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Tous les autres exempleires origlnaux sont filmte en commenqant par la pramlAre page qui comporte une empreinte d'impression ou d'illustration et en terminant par la darniAre page qui comporte une telle empreinte. Un des symboles suivants apparaltra sur la darnlAre image de cheque microfiche, selon le cas: le symbole — ► signifie "A SUiVRE ", le symbols ▼ signifie "FIN". Les cartas, planches, tableaux, etc., peuvent fttre filmAs * des taux de reduction diffArents. Lorsque le document est trop grand pour Atre reproduit en un seul clichA, il est film* A partir de Tangle supArieur gauche, de gauche A droits, et de haut en bas, an prenant le nombre d'images nAcessaire. Las diagrammes suivants illustrent la mAthoda. 1 2 3 4 5 6 ^I^m^m^ ILli«R4iw^^>«B^^W* ■ ^IIIMIW >f»>Y.|>.>» Wll ]«■« II I I INTRODUCTION TO THE STUDY or INORGANIC CHEMISTRY. BY WILLIAM ALLEN MILLER, M.D. D.CL. LL.D. LmU Treasurer mnd Vice-PrttidtKt c/ tht Royal Society: Vice-Prttidieit a/tht Chemical Socuty : Profetsor of Chemistry in King't College, London ; Fellow of the Univernty of Londomi Honorary Fellow of Kim^e College, NEW EDITION, WITH QUESTIONS FOR EXAMUfATIOH, TORONTO: CANADA PUBLISHING COMPANY (LIMITED), x88o. ax)i5i .5 M5 mo Xntered Mscordlngr to the Act of the Parliament in Canada, hi tht /ear one thnuraihl elffht hundred and eigiay, by Lokumanb, Crwm and CoHFj^.r, in the Oflloe ol thn Minister o( Agriculture. NOTE. My friend Professor Miller completed this work, and placed the whole of the MSS., including the Preface, in the hands of the Printers. He was actually engaged in reading the proof sheets tip to the time of his visit to the British Association Meeting at Liverpool, when he was seized with a sudden and fatal illness. Professor Miller placed the first few sheets of the work in my hands, and requested me to read them and give him my opinion as to the mode of treatment I accordingly did so, and suggested certain changes in the style and arrangement which, if adopted, might add to the clearness of the book and so far assist the young student in Chemistry. He ap- proved of these suggestions, and in hitf last illness left a written request that I would see the work through the press. I have to the best of my ability complied with his wishes. C. TOMUNSON. HiGHGATB, N. Novtmbtr lo^ 187a •^^^ PREFACE -••• This book is written expressly for beginners. In order that they should really understand the state- ments which it contains, it will be necessary for them to begin at the beginning, and to go straight through it Among other reasons for adopting this course, it is to be noted that it is impossible to avoid the use of technical terms in discussing a scientific subject ; since we often have to deal with matters for which no expressions are in use in ordinary langruage. In this book, when a technical term is introduced for the first time, its meaning is explained, but the explana- tion is not afterwards repeated. Processes are also described in detail when first mentioned, but when afterwards referred to, they are simply directed to be followed. Most of the experiments described are of a simple kind, and only require such apparatus and materials as may be easily constructed or procured. The student is strongly advised never to omit the per- formance of any experiment which he has the means of making. No useful knowledge of Chemistry can be acquired by any one unless he constantly makes experiments as he proceeds with the study. W. A. MiLLBB. I t CONTENTS. -••^ CHAPTER I. CHSMICAL ILKMBNTS— COMBINATION. PAOB \ M ip« Mid aim of OieniistiT t g. dnUmi Elements : their •node of oooanenee . 4 ^ Oemlcel Notatioo 6 4. WeMits and Meuuiee c Phjrucel States of Matter . li o. Mixture distingniahed firon Combination ... 13 CHAPTER II. A. THB NON-MRTALS. ATMOSPHERIC AIR— OXYGEN— NITROGBN. I rhe Atmospbeie not an Ele* ^ «S t Oxygen • '9 The Pneumatic Tkwt^— Oglefting Oaees . so la Measurement of Gases under Standard Conditions . aB II. Adds. Bases, and Salts . 90 la. Osone ja 13. Nltrofsn .... 96 14. Air^ a Mixture of several • • • • 3* CHAPTER III. WATBR— HYDROGEN. Decomposition of fteeri ng and boiling of E w ip o iatt on ManMun denaily RalnW alw. Sniag Walsr Hard and Soft Wnlsr Tests fiar MhMsl Wains . Water of QiHilihillwi 4« 47 49 S» a S9 ss V id. Hydrogen . . • • jf' Ccdlecmig Gasss bf dlsplaaa* 01 % Dfadih IVMibAe. 7s The Mixed Gases Synthesis of Water TbeCtaTh ydrogenJol Atomie Weight of Hidrogan Ibdrofn the Unit via Contents. CHAPTER IV. OXIDBS or CARBON— KIARBON. 17. CAibonle Anhydride Souroetof . VmtiUition . Srutbetii of cO. COi in the Air It. Carbon The Diamond Graphite Pit Cod rAOB :3 - 84 : U PAoa ; S Coke .... Charcoal Animal Charcoal— Filtration 90 Allotropy . . . . 9e 19. Carbonic Oxide . • • 9S Washing of Oaiei . 96 aa Classification of CkystaU . 97 Isomorphism « .103 CHAPTER V. OXIDBS OP NITROOEN— NITRIC ACID— AMMONIA. •I. Nitric Add . .104 M. Other Oxides of Nitrogen- Nitrous Oxidt . .no Nitric Oxide . . . iia Nitrous Anhydride .1x3 Nitrogen Peroxl lu 83. Ammonia . Ammoniacal Qas . Absorption of by Charcoal Solution of Ammonia . "4 "4 IX' "'/ 1x8 CHAPTER VI. SKA SALT— HYDROCHLORIC ACID. 84. Chlorine •5. Hydrochloric Add Analysis of . Sohitionof . ■6. Oxides of Chlorine . xao . X33 . 109 07. Bromine . • a8. Iodine . . . HydriodicAdd . •9. Fluorine Hydrofluoric Add . 13a • 134 . 138 CHAPTER VII. SULPHUR GROUP., 30. Snlphnr .141 31. Snlphurous Anhydride. . 145 3a. Sulphuric Add . .147 Nordhansen Add . 148 Sulphuric Add Chambers . X49 Salts and Testt . . .151 33. Hyposulphites . 34. Sulphuretted Hydrogen Hydrosulphates . . 35. Carbon Disulphide . Sdenium— TeUurium . . 151 . X53 • 155 . 158 CHAPTER VIII. PHOSPHORUS GROUP. 36. Phosphorus . . ay. OiMes of Phosphorus . x|9 . X03 Sodic Phosphates . sfia 37 a. Pfaosphuretted Hydrogen . |0C ConUnts. CHAPTER IX. SIUCON AND BORON. A Silieoa. . 99. SiUoUM : OlMt PAOB l68 3fa. Boron • >74 170 Boradc Anhydrld* « . «7S CHAPTER X. COAL OAS, AKD OTHER COMPOUNDS OF CARBON. Hydrocarbons OlefiantOtu . ManhOiu . The Safety LAinp Flame . Bunsen'i Burner . The Blowpipe . 17,' 177 • 'Z* . 180 . t8i . i8a .183 ;8 190 CoalOai .181 41. Cyanogen .... 4a. lite Atoni>uiiiiils Of Tin 349 350 350 351 Tests ^53 Titanium, Zirconium, Thori- num. Molybdenum . . 953 li 1. CHAPTER XV. 1. ARSENICUM. 2. ANTIMONY. 3. BISMUTH. Tests for Ai K imiuictted Hydrogen 3S3 f»S5 »SS 357 58. Antimony .... R58 Compounds of Antimony . 859 59. Bismuth .... 1160 Compounds of Bismuth . a6f Contents. CHAPTER XVI. I. COPPER. ?. LEAD. 3. THALLIUM. 40, Copper Smeitiiif of Copper Oxides SalU aiid TesU . 61. Lead . rACB . 961 . 263 . 964 .a6S rAOk ActioD of Water oa Lead . 966 Oxides 067 Salts . 63. Thallium .969 63. MercuiT lu Oxides . Its Chlorides Iodide and TesU 64. SilTer . Its Compounds 65. Gold . CHAPTER XVII. THE NOBLE METALS. . 970 . 979 • "73 • "74 • ^o . 978 Its Chloride. . . 979 Purple of Cassias . . 980 66. Platinum .... a8o lu Chlorides . .981 Palladium, Rhodium. Os- nuium, Iridium, Ruthenium 989 APPENDIX a83 QUESTIONS FOR EXAMINATION . . 386 Ill INORGANIC CHEMISTRY. CHAPTER I. CHEMICAL ELEMENTS — COMBINATION. (i) Scope and aim of Chemistry, — Many of the changes in natural objects which are taking place around us every day — some slowly, some quickly — are the -"suit of a class of actions which are called chemical When, for instance, a piece of iron is exposed to the open air and becomes covered with rust, or when a fallen leaf crumbles away, or when milk becomes sour after it has been kept for a few days, the change which has occurred in each case is of a chemical nature : in all of them an alteration in the com- position of the substance has taken place, and new sub- staL ;es, with properties quite different from those of the original material, havt been formed. The iron has taken up something from the air which has altered its colour and lessened its strength ; the leaf has furnished new bodies, some of which have passed off unseen into the atmosphere ; while the sugar in the milk has become changed into ao acid, and the curd has been separated from the whey. It is tlie business of the chemist to find out what these various substances are made of, as well as the exact nature of the alteration in composition which has occurred in these cases, and the means by which such changes can be 111! '■'{ III 1 ■ '' ■ 2 Obj^ts of Oieinistry. forwarded or varied, or altogether prevented. Chemistiy it in fact the science which teaches us the composition of bodies. Whenever, therefore, a new substance is put into the hands of the chemist, whether it be derived from the mineral, the vegetable, or the animal creation, one of his first questions is. Of what is this body made ? Is it com- posed of one kind of matter or of several kinds? In order to obtain answers to these questions we must learn to observe carefully the changes which are going on around us ; and we must also contrive fresh arrangements, more or less altered, in which the exact circumstances have been planned by ourselves for the purpose of seeing what will happen under these altered conditions. Such planned observations are what are commonly called experi- mmts\ and the better they are planned and performed the more we shall be able to learn if we reason accurately upon the result obtained. Chemistry is in the best sense an experimental science, calling into action alternately the head to plan, the hands to perform, and the head again to explain the results of our experiments. Various substances may easily be shown to contain more than one kind of matter ; while others have hitherto foiled all the efforts made to separate from them any second sub- stance. For example, from a mass of pure silver nothing can be obtained but silver itself, copper will furnish nothing but copper, and from sulphur the chemist can ex- tract nothing but sulphur. Such bodies have therefore been called undecomposed or simple substances, or chemical elements. On the other hand, such bodies as table salt, iron rust, water, chalk, wood, mercuric oxide, may each by the use of suitable means be made to yield more than one kind of matter. Experiment i. — Place a scrap of wood in a test-tube, which is a glass tube about the size of the forefinger, and closed at one end. Heat it by holding it just above the flame of a spirit lamp. The wood will become charred ar pound into its elements, but he can, out of those elements, by synthesis, or putting them together again, build up the compound — as may easily be done with the iron nisi, and the mercuric oxide just mentioned. When a body can be thus separated into its elements, and can be re- produced by combining those elements again with each other, we possess the most complete proof of its chemical composition, though much remains to be discovered respect- ing the mode in which the different substances are arranged in the compound. We may know, for example, what letters are wanted to spell a particular word, but in order to spell the word correctly we must also know the order in which these letters are to follow one another. Just so it is necessary to discover if possible the arrangement of the elements in a chemical compound before we can be said truly to know its constitution. Every material object with which we are acquainted is, in a chemical point of view either an element or a compound, or else a mechanical mix- ture of two or more elements or compounds. By far the greater number of natural objects are com- B a III ■'' Chemical Elements — AtiractioH. j^ilii I K. ri pounds. These compounds consist of two or more simple substances united according to certain fixed rules or laws. The simple bodies have no more likeness to the com- pounds which they form than the separate letters of the alphabet have to the words which may be made from them. The power which causes the various elements to unite one with another, and which holds them together after they have united, is called chemical attradion. It is much stronger between some elements than others, and is exerted accord- ing to special rules, which will be explained hereafter. (a) Chemical Elements : their mode of occurrence. — Two of the most important of the elements, oxygen and nitrogen, form the principal portiop of the atmosphere, and they occur in it mixed with ea' i other, but not chemically com- bined. The only other elements of importance which are met with in their separate or native state are sulphur or brimstone, carbon (in the very different forms of black-lead and diamond), iron, copper, bismuth, mercury, silver, gold, and platinum; but some of these are found much more abundantly in combination with other elements than in the separate form. The chemical elements are little more than sixty in number. Most of them occur in combination in the strata of the earth. Some, indeed, are found so sparingly that their properties have been but little examined. Others again are extremely abundant, particularly hydrogen, oxygen, nitrogen, and carbon ; two or more of these four elements enter into the formation of most of the objects familiar to us, except the ordinary metals, which are themselves elementary bodies. Taking the earth as a whole, so far as man has been able to penetrate into and examine it, more than one-third of it has been found to consist of oxygen either combined or un- combined, and nearly one-fourth consists of silicon in com- bination, for the most part, with oxygen. Besides this, com- pounds of aluminum, calcium, iron, carbon, magnesiunii Chemical Ela^tents— Metals— Non-metals. 5 sodium, potassium, and sulphur, are found in considerable proportion ; some confined to special places, and the others very generally diffused : while, dissolved" in sea water, we have, independently of the oxygen and hydrogen of the water, compounds of sodium, chlorine, magnesium, calcium, and potassium, in addition to combinations of about twenty other elements in extremely small proportions. For the sake of convenience the elements are divided into the two classes of metals and non-metals, though the two classes run into each other. Fifty of the elements are commonly reckoned as metallic, and thirteen as non-metallic in their nature. The thirteen elements commonly enume- rated as non-metals are oxygen, nitrogen, hydrogen, carbon, chlorine, bromine, iodine, fluorine, sulphur, selenium, phos- phorus, silicon, and boron. In the following list those of the greatest importance are printed in capitals, as Oxygen. The chemical properties of these we shall examine hereafter ; those in ordinary type, as Bromine, will be touched upon less fully ; whilst of those in italics, such as Tantalum, owing to their rarity, and the absence of any important application of them in the arts, few will need more than a passing mention. Elements with their Symbols and Atomic Weights. Name Symbol Atomic Weight Name Symbol Atomic Weight Aluminium. Al 27*5 .Chlorine . CI 35*5 Antimony(Stibium) Sb 122 Chromium . Cr 52-5 Arsenicum . As 75 Cobalt Co 59 Barium Ba 137 -Coi'PER (Cuprum). Cu 63-5 Bismuth Bi 2IO Diiiyvtium . D 96 Boron . B II Erbiiim E 112 Bromine Br 8o 1 'Fluorine F 19 Cadmium Cd I'^2 Glucinum G 9'S Casium Cs »33 Gallium Ga ' -Calcium Ca 40 Gold (Aurum) Au 196*6 i-CARBON C 12 •Hydrogen . H I Cerium Ce 92 v.^. wmmmmmmim^ List of Elements — Notation, EUtMXNTS WITH TIIKIR SYMBOLS AND ATOMIC WEIGHT8->MN^. itiH Nam Symbol Atondc Weight Name Symbol AUMriDl W«i|ht Ittdmm In ii3'4 Rhodium , . Ro > Silver (Aigentum) Ag 108 IMAium L 7 1 Sodium (Natrium) Na 23 Magnbsium . Mg 24 ' Strontium Sr 875 Manqanbsx. Mn 55 Sulphur . S Al Mercury (Hy- drargyrum) Hg Tantalum . . Ta 200 Tellurium Te 129 Afolybdetium . Mo 96 Thallium Tl 204 Nickel . Ni 59 Thorintfm Th '.'.I-' Niobium . . Nb 94 Tin (Stannum) Sn Nitrogen . N 14 Titanium Ti 50 Osmium , , Os 199 Tungsten (Wol- 1 framium) . ) W 184 Oxygen . . 16 Palladium . Pd 106 Uranium U 120 Phosphorus P 31 Vanadium . V 51 Pt 197 Yttrium Y 59-7 Potassium (Ka- linm). K 'vn Zinc . Zn 65 39 ' Zirconium . Zr 89 ill Ml I (3) Chemical Notation. — In the foregoing table it will be seen that opposite to the name of each element is placed its chemical symbol^ which consists of the first letter of its I^tin name. Where two or more of these names begin with the same letter, a second letter is added to distinguish such symbols from each other. These symbols form a simple and easy kind of shorthand, by means of which chemical changes may be clearly and compactly represented. It is important to remark that whenever the symbol of any element is used, it represents not merely the element itself, but a definite quantity of that element. For instance, the symbol O always stands for 16 parts by weight of oxygen ; the symbol H always stands for i part by weight of hjrdrogen \ and in the table opposite to the symbol qf Chemical Symb^— 'Notation. f etch element is placed the number of parts of the element which that symbol represents. To render our ideas precise, we will suppose that H stands for i gram of hydrogen ;* then O wiU represent, not i gram, but i6 grams of oscygen ; C will represent la grams of carbon ; S ja grami of sul- phur, and so on. The reason why these particular numben are appropriated in the table to their corresponding elementi will be explained hereafter. They constitute a very impoi^ tant series of constants, which, in the case of the mom important elemenCft, it will be found highly useful to commit to memory. These numbers represent what chemists have termed the atomic w^hts of the elements. Every element is supposed to be made up of excessively small particles or atoms exactly of the same size and weight in the same body. If the atom of hydrogen be supposed to weigh x, the number opposite to each element in the table represents the weight of its atom, or smallest particle, compared with that of the atom of hydrogen. Compound bodies may also be represented by symbols ; and the proportion as well as the nature of the elements concerned is easily expressed by writing the symbols side by side : HCl, for instance, represents hydrochloric add, a compound of hydrogen with chlorine, in which the proper* tion of I gram of hydrogen is united witii 35*5 grams of chlorine; H2O indicates water, a compound of hydrogen with oxygen, the figure % below the symbol H multiplies Uie quantity of hydrogen by 2, and represents a grams ol hydrogen combined with x6 grams of oxygen. When two or more chemical ^mbols are thus written side by side, they constitute a chemical formula. Whenever the sign 4- is placed between two formulae, it is employed to show that the two bodies have been mixed with each other. The * Another unit of wdght might have been taken, such, for instauce^ as I grain, or i ounce, or i pound ; then O would stand for 16 graios of oxygen, i6ounces of oxygen, or i6pounds of oxygen, according as a grain, an ounce, or a pound of nydr^^en was the unit diosen fiv the oomparisoiit 9 dMJMMIf SytliOOUt i|pi«do«iMt indietfe identic or abMhile 6qM%, Iml ii MWJly — p tojfod in the leme of the word 'yieldtj'aiid iiImb it eooBOCli tfie tiro hahret of a cfaemioal eqaatkni, it mwnnti that if tiie oompoundi which aland before it ait fliked with each other, widi due precaution, a chemical chaaie will oocnr iriiich may be lepresented by the anaofe- meot of the qrmbola placed aiier the sign ■■. For iutanoe^ hi the chemical equation, CaCOj -f iHG • CaOt 4- HtO + Cpi» CaCQi if the diemical formuUi for calcic carbonate^ of whidi maiUe ia one of the many forms ; and if H represents I gram of hydrogen, CaCOf will represent loo gnuns of maible^ smce Ca stands for 40 grams of calcium, C for is grams of caibon, Oj for 3 times 16 or 48 grams of oxygen, making together 100 grams. HCI is die chemical symbol for hydrochloric add ; and since H means i gram of hy- drogen, CI 35*5 grams of chlorine, aHCl will mean twice that quantity, or 73 grams of hydrochloric add. As soon as the hydrochloric add is poured on the marble, a chemical change occurs; the marble is dissolved, and an efferves- cence* is produced, the result being die production of caldc chloride^ CaCla, containing 40 grams & caldum, twice 35*5 or 71 grams of chlorine, making together ixi grams of caldc chloride; HaO, x8 grams of water, con- taining a grams of hydrogen,, and 16 grams of oxygen ; while COa stands for 44 grams of carbonic anhydride (or carbonic add), containing 13 grams of carbon with twice 16 or 39 grams of oxygen^ and this has passed off as a gas, and produced the effervescence. The whole may be represented as follows, where the Qgures written under each symbol represent the number of grams of eadi element or combination of elements : — * A body ii laid to efftrvetee when it gives off gas suddenly wi^ «■ ofboiliiy. CaCO« 4> aHQ - CaCl, jo-fi a^iexj i « (i ♦ 3S'5 ) y-»-35'5 Ik^ 73 173 III MS 1.^ 4 H,0 •!• CO. ixa-»>i6 iS'fidMa i8 173 Or in wordit Mix loo gnmi of maible with a idtttum of 73gnmiofhydiocliloric add: it will yield iii grunt of calde chloride, i8 gnunt of water, and 44 of carbonic anhydride. Whenever a chemical compound i> formed, the lame compound ii always found to contain the tame dement^ united in fixed and invariable proportions ; 100 parti of maible always contain 40 of calcium, la of carbon, and 48 oi oigfgen : and in like manner 18 parta, whether grams, pounda, or tons of water, always contain a parts of hydro gen and 16 parts of oxygen, be they grams, pounds, or tons. (4) WagMs and Measures. — The weights and measurea used in this work are those of the metric system, which, on account of their simplicity and convenience, are now commonly employed by men of science throuji^out the worid. This uniformity of usage does away with the waste of time formerly incuired in converting the weights and measures of one countxy into those of their neighbours. As, however, most persons in this kingdom have been ac- customed firom infancy to a different system in the tranr actions of daily life, it will be necessary to explain the principles of the metrical systent It will be needful to bear in mind that the mOre or unit of len^h is equal to 39*37 English inches; and consequently that 10 centimetres re- present very nearly 4 mches, while a millimetre is almost exactly ^th of an inch. The subdivisions of the metre are marked by the Latin prefixes deci^ ten, centi^ a hundred, and miUi^ a thousand; so that the tenth of a metre is called a dedmehrt, the hundredth of a metre a centimetre^ and the thousandth of a metre a miUimOre, The higher multqplea are indicated by the Greek prefixes deca, ten, hedOt opf ,,llilpfll "T*^ P5W^ r i.p ijinf|,iiji|| i tVeights and Measures, jrandred, kih^ one thousand ; but the prefix kih^ or niultiplt by one thousand, is almost the only one used in practice. For instance, the higher multiple, or looo metres, is called a kilometre. It is used as a measure of distance by road, and represents about X094 yards, 16 kilometres being equal to nearly zo English miles.* Fig. I. Each side of this square measures I Decimetre, or ID Centimetres, or 100 Millimetres, or 3*937 Snglisli incites. A tiirt is a cubic measure of i decimetre in the side, or a cube each side of which has the dimensions of this figure. When full of water at 4° C. a litre weighs exactly i kilogram 01 1000 grams, and is equivalent to 1000 cubic centimetres; or to 6i'024 cubic inches, English. A gram is the weight of a centimetre cube of distilled water; at 40 C. it weighs 15-432 grains. I s^. Centim. 4 inches. • The metre Is a bar of platinum deposited in the archives of France, and when made it was believed to represent exactly the ten-millionth part of a quadrant of a great circle encompassing the globe of the earUi gu Metric System. II >le :e. la nd to , : - -1 -a -3 -s -1 -4 isq. entim. —II The measures of (Opacity are connected with those ol length by making the unit of capacity in this series a cube of one decimetre, or 3 '93 7 English inches, in the side; this, vihich is termed a litre^ is equal to 17637 imperial pints, or to 6i'oa4 cubic inches. Finally, the system of weights is connected with both the preceding systems by taking as its unit the weight of a cubic centimetre of distilled water at 4° C. : it weighs 15 '43 a English grains. The gram^ as this quantity is called, is further subdiWded into tenths or decigrams^ hundredths or eentigramSf and thousandths or milligrams^ the milligram being equal to about ^ of a grain. The higher multiple of 1000 grams constitutes the kilogram. It is the commercial unit of weight, and represents 15,43a English grains, or rather less than 9\ lb. avoirdupois. The weight of 1000 kilograms, or a cubic metre, of water, is 0*9843 of a ton, which is sufficiently near to a ton weight to allow of its being reckoned as one ton in rough calcu- lations. The temperatures given in this bouk are expressed throughout in degrees of the centigrade thermometer, unless otherwise specified. The following is a short comparative table of the two scales, Centigrade and Fahrenheit c r. C P. c F. i c 75^ F. 1 670 -20P -4» I5» 5f 45" 1 113° -«5 + 5 20 6S 50 122 80 176 -10 14 as IJ 51 I3» «5 185 - 5 *3 30 60 140 90 194 3a 35 95 65 149 95 ao3 5 41 40 104 70 i5« 100 213 1 '0 50 rl U the meridian of Paris. But it has been found by later and more ac- curate measurements that this assumption is erroneous. The metric system is, however, no way dependent upon the accuracy of this assumption, and the actual h&x of platinum then made continues not- withstanding to be the unit of the metric system. ■ifll IS Solids — Liquids — Gases. 1 m m (5) Physical States of Matter. — Most of the simple bodies of the chemist occur as solids at the common temperature of the air ; two only, mercury and bromine, exist as liquids ; while four others, viz. oxygen, hydrogen, nitrogen, and chlcHine, are known as gases ; but in one or ether of these three fonns of solid^ liquid^ or gaseous every substance exists, whether it be simple or compound. Solid bodies, such as a bar of iron or a block of wood, have a definite form, which cannot be altered without the application of some force more or less considerable. Liquids, on the contrary, like watc, when placed in an open vessel yiel and connect the other platinum wire with the remaining pole of the battery. Gas will begin at once to rise from both plates, and will collect in the tubes : one of these tubes will receive just twice as much gas in the same time as the other. When sufficient gas has been collected, remove the tube with the smaller quantity of gas, closing it with the thumb before lifting it out of the water. Turn it mouth upwards, and introduce a splinter of wood red-hot at the point. It will be rekindled. This we know is a characteristic property of oxygen. Now remove the other tube in a similar manner, and apply a lighted taper. The gas will take fire, and bum with the pale flame pecu- liar to hydrogen. In this experiment it is to be noted that for each cubic centimetre of oxygen obtained from the water 2 c. c. of hydrogen have been procured. Further, it may be easily shown that these two gases may be made to combine again chemically in the same proportions, and that they then reproduce water. For this purpose the last experiment must be altered in form as follows : — Exp, 33. — Fit a good cork to the neck of a bottle which will hold 100 c. c. ; adjust a tube, bent as in Fig. 10, to the cork, having its lower end turned upwards, and pass the wires con- nected with the two platinum plates through the cork, taking care that the metals do not touch each other. Nearly fill the bottle with water slightly acidulated with sulphuric acid, and insert the cork with its bent tube and platinum plates. Connect each plate with one of the wires of the voltaic battery, as before ; allow the air in the tube to be displaced by the gas, and then collect the mixed gases, as they rise from both plates, in a strong li n -•i^ should be placed in a jug or earthenware vessel ; it should be stirred round and round with a glass rod, and the acid should be poured into the water (not the water into the acid) in a slender stream, the whole bein^ kept stirred till the mixture is complete* 44 Decomposition rf Water. dry tube filled with mercury, and supported in a wooden vice, and inverted in a small Wedgwood- ware mortar containing mer- cury. When the tube has become full of gas, close the end of it with the finger, raise it out of the mercury, and apply a Ught : Fig. ID. I ! ^m a sharp report will be heard ; the two gases will suddenly unite, and the sides of the tube will become dewed with moisture, showing that water has been formed by the union of the oxygen and hydrogen. Another mode of making this important experiment will be described when we come to treat of hydrogen. Each litre of oxygen gas unites with exactly two litres of hydrogen ; and if the gases be heated to above loo" C. before causing them to unite, and the heat be kept up to the same point after they have united, exactly two litres of steam or watery vapour will be obtained. Hence, in representing the composition of water by symbols, its formula is written H2O, and its combining number is 18. When converted into vapour 9 grams of water furnish a bulk of steam exactly equal to that of i gram of hydrogen at the same temperature and pressure ; so that the relative weight of steam is 9, and the specific gravity of steam is 0*622; or the weight of a quantity of steam, compared with that of a quantity of air which weighs i gram at the same temperature and pressure, is 0*622 gram. It is also convenient to bear in mind that I litre of water will at 100° furnish 1696 litres of stes^m, of Freezing and Boiling of Water. 4S an elasticity sufficient to balance the pressure of a column of mercury of 760 millimetres, i cubic inch of water producing nearly a cubic foot of steam. Pure water has neither taste nor smell, and it is generally supposed to be colourless, though when seen through a depth of 5 or 6 metres it has a delicate and faint tinge of blue. Wlien cooled sufficiently, it becomes converted into the transparent solid form of ice. The point at which pure ice melts, or the freezing point, as it is usually called, always occurs at exactly the same temperature, if the ice is not exposed to pressure. Hence the melting point of ice has been made the starting point or 0°, the zero, as it is termed, of the centigrade thermometric scale.* Again, if the tem- perature of water be raised sufficiently high, the liquid assumes the form of gas, while bubbles of steam rise through the heated liquid and break upon its surface, passing off as invisible vapour. The water is said to boil, and its vapour is then of an elastic force just sufficient to balance the pres sure of the air upon its surface, whatever that pressure may be. The temperature at which pure water boils under equal pressures is found to be quite as uniform as its freezing point. This boiling point of water serves, therefore, as a second fixed point upon the thermometric scale, and it has been agreed to call the point at which the mercury stands in boiling water 100" on the centigrade scale; the observa- tion being always made when the pressure of the air upon the surface of the boiling water, as indicated by the baro- meter, is equal to that of a mercurial column 760 mm. long when measured at 0° C. One degree of the centigrade scale represents the looth part of the apparent expansion of the mercury in the thermometer between the freezing and the boiling points of water.f * If the water holds salts dissolved in it, the freezing point is lowered to an extent depending on the quantity and kind of salt. t If salts are present in the water, the boiling point may be raised several degrees, the amount varying according to he quantity and kind of salt in solution. ' K' m 'X%1 i;! i ■ :: I i:i 46 Evaporation of Wate/. ii.ii;i But water evaporates^ or slowly passes off into the air in the invisible form of vapour or steam at all temperatures — even from ice itself; and this evaporation is going on more or less actively almost everywhere upon the surface of the earth, so that the air is at all times charged with moisture, the proportion of which is perpetually varying. In dry weather the quantity of vapour found is always less than Ihat which could exist unseen in the air at the time. It is owing to this circumstance that wet bodies, when exposed to the air, become dry in a few hours. By the process of evaporation from the surface of the land, as well as of the ocean, a natural distillation and purification of water, of the utmost importance, is always taking place around us. The water discharged by rivers into the sea returns unperceived into the air. The vapour is at first unseen, but as it rises into the colder regions of the atmosphere it is condensed into masses of visible cloud. These at last become too heavy to stay aloft. High ridges or mountains are especially .active, in arresting the clouds, which then fall in showers, and supply the high lands with water. This flows down the sides of the hills, collects into rivulets, and these again into rivers ; or else the water sinks into the earth through the porous strata, and passes down until it meets with a bed of clay or some stratum through which water cannot pass. The liquid, when thus stopped, flows along over the face of the imbedded stratum until it reaches the surface of the soil at some lower level in the valley, where it bursts forth in the fonn of a spring. Water exhibits a remarkable exception to the law of con- traction by the removal of heat, which all other bodies obey. When exposed to a falling temperature, it diminishes in bulk regularly till it has become cooled down to 4° C. ; and then, instead of contracting, i.t begins slowly to expand, and continues to do so until it reaches the freezing point, when the ice which is formed suddenly expands still more. This exceptional expansion of water as it cools is attended with W Maximum Density of Water. M very important consequences to our well being. During the frosts of winter a rapid process of cooling occurs from the surface of all lakes and streams ; the colder water sinks to the bottom until the whole has become reduced to 4° C, but below this point the colder water becomes the lighter, and remains at the top, so that it protects the mass beneath from the winter cold. In this way it prevents such a reduc- tion of temperature in deep pools as would be fatal to fishes and aquatic animals. The ice also floats upon the surface, and thus the bottoms of lakes and rivers are preserved from the accumulation of masses of ice, which, if it sank as fast as it is formed, could never be melted even by the summer's sun. The temperature of 4" C. is that at which water is heavier than at any other, and is hence called its point of maximum density. A litre of water at this temperature weighs exactly 1000 grams, or i kilogram. Water is 773 times as heavy as air at o® C, when the barometer is at 760 mm. In taking the specific gravity of solids and of liquids, they are always compared with the weight of an equal bulk of pure water at 4° C. For example, if gold be said to have a specific gravity of 19*34, it is meant that i c. c. of water at 4° weighs i gram, while a cub. centim. of gold at the same temperature weighs I9'34 grams. In order to obtain pure water for this and various other purposes, it must be distilled. This is usually performed by means of a still and worm-tub ; but if these be not at hand, a small quantity of water may be distilled in the following manner: — Exp. 34. — Procure a clean tinplate 9-litre (or 2-gallon) oil can ; bend a glass tube into the form shown in Fig. 1 1 ; adapt it to a sound bung which exactly fits the neck of the can, and fill the can about two-thirds full of water. Then adjust the bent tube to the condenser shown in the figure. Place the can upon the fire, and heat it till the water boils steadily, whilst a small stream of cold water is kept running through the outer tube of the ■y-mm 48 Distillation of Water, .■y\ i' ■ ■ '1' condenser. Allow the water as it distils over from the can to flow into a flask placed for its reception. Throw away the first 40 or 50 cub. cm., which are apt to contain a little ammonia and semi-gaseous impurities. Then collect 3 or 4 litres. This will be distilled water i and if the experiment is performed carefull)^, Fig. II. the liquid so condensed will be pure from all solid substances in solution. A few drops when allowed to evaporate from a slip of clean glass will leave scarcely a perceptible mark behind ; but if a few drops of the water before distillation be so treated, a distinct residue will be obtained. A sufficient condenser maybe made without difficulty as follows : — Select a piece of glass tube Rain Water. 49 of about 80 centim. in length and 2 centim. in diameter ; fit it by means of corks into a second tube of glass or of tinplate about 60 centim. in length and 4 centim. in diameter. Into the space between the two tubes pass a bent quill tube through one of the corks, and introduce through the other cork a second similar tube ; cold water is to be supplied through the tube at the lower end, while the hot water runs off at the upper end, as shown in the figure. Water, in consequence of its extensive power of dis- solving bodies of various kinds, is not met with naturally in a state of perfect purity. Rain watery collected in the open country after continued wet weather, is nearly pure ; but even this contains the gases of the atmosphere dis- solved in it, usually to the extent of from about 30 to 50 c. c in a litre of water, besides particles of solid suspended matters. * The presence of air in water is necessary to the life of fishes and aquatic animals generally, for it is by means of the oxygen thus dissolved that they maintain respiration. Its presence may be shown as follows : — Fig. 12. .1 i !* Exp. 35. — Fit a quill tube, a (Fig. 12), by means of a sound cork to a Florence flask, having first filled the flask with rain water, or with spring water ; fill the tube also completely with water, and adapt it to a small glass jar, by also filled with water, and standing in the water-trough. Heat the water in the flask till it E ^m 50 ^Impurities which occur It I boils briskly; bubbles of air will gradually be driven out of the water, and may be collected in the glass receiver, b. Rain water which falls in mountainous or rocky districts formed of millstone grit, mica slate, and other rocks which contain but little soluble material, generally runs off nearly free from anything except a little vegetable matter and dissolved gases -, but spring water, although it may be perfectly colourless and transparent, contains some salts in solution. The quantity and the kind of these salts varies with the kind of rock or soil in which the spring originates. The salts most often found in si)ring water are sodic chloride or common salt, calcic carbonate from chalk, and calcic suli)hate, as well as small amounts of magnesic carbonate and sulphate. The waters of town wells also generally contain traces of ammonia, and more or less of the nitrates and nitrites of calcium or of sodium. The nitric acid in these salts is the result of the gradual oxidation of the drainage from animal refuse, which, though in its recent state one of the most noxious impurities that can be found in water, yet when completely oxidized into nitrates is no longer dangerous to health. Nearly all spring waters contain also a very small quantity of silica in solution. ' Wholesome waters do not contain in solution more than one gram of saline substances per litre ; and the most highly prized sources contain but a few centigrams only in a litre of water. ^ Exp. 36. — Select a thin porcelain dish which will hold 60 or 80 cub. cm. ; place it in one pan of the balance, and cut a piece of lead till, when placed in the other scale-pan, it counterpoises or exactly balances the dish. Measure off half a litre of spring water, and pour some of this water into the weighed dish ; place it over a very small gas flame, so as to evaporate the water gently without allowing it to boil ; add the rest of the water from time to time until the half litre has been completely evaporated away. Dry the salts thus obtained, and weigh what is left as accurately in Natural Waters. 51 as you can. By multiplying this quantity by 2 you will obtain the amount of soluble solid substances per litre which that par- ticular specimen of water contained. This is the basis of the plan which, with many additional precautions, is adopted for determining the quantity of salts in the process of analysing waters to be used for drinking or manufacturing purposes. River water often holds a smaller proportion of salts dis solved in it than spring water ; and yet it may be less fit for drinking, for it generally contains a much larger quantity of organic matter ; that is to say, it contains a larger propor- tion of soluble drainage products of a vegetable or animal nature, which have been washed off the surface of the soil by the rain, or which have been emptied from sewers into the stream. Such sewerage products should not be allowed to escape into rivers until they have been more or less purified by allowing the liquid to run over cultivated land, which is manured by it in its progress. The liquid afterwards runs away comparatively harmless. Happily for mankind, running water is endowed with a considerable amount of purifying power, due to the oxygen of the air which it holds in solution. Vegetable matters consist almost entirely of carbon, oxygen, and hydrogen, with a very small proportion of nitrogen ; whilst animal matters, in addition to carbon, oxygen, and hydro- gen, contain a considerable proportion of nitrogen ; both vegetable and animal matter likewise contain a little sulphur, either as sulphates or in some other form. During putre- faction these organic bodies give out a disgusting odour, and, if swallowed in this state, even when largely diluted with water, may cause serious illness. By the action of the oxygen dissolved in the water, the hydrogen of these com- pounds becomes changed into water, the carbon into car- bonic acid, and most of the nitrogen into nitric acid. The continual motion of the water exposes fresh surfaces to the B 3 A\^ n $2 Impurities found in Water. air ; fresh oxygen is in consequence always being absorbed, and tho oxidation wliicli takes place is generally sufficient to preserve the stream in a wholesome state. But if the water be overloaded with organic refuse, or if it become stagnant, the whole of the dissolved oxygen may become absorbed by the decaying matter without renewal from the air, and the jxjol will then emit an offensive odour, and may become a centre of disease. The filtration through the well aerated porous soil which water naturally undergoes before it issues in the form of springs, is attended with an oxidizing and purifying action of the highest importance. River water should always be filtered through sand or through a charcoal filter before it is used for drinking. Suspended matters, such as clay, fish spawn, or small animals may be thus removed, but the salts in solution are not sensibly affected by such filtration. Exp. 37. — Dissolve 0*395 gram of potassic permanganate in 1 litre of water, and add 3 c. c. of this solution to a mixture of 2 c. c. of dilute sulphuric acid (40 of water and 1 of acid) with kalf a litre of distilled water, in a glass flask, so as to give the liquid a distinct purplisii tinge ; little or no change of colour will be seen at the end of three hours, if the mixture be left to itself. Do the same thing with an equal quantity of river water : in three hours' time the tint will have become reddish or brownish, if any considerable quantity of organic matter be dissolved in the water. ^ The foregoing result may I explainer" : The sul- phuric acid separates permangi. acid from Uk salt, and in the presence of organic matter tins acid loses a portion of it' oxygen, which combines witii the constauents of the organic matter, while the permanganic acid becomes converted in > a compound of manganese of a different and less intense colour, and containing less oxygen. A weak solution of the permanganate, indeed, furnishes a valuable comparative test of the fitness of water or drinking. If the permanganate does not alter sensibly in Hard and Soft Water. 53 colour in such an experiment, there is no organic impurity to be feared in the water. Water is commonly spoken of as hard or sojt^ according to its action upon soap. Soap is a combination of a fatty or oily acid with soda ; and this compound is readily soluble in pure water. Waters which contain salts of calcium or magnesium cause the soap to curdle, since these metals furnish with the fatty acid of the soap compounds which are not soluble in water. Such waters are said to be hard. Soap which is thus curdled is consumed in waste. In such water soap neither cleanses nor produces a lather until the whole of the earthy salts have been decomposed and an ex- cess of soap is present. Soft waters, on the contrary, do not contain these earthy salts, and they dissolve the soap without difficulty, and without destroying either its cleansing power or its tendency to form a lather. Many waters exhibit what is called temporary hardness; such waters become softer by boiling. The hardness in this case is due to the presence of calcic or magnesia carbonate. These compounds are scarcely soluble at all in pure water, but they become soluble to a considerable extent in water charged with uncombined carbonic acid. When such waters are boiled, the carbonic acid is driven off by the heat, and the calcic and magnesic carbonates which the acid had dis- solved become deposited, and a * fur' or incrustation takes place on the inside of the boiler, as may be seen by examin- ing a kettle used for boiling such waters. Exp. 38. — Place half a litre of a water of the kind just referred to, such as that of the Thames or of the New River, in a glass flask, and boil it over a lamp for a quarter of an hour : little crystalline grains of the earthy carbonates which were in solution will gradually be deposited, and the water will be found to be considerably softened. Exp. 39. — Mix another half litre of such a water before it is boiled with about one-eighth of its bulk of limewater. The liquid will become turbid, and on standing for a few hours, till it U clear, it will be found to be much softer than before. I'-'^M ' ■ :il 1 ' ' '» ' 'ra '^'■-^■k^ *■ 1 ■■■■ ■■'ai i4 Soap-test for Water. The reason of this result is, that the lime in the limewater has combined with the carbonic acid which the river water held dissolved. Chalk is thus formed, and at the same time the chalk previously dissolved by the carbonic acid becomes separated ; so that both the lime of the limewater, if it be not added in too large a proportion, and that originally in the water dissolved as chalk, become precipitated * together, and the water is softened. Exp. 40. — Prepare a mixture of about equal parts of strong spirit and water, so as to obtain a liquid of sp. gr. 0*920, and in half a litre of this dissolve o'l gram of curd soap. Into a glass bottle fitted with a stopper, and capable of holding about 100 c. c, measure oif 50 c. c of such a hard water ; then add, little by little, some of the spirituous solution of soap. Put the stopper into the botrle. and shake it briskly for a minute : no lather will be formed at first, but the soap will be curdled. Continue to add the solution- shaking briskly between each addition. At length there will be more soap added than the lime salts can decompose, and as soon as this happens a lather will be formed in the botde. This is the principle upon which Dr. Clark's soap test for determining the hardness of water is based. In applying this test the stren rth of the soap solution is first carefuPy ascertained, and th^n the exact proportion necessary to produce a lather is determined for each particular water ; by means of tables constructed for the purpose, the hardness of the water is then easily calculated. Besides this temporary hardness in v ater, there is a per- manent form of hardness. Indeed, vf ry commonly the same water exhibits hardness of both kin s. The amount of each may be found by applying the soap test to the water before it has been boiled, and again after boiling it for half an hour, • 'VMien a clear liijuid becomes cloudy or milky from the addition of another denr liquid, the chemical change is attended with the formation of 3ome insolable compoind, which is separated, or, in chemical lan- guage, is precipitated from the liquid. The insoluble substance is called %pricipitate, whether it sinks to the bottom or floats in the .solution. Permanent Hardness — Mineral Waters. 55 \:% taking care to add distilled water if necessary to supply the exact quantity which has been boiled away. The difference between the hardness of the water before it was boiled and that found afterwards gives the temporary hardness ; while the degree of hardness which remains after the boiling represents the amount of permanent hardness. This permanent hardness is due to the presence of salts of calcium or magnesium other than the . carbonates, such as the sulphates or nitrates. Waters having tliis permanent kind of hardness may be softened by a method well known in the laundry ; for by the addition of sodic carbonate, or common washing soda, the calcium or magnesium is precipitated as carbonate, while sodic sulphate or nitrate remains dissolved. For instance, with calcic sulphate the change may be thus represented : Calcic Sulphate Sodic Carbonate CaSO^ + Na,COj Sodic Sulphate Calcic Carbonate Na,S04 + CaCOj The sodic sulphate which is formed does not curdle the soap. Mineral ivaters hold a much larger quantity of substances in solution than waters used for domestic purposes. If such waters contain iron, they have an inky taste, like some of those at Tunbridge Wells. They are called chalybeate \i2Xtx%^ and may be known by the rusty deposit which they form when exposed to the air. Others are strongly effervescent^ like seltzer water, owing to the escape of carbonic acid ; while others have a strong sulphuretted odour^ like the Harrogate water, owing to the presence of sulphuretted hydrogen. Others, again, are strongly saline, like the springs at Epsom and at Cheltenham ; whilst in some cases in volcanic districts, as in the Geysers of Iceland, the water is actually boiling hot, and holds silica dissolved ; and in the Bath waters the springs, though not boiling, are much hotter than the surface of the soil from which they come forth, owing to the action of subterraneous heat MM Saturation — Crystallisation. ni ill ,!:'; Sea water is largely loaded with common salt, and with magnesic chloride and sulphate, to which last the bitter taste is due. It contains also a large number of other salts ; among these are small proportions of bromides and iodid«s. A litre of sea water contains about 37 "5 grams of various salts dissolved in it; about 29 grams of these consist of sodic chloride. Water dissolves certain bodies, such as common salt, nitre, and Epsom salt, with great ease; but other salts, such as calcic sulphate, are soluble in much smaller pro- portion in the same quantity of water. When water has dissolved as large a proportion of any substance as it can take up, it is said to be saturated with that substance. Some substances, such as silver chloride and siliceous sand, are not soluble in water to any sensible extent. Generally speaking, water, though saturated with any parti- cular salt when cold, will dissolve a larger quantity of the same salt when heated. Exp. 41. — Grind up in a mortar 50 or 60 grams of sodic sul- phate with about twice its weight of water at 15° C. The water will dissolve a considerable proportion, but not the whole of the salt. Pour this saturated solution into a flask, and warm it gently ; it will now dissolve 50 grams more of the salt without difficulty. Allow the solution to cool down to the temperature of the air, say 15° C. : long four-sided prisms will crystallise from the liquid. Pour off the liquid, and dry the crystals by pressing them between a few folds of blotting-paper. When they appear to be dry, put a small quantity of the crystals into a test-tube, and apply a gentle heat : the salt will liquefy, and on continuing to apply the hcnt a large quantity of water will be driven off, and a dry white po vder will be left in the tube. The water thus given off was chemically combined with the crystals. Many other salts which appear to be perfectly dry to the touch, give off water when heated, and crumbl« down to a shapeless mass ; such, for example, as alum, cupric sulphate, and sodic carbonate; but they all \om the dis- Efflorescent and Deliquescent Salts. %1 tinctive form of their crystals when the water has been expelled. If the dry residue be again dissolved in water, new crystals similar to the original ones are obtained, and they are found also to contain water as before. The quan- tity of water is definite for each salt ; for instance, sodic sulphate contains lo atoms of water combined with each atom of the salt, and its composition is represented by the formula Na2S04, 10H2O; cupric sulphate has 5 atoms (CUSO4, 5H2O), sodic carbonate 10 atoms to each atom of the salt (NaaCOj, 10H2O), and so on. Such water which is necessary to the form of the salt, but which can be driven off without altering its chemical character, is called water of cryJallisation. Sometimes mere exposure of the salt to the air is sufficient to get rid of this water of crystal- lisation. Exp. 42. — Take some of the fresh crystals of sodic sulphate ; let them lie exposed on a piece of blotting-paper for two or three days. They will gradually lose their water, and crumble down, or effloresce into a white powder. Other salts act in the opposite manner. They absorb moisture from the air, and become dissolved in it : they deliquesce. £rp. 43. — Put a little calcic chloride in a watch-glass, and expose it to the air; do the same with a few decigrams of potassic carbonate ; in two or three days both salts will be found in a liquid state. The compounds of water are often called hydrates (from the Greek u^wp, water) ; and when a substance is entirely free from water in combination, it is said to be anhydrous. When a salt is dissolved in water, it is not considered by the act of solution to have entered into true chemical combina- tion ; the water and the salt may be separated from each other unchanged by merely altering the temperature a few degrees. Many other substances besides water dissolve bodies without acting chemically on them. Spirit of wine -\ fa, r i 'J m > w 58 Hydrogen. m dissolves camphor, coal nai)htha dissolves caoutchouc, and each is left unchanged when the spirit or the naphtha evaporates. In a case of true chemical action, the result is different j the product obtained differs in properties from the original bodies. When potassium is thrown into water, the metal disappears, and seems to dissolve, but it cannot be removed by evaporation. The water has been decomposed, hydrogen escapes, and on evaporation a solid compound of potassium and hydrogen with oxygen, in perfecUy definite proportions, is obtained (KHO), and this may be made red hot without being chemically altered. (i6) Hydrogen: Symb. H; Atomic Wt. i; Atomic Vol. Q ; Mol. Wt Ha, 2 ; Mol. Vol. PH i Sp. Gr. 0-0691 ; Rel Wt. I. We have already found that when sodium or potassium is placed in water an immediate escape of hydrogen occurs, as a colourless inflammable gas. Potassium and sodium are among the few bodies which act powerfully upon water at common temperatures : there are some other metals which, when cold, have scarcely any action upon it, though when made red hot they easily decompose it. Iron is one of these metals. Exp, 44. — Procure an iron gaspipe about 60 centim. long and 2 centim. in diameter ; fit a cork and a short piece of glass tube to each end. Introduce some iron filings into the iron tube. To one end attach a quill tube by means of a flexiVjlc caoutchouc tubing: and to the other, also by means of a viilcmised rubber tube, fasten a Florence flask about one-third full of water, fitted with a cork and quill tube. Make a temporary furnace (as shown in Fig. 13) by means of six or eight bricks, with a grating, which may consist simply of a coarse piece of wire gauze ; support the iron tube across the furnace, and make it red hot by surroundmg it with burning charcoal. Then cause the water in the flask to boil with such force as to drive the steam Preparation of Hydrogen, S9 through the red-hot pipe over the heated iron filings. Gas will come off at the other end, and may be collected in jars over the Fig- 13- pneumatic trough. When a light is applied to it, it will bum with a pale yellowish flame. It is, in fact, hydrogen. In this process the red-hot iron has removed the oxygen irom the vapour of water, and left the hydrogen in a jeparate form, magnetic oxide of iron being produced. The decomposition may be thus represented : Iron Water Magnetic Oxide 3Fe + 4HaO « Fe304 3x56 4(2x1 + 16) 3x56 + 4x16 Hydrogen 4H. 4x2x1 — Y 72 232 8 240 ■~~Y 240 The usual and the most convenient mode of preparing hydrogen is the following : — Exp. 45. — Melt about half a kilogram of zinc in an iron ladle, and pour it in a thin stream from a height of about a metre into a pailful of cold water ; the metal will be obtained in flakes, and is said to \i^ granulated. Introduce into a bottle which wil! hold about 300 c. c. about 15 grams of granulated zinc; fit a good cork to the neck of the bottle ; then remove the cork and pierce two holes in it with a round file ; through one hole pass a glass tube funnel, and through the other a tube bent as in Fig. 14. To the bent tube attach another bent glass tube, by means of a ':H I i 60 formation of Hydrogen. piece of vulcanised rubber tubing. Next pour upon the nnc through the funnel about 70 c. c. of diluted sulphuric acid (i mea- Fig. 14. ^"""^ ^^ strong acid to 7 measures 0/ water). A brisk effervescence v.'iU occur, and a colourless gas will como off, which may easily be collected in jars over the pneumatic trough. In this case the zinc appears to displace hydrogen from the acid ; a new salt (zinc sulphate) is formed, and becomes dissolved in the water. The reaction is shown in the fol- lowing equation : — Sulphuric Acid Zinc Zinc Sulphate Hydrogen HaSO^ + Zn ZnSO^ + H, 2x2 + 32+4x16 65 65 + 32+4x16 2x1 Scraps of iron may be used instead of zinc in this experi- ment; but the gas then lias a disagreeable smell, owing to the presence of carburetted hydrogen derived from the carbon in the iron. Ferrous sulphate (FeS04) ^^ now formed instead of zinc sulphate. Hydrogen is not a poison when breathed, but it cannot support life. It is very slightly soluble in water j 100 c. c of water dissolve only i "93 c. c. of the gas. Hydrogen is a colourless gas ; when pure it is without either taste or odour. It has never been liquefied by cold or pressure. Owing to its lightness it was at one time used for filling balloons ; but coal gas is now substituted for it, as, though not so light as hydrogen, it is more easily obtained in sufficient quantity. Exp. 46. — Hold a small jar, with its mouth downwards, over the tube of the hydrogen bottle while it is giving off gas freely, as shown in Fig. 1 5. The hydrogen will gradually displace the heavier air, and may be found in the jar even after the lapse of two or three minutes, if the mouth of the jar be kept downwards, Properties of Hydrogen. 6i as may be proved by applying a flame, when it will take fire ; but if the mouth be turned upwards, the gas will escape in a few Fig. IS. seconds, and no flash will occur on applying a light. Hydrogen in burning gives out little light, but much heat ; a jet of the gas burns with a pale yellowish flame. All gases which are formed in contact with water neces- sarily contain a certain small amount of moisture in the invisible form ; but they may be freed from this when neces- sary by causing the gas to pass slowly over some salt, which, like calcic chloride, has a strong attraction for moisture. For the purpose of removing this small quantity of moisture from hydrogen, as ordinarily prepared, the following arrange- ment may be made : — Exp. 47. — Fill a tube of about 20 centim. long with calcic chloride broken into pieces about the size of a pea ; plug each end loosely with cotton wool; then fit a cork, pierced with a quill tube 5 centim. long, into each end ; fasten this drying ap- paratus to the hydrogen bottle by means of the caoutchouc tube. The gas as it comes out at the other end of the drying tube will be dry. Now set fire to the dry gas as it escapes, and hold a cold glass jar over the burning jet. The side of the glass will quickly become bedewed with moisture, owing to the union of the burning hydrogen with oxygen obtained from the atmo- sphere. Oxygen and hydrogen may be kept mixed together at ordinary temperatures for any length of time without com- bining J but if an electric spark be applied to the mixture, or a lighted or even a glowing match, immediate combination 0cc;irs, with a bright flash and a loud report f - k 1 -'I 62 The Mixed Gases, Exp. 48. — Fit a good cork into the neck of a gas jar, and pass a quill tube 5 centim. long through it. Bind a short piece of caoutchouc tube firmly to the quill tube, and close this elastic tube with a small screw vice or tap made for such purposes. Fill the jar with water over the pneumatic trough. Now fill a small jar which will hold about half a litre with oxygen, and transfer it by manipulating, as shown in Fig. 16, without loss to the gas jar. Fill the same jar with hydrogen, and transfer it to the large jar. Repeat the operation with the hydrogen, so as to obtain in the larger jar a mixture of half a litre of oxygen Fig. 16. and I litre of hydrogen. Having previously softened a thin bladder by soaking it in water, tie into the neck of it a glass quill tube 5 centim. long : then adjust to the projecting portion a piece of vulcanised caoutchouc tubing provided with another screw tap. Press the air out of the bladder ; connect by means of a short piece of glass tubing the two pieces of vulcanised tube ; depress the jar in the pneumatic trough, and then open each screw tap. The gas will now pass into the bladder ; close both screw taps, and remove the bladder. Now place the end of the tube attached to the bladder under some soapsuds, and Union of Hydrogen and Oxygen. «3 force out the mixed gas by squeezing the bladder so as to make a lather. Carefully remove the bladder to a distance, and then apply a light to the froth of soapsuds. A loud explosion will immediately follow. In this experiment steam is formed ; this first expands con- siderably, owing to the heat produced by the combination of the oxygen and hydrogen, and immediately afterwards the steam becomes condensed, the particles of the surrounding air rush in to fill the void, and by striking one against the other produce the report. If the hydrogen be mixed with air, instead of pure oxygen, a similar but weaker explosion occurs when a light is applied. In all experiments with hydrogen it is therefore necessary to allow time for the expulsion of the air from the apparatus before setting fire to the gas as it comes out. If the mixture be diluted with a large excess of hydrogen or of air, the explosion becomes less sudden, and less heat is given out ; until, when the dilution reaches a certain point, the mixture only burns quickly without explosion, and, if still more diluted, the combustion only takes place at the spot where heat is applied. The proportion of oxygen and hydrogen which unite together is perfectly defined, no matter in what proportion they are mixed. One measure of oxygen invariably unites with exactly two measures of hydrogen. If the gases before firing are heated beyond the temperature of boiling water, and be kept at the same temperature after the explosion,* the three measures of gas which have united will form exactly two measures of steam — H H + [0] = It might be considered that we now have proved the true composition of water, for we have found that water may by analysis be made to yield both oxygen and hydrogen, and * This form of the experiment requires special apparatus, and, except in practised hands, is rather difficult of performance f'' .« te- I- *'t if* 64 Composition of Water. Fig. 17. that when oxygen and hydrogen are burned water is formed ; but at present we have not shown absolutely that oxygen and hydrogen are the only sub- stances which enter into the formation of water. The following mode of ex- A Hll'll I periment, for which a some- what costly form of apparatus is required, proves this fact, C " however, in a conclusive manner. Exp. 49. — Fig. 17 repre- sents a strong glass vessel A, through the upper part of which two platinum wires are inserted; the vessel can be closed by a glass stop-cock c ; by means of a second stop- cock it can be attached to an air-pump, not shown in the figure, and the air exhausted. The stop-cocks having been closed, the vessel is screwed upon the top of a jar, B, containing a mixture of two measures of hydrogen and one measure of oxygen. On opening the stop-cocks a portion of the mixture enters the vessel ; the cocks are then closed, and an electric spark passed through the mixture. A bright flash occurs; the gases com- bine, and the whole of the two gases become condensed into water, which trickles down the sides of the glass. On again opening the stop-cocks a fresh quantity of gases may be ad- mitted, to supply the place of those just condensed. The spark may be again transmitted, and the process may be repeated until the whole of the gases are consumed and a considerable quantity of water formed. If in this experiment oxygen or hydrogen be used in ex- cess, that excess will be found in the vessel unacted on after firing the mixture, * Synthesis of Water. «s Fig. i8. Hxp. 50. — Provide a stout tube bent into the form shown in Fig. 18, open at one end and sealed at the other, the sealed limb having been divided into cubic centimetres, or other equal divisions. Into the sides of the tube, near the sealed extremity, two platinum wires are fused, with two of the ends inside the tube, nearly touching each other. Fill the tube with mercury ; then introduce a mixture of 4 volumes of oxygen and 2 volumrs of hydrogen. The bulk of this gas is to be carefully measured ; say it fills 6 divisions after causing the liquid metal to stand at the same level in both tubes; this may be easily effected either by a n t J.- i? !t. M 'M ^. IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I (I^ Ii2 12.2 IL lis 1110 1.25 |U ,,.6 ^ 6" ► "F /^ §>> c>^ '/ Hiotograpbic Sciences Qirporation 23 WIST MAIN STRUT WEftSTER.N.Y. 14580 (716) 872.4S03 m \ iV 4 ^ ft :\ \ <«■ O^ •%"■ %' m «^ 9o Decomposition of Carbonic Anhydride, divide the aii-way through the chimney by placing a long slip of card down the middle; a downward current will then be established on one side of the card, and an ascending currenl on the other, and the taper will bum freely. It is on this principle that small mines are often ventilated for a time, the shaft being divided by a wooden partition into a downcast and an upcast shaft In the best ventilated mines, hov^rever, this is done by two separate shafts, sunk at some distance from each other, and in one of these shafts a fire is kept burning, for the purpose of producing an ascend- ing current of hot air. Ventilation by means of fans driven by machinciy is, however, bodi much safer and more effectual in producing the necessary movement of the air. Carbon may without difficulty be separated from carbonic anhydride. Exp. 67. — Cause a current of the gas to pass through a dr}'ing-tube containing calcic chloride (Fig. 24), and then through Fig. 24. a bulb tube containing a small piece of potassium. Heat the potassium in the gas : it will soon take fire, and bum brilliantly. Let the tube cool, and then plunge it into water. In this experiment potash is formed in the tube at the expense of oxygen derived from the gas ; the alkali is dis- solved by the water, and black particles of charcoal become diffused through the liquid. Exp. 68. — Kindle a strip of magnesium foil, by holding it Synthesis of Carbonic Anhydridi. Si with the tongs in the flame of a spirit lampt- and when burning brightly, introduce it into a jar filled with carbonic anhydride. The metal will continue to bum ; white flakes of magnesia, mixed with black particles of carbon, will be deposited. Add a little dilute nitric acid : this will dissolve the magnesia, and leave the carbon. v Carbonic anhydride is not only absorbed by limewater, but it is also quickly absorbed by any alkali, such as a solu- tion of potash. Exp. 69. — Fill a strong graduated test-tube with carbonic an- hydride by displacement, and invert it in a deep glass containii^ mercury, as shown in Fig 8. Then introduce the curved beak of a pipette, filled with a strong solution of potash, beneath the edge of the tube, and blow from the lungs with just sufficient force to drive a few drops of the liquid into the tube. The solu- tion of potash will quickly absorb the gas, and mercury will rise in the tube. A strong solution q£ potash is in fontiniwU use in th« iaboiatory for separating carbonic anhydride from other gases which, like oxygen, nitrogen, and hydrogen, are in- soluble in the potash solution. In this way it is easy to estimate the quantity of carbonic anhydride in respired air. We have thus proved by synthetic experiments that when charcoal is burned in air or in oxygen, carbonic anhydride is formed; and we have found by analysis that the gas con- tains both oxygen and charcoal. It may be shown that it contains nothing but carbon and oxygen, and the exact pro- portions may be determined by means of the apparatus shown in Fig. 25. A is a gas-holder filled with pure oxygen, b a strong solu- tion of potash, o a tube filled with calcic chloride in lumps, B a sheet-iron furnace containing a tube of hard glass : at r, within the tube» is a platinum tray containing the carbon ; g is a tube containing calcic chloride, h a seriej of bulbs filled with solution of potash, while i is a tube fiUed with lumps ot potash. The platinum tray with tlie carbon, whether in the fonn of d2 Synthesis of Carbonic Anhydride, diamond, graphite, or charcoal, is weighed accurately at first Then the oxygen dried in its passage is allowed to stream slowly through the tube, which is gradually made red hot by placing glowing charcoal round it in the furnace. The carbon in the platinum tray bums brilliantly in the stream of oxygen, and becomes converted into carbonic anhy- dride. The tube should also contain cupric oxide, by which any trace of carbonic oxide which might be formed would be at once converted into the anhydride. This is completely anrested by the potash in the bulb tubes h, no gas but pure and dry oxygen escaping into the air. The gain in weight of H and I together shows how much carbonic anhydride has been formed. The loss of weight of the platinum tray f shows how much carbon has been burnt, and the difference betAveen this weight and that of the carbonic anhydride shows how much oxygen has combined with the carbon. No chemical experiment has ever been made with greater care than this for the purpose of arriving at accurate results, since the composition of carbonic anhydride is a fundamental datum in all analyses of organic compounds. It has been found by repeated trials of this process that 12 grams of car- bon require exactly 32 grams of oxygen to convert them into 44 grams of carbonic anhydride ; so that, assuming for the present the atomic weight of carbon to be 12, the molecular weight of a carbonic anhydride is 44, and the formula re- presenting its composition is COa. Carbonic Acid in the Atmosphere. »i ir If carbon be burned in a jar of oxygen over mercury, so as to prevent any loss of the gas, it is found that the gas, when it has cooled down again and is measured with due care, is not altered in bulk. The carbonic anhydride formed occupies the same volume as the oxygen which has entered into its composition, so that the gas contains its own bulk of oxygen. Carbonic acid, though a weak one, forms a numerous and important series of salts, called carbonates. Except those of tlie alkaline metals, thay are nearly insoluble in water ; and all, whether soluble in water or not, dissolve with efifer- vescence in dilute nitric acid. The gas which comes off is colourless, with scarcely any smell; and if passed into limewater, it makes it turbid, thus showing it to be Carbonic acid. Many of the carbonates occur in immense quantities as natural products, particularly calcic and magnesic car- bonates. The quantity of carbonic anhydride in the atmosphere is tending continually to increase, in consequence of the numerous chemical processes by which it is being produced; and it would accumulate to a serious extent, were it not pre- vented by a remarkable counteracting power possessed by growing plants. The green parts of plants, when in the sun's light, decompose carbonic acid, and lay up the carbon in the wood and other parts, whilst they give back most of the oxygen to the air, thus converting again into fuel that material which has been diffused through the atmosphere, and has, by being burned, lost for the time its chemical activity. The rain as it falls dissolves the carbonic anhy« dride, and carries it down to the earth; and the roots of the plants absorb it, and carry it up into the leaves, where it undergoes the necessary chemical change, so long as the sun's rays fall upon the plant. In the dark, no such removal of carbon from the gas and restoration of oxygen to the air occurs. o a 1. <♦ ^4 Varictia of Carbon. Exp. 70. — Into a small gas jar (Fig. 26) fit a good coric, instead of the stopper, and pass a test-tube tightly through a hole bored through the cork. Place the jar in a large beaker filled with p. , spring water, which has been mixed with a fourth of its bulk of solution of carbonic acid in water. Fill the tube with water, and place it in the neck of the jar, having introduced a few sprigs of mint or the leafy branches of any succulent plant in the jar, and then expose it for an hour or two in direct sunshine. Bubbles of gas will be seen studding the leaves ; and on shaking the jar, these will become detached, and will rise into the test-tube. After a time the cork and tube may be withdrawn, keeping the mouth of the tube beneath the surface of the water ; then close it with the thumb, turn the tube mouth upwards, and test the gns with a glowing splinter. The wood will burst into a blaze, showing that the gas consists mainly of oxygen. (18) Carbon: Smyb. C; Atomic Wt. \z\ Sp. Gr. as diamond, about 3 "4. Carbon is an elementary body of the greatest importance, and it occurs in various familiar forms, viz. naturally as diamond, and as graphite or black-lead, as well as less pure in the different artificial substances known as charcoal anc > coke. It is also abundant in combination : chalk contains not less than an eighth of its entire weight of carbon, and magnesic carbonate more than one-seventh. Carbon also occurs combined with other elements ; for it is the cha- racteristic constituent of those substances which are called organic and are of vegetable or animal origin. a. The diamond is the hardest of known substances, and the most valuable of gems. It consists of pure carbon crystallised in forms derived from the regular octahedron and dodecahedron, and often in the form of rolled pebbles, with a dingy exterior, which would cause them often to be over- Diamond — Plumbago. 8S looked by an unskilled observer, i'he diamond can only be cut and polished by grinding it with its own powder. Its most important use is familiar to us in the hands of the glazier for cutting sheets of glass. Owing to its rarity, its high refracting power, and brilliant lustre, it has been prized for ornamental purposes from time immemorial. Diamond may be burned in oxygen gas, when it con- mimes iiway almost without residue. Twelve mgrams. of diamond have been found to yield when thus burned exactly 44 mgrams. of carbonic anhydride, an'^ no other product It has never been melted. It is a non-conductor of electricity, though other forms of carbon conduct it well. When heated intensely in the arc of the voltaic battery, as soon as it becomes white hot, it swells up, loses its transparency, acquires the power of conducting electricity, and is con- verted into a black opaque mass resembling coke. b. Plumbago, or graphite^ frequently from its appearance called black-lecuU though it contains no lead, is another form in which carbon is found naturally, but in tolerable quantity. It has a sp. gr. of about 2*2, and occurs sometimes in crys- talline six-sided plates. It has a leaden-grey lustre, leaves a streak upon paper on which it is rubbed, on which account the finest kind is used in making artists' drawing 'pencils. It is a good conductor of electricity. When it is burned in oxygen, it always leaves from 2 to 5 per cent, of ash, which; however, is not a necessary part of it. The gas which it furnishes when thus burned in oxygen is pure carbonic anhydride. Owing to its perfect indifference to the action of oxygen at common temperatures, it forms a serviceable coating for the protection of ironwork from rust, as is com- monly practised with fire-grates and stoves. Graphite, when mixed with clay, is oflen made into crucibles, because they are not liable to crack in the fire. Molten iron dissolves carbon readily ; much of it separates from the iron again if the melted metal is allowed to cool slowly. It is then in the form of graphite. 96 Pit Coal— Anthracite. Pit Coal. — This is one of the most important natural sub- stances rich in carbon. It is a material, of vegetable origin, which has become altered during the lapse of ages, while exposed, under great pressure in the strata of the earth, to the combined action of water holding in solution oxygen derived from the air, and moderate heat. The composition of pit coal varies greatly according to the length of time during which it has been thus acted on, the older deposits being those which contain the largest proportion of carbon. The elements of which the original vegetation consisted are car- bon in large proportion, oxygen in smaller quantity, still less hydrogen, and a very small proportion of nitrogen; but besides these there is a variable quantity of saline and earthy substances which always occur in vegetable juices ; added to which are earthy impurities derived from the adjacent strata, as well as a portion of iron pyrites (FeSi), which is always gradually formed in the coal. When coal is burned in the open fire, if there be a sufficient supply of air, the carbon becomes carbonic anhydride, the hydrogen burns into water, the nitrogen escapes chiefly as gas. and the ash which remains is composed of the saline and earthy residue. Much of the South Wales coal is of the modification called culm w anthracite, which contains upwards of 90 per cent, of carbon, and but little volatile matter. It burns without flame, and with a steady glow. House coal, such as is used in London, is of a different kind. It softens when heated, and forms a pitchy or bituminous mass, which causes the pieces to cake together. Such coal is never burned com- pletely, even in an open fire ; but in the act of burning it gives off a quantity of gaseous or tarry matter, holding finely divided carbon or soot in suspension. When a quantity of fresh coal of this kind is thrown upon a hot fire, it at once begins to be decomposed ; considerable quantities of the compounds of carbon and hydrogen are formed, and pass off in the condition of gas or vapour. A portion of these sub- stances immediately takes fire and hums with a bright light Combustion and Distillation of Coal, it and a smoky flame; but a laige portion of them, when they pass over the glowing embers, is more or- less completely decomposed; the carbon and hydrogen become part:'illy separated from each other in a part of the fire where there is but little uncombined oxygen ; the hydrogen, being the more combustible element of the two, seizes upon such oxygen as it finds, or else it escapes unbumt in the form /f gas ; while the carbon, still containing a notable proportion of hydro- gen, is carried away in very fine particles, and passes off as smoke, suspended in the heated gases. The formation of this black smoke may, however, be pre- vented by throwing the coal upon the fire in small quantities at a time, taking care to keep up a strong steady heat, so as to consume the gases as they are formed ; but this can only be secured by a sufficient supply of atmospheric air, a con- dition not so easily fulfilled in manufacturing furnaces as might be expected, though with proper care it can be done. When bituminous coal is heated in long closed iron cylinders, out of contact with air, a large quantity of gas and of tar is formed ; they contain the oxygen, hydrogen, nitrogen, and part of the carbon of the coal, while the greater portion of the carbon is left behind as a porous mass, called coke. Coke resembles graphite in properties, but it retains all the ash and earthy impurities of the coaL It bums with a steady glow, without emitting flame or smoke ; it is less combustible than coal, and requires a brisk current of air to keep it burning. The more highly the coke is heated during its preparation, the more compact does it become^ the better does it conduct heat, and the more slowly does it bum. Exp. 71. — Get a blacksmith to weld up one end of a wrought- iron gas-pipe 25 mm. (i inch) in diameter, and 50 centim. long. Fit a cork and a bent tube to the open end ; put from 50 to 100 grams of coarsely broken coal into the iron tube;* heat the * A hard f^a» tube may be used instead of the iron tube^ and may be heated in a flame, but it does not yield the gas so Miity. it Coke — Preparation of Charcoal. closed end in a common fire, and direct the gas into the pneu- matic trough. Some tarry matter will pass over, and a con- siderable quantity of gas may be collected, which will burn with a bright flame. When all the gas appears to have been driven off, take the tube out of the fire, let it cool, and then, with an iron rod, detach what is left in the inside of the tube. It will be found to be common coke. Put some of this coke in a small open clay crucible, and heat it in the fire : the coke will gra- dually bum away, leaving nothing but a little ash. The dense coke required for burning in the powerful draught created under the boiler of a locomotive engine is usually prepared by burning the coke in massive brick ovens, in each of which several tons of coal can be charred in a single operation, the ovens being provided with a sliding door, for regulating the admission of air, which plays over the surface of the heap and bums off the volatile matters, and so chars the whole mass at a very high temperature, each charge requir- ing 48 hours for its conversion into coke. If, instead of heating coal in an iron retort, wood be treated in the same way, a still larger quantity of \olatile and liquid products will be given off, and what is left behind is a black porous substance, of the same shape as the wood, familiarly called charcoal. Wood tar, vinegar, and wood naphtha are among the liquid products, which redden litmus paper strongly, but the gas has little illuminating power. A more compact charcoal, better suited for use as fuel, is made by burning wood in heaps. A stake is driven into the ground, brushwood is placed round the bottom, and logs of wood are piled up regubrly around the stake. The heap thus formed is often 10 metres or more in diameter; it is covered with powdered charcoal, turf, and earth. It is then kindled by introducing lighted fagots at openings left for the pur- pose. Large quantities of moisture are driven off, and the fire spreads gradually through the mass, the admission of air being carefully regulated, so to cause one part of the wood in burning completely to char and drive off the volatile matters Charcoal— Carbon Puet. from the rest When gas and vapours cease to come oflf, the fire is extinguished by closing all the openings for the admission of air, and adding a thicker layer of mould and turf. S/ach a heap takes nearly a month to bum out, and never furnishes more charcoal than a quarter of the weight of the wood used. The gas and the liquids which are obtained from the coal and the wood during this process of destructive distiUa- tion do not exist ready formed in these substances. They are the result of chemical changes produced under the influence of the heat ; the carbon and hydrogen combine together in new proportions, and thus furnish substances quite different in properties from th« original coal and wood. Nearly all vegetable and animal matters, when heated out of contact with air, furnish charcoal more or less pure. Exp. 72. — Put a few pieces of wood into a clay crucible ; cover the wood completely with sand, and heat the whole for 20 minutes in a fire. Gas will be given off, and bum. Take the crucible out of the fire, let the whole cool, then empty the crucible : the wood will be found to be converted into charcoaL Charcoal gives out more heat in burning than an equal bulk of wood, as the moisture and volatile matters given off by the wood carry away much of the heat in the latent state. But in the economy of fuel it is not sufficient to consider simply the absolute amount of heat which a given weight of It emits in burning. A fuel which burns with flame is necessary where it is desired to communicate an elevated and unifonn temperature to objects at a distance from the fire-grate, as in heating glass pots or the contents of a porce- lain kiln ; whilst in heating boilers and objects where direct radiation from the fuel can act fully, coke, charcoal, or anthracite is very valuable; and in an ordinary open fire these same fuels radiate much more heat into the room, though they do not look so cheerful, as the bituminous coal, with iti fitfUl, fliinkering flame. ■0 3 form or other is employed to remove oxygen from its combinations with other elements, particularly from tlie oxides of the metals, which, when heated with carbon, are reduced qx brought back to the metallic state. Hence carbon is spoken of as a reducing agent by the metallurgist This action may be shown as follows : — Exp. 78. — Mix in a mortar 20 grams of litharge or lead oxide (PbO) with 40 grams of conmon salt and i gram of powdered charcoal ; cover it with a little more salt, and place the mixture in a small clay crucible ; heat it to bright redness in the fire. When the mixture is melte*!, take the crucible out of the fire and let it cool. When quite cold, break the crucible, and a bead of lead will be found at the bottom, under the melted salt, the carbon having taken the oxygen from the oxide of lead. Twelve grains of pure charcoal,* free from ash, when burned in a current of oxygen, yield exactly 44 grams of carbonic anhydride. Equal weights of diamond, plumbago, and charcoal are thus shown, when heated with oxygen, to yield equal weights of carbonic annydride; and though so different in appearance, they still consist of the same ele- mentary body. Many of the elements have the power of assuming forms which differ in appearance and properties quite as much as these three different conditions of carbon. Such elements are then said to assume different allotropk * Common charcoal, however, always retains a little hydrogen. Carbonic Oxide. 93 states, which is as much as to say that in each different modification, though all the atoms are alike, yet they are arranged in a different way. The atoms of carbon, for in- stance, which constitute diamond, are arranged very dif- ferently from those which form graphite, and the atoms of carbon in charcoal are differently arranged from those of cither diamond or graphite. Carbon unites with sulphur if strongly heated with it, and if heated intensely in hydrogen gas a small quantity of acetylene (C2H2) is formed; but it has Httle tendency to unite with the otiier non-metals. Some of the compounds of carbon with the metals are important. They are termed Carbides. (19) Carbonic Oxide: Symb. CO) Atomic atid Mol. Wt. 2%) Sp. Gr. 0-967; Rd. Wt. 14. Carbon forms only two compounds with oxygen, so far as is known. One of these is carbonic anhydride ; the other, also a gas, containing just half as much oxygen, is called car- bonic oxide. Exp. 79. — Fill the iron tube (Fig. 13) with small lumps of charcoal, instead of with iron turnings; make it red hot in the furnace, and drive steam over the ignited charcoal. Collect the gas which is formed : it will bum with a pale blue flame. Shake up a little limewater with another of the jars of gas : it will be ♦•endered milky. Three gases, viz. hydrogen, carbonic anhydride, and car- bonic oxide., are formed in this case. These changes may be thus explained : the carbon takes the oxygen from the water, forming a mixture of carbonic oxide and carbonic anhydride, whilst its hydrogen is set at liberty — H2O -1- C = CO -1- Hz; and 2H2O + C = CO2 + aH,. Exp. 80. — Mix some chalk with its own weight of iron filings; place 40 or 50 grams of the mixture in an iron tube arranged as in Exp. 71. Heat the closed end of the iron tube to redness in the fire : a gas comes off, which may be collected over watw. ^ Experiments with Carbonic Oxide. The heat expels carbonic anhydride from the chalk, acd the iron takes half the oxygen from the carbonic anhydride, and forms carbonic oxide ; CaO, CO, + Fe becoming CaO f FeO + CO. Exp. 8i. — Plunge a taper into a jar of the gas ; the light will be extinguished, but the gas will burn at the mouth of the jar with a blue flame. Carbonic oxide is often formed largely in stoves and fiihiaces, owing to the manner in which heated carbon acts on carbonic anhydride. When air- enters at the bottom of a clear fire, the oxygen bums a part of the carbon at once into carbonic anhydride; and this gas, with the nitrogen of the air, passes through the red-hot embers. The nitrogen undergoes no change, but the carbonic anhydride takes up a further quantity of carbon, and becomes converted into carbonic oxide : C + CO2 = 2CO, the carbonic anhydride being exactly doubled in bulk in consequence. This mode of the formation of the gas is important, because, if the supply of air to a furnace is too small, the carbonic oxide passes up the chimney unbumt, and much heat is wasted, which would be saved if the gas were properly consumed. Sometimes we see the carbonic oxide burning on the top of a clear glowmg fire, where it again mixes with fresh oxygen of the air while the gas is still hot enough to bum. Furnaces are sometimes made to supply air just above the top of the fire-grate, so as to burn the carbon oxide completely. Exp. 82. — Make the iron tube and charcoal red hot, as in Exp. 79; but instead of sending steam through it, attach to the tube a bottle which is giving off carbonic anhydride steadily. Collect the gas over water as it escapes at the other end : it will bum with the blue flame which distinguishes carbonic oxide. Exp. 83. — Collect some carbonic oxide in a jar provided with astop-cock at the top, or fitted up in the way directed in Exp. 48 (Fig. 16), with a flexible tube and screw-tap. Fasten a glass quill tube tu the vulcanised tube ; depress the jar in the pneumatic trough, ard allow a Uttle of the gas to escape, by relaxing the Preparation of Carbonic Oxide, 95 screw ; set fire to the issuing gas, and hold over it a small gas jar. No water will be condensed on its sides ; but if the jar be closed with a glass plate, and limewater be poured into it, a white precipitate of chalk will be produced. The carbonic oxide in burning becomes converted into carbonic anhydride ; 2 litres of carbonic oxide require i litre of oxygen for its complete combustion, and 2 litres of carbonic anhydride are produced : CO + O = CO2 There are several other ways of preparing carbonic oxide. The best of these consists in drying the yellow salt known as potassic ferrocyanide, K4FeC6N6, 3H2O (prussiate of potash), till it crumbles down to a white powder. Exp. 84. — Mix 5 grams of this dry powder with 50 c. c. of oil of vitriol in a Florence flask ; adjust a cork and a wide bent tube to the mouth of the flask, and heat the mixture. When the heat reaches a certain point, the gas will come off very quickly. In this experiment the decomposition is complicated,* but the result is, that the whole of the carbon of the salt comes off as pure carbonic oxide, while the whole of its nitrogen remains behind as an ammonium salt with the acid em- ployed. Another plan commonly practised for obtaining carbonic oxide is to heat crystals of oxalic acid with about 10 times their weight of oil of vitriol ; but in this oase the carbonic oxide is mixed with an equal volume of carbonic anhydride : Oxalic Add Water Carbonic Anhydride Carbonic Oxide H,C,04 - H,0 - CO, + CO In this process the oxalic acid is deprived of the elements Potassic Ferrocyanide K^FeCcNs Water 6H,0 ilph Acid 6H,S04 Carbonic Oxide 6CO Potassic Sulphate aK;S04 Ferrous Sulphate KeS04 Ammouic Sulphate 3[(H4N)^04J. 9« Properties of Carbonic Oxide. of water by the sulphuric acid, and the remaining carbon and oxygen pass off in the form of equal measures of the two gases. The carbonic anhydride may be removed by causing the mixture of gases to pass through a solution of caustic soda \ and the apparatus may be arranged as shown in Fig. 28, in which the gas generated in the flask a is transmitted through the tube b, which passes loosely through the wider tube c below the surface of a solution of soda contained in the bottle D. From this bottle the gas passes off, by a tube the end of which is above the solution, into the jar e standing in the pneumatic trough. Carbonic oxide is a gas without colour, but with a faint oppressive odour. It is very poisonous when breathed, so small a quantity as i measure of the gas in 100 of afar speedily producing a peculiar sensation of oppression and tightness of the head. The fumes of burning charcoal owe their most active poisonous property to the presence of car- bonic oxide, which is always largely mixed with carbonic anhydride in the products of a slowly-burning charcoal fire. This gas has not been liquefied, either by cold or pressure. It is but slightly soluble, 100 c. c. of water dissolving about 2*4 c c. of the gas. A solution of cupreous chloride (CuCl) in hydrochloric acid dissolves carbonic oxide gas slowly if On Crystaliisation. 97 agitated with it, but the gas is not soluble in a solution of potash. (20) Classification of Crystals. — We have had occasion to allude to the crystalline form of the diamond and some other substances, and different varieties of crystals will continually need notice. It will therefore be necessary to acquire some general notions of what is meant when crystals are spoken of, how their different varieties are designated, and what are the principles on which their different forms are classified. Exp. 85. — Dissolve 250 grams of nitre in half a litre of boiling water, and allow the solution to cool slowly in a basin. Six-sided prisms will gradually be formed in the liquid, owing to the separation of part of the salt. Exp. 86. — Dissolve some common salt by grinding it with about twice its weight of water in a mortar. Pour off the clear liquid, and set it aside for several days in a soup plate or other shallow vessel : the water will gradually evaporate, and little cubes of salt will be formed. Exp. 87. — Prepare in like manner a solution of alum, and leave it to evaporate slowly, when transparent octahedra will be obtained. In most cases, where solid bodies are allowed to separate undisturbed from their solutions, they are found to assume the form of some regular geometrical solid, bounded by flat faces, called planes. Each substaixe has its own peculiar form, and the regular geometrical solids thus obtained are called crystals. By these differences in form many substances may be at once distinguished from each other. The process of crystallisation is commonly used as a means of freeing salts from small quantities of foreign admixture; as, for instance, for separating nitre from small quantities of com- mon salt. The impure nitre is dissolved in hot water, and the nitre as it cools crystallises, whilst the liquid, or mother liquor J retains in solution the small proportion of common salt The principle upon which the classification of crystals is founded is the symmetry of their form. By symmetry is meant a complex uniformity of figure; in other word^ a ■Ml ■■i'lii m w ■vf\ -?■■ i- \ 98 Axts of Crystals. Fig. 29- similar arrangement of two or more corresponding forms round a common centre. This, indeed, is the general law of creation. It is seen in the correspondence of external form of the two sides of the body in animals ; of the two halves of a leaf on either side of its midrib in plants ; in the two halves of most seeds; and still more rigidly in the constitu- tion of every crystal. The imaginary line round which the parts of a crystal are symmetrically disposed is called the axis of symmetry^ or, simply, the axis of a crystal. Select an octahedral crystal of alum, and place it with one of its angles uppennost ; an imaginary line, a a, Fig. 2ga, pass- ing through the middle of the crystal to the opposite angle is an axis u/ the crys- tal. Each end of this axis is formed by the meeting of four sides or planes of the crystal. Every one of these sides is similar to its fellows, and each is in- clined to the axis at an equal angle. Elach of the four faces therefore is sym- metrically disposed around the axis. If any internal force act upon the particles during the formation of the crystal, so as to produce a bevelling of one of the edges of any one of these planes, the same cause will act upon the other corresponding edges, and will pro- duce a corresponding modification of a symmetrical charactei upon each of the other corresponding edges. This regu- larity is often interfered with mechanically, as when many crystals are formed in the same mass, or by the accident of its position during its formation. In describing crystals, several of these imaginary lines ar» supposed to exist) around which their faces are arranged. Generally speaking, these axes may be reduced to three, all of which intersect each other in the centre of the figure. For the purpose of making the direction of these axes more easily understood, let a piece of soap be cut m the form of a cube, or figure of 6 equal squart tides, each of CUavtige of Crystals. ^ Fig. a9«. which is 6 or 8 centimetres long; through the middle of one of its sides thrust a piece of wire i8 centimetres long^ so that it shall pass out in the middle of the opposite side, and project equally on either side, as shown at aa^ Fig. 29 a; do the same through two of the other sides, as at bb. These two wires will represent the direction of two out of the three axes of the cube which cross each other at right angles at its centre. Now repeat the process on the remaining two sides. The third axis of the cube will be represented by this third wire, which will be at right angles to both the others. Fig. 31. Fig. 32. Fig. 33. Twist a piece of thread round the end of one of the wires, and connect each point of the wires in succession with each of the four points nearest to it, stretching the thread across from one to the other. An outline of the regular octahedron will thus be formed. Take another cube of soap, and pare off each of its 8 corners, as at ooj Fig. 30, by a plane inclined equally to each of the three adjacent faces of the cube. If these new faces be gradually enlarged by continuing to pare away the comers, as shown in the Figs. 31 and 32, the cube will by degrees be converted into the octahedron (Fig. 36), an 8-sided solid, in which the three axes of the cube, aa, aa,aa, end in the six solid angles of the octahedron. If in another cube of soap the 12 edges u z 6 j i h \ A too First aftd Second Systems. of the cube be pared off so as to form i a planes, b^ b^ Pig. 33, sloped equally towards the adjacent faces, the cube will gradually be converted into a regular 12-sided figure, the rhombic dodecahedron (Fig. 34), which is also symmetrically F'g- 35- ^■^ 1 a ^--1 sphere containing ammonia, produces a white cloud, by com> bining with the ammonia and forming a white solid salt This property is often used to detect small quantities of ammonia. Exp. III.— Mix common hydrochloric acid with half its bulk of water; dip a glass rod into the mixture, and hold it near the mouth of the flask which is giving off' ammonia. Dense white fumes of sal ammoniac will appear around the rod. Gaseous ammonia becomes liquid at a cold of — 4o*'C., and by a pressure of about 7 atmospheres at 15". It may even be frozen at - 75" C. into a transparent solid. Exp. 112. — Slip a piece of frcshly-bumed charcoal under the edge of a long tube previously filled with dry ammonia gas, and standing over mercury. The charcoal will quickly absorb the ammonia ; if pure, the whole of the gas will disappear, and the mercury will fill the tube. Charcoal has this power of absorbing all gases to a greater or less extent ; but such gases as are freely soluble in water are more easily absorbed by charcoal than those which are sparingly soluble. One c. c. of boxwood charcoal will take up fully 90 c. c. of ammonia; so that the gas is subjected to a much greater degree of condensation by this absorptive action than would be necessary to liquefy it by pressure. A solution of ammonia is in constant use in the laboratory. It may easily be prepared as follows : — Exp. 113. — Mix from 30 to 50 grams of powdered sal ammo- niac with an equal weight of slaked lime, and place the mixture in a flask ; then add 30 or 40 c c. of water, and let the flask be fitted with a good cork and bent tube, as shown in Fig. 57. Next, by means of a piece of vulcanised tubing, connect the bent I m III ti8 Solution of A mmonia. tube of the flask with a three-necked bottle containing water, ts with a wide-mouthed bottle fitted with a cork and three tubeS| two of which are bent at right angles. Neither of these bent tubes must dip into the water. The second bent tube may pass Fig. 57. into another three-necked bottle containing water, the first bent tube of which passes below it, and the second bent tube into a bottle also containing water, for the purpose of condensing any of the gas which may escape' from the first two vessels. A bottle of this kind is known as a Woulfis bottle \ and the middle tube, open at both ends and dipping into the liquid, is intended to admit an, n the gas is absorbed by the water faster than it is supplied ; at the same time, noi.e of the gas can escape through it into the atmosphere. By this contrivance air can enter the partial vacuum, and the water in the outermost bottle is prevented from being driven back by atmospheric pressure. The solution of ammonia is lighter than water, the sJJecific gravity of the solution diminishing as the quantity of gas contained in it increases. The water also increases in bulk as it dissolves the ammonia; and when saturated at 15**, it contains more than a third of its weight of the alkali It has the intensely pungent odour of ammonia, and, when gently heated, gives off the gas in large quantise Analysis of Ammonia GaS. "9 JS!sei^, 114. — Boil a little of mercury until it stands at the same level in both Hi.i 'ow slip a small elastic ring over the sealed tube, so as to mark the height at which the mercury stands ; fill jK) the open limb with an amalgam of sodium, prepared by dissolvi.ig diji 6 pieces of sodium the size of a pea in 30 c. c of mercury. Close the tube with a good cork. Transfer the gas into the limb containing the amalgam, and agitate it briskly: sodic chloride will be formed. Retransfer the gas to the closed limb, allow mercury to run off till it stands at the same level in both limbs : it will be found that the gas has been reduced to half its original bulk, and that which is left is hydrogen, for it will bum on the approach of a light. Exp. 128. — Fill a dry bottle with hydrochloric acid gas, and close the mouth with a glass plate. Withdraw the stopper from a bottle of ammoniaral gas of the same size ; invert the jar oi hydrochloric acid over the one containing the ammonia, and remove the glass plate. The two invisible gases will suddenly combine, a dense white cloud will be formed, and a solid salt (sal ammoniac, or ammonium chloride) will be produced. Equal bulks of the two gases unite and condense each other, HCl -h H3N becoming H4NCI. The group H4N has never been obtained in a separate form ; but many chemists regard it as a compound metal, called ammonium^ which com- bines with chlorine, and completely neutralises its activity, just as sodium does in common salt, NaCl resembling (H4N)C1 in many important points. A solution of hydrochloric acid in water forms an im- portant and powerful chemical agent. It is frequently spoken of as /««r/a/«-acid, from the word m»r/a, brine. The HydrocMaric Acid. 127 oommon commercial acid has often a yellow colour, owing to the presence of a little iron. It is a fuming liquid, of sp. gr. about 1*17, and contains about a third of its weight of the gas. A solution of hydrochloric acid may readily be prepared by connecting a flask charged with a mixture of fused salt and oil of vitriol with an apparatus similar to that employed for obtaining a solution of ammonia (Fig. 5 7). This acid dissolves those metals which decompose steam when passed over them at a red heat, such as zinc, iron, nickel, and tin, with escape of hydrogen, while chlorides of the metals are formed : Zn + 2HCI = ZnClj + Hj. Exp. 129. — Dilute a little hydrochloric acid with 6 or 8 times Its bulk of water, and add caustic soda cautiously, until the liquid is exactly neutral, and neither reddens blue litmus nor restores the blue to red litmus paper. Pour the liquid into a basin, and evaporate it slowly : crystals of common salt will be deposited in cubes. In this case the whole of the hydrogen of the acid, in combination with oxygen derived from the soda, will pass off as water, the change being as follows— HCl + NaHO = NaCl + HaO. Exp. 130. — Pass a piece of quicklime into a tube filled with hydrochloric acid gas standing over mercury : the gas will be quickly absorbed. The change is the following : — CaO + 2HCI = CaCU + HaO, calcic chloride and water being formed. Most of the chlorides are soluble in water ; and when a solution of a strong base, such as potash, is added to the solution of a chloride of one of the metals which forms an insoluble oxide, the oxide, and not the metal, is pre- cipitated. Exp. 131. — Add a solution of caustic potash to a diluted solu* tion of cupric chloride. 128 Hydrochloric Acid. In this case hydrated ciipric oxide is thrown down, of a pale blue colour — CuCla + 2KHO = 2KCI + CuHaOa. If a more complex oxide be acted on, a corresponding chloride is formed, if the formation of such a compound be possible. For instance, ferric oxide may be dissolved by hydrochloric acid, and the change is thus shown — FeaO^ + 6HCI = Fe^Cle + sHaO. But if there be no chloride corresponding to the oxide, part of the chlorine escapes, while a chloride of simpler com- position is formed, as in the common process of obtaining chlorine gas, by acting on manganese dioxide, to which there is no corresponding chloride, MnOa + 4HCI becoming MnCla + 2H2O -I- CI2. Hydrochloric acid and the chlorides are easily distin- guished when present in solution by the following tests : — Exp. 132. — Dissolve 0*2 gram of sodic chloride in 100 c. c. of water, and divide it into two portions, (i) To one of these add a few drops of a solution of argentic nitrate : an abundant white cloud of argentic chloride (AgCl) will be formed. Divide this milky liquid into two portions. To one of them add a few drops of nitric acid : no change will be perceptible. To the other add a few drops of ammonia solution : the liquid will become clear, since anmionia dissolves argentic chloride readily. (2) To another portion of the sodic chloride solution add a few drops of a solu- tion of mercurous nitrate : a white precipitate of calomel will appear. Divide this turbid solution into two portions. Add a few drops of nitric acid to one : no change will occur. To the other add ammonia : the precipitate will become black. Exp. 133. — Boil hydrochloric acid in a test-tube with frag- ments of gold leaf: they will not be dissolved. Now add a drop or two of nitric acid : a yellow solution of auric chloride (AuClj) will be quickly formed. Scraps of platinum are not dissolved by hydrochloric acid, but they enter slowly into solution if nitric acid be added and tlie mixture be warmed. This mixture of hydro- chloric with nitric acid is often called aqua r^ia (royal water)^ Compounds of Chlorine and Oxygen. 1 29 from its power of dissolving gold, which was regarded by the alchemists as the king of metals. This mixture of acids is often useful for dissolving ores which resist either acid singly. It owes its activity to the chlorine which is set free. Id using the liquid, it should be only gently wanned, because if boiled the chlorine is quickly expelled to waste. Some oxychlorides of nitrogen are formed at the same time, and pass off in red vapours ; but the chlorine is really the active substance — 2HCI + HNO3 = HaO + HNOa + Cla. If the hydrochloric acid be used in excess, chlorides only remain in the liquid, the whole of the nitric acid being de* composed and going off with the gases. (a 6) Oxides of Chlorine. — Chlorine does not combine directly with oxygen, but it forms with it three gaseous com- pounds, all of which have a red or yellow colour, a peculiar irritating odour, a corrosive action, and are all so unstable that they are easily decomposed by heat, and explode with violence. These gases are : Hypochlorous anhydride . . . C1,0 Chlorous anhydride .... Cl,Oj Chloric oxide CIO, The first two, when acted on by watei', furnish acids; and, in addition, two other acids containing chlorine and oxygen are known. These acids form a regular series, in which the oxygen increases step by step as follows : Hypochlorous acid .... HCIO Chlorous acid ... . HCIO, Chloric acid HClOj Perchloric acid HCIO4 All these acids are very unstable, and they are seldom prepared. Some of their salts, particularly the hypochlorites and chlorates, are important. Some of these salts are formed by acting upon a strong base with chlorine ; but the result varies according to the tempeiature employed. m 130 Chlorine Acids. Exp. 134. — Cause a current of chlorine gas to pass slowly into a dilute solution of potash which is to be kept cool In this case a liquid is obtained which possesses bleaching properties, and in which a mixture of two salts (potassic chloride and potassic hypochlorite) is formed — Cla + 2KHO « KCl + KCIO + HjO.* Exp. 135. — Repeat the experiment on a stronger solution of potash (i of potash to 3 of water) which is to be heated. In this case also the chlorine will be absorbed, but potassic chlorate and potassic chloride will now be formed, and no bleaching liquor will be obtained — 3Cla + 6KH0 - 5KCI + KCIO3 + 3HaO. The potassic chlorate is sparingly soluble ; and if the solu- tion be evaporated to a small quantity, and then allowed to cool, flat tables of the salt will crystallise out. If the solu- tion be poured off from these crystals, and they be re- dissolved in a small quantity of boiling water, the second crop of crystals will be nearly pure. This is the salt usually employed for obtaining oxygen by decomposing it at a high temperature. {See Appendix.) Exp. 136. — Dissolve a few crystals of the pure. chlorate in water, and add a little solution of argentic nitrate. In this case no precipitate is formed, because argentic chlorate is soluble. Exp. 137. — Heat some of the crystals in a test-tube as long as they give off oxygen. When cold, dissolve the white residue in water. The solution will now precipitate the argentic nitrate abundantly j the chlorate has been decomposed into oxygen and potassic chloride, and this salt immediately forms ar- gentic chloride with the nitrate — m^ 2KCIO3 = 2KCI -t- 3O2. • Bleaching powder, or chloride of lime, is a similnr compound. It is Kianufactured on a large scale by passing chlorine gas through boxes coutaining trays of slaked lime. . Chlorides and Chlorates. I3i Chloric acid is very unstable, and is rarely prepared. No attempt . :ust be made to obtain it by distilling potassic chlorate with sulphuric acid, in imitation of the process for nitric acid. Exp. 138.— Put two drops of oil of vitriol in a test-tube j throw in a crystal of potassic chlorate of about the size of a split pea, holding the mouth of the tube away from you, and warm the mixture. A dense brownish-yellow gas, of peculiar irritating odour, will come off, and at a heat below that of boiling water a loud cracking sound or small explosion will occur. The sulphuric acid in this case decomposes the chlorate, and liberates chloric acid, which immediately breaks up into chloric oxide, and potassic perchlorate, while the chloric oxide when heated is in turn decomposed with explosion. The following equation represents the change : — Potassic Chlorate Sulphuric Acid Chloric Oxide Potassic Perchlorate Hydric Potassic Sulphate Water 3KCIO, + 2H,S0^ = 2CIO, + KCIO4 + 2KHSO4 + H.O Exp. 139. — Put two or three crystals of potassic chlorate into a wineglass, and pour some water upon them. Add a piece of phosphorus of the size of a split pea. I'iar:c the glass upon a soup plate, and with a long-necked funnel reaching to the bottom of the glass pour in quietly about a teaspoonful of oil of vitriol. As soon as the acid reaches the bottom a crackling noise is heard, and flashes of a green light are produced, owing to the burning of the phosphorus under water in the chloric oxide as it is formed. Exp. 140. — Melt a little potassic chlorate in a icdt-tube, and heat it moderately as long as it gives off gas freely. If the ex- periment be carefully watched, the salt will be seen gradually to become pasty ; when this occurs, remove the tube from the lamp and set it to cool. Treat what is left first with cold water, and then dissolve the sparingly soluble residue in boiling water; as it cools a new salt, the potassic perchlorate, will crystallise. The chlorate in this operation loses one-third only of its oxygen. When heated, it becomes separated into two new salts, potassic chlorite and potassic perchlorate — 2KCIO3 = KClOj -I- KCIO4J K 3 132 Sources of Bromine. but the chloiitc is decomposed, as fast as it is formedi ' oxygen gas and potassic chloride — KClOa = KCl + OaJ and the chloride, which is very soluble, is easily separated from the sparingly soluble potassic perchlorate. If the per- clilorate be heated still more strongly, it in turn is decom- posed into oxygen gas and potassic chloride — KCIO4 = KCl + 20a. (27) 2. Bromine: Symb. Br; Atom. Wt 80; Atont. Vol. □; Mol. Wt. (Bra) 160; Mol. Vol. m ; Hel. Wt. 80 ; Sp. gr. of vapour f 5*54 ; of liquid at 0° C. 3*187 ; Boils at 63° C. ; Freezes at — la'S**. Bromine is the only element except mercury whic" liquid at ordinary temperatures. It is of a deep red cc^v, , and gives off abundant dark red vapours, which have a very irritating effect upon the eyes and the back of the throat, with a peculiar disagreeable odour, whence its name is derived. It is about three times as heavy as water, and is but sparingly soluble in it, but freely so in alcohol and ether. Its chemical properties are similar to those of chlorine, but less active. It forms a gaseous compound with hydrogen, the hydrobromic acid (HBr = 81 ; Sp. Gr. 2731 ; Rel. Wt. 42*5), which fumes in air and is extremely soluble in water ; it is powerfully acid, and much resembles hydro- chloric acid. It may be obtained by decomposing potassic bromide with phosphoric acid. Bromine also forms acids in which oxygen is present; but only two of them — the bromic (HBr03), corresponding to the chloric, and per- bromic (HBr04), corresponding to the perchloric — have been examined carefully. Bromine is contained in sea water, as magnesic bromide (MgBra), in quantity varying from 4 to 14 mgrams. per litre. Sea water is concentrated in large quantities for the sake of its common salt and potassic and magr^-^sic salts ; and when these have been separated by crystallisation, the mother Formation of Bromine. 133 liquor, or bittern^ is treated for the bromine. Many strong brine springs, such as those of Kreuznach and Rissingen, also contain small quantities of the bromides. The bittern is made to yield its bromine by transmitting into it a current of chlorine gas, avoiding' an excess of it. All the bromidej^i of the metals are decomposed by chlorine, which has a more powerful attraction for the metals than bromine has. The liquid acquires a beautiful golden yellow colour, due to the liberated bromine, MgBrj + Clj becoming MgCU + Br,. This yellow liquid is then mixed with ether and shaken up with it. The ether dissolves the bromine ; and if the mixture be placed in a glass globe, pro ided with a stopper at top and a glass stop-cock at bottom, the ether rises in a ) ^llow layer to the surface, and the mother liquor is easily drawn off from below. The ethereal solution is then shaken up with a solution of caustic potash, by which the yellow colour is immediately destroyed: potassic bromide and bromate are formed, and become dissolved in the water, while the ether rises to the surface, and may again be used in a similar manner with fresh portions of bittern. The action of potash upon bromine resemhles that which it exerts upon chlorine, 3Bra + 6KH0 yielding KBrOa + sKBr + 3H2O. When the solution of potash has become neutralised by the action of repeated charges of bromine, the liquid is evaporated to dryness, mixed with a little charcoal, and gently heated, to remove the oxygen from the bromate ; after which the residue, consisting of bromide and the excess of charcoal, is mixed with manganese dioxide and sulphuric acid in a retort On applying heat, red vapours of bromine pass over — 2KBr+Mn02 + 3H2S04=2KHS04-f MnS04 -I- sHjO + Bra. The reaction resembles that by which chlorine is obtained. Exp. 141. — Dissolve 2 or 3 decigrams of potassic bromide in 20 c. c. of water. Mix the solution in a long and wide test- tube, with 5 c. c. of solution of chlorine, and add 5 c. c. of ether. Agitate the mixture : a yellow solution of bromine in ether will rise tp the surfiice. Decant this ethereal solution into anoth^ ;*'- 134 Iodine. I tube, and shake it with an equal bulk of a solution of caustic potash. 1 he yellow colour will disappear, and the ether will rise to the top, and form a colourless layer. Bromine combines directly with phosphorus, and with many of the metals. The compound formed by the union of bromine with any other element is called a bromide. Argentic bromide is a substance of importance to the photographer. Exp. 142. — Add a little of a solution of argentic nitrate to a weak solution of potassic bromide : a white precipitate is formed. Divide the liquid with the precipitate into three portions. To one of them add a little nitric acid, to another a few drops of a solution of ammonia : no solution occurs in either case. To the third add a little of a solution of sodic hyposulphite : the liquid becomes clear, a double hyposulphite of silver and sodium being formed. The bromides also form a white precipitate of mercurous bromide (HgBr) with a solution of mercurous nitrate ; and a white precipitate with lead nitrate, consisting of lead bromide (PbBra). Chlorine water decomposes both, setting bromine free, and forming a chloride of mercury or of lead. (28) 3. Iodine: Symb.l', Atomic Wt 127 ; Atomic vol. 0/ vapour □ ; Mol. Vol. | , \ (I2); Rel. Wt. 127; Sp. gr. of vapour, 8716; of solid, 4*947; Melting Ft. 107° C-; Boiling Pt. 175° C. Iodine is a solid, which crystallises in bluish-black scales, resembling plumbago in lustre. It is volatile at ordinary temperatures, and emits a feeble smell, resembling that of chlorine, and sublimes* slowly in the bottles in which it is kept, and is deposited in crystals on the sides. When heated to a little beyond 100" C. it melts, and at a higher tem- peratiir2 gives off dense vapours, of a rich violet hue, whence it derives its name. • A body which rises in vapour and condenses in the solid form it snid to sublime, in opposition to on» which condenses in the liqai4 fonn, when it is said to distil. •*': \ Tests for Iodine, 135 Exp. 143. — Place about 0*2 gram of iodine in a flask ; wann it over a lamp. The iodine will melt to a brown liquid ; and if the flask be heated gradually and uniformly, beautiful violet vapours will All it When allowed to cool, its interior will be coated over with small crystals of sublimed iodine. Iodine stains the skin and most organised substances brown, and gradually corrodes them. Water dissolves it but sparingly, alcohol and ether freely; solutions of the iodides in water also dissolve it. Exp. 144. — Take four test-tubes, and place about a decigram of iodine in each. Pour into the first 2 c. c. of water, into the second the same quantity of alcohol, into the third the same quantity of ether, to the fourth add 0*2 gram of potassic iodide, and then a little water. A pale-yellow liquid will be formed in the first tube, and scarcely any iodine will be dissolved, whilst the iodine will be dissolved in each of the other tubes, and will form a deep-brown solution. Mix the solution in alcohol with twice its bulk of water : most of the iodine ^vill separate in scales, as it is not soluble in water, and the water immediately separates the alcohol from the iodine. Mix the solution in the fourth tube with water : no precipitation will occur, because the potassic iodide retains the iodide dissolved. Exp. 145.— Place about 0-3 gram of iodine in a test-tube with a few drops of water, and add about O'l gram of iron filings : a green solution of ferrous iodide will be formed. Exp. 146. — Let zinc filings be substituted for iron, - 140 Hydrogen and the Halogens, All the halogens — fluorine, chlorine, bromine, and iodine — are regarded as monads, since they are characterised by forming a very soluble powerfully acid gas when united with hydrogen, such as the hydrofluoric, hydrochloric, hydro- bromic, and hydriodic. No condensation accompanies the combination, for analysis shows that in each case the acid contains half its bulk of hydrogen, the hydrogen being united with its own volume of the halogen, the gaseous acid occupying the same bulk as its component gases of vapours did in their separate form. With the exception of fluorine, each of these elements einits a coloured vapour; each, though incombustible in oxygen, yet forms acids with it, the series known being the following: — HF — _ — _ HCI HCIO HCIO, HCIO3 HRr HI HBrO? HBrOj HIO. HCIO4 HBrO^ HIO^ In comparing the halogens with each other, the chemical activity of fluorine, which has the smallest atomic weight, is the most powerful ; next in the order in activity is chlorine, then bromine, and, lastly, iodine, the atomic weight increas- ing as the chemical energy declines. Chlorine is gaseous, bromine liquid, and iodine solid. The specific gravity, the fusing point, and the boiUng point, rise as the atomic weight increases. The halogens combine energetically with the metals, and, when united with the same metal, furnish com- pounds which are isomorphous ; that is to say, they all crys- tallise in the same form - potassic fluoride, chloride, bromide, and iodide, for example, all crystallise in cubes. 141 CHAPTER VII. SULPHUR GROUP. I. Sulphur. 2. Selenium. 3. Tellurium. V30) 1. Sulphur: Symd. S; Atom. Wt. 32; Melting Pt. 115"; Boiling Pt. 446*^ C. Sulphur, or brimstone^ has been known from time imme- morial, as it is an element found uncombined in considerable quantities in volcanic districts. It is also found in com- bination with many of the metals ', for instance, when united with iron it forms the yellow brassy-looking mineral known as iron pyrites ; with lead it furnishes galena, the principal ore of lead ; and ^iith zinc it gives tlie brown mineral called blende. In combination with oxygen, it is found forming salts with other metals, known as sulphates, among which those of calcium, magnesium, and barium are of most frequent occurrence. Sulphur also occurs in combination in white of egg, in muscle, and some other animal products. Sulphur is a yellow brittle solid, which is not soluble in water, but is soluble in carbon disulphide, oil of turpentine, and in benzol, as well as to a slight extent in hot alcohol It is highly inflammable, and bums with a blue flame, emitting pungent suffocating vapours of sulphurous anhy- dride. When heated to 115** C. it melts, forming a trans- parent yellow liquid, which undergoes a series of curious changes by the continued application of heat Exp. 154. — Place a few grams of sulphur in a wide test-tubCi and apply the heat of a lamp cautiously. The sulphur melts and forms a pale yellow liquid, which flows easily. Pour part of the melted mass into cold water : a yellow brittle solid is formed. Heat the portion still left in the tube more strongly : it gradually deepens in colour, and becomes thick, assuming a treacly appearance. On heating the sulphur still higher, it again becomes somewhat more fluid. Pour it now in a thin stream into cold water : the sulphur forms into tough, elastic, semi- transparent strings Si 142 Crystals of Sulphur. The colour of these cooled threads varies from a pale amber to a deep brown, becoming darker in proportion as the heat applied is greater. If kept for a day or two, this elastic sulphur gradually becomes hard, opaque, and brittle. Sulphur may easily be obtained in crystals. Exp. 155. — Melt from a quarter to half a kilogram of sulphur in an earthen pipkin at a low and carefully applied heat. When completely melted, set it aside to cool slowly. Allow it to stand for a short time after it has become solid over the surface ; then, with a hot wire, pierce two holes through the crust near the edge on opposite sides, and pour out the still liquid portion. When the mass is cold, remove the solid crust carefully, and the interior will be found to be lined with transparent honey-yellow needles, which, when scratched, or even when left to themselves for a few hours, gradually become opaque. The crystals thus obtained belong to the class known as the oblique prismatic Sulphur may also be obtained in crystals of a different form, the octahedron with a rhombic base. Native sulphur assumes this shape ; and it may be obtained by dissolving sulphur in carbon disulphide, and allowing the solution to evaporate spontaneously. This form has a sp. gr. of 2*05, while the crystals obtained by fusion (Exp. 155) are less dense, being only of sp. gr. 1-98. They also have different fusing points, the octahedral sulphur fusing at 115°, and the prismatic requiring a temperature at 120" C. for its fusion. Bodies which, like sulphur, can be obtained in forms which belong to two distinct classes of crystals are said to be dimorphous. Sulphur also offers a good instance of allotropy. In these two varieties of crystalline form, and in the elastic threads, or viscous state obtained by sudden cooling from a high temperature, we have three different modifications of the same element. A fourth may also be procured by placing in carbon disulphide the hard mass furnished by keeping the viscous sulphur till it becomes solid. The carbon disulphide Distillation of Sulphur. 143 Fig. 60. dissolves all that can be removed from the mass, and a grey amorphous (or non-crystalline) powder is left; this differs from the crystalline varieties in its singular insolubility m carbon disulphide, which dissolves both the crystalline forms readily. All these different varieties of sulphur may be distilled by the application of sufficient heat, provided air be excluded, otherwise they would take fire. The distilled sulphur thus obtained exhibits no difference in properties, whichever allo- tropic modification may have been used. Exp. 1 56. — Place a few pieces of sulphur in a Florence flask. Cut off the neck of a second flask, so as to enable the neck of the first flask to pass into the second, as shown in Fig. 60. Heat the flask containing the sulphur, covering the upper sur- face with a cone of thin sheet iron, to keep it hot. The sul- phur first melts, then boils, and ultimately distils over into the second flask. The vapour of sulphur, at temperatures of about 500**, is 96 times as heavy as that of an equal volume of hydrogen at the same temperature ; but if the sulphur vapour be heated to 1000° C. it becomes expanded, until its density is only 32 times that of hydrogen at the same temperature and pressure. Selenium and tellurium show the same curious exceptional effect of heat upon their vapours. The compounds which sulphur forms with any of the other elements are termed sulphides, or sometimes sulphurds. 144 Sulphur and Oxygen. Advantage is taken of the volatility of sulphur to purify it from earthy matters. It is usually distilled roughly on the spot where it is found, and afterwards purified by a second more careful distillation. The roll sulphur of com- merce is obtained by pouring the melted sulphur into cylin- drical wooden moulds, in which it is allowed to cool. Flowers of sulphur, as they are called, occur in the form of a harsh yellow crystalline powder, which is procured by distilling sulpnur slowly into a large brickwork chamber, where the fumes become condensed in this form. If distilled more quickly, the brickwork becomes hot, and then the sulphur melts and mns down the sides, forming a solid mass as it cools. Sulphur, from its ready inflammability, is used in the pre- paration of matches. Large quantities are also employed in the manufacture of gunpowder ; but its principsd con- sumption is in the production of sulphuric acid. Sulphur combines directly with many of the metals, and gives out much heat in the process. Exp. 157. — Mix 3 or 4 grams of copper filings with half their weight of flowers of sulphur, and heat them in a large test-tube. At a temperature a little above the melting-point of sulphur the two bodies will begin to unite, and a bright glow will spread through the mass. When the tube is cold, break it and examine the product. A substance in no way resembling copper or sulphur will be found : it consists of the sulphide of the metal. Two compounds of sulphur with oxygen are known, sul- phurous anhydride (SO2) and sulphuric anhydride (SO^), both of which furnish important acids when combined with water. There are also other acids of sulphur containing oxygen : these are known as the polythionic series, in refer- ence to the multiple proportion in which sulphur (0c7ov) enters into their formation. It will be sufficient merely to give their formulae. The series of oxygen-sulphur acids is as follows — Hydrosulphurous acid H,SO, Sulphurous acid H^SOj Sulphuric acid H,S04 Hyposulphurous acid H,S,03 Dithionic acid Trithionic acid Tetrathionic acid Pentathionic acid H.S.O5 H,S,06 H,S50, Sulphurous Anhydride. 145 (31) Sulphurous Anhydride (or Sulphur Dioxidi) : Symb. SOa ; Atom, and Mol. Wt. 64 ; Atom, and Mol. Vol, I \ I ; Sp€c. grav. of gas, ri^'j ; Rel. Wt. 32 ; Boiling Pt, -id'*C.; Melting Pt. -76". Sulphur burns in oxygen with a lilac flame, and produces a permanent gas, which, after it has again become cool, occupies the same bulk as the original oxygen, but it has become doubled in density. Two volumes of oxygen unite with one volume of sulphur vapour, the three volumes be coming condensed into two^ roTol + 11] = riToH * The gas so produced has a pungent and suffocating odour; in a concentrated form it cannot be breathed, but in a diluted state it excites the symptoms of a common cold. It is trans- parent and colourless, is not inflammable, and immediately extinguishes the flame of burning bodies. Water dissolves more than 40 times its bulk of the gas, and furnishes sulphur- ous acid— H,0 + SOj = HjSO,. The solution has the smell and taste of the gas, which readily escapes from the water when heated. Sulphurous anhydride is usually obtained by heating sul- phuric acid in contact with a metal, such as copper : sul- phurous anhydride comes off, while water and cupric sulphate are formed— 2H2SO4 + Cu = CUSO4 + SO2 + 2HaO. Exp. 158. — Place about 5 grams of copper clippings in a flask provided with a cork and bent tube, and pour upon it 30 c c of oil of vitriol. Heat the mixture strongly, and collect, by downward displacement, 2 or 3 jars of the gas that is given ofi Test one jar with a piece of blue litmus paper : the blue will immediately be reddened. Plunge a lighted taper into another jar : it will be extinguished. Exp. 159. — Suspend a bunch of violets or a rose in a jar ot the gas : they will be bleached completely. Throw the flowers into a very weak solution of ammonia : the colour will first be restored, and will then be changed to green by the alkali. I, 146 The Sulphites. The bleaching action of this gas differs from that of chlorine in not destroying the colour, for this is again restored by the action of an alkali or a stronger acid. Flannel, sponge, silken goods, isinglass, and many articles which would be injured by chlorine, are bleached by suspend- ing them, in a damp state, in a closed chamber, and then ex- posing them to the fumes of lurning sulphur. (6>^ Appendix.) Sulphurous anhydride is useful as a fumigation for destroy- ing infection. By its action, meat is also preserved from putrefying for a while ; and it is frequently employed to check fermentation in cider and home-made wines, for which pur- pose a little sulphur is burnt in the cask before filling it with the liquor. There are various other modes of obtaining the gas. One of these consists in heating a mixture of powdered black manganese oxide with about its own weight of sulphur ; half the sulphur combines with the oxygen, the other half with the manganese — MnOa + Sa = MnS -|- SOa. If charcoal is boiled with sulphuric acid, a mixture of sul- phurous and carbonic anhydrides are evolved — C -1- 2HaS04 = 2SO2 + COa + 2HaO. In the manufacture of sulphuric acid, sulphurous anhydride is supplied simply by burning sulphur or iron pyrites in a current of air. In this way it is obtained mixed witV a large bulk of nitrogen. Sulphurous anhydride i emitted largely from the craters of volcanoes. When dissolved in water, the gas furnis. sulp^ iirous acid, and this acid furnishes the salts known as s, fphites. The sulphites of the alkalies may be obtained by passing the gas into a solution of potash or soda. It foims two kinds of salts : one of these contains two atoms of the metal, such as the common disodic sulphite (NajSOa, 10H2O), while the other kind of salt is frequently called a bisulphite, and con- tains but a single atom of the metal. Hydric potassic lulphite (KHSO3) is the best example of this class. Sulphuric Acid. '47 Tlie sulphites are easily distinguished by their efTervescing when treated with a strong acid, such as the hydrochloric, giving off a colourless gas, with the pungent characteristic odour of sulphurous anhydride. Exp, i6o. — Add a little of a solution of baric chloride to a solution of a sulphite. A white precipitate of baric sulphite (BaSOj) is formed. In this case, if the sulphite be free from sulphate, the pre- cipitate will be dissolved on adding a little hydrochloric acid ; but the clear liquid will be rendered milky by the addition of chlorine water, which will convert the sulphurous into sulphuric acid, and this will give a wiiite precipitate of baric sulphate, which is insoluble in acids. The chlorine takes hydrogen from the water, forming hydrochloric acid, and the oxygen which is set free converts the sulphurous into sulphuric acid — HaSOa + Cla f H2O = H2SO4 + 2HCI. (32) Sulphuric Acid {Dihydric Sulphate) : Symbol, H2SO4 ; Mol. Wt. 98 ; Sp. grav. of liquid, i '846 ; Meltifig Ft. lo-s" C.J Boiling Ft. 338°. This is the most important of the acids, and is the basis of our chemiail manufactures. The consumption of it annually in this country considerably exceeds 100,000 tons, or one hundred million kilograms. Exp, 161.— Dry some of the green crystals of ferrous sulphate (the salt formerly called ^r^^« vitriol), and place the dried salt in a test-tube, and heat it nearly to redness. White acid fumes are given off, which condense in oily-looking drops ; they are mixed with the pungent vapours of sulphurous anhydride. When all the acid is expelled, a red powder, consisting of ferric oxide, or colcothar, as it is called, is left in the tube. The changes may be thus represented — 2FeS04 = FezOa + SO3 + SOj. From the oily appearance of the product the old name of HI of vitriol was derived. I. a i. ■>> •; :r> -r «9p.p \ 148 Formation of Sulphuric Anhydride. When thus prepared, the distilled liquid consists of a mixture of sulphuric acid with sulphuric anhydride (H2SO4, SO3). Some sulphuric acid is always formed during the operation, because the ferrous salt cannot in practice be completely freed from water before it is distilled. This water comes away during distillation ; and as soon as the anhydride, which distils off also, becomes mixed with water, combination between the two occurs, and sulphuric acid is formed, SO3+H2O becoming H2SO4. The distillation of dried sulphate of iron has long been conducted on a considerable scale at the town of Nord- hausen, in Saxony, where it is made for the puipose of dis- solving indigo for the preparation of Saxony blue, and hence the acid so prepared is generally called Nordhatism Sulphuric Acid. When such sulphuric acid, holding sulphuric anhy- dride in solution (H2SO4, SO3), is heated, the sulphuric anhydride (SO3) comes off in dense white fumes, which, if immediately shut up in a vessel excluded from the moisture of the air, become converted, as it cools, into a silky-looking white fibrous mass. This substance is not acid, though it immediately becomes so when mixed with water. It com- bines with water with the production of a very high tempera- ture, emitting a hissing sound, like that produced by quenching a red-hot body in water. After the water has thus combined with the anhydride the two are not separated readily by simple heat If the acid thus obtained be further diluted with water, this additional quantity of watci may be removed by evaporation. During this process t le boiling point gradually rises till it reaches 338°; when v.x% point is attained, the acid has become reduced to the state repre- sented by the formula H2SO4 ; the whole then distils over, and condenses again unaltered. The great bulk of the sulphuric acid required in the arts is, however, obtained by a different process from that just described. When sulphur is burned in dry air or in oxygen, the product is always sulphurous anhydride ; it never occurs Sulphuric Acid Chamber. 149 as a higher state of oxidation of sulphur, although a higher oxide — namely, the sulphuric anhydride — may be obtained by indirect means. If sulphurous anhydride be mixed with oxygen in the presence of water, and be presented to nitric oxide, or to any other of the higher oxides of nitrogen, the further oxidation of the sulphur may be effected with great rapidity. Moreover, a small proportion of the oxide of nitrogen will effect the combination of an indefinite amoi^nt of sulphurous anhydride and oxygen. Nitric oxide (NO) in the presence of oxygen immediately becomes nitrogen peroxide (NO2), and this, when mixed with sulphurous anhydride and a large quantity of water, furnishes sulphuric acid and nitric oxide. The sulphuric acid remains dissolved in the water, while the nitric oxide, by absorbing oxygen from the air, again becomes nitrogen peroxide; this combines with fresh sulphurous anhydride, which, when acted on by water, becomes sul- phuric acid, the nitric oxide being again liberated, to go through the same series of changes with fresh portions of oxygen and sulphurous anhydride as long as any remain in presence of each other uncombined, NO2 + SO2 + x H2O yielding NO + H2SO4 + x — \YL^O. In making sulphuric acid on a large scale, sulphur cr iron pyrites is burned in a current of air in furnaces (a a. Fig. 61). In the stream of heated gas is suspended an iron pot {b\ charged with a mixture of sodic nitrate and sulphuric acid. Vapours of nitric acid are thus set free, and these pass on mixed with sulphurous anhydride and excess of atmospheric air. The mingled gases pass into immense chambers (f f), constructed of sheet lead, supported by a framework of timber. A shallow layer of water {d) covers the bottom of the chamber, and the intermixture and chemical action of the gases are further favoured by the injection of jets of steam {eee)^ supplied from the boiler (o). (^^v? Appendix.) The vapours of nitric acid lose part of their oxygen, and are quickly reduced by the sulphurous acid to the state of nitric oxide ; then the changes already described succeed each % '•is I \ 1^-;! h I ISO Properties of Sulphuric Acid, other rapidly, leaving ultimately nothing but nitrogen and nitric oxide, which pass off into the atmosphere by a flue (c). Fig. 61. The sulphuric acid which collects at the bottom of the chamber is concentrated by evaporation in shallow leaden pans, till it reaches a sp. gr. of 1720, when it fonns the brown sulphuric acid of commerce. In this state it is largely employed in making manures, and for converting common salt into sodic sulphate. The further concentration must be completed in glass or platinum stills, as the leaden pans would melt at the heat required. In these it is further evaporated till the boiling point has risen to 338° C, and then nothing but the concentrated acid (HaS04) remains. If the application of heat were continued further, the acid would distil over. The oil of vitriol of commerce is a dense oily-looking colourless liquid, without odour, and of sp. gr. 1*842. It is intensely caustic, and chars almost all organic substances, owing to its powerful attraction for moisture. If exposed in a shallow dish to the air for a few days, it increases in weight considerably, by absorbing watery vapour from the air. This pioperty may be made use of for the purpose of drying gases and various other bodies in the laboratory. When Salts of Sulphuric Acid. 151 mixed with water, it gives out great heat, so that much care is required in diluting the acid. Exp. 162. — Pour a little of the strong acid into a test-tube. Place a splinter of wood in it : the wood will be blackened in a few minutes. Exp. 16^. — Pour a cub. centim. of the strong acid into a tube containing 3 or 4 c. c. of water : considerable heat will be felt to attend the mixture. Take a little of this diluted acid, and with a feather dipped into it trace a few letters upon writing- paper. Hold the paper near the fire : the water will evaporate, leaving the acid behind ; this will soon blacken the paper. It is owing to this kind of action that even a very dilute acid, if left upon linen, will cause it to fall into holes when exposed to the air; the water evaporates, and the acid, which is not volatile, destroys the fibre. Tests. — The sulphates, when dissolved in water, may be known by producing a white precipitate when mixed with a solution of a salt of barium, such as baric chloride. This precipitate consists of baric sulphate (BaS04). It is not dissolved by nitric acid. The sulphuric belongs to the class of acids known as dibasic ; that is to say, it contains two atoms of hydrogen, which admit of displacement by a metal ; and, like all acids of this class, it furnishes two sets of salts with metals of which the atom, like the sulphides of the alkali-metals, is chemically equivalent to one atom of hydrogen. Such metals are called monads. In one set of these salts one atom only of hydro- gen is displaced by the metal, in the other set both atoms of hydrogen are so displaced. A salt of the first series is often spoken of as an acid salt ; for instance, they may be thus represented, if the formula of sulphuric acid be written as dihydric sulphate (H2SO4); then — Hydric potassic sulphate, is HKSO4 ; Dipotassic sulphate, or normal sulphate, K1SO4. But there are cases in which a single atom of a metal, like calcium, displaces both atoms of the hydrogen, and then &'■ iS-d Sodic Hyposulphite. but one salt of such metal can be formed. Copper, lead, and barium are metals of this kind. These metals, of which the atom is thus equivalent chemically to two atoms of hydrogen, are called dyads ; so that we write — Baric sulphate Ba"S04 Calcic sulphate Ca''S04 Lead sulphate Ph'^SO^ and so on. The two dashes ("), when used, imply that the metal has supplied the place of two atoms of hydrogen. Lead sulphate is nearly as insoluble as baric sulphate, and strontic sulphate is but little less so. Calcic sulphate is more soluble, though still but slightly so j but most of the other sulphates are freely soluble. The soluble sulphates are often easily formed by dissolving the metal in dilute sulphuric acid ; where this cannot be done, the oxide or the carbonate of the metal may be dissolved in the acid — (i)Zn + H.SO^ = ZnSO^ + H„ (2) CuO + H.SO^ = CUSO4 + H.O ; or (3) MnCOj + H,S04 = MnSO^ + H,0 + CO,. (33) Hyposulphites. — Sodic hyposulphite is a salt which is used extensively by the photographer. This use depends upon the fact that the hyposulphite has the power of dis- solving many of the salts of silver which are insoluble in water. Exp. 164. — ^Add a solution of sodic hyposulphite to some freshly precipitated argentic chloride (p. 276) ; the latter will be completely dissolved owing to the formation, by double decom- position, of argentic sodic hyposulphite roadily soluble in water— Na,S,Oj + AgCl - AgNaS.O, + NaCL Argentic bromide and argentic iodide may also be dis- solved by the hyposulphite, though not so readily. When a photograph is washed in water, the excess of soluble argentic nitrate is washed out, but the chloride of iodide remains in the paper. If now this be plunged into a solution of sodic hyposulphite, the portion of unaltered in- soluble silver salt becomes dissolved in the liquid, while the 1 Sulphuretted Hydrogen. iS3 part which has been blackened by light is unacted on. If the picture is then thoroughly washed in pure water it is fixed \ that is, it becomes no longer liable to change on exposure to light There are several ways of preparing sodic hyposulphite. One of the simplest consists in digesting a solution of sodic sulphite upon flowers of sulphur — NajSOa + S = NajSzOs- A colourless solution is obtained, from which, on evapora- tion, large colourless striated crystals of sodic hyposulphite are easily procured (Na2S203, 5H3O). Many other hypo- sulphites may be obtained, but they are unimportant The acid cannot be isolated, as it immediately begins to undergo decomposition into sulphur and sulphurous acid. Exp. 165. — Add to a solution of sodic hyposulphite a little hydrochloric acid. In a few minutes a pungent smell of sul- phurous acid will be perceived, while the liquid becomes milky from the deposition of sulphur — Na,Sa03 + 2HCI - 2NaCl + H.SOj + S. (34) SuLPHURETfED Hv DROG EN : Synth. H2S ; Atomic and Mol. Wt. 34; Mol. Vol. r"n ; ^P- Gr. 1-1912; Relative Wt. 17. , Exp. 166. — Place 10 or 15 Fig. 62. grams of ferrous sulphide in small lumps in a gas bottle (Fig. 62), and pour upon it about 100 c. c. of diluted sul- phuric acid (i of acid to 6 of water) : an effervescence, with escape of this offensive gas, immediately occurs — H.SO^ + FeS = FeSO^ + H,S. Other sulphides also furnish the gas — sulphide of anti- mony, for example, when heated with hydrochloric acid. This gas is often wanted in the laboratory for the analysis I if I 154 Sulphuretted Hydrogen. of ores, and Fig. 62 shows a convenient mode of arranging the apparatus for liberating it. The small bottle contains a little water, through which the gas bubbles, in order to re- move any particles of acid or of iron salt which may have been splashed over by the effervescence, before it is passed mto the solution for analysis. Sulphuretted hydrogen is colourless and transparent ; it has a disgusting odour of rotten eggs, and is very poisonous if breathed. It is .'oluble in about one-third of its bulk of water, and the soli tion, which has the smell of the gas, is a useful test for certain metals. But if the solution be kept in bottles only partially filled, the oxygen of the air combines with the hydrogen of the compound, water is formed, and the liquid becomes milky from deposited sulphur — 2HaS + 02 = 2H2O -f- S2. Sulphuretted hydrogen burns in the air with a pale bluish flame, furnishing water and sulphurous anhydride. It con- tains its own bulk of hydrogen, and half its volume of the vapour of sulphur — m + [D = EU; the three volumes of the constituents becoming condensed into two volumes, just as, in the analogous case of water, the two volumes of hydrogen and one volume of oxygen furnish two volumes of steam. ^ Sulphuretted hydrogen, though soluble, may be collected over warm water, if the gas be made in a retort or in a flask fitted with a gas tube. Exp. 167. — Fill two small bottles of 250 or 300 c. c. capacity with the gas; prepare a bottle of sulphurous anhydride of similar size ; withdraw the stopper, and close the bottle with a glass plate. Do the same with one of the bottles of sulphuretted hydrogen, and invert the sulphurous anhydride over this bottle. The two gases will immediately, in the presence of the moisture, react on each other ; the oxygen of the sulphurous anhydride uniting with the hydrogen of the sulphuretted hydrogen, while sulphur is deposited. Hydrosulphates. 155 A. little pentathionic acid (H2S5O6) is always formed at the same time — 5H2S + sSOz = 58 + 4H2O + H2S5O6. Chlorine, iodine and bromine also immediately decompose sulphuretted hydrogen, with separation of sulphur. Exp. 168. — Repeat the experiment above described, substita- ting a bottle of chlorine for one of sulphurous anhydride : hydro- chloric acid is formed, and sulphur is deposited — H,S + CI, = 2HCI + S. Sulphuretted hydrogen is often produced spontaneously under various circumstances. Whenever a soluble sulphate of the metal of one of the alkalies or alkaline earths is kept in contact with decaying organic matter, where air does not find free access, the sulphate becomes reduced to the form of sulphide, so that soluble ^ sulphides become formed, the organic matter removing the oxygen and furnishing water and carbonic acid. The deoxidising action on sodic sul- phate is as follows : Na2S04 - 2O2 = NajS. In this way soluble sulphides are formed in certain springs, such as those of Harrogate and Moffat, giving to them their nauseous odour ; since the sulphuretted hydrogen is liberated by the action of even so feeble an acid as the carbonic — NajS + H2O + CO2 = NaaCOs + H^S. Owing to the great tendency of sulphur to unite with metals the hydrogen in sulphuretted hydrogen may be rea- dily replaced by metals forming sulphydrates or sulphides. Thus if the gas be passed into a solution of potash it is quickly absorbed and potassic sulphydrate is produced — KHO + H2S = KHS + H2O. Since, however, potassic sulphydrate and potassic hydrate react to form potassic sulphide and water (KHS -f KHO = KaS + H2O), the solution if only half saturated with sulphuretted hydrogen contains potassic sulphide. ^ I $6 Sulphuretted Hydrogen and the Metals, A solution of ammonia, when saturated with sulphurette;^- Silica. 169 mixture of crystalline and amorphous quartz. Agate consists of a succession of layers of crystalline and amorphous silica. Flint is a form of calcedony chiefly found in the upper chalk ; and opal is a hydrated variety of amorphous silica. Silica, when once crystallised, is insoluble in water, and in all acids except the hydrofluoric. Silica, in fine powder, looks like a \'hite earth, but it has a strong tendency to unite with bases, a property which may be employed to obtain it in a pure fonn. Exp. 182.— Place about 60 grams of a mixture of potassic and sodic carbonates in a clay crucible, and raise it to a red heat; when fused add 15 grams of ground flint or of flne sand to the melted mass : eflervescence is produced slowly, due to the escape of carbonic anhydride, and the silica is gradually dis* solved. When the decomposition is over, pour out the mass on a stone slab, and after it has cooled let it digest in water : most of it will dissolve, with the exception of some impurities, such as oxide of iron. The solution thus obtained consists of a mixture of sili- cates of potash and soda, with a large excess of the alkalies. A smaller proportion of alkali might have been used, but it would have required a stronger heat to melt the silicate, and the product would have been less easily soluble. Exp. 183. — Add gradually to a portion of this solution dilute nydrochloric acid in excess : the mass becomes partly or wholly redissolved, but on evaporating it the silica separates at first as a jelly-like hydrate, and this, by further drying, becomes con- verted into a white earthy-looking powder, no longer soluble in acids. Wash the dry mass with water as long as anything is dissolved; the soluble chlorides may thus readily be removed, leaving silica in a nearly pure state, in the amorphous form. Exp. 184. — Heat some common flints to redness in the fire, and suddenly quench them in water : they become very friable, and are easily reduced to a fine powder. Heat this, add hydro- chloric acid, and wash thoroughly, and the result is nearly pure silica. Exp. 185. — To another portion of the solution of silica in the alkalies a4d hydfochloric acid in excess, so as to redissolve t)t9 r^ mJ V ■ ■'^m ' "I I/O The Silicates. I i whole. Place the clear solution in a shallow tray fonned by tying a piece of parchment paper over a hoop of wood or of gutta percha, lo or 12 cm. in diameter, and float this little vessel in a dish of water. The acid and saline substances are separated by dialysis from the silica, and pass out into the water. If the water in the dish be changed twice a day, the liquid left in the hoop will, in three or four days' time, be found to consist of a solution of pure silica in water, and may be further concentrated by cautious evaporation. In this experiment the parchment paper, or dialyser, retains the colloid, or gelatinous form of silica, while it allows the crystalline and acid particles to pass through its pores into the water on the other side. The solution of silica is tasteless, limpid, and colourless ; but if the evaporation be carried too far, the silica separates in the form of a jelly. ' Finely divided silica may be gradually dissolved by boil- ing it with the alkalies or their carbonates, and even flints in their unground condition may be dissolved in strong solu- tions of caustic alkali if the solution be digested upon them under pressure. The Geysers, or hot springs of Ice- land, contain large quantities of silica dissolved, and as the liquid cools deposit a considerable portion upon objects exposed in the stream. They are then often said to be * petrified,' or converted into stone, the silica being deposited in the interstices, and preserving the appearance of the original structure. (39) Silicates: Glass. — The silicates are very abundant natural productions. Silica combines with bases in several different proportions, and forms a great variety of crystal- lised minerals, many of which are double silicates of complex nature. Glass consists of a mixture of several silicates, which, when heated to a particular temperature, are plastic and viscous, and retain their transparency on cooling. The nature and proportions of the silicates present are made to vary accord- ing to the use to which the glass is to be applied. The degree Varieties of Glass. 171 of fusibility of the silicates varies widely. Fire-clay, or alumina dilicate (AI2O3, 2Si02), is nearly infusible in the furnace, and it is the material of which fire-bricks and crucibles are made. Calcic silicate is also very infusible, whereas the ferrous siUcate (FeO, 2Si02) constitutes the * bull-dog' or fusible slag, of iron refiners. Lead silicat? (2PbO, 3SiOz) is still more fusible, and furnishes a clear yellowish glass. The silicates of potash and soda are also very fusible. All these siUcates, when mixed with each other, melt at much lower temperatures than they do when separate. Many of them, when thus melted, possess the exceptional property of viscosity, between the point of perfect liquidity and solidifi- cation. It is this viscous condition which enables glass to be moulded into the countless forms required for art or luxury. Good glass also has the valuable property of not crystallising as it cools ; in certain cases some of the silicates, however, do crystallise out, and then the glass becomes opaque, and though the separate silicates of which it con- sists are more or less readily attacked by water and acids, if the proportions of the mixture are properly selected, glass formed from these silicates is no longer soluble. The diflferent varieties of glass are not to be regarded as definite compounds, but as mixtures in varying proportions of their component silicates, which, however, in the best kinds generally approach some simple atomic proportions. Much care is requisite in selecting the materials for the finer kinds of glass. Potash is preferred to soda, because the glass made from soda has a bluish green tinge. Soda gives a more fusible glass. The addition of lime increases its hardness and lustre, but diminishes its fusibility. An excess of lime is apt to make it milky-looking. I. Window glass, or crown glass, is made of a mixture of silicates of soda and lime. 100 parts of pure white sand, 35 or 40 of chalk, 30 of soda ash, and from 50 to 150 of broken glass, or cullet^ are the proportions often used. The mixture is heated gradually, to prevent it from frothing up, and is afte^r- ' if*! m^ lijiisr^i- %} I r I i;2 Properties of Glass, wards raised to a very intense heat. Plate glass contains the same materials in different proportions. 2. Bottle glass contains a smaller proportion of silica than either window or plate glass, and is made of much coarser materials. It con- sists of a mixture of silicates of soda, lime, alumina, and iron. 3. Bohemian glass, which is very hard and infusible, is a mixture of silicates of potash and lime. It is used for making the combustion tubes employed in the analysis of or- ganic substances, and hence is much prized in the laboratory. 4. The ordinary white, ox flint glass ^ consists almost entirely of silicates of potassium and lead. The proportions of ma- terials used are — 300 of fine sand, 200 of red lead, 100 of refined pearlash, and about 30 parts of nitre. The oxide of lead renders the glass much heavier and more fusible, giving it a higher refractive and dispersive power upon light, and greater brilliancy, but it makes it softer and more easily tarnished, and it is also liable to be corroded by alkaline solutions. Glass, when meltei, dissolves many of the metallic oxides without losing its transparency, but becomes coloured with tints varying according to the metallic oxide employed. Cobalt gives a splendid sapphire blue, manganese a violet, uranium a yellow, ferrous oxide a green, ferric oxide a yellow or reddish-brown, cupric oxide a green, and cupreous oxide a ruby-red. Well-made glass is not acteH on by any acid or mixture of acids, except the hydrofluoric, which last removes its silica ; but it is not quite insoluble. If left long m water, or buried in moist earth, it becomes slowly decomposed. This is often seen in wine bottles, which exhibit the brilliant colours of thin plates, due to the scaling off from the surface of flakes detached by slow chemical action of moisture. E:^. 186. — Grind a little glass to a fine powder in a mortar ; place it on a piece of moistened turmeric paper : sufficient alkali will be dissolved by the water to tinge the turmcriq brown Compounds of Silicon. m If glass articles are allowed to cool rapidly by exposing them while red hot to the air, they become inconveniently brittle. The outer surface becomes solid, whilst the inner portion remains dilated by the heat : as the mass cools, the particles within, by their adhesion to the external solid por- tion, are still held in their dilated state. A very slight force, such as a scratch on the surface, or the change of tem- perature from a cold room to a warm one, will often cause them to crack. In order to avoid this inconvenience, the glass is annealed, or placed in a chamber heated nearly to redness, where the material is allowed to cool very slowly, by which means the particles are enabled to assume their natural position with regard to each other. Glass, however, is a bad conductor of heat, but dilates considerably when heated, so that even after annealing it is liable to crack when exposed to sudden changes of tem- perature, such as that produced by pouring boiling water into a cold glass, especially if it be thick. . Exp. 187. — Take one of the drops of glass formed by allow- ing melted glass to fall into water, and suddenly nip off the tail : the glass flies to pieces with a kind of explosion, and is reduced almost to powder. Exp. 188. — Grind 3 or 4 grams of fluor spar to fine powder, and mix it with an equal weight of powdered glass or fine sandi Introduce it into a Florence flask previously fitted with a sound cork and a tube bent downwards for delivering gas. Pour upon the mixture about 30 grams of oil of vitriol, insert the cork and tube, and apply a gentle heat : a densely fuming gas is dis- engaged, consisting of silicic fluoride. The change that takos place may be thus represented — 2CaF2 + 2H2SO4 -h SiOz = SiF4 + 2CaS04 + 2H2O. The gas (SiF4) must not be inhaled, as it is very irritating, and produces coughing. When dry, it is colourless and transparent. Water produces a remarkable change in it. ■ Exp. 189.— Pass the gas into a glass of water. Each bubble ae it ribcs becomes coated with a white opaque film, composed of li'li f I, :\ FT"' «i "'I V . m m ^, IMAGE EVALUATION TEST TARGET (MT-3) 1.0 I.I 11.25 Ui|28 12.5 o' m 12.2 t m ■■ 1.4 III 1.6 Photographic Sciences CorpoRtiion 33 WIST MAIN STREiT WnSTIR.N.Y. I4SSC (716) 872-4S03 .\ ^ iP o sN*. <^ <*"* ;\ '^.V^ % I* t74 Boron, hydrated silica, while lite liquid becomes intensely acid, from the formation of a new acid (the hydrofluosilicic), water being de- composed at the same time — 3SiF^ + 2H,0 - SiO. + 2(2HF, SiFJ. It is owing to the strong tendency to the formation of siiidc fluoride that hydrofluoric acid corrodes glass so rapidly. Silicon also forms a compound with chlorine (SiCl4), and wUh bromine (Si6r4), both of which are volatile'^ liquids which arc decomposed by water. A remarkabU gaseous compound \«ith hydrogen (SiH4) is also known. It takes fire as soon ^s it escapes into the air, and may be proaired, mixed with hydrogen, by decomposing a compound of silicon and magnesium by means of hydrochloric acid. Silicon belongs to the group of tetrad elements: it has certain points of resemblaflce with the rare substances titanium and zirconium on. the one hand, and with carbon on the other. All these elements form volatile compounds with four atoms of chlorine (CCI4, SiCl4, TiCl4, ZrCl4) These chlorides are colourless liquids, except zirconic chloride, which is solid. (39 a) Boron: Symb. B; Atom. Wt. 11. This is the characteristic element in boracic acid, which enters into the formation of borax, the sodium salt of this acid. It is an olive-brown powder, which may be obtained by fusing 5 parts of boracic acid with 3 of sodium in a covered iron crucible, previously made red hot, covering the mixture with three parts of common salt, previously fused, and broken into coarse powder. An intense action occurs, and the mass becomes melted. It is to be poured in this red-hot condition into a large and deep vessel containing water acidulated with hydrochloric acid. The boron re- mains undissolved. By fusing it with aluminum, in which metal it is dissolved, boron has also been obtained in crystals, which are transparent, and nearly as hard as ProperUes of Borax. t;$ diamond. This element is remarkable for its power (rf combining directly with nitrogen when heated in the gas, forming a grey powder. When heated with chlorine it bums freely, and combine? with it, furnishing a gas (BCIj)» which is immediately decomposed by water into boracic and hydrochloric acids — aBClj + 4HaO =r :hC1 + aHBO,. Boracic Anhydride {Symb. BaO^) is the only known oxide of boron. It combines with watet, and then forms boracic add, which crystallises in white, pearly-looking scales (HBOa, H,0) J for— BaO, + 3HaO = a(HBOaHaO). The most abundant source of boracic acid is the district called the Maremma, in Tuscany, where it occurs in the un- combined state. It issues in small quantities in the jets of steam called soffioni^ which are produced by volcanic heat These jets are directed into basins formed of brickwork and filled with water, when the steam is condensed, and a weak solution of boracic acid obtained. This solution is con centrated in shallow pans by the heat of the jets of steam themselves, directed beneath them, and the acid is finally crystallised out on cooling. Borax (NaaO, aBaO^, loHaO) is the most important salt of the acid. It is a natural production obtained by the drying up of certain lakes of Thibet, and it has lately been found in California and in some other localities. The crude Indian borax is called tincal. Borax is used as a flux in soldering, as it dissolves most metallic oxides and leaves a clean surface of the metal : it is often added to enamels, for the purpose of rendering them more fusible, and is used by the refiner in melting gold and silver, for making his cru- cibles less porous, arid foi rendering the collection of the metal more easy. Exp. 190. — Bend the end of a piece of thin platinum wire, 8 or 10 cm. iongi into a small hook; heal the wire to redoes^ and 176 Boracie Acid. instantly touch a crystal of borax as lar];e as a split peawHh dM wire : it will adhere to the wire. Then introduce the wire and crystal into the flame of a spirit lamp. The borax will swdl up, become opaque and white, and will then melt into a dear S^sissy bead. Borax dissolves many metallic oxides when melted with them, and hence is often used as a test before the blow- pipe (Fig. 66). Exp, 191. — ^Touch the bead just made with a wire moistened with a solution of cobalt nitrate. Then melt the borax again in the flame. A beautiful blue bead is obtained, which is almost opaque if the quantity of cobalt be considerable. If a scarcely visible fragment of manganese oxide be used, a pur|dish bead is obtained. Boracie add is easily obtained from borax. Exp. 192. — Dissolve 40 grams of borax in about 4 times its weight of boiling water; add to the hot solution ro grams of oil of vitriol, previously mixed with its own bulk of water. Sodic sulphate is formed, and remains in solution, while pearly crystals of boracie acid are deposited as the liquid cools. Pour off" the solution, dry the crystals by pres'^ure between pieces of blotting- paper. Place a few of them on a slip of platinum foil, and heat them in il\e flame of a spirit lamp. Water is driven off*, and the anhydride which U left melts into a clear glass. Exp. 193. — Dissolve a few crystals of the boracie acid in a small dish with a teaspoonful of alcohol Set fire to the spirit: it bums with a green flame, which is a good test for boracie acid. A similar green flame is obtained if a crystal of borax be moistened with sulphuric acid and alcohol added, and kindled as before. This green flame, when seen in the spectroscope, contains a series of peculiar green bands. Boron forms with fluorine a gaseous trifiuoride (BFlj), which is easily obtained by heating boracie anhydride with twice its weight of powdered fluor spar to redness in an itofi tube. Boron belongs to the class of triad elements, but in many properties it resembles silicon more than any other element. ipHIPPlace a sheet of iron or copper wire gaus^ con- taining about ICO meshes in a square centimetre, over the flame of a spirit lamp : the flame will not pass through the gauze, owing to its being cooled down below its inflaming point A piece of coarse gauze containing from 4 to 9 meshes in the sq. centim. %rill not prevent the flame from passing through. Sir H. Davy's safety lamp is merely an oil lamp, enclosed "T^BI > III t\^*'^M"t.m:ll>l'yll^fW #IJ-WI',^ "*• Nature of Flami, i8l within a cylinder of fine wire gauze provided with a double top, and with a crooked wire passing up through the body of the lamp to trim the wick. When such a lamp u intro- duced into an atmosphere containing fire-damp, the flame if seen to enlarge until, when the proportion of marsh gas becomes large, it bums on the inner surface of the cylinder. Whenever this pale enlarged flame is seen, the miner must withdraw; for though no explosion can occur while the gauze is sound, yet the metal at that high temperature becomes corroded, and might easily break into holes, and a single large hole would be sufficient to cause an explosion. Flame is never produced by a burning body, unless that body is converted into vapour before it bums ; charcoal and iron, for instance, are not volatUe, and they do not bum with flame ; but phosphoras, sulphur, and zinc, all of which are volatilised before they take fire, bum with flame. Flame is hollow, and contains unburoed combustible matter within, forming in fact a sort of luminous bubble. Exp, 200. — Support one end of a glass tube, is or 14. cm. long and 6 or 8 mm. in diameter, just above the wick in the flame of a lifted candle. Vapours will pass up the tube, and may be burned at the other end. The light and heat of flames are not proportioned to each other. The oxyhydrogen jet is the hottest flame known, but it gives out scarcely any light If, however, a litde solid matter, such as a piece of lime or Uie stem of a tobacco- pipe, be introduced, the light becomes very intense, although the efliect of these solids is to lower the temperature of the flame. At high temperatures a solid body, when heated, even though it does not bum, gives out light At first the light is dull red; as the heat increases it becomes yellow, then full white, and, when extremely intense, it has a tinge of violet All our common luminous flames contain carbon in the solid state, which, when heated strongly, gives out light Exp. aoi. — Place a cold saucer in a jet of burning coal gas : h is quickly covered with soot Do the same in a candle flame : I83 Structure of Flame. the nueer is blackened. Try the experiment with the scaroely luminous flame of a spirit lamp : no soot is formed. The deposit of soot is occasioned by the decomposition of olefiant gas and marsh gas under the influence of a high temperature ; hydrogen is partially separated from the carbon, and, being more inflammable, bums first, heating the carbon intensely. If the carbon reach the oxygen of the air at this high temperature, it bums away also ; but the cold surface cools it before it enters into combination, and so it is deposited. Exp, 202. — Kindle a common Argand gas-bumer and place a glass chimney over it Observe the strong light it gives out Remove the chimney, blow out the flame, replace the chimney, covering the upper end with a cap of fine wire gauze; then kindle the gas above the gauze. The gas will have become mixed with air; it will burn quietly above the gauze, but will not give out light, nor will it smoke a cold saucer. The air bums the carbon and hydrogen together before they can separate. What is called Bunsen's burner acts upon a similar principle; it con - Fig. 63. F«. 64. 5i3j3 Qf ^ .gj ^f ^ ^^^ Fig- 63), which is sur- rounded by a tube of metal (c)y at the bottom of which are openings for the admis- sion of air {d)i the gas passes up the tube, and becomes mixed with the air which enters at the open- ings near the bottom, and it bums without smoke when kindled at the top. A sufficient supply of gas must be kept up, or else the flame will recede into the tube, and the gas will bum at the bottom. The structure of flame may be examined easily in the flame of a candle. It will be seen to consist of several distinct portions, as shown in Fig. 64. TluBlvwpipt. Its The iUme is maintained by the decomposition of the melted wax or tallow which rises in the wick, where it ii converted into gases by the heat At the lower part of the flame these gases become at once mixed with atmospheric air, no separation of carbon occurs, and they bum with a pale blue light at a. The greater part of the combustible vapours are still unbumed ; they rise above the wick, and form the central dark part of the flame b. Here they are decomposed by the heat produced by the combustion of the parts below. This heat causes the separation (^ solid par> tides of carbon, which become intensely hot, and give out light chiefly in the part marked c. This carbon itself bums away gradually as it rises to the surface of the flame, where it meets with fresh oxygen, and disappears in the form of transparent carbonic anhy- ** ^ dride<£ By directing a jet of air into a flame the combustion may be rendered more active, and may be concentrated into a small space, so as to aflbrd a very high temperature. It is upon this principle that that very useful instmment Uie mouth blow-pipe acts. Fig. 65 shows a convenient form of it If by its means a current of air be directed horizontally across the flame a little above the wick, the flame loses its brilliancy, and is thrown to one side in the form of a beautiful pointed cone (Fig. 66),in which three dis- tinct parts are visible. In the centre is a well-marked blue cone ending at a ; outside this is a whiter and more luminous cone, and again outside this brilliant cone, which ends at h^ is a third pale yellow flame c. The different parts of the flame vary in the effects which they produce ; the blue cone is produced by the complete com bustion <^ part of the vapour in the excess of oi^en supplied by die jet of air to that part of the flame. Beyond this the combustible vapour continually rising from the wick forms the luminous portion, which is veiy hot, and fioiil •d4 Vst of the Blowpif^. iti ooDttining an exceii of combustible matter, ii ready to take oxygen nom any substance which is exposed to it It is called the ndudngjlame. At the outer point of the flame the eftcti are reversed ; atmospheric oxygen is csiried for- Fig. 66. ward by the jet of flame, and becomes heated by it, so that an oxidising action occurs : if a fragment of a metal be ex- posed to the action of this part of the flame, it will be con- verted into oxide. Exp. 203. — Introduce a small piece of common flint glass tube into the reducing flanu^ between a and b (Fig. 66), obtained by blowing gently through a candle flame. The glass will be- come opaque and black, because the lead will be reduced from the transparent form of oxide to the opaque condition of metal When thb has happened, place the black portion just in front of the oxidating flame at c. The discolouration will slowly dis- appear, and the lead will recombine with oxygen from the air, and again become transfMrent In skilful hands the blowpipe enablei the observer to obtain quickly resuks of great valnt. Many compounds, when heated on a piece of charcoal in tho reducing flame, immediately yield up their metallic buii; a^d by the colour of the little bead, and its malleability or britil^ness, it may easily be known what metal is present Sometimes when the body does net yield a metal readily, a platinum wire, d (Fig. 66), bent into a hook at one end, forms a convenient support for the substance, which should not exceed a mustard seed in bulk. It will easily be ascertained whether tfie substance melts \ whetiier it yields a transparent an opaque^ or a coloured bead ; whether it changes the Manufacture of Coal Cos. Its colour of the flame, and whether the effect of the ledndiig dame differs from that of the oxidising dame upon the body onder examinatfon. A little borax or phosphate of sodium and ammonioBi, commonly called microcosmic salt, sometimes assists the examination. When the substance is placed on charcoal sodic carbonate furnishes a flux which is often very useful. Exp, 204.— Select a small stick of charcoal, and with the pmnt of a knife make a small cavity r'* the ^ixe of 9. split pea upon the side near one end. Put a litL;^ white lea(^ \u the cavity, ^r \ heat it before the blowpipe in the redu< -^.g vlame. A little bead of lead will easily Le obtained, surroimcied by a border of yellow lead oxide. The lead will flatten under the hammer. Exp. ^05. — Place in a cavity in another piece of charcoal a small fragment of copper oxide, with about its own bulk of sodic carbonate. The metal will require a stronger heat, but may be reduced in like manner. If the little bead be placed between two folds of paper it may be flattened with the luunmer, and win show the red colour of copper. CW^dx.— Certain )cinds of coal, such as cannel coal and the bituminiferous house coal used in London, when heated, undeigo decomposition, tlieir constituents rearrange them- selves in new fomu, and give out a large quantity of gas, which bums with brilliant jets of flame. If such coal, instead of being allowed to bum in the open fire, is heated out of the air in iron or clay retorts provided with an escape-tube^ a large quantity of gas may be collected, avd may be used for illuminating or heating purposes. This is the common process of making coal gas. The products obtained by heating coal in this manner are very numerous. The solid residue in the retort, after the volatile matters have been driven off, constitutes 'gas coke.' Among the volatile matters are water, along with which condense the sulphide and carbonate of ammonium ; besides this there is a dense Mack offensive viscid liquid, known as coal tar, which is a \ 1^6 Anaiysi' of Coed. \ \ very complex mixture, chiefly consisting ot hydrocarbons and carbolic acid ; some portions of these hydrocarbons supply the material from which aniline, the basis of most of the coal- tar dyes, is procured. The gaseous products are also very numerous ; among them are oletiant gas, and some other gases of greater density, but of a similar character, which furnish the most important illuminating constituents ; marsh gas, hydrogen, and carbonic oxide are also present; but they have little illuminating power. There are also small quantities of sulphuretted hydrogen, carbonic ?\nhydride, cyanogen, and carbon disulphide, all of which it is the object of the gas-maker to remove. This is done by pass- ing the gas over hydrated ferric oxide and slaked lime ; the iron oxide removes the sulphuretted hydrogen and cyanogen, while the carbonic anhydride is stopped by the lime. The gas, when thus purified, is washed with water to get lid of small quantities of ammonia and is afterwards stored up in vast iron reservoirs or gas-holders, from which it is dis- tributed for consumption. The removal of the sulphur compounds is especially neces- sary; because, when burned, they furnish sulphurous and sulphuric acids, which are very injurious to furniture, books, and paintings exposed to their action. The other materials furnish only water and carbonic anhydride, when burned with a sufficient supply of air. Coal gas has a peculiar offensive odour, due in part to a compound of carbon and hydrogen called acetylene (C2H2). If coal gas escape into the atmosphere, it forms nn explosive mixture. Hence, if a smell of gas be perceived in a room, no light must be admitted ; the supply of gas should be at once shut off from the main, and the doors and windows thrown open to ventilate the house or the room. After- wards the cause of the escape may be sought Exp, 206. — Place 15 or 20 grams of coal in small fragments in a tube of Bohemian glass, a (Fig. 67), 18 or 20'Centimetret long, and sealed at one end ; to the other end fit a good cork, Destructive Distittation of Coal, i«7 through which passes a quill tube bent at a right angle, and fitted into a phial ip). In one limb of the bent tube {c) place a piece of reddened htmus paper; in the other {d\ a piece of filtering-paper moistened with a solution of lead acetate. Place a little limewater in the test-tube ^, and collect the gas which comes over in a gas jar (/) provided with a stop-cock. Heat the tube a gradually by placing it in a tray of coarse wire gauze, and surrounding it with lighted charcoal ; let it rise to Fig. 67. dull redness. Tar will become condensed, mixed with water in by the red litmus in c will become blue from the ammonia, the lead salt will be blackened by the sulphuretted hydrogen, the lime- water rendered milky by the carbonic acid, while an inflammable gas Will be collected in the jar, and may be burned by transferring the jar to the deep part of the trough, depressing it in the water, and lighting the gas as it escapes on gradually opening the stop- cock. Coke will be left in the glass tube. Exp, 207. — Hold a cold wide glass tube, of a metre or more in length, over a jet of burning coal gas : moisture will speedily become condensed on the cold sides of the tube, owing to the formation of water by the burning of the hydrogen. Exp. 208. — Pour a little limewater into the tube, having closed one end with the hand after withdrawing it from the flame : the Umewater will become turbid by 'bsorbing carbonic acid. A single jet of coal gas, consuming about 136 litres (5 cubic feet) of gas per hour, will produce nearly a quarter of a litre of water as it bums. i88 Cyanogen. (41) Cyanogen: Symb. Cn Chemicai £quiv pound, expand equally for an equal rise of temperature, if both are compared under equal pressures, and at the same temperatures. It is also true that all gases and vapours expand or contract equally when equal volumes of the different gases are submitted, at the same temperatures, to an equal diminution or increase of pressure. Hence it Atomic Weights. 19$ appean to be a necessary conclusion that equal volumes of all gases contain an equal number of molecules, whether those molecules be simple or compound. Further, the molecules of the same substance are all absolutely similar to each other in size, weight, and chemical properties, if com- pared under similar circumstances. The term molecular volume is used to signify the space occupied by a molecule of the body in the form of gas or vapour, compared with that of the atom of hydrogen, or the atomic volume of hydrogen. Now the volu me of t he molecule of a compound body in the aeriform state \ \ J is exactly double the volume of the atom of hydrogen |h]. The atom is defined to be the smallest and chemically fndivisible particle of each element which can exist in a compound, united with other particles, either of the same or of different elements, but which is not known in a separate form ; and the molecule of an element is defined to be the smallest quantity of that elementary substance supposed to be capable of existing in a separate form. If H, for instance, represent the atom of hydrogen, Hx will represent its mole- cule. Each molecule of chlorine and of the other allied elements when in the gaseous state appear, for reasons to be explained immediately, to consist of two atoms. When a molecule of hydrogen is made to react chemically upon a molecule of chlorine, two molecules of hydrochloric acid are formed, the half molecule of hydrogen exchanging places with the half molecule of chlorine — |h!h1 + ICIQI becoming IHCTJ + IhctI . It will be desirable to develop these considerations a little more fully. The number adopted for the atomic weight of any element is based upon a careful chemical analysis of several compounds of that element. Suppose, for example, the atomic weight of copper to be the subject of experiment, and that a quantity of the pure oxide of the metal has been prepared, and a portion carefully weighed, and heated in o a < <■ * . J.I T96 DetermitMtion of Atomic Weights, a stream of pure hydrogen gas. The hydrogen gradually removes all the oxygen in the form of steam, leaving nothing but pure copper behind. On weighing this copper, the quantity of oxygen originally combined with it in the oxide is ascertained by the loss of weight experienced. Then the relative proportions between the combining proportion of copper and oxygen, referred to hydrogen as the unit, can be easily calculated. But this determination would not be sufficient to settle die atomic weight if taken alone, even if other analyses of this same oxide and of other compounds of copper gave results which showed that the experiments had been made with exactness. It is necessary also to know the number of atoms in the molecule of the different compounds of the substances analysed ; whether, for instance, the number of atoms of copper in the molecule of its oxide be one of copper to one of oxygen, two of copper to one of oxygen, or two of oxygen to one of copper, two of copper to three of oxygen, or any other proportion. In the case of solid bodies, not convertible easily into vapour, this determination is often attended with difficulty and uncertainty. There are, however, various considerations by which this conclusion may be arrived at with more or less probability. One of the best methods consists in comparing together all the com* pounds of the element under examination, for the purpose of finding out the smallest proportion in which that element enters into any compound molecule, for this must repre* sent its atom, by the definition of tlie word which we have adopted. In cases where bodies can be converted into vapour, this task is much facilitated by that very circumstance. For example, a large number of compounds of hydrogen have been analysed. Most of them may be obtained in the form of gas or vapour ; in which case their specific gravities in the aeriform condition may be ascertained by experiment From these specific gravities the relative weights, or weights corn* Atomic and Melccnlar Weights. "97 pared with that of an equal bulk of hydrogen, and the molecular weights are at once easily obtained. Some of the more important of these compounds have been already described, and they are mentioned in the following list : — Conipoundf of Hydrogen Molecular Volume Weishu referred to Hydrogen Weights of Hyorogea inMolecuk Hydrochloric Acid Hydiobromic Acid 1 Hydrogen Gas . Water .... Sulphuretted Hydrogen Ammonia .... Phosphuretted Hydrogen defiant Gas . . . Marsh Gas .... LLI 365 810 2'0 180 340 170 340 280 i6-o I I 3 a 2 3 3 4 Now if the molecule of hydrogen weigh 2, the smallest weight of hydrogen which is contained in an equal volume of vapour of any of the compounds of hydrogen in this list, and it may be added in any others that are known, is half that amount, or i. Hence chemists have concluded that this quantity of hydrogen is the smallest that can enter into combination, or, according to the supposition with which we began, that it is to be regarded as the atom of hydrogen. Now hydrogen has the smallest combining number of any element known, so that it has been found convenient to take the hydrogen number as i, or the unit of the scale with which the atomic weights of all the other elements are com- pared, as has been done in the table given at page 1^8 ; so 19^ The Metals. that supposing the weight of the atom of hydrogen to Tie known, the atomic weight of any other element would be the number which represents how many times this atom is heavier than the atom of hydrogen. The following table contains a list of such of the elemen- tary bodies as have been converted into vapour in such a manner as to admit of determining their specific gravity in that form, and thus of ascertaining the number of atoms in the molecule, on the supposition that equal volumes of every gas or vapour contain an equal number of molecules : — Eleownt Atomic WeighU Weights of eqvial Volumes of Vapour Atoms in I Molecule Specific Gravity of Vapour Observed Cadmkun Zinc . Mercury Hydro^n Chlorine ! Bromine 1 Iodine . Oxyeea. Sulphur. Selenium Tellurium Nitrogen Phosphorus . Arsenicum . 112 65 aoo 127 i6 3* 795 129 14 31 75 56 3*5 100 b 3* 795 129 14 62 150 I I I a 2 2 % a a a a a 4 4 394 6*976 0-0692 2-47 1*1056 ?s 900 0-9713 4*42 10-60 38690 6*9101 0*0691 a'453i §•5281 8*7560 1*1056 2*2168 $4680 8*9130 09674 4*2840 10*1670 CHAPTER XI. A THE METALS. (43) JTu Metals in General. — There is no absolute dis- tinction between the non-metals and the metals, but the •ubdivision is practically convenient, and it is usual to con- fide a body which has a high lustre, great opacity, and 19 ft Ai . MelHftfr Points of Metals 199 good- conductor of heat and electricity, m a metal But on the one hand, graphite, although it has all these properties, is not reckoned amongst the metals ; and on the other, arsenicum and tellurium, though possessing them, are by some chemists considered as non-metals. The metals differ very much in chemical p roperties ; some, like potassium and sodium, have an intense attraction for oxygen, whilst others, like gold and silver, have but a feeble attraction for it As a rule, the lighter metals are those which are most easily oxidized. In the following table the lightest metals are placed first. The metals exhibit a very great variation in density. Three of them are light enough to float in water, and lithium is lighter than any known liquid, while platinum is the heaviest of all known •ubstances. Specific Gravities and Fusing Points op Metal& Specific Gravity Fulng Point Uravii^ Fimng Point Lithium . OS93 0865 180O Molybdenum . 8-63 Potassium . 62-5 97-6 Nickel . 883 Sodium . 0972 Copper Cobalt 8-95 1090" Rubidium . 152 385 8-95 Calcium . 1-573 Bismuth . 980 364 Magnesium 1743 Silver IO-53 11-30 IOS3 Glucinium . 2-1 Lend 335 Strontium . 254 Ruthenium 1 1-8 Aluminum 267 Palladium Arsenicum 595 Thallium 1 1-9 394 TeUuiium . > 625 Rhodium I3'I Antimony . 671 6-8i 450 Mercury 13596 -39 Chromium Tungsten 17-6 Zinc. 715 413 Uranium 184 Tin . 729 228 Gold. 19-34 II03 Iron . 784 Iridium 21*15 Manganese 8-OI Osmiam 31*4 Cadmium . . 869 228 Platinum . 31*53 The melting points of the metals also vary very widely. In die table the melting points of all the metals, so far as they have been ascertained, are given. M^cury is liquid at all O^F 900 Properties of the Metals, ordinary temperatures ; potassium and sodium melt beneath the boiling point of water. Zinc melts below, and copper above, a red heat j silver, gold, and copper require a very bright red heat to fuse them. Cast iron melts at about 1500°, and wrought iron not lower than 1800° C. Cobalt, nickel, and wrought iron require the strongest heat of the forge to melt them. Molybdenum, chromium, tungsten, and palladium do not completely melt even at this tempera< ture ; and platinum, rhodium, iridium, vanadium, ruthenium, And osmium cannot be melted but in the heat of the oxy- hydrogen blowpipe, or that of the voltaic arc. Some few of the metals may be converted into vapout readily, and are ordinarily purified by distillation. Mer- cury, arsenicum, tellurium, cadmium, zinc, magnesium, potas- sium, sodium, and rubidium are thus purified. Mercury boils at 350" C. Arsenicum is volatilised below icdness. Cadmium requires a full red heat (860**), at which point it boils, and may be distilled ; and the boiling point of zinc, though as high as 1040'', is equally fixed. Potassium, sodium, magnesium, and rubidium require a still higher temperature, which has not been measured. Many of the other metals, including silver and gold, may be volatilised by the intense heat of the sun's rays when brought to a focus by a very large convex lens. Several of the metals when rubbed give out a character- istic odour, as is the case with iron, tin, and copper. Arse- nicum, when volatilised, emits a strong odour of garlic. The taste of many of the soluble salts of the metals is astringent or acrid, and of the peculiar kind termed metallic. The most usual colour exhibited by the metals is a white, of varying shades. It is nearly pure in silver, platinum, cadmium, and magnesium; yellowish in tin ; bluish in zinc and lead ; grey in iron and arsenicum ; and is reddish in bismuth. Calcium is pale yellow, gold fuU yellow; ftnd copper is red. alt, Metallic Alloys. 20I Many of fhe metals show the properties of fnalleabilityt or the power of being flattened under the hammer. They may also be extended into ribbon or foil, by passing them be- tween steel rollers : among these are gold, silver, platinum, palladium, copper, iron, aluminum, tin, lead, zinc, and thallium. Gold is the most malleable of the metals, but silver and copper may also be hammered into very thin leaves. The same metals are likewise dttctiU; that is, they admit of being drawn into wire, often finer than a hair, by drawing them through holes in a hard steel plate, termed a draw-plate j the holes through which the wire is made to pass being successively smaller and smaller. On the other hand, there are metals so brittle that they may bo powdered without difficulty: such are arsenicum, antimony, and bismuth. These metals have a crystallme structure, and are very hard. Metals which have a fibroui texture, like bar iron, are, on the contrary, very tough. When the metals are combined with each other, the resulting substance is called an alloy. Many of these, such as brass, German silver, bronze, and pewter, are used largely in the arts, on account of advantages which they offer over their constituent metals in increased hardness and elasticity, as well as increased fusibility. Brass is a hard, somewhat fusible alloy, consisting of about two-thirds of copper and one-third of zinc. If brass be melted with about a fifth of its weight of nickel, it furnishes German silver. Bronze is an alloy of tin and copper, of which there are several varieties : with 10 per cent, of tin it forms the tough gun-metal ; with 20 per cent, of tin it furnishes the sonorous, elastic bell- metal ; and with 33 per cent of tin the hard, white, brittle metal used for the mirrors of telescopes. The white metal used in types for printing is an alloy of a1)0ut I part of antimony, i of tin, and 2 of lead ; it is fusible, expands on becoming solid, so as to fill the mould, and is hard enough to bear pressure, but will not cut the paper. All the alloys pielt at a lower temperature tbMi t ii fa il 202 Native Metals. that which would he the mean of the fusing points of their components. Exp. 211. — Heat in a small iron ladle 20 grams of lead ; as soon as it is melted add 40 grams of bismuth and 10 of tin ; they will fuse quickly, and an alloy will be thus obtained known as fusible metal; it melts when thrown into boiling water, although tin, the most fusible of its components, does not melt below 228'» C. A combination of a metal with mercury forms an amalgam. Some amalgams are soft and semi-solid ; others are brittle and crystalline. Alloys and amalgams appear to consist of definite compounds, which are often mixed with, or dissolved by, an excess of one of the metals employed ; for the pro- portion of the metals used in an alloy can be varied within any limits. Some few of the metals are found in the native^ or uncom- bined, state in the earth. Among these the most important are gold, silver, platinum and a few rare metals which accompany it, mercury, bismuth, and copper. More usually the metals occur united with sulphur, when they preserve their metallic brilliancy, but not their ductility or tenacity. Lead, antimony, mercury, copper, iron, and zinc are often, and some of them almost always, found in the condition of sulphides. Other metals — such, for instance, as tin, iron, manganese, and chromium — are met with as oxides, under the aspect of dull blackish or earthy bodies. The metals of the earths, and of the alkalies, are generally found in the form of salts, such as sulphates, carbonates, silicates, or chlorides. Further particulars respecting the ores of the metals, their distribution over the surface of the earth, the formation of mineral veins^ and the methods employed for extracting the metals for use in the arts, will be found in the text-book on •Metallurgy.' (44) Classification of the Metals. — ^The metals may be divided into 10 groups, founded upon their different degrees of attraction for oxygen, and the properties of the oxides n^hich the^ form* Classification of the Metals. 203 Group 1 : 5 Metals of the Alkalies, viz. i. Csesium ; 2, Rubidium; 3. Potassium ; 4. Sodium; and 5. Lithium, with which it is convenient to arrange the salts of ammonium, although it is not a simple body. — These metals are monads, and displace i atom of hydrogen from the radicals of the acids. They are soft, easily fusible, and volatile at high temperatures. They have an intense attraction for oxygen, and become tarnished as soon as they are exposed to the air. They decompose water instantly at all temperatures, with rapid disengagement of hydrogen, and form a soluble, powerfully caustic and alkaline compound, which may be regarded as water in which half the hydrogen is replaced by metal. They form but one set of salts with the halogens. Though they furnish but a single chloride, they yield several sulphides, all of which are soluble. When exposed to the air their oxides absorb carbonic acid greedily, and foim soluble carbonates. Only two of them, potassium and sodium, are sufficiently abundant to require description. Caesium and rubidium are of quite recent discovery, and were found in minute quantity in the water of a mineral spring, of which the saline residue was submitted to exami- nation by the method of spectrum analysis, lately discovered, and they have since been found in minute quantity in the ash of various plants, and in some crystallised minerals. Group 3 : 3 Metals of the Alkaline Earths, viz. x. Ba- rium ; 2. Strontium ; and 3. Calcium. — ^These are dyads ; they displace two atoms of hydrogen from the radicals of the acids. When thrown into water they decompose it with avidity, and set hydrogen free. They form powerfully basic oxides, which are soluble in water, though lime is only sparingly so. These oxides absorb carbonic acid rapidly, and form carbonates which are insoluble in water, but some- what soluble in a solution of carbonic acid. Their phos- phates are insoluble in water. Group 3 : Metals of the Earths. — ^The only one of prac- ^cfil importance is i. Aluminum ; biit a. Qliicinium ; ^ 'm 904 Classification of the Metals, I Yttrium ; 4. Erbium ; 5. Cerium ; 6. Lanthanium ; and 7. Didymium, are commonly included in this division. The last six are, however, very rarely met with, and their pro- perties are only imperfectly known. Aluminum is a triad : it forms but one oxide ; this i& insoluble Ai water, and is but feebly basic. Group 4 : 4 Magnesian Metals, viz. i. Magnesium ; a. Zinc ; 3. Cadmium ; 4. Indium. — These metals are dyads ; they form but a single oxide, which is insoluble in water. They decompose steam at a red heat, but are without action on water at common temperatures. They form a single soluble chloride, and a single nearly insoluble sulphide. Group 5: 6 Metals allied to Iron, viz. i. Cobalt; a. Nickel ; 3. Uranium ; 4. Iron ; 5. Chromium ; and 6. Man- ganese. — ^These metals are remarkable as forming two sets of compounds, in one of which the metal is dyad, in the other triad. They furnish several oxides : those which con- tain least oxygen are basic and insoluble; those which contain most are often soluble, and are then distinctly acid. Several of these metals are magnetic ; they are oxidized by passing steam over them when heated to redness, though they do not decompose water at ordinary temperatures. Group 6 : 4 Metals allied to Tin, viz. i. Titanium ; a. Tin ; 3. Zirconium ; and 4. Thorinum. — They are all tetrad, or equivalent to 4 atoms of hydrogen. Tin is the only one of practical importance : it furnishes two oxides, both capable of acting as bases ; but the higher oxide is more often acid. Group 7 : a Metals, Molybdenum and Tungsten, which are hexad, or equivcolent to 6 atoms of hydrogen. — ^They yield trioxides, which furnish metallic acids; but we shall not enter into any description of them. Group 8 : 6 Metals. They present in their combinations an analogy with phosphorus, viz. i. Niobium; a. Tantalum; 3. Vanadium ; 4. Arsenicum ; 5. Antimony ; and 6. Bismuth. —They furnish at least two oxj^es, We shal] not enter further Metals of the Alkalies. 105 into any description of the first three of these metals, but the last are of practical importance. Group 9 : 3 Metals, viz. i. Copper ; a. Lead ; and 3. Tliallium, which are not closely related. Group 10 ■ 9 noble Metals, viz. i. Mercury; 2. Silver; 3. Gold ; 4. Platinum, vrith which are associated 5 other rare metals, viz. 5. Palladium; 6. Rhodium; 7. Ruthenium; & Osmium ; and 9. Iridium, which we need not further notice. — The first four metals form more than one oxide, but have so slight a tendency to union with oxygen that their oxides are decomposed by exposure to a heat below redness. All the metals of this group are commonly found in the native state ; but mercury anu silver also occur as sulphides. Their attrac- tions both, for chlorine and for sulphur are much stronger than for oxygen. Each forms more than one chloride; their compounds have a tendency to combine with the chlorides of the alkali-metals to form double salts. Group I. — Metals of the Alkalies. I. Potassium. 2. Sodium. 3. Lithium. 4. Cmsivu, 5. Rubidium.— (Ammonium). (45) Potassium : Symb. K ; Atom. IVt 39 ; Sp. Gr. 0*865 » Fusing Pt. 62-5^ This metal was originally obtained by decomposing a fragment of caustic potash by means of a powerfiil voltaic battery, when globules of potassium were separated at the negative wire. It is now prepared by distilling potassic carbonate mixed with charcoal, at an intense heat, in iron botdes, and condensing the green vapours of potassium in receivers containing naphtha, carbonic oxide being dis- engaged during the process — KjCOa + 2C = Ka + 3CO. This is a difficult and dangerous operation. Potassium vapour takes fire instantly in the air or on contact with water ; it also absorbs carbonic oxide, and the compound thus formed, if kept, gradually becomes changed into a black, powerfidly 206 Potassium Oxides and Hydrate. explosive compound. To avoid this danger potassium if always redistilled, immediately after its preparation, in a small iron retort containing naphtha vapour. Potassium is a brilliant silver-white metal, soft enough to be spread with a knife. It tarnishes immediately that it is exposed to the air, and decomposes water, evolving hydro- gen as soon as it is thrown into the liquid. (Exp. 30.) The gas takes fire from the heat produced by the action. It is necessary to preserve the metal either in vessels dosed so as to prevent access of air, or under some liquid, such as naphtha, which contains no oxygen. It combines imme- diately with chlorine, bromine, iodine, and sulphur, if heated with them. Potassium furnishes an important basic oxide (KxO)i potash ; besides this, there are two other oxides (KxOa and K2O4), which, when thrown into water, give oflF oxygen, and furnish a solution of potash. The anhydrous potash -is difficult to obtain pure, and is seldom prepsired ; but its hydrate is a very important substance, and is known as caustic potash, or potassic hydrate (KHO). This, when dissolved in water, furnishes potash ley. It is prepared by mixing a solution of potassic carbonate with slaked lime — KaCOa -t- CaO, H^O = 2KHO -|- CaCO,. If the solution is poured off from the calcic carbonate and evaporated down in a silver dish, an intensely caustic solid substance is left, which fuses at a red heat, and may be cast into metallic moulds. It furnishes the hydrate of potash. This substance absorbs both moisture and carbonic acid from the air. Caustic potash, if fused in glass or porcelain dishes, coirodes and dissolves them. It also attacks platinum vessels, but has little action on silver. It is very soluble both in water and in alcohol. The solution decomposes the fats and oils, and converts them into soluble soaps. Ordinary soft soap contains potash as its base. Caustic potash is also a valuable agent in the laboratory, where it is used for the Salts of Potassium, 20; purpose of absorbing acid gases, such as the carbonic In consequence of its powerful attraction for acids, it readily decomposes the salts of all metals which form oxides in- soluble in water, and it precipitates the oxide of the metal in the form of hydrate, while the radical of the acid forms a potassic salt, which remains in solution; such a salt, for example, as the cupric sulphate is decomposed as follows : — CUSO4 + 2KHO =» K,S04 + CuO, H,0. Potash is found in all fertile soils, generally in the clay derived from the felspar, which, after crumbling down, has become mingled with other substances. Growing plants require potash to aid in forming their tissues* The alkaline salt is dissolved by the rain-water from the soil, absorbed by the roots, and carried by the circulation of the sap into the plant, where it becomes combined with the radical of some vegetable acid. \v^hen the plant is burned the salt of the vegetable acid is decomposed, and the potassium remains in the ash, chiefly in the form of carbonate. The more soluble portions of this ash are washed out by the action of water, which when evaporated leaves the potassic carbonate, ox potash^ of commerce, which is imported largely from North America and Russia. Pearlash is the first pro- duce, refined by a second solution in a very small quantity of water, and evaporation to dryness. Potassic chloride has also been found native, in consider- able amount, in the salt beds of Stassfurth, near Magdeburg ; and it is present in sea water in quantitv sufficient to render this a very important source of supply. Potassium forms five sulphides : K2S. K2S2, KaS3, YiS^ and K2S5. They are all soluble, and have a strongly alkaline reaction. When mixed with an acid, they all give off sul* phuretted hydrogen, and also, except in the case of KaS, deposit sulphur. Potassic Carbonate (K2CO3) is a very soluble salt, which, \f exposed to the air, attracts moisture from it, and soon do8 Nitre or Saltpetre. becomes liquid. It is strongly alkaline, and restores the blue colour of red litmus paper. Exp, 212. — Bum some dry brushwood; collect the ash, and frash it with five or six times its bulk of water. Filter off from the undissolved subsUmces. Test the solution with a piece of reddened litmus paper, which will at once become blue. Eva- porate the solution to dryness in a small porcelain dish. If the dry mass be left exposed to the air for a few hours it will become moist The potassic carbonate, of which it chiefly consists, attracts moisture rapidly and deliquesces. To a portion of the salt add a few drops of hydrochloric acid : brisk effervescence occurs. Exp, 213. — Place 30 grams of pearlash in a half-litre bottle, and dissolve it m 250 c c of water. Shake 20 grams of quick- lime with five or six times its bulk of boiling water, and add the pasty mixture (about 120 c c in bulk) to the solution of pearl- ash. Agitate the mixture, and let it stand till it is clear. Pour off a portion of the liquid : it is a solution of caustic potash. Add to it some hydrochloric acid : no effervescence will occur. Agitate a tablespoonful of olive oil in a small phial with 3 or 4 c c of the caustic solution diluted with ten times its bulk of water : a milky-looking liquid will be formed, which is the first stage in the making of soap. Potassic Hydric Carbonate (KHCO3). — If a current of carbonic acid gas be passed through a strong solution of potassic carbonate, it is quickly absorbed, and crystals of a less soluble salt, often called the bicarbonate^ are formed — KaCO, + COa + H,0 = 2KHCO3. Potassic Nitrate (KNO3). — Another important salt, usually called nitre or saltpetre^ is found on the surface of the soil in some parts of tropical India. It is also obtained in temperate climates by allowing animal matter mixed with lime rubbish to decay in heaps, which are moistened from time to time, and from which the nitre is at intervals removed by washing. The nitrogen in the animal refuse becomes slowly oxidized into nitric acid, and this combines with the lime and potash preseiTt Gunpowder, ao9 Nitre has a cooling saline taste, and is soluble in about 3^ times its weight of cold water. Ejcp. 214. — Dissolve 150 grams of nitre in a quarter of a litre of boiling water, and allow it to cool slowly : six-sided prisms of nitre will crystallise from the liquid. Exp. 215. — Mix a portion of the solution with three or four times its bulk of water, and dip some strips of filtering-paper into the liquid. When dry the paper, called touch paper^ will smoulder if kindled. Exp. 216. — ^Throw a little nitre into a clear fire : the embers will bum with brilliant sparks. Exp. 217. — Put a few dry crystals of nitre into a test-tube^ and heat them over a lamp : they will melt to a clear liquid. Heat them more strongly : they vrill be decomposed, gas wiU escape, which will rekindl* a glowing match, and which at first consists of pure oxygen, potnssic nitrite being formed — 2KNO, - 2KNO, + O,. The principal use of nitre depends upon this readiness to part with oxygen, of which it contains nearly 48 per cent, and which enables it to add great intensity to combustion. Gunpowder is a mechanical mixture of about 75 parts of nitre, 15 of charcoal, and 10 of sulphur; the quantities of the ingredients used being nearly in the proportions of i atom of sulphur, 2 of nitre, and 3 of charcoal. An excess of sulphur is to be avoided, as it corrodes the gun. The application of a spark, or even of a temperature of about 350'' C, produces an instantaneous decomposition of the mixture, attended with an immense production of gas (chiefly carbonic anhydride and nitrogen) at a very high temperature, so that the gases at the moment of firing become expanded to at least 1500 times the bulk of the gunpowder. The chemical change is sometimes roughly represented as follows : — S -I- sC H- 2KNO3 = 3C0a + Na -f. KaS; though it is really much more complex. Gunpowder thus contains within itself the oxygen necessary to enable it to bum in a space excluded from ainor even underwater; die p ^ "i •^f??f "mi 310 Sodium and its Compounds. oxygen fonning either carbonic oxide or carbonic anhydride, while nitrogen is set free, and the sulphur r^'.nains combined with the potassium. (46) 2. Sodium: Symb. Na; Atomic Wt. 33; 1^. Gr» 0*972 ; Fusittg Pt. 97*6*'. Sodium much resembles potassium. It is obtained from its carbonate, by heating it with charcoal, in a similar way to that followed with potassium, hut it is more easily managed. It is made in laige quantities as a preparatory process in the extraction of aluminum and magnesium. Sodium gives off a colourless vapour, which bums with a bright yellow flame. When thrown into water it rises to the surface, and disengages hydrogen freely ; but the gas does not generally take fire unless the water is heated first, or is small in quantity. Common salt, sodic chloride (NaCl), is the great source from which all compounds of sodium are obtained. This is met with in large quantities in sea water, which contains more than a quarter of a pound in a gallon, or about 27 parts in 1000. It is also found in extensive deposits in Cheshire, and still more abundantly in the mines of Wielitzka, in Poland. Sodium is also found in Atacama as nitrate, and in many rocks and minerals, as, for instance, in soda felspar or albite, and in cryolite (sNaF, AIF3), a fluoride of sodium and aluminum. Sodium forms two oxides, NaaO and NaaOa. The first is the only one of importance. It is the base from which the salts of sodium are derived, but is seldom obtained in a pure state. Caustic Soda^ or sodic hydrate (NaHO), is a white solid, very soluble in water. Caustic soda is formed on a large scale in the alkali works, but it is easily prepared by treating a solution of sodic carbonate with slaked lime, in a manner ■imilar to that directed for obtaining caustic potash, which it "^m Sodium Salts. 2ZI closely resembles. Soda ley, or the solution of this hydrate in water, is largely used in the manufacture of ordinary hard soaps. Sodu Chloride^ or common sea salt (NaCl), is oflen ob- tained from sea water, by allowing it to flow into very shallow pools^-constructed for the purpose, and called saltpans, or salterns — where the water evaporates, and becomes concen- trated in the heat of the sun. The salt crystallises out in cubes, and forms the bay salt of commerce. The mother liquor, or bittern, retains salts of potassium and magnesium^ which are extracted ; and it also furnishes the principal source of bromine. In some inland countries brine springs furnish important sources of supply of this chloride. Vast beds of rock sait also occur in several countries, as in Galicia, Canada, Spain, and in several parts of the British Islands, especially in Cheshire. It is a common practice where coal is cheap to allow water to flow down into the bed of salt, and to pump up the liquor when it has become saturated. The brine is then boiled down and crystallised. Our common table salt is obtained m this way. Sodic chloride in small quantities is essential to life. It is soluble in less than three times its weight of water. When heated suddenly it decrepitates, and may be melted at a bright red heat. Fish and meat are often salted to preserve them from putrefaction j but when so prepared they are much less nutritious than when fresh, as the salt extracts the nutritive and flavouring juices, which become saturated with it and form brine. Salt is used largely as a manure to land. It is consumed in immense quantities in the alkali works for preparing other compounds of sodium j and it furnishes the supply of chlorine and hydrocnlonc acid. Sodic Sulphate (Na2S04, loHaO) was fonnerly known as Glauber's salt It crystallises in four-sided prisms, which crumble down to a white powder, and lose their water when exposed to the air. It is very soluble in water, but more so at 33' C. than either at a higher or lower temperature. Salt p 2 !'-"'nrf ■^.,.)/" ■ ',. ■■"(5! '0i \ mmm^r^ WHiVMPipMPPffpiV* ai3 Sodic Carbonate. take is the name given to the sulpliate when prepared by decomposing common salt in a furnace with sulphuric acid, at a high temperature, as a preliminary in the manufacture of soda ash. Immense volumes of hydrochloric acid gas are then given off, and these are condensed by causing the fumes to pass through large towers filled with broken coke or stone, over which a strttim of water is kept con- stantly trickling. A solution of hydrochloric acid is thus obtained, while the sodic sulphate is left in the furnace. The decomposition occurs in two stages ; in the first, one half only of the salt is decomposed, hydric sodic sulphate being formed, and the first half of the hydrochloric acid comes off easily. The expulsion of the last half of the acid requires a higher temperature, and* is driven off by the action of the fusible hydric sodic sulphate on the other half of the sodic chloride — (1) NaCl + H,S04 - HCl + NaHSO^; and (2) NaCl + NaHS04 - HCl + Na,S04. Sodic Carbonate (NaaCOj, loHjO). — This salt crystallises in large transparent prisms, which effloresce in the air. It has a soapy disagreeable taste, and restores the blue colour to reddened litmus paper. It is very soluble in water ; and when heated melts in it^ water of crystallisation, which amounts to 63 per cent of the >alt. The dried residue melts at a bright red heat The cay salt is made in enomous quan- tities, and sold as soda-ash^ which is used in the manufacture of glass, in soap-making, in cleansing calicoes, and for a variety of other important purposes. In order to prepare this carbo- nate, salt cake is mixed with about its own weight of chalk and rather more than half its weight of coal dust. This material is then thrown in charges of about 125 kilog. upon the floor of a hot reverberatory furnace (Fig. 69), divided into two beds : on the more distant bed (b) it is first heated, and then thrust on to the bed a, nearest the fire (c). There it melts, and gives off jets of gas, which take fire, and bum with a yellow flame. As soon as this escape of gas ceases, the Manufacture of Soda, 213 mixture is mked out into an iron trough, the next charge is pushed dtv/n to the lower bed, and a fresh charge is in- troduced. The chemical change which occurs in this fusion Fig. 69. consbts mainly : ist, in reducing the sodic sulphate to sul- phide, while carbonic oxide is formed and escapes, taking fire, and becoming converted into carbonic anhydride — NaaS04 + 4C = NaaS H- 4CO. 2nd. The sodic sulphide is immediately decomposed by the chalk into calcic sulphide and sodic carbonate-* NaaS + CaCOa = NaaCO, + CaS. This sodic carbonate is always mixed in the process with quicklime, as it is found necessary to employ chalk in excess, and this chalk becomes lime in the high temperature of ihe furnace. A certain quantity of coal is also always used in excess, and this likewise remains mixed in the fiised mass, technically known as ball soda or black ash. This ball soda is now broken up, and placed in water at about 45° C, which dissolves out the sodic carbonate, but leaves the calcic sulphide undissolved. This undissolved residue is the soda waste, so troublesome to the manufac- turers. The solution of soda is next evaporated down, and when calcined furnishes the soda-ash or crude alkali of commerce, which contains from 50 to 56 per cent, of caustic soda (NaaO), in the form of carbonate and hydrate. If this soda-ash be dissolved in water, and the liquid allowed to cool slowly in a tank, beautiful transparent crystals of the carbonate {soda crystals) are gradually formed. ■ 'it ' i! I ' 'I I li i 1. 'I J "ii" .ill "' 1 M ■'in 214 Tests for the Alkalies. Hydric Sodic Carbonate (NaHCOa), often called bicar- bonate, is obtained by saturating a solution of the carbonate with carbonic acid. It is deposited in white crystalline grains, and is the substance commonly used for producing an effervescing drink with lemon juice. Tests for the Alkali Metals in Combination. — The salts of potassium are easily distinguished from those of sodium. Exp. 218. — To a pretty strong solution of the salt in question add a solution of tartaric acid, and stir the mixture with a glass rod. If potassium be present, white gritty crystals of cream of tartar (KHC4H4O6) will be deposited, but no such precipitate will occur with salts of sodium. Sodium forms salts all of which are soluble in water, so that it does not produce any precipitate with Ordinary test solutions. It also gives a yellow colour to a colourless flame, such as that of a spirit lamp or a Bunsen gas burner, whereas potassium gives a violet-coloured flame. The alkalies are all well distinguished from each other by the colour which they give to flame, especially if the flame be examined by means of the spectroscope. Potassium is then recognised by a single line in the red and another in the violet ; sodium, by a pair of intense lines, so close that they generally seem but one, in the yellow ; lithium, by a single intense crimson line, and sometimes a faint one in the orange if the flame be of a very high temperature \ rubidium, by two lines in the red and two in the blue ; and caesium by two intense lines in the blue, but not so refrangible as those of rubidium, though in these two last-mentioned spectra there are other lines of less importance. Potassium . salts may further be distinguished from sodium by means of platinic chloride, which forms with the chlorides of both metals a double salt ; that with potassium (2KCI, PtCl4) is nearly insoluble, that with sodium (aNaCl, PtCl4, 4HaO) cr/stallises in long soluble needles. Exp. 219.— Add to the solution of two or three decigrams of potassium chloride in a small porcelain dish, a few drops of hydro- Ammonia. 215 Fig. 7a chloric acid, then an excess of solution of platitilc chloride} evaporate to dryness over a saucepan of boiling water, arranged so as to form a water-bath, a circular disk of tin, large enough to project a little way beyond the edge of the saucepan, being substituted for its lid, and a circular hole a little smaller than the dish having been made in this lid, as shown in Fig. jo. When cold, the residue is to be re- dissolved in a few drops of water, which will remove the soluble ma- terials, and leave the sparingly soluble salt of platinum and potassium in small octahedra. Caesium and rubidium also form similar double chlorides with pla- tinum chloride, but they are much less soluble in hot water than the potassium salt, a difference which is sometimes made use of to separate these bases from potassium. (47) 3. Ammonium (H^'S). — This is not a metal, nor is it even known in a separate form ; but it is generally considered to be the com- pound fuasi metal contained in the salts formed by the action of the volatile alkali ammonia on the acids : such, for instance, as sal ammoniac, the compound obtained by neutralising hydrochloric acid with ammonia; ammonic nitrate, the salt obtained by neutralising nitric acid widi ammonia; and ammonic sulphate, the salt obtained by neutralising oil of vitriol with ammonia. All these salts crystallise in the same form as the corresponding salts of potassium with the same acids, and in every case the quantity of hydrogen present in the salt formed from am* monia is sufficient to convert it into the body ammonium, which seems to act as a compound metal, much in the same way as cyanogen is found to act like a compound halogen. For instance i-— m If, j mm ii6 Carbonate of Ammonia. Ammonia Salt Ammonkim Salt Oivfupondiiif to Potasttum &k Hydrochlorate H3N, HCl - (H4N)C1 (K)C1 Nitrate HjN, HNO3 - (H4N)N0j (K)N03 Sulphate (H,N)„ H,S04 - (H4N),S04 (K),S04 A solution of ammonia in water may, in fact, be regarded as ammonium hydratei the analogous compound to potas- sium hydrate — HNO3 + (K)HO = (K)N03 + H,0. Upon this supposition it is easy to explain the diverse position of a metallic salt and the separation of the oxide, on adding to it a solution of ammonia ; as, for instance : — Fe,CU + 6[(H4N)HO] - Fe.Oj, 3H,0 + 6[(H4N)C1] Fe,Cl« + 6[(K)H0] - Fe^Oj, sH.O + 6[(K)C1]. Exp. 23a — Dissolve a piece of sodium of tho size of a pea, in about 2 cub. cm. of pure mercury, in a test-tube : the two metals unite suddenly with flame. When cold, pour the amalgam Into a large watch-glass, and cover it with a saturated solution of sal ammoniac : the amalgam will gradually swell up and become pasty, and will often float when thrown into water. This at one time was held to be an amalgam of ammonium [(NH4)aHg] dissolved in excess of mercury, but there is little doubt that it is simply mercury distended by hydrogen and ammonia gases, its bulk having been found to vary accord- ing to the pressure upon it — 2NH4CI + NatHg = 2NH, -I- H, + 2NaCl -I- Hg. It gives off hydrogen and ammonia on standing, and also when thrown into water. One of the most remarkable of the salts of ammonium is the common smelling-salt, or sesquicarbonate 2[(H4N)aO], 3C0a, which is obtained by heating a mi^iture of chalk with half its weight of powdered sal ammoniac, and subUming it gradually — 6H4NCI + 3CaC0, « aCaCl, + *[(H4N),0], 3CO, + 2H3N + H,0. A laige quantity of free ammonia escapes in the operation, Baryta, 2f7 and the salt is always losing carbonate of ammonia, which causes its pungent smell ; and a white powder, the bicarbon- ate, or hydric ammonic carbonate, is left, 2[(H4N)aO], jCOa becoming 2H4NHCO3 + {n^\i)zC02. A solution of sal ammoniac gives a yellow nearly insoluble double salt with platinic chloride (2H4NCI, PtCl4), which crystallises in cubes or octahedra, like the potassium salt It is often used for ascertaining the quantity of an ammonium salt in solution. A still more delicate test is that known as Nessler's,* which gives a brown stain when the solution contains less than a millionth of its weight of a salt of ammonium. Group II. — Metals of the Alkaline Earths. I. Barium. 2. Strontium. 3. Calcium. (48) 1. Barium : Symb. Ba; Atomic JVt. 137. This metal is scarcely known in a separate state. When combined with oxygen, it forms Baryta (BaO), and a dioxide (BaOa). Baryta (BaO) may be obtained by treating baric nitrate in a crucible till the salt, which decrepitates and melts, again becomes solid, and finally ceases to give oiT oxygen at a bright red heat. The baryta is left as a grey porous mass, which absorbs moisture and carbonic acid from the air. If mixed with half its weight of water it slakes, forming a hydrate, whilst great heat is given out This hydrate is largely soluble in boiling water, and the solution deposits a crystalline hydrate of baryta as it cools. The liquid is strongly alkaline, and becomes milky by the action of carbonic acid. The dioxide (BaOz) may be formed by passing oxygen * Nessler's test for ammonia is prepared thus : add to a solution of mercuric chloride a solution of potassic iodide till the red precipitate first formed is nearly all dissolved. Then add a large excess of caustic potash; let the mixture stand in a stoppered bottle for three or four days, and decant when clear. It gives a brown precipitate when added to a solution containing a salt of ammonium. This consists of IlgllaNL " 21$ Saits of ^ariufH. over anhydrous baryta at a low red heat ; but if the heat be raised to full redness, the second atom of oxygen is gi ^en off again, and baryta is reproduced. If this oxide be dissolved at a low temperature in hydrochloric acid, baric chloride is formed, and the remarkable body H2O2, hydrogen peroxide, is formed in the liquid — BaO, + 2HCI -« BaCla + HaC The most abundant compounds of baryta are the sulphate and the carbonate. 7^ sulphate (BaS04) is a very heavy mineral, sp. gr. 4'6, the name baryta having been given to the earth in allusion to its weight, from /Sapvc, ' heavy.* It is found crystallised in right rhombic prisms. It is insoluble in water and in solutions of the acids. It is easily obtained artificially by mixing a solution of a sulphate with one of baric chloride, or any soluble barium salt This sulphate, although in- soluble, furnishes a sulphide soluble in dilute acids if it be heated with carbon. Exp. 221. — Grind about 10 grams of the sulphate to a very fine powder ; mix it with an equal weight of flour, and make it into a paste with oil; place this mixture in a crucible, with a little charcoal ; lute on the cover of the crucible with fireclay, and when the lid is dry raise the cmctble gradually to an intense heat in a furnace, keeping it up for about an hour : then allow it to cool. In this process the sulphate becomes reduced to sulphide^ while carbonic oxide escapes — BaS04 + 4C = BaS + 4CO. Exp. 222. — Treat the residue, when cold, with a large qnantity of boiling water. Everything should dissolve except the excess of carbon. The sulphide thus obtained, if treated with hydrochloric acid, is dissolved, baric chloride is formed, and sulphuretted hydrogen escapes — BaS + 2HCI » BaCla -h Ha& Compounds of CatciutH, dt9 This chloride is one of the salts most often used for pre- cipitating sulphuric acid from the sulphates. Baric Car- bonate (BaCOj) forms the mineral called Witherite^ found occasionally in the lead veins in the north of England. It is insoluble in water; soluble with effervescence in dilute acids; and is ea-^'ly obtained in the form of a white powder by mixing a solution of sodic carbonate with one of baric chloride or nitrate. This carbonate, and all the soluble barium salts, are strongly poisonous, the best antidote being Epsom salts. Tests for Barium Salts. — The best test for the barium salts in solution is the formation of a white precipitate, in- soluble in nitric acid, on adding a solution of calcic sulphate. They communicate a green tinge to flame, and form, with a solution of sodic hyposulphite, a white sparingly soluble hyposulphite. This last test is useful as a means of dis- tinguishing them from strontium salts, which, however, give a crimson colour to flame. 2. Strontium : Symb. Sr ; Atomic Wt. 87*5 ; Sp. Gr, This metal occurs chiefly combined as sulphate and carbonate in forms resembling the same compounds of barium, for which it was long mistaken ; but its compounds are much less abundant Its salts are not poisonous. The nitrate is used to give a red fire in the manufacture of fireworks. Strontic sulphate is rather more soluble than baric sulphate. (49) 3. Calcium: Symh, Ca; Atomic Wt. 40; Sp. Gr* 1-578: This is a malleable metal of a very pale yellow colour. It is seldom prepared, but may be procured by decomposing its fused chloride by the voltaic battery. Calcium tarnishes quickly when exposed to the air. It forms but a single oxide (CaO), the very important substance known as lime^ which is extremely abundant, both as carbonate and ai li'SE ""a :'- 'C. dio Limestom. sulphate; the chalk and limestone rocks, as well as the different forms of marble, all consist of carbonate more or less pure. Compounds of calcium are also found in all fertile soils, and they occur in a large number of crystallised minerals, amongst which fluor spar, calcic fluoride, is one of the most important Calcic Oxide. — Lime (CaO): Atomic Wi. $6. — ^This is obtained by heating the pure carbonate for some time to brigl ; ?dness, carbonic anhydride being expelled — CaCOj = CaO + CO,. Exp. 223. — Place a few lumps of black marble in the open fir . cr in an open crucible, with a hole at the bottom, and heat it stroiiii / fci t?r. 2 •67. This mi!tal derives its name from alum, of which material It constitutes between 5 and 6 per cent Its compounds are among the most abundant constituents of the rocks, including felspar, hornblende, and slate. Aluminum may be obtained from cryolite (sNaF, AIF3) by fusing it with sodium ; Out the method usually practised consists in decomposing wdic >luwnic chloride (NaCl, AlCl,) by heating it with ii' ■m :. -ii 224 CaHco Printing, sodium : an intense action occurs, and the aluminum is 6b tained in a melted state under the fused sodic chloride — NaClAlCl, + 3Na = 4NaCl + Al Aluminum is a white malleable metal, resembling zinc in colour and hardness. It may be rolled into foil, and drawn into wire. When struck, it gives a clear musical sound. It melts at a temperature below that needed for the fusion of silver. It preserves its brightness in the air, and is but slowly oxidized at a red heat. Nitric acid attacks it with difficulty, but it is rapidly dissolved by hydrochloric acid, and by solutions of the alkalies, hydrogen being given off. This metal, with about 90 per cent of copper, forms a golden yellow alloy, called aluminum bronze^ well fitted for castings. Alumina (AlaOs). — There is only one oxide of this metal, the earth alumina, which, when crystallised, constitutes the Oxiental ruby, the sapphire, and corundum. Emeiy is an- other form, of less purity. All these minerals are very hard ; their colour is due to small quantities of the oxides of chro- mium, iron, or manganese. Alumina, combined with silica, forms the different varieties of clay, and is the basis of porce- lain and earthenware. The soluble salts of alumina are of value to the calico printer. Hydrated alumina combines intimately with many vegetable colours, and forms with them pigments, called lakes. Exp. 225. — Grind some madder root into a coarse powder, and pour a litre of boiling water upon three or four grams of it Stir it up occasionally; then let it settle for three or four hours ; pour off the red liquor. Mix it with a solution of 4 grams of alum, and add a solution of 4 grams of sodic carbonate. Let the solution rest in a tall glass jar : a red deposit or lake, con- sisting of the colouring matter combined with the alumina, will be produced. If a pattern be stamped on calico with a solution of alum, and be then boiled with a solution of madder, the figures will be permanently dyed, while the colour may be easily washed out of the remainder of the cloth. In this case the alumina Alumina. 995 in the alum fixes itself upon the cloth, and acts as a mordantf which ' bites in ' the colour, or attaches it to itself, and thus renders the dye fast Other oxides, such as those of iron, chromium, and tin, are used for the same purpose, but they change the colour of the dye stuff at the same time that they fix it upon the calico. All metallic oxides used for such a purpose are termed mordants by the dyer. Alumina may be precipitated from its salts by a solution of potash, but an excess of potash redissolves the precipitate. Ammonia also precipitates the alumina as a bulky jelly-like hydrate, but does not redissolve it. This hydrate is freely soluble in diluted acids, but the solu- tion has the property of reddening litmus ; so that, while the hydrate acts the part of a feeble acid towards potash and soda, which dissolve it, it also acts the part of a base towards acids, though it is but a weak base, compared with either potash or soda, or bases which contain, like them, i atom of oxygen with 2 atoms of a monad, or, like calcium, i atom of a dyad metal. Alumina resembles ferric and chromic oxides. It crystallises when united with acids in the same form as these oxides do when acted upon by the same acids, and con- sequently it is regarded as a sesquioxidc. The different basic oxides may be compared together in this manner : — Sbsquioxidbs AljOj Aluminic Oxidt Fe,Oj Femr Oxide Cr.Oj C ric Oxide Monoxides Monads Dyads K,0 Potassic Oxide CaO Calcic Oxide Na,0 Sodic Oxide FeO Ferrous Oxide Ag,0 Ai^entic Oxide CrO Chromous Oxide Almnina forms a yellow chloride (A^CU), which is vola- tile below a red heat. It is obtained by mixing alumina and powdered charcoal into a paste with oil, heating the mixture to redness, and sending a current of dry chlorine gas over it : the chlorine unites with aluminum, and the carbon with the oxygen — AlaOs + 3C -f zC\^ = AI2CI6 -H 3CO. The chloride is used in extracting the metal Q V! '11 236 jAhitHs. fiut the most important salt is the sulphate, which U obtained by treating clay for some days with sulphuric a ''' at a heat nearly sufficient to make the acid boil. This phate (AI23SO4) is very soluble j but if mixed with a due pro- portion of potassic sulphate, it forms a salt, which crystallises in fine octahedra, and is well known as potassium alum (KAI2SO4, i2H,0). Alum is a double salt, which is made in vast quantities for the use of the calico printer. Amnionic sulphate is now largely employed instead of the potassic salt It then pro- duces ammonium alum (H4N, AI2SO4, 12H2O), which crys- tallises quite as readily and in exactly the same form as the potassium salt. The place of the aluminic sulphate may be supplied by ferric sulphate, chromic sulphate, ?nd manganic sulphate. In each case a salt is formed, whi \ different in colour from true alum, but like it, and crysta. in octahedra, resembling those of alum ; so that there are a number of alums known, some of which may be represented as follows : — Ammonium Alum . . (H4N)Al2S04, I2H,0 Potassium Alum Iron Alum Manganese Alum Chrome Alum . KAI2SO,, I2H,0 4» KFe2S04, I2H,0 KMn2S04, i2H,0 KCr2S04, i2H,0 Alum has a sweetish, astringent taste. Its solution reddens litmus strongly. When heated it melts, first in its water of crystallisation, then it froths up, forms a tenacious paste, and at last becomes a white, bulky, porous, infusible mass, called burnt alum. A good deal of alum is made by roasting alum schist (a kind of black bituminous clay, which contains a good deal of pyrites) for some weeks at a low temperature. The pyrites absorbs oxygen, and becomes gradually converted into ferrous sulphate, while the second atom of sulphur in the pyrites combines with oxygen, and the product unites with alumina, forming a mixture of aluminic and ferrous sulphates — 2FcSa + 7O2 = 2FeS04 + 2SO, ; CUys — Varktii's of Felspar. 33/ and on adding potassic chloride, alum crystallises out from the mixed sulphate and chloride of iron — FeSO^ + Ala3S04 + 2KCI = FeCl, + aKAlaS04. Silicates of Alumina — Clays. — Alumina forms a great number of silicates. All the varieties of clay consist of aluminic silicate, more or less mixed with other matters derived from the rocks which, as they have crumbled down, have furnished the clay. The best fire clay consists of AlaOjaSiOa, aHaO. It is used in making bricks for lining furnaces, and for crucibles and glass pots, as well as for other purposes where resistance to a high temperature is required. But many kinds of clav contain lime, magnesia, or ferric oxide intermixed, and they greatly increast its fusibility, and diminish its plasticity, or fitness for kneading and moulding while in a moist state, and cause it to be more readily attacked by acids, while an excess of silica renders it less fusible. The more mixed varieties of clay constitute marl and loam. Pure clay forms, before it has been ignited and when kneaded with water, a tenacious plastic insoluble paste, which, when slowly dried and exposed to a high heat, shrinks very much, often splits, and becomes extremely hard, but does not melt in the furnace. Clay is not attacked readily by any acid except the hydrofluoric. Strong sulphuric acid, when strongly heated with it, gradually decomposes it When breathed upon, or slightly moistened, clay gives out a peculiar odour, and if applied in a dry state to the tongue or lips, it adheres to them strongly, and absorbs the saliva. Felspar is a very abundant and important double silicate of aluminum and potassium (K2O, AI2O3, 6Si02), often called adularia. When it contains sodium it is white, and is termed albite \ and when it contains lithium, the mineral is known as petalite. Felspar is a very abundant constituent of the Older rocks. Mixed with mica and quartz, it forms granite and gneiss. Porphyry is a compact felspar with crystals of felspar dispersed through it Basalt is a dark- 'M! iiS Pottery Ware. coloured volcanic rock, containing crystals of augite diffUsed through compact felspar. The porous pumice of volcanoes is chiefly felspar altered by high temperature ; and obsidian is melted pumice. Mica is a more complex silicate of alumina, containing a little fluoride. Earthenware and China. — The basis of "these articles is silicate of alumina, but to diminish the tendency to crack during drying, which it has if used alone, the clay is mixed with ground flints, which, however, lessens its tenacity.* To make up for this defect, it is usual to add some fusible material which, at the temperature requu-ed for fusing, be- comes softened, and greatly aids in binding the particles together. The clay thus mixed and tempered is moulded, while moist, upon the potter's v/heel, after which the dif- ferent articles are dried in a warm room, and are then fired at a comparatively moderate heat : they are thus obtained in a porous state, called biscuit. The patterns or designs are next applied, the colouring matter consisting usually of some metallic oxide ground up into a paste with turpentine or linseed oil Blue is generally given by cobalt oxide, green by chromic oxide, brown by a mixture of the oxides of iron and manganese, black by uranium oxide, and so on. The ware, when painted, is much too porous for use ; it is therefore glazed by dipping each article into water containing a fusible mixture, finely ground, in suspension. The porous mass quickly absorbs moisture, leaving a thin uniform layer of glaze upon the surface. The goods are then enclosed in fireclay vessels, and exposed to a furnace heat The glaze melts, and leaves a smooth surface, so that the material is no longer porous and absorbent. Stoneware is glazed differently. The pots are raised to a strong red heat in the furnace, and a quantity of damp salt is thrown in. The material is rapidly volatilised. The salt is decomposed by the silica and ferric oxide of the clay in * In making crucibles and firebricks, old pots, finely powdered, are generally used instead of ground flints, but for the same purpose. Magnesium. 239 the presence of steam. Ferric chloride and hydrochloric acid pass off with the excess of salt employed, and form the dense brownish fumes which are seen escaping at intervals from the kilns on glazing days, while sodic silicate fuses on the surface of the ware, and makes it impervious to water, the actions being as follows :— H,0 + 2Naa + SiO, - 2HCI + Na,0, SiO, ; and Fe,Oj + 6NaCl + sSiO, - Fe.CU + 3(Na,0, SiO,). Tests for Aluminum Salts. — The solutions have a sweet, astringent taste. Potash gives a white precipitate, soluble in excess of the alkali. Ammonia, a white precipitate, in- soluble in excess of the alkali. Carbonates of the alkalies, a white precipitate, insoluble in excess of the alkaline car- bonate. Ammonic sulphide gives a white precipitate of hydrated alumina. Exp. 226. — Heat a little alum on a platinum wire, bent into a small hook, in the outer flame of a Bunsen gas-burner. After the salt has been touched with a drop of a solution of cobalt nitrate, a pale blue compound of alumina and cobalt oxide will be formed. It is used as a blowpipe reaction for alumina. 2. Glucinum is the characteristic ingredient in the beryl and emerald. 3. Yttrium and (4) Erbium are both found only in a few rare minerals. 5. Cerium is met with rather more abundantly, accompanied by two other metals, (6) Lanthanum and (7) Didymium, in a mineral called cerite, but none of tnese are of sufficiently frequent occurrence t( need further notice here. Group IV. — Magnesium Metals. I. Magnesium. 2. Zinc. 3. Cadmium. 4. Indium. (51) I. Magnesium : Symbol, Mg ; Atom. Wt. 24 ; Sp, Gr. 174, This metal is obtained by decomposing its chloride by ipeans of sodium. It is purified by distilling it at a bright I ' Ml' ■\ 'I 1 ; I It! J rhsilii ii.iMI ■•iiif 230 Compounds of Magnesia. red heat in a current of hydrogen. Magnesium is a malleable, ductile metal, of the colour of silver. It takes a high polish, which it preserves in a dry air ; but it becomes slowly oxidized in a moist atmosphere. At a moderate red heat it melts. Exp. 227. — Heat a piece of magnesium wire in dry air or in the flame of a lamp : it takes fire, and becomes oxidized, pro- ducing white fumes of magnesia, giving out an intense white light. This light is occasionally used for photographic purposes, or in lighting up the interior of buildings. Magnesium is dissolved rapidly by diluted hydrochloric acid, giving off hydrogen ; and it is freely soluble in a solu- tion of sal ammoniac. When heated in chlorine, or in the vapour of bromine, iodine, or sulphur, it bums brilliantly. Magnesia (MgO). — This is the only known oxide of the metal It occurs abundantly in combination as dolomite^ or magnesic calcic carbonate ; as Epsom salts, or sulphate ; as chloride in sea water; and as silicate in a variety of forms, both alone, as in talc and serpentine, and in com- bination with the silicates of alumina and other bases, as in augitey hornblende, and asbestos ; so that it is an important and frequent constituent of rocks. Magnesia is a bulky, white, tasteless, and nearly insoluble powder, obtained by strongly heating the carbonate or nitrate of the metal. Exp. 228. — Place a little magnesia on moistened turmeric paper : it is sufficiently soluble to render the parts moistened, on which it rests, brown. Exp. 229. — Place a small quantity of magnesic carbonate in a crucible ; put on the cover, and heat the crucible in the fire for an hour. Take it out, and allow it to cool : caustic magnesia will be left. When moistened with water, it will not slake ; but if hydrochloric or nitric acid be poured upon the moistened earth, it will dissolve slowly, without effervescence. Magnesic Chloride (MgClz) may be obtained by adding to a solution of one part of magnesia in hydrochloric acid three times its weight of sal ammoniac, evaporating to dry- ness, and heating the mixed salts to redness in a covered ■■« Tests for Magnesium Salts. 23^ crucible : the magnesic salt fises, while the ammoniacal salt goes off in vapour. This chloride is deliquescent ; but if its solution be evaporated by itself, a good deal of hydrochloric escapes, and magnesia is left. Ma^esic Sulphate (MgS04, 7H2O), familiarly known as Epsom Salts. — This is the most important soluble salt of the metal. It crystallises in four-sided solid prisms, which are very soluble, and have a bitter taste. Tests for Magnesium Salts : — Exp. 230. — Pour over 25 grams of Epsom salts 50 c. c of boiling water : the salt dissolves, and part crystallises out as the solution cools. To a portion of the cold solution add a solution of sodic hydric carbonate : no precipitate occurs. Boil this mixture, and a white precipitate (the white magnesic carbonate), mi.:ed with magnesic hydrate, is immediately separated. Exp. 231. — Add to u solution of magnesic sulphate some ammonic chloride ; then add a solution of hydric disodic phos* phate. Stir the mixture \ cx^^XsXs oi ammonic magnesic phosphate are deposited in crystalhne grains (MgH4N, PO4, 6H,0), in- soluble in water, containing ammonia in solution, but appreciably soluble in pure water. This is a very delicate test for mag- nesium salts, but it is readily dissolved by acids. Add a few drops of hydrochloric acid to the neutral solution : the precipi tate disappears. Exp. 232. — Collect a little of the crystalline precipitate in a filter ; dry it over a steam bath. Place a few decigrams of the dry salt in a small crucible, cover it, and weigh the whole ; then heat it for ten minutes in a Bunsen gas-flame. Water and am- monia will be expelled. Allow the crucible to cool ; then weigh it a second time : it will be found to hare lost weight con- siderably. The salt which is left is magnesic pyrophosphate^- 2(H4NMgP04) - 2H,N + H,0 + Mg,P,0;. Exp. 233. — Add to a solution of any magnesic salt, such as the sulphate, a solution of potash; a white precipitate of hydrated magnesia is formed. Excess of alkali does 90t re- dissolve it. Limewater produces a similar precipitate. Am- monic oxalate^ if mixed with an excess of solution of sal am- moniac, gives no precipitate with solutions of magnesium salts. fP >.i •I' , ff. 2Z2 Properties of Zinc. Exp, 234.— Place a little of the magnesium salt on a platintim wire moistened with a solution of cobalt nitrate. A pink residue will be obtained on heating the wire in the outer part of a Bunsen gas-flame. (52) 2. Zinc or Spelter : Symbol^ Zn ; Atom. Wt. 65 ; Sp, Gr. 7-15 ; Fusing Pt. 412. This well-known metal occurs chiefly in the form of sul- phide, constituting blende (ZnS), or in tliat of carbonate, known to mineralogists as calamine (ZnCOj). In order to extract the metal the sulphide is roasted, or heated mode- rately in a current of air : the sulphur bums off, and leaves the oxide. When calamine is roasted, water and carbonic anhydride are expelled, and zincic oxide is also left The oxide, in either case, is next mixed with powdered coke, and heated. The carbon removes the oxygen as carbonic oxide, while the zinc, which is volatile at a full red heat, distils over, and may be condensed. Zinc is a hard bluish-white metal, which, when a mass of it is broken across, shows a beautiful crystalline fracture. At ordinary temperatures it is rather brittle ; but between loo** and 150" it may be rolled, and wrought with ease, though between 200" and 300" it again becomes brittle, and may be powdered. At 412° it melts, and it boils steadily at 1040**, and may be distilled at a bright red heat. Exp. 235. — Heat a crucible to a bright red heat, and throw into it a few fragments of zinc. The metal will melt, and give off vapours which bum with great brilliancy^ depositing white clouds of zincic oxide. Zinc soon tarnishes in a moist atmosphere ; the thin film of oxide adheres closely to the metal, and protects it from further change. Dilute sulphuric and hydrochloric acids dissolve zinc rapidly, and give off hydrogen. Nitric acid also attacks it powerfully, but the acid itself is at the same time partly decomposed. Zinc is often used as a substitute for lead in roofing ; it is lighter and cheaper, but less durable. It is also used as th9 Salts of Zinc. 233 active metal in the voltaic battery, and becomes dissolved in proportion as the electricity is liberated. Sheet iron is often coated with zinc, to render it less liable to rost ; it then forms what is called galvanised iron. Brass is the most important of the alloys of zinc. It contains about two parts of copper to one of zinc, but the proportions of the two metals may be varied according to the purpose to which the alloy is to be applied. German silver is brass whitened by the addition of nickel Zinc Oxide (ZnO). — Zinc forms but one oxide, which is generally obtained in the form of a white flocculent powder by burning the metal in a current of air. When heated, this oxide becomes yellow, but on cooling it recovers its white- ness. It is easily soluble in the acids. If a solution of potash be cautiously added to a solution of a salt of zinc, such as the sulphate, a white gelatinous hydrated oxide is precipitated, but it is redissolved by an excess of potash : ammonia has a similar effect. Zinc Sulphate (ZnS04, 7H2O) is obtained in the ordinary process of preparing hydrogen by dissolving zinc in diluted sulphuric acid It crystallises in white soluble prisms, re- sembling those of magnesic sulphate. It produces vomiting if swallowed in quantities, such as one or two grams. The zinc salts are colourless ; they have an astringent metallic taste. Sulphuretted hydrogen produces no precipi- tate in their acidulated solutions ; but if mixed with a solution of ammonic sulphide, a white gelatinous zinc sul- phide is formed. A solution of sodic carbonate gives, with zinc salts, a white precipitate of hydrated basic zinc car- bonate, not soluble in excess of the alkaline carbonate ; but if ammonic carbonate be used instead, the precipitate is redis- solved by the addition of the ammonic carbonate in excess. Zinc salts yield, with potassic ferrocyanide, a white pre- cipitate. Before the blowpipe, in the reducing flame, on charcoal, the metal is reduced ^n^ volatilised, burning into whit^ s 1 1 1 ill i u ( 234 Cadmium — Indium. fumes of the oxide. If placed on charcoal, and moistened with a solution of cobalt nitrate, they give, when heated in the oxidating flame, a green infusible residue. 3. Cadmium : Symb. Cd ; Atom. Wt. 112. — ^This is a com- paratively rare white, sofl, easily fusible, volatilisable metal, usually found as sulphide, accompanying the ores of zinc in small quantity. Being more volatile tiian zinc, it comes over in the first portions which distil over during the reduction. It may be separated from zinc by dissolving these portions df the metal l:i sulphuric acid, and transmitting a stream of sulphuretted hydrogen gas through the solution ; a yellow cadmium sulphide is thus separated. This precipitate may be dissolved in hot hydrochloric acid, precipitated from the solution by the addition of ammonic carbonate, and reduc- ing the carbonate by heating it in an earthen retort with powdered charcoal ; the metal distils over at a red heat. It takes fire when heated strongly in air, and bums, forming a brown oxide. The addition of cadmium to the more fusible metals furnishes alloys of low melting point without destroy- ing their toughness and malleability. Cadmium furnishes a single oxide (CdO), which is brown when anhydrous, and white when hydrated. Ammonia dis- solves it easily, but ammonic carbonate does not dissolve it. Chloride and iodide of cadmium are used by the photo- grapher. They crystallise easily. 4. Indium is a white soft metal, which has been found in small quantity occasionally associated with zinc. It was discovered by its property of furnishing, when heated in a colourless gas-flame, a light which is characterised by two strong lines in the indigo portion of the spectrum* 235 CHAPTER XIII. Group V. — Metals allied to Iron. I. Cobalt. 2. Nickel. 3. Uranium. 4. Iron. 5. Chromium. 6. Manganese. (53) '• Cobalt : Symb. Co ; Atom. Wt. 59 ; Sp. Gr. 895. — ^This metal is never used in the arts in the metallic state, but it furnishes several compounds which are much valued for their beautiful colour. It generally occurs in combina- tion with arsenicum, and is almost always found associated with nickel. Metallic cobalt is obtained with difficulty in a pure state by a complicated process, for details of which some larger works on chemistry should be consulted. It is nearly as infusible as iron, is of a reddish grey colour, hard, ductile, and strongly attracted by a magnet. Cobalt furnishes several oxides : two are well known — the protoxide (CoO), which, when treated with acids, yields the common salts of the metal, and the sesquioxide (CoaOj). These two oxides may be combined with each other in more than one proportion. The protoxide is soluble in acids, and forms salts which, when anhydrous or in concentrated solutions, are of a beauti- ful blue colour ; but they become pink in dilution. At a particular stage of dilution they become blue when heated, although when cold the solution is pink. This oxide is largely used for painting on porcelain, to which it imparts a rich blue colour. Smalt is a beautiful blue glass coloured with this oxide of cobalt When finely powdered it forms the stone-blue used by laundresses to correct the yellow tinge in linen. Cobalt Nitrate (C02NO3, 6H2O) is prepared by dissolving cobalt oxide in nitric acid. Its solution is sometimes em ployed as a test before the blowpipe. A fragment of the compound suspected to contain alummum, magnesium, or tine, is supported on charcoal, and touched with a minu^^ 11 I" I 336 Salts of Cobalt -Nickel. quantity of a solution of the nitrate : aluminous compounds give a blue residue if heated in the outer flame, those of magnesium a pink, and those of zinc a green residue.- Tests for Salts of Cobalt. — All the compounds of cobalt are easily distinguished before the blowpipe by tjie intense blue colour which they impart, even in minute quantity, to a bead of borax when fused v.dth it on a loop of platinum wire. If the quantity of cobalt be large, the colour is so intense that it seems to be black. Acid solutions containing cobalt are not precipitated by sulphuretted hydrogen, but ammonic sulphide yields a black sulphide of cobalt. Solution of potash precipitates a rose- coloured hydrated oxide, insoluble in excess of the alkali. Ammonia and its carbonate also give a rose-coloured pre- cipitate, soluble in excess, of the alkali, forming a brownish solution, which absorbs oxygen from the air, and becomes red. It forms one of a large series of ammoniacal com* pounds which contain cobalt. 2. Nickel : Symb. Ni ; Atom. Wt. 59 ; Sp. Gr. 8'82. — This metal has a remarkable analogy with cobalt. It occurs associated with it in nature, has the same atomic weight, and is, like cobalt, powerfully attracted by the magnet. Its most abundant ore is kupfemickel^ the arsenide (NiAs). Tne mode of its extraction is described in the book on * Metal- lurgy.' Nickel is a brilliant silver-white, hard, ductile metal, nearly as infusible as iron. Its most important alloy is Ger- man silver, which is a kind of brass whitened by the addition of about 20 per cent, of nickel. There are two oxides of nickel, a protoxide (NiO) and a sesquioxide (NiaOj) ; the first is the only one of importance. It is obtained by heating the nitrate or the carbonate to redness. It furnishes an olive-green powder. The hydrated oxide is of a delicate apple-green, and may be precipitated from its salts by the addition of a solution of potash, which do^s i|pt redissolve it when added in excess. Acids dissolve Uranium — Tron, nr it and riiniish pale green solutions. Ammonia precipitates the hydrated oxide from these solutions, but, if added in excess, redissolves the precipitate, and furnishes a blue liquid. Ammonic carbonate precipitates a green carbonate of nickel, soluble in excess of the alkaline carbonate. 3. Uranium : Symb. U ; Atom. Wt. 120. — This metal is scarcely known in its pure state. It occurs chiefly in the foim of the black oxide (2UO, UaOa), which constitutes about 80 per cent of the mineral pitchblende. The metal furnishes several oxides. The black oxide just mentioned is used as an intense black for painting on porcelain. The sesquioxide (U2O3) combines with the alkalies potash and ammonia, and forms a yellow compound. It is also soluble in acids, such as the nitric and acetic, and forms yellow salts, the solutions of which give a brown precipitate with potassic ferrocyanide, and a yellow precipitate with ammonia, not soluble in excess of the alkali. This oxide is used to communicate a peculiar opalescent yellow colour to glas?, which exhibits the optical property of fluorescence in a re- markable degree. (54) 4. Iron : Symb. Fe ; Atom. Wt. 56 ; Sp. Gr. 7-84. — This, the most important of the metals, is also very abundant. It is found now and then in the metallic state, associated with nickel, cobalt, and some other elements, in those remarkable masses known as meteorites, which fall in an ignited state from the atmosphere from time to time — possibly the fragments of some formerly existing planet For the supply of the vast demand for iron the ores chiefly wrought are magnetic ironstone, or loadstone (FeO, FejOj) ; specular iron ore (FcaOa), or red haematite, which is a more abundant form of the same oxide ; brown haematite (aFeaOa, 3H2O), the hydrated sesquioxide ; and spathic iron, or ferrous carbonate (FeCOa). This last is the material which, when mingled with clay, furnishes the immense de- posits of day-ironstone which occur in what are called the '! A 1 'A ^3^ Ores of tron Cast troH. !lt it is not a pure carbide, for in the intense heal Iron atid Steel. ^30 the carbon of the fuel reduces not only the iron oxide, but also portions of silica, alumina, and lime, as well as phos- phates and sulphates which are present. The cast iron, therefore, varies much in its quality, according as it contains more or less of carbon, silicon, sulphur, phosphorus, and other elements. When melted cast iron is allowed to cool slowly, part of the carbon crystallises out, and remains diffused through the mass in small flakes of graphite. This variety of the metal is known as grey cast iron. The same iron, if cooled rapidly, is ciystalline in structure, and contains the carbon chemically combined, forming what is known as white cast iron. In order to purify the pig iron, it is melted in a current of heated air, so as gradually to bum off the carbon, silicon, and other impurities, which are more combustible than the iron itself, the carbon escaping as carbonic oxide, the silicon as silica, and the phosphorus as phosphates. The silica, with the phosphates, unite with oxide of iron, and form a slag. The metal is thus rendered less and less fusible : it is collected by the workman into large balls, which are sub- jected while white hot to the blows of a powerful hammer, which squeeze out the melted slag ; and the metal, after being passed through grooved rollers, becomes converted into malleable iron, or wrought iron. Iron, when combined with a smaller proportion of carbon than is contained in cast iron, furnishes steely of which there are several varieties. The quantity of carbon in good steel varies between 07 and 17 per cent. That which possesses the greatest tenacity has been found to contain from i '3 to I '5 per cent, of carbon and about o'l of silicon. Fuller details of the mode of making cast iron, wrought iron, and steel, will be found in the text book on ' Metallurgy.' Steel is more fusible than iron ; it is brittle, and when broken across shows a fine granular texture ; but its most characteristic property is that of becoming almost as hard as diamond when heated to redness and then suddenly cooled H^i •(■'! u l,.. IP M wm 340 Properties of Iron. Xsy plunging into water or oil. It is thus rendered extremely br ,ile and almost perfectly elastic. This extreme hardness and brittleness may be removed by the process of tempering^ which consists in reheating the hardened steel moderately, and then allowing it to cool. The higher the temperature to which it is raised in the second heating, the softer is the steel. Exp. 236. — Allow a drop of nitric acid to fall upon a slip of polished steel : a dark grey spot is produced, owing to the solu- tion of the metal in the acid, while the carbon is left If the acid be dropped upon a slip of iron a green stain is formed. Bar iron generally contains about 0*2 per cent, of carbon. It is hard, takes a high polish, is tough and fibrous, with a peculiar bluish-grey colour. It has a spec. grav. of 77. It requires the most intense heat of a wind furnace to melt it It passes through a soft intermediate condition between actual fusion and solidity. This property is of the highest practical importance \ and it is owing to this fact that the smith is enabled, after sprinkling the surface of two white bars with sand, to weld them together so completely that the junction is as tough as any other part The sand acts as a flux to the layer of oxide which forms upon the surface of the hot metal. A slag is thus formed upon each bar. By the blow of the hammer the film of melted matter is forced out, and the two clean surfaces of the metal become united. Iron is susceptible of magnetism to a greater dicgre than any other known substance. At a high temper-^' , bums readily, as is seen in the vivid sparks thrown o* ^m it when being forged, and the brilliant combustion exhiL <'d by n coil of watch-spring or of wire, when heated and introduce! into oxygen gas (Exp. 14). In dry air polished iron remains unaltered \ but if exposed to a moist atmosphere, so that liquid water be deposited on the metal, it quickly becomes rusty, and when once a spot of rust is formed the action proceeds rapidly. Iron may, however, be kept for any Oxides of Iron. nt length of time unchanged in water quite free from air, at well as in limewater, or in water containing a little caustic alkali If steam be passed over red-hot iron, minute crystals of the magnetic oxide are formed, and hydrogen is given off (Exp. 44, Fig. 13). Chlorine, bromine, and iodine combine quickly with iron, and dissolve it easily at common temperatures, as may be easily seen by placing a few drops of bromine under water in a test-tube and allowing a small quantity of iron filings to fall into the bromine. The iron will disappear, with a strong evolution of heat Diluted sulphuric and hydrochloric acid dissolve the metal with escape of hydrogen (Exp. 45 and p. 60). The metal is rapidly attacked by nitric acid, with abundant escape of nitric oxide. Iron may, however, be kept unaltered in nitric acid of sp. gr. 1*45, or upwards; but if the acid be diluted below 1-35, it dissolves the metal with violence. Iron yields four definite oxides : i. The protoxide (FeO), the base of the green or ferrous salts ; a. The sesquioxide, the base of the red or ferric salts ; 3. The black or magnetic oxide (FeO, Fea03), a compound of the two preceding oxides, which, when treated with acids, yields a mixture of ferrous and ferric salts, but no distinct saline compounds referable to it in constitution; and 4. Ferric Acidy an vnstable metallic acid, the anhydride of which is unknown, but which forms salts, of which potassic ferrate (KaFe04) is the representative. Ferrous Oxide (FeO) is scarcely known in a pure state, it absorbs oxygen so rapidly. It forms a white hydrate ; and if obtained by adding an alkali, such as ammonia, to a solution of ferrous sulphate, the white precipitate becomes green, passing into bluish green, black, and finally ochre-coloured, by the formation of sesquioxide. Ferrous salts, such as the chloride or sulphate, are obtained by dissolving the metal or its sulphide in hydrochloric or sulphuric acid, and allowing the solution to crystallise out of contact with air. These ! 242 Sulphides of Iron, salts have a delicate bluish-green colour, and an astringent, inky taste. If ex]K)sed to the air while moist, they become grass green, and slowly absorb oxygen. Ferric Oxide (FtzO^) is an abundant ore of iron. When anhydrous and crystallised, it forms specular iron ore. When in masses it furnishes haematite. Brown haematite, a hydrate (2F2O5, 3H20),is another abundant and valuable ore. In this form it is readily dissolved by acids. Jewellers' rouge ia a finely-powdered red oxide, obtained by igniting the sulphate as in the process for preparing the Nordhausen oil of vitriol When a ferric salt in solution, such as the chloride, i» mixed with potash or ammonia, a milky reddish-brown hydrated ferric pxide is precipitated. Iron combines with sulphur in several proportions. The Protosuiphide (FeS) may be obtained as follows : — Exp. zyj, — Heat a bar of iron white hot in the fire, and bring it in contact with a roll of sulphur over a pail of cold vrater. The sulphur and iron immediately unite, and form drops of a reddish-brown colour, which run down into the water. This sulphide is used in the laboratory for preparing sulphuretted hydrogen, which is disengaged without heat, by pouring upon it sulphuric acid diluted with 5 or 6 times its bulk of water. The Disulphide (FeSa) is an abund.mt natural product. It forms the yellow brassy-looking mineral known as iron pyrites^ often found crystallised in cubes. Exp. 238.— Place a few fragments of pyrites in a small sealed tube, and heat it to dull redness in a lamp-flame ; sulphi^/: will gradually be sublimed. When heated in the air the sulphur bums off, and f jnishes sulphurous anhydride, which is largely prepared firora it for conversion into sulphuric acid. An impure oxide of iron is then left. Iron pyrites is not easily dissolved, except by nitric acid, or, still better, by a mixture of nitric with hydro- chloric acid. Mispickel (FeAsS) is the name given to an arsenic sulphide of iron, which furnishes a good deal of the w Tests for Iron. 243 arsenic of commerce. When heated in a current of air, it is converted into ferric oxide, while sulphurous and arsenious anhydrides are produced. A solution of a ferrous salt, such as the sulphate, when mixed with amnionic sulphide, yields a black hydrated ferrous sulphide, and in a similar way a solution of a ferric salt, such as the chloride, yields a hydrated sesquisulphide— . FeSO^ + (H^N),S = (H4N),S0^ + FeS ; and Fe.Clfi + 3[(H4N),S] = 6H4NCI + Fe.Sj. Both these sulphides, when exposed to the air, become converted into hydrated oxide, while the sulphur is separated without undergoing oxidation — 4(FeS, HjO) + 3O2 = 2(Fe203,2H,0) + 2S,. Ferrous Chloride (FeCU, 4H2O) may be obtained by dis- solving the metal in hydrochloric acid, and evaporating the solution till it crystallises. Ferric Chloride^ formerly known as sesquichloride (FejCU), may be obtained sublimed in anhydrous brown scales by heating iron wire to redness in a current of dry chlorine gas ; it is very deliquescent. A solution of ferric chloride may also be obtained by passing a current of chlorine gas through a solution of ferrous chloride as long as the gas is absorbed, or it may be procured by dis- solving hydrated ferric oxide in hydrochloric acid. Ferrous Carbonate (FeC03) is found native in immense quantities. When crystallised, it is known as spathic iron ore ; when mixed with clay, it forms the clay-ironstone j and when with bituminous matter, furnishes the blackband iron- stone. Ferrous carbonate is also the salt which is found in chalybeate springs, in which it is held in solution by free carbonic acid. Mere exposure to air then causes its sepa- ration : the acid escapes, oxygen is absorbed, and hydrated ferric oxide, mixed with a srnall quantity of organic matter, subsides, forming the ochry deposits so common around ferruginous spnngs. Tests for Iroti. — The salts of this metal have an inky anil astringent taste. The ferrous salts are known by the deep & 2 w ff w IE i H ' |; if irb m% if;,,;: 'i ■m I: >■■.% 'm I';, lii 244 Compounds of Chromium. blue precipitate which they give with the red prussiate (potassic ferricyanide) in solution. If one of the ferrous salts be boiled with nitric acid, it is converted into a solution of ferric salt, while one of the lower oxides of nitrogen escapes. Ferric salts in solution are known by the rusty-brown precipitate of hydrated ferric oxide which they give with ammonia, by the blood-red solution produced by potassic sulphocyanide when added to an acid or neutral solution, by the bright Prussian blue precipitate occasioned by a solution of yellow potassic ferrocyanide, and by the bluish-black inky precipitate produced by tincture of galls in neutral solutions. This last is the colouring matter in ordinary writing-ink. Potassic ferricyanide gives no precipitate in ferric solutions, and thus may be used to distinguish them from those of ferrous salts. Exp. 239. — Add to a solution of a ferric salt, mixed with a little solution of a salt of cobalt, a weak solution of ammonia, drop by drop, stirring the liquid between each addition, until the pre- cipitate just begins no longer to be dissolved. The solution will become of a deeper red or yellow tinge. Dilute the liquid freely with water, and then boil it ; an insoluble basic salt of iron will be formed, and every trace of iron may thus be precipitated, whilst the cobalt will remain dissolved, and may be found by adding a little more of ammonia. (55) 5' Chromium {Syml Cr; At. Wt. 52-5) is never used as a metal, or even as an alloy, but is highly prized for the numerous brilliant-colo ^red compounds which it forms. The name chromium is derived from XP'^A**** colour. It is 1 rather rare element, anf' is most usually found in the chrome ironstone (FeO, Cr203). The metal is very hard and infusible. It is sometimes obtained by heating chromic chloride with sodium. Chromium forms four well-known oxides : chromous oxide (CrO), which is unimportanl ; chromic oxide (CraOa), the basis of the common green or violet salts of the metal : it is prized as a green pigment for colouring porcelain ^these two oxides corr» Salts of Ckromium. 245 spond to ferrous and ferric oxide in composition); a brown oxide (CrO, Cr203), corresponding with the magnetic oxide of iron, but which is unimportant; and a stable metallic anhydride (CrOj), which, when dissolved in water, furnishes an important acid, from which the class of chromates is obtained. The chromates are prepared on a large scale by heating chrome ironstone to redness, quenching in cold water to render it friable, then reducing it to an extremely fine powder, and heating to bright redness in a current of air, with a mixture of chalk and potassic carbonate. The mixture absorbs oxygen, and becomes yellow. When cold, it is treated with water, which dissolves out the chromates. Potassic carbonate is added as long as it occasions any pre- cipitate of chalk from the solution of calcic chromate. The yellow solution is drawn off, mixed with nitric acid, and on evaporation potassic dichromate crystallises out in large red anhydrous prisms (K2Cr04, Cr03), whilst nitric acid remains in solution. This dichromate is the common commercial salt. It is a salt of exceptional composition, being a compound of the chromic anhydride with the normal potassium salt. If formed in the regular way it would be composed as follows : KHCJ^>4, or KaCr04, HaCr04 ; b\it such a salt is not known. The dichromate is soluble in about ten parts of cold water. If 4 measures of the cold saturated solution of this salt be mixed with 5 of oil of vitriol, and the liquid be allowed to cool, chromic anhydride crystallises in crimson needles, which may be drained and dried upon a brick. Besides the dichromate, there is a normal chromate of potassium (K2Cr04), which is yellow, and does not crystal- lise easily ; and there are also potassic salts known which contain two and three atoms of chromic anhydride combined with one atom of the normal salt Baric chromate i$ a canary-yellow insoluble powder. n ;i.i m 'i'^n !;K>-St! ;.' H' um ''5!1 :i ^im ■ ''^i9 ':;:|n J il^l 1' '1^9 y, -^ Wk p: ^^''IH !' '^^'^'fl ' '' ^^m F : ' -' '"{JM ll!i|H -^ 1 '1 1 '"* •■ 1 ■^ii ;9 jjH ; ; i^n |;|| '^^H iilH 1 i '"ni 1 m m m ■ 946 Oxides of Manganese. Chrome Yellow is the normal lead chromate (PbCr04). It falls as a bright yellow insoluble powder when a solution of lead acetate or lead nitrate is mixed with one of potassic chromate or dichromate. Argentic chromate (Ag2Cr04) is of a dark red colour, and is insoluble. Mercurous chromate (3Hg2Cr04, HgaO), obtained by adding mercurous nitrate to a sohition of a chromate, is orange coloured and nearly in- soluble. The chromates of cadmium and bismuth are yellow. If a soluble chromate, such as potassic chromate, be mixed with hydrochloric acid, chromic acid and a chloride of the metal are formed in the sslution ; aiid if a little alcohol or sugar be added, and the liquid be boiled, it becomes green, owing to the reduction of the chromic acid to chromic oxide, which becomes dissolved in the excess of hydrochloric acid. If to this green solution ammonia be added in excess, a pale green hydrated chromic oxide is precipitated. This may serve as a distinctive test for the chromates. 6. Manganese : Symbol^ Mn ; Atomic Weightf 55. — This is an element which is widely diffused, and enters into the formation of many minerals in small quanti^, but its only important and valuable ore is the black oxide, found either in masses or in radiated groups of crystals. The metal is not used alone, but it is often present in small quantity in cast iron. It is difficult to obtain manganese in a state of purity, as it possesses a powerful attraction for carbon, so that, if reduced, as it may be without much difficulty, by making the carbonate into a paste with oil, and heating it in a covered crucible lined with charcoal, and keeping it for an hour at the highest heat of a forge, the button of metal is always combined with carbon. It also, like iron, combines widi silicon. Manganese is a hard, brittle, greyish-white metal, and is feebly magnetic It is remarkable for the number of oxides which it ^rms. Man- ganous oxide (MnO) is the basis of the common salts of the Compounds of Manganese, H7 metal ; the sesquioxide (MnjO^) is unimportant, and does not furnish stable salts. The red oxide (Mn304) may be regarded as the compound of the two preceding ones ; it corresponds to the magnetic oxide of iron, and furnishes no corresponding salts. The black oxide or dioxide (MnOa) is the most important native compound of the metal ; when treated with jtcids, it gives off haU* its oxygen, and furnishes manganous salts — sMnOa + 2HaS04 = 2MnS04 + aHaO + Oa. With hydrcchidtic acid -it' yields chlorine and manganous chloride — MnOa + 4HCI = MnCla + 2HaO + CU; and if heated alone, it yields oxygen and the red oxide, giving off one-third of its oxygen — 3MnOa = Mn504 + O2. When found native, it is called grey manganese ore, ox pyro- lusite. Another variety, in warty masses, is psilomdane^ and a hydrated form is called wad. It is often found mixed with earthy carbonates, and other impurities. Besides the above-mentioned oxides, manganese forms two others, which are not known in a separate state (MnO^ and MnaO;), which, when dissolved in water, furnish manganic and permanganic acids. The manganates are of a green colour. Sodic Man- ganate (Na2Mn04)'is prepared on a large scale by heating a mixture of caustic soda and finely-powdered manganese to dull redness for several hours in shallow vessels. Its solu- tion forms Condy's green disinfecting liquid. This green substance furnishes an excellent method of distinguishing before the blow-pipe, for if the substance be heated on pla- tinum foil, with a little sodic carbonate, it gives a green colour to the melted mass if a trace of manganese be present. ,, Solutions of the manganates part very readily with oxygen : they must not even be filtered through paper. A small quantity of a free acid changes their solution from green to ll Ml H Uili i % If \ :l!| 248 Tests for Manganese' red, owing to thfO formation of a permanganate and ot k manganous salt — SK.MnO^ + 4H,S04 - 2K,Mn,08 + MnSO^ + 3KaS04 + 4HaO. Potassic Permanganate (Yi^x\S)i^^ may be obtained on a small scale by mixing 40 grams of finely-powdered man- ganese dioxide with 35 grams of potassic chlorate, and adding a solution of 50 grams of caustic potash to the mix- tiu-e, evaporating to dryness, and heating the powdered residue to dull redness in a clay cmcible. When cold, the mass is treated with w^ter, and decanted from the insoluble residue ; a splendid purple liquid is obtained, which on evaporation )rields needles of the permanganate. A solu- tion of this salt is very readily deoxidised and deprived of colour. It furnishes a valuable test liquid in many cases of volumetric analysis. Exp. 240. — Dissolve two or three decigrams of iron wire in diluted sulphuric acid ; then add water till the liquid measures about half a litre. Add gradually a solution of the permanganate, and stir the mixture : the colour will disappear until the whole of the iron has passed from the state of ferrous into that of ferric salt. When this point is reached, the pink colour of the per- manganate will remain unchanged. The change may be thus represented — ioFeS04 + K^Mn^Og + 8HaS04 - 5Fe,3S04 + K,S04 + 2MnS04 + 8H,0. Tests for Mattganese. — Manganous chloride is formed in large quantities in the ordinary mode of preparing chlorine. The manganous salts are of a delicate pink colour, and give nearly colourless solutions. They give with ammonia a white hydrated manganous oxide, soluble in excess of the alkali; but the solution quickly absorbs oxygen, and deposits a brown hydrated peroxide. Ammonic sulphide precipi- tates a flesh-coloured hydrated manganous sulphide. Solu- tion of potassic carbonate precipitates a white manganous carbonate. Before the Uowpipe they give, with sodic car^ Tin. 24* bonate on platinum foil, the characteristic green-coloured manganate ; and they give in the oxidising flame, witli a bead of borax, a violet colour, which disappears in the re- ducing flame. CHAPTER XIV. Group VI. — Tin and Allied Metals. I. Tin. 2. Titanium. 3. Zirconium. 4. TiiORiNUii. (56) Tin: Symb.^n, Atom. Wt. 118; Sp. Gr. 7*29; Fusing Pt. 228^ This familiar metal was known in the early ages of the world. It is not found in many places, Cornwall and Malacca supplying the greatest portion. The only ore of tin of importance is its dioxide, or tinstone, which is often found crystallised. After the ore has been crushed, and roasted to get rid of arsenicum and sulphur, and washed to remove the oxides of iron and copper which are formed from the P3rrites by which it is accompanied, the metal is reduced by heating the residue with powdered anthracite or char coal. Tin is a white metal, with a tinge of yellow, and a high lustre, which it preserves unchanged in the atmosphere. It is rather soft, and very malleable, so that it is easily reduced into sheets of tinfoil, but it is not sufliciently tough to be drawn readily into wire. It melts easily (about 228** C), but is not volatilised in the furnace. It has a considerable tendency to crystallise. Exp. 241. — Warm a sheet of tinplate over a lamp, and then pour over its surface a mixture of nitric and hydrochloric acids diluted with 8 or 10 parts of nvater. In a few minutes crystalline flakes will appear. They may be rendered permanent by wash- ing off" the acid, drying the plate, and varnishing it If heated to bright redness in the air, tin bums with a white light, and fiimishes the dioxide. 11 I!, : I! :'l3 ilFff aso Oxides of Tin. Hydrochloric acid, if heated with tin, dissolves it slowly, with escape of hydrogen, forming stannous chloride (SnCla)> one of its most important salts. Nitric acid of sp. gr. 1*3 oxidises it violently, and forms a white hydrated oxide, known as metastannic acid, but does not form a nitrate. Tin also combines easily with sulphur, phosphorus, chlorine, and bromine, when heated with them. Tin forms several important alloys. Tinplate consists of sheet iron which has been cleansed from oxide, and coated with tin by plunging it into a bath of the melted metal Pewter is an alloy of 4 parts of tin and i of lead. Plumben? solder is a fusible alloy of equal j)arts of tin and lead. Britannia metal is composed of equal parts of brass, tin, antimony, and bismuth ; it is much used for making common spoons and teai)ots. Copper and tin form several valuable alloys. Bronze is a combination of copper, tin, and zinc, with 5 or 6 per cent of tin and 3 or 4 of zinc. Gun metal contains 9 or 10 per cent, of tin, bell me/al about 22 per cent., and speculum metal about 33 per cent. Tinfoil, when amalgamated with mer- cury, forms the silvering applied to the backs of mirrors. Tin forms two oxides, stannous oxide (SnO) and stannic oxide (SnOz). The Stannous Oxide may be obtained as a white hydrate by adding a solution of sodic carbonate to one of stannous chloride : carbonic anhydride escapes, and the hydrated tin oxide is precipitated. It is soluble in an excess of caustic potash, but not in excess of ammonia. This oxide, when moist, absorbs oxygen from the air. It is soluble in acids, and furnishes the stannous salts, of which, how- ever, stannous chloride is the only one of considerable im- portance. Stannic oxide, the dioxide (SnOj), consrtitutes the ore of tin. It is in this form very hard, and is insoluble ia acids ; but when powdered and fused with potash or soda, it com- bines with the alkali, and becomes soluble in water. When combined with water, this oxide furnishes a feeble metallic \f'\ Til Compounds of Tin. 25 1 acid, which is itself readily soluble in diluted acids, though it furnishes salts called stannates. Sodic Stannate (NaaSnO^, 3H2O) may be prepared by fusion, as. above described ; it is used, under the name of tin-prepare liquor, by the calico printer as a mordant for fudng certain colours. Another hydrate of this oxide, possessed of entirely dif- ferent properties, is obtained by treating metallic tin with nitric acid. It is called Metastannic Acid (HjSnsOn, 4HaO), and is quite insoluble in other acids. It also forms unstable salts, such as potassic metastannate (KsSn^Oii, 4HaO). When metastannic acid is heated to redness, it loses all its water, and furnishes a pale buff-coloured substance, some- times calltA putty powder. Tin forms two well-marked sulphides. Stannous Stilphitie (SnS) is thrown down as a chocolate-brown hydrate when a stream of sulphuretted hydrogen is passed through a solution of stannous chloride or other stannous salt It is dissolved by a solution of ammonic disulphide. Stannic Sulphide (SnSa) may be obtained as a hydrate, of a dingy yellow colour, by transmitting sulphuretted hydrogen through a solution of a stannic salt, such as stannic chloride ; and it is readily dissolved by ammonic sulphide, with which it forms a soluble double sulphide. A similar double salt may be obtained in crystals (aNajS, SnSj, laHxO), if sodic sulphide be iised as the solvent Stannic sulphide may be obtained in beautiful yellow flakes, forming mosaic gold^ by heating an amalgam of tin with sulphur and sal ammoniac ; but the operation requires care. Stannous Chloride (SnClj, 2H2O), the tin salts of the dyer, may be obtained crystallised in needles by dissolving tin in strong hydrochloric acid, and evaporating the liquid. It has a strong attraction both for chlorine and for oxygen. It therefore acts as a powerful reducing agent Exp. 242. — ^Add to a solution of corrosive sublunate a drop . If i I I ' i.'f I i$2 Tests for Tin. or two of a solution of stannous chloride : a white precipitate of calomel is formed — zHgCl, + SnCl, - 2HgCl + SnCl^. Now add the tin salt in excess : the precipitate becomes dark grey. It consists of metallic mercury, which may be collected into globules — 2HgCl + SnCl, - 2Hg + SnCV The calomel loses the whole of its chlorine. Stannous chloride is used by the dyer for deoxidising indigo and the peroxides of iron and manganese. Stannic Chloride (SnCl4) is a colourless liquid, which emits dense fumes in the air, boiling at 1 15° C, and combining with water greedily, to form a crystalline hydrate, which is soluble in a further quantity, but is decomposed by copious dilution, stannic acid being precipitated, while hydrochloric acid is set free. The precipitate is readily redissolved by an excess ol acid. Stannic acid is easily obtained from this chloride by the cautious addition of sodic carbonate to the solution. This chloride is prepared without difficulty by distilling I part of tin filings with 4 parts of corrosive sublimate, aHgCla + Sn yielding SnCl4 + 2Hg. Exposure to the fumes must be carefully avoided. Tests for Tin, — In addition to reactions mentioned when speaking of stannous oxide and stannous chloride, the stan- nous salts are characterised by giving in a dilute solution, if mixed with a solution of auric chloride, a beautiful piuple precipitate, * the purple of Cassius ' ; but if the tin salt be in excess, a brown precipitate of reduced gold is formed. Before the blowpipe on charcoal, tin salts yield a malleable white bead of the metal. Tin belongs to the group of tetrad elements, and presents a certain analogy with silicon in its mode of combination. It is still more closely allied to the rare bodies titanium^ zir- conium, and thorinum, which, however, are not of sufficient practical importance to need notice here. Molybdenum is found as a sulphide resembling blacklead ArsmicufH, ^$3 ii . appearance ; and tungsten in a heavy, black, hard mineral, called wolfram. It is unnecessary to describe further the compounds of molybdenum and tungsten, or those of colufn- dium, tantalum, and vanadium : for particulars respecting them the reader is referred to systematic treatises on Chemistry. CHAPTER XV. I. ARSENICUM. 2. ANTIMONY. 3. BISMUTH. (57) I. Arsenicum : Symb. As; Atom. Wt. 75; Sp. gr, cf sol id f 5'95 ; of vapour, io-6 ; Atom. Vol. ^ or^ j Mol. Vol. [m, As, ; Rel. Wt 150. This highly poisonous substance exhibits characters inter- mediate between those of the non-metals and the metals. It conducts electricity in a moderate degree, and possesses high metallic brilliancy ; but it much resembles phosphorus in general properties, including its anomalous vapour density. It is usually found in the form of an alloy with some other metal, especially with iron, cobalt, nickel, or copper. Now and then it is found native, and occasionally in the form of a metallic arseniate. In the preparation of the metal native arsenide of iron or of cobalt is roasted, or heated in a current of air. The arsenicum becomes oxidized, and forms arsenious anhydride (AS2O3), or white arsenic, which is volatilised below a red heat, and becomes co.\densed again as it cools in the flues, yt in chambers consti acted to receive it. In order to obtain the metal, this white oxide is powdered, mixed with charcoal, and heated in a crucible, upon the top of which a second inverted crucible is luted ; and this is screened from the fire by means of a perforated iron plate. Carbonic oxide is formed, and escapes, while the metal, which is also volatile below redness, sublimes, and is con- densed m the cool inverted crucible. The metal, however, "1- 'i: •■:H 254 Arsenicum. is not often wanted. It is very poisonous, both alone and when in combination, and requires great care in experiment- ing with it. Exp. 243.— Take a fragment of white arsenic, the size of a pin's head ; crush it to a fine powder, and mix it with 3 or 4 times its bulk of powdered charcoal. Introduce the mixture into a glass quill tube, scaled at one end and 8 or 10 cm. long. Warm the mixture gently, so as to drive off the moisture which the char- coal usually contains. This, when condensed, may be removed from the tube by introducing a small roll of filtering-paper. Then heat the end of the tube containing the mixture to red- ness. A dark steel-grey metallic mirror-like sublimate of reduced arsenicum will be condensed on the cool sides of the tube, and a distinct garlic-like odour will generally be perceived. Arsenicum is very brittle; it has a brilliant dark steel- grey lustre, and volatilises before it melts, at a temperature of about iSo*' C. It gives ofT a colourless vapour, with an op- pressive garlic-like smell. If heated in air, it combines with oxygen, and becomes converted into arsenious anhydride, which condenses upon somewhat warm surfaces in trans- parent brilliant octahedra. Exp. 244.— Cut off with a triangular file the portion of the tube containing the mirror of arsenicum obtained in the last experiment Crush the glass and put the fragments into another sealed quill tube, and heat the broken portions gently: the metal will be sublimed, but will combine with the oxygen of the air in the tube, on the cool sides of which, by the aid of a pocket lenSf octahedra of arsenious anhydride may be seen condensed. Arsenicum takes file if thrown in powder into chlorine ga^ and '1 combines readily with bromine, iodine, and sulphur, if gently heated with them. Nitric acid oxidises the metal rapidly. Hydrochloric acid has but little action, unless a little nitric acid or nitre be added. Arsenicum is alloyed in small quantity with lead, to facili- tate its taking a globular form in the manufacture of shot [t is also used in combination with copper and oxygen in the preparation of certain green pigments j and orpiment^ Tests for A rsenic. 3$S which is a yellow largely employed, is one of the sulphides of the metal. Arsenicum forms two compounds with oxygen (AstOj and AsjOs), both of which, when combined with water, form acids. Arsenious anhydride, or White Arsenic (AsjOj), is obtained usually as an opaque milk-white mass, often containing small portions or layers of the transparent crystalline form of the compound^ It is but sparingly soluble in cold water, but more so in boiling water, and still more readily in hydro- chloric acid. Alkaline solutions dissolve it easily, and furnish a solution of arsenite of the metal, which does not crystallise. When heated to about 190° the anhydride softens, and sub- limes before fusing. Its vapour is colourless, extremely dense (of sp. gr. 13*8), and it contains i volume of the vapour of the metal and 3 of oxygen condensed into i volume, being double the density that its composition would have led us to expect Exp. 245. — Boil I gram of arsenious anhydride with 3 of potassic carbonate in 100 c. c of water till it is dissolved, and add it to a solution of 3 grams of cupric sulphate in 100 c c. of water: a beautiful green precipitate oiScheel^s Green (CuHAsO,) will be obtained. Exp. 246. — Add a few drops of a solution of arsenio^ : anhy- dride to 200 or 300 c. c. of water, and then 3 or 4 c. c. of hydros chloric acid; place in the liquid two or three slips of bright copper foil, and boil the whole for a few minutes : the copper foil will become coated with a steel-grey film. Part oi' the copper becomes dissolved, and displaces the arsenicum, which is thrown down on the undissolved portion. Pour off the water, dry the copper on blotting-paper, and heat the foil in a quill tube, sealed at one end. The arsenicum will be oxidized and will sublime, condensing in minute octahedra on the cold sides of the tube. This is ReinscKs test for arsenic. MarsKs test may be made as follows : — Exp. 247. — Into a wide-mcuthed flask of the capacity of 150 {., m i!;f \}Ai!i 35^ Arsenic Compounds. or 200 c. c, fit a cork provided with a tube funnel passing nearly to the bottom, and with a second bent tube, which may have a bulb blown upon it, as shown in Fig. 71. This is to be connected by means of a cork with a wider tube loosely filled with calcic chloride. To the end of this drying-tube attach a piece of quill tube, free from lead, drawn out into a capillary end. In the flask place a few fragments of pure zinc, or, better still, of magnesium foil. Then pour on sor : water, and add a sufficient quantity of pure sulphuric acid to cause a steady Fig. 71. formation of hydrogen. When all the air has had time to be displaced, apply the flame of a lamp to the shoulder or begin- ning of the narrowed part of the tube. Add through the funnel two or three drops of a solution of arsenious acid. Immediate voltaic action will occur ; the arsenious acid will be deprived of its oxygen, and part of the metal will at the instant combine with hydrogen, forming arseniuretted hydrogen. This gas will be separated into arsenicum and hydrogen as it passes through the heated tube, and the metal will be deposited as a steel-grey ring just beyond the spot at which the heat is applied. Arsenic Anhydride (AS2O5) may be obtained by boiling arsenious anhydride with nitric acid, and evaporating to dry- ness. It is very soluble in water, and fornis a powerful tribasic acid, which furnishes salts ; these present a very close resemblance to the tribasic phosphates. When united with the same metal, the arseniate and phosphate crystallise in Arseniuretted Hydrogen. 257 exactly the same form, and with the same number of mole- cules of water of crystallisation. The hydric disodic arseniate (Na2HAs04, 12H2O) is made in large quantity for the calico printer and dyer. The potassic dihydric arseniate (KH2ASO4) crystallises in fine octahedra, which are easily obtained by throwing a mixture of equal parts of nitre and arsenious anhydride into a red-hot clay crucible. Allow the mass to cool, dissolving the residue in a small proportion of water, and setting it aside to crys- tallise. Arsenicum and sulphur combine in several proportions: the red compound (AS2S2) is called realgar -y orpimmt is AsjSaj and there is another sulphide, AS2S5; these two last 'correspond to arsenious and arsenic anhydride. Orpiment is easily made by passing sulphuretted hydrogen ihrough a dilute solution of arsenious acid in hydrochloric acid. Orpiment melts easily : it is soluble in ammonia, as well as in potash and soda, and in a solution of an alkaline sulphide. Only one compound of chlorine and arsenicum, the tri- chloride (AsClj), is known. It is liquid and volatile. Corre- sponding compounds with bromine and iodine are solid. Arseniuretted Hydrogen (AsHj). {Mol. and Atomic Wt. 78; Sp. Gr. 2-695; Relative Wt. 39; Mol. Vol. m )— Arsenicum forms a remarkable gaseous compound with hydrogen, which is a deadly poison, It is neither acid nor alkaline, but it has a close analogy with phosphuretted hydrogen, and with ammonia. It is nearly insoluble in water, but is absorbed with decomposition by solutions of cupric sulphate, of corrosive sublimate, and of aigentic nitrate. In the last case, metallic silver and arsenic acid are formed — AsHa -I- SAgNOa + 4H2O = 8HNO3 + H^AsG^ + 4Aga. Its decomposition, when heated, is turned to account in Marsh's test for arsenic. *li i 258 AntinKMty. (58) Antimony: Symb. ^h-, Atom. Wt. 122; Sp. Gr. 671 ] Fusing Ft. about 450°. This metal is always extracted from the sesquisulphide, which is a bluish-white lustrous mineral, crystallised in four- sided prisms, striated across their length. This sulphide is brittle, and melts below a red heat, crystallising as it cools. The crude antimony of commerce is the sulphide freed by fusion from its earthy impurities. The metal is easily ob- tained in small quantities by mixing 4 parts of this sulphide with 2 of pearlasb and i^ nitre, powdering and mixing them intimately, and throwing the powder in small portions at a time into a crucible kept at a bright red heat. The quan- tity of nitre used is not sufficient to oxidise both the sul- phur and the metal ; and as the sulphur is the more com bustible element, it burns, while the metal melts, and collects beneath the melted slag of potassic sulphate. Antimony is a brilliant bluish-white metal, crystallising in plates, and is so brittle that it may be easily powdered in a mortar. It melts just above a red heat, and burns brilliantly in a current of air, giving off white fumes, composed chiefly of antimonious oxide. Powdered antimony takes fire when thrown cold into chlorine gas, and it combines energetically both with bromine and with iodine. Ni^'ic acid ana aqua regia oxidize it with violence; and if powdered, and boiled with sulphuric acid, it is converted into a sulphate. The irtctal, in fine powder, digested with a persulphide of one of the alkali metals, is dissolved. Antimony is too brittle to be used alone, but it is useful for hardening other metals when alloyed with them. Type metal is an alloy of lead with about one-ff)urth of antimony, and often about the same quantity of tin is added. The oxide, when ground up with linseed oil, furnishes a white pigment, inferior, however, to cornmon white lead ; and tartar emetic, a salt of tartaric acid with potassium and antimony 2[K(Sl)0)C4H406]H20. is a very active medicine. »? Compounds of Antimony. 259 Antimony forms three oxides : Sb203, the sesquioxide, is a feeble base, which is freely soluble in hydrochloric and in tartaric acid ; SbjOs is a metallic anhydride ; it furnishes salts with bases called antimoniates ; and Sb204 is a com- pound of these two, which is formed by heating either of the other oxides in a current of air. Antimony combines with hydrogen, and forms a colourless gas, much resembling arseniuretted hydrogen, but with no special odour. It may be obtained by dissolving an alloy of zinc and antimony in diluted sulphuric acid. When a solu- tion of any antimonious salt is added to a mixture of zinc and sulphuric acid which is giving off hydrogen, the antimonial salt is decomposed, and antimoniuretted hydrogen comes off mixed with the free hydrogen. It is decomposed when passed through a red-hot tube, and a brilliant crust of me- tallic antimony is deposited. When the gas is burned in the air, white clouds of antimonious oxide are formed. Antimony forms two sulphides (SbjSa and SbzSg), which correspond to the two principal oxides. They are both soluble in the solutions of the sulphides of the alkali metals,^ and combine with them to form definite crystalline com- pounds, or sulphur salts. The sesquisulphide (SbaSg) is the ore of the metal, but it may also be obtained artificially in beautiful orange-coloured flocculi, by sending a current of sulphuretted hydrogen through a solution of tartar emetic, or other soluble antimo- nious salt. The formation of this compound furnishes one of the b.'*st tests for antimony. It is soluble with escape of sulphuretted hydrogen in hoc hydrochloric acid. The metal forms two chlorides (SbCla andSbCy, which correspond to the oxides and sulphides. The trichloride (SbCl^) is a fusible solid, which is a strong caustic. It is soluble in hydrochloric acid ; but, on dilution, unless the quantity of acid be very large, an insoluble oxychloride (SbCl3. Sb203) fiills as a white powder, readily soluble in tartaric acid. \.i autiinony is heated with chlorine in excess, & 2 ii'ii : I -i m 9fo Oxides of bismuth. it fonns the pentachloride (SbCls), a fuming volatile liquic , which is decomposed by a large quantity of water. The compounds of antimony are powerful irritant poisons. Antimony is more likely to be mistaken for arsenic than for any other metal. The crust which is formed by decom- posing antimoniurctted hydrogen in Marsh's apparatus does not )deld octahedra, when sublimed in a tube with air, but prisms. The metal is also easily soluble in yellow ammo- nium sulphide, which is nearly without effect upon arsenical crusts. (59) Bismuth: Symb. Bi; Atom. Wf. 210; Sp. Gr. 9-8; Fusing Pt. 264". This metal is found but rarely, and is generally met with in the native state in quartz rock, from which it is commonly separated by simple fusion. It is hard, brittle, and of a reddish-white colour. It may be crystallised more readily than any other metal ; and. it furnishes large hollow cubes by fusion and slow cooling, pouring off the inner part before '^the whole has become solid. Bismuth does not become tarnished by exposure to the air at ordinary temperatures, but it is rapidly oxidized in a current of air at a red heat. If thrown in powder into chlorine gas, it takes fire ; and it combines easily with bromine, iodine, and sulphur. Nitric acid is its best solvti?t. The nitrate crystallises in flat, trans- parent, colourless prisms. This metal is not used alone, but it enters into a remark- ably fusible alloy, which may be prepared by melting to- gether 2 parts of bismuth, i of lead, and i of tin. This mixture melts at a little below 100° C; and as it expands in setting, it is valuable to the die-sinker, as it enables him to take sharp and faithful impressions of his work from time to time during its progress. Bismuth forms two principal oxides: BijOa, which is basic, and is easily obtained by heating the nitrate to low redness ; it is yellow, fuses at a red heat, and may be obtained as a white hydrate by Copper, 961 adding ammonia to a solution of one of the bismuth salts ; the other oxide (BijOs) is brown, and furnishes unstable compounds with bases. A native sulph'uk (fJi.S^) is occasionally found crystallised in needles, and is formexi as a black precipitate when solu- tionR of the metal are treated with sulphuretted hydrogen. A trichloride (BiClj) may be obtained as a very fusible, volatile; and deliquescent substance. It is decomposed by water, and a white oxychloride is formed, "hile hydrochloric acid is set free. Bids + H2O = BiOCl + 2HCI. The Nitrate (Bi3N03, 5H2O) is the most important solu- ble salt of this metal. It is soluble in excess of acid, but if largely dilutt'l with water a white basic nitrate (BizOa, i^HNOa) is precipitate , while an acid salt is formed in the liquid — 3(Bi3N03) + 3H,0 = Bi^Oj, 2HNO3 + BisNOj, 4HNO3. Bismuth salts generally become milky when their solutions are diluted with water, owing to the formation of an in- soluble salt containing excess of the oxide. This precipi- tate is easily dissolved by acetic acid. Solutions of the alkalies give a precipitate of the white hydrated oxide, not soluble in excess of the alkali. Solutions of the carbonates and phosphates give a white precipitate with bismuth salts ; but the yellow, with potassic chromate, insoluble in caustic potash, is used to distinguish bismuth from lead, as the lead chromate is dissolved by excess of nntosh. Before the blow- pipe bismuth salts on charcoal yield a brittle bead of metal, surrounded by a ring of yellow oxide. "Ff Mi 1 li li '1 w CHAPTER XVI. I. COPPER. 2. LEAD. 3. THALLIUM. (60) I. Copper: Sytnb. Cu ; Atom. Wt. 63 "5. — This valuable metal is frequently found native, but its most common ore is the sulphide of copper and iron, known as il* 262 Properties of Copper. copper pyrites (CujS, FejSa) ; and other less common ores are the green carbonate, malachite (CuCOj, CuO, HjO), and the bhie carbonate (2CUCO3, CuO, H2O). In the Welsh process of copper smelting, the pyrites is roasted at a dull red heat, to get rid of portions of the sul- phur. The calcined ore is then melted with a siliceous slag, which removes the iron in the form of silicate of the oxide, leaving the copper in the condition of a heavy fusible sub- sulphide. This is separated from the slag, which floats above it, and is then roasted, so as partly to get rid of the sulphur as sulphurous anhydride, and partly to convert the copper into oxide. When this point is reached, the smelter stirs in this oxide, and mixes it with undecom posed cupreous sulphide. The copper, both from the oxide and the sulphide, then becomes reduced to the metallic state, and the sulphur and oxygen pass off together as sulphurous anhydride — CUaS -f 2CuO 4Cu -I- SO2. The crude or blistered copper thus obtained is then melted in large quantities in a reverberatory furnace, where it is poled', that is to say, the trunk of a young tree is thrust into the melted metal, and thus the last portions of oxide are reduced to the metallic state by the combustible gases given off by the wood, and the copper is brought into the pure and tough condition in which it is required for use. Copper is a tough, tenacious, and somewhat hard metal, with a well-known red colour. It emits a peculiar odour when rubbed. It may be drawn into very fine wire, can be roUetl into foil, and hammereCO^, or white leac}. is one of the most TtaUbm. *69 bnportant insoluble compounds of the metal When ground into a paste with a drying oil (linseed oil being generally used), it forms the basis of our common house paints. Lead forms a very large number of insoluble compounds. The sulpliate, iodide, chr^^mate, and sulphide are often used as tests of the metal. If a water contain lead, even in minute quantity, its presence is easily ascertained by takii^ two similar jars of 25 cm. high, of colourless glass, filling both of them with the water, and adding to one of the jan 3 or 4 c c. of a solution of sulphuretted hydrogen. A quantity of lead less than one part in two millions is easily perceived, by the brown tinge occasioned, on looking down upon a sheet of white paper ; the jar to which the test has not been added serving as a standard of comparison. Exp. 253. — Dissolve 30 grams of lead acetate in a litre of distilled water in a flask, and hang up in the solution a lump of zinc. If the glass is left undisturbed for three or four days, beautiful crystalline plates of lead, forming what is often called the ' lead tree,' will be deposited upon the zinc Zinc will have been dissolved, while the lead, which has a smaller attraction for the radical of the acid, is separated. Before the blowpipe on charcoal the salts of lead yield a soft, white, malleable bead of the metal, surrounded by a yellow ring of oxide. (6a) 3. Thallium : Symd. Tl ; A/am. Wt. 204.— This 18 a metal which accompanies certain kinds of pyrites in small quantity. It was discovered quite recently by the beautiful green colour which it gives to flame ; and this, when viewed by the spectroscope, is found to be concen- trated into a single intense green line. It is a heavy metal, resembling lead in appearance, but it quickly tarnishes in the air. Its principal oxide is soluble in water, and has an alkaline reaction on red litmus. The sulphate, nitrate, and carbonate, are white soluble salts. Hie sulphide is brownish-black ; the chloride yellowish-white, and sjjaringly soluble. \\ ti 1/0 CHAPTER XVII. THE NOBLE METALS. I. IfEkcuRV. 2. Silver. 3. Gold. 4. Platinum. 5. Palladium. 6. Rhodium. 7. Osmium. 8. Iridium. 9. Ruthenium. (63) 1. Mercury : Symb. Hg ; Atom. Wt 200 ; Sp. Gr, at 0°, 13*596 ; of Vapour^ 6*976 ; Melting Pt.—yf ; JBoilif^ Pt. 35o«; Atom, and Mol. Vol. PTH \ * ^'i- ^'- loo- This remarkable and interesting metal, often called quick- sUver^ is the only one that is liquid at common temperatures. It is found in but few places, and then usually as sulphide in the red we known as cinnabar^ accompanied by small quantities of the metal itself. It is extracted from this ore by simply roasting it in a current of air, and passing the vapours through long earthen pipes. The mercury condenses, and the sulphurous anhydride passes off into the air. Mer- cuiy possesses a lustre like that of polished ^Iver. It volatilises slowly at all temperatures above 4° C. ; and when heated, it boils at 350**, giving off a heavy transparent vapour, which is 100 times as dense as hydrogen. It freezes at —39**, and foiins a white malleable mass, which contracts suddenly as it becomes solid. When pure, it is not tarnished by exposure to the air; but if kept at a temperature of 300' or 400", it absorbs oxygen slowly, and becomes converted into crystalline scales of the red oxide. The purity of the metal may be judged of by the perfect mobility and spheri* city of its globules, which do not wet non-metallic surfaces. If any other metals, such as zinc, lead, or bismuth, be present, the globules assume an irregular elliptical form, and have a tail-like prolongation as they roll about. Exp. 254. — Dissolve a fragment of lead of about the size of a mustard seed in 40 or 50 grams of clean mercury. Cork it up in a glass bottle which will hold 200 or 300 c. c. and agitate the * The molecule of the vapour of mercury, like that of zinc, cadmium, and other metallic dyads, contains only i atom of the metal. Properties of Mercur;^> tfl mercury briskly : a black film will be found over the surface. Withdraw the coik, blow out the air with a pair of bellows, and then renew the shaking. Repeat this three or four times until the black powder ceases to increase. Then pour the mercury into \ cone of writing-paper folded like an ordinary filter, but pierced at the point with a pin-hole, and supported in a funnel : the metal will run through, and leave the oxide of lead, mixed with finely divided mercury, adhering to the paper. If a little finely-powdered loaf-sugar be added before agitating the mercury, the process is effected more quickly. If a large quantity of mercury is to be purified from foreign metals, it is best to place it in a shallow layer on the bottom of a dish, and to cover it with nitric acid diluted with ten or twelve times its bulk of water, leaving it for a few days at ordinary temperatures, frequently stirring the acid and mercury together ; after which it may be washed, and dried with a cloth. Mercury is attacked immediately by chlorine and by bro- mine ; more slowly by iodine. It also dissolves most of the metals, except iron and platinum. Gold, silver, and tin amalgams are used in the arts. It nlso combines readily with lead, bismuth, antimony, zinc, and copper. The amalgamation is immediately effected by cleansing the sur- face of the metal with a solution of mercury in nitric acid, and then placing the metal in the mercury. Nitric acid dissolves mercury with great energy and liberation of nitrous fumes. Hydrochloric acid is without action on the metal Sulphuric acid, when boiled upon it, dissolves mercury, while sulphurous anhydride is given off; but it has no action upon it in the cold. Mercury is used in medicine, mixed, by simple grinding with chalk, into a grey powder ; and when incorporated with a proper proportion of conserve, it forms what is well known as blue pill. It acts as a powerful metallic poison. Work- men exposed to its vapours in the operations of gilding suffer from a peculiar tremulous affection, called mercurial palsy ; and it often produces salivation, mth ulceration of 2^9 Compounds of Mercury, the mouth and throat Some of its salts, such as conoiive sublimate, when swallowed, act as immediate and powerfiil irritants, producing speedy death. Mercuiy is largely used in philosophical enquiries. Its expansion in glass is employed as a measure of temperature in the thermometer ; and it is not only a requisite in the construction of the barometer, but it furnishes an indispen> sable liquid in the apparatus used for the accurate collection and measurement of gases. Mercury forms two oxides: the grey or black oxide (HgtO), and the red oxide (HgO) : both of them yield salts when treated with acids. Mercurous Oxide (HgaO) is a powerful base, but is unstable when isolated. Exposure to light or to a moderate heat causes it to separate into the metal and the red oxide, HgaO becoming Hg + HgO. It is best obtained by grinding calomel with caustic soda in excess, and washing out the sodic chloride — 2HgCl + 2NaH0 = HgtO + sNaCl + HaO. Mercuric Oxide^ or the red oxide (HgO), is obtained slowly, in red scales, by heating mercury to 300° or 400** in an open flask with a long neck for some days ; but it is more conveniently procured by heating the nitrate cautiously till it is converted into a bright scarlet powder. It may also be precipitated as a yellow powder by adding a solution of potash or soda to one of corrosive sublimate. The red oxide, when heated, becomes black ; and at a higher temperature is separated into metallic mercury and oxygen. It is easily dissolved by acidc. Mercury forms two sulphides, HgaS and HgS, the latter, cinnabar^ constituting the principal ore of the metaL It is formed artificially by subliming mercury with about a sixth of its weight of sulphur, when it furnishes the beautiful red pigment known as vermilion. This sulphide is also obtained as a black precipitate by decomposing a soluble mercuric salt with sulphuretted hydrogen in excess. Aftrcufy and Chlorim. ars Mercuiy also forms two chlorides, calomel (HgCl) and ooiTOsive sublimate (HgCla). Cahmdy or M€rcurou$ Chloride (HgCl), is a heavy, white, insoluble powder, which may be obtained by mixing a solu- tion of sodic chloride with one of mercurous nitrate ; but it is more commonly obtained by converting 4 parts <^ mercuiy bto sulphate by boiling it to dryness with 6 parts of ofl of vitriol, and then grinding the dry mass with 4 parts more of mercury and 3 parts of sodic chloride, and heating the mixture. Mercuric sulphate is first obtained — Hg + aH.S04 a HgS04 r 9H,0 + SO.. This sulphate is then converted, by the additional mercury, •nto the mercurous sulphate^ Hg + HgS04 = HgaSO^; and this, by sublimation with common salt, is converted into calomd and sodic sulphate — sNaC? + Hg,S04 =» sHgCl + NaaS04. Exp, 255.— Heat a little calomel in a test-tube : it will sutv lime without melting, and condense on the cold sides of the tube. Exp. 256. — Place a small quantity of calomel at the bottom ol a short quill tube, cover it with a layer of dried sodic carbonate 15 mm. thick, heat the sodic carbonate to redness, and gradually sublime the calomel through it : white metallic globules ci the metal will condense in the cold part of the tube. Corrosive Sublimate^ or Mercuric Chloride (HgCls), is usually prepared by grinding 5 parts of mercuric sulphate with a of common salt, and subliming the mixture — HgS04 + aNaCl = HgCl, + NatSO^. Its fumes are very acrid and poisonous. Corrosive sublimate melts easily ; and when heated further, boils (at 295°), furnishing vapours, which condense in semi- transparent or in white crystals. It is freely soluble in water, alcohol, and ether. It is the most important of the soluble mercuric compounds. It is a strong antiseptic. Exp, 257. — ^Whip up the white of an egg with water; strain it T i i 1 ; I m Ttstsfor Mercury. through muslin. Add a little solution of corrosive sublimate : an immediate coagulation of the white of egg will occur. Such coagulated albumen is not liable to putrefy. Wood, cordage, and canvas are sometimes soaked in a solution of the salt, and are thereby rendered less likely to decay. Mercuric Iodide (Hgia). — Add to a dilute solution of potassic iodide a few drops of a solution of corrosive sub- limate : a yellow precipitate of mercuric iodide, becoming sahnon-coloured, and ultimately brilliant scarlet (HgIa), is formed. This iodide is redissolved by an excess of potassic iodide, or by one of corrosive sublimate : with the iodide it forms a soluble double salt (KI, Hgis), and a similar double salt with corrosive sublimate (Hglx, 2HgCl2). Exp. 358. — Heat a little of the mercuric iodide in a dry test- tube : it will melt and sublime, and condense in yellow crystals. Shake out the sublimate upon a piece of paper, and draw a glass rod firmly across the heap of crystals : a scarlet colour will be produced. This change is brought about by the conversion of the yellow rhombic plates into a dimorphous red octahedral form by the molecular disturbance occasioned by pressure. Tests for Mercury. — All the salts of this metal are vola- tilised by heat They are all reduced to the metallic state, whether soluble or insoluble, by being boiled with an excess of stannous chloride. If a slip of copper be boiled in a solution of a salt of mercury, it becomes coated with a white amalgam ; and if the copper be heated in a small tube to redness, globules of mercury are driven off, and condense upon the sides. Mercurous salts give a black precipitate with sulphuretted hydrogen ; a white, consisting of calomel, with a soluble chloride ; and this white precipitate is black- ened by the addition of ammonia, but is not redissolved by it It is soluble in chlorine water or in boiling nitric acid. Mercuric salts give a yellow precipitate vnih solution of potash, and a white one with ammonia ; with sulphuretted Properties of Silver. »7$ hydrogen a white, passing through brownish-red into bUck. Their reactions with potassic iodide have been already noticed. (64) 9. Silver : Sym^. Ag ; Afom. IVt. 108. — This beautiful metal has been known and prized from the earliest ages. It is found commonly in the native state, and almost invariably accompanies galena in small quantity, in the form of sulphide. Mercury is used on a large scale for dissolving metallic silver, and separating it from earthy and other im- purities, but the metallurgic processes by which silver is extracted are somewhat elaborate, and are described in the text book on * Metalluigy.' Silver has a white colour, with a tinge of red. It pbs* sesses considerable tenacity and malleability, so that it may be drawn into very thin wire, and hammered into leaf. It is softer and more fusible than copper, and zequires a tem- perature of 1033° C. for its fusion : though it is scarcely volatile in ordinary furnaces, it may even be made to boil under the veiy intense heat of the oxyhydrogen jet As a conductor of heat and electricity, it is unsurpassed. It does not become oxidized at any temperature ; but it has a sin- gular power of absorbing oxygen when in a state of fusion, and giving up the gas suddenly when it solidifies. It com- bines slowly with chlorine, bromine, and iodine. Its attrac- tion fur sulphur is very considerable ; the brown tarnish that silver acquires by exposure to the air is due to the formation of a thin film of argentic sulphide, in consequence of the action of the metal on the traces of sulphuretted hydrogen occasionally present in the air. This tarnish may be removed by rubbing the surface with a solution of potassic cyanide. Nitric acid is the best solvent for silver ; but it may also be dissolved by boiling sulphuric acid, with escape of sulphurous anhydride. Silver is seldom used alone, as it is too soft to resist wear ; but when allcycd 7'?th either 7^ or 10 per cent Ta 976 Experiments on Siher Solutions, of copper, it is extensively employed in coinage and in tlit manufacture of plate. When a tliin layer of silver is applied to the surface of cooper or of steel articles, it furnishes what are called ' plated goods/ Mirrors for lighthouses are plated, as from its high lustre silver furnishes the best reflecting sur- fact for such purposes. Exp. 259. — Dissolve a sixpenny-piece in nitric acid. The solution has a bluish colour, owing to the presence of the copper which is always added before coining, for the purpose of harden* Ing the metal Dilute the solution with 200 c c. of water ; then add a solution of common salt so long as it forms a precipitate : white flakes of argentic chloride are formed. Stir the mixtuie briskly with a glass rod : the precipitate will collect into clots — AgNO, + NaCl - NaNO, + AgCl Filter the solution. The presence of copper may be proved in the clear liquor by adding ammonia in excess to a portion of the liquid : a blue solution is formed. Exp. 260.-- Place the blade of a knife in another portion of the filtrate: it will become coated with metallic copper. Exp. 261. — ^Take the precipitated argentic chloride obtained in Exp. 259, and after having washed it well on a filter, place it in a test-glass with a little water; add two or three drops of sulphuric acid, and then place a slip of zinc in contact with the chloride, and leave it for twenty-four hours. The chloride will be reduced to metallic silver, which will have a grey porous aspect, while zinc chloride will be found in solution. Lift out the piece of zinc carefully ; wash the silver first with water coa« taining a little sulphuric acid, then with pure water. Dry the residue. Place a small quantity of it upon an anvil, and strike it a blow with a hammer : a burnished metallic surface will be produced Place a little of the grey powder upon charcoal, and heat it in the flame of the blowpipe : it will become melted into a brilliant malleable bead. Dissolve another portion in nitric acid: red fumes of nitrogen peroxide escape, and argentic nitrate is obtained in solution. Silver belongs to the class of monads ; it forms only one oxide of practical importance (AgjO). It may be obtained M a brown hydrate by adding caustic potash to a solution Compounds of Silver. V7 of u|;entic nitrate. An excess of potash does not redis* solve it ; but it is easily dissolved by an excess of ammonia. Other oxides (Ag40 and aAgaOa) are, however, known. The most important soluble salt of silver is the nifrate (AgNOj), which crystallises in colourless anhydrous tables ; it milts at a moderate heat, and when cast into small round sticks forms the ' lunar caustic ' of the surgeon. This salt is readily decomposed by the action of organic matter, espe- cially when exposed to light ; hence it is used for the pre- paration of ink for marking on linen, u the stain cannot be removed by washing with soap. If it fall upon the skin, it blackens it A strong solution of potassic iodide, or of the poisonous potassic cyanide, will remove these stains from the skin, or from linen. The sulphide {higS) often occurs naturally, mixed with lead sulphide in small quantity. It may also be precipitated as a black hydrate when any silver salt, soluble or insoluble, is exposed to a solution of sulphuretted hydrogen. The chloride (AgCl) is white, insoluble in water and in nitric acid, even if boiling, but freely soluble in ammonia. If heated to redness, it melts into a homy-looking mass. The precipitated chloride becomes of a dark purple colour when exposed to \iit light, owing to the formation of a subchloride. The bromide (AgBr) is white, insoluble in water and nitric add, and sparingly soluble in ammonia. Tlie iodide (Agl) is of a pale yellow, and is nearly in* soluble in ammonia. The chloride, bromide, and iodide of silver may be re- duced to the state of metallic silver by fusing them in a clay crucible with half their weight of dry sodic carbonate For example — 4AgCl -I- aNaaCO, = 4NaCl -f aAg, -f aCO, + O, They are all soluble in a solution of sodic hyposulphite, and form an intensely sweet solution with it When exposed to light in the presence of aigentic nitrate and some organic '1 I h: ijrS Properties of Gold. matter, tliey undergo chemical changes which form the basb of the common processes of photography. The formation of the chloride, bromide, and iodide of •ilver, and the properties above described of these com- pounds, furnish ready tests for the presence of silver; but the phosphates, chromates, oxalates, tartrates, and citratei all form insoluble precipitates with salts of silver. Copper placed in a solution of silver nitrate or sulphate separates the silver in crystalline plates ; zinc also reduces the xalt, as does also a stick of phosphorus ; but the most beautiful effect is produced by adding a few drops of mercury to a solution of silver nitrate containing 5 or 6 per cent, of the salt A beautiful crystallisation, known as the * silver tree,' will be formed in a few days. (65) 3- Gold : Symb. Au ; Atom. Wt. 196-6.— This valuable metal has been known from the earliest times, for it is found in small quantity in almost every country, and it always occurs in the native state alloyed with silver, gene- rally in a proportion varying from 4 to 12 per cent Many rivers contain it in their sands. In Australia the gold is associated with quartz and slate, and in California it is found in the detritus of quartz and granite. Gold is ex- tracted by a mechanical process of washing, and afterwards dissolving in mercury such portions of the gold as are in a very finely divided state. The mercury is afterwards dis- tilled off, and condensed again for use. Pure gold is of a rich yellow colour and high lustre ; it is nearly as soft as lead. It is very ductile, and is the most malleable of the metals, so that it may be hammered into leaves 11,200 of which would not be thicker than i milli- metre, or 280,000 would not exceed nn inch in thickness. A leaf of gold, attached to a pane of glass, and held up between the eye and a light, will allow a green or puiple light to pass through. Gold leaf is extensively used for gilding on wood, papier m&ch^, and metal, to the surface of which it is attached by means of an adhesive varnish. Compounds of Cold, ^n Gold fuses at about i loo* C. It is scarcely volatile in tht furnace, but in the intense heat of the oxyhydrogen jet it may be dissipated in purple vapours Sulphuric acid does not attack it ; neither does the nitric or the hydrochloric acid separately, but a mixture of the two liberates chlorine and this gradually dissolves it, forming a yellow solution. Exp, a6a.— Place a little gold leaf in two test tubes ; to OM add nitric, to the other hydrochloric add. Even when heated with the acid the gold leaf remain.^ unaflfected. Pour the con- tents of one tube into the other : the ;, '!d will disappear with effervescence. Evaporate this solution in a small porcelain capsule till the acid is nearly all driven off : auric chloride will be left Exp. 263.— Dilute the solution with 3 -^r 4 c. c. of water. To a portion of this liquid add a solution of ferrous sulphate: a brown precipitate of finely divided reduced gold is obtained, and ferr*. chloride is formed — 6FeS04 + 2AuClj - 2(Fe,3S04) + FeaCi« f sAu. This is a common mode of separating gold from its solutions. Add to another portion of the auric chloride a solution of sul- phurous acid : on warming the mixture gold will be precipitated— 3Aua, + 3H,0 + 3H,S0, - 6HC1 + 3H,S04 + aAu. A solution of oxalic acid will have a similar effect— aAuQ, •(- 3H,C,04 - 2Au -t- 6HC1 -f 6C0« carbonic acid being produced. All these liquids look purple when viewed by holding them between the eye and the light, owing to the trans- parency of the finely divided gold. Gold in its pure state is too soft to be used for the pur- poses of coin or plate. It is hardened by alloying it with about a tenth or a twelfth of its weight of copper. Gold is usually triad in combination ; it however forms two oxides (AuaO and AujO^), but they are seldom prepared. The /rr- cMoride (AuCl^), obtained by dissolving gold in a mixture of nitric and hydrochloric acids, as above directed, is the most important compound of the r^etal. When heated gradually i%o PiattfiHfti. to about 175°, it loses chlorine and furnishes ai, rous chlorido (AuCl), a pale yellow, sparingly soluble compound ; and by a heat below redness all the chlorine is expelled, and roe* tallic gold is left. A solution of the trichloride is easily decomposed by organic matter. It stains the skin and other organic substances, such as white silk, of a purple colour. Its solution is reduced to the metallic state by many metals, such as copper, mercury, iron, and zinc, aa well as by phosphorus, and by several other substances. Stannous chloride, if added to its solution in quantity not sufficient to reduce the whole of the gold, gi\£S a fine purple, known as purple of Cassius (Au2Sn306, 4H4O). It is used for colouring the ruby glass of Bohemia. (66) 4. Platinum : Symb. Pt ; Atom. Wt. 197. — This is a hard, tough, white metal, a good deal resembling silver in appearance, with which in earlier times it appears to have been confounded. It is the densest substance known, except osmium and iridium, which accompany it in its ores, and are equally dense. It may be drawn into very fine wire, and rolled into thin foil. On account of its great infusibility and its power of resisting all acids except a mixture of the nitric and hydrochloric, it is extremely valuable to the chemist, as it furnishes him with crucibles and other apparatus in which he can in most cases where accuracy is required fuse and heat the various bodies subjected to analysis. It is also used as the negative metal in Grove's voltaic battery. Platinum is of comparatively rare occurrence. It is found in metallic grains, sometimes associated with gold, silver, copper, iron, and lead, but it is almost always accompanied by certain other metals, which are never found without it, viz. palladium, osmium, iridium, rhodium, and ruthenium. On account of the extreme infusibility of platinum, it re- quires a peculiar and complicated mode of treatment The ore is treated first with nitric acid, to dissolve out the common metals ; then washed, and treated with hydrochloric acid, !i 'I Compounds of Platinum, 3dT and again washed ; after which the residue is digested at a very high temperature in 4 parts of hydrochloric acid, to which about I part of nitric acid is added little by little. When nothing more is dissolved, the acid liquor is decanted, and mixed with a strong solution of sal ammoniac. Most of the platinum is thus precipitated as a yellow double chloride of ammonium and platinum (2H4NCI, PtCl4). This is washed and then heated ; the whole of the ammonia and chlorine are expelled, and the platinum is left as a grey porous mass, commonly known as spongy platinum. This is then pressed, and forged at a high heat into bars or plates, which are afterwards hammered into dishes or vessels, rolled into sheets, or drawn into wire. This method is now, however, gradually being displaced by a mode of melting the ore by means of the oxyhydrogen blo^vpipe. Platinum, if heated alone, does not combine with oxygen at any temperature, but it becomes slowly oxidized if heated with the caustic earths or alkalies. It alloys readily if ignited with lead, tin, bismuth, antimony, or any of the more fusible metals, which would melt a hole in a platinum crucible if heated in it. Platinum belongs to the group of tetrad metals. It forms two oxides (PtO and PtOa). > They both correspond to salts of the metal, but these are seldom prepared. Flatinous oxide (PtO) is soluble in a solution of potash, furnishing a dark olive-green liquid ; and the alkalies also combine with and dissolve platinic oxide (PtOz). There are two chlorides. Platinic Chloride (PtCl4) is the salt obtained by dissolving platinum in a mixture of hydro- chloric and nitric acids, and evaporating the solution to dry* ness at 100° C. It is an orange-coloured deliquescent sub- stance. If heated for some time to about 235° C. it loses half its chlorine, and beromes converted into the olive- coloured insoluble platinous chloride (PtCla). At a heat below redness the whole of the chlorine is driven off, and metallic platinum is left. Platinic chloride forms double salts with the chlorides of the alkali metals ; that with potas* ii 282 Noble Metals. sium (aKCl, PtCl4) forms yellow octahedra, msoluble in alcohol, and nearly so in cold water. The ammonium com- pound (2H4NCI, PtCl4) is commonly employed to separate platinum from its solutions. The sodium salt (afJaCl, PtCl4, 6HiO) is soluble, and crystallises in long red needles. All these salts are decomposed at a red heat : metallic platinum is left, and by washing may be obtained free from the alkaline chlorides. S'Mutions of platinic salts are not reduced by ferrous sul. phate, but they are so by mercurous nitrate, which precipitates inely divided metallic platinum. Oxalic acid does not re- duce them, but a solution of a formiate will, if heated with a neutral solution of platinum, cause the metal to be separated in a powder. 5. Palladium is a white metal, nearly as infusible as pla- tinum. It forms a brown solution when dissolved in nitric add. 6. Rhodium is a very hard white metal, very difficult of solution, even in the mixture of nitric and hydrochloric acids. Its salts are 01 a beautiful rose colour. 7. Osmium occurs in extremely hard scales alloyed with iridium &nd ruthenium. When heated in a current of air, it becomes oxidized, and gives off a remarkable volatile oxide (OSO4), which has a peculiar pungent smell, and is freely soluble in water. Osmium is the least fusible of the metals 8. Iridium accompanies osmium in the ore of platinum, and is sometimes found native and nearly pure. It is a white, very hard, and brittle metal, which furnishes three oxides. They pass readily one into the other, and furnish salts which differ in tint ; hence the name Iridium, from f'm, the rainbow. 9. Ruthenium is a very hard brittle metal, scarcely fusible before the oxyhydrogen blowpipe. It absorbs oxygen at a red heat, and yields several oxides. These metals last mentioned are found, in small quantities, acpompanying the ore of platinum ; but they are so rare as not to need further description. APPENDIX. Page 69 This tendency of gases to mix may be shown in a still more striking manner by the following highly instructive experiment. Adapt to one Fig. 3 1 A. end of a glass tube, about 1,000 mm. long and lo mm. wide, by means of a well-fitting cork, a short circular porous cell, such as is used for galvanic bat* terics ; cover the cork with a layer of sealing-wax. Support the tube in an upright position, with the open end dipping under water, and invert a glass bell jar over the porous cell (fig. 21A). Now pass up hydrogen into the jar: immediately gas will escape firom the open end of the tube ; the hydrogen passing more rapidly through the sides of the porous cell than the oxygen and nitrogen (air) can pass out, thus forcing these latter out of the tube. So soon as the bubbles cease to escape remove the bell jar : the water now rises in the tube owing to the rapid d'Tusion of the hydrogen into the atmosphere. By the aid of this apparatus the student can investigate for himself the phenomena of diffusion ; he will find that whenever the porous cell is lurrounded by a gas lighter than air, bubbles will escape from the tube ; when surrounded by a denser gas the water will rise in the tube, the rise being strictly proportional to the density of the gas. Page no Detection of Nitric Acid or Nitrates. Exp. 93. — ^Add to a fragment of a nitrate in a test-tube a few scrape of copper and pour on it three or four drops of sulphuric acid. Ileek the mixture gerjtly ; red fumes will be given ofil.and may be diitiiiKuiihdl i ■ !: ;l 284 Appendix, readily, even when very small in amonnt, by looking through the tube obliquely over a sheet of white paper. The sulphuric acid decomposes the nitrate, setting nitric acid free } and this in its turn is decomposed by copper with formation of nitric oxide, which unites with the oxygen of the air to form the red fiimes of nitrogen peroxide. Exp, 94. — Dissolve a crystal of a nitrate in a little water in a test* tube ; now add carefully an equal volume of concentrated sulphuric acid, cool the mixture perfectly, then pour in a cold solution of ferrous sul> phate so as to form a layer above the acid mixture. A characteristic dark brown ring will be formed at the line of contact of the liquids. In this case the sulphuric acid reacts on the nitrate, producing nitric acid, which is deoxidised by the ferrous sulphate, nitric oxide, ferric sulphate and water being formed — HNO3 + + KHSO^ H,S04 + KNO3 aHNOj + 3H,S04 + 6FeS04 - 2NO + 3Fe,3S04 + 4OH,. The brown ring is a solution of the nitric oxide in the excess of fer< rous sulphate, as the following experiment proves. Exp, 95. — Introduce concentrated solutions of about five grms. of potassic nitrate and 25 grms. of fcrrous sulphate into a flask closed by a cork through which a bent tube and tube funnel are passed (fig. 22). Pour in about eight grms. of sulphuric acid through the funnel and warm gently : a gas is evolved (nitric oxide) which forms red fumes with the oxygen of the atmosphere. Pass the gas into a cold solution of ferrous sulphate : a dark brown solution is obtained. Afterwards pass the gas through a warm solution of ferrous sulphate : the nitric oxide does not dissolve in this case, and, if protected from the air, the solution remains colourless, thus proving the necessity of employing cold solutions when testing for nitric acid. - Page 114 Water decomposes nitrogen peroxide, forming nitrous and nitric acids — N,04 + H,0 = HNO, + HNO,. Nitric Anhydride (N,Oj). — Owing to the fact that this body decom* poses spontaneously it is extremely difficult to prepare. It has been obtained by decomposing silver nitrate with chlorine — aAgNO, + CI, = N.Oj + 2AgCl + O. Nitric anhydride is a white crystalline substance, which is converted by water into nitric acid — N4O, + H.O - 2HNO,. Appendix. sSj Page 130 The formarion of potassic chlorate by the action of chlorine on the hot solution of potash is at once explained by the fact that on heating a solution of potassic hypochlorite it splits up into potassic chlorate and potassic chloride — 3KCIP = KCIO, + 2KCL Page 139 Anhydrous hydrofluoric acid has been obtained by strongly heating the compound (KF, HF) in platinum vessels, when it breaks up into potassic fluoride and -hydrofluoric acid. The latter is condensed in a well-cooled receiver, to a colourless, transparent, mobile liquid, which boils at 19*40°, and does not attack glass, provided all moisture be ex* eluded. Page 146 Whereas bleaching by chlorine is generally a process of oxidation, bleaching by sulphurous acid is always a process of reduction : chlorine decomposes water, setting free oxygen ; sulphurous acid in the presence of a boily prone to take up hydrogen decomposes water, setting free Sydrogen, itself combining with the oxygen — CI, + H,0 = O + 2HCI. H,SO, + H.O - H, + H,S04. T he bleaching is therefore in both cases usually the result of a secondary reaction. Page 149 The following equations represent the reactions which occur in the process — FCaOj + 4SO,. H.SO^ i- 2NO,. H,S04 + NO. NO,. The nitric peroxide in contact with water and SO, is again reduced (0 nitric oxide, &c. 2FeS, + iiO SO, + 2HNO3 NO, + SO, + H.O NO + O QUESTIONS FOR EXAMINATION. -M*- The following questions have been framed in ac( )rdancc with the Syllabus issued by the Science and Art Department of the Committee of Council on Education, under the head of ' Inorganic Chemistry. First Stage or Elementary Course — Second Stage or Advanced Course/ pp. 90, 91. The student will do well to exercise himself from time to time in answering these questions without reference to the text; and the general reader will find his knowledge of Chemistry become much improved by adopting the same course. Should he not be able to answer any particular question, he will have to refer to the page of the book as in- dicated in the right-hand column, but he is recommended not to write his answer immediately, but to wait until he has tlioroughly mastered the text. The answer should as far as possible be given in the student's own language, not in that of the book. Teachers who prepare their lectures from this book are recommended to set their pupils a number of these questions the day after each lecture : the answers are to be written in full, and marks given to each paper. Those pupils only who thus acquire a certain number of marks should be allowed Questions for Examination. 2^7 to compete for the prize or prizes at the end of the term or half-year. The Teacher can easily frame other questions on the text, and he is recommended to exercise his class in the use of chemical formulae and the numerical statements connected therewith, the measurement of gaseous volumes, the con- version of Fahrenheit into Centigrade degrees, the use of the metric system, &c. C. T. HO. or QUEST. ^«- 3- 5- 6. 7- 8. 9- lO. ri. IS. Tags Give a definition of Chemistry .... 2 What is the difference between a simple and a compound body? ....... 2-5 What do yott mean by the words analysis and synthesis ? . 3 State some of the different modes of chemical action . 4 Write out the symbols of the non-metallic elements with their combining weights . . . • 5i 6 Do the same for the metals . . . • St 6 Describe the difference between combining weights and volume weights .... 196-8 Explain the equation CaCOa + 2HCI = CaCl, + H,0 + CO, and write out the combining numbers for each element, I [ representing one gram of hydrogen . . .8 What is the length in inches of the French metre, or unit of length, the decimetre being 3*937 inches? . .11 Using the same figures (but adding cyphers where neces- sary), write out the value in inches of the decimetre, the centimetre, and the millimetre. Also the decametre, the hectometre, the kilometre, and the myriometre . 9 What is the weight of a gram in grains English? and, if a gram be represented by i 'O, how do you write a deci- gram, a centigram, a milligram, a hectogram, a kilo- gram, and a myriogram ? . . . .11 How many cubic inches does the litre contain ? Also how manypinte? . . . . . , fo 2»S Questions for Examination, HO. or Qunr. 13. 14- 15. 16. 17. 18. 19. 23. 24. 25. a6. 27. 28 i9 30. 31. Using the same figures that express cubic inches or pints, give the decalitre, the hectolitre, the kilolitre, and the mpiolitre. Also the decilitre, the centilitre, and the millilitre . . .10 What is the weight of a cubic metre of water? . . 11 The formula for converting degrees' on Fahrenheit's scale to corresponding degrees on the Centigrade «^calc is |(F.*'-32) = C.° ; and for converting Centigmde to Fahrenheit, gC.** + 32 = F.°. Convert 112®, 45°, 37<*, and 2I4°F., into corresponding degrees on the Centigrade scale ••••••• — ^ Convert 9°, 84", 950 C. into F.® . . . . — Convert -7<»,-450,-390F. into C.° . . . — Convert -1 7",- 30", -8«>C. into F.® . . . — Give examples of the three states of matter . .12 Which of the elements has never been melted, and what gases have never been liquefied ? . . '13 How do you distinguish between mixture and combi- nation? . . . I3> 14 Is atmospheric air a mixture, or a chemical compound ? 15, 38 Write down the symbol, atomic weight, the atomic volume, the specific gravity, the relative weight, the molecular weignt, and the molecular volume of oxygen . 19 Show how you get from 245 gmms of potassic chlorate, 96 grams of oxygen . . . . .21 How many grams of oxygen are there in 1,000 grams, or I kilogram, of potassic chlorate ? . . . — iLxplain some of the properties of oxygen . 22-2P 50 cubic centimetres of a gas are measured at 10° C. ; how much will it measure at 24° C. ? . . . 2& 30 cubic centimetres of a gas at cfi C. are measured at 730 mm. pressure ; what is its volume at 750 mm. the tem- perature being the same ? . . . 28, 29 [ measure 100 cubic centimetres of a gas at 12° C. ; the gas is heated until it becomes 145 cubic centimetres. What is the temperature of the gas under these altered con- ditions? . . . . .28 A litre of gas is measured at 20° C. and 730 mm. What is its volume at the standard pressure and temperature ? 28, 29 Correct for temperature 50 cubic centimetres of gas mea- sured at 5° C. • • t • . tS Questions for Examination. 2«9 MO -V 32. 33. 34- 35- 36. 37. 38. 39. 40. 41- 42. 43. 45. 46. ^47. 48. 49. > 52- / 53. PAGB Ccrrect for pretsore 18 cubic centimetres of • gas at O^C. and 730 mm. .... 38-29 What is the difference between the specific gravity and the relative weight of a gas? . . 39-30 What is the diflierence between an acid and an anhydride? 31 What is the usual test for an acid ?— for an alkali ? • 3' What is a base ? . . •31 State the difference between an acid ending in ous and one ending in «r, and between a salt ending in iu and one ending in ate . . , • 3> ExpUin thu equation : H,SO« + 2KHO « KaSO^ -f 2H,0 33 State the difference between ferrous oxide and ferric oxide, ferrous sulphate and ferric sulphate . . •33 What b ozone sttpp<^ed to be f Name a test for it, and describe its properties .... 34-3^ What is the specific gravity, relative weight, and molecular weight and volume of nitrogen ? . '36 How is nitrogen prepared ? and describe its leading pro* perties . . . '36 When limewater turns milky in the presence of atmospheric air, what does that show ? . . . •39 What is the weight of a litre of dry air at the standard temperature and pressure f . . '39 What are the accidental ingredients of the atmosphere ? . 40 What is the symbol of water ; its atomic and molecular weights ; its specific gravity at 4** C. ? The specific gravity of ice and steam ? The relative weights of water- gas or vapour, and its atomic and molecular volumes ? 41, 44, 65 State some of the methods by which water is decomposed and hydrogen collected, and what becomes of the oxygen ..... 4i~44 How much steam does a litre of water at 100° C. produce ? 44 How are the fixed points in the thermometer determined, and what precautions must be taken with respect to the boiling point ? . . . . •45 Describe some of the physical properties of water . . 45 What takes place during the cooling of water, and what is meant by the point of maximum density of water ? . 47 What is the freezing point of water on the C. and F. scales? — What is meant by the specific gravity of a solid — ^gold, for example? . . . . '47 1 |i^ I fit 290 Qiusiions for Examinmtion, no. or <|OMT. 54. How i« pare water obtained ? 47 ^55. Name some of the impurities that occur iu water, knd how they are detected .... 49-5> ^56. What it the difference between hard and soft water ? . 53 .x^How do you distinguish between the temporary and the permanent hardness of water f . 53-54 58. Describe Clark's soap test ..... y 59. What is meant by a saturated solution f . In the formula Na^COs, 1011,0, what is the loHaO called ? Describe the difference between an efflorescent and a de- liquescent salt ; also between a hydrated and an anhy- drous salt ...... 60. 61. 54 56 57 57 62. Describe the processes for obtaining hydrogen as represented in the following equations : 3Fe-(-4HaO»Fes04 -1-411,; H9SO4 •<- Zn = ZnSO* -f H, 59,60 63 Describe some of the properties of hydn^n . 60,61 y^ 64. What is meant by collecting a gas by displacement T .61 65. How are gases dried ? ... .61 66. What is meant by the mixed gases ? . . .61 67. Describe some of the methods of showing the composition of water by synthesis, such as by the use of the Cavendish apparatus, fig. 17, and the Eudiometer, fig. iS. 65 68. Describe the oxy-hydrogen blow-pipe . . • 67 ^^69. Give some account of diffusion . . . • ^ 70. Why is hydrogen selected as the unit or standard of com- paxison for atomic weights and combining volumes ? 70, 195 V- 71. What is meant by a gas volume ? . . 70» 197 72. The Critk being the weight of i litre of hydrogen at 0° C. and 760 mm. pressure, what is the weight of 10 litres, and also of a cubic metre of hydr«gen ? . — 73. What is the relative weight of oxygen in criths? of chlorine ? of hydrochloric acid ? of ammonia ? . . — 74. What is the weight in criths of 4 cubic nr i^tres of hydriodie acid, and also of ammonia ? . . — 75. What is meant by a monad, a dyad, a triad, and a tetrad ? and give examples . •7' 76. Explain the terms uniiMdent, bivalent, tervalent, and quad- rivalent elements. Also perissad and artiad elements . 72 77. W1utisahydiid«t . • . . '73 Questions for BxaminaHon, ^t Ha or QVUT. 78. 79- 80. 81. 82. 83- 84. 85. 86. 87. 88. 89. 90. 91. 92. /93. 94- 95. 96. 97. 98. 99. 100. lOI. 102. rAOB Write down the symbol, atomic weight, atomic and molecular volume, s[)ecific gravity, and relative weight of carbonic anhydride . . . •73 What do you undeitand by the term carbonate ! . . 74 Explain the equation CiCOa + 2I ICl '■^ CaCl, -f HaO -f CO, 74 Describe some of ^.he properties of carbonic anhydride 75 How do you collect this gas by displacement, and how does the process difler from that for collecting hydrogen ? 76 Show the composition of carbonic anhydride by synthesis 80-81 How is carbonic anhydride disposed of in the atmosphere ? 83 Describe some of the varieties of carbon and their prope;-ties 84 What is meant by allotropy ? . . . • 9^ How is carbonic oxide prepared ? . . . 93i 95 Write in double columns the different properties of car- bonic anhydride and carbonic oxide, such as CO, is CO is non-inflammable inflammable and 10 on . 73-84, 93-96 What is the axis of a crystal ? . . . -98 What are the systems under which crystals are arranged ? and give an example of each . 100-103 Describe the terms amorphous, dimorphous, and isomor- phous ...... 103, 140 Explain the formation of nitric acid from nitre or from sodic nitrate ...... Give an example of double decomposition . Describe the properties of nitric acid What is the difference between N-O. and HNO. ? 106 107 109 no 112 112 Describe the process for obtaining nitrous oxide, and state some of its properties ..... Explain 3CU + SHNO, - 3 (Cu2NOa) + 2NO + 4HaO What is nitric oxide a good test for ? What is the acid in a nitrite ? and give the formula for it 1 1 3- 1 14 Give a list of the chemical compounds of nitrogen and oxygen, and state why atmospheric air is not included in this list . ' . . . . I04> 38 What is meant by multiple proportion ? . . -194 Write down the symbol, atomic weight, atomic and molecular volume, specific gravity, and relative weight of ammoniacai gas . . . • • II4 ua S93 Quistums for Examinaiiam* \ QU -^ 104. 106. 108. 109. iia III. 113. 113. 114. 115. 116. 117. 118. 119. 120, 121. 122. 123. 124. 125. rAOB Describe the procen for collecting and drying ammoniacal gas ..... . 1 15-116 Describe some of the properties of ammoniacal gas 1 16-1 1 7 How much of this gas does box-wood charcoal absorb f . 117 At what temperature does ammoniacal gas become liquid ? also solid? . • 117 What is the difference between liquid ammonia and liquor ammonise? . •1*7 What condensation takes place when nitrogen and hydrogen combine to form ammoniacal gas ? . . .119 Explain the following equation : MnO, ■¥ 2NaCl ••• aHaSO« -MnS04 + NaHSO^ + 2HaO + Cl, . . .120 AlsoMnOB + 4HCl-MnCl,-f 2HaO-t-Cla . . 121 Describe some of the leading properties of chlorine, and why it is called a halogen . . 120, 121 What are the other halogens, and what is their atomicity? ..... 120, 140 What is the bleaching action of chlorine? . . .123 How is hydrochloric acid di^-ectly formed, and what is its relative weight ? . . . . '123 Explain NaCl+HaSO^-HCl + NaHSO* . .125 What is the analytical method of showing that H and CI are present in hydrochloric acid gas ? . . • ^^S What tests may be used for the detection of hydrochloric add and the chlorides ? . . .128 Give a list of the compounds of chlorine and oxygen 129 Show, by means of precipitation, the diflerence between potassic chlorate and potassic chloride . . .130 How is bromine obtained ? . . . .132 Compare hydrobromic with hydrochloric add . 73, 140 What is the acid in argentic nitrate? and what takes place when its solution is added to a weak solution of potassic broriide? . . . . . •134 Give some numerical data respecting iodine . • 134 When a solution of starch is added to one of potassic iodide, the characteristic blue colour is not produced: why is this? ....... 136 What is the symbol, atomic and molecular weight, mole- cular volume, specific gravity, and relative weight of bydriodicadd? • . . • •137 Qutstionsfor Examinatum, 293 NO. or QUUT. 196. 127. 128. 129. 130- 131. 132. 133- »34- «35- 136. »37- 138. 139- 140. 141. 14a. 143 144. 145. 146. »47. 148. 149. PAOB 140 I3« 138 139 Explain the equation PI, -i- 311,0 * HaPHOj ■¥ 3HI Compare hydriodic acid gas with HCl, HBr, and HF 73, What are the properties of HI? .... What are the symbols of iodic and periodic acids ? Why cannot you describe the properties of fluorine ? Explain this equation : CaF, ^ HSaO« - CaSO, > aHF . What is the most remarkable property of hydrofluoric acid, and how may it be exhibited ? . . . 139> 174 Explain this equation : SiOa-t-4HF-SiF«-i-2HaO . 139 What is meant by the term dimorphous ? and give an ex- ample ....... i/^ Describe some of the properties of sulphur, and state its aUotropic modifications, and how they are obtained 141-143 Are roll sulphur and flowers of sulphur allotropic modifica* tions? ....... 144 Give some of the leading data respecting sulphurous anhy- dride ....... 145 Explain the equation: aH^SOf •«■ Cu » CuSO^ -i- SO, + 2HgO 14$ Describe some of the properties of sulphurous anhydride 145-7 Why is oil of vitriol so named, and why is Nordhausen sulphuric acid so called ? 147,148 Describe the English process tor manufacturing sulphuric add on a large scale 149 What is the function of nitric oxide in the manufacture of sulphuric acid ? ..... 149 Name soiae of the properties of sulphuric acid, and the test for detecting it . . . . 150,151 What is meant by the term dibasic ? . . .151 What is meant bv monad metals, and by dyad metals, and by what mark are the latter distinguished from the former? ...... i5» What is the difference between a hyposulphite and a sul- phite? and explain the use of sodic hyposulphite in photography . . . . . .153 Explain the equation Na-jSOa + S = NaaSgO, . • '53 What is the difference between a sulphide, a sulphite, ai^ a sulphate ? . . . . . . — Explain the process for obtiiiiini; sulphurettted hydrogen, and describe the properticN uf this gas, and of its aqueous soliition ..... '$^~$ Ml 394 Questions f$r Examination. NO. or QUBST. 150. »52- IS3- 154. 15s. 156. 157- 158. «S9- 160 161. 162. X163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173. / «74. «7S. rAOi What metals may be precipitated by means of sulphurettad hydrogen? ...... 156 Describe the properties of carbon disulphide . •157 What is there peculiar about the atomic and molecular volume of phosphorus ? . . . 159, 162 State, in a double column, the chief differences between crystalline and amorphous phosphorus . 16 1 -2 Give the formulae for the chief compounds of phosphorus and oxygen ...... 163 What are the three forms of phosphoric acid ? . .164 What is the difference between a phosphate t.nd a pyro- phosphate? . . . . . .165 What is a monobasic, a tribasic, and a tetrabasic acid ? . 166 How is phosphuretted hydrogen prepared ? and what are its properties ? ..... 166-7 Describe some of the crystallised and amorphous forms of silica ....... 168 How is pure silica obtained ? . . . .169 What do you mean by dialysis ? . . . . 1 70 Give the formulae for fire-clay or alumina silicate, ferrous silicate, and lead silicate . . . • 17) What is the composition of different kinds of glass ? .17^ Explain the equation : 2CaFa + 2HaS04 + SiOa = SiF^ -f 2CaS04 + *H ,0 . 1 73 How does boron occur in nature ? . . • I75 Under what forms has boron been obtained ? . .176 Give the formulae for boracic anhydride, boracic acid, and borax ...... What is the atomicity of bo. on? » ♦ What are polymeric bodies ? and give examples How is olefiant gas prepared, and why is it so named ? V/hat is marsh gas? and give its atomic and molecular weights, its specific gravity, and relative weight . 179 What is the principle of the Davy lamp ? . 180-1 Describe Bunsen's burner . . .182 Describe the blow-pipe, and distinguish clearly between the reducing flame and the oxidismg flame . .184 What are the chief products of the destnictive distillation pf^oal? ..... |86-jf 175 176 177 178 *^ Qutstiotts for Examination. 395 Ha ap QVMT 176. FAru 188 189 189 189 Gire the formule for potassic ferrocyanide, and describe how it is prepared ..... 177. What is the difference between a simple and a compound radical ? ...... 178. Which is the radical in NaCl, HNO,, and also in KCN, and which of the three contains a nitrion, and what is it ? 1 79. BxpUin the equation : KCy + HgSO^ » HCy + KHSO4 . 180. Give some account of the atomic theory, and distinguish clearly the four laws of chemical combination . 191-3 181. How do you distinguish between the terms atomic weight and chemical equivalent ? . . . 193-4 182. What is meant by the terms atom, molecule, atomic volume, and molecular volume ? . . • I9S 183. How are the atomic weights of the eleoieats determined ? 195-8 ^ 184. What are the general characteristics of the metals ? 198 -201 185. What is the specific gravity of sodium, magnesium, alumi- num, antimony, zinc, tin, iron, copper, silver, lead, mercury, gold, and platinum ? and give also their fusing points ...... 199 1 86. What is the differenc* between an alloy and an amalgam ? 20 1 , 202 ^187. What is meant by a native metal ? . . . 202 188. Name the metals of the alkalies and their atomicity . 203 189. What is the atomicity of the metals of the alkaline earths ? 203 290. What is there peculiar about the atomicity of the six metals allied to iron ? . . . . 204 191. Name the nin* noble metals .... 205 193. How is potassium prepared ? . . . . 205 93. Explain the term basic oxide .... 206 X94. Explain K9COa + CaO,H,0->3KHO-fCaC03 . . 206 195. Describe seme of the properties of potassic carbonate 307 196. What is nitre ? and state some of its properties and uses 208-9 yi97. What is sea-salt, and how is it obtained ? . .211 198. Describe briefly the manufacture of soda from sea-salt, and explain the terms ball soda, black ash, and soda ash 211-13 199. How do you distinguish between the salts of potassium and those of sodium 7 ..... 314 200. What is Nessler's test ? ..... ai7 201. How is baryta obtained? and describe its properties 217 39a. How is baric sulphat* converted imto a M^ubl* sulphide ? . 218 • I 296 Questions for Examination. NO. or QVBST. 203. 204. y 205. ^ .»• 206. 207. 208. 209. 210. 211. 212. 213. 214. 215. 2l6. 217. 218. 219. 220. 221. 222. 223. 224. 22$. 226. 227. 228. 229. 230. 231. 232. ?33. «^4. MOS Describe the tests for barium salts . . .219 Give a few particulars respecting strontium . .219 How is lime obtained, and what is meant by quick lime and slaked lime ?..... 220 What is plaster of Paris ? ..... 221 Describe some of the varieties of calcic carbonate . . 232 Name some tests for calcium salts .... 223 How is aluminum obtained, and what are its chief pro* pertiesi ..... '223-4 What is a lakc^ and what is a mordants . . •224-5 State some of the properties of hydrate of alumina . 225 Explain Ala03 + 3C + 3Cla = AlaCle + 3CO . . 225 Explain the constitution of the alums . . . 226 What is the formula for the best fire-clay ? . . 227 What is biscuit ? . . . . . . 228 Describe some of the tests for aluminum salts . . 229 Name some of the chief salts of magnesium with their for- mulae and tests ..... .230-1 How is zinc obtained from its ore ? . . . 232 Describe some of the properties of zinc . . . 232 Give some account of the salts of zinc . . . 233 How is cadmium distinguished from zinc ? . . 234 Give some account of cobalt and its oxides . . 235 How are compounds of cobalt distinguished before the blow-pipe? ...... 236 What is the chief ore of nickel ? . . . . 236 What are the more important ores of iron ? . . 237 How is iron obtained from clay iron-stone ? . . 238 How is cast iron converted into wrought iron ? . . 239 What is steel, and how do you distinguish it from iron ? 239-240 Describe the compounds of iron and oxygen . •241 How do you distinguish between ferrous and ferric salts ? . 243 How are the chromates prepared on a large scale f . 245 Describe some of the peculiarities of the manganates . 247 How is potassic permanganate prepared ? and give an illustration of its use ..... 248 Give some tests for man^es^ . f f , 2^ Questiotis for Examination. 297 na OP Qvnr 235- 236. 237- 238. 239. 240. 241. 242. 243- 244. 245. 246.* 247. 248. 249. 250. 251. 252. 253. 254. 255- 256. 257. 258. 259. 260. 261. 262. rAOD Name some of the alloys of tin . . . 250 How are stannous chloride and stannic chloride prepared ? 251-2 What are the atomic and molecular volumes, and the rela- tive weight of arsenicum? .... 253 Describe the two compounds of arsenicum with oxygen 255 Give an account of Reinsch's test for arsenic; also of Marsh's ..... 255-6 What is NaaHAs04, i2HaO? . . .257 Give the molecular and atomic weights, the specific gravity, the relative weights, and mole(»lar volume of arseniu- retted hydrogen ..... What is the action of a solution of argentic nitrate on this How is antimony obtained ? . . Describe the chief properties of antimony . What are the compounds of antimony with oxygen, hydro- gen, sulphur, and chlorine ? . How do you distinguish in Marsh's test between antimony and arsenic ? . Describe some of the properties of bismuth . . What is the formula for the basic oxide of bismuth ? What is the most important soluble salt of bismuth ? Why do bismuth salts in solution generally become milky when diluted ? . Describe briefly the Welsh process of copper-smelting Describe the more important properties of copper . How is cupric oxide obtained ? . What is the formula for blue vitriol ? . . . Describe the tests for copper .... How is lead obtained from its sulphide ? . . What are the chief properties of lead ? . . What is the action of pure vroter on lead ? What is litharge, and what is minium ? . Describe some of the salts of lead .... How is the presence of lead detected in water 7 . Give some of the numerical constants of mercury, such as its specific gravity, melting and boiling points, atomic weight, &C. ...... 257 257 258 258 259 260 afo 260 260 261 262 262-3 263 264 264 265 265 266 267 268 269 270 9b%. What is cinnabar^ and how is (quicksilver obtained from it? a^ 298 Questions for Examination, QUEST. '*°* 264. How may mercury be purified ? . . . 270-1 265. What is the action of acids oc mercury? . . . 271 266. What is vermilion ?..... 272 267. Describe the chlorides of mercury, and give the formulae . 273 26S. What tests are employed for mercurous and mercuric salts? 274 269. Write down some of the leading properties of silver . 275 270. What is the action of common salt on argentic nitrate ? and express the reaction in the form of an equation . 276 271. How are the argentic chloride, bromide, and iodide re- duced to metallic silver ? . . . . 277 272. Describe some of the properties of gold . . . 278 273. What acid dissolves gold, and how does it act ? . . 279 274. How is the purple of Cassius formed ? . . . 280 275. What are the properties of platinum ? . . . 280 276. What is the atomicity of platinum ? . . . 281 377 Describe a few of the salts of platinum . . . aSi I r* INDEX. -•o*- ACl A cms, 30 , Jt~\. — names of, 33 Adularia, 327 After-damp of mines, 180 Aeatc, 169 Albitc, 397 Alkalies, 30 — metals of the, 203, 305 tests for, in combi- nation, 214 Allotropy, 93 Alloys, metallic. 301 Alum, 336 — various kinds of, 226 — properties of, 336 Alumina, 234 — properties of, 224, 335 — sulphate of, 336 — silicates of, 171, 337 Alumiiium, 2*3 — properties ofj 234 — tests for aluminum salts, 339^ Aluminum bronze, 334 Amalgam, 303 Amethyst, 168 Ammonia, 114, x6o ^ sources of, 114 — preparation of, 115 — properties of ammonia- cal gas, 116 — absorption of ammonia, "7 — solution of, 117, 118 — analysis of, 119 — solution of, in w«tcr,2i6 — Nessl«^s test for, 317, note Ammonia oxalate, 233 Amnionic carbonate, hy- dric, 317 Ammonic magnesic phos- phate, 165, 331 Ammonium, 315 — hydrate, 316 — nitrate, no — sulphide and carbonate of, 185 Amorphous bodies, 103 Amorphous phosphorus. 59 . Antimonic anhydride, anhydride, hydro- ATM Analysis, 3 Anhydrides, 74 note Anhydrous substances, 57 AnilinCj t86 Anneahng glass, 171 Anthracite, 86 Antiraoniates, 3J9 ionic an 160 Antimonious 160 Antimoniuretted gen, 160 Antimony, 358 — crude, of commerce, 358 - oxides of, 359 — sulphides o^ 259 — chlorides of, 259 — compounds of, 260 Antimony sulphide, is6 Antiseptic powers of char- coal, 91 ^ — properties of sulphu- rous anhydride, 146 Aqua-fortis, 104 Aiagonite, 232 Argentic bromide, 134 — chlorate, 130 — chloride, 130 Arsenic, whence obtained, 343 Arsenic anhydride, 160, 256, 357 Arsenic, white, 255 Arsenicum, 253 — preparation of, 253 — properties of, 254 — alloy of, 254 — compounds of, 355 — tests for, 355 Arsenious anhydride, 160, 354.. 255, 'S? ^ Arseniuretted hydrogen, 160, 257 Asbestos, 230 Atmospheric air, 15 — not an element, 15 — experiments on, i6 — a mixture of several leases, 38 BUT Atmospheric air— te — properties of sulphu rous anhydride, i^ 300 Index. ,■>•' BT.K Blende, 141, 039 riuwpipc, mouth, xSj — utt of the, 184 Blue pill, 371 Bohemian glass, 280 Boiling point, 45 Bones of animals, prin- cipal earthy component of, 160 Boracic acid, 175, 176 Boracic anhydride, 175 — source of, 175 Borax, \^% — where found, 175 — uses and properties of, 175, X76 Boron, 17^ — properties of, 174-176 — mode of obtunmg, 174 — crystals of, 174 — compounds of, 175 — oxide of, 175 — combinadon with fluo- rine, 176 Brass, aox Bromide, 134 — of silver, 277 Bromine, 132 — properties of, 13a — sources of, 133 — formation of, 133 Bronze, aoi, aso ' Bull-dog ' slag, 171 Bunsen's burner, i8a CADMIUM, 334 — oxide of, 334 Qesium, 314, 315 Calamine, 333 Calcedony, 168 Calcic aurbonate, 333 — chloride, 331 — fluoride, 138 — i>hosphate, 160 — silicate, 171 — sulphate, 153, 160^ asx — sulphide, 156 Calcium, 141, axp — compounds of, 319, 330 — tests for calcium nits, 333 Calico printing, colours in, 334 Calomel, 373 Carbides, 93 Carbolic acid, x86 Carbon, 73, 84 — varieties of, 84-90 — properties of, 93 — compounds of, 177 Carbon disulphide, 157 — properties of, 157 •- i^'eparation of, 158 CHR Carbonate of ammonium, i8<, — of lime, 330 Carbonates, 74, 83 Carbonic acid, 39, 83 Carbonic anhydride, 73 — formation of^ 74 — properties of, 75 — density of, 76 — test for, 77 — sources o() 77, 78 — decomposition of, 80 — synthesis of, 81 — carbonic acid in the atmosphere, 83 Carbonic oxide, 93 — formation and prepara- tion of, 94, 95 — properties of, 96 Cast iron, 338 — grey and white, 339 Cente, 339 Cerium, 339 Cetylene, 177 Chalybeate waters, 55 Charcoal, lamp-black, 90 — antiseptic powers of charcoal, 91 — preparation of, 88 — as a fuel, 89 Charcoal, animal, or ivory black, 90 — preparation of, 90 Chemical formulae, 7 Chemistry, scope and aim of, X China, basis of, 124, saS Chlorates, X3X Chloric acid, 139 preparation of, 131 — oxide, 13a Chloride of lead, 134 — of lime, 130, note — of mercury, X34 — of silver, 377 Chlorides, 133, 130, 167, x68 Chlorine, iso — mode of obtaining, iso — solution of, 131 — properties of, X33. 133 — compounds of chlorine and oxygen, 139 — combination of sulphur with chlorine, 158 Chlorine acids, 130 Chlorous acid, 139 — anhydride, 139 Choke damp, ^8 Chromate of bismuth, 246 — of cadmium, 346 Chromates, the, 345, 346 Chromic anhydride, 335 Chromium, 3^4 CUL Chromium— x n, I03 loa system. cur Cupreous oxide, 963 Cupric chloride, 364 — oxide, 363 — sulphate, 143 -• sulphide, 150, 364 Cyanogen, 188 — preparation of, 188 - properties of, 188 • - Its proi^rty of com- bining with the metals, 188, 189 and with hydrogen, 188, 189 DAVY'S safety lamp, 180, x8i Decomposition, 3 Destructive distillation, 89 Dialysis, 170 Diamond, 84 Didymium, 339 Dihydric sodic phosphate, 164, 165 Dimorphous bodies, 103, 143 Djoxide of banum, 317 Dipotassic sulphate, or normal sulphate, 151 — sulphide, 156 Disodic hydric phosphate, formation of, 164 — sulphite, 146 Distillation^ 134 — _ destructive, 89 Disulphates, x^x Disulphide of iron, 343 Dithionic acid, X44 Dolomite, 330 Ductility of metals, sox Dutch kquid, 178 Dyads, or bivalent ele- ments, 73, 73 EARTHENWARE, basis of, 224, 228, — manufacture of, 228 Effervescent vi^aters, 55 Elements, chemical, 6 — combination, i — mode of occurrence, 4 — number of, 4 — • division )iaq metals and non-metals, 5 — list of, with their sym- bols and atomic weignu, 6 Emerald, 339 Emery, 334 Epsom salts, 330, 331 Erbium, 339 EthYlsuiphuric acid, 178 Eudiometer, the, 65 OOL FELSPAR, or adu- laria, 337 — varieties of, 337 Fermentation, carbonic anhyd-ide formed by, 77 — mode of checking, 146 Ferric oxide, 33, X47, 341, 343 Ferrous carbonate, 337, 343 — chloride, 3X, 343 — oxide, 33, 341 — salts, 343, 344 — sulphide, 343 Filter, paper, how to make a, 90 — for water, 91 Fire-bricks, 171 — clay, 171 — damp of mines, 179 Flame, structure and pro- perties of, 181, 183 — the blowpipe, 184 — the reducing and the oxidising flames, 184 Flint, 169 Fluorides, 138 Fluorine, X38 — compound of, with hy- drogen, X40 Fluor spar, 138 Foil, of metals, sox Freezing point, 45 Fur inside a boiler, 53 GALENA, 141, 265 Gas coke, 185 Gases, 13 — experiments with, 20 — measurement of, 29 Gaseous compounds of the different elements, 72, 73 German silver, 201, 236 Geysers of Iceland, silica dissolved in the, 170 Glass, action of hydro- fluoric acid on, 139 — manufacture of, 170, 171 — window glass, or crown glass, 171 — plate glass, 173 — bottle glass, 173 — Bohemian glass, 172 — flint glass, 172 — properties of, 172, 173 — annealing, 173 Glaze for stoneware, 3s8 Glucinuni, 229 Gneiss, 327 Gold, 378 HYC Gold— CM*/. — properties of, 978, 379 — alloy of, 379 — oxides of, 379 Granite, 337 Graphite, 85 Guano, phosphorus in, x6o Gun-metal, aox, 350 Gunpowder, 309 Gypsum, 33x HiEMATITE, red, 337 — brown, 337 Haematite auhydratei brown, 349 Halogens, x^ — compounoi of the, 140 — compared with each other, 140 Harrogate water, 155 Hartshorn, 114 Hornblende, 330 Hydrates^ 57 Hydric disodic arseniate, ■57 — disodic phosphate, 165 — nitrate, X05 — potassic sulphate, or |(en -unds with metals, — tests of, 157 I Sulphuretted waters, 55 Sulphuric it' id, 147 — importn:;cc ol the manufacture of, 147 — mode of preparing, 148 — manufacture of, on a large scale, 149, 150 — salts of, 151 Sulphuric anhydride, for- mation of, 148 Sulphurous acid, 144, 145, 146 Sulphurous anhydride, MS. 843 . — production of, 145, 146 — properties of, 145 — acid and salts, 146 Superphosphate of lime, 161 Symbols, chemical, 6 TANTALUM, 253 Tartar emetic, 258 Telluretted hydrogen, 159 Telluric acid, 159 Tellurium, 158 — properties of, 158, 159 Teilurous acid, 199 Test-papers, 31, note Tests, in chemistry, 31, note Tetrabasic acids, 166 Tetrads, or quadrivalent elements, 73 Tetrathionic acid, 144 Thallium, 269 — properties of, 269 Thorinum, 253 Tin, 949 — alloys of, 950 — oxides of, 250 — compounds of, 351 — tests for, 253 Tjn salts, 251 Tincal, or crude Indian borax, 175 Tinfoil, 249 Tinstone, 249 Titanium, 359 Touch ^aper, 309 Travertine, 933 Triads, or tervalent ele- ments, 7a, 73 Tribasic acids, 166 — phosphoric acid, 165 Tncalcic phosphate, 161 Trifluorides, 176 Trisodic phosphate, 164, 165 Trithionic acid, 144 Tufa, 933 nrn Tungsten, 953 Type-metal, aot, 13! T TRANtUM, 837 VANADIUM, 253 Ventilation of rooms. 79 . Vermiliun, pigment, 379 Vitriol, blue, 964 — green, 147 — white, 333 — oil of, 147, «5o WATER, 41 — decomposition of, 4a — freezing and boiling of, 45 . — distillation of, 48 — rain water, 49 — presence of air in, 49 — spring water, 50 — impurities in natural waters, 50-53 — hard and soft, 53 — fur iiiside a boiler, 53 — soap test for, 54 — mineral waters, 55 — sea water, 56 — saturation, 56 — crystallisation, 58 — efflorescent and deli- quescent salts, 57 — compounds of, 57 — comnosition of, 63, 64 — svn thesis of, 65 — tne eudiometer, 65 Water of crystal lisation, 57 Water cisterns, lead, 366 slate, 266 Weights and measures, 9 Witherite, 219 Wolfram, 253 I Woulfe's bottles, 218 Writing-ink, 334 Y^T RIUM, a99 ZINC, 232 — properties of, aja — alloys of, 233 — salts of, 333 — oxide, 233 — sulphate, 9» \ Zirconic chloride, 174 Zirconium, 353 al