a portion of the water flows back into the chamber A ; the float sinks, 
 the piston in the regulating valve is raised, and more steam passes in from the boiler. 
 
 By means of this regulator, the work of the apparatus can be so equalised that the 
 quantity of distillate per hour does not vary more than a quart. This regularity of 
 production is most difficult to attain, but it is, however the most important part of the 
 rectification. It may be accepted that, of three parts of alcoholic vapour produced in 
 the still, one part should reach the condenser, whilst two parts should be previously 
 condensed and re- worked in the column. Every irregularity in the apparatus or 
 alteration in the inflow of steam for heating, affects the quantity of vapour reaching 
 the condenser. If too much steam be admitted, too much water vapour passes un- 
 condensed through the dephlegmator, and the product is weak, while the fusel oil 
 vapour being insufficiently condensed the distillate is impure. On the other hand, if 
 there be not enough steam in the heating pipes, insufficient alcoholic vapour is pro- 
 duced in the still, and the whole is condensed in the column and the dephlegmator ; 
 the flow of spirit is consequently interrupted, and the fuel used during the standstill 
 is wasted. All these inconveniences can be overcome by using the automatic 
 regulator. 
 
 CHEMICAL PUBIFICATION OF KAW SPIRIT. Many methods have been proposed for 
 the separation or destruction of the foreign constituents of raw spirit by chemical 
 agents. Most frequently the agents suggested have been oxidising substances, such 
 as chloride of lime, potassium chromate, ferric chloride, and cupric salts, which decom- 
 pose alcohol more readily than the more stable foreign bodies. Compounds are thus 
 produced from the alcohol, many of which are distinguished for their aroma, and the 
 smell of these can cover the fusel oil, although it is not separated. The alkalies 
 potash, soda, and lime and potassium carbonate can combine with certain mal- 
 odorous acids ; probably also the ethers of many acids are broken up by combination 
 with the acids, and aldehyd may be partially decomposed ; but amylic and similar 
 alcohols are never separated. The only tolerably effective method is filtration of the 
 spirit, diluted to about 50 per cent, strength, through wood charcoal, and this is 
 carried out in all well-conducted German distilleries. 
 
 For this purpose a filter battery is used, essentially similar in construction to that 
 used in a sugar refinery (see SUGAR). Each separate filter is covered with freshly 
 burnt charcoal, and then filled with the dilute spirit. After passing through the first 
 filter it flows through the others, and is then ready for rectification. When the ab- 
 sorbent action of the charcoal is exhausted, the spirit is allowed to run off at the foot 
 of the filter and steam is admitted, which vapourises any alcohol remaining in the 
 charcoal, together with many other substances absorbed by it, and carries them for- 
 ward into a condenser connected with the filter. The charcoal is then carbonised in 
 iron retorts and can again be used. 
 
 EXTRACTION OF ALCOHOL FROM WINE, BEER, ETC. When there is an excessive pro- 
 duction of wine or cider or the quality is inferior, the alcohol it contains may be profit- 
 ably extracted and a better price obtained for it in the more portable form of spirit 
 than its natural condition. Beer that is turning sour or is otherwise deteriorated may 
 also be treated in the same way. This is the object of the distillation of wine, which 
 is carried on largely in the south of France, and is there an important branch of 
 industry, though the extent to which it is practised varies from year to year according 
 to the quantity of wine produced. 
 
 In the purchase of these liquids, apart from the amount of alcohol they contain, 
 the distiller has to take into consideration the special character of the raw material, 
 especially its aroma or bouquet, as this sometimes imparts to the spirit a special value. 
 Thus, the Montpellier spirit, having a strength of 84-4, prepared from ordinary wine, 
 is valued at from 3d. to 6d. per gallon more than well-rectified spirit having a strength 
 of 89 0> 6, prepared from molasses, grain, or potatoes. Still greater is the difference 
 in value in the finer kinds of brandy and the spirit used in the manufacture of brandy. 
 Thus whilst beet spirit of 90 is of less value than spirit of wine of the same strength, 
 and that from grape residues of less value than either, the brandy of Armagnac and 
 of Cognac of 60 alcoholic strength is worth twice to even six times as much, accord- 
 ing to its age, aroma, and delicacy of flavour. In the article on WINE it is pointed 
 out that red, white, or slightly coloured wines can be prepared at will from red 
 grapes, according as the must is allowed to ferment in contact with the skins of the 
 grapes or not. White wines prepared from red grapes are the most esteemed for the 
 brandy manufacture, as they contain in the smallest proportion the constituents of 
 
908 ALCOHOL. 
 
 the skins, which would impart to the brandy prepared from wine containing them an 
 unpleasant flavour, and reduce the value of the spirit prepared from the grape 
 residues. In brandy,- as in wine, various volatile substances occur, part of which are 
 probably first formed during the distillation; those of one class are characterised 
 by an unpleasant odour, and originate from the constituents of the skin; those of 
 the other class have an agreeable smell and originate in the fleshy portion of the 
 berries. 
 
 In Germany the distillation of wine is not very prevalent, as there is not any over- 
 production of low-priced wines such as occurs in France. In the Ehine provinces occa- 
 sional experiments have been made to produce Cognac from wine, but at no time to 
 any great extent. In France, however, the case is quite different, for there the distil- 
 lation of wine yields by far the greater part of the spirit manufactured. 
 
 TREATMENT OF SACCHARINE MATERIALS. In operating upon saccharine materials, a 
 further process is requisite in order to obtain alcohol : viz. the conversion of the sugar 
 into alcohol by fermentation. This operation is conducted in various ways, either by 
 spontaneous fermentation or by the addition of yeast. The starting point of this 
 operation is almost without exception the yeast produced in brewing, but in the 
 manufacture of spirit, a sufficient supply of brewer's yeast cannot always be obtained, 
 and therefore the manufacturer is under the necessity of producing yeast for the pur- 
 pose. This is done in two different ways. 
 
 According to one method, the saccharine liquid is mixed with enough yeast to set 
 up fermentation, and when this has advanced to a considerable extent, the liquid is 
 divided into two portions, one of which is allowed to continue fermenting while the 
 other is mixed with a fresh quantity of the liquid to be fermented. When the fer- 
 mentation is sufficiently far advanced in this second portion of liquid, it is divided 
 into two parts and one portion mixed with fresh liquid, while the other is allowed to 
 continue fermenting. This is continued with fresh quantities of the liquid, until the 
 whole is brought into a state of fermentation. 
 
 According to the other method, a concentrated saccharine liquid is prepared by 
 infusing malt with warm water ; when cold it is mixed with beer yeast, and. left 
 until vigorous fermentation has commenced ; meanwtiile the liquid to be fer- 
 mented is made ready by the time the fermentation is at its height. The yeast is 
 then divided, and a portion used to set up fermentation in the liquid that is to bo 
 fermented, while the rest is preserved for the production of a further supply of yeast 
 by mixing it with a fresh quantity of malt infusion. This is again divided into two 
 portions and used as before. 
 
 Both these methods differ only in so far that, in the first mentioned, the yeast in- 
 tended for setting up the fermentation is produced in the bulk of the liquid to be fer- 
 mented, while in the other a special liquor must be prepared for the purposes of pro- 
 ducing the yeast. The latter method has the disadvantage that since the yeast 
 remains for some time exposed to the atmosphere, acidification takes place by the 
 formation of acetic acid and lactic acid, in consequence of the development of other 
 forms of fermentation besides alcoholic fermentation, and in this way loss of material 
 arises. It is therefore necessary to exercise great care in the production of the yeast. 
 During the time that elapses before it can be mixed with a fresh quantity of malt in- 
 fusion, it should be kept carefully covered to prevent contact with atmospheric air, 
 and also cooled to a low temperature by enclosing it in sheet-iron boxes, immersed in 
 ice-cold water. If, in spite of these precautions, the yeast shows signs of any con- 
 siderable formation of acid, which is best ascertained by the taste, it is advisable to 
 throw away the whole and prepare a fresh supply with beer yeast. 
 
 In the treatment of beet sugar and molasses, which is now largely carried out, 
 a further point has to be observed. The material is always alkaline, in consequence 
 of the presence of a compound of sugar with alkalies or lime ; and since yeast does 
 not cause fermentation in alkaline liquids, the molasses must be mixed with enough 
 acid before the addition of the yeast to neutralise the alkali. Sulphuric acid is gener- 
 ally used for this purpose, and the state of neutralisation is judged of by means of blue 
 litmus paper, which should be only feebly reddened by the liquid. Excess of acid 
 must be equally avoided. 
 
 A similar addition of sulphuric acid is made in operating upon beet- root juice, not 
 because it is alkaline, but because it has been found by experience that the fermenta- 
 tion goes on in this material with very much greater regularity when it is feebly 
 acid than when it is neutral. If the addition of acid is omitted, the fermentation 
 goes on very irregularly, the liquid assumes a slimy character, and the evolution 
 of carbonic dioxide causes a violent frothing, by which considerable loss is occasioned. 
 On the contrary, the fermentation proceeds quite uniformly when from one to two 
 parts of sulphuric acid are added to 1 000 parts of beet-root juice. The explanation 
 of the influence thus exercised by sulphuric acid has not been ascertained with cer- 
 
MANUFACTURE OF SPIRIT. . 909 
 
 tainty. but it has been stated that the acid precipitates a black ferment, though the 
 further examination of this substance has not been undertaken. 
 
 In molasses as well as in beet roots the sugar is cane sugar, which is not directly 
 capable of undergoing fermentation. However, by heating cane sugar with a small 
 quantity of sulphuric acid to a temperature of 70, it can be converted into a mixture 
 of equal molecules of grape sugar and fruit sugar in a yery short time, and both these 
 kinds of sugar are susceptible of fermentation. Some manufacturers carry out this 
 operation by heating the acidified solution of molasses up to- the boiling point ; but 
 this is not necessary, since yeast has the power of converting cane sugar rapidly into 
 grape sugar. 
 
 The progress of the fermentation is regulated by the amount of yeast, and by the 
 temperature of the liquid. If it is required to take place rapidly, the saccharine 
 liquid is mixed with yeast at a temperature of about 20 or 22, and when it is re- 
 quired to take place slowly, a temperature of 17 or 18 is necessary. The quantity 
 of yeast added is also of influence upon the rate of fermentation, but no general rule 
 can be laid down, since it is also affected by a number of other conditions. The tem- 
 perature of the place where the fermentation is conducted, the extent of surface ex- 
 posed, the conductibility and radiating capacity of the vessel in which the fermenting 
 liquid is contained, the variations of temperature caused by changes of atmospheric 
 conditions, the quality of the saccharine solution, and its relative susceptibility to fer- 
 mentation, as well as the quality of the yeast, are all circumstances which, together 
 with others, influence to some extent the fermentation, and must therefore be taken 
 into consideration. 
 
 When the fermentation is completed, the liquor is treated in the same manner 
 that has been already described in the case of the distillation of alcoholic liquids. 
 
 Fermentation of Fruit. All kinds of fruit can be made to yield alcoholic bever- 
 ages, each having a peculiar aroma. One of the most agreeable of these is kir sch- 
 wa sser, the best qualities of which are produced in the Black Forest, but it is also 
 prepared in many districts in France and Switzerland. Its preparation is simple. 
 The sound ripe cherries are plucked and^freed from their stalks, and after slightly 
 crushing the entire mass, about one-fourth of the whole is removed in order to crush 
 the stones, and then again placed with the remainder. The kernels contain amyg- 
 dalin, which by decomposition is converted into oil of bitter almonds, hydrocyanic 
 acid and sugar, the first two imparting to the product a peculiar and agreeable aroma. 
 According to the degree to which it is desired that this aroma should be predomi- 
 nant, the proportion of crushed kernels must be varied, the taste and smell of kirsch- 
 wasser becoming more intense the larger the proportion of kernels crushed. The 
 pulpy mass passes gradually into fermentation. As soon as this is over the distil- 
 lation is proceeded with by forcing steam through the pulp, and collecting the distillate 
 as long as it is sufficiently strong. The after running is collected separately, and added 
 to the next quantity of pulp to be distilled. 
 
 Manufacture of Alcohol from Sugar Beet. The production of alcohol from 
 the juice of the beet was first attempted by Dubrunfaut in 1824, but the manufacture 
 was very soon relinquished on account of the low price of spirits at that time. In 
 1837 a manufactory was established in Valenciennes for the working of beet molasses 
 for alcohol and potassium salts. Since 1845 the beet spirit manufacture in France 
 has increased considerably ; many sugar manufactories have been converted into dis- 
 tilleries, and in others arrangements exist for producing spirit or sugar, according as 
 the price of either may make its manufacture the most profitable. For the conver- 
 sion of a beet sugar manufactory into a distillery only the addition of fermenting vats 
 and distillatory apparatus is necessary, whilst the existing utensils, the beet wnshers, 
 raspers, juice presses, defecating pans, reservoirs, and piping, all are utilised. By the 
 addition of a column to the vacuum apparatus it can be easily converted into a dis- 
 tillatory apparatus. 
 
 The method of procedure, which is subject to many modifications, is in general as 
 follows : 
 
 The cold juice flowing from the press is heated to 20 in the defecation pan, passed 
 into the fermenting vat, and mixed with about 4 Ibs. of concentrated sulphuric acid 
 diluted with ten times its weight of water for every 220 gallons of juice. This 
 acidification converts the unfermentable cane sugar into glucose, and also prevents 
 the development of a peculiar ferment which induces a mucous fermentation. 
 
 In the first operation fermentation is started by the addition of beer yeast, and 
 the yeast is propagated by proper sowing. For a vat containing about 3,300 gallons 
 of juice 16 to 18 Ibs. of yeast are used, carefully distributed through 10 or 12 gallons 
 of water. In cold weather the fermentation is stimulated by warming the juice in the 
 fermenting vat, after the addition of the yeast, to a temperature of 21 to 22. The 
 fermenting vats, in order to protect the contents from cooling, are closed with covers 
 
910 ALCOHOL. 
 
 provided with a trap door, through which the fermentation can be observed. The 
 progress of the fermentation is controlled by testing with the saccharometer. Im- 
 mediately after the addition of the yeast to the juice the saccharometer indicates 13, 
 and the indication sinks gradually until the fermentation is ended, when it is constant 
 at 1 to 2. 
 
 The fermentation lasts from three to four days. By regularly filling two or three 
 vats daily, there will be altogether 8 or 10 vats required, so that one may always 
 be ready for filling and one in reserve. 
 
 When the fermentation in the first vat is concluded, tfie nearly clear contents are 
 drawn off for distillation. The yeast formed during the fermentation lies upon the 
 bottom, and is left in the vat, in order to set up the fermentation in the fresh juice 
 with which the vat is then filled. Besides the fresh yeast, however, there remains 
 also the old decomposed yeast, which favours the collection of a large quantity of 
 foreign ferments. One frequent result of this is an irregular progress of the fer- 
 mentation. Instead of the liquor entering quickly and regularly into alcoholic fer- 
 mentation, showing a regular rise in the temperature, there is frequently observed, in 
 consequence of the foreign ferment, only a slight evolution of carbonic anhydride, and 
 a slow rise of temperature, the liquor becoming continually more acid ; so that when 
 it is distilled only a small quantity of alcohol is obtained, and the wash contains much 
 acetic acid or lactic acid. It may also happen that the liquor suddenly enters into 
 energetic fermentation, forming a thick scum and foaming over the sides when the 
 vats are nob sufficiently capacious. 
 
 Whenever an irregularity of this kind takes place the yeast should be completely 
 removed, the vat washed with boiling water, then with milk of lime, and afterwards 
 with pure water, and fresh beer or pressed yeast used for the next lot of juice. It is 
 advisable always to avoid allowing the yeast to collect in the vat for any long time, 
 and to effect a partial renewal of it at each operation. 
 
 The wash from the beet roots, being mixed with the pressings, yields a fodder 
 having the same relation to the beet root used as. the potato refuse to potatoes. 
 In both cases the relative proportions of the constituents have been rendered more 
 suitable for feeding purposes ; the excess of sugar being separated from the beet 
 roots, as some of the starch is from the potatoes, while the whole of the albuminous 
 substances and mineral constituents are retained. The refuse from a beet-root dis- 
 tillery has therefore a very high agricultural value. 
 
 The only disadvantage attending its use arises from the large amount of water in 
 the spent wash, which is greater than in the juice of the beet root when in the extrac- 
 tion of the juice water is added as in the manufacture of sugar. This disadvantage 
 may however to some extent be obviated, and at the same time a complete extraction 
 of the juice may be secured by using spent wash instead of water. Further concen- 
 tration of the juice is effected by using coils or jacketed vessels for the steam used in 
 the distillation, in place of blowing it directly into the stills ; and further by attaching 
 to the distillatory apparatus a special rectifier for separating the water condensed, as 
 shown on p. 897. 
 
 The extraction of the juice is sometimes effected by a process of diffusion some- 
 what similar to that practised in the manufacture of sugar from beet root. This 
 method of extracting the juice however may be carried out for the purposes of spirit 
 manufacture with more simple apparatus that involves little cost in its erection. In 
 addition to the machine for cutting up the beet roots, it consists of a series of eight or 
 more wooden vats or tubs with perforated false bottoms. The bottom of each of these 
 vats is connected by means of a wooden pipe with the top of the next succeeding vat. 
 The vats are also fitted with wooden pipes for completely discharging the liquid con- 
 tents, and with steam pipes, by means of which steam can be blown into the pipes 
 connecting the vats. In carrying out this process, that part of the juice contained in 
 the cells ruptured in cutting up the beet roots is simply washed out, but the far greater 
 part contained in the cells which remain intact can only be obtained by passing through 
 the membrane of the cells by diffusion. The first and the eighth vats of a series, 
 communicating by moans of a pipe and a cock, are placed out of communication by 
 closing the cock! About 10 cwts. of beet-root slices are placed in the first vat, which 
 is then filled up with water. The second vat is then filled with slices. While the 
 water is flowing into the first vat, steam is passed in through the pipe by which the 
 first and second vats communicate. The water is thus heated, and comes upon the 
 slices in the second vat almost boiling, and thus disintegrating the cells facilitates the 
 process of diffusion. After some time the third vat is tilled with slices, and steam 
 pissed into the tube connecting the second vat with the third, while cold water is run 
 into the first vat and the liquid thus displaced from it into the second, where it is 
 heated by steam, passes hot into the third vat, while cold water is again run into the 
 first. In this way the whole of the vats are filled with slices and liquid, fresh water 
 
BEET HOOT SPIRIT. - 911 
 
 being always run into the first vat and the liquid heated by a jet of steam every time 
 it comes into contact with fresh slices. When all the vats are filled the contents of 
 the first vat are exhausted. Communication between the first and second vats is cut 
 off, the water run away from the bottom, the exhausted slices removed, and a fresh 
 supply put into the vat. On the other hand, the juice in the eighth vat contains 
 sufficient sugar for fermentation, and it is then drawn off. Fresh water is then run 
 into the second A r at so as to drive the contents of the seventh into the eighth, after 
 which the liquid in the eighth vat is heated by steam and driven into the first vat. 
 The second vat is then cleared out and refilled, water being run into the third, and 
 the second then yielding a fermentable liquor. The disadvantage of this method is the 
 loss of the spent wash, which is too bulky to be consumed by such a number of cattle 
 as can conveniently be kept in connection with the works, and^ it has been in many 
 places superseded by the method introduced by Champonnois, which admits of the 
 consumption of the spent wash and other residues. 
 
 By Champonnois's method the beet slices are placed in a vat having a false bottom, 
 and for every ton of beet 4 Ibs. of sulphuric acid, previously diluted with thirty 
 times its weight of water, are added, and then 50 gallons of boiling wash poured 
 on. Water is used only at the first stage of the operations ; afterwards the spent 
 wash from previous operations is used. After standing an hour the liquor is 
 drawn off and brought into a second vat filled with fresh slices, the first being 
 refilled with fresh wash. The maceration is continued in both vats for another hour, 
 when the liquor is run from the second vat into a third vat containing fresh slices, 
 and that in the first vat is transferred to the second. After being macerated with 
 the third quantity of slices, the liquor, which has been increased about one-fourth in 
 volume by the beet juice it has taken up, has become sufficiently rich in sugar to 
 be passed into one of three fermentation vats. The first vat, the beet in which has 
 already been exhausted with two quantities, is again filled with wash ; but this is 
 only left in contact during half an hour, to allow time for a portion of the adherent 
 liquor to drop through the perforated bottom before the residue is removed for fodder. 
 The operation is repeated so that the vat containing the fresh slices is filled with the 
 liquor which has been in contact during an hour with the slices in the next previous 
 vat, whilst the slices in that vat undergo a second maceration with the liquor from 
 the next previous. The liquor from the slices undergoing a third maceration before 
 it is passed into the next vat is heated in a special vessel nearly to boiling, in order 
 to exhaust the beet with which it comes into contact as much as possible. Each 
 quantity of beet slices undergoes consequently three successive exhaustions, in which 
 the greater portion of its sugar is exchanged for the constituents of the wash, and 
 thus a large part of the beet constituents are removed before the residue is used for 
 fodder. 
 
 The work can be considerably simplified by connecting the three vats by means of 
 pipes, in such a manner that a pipe passes from below the perforated bottom of one 
 vat over the top of the next. By the introduction of 
 a three-ways cock these pipes can then be used for 
 drawing off the finished liquor. A section of such a 
 cock in connection with the piping is represented in 
 fig. 674. With the position of the cock there shown, 
 the pipes (A and B) between the two vats are con- 
 nected; but. upon turning the cock one-fourth round 
 the perforation (a b) connecto the channels (A and c). 
 The connection being open between A and c the 
 liquor can be run off entirely ; but when it is open 
 between A and B it passes from one vat into the other 
 as soon as the level of the liquid is higher in the first 
 than in the second. 
 
 The fermentation is so carried on that a propor- 
 tionally large quantity of continually renewed yeast 
 acts upon the sugar at one time, by which means the 
 most perfect fermentation possible is produced in the y 
 
 shortest time. The juice begins to ferment at a tem- 
 perature of 16 to 17, which, as a rule, it attains without further attention, as tho 
 wash comes almost boiling on to the slices, and the first liquor drawn off has a tem- 
 perature of 40 to 50, which is reduced during the last maceration to the given 
 point. During the fermentation the temperature of the fermenting liquid should not 
 rise above 23 to 25. 
 
 Arrangement of a Beet Spirit Distillery. Figs. 675 and 676 are plans of a spirit 
 distillery, suited to the operations carried out in the agricultural districts of France, 
 according to the method of Champonnois. Fig. 675 is a ground plan, showing the 
 
912 
 
 ALCOHOL. 
 
 shed (A) into which the beet roots are brought through the large door from the pits, in 
 order to be cleansed in the washer (B), and made ready for the slicing machine (c), 
 both of which are set in motion by the horse mill (Q). The beet roots are cut into 
 thin slices and placed in one of the macerating vats (D D), and the exhausted slices 
 
 FIG. 675. 
 
 Fio. 676. 
 
 FIG. 677. 
 
 are then mixed with coarse fodder in the receivers (E B), and run upon a tramway to 
 the cattle stalls for consumption. The juice obtained by macerating the sliced beet 
 roots witli wash, is run first through an open and then through an underground 
 trough to the fermentation vats (H H, figs. 676 and 677). In the middle of the fer- 
 
BEET ROOT SPIRIT. 
 
 913 
 
 
 
 meriting room is a deep reservoir (i, fig. 675), into which the fermented liquor passes 
 from the fermentation vats, and from this it is raised by a pump into the two higher 
 reservoirs above, whence it can flow into the distilling apparatus (F G). The distillate 
 runs into a reservoir (L) in the store-room (K), which is separated by massive walls 
 from all the other rooms in the distillery. Here it is filled into casks ready for 
 transport. 
 
 Vertical and horizontal sections of the maceration vats are shown in figs. 678 and 
 679. In the lower part of these is a false bottom (h) perforated with holes, upon which 
 the slices of beet root rest. Above is another shelf (i), also perforated, by means of which 
 1 FIG. 678. 
 
 FIG. 679. 
 
 the wash and water to be used in the maceration are distributed over the beet root. 
 These liquors are run into the vats from special vessels placed at a higher elevation. 
 The vats are emptied by means of pipes (B c G) opening into the space below the lower 
 false bottom and controlled by a three-ways cock. Through these pipes ^the liquor 
 rises to the trough (G G), at the end of which is a pump, by which the liquor is raised to 
 the hiffher trough (D E), and then flows on to the fermentation vats. The exhausted 
 slices are removed from the maceration vats through openings (L L), on a level with 
 the false bottom. During the working, these openings are closed by strong doors 
 fastened by a screw, as shown in figs. 680 and 681. More detailed information 
 M to the method of obtaining the juice has been given under SUGAR. 
 
 FIG. 680. 
 
 FIG. 681. 
 
 The fermenting vats are sufficiently large to contain about 550 gallons. The 
 fermentation is started by running the first yield of 55 gallons of liquor from the 
 maceration vats into the fermentation vat, and adding to it about 10 Ibs. of beer 
 yeast suspended in water or in juice. Fermentation commences at once. After 
 
 3 ^ 
 
914 ALCOHOL. 
 
 standing an hour another 55 gallons of juice is obtained from the second maceration 
 vat, and this is run into the fermenting liquor. Fresh additions of juice are similarly 
 made every hour until the vat is full. 
 
 The full vat is allowed to stand twenty-four hours ; a cock is then opened near 
 the bottom, communicating with the second fermentation vat, into which half of the 
 liquor from the first one passes. As each fresh quantity is added hourly from the 
 maceration vat, it distributes itself equally between the two vats and passes into fer- 
 mentation. Twelve hours after the filling is ended, the principal fermentation is ex- 
 hausted. The connection between the two vats is then shut off; the liquor in the first 
 vat is allowed to stand for a further twenty-four hours for the after fermentation, 
 and is then ready for distillation ; and half of the contents of the second vat are 
 similarly run into a third. Whilst the after fermentation is going on in the first vat, the 
 second and third are being filled with fresh juice, and the liquor in the second vat is 
 then in its turn allowed to stand for the after fermentation. When once the work is 
 in operation, there is thus provided every morning : I. A vat containing perfectly 
 fermented liquor, which is distilled in the course of the day ; 2. Another in which 
 the after fermentation will be completed during the next twenty-four hours ; 3. A 
 third, in which fermentation has arrived at the same stage as the next previous one, 
 the contents of which will be divided and mixed with fresh juice. 
 
 The progress of the fermentation is examined with the thermometer and saccharo- 
 meter. The temperature of the liquor rises gradually from 16 or 17 to 22 to 25, 
 and at this point it remains constant during the first fermentation, and then gradually 
 falls. The saccharometer indication is lower in proportion as the fermentation of the 
 sugar progresses. 
 
 Four fermenting vats are always worked together. In emptying the one in which 
 the liquor is ready for distillation, the precaution is taken not to draw off the whole 
 of the liquor, a small quantity about 100 gallons being left. During the fermenta- 
 tion, the inactive and exhausted portions of the yeast are deposited at the bottom of 
 the vat together with impurities from the jliice. These are now stirred up with the 
 last portion of the liquor, and the whole run off into a special vessel, in order to bring 
 it immediately into the distilling apparatus. This is done because the impurities 
 would otherwise be deposited upon the plates of the column, and contaminate them. 
 Being submitted to continued boiling during the distillation, these substances, in con- 
 sequence of the amount of albumin they contain, can only increase the value of the residue. 
 They are therefore left in the wash, and when used in the maceration of the slices of 
 beet are retained by them as in a filter. After the separation of these deposits, each 
 fermenting vat undergoes a carefulpurification before it is again used in order to pre- 
 vent as far as possible the accumulation of foreign ferments. It is further very ad- 
 vantageous if every evening, after the work is finished, all the maceration vats are 
 emptied and perfectly cleansed, since the liquor remaining in contact with the slices 
 frequently becomes slimy during the night, and then interferes with the normal pro- 
 gress of the fermentation. The liquor last drawn off from the slices, but not yet rich 
 enough in sugar, is left all night in the boiler, in order that in the morning it may be 
 heated and passed boiling on to the fresh slices. This inconvenience is avoided in 
 those establishments where the work is carried on day and night. 
 
 If in obtaining the beet juice a larger quantity of wash be used about double the 
 quantity of the juice to be obtained the slices can be exhausted at a lower tempera- 
 ture. The re-heating of the juice can thus be dispensed with ; or its temperature 
 may even be lowered, and the excess of heat used to warm the already fermented liquor. 
 The liquor thus obtained is less concentrated, but as it contains a smaller quantity of 
 those substances that are dissolved at a high temperature, it is purer, and the fer- 
 mentation goes on more easily and regularly, and it is not liable to so many accidents 
 through acetic, lactic, and other fermentations. Champonnois has so far modified his 
 method that at present he uses double the quantity of wash at a temperature of 70. 
 For cooling the wash which comes boiling hot from the distill ing apparatus, a cooler is 
 introduced between the condenser and the dephlegmator, which has essentially the 
 construction of the English condenser represented on p. 899. The fermented liquor 
 to be distilled flows first from the reservoir into the condenser of the apparatus, in 
 order that all alcohol vapour may be condensed. Becoming somewhat heated, it 
 passes then into the outer portion of the cooling apparatus, whilst the boiling wash 
 circulates through the worm, by which means the temperature of the wash is reduced 
 to about 70, while that of the liquor to be distilled is raised to 55 or 60. 
 
 The distillation is carried out with the column and double still apparatus, in such 
 a manner that one still can be emptied every hour, its capacity corresponding exactly 
 with that of one of the maceration vats. 
 
 Use of the Residues. In a working day of ten hours about 4,000 Ibs. of exhausted 
 slices are produced. These are at once removed to the cattle stalls and mixed with 
 
BEET ROOT SPIRIT. 915 
 
 oat. rye, or barley straw, or chopped straw, hay or clover, in such proportions as to 
 give three volumes of dry fodder for every volume of wet residue. When a quantity 
 of this has been prepared, it is stored up in large wooden chests or pits with cemented 
 brickwork sides. The wash absorbed by the beet slices moistens the dry substance ; 
 it rapidly becomes heated, and fermentation of its constituents takes place. This 
 goes on during thirty-six hours, when the previously hard, dry mass becomes com- 
 pletely softened and uniformly moist, and acquires a pleasant aromatic vinous smell. 
 In this condition the fodder is acceptable to all kinds of cattle. 
 
 This fodder has a considerably higher value than the pressings obtained from the 
 sugar factories, because it contains all the nutritive constituents of the beet root, 
 whilst in the sugar factories a large portion passes into the defecation and saturation 
 slime, another portion is absorbed by the animal charcoal, and lastly the principal 
 part goes into the molasses and is thus lost as fodder. 
 
 The high value of the refuse adapts this method for agricultural requirements, and 
 it has been widely adopted in France. The spirit manufacture is there, as in the 
 German potato spirit factories, looked upon as an economic means of providing fodder, 
 and the operations are regulated by the requirements of the cattle. As a partial al- 
 teration of the sugar has not here the importance it has in the sugar manufacture, 
 the season of work may be extended over a far longer time ; usually it lasts from the 
 beginning of October to the beginning of May ; consequently, during the whole of the 
 time that fresh fodder is scarce. This use of the beet root has the further advantage 
 that less consideration has to be given to the essential condition of the sugar factories, 
 the highest possible amount of cry stalli sable sugar and the least possible non-saccharine 
 matter. The beet roots for the distillery can therefore be cultivated with fresh 
 stable manure, and the largest quantity obtained that a given surface will yield. 
 
 Leplay Dubrunfaut's Method. In the year 1 854, Dubrunfaut published the obser- 
 vation that beet roots cut into slices can undergo alcoholic fermentation when they 
 are placed in a fermented or fermenting liquid ; a maceration and a diffusion process 
 go on simultaneously, the alcohol formed occurring both in the beet and the surround- 
 ing liquor. Upon this observation he based a new industry, which was carried out in 
 the following manner : 
 
 At the commencement of the operation a quantity of beet juice is provided, either 
 by pressure or maceration, equal to double the quantity of beet roots to be worked up 
 on the first day. 1 ,000 parts of juice are mixed with 2 parts of sulphuric acid, 
 heated to 20, and placed with some yeast in a vat. As soon as the fermentation be- 
 comes lively, a large cylinder, made like a sieve of perforated sheet iron, is let down 
 into the liquid, and this is filled with slices of beet, l inch wide and % inch thick, 
 previously acidified with 3 parts of sulphuric acid to 1,000 parts of beet. After the 
 introduction of the slices, the temperature of the fermenting liquor must be kept at 
 20 to 24. 
 
 The fermentation of the juice appears then to be propagated in the inner tissue of 
 the beet, since it is found that after the lapse of twelve to twenty-four hours, the cells 
 contain alcohol and no sugar. But it is quite likely, from what is known of the 
 action of ferments, that this fermentation of the juice within the cell is only an ap- 
 parent one. Every fermentation requires the direct contact of the sugar with the 
 ferment. But since the fungus cannot penetrate into the separate cells of the beet 
 roots, it is not probable that fermentation takes place within the cell. The more pro- 
 bable explanation is that in the fermenting liquid there is less sugar than in the beet, 
 so that a process of diffusion is set up. The particles of sugar are drawn out from 
 the beet roots and pass into the liquor, where they are at once decomposed by fer- 
 mentation, so that gradually all the sugar passes out of the cells. On the other hand 
 the alcohol makes its way into the cells, and this process of diffusion goes on until 
 the proportion of alcohol in the cells equals that in the surrounding liquid. 
 
 After the fermentation is ended the sieve cylinder is withdrawn, and when the 
 greater part of the liquor has drained off" through the perforated bottom of the sieve, 
 the beet slices are submitted to distillation. 
 
 For this distillation a special apparatus is used. The beet slices are placed in 
 shallow perforated iron dishes, having an opening through the middle, through which 
 the dishes can be piled one above another upon a movable iron rod. The lowest dish 
 rests upon the foot of the rod ; this is filled with fermented beet slices, and then a 
 second empty dish is placed above it and filled, and this is repeated until a pile of 
 
 dishes, 10 feet high, is formed. The upper part of the iron rod is then hung from a 
 pulley, and swung into a cylinder of the distilling apparatus, about 4 feet wide, the 
 cylinder being then hermetically closed by a cover. In the upper part of the cylinder 
 
 there is an escape pipe, connected with a rectifier and a condenser, and steam is 
 passed in through a. pipe at the lower part so as to heat the beet slices ; this converts 
 the alcohol into vapour, whioh escapes into the rectifier. 
 
 3 a 2 
 
916 ALCOHOL. 
 
 Immediately after the removal of the beet slices from the fermenting vat, a fresh 
 cylinder full is sunk into the liquid, and the fermentation can be thus carried on for a 
 period of a month, fresh slices being supplied as needed. 
 
 During the fermentation, the volume of the juice that passes out from the beet, 
 slices is greater than that of the fermented liquor which is absorbed. At each filling 
 of the distilling apparatus, therefore, sufficient liquor is removed from the fermenting 
 vat to prevent an overflow upon the immersion of a fresh sieve full of beet slices. 
 This liquor is brought into the distilling apparatus together with the fermented slices. 
 Three stills are advantageously used connected with one another, and with the recti- 
 fier. At the commencement of the operation they are each filled with freshly fer- 
 mented beet and a corresponding quantity of juice. Steam is then admitted to the 
 first apparatus, and communication opened with the condenser. At first, and so long 
 as the upper layers act as a dephlegmator to the vapour, a distillate rich in alcohol is 
 obtained ; but in proportion as the upper layers become heated, the distillate becomes 
 weaker. The direct communication with the condenser is shut off, and the vapour 
 passes into the second cylinder, where, coming into contact with the cold liquor, the 
 greater part is at first condensed. Gradually the liquor and the lower dishes become 
 heated, and the vapour that is then formed is strong in alcohol and is passed into the 
 condenser. 
 
 By this time, the contents of the first cylinder have been completely freed from 
 alcohol. The steam is therefore shut off from it and admitted directly into the second 
 cylinder, which is set in communication with the third. Meanwhile, the first cylinder 
 is being emptied and filled with fresh slices, so that by the time the distillation of the 
 second cylinder is finished, the third can be connected with the freshly filled first 
 cylinder and the operation made continuous. 
 
 It is essential for the success of this method, that the presence of all foreign fer- 
 ments should be avoided. According to experience this is best effected by the addition 
 of sufficient sulphuric acid to represent 2 parts of acid to 1,000 of liquid. In the 
 normal course of the fermentation, the acidity of the juice is always somewhat less 
 than might be expected from the quantity of sulphuric acid added, and Leplay was of 
 opinion that this neutralisation was due to ammonia or some other alkaline substances 
 formed during the fermentation. This, however, is not the case, and it is more pro- 
 bable that the partial neutralisation is due to the decomposition by the sulphuric acid 
 of the pectic salts, which occur in considerable quantity in beet root, with the forma- 
 tion of insoluble pectic acid. 
 
 The slices remaining after the fermentation amount to about 40 per cent, of the 
 weight of the beet root used. These form a fodder, containing a large quantity of 
 water, but it can be preserved for a long time pressed down in pits. The residuary 
 liquor is much diluted by the condensed steam, and is not usually used, although it 
 contains all the soluble constituents of the juice except the sugar. 
 
 Spirit from the Molasses of the Sugar Factory. In commerce three kinds 
 of molasses are met with, that from the colonial sugar factories, that from the sugar 
 refineries, and that from the beet-raw sugar factories. Of these, only the last is of 
 importance in the European spirit manufacture. The first is used in the colonies 
 either alone or with an addition of cane juice, and especially that from damaged canes, 
 for conversion into rum by fermentation and distillation. The portion of colonial 
 molasses coming into the European market is, in consequence of its value as a food 
 material^ too high in price to be worked for spirit. The refinery molasses is more 
 frequently used for the sophistication of West Indian molasses, and only the most 
 inferior portion of it is used with the raw sugar molasses in the distillery. 
 
 In the concentrated condition, as yielded by the sugar factories, molasses has not 
 the power of fermentation ; it therefore has to be diluted with water. This is best 
 done by tilting the cask with the bunghole opened over a vessel filled with boiling 
 water. The thick syrup becomes liquefied by the heat and runs into the water, with 
 which it is mixed by stirring with a spatula. After the greater part of the molasses 
 has run out of the cask, steam is passed into the bunghole ; and, condensing on the 
 cold sides, liquefies and washes away the syrup still adhering, thus effecting at the 
 same time a purification of the cask. 
 
 The hot concentrated solution of molasses is mixed with sufficient cold water to 
 indicate 20 by the saccharometer. Sulphuric acid is then added until any alkalinity 
 due to the presence of sugar lime, alkali, etc., disappears, and the liquor clearly 
 reddens blue litmus paper. 
 
 The temperature of the concentrated liquor is regulated so that after the addition 
 of the cold water required it falls to about 22 : in winter one or two degrees higher,, 
 in summer as much lower. Fermentation is then induced in the liquor by the addition 
 of the pressed yeast, or in German factories more frequently by malt yeast. The fermen- 
 tation commences quickly and is recognised by the burst ing of small bubbles of carbonic 
 
SPIRIT FROM MOLASSES. . 917 
 
 acid at the sides of the vat ; gradually the evolution uf carbonic acid spreads over the 
 entire surface and a white scum is formed. If the scum be so strong that the liquor 
 threatens to rise over the side of the vat, water containing a little soft soap in solution 
 is poured over the scum, which generally causes it to collapse, and at the same time 
 the evolution of carbonic acid subsides. During the progress of the fermentation, the 
 temperature of the liquor rises while its density becomes less. The rise of tempera- 
 ture and the saccharometer indications should be observed morning and evening and 
 noted. 
 
 The fermentation of the molasses is ended when the scum disappears from the 
 surface, and the evolution of carbonic acid ceases. The distillation should be commenced 
 at once in order to prevent any secondary changes and the formation of acids in the 
 fermented liquor. 
 
 The following observations were made in a well-conducted molasses distillery 
 during the progress of a fermentation. The fermenting vat had a diameter of 9| feet ; 
 the inside height was nearly 9^ feet, the height of the liquor (molasses of 20 S.) was 
 8 feet. The total contents was about 5,750 gallons, representing upwards of 12,600 
 Ibs. of molasses of 75 S. (sp. gr. r357)j neutralised with sulphuric acid, and 176 Ibs. 
 of yeast added : 
 
 Succharometer 
 
 Degrees. Temperature. 
 
 At starting 20 22'25 
 
 Second day 18 24 
 
 Third day 12-6 30 
 
 Fourth day 6'6 3375 
 
 Fifth day 5-5 35 
 
 The fermented liquor yielded 6 '8 per cent, of pure alcohol, or about 3 gallons for 
 every 100 Ibs. of molasses. 
 
 During the fermentation a rise in the temperature of the liquor beyond 36 should 
 be avoided, as at a higher temperature a conversion of the alcohol formed into acetic 
 acid readily takes place. This is best done by commencing at a low temperature. 
 Should the fermentation notwithstanding become so vigorous as to threaten to ex- 
 ceed this temperature, the fermenting liquor can be passed into another vat previously 
 cooled with cold water, or run through a cooling apparatus. 
 
 The inconveniences of secondary fermentations may be produced by the use of bad 
 ferment. Besides the alcoholic fermentation, lactic fermentation is set up, and 
 also, by a special ferment, the so-called mucous fermentation, by the latter of which 
 the whole of the liquid is converted into an almost jelly-like mass. Moreover, when 
 putrefying yeast is used, the evolution of carbonic acid is accompanied by red-brown 
 vapours of hyponitrous acid, very irritating to the lungs, and arising from the 
 decomposition of nitrates, which are always present to some extent in molasses. 
 
 But care as to the ferment is only a partial remedy against the secondary fermen- 
 tations ; the most absolute cleanliness is requisite in all the vessels, and throughout 
 the whole building. Every fermenting vat after each fermentation should be most 
 carefully purified ; every trace of deposit that may be the carrier of foreign ferments 
 should be completely removed ; the entire space in which the vats are placed should 
 be regularly cleansed, ;md provided with a non-porous floor from which all liquids 
 rapidly drain off. Accidents to the fermentation are very frequently referable to 
 neglect in this respect. If, notwithstanding all precautions, the wrong fermentation is 
 induced, nothing can be done but to remove all the ferment, thoroughly purify all the 
 utensils, and commence again with fresh yeast. 
 
 Preservation of Yeast. Many attempts have been made to preserve yeast for a 
 longer time. It has been mixed with concentrated molasses, or, after pressing, dried 
 at a low temperature with an admixture of powdered wood charcoal or starch. These 
 methods are however of very doubtful utility. The death of a considerable portion 
 of the yeast, when kept for some time, cannot be prevented. Also during the drying, 
 unless great care is exercised the yeast i.s destroyed, whilst thousands of spores of 
 foreign ferments may be carried by the air to the yeast during the operation. The 
 preservation of yeast is however of less importance, because good pressed yeast can be 
 had almost daily in most places, and by the proper treatment of malt yeast the want 
 can always be supplied. 
 
 If the recovery of the potash salts contained in the molasses (see before) be com- 
 bined with the working for spirit, it is desirable that the spent wash should be ob- 
 tained in as concentrated a condition as possible, in order to lessen the cost of evapo- 
 ration. This is accomplished by a modification of the distilling apparatus. 
 
 The column of the second still of Derosne's apparatus is divided into two parts, 
 and it can then be so worked that only a small portion of the liquor from the con- 
 densed vapour flows back into the still, the bulk of it being rectified in a special still. 
 
918 
 
 ALCOHOL. 
 
 Such an arrangement is shown in fig. 682. The first still (A) communicates in the 
 ordinary way with the second (B), and this supports a comparatively low column (c), from 
 which the vapour passes through the pipe (D') into the third still (B')> with its column 
 
 FIG. 682. 
 
 (c'), and from thence through the pipe (E) into the dephlegmator (F), and the con- 
 denser (H). On the other hand, the liquor to be distilled runs from the reservoir 
 fixed at a higher elevation, into the condenser and thence into the dephlegmator, and 
 becoming thus heated, flows directly into the column (c) of the second still, without 
 passing through the third still (B') with its column (c'). The liquor which is con- 
 densed in the dephlegmator (F) on the contrary runs through a bent pipe (o) into the 
 column (c'), and passes in the opposite direction to the alcoholic vapour into the third 
 still (B'). This still is moderately heated by being placed over the draught from the 
 boiler furnace. From time to time, when it has become nearly filled with alcoholic 
 liquor collected in it, direct steam is admitted and the alcohol is distilled off ; the re- 
 maining liquor, which, besides water, contains the whole of the fusel oil condensed in 
 the column and in the dephlegmator, is run off through a pipe (B") at the bottom. 
 Another method is to run off the whole of the condensed liquor at B'', and rectify it in 
 a special apparatus. 
 
 TREATMENT OF AMYLACEOUS MATERIALS. In this case another operation has to be 
 carried out in addition to those already described, viz. the conversion of the starch 
 into fermentable substances. This is done essentially in the way described already, 
 in treating of dextrin and starch sugar (pp. 800 and 806), but with some slight modi- 
 fications. The conversion of starch takes place under the influence of the diastase 
 in malt, which determines the combination of starch with the elements of water, and 
 its partial conversion into grape sugar according to the equation : 
 
 Starch Grape sugar 
 
 C 6 H 10 5 + H 2 = C 6 H 12 8 
 
 According to recent observations, which appear to confirm previous statements, the 
 alteration of starch does not seem to be altogether so sharply defined, and it is 
 probable that there is produced with each molecule of grape sugar a molecule of 
 dextrin, so that the change would be expressed by the following equation : 
 
 Starch Dextrin Grape sugar 
 
 2C 6 H 10 5 + H 2 . C H 10 5 + C 6 H 12 6 
 
 Whether this is strictly correct or not must, however, bo determined by further 
 investigation. According to many observations the mode in which the alteration of 
 starch takes place depends essentially upon the temperature, in such a manner that at 
 all temperatures below 65 grape sugar is chiefly produced, while at temperatures 
 approaching 75, at which diastase is itself altered, chiefly dextrin is formed. Though 
 dextrin is not itself susceptible of fermentation, it does in the presence of sugar take 
 part in the fermentation, perhaps after having been converted into sugar ; but in all 
 
SPIRIT FROM STARCH. 919 
 
 BS the presence of a large amount of dextrin has the effect of retarding fermenta- 
 tion, and frequently this substance remains entirely unchanged by it. Consequently, 
 it is above all things essential to conduct the process of sacchariflcation in such a man- 
 ner that as much sugar as possible may be produced together with the least dextrin ; 
 and this object is sought to be attained by keeping the temperature of the liquid in 
 which the starch is being acted upon by diastase from rising above 65. At the same 
 time it is advisable not to reduce the temperature much below this point, because the 
 conversion of the starch takes place in that case too slowly. 
 
 By means of the diastase of malt all kinds of amylaceous materials can be sacchari- 
 fied, provided care be taken to provide for the diastase being brought into contact with 
 the whole of the starch. According to the nature of the particular material to be 
 operated upon with this object, various preparatory operations have therefore to be 
 carried out which will be subsequently described. 
 
 Although the spirit manufacturer and the beer brewer make use of diastase for the 
 same purpose, still it has a different significance for each. Malt is the material from 
 which the brewer prepares his beer, but with the spirit manufacturer it is rather the 
 means by which he attains the object of converting into sugar a large quantity of 
 starch over and above that actually contained in the malt itself. The brewer has, 
 however, to provide that the raw material he uses does not introduce into his saccha- 
 rine liquor substances \vhich would afterwards communicate to the beer an objection- 
 able flavour ; and since it is possible for him to employ a proportionately large quan- 
 tity of diastase to convert into sugar a proportionately small quantity of starch, the 
 malt he employs does not require to contain a large amount of diastase. In the pre- 
 paration of malt for the brewing of beer, therefore, the germination is stopped as 
 soon as a sufficient amount of diastase has been produced, and the shoots growing 
 out of the grain are carefully separated, because they would communicate to the beer 
 a disagreeable taste. At the same time, by drying and roasting the malt, it is sought 
 to produce certain substances which give to the beer either colour or aroma, and this 
 is done even at the risk of destroying a portion of the diastase in the malt. 
 
 None of these considerations have to be taken into account by the spirit manu- 
 facturer; in his case it is merely necessary to obtain a material possessing the highest 
 possible sugar-producing capability. This object is secured by allowing the malt to 
 germinate longer ; and while the brewer stops the germination as soon as the shoot 
 has attained the same length as the barleycorn itself, the malt used for making spirit 
 is allowed to grow until the shoot is almost twice as long. During the growth of the 
 shoot a large quantity of diastase is formed, not only in the grain but also in the 
 shoot ; and therefore the shoots are not removed, but' used together with the malted 
 grain. Moreover, since the kiln-drying of malt has the effect of destroying much of 
 the diastase, the spirit manufacturer uses the malt chiefly or almost entirely in the 
 green state. The production of malt should be so arranged that it can always be used 
 in the fresh green condition ; or, if it be desirable for any special reason to use kiln- 
 dried malt, it must be remembered above all things that the temperature at which 
 it is dried should be as low as possible so as to prevent the loss of diastase to the 
 utmost. 
 
 In conducting the operation of converting the starch into sugar technically termed 
 the mashing very different plans arc followed, according to the natiire of the mate- 
 rial operated upon and the custom of different localities. In England, for example, 
 this operation is conducted exactly in the same manner that the beer brewer makes 
 his infusion of malt. When the formation of sugar is completed the clear wort is 
 drawn off, the grains are washed out with water, and the wort is set to ferment. In 
 Germany a simpler procedure is adopted, and the entire liquid is fermented, together 
 with the grain, whatever the nature of the material operated upon. The apparatus 
 used for this purpose is essentially the same as that employed by the beer brewer, in 
 preparing wort (see p. 946), and the only difference is that the mash tuns have no 
 false bottom for the separation of the grains. 
 
 When the formation of sugar is at an end, it is above all things requisite to cool 
 the mash as rapidly as possible, and bring it to the temperature suitable for the fer- 
 mentation, because when the cooling takes place slowly lactic fermentation is apt to 
 take place. For effecting this object the same kind of apparatus is used that the 
 brewer employs for cooling wort, as subsequently described under the head of 'BEER 
 SKEWING ' (see p. 952) ; but while the brewer requires to clear his wort while it is 
 being cooled, the spirit manufacturer does not need to do this, and he is able therefore 
 to have recourse to other means by which the cooling of the mash is very much more 
 rapidly effected. 
 
 In places where there is abundance of water, and it can be obtained with little cost 
 for use in the works, it may be advantageously used for cooling the mash. For this 
 purpose the apparatus represented by fig. 683 may be employed. 
 
920 
 
 ALCOHOL. 
 
 FIG. 683. 
 
 It is constructed so that the liquid to be cooled is made to pass through very 
 narrow passages, while a stream of cold water is made to flow through similar adjoining 
 
 passages in such a manner as to lower 
 the temperature of the hot liquor. In 
 the apparatus represented in the draw- 
 ing, cold water is introduced through 
 the funnel (a) and after passing through 
 the channels escapes through the dis- 
 charge pipe (d). The hot liquor is in- 
 troduced through the funnel (/) and 
 escapes through the discharge pipe (i). 
 Various arrangements of this kind are 
 in use for this purpose. 
 
 The cooling apparatus most gener- 
 ally employed, and that which is in 
 most cases the best suited for the pur- 
 pose, consists of a shallow round vat 
 made of cast-iron plates, the joints of 
 which are made tight by caoutchouc 
 strips, and held together by screw bolts. 
 In the centre of the vat is a vertical 
 shaft carrying two horizontal arms, 
 upon which a number of iron blades 
 are fixed. The shaft is driven by a belt 
 and made to rotate slowly, so that the mash is stirred up in all directions by the iron 
 blades, and fresh portions are constantly brought into contact with the air, and in this 
 way the radiation of heat, as well as the evaporation of water, are very much facilitated. 
 To promote the cooling by these means still further care is taken to ensure constant 
 renewal of the air surrounding the vat, by fixing over the vertical shaft a second hollow 
 wheel which carries, immediately above the arms of. the other, two fans set at an angle. 
 This hollow wheel moves in the opposite direction to the other, and is driven at twice 
 the speed. The fans drive the air before them against the circulating mash, and in 
 this way, by using air alone, the mass is sufficiently cooled. 
 
 A .more efficient apparatus than that just described is the cooler constructed by 
 Siemens. It consists of a vertical iron cylinder in the axis of which is fitted a re- 
 volving wheel which carries a number of horizontal iron discs, and between each pair 
 of these discs there is a ring-shaped projection upon the side of the cylinder. During 
 the operation the wheel is driven at the rate of 600 to 800 revolutions per minute. 
 The hot mash flows through a tube upon the uppermost disc revolving with the wheel, 
 and is thus driven by centifrugal force against the side of the cylinder, collects there, 
 and flows along the ring-shaped projection downwards to the second disc, where it is 
 again forced against the side of the cylinder; then flows over the following ring- shaped 
 projection to the third disc, and so on until it arrives at the foot of the cylinder, where 
 it comes into contact with a strong blast of air forced against it by a fan fixed to the 
 upper part of the wheel that drives the air out of the cylinder with great force, so 
 that, since there is no other opening for the access of air, the air at the foot of the 
 cylinder is made to flow on with the same velocity. Therefore, while the mash is 
 spread out in thin layers upon the several discs, fresh air passes with great velocity 
 against its surface, and thus abstracts the heat so completely that in a very short space 
 of time the mash acquires a temperature several degrees below that of the surrounding 
 atmosphere. 
 
 It has recently been the practice to make frequent use of tubular coolers constructed 
 on the same principle as Liebig's condenser. An inclined tube, which, for the sake of 
 saving space, is bent several times backwards and forwards, is surrounded throughout 
 its entire length with a second wider tube. The hot mash is made to flow along the 
 inner tube in such a way that it rises gradually in* the tube until it fills it and flows 
 out at the upper end. Through the outer tube cold water is passed in a constant 
 stream, and in a direction opposite to the mash. The heat is thus transferred from 
 the mash to the water in the outer tube, and, according to the rate at which the mash 
 and water are made to flow through the tubes, a proportionate degree of cooling is 
 obtained, together with the advantage that by this means of cooling the mash is kept 
 out of contact with atmospheric air while it is being cooled. 
 
 Lastly, there is another kind of cooling apparatus to be mentioned which is fitted 
 in the mashing tun itself. To the stirring apparatus is attached a long tube extend- 
 ing from the upper part of the mash tun to the bottom, then bending upwards and 
 downwards several times, and terminating at the one end in a pan and at the other 
 
 
POTATO SPIRIT. 921 
 
 end over an open gutter outside the mash tun. When the mashing process is finished, 
 cold water is run into the pan so that it flows along the whole length, of the tube and 
 escapes heated into the gutter outside. Since the tube, together with the pan, is fixed 
 to the wheel-work, it can be kept in motion while the water is flowing through it, and 
 the cold water is thus brought everywhere into contact with the hot mash. This 
 apparatus has the advantage that it does away with the necessity for a separate cool- 
 ing vat ; but, on the other hand, it has the disadvantage that during the time required 
 for cooling, the mashing tun cannot be used, and not only has the mash to be cooled 
 with water, but also the entire apparatus. On account of the interruption thus caused 
 in the working, this method of cooling the mash is less suitable for large works than 
 for small ones. 
 
 Potato Spirit. In the German spirit industry the potato is by far the most im- 
 portant raw material. In order to make use of the refuse as fodder, which is specially 
 useful for fat and milk cattle, and to supply it to the farm at the lowest price, the 
 spirit manufacture has there become exclusively an agricultural business. 
 
 The potatoes are first purified in the potato washer described under ' STARCH ' (p. 
 764). In order to expose the starch to the action of malt diastase in the subsequent 
 saceharification it is necessary that the cells in which it is enclosed should be rup- 
 tured. By boiling the potatoes, the starch in the cells is caused to swell until the 
 cell membranes are stretched to the maximum of their elasticity. If the cells in this 
 state are subjected to pressure, the cell membranes burst and the starch is set free, 
 swollen and in a condition specially favourable for the formation of sugar. 
 
 The boiling of the potatoes is carried out in tall narrow cylinders, hermetically 
 closed, with the exception of an opening for the escape of condensed water. When the 
 cylinder is filled, steam is admitted to the lower part, which coming into contact with 
 the cold potatoes, is at first condensed, but gradually heats the entire mass until the 
 potatoes are sufficiently cooked. This is ascertained by testing some of the potatoes 
 lying in the upper part of the cylinder with an iron rod. The softened potatoes are 
 then allowed to fail through an opening in the steaming cylinder, and roll along an in- 
 clined surface and between two heavy smooth rotating iron rollers, where they are 
 crushed, after which they fall as a mealy mass into the mash tub placed beneath the 
 rollers. This already contains malt, stirred up in a little cold or lukewarm water, 
 in the proportion of 1 part of the best green malt to 15 or 16 parts of potatoes to 
 be worked, and the mixture is kept in constant motion by a stirring apparatus. 
 As the potatoes fall almost boiling into the malt liquor its temperature soon rises, and 
 this accelerates the process of saceharification. Solution of the starch is immediately 
 observable : the mash becomes continually thinner through the setting free of the 
 water of the cell juice, whilst the swollen starch is converted into sugar. When the 
 entire contents of the steaming cylinder have reached the mash tub, the temperature 
 of the mash will be from 50 to 60, or that most favourable to the formation of sugar. 
 This temperature is ensured by more or less heating the water in which the malt is 
 first stirred. In the colder parts of the year lukewarm water is used, but in hot 
 weather the coldest water possible is used. The principal point to be kept in view is 
 that the temperature of the mash shall not rise above 65, because above this the action 
 of the diastase is affected, so that a larger quantity of dextrin is formed, and above 75 
 the diastase is destroyed. Should the temperature of 60 not be reached, the stirrer 
 is set in motion more rapidly and a little steam is admitted, by which the proper 
 degree of heat is rapidly and certainly attained. 
 
 During the crushing of the potatoes the stirrer is kept continually in motion, so 
 as to mix thoroughly the whole of the potato mass with the malt liquor. After all 
 the potatoes have come into the mash tub, the stirrer is stopped, the mash tub is well 
 covered up, and the saceharification is allowed to go on quietly for an hour. The 
 stirrer is then again set in motion, and kept working vigorously for an hour or an hour 
 and a half. This has for its object the thorough mixture of the entire contents of the 
 mash tub, and by the bursting of any still unruptured cell membranes to set free the 
 enclosed starch and to bring it into contact with' the diastase. About two and a half 
 hours after the introduction of the potatoes the mashing process may be considered 
 ended. A drop of the mash liquid, after cooling, should not become blue when mixed 
 with solution of iodine, indicating that no more dissolved starch remains undecom- 
 posed. The finished mash can then at once be cooled. 
 
 This method of crushing the boiled potatoes has the disadvantage that it is not 
 possible to rupture all the cell membranes enclosing the starch, so that a correspond- 
 ing quantity of starch is kept from the action of the diastase. When this is the case, 
 even in the best managed distilleries the full yield of alcohol that might be expected 
 from the quantity of starch used can never be obtained. 
 
 This disadvantage appears to be completely overcome by a new method introduced 
 by Hollefreund. It consists in first steaming the potatoes under very high pressure, 
 
922 ALCOHOL. 
 
 and then suddenly, by the blowing off of the steam and the production of a vacuum, 
 bringing them to the mashing temperature, when they are crushed by a stirrer. The 
 apparatus used is a fixed strong sheet-iron cylinder, through the axis of which passes 
 a revolving shaft provided with arms. Above there is a manhole which can be her- 
 metically closed, through which the cylinder can be filled with potatoes, and the 
 cylinder is connected with a steam boiler by one pipe, and with a condenser and air 
 pump by another ; there is also a pipe for the introduction of the malt. The temperature 
 and pressure in the apparatus are shown by a thermometer and a manometer. When 
 the cylinder has been filled with potatoes steam is admitted, until the pressure corre- 
 sponds to a temperature of 125 to 130. After about forty minutes the stirrer is set 
 in motion, and for about twenty minutes makes from 44 to 48 revolutions per minute. 
 The connection with the steam boiler is then shut off, the steam present in the 
 cylinder is allowed to blow off, and connection is made with the condenser and the 
 air pump. In the vacuum a sudden and violent development of vapour takes place in 
 the interior of each cell through which the membranes are burst open from within. 
 This development of vapour causes a very rapid lowering of the temperature, so that 
 in about twenty minutes it falls to the mashing temperature of 60. Malt stirred up 
 in a small quantity of water is then admitted, in the proportion of 175 parts of green 
 malt to '2,500 parts of potatoes, and the stirrer is again set in motion, the ordinary 
 atmospheric pressure being restored by the opening of an air valve. The sacchai-ifi- 
 cation proceeds very rapidly in the completely disintegrated potato mass ; it com- 
 mences almost immediately, as can be observed in the liquefaction of the mass, and is 
 completed in about fifteen or twenty minutes. The mash so obtained differs essen- 
 tially from the mash obtained by the ordinary treatment. In the latter can always 
 be seen a quantity of potato fragments that have escaped the action of the crushing 
 rollers, and there can be detected by chemical examination a not inconsiderable quan- 
 tity of undecomposed starch. The mash obtained by Hollefreund's method is, on the 
 contrary, perfectly homogeneous ; only the husks of the malt and the broken potato 
 skins float about in it, whilst the quantity of undecomposed starch is reduced to a 
 minimum. It is therefore evident that from an equal quantity of material a higher 
 yield of spirits is obtained. Moreover, when, as in Germany, the volume of the fer- 
 menting mash is the object of taxation, the more perfect saccharification must result 
 in a saving of duty. The only disadvantage presented by this method is that the cost 
 of the apparatus and the amount of power required to work it are somewhat higher 
 than for the ordinary method. But the advantage gained amply covers the increased 
 capital used. 
 
 The fermentation of potato mash is almost exclusively effected by artificial yeast. 
 This is prepared by steeping in water in special vessels, at a temperature of 65 to 
 70, a mixture of potatoes with 2 or 3 per cent, of dried malt or green malt, or a 
 mixture of the two, or with an addition of unmalted grain. The mixture is usually 
 left to cool to the fermentation temperature, 18 to 22, and then pressed yeast or 
 common beer yeast is added. During the cooling a considerable quantity of lactic acid 
 is produced, which in the opinion of most distillers is of advantage, inasmuch as a 
 larger quantity of gluten is dissolved from the malt, and more material is thus pro- 
 vided for the formation of the yeast. If, however, the presence of an acid be required 
 for this purpose, it cannot be obtained in a more disadvantageous manner than by the 
 cultivation of the lactic ferment in a substance that is to be used for the manufacture 
 of the alcoholic yeast, as the lactic ferment would be afterwards added with it to the 
 mash. It is far preferable that the mixture should be cooled rapidly by placing it in 
 vessels filled with iced water, and the necessary acid supplied by adding a small quan- 
 tity of phosphoric acid. Pure phosphoric acid need not be used, but acid calcium 
 phosphate, the so-called superphosphate, may be added in the proportion of 1 to 2 per 
 cent, of the yeast materials. 
 
 When this mixture is in full fermentation it is thoroughly mixed by stirring, and 
 the greater part of it is removed for adding to the mash. The remainder, the mother 
 yeast, is kept for use, instead of yeast, in making the next lot. 
 
 The preparation of the artificial yeast has to be so regulated that the time at 
 which it enters upon the fullest fermentation always corresponds with.the time when 
 the mash has finished cooling and is ready to be run into the fermenting vats. 
 
 Respecting the preparation of artificial yeast many contradictory opinions exist, 
 almost every manufacturer having a special method. But there is really no mystery 
 in the preparation of artificial yeast, and it can be produced from the most diverse 
 materials, if only the conditions that govern the life of the yeast plant be kept in view. 
 
 The fermentation begins almost immediately after the addition of the yeast, and a 
 light white scum of bubbles of carbonic acid forms upon the surface. As it increases 
 the potato skins and refuse contained in the liquid rise to the top, and form a covering 
 that is soon in active movement. The carbonic acid collecting beneath it bursts 
 
CORN SPIRIT. . 923 
 
 through, and when the fermentation is in full operation the action is so violent that 
 portions of the mass are spirted upwards a distance of 2 or 3 feet. At the same time 
 the temperature of the liquid rises considerably. After a time the fermentation 
 slackens ; the carbonic acid is evolved more slowly, and finally ceases to be noticeable ; 
 the scum lies quietly above the still slowly fermenting liquid, and the temperature 
 falls. The fermentation is then considered to be ended. The time required for this 
 operation is to some extent under control. At a high temperature, and with a large 
 quantity of yeast, the fermentation can be completed in twenty-four hours ; but there 
 is then a danger that the fermentation may become so violent that the whole of the 
 liquid froths up and runs over. Usually the fermentation is so managed that it is 
 completed in three days, being carried on at a low temperature and with the addition 
 of a small quantity of good ferment. 
 
 Immediately after the fermentation is ended the distillation is proceeded with, in 
 order to avoid as much as possible any formation of acetic acid. 
 
 Corn Spirit. The working of grain barley, rye, wheat, oats, or maize is essen- 
 tially .similar to that of potatoes, certain modifications being required to suit the external 
 characters of the materials. In order to expose the starch contained in the grain it 
 requires to be crushed, but with the exception of maize it is not necessary to grind it 
 into flour. A mill is therefore used which only breaks the outer husk and crushes 
 the grain. Maize must be ground to a fine flour, because in it the layers of starch 
 grains are so compact that they are not otherwise sufficiently exposed to the action of 
 the diastase. The crushed grain is placed with the malt in the vats, about 1 part of 
 green malt to 6 of grouts, and first mixed with a little warm water by vigorous stir- 
 ring with a mechanical arrangement. As soon as the mass has become uniform hot 
 water is admitted, until the temperature of the entire mixture reaches 60 to 65. 
 The proportion of corn and water is so regulated that there are not more than 3 or 3| 
 parts of water to 1 part of dry substance, otherwise too great a volume of liquid would 
 be produced. If the water is not sufficient to bring the liquid to the proper mashing 
 temperature, a little steam is admitted, the heat of which easily raises it to the desired 
 point. The saccharification proceeds in the same manner as in the mashing of 
 potatoes. In maize a further preparation is requisite to render saccharification per- 
 fect. This consists in boiling the meal with water before the addition of the malt, 
 until the granules are completely softened. The boiling liquid is then cooled to the 
 mashing temperature of 60, in order to prevent the destruction of diastase, and this 
 is usually done by bringing the boiled mass into the cooling galley. The disinte- 
 gration and working of maize might be much facilitated by using Hollef round's appa- 
 ratus. The further treatment is essentially the same as that of the potato mash. 
 
 The yield of alcohol from these various materials is dependent' upon the amount of 
 starch they contain ; but as this varies, and since the manner of treatment during the 
 manufacture has great influence, no general rule with respect to it can be laid down. 
 Pure starch yields, under the most favourable conditions, half its weight of alcohol ; 
 but this yield is never obtained in practice. It may be assumed that on the average 
 only about 75 per cent, of the calculated amount of alcohol is obtained. By Holle- 
 freund's method the yield is better, and can without difficulty be brought up to 90 per 
 cent. According to Payen, 100 kilos of wheat groat yield on the average 29 to 30 
 litres of 95 per cent, alcohol ; rye yields 27 to 28 ; barley, oats, buckwheat, and maize 
 yield 20 to 25 ; and rice 32 to 36 litres. This small yield from maize, in proportion 
 to the amount of starch it contains, is doubtless due to very badly conducted manu- 
 facture. 
 
 In the manufacture of spirit from wheat, the grain is mixed with 15 per cent, of 
 malt suspended in 500 parts of water, and heated gradually to 72. After standing 
 four hours the wort is drawn off, and a second infusion of water at 50 is made. The 
 two worts are united, cooled to 20 J , and after they have been mixed with one-third or 
 one-fourth of the residue from the previous distillation, beer yeast is added. By the 
 addition of this residue fermentation is facilitated. A third infusion is made from 
 the husks with water at 70, and this weak wort is used instead of water in the next 
 mashing. 
 
 In England a mixture of 10 parts of dry malt, 80 parts of barley groats, and 10 
 parts of oat groats are mashed with the water in the mashing machine in such a way 
 that the resulting wort, after fermentation, shall contain 10 per cent, of its volume of 
 58 per cent, spirit. The wort is cooled in shallow cooling troughs, or in tubular 
 coolers, the pipes of which are arranged like the boiler pipes of a locomotive, and for easy 
 purification are constructed of copper. The exhausted husks or grains are used 
 for feeding cattle. For the fermentation only clear wort is used. The fermentation 
 tanks hold 40,000 gallons, and fermentation lasts six or seven days. No yeast is 
 manufactured, as this can be purchased more cheaply from the brewer. In the 
 
924 ALCOHOL. 
 
 English breweries a considerable excess of yeast is produced, and on account of the 
 brown colour, communicated to it by the strongly dried malt of the porter brewery, 
 it is not suitable for the baker's use. Each quarter of the above materials yields about 
 20 gallons of 58 per cent, spirit. 
 
 In Belgium and in some parts of North France the mash is prepared in sheet-iron 
 fermentation or mash vats, provided with a stirring apparatus and a perforated false 
 bottom. The mash vats are two-thirds filled with water at 80. The grain worked 
 consists of 33 parts of barley malt and 67 parts of ground rye. The proportions of 
 grain and water are so arranged that there are 3 parts of water to 1 of groats and 
 malt. After two hours' working, during which it becomes cooled, the wort is run off 
 by means of a tap at the bottom of the mash vat, and cold water admitted in its place. 
 The whole is united in the fermentation vat, and mixed with so much clear wash as 
 will bring up the proportion of liquid to 7 or 8 parts to 1 of grain, a little more grain 
 being used in the summer than in the winter. In the summer the fermentation is 
 conducted at the lowest possible temperature, and about 9 Ibs. of yeast are used to 
 500 gallons of liquor. In Belgium, on account of the local tax, the fermentation lasts 
 only twenty-four hours. From 100 parts of material, about 25 or 26 parts of 95 per 
 cent, spirit are obtained. 
 
 MANUFACTURE OF SPIRIT FROM VARIOUS OTHER MATERIALS. Besides the raw 
 materials already described as being used in the production of alcohol, various others 
 have been proposed, and some have been utilised. 
 
 Chestnuts and Acorns. These amylaceous materials can undoubtedly be used in 
 the spirit manufacture, where they can be collected in sufficient quantity and at a low 
 price. They only require to be steamed and crushed, and their starch am then be 
 converted into sugar by malt or sulphuric acid. 
 
 Asphodel. The bulb of this liliaceous plant is very rich in sugar, and in the 
 South of France and Algeria, where it grows wild abundantly, it can be used in the 
 spirit manufacture. Its cultivation, however, could scarcely be recommended, as the 
 bulb requires from three to five years to grow to any size. Alcohol has been obtained 
 from the bulbs by rasping them, pressing out the juice, treating the residue with 
 water and again pressing ; then inducing fermentation in the liquor by the addition of 
 yeast; 220 Ibs. of bulbs yielded 14 pints of pure alcohol. 
 
 Jerusalem Artichoke. The tubers of the Jerusalem artichoke (Helianthus tuberosus) 
 contain, besides a large quantity of sugar, another body, inulin, closely allied to 
 sugar and easily converted into it. The tubers are either rasped like beet roots, or 
 steamed and crushed like potatoes, saccharised with a small quantity of malt, and 
 then fermented like potato mash. The yield of alcohol amounts to 4| per cent, of the 
 weight of the tubers. The residue is good fodder for all kinds of cattle. As the cul- 
 tivation of this plant is extraordinarily easy, it is worthy of more attention in the 
 spirit manufacture than it receives at present. 
 
 Carrots contain a small quantity of sugar, and might be worked in a similar way 
 to beet root, but probably not remuneratively. 
 
 Sugar Grass (Sorghum saccharatum). At the time of ripening the sap through- 
 out the entire plant is rich in sugar: it could be obtained by crushing and maceration. 
 But as in temperate climates it is quite exceptional for this plant to ripen, it is of no 
 importance to the spirit industry, although for several years it has been warmly re- 
 commended. 
 
 THE REFUSE WATERS OF THE SPIRIT MANUFACTURE. The effluent water from 
 the raw spirit factories where the residues are utilised, may be considered as 
 harmless ; the impurities from the washing of the potatoes are easily collected in 
 settling pits ; further, the water used in cleaning the fermenting vats and distillatory 
 apparatus contains so little impurity, that it may be allowed to escape into the next 
 watercourse. But the case is different with the water from the beet spirit factories, 
 where the wash is not utilised or only partially so. Such water allowed to run into 
 the streams or ditches would rapidly become putrescent, and produce all the evils, 
 though in a higher degree, described under the sugar manufacture. Such impurities 
 are best separated by filtration through the soil, but when land is not available the 
 water maybe disinfected according to Suvern's method, described before (p. 860). 
 
 When the spirit manufacture is combined with arrangements for the carbonisation 
 of the residues, the gases issuing from the furnaces are no less offensive ; they fill the 
 air with repulsive smells, and give occasion to well-grounded complaints from the 
 neighbours. The stinking substances, products of the dry distillation, and of the im- 
 perfect combustion of non-fermentescible constituents of the molasses, can be partially 
 destroyed by maintaining behind the carbonising space a brightly burning fire, 
 through which the gases pass before they escape into the air, But this only imper- 
 fectly accomplishes the object, since, it being necessary to obtain a good draught for 
 
ALCOHOLIC BEVERAGES. 
 
 925 
 
 the oven, the gases necessarily pass too rapidly through the fire to be burnt to carbonic 
 acid, water, and nitrogen. The difficulty is overcome in an imperfect way by carry- 
 ing the vapour up through a tall chimney into a higher layer of the atmosphere, where 
 it becomes diluted with so much pure air that its smell is less obvious. 
 
 DISTILLATION OF WINE KESIDTJES. The residues left from the fermentation of 
 wine, consisting of the skins, pulp, and stalks of the grapes, are saturated with wine, 
 the alcohol in which can be recovered by distillation. For this purpose the simple 
 apparatus shown in fig. 684 is used. The still (A) is surrounded by the fire space (B), 
 and at a third of its height supports a perforated sheet-copper false bottom consisting 
 
 FIG. 684. 
 
 of two portions. The head of the still has a cover that can be hermetically closed, by 
 the removal of which the lower part of the still up to the false bottom can be filled 
 with water, the grape residues being placed on the false bottom. In the head of the 
 still is a pipe (D) connecting it with the worm (E). The worm lies in the cooling 
 vessel (F), which receives its supply of cold water at G. The fire (B) heats the water in 
 the lower part of the still to boiling ; the steam passes through the residues, con- 
 verts the alcohol contained therein into vapour, and carries it forward into the worm. 
 The heating is continued until only water passes over, the charring of the grape skins 
 being prevented by the false bottom. When the distillation is ended the still is 
 opened, the exhausted residue, which can be used for fodder, removed, and the still 
 freshly charged. Of course such an apparatus could be much improved by a little 
 modification. 
 
 PRODUCTION OF ALCOHOLIC BEVERAGES. 
 
 A variety of alcoholic liquors, prepared by fermenting the juice of grapes or other 
 kinds of fruit, are in common use as beverages in most countries under the name of 
 win e. Similar alcoholic liquids known under the name of beer, are prepared from 
 infusions of malted grain and sometimes also from honey, molasses, and other sac- 
 charine materials. In Tartary another kind of alcoholic liquid known as koumi ss is 
 prepared from mare's milk. 
 
 WINE. The art of making wine has been known from the remotest time of which 
 there is any record. Among the early inhabitants of India, the use of wine by the 
 Brahmins was prohibited, and only those not belonging to the caste were permitted 
 to indulge in it. In Egypt also only the common people were allowed to drink wine, 
 and the kings were required to abstain from it. The oldest records of the Israelites 
 show that wine was known to them, but the priests were not, allowed to drink 
 wine upon the days when they had religious duties to perform. Wine was also known 
 to the ancient Greeks, and it figures prominently even in their mythology. The 
 Greeks further communicated a knowledge of the use of wine to the Romans, 
 amongst whom women and children were by law prohibited from drinking wine, 
 though, in spite of this restriction, the consumption of wine by all classes of Romans 
 became very considerable at a later period. It was from the Romans that the Gauls 
 and Germans learnt the art of making wine. 
 
926 WINE. 
 
 The original habitat of the vine is said to be the ccrantry on the shores of tho 
 Black Sea and Caspian Sea, where at tho present time entire forests are overgrown 
 by gigantic vines. 
 
 It is remarkable that, on the discovery of America, the vine was found to be 
 flourishing there. More recently European varieties have been imported into that 
 continent. 
 
 Constituents of Wine. As regards composition, wine is to be regarded as more or 
 less diluted alcohol, which also contains a number of other substances that com- 
 municate to it specific characters, Sweet wine contains sugar that has not undergone 
 fermentation, and it is principally those kinds of wine that are made from highly 
 saccharine must which contain sugar. In must of that nature, the whole of the sugar 
 does not undergo conversion into alcohol, because fermentation is stopped as soon as 
 a certain amount of alcohol has been formed. The sweetness of wine may sometimes 
 be due to the presence of a large amount of glycerin. Sour wine contains a large 
 amount of free acid, but the sour taste of wine is influenced by other circumstances 
 besides the amount of free acids it contains. A wine containing comparatively 
 little acid may taste more sour than another kind of wine containing more acid, 
 provided it also contains a large amount of alcohol or glycerin, both of which mask 
 the sour taste. 
 
 The strength of wine depends upon and is proportionate to the amount of alcohol 
 it contains. Some wine contains, in addition to a large amount of alcohol, considerable 
 proportions of the homologues of alcohol, viz., propyl alcohol, butyl alcohol, amyl 
 alcohol, and the corresponding aldehydes. According to Maumene, the average com- 
 position of wine may be represented as follows : 
 
 Water from 89 -1 to 90'0 
 
 Alcohol 7'9 8-0 
 
 Alcohol homologues . . . \ 
 
 Ethers .... 
 
 Ethereal oil ... 3'0 2*0 
 
 Grape sugar ... I 
 
 Glycerin . 
 
 Some of these substances were contained in the must, but others, such as the 
 alcohol and its homologues, as well as the ethers and aldehydes, glycerin, succinic acid, 
 lactic acid, acetic acid, and carbonic acid, are products resulting from the fermentation. 
 Lately an alkaloid has been detected in wine, as well as trimethylamine. 
 
 The proportion of solid residue left on evaporating wine to dryness at a steam heat 
 varies very much according to the kind of wine ; it may amount to only 1 per cent, 
 or be as much as 20 per cent. Generally it ranges from 3 to 5 per cent., and it is 
 only in the sweet wines which contain sugar that the extract amounts to more than 
 5 per cent. 
 
 The amount of alcohol in wine depends upon the proportion of sugar in the must 
 before fermentation, and it varies considerably, as will be seen from the following 
 table, which gives the average alcoholic contents of different kinds of wine : 
 
 Port . . . . . . . from 18 to 20 per cent. 
 
 Madeira . . . . 18 ,, 19 
 
 Teneriffe . . . . / . ,16 18>- 
 
 Greek 
 
 Lachryma Chri u ti 
 Tokay . . ' : , 
 
 15 18 
 12 16 
 12 15 
 10 20 
 10 13 
 10 14 
 9 ,, 12 
 9 11 
 9 10 
 
 Lunel 
 Calif orni an 
 Bordeaux 
 Burgundy 
 Hungarian 
 
 In Spain, Pomigal, and France it is often customary to add some alcohol to wine, 
 and in this case the whole of the alcohol in the wine of these countries does not origi- 
 nate from the sugar of the must. 
 
 The smell of wine, or, as it is termed, the bouquet, is due to a large number of 
 substances that are present only in very minute proportions. At one time it was 
 supposed that the odour of wine was due almost entirely to a substance called cenan- 
 thic ether, but it has since been ascertained that there are in wine several ethers 
 besides that, as well as other compounds which contribute to the smell and modify it 
 in different wines, viz., a great number of ethers of the fat acids, as ethylic acetate, 
 ethylic propionate, ethylic butylate, caprylic, cenanthylic, capric, and caproic ethers ; 
 amyl and caprylic acetates, propylio Imtyrate, amylic valerianato, amylic malate, 
 
CONSTITUENTS OF WINE. 927 
 
 ethylic tartrate, and amylie tartrate ; also amylic, propylic, and butylic alcohols, with a 
 small quantity of aldehyd and acetal, and probably some oleates, originating from 
 the fatty oil of the gape kernels, contribute to the wine bouquet. 
 
 The formation of these ethers is due to the action of the wine acids on the alcohols, 
 as shown in the following equation, taking, by way of example, the production of 
 ethylic acetate by the action of acetic acid and alcohol : 
 
 The bouquet is produced partly during the fermentation and partly after, as well 
 as during the storage. -There is no fixed rule. Some wines acquire the chief bouquet 
 after the completion of the fermen ation and lose it by longer storing, whilst other 
 kinds of wine obtain the maximumt bouquet in the latter stage. The alcohol is pro- 
 duced by fermentation, and aldehyd is an intermediate product of the transition of 
 alcohol into acetic acid, with possibly some acetal. 
 
 The acids and acid salts, if not present in too large a quantity, improve the taste 
 of wine. These are chiefly tartaric acid and acid tartrate of potash (tartar), acetic 
 acid, and in Italian wines also racemic acid, and in red wines, tannic acid. Citric 
 acid and malic acid exist in wine in small quantities, together with succinic, and 
 under some circumstances, lactic acid. 
 
 The total acidity, whether as free acids or as acid salts, varies between 0'2 and 
 0'8 per cent., calculating as free tartaric acid. Nevertheless, the taste of wine depends 
 less upon the absolute quantity of acid present than upon the proportion the acid 
 bears to the alcohol. 
 
 The amount of carbonic acid diminishes during the storing by diffusion through 
 the pores of the casks, and becomes replaced by atmospheric air, of which the nitrogen 
 only is dissolved, while the oxygen forms oxidation products. 
 
 New wine contains more than its own volume of carbonic acid, but this quantity 
 decreases during the storage to one-fourth, and even less. 
 
 The colouring material of white wine existing only in small amount is but little 
 known, but probably it is extracted partly from the grapes and partly from the wood 
 of the casks. 
 
 The colouring matter of red wine, cenocyanin, is of a bluish-black colour, insoluble 
 in water and in pure alcohol, but soluble in water containing a small quantity of 
 tartaric acid. It is to be presumed therefore that th wine colour is dissolved by the 
 alcohol and free acid, during the fermentation of the must with the husks. The 
 colour is turned blue by alkalies, and is reddened by acids. 
 
 Bottger's test to distinguish the genuine red from the spurious colouring matter, 
 which may be due to elderberries and alum water, or to mallow, bilberries, etc., is 
 to dip a well-washed and white sponge into dilute hydrochloric acid, then into water, 
 finally immersing it forsome minutes in the suspected wine ; the sponge is then washed 
 with spring water, and if a spurious colouring matter has been employed, the sponge 
 presents a bluish grey colour, whilst in the case of a natural wine it is hardly tinged. 
 In course of time the colouring matter of red wine forms with the tannic acid a 
 compound which is precipitated on the sides of the bottles, thus gradually discolour- 
 ing the wine. 
 
 Glycerin occurs in wine to the extent of 3 per cent., although generally under 
 1 per cent. ; by long storage the quantity gradually decreases, so that hardly any is 
 to be found in old wines. 
 
 The gum, or oenanthin, found in many kinds of wine, and supposed to be produced 
 from sugar, gives the wine a thick consistency, but it is injurious if present in large 
 quantity. 
 
 The ash of wine amounts to 0-2 or 0'3 per cent, by weight, and for the most part 
 has the same composition as the ash of the must, with the exception that there are 
 less carbonates, and that is accounted for by the separation during fermentation of 
 tartar, which on ignition gives carbonate of potash. The constituents are chiefly 
 potash and phosphoric acid ; soda, lime, magnesia, ferric oxide, manganic oxide, 
 carbonic acid, sulphuric acid and chlorine are also present. 
 
 The acid potassium tartrate that separates gradually in the crude tartar as the 
 alcohol is formed, varies considerably in quantity. According to Faur white 
 Bordeaux contains between O'l and 0'15 per cent., and red Bordeaux between 0'06 
 and 0'2 per cent. The crude tartar also contains a small quantity of calcium tartrate. 
 The Grape and its Constituent^. A bunch of grapes consists of two parts, the 
 stalk and the berry. The former consists chiefly of ligneous tissue, but contains 
 among other substances a considerable amount of tannin, which passes into the must 
 when the grapes are pressed with the stalks. In that case other constituents also 
 
928 WINE. 
 
 pass into the must besides tannin, such as acid salts, etc., and on this account, in 
 making the finer kinds of wine, the stalks are separated from the grapes before these 
 are pressed. 
 
 The grape consists of skin, juice, and kernel. The skin consists of a fine mem- 
 brane formed of thick cellular tissue, and containing also some nitrogenous substances 
 and silica. Immediately under the epidermis layer of the skin, there is a vascular 
 tissue, which contains the colour substances, as well as tannin, nitrogenous substances, 
 some ethereal oil and salts. The juice is hermetically enclosed in the skin, and is dis- 
 tributed between the cells and vessels. As regards composition it is to be considered 
 as essentially a solution of grape sugar and fruit sugar in water. Besides these 
 constituents it contains albuminous substances, pectin, colour substances, organic 
 acids and salts ; see p. 930. The juice amounts to about 94 or 97 per cent, of the 
 total weight of the grape. The kernels contain cellulose, incrusting substance, fatty 
 oil (about 12 per cent.), ethereal oil, tannin, nitrogenous substances, and ash. 
 
 There are upwards of a thousand different varieties of vines, corresponding to 
 which there are as many different kinds of grapes. The most important are the fol- 
 lowing : 
 
 1. Orleans; yellow berries which are highly saccharine. "This variety is now less 
 cultivated than formerly, as it yields a wine too poor in bouquet. 
 
 2. Eiessling. The bunches are small and compact ; the single berries are also small, 
 and of a fine greenish-yellow colour, yielding a strong wine of a fine bouquet : this 
 grape is used to produce the best Rhine and Moselle wine, e.g. Johannisberg, Riules- 
 heim, and Brauneberg. 
 
 3. Traminer ; small fleshy berries of red colour, yielding a very strong wine, such 
 as those known in Grermany by the names of Forster, Wachenheimer, St. Johann, etc. 
 
 4. Ked Cleve or Eiilander ; the berries are red and ripen early. 
 
 5. Blue Cleve is grown in Burgundy and in the neighbourhood of Bordeaux, also 
 in the Aar valley and on the Rhine. 
 
 6. Elbling; greenish-yellow berries, which do not yield a very strong wine. This 
 kind of grape is very largely grown. 
 
 7. Ghitedel comes from Spain ; the berries are of a deep yellow colour, very trans- 
 lucent, and have very sweet juice. 
 
 The following kinds of grape are the most important as a source of wine : of the 
 white kind of grapes, Sylvan or Austrian ; Veltlin, Muscatel (Spain) ; Ortlieb 
 (Alsace) ; of the blue or black kind, Sylvan (Austria) ; Tokay, Klopf (Palatinate) ; 
 Gansfiiss (Italy); Trolling (Italy) ; Malvoisie (Italy) ; and black Traminer, Elbling, 
 Affenthal, Tiirkheim, etc. 
 
 Preparation of the Must. The expressed juice of the grape is commonly known 
 by this name, and it yields wine after having undergone fermentation. Its prepara- 
 tion involves two operations: First, the gathering of the grape, and secondly, the 
 expressing of the juice. The maximum quantity of sugar is found in the grapes 
 which are the most ripe, and the ripening depends on the kind of grape, on the 
 general climatic condition of the locality where it grows, as well as on the season. 
 There are various kinds of grapes that ripen under equal climatic conditions at diffe- 
 rent times, and one and the same kind ripens earlier in warm and sunny places than 
 m those which are less favoured. It is therefore impossible to have a definite period 
 of the year for the grape gathering, and it is quite an irrational procedure to set 
 apart a certain day in each year, as is customary in some parts of Austria, for the 
 purpose of the grape gathering. In France it generally takes place in the first half 
 of the month of October. 
 
 The grapes are cut very carefully with pruning knives or with shears, and in such 
 a manner that not a single grape is spoilt by handling ; then the bunches are placed 
 in tubs and carried to the press-room. Here, if destined for making fine wine, they 
 are sorted the rotten and unripe grapes being separated for making poorer wine. 
 
 In many places the sorting is carried out during the process of gathering the 
 grapes. The ripe grapes are first plucked, and the unripe grapes are left on the 
 vines in order to ripen, and are then plucked in the same way. The grapes first 
 gathered make the best wine. For the ordinary kinds of wine the grapes are pressed 
 as gathered from the vines, but for fine wines it is necessary to separate the stalks 
 before the pressing or treading operation to prevent the excessive contamination of 
 the must with tannic acid. The grapes are generally separated from the stalks by hand 
 labour, although machines have been constructed for the purpose. In the former 
 method the grapes are plucked either by the hand or by a three-pronged fork, or 
 rubbed over a wooden or iron grating, which onlv^ allows the grapes to pass. The 
 machines are constructed to emulate the hand process, and consists either of a sieve 
 on which the bunches of grapes are stirred round by an agitatory movement, so that 
 the grapes fall through, or of forks by which the grapes are stripped off. 
 
PREPARATION OF MUST. - 929 
 
 The squeezing or bruising of the grapes has the object of breaking up the skins 
 so that the juice may flow out. It can be performed by hand labour or by machinery. 
 
 Where it is customary not to separate the stalks from the grapes, the crushing 
 is performed in large wooden vats, either by the naked feet, or by wooden pestles. 
 Sometimes the vats are provided with false bottoms perforated to allow the juice to 
 flow through, so that it can be drawn off, or the crushing vats themselves have perforated 
 bottoms through which the expressed juice can flow into receivers. 
 
 The grape-crusher has latterly been employed with advantage, instead of the 
 feet and hand processes ; it generally consists of two smooth wooden or -iron rollers 
 revolving in opposite directions, on which the grapes fall through a wooden cropper. 
 The rollers, instead of being smooth, may be fluted. 
 
 Generally the bruised grapes are at once pressed, but sometimes the entire mass 
 is allowed to stand for some days to acquire bouquet. 
 
 It is necessary to deviate from the usual procedure in order to prepare red wine. 
 The blue or red grapes can be pressed at once after the gathering or bruising process ; 
 so can the white grapes when only a white wine is required, as the colouring matter 
 is insoluble in water ; but for red wine the grapes must stand in a loosely covered vat 
 or tub for two to three days, or longer, up to three weeks and more, before being pressed. 
 The alcohol meanwhile developed, together with the tartaric acid present, dissolve 
 the colouring matter, which gives the red colour to the wine. At the same time, if 
 the stalks have not been separated, a considerable quantity of tannic acid is dissolved 
 from the skins and stalks. The wine thus acquires a harsh taste, but it keeps better, 
 since the tannic acid also precipitates a part of the ferment. 
 
 As soon as the juice ferments, the skin and stalks are carried by the evolution of 
 gas to the surface and form what is termed the head. Acetic acid is liable to be 
 formed at this stage, and for this reason the long exposure to air in this state must 
 be prevented as much as possible, either by frequently stirring up the mass, or by 
 placing a grating on the surface, which will serve to keep down the head from the 
 air. 
 
 The pressing is carried out by means of a lever press or screw press, employed either 
 on the bruised grapes, or on the skins after the juice has drained out. The lever press is 
 worked by means of a heavy wooden lever of about 30 to 50 feet in length, acting 
 by its own weight, or loaded with a movable cradle filled with stones. The screw 
 press is of a construction similar to a bookbinder's press. The pressing-plate has a 
 raised edge to make the expressed must flow off at one point. Latterly, the press 
 plates have been made of iron, having the advantage over wooden plates in not absorb- 
 ing the juice, and in being more easily cleansed. The press of Orthlieb differs from 
 the last described in having an iron cylinder instead of a flat plate, to contain the 
 mass to be pressed. 
 
 "Weniger's press consists of a cylindrical vessel made of oak laths bound by 
 strong hoops. A wooden piston is set in motion by a crank working at the top, 
 whilst a similar piston is worked from below. The expressed juice flowing through 
 the laths is collected in a trough placed round the lath cylinders. This press has the 
 advantage over the last one described that the grapes are pressed equally top and 
 bottom, whilst by the one-sided pressure in the other case, and in consequence of the 
 elasticity of the grape husks, the upper portion is more strongly pressed than the 
 lower. Hydraulic presses have also been recommended, and there is no reason why 
 they should not do good service where wine is extensively made, but it is necessary 
 to guard against exerting too heavy a pressure, or other juices besides the true must 
 will be expressed. Centrifugal machines have been latterly proposed instead of 
 presses. Balard and Alcan obtained the following results from the same kind of 
 grapes by the centrifugal process (with a previous pressure between two fluted rollers) 
 and by simple pressing : 
 
 100 kilograms gave : 
 
 By the Centrifugal Process. By Pressing. 
 Must . . . . . . 79-141 kilograms 77'068 
 
 Skins, etc 20-214 18-601 
 
 Loss 0-645 4-331 
 
 A better yield is obtained by the centrifugal process, and it must also be taken 
 into account that the necessary labour is a little less. This method has not at present 
 found extensive use. 
 
 At different stages the must varies in quality. The first runnings obtained by 
 bruising and by slight pressure from the ripest grapes is the sweetest. Stronger 
 pressing yields a juice richer in the vegetable acids, and is therefore often separated 
 from the first. By mixing the expressed skins with water, and then pressing the 
 mass, a further quantity of must is obtained, forming by fermentation a thin wine. 
 
 The grape skins remaining after the extraction of the juice have been used for 
 
 3 
 
930 
 
 WINE. 
 
 various purposes. According to Petiot there is obtainable, by mixing them with 
 sugar and water, then fermenting and pressing, a drinkable wine having a sufficient 
 bouquet given to it .by the skins and stones. The skins are also worked up for brandy, 
 vinegar, and for potash ; further they can be used as manure, for cattle provender, 
 making verdigris, for gasmaking and for Frankfort black. Ilgen obtains by his pro- 
 cess of dry distillation an illuminating gas, and a fine black residue of carbon. 
 
 Constituents of the Must. The expressed grape juice consists essentially of an 
 aqueous solution of grape sugar and fruit sugar. It contains also a great number of 
 other substances which exist in relatively small quantity : for example, albuminoids, 
 pectin, pectose, mucilage, organic acids, especially tartaric acid, together 
 with some malic, tannic, and citric acids ; a varying quantity of colouring material, 
 fatty oils, and the ash constituents consisting of potash, soda, lime, magnesia, alumina, 
 iron oxide, and manganese oxide. The bases are partly combined with the vegetable 
 acids, and partly with chlorine, sulphuric acid, phosphoric acid, and silica. 
 
 Fresenius and Schliefer give the following analyses of must : 
 
 
 Klein- 
 berger 
 
 White 
 Austrian 
 wine 
 
 Riessling 
 
 RedAss- 
 manhauser 
 
 Johannis- 
 berg 
 
 Grape and fruit sugar 
 
 10:590 
 
 13-780 
 
 15-14 
 
 17-28 
 
 19-24 
 
 Free acid 
 
 0-820 
 
 1-020 
 
 0-56 
 
 0-75 
 
 0-66 
 
 Albuminoids .... 
 
 0-622 
 
 0-832 
 
 
 
 
 
 
 
 Soluble pectin, mucous, and) 
 colouring matter . . . J 
 
 
 
 
 
 3-46 
 
 
 
 2-95 
 
 Fatty substance and organic acids 
 
 0-220 
 
 0-498 
 
 
 
 
 
 
 
 Ash 
 
 0-377 
 
 0-360 
 
 
 
 
 
 
 
 The amount of sugar varies between 8 and 30 per cent. The ash has a very 
 variable composition ; it contains from 17 to 30 per cent, of potash, and in some 
 cases as much as 70 per cent., 3 to 17 per cent, of phosphoric acid, a considerable 
 quantity of lime (1 to 5 per cent.), to 5 per cent, of magnesia, 1 to 5 per cent, sul- 
 phuric acid and carbonates. The sugar is estimated by the specific gravity method, 
 which will be fully described in a succeeding section. 
 
 Fermentation of the Must. This is caused by the same kind of ferment which 
 serves to ferment beer wort, and the resulting products are much the same in 
 character. The action of the ferment on the sugar of the must is to convert it into 
 alcohol and carbonic acid, with the formation of some glycerin and succinic acid. A 
 portion of the sugar is consumed in the production of the yeast cells. 
 
 The constituents to which the bouquet of wine is due, especially the ethers, are 
 not direct products of the fermentation, but are formed partly during and partly after 
 the fermentation. 
 
 The fermentation of wine appears to take place in three stages ; the first or chief 
 fermentation, the after fermentation, and the vat fermentation. 
 
 When the grapes are pressed, a sufficient number of the ferment germs to cause fer- 
 mentation pass into the must, but their development depends on the must containing the 
 nutriment, such as albuminoids, sugar, potash salts, and phosphates, necessary for the 
 growth of the yeast fungus. The wine ferment is in every respect the same as beer 
 yeast, which would ferment the must equally well. 
 
 Wine fermentation takes place in two ways, the superficial fermentation and the 
 sedimentary fermentation, but the same care is not taken to ensure this as in beer 
 fermentation. The first process occurs at a temperature of from 15 to 20, and it 
 serves chiefly for the production of the highly alcoholic wines of the south of France. 
 Spain, Italy, Austria, and Hungary. These wines, however, have the disadvantage of 
 being poor in bouquet ; but by fermenting more slowly, and at a temperature of 5 to 
 15, wine is produced, which, although poor in alcohol, is richer in bouquet. The 
 sedimentary fermentation is practised chiefly in Germany, and especially in the Khine 
 provinces; but even in these places, at least to some extent, the must is subjected to the 
 superficial fermentation, which very easily happens when the preliminary operations 
 take place in hot weather, and the must has a proportionally high temperature. 
 
 The after fermentation is, under all circumstances, a very slow sedimentary fer- 
 mentation, in consequence of the low temperature and the small amount of sugar 
 remaining to be split up into alcohol and carbonic acid, with the formation of a little 
 glycerin and succinic acid. The best temperature lies between 5 and 10, but it 
 must be low enough to extend the fermentation over a period of three months. In 
 many places it is allowed to occupy five to six months. Besides the fermentation 
 
FERMENTATION OF MUST. 931 
 
 proper, a series of other chemical changes occurs at this stage, and by the combination 
 of acetic acid and its homologues, propionic and cenanthic acids, or lactic and succinic 
 acids, with ethylic and amylic alcohol, the ethers which give the bouquet to the wine 
 are formed. 
 
 Experiments which have been made recently tend to show that after the fermenta- 
 tion is quite over the wine hardly contains any sugar, and that the sweet taste of the 
 wine is due to glycerin (amounting to 3 per cent.) 
 
 The ethers and the bouquet increase during the store fermentation, but as sugar is 
 now absent no fermentation proper takes place ; the wine becomes stronger, that is, 
 richer in alcohol, which arises from water being diffused through the pores of the 
 wooden vat and evaporating from its surface whilst the alcohol is unaffected. 
 
 It is a common opinion that in spring wine undergoes a renewed fermentation. 
 This is erroneous. The escape of wine from the bung-holes of the cask in spring 
 time is more probably due to the expansion of the wine in the casks. The gases 
 which have been absorbed in great quantity by the cold wine in winter also escape as 
 the temperature rises, and it is this fact which has given rise to the supposition that 
 a further fermentation takes place. 
 
 In stored wine there is a gradual loss of carbonic acid, but not to such an extent 
 as might be expected when it is considered that, even in a well-bunged vat, there is a 
 continual diffusion of the carbonic acid and the external air through the pores of the 
 cask. Wine can be stored up for ten years without losing more than one half to a 
 third of its carbonic acid. This is due to the solubility of carbonic acid in alcohol 
 and in alcoholic liquids. 
 
 It is still a doubtful question whether air should have access to wine during fer- 
 mentation. It is certain that the chief fermentation proceeds more quickly if air has been 
 driven through the must at the commencement. Various kinds of apparatus have 
 been constructed for the purpose of aerating the must. In some cases, a centrifugal 
 machine is used, or air is forced in by a bellows provided with a rose nozzle. Wine 
 so aerated will keep better, because the oxygen of the air oxidises and precipitates the 
 nitrogenous compounds which are easily decomposed in this way. It is very important, 
 however, in this manner of operating to keep the temperature very low, otherwise a 
 considerable quantity of the bouquet will be carried away. As the ethereal oils are only 
 formed and retained when the action of the atmospheric oxygen is exerted it is necessary 
 to determine by experiment whether the bouquet is being increased or lessened by the 
 continued action of the air. 
 
 It has been also proposed to let the after fermentation proceed at a low temperature 
 in open vessels, somewhat similarly to the plan carried out during the fermentation of 
 beer wort. The wine, thus made, keeps better, but there is generally a loss of bouquet, 
 in consequence of the separation of nitrogenous substances. 
 
 During the vat fermentation there is a slow oxidation of certain nitrogenous com- 
 pounds, which, if not thus destroyed, would spoil the wine by favouring the formation of 
 acetic acid. Air gains access to the wine through the pores of the vat. But the quantity 
 of air entering in this way being small, it is recommended in some cases to stop the 
 bung-hole of the vat with wadding in order that there may be more free access of air. 
 If this plan be adopted the vat is varnished, so that air can only enter through the 
 wadding which serves to filter the spores and germs, because by so much exposure to 
 air there is much scope for acetous formation. 
 
 For the first fermentation of must capacious vats either of wood, sandstone, or brick 
 set in cement, are generally used. Latterly glass has been proposed, but it has had 
 no general application. A suitable cover serves to prevent the admission of a supera- 
 bundance of air, whilst a hole in the cover, or a small tube, serves as an exit for the 
 carbonic acid gas. In some places, in order to prevent the admission of air, a valve is 
 fitted to the apparatus, and can only be opened from within by the pressure of the 
 carbonic acid gas. The fermentation tube of Ko'lges and Bamberger effects the same 
 pujpose ; it consists of a glass tube bent twice at right angles, having one end through 
 the bung-hole, with the other or exit end reaching into water. The carbonic acid gas 
 bubbles through the water, and the admission of air is thus prevented. If the top of 
 the vat be fastened down, or is very large, it is provided with a hole for the purpose of 
 running in the must with or without the skins and emptying out the residue. A ther- 
 mometer also passes through the top into the wine. At the lower part of the vat a 
 cock is placed for the purpose of drawing off the wine. In Germany, instead of using 
 large vats, it is the custom to employ many large casks, either having an open bung- 
 hole, or an arrangement as above described. In the fermentation of red wine, which 
 is always carried out without separating the grape skins, an open vat is used, provided 
 with a perforated inner shelf, and this is placed some inches below the level of the 
 liquid in order to prevent the rising up of the husks. 
 
 After the must has been a short time in the fermenting vat it shows signs of 
 
 3 o 2 
 
932 WINE. 
 
 working; the temperature rises, a foam forms on the surface, and there is a disen- 
 gagement of carbonic acid. The skins are carried to the surface, and, if for too long a 
 time exposed to the air, an acid fermentation results ; and it is to prevent this surface 
 exposure of the husks that the above-mentioned perforated shelf is fitted below the 
 level of the liquid. In the first few days the temperature rises until it is about 5 
 above the temperature of the air, and at the same time the disengagement of carbonic 
 acid increases, but after the first fermentation the evolution diminishes to such a degree 
 that there is no further perceptible disengagement of gas. The time occupied in the 
 first part of the fermentation depends upon the temperature of the fermenting room. 
 In Germany it varies from 8 to 14 days, in France for the ordinary kinds of wine from 
 3 to 8 days, in the department of Herault from 12 to 14 days, and in some places, 
 where the finer sorts of wine are prepared, the fermentation proceeds during 4 to 6 weeks. 
 
 In proportion as the must ceases to ferment, and in consequence of the conversion 
 of sugar into alcohol, the specific gravity of the liquid diminishes, this furnishing a 
 very ready means of- ascertaining the progress of the fermentation. Since alcohol as 
 well as the ethereal and bouquet-giving compounds would be carried away by a very 
 brisk first fermentation, it is advisable to cool the must by means of cooling tubes or 
 by ice, so as to moderate the fermentation. 
 
 Various contrivances have been proposed to collect the alcohol escaping with the 
 carbonic acid gas, and a very simple one consists in making the gas pass through 
 water by means of what is termed an hydraulic bung. The quantity of alcohol escap- 
 ing may be as much as | per cent, of the total quantity present in the wine. 
 
 The carbonic acid gas evolved can be used for the preparation of bicarbonate of 
 soda, white lead, etc., but it is not generally utilised. 
 
 After the chief fermentation is over the wine is run into large casks, care being 
 taken that the yeast and lees remain behind ; the casks are filled to the bung to pre- 
 vent as mueh as possible acetic acid forming by the atmospheric action. 
 
 During the after fermentation the yeast is deposited at the bottom of the casks, 
 the sides of which are also gradually coated with a crust of tartar which is insoluble 
 in the alcohol now present in the wine. 
 
 The crude tartar, which is from time to time removed from the empty casks, consists 
 chiefly of acid tartrate or potash, generally with some admixture of calcium carbonate 
 and calcium tartrate, ferric oxide, colouring matter, yeast residues, etc. 
 
 "When the after fermentation is finished the casks are either filled up and closed 
 or the wine is at once run into the storing casks, where it is bunged up until a con- 
 siderable further deposition of tartar has taken place, and then it is racked off either 
 into casks or bottles. This racking process must be repeated from time to time with 
 wine that is being stored for a very long time. 
 
 Before filling the casks with wine, they must be thoroughly cleansed from any 
 mildew which would tend to cause the production of acetic acid ; for the destruction 
 of such fungi the casks are steamed and fumigated with sulphur. 
 
 Fining or clarifying is carried out only with wine which is not clear after fermen- 
 tation. It serves to get rid of the suspended matter, which if allowed to remain would 
 cause an after fermentation in the hot seasons of spring and summer. In the case 
 of red wine, which contains tannin, the fining is effected with albumin or gelatin in 
 the form of blood or solution of glue, which form insoluble compounds with the tannin, 
 and in this way the suspended matter in the wine is precipitated. 
 
 White wine, which contains no tannin or but very little, has the required quantity 
 of tannin added in the form of oak bark or gall nuts, and it is then clarified with 
 isinglass, as in beer fining. The precautions necessary in fining wine are that the 
 wine is not disturbed and that the finings are not in separate pieces but in a coherent 
 net-like mass. 
 
 Milk, acting by the coagulation of the casein, has also been used for wine fining, as 
 well as wood shavings, which act by virtue of the tannic acid they contain, and even 
 paper pulp, gypsum, alumina, alum, etc., have been recommended for the same purpose, 
 but isinglass or albumin is usually preferred. Fining powders generally contain one 
 or more of the above-mentioned substances. 
 
 In order to effect the improvement of inferior wines, either of two purposes or 
 both may have to be served, viz., to increase the amount of alcohol and to decrease 
 the acidity. Sometimes also bouquet is given to the wine by artificial means. 
 Either the must or the wine is operated on according to the object desired. 
 
 One of the oldest methods is that known as the Chaptal process, according to 
 which, if there be more than 0-6 per cent, of acid in the must, enough carbonate of 
 lime is added to reduce the acid to that amount. To increase the amount of alcohol 
 raw sugar is added. The Gall process is intended to be applied to the wine produced 
 in bad seasons by adding sufficient water to reduce the amount of acid to 0'5 or 0-6 
 per cent, and then mixing with diluted must enough grape sugar to make the total 
 
DETERIORATION OF WINE. 933 
 
 quantity about 20 per cent. The fermentation is then carried out in the ordinary 
 way. The process is to be recommended when the must is poor in sugar but rich in 
 acid, and it is quite capable of producing drinkable wine. 
 
 The grape sugar employed in the Gall process is prepared by the action of dilute 
 sulphuric acid on starch. It is commonly known under the name of starch sugar, 
 and differs from pure grape sugar by containing in addition a considerable quantity of 
 dextrin. 
 
 Neutral potassium tartrate, calcium carbonate, or sugar lime may also be used 
 to neutralise the excess of free acid. 
 
 The amount of alcohol may be increased by freezing the wine and, removing the 
 frozen portion with the adhering albumin and tartar ; or by the direct addition of 
 alcohol obtained by the distillation of wine or by adding pure spirit. Gypsum, 
 through its affinity for water, will effect this object to some extent. 
 
 In Scheele's process, the sour taste is masked and the sweetness increased by adding 
 from 1 to 3 per cent, of pure distilled glycerin. The glycerin preserves the wine, 
 and there is no fear of the sweetness of the wine diminishing, whilst wine sweetened 
 with sugar is liable to fermentation, which may alter its character. 
 
 An extract of grape blossom is frequently used to improve the bouquet of wine. 
 
 Some years ago experiments were made in France with the view of applying elec- 
 tricity to the preservation and improvement of wine. It had been observed that 
 some wine which had run out of casks destroyed by lightning had a very fine flavour. 
 
 The method of obtaining wine from the grape skins, according to Petiot, depends 
 upon the fact that the skins after pressing still contain so considerable a quantity of 
 bouquet-forming substances that, by digesting them with a solution of sugar, an arti- 
 ficial must is obtained, which, by fermentation, acquires the odour and taste of good 
 wine. The constituents which it may be deficient in, such as tannin, tartar, etc., can be 
 subsequently added. 
 
 At present Petiot's method is only carried out with the residuary skins from the 
 preparation of red wine. The wine produced in this way is strong, rich in bouquet, 
 retains its properties, is of a fine colour, and not unfrequently it is of a better taste 
 than that produced from the first must, which in bad years easily becomes sour. 
 
 By good management the deterioration of wine can be prevented, and, if it takes 
 place, artificial means may be employed to remedy the defects. 
 
 Wine becomes sour by acetous fermentation, or by the formation of lactic acid, 
 especially when it contains a considerable amount of albuminous substances and little 
 alcohol. The best means of prevention is to keep theXrine as much as possible from 
 contact with atmospheric oxygen by filling the casks to the bung, or by soundly bung- 
 ing them up when the after fermentation is completed. In the event of mildew ap- 
 pearing, the wine must be quickly racked off into fresh casks : the introduction of 
 carbonic acid has the effect of killing the Mycoderma aceti, and the neutralisation 
 of the acid with concentrated potash solution will sometimes produce drinkable wine. 
 
 Mould is sometimes formed upon the surface of wine when the casks are not 
 full, and the cellars are too warm, and the bungs are not closed. This defect can 
 be counteracted by sulphuring, either by burning some sulphur in the- empty part 
 of the cask, or by racking off the wine into a fresh cask in which sulphur has been 
 previously burnt. Solution of sulphurous acid may be used for the same purpose. 
 
 The bitterness in wine, more prevalent in old than in new wines, is likewise 
 due to a peculiar ferment which produces a bitter principle of an unknown chemical 
 constitution, and although present in small quantities it gives a very bitter taste to 
 the wine. It is stated that isinglass or carbonate of lime will sometimes remove the 
 bitterness. 
 
 Sweetness, due to the presence of unconverted sugar, occurs when, in consequence of 
 a late vintage, the temperature of the air is too low to admit of complete fermenta- 
 tion, which will then frequently proceed so slowly that after ifionths or even years 
 the wine remains sweet. 
 
 Wine is rendered thick or turbid by a peculiar ferment which decomposes thetartaric 
 acid of the tartar with evolution of carbonic acid, and also decomposes any sugar and 
 glycerin that may be present. The ferment floating about the wine causes a dis- 
 turbed and thick appearance, and ultimately the wine becomes sour. The evil can be 
 obviated by decanting the wine when the contact with air causes the fermenting agent 
 to be precipitated. Eed wine chiefly suffers from this defect. Viscidity or ropiness 
 is due to mucous fermentation, by which sugar is converted into manniteand mucilage. 
 It has been stated that the ferment by which this change is produced originates from 
 vegetable gelatin left in solution during the fermentation and storing, owing to in- 
 sufficient contact with atmospheric oxygen. The evil may sometimes be remedied by 
 adding tannin in the form of a decoction of the grape stalks and kernels. Exposure 
 to air is less efficacious. 
 
934 
 
 WINE. 
 
 The taste of the cask is due to the use of dirty casks and is very difficult to be got 
 rid of. The best plan is to rack the wine off quickly into a new cask, and to mix xvith 
 it about per cent, by volume of olive oil, which helps to remove the unpleasant 
 taste. 
 
 Red wine sometimes presents a bluish or brown discoloration, when the tartar has 
 been converted by putrid fermentation into carbonate of potash. The original colour is 
 restored by careful addition of tartaric acid sufficient to reproduce the tartar. 
 
 Preservation of Wine. Weak wines do not bear exportation so well as strong 
 wines ; it is the custom therefore to mix with them two to three per cent of alcohol. 
 
 Although wine generally keeps better in bottles than in the casks, there is the dis- 
 advantage that the cork may give a taste to the wine. This especially occurs when 
 the cellar is damp and mildew accumulates on the cork ; to prevent this the corks are 
 covered with rosin or with tin capsules. 
 
 Freezing is one of the means by which wine may be preserved. This treatment 
 facilitates the precipitation of the dissolved or suspended nitrogenous substances which 
 give rise to the formation of ferments, and at the same time, when the frozen portion, 
 is removed, the wine is rendered stronger or more alcoholic since only the water is 
 frozen. 
 
 Another method of greater importance consists, according to Oppert, in heating 
 the wine contained in bottles or in hermetically sealed vessels in a water bath at 70 ; 
 this process is said to give a wine which afterwards retains its properties for many years. 
 Beaune wine treated in this way remained good after it had been two years at sea. 
 The preservative effect of this treatment is no doubt due to the destruction of ferment 
 vegetation. 
 
 Several forms of apparatus have been devised for treating wine by this method. 
 
 The arrangement adopted by Rossignol is represented by fig. 685. It consists of 
 a cask having the bottom replaced by the copper pan (c) which is tinned on the out- 
 side and ends in an open tube (c). The wine to be treated is run into the cask, and 
 the copper vessel is filled with water which is heated by the furnace underneath. 
 Care must be taken to keep the water below the boiling point, and to maintain it at a 
 temperature just higher than that to which the wine requires to be heated. 
 
 FIG. t>86. 
 
 FIG. 685. 
 
 When the proper temperature of 50 to 60, as shown by the thermometer (t\ has 
 been reached, the wine is drawn off into the cask (F) by the cock (r) and the india-rubber 
 pipe (/). The cask (T) is refilled with wine, and the same operation carried out as before. 
 At intervals water is run in to cleanse the cask, otherwise the wine dregs deposited 
 during the operation would decompose on the admission of air, and would impart an 
 unpleasant taste to the wine subsequently heated. 
 
 In fig. 686 is shown the connection at the bottom of the apparatus between the 
 wine cask and water vessel, (a) is a tinned copper ring soldered to the water reservoii 
 
ADULTERATION OF WINE, ETC. 935 
 
 (c) fig. 685, and between the ring and the edge of the cask lies the india-rubber ring (i7), 
 against which a is so strongly pressed by screw bolts fixed on one side in a strong 
 iron ring (b), and on the other in a piece of angle iron (<?) fastened to one of the iron hoops 
 of the ca'sk, that a perfect joint is made. 
 
 As it is necessary to keep the wine from contact with air on account of its action 
 on the colour and taste of the wine, and as the cask must be quite filled with wine, 
 a pipe (B) made of glass or tin conducts the overflow due to expansion into the bottle 
 (a). 
 
 The wine is drawn off into casks whilst hot, and as it cools an air space results 
 through contraction which must be quickly filled up with hot wine. .Instead of this 
 method the casks used for racking the hot wine are connected with each other by a 
 bent pipe, so that the wine passes from one to another as the contents cool. 
 
 Wine which has been put into casks in this manner can be transported without 
 risk of deterioration, in addition to which the wine can be stored in casks for a 
 longer time without being racked off, and there is no need for cool store cellars. 
 
 Kesults obtained by this method are very favourable, inasmuch as it turns out a 
 wine which will retain its properties, and has no tendency to the ordinary wine 
 maladies ; the method is extensively used in France. 
 
 Adulteration of Wines. Wine may be considered adulterated when mixed with 
 substances injurious to health, either for the purpose of imitating a wine of a finer sort, 
 or to raise its value. In this class must be included those wines which have had a 
 substance added to counteract some objectionable character, such as too great acidity. 
 Large quantities of wine are mot with which are merely imitations of the better 
 kinds of wine, and they are prepared partly from inferior wine by the addition of arti- 
 ficial ethers, extracts, and essences ; sometimes also without any basis of real wine. 
 For the detection of such falsifications there is a want of any decisive test beyond the 
 indications afforded by the toste or smell. 
 
 Wine that has 'become sour is sometimes treated with acetate of lead, in order to 
 remove the acidity, and in such cases the wine is liable to contain lead, which can be 
 readily detected by means of sulphuretted hydrogen. 
 
 Copper or zinc, derived from the copper or brass vat fittings, can be detected in a 
 similar manner. 
 
 Sulphate of iron, which is sometimes added to wine, may be detected by the blue 
 colour which is produced upon the addition of potassium ferrocyanide. 
 
 The colour of wine is produced artificially in many instances. Light red or white 
 wines are coloured by the addition of some innocuous -fred colouring matter. 
 
 In France the colouring of red wines by means of fuchsine, or aniline red, is said 
 to have been extensively practised within the last few years ; and since this material 
 is liable to contain arsenic, its use for such a purpose would be highly objectionable. 
 Much attention has recently been paid to this subject in France with a view to detect 
 the admixture of this colouring matter. 
 
 The distinguishing features of the genuine colouring matters have already been 
 given, and the following reactions with acetate of lead, and alum and carbonate of 
 ammonia, may serve for the detection of the common spurious materials which are 
 used : 
 
 With Acetate of Lead With Alum and Carbonate of Ammonia. 
 Pure red wine bluish grey dirty green 
 
 Poppies dirty grey slate grey 
 
 Elder berries dirty green bluish grey 
 
 Bilberries greyish green bright violet 
 
 Privet berries green ,, green 
 
 Dwarf elder berries bluish grey to violet bright violet 
 
 in the fresh berries, 
 and fine green in the 
 fermented extract 
 
 Mallow flowers dark green bluish violet 
 
 Logwood feeble dark blue dark violet 
 
 Brazil wood wine red carmine red 
 
 In the event of the colouring matter having been added after or before fermenta- 
 tion, the adulteration may be detected by the microscope ; for, if a drop of uncoloured 
 wine be examined under the microscope, it appears when dry quite homogeneous, whilst 
 in case of the addition of colouring matter after fermentation separate clots of colour 
 can be seen. 
 
 White wine is coloured with burnt sugar. Dark wines can be decolourized by 
 agitation with animal charcoal. 
 
 The testing of Must and Wine. Must is chiefly tested for its amount of sugar, 
 and less frequently for the amount of acid. 
 
936 WINE. 
 
 The amount of sugar is determined by a special form of hydrometer, the degrees of 
 which show the amount of sugar. 
 
 In estimating the percentage of sugar in must by the specific gravity, it is assumed 
 that it is only the sugar which affects the specific gravity. It must, however, be 
 borne in mind that the dissolved protein compounds, organic acids, and the ash con- 
 stituents all tend to raise the specific gravity. 
 
 The following table gives the specific gravity corrected for the soluble compounds 
 other than sugar : 
 
 Corrected sp. gr. Per cent, of sugar. 
 
 1-010 3 
 
 1-016 4 
 
 1-020 5 
 
 1-024 6 
 
 1-028 7 
 
 1-032 8 
 
 1-036 9 
 
 1-040 10 
 
 1-042 11 
 
 1-044 12 
 
 1-048 13 
 
 1-053 14 
 
 1-0572 15 
 
 1-0614 16 
 
 Corrected sp. gr. Per cent, of sugar. 
 
 1-0657 17 
 
 1-0744 18 
 
 1-0788 19 
 
 1-0832 20 
 
 1-0877 21 
 
 1-0922 22 
 
 1-0967 23 
 
 1-1013 24 
 
 1-1059 25 
 
 1-1106 26 
 
 1-1153 27 
 
 1-1200 28 
 
 1-1247 29 
 
 1-1295 30 
 
 The amount of acid in must is determined volumetrically by means of a solution 
 of lime of such a strength that 27'5 cubic cent, equal 0'06125 grm. sulphuric acid ; 
 0-075 grm. acetic acid; 0'09375 grm. tartaric acid ; and 0'235 grm. acid tartrate of 
 potash. 
 
 Teh c.c. of the clear must are brought into a beaker without litmus, and the lime 
 water is added from a burette until by the change in the colour the neutral point is 
 obtained. The reading of the burette is taken, and the percentage of acid can be cal- 
 culated. 
 
 When the must is not clear, lime water is added, insufficient to saturate the acid ; 
 the liquor is then filtered, and more lime water is added to the filtrate until alteration 
 of colour takes place. 
 
 Wine is chiefly tested to ascertain the amount of alcohol, and seldom for the acidity 
 or the amount of extract. 
 
 Direct determination of specific gravity is of no value, because it is influenced by 
 other constituents besides the alcohol. 
 
 Gruy-Lussac's apparatus, or a modification of it, is used for the purpose of ascertain- 
 ing the alcoholic contents of a wine. A measured volume being taken, it is distilled 
 into a graduated receiver, and the distillate made up to the original quantity. In the 
 distillate the alcohol is estimated by an alcoholometer. 
 
 Silbermann proposes a method which is much quicker than that just described. It 
 depends upon the expansion of alcohol between and 78 being three times as great 
 as that of water. 
 
 Conaty's ebullioscope indicates the amount of alcohol in a mixture of alcohol and 
 water, by the temperature of the vapour given off from the boiling liquid. 
 
 The vaporimeter of Geissler is based upon the fact that the tension of alcohol vapour 
 is much greater than that of water vapour. The alcoholic liquid is heated in an en- 
 closed vessel, in connection with a kind of manometer, in the outer arm of which the 
 mercury rises to an extent proportionate to the amount of alcohol, which is indicated 
 upon a scale. 
 
 The volatile ethers and the homologous alcohols affect the result. In using this 
 method carbonic acid must first be removed by shaking with caustic lime. 
 
 The acidity of wine is ascertained by titration. Instead of litmus as an indicator 
 Mohr recommends an alcoholic tincture of logwood, and to add the normal soda solu- 
 tion until the yellow colour of the logwood changes to violet. 
 
 The amount of extract is determined by evaporating a known quantity of wine to 
 dryness on a platinum disk on the water bath, and weighing the residue dried at 100 
 to 110. 
 
 Treatment of the Wine Residues. The grape skins, after the expression of the 
 juice, are frequently distilled to make brandy. With this object the skins are sub- 
 jected to fermentation, and then distilled. 
 
 Crude tartar can be obtained from the residue of distillation. For this purpose 
 the skins are separated by a sieve from the hot liquor, which is allowed to stand for 
 some time until the tartar is deposited. The residue on the sieve can be either 
 
CONSTITUENTS OF BEER. 937 
 
 incinerated to obtain potash, or merely carbonised for vine-black. It has also been used 
 for making gas. 
 
 In some places the skins are used as cattle fodder or as manure, and for preparing 
 verdigris. By allowing them to undergo acetic fermentation, and filling them alter- 
 nately with sheet copper in a warm place, a coating of neutral cupric acetate is thus 
 formed, which is gradually converted into basic acetate, or verdigris. 
 
 Tannic acid, and a fat oil which can be extracted by carbon bisulphide, are to be 
 obtained from the grape stones. 
 
 The wine lees are distilled for brandy; the last product which passes over 
 consists of wine oil, which is essentially oenanthic ether. The residue of the distilla- 
 tion can be used for preparing crude tartar or potash. 
 
 The crude tartar deposited in the after fermentation is purified, and also used in 
 the preparation of tartaric acid. 
 
 BEER. Beer was known to the Egyptians, and it is probable that the Greeks learnt 
 from them the art of brewing. The Komans obtained their knowledge of beer from 
 the Gauls, and like them, called it cerevisia. In Germany the brewing of beer 
 has been carried on during many centuries, it being mentioned by Tacitus. As long 
 as the malt required was prepared in each house, the beer industry remained com- 
 paratively undeveloped, but when the monasteries began to brew on a larger scale it 
 attained a considerable perfection. The monks were the first to make a distinction 
 between single beer and doiible beer, the former being called convent, the 
 latter pater beer. The use of hops in brewing dates from the ninth centiiry. 
 White beer was first brewed in Nuremberg in 1541. The brewing of ale and porter 
 dates only from the eighteenth century. 
 
 Beer contains, besides the alcohol produced by fermentation, some dextrin, small 
 quantities of nitrogenous substances, some of the ash constituents of the malt, and 
 dissolved carbonic acid, which contributes essentially to its good quality. When beer 
 is kept, carbonic acid is given off continually to a small extent; so that, to keep the 
 liquor saturated with this gas, a constant reproduction of it within the beer itself is 
 necessary. Beer is a beverage drunk while in a state of fermentation, thus differing 
 essentially from wine and like beverages, which are only fit for use when the fermen- 
 tation is over. As soon therefore as beer, through standing in partly filled vessels, 
 in too warm a place, or any other cause, ceases to evolve as much carbonic acid as is 
 given off, it loses its freshness ; the same thing happens when fermentation is stopped 
 either by too low a temperature or complete decomposition of the sugar. 
 
 Beer left to stand exposed to the air easily turn's sour, especially when it contains 
 much ferment, as is the case with superficially fermented beer, acetic acid being 
 formed from the alcohol. Beer that has once turned sour, cannot be reconverted into 
 good beer, and the best use that can be made of it is to treat it for vinegar. 
 
 In order to preserve beer, especially for export, a number of plans have been pro- 
 posed. One of the best of these is that recommended by Velten. It consists in heat- 
 ing the beer during twenty minutes or an hour in closed vessels to a temperature 
 of 48 or 50. To secure quick heating, so that the temperature does not remain 
 long between 25-40, when too strong fermentation would ensue, the vessels are 
 heated in a water bath. The most suitable vessels for the purpose are made of 
 metal, and furnished with a stirring apparatus made of pipes, through which steam 
 is passed. The beer is then filled into casks and charged with carbonic acid gas. 
 In using the above method, it is necessary that the escape of carbonic acid during 
 the heating process should be entirely prevented. 
 
 According to the relative proportions of the several constituents alcohol, aromatic 
 substances, and the non-volatile constituents which are collectively designated malt 
 extract beer has different characters. Beer with body, as ale and porter, the 
 Brunswick Mum, etc., contains from 8-15 per cent, malt extract, while thin beer con- 
 tains only from 4-6 per cent, of extract. The amount of alcohol in beer also varies, 
 though dry or thin kinds of beer sometimes contain more alcohol than beer with body. 
 The strong English beer contains 5 and even 8 per cent, of alcohol, Bavarian beer 
 from 2 to 5 per cent, and the more ordinary kinds from 2 to 3 per cent. The 
 relative quantity of carbonic acid in beer varies between 0*1 and 0*2 percent.; the 
 sugar from 0'2 to 1-9 per cent., the dextrin from 3 to 5 per cent, and upwards, the al- 
 buminous substances from to f per cent. Besides carbonic acid, acetic, lactic, and 
 some succinic acids are contained in beer. According to A. Vogel's researches the 
 proportion of lactic acid to acetic acid in fresh beer is tolerably constant, as 32 to 1 ; 
 in beer exposed to the air the proportion of acetic acid increases rapidly. Tannic 
 acid is not always present in beer, and then only in Tery small quantity. The amount 
 of ash yielded by beer varies between O'l and 0*3 per cent. According to Martino, who 
 analysed Erlanger beer, it consists essentially of potash (37 per cent.), soda (8 per cent.), 
 magnesia (5 per cent.), phosphoric acid (32 per cent.), silicic acid (11 per cent.), and 
 
038 
 
 BEER. 
 
 naturally varies according to the raw material used in brewing. According to Lermer, 
 beer contains an organic base the nature of which is at present unknown. Besides 
 the constituents mentioned, beer also contains the entire constituents of the hop, as 
 well as glycerin and caramel. 
 
 The following table shows the results of Lermer s analysis of different kinds of 
 Munich beer. 100 parts were found to contain: 
 
 
 
 
 
 
 Phosphoric 
 
 
 Alcohol 
 
 Extract 
 
 Albumen 
 
 Ash 
 
 acid in 
 100 parts 
 
 
 
 
 
 
 of ash 
 
 Bock beer from the Court brewery . 
 
 5-08 
 
 7'83 
 
 0-87 
 
 0-28 
 
 34-18 
 
 Summer beer 
 
 3-88 
 
 4-93 
 
 0-43 
 
 0-23 
 
 32-05 
 
 White beer 
 
 3-51 
 
 4-73 
 
 0-53 
 
 0-15 
 
 26-57 
 
 Spaten Bock beer .... 
 
 5-23 
 
 8-50 
 
 
 
 
 
 
 
 Zacherl Salvator beer 
 
 4-49 
 
 9-63 
 
 0-67 
 
 
 
 
 
 Lowenbran winter beer 
 
 3-00 
 
 5-92 
 
 
 
 0-25 
 
 29-28 
 
 The following table shows the percentage of alcohol and extract in English, 
 G-erman, and other kinds of beer : 
 
 
 Alcohol 
 
 Extractive matter 
 
 Porter (Barclay and Perkins) . 
 
 5-4 
 6-9 
 
 6-0 
 6-8 
 
 Burton ale . . ' , ' .-. 
 
 5-9 
 
 8-5 
 
 14-0-19-3 
 10-9 
 
 
 3-3-4 
 
 5-6 
 
 
 4-4-5-1 
 
 4-5 
 
 Munich schenk beer 
 ,, lager beer f ',.. .. v.- t 
 Wiirzburg lager beer 
 Munich bock beer . . . , *' 
 salvator beer J '.. . 
 Prague lager beer . . . . *; 
 Nuremberg lager beer . . . ... 
 Bainberg schenk beer .... 
 
 3-8-4 
 4-3-5-1 
 4-0-4-7 
 4-3-4-8 
 46 
 4-8 
 3-8-4-0 
 4-2 
 4-2 
 
 5-4-6-3 
 5 
 4-4 
 8-6-9-4 
 9-0-9-4 
 10 
 4-6 
 5-9 
 4-6 
 
 Brussels lager beer 
 Culnbach lager beer 
 
 6-5 
 
 4-2 
 3-8 
 
 3-4 
 4-6 
 4-6 
 
 Brunswick mum . . . . ' f 
 
 2-4 
 
 39-0-45 
 
 The residue left in the mash tuns and known under the name of brewers' grains is 
 used as fodder for cattle. The germs separated from the malt by sifting as well as 
 the exhausted hops form a good manure. Brewer's yeast is extensively employed in 
 bread making, and in spirit manufacture. 
 
 The different kinds of beer are prepared by fermenting infusions of malted gram 
 generally barley so as to convert the sugar they contain into alcohol. 
 
 Raw Materials of Brewing. The principal material used in brewing is barley; 
 and though wheat, oats, maize, potatoes, rice, and starch, are capable of undergoing 
 the necessary changes for the development of sugar, they are scarcely ever used. 
 
 The barley used for brewing is the product of a species of Hordeum. It requires to 
 be ripe and sound ; this may be in part ascertained from its external appearance. 
 Each grain should have a uniform light yellow colour extending to the tips; it should 
 be full, plump, quite white and mealy inside, and free from odour ; and there should 
 be no admixture of foreign or dead grains. Especially the barley should be heavy, as 
 when malted it yields the saccharine principle nearly in proportion to its weight. 
 Scotch barley weighs from 54 to 59 Ibs. per bushel.; English barley 52 to 58 Ib's. ; 
 and Saale (German) barley 50 to 54 Ibs. In order to promote its uniform germina- 
 tion, the barley used in a malting operation should, as far as possible, have been 
 grown under similar conditions and on the same soil. This may be tested by placing 
 some of the grains in H shallow dish, covering them to of an inch with water, and 
 then exposing them without drying to a temperature of 25-30. When the barley 
 is good, the grains will germinate simultaneously. 
 
MATERIALS USED IN BREWING. 
 
 939 
 
 In the individual grains, the mealy interior alone is of value in beer brewing; the 
 husk, owing to its containing easily decomposable substances, which would give the 
 beer an unpleasant taste and smell, should be removed as far as possible. 
 
 ^ The principal constituents of the internal mealy portion of the grain, which is 
 built up of concentric rings increasing in thickness towards the outside-, are starch and 
 gluten ; besides which there are small quantities of albumin, a fatty oil, and inorganic 
 matter. As starch is the constituent most important in beer brewing, its properties in 
 this respect may be briefly enumerated. When heated with water, starch forms a 
 paste which, in contact with decomposing nitrogenous substances, is easily converted 
 into lactic acid ; with tannic acid, however, it forms a compound insoluble in water, 
 that readily sinks to the bottom. When starch is roasted, dextrin, a substance 
 soluble in water, is formed, which constitutes a chief constituent of beer ; other empy- 
 reumatic substances are also produced, upon which the flavour of the beer essentially 
 depends. The diastase, formed from the gluten during malting, changes the starch 
 most favourably at a temperature of from 60-75 into dextrin and sugar, and these 
 in their turn by fermentation yield alcohol and carbonic acid. 
 
 In this country and in France sugar has also been used as a brewing material, raw 
 sugar, molasses, or grape sugar being available for this purpose. Such an addition is 
 generally economically advantageous, since a part of the grain is saved and the work 
 facilitated. Further, beer thus prepared keeps better, because less barley being used 
 there is introduced into it a smaller quantity of the nitrogenous compounds which 
 render it more liable to spoil. But this beer, rich in sugar, is less pleasant to the 
 taste than that containing more dextrin, on which account it appears to be preferable 
 to add an amylaceous substance to the grain, and potato starch is often employed. 
 Still, the oily constituent of potatoes may easily impart an unpleasant taste to the beer ; 
 Zehling therefore recommends that the potatoes should be treated with soda previous 
 to use. 
 
 Hops. The peculiar aromatic taste of beer is in great part due to hops, the un- 
 fructified female flowers of the hop plant (Humulus lupulus). The strobiles of this 
 plant the hops of the brewer contain between the bracts at the base a peculiar 
 granular sticky substance, known as yellow powder, hop meal, or Inpul'in, 
 which, together with the scales, contain the essential constituents of the hop for the 
 purpose of brewing. Wild hops produce these constituents in only very small 
 quantities, therefore cultivated hops can alone be used by the brewer. 
 
 According to Winmer (I and II), and Kaubert (III), there is contained in 100 
 parts : 
 
 
 I II 
 
 III 
 
 
 Scales 
 
 Yellow powder 
 
 Ellinger Stadt hops 
 
 Oil of hop 
 
 
 
 0-12 
 
 0-50 
 
 Resin 
 
 2-60 
 
 2-91 
 
 15-90 
 
 Peculiar bitter substance 
 
 4-68 
 
 3*01 < not determined 
 
 Tannic acid ..... 
 
 1-61 
 
 0-63 
 
 3-02 
 
 Gum 
 
 5-83 
 
 1-26 11-10 
 
 Cellulose . , 
 
 63-95 
 
 8-99 48-33 
 
 Extract solution in water 
 
 12-12 
 
 4-92 6-40 
 
 The aromatic taste and smell of beer is chiefly due to the oil of hop, while the 
 bitter resin contained in the strobiles, which, owing to its solubility in alcohol, passes 
 into the beer, often imparts to it an unpleasant bitter taste. The- peculiar bitter 
 substance mentioned in the above apalysis is soluble in water, and consequently also 
 passes into the beer, imparting to it a part of its bitter quality, but at the same time 
 rendering it more permanent and wholesome. 
 
 The tannic acid contained in hops is so far of importance that a quicker clarifica- 
 tion of the wort is dependent upon it, as it forms, with the mucilaginous substances in 
 the wort, insoluble compounds which readily settle to the bottom. 
 
 The relative proportion of the active constittients in the hops varies considerably, 
 depending upon culture, the season, soil, and other circumstances. Certain districts 
 are especially celebrated for the hops produced by them ; such are Kent and Notting- 
 ham in this country, Saatz and Pilsen in Bohemia, Nuremberg and Spalt in Bavaria, 
 Schwetzingen and Mannheim in Baden, in Brunswick, Thuringia, and other districts. 
 
 The quality of a sample of hops may be to some extent judged from external 
 appearances. The strobiles should be clean and of good size, not mixed with leaves or 
 stalks, and should be either light red or greenish yellow in colour. Very ripe hops 
 
940 BEER. 
 
 are blood red, -while those which are unripe are quite greeu. The sample should be 
 rich in yellow powder, and this .should be sulphur yellow, not brown, as is the case in 
 old hops ; when rubbed between the fingers it should leave a resinous sticky mark, 
 and at the same time evolve a strong pure hop odour. Seeding hops are not so good. 
 Hops should ndl be more than one year old, since they quickly lose their active pro- 
 perties, and may impart to the beer an unpleasant taste and smell from the hop oil 
 having turned rancid. Old hops may be detected by the seeds falling out when the 
 strobiles are broken, while the seeds of fresh hops remain fast. 
 
 The proper carrying out of the hop harvest is a matter of great importance to the 
 quality of the beer to be produced. It is essential to choose for it dry weather, and a 
 selection should be made of the ripe hops, the unripe being left to ripen. 
 
 Great care is also required in drying the hops ; they must be dried quickly and 
 thoroughly. The drying is carried out either in large airy garrets or in special drying 
 apparatus of which the Hohenheim hop kiln presents the most advantages. It con- 
 sists of a large inclined drying surface, formed of hurdles covered with warm sack- 
 cloth, the hurdles being laid over shallow boxes through which warm air is driven by 
 means of a ventilator. The air passes through the hurdles upon which the hops are 
 laid and rapidly effects their drying. The hops are turned by placing an empty 
 hurdle upon a full one. and turning both over in such a way that the fresh one comes 
 to be the bottom one, the other is then removed. 
 
 Hops also require careful storing. The plan of storing up hops in lofts is 
 objectionable, since the exposure to air and moisture rapidly changes them. In order 
 to exclude air as completely as possible, the thoroughly dried hops should be packed 
 tightly together. A very common way of packing hops consists in placing them in 
 sacks and pressing them down with the feet; this is, however, insufficient. In this 
 country, as well as in America, hydraulic presses are used for pressing hops, the 
 resinous nature of the hops then causes them to stick well together, and hops thus- 
 pressed will keep for two or three years without deterioration. Hops are said to 
 keep still better when the sacks in which they are pressed are papered externally. 
 
 The bad appearance of old hops may often be diminished by sulphuring. Sulphu- 
 rous acid, however, admits of ready detection. By Wagner's method a small quantity of 
 the hops to be tested is placed in a glass flask with a small quantity of zinc and 
 dilute hydrochloric acid, and the gas evolved is conducted into a very weak solution 
 of sodium nitroprusside. If the hops have been treated with sulphurous acid, sul- 
 phuretted hydrogen is given off, which produces a beautiful violet coloration in the 
 solution of sodium nitroprusside. The presence of sulphurous acid does not, however, 
 always indicate old hops, because frequently in this country fresh hops arc sulphured 
 in order to preserve them. 
 
 Brainard's method of preserving hops consists in storing them up in chambers at 
 an average temperature varying as little as possible from 10, and not exposed to 
 light and air. 
 
 With this object the thoroughly dry hops are packed in dry sacks and stored in 
 chambers situated on the north side of a building, built of waterproof materials, and 
 which can be well closed. The hop-chamber is furnished with a double wall all round, 
 the space between the two walls communicating with an ice-house, so as to keep the 
 temperature of the interior as low as possible. Hops thus stored in such chambers 
 are said to keep for years without altering. 
 
 Schaar's method is somewhat similar to the above, consisting in burying the hops 
 in pitched tubs in ice. 
 
 ^ Instead of using the hops themselves in beer brewing, it has been suggested to 
 boil the hops in suitable distilling vessels, so as to separate the essential oil as a dis- 
 tillate, which together with the thick extract left behind is preserved for subsequent 
 addition to the beer. 
 
 But, setting aside the fact that in the preparation of this extract changes take 
 place in the essential constituents which impart to the product an entirely different 
 taste and smell, the method cannot be recommended owing to the facility it affords for 
 adulteration. 
 
 Water. It is by no means a matter of indifference what kind of water is used in 
 beer brewing, inasmuch as each admixture contained in natural water has an effect 
 upon the quality of the beer. 
 
 Rain water is fit only for softening the grain, because it is contaminated with 
 organic germs floating in the air, which easily produce decomposition. Filtered 
 rain water freed from such germs is on the other hand well adapted for beer brewing. 
 
 Of tho different kinds of well and spring water the softest, i.e., that which contains 
 relatively the least calcium salts in solution, is the most suitable for the brewer. A 
 hard water may be to some extent softened by exposing it for some time in largo re- 
 servoirs to the action of the air. Water thus prepared may be used for brewing. 
 
PREPARATION OF MALT. - 941 
 
 River water, which as a soft water would generally be adapted for brewing pur- 
 poses, has the disadvantage of being turbid from the presence of suspended organic and , 
 inorganic or earthy matter. This may, however, be removed by filtration through 
 gravel, sand, or charcoal. 
 
 According to Siemens a water adapted to brewing purposes must have the follow- 
 ing properties : it should be pure and clear, it should possess neither smell nor harsh 
 flavour, it should not be rendered cloudy by solution of soap, nor should it yield any 
 perceptible deposit when boiled; legumes, such as peas and lentils, when boiled in it, 
 ought very speedily to soften, and it should not evolve any odour when kept for some 
 time in a warm place. 
 
 Yeast. Yeast also belongs to those substances indispensable in brewing, and has 
 been already considered under FERMKNTATION (see p. 881). 
 
 Malting. The conversion of grain into malt has for its object the formation of 
 diastase, which originates in the gluten during the malting. Partly during the malting 
 and partly in the following mashing process, this diastase effects the conversion of the 
 starch contained in the grain into grape sugar and dextrin. There are also produced 
 during the drying of malt in kilns some dextrin, together with caramel and empy- 
 reumatic substances, which communicate to beer its colour, and have some influence on 
 the flavour and aroma. 
 
 The process of malting comprises the following operations: (1) Steeping or 
 softening the grain. (2) Germination. (3) Drying. (4) Removing the germs. 
 (5) Bruising the malt. 
 
 The steeping or softening of the grain has for its object to impregnate 
 the grain with sufficient water to cause germination, and also to remove from the 
 husks extractive substances which would spoil the taste of the beer. The barley is 
 placed in large cisterns of wood, or preferably of stone or cast iron, with four times its 
 volume of water, and kept in the cisterns until the points of the grains upon being 
 pressed with the hand allow of the ready separation of husk and contents. Such 
 grains as after two or three hours, during which time the mixture is frequently stirred, 
 remain floating on the surface, are taken off and separated. The most suitable 
 temperature for the steeping is 15 ; and the water is usually changed every twelve or 
 twenty-four hours, in summer more frequently than in winter. The time during which 
 the grain requires to Le steeped varies ; old barley containing much gluten requires 
 from four to six days, while young grain does not require more than thirty-six or 
 thirty-eight hours. In winter the process proceeds more slowly than in summer. Too 
 long steeping deprives the grain 'of its germinating power. 
 
 When the operation is completed the water is let off as quickly as possible by 
 means of cocks with a large bore, so as to prevent one part of the grain from remain- 
 ing immersed much longer than the rest. The water drawn off has a yellow colour due 
 to the substances dissolved. 
 
 Wheat, on account of its weaker husk, requires less time for steeping than barley. 
 
 Barley loses during steeping from 1 to 2 per cent, of dry substance ; but by the 
 absorption of water its weight is increased about 47 per cent. 
 
 Germination. The object of germination is the formation of diastase from the 
 gluten of the grain during the development of the cotyledon, in order to make use of 
 this diastase afterwards for changing the starch into sugar and dextrin. The proper 
 germination of the grain is therefore one of the most important operations in beer 
 brewing. Diastase must be formed in quantity sufficient to change the entire 
 quantity of starch, otherwise starch would be lost. The germination should not 
 however be allowed to proceed too far, since then starch would again be lost by being 
 used up by the young plant in the formation of cellular tissue. The germination 
 must be stopped as soon as the germs have attained a length of 1^- If of the length of 
 the grains, or when the cotyledon has penetrated about half way into the interior of 
 the grain. 
 
 The chamber in which the germination is carried out should be as independent as 
 possible of fluctuations of temperature and changes of weather, the most suitable 
 temperature being 10 to 15. Although a moist chamber is required for due growth 
 it should not be mu,sty, since that is apt to cause fungoid growth. Constant change 
 of air is necessary. If the chamber should be insufficiently humid a spray of water 
 or a jet of steam may be introduced. In Germany a cellar is usually employed 5 to 
 6^ feet high, and called the germinating floor. The floor of the malting room should 
 be hard and impenetrable to moisture ; it is generally made of good cement or stone 
 flags lying close together, the bedding beneath depending upon the situation. On a 
 damp soil building rubbish is used, and clay in dry places. The sides and ceiling of 
 the chamber are covered with hydraulic cement. It is essential to avoid having any 
 ruts or holes, into which grains can fall, because they quickly rot, and mould is formed 
 
942 BEER, 
 
 by which the sound grain in subsequent operations may be easily injured. Spring is 
 better suited for malting than summer or winter, the temperature in March or April 
 'being more constant, and the germination taking place more uniformly. Beer brewed 
 in March owes its good quality partly to this fact. Autumn is equally favourable for 
 the operations of malting. 
 
 The treatment of the germinating grain upon the malting floor varies. In this 
 country and in North Germany the swollen barley, after the water has drained off, 
 is made up into heaps, 4 to 6 inches high, and when these have got dry on the surface 
 they are turned over in order to secure an equal temperature of 10-15 and equal 
 moisture throughout the whole heap. Directly the grains exhibit a whitish projection 
 they are made up into heaps, 12 to 14 inches high. The vital activity of the grains 
 causes a rise of temperature in the heaps, and when it has risen to 25-27 the so- 
 called sweating takes place, the hand becoming moistened when thrust into the mass. 
 The heaps are now so turned that the upper and lower layers come more into the 
 centre, the middle layer being brought to the surface and next the floor, so as to re- 
 duce its temperature. Should the grain not be sufficiently moist, or if it has been too 
 suddenly dried, it is then carefully moistened with lukewarm water. 
 
 In turning over the heaps the grain gets more and more spread out. When the 
 plumules are sufficiently developed the malting heap is spread out in a heap, 4 inches 
 deep, so as to avoid further heating of the grains, and allow the further development 
 of the germs to go on slowly. The germination is considered complete when the 
 germs in the case of barley have attained the length of lg--lf of the original grain. 
 
 In Bavaria the following plan is universally adopted. The softened barley is 
 spread out upon the malting floor in level heaps, 5 to 6 inches high, and turned as 
 often as the surface becomes dry, which takes place about two or three times daily. The 
 turning is effected with a flat shovel in such a way that the lower layer is brought to 
 the surface and vice versa. The grains begin to germinate in two or three days and then 
 the heap is made higher, about 10 to 12 inches, and left until the temperature of the in- 
 terior has attained at most 25 or 27, and a strong sweating appears on the surface. 
 The heap is then again turned, divided into three parts so that the middle or warmed 
 part of it is brought next the floor, upon it what was the uppermost portion, and 
 finally upon that which was lowest. In the course of about ten hours a further sweating 
 takes place, and a further turning of the heap is necessary. After three turnings the 
 germs generally attain the desired length of half an inch, and the grain is again spread 
 out. The heap is thus reduced 3 to 4 inches in depth and the operation repeated as 
 often as is necessary to avoid any further important rise of temperature. The process 
 is generally complete after three spreadings. 
 
 During the warm part of the year the germination lasts on an average ten or 
 twelve days, at the end of the autumn fourteen days to three weeks are necessary. 
 
 To prevent further growth of the germs, the grain is removed to the drying floor, 
 or, as the case may be, to the charring floor. The drying floor is a spacious airy room, 
 upon the floor of which the grain is spread out in thin layers, and turned from time to 
 time. 
 
 The loss of dry substance in malting is about 3 per cent. A considerable quantity 
 of carbonic acid is given off" during the operation ; well- ventilated chambers are there- 
 fore necessary to prevent danger to the workmen. 
 
 The change which takes place in the composition of grain during malting may be 
 seen from Saussure's analysis of germinated and ungerminated barley. 
 
 
 Ungerminated 
 
 Germinated 
 
 Starch . . .... 
 
 Cellulose . . . ' . 
 
 727 
 5-5 
 
 65-8 
 5'6 
 
 Sugar . . . . ... 
 Dextrin . . . . . ^ 
 
 2-4 
 3-5 
 
 5-1 
 
 7-9 
 
 Gluten and mucin . . . , 
 Albumin ..... 
 
 11-8 
 1-4 
 
 7-6 
 27 
 
 
 
 
 The subsequent operations depend upon whether the germinated grain is to be 
 treated for air-dried or roasted malt. The brewer uses almost exclusively roasted 
 malt, but some kinds of beer of fine quality are prepared from air-dried malt alone. 
 
 Malt roasting. The object of roasting malt is not only to dry it, but also to pro- 
 duce empyreumatic substances which influence the colour and taste of the beer brewed 
 from it. 
 
 The roasting must be so conducted that the malt is uniformly heated, but at the 
 beginning, while the grain is yet moist, not too strongly, so as to avoid formation of 
 
MALT KILNS. 
 
 943 
 
 paste, which upon drying would leave a horny mass impervious to water. As soon 
 however us the malt is dry, the temperature is raised to 90 or even 100, since at 
 this temperature diastase no longer acts upon the starch except in the presence of 
 water, nor is it itself decomposed. 
 
 The kilns used for roasting malt are known as smoke kilns, air kilns, and steam 
 kilns. 
 
 A smoke kiln of old construction, but which is in use at the present day, con- 
 sists of a horizontal perforated metal plate or wirewove frame of copper or iron wire, 
 16 to 20 feet long, the holes or interstices in which must be small enough to prevent 
 the grain slipping through. The roasting plate is supported by cross beams and iron 
 pillars, the whole being mounted upon brickwork narrowing towards its lower end. 
 The hot air from the fire passes through the apertures in the plate into the lower part 
 of the kiln, where it mixes with cold air admitted from outside, the rate of trans- 
 mission of which can be regulated so as to lower or raise the temperature as may be 
 required. 
 
 The most suitable fuel for these kilns is that which yields as little smoke as pos- 
 sible ; dry coal, or what is still better, the best quality of coke is the most convenient 
 fuel. If wood, brown coal, or turf be used, the malt would acquire a darker colour 
 and a smoky taste which afterwards passes into the beer. 
 
 In air kilns the roasting plate is heated by hot air, which is admitted below or 
 produced in the lower part of the roasting chamber by heating tubes through which 
 hot air from a furnace is made to pass. 
 
 The Overbeck kiln, with a new combination of roasting plate, is represented by 
 fig. 687- Each of the three stories (A B c) consists of three endless cloths running upon 
 a pair of rollers. The malt is carried along upon 
 the cloths in an upward direction ; the cloths 
 themselves are made of material specially con- 
 structed for the purpose, and are furnished at 
 the sides with edges bent at right angles, to 
 prevent the malt falling out. The texture of 
 t,he cloths is such as to enable them to bear the 
 continual bending and stretching to which they 
 are subjected without injury. Between the 
 roasting cloths of the two upper stories are 
 turning arrangements; by which the malt falling 
 from the highest parts of the wire cloths is 
 
 thrown about 3 feet high against a peculiarly 
 
 bent metal cover, which then conducts it to the 
 
 beginning of the cloth next following in succes- 
 sion. At the end of the floors where at a and b 
 
 the malt falls from a height of 9 feet upon the 
 
 hurdle beneath, as well as between the cloths of 
 
 the lower stories, turning arrangements have 
 
 been found to be superfluous. The way in 
 
 which this turning apparatus works is of great 
 
 utility in brewing, since not only is the mixture 
 
 of green malt and germs completely separated, 
 
 but the malt is mixed at regular intervals, the 
 
 individual grains being projected through the 
 
 air, forming upon falling layers of malt of the 
 
 same evenness and equality of depth as they 
 
 passed from the feeding hopper (E). The most 
 
 practised hands are not able to turn the malt 
 
 with anything like the regularity effected by 
 
 this apparatus. By means of special simple 
 
 contrivances, consisting in bringing rims along 
 
 the edges of the chambers, the roasting chambers 
 
 are so thoroughly closed that hot air from the 
 
 furnace (6) is compelled to pass over the malt. 
 
 As a rule, the malt takes about two and a half 
 
 hours to pass over the first roaster, completing 
 
 FIG. 687. 
 
 the second one in about three and a quarter hours, and the lowest in about four hours. 
 This different ratio of time admits of an almost equal spreading of malt in all three 
 stories, since the volume of malt diminishes in drying in about an inverse ratio. The 
 7-oasting process is generally complete in about ten hours ; it admits however of being 
 lengthened or shortened by altering the driving belts. After passing the last 
 chamber, the malt finally falls upon a travelling bed (p), which removes it from the 
 
944 
 
 BEER. 
 
 kiln. The kiln admits of being worked by one man, and gives excellent results both 
 quantitative and qualitative. 
 
 Figs. 688 and 689 represent an air kiln of Siemens' construction, in which the heating 
 is effected either by waste hot air from the boilers, or by means of special heating arrange- 
 
 FIG. 688. 
 
 FIG. 689. 
 
 ment. A couple of roasting plates are placed one above the other, an alteration which 
 has recently been much introduced in the air kilns. The upper plate is for drying, 
 
 
DRYING MALT. 945 
 
 the lower one for the actual roasting process. A is a common chimney for hot air from 
 the boilers and kiln fire, x a fire-proof wall, B an iron cylinder into which passes the 
 hot air of a special oven (c), or the hot air escaping from the boilers is conducted 
 by means of the flue (D) which is furnished with a valve (a) for turning the hot air 
 into the cylinder (B) or the chimney (A). At a distance of 4 or 5 inches the cylinder 
 B is surrounded by a casing of fire brick closed above, and communicating with the 
 lower part of the roasting chamber by a number of flues. A hollow space formed by 
 the casing of the oven (c) communicates with this series of flues ; cold air from outside 
 passes through the side apertures (c c), beneath the heating tubes (b b), and from 
 thence beneath the roasting plate. The heating or smoke tubes (b b) extend from the 
 cylinder (B) through the roasting chamber, and join again in the chimney (j), which 
 conducts the gases into the air through the steam pipe (G), and at the same time by its 
 heat promotes the quick evaporation of moisture from the kiln. There is also another 
 series of flues (dd) through which air heated at the outside of the cylinder (B) by the 
 oven (c) is at once conducted to the roasting plate. The hot air rises from it 
 through slits which increase in width with their distance from the cylinder B and the 
 furnace c, so as to obtain as great an equality as possible. F and E are the two roast- 
 ing plates. 
 
 In the steam 'dins the air conducted beneath the roasting plate is heated by 
 making superheated steam circulate in iron or copper tubes in the lowest part of the 
 roasting chamber. This kind of kiln is only fit for preparing a pale kind of malt, and 
 is little employed. 
 
 The malt is spread out on the several roasting plates in layers about 3 to 5 inches 
 deep, a little shallower in the case of double roasting plates than where simple roasting 
 plates are used, since otherwise the draught would be insufficient. For the reason 
 already given, the temperature before the water has been got rid of requires to be very 
 moderate ; it ought not to exceed 60. Subsequently the temperature is raised to 90 
 and 100, in Bavaria indeed to 120 and still higher. The temperature is regulated 
 according to the degree of roasting desired : for pale malt and that used in distilleries 
 the roasting temperature is not allowed to exceed 60. 
 
 As already mentioned, beer is also prepared from air-dried malt. As a rule the 
 colour of beer depends upon the duration of the roasting, and the temperature at 
 which it is carried out ; the longer the roasting process, and the higher the tempera- 
 ture, the greater is the proportion of dextrin formed and the darker is the beer. It is 
 now very usual to impart to beer a dark brown colour by adding strongly roasted 
 malt or sugar to the wort prepared from pale malt. 
 
 Working with a kiln with a simple roasting plate, the proportion of malt daily 
 roasted is reckoned for every 100 square feet roasting surface as follows : once empty- 
 ing, about 4 cwts. ; twice emptying, about 6 cwts. ; three times emptying, 8 to 10 cwts. 
 
 The removal of the shoots or comings must follow directly after the roasting, 
 since they absorb moisture upon keeping, lose their brittleness, and become after- 
 wards hard to remove. The removal is necessary, because they contain no constituents 
 essential to beer, and they would increase the volume of the malt without im- 
 proving it, and would furthermore render the beer liable to turn sour. 
 
 The methods of removing the comings are very various. An old plan which is 
 still much in use consists in treading the roasted malt with the feet and then passing 
 it through sieves. This method, however, involves the loss of a good deal of malt. 
 A newer method consists in passing the freshly roasted malt through a sieve drum, to 
 the axis of which arms furnished with brushes are attached, and finally through a 
 winnowing machine. In the former the comings are broken off by the motion of the 
 drum and the brushes, and in the second they are separated from the malt graii s. 
 Drums, with pieces of metal attached to the sides, by means of which the grains are 
 raised and thrown down upon the axle of the drum, are also in use for effecting 
 separation. 
 
 The comings amount to about 3 per cent, of the entire weight of the malt, and 
 they are used either for fodder or manure. Including this 3 per cent, the total loss 
 during malting amounts to about 8 or 10 per cent, of the dry substance of the grain 
 employed. Besides this, the loss of moisture amounts to about 10 or 12 per cent. 
 
 According to the recent researches of John, the loss of dry substance in malting is 
 still more considerable, 100 parts of dry barley yielding 
 
 Malt (excluding plumules and radicles) . . . 83*09 85*88 
 
 Plumules . . 3-56 3-09 
 
 Kadicles 4'99 4-65 
 
 Evolved as gas 8*36 6-38 
 
 100-00 100-00 
 
 3P 
 
946 BEER. 
 
 Bruising. Malt contains about two-thirds of its weight of soluble substances. In 
 order to facilitate the solution of these substances, it is first of all necessary to break 
 the malt grains, a process known as malt bruising. In this operation the malt grains 
 are rather crushed than ground, the husks being thus removed, but not ground up. 
 The malt, before being submitted to the bruising process, is moistened either by ex- 
 posing it to the air and allowing it to absorb moisture naturally, or it is sprinkled 
 over with from 7 to 10 percent, of water. Millstones or iron rollers are used in 
 malt bruising, care being taken that they are not set too near one another, but so far 
 apart as to crush without pulverising the malt. 
 
 The bruising mills consist of a couple of smooth cast-iron rollers of different 
 diameter revolving in opposite directions, the malt being passed to them by means of 
 a sloping perforated plate of sheet iron, through which dust and fragments of comings 
 fall into suitable receptacles. At the extremity of the plate, where the malt falls 
 over, revolves a wooden roller, the periphery of which is furnished lengthwise with 
 knife blades just long enough to touch the iron plates. A slow motion being given 
 to this drum, the knife blades push forward just enough malt to feed the mill, so that 
 the latter can never get over-filled. The whole is surrounded by a wooden casing, 
 narrowed beneath the rollers to the shape of a funnel, through which the bruised malt 
 falls either into some vessel for collecting it or direct into the mash tub. 
 
 The moistening causes an increase of 16 per cent, in the volume of the malt, and 
 the bruising a further increase of 16-18 per cent. 
 
 The composition of malt is shown by the following analyses by Oudemanns : 
 
 
 
 Pale 
 roasted malt 
 
 Strongly 
 roasted malt 
 
 
 58-6 
 
 47'6 
 
 
 0-7 
 
 0-9 
 
 
 6-6 
 
 10-2 
 
 
 7-3 
 
 14-0 
 
 Cellulose 
 
 10-8 
 
 11-5 
 
 
 10-4 
 
 10-5 
 
 Fat . . . . . 
 
 2-4 
 
 2-6 
 
 Ash 
 
 2-7 
 
 2-7 
 
 In this country malt is generally prepared in buildings especially erected for that 
 purpose situated in grain districts, the owners of such malt kilns selling the malt to 
 the brewer; but in Germany and France malting is carried on for the most part in the 
 breweries. Recently the English system has been partly adopted in Germany. 
 
 In this place may be mentioned Fleck's process of preparing malt without germi- 
 nation, which consists essentially in treating barley with dilute (1 per cent.) mineral 
 acids, those most adapted for the purpose being sulphuric acid and nitric acid. In 
 this process care must be taken to avoid the use of more liquid than is absolutely 
 necessary, as what is called glass malt is apt to be produced in the subsequent opera- 
 tion of roasting. For complete softening 100 parts of barley would require 80 parts 
 of acidulated water, but complete softening is not allowed. The conversion of starch 
 into sugar by means of acidulated water is accelerated by gentle heating. After 
 heating 50 parts of barley and 30 parts of acidulated water, containing 1 per cent. 
 of sulphuric acid, for seventy-two hours over a water bath at a temperature of 40, the 
 conversion of the starch is so far complete that after drying and roasting good malt 
 is obtained. 
 
 A disadvantage attending this process consists in the loss of phosphoric acid, it 
 being replaced by the mineral acid and passing into solution. On the other hand, 
 the loss of starch (sugar) and of organic substances in general is considerably less 
 than in the germinating process, since the change effected by mineral acids is not 
 accompanied by the formation of shoots. 
 
 Brewing. In making beer from malt, the first consideration is the conversion of 
 the starch still contained in the malt into dextrin and sugar, then the fermentation 
 of this sugar, and its conversion into alcohol and carbonic acid. Beer brewing 
 comprises the following operations : 1. Mashing and solution of soluble extractive 
 constituents. 2. Boiling and hopping of the wort. 3. Cooling of the wort. 4. 
 Fermentation of the wort. 
 
 1. Mashing. The object of mashing is to convert the starch still contained 
 in the bruised malt into dextrin and sugar by the action of the diastase. This 
 conversion is effected by stirring up the malt with warm water, in which the diastase 
 dissolves and then acts upon the starch. The temperature at which the mashing is 
 
BREWING. 
 
 947 
 
 conducted is of great influence upon the rapidity of the mashing process. Schwarzer's 
 researches hare proved that diastase, when heated above 65, is gradually decom- 
 posed, and is then no longer capable of converting starch into sugar and dextrin. 
 Hence when it is desired to mash with as little malt (diastase) as possible a tempe- 
 rature of 60 or 65 must not be exceeded. When, however, a quick conversion of 
 starch into sugar is desired, the mashing temperature is allowed to come as high as 75, 
 although at this temperature a considerable loss of diastase ensues, and consequently 
 more malt is required. The mashing temperature is further of considerable influence 
 upon the proportion of sugar and dextrin produced. At all temperatures from 60 
 down to 0, whatever the quantity of diastase used, there is always produced from 50 
 to 53 per cent, of sugar from the starch extract. At higher temperatures propor- 
 tionally less sugar and dextrin is formed. 
 
 It is a matter of importance in mashing that the water should come into intimate 
 contact with the starch of the bruised malt, both to dissolve the sugar formed and to 
 secure the complete action of the diastase. 
 
 According to the way in which the mashing is effected two distinct operations 
 may be distinguished the infusion method, and the decoction method. 
 
 The mash tuns are large round or square tubs with double bottoms, generally made 
 of oak, sometimes of iron or stone. The upper bottoms set a few inches above the 
 lower ones are perforated, and they are generally made of wood, although copper or 
 iron is preferable, since metallic bottoms allow of finer perforations than wooden ones, 
 thus rendering a more complete separation of the malt residue from the wort possible. 
 Between the two bottoms is a tap for running off the liquor passing through the 
 perforated bottom. A tube let in below feeds the tub with hot water. A more 
 recent construction does away with false bottoms, instead of which strips of metal 
 grating are let in with channels beneath them for conducting away the liquor. 
 
 The stirring of the mash in the mash tun was formerly always effected with an 
 iron rake. At the present time, it is more frequently effected by machinery, especi- 
 ally in large breweries. 
 
 FIQ. 690. 
 
 Fig. 690 represents a mash tun with stirring apparatus. The tun itself (a a) is 
 made of wooden staves hooped together. In the centre is fixed a perpendicular 
 shaft (b b), which can be revolved slowly by the bevelled wheels (t u) at the top. 
 From one side of this shaft project two arms (c <?), attached to the spur-wheel (to), 
 and carrying at the other extremity a shaft (d} which is furnished with a number of 
 arms (e e) placed obliquely and made to revolve by the wheel (or), so that when the 
 shaft is turned, these arms stir the malt in the tun and constantly lift it upwards 
 from the bottom. 
 
 Another form of mash tun is represented by fig. 691. The stirrers (A and B) 
 are turned by the pulley (p\ the pinion (b), and the driving-wheels (c F F and o). 
 Outside the lower part of the side of the wooden vat (i i ) is a casing, allow- 
 
 3 P'2 
 
948 
 
 BEER. 
 
 ing sufficient free space for heating the mash in it by opening the steam cock (o), the 
 steam passing to the pans through the valve (m) or escaping through the cock (r). In 
 most cases, however, this arrangement for warming the mash tun is omitted. 
 
 FIG. 691. 
 
 Above the mash tun is often fitted a movable lid by which it may be partly or 
 entirely covered. 
 
 Beneath the mash tun is a reservoir (K) called the underback, for the reception 
 of the wort escaping from the tun through the discharge pipe (K n). 
 
 An apparatus for quickly wetting the bruised malt has been devised by Steel, and 
 has been adopted in a number of breweries. It consists of a horizontal iron cylinder 
 2 feet long and l to 1 foot in diameter, one end of which is completely closed with 
 an iron plate, the other extremity partly so. A spiral shaft furnished with knives 
 passes along the interior of the cylinder, and is set in motion when the cylinder is in 
 use. Bruised malt and water are thrown in together through a wide tube towards 
 the closed end of the cylinder, and having been well worked up together by the 
 stirrer, fall out into the mash tun at the other end of the cylinder, the upper half of 
 which only is closed. 
 
 The brewing vats serve either for heating water and wort, or for boiling and 
 hopping, or the two operations are carried out in separate vessels. In the latter case 
 the mash tun is made somewhat larger than the brewing vat. 
 
 The brewing vessels are round with flat bottoms, and are generally made of copper, 
 although recently iron has been used in their construction. The hot air circulates 
 round and below them. 
 
 A matter of great importance in the production of a good wort is the temperature 
 at which the mashing is carried on. The proper mashing temperature, i.e. the tem- 
 perature most favourable for the action of diastase upon starch, is between 65 and 
 75 ; it is not advisable however to start with this temperature, but the mash should 
 be gradually heated to it, the rise of temperature being made slower when working 
 with slightly roasted malt than when strongly roasted malt is operated upon. 
 
 Infusion method. This method, which is adopted in this country and in France, 
 and to some extent in Germany, is as follows: Directly the malt is placed upon the 
 perforated bottom of the mash tun a quantity of water at a temperature of 60, equal 
 to about one and a half times the weight of the malt, is passed into the mash tun 
 from below, the whole being well stirred by some suitable arrangement, and then 
 allowed to stand about half an hour, so as to secure the penetration of the water. A fresh 
 quantity of water at a temperature of 90 is then run in, so as to raise the whole to 
 70-75. After again well stirring, the mash tun is covered and left quiet for about 
 three hours, during which time the diastase acts upon the starch, forming sugar and 
 dextrin. Upon opening a cock, the liquid or wort passes through the perforated 
 bottom of the mash tun into the wort reservoir or underback, from whence it is 
 pumped into the copper, or in some cases, as above mentioned, it is pumped at once 
 into the copper. 
 
BREWING. 949 
 
 The first extraction withdraws from malt about three-fifths of its soluble con- 
 stituents, but a portion still remains with water in the malt grains : 100 Ibs. of malt 
 retaining from 100-120 Ibs. of water. In order therefore to extract the malt, as well 
 as to render soluble the still undissolved farinaceous constituents, the residue is 
 treated with about half the quantity of water employed in the first instance at a tem- 
 perature of 80, again mashed, and after standing an hour, during which time the last 
 portion of starch is converted into sugar, the wort is run off and mixed with the 
 results of the first mashing. 
 
 The boiling method. This method is especially adopted in Bavaria and neigh- 
 bouring parts. The bruised malt is first of all made into a paste, in the mash tun, 
 with a small quantity of cold water. After four to six hours, another portion of water 
 is heated in the copper to boiling, and gradually run into the mash tun until the 
 liquid has attained a temperature of 30-36. After a short time the thicker portion 
 of the liquid is brought into the brewing vat, where it is boiled under constant stirring 
 for half an hour or an hour, and then again run into the mash tun, raising the tem- 
 perature to 55. After protracted mashing, another portion of the mash is brought 
 into the vat, again boiled, and this second thick mash is returned, by which the tem- 
 perature of the contents of the mash tun are raised to 70. The clear mash is then 
 run off through the perforated bottom of the mash tun, brought into the boiling vat, 
 where it is boiled for a quarter of an hour, and then again run into the mash tun, the 
 temperature of the latter being thus raised to 75. After protracted stirring the mash 
 tun is covered, and its contents are left quiet for one to one and a half hours ; the 
 wort is then run off through the perforated bottom. 
 
 Augsburg method. The essential difference between this and the foregoing 
 method consists in the liquor yielded in the first mashing with cold water being run off 
 through the perforated bottom into the under back. This liquor, called kaltersatz, 
 contains a considerable quantity of dissolved albumen. A portion of it is mixed with 
 the water to be heated in the copper, and boiled for half an hour. The albumen co- 
 agulating rises to the surface and carries with it mechanically the impurities of the 
 water, which can then be readily removed. The clarified water is now brought into 
 the mash tun so as to raise the temperature of the latter to 65 ; a mashing is made, 
 and the whole left to stand for a quarter of an hour ; the wort is then drawn off and 
 brought with the remainder of the cold mixture into the vat. From the clear wort 
 thus obtained, a quantity equal to about ten gallons for every hundredweight of bruised 
 malt employed is drawn off and cooled. This liquor warmer satz is added to the 
 wort in the subsequent operation of boiling and hopping, by which means a mild and 
 bright beer is said to be produced. 
 
 In the Franconian, also known as the Bamberg method, the bruised malt is 
 gradually mixed in the mash tun with water at a temperature of 80, a mash being 
 obtained of about 60 or 63. After well stirring up and allowing to stand a short 
 time, the wort is drawn off and boiled, and again brought into the mash tun, by 
 which means the temperature of the latter rises to 75, again mashed, and the whole 
 allowed to stand for one hour. 
 
 The quantity of water used in mashing varies with the district. In Old Bavaria 
 the quantity of water used amounts to about eight times the weight of the malt, while 
 in the Augsburg and Franconian methods the proportion of water is from six to seven 
 times the weight of the malt. 
 
 In the Bohemian method four-fifths of the water to be used is brought into the 
 mashing tun, previously heated, in summer to 32 and in winter to 40 ; the malt is 
 mashed and stirred, and then the remainder of the water, with the exception of about 
 one-thirteenth part of the whole, which has meanwhile been heated to boiling, is 
 added. After vigorous stirring the thick mash is withdrawn, boiled in the copper 
 during thirty minutes, again returned and stirred. This operation is repeated twice, 
 but the boiling on the second occasion is only continued for twenty-five minutes, and 
 on the third for twenty minutes. The temperature of the mash has by this time- 
 reached 75. The small quantity of water reserved is then heated to boiling, and 
 wort is added to it until it shows signs of turbidity ; the mixture is then boiled and 
 added to that in the tun. After standing from half an hour to an hour the wort is 
 drawn off. 
 
 The preparation of the wort for the Berlin white beer is described by Stahl- 
 schmidt : 36 bushels of crushed malt are mashed with 225 gallons of water at the 
 ordinary temperature, and then scalded with 7oO gallons of water sufficiently hot to 
 raise the temperature of the whole mash to about 35 or 40. From this 200 gallons 
 of clear mash are taken and boiled in the copper with the hops for a quarter of an 
 hour, Ib. to 1 lb. of hops being taken for each bushel of malt ; it is then returned to 
 the mashing tun and well mashed. 350 gallons are then drawn off, boiled in the 
 
950 
 
 BEER. 
 
 topper, and returned and thoroughly mashed. Finally, another 450 gallons of clear 
 ash is withdrawn, heated to boiling, and then brought into the straining vat, which 
 usually has a wooden straining bottom, generally covered with straw. The inter- 
 space between the perforated bottom and the true is also lined with straw. After the 
 clear mash has been brought into the straining vat, the remaining thick mash from 
 the mashing tun is added, taking care that the thick mass of crushed malt is first in- 
 troduced. The greater part of the hot cloar mash collects in the space under the 
 false bottom, and warms the vat and also the added mash, so that the whole is heated 
 to 70. The mash remains in the straining vat an hour or an hour and a half, and is 
 then clarified, the residue being treated with warm water. Both worts are at once 
 brought into the cooling vessel. 
 
 The wort obtained by the infusion method is rich in sugar, consequently yielding 
 an alcoholic beer, which however does not keep so well. By the decoction method, 
 the solution and separation of the wort is facilitated and accelerated by the boiling, 
 but at the same time the action of the diastase is partially impeded, so that the 
 greater part of the starch is only converted into dextrin. A wort is consequently ob- 
 tained containing much dextrin, and but little sugar and nitrogenous compounds, 
 which yields a weaker kind of beer, but one that keeps well ; the dextrin in this beer 
 also determining the retention of carbonic acid, and its gradual evolution. 
 
 In whatever way the wort may be produced, a small quantity of extract is always 
 retained in the grains. In order to recover this, after the removal of the upper 
 dough-like mass, fresh water may be added, and the resulting thin wort may be used 
 in the mashing of fresh malt, in the preparation of small beer, or in the manufacture 
 of brandy or vinegar. 
 
 The residue, when exhausted as much as possible, contains the husks, nitrogenous 
 constituents, fat, a small quantity of starch, calcium phosphate, and other salts, to- 
 gether with from 60 to 80 per cent, of water. 
 
 The strength of the wort varies according to the strength of the beer to be pro- 
 duced; it having a sp. gr. of T056 to T070 for strong beer, and less, as low as T020, 
 for weak beer. The quantity of extract obtained from the crushed malt varies 
 according to the quality and preparation of the raw material. It ranges ordinarily 
 between 55 and 65 per cent, of the weight of the malt; sometimes however it amounts 
 to 70 per cent. 
 
 An addition of amylaceous material may be made to the malt during mashing, as 
 the quantity of diastase contained in the malt is so large that it is capable of convert- 
 ing into sugar and dextrin considerably more starch than is contained in the malt 
 itself. In this respect potatoes are especially important, but the starch should be 
 separated before it is added to the mash. 
 
 . According to Siemens, in the Hohenheim brewery, 100 parts c^f potato are sub- 
 stituted for 25 parts of malt ; and this quantity yields about 15 parts of extract. In 
 the preparation of six barrels of beer, 450 to 500 Ibs. of malt are used with 900 to 
 1000 Ibs. of potatoes, or the amount of starch to be obtained from that quantity of 
 potatoes. When the potatoes themselves are used, they are first converted into a 
 paste, which is stirred and washed with fresh water. 
 
 About two-thirds of the entire quantity of water to be used, previously heated to 
 80 or 90, is brought into the mashing tun ; then five-ninths of the malt, moderately 
 dried, is added ; next the potato paste or the starch representing it, and the whole is 
 stirred. The temperature of the mash is now brought to 60 or 65, and maintained 
 at that point until the starch is converted into sugar and dextrin ; the mash is then 
 boiled until it becomes clear, which takes place more quickly when starch is used than 
 with potatoes. Meanwhile, the remaining four-ninths of the crushed malt, in a 
 strongly dried condition, is mixed with the remainder of the water in the mashing 
 tun ; to this the boiling thick mash is added, and the whole vigorously stirred and 
 then allowed to stand for an hour or an hour and a half. The residuary grains are 
 afterwards again exhausted with hot water. 
 
 The constituents of the wort obtained according to different methods are shown in 
 the following table, according to the results obtained by Gschwandler : 
 
 
 Decoction 
 
 Satz 
 method 
 
 In n 
 
 With 10 
 per cent. 
 of starch. 
 
 Sugar 
 Dextrin 
 
 4-85 
 6*24 
 
 4-37 
 7'61 
 
 5'26 
 6*68 
 
 5-31 
 6-23 
 
 Nitrogenous matter . 
 
 0*79 
 
 
 
 0-67 
 
 Other constituents 
 
 0-41 
 
 0-95 
 
 070 
 
 0-22 
 
BOILING THE WORT. 
 
 951 
 
 In Germany the boiling and hopping of the wort is mostly carried out in open 
 boilers or pans, which are either used as well fur heating the mash, or are placed next 
 the mash tubs. The entire operation has for its objects the concentration of the wort, 
 the coagulation and separation of the dissolved albumin, as well as the mucilage by 
 tannic acid, and the extraction of the essential constituents of the hops. 
 
 As before mentioned, the brewing cauldrons are frequently identical with the mash 
 pans ; in other cases, however, they are about one-fifth smaller, the shape remaining 
 the same, being more or less shallow flat-bottomed pans of sheet copper or iron. 
 The further the concentration has to be carried the shallower the boiler should be. 
 
 In France, and especially in England, closed vessels are frequently used. This 
 method has the advantage that during the boiling less of the aromatic constituents of 
 the hops are lost ; the requisite concentration is then often effected by the addition of 
 sugar or molasses. The form of this brewing cauldron is a sphere, but pressed in so 
 as to become convex at the bottom (fig. 692). At the top is ti cylindrical dome (c), 
 
 FIG. 652. 
 
 from which pass five narrow pipes (dd\ four of which are carried upwards and lead 
 the steam into the preliminary heating vessel, which is placed directly over the brew- 
 ing copper, whilst the fifth pipe (V) carries the surplus steam upwards into the 
 chimney. Through the dome there passes an axis (e c) which can be rotated by means 
 of a toothed wheel (<?), and to this is attached a stirring apparatus, by which the 
 wort can be kept stirred during the boiling. The fire is placed under the copper, the 
 heated air playing over the bottom and the lower part of the sides of the copper. 
 
 The different methods vary in the length of time during which the boiling is 
 carried on. In Bavaria, in the preparation of new beer in open pans, it lasts from an 
 hour to an hour and a half; for lager beer the wort is boiled two to three hours; 
 dark beer is boiled longer than light. In England, where closed vessels are used, the 
 boiling lasts from four to six hours. The scum formed during the boiling is continu- 
 ally removed. 
 
 The addition of the hops is made either at the commencement of the boiling or 
 after it has progressed some time, the object in the latter case being that too much of 
 
952 BEER. 
 
 the aromatic constituents shall not be lost, and that too much of the bitter substance 
 shall not pass into the beer. 
 
 It has also been recommended to add a small portion of the hops at the commence- 
 ment, and the remainder at the end of the operation ; or to extract the aromatic con- 
 stituents of the hops by means of steam in closed vessels, and add the residue to the 
 boiling wort, and the aromatic extract to the cooled wort. Also, a complete extraction 
 of the hops in closed vessels is frequently carried out. In any case, it appears to be 
 the most rational plan not to boil all the hops with the wort during the whole of the 
 operation, because much of the aromatic matter would be thus lost. 
 
 The quantity of hops to be added varies according to the length of time the beer 
 requires to be kept. For winter beer 1 to H Ibs. of hops are used for 100 Ibs. of 
 malt ; for lager beer, 2 Ibs. ; in beer which should keep till October, 3 Ibs. In 
 England, the quantity varies between one-twentieth and 4 Ibs. of hops to 100 Ibs. of 
 malt. The older the hops are, the more it is necessary to use ; moreover, old hops are 
 best used for weaker beer. 
 
 After the boiling, the wort must be allowed to settle, and it is then drawn off 
 through a perforated chamber called the hop sieve. In order to obtain it as clear as 
 possible, a floating funnel of flexible metal gauze is used, which draws together like a 
 bellows in proportion as the liquor sinks, so that only the uppermost clear liquor flows 
 off through the pipe of the funnel. 
 
 The cooling of the wort has for its object the rapid reduction of the tempera- 
 ture of the hopped wort, so as to prepare it for alcoholic fermentation. If the hot 
 liquid were left to cool slowly in the air, there might easily be a formation of lactic 
 and acetic acids, especially between 25 and 50. It must therefore be rapidly 
 cooled to a temperature of from 10 to 20, according to the nature of the fermentation 
 to be subsequently effected. 
 
 The cooling is effected in large shallow reservoirs, in which the liquors stands 
 from 3 to 4 or at most 6 inches high. The cooling vessels are so placed that a 
 continual change of air takes place above them. The cooling takes from six to twelve 
 hours, and is effected chiefly by the evaporation of the liquor ; the strength of the 
 current of air, and especially its dryness, consequently influence the rate of cooling, as 
 also to a less degree does its temperature. During this cooling a further settlement 
 of mucilaginous matter takes place, consisting partially of nitrogenous substance dis- 
 solved by the heat, and partially of the compound of tannic acid with mucilage. 
 
 Formerly wood was the materia^ used in the construction of the cooling vessels, 
 but in consequence of the non-conductivity of wood, and the practical difficulties in 
 repairing and thoroughly cleansing such coolers, they have since been constructed of 
 sheet copper, sheet iron, or cast-iron plates, and recently glass plates have been pro- 
 posed. Copper is a better conductor of heat than iron, but their difference in this 
 respect is so small as not to be of much importance, especially as the radiating power 
 is at least equally important, and that in the two metals is similar and is greatest 
 when the outside is painted a dull dark colour. Iron has the disadvantage compared 
 with copper that it colours the wort, but this may be prevented by providing the iron 
 with a coating that will impede the direct action of the wort upon it. According to 
 Heiss, this may be done in the following way : The inner side of the cooling vessel 
 is scoured smooth with sand, and then etched with 7 to 10 per cent, solution of 
 hydrochloric acid. After perfect drying, the etched surface is painted three times with 
 a liquor obtained by digesting finely divided galls in water, with frequent agitation, 
 for twenty-four hours, and decanting. After the third coat is dry, cold water is run 
 into the vessel and allowed to stand for twelve hours, and then an extract obtained by 
 boiling crushed malt and old hops is added. After standing twelve hours the liquor 
 is run off, and the cooling vessel may then at once be brought into use. 
 
 As the cooling takes place chiefly through evaporation, of from one eighth to one 
 tenth of the liquid, this is sought to be increased by a change of atmosphere by 
 draughts artificially created by means of ventilators, windmills, and the like, but con- 
 tact of the wort with too great a quantity of air may easily have an unfavourable in- 
 fluence. The stirring machines which are frequently placed over the cooling vessels 
 have the same object; the augmented contact with the atmosphere being effected by 
 continual renewal of the surface of the liquid. The stirring machines have the 
 disadvantage that they impede the settlement of the turbid portion. 
 
 In the course of time, there is deposited upon the sides of the cooling vessels, as well 
 as in the pipes through which the wort is run into them, a crust, known as beer - 
 stone, which washing will not remove. This coating protects the metal of which 
 the apparatus is made from the action of the wort. It contains 64 per cent, of 
 organic matter (including 13 per cent, of protein substances), 29 per cent, of ash free 
 from carbonic acid (chiefly lime), and 7 per cent of water. 
 
 Various other cooling arrangements have recently been adopted, such as the cooling 
 
FERMENTING THE WORT. 
 
 953 
 
 with tinned iron or copper pipes, through which cold water is made to flow, sometimes 
 previously cooled by ice. The method of cooling wort by a current of water has been 
 introduced into England and France. The ice float is also used for the cooling of 
 wort ; most frequently, however, in the fermenting vat, and it is especially used in hot 
 summer weather. It consists of a painted sheet-iron tray filled with ice, which is 
 placed in the wort. 
 
 The most suitable time for cooling is in the spring and summer months, when dry 
 winds and clear skies promote the evaporation of the wort from the cooling vessels. 
 The situation and plan of the brewery also influences the cooling ; evidently the 
 building should be so placed that the coolers are exposed as much as possible to the 
 wind. For this reason breweries situated on high ground (as at Munich), or in airy 
 valleys, yield excellent beer. 
 
 Some very important experiments have recently been made by Jicinsky upon the 
 use of the vacuum pan in the beer brewery. According to him, by treating the wort 
 in a vacuum apparatus, concentration and cooling may be combined, and the cooling 
 vessels may be entirely dispensed with. To lower the temperature cold water is 
 added to the wort in the vacuum apparatus, to replace that which has been driven oft' 
 by the evaporation. As in consequence of the depth of the layer of liquor in the 
 vacuum pan, deposition of suspended substances does not take place, it becomes neces- 
 sary to filter the wort before it is passed into the fermenting vat. The advantages 
 presented by the use of the vacuum apparatus are : 1. Rapid cooling of the wort in 
 the brewing vat ; 2. Saving of space by dispensing with cooling vessels ; 3. Simplifi- 
 cation of the manipulation, since the wort passes direct from the brewing vat into the 
 fermenting vat ; 4. Avoidance of danger of acetification, the wort remaining sheltered 
 from air ; 5. Reduction of the consumption of ice. 
 
 The fermentation of the wort has for its object, through the action of the 
 yeast as a ferment, to convert the sugar contained in it, together with a great part of 
 the dextrin, into alcohol and carbonic acid, and at the same time to separate dissolved 
 nitrogenous substances in the insoluble form of yeast. According to Lermer's experi- 
 ments, dextrin alone is not fermented by yeast ; but, according to Grschwandler, when 
 dextrin is mixed with sugar, from 22 to 40 per cent, of it undergoes alteration. The 
 manner in which the yeast operates has been particularly described on p. 881. 
 
 Occasionally the fermentation takes place in casks ; most frequently, however, it 
 takes place in open vats, the fermentation vats, and but seldom in closed 
 vats from which only the resulting carbonic acid can escape. In the latter case the 
 arrangement shown in fig. 693 may be used to prevent access of air to the fermenta- 
 tion vats. It consists of a wooden bung (B), stuck into the cover of the fermentation 
 vat or into the top of the cask, and having a hole bored through its axis opening above 
 into a hemispherical depression. In this lies a ball (c) by which the opening is 
 closed, so that only the gases from the inside can gain a passage by forcing up the ball 
 from time to time. 
 
 FIG. 693. 
 
 FIG. 694. 
 
 FIG. 695. 
 
 Another arrangement, having the same purpose, is shown in fig. 694 in section. 
 The space (A) communicates through the pipe (/), with the interior of the vessel. 
 Between the spaces A and B is a partition (c D), which does not reach quite to tne 
 bottom, so that the water placed there can pass from side to side. As soon as gas 
 enters through the pipe (/), it exercises a pressure upon the surface of the water in 
 A, until it can escape under the partition at D. The level of the water in B is con- 
 sequently raised and with it the float (H o), indicating the progress of the fermenta- 
 tion. A float of the simplest construction is represented in fig. 695. H G' is an iron 
 wire and a is a piece of cork by which it is floated. 
 
 After trying the most diverse materials, in order to replace wood in the fermenta- 
 tion vats, because it becomes strongly impregnated with the fermenting liquid and 
 very difficult to purify, experiment has lately been made with glass. Brickwork 
 reservoirs are covered with large glass plates, the joints being closed with good cement 
 and having a substratum of water glass. 
 
954 BEER. 
 
 The place -where the fermentation is carried on should have an equable tempera- 
 ture of from 8 to 12. Ordinarily an arched vault is chosen, which must be kept 
 very clean, because impurities would have an injurious influence upon the keeping 
 property of the beer prepared in it. 
 
 The nature of the fermentation is determined by the character of the yeast em- 
 ployed and the temperature at which the liquid is maintained during the fermentation. 
 It is either of the kind called surface fermentation or sedimentary ferment- 
 ation. Surface fermentation is produced by ordinary yeast, which is used in those 
 cases where it is desired to prepare rapidly drinkable beer and to conduct the fer- 
 mentation within the ordinary range of temperature. Wort which contains so much 
 sugar that sufficient alcohol is formed by a partial fermentation is also fermented by 
 surface yeast. This kind of fermentation takes place most readily and with the* 
 greatest rapidity, for which reason it is employed in working wort that is not com- 
 pletely fermentable with ease, as is the case with wort that has been boiled for a 
 long time or has been prepared from highly roasted malt. 
 
 In carrying out surface fermentation the wort is brought to a temperature ranging 
 between 12 and 16, in the fermenting tun, and mixed with surface yeast from a 
 previous operation, in the proportion of from 2 to 4 Ibs. to the hundred gallons. 
 The rapidity with which fermentation commences depends upon the external tempera- 
 ture. At the commencement a white froth collects at the surface of the liquid and 
 rapidly increases, moving in concentric rings from the circumference to the centre. 
 This froth consists chiefly of resinous constituents from the hops ; it has on this ac- 
 count a very bitter taste, and is removed so as not to become mxed with the yeast 
 afterwards produced. Subsequently there is formed a light yellowish froth, inter- 
 spersed with large bubbles, which constitutes the new yeast, or barm, that is formed 
 from the nitrogenous constituents of the wort and a part of the sugar. During this 
 formation of yeast carbonic acid gas is abundantly evolved, and by adhering to the 
 particles of yeast separated in the liquid floats them to the surface, forming the sur- 
 face yeast, while another portion is deposited as bottom yeast. After the lapse of 
 from four to eight days the rapid evolution of carbonic acid ceases and the first stage 
 of the fermentation is at an end. The product in this condition is called young 
 beer. A further fermentation that progresses very slowly, and is called the after 
 fermentation, then commences under the influence of the bottom yeast that is 
 mixed with the beer. This fermentation is generally allowed to go on in casks, or 
 smaller tuns, having only a small opening through which carbonic acid can escape 
 and the yeast froth can run away. As soon as the froth becomes white the beer is 
 ready to be transferred to the store casks, which are securely closed when filled. In 
 these casks a second after fermentation takes place, which has the effect of saturating 
 the beer with carbonic acid and keeping it in a fit state for consumption. The beer 
 must be drunk while this fermentation is still in progress. Its capability of being pre- 
 served depends upon a continuance of this fermentation and upon the temperature of 
 the store cellar, which should be as cool as possible. The size of the casks is 
 also of some influence, for the larger they are the less is the beer affected by changes 
 of temperature in the store cellar. 
 
 In order to make drinkable beer in a short time the wort is brought to a tempera- 
 ture of from 16 to 24, mixed with some yeast, and immediately after the commence- 
 ment of the fermentation run into casks, where it rapidly ferments within the space of 
 one. or two days, the yeast escaping out of the bunghole meanwhile. The beer is 
 then drawn off into small casks where the after fermentation takes place. After a few 
 days the beer can be drawn off into bottles in which it becomes impregnated with 
 carbonic acid by the progress of the after fermentation. 
 
 The sedimentary fermentation progresses much more slowly than the surface 
 fermentation, and it is specially employed in the preparation of beer that is required 
 to be kept. Bavarian beer is generally prepared in this way. The wort is cooled 
 down to a temperature ranging from 6 to 10 and is mixed with from % to f per 
 cent, by measure of bottom yeast. After about twelve hours a light froth appears 
 at^the surface forming rings diminishing towards the centre. Evolution of carbonic 
 acid soon commences, but the gas given off is not sufficient to lift the yeast to the 
 surface, and on account of its remaining at the bottom of the liquid it is termed 
 bottom yeast. At the end of from seven to ten days the chief fermentation is 
 completed ; the beer is then run off into casks in which the after fermentation takes 
 place. During this stage some frothy yeast is produced which runs away from the 
 bunghole and is removed. 
 
 When the beer has become clear the casks are closed, and the slow fermentation 
 
 commences, during which sufficient carbonic acid is formed to make the beer sparkling. 
 
 It is very essential that the place where this slow fermentation goes on, and in 
 
 which the beer is kept, should be kept very cool. The temperature of the store cellar 
 
FINING BEER. 955 
 
 especially should not exceed 5, and if necessary it should be kept cool by means of 
 ice. 
 
 During this fermentation the amount of extract decreases, and at the same 
 time the specific gravity of the beer diminishes progressively, so that the progress of 
 the fermentation may be judged of from the specific gravity of the beer. 
 
 If the various operations are not properly carried out, the beer occasionally clears 
 with such difficulty that it has to be assisted by artificial means. The best clarifying 
 material is isinglass, the dried swimming bladder of several species of sturgeon. 
 This is soaked in water for twenty-four hours, and afterwards dissolved by heating it 
 with 16 or 20 parts of weak spirit, beer, or water. This preparation is thoroughly 
 mixed with a portion of the beer to be clarified, and the mixture is added to the re- 
 mainder of the beer. After some time the isinglass settles to the bottom, carrying 
 with it the suspended particles, and the beer becomes clear. About 4 or 5 parts of 
 isinglass are used to 100,000 parts of beer. The action of this substance depends 
 upon the peculiar structure of the tissue of the bladder, which consists of a fine net- 
 work of small fibres that swell to 100 times their original volume when soaked in 
 water or weak spirit, especially under the influence of slight acidity. When this 
 voluminous jelly is mixed with the beer, the fibres are again contracted under the 
 action of the alcohol, and the network closing upon the turbid particles in the beer 
 carries them to the bottom. 
 
 The Berlin white beer is frequently clarified with isinglass that has been swelled 
 with tartaric acid before being set to ferment. The tartaric acid then increases the 
 peculiar sour taste of that beer. 
 
 Fleck recommends the addition of glycerin to the wort before it conies into the 
 fermenting vat, in order to impart to the beer a full flavour, and to remove the bitter- 
 ness arising from the use of a large quantity of old hops. According to the quantity 
 of hops used, to 1 part of glycerin is added to 100 parts of beer ; the glycerin is 
 shaken with four times its volume of cooled beer, and this mixture is distributed 
 through the fermenting vat before the yeast is added. The glycerin is not added at 
 an earlier stage because too much of it would be evaporated with the vapour of water 
 during the boiling and cooling of the wort. 
 
 The investigations of Pasteur have thrown much light on the life history of the 
 yeast plant or plants ; and, although all the inferences he has drawn from his observa- 
 tions have not met with full acceptance, there can be no doubt that his researches will 
 greatly influence the future of beer brewing. 
 
 Pasteur starts with the admitted fact that there exists a close relation between 
 the facility with which beer wort or the finished beer undergoes alteration and the 
 processes adopted in its manufacture. This is practically indicated in the rapid 
 reduction of the temperature of the wort from about 50 to below 20 in order to 
 avoid the lactic and acetic fermentations that readily occur between those points. In 
 seeking for the cause of the changes which spoil the beer he finds that they are 
 always coincident with the development of microscopic organisms foreign to the 
 nature of true beer yeast. The organisms act as ferments and their multiplication is 
 always accompanied by the production of acid, putrid, viscous, or bitter substances 
 which render the beer unpalatable ; they are therefore designated as ferments de 
 maladie. Most of them, if not all, differ considerably in size and shape from the 
 spherical germs of beer yeast. The organisms present in turned beer are simple or 
 articulated filaments, about one-thousandth of a millimetre in diameter, which, when 
 very strongly magnified, are seen to consist of a series of short rods. The organisms 
 in lactic beer are small particles, slightly contracted in the middle, of rather greater 
 diameter than the preceding, generally isolated, but sometimes joined in chains of two, 
 three, or more. The organisms in putrid beer are vibrios, moving more or less rapidly 
 according to the temperature ; these make their appearance in the wort more readily 
 than in the beer. The organisms in viscous beer consist of strings of nearly spherical 
 granules. 
 
 Tart or acetic beer contains chaplets of articulations of Mycoderma aceti, ex- 
 tremely similar in appearance to those of the lactic ferment, but differing very much 
 in their physiological functions. All these are more or less filamentary, and, accord- 
 ing to Pasteur, their presence in beer is an infallible sign that deterioration has 
 either commenced or is impending. They have their origin in germs deposited from 
 the air in the beer or on the vessel during the operations, or present as a contamina- 
 tion with the beer yeast used. These organisms may, under certain conditions, 
 increase so as to materially affect the nature of the deposit of yeast, sometimes even 
 to the extent of entirely displacing the alcoholic ferment ; hence the necessity that 
 arises in a brewery occasionally of getting a supply of fresh yeast from another 
 establishment. Pasteur has also found that the absence of these ferments de maladie 
 is coincident with the production of an unalterable beer. 
 
956 BEER. 
 
 The predominance of one or other of these ferments under particular conditions 
 has given rise to the belief that they are all modifications of the same vegetable 
 organism, brought about by the media in which they occur. This, however, is denied 
 by Pasteur, who maintains that under no conditions is one form converted into an- 
 other, such as, for instance, the beer ferment into the lactic ferment. The explana- 
 tion is found by him in the greater appropriateness of certain liquids for particular 
 growths. Thus an acid liquid, such as the must of grape, may have deposited in it 
 simultaneously the spores of mucedines, and the germs of bacteria, lepto trices and 
 vibrios ; but the latter would be hindered in their development, if not killed, by the 
 acidity of the liquid, so that they would not be met with in the adult state. Most of 
 the moulds, on the contrary, flourish in acid liquids, excluding all other growths. 
 But if the must when fresh be saturated with carbonate of lime, the reverse conditions 
 obtain ; bacteria, lac tic ferment, and butyric vibrios invade the liquid to the exclusion 
 of moulds, which only languish in alkaline solutions. When one kind of growth is 
 established it hinders for the time all others, by appropriating all the alimentary 
 material, especially the oxygen. 
 
 It is to be noted, however, that a period of vigorous growth of a particular ferment 
 is often followed by a gradual slackening, and finally a cessation in the development, 
 caused by the exhaustion of the necessary aliment from the liquid, which may thus 
 become favourable for the growth of another ferment. 
 
 This difference in the suitability of certain liquids for the development of particular 
 growths Pasteur proposes to utilise for the elimination of objectionable ferments 
 present in beer yeast, by repeated cultivations of the yeast in liquids unfavourable to 
 their development. 
 
 Although, according to Pasteur, no other fungoid vegetation is capable of being 
 converted, even under the most favourable conditions, into beer yeast, some of them, 
 such as Penicillium glaucum and Aspergillus glaucus, are capable of acting to a certain 
 extent as alcoholic ferments. If these fungi are growing in a saccharine liquid in 
 contact with atmospheric air, they appear to effect a complete combustion of the 
 sugar by means of the free oxygen contained in it ; but if they be submerged, so as to 
 deprive them o a supply of oxygen, they then appear to act as alcoholic ferments, by 
 decomposing the sugar with formation of alcohol, carbonic acid, and other undeter- 
 mined substances, possibly varying with the plant acting as a ferment. But in this 
 case, with the moulds mentioned a marked alteration in their shapes takes place ; the 
 growth becomes languid from want of oxygen, the mycelium becomes thickened, and 
 instead of appearing in long filaments takes the form of chains of more or less ovoid 
 cells, and after a time development entirely ceases. Pasteur designates this class of 
 fungoid growths, which are not capable of flourishing if deprived of access of air, 
 aerobies, and those that can live without a supply of atmospheric oxygen, or the 
 true ferments, he calls anaerobies. 
 
 As elsewhere stated, two kinds of fermentation are recognised in the beer industry, 
 superficial fermentation, which is that almost exclusively at present practised in this 
 country, and bottom fermentation, which is largely practised on the continent. The 
 ferments which are used to produce these fermentations differ but little in respect to 
 their development ; the cells of bottom yeast are slightly smaller, a little more oval, 
 and have a perceptibly less ramification in the germination than those of surface 
 yeast. But the most marked difference is that from which they take their respective 
 names ; whilst one is floated to the surface of the liquid, and kept there by carbonic 
 acid gas evolved, the other remains at the bottom of the vessel, and, as might be 
 expected from what has been said above, its action, remote from the air, is much the 
 slowest of the two. Moreover, there is a great difference in the temperature at which 
 they each manifest their activity, the superficial fermentation being usually carried on 
 at a temperature of 16 to 20, whilst the bottom fermentation is never carried on 
 above 10, and preferably at from 6 to 8, a temperature at which the superficial yeast 
 would be without action. Notwithstanding these differences it is considered by many 
 that these two ferments are identical, and maybe transformed one into the other under 
 favourable conditions. This is contrary to the opinion of Pasteur, who admits, how- 
 ever, that probably they present an example of modifications that have become 
 hereditary by prolonged cultivation, since beer cannot be said to have a natural 
 ferment in the same sense as the juice of the grape. 
 
 The contact of an excess of atmospheric air exercises an important influence upon 
 the phenomena of fermentation. In such a case the yeast vegetates like a mould, 
 and there may even be a considerable development of yeast cells upon the surface of a 
 saccharine liquid before any formation of alcohol takes place, the quantity of alcohol 
 produced in relation to the weight of yeast present being always in inverse proportion 
 to the quantity of free oxygen available for the life of the plant. On the other hand 
 the condition in which the yeast cells are most capable of developing and multiplying 
 
STONE SQUARE SYSTEM. . 957 
 
 within the fennentescible liquid is while they are still very young, and still under the 
 influence of the active vitality due to contact with free oxygen, which possibly they 
 may to some extent be able to store up within them. Upon these grounds Pasteut 
 refers the phenomenon of tumultuous fermentation to the presence of excess of free 
 oxygen in the fermenting liquid. 
 
 It will be evident that, if the foregoing views of Pasteur are correct, it will be im- 
 portant that not only should pure yeast be used, but that the beer should be protected 
 during its manufacture from contamination with foreign ferments by the deposition of 
 spores floating in the air. For this purpose he has devised some apparatus in which 
 the cooling and fermentation would take place in contact only with filtered air. At 
 present this experiment has not been adopted to any extent. Pasteur, however, does 
 not look upon all the foreign ferments as injurious, but considers that some of them 
 might probably be utilised in the production of different flavoured beers. For 
 instance, he has recognised that an admixture of a special ferment that has been 
 named after himself, Saccharomyces Pastorianus, yields a beer that has a distinctly 
 vinous flavour. 
 
 The relative amounts of dextrin and sugar present in the wort have an important 
 influence upon the rapidity of the fermentation, and consequently the durability of the 
 beer produced. Sugar enters into fermentation readily, and this fermentation pro- 
 gresses rapidly, and cannot easily be checked at ordinary temperatures until it has 
 run its course, when carbonic acid ceasing to be evolved the beer becomes flat and 
 more liable to acetification by absorption of oxygen from the air. Dextrin, on the 
 contrary, ferments but sluggishly, especially at low temperatures, so that its fermen- 
 tation is prolonged after all the sugar has been decomposed, giving rise to a continual 
 development of carbonic acid, and thus contributing to the permanence of the beer. 
 Hence for the production of a beer for early and rapid consumption a large propor- 
 tion of sugar in the wort is eminently suitable ; whilst for a beer that requires to be 
 kept a considerable time dextrin should predominate. Moreover the time of the year 
 should also be considered, as whilst in the summer time a little more dextrin would 
 be useful as a clog to too rapid fermentation, in winter it might have a deleterious 
 influence and favour viscous fermentation. 
 
 In Yorkshire and other of the northern counties of England, a method of ferment- 
 ation is adopted known as the stone square system, which is alleged to be not only 
 economical in its working but capable of producing a very full beer in proportion to 
 the original gravity of the wort used. The square consists of an outer jacket or shell, 
 built of four massive stone slabs fixed upon another slab that forms the bottom, and, 
 within this, the wort cistern, similarly formed of stone slabs, and of a size that allows 
 a clear space of about 2 inches between its walls and those of the jacket, but 2 or 3 
 inches higher. Over this is a covering slab having three holes in it, and supporting 
 another stone cistern called the yeast back, which is large enough to hold all the yeast 
 formed during the operation. The principal hole in the cover is surrounded by a 
 stone ring about 6 inches high ; a smaller hole (about 2 inches in diameter) is fur- 
 nished with a valve, and fitted on the under side with a long tin pipe, reaching to 
 within 2 inches of the bottom of the wort cistern ; a third hole, with a plug, is used 
 for running off the yeast The wort cistern is provided with one or more cocks passing 
 out through the sides of the jacket and used for drawing off the beer for racking. 
 There are also the necessary pipes and cocks for supplying the interspace between the 
 jacket and the wort cistern with hot or cold water as it may be required to control the 
 temperature of the wort. 
 
 The wort is run into the cistern until it rises through the smaller opening of the 
 cover, the valve of which is left open, into the yeast back to a height of 2 or 3 inches ; 
 the valve is then closed. Sometimes the yeast is added as the wort is run in, and the 
 whole is left undisturbed until the fermentation is finished, when the yeast is run off, 
 and the wort having become perfectly still is ready for racking. But generally the 
 yeast is added after the wort is in the square, a comparatively small quantity being 
 used. Fermentation commences in about 12 hours, and when in full vigour the yeast 
 head and the wort in the yeast back are well roused together, and the valve being 
 opened, the mixture is run through the tin pipe to the bottom of the wort cistern. 
 The valve is then closed, and after an interval which must be decided by the judg- 
 ment of the operator some wort is pumped up into the yeast back by means of a hand- 
 pump passed through the principal opening of the cover to nearly the bottom of the 
 wort cistern. The fresh head and this wort are roused together, and run down 
 through the tin pipe as before, and these operations are repeated until the degree of 
 attenuation desired is obtained. The yeast is then allowed to separate from the beer, 
 which it does completely in the course of a few hours, discharging itself into tho 
 yeast back, whence it is removed, and the beer after standing until bright is ready for 
 racking. 
 
958 . BEER. 
 
 The temperature found most suitable for this method is from 15 to 16 at the 
 commencement, with a maximum of 70. When the latter temperature is reached 
 cold water is admitted into the jacket to prevent a further rise. 
 
 Beer Analysis. The percentage of carbonic acid in beer may be determined by 
 treating a known quantity of the beer with baryta water, filtering off the precipitate, 
 and drying and washing it. The precipitate thus formed is not pure barium car- 
 bonate, therefore the carbonic acid must be determined by any of the known methods. 
 In treating with baryta water care must be taken to exclude atmospheric air. 
 
 Another method of determining the quantity of carbonic acid present in beer con- 
 sists in heating a known quantity of beer to 40, the vessel containing the liquid 
 being shaken to liberate the carbonic acid ; upon again weighing, the loss in weight 
 represents the carbonic acid disengaged. 
 
 For the determination of the total amount of extract, a known quantity of beer is 
 weighed in a Liebig's drying tube, then evaporated in a stream of dry air over a salt 
 or oil bath at a temperature of 100 or 120, the application of heat being continued 
 so long as loss of weight takes place. The weight of the residue represents the total 
 extract of the sample of beer taken. Another method consists in evaporating a known 
 quantity of beer in a platinum dish over a water bath, then drying the residue at a 
 temperature of 100 or 110 and weighing; in this operation it is advisable to mix 
 the beer with a weighed quantity of sand before evaporating. 
 
 An easier and simpler method of testing beer is Fuch's hallimetric test, based upon 
 the fact that 100 parts of water dissolve 36 parts of common salt, or 1 part in 2' 77 8, 
 and that a liquid dissolves less salt the greater the quantity of alcohol and extract it 
 contains. Two tests are therefore necessary : 1,000 grains of beer are weighed off, 
 and boiled down in a flask to one-half or one-third its volume, by which the whole of 
 the carbonic acid, the alcohol, and a part of the water are driven off; the liquid is then 
 mixed with water so as to make it up again to exactly 1,000 grains. 360 grains of 
 salt, as nearly as possible of the same degree of fineness, is added to this liquid, and 
 the whole shaken. A portion of the salt will remain undissolved, and in 
 order to determine the quantity the whole is poured into an instrument 
 termed the hallimeter (fig. 696), which consists of a glass tube closed at 
 one extremity, the upper and open part being wide and cup-shaped, the 
 lower portion narrower. The salt deposits in the lower tube, and when 
 the particles are small and uniform (which may be secured by sifting) the 
 volume corresponds to a definite weight. The weight of the undissolved 
 v'^v' salt is easily determined from its volume, since the graduations on the 
 7 \Wf lower limb of the hallimeter correspond each to one grain of salt. Thus, 
 'M25 f or instance, if 21 grains of salt remain undissolved and 339 grains have 
 20 been dissolved, the 1,000 grains of boiled beer contain 339 x 2'778 or 942 
 water and 58 grains of extract. 
 
 In a second experiment 1,000 grains of beer are treated with 330 
 grains of salt, heated over a water bath to 35-40, and freed from car- 
 bonic acid by shaking. The quantity of carbonic acid is ascertained 
 from the loss of weight. The salt added will not dissolve completely in 
 the beer, and the weight of the undissolved portion is ascertained by 
 FIG. 696. measuring as above described. The quantity of salt dissolved multiplied 
 by 2'778 gives again the quantity of water, and the difference the quantity 
 of extract and aqueous alcohol. The amount of extract having been ascertained in the 
 first experiment, the difference gives the quantity of aqueous alcohol contained in the 
 beer. However the amount of absolute alcohol in the aqueous alcohol is not constant, 
 and since it would contain relatively more water in proportion as the beer is rich in 
 alcohol, the table II. must be referred to. 
 
 An example will serve to explain the method of calculation. 1,000 grains of fresh 
 beer, shaken up with 330 grains of common salt, lose 2 grains in weight = carbonic 
 acid. There remains undissolved 22 grains =144 grams of extract and aqueous 
 alcohol (table I. B). In the above experiment the boiled beer left 21 grains of salt un- 
 dissolved, 360 having been employed ; hence the beer contains, according to I. A, 58 
 grains of extract, and accordingly 144 58 = 86 grains of alcohol. 100 parts of the 
 beer therefore contain 
 
 Carbonic acid 0*2 
 
 Extract 5-8 
 
 Alcohol 4-7 
 
 Water . 89'3 
 
 100-0 
 
 Column A in Table 1. gives the quantity of extract contained in the. wort or boiled 
 beer, calculated from the residue remaining from 360 grains. Column B of the same 
 
ANALYSIS OF BEER. 
 
 959 
 
 table shows the quantity of extract and aqueous alcohol in unboiled beer, correspond- 
 ing to the salt residue from 330 grains. The percentage of absolute alcohol in this 
 aqueous alcohol is then found by reference to B. 
 
 TABLE I. 
 
 
 
 Extract 
 
 
 
 Extract 
 
 
 
 Extract 
 
 Salt 
 residue 
 
 Extract 
 A 
 
 and 
 alcoholic 
 
 contents 
 
 Salt 
 residue 
 
 A 
 
 Extract 
 A 
 
 and 
 alcoholic 
 contents 
 
 Salt 
 residue 
 
 Extract 
 A 
 
 and 
 alcoholic 
 contents 
 
 
 
 B 
 
 
 
 B 
 
 
 
 B 
 
 
 
 
 
 83 
 
 14 
 
 39 
 
 122 
 
 28 
 
 78 
 
 161 
 
 1 
 
 
 
 86 
 
 15 
 
 42 
 
 125 
 
 29 
 
 81 
 
 164 
 
 2 
 
 
 
 87 
 
 16 
 
 44 
 
 128 
 
 30 
 
 83 
 
 167 
 
 3 
 
 
 
 92 
 
 17 
 
 47 
 
 131 
 
 31 
 
 86 
 
 169 
 
 4 
 
 
 
 94 
 
 18 
 
 50 
 
 133 
 
 32 
 
 89 
 
 172 
 
 5 
 
 
 
 97 
 
 19 
 
 53 
 
 136 
 
 33 
 
 I 
 
 175 
 
 6 
 
 
 
 100 
 
 20 
 
 56 
 
 139 
 
 34 
 
 
 
 178 
 
 7 
 
 
 
 103 
 
 21 
 
 58 
 
 142 
 
 35 
 
 
 
 181 
 
 8 
 
 22 
 
 106 
 
 22 
 
 61 
 
 144 
 
 36 
 
 
 
 183 
 
 9 
 
 25 
 
 108 
 
 23 
 
 64 
 
 147 
 
 37 
 
 
 
 186 
 
 10 
 
 28 
 
 111 
 
 24 
 
 67 
 
 150 
 
 38 
 
 
 
 189 
 
 11 
 
 31 
 
 114 
 
 25 
 
 69 
 
 153 
 
 39 
 
 
 
 192 
 
 12 
 
 33 
 
 117 
 
 26 
 
 72 
 
 156 
 
 40 
 
 
 
 194 
 
 13 
 
 36 
 
 119 
 
 27 
 
 75 
 
 158 
 
 
 
 
 TABLE H. 
 
 Aqueous 
 alcohol 
 A 
 
 Absolute 
 alcohol 
 B 
 
 Aqueous 
 alcohol 
 A 
 
 Absolute 
 alcohol 
 B 
 
 Aqueous 
 alcohol 
 A 
 
 Absolute 
 alcohol 
 B 
 
 Aqueous 
 alcohol 
 A 
 
 Absolute 
 alcohol 
 B 
 
 39 
 
 21-5 
 
 67 
 
 37'6 
 
 95 
 
 52-1 
 
 123 
 
 66-5 
 
 40 
 
 22-0 
 
 68 
 
 38-1 
 
 96 
 
 52-6 
 
 124 
 
 67-0 
 
 41 
 
 22-6 
 
 69 
 
 38-6 
 
 97 
 
 53-1 
 
 125 
 
 67'6 
 
 42 
 
 23-2 
 
 70 
 
 39-1 
 
 98 
 
 537 
 
 126 
 
 68-1 
 
 43 
 
 237 
 
 71 
 
 39-6 
 
 99 
 
 54-2 
 
 127 
 
 68-6 
 
 44 
 
 24-3 
 
 72 
 
 40-2 
 
 100 
 
 547 
 
 128 
 
 69-1 
 
 45 
 
 24-8 
 
 73 
 
 407 
 
 101 
 
 55-2 
 
 129 
 
 69-6 
 
 46 
 
 25-4 
 
 74 
 
 41-2 
 
 102 
 
 55-7 
 
 130 
 
 70-1 
 
 47 
 
 25-9 
 
 75 
 
 41-7 
 
 103 
 
 56-2 
 
 131 
 
 70-6 
 
 48 
 
 26-5 
 
 76 
 
 42-2 
 
 104 
 
 56-8 
 
 132 
 
 71-3 
 
 49 
 
 27-0 
 
 77 
 
 42-8 
 
 105 
 
 57-3 
 
 133 
 
 71-8 
 
 50 
 
 27'6 
 
 78 
 
 43-3 
 
 106 
 
 57-8 
 
 134 
 
 72-3 
 
 51 
 
 28-2 
 
 79 
 
 43-9 
 
 107 
 
 58-3 
 
 135 
 
 72-8 
 
 52 
 
 28-7 
 
 80 
 
 44-3 
 
 108 
 
 58-8 
 
 136 
 
 73-3 
 
 53 
 
 29-3 
 
 81 
 
 44-8 
 
 109 
 
 69-3 
 
 137 
 
 73-8 
 
 54 
 
 29-8 
 
 82 
 
 45-4 
 
 110 
 
 59-8 
 
 138 
 
 74-3 
 
 55 
 
 30-4 
 
 83 
 
 45-9 
 
 111 
 
 60-4 
 
 139 
 
 74-8 
 
 56 
 
 30-9 
 
 84 
 
 46-4 
 
 112 
 
 60-9 
 
 140 
 
 75-3 
 
 57 
 
 31-6 
 
 85 
 
 46-9 
 
 113 
 
 61-4 
 
 141 
 
 75-8 
 
 58 
 
 32-2 
 
 86 
 
 47'4 
 
 114 
 
 61-9 
 
 142 
 
 76-3 
 
 59 
 
 32-8 
 
 87 
 
 48-0 
 
 115 
 
 62-4 
 
 143 
 
 76-8 
 
 60 
 
 33-4 
 
 88 
 
 48-5 
 
 116 
 
 62-9 
 
 144 
 
 77-3 
 
 61 
 
 34-0 
 
 89 
 
 49-0 
 
 117 
 
 63-4 
 
 145 
 
 77-8 
 
 62 
 
 34-6 
 
 90 
 
 49-5 
 
 118 
 
 63-9 
 
 146 
 
 78-3 
 
 63 
 
 35-2 
 
 91 
 
 50-0 
 
 119 
 
 64-5 
 
 147 
 
 78-8 
 
 64 
 
 35-8 
 
 92 
 
 50-5 
 
 120 
 
 65-0 
 
 148 
 
 79-3 
 
 65 
 
 36-4 
 
 93 
 
 51'1 
 
 121 
 
 65-5 
 
 149 
 
 79-8 
 
 66 
 
 37'0 
 
 94 
 
 51-6 
 
 122 
 
 66-0 
 
 150 
 
 80-3 
 
 To determine the Sugar and Dextrin. A weighed quantity of beer is evaporated to 
 a syrupy consistency, and the residue treated with alcohol to dissolve out the sugar, 
 this operation being repeated until all the sugar has dissolved ; the alcoholic extracts 
 
960 BEER. 
 
 are collected and heated to dryness, and the sugar dried and weighed. The dextrin is 
 determined by diluting with water the residue insoluble in alcohol and boiling with 
 sulphuric acid, by which the dextrin is converted into sugar, and may be determined 
 by means of Fehling's copper solution. ^ 
 
 Determination of the Alcohol. Besides the hallimetric test, a method often em- 
 ployed consists in placing a weighed quantity of beer in a flask connected with a 
 Liebig condenser, and distilling off about one-third of the beer. 
 
 By means of G-eissler's vaporimeter the alcoholic contents of any aqueous liquid is 
 determined from the tension exhibited by the liquid when heated to 100. When 
 beer is to be tested in this way it requires previously treating with lime, so as to 
 remove from it carbonic acid. 
 
 The tension of a liquid thus treated is of course greater in proportion to its alcoholic 
 contents. The apparatus consists of a glass vessel for holding the beer or other 
 liquid to be determined, and which can be heated by steam to 100. The vessel is 
 connected with the short arm of a doubly limbed tube, the long limb of which dipping 
 in mercury shows by means of suitable graduations the tension which corresponds 
 with the alcoholic contents of the liquid. 
 
ACETIC ACID. 
 
 History. Acetic acid was known in the form of vinegar at a very remote 
 period, the Jews, Greeks, and Komans having been acquainted with its medicinal pro- 
 perties as well as its domestic uses. Dioscorides and Pliny also treat of the applica- 
 tion of vinegar in medicine. The alchemists first obtained acetic acid by distillation, and 
 in the eighth century Geber prepared it in a concentrated form. Basil Valentin was 
 probably the first chemist to prepare acetic acid from an acetate, using crystallised 
 verdigris and basic acetate of copper. The production of pure and concentrated 
 vinegar was improved at the commencement of the eighteenth century by Stahl, who 
 showed that the concentration of vinegar was to be accomplished by freezing out the 
 water, and that the strong acid could be obtained by distilling acetate of potash 
 or sugar of lead with sulphuric acid. The production of acetic acid by dry distillation 
 of vegetable substances was mentioned by Glauber in 1648, but H. Kopp is of opinion 
 that wood vinegar was known anterior to that time. 
 
 Occurrence. Acetic acid occurs in the juice of various plants, partly in the free 
 state, and partly in combination with lime or alkalies. It is a normal constituent of 
 many animal liquids, and it has been observed in sweat and in putrefying animal and 
 vegetable substances. It occurs also as a product of the oxidation of alcohol, and the 
 alteration of dilute alcoholic liquids, such as wine, beer, etc., which become sour when 
 exposed to contact with atmospheric air, consists essentially in the conversion of the 
 alcohol they contain into acetic acid. This phenomenon, which is termed acetous 
 fermentation, is promoted by the presence of a peculiar fungus or mildew, which 
 is readily developed in such liquids. Acetic acid likewise occurs among the products 
 obtained by the action of heat upon wood and other analogous materials. 
 
 f 1 TT O ) 
 Composition. Pure acetic acid has the formula 2 Vr [ 0, and is the hydrate of 
 
 an oxygenated radical acetyl, C 2 H S 0, which is derived from alcohol by the sub- 
 stitution of oxygen for part of the hydrogen in the ethyl, as shown by the following 
 equation : 
 
 P TT O ) 
 
 The anhydrous acid or acetic anhydride has the formula Q jjO [ Q- 
 
 Cnaractem. At ordinary temperatures acetic acid is a pungent and colourless 
 liquid, which solidifies by cooling to a crystalline mass. The solid acid melts at 16, 
 but the liquid must be cooled far below that point to make it solidify. A very small 
 quantity of water lowers the solidifying point very considerably. The boiling point is 
 about 1 19, and the vapour is inflammable. Acetic acid has a specific gravity of 1 '063 at 
 12'6 ; it is miscible in all proportions with water ; the gravity first increases and then 
 decreases as shown in the following table. For this reason a solution containing 54 
 per cent, of pure acetic acid has the same specific gravity as the pure acid. 
 
 Acetic acid Acetic acid 
 
 per cent. sp. gr. per cent. sp. gr. 
 
 100 1-0635 
 
 90 1-0730 
 
 80 1-0735 
 
 70 1-070 
 
 60 1-067 
 
 50 1-060 
 
 35 1-046 
 
 30 1-040 
 
 25 1-034 
 
 20 1-027 
 
 15 1-022 
 
 10 1-015 
 
 45 1-055 5 T007 
 
 40 1-051 1 1-001 
 
 Consequently specific gravity does not indicate the amount of acetic acid. It 
 would be better, at least with an acid which is not too dilute, to estimate its strength 
 by the solidifying point, 
 
 3Q 
 
962 ACETIC ACID. 
 
 The following table by H. Riidorff gives the solidifying points of acetic acid of 
 
 different strengths 
 
 
 
 Water, per cent. 
 
 . Solidifying point. Water, per cent. 
 
 Solidifying point. 
 
 O'O 
 
 16-7 C 
 
 7-407 
 
 G-2o C 
 
 0-497 
 
 15-65 
 
 8-257 
 
 5-3 
 
 0-990 
 
 14-8 
 
 9-090 
 
 4-3 
 
 1-477 
 
 14-0 
 
 9-910 
 
 3-6 
 
 1-961 
 
 13.25 
 
 10-714 
 
 2-7 
 
 2-912 
 
 11-95 
 
 13-043 
 
 -0-2 
 
 3-846 
 
 10-50 
 
 15-324 
 
 -2-6 
 
 4-761 
 
 9-4 
 
 17-355 
 
 -5-1 
 
 5-660 
 
 8-2 
 
 19-354 
 
 -7-4 
 
 6-542 
 
 7-1 
 
 
 
 As sulphuric acid exerts a considerable influence on the solidifying point of acetic 
 acid, no value can be attached to the solidifying point when this acid is present. 
 
 Acetic acid is also miscible with alcohol, and with ether in all proportions ; in 
 many ethereal oils it is insoluble, and it is the more insoluble as the hydration of the 
 acid increases. 
 
 A good test of the purity of acetic acid is the degree to which lemon oil dissolves 
 in it ; the pure acid should entirely dissolve one-tenth of lemon oil. Gelatin, fibrin, albu- 
 min, camphor, and gun cotton are dissolved by cold acetic acid. Acetic acid is expelled 
 from its salts by sulphuric acid, hydrochloric acid, or phosphoric acid, but it decom- 
 poses carbonates and expels many volatile organic acids from their respective salts. 
 
 The salts of acetic acid are variously affected by heat. Some lose a portion of the 
 acid, others yield acetone. 
 
 Acetic anhydride is a liquid boiling at 117'5 ; its specific gravity is 1-0799. It 
 combines very energetically with water, forming the hydrate or hydrogen salt called 
 acetic acid, the corresponding compounds of the oxide with basic oxides being called 
 acetates. 
 
 An aqueous solution containing from 3 to 10 per cent, of acetic acid is known by 
 the name of vinegar, and used for domestic purposes. It also contains small quantities of 
 alcohol, ethereal oils, sugar, dextrin, colouring matters, and soluble salts. The nature 
 of the other constituents, which impart the characteristic smell and taste, depends upon 
 the kind of material the vinegar has been made from. Wine vinegar has a better flavour 
 than the vinegar made from brandy or beer. 
 
 Preparation. The principal source of acetic acid is the aqueous liquid ob- 
 tained, together with tar and combustible gases, when wood is subjected to destructive 
 distillation. 
 
 The nature of the product obtained in this way depends upon the kind of wood 
 operated upon, and the temperature at which the operation is conducted. 
 
 The best wood for the purpose is that of foliaceous trees grown on dry soil. The 
 wood of pine and fir trees is not so productive. 
 
 According to the experiments of Peters the following results are obtained from 
 various kinds of wood : 
 
 Wood Acetic 
 
 vinegar acid Tar Carbon 
 
 p. cent. p. cent. p. cent. p. cent. 
 
 Beech .:.... 48-3 6'1 4-9 23'9 
 
 Birch 48-0 5'7 6-0 21-1 
 
 Alder 477 3'9 5'2 24-0 
 
 Oak 47-6 5-4 6'4 24'9 
 
 Ash 46-8 4-0 6-4 237 
 
 Copper beech 46.3 5-3 6-2 23'8 
 
 Lime . . . . . . 46'2 j6'3 8-9 21 -8 
 
 Fir (Scotch) 44-9 '27 10-1 28'0 
 
 Willow 43-4 6-3 6-2 23'6 
 
 Larch 42-8 2-9 9-5 22'6 
 
 Maple 42-2 5'5 6'2 26'3 
 
 Silver fir 40-9 2-4 1 1-0 26-1 
 
 Pine 40-6 2'8 9'4 28'3 
 
 In England the wood for this purpose is obtained from the oak, beech, birch, hawthorn, 
 and apple trees, less frequently from the hazel, alder, ash, and maple, and seldom from 
 the poplar, elm, and pine. Chapman has stated that the oak, which is almost always 
 taken stripped of its bark, yields the best wood vinegar, but a friable charcoal which 
 has a small bulk. Beech wood yields very good charcoal, together with a considerable 
 
PRODUCTION OF ACETIC ACID. . 963 
 
 quantity of wood spirit and creasote. Birch, hawthorn, and apple trees give very 
 pure wood vinegar. 
 
 The roots of trees yield a very good product, but they are difficult to cut up, so 
 as to be suitable for distillation only. They must not be rotten, nor must rotten wood 
 of any kind be used for distillation. 
 
 Next to the kind of wood, the temperature employed in the distillation is of im- 
 portance as regards the yield. Chapman obtained results varying from 13 to 27 per 
 cent, of charcoal, according as he used a higher or lower temperature in distilling 
 oak sawdust. 
 
 The higher the temperature the less charcoal is obtained, A better yield is ob- 
 tained by slowly increasing the temperature ; the quicker the temperature is raised 
 the less liquid products are obtained, but more gaseous products are produced. Slow 
 carbonisation is therefore to be recommended. 
 
 The kind of apparatus to be used varies according to the nature of the raw 
 material. For heavy wood which can be brought in logs the refuse from dockyards 
 of timber, etc. it is customary to use a horizontal cast-iron retort, somewhat similar 
 to a gas retort. It is from 7 to 10 feet long and 2| to 3 feet in diameter. A vertical 
 cylindrical vessel would equally serve the purpose. The retort is fed with the logs, 
 and the cover having been fitted on, the required heat is obtained from a fire under- 
 neath. 
 
 The volatile products escape through an outlet in the upper part of the cylinder, 
 and the charcoal remains behind. The distilled products are passed through a con- 
 denser surrounded with cold water, into a receiver where the tar, water, vinegar, and 
 wood spirit are condensed, and the noncondensable gases escaping through an open- 
 ing in the lower part of the condenser are generally carried to the furnace, so as to 
 effect a saving of fuel, as these gases consist of marsh gas, olefiant gas and other 
 combustible gases. At the end of the distillation, which in a large retort will take about 
 twenty -four hours, the hot charcoal is as quickly as possible placed either in a closely 
 fitting sheet-iron vessel or in a well-closed brick chamber. 
 
 When light wood and irregularly sized pieces are to be worked up with small 
 branches, brick ovens with direct or indirect firing are advantageously used instead of 
 retorts. The oven is either closed with an arch or open at the top, in which case, 
 after the wood has been placed in the oven, it is covered with a layer of earth and 
 turf. In Reichenbach's oven the heating is effected by means of iron tubes passing 
 through the oven, and heated to a red heat by a fire outside. 
 
 Halliday has constructed a very excellent apparatus for the distillation of saw- 
 dust and such like wood refuse. It is a horizontal cast-iron retort, heated externally 
 by a furnace. On the front end is a filling hopper, in the cylindrical neck of which a screw 
 turns to regulate the filling. In the retort, also, another screw revolves, and gradu- 
 ally drives the sawdust from the feeder through the retort. In this way perfect car- 
 bonisation is effected. 
 
 The volatile products are led off and condensed, and the charred residue is allowed 
 to fall from the end of the retort into an air-tight iron box, or into water, in which 
 case, the discharge pipe dips into the water. 
 
 Treatment of the Crude Distillate. The crude distillate obtained by the dry dis- 
 tillation of wood is allowed to rest for some time in a reservoir where it separates 
 into two layers, the upper one containing, besides much water, the acetic acid and 
 wood spirit, while the lower layer consists of tar. The aqueous layer having been 
 drawn off as clear as possible, and filtered through sand, is subjected to fractional 
 distillation in a copper retort, heated by steam pipes. The wood spirit, coming over 
 in the first fifth of the distillate, is again fractionated over quicklime, and finally 
 treated with a little sulphuric acid to remove the ammonia. It still contains such 
 impurities as acetone, empyreumatic oils, ethers, etc. After the removal of the spirit 
 the distillation is continued, and the wood vinegar distilling off is condensed and 
 collected in a fresh receiver. The tar remaining in the still is run off by a cock from 
 the bottom. 
 
 In many works the acid is neutralised with lime before distilling off the wood 
 spirit. In this case the residue in the retort contains acetate of lime ; iron instead of 
 copper retorts can be employed in working by this method. 
 
 The crude acetic acid is purified by first neutralising with lime or soda, either 
 before or after distillation. When the liquor has settled it is drawn off clear and 
 evaporated until it crystallises. The calcium or sodium acetate thus obtained is 
 separated from the mother liquor, dried between 230 and 250 C., and distilled with 
 sulphuric acid to obtain pure acetic acid. Acetate of lime has previously to be 
 treated in solution at a specific gravity of 1-2, with powdered sulphate of soda, so as 
 to form the sparingly soluble double sulphate of lime and soda, and leave in solu- 
 tion the acetate of soda, which can be recovered by crystallisation. 
 
 3Q 2 
 
964 ACETIC ACID. 
 
 Hydrochloric acid might be employed to decompose the acetate of lime instead of 
 converting the calcium salt into sodium acetate, but care must then be taken to avoid 
 using any great excess of hydrochloric acid or the distillate would be impure. 
 
 When the crude product is neutralised with lime before distilling off the wood- 
 spirit, the residual liquor is evaporated down and the dry mass is heated until oil and 
 tarry vapours are no longer disengaged. 
 
 MANVFACTUBE OF VINEGAR. The conversion of the alcohol in beer or wine into 
 acetic acid is a phenomenon familiarly known as the acetous fermentation, and the 
 dilute solution of acetic acid, known as vinegar, is usually made in this way. Various 
 dilute alcoholic liquids, such as wine or fermented malt infusion, are employed for this 
 purpose ; the change that takes place consisting in oxidation of the alcohol they 
 contain, and being associated with the development of the mildew fungus called Mt/co- 
 derma aceti, ordinarily known as mother of vinegar, or vinegar mould, which 
 forms a coating upon the surface of the liquid undergoing acetous fermentation. A very 
 small quantity of this fungus placed on the surface of a dilute alcoholic liquid will 
 in a short time convert the alcohol into acetic acid. If the alcoholic liquid contain 
 albuminous substances and alkaline phosphates, as is the case with wine and beer, the 
 fungus rapidly multiplies and the formation of vinegar is accelerated. 
 
 The conversion of the alcohol into acetic acid always takes place at the surface of the 
 liquid and continues only so long as the fungoid growth floats upon the liquid. When 
 it sinks below the surface out of contact with the air, the action ceases. It is still a 
 matter of doubt whether the action of the Mycoderma aceti is physiological or merely 
 physical. The fact that it can also oxidise acetic acid into carbonic acid and water 
 speaks in favour of a physical action. It has also been suggested as explanatory of 
 this change that the mother being itself a material in a state of decay by oxidation, 
 it induces the same change in alcohol. This view receives support from the fact 
 that alcohol vapour brought into contact with decaying wood is slowly converted into 
 acetic acid. This assumption is not opposed to the action of atmospheric oxygen 
 causing this change. 
 
 The concentration and temperature of a liquid have an important influence on the 
 formation of acetic acid. The amount of alcohol in the liquid must not exceed 1 1 
 per cent., since acetification does not take place in liquids containing much alcohol ; on 
 the other hand the change takes place very slowly in liquids containing but very 
 little alcohol. Usually, therefore, no liquid is used containing less than 2 or 3 
 per cent of alcohol. The temperature must be kept above 20, or even higher, in order 
 to hasten the action, but it should not exceed 40, otherwise alcohol may be carried 
 off by evaporation. 
 
 Only such liquids as wine, beer, malt infusion, or beet-root juice, are employed for 
 making vinegar, according to the old method, as these contain, in the form of albu- 
 menoids and various salts, a considerable quantity of nutriment for the fungoid 
 growth. 
 
 Wine Vinegar. In the manufacture of wine vinegar, as carried on in wine-pro- 
 ducing districts, both sound wine and wine that has become sour are used. 
 As the wine must be clear, it is necessary to filter or otherwise clarify muddy 
 wine. White wine is quickly acetified, and old wine more quickly than new 
 wine containing much sugar. Wine containing more than 11 per cent, of alcohol 
 requires to be diluted. The oak casks called ' mothers,' which are employed in 
 making vinegar, have a capacity varying between 25 and 100 gallons. They are bored 
 at both ends so as to give free access to air in the space above the liquid contents, and 
 each cask is provided with a hole for manipulation, emptying, etc. Small casks are 
 preferable to those of large capacity, for the reason that a greater surface of liquid 
 is exposed in several small casks than in one large one. The casks are filled one 
 above another on a wooden stand in the fermenting chamber, where the temperature 
 is maintained between 25 and 30. As the heat generated by the conversion of the 
 alcohol is not inconsiderable, great care is necessary in places where the casks are 
 closely packed, and proper ventilation maintained. 
 
 At the commencement of the operation the casks are filled to one third of their 
 capacity with old and previously-heated vinegar, and to this two or three gallons of 
 wine are added. The mixture is allowed to stand for eight days, during which time 
 the acetic fungi in the old vinegar convert the alcohol in the added wine to vinegar, 
 and increase at the expense of the nutriment present in the wine. Another similar 
 quantity of wine is then added, and this is repeated twice more at the same interval 
 of time. Eight days after the last addition, vinegar, equal to the total quantity of 
 wine added, is drawn off, and the same operation is repeated. 
 
 Occasionally it happens that without any visible cause the acetous fermentation 
 gradually diminishes in a striking manner and almost entirely ceases. According to 
 
WINE VINEGAR. 965 
 
 Pasteur this is due to the presence of minute animalcules called vinegar eels, which 
 consume the oxygen necessary to the development of the Mycoderma aceti. When 
 this has proceeded so far that these animalcules rise to the surface of the liquid in 
 the place of the mycoderma, the progress of the fermentation is arrested. The readiest 
 method to overcome the difficulty is to empty the casks and refill with hot vinegar, 
 whilst in many cases the same result can be obtained by adding stronger wine or by 
 increasing the temperature. 
 
 In the usual course, every six or eight years the casks require to be emptied and 
 purified from the large mass of dead fungi (mother of vinegar), tartar and other 
 salts adhering to the bottoms and sides. 
 
 According to the Orleans method, originated by Pasteur, the wine, or other alco- 
 holic liquid, is placed in a vat, together with vinegar fungi, obtained in a previous 
 operation. The fungi rapidly spread over the surface when the liquid contains the 
 necessary food, and at the same time acetic acid is formed by the oxidation of the 
 alcohol. Fresh wine is added daily ; and, when the acetification is over, the vinegar 
 is drawn off. The fungi, after being washed, can be used for a fresh operation. A 
 barrel of from 10 to 20 gallons capacity will daily turn out a gallon to a gallon and 
 a quarter of vinegar. If dilute alcohol be used, the food of the fungus in the shape 
 of alkaline and magnesian phosphates must be added. Breton-Laugier uses a mixture 
 of vinegar and wine, andkeeps it in barrels of about 27 gallons capacity, at a tempera- 
 ture of 25-50 C. with vinegar fungi. After eight to ten days the entire quantity is 
 acetified. 
 
 Beer Vinegar. Only soured beer is used for this purpose, since, on account of its 
 containing hop extract, it is not generally suitable for vinegar making. As it is poor 
 in alcohol some spirit is added, together with water in order to dilute the extractive 
 constituents. Beer that has been made by surface fermentation, on account of it 
 containing less hops, is more suitable than that made by bottom-fermented beer. The 
 acetification of beer is carried out in a manner similar to the manufacture of wine 
 vinegar. 
 
 Malt and Grain Vinegar. The manufacture of vinegar from malt or grain is 
 largely carried on in England. The wort is prepared from a light kiln-dried malt, or 
 from a mixture of malt and grain, by the mashing process as described under the ar- 
 ticle BEER (p. 946), with the exception that the mash is neither boiled nor are hops 
 added to it. The wort having been brought to the fermenting temperature, and al- 
 lowed to ferment, is run into the vinegar casks, which are either placed in rooms or 
 exposed in the open air. When the acetification is completed the vinegar is siphoned 
 off as clear as possible into a wooden trough connected with the common reservoir. 
 Before the vinegar is run into the store vats it must be made quite clear by being 
 passed through suitable clarifying vats, which consist of large vessels provided with 
 sieve bottoms covered with such materials as straw, wood shavings, or better with 
 grape stalks. 
 
 Beet-root Vinegar. Although the preparation of vinegar from this source is but 
 recent a number of recipes are extant ; but this method has not yet met with much 
 favour. The juice obtained in the ordinary way, by grating and" pressing, is used 
 either crude or purified with tannic acid or lime (see p. 834), being subjected first to 
 the alcoholic fermentation and afterwards to the acetic fermentation. It is then 
 clarified by subsidence in vats or by filtration. Leplay's method consists in cutting 
 beet roots into slices and setting up fermentation by immersing them in already fer- 
 menting beet-root juice. The sugar thus undergoes alcoholic fermentation in the cells 
 of the roots, and upon exposure of the slices to air the alcohol very soon undergoes aceti- 
 fication. The vinegar can be either distilled with steam or by washing the fermented 
 mass. To make vinegar from brandy by the old method the plan followed is the same 
 as described for wine vinegar. The brandy, or spirit, is diluted with water until it 
 contains only 6 or 7 per cent, of alcohol, then heated to 35 or 40, and finally mixed in 
 the fermenting vats with ' mother of vinegar,' the growth of which is sustained 
 by adding partly fermented malt extract. The conversion of brandy into vinegar is 
 now more frequently carried out by the quick process. 
 
 The Quick Vinegar Process. The production of vinegar by this method has to a 
 great extent superseded that of fermentation above described : it consists in exposing 
 a weak alcoholic liquid to the action of atmospheric oxygen in such a manner as to 
 present a very extended surface, and thus to accelerate the oxidation of the alcohol and 
 its conversion into acetic acid. For this purpose the alcoholic liquid operated upon is 
 made to flow continuously through a capacious vessel into which air is admitted so as 
 to come into contact with the liquid to be converted into vinegar. It is important that 
 an abundant supply of air should be passed into the vessel, because when the oxida- 
 tion of the alcohol takes place slowly aldehyd is formed instead of acetic acid, and 
 
ACETIC ACID. 
 
 FIG. 697. 
 
 on account of the great volatility of this substance considerable loss would be incurred 
 by its escaping in the state of vapour. Part of the vessel in which this operation is 
 carried out is therefore filled with some porous matt-rial, such as wood shavings, over 
 the surface of which the alcoholic liquid is distributed, and thus brought more in- 
 timately into contact with the atmospheric air passing through the vessel. By this 
 method it is possible, owing to the large surface exposure, to convert alcohol into 
 acetic acid in three days, whilst by the old method it would take several weeks. The 
 apparatus, represented by fig. 697, consists of a wooden cask, or vinegar generator, 
 6 feet high by o^ feet in diameter, and slightly conical. A shelf (B B), perforated 
 
 with small tapering holes, is fixed 
 about 6 inches below the cover (A A) of 
 the vat. The shelf rests on a beech- 
 wood ring fixed inside the vat. In each 
 hole is a piece of string 6 inches in 
 length which half closes up the hole 
 and is retained by a knot. This shelf 
 is also provided with larger holes to 
 contain glass or wooden tubes (c c c) to 
 act as air vents. About 16 or 20 
 inches above the bottom of the tub is 
 placed a second perforated shelf (D), 
 also resting on a beech- wood ring, and 2 
 inches above it, at intervals so as to 
 encircle the tube, ten to fifteen holes 
 (E E) are made which have a downward 
 inclination in order that the down fall- 
 ing liquor shall not leak from the tub. 
 The space (F) between the two shelves 
 is filled with shavings. The exit pipe 
 (G) is placed 2 inches above the bottom 
 of the tub and is bent like a siphon, 
 
 but with the outer arm shorter than the inner one, so that the vinegar can only flow 
 out to a certain level. A thermometer passing through the upper perforated shelf 
 serves as a guide to the progress of the operation. A new generator, before being used, 
 requires to be percolated for some time with hot old vinegar, until the shavings are 
 completely saturated ; then dilute spirit, containing 6 to 10 per cent, of alcohol, is 
 added. The liquor flows through the holes partly plugged with twine in small and 
 very finely divided drops, falling upon the shavings below, where, under the influence 
 of the in-coming air and the vinegar ferment, the alcohol is oxidised, and it collects 
 below the second perforated shelf. From the first cask the partly converted liquor 
 is passed through a second one, and then through a third similarly constructed vessel ; 
 or, instead of this, one vessel can have the liquor passed thrice through it. 
 
 Should the acetification be incomplete after a third passage through the casks the 
 operation must be repeated again. 
 
 Otto has proposed that, instead of adding the alcohol all at once, a part of it should 
 be mixed with vinegar and passed once through the generator, then to pass through 
 another portion of the alcohol, and to add the remainder after repeated percolations 
 of the earlier portions. In this way less vinegar is required to be added to the 
 alcohol. 
 
 Only about one-tenth, or at most one-fifth, of the oxygen in the air passing through 
 the generator is absorbed in the oxidation of alcohol, and consequently a large 
 quantity of air is discharged above, which causes considerable loss of alcohol and 
 acetic acid vapour. Payen has proposed, therefore, to pass the escaping vapours 
 through a worm condenser fitted to each generator ; or to pass the air over copper 
 turnings and form verdigris. 
 
 At the commencement of the process the temperature in the vinegar room is 
 brought to 38 C., but as the operation progresses and the temperature rises in the 
 generator, the heat is lowered to 20 or 23 C. The alcoholic liquid first used for 
 the generator is heated to 50 to 52 C., but when the process is in full operation the 
 temperature of the liquor is maintained between 26 and 27 C. 
 
 Payen describes a new method as carried out in the manufactory of Koelitz. In 
 an enclosed chamber on an upper floor are placed fifty-four conical vessels provided 
 with false bottoms. Each vessel is 4 feet high, has a width at the top of 4 feet, and 
 at the bottom of 4 feet 10 inches ; on the perforated bottom are placed fourteen hori- 
 zontal layers of beech-wood shavings rolled in a spiral form and pressed together. 
 Each spiral, held together by a cross band, measures about 8 inches by 6 inches 
 in diameter, and is 2 inches high. Each layer contains forty-eight such spirals ; 
 
VINEGAR MAKING. 
 
 967 
 
 therefore the fourteen layers contain 672 spirals, and these, having twenty-eight twists 
 and being one twenty-fifth of an inch thick, represent a total surface of about 42,800 
 square feet. The chamber is maintained at a temperature of 25 C. The alcoholic 
 liquid to be acetified is prepared so as to contain about 7 per cent, by volume of 
 alcohol, and it is passed through a kind of rose feeder from a vessel over the casks 
 upon the beech-wood spirals ; the oxidation which follows raises the temperature to 
 27, and the liquor collects in the space under the perforated bottom completely con- 
 verted into vinegar containing about 11 to 12 per cent, of acetic acid. In order 
 to oxidise the alcohol a stream of air is passed through each generator by a wooden 
 pipe at the bottom, and is conducted into a chimney common to the entire apparatus. 
 By slowly allowing the mixture to flow over the beech shavings the acetification is 
 finished in two hours, and by adding at such intervals about 10 pints of liquid containing 
 5 pints of 14 per cent, alcohol and 5 pints of 7 per cent, vinegar, a yield of upwards 
 of 800 gallons in twenty-four hours can be obtained from fifty-four generators. 
 
 Mr. Singer has described a generator where the wood shavings are not used. The 
 liquor flows continuously in a thin stream through vertical pipes upon eight channels 
 placed some distance apart. Air has access to the pipes through slits at the lower 
 part. The diameter of the apparatus is about 5 feet and the pipes number 138, each 
 of which measures 21 inches in length and one-fifth of an inch in diameter. 
 
 Vinegar is conveniently tested by Otto's method with the acetometer, which is a 
 graduated tube represented by fig. 698, of about 1 foot in length and inch in diameter. 
 From the bottom of the tube to a = 1 cubic centimetre or 1 gram, 
 from a to b = 5 cubic centimetres or 5 grams, from b to c = 5 cubic 
 centimetres or 5 grams, in all cases of water. Each division above 
 c answers to 2'07 grams of ammonia solution of sp. gr. T369, 
 and this quantity exactly saturates O'l gram of acetic acid. The 
 tube is filled to a with litmus solution and from a to b with the 
 vinegar under examination. If the vinegar is strong, only sufficient 
 is taken to fill up to b, this diluted with water to c ; in that case the 
 result must be multiplied by two. The standard ammonia is added 
 with frequent shaking until the red litmus tint is changed to the 
 neutral tint. The number of divisions to which ammonia is added 
 gives at once the percentage of acetic acid. For example, if ammo- 
 nia has been added to the seventh division, then the quantity of acetic 
 acid = 7 x O'l = 0'7 grams in 10 grams of the vinegar, or 7 per 
 cent. 
 
 Instead of ammonia solution a 10 per cent, soda solution can be 
 used equally well. 
 
 The older method, in which to a known quantity of vinegar solid 
 carbonate of potash is added until the neutral tint is obtained, after 
 boiling the liquid, gives less exact results. The same applies to the 
 method of estimation by the loss occasioned by a weighed piece of carbonate of lime 
 or marble when immersed in the vinegar. An equivalent quantity of carbonate of 
 lime is dissolved by the acetic acid ; 5 grams of carbonate of lime = 6 grams 
 acetic acid. 
 
 As already mentioned the areometer is not suitable for acetic acid testing, as its 
 specific gravity increases by adding water to a certain point, and then again diminishes. 
 
 Kieffer titrates the vinegar with a standard solution of ammonio-cupric sulphate 
 until a precipitate ensues. 
 
 Other acids are frequently added to increase the strength of vinegar. This prac- 
 tice when carried out to a considerable extent is prejudicial to the health. The acids 
 chiefly used for the purpose are sulphuric and tartaric acids, and, exceptionally, hydro- 
 chloric and nitric acids. 
 
 To detect sulphuric acid, a drop of baric chloride is added; if only a slight precipi- 
 tate is formed, it would be due to the sulphates of the water used in the manufacture, but 
 if a considerable precipitate is formed, free sulphuric acid must be tested for as follows. 
 Some of the vinegar is mixed with a little starch, and distilled in a retort to one half 
 its original volume. If free sulphuric acid is present, it converts the starch into sugar ; 
 and, on adding to the cold liquid iodine solution, the blue coloration characteristic of 
 starch is not produced. 
 
 Tartaric acid is only to be tested for in wood vinegar, etc., as wine vinegar contains 
 it naturally. The procedure is as follows : The vinegar is evaporated on the water 
 to a syrup ; the residue mixed with a very little water and a small quantity of 
 ferric chloride, and boiled ; caustic potash is then added until the liquid has an 
 alkaline reaction, and the whole is filtered. If upon sulphuretted hydrogen being added 
 to the filtrate, it gives a black precipitate, the presence of tartaric acid is indicated. 
 
 To test for hydrochloric acid, some of the vinegar is distilled in a retort. If the distil- 
 
 FIG. 698. 
 
968 ACETIC ACID. 
 
 late tested with nitrate of silver solution gives a precipitate of chloride of silver, the 
 presence of free hydrochloric acid is indicated. Nitric acid is detected by neutralising 
 with carbonate of soda, evaporating to dryuess, and boiling with copper foil and sul- 
 phuric acid ; a disengagement of red fumes of nitrous acid gives evidence of the pre- 
 sence of nitric acid. 
 
 Vinegar is frequently mixed with cayenne pepper and other hot spices in order to 
 give it a pungent or aromatic taste. These are easily discovered by their taste when the 
 acid of the vinegar is neutralised with carbonate of soda. The vinegar is sometimes 
 contaminated with poisonous metals derived from the vessels used in the manufacture, 
 as lead, copper, tin, and zinc, all of which can be detected by their precipitate with sul- 
 phuretted hydrogen. 
 
 Uses. Besides the domestic uses of acetic acid in the form of vinegar, this sub- 
 stance is of importance in the arts. It is employed for the preparation of the salts 
 called acetates, such as calcium acetate, into which form the crude acetic acid obtained 
 by the distillation of wood is generally converted, either for convenience of transport 
 or as a first stage of purification. This salt is also used in the preparation of some 
 other acetates, such as aluminum acetate and sodium acetate, by mixing a solution 
 with aluminum sulphate or sodium sulphate sufficient to separate the calcium in the 
 form of sulphate. An addition of acetic acid of 7 per cent, strength is made to 
 dilute wine vinegar in order to strengthen it and to render it more durable. Dilute 
 acetic acid has also been substituted for wine vinegar, some dilute wine being added 
 to supply the necessary aroma. A great quantity of acetic acid is used in the manu- 
 facture of white lead (see p. 393), and in the preparation of aniline from nitro-benzol. 
 It is also extensively used in chemical laboratories, and for medicinal purposes. 
 
TEA, COFFEE, COCOA, ETC. 
 
 The products of various plants, known by the above names, are extensively used in 
 various countries as articles of food, and from a chemical point of view they present 
 many features of resemblance in composition. 
 
 Tea, consists of the dried leaves of several varieties of Thea sinensis, a plant in- 
 digenous in China, Japan, and the northern parts of India, where it is extensively 
 cultivated. The tea plant appears to be capable of flourishing in all latitudes between 
 the equator and 40, and its cultivation has been introduced upon the southern decli- 
 vities of the Himalayas in British India, in Java, Western Africa, Brazil and 
 Madeira. 
 
 The difference between black tea and green tea was formerly supposed to be 
 due to a difference in the plants from which the leaves were obtained, but it has now 
 been ascertained that green tea is prepared from young leaves by a rapid process of 
 drying, whereas the black tea consists of older leaves which are allowed to lie in 
 heaps for some time after having been gathered, and to undergo a kind of fermentation 
 or change somewhat similar to that taking place in making hay. 
 
 Coffee beans are the perisperms or endosperms of the fruit of the coffee tree 
 (Coffea arabica, Fam. Bubiacese), deprived of the pericarp. The horny mass of the 
 beans consists of thick-walled pitted cells. When treated with sulphuric acid and 
 iodine, the cellulose assumes a peculiar blue colour ; by prolonged contact the cell 
 walls dissolve to a mucilaginous liquid. The remaining parts of the bean when 
 similarly treated assume an orange tint. The bean may be considered as consisting 
 of: 1. Cuticle surrounding the surface of the perisperm and permeated with fat, 
 nitrogenous substances, and ash constituents; 2. Spongy nitrogenous substances 
 which, together with oleaginous substances, fill up the cells of the epidermis; 
 3. Granular fatty masses filling the innermost cells ; 4. The membranes impregnated 
 with albumin filling the intercellular spaces. 
 
 Cocoa consists of the kernels of the beans or seeds of the Tkcobroma Cacao, a tree 
 indigenous in the West Indies and Central America, and growing extensively in 
 Mexico, Caraccas and Demerara. It is cultivated in the Mauritius and Bourbon ; the 
 roasted kernels are either simply ground and sometimes pressed to separate part of the 
 fat they contain, or they are ground with sugar into a paste which is called chocolate, 
 and is sometimes flavoured with vanilla. 
 
 Paraguay tea or Mate consists of the dried leaves of the ttcx Paraguaycnsis, a kind 
 of holly, growing in Paraguay and Brazil, where it is known by the name of y erba 
 mate. 
 
 Guarand is a substance that comes from South America, where it is prepared by 
 the Indians; it consists of a hard paste prepared from the ground and slightly 
 roasted seeds of Paullinia sorbilis. It is used by the natives much in the same way as 
 tea and coffee are used in other countries. 
 
 The peculiar effect produced by tea or coffee upon the human organism is the result 
 of a number of their constituents, among the chief of which are the substances called 
 thein or caffein (C 8 H, N, (X) according to the source from which it is obtained, 
 and some ethereal oils which are chiefly produced in the roasting of the beans. 
 Probably this is also the case with regard to mate and guarana, the former of which 
 contains, according to Byasson, nearly 2 per cent, of thein, while the latter contains 
 as much as 4 or 5 per cent. Cacao beans contain a similar substance called theobromin 
 (C 7 H 8 N 4 2 ). 
 
 Caffein occurs in tea leaves and in the coffee bean, partly in the free state, but, in 
 the latter case, according to Payen's researches, chiefly in combination with tannic 
 acid. 
 
 In order to prepare caffein from coffee, the beans are first dried at 100 until 
 sufficiently brittle to be powdered. The powder is then treated with ether in a per- 
 colator, until the ether passing through no longer leaves a stain upon paper. The 
 ethfereal solution contains the entire amount of fat and caffein present in the beans. 
 The ether is distilled off, the residue boiled up with several quantities of fresh water, 
 and the aqueous solution of caffein separated by filtration from the insoluble fat 
 
970 TEA, COFFEE, COCOA, ETC. 
 
 The aqueous solution is evaporated to dryness in a water bath, and the residue boiled 
 with absolute alcohol so long as anything is dissolved. On cooling the alcoholic 
 solution the caffein crystallises out. 
 
 Caffein in a pure state forms white silky needles, soluble in 90 to 100 parts of 
 cold water ; it is much more soluble in hot water, and sparingly soluble in alcohol 
 or ether. The crystals obtained from aqueous solutions contain water of crystallisa- 
 tion, which is given off entirely at a temperature of 100. At a temperature some- 
 what higher the caffein begins to volatilise. At 234 to 235 caffein melts without 
 decomposing, boils at 384, and sublimes, the vapour condensing upon cooling in 
 hair-shaped needles. The caffein crystallised from water has the formula : 
 
 C 8 H 10 N 4 2 + K 2 0. 
 
 Caffein is soluble in acids, but enters into combination with very few. Upon 
 evaporating the aqueous solutions, in most cases pure caffein crystallises out. 
 Caffein forms a stable compound with hydrochloric acid, which compound is prepared 
 by dissolving caffein in the concentrated acid, evaporating and crystallising ; from 
 weak aqueous solutions of caffein in hydrochloric acid the caffein crystallises out in 
 the free state upon evaporating the liquid. The hydrochlorate yields double salts 
 with the chlorides of platinum, gold, and mercury. Caffein itself enters into combina- 
 tion with silver nitrate and mercury cyanide. The so-called caffein citrate used in 
 pharmacy is not a true compound, but merely a mixture of citric acid and caffein. 
 
 Both tea and coffee contain astringent substances belonging to the class of tannins. 
 The tannin of tea leaves gives a blue-black precipitate with iron salts, and according 
 to Stenhouse it is distinct from the tannin of nut galls. The tannin of the coffee 
 berry colours ferric salts green, and does not precipitate ferrous salts. When exposed 
 to the air in contact with alkalies it gradually acquires a brilliant green colour, and is 
 converted into a substance called viridic acid. 
 
 According to Payen, caffein exists in coffee partly in the state of combination 
 with tannic acid and potash. To obtain this salt, the coffee beans that have been ex- 
 hausted with ether are treated with alcohol of 60 per cent., the solution evaporated to 
 a syrupy consistency, and the residue mixed with three times its volume of alcohol of 
 85 per cent. The liquid separates into two layers, the lower one being a sticky 
 liquid of considerable density, above which floats a light mobile liquid. The latter 
 contains the chief quantity of the salt in question ; it is poured off from the heavier 
 liquid, and the residue shaken up with alcohol of 85 per cent., so long as a drop of the 
 liquid, when mixed with a little water and heated, gives a greenish colour with 
 ammonia. The total quantity of alcohol that has been used is then distilled off, and 
 there remains a residue of syrupy consistence, which is then mixed with a quarter of 
 its volume of alcohol of 90 per cent. After a lapse of twenty-four to forty- eight hours, 
 the whole solidifies to a crystalline mass, which is first washed upon a filter with cold 
 alcohol of 65 per cent., and then re-crystallised several times from boiling alcohol, so 
 as to obtain it in a state of purity. In the preparation of this salt, great care is 
 required to keep it out of contact with vapours of ammonia, which is effected by 
 placing the solutions over vessels containing sulphuric acid, the whole being protected 
 by a glass bell jar ; in like manner the water used for diluting the alcohol must be 
 entirely free from ammonia, since mere traces of ammonia exert a decomposing action 
 upon the salt. 
 
 Potassium and caffein caffetannate possesses electrical qualities in a high degree. 
 Upon rubbing crystals of the salt, previously dried at 100, upon a piece of warm 
 paper, and bringing a blade of a knife in contact with them, they adhere to the blade 
 in little groups. The salt admits of being heated to 150 without undergoing any 
 change; it melts at 185, assuming a fine yellow colour, begins to boil, swells up to 
 five and six times its original volume, and is converted into a porous brittle yellow 
 mass. At 230 it becomes brown and is partly decomposed. The vapour evolved at 
 this temperature yields crystals of caffein by condensation. By further heating the 
 substance becomes dark brown, again melts, evolving alkaline vapour, and finally 
 swells up to twenty times its original volume, leaving a light iridescent charcoal. 
 The increase in volume observed in roasting coffee beans is due to the alteration in 
 this compound. 
 
 The double salt of potassium and caffein caffetannate is scarcely soluble in ab- 
 solute alcohol. From hot alcohol of 95 per cent, it crystallises in prisms radiating 
 from a common centre. The salt is more readily soluble in hot alcohol of 85 per 
 cent., from which it crystallises out abundantly upon cooling. The solubility of the 
 salt increases with the dilution of the alcohol. The salt is easily soluble in water, a 
 hot concentrated solution solidifying to a kind of magma upon cooling. An aqueous 
 solution of potassium and caffein caffetannate decomposes in contact with atmo- 
 spheric air, assuming first a yellow and afterwards a brownish-green tint. 
 
CONSTITUENTS OF COFFEE, ETC. . 971 
 
 Upon slightly warming the salt with potash, the crystals assume a hue varying 
 between vermilion and orange. At a higher temperature they melt, turn yellow, 
 evolve ammouiacal vapour, then become brown and decompose. Heated with concen- 
 trated sulphuric acid the crystals assume an intense violet colour, and become covered 
 with an iridescent film. Concentrated hydrochloric acid produces the same effect, and 
 nitric acid produces an orange-yellow colour. Lead acetate produces in aqueous solu- 
 tions of potassium and caffein caffetannate a flocculent pale yellowish-green precipi- 
 tate. With basic lead acetate a similar precipitate is formed, but of a yellow colour. 
 Neutral silver nitrate has no effect upon aqueous solutions of the salt, while the 
 slightest trace of ammoniacal silver nitrate produces a cloudiness, metallic silver 
 separating out on the sides of the test glass. 
 
 In order to separate the caffein from this compound, an aqueous solution is 
 mixed with a quantity of sulphuric acid equivalent to the potash it contains, and 
 evaporated to dryriess with powdered marble to neutralise any possible excess of sul- 
 phuric acid. From the residue, tannate of caffein is dissolved out with alcohol, and 
 basic lead acetate added to precipitate the tannic acid, and the precipitate is washed 
 with hot alcohol, from which the caffein crystallises out on cooling. 
 
 Caffetannic acid is obtained by decomposing the above-mentioned lead pre- 
 cipitate with sulphuretted hydrogen ; upon evaporating the solution, the caffe tannic 
 acid separates in small irregular crystals which are washed with cold absolute alcohol. 
 They are white, sparingly soluble in absolute alcohol, more readily in dilute alcohol, 
 and very soluble in water. A hot saturated aqueous solution of caffe tannic acid 
 crystallises slowly upon cooling, forming microscopic prisms grouped in little bundles 
 round a common cf-ntre ; after standing for three or four weeks the prisms unite, 
 forming granules 1 to 2 mm. in diameter. A solution of caffetannic acid has a strong 
 acid reaction. The crystallised acid melts when heated, turns yellow, boils, and 
 leaves light por9us brilliant charcoal. Its composition is represented by the formula 
 C 14 H 18 O f . 
 
 Coffee beans contain about 1 2 per cent, of fat, and the kernels of the cacao nuts 
 contain from 52 to 53 per cent, of a peculiar fat, which is used in pharmacy under the 
 name of cacao butter. 
 
 The Aromatic Oils . Although the aromatic constituents of articles of food 
 are devoid of direct nourishing power, they are nevertheless of importance, owing to 
 the effect produced by them upon the nervous system, which latter in its turn supports 
 the processes of digestion and assimilation. Among these aromatic substances are 
 the volatile oils which exist in the coffee bean, or are formed during the roasting. 
 The aroma of coffee may be isolated by distillation ; the amount, however, is so small 
 that very little is known of it beyond the fact that it is soluble in water. 
 
 The volatile oil of tea may be obtained either by distillation or by extraction with 
 ether. It is yellow, lighter than water, has the smell and taste of tea, and a powerful 
 stimulating action. 
 
 The kernels of the cacao nuts or beans contain, in addition to the fat above 
 mentioned, about 17 per cent, of albuminous substance, 11 per cent, of starch, 8 per 
 cent, of gum or mucilage, together with theobromine and a bitter substance. The 
 beans when fresh gathered are either dried at once or after being subjected to a kind 
 of fermentation or curing, by means of which the natural bitterness is removed. 
 They are slightly roasted before being ground, and in this operation the aroma is 
 developed, while part of the starch is converted into dextrin. In grinding the roasted 
 kern els into the paste that is known as flake coco a, or rock coco a, starch and sugar 
 are sometimes added in considerable proportions, and chocolate always contains admix- 
 tures of this kind, as well as flavouring substances, such as vanilla. In making the 
 better kinds of cocoa or chocolate, the husks of the beans are separated ; but in the 
 inferior kinds they are sometimes ground up together with the kernels. 
 
 Characters of different kinds of Tea and Coffee. The differences in quality of 
 the tea and coffee met with in commerce are due to the plant from which they are 
 obtained, partly also to the differences in soil, climate, cultivation, and harvesting. 
 
 The quality of tea depends very much on the season at which the leaves are 
 picked, the mode in which they are prepared, and the district where they are grown, 
 and it is chiefly to these conditions that the distinction between the varieties known 
 as Bohea, Congou, Souchong, Pekoe, Hyson, etc., is to be ascribed. The amount of 
 substance extracted by water varies considerably, as shown by the following average 
 results obtained by Stenhouse : 
 
 Per cent. 
 
 Dry black tea 43'2 
 
 Dry green tea 47'1 
 
 Black tea, as met with in commerce ..... 38*4 
 Green tea, as met with in commerce . . . 43'4 
 
972 TEA, COFFEE, COCOA, ETC. 
 
 The average percentage composition of dried tea is as follows, according to Mulder 
 
 Volatile oil 
 Chlorophyll .... 
 Wax 
 Resin . . 
 
 Chinese tea 
 
 Java tea 
 
 H-yson 
 
 Congou 
 
 Hyson 
 
 Congou 
 
 0-79 
 2-22 
 0-28 
 2-22 
 8-56 
 17-80 
 0-43 
 22-80 
 
 23-60 
 3-00 
 17-08 
 5-56 
 
 0-60 
 1-84 
 
 3-64 
 7-28 
 12-88 
 0-46 
 19-88 
 1-48 
 19-12 
 2-80 
 28-82 
 5-24 
 
 0-98 
 3-24 
 0-32 
 1-64 
 12-20 ' 
 17-56 
 0-60 
 21-68 
 
 20-36 
 3-64 
 18-20 
 4-76 
 
 0-65 
 1-28 
 
 2-44 
 11-08 
 14-80 
 0-65 
 18-64 
 1-64 
 18-24 
 1-28 
 27-00 
 5-36 
 
 Tannin 
 Thein 
 
 Extractive. 
 
 Extracted by hydrochloric acid . 
 Albuminous substance 
 Woody fibre .... 
 Ash .... 
 
 
 104-34 
 
 104-04 
 
 105-18 
 
 103-06 
 
 The Martinique coffee beans are generally large, and of a greenish colour with 
 flattened surface ; individual beans have sometimes an elliptic shape, owing to the non- 
 fructification of an ovule ; sometimes, but less often, beans having a somewhat angular 
 form are found, produced by the mutual pressure during growth of three fructified 
 ovules in the same fruit. 
 
 Mocha coffee differs from the former, inasmuch as the beans have a yellowish 
 grey colour, and are smaller and less regular in shape. Owing to the development of 
 two beans in a fruit, one side is in most cases flattened, only a few berries being 
 rounded ; as occurs when only one ovule is fructified. Mocha coffee differs further 
 from all other kinds of coffee in being richer in fat, the amount being as much as 13 
 per cent. The fat has a yellowish colour, and is softer than that found in other sorts 
 of coffee. Payen found in it two distinct kinds of fat, with different melting points. 
 The fat retains the aromatic constituents with great energy ; the quantity of which 
 latter constituents is relatively greater in Mocha coffee than in other sorts. 
 
 The fat of Martinique coffee is of a darker colour, of greater consistency, and can 
 be separated into four distinct fats, having melting points about 5, 20, 50, and 90, 
 the latter being very similar to the wax found in the leaves. 
 
 The occurrence of the wax-like substance and the green colour are probably due 
 to the time at which the berries are collected, and the shelling of the pods. Upon 
 removing the fleshy part of the fruit while it is filled with sap, the perisperm being 
 exposed to the air is altered by the action of oxygen ; the caffetannic acid becomes 
 green, and the fat substances are altered, while the soluble substances to which the 
 aroma is due, may be decomposed and volatilise. For this reason it would be better 
 especially for inferior sorts of coffee to allow the fruit to become as ripe as possible, 
 before gathering and shelling them. 
 
 The average percentage composition of coffee berries is as follows : 
 
 Cellulose . 
 
 Moisture 
 
 Fat 
 
 Glucose, dextrin, and undetermined acid 
 Legumin, casein (gluten ?) . 
 Potassium and caffein caffetannate 
 Nitrogenous substance .... 
 
 Free caffein 
 
 Solid essential oil, insoluble in water . 
 Two different aromatic oils, soluble in water 
 Ash constituents. . * . . , 
 
 12 
 
 10 to 13 
 
 15-5 
 
 10 
 
 3-5 to 5-0 
 
 3-0 
 
 0-8 
 
 0-001 
 
 0002 
 
 6-697 
 
 Coffee is always roasted before being used, and in this operation it undergoes con- 
 siderable alteration, losing about 12 or 18 per cent, of its weight and becoming darker 
 coloured according to the degree of heat employed ?n the roasting. The beans also 
 lose their toughness, swell up and become so brittle that they can be readily ground 
 to powder, while at the same time an agreeable aroma is developed. In roasting 
 
COMPOSITION OF COFFEE. 973 
 
 coffee the heat requires to be carefully regulated, and the beans must be kept in 
 motion so that all of them are equally heated. For this purpose rotating vessels of 
 a cylindrical or globular shape and made of sheet iron are generally employed. 
 
 Uses. Although tea, coffee, and cocoa or chocolate, are articles of daily con- 
 sumption, and although their use extends over all parts of the earth, so that they 
 may be almost considered as necessary articles of food, still their actual value as 
 food material is but slight, and the nutritive effects produced by them bear no pro- 
 portion to the quantity consumed. 
 
 As regards the physiological effects of coffee, it was at one time supposed that the 
 use of coffee might reduce the consumption of albuminous constituents in the body, 
 but this has been shown by the researches of Voit to be entirely erroneous. 
 
 The influence of coffee is chiefly to be ascribed to caffein, which has an energetic 
 action on the system, in small doses as a stimulant exciting the imagination, and in 
 large doses giddiness, headache, and even delirium and convulsions. Animals have 
 been poisoned with caffein under precisely the same symptoms that are produced by 
 strychnine. 
 
 A certain amount of stimulus to the nervous system seems to be indispensable to 
 the human economy. A variety of different substances are consumed for this pur- 
 pose, for instance, wine, spirit, tobacco, coffee, tea, broth, opium, haschisch, etc., every 
 nation having its own peculiar stimulant, which, although not directly nutritive, has 
 considerable influence on the general condition of the system. Coffee is one of the 
 most important materials of this class. 
 
INDEX, 
 
 ACE 
 
 ACETIC ACID, 961 
 
 -H- History, occurrence, composition, and 
 characters, 961 
 
 Preparation, 962 
 
 Uses, 968 
 A old, acetic, 961 
 
 caffetannic, 971 
 
 gummic, 755 
 
 metapectic, 654 
 
 oleic, 664 
 
 palmitic, 664 
 
 parapectic, 654 
 
 pectic, 653 
 
 pectosic, 653 
 
 potassium carbonate, 209 
 oxalate, 211 
 
 sulphate, 210 
 
 tartrate, 211 
 
 sodium bicarbonate, 273 
 carbonate, 273 
 
 stearic, 663 
 
 sulphurous, 103 
 
 viridic, 970 
 
 Acids, fatty, preparation of, 673 
 Aerated waters, 72 
 
 bottling of, 74 
 
 Aggregation, 2 
 Air balloons, 29 
 Alban, 750 
 Albumin, 658 
 
 Compounds, 659 
 
 Uses, 660 
 
 Albuminous substances, 657 
 Alcohol, 881 
 
 Characters, 885 
 
 Preparation, 886 
 
 Extraction from wine, beer, etc. 907 
 Alcoholic beverages, 925 
 
 liquors, treatment of, 887 
 Alkaloids, 69 
 
 Alum, 307 
 
 History, occurrence, composition, and 
 characters, 307 
 
 Preparation, 308 
 
 Uses, 311 
 Alum cake, 305 
 Alum potash, 307 
 
 Alum slates and earths, analyses of, 309 
 Alum stone, composition of, 308 
 Alumina, 304 
 Aluminum. 301 
 
 History, occurrence, characters, and 
 preparation, oOl 
 
 Uses and compounds, 302 
 
 AQU 
 
 Aluminum and sodium chloride, prepara- 
 tion, 304 
 
 Aluminum chloride, preparation, 304 
 Aluminum oxide (alumina), 304 
 
 History, occurrence, characters, and 
 
 preparation, 304 
 Aluminum sulphate, 305 
 
 Characters, 305 
 
 Analyses, 305 
 
 Preparation, 306 
 
 Uses, 307 
 Amber, 729 
 Ammonia, 49 
 
 History, occurrence, composition, and 
 characters, 49 
 
 Preparation, 50 
 
 Uses and compounds, 51 
 Ammonia alum, 311 
 Ammonia from gas liquor, 52 
 Ammonia, solutions of, 50 
 Ammoniacum, 727 
 Ammonium arsenate, 498 
 Ammonium arseaites, 494 
 
 carbonates, 52 
 Ammonium chloride, 51 
 
 History, occurrence, characters, prepa- 
 ration, and uses, 51 
 Ammonium sulphate, 52 
 
 Occurrence, characters, preparation, and 
 
 uses, 52 
 
 Amorphous phosphorus, 150, 156 
 Amylaceous materials, production of spirit 
 
 from, 918 
 
 Animal charcoal, 61, 63 
 Animals, substances derived from, 609 
 Anime, 725 
 Antimonic chloride, 504 
 
 oxide, 504 
 
 sulphide, 503 
 Antimonous chloride, 504 
 
 oxide, 504 
 Antimonous sulphide, 502 
 
 History, occurrence, and characters, 502 
 
 Preparation and uses, 603 
 Antimony, 500 
 
 History, occurrence, characters, and 
 preparation, 500 
 
 Uses and compounds, 501 
 Antimony, butter of, 504 
 Antimony vermilion, 503 
 Apiin, 656 
 
 Apparatus. See under DIAGRAMS 
 Aqua fortis, 42 
 Aqua regia, 49 
 
976 
 
 INDEX. 
 
 ARG 
 
 CAL 
 
 Argand burner, 714 
 Argentic chromate, 524 
 Argillaceous iron ore, 557 
 Arrow root, Brazilian, 759 
 
 East India, 759 
 
 Portland, 759 
 
 Tahiti or Tacca, 758 
 
 West India, 758 
 
 Arrowroot starch, 758 
 Arsenic, 492 
 
 Historj', occurrence, characters, and 
 
 preparation, 492 
 Uses and compounds, 493 
 Arsenic acid, 497 
 Arsenic clisulphide, 499 
 
 History, occurrence, and characters, 
 
 499" 
 Arsenic oxide, 497 
 
 History, occurrence, and characters, 
 
 497 
 Arsenous oxide, 494 
 
 History, occurrence, and characters, 
 
 494 
 
 Preparation, 495 
 Arsenous sulphide, 499 
 
 History, occurrence, and characters, 
 
 499 
 
 Artificial lighting materials, 684 
 Artificial stone, 341 
 Asparagin, 819 
 Assafcetida, 727 
 Atmosphere, the, 53 
 Atmospheric air, 65 
 Atomic theory, 9 
 Auric chloride, 529 
 
 oxide, 528 
 Aurous chloride, 529 
 
 oxide, 528 
 Autogenous soldering, 28 
 
 BAKING OVENS, 793 
 Balloons, air, 29 
 
 light gas, 742 
 Balsam of Copaiba, 720 
 
 Canada, 720 
 
 Gurjun, 720 
 
 Peru, 728 
 
 Tolu, 729 
 Barilla, 255 
 Barium, 298 
 Barium arsenate, 498 
 Barium chloride, 298 
 
 Composition, characters, and prepara- 
 tion, 298 
 
 Uses, 299 
 Barium sulphate, 299 
 
 Occurrence, characters, and preparation, 
 299 
 
 Uses, 300 
 Baryta white, 299 
 Bdellium, 728 
 Beer, 948 
 
 Analysis, 958 
 
 Constituents, 937 
 
 Fining, 955 
 Bees' wax, 680 
 Beet potash, 205 
 Beet root, constituents, 819 
 lient roots, 823 
 
 Preparation, 823 
 
 Lxtraftion of juice from, 825 
 
 Beet, the sugar, 814 
 
 Culture, 814 
 
 Anatomical structure, 816 
 
 Composition, 818 
 Benzoin, 728 
 
 Bessemer's steel, manufacture, 603 
 Betaine, 819 
 Bismuth, 505 
 
 History, occurrence, characters, and 
 preparation, 505 
 
 Compounds, 506 
 Bismuth nitrate, 507 
 Bituminous coal, 86 
 Blanquette, 255 
 Blasting powder, Nobel's, 226 
 Bleaching paper, 642 
 Bleaching powder, 169 
 Bleaching preparations, 168 
 Bleaching wax, 681 
 Blister steel, 602 
 Blowpipe, oxyhydrogen, 28 
 Blue vitriol, 425 
 Bohemian glass, 317 
 Boiling point, 4 
 Bone phosphate, 291 
 Bones, calcination, 150 
 Boracia acid, 187 
 
 History, occurrence, and characters, 187 
 
 Preparation, 188 
 
 Purification, composition, and uses, 190 
 Borax, 277 
 
 Octahedral, 279 
 Boron, 186 
 
 History, occurrence, characters, and 
 
 compounds, 186 
 Bottle glass, 316 
 Bread, 776 
 
 Making, 789 
 
 Dr. Dauglish's process of baking, 79 1 
 
 Alterations in bread, 799 
 Brewing, 938 
 Bricks, 340 
 Brimstone, 92 
 Brine springs, 239 
 Bromine, 177 
 
 History, occurrence, characters, and 
 preparation, 177 
 
 Purification, 179 
 
 Uses and compounds, 179 
 Buccia, 148 
 
 Burnt ivory or bone black, 63 
 Butter of antimony, 504 
 
 CADMIUM, 858 
 \J Ceeruleum, 514 
 Cesium, 280 
 Caffein, 969 
 Caffetanic acid, 971 
 Calamine, 357 
 Calcium, 281 
 
 Occurrence, 281 
 Calcium arsenates, 498 
 Calcium carbonate, 286 
 
 Occurrence, characters, and uses, 286 
 Calcium fluoride, 287 
 hydrate, 286 
 Calcium oxide (lime), 281 
 
 Occurrence, characters, and prepara- 
 tion, 281 
 
 Uses, 285 
 
 Calcium phosphate, 291 
 Characters and uses, 291 
 
INDEX. 
 
 979 
 
 EAR 
 
 17' ARTHENWARE, 337. See POTTERY 
 J-J Efflorescent substances, 32 
 Elementary substances, 6 
 
 Table of, 6 
 
 Classification, 7 
 Elemi, 726 
 Enamel, 331 
 Enamelling, 331 
 Epsom salts, 343 
 Erbium, 488 
 
 Essential oils, 719. See OILS, Essential 
 Euphorbium, 728 
 Explosive materials, 218 
 Explosive paper, 229 
 starch, 229 
 
 17 AT, 663 
 
 I Extraction, 144 
 
 Characters and composition, 663 
 Preparation, for burning, 670 
 
 Fat from wool, 146 
 
 Fats, solid, 667 
 
 Fatty acids, preparation, 673 
 
 Fermentation, 883 
 
 Fermentation, stone square system, 957 
 
 surface or sedimentary, 954 
 Fermentation vats, 953 
 Ferric acid, 544 
 
 arsenate, 498 
 
 chloride, 545 
 
 oxide, history, occurrence, and cha- 
 
 racters, 543 
 
 sulphate, 550 
 
 Ferroso-ferric or magnetic oxide, 544 
 Ferroso-ferric sulphide, 546 
 Ferrous arsenate, 498 
 
 carbonate, 550 
 
 chloride, 544 
 
 iodide, 545 
 
 oxide, 543 
 Ferrous sulphate, 647 
 
 Characters, 547 
 
 Preparation, 548 
 
 Uses, 549 
 Ferrous sulphide, 545 
 
 Occurrence and characters, 545 
 
 Preparation, 546 
 Filtration of water, 34 
 Finery slags, analyses, 581 
 Fining beer, 955 
 Fire clay, 334 
 Fish oil, 667 
 Flax, preparation, 619 
 Flour, 776 
 
 Characters and adulteration, 781 
 Flowers of sulphur, 97 
 Fluavil, 750 
 Fluorine, 184 
 
 History, occurrence, characters, and 
 
 compounds, 184 
 Flux, white and black, 21 1 
 Frankfort black, 67 
 Friction matches, 157 
 Fuel, 84 
 
 History, composition, and characters, 84 
 
 Composition of fuels, 85 
 
 Table of calorific power, 87, 89 
 
 Practical effect, 89 
 Fuel, gaseous, 589 
 
 Fuming sulphuric acid, preparation, 113 
 Furnaces, gas puddling, 591 
 
 3 
 
 GLY 
 
 Fusel oil, 888, 900 
 Futenang, 510 
 
 p ALBANUM, 727 
 
 IT* Galena, 391 
 
 Galipot, 725 
 
 Gamboge, 728 
 
 Gas balloons, light, 742 
 
 Gas burners, 714 
 
 Gas, composition in smelting furnaces, 577 
 
 coal, composition of, 693 
 Gas, carburetting, 712 
 
 illuminating. 691 
 Gas manufacture, 692 
 
 Chemistry, 692 
 
 Different kinds of coal used in gas 
 
 making, 694 
 Purification of ga.s, 705 
 Improvements in gas making 7 1 1 
 Gas, marsh, 76 
 
 oleiiant, 78 
 
 oxygen, Du Motay's, 716 
 Gas metres, 708 
 
 puddling furnaces, 591 
 
 retorts, 695 
 
 retort furnaces, 697 
 Gas tar, 716 
 Gaseous fuel, 589 
 Gelatin, 661 
 
 Gelose, 655 
 
 Geological chemistry, 16 
 Gerstenhoefer's kiln, 122 
 Glass, 312 
 
 History, 312 
 
 Composition and characters, 313 
 
 Devitrification, 314 
 
 Colouration hy sunlight, 314 
 
 Preparation, 315 
 Glass, soluble or water, 332 
 
 Composition, characters, and prepara- 
 tion, 332 
 
 Uses, 333 
 Glass, blown, 324 
 
 Bohemian, 317 
 
 bottle, 316 
 
 coloured, 319 
 
 corrugated sheet, 327 
 
 crown or moon, 326 
 
 crystal or flint, 317 
 
 cylinder, 326 
 
 enamel, 331 
 
 mixtures, various, 317 
 
 optical, 318, 330 
 
 plate, 318, 328 
 
 sheet, 317 
 
 soda, 318 
 
 wiudow, 3] 7 
 Glass blowing, 324 
 
 making. 315 
 
 painting, 320 
 
 Glass pots and furnaces, 321 
 Glauber's salt, 249 
 Glazed boards, 650 
 Glucinum, 487 
 
 chloride, 487 
 
 Glucose, or grape sugar, 802 
 
 Manufacture, 809 
 ! Gluco-sulphuric acid, 803 
 i Glue, 661 
 j Gluten, 779 
 
 Granulated, 799 
 Glyceril stearate, 664 
 u 2 
 
980 
 
 INDEX. 
 
 GLY 
 
 Glycogen, 764 
 Gmelin's salt, 82 
 Gold, 526 
 
 History, occurrence, characters, and ex- 
 traction, 526 
 
 compounds, 527 
 Goloshes, 743 
 Goulard extract, 398 
 Grape sugar, 803 
 
 Grape, the, and its constituents, 927 
 Graphite, 56 
 
 Grindstones, artificial, manufacture, 746 
 Guaiacum, 727 
 Guarana, 969 
 Gum, 755 
 Gum Arabic, 755 
 
 artificial, 756 
 
 Bassora, 755, 756 
 
 cherry tree, 755, 756 
 
 Senegal, 756 
 
 tragacanth, 756 
 Gummic acid, 755 
 Gun cotton, 227 
 
 History and composition, 227 
 
 Characters and preparation, 228 
 
 Uses, 230 
 
 Testing, 230 
 Gunpowder, 218 
 
 History and composition, 218 
 
 Characters, 220 
 
 Preparation, 221 
 
 Pulverisation, 223 
 
 Granulation, 224 
 
 Polishing and drying, 225 
 
 Testing, 226 
 Gunpowder making, 221 
 Gurjun balsam, 720 
 Gutta percha, 748 
 
 Composition, 749 
 
 Preparation, 751 
 
 Vulcanisation, 753 
 
 For insulating telegraph wires, 753 
 Gypsum, 287 
 
 HAEMATITE, or red iron ore, 552 
 Hartshorn, spirits of, 49 
 Heat, specific, 4 
 
 unit, 4 
 Hops, 939 
 
 Preservation, 940 
 Hydraulic lime, 292 
 
 mortar, 297 
 Hydrocarbon oils, 683 
 Hydrocarbons, 68 
 Hydrochloric acid, 172 
 
 History, occurrence, composition, and 
 
 characters, 172 
 Table of strength, 172 
 Of aqueous solutions, 173 
 Preparation, 174 
 Uses, 175 
 Hydrofluoric acid, 185 
 
 History, characters, preparation, and 
 
 uses, 185 
 Hydrogen, 26 
 
 History, occurrence, and characters, 
 
 26 
 
 Preparation, 27 
 Uses, 28 
 Application, 29 
 Compounds, 30 
 
 LAM 
 
 Hydrogen peroxide, 36 
 
 Composition and characters, 36 
 Preparation and uses, 87 
 Hydrometer, the, 3 
 Hygroscopic substances, 32 
 
 TCE, 31 
 
 -L Illuminating gas, 691 
 
 Indian ink, 67 
 
 India-rubber tubes, 739 
 
 Indium, 485 
 
 Industrial chemistry. See CHEMISTRY 
 
 Ink, alizarin, 550 
 
 blue, 550 
 
 copying, 550 
 
 Indian, 67 
 
 red, 550 
 
 writing, 549 
 
 Ink, preparation of, 549 
 Inorganic chemistiy, 15 
 Inorganic substances, 609 
 Inulin, 764 
 
 Inventions. See under DIAGRAMS 
 Iodine, 180 
 
 History, occurrence, and characters, 180 
 
 Tests, 181 
 
 Preparation, 181 
 
 Sublimation, 182 
 
 Extraction, 182 
 
 Uses and compounds, 183 
 Iodine solution, 171 
 Iridium, 538 
 
 History, occurrence, characters, pre- 
 paration, and compounds, 538 
 Iron, 541 
 
 History, occurrence, and characters, 541 
 
 Compounds, 542 
 Iron disulphide, 546 
 
 History and occurrence, 546 
 Iron, malleable, manufacture, 578 
 Iron, metallurgy, 551 
 Iron smelting, 571 
 Iron ore, 559 
 
 Roasting, 559 
 
 Production of pig iron, 561 
 Iron ore, argillaceous, 557 
 
 brown, 553 
 
 magnetic, 551 
 
 red or haematite, 552 
 
 spathic, 554 
 
 Isinglass, 661 
 
 JET PHOTOMETER, 717 
 
 KELP, 194 
 Kermes' mineral, 502 
 Kilns, air, 943 
 
 charcoal, 879 
 
 malt, 943 
 
 smoke, 943 
 Kirschwasser, 909 
 
 T AC RESIN, 726 
 
 J-J Lactose, or milk sugar, 807 
 
 Ladanum, 728 
 
 Lamp black, 64 
 
 Lamp, Davy's safety, 77 
 
 Doebereiner's, 28* 
 
INDEX. 
 
 ' 981 
 
 LAN 
 
 Lanthanum, 484 
 Lapis lazuli, 244 
 Lead, 359 
 
 History, occurrence, and characters, 359 
 
 Preparation, 360 
 
 Roasting, 361 
 
 Smelting, 362 
 
 In shaft furnaces, 367 
 
 In reverberatory furnaces, 378 
 
 Refining, 387 
 Lead acetate, 398 
 
 History, characters, preparation, and 
 
 uses, 398 
 
 Lead arsenate, 498 
 Lead carbonate, 392 
 
 History, occurrence, and composition, 
 392* 
 
 Characters and preparation, 393 
 Lead oxide, 389 
 
 History, occurrence, and characters, 389 
 
 Preparation and uses, 390 
 Lead peroxide, 390 
 
 Characters, 390 
 
 Preparation, 391 
 Lead sulphate, 392 
 sulphide, 391 
 Leather manufacture, 662 
 Light, artificial, 670 
 Lighting materials, 670 
 Lignite, or brown coal, 85 
 Lime, 281 
 
 Applications, 285 
 
 Analyses of limestones, 285 
 Lime burning, 282 
 Lime, hydraulic, preparation, 292 
 Litharge, 389 
 Lithium, 280 
 Loadstone, 544 
 Lunar caustic, 450 
 
 MACARONI, manufacture, 797 
 Machinery. See under DIAGRAMS 
 Magnesium, 342 
 
 History, occurrence, characters, pre- 
 parations, uses, and compounds, 342 
 Magnesium arsenates, 498 
 Magnesium carbonate, 343 
 
 Occurrence and characters, 343 
 Magnesium sulphate, 343 
 
 Characters and preparation, 343 
 Magnetic iron ore, 551 
 Magnetic oxide, 544 
 Malleable iron, 578 
 
 Characters, 597 
 Malt, preparation, 941 
 Malting, 941 
 Malt kilns, 943 
 Malt roasting, 942 
 Manganates, 519 
 Manganese, 516 
 
 History, occurrence, characters, pre- 
 paration, uses, and compounds, 516 
 Manganese, binoxide, 518 
 Manganic oxide, 517 
 Manganoso-manganic oxide, 518 
 Manganous chloride, 520 
 
 oxide, 517 
 
 sulphate, 520 
 
 Manufactures. See under DIAGRAMS 
 Marsh gas, 76 
 
 Occurrence, characters, composition, 
 and preparation, 76 
 
 NIT 
 
 Massicot, 389 
 Mastic, 726 
 Mastic cement, 745 
 Matches, sulphuration, 158 
 
 Composition, 159 
 Matches, amorphous phosphorus, 161 
 
 friction, 157 
 
 wax or vesta, 160 
 
 without phosphorus, 204 
 sulphur, 160 
 
 Mate', or Paraguayan tea, 969 
 Melting point, 4 
 Mercuric chloride, 461 
 
 History, characters, and preparation, 
 
 461 
 
 Mercuric nitrate, 463 
 Mercuric oxide, 459 
 
 History, characters, and preparation 
 
 459 
 
 Mercuric sulphate, 463 
 Mercuric sulphide, 461 
 
 History, 461 
 
 Occurrence, characters, preparation, 
 
 and uses, 462 
 Mercurous chloride, 460 
 
 History, occurrence, characters, pre- 
 paration, and uses, 460 
 Mercurous nitrate, 463 
 Mercurous oxide, 459 
 
 History and characters, 459 
 Mercurous sulphate, 462 
 Mercury, 451 
 
 History, occurrence, and characters, 451 
 
 Preparation, 452 
 
 Extraction, 453 
 
 Uses and compounds, 458 
 Metalloids, 7 
 Metallurgy of iron, 551 
 Metals, 7 
 
 Metapectic acid, 654 
 Metastannic acid, 472 
 Milk sugar, 807 
 Milk used for wine fining, 932 
 Millboard, 650 
 Mineral waters, 72 
 
 Bottling, 74 
 
 Minerals, substances occurring as, 15 
 Molasses, 857, 876 
 Molybdenum, 479 
 Molybdenum trioxide, 480 
 Molybdic oxide, 480 
 
 sulphide, 480 
 Molybdous oxide, 479 
 Mother of vinegar, 964 
 Mucilage, 756 
 
 Must, 928 
 
 Preparation, 928 
 
 Constituents and fermentation, 930 
 
 Testing, 935 
 Myrrh, 727 
 
 NAPLES YELLOW, 389 
 Nickel, 508 
 
 History, occurrence, and characters, 508 
 
 Preparation and uses, 509 
 
 Compounds, 510 
 Nickel arsenate, 498 
 oxide, 511 
 Nickelous sulphate, 511 
 Niobium, 482 
 Nitric acid, 42 
 
 History and occurrence, 42 
 
982 
 
 INDEX. 
 
 NIT 
 
 Nitric acid, cont. 
 
 Composition and characters, 43 
 
 Strength, 43 
 
 Preparation, 45 
 
 Distillation, 45 
 
 Bleaching, 46 
 
 Uses, 48 , 
 Nitric acid, fuming, 48 
 Nitric oxide, 40 
 
 Composition, characters, preparation, 40 
 Nitrogen oxides, 134 
 Nitrogen pentoxide, 42 
 
 Composition, characters, preparation, 
 
 and compounds, 42 
 Nitrogen peroxide, 41 
 
 Composition, characters, preparation, 
 
 and compounds, 41 
 Nitroglycerin, 231 
 Nitrous anhydride, 41 
 
 Composition, characters, preparation, 
 
 and compounds, 41 
 Nitrous gases, 124 
 Nitrous oxide, composition, 40 
 
 Characters, preparation, uses, and 
 
 compounds, 40 
 Nobel's blasting powder, 226 
 blasting oil, 231 
 
 Nomenclature and notation in chemistry, 1 1 
 Nordhausen oil of vitriol, 111 
 
 Extraction, 145 
 
 AIL, 663 
 
 V/ Preparation of, for burning, 670 
 
 Rectification of crude oil, 689 
 Oil (essential), anise, 723 
 
 bergamot, 723 
 
 birch, 722 
 
 bitter almond, 724 
 
 cajeput, 724 
 
 camphor, Borneo, 722 
 Japan, 722 
 
 caraway, 723 
 
 cassia, 722 
 
 cedar, 721 
 
 chamomile, 723 
 
 cinnamon, 722 
 
 citronella, 722 
 
 clove, 724 
 
 cubeb, 722 
 
 cumin, 723 
 
 eucalyptus, 724 
 
 grass, East Indian, 722 
 
 hemp, 722 
 
 hop, 722 
 
 jasmine, 724 
 
 juniper, 721 
 
 lavender, 723 
 
 lemon, 723 
 
 lemon grass, 722 
 
 lime, 723 
 
 meadow sweet, 723 
 
 mustard, 724 
 
 neroli,724 
 
 nutmeg or mace, 722 
 
 orange. 723 
 
 otto of rose, 723 
 
 patchouli, 723 
 
 pepper, 722 
 
 peppermint, 723 
 
 pimento, 724 
 
 rosemary, 723 
 
 rosewood, 723 
 
 PAP 
 
 Oil (essential), rue, 724 
 
 sandal wood, 721 
 
 sassafras, 722 
 
 savin, 721 
 
 thuja, 721 
 
 thyme, 723 
 
 valerian, 722 
 
 wintergreen, 723 
 
 wormwood, 723 
 
 Oil, fish, purification, 667 
 
 Oil from shale, coal, etc., 685 
 
 Oil, fusel, 888 
 
 Oil gas, 713 
 
 Oil, hydrocarbon, 683 
 
 Oil, solar, 691 
 
 Oil, turpentine, 721 
 
 Oils, aromatic, of the coffee bean, 971 
 
 Olefiant gas, 78 
 
 Characters and preparation, 78 
 
 Uses, 79 
 Oleic acid, 664 
 Oleoresins, 720 
 Olibanum, 727 
 Opoponax, 728 
 Ores, copper, 400 
 
 gold, 527 
 
 iron, 552 
 
 lead, 372 
 
 mercury, 454 
 
 silver, 429 
 
 tin, 464 
 
 zinc, 345 
 
 Organic chemistry, 609. See CHEMISTRY 
 Organic substances, 609 
 
 Groups of, 614 
 Osmium, 539 
 
 History, occurrence, preparation, 
 
 characters, and combinations, 539 
 Ovens, baking, 793 
 Oxides, composition, 21 
 Oxygen, 17 
 
 * History, occurrence, oharacters, and 
 preparation, 17 
 
 Compounds, 20 
 
 Composition, 21 
 
 Combustion, 22 
 Oxygen, allotropic form, 26 
 Oxyhydrogen blowpipe, 28 
 Ozokerite, 680 
 Ozone, 24 
 
 History, occurrence, and characters, 24 
 
 Preparation and uses, 25 
 
 T)ACKFONG, 510 
 1 Palladium, 534 - 
 
 Alloys and compounds, 535 
 Palmitic acid, 664 
 
 Palmitin, 664 
 Paper, 633 
 
 History, 633 
 
 Composition and properties, 634 
 
 Preparation and materials, 684 
 
 Testing, 651 
 Paper, coloured, 648 
 
 filter, 649 
 
 gold, 649 
 
 granite, 649 
 
 hand, (54(! 
 
 machine, 646 
 
 marble, 649 
 
 morocco, tM9 
 
 mottled, 649 
 
 
INDEX. 
 
 PAP 
 
 Paper, parchment, 650 
 
 rainbow, 649 
 
 rep or filagree, 649 
 
 silver, 649 
 
 surface-coloured, 648 
 Paper making, 641 
 
 Bleaching of paper stuff, 642 
 
 Sizing, 644 
 
 Tinting, 644 
 Papier mache, 650 
 Paraffin, 683 
 Paraffin candles, 683 
 Parapectic acid, 654 
 Parapectin, 653 
 Parchment, 633 
 
 vegetable, 650 
 Pasteboard, 650 
 Pearl ash, 208 
 Peat, 85 
 Pectase, 652 
 Pectic acid, 653 
 Pectin, 652 
 
 Pectinose, or pectin sugar, 654 
 Pectose, 652 
 Pectosic acid, 653 
 Pectous substances, 652 
 Permanganates, 520 
 Peru balsam, 728 
 Petroleum, 683, 691 
 Pewter, 470 
 Phosphorescence, 149 
 Phosphorus, 149 
 
 History, occurrence, and characters, 149 
 
 Preparation, 150 
 
 Distillation, 152 
 
 Uses, 157 
 
 Compounds, 161 
 Phosphorus, amorphous, 150, 156 
 
 crude, purification, 154 
 
 granular, 155 
 Photogen, 691 
 Pig iron, 561 
 
 Production, 561 
 
 Characters, 565 
 
 Composition, 569 
 
 Refining, 585 
 Pink salt, 474 
 Plants, 609 
 
 Substances derived from, 609 
 
 Composition, 610 
 
 Growth, 612 
 Plaster of paris, 287 
 Plate glass, 318 
 Platinic chloride, 534 
 
 oxide, 533 
 Platinous chloride, 533 
 
 oxide, 533 
 Platinum, 530 
 
 History, occurrence, and characters, 530 
 
 Preparation, 531 
 
 Uses, 532 
 
 Compounds, 533 
 Plumbic chromate, 524 
 Podophyllin, 726 
 Porcelain, 339 ' 
 Portland cement, 295 
 Potash, 205 
 
 Calcination, 207 
 
 From wood ashes, 206 
 
 schonite, 208 
 
 sea weed, 208 
 
 suint, 208 
 
 wine lees, 208 
 
 PUD 
 
 Potash, cont. 
 
 From molasses, 208 
 
 Refining, 209 
 Potash alum, 307 
 Potassium, 194 
 
 History and occurrence, 194 
 
 Characters, 195 
 
 Preparation and compounds, 196 
 Potassium and aluminum sulphate, 307 
 Potassium and caffein caffetannate, 970 
 Potassium arsenate, 498 
 
 arsenites, 495 
 
 bromide, 200 
 Potassium carbonate, 205 
 
 History and characters, 205 
 
 Preparation, 206 
 
 Uses, 209 
 
 Potassium carbonate, acid, 209 
 Potassium chlorate, 202 
 
 History, characters, andpreparation,202 
 
 Uses, 203 
 Potassium chloride, 197 
 
 Occurrence, characters, and preparation, 
 197 
 
 Extraction from sea-weed, 198 
 
 Uses, 200 
 
 Potassium chromate, 523 
 Potassium cyanide, 80 
 
 Characters, preparation, and uses, 80 
 Potassium dichromate, 523 
 Potassium ferricyanide, 82 
 
 Composition, characters, and prepara- 
 tion, 82 
 
 Uses, 83 
 Potassium ferrocyanide, 80 
 
 History, characters, and preparation, 80 
 
 Uses, 82 
 Potassium hydrate, 196 
 
 Characters, 196 
 Potassium iodide, 201 
 
 Characters and preparation, 201 
 Potassium metastannate, 472 
 Potassium nitrate, 211 
 
 Preparation, 215 
 
 Testing, 216 
 Potassium oxalate, acid, 211 
 
 oxide, 196 
 
 stannate, 472 
 Potassium sulphate, 209 
 
 Characters, 209 
 
 Preparation, 210 
 Potassium sulphate, acid, 210 
 Potassium tartrate, acid, 211 
 Potato disease, 788 
 Potato flour, 783 
 
 spirit 921 
 
 starch, 758 
 Potatoes, 787 
 
 Composition and preservation, 787 
 Pottery, or earthenware, 333 
 
 Composition of clays, 334 
 
 Analyses, 335 
 
 Common pottery ware, 336 
 
 Glazing and decoration, 337 
 Preparations. See under DIAGRAMS 
 Printer's blue, 514 
 Prussian blue, 83 
 
 Soluble, 84 
 
 Uses, 84 
 Prussiate, red, 82 
 
 yellow, 80 
 
 Puddle balls, treatment, 595 
 Puddling furnaces, rotatory, 593 
 
984 
 
 INDEX. 
 
 PUZ 
 
 Puzzolane, 294 
 
 Pyrites, 117 
 
 Pyrites burner, 120 
 
 Pyropissite, 685 
 
 Pyroxam, or explosive starch, 229 
 
 Pyroxylin, 227 
 
 p AGS, treatment of, in the manufacture of 
 11 paper, 638 
 Realgar, 499 
 
 Recipes for making combustible composi- 
 tions for matches, 204 
 Rectification of spirit, 900 
 Red lead, 390 
 Red precipitate, 459 
 Red prussiate, 82 
 Resin, 719 
 
 Botany Bay, 726 
 Retort furnace, 696 
 Retorts, gas, 695 
 Rhodium, 536 
 
 Compounds and alloys, 536 
 Rinman's green, 514 
 Rock ash, 207 
 Rock salt, 236 
 Roll sulphur, 97 
 Roman alum, 308 
 Roman cement, 293 
 Rubidium, 280 
 
 Rupert's drops, or devil's tears, 313 
 Ruthenium, 537 
 
 Q ACCHARIMETRY, 871 
 
 O Saccharose, 803 
 
 Safety lamps, 77 
 
 Sagapenum, 727 
 
 Sago, 758 
 
 Sal ammoniac, 51 
 
 Salicor, 255 
 
 Salt, artificial sea, 201 
 
 Gmelin's, 82 
 
 rock, 236 
 
 Salt cake, manufacture, 251 
 Salt garden, 241 
 Salt of sorrel, 211 
 Saltpetre, 211 
 
 Natural saltpetre, 212 
 
 Formation, 213 
 
 Refining of crude and Indian, 215 
 
 Testing, 216 
 Sandarac, 725 
 Santorin earth, 295 
 Sanza, 148 
 Saxafragin, 226 
 Sea salt, artificial, 201 
 Seidlitz powders, 275 
 Sheet glass, 317 
 Shell lac, 726 
 Silica, 193 
 Silicates, aluminum, 192 
 
 calcium, 192 
 
 ferrous, 193 
 
 lead, 193 
 
 magnesium, 192 
 
 manganous, 193 
 
 potassium, 192 
 
 zinc, 193 
 Siliceous materials, 315 
 Silicic oxide, 193 
 Silicon, 191 
 
 History, occurrence, diameters, and 
 compounds, 191 
 
 SOD 
 
 Silver, 427 
 
 History, occurrence, and characters, 427 
 
 Preparation, 428 
 
 Amalgamation of silver ores, 429 
 
 Separation of silver from copper, 431. 
 441 
 
 From lead, 433, 439 
 
 Cupellation, 435 
 
 Refining, 445 
 
 Uses, 446 
 
 Compounds, 447 
 Silver arsenate, 498 
 Silver chloride, 448 
 
 History, occurrence, characters, and 
 
 preparation, 448 
 Silver nitrate, 450 
 
 Characters and preparation, 450 
 Silver oxide, 448 
 
 Characters and preparation, 448 
 Silver sulphate, 449 
 
 Characters, 449 
 
 Preparation, 450 
 Silver sulphide, 449 
 
 Occurrence and characters, 449 
 Size, 662 
 
 Slags, finery, analyses of poor and rich, 581 
 Smalt, 513' 
 Smaltine, 512 
 Smoke, 91 
 
 Soap, manufacture, 668 
 Soap, hard, 669 
 
 mottled, 670 
 
 silicated, 670 
 
 soft, 669 
 
 toilet, 670 
 Soda, caustic, 233 
 Soda crystals, 266 
 
 natural, 255 
 
 sesquicarbonate, 274 
 Soda waste, 271 
 
 Soda water, 275 
 Sodium, 232 
 
 History, occurrence, characters, and 
 
 preparation, 232 
 Sodium alum, 311 
 
 aluminate, 312 
 
 arsenate, 498 
 
 arsenites, 495 
 
 Sodium biborate (borax), 277 
 
 History, occurrence, and characters, 277 
 
 Preparation, 278 
 
 From the water of the borax lakes, 278 
 
 From native calcium borate, 278 
 
 From boracic acid, 278 
 
 Uses, 280 
 Sodium bicarbonate, 273 
 
 Characters and preparation, 273 
 
 Uses, 275 
 Sodium carbonate, 255 * 
 
 History and occurrence, 255 
 
 Preparation, 256 
 
 Uses, 271 
 Sodium carbonate, acid, 273 
 
 Tests, 274 
 Sodium chloride, 235, 
 
 History and occurrence, 235 
 
 Preparation, 236 
 
 Uses, 243 
 
 Sodium chromate, 524 
 Sodium hydrate (caustic soda), 23;! 
 
 Characters, 233 
 
 Preparation, 234 
 
 Uses. 235 
 
INDEX. 
 
 985 
 
 SOD 
 
 Sodium nietastannate, 472 
 Sodium nitrate, 276 
 
 characters and uses, 276 
 Sodium oxide, 233 
 
 phosphate, 276 
 
 stannate, 472 
 Sodium sulphate, 249 
 
 Occurrence, characters, and prepara- 
 tion, 249 
 
 Uses aiid purification, 254 
 Sodium sulphides, 243 
 Sodium tbiosulphate, 248 
 
 Characters and preparation, 248 
 Solar oil, 691 
 
 Soldering, autogenous, 28 
 Sonibrerite, 149 
 Soot, 91 
 
 Spathic iron ore, 554 
 Specific gravity, 3 
 
 heat, 4 
 
 Speculum metal, 471 
 Speise, 372 
 
 Speiss glass, 502 
 Spelter, 344 
 
 Spermaceti candles, 682 
 Spirit, 900 
 
 Rectification, 900 
 
 Purification, 907 
 
 Manufacture, 909 
 
 Refuse waters of, 924 
 Spirit from acorns, 924 
 
 artichokes, 924 
 
 asphodel, 924 
 
 beet root, 911 
 
 corn, 923 
 
 molasses, 916 
 
 potatoes, 921 
 
 starch, 919 
 
 sugar grass, 924 
 
 Spirit stills, 889 
 
 Spiritus fumans, Libavius', 474 
 
 Splints for matches, preparation, 158 
 
 Stannic acid, 472 
 
 Stannic chloride, 474 
 
 History, characters, and preparation, 
 474 
 
 Uses, 475 
 Stannic oxide, 472 
 
 History, occurrence, characters, and 
 compounds, 472 
 
 Preparation and uses, 475 
 Stannic sulphide, 475 
 
 History, occurrence, and characters, 475 
 
 Preparation and uses, 476 
 Stannous chloride, 473 
 
 History, characters, preparation, 473 
 
 Uses, 474 
 
 Stannous metastanuate, 473 
 Stannous oxide, 471 
 
 History, characters, and preparation, 
 
 471 
 Stannous sulphide, 475 
 
 History and characters, 475 
 Starch, 757 
 
 Occurrence and characters, 757 
 
 Preparation, 764 
 
 Uses, 776 
 Starch, barley, granules, 780 
 
 bean, granules, 780 
 
 maize, granules, 781 
 
 oat, granules, 780 
 
 rice, granules, 781 
 
 rye, granules, 781 
 
 SUL 
 
 Starch, hydrates, 760 
 Starch manufacture. 769 
 
 from beans, 775 
 
 maize, 775 
 
 potatoes, 764 
 
 rice, 775 
 
 wheat, 771 
 
 Starch spirit, 919 
 Stassfurt salts, 197 
 Stearic acid, 663 
 
 Stearin, or glyceryl stearate, 664 
 Steel, 600 
 
 Manufacture, 600 
 
 Carburation method : cementation, 601 
 
 Decarburation method : Bessemer's, 603 
 
 Characters, 606 
 
 Table of compositions, 608 
 Stills, Coffey's, 899 
 
 Laugier's, 891 
 
 Spirit, 889 
 Stone, artificial, 341 
 Storax, 728 
 
 Straw, as a material for paper, 637 
 Strontium, 297 
 Stucco, 290 
 Substances, 2 
 
 Physical characters of, 2 
 
 Table of elementary, 6 
 
 Occurring as minerals, 15 
 
 Derived from plants and animals, 609 
 Sugar, 802 
 
 Characters, 803 
 
 Occurrence, 802 
 
 Preparation, 808 
 
 Clarification of the juice, 833 
 
 Defecation and refining, 860 
 Sugar beet, 814 
 
 Culture, 814 
 
 Anatomical structure, 316 
 Sugar beets, 877 
 Sugar candy, 869 
 Sugar cane, the, 811 
 
 Constituents, 813 
 Sugar, cane, 803, 809 
 
 Manufacture, 821 
 Sugar, crystallised, 875 
 
 grape, 803 
 
 lime, 805 
 
 milk, 807 
 Sugar of lead, 398 
 Sulphantimonic acid, 503 
 Sulphantimonites, 503 
 Sulphur, 92 
 
 History, occurrence, and characters, 92 
 
 Preparation, 93 
 
 Extraction, 93 
 
 Distillation, 95 
 
 Refining, 96 
 
 Uses, 100 
 
 Compounds, 103 
 Sulphur chloride, 176 
 
 History, characters, preparation, and 
 
 uses, 176 
 Sulphur, flowers of, 97 
 
 milk of, 93 
 
 roll, 97 
 
 Sulphur from pyrites, 99 
 
 soda waste, 100 
 
 Sulphur furnace, 116 
 Sulphuretted hydrogen, 136 
 
 History, occurrence, and characters, 
 136 
 
 Preparation and uses, 137 
 
986 
 
 INDEX. 
 
 SUL 
 
 Sulphuric acid, 109 
 
 History, occurrence, composition, and 
 characters, 109 
 
 Table of strengths, 110 
 
 Preparation, 111 
 
 In lead chambers, 113 
 
 In shaft furnaces or kilns, 118 
 
 The chamber process, 127 
 
 Concentration, 130 
 
 The continuous process, 131 
 
 In glass retorts, 133 
 
 Uses, 135 
 Sulphuric oxide, 108 
 
 Characters, preparation, and com- 
 pounds, 108 
 Sulphurous acid, 107 
 
 Uses, 108 
 Sulphurous oxide, 103 
 
 History and occurrence, 103 
 
 Composition, characters, and prepara- 
 tion, 104 
 
 Uses and compounds, 107 
 
 Manufacture from pyrites, 107 
 Surrogate, for rags in paper making, 634 
 
 Preparation, by mechanical treatment, 
 
 By chemical treatment, 635 
 
 WALLOW, 665 
 
 1 Purification, 665 
 
 Melting, 665 
 Tantalum, 482 
 Tapioca, 759 
 Tar, condensation, 701 
 Tea, 969 
 
 Tea, dried, composition, 972 
 Telegraph wires, insulation with gutta 
 
 perch a, 753 
 Tellurite, 148 
 Tetradymite, 148 
 Textile fibres, 617 
 Thallic oxide, 483 
 Thallium, 483 
 Thallous chloride, 483 
 
 oxide, 483 
 Thenard's blue, 514 
 Theobromin, 969 
 Thorium, 487 
 
 Compounds, 488 
 Thornstone, composition, 239 
 Tin, 464 
 
 History, occurrence, characters, and 
 preparation, 464 
 
 Roasting of tin ore, 465 
 
 Smelting in reverberatory furnaces, 467 
 
 In shaft furnaces, 468 
 
 Uses and compounds, 469 
 Tin, butter, 474 
 
 nitromuriate, 475 
 Tincal, purification, 279 
 Titanic chloride, 477 
 
 fluoride, 478 
 
 oxide, 477 
 
 sulphide, 477 
 Titanous chloride, 477 
 
 oxide, 477 
 Titanium, 476 
 Tolu balsam, 729 
 Tous-les-mois, 75H 
 Tragacanthin, 756 
 Trass, 294 
 Tungsten, 478 
 
 WAX 
 
 179 
 
 Tungstic chloride, 
 oxide, 478 
 Tunicin, 618 
 Turf, 85 
 
 Turnbull's blue, 84 
 Turpentine, 720 
 Turpentine oil, 721 
 
 ULTRAMARINE, 244 
 History, occurrence, composition, 2 44 
 Characters, 245 
 Preparation, 246 
 Uses, 247 
 Uranates, 491 
 Uranic oxide, 491 
 Uranite, 489 
 Uranium, 489 
 
 History, occurrence, characters, and 
 
 preparation, 489 
 Compounds, 490 
 Uranous oxide, 491 
 
 yACUUM PANS, 849 
 
 Vanadic pentasulphide, 481 
 Vanadic peutoxide, 481 
 Vanadium, 480 
 Varec, 195 
 Varnishes, 729 
 Vats, fermentation, 953 
 Verdigris, 422 
 
 Vermicelli, manufacture, 797 
 Vermilion, antimony, 503 
 Vesta or wax matches, 160 
 Vinegar, beer, 965 
 
 beet root, 965 
 
 malt and grain, 965 
 
 wine, 964 
 Vinegar making, 964 
 
 The quick process, 965; 967 
 Viridic acid, 970 
 
 Vitriol, fuming oil of. manufacture, 112 
 Vitriol, blue, 425 
 
 white, 356 
 Vulcanite, manufacture, 745 
 
 WAD, or bog manganese, 516 
 Water, 30 
 
 History and occurrence, 30 
 Composition and characters, 31 
 Purification and filtration, 34 
 Water for brewing, 940 
 Water glass, 332 
 Water mark in paper, 649 
 Water, natural, 32 
 
 rain or snow, 32 
 
 river, 33 
 
 sea, 33 
 
 spring, 32 
 
 table of the composition of various river 
 
 waters, facing 34 
 
 well, 32 
 
 Waterproof fabrics, 739 
 Wax, Andaquics, 681 
 
 bleaching, 681 
 
 bees', 680 
 
 Carnauba, 681 
 
 Chinese, 680 
 
 Japanese, 680 
 
 myrtle, 681 
 
 palm, 681 
 
 Ocuba, 681 
 
INDEX. 
 
 987 
 
 WAX 
 
 Wax candles, 681 
 
 Wax candle making, 681 
 
 Wheat grain, structure, 777 
 
 Wheat, spelt, 777 
 
 true, 777 
 
 Wheat stacks, 784 
 
 Wheaten flour, Holland's test, 783 
 
 White lead, 393 
 
 Dutch method of preparing, 393 
 
 French method, 396 
 
 English method, 397 
 
 From lead sulphate, 397 
 White precipitate, 458 
 White vitriol, 356 
 Window glass, 317 
 Wine, 925 
 
 Constituents, 926 
 
 Fermentation, 930 
 
 Deterioration, 933 
 
 Preservation, 934 
 
 Adulteration, 935 
 
 Testing, 935 
 
 Wine residues, treatment, 936 
 Wood, 85, 619 
 
 Composition, 620 
 
 Uses, 622 
 
 Preservation, 623 
 Wood ash, 206 
 Wood charcoal, 59 
 Wort, fermentation, 953 
 
 VYLOIDIN, 762 
 
 ZIR 
 
 YEAST, 882 
 Preservation, 917 
 Yeast, bottom, 954 
 Yttrium, 488 
 
 7AFFRE, 514 
 L Zinc, 344 
 
 History, occurrence, characters, and 
 preparation, 344 
 
 Smelting, 345 
 Zinc acetate, 358 
 
 arsenate, 499 
 Zinc carbonate, 357 
 
 History, occurrence, character^^and 
 
 preparation, 357 
 Zinc chloride, 357 
 Zinc oxide, 347 
 
 History, occurrence, and characters, 347 
 
 Preparation, 348 
 
 Uses, 355 
 Zinc sulphate, 356 
 
 History, occurrence, characters, and 
 preparation, 356 
 
 Uses, 357 
 Zinc sulphide, 355 
 
 History, occurrence, and characters, 355 
 Zinc white, siccative for, 354 
 Zinc white oil colours, preparation, 355 
 Zirconic chloride, 486 
 Zirconium, 486 
 
 oxide, 486 
 
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