MANUAL OF TECHNICAL ANALYSIS A GUIDE FOB THE TESTING AND VALUATION OF THE VARIOUS NATURAL AND ARTIFICIAL SUBSTANCES EMPLOYED IN THE ARTS AND IN DOMESTIC ECONOMY. IOVNDED UPOH THE HANDBUCH DER TECHNISCH-CHEMISCHEN UNTERSU CHUN GEN OF DR. P. A. BOLLEY, PROFESSOR OF CHEMISTRY AND TECHNOLOGY IN THE UNIVERSITY OP ABAU. BY BENJAMIN H. PAUL, PH.D., P.C.S., AT UNIVERSITY COLLEGE. LONDON: HENRY a. BOHJir, YOKE STEEET, COYENT GARDEN. 1857. Printed by Taylor and Francis, Red Lion Court, Fleet Street, London, PREFACE. THE preparation of this Manual has been undertaken in the belief, that the increasing recognition of the value of chemical data for commercial and technical purposes, renders it desirable that the capability of executing chemical ana- lyses and examinations of a certain class, should be a more frequent qualification than hitherto. It is believed, too, that there are a great number of questions of considerable technical importance, for the determination of which it is not at all necessary that the operator should be possessed of any greater chemical know- ledge than may be assumed to belong to the occupation in which he is habitually engaged. It is not at all my intention, by these remarks, to question the value of sound scientific training, or to imply that a thorough acquaintance with physical science would not be very desirable in many cases where it is commonly wanting. I merely propose to point out, that, even in the absence of such qualifications, there are many well-defined lines of analytical inquiry, which may be advantageously pursued by persons, engaged in business, who may be unable to avail themselves of the very scanty means that exist in this country of acquiring really practical and useful scientific knowledge. It is to serve as a guide in such cases that this Manual is intended. For the general plan of it, I am indebted to the "Handbuch der technisch-chemischen Untersuchungen" by Dr. Eolley of Arau. In the first instance a translation of r PREFACE. that work was contemplated, but afterwards it appeared advisable to make very considerable alterations and additions. Chapters I. II. VIII. IX. and X. have been entirely re- written, and much new matter introduced into the others. It is with great satisfaction in this respect, that I am able to state, that these alterations have met with the entire approval of Dr. Bolley, who in a letter to me says, " The " very essential alterations in the arrangement and contents "of the book were soon evident to me. I consider them "much to its advantage, and perceive from the general " treatment of the subject, that the book has fallen into just " the right hands to be presented to English readers in an " appropriate manner.*' In conclusion, I may remark that in a work of this kind, which cannot lay claim to originality other than that which may appertain to the adaptation and arrangement of exist- ing material, there will of course be much that is borrowed. Supposing this to be generally understood, I have limited myself to the endeavour to describe briefly and simply the methods of carrying out diiferent examinations, and have availed myself of what has been published on the subject by various chemists, without especial reference to the authors. I have to express my thanks to Mr. Phillips of the Excise, for tables of the relation between the density of spirit and the per-centage of alcohol, and for a drawing of the appara- tus devised by him for estimating original gravities. J trust that the object with which the book has been written, will be borne in mind by those who may give an opinion of its value, and hope that it may be found worthy of approval as well as useful. BENJ. H. PAUL. London, May 1857. PREFACE BY DR. BOLLET. SINCE the publication of the German edition of this Manual, the labours of chemists have led to a knowledge of much that falls within the plan of the work. The necessity of making known, as quickly as possible, whatever may be discovered or suggested in connexion with the industrial arts, and also of putting it to the test of practice, is so essentially a part of technical requirements at the present time, that the introduction into the work of results, which the progress of investigation has furnished, could not with propriety be omitted before its publication in the language of a country where the most powerful minds and the most gigantic material appliances are conjointly directed to the advancement of technical knowledge. It was with great willingness, therefore, that I complied with Dr. Paul's wish, that the text should be revised and such new matter added as will, I hope, increase the use- fulness of the book. DE. BOLLEY. TABLE OF CONTENTS. INTRODUCTION. P.*. Objects of chemical and technical analysis, 1 ; Analytical methods, 2 j Gravimetric analysis, 3 5 Volumetric analysis, 4. CHAPTER I. THE OPERATIONS CONNECTED WITH CHEMICAL INVESTIGATIONS, AND THE APPARATUS NECESSARY JFOR CONDUCTING ANALYSIS ... 5 Solution, 5 ; Precipitation, 7 ; Decantation, 9 ; Filtration, 10 ; Washing Precipitates, 11 ; Evaporation, Distillation, &c., 13 ; Drying, Ignition, &c., 15 ; Roasting, 18 ; Melting, 19 ; Cupel- lation, 20 ; Blowpipe operations, ib. ; Measures, 22 j Opera- tions with gases, 25 ; Weighing, 26. CHAPTER II. REAGENTS AND THEIR TTSES 27 Methods of testing, 27 ; Precautions to be -observed, ib ; Sol- vents, 28 ; General reagents, 30 ; Special reagents, 33 j Volu- metric reagents, 36. CHAPTER III. ACIDS EMPLOYED IN THE ARTS ; THEIR CHARACTERS, THE TESTS OP THEIR PURITY, AND ADULTERATIONS 38 Inorganic acids, 38 ; Organic acids, 41 5 Examination of vine- gar, 43. CHAPTER TV. THE ALKALIES AND THEIR COMPOUNDS; THE TESTS OF THEIR PURITY AND ADULTERATIONS 46 Potassium compounds, 46 ; Sodium compounds, 50 ; Ammoniacal compounds, 54. Till TABLE OF CONTENTS. CHAPTER V. THE VALUATION OP ALKALIES, ACIDS, AND THEIR COMPOUNDS 55 Alkalimetry, 55 ; Sources of error, and collateral operations for the correction of alkalimetric results in certain cases, 60 ; Gravime- trical valuation of alkalies, 65 ; Acidimetry, 69 ; Volumetrical method of valuation for acids, ib. ; Gravimetrical method of valuation for acids, 75 ; Estimation of acids in combination with bases, and valuation of the saline compounds of the alkalies. Halimetry, 78 ; Estimation of sulphuric acid in salts, ib. ; Esti- mation of nitric acid in salts, ib. ; Valuation of nitre, 79 ; Ana- lysis of gunpowder, 83 ; Valuation of borax, 86. CHAPTER VI. THE ALKALINE AND TRITE EARTHS, AND THEIR COMPOUNDS ; THE TESTS OF THEIR PUEITY, AND METHODS OF VALUATION, ETC 87 Barium com pounds, "87 ; Strontium compounds, 88 ; Calcium com- pounds, ib. ; Analysis of cement and mortar, 89 ; Chlorimetry, 97 ; Magnesium compounds, 100 ; Aluminium compounds, 101 ; Examination of mordants, 103. CHAPTER VII. COMPOUNDS OF THE HEAVY METALS: THEIR CHARACTERS, THE TESTS OF THEIR PURITY, AND METHODS OF ESTIMATION 105 I Chromium compounds, 105 ; (Estimation of chromium, 107 ; 1 Zinc and its compounds, 108 ; lEstimation of zinc, 109 ; Manganese compounds, 110 ; Estimation of manganese, 111 ; Volumetrical methods, ib. ; Gravimetrical methods, 113 ;i Iron and its com- pounds, 117 ; Valuation of ferrocyanide of potassium, 118 ; Valuation of pigments containing prussian blue, 122 ; Volume- trical estimation of iron, ib. ; Use of alkaline permanganate in analysis, 126 ; Uranium compounds, 127; Cobalt compounds, ib.; Nickel and its compounds, 128; Compounds of arsenic, 129; Detection of minute quantities of arsenic, ib. ; Estimation of arsenic, 130; \Corn pounds of tin, 131; Estimation of tin, 132; Volumetrical estimation of tin, 133 ; Application of chloride of tin in analysis, 134 ; Antimony and its compounds, 135 ; Esti- mation of antimony, ib. ; Compounds of platinum, 137 ; Gold and its compounds, ib. ; { Estimation of gold; 138 ; Assay of gold alloys, ib. ; Bismuth and its compounds, 140 ; Estimation of bis- muth, ib. ; : Copper and its compounds, 141 ; 'Estimation of copper, 144 ; Colorimetric method, 145 ; \ Lead and its com- pounds, 146 ; lEstimation of lead, 147 ; Mercury and its com- pounds, 150; Estimation of mercury, 151; \Silver and its com- pounds, 152 ; Estimation of silver, ib. ; Volumetric method, 153 ; Assay of silver alloys, ib. ; Qualitative analysis of alloys, &c., 158 ; Composition of alloys, 165 ; Tests of the purity of metals, &c., 171. TABLE Or CONTENTS. IX CHAPTEE VIII. NON-METALLIC ELEMENTS, AND THEIE COMPOUNDS KNOWN IN COMMEECE ; THEIE CHAEACTEES, THE TESTS OP THEIE PUEITY, AND THE METHODS OF VALUATION 176 Estimation of phosphoric acid, 178 ; Estimation of chlorine, 180 j Estimation of iodine, 182 ; Quantitative separation of chlorine, bromine, and iodine, 185 ; Estimation of hydrocyanic acid, 186 ; Elementary analysis of organic substances, 189 ; Gas combustion furnace, 191 ; Estimation of nitrogen, 197; Examination and valu- ation of coal and other kinds of fuel, animal charcoal, &c., 200. CHAPTEE IX. SPECIAL METHODS OF ANALYSIS, QUALITATIVE AND QUANTITATIVE, ADAPTED FOE THE EXAMINATION OF PAETICULAE CLASSES OF SUBSTANCES 207 Examination of pigments, 207 ; Analysis of soils, marl, limestone, clay, plant-ashes, well, spring, and mineral water, &c., 219 ; Pre- paration of substances for analysis, 220 ; Estimation of the reten- tive power of soils for water, 222 ; Estimation of hardness and alkalinity of water, 224; Solution by water, 230; Solution by hydrochloric acid, 231 ; Solution by sulphuric acid, 232 ; Solu- tion by fusion with alkali, ib. ; Solution by hydrofluoric acid or fluoride of ammonium, ib. ; Solution by fusion with bisulphate of potash, 233 ; Examination of the water solution, 235 ; Examina- tion of the hydrochloric solution, 238 ; Separation of silica from all the bases, 239 ; Separation of phosphoric acid from magnesia, 240 ; Separation of phosphoric acid from lime, 241 ; Separation of phosphoric acid from alumina, ib. ; Separation of phosphoric acid from oxides of iron, or manganese, ib. ; Separation of iron from potassium or sodium, 243 ; Separation of iron from magne- sium and calcium, ib. ; Separation of iron from aluminum, ib. ; Separation of iron from manganese, 244 ; Separation of manga- nese from magnesium, 246 ; Separation of manganese from cal- cium, ib. ; Separation of manganese from aluminum, ib. ; Separa- tion of aluminum from potassium or sodium, 247 ; Separation of aluminum from magnesium, ib. ; Separation of aluminum from calcium, 248 ; Separation of calcium from potassium, sodium, or magnesium, 249 ; Separation of magnesium from potassium or sodium, 250 ; Estimation of alkaline compounds, ib. ; Separation of potash from soda, 252 ; Eeduction of results obtained in analy- sis, 254 ; Tables for reducing analytical results, 255. CHAPTEE X. SYSTEMATIC QUALITATIVE ANALYSIS 265 Classification of elements and acids, 265 ; Preliminary examina- tion, 266 j Eelation to solvents, 267 ; Effects of heat, 268 j Blow- X TABLE OF CONTENTS. h pipe tests, 270; Table of reactions characteristic of metallic oxides, 272,273; Reduction test, 274; Preliminary tests for acids, &c., 275 ; Systematic testing, 276 ; General reagents, ib. ; Analytical groups, ib. ; Tables of compounds constituting analy- tical groups, 277, 278 ; Examination for basic or electro-positive constituents, 279 ; Separation of metals belonging to the first from others and from each other, 279, 280 ; Separation of metals belonging to the second group from others and from each other, 280-286 ; Separation of metals belonging to tho first division of the second group from those belonging to the second division of of the same, 281 ; Separation of metals belonging to the third group from others and from each other, 286-290 ; Separation of metals belonging to tlie fourth group from others and from each other, 290 ; Separation of metals belonging to the fifth group from others and from each other, 291 ; Examination for acids or electro- negative substances, 291 ; Preparation of solutions to test for acids, &c., 291, 292 ; Separation of acids belonging to the first 1 group from others and from each other, 292, 293 ; Separation of acids belonging to the second group from others and from each other, 294-296 ; Tables showing the relation of compounds to the principal solvents used in analysis, 297. CHAPTER XI. DTE STUFFS; TESTS OF THEIB PTJEITT, AND THE METHODS OF VALUATION 300 Examination of dye stuffs, 300 ; Dye test of madder, 301 ; Colori- metric test of madder, 302 ; Examination of dyed or printed fabrics, 305 ; Tables of characters of dyed stuffs, 307-315. CHAPTER XII. OILS, FATS, ETC. ; SOAP, VOLATILE OILS, AND MATERIALS USED FOB LIGHTING ; THE TESTS OF THEIR PURITY, AND THE METHODS OF VALUATION 316 Examination of oils and fats, 316 ; Examination of olive oil, 317 ; Examination of rape oil, 321 ; Tests for fat or oil, 322 ; Exami- nation of wax, 323 ; Estimation of fat, ib. ; Examination and valuation of soap, ib. ; Examination of ctherial oils, 325 ; Valua- tion of oil, candles, gas, and other materials used for lighting, 327 ; Estimation of luminous intensity of flame, ib. ; Photo- metry, 328. CHAPTER XIII. ALCOHOL, SPIRITS, WINE, BEER, ETC. ; THE TESTS OF THEIR PURITY, AND THE METHODS OF VALUATION 331 Estimation of alcohol, 332 ; Determination of the original gravity or density of beer-wort, 336 ; Tables to be used in ascertaining TABLE OF CONTENTS. XI Page original gravities, 337, 338 ; Spirit-indication, 339 ; Acetic acid, ib. ; Estimation of alcohol and extract in beer, by means of chlo- ride of sodium, 341 ; Average amounts of alcohol in various kinds of beer, wine, spirit, &c., 346. CHAPTEE XIV. SUGAE, STARCH, FLOT7E, BEEAD, MILK, BTTTTEB, TEA, COFFEE, CHOCO- LATE, ISINGLASS, ETC. ; THE TESTS OF THEIR PUEITY, AND THE METHODS OF VALUATION.... 348 Varieties and sources of sugar, 348 ; Estimation of sugar, ib. ; Esti- mation of sugar by fermentation and by test acid, 349 ; Estima- tion of sugar by alkaline solution of copper, 350 ; Estimation of gugar by washing, 352 ; Examination of honey, 354 ; Characters of starch, ib. ; Examination of flour, meal, &c., 358 ; Examina- tion of milk, 361 ; Examination of butter, 363 ; Examination of tea, coffee, and chocolate, 364, 365 ; Examination of gelatin and isinglass, 365, 366. CHAPTEE XV. TEXTILE MATEEIALS ; WOOLLEN CLOTH, SILK, COTTON, AND LINEN 367 Characters of fibres, 367-370 j Tests for fibres, 370-372. APPENDIX. HYDBOMETEY; TABLES OF DENSITY, ETC 373 Principles involved in the determination of densities, 373, 374 ; Hydrometry, 375 ; Table for ascertaining the density of liquids heavier than water, from the hydrometer degrees of Beaume and Beck, 376 ; Table for ascertaining the density of liquids lighter than water, from the hydrometer degrees of Beaume and of Beck, 377 ; Per-centage amounts of anhydrous sulphuric acid (SO 3 ) and monohydrated acid (SO 3 ,HO) corresponding to different den- sities, 378; Per-centage amounts of chlorine and hydrochloric gas corresponding to different densities of hydrochloric acid solu- tion, 397 ; Per-centage amounts of anhydrous nitric acid (NO 5 ) and of hydrated acid (N0 5 HO) corresponding to different densi- ties of nitric acid, 380 ; Per-centage amounts of hydrated acid (C 4 H 4 4 ) corresponding to different densities of acetic acid, 381 ; Per-centage amounts of ammonia (NH 3 ) corresponding to different densities of solution of ammonia, 382 ; Per-centage amounts of anhydrous potash (KO) corresponding to different densities of solution of potash, ib. ; Per-centage amounts of anhydrous soda (NaO) corresponding to different densities of solution of soda, 383; Per-centage amounts of anhydrous carbonate of soda correspond- ing to different densities of solution of soda, ib. ; Per-centage Xll TABLE OF CONTENTS. amounts, by weight and volume, of absolute alcohol, corre- sponding to different densities of diluted spirit, 384-400 ; Table snowing the amounts of crystallizable sugar corresponding to different densities of solution of sugar; and the amounts of extract in wort or in beer deprived of alcohol, 401 ; Comparison of the specific gravities of solutions of cane-sugar, starch-sugar, pale and brown malt, dextrin, caramel from cane-sugar, and of the extract substance produced in the fermentation of sugar, all containing equal amounts of carbon, 402 ; Equivalent weights of the Elements, 403 ; Relation of the scales of Celsius, Reaumur, and Fahrenheit, 404; Table showing the relation between the weights of different countries, 405 ; Relation between French and English measures, 406 ; English measures of weight, 407, 408. MANUAL TECHNICAL ANALYSIS. INTEODUCTION. CHEMICAL analysis, to the extent at least in which it is treated of in this work, is essentially an art, inasmuch as it is the application of the recognized principles and facts of chemical science to the solution of questions of more or less frequent recurrence and practical utility. The general object of analytical operations is to ascertain the chemical nature of substances ; their special object may be either to ascertain what are the elements of which a substance consists, and what their state of combination, or, these particulars being known, to learn their relative proportions. Thus analysis is either qualitative or quantitative. Ifc may sometimes be desirable in both instances to extend the examination to all the elements contained in a substance, however small their proportion ; sometimes it will only be necessary either to ascertain the presence or absence of some one or more elements or compounds, or to estimate the proportion of some particular constituent of the substance examined. . Complete and minute analyses of the former kind belong almost exclusively to the more purely scientific portion of chemistry, those of the latter kind relate to the technical applications of chemistry, and are had recourse to for the purpose of determining certain points which* have a com- mercial or technical importance, rather than any direct bearing upon the cultivation of science. The chemical nature of any substance is always ascer- tained by subjecting it to certain treatment called the test, and the presence of any element or compound is indicated by the consequent production of some change, generally a 2 rNTBODUCTIOIT. through the agency of some other substance, and always under certain definite conditions. This change, which is called the reaction, usually consists in the formation of a compound of the substance sought, possessing marked and distinctive peculiarities. The substances used for this pur- pose are called reagents. It is, of course, essential that the criterion by which we judge of the presence or absence of any element or compound should be infallible, and if there should be any exceptions to its general applicability, the con- ditions upon which they depend must be understood and provided against. When the substance to be examined contains a great number of elements in various states of combination, its behaviour with reagents, which would otherwise indicate their presence, would in many instances be so modified or disguised as to render their detection extremely difficult and tedious. In order to obviate the inconvenience which would result from such a circumstance, the elements have been arranged in several analytical groups, according to general analogies obtaining, either between the conditions under which they yield compounds of particular types, or in the behaviour of their compounds with certain reagents, and of such a nature that the application of a particular test will at once indicate either the absence of a whole group of elements, or the presence of some or all of its members. By a systematic application of such tests it is possible, not only to learn what groups the elements of any substance belong to, but likewise to separate these groups, and thereby greatly to facilitate the special recognition of the individual elements. As regards heavy metals, their sulphurets have been found admirably well suited to this purpose ; for the light metals, their carbonates ; for acids, their silver, lime and baryta salts. The elements, belonging to groups thus separated, are then subjected to further separation, and, lastly, the several ele- ments are obtained in such an isolated state as to be recognized without any doubt. The qualitative examination of substances for technical and commercial purposes is made, not for the purpose of ascertaining their chemical nature, for that in all ordinary instances is known beforehand, but with reference to certain ANALYTICAL METHODS. 3 possible or probable impurities and admixtures, either acci- dental or fraudulent, which may lessen their market value or prove detrimental in the operations for which they are required. The nature of these impurities or admixtures may generally be anticipated, and the necessary operations of testing are therefore brought within a more limited range than is the case in the examination of substances whose chemical nature is more or less unknown, and when the probable nature of the elements or compounds present can- not always be determined beforehand even by the profes- sional chemist. In the general system of qualitative examination sub- sequently described, those elements only have been taken into account which are likely to be of interest commercially or technically. Although a rigid adherence to the entire system is not always necessary, still, to lay down any rules for deviating from, or omitting any portion of it, would be attempting a royal road to a knowledge which the analyst can only acquire by experience and careful observation of chemical phenomena. In quantitative analysis a knowledge of the elements pre- sent in the substances to be examined is presupposed. It is here necessary to devise means of effecting a perfect separa- tion of each element without loss, and in such a form that its proportion can be accurately estimated. This has hitherto generally been effected by successively converting the several elements into insoluble and definite compounds which may be collected and weighed. Then by means of the law of com- bining proportions, the quantity of the element sought may be calculated. Thus, for instance, in the estimation of silver or chlorine, the compound weighed in either case is repre- sented by the symbolic formula Ag+Cl, and substituting for the symbols their numerical equiva- lents, 107'973 + 35-462, we obtain the relative proportion of these substances in the compound weighed, and can calculate the quantity of either constituent in the weight of chloride of silver obtained, by a simple proportion. Thus if the substance sought is silver B 2 4 DfTEODUCTIOIT. =s #, and the weight of chloride of silver obtained = y, then Ag x y __ 107-973 x y Ag + Cl 107-973 + 35-462* If y = 1-726, then x = T299. With good manipulation this method of analysis satisfies all the requirements of precision and accuracy. It is unex- ceptionable for scientific research, but for many technical pur- poses, where the time occupied by an analysis is as much an element of its value as accuracy, it is wholly inapplicable. However, as the law of definite proportions obtains not only in the composition of substances, but likewise for the reactions which take plae between them, and as the greater number of quantitative analytical operations which come within the province of the manufacturer are of that kind to which the term assay may be very appropriately extended, their sole object being to estimate the proportion of some one ingredient of the raw material, it is not difficult to make such an application of this principle as will meet the want* of those engaged in commerce 'and the arts, be free from thf disadvantages of the above method, and at the same time not be inferior to it in the accuracy of its results. According to the formula for chloride of silver, Ag+Cl, 108 parts of silver require for conversion into chloride 35-5 parts of chlorine. Now by estimating the quantity of some suitable, definite compound of chlorine such as chloride of sodium requisite for converting into chloride, the silver x in a given weight of the substance to be assayed, the quan- tity of silver x may be easily ascertained, for it will bear the same proportion to the chloride of sodium consumed =2 aa the numerical values of their symbols, x : z= Ag : Na Cl. And if the chloride of sodium is added to the solution of the silver in the form of a solution, a given volume of which contains a known weight of the salt, the quantity z may be readily estimated by measuring the solution used. This method of analysis, which is called the volumetrical method, consists therefore in estimating the quantity of reagent neces- sary to complete some particular reaction, and is the reverse of the gravimetrical method, which consists in estimating the OPERATIONS AND APPAEATUS. 5 quantity of some definite compound produced by such a re- action. The insolubility of chloride of silver and the rapi- dity with which it is deposited on agitation, render the ap- plication of this method to the estimation of silver extremely appropriate, but, as will subsequently be shown, there are few reactions of a definite character that may not with some in- genuity be made available for a similar purpose. CHAPTEE I. THE OPEBATIONS CONNECTED WITH CHEMICAL INVESTIGA- TIONS, AND THE APPAEATUS NECESSAET FOE CONDUCTING ANALYSIS. IT has always been customary among chemists to make a distinction between the means employed for the purpose of effecting chemical alteration in substances, whether it be combination, the separation of one or more of their consti- tuents, or their conversion into other compounds, &c. The distinction is founded upon the nature of the operations, which is twofold, the wet process, which consists in acting upon the substance in question while in solution, and the dry process, which consists in submitting it either alone, or together with certain other substances, to the in- fluence of heat. The operations involved in the preparation of elementary substances or chemical compounds, their de- tection, separation and quantitative estimation, in short, general synthetical and analytical chemistry, may be con- veniently classified under these two heads, and they are so much alike in all cases, that it is advisable to obviate repe- tition in the description of apparatus and manipulation, by giving at the outset a brief account of those which are of most general importance, and which will be necessary in carrying out the experiments treated of in this work. Solution. The term solution in its widest sense may be under- stood to denote an homogeneous liquid mixture of any sub- stance solid, liquid or gaseous with a greater or less quan- tity of some liquid which is called the solvent. Solution may be of two kinds, physical or chemical j the 6 OPERATIONS AND APPARATUS. former is a simple mixture of the substance dissolved, with the solvent, as, for instance, a solution of salt, of sulphuric acid or hydrochloric acid gas in water. Chemical solution involves an alteration of the substance dissolved and its com- bination in part with the solvent, for example, the solution of marble in hydrochloric acid. All chemical solvents are themselves solutions of certain substances in water, therefore chemical solution may be regarded as the formation of a soluble substance and its subsequent physical solution in that water. Thus in the above instance it is not carbonate of lime which is in solution, but chloride of calcium. No general law of proportionality between the solvent and substance dissolved has yet been obtained for physical solu- tions. The solution of a substance is said to be saturated when it cannot dissolve any more. As a general rule, solu- tion takes place more readily with the aid of heat, and as the solvent power of liquids increases with the temperature, saturation is determined by it. As in chemical solution there is an actual combination, this of course takes place in accordance with the law of definite proportion, so much only of the substance being dissolved as may be equivalent to the quantity of reagent present. Chemical solution is facilitated by heat, because chemical action takes place more readily at somewhat elevated tem- perature, but the quantity of substance dissolved by a given quantity of solvent is constant and independent of tem- perature. Solution is generally effected in flasks or beakers, bedded nearly to the level of the liquid in sand contained in an iron pan, and heated by a gas burner. (Fig. 1.) Fig. 1. SOLUTION. 7 Solution is always effected more readily the greater the surface of contact between the solvent and the substances to be dissolved. The latter should consequently be exposed in the state of powder to the action of solvents whenever it is practicable. For the same reason the mixture should likewise be frequently shaken. When in the chemical solution of substances the reaction is violent or a gas is disengaged, precautions p- 2 must be taken that none of the liquid is thrown out of the vessel by spirting. In quantitative experiments this is particularly important. The best means of preventing loss in this way is to introduce the sub- stance into a rather capacious beaker, the top of which is covered with a very short- necked funnel or a thin hemispherical glass with a hole in the centre, through which the solvent is gradually added. After the solu- tion is complete, the portions of liquid pro- jected against the under surface of the glass can be washed off into the beaker with a dropping bottle. (Fig. 7.) In preparing solutions from organic substances which are but partially soluble, they are macerated or kept in contact with the solvent for some time, and the liquid then strained off. The process is termed decoction when the mixture is boiled; infusion, when conducted without the continued application of an elevated temperature. Precipitation. This operation is the direct reverse of solution, and is very frequently adopted for the purpose of separating sub- stances, or of collecting them in a convenient form for weighing. Like solution it is of two kinds. Physical precipitation is effected by altering the solvent in which a substance is diffused; thus sulphate of lime is precipitated from its solu- tion in water by the addition of alcohol, and phosphate of lime from its solution in hydrochloric acid, by the addition of ammonia, the salts named being respectively insoluble in weak alcohol and in chloride of ammonium. 8 OPEBATIONS AND APPARATUS. Chemical precipitation, on the contrary, involves an altera- tion in the substance dissolved ; thus from a solution of sul- phate of alumina, ammonia precipitates alumina by abstract- ing the acid combined with it. The substance which, in this operation, is converted into the insoluble solid form, is called the precipitate, that which determines its separation, the precipitant. The physical characters of precipitates are extremely varied. According to their aggregation they are called crystalline, pulverulent, curdy, Socculent, gelatinous, &c. } and these characters, together with colour, are under certain circumstances trustworthy means of recognition. But it is not admissible to take these facts alone as indicative of their chemical nature. This must be confirmed by subsequent ob- servation of their behaviour with appropriate reagents. The vessels in which precipation is best effected, are the thin glass beakers, flasks, or test tubes (figs. 1, 5, and 8), which admit of being heated without risk of breakage, for as a general rule, precipitates separate more readily from hot liquids. In qualitative analysis the principal points to be attended to in precipitation are the conditions under which a reagent is to be applied, for instance, the temperature, alkalinity or acidity of the solution, &c. When the quantity of a sub- stance tested for by precipitation is very minute, it may happen that no visible nrecipitate is formed on the addition of the reagent, but this must not at once be taken as a negative indication ; the tube must be allowed to stand some hours and then examined. If no precipitate is yet visible, the liquid should be shaken, heated, or perhaps evaporated somewhat, and again examined when cold. In some delicate experiments a neglect of these precautions will involve error. In quantitative analysis, where it is essential that there should not be the slightest loss, either of precipitate or of bhe liquid from which it is thrown down, beakers are the most convenient vessels for precipitation, because, when collecting the precipitate for weighing, any particles ad- hering to the sides may be more easily detached by means of a feather, stripped bare with the exception of a tiny tuft at the end, and washed out by a fine jet of water from the wash bottle (fig. 6). When this is ineffectual, the adherent DECANTATION. 9 particles must be dissolved off, and again precipitated. Glass rods used for stirring must always be washed before removal from the vessel containing the precipitate. Sometimes it may be desirable to use only just so much of a precipitant as will completely precipitate the substance to be removed from solution. In such cases great caution must be exercised, and the liquid frequently cleared, either by stirring or heating, so as to show distinctly whether on the addition of more reagent any further precipitate is formed. A very delicate mode of ascertaining this is to dip into the perfectly clear liquid a glass rod moistened at one end with the precipitant. The separation of precipitates from the liquids with which they are mixed is effected by one or other of the following operations. Decantation. "When the precipitate to be separated is of considerably greater density than the liquid with which it is mixed, de- cantation is convenient, because it occupies little time. The vessels in which precipitates are to be collected or washed by decantation should have an area that is very small in proportion to their height. The clear supernatant liquid may be poured off by gently inclining the vessel, or it may be drawn off by means of a pipette or siphon. The vessel is then filled with water, the precipitate stirred with a glass rod, allowed to settle, and the water drawn off as before. Precipitates which, like chloride of silver, do not adhere to the sides of the vessel in which they are thrown down, may be advantageously washed by decantation, and collected without using a filter, in the following manner. The pre- cipitate is thrown down in a very narrow-necked taper flask, with an even rim capable of being closed by a watch-glass. After the washing is completed, the flask is filled with water ; the mouth covered with a crucible, the whole rapidly inverted and allowed to stand until the precipitate has com- pletely subsided into the crucible. The flask is then very carefully raised, so as to admit of a watch-glass being slipped under its mouth without disturbing the precipitate, and rapidly removed from the crucible. The water left in the crucible may be decanted off. This operation requires some 10 OPERATIONS AND APPARATUS. little dexterity, which, however, it is well worth while to acquire. Filtration. When a precipitate is deposited but slowly, recourse must be had to filtration, which is a mechanical mode of separa- tion by means of unsized paper, and is analogous to sifting, for while the liquid passes through the pores of the paper, the precipitate is retained upon its surface. Filtration is convenient in quantitative analysis, because the precipitate, as it is contained in a filter, can be trans- ferred to the drying bath or crucible more readily than when collected by decantation. The paper used for this purpose should be as much as possible free from mineral substance, thin and compact in texture, and should allow water to pass rapidly through it. It should be cut into discs from 2 to 10 inches in diameter. The filter is made by folding one of these YI%. 3. discs diametrically at right angles, and then opening it so as to form a cone which is supported upon a glass funnel. The funnels used for filtration should be quite even, the spout should be ground obliquely, and form an abrupt angle of about 60 with the expanded part, so that the greater part of the paper cone may fit close, "while its apex remains out of contact with the funnel. The filter should never extend quite so far as the rim of. the funnel. The vessel into which a liquid is to be filtered must always be large enough to hold considerably more than the whole of it, and the spout of the funnel should rest against its side so as to prevent splashing. In quantitative experiments any loss in transferring a pre- cipitate to the filter must be guarded against. For this pur- pose the edge of the vessel should be slightly greased, and a glass rod held against it while pouring so as to direct the stream of liquid upon the thick folded side of the filter, and prevent it from piercing the paper. WASHING PEECIPITATES. 11 Sometimes, when a precipitate is in a very fine state of division, it passes through the pores of the filter. It may happen that a double filter is the only remedy for this inconvenience, but it may often be prevented by allowing some time to elapse before trans- ferring the precipitate to the filter, or by the application of heat. In either case the precipitate acquires a granular or crystalline condition which renders it more readily se- parable. Washing ^Precipitates. Precipitates, as collected upon a filter, always retain a portion of the liquid with which they were mixed, greater or less in proportion to their bulkiness. When this liquid does not contain any saline or fixed substance, simply drying the filter and its contents is all that is necessary. But as the liquid from which a precipitate is thrown down will seldom be free from dissolved substances, washing is an operation that is almost always supplementary to precipita- tion. It may be effected by decantation, or, when the pre- cipitate has been collected upon a filter, by repeated addition of water, until the filtrate no longer shows indications of dissolved substances, either when evaporated on platinum foil or when tested with an appropriate reagent. Some precipitates which are not wholly insoluble in pure water, or which are mechanically carried through the paper by it, are to be washed with a very dilute solution of some substance which is not fixed, as chloride of ammonium, nitric acid, &c. In washing precipitates by filtration, it is generally ad- visable to collect them as much as possible into the corner of the filters, by means of a fine jet of water directed against the upper edge of the filter, so as to wash down the precipi- tate. The apparatus used for this purpose is the wash flask, which consists of a flat-bottomed flask with two tubes fitted in the neck by means of a good cork' (fig. 6). One end of 12 OPEBATIONS AITD APPARATUS. Fig. 6. the tube ale terminates just below the lower surface of the cork, at the other end it is bent at an angle, and the bore is contracted, so as to leave only a very small aperture at e. The bent tube def extends to the bottom of the flask. When the flask stands upon its bottom there is free communication between the exterior and interior air by the bent tube dbc\ when, on the contrary, it is reversed (fig. 7), air enters through the tube def, and the water flows out through the tube abc in a fine stream, which may be directed upon different portions of a pre- cipitate contained in a filter, or upon the sides of a vessel, for the purpose of removing adhering particles of a precipi- tate. The velocity, and consequently the force of the stream, is proportionate to the difference of level h, and may be augmented by increasing the length of the tube abc. Another form of wash flask (fig. 8) is very convenient when the precipitate is gelatinous, or requires considerable washing, or when the water passes very slowly through the filter. It consists of a large flask A, into the mouth of which is fitted, by means of a cork, a tube of the form represented on a larger scale by fig. 9. The flask is completely filled with water, and inverted above the funnel in such a manner that the fine curved aperture d dips about half an inch below the water in the filter. It is re- tained in this position by means of a support. The pressure of the atmosphere is exerted equally upon the liquid in the narrow tube fie, and upon the surface of the liquid in the filter, EVAPOBATIOK, DISTILLATION, ETC. 13 and consequently upon the liquid in the tube aid. The water in the flask tends to flow in virtue of the pressure of a column of water Ji, equal in height to the difference between the surface of the liquid in the filter, and the surface of that in the lateral tube eb ; but as the tube cb is very narrow, the capillary action prevents air from entering the flask through it, and is equal to the pressure of a small column of water ; therefore the water cannot flow from the flask so long as the capillary action in cb is more than equivalent to the hydrostatic pressure of the column of water k. ' In proportion as the water in the filter passes through, the height of the column Ti increases until, when its pressure just exceeds the capillary action in cb, air enters by the lateral tube cb, and water flows from the flask into the filter again, establishing the equilibrium by elevating the level of the water in the filter. When this apparatus has been adjusted, it requires no further attention, the filter is kept filled with water to an almost constant level, and the fresh water always occupies the upper portion, a circumstance very favourable for perfect washing. Evaporation, Distillation, etc. When, in the course of analysis, substances which are capable of assuming the vaporous state at a more or less elevated temperature are to be separated from others which are fixed under the same circumstances, it is often con- venient to effect their separation in this manner. When the fixed and volatile substances are in the state of physical intermixture, and it is not necessary to save the latter as in the separation of water and some dissolved sub- stances, the operation is called evaporation, and is conducted in shallow porcelain or metal dishes over a gas flaine. The necessity for evaporating liquids for the purpose either of concentration or of obtaining dissolved substances in a dry state, is of very frequent occurrence in analysis. The most convenient arrangement for evaporation (fig. 10) consists of a simple cylinder of sheet iron, pierced at the top and bottom with holes, to admit a current of air, and OPEEATIONS APPAUATTIS. furnislied with a circular gas burner in the middle. The whole apparatus should be placed upon a square clay slab, in order that the table may not ^.^^^^ Fig. 10. be burned. With the aid of a triangle of iron bar and some flat rings of various sizes, it may be made to answer all the requirements of ordinary analy- tical operations. In quantitative analysis it is better to apply heat in evapora- - ^"T^. i tion through the medium of sand, steam, or hot air, because then the evaporation is more uniform than it is over an open fire, and there is less danger of any portion of the liquid being thrown out. . When the volatile substance is to be collected the opera- tion is conducted in a close vessel, either a retort, fl ak, or tube, and the vapour passed into another ves- sel, where it is condensed. The operation is termed distillation when the sub- stance to be separated is a liquid; sublimation when it is a solid. The general form of apparatus used for distillation upon a small scale is shown in 11 12. In many instances it is necessary to pass the DETIKG, IGNITION, ETC. 15 vapour through a tube cooled externally by a stream of water, in order that it may be condensed. This tube is par- tially enclosed by means of perforated corks within a larger metal tube DE, furnished with a spout at f and a funnel at d. This condenser is arranged in an inclined position, so that the water, heated by the condensation of vapour, rises to the higher end, and is forced out by the cold water entering at d. Slight modifications which may be requisite to meet particular cases, will naturally suggest themselves to the operator. Sublimation for analytical purposes may generally be con- ducted in glass tubes, sealed at one end and closed at the other by the fingers. Drying, Ignition, etc. "When in quantitative analysis, precipitates or other sub- stances are to be weighed, it is essential not only that all adherent soluble substances should be washed out, but like- wise that they should be perfectly dry. Moreover, as most substances are more or less hygro- scopic, while others contain water in a state of loose chemi- cal combination, it is generally advisable, before weighing any substance for analysis, to ensure either the total absence of moisture, or a definite state of hydration of the substance in question. This may be effected in various ways according to circumstances. Precipitates may be weighed in three different ways; when washed by decantation they may be transferred to a porcelain capsule or crucible of known weight in the manner above described, and after being dried by exposure to a proper temperature, weighed. When precipitates have been collected by filtration, they may be weighed, after per- fect drying, together with the filters, the weight of which, in an equal state of dryness, has been previously ascertained. Results of sufficient accuracy for some purposes may be ob- tained by using another dried filter as a counterpoise for the one containing the precipitate ; but the method more usually adopted, which involves the least probability of error, and which must necessarily be had recourse to, when the preci- pitate has to be exposed to an elevated temperature previous to weighing, is to burn away the paper. 16 OPEBATIONS AND APPABATUS. "Water which is merely adherent may generally be re- moved by exposing the substances in a confined space, to air dried by contact with a large surface of concentrated sul- phuric acid, which absorbs with avidity the water suspended in the air. A very convenient arrangement for this purpose consists of a large bell glass, ground at the bottom to fit air-tight upon a glass Fig 13. plate, upon which stands a porcelain dish contain- ing sulphuric acid, and furnished with a support for receiving crucibles, watch-glasses, &c. (fig. 13). A dry air-chamber of this kind is an indis- pensable companion to the balance, for the pur- pose of allowing substances, which have been dried by heat or ignited, to cool without any fear of their absorbing moisture. When water is chemically combined, and when it is in that state intermediate between chemical and mere physical mixture, as in deliquesced salts, the influence of a more or less elevated temperature and a full current of air is requisite for the perfect separation of water. For this purpose the hot air-chamber is used, and as a temperature of 212 E. is in the greater number of instances quite sufficient to ensure at least a definite state of hydra- jig. 14. tion, boiling water is a very con- venient medium for the applica- tion of heat. The best form of apparatus (fig. 14) consists of a square copper box, so con- structed as to admit of water being boiled in a space formed by double walls on five sides of the box. The front is closed by a door with two holes to admit a current of air. In the interior, a, there should be a light wooden frame for holding crucibles, &c. Care should be taken that this vessel always contains water while in use, otherwise the temperature may rise far above 212* E. DRYING, IGNITION, ETC. 17 "When a temperature considerably Fig. 15. above the boiling-point of water is re- quired for drying, it is advisable to employ a simple copper box A (fig. 15) of convenient form, and heated by a gas flame. Through an aperture in the lid E, a thermometer D is introduced to indicate the degree of heat attained. When the filter in which a precipi- tate is contained is to be burnt, the first step is to render it thoroughly dry by exposure in the hot air-chamber. The filter is then unfolded, and its contents transferred as perfectly as possible into a clean porcelain crucible, placed upon a sheet of highly glazed paper for the purpose of saving any minute particles which may be dropped. The filter is again folded up into the shape of a closed fan, and ignited at the lower part, while held by the upper part with a pair of platinum pointed tongs so that the ash may fall into the crucible, which is then gradually heated to redness, and kept at that temperature until the whole of the carbon has been burnt off. The ignition of substances for the purpose of bringing them to a definite composition requires several precautions. When water or any other constituent is separated on the application of heat, it is in the gaseous state, and if the dis- engagement of vapour is too rapid, portions of the substance may be projected out of the crucible, especially when the substance is in very fine powder. This danger must there- lore always be provided against by first thoroughly drying the substance in an air-bath, and then raising the tempera- ture of the crucible very slowly to the point of ignition., In the case of substances, which, like chloride of silver, are decomposed when ignited in contact with carbon, it is desirable to avoid collecting them by filtration, but when that is impossible, they must be carefully detached from the paper, which is burnt separately upon the lid of the crucible. Sometimes there is great difficulty in burning off the last traces of carbon from the filter ash ; when long-continued ignition does not suffice for this purpose, and there is no reason to fear decomposition of the substance, the filter ash c 18 OPEBATIONS AND APPABATT7S. may be moistened with nitric acid, dried, and again gently heated. As soon as the ignition of a substance to be weighed is completed, the crucible is transferred to the dry air-chamber (fig. 13) to cool. Fig. 16. The temperature requisite for ignition of precipitates, &c., previous to weighing, may almost always be obtained by the use of the gas furnace (fig. 16), which consists of a stout copper cylinder, 5 inches high, and 2 inches wide, fitting over a gas jet in the same way as a lamp- chimney. The bottom of the cylinder is open and admits of the mixture of air with the gas as it issues from the jet, and the top is covered with a cap of wire gauze, above which the mixture of gas and air burns. This contrivance ensures a higher temperature than is attainable with an ordinary gas-flame, and, by facilitating combustion, prevents the deposition of carbon upon the exterior of the crucibles or other vessels heated. Crucibles may be supported in this flame upon a triangle made of three pieces of tobacco-pipe strung upon wire, the ends of which are twisted together, or when a higher tem- perature is required, the crucible jacket (fig. 16) may be used. This consists simply of two truncated cones of stout sheet iron, fitting together at their bases. The lower cone is furnished with a circular ledge inside, upon which the tri- angle rests, and a handle for removing it while hot. Roasting. This operation consists in exposing substances under the influence of a more or less elevated temperature, to the action of some gaseous substance, capable of combining with some of their constituents, and is adopted for the purpose either of separating them, or of converting them into some other state of combination. The most usual gaseous reagent employed in roasting, is oxygen ; the powdered substance, spread thinly over a metal or earthen plate, being heated to dull redness in the air. MELTING. 19 The sulphur of many ores is removed in this manner previous to the assay by the dry process. It is sometimes desirable to use pure oxygen, chlorine, or some other gas, as reagent in roasting operations, and in such a case the substance is ex- posed to the action of the gas in a small tray of platinum or porcelain, contained in a tube of glass or porcelain, through which the gas is passed in a slow stream. Melting. The object of this operation may be, 1st, to convert sub- stances under analysis into a form soluble in water or by the aid of acid; 2ndly, to effect the separation of some constituent sought to be estimated. A great number of assays in the dry way are made by acting upon the ore in question according to the latter method. The small gas furnace (fig. 16) is capable of producing a temperature sufficiently high for some few purposes, but there are many which require such a tem- perature as can only be obtained in a well-constructed coke furnace. The other apparatus requisite for fusions consists of crucibles of baked clay, iron, porcelain, or platinum. For rough operations and for metal assays the former two are best adapted, but for the more delicate operations of analysis crucibles of porcelain or platinum must be used. Some judgement must be exercised in the selection of crucibles for certain purposes, so as to avoid, on the one hand, destruction of the crucible, and on the other, contami- nation of the substance under examination. Thus porcelain crucibles cannot be used for fusions in which alkalies are used or formed in the reaction Platinum crucibles must not be used for fusions in which chlorine will be generated ; in which nitrate of potash, caustic alkalies, sulphurets, cya- nides, salts of easily reducible metals, phosphoric or organic acids are present. So likewise, when crucibles of porcelain or platinum are to be exposed to very high temperatures in a coke furnace, it is advisable to place them within a larger earthen crucible, containing some calcined magnesia, in order to prevent the small crucible from being upset or damaged by contact with the fuel. c2 20 OPERATIONS AND APPABATUS. A coke furnace, made of sheet-iron, lined with clay, and of the form represented by fig. 17, will answer for most pur- poses in which a high temperature is required, as well as for some cases of distillation or evaporation. It should be placed upon stone slabs, near a flue, into which is inserted a piece of jointed iron pipe to carry off the smoke. Fig. 17. Cupellation. This operation is a combination of roasting and melting, and relates particularly to the separation of certain metals. It is conducted in a muffl* (fig. 18), which Fig. 18. is a semi-cylindrical chamber of baked clay or iron fitting into the aperture M at the side of the melting furnace (fig. 17) . Small shallow vessels of compressed bone-ash, called cupels, are used in this operation instead of crucibles. A muffle may be advantageously used for other purposes besides cupellation, as roasting, melting, ignition of precipi- tates, &c. Blowpipe Operations. These may be regarded as miniature imitations of several kinds of operations in the dry way, practised in the arts for BLOWPIPE OPEBATIONS. 21 the extraction of metals from their ores, the production of glasses, &c. The indications which they furnish are in many instances very valuable, owing to the rapidity with which they may be obtained. Fig. 19. The -apparatus requisite for this kind of testing consists of, 1. The blowpipe, which in its simplest form is a narrow curved tube of brass, with a small orifice, through which a current of air may be forced by means of the mouth or bellows against a small flame, so as to ac- celerate the combustion, and increase the temperature of the flame. The best form of mouth blowpipe (fig. 19) has a box at a, in which the moisture of the breath may collect, and likewise a funnel- shaped mouth-piece c of horn or ivory, which enables the operator to keep up a continuous and uniform blast with much less fatigue. The blast is obtained by the action of the cheek muscles, not by the lungs, air being inhaled through the nos- trils meanwhile. The blowpipe should be furnished with three or four platinum noz- zles d with various-sized orifices. . 2. The flame to be used in blowpipe experiments may be that of a candle, oil, or gas. The latter is perhaps Fig. 20. the most convenient, when used with a burner (fig. 20) made of a piece of tube somewhat flat- tened at the end, and with notches opposite each other in the direction of the greater diameter. The nozzle of the blowpipe is placed upon one of these notches, and a current of air forced through the flame, by which means it is bent down and directed against the substance to be tested. The chemical effect produced under the influence of the blowpipe flame is of two different kinds at different parts of it, and is dependent upon the relation existing between the burning material and the current of air which supports its 22 OPEBATIOtfS AND APPABATTJS. combustion. In the luminous part of the flame, (fig. 21), immediately in front of the obscure cone aa, the carbona- ceous gases are present, Fig t 21. together with the car- bon, in greater propor- tion than oxygen ; the combustion is imper- fect, and consequently metallic compounds are more or less reduced. Beyond this part of the flame at c, on the con- trary, there is more oxygen than is sufficient for perfect combustion, the temperature is higher, and all the condi- tions for oxidation exist. The reducing or oxidizing flame may likewise be produced separately by regulating the blast and the size of the flame. 3. Supports, &c. Charcoal is used as a support for sub- stances while exposed to the action of the blowpipe flame whenever reduction is to be effected, oxidation prevented, 01 when the reducing influence of the charcoal will not affect the experiment. It should be of fir-wood, well burnt, com- pact, and free from knots. 4. Platinum wire, about the thickness of a fine needle, is used for holding substances, while exposed, with fluxes, tc influence of the flame. 5. Platinum foil or spoon, for supporting such substances as do not admit of being heated upon charcoal. 6. Pincette. The most conve- Fig. 22. nient kind for holding small frag- ments (fig. 22), is so constructed, that, when at rest, the platinum points aa are close together, and are separated by pressure. Measures. Vessels of known capacity are in frequent requisition foi measuring liquids. For some purposes the ordinary glass measures, used by apothecaries, answer sufficiently well Narrow-necked flasks, with a mark upon the neck indicating a certain volume, are much more accurate. In the measure- MEASURES. 23 Fig. 23. ment of liquids for analytical purposes, it is requisite not only that the instruments should be exact, but likewise that they should be graduated so as to indicate certain fractional parts of the volume unit. The instrument which has hitherto been most generally used for measuring liquids in analytical operations, is the burette of Gay-Lussac (fig 23). It is a cylindrical glass tube AB with a long spout CD attached to the lower extremity, termi- nating above in a curve and slightly con- tracted at the mouth. The burette is graduated decimally, according to any de- sired metrical system, and from above downwards, so as to indicate the volume of liquid poured out. Although it cannot be doubted that this form of burette has been of very im- portant service in the hands of chemists, it possesses some slight defects, which render it less adapted for the use of in- experienced manipulators. As it is neces- sary to incline the burette when pouring, the volume of liquid cannot be read off during the flow. After the liquid has been allowed to run back, the addition of small quan- tities is very difficult, in consequence of the frequent ad- hesion of a drop in the mouth of the spout, and this is a great inconvenience towards the end of an operation, when it is desirable to read off the volume frequently so as not to spoil the experiment by adding more than is sufficient to complete the reaction. The most valuable modification in the form of the burette has been devised by Mohr (fig. 24). It consists of a tube half or three-eighths of an inch wide, contracted at the lower extremity and graduated. A short collar of vulcanized caoutchouc is fitted at one end upon the contracted neck, and a small glass spout is inserted into the other end. By means of a wire, bent in the manner shown at , and fur- nished with knobs, the caoutchouc collar may be opened or OPEKATIONS AND APPABATUS. closed at pleasure so as to serve the purpose of a stopcock. The advantage of this instrument is, that very small quanti- ties of liquid may be added from time to time, and the volume used can be observed throughout the experiment. Fig. 24. Unfortunately, however, it cannot be used with some volu- metrical reagents, as permanga- nate of potash, for instance, and in such cases the form of burette represented by fig. 25 may be had recourse to, as it possesses several advantages over that of Gray-Lussac. It is less liable to fracture, and small quantities Fig. 25. may be poured from it without difficulty. The capacity of the burette should be from 20 to 100 cubic centimeters, and the length and width so proportioned that a small volume may be read off. The graduation should in- dicate 0*5 cubic centimeter, and smaller quantities may be estimated by counting the drops ; a cubic centimeter con- tains from 12 to 16 drops. Burettes may be graduated by MEASUEES. 25 measuring in successive quantities of 10 cubic centimeters, marking the spaces occupied by each with a file, and then Fig. 26. dividing them equally into Fig. 27. ten parts. For measuring small quan- tities and for transferring li- quids from one vessel to an- other pipettes are used (figs. 26 and 27). They are tubes expanded at one point ijito a bulb and contracted at the lower extremity or beak. They are sometimes gradu- ated and sometimes gauged to deliver certain volumes or weights of liquid, and are filled by sucking out the air while the beak dips into the liquid. The upper orifice is then rapidly closed by the fore-finger, the liquid allowed to fall to the mark on the stem by slightly relaxing the pressure, and the measured quantity run into the vessel prepared for it. In measuring liquids with a burette 'or pipette, care must be taken to have the vessel in an upright position, and that no bubbles of air remain attached to the side. The eye is then brought to a level with the surface of the liquid, and the point of the graduation, which coincides with the lowest point of the curved surface, observed. Operations with gases. Gases are frequently used as reagents in analysis ; they are generated either in vessels of the form shown at A, fig. 28, 26 OPEKATIONS AND APPARATUS. or when the application of heat is necessary, in flasks fitted with a delivering-tube passing through a sound cork. When it is desirable to wash the gas before using it, a small three- necked bottle 5 containing a little water is arranged so that the gas has to traverse it. When the gas is to be dissolved, as in the preparation of hydrochloric acid, ammonia, sulphuretted hydrogen, &c., it is passed into bottles CD containing water. Fig. 28. Weighing. Great accuracy is requisite in the weighings made for analytical purposes; the balances used must therefore be very sensitive. For most purposes they must be capable of indicating distinctly YQ ^0 o f tne weight they are capable of carrying in each pan. For rough weighings the ordinary druggist's balance is very well adapted. Whatever unit of weight is adopted, the weights used for chemical purposes should be decimal multiples, or submul- tiples of it. The French system of weights and measures is now very generally adopted by chemists, and is on every ground to be preferred. Substances should never be weighed while hot, because by heating the surrounding air, an ascending current is pro- duced which raises up the pan of the balance, and makes the weight of the substance appear less than it really is. BEAGENTS. 27 CHAPTER II. BEAGENTS AND TIIEIE USES. THE reagents which are employed in analysis for the solu- tion or chemical alteration of substances under examination, for indicating the presence of the several elements or their compounds, and for effecting their separation, must always be perfectly pure, so that the analyst may never be in any doubt as to the results which he may obtain. The reactions which are had recourse to for the purpose of qualitative analysis are, with the exception of blowpipe tests, for the most part such as are effected by the wet pro- cess. They may be classified under the following heads : 1. Formation of an insoluble compound ; precipitation. 2. Disengagement of some constituent 1 e ff ervescence in a gaseous state ; / 3. Alteration of colour. 4. Solution of a precipitate. Reactions in the dry way serve less for detecting the pre- sence of substances than as a preliminary to subsequent testing. They are for the most part essentially of the same character as the first two kinds of reactions in the wet way. The various reactions applied in analysis take place only under certain conditions, physical and chemical, which may be more or less special; it is therefore indispensable to ensure the existence of these conditions, in testing for any substance, or in applying any chemical treatment. He- actions are likewise definite in their quantitative as well as their qualitative relations, and the analyst must acquire a capability of judging how much of a reagent will be suffi- cient or requisite in particular cases. The data for such an estimation, which should always be present to the mind in every analytical operation, are, the per-eentage of reagent in a given volume of solution, its equivalent number, the probable or possible quantity and equivalent number of the substance sought, and lastly, the equation representing the 28 BEA. GENTS. reaction that takes place between them. Although the ad- dition of a larger quantity of reagent than is actually necessary may not involve any chemical inconvenience, its presence will generally become a mechanical impediment at a subsequent stage of the analysis. Moreover, such a mode of proceeding tends to confirm a slovenly and inconsiderate habit of working. The test for any particular substance by the wet process is generally applied in a thin glass tube, closed at one end, six inches long, and from half an inch to two inches wide. These test-tubes should be arranged in a stand, capable of holding about twenty-four, either inverted on pegs, when clean and ready for use, or supported by a perforated shelf, when containing liquids under examination. (Fig. 29.) Fig. 29. The reagents employed in the wet process are always pre- served for use in solution ; those for the dry process, in the state of powder. Water, HO. In consequence of its very general solvent property, pure water is most frequently used in chemical operations by the we't process for dissolving substances under examination, either with or without previous chemical alteration. It is likewise used in some few instances for effecting chemical alteration. The water used for analytical operations must always be quite pure. Sometimes rain-water, after being boiled and filtered, is good enough, but it is generally necessary to purify water from its fixed and gaseous impregnations. For this purpose distillation from a copper still, with a tinned head, is the most effectual, care being taken that none of the water is thrown over mechanically into the condenser in BEAGKENTS. 29 consequence of too violent ebullition. The first and last tenths should be rejected, and that portion only of the water collected which gives no indications of impurity when treated with suitable reagents. Water should not leave any residue on evaporation, nor alter the colour of litmus paper. It should not become turbid on the addition of nitrate of silver, chloride of barium, or lime water. Alcohol, 2EO, HO. This is used either anhydrous or diluted, for the separation of substances by the solution of some one or more of them, and likewise to effect the perfect precipi- tation of some compounds for quantitative estimation ; for example, sulphate of lime, and the double chloride of plati- num and potassium. The commercial alcohol is generally pure enough for most purposes. It may be rendered anhydrous by repeated treat- ment with sulphate of copper which has been heated in an iron pan, until it becomes a white powder (CuO S0 3 HO). After some days the alcohol is decanted off and distilled. Alcohol should not redden litmus paper, nor leave any residue on evaporation. TEther, JEO. Used only for the separation of bromine. The commercial aether is sufficiently pure. Hydrochloric acid. Solution of HC1 in water. This acid is very largely used as a solvent for substances which are in- soluble in water. The action of hydrochloric acid in effect- ing solution is generally chemical and indirect, for it con- sists in the formation of chlorides, compounds which are characterized as a class by their ready solubility in water. The exceptions are chloride of silver and subchloride of mer- cury, insoluble; chloride of lead, sparingly soluble. The chlorides of antimony and bismuth, and to a less extent, the lower chloride of tin, are decomposed by water, and dissolve only in the presence of free acid. The reaction which takes place on treating substances with hydrochloric acid varies according to their constitution. The most simple case is the solution of a protoxide : 1. MO + HC1 = MC1 + HO. "When the protoxide is combined with an acid displaceable by chlorine, it may remain in solution, or be separated in a gaseous state, or as a precipitate. 30 BEAGEtfTS. Peroxides and their salts, when treated with hydrochloric acid, give rise to the disengagement of chlorine : 2. M 2 3 + 3HC1 = 2MC1+C1 + 3HO. The solution of some saline compounds by hydrochloric acid may very probably consist in the formation of an acid salt, soluble in water, together with some portion of chloride, but in the case of acids and bases which do not form soluble acid compounds, the solution must be regarded as merely physical. Sulphuret of hydrogen, HS. This reagent is employed in qualitative analysis, either in the gaseous state or as a satu- rated solution in water, which takes up between two and three times its volume, for the separation of metals belonging to different groups. The reaction consists in the formation of sulphurets, and the conditions under which they are formed admit of the metals being separated with ease. The metals which are precipitated by sulphuretted hydro- gen from solutions containing a, free mineral acid are enume- rated below : Copper CuS . . black. No precipitation when a large excess of acid is pre- Lead Bismuth Cadmium Mercury Arsenic PbS.. BiS 3 . . CdS . . yellow. HgS . . black. sent until diluted. the solution is fAsS 3 lAsS, Precipitate first white, then yellow, brown, and lastly black. -j T In dilute solutions the preci- 3 > yellow, { pitation is tardy: it is faci- 6j I litated by heat. r QJl^QJ ~\ Antimony < g^g 3 f orange. rjv f SnS . . black, f Precipitated more readily on \ SnS 2 . . yellow. 1 heating the solution. Gold AuS 3 . . black. Platinum PtS 2 . . Precipitation requires heat. EEAGENTS. 31 Sulphuret of Ammonium. Solution of NH 4 S, HS in water. This reagent is employed for the separation of those metals which are not precipitated from. acid solutions by sulphuret of hydrogen. They are, with two exceptions, precipitated as sulphurets, but only from solutions which are alkaline, or at least neutral, because their sulphurets are soluble in weak acids. The basic constituent of the sulphuret of ammonium serves to neutralize the acid produced in the reaction which is represented by the equation MCI + NH 4 S = MS + NH 4 C1. Aluminium A1 2 3 . . white. Chromium Cr 2 O 3 . . green. Zinc ZnS . . white. Iron FeS ..black. Cobalt CoS .. Nickel NiS . . Manganese MnS . . flesh colour. Uranium UrS . . black. Sulphuret of ammonium is likewise employed for the further separation of the sulphurets precipitated from acid solutions by sulphuret of hydrogen, because some of them combine with it, forming soluble double compounds, while the remainder do not. Sulphurets soluble in sulphuret of ammonium. AuS^ The presence of an excess of sulphur in the re- PtS 2 > agent, indicated by a yellow colour, facilitates SbS 3 J the solution. oaf Very sparingly soluble in NH 4 S, except when S is _ present in excess, when it is converted into SnS 2 . AsS 3 \- Eeadily soluble. This reagent is prepared by passing washed sulphuretted hydrogen into solution of ammonia until it is no longer absorbed. When first prepared it is colourless, and acids do not cause precipitation of sulphur. In time, however, it acquires a yellow tinge, and then acids precipitate sulphur; if this precipitate is not considerable, the reagent is fit for use. 32 HEAGENTS. Sulplmret of ammonium should not give any precipitate with sulphate of magnesia, nor leave any fixed residue on evaporation to dryness. Carbonate of ammonia, NH 4 0, C0 2 ; dissolved in 4 parts of water. This reagent is employed for the separation of barium, strontium, and calcium from magnesium (in the presence of choride of ammonium), and the alkali metals in solutions free from heavy metals. The carbonates of barium, strontium, calcium, and magne- sium are insoluble in water. The former three metals are not, however, entirely separated from acid solutions by car- bonate of ammonia, without the aid of heat, owing to the formation of soluble bicarbonates. At the ordinary tempe- rature magnesium is not precipitated at all, and only imper- fectly on boiling. The precipitation of magnesium is like- wise entirely prevented by the presence of ammoniacal salts, owing to the formation of soluble double compounds. Tests for purity, see Chap. IV. Carbonate of potash, KO,C0 2 , or Carbonate of soda, NaO,C0 2 ; dissolved in 6 parts of water. All the metals are precipi- tated as carbonates by carbonate of potash, and the colours of the precipitates are frequently distinctive. Alkaline car- bonates are used as reagents in the dry way for decomposing by fusion silicates, sulphates, and other salts, HO 9 14-8 60 100-0 The strongest liquid acid usually met with has a density of about 1'035, containing about 35 per cent, of water. The usual impurities are, Empyreumatic oils, indicated by the odour, and sometimes by a yellow tinge in the acid ; likewise by a dark-coloured residue left on evaporating to dryness the neutralized acid. Sulphurous acid, indicated by the evolution of sulphu- retted hydrogen, when mixed with pure sulphuric acid and zinc. ^Nitric acid, indicated by the decoloration of indigo solution. Fixed or non-volatile substances, indicated by residues left on evaporation to dryness and ignition. Sulphuric acid or chlorides, indicated as in previous in- stances. Acetic acid, when heated with alcohol and sulphuric acid, gives off an odour of acetic aether. Vinegar is generally the product of a peculiar fermentation of alcoholic liquid's, such as wine, beer, cyder, perry, malt wort, &c. Sometimes vinegar is made by diluting acetic acid, obtained from the distillation of wood, and deprived as far as possible of any impregnation, with water, and adding other substances for the purpose of giving it colour and flavour. There are a great many kinds of vinegar, differing in va- rious respects according to the source from which they have 44 ACIDS. been obtained. These differences relate principally to flavour and colour. Wine and malt vinegar are preferred for culi- nary purposes on account of their more agreeable flavour. The latter ought to contain nearly 5 per cent, of acetic acid. The probable impurities and admixtures are, Free mineral acids. These are sometimes fraudulently added for the purpose of giving vinegar a factitious strength. Vinegar will always be found to contain small proportions of sulphates and chlorides, derived partly from the substances fermented, grapes, malt, &c., and partly from the spring or river water used in the process, so that in testing vinegar due allowance must always be made for this circumstance. More- over, the addition of y^ ^ th by weight of sulphuric acid is a practice legally recognized in this country. For detecting adulteration with mineral acids the following tests may be applied : Sulphuric acid, said to be indicated by the permanent reddening of litmus, while the red colour produced by acetic acid disappears as the paper dries. However, tartaric acid would have the same effect. Bunge recommends mixing some of the suspected vinegar with a little white sugar, evaporating to dryness. When free sulphuric acid is present the residue is more or less charred. Bottcher boils the suspected vinegar with a concentrated solution of chloride of calcium. A precipitate of sulphate of lime, after the liquid has cooled, indicates the presence of free sulphuric acid. This test has the advantage of being unaffected by the presence of the sulphates in vinegar. Garnier states that when pure vinegar is boiled with a very little starch, merely a drop of alcoholic solution of iodine immediately produces the blue colour of iodized starch, but that when free sulphuric acid is present the colour is not produced. Hydrochloric acid is to be tested for in the distillate from the suspected vinegar. Its presence is indicated when the white precipitate (AgO,A) formed with nitrate of silver does not dissolve completely in water. Nitric acid detected as in acetic acid. Tartaric acid is likewise used for adulterating vinegar. It is tested for by evaporating 200 cub. cent, of the vinegar to R. 45 dryness, treating the residue with alcohol, and adding chloride of calcium to the filtered solution. The presence of tartaric acid is then indicated by a precipitate of (CaO, T). The adulteration of vinegar with tartaric or sulphuric acid may likewise be ascertained by a volumetrical estimation of the acid which remains after the acetic acid has been sepa- rated from a known quantity of it by evaporation. Another experiment with an equal quantity of the vinegar in its na- tural state will give the total quantity of acid present, and from the two results the acetic acid is ascertained by the difference. Sot flavouring substances pepper, capsicum, &c. may be detected by the taste of the residue left on evaporation to dryness. The question whether a sample of vinegar has been pre- pared from malt, wine, beer, sugar, or other substances, may sometimes be decided by the examination of the residue left on evaporation. Wine vinegar yields a residue containing tartar, and ha- ving a somewhat astringent taste. Beer vinegar yields a bitter residue without tartar. Wood vinegar yields the smallest proportion of residue, which is frequently rather empyreumatic. Starch-sugar vinegar, and sometimes beer vinegar, give, when mixed with twice their volume of alcohol (0'832 sp. gr.), a flocculent precipitate which is very slowly deposited; it consists of dextrine, and is more bulky than the precipitates formed in the same manner in other kinds of vinegar. 46 ALKALIES. CHAPTEE IV. THE ALKALIES AND THEIE COMPOUNDS ; THE TESTS OF THEIR PUEITT AND ADULTEEATIONS. Potassium compounds. Carbonate of potash, KO, C0 2 . 69-2. KO,C0 2 + 2HO. 87-2. The pure salt should be perfectly white and wholly soluble in less than its weight of water. The ordinary impurities are, Silica, remains undissolved in the form of white flocks when the salt is neutralized with hydrochloric acid, eva- porated to dryness, and treated with water. Sulphuric acid, indicated by a white precipitate (BaO, S0 3 ), with chloride of barium, after the addition of an excess of hydrochloric acid. Chlorides, indicated by a white precipitate (Ag Cl), with nitrate of silver, after the addition of an excess of nitric acid. For many purposes the presence of minute traces of sul- phuric acid or chlorides is not of any consequence. The substance known in commerce under the name of potash is a mixture of carbonate of potash with several other substances. It is never wholly soluble in water, but the quantity of insoluble substance, which is wholly value- less, consisting of silica, carbonates, and phosphates of lime and magnesia, oxide of iron, clay, sand, and carbon, is some- times very small, and in good samples should not amount to more than 1 or at the utmost 3 per cent. The soluble portion, even of potash which is not adulterated, does not consist entirely of carbonate of potash, but contains more or less chloride of potassium, sulphate and silicate of potash, and with these may be associated carbonate of soda, phosphate of potash, sulphur^t of potassium, caustic potash, and organic substances. Besides these substances, originating from the ashes or the mode of preparation, and diminishing the value of the alkali, adulteration is sometimes practised. The substances CAEBONATES OF POTASH. 47 employed for this purpose are chloride of sodium, soap-boilers' lye, soda-ash, sand, chalk, &c. The potash of commerce sometimes contains caustic alkali. Its presence is detected by mixing a solution of one part of the alkali with a solution of two or three parts of chloride of barium ; the precipitate formed, consisting for the most part of carbonate and sulphate of baryta, is separated by filtration, and when the alkali contains caustic potash a slip of turmeric paper dipped into the clear filtrate becomes brown. Sulphuret of potassium is indicated by the disengagement of sulphuretted hydrogen when the alkali is treated with an acid. Chloride of sodium is sometimes fraudulently mixed with potash to the extent of 70 or 80 per cent. It may be detected by neutralizing a portion of the alkali with hydrochloric acid and then adding a solution of antimoniate of potash, which gives a precipitate when soda is present. Since however unadulterated potash contains a certain per-centage of soda salts, it is necessary in making this experiment to compare the precipitate formed with that yielded by an equal quantity of potash, known to be genuine, and treated in the same way. Sulphate of soda is detected in the same manner as the chloride. The alkalimetric valuation, p. 57, would indicate the inferiority of alkali adulterated with either of these salts, but when the adulterating substance is soda-ash, the alkali- metric result gives no indication of its presence. "When therefore a sample of potash gives more than a normal pre- cipitate with the antimoniate, and does not otherwise appear to be inferior in value, there is reason to suspect adultera- tion with soda-ash, and a special experiment must be made to decide this point (p. 62) . Nitrate* of potash or soda may be detected by adding a slight excess of sulphuric acid and some solution of proto- sulphate of iron, which gives a deep red colour when nitric acid is present. Bicarbonate of potash, j > ^ 2 j . 100-2. Should be white and perfectly soluble in 4 parts of water. It should not deliquesce in a moist atmosphere, and its solu- tion treated with bichloride of mercury should not give a 48 ALKALIES. precipitate, but at the most only become turbid (showing the absence of carbonate). Sulphuric acid and chlorine are tested for as in the carbonate. Caustic potash, KO, HO. 56*2. Whether solid or in solution, should not effervesce with acids (absence of carbonate) or evolve sulphuretted hydrogen. The solid potash should dissolve completely in water or al- cohol, without leaving any yellow flocks (peroxide of iron) . Sulphate of potash, KO, S0 3 . 87-2. Should be colourless, not redden litmus paper, not give any precipitate with sulphuret of ammonium (metallic salts), with carbonate of soda (alkaline earths), with nitrate of silver (chlorides), or with antimoniate of potash (soda salts). With the exception of an acid reaction, the bisulphate should possess the same characters. Chlorate of potash, KO, C10 5 . 122-7. White scaly crystals which should not deliquesce; the solution should not give any precipitate with nitrate of silver (chlorine). After ignition of the salt its solution should not redden turmeric paper (indicating the presence of nitrate of potash, which is converted by ignition into caustic potash), become turbid with sulphuretted hydrogen (copper or lead), nor give any precipitate with chloride of barium (sulphates). Nitrate of potash, KO, N0 5 . 101-2. Should dissolve in water without leaving any residue, should not deliquesce, nor give any precipitate with nitrate of silver (chlorides), chloride of barium (sulphates), or car- bonate of soda (lime or magnesia). Iodide of potassium, KI. 166-2. Should be white, colourless, and completely soluble in water. Carbonate of potash, indicated by an alkaline reaction and by deliquescence. lodate of potash, indicated by a brown coloration of the solution on the addition of hydrochloric or tartaric acid. Sulphates, indicated by a precipitate with chloride of barium in the presence of hydrochloric acid. CYANIDE OF POTASSIUM. 49 Sulphur and organic substances, indicated by the offensive odour evolved and by a grey colour when the salt is melted. Chlorides, indicated by the partial solubility in ammonia of the precipitate produced with nitrate of silver, and by a white precipitate on the addition of nitric acid to ammonia, with which the precipitate produced by nitrate of silver has been treated. Cyanide of potassium, K Cy. 65-2. Should be perfectly white and readily soluble in water. The fresh salt is without odour, but when it becomes moist it evolves a smell of hydrocyanic acid. The probable impurities are, Carbonate of potash^ indicated by its insolubility in weak alcohol. Sulphur et of potassium, indicated by a dirty-brown preci- pitate on the addition of acetate of lead. Sulphate of potash. Chloride of potassium, indicated, after igniting the cyanide with twice its weight of nitrate of potash and ten times its weight of carbonate of soda, and adding an excess of nitric acid, by a white precipitate with nitrate of silver. Ferrocyanogen, indicated by a blue precipitate on the addi- tion of bichloride of iron and hydrochloric acid. Sulphocyanogen, indicated, after the addition of an excess of hydrochloric acid, by the production of a red colour with persalts of iron. Silica, remains as an insoluble residue when the solution is mixed with excess of hydrochloric acid, evaporated to dry- ness, and again treated with water. Gyanate of potash, indicated by effervescence when the solution of cycanide in alcohol of 0*84 sp. gr. is mixed with hydrochloric acid. Formiate of soda, indicated by the blackening of the cyanide when heated to redness. Oxalate of potash, KO + aq. 92-2. The solution should not redden litmus. Binoxalate of potash, I'!! \ +2 aq. 146-2. I KO, J The probable impurities are, E 50 ALKALIES. Bitartrate of potash, indicated by the blackening of the salt when heated. Quadroocalate of potash is detected, when a portion of the salt is ignited, dissolved in water, and mixed with an equal quantity of the original salt, by the acid reaction of the mixture. auadroxalate of potash, ' + 4aq. 254-2. This is the salt usually met with in commerce. Tartrate of potash, (K0) 2 T. 2264, Should be white, soluble in its own weight of cold water and without acid reaction. Bitartrate of potash, KO, HO, f . 188-2. The pure salt should be perfectly white. The usual impurities are, Tartrate of lime, indicated by a precipitate with oxalate of ammonia. Chlorides and sulphates, indicated in the presence of free nitric acid by precipitates with AgO, N0 5 and Bad. Metals, indicated by a precipitate with HS. The crude tartar of commerce should leave after ignition a residue containing carbonate of potash, amounting to 80 per cent, of the original substance. Potash salts in solution are recognizable by their not giving a precipitate with carbonate of soda or ammonia, and by the formation of a yellow precipitate with chloride of platinum mixed with alcohol. Sodium Compounds. Carbonate of soda, NaO,C0 2 . 53-0. NaO,C0 2 + 10 aq. 143-0. The pure salt should be perfectly white,' soluble in 2 parts of cold water. The soda salt of commerce should be nearly anhydrous ; the crystallized salt contains about 63 per cent. of water. The usual impurities are, Chloride of sodium, indicated by a white precipitate on the addition of nitrate of silver to the solution mixed with excess of nitric acid. BICAEBOtfATE AND BIBOEATE OF SODA. 51 Sulphate of soda, indicated by a precipitate with chloride of barium in the presence of free hydrochloric acid. Hyposulphite of soda, indicated by evolution of sulphurous acid, and after some time deposition of sulphur on the addi- tion of hydrochloric acid. Ferrocyanide of sodium, indicated by a blue or green colour on the addition of a mixture of proto- and persalt of iron and hydrochloric acid. Potash salts, indicated by the precipitate formed on adding an excess of tartaric acid and alcohol. Carbonate of lime or magnesia may be present, as they are slightly soluble in carbonate of soda. Oxalic acid indicates the presence of lime by a precipitate. Caustic soda is detected in the same manner as caustic potash in potashes. The soda 4f commerce contains most of these impurities, but the salt used in pharmacy and as a reagent should be quite free from any of them ; so likewise Bicarbonate of soda, {HOCO 2 }* 84 ' 0< Should not contain any of the above impurities, nor any carbonate or sesquicarbonate of soda; it should not therefore make turmeric paper brown, nor give a precipitate with a dilute solution of chloride of mercury ; with a stronger solu- tion of chloride it gives a precipitate which is at first white and gradually becomes reddish-brown, while carbonate or sesqui- carbonate immediately produce a reddish-brown precipitate. Caustic soda, NaO, HO. 40-0. Now occurs frequently in commerce. Treated with acids it should neither effervesce (carbonic acid), nor disengage an odour of sulphuretted hydrogen (sulphuret of sodium) or sulphurous acid (hyposulphite of soda). Sulphates and chlorides are detected as in soda. The valuation of soda alkalies is effected in the same manner as that of potash alkalies (p. 55). Biborate of soda, NaO, 2B0 3 + 10 aq. 190-8. Should be quite white and soluble in 20 parts of water. The residue left after ignition should amount to 52 per cent. The probable impurities are, E2 52 ALKALIES. Nitrate of potash, indicated by deflagration when the salt is thrown upon ignited coals. Alkaline earths, indicated by a precipitate with carbonate of soda. Sulphates and chlorides, indicated by precipitates with chloride of barium and nitrate of silver in the presence of free acid. Alum, indicated by the astringent taste and acid reaction upon litmus. Phosphate of soda, indicated by a yellow granular precipi- tate on the addition of molybdate of ammonia to the solu- tion mixed with excess of nitric acid. This impurity some- times amounts to as much as 20 per cent. The method of valuation is described at p. 86. Phosphate of soda, (NaO) 2 HO,P0 3 + 24 aq. 358-3. Should be colourless, perfectly soluble in 4 rJkrts of water at 60? F. The solution should not effervesce with acids, nor turn turmeric paper brown. The usual impurities are, Sulphates arid chlorides, indicated by precipitates with chloride of barium in the presence of free hydrochloric acid, or with nitrate of silver in the presence of nitric acid. An impure phosphate of soda occurs in commerce con- taining lime salts, chlorides, and sulphates ; but it should be free from carbonate of soda, and consequently not effervesce with acids. Sulphate of soda, NaO, S0 3 -f 10 aq. 161-0. The neutral suit should be in colourless crystals, perfectly soluble i.: of water and without acid reaction. The ' 'tnriiit's ;nv, Siityhate of . indicated by a precipitate with car- bonate of soda. Metallic salts, indicated by a precipitate with sulphuretted hydrogen. Ammoniacal salts, indicated by the evolution of ammonia whoBLtreated with caustic potash. Cluorides, tested for as above. HyposulpMte^of soda, NaO, S 2 2 . 79-0. Should be colourless, unalterable when exposed to the air, readily soluble in water, insoluble in alcohol, and without alkaline reaction. CHLORIDE OF SODIUM. 53 The usual impurities are, Sulphite of soda, indicated by deliquescence of the salt. The solution of this salt should dissolve iodine without becoming coloured and without depositing sulphur (indica- tive of sulphate of soda or sulphur 'et of sodium). Sulphuretted hydrogen, indicated by the immediate brown colour of the precipitate with acetate of lead. Nitrate of soda, NaO, N0 5 . 85-0. Should be colourless, transparent, readily and perfectly soluble in water ; the solution should be neutral. The usual impurities are, Chloride of sodium, indicated by a precipitate with nitrate of silver. The commercial salt is seldom free from chloride of sodium, but it should not amount to more than 2 per cent. Sulphates, indicated by a precipitate with chloride of barium. Iodine, tested for in the same manner as in nitrate of potash. Chloride of sodium, Na Cl. 58-5. Should be white, unaltered by exposure to the air, and perfectly soluble in water. The usual impurities are, Sulphates, indicated by a precipitate with chloride of barium. Chlorides of calcium and magnesiivm, indicated by a precipi- tate with carbonate of soda. Iron, indicated by a blue precipitate with ferrocyinide of potassium. Copper, &c., indicated by a precipitate with sulphuretted hydrogen. Iodine, tested for as in nitrate of potash. The quantity of sulphate of lime may be estimated by treating a known weight of the chloride with a saturated solution of sulphate of lime, collecting the residue on a filter, where it is washed with the sulphate solution, drying and weighing. Solutions of soda salts do not give any precipitate with carbonate of ammonia, nor with chloride of platinum and alcohol, as potash salts do ; with antimoniate of potash on the contrary, when not too dilute, they give a white precipitate. ALKALIES. Ammonia, NH 3 , 17'0, or in solution NH 4 0. 26-0. The solution should be a clear colourless liquid without any empyreumatic odour, and volatilizable without any residue. The usual impurities are, Carbonate of ammonia, indicated by a precipitate with lime- water. Lime, indicated by a precipitate with oxalate of ammonia after neutralization with nitric acid. Chlorides and sulphates, tested for in the usual manner. Metallic impregnations are indicated by a precipitate with sulphuretted hydrogen. It sometimes contains traces of lead. The solution of ammonia of commerce is rarely free from some one or all of these impurities. Their presence in minute quantity does not lessen its value for most technical purposes, but when used in analysis it is indispensable that it should be absolutely pure. Carbonate of ammonia, 2NH 4 0, 3C0 2 . 188-0. Should be perfectly colourless, translucent, readily soluble in water, and have a strong ammoniacal odour. The salt is very frequently covered with a white powder, which colours turmeric less deeply and has a less pungent odour. The usual impurities are, Chlorine, TThey are tested for Fixed substances, especially metallic < as in the case of impregiiai [__ ammonia. Chloride of ammonium, NH, Cl. 53-5. Should be colomiel^ translucent, and inodorous, not de- liquesceW^^^alkaline to litmus; readily soluble in hot w r ater, and volatilizable without residue. Impurities and tests are the same as in the other ammo- niacal compounds. Ammoniacal salts give with caustic alkalies, even at the ordinary temperature, pungent vapours of ammonia, which assume the appearance of a white cloud when a rod moistened with hydrochloric acid is brought near. Solutions of these salts give a yellow precipitate with chloride of platinum and alcohol, from which, when dried and heated, evolves a white vapour of chloride of ammonium. ALKALIMETRY. CHAPTER V. THE VALUATION OP ALKALIES, ACIDS, AND THEIR COMPOUNDS. Alkalimetry. THE process of alkalimetry is based upon the facts, that the compounds of the alkalies with acids are constant and definite in their composition, and that their carbonates are readily decomposed by strong acids and converted into neutral com- pounds. The change inajr be generally represented by the equation MO, CO 2 + acid = MO acid + CO 2 . This reaction may be taken advantage of for the analysis of substances whose value depends upon the proportion of caustic or carbonated alkali which they contain, in two ways, viz. by estimating either, 1. The quantity of acid requisite for neutralizing the alkali in a given quantity of the substance ; or 2. The quantity of carbonic acid disengaged from a given quantity of the alkali by an excess of some stronger acid. The latter method is applicable only when the alkali is in the state of carbonate, and the estimation of the carbonic acid must be made by weighing ; but the former, or Volumetrical method, is applicable to the valuation of either carbonated or caustic alkalies, and the marked effects of very minute quantities of acid or alkali upon the colour- ing principle of litmus furnish a very delicate means of ascertaining the point of saturation. Sulphuric acid is generally used for the purpose, and the normal solution is prepared according to the principle laid down in the chapter on reagents. A given quantity ,of any acid requires for neutralization a quantity of any caustic or carbonated alkali, which bears the same proportion to it as the equivalent number of the alkali bears to that of the acid. In the case of sulphuric acid, 56 ALKALIMEHTT. 49 parts by weight will be neutralized by the following quantities of the alkalies respectively : grms. 47-20 KO. grrns. 49 S0 3 HO "I containing \- equivalent to - 40 S0 3 J 69-20 KO,C0 2 . 91-20 KOHO,2C0 2 . 31-00 NaO. 53-00 NaO,CO 2 . 84-00 NaOHO,2CO 2 . 17-00 NH 3 . 26-00 NH 4 0. 1. 188-00 2NH 4 0,3CO,. Cfye normal Solution for alkalimetry is therefore prepared by diluting 49'00 grms. of pure sulphuric acid (sp. gr. T848) with water to the volume of one litre. Fig. 31. 100 cubic centimeters of this solution will be equivalent to ^ of the above quan- tities, and each cubic centimeter equi- valent to jQ 1 ^ of the same. The acid may be measured in a narrow- necked flask (fig. 31) gauged for the pur- pose ; mixed with rather less than the necessary quantity of water, and when the temperature has fallen to 60 P., the volume made up to one litre. The normal solution should be kept in a well-closed vessel, and before being used its value or " titre" should be verified by a direct experiment with a known quantity of pure alkali. The amount of any alkali x may then be estimated by multiplying the quantity of alkali to which one cubic centi- meter is equivalent, by the number of cubic centimeters C n required for neutralization; the general formula being x = a x C tt . Thus, in the case of a solution containing potash, if 28'3 cubic centimeters of normal solution were required, x (KO) would be T335 grm., x = 0-0472 x 28-3. When a more minute estimation is desirable, two experi- ments should be made, one in the ordinary way, which gives a tolerably approximative result ; then, in the second experi- ment, a volume of normal solution, rather less than has been ALKALIMETET. 57 found sufficient for neutralization in the former experiment, is measured by a pipette, as described under the estimation of silver (Chap. VII.) , and added to the solution, the neu- tralization being completed with a solution only -^ the value of the normal solution. Thus, in the above instance, 25 cubic centimeters of normal solution would be added in the second experiment, and, supposing the first result exact, 33 cubic centimeters of decimal solution would be requisite to com- plete the neutralization. If the alkaline solutions in each experiment were accu- rately-measured fractions of a solution obtained in the course of some analysis or operation, in which it was desirable to ascertain the amount of alkali, this is, of course to be found by multiplying the alkalimetric result by a number corresponding with the fraction. The application of this method will be shown in a sub- sequent chapter. When the per-centage of alkali # ' is sought, the quantity of substance q operated upon must be known, and it is then calculated by a simple proportion from the quantity of alkali found = x, for # r : 100 = x : q; or it may be ascertained directly from the number of cubic centimeters of normal solution required for neutralization when q represents the equivalent of the alkali sought. (JSuantttj) ol Material. The numbers above therefore in- dicate for each of the alkalies the quantities q that must be taken by weight of substances in which the amount of any one of them is to be estimated, when it is desired that the number of cubic centimeters of normal solution required for neutralizing shall give at once the per-centage of alkali sought. Thus, for instance, in the valuation of commercial potash it may be required to ascertain, 1. The per-centage of caustic alkali. 2. The per-centage of carbonated alkali. In the former case 4- 72 grins, and in the latter 6' 92 grms. of the raw material are to be taken, for as 100 cubic centi- meters of normal solution neutralize exactly these quanti- ties of the pure alkalies, each cubic centimeter will represent 0-0472 KO or 0'0692 KO, C0 2 . 58 ALKALIMETRY. If, then, in any experiment the 6'92 grins, require for neutralization 58 6 cubic centimeters of normal solution, the substance would contain 58'6 per cent, carbonate of potash, for 0-0692 x 58-6 = 4-11512, and 4-11512 : 6'92 = 58'6 : 100, To ascertain the per-centage of potash 4'72 grms. are to be taken ; an alkali with 58'6 per cent, of carbonate would require 40 cubic centimeters for neutralization, indicating 40 per cent. KO, for 0-0472 x 40 = 1-888, and 1-888 : 4'72 = 40 : 100. "When the substance under examination contains but a small amount of alkali, it is always advisable to take a multiple of the above quantities twice, ten, or twenty times as much, according to circumstances. This quantity is treated with hot water, the insoluble residue separated and washed by filtration, and the whole or a part of the clear solution used for the experiment. The per-centage result is then obtained by dividing the number of cubic centimeters of normal solution required by the multiple used in any parti- cular case. If, for instance, the solution from 69' 2 grms. of an ash required for neutralization 100 cubic centimeters of normal acid, it would contain 10 per cent, .of carbonate of potash. Sometimes it is necessary to repeat the experiments made for the valuation of alkalies. When this is probable, it is convenient to w^eigh two or four times as much of the sub- stance as is needful for one experiment, to dissolve it in water, separate any insoluble residue by nitration, and then to take such a fraction of the solution as will represent the weight of substance to be operated upon. Thus, in valua- tion of commercial potashes, 27'68 grms. may be treated in this way, and one fourth of the solution used for an experi- ment. Caustic lye must be taken in multiple quantities according to the strength, which is approximatively indicated by the density. Density. Quantity for experiment. Under 1-08 50 cubic centimeters. 1-08 to 1-2 20 to 25 1;2 to 1-3 18 to 20 In this way the per-centage of caustic alkali for a certain ALKALIMETEY. 59 volume of lye is ascertained, and this is generally the most convenient form of expression for the result. In the valuation of ammoniacal solution likewise, multiple quantities must be taken, since even the most saturated solution of ammonia (NH 3 ) does not contain more than 32 per cent, by weight of the dry gas. When the solution to be valued is strong, it should always be diluted with three or four times its volume of water, otherwise ammonia would be lost. Cfye experiment is conducted as follows. The solution of al- kali is introduced into a flask or beaker of such capacity that there will be no risk of loss from effervescence.' A similar vessel containing an equal volume of water is placed beside it upon 'a sheet of white paper, a few drops of tincture of litmus added to each liquid, and red colour given to the litmus in the water by a single drop of normal acid. The burette (fig. 32) is then filled to the mark with normal acid, which is gradually added to the solution of alkali, towards the end of the experiment, drop by drop. The appearanceswhich present ^ themselves, and to which especial attention must be directed, are the following : In the valuation of carbonated alkalies, the first addition of acid produces but a slight effervescence in consequence of the formation of bicarbonate of the alkali, but a point is soon reached at which the effervescence becomes brisker, and the litmus begins to assume a claret tint ; about one half of the alkali will then be neutralized, while the remainder will be in the state of bicarbonate. The volume of normal 60 ALKALIMETET. solution used is then to be observed ; it will amount to about of the quantity requisite for perfect neutralization. The urther addition of acid causes a brisk disengagement of carbonic acid, which gives the claret colour to the litmus. When the effervescence at the spot where the acid falls be- gins to be less distinct, not more than a drop or two must be added at a time ; after each addition the liquid should be agitated by giving the flask a rotary motion, and the progress of the neutralization observed by drawing the end of a glass rod that has been dipped into the liquid along the surface of litmus paper. When the claret colour of the liquid sud- denly passes into red, the paper is permanently reddened, the neutralization is complete, and the volume of normal solution used is read off and noted. A deduction of two drops, cubic centimeter, is then to be made for each of the streaks upon the litmus paper that remain red after drying, and another two drops as a correction for the retarding influence which sulphates exercise upon the reddening of litmus by acids. In the case of caustic alkalies, the claret colour is not produced, and there is a sudden transition from blue to red. In other respects the experiment is the same for all alkalies. Estimation of OTater. When it is required to ascertain the per-centage of water in a sample of alkali, a weighed quantity is heated in a porcelain capsule ; the loss of weight gives the amount of water. Sources of error and collateral operations for the correction of alkalimetric results in certain cases. Both, the raw potash and soda of commerce sometimes contain substances which behave with acids exactly in the same manner as the pure alkalies. The presence of such substances would lead to a false result, inasmuch as by appropriating a portion of the normal solution, the per- centage result obtained would be too high. It is therefore necessary in all instances, before entering upon the valuation of any sample of raw alkali, to ascertain by means of some preliminary tests, whether any substances are present which would affect the result obtained by the volumetrical experi- ment. The probable impurities of the several alkalies, and the SOUKCES OF EEKOB, ETC. 61 means of detecting them, have already been pointed out, and it will only be necessary here to refer to those which may influence the estimation of the alkali, and which it may be necessary to estimate quantitatively, in order to correct the error resulting from their presence. Some of these substances are insoluble carbonates of lime and magnesia ; and they may consequently be removed by filtering the solution of alkali before adding the normal solution." Others are soluble alkaline silicates and phosphates', these sometimes amount to as much as 1 per cent., and no sufficiently simple means has yet been devised for obviating the error arising from their presence. In cases where it is desirable, they may be detected and estimated according to the methods described in Chap. VIII., and a corresponding correction made upon the result obtained by the volumetrical experiment. Alkaline sulphurets are very likely to be present, especially in the raw soda of commerce, owing to a partial decomposi- tion of the basic sulphuret of calcium, when the water used for extracting the alkali in the process of fabrication was too hot. Alkaline sulphite, and even hyposulphite, arising from the oxidation of sulphuret, may likewise be present. All these substances are decomposed by sulphuric acid in the same manner as the alkaline carbonates, but the error which they would thus cause may be prevented by igniting the alkali with a small quantity of chlorate of potash in a porcelain crucible. Alkaline sulphurets and sulphites are thus converted into sulphate, while the chlorate used remains in the state of chloride, neither salts having any influence upon the volumetrical result. If, however, hyposulphite is present which is fortunately seldom the case there is formed on ignition with chlorate twice its equivalent of sulphuric acid, half of which neu- tralizes a part of the alkali, in consequence of which the value of the substance is correspondingly under-estimated. When these sulphur compounds are present, it is some- times desirable to estimate their amount, and in that case a double volumetrical experiment must be made, first with the alkali in its natural state, and then with alkali that has been ignited with chlorate. When the impurity is sulphuret G2 ALKALIMETRY, alone, the difference between the two results gives the amount of soda equivalent to it. When it is sulphite, double the difference gives the amount of soda present as sulphite. Thus, in the case of a sample of soda containing 20 per cent, of soda existing as carbonate, and 10 per cent, of soda existing as sulphuret or sulphite, the results would be, Before ignition. i MA. ^i/i ortf cubic centimeters 20 p. c. NaO comb, with C0 2 require 20| ofnormalsolution 10 HS W_ 30 20 CO, 20 10 S0 2 _50 25 After ignition. TVT r\ -u -4.1. nrk on / cu ki c centimeters 20 p. c. NaO comb, with C0 2 require 20 1 of normalsolution . 10 S0 3 none 20 20 C0 2 20 10 S0 3 none 20 On the gradual addition of the normal acid to soda con- taining sulphite only, one half of the soda of this salt is neutralized, the other half remaining more or less completely in the state of bisulphite. Another probable admixture in potash, which would be a very fertile source of error, is carbonate of soda. When the presence of soda to . any amount has been detected in a sample of potash, the volumetrical experiment is made as usual, and the result corrected by means of a control experi- ment, the object of which is to determine the per-centage of soda. For this latter purpose a great number of methods have been proposed. One is based upon the fact that a saturated solution of sulphate of potash dissolves sulphate of soda, but not sulphate of potash. For this experiment the alkaline carbonate must be converted into sulphate. The alkalime- trical experiment having been already made, a weighed SOURCES OF ERROB, ETC. 63 quantity of the potash is mixed with water and a slight ex- cess of sulphuric acid ; the liquid evaporated to dryness, and the residue ignited and weighed. The powdered saline mass is then placed in a graduated cylindrical vessel, six times its weight of a saturated solution of sulphate of potash added, and the whole stirred. When the liquid has become clear, it is drawn off by a siphon, and a fresh quantity of sulphate of potash solution added. Afte"r some time the saline residue is transferred to a weighed filter, the funnel covered with a glass plate, and when the liquid has ceased to drop through, the filter with its contents is weighed, dried at 212 F., and again weighed. The difference between the two weighings gives the quantity of water evaporated from the sulphate of potash solution retained by the filter, and as the concentra- tion of that solution is known, the quantity of sulphate of potash which it held in solution may be ascertained; the weight of this is deducted from the weight of the saline mass dried at 212 F. When the potash thus treated is free from soda, the remainder should be equal to the original weight of sulphate. But when soda is present in the potash, it is dissolved as sulphate, and the weight of salt after treat- ment with sulphate of potash solution is less than the original weight. The loss of weight in the latter case furnishes a means of calculating the per-centage of soda in the raw material. This loss of weight y bears the same pro- portion to the per-centage of soda x that the equivalent of sulphate of soda bears to the equivalent of carbonate of soda : y : x = NaO, S0 3 : JNaO, CO 2 = 71 : 53. It must, however, be remembered that the soda used for adulterating potash would probably contain 20 per cent, of sulphate of soda. A correction must therefore be made when the amount of soda is large. In making this experiment it is always desirable before proceeding to the weighings, to take the specific gravity of the sulphate of potash solution drawn off from the salt ; if it is the same as before, there is no soda in the potash, but if sulphate of soda has been dissolved, the specific gravity is increased. The marked difference in the reduction of temperature attending the solution of the alkaline chlorides in water, has been applied to the estimation of soda in potash. 64 ALKALIMETEY. a. When 50 grms. of chloride of potassium dissolve in 200 grms. of water, the temperature is i educed 11 0> 4 C. = 20-52 E. 5. When 50 grms. chloride of sodium dissolve in 200 grins . of water, the reduction of temperature is only 1*9 C. = 3'42 P. The reduction of temperature attending the solution of a mixture of both salts is dependent upon their relative pro- portion, and the per-centage of chloride of potassium x in the mixture may therefore be ascertained from the observed reduction of temperature y in any particular instance by means of the formula 100 x y 342 17-1 in which y represents the difference between the tempera- ture before and that after the solution of the saline mixture, x the per-centage of chloride of potassium, and z the amount of chloride of sodium. About 60 grms. of the potash in which soda is to be estimated is neutralized with hydrochloric acid, the sulphuric acid separated by means of a normal solution of chloride of barium (p. 78), so as not to introduce any excess of baryta. The sulphate of baryta is collected upon a filter, and the clear filtrate containing only chloride of potassium and sodium, evaporated to dryness. Cfye experiment is made in a beaker-glass, weighing about 185 grms., and kept expressly for this purpose, so that the influence exercised by the cooling of the glass may be the same in all instances. 200 grms. of water are introduced into the beaker, the temperature observed, and 50 grms. of the dry residue thrown in. The whole is then stirred with the thermometer so that the solution of the salt may take place rapidly, and the lowest degree to which the tempera- ture falls observed. If the temperature of the water before adding the salt was 60 - 8 P., and the lowest temperature reached during the solution 44-6 P., then y = 16'2, and 100 x 16-2) - 342 1278 ~mr ' ITT = 74 ' 7 P er cent - The presence of chloride of calcium or magnesium in- ALKA.LIMETET. 65 fluences the result so much as to render the method in- applicable in such cases. Another method is based upon the solubility of the ace- tates of potash and soda in alcohol (0'83 sp. gr.), and the insolubility of perchlorate of potash in the same liquid ; but it refers only to the soda present as carbonate. The potash to be examined is first dissolved in water in such a proportion that 100 cubic centimeters represent the test quantity of material, and the usual alkalimetric experiment is then made with the normal acid ; 10 cubic centimeters of the solution are then neutralized with acetic acid, the solution evaporated to dryness, and the residue treated with alcohol. Chlorides, sulphates, silicate, &c., remain undissolved; the so- lution, which will contain only acetates of potash and soda, is filtered into a beaker glass, and the quantity of soda estimated by means of a normal solution of perchlorate of soda in alcohol. This normal solution is made by dissolving perchlorate of soda (NaO, C10 7 ) in alcohol (0'83), in such proportion that 100 cubic centimeters contain 1'226 grm. of the salt. This quantity is just sufficient to precipitate as perchlorate 0'472 grm. KO (= 0-692 KO, C0 2 ) ; consequently if 10 cubic centi- meters of potash solution representing 0'472 grm. of the pot- ash under examination required for perfect precipitation 50 cubic centimeters of perchlorate solution, the potash would contain 50 per cent, of KO, and if the previous volumetric experiment with normal acid indicated a higher per-centage of alkali, the per-centage of soda in the state of carbonate may be calculated from the difference between the two results. If, for instance, the quantity of normal acid required was 65 cubic centimeters, and the substance contains only 50 per cent, of potash, then 15 cubic centimeters were neutralized by the carbonate of soda, and as each cubic centimeter of normal acid is equivalent to 0*053 grm. NaO, C0 2 , the car- bonate of soda in the test quantity of potash will amount to 0-53 x 15=0-795 grm. NaO, CO 2 , and its per-centage z in the substance examined would be 16-8, for 16-8 : 100=0'795 : 4-72. Gravimetrical valuation of alkalies. In the valuation of alkalies according to this method, the immediate experimental result is the quantity of carbonic 66 ALKALIMETRY. acid disengaged from a known quantity of the alkali by an excess of sulphuric acid. In order to ensure a sufficient degree of accuracy the quantity should not be less than 1 grm., nor for convenience sake more than 2 grms., and from it the quantity of alkaline carbonate x is ascertained by the proportion JKO,C0 2 or x : c = X C. Fig. 33. If it is desired, the quantity of material experimented upon may likewise be regulated so that the quantity c expressed in centigrammes may give directly the per-centage of alkaline carbonate. Thus 6'92 grms. of carbonate of potash give 2'20 grins . of carbonic acid, and centignns. grms. 2-20 : 6-92 = 100 : 3*14, 5'30 grms. of carbonate of soda give 2*20 grms. of carbonic acid, and centigrms. grms. 2-20 : 5-30 = 100 : 2'42 ; so that to obtain direct per-centage indications the quantity to be taken is, for carbonate of potash 3'14 grms., and for carbonate of soda 2*42 grms. When the per-centage of alkali is known to be small, or when the balance used is not sufficiently delicate to indicate a centigramme with certainty, it is ad- visable to take some multiple of these quantities, and to make a correspond- ing division of the result. Cf)e apparatus used for this experi- ment (fig. 33) consists of two very light glass flasks, each fitted with tight corks, through which are in- serted three tubes, c extending to the bottom of one flask, /extending a little below the cork of the other flask, and a connecting tube e bent twice at right angles, and with one limb much longer than the other, as shown in the figure. Cfje experiment is made as follows. The flask I is one- third filled with concentrated sulphuric acid, and the weighed ALKALIMETRY. 67 quantity of alkali introduced into a together with enough water to dissolve it. The corks are then tightly fitted in, the upper part of the tube c closed with a plug of wax, and the whole apparatus weighed in this state. A piece of clean caoutchouc tube is then fitted upon^ and air sucked out by the mouth, until a few bubbles have passed through the sulphuric acid from the flask , which is rendered air-tight by the wax plug ; air is then allowed to enter the flask b through the caoutchouc tube, and a portion of sulphuric acid is thus forced over into the flask , where it disengages carbonic acid from the alkali. This carbonic acid escapes by the tube 0'239; and if 4*84 grrns. of substance were taken, that for the per- centage x' would be, of : 100 = 0-239 : 4-84; or a? = Ac The per-centage value of acids may frequently be ascer- tained with tolerable accuracy by their physical characters, of density or boiling-point. The instruments used for this purpose, and the methods of operating, are described in the chapter on Hydrometry. The chemical methods of valuation are precisely reverse applications of the principles upon which the value of alkalies is determined, Volumetricol method of valuation for acids. The reagent used may be either carbonate of soda, caustic poda, or caustic ammonia. Of the former reagent 5'3 grms. neutralize quantities of the several acids indicated by the numbers below : 'S0 3 HO 4-9. . S0 3 4-0, NO.HO 6-3.. N0 5 5-4, 5-3 grms. | A, HO 6'0. . A 5-1, !NaO,C0 2 equi-^ C1H 3-65 Cl 3'55, valent to P0 6 HO 8 05 PO 5 7-13, I (C 8 H 4 10 + 2HO)15-0..(C 8 H 4 10 ) 13-2, L(C 12 H 3 11+ 4HO)20-1. . (C 12 H 5 O n ) 16-5. 70 ACIDIMETET. Cf)* normal Solution is therefore made by dissolving 53 grms. of pure dry carbonate of soda in water to the volume of one litre; 100 cubic centimeters of this solution will neutralize the quantities of acid given in the table, and each cubic centimeter will contain yoVo P ar ^ f 53 grms. or 0'053 grm. NaO, CO 2 . The amount x of any acid represented by a certain volume of normal solution is found exactly in the same manner as in alkalimetry, by multiplying the number of cubic centi- meters C n by the quantity a of the particular acid to which, a cubic centimeter of the normal Fig. "" solution is equivalent, the general formula being x a X C n . When the per-centage x' of acid is sought, it may be calculated from the quantity q operated upon, and the amount of acid x found, by the proportion, d : 100 = x : q, or it may be ascertained at once from the number of cubic centi- meters of normal solution re- quired for neutralization when q corresponds with the equivalent of the acid sought. Cfyc (juantttj) of material = q to be taken in order to obtain direct per-centage results, is indicated for the several acids by the num- bers in the table above ; those in the first column referring to the per- centage of hydrated acid ; those in the second column referring to theper-centage of anhydrous acid. Cfj? erpmmwt is made .with the burette (fig. 35) in precisely the same manner as in alkalimetry, ~~ and resembles it, with the excep- tion that the blue coloration of the litmus shows the end of the reaction. The evolution of carbonic acid is some ACIDIMETET, 71 hindrance to the decisive indication of this point, inasmuch as it communicates a claret colour to the litmus, and owing to this circumstance, the addition of normal solution may be carried too far and the experiment spoiled. This incon- venience may be obviated in the case of acids that are not volatile by boiling the liquid after each addition of normal solution, and so expelling the carbonic acid. When the acid to be examined is concentrated, it should be diluted with 3 or 4 times its volume of water. In the case of concentrated sulphuric or nitric acids, half the above quantities may be taken, and of dilute acids, appropriate multiple quantities, and a corresponding reduction of the results made. The estimation of the acidity of wines is an exceptional case. For this purpose the normal solution must be diluted to 10 times its volume, and the quantity of wine cannot be weighed according to the equivalent of the acid sought. If in any experiment 100 cubic centimeters of wine require for neutralization 30 cubic centimeters of this decimal solu- tion, this will correspond to 3 cubic centimeters of normal solution. This quantity will have been consumed in neu- tralizing two acids, tartaric and acetic ; the small quantity of citric acid which is usually present in wine may be disre- garded. In order to ascertain the amount of each of these acids separately, another 100 cubic centimeters of the wine is evaporated to one-fourth on a water bath, by which means the acetic acid is expelled. The residue is then diluted somewhat and a second volumetrical experiment made, in which perhaps only 20 cubic centimeters of decimal solution are required for neutralization. This quantity corresponds to 2 cubic centimeters of normal solution, and represents the amount of tartaric acid present. The difference between the two results gives the quantity of acetic acid. These quantities are calculated from the volume of normal solution requisite for neutralization. A cubic centimeter of normal solution (containing 0'053 grm. NaO,C0 2 ) is equi- valent to 0'06 grm. of hydrated acetic acid (A, HO) and 0'15 grm. of crystallized tartaric acid. Consequently the 100 cubic centimeters of wine would contain Acetic acid 0'06 x 1 = 0'06 grm. Tartaric acid . . 0'15 x 2 = 0'30 72 ACIDIMETBY. In the valuation of vinegar likewise a decimal solution should be used, or 4 or 5 times the equivalent quantity for acetic acid taken, and the number of cubic centimeters of normal solution required for neutralization correspondingly divided, in order to obtain the per-centage value. Fig. 36. The valuation of vinegar may be effected with a normal solution of ammonia, containing I 1 369 per cent, of the dry gas as the reagent. The apparatus required (fig. 36) is a tube closed at the bottom, about 12 inches long and O5 inch wide. The space below the mark a holds 1 grm. of water at 6ri6F. The space between a and b holds exactly 10 gfms. of water at the same temperature. From b up- wards the tube is graduated for degrees of 2'08 grms. of water each, or 2 '07 grms. of ammonia solution of 1-369 per cent. Each of the 12 degrees is divided into four parts. In making an experiment the tube is filled to a with litmus tincture, to b with the vinegar to be ex- amined, and then the normal solution of ammonia added until the litmus becomes blue. The volume of normal solution used gives the per-centage of acetic acid (A, HO). After each addition of acetic acid, which must be made in very small quantities, the tube is closed by the thumb, the contents shaken, and the thumb scraped along the edge so as not to remove any of the liquid. When the vinegar is very strong, the tube is only filled to /3, the remaining space between that point and b being made up with water, and the result doubled in order to ob- tain the per-centage value of the vinegar in acetic acid. The accuracy of the results depends entirely upon the care with which the normal solution is prepared. The following table indicates the proportions of water and ammonia solu- tion of different strengths to be used in making it. ACIDIMETET. 73 Solution of ammonia, containing in has a density 100 parts of 12,000 NH 3 0-9517 For 1000 parts of normal solution, containing 1-369 per cent. NH 3 , there are required Solution of ammonia. Water. 11,875 0-9521 11,750 0-9526 11,625 0-9531 11,500 0-9536 11,375 0-9540 11,250 0-9545 11,125 0-9550 11,000 0-9555 10,954 0-9556 10,875 0-9559 10,750 0-9564 10,625 0-9569 10,500 0-9574 10,375 0-9578 10,250 0-9583 10,125 0-9588 10,000 0-9593 9,875 0-9597 9,750 0-9602 9,625 0-9607 9,500 0-9612 9,375 0-9616 9,250 0-9621 9,125 0-9626 9,000 0-9631 8,875 0-9636 8,750 0-9641 8,625 0-9645 8,500 0-9650 8,375 0-9654 8,250 0-9659 8,125 0-9664 8,000 0-9669 7,875 0-9673 7,750 0-9678 7,625 0-9683 7,500 0-9688 7,375 0-9692 7,250 0-9697 7,125 0-9702 7,000 ' 0-9707 6,875 0-9711 6,750 0-9716 6 3 625 0-9721 6,500 0'972Q 114-08 886-02 115-3 884-7 116-5 883-5 117-8 882-2 119-0 881-0 120-0 880-0 121-7 878-3 123-0 877-0 124-5 875-5 125-0 875-0 126-0 874-0 127-3 872-7 129-0 871-0 130-4 869-6 132-0 868-0 133-5 866-5 135-0 865-0 137-0 863-0 138-0 861-4 140-4 859-6 142-2 857-8 144-0. 856-0 146-0 854-0 148-0 852-0 150-0 850-0 152-0 848-0 154-0 846-0 156-4 843-6 158-7 841-4 161-0 839-0 163-5 836-5 166-0 834-0 168-5 831-5 171-0 829-0 173-8 826-2 176-6 823-4 179-5 820-5 182-5 817-5 185-6 814-4 188-8 811-2 192-0 801-0 195-6 804-4 199-0 801-0 202-8 797-2 206-6 793-4 210-6 789-4 74 ACIDIMETBT. Solution of ammonia, For 1000 parts of normal solution, containing containing in has a density 1 -369 per cent. NH 3 , there are required 100 parts of Solution of ammonia. Water. 6,375 NH 3 0-9730 2147 785'3 6,250 0-9735 219'0 781*0 6,125 0-9740 223-5 776'6 6,000 0-9745 228-0 772-0 5,875 0-9749 233-0 767'0 5,750 0-9754 238'0 762'0 5,625 0-9759 243'4 756'5 5,500 0-9764 249-0 751-0 5,375 0-9768 254'7 745'3 5,250 0-9773 260-8 739'2 5,125 0-9778 267-0 733-0 5,000 0-9783 273-8 723-2 An example will render the use of this table obvious. If, for instance, normal solution is to be prepared from ammonia solution of unknown strength, the density must be carefully estimated at a temperature of 61' 16 E. Supposing it to be 0*971, on referring to the table it will be found that this density corresponds to 6*875 per cent, of NH 3 , and that 199 parts must be diluted with 801 parts of water in order to obtain normal solution containing 1*369 per cent. NH 3 . There is, however, a peculiar source of error in the estima- tion of acetic acid by neutralization, resulting from the re- tarding influence which alkaline acetates exercise upon the blue coloration of litmus. The difficulty may be obviated by the use of a solution of saccharate of lime as the reagent. This is prepared by igniting pure marble until the carbonic acid is expelled, mixing the slacked lime into a paste with water, and then adding pure sugar and water until the whole is dissolved. The liquid then contains from 50 to 56 per cent, of lime ; it is diluted in such proportion that 100 cubic centimeters are exactly equivalent to 4-9 grms. of sulphuric acid (S0 3 HO), or 6*0 grms. of acetic acid (A, HO). It is well likewise to have a decimal solution, and both must be kept in well-stoppered vessels on account of the tendency to change by absorption of carbonic acid. In other respects the experiment is conducted the same as any other volume- trical estimation of acid. The normal solution of carbonate of soda is perhaps the best in a practical point of view for acidimetric experiments that have a commercial or technical bearing, because it is ACIDIMETET. 75 most easily prepared, and with some practice on the part of the operator very good results may be obtained with it. But for estimations in which a higher degree of accuracy is desirable, the influence of the carbonic acid disengaged becomes a serious inconvenience. One of the various means of obviating this is to use instead of litmus a solution of pergallate of iron, which gives scarcely any tinge to the acid, but becomes intense violet colour with the minutest excess of alkali. This solution is prepared by adding to boiling dilute hydrochloric acid, an excess of the bluish black preci- pitate, formed by mixing gallic acid with a neutral solution of perchloride of iron, and separating the undissolved portion by nitration. The plan, however, which most fully ensures a high degree of accuracy in the results is the use of a normal solution of caustic alkali, which, to prevent the absorption of carbonic acid, is kept in a glass vessel, closed by a tight cork, through which passes a bulbed tube, containing a mixture of sulphate of soda and caustic lime. A free communication is thus maintained between the air within and without the bottle, while the access of carbonic acid is perfectly prevented. Qravimetrical method of valuation for acids. This method is based upon the fact that all the stronger acids readily and completely decompose an equivalent weight of carbonate of soda, so that when any acid is added to an. excess of carbonate of soda it is easy to ascertain the amount of real acid x in the substance from the quantity of carbonic acid c disengaged, by the proportion x : c = acid : C0 2 ; and when the quantity q operated upon, whether weight or volume, is known, the per-centage x' will be x 1 : 100 = x : q. It is necessary to use bicarbonate of soda for experiments by this method, because when an acid is added to an excess (which there must necessarily be) of neutral carbonate, the full equivalent of carbonic acid is not disengaged, a portion being retained by the excess of carbonate in the form of bicarbonate, and the consequence of this would be that the results obtained would be always too low. 76 ACIDIMETET. The trouble of calculation may be avoided by taking for the experiments such quantities of the acids, that the quan- tity of disengaged carbonic acid expressed in centigrammes will give at once the per-centage of real acid in the sub- stance examined, Here, as in alkalimetric experiments by this method, the quantity of carbonic acid disengaged should not be less than 1 grin., nor more than 2 grms. 44 parts of carbonic acid are disengaged from bicarbonate of soda by 40 parts of SO 3 , 49 parts SO 3 HO, or an equivalent quantity of any other acid, and the quantities x of any acid which are equivalent to 100 centigrammes of C0 2 are shown in the following table : gwns. 9-1 SO 3 ). 12-3 NO 5 ). 8-3 HC1). 11-6 A). 30-0 T). 37-5 C). gnus. 44C0 2 centigrms, 100 gnus. 40 (SO 3 ) = 54 (NO 5 ) = 36-5 (HC1) = 51 (A) = 132 (T) = 165 (C) = The numbers in the latter columns indicate the quantities of substance to be taken in order to ascertain directly the per-centage of anhydrous acid. If 123 centigrammes of a sample of nitric acid is found to disengage 50 centigrammes of carbonic acid, it will contain 50 per cent, of N0 6 . As most of the acids met with in commerce are more or less dilute, it will sometimes be necessary to take multiples of the above quantities, and to divide the result obtained. Thus, if in the examination of nitric acid 2*46 grms. give 40 centigrammes C0 2 , then the per-centage of NO 5 would be 20. If 69-6 grms. (60X116) of vinegar gives in experiment 180 180 centigrammes CO 3 ; then as -^ = 3, it would contain 3 per cent, of anhydrous acetic acid. In the valuation of acids by this method, as well as by the volumetrical method, preliminary experiments must always be made for the purpose of ascertaining whether they are -free from any substances which would act in the same manner as the acid sought to be estimated, and so lead to e ACIDIMETET. 77 false result. Thus, when nitric acid contains hydrochloric or sulphuric acid, the per-centage result obtained for NO 5 would not only be too high, but, inasmuch as the equivalents of these acids are about two-thirds that of NO 5 , 2 per cent, of these impurities will be taken as 3 per cent, of N0 5 . In such cases the valuation experiment becomes more com- plicated. The result will therefore require correction, which may be made by estimating the quantity of sulphuric hydrochloric acid or other foreign acid =z, in the quantity experimented upon, either by means of suitable normal solutions, or by weighing the precipitates, and then calcu- lating the quantity of C0 a = c' that would be disengaged by it from NaO, 2CO a , by the proportion, z : c' = S0 3 : 2CO 2 or z : c' = HC1 : 2C0 2 . The value thus obtained for c' is then to be deducted from the result obtained in the first experiment ; the remainder gives the true per-centage of N0 5 in the acid examined. Cfje apparatus used is the same as -p- 3 ^ that for the valuation of alkalies, but it is necessary to have a small glass tube that will pass through the neck of the flask for containing the car- bonate of soda. This tube is fur- nished with a small piece of very thin platinum wire (fig. 37). Cije ejrptrtment i g a l so made much in the same manner. The acid to be examined is introduced into the flask a, if necessary diluted, so as to make up about 30 or 40 grms., and the small tube, filled with dry bicarbonate of soda, is suspended in the flask by means of the wire which is clamped between the cork and the neck of the flask, so that the acid maybe brought in contact with its contents by a slight inclination of the apparatus. In this state the apparatus is weighed, and the acid then brought in contact with the bicarbonate. The carbonic acid disengaged is dried by passing through the sulphuric acid in b, and when the reaction is completed, the flask a is placed in water of about 160 F. to expel carbonic acid from the liquid, and the residual atmosphere of the gas in the 78 HALIMETET, flasks removed by loosening the wax plug in c and drawing air through them. The apparatus is then dried, allowed to cool, and again weighed. The difference between the two weighings gives the amount of carbonic acid disengaged, and when the quantities of substance taken for the experiment are those given in the table, this difference, expressed in centigrammes, gives the per-centage of acid sought. Estimation of acids in combination with bases, and valuation of the saline compounds of the alkalies. (Halimetr y.) The valuation of saline compounds of the alkalies is generally effected by estimating the amount of the acid they contain by means of some reaction that admits of being adapted to the volumetrical method. In some in- stances the valuation must be effected by means of some physical peculiarity of the substance sought. Estimation of sulphuric acid. The precipitation of sulphuric acid, as sulphate of baryta (BaO, S0 3 ), by soluble baryta salts may be applied to the estimation of this acid in soluble compounds. According to the equation BaO,S0 3 , 4 parts of sulphuric acid (SO 3 ) are equivalent to 7' 65 baryta (BaO), and the normal solution may be made by dissolving 122 grms. of chloride of barium in water to the volume of one litre ; each cubic centimeter will then be equivalent to O04 grmi. of sulphuric acid (S0 3 ). The amount of sulphuric acid may then be found by multiplying the number of cubic centimeters required for perfect precipitation by 0'04. The very tardy separation of the sulphate of baryta pre- cipitate is, however, a serious obstacle to the application of this process. In some instances it may be the only one applicable, and then it would be better to collect and esti- mate the sulphate of baryta by weighing ; the amount of sulphuric acid, or of the sulphate sought being calculated in accordance with the above formula and that of the salt. In the absence of a balance or other conveniences for the pur- pose, recourse must be had, in the volumetrical experiment, YALT7ATION OF NITEE. 79 to the application of heat to the liquid in which the sulphate of baryta is suspended, or nitration. A much better mode of estimation consists in precipitating the acid, as sulphate of lead (PbO, S0 3 ), by nitrate of lead : and the reaction between iodide of lead and alkaline sulphates, KO, S0 3 + Pbl = KI + PbO, S0 3 , furnishes a very marked indication of perfect precipitation ; so that when the liquid in which sulphuric acid is to be estimated is mixed with a few drops of iodide of potassium solution, there is, on the subsequent addition of the normal solution of nitrate of lead, no permanent formation of iodide of lead until the whole of the sulphuric acid has been re- moved from solution, and then the yellow colour of the pre- cipitate does not disappear on shaking the mixture.. The normal solution is made by dissolving 41'33 grms. of nitrate of lead in water to the volume of one litre, and the results are calculated as in the case of the baryta solution, each cubic centimeter being equivalent to O'OIO grin. S0 3 . The absence of any substances which might be pre- cipitated, like sulphuric acid by the normal solution, must always be ascertained by appropriate tests. Estimation of nitric acid. The conversion of protochloride of iron (Fe Cl) into perchloride (Fe 2 C1 3 ) by nitric acid, together with the esti- mation of iron by permanganate of potash, has been applied to this purpose. The reaction is 6FeCl + N0 5 + 3HC1 = 3Ee 2 C1 3 + N0 2 + 3HO. The amount of nitric acid x sought is then calculated from the quantity of iron E converted into perchloride by the proportion a : F = N0 3 : Fe 6 . Valuation of nitre. For the manufacture of gunpowder it is of great import- ance to be able to estimate the amount of impurities in the commercial nitrate of potash by some brief and easy operation. The method followed in France depends upon the fact that a solution of nitrate of potash, saturated for a certain temperature, is incapable of dissolving any more of the salt, although it will dissolve the other salts with which it is usually contaminated. 80 HALIMETET. For testing a sample of nitrate, 400 grins, of the powdered salt are mixed with 500 cubic centimeters of a saturated solution of pure nitrate in a bottle and well shaken for 10 or 15 minutes, the liquid poured off into a filter, the remain- ing salt agitated with 250 cubic centimeters more of the pure nitrate solution, and the whole thrown upon the filter. When the solution has passed through, the salt is freed as much as possible from adherent liquid by pressure against bibulous paper, completely removed from the filter, dried, and weighed. The loss of weight which it is found to have suffered in this operation represents the quantity of impuri- ties present in the nitrate. It has, however, been ascertained that a serious source of error attaches to this method of valuation It consists in the circumstance that a saturated solution of nitrate becomes capable of dissolving an additional quantity on the addition of chloride of sodium, and that the quantity so dissolved and the consequent error is greater in pro- portion to the amount of chloride of sodium present. The presence of chloride of potassium likewise involves an error in the opposite direction, and this method of valuation should not be adopted without very great precaution. Another method has been adopted in Austria. It depends upon the decrease of the solubility of nitrate of potash in water consequent upon reduction of temperature, or, in other words, the more or less speedy separation of solid nitrate from a hot solution containing a known quan- tity of crude nitrate when allowed to cool. The temperature at which the first signs of crystallization appear is taken as an indication of the per-centage of pure nitrate. The dis- advantage attending this method is, that the point of satura- tion for a given temperature varies according to the amount of chloride of sodium present. There are likewise other sources of error attached to this method, and the possible variation in the results it furnishes are too great to admit of its being considered satisfactory. In Sweden the appearance of the fracture of the salt after melting is taken as an indication of its value. The fracture of the pure nitrate has a lustrous, radiated, crystalline appear- ance; but when chloride of sodium is present, to the amount of 2*5 per cent., the fracture is dull, more granular, and com- VALUATION OP KITRE. 81 pact. The intermediate' gradations, however, are so little characteristic, that it is hardly possible by their aid to form. any trustworthy opinion as to the per-centage of chloride in particular specimens. The chemical methods of valuation are far more accurate. One is based upon the convertibility of nitrate of potash into carbonate by ignition with carbon, and the fact that chloride of sodium or potassium are not affected under the same conditions. By estimating the quantity of carbonate by a given weight of crude nitre, it is therefore possible to calculate its per-centage of pure nitrate. The ignition must be made with some precaution, on account of the violent action that takes place, to moderate which it is advisable to add 3 or 4 times as much chloride of sodium, and to project the mixture in small portions into a red-hot iron crucible. When the reaction is at an end the crucible is allowed to cool, the contents dissolved in water, and the volume of the filtered solution made up to 200 cubic centimeters. The estimation of the carbonate of pot- ash is made as directed at p. 56. Unfortunately nitrate of soda is converted into carbonate by the same treatment, and when alkaline sulphates are present, they are converted into sulphurets, which likewise affects the result, so that this method is inapplicable to the valuation of nitre containing these salts, unless at the same time other experiments are made to ascertain their amount. The process already described for the estimation of nitric! acid (p. 79) may in most instances be applied to the valua- tion of nitre. The experiment is made in the manner there described, and the amount of nitrate of potash x sought, calculated from the quantity of iron F converted into per- chloride by the proportion : x : F = KO NO 5 : Fe 6 . (JBjqperimmt. Two grammes of clean iron wire are dissolved by hydrochloric acid in a flask of 200 cubic centimeters' capa- city, with a narrow neck, closed by a perforated cork, through which passes a glass tube, drawn out to a small bore for the escape of gas. To the solution of protochloride of iron, con- taining excess of acid, is added 1*2 grm. of the crude nitre, the flask closed, and the whole heated to boiling. The greater the per-centage of nitrate in the nitre, the greater G 82 HALIMETET. the quantity of perchloride of iron formed. Chloride of potassium or sodium and sulphates do not affect the result. It remains then to ascertain how much iron F has been converted into perchloride. For this purpose the normal solution of permanganate of potash is used precisely in the same manner as for the estimation of iron (Chap. VII.). The solution is used of such value that 50 cubic centimeters are sufficient to convert 1 grm. of iron, in the state of proto- chloride, into perchloride, and it thus indicates the amount of iron F still remaining in the state of protochloride. 2 grms. of iron in the state of protochloride require for conversion into perchloride 1*216 grm. of pure nitrate of potash. If in a particular experiment 10 cubic centimeters of nor^ mal permanganate solution suffice to complete the formation of perchloride of iron after the reaction of the protochloride and nitrate, the quantity of iron F converted into perchloride by the nitre is 2 grms. minus the quantity of iron F, equi- valent to this volume or 1*8 grm., and the quantity of pure nitrate x requisite for this purpose is ascertained by the proportion : 2-00 : 1-216 = 1-80 : y (y = 1/0944). Then, as 1*2 grm. of nitre was used, its per-centage of pure nitrate #' is found thus : 1-2 : 1-0944 = 1-00 : x (x = 9V2 per cent.). The per-centage of sulphates or chlorides may be estimated by means of normal solutions of baryta or silver salts, or by the methods described at p. 79 and Chap. VIII. It has been found, by the examination of a great number of samples of crude nitre, that the proportion of the chlorides of potassium and sodium is one Na Cl to two KC1, and the per-centage of each chloride may be calculated from the quantity of chlorine found in accordance with this result. In the case of East. Indian nitre at least, it is more im- portant to estimate the per-centage of alkaline earths rather than that of sulphates, which is very small. For this purpose lime and magnesia may be precipitated by carbonate of soda, and estimated as described in Chap. IX. In most instances the per-centage of magnesia is nearly as great as that of lime, and no great error is made by regarding the precipitate as half lime and half magnesia. None of these methods give any indication of the per- ANALYSIS OP POWDER. 8$ centage of nitrate of soda, Except as an adulteration it is rarely present in East Indian nitre, but some kinds of nitre contain a considerable amount, for ascertaining which there is no trustworthy means besides the direct estima- tion of the potash. The fact that nitrate of soda attracts moisture from the atmosphere, is had recourse to for an approximative estimation of this salt. Pure nitrate of potash exposed for 14 days under a bell-jar with a basin of water attracts no moisture, but when nitrate of soda is mixed with it an increase of weight is observed. Per-centage of nitrate of soda. , . . O5, 1, 3, 5, 10. Increase of weight in 14 days, ... 2 '5, 4, 10, 12, 19. Analysis of gunpowder. This operation is tedious and difficult when it is necessary to separate perfectly the several ingredients. The first step is to estimate the amount of moisture by exposing 5 or 6 grms. of the powder under a bell-jar with a basin of sulphuric acid for some days, and weighing several times, until no further decrease of weight takes place. The per-centage of nitrate of potash is ascertained by treat- ing about 10 grms. of the powder with warm water. The insoluble residue, consisting of sulphur and carbon, is washed upon a weighed filter, dried and weighed. The difference in the weight gives the amount of nitrate of potash, which may be confirmed by evaporating the filtrate to dryness and weighing the saline residue. The estimation of the sulphur is effected by melting 1 or 2 grms. of the powder with equal quantities of pure carbo- nate of soda and nitrate of potash, and four times as much chloride of sodium, until the whole becomes white. The carbon is thus converted into carbonic acid, the sulphur into sulphuric acid- The fused mass is dissolved in water, treated with an excess of hydrochloric acid, and the sulphuric acid estimated either by weighing as sulphate of baryta, or by means of a normal .solution of chloride of barium, one cubic centimeter of which is equivalent to 0*004 grm. S0 3 . If there- fore the sulphuric acid y yielded by 1 grm. of gunpowder requires for precipitation, as BaO,S0 3 , 62'5 cubic centimeters of normal solution, it will amount to 4 X 62'5 = '250 grm., 84 ANALYSIS OF and the quantity of sulphur x represented by it may be ascertained by the proportion : x : y = S : SO 3 , or as 16 : 40 ; accordingly # = '100 grm., and the powder would contain 10 per cent, of sulphur. The per-centage of carbon may be ascertained by deducting from the weight of powder operated upon, the sum of the quantities of moisture, nitrate of potash and sulphur, found, and calculating for 100 parts. When, as is sometimes the case, it is desirable to ascertain what kind of charcoal has been used for the preparation of gunpowder, the separation of the sulphur must be effected in a different manner. A weighed quantity of the mixture of sulphur and carbon is digested for some time with a solu- tion of sulphuret of carbon in absolute alcohol, by which means the sulphur is dissolved, and the carbon left un- altered. It may likewise be necessary to estimate sand and similar admixtures, which is done by washing out the nitrate, burn- ing off the sulphur and carbon, and weighing the residue. This residue will, however, contain the fixed substances originally contained in the sulphur and charcoal. The compositions used for fireworks are analogous in composition to gunpowder. They may be classified as a. Mixtures containing nitre with charcoal, sulphur, or- ganic substances (rosin, glue), and salts which colour the flame. b. Mixtures containing chlorate of potash with sulphur, charcoal, and sometimes sulphuret of antimony, or other substances for colouring the flame. The first group comprises' the gray composition, and the firework charges prepared from it and from meal powder. The second group comprises the charges used for signal rockets and fusees. Compositions containing nitre may be analysed in the same manner as gunpowder, but the operation is rendered somewhat more difficult by the presence of the organic sub- stances, which it is difficult to estimate, and which even hinder the accurate estimation of the other ingredients. Colophony is a frequent ingredient of these compositions ; it is separated most conveniently by boiling a weighed PYROTECHNIC MIXTURES. 85 quantity of the substance with alcohol of 0'81 sp. gr., eva- porating the filtered solution, and weighing the dry residue. Glue or gum must be separated by water, which likewise takes up the soluble salts. When it is desired to estimate these substances, the solution is evaporated to dryness, weighed, ignited in a crucible treated with hydrochloric acid, the solution again evaporated to dryness, ignited, and the quantity of nitrate of potash calculated from the chloride of potassium found (100 parts of KC1 represent 134 KO,IS 5 ). The difference between the calculated weight of nitrate and the total weight of the substances dissolved out by water, gives the amount of organic substance. Sulphuret of antimony is easily detected by the glittering appearance of the portion insoluble in water, >and by its density. It is estimated by boiling the residue, left after separating nitre, with strong hydrochloric acid, treating the filtered solution with sulphuret of hydrogen, collecting and weighing the precipitate of sulphuret of antimony. The most important of the compositions containing chlorate of potash is that used for friction fusees. This consists of varying quantities of sulphuret of antimony with chlorate of potash, agglutinated by a little isinglass. The chlorate of potash is estimated by treating the mass with water, gently warming, and after the addition of a few drops of infusion of galls, filtering. The filtrate contains, after the insoluble residue has been washed, all the chlorate of potash ; it is evaporated to dryness, ignited, mixed \vith a little hydrochloric acid, again dried, ignited, and the quan- tity of chlorate calculated from the chloride of potassium ob- tained (100 KC1 represent 164 KO, CIO,). The difference between this calculated weight and that of the substance operated upon gives the quantity of sulphuret of antimony. The cementing substances never amount to more than 0*25 or 0'50 per cent. The mixtures for coloured fires containing nitrate of baryta, sulphate of copper and ammonia, nitrate of strontia and sulphuret of antimony, likewise contain, besides these sub- stances which produce the colour, sulphur, carbon, and chlorate of potash. Their analysis is conducted by separating in the first instance the soluble from the insoluble ingredients. Baryta is separated and weighed as sulphate (100 BaO, S0 3 86 TALTJATION OP BOEAX. represent 111*5 BaO, N0 3 ) ; the filtrate containing excess of sulphuric acid, leaves on evaporation sulphate of potash, from the quantity of which the quantity of chlorate of pot- ash is calculated (100 KO,S0 3 represent 140 KO, C10 5 ). Mixtures containing strontia are treated in exactly the same manner (100 SrO, S0 3 represent 115 SrO, N0 5 ). Copper is estimated in the solution from cupreous mixtures by treat- ment with sulphuretted hydrogen, collecting the precipitate, which is washed with solution of sulphuretted hydrogen, dried and ignited, first alone, and then with carbonate of ammonia until its weight remains constant. The quantity of sulphate of copper and ammonia is calculated from the weight of oxide of copper found (100 CuO represent 307 of the salt). The insoluble portion of these mixtures is either charcoal, sulphur and charcoal, or these ingredients together with sulphuret of antimony ; they are estimated in the manner described above. It is sometimes necessary in the first instance to make a qualitative examination of such substances according to the system described in Chapter X. Valuation of borax. Borax has a slight alkaline reaction upon litmus, while free boracic acid colours it like carbonic acid, and the red colour is produced only when there is an excess of some stronger acid, as sulphuric acid. Consequently the normal solution used in alkalimetry may be applied to the valuation of borax, and in the same manner. The quantity of the crystallized salt to be taken for ail experiment is 19*08 grms., and from the volume of normal solution requisite to produce the red colour 0*5 Cubic centi- meter is to be deducted, because the presence of sulphate of potash retards the action of the acid. EARTHS. 87 CHAPTER VI. THE ALKALINE AND TRUE EARTHS, AND THEIR COMPOUNDS ; THE TESTS OF THEIR PURITY, AND METHODS OF VALUA- TION, ETC. Barium compounds. Caustic baryta, chloride of barium, nitrate of baryta, and carbonate of baryta are employed as chemical reagents for a variety of purposes. Chlorate of baryta is used in the pre- paration of fireworks, and sulphur et of barium for separating arsenic and nitrogen acids from sulphuric acid. The native sulphate of baryta is used as a pigment, either alone or mixed with others. Sulphate of baryta is rarely free from oxide of iron, stron- tia, and lime, and as it is the source from which all baryta compounds are derived, these impurities may probably be present in them. Iron is indicated by a blue precipitate with ferrocyanide of potassium. Strontia is indicated by the carmine colour which its chloride communicates to the flame of alcohol. In testing the substances 1, 3, 4, 5, and 6, they are treated with hydro- chloric acid, and evaporated to dryness ; sulphate of baryta is boiled with a solution of carbonate of soda, the liquid filtered hot, neutralized with hydrochloric acid, and eva- porated to dryness. The dry residue of chloride obtained in each case is digested for some time with strong alcohol, which is ignited in a basin after filtration. Lime is indicated by the solubility of its sulphate and by a white precipitate with oxalate of ammonia in the neutral solution, from which baryta has been precipitated as sulphate. Heavy metals are indicated in soluble baryta compounds by a precipitate with sulphuretted hydrogen, in the presence of excess of hydrochloric acid. The above-mentioned barium compounds should be per- 88 EARTHS. fectly white, with the exception of the sulphuret, which has a yellow tinge ; 1, 2, 3, and 5 should be perfectly soluble in water, 4 in hydrochloric, nitric, or acetic acids. The conta- mination of one baryta salt by another is indicated by the test for the corresponding acid. The most distinctive character of soluble barium com- pounds is the formation of an insoluble compound when treated with sulphuric acid, or a soluble sulphate, and the perfect insolubility of this compound (BaO, S0 3 ) in water or acids. Strontium compounds. Chloride and nitrate of strontium are used in the prepara- tion of coloured fires and fireworks. They much resemble the corresponding barium compounds. The most probable impurities are, Barium or calcium salts. They are indicated by a preci- pitate on the addition of a few drops of ferrocyanide of potas- sium to a moderately strong solution of the salt. Calcium may be especially tested for in the same way as in barium compounds. The distinctive character of soluble strontium compounds is, that when mixed with burning alcohol they communicate to the flame a carmine colour. Calcium compounds. Carbonate of lime, CaO, C0 2 , and caustic lime, CaO. Lime, as it is used for various purposes in the arts, is ob- tained by igniting, in a suitable furnace, carbonate of lime in the form either of limestone, chalk, or marble, and the pro- cess has been named after the product, calcination. All these materials are more or less impure, and their value for the preparation of lime depends greatly upon the nature and amount of foreign substances. Among the very numerous uses of lime in the arts, there are some for which it is necessary that the lime should be pure, while for others the presence of certain other sub- stances is even advantageous. Thus in the preparation of caustic alkalies, and other chemical operations, as well as in soap-making, bleaching, dyeing, tanning, sugar-refining, purification of gas, and glass-making, the Hme used should CEMENTS. 89 be as pure as possible. For the preparation of mortar, plaster, and other building purposes, the purity of the lime is less essential, and for the preparation of cements, certain kinds of lime containing other substances are preferable. Lime obtained by calcining a tolerably pure limestone should, when moistened with a little water readily crumble down with considerable evolution of heat, or as it is called, slake, and when mixed with more water form a smooth paste. Lime containing a considerable proportion of foreign sub- stances clay, magnesia, peroxide of iron, &c. slakes less readily, absorbs less water, and forms a granular paste. The difficulty in slaking may, however, be owing to de- fective calcination as well as to the presence of foreign sub- stances. Different kinds of lime vary in other respects in their be- haviour with water ; some kinds of lime have the peculiar property of becoming perfectly compact and hard after a time under water. This is called hydraulic lime. The hardening is owing to the presence of a certain proportion of aluminous, siliceous, and alkaline substances. Cements are variable mixtures of lime with siliceous or argillaceous materials, which communicate to it the property of hardening under water. The value of lime, carbonate of lime, marl, &c. for various purposes is generally ascertained in the same manner. When it is necessary that the examination should be comprehen- sive, the method described in Chapter IX. must be adopted, but for most practical purposes the following experiment, referring more specially to lime, will afford sufficient indica- tion of the essential characters of any of these materials. 1. Water is detected and estimated in lime, limestone, marl, &c., by igniting a weighed quantity in a porcelain cru- cible, and again weighing. When the two latter contain organic matter, the loss of weight will represent both it and water. For the estimation of water alone a temperature of 212 or 250 F. must be applied. 2. Carbonic acid may be present in a sample of lime either from imperfect calcination, or in consequence of absorption from the atmosphere when the lime has been long kept. It is at once indicated by effervescence on the addition of an acid. The carbonic acid in limestone or lime is estimated 90 EAETHS. by means of the apparatus (fig. 38), in the same manner as the value of an alkali. Fig. 38. 3. Limestone frequently contains organic substance. It is generally evident from the dark colour of the mineral, and is estimated by strong- ly igniting a weighed quantity of the powdered limestone, previously dried at 212 F., then moistening it with a few drops of carbonate of ammonia solution, drying, gently igniting, and weighing the residue. The loss of weight gives the amount of organic substance with sufficient accuracy for all practical purposes. 4. Silica, alumina, oxide of iron, magnesia, and alJcalies. The various kinds of native carbonate of lime, and conse- quently caustic lime, are seldom free from one or more of these substances in greater or less proportion, sometimes associated with very small quantities of phosphoric and sul- phuric acids. The partial insolubility of some limestone in dilute acids is chiefly owing to the presence of silica and alumina. These substances may, however, exist in limestone, &c. in two dif- ferent states, in the one case soluble in acids, in the other insoluble ; but, generally speaking, the silica and alumina in limestone, &c. is, for the most part at least, insoluble in acids, while in the caustic lime they are soluble in acids, the calcination having converted them into the state of soluble compounds with lime. The question whether a particular kind of limestone would be suitable, when calcined, for the preparation of mortar, was for a long time determined by the chemical characters, according to a simple method proposed by Vicat, a very high authority on the subject of hydraulic lime. Limestone which contains argillaceous ingredients may be regarded as a mixture of carbonate of lime and silicate of alumina (clay), in which the latter exists in very variable proportion. As carbonate of lime (also carbonate of mag- nesia) is readily soluble in dilute hydrochloric acid, while the argillaceous portion is for the most part insoluble in the CEMENTS. 91 same reagent, the hydraulic property of a sample of limestone was estimated according to the amount of insoluble residue left after treatment with dilute hydrochloric acid. This was collected on a filter, washed, dried, ignited, and weighed. This method, which is still adopted, is, however, very imperfect, and altogether inadequate for the purpose to which it is applied. Yicat has himself pointed out that it is only capable of furnishing very rough approximative indications, and that it is by no means sufficient to estimate merely the amount of ingredients insoluble in hydrochloric acid, gsince their influence upon the value of limestone for mortar may be of a twofold nature. One portion of them is by the process of calcination rendered soluble by the aid of hydrochloric acid, as is shown by the separation of gelatinous silica on evaporating the hydrochloric solution of the lime, and by the formation of a hard mass insoluble in w r ater when the lime is mixed with water. The other portion of the insoluble ingredients consists of mechanical admixtures, frequent coarse granules of quartz sand, and fragments of disintegrated siliceous minerals. It is therefore far preferable to calcine the limestone before applying Vicat's test, because it is then at once seen how much of the ingredients, insoluble in hydrochloric acid, are converted into the soluble state by calcination. "When the time and other requisites for a complete chemical analysis of the limestone are wanting, the following plan may be adopted as likely to furnish some useful indications : Several fragments of three or four inches diameter, and selected as representing the average character of the mate- rial, are broken into two pieces, one of each being introduced into a large earthen crucible with holes bored through the bottom, and exposed to a suitable temperature for calcination, either in a lime-kiln or in the laboratory furnace (fig. 17). The other pieces are powdered and thoroughly mixed. A weighed quantity, 2 or 3 grms., is reduced to a very fine state of division in an agate mortar, dried at 212 F., and treated with moderately dilute hydrochloric acid at a gentle heat. The insoluble residue is collected on a filter, washed, dried, and weighed. The calcined portion is treated in exactly the same manner, but to render the results comparable an allowance 92 EARTHS. must be made for the loss of weight by calcination. This is best done by weighing the limestone calcined both before and after calcination. If, for instance, the loss amounted to 35 per cent., then 65 parts of calcined lime would represent 100 parts of the limestone, and the residue, insoluble in hydrochloric acid, from that quantity would be equal to the mechanical ingredients of 100 parts of limestone. The necessity for calculation may be avoided by taking for the experiment 3'00 grms. of the raw material, and of the calcined lime 3 times as many centigrammes as there are hundredths of lime yielded by the limestone when calcined. Thus, in the above instance, there would be taken as equiva- lent to 3'00 of raw material 3 x 65 centigrammes = 1*95 grm. The insoluble residue from that quantity would represent the portion not rendered soluble by calcination, and the mecha- nical admixtures of 3 '00 grms. of raw material, and the per- centage would be obtained by division of that quantity by 3. In examinations of this kind a repetition of the experi- ment is always desirable, in consequence of the variation in the chemical character of limestone, and of the differences arising from dissimilar calcination. Alkalies. It has been satisfactorily proved that the pre- sence of alkalies in calcined argillaceous lime has a very great influence upon its hydraulic properties, and it is one of the chief defects of Vicat's method that it gives no indi- cations with reference to this particular. The alkalies may, as well as silica and alumina, exist partly in the soluble and partly in the insoluble state. The marls of looser texture are always mixed with disintegrated frag- ments of rock, which, although they resist the action of acids, even after calcination, still contain alkalies. Since, however, such ingredients contribute little, if at all, to the hydraulic character of lime, it would be exceeding the limits of practical inquiry to direct attention to them any further than to include them under the head of insoluble ingredients. That portion of the alkalies, however, which is rendered soluble by calcination is of considerable importance. It may be estimated with sufficient accuracy by the method proposed by Fehling and Faisst: 40 or 50 grms. of the calcined lime are mixed with water in a capsule (lime which hardens with water should be mixed with solution of car- CEMENTS. 93 bonic acid), the whole allowed to rest for awhile, the clear liquid poured off, and a stream of carbonic acid passed through it to separate the lime ; the remaining liquid evaporated to dryness and dissolved in water, filtered, and the residue obtained by evaporating the clear filtrate, weighed as carbonate of potash and soda with traces of chloride of sodium. Another chemical test for ascertaining the relative value of cements, which gives, however, no indication as to their composition, depends upon their power of precipitating lime from its aqueous solution. Weighed quantities of the cements are taken in fine powder and gradually mixed with equal quantities of lime-water, constantly stirred meanwhile, and the addition continued until the whole of the lime is removed from solution, which may be ascertained by testing with carbonate of soda. The remainder of each sample of cement is then weighed, and the value of the cement estimated as inversely proportional to the quantity required to precipitate a certain quantity of lime. The quality of a sample of cement or hydraulic lime may also be estimated by trials as to the time taken in hardening, and the degree of hardness acquired. This test should never be omitted, even when a complete chemical analysis is made. It may happen that a native or fabricated mixture of argillaceous and calcareous ingredients, which corresponds fully with all the requisites for the production of a good cement or hydraulic lime, will, after calcination, when ex- posed for a long time to atmospheric influences, become so altered as to be wholly valueless as a cement. When such an alteration has merely amounted to the absorption of carbonic acid, repeated calcination will restore the value of the material ; but the absorption of water, how- ever, has a further prejudicial effect, which is not so easily remedied, for the change which renders the material useful as a cement takes place the siliceous ingredients and the lime combine, forming a hydrated silicate ; and even when this is only partially the case, the property of hardening when mixed with water is diminished in a corresponding degree. The particulars to be observed in testing cement with a view to the property of hardening are described by Pasley and Schafhautl, as follows : 94 EAUTHS. 1. The cement in very fine powder is mixed with just enough water to make it into balls about ar inch in diameter. During the absorption of water these balls should become warm, but not positively hot. "When they have cooled, (which, with good cement, will be in about half an hour,) they are laid in a vessel of water, and when they continue to become harder, and after the lapse of a few days are perfectly hard throughout the entire mass, the cement may be considered good, and the contrary when the balls have not acquired a considerable degree of hardness. 2. When the balls of cement do not become hard under water, it may be desirable to ascertain whether it is owing to the natural inferior quality of the material, to deteriora- tion by keeping, or to adulteration. For this purpose the balls are heated to redness in a crucible until they no longer effervesce with acids, then powdered, and again mixed with water into balls as before. If the hardening under water take place, then it may be inferred that the cement has been spoiled by keeping, or was not well prepared. If, on the other hand, the calcination does not effect any difference in the behaviour of the cement under water, it may be inferred that the material is bad, or that it is adul- terated. Sulphate of lime, CaO,S0 3 , 68. CaO,S0 3 + 2aq. 86 (gypsum). The foreign substances likely to be present in gypsum, when not in considerable quantity, do not lessen its appli- cability for most purposes. When their proportion is large, they are sufficiently indicated by the appearance. It may happen, however, that gypsum does not absorb water and harden, or "set," as it is called. This maybe owing either to imperfect calcination or to the application of too high a temperature. In the former case, a little of the substance, heated in a tube, disengages water, which con- denses in drops at the upper cold portion of the tube. The quantity of water may be estimated by igniting a weighed quantity, and then weighing again. Raw gypsum contains from 20 to 21 per cent, of water ; calcined gypsum should not contain at the utmost more than 5 or 8 per cent. Phosphate of lime, 3CaO,P0 3 . The principal constituent of bone ash. CHLORIDE, FLUORIDE, AND SULPHURET Or CALCIUM. 95 Bone ash should be perfectly soluble in hydrochloric acid ; an insoluble residue indicates the presence of clay or sand. Digested with water, very little should be dissolved. The liquid should not redden litmus ; should not give a pre- cipitate with lime-water, which would indicate vegetable ashes, nor with oxalate of ammonia, which would indicate adulteration with gypsum. With acids it effervesces, but the carbonate of lime should not amount to more than 4 per cent. It may be estimated by means of the apparatus (fig. 33) for the estimation of carbonic acid in alkalimetry. The loss of weight in this experiment should not exceed 3 per cent. ; when greater, there is reason to suspect adul- teration with cJialJc. See Examination of manures. Chloride of calcium, Ca Cl. 55-5. Should be colourless, readily and perfectly soluble in water ; the solution should not redden turmeric paper, nor become brown with sulphuretted hydrogen ; caustic ammonia should not produce any precipitate. The salt when heated alone should not give off any volatile substance, nor when heated with lime evolve ammonia. Fluoride of calcium, CaFl. 39-0 (fluor-spar). The frequent natural association of quartz is, when con- siderable, indicated by the great degree of hardness and other exterior characters ; in small proportion it is not detrimental for most of the applications of fluor-spar. It may be easily detected by heating the fluor-spar with four times its weight of sulphuric acid in a platinum retort, and passing the gas disengaged into water. When silica is present it is separated from the gas in white flocks. Sulphuret of calcium, CaS and CaS, HS. The former is used mostly in pharmacy, the latter as a depilatory. Both substances should dissolve in hydrochloric acid with disengagement of sulphuretted hydrogen. The former should not leave any considerable residue of sulphate of lime, nor present any great precipitation of sulphur. The latter should not contain any sulphate, and the pre- cipitate formed with hydrochloric acid should be pure sulphur. The solution should not redden turmeric paper, indicative of caustic lime. 96 EABTHS. The latter substance is frequently obtained from tl: lime-purifiers of gas-works, and consequently contains car- bonate of lime, which may be detected by adding, first, an excess of a concentrated solution of bichromate of potash, and then sulphuric acid; when by this treatment effer- vescence is produced, it is indicative of the presence of carbonate of lime. The quantity may be ascertained by introducing a weighed quantity of the substance into the flask a of the carbonic acid apparatus (fig. 33), together with two or three times as much bichromate of potash, and estimating, in the usual manner, the quantity of carbonic acid disengaged. Every 22 parts of carbonic acid cor- respond to 50 parts carbonate of lime. Acetate of lime, CaO, A. 79. When pure is a white salt; that prepared with acetic acid from the distillation of wood is generally yellow or brown. This salt should be perfectly and readily soluble in water and alcohol. The dilute aqueous solution should not give any precipitate with nitrate of silver that is not soluble on the addition of more water. A precipitate with chloride of barium indicates the presence of sulphates, and a brown colour with sulphuretted hydrogen the presence of heavy metals lead, copper, &c. A blue precipitate with ferro or ferricyanide of potassium in the presence of hydrochloric acid indicates iron. The crude acetate is rarely free from one or all of these impurities in greater or less proportion. The amount of water in the salt is very variable ; it is estimated in the usual manner, by drying the powdered substance at 212 F. and weighing. Hypochlorite of lime, CaO, CIO. The essential ingredient of bleaching powder, or, as it is called, " chloride of lime." The empirical formula of the substance is CaO + HO + Cl. Whatever may be its true chemical constitution, it does not contain, when saturated to the utmost with chlorine, more than 53 per cent, of the gas to 47 per cent, of hydrate of lime. But this degree of saturation is, in most instances, purposely avoided, because the presence of a small quantity of hydrate of lime prevents CHLOKIMETBY, 97 it from such speedy alteration as it otherwise would undergo. - This alteration is a main source of variation in the value of bleaching powder ; for while that depends wholly upon the amount of chlorine capable of bleaching, its conversion into chloride of calcium a substance valueless for the purposes to which this is applied takes place very readily, especially when the temperature is somewhat raised, and the carbonic acid of the atmosphere likewise causes a small but constant evolution of chlorine. It is therefore evident that, with all these possible sources of difference in the value of the material, it is a matter of the greatest importance to the manufacturer, who consumes enormous quantities of it, to possess some means of ascertaining the value of any sample of bleaching powder with ease and certainty. The various processes which have been adopted or pro- posed for the valuation of chlorinated lime are all based upon the fact, that when the evolution of chlorine takes place in the presence of some oxidizable substances and of water, a reaction takes place, which consists in the decom- position of water and a partition of its elements between the chlorine and the oxidizable substance. As the quantity of the latter which is oxidized is equivalent to the quantity of chlorine evolved, it is possible, by means of the equation representing the reaction, to calculate the amount of avail- able chlorine in any sample of bleaching powder, either from the quantity of substance oxidized by a known weight of the bleaching powder, or from the quantity of bleaching powder necessary to oxidize a given weight of that sub- stance. As might be supposed, a great number of substances have been used for this purpose with more or less advantage. Those best calculated for this application are arsenious acid As0 3 and protosulphate of iron FeO,S0 3 . The reactions being respectively 1. As0 3 + 2HO + 2C1 = As0 5 + 2HC1. 2. 2FeO,S0 3 + HO + Cl = Fe 2 O 3 SO, 4- HC1. In consequence of the ready disengagement of chlorine from the solution of bleaching powder, it is necessary to add it to the normal solution. The normal solution of arsenious acid is prepared by dis- solving 4r95 grms. of arsenious acid by the aid of heat in 98 CHLOEIMETET. dilute hydrochloric acid, and making up the volume with water to a litre. The normal solution of protosulphate of iron should always be made fresh, at the time it is required, by dissolving 278 grms. of pure crystals in water. A cubic centimeter of either solution will then be equivalent to 0-0355 grm. of chlorine. The solution of hypochlorite should be prepared in some- what larger quantity than will be required for the actual experiment, so as to avoid inaccuracy which might arise from the circumstance that, in the case of such a substance, a small quantity is less likely to represent the average value. According to the equation (1.) 4 - 95 grms. of arsenious acid are converted into arsenic acid by 3*55 grms. of chlorine, and as the per-centage of chlorine in the bleaching powder is to be ascertained, the quantity used for an experiment must be regulated according to this proportion. 35'5 grms. of the bleaching powder are mixed with water to the volume of one litre, and the whole allowed to stand until the solu- tion becomes clear. Each cubic centimeter of this solution will represent 0'0355 grm. of the material, and the number of cubic centimeters of normal arsenious acid solution required to complete the reaction, with 100 cubic centi- meters of hypochlorite solution, would give the per-centage of chlorine in the sample of bleaching powder. As there is always a loss of chlorine when, as in other volumetrical experiments, the normal solution is added to that of hypochlorite, it is necessary to avoid the error which would thus be involved, by reversing the operation, and add- ing the hypochlorite solution to the solut jon of arsenious acid. The result is then obtained in a somewhat different manner. If, for instance, 40 cubic centimeters of hypochlorite solu- tion are required for the oxidation of the 0'495 grm. of arsenious acid contained in 100 cubic centimeters of normal solution, the 40 cubic centimeters of hypochlorite solution will contain 0*355 grm. of chlorine, and as the 40 cubic centi- meters represent 40 x 0'0355 = T420 grm. of the bleaching powder, the per-centage of chlorine x will be found by the proportion 100 x 0-355 * : -T420- = 25 ' The result may likewise be obtained by dividing 1000 by CHLOEIMETET. 99 the number of cubic centimeters of hypochlorite solution required to oxidize the arsenious acid in 100 cubic centi- meters of normal solution. Thus, in the above instance, 1000 ~4?r~ = 25, and if 50 cubic centimeters were required, then the per-centage of chlorine would be ^- = 20. "When the bleaching powder to be examined is either very strong or very weak, a fraction or multiple of the above quantity may be taken in making the hypochlorite solution, and the result multiplied or divided as the case may be. . 100 cubic centimeters of normal solution are measured into a beaker and mixed with a few drops of indigo solution, which serves to indicate the end of the reaction, for in the presence of arsenious acid it is not decolorized by chlorine, although this takes place imme- diately when the whole of the arsenious acid is oxidized. The beaker containing the coloured solution is then placed upon a sheet of white paper, and the hypochlorite solution added from a burette until the blue colour suddenly dis- appears. When protosulphate of iron is used as a reagent the same course is pursued, except that the end of the experiment is ascertained by testing the liquid with a solution of ferri- cyanide of potassium. Several drops of this reagent are placed on a white porcelain slab, and from time to time a drop of the liquid is taken out of the beaker by a glass rod and added to one of them. So long as any protosalt of iron remains a blue colour is produced, but as soon as the oxida- tion, is complete only a greenish-brown colour. All those methods in which it is necessary to ascertain the progress of the reaction by testing a drop of the liquid under examina- tion are objectionable, because in this way a source of error is introduced that it is difficult to make allowance for. A very convenient modification of the arsenious acid pro- cess for estimating the value of hypochlorites is to use arsenite of soda as the reagent. The normal solution is prepared by dissolving 4'95 grins. arsenious acid with 14r5 grms. of pure carbonate of soda, and about 800 grms. of water, afterwards making up the volume 100 EAETHS. to one litre. 35'5 grms. of the hypochlorite are treated with water, and this solution likewise made up to one litre. 100 cubic centimeters of each solution are then measured off, and the hypochlorite gradually added to the normal solution of arsenite. The perfect oxidation of the arsenious acid is ascertained by means of a test-paper saturated with iodide of sodium and starch. After each addition of hypochlorite the solution is stirred with a glass rod and a drop allowed to fall upon the test-paper, which remains unchanged in colour so long as there is no excess of hypochlorite, but a single drop more than is sufficient to oxidize the arsenious acid is sufficient to produce a blue colour in the paper. The iodide of sodium and starch paper is prepared by dis- solving 1 grm. of iodine, 7 grms. of crystallized carbonate of soda, and 3 grms. of potato starch in about half a pint of water, and then making up the volume to half a litre. Strips of white paper are saturated in this solution, dried and kept for use. 2 grms. of iodide of notassium may be substituted for the iodine and carbonate of soda. . The calculation of the results is made precisely in the same manner as described above. The distinctive character of soluble calcium compounds is the formation of a white precipitate CaO, O with oxalate of ammonia in the presence of free ammonia, even when the solutions are very, dilute. Magnesium compounds. Magnesia, MgO. 20. Used in pharmacy and as a polishing powder, &c. It should not effervesce with acids nor yield any saline sub- stance to water. When moistened it should not become very hot, and the neutral solution in hydrochloric acid, somewhat diluted, should not give any precipitate with oxalate of ammonia in the presence of chloride of ammonium, which would indicate the presence of lime. It should be perfectly soluble in dilute sulphuric acid, and the solution should not become turbid or brown with sulphuretted hydrogen, Carbonate of magnesia, 3(MgO,C0 2 ) + MgO,HO 4- 3 aq. . Used in medicine and as tooth-powder, &c., as well as for. SULPHATE OF MAGNESIA. 101 mixing with pigments and for various chemical purposes. With the exception of effervescing with acids, it should pre- sent the same chemical characters as magnesia. Sulphate of magnesia, MgO, S0 3 + 7 aq. 123. Besides the medicinal uses of this salt, it serves as the source of other magnesian preparations. It should be white and perfectly soluble in water. A rather dilute cold solu- tion should not give any precipitate with bicarbonate of potash, but with neutral carbonate it forms a thick pasty precipitate. When mixed with carbon and heated upon charcoal in the blowpipe flame, the remaining mass should not evolve sulphuretted hydrogen (indicative of an admixture of sulphate of soda) when moistened with an acid. Sulphate of soda is the most frequent impurity, and it is sometimes substituted for sulphate of magnesia. It may be detected by dissolving a weighed quantity of the salt, and adding baryta-water or sulphuret of barium so long as a precipitate is formed, then heating the mixture and filtering. If the filtrate contains baryta, it must be precipitated by carbonate of ammonia and again filtered. The clear liquid evaporated to dryness should not leave any residue when the sulphate of magnesia is free from sulphate of soda. The distinctive characteristic of magnesium compounds is the production of a pale red colour when moistened with nitrate of cobalt and heated on charcoal with the aid of the blowpipe. Emery. A massive variety of corundum, occurring com- mercially in fine powder, used for grinding and polishing. Many natural and artificial substances are sold as substitutes for emery, either confessedly so or under its name. Among these are powdered slags, iron ores, &c. While true emery contains but little iron, from 3 to 4 per cent., and scarcely any silica, considerable quantities of these substances together with some lime and alkalies are contained in these factitious mixtures. Alumina is almost insoluble in hydrochloric acid, while the substances fraudulently substituted for it soon dissolve more or less in this acid. The nature of the admix- tures may be ascertained by treating the solution according to the system described in Chap. X. ; and if it is desirabie 1G2 EAETHS. to estimate the various ingredients, the necessary instruc- tions will be found in Chap. IX. Sulphate of alumina is sometimes brought into the market/ It is a very variable substance, containing, among other impurities, iron, zinc, and lime. A solution of the salt should not give any precipitate with tincture of galls, with ferro- or ferricyanide of potassium, which would indicate the presence of iron. Oxalate of am- monia should not give a precipitate. When an excess of caustic potash is added, and the solution heated until it is tolerably clear, sulphuretted hydrogen ought not to give a, white precipitate, which would indicate the presence of zinc. The per-ceutage of water ur the commercial salt varies from 46 to 57 per cent. It is estimated by heating to red- ness a weighed quantity. HAW+W + *.* 502-0. Alum. There are three kinds of true alum potash alum, soda alum, and ammonia alum. The first and last of these are far more frequent than the soda alum. They crystallize in octohedrons. Cubical alum contains a larger proportion of alumina than the octohedral. Roman alum is of this kind. Ammonia alum, when heated with lime, gives off ammo- niacal vapour, recognizable by its odour and by the brown colour it produces in moistened turmeric paper. Soda alum is distinguished from potash alum by its tendency to effloresce and by its greater solubility. Its solution gives a precipitate with antimoniate of potash. Impurities, among which oxide of iron for many of the pur- poses to which these salts are appKed is the most prejudicial, may be detected in the same way as in sulphate of alumina. The quantity of iron in Roman alum is inconsiderable, and the adherent red oxide of iron is innocuous, as it is not soluble in water. The alums do not lose the whole of their water at 212 F. The per-centage of water in soda or potash alum is indicated by the loss of weight on ignition. The water in ammonia alum cannot be estimated in this way, because it decomposes when heated, and sulphate of ammonia is volatilized. The per-centage of alumina may be estimated by treating ACETATE OP ALUMINA. 103 the solution of a known weight of the alum with carbonate of ammonia until nothing more is precipitated. The alumina is then collected on a filter, well washed, dried, ignited, and weighed. Acetate of alumina. As used for dyeing and calico print- ing, it is prepared by treating alum with acetate of lime or soda; more frequently with acetate of lead. It is very variable in composition. The differences are owing partly to the kind and partly to the quantity of substance used for decomposing the alum. The impurities which are most injurious for the purposes to which the aluminous mordants are applied, are copper and iron. The former may be detected by immersing in the liquid a clean iron rod, upon which the copper is deposited. Iron may be detected as in alum. Aluminous mordant is sometimes mixed with substances which will prevent it from drying quickly upon the fabric ; these are chlorides of zinc, ammonium, or sodium. The pre- sence of one or other of these substances is indicated when nitrate of silver gives a white precipitate soluble in ammo- nia. Zinc is detected as in sulphate of alumina; chloride of sodium by precipitating with an excess of carbonate of ammonia, filtering, evaporating the filtrate to dryness, and driving off the ammoniacal salt by heat. "When chloride of sodium is present, there is a residue, the solution of which gives a precipitate with antimoniate of potash. When the mordant gives a precipitate with nitrate of silver and no indication of chloride of sodium, it contains chloride of ammonium. The detection of ammonia alone does not in- dicate the presence of chloride of ammonium, because the alums of commerce frequently contain ammonia in the place either of potash or soda. "When acetate of lead has been used for preparing acetate of alumina, it gives a slight brown precipitate with sul- phuretted hydrogen. "When acetate of lime has been used, it gives a precipitate with oxalate of ammonia. "When acetate of soda has been used, the acetate of alumina should be free from either lead or lime. When it contains soda, without giving a precipitate with nitrate of silver, either 104 EAETHS. there is an admixture of acetate of soda or of carbonate of soda, which may be mixed with acetate of alumina in a certain proportion without causing a precipitate, or soda alum has been used for preparing it. In both the former cases the proportion of soda to alumina is much greater than in the latter case. In order to ascertain which of these cir- cumstances the presence of soda is owing to, a weighed quantity of the acetate is treated with a slight excess of car- bonate of ammonia, the nitrate and washings from the alu- mina, mixed with enough sulphuric acid to displace the acetic acid, evaporated to dryness, ignited, and weighed. When the proportion by weight of the ignited residue to the alu- mina is greater than 9 : 5, acetate of soda has been used. Acetate of alumina, prepared with -acetate of soda, contains the sulphate of soda resulting from the decomposition, and cannot on that account be thickened with starch. The composition of acetate of alumina depends still more upon the proportion of acetate used for decomposing the alum. Most frequently acetate of lead is used for this pur- pose, and it is important to know how much has been used for a certain quantity of alum. This is ascertained as follows : About a pound o aluminous liquor is treated with an ex- cess of carbonate of ammonia, the alumina collected on a filter, washed, ignited, and weighed. The quantity of alum d, represented by a pound of the liquor, is calculated from the result x obtained. All three kinds of alum contain nearly 11 per cent, of alumina, therefore the proportion x : x 1 11 : 100 may be used in all instances. The filtrate is treated with nitric acid to decompose the excess of carbonate of ammonia, and the sulphuric acid estimated by the volumetrical method with the normal solu- tion of nitrate of lead, as described at p. 79. The distinctive character of aluminium compounds is the production of a blue colour when moistened with nitrate of cobalt and heated with the aid of the blowpipe. CHROMIUM COMPOUNDS. 105 CHAPTEE VII. COMPOUNDS OP THE HEATT METALS: THEIR CHARACTERS, THE TESTS OE THEIR PUBITY, AND METHODS OF ESTI- MATION. Chromium compounds. Oxide of chromium, Cr 2 3 . 77-4. Known in commerce under the name of chrome-green, as a pigment for oil and enamel painting. It is not easily soluble in acids, and may contain acci- dental admixtures of soluble salts, alkaline chlorides, sul- phurets, and sulphates, but is not likely to be adulterated. A mixture of chromate of lead, prussian blue, and heavy spar is not unfrequently sold as chrome-green. Chrome- yellow, carbonate of copper, or chalk may be easily detected by treatment with hydrochloric acid. Oxide of chromium should, when melted with its weight of nitrate of potash, yield a yellow mass, perfectly soluble in water. Chloride of chromium, Cr 2 C1 3 9HO. 240-0. Eecently employed as a pigment. When heated strongly a residue of oxide is left. It behaves in other respects like the oxide. Sulphate of chromium, Cr^Og, 3S0 3 . 173-4. Used in the preparation of green ink. It may be tested like other compounds of chromium, and the ink made with it may be distinguished from green ink made with acetate of copper by the addition of ammonia in excess, which gives the characteristic blue solution in the latter case, and in the former a greyish green precipitate of hydrated oxide of chromium, Chromate of potash, KO,Cr0 3 . 97-9. Opaque yellow crystals, perfectly soluble in two parts of water at 60 E. ; insoluble in alcohol. 106 METALS, ETC. Bichromate of potash, KO, 2Cr0 3 . 148-6. Deep red crystals, perfectly soluble in ten parts of water at 60 P., insoluble in alcohol. The probable impurities- in this and the previous salt are, Sulphate of potash, indicated by a precipitate with chloride of barium in the presence of free nitric acid. The amount x may be calculated from the quantity of sulphate of baryta a found : x : a = KO,S0 3 : BaO,SO 3 = 87'2 : 116'5 Chloride of potassium, indicated by a precipitate with nitrate of silver in the presence of free nitric acid, and may be estimated from the (Ag Cl) found. Nitrate of potash may be detected by distilling the salt with sulphuric acid, and testing the distillate for nitric acid. Alumina may be detected by reducing the acid to the state of oxide by boiling with alcohol and hydrochloric acid, then boiling the green liquid with an excess of caustic soda, and testing for alumina in the filtrate with chloride of am- monium. Chromates of lead, PbO,Cr0 3 , 1224, and 2PbO,Cr0 3 . 274-1. The former salt is pale yellow, the latter red. The pure salts are perfectly soluble in nitric acid. The substances met with in commerce under the names of chrome-yellow and chrome-red consist essentially of these salts in various pro- portions, and sometimes mixed with a variety of other sub- stances, the most usual being Sulphates of lime, lead, baryta remain undissolved by nitric acid (the two former for the most part). The residue may be examined further, as directed in Chapter X. Carbonate of lime is indicated by effervescence with acids, and the lime may be tested for after reducing the chromic acid and removing the oxide from solution. Chromate of zinc, ZnO,Cr0 3 . 91-3. A yellow powder, insoluble in water, liable to contain the same admixtures as the lead salts, and may be tested in a similar manner. The distinctive character of chromium (as a base) com- pounds in solution is the formation with caustic potash of a bluish-green precipitate, Cr 3 3 ,HO, soluble in an excess of CHROMIUM. 107 the reagent, forming a green liquid, from which the oxide may be again precipitated by boiling with chloride of ammonium. The red or yellow colour of all chromates is to some extent indicative of chromium existing in the state of acid, and the change to green by boiling with hydrochloric acid and alcohol, furnishes a satisfactory confirmation. The estimation of chromium, when in the state of chromic acid, may be effected very easily, in virtue of the readiness with which it gives up oxygen to some other substances. The reaction with protochloride of iron in the presence of hydrochloric acid, 6FeCl + 2Cr0 3 + 6HC1 = 3Fe 2 C1 3 + Cr 2 C1 3 + 6HO, is well suited to this purpose. The amount of chromic acid x is calculated from the quantity of iron F converted into perchloride,' and this is found by estimating, as described at p. 126, how much of a known quantity of iron used remains in the state of protochloride; then x : F = Cr : Fe 3 . Ci)e quantity of material to be operated upon in order to obtain direct per-centage results is according to the sub- stance sought for. grin. Chromium Cr 0'560 Oxide of chromium Cr 2 3 O800 Chromic acid Cr0 3 T040 Ci)C ifpmnunt is made by dissolving 1'68 grm. of clean iron wire in 20 or 30 cubic centimeters of hydrochloric acid, and adding the substance in which chromium (in the state of chromic acid) is to be estimated. The liquid immediately acquires a deep green colour and, when a sufficient excess of hyarochloric acid is present, remains clear. When too, little acid is used a precipitate (Cr0 3 + Cr 2 3 ) is formed. Insoluble substances, in which the chromium exists in the state of oxide, must be subjected to a preliminary treat- ment, for the purpose of converting it into the state of chromic acid. A weighed quantity of the substance in fine powder and well dried is projected in small portions into melted hydrate 108 METALS, ETC. of potash contained in a silver crucible, and when the whole is well mixed, small fragments of fused chlorate of potash (KO,C10 3 ) are added from time to time, so that there may be no loss from effervescence. The mass gradually becomes yellow, and finally trans- parent ; it is then allowed to cool, placed in a beaker with water, and, when dissolved, the crucible removed; hydro- chloric or sulphuric acid is then added to the cold liquid until it becomes orange-coloured. When hydrochloric acid is added to the liquid while hot, an error would be caused by the reduction of chromic acid. The end of the reaction between the residual protochloride of iron and the normal solution of permanganate is not at all disguised by the green colour of the liquid. Zinc and its compounds. Sulphate of zinc, ZnO,S0 3 HO, + 6 aq. 143-6. The pure salt forms transparent colourless crystals, readily and perfectly soluble in two or three times their weight of water at 60 F. Of the usual impurities the most im- portant is Iron, indicated on the addition of ammonia by a brown precipitate insoluble in an excess of the reagent. Adulteration is not probable except in the insoluble com- pounds. Carbonate of zinc, ZnO, C0 2 . 82-6. The native carbonate, known under the name of calamine, is the chief source of zinc and its compounds. When puri- fied by washing, it is used in medicine, and likewise the pre- cipitated salt 2ZnO,CO 2 + 3ZnO,HO. Oxide of zinc, ZnO. 40-6 Is used as a substitute for carbonate of lead as a pigment, and is sometimes adulterated with Sulphates of baryta and lime, clay, chalk, fyc. The former may be detected by their insolubility ; the latter by effer- vescence with acids. The distinctive character of zinc compounds in solution is the formation with sulphuret of ammonium of a white gela- tinous precipitate ZnS, insoluble in excess of the reagent and in potash. ZINC. 109 In the estimation of zinc it is always weighed in the form of oxide, which is obtained by igniting the precipitate of carbonate or sulphuret ; but, as there is a liability to error by this method, unless greater precautions are taken than would be consistent with the object of the experiment in most instances, it is better to have recourse to the volu- metrical method, based upon the reaction between sulphuret of zinc and perchloride of iron : ZnS + Fe 2 C1 3 = Zn 01 + 2Fe Cl + S. Any of the compounds, ores, or alloys of zinc may be examined by this method. The zinc is converted into the state of sulphuret, and the direct experimental result is the quantity of iron /"reduced to the state of protochloride, while the quantity of zinc x which it represents is found by the proportion x :/= Zn : Fe 2 . "When the quantity of substance qr represented by the sulphuret of zinc operated upon is known, the per-centage x* of zinc, or of its compound sought, may be calculated ; for x 1 : 100 = a; : q. "When q = 1*6 grm. and the solution of permanganate is of the usual normal value (p. 123), the number of cubic centi- meters requisite to perchloridize the iron reduced by the sulphuret of zinc gives at once the per-centage of zinc in the substance examined. cork with the flask 5, containing sul- phuric acid, and the whole weighed. The tube c is then closed, and some of the acid transferred to a by sucking out air at/! When the reaction has subsided, a second portion of acid is transferred to a, and this is repeated until carbonic acid is no longer gene- rated, and no particles of manganese remain undecomposed. When it is ascertained that there is an excess of sulphuric acid in a, the cork is re- moved from c, carbonic acid completely displaced from both the flasks, by drawing air through them, and the apparatus again weighed. The loss of weight represents carbonic acid, and the result is calculated as above. When, as is not unfrequently the case, manganese con- tains an admixture of carbonates, the oxalic process would give a deceptive result, if this source of error were not removed, for their carbonic acid would be disengaged together with that generated from the oxalic acid. The presence of carbonates in the manganese is easily detected by the effervescence which occurs when a fragment is moistened with an acid. In order, therefore, to remove this source of error, in the valuation of manganese containing carbonates, the weighed quantity of substance must be treated in the flask a with an excess of dilute nitric acid. The clear liquid is drawn off with a siphon, the manganese washed several times with water, and the valuation experiment then made as above. b. Sulphurous acid process. When chlorine is brought in contact with a solution of sulphurous acid, an equivalent quantity of sulphuric acid is produced. S0 2 + Cl + HO = S0 3 + HC1. A solution of sulphurous acid, when kept for any time, always becomes more or less oxidized, and as the accuracy of the result furnished by this process depends upon the MANGANESE. 115 absence of sulphuric acid, it is advisable to conduct the operation in the following manner. The flask A is half-filled with water freed from air by boiling, and a certain quantity of chloride of barium added. A current of hydrogen, generated in the vessel B, is the*, passed through the water until it becomes cold. Fig. 42. The air having been displaced from the flask A, sulphurous acid is generated by heating a mixture of sulphuric acid and copper in the flask C. This gas is washed in the small bottle D, containing water. Lastly, the weighed quantity of man- ganese is rapidly introduced into the flask E, containing hy- drochloric acid. The chlorine here generated passes into A, where an equivalent quantity of sulphuric acid is formed. "When the whole of the chlorine has passed over, the liquid in A is boiled to expel the excess of sulphurous acid, oxida- tion of which meanwhile is prevented by keeping up the current of hydrogen. The sulphate of baryta is then collected on a filter, weighed, and the result calculated according to the above equation. The binoxide of manganese (pyrolusite) is sometimes ac- companied by other oxides of manganese, or by substances which consume hydrochloric acid without generating chlorine. In order therefore to estimate completely the value of a sample of manganese, it is not alone sufficient to ascertain the quantity of chlorine it is capable of liberating, but the quantity of acid consumed must likewise be taken into account. i2 116 METALS, ETC. The substances which are likely to be present in manganese and cause a larger consumption of acid, are earthy carbonates, oxide of iron, and likewise some other oxides of manganese. The former act simply by neutralizing a portion of the acid, and the sesquioxide of manganese has to a certain extent the same influence. Thus : Mn0 2 + 2HC1 = MnCl + 2HO + Cl. MD^ + 3HC1 = 2MnCl + 3HO + Cl. It is therefore evident, that to produce a given quantity of chlorine, there is required not only more sesquioxide than binoxide, but also more hydrochloric acid. The estimation of the quantity of acid required is con- ducted as follows : 4'36 grms. of the manganese, in fine powder, are mixed in a glass flask with 40 grms. of hydrochloric acid (1*09 sp. gr. or 18*2 per cent. HC1), and one end of a bent tube fitted by means of a cork into the neck of the flask, while the other is inserted into a wet flask, so that any hydrochloric acid that distils over may be condensed. The evolution of chlorine is then facilitated by heat, and when at an end, the liquid is diluted and the quantity of acid remaining ascertained, either by means of a normal solution of alkali, or by the following method. Some pieces of marble, of known weight, are dropped into the liquid, and when, after the application of a gentle heat, there is no further evolution of carbonic acid, the pieces of marble are taken out, washed, dried, and weighed. The quantity of acid taken for the experiment, less that neutra- lized by the marble, or indicated by the volumetrical experi- ment, gives the quantity consumed in generating chlorine. The quantity for 4*36 grms. of substance would be 7*30 grms. for MnO 2 , and 6*00 grms. Mn 2 3 . If in an experiment the quantity of hydrochloric acid taken represents 7*30 grms. HC1, and the remainder is estimated at 0*73 grm., the quantity consumed in generating chlorine will be 7-30 - 0'73 = 6'57. Supposing that in a previous experiment 4'36 grms. of the manganese have been found to generate with hydrochloric acid 2' 6 grms. of chlorine, then as the HC1 consumed in generating chlorine by means of Mn0 2 should bear the same 117 proportion to the quantity of chlorine liberated, as 73 : 35'5, the acid x, consumed in generating 2'6 grms. of chlorine, should be x : 2-6 = 73 : 35'5 (x = 5'34 grms.). But in the above experiment it was found to be 6*57 grms., consequently T23 grm. were consumed by impurities, and for generating a given quantity of chlorine with such man- ganese, 25 per cent, more hydrochloric acid would be required than with pure binoxide. Iron and its compounds. Sulphate of iron, FeO, So 3 + 7HO. 139. Transparent crystals of a uniform pale green colour, with- out white or brown spots or incrustation, perfectly soluble in water, and when dried at 212 F. loses 44 per cent, of water. The probable impurities are, Copper, indicated by the blue colour of the liquid remain- ing after the addition of ammonia, in excess, to the solution ; and by a red metallic coating upon a piece of bright iron dipped into the solution. Per salts of iron, indicated, on the addition of ammonia, by a brown or dark green colour of the precipitate, which should be dirty white. Zinc, indicated by the formation of a white precipitate on evaporating the nitrate after precipitation with ammonia. Alumina, and also zinc, are indicated, when the solution is mixed with excess of caustic soda, the nitrate neutralized with acid and treated with carbonate of soda, by a white gelatinous precipitate. Persulphate of iron, Fe 2 3 , 3S0 3 . 200. The dry, neutral salt is white, dissolves in water, slowly but completely, with a reddish-brown colour. Ferricyanide of potassium should not give a blue colour with it. As this salt is mostly prepared from protosulphate, it may contain the same impurities, and is to be tested in the same manner. Nitric acid is indicated by the decoloration of a drop of indigo solution when heated with a solution of the salt. Pernitrate of iron, Fe 2 3 , 3N0 5 . 240. Occurs in commerce in solution. It should not contain 118 METALS, ETC. any considerable excess of nitric acid; this may be ascer- tained by digesting the solution with clean iron filings in a warm place; no evolution of red nitrous vapour should appear, and when the dilute solution is boiled, a basic salt should be precipitated. Sulphuric acid should be tested for, because sulphate of iron, treated with nitric acid, is sometimes fraudulently sub- stituted for this salt. Acetates of iron, FeO,A. 87, and Fe 2 3 3A. 233. For most purposes the protacetate is required, but per- acetate is always present. The proportion of each may be ascertained by one of the processes described at p. 125. Protochloride, Fed. 63-5, and Perchloride of iron,Fe,Cl 3 .162-5. The former salt should not give a blue precipitate with ferrocyanide of potassium, indicative of persalt. The latter should not contain nitric acid, or give a blue precipitate with ferricyanide of potassium. Ferrocyanide of potassium, K 2 Cfy.l844. K.Cfy + 3HO. 211-4. Yellow semitransparent crystals. The probable impurities are, Alkaline carbonates, indicated by effervescence when a crystal is dipped into hydrochloric acid. Sulphates, -indicated by a precipitate with chloride of ba- rium in the presence of free acid. Alkaline chlorides, in small proportion, are generally pre- sent in ferrocyanide of potassium, and must be considered as an adulteration only when the quantity is large. They may be detected and, if required, estimated by treating a known quantity of the substance with two or three times a# much nitrate of potash and ten times as much carbonate of soda, igniting the mixture, and testing the filtered solution, to which a slight excess of nitric acid has been added, with nitrate of silver. Valuation of ferrocyanide of potassium. The reaction between this compound and persalts of iron may be applied to this purpose. 3(K 2 Cfy) 4- 2(Fe 2 3 ,3S0 3 ) = Fe 4 Cfy 3 + 6KO,SO 3 . Cfye test tfolutum is prepared by treating a hot solution of IBOtf. 119 87'67 grms. of pure crystallized sulphate of iron with nitric acid, added in small quantities until red vapours are no longer generated and the liquid ceases to give a blue colour with ferricyanide of potassium. It is then diluted with water to the volume of one litre. 100 cubic centimeters of this solu- tion are equivalent to 10 grms. of ferrocyanide. The test solution may likewise be prepared by estimating the quantity of iron in 100 cubic centimeters of a moderately dilute solution of a persalt of iron, and thence calculating the quantity of substance to be taken for an experiment as the equivalent weight of ferrocyanide. CI)e quantity of material for an experiment is 10 grms., which is dissolved in water and slightly acidulated with hydro- chloric acid. A correction of the results obtained by this process is necessary, on account of the mechanical abstraction of a portion of the ferrocyanide from solution by the preci- pitate formed. This, under the conditions of the experiment, amounts to about -^th of the ferrocyanide present, so that if with 10 grms. of substance, the reaction is completed by 60 cubic centimeters of test solution, it would contain 63 instead of 60 per cent, of ferrocyanide of potassium. Cfye experiment is made in the usual manner with a burette, but as the precipitate of prussian blue remains for a long time suspended in the liquid, communicating to it an intense blue colour, a special contrivance for ascertaining the end of the reaction is necessary. This consists in allowing a drop of the liquid, coloured by the suspended precipitate, to fall upon a piece of white bibulous paper, and touching the moist ring, which is formed round the spot where the drop fell, with a glass rod moistened with an appropriate reagent. A blue colour will then be produced, before the end of the reaction, by a persalt of iron, and after it by ferrocyanide of potassium. It must be remembered, 1st, that the colour is not pro- duced at the outer edge of the moist ring, but more towards the centre ; and, 2nd, that it does not become visible until after a few moments. The presence of sulphocyanides does not invalidate the result, because sulphocyanide of iron is not precipitated until all the ferrocyanide is removed from solution. 120 METALS, ETC, Ferricyanide of potassium, K 3 Cfy 2 . 329-6 (red prussiate). The pure salt forms transparent, columnar crystals of a ruby colour, soluble in 3'8 parts of water and in less alcohol. The solution of this salt, and the pulverulent material sold for dyeing purposes, are more liable to contain admixtures, and require valuation on account of the possible variation in the amount of red prussiate they contain. As ferricyanide of potassium may be converted into ferro- cyanide by reducing agents, the process already described for the estimation of ferrocyanide may likewise be applied to this salt. For this purpose the substance in solution is boiled with a few grammes of sulphite of soda and a little caustic potash. Generally there is not any precipitate, but when there is, it must be separated by filtration. The solution of ferro- cyanide thus obtained is then acidified, the normal solution of persalt of iron added from the volumeter, and the experi- ment conducted in the manner already described, p. 119. Cfye quantity of material to be operated upon in order to obtain a result expressing the per-centage of red prussiate, is 7'99 grms., or some multiple of it. The amount of ferri- cyanide x' may in any instance be calculated from the quantity of ferrocyanide #, indicated by the volume of test solution re- quired to complete the reaction, by means of the proportion : of : x = K 3 Cfy 2 : 2K 2 Cfy. The reduction of ferricyanide of potassium into ferro- cyanide may be effected by iron and caustic potash, but even then filtration is necessary, The reaction between ferricyanide of potassium and sul- phide of sodium, K s Cfy, + NaS = 25Cfy + S, would furnish a direct indication of the amount of the salt, but as sulphide of sodium is not a very stable compound, sulpharsenate of sodium (3NaS, AsS 5 + 15 aq.) has been sub- stituted for it. To obtain the desired reaction with this salt, it is requisite that the solution of ferricyanide should be alkaline : GK 3 Cfy 2 + 3]S T aS,AsS 5 + 3NaO = ^[Cfy + As0 5 . IEON. 121 The point at which the reaction ends is indicated by the addition of a drop of cochineal decoction, which is imme- diately bleached so long as a trace of ferricyanide remains in solution. The reagent is prepared by dissolving pentasulphide of arsenic in solution of sulphide of sodium. The crystals formed on evaporation are pressed between bibulous paper, dried at 212 E., and preserved in a well-stopped bottle. Cf)e experiment is made with 5 grins, of the red prussiate and 1 grm. of the sulpharsenate, dissolved with 3 grms. of carbonate of soda, in water to the volume of 100 cubic centimeters. Each cubic centimeter is then equivalent to O'l grm. of red prussiate. At the ordinary temperature the presence of carbonate of soda does not effect the decomposition of ferricyanide with sufficient rapidity to influence the results, but it is probable that the whole method is too operose to answer the require- ments of technical analysis. The reaction between ferricyanide and protochloride of tin in the presence of hydrochloric acid may be applied to the valuation of this substance. It is : 2(K 3 Cfy 2 ) + 2HCl + 2SnCl= 3(K 2 Cfy) + H 2 Cfy + 2(SnCl 2 ). The end of the reaction is indicated by the transition from the green colour, at first assumed, to a distinct violet or blue. Ferrocyanide of iron, Fe 4 Cfy 3 . This substance, in a pure state, is a compact, amorphous mass of an intense blue colour. The fracture is conchoidal, and when rubbed assumes a copper lustre. It occurs in commerce in various states of purity, and under the names of Chinese, Paris, and Prussian blue. The substances with which it is usually mixed are alumina, oxide of zinc, clay, chalk, and gypsum. Most of them may be detected by treating the material, in fine powder, with a little hydrochloric acid, by which they are dissolved. Their farther recognition may be effected in the filtered liquid by means of the usual tests. Oxide of zinc may be detected by digesting a portion of the material with caustic soda, and testing the filtrate with sulphide of ammonium. Sulphate of baryta or gypsum may be detected, after igniting the powdered material together with a small quantity of 122 METALS, ETC. sugar, by treating the residue with hydrochloric acid, when sulphuretted hydrogen is evolved, and baryta or lime may be tested for in the solution. Starch is indicated when the material is boiled with a little water, by the formation of a gelatinous mass, which again becomes liquid when boiled with a few drops of sulphuric acid. Valuation of pigments containing prussian Hue. A. number of blue pigments, occurring in commerce, con- sist of prussian blue mixed with a variable proportion of some white powder. Some green pigments likewise consist of prussian blue and chrome-yellow, frequently with a white powder, or a yellow inorganic substance. A simple method of determining the quantity of prussian blue in such pig- ments would often be serviceable, and as prussian blue may readily be converted into ferrocyanide of potassium, the above method may be applied for this purpose. The experi- ment is conducted as follows : In order that the test liquid prepared as above may be used, 6'790 grms. of the pigment to be examined is weighed, boiled with caustic potash until the blue or green colour is destroyed, the liquid filtered, the residue well washed with hot water, and the filtrate containing ferrocyanide 'of potas- sium treated in the manner already described. As in this case there is no sulphocyanide of potassium present, the addition of the test solution of iron and the testing of the liquid on paper with a persalt of iron may be continued until the reaction with the latter ceases. If it so happens that the blue precipitate does not settle readily upon the paper, but spreads out over the moist ring, this inconvenience may be prevented by the addition of some solution of chloride of sodium, or any other indifferent salt. This spreading of the colour is owing to the formation of a little prussian blue that is soluble in water, though not in a strong saline solution. The distinctive character of iron compounds in solution is the formation with ferrocyanide or ferricyanide of potassium of blue precipitates ; the former reaction being indicative of persalts, the latter of protosalts. Volumetrical estimation of iron. All the processes by which this is effected are based upon the conversion of protochloride of iron, Fed, into per- 123 chloride, Fe 2 Cl 3 , and the ease with which iron in solution may, for the purpose of estimation, be reduced to the state of protochloride. The reagents used for the estimation of iron by this method are various ; with permanganate of potash the re- action is represented by the equation : lOEeCl + 7HC1 + Mn 2 O 7 = 5Ee 2 Cl 3 + 2MnCl + 7HO. Ci)e normal Solution is prepared by estimating the volume- trical value of a solution containing about the proper pro- portion by a direct experiment with pure iron. For this purpose 1*4 grm. of clean iron wire is dissolved in a flask by 25 cubic centimeters of pure hydrochloric acid, diluted with water. It is not necessary that the water should be boiled free from air, nor is there any danger of the iron passing into the state of perchloride in the presence of the excess of acid used. The pale green solution is diluted with thirty times its volume of water, and when quite cold, the solution of per- manganate gradually added from a burette, the mixture being well agitated after each addition. As soon as the iron is con- verted into perchloride, a single drop of permanganate is sufficient to give to the liquid a very decided red colour, which indicates the end of the reaction. The number of cubic centimeters used is then observed, and water added to the permanganate in such proportion as to make 100 cubic centimeters represent 2*8 grms. of iron. Thus if 1'4 grm. of pure iron requires 40 cubic centimeters, the solution must be diluted with ^ its volume of water to bring it to the normal value. A cubic centimeter of this solution is equivalent to 0*028 grm. of iron, and the amount of iron a? in a solution may be ascertained by multiplying the number of cubic centi- meters O n required for its conversion into persalts by this number, x = C n x 0-028. When the quantity q of material represented by x is known, the per-centage of iron x 1 may be found by the pro- portion : x< : 100 = X : q. If % corresponds with the equivalent of iron, or of the 124 METALS, ETC. compound of iron sought, the number of cubic centimeters of normal solution used expresses at once their per-centage. (Ohiantttg of material. The numbers below indicate the quantities *fco be taken in order to find the per-centage of iron or the compounds sought : Iron Fe 2'8. Oxide of iron FeO* 3'6. Peroxide of iron Fe 2 O 3 4 - 0. Sulphate of iron FeO,S0 3 + 7HO 13'9. The iron solution must be dilute and cold before the per- manganate is added, because otherwise an error woulcl be caused by the evolution of chlorine, owing to a reaction re- presented by the equation : Mn 2 7 + 7HC1 = 5C1 + 2MnCl + 7HO. Crpmnunt The first step is to obtain a solution of the iron in the state of protochloride. The assay mass is introduced into a flask, and boiled with concentrated hydrochloric acid until the whole is dissolved, or the residue of silica, clay, &c. has a pure white colour. Metallic iron is weighed in the form of turnings ; most ores require to be powdered. The solution is generally effected very readily, but when this is not the case a few drops of nitric acid must be added. The perchloride of iron thus formed, or arising from the presence of peroxide in the ore or other substance examined, must, of course, be reduced before adding the normal solution. The reduction of perchloride may be best effected by heating the iron solution with metallic zinc, Fe 2 Cl 3 + Zn = 2FeCl + ZnCl. For this purpose the zinc, which must of course be per- fectly free from iron, is cast in the form of a ball upon a thin platinum wire. The reduction may likewise be effected by boiling the iron solution with 4 or 5 grms. of crystallized sulphite of soda, but the time occupied in separating the excess of sulphurous acid renders this method inferior to the former, which, more- over, presents the additional advantage of ensuring the sepa- ration of any traces of copper or arsenic. The occurrence of these metals in iron ores is not unfrequent, and as they 125 resemble protosalts of iron in their behaviour with perman- ganic acid, their presence in the chloride solution would lead to inaccurate results. Besides copper and arsenic, none of the other metals which usually occur in iron ore have any prejudicial influence upon the experimental results obtained by this method. When cast iron is dissolved in hydrochloric acid, it fre- quently happens that some oily or carbonaceous substance is separated, and as this would reduce a certain amount of permanganate, the chloride of iron must in such cases be evaporated to dryness, ignited with chlorate of potash, re- dissolved in hydrochloric acid, and then reduced by zinc. Care must always be taken to prevent the introduction of any organic substance into the iron solution. When the whole of the iron in the solution has been re- duced to the state of protochloride, it is considerably diluted with water and the normal solution of permanganate added from a burette, in the same manner as described for the valuation of the latter by means of pure iron. It may sometimes be desirable, as for instance in the case of iron ores, to ascertain the relative quantities of iron pre- sent in the state of proto- and peroxide. For this purpose two experiments must be made ; one, with the simple solution of the substance in hydrochloric acid, gives the quantity of protoxide ; a second, with the chloride solution, previously reduced by zinc, gives the total amount of iron, and the difference between the two, the quantity of peroxide. The solution of permanganate decomposes gradually, and when kept for any time its value is consequently reduced, so that before using it, a preliminary experiment with iron wire must always be made, and, if necessary, valuation results corrected. Thus, if T4 grm. of iron require 51/3 instead of 50 cubic centimeters of solution, a corresponding deduction from the result of each experiment must be made. The mutual convertibility of proto- and perchloride of iron by oxidizing or reducing substances is frequently applicable to purposes of valuation. Thus the amount of any reducing substance, which has a definite reaction with perchloride of iron, may be indirectly estimated according to the equation representing the reaction from the quantity of protochloride formed, this being ascertained by means of the normal solu- 126 METALS, ETC. tion of permanganate. Let x be the substance sought, /the iron converted by it into protochloride, A and B their pro- portions in the reaction, the amount of x may be found by the proportion : at :/= A : B. The amount of any oxidizing substance #' which has a definite reaction with protochloride of iron may be found in a similar manner by operating with a known quantity of iron (2 '8 equivalent to 100 cubic centimeters of permanganate solution) in the state of protochloride, and estimating how much iron / remains in that state after the reaction. The quantity of iron F converted into perchloride will then be : F = 2'8 - /, and of : F = A : B. Such a general applicability of a volumetrical reagent con- siderably enhances its practical value. The substances to which it may be applied, and the equations by which their amount is found, are as follows : Nitric acid # : F = NO 5 Chromic acid # : F = CrO 3 Binoxide of manganese x : F = Mn0 3 Zinc x : f == Zn Copper x \ f = Cu Copper #:/ = Lead. . x : F = Pb Fe 3 . Fe. gi- st Iodine # : F = I The reaction between protosalts of iron and chromic acid, GFeCl + 6HC1 + 2Cr0 3 = 3Fe 3 Cl 3 + Cr 2 Cl 3 + 6110, may be taken advantage of for the volumetrical estimation of iron. The normal solution is made by dissolving bichromate of potash in water, in such proportion that 100 cubic centi- meters contain 1*477 grm. The substance to be examined is dissolved, if necessary, in hydrochloric acid, the iron reduced to the state of proto- salt by means of zinc, and the normal solution added from the volumeter. The end of the reaction is ascertained by means of a solu- tion of ferricyanide of potassium, several drops of which are placed on a white porcelain slab, and when a drop of the URANIUM AND COBALT. 127 liquid ceases to give a blue colour with this reagent, the whole of the iron is converted into persalt. This process is inferior to that with permanganate. Uranium compounds. Oxide of uranium, U 2 3 . This substance, in the anhydrous state, is a brick-red powder : the hydrate is yellow. It is used in enamel painting and for colouring glass. The impure native oxide, known as pechuran or pitch- blende, is the principal source of uranium compounds. Nitrate of uranium, U 2 3 N0 5 + 6HO. This is the only salt met with in commerce ; it is in pale yellow crystals, very soluble in water. The distinctive character of uranium compounds in solu- tion is the formation of a yellow precipitate with caustic potash. Cobalt compounds. The most important application of cobalt is the prepara- tion of blue pigments. The substances met with in com- merce for this purpose are cobalt ore in various states, either raw, or, when roasted, under the name of zaffre and smalt, which is a glass coloured with cobalt. The ores in their native state contain sulphur, and the roasted as well as the raw ores, arsenic, iron, copper, lead, and bismuth. The following process may be adopted for the analysis and valuation of these substances, A weighed quantity, reduced to very fine powder, mixed with two parts nitrate of potash and two parts anhydrous carbonate of soda, is gradually heated in a platinum or porcelain crucible until the whole is in quiet fusion. The cooled mass is then treated with warm water, which dis- solves alkaline sulphate and arsenate, to some extent also, silicate. The solution is separated by filtration, and, if ne- cessary, preserved for the estimation of sulphur and arsenic. The insoluble portion is treated with hydrochloric acid, the solution evaporated to dryness at 212 F., dilute hydro- chloric acid added, and the insoluble residue, consisting of silica and sand, collected on a filter. 128 METALS, ETC. The filtrate containing the cobalt together with other metals is treated with sulphuretted hydrogen until no further precipitate is formed, the sulphuret precipitate se- parated by nitration, and, if desirable, examined as directed in Chapter X. The filtrate, then containing only cobalt, nickel, and iron, is carefully mixed with a solution of carbonate of soda till nearly neutralized, acetate of soda added, and the whole boiled. By this means the iron is separated. For the separation of the nickel and cobalt, they are both precipi- tated as carbonates by adding an excess of carbonate of soda ; the precipitate collected on a filter, washed, and treated with a solution of oxalic acid. The oxalates of cobalt and nickel are then dissolved in solution of ammonia, and the liquid left for some days in an open porcelain basin, when, by the evaporation of ammonia, the nickel salt is gradually deposited. The cobalt solution is then poured off, evaporated to dryness in a small crucible, and the residue ignited and weighed. The distinctive character of cobalt compounds is the fine blue colour which they communicate to borax when fused with it. Their colour is likewise characteristic in most in- stances. Nickel and its compounds. The native arsenide of nickel and the spiess obtained in the preparation of smalt are the chief sources from which nickel is procured. These may be analysed in the same manner as cobalt ores. The compounds of nickel are not employed in the arts, but the metal, alloyed with others, is largely used as a sub- stitute for silver. The distinctive characters of nickel compounds in solution are, the production with caustic potash of a pale green pre- cipitate (NiO,HO), insoluble in excess of the reagent, and the production of a greenish-white precipitate with ferro- cyanide of potassium. Nickel may be estimated volumetrically by means of the reaction between the peroxide and protochloride of tin, Ni 2 O 3 + SnCl = Ni 2 Cl 2 + SnCLj, the equivalent of tin in each experiment being estimated according to the method described at p. 134. ABSENIC. 129 For this purpose the compound, dissolved in acid, is treated with potash and hypochlorite of lime, and the oxide formed (Ni 2 O 3 ), collected on a filter, and reduced with the solution of protochloride of tin. The quantity of substance to be taken for the experiment is 5 "92 grms., or a fraction of that quantity, and the amount of nickel x is calculated by the proportion, x : Sn = Ni a : Sn. Compounds of arsenic. Arsenious acid, As0 3 . 99. Occurs in the form of a brittle colourless mass, or as a white powder. It is sparingly soluble in water, more soluble in dilute hydrochloric acid. The probable impurities are, Sulphates of baryta or lime, which are indicated, when the acid is sublimed in a test tube, by a fixed residue, which may be further tested in the usual manner. Arsenate of potash, KO(HO) 2 ,As0 5 . Should be readily and perfectly soluble in water ; nitric or hydrochloric acid should not cause a precipitate. Nitrate of potash may be detected by testing with solution of indigo and sulphuric acid. Tersulphuret of arsenic, AsS 3 . 123. Known under the name of orpiment. The usual impuri- ties are, Arsenious acid, detected by boiling with dilute hydro- chloric acid, and testing the liquid with sulphuretted hy- drogen. Sand, clay, chalk, fyc., remain undissolved by caustic soda. Bisulplmret of arsenic, AsS 2 . 147. Should be perfectly volatilizable. The distinctive characteristic of arsenic compounds is, that when heated with soda upon charcoal in the blowpipe flame, they evolve a peculiar alliaceous odour. Arsenic may like- wise be tested for in solution by sulphuretted hydrogen, and the yellow precipitate examined as above for confirmation. For the detection of minute quantities of arsenic, Marsh's test may be applied. It is based upon the conversion of arseniuretted hydrogen into arsenious acid when burnt, or, K 130 METALS, ETC. under certain conditions, the separation of metallic arsenic from the burning gas. Metallic zinc and dilute sulphuric acid are mixed in a small glass flask, furnished with a long bent tube, drawn out to a capillary opening at one end, and fitted into the flask by a cork. After the generation of hydrogen has continued for some minutes, the substance to be examined for arsenic is introduced, and the cork fitted tightly in. The gas issuing from the tube is then lighted, and a small porcelain capsule held close over the flame for a few seconds at a time. When arsemc is present, it is deposited upon the porcelain in the form of a black spot with a brilliant metallic lustre, which is dissolved in nitric acid, and the usual tests applied. Or a small beaker may be held over the flame at a greater distance, and then the arsenic is deposited as a sublimate of arsenious acid, which may be dissolved and tested as above. In both cases the arsenic must be in solution in an oxi- dized state. When it is supposed to exist as sulphuret, the substance to be tested should first be melted with carbonate of soda or dissolved in nitric acid. It is, of course, indispensable that both the zinc and sul- phuric acid used should be pure, and, for the sake of cer- tainty, the hydrogen generated should always be lighted and tried with the porcelain capsule, before adding the substance to be tested. It is unfortunate that this test, though capable of in- dicating very minute quantities of arsenic, is to some extent inapplicable when antimony is present, since this substance behaves in a similar manner. When there is reason to suspect the presence of antimony, the metallic mirrors on the porcelain should be exposed over a glass containing sticks of phosphorus, partly immersed in water ; the arsenical spots then disappear in a few hours, while those produced by an- timony remain much longer unaltered. The analyst should familiarize himself with these reactions by comparative ex- periments. Estimation of arsenic. In the estimation of arsenic in alloys three cases may occur, for each of which a different method must be adopted. 1. When arsenic is to be separated from gold or platinum, ABSENIC AND TIN. 131 the substance is treated either with nitric acid, which dis- solves the arsenic and other metals, or, when tin or antimony is also present, with nitro-hydrochloric acid, the platinum or gold being precipitated as directed at pp. 137, 138. 2. When arsenic is to be separated from silver, mercury, lead, bismuth, zinc, iron, or nickel, the substance in fine powder, or the dry saline residue left on evaporating the solution, from which gold or platinum have been separated, is ignited with twice its weight of carbonate of soda, and two and a half times its weight of nitrate of potash, by which means the arsenic is rendered soluble in water. The solu- tion, when free from antimony or tin, is mixed with some nitric and hydrochloric acids, boiled^ a solution of tartaric acid added in excess, then ammonia and sulphate of magnesia, which precipitate the arsenic acid as arsenate of ammonia and magnesia. The precipitate is collected upon a filter, washed with ammoniacal water, dried at 212 E., and weighed. It contains 41*4 per cent, of arsenic. 3. When arsenic is to be separated from tin or antimony, the substance is treated with nitric acid, excess of which is afterwards removed by evaporation. The dry oxides are then melted with six or eight times their weight of hydrate of soda in a silver crucible, the cooled mass treated with dilute alcohol, which dissolves tin and arsenic. The solution is evaporated to dryness, and treated with water, which dis- solves only arsenic as arsenic acid, which is estimated as arsenate of ammonia and magnesia as above. The results obtained in this manner do not indeed possess extreme accuracy, but they will in most instances be quite adequate to the objects desired, if the manipulation is care- fully conducted. Arsenious acid may be estimated volumetrically by means of a solution of hypochlorite of lime, according to the method described for the valuation of that substance (p. 97). Compounds of tin. Oxide of tin, SnOo. 74-8. This substance is known in commerce under the name of putty powder. It generally contains the impurities found in metallic tin, and is sometimes adulterated with Oxide of lead, detected by its solubility in dilute nitric acid. K2 132 METALS, ETC. Chalk, indicated by effervescence with acids. Sulphates of baryta or lime may be detected by their in- solubility in caustic soda, which dissolves oxide of tin. Chloride of tin, SnCl+2HO. 112-3. Occurs in commerce in a solid form under the name of tin salt. It should be perfectly soluble in water mixed with a little hydrochloric acid or chloride of ammonium. The impurities which are of most consequence are, Copper, lead, zinc, and iron, which may be detected by treating the solution with sulphuret of ammonium contain- ing sulphur, and digesting the precipitate in an excess of the reagent, which dissolves the sulphuret of tin and leaves the other sulphurets in the form of a black residue. Alkaline chlorides, with which the salt is sometimes adul- terated, may be detected by precipitating the tin by sul- phuretted hydrogen and evaporating the nitrate to dryness. In the absence of such substances it should not leave any residue. f Perchloride of tin, SnC^. 129-8. Generally in the liquid state, and may be tested in the same manner as the chloride. Stannate of soda^ NaO,Sn0 2 + 3 aq. 132-8. This salt should be perfectly soluble in water, and on the addition of dilute nitric acid to the solution, a precipitate should be formed at once, without effervescence, which would indicate the presence of carbonate of soda. The distinctive character of tin and most of its compounds is, that when treated with nitric acid, the white insoluble oxide, Sn0 2 , is formed, which, when heated with soda upon charcoal in the blowpipe flame, gives metallic beads without any incrustation (Chap. X.) . Tin compounds in solution give with sulphuretted hydrogen, in the presence of free acid, a brown or yellow precipitate ; the former reaction is indica- tive of protosalts, the latter of the persalts of tin. Estimation of tin. The estimation of tin is frequently effected by means of the insolubility of its oxide (Sn0 2 ) in excess of nitric acid. This compound contains 78'61 per cent, of tin. When the tin is in solution in a state of combination corresponding to TIN". 133 Sn0 2 , it is precipitated by boiling with an excess of carbo- nate of ammonia. Protosalts of tin are to be converted into persalts by previous treatment with chlorine. Metallic sub- stances may be heated with moderately strong nitric acid until the oxidation is complete, and the binoxide collected by nitration, washed and weighed. The details of the pro- cess are given at p. 136. Volumetrical estimation of tin. The process by which this is effected resembles the esti- mation of iron, inasmuch as tin forms with chlorine two com- pounds, SnCl and SnCl 2 , which are mutually convertible. The reagent used for the purpose is bichromate of potash, and the reaction is represented by the equation 3SnCl + 2Cr0 3 + 6HC1 = 3SnCl 2 + Cr 5 Cl 3 '+ 6HO. The point at which the reaction is completed is indicated by the intense blue colour produced by starch and free iodine, and as the liberation of iodine from iodide of potas- sium by bichromate of potash does not take place in the presence of protochloride of tin, a few drops of iodide solu- tion and some starch-paste are mixed with the tin solution before adding the reagent. Cfje normal Solution is made by dissolving 41'6 grms. of bichromate in water to the volume of one litre ; each cubic centimeter will be equivalent to 0*1 grm. of tin, and this quantity multiplied by the number of cubic centimeters (C M ) required to complete the reaction, gives the amount of tin. (uantttp of material. Per-centage results may be ob- tained directly by operating with 5'0 grms, of the substance in which tin is to be estimated. ClBrpmment. For the valuation of protochloride of tin in solution, a known volume may be taken ; of the crystallized salt an average sample is selected, and the weighed quantity dissolved in water with addition of hydrochloric acid ; a little solution of starch and a few drops of iodide of potassium solution are mixed with it, and the normal solution added from the volumeter until the blue colour appears. In the case of alloys and other substances soluble in hydrochloric acid, the solution of the weighed quantity ia boiled with iron wire, by which means perchloride of tin is 134j METALS, ETC. reduced to the state of protochloride,, while arsenic, anti- mony, copper, lead, and mercury are precipitated at the same time in the metallic state. Alloys, &c., insoluble in hydrochloric acid, are dissolved in nitre-hydrochloric acid, and the perchloride of tin reduced by boiling with iron wire. Even the oxide of tin, formed by treat- ment with nitric acid, is dissolved as protochloride by con- tinued digestion with strong hydrochloric acid and iron wire. The protochloride of iron, formed by this treatment, does not affect the reaction of the bichromate with the tin, because it is not converted into perchloride by that reagent in the presence of protochloride of tin. The reaction of protochloride of tin with bichromate of potash, and the powerful as well as definite reducing action of protochloride of tin, renders this process applicable to the indirect estimation of a number of other substances, in a manner similar to that by means of the chloride of iron and the normal solution of permanganate. The general principle of these indirect estimations is essentially the same as that involved in the permanganate process ; the material in which some substance is to be esti- mated is treated with a known quantity Q of protochloride of tin in excess, and the quantity of tin, T, converted into perchloride, ascertained by estimating, with the normal solu- tion of bichromate, the quantity of tin t still remaining in the state of protochloride ; then, T = Q - t. The amount of the substance sought is then calculated by means of the equation representing the reaction for the particular case. The details of the experiments, and the formulae for cal- culating the results-,, are given under the head of the sub- stances that may be estimated in this manner. The substances to which this process is applicable are enumerated below, together with the equations by which their amount is found. Chromic acid x : T = 2Cr0 3 : Sn 3 . Oxide of manganese .... x : T = Mn0 2 : Sn. Ferricyanide of potassium x \ T = (K 3 Cfy 2 ) : Sn. Nickel. , . x : T = Ni, : Sn. ANTIMONY. 133 Tin x Copper x Lead x Mercury < Chlorine x Iodine . . . x Sn 3 Cu 6 Pb Hg = I Cr 2 . Cr, Sn. Sn. Sn, Sn. Sn. Antimony and its compounds. Sulphuret of antimony, SbS 3 . 177. Known in commerce under the name of crude antimony. It is a dark gray mass with a radiated crystalline structure, yielding a blackish-brown powder, and easily fusible (thus distinguished from manganese). It should be perfectly so- luble in hydrochloric acid, and the solution should not be- come turbid on cooling (indicative of lead). When melted with four times its weight of nitrate of potash, it should yield a white mass ; iron or lead are indicated by a yellow colour of this mass. Arsenic is frequently present, and is to be tested for by fusion with soda upon charcoal by means of the blowpipe, when the characteristic garlic odour is evolved. See p. 129. Chloride of antimony, SbCl 3 . 235-5. The pure salt is white and semi-solid, but it is generally met with in commerce as an acid, oily solution, sometimes of a dark brown colour, under the name of butter of antimony. Its density varies from 1*2 to 1'5. With water it gives a copious white precipitate. The distinctive character of antimony compounds in solu- tion is the formation, with sulphuretted hydrogen in the presence of free acid, of an orange precipitate, SbS 3 , soluble in sulphuret of ammonium. When oxidized by means of strong nitric acid, antimony, like tin, gives a white insoluble residue, which may, however, be distinguished from the bin- oxide of tin by its giving brittle globules and a white in- crustation when fused with carbonate of soda on charcoal in the reducing blowpipe flame. Estimation of antimony. In the case of soluble compounds corresponding to the teroxide (Sb0 3 ), this metal may be estimated as sulphide, by 136 METALS,. ETC. treating the acid solution with sulphuretted hydrogen and weighing the precipitate (SbS 3 ), dried at 212 F. In the case of compounds corresponding to the higher oxide (Sb0 5 ), it may be estimated as antimonious acid by evaporating the solution to dryness with a large excess of nitric acid, and weighing the ignited residue (Sb0 4 ). The method of estimating antimony in alloys varies accord- ing to their composition : 1. When the alloy is free from tin, a weighed quantity is heated with nitric acid until the whole of the metal is oxi- dized, and the excess of acid evaporated off. The dry residue is ignited, digested with very dilute nitric acid, collected on a filter, washed, and weighed as antimonious acid, containing 80' 1 per cent, of the metal. 2. When the alloy contains tin, but no other metals, it is dissolved in hydrochloric acid by means of the gradual addi- tion of nitric acid, the diluted solution digested at a moderate heat with a strip of clean pure tin, and hydrochloric acid added from time to time. The antimony is thus precipitated, after a time perfectly, as a black powder, which is collected upon a weighed filter, washed, dried, and weighed. 3. When the alloy contains, besides antimony and tin, other metals, as lead, bismuth, &c., it must be treated with nitric acid as in 1, and the mixture of antimony and tin oxides weighed. In the solution of another quantity of the alloy, the tin is estimated by the volumetrical method (p. 133), and from these data the amount of antimony may be calculated : If, for instance, a given weight of the alloy gives T32 grm. of a mixture of binoxide of tin with antimonious acid, and the volumetrical experiment with an equal weight of the alloy indicates 0*84 grm. of tin, the alloy would contain O20 grm. of antimony ; for the quantity of binoxide of tin y equivalent to 0'84 grm. of tin is 58 (Sn) : 74 (Sn0 2 ) = 0'84 : y (= 1'07 grm.), and this, deducted from the weight of the mixed oxides, gives 1-32 1-07 = 0'25 grm. as the weight of the antimonious acid, equivalent to O20 grm. of the metal. PLATINUM AND GOLD. 137 Com/pounds of platinum. Bichloride of platinum, PtCl 2 . 169-7. Is generally met with in solution, which, when evaporated, leaves a reddish -brown mass, soluble in alcohol, aether, and water. It forms with potash and ammonia salts, yellow com- pounds, very sparingly soluble in water and insoluble in alcohol. "When the solution of bichloride of platinum in alcohol is mixed with a slight excess of chloride of ammo- nium, the filtered liquid should not leave any residue when evaporated to dryness, and ignited to drive off the ammo- niacal salt. The distinctive character of platinum compounds in solu- tion is the formation with chloride of potassium or ammo- nium of the yellow, sparingly soluble compounds. 'Platinum is always estimated by weighing the metal left on igniting the double chloride of platinum and ammonium. Gold and its compounds. Chloride of gold, AuCl 3 . 303-5. The crystallized salt has a pale yellow colour, is deliques- cent, and readily soluble in water, alcohol, and aether. The solution stains the skin deep purple. The amount of gold is estimated according to the method described below, and the presence of alkaline chlorides may be detected by strongly heating a portion of the salt so as to decompose it, and then treating the residue with water, which would dissolve the alkaline chlorides. Purple of Cassius, Au 2 + 3Sn0 2 + 4HO. This substance is used for painting glass and porcelain. The proportion of gold and the presence of any foreign sub- stance may be ascertained by igniting a weighed quantity, treating it with nitre-hydrochloric acid, separating the oxide of tin by filtration, and estimating the gold in the filtrate. The amount of gold in this substance varies greatly, from 24 to 79-5 per cent. The loss by ignition should not amount to more than about 8 per cent. The solutions used for galvanoplastic purposes consist of, chloride of gold with , bicarbonate of potash ; b, phosphate of soda ; c, hyposulphite of soda ; d, cyanide of potassium, or e } ferrocyanide of potassium, The amount of gold in 138 METALS, ETC. these solutions may be ascertained by evaporating to dry- ness a known quantity, igniting the residue with twice its weight of chloride of ammonium until no more vapour is given off. The mass is treated with dilute hydrochloric acid, the insoluble portion consisting of gold perhaps with oxide of iron dissolved in nitro-hydrochloric acid, and the gold estimated by precipitation. The solvents a, same manner as the Sulphate of copper and ammonia, i S11 i n hate CuO,S0 3 NH 4 0,S0 3 , J The native carbonates, azurite (a) and malachite (m), as well as the corresponding artificial carbonates, mountain blue, Bremen blue, or blue verditer, and Bremen green, are mixtures of carbonate of copper, with oxide of copper and water in variable proportions, and are met with in commerce as pig- ments, sometimes containing more or less earthy matter chalk, carbonate of magnesia, alumina, &c. glue, starch, &c. The latter may be detected by digesting the substance in hot water, and evaporating the liquid. The portion inso- 142 METALS, ETC. luble in water should be perfectly dissolved by hydrochloric acid, and on the addition of carbonate of ammonia in suffi- cient excess to redissolve the carbonate of copper, the earthy admixtures will remain undissolved ; they may be collected by nitration and estimated. Oxide of zinc is to be tested for in the ammoniacal solution as in the case of sulphate of copper. Oxide of copper, CuO. 39-7. The pure oxide should not give off any red nitrous vapour or smell when heated ; it should be perfectly soluble in dilute nitric acid, and the precipitate formed on adding carbonate of ammonia to the solution should dissolve completely in an excess of the reagent. The probable impurities are, Oxide of iron, indicated by brown flocks, which remain un- dissolved when an excess of carbonate of ammonia is added to the solution. Earthy substances would likewise remain undissolved on applying the above test. The precipitate may be further examined as directed in Chapter X. Hydrated oxide of copper. Occurs in commerce as a pigment under the name of Bremen blue, and is tested in the same manner as the pre- vious substances. It frequently contains an admixture of glue, which may be separated by warm water, and estimated by evaporating the solution to dryness. Arsenite of copper, CuO,As0 3 (a), and Arsenic-acetate of copper, CuO,A+3CuO,As0 3 (5). Known in commerce under the names of Scheele's green and Schweinfurt green, and used as pigments. They are insoluble in water, but soluble both in acid and ammonia solution. Schweinfurt green evolves a very peculiar and offensive odour when heated in a test-tube ; Scheele's green evolves only the characteristic odour of arsenic. (The va- pours in both cases are very poisonous.) The proportions between the arsenious acid and oxide of copper vary much. The probable impurities are, Carbonate of copper, indicated by effervescence with acids. Clay, heavy spar, gypsum, remain undissolved by acids, and COPPEE. 143 "Earthy substances, are detected as in the case of the car- bonates of copper. Ckromate of lead, with which they are sometimes adul- terated, may be detected by dissolving in hydrochloric acid, adding water and sulphuric acid, which precipitates the lead. The nitrate from the sulphate of lead is mixed with alcohol, boiled, and ammonia then precipitates green oxide of chro- mium. The neutral erystallized salt , erroneously called distilled verdigris, should be perfectly soluble in water; the basic salt b, ordinary verdigris, is only partially soluble in water, but should dissolve perfectly in acetic acid. The impurities are most likely to be mechanical. Fragments of copper and vegetable substances remain un- dissolved. The solutions used for galvano-plastic purposes consist of,- a. Copper salts, dissolved by cyanide of potassium. b. Carbonate of copper, dissolved by tartrate of potash and carbonate of potash. c. Hydrated oxide of copper, dissolved by sulphite of soda. The nature of the solvent may be ascertained by the addi- tion of sulphuric acid, with which a disengages the odour of hydrocyanic acid, c sulphurous acid ; tartrate of potash is detected by adding hydrochloric acid and evaporating the liquid, when bitartrate of potash separates. The solution b has always, and a generally, an alkaline reaction. The amount of copper in any one may be ascer- tained by evaporating a certain quantity to dryness, and igniting the residue with twice its weight of chloride of am- monium. The mass is then dissolved in nitric acid, warmed, and the solution filtered. An insoluble residue may consist of oxide of iron from ferrocyanide. The copper is estimated as directed below. The distinctive character of copper compounds is the in- tense blue colour produced when ammonia is added in excess to the solution. 144 METALS, ETC. Estimation of copper. The most advantageous method is probably that based upon the definite reaction between suboxide of copper and perchloride of iron in the presence of hydrochloric acid, Ci^O + Fe 2 Cl 3 + HC1 = 2CuCl + 2FeCl + HO. The experiment is carried out in the following manner. The weighed copper compound or alloy is dissolved in water or hydrochloric acid, the solution introduced into a capa- cious porcelain or platinum dish, and mixed when cold with a solution of tartrate of potash and excess of caustic potash. The deep blue liquid thus obtained is mixed with an aqueous solution of grape-sugar (honey), or still better milk sugar, in sufficient quantity, and the whole heated upon a water-bath to 176 or 194 F. until the liquid begins to assume a brownish colour at the edges, a sign that all the copper is precipitated, and that the reaction between the sugar and potash has commenced. "When the precipitate has settled, which takes place very readily, it is collected upon a paper filter ; the liquid filtered through is almost opake, and at the surface of contact with the wash water there sometimes appears to be a yellowish turbidity, which, however, is not owing to the presence of suboxide of copper, and disappears on mixing the liquids. The precipitate must be washed with hot water until the filtrate is colourless. Sometimes, and especially when the mixture has been much heated, the suboxide has a dirty colour, but this is merely owing to its being in a rather denser state, and has no influence whatever upon the experi- mental result. It frequently happens that some of the suboxide of copper adheres to the sides of the flask or basin, but this is of no consequence, as the same vessel is used for the treatment with perchloride of iron. By gently heating the mixture of suboxide and per- chloride, the subchloride of copper at first formed readily dissolves. The green liquid is then filtered into a capacious flask, the filter thoroughly washed, a little hydrochloric acid added, and then water until the temperature is about 96 F. The quantity of protochloride formed is then estimated by means of a solution of permanganate. COPPEE. 145 "When other metals are present in the substance analysed, they may either be separated before the precipitation of the suboxide, or remain in solution after that has been effected, when they are removed by mere nitration. Silver and mer- cury may be separated as chloride, or equally well with chloride of mercury by potash, even in the presence of tar- taric acid. The other oxides soluble in potash are not pre- cipitated, with the exception of oxide of nickel, and that only partially, and as it has no reducing action, the result is not affected. Peroxide of iron dissolves in potash and tar- taric acid, giving a brown solution, which deposits peroxide after long boiling, but not when heated only to 212 F. ; and even if the suboxide of copper should be mixed with a small quantity of peroxide of iron, it would merely give .rise to the formation of a little more perchloride, without in any way influencing the result. Colorimetric method. All the salts of oxide of copper, when mixed with an ex- cess of ammonia, acquire a blue colour, the intensity of which is proportionate to the quantity of oxide dissolved. This fact has been applied to the estimation of copper in the following manner. A normal solution is prepared by dissolving O500 grm. of pure copper in nitric acid, adding an excess of ammonia and water to the volume of one litre. Of this solution 5 cubic centimeters are introduced into a glass tube, which is then sealed by the blowpipe. 2-000 grms. of the alloy to be examined are then dissolved in nitric acid, mixed with an excess of ammonia and water to the volume of 100 cubic centimeters. 5 cubic centimeters of this solution are then introduced into a tube of the same width as that containing the normal solution, and graduated into cubic centimeters. A sheet of white paper is then placed behind the two tubes, and water added to the liquid until it acquires the same shade of colour as the normal solution. In order to ascertain this point more exactly, the observations are made through a blue glass. When, for example, the 5 cubic centimeters require to be diluted to 30 cubic centimeters before the colour is of the same intensity as the normal solution, then every 5 cubic 146 METALS, ETC. centimeters will contain as much as 5 cubic centimeters of the normal solution, that is O0025, consequently the 30 cubic centimeters, or the 5 cubic centimeters of the alloy solution, contain 0'0025 x 6 = O0150 grm. of copper ; the 200 cubic centimeters of alloy solution, or the 2*000 grms. of alloy, O'GOO copper. The alloy will therefore contain 30 per cent, copper. The presence of nickel or cobalt in the alloy renders the method inapplicable, and the colour of the normal solution appears to alter somewhat when it is kept. Lead and its compounds. Oxide of lead, PbO. 111-7. Occurs in commerce under the name of litharge ; it should be perfectly soluble in nitric acid without effervescence. The probable impurities are, Carbonate of lime, may be detected by dissolving the litharge in dilute nitric acid, precipitating the lead by sul- phuretted hydrogen, and treating the filtrate with oxalate of ammonia. Copper, detected by digesting the substance in ammonia. Earthy substances, either remain undissolved by dilute nitric acid, or may be detected in the liquid from which the lead has been separated by sulphuretted hydrogen. Red oxide of lead, 2PbO+Pt>0 2 . 343-1. Only partially soluble in dilute nitric acid ; in other respects resembles litharge. Carbonate of lead, PbO,CO, + PbO,HO. 133-7. The substance 'met with in commerce as a pigment varies in composition ; it sometimes contains basic acetate of lead, and is known under several names. The amount of carbo- nate may be ascertained by means of the apparatus (fig. 33) . The amount of acetic acid may be ascertained by distilling a weighed quantity with dilute sulphuric acid, and estimating the acetic acid in the distillate by means of normal solution of alkali, &c. The probable impurities are, Sulphates of baryta, lead or lime, all of which remain un- dissolved by dilute nitric acid, and may be further examined as directed in Chap. X. Carbonates of lime or zinc are detected in the hydrochloric solution after precipitating lead by sulphuretted hydrogen. LEAD, 147 Zinc is precipitated by sulplmret of ammonium, and in the filtrate, lime is precipitated by oxalate of ammonia, Phosphate of lime from adulteration with bone-ash is detected by treating the nitric solution with an excess of caustic soda, which, unless phosphate or carbonate of lime is present, should perfectly redissolve the precipitate first formed ; or, by evaporating the nitric solution to dryness on a water-bath, and digesting the residue with alcohol, which dissolves acid phosphate of lime. Acetate of lead, PbO, A + 3HO. 1897. Known in commerce under the name of sugar of lead. The pure salt should be perfectly white, soluble in water, and the liquid remaining after precipitating the lead by sulphuretted hydrogen should not leave any residue on evaporation. The distinctive characters of lead compounds in solution, are the production with sulphuric acid of a white precipitate (PbO,SO 3 ), and with sulphuretted hydrogen of a blackish- brown precipitate (PbS) in acid solutions. Estimation of lead. The insolubility of sulphate of lead admits of the estima- tion of this metal gravimetrically with tolerable accuracy. The solution containing the lead is mixed with a slight excess of dilute sulphuric acid, then with alcohol, the precipitate (PbO,S0 3 ) collected on a filter, washed with alcohol, dried, and weighed. Among the volumetrical methods, which are all somewhat operose, that based upon the reaction between binoxide of lead and protochloride of tin is probably the best : Pb0 2 + SnCl + 2HC1 = PbCl + SnCl 2 + 2HO. The amount of lead oc in a given quantity of material is found by ascertaining, as described at p. 133, how much (T) of a known quantity of tin, in the state of protochloride, is converted into perchloride by that lead, previously converted into binoxide : x : T (= Q - = Pb : Sn. The lead to be estimated is converted into binoiide bj means of hypochlorite of lime. <)rpmment. A solution of the material in water or acid is mixed with an excess of potash, solution of hypochlorite 148 METALS, ETC. of lime added in excess, and the whole heated to 208 F. for some time, until the whole of the lead is peroxidized. Galena is in the first instance oxidized by nitric acid, and the sulphate of lead, dissolved in potash, treated in the same manner. The precipitate of binoxide is collected upon a filter, washed with boiling water, and transferred into a wide- mouthed flask by breaking the filter with a glass rod, and washing off adherent portions, first by the protochloride of tin and then by hot water. Hydrochloric acid is then added in excess, and Iteat applied until perfect solution is effected. The clear liquid is poured into a beaker, mixed with iodide of potassium and starch, and the excess of protochloride of tin estimated with the normal solution of bichromate of potash. The reaction between chromate of lead and protochloride of iron, 2PbO,Cr0 3 +6FeCl+8HCl=2PbCl+Cr 2 Cl 3 +3Fe 2 C] 3 ^HO, is likewise available for the estimation of lead. The entire quantity of lead in a solution may be readily converted into neutral chromate (PbO,CrO 3 ), which, on the application of a gentle heat, settles rapidly, and may be collected and washed with little trouble. Even sulphate of lead, at least when freshly precipitated, is completely converted into chro- mate when digested with an excess of bichromate of potash. The amount of lead x is found by ascertaining, as described at p. 124, how much of a known quantity of iron, f, in the state of protochloride is converted into perchloride by the chromate, x : P (= f - /) = Pb 2 : Fe 6 . (JBrpmutent. In the case of acid solutions an excess of bichromate is essential, because then the acid combines with the potash, and the solution or decomposition of the chromate of lead is prevented. The precipitate of chromate of lead is washed by decantation, mixed with a known quantity of pro- tochloride of iron and an excess of hydrochloric acid. At a moderate temperature, the chromate of lead dissolves rapidly and completely ; the liquid assumes a green colour, and some chloride of lead separates in crystals, The liquid is rapidly filtered into a flask, the filter washed with hot water, and the residual protochloride of iron is estimated by means of the normal solution of permanganate, p. 123. The end of LEAD. 149 the reaction is distinctly perceptible, notwithstanding the green colour of the solution. Cfye quantity of material to be taken for experiment in order to ascertain directly the per-centage of lead is, for metallic substances, 1/03 grm. Among the metals usually associated with lead in alloys^ tin and antimony are separated as insoluble oxides by the treatment with nitric acid ; silver may be separated by hydro- chloric acid sufficiently dilute not to cause precipitation of lead ; mercury in compounds, corresponding to Hg 2 O, may likewise be separated by hydrochloric acid, or better, by boiling the solution with nitric acid, so .as to convert them into compounds corresponding to HgO, the chromate of which is soluble in acids. Bismuth is the only metal which there is any difficulty in separating. The chromate of bismuth is soluble in con- centrated nitric acid, but in the presence of the excess of bichromate of potash, requisite for the perfect precipitation of lead, basic chromate of bismuth is precipitated. The best, although not quite exact, method of separation is to boil the nitric solution of the metals with acetate of soda in excess, when the bismuth is for the most part precipitated, while lead remains in solution. Lead may also be estimated by the reaction between per- manganate of potash and oxide of lead dissolved in caustic potash : 3PbO + Mn0 7 = 3Pb0 2 +2Mn0 2 . However, the reaction takes place only at 212 F., and towards the end of the experiment, when the quantity of lead is small, it is very sluggish, and on account of the irregu- larity and violence with which the evolution of vapour takes place, there is danger that the flask may be broken or the liquid thrown out. Another method of estimating lead is based upon the reac- tion between this metal in solution and sulphuret of sodium. : PbO + JN T aS = PbS + NaO. Its principal advantage, without which indeed it would be valueless, consists in the circumstance that very few of the oxides of other metals, precipitable by sulphuret of sodium, are soluble in caustic potash. Zinc and arsenic 150 METALS, ETC. are the only metals whose oxides are soluble in potash that are likely. to be associated with lead ; the latter is not preci- pitated from an alkaline solution by sulphuret of sodium, and the former is not precipitated by sulphuret of sodium until the whole of the lead has been removed from solution. The metals most frequently associated with lead tin and antimony may be separated by treatment with nitric acid. Bismuth alone would affect the accuracy of the results, but it is not likely to occur, except in special instances, and then it would be better to adopt the metho^L first described. Mercury and its compounds. Chloride of mercury, Hg Cl. 135-5. Should be colourless, translucent, perfectly soluble in two parts of boiling water and in alcohol. It should volatilize without leaving any residue. Nitrate of mercury, 2HgO,NO s + 2 aq. 288. Decomposed by water, but perfectly soluble in dilute nitric acid. The solution should not give any precipitate with chloride- of sodium (indicative of the lower nitrate). Ammonia should give a white precipitate. Sulphuret of mercury, HgS. 116. Known in commerce under the name of cinnabar or ver- milion. The latter is most likely to be adulterated or to contain impurities. Pure sulphuret of mercury is not acted upon by dilute nitric acid, but when Metallic mercury is present, it is dissolved, and the acid liquid gives a precipitate with sulphuretted hydrogen. Nitrate of mercury is indicated by a darkening of colour on pouring a cold solution of sulphuret of sodium upon the substance. Realgar is detected by boiling the substance with caustic soda, which dissolves the sulphuret of arsenic ; on adding to the liquid a slight excess of nitric acid and then sulphuretted hydrogen, the arsenic is precipitated as sulphuret. Dragon's-blood is detected by its solubility in hot alcohol. Red lead, oxide of iron, Sfc. are indicated by a fixed residue after the application of a strong heat. Iodide of mercury, HgL 2271. A red powder, perfectly insoluble in water, soluble in MEECUEY. 151 boiling alcohol, and is thus distinguished from vermilion. It should be perfectly volatilized by heat. Subchloride of mercury, Hg 2 Cl. 235-5. (Calomel) The pure substance should be volatilizable without residue, and when shaken with boiling water, the nitrate should not give any precipitate w T ith sulphuretted hydrogen or potash, which would indicate the presence of chloride of mercury. Subnitrate of mercury, Hg 2 0,N0 5 + 2 aq. 280. This salt is decomposed by water into an insoluble basic salt, and an acid salt which dissolves. It is soluble in weak nitric acid. Chloride of sodium should precipitate the whole of the mercury, so that caustic soda will not produce any precipitate in the filtrate. Caustic ammonia should pro- duce a black precipitate, and not one that finally becomes white. These two reactions would indicate the presence of nitrate of mercury. The distinctive character of mercury compounds is, that when heated in a long test-tube with a little moist carbonate of soda, a sublimate of metallic mercury is deposited on the cool portion of the tube. Estimation of mercury, The method to be adopted for the estimation of mercury in amalgams depends upon the nature of the metals with which it is associated. When these metals are neither vola- tilized nor oxidized by heat, the mercury may be estimated by the loss on ignition for some time in a porcelain crucible. When the accompanying metals are oxidized by heating in the air, the mercury must be distilled off in a small retort, made of glass tube, the neck of which is sealed as soon as the whole of the mercury has been driven off. When the mercury is accompanied by a volatile metal, such as zinc, the above methods cannot be adopted. The material must then be dissolved in hydrochloric acid, a few drops of nitric acid being added from time to time, and the solution, afterwards boiled with an excess of hydrochloric acid so as to ensure the absence of nitric acid, mixed with protochloride of tin, and boiled for two or three minutes. By this means the mercury is precipitated in the metallic state ; it may be collected by decantation, dried with filter paper, and weighed. 152 METALS, ETC. Silver and its compounds. Nitrate of silver, AgO,NO.,. 1701. The pure salt forms transparent colourless crystals. It is also met with in sticks-, which should be without any green colour, and perfectly soluble in an equal weight of water. The probable impurities are, Copper, indicated on the addition of an excess of ammonia (see p. 143). Nitrate of potash, with which the melted salt is some- times adulterated, may be detected by precipitating the silver by hydrochloric acid, and evaporating the nitrate to dryness. "When the salt is pure there should be no residue. The silver solutions used for galvano-plastic purposes con- tain: a. Cyanide of silver, dissolved in cyanide or ferrocyanide of potassium. b. Silver salts dissolved in mixtures of chloride of sodium and tartrate of potash; or, in hyposulphite of soda, and frequently mixed with alcohol and gallic acid; and solid mixtures containing chloride of silver are likewise used for plating. The amount of silver in any of them may be ascertained }jy heating the dry substance (in the case of liquids, the re- sidue obtained by evaporating a certain quantity) with twice its weight of powdered chloride of ammouium, until vapour is no longer given oft', treating the residue with successive portions of ammonia solution until, on the addition of hydro- chloric acid in slight excess, the liquid no longer becomes turbid, and then boiling the ammoniacal solution containing the silver as chloride with sugar and caustic potafih or soda. The silver is by this means precipitated in a metallic state, and after thorough washing with boiling water, may be collected and weighed. The distinctive character of silver compounds in solution, is the formation with soluble chlorides of a white curdy preci- piiate (AgCl), which becomes dark blue or black on exposure to light, and when freshly precipitated is soluble in ammonia. Estimation of silver. This metal may be estimated with great accuracy in the form of chloride. The solution is slightly acidulated with SILYEE. 153 nitric acid, hydrochloric added in slight excess, the whole warmed for a few minutes, and the chloride washed by de- cantation, transferred to a porcelain crucible in the manner directed at p. 9, melted and weighed. Volumetrical method* The readiness with which the chloride of silver subsides in a liquid from which it is precipitated, admits of the point of perfect precipitation being observed with great delicacy ; and this method of estimation has superseded all others, on account of its simplicity and accuracy. The reagent used is chloride of sodium, and the reaction, supposing the silver to be dissolved in the state of nitrate, AgO,N0 5 + Ss T aCl = AgCl + NaO,Np 5 . Cfye normal Solution may be made by dissolving 5*86 grms. of chloride of sodium in water to the volume of one litre. A cubic centimeter of this solution (containing 0'00586 grm. NaCl) will be equivalent to O01 grm. of silver. In a great number of instances this normal solution may be used for estimating silver in a solution by simply obser- ving the volume required for perfect precipitation, and then multiplying O01 by the number of cubic centimeters. Thus, if 20' 5 cubic centimeters are used, the quantity of silver x will be x 0-01 x 20-5 = 0-205. Another solution, containing in one litre a tenth of the above quantity of chloride of sodium (= 0'586 grm.), is required in many instances for estimating small quantities of silver, and for attaining a greater degree of accuracy in the results. Ci)e quantity of material to be taken for an experiment, to obtain direct per-centage results, will depend upon its composition. In the case of nitrate of silver, for instance, 1'70 grm. must be taken to ascertain the per-centage of AgO,N0 5 , and T08 grm. to ascertain the per-centage of silver. Ctye typcrinunt. The solution of the substance is intro- duced into a tolerably capacious stoppered bottle, mixed with a few drops of nitric acid, and the normal solution added from the volumeter in small quantities. After each addition, the 154 METALS, ETC. liquid is well shaken and allowed to stand until it becomes clear ; a single drop of the solution is then added, and if* a further precipitate is produced, the liquid is cleared by shaking, another drop added, and this repeated un- til a drop of normal solution does not pro- duce any precipitate, or at most a very slight cloud at the surface after a few minutes* rest. In the valuation of alloys containing a to- lerably constant pro- portion of silver, such as silver coin, it is far preferable to take a quantity of the al- loy that will contain rather more than TO gnn. or 0'5 grm. of silver, and to add a-t once such a volume of normal solution as* will precipitate nearly the whole of the silver, and then to complete the precipitation with the decimal solution. The apparatus for this purpose consists of a bulbed pipette A (fig. 43), with a nar- row neck, and spout with a very small aperture. Upon the neck is a scratch, in- dicating the required Fig. 43. SILVEE. 155 volume, and the upper end has a collar of caoutchouc tube, by means of which jt may be fitted to the delivery-pipe of a large vessel containing the normal solution. This delivery- pipe is a siphon, upon the longer limb of which is fitted a platinum cap, closed by a stopcock r", with a narrow spout 3 inches long. To admit of the escape of air while the pipette is being filled from above, the spout of the cock r 11 is enclosed in a wider tube screwed to the lower side of the cock, and furnished with a lateral valve-cock r' at about 2 inches above the end of the spout of r". Upon this tube the pipette is fitted by its caoutchouc collar, and when it is to be filled, the fore-finger is placed firmly against the beak, and the cocks r 1 and r" opened successively. When the solution has risen just above the scratch on the neck of the pipette, the cocks' are both closed in the reverse order, the finger removed, the cock r 1 very slightly opened, so as to let the solution run out of the pipette until it reaches the mark on the neck, when it is closed, the beak of the pipette wiped with a sponge, and the solution run oif into the bottle con- taining the solution of silver by opening the cock r 1 . A thermometer may be fitted in the longer limb of the siphon to indicate the temperature of the solution. In order to save time, and for the sake of convenience when a considerable number of silver estimations are to be made, the sponge is fixed upon a support, together with a receptacle c, for the aste solution, and another 5, for the bottle con- taining th silver solution, arranged to slide backwards and forwards to such a distance, that the sponge or the mouth of the bottle is brought exactly under the beak of the pipette. When any number of experiments are to be made, this plan is the only one that can be adopted, because it is much quicker than the other, and affords less chance of error. The experiments are made in series of ten ; the weighed quanti- ties of alloy are introduced into bottles, numbered from 1 to 10, arranged in a stand (fig. 44), 5 or 6 grms. of nitric acid added to eacli by means of a pipette measure, and the stand, together with the bottles, placed in hot water, in order to facilitate solution. 156 METALS, ETC. When the metal is completely dissolved, the bottles are allowed to cool, and the nitrous vapour displaced by blowing into them through a piece of Fig. 45. bent tube. 100 cubic centi- meters of normal solution are then measured into each bottle, the stoppers put in, and the whole transferred to another stand, suspended be- tween two steel springs, so that the ten bottles may be shaken at the same time (fig. 45). When the liquids are clear, the bottles are ranged upon a black shelf with ten com- partments, numbered to cor- respond with the bottles, the stoppers hung upon wires at- tached to each compartment, and a cubic centimeter of de- cimal solution added to each bottle by means of a small tube- pipette passing through the cork of the decimal solu- tion bottle (fig. 40). For each of the bottles in which a precipitate is formed by the decimal solution, a mark is made on its compartment of the shelf; the bottles are again shaken, and the same operation repeated until no further precipitate is formed on the addition Fig. 46. of a cubic centimeter of decimal solution. Then supposing that 100 cubic centimeters of the normal solution at 60 P. precipitates exactly TO grm. of silver, in the state of chloride, the quantity of silver in each in- stance will be found by adding to 1000 the number of cubic centimeters of decimal solu- tion required to complete the precipitation. If, for instance, a certain quantity q of an alloy requires over and above SILYEK. 157 the 100 cubic centimeters of normal solution, 5 cubic centi- meters of decimal solution^ the quantity of silver in it will be 1-005 grm. The per-centage of silver x 1 is then found by a simple pro- portion, a? : 1000 = x : q; and when, as in the valuation of alloys that are uniform in composition, q is a constant quantity containing as a mini- mum 1*0 grm. of silver, a table may be constructed, in which the value in thousandths is indicated by reference to numbers corresponding with the number of cubic centimeters of deci- mal solution used in each instance. The quantity of alloy q will, of course, vary according to its value in silver, and the tables likewise will refer only to particular standards. In this country the standard of silver 925 coin is -p^r, and the following table expresses the value of the alloy within the limits/of variation : Quantity of alloy for experiment T085 grm. 1 2 3 ,4 5 6 921-6 922-6 923-5 924-4 925-3 926-2 927-2 0-25 921-9 922-8 923-7 924-6 925-6 926-5 927-4 0-50 922-1 923-0 923-9 924-9 925-8 926-7 927-6 0-75 922-3 923-6 924-2 925-1 926-0 926-9 927-9 The numbers in the first column express fractions of thousands, which it is quite possible to estimate after some practice, from the relative thickness of the last precipitate produced by the decimal solution. In the above example, the value of the alloy will be found at the top of the column Q')f?>Q under 5, as containing ; or if the fifth cubic centimeter 1000 of decimal solution gave a precipitate equal only to '0005, the value will be found at the third line of the column under QrtfT.Q 4, corresponding to 4'50, as It is difficult to ensure the constant equivalence of 100 cubic centimeters of chloride solution to 1 grm. of silver, by reason both of evaporation and change of temperature, and it is ad- 158 METALS, ETC. visable never to make the attempt, because accurate results may be obtained with greater certainty otherwise. "With each set of experiments the exact value of the solu- tion for the time is estimated by means of pure silver, of which rOOl grm. is dissolved and treated with 100 cubic centimeters of normal solution in the usual way. If that volume is exactly equivalent to 1*0 grm. of silver, a precipi- tate will be produced by the first cubic centimeter of decimal solution, but none by the second. But if a second and third cubic centimeter of decimal solution are required to complete the precipitation in this proof experiment, then the 100 cubic centimeters will be equivalent to only 1-001 '003 = '998, so that to ascertain the amount of silver in the several experi- ments, it will be necessary to deduct from the number of cubic centimeters of decimal solution required for perfect precipitation, the number required, by the 1*0 grm. of pure silver. In the present instance this correction is 2, and the result of an experiment, in which 5 cubic centimeters of deci- mal solution was required, would be 1*003 grm. of silver. Other metals do not by their presence influence the results obtained by this process, except mercury, which is precipi- tated in the state of chloride. However, when the propor- tion of mercury is at all considerable, it is easily recognized by the difficulty of rendering the liquid clear by agitation, and by the precipitate of chloride remaining white. In such a case the inaccuracy of the results may be obviated by adding to the nitric solution of silver some acetate of soda, which prevents the precipitation of the mercury. The approximative estimation of the value of the alloy, necessary as a preliminary to this process, may be made either by cupellation with lead, or by the ordinary volume- trical experiment with a burette. QUALITATIVE ANALYSIS OF ALLOTS OB, METALS SUSPECTED TO CONTAIN IMPUBITIES. For the qualitative examination of metallic substances, the following systematic treatment should be adopted. The substance is treated with nitric acid in a glass flask, and the reaction assisted by the application of heat. In almost all probable cases the result will come under one of the following heads. QUALITATIVE ANALYSIS OF ALLOTS, ETC. 159 I. A reaction takes place, red nitrous fumes being evolved ; and in this case A. The solution of the substance takes place without any residue, indicating the absence of gold (plati- num ?), antimony, and tin. a. The solution may contain all the other metals likely to be present in alloys, &c. ; copper, lead, silver, bismuth, mercury, arsenic, zinc, nickel, cobalt, iron. B. The solution is partial, and the residue is t b. metallic, or a black powder, indicating the pre- sence of gold, platinum, and perhaps antimony and tin in small proportions. (3. white, indicating the presence of antimony or tin, and perhaps gold and platinum in small proportions. C. JN~o solution takes place, indicating the absence of all metals but gold, platinum, antimony, tin, and perhaps silver and lead in small proportions. The residue may be c. white, indicating the same as /3 ; or : II. No reaction takes place, and D. The substance remains unaltered, indicating the pro- bable absence of all metals but gold and platinum. The solution a is in all cases treated in the same manner. "When a residue remains, it is separated by decantation or by nitration, after the excess of acid has been removed by boiling. The metals are tested for in the following manner, or according to the system described in Chapter X. 1. Copper. When in any considerable proportion, the blue colour of the solution indicates its presence ; when in small quantity, it is indicated by the production of an intense and characteristic blue colour on the addition of an excess of ammonia, the reactions of any other metals that may be present in the solution being disregarded. 2. Lead is indicated by the formation of a white precipi- tate of sulphate of lead on the addition of a few drops of dilute sulphuric acid. 160 METALS, ETC. This indication may be confirmed by collecting the pre- cipitate and fusing it with carbonate of soda on charcoal be- fore the blowpipe. The sulphate is reduced, yielding soft beads of metal and a yellow incrustation upon the charcoal. 3. Silver is indicated by the formation of a white precipi- tate (AgCl) on the addition of hydrochloric acid. When the alloy contains lead, this test should be applied to the liquid filtered from the sulphate of lead in the previous experiment, because, as chloride of lead is precipitated under the same circumstances, it might lead to a false result. Chloride of lead and chloride of silver may, however, be distinguished by their behaviour with ammonia ; the former is unaltered, while the latter is dissolved by this reagent. 4. Bismuth is indicated by the formation of a white preci- pitate when the nitric acid solution, evaporated, not to dry- ness, but so as to remove excess of acid, is poured into water. When the experiment 3 has shown the presence of silver, the presence of bismuth is improbable ; and this is likewise the case when the solution of the alloy by nitric acid is com- plete and 1 has indicated the presence of copper, for alloys containing copper and free from tin or antimony, as well as alloys of silver, in which there is an intentional admixture of bismuth, are not known. In these instances therefore the application of the test 4 may be omitted. As a confirmation of the above reaction, the precipitate is fused on charcoal by means of the blowpipe. It should be- come yellow, and on the addition of carbonate of soda yield reddish-white brittle beads of metal. 5. Mercury. When a fragment of the metal heated in a dry test-tube yields a sublimate, it may contain either mer- cury or arsenic. (Likewise antimony, which w r ould have been already indicated by the treatment with nitric acid.) The mercurial sublimate is in the form of a gray film, which, when rubbed with a roll of paper, collects into metallic globules. The presence of mercury is confirmed by the reduction of its salts in contact with copper, and the formation of an amalgam on the surface of the latter. For this purpose a few drops of the nitric acid solution are freed from excess of acid by heating in a porcelain capsule, a little water added, QTJALITATIYE ANALYSIS OF ALLOTS, ETC. 161 and a piece of bright copper laid in the liquid. "When mer- cury is present it becomes grayish, and when rubbed with the finger takes a white metallic lustre. 6. Arsenic is indicated when the sublimate obtained, as in the last experiment, forms upon the glass a blackish brilliant film, the appearance of which is preceded by the evolution of white vapour and the odour of garlic peculiar to this metal. The detection of arsenic in small quantity is best effected by means of Marsh's apparatus, into which a few drops of the nitric acid solution are introduced for the purpose, and the experiment conducted with the precautions and in the manner described at p. 129. In order to confirm these indications of arsenic, the por- celain plate, upon which the films have been produced, is laid over a capsule containing sticks of phosphorus half-immersed in water. When the films are arsenical they disappear in a few hours, while those of antimony remain for a much longer time unaltered. The remarks made above as to the occurrence of bismuth in alloys, apply equally to arsenic. 7. Zinc. Indicated by the formation of a white precipitate (ZnS) on treatment with alkaline sulphurets. When the solution of the alloy has given indications of any of the above metals, whose coloured sulphurets would disguise the zinc reaction, they must be separated, before testing, by sulphuretted hydrogen, and the filtered liquid boiled with a few drops of nitric acid to remove the excess of this gas. When zinc is present the addition of caustic soda produces a white precipitate, which dissolves in excess of the reagent, and from this solution sulphuretted hydrogen throws down zinc in the form of a white precipitate (ZnS). As a confirmatory test, the precipitate of oxide is moist- ened with cobalt solution and heated by means of the blow- pipe. Under these circumstances the mass acquires a green colour, owing to the formation of a compound of oxide of zinc and protoxide of cobalt. 8. Nickel. Indicated by the formation of an apple-green precipitate (MO,HO) on the addition of caustic soda. The oxide of nickel does not, like oxide of zinc, dissolve in caustic soda ; and as zinc and nickel may occur together in an alloy, M 162 METALS, ETC. it is always necessary, when a green precipitate is obtained by treatment witb caustic soda, as in this and the last expe- riment, to employ an excess of the reagent and to test the alkaline solution for zinc by sulphuretted hydrogen. 9. Iron. Indicated when the precipitate produced by caustic soda, and not dissolved by an excess of that reagent, has a dirty green or brown colour, instead of a bright apple- green. This precipitate is dissolved in hydrochloric acid, carbonate of soda added to the liquid, drop by drop, until it becomes reddish-brown. Some acetate of soda is then added and the whole boiled. Iron is precipitated as hydrated peroxide (Ee 2 O 3 ,HO) ; nickel, when present, remains in solution, and may be tested for as above with caustic soda. There is little probability that iron would be intentionally present in an alloy of copper free from tin, which would be perfectly soluble in nitric acid. It may, however, occur ac- cidentally, but then only in very small proportion. When on treatment with nitric acid there is produced an insoluble residue, /5, it is washed upon a filter and boiled with tartaric acid in a flask. 10. Tin. Indicated by the insolubility of the oxide in solution of tartaric acid. As a confirmatory test, the powder undissolved by tartaric acid is fused with carbonate of soda on charcoal by means of the blowpipe. The oxide of tin is reduced, yielding mal- leable globules of metal. 11. Antimony, Indicated by the solubility of the oxide in boiling solution of tartaric acid. As a confirmation, the solution is evaporated to dryness and the residue heated upon charcoal by means of the blow- pipe. The oxide of antimony is reduced, yielding brittle metallic globules, which burn and give off" a thick white vapour of oxide of antimony. QUALITATIVE ANALYSIS OF ALLOTS, ETC. 163 When the substance is not acted upon by nitric acid, and when it is but partially dissolved, the residue, b, left is treated with a mixture of 3 parts hydrochloric acid and 1 part nitric acid with heat. The result of this treatment may be either a. Partial solution and the separation of a white insoluble powder, chloride of silver, or (less probable) chloride of lead. Although silver is soluble in nitric acid and therefore be- longs to the previous group, it possesses the peculiarity of being insoluble when alloyed in certain proportions with gold and some other metals. b. Complete solution. In both the above cases the metals belonging to this group will be in solution. 12. Gold. Indicated by the formation of a brown preci- pitate of metallic gold on the addition of protosulphate of iron. The precipitate,' collected on a filter and rubbed when dry with some hard substance, acquires metallic lustre. When the proportion of gold in solution is very small, the gold remains for a long time suspended. It is essential for the success of this experiment, especially when the quantity of gold is small, that the liquid should be freed from nitric acid before the test is applied, for the in- tense colour produced by the reaction of nitric acid and proto- salts of iron would render the gold reaction less perceptible. 13. Platinum.' Indicated by the formation of a yellow pre- cipitate (PtCl 2 ,]SrH 4 Cl) on the addition of chloride of ammo- nium to the chloride solution. As platinum is not reduced by sulphate of iron, the liquid which has been tested for gold, or from which gold has been separated, may be employed. The liquid from which gold or platinum has been separated may contain irietals, which are only partially dissolved by nitric acid, when alloyed with either of these. Their presence in the alloy would be already indicated in the examination of the nitric acid solution as above. The chloride solution may moreover contain metals which give rise to the formation of an insoluble white residue when treated with nitric acid antimony and tin. Their occur- rence is unfrequent. M2 164 METALS, ETC. A. COPPER ALLOYS. a. Consisting of two metals. I. Copper and tin. COPPER. TIN. 1. Chrysocole ....................................... 95'00 5'00 2. ^ell-metal ....................................... 8OOO 20'00 3. ....................................... 60-00 40-00 4. &un-metal ....................................... 90'90 9'10 5. Chinese gong-gong ........................... 78'00 22-00 6. Clock bell-metal ................................. 75-19 24-81 7. 2 Metal for the sockets of axle-trees for loco- T Q p. n o n a - 1G2 )' Copper . . \ Tested for in the nitrate solution a, 1 and Lead .... / 2 (p. 159). Arsenic .... Tested for as in 6 (p. 161). Cadmium. . . . Frequently associated with zinc. It is tested for in the precipitate produced by sulphuretted hydrogen. When this is dissolved by nitric acid, the solution separated from sulphur by filtration, mixed with excess of carbonate of am- monia, and allowed to remain for some time in a covered vessel, the cadmium perhaps with lead and bismuth is ob- tained as a precipitate. It may be ob- tained separately by dissolving the pre- cipitate by hydrochloric acid, and adding excess of ammonia, which dissolves oxide of cadmium, but not the oxides of lead or bismuth. Nickel ' ' } Tested for as in 8 and 9 (P; 161 and 162 )' TESTS OF PURITY, ETC. 171 These metals react with caustic soda in the same manner as iron and nickel, and Cobalt . , J would therefore be contained in the Manganese \ precipitate produced by that reagent as in 8 (p. 161). They may be separated as directed at p. 128: Sulphur .... Tested for in the nitrate solution by chlo- ride of barium, as it would be converted into sulphuric acid by treatment with nitric acid. Iron may contain : Copper .... Tested for in the solution a, 1 (p, 159). Arsenic .... Tested for as in 6 (p. 161). Manganese. . Tested for in the precipitate produced by caustic soda. It is dissolved in nitro- hydrochloric acid, the iron precipitated as succinate by adding to the solution, mixed with ammonia until a very slight permanent precipitate is produced, a neutral solution of succinate of am- monia, as long as any precipitate is produced. The manganese is then pre- cipitated from the nitrate by sulphide of ammonium, washed, dissolved by hy- drochloric acid, and precipitated in the state of carbonate for estimation. Sulphur .... Tested for in the nitric solution with chlo- ride of barium, and estimated as sul- phate of baryta in the manner described at p. 78. Carbon .... Always present in iron of all kinds. When the metal is dissolved in weak hydro- chloric acid, a portion of the carbon is converted into gaseous carburetted hy- drogen, which may be recognized by the odour. Another portion remains as an insoluble black residue. This latter car- bon exists in the iron in an uncombined state as graphite, while the former is combined with iron as a true carburet. 172 METALS, ETC. The uncombined carbon is estimated by collecting upon a dry weighed filter the residue, consisting of carbon and silica, left on solution, washing it with water, then with a little aether, and weighing the whole after desiccation at 212 P. The filter with its contents is then ignited in a platinum crucible until the whole of the carbon is burnt, when the residue is weighed, and the difference between the two weights gives the amount of carbon. The total amount of carbon is esti- mated in the manner described at p. 194. Siliciim. . . . Tested for in the nitric solution, by evapo- rating to dryness at 212 E., and digest- ing the residue with weak hydrochloric acid, when it remains as a white in- soluble powder of silica. Care must be taken to prevent any error in this estimation that might arise from the presence of particles of slag, which are not unfrequently disseminated through the mass of metal. When this is the case, it should be treated with very weak hydrochloric acid, which dis- solves the iron without seriously attack- ing the slag. Phosphorus. . Tested for in the solution from which silica has been separated as above, and iron and manganese, by digesting with an excess of sulphide of potassium at 212 F. for several hours. The phos- phorus will then be in solution as phos- phoric acid ; it may be separated from the iron by filtration, and estimated as directed at p. 178. Nickel may contain ' ' I solution. v TESTS OF PUEITY, ETC. 173 Arsenic .... Tested for by Marsh's test, or as in 6 (p. 161). Iron .... I Cobalt . . > Tested for in the precipitate from 8, p. 161. Manganese J Carbon . . 1 m , , i 077 > lested tor as in iron and zinc. bulpnur . . j Tin may contain : Jtismuth. . ^1 Copper . Lead .... \- Tested for in the nitric acid solution. Iron . . . Zinc ... Antimony . . Tested for in the residue /3, as in 11. Arsenic .... Detected by Marsh's test. Tin-foil is immediately and completely converted into a white powder when treated with moderately dilute nitric acid, and it may thus be distinguished from lead-foil coated with tin, which by the same treatment leaves the lead un- acted upon. Antimony may contain : Sulphur. . . . Tested for in the nitric acid solution. Arsenic. . . . Tested for as in 6 (p. 161). Gold may contain : . 7 f Indicated on solution in nitrohydrochloric ' \ acid, by a white residue, AgCl. Copper .... Tested for in the solution a. Platinum . . Tested for as in 13, p. 163. Gilt surfaces may be tested by treatment at different spots with metallic mercury and subnitrate of mercury. When a globule of mercury is rubbed with a piece of kid leather upon the surface of true gilding, a white silvery spot is im- mediately produced, while imitation gilding suffers no altera- tion of colour. But when a drop of subnitrate of mercury is rubbed upon the surface, the latter containing copper and tin becomes white in a few minutes, while true gilding remains unaltered. Varnish or grease must be removed by means of alcohol before these tests are applied. Electro-gilding may -be distinguished from fire gilding by 174 METALS, ETC. dissolving the underlying metal in moderately strong nitric acid, so as to separate the gold in small laminae, which in the case of electro -gilt surfaces are of the same colour and brightness on both sides, while in the case of fire gilding, the under surface next to the metal basis is darker, dead and brownish. Further, the laminae from fire gilding present fine pores when held against the light, while those from electro-gilding appear continuous. Copper may contain : .. > Tested for in the residue /3. Antimony J Bismuth. Lead . . . Iron . Zinc . . . Arsenic . Sulphur. Carbon . > Tested for in the solution a. Lead may contain : Tested for ^ the residue Copper . . ^ Silver . . ^ Tested for in the solution a. Zinc J Arsenic .... Tested for as in 6 (p. 161). Mercury may contain : L d d C which, when not volatile, may be easily de- other J tected by distilling a small portion in a metals 1 ^ ass re * ort - ^he residue is tested in L the usual manner. Silver may contain : Copper Indicated by the colour of the nitric solu- tion, and when in small proportion by a brown precipitate with ferrocyanide of potassium after the separation of the silver by hydrochloric acid. Gold Frequently present in small proportion. Remains undissolved by nitric acid as a black sediment. TESTS OF PUBITY, ETC. 175 Imitations of silver may be distinguished from the ordi- nary alloys of silver and copper by the following test : The metal to be examined is immersed in a mixture of bichro- mate of potash (0*6 grm.) with sulphuric acid (I'D grm.) and water (8 grms.), by the action of which silver acquires a red colour, which is darker the larger the proportion of silver. Or : The metal is rubbed upon a piece of slate, the streak wetted with nitric acid, by which it is dissolved, and then a drop of hydrochloric acid added by a glass rod ; when a curdy precipitate is produced, or, in the case of very small propor- tions of silver, only an oily glitter at the surface of the liquid, the presence of silver is certain. The precipitate of chloride of lead that might in some instances be formed,, is readily distinguishable irom the chloride of silver by its disappear- ance on the addition of a larger quantity of water. 176 NON-METALLIC ELEMENTS, ETC. CHAPTEE VIII. NON-METALLTC ELEMENTS AND THEIR COMPOUNDS KNOWN IN COMMERCE ; THEIR CHARACTERS, THE TESTS OF THEIB PURITY, AND THE METHODS OF VALUATION. Sulphur, S. 16. This substance occurs in a crude state, in the form of rolls ; as a yellow powder ; and, for medical purposes, as a very fine white powder. The probable impurities are, Earthy substances, indicated by a residue left on sublunar tion. Precipitated sulphur is sometimes largely adulterated with burnt gypsum or sulphate of lime. Arsenic, tested for by digesting the finely powdered sul- phur in caustic ammonia for some time, and indicated in the filtrate by a yellow precipitate of sulphuret of arsenic on the addition of hydrochloric acid. When the quantity is very small, the hydrochloric acid may not produce a pre- cipitate immediately, until the filtrate, mixed with a few drops of potash solution, is evaporated to a small bulk. Sulphuric acid, in small proportion, owing to a gradual oxidation by the atmosphere. The reactions presented by sulphur vary according to its state of combination. The compounds of sulphur with metals (sulphides) are for the most part insoluble, and when heated evolve the peculiar odour of burning sulphur, owing to the formation of sulphurous acid. Many of these sul- phides, and all those which are soluble, evolve sulphuretted hydrogen when treated with dilute sulphuric acid. The sulphur of sulphides is generally estimated as sul- phuric acid into which it is converted by means of strong nitric acid or nitrohydrochloric acid either by weighing the sulphate of baryta obtained, or by the volumetrical method (p. 78). "When in the state of sulphide of hydrogen or sulphurous acid, sulphur, or these compounds themselves, may be esti- PHOSPHOEUS. 177 mated by the volumetrical method with bichromate of potash in the same manner as tin (p. 133), the reactions in each case being 1. 2(Cr 2 O 3 ) + 3HS = Cr 2 3 + 3S + 3HO. 2. 2(Cr0 3 ) + 3S0 2 = Cr 2 3 ,3S0 3 . The end of the reaction is indicated, as in the estimation of tin, by means of iodide of potassium and starch ; and when the sulphuretted hydrogen or sulphurous acid to be esti- mated is in small proportion, as in mineral water, &c., the normal solution of bichromate may be diluted so as to furnish more accurate results. Phosphorus, P. 31. Colourless, or slightly yellow, translucent, solid. It fuses at 111 F. to a transparent oily liquid. The so-called amorphous phosphorus is a dark red powder, which may be heated to 482 E. without melting. At the ordinary temperature it is without odour. The possible im- purities are, Sulphur, tested for by adding chloride of barium to a solu- tion of the phosphorus in nitric acid. Arsenic, tested for by sulphuretted hydrogen in the solu- tion from which excess of nitric acid has been removed by boiling. The reactions indicative of phosphorus vary, as in the case, of sulphur, according to its state of combination. When combined with metals as phosphides, it is oxidized by nitric or nitro-hydrochloric acid, and dissolved as phosphoric acid. The excess of nitric acid is removed by evaporating the solu- tion to dryness ; the residue dissolved in water ; the metals separated by sulphuretted hydrogen, or by digestion for some hours with sulphide of potassium, and phosphoric acid tested for in the nitrate. The distinctive character of phosphoric acid in a free state, and in such of its compounds as are soluble in water, is the formation, with sulphate of magnesia, in the presence of am- monia and chloride of ammonium, of a colourless crystalline precipitate of phosphate of magnesia and ammonia \2MgO, NH 4 0,P0 5 ). Phosphoric acid may be best tested for in compounds in- soluble in water, by molybdate of ammonia, which produces H 178 NON-METALLIC ELEMENTS, ETC. in the cold nitric acid solution of the substance a yellow precipitate, insoluble in dilute acid, but soluble in caustic or carbonated alkalies. -Phosphoric acid is estimated as pyrophosphate of magnesia (2MgO,PO,), by igniting the precipitate of phosphate of am- monia and magnesia. Phosphoric acid may also be estimated indirectly by the volumetrical method, when alumina is absent. The process is based upon the facts that 1. Phosphoric acid (tribasic) is precipitated by neutral acetate of iron (Fe 2 O 3 3A) from solutions containing no free acid but acetic, as phosphate of iron (Fe a 3 ,PO 3 ) ; and 2. That the phosphates insoluble in water are, with the exception of the phosphates of iron and alumina, dissolved by acetic acid. Therefore, by estimating the amount of iroufe in the pre- cipitate of phosphate of iron obtained, the quantity of phos- phoric acid x may be calculated by the proportion x : fe = P0 6 : Fe 2 . The iron is estimated, after reduction to the state of protoxide, by the normal solution of permanganate of potash diluted to five times its volume, so that 100 cubic centimeters are equivalent to 560 grm. of iron or 0*713 grm. phosphoric acid. The quantity of the phosphoric acid may be found by multiplying 0'00713 by the number of cubic centimeters of permanganate solution required. Ci)C quantttn of material to be taken for experiment is 0'713 grm., and then the number of cubic centimeters of solution indicate directly the per-centage of phosphoric acid. Cfye trpmmtnt. To obtain a solution fit for the precipi- tation of the phosphoric acid, phosphates soluble in water are mixed with a tolerably large excess of acetic acid ; those insoluble in water are dissolved in hydrochloric acid, and the liquid mixed with sufficient acetate of soda to neutralize all the hydrochloric acid. This solution is then mixed with neutral acetate of iron (FegO^SPO,,) until there is no further precipitation and the liquid acquires a brownish-red colour. The yellowish-white precipitate is collected upon a moistened filter washed with cold water until all the excess of iron is removed, and then PHOSPHOBUS. 179 dissolved in hydrochloric acid, the iron reduced to the state of protoxide by means of zinc (see p. 124), and lastly, the iron estimated by permanganate solution. The reagent (Fe 2 3 ,3A) for precipitating the phosphate of iron is liable to decomposition when kept, and it is there- fore advisable to prepare it fresh for each experiment by mixing together equal volumes of solutions containing re- spectively in a litre 48 grms. of double sulphate of iron and ammonia (Fe 2 O 3 3S0 3 -f JN T H<0,S0 3 + 24 aq.) and4O86 grms. of crystallized acetate of soda (J^aO,A-f 6 aq.) and kept ready for the purpose. Compounds of phosphoric acid with peroxide of iron are weighed in a dry state, dissolved in hydrochloric acid, the iron reduced by zinc, and estimated with the permanganate solution. The quantity of phosphoric acid is estimated by deducting from the total quantity of substance experimented upon, the quantity of oxide of iron (Fe 2 3 ) equivalent to the iron found. For the estimation of phosphoric acid in phosphate of alumina, which, like phosphate of iron, is insoluble in acetic acid, the substance is melted with silica and carbonate of soda. By this treatment there are formed silicate of alumina and phosphate of soda : the latter is separated by water and the solution treated as above directed (p. 178). Or when the melted mass is covered with nitric acid, mixed with metallic mercury, and heated until all the nitric acid is neutralized, the phosphoric acid is precipitated as phosphate of suboxide of mercury, which may be heated with carbonate of soda and the acid estimated in the solution. The bibasic modification of phosphoric acid may be esti- mated in a similar manner, the precipitation of the acid being effected by iron alum and not with acetate of iron. To obtain direct per-centage results, the quantity of material to be taken for experiment is 4284 grm., and the perman- ganate solution must be diluted to ten times its volume, so that 100 cubic centimeters are equivalent to 0'280 grm. of iron. Phosphoric acid may be estimated in urine by means of a normal solution of chloride of iron (Fe 2 Cl 3 ), as free as possible from excess of acid. It is prepared by dissolving 15'556 grms. of pure iron in hydrochloric acid, adding enough nitric acid 82 180 NON-METALLIC ELEMENTS, ETC. to convert the whole into chloride, then evaporating to dry- ness, and dissolving the residue in water to the volume of one litre. A cubic centimeter of this solution is equivalent to O'OIO grm. of phosphoric acid. Cfye experiment is made with 100 cubic centimeters of urine mixed with acetic acid, and the normal solution added until a drop of the urine produces a blue colour in paper saturated with ferrocyanide of potassium. This test is applied by letting the drop fall upon a piece of filter paper placed above the test paper, and thus doing away with the necessity for filtration. Chlorine, Cl. 35-5. This substance may be detected in a free state by the liber- ation of iodine from iodide of potassium. Paper saturated with a solution of this salt and starch, immediately becomes blue, when moistened and brought in contact with free chlorine. The distinctive character of chlorine, combined with metals as chlorides, is the formation with nitrate of silver of a white curdy precipitate (AgCl), insoluble in nitric acid and soluble in ammonia. In testing for chlorine in substances insoluble in water, they must first be fused with an excess of carbo- nated alkali, and the filtered solution, mixed with excess of nitric acid, tested with nitrate of silver. Chlorine, in a free state, is estimated by digesting the aqueous solution with a known quantity of subchloride of mercury until the smell disappears. The subchloride is converted into soluble chloride, and the amount of chlorine x may be calculated from the difference y in the weight of the subchloride before and after the experiment by the pro- portion x : y = Cl : Hg 2 Cl. Chlorine, in combination with metals, may be estimated by precipitation as chloride of silver, either by weighing the precipitate, or by means of a normal solution of silver, in a similar manner to the estimation of silver. In the latter case, the end of the reaction may be rendered more easily ascertainable by adding to the solution of chloride a few drops of phosphate of soda solution. So long as any chlorine remains in solution, there is no permanent formation of phos- BKOMINE AND IODINE. 181 phate of silver, but as soon as the whole of the chlorine has been removed from solution, as chloride of silver, the pre- cipitate retains a faint yellow tinge. The first drop of the silver solution produces a yellow precipitate, because it is for the moment in excess at that part of the liquid ; but this colour disappears rapidly and entirely on agitation, so long as a trace of chlorine remains in solution. Bromine, Br. 80. A clear, heavy liquid of a dark red colour ; density 2*97. It should be perfectly volatilizable by heat, and soluble in 34 parts of water. Impurities and adulterations are not probable. The distinctive character of bromides is the evolution of a reddish-brown coloured vapour, when heated with binoxide of manganese, which dissolves with scarcely any colour in am- monia. Soluble bromides yield with nitrate of silver a white precipitate (AgBr), insoluble in nitric acid or ammonia. Bromine is estimated as bromide of silver, by precipitation with nitrate of silver, in like manner as chlorine. Iodine, I. 127. Should be in the state of blackish scaly crystals perfectly soluble in alcohol, and should not leave any residue when sublimed. The probable adulterations are, Graphite, sulphuret of antimony, charcoal, sand, &c., indi- cated by a residue insoluble in alcohol. This may be collected by filtration, estimated, and further examined. Water cannot be estimated in the usual manner, on ac- count of the volatility of iodine. It may, however, be esti- mated by combining the iodine with an excess of mercury, and weighing the mixture, dried at 212 P. The amount of water is then indicated by the loss of weight. The iodine to be examined should be weighed in a small capsule containing about eight times as much mercury, together with a light agate pestle. The substances are then thoroughly well mixed by rubbing together with the pestle ; the capsule with its contents placed in the drying bath, and when quite dry, weighed again. The distinctive character of iodine is the production of an intense blue colour when brought in a free state in contact with solution of starch. 182 NON-METALLIC ELEMENTS, ETC. This test may be applied to iodides by mixing the neutral or slightly acid solution, with starch solution, and then adding chlorine water. Great care must be taken in testing for small quantities of iodine, not to add more chlorine than will be sufficient for the liberation of iodine, since the iodine would then be converted into iodic acid, which has no action upon starch. Iodine is estimated either as iodide of silver (Agl) pre- cisely in the same manner as chlorine, or when it is accom- panied by chlorine or bromine as iodide of palladium (Pdl), by means of a solution of chloride of palladium, the brownish black precipitate being dried in a vacuum over sulphuric acid. Iodine may be estimated volumetrically by means of the reaction between iodides and perchloride of iron, IH + Fe 2 Cl 3 = HC1 -f 2FeCl + I. The quantity of iron f, reduced to the state of proto- chloride by a given quantity q of the material in which iodine or an iodide is to be estimated, is estimated by means of a solution of permanganate of potash (100 cubic centimeters of which are equivalent to 0'56 Fe) according to the method described at p. 124, and the amount of iodine x calculated by the proportion :/=!: Fe a . Cfye quantity of material to be taken in order to obtain per-centage results, is for grm. Iodine 1'27 Iodide of potassium T66. Cfye tvpcrimeut is made by boiling the mixture of the material in which iodine is to be estimated, with an excess of perchloride of iron, in a narrow-necked flask, so that the iodine may be volatilized, then diluting largely with water, and estimating the amount of iron f in the state of proto- chloride. It is necessary that the iodine should be in combination as an iodide. Compounds of iodine with oxidizing substances should be evaporated to dryness with excess of caustic potash, and converted into iodide of potassium by ignition. When it is desirable to estimate the iodine directly, this IODINE. 183 is effected by means of the reaction between free iodine and hyposulphite of soda, I + 2JNaO,S 2 2 = INa + NaO,SO 5 . Cfye normal Solution of hyposulphite is made by dissolving 24'84 grms. in water to the volume of a litre ; 100 cubic cen- timeters of it are equivalent to 1*27 grm. of iodine, and one cubic centimeter is equivalent to 0'0127 grm. The value of this solution varies gradually, and must be estimated from time to time with a solution of iodine in alcohol. , b. The lower end of each pair of the tubes is connected by vulcanized caoutchouc with a similar-sized tube screwed into the side of the brass cylinder c, made to serve the purpose of a stop-cock by means of a moveable leather piston, which as it is drawn back from the position shown in the drawing, admits the passage of the gas supplied at d to any number of the tubes. By means of this arrangement, and the cock regulating the gas supply, the decomposition of the substance is per- fectly under control. The apparatus is likewise very useful for other purposes. The vaporous products evolved are oxidized in traversing the oxide of copper, and issue from the combustion tube at a in the form of carbonic acid and water, which are separated and collected in the chloride of calcium tube and potash bulbs. When the substance in the tray is perfectly charred, the other part, B, of the furnace is put in its place, the gas lighted, the cock of the oxygen reservoir is slightly opem-d, and the temperature of that portion of the tube raised sulil- ciently high to ensure the perfect combustion of the carbo- naceous residue ; then the current of oxygen is stopped, the reservoir disconnected, the gas turned off, and while the combustion tube is cooling, any remaining traces of carbonic acid swept out by passing a current of air through the appa- ratus by opening the cock r' of the aspirator and closing r. When about a litre of air has been passed through the appa- ratus, the potash tube and bulbs, and the chloride of calcium tube are detached and weighed as quickly as possible. The increase of weight in the former two are added together and calculated as carbonic acid, and the increase in the chloride of calcium tube calculated as water. When the substance analysed contains inorganic consti- tuents, they will remain in the form of ash in the tray, and the amount should be estimated as a check upon the results obtained for carbon and hydrogen ; when the substance ana- lysed is free from oxygen, nitrogen, &c., the sum of the three should be equal to the original weight of the substance. In the case of substances containing nitrogen, a portion of this element would, on ignition with oxide of copper or chromate of lead, be evolved in a free state, while another ELEMENTABY ANALYSIS OF ORGANIC SUBSTANCES. 197 portion would be more or less oxidized, and the products absorbed by the solution of potash. In order to prevent the inaccuracy that would thus attach to the estimation of the carbon in the case of nitrogenous substances, the tube used for the combustion should be about 6 inches longer than usual, and some 5 inches of this space in front of the oxide of copper is filled with copper turnings, which during the experiment are kept at a bright red heat. In contact with copper at this temperature, the oxides of nitrogen are perfectly decomposed, and the nitrogen evolved in a free state passes out of the apparatus without influencing the estimation of the other constituents. When the substance contains sulphur, sulphurous acid is generated in the com- bustion ; and as this would affect the accuracy of the carbon estimation in the same manner as the oxides of nitrogen, it must be prevented from entering the potash bulbs by in- serting, between them and the chloride of calcium tube, another tube, of the same shape, filled with small lumps of peroxide of lead (Pb0 2 ), which absorbs the sulphurous acid. Estimation of oxygen. No method of estimating directly the oxygen in organic substances is known ; its amount must therefore be ascertained by deducting from the original weight of the substance the sum of its other constituents. Estimation of nitrogen. The estimation of nitrogen in organic substances requires a special experiment, and the reaction upon which it is based is the same as that by which its presence in organic substances is detected, viz. its perfect conversion, by ignition with a considerable excess of hydrate of soda, into ammonia which is collected by absorption in hydrochloric acid, and weighed in the form of chloride of platinum and ammonium (PtCl 2 ,NH 4 Cl). The quantity x of nitrogen is calculated from the quantity of double chloride q obtained, by the proportion x : q = N : PtCl 2 ,NH 4 Cl. The reagents required for this purpose, are : 1. A. mixture of hydrate of soda with hydrate of lime, pre- pared by slaking lime with a solution of soda in such pro- portion that there are two parts of hydrate of lime to one of hydrate of soda. The mixture is ignited for some time in 198 NON-METALLIC ELEMENTS, ETC. an earthen crucible and preserved, in fine powder, in a well- stoppered glass bottle. The reaction which takes place when substances contain- ing nitrogen in any form but nitric acid are ignited with the soda-lime, consists in the decomposition of the water of the hydrate of soda, its oxygen combining with the carbon of the organic substance forming carbonic acid, while its hydrogen combines with the nitrogen, forming ammonia. 2. Hydrochloric aeid (sp. gr. 1'13), for absorbing the am- monia produced. The apparatus required consists of, 1. Combustion tube, 16 or 18 inches long, sealed at the end p, and drawn out to a point which is turned upwards, as shown in fig. 59. Fig. 59. a 2. Bulbed tube for the hydrochloric acid (fig. 35). ^pertinent. The substance is mixed in a perfectly dry mortar with sufficient soda-lime to fill one half of the com- bustion tube, and transferred to the tube after the end p has been filled about an inch high with soda-lime. The mortar is rinsed two or three times with soda-lime, enough to fill the tube within an inch of the mouth, a loose plug of as- bestos placed in front of the charge, and a channel made along its entire length by knocking the tube upon a table. The bulb-tube containing hydrochloric acid is then attached by means of a sound cork fitting upon p and into the end a of the combustion-tube. Heat is applied to the tube, either by a gas-furnace, in which the supply of gas is regulated by a piston working in the gas-tube (see fig. 50, p. 192), or by ignited charcoal in the furnace (fig. 49), commencing at the anterior part, which must be kept at a bright red heat throughout the operation, and gradually extending it to the whole length of the tube, so as to keep up a moderate and continuous evolution of gas. When this ceases, and the mixture in the tube has become quite white, the hydro- chloric acid rises into the bulb 1 ; the end p of the tube is ELEMENTARY ANALYSIS OP ORGANIC SUBSTANCES. 199 then broken with a pair of forceps, and air drawn through the apparatus by an aspirator. The contents of the bulb-tube are poured into a porcelain basin, the adherent portion washed out with a mixture of alcohol and aether, and lastly with water; an excess of chloride of platinum solution added, the whole evaporated to dryness on a water-bath, the residue digested with a mixture of two parts of alcohol with one of aether, and the chloride of platinum and ammonium collected by filtration, washed with alcohol and aether, and weighed. When an approximative estimation of nitrogen is sufficient, instead of the hydrochloric acid, a solution of tartaric acid in absolute alcohol may be used for collecting the ammonia. In this case the nitrogen is estimated in the form of bitartrate of ammonia, which being insoluble in alcohol, is precipitated in the bulb-tube, and may be collected by filtration, washed with absolute alcohol, dried at 212 F., and weighed. It contains 8*4 per cent, of nitrogen. The amount of nitrogen may likewise be estimated volu- metrically by collecting the ammonia by means of the bulb- tube, in 20 cubic centimeters of the normal solution of sul- phuric acid (containing O80 grin. SO 3 ), and then estimating by means of the equivalent solution of saccharate of lime (p. 74), or of carbonate of soda (p. 70), how much acid, S, remains in a free state. The quantity of ammonia, y, will be equivalent to the acid neutralized, s y : s (=0-80-8) = NH 3 : S0 3 , and from it the amount of nitrogen x may be calculated by the proportion x : y = N : NH 3 . The presence of sulphur does not affect the estimation of nitrogen. Estimation of sulphur. The sulphur in organic substances is always estimated in the form of sulphate of baryta, BaO,SO 3 . The amount of sulphur x being calculated from that of the sulphate of baryta y obtained, by the proportion x : y = S : BaO,S0 3 . The reagent used for the oxidation is, Nitrate of potash mixed with two parts of carbonate of baryta. The substance, mixed with about 25 times its weight 200 NON-METALLIC ELEMENTS, ETC. of the dry powder, may be transferred to a short, narrow combustion-tube sealed at one end, and gradually heated to redness, commencing at the anterior end ; or, the mixture may be projected in small successive portions into a tolerably capacious platinum crucible kept at a red heat. In both cases the product of the fusion is dissolved in water, a slight excess of hydrochloric acid added, and the sulphate of baryta collected by nitration and weighed. Examination and valuation of coal and other kinds of fuel, animal charcoal, fyc. None of the varieties of coal consist wholly of combustible carbonaceous substance. In anthracite the proportion of earthy (ash) ingredients is sometimes extremely small, but in the bituminous or caking coal ordinarily used, it is gene- rally much larger and moreover very variable. The analysis of coal may be effected in the manner described above, under the head of carbon estimation, but the results thus obtained, although by no means without value, are not alone sufficient for the desired result. The general value of coal or any other kind of fuel, is dependent upon the amount of heat generated by the combustion of a given quantity ; the special value for certain purposes is de- termined in a great measure by the absence of substances occurring in some kinds, and by the mode in which heat is generated by the combustion, and as this varies greatly for different kinds of fuel, it is always necessary, in ascertaining the value of fuel for practical purposes, to apply some more direct test of its capabilities than the elementary analysis. The physical characters are to a considerable extent indi- cative of the applicability of fuel to certain purposes, and these, together with the actual heating effect of a given weight, as well as the per-centage of ash and water, furnish in many instances the best data for estimating its value. Estimation of water. Coal and similar kinds of fuel should be very finely powdered, and a weighed quantity exposed to a temperature of 212 F. until no further decrease of weight takes place. It should then be exposed to a higher tempe- rature, because very frequently the water is not otherwise separable. The dried coal must be allowed to cool in the YALTJATION OF COAL, ETC. 201 dry air chamber and weighed in a covered vessel, and the amount of loss calculated for 100 parts of the fuel. Wood, turf, &c., are dried in the form of chips at a tem- perature of 212 F. Estimation of ash. In the case of coal, a weighed quantity of the powdered substance is ignited in a wide porcelain cru- cible, the heat being gently applied in the first instance, so that none of the powder may be forced out by disengaged gas. When the carbonization is complete, the crucible is laid somewhat on one side, so as to facilitate the access of air, and a strong heat applied to the crucible by means of the gas furnace (fig. 16) until all traces of carbon are perfectly burnt away. The residue is then weighed, and the per- centage of ash calculated. It is always advisable .to make two or more experiments, and to take the mean result. 'Estimation of the calorific power of fuel. There is no means of estimating the actual amount of heat generated by com- bustion, and therefore the capability of fuel in this respect can only be ascertained relatively. It is generally expressed by the number of pounds of water that may be heated from 32 to 212 F. by the combustion of a given quantity, by weight or volume, of the fuel. The effect produced by the combustion of pure carbon is taken as the standard of com- parison, and that amount of heat which raises the tempera- ture of a pound of water one degree, as the unit of heat. This estimation is attended with considerable difficulties, in the exclusion of all disturbing influences which might render the results incomparable with each other. Cfye experiment may be conducted in a small furnace, the chimney of which is connected with a long spiral tube, im- mersed in a large vessel filled with water at a known tem- perature ; but perhaps the best mode of making such experi- ments, when they are at all applicable, is to burn a given quantity of the fuel in a furnace of suitable construction, and observe how much water can be evaporated by it. The fuel should be added only in small quantities, sufficient to keep up a steady evaporation without waste of heat. The experiment should be continued for six or eight hours, and the boiler kept filled meanwhile, to a constant level by a very gradual supply from a known quantity of water at a known 202 NON-METALLIC ELEMENTS, ETC. temperature. The result thus obtained is always under the true value in consequence of loss of heat by radiation, but if the experiment is well managed this loss will be tolerably constant. From the quantity of water evaporated by the combustion of a given quantity of the fuel, an approximative indication of its calorific power, as compared with other kinds, may be obtained. The experimental results thus obtained may easily be reduced to a common form of expression, for the quantity of heat requisite for converting one pound of water at 212 F. into steam under the ordinary atmospheric pressure is equal to that required for raising the temperature of 5'5 pounds of water from 32 to 212 F. ; so that if, in an experiment to ascertain the calorific power of turf, it has been found that for every pound of fuel burnt, four pounds of water have been evaporated, the quantity of water x that w r ould be heated from 32 to 212 F. by the combustion of the same quantity is found by a simple multiplication, x = 5-5 x 4 = 22 pounds. The result may also be expressed in heat-units ; for as equal quantities of heat are required to raise x pounds of water y degrees, or y pounds of water x degrees, the number of pounds of water heated from 32 to 212 by the combustion of one pound of fuel, multiplied by 180, will give, x', the number of pounds of water in which the temperature would be raised one degree, or the number of heat-units generated ; thus in the above instance, x' = 22 x 180 = 3960. The quantity of water of which the temperature may be raised any given number of degrees between 32 and 212 is found in the same manner ; thus the quantity of water heated by the combustion of a pound of fuel will be in- versely proportionate to the number of degrees that the temperature is raised, because the quantity of heat capable of heating 22 pounds of water from 32 to 212 F. (180 de- grees) will raise the temperature of 25- 88 pounds from 59 to 212 F. 22 x 180 = 25-88 x 153. The following table gives the calorific power of several combustible substances used as fuel. VALUATION OF COAL, ETC. 203 Quantities of water heated by the Relative calorific power combustion of one pound of fuel, for equal for from 32 to 21 2 F. from t to t + 1 F. weights. volumes. Hydrogen ......... 236 ......... 42,480 ......... 3'03 ...... -0077 Oil .................. 90 ......... 16,200 ......... T15 ...... 30'2000 ^Ether ............... 80 ......... 14,400 ......... T02 ...... 21-1000 CARBON ......... 78 ......... 13,640 ......... TOO ...... lOO'OOOO Coal-gas ............ 76 ......... 13,680 ......... 0*70 Charcoal ............ 75 ......... 13,500 ......... 0'96 ...... 4.9400 Alcohol ............ 67 ......... 12,060 ......... 0'86 ...... 19*8000 Coal .................. 60 ......... 10,800 ......... 0-77 ...... 33'0000 Wood (dry) ...... 36 ......... 6,480 ......... 0*46 ...... 5'2600 *> ......... **> ......... ...... Turf .................. 27 ......... 4,860 ......... 35 The calorific power for equal volumes is found by multi- plying the number expressing the calorific power for equal weights by the specific gravity of the substance. It may for practical purposes be assumed that the calorific power of hydrogen is three times as great as that of carbon ; consequently the calorific power of fuel will be propor- tionately greater, the greater the amount of hydrogen it con- tains, so that when the per-centage composition of fuel is known, its calorific power may be ascertained by calculation from these data. For fuel consisting solely of carbon and hydrogen, the calorific power x is found by the following formula : x = 3H + C, in which H represents the per-centage of hydrogen, C that of carbon. In the case of fuel containing besides carbon and hydro- gen, a certain amount of oxygen which must be regarded as if already combined with equivalent quantities of carbon or hydrogen, as carbonic acid or water, a corresponding allow- ance must be made in the calculation, and as oxygen is com- bined in carbonic acid with f- of its weight of carbon, and in water with i of its weight of hydrogen, the formula for the calorific power will be either : x = 3H + C - | O, o or, x = 3( H - - 0\ + C. in which represents the per-centage of oxygen. 204 NOF-METALLIC ELEMENTS, ETC. The calorific power of fuel may likewise be ascertained from the amount of oxygen required for its perfect com- bustion. Thusccarbon requires for combustion to carbonic acid, two equivalents of oxygen, hydrogen for combustion to water, one equivalent ; and as the equivalent numbers of these elements are as 6 to 1, the quantities of oxygen re- quired for perfect combustion of equal weights will be for: 6 pounds of carbon. . 2 equirs. oxygen = 8 x 2 = 16, 6 pounds of hydrogen 6 equivs. oxygen = 8x6 = 48, so that the amount of oxygen required for the perfect com- bustion of hydrogen, is three times as great as that required for the combustion of an equal weight of carbon. Thus the calorific powers of carbon and hydrogen bear the same rela- tion to. each other as the quantities of oxygen consumed in the combustion of equal quantities. It follows from this, that for a certain quantity of oxygen consumed in combustion, there is always the same amount of heat generated. For as Carbon requires for combustion 2-J its weight of oxygen, Hydrogen requires for combustion 8 its weight of oxygen, while by the combustion of equal weights of Carbon . . 78 parts of water are heated from 32 to 212 F., Hydrogen 236 parts of water are heated from 32 to 212 F., it follows that the quantity of water heated from 32 to 212F. by the consumption of equal weights of oxygen will be 78 in the combustion of Carbon .... ~ = 29*25, ^ 236 in the combustion of Hydrogen ... - = 29 '50, 8 so that the calorific effect of oxygen may be expressed in round numbers as 30, and in heat-units as 5400 (=30 x 180). The mode in which this relation between the calorific power and the amount of oxygen consumed in combustion is applied to the valuation of fuel, consists in exposing it to the joint influence of a high temperature and of some sub- stance which does not by mere heating lose oxygen, while it readily yields it to the fuel, and at the same time admits ANIMAL CHAECOAL. 205 of the oxygen thus lost, being estimated. The substance used for this purpose is oxide of lead (PbO). (JErpmmmt. One gramme of the finely powdered fuel is- mixed with 40 grins, of oxide of lead, introduced into a large earthen crucible, and covered with 30 grms. more oxide of lead. The crucible, which should not be more than half- full, is covered with a lid and placed in a furnace, from which greater part of the fuel has been removed, and surrounded with hot fuel, leaving the upper part free, so that the pro- gress of the operation may be observed by removing the lid. The heat is very gradually raised until the mixture begins to swell up in consequence of the disengagement of carbonic acid, and when this is at an end, the crucible is covered and kept for about ten minutes at a sufficiently high tempera- ture to make the reduced lead melt into a single mass. The crucible is then removed from the furnace, and when cold broken, the button of lead separated from the melted oxide of lead, and weighed. Pure carbon treated in this manner would reduce to the metallic state 34*56 times its weight of lead, and the amount of lead reduced by any fuel in the same manner is directly proportionate to its calorific power. This process is applicable for the valuation of most kinds of fuel, but more particularly such as are highly carbona- ceous, as anthracite. Bituminous substances cannot be ex- amined in this way, because there is too great a loss by vola- tilization. The results obtained are generally below the truth, but when the experiment is not well managed, oxide of lead may remain mixed with the lead, and thus render the result too high. Animal (bone) charcoal. Bone charcoal is principally employed as a decolorizer in refining sugar, &c. In the usual state it contains from 80 to 85 per cent, of inorganic substance. The probable adul- terations are, Charcoal from ferrocyanide factories, "I indicated by a small Wood charcoal, J per-centage of ash. Iron scales, schist, and earthy substances, fyc., indicated by analysis of the ash (see Chap. IX.). 206 NON-METALLIC ELEMENTS, ETC. The valuation of animal charcoal must be effected by some process capable of indicating its relative decolorizing and absorbent powers. This is effected by means of a solution of caramel (burnt sugar) . A quantity of the charcoal to be examined is placed in a filter, and the caramel solution passed through until it is no longer decolorized ; a similar experiment is made with an equal quantity of charcoal of known good quality and the same solution of caramel. The relative value of the charcoal will be indicated by the amount of solution decolorized. The apparatus used for estimating degree of colour in the liquids is described in Chapter XI. The absorbent power of animal charcoal may be estimated by means of a solution of saccharate of lime of known volu- metric value. For this purpose, 50 grms. of the charcoal are boiled with 100 cubic centimeters of the saccharate solution in a flask for about an hour, the liquid separated by nitra- tion, and the volume of normal acid required for neutral- ization ascertained in the usual manner (p. 74). The difference between this result and that representing the original value of the saccharate solution, indicates the ab- sorbent power of the charcoal. When several samples of animal charcoal are treated in the same manner, under similar conditions, the respective results will show the relative values of the charcoal. EXAMINATION OF PIQMENTS. 207 CHAPTEE IX. SPECIAL METHODS OF ANALYSIS, QUALITATIVE AND QUANTI- TATIVE, ADAPTED FOE THE EXAMINATION OF PAETICULAE CLASSES OF SUBSTANCES. I. EXAMINATION OF PIGMENTS. IT will frequently happen that the external characters and general history of substances will indicate that they belong to some one or other class of analogous substances whose constituents are with little exception few and constant, and in many instances the object of the analysis is rather to determine their proportion than their nature. For such classes of substances special methods of analysis may be adopted which provide only for the detection or separation of such constituents as are likely to be present in substances of any particular class. The most simple means of ascertaining the chemical nature of pigments, together with the reactions characteristic of the several kinds, are contained in the following table. The hydrochloric acid and caustic soda tests may be applied in ordinary test tubes to the raw materials as they occur in commerce, or when they have been used as paint, &c., by moistening the surface with these reagents. The incinera- tion test may be made in a shallow platinum capsule or upon platinum-foil, either over a gas flame or with the aid of the blowpipe, as the occasion may require. In the examination of mixed pigments it is frequently necessary to separate the liquid vehicle oil, varnish, alcohol as far as possible by nitration, and if there is any reason to suppose that the portion still adhering should interfere with the indications of the tests applied, it must be removed by means of an appropriate solvent, such aa a mixture of alcohol and aether. 208 PIGMENTS. JJ . |3 & ?1 *< * Hill I TO ^ O is '5 I. II a a PIGMENTS. 209 a g-3 Iff'il * 8 *' " o i .3 210 PIGMENTS. II . * TH n fe 3 III ci o PIGMENTS. 211 so SJ5" & "3 iillf-lli-j SH - . J * 'SJ -M rr^ i OJ 03 i w I t w be ., .s s t W 111 ?J8 , Il^ld SB, gill ^ g w^cSt^'^ w 06 e W -d 212 PIGMENTS. i PQ II O ,0 a ~ > $ O sh lu PIGMENTS. 213 1 I i 1 ^ , .^i?l Ipl I III ^ ,2 ^U S .e8 8 g S 1 g C ^5 S w !^i *-H -r-i 03 fl} hf) ^11 * I I *l fflX ril 1^ u 13 ft.) I II l ra 1 1 in s-IJ, Is- 214 PIGMENTS. Vo '-4- vo t~> OO ON O c> T*- t-N ON w 'd' OOVO Tl-pJ w ON ? ^ vo C- 00 ON U^QVO WVO CO f- 'C* t^- oovo -^-rl >-> ON t^ *o * O w *c< ro Vi- vo vb K t> ON M VO ON ro VO v~\ * vO Vn to T*- xovo t-oo ON 256 TABLES TOE DEDUCING ANALYTICAL EESULTS. TABLES FOR REDUCING ANALYTICAL RESULTS. 257 E I *5 OJ d 3 1 l f -4- oo o\ M M ii O CO rj- J~> t^ OO O O O vo c* OO CO ON Th CO CO T*- oooooooo oooooooo 8 ooooooo ooooooo U-IMVO r) u-ir-^ ri-00 ri ON ON oo oo oo OO t">. vp vo TJ- VOO vo ro VO CO 258 TABLES FOB EEDUCING ANALYTICAL RESULTS. I "S w i OOOVO TfONrJ- OOVO vr^ b 8^1-vO O\>i rovooo O Q O JP M M; -M IM rt rovo C\H ^->oo Tj-t^ rovo O t^rhc4 ON ON ON ON 00 00 \0 co p J*. TJ- M UIMVO MOO rnON cot~xO Tj-r^ ^- Tj-oo rot~^'-'vo O o-iO*^ 11 t^NOO CO OO t) r) o ooo t^O ^J- w O\vO t^Tj-1 C\vO rOQOO c> moo O rovo cr\i O O O M 'M 'M *i V> TABLES FOE REDUCING ANALYTICAL EESULTS. 259 S'l VOOO w ONN 1000 t^TJ-ovo M Sosp, T}-(-(COVO i O 00 VO vo OOVO^J-HOOOVoto OOVO VOCOM OOO t^ d vo OO Ht ^- t ON N ON oo t~^ t^ vp vo -s^- rt- OOOO oooo OOOO OO oo OO oo oooo 0000 oooo oooo O M d c< oovo ^J-N OOO t^voro r^- ^ M oo vo c^ ON vo ro b "I Vj V> VoVj-Vj-vovb ri vo t^x o to vo oo O *j-oo N r>i-> voos^ OO*iMNcJrim i-OO plvo O ^J-OO rl H H COTj-VOVO t^OO O >-> fi CO-^-VOVO t^OO O 1 N COTJ-VOVO t-^OO O ci rorhy^vp f^?/ 3 O b b b b b b b b '<-> 260 TABLES TOR REDUCING ANALYTICAL RESULTS. O i! a Q & s I Si, is i s M TJ-C* O cn t-^O rJ-t-- M POrJ-u-it^OO O\M tOVO OxH u-sOO HI VO o jo Q ** M M..M H r^vo O\r4 w-,oo ~ ^ M f VO 00 O H b '<-> O t^ rj- S S 8 CO VO O b b ~ CO VO ro vO rt Tl-VOOO 8 8 8 GOO O O O rt- VO OO OOOOOOOOO OOOOOOOOO vp c4 00 Tj- O vp N 00 Tt- b M *M V Vo Vo Vj- Vj- lo 1^-00 CN TABLES FOB, REDUCING ANALYTICAL RESULTS. 261 w *I ^ S I "Si vp ON O w M O H Hi i! 11 IS" S fi H ft 65 M tou-ivooo O c< b b b b *o M oovo vncorn ooovo LO i-> couit^O>i-c p< ^t"VO T}-OO rJvO O u-ic^cnr^ 11 N -sj-u-ir^oo ON" rj b b b b b b b vo d o> ""> N oo lowoo w ro rj- vO oo O\ i co^J- n H **^ ^" *^ vo oo Ox O b b b b b b b b ' vo coc?\ M rorj- VO OOO OOOOOOOOO H>-riOOO rovo O\ >-< -<4- vo rioo u-in r-xmovo b b b b b b b b b OOOOOOOOO OOOOOOOOO OOOOOOOOO OQVO ^-N OOOVO ^J-N M c* Vo V^ lo MD V^ OO C7\ OOO OO OO HI to vb >o s t-^oo ON 262 TABLES FOR SEDUCING ANALYTICAL BEST7LTS. M " 1 o PH g S S -M H'-H M g-a , I, I M Pn 'o O PH <, ^ * 1 OO t^ vo VO r r r*" *? r^ ON N ^t- b b b b b b M t^rJ-M CNVO COO rx OO C"^ VO ^* rO H t^t Q\ tovo O\r> vnoo 1-1 ^> vp NOO U-IM t^ + Q covo O r< rhr^ vrO ui f">vo ONrJ moo M Tj-t^ N 'i-vo ONW mvooo O rj-00 NVO O 5-00 HVO vo CNN *i- csr-vo rh oo moo ro vo w->o T}-OO r^vo O TJ-OO wm oxONOooooo r^t^t^vo" OOVO f4^ ONOO w CNt^-vn i rovo CN t^vo u-t ^- i-i ONt-^m ntOVOCN b b b M M irivo t TABLES FOR REDUCING ANALYTICAL EESTTLTS. 263 00 to 1 i"! - t^ TJ- w oo OH ONVO ro N^>OO O mvOOO M rj- ^1- M g *-i o X VO N CNW-(COO rJ-M f^ 'OM^ NOO coovoo t 1 GQ ^^ CM CQ M O w c> N to "rn '^J- '-^ H ft S Tj-o\rooo tooo r> O O '>-i M 'd rt to Vo Vh | S o w ll M ro^vo t^ONO IH to ONOO t--vO i^^rJ-coN CNONONONONONONONON M vnoo 1-1 Tj-t^O tovo >j-io *o i-t vo i-i t-^N t- s ^ *s ^ . OWMclcJCOCOTl-^- en 1 ^ 3 c ^3 J^ VO c* ON O . w t^COQVO corhvooo ONM corj- covo csrl ^ooo fl vr>oo c o to t>- M voONror^i-i u-> a g 02 OOWHIMCJNtOtO p O 02 j ! | ' el 6 I r^-^-voooOcl^-^OOO vo NOO ^" " r-^cocN^i VO COON^O roONVO N o\ tot^O ^OO *i vj-iCNri ^-OO tot^t-ivo O rl-CN < o 02 05 ~ CO OOi-iM^cltototo 1 | ' 9 ^ 1 S C3 1 h rj-CNtor-r<^o O J-ION CNOOOO t-^t^-vovo ^n-3- ro r>> i-i vn ON to t^ n '^ cl ^- t^ ON w ^t-vo ONI-I tovo CNdvo Osrt VOON .00 09 3 OOO"-iHitHcicc< tf w 11 d 1 JP HI N Tj-u->VQOO ONO C r>oo rt-O'O rl ON*O t> , 1 li | i U-)Q U-lMVO IHVO d t^ t>. vo c* O t^opj O t-^ p OQ g'S O HI N toto^-u-vbvi rt Vh i - 1 i B ^ a O O ONONONONONONON ST^- XO t^. ON H( CO *J""> t^ OOOQHIHII-IHI t~. * w 00 V>M ONVD to Tj-ON^l-OO tOOO M t^N 2 H 9 n 02 GO Hii-iVjVltOtO'i- ^ Element i ! | 11 i ll fO Q IJ 11 c5 co^-^>vO t^-oo ON 264 TABLES FOB BEDTJCING ANALYTICAL BESULTS. * *S & o> g o O _; 1 N vo M vo r oo co ON ON oo oo f^ t^> N vo oo w TJ- t^ O O O -> >-> M 00 VO -<4- N O 00 ON T!- O vo vo vo O co vo o csj. M N CO Tj- Tj- vo vo t^ "8 . o> fl O ON OO t-~- t-^ VO vo oo r^ vo vo T^- co * co M d M o *b3 ^^ * i i " O OO r^- VO vo rj- ro >1 V CO Tj- VO 5* r p VO tv. 00 I * OO t^ VO CO f O OO VO vo CO IH O 00 t-^ vo <4- N O VO rt- oo r^ vo ^~ C4 O O M rl co co ^J- vo VO t^ .2 a| o co vo O co vO O Tj- OO CO f^ HI VO co vo O co t^ O O O M w w rt CO 00 CO co \o O ? ? V N co d g B 'S o vo ro O t^ co o I-- rj- M N r d jj M vo 00 O co vo Os ^ r W ^ p 03 m OQ rfi 1 *H 'p3 2 22 1* ON OO f-~ vo VO vo vo >-" r^ co ON vo rt- ON co oo rl r^ >-> d ^ vo i-^ oo b b b b b b vo oo O rj- CO CO M r^ co Cl VO M co W M M 1- co vO O co vo O l-~ rj- H ON vo Tf- *-> & . Tj- vo VO OO r~. w vo co r-- o w OO VD vo ON co ON O r L M 000000 M ' ^ " 1 11 1 j| M ri co 4- vo SO t^ 00 ON QUALITATIVE ANALYSIS, 265 CHAPTEE X. SYSTEMATIC QUALITATIVE ANALYSIS. THE system of analysis laid down in this chapter is applicable to all inorganic substances and most compounds of organic acids that are of frequent occurrence in commerce. The methods of testing for substances that are of rare occurrence are omitted, for the sake of rendering the system more especially applicable to ordinary technical practice. The constituents that, in ordinary practice, are likely to be met with in substances whose chemical nature is sought to be ascertained, may be divided into three groups : I. Basic or electro-positive substances. POTASSIUM, SODIUM, AMMONIUM, MAGNESIUM, CALCIUM, STRONTIUM, BARIUM, ALUMINUM, CHROMIUM, ZINC, CAD- MIUM, MANGANESE, IRON, COBALT, NICKEL, URANIUM, PLATINUM, GOLD, TIN, ANTIMONY, ARSENIC, BISMUTH, COPPER, LEAD, MERCURY, SILVER. II. Electro-negative substances. OXYGEN, CHLORINE, BROMINE, IODINE, CYANOGEN, FLUORINE, SULPHUR, PHOSPHORUS, CARBON. III. Acids. SULPHURIC, PHOSPHORIC, ARSENOUS, ARSENIC, CARBONIC, SILICIC, BORACIC, CHROMIC, CHLORIC, OXALIC, TARTARIC, CITRIC, MALIC, BENZOIC, SUCCINIC, ACETIC, or EORMIC ACIDS. It is highly improbable that all, or any large majority of the members of these groups should be present in any sub- stance to be analysed. It will, in most instances, consist of one or more of the first group combined either with one or more of the second group, or, in the state of oxide, with one or more of the third group. It may likewise be a 266 QUALITATIVE ANALYSIS. definite cliemical compound, or a mixture of two or more such compounds. The object of the qualitative analysis is therefore twofold : to ascertain, viz. 1. what are the constituents elementary or other and 2. their state of combination or of mixture. The external physical characters of a substance colour, state of aggregation, density, taste, smell, &c., will fre- quently warrant some general inference as to its chemical nature, especially in the case of homogeneous substances, but such indications must not be estimated at more than their true value, which consists merely in serving, more or less, as a guide in the actual analysis. The systematic course of qualitative analysis applies only to solutions, and the chemical nature of some members of the above groups precludes the possibility of their 'existing together in solution, so that, in addition to the general im- probability of the presence of a great number of constituents, the presence of some will be a sufficient indication of the absence of others thus, for instance, sulphuric acid cannot be present in a substance containing baryta, and soluble in water, nor can silver be present in a substance soluble in hydrochloric acid, gold in a solution containing proto-com- pounds of tin or iron, and the reverse. For the analysis of metallic substances and some others, in which the number and kind of constituents are always very limited, the special methods, described at pp. 158- 163, 170-175, and in Chapter IX., may be advantageously adopted. PBELIMINABY EXAMINATION. Besides the indications that may be furnished by the physical characters of a substance, there are several others which may be obtained by submitting it to two or three simple tests, for instance, to ascertain its behaviour with solvents, and when heated, either alone, or together with other substances. This preliminary examination should never be omitted in the analysis of a substance of unknown chemical nature, because a* knowledge of its results will PBELIMINARY EXAMINATION. 267 often considerably reduce the number of necessary experi- ments, and ensure a great saving of time. When the substance to be examined is solid : I. A portion is powdered, covered with water in a test-tube and boiled. When the substance appears little altered, a portion of the clear filtered liquid is evaporated to dryness upon plati- num foil to ascertain whether any substance is dissolved. Note. In some instances a very small residue may be obtained in tbis way, arising either from the admixture of a minute quantity of soluble substance, or from the substance being very sparingly so- luble. This may generally be disregarded, and the substance 'treated as if insoluble in water. Sulphate of lime, which requires 430 parts of water for solution, may in practice be taken as the limit of solu- bility in water. a. Substances tliat prove insoluble in water, or the portion tliat remains undissolved, must be heated with hydrochloric acid. Attention should be paid to any reaction that may take place when the acid is added. - , / presence of carbonates, sul- 1. Effervescence ........ j phides, peroxides, cyanides. Test the gas with lime water, acetate of lead, iodide of potassium, and starch, and observe the smell. C absence of silver, mercury 2. Complete solution . . . . J * Ld L lead. b. Substances that prove insoluble in water and hydrochloric acid are heated with nitric acid or nitrohydrochloric acid. c. Substances that prove insoluble in water and acids are submitted to the preliminary tests described under II. and III. Such substances will most likely consist of one or other of the saline compounds indicated by I in the table of 268 QUALITATIVE ANALYSIS. relation to solvents. The method by which they are to be rendered soluble depends upon their composition. "When the substance does not contain metallic compounds that would be reduced and injure a platinum crucible, it may be melted with alkaline carbonate, the melted mass digested with water, and the residue boiled with nitric acid. When the substance contains metals, it is best to boil it with caustic alkali, and then treat any residue that may remain, with nitric acid. The solutions thus obtained are examined as directed below. When the substance to be examined consists of silicates, the method of analysis described at pp. 230, 235 are to be adopted. When the substance is metallic, a special method of ana- lysis (p. 158) is to be adopted. When the substance is liquid, it is to be tested with litmus paper to ascertain whether it is acid or alkaline. Any pecu- liarities of colour, smell, or taste should be noticed. A portion is evaporated to dryness in a platinum capsule. Any residue that may be left is examined in the same way as a solid. When it is desirable to obtain the liquid apart from any substance that may be held in solution, it should be distilled from a small flask. When the liquid has an acid reaction and leaves a residue on evaporation, a portion should be mixed with a large quantity of water. 3. It becomes opalescent, the precipitate redissolving again on the addition of hydrochloric acid f presence of antimony, bis- \ muth, or tin. II. A small portion of the substance is heated upon platinum foil. 4. It volatilizes, either wholly or partially. To obtain further indications of the nature of the vola- PRELIMINARY EXAMINATION. 269 tilizable substance, a portion is heated in a dry test-tube, or in a tube open at both ends (fig. 65) . Kg. 65. a. Clear colourless drops "j collect at the upper part > water. of the tube J Note. These drops should be tested with litmus, so as to ascertain whether the liquid is acid or alkaline. 5. A grey film is deposited,"^ and when rubbed with [ a feather metallic glo- {' bules appear J c. A dark lustrous metallic"^ film is deposited, and an I odour resembling garlic [ * evolved J Note. When an open tube is used, the presence of arsenic is indi- cated by a white sublimate of arsenous acid, from which the metallic sublimate may be produced by heating it with black flux. d. A yellow film is depoO sited and a sulphurous > sulphur. odour evolved J Note. A yellow sublimate may in some instances consist of sulphide of arsenic. mercury. arsenic. *' antimony or arsenic. Note. A white sublimate may also be produced in some instances by mercurial compounds, chloride of lead, oxide of bismuth, sulphides of lead or tin, and some ammoniacal salts. When a substance contains sulphur or arsenic, it is advisable 270 QUALITATIVE ANALYSIS. to separate them before applying the tests described in 7 ; this is best effected by roasting the powdered substance in an open tube or in the outer blowpipe flame on charcoal. Sometimes the separation of sulphur or arsenic is difficult, and in such cases the substance should be frequently powdered during the roasting. Alternate oxida- tion and reduction by means of charcoal powder, is sometimes advantageous in facilitating the separation of sulphur and arsenic. 5. It melts readily, either with or without expulsion of vapour f presence of saline compounds < of the alkaline or earthy L metals. ' Note. As a test for nitrates or chlorates, a piece of paper is dipped into the melted substance. The presence of these salts is indicated by deflagration. 6. It chars, or blackens and becomes lighter coloured again when strongly ignited f presence of fixed organic sub- stance. Note. The coal should be strongly heated so as to burn off the car- bon ; when fixed mineral substance is present, it remains as ash, and may be subjected to the further preliminary tests. When a substance contains organic admixtures, it is advisable to destroy them by ignition, because in many cases the normal reactions of inorganic substances are prevented or .modified by the presence of organic substances. 7. It acquires a darker colour, that is permanent after strong ignition {presence of compounds of the heavy metals. To obtain further indications of the nature of the sub- stance, small portions of the residue that has been well roasted when the substance contains sulphur or arsenic are melted with borax or microcosmic salt, both in the outer and inner blowpipe-flame. The colour presented by the beads thus obtained is often indicative of the metals present, as shown in the following table. In order to test substances by fusion with borax or micro- cosmic salt, a piece of thin platinum wire, bent at the end, PEELIMINAET EXAMINATION. 271 as shown in fig. 66, is heated to redness and dipped into the salt ; the portion that adheres is melted in the outer blow- Fig. 66. i; ipe-name, and this operation repeated until the bead is arge enough to fill the loop of wire. It should be perfectly colourless when cold. A very small fragment of the substance to be examined is attached to the bead by moistening its surface, and it is then brought into the outer blowpipe-flame and melted. Any reaction that may take place during the fusion is noted, as well as the colour of the bead while hot and when cold. The colour of a bead is generally ascertained best by placing it in front of a piece of white paper. When the bead contains a substance that does not dissolve, it should be examined by means of a magnifying glass. The bead is then to be melted in the reducing flame, either upon the platinum wire or on charcoal, and the same points noted. Note. When the substance is suspected to contain zinc, nickel, cad- mium, lead, bismuth, copper, silver, or antimony, the reduced metal would alloy with the platinum, and to avoid this, the bead must be detached from it and melted upon charcoal in the reducing flame. The action of borax in testing substances consists in the pro- duction of compounds which, whether containing excess of base or acid, are very fusible. The action of microcosmic salt consists chiefly in the solution of substances by the phosphoric acid it contains, and the formation of fusible double salts. The colour of the bead produced with borax or microcosmic salt depends very often upon the proportion of the metallic oxide to which the colour is due. In all instances the experiment should be made at first with a very small quan- tity of substance, and, if desirable, repeated with a larger quantity, so as to produce a glass saturated with the oxide. 272 QUALITATIVE ANALYSIS. J 3 I *a 8 * OJ O *S "fi ^^ C^ I o P ll i i I M H 2 2 ? PH S ikl S^ ^3 S fl pq PBELIHINABY EXAMINATION. 273 %1 2^ R W 14*1 I O 2 2 111 ! CT 1 . fell |Ss fS|| 8 * -sl s - r 274 QTJALITATIYE AXALYSIS. 8. No apparent alteration, either permanent or temporary ; absence of organic substance. "When the substance leaves an infusible white residue, it should be moistened with cobalt solution and strongly heated upon charcoal by means of the oxidizing blowpipe-flame. . Colour is sometimes produced in this way, that indicates the presence of some substances. a. Hose colour magnesia. 1. Blue alumina. c. Yellowish green oxide of zinc. d. Blueish green oxide of tin. e. Olive green oxide of antimony. III. The substance is mixed with carbonate of soda and heated upon charcoal, in the reducing blowpipe-flame. 9. It melts, and is entirely absorbed by the charcoal presence of alkaline salts ; absence of compounds of other bases. 10. Metallic globules appear f presence of gold, silver, tin, \ or copper. 11. An incrustation is produced on the charcoal, besides or without metallic globules presence of bismuth, lead, antimony, cadmium, or zinc. The colour of the incrustation may sometimes furnish a clue to the substances present. a. A yellow incrustation,"! becoming white when > indicates zinc, cold J b. A yellow or brown in- "I indicates bismuth, lead, or crustation j cadmium. c. A white incrustation. . indicates antimony. \ " PBELIMINABY EXAMINATION. 275 d. soft globules, easily 1 . -,. , , , flatten!* J \ mdlcate lead ' Note. The incrustation produced by lead is very like that produced by bismuth, but the globules of bismuth are brittle. brittle globules ..... . { Msmuth Note. The globules of antimony burn after the blast has ceased, giving off vapour, and generally become enveloped with crystals. 12. It is dissolved with effervescence by the melted soda presence of silica. I Y. A portion of the substance is covered with concentrated sulphuric acid in a test-tube, and heated. 13. Effervescence indicates the presence of carbonates, sulphides, sulphites, or cyanides. Observe the smell of the gas, and test it with lime water, acetate of lead, &c. 14. Acid vapour is evolved presence of chlorides, bromides, iodides, or nitrates. "When the vapour is brown, test with starch solution ; a. A blue coloration .... indicates iodides. I. An orange coloration. . indicates bromides. c. No coloration ........ indicates nitrates. 15. The liquid becomes dark coloured presence of organic sub- stances. After the application of these preliminary tests, some general notion may be formed as to the chemical nature of the substance under examination and its probable consti- tuents. T2 276 QUALITATIVE ANALYSIS. When the substance is solid, a quantity amounting to 1 or 2 grammes is then to be dissolved by such means as may have been found most suitable for the purpose, and the clear solution submitted to the operations described below. Any residue that cannot be dissolved is separated by fil- tration and examined separately. ACTUAL ANALYSIS. It has already been remarked, that in qualitative analysis, the application of special tests must be preceded by opera- tions whose object is to effect the separation of the ele- mentary constituents of substances in groups, the members of each of which present some reaction that is characteristic and distinctive as regards other groups. The analytical groups comprising the metallic elements are five in number, and two of them are subdivided into secondary groups ; the reagents, by means of which the con- stituents of a substance are separated in groups, are Hydrochloric acid, Sulphuretted hydrogen, Sulphide of ammonium, and Carbonate of ammonia. The analytical groups comprising the acids and electro- negative elements are three in number, and one of them is subdivided into two secondary groups, each of which is again subdivided into two others ; the reagents, by means of which these constituents of a substance are separated in groups, are Nitrate or acetate ofbaryta i Nitrate of silver, and Chloride of calcium. The examination for acids is generally made to follow that for bases. S o ** 02 ,, << 35| a S. a g s o GO , O * , So EXAMINATION TOE BASES, ETC. 279 In applying the several tests it is advisable to operate upon a small portion of the filtrates, and, if a negative in- dication is obtained, to pass on to the next test, or if a positive indication is obtained, to treat the whole of the liquid in the same way. Examination for basic or electro-positive constituents. A. The solution is mixed with hydrochloric acid until it has a decided acid reaction. , ^ r . ., f absence of mercury, silver, 1. JSb precyitate ...... 2. Wliite precipitate, inso- f may contain one or more luble in excess of the < metals belonging to the reagent ............ [ first group. AgCl, Hg 2 Cl, PbCl. Note. When the solution has an alkaline reaction, there may be an evolution of gas on the first addition of hydrochloric acid ; evolution of carbonic acid, sulphuretted hydrogen, or hydrocyanic acid would indicate the presence of an alkaline carbonate, sulphide, or cyanide ; a precipitate may also be produced, consisting of alumina, oxide of zinc, metallic sulphides, or cyanides, or some other substance soluble in alkali. When the solution has an acid reaction, a precipitate may be produced, consisting of antimonic acid, basic chlorides of antimony, or bismuth ; but all these precipitates are readily distin- guishable from the chlorides of silver, mercury, and lead, in being redissolved by an excess of hydrochloric acid. When the solution is neutral or alkaline, a precipitate may sometimes be produced by hydrochloric acid, consisting of benzoic or boracic acid, both of which redissolve when the liquid is warmed or diluted. The precipitate, P. 1, is collected upon a filter, twice washed with water, the nitrate, P. 1, set aside for treatment with sulphuretted hydrogen. The chloride precipitate, P. 1, is boiled with water in a small flask. ~ 7 , 7 , . f absence of mercury and Complete solution ...... j B ii ver ..-777 . 7 f may contain mercury and Insoluble residue ........ < s {i v er The residue, P. 2, is separated by filtration while the liquid is hot, washed with boiling water, and the filtrate, F. 2, set aside for testing with sulphuric acid. 280 QUALITATIYE ANALYSIS. The residue, P. 3, is covered with solution of ammonia. Complete solution ...... absence of mercury. It lecowxllack ........ J presence rf merrary The nitrate F. 3, from the oxide of mercury or the ammo- niacal liquid, is neutralized with nitric acid, No precipitate .......... absence of silver. ...... presence of silyer. The filtrate, P. 2, is mixed with sulphuric acid. No precipitate .......... probable absence of lead. e of lead - Note. A white precipitate with sulphuric acid indicates with cer- tainty the presence of lead, but, when no precipitate is produced with sulphuric acid, the absence of lead must not be regarded as certain, because lead is not separated from dilute solutions by hydro- chloric acid, and in such cases must be sought in the nitrate, F. 1. B. The acid filtrate, F. 1, or the solution that has been mixed with excess of hydrochloric acid, is saturated with sulphuretted hydrogen and warmed for ten minutes. vr . ., f absence of all elements be- No predate .......... j longingtothesecondgroup. f may contain one or more Coloured precipitate . . . . < metals belonging to the [ second group. HgS, PbS, BiS 3 , CuS, CdS, AuS, PtS, SnS, SnS 2 , AsS 3 , AsS 5 , SbS 3 , SbS 5 . Note. When the solution contains arsenic acid (AsO 5 ), it is advisable to saturate it with sulphurous acid and boil, before treatment with sulphuretted hydrogen. By this means arsenic acid is converted into arsenous acid (AsO 3 ), which is converted into sulphide much more readily than arsenic acid. A white precipitate, consisting of sulphate of lead, strontia, or baryta, may be produced by the sul- phurous acid; this should be separated and warmed with hydro- chloric acid, and the liquid mixed with that from which the preci- pitate was separated, EXAMINATION FOR BASES, ETC. 281 After perfect precipitation the sulphide precipitate, P. 5, is collected on a filter, washed with sulphuretted hydrogen water, and the filtrate, F. 4, set aside for treatment with sulphide of ammonium. Note. The colour of the precipitate produced by sulphuretted hy- drogen will sometimes afford an indication .of its probable nature. When the solution contains persalts of iron, chromic, chloric, bromic, iodic, or sulphurous acids, a precipitate of sulphur is formed with sulphuretted hydrogen, eyen in the absence of metals of the second group, but it is white, and therefore not likely to be mistaken for the positive indication, except in the case of solutions containing chromic acid, when the white precipitate may appear for a time green. /3. The sulphide precipitate, P. 5, is thoroughly washed, and digested in a flask with sulphide of ammonium. * {absence of metals belonging to the first division of the second group, C may contain one or more me- Coloured residue ^ tals belonging to the first ^ division of the second group. HgS, PbS, BiS 3 , CuS, CdS. The insoluble residue, P. 6, is separated by filtration, and the filtrate, P. 5, set aside for subsequent examination. The insoluble residue, P, 6, is thoroughly washed, and boiled with nitric acid in a flask. Complete solution absence of mercury. Black residue . . .1 /> jj g ' > presence of mercury. Note. When the solution contains tin and cadmium, this residue may contain a small quantity of the sulphides of both metals. The residue, P. 7, is collected upon a filter, washed, and the filtrate, F. 6, set aside for treatment with sulphuric, acid. The residue, P. 4, is dissolved by nitro-hydrochloric acid, the solution mixed with excess of ammonia, and boiled with pieces of copper wire, upon which the mercury is precipi- tated, and is afterwards tested for by subliming in a dry test-tube. 282 QUALITATIVE ANALYSIS. The filtrate, F. 6, is mixed with dilute sulphuric acid, heated, and left for half an hour. No precipitate .......... absence of lead. P resence of lead - The precipitate, P. 8, is separated by filtration, dried, and tested with soda before the blowpipe to confirm the indica- tion of lead. The filtrate, F. 7, is mixed with excess of ammonia. No precipitate .......... absence of bismuth. WhUe precipitate ...... J presence of biamuth . The precipitate, P. 9, is separated by filtration, washed, pressed between paper, dissolved by hydrochloric acid, the solution evaporated to a small bulk, and mixed with a large quantity of water ; a white precipitate remaining suspended in the liquid confirms the indication of bismuth. The filtrate, F. 8, from the oxide of bismuth, or the solu- tion that has been tested with ammonia, is mixed with excess of sulphuretted hydrogen, and the precipitate mixed with cyanide of potassium solution. Complete solution ...... absence of cadmium. Yellow residue , /. 3 Q ng > presence of cadmium. The precipitate, P. 10, is separated by filtration, washed, and the filtrate, F. 9, mixed with hydrochloric acid. No precipitate .......... absence of copper. Black precipitate ...... J presence Note. The presence of copper would generally be indicated by the colour of the filtrate, F. 8, or of the ammoniacal liquid that has been tested for bismuth ; in the absence of copper, the precipitate, P. 10, would be of a pure yellow colour. Very minute quantities of copper may be tested for, by means of ferrocyanicle of potassium, in a portion of the ammoniacal liquid, evaporated and mixed with acetic acid. EXAMINATION FOE BASES, ETC. 283 The filtrate, P. 5, is diluted with four times its volume of water, and mixed with dilute hydrochloric acid. f absence of metals belonging No precipitate .......... < to the second division of L the second group. f may contain one or more me- Coloured precipitate ....< tals belonging to the second (_ division of the secondgroup. SnS 2 , SbS 5 , AsS 5 . The sulphide precipitate, P. 12, is separated by filtration, washed, dried, mixed with equal weights of dry carbonate of soda and nitrate of soda, and the mixture projected in small portions into twice the weight of nitrate of soda melted in a porcelain crucible. The cold melted mass is then digested with cold water. Iniolulle The residue, P. 13, is collected upon a filter, washed with alcohol (0'92 sp. gr.), and the filtrate, F.10, set aside, apart from the washings, for subsequent examination. The residue, P. 13, is boiled with caustic soda, the liquid mixed with an equal volume of alcohol, and left for half an hour. contain antimony, gold, or platinum. The residue, P. 14, is collected upon a filter, washed with alcohol, and the filtrate, F. 11, set aside for subsequent exami- nation. The residue, P. 14, is boiled with hydrochloric acid, and some tartaric acid added. Complete solution .... absence of gold and platinum. Insoluble residue ...... may contain gold or platinum. The residue, P. 15, is collected upon a filter, washed, and the filtrate, F, 12, set aside for subsequent examination. 284 QUALITATIVE ANALYSIS. The residue, P. 15, is dissolved by nitro-hydrochloric acid, the solution evaporated to dryness, the residue dissolved in a small quantity of water, and the solution mixed with proto- chloride of iron. No precipitate .......... absence of gold. Xeddish-yelkw precipitate J Note. When the quantity of gold is very minute, the precipitate is not perceptible for some hours, but the liquid acquires a blue tinge when mixed with the protochloride of iron. The precipitate, P. 16, is separated by nitration, the nitrate, F. 13, evaporated to dryness with chloride of ammonium, and the residue covered with alcohol. Complete solution ...... absence of platinum. - l ' ' ' ' | presence of platinum. The nitrate, F. 10, is mixed with a very slight excess of nitric acid and with nitrate of silver solution, and the liquid then covered wdth a layer of very dilute ammonia. No precipitate .......... probable absence of arsenic. of arsenic. Note. In order to obtain a more positive indication of the presence of arsenic, especially when the amount is very small, a portion of the filtrate, F. 10, is evaporated to dryness, the residue heated with a mixture of dry carbonate of soda and cyanide of potassium in a small bulbed tube. By this means the arsenic is reduced and sublimes as a dark metallic film. The filtrate, F. 11, is mixed with hydrochloric acid in slight excess, evaporated to remove alcohol, then saturated with sulphuretted hydrogen, and heated. No precipitate .......... absence of tin. cipitate ...... pre3ence Yellow precipitate ...... j The precipitate, ?. 19, is washed, dried, and melted with cyanide of potassium and alkaline carbonate by the reducing- EXAMINATION FOB BASES, ETC. 285 flame of the blowpipe, in order to confirm the indication of tin. The nitrate, F. 12, is saturated with sulphuretted hydro- gen, and heated. No precipitate .......... absence of antimony. Orange precjpjate ...... "When neither gold nor platinum is present, the following method may be adopted in testing for tin, antimony, and arsenic. The precipitate, P. 12, is digested for half an hour with solution of sesquicarbonate of ammonia, at a moderate tem- perature, and frequently shaken meanwhile. 7 . 7 .. f absence of antimony and Complete solut l0 n ...... probaMy Insoluble residue ........ may contain tin or antimony. Note. In the presence of sulphides of arsenic, bisulphide of tin is dis- solved by sesquicarbonate of ammonia solution ; consequently when arsenic is present, complete solution does not positively indicate the absence of tin ; and for this reason, the sulphide of arsenic, P. 18", must always be tested for tin as directed below. The residue, P. 13", is separated by filtration, and washed with sesquicarbonate of ammonia solution. The filtrate, P. 10", is mixed with excess of hydrochloric acid and sulphuretted hydrogen. No precipitate .......... absence of arsenic. Yellow predate ...... J preseace The precipitate, P. 18". is collected upon a filter and washed; a portion is dissolved by ammonia, the solution evaporated to dryness, and the residue tested to confirm the indication of arsenic. Another portion of this precipitate is melted with nitrate of potash, the mass digested with boiling water, the solution mixed with nitric acid, and boiled, in order to ascertains whether tin is present. 286 QUALITATIVE ANALYSIS. The residue, P. 13", is dissolved by nitro-hydrochloric acid, the solution mixed with excess of sesquicarbonate of ammo- nia solution, and boiled. Complete solution absence of tin. Insoluble residue probable presence of tin. The residue, P. 19", is separated by filtration, washed with sesquicarbonate of ammonia solution, and the filtrate, F. 12, set aside for subsequent examination. The residue, P. 19", is dried, melted with cyanide of potas- sium ; the reduced metal dissolved by hydrochloric acid, and the solution tested with chloride of mercury to confirm the indication of tin. Note. This confirmatory test is necessary, because the residue, P. 19", insoluble in sesquicarbonate of ammonia solution, may, in some cases, con- sist wholly or partially of oxide of antimony. The filtrate, F. 12 a , is mixed with hydrochloric acid and excess of sulphuretted hydrogen. No precipitate . . . . < Orange-colonred^rccipitate J C. The filtrate, F. 4, or the solution that has been tested with sulphuretted hydrogen, is mixed with excess of ammo- nia, and then with sulphide of ammonium. No precipitate. . . { ab t 8e ?f e . m ^ 3 ^elongmg \ to the third group. Precipitate.. . ( m y contain one or more L metals oi the third group. FeS ; CrO 3 ; UrS ; MnS ; NiS ; CoS ; A1 2 3 ; ZnS. Note. The colour of the precipitate produced by sulphide of ammo- nium will sometimes afford an indication of its probable nature. When the substance under examination is insoluble in water, the precipitate produced by sulphide of ammonium may contain phos- phates or oxalates of baryta, strontia, lime, or magnesia, which must be specially tested for, as directed below. The precipitate, P. 21, is separated by filtration, washed with water containing some sulphide of ammonium, and the filtrate, F. 14, set aside for treatment with carbonate of ammonia. EXAMINATION FOR BASES, ETC. 287 The precipitate, P. 21, is covered with dilute hydrochloric acid, upon the filter. Complete solution ...... { ***%* f ** Black residue .......... "I may contain cobalt and CoS and MS. / nickel. The black residue, P. 22, is washed, and tested for cobalt and nickel before the blowpipe. Note. The sulphide of nickel (NiS) and the sulphide of cobalt (CoS) are not quite insoluble in dilute hydrochloric acid ; consequently the absence of a residue, P. 22, does not positively indicate the absence of nickel and cobalt, and even when a residue remains, these metals must be sought for subsequently. The solution, P. 15, is boiled with a few drops of nitric acid, so as to remove sulphuretted hydrogen and convert iron into the state of combination corresponding to Fe 2 3 , diluted with water, mixed with a considerable excess of caustic potash, and boiled. f absence of all metals belong- Complete solution ...... < ing to the first division of L the third group. f may contain one or more metals belonging to the first division of the third Insoluble residue ........ -{ group, and when the sub- stance analysed is insoluble in water, the salts enume- rated above. Pe 2 3 ; WO 3 ; CrW; MnO ; MO ; CoO. The residue, P. 23, is separated by filtration, washed, and the filtrate, P.16 r set aside. A portion of the residue, P. 23, is dissolved off the filter by warm hydrochloric acid ; the solution mixed with some chloride of ammonium and an excess of ammonia. 73 -,,/? /. T C absence of iron and uranium. Precipitate first formed^ bable abgence of redissolves completely. . - T -, -,-. . , f may contain iron, uranium, Insoluble residue ........ | a d chromium< Note. When the ubstance under examination is insoluble in water, the 288 QUALITATIYE ANALYSIS. residue, P. 23, may contain phosphates of magnesia, lime, strontia, or baryta, and in such instances the phosphoric acid may be separated, as directed at p. 242. from the solution of the residue, P. 23. The precipitate, P. 24, is rapidly collected upon a filter, washed without access of air, and the filtrate, F. 17, set aside. The precipitate, P, 24, is dissolved by hydrochloric acid, the solution neutralized with ammonia and mixed with car- bonate of ammonia solution. Precipitate first formed f absence of iron and probable redissolves completely \ absence of chromium. -r 7 7 7 ., f may contain iron and chro- Insoluble residue < mium The precipitate, . 25, is washed, and the filtrate, F. 18, set aside for subsequent examination. The precipitate, P. 25, is dried, melted with 3 times its weight of nitrate of potash and its own weight of carbonate of soda in a porcelain crucible, and the mass digested with warm water. Complete solution absence of iron. Insoluble residue 1 Fe 2 3 . J The filtrate, F. 19, is mixed with acetate of lead solution. No precipitate .......... { P r * e absence of <* a0 ' J The filtrate, F. 18, or the solution that has been tested with carbonate of ammonia, is evaporated to a small bulk, neutralized with hydrochloric acid, and mixed with ammonia. No precipitate .......... absence of uranium. Yellow precipitate ... 1 /, J P reaence f tiramum. The yellow precipitate, P. 28, is tested before the blowpipe to confirm the indication of uranium. EXAMINATION FOE BASES, ETC. 289 The filtrate, P. 17, is evaporated to dryness, with excess of hydrochloric acid, and nitric acid added meanwhile, so as to remove ammoniacal salts, the residue dissolved in water, the solution mixed with excess of carbonate of ammonia solution, and warmed. No precipitate .......... absence of manganese. ^red precipitate J presence o The filtrate, P. 20, from the carbonate of manganese is mixed with hydrochloric acid, then with cyanide of potas- sium solution, until the precipitate that may be produced is redissolved, the solution boiled, and hydrochloric acid added occasionally until hydrocyanic acid is no longer evolved ; the solution then mixed with excess of potash, and again boiled for a few minutes. No precipitate .......... absence of nickel. Pale-green^r^itate. . . . J The filtrate, P. 21, is mixed with nitric acid in excess, eva- porated to dryness, the residue melted in a porcelain crucible. and the mass digested with water. Complete solution ...... absence of cobalt. Slack residue^. ......... J prefjence Note. The black residue, P. 22, left undissolved by hydrochloric acid, may be dissolved by nitro-hydrochloric acid, and the solution tested in the same manner for nickel and cobalt. The filtrate, P. 16, is neutralized with hydrochloric acid, mixed with a very slight excess of ammonia, and heated. No precipitate .......... absence of aluminum. White predate ...... J pregence Note. The alumina precipitate may contain phosphoric acid, to detect which it is dissolved by hydrochloric acid, and tested for with molybdate of ammonia. TT 290 QUALITATIVE ANALYSIS. The precipitate, P. 32, is separated by filtration, and the nitrate, F. 22, mixed with sulphide of ammonium. No precipitate .......... absence of zinc, White precipitate ..... J presence The filtrate, F. 14, or the solution that has been tested with sulphide of ammonium, is mixed with carbonate of ammonia solution. BaO, CO 2 ; SrO, CO 2 ; CaO, CO 2 . The precipitate, P. 34, is collected upon a filter, washed, and the filtrate, F. 23, set aside for subsequent examination. A portion of the precipitate, P. 34, is dissolved by hydro- chloric acid, the solution mixed with hydrofluosilicic acid in excess, evaporated to a small bulk, and the residue mixed with alcohol. No precipitate . ......... absence of barium. ' ' Presence of barimn. The filtrate, F. 24, is mixed with solution of sulphate of soda, left for an hour, and then boiled. No precipitate .......... absence of strontium. Presence of strontium. Note. This precipitate should be tested before the blowpipe, to con- firm the indication of strontia by the production of the characteristic red-coloured flame. The filtrate, F. 25, is mixed with ammonia and oxalate of ammonia solution. No precipitate .......... absence of calcium. White precipiMe ...... J EXAMINATION FOE ACIDS, ETC. 291 The filtrate, F. 23, or the solution that has been tested with carbonate of ammonia, is mixed with phosphate of ammonia solution, and kept warm for some hours. No precipitate absence of magnesium. White precipitate . /. 2MgO, NH 4 0, PO 5 . / P resence of magnesium. Note. Before testing for magnesium, it is advisable to add a few drops of sulphate of ammonia solution, and if a precipitate is produced, to separate it by nitration, so as to be sure of the absence of barium and strontium. The filtrate, F. 26, is evaporated to dryness, nitric acid added meanwhile, and the residue ignited, so as to separate ammoniacal salts, then dissolved in water, and the solution mixed with bichloride of platinum and alcohol. Ho precipitate absence of potassium. Yellow^precipitaU ...... J The filtrate, F, 27, is evaporated to dryness on a steam- bath, the residue ignited with some oxalic acid, then dis- solved in water, and the solution mixed with antimoniate of potash solution. No precipitate absence of sodium. } P-ence of sodium. Note. When the substance under examination contains barium, stron- tium, calcium, magnesium, or phosphoric acid, it is advisable to pre- pare a portion of the nitrate, F. 14, to test for potassium and sodium, by mixing it with baryta solution and boiling, then separating baryta from the clear filtered liquid by means of carbonate of ammonia, evapo- rating the clear liquid to dryness, and dissolving the residue in water. Examination for acids or electro-negative substances. The acids of arsenic, antimony, and chromium would be detected in the examination for bases, &c. ; the presence of carbonates, sulphides, or sulphites would also be indicated. "When the acids, &c. are combined with other substances than those belonging to the groups 4 and 5, these must be separated from the solution, either by boiling it with car- bonate of soda, or by means of sulphuretted hydrogen, or u2 292 QTJALITATIYE ANALYSIS. sulphide of ammonium, according to the nature of the sub- stances to be separated. In the case of substances soluble in acids but not in water, the solution must be effected by means of nitric acid, unless the preliminary examination shows the presence of organic acids, chlorides, bromides, iodides, or cyanides, in which case the substance should be boiled with carbonate of soda solu- tion, the clear liquid mixed with nitric acid, and then neutral- ized with ammonia. An opinion as to the acids, &c. present may generally be formed from the relation of the substance to solvents and the nature of the bases, &c. which it contains. In all instances the determination of the presence or ab- sence of organic acids in the preliminary examination, must be carefully attended to. The neutral solution, containing ammoniacal salts, is mixed with nitrate of baryta solution. No precipitate. . . ( abs , e t n , ce fl of , al1 the members \ of the first group. White precipitate . . I ma ? ctotain one or more I members ol the nrst group. BaO,S0 3 ; 2BaO,HO,P0 5 ; BaO,Si0 3 ; BaO,S0 2 ; BaO,C0 2 . Note. When the solution contains a sufficient amount of ammoniacal salts, the precipitate, P. 41, will not contain borate, oxalate, tartrate, or citrate of baryta, as might be the case in the absence of ammoniacal salts. Fig . 67 . The precipitate, P. 41, is collected upon a filter, washed, and the filtrate, P. 28, set aside for subsequent exami- nation. The precipitate, P. 41, is trans- ferred to a small flask, fig. 67, and hydrochloric acid poured upon it through the funnel, while the deli- vering-tube dips into baryta water. Complete solution absence of sulphates. Insoluble residue. . , , . ., BaO SO 3 I P reseuce f sulphuric acid. EXAMINATION FOB ACIDS, ETC. 293 When hydrochloric acid is poured on the precipitate, P. 41, No gas is evoked. ....... { a ^^ SUlpMteS and ^ n - i j f presence of sulphurous or da. Devolved .......... { P carbonic acid. The gas evolved is passed into baryta water. No precipitate .......... absence of carbonates. presence The gas evolved is passed into a saturated solution of sulphuretted hydrogen. No precipitate .......... absence of sulphites. White precipitate ...... J presence rf 8ulphurotis acid> Note. In the analysis of substances insoluble in water, the precipitate, P. 41, cannot contain carbonic or sulphurous acids, and these acids must be tested for with a separate portion of the substance as above directed. The insoluble residue, P. 42, is separated by nitration, and the filtrate, F. 29, evaporated to dryness in a steam bath, the residue moistened with hydrochloric acid and covered with water. Complete solution ...... absence of silicates. White residu^ ......... J presence of ^^ The insoluble residue, P. 45, is separated by filtration, and the filtrate, F. 30, mixed with ammonia and sulphate of magnesia. No precipitate .......... absence of phosphates. O^' } presence of phosphoric acid. Note. When the substance does not contain organic acids, and those above mentioned have been separated by nitrate of baryta, or proved to be absent, the only inorganic acid that remains to be tested for, besides the salt radicals, is boracic acid. For this purpose it is pre- ferable to mix a separate portion of the substance with concentrated sulphuric acid and alcohol. The presence of boracic acid is indi- cated by the green colour of the flame. The filtrate, F. 28, or the solution that has been tested 294 QUALITATIVE ANALYSIS. with nitrate of baryta, is mixed with nitrate of silver solution. Agl; [AgS ;Ag 2 Cfy; AgCsy;] AgCl; [AgBr;] AgCy; [AgCfdy ; ; AgO,0 ; AgO.T ; AgO,C; AgO.M ; AgO,Bz ; AgO,Su ; AgO.A. Note. The substances indicated by brackets would not often be met with. The precipitate, P. 47, is collected upon a filter, washed, and mixed with dilute nitric acid. Complete solution . . / ab f. enc . e of f mbers of 1st | division of 2nd group. ( may contain one or more Insoluble residue ........ < members of the first divi- L sion of the second group. Agl ; [AgS ; AgWy ; AgCsy ;] AgCl ; [AgBr ;] AgCy ; [Ag 3 Cfdy] The residue, P. 48, is collected upon a filter, washed, and the filtrate, F. 31, set aside for subsequent examination. The precipitate, P. 48, is digested with ammonia. absence of all members of 1st group. n T + T A - f absence of all membe Complete S olut t on ( subdivision of 2nd f may contain one or more Insoluble residue < members of the first subdi- Agl; [AgS; Ag^fy ; AgCsy]. ^ vision of the second group. The residue, P. 49, is collected upon a filter, washed, and tested with sulphuric acid to confirm the indication of iodine. The filtrate, F. 32, is neutralized with nitric acid. TO- . ., f absence of all members of 2nd No precipitate ( subdivision of 2nd group. f may contain one or more Precipitate < members of the 2nd subdi- l_ vision of the second group. AgCl; AgCy; [AgBr ; Ag 3 Cfdy]. The filtrate or solution, F. 31, is mixed with chloride of sodium solution sufficient to precipitate the silver, the clear liquid neutralized with soda, mixed with chloride of calcium solution, well shaken, and left for half an hour* EXAMINATION FOB ACIDS, ETC. 295 No precipitate { a^eof borates.tartrates, rrrT,., v , / may contain boracic, tartaric, White precipitate j J Q ^ Q ^ The residue, P. 50, is collected upon a filter, washed, and the nitrate, F. 33, set aside for subsequent examination. Note. Boracic acid may be present in F. 31. The residue, P. 50, is digested with cold solution of potash. Complete solution absence of oxalates. Insoluble reside 1 presence Q ^^ ^ \^Si(j) \J. J The residue, P. 51, is separated by filtration, and the ni- trate or solution, F. 34, boiled. No precipitate absence of tartaric acid. White gelatinous precipi- f tate 1 presence of tartaric acid. 2CaO,f. I The filtrate, F. 33, or the solution that has been tested with chloride of calcium, is boiled for ten minutes. No precipitate absence of citrates. White precipitate 1 presence of citric acid . 3OaO, 0. J The precipitate, P. 53, is separated by filtration, and the filtrate, F. 35, or the solution that has been boiled with chloride of calcium, mixed with alcohol. No precipitate absence of malates, White precipitate J presence rf ^ ^ Note. When the substance contains citric acid, the production of a precipitate by alcohol is not a positive indication of the presence of malic acid, because citrate of lime is to some extent soluble in water, and is precipitated by alcohol as well as malate of lime. The filtrate, F. 36, or the solution that has been mixed with alcohol, is evaporated to separate alcohol, made per- fectly neutral, and mixed with sesquichloride of iron. IT -. . f absence of succinates and If*, predate | benzoates . -rt ... f presence of succinic acid or Brown precipitate \ P benzoic acid. 296 QUALITATIVE ANALYSIS. The precipitate, P. 55, is collected upon a filter, washed, heated with ammonia, the liquid filtered, the filtrate eva- porated nearly to dryness, and a portion mixed with chloride of barium and alcohol. No precipitate absence of succinates. White precipitate 1 nce of succinic BaO,Su. J The remainder of the filtrate, P. 37, is evaporated to a small bulk, and mixed with hydrochloric acid. No precipitate absence of benzoates. Crystalline precipitate . 1 presence rf benzoi( . Nitric acid is best tested for as directed at page 237, in a portion of the solution, from which bases have been separated by carbonate of ammonia. Acetic acid is tested for with sesquichloride of iron in a portion of the same solution. Formic acid is tested for with nitrate of silver, and its presence is indicated by the separation of metallic silver after a few minutes, from the white precipitate first pro- duced. These acids may be obtained apart from others, by distilling a portion of the solution with dilute sulphuric acid, and may then be tested for in the distillate. The following tables serve to point out, in a general way, the relation of compounds to various solvents. For this purpose they are divided into four classes : 1. Substances soluble in water; the solubility of sulphate of lime in 430 parts of water at 60 F., being taken as the extreme limit. 2. Substances insoluble in water, but dissolved by hydro- chloric or nitric acids. 3. Substances dissolved by nitric acid, but not by hydro- chloric acid. 4. Substances that are not dissolved by either hydrochloric or nitric acid. The number in the table opposite the symbol of a metal, or of a metallic oxide, and under that of a salt radical, or of an. acid, indicates the class to which, as regards solubility, the compound of those two substances belongs. TABLE OF SOLUBILITY. 297 TABLES showing the relation of various compounds to the principal solvents used in analysis. S Fl Cl Br I Cy As *g 3 3 I 4 Sol. in HBr 3 4 ? Hg20 3 Hg2Fl ? Hg2Cl z Hg2Br Z Hg2i 1 i ? Eg HgO z 4 HgFl HgCl HgBr I Hgl Z Pb 2 2 2 I 2 2 p Bi 2 3 2 I I 3 Cd 2 2 2 I I i i ? Cu 2 2 I? I I 2 p AuBr ? AuCy 4 ? An 2 I AuBr3 I AuCy^ I PtCl z pti 4 . PtCy 4 9 Pt 2 4 I PtCl 2 I Ptl2 ? Sn 2 m part 2 I I I P 2 Sb 2 2 I I 2 2 ' As 2 2 I I 2? I Ni 2 2 I I I I 4 Sol-inHCy 3 Co 2 2 I I I * 3 MIL 2 2 I I I i 2 3 Ur 2 3 I I I i 3 5 Fe 2 2 I I I i 4 3 Cr 2 4 2 I I ? 2 ? Al 2 2 I I I a 2 Zn 2 2 2 I I i 2 ? Ba 1 J I 2 I I I I ? Sr I I 2 I I I ? Ca I I 4 I I I I ? Mg 2 I 4 I I i I ? Na ! I i I I i I ? I I i I I I 1 ' ? NH 4 X I i I I I 1 ' 1 M M N M - M M : : ' : M \ b i fc i r* * ~ 9 M M M M ' : t< rt - N - H :5 CO c el rl .1 Jj M M ; ' M M : M r. iffi IS co to t S. _B CO : ; ; ; - 10 co co to CO : M M : ; : ; N " I to ; ; to M M M : ' M : N c IH to TO to CO H N (4 ; N : - M > lo * b co to H CO M O H ; ' ; ' ; M i : M M - M : - ; ' f N < ?> ~. rh C^ ^'o |i||| j^^- |a | ^ ^ s d 3 ro -Si' o S3 g ^^3 a -3 J*l 307 I I I i s "8 It I 11 I II eo ta x2 II 308 Jtf 1 ill! S jg .2 S'o* *1 II ^8 & Isl -3 S 8 S g ^ s * & S 1 ft j o o -e ra ,* ^^r *| -o 2 I 2 i ^ S . ' !fj HP 111 dis- , Colou char t fi* * *m8Tn " aJIIIIII -s rSS 1 I 309 M i .a t I II T3 - .O ffifi il|j 1C! 1-S-s.s li i! 11 ii 1! - So o 1^ S A - || 1 : 1 s ! ll-ll l^ig 81*1 a 3 a 33 Ills 1 g - 9 aim 'M- 2 i 12 8 "S fc II sS II IN ^* 1 i ^ ^ ^ i g, i fei j g ^ ^ 310 13 a S Becomes brownish. white spot 11 ", PP 311 !?! II 1 60 T3 .H 8 .a S.S 8 -a a, & W with ali. 1 1 M II 1! i 5 S fi ened with orite of lime ution. = 11 Ash g ntain f chro '2 1 11 l 11 ns O red ins ntai of A * i 312 O) O Q a II FU I J 313 I i Hi lii is Hi of > nr a > a o 432 I 3 I" W I" S s 2 = S'S I- o III - c"J^ pd o"^ | S f I ^11 ill 1 S3 o C ^ rj I 314 "o ^ -5 III g g a 8 1> 2 II '! 315 316 OILS, FATS, ETC. CHAPTER XII. OILS, FATS, ETC.; SOAP, VOLATILE OILS, AND MATERIALS USED FOE LIGHTING ; THE TESTS OF THEIE PURITY, AND THE METHODS OF VALUATION. THE substances to which this chapter relates are all products of plants or animals, and consist either of compounds of fixed fat acids with organic or inorganic bases, or of mix- tures of different compounds of carbon and hydrogen. I. EXAMINATION OF OILS AND FATS. It may be taken as a general rule in reference to the exa- mination of oils, that although there may be physical cha- racters or chemical reactions, by means of which certain oils may be distinguished from others with tolerable certainty, still when it is necessary to test for adulteration, all general characters are totally fallacious. The density of some oils has been considered characteristic, and the fact that the density of oils differs only within very narrow limits, was sought to be met by the use of very delicate hydrometers, such as those of Fischer, Gobley, and others ; but the use of delicate instruments is attended with serious difficulties, and hence a proposition has been made by Laurot to conduct the experiment at 212 F. However, none of these methods have been found adequate, because the variation in the density of a particular oil, according to its age, mode of preparation, &c., is frequently quite as great as the difference between it and the density of some other oil which is used for adulteration. This want of uniformity is evident from the following table : Scharling. Leftbre. SchUbler. Bape oil (winter)... 0-9228 0-9154 ...0-9128 Linseed oil 0'9383 0'9350 Poppy oil (old) 0-9630 0'9253 Fish oil 0-9175 to 0-9317 0'9240 Olive oil . .. 0-9180 . 0-9347 . 0-9243 . 0-9231 . 0-9176 EXAMINATION OF OLIVE OIL. 317 Moreover oils do not expand equally when heated, so that an oil which at 60 is heavier than another, may at 212 F. be much lighter. Hence it appears that the determination of density as a means of detecting the adulteration of fat oils is applicable only in a very few instances, and is generally inadequate for the purpose. As a preliminary test it is frequently advantageous to heat a few drops of the oil in a porcelain capsule, by which means the peculiar odour is rendered far more distinct, and the pre- sence of admixtures may sometimes be detected in this way. Besides the adulteration with other oils of inferior value, oils are sometimes mixed with the following substances : a. Colophony or other kind of resin ; indicated by a white clotty precipitate on the addition of an alcoholic solution of acetate of lead, to the clear liquid obtained by shaking and boiling the oil with alcohol O88 sp. gr. b. Oleic acid (obtained in the preparation of stearic candles) ; indicated, even in oils which have become rancid, by the acid reaction upon moistened blue litmus. The litmus paper should be dried by pressure between bibulous paper after being dipped into the oil. The acid reaction in such a case may however be owing to a trace of sulphuric acid introduced in the rectification of the oil. c. Sulphuric acid, lead, alum are met with in many oils ; the tests for their detection are described at p. 320. Olive oil ; the produce of varieties of Olea europcea. The most probable adulteration is, Poppy oil ; indicated when the oil is shaken, by the pro- duction of a froth. .Rousseau having observed that pure olive oil is a very feeble conductor of electricity, and that when mixed with poppy oil it conducts much more readily, proposed for this purpose the use of an instrument called a diagometer, con- structed so as to show the electrical conductivity of the oil to be examined ; but the diagometer does not furnish trust- worthy indications, for Soubeiran arid Blondeau have found that many kinds of olive oil conduct as well as olive oil con- taining 5 per cent, of poppy oil. These oils, although un- adulterated, are mostly inferior in quality, being obtained from fermented olives. 318 OILS, FATS, ETC. Poutet employs a solution of six parts mercury in 7*5 nitric acid (1-356 sp. gr.) without the aid of heat. The oil in question is mixed with one-twelfth of this solution, shaken at intervals of ten minutes for two hours, and then allowed to rest for a day. After this treatment olive oil appears perfectly solid when lightly tapped upon its surface with a glass rod. When it contains 5 per cent, of poppy oil, the consistence of the mass is not, at the utmost, greater than that of tallow ; with 10 per cent, about the same as lard. Soubeiran and Blondeau have tried this test among others, and they admit the perfect certainty of its indications for olive oil containing 10 per cent, of poppy oil, as well as the possibility of detecting 5 per cent., although with less cer- tainty. However, the method is inapplicable to quantitative valuation. Boudet, and subsequently Faure, have modified Poutet' s test ; the former, ascribing the action of the solution to the presence of hyponitrous acid, proposed treating the oil with 4 per cent, of a mixture consisting of 3 parts nitric acid (1'319 sp. gr.) and 1 part hyponitrous acid (1*255 sp. gr.) prepared by distilling 1 part of starch with 8 parts of nitric acid at a very gentle heat shaking and allowing it to rest at 50 F. until the oil becomes so solid that the vessel may be turned upside down without its running out, and to estimate the purity of the oil from the time which elapses between the mixing and the degree of the solidifi- cation. Soubeiran and Blondeau found that pure olive oil, treated in the same manner, always solidifies sooner than the same oil mixed with poppy oil. By experiments with twenty-five samples of pure olive oil, differing in age and source, they found that solidification took place in from 45 to 49 minutes ; with 10 per cent, of poppy oil from 48 to 97 minutes. Con- sequently this method of testing is as defective as the former, for the differences that exist among the unadulterated olive oils are too great to admit of any accurate results being ob- tained by means of it. Soubeiran and Blondeau likewise found that ammonia, which when shaken with some oils forms a doughy and with others a clotty mass, fails to give any trustworthy indications when applied to mixtures of the oils. EXAMINATION OF OLIVE OIL. 319 The inferior viscidity of pure olive oil as compared with oil adulterated with poppy oil, may afford some approxima- tive indication of its purity, and the test is very simple. When a small quantity of pure ob've oil is shaken in a test- tube, the air-bubbles are found to disappear very quickly. But this is not the case with oil containing poppy oil. With 10 per cent, of the latter oil, the bubbles disappear very slowly, gradually flattening at the surface ; with 5 per cent, of the latter oil, the difference is still perceptible, but is not so decisive. This test does not admit of any great accu- racy, but it and that of Poutet appear to be preferable to the others. The action of potash upon olive oil is recommended as a safe test of the goodness of olive oil for the purpose of dyeing Turkey-red. About 20 cubic centimeters of 'the oil are shaken with 10 times the volume of potash solution (1'03 sp. gr.) in a cylindrical glass vessel. The experiment is made comparatively, a sample of known good quality being taken as the standard. Several samples of oil may be tested at the same time, and they must all be equally shaken. Grood olive oil treated in this manner gives a milky liquid with a strong persistent froth upon the sur- face ; inferior kinds give a thinner, bluish or yellowish, translucent liquid and a light froth which soon disappears. After the mixtures have stood for twenty-four hours, they are examined. There should not then be any large oil- globules among the froth, and it should appear curdy ; the liquid beneath should not be thin and bluish, all these cha- racters being indicative of inferior oil. When the froth con- ' sists of small bubbles, and is tolerably persistent, and when the whole mass of liquid is white and mucilaginous, the oil is of good quality. Oils of intermediate value present appearances which exhibit more or less of both these ex- tremes. Maumene has quite recently made known a method which he states to be applicable for distinguishing all drying oils from those that do not dry, but his experimental data refer particularly to the adulteration of olive oil with poppy oil. This method is based upon the different elevation of tem- perature which takes place when poppy oil is mixed with sulphuric acid, compared with that resulting from the 320 OILS, FATS, ETC. mixture of olive oil with the same acid, under precisely similar circumstances. The experiment is made as follows. 50 cubic centimeters of the oil to be examined is introduced into a beaker glass, and the temperature observed ; 10 cubic centimeters of sulphuric acid at the same temperature are then added ; the whole well mixed together, and the greatest elevation of the thermometer observed. With pure olive oil, tjie temperature rises 76 F. above the temperature of the liquids before mixing. With poppy oil, on the contrary, the increase of temperature amounts to 128 or 76 F. Maumene considers that when a sample of olive oil, treated in this manner, gives an elevation of temperature amounting to more than 76 F., it is a sufficient proof of adulteration. Rape oil. According to Davidson, the adulteration of olive oil with rape oil, which is sometimes practised, may be detected by means of Poutet's teat. When amounting to 10 per cent., the detection is easy, but the experiment should always be made comparatively. Chevallier states that honey is sometimes mixed with olive oil ; its presence is indicated, when the oil is shaken with water, by its solubility. Stearine is indicated by the separation of sand-like granules at the bottom of the vessel when the oil is cooled to 50 F. Pure olive oil does not begin to solidify until cooled to 36*5 F. ; and then the granules float in the liquid oil. Sulphuric acid is sometimes employed for the purpose of bleaching, or separating mucus from the oil, and is not always perfectly removed. Its presence is indicated by the acid reaction of water that has been shaken with the oil, and the precipitate which it gives with chloride of barium in the presence of free hydrochloric acid. Oxide of lead. Eancid oil is sometimes treated with litharge for the purpose of making it sweet and of decoloring it. The presence of lead is indicated, when the oil is shaken with an equal volume of weak acetic acid and a few drops of nitric acid, by a white precipitate (PbO, SO 3 ) on the addi- tion of sulphuric acid to the liquid, and by a black precipitate with sulphuretted hydrogen. Alumina is employed for separating mucus from the oil. Its presence it indicated, when the oil is shaken with water EXAMINATION OF EAPE OIL. 321 and a few drops of sulphuric acid, by a flocculent precipitate on the addition of ammonia to the concentrated liquid. Almond oil ; the produce of Amygdalus communis. This oil is distinguished from olive oil, poppy oil, and nut oil by agitation with basic acetate of lead solution. Almond oil gives a white turbid liquid ; all the other oils a yellowish liquid. It is sometimes adulterated with cheaper oils. Eape oil ; the produce of several species of Brassica. The most probable adulteration is, Fish oil; indicated, when the oil is impregnated with chlorine, by a brown coloration. According to Lefebvre, fish oil, when mixed with rape oil, separates completely in a layer at the bottom when the mixture is allowed to stand for some days. Heidenreich observed that a drop of sulphuric acid, mixed with a few drops of rape oil, produces effects different from those which result from the mixture of the same acid with fish oil under otherwise similar conditions. The experiment is made upon a glass plate laid upon white paper, with 10 or 15 drops of the oil and 1 drop of sulphuric acid. It is advisable always to make two experiments ; in the first in- stance, to let the acid fall gently into the midst of the oil, and observe the gradual action, afterwards at once to stir the oil and acid together. With pure rape oil a greenish-blue colour is developed round the drop of acid, and in the centre, a few yellowish- brown streaks appear. When the oil and acid are at once stirred together, the whole assumes a greenish-blue colour, which does not become brown until 5 or 6 times as much acid is added. With fish oil there is at first a peculiar motion from the centre towards the circumference, and a red colour is deve- loped, which gradually becomes brighter, and after 12 or 15 minutes, passes into violet. When the oil and acid are at once mixed together, the red and violet colours are rapidly developed without any tinge of green. With linseed oil and oleic acid, a brown colour is deve- loped round the drop of acid. When mixed together with the acid, the former becomes at first thickish, and more so upon the addition of more acid ; this is not the case with T 322 OILS, TATS, ETC. any other oil in the same degree. Oleic acid stirred with sulphuric acid becomes dark-brown. By means of this test 10 per cent, or less fish oil can be detected in rape oil from the development of the red colour as well as the greenish blue, peculiar to rape-oil. The amount of the adulteration may be approximately estimated by com- parative experiments with known mixtures. The above-mentioned indication afforded by the smell of the oil when heated, may be of some assistance in estimating the proportion of fish or linseed oil, and particularly oleic acid. The behaviour of the oils with a solution of bicarbonate of potash does not furnish very characteristic results. Palm oil ; produce of the Avoira dais. Not only is this oil sometimes mixed with other sub- stances, but a perfectly fictitious substance is sometimes sold under the name of palm oil, and consisting of MMX, tallow, lard, coloured with turmeric and scented with violet root. From such mixtures palm oil is distinguished by its solubility in acetic ether. The presence of turmeric is in- dicated by the brown colour developed with caustic soda solution. Fish oil, train oil ; the produce of various species of Del- phinus and Halena. Fish oil is often adulterated with an inferior kind of lin- seed oil of brown colour. Except when bleached linseed oil has been used, its presence is indicated, when the oil is agitated with an equal volume of alcohol (O815 sp. gr.), by the greenish-yellow colour communicated to the alcohol. Greasing oils for machinery are tested by means of rarious apparatus capable of indicating the degree of re- sistance which they oppose to the motion of the machinery. Arrangements for this purpose, devised by Thomas, Sinclair, Nasmyth, &c., are described in most works on machinery. Butter. See Chapter XIV. In order to detect the presence of fat or oil in substances, the best method is to warm the substance with ether, and evaporate the liquid- EXAMINATION OF WAX AND SOAP. 323 The estimation of the amount of fat in any substance may be effected in the same manner, the digestion with ether being, of course, repeated until the whole of the fat is extracted. Wax ; the produce of Apis mellifica. The probable impurities and adulterations are, Tallow, indicated, when the amount is considerable, by the inferior consistence, and greasy feel of the wax ; by the absence of the granular fracture, and by the taste when chewed. The distillate from wax, containing only 2 per cent, of tallow, gives, when shaken with water and filtered, a liquid from which acetate of lead throws down a precipitate^ while this is not the case with pure wax. Stearic acid-, indicated, when the wax is boiled with lime- water, by a precipitate stearate of lime that remains sus- pended in the liquid, and by the neutralization of the lime. Resin ; indicated by the inferior brittleness of the wax, and by its adhesiveness. The resin is separated by alcohol. Starch or meal, earthy substances, &c. ; indicated, when the wax is dissolved in turpentine, by an insoluble residue, which is further examined to ascertain its nature. ' In order to estimate the amount of stearic acid in adul- terated wax, a known quantity is boiled for a few minutes with a solution of carbonate of soda in 50 parts of water, alcohol added until the liquid becomes clear, the insoluble portion separated by straining through linen, washed with water, melted, and weighed. The loss of weight represents stearic acid. IL EXAMINATION AND VALUATION or SOAP. The probable admixtures, impurities, and >adulterations are, Water ; in very varying amount, which is indicated only by direct quantitative estimation. Sand, pumice stone, clay, talc, sulphate of baryta, starch, &c. ; indicated, when the soap is dissolved in alcohol, by a residue, which may be further examined to ascertain its nature. Y2 324 OILS, TATS, ETC. In order to estimate the value of soap, several operations are requisite. Estimation of water. The soap, as thin shavings, is dried in a water-bath, and the diminution of weight observed; or a known quantity of the soap is boiled with a saturated solution. 01 chloride of sodium, the mass dried, and weighed. The separation of the last traces of water by drying is very difficult. ^Estimation of the fat acid and alkali. About 1 gramme of soap is weighed in a small beaker, fig. 68, and covered with ether and acetic acid. By this means the soap is decomposed ; two layers of Fig. 69. liquid are formed, the ether containing the fat acid or resin ; the lower layer con- taining water, the alkali combined with acetic acid, free acetic acid, and the salts chloride of sodium and alkaline sul- phate usually present in soap. Any in- soluble admixtures remain at the bottom of the beaker, or suspended in the lower layer of liquid. When the soap is completely decom- posed, the whole mass of liquid is de- canted into a larjre pipette, fig. G9, pipette, allowed to remain in the bulb until the two layers have separated completely, the beaker rinsed with ether and water, which are also poured into the pipette. Then by inclining the pipette, the water solution may be almost entirely separated from the ether solution, which is after- wards washed with successive quantities of distilled water, the separation being effected in the same manner. After washing the ether solution it is poured into a small weighed beaker, the adherent portion rinsed out of the pipette with a mixture of strong alcohol and ether, the ^rhole evaporated to dryness upon a water-bath, and EXAMINATION OF ETHEEIAL OILS. 325 the residue weighed several times until the weight ceases to diminish. This residue of fat acid or resin may be further examined to ascertain its melting-point. . The water solution, together with the washings of the ether, containing the alkali, is evaporated to dryness in a small capsule, the residue ignited, and weighed. If desirable, this residue may be further examined, as directed in Chapter IX. "When the soap contains starch, gelatine, &c., the appear- ance of the residue left on evaporating the water solution to dryness, and its becoming charred when ignited, will afford sufficient indication of their presence. The amount of such substances may be ascertained approximatively by weighing the dry residue before ignition. III. EXAMINATION or ETHEEIAL OILS. The most frequent and probable adulterations are, Alcohol ; indicated, when the oil is mixed with water in a graduated tube, by the diminution of the volume of the oil. The presence of alcohol may also be ascertained by heating the oil with chloride of calcium, which becomes soft or liquid according to the amount of alcohol present, but remains un- altered when the oil is free from alcohol. Acetate of potash may be substituted for chloride of cal- cium for the same purpose. fbt oils ; indicated by the viscidity of the liquid, by air- bubbles remaining at the surface after the oil has been shaken, and by the production of a persistent greasy spot upon paper, which is not removeable by alcohoL Resin ; indicated by the production of a greasy spot upon paper, that is removeable by alcohol. Inferior volatile oils, turpentine ; indicated, probably with most certainty when a drop of the oil is rubbed on the hands, by the smell. But the detection of admixtures of this kind is generally very difficult. Turpentine is in some cases indi- cated by the perfect solution of the etherial oil in question, by an equal volume of poppy oil. Rose oil, attar of roses ; the produce of Rosa centifolia, and JR. sempervirens. 26 OILS, FATS, ETC. The substances with which rose oil is adulterated are, besides those already mentioned, Spermaceti ; indicated by the higher temperature requisite for liquefaction. Geranium oil ; indicated, when the oil is mixed with con- centrated sulphuric acid, by a peculiar unpleasant odour. The odour of pure rose oil is not affected by sulphuric acid. Rose-ivood oil ; the produce of Convolvulus scoparius ; indi- cated, when the oil is mixed with sulphuric acid, by a brown coloration ; or when the oil is exposed in a watch-glass beside some iodine in another watch-glass, under a bell-jar, by the brown coloration or blackening of the oil. A gelatinous substance impregnated with rose oil may be detected by warming the bottle. Neroli oil ; the produce of the flowers of Citrus aurantium. Sometimes adulterated with Oil from the calyces and flower ^buds of the orange-tree-, which is said to be indicated, when sugar is immersed in the oil and dissolved in water, by the bitter taste of the solution. Cinnamon oil and cassia oil; the produce of Laurus cin- namomum and L. cassia. Sometimes adulterated with Clove oil ; indicated, when the oil is dissolved in alcohol and mixed with a few drops of perchloride of iron solution, by a greenish coloration. Pure cinnamon oil gives a pure brown colour. The presence of clove oil is also indicated, when the oil is mixed with fuming nitric acid, by frothing and a reddish coloration; and when the oil is mixed with strong caustic alkali, by solidification. Pure cinnamon oil treated in a watch-glass gives oft' a mild fragrant vapour ; the vapour of clove oil is acrid and excites coughing. Bitter almond oil; the produce of Amygdalus communis amnra. Boils at 348*8 F. ; density 1'043. Sometimes adulterated with or substituted by Nitrobenzol\ indicated by its insolubility in water, or when the oil is warmed with caustic potash, by a red colora- tion and production of a red crystalline distillate. Pure bitter almond oil treated with caustic potash, solidifies with production of benzoin and benzoate of potash. The density of nitrobenzol is 1*209 ; it boils at 415 E. YALUATION OF LIGHTING MATEEIALS. 327 Alcohol-, indicated, when the oil is mixed with twice its volume of nitric acid (1/50 sp. gr.), by evolution of nitrous acid vapour. Pure bitter almond oil treated in the same manner presents no reaction at first, but after two or three days is converted into yellowish crystalline benzoic acid. Mineral naphtha. Sometimes adulterated with Turpentine ; indicated, when the oil is mixed with a few grains of iodide of potassium and water, by a yellow or orange coloration, and by the production of a crystalline substance when dry hydrochloric acid gas is passed into the oil at a low temperature. Distilled waters sometimes contain copper and lead, which may be detected by evaporating to a small bulk and treating the residue with sulphuretted hydrogen. IY. VALUATION or OIL, CANDLES, GAS, AND OTHEE MATEEIALS USED TOE LIGHTING. The value of any material used for producing light can only be estimated relatively. The luminous effect of any substance depends upon 1. The intensity of the light produced, and 2. The quantity of material consumed in its production ; so that it may be expressed numerically by the quotient of the luminous intensity, i, divided by the consumption of material, q, within a given time The luminous intensity is estimated comparatively by means of the photometer, an instrument constructed upon the principle that the luminous effect is inversely proportio- nate to the square of the distance from the source of light. Thus when two sources of light produce respectively equal luminous effects at distances of 2 and 3 feet, the luminous intensity of the one would be 4, and that of the other 9. The luminous intensity cannot be estimated directly, but only indirectly from the comparison of the shadows; the brighter light giving the darker shadow. 328 OILS, TATS, ETC. The photometer consists of a blackened iron rod, fig. 70, fixed upon a stand at some little distance from a wooden frame upon which a sheet of white transparent paper is Tig. 70. stretched. The lights to be examined are placed so that each throws a shado'w of the iron rod upon the paper, and that the two shadows are near each other. The distances of the lights from the rod are then adjusted so that both the shadows appear equal, which may be best ascertained at the back of the screen from the simultaneous disappearance of the shadows when a lighted candle is brought near to it. In such observations a definite and constant source of light, such as a wax candle, is employed as the standard of comparison. If, for instance, the squares of the distances at which the flame of a wax candle and that of a tallow candle, of the same size, produce equal shadows upon the paper screen, are respectively 14'6 and 13'2, the relative luminous intensities of the flames will be =100 : 90*41. Then, if the consumption of wax is 9'56 and that of tallow 10-51 in the same time, the respective luminous effects will be, Wax. Tallow. 14-60 = 1-527, and 13-20 = 1-256, or = 100 : 82'25. 9-56 10-51 Then to estimate the light-value, the price of the material must be taken into account, for if the prices of wax and of tallow were =7:3, the cost of producing the same luminous effect with wax and with tallow would be = 100 : 39-14, for 7 x 100 = 700 and 100 x ?^ = 274. 3 In estimating the luminous effect of gas, the quantity consumed should be measured in cubic feet, and it must VALUATION OF LIGHTING MATERIALS. 329 be remembered that the luminous effect of gas varies ac- cording to 1. The shape of the flame, depending upon the kind of burner used, and 2. The height of the flame, depending upon the pressure. Another method of estimating the luminous intensity of a flame is based upon the fact that a diaphragm of unequal transparency at different parts appears uniformly bright only when illuminated on both sides by light of equal intensity. The reason of this is obvious : supposing a sheet of paper, half of which is rendered transparent by means of grease, to be illuminated on one side only, the greased portion seen from the same side, will appear darkest, because more light is transmitted, and less reflected than at the other portion. When, however, the sheet of paper is equally illuminated on the other side by another light, the loss of brightness, con- sequent upon the greater transparency of the greased portion of the paper, will be exactly compensated by the light trans- mitted from the other side, and the whole surface will appear uniformly bright, however unequal the transparency of the two halves may be. It also follows that when the light behind the paper is more intense than that in front of it, the greased portion will appear proportionately brighter; and when the light is less intense, it will appear darker than the portion that is not greased. The photometer, fig. 71, used for estimating the value of lighting materials by this method, consists of a small tin box, c, blackened inside, and furnished with a sliding tube, d, and a lamp, L, or holder for a wax candle or gas-burner. The end of the sliding tube is covered with a diaphragm of white paper rendered uniformly translucent, by means of a solu- tion of spermaceti in mineral naphtha, with the exception of a ring about six or eight lines diameter, at the centre. This box is attached to a metal bar, b, b, by means of a support, so arranged as to slide along the bar, which is graduated in feet and inches. The light to be examined is placed in front of the dia- phragm, and the box moved towards or from it until the difference between the brightness of the ring and that of the rest of the diaphragm disappears entirely; then the square of the distance at which this effect is produced gives 330 OILS, FATS, ETC. the relative luminous intensity of the flame as compared with that which serves as a standard of comparison. Fig. 71. The value of coal-gas may be estimated by a chemical method, based upon the action of chlorine upon heavy car- buretted hydrogen (olefiant gas). For this purpose the gas is mixed over water with an equal volume of chlorine in a glass cylinder, 12 inches long, \ inch diameter, the capacity of which is divided into 100 equal parts. The vessel containing the mixture is imme- diately covered with a tin sheath. After about five minutes the heavy carburetted hydrogen will have been condensed by combination with chlorine, and by exposing the remaining gas to light, the marsh gas is also condensed. In reading off the amount of contraction of the mixture, allowance must be made for the absorption of chlorine by water, amounting in this case to about 1 degree of the cylinder, which is to be deducted from the volume repre- senting the condensed gases. The amount of contraction is then observed ; and since there were equal volumes of both gases, and there is an equal condensation of both, the number of degrees by which it is represented expresses the per-centage of heavy car- buretted hydrogen in the gas examined. EXAMINATION OF ALCOHOL. 331 CHAPTEK XIII. ALCOHOL, SPIRITS, WINE, BEER, ETC. ; THE TESTS OP THEIE PURITY, AND THE METHODS OF TALTJATION. THE characteristic ingredient of these and similar liquids is alcohol ; the differences in colour, taste, smell, &c: which they present, arise from the presence of substances derived incidentally from the raw material from which they are pro- duced, and varying according to the mode of production. The individual value of these liquids does not in all in- stances depend merely upon the amount of alcohol they con- tain, but is to a great extent conventional. Alcohol ; spirit of wine, C 6 H 4 O 2 , with rarying amount of water. Colourless liquid, with peculiar odour ; density of the anhydrous substance O79381 at 60 F., boils at 173 F. ; density of proof spirit O91984 ; boils at 81 F. The probable impurities are, Fusel oil, indicated, when a glass is rinsed with the spirit and then emptied, by the smell of the portion adhering to the sides. Alcoholic liquids containing fusel oil give, when mixed with a few drops of nitrate of silver solution and ammonia, and exposed to direct sunlight, a reddish or black precipitate. This is not the case with pure alcohol, but, in the presence of other oily or organic substances, the same effect is produced. Or, the spirit may be mixed with -^th of hydrate of potash, evaporated to dryness on a steam-bath, and the residue mixed with dilute sulphuric acid, when, if fusel oil is present, its odour will become perceptible. Wood-spirit, or naphtha, indicated by the smell, by the lower boiling-point anhydrous wood-spirit boils at 152 F. and by the coloration of the liquid when digested with hydrate of potash. 332 ALCOHOLIC LIQUIDS, ETC. Soap, alum, or chloride of calcium, would be detected by the usual tests, applied to the residue left on evaporation. Estimation of alcohol. The valuation of alcoholic liquids is, in many cases, effected by estimating the amount of alcohol they contain. When the liquid does not contain any other substance than alcohol and water, the amount of alcohol is indicated by the density of the liquid, and the value is expressed in degrees having reference to a legalized standard or " proof spirit," consisting of By weight. By volume. Alcohol.... 49-24 57-05 Water . 50-76 42 95 100-00 100-00 In ordinary practice an hydrometer is used for deter- mining the density of alcoholic liquids, and the per-centage of alcohol by weight or volume, or the commercial expression of its value 'is found by reference to a table (see Appendix). When the liquid, in which the amount of alcohol is to be estimated, contains other substances than alcohol and water, as in the case of cordialized spirits, wine, or beer, it is necessary in the first instance to separate the alcohol by distilling a measured quantity of the liquid, and carefully condensing the vapour. When the liquid contains only a small amount of alcohol, it is not necessary to distil over more than one-sixth part in order to obtain the whole of the alcohol, but when the amount of alcohol is considerable, the distillation must be continued until half or two-thirds of the liquid has passed over. The volume of the distillate is then accurately observed, its density determined, and, to ascertain the amount of alcohol in the liquid under examination, the amount of alcohol cor- responding with the density of the distillate, is divided by 6, 2, &c., according as the distillate amounts to --, \, or other fraction of the liquid operated upon ; thus if the density of the distillate were 0'920 at 60 F., it would contain 57'05 per cent, by volume, and 49*24 per cent, by weight of alcohol, and if its volume amounted to one-sixth of the liquid operated upon, the amount of alcohol in the latter would also be one- EXAMINATION OF ALCOHOL. 333 sixth of that in the distillate, or 9*508 per cent, by volume, and 8-206 per cent, by weight. The apparatus best suited for this operation is represented by fig. 72. The condenser, B, is a square copper box, with a flat worm, A, of tinned copper, and two tubes, C C', by means of which a current of cold water is passed through the condenser. The front side of the condenser is supposed to be removed for the purpose of showing the interior arrangement. / One end c f the worm terminates in a delivery pipe through which the condensed spirit runs into the receiver, E, and at 334 ALCOHOLIC LIQUIDS, ETC. tl^ other end there is a metal cap, D, with a flanged lining, G, fitting close upon a metal collar, C, cemented upon the neck of the distilling flask, which is connected with the worm by screwing the cap, D, upon the collar, C. The examination of cordialized spirits, wine, beer, &c., will generally be limited to the determination of two points, viz. 1. The amount of alcohol ; and 2. The presence or absence of injurious or fraudulent ad- mixtures. Cordialized spirits contain, as normal ingredients, besides alcohol and water, a variety of flavouring and colouring sub- stances, and sometimes sugar. The probable impurities, besides those already mentioned as likely to be present in raw spirit, are, Copper, tin, lead, zinc, originating from the vessels in which the spirits are distilled or stored; these substances would be indicated by the usual tests, in the residue left oil evaporation. Sulphuric acid would also be recognizable in the residue. Ginger, pepper, pimento, &c. would be recognizable by the taste and smell of the extract left by evaporating the spirit to one-tenth its bulk. Wine contains, as normal ingredients, besides alcohol and water, sugar, gum, and albuminoid substances, organic acids chiefly tartaric acid colouring and flavouring organic sub- stances of various kinds, both fixed and volatile, the latter constituting the "bouquet." "Wine may contain, besides the ingredients proper to it, admixtures of Alcohol, sugar, flavouring or colouring substances, in greater or less amount, or it may be wholly factitious, but generally speaking there are not any means of ascertaining with cer- tainty whether these substances have been added fraudu- lently or not. The amount of alcohol in wine is estimated in the manner already described, by distilling a measured quantity and ob- serving the density of the distillate, &c. "When the distillate contains acetic acid,\it must be neu- tralized with carbonate of soda ; and again distilled before the density is taken. ESTIMATION OF ALCOHOL. 335 The amount of extract in wine is estimated in the same manner as the extract of beer, p. 336. The amount of free acid in wine may be estimated volume- trically by means of a dilute alkaline solution. The amount of free tartaric acid in the extract of wine is estimated in a weighed quantity of wine by adding an excess of a concentrated solution of neutral tartrate of potash, col- lecting the precipitate of bitartrate of potash, and weighing it. Bitartrate of potash contains 70 per cent, of tartaric acid, and one-half of the quantity in the precipitate would be derived from the wine, the other half from the neutral tar- trate of potash. The presence of other acids citric, malic, and acetic acids tends to augment the results thus obtained ; but this is not of any account, as the tartaric acid prepon- derates over them so largely. The amount of bitartrate of potash in wine is estimated by evaporating a portion until the residue becomes syrupy, then mixing it with alcohol (O858 sp. gr.), filtering and washing with alcohol until the filtrate passes colourless. The insoluble portion is then burnt in a platinum basin, the car- bonaceous residue extracted with hot water, the quantity of carbonate of potash estimated by means of a test acid, and the corresponding quantity of bitartrate of potash ascer- tained by calculation. The amount of sugar in wine is estimated by fermenting the extract with beer yeast, distilling off the alcohol pro- duced, estimating it as already directed, and calculating from the quantity obtained the corresponding quantity of sugar, upon the assumption that 100 parts absolute alcohol represent 59 parts of anhydrous grape-sugar. See also Chapter XIV. Beer contains, as normal constituents, alcohol, sugar, dextrine, colouring and flavouring substances, and carbonic acid. Besides these substances beer may contain, Acetic acid, indicated sufficiently by the smell and taste. Soda or potash, added for the purpose of neutralizing the acid of beer that has become sour ; tested for by evaporating the beer to dryness, burning the residue, and examining the ash in the usual manner ; an addition of alkali is indicated when the amount of alkaline carbonate exceeds 5 grains in the pint. 336 ALCOHOLIC LIQUIDS, ETC. The amount of alcohol in beer is estimated by distillation in the manner already described. The amount of extract may be estimated approximatively, by diluting the residue left after separating the alcohol by distillation, until it measures exactly as much as the quantity of beer operated upon, then observing the density of the liquid, and referring to table XII. in the Appendix to ascer- tain the corresponding amount of extract. Determination of the original gravity or density of leer-wort. This is effected best by a modification of the method already described for estimating the amount of alcohol and of extract in beer. This method is now adopted by the Excise for the purpose of ascertaining the amount of drawback to be allowed upon beer exported. It is based upon the fact that In beer-brewing, there is a uniform or nearly uniform rela- tion, between the production of alcohol and that of extractive substance ; and upon The direct estimation of the attenuation, or reduction of density of wort, consequent upon the conversion of sugar into alcohol. The numerical values of this reduction of density cor- responding to different amounts of alcohol have been deter- mined experimentally, and are given in the following table A. The amount of alcohol, or spirit indication of the beer, is expressed in degrees, which form the first column of the table, and the diminution of density corresponding to degrees and fractions of degrees of spirit indication, is ex- pressed by the numbers opposite the degrees and under the fractions. Then, by adding together, the value thus obtained for the reduction of density consequent upon the fermentation of the wort, and the extract gravity, or the observed density of the beer when deprived of alcohol and made up to the original volume, the density of the wort, or as it is techni- cally termed, the original gravity of the beer, is found. Thus if the spirit-indication is found by experiment to be 9'9, the loss of gravity, or attenuation, will amount to 43' 7 degrees ; and if the extract gravity of the beer is 10447, the original gravity would be 1088 '4. DETEEMINATION OF OEIGUNAL GEAYITT. 337 Cl VO O Tj- ON CO OO COOO COOO COOO i-s Vi r^cJ t-^ e* t^coo*o M M M c* coco-5j-rj-iiovovo OO w O co t^s N ON t^* O cl O C< ^ t^ cl W w CJ c COCOT^-^-lOVOVOVO vo oo vp ON co oo rj- cj 10 t^ *ri t^ ON cl vo M Vj-oo ci t^Mvb wvb MVD wvb Vi K. HI M c) Cl CO CO ^* ^" 1O 1O VO VO J* Tj- CJ Th 00 CO O t^ ON O <* Th VO M W HI c> C> COCOTj-^}-lOlOVOVO ON '"' OO O ^4" ON *O cJ ^" t^ *O VO ON w 1O ^c^Vjvb b iob iob 10 b IOMVO HI 1-4 {sj c4 COCO^^-VOIOVOVO vo t^^ioo ^p r^^ r* ? "r^"^. ^ Vot^Hivb b uiONVj-b iob ii-ib o M M tf CC COTJ-Tj-VOlOVOVO t< coo w IOONVO cl ot^J^.M3 ONO rj- * cOC^^iobNVj-ONrJ-O^Vj-ONTl-biO HI HI HI e* rl cocO'^-'^-iovovo O v t^* *H 10 HI oo t^ *H cl O co ^ oo 10" * t. ^N COTJ-OO T}-OOO covor^o TJ-ON^ *> ClvO O ^*-00 roOO dOO COOO Tj-ONTj-Q OOONO-^O OHvoONCOOO ' t^^vovo ONVOOOO M ovo O cooo d "1 11 d COCOTj-Tt-VOlOVOVO T-OicTt-MVOcovoOivoooct^ HI ooNcor^.cvo HIVO cJ t^-rJ r^rooo HI M M H COCOTj-Tj-VOVOVOVO Ovo l~-00 OVO HI ONO vovoONCOt^M ep n ^-OO d l^wvO OVO HIVO HI r- N OO Hi Hi (4 M COCO^-^-VOVOVOVO rJ-OO dvo HIVOOVOHIVO wvo d t-^ HI HI d d cocoTj-Tj-vovovovO cooooo o\d r^d O ONVorj-ONdvo o cot-~Hivo o VOQ ^j-o VOQVO i t~x HI HI d d coco^t-^-ioiovovo vo^vooo cooo vocoQ ONCOVO O vo HI HI d d d COT$-T$-VOVOVO\O II! O"1f>COTl-VOVOt^OOONOHldCO-. O c vooo O covo M cj ^- vo vo i"^ ON O M 00 C4 O T}- CO rl NO O* HI ^- ^ ON Cl VO HiNcovovor^ooOHi r^ HI e >^- M M Hl HI ^ MVOOOQCONOOOHlTj. HICOVONOr^OOOHi NO rt * M M HI HI CO ONCONOOO HI T*-NO ON O rt co ^ vo I s - oo ON HI 4- oo N CO M HI HI oo H vot^o covooo HI o < r^r*"*? r^? 3 f^ r * t^ C< CO HI M r^Hi T|-NO ONN -^- r^ O O rt co^vor^oo ONW ct VO N CO M HI HI NO O covooo HI covo ON HI VO cJ co HI HI VOI^ONO vo ON HI H HI 11 Pr cent, acetic acid. "--* -- ON M DETERMINATION OF ORIGINAL GRAYITY. 341 Cjrperimwt. For the purpose of determining the original gravity of a sample of beer, the most convenient quantity to be taken is 1500 grain measures at 60 F. This is shaken in order to remove carbonic acid, transferred to the flask E, and the portion adhering removed by rinsing the measure with a little water. The beer is then distilled until the whole of the alcohol has passed over, the distillate made up with water to the volume of 1500 grain measures at 60 E., and its density observed. The residue in the flask E is made up with water to the volume of 1500 grain measures at 60 F., and its density observed. Then from these two data the original gravity is ascertained as above directed. For estimating the amount of acid, 1000 grain measures of the beer is mixed with a solution of ammonia (sp. gr. 0;9986) until neutralized. The number of grain measures required indicates the per-centage of acetic acid. Another method of examining beer consists in estimating the amount of water, by observing the quantity of chloride of sodium dissolved by a known quantity of the beer, before and after removing the alcohol, and is based upon the follow- ing data: 1. The solubility of chloride of sodium is constant for a range of temperature from 50 to 100 F. ; 36 parts of the salt dissolving in 100 parts of water, and the saturated solu- tion contains 2'7778 parts water for 1 part of the salt. 2. The presence of alcohol and extract does not augment the solvent action of water upon chloride of sodium ; so that the amount of this salt dissolved by beer will be inversely- proportionate to the amount of these constituents ; thus, if 1000 grains of the beer dissolves 3127 grains chloride of sodium, the amount of water would be 868 61 grains, for 36 : 100 = 312-7 : 868'61, and the remainder, 131'39 grains, would be the sum of the other ingredients of the beer, alcohol, extract, and carbonic acid. The amount of extract is estimated in the same manner, after separating the alcohol, and the amount of alcohol is found from the difference between the two results. The apparatus, fig. 73, used for this experiment is called a " hallimeter," and consists of a tube 5 inches long, an inch and a half wide at the upper end, and a quarter of an inch 342 ALCOHOLIC LIQUIDS, ETC. wide at the lower closed end, which is graduated so that each division, represents the volume of one grain of chloride of sodium powdered, and passed through a sieve with meshes CK)673 line by 0'0757 line, and wires 0*0458 line thick. (ZErpertnunt For estimating the sum of alcohol and extract, 1000 grains of the beer is weighed in a glass flask, 330 grains of powdered chloride of sodium introduced, the flask immersed for ten minutes in water at 100 F., and frequently shaken meanwhile. By this means the solution of the salt is facilitated and the carbonic acid is expelled. The flask is cooled, dried, and weighed ; the loss of weight represents carbonic acid. Then by closing the mouth of the flask with the thumb and reversing it, the salt remaining undissolved may be collected in the neck, transferred, together with the liquid, to the hallimeter tube, and its depo- sition in the narrow portion of the tube facilitated by stirring with a wire and by shaking the tube.. The volume of the salt is then read off, the quantity deducted from 330 grains, and the quantity, #, of water cor- responding to the quantity, ^, of salt dissolved, calculated fcy the proportion, x i q = 100 : 36. The total amount of alcohol and extract is found by deduct- ing this quantity of water from that of the beer operated upon. If, for instance, the quantity of salt remaining undissolved is 17*3 grains, the quantity of water corresponding to the 3127 grains dissolved will be 868'61 ; for, 36 : 100 = 3127 : 868-61. Consequently the beer contains in 1000 parts 868 61 parts of water, and the remainder, 131' 39 grains, is the sum of the carbonic acid, alcohol, and extract. It then remains to estimate the amount of extract alone, and for this purpose 1000 grains of the beer is evaporated EXAMINATION OF BEEB. 343 to rather less than one-half, in a similar flask, so as to remove the whole of the alcohol and carbonic acid, water added until the residue weighs 500 grains, then 180 grains of salt, and the operation repeated as before. The quantity, q 1 , of salt dis- solved is found by deducting the residue from 180, the cor- responding quantity, #', of water calculated as in the former experiment, and when deducted from the weight of the liquid gives the quantity of extract as residue. If, for instance, the quantity of salt remaining undissolved is 21-3 grains, the quantity of water corresponding to the 158*7 grains dissolved will be 440'83 grains ; for, 36 : 100 = 1587 : 440'83. Consequently the liquid would contain in 500 parts 440*83 parts water, and the remainder, 59*17 grains, would be the amount of extract in 1000 parts of beer. Then by adding to this amount, that of the carbonic acid estimated in the first instance and deducting the sum of both constituents from the total amount of carbonic acid, extract, and alcohol previously estimated, the amount of alcohol is found as remainder. Supposing the amount of carbonic acid in the previous instance to be 1*5, the amount of alcohol would be 7072, for 59-17 + 1*5 = 60*67, and 131*39 - 60*67 = 70*72. "When the proportions of beer and salt used are those in- dicated above, the following table obviates the necessity of calculating in each instance the total amount of extract and alcohol, or the amount of extract corresponding to the quan- tity of salt left undissolved. For the first experiment, the number of grains of salt undissolved is found in the first column, and opposite to it in the second column is the cor- responding amount of alcohol and extract conjointly. In the second experiment, the number of grains of salt left undis- solved is found in the first column, and opposite to it in the third column is the corresponding amount of extract. When the quantity of salt in either case contains a fraction, the corresponding amounts of alcohol and extract, or of extract alone, are sought in the small table below and added to the amounts already obtained for the whole numbers. 344 ALCOHOLIC LIQUIDS, ETC. Residue of salt in grains. Correspond- ing amount of alcohol and extract. Correspond- ing amount of extract. Residue of salt in grains. Correspond- ing amount of alcohol and extract. Correspond- ing amount of extract. O I 83 86 21 22 142 144 i 8 2 87 2 3 H7 64 3 92 24 150 67 4 94 25 153 6 9 5 97 26 I 5 6 72 6 1 00 27 I 5 8 75 7 103 28 161 8 106 22 29 164 Si 9 108 25 3 167 83 10 in 28 3 1 169 86 ii 114 31 172 89 12 '3 117 119 ll 33 34 178 t J 4 122 39 35 ill 15 125 42 36 183 16 128 44 37 186 '7 131 47 38 189 ll 133 5 39 192 19 I 3 6 53 . 40 194 20 I 39 56 Residue of salt in fractions of grains. Correspond- ing amount of alcohol and extract. Correspond- ing amount of extract. Residue of salt in fractions of grains. Correspond- ing amount of alcohol and extract. Correspond- ing amount of extract. O'l O 0-4 I o*7 2 2 1 5 2 8 2 ; 3 I 6 2 9 3 ATI important correction is still to be made in order to ascertain the amount of absolute alcohol. This is owing to the fact that the quantity of water estimated in the first experiment from the quantity of salt dissolved, does not represent the whole of the water in the beer, a certain por- tion always remaining combined with the alcohol. In the second experiment this is not the case, and the calculated result represents the true amount of water. The quantity of water thus retained by the alcohol is pro- portionate to the amount of alcohol in the beer, consequently it is requisite to have a table constructed so as to show the EXAMINATION OP BEEE. 345 amount of absolute alcohol and water in any quantity of alcohol indicated in the first experiment. This table has been constructed from experimental data obtained with liquids containing known proportions of absolute alcohol. Quantity of alcohol found. Amount of bsolute alcohol by volume. Differences. Quantity of alcohol found. Amount of bsolute alcohol by volume. Differences. 39 21-496 79 43*899 0-519 40 22-052 0*556 80 44*347 0-519 41 22-608 O'SS 6 81 44*847 0-525 42 23-165 o*557 82 45'366 0-519 43 23-721 o*556 83 45*885 0-519 44 24-277 0-556 84 46*404 0-519 45 46 25-389 0-556 o*556 85 86 46-923 47*442 0-519 0-519 47 25-946 o*557 87 47*961 0-519 48 26*502 0*556 88 48*480 0-519 49 27-058 0-556 89 48'999 0-519 50 27-615 o-557 90 49-5I8 0-519 28-171 0-556 9 1 50-037 0-519 S 2 28-727 0-556 92 0-519 53 29-284 o-557 93 51-075 0-519 54 29*840 -0-556 94 5 1 *54 0-519 55 30-396 0-556 95 52-113 0-519 56 0-556 96 52-632 0-519 57 31*561 0-609 97 53*15! 0-519 58 32-170 0-609 98 53-670 0-519 59 32-779 0*609 99 54*187 0-517 60 33'388 0*609 100 54-702 0-5I5 61 33-996 0*608 101 55-217 0-5I5 62 34-605 0-609 102 55*732 63 0*609 103 56-247 0-515 64 35*823 0*609 104 56-762 *5 X S 65 36-432 0*609 57*277 0-515 66 37-041 0*609 106 57792 0-515 67 37*597 o'556 107 0*515 68 38-102 0-505 108 58-821 0*515 69 38*620 0-518 109 59*373 0-515 70 39-138 0-518 no 59-852 0-515 7 1 39-656 0-518 III 60-368 0-516 72 4o*i75 0-519 112 60-883 0-515 73 40*694 0*519 "3 61-398 0-515 74 41*213 0*519 114 61*913 0-515 75 41-732 0*519 115 62-428 0-515 76 42-251 0*519 116 62*943 0-515 77 42*770 0-519 117 63*458 0*515 78 43*289 0-519 118 63-973 0-515 346 ALCOHOLIC LIQUIDS, ETC, . TABLE or ALCOHOL PBOPOBTIONS (continued). Quantity of alcohol found. Amount of absolute alcohol by weight. Differences. Quantity of alcohol found. Amount of absolute alcohol by volume. Differences. 119 64-488 Q'5'5 '35 72-790 0-504 120 65-004 516 I 3 6 73-295 0-504 121 65-519 0-515 137 73799 0-504 122 66^034 0-515 I 3 8 74'33 0-504 123 66-549 0-515 '39 74-808 0-504 IZ4 67-064 0-515 140 75-312 0-504 125 67-579 0*516 141 75-817 0-504 126 68-095 0-516 142 76-322 0-504 127 68-610 0-515 '43 76-826 0-504 128 69-125 0-515 144 77 - 33 o 0-504 I2 9 69-636 0-511 145 77-835 0-504 130 70*134 0-058 146 7^339 0-504 '3 1 70-642 0-508 J47 78-844 0-504 132 71-277 0-504 148 79'348 0-504 133 7 I- 7 8l 0-504 149 79'853 0-504 134 72-286 0-505 150 8o-357 0-504 Thus the quantity of alcohol, 70*72, indicated by experi- ment, in the above instance would be found by reference to the table to contain 39*51 parts by measure of absolute alco- hol, and 31'21 parts of water, which may be added to the quantity of water indicated by the salt dissolved. The following tables show the average amounts of alcohol in various kinds of beer, wine, spirit, &c. Per-ce Absolute alcohol. ntage by we Extract. ight of Carbonic acid. Ale, Barclay's 6*90 8-08 6-62 / 476 I 6- 9 I 6-10 4-20 4'94 J" 4-10 I 470 3-00 2-50 6'02 15-88 H'97 7-53 6-80 5-98 3-84 13-03 7-61 7-48 4-00 4-50 0-15 0*04 < - 0-18 0-77 0*19 0-18 0-18 o- 5 London Bock-beer Darmstadt beer (for storing) about Bohemian (draught) AMOTTNT OF ALCOHOL IN WIITE, ETC. 347 Per-centage Proof-spirit by measure. amount of Absolute alcohol by measure. / Fer-centage Proof-spirit by measure. amount of Absolute alcohol by measure. ine 26-195 23-886 22*II3 r 7-162 1 18-199 20-184. 21*121 19-247 20'6l9 20-5I 9 l8*288 I7-OI7 J" 5794 I 12-601 r 7'i86 \ I5-459 1 19*436 13739 r 9-271 O5-424 L 14*274 19-838 13-683 19*225 21*75 22-61 18*37 6*18 15-11 16-76 i7'45 15*98 17-22 17-04 15*91 14-31 5*00 10*46 6*19 13-34 16*14 11*40 8*00 13*31 11*84 11*84 11*36 15*96 Cape Madeira Muscat 20*195 20-351 22*024 14-831 17-307 17*039 16-315 11*018 28*737 20*195 21*968 22*916 13*203 11*006 r583 9-902 4*684 59-861 57-542 60*575 60*107 1677 17*00 18-29 12-32 14-35 I4-I5 13*64 9-I5 23*86 16*77 18-24 19*03 10*96 9*14 6*30 8*00 3-89 49*71 4777 50*20 49-91 a Constantly . . . ux, Claret ?lla Tinto Schiratz Syracuse .... Nice Tokay is Raisin wine Drained grape wine Lachrymse Christi Currant wine G-ooseberry wine. . . Elder wine n Cyder I Perry J adeira ev . . . a agne. . . , % Hermitage Brown Stout Ale Porter . "Riirn Grave mac Hollands ! Scotch Whiskey... oti lion 348 SUBSTANCES USED AS FOOD, ETC. CHAPTEE XIY. SUGA.E, STAECH, FLOUE, BEEAD, MILK, BUTTEE, TEA, COFFEE, CHOCOLATE, ISINGLASS, ETC. ; THE TESTS OF THEIE PUEITT AND THE METHODS OF VALUATION. THE substances treated of in this chapter are mostly im- portant either as articles of food, or as constituents of food. Some of them are also used for other purposes in the arts. The methods of valuation applicable to them depend in great measure upon the purposes for which they are employed. Sugar. The varieties of sugar that are of any great im- portance in commerce, &c>, are cane-sugar, C I2 H" O 11 , grape- sugar, C 12 H 14 O", and starch-sugar, C 12 H U O 14 , together with the uncrystallizable sugar, C 12 H 9 O 9 , and fruit-sugar, C 12 H 12 O 12 , usually associated with the two former kinds. Other kinds of sugar, such as milk-sugar, mannite, &c., are less important. The most frequent and probably the most important kind of sugar is that obtained from sugar-cane, Saccliarum qffici- narum ; beet-root, Seta vulgaris, and more rarely from the stalks of maize, Zea metis, or the sap of the maple, Acer saccharinum, &c. The sugar originating from all these sources is chemically the same, and for all practical purposes there is so little difference between the products obtained from them, that there is no great probability of any question arising as to what may be the plant from which any parti- cular sample of sugar was obtained. On the other hand, it is more frequently desirable to know whether grape-sugar is mixed with cane-sugar, and whether grape-sugar syrup is not mixed with honey or cane-sugar syrup. Estimation of sugar. The amount of sugar either cane-sugar or grape-sugar in any substance may be estimated from the quantity of car- ESTIMATION OF STTGAB. 349 bonic acid produced by the fermentation of the sugar with yeast. Eor this purpose a known quantity of the substance is dissolved in water, the solution introduced into the flask, #, fig. 33, and mixed with yeast. The flask, &, containing sulphuric acid, is then attached as in the alkalimetric opera- tion (p. 66), and the apparatus kept for some days at a tem- perature of 77 F. until the evolution of gas has ceased. The loss of weight then gives the quantity, q, of carbonic acid, and the quantity, #, or #', of sugar is calculated thence by one of the proportions : x : q = C 12 H n O u : 4C0 2 , or = 171 : 88, #': = C 12 H 14 14 : 4C0 2 , or = 198 : 88, according as the sugar to be estimated is cane- or grape-sugar. If it is desirable, the result thus obtained may be checked by estimating the quantity of alcohol, produced at the same time, by distilling the contents of the flask a, and proceeding as directed at p. 332, for the estimation of alcohol. Cane-sugar may also be estimated, even when associated with grape-sugar, by a method based upon the following data : 1. Cane-sugar combines with lime in definite proportions, forming a substance that has the alkalinity of lime, and is not decomposed at 212 F. 2. The corresponding compound of grape-sugar and lime is decomposed when its solution is heated to 200 P. with production of a substance that is perfectly neutral. 3. Water dissolves only O'l per cent, of lime, while sugar solution dissolves considerably more, owing to the pro- duction of the lime-sugar compound, 2C 12 H n O u , 3CaO, which is soluble in water. The experiment is made with 10 grms. of the sugar, which is intimately mixed with about an equal weight of slaked lime and a few drops of water, the mass transferred to a filter, and the filtrate passed through the lime again so as to saturate the whole of the sugar, the residue washed with water, and the liquid diluted with water- to the volume of one litre. A tenth of this solution is then diluted with twice or three times its volume of water mixed with litmus, and the alkali - metric experiment made with 20 cubic centimeters of the normal sulphuric acid solution (p. 56) diluted to 100 cubic centimeters. The number of centimeters of test-solution 350 SUBSTANCES USED AS FOOD, ETC. requisite to neutralize the lime will express the per-centage amount of sugar, after deducting 2 cubic centimeters as a correction for the lime dissolved by the water. When cane-sugar is associated with grape-sugar, the liquid that has been saturated with lime is boiled previous to the alkalimetric experiment; by this means the compound of grape-sugar with lime is decomposed, and the lime combined with cane-sugar, alone remains recognizable by the test acid. In examining saccharine liquids such multiples of 10 cubic centimeters as correspond with the amounts of sugar they contain are measured and treated in the same manner as the sugar solution. If it is desirable to estimate the total amount of sugar when the two kinds are associated together, two experiments must be made, in one of which the quantity of lime is esti- mated before boiling the liquid, and the difference betwtvn the two results thus obtained indicates the amount of grape- sugar. Another method of estimating sugar is based upon the following data : 1. Grape-sugar precipitates red suboxide of copper from alkaline solutions containing oxide of copper at 140 F. 2. Cane-sugar does not exercise this reducing action under the same conditions. 3. Cane-sugar may be easily converted into grape-sugar. The reaction that takes place between grape-sugar and oxide of copper under these circumstances is of such a nature that 180 parts of grape-sugar effect the reduction of 10 equi- valents gf oxide of copper. The test-solution is made by dissolving 140 grms. of neutral tartrate of potash in a small quantity of water, mix- ing it with from 600 to 700 grms. of caustic soda solution (T12 sp. gr.), then adding a solution of 36'46 grms. sulphate of copper in water, filtering and diluting with water to the volume of one litre. A dark blue liquid is thus obtained which may be kept for some time, in the dark, without decomposition, and is not altered by boiling. Its volu- metric value is estimated by direct experiment. For this purpose 1 grm. of pure crystallized cane-sugar is dissolved in water, and converted into grape-sugar by boiling the liquid for half an hour with a few drops of sulphuric acid. ESTIMATION OF SUGAR. 351 This solution is diluted with water to the volume of 100 cuhic centimeters ; consequently each cubic centimeter contains 0-0116 grin, grape-sugar and represents O'Ol grm. of cane- sugar. Then 50 cubic centimeters of the copper solution is placed in a capacious porcelain dish, mixed with some strong caustic potash solution, heated to the boiling-point, and the sugar solution gradually added from a burette, until the liquid becomes colourless, and the whole of the copper is preci- pitated as red suboxide. The best way of ascertaining whether the whole of the copper is precipitated, is to test a drop of the liquid from time to time towards the end of the operation with ferro- cyanide of potassium solution, feebly acidified, which pro- duces a reddish-brown precipitate or coloration so long as a trace of copper remains in solution. The number of cubic centimeters of sugar solution requisite to precipitate the whole of the copper gives the quantity of cane-sugar which, when converted into grape-sugar, is equi- valent to 50 cubic centimeters of the copper solution, which is diluted, if necessary, so that 100 cubic centimeters repre- sent exactly 0'5 grm, of cane-sugar. In order to examine a mixture of cane-sugar and grape- sugar by this method two solutions are made, each con- taining 10 grms. of the sugar ; one of the solutions is boiled for half an hour with sulphuric acid, for the purpose of con- verting the whole of the cane-sugar into grape-sugar, and then both solutions are diluted with water to the volume of a litre. An experiment is then made as above directed with each of these solutions, 50 cubic centimeters of the copper solution being used in each, and the volume of sugar solution requisite for precipitating the copper in each indicates the amount of grape-sugar present, the difference between the two results giving the quantity of grape-sugar equivalent to the cane-sugar present. Thus, for example, if 100 cubic centimeters of the sugar solution that has not been boiled with acid, representing I'O grm. of the sugar under examination, exactly precipitates the copper from 50 cubic centimeters of the test-solution, that quantity will contain as much grape-sugar as is equivalent to 0'250 grm. cane-sugar, or 0'289 grm., and the amount of grape-sugar in the sample examined will be 28'95 per cent. 352 SUBSTANCES USED AS TOOD, ETC. If, in the experiment with the sugar solution that has been boiled with acid, 30 cubic centimeters precipitate the copper from 50 cubic centimeters of the copper solution, this quantity will contain as much grape-sugar as is equivalent to 0'250 grm. cane-sugar, or 0-289 grm., and the total amount of grape-sugar would be 83*33 per cent. Then the difference between the two results will give the amount of grape-sugar equivalent to the cane-sugar con- verted by boiling with acid ; thus : Total amount of grape-sugar 96'49 Ac^per-centage of grape- j 28 . 95 28 . 95 ^.^^ Amount of grape-sugar equi- j &m ^ cane-sugar, valent to cane-sugar present J 12'72 impurities. 100-00 For 67-54 : 58'33 = 198 : 171. The amount of crystallizable cane-sugar may also be esti- mated by washing a known quantity of the sample with a saturated solution of sugar, which removes only the syrup and uncrystallizable sugar, &c. For this purpose 10 grms. of the finely powdered sugar, mixed with 4 cubic centimeters of alcohol, is shaken with 10 cubic centimeters of a liquid consisting of 800 cubic centimeters alcohol, 40 cubic centi- meters acetic acid, and 40 grms. of sugar; the coloured liquid is poured off, and the operation repeated, if requisite, with a fresh quantity of the liquid. "When the sugar appears sufficiently washed, it is transferred to a weighed filter, the funnel covered with a glass plate, and when the liquid has ceased to drop through the filter, the sugar is weighed, dried at 212 F., and again weighed. The difference between the two weighings gives the quantity of liquid evaporated from the sugar solution, and as the amount of sugar in that solu- tion is known, the corresponding quantity of sugar may be calculated and deducted from the weight of the filter and its contents. The solution used for this experiment should be kept saturated by hanging in it a bag of sugar crystals. The raw sugar met with in commerce is never pure, but contains admixtures of moisture, colouring, gummy and albuminous substances, fragments of cellular tissue, sand EXAMINATION OF SUGAB AND HONEY. 353 and earthy particles, soluble salts, uncrystallizable sugar, certain organic acids, &c. Some of the admixtures are in no other way detrimental than in reducing the value of the sugar according to their amount ; others are, in addition to this, prejudical in the refining operation, and determine the conversion of a considerable amount of sugar into molasses. Water is indicated to some extent by the appearance of the sugar ; its amount may be estimated by heating a weighed quantity of the sugar to 230 F. until the weight remains constant. Sand, Sfc. are indicated by a residue insoluble in water, and may be estimated by weighing the washed and dried residue obtained from a known quantity of sugar. Gkimmy and albuminous substances are indicated, on the addition of basic acetate of lead solution, by a precipitate, and may be estimated by weighing the washed and dried precipitate obtained from a known quantity of sugar, and then igniting the precipitate to ascertain the amount of organic substances it contains. Mineral salts are indicated by the usual tests in the resi- due obtained by heating 5 or 10 grms. of the sugar upon a clean plate in a muffle, until all the carbon is burnt. Glucose or starch-sugar, indicated, when a solution of the sugar is boiled with caustic soda, by a brown coloration ; or when a concentrated solution of the sugar is mixed with hydrate of potash, heated to 212 F., diluted with water, and mixed with a few drops of nitrate of cobalt solution. In the absence of starch- sugar, a blue precipitate is produced directly, and it becomes green after some time, but when starch-sugar is present, this reaction is not produced. Con- centrated solutions of starch-sugar give a dirty brown preci- pitate. Starch-sugar is also indicated when a solution of the sugar is heated to 140 F. with an alkaline solution of oxide of copper, by a red precipitate of suboxide of copper. Cane- sugar solution does not give this reaction, until after it has been boiled some considerable time with the copper solution. Honey is the only kind of grape-sugar that is met with in commerce. It contains, besides crystallizable grape-sugar, glucose or uncrystallizable fruit-sugar. 2 A 354 SUBSTANCES USED AS FOOD, ETC. The substances with which it is most frequently adul- terated, are, Starch-sugar ; indicated probably, when the honey is boiled with six or eight times its volume of alcohol (80 per cent.), by an insoluble residue which, when dried, presents the appearance of gum. Such a residue may consist wholly or in part of gelatin, so that it must be tested to ascertain whether this is the case. For this purpose the test by charring with lime gives the quickest indication, and a solu- tion of tannic acid, mixed with the water solution of the residue, gives a precipitate with gelatin but not with dextrin. However, no means are known by which starch-sugar can be detected or estimated with certainty in honey. Starch or flour \ indicated, when the honey is mixed with cold water, by a residue, which gives with solution of iodine the blue colour characteristic of starch, see p. 358. The amount may be estimated by collecting and weighing the residue. Gelatin-, indicated, when the honey is dried and heated in a test-tube with caustic lime, by the evolution of ammo- nia, which gives a blue colour to litmus paper held over the mouth of the tube. Fi 74 Starch ; an almost universal constituent of certain parts of plants. This substance con- sists of small granules with a cellular structure varying in size and ap- pearance according to the plant from which it is derived. The general characteristics of starch- granules are best illus- trated by the starch of the potato, which, when examined by the aid of the microscope, pre- sents the appearance shown in the accompanying woodcut (fig. 74). In most kinds of starch-granules there is a point, a, round which the substance of the granules is arranged in regular layers represented by concentric lines. . STAECH. 355 Fig. 75. This point is called the hilum, and its appearance is more or less characteristic ; in some kinds of starch the hilum is not so marked as in others, and as a general rule it is more apparent when the granules are dry. In the accom- panying drawings of starch -granules, those marked a are repre- sented as seen when dry, and those marked 1} are represented as seen when moist. The symmetric struc- ture, and the position of the hilum, are ren- dered still more appa- rent when the granules are examined by the aid of polarized light, as shown by fig. 75. _ ^ The starch of com- merce is generally the produce of varieties of Triticum, of Oryza sa- tiva, and of Solatium tu- beroswm. The starch of other plants also con- stitutes, under various names, articles of com- merce. The granules of wheat- starch (fig. 76) appear by aid of the micro- scope to vary in size ; the smaller being nearly spheroidal, the larger ones lenticular. The hilum is round or elongated and sur- rounded by concentric rings. The starch-granules of barley, oats, and rye much resemble those of wheat ; those of barley-starch (fig. 77) are somewhat larger, their shape less regular, and the hilum and rinirs are 2A2 356 SUBSTANCES USED AS POOD, ETC. Fig. 77. scarcely perceptible; those of oats (fig. 78) are for the mosl part more angular, the hilum is tolerably distinct, but no rings are perceptible, and crosses do not ap- pear when they are seen by polarized light ; ^^mm^^r those of rye (fig. 79) are ^ d>0 - ^B& for the most part the largest of the four with fewer small granules, their shape is irregu- larly lenticular, rarely angular; the hilum is very marked, and gene- rally radiate. The starch -granules of rice (fig. 80) are very small, polygonal, deci- dedly angular, and with- out visible hilum or concentric rings. The substances with which starch is likely to be adul- terated, are, Mineral substances ; indicated, when a weigh- ed quantity of the starch is incinerated, by the amount of ash exceed- ing 1 per cent. When there is reason to sus- pect the presence -of such admixtures, the ash may be further exa- mined, as directed at p. 219, to ascertain its nature. Other kinds of starch ; indicated, when the starch is examined by the aid of the microscope, by the appearance of the granules, Potato-starch mixed with wheat-starch is indicated, wheE the starch is gently rubbed with water, and the filtered Fig. 78. STABCH- GRANULES. 357 Liquid mixed with iodine solution, by the production of a blue colour. Wheat-starch treated in this way gives a liquid that becomes only yel- low or reddish-yellow. It is necessary, how- ever, to be careful in rubbing the starch, not to exercise too much force, so as to break the granules of wheat- starch, since in that case a blue colour would be produced even in the ab- sence of potato-starch. Potato -starch may be distinguished from wheat-starch also by the effects produced upon them by an alkaline so- lution containing 1*75 per cent, caustic potash. "Wheat-starch is scarcely altered in appearance when mixed with thirty times its weight of this solution ; the liquid remains thin and the starch-granules sink to the bottom when the liquid is diluted. Po- tato-starch gives under the same circumstances a thick opaline jelly within a minute of mix- ing ; the granules swell considerably, and when more liquid is added ap- pear as if completely dis- solved. A mixture of equal parts wheat-starch and potato-starch gives a jelly within two mi- nutes. A mixture of four parts wheat-starch and one part potato-starch gives a thick opake milky muci- lage. A mixture containing one- tenth potato-starch gives 358 SUBSTANCES USED AS FOOD, ETC. an opake milky mucilage, which does not run in drops like the liquid obtained with pure wheat-starch. The most distinctive character of starch is the production of an intense blue colour when iodine is mixed with its so- lution in water. Flour ; the ground seeds of certain grasses and leguminous plants. The various kinds of flour contain as normal ingredients starch, albuminoid substances, dextrin, sugar, cellulose, water, fat, and a certain amount of mineral substance. The various kinds of flour differ considerably, not only according to the grain from which they are prepared, but also according to the quality, age, or condition of the ,<*rain, the mode of grinding, and the sifting or dressing it undergoes. The quality of flour and the characters it presents will therefore be materially influenced by one or other of these circumstances, and. as a general rule, the determination of these particulars calls for greater attention, in the exami- nation of flour, than the search for admixtures, either acci- dental or fraudulent. The substances with which flour is likely to be adul- terated, are, . Mineral substances ; indicated, when a weighed portion of the flour is incinerated, by the amount of the ash exceeding 2 per cent. Other kinds of flour ; this is probably the most frequent adulteration. Although examination of the starch-granules by the aid of the microscope may serve to distinguish between wheat-flour and that of other grain, it is question- able whether the presence of other kinds of flour mixed with wheat-flour can be detected with certainty by the use of the microscope even when the amount is considerable, on account of the great similarity of the starch-granules from different plants, the diversity of those from the same plant, and also the small number of granules that can be brought within the microscopic field. Potato-starch or flour may be detected by means of a weak solution of caustic potash (p. 357). Besides barley, oat, rye and rice-meal, wheat-flour may be adulterated with the meal of maize or leguminous plants. i FLOTJR. 359 Fig. 81. The starch-granules of maize (fig. 81) are rounded, more or less irregular, and sometimes mullar-shaped ; the hilum is either circular or ra- diate, and very distinct : no rings are perceptible. The starch -granules of peas (fig. 82) are long, irregularly shaped and more uniform in size than those of wheat; the hilum presents the appearance of a longitu- dinal depression or slit, sometimes with lateral or transverse branches. The presence of meal of leguminous plants is also indicated by the deliquescent character of the ash, by its alkaline reaction upon turmeric paper, and when its aqueous solution is mixed with nitrate of silver solu- tion, by the production Fig. 82. of a white precipitate, which is darkened by ex- posure to light. The ash of pure wheat-flour is granular, sandy, the a- queous solution does not affect turmeric paper, and the precipitate pro- duced with nitrate of| silver does not darken by exposure to light. In the quantitative examination of flour, the several data to be ascertained are the amounts of Moisture ; estimated by drying a known quantity of the flour at 212 E., and weighing'again until the weight remains constant. 360 SUBSTANCES USED AS FOOD, ETC. Fat; estimated by digesting a weighed quantity of the dried flour with successive quantities of ether ; evaporating the clear liquid and weighing the residue, dried at 212 F. Starch; estimated from the quantity of grape-sugar it yields. For this purpose the residue, left after separating tat and dextrine, is boiled with a small quantity of sulphuric acid, until iodine no longer produces a blue colour in the liquid, the sulphuric acid separated by agitating the liquid with carbonate of baryta, and filtering ; the filtrate is then evaporated to dryness at 212 F., the residue of grape-sugar weighed, and the corresponding amount of starch ascertained by calculation, 18 parts of grape-sugar representing 16 parts of starch. Dextrine ; estimated by digesting a known quantity of the flour with water at the ordinary temperature, evaporating the liquid to dryness at 212 F., and weighing the residue. Gluten, albumen, fyc.\ estimated from the quantity of nitrogen obtained in the state of chloride of ammonium and platinum, as directed at p. 197 ; 16 parts of nitrogen repre- senting 100 parts of dry albuminous substance. The amount of gluten in wheat flour may be estimated approximative^ by kneading the flour with water and wash- ing the dough upon a cloth in a current of water, by which means the starch is removed and the greater part of the gluten remains adhering io the cloth. Bran ; estimated by warming a known quantity of the flour with water upon a steam-bath, straining the liquid through fine muslin, washing the residue until the water passes through clear, then drying and weighing it. This dry resi- due represents twice its weight of bran in the natural state. Cellular membranes, lignin ; estimated by covering a known quantity of flour with sulphuric acid diluted with rather more than its own weight of water, digesting the mixture for twenty -four hours, heating it on a steam-bath until the acid liquid no longer becomes turbid on the addition of water ; it is then diluted with water, filtered, the contents of the filter washed with warm water, dried at 212 F., and weighed. Mineral substances ; estimated as ash, by igniting a known quantity of the flour in a shallow platinum capsule until the whole of the carbon is burnt, and weighing the residue. BEEA.D AND MILK. 361 The ash thus obtained will contain, besides the mineral con- stituents of the corn, a certain quantity of substance origi- nating from the grinding stones, but this should not amoui to more than half an ounce in the hundredweight of flour, an amount much less than that of the mineral constituents of various kinds of flour separated from bran which in wheat- and rye-flour is about 1 per cent in ^rley-flour 1-5 per cent., and in oat-flour 2*0 per cent., so that when any kind of flour is found to contain more than 2 per cent of mineral substances, it may be safely inferred that they have been mixed with the flour either accidentally or irau- ifitis desirable, the ash may be examined, as directed in Chapter IX., to ascertain the substances it contains, in case there is reason for suspecting adulteration with mineral sul stances. Bread is liable to adulteration with the same materials as flour ; it may also contain . Alum ; indicated by the presence of alumina in the ash Sulphate of copper; indicated by the presence of copper n Both Substances are tested for as directed in Chapter X. Milk; an animal secretion; chiefly the produce of Bos TttUTUS. -i It is essentially a water solution of casein, of * peculiar kind of sugar and certain saline substances, in which are suspended small globules of fat that communicate to the L P id its opacity. The amount of the several mgredients of milk varies according to the species, age, food and mode of life of the animal yielding it. The density of normal cow's milk may vary between 1 026 and 1-032 but as this character is influenced in opposite s by tne amount of butter and by that of casein and Tugar, it does not afford any precise indication of the goo< ae The substances with which milk is most likely to be adul- a^oably indicated, when a drop of the milk is placed on the finger nail, by the thinness and flattening of ?he drop* while the case of good milk the drop retains its 362 SUBSTANCES USED AS FOOD, ETC. convex form. This test is not very trustworthy, especially in its negative indications. Dextrin, starch or flour ; indicated, when the milk is mixed with a drop of iodine solution, by the production of a deep blue or brown colour. Brains of sheep, calves, &c. ; indicated by the greyish colour of the milk, and, when it is left for a time undisturbed, by the deposition of a white sediment, containing fine threads of the cellular substance of the brain. Microscopic examina- tion would be the best means of detecting the presence of brain. Normal milk seen by the aid of the microscope presents the appearance represented by the drawing (fig. 83). Chalk or carbonate of magnesia ; indicated by a sediment which effervesces with acids. Alkaline carbonates-, indicated, when the heated milk is mixed with acetic acid, by the curdling not taking place immediately. The presence of alkaline carbonates is also indicated, when the milk is mixed with acetic acid, heated, the curd separated by filtration and washed, the filtrate then evapo- rated nearly to dryness, the residue mixed with absolute alcohol, the clear liquid evaporated to dryness, the residue ignited, and the ash weighed. This should not amount to more than 0'35 per cent. Metallic substances ; originating from vessels in which the milk has been- kept, would be tested for in the ash as directed in Chapter X. For the purpose of estimating the goodness of milk that does not appear to be adulterated, the best criterion is pro- bably the amount of dry residue left after evaporation to This is estimated by mixing with a known quantity MILK AND BUTTER. 363 of the milk an equal weight of powdered gypsum, and eva- porating until it becomes pasty, and then drying the residue upon a steam-bath until its weight remains constant. The difference between the weight of the residue and that of the milk and gypsum, gives the quantity of water in the milk and, by subtracting this from the quantity of milk taken, the quantity of dry substance. The amount of dry substance should be at least 12 per cent., and may be taken as an indication that no great abstraction of cream or dilution with water has been practised ; some- times it is as much as 14 per cent. The amount of fat may be estimated by repeatedly digest- ing the dry residue, from the last operation, with ether, until nothing more is extracted, then filtering the liquid, .evapo- rating, and weighing the dry residue. The normal amount of fat varies from 3 '5 to 5 per cent. The amount of sugar may be estimated by the method already described for estimating grape-sugar by means of an alkaline solution of copper. For this purpose the fat and casein must be separated previously, and this is effected by heating a known quantity of the milk with a few drops of acetic acid, separating the curd by filtration, and then pro- ceeding as directed at p. 350. The normal amount of sugar is 5*27 per cent. The amount of cream that milk is capable of yielding may be estimated by leaving a known quantity at rest for some hours in a tall graduated tube, and then observing the volume of the cream collected at the surface. Butter ; the fat obtained from cow's milk. The substances with which butter is likely to be adul- terated, are, Water, flour, &c., and perhaps earthy substances ; indicated, when a known quantity of the butter is melted with water, then allowed to solidify, and weighed, by the reduction of weight amounting to more than 5 per cent. The presence of amylaceous substances would be indicated by means of iodine solution added to the liquid ; earthy sub- stances or casein would appear as a sediment in the liquid, and colouring substances would be indicated by the appear- ance of the liquid. 364 SUBSTANCES USED AS FOOD, ETC. Tea ; the dried leaves of Tkea bohea. The substances with which tea is adulterated, are, Prussian blue or indigo ; indicated, when the tea is exa- mined by the aid of the microscope, by the presence of a powder adhering to the surface ; they may also be detected by shaking the tea with water, separating the leaves by filtering through muslin, then collecting the sediment, and examining it to ascertain whether it consists of prussian blue or indigo ; the latter is less frequent. Gypsum-, indicated, when the tea is shaken with water, by the production of a white precipitate in the liquid, by chloride of barium. Chromate of lead ; tested for in the sediment obtained by shaking the tea with water, as directed in Chapter X. Copper salts ; tested for in a similar manner, either in the sediment or in the decoction. Lie tea a fictitious tea, made of tea dust, or ground rice, and gum, indicated, when the tea is digested with water, by not unfolding like tea leaves, and when digested with hot water by falling to powder. The amount of ash yielded by good tea is 5 per cent, or at the most 6 per cent. ; lie tea yields from 37 to 45 per cent. ash. Coffee ; the dried berries of Cqffea arabica. The only adulteration of raw coffee is the colouring of yellow berries. This is effected with the same substances that are used for colouring tea, and they may be detected in a similar manner. The substances with which roasted and ground coffee are adulterated, are, Chicory, indicated, when the suspected coffee is placed upon water in a test-tube, by the immediate brown colora- tion of the water. Pure coffee is not wetted at once and does not colour water until it has been in contact with it for some time. When chicory or a mixture of chicory with coffee is placed upon water, streaks of coloured liquid are seen to fall down through the water more or less rapidly, according to the amount of chicory. With some little practice the amount of chicory mixed with coffee may be ascertained with tolerable accuracy. Roasted corn, acorns, and leguminous seeds ; indicated, when CHOCOLATE AND GELATIN. 365 the decoction is mixed with iodine solution, by the pro- duction of a blue colour, which is not the case with a decoction of pure coffee. Coffee grounds ; indicated best by estimating the amount of extract yielded by the coffee. This is effected by boiling the coffee several times with water, filtering the liquid, eva- porating to dryness upon a water-bath, and drying the residue. Good coffee ought to yield about 37 per cent. A number of other substances more or less improbable are stated to be used for adulteration of coffee. Chocolate ; a preparation of the seeds of Theobroma cacao. The substances with which chocolate is adulterated, are, Starch or amylaceous substances ; indicated, when the filtered hot infusion of the suspected substances is mixed with iodine solution, by the production of the deep blue colour characteristic of starch. Sugar can hardly be regarded as an adulteration of choco- late except when exceeding a certain amount. Iron ochre and other mineral substances ; indicated, when the chocolate is incinerated, by the usual tests applied to the ash. The determination of the quality of chocolate is to be effected by estimating the amount of the several normal in- gredients, and in the case of inferior kinds, of the admixtures present, by the methods already described for estimating sugar, fat, gum, starch, &c., but the results obtained will in all instances be somewhat indefinite as there is no absolute standard of quality with which they may be compared. Gelatin; a nitrogenous constituent of bones and other parts of the animal organism. The quantity of gelatin in the different states of glue, &c., may be ascertained by estimating the amount of water it is capable of absorbing, because the amount of water contained, either chemically or otherwise, in different kinds of gelatin, varies very much. For this purpose a weighed quantity of the gelatin is immersed in cold water for twenty-four hours, the water that is not absorbed is then poured off, and the gelatin weighed. Very good kinds are thus increased in weight thirteen times, average kinds ten times, and inferior kinds six times. 366 SUBSTANCES USED AS FOOD, ETC. The consistence of the residual jelly should also -be ob- served ; the more solid it is in proportion to the amount of water the better is the gelatin. Isinglass ; the dried coats of the sound or air-bladders, &c. of varieties of sturgeon (Accipenser), cod (GW#$), and other fish. Isinglass is adulterated with Gelatin, which is inserted between the leaves and rolled up with it. The best indication of this adulteration is the amount of ash ; isinglass yields only 0'9 per cent., while gelatin yields 4 per cent., and adulterated isinglass 1'5 per cent, or more. TEXTILE MATERIALS, ETC. 367 CHAPTEE XV. TEXTILE MATEEIALS ; WOOLLEN CLOTH, SILK, COTTON, AND LINEN. TEXTILE materials may be divided into two classes, according as they are derived from animals or plants. The most im- portant of these are wool, silk, cotton, flax or linen, and hemp. The structure and configuration of these fibres, as seen by means of the microscope, are their most characteristic features, and admit of their being distinguished from each other with greater certainty than is furnished by any chemical tests. Silk ; the produce of Hornby x Mori. This fibre (fig. 84) has the most simple structure of any of those above mentioned. It consists of an indurated secretion, and by the aid of the microscope appears cylindric, smooth, Fig. 84. without organic structure or longitudinal cavity, presenting here and there at both sides a kind of narrow margin. Tin* surface of the fibre is bright and the thickness uniform, although some fibres are thicker than others. 368 TEXTILE MATEBIALS, ETC. Wool ; the produce of varieties of Ovis, &c. This fibre (fig. 85) consists of a cylindrical aggregation of numerous cells, and appears by the aid of the microscope as a tube covered with epidermoid scales, which overlap each other like tiles, and are the chief distinctive characteristic of this fibre. Fig. 85. Linen ; the produce of Linum usitatissimum. This fibre (fig. 86) consists of longitudinal bast-cells, and appears by the aid of the microscope as a thin, round thread with a narrow longitudinal cavity ; the surface is generally smooth and the fibre tapers oft 7 towards the end, and ter- minates in a blunt point. The diameter is not uniform, but greater at some places where the fibre appears flattened. Fig. 86, Cotton ; the produce ofGossypium herbaceum, religio8wn,8fc. This fibre (fig. 87) appears by the aid of the microscope as a flat ribbon-shaped cell, thicker at the edges than the middle, and twisted like a corkscrew, or irregularly curved. There is frequently a kind of reticular striation apparent on HEMP. 369 the surface, and a broad longitudinal cavity more or less distinctly marked. Fig. 87. Hemp ; the produce of Cannabis sativa. This fibre (fig. 88) appears by the aid of the microscope of unequal thickness, terminating with a blunt point and fre- quently split at the ends ; it has a tolerably wide longitu- dinal cavity, and the surface presents longitudinal striae and pores appearing as transverse stria?. Fig. 88. Manilla or New Zealand hemp ; the produce of Pkormium tenax, This fibre (fig. 89) appears by the aid of the microscope bright, colourless, cylindrical, terminating gradually in a Fig. 89. blunt point, with a longitudinal cavity, generally appearing like a simple line, and the surface destitute of any striatiou. 2 B 370 TEXTILE MATERIALS, ETC. Chinese grass ; the produce of Corchorus capsularis. This fibre (fig. 90) appears by the aid of the microscope flat and ribbon- shaped, but not twisted like cotton, with a wide longitudinal cavity, and pores that frequently appear like transverse striae. Fig. 90. The chemical tests by means of which the various fibres may be distinguished from each other, furnish results which are as a general rule less trustworthy than those obtained by the use of the microscope, especially when the fibres are woven together, but there is not much difficulty in distin- guishing between animal and plant fibres by chemical means. 1. When the fibres are set fire to : Animal fibres swell up, evolve vapour that has a peculiar odour, and turns lit- mus paper blue ; leaving at the same time a bulky shi- ning coal which is difficult to burn, and leaves a copious ash when burnt. 2. "When the fibres are boiled with caustic soda solution (105 sp. gr.) : Animal fibres dissolve. Plant fibres burn readily, evolve vapour that has an em- pyreumatic odour, and red- dens litmus paper ; leaving at the same time a coal that has the form of the fibre, and leaves little ash when burnt. Plant fibres are little af- fected. 3. When the fibres are boiled for twenty minutes with solution of nitrate of mercury : Animal fibres acquire a red colour. Cotton and linen fibres re- main colourless. TESTS FOE FIBEES. 371 4. When the fibres are boiled with nitric acid : Cotton and linen remain colourless. Wool acquires a yellow co- lour, silk also, but in less de- gree. 5. When the fibres are immersed in a mixture of equal parts of sulphuric acid and nitric acid, for twenty minutes or less, and then washed with a large quantity of water : Groat hair and silk are en- tirely dissolved. Wool becomes yellow or brown. Plant fibres do not become coloured and their substance apparently little altered, but when dried, they burn with explosion. 6. When the fibres are moistened with a drop of chloride of tin, dried, and then heated : Wool and silk do not ap- pear altered. Plant fibres soon become distinctly brown. 7. When white or bleached fibres are immersed in a solu- tion of oxide of lead in caustic soda : Plant fibres remain colour- less. Wool and hair acquire a brown colour. Silk is not altered. 8. When the fibres are moistened with solution of picric acid: Wool and silk yellow colour. acquire a Cotton and colourless. linen remain 9. When the fibres are burnt separately : Linen fibre appears at the Cotton fibre is splayed out charred end, smooth and at the end like a brush. round. 10. When a piece of the dry stuff, free from dressing, is immersed in concentrated sulphuric acid for half a minute or two minutes, according to the strength of the fabric, then washed with water, immersed in dilute solution of ammonia, so as to separate acid completely, and then dried : Linen fibres remain un- I Cotton fibres are converted altered or but little acted | by the acid into a gummy sub- up on. stance which is dissolved by water. 2u2 372 TEXTILE MATERIALS, ETC. A mixed fabric treated in this manner presents gaps which represent the position of the cotton fibres. 11. When a piece of the stuff is immersed in an alcoholic solution of madder for a quarter of an hour : Linen fibres acquire a dirty I Cotton fibres become bright reddish-yellow or orange-yel- yellow. j & j i j low colour. "With an alcoholic tincture of cochineal : Linen fibres become violet red. red. Cotton fibres become bright 12. "When a piece of the stuff, free from dressing, is immersed in olive oil : Linen fibres become trans- I Cotton fibres remain opake lucent like greased paper. | and white. A mixed fabric treated in this manner presents a striped appearance, which is more apparent by the aid of the micro- scope or a magnifying glass. 373 APPENDIX. HTDEOMETET ; TABLES OF DENSITY, ETC. . THE density, or the relative weight of equal volumes, of different substances is a character which sometimes affords indications of their chemical nature, and also of their value, particularly in the case of liquids ; it is also frequently ser- viceable for other purposes, as in the analysis of water, soils, &c. The density, or as it is frequently called, the specific gravity of a substance is expressed numerically by comparison with water which is taken as unity. The specific gravity of liquids is estimated by weighing in a narrow-necked flask (fig. 91) of known capacity for water at a given temperature. The point to Fig. 91. which the flask is to be filled may be indicated by a scratch on the neck, or the flask may be fitted with a stopper made of thermometer tube, which, when inserted, admits of the escape of any excess over the proper volume. The temperature at which the specific gravity of substances is to be estimated is generally 60 P. or 62 F., as pre- scribed by law, with an atmospheric pressure equal to 30 inches of mercury. The flask used for the purpose should contain 1000, 500 or 250 grains of pure water, and should be exactly counter- poised by a weight in the opposite pan of the balance. The density of water being taken as unity, that of any other 374 HTDEOMETET, ETC. liquid is found by dividing the weight, w, of a given volume of the liquid in question, by the weight, W, of an equal volume of water at the same temperature. When the flask holds exactly 1000 grains of pure water, the specific gravity of any other liquid with which it may be filled is indicated at once by the weight of that volume of the liquid. But when the capacity of the flask is more or less than 1000 grains, the specific gravity, x, must be found by calculation, the requisite data being the weight, W, of water held by the flask and the weight, w, of an equal volume of the liquid in question. W : w = 1000 : x. The hydrometer is an instrument for ascertaining the density of liquids in accordance with the physical principle, that when a solid is immersed in a liquid its weight is to a certain extent supported or counterpoised. The extent to which this apparent reduction of weight takes place, depends upon the relative densities of the solid and liquid. When the density of the solid is greater than that of the liquid in which it is suspended, the reduction of weight will be equal to the weight of a volume of the liquid that is equal to the entire volume of the solid. When the density of the solid is less than that of the liquid, only a portion of the solid will be immersed, and the volume of this portion will be equal to a volume of liquid whose weight is equal to the entire weight of the solid. Con- sequently the greater the density of the liquid as compared with the solid, the smaller will be the volume of liquid dis- placed by the solid, and the reverse. Thus, for example, when a solid, having a volume of 2 cubic centimeters, and weighing 1 gramme, is immersed in a liquid having double the density, 1 cubic centimeter of which weighs 1 gramme, the solid will be half immersed in the liquid. If the liquid was four times as dense as water, only one-fourth of the solid would be immersed, and if the liquid was three-fourths as dense as water, two-thirds of the solid would be immersed; or, in other words, the portions of the solid immersed in liquids whose densities were in the relation of 2 : 1 : -J, would be in the relation of \ : ^ : J-, or inversely as the densities of the liquids. DETEBMINATION OF SPECIFIC GBA.YITY. 375 The hydrometer (fig. 92) is constructed of glass or metal,' and by making the upper part hollow, while the lower part is loaded with lead, such a relation is effected between the volume and the weight of the instrument, that it F - 92 sinks to a depth, inversely proportionate to the density of the liquid in which it is immersed. By making the instrument spindle-shaped, with a stem sufficiently long, and so adjusting the weight and volume that it floats upright in water, with about half the stem above the surface, the specific gravity of any liquid might be ascertained by means of it, but owing to the practical in- conveniences that would attend the use of such an instrument, hydrometers are always specially adapted for liquids, either heavier or lighter than water, the zero or point to which the instrument sinks in water, being in one case at the bottom, in the other at the top of the stem. The graduation of the stem of the hydrometer is made in two ways : either, so as to indicate directly the specific gravity, or by an arbitrary division into degrees, from which the specific gra- vity must be found by calculation. The hydrometers in most frequent use are, in this country, Sikes' ; in France, Germany, &c., those of Beaume and of Beck. The hydrometers of Gray-Lussac and Cartier are less generally employed. The following tables indicate the relations that exist between the indications afforded by the different kinds of hydrometers, and between the densities and per-centage value of various liquids. 376 HYDBOMETBY, ETC. I. TABLE for ascertaining the density of liqnids heavier than water, from the 'hydrometer degrees of Beaume and of Beck. 1 Beaume at 14-4 Cels. Beck. 1 Q Beaume at 14-4 Cels. Beck. o I'OOO I -0000 39 1-336 1*2977 I 1*007 1*0059 40 1-347 1*3077 2 1*013 1*0119 4' '"359 1*3178 3 1-020 1*0180 42 I-37I 1*3281 4 I-O27 1-0241 43 I-384 1*3386 1 1-033 1-0303 1*0366 44 1*396 1*408 1*3492 1*3600 7 1-047 1*0429 46 1*3710 8 1-055 1*0494 47 1*3821 9 1*062 1*0559 48 i'3934 10 1*069 1*0625 49 1*4050 ii 1*077 1-0692 5 1-4167 12 1-084 1-0759 5 1 1*4286 13 1*092 1-0828 1*4407 1-099 1*0897 53 1*4530 *s I-I07 1*0968 54 1*4655 16 1*115 1*1039 55 I-4783 17 ri2 3 rim 56 1*4912 18 I-I32 1*1184 57 1*5044 '9 1-I40 1-1258 58 1*5179 20 I-I48 J-I333 59 21 1*I57 1-1409 60 r 5454 22 1-166 1*1486 61 r 559 6 23 1-174 1*1565 62 24 1-183 1-1644 63 1*5888 25 1*192 1-1724 64 1-6038 26 1-201 1-1806 65 1-6190 27 I'21I 1-1888 66 1*6346 28 1*220 1-1972 67 1-6505 2 9 1-230 1-2057 68 1-6667 3 1-239 1-2143 69 1*6832 31 1-249 1-2230 70 1*7000 32 I-260 1-2319 1-7172 33 I-270 1*2409 72 i'7347 34 l*28l 1-2500 73 1*7526 35 1-291 1-2593 74 1*7708 36 I-302 1-2687 75 1*7895 37 1*313 1-2782 76 1*8085 38 I-325 1-2879 HTDEOMETBIC EQUIVALENTS. 377 II. TABLE for ascertaining the density of liquids lighter than water, from the hydrometer degrees of Beaume and of Beck. ! Beaumt* at 12-&Cels. Cartier at 12-5 Cels. Beck. J Beaum& at 12-5 Cels. Cartier at 12-5 Cels. Beck. I -0000 3 1 0-8742 0-8707 0'8457 I 0-9941 32 0-8690 0-8652 0-8415 2 0-9883 33 0-8639 0-8598 0-8374 3 0-9826 34 0*8588 0*8545 6-8333 4 0-9770 35 0-8538 0-8491 0*8292 5 0-9714 36 0-8488 0-8439 0*8252 6 0-9659 37 0*8439 0-8387 0-8212 7 0*9604 38 0*8391 0*8336 0'8I73 g 0-9550 39 0-8343 0-8286 0-8133 9 0-9497 40 0*8295 0-8095 10 I '0000 0-9444 4 1 0*8249 0-806 1 ii 0-9932 0-9392 42 0*8202 0-8018 12 0-9865 0-9340 43 0-8156 0-7981 J 3 0-9799 0-9289 44 O8lll 0*7944 H 0-9733 0*9764 0-9239 45 0-8o66 0-7907 15 0-9669 0*9695 0-9189 46 0*8022 0-7871 16 0-9605 0*9627 0-9139 47 0-7978 07834 '7 0-9542 0*9560 0*9090 48 0-7935 0-7799 18 0*9480 0-9493 0-9042 49 0-7892 0-7763 J 9 0-9420 0-9427 0-8994 5 0-7849 0-7727 20 0-9359 0-9363 0-8947 5 1 0-7807 0-7692 21 0-9300 0*9299 0*8900 5* 0*7766 0-7658 22 0-9241 0-9237 0*8854 53 0-7725 0-7623 2 3 0-9183 0-9175 0*8808 54 0-7684 0-7589 24 0-9125 0-9114 0*8762 55 0-7643 0*7556 2 5 0-9068 0-9054 0*8717 56 0-7604 0-7522 26 0*9012 0-8994 0-8673 57 0*7565 0-7489 27 0-8957 o'8935 0-8629 58 0-7526 0*7456 28 0*8902 0-8877 0-8585 59 0-7487 0-7423 29 0-8848 0*8820 0-8542 60 0-7449 0-7391 30 0*8795 0-8763 0*8500 378 HTDEOMETET, ETC. III. PEU-CENTAGE AMOUNTS of anhydrous sulphuric acid (SO 3 ) and monohydrated acid (SO 3 , HO) corresponding to different densities. Density. Anhydrous sulphuric acid. Monohy- drated acid. Density. Anhydrous sulphuric acid. Monohy- drated acid. 1-849 81-5 100 466 47'3 58 1-848 80-7 99 456 46-6 57 1-846 79-9 98 446 45'7 56 1-844 79-1 97 436 44'9 55 1-841 78-3 96 427 44-0 54 1-838 77'4 95 417 43-2 53 1-834 76-7 94 407 42-4 5 2 1-829 75'8 93 398 41-6 51 1-823 75-0 388 40-8 5 1-818 74-2 9 1 '379 40*0 49 1-812 , 73'4 90 370 39'i 48 1-804 72-6 89 36! 47 1-796 71-8 88 '353 37'5 46 1-787 70-9 87 '344 36-7 45 1-777 70-1 86 '335 35'9 44 1-769 69-3 85 326 35' 1 43 1*757 68-5 84 -317 34'3 42 ''747 67*7 308 33'4 1-736 66-9 82 300 3 z-6 40 1-725 66-1 Si 291 31-8 39 1-712 65-2 80 282 31-0 38 1-699 64-4 79 274 30-2 37 1-687 63-3 78 -265 29-4 36 1-675 62-8 77 257 28-5 35 1-663 62'0 76 248 27-7 34 1-652 1*642 61-2 60-3 75 74 241 26-9 26-3 33 32 1-632 59-6 73 225 2 5'5 3 1 1-620 58-7 72 218 24-1 3 1-609 57'9 71 -2H 23-7 29 1-598 57*i 70 203 22-8 28 1-587 56-3 69 '196 27 1-576 55*5 68 188 21-2 26 r 5 6 5 54-6 67 179 20-4 1-550 53'8 66 171 19-6 24 r 539 53' 65 163 18-8 23 1-528 52-2 64 17-9 22 1-517 51*4 63 14! 17-1 21 1-507 50*6 62 141 16-3 20 1-496 49'7 61 -I 33 1-486 48-9 60 i5 14-7 it 1-476 48-1 59 117 13-9 HYDROCHLORIC ACID TABLES. 379 TABLE III. (continued). Density. Anhydrous sulphuric acid. Monohy- drated acid. Density. Anhydrous sulphuric acid. Monohy- drated acid. 109 *3'! 16 054 6-5 8 "IO2 I2'2 J 5 048 57 7 095 1 1-4 H 041 4"9 6 089 io'6 13 034 4' i 5 08 I 9-8 12 027 n 4 074 9-0 II 021 2-4 3 ro68 8'2 10 014 r6 2 ro6i 7'3 9 007 0-8 I IV. PER-CENTAGE AMOUNTS of chlorine and hydrochloric acid gas corresponding to different densities of hydro- chloric acid solution. Density. Chlorine. Hydrochloric acid gas. Density. Chlorine. Hydrochloric acid gas. 2000 39-675 40-777 1494 29-361 30-174 1982 39-278 40-369 1473 28*964 29-767 1964 38-882 39-961 1452 28-567 29-359 1946 38-485 39-554 H3I 28-171 28-951 1928 38-089 39'i46 1410 27-772 28-544 1910 37-692 38738 1389 27-376 28-136 1893 37-296 38-33 1369 26-979 27-728 I8 75 36-900 379 2 3 1349 26-583 27-321 I8 57 36-503 37-516 1328 26-186 26-913 I8 4 6 36-107 37-108 1308 25-789 26-505 1822 35'77 36700 1287 25-392 26-098 1802 35"3 10 36-292 1267 24-996 25-690 1782 34*9 x 3 35'884 1247 24-599 25-282 1762 34'5 J 7 35-476 1227 24-202 24-874 1741 34-121 35-068 1206 23-805 24-466 1721 33724 34'66o 1185 23-408 24-058 1701 33-328 34^5 2 1164 22*012 23-650 1681 32-931 33-845 1143 22-6I5 23-242 1661 32-535 33'437 1123 22-218 22-834 1641 32-136 33-029 "IIO2 21-822 22*426 1620 3 r 74 6 32*621 1082 21-425 22*019 1599 3 r 343 32-213 1061 21-028 2I'6lI 1578 30-946 31-805 "1041 20-632 21*204 1557 30-550 3i'398 '1020 20-235 20*796 '1537 30-153 30-090 I 000 I9-837 20-388 1515 29-757 30-582 0980 19-440 19-980 380 HYDBOMETBY, ETC. TABLE IV. (continued). Density. Chlorine. Hydrochloric acid gas. Density. Chlorine. Hydrochloric acid gas. 1-0960 19-044 19-572 1-0477 9-522 9-786 1-0939 18-647 19-165 1-0457 9-126 9-379 1-0919 18-150 18757 1-0437 8-729 8-971 1*0899 17-854 18-349 1-0417 8-332 8*563 1-0879 I7'457 17-941 1-0397 7-935 8-155 1-0859 17-060 17*534 1-0377 7-538 7747 1-0838 16*664 17*126 1*0357 7-141 7-340 1-0818 16-267 16-718 1*0337 6 745 6932 1-0798 15-870 16-310 1*0318 6-348 6-524 1-0778 I5'474 15-902 1-0298 5-951 6-116 1-0758 15-077 I5'494 1-0299 5-554 5-709 1-0738 14-680 15-087 1-0259 5-158 5-301 1-0718 14-284 14-679 1-0239 4-762 4-894 1-0697 I3-887 14-271 1-0220 4-365 4-486 1-0677 13-490 13-863 1*0200 3-968 4-078 1-0657 13-094 13*457 1*0180 3-571 3-670 1-0637 12-697 13-049 1*0160 3-174 3-262 1-0617 12*300 12-641 1*0140 2-778 2-854 1-0597 11-903 12-233 roi2o 2-381 2-447 1-0577 11-506 11-825 1*0100 J> Q84 2-039 1-0557 11*109 11-418 1*0080 ^588 1-631 1-0537 10-712 iroio i -0060 1-I 9 I 1-124 1-0517 10-316 10*602 1-0040 7 '7Q<; 0-8 1 6 1-0497 9-919 10-194 I'002 o / 7 J *397 0-408 V. PEB-CENTAGE AMOUNTS of anhydrous nitric acid (NO 5 ) and of hydrated acid (NO 5 , HO) corresponding to different densities of nitric acid , Density. An- hydrous acid. Hy- drated acid. Density. An- hydrous acid. Hy- drated acid. Density. An- hydrous acid. Hy- drated acid. 1-500 79*7 100 1-470 70*9 89 1-431 62-2 78 1-498 78-9 99 1-467 70*1 88 1-427 61-4 77 1*496 78*1 98 1-464 69*4 87 1-423 60*6 76 1-494 77*3 97 1*460 6 9*3 86 1-419 59*8 75 1-491 76-5 96 1-457 67-7 85 1-415 59*0 74 1-488 75*7 95 1-453 66-9 84 1-411 58*2 73 1-485 74'9 94 1-450 66-1 83 1-406 57*4 72 1-482 74-1 93 1-446 65-3 82 1*402 56*5 7i i'479 73'3 92 1-442 64-5 81 1-398 55*8 70 1-476 72-5 9 1 1-439 63-8 80 r 394 55' 69 i*473 71-7 9 i*435 63-0 79 1-388 54*2 68 NITBIC AND ACETIC ACID TABLES. 381 TABLE V. (continued). Density. An- hydrous acid. Hy- drated acid. Density. An- hydrous acid. Hy- drated acid. Density. An- hydrous acid. Hy- drated acid. I-383 53'4 6 7 *2 5 8 35'i 44 1-123 17*5 22 1-378 52-6 66 252 34-3 43 1*117 1*7 21 1-373 5 I-8 65 246 33-5 42 I'll! 15-9 20 1-368 51-1 64 240 3*7 4 1 1-105 '5' 1 J 9 1-363 50-2 63 234 31-9 40 1-099 H'3 it 1-358 49 '4 62 228 31-1 39 1-093 '3-5 17 i-353 48-6 61 *22I 3'3 38 1-088 12-7 16 1-348 47-8 60 215 29-5 37 1-082 11-9 15 i-343 47-0 59 208 28-7 36 1-076 11*2 14 r 33 8 46-2 58 202 27-9 35 1-071 10-4 13 1-332 45'4 57 I 9 6 27-1 34 1-065 9'6 12 1-327 44-6 56 189 26-3 33 1-059 8-8 II 1-322 43-8 55 I8 3 *5'5 3* 1-054 8-0 10 1*316 43' 54 177 24-7 31 1-048 7-2 9 r 3 n 42-2 53 171 23-9 30 i'43 6-4 8 1*306 41-4 5 2 l6 5 23-1 29 1-037 5-6 7 1-300 40-6 5 1 IJ 59 22-3 28 1-032 4-8 6 1-295 39*8 5 153 21-5 27 1-027 4-0 5 1-289 39-0 49 146 20-7 26 I'02 I n 4 1-283 38-3 48 140 19-9 25 1*016 2-4 3 1-276 37'5 47 134 19-1 24 1*011 r6 2 1*270 367 46 129 18-3 23 1-005 0-8 I 1-264 35'9 45 VI. PEB-CENTAGE AMOUNTS of hydrated acid (C 4 H 4 4 ) corresponding to different densities of acetic acid. Anhydrous acid. Density at 60 F. Anhydrous acid. Density at 60 F. Anhydrous acid. Density at 60 F. O 1*0000 14 1-0245 28 1*0460 I 1-0019 15 1-0261 29 1-0472 2 1-0037 16 1-0277 30 1-0485 3 1-0055 17 1-0293 31 1-0498 4 1-0072 18 1-0310 32 1-0510 5 1-0089 19 1-0326 33 1-0522 6 1-0107 20 1-0342 34 1-0537 7 1-0124 21 1-0358 35 1-0546 8 1-0141 22 1-0373 36 1-0558 9 1-0159 23 1-0389 37 1-0569 10 1-0177 24 1-0404 38 1*0580 ii 1-0194 2 5 1-0419 39 1-0591 12 I-02II 26 1-0433 40 I -060 1 13 I-0228 27 1-0447 41 ro6n 382 HYDBOMETBY, ETC. TABLE VI. (continued). Anhydrous acid. Density at 60 F. Anhydrous acid. Density at 60 F. Anhydrous acid. Density at 60 F. 42 1*0621 57 1-0735 7 2 1-0759 43 1*0631 58 1*0740 ' 73 1-0754 44 1-0640 59 1-0745 74 1*0748 45 1*0649 60 1*0749 75 1*0741 46 1-0658 61 1*0753 76 1*0732 47 1*0667 62 1*0756 77 1*0722 48 1-0675 63 1*0759 78 1*0710 49 1*0683 64 1*0762 79 1-0696 5 1*0691 65 1*0764 80 1*0681 5 1 1*0698 66 1*0765 81 1*0664 5i 1*0705 67 1*0766 82 1-0646 53 1*0711 68 1*0766 83 1*0626 54 1*0717 .69 1*0766 84 1-0603 55 1-0723 70 1*0765 85 1-0574 56 1*0729 7' 1*0763 85*11 1-0570 VII. PEB-CENTAGE AMOUNTS of ammonia (NH 3 ) corre- sponding to different densities of solution of ammonia. Density. Per- centage. Density. Per- centage. Density. Per- centage. 0*8750 0*8875 0-9000 0*9054 0*9166 0*9254 32*50 29-25 26*00 *5'37 22*07 !9'54 0*9326 0*9385 '9435 0-9476 0-9513 '9545 17*52 15-88 H-53 13-46 12*40 11-56 0-9573 0-9597 0*9619 0*9692 18*82 10*17 9*60 9*50 VIII. PEB-CENTAGE AMOUNTS of anhydrous potash (KO) corresponding to different densities" of solution of potash. Density. Per- centage. Density. Per- centage. Density. Per- centage. 1*3300 28-290 1979 18-671 1*0819 8-487 I'S'Si 27-158 1838 17-540 1*0703 7*355 1*2966 26*027 '1702 16*408 1-0589 6-224 1*2805 24-895 1568 15^77 1-0478 5-002 1*2648 1*2493 23*764 22*632 '437 1308 14*145 13*013 1-0369 1*0260 3-961 2-829 1*2342 21*500 1182 11*882 1-0153 1-697 1-2268 20-935 1059 10*750 1*0050 0*5658 1*2122 19*803 0938 9*619 SODA AND AMMONIA TABLES. 383 IX. PEE-CENTAGE AMOUNTS of anhydrous soda (NaO) cor- responding to different densities of solution of soda. Density. Per- centage. Density. Per- centage. Density. Per- centage. 1-4285 30-220 2912 19.945 1-1330 9-066 I-4I93 29-616 2843 J9-34 1 1-1233 8-462 1-4101 29-011 2775 18-730 1-1137 7-857 1*4011 28407 2708 17-132 1*1042 7-253 1-3923 27-802 2642 17-528 1-0948 6-648 1-3836 27*200 2578 16-923 1-0855 6-944 1*3751 26-594 2515 16-319 1-0464 5'54 1-3668 25-989 '2453 15-814 1-0675 4-835 1-3586 25-385 2392 15-110 1-0587 4-231 i-355 24-730 2280 14-506 1-0500 3-626 1-3426 24-176 2178 13-901 1-0414 3*022 1-3349 23-572 2058 13-297 1-0330 2-4I8 1-3273 22-967 1948 12-692 1*0246 1-813 1-3198 22-363 1841 12-088 1-0163 I-209 1-3143 21-884 1734 11-484 1-0081 0-604 1-3125 21-894 1630 10-879 1-0040 0*302 i'353 21-154 1528 10-275 1-2982 20-550 1428 9-670 X. PEE-CENTAGE AMOUNTS of anhydrous carbonate of soda corresponding to different densities of solution of soda. Density. Per- centage. Density. Per- centage. Density. Per- centage. 1-4812 40-504 3177 26-432 1-1282 11*748 1-4750 40-139 3078 *5-454 1*1166 10*769 1*4626 -ig'l6o 2980 24-475 1*1052 9-760 1-4504 38-181 2836 23-496 1-0940 8-811 1-4384 37-202 2694 22-517 1*0829 7-832 1-4265 36-223 2554 21-538 1-0719 6-853 1-4147 35' 2 44 2417 20-539 ro6ir 5-874 1-4030 34' 26 5 2282 19-580 1-0505 4^95 1-3915 33*286 2150 18-601 i -040 1 3-916 1-3808 32-307 2020 17-622 1-0299 2-934 1-3692 31-328 -.1892 16-643 roio8 l- 95 8 I-3585 1-3480 30*349 29*360 1766 '1642 15-664 14-685 1*0098 1*0048 0-979 0-489 1-3378 28-391 1520 13-706 1-3277 27-412 1400 12-727 384 HYDBOMETRY, ETC. TABLE XI. PER-CEFTAGE AMOUNTS, by weight and volume, of absolute alcohol, corresponding to different densities of diluted spirit. Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. r 7938 F 1 7946 JOO'OO j OO'OO 1 Absolute alcohoL 7969 F 99-00 7995 .... 99-00 8001 F 98-00 8031 F 97-00 8041 98-00 8o6l F 96-00 8084 .... 97-00 8089 F 95-00 97-61 8118 F 94-00 8125 96-00 8i 45 F 93-00 8156 .... 67-0 O" 8160 .... .... 66-8 0-2 8163 .... .... 66-6 0-4 8164 92-46 95-00 8167 .... 66-5 0-6 8170 .... .... 66-3 0-8 8172 F 92-00 8174 .... .... 66-1 1*0 8178 .... .... 65-9 1*2 lift .... .... 65-8 i*4 8185 .... 65-6 r6 8188 .... .... 65-5 1-8 8192 .... .... 65-3 2*0 8196 .... .... 65-1 2'2 8199 F 91-00 .... 65-0 2-4 8201 .... 94-00 8203 .... .... 64-8 2-6 8206 .... .... 64-7 2-8 8210 .... .... 64-5 3-0 8214 .... .... 64-3 3'2 8218 .... .... 64-1 3 '4 8221 .... .... 8224 .... .... 63*8 3 -8 8227 8228 F 90-00 94-46 63-6 4-0 8231 .... .... 63-4 4-2 The densities marked F, and the corresponding per-centages of alcohol by weight, are those estimated by Fownes. ALCOHOL TABLES. TABLE XI. {continued). 385 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 8234 .... .... 6 3 *2 4'4 8238 . . . 93*00 8237 ... 63*1 4*6 8242 . . . .... 62-9 4'8 8245 ... .... 62*7 c*o 8249 .... 62*5 S'* 8252 ... .... 62-3 5 '4 8254 F 89*00 1 8256 .... .... 62*2 5'6 8259 .... .... 62*0 5*8 8263 .... .... 61*8 6*0 fc 8266 .... .... 6r6 r* 8270 .... .... 61*4 6-4 8270 .... 82 7 2 .... 8273 .... 92-00 61*3 6-6 8277 .... .... 6ri 6-8 8279 F 88-00 8280 .... .... 60*9 7-0 8284 .... .... 60*7 7-2 8287 .... .... 60-5 7*4 8291 .... .... 60*4 7*6 8294 .... .... 6o'2 7'8 8298 .... .... 60-0 8-0 8301 .... .... 59-8 8*2 8305 F 87*00 .... 59-6 8-4 8306 .... 91*00 8308 .... .... 59'5 8-6 8 3 I2 .... .... 59]3 8-8 8315 .... .... 9-0 8319 .... ...... 58*9 9 *2 8322 .... .... 58-7 9*4 8326 .... .... 58-6 9-6 8329 .... .... 58*4 9-8 8331 F 86-00 8333 .... .... 58-2 I0'0 8336 .... .... 58-0 10*2 8339 8575 90*00 8340 .... 57*8 10*4 8344 .... 57*7 io"6 8347 57'5 10-8 8351 .... 57'3 11*0 8354 .... . . . 57*1 11*2 8358 .... ... 56*9 I J> 2 386 HTDKOMETET, ETC. TABLE XI. {continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 8357 F 8362 8365 85-00 90-88 5 6-8 56:6 n-6 u-8 8369 .... .... 56-4 I2'0 837* .... .... 56-2 ia*z 8373 .... 89-00 8376 .... .... 56*0 12-4 8379 .... .... 55'9 12-6 8382 F 84*00 8383 .... .... 557 12-8 8386 .... .... 55'5 13-0 8390 .... .... 55'3 13-2 8393 .... .... 55'i i3'4 8 39 6 .... 55-0 13-6 8400 .... 54-8 13-8 8403 ... .... 54-6 14-0 8405 88-00 8407 .... 54'4 14-2 8408 F 83-00 8410 .... .... 54-2 14-4 8413 .... .... 54' 14-6 8 4 I7 .... .... 53'9 14-8 8420 .... .... 537 15-0 8424 .... 53'5 15-2 8427 .... .... 53'3 i5'4 8431 .... .... 53'i 156 8434 F 82-00 .... 5*'9 15-8 8436 .... 87-00 8438 .... .... 5*7 16-0 8441 .... .... S*'S 16-1 8445 .... .... 52-3 16-4 8448 .... .... 52-1 16-6 8452 .... .... 51-9 16-8 8455 .... . .-. . 5*7 17-0 8459 F 8 1 -oo .... 5*'5 17-2 8462 .... sn 17*4 8465 .... .... 51-1 17-6 8466 .... 86-00 8469 .... .... 5*9 17-8 8 47 2 .... .... 50-7 18-0 8476 .... . . .-. 5'5 18-2 8480 50-3 18-4 8482 ; .... .... 50-1 If* 8483 F 80-00 86-97 ALCOHOL TABLES. TABLE XI. (continued). 387 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 8486 .... .... 49*9 1 8-8 8490 .... .... 497 19-0 8493 .... ... .-, 49'5 19-2 8496 79-50 85-00 49'3 19-4 8499 49' ' 19-6 8503 . . . .... 48-9 19-8 8506 . .. .... 487 20*0 8508 F 7900 8510 .... 48-5 2O'2 85*3 . . . 48-3 20-4 8516 . . . .... 48-0 20*6 8520 . .. .... 47'8 20-8 8523 . . . .... 47* 21'0 8526 . .. 84-00 8527 . . . .... 47'4 21*2 853 . .. .... 47-2 21-4 8533* 7800 .... 47-0 21-6 8537 . .. .... 46-8 21'8 8540 . . . .. 46-6 22-0 8543 . . . .... 46-4 22'2 8547 . . . ...... 46-2 22*4 855 . .. .... 46-0 22-6 8553 .... .... . 45*8 22*8 8555 .... 83*00 8556 .... ... . 45-6 23-0 8557F 77-00 8560 .... .... 45'4 23-2 8563 .... ... 45'* 23-4 8566 .... .... 45-0 23-6 8570 .... .... 44'8 23-8 8573 .... .... 44-6 24*0 8577 .... .... 44'4 24-2 8580 .... . . . . . 44-2 24-4 g rgl f 76*00 8583 .... 82-00 43*9 24-6 8587 .... 437 24-8 8590 .... .... 43*5 25-0 8594 .... .... 43'3 25-2 8597 .... .... 43'J 25-4 8601 .... .... 42-8 25-6 8604 .... .... 42-6 25-8 8603? 8608 75-00 82*80 42-4 26-0 8611 8roo 42-2 26-2 388 HYDEOMETBY, ETC. TABLE XI. (continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 8615 ... ... 42-0 26-4 8618 .... . . * 41-7 26*6 8622 .... .... 26-8 8625 P 74-00 .... 41-3 27-0 8629 .... 41-1 27-2 8632 .... .. .* 40-9 27-4 8636 .... .... 40-6 27-6 8639 73*59 So'OO 40-4 8643 .... 40-2 28*0 8646 .... .... 40-0 28*2 8649 F 73-00 8650 .... 39-8 28-4 8653 .... .... 39*5 28-6 8657 .... .... 39'3 28-8 8660 .... .... 39*' 29*0 8664 .... .... 38-9 2 9 *2 8665 .... 79*00 8667 .... .... 387 29*4 8671 8672 F 72-00 .... 38> 29-6 8674 .... .... 38-2 29*8 8778 .... .... 38-0 30*0 868l . . * . .... 30-2 8685 .... .... 37-6 30-4 8688 .... .... 37*3 30*6 8692 .... .... 37'i 30-8 8693 .... 78-00 8695 36-9 31-0 8696 F 71*00 8699 .... .... 36-7 31*2 8702 .... .... 36-4 3 r 4 8706 .... .... 36-2 3 r6 8709 .... .... 35'9 31-8 8713 8 7 l6 .... .... 35*7 35*5 32-0 32-2 8720 .... 77-00 35'* 32-4 87^1 F 8723 70-00 78-40 35' 32-6 8727 .... . 34*7 32-8 8730 .... . 34*5 33' 8734 .... . 34'3 33** 8737 .... . 34'i 33'4 8741 .... . 8744 33'6 33-8 ALCOHOL TABLES. TABLE XI. (continued). 389 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication . 8745 F 69*00 8747 .... 76*00 8748 .... .... 33'4 34-0 8751 .... .... 33;* 34*2 8755 .... .... 34*4 8758 .... .... 3*7 34-6 8762 .... .... 34-8 8765 .... .... 32*2 35' 8769 F 68-00 .... 32*0 35*2 8771 .... .... 317 35'4 8773 67-93 75-00 8776 3 r 5 ' 35-6 8779 8783 . . . :::: 31-2 31-0 35-8 36*0 8 7 86 ... .... 30-8 36*2 8790 . . . .... 3'S 8793 F 67-00 .... 3'3 36*6 8797 .... .... 30-0 36-8 8799 .... 74-00 8800 .... .... 29-8 37' 8804 .... .... 29*5 37-2 880 7 .... .... 37*4 8811 .... .... 29*0 37*6 8814 .... .... 28-8 37-8 88i6F 66*00 8818 .... .... 28-5 38*0 8822 .... .... 28-3 38*2 8825 .... 73-00 28-0 38-4 8829 .... .... 27-8 38-6 8832 .... .... 27-5 38-8 8836 .... .... 27*3 39-0 8840 F 65-00 7379 27*0 39'* 8843 .... 26*8 39'4 8847 .... .... 26*5 39' 6 8850 .... 72-00 26-3 39*8 88 5 4 .... 26*0 40-0 88 5 8 .... .... 25*8 40*2 886l .... ... *5'5 40-4 8863 F 64-00 8865 .... .... 25*3 40*6 8869 .... .... 25*0 40-8 8872 .... .... 24-8 41-0 8875 .... 71*00 88 7 6 .... .... 24-5 41-2 "390 HYDROMETRY, ETC. TABLE XI. (continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indic&tion. 8879 .... ... 24-3 41-4 8883 ... .... 24-0 41-6 8886 P 63-00 .... 23-8 41-8 8890 .... .... 23*5 42-0 8894 .... .... 23-2 42-2 8897 .... .... 2 3 -0 42-4 8900 62*51 70*00 8901 .... .... 22-7 42-6 8904 .... .... 22-5 42-8 8908 P 62-00 .... 22-2 43-0 8912 * .... .... 2I- 9 43'* 8915 .... ... . 217 43*4 8919 .... .... 21-4 43-6 8922 .... .... 21'2 43-8 8925 8926 .... 69-00 20-9 44-0 8930 .... 20'6 44-2 8932 p 6roo 8933 .... .... 20-4 44*4 8937 .... .... 2O. I 44-6 8940 .... .... 19-9 44;8 8944 .... .... 19*6 8948 .... .... 19-3 45-2 8949 8951 .... 68-00 I9-I 45*4 8955 .... .... 18-8 45-6 8956 P 60-00 68-97 8959 .... .... ig-6 45-8 8963 .... .... 18-3 46-0 8966 .... .... 18-0 46-2 8970 .... .... 17-7 46-4 8973 .... 67-00 8974 .... .... X 7'5 46-6 8977 .... .... ifz 46-8 8979 P 59-00 8981 .... 16-9 47* 8985 .... .... 16-6 47.2 8989 .... 16-4 47 '4 8992 .... .... 16-1 47-6 8996 .... .... 15*9 47-8 8997 .... 66-00 9000 .... 15-6 48-0 9001 P 58-00 .... 9004 .... [ J 5'3 48-2 . ALCOHOL TABLES. TABLE XI. (continued). 391 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9008 .... .... 15*0 48-4 9011 .... .... 48-6 9 OI 5 '4*5 48-8 9019 .... .... 14-2 49* 9021 57*25 65-00 9023 .... .... 13*9 49-2 9025 p 57*oo 9026 .... 13*6 49'4 9030 .... .... !3*4 49*6 934 .... .... 49-8 9038 .... .... 12-8 50*0 9041 .... .... 12-5 '50-2 9044 64-00 9045 .... .... 12*2 50*4 9047 P 56.00 9049 .... .... I2'0 50*6 9052 .... .... 117 50*8 9056 .... .... 11*4 51*0 9060 .... .... 1 1*1 . 51*2 9064 .... .... 10-8 51*4 9067 .... 63-00 10-6 51*6 9069 P 55*0 63-97 9071 .... ... 10-3 51-8 9075 .... 10*0 52-0 9079 .... .... 9*7 52-2 9082 .... .... 9'4 52*4 9085 .... .. ... 9:2 52*6 9089 9090? 54*oo 62*00 8-9 52-8 993 .... 8-6 53*o 9097 .... .... 8*3 53*a 9100 .... 8*0 53*4 9104 .... .... 7*7 53*6 9107 .... .... 7*4 53'8 9111 .... .... 7*1 54*o 9112 .... 6roo 9"3 F 53* 00 9115 .... 6-8 54-2 9118 9122 9126 9130 .... *s 6-2 5-9 5*6 54*4 54-6 54*8 55*o 9'34 52'2O 60-00 5*3 55** 9135 p 52-OO 392 HYDBOMETBY, ETC. TABLE XI. (continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9'37 ... .... 5-0 55'4 9141 .... .... 4'8 55'6 9H5 .... .... 4'5 55-8 9148 .... .... O 560 9152 9156 .*:;; 59-00 i? 56-2 56-4 9'59 9100 F 51*00 3'3 56-6 9163 .... .... 3-0 56-8 9167 .... .... a'7 57'o 9170 .... .... 2-4 57-2 9 '74 .... .... 2'I 57*4 9178 .... 58-00 I- 9 57-6 9182 .... .... r6 57-8 9i8 4 F 50-00 5879 9185 .... J'3 58-0 9189 .... .... o-o 58-2 9192 . .. .... 0.7 58-4 9196 .... .... 0-3 58-6 9198 I 9200 J 49-24 57'05 57-00 /Proof! 1 spirit./ 58-8 9204 .... .. . . '3 59-0 9206 F 49-00 9207 .... .... 0-6 59'* 9210 .... .... 0-9 59'4 9214 .... . . .. J '3 59' 6 9218 .... .... r6 59'8 9221 .... 56-00 9222 .... .... 1-9 6o'o 9226 .... . . 2'2 6o-a 9228 F 48-00 922 9 .... .... 2'5 60-4 9233 .... .... a-8 60-6 9237 .... .. .. 3'i 60-8 9241 .... .... 3 '4 6ro 9242 47-29 55-00 9244 .... 3*7 6ra 9248 47-00 .... 4:0 61-4 9252 .... .... 4'4 6r6 9*55 .... . . . 47 6r8 9259 . .... 5-0 62-0 9263 i 54-00 5'3 62-2 ALCOHOL TABLES. TABLE XI. (continued). 393 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9267 .... .... 57 62-4 9270 46*00 .... 6*0 62-6 9274 .... .... 6-4 62-8 9278 .... .... 67 63*0 9282 .... .... 7-0 63-2 9283 53' 9286 .... .... 7*3 63-4 929 IF 45-00 53'43 77 63*6 9295 .... 8-0 63*8 9399 .... .... 8'3 64*0 9302 .... .... 8'6 >6 4 '2 9303 .... 52-00 9306 . . . .... 9-0 64*4 9310 .... ui .... 9'3 64*6 93*4* 44-00 .... 97 64*8 9318 .... .... i o-o 65-0 9322 .... .... JO'O 65-0 93*3 .... 51-00 10*3 65-2 9326 .... ..... 10*7 < 5 'i 9329 .... .... 1 0*0 65-6 9333 .... .... 11*4 65-8 9335 * 9337 934 1 43-00 .... 11*7 12* I 66-0 66-z 9343 9345 9349 9353 9357' 9360 42-52 42-00 50*00 12*4 12-8 13-1 13-5 13-9 66*4 66-6 66-8 67-0 67*2 9362 9364 6368 :::: 49*00 14-2 14-6 67-4 67-6 937* 9376 F 9380 938i 934 9388 9392 9396 F 9399 9403 41*00 40-00 48*00 47-91 47*00 14-9 15*3 157 1 6-0 16-4 16*7 17*1 ITS I7'8 18*2 67-8 68-0 68-2 68*4 68*6 68-8 69-0 69*2 69-4 69*6 9407 394 HTDROMETET, ETC. TABLE XI. (continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9411 ... >... 18-5 69-8 9415 .... * . . 18-9 70-0 9417 F 39-00 46-00 9419 .... 19-3 70-2 9422 .... .... 19-7 70-4 9426 .... .... 20'0 70*6 943 .... .... 20-4 7 0-8 9434 F 38-00 .... 20-8 7 ro 9435 37-90 45-00 9437 . . . 21'2 71-2 9441 .... . . 21-6 7 "-'4 9445 .... 21-9 71-6 9448 .... *. . . 22'3 71-8 9452 F 37-00 44-00 22-7 72*0 9456 .... .... 23-1 72-2 9460 .... _ 72*4 9464 9468 .... 23-9 24-3 72-6 72-8 9470 F 36-00 43-00 9472 .... 24-7 73-0 9476 .... ... 4 25-1 73*2 9480 .... 73*4 9484 .... .... 25-9 73-6 9487 9488 .... 42-00 26-3 9490 F 35-00 42-25 9492 .... 26-7 74*o 9496 .... t . . 27-I 74-2 9499 .... .... 27.5 74*4 9503 .... 4I-00 28-0 9507 .... .... 28-4 ^8 95UF 34-00 .... 28-J 75*o 9515 * 29-2 75*2 9519 33*39 40-00 29-7 75 .' 4 9522 .... .... 30-1 9526 .... .... 30-6 75*8 9528 F 33-00 9530 .... .... 31-0 76-0 9534 .... .... 31-4 76-2 9535 .... 39.00 9538 .... 31-9 76-4 9542 .... .... 76-6 9544F 32-00 9546 .... ... 32-8 76-8 ALCOHOL TABLES. TABLE XI. (continued). 395 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 955 .... 38*00 33** 77*0 9553 .... .... 337 77*2 9557 .... 34-2 77*4 9561 P 31*00 .... 34* 6 77*6 95 6 5 .... 37*00 35*^ 77*8 9567 .... 35*6 78*0 9573 .... .... 36*1 78*2 9577 F 30*00 3 6 *45 36*6 78-4 9579 .... 36*00 9580 .... .... 37'i 7 8'6 9584. .... .... 37-6 78*8 9588 .... .... 38*1 79-0 9592 .... .... 38*6 79-z 9593 F 29*00 9596 28-99 35-00 39-1 79*4 9599 39*6 79 -6 9603 .... .... 40-1 79*8 9605 .... 34*00 9607 .... .... 40*6 80-0 96091 28*00 9611 .... .... 41-1 80-2 9615 .... 41*7 80*4 9618 .... 33*00 9619 .. . 42-2 80*6 9623 F 27*00 ' . . 42-8 80-8 9627 .... .... 43'3 8ro 9631 .... 32-00 43*9 8 1*2 9 6 35 .... 44*4 81-4 9638 F 26*00 .... 45*0 81*6 9642 .... .... 45'5 8rl 9643 .... 31*00 9646 .... .... 46*1 82*0 9650 .... .... 46*7 82*4 9652 F 25*00 30*55 9654 .... .... 47*3 84-4 9 6 55 24*69 30*00 9657 .... .... 47*9 82*6 9661 9665 F 24*00 .... 48*5 49-1 82*8 83*0 9666 .... 29*00 9669 9673 9677 F 9681 23*00 28*00 49'7 5'3 5'* 51*6 83*2 83*4 83*6 83-8 396 HTDEOMETET, ETC. TABLE XI. (continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9685 .... .... 52*2 8 4 -0 9688 .... 27-00 9689 .... .... 5**9 84'* 9691 F 22*OO 9693 .... .... 53*5 84-4 9697 .... .... 54-2 84-6 9698 .... 26-00 9701 .... .... 54-8 84-8 9705 F 21*00 .... 55'5 85-0 9709 20-46 25*00 *^> "* 56-2 85-2 9713 .... .... 56-9 85-4 9716 F 2O*OO 24*57 97 l8 .... 57*6 85-6 9719 .... 24-00 9722 9726 .... .... 58-3 59-0 85-8 86-0 9729 F I9*OO 23*00 9730 .... .... 59'7 86.2 9734 .... .... 60*4 86-4 9738 .... .... 61*1 86-6 9740 F 1 8*00 22*00 9742 .... .... 61*8 86-8 9746 .... .... 62-5 87-0 975 .... 2I*OO .63'* 87-1 9754 * 17-00 .... 63-9 87*4 9758 .... .... 64-6 87-6 9760 16-28 2O'OO 9762 .... .... 65*3 87-8 9766 F 16-00 .... 66-0 88-0 9770 . .. I9-00 66.7 88-2 9774 .... .... 67*4 88-4 9778 F 15-00 18-52 68-0 88-6 9780 .... 1 8 -oo 9782 .... .... 68-7 88-8 9786 .... 69-4 89-0 9790 F 14*00 17*00 70*1 89-2 9794 .... .... 70-8 89-4 9798 .... .... 89-6 9800 .... 1 6*00 9802 F 13*00 . . 72*1 89-8 9806 .... .... 72-8 90-0 9810 .... .... 73*5 90-2 9811 12*15 15*00 9 8i 4 F 12*00 74' i 90-4 ALCOHOL TABLES. TABLE XI. (contmmd). 397 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9818 .... .... 74-8 90*6 98?.! 14-00 9822 .... .... 75'4 90-8 9826 .... 76-1 91*0 9828 F 1 1 '00 9830 .... .... 76-7 91*2 9832 .... 1 3 'oo 9 8 34 .... .... 77*3 91-4 9838 10-07 12-42 78-0 91-6 9839 9'99 9840 9-92 . 9841 9'8S 9842 9 8 43 9-78 9-70 I2'00 78-6 9*1 9844 9-63 9 8 45 9-56 9846 9'49 .... 79'* 92*0 9847 9-41 . 9848 9*34 9849 9850 9-27 9'2O .... 79-8 92-2 9851 9-12 9852 9'5 9853 9854 8-98 8-91 iroo 80-4 92-4 9 8 55 8-84 9856 8-77 9857 9858 8-70 8-63 .... 8ri 92*6 9859 8'55 9860 8-48 9861 9862 8-41 8-34 .... 8 1-7 92-8 9863 8-27 9864 8'20 9865 9866 8-13 8-06 lO'OO 82-3 93-0 9867 7'99 9868 7-92 9869 9870 7-85 778 .... 82-9 93** 9871 771 9872 7-64 9873 7*57 398 HYDBOMETRY, ETC. TABLE XI. (continiied). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9874 7-50 .... 83--S 93*4 9875 7'43 9876 7'37 9877 7-30 9878 7-23 .... 84-0 93 -6 9879 7-16 9*00 9880 7-09 9881 7-02 9882 6-95 .... 84-6 93-8 9883 6-89 9884 6-82 9885 6-75 9886 6-69 .... 85-2 94' 9887 6-62 9888 6-55 9889 6-49 9890 6-42 9891 9892 6-35 6-29 8-00 85-8 94-2 9893 6-22 9894 9895 6-I 5 6-09 .... 86-3 94*4 9896 6'02 9897 5-96 9898 9899 5-89 5-83 86-9 94'9 9900 5'77 9901 5*70 99 oz 5-64 .... 87-4 94-8 993 S-SS 9904 5'S 1 7-00 9905 5'45 9906 5'39 .... 88-0 9S'<> 9907 S'3 1 9908 5-26 9909 5-20 9910 5*i3 .... 88-5 95'* 9911 5'7 9912 5-01 6-25 9913 4'94 99 H 4-88 .... 89-1 95'4 99'5 4-82 9916 476 6'oo 9917 470 ALCOHOL TABLES. TABLE XI. (continued). 399 Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9918 4-64 .... 89-6 95-6 9919 4*57 9920 4*5! 9921 4'45 9922 4*39 .... 90^2 95-8 99*3 4*33 9924 4-27 9925 9926 4-20 4-14 .... 907 96-0 9927 4-08 9928 4*02 5-00 9929 993 3'9 6 3'9 .... 91-2 96-2 9931 3-84 993* 378 9933 9934 373 3-67 .... 917 96-4 9935 3-61 9936 3*55 9937 9938 3'49 3'43 .... 92-3 96-6 9939 3*37 9940 3-32 9941 9942 3-26 3-20 92-8 96-8 9943 3* J 5 9944 3-08 9945 9946 3-02 2-97 .... 93*3 9?' 9947 2-91 9948 2-85 9949 995 2-74 .... 93-8 97-2 2*69 9952 2-62 9953 9954 2-57 2-51 .... 94*3 97'4 9955 2-45 9956 2-39 9957 9958 2-34 2-28 .... 94'9 97-6 9959 2*22 9960 2'17 9961 2'II 400 HYDBOMETBY, ETC. TABLE XI. {continued). Density. Alcohol by weight. Alcohol by volume. Strength. Hydrometer indication. 9962 2-05 .... 95'4 97-8 99 6 3 r 99 9964 1-94 9965 1*9 9966 i*j .... 95'9 98*0 9967 179 9968 J'73 9969 r6 7 9970 r6i 2*OO 96-4 98-2 9971 r 5 6 997* 1-51 9973 i'45 9974 1-40 .... 96-8 98-4 9975 i'34 9976 1-29 9977 1-23 9978 rig .... 97'3 98-6 9979 i'ia 9980 . 1-07 9981 ro2 9982 0*96 .... 977 98-8 9983 0*91 9984 0-85 9985 0-80 9986 9987 0-74 0-69 .... 98-2 99* 9988 0-64 9989 0-58 999 0-53 987 99-2 9991 0-47 9992 0-42 9993 0-37 .... 99-1 99'4 9994 0-32 9995 0*26 9996 0'2I 9997 0*16 .... 99-6 99-6 9998 0*11 9999 0*05 1 0000 .... lOO'OO 99-8 lOO'O SUGAB AND WOET TABLES. 401 XII. TABLE showing the amounts of crystallizable sugar corresponding to different densities of solution of sugar ; and the amounts of extract in wort or in beer deprived of alcohol. Amount of sugar, or of malt extract. Densities of sugar solution at 56-2 F. Niemann. Densities of beer wort. Zennek. Densities of malt infusion or sugar solution. Balling. Amount of sugar, or of malt extract. Densities of sugar solution at 56-2 F. Niemann, I -0000 25 .1-1056 I 1-0035 26 1103 2 1-1:070 27 1150 3 roio6 1-01140 I'OI2 28 1197 3'5 1-01340 29 1245 4 1-0143 1-01550 1*016 30 1293 4*5 1-01780 3 1 1340 5 1-0179 1-01970 I-02O 32 1388 5*5 1*02190 33 '-43" 6 1-0215 1*02410 1-024 34 1484 6 '5 1-02610 35 1533 7 1-0254 1-02820 1-028 36 1582 7*5 1-03030 37 1631 8 1*0291 1-032 38 1681 9 1*0328 1-036 39 '1731 10 1-0367 1-040 40 1781 ii 1-0410 1-044 41 1832 12 1-0426 1-048 42 1883 13 1-0504 1-053 43 '935 4 1-0552 1-057 44 1989 I C 1*0600 1*061 45 2043 16 1-0647 1-065 46 2098 ij 1-0693 1-070 47 2153 18 1-0738 1-074 48 2209 T 9 1-0784 1-078 49 2265 20 21 1-0830 1-0875 1-083 1-087 5 2322 2378 22 1-0920 1-092 52 2434 23 24 1-0965 I'lOIO 1-095 I'lOI 53 54 2490 2546 402 HYDBOMETBY, ETC, Xll o\ 00 *0 t^ ON r^ to 111 III oo o o O O r-> Tj- vr> vo t^ OO O O O O O O 2-81 's . K ro N ON 00 00 to 00 to 1] i Th to H H w it to rj- ui so t^ OO O < O O O O u s . ^ co oo *0 ON to ON VO to 00 11 r ON OO S S to Tj- u-, VO NO 00 o o o o o U*N ON O r *4 o rt SO rt ON ^ S a a s o o cT r H * ^ r^ rj- vo vo t- oo ON 000000 J 21 "3- 9 m vo (i H o H !- w> VO t^ 00 ON O O O ( O O ON O ft y~i ^ 00 m * ^ ON ?> ^> ^ l-g|j o O S S 1 5- Jo vo" "R ON" > O O O ~ O M j-p i rt A i^ S/B~ g, M r H VO 00 ON 00 rt ^ S'Sgf o j^- r; J> o o cT T^- w-i \o t^ oo ON O O O O O O 2 ill is o oo O o to vo oo ~ to VO "!1 o M i-t <* o vo r^ oo ON * o * tr> o 80s co pi O ^~ co 8^00 O O -i ;s e < fijfi Os x M o" 0^ Q" O O oo O O w Os & <* M H O ON ^ Q. 5; ^ S ^ j: ^1 GO , Cs r p P ? M p> OS c . 5^3 If S v^ 0s S ^ fiS, O H M M M M 000 13 -u J? * g tj C O O Os O O O "1 8, ^ ^ K|K|p, O M o 0000 3-2 || co vo Os O ON U-> M CO IH O W O OS Os OS OS w& M MM M 0000 ^ vo ^ ro M t^ Os III Os O 2" M "S Os Os Os Os O cl HI O " O O O O l'3-l'i O *O 00 00 t^ b M rl co O TJ- \> CO t-- vo cs 11 00 00 00 b b b M O vo O u-^ ^r, ^- co OO OO OO OO b b b b lit O &&a Lb """ ^ to o o o o 0000 ||| O U-l H rj O so oo oo rj- 00 vo t^ co r^- vo co rt O O O O t-- oo o ^ CO CO CO N O O O O W 1 406 WEIGHTS JLSD MEASUEES. H 12lb8. grains Cwts. =784 '1111 si o b f. bbbbbotiN 5 -* OT C-l ^ -T b io -? r: " 2S ss It Off O T; - 111 gallons ts=277'27 bic inche 3 3 8 s-l- CO.: "s II In cubic feet = 1 7'-2H cubic inches. I O ?J "N O O 04 W ^. 5 uvii '=.':. ^j 'w "^ C esc.,; = C o J . - J |-g lillllap -ooooo oo ? J; II S I" a glish = 3 f iilflill -H^ li ill o o ~o)^!O 88 'lSlilili |.l iplllll i 7i bbooo^ooboo U II ^ _ > r: r,. = Ills llli zn o-^cjoo** - ENGLISH WEIGHTS. English measures of weight. Troy weight. Pound. Ounces. Dwts. Grains. I 24 I 20 480 1 12 240 5760 Avoirdupois weight. Apothecaries weight. 407 Ton. Cwt. Pounds. Ounces. Drachms. Grains. I 16 437-a- I 16 7000 I 112 1792 I 20 2240 35840 Pound. Ounces. 3 Drachms. 9 Scruples. S r - Grains. I 20 I 3 60 I 8 24 480 I 12 96 288 5760 The grain is the same in all of these weights. English measures of capacity. Dry measure. Load or Wey. Quarters. Bushels. Pecks. Gallons. I 2 I 4 8 I 8 3 2 64 I 5 40 1 60 3 20 The imperial gallon contains 277'274 cubic inches. This quantity of pure water at 62 F., under an atmospheric pressure of 30 inches, weighs 10 pounds avoirdupois or 70'000 grains. A cubic inch of water weighs 252-458 grains. 408 WEIGHTS AND MEASTTBES. Liquid measure. Barrel. Kilder- kin. Firkin. Gallons. Quarts. Pints. Gills. TTogslipftd of alfi I I 2 I 2 4 I ,1 36 CA i i 4 36 72 144 216 } 2 8 72 144 288 412 I 4 wine 6l 2 12 1O4. Puncheon 84. 1l6 672 Butt of ale 108 864 Pipe 2 Hogsheads 126 ^.jz. IOO8 Tun 2 Pipes IOo8 .6^2, Cubic measure. Yard. Foot. Inch. I 1728 I 27 46656 The bulk of a barrel is 5 cubic feet. Linear measure. Mile. Furlong. Chain. Pole. Yard. Foot. Inch. 1 12 I 3 36 1 Si lli 198 I 4 22 66 792 I 10 40 220 660 7920 I 8 80 320 1760 5280 63360 The length of a pendulum that vibrates seconds of mean time in the lati- tude of London, at the level of the sea, and in a vacuum, is 39'1393 inches. END. INDEX. Acacia catechu, characters of stuff dyed Avith, 309; detection in madder, 301. Acetate of alumina, 103 ; of lead, 147 ; as reagent, 35. Acetates, of copper, 143, 211 ; distinctive characters of, 43. Acetic acid, 43 ; estimation of, 71, 74, 334, 339; examination of, 43 ; impurities in, 43 ; as re- agent, 34; tests for, 43, 296; tables, 340, 381. Acethneter, 72. Acid, acetic, 43 ; impurities, 43 ; as reagent, 34 ; test for, 43 ; estimation in beer, 339, 341 ; in wine, 71, 335 ; arsenious,99; estimation of, 100 j citric, 42 ; estimation of, 38 ; hydrochloric, 39 ; as reagent, 29 ; solvent action of, 29 ; tests for, 40; muriatic, 39 ; nitric, 40 ; as reagent, 34 ; tests for, 41 ; estimation La salts, 79; impurities in, 38 ; oxalic, 41 ; impurities in, 41 ; tests for, 41 ; phosphoric, 41 ; impurities in, 41 ; tests for, 41 ; stannic, 131 ; sulphuric, 38 ; as reagent, 34 ; tests for, 39, 292; estimation in salts, 78, impurities in, 38 j tartaric, 42. Acidimetry, 69 ; gravimetric me- thod, 75 ; normal solution for, 70, 72, 74 ; volumetric method, 69. Acids, 38 ; estimation in salts, 78 ; analytical classification of, 278 ; preliminary examination for, 275; separation from bases, 291 ; of 1st group from others, 292 ; of 2nd group from others, 293 ; solvent action of, 6 ; systematic qualitative analysis for, 291 ; special tests for, 296. JEther as reagent, 29. Air-bath, 16. Alcohol, 331 ; amount in beer, 346; in wine, &c., 347 ; in spirit of different densities, 384; as re- agent, 29 ; detection in etherial oils, 325; estimation of, 332; impurities in, 331 ; tables, 384- 400. Alcoholic liquids, 331. Ale, amount of alcohol in, 346, 347. Alkalies, 46; estimation of, 250 j in soap, 325; impurities in, 46, 60. Alkalimetry, 55 ; sources of error, 60; volumetric method, 250; correction of results, 60, 68 ; gravimetric method, 65 ; nor- mal solution for, 56. Alkaline metals, tests for, 291. Alkanet, violet, characters of, 315. 410 INDEX. Alloys, of antimony, 166, 169 j of arsenic, 166-168 ; of bismuth, 166, 168 j classification of, 164 ; composition of, 164,- of copper, 164-167 ; of gold, 165, 168, 169 ; of lead, 165-169 ; of mer- cury, 165, 168, 169 ; of plati- num, 167, 169 ; quantitative analysis of, 158 ; of silver, 164, 165, 167, 168, 169; of tin, 164- 169 ; of zinc, 164-169. Almond oil, 321. Alum, impurities, &c., 102. Alumina, 101 ; acetate, 103 ; phos- phate, 102 ; separation from oxide of zinc, 289 ; from 2nd division of 3rd group, test for, 289 j salts, distinctive characters of, 274; separation from earthy metals, 290. silicates, solution of, 232, 233 ; sulphate, 102 ; tests for, 289. Aluminous mordants, examination of, 103. Aluminum compounds, distinctive characters of, 104, Amalgam, analysis of, 151; for anatomical injections, 168 ; Dentists', 165; for electrical ma- chines, 169; for mirrors, 168, 169. American coin, composition of, 164, 165. Ammonia, 54; carbonate of, 54; estimation of, 238 ; impurities of, 54 ; molybdate, as reagent, 35 ; muriate, 54 ; as reagent, 32 ; oxalate of, as reagent, 35 ; solution, strength of, 383. Ammoniacal compounds, 54; di- stinctive character of, 54 ; valuation of, 54. Ammonium, chloride of, 54 ; as re- agent, 33 ; chloride of platinum and ammo- mum, 238 j sulphide of, 31. Analyses, calculation of, 254 ; for acids, 278 ; for ashes, 221 ; for bases, 297, Analysis, definition of, 1 ; of cafcv mine, 110 ; of cast iron, 171 ; of chrome iron ore, 107 ; of clay, 219 ; of coal, 200 ; of coal gas, 330 ; of copper ores, 144 j of flour, 353 ; of glass, 219 j of gunpowder, 83 ; of insoluble silicates, 232 ; of insoluble sub- stances, 267 ; of iron ores, 124 ; of limestone, 219 ; of mineral water, 219 ; of organic sub stances, elementary, 189 ; of plant ashes, 219 ; preparation of substances for, 219 ; qualita- live, 265; quantitative, 219 ; of soap, 323 ; of soils, 219 ; of speiss cobalt, 127; of water, 219 ; of wax, 323. Animal charcoal, 205. Annotto yellow, characters of stuff dyed with, 311. Antimoniate of lead, 214 ; of potassa, as reagent, :( I ; of soda, 291 - T of teroiide of anti- mony, 136. Antimony, alloys of, 166-169; anti- moniate of, 136 ; butter of, 135 ; chloride of, 135; compounds, 135; distinctive character of, 135, 162, 275, 268, 269, 273, 274, 275, 283, 285, 28(5 ; estimation of, 135 ; impurities in, 173; sulphide, 135; tests for, 135, 162, 285, 286 ; oxide of, reactions with borax and microcosmic salt, 273 ; with nitrate of cobalt, 274. Apparatus, 6-26 ; carbonic acid, 66 ; distillatory, 333 ; gas, 26 j pot- ash, 192. Aqua regia, 163. Arsenate of silver, 384. Arsenic, alloys of, 166-168 ; compounds of, 129 ; distinctive characters of, 130, 161, 269, 284, 285 ; INDEX. 411 estimation of, 130; oxide of, 129; sulphides, 129, 215, 311 ; test for, 129, 161, 284, 285 ; white, 129. Arsenite of copper, 142, 212, 312 ; character of cloth dyed with, 311. Arsenous acid, 129 ; impurities in, 129. Asbestos, 190. Ashes, analysis of, 219 ; estimation in coal, 201 ; in or- ganic substances, 196, 221 ; of chlorine in, 236 ; of flour, 361 ; of isinglass, 366 ; of starch, 356 ; of tea, 364. Assay of gold alloys, 138 ; of iron ores, 124 ; of silver alloys, 153. Attar of roses, 325. Azure blue, 208. Azurite, 209. Balances, use of, 26. Barium, chloride of, 33, 87 ; compounds of, 87 ; distinctive character, 88 ; tests for, 290 ; sulphide, 87. Baryta, carbonate, 87 ; as reagent, 34 ; sulphate, 87, 218 ; separation from strontia and lime, 290. Bath metal, composition of, 164. Bases, qualitative examination for, 279. Bavarian beer, amount of alcohol in, 346. Beer, 335 ; amount of alcohol in, 346 ; constituents of, 335 ; esti- mation of alcohol in, 336, 342 ; original gravity of, 336 ; esti- mation of extract, 336, 341 ; halimetric examination of, 341. Beet-root sugar, 348. Bell metal, composition of, 164, 166. Benzoic acid, test for, 294. Berlin blue, 209. Biborato of soda, 51. Bicarbonate of potash, 47; of soda, 51. Bichloride of platinum, as reagent, 35 Bidery, composition of, 166. Binoxide of manganese, 110; valua- tion of, 111-117. Bismuth, alloys of, 166-169 ; compounds of, 140; distinctive characters of, 140, 160, 273, 274, 275 ; oxide of, 140 ; reac- tions with borax and microcos- mic salt, 273 ; solder, 169 ; test for, 140, 160, 282 j trisnitrate of, 140. Bistre mineral, 213. Bitartrate of ammonia, 199 ; of potash, 50. Bitter almond oil, 325. Black pigments, 213; dyes, 314; lead, 213 ; examination of cloth dyed, 314. Blasengriin, 212. Blowpipe, 21 ; flame produced by, 22; reactions, 272; reagents, 32, 270 ; supports, 22 ; use of, 270. Blue, a/Aire, 208; Bremen, 141; Berlin, 209 ; Cassel, 209 ; che- mical, 307 ; Chinese, 209 ; co- balt, 208 ; English, 209, 307 ; examination of cloth dyed, 307 ; Hamburg, 209; indigo, 209, 307 ; lichen, 210 ; logwood, 307 ; mineral, 209 ; mountain, 141, 209; Neuwied, 209; Paris, 209 ; Prussian, 208, 307 ; Saxon, 208, 307; stone, 209; The- nard's, 208 ; ultramarine, 208 ; vat, 307 ; washing, 209. Bone black, 213 ; earth, 218. Boracic acid, test for, 293. B orate of copper, 212. Borax, 51 ; impurities, 52 ; valua- tion of, 86. Boi'deaux wine, amount of alcohol in, 347. Brass, composition of, 164 ; solder, 164, 175. Brazil wood, red, character of stuff dyed with, 308. Bread, 360. Britannia metal, composition, of, 166-168. 412 INDEX. Bromide of palladium, 186 ; of sil- ver, 181 ; action of chlorine upon, 185. Bromides, distinctive characters of, 181, 275 ; reaction with sulphu- ric acid, 265. Bromine, estimation of, 181 ; in water, 238; test for, 238; re- action with starch, 275 ; sepa- ration from chlorine and iodine, 185. Bronze, composition of, 164-166. Brown, catechu, 309 ; dye-wood, 309; madder, 309; manganese, 213, 309; Spanish, 213; Van Dyk, 213. cefia BuceUas wine, amount of alcohol in, 347. Buckthorn green, 212. Burettes, 23, 226. Burgundy wine, amount of alcohol in, 347. Butter, 363 ; adulteration of, 363 ; of antimony, 135. Button metal, composition of, 165. Cadmium, distinctive characters of, 272; oxide of, reactions witli borax and microcosmic salt, 272; test for, 282, Cakmine, 108 ; analysis of, 110. Calcium, chloride of,' 33, ( Jo ; compounds, 88 ; distinctive cha- racters of, 88 ; fluoride, 95 ; sulphides, 95 ; separation from strontium and barium, 290 ; tests for, 290. Calculation of analytical results, 3. Calomel, 151. Calorific power of fuel, 201. Cane-sugar, 348; estimation of, 349, 352 ; compound with lime, 349 ; distinction from grape-sugar, 350. Caoutchouc tube, 193. Carbon, 189 ; estimation of, 189 ; mineral, 213 j vegetable, 213 j bone, 213. Carbonate of ammonia, 32, 54 j of baryta, 87 ; of copper, 141 ; of lead, 146 ; of lime, 88 ; of mag- nesia, 100 ; of potash, 32, 46 ; soda, 32, 50 ; zinc, 108. Carbonates, analysis of, 223; di- stinctive characters of, 267, 275 ; reactions with sulphuric acid, 275 ; tests for, 293. Carbonic acid, distinctive character of, 293 ; estimation of, 66, 223, 237 ; test for, 293. Carmine, 216. Cassel blue, 209 ; yellow, 214. Cassia oil, 326. C'a.-t iron, analysis of, 171 ; impuri- ties in, 171. Catechu, acacia, 309 ; brown, 309. Caustic ammonia, 54 ; baryta, 87 ; lime, 88; potassa, 48 j soda, 51. Cements, 89; analysis of, 89, 219 ; composition of,'()0 ; tots of, 91. Chalk, 88 ; behaviour with reagents, 218. Champagne, amount of alcohol in, Charcoal, animal, 205 ; estimation of absorbent power, 206 ; valua- tion of, 206 ; use in testing with the blowpipe. 22, 274. Chemical blue, 307 ; analysis, definition of, 1 ; objects of, 1. Chicory, detection in coffee, 364. Chili saltpetre, 53, 83 ; impurities in, 53. Chinese blue, 209 ; gong-gong metal, composition of, 164; grass, 370. Chlorate of potash, 48. Chlorates, distinctive characters of, 48, 270, 296 - t tests for, 270. INDEX. 413 Chloric acid, tests for, 296. "Chloride of ammonium, 33, 54 ; of antimony, 135 ; of barium, 87 ; as reagent, 33 ; of calcium, 95 ; as reagent, 33, 190; of chromium, 105 ; of iron, 34, 118; of lead, 279. of silver, 153 ; of sodium, 53 ; of strontium, 88. Chlorides, distinctive characters of, 40, 180, 275 ; of iron, 118 ; of lime, 96 ; of mercury, 150 ; as reagent, 35 ; of platinum, 35; oftin,132; tests for, 40, 180 ; reactions with sulphuric acid, 275 ; reactions with phosphate of silver, 180 ; reactions with silver salts, 180. Chlorimetry, 97. Chlorinated lime, 96. Chlorine, 180; estimation of, 180, 236 ; in ashes, 236 ; as reagent, 35 ; separation from bromine and iodine, 185 ; tests for, 180 ; in substances inso- luble in water, 180 ; reaction with iodide of potassium, 180, 182, 184; reaction with subchloride of mercury, 180 ; reaction with bromide and io- dide of silver, 185. Chocolate, 365. Chromate of baryta, 215 ; of lead, 106, 214, 311 ; as reagent, 190; of potassa, 105 ; as reagent, 35 ; of zinc, 106. Chrome black, 314 ; green, 212 ; characters of cloth dyed with, 312 ; yellow, 214 ; ' orange, 214. Chromic acid, distinctive character of, 107, 281 ; estimation of, 107 ; tests for, 107. Chromium, chloride of, 105 ; compounds, 105; distinctive cha- racters of, 107, 287, 288 ; esti- mation of, 107 ; oxide of, 105, 276 ; reactions with borax and microcosmic salt, 273 ; sepa- ration from manganese, 287; from iron, 288 ; from uranium, 288 ; sulphate of, 105. Chrysocole, composition of, 164. Cinnabar, behaviour with reagents, 216 ; green, 212. Citric acid, 42 ; impurities in, 42 ; tests for, 43. Claret, amount of alcohol in, 347. Clay, analysis of, 219. Clock-bell metal, composition of, 164. Clove oil, detection in cinnamon oil, 326. Coal, analysis of, 200; calorific power of, 201-205 ; fuel, value of, 200 ; gas, 330. Cobalt, compounds of, 127 j nitrate of, 274 ; oxide of, reactions with borax and microcosmic salt, 272 ; separation from nickel, 289 ; from manganese, 289; sulphide of, 277 ; speiss, 127 ; tests for, 289 ; ultramarine, 208; distinct- ive characters of, 128. Cochineal, 303 ; adulteration of, 303 ; estimation of colour-sub- stance, 304; red, 308; facti- tious, 304. Coffee, 364 ; amount of extract in, 365. Cologne umber, behaviour with reagents, 213. Colorimetric method of valuation, 145 ; test of madder, 302. Combustion, apparatus for, 194, 201; furnace for, 190-192; tubes, 190, 198. Condensing apparatus, 14, 333. Constantia, amount of alcohol in, 347. Copper, acetates of, 143 ; alloys of, 164-167 ; arsenites of, 142, 312 ; assay of ores, 144-146 ; carbo- nates of, 141 j compounds of, 414 INDEX. 141 ; distinctive characters, 145, 159; estimation of, 144; hy- drated oxide of, 142 ; impurities iu, 174 ; nitrate of, 141 ; oxide of, 142 ; reactions with borax and microcosmic salt, 273 ; sul- phate, 141 ; sulphide, 277 ; tests for, 145, 159 ; use in organic analysis, 190, 197. Corrosive sublimate, 150. Cotton, 368 ; distinctive characters of, 370-372. Crucible jacket, 18. Crucibles, 18; supports for, 18; platinum, 19 ; porcelain, 19. Cubic nitre, 53, 83. Cupellation, 20. Cupels, 20. Cyanide of potassium, 49 ; conver- sion into ferrocyauide, 187 ; im- purities in, 49; reaction \\itli iodine, 186 ; valuation of, 186 ; of silver, 188. Cyanides, 186 ; distinctive charac- ters of, 186, 275 ; estimation of, 186-188; reactions, with sul- phuric acid, 186, 275 ; with salts of iron, 186 ; with ni- trate of silver, 188. Cyanogen, compounds of, 49, 118, 120, 186; distinctive characters of, 186, 275 ; estimation of, 186-188 ; tests for, 186. Cyder, amount of alcohol in, 347. Cyprian green, 210 ; umber, 213. Decantation, 9 j washing by, 9. Decoction, 7. Density of beer wort, determination of, 336. Dentists' amalgam, composition of, 165 ; gold, 169. Distillation, 13 ; apparatus for, 14 ; as a means of separation in ana- lysis, 268. Distilled waters, 327. Drying, 15-17,193; tubes, 192,193. Dry-air chamber, 16. Dry process, 5. Dye-stuffs, 300 ; test, 301. Dye-wood, brown, characters of cloth dyed with, 309. Dyed fabrics, examination of, 307- 315. Earths, 87 ; tests for, 290. Effervescence, 27, 267. Electrical amalgam, composition of, 169. Elementary analysis of organic sub- stances, 189-200. Elements, chemical, -105 ; classifi- cation of, 265 ; table of, 406. Emery, 101. Enamel solder, composition of, 165, 168. English blue, 209 ; coin, composi- tion of, 164, 165 ; tfnvn, 211. Equivalents, 406; tlieniioiiu-tric, 408, 409. Estimation of carbonic acid, 66. Estimation of sulphur, 199 ; of oxy- gen, 197; of nitrogen, 197-199; of carbon, 189 ; of hydrogen, 189. Ether as reagent, 29. Evaporation, 13; furnace for, 14; ae test for substances in solution, 268 ; as test of solubility, 208. Examination of fuel, 200; of animal charcoal, 206. Fabrics, examination of dyed or printed, 305-315. Fat, detection of, 322 ; estimation of, 323 ; in soap, 324. Fermentation of sugar, 319. Ferricyanidc of potassium , 120 ; as reagent, 35. Ferrocyanide of potassium, 118 ; as reagent, 35. Fibres, distinctive characters of, 367-372; animal, 370; plant, 370-372; chemical tests of, 370- 372. INDEX. 415 Filtration, 10; vessels used, for, 10. Filtering paper, 10. Fish oil, 322. Flake white, 217. Flame, blowpipe, 2L Flask, measure, 37 ; use in analysis, 66, 77, 111, 115, 268. Flour, analysis of, 359 ; detection of admixtures in, 358. Fluoride of ammonium, as solvent, 232 ; calcium, 95. Fluorides, distinctive character, 95. Fluor-spar, 95. French coin, composition of, 164, 165 ; green, 210. Fuel, calorific power of, 201; valua- tion of 200-205. Funnels, 10. Furnaces, 14, 18, 20. Fusible alloy, composition of, 169. Fusion, 19, 270; solution by, 232, 234; with soda on charcoal, 274 ; with borax or microcos- mic salt, 270. Gamboge, behaviour with reagents, 215. Garancine black, characters of cloth dyed with, 314. Gas, analysis of, 330 ; apparatus, 26; coal, 330; furnace, 191; generator, 26; olefiant, 330; operations with, 24 ; tests of, 267 ; valuation of, 328. Gelatin, 365 ; detection in isinglass, 366. Geranium oil, detection in attar of roses, 326. German silver, 166. Gilding, tests of, 173. Glass, analysis of, 219. Glauber's salt, 52. Gold, alloys of, 165, 168, 169 ; amal- gam, 168 ; assay, 137 ; .chloride of, 137 ; coin, composition of, 165 ; compounds of, 137 ; cu- pcllation of, 138; distinctive characters of, 138, 163, 274, 284 ; dentists', composition of, 168 ; estimation, 138 ; green, composition of, 168 ; gray, com- position of, 169 ; quartation, 139 ; Manheim, composition of, 165 ; mosaic, composition of, 164; parting of alloys, 139; red, composition of, 165; solder, composition of, 165, 167 ; solu- tion for gilding, 137 ; and steel alloys of, 168; tests for, 138, 163, 284; yellow, composition of, 165, 168. Grape-sugar, 348 ; reaction with al- taline and cupreous solutions, 349, 350. Graphite, behaviour with reagents, 213. Grass, Chinese, 370. Gravimetric method of analysis, 3 ; for alkalies, 65. Greasing oils, 322. Green, examination of cloth dyed, 312; Bremen, 211 ; Brunswick, 211 ; cinnabar, behaviour with re- agents, 212; cupreous pigments, behaviour with reagents, 211 ; Naples, 212; oil, 212; quer- citron, 212; sap, 212; Scheele's, 211 ; Schweinfurt, 211 ; Swe- dish, 211. Grey, examination of cloth dyed, 314. Groups, analytical, 277, 278 ; sepa- ration of, 276-294. Gun-metal, composition of, 164. Gun-mountings, composition of metal for, 165. Gunpowder, analysis of, 83. Gypsum, behaviour with reagents, 218. Halimetry, 78. Hamburg blue, 209. Hardness of water, 224 ; estimation of, 225. Hartshorn, prepared, 218. 416 INDEX. Hemp, 369 ; distinctive characters of, 370, 371 ; Manilla, 369. Hock, amount of alcohol in, 347. Hollands, amount of alcohol in, 347. Honey, 358 ; adulteration of, 359. Hydrate of baryta, 87 ; as reagent, 34. of lime, 88 ; as reagent, 34 ; of lime and soda, 197 ; of potassa, 48 ; as reagent, 32, 190; of soda, 51 ; as reagent, 32 ; use in analysis, 192, 193. Hydrate of potassa, 48. Hydrochloric acid, 39; impurities in, 39 ; as reagent, 29, 198 ; sol- vent action of, 29 ; table, 379 ; tests for, 40. Hydrocyanic acid, reaction with salts of iron, 186 ; estimation, 188. Hydrofluoric acid, as solvent, 232. Hydrogen, use in analysis, 244 ; sulphuretted, 30 ; estimation in organic substances, 189. Hydrometers, 374, 375. Hydrometric equivalents, 376, 377. Hydrometry, 373. Hydrosulphate of ammonia, 31. Hydrosulphuric acid, 30 ; distinct- ive characters, 176, 293 ; esti- mation of, 176 ; tests for, 293. Hypochlorite of lime, 96. Hyposulpliite of soda, 52. Ignition, 17. Imitation gold, composition of, 164 ; detection of, 173. silver, detection of, 175. Impurities, detection of, 3 ; in alco- hol, 331; in animal charcoal, 205 j in antimony, 173 ; in beer, 335 ; in bread, 361 ; in butter, 363 ; in chocolate, 365 j in cochi- neal, 303; in coffee, 364; in copper, 174 ; in cordialized spi- rits, 334 ; in etherial oils, 325- 327 j in flour, 358 j in gold, 173 ; in honey, 354 ; in iodine, 181 ; in iron, 171 ; in lead, 174 ; in madder, 300 ; in meal, 358 ; in mercury, 17 i; in metals, 170- 174; in milk, 362; in nickel, 172; in oils, 317-322; in phos- phorus, 177; in silver, 174; in soap, 323 ; in spirits, 334 ; in starch, 356 ; in sugar, 353 ; iu sulphur, 176; in tea, 36 1 ; in tin, 173 ; in wax, 323 ; in zinc, 170. Incineration, 7. Indigo, 305 ; behaviour with re- agents, 209 ; blue, 209 ; charac- ters of cloth dyed with, 307 ; as reagent, 35 ; valuation of, 305. Infusion, 7. Insoluble silicates, analysis of, 233. lodate of potassa, test for, 48. Iodide of mercury, 150; of palla- dium, 182, 186; of potassium, 48; impurities in, 48 ; anulv.-is of, 182 ; of silver, 182 ; valua- tion of, 182-1 SI. Iodides, analysis of, 123 ; di>tinetive characters of, 182, 275 ; test for, 182; reaction with pm-hloride of iron, 182; with chlorine, IS:.', ] s I ; with sulphuric acid, 272 ; with hydrochloric acid and io- dates, 183 ; of the heavy metals, analysis of, 183. Iodine, 1S1 ; adulteration of, 181; distinctive character of, 181 ; estimation of, 182, 184, 238 ; in water, 238 ; estimation of water in, 181 ; impurities in, 181 ; as reagent, 3 5 ; reaction with starch, 181, 272; with hyposulphite, 183 ; with water in presence of chlorine, 184; conversion into iodic acid, 184 ; with hypochlo- rites, 184 ; separation from chlo- rine and bromine, 185, 186 ; test for, 181, 238 j valuation of, 181, 183, 184. Iron, 35, 117, 171 ; acetate of, 118 j as reagent, 35 ; chlorides of, 118 ; compounds of, IHDEX. 417 117 ; distinctive characters of, 122, 162, 272, 288 ; estimation of, 122, 243 ; ferro- cyanide of, 121 ; impurities in, 171 ; nitrate of, 117 ; ochre, 215 ; oxide, 216 ; reactions with borax and microcosmic salt, 272;" perchloride, 118 ; as reagent, 34 ; pernitrate, 11 7; persulphate, 117; phosphate of, 178, 179 ; sepa- ration from other metals, &c., 243-245; sulphate, 117; as reagent, 35 ; sulphide, 31 ; se- paration from chromium and uranium, 288 ; separation from potassium or sodium, 243 ; se- paration from magnesium or calcium, 243 ; separation from aluminum, 243; separation from manganese, 244 ; tests for, 122, 162, 272, 288. Isinglass, 366 ; adulteration of, 366. Kelp, valuation of, 182. King's yellow, 215. Lachrymse Christi, amount of alco- hol in, 347. Lake, cochineal, 217; crimson, 217; Florentine, 217; green, 212; gum-lac, 217 ; logwood, 217 ; madder, 217; scarlet, 217; Vene- tian, 217 ; Vienna, 217. Lamp-black, 212. Lapis lazuli, behaviour with re- agents, 208. Lead, 146 ; acetate of, 147 ; as re- agent, 35 ; alloys of, 165 ; basic acetate of, 147 ; as reagent, 35 ; basic cliromate, 216 ; binoxicle, use in organic analysis, 197 ; carbonate of, 146 ; com- pounds of, 146 ; distinctive characters of, 159, 272, 274, 275, 280, 282 ; estimation of, 147 ; impurities in, 174 ; oxide of, 116; reaction with borax and microcosmic salt, 272 ; red, behaviour with reagents, 216 ; oxide of, 146 ; separation from other metals, 149, 150, 279, 282 ; tests for, 147, 159, 280, 282 ; valuation of fuel with, 205 ; white, behaviour with reagents, 217. Leipzig yellow, 214, Lichen blue, 210. Light-value, 328. Lighting, valuation of, materials used for, 327. Lime, 88 ; acetate of, 96 ; carbonate of, 88, 218 ; compounds of, 88 ; caustic, 88 ; chloride of, 96 ; di- stinctive characters of, 2 ; esti- mation of, 100; hypochlorite, 96 ; sugar, 349 ; as reagent, 34 ; phosphate of, 94; sulphate of, 94, 218 ; separation from other bases, 249 ; sepa- ration from phosphoric acid, 241 ; tests for, 290. Limestone, 88 ; analysis of, 89, 219. Linen, 368. Linseed oil, 321. Lisbon wine, amount of alcoliol in, 347. Litharge, 146. Litmus, 35, 210 ; paper, 35 ; use in analysis, 268. Logwood black, 314 ; blue, charac- ters of cloth dyed with, 307, 313 ; violet, 315. Luminous effect, estimation of, 328. Maceration, 7. ^ Madder, 300; black, 314; brown, 308 ; red, 308 ; violet, 315. Madeira wine, amount of alcohol in, 347. Magnesia, 100; ammonio-pluxsphate of, 349; carbonate of, 100; distinctive characters of, 101 ; estimation of, 349 ; phosphate of, 240 ; pyrophosphate of, 249 ; reaction with nitrate of cobalt, 274; sulphate of, 101 j as re- agent, 31 ; separation from alka- 2E 418 INDEX. Jine metals, 291 ; from metals of 4th group, 290. Magnesium compounds, 100; di- stinctive characters of, 101 ; tests for, 291. Malaga wine, amount of alcohol in, 347. Malt infusion, amount of sugar in, see table at end ; density of, see table at end. Manganese, binoxide of, 110; brown, 213, 309 ; compounds of, 110; distinctivecharacters of, 272 ; estimation of, 110, 245 ; oxide of, reactions with borax and microcosmic salt, 272 ; se- paration from cobalt and nickel, 289 ; separation from magne- sium, 246 ; separation from cal- cium, 246 ; separation from alu- minum, 246 ; tests for, 289. Manilla hemp, 368. Marl, analysis of, 232 et seq. Marsala, amount of alcohol in, 347. Marsh's test, 129. Massicot, behaviour with reagents, 215. Measures, 22. Melting, 19 ; crucibles used for, 19 ; furnaces, 20 ; object of, 19. Mercury, amalgam of, 165, 169 ; chlorides of, 150; as reagent, 35 ; compounds of : 150 ; distinctive characters of, 151, 160 ; estima- tion of, 151 ; impurities in, 174; iodide of, 150 ; nitrate of, 150 ; oxides of, reactions with borax and microcosmic salt, 272, 273 ; sulphide of, 150, 216 ; separa- tion from other metals, 280, 281 ; testa for, 151, 160, 269, 280, 281. Metals, alkaline, separation from magnesium, 291 ; analytical clas- sification of, 277 ; examination of 158-163 ; impurities in, 170- 175 ; qualitative analysis of, 158- 163 ; as reagents, 35 ; separation of 4th group from 5th group, 290 ; test for 1st group, 279 ; test for 2nd group, 280; test for 3rd group, 286 ; test for 4th group, 290 ; test for 5th group, 291 ; tests of purity, 170-175. Methods, analytical, 2 ; gravime- tric, 3 ; volumetric, 4. Microcosmic salt, 270. Microscopic appearance of fibres, 367-370; of starch-granules, 354-359. Milk, 361; adulteration of, 361; microscopic appearance of, 362 ; valuation of, 363. Mineral naphtha water, 327 ; ana- lysis cf, 219 ; bistre, 213 ; blue, 209 ; green, 211 ; substance in water, 221 ; estimation of, 236 ; white, 218. Minerals, analysis of, 219 ; breaking lumps of, 220. Minium, 216. Molybdate of ammonia, as reagent, 35 ; as a test for phosphoric acid, 177. Mordant, aluminous, 103 ; exami- nation of, 104; detection in dyed or printed fabrics, 306. Mortar, 90. Mosaic gold, 164. Mountain blue, 141 ; behaviour with reagents, 209. Muffle, uses of, 20. Muriatic acid, 39. Muscat wine, amount of alcohol in, 347. Nankeen yellow, characters of stuff dyed, 311. Naphtha, mineral, 327 ; adultera- tion of, 327. Naples yellow, behaviour with re- gents, 214 ; earth, 214. Neroli oil, 326. Neuwied blue, 209. Newton's alloy, see table of alloys. Nice wine, amount of alcohol in, 347. Nickel, compounds of, 128 ; distinc- tive characters of, 128, 161, 272, INDEX. 419 287, 289; estimation of, 128; impurities in, 172 ; oxide of, re- actions with borax and micro- cosmic salt, 272 ; separation from manganese and cobalt, 289; tests for, 128, ] 61, 289. Nitrate of baryta, 87 ; of bismuth, 140; of cobalt, 277; of copper, 141 ; of mercury, 150 ; of pot- assa, 48 ; of silver, 152 ; as re- agent, 33 ; of soda, 53 ; of strontia, 88 ; use in analysis, 189, 199. Nitrates, distinctive characters of, 270, 275 ; reaction with sulphu- ric acid, 275 ; reaction with sul- phate of iron, 237 ; tests for, 270. Nitre, adulteration of, 48 ; analysis of, 79 ; cubic, 53 ; impurities in, 48 ; valuation of, 79. Nitric acid, 40 ; distinctive charac- ters of, 41 ; estimation of, 78 ; in water, 237 ; impurities in, 40 ; as reagent, 34 ; specific gra- vity table, reaction with, 380 ; tests for, 41. Nitrobenzol, 326. Nitrogen, conversion into ammo- nium, 189 ; estimation of, 197 200 ; oxides of, reaction with copper, 197 ; test for, 189. Nitromuriatic acid, 163. Normal solution for alkalimetry, 56, 65 ; for estimation of cyanides, 186, 188 ; for estimation of io- dine, 183, 184; for estimating hardness of water, 225 ; for sil- ver assays, 153. Nut gall black, 314. Ochre, yellow, behaviour with re- agents, 215. Oil, almond, 321 ; bitter almond, 326 ; cassia, 326 ; cinnamon, 326 ; detection of, 322 ; etherial, 325 ; estimation of, 323 ; adul- teration of, 325-327 ; fat, 316 ; adulteration of, 316 ; detection of, 322; in etherial oil, 325; fish, 322 ; greasing, 322 ; neroli, 326; olive, 317; palm, 322; rape, 321 ; rose, 325 ; train, 322 ; examination of, 316. Olefiant gas, 330. Oleic acid, detection .in oils, 317. Operations, analytical, 5 ; blowpipe, 20 ; with gases, 25. Orange, chrome, behaviour with re- agents, 214. Organic acid, 41 ; analysis of, 189 ; nitrogenous, reaction with cau- stic alkalies, 189 ; substance, estimation of, 223 ; re- action with sulphuric acid, 275 ; tests for, 270, 274, 275. Original gravity of beer, 336. Orpiment yellow, characters of stuff dyed with, 311 ; behaviour with reagents, 215. Oxalate of ammonia, 35 ; as re- agent, 35 ; of lime, 100 ; of potassa, 49. Oxalates, tests for, 42. Oxalic acid, impurities in, 41 ; tests for, 42. Oxide of antimony, reactions with borax and microcosinic salt, 273 ; of copper, as reagent, 190. Oxides, distinctive characters, 272, 273 ; metallic, reactions with borax and microcosmic salt, 272. Oxygen, estimation of, 197, 203 ; use in analysis, 194. Packfong, composition of, 168. Palladium, bromide of, 186 ; chlo- ride of, 186 ; nitrate of, 186. Palm-oil, 322. Paris, plaster of, 94. Parting, 139. Pearlash, 48. Pearl-white, 140. Perchloride of iron, 118; as reagent, 34. Permanganate of potash, 242. Perrotine blocks, composition of metal for, 169. 2E2 420 INDEX. Perry, amount of alcohol in, 347. Pewter, composition of, 167. Phosphate of alumina, analysis of, 179 ; test for, 289 ; of lime, 218 ; of iron, 178 ; analysis of, 179 ; of soda, 34 ; of magnesia and ammonia, 177. Phosphates, distinctive characters of, 177. Phosphides, 177. Phosphoric acid, 41 ; impurities in, 41 ; distinctive characters of, 177; estimation of, 178, 179, 239 ; separation from second group of acids, 292 ; from silica, 293 ; from sulphuric acid, 293 ; from bases, 241 ; from alumina, 179, 241 ; from magnesia, 240; from lime, 241 ; from oxides of iron or man- ganese, 241 ; in urine, 179. Phosphorus, 177 ; compounds of, 177 ; estimation of, 177 ; impu- rities in,l77 ; salt, as rcagent,270; reactions of metallic oxides with, 272. Photometer, 328, 330. Photometry, 327. Picric acid, characters of cloth dved with, 311; black, 213; blue, 208 ; brown, 213 ; green, 210 ; red, 216 ; white, 217 ; yellow, 214. Pig-iron, 171. Pigments, 207-218 ; containing prussian blue, valuation of, 122; examination of, 207. Pincette, 22. Pinchbeck, composition of, 164. Pipettes, 25. Pitchblende, 127. Plant-ashes, analysis of, 219-254 ; constituents of, 219. Plaster of Paris, 94. Plating for buttons, composition of, 164. Platinum, alloys of, 167, 169 ; am- raonio -chloride of, 137, 197; bi- chloride of, as reagent, 35, 137 ; crucibles, 19 ; distinctive cha- racters of, 137, 163, 284; estima- tion of, 137 ; sulphide of, 30, 31 ; tests for, 137, 163, 284 ; vessels of, 22 ; use in analysis, 268 ; wire, 22 ; capsule, use in ana- lysis of water, 236. Plumbago, test for, in iodine, 181 ; behaviour with reagents, 213. Poppy-oil, detection in olive-oil, 317. Porcelain-vessels, 19; crucibles, 19 ; tubes, 19. Porter, amount of alcohol in, 316, 347. Portland cement, 89. Port wine, amount of alcohol in, 347. Potashes, 46 ; estimation of soda in, 62 ; impurities in, 60 ; valua- tion of, 55. Potassa, antimoniate of, 34 ; bicar- bonate of, 47 ; bitartrate of, 50; bichromate of, 106 ; binoxalato of, 49 ; bisulphate of, use in effecting solution, 233 ; carbonate of, 46 ; as reagent, 32; caustic, 48 ; as reagent, 32 ; chlorate of, 48 ; chromate of, 105 ; as reagent, 34 ; compounds of, 46 ; estimation of, 250 ; hy- drate of, 32 ; hydriodate of, 48; iodate of, tost for, 48; nitrate of, 48 ; oxalate of, 49 ; permanganate of, 123 ; qua- droxalate of, 50 ; as reagent, 32 ; sulphate of, 48 ; tartrate of, 50. Potassium, ferricyanide of, 120 ; as reagent, 35 ; ferrocyanide of, 118 ; as reagent, 35 ; iodide of, 48 ; cyanide of, 49 ; separation from magnesium and sodium, 291 ; from earthy me- tals, 290. Pouring, 10. Precipitant, 8. Precipitation, 7, 27 ; apparatus for, 8 ; chemical, 8 ; definition of, 7 ; characters of, 8. INDEX. 421 Precipitates, 8 ; collecting, 8, 11 ; drying, 15; ignition, 15, 18; washing, 11 ; weighing, 15. Preliminary tests in qualitative ana- lysis, 266-275. Preparation of substances for ana- lysis, 220-222. Prince's metal, composition of, 164. Protosulphate of iron, 117; as re- agent, 35. Prussian blue, 1.21 ; character of cloth dyed with, 307 ; behaviour with reagents, 208. Pulverization, 7, 220. Purple of Cassius, 137. Pyrolusite, 110. Pyrophosphate of magnesia, 178. Pyrotechnic mixtures, analysis of, 84. Qualitative analysis, 1, 2. Quantitative analysis, 1, 3. Quartation, 139. Queen's metal, composition of, 169. Quicklime, 88. Quicksilver, 174. Raisin wine, amount .flf alcohol in, 317. Rape-oil, 321. Reaction, definition of, 2. Reactions, 27 ; of acetates, 43, 296 ; of aluminum compounds, 104 ; of ammoniacal compounds, 54 ; of antimony compounds, 135, 268, 274, 285 ; of arsenic com- pounds, 129, 269, 280, 284; of barium compounds, 88 ; of benzoates, 294, 296 ; of bismuth compounds, 140, 272, 274; of borates, 293 ; of calcium, com- pounds, 100 ; of carbonates, 267 ; of chlorates, 270 ; of chlo- rides, 40; of chrornates, 107; of clrromium compounds, 105 ; of citrates, 295 ; of gold com- pounds, 137 ; of cobalt com- pounds, 128 ; of copper com- pounds, 141 ;. of cyanides, 267 ; of hydriodates, 182 ; of hypo- chlorites, 97 ; of iodides, 182 ; of iron compounds, 122 ; of lead compounds, 147 ; of mag- nesium compounds, 101 ; of manganese compounds, 116, 272; of mercury compounds, 267 ; of nitrates, 97, 237 ; of oxalates, 42, 295 ; of peroxides, 267 ; of phosphates, 177, 239 ; of plati- num compounds, 137 ; of potas- sium compounds, 50 ; of sili- cates, 275 ; of silver compounds, 152, 267; of sodium compounds, 53 $ of strontium compounds, 88 ; of succinates, 296 ; of sul- phates, 39 ; of tartrates, 42 ; of tin compounds, 132 ; of uranium compounds, 127 ; of sulphides, 267 ; of zinc compounds, 108. Reagents, 27 ; definition of, 2 ; use of, 27 ; in the dry way, 27 ; iu the wet way, 27 ; used in roast- ing, 18 ; volumetric, 36 ; for separating elementary sub- stances in groups, 276. Red, examination of cloth dyed, 308 ; lake, 217 j lead, behaviour with reagents, 216 ; Madeira, amount of alcohol in, 347 ; English, 216; chrome, 216 ; bole, 216 ; stone, 216. Reduction of results obtained in analysis, 254. Reflector metal, composition of, 166-168. Resin, detection in wax, 323 ; in soap, 325 ; in oil, 317. Retorts, 14. River- water, 221. Roasting, 18 ; object of, 18. Roman cement, 89. Rose oil, 325. Rosewood oil, 326. Rouge, 216. Roussillon, amount of alcohol in, 347. Rubia tinctorum, 300. Rum, amount of aloohol in, 347. 422 I2TDEX. Safflower-red, 308. Salt of tartar, 46; sal-ammoniac, 64. Saltpetre, 48. Sap green, 212. Saxon blue, 208. Scheele's green, 211. Schiratz wine, amount of alcohol in, 347. Schweinfurt green, 211. Scotch whiskey, amount of alcohol in, 347. Separation of acids, 292 ; bases, 279 ; of aluminum, calcium, 248 ; iron, 243 ; manganese, 246 ; potas- sium and sodium, 247 ; from zinc, 289. of antimony from tin, 284, 286 ; from arsenic, 283, 285 ; of arsenic from other metals, of group 2, sec. 2, 281 ; from tin and antimony, 285 ; of bismuth from cadmium and copper, 282 5 of cadmium from copper, 282 ; of chlorine from iodine, 294; of cobalt from nickel, 289 ; of gold from platinum, 284 ; of iodine from chlorine and bro- mine, 294 ; of iron from aluminum, 243 ; from chromium and uranium, 288 ; manganese, 2-1-4 ; magne- sium and calcium, 243 ; potas- sium and sodium, 243 ; of lead from bismuth, 282 ; from silver, 280 ; of manganese from aluminum, 216 ; calcium, 246 5 iron, 244 ; magnesium, 246 ; nickel and cobalt, 289 ; of mercury from lead, 279, 281 ; from silver, 279 ; of nickel from cobalt, 289 ; of phosphoric acid from alumina, 241 ; from other acids, 293 ; oxide of manganese, 241; oxide of iron, 241 ; lime, 241 ; mag- nesia, 240 ; ot potash from soda, 252 ; of silica from other substances, 239, 293 ; of silver from lead, 280 ; of sulphuric acid from other acids, 292 ; of tin from arsenic, 283 ; of zinc from aluminum, 289. Sherry, amount of alcohol in, 347. Shot, composition of metal for, 168. Sicilian umber, 213. Silica, distinctive character of, 275 ; estimation of, 238 ; as reagent, 179 ; separation from other acids, 293 ; from bases, 239. Silicates, analysis of, 232-254 ; so- lution of, 2:^1'. Silk, :W7 ; distinctive characters of, 370, 371. Silver, alloys of, 164-169 ; assay, 153-158 ; bromide of, 181 ; coin, composition of, 164 ; chlo- ride of, 153, 277, 280; com- pounds of, 152 ; cyanide of, 188; distinctive characters, 152, 160, 273, 274 ; estimation of, 152 ; German, composition of, 166 ; iodide of, 182 ; leaf, composition of spurious, 167; nitrate of, 152; oxide of, reaction with micro- cosmic salt, 273 ; as reagent, 33 ; sulphide of, 280 ; solder, composition of, 165, 168 ; solu- tions for plating, 152 ; tests for, 152, 160. Smalt, 208. Soap, examination and valuation of, 323 ; estimation of fat in, 324 ; normal solution of, 225. Socket -metal, composition of, 164- 167. Soda, 51; biborate of, 51; bicar- bonate of, 51 ; as reagent, 75 ; carbonate of, 50 ; as reagent, 32 ; caustic, 51 ; as reagent, 51 ; estimation of, 252 ; hydrate of, 51 ; hyposulphite of, 52 ; ni- INDEX. 423 trate of, 53 ; phosphate of, 52 ; as reagent, 34 ; stannate, 132 ; sulphate, 52 ; valuation of, 58. Sodium, chloride of, 53 ; compounds of, 50 ; tests for, 291 ; separation from potassium and magnesium, 291 ; from earthy metals, 290. Soils, analysis of, 219-254; sepa- ration of gravel, &c., 220. Solder, composition of, 164, 165, 169. Solubility, tables of, 297-299 ; de- termination of, 267. Solutions, 5 ; definition of, 5 ; che- mical, 6 ; apparatus for, 6, 7 ; by fusion, 232, 234; methods of effecting, 230-233, 267. Solvents used in analysis, 28, 29, 230, 267. Soot, 213. Spanish brown, 213. Specific gravity, 373 ; determination of, 373-375 ; tables of, 378-400. Speiss cobalt, 127. Spelter, im purities in, 170. Spirit indication, definition of, 339 ; determination of, 339. Spirits, cordialized, 334; impurities in, 334. Standard lime-solutions, 225. Stannate ol soda, 132. Stannic acid, 131. Starch, 354 ; distinctive character of, 358; microscopic appearance of, 354-359 ; sugar, 348 ; reac- tion with iodine, 181. Stearic acid, detection in wax, 323. Steel and gold, alloys of, 168. Stone blue, 209 ; green, 210. Strontia, separation from baryta and lime, 290. Strontium compounds, 88 ; di- stinctive characters of, 88; teats for, 290. Stout, amount of alcohol in, 346, 347. Sublimate in qualitative analysis, Sublimation, 15, 269. Sugar, 348 ; action of alkaline solu- tions of copper upon, 350 ; of beet-root, 348 ; cane, 348 ; esti- mation of, 348 ; in urine, 335 ; fermentation of, 349 ; grape, 348 ; impurities in, 352 ; kinda of, 348; lime, 349; reaction with alkaline solutions, 349 ; starch, 348. Sugar lime, 349. Sulphate of alumina, 102; of baryta, 87 ; of copper, 141 ; of iron, 117 ; of lead, 280 ; of lime, 94 ; of magnesia, 101 ; as reagent, 34 ; of potassa, 48 ; of soda, 52 ; of zinc, 108. Sulphates, distinctive characters of, 39. Sulphide of ammonium, 31 ; of antimony, 30, 31, 277, 280, 283, 285, 286; of arsenic, 30, 31, 269, 277, 280, 284, 285 ; of barium, 290 ; of bismuth, 30, 277, 280 ; of cadmium, 30, 277, 280-282 ; ot cobalt, 31, 277, 287; ot copper, 30, 277 ; of gold, 30, 31, 277 ; of indigo, 209 ; of iron, 31, 277, 286 ; of manganese, 31, 277, 286 ; of mercury, 30, 277, 280, 281 ; of lead,' 269 ; ot nickel, 31, 277, 287 ; of plaf- num, 30, 31, 277 ; of tin, 30, 3i, 269, 277 ; of uranium, 31, 277, 286 ; of zinc, 31, 277, 286. Sulphides, precipitation of, 30, 31, 280, 286 ; soluble in sulphide of ammonium, 31, 281 ; distinctive characters of, 275; reactions with sulphuric acid, 176, 275 ; tests for, 275. Sulphates, distinctive characters of, 38. Sulphite of baryta, 292. Sulphites, test for, 293 ; distinctive characters of, 275, 293 ; reactions with sulphuric acid, 176, 275. Sulphur, 176; distinctive characters of, 269 ; impurities in, 176 ; 424 INDEX. compounds of, 176 ; estimation of, 176, 179 ; tests for, 189. Sulphurets : see Sulphides. Sulphuretted hydrogen, 30; esti- mation of, 177, 224 ; generation of, 26 ; in mineral water, 224 j tests for, 176 ; use in analysis, 30; reaction with chromic acid, 177. Sulphuric acid, 38 ; adulteration of, 38; estimation of, 39, 71, 76, 78, 236, 239; impurities in, 38; separation from other acids, 292 ; as reagent, 34; tests for, 39, 292. Sulphurous acid, estimation of, 177; test for, 293 ; reaction with chromic acid, 177. Supports, 22. Symbols, 403. Syraeus wine, amount of alcohol in, 347. Tables : allowing the proportion of lead to be used in cupelling alloys of gold and copper, 139 ; to be used in assaying silver, 157. showing the composition of alloys, 164-169. of amount of alcohol in wines, beer, spirit*, etc., 346, 347. of amount of alcohol in spirit estimated by solution of salt, 345. (showing amounts of alcohol and extract corresponding to resi- dues of salt, 344, showing spirit indication for ace- tic acid, 340. to be used in ascertaining original gravities, 337, 338. of reactions with borax and mi- crocosmic salt, 272, 273. for reducing analytical results, 255-264. for converting hydrometric de- grees, 376, .377 ; sulphuric acid, 378 ; hydrochloric acid, 379 j nitric acid, 380 ; acetic acid, '' U ; ammonia, 73, 382 ; pot-ash. 382 ; soda, 383 ; carbonate of soda, 383; alcohol, 384 ; sugar and wort, 401, 402 ; of elementary equivalents, 403. of weight equivalent?, 404. shown g the behaviour of dved fabrics with reagents, 307-315. showing the relation of substances to solvents, 297-299. of analytical groups, 277 ? 278. to be used in estimating hardness of water, 226, 229. showing the behaviour of pig- ments with reagents, 208-218. of calorific power, 203. Tallow, detection in wax, 323. Tartaric acid, 42 ; impurities in, 42 ; tests for, 42. Tartratc of ]><>ta- Tart rates, distinctive characters of, 4 Tea, :W!, Terra cli Sienna, 215. Testing, precautions to be observed in, 27. Test-tubes, 28. Tests, 1 ; formetalsof lstgroup,279; for metals oi" 2nd group, 280 ; for metals of 3rd group, 286 ; for metals of 4th group, 290 ; for metals of 5th group, 291 ; for organic substance, 271, 275 ; reduction, 274. Thenard's blue, behaviour with re- agents, 208. Thermometric degrees, table of, eoe table, Appendix. Tin, alloys of, 164-169; chloride of, 132 ; compounds of, 131 ; distinctive characters of, 132, 162, 268, 273, 274, 284, 286 ; estimation of, 132 ; impurities in, 173 ; oxide of, 131 ; perchloride of, 132 ; reactions INDEX. 425 with borax and microcosmic salt, 273 ; with nitrate of co- balt, 274; sulphide of, 283 j tests for, 132, 162, 284, 286. Tinto, amount of alcohol in, 347. Tokay, amount of alcohol in, 347. Train-oil, 322. Tubes, test, 28 ; stand, 28. Turf, estimation of fuel value, 201. Turmeric, as reagent, 35 ; characters of cloth dyed with, 311. Turpentine, detection in mineral naphtha, 326 j in etherial oil, 325. Type-metal, composition of, 168. Tyrolese green, 210. Turkish umber, 213. Ultramarine, 305 ; character of stuff dyed with, 307 ; valuation of, 305 ; cobalt, behaviour with reagents, 208; green, 210 ; yellow, 215. Umber, behaviour with reagents, 213; Cologne, Cyprian, Turkish, Sici- lian, 213. Uranium, compounds of, 127 ; di- stinctive character, 127 ; oxide of, 127, 273, 288 ; tests for, 127, 288 ; oxide of, reactions with borax and microcosmic salt, 273 j separation from iron and chro- mium, 288. Valuation of acetic acid, 71 ; of acids, 69 ; of alcoholic liquids, 232; of alkalies, 55-69 1 of borax, 86 ; chloride of lime, 97 ; of coal-gas, 327 ; of kelp, 182 ; of nitre, 79 ; of oil and othermaterials used for lighting, 327 ; of potashes, 55 ; of varec, 182. Value, fuel, 200 ; estimation of, 201-205. Van Dyk brown, 213. Varec, valuation of, 182. Verdigris, 211. Verditer, behaviour with reagents. 210. Vermilion adulteration, behaviour with reagents, 216. Veronese earth, 210. Vert de vessie, 212. Vinegar, 43 ; adulteration, 44 ; va- luation of, 72. Violet, alkanet, 315 ; examination of cloth dyed, 315 ; logwood, 315 ; madder, 315. Vitriol, blue, 141; oil of, 38; white, 108. Volumetric analysis, principle of, 4, 36; normal solutions for, 36; reagents for, 36 ; method of conducting, 36. Wad, behaviour with reagents, 213. Washing, 11; blue, 209; bottle for, 12 ; of precipitates, 11, 13. Water, aerated, 223 ; alkalinity of, 224; analysis of, 219-238; bath, 16; carbo- nated, 223 ; collected for ana- lysis, 221 ; distillation of, 28 ; distilled, 327; estimation of, 222; hardness of, 224 ; estimation of, 225 ; latent, 227 ; permanent, 228 ; standards of, 225 ; tem- porary, 228 ; influence of mag- nesian salts, 227 ; in iodine, 181 ; in soap, 324 ; in soils, &c., 222 ; impurities in, 28 ; mineral, 221 ; as reagent, 28 ; tests of purity. 29; for substances present in very small amount, 230, 237, 238. spring, 221 ; substances dissolved in, 221; sulphuretted, 224; suspended substance in, 229 ; temperature of, 222. Wax, 323 ; adulterations and im- purities in, 323. Weighing, 26. Weights and measures, decimal, 37. 2i 426 INDEX. "Wet process, 5. Whiskey, amount of alcohol in, 347. White lead, behaviour with reagents, 217 ; mineral, 218 ; pigments, 218 ; zinc, behaviour with re- agents, 218. Wine, 334 ; amount of alcohol in, 347; constituents of, 334 ; estimation of acid in, 71, 335; of bitartrate of potash in, 335 ; of sugar in, 335 ; estimation of, 334. Wood, estimation of fuel value, 201. Wool, 368; distinctive characters of, 370, 371. Wort, determination of density, 336. Woulfe's bottles, 26, 192. Yellow, annotto, 311 ; chrome, 311 ; behaviour with reagents, 214 ; citron, 214 ; Cologne, 214 ; ex- amination of cloth dyed, 310 ; fustic, 310 ; king's, 215 ; nan- keen, 311 ; Naples, behaviour with reagents, 214 ; new, 214 ; quercitron, 310 ; orpiment, 311 ; Paris, 214 ; Persian, 215 ; sap, 310 ; turmeric, 311 ; Gotha, 214 ; Leipzig, 215 ; Hamburgh, 214; imperial, 214; Zwickau, 214 ; Cassel, behaviour with re- agents, 214 ; chemical, mineral, Montpelier, Paris, Turner's, Veronese, 214; Chinese, Spa- nish, 215 ; ochre, behaviour with reagents, 215; ultramarine, 215 ; woad, 310. Zaffre, 127. Zinc, alloys of, 164-169 ; carbonate of, 108 ; compounds of, 108 ; distinctive characters, 108, 161, 272, 274, 290; estimation of, 109 ; impurities in, 170 ; oxide of, 108, 218 ; reaction with nitrate of cobalt, 274; with borax and microcosmic salt, 272 ; separation from alumina, 289; Bulphateof, 101 ; sulphide of, 31, 108 ; tests for, 108, 161, 290 ; white, 108 ; behaviour with reagents, 218. Taylor and Francis, Red Lion Court, Fleet Street. MESSRS. BELL AND DALDY'S CATALOGUE OF BOHFS VARIOUS LIBRARIES AND OP THEIR OTHER COLLECTIONS, WITH A CLASSIFIED INDEX. LONDON : YORK STREET, COVENT GARDEN. 1867. Bohn's Libraries. A complete Set, in 624 Volumes, price 128Z. Us. SEPAKATE LIBRARIES. STANDARD LIBRARY (including the Atlas to Coxes Morlborough) HISTORICAL LIBRARY LIBRARY OP FRENCH MEMOIRS .... UNIFORM WITH THE STANDARD LIBRARY . PHILOLOGICAL LIBRARY BRITISH CLASSICS ECCLESIASTICAL LIBRARY ANTIQUARIAN LIBRARY ...... 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These Libraries have been created by Mr. Bohn during the past twenty years by an amount of energy and industry, bibliographical knowledge and literary skill never, before united with the requisite amount of capital ; and they repre- sent an accumulation of valuable works unexampled in the history of literary undertakings. Such a choice, so varied, and at so low a price, does not exist in this country or elsewhere ; and Mr. Bohn is entitled to the gratitude of all who value the humanizing effects of literature. Since the commencement of these Libraries at least three million volumes have been issued, and these may fairly be taken to represent thirty million readers. In accepting the responsibility of so large an under- taking, Messrs. Bell and Daldy desire to carry on the pro- jects of Mr. Bohn with the same spirit and energy which have influenced him, and they are happy to announce they will have the advantage of his bibliographical knowledge and large experience. These Libraries and Collections together afford a choice from about 800 volumes on general literature and educa- tion. To assist purchasers in making their selections a classi- fied index is attached, by which they will be guided to the subjects of the books. Messrs. Bell and Daldy venture to add, that the Aldine Poets, Aldine Series, British Worthies, Elzevir Series, and Pocket Volumes, are specially prepared for the lovers of choice books, and are specimens of careful editing combined with the most finished workmanship in all external IVatures. They believe that they are not surpassed in these respects by any similar productions of the present day. CLASSIFIED INDEX. PAG AMUSEMENTS. Angler, Walton 31, 4 Angler's Manual, Hofland ... 1 Chess Congress 3 Games of, Morphy ... 4 Player's Companion ... 4 Handbook .... 4 Praxis, Stauuton .... 4 Tournament 4 Games, Handbook of .... 3 Manly Exercises, Walker ... 3 Shooting, Recreations in . . . 3( ABT. Didron's Iconography .... 2' Flaxman's Sculpture .... 27 Holbein's Bible Cuts .... 27 Dance of Death ... 2 Lanzi's Painting 12 Lectures on Painting .... Michael Angelo and Raphael . . 28 Reynolds' (Sir J.) Works ... 13 Schlegel's Esthetic Works ... 14 Stanley's Synopsis of Painters . . 40 Vasari's Lives of the Painters . . 15 ATLASES. Classical Geography Long's . . . Grammar School Atlas Marlborough's Campaigns BIOGRAPHY. Burke'sLife 19 Cellini, Memoirs of .... 9 Coleridge's Biographia Literaria . 9 Craik's Pursuit of Knowledge . . 26 Foster's Life, &c 10 Franklin's Autobiography ... 23 Irving's Life and Letters . . 17, 24 Johnson's Life, &c 23 Locke's Life and Letters ... 12 Luther's Life, Michelet . ... 12 Nelson's Life, Southey . . . 30, 41 Pope's Life, Carruthers .... 30 Walton's Lives .... .41 Washington's Life . . . . 17 2t Wellington, Life of *31 Wesley's Life, Southey ... i 15 BRITISH CLASSICS. Addison's Works . . 19 Burke's Works ....!! 19 Speeches 19 Cowper's Works 10 Milton's Prose Works .... 12 DIVINITY. Butler's Analogy 43 and Sermons . . 9 Sermons .... 43 Works 43 Chillingworth's Religion of Pro- testants 16 Gregory's Evidences 11 Henry on the Psalms .... 17 Kitto's Scripture Lands .... 27 DIVINITY continued. . Kruinmacher's Parables . . , Neander's Christian Dogmas Christian Lite . . Life of Christ . . Light in Dark Places New Testament Greek Lexicon to . 27 13 13 13 !3 16, 44, 45 . . 16 . . 13 . . 14 14, 43 15 Pearson on the Creed Sturm's Communings Taylor's Living and Dying Wheatley on the Common Prayer . DRAMATIC LITERATIM:! . Beaumont and Fletcher .... 9 Lamb's Dramatic Poete .... 22 Tales from Shakespeare . 41 Schlegel'a Dramatic Literature . . 14 Shakespeare's Plays . . . IS, 41, 46 Sheridan's Dramatic Works. . . 14 FICTION. Andersen's Tales 26 Berber, The 23 Bremer's Works 9 Cutter-mole's Haddon Hall ... 26 Cinq-Mars 23 Classic Tales 16 Defoe s Works 20 Folding's Novels 46 Gil Bias 27 Grimm's Gammer Grethel ... 27 .Hull s .Mi'Miipniaii 41 Lii'iit-iiant 41 Hawilinrin-'s Tali-s 24 H'.witt's Iviglish Life .... 27 Hum's Book for a Corner ... 27 Irving' s Talcs .... 17, 24, 41 Keightley's Fairy Mythology . . 22 Lamartine's Genevieve .... 25 Sl.Jiiriiia-on, kc. . . 25 Longfellow's 1'p.sc Works ... 28 ^iarryat'a Works 28 Mayliew's 1 map- ofhis Father . 25 Mitford's Our Village .... 12 Modern \ovHis'-; of France . . 25 Munchausen's Life 25 Robinson Crusoe 30 Sandford ami M> rton .... 25 Smolli-tt's Novels 46 Tali-s of tlie (Jenil 31 Taylor's Kl Dorado 25 Uncle Tom's Cabin . . . . 18, 25 Whiti- Siav.-" 25 Wid-, Wid- World 18 Willis's Tales 25 Yule Tide Stories 23 AtTHoKS. Fdndlon's I'elermque .... 45 La Fontaine's Fables .... 45 Picciola 45 Voltaire's Charles XII 45 GERMAN ArriKi::>. German Bal'ads 45 Schiller's Wallenstein .... 45 CLASSIFIED INDEX. PAGE GERMAN (THE), TRANSLATIONS FROM. Goethe's Works 11 Heine's Poems 11 Schiller's Works 13 GREEK AUTHORS. ^Eschylus 44,45 Demosthenes 44 Euripides 44, 45 Herodotus 44, 45 Hesiod 44 Homer 44 Plato 44 Sophocles 44 Thucydides 45 Xenophon's Anabasis . . . 44, 45 Cyropsedia .... 44 GREEK (THE) TRANSLATIONS FROM. Achilles Tatius 34 jEschines 16 .flSschylus 32 Anthology, Greek 34 Aristophanes 32 Aristotle's Ethics . . 32 History of Animals . Metaphysics . . . Organon Politics and Economics Rhetoric and Poetics Athenajus 33 Bion 36 Callimachus 34 Demosthenes' Orations ... 16, 33 Diogenes Laertius 34 Euripides 34 Heliodorus 34 Herodotus 34 Analysis of .... 18 Notes 18 Hesiod 34 Homer's Iliad 34 Cowper .... 10 Pope 30 Odyssey 34 . Cowper . . . 10 Pope .... 30 Longus 34 Moschus 36 Philo-Judaeus 20 Pindar 35 Plato 35 Sophocles 36 Theocritus 36 Theognis 34 Thucydides 36 . Analysis of .... 19 Tyrtseus 36 Xenophon 36 HISTORICAL MEMOIRS. Carafas of Maddulonl 9 Coxe's Life of Marlborough . . 10 Memoirs of the House of Austria 10 Guizot's Monk and his Contempo- raries 17,24 Irving'* Life of Washington . 17,24 . Life of Mahomet . . 17,24 PAGE HISTORICAL MEMOIRS continued. Jrving's Life of Columbus . . 17, 24 Companions of Columbus 17,24 James's Louis XIV 11 Richard Cceur de Leon . 11 Kossuth, Memoirs of .... 11 Lodge's Portraits of Illustrious Per- sonages 28 Memoir of Colonel Hutchlnson . 1 1 Duke of Sully ... 16 Hampden, by Lord Nu- gent 15 Philip de Commines . 15 Naval and Military Heroes of Britain 29 Fault's Life of Alfred the Great . 22 Roscoe's Life of Leo X 13 Lorenzo de Medici 13 Strickland's Queens of England. . 15 HISTORY AND TRAVELS. Anglo-Saxons, Miller .... 28 Antiquities, Popular, Brand . . 21 Arabs in Spain, Condd .... 9 Christianity, First Planting of, Neander 13 CHRONICLES. Anglo-Saxon Chronicle, Bede . 21 Florence of Worcester's . . 21 Geoffrey de Vlnsauf ... 21 Henry of Huntingdon's . . 21 Ingulph's Chronicle ... 22 Lord de JoJnville .... 21 Matthew of Paris .... 22 Westminster . . 22 Richard of Devizes .... 21 Roger de Hovenden . . . 22 Six Old English Chronicles. . 23 William of Malrmsbury . . 23 Chronological Tables, Blair ... 37 Church History, Neander ... 13 Civilization, Guizot 11 Conquest of England, Thierry . . 14 Diary, P>elyn 15 Pepys 15 Ecclesiastical History, Bede . . Eusebius Ordericus Vi- ta lis . . Socrates Sozomen Theodoret & Evagrius . Egypt, Lepsn England, Hisl ius History of, Hughes . . Hume . . . Smollett . . English Constitution, DHolme . Revolution of 1640, Guizot Florence, Machiavelll .... French Revolution of 1848, Lamar- tine French Revolution, Michelet . . Mignet . . . Smyth . . . 72 U I'l 14 Germany, Menz.el 12 Giraldus Cambrcnsls, Historical \\7^b- D 91 CLASSIFIED INDEX. HISTORY AND TRAVELS continued. Girondists, Lamartine .... History Philosophically Considered, Miller . Hungary, History of Index of Dates Jesuits, History of, Nicolini . . Modern History, Schlegel . . . Smyth . Naples under Spanish Dominion Naval Battles, Allen . . . Nineteenth Century, Gervlnus . Northern Antiquities, Mallet . Philosophy, Tentv-mnn . . . of History, Hegel . Schlegel . i* Popes, Ranke 13 Pretenders, Jesse 15 Representative Government, Gui/ot 11 Restoration of the Monarchy, La- martine 12 Revolution, Counter, in England, Carrel 9 Roman Empire, Gibbon .... 20 Republic, Michelet ... 12 Russia, History of 13 Saracens, Ockley 13 Servia, Ranke 13 Stuarts, Jesse 1 "> Time Months in Power, Lamartine 25 Tiers Etat, Thierry 15 Travels, Karly, in Palestine . . 21 in America, Humboldt . 39 in \Vai.s. I: of Marco Polo . . . Wellington, Victories of . . ITALIAN (THK) TRANSLATIONS FROM. Ariosto's Orlando Funosa . . Dante, Cary Wright 26 Tasso's Jerusalem Delivered . . 31 LATIN AUTHORS. Cassur, De Bello Gallico . . . Bks. 1-3 . . Cicero's Cato Major . . . . Orations Horace Juvenal, Satires, 1-16 . . . and Persius . . . Lucretius Ovid's Fasti Sallust Tacitus, Germania, &c. . . . Terence Virgil Walker's Corpus Poet. Lat. . . LATIN OHE), TRANSLATION* Fitoir. Ammianus Marcellinus . . , Antoninus's Thoughts . . . Apuleius, the Golden Ass . . Boethius Caesar Catullus Cicero's Academics, &c. . . . Nature of the Gods, &c Offices, c 44, 45 . 44 44,45 44,45 44,45 . 44 44, 45 . 45 . 44 44, 45 . 44 . 44 44, 45 . 46 . 32 . 43 . 32 . 21 . 33 . 33 . 33 . 33 . 33 PAOJt LATIN (THE) TRANSLATIONS FROM continued. Cicero's On Oratory 33 Orations 33 Cornelius Nepos 34 Eutropius 34 Floras 36 Horace 17, 34 Johannes Secundus 35 Justin 34 Jim-nal 34 Livy 34 Lucan 35 Lucilius 34 Liuivtius 35 Martial's Fpigrams 35 Ovid 35 Persius 34 IVtroiiius P.a'illl- Pliny's Natural Hi, lory . . Pnip'TtiUS Qitintilian's Institutes . Sallust :> Ml'-t.'tlluS 36 Su'picia 34 Tacitus 36 Ten-nee 36 Tibnllus 3.". Velieius PutenulUS 30 Virgil 36 LlTKUAUV HlsTDKY, &C. LowndeVe Bibliographei't XMNMI 18 jel'i llisiory oi Literatim; . 14 Dramatic Literature . . 14. Hindi's Literature of South of Llll-opC 14: ' Ascham's >cli"l- Master ... 43 P.rovvn- s (Sir T.) Works ... 21 Cape and ih- Kaffirs 23 Clark's Heraldry Coin Collector's Manual, Hum- phreys Coleridge's (S. T.) Friend . . . Costume in Ennland, Fairholt . . Col ion Manutactures, Ure . . . Cniiksliank'.s Three Courses, &c. . J Dictionary of Obsolete Words . . of Painters, Bryan . . Emerson's Orations and Lectures . _ Representative Men . Complete Works . . l-pitaphs 21 Field im s Works 46 Foster's LVays, Sec 10 Lectures, Src 10 Miscellaneous Works . .10 Fosteriana 10 Fuller's Works 10 dray's Works 43 Hall's (Basil) Lieutenant ... 41 Midshipman ... 41 (Robert) Works .... 11 CLASSIFIED INDEX. Vll MISCELLANEOUS continued. Herbert's Works 41,43 Jesse's Dogs, &c 27 Junius's Letters 11 Lamb's Elia and Eliana .... 12 Lion Hunting 25 Locke's Conduct, &c 43 Luther's Table Talk 12 Magic (Ennemoser's) 38 Manufactures (Philosophy of), Ure 40 Moral Sentiments, Smith ... 14 Political Cyclopaedia 18 Tottery and Porcelain .... 30 Preachers and Preaching ... 25 Prout's (Father) Reliques ... 30 Richardson's Dictionary .... 46 Smith's (Archdeacon) Synonyms and Antonyms 19 Smollctt/s Works 46 Starling's Noble Deeds of Women. 30 Swift's 'Works 46 Taylor's Logic in Theology ... 43 Physical Theory ... 43 Ultimate Civilization . . 43 Temperance, Carpenter . . . . 23 W;-bsier's Dictionary .... 46 Wheeler's Dictionary of Fiction . 19 Wines, Redding on 30 Young Lady's Book 31 NATURAL HISTORY. British Birds, Mudie . . . . Cage Birds, Bechstein . . . Insect Architecture, Eennie Poultry, Dickson and Mowbray Seasons, Howitt Selborne, White . 26 27,40 . 16 . 27 31,41 Warblers, Sweet 26 POETRY. Akenside's Poems 42 Bailey's (P. J.) Festna . . . . 16 Seattle's Poems 42 British Poets Milton to Kirke White 1 Eurns's Poems 41, 42 Butler's Poems 26, 42 Chaucer's Poems 45 Churchill's Poems 42 Coleridge's Poems 4 Collins's Poems 4 Cowper's Poems 10, Dibdin's Sea Songs .... 23, Dryden's Poetical Works . . . Ellis's Metrical Romances , . . Falconer's Poems Goldsmith's Poems Gower's Confessio Amantis . . . Gray's Poems 42, Herbert's Poems 41, Kirke White's Poems .... Longfellow's Poems .... 28, Milton's Poems .... 28,41, Parnell's Poems Petrarch's Sonnets Pope's Poetical Works . . . 30,4 Prior's Poems 4 Robin Hood Ballads 4 PAGE OETRY continued. Sea Songs and Ballads .... 41 Shakespeare's Poems ... 18, 43 Spenser's Poems 42, 43 Surrey's Poems 42 Swift's Poems 42 Thomson's Poems 42 Vaughan's Poems 43 Wyatt's Poems 42 Young's Poems 42 PKOVERBS AND QUOTATIONS. Dictionary of Greek and Latin Quo- tations 34 Handbook of Proverbs .... 21 Polyglot of Foreign Proverbs . . 22 SCIENCE AND PHILOSOPHY. Anatomy, Comparative, Lawrence . 17 Animal Physiology, Carpenter . . 38 Arts and Sciences, Joyce ". . . 17 Astrology, Lilly 17 Astronomy, Carpenter .... 38 . Hind 39 Bacon's Works .... 9,37.43 Botany, Carpenter 38 Botany, De Jussieu 39 BRIDGEWATER TREATISES. Bell on the Hand .... 37 Buckland's Geology and Mine- ralogy 2 Chalmers on Moral Man . . 37 KiddonMan 3 Kirby on Animals .... 37 Prout on Chemistry . . .37 Roget's Animal and Vegetable Physiology 37 Whewell's Astronomy and General Physics .... 37 Brougham's Political Philosophy . 46 CHEMISTRY. Agricultural, Stockhardt . .40 Elementary, Parkes .... 1 Principles of, Stockhardt . . 4 Chevreul on Colour 3 Comparative Physiology, Agassiz . 37 Comte's Philosophy of the Sciences i Cosmos, Humboldt's 39 GEOLOGY. General, Richardson . . . Medals of Creation, Mantell . Of Isle of Wight, Mantell . . Of Scripture, Pye Smith . . Petrifactions, &c., Mantell . . Wonders of Geology, Mantell Horology, Carpenter . . . . . Inventions, Beckmann's History of . Joyce's Scientific Dialogues . . . Kant's Pure Reason Knight's Knowledge ta Pow . Life, Philosophy of, Schlegel . . IxKke's Philosophical \Norks . . Logic, Devey . . .Mechanical Philosophy, Carpenter . Medicine, Domestic Natural Philosophy, Hogg . . . Vlll CLASSIFIED INDEX. SCIENCE Aim PHILOSOPHY continued. Oersted's Soul in Nature . . Physics Hunt . . . , . PAGE . 40 39 Races of Man, Pickering. . . Schouw's Karth, Plants, Man . Science, Poetry of, Hunt. . . Technical Analysis, Bolley . . Vegetable Physiology, Carpenter Views of Nature, Humboldt . Zoology Carpenter 29 40 39 37 38 39 37 TOPOGRAPHY. Athens, Stuart and Revett . . . 31 TOPOGRAPHY continued. 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