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BOHN'S SCIENTIFIC LIBRARY. 
 
 EXPERIMENTAL CHEMISTRY. 
 
EXPERIMENTAL CHEMISTRY, 
 
 FOUNDED ON THE WORK OF 
 
 DE. JULIUS ADOLPH STOCKHAEDT. 
 
 A 
 
 HANDBOOK FOE THE STUDY OF THE SCIENCE 
 BY SIMPLE EXPEEIMENTS. 
 
 By 0. W. HEATON, F-I.C, F.C.S., 
 
 LECTURER ON CHEMISTRY IN THE MEDICAL SCHOOL OF CHARING CROSS HOSPITAL, 
 EXAMINER IN CHEMISTRY TO THE ROYAL COLLEGE OF PHYSICIANS 
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 NEW EDITION REVISED. 
 
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 COVENT GARDEN. 
 1886. 
 
LONDON: 
 
 PRINTED BY WILLIAM CLOWES AND SONS, Limiteix, 
 
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PKEFACE. 
 
 " Stockhardt's Principles of Chemistry," in its English 
 dress, has for many years filled a definite and useful place 
 among elementary text books. It has appealed to the 
 numerous class of students, both men and boys, who in 
 spite of limited means and opportunities are anxious to 
 acquire some experimental knowledge of the science — who 
 intend to worlc at chemistry instead of merely reading 
 about it. - To such students it is useless to describe experi- 
 ments which can only be performed with the aid of costly 
 and elaborate apparatus, or with the skill derived from 
 long practice. 
 
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 the experiments are clearly described and very numerous, 
 they do not require for their successful performance any 
 but the simplest and cheapest forms of apparatus. It is 
 astonishing what an amount of good work may be done in 
 chemistry with Florence flasks, tumblers, medicine bottles, 
 basins, saucepans, tin plate, iron wire, corks and other 
 articles, which are always at hand. If to these are added 
 some glass and caoutchouc tubing, a few funnels, test- 
 tubes and beakers, a mortar and pestle, spirit lamp (if 
 gas cannot be used), a small set of scales and weights, 
 
 64848 
 
vi 
 
 PREFACE. 
 
 and a measuring glass, the student will be able to per- 
 form the great majority of the elementary experiments of 
 chemistry. 
 
 Of course other apparatus may be added with great 
 advantage, and apparatus is so cheap in the J)resent day 
 that almost every student will find it possible to make 
 such additions to his stock as he goes on. But it is better 
 not to begin with too much, as the beginner is almost 
 sure to order many things which he will not really 
 require. 
 
 When the publishers put Dr. Stockhardt's work in my 
 hands, I hoped that it might be possible to bring it into 
 accordance with modern chemical ideas, without entirely 
 altering its plan. This soon proved to be impracticable, 
 and I found myself compelled to re-cast, and to a great 
 extent to re-write the book. In doing so I have tried to 
 preserve as far as I could the spirit of the original ; but 
 so much has been added, so much subtracted and so much 
 altered, that I have not thought it right to retain the 
 original title of the work. Nearly the whole of the 
 original work which remains consists of experimental 
 details and technical descriptions, which, though they 
 have required much pruning and revision, are as useful 
 now as when first written. A great many new experiments 
 have been added in every part of the work. 
 
 The systematic classification adopted in Parts II. and 
 III. has not been attempted in Part IV. (Organic Chemis- 
 try), because the more old-fashioned arrangement seemed 
 better adapted for the purposes of a simple experimental 
 study. But I have endeavoured, in two introductory 
 chapters, to give the student some idea of the modern 
 
PREFACE. 
 
 Vll 
 
 system of classification, and have, in the subsequent pages, 
 referred constantly to these chapters. 
 
 In Part I., a somewhat lengthy chapter (Chapter III.) 
 has been devoted to the laws of chemical force. This 
 chapter is longer than it might otherwise have been, 
 because I have thought it right to establish the laws of 
 constitution and chemical action, and the primary mean- 
 ing of symbols and formulae, before taking advantage of 
 the great assistance of the atomic hypothesis. I trust I 
 have succeeded in proving to the careful student that the 
 symbols and formulas of chemistry might be used with 
 propriety and advantage, even if the atomic hypothesis 
 were swept away. 
 
 In Parts II. and III. I was much assisted by Mr. 
 E. Francis, F.C.S., Demonstrator of Chemistry in the 
 Medical School of this Hospital. It is a pleasure to me to 
 take this opportunity of thanking him for his valuable 
 help in this and in many other things. 
 
 Chaking Cross Hospital, 
 Christmas, 1871. 
 
 C. W. H. 
 
PEEFACE TO NEW EDITION. 
 
 After careful consideration I have decided to make no 
 change in the plan of the book, in the part devoted to 
 Organic Chemistry. Of course many alterations in detail 
 have been necessary, but I still think that for students 
 working with limited means, the system adopted by 
 Dr. Stockhardt, although now old-fashioned, is, on the 
 whole, the best. 
 
 C. W. H. 
 
 Charing Cross Hospital, 
 July, 1886. 
 
CONTENTS. 
 
 PAET I. 
 GENEEAL PEINCIPLES. 
 
 CHAPTER T. 
 
 MATTER AND FORCE. 
 
 PAGE 
 
 Matter and Force 1 
 
 Energy 1 
 
 Different forms of force ........ 2 
 
 Gravity — weight. ....... 2 
 
 Cohesion — Adhesion 3 
 
 Heat 4 
 
 Light 4 
 
 Electricity 4 
 
 Chemical force — chemical affinity ..... 5 
 
 Relation of the forces to one another ..... 8 
 
 Photography 11 
 
 Decomposition by electricity ..... 12 
 
 Objects of chemical inquiry . . . . . . .15 
 
 Elements, compounds, mixtures 16 
 
 The ancient elements . . . . . . . .18 
 
 CHAPTER II. 
 
 gravity — heat — pressure. 
 
 Gravity . . 19 
 
 Weighing and measuring . . . . . . ..19 
 
 Weighing ......... 19 
 
 Metrical system ........ 20 
 
 Measuring liquids and gases 21 
 
 Specific gravity 22 
 
 Specific gravity bottle 23 
 
 Hydrometer . 25 
 
X CONTENTS. 
 
 PAGE 
 
 Heat 26 
 
 Sources of heat — lamps 27 
 
 Effects of heat 27 
 
 Expansion of liquids — the thermometer. ... 27 
 
 Tliermometric scales ....... 29 
 
 Expansion of solids . . . . . . •SI 
 
 Expansion of gases ....... 33 
 
 Change of state . . ' . . . . . . . . 35 
 
 From solid to liquid — latent heat ..... 35 
 
 From liquid to gas — boiling ...... 37 
 
 Latent heat of steam ....... 38 
 
 Evaporation — Aqueous vapour ..... 40 
 
 Distillation. ........ 42 
 
 Diffusion of heat . . .43 
 
 Conduction. ........ 43 
 
 Convection 44 
 
 Ventilation. ........ 46 
 
 Kadiation ......... 46 
 
 Formation of dew ....... 47 
 
 Solution and crystallization ....... 48 
 
 Pressure 53 
 
 Pressure of the atmosphere 54 
 
 Barometer ......... 55 
 
 Elasticity of gases ....... 57 
 
 Correction for pressure ....... 57 
 
 Variations of boiling-point . . . . . .58 
 
 CHAPTER III. 
 
 FUNDAMENTAL LAWS OF CHEMISTRY. 
 
 Modes in which chemical action takes place .... 61 
 
 Combination ........ 61 
 
 Decomposition ........ 62 
 
 Double decomposition . ..... 63 
 
 Substitution or displacement ..... 63 
 
 Quantities concerned in chemical changes .... 64 
 
 Law of constant composition. ..... 64 
 
 Difference between combination by weight and by volume 64 
 
 Chemical action between gases — Constitution of gases . . 65 
 
 Law of gaseous volumes ..... 65 
 
 Standard of volume for gases ..... 67 
 
 Symbols and formulae ....... 68 
 
 Relative weight of gases ...... 69 
 
 Constitution of elementary gases ..... 70 
 
 Atoms ........ 70 
 
 Constitution of compound gases . . . . .71 
 
 Compound gases containing non-volatile elements . . 71 
 Calculation of the specific gravities of gases from their 
 
 foimula3 ......... 75 
 
CONTENTS, . xi 
 
 TAGK 
 
 Composition as determined by weight — Laws of combination by- 
 weight 75 
 
 Percentage composition ...... 75 
 
 Simplest numerical proportion of the constituents . . 70 
 Units of combining weight — Combining weights — Atomic 
 weights ......... 79 
 
 Use of symbols ........ 79 
 
 Modes of fixing atomic weights ..... 80 
 
 Specific heat ........ 82 
 
 Isomorphism ........ 84 
 
 Equivalent value of atoms — valency, atomicity, or quantivalence 86 
 Perissiad and Artiad atouiS ...... 87 
 
 Vai iations of valency ....... 87 
 
 Radicals ......... 88 
 
 Table of radicals. ....... 89 
 
 Nomenclature ......... 89 
 
 Atomic and molecular hypotheses ...... 90 
 
 Atoms.— Atomic weights .90 
 
 Molecules — Molecular weights . . . . .91 
 Hypotliesis of Avogadro and Ampere .... 92 
 Structure of gases. — Summary of hypothesis ... 92 
 Molecules of solids and liquids ..... 93 
 Hypothesis to account for valency ..... 93 
 
 Equations, or formulse of chemical change .... 94 
 
 Acids, Bases, Salts 97 ' 
 
 Basity of acids ........ 98 
 
 Oxygen acids, or oxy-acids ...... 98 
 
 Formation of salts . . . . . . .99 
 
 Newland's Periodic Law .101 
 
 PAET II. 
 NON-METALLIC ELEMENTS. 
 
 CHAPTER I. 
 
 non-metallic monads. 
 
 Introduction ......... 102 
 
 Hydeogen 104 
 
 Preparation . . . . . . . .104 
 
 Collection of gases 106 
 
 Properties ......... 107 
 
 Chlorine . 109 
 
 Preparation . . . . . . . .110 
 
 Properties ......... Ill 
 
 Hydrochloric Acid 114 
 
xii CONTENTS. 
 
 . PAGB 
 
 Bromine 118 
 
 Iodine 119 
 
 Hydrobromic and hydriodic acids ..... 121 
 
 Fluorine 121 
 
 Hydrofluoric acid 122 
 
 CHAPTER II. 
 non-metallic diads. 
 
 Oxygen 123 
 
 Preparation . . . . . . . .124 
 
 Properties . . 125 
 
 Combustion. ........ 128 
 
 Respiration. ........ 129 
 
 Deflagration . . . . . . . .130 
 
 Ozone 130 
 
 Water 132 
 
 Oxy-hydrogen blow-pipe 133 
 
 Lime light .134 
 
 Hydrogen peroxide ....... 136 
 
 Compounds of Oxygen and Chlorine .... 136 
 
 Hypochlorous anhydride . . . . . .136 
 
 Chlorine peroxide 137 
 
 Chloric acid 138 
 
 Sulphur .......... 139 
 
 Hydrogen Sulphide, or Sulphuretted Hydrogen. . 143 
 Compounds of Sulphur and Oxygen .... 146 
 
 Sulphurous anhydride and sulphurous acid . . . 146 
 Sulphuric anhydride and sulphuric acid . . . 148 
 Fuming, or Nordhausen sulphuric acid .... 149 
 
 Manufacture of sulphuric acid . . . . . 150 
 
 Selenium and Tellurium 153 
 
 CHAPTER III. 
 non-metallic triads. 
 
 Nitrogen .154 
 
 The atmosphere 156 
 
 Ammonia 157 
 
 Ammonium compounds . . . . . .158 
 
 Compounds of Nitrogen and Oxygen .... 159 
 
 Nitric acid . . .160 
 
 Nitrous oxide .163 
 
 Nitric oxide .164 
 
 Nitrous anhydride . . . . . . .165 
 
 Nitric peroxide . . . . . . . .165 
 
 Phosphorus 165 
 
 Preparation . . . . . . . .166 
 
 Experiments with phosphorus . . . . .166 
 
CONTENTS. xiii 
 
 Phosphorus — continued. page 
 
 Phosphine, or phosphuretted hydrogen .... 169 
 Compounds of Phosphorus and Oxygen . . .170 
 
 Phosphoric anhydride 170 
 
 Phosphoric acid 171 
 
 Boron 173 
 
 Boric anhydride and boric acid 174 
 
 Borax 174 
 
 CHAPTER IV. 
 non-metallic tetrads. 
 
 Carbon 175 
 
 Charcoal 176 
 
 Lamp-black . 177 
 
 Coke 177 
 
 Bone-black, or animal charcoal 177 
 
 Graphite, or plumbago 178 
 
 Diamond . . .178 
 
 Dimorphism. — Polymorphism 178 
 
 Compounds op Carbon and Oxygen .... 179 
 
 Carbonic anhydride ....... 179 
 
 Diffusion of Gases 180 
 
 Carbonates 181 
 
 Carbonic oxide . . . . . . . . 181 
 
 Compounds of Carbon and Hydrogen . . . .182 
 
 Methane, or marsh gas 182 
 
 Ethylene, or defiant gas 184 
 
 Acetylene . . . 185 
 
 Carbon Disulphide 185 
 
 Cyanogen 186 
 
 Hydrocyanic, or Prussic acid 187 
 
 Destructive Distillation. — Flame 188 
 
 Distillation of coal 188 
 
 Flame 189 
 
 The blowpipe 191 
 
 The Davy lamp 192 
 
 Argand burner 192 
 
 Silicon 193 
 
 Silicic anhydride, or silica 193 
 
 Soluble glass 193 
 
 Silicates ......... 195 
 
 Silicon fluoride 195 
 
xiv 
 
 CONTENTS. 
 
 PAET III. 
 METALS. 
 
 CHAPTER I. 
 
 METALLIC MONADS. 
 
 PAGF, 
 
 Potassium . . . 196 
 
 Potassium oxide ........ 197 
 
 „ hydrate .197 
 
 „ carbonate . . . . . . . 198 
 
 „ sulphate 199 
 
 „ nitrate, or nitre ...... 200 
 
 Gunpowder 200 
 
 Potassium chlorate ....... 201 
 
 „ chloride . . . . . . .202 
 
 „ iodide 202 
 
 „ sulphide. — Liver of sulphur .... 203 
 
 Sodium . . .208 
 
 Sodium oxide and hydrate ...... 204 
 
 chloride (common salt) ..... 204 
 
 Water of Crystallization 205 
 
 Sodium sulphate 205 
 
 „ sulphide 207 
 
 „ carbonate (carbonate of soda) .... 207 
 
 „ nitrate 209 
 
 „ phosphate ....... 209 
 
 „ borate (borax) 209 
 
 „ silicates . 210 
 
 Glass 210 
 
 Ammonium . 211 
 
 Ammonium hydrate . . . . . . .212 
 
 chloride v . 212 
 
 sulpliide ....... 212 
 
 „ carbonate 218 
 
 ,, nitrate ....... 218 
 
 Silver 218 
 
 Silver nitrate 214 
 
 „ chloride ........ 215 
 
 „ sulphide . .215 
 
CONTENTS. XV 
 CHAPTER II. 
 
 METALLIC DIADS. 
 
 PAGK 
 
 Gkoiip i 21(; 
 
 Calcium 216 
 
 Calcium oxide— lime ....... 210 
 
 „ hydrate — slaked lime ..... 216 
 
 „ carbonate ....... 217 
 
 „ sulphate — gypsum — plaster of Paris. . . 217 
 
 chloride 218 
 
 „ fluoride — fluor spar ..... 218 
 
 Stkontium 218 
 
 Barium . . 219 
 
 Magnesium . . . 219 
 
 Magnesium oxide — magnesia . . . . .220 
 
 carbonate . . . . . ... 220 
 
 „ sulphate — Epsom salts .... 220 
 
 chloride 220 
 
 Zinc 221 
 
 Zinc oxide 222 
 
 „ hydrate 222 
 
 „ sulphate — white vitriol ..... 222 
 
 Group ii . . . 223 
 
 Copper 223 
 
 Ores of copper ........ 225 
 
 Alloys of copper ........ 225 
 
 Cuprous oxide ........ 225 
 
 Cupric oxide ........ 225 
 
 Cuprous and cupric chlorides ..... 226 
 
 Cupric nitrate . . . . . . . . 226 
 
 „ sulphate — blue vitriol ..... 227 
 
 Mercury, or Quicksilver ....... 228 
 
 Oxides 230 
 
 Nitrates 230 
 
 Chlorides. — Calomel and corrosive sublimate . . . 231 
 
 Mercuric iodide ........ 232 
 
 sulphate . ... . . . . 233 
 
 „ sulphide 233 
 
 Amalgams ......... 233 
 
 Lead .234 
 
 Lead oxide — litharge . . . . . . . 235 
 
 „ dioxide 236 
 
 „ red oxide— red lead ...... 236 
 
 „ hydrate 236 
 
 „ nitrate . . . . . . . . 236 
 
 chloride . 237 
 
 „ acetate ........ 237 
 
 „ basic acetate ....... 237 
 
 „ sulphate ........ 237 
 
 „ carbonate — white lead 237 
 
Xvi CONTENTS. 
 
 Lead — continued, tage 
 
 Lead tree 238 
 
 „ tartrate 239 
 
 „ sulphide 239 
 
 CHAPTER IIL 
 
 METALLIC DIADS, OR TETRADS. 
 
 Group i 240 
 
 Iron 241 
 
 Smelting of iron — cast iron 241 
 
 Wrought iron ........ 244 
 
 Steel 245 
 
 Iron oxides' 247 
 
 „ chlorides 249 
 
 „ sulphates ........ 249 
 
 „ nitrate ........ 249 
 
 „ acetate , 250 
 
 „ sulphides 250 
 
 Chromium 251 
 
 Chromic oxide and hydrate 252 
 
 „ anhydride ....... 252 
 
 Potassium chromate 253 
 
 Ammonium dichromate . . . . . . 254 
 
 Chloro-chromic anhydride ...... 255 
 
 Manganese 255 
 
 Manganese oxides 256 
 
 „ sulphate 256 
 
 „ chloride 257 
 
 Manganic and permanganic acids 257 
 
 Potassium manganate (chameleon) .... 257 
 
 „ permanganate ...... 258 
 
 Aluminium 259 
 
 Aluminium oxide — alumina 260 
 
 „ sulphate 260 
 
 Alum 261 
 
 Ultramarine ........ 262 
 
 Cobalt and Nickel 263 
 
 Group ii 265 
 
 Tin . . ■ 265 
 
 Alloys 266 
 
 Oxides 268 
 
 Chlorides 269 
 
 Sulphides 269 
 
 Platinum . 270 
 
 Platinic chloride 271 
 
 Potassio-platinic chloride ...... 271 
 
 Ammonio-platinic chloride ...... 272 
 
CONTENTS. xvii 
 CHAPTER IV. 
 
 METALLIC TBI ADS, OR PENTADS. 
 
 PAGK 
 
 Group i 273 
 
 Gold 273 
 
 Auric chloride . . . . . . • . . 276 
 
 Purple of Cassius . . . . . . . 277 
 
 Group ii 277 
 
 Arsenic 277 
 
 • Arsenious anhydride — white arsenic . . 278 
 
 Scheele's green ........ 280 
 
 Arsenic anhydride ....... 280 
 
 Arsenious sulphide ....... 280 
 
 Arsine — arseniuretted hydrogen . . . . .281 
 
 Marshes and Reinsch's tests for arsenic .... 281 
 
 Antimony .......... 282 
 
 Antimonious oxide ....... 283 
 
 Antimonic oxide ........ 283 
 
 Antimonious chloride ....... 284 
 
 Potassio-antimonious tartrate ..... 284 
 
 Stibine — antimoniuretted hydrogen .... 285 
 
 Antimonious sulphide ....... 285 
 
 Bismuth 285 
 
 Fusible metal 286 
 
 Bismuth oxide 286 
 
 „ nitrate ........ 287 
 
 „ chloride. ....... 287 
 
 PAET IV. 
 
 OEGANIC CHEMISTEY, OR THE CHEMISTRY OF 
 CARBON COMPOUNDS. 
 
 CHAPTER I. 
 introduction. 
 
 structure of the simpler carbon compounds .... 288 
 
 Structure of the hydrocarbons ....... 288 
 
 Saturated and unsaturated hydrocarbons . . . 289 
 
 Humologues. — Homologous series ..... 289 
 
 Hypothetical explanation of homology .... 290 
 
 Hydrocarbon radicals ........ 292 
 
 Their valency ........ 293 
 
 Compounds containing hydrocarbon radicals . . , 293 
 
 Their nomenclature ....... 294 
 
 Modes in which they are formed ..... 294 
 
 Isomerism, Metamerism, Polymerism ..... 295 
 
 Analysis of carbon compounds ...... 296 
 
xviii 
 
 CONTENTS. 
 
 CHAPTER 11. 
 
 PAGK 
 
 Classification of the simpler Carbon Compounds . . . 297 
 
 Hydrocarbons . 297 
 
 Series C„H2«+ 2-— Paraffins 298 
 
 „ C„H2„. — defines 298 
 
 „ C,H2„ - 2.— Acetylene 298 
 
 „ C„H2„ - 4.— Turpentine 298 
 
 „ C„H2„ - 6.— Benzene 298 
 
 „ C„H2„ -12.— Naphthalene 298 
 
 „ C„H2„ -18- — Anthracene ..... 298 
 
 Alcohols. — (Hydrates of hydrocarbon radicals) . . . 298 
 Monatomic : — 
 
 Series C,,H2«+iH0.— Methyl . . .• . . 299 
 
 „ C„H2«-iH0.— AUyl . . . . 299 
 
 „ C„H2„-7HO.— Benzyl 299 
 
 Phenols 299 
 
 Diatomic alcohols, or glycols ..... 299 
 
 Triatomic, or glycerines ...... 299 
 
 Ethers. — (Oxides of hydrocarbon radicals) .... 299 
 
 Salts of Hydrocarbon Radicals.— (Compound ethers) . . 300 
 
 Acids 300 
 
 Series C„H2„ - lOHO — Formic (fatty acids) . . .301 
 
 „ C.H2„ - aOHO.—Acrylio 302 
 
 „ C.H2n-90HO.— Benzoic 302 
 
 Other acids . .302 
 
 Ammonia Derivatives ........ 303 
 
 Amines 303 
 
 Compound ammoniums ....... 304 
 
 Amides ......... 305 
 
 Alkaloids, or natural bases ...... 305 
 
 Substitution Compounds ....... 305 
 
 Chloro-, bromo-, and iodo- compounds .... 305 
 
 Nitro-compounds . ....... 305 
 
 CHAPTER III. 
 
 Cellulin, Starch, Gum and Sugar Group .... 307 
 
 Table of the group 307 
 
 Cellulin or Cellulose ........ 308 
 
 Vegetable parchment . . ..... 310 
 
 Gun cotton (pyroxylin) . . . . . .311 
 
 Starch 312 
 
 Potatoes 312 
 
 Peas 313 
 
 Wheat flour— glutin 314 
 
 Arrowroot ..... ... 315 
 
 Dextrin — (British gum). . . . . . . . 316 
 
 Starch sugar — (glucose). ....... 317 
 
 Malt — Diastase 317 
 
CONTENTS. xix 
 
 I'AGK 
 
 Gums 319 
 
 Gumarabio. ........ 319 
 
 „ tragacanth ........ 320 
 
 Sugars 320 
 
 Glucose (sugar of fruits) ...... 320 
 
 Sucrose (cane sugar) . 320 
 
 Fehling's test 322 
 
 Lactose (milk sugar) . 324 
 
 Mannite 324 
 
 CHAPTEK IV. 
 
 Albuminoid Group 325 
 
 Table of the group 325 
 
 Albumin 326 
 
 Fibrin 327 
 
 Casein 328 
 
 Milk, cheese, butter 328 
 
 Gelatin. — Ossein ......... 330 
 
 Bones 331 
 
 CHAPTER V. 
 
 Fermentation. — Ethyl Compounds 332 
 
 Fermentation 332 
 
 Yeast 333 
 
 Wine 334 
 
 Beer 335 
 
 Spirits 337 
 
 Bread 341 
 
 Alcohol (ethyl hydrate) 343 
 
 Other alcohols 344 
 
 Ether (ethyl oxide) . . . . . . . .345 
 
 Other ethers 347 
 
 Salts of ethyl (compound ethers) 347 
 
 CHAPTER VI. 
 
 Organic Acids 349 
 
 Monobasic Acids 349 
 
 Acetic acid .......... 349 
 
 Acetous fermentation. — Vinegar . • . . . . 349 
 
 Aldehyde 352 
 
 Wood vinegar 352 
 
 Acetic anhydride ........ 352 
 
 Acetates 353 
 
 Lactic acid .......... 353 
 
 Lactic fermentation ....... 353 
 
 Butyric fermentation ....... 353 
 
 Bejizoicacid 353 
 
XX CONTENTS. 
 
 PAGE 
 
 Dibasic Acids 354 
 
 Oxalic acid . . . . . . . . . . 354 
 
 Tartaric acid . . . . . . . . . 356 
 
 Tribasic Acids 358 
 
 Citric acid .......... 358 
 
 Gallic acid. — Tannin ........ 358 
 
 Writing ink 360 
 
 Pyrogallic acid 360 
 
 CHAPTER VII. 
 
 Fats and Fixed Oils. — Soap, &c. . . . . . . 361 
 
 Group i. — Non-drying Fats and Oils ..... 361 
 
 Proximate constituents . . . . . . . .361 
 
 Glycerides ......... 361 
 
 Stearin, palmitin, olein ...... 361 
 
 Animal Fats and Oils 362 
 
 Lard, suet, tallow 362 
 
 Train oil. Sperm oil . . . . . . . 363 
 
 Cod liver oil . .363 
 
 Cream, butter . . . . . ' . . . 363 
 
 Vegetable Fats and Oils 364 
 
 Almond oil 364 
 
 Palm oil 364 
 
 Cocoa-nut oil ....... . 364 
 
 Olive oil . .364 
 
 Colza and rape oils . . . . . . . 365 
 
 Castor oil 365 
 
 Saponification. — Soap ........ 365 
 
 Composition of soaps ....... 366 
 
 Hard and soft soap ....... 366 
 
 Liniments ......... 367 
 
 Action of soap in washing ...... 367 
 
 Yellow soap 368 
 
 Marine soap . 368 
 
 Glycerine .369 
 
 Acrolein.— Acrylic acid .... . 369 
 
 Group ii.— Drying or Varnish Oils 370 
 
 Linseed oil 370 
 
 Printing ink 371 
 
 Group iii. — The Waxes and Spermaceti 371 
 
 CHAPTER VIII. 
 
 Volatile Oils, Resins, and Allied Bodies .... 373 
 
 Classification . 373 
 
 Group i. — Volatile, or Essential Oils 373 
 
 Stearoptens and elseoptens ...... 373 
 
 List of oils • ... 374 
 
 Group ii. — Resins 375 
 
 List of resins 375 
 
CONTENTS. Xxi 
 
 PAGE 
 
 Group iii. — Balsams (mixtures of volatile oils and resins). . 375 
 
 List of balsams . . . . . . . . 375 
 
 Animal balsams ........ 376 
 
 Group iv. — Gum resins (mixtures of resins with gum) . . 370 
 
 List of gum resins ....... 370 
 
 Group v. — Camphors 376 
 
 Group vi. — Caoutchouc and gutta-percha ..... 376 
 
 Volatile Oils 376 
 
 Their preparation ....... 376 
 
 Their properties ........ 377 
 
 Oil of turpentine ........ 377 
 
 Resins 380 
 
 Colophony, or rosin . . . . . . .381 
 
 Sealing-wax ........ 382 
 
 Rosin gas 382 
 
 Lamp-black ........ 383 
 
 Varnishes 383 
 
 Caoutchouc and Gutta-percha ...... 385 
 
 Caoutchouc, or India-rubber ..... 385 
 
 Marine glue 386 
 
 Caoutchoucine ........ 386 
 
 Vulcanized caoutchouc ....... 386 
 
 Ebonite .... .... 387 
 
 Gutta-percha 387 
 
 CHAPTER IX. 
 
 Derivatives of Ammonia. — Alkaloids ..... 388 
 
 Aniline 388 
 
 Aniline colours ........ 389 
 
 Urea 390 
 
 Natural Alkaloids . .391 
 
 Tobacco — nicotine ....... 392 
 
 Hemlock — conine ....... 393 
 
 Peruvian bark — quinine, &c 393 
 
 Quinine .393 
 
 Cinchonine 393 
 
 Quinic acid ........ 393 
 
 0[)ium — morphine, &c. ....... 394 
 
 Morphine 394 
 
 Meconic acid 394 
 
 Nux vomica — strychnine, brucine ..... 395 
 
 Other alkaloids 395 
 
 CHAPTER X. 
 
 Colouring Matters 397 
 
 Mineral pigments 397 
 
 Colouring matters of flowers — cyanin ..... 397 
 
 Colouring matter of leaves— chlorophyll 398 
 
xxii CONTENTS. 
 
 PAGE 
 
 Indigo .399 
 
 Madder. — Alizarin, purpurin ....... 400 
 
 Lakes. . . . . . . . . . 401 
 
 Mordants 402 
 
 Cochineal. — Carmine ........ 403 
 
 Other colouring matters ........ 404 
 
 CHAPTEE XI. 
 
 Products of Destructive Distillation ..... 408 
 
 Coal Tar 408 
 
 Distillation of tar. . ...... 408 
 
 Naphtha 409 
 
 Heavy oils 410 
 
 Solid portion . 410 
 
 Pitch 410 
 
 Proximate constituents of Coal Tar 410 
 
 Benzol, or benzene ....... 410 
 
 Phenol, or carbolic acid ...... 410 
 
 Picric acid ........ 413 
 
 Paraffin, Paraffin Oil, Petroleum . . . . .413 
 
 Paraffin - 414 
 
 Boghead coal 414 
 
 Petroleum . . 414 
 
 Asphalt — bitumen 415 
 
( xxiii ) 
 
 TABLE OF ELEMENTS. 
 
 Simplified from the Table of Mr. Frank Wigglesworth 
 Clarke. 
 
 The atomic weight of an element, denoted by its symbol, is the 
 number which most nearly fulfils the following conditions : — 
 
 1. It is the least weight of the element ever found in two 
 volumes of any gas, elementary or compound, at standard pressure 
 and temperature ; the least weight of hydrogen so found being 
 taken as unity. When greater weights are found they are always 
 multiples of the least weights. 
 
 2. It is the weight of the element that is equivalent, in com- 
 bination or substitution, to 1, 2, 3, 4, &c., parts of hydrogen. The 
 valency of the element is determined by the number of atoms of 
 hydrogen to which the atom is equivalent. 
 
 3. With most solid elements it is the number which agrees with 
 the law of atomic heats, that is, it is the number which, multiplied 
 by the specific heat, gives an approximation to the constant 6*3. 
 
 4. It is the number which best agrees with the isomorphous 
 relations of the element. 
 
 Name. 
 
 SymboL 
 
 Atomic 
 Weight. 
 
 Aluminium .... 
 
 Al. 
 
 27- 
 
 
 Sb. 
 
 120- 
 
 
 As. 
 
 75- 
 
 
 Ba. 
 
 137- 
 
 
 Bi. 
 
 208- 
 
 
 B. 
 
 11- 
 
 
 Br. 
 
 80- 
 
 
 Cd. 
 
 112- 
 
 
 Cse. 
 
 133- 
 
 Calciom 
 
 Ca. 
 
 40- 
 
 
 C. 
 
 12- 
 
 
 Ce. 
 
 141- 
 
 
 CI. 
 
 35-5 
 
 Chromium .... 
 
 Cr. 
 
 52- 
 
 Cobalt 
 
 Co. 
 
 59- 
 
 Columbium .... 
 
 Nb. 
 
 94- 
 
 
 Cu. 
 
 63- 
 
 Didymium .... 
 
 Di. 
 
 145- 
 
 
 Er. 
 
 it;6- 
 
 
 F. 
 
 19- 
 
 
 Ga. 
 
 69- 
 
XXIV 
 
 TABLE OF ELEMENTS. 
 
 Name. 
 
 Symbol. 
 
 Atomic 
 Weight. 
 
 Glucinum 
 
 Be. 
 
 9- 
 
 Gold 
 
 Au. 
 
 196* 
 
 Hydrogen 
 
 H. 
 
 1- 
 
 IndiuEQ. 
 
 In. 
 
 113*5 
 
 
 I. 
 
 127- 
 
 
 Ir. 
 
 193- 
 
 
 Fe. 
 
 56- 
 
 Lanthanum .... 
 
 La. 
 
 139- 
 
 Lead 
 
 Pb. 
 
 207- 
 
 
 Li. 
 
 7- 
 
 Magnesium .... 
 Manganese .... 
 
 
 24* 
 
 Mu. 
 
 54- 
 
 Mercuiy 
 
 
 200- 
 
 Molybdenum .... 
 
 Mo. 
 
 96* 
 
 Nickel 
 
 Ni. 
 
 58. 
 
 Nitrogen 
 
 N. 
 
 14* 
 
 Osmium 
 
 Os. 
 
 199* 
 
 Oxvffen 
 
 0. 
 
 16* 
 
 Palladium .... 
 
 Pd. 
 
 106* 
 
 Phosphorus .... 
 
 P. 
 
 31- 
 
 Platinum 
 
 Pt. 
 
 195* 
 
 Potassium 
 
 K. 
 
 39* 
 
 Rhodium 
 
 Rh. 
 
 104* 
 
 Rubidium. 
 
 Rb. 
 
 85* 
 
 Ruthenium .... 
 
 Ru. 
 
 104* 
 
 
 Sc. 
 
 44* 
 
 Selenium 
 
 Se. 
 
 79* 
 
 Silicon 
 
 Si. 
 
 28* 
 
 Silver • .... 
 
 
 108* 
 
 Sodium .... 
 
 Na. 
 
 23- 
 
 Strontium • . 
 
 Sr. 
 
 87*5 
 
 Sulphur . 
 
 S. 
 
 32* 
 
 
 Ta. 
 
 182* 
 
 Tellurium . . 
 
 Te. 
 
 128* 
 
 Thallium 
 
 Th. 
 
 204* 
 
 Thorium 
 
 Th. 
 
 234* 
 
 Tin 
 
 Sn. 
 
 118* 
 
 Titanium .... 
 
 TL 
 
 50* 
 
 
 W. 
 
 184* 
 
 
 U. 
 
 239* 
 
 Vanadium .... 
 
 V. 
 
 51* 
 
 
 Yb. 
 
 173* 
 
 
 Y. 
 
 90* 
 
 
 Zn. 
 
 65* 
 
 
 Zr. 
 
 89-5 
 
EXPERIMENTAL CHEMISTEY. 
 
 PAET I. 
 GENERAL PRINCIPLES. 
 
 CHAPTEE L 
 
 MATTER AND FORCE. 
 
 Putting on one side as unsolved, and probably for ever 
 insoluble, the great metaphysical question whether the 
 various objects and the complex phenomena we observe in 
 nature have any real existence, or are merely images 
 created in our own consciousness; and the farther and 
 scarcely less recondite question whether, even if we admit 
 the external existence of such objects and phenomena, we 
 may not account for them without assuming the existence 
 of any material substance ; let us take the ordinary, and 
 what may be called the common-sense view of the uni- 
 verse around us. In doing so, however, we must not 
 venture to assert it dogmatically, or to stigmatise as absurd 
 either of the other views above referred to, startling 
 though they may appear. Both of them have been held 
 by profound thinkers ; neither can be proved to be erro- 
 neous, neither can be said to be in direct discord with 
 known facts. The thoughtful student will find it good to 
 revert to them from time to time as he advances in know- 
 ledge, and as he gains a clearer conception of their 
 meaning he will find them less incredible than they 
 appear at first. 
 
 Taking then the current view, we bold that ail sub- 
 stances known to us, whether in the state of solid, liquid, 
 
 B 
 
2 
 
 EXPERIMENTAL CHEMISTRY. 
 
 or gas, consists of matter which has an absolute existence. 
 Matter is subject to the operation of certain agents called 
 forces, which determine its position in space and its move- 
 ments and properties. Whatever can produce or change 
 motion is called a force. The forces can only be known 
 to us by their operations on matter, just as motion cannot 
 be conceived of except as of something moved. On the 
 other hand, it is no less true that, apart from force, we 
 can form no conception of matter. 
 
 Energy, — The power of doing work is called Energy. A 
 body charged with electricity, a body hotter than its 
 surroundings, and a moving mass are said to possess energy 
 Sometimes the energy is in action, as when a bullet is 
 flying through the air, or an electric spark passing. In 
 that case the energy is said to be kinetic. Sometimes the 
 energy is quiescent, or passive, as when a cross-bow is bent, 
 or an air-gun charged, then the energy is said to be 
 potential. Potential energy is stored energy, and may at 
 any time become active, or kinetic. The pulling of the 
 trigger converts the potential energy of the cross-bow 
 into kinetic energy. Gunpowder is a good example of 
 potential energy. 
 
 Different Forms of Force. — The following are the chief 
 kinds of force. 
 
 I. Gravity. — If a stone is suspended by a string, every 
 one knows that the string is pulled by it. The stone and 
 the earth attract one another, and if the string be cut, the 
 stone will fly to the earth and come to rest. This kind of 
 attraction is called gravitation, and it is said to be due to 
 the force of gravity. It is found to exist in all forms of 
 matter. Solids, liquids, and gases all tend to fly to the 
 earth, and therefore all exhibit the force of gravity, 
 though in very various degrees. Near its surface the 
 great bulk of the earth causes its attraction to be so very 
 much greater than that of any other body that the term 
 gravity is ' generally applied only to the tendency of 
 bodies to fly to the earth. In other words, gravity is 
 generally taken as identical with weight. But it is right 
 to remember that all bodies attract one another. One 
 stone attracts another, one drop of water another drop ; 
 but the masses of the stones and the drops are so small 
 
MATTER AND FORCE. 
 
 3 
 
 that the attraction is too slight to be noticed. That the 
 force of gravity keeps the planets in their orbits, and 
 regulates the movements of the heavenly bodies, is known 
 to all. It is the most important doctrine of astronomy. 
 
 When the force of gravity is not resisted by some other 
 force equal in power to itself, motion is produced. 
 
 The special case of gravity that we call weight is so im- 
 portant in the study of chemistry that it will be con- 
 sidered separately in the next chapter. 
 
 2. Cohesion, — The force which binds together the 
 minute particles of which matter consists is called 
 cohesion, but it is probably identical in nature with 
 gravity. It varies very much in different substances, 
 and even in the same substance in different states. To 
 divide ice into smaller portions requires greater force than 
 to divide water, and no force at all is required to divide 
 steam. In solid bodies cohesion is stronger than in 
 liquids ; in gases scarcely a trace of it can be perceived. 
 The hardness of a solid is the measure of the force of 
 cohesion among its particles. 
 
 When cohesion is exerted between dissimilar sub- 
 stances it is often called adhesion. The use of glue is a 
 good example of adhesion. 
 
 Experiments, — To prove that the force of cohesion exists 
 in liquids, allow one pan of a pair of scales to rest on the 
 surface of water. A number of weights must now be 
 introduced into the other pan, before the first one will be 
 removed from the water. When at last it rises, some 
 water will still adhere to its under surface. The adhesion 
 between the scale-pan and the water is not overcome, but 
 only the cohesion between one portion of the water and 
 the rest. 
 
 If only half the weights required in the above experi- 
 ment be introduced, and a little ether be then poured on 
 the surface of the water, the scale-pan will rise at once. 
 The adhesion between the ether and the scale-pan is very 
 slight. 
 
 Cohesion may also be illustrated by cutting a bullet in 
 half, and pressing together with the hands the two clean 
 and recently cut surfaces. If the cuf has been well made, 
 they will unite again with great force. Two pieces of 
 
 B 2 
 
4 
 
 EXPERIMENTAL CHEMISTRY. 
 
 plate-glass will do the same, and the glass-makers have to 
 be very careful not to allow large sheets of plate-glass to 
 lie on one another. 
 
 3. Heat is an extremely powerful and important form 
 of force. Its influence in chemistry is very extensive, 
 and, like gravity, it will be considered in some detail in 
 the next chapter. 
 
 4. Light is a force closely allied to heat, and is also 
 closely concerned in many of the changes of chemistry. 
 Almost the whole of the light and heat of our globe comes 
 to us directly or indirectly from the sun. 
 
 5. Electricity, — Experiment 1. — Take a stick of sealing- 
 wax, rub it briskly with a piece of flannel and hold it 
 near some scraps of paper. They will be attracted by it 
 and will fly upward and adhere to its surface. A tube 
 of glass rubbed with silk will produce the same effect, 
 but the substance called ebonite is more powerful than 
 either. An ebonite comb that has been passed through 
 dry hair will not only attract scraps of paper and small 
 feathers, but in dry weather will emit a crackling sound 
 and a torrent of small sparks, quite visible in a dark room. 
 
 In all these cases the strange and interesting force 
 called Electricity is set in motion. The " electrical 
 machine " is only a plate or cylinder of glass or ebonite, 
 which, by turning a handle, can be made to rub against a 
 silk cushion covered with amalgam. Electricity produced 
 in this way is called frictional electricity. 
 
 Another kind of electricity is known, which is called 
 Voltaic, or Galvanic Electricity. The following experi- 
 ment will illustrate the way in which it is produced. 
 
 Experiment 2. — Take a tumbler two-thirds full of water, 
 pour into it gradually an ounce and a half by measure 
 of sulphuric acid, and fill the tumbler up with water. 
 The mixture will become very hot, and must be allowed 
 to stand until cold. Take a strip of sheet copper, and 
 another of zinc, not too large to go to the bottom of the 
 tumbler, and high enough to reach to the top. Brighten 
 one of the small ends of each with sand-paper, and solder 
 on each bright patch dJ^ copper, wire about a foot long. It 
 will improve the experiment very much if you can 
 amalgamate the zinc plate ; that is, coat it with mercury 
 
MATTER AND FORCE. 
 
 5 
 
 (quicksilver). To do this the zinc must be cleaned by 
 immersing' it for a minute in the weak sulphuric acid, and 
 then, while covered with the acid, pouring a little mercury 
 on it and rubbing it over the surface with a small rag. 
 The surface of the metal will then become as bright as a 
 looking-c^ass. 
 
 The two metals are now to be immersed in the acid 
 with the wires out. They should be about half an inch 
 apart, and must not touch one another. They can be 
 kept in their places by wedges of cork or wood. If the 
 zinc plate ha-s been amalgamated no action will take place 
 until the ends of the wires are wade to touch one another, when 
 the zinc will immediately begin to dissolve in the acid 
 and electricity to pass along the wires. Such an arrange- 
 ment constitutes a simple and not very powerful form of 
 voltaic or galvanic battery. It is called a " simple cell," 
 and the ends of the wires farthest from the plates are 
 called the " poles." If ten such cells are made, and are 
 joined together by thick copper wires, the zinc of one cell 
 to the copper of the next, long wires proceeding from the 
 last zinc at one end and the last copper at the other, a 
 tolerably powerful battery will be obtained, capable of 
 decomposing water and doing other chemical work, but 
 the arrangement is never a very powerful one, and it is 
 better to buy or make one of the more powerful forms of 
 the instrument. 
 
 If the two wires from the simple cell are brought to 
 within half an inch of one another, and are then joined 
 with a piece of fine platinum wire, the platinum will 
 immediately become red-hot. With a more powerful bat- 
 tery a much greater length of wire may be heated to white- 
 ness, and even melted by the electricity. Fine iron wire 
 may be burned in the same way, but not quite so easily. 
 
 Magnetism is only a peculiar operation of electricity. 
 
 6. Chemical Force, or Chemical Affinity. — The last force 
 , that we have to consider is called chemical force, because the 
 science of chemistry is almost entirely occupied with its 
 nature and effects. Its operations are spoken of as chemical 
 action. 
 
 Every one knows that iron, heated to redness, changes 
 into black, brittle scales, and that exposed to moist air 
 
 I 
 
6 
 
 EXPERIMENTAL CHEMISTRY. 
 
 or earth, it is converted into rust ; ttat the expressed juice 
 of the grape gradually turns to wine, and this again to 
 vinegar ; that wood in a stove, or oil in a lamp, disappears 
 in burning ; and that animal and vegetable substances in 
 time putrefy, disintegrate, and finally disappear. 
 
 Iron scales and rust are iron altered in constitution : iron 
 is hard, tenacious, of a greyish- white colour and brilliant ; 
 by heating to redness it becomes black, dull and brittle ; 
 on exposure to moisture it is converted into a powder of a 
 yellowish-brown colour. Wine is altered must, in which 
 nothing of the sweet taste peculiar to the grape-juice can 
 be perceived ; but it has acquired a spirituous flavour, 
 together with a heating and intoxicating power, which 
 was not in the must. Vinegar is altered wine ; it has an 
 acid smell and taste, and has lost its spirituous flavour, as 
 well as its exhilarating properties, its tendency being 
 rather cooling and sedative. Search much be made in the 
 air for the oil and wood which have disappeared during 
 combustion ; both these substances are converted into 
 va|>onr or gas, and heat and light are thereupon evolved 
 with the phenomenon of fire. Of a similar nature are the 
 changes which animal and vegetable substances undergo 
 if kept for a sufficient length of time ; they are gradually 
 converted, as they putrify or decay, into various kinds of 
 gas, some of which emit a very disagreeable odour. 
 
 Such processes, by which the weight, form, solidity, 
 colour, taste, smell, and action of the substances become 
 changed, so that new bodies with quite diflerent properties 
 are formed from the old, are called chemical processes, or 
 chemical action. 
 
 Wherever we look upon our earth, chemical action is 
 seen taking place, on the land, in the air, or in the depths 
 of the sea. The hard basalt, the glass-like lava, become 
 gradually soft, their dark colour becomes lighter, they 
 crumble to smaller and smaller pieces, and are finally 
 changed to earth. A potato placed in the earth grows 
 soft, loses its mealy taste, becomes sweet and finally 
 decays. The bud that sends forth a sickly pale shoot in 
 a dark cellar, when exposed to the light and air grows 
 up a vigorous, firm, and green plant, which, imbibing its 
 nourishment from the moist air and soil, forms from their 
 
MATTER AND FORCE. 
 
 7 
 
 elements new bodies, not to be found previously in the 
 water or the air. A delicate network of cells and tubes 
 pervades the whole plant, imparting to it firmness ; these 
 we call vegetable tissue, or woody fibre. We find in the 
 sap, which passes up and down through these cells, albumin 
 and other viscous substances ; in the leaves and in the stalks, 
 a green colouring matter — chlorophyll ; and in the ripe 
 tubers, a mealy substance — starch. 
 
 The potato forms one of our most important articles of 
 food. The starch contained in it is not soluble in water, 
 but when received into the stomach, quickly undergoes 
 such a change that it can be dissolved or digested, and 
 then introduced as a liquid into the blood. The blood 
 comes in contact in the lungs with the inhaled ^ir ; the 
 blood changes its colour, the air changes its constitution, 
 and the heat which we feel in onr bodies is developed. 
 We must conclude, from these changes, that chemical 
 action is going on in our own bodies. 
 
 If a piece of iron be heated to redness, till a thick crust 
 of scales is formed around it, and then weighed, it will be 
 found to have increased in weight ; consequently, it must 
 have been supplied with something ponderable from the 
 air. This ponderable substance is a species of gas, called 
 oxygen ; but its union with the iron has become fixed, 
 yet by other chemical processes it can be reconverted into 
 its gaseous form. Accordingly, the crust consists of iron 
 and oxygen, which have become most closely united with 
 each other ; — they are chemically combined. 
 
 The force which produces such changes as these is called 
 Chemical Force. In some books it is described as 
 " chemical affinity," because it is assumed that the tendency 
 of substances to combine with one another is due to a kind 
 of liking that they have for each other. Iron is so very 
 fond of oxygen that it cannot help combining with it 
 whenever it gets the chance. But it is unsafe in scientific 
 matters to use names which assert more than we really 
 know. Now we know that iron combines with oxygen, 
 but we do not know that there is any affinity " between 
 the two. We know that force is exerted, but we do not 
 know why. The conditions under which the force is 
 exerted will be discussed in a future chapter. 
 
8 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Belation of the Forces to one another, — The forces we have 
 "been considering, unlike as they are in their manifestations, 
 are very closely connected together. Almost any one of 
 them may, under suitable circumstances, be made to pro- 
 duce another, and it has duriiig the present century been 
 shown that the one is directly evolved from the other. 
 It has long been perceived to be impossible, under the 
 present arrangement of the universe, for matter to be 
 created or destroyed. It may change its form and pass 
 ever so many times from one state of combination to 
 another ; but the total quantity remains always, as far as 
 our means of observation enable us to judge, the same. 
 The grandest generalisation of modern science is that 
 which has taught us that energy is equally indestructible ; 
 that it also, like matter, may undergo various and count- 
 less changes ; may appear, now as heat, now as electricity, 
 now as chemical action, and now as visible motion, and 
 yet its sum will always remain fixed and unalterable. 
 There is no new creation of energy within the limits of 
 our knowledge. It may lie hid for a time — for any time — 
 but whenever we meet with any of its operations in 
 nature we may confidently look for the cause in the dis- 
 appearance of some previously active form of energy. The 
 birth of one form of energy is always the death of some 
 other, and the two are equivalent to one another in 
 quantity. 
 
 This grand doctrine, which is known as the doctrine of 
 the conservation of energy, requires complex apparatus, 
 and great knowledge for its verification. The demon- 
 stration of it is indeed still incomplete, though it has gone 
 far enough to satisfy evei y rational mind ; but a few simple 
 experiments will serve to illustrate the manner in which 
 one force may give rise to others. In other words, we may 
 prove the correlation of various forces, though the conser- 
 vation of energy must be taken on trust. 
 
 Experiment 1. — Kub a piece of copper wire briskly with 
 sand-paper for a minute or two. It will become so hot 
 that the hand cannot bear to touch it, and it will readily 
 ignite phosphorus or the tip of a lucifer-match. 
 
 Similar illustrations will occur to all. When the axle 
 of a railway carriage gets dry, so much heat is produced 
 
MATTER AND FORCE. 
 
 9 
 
 that the carriage is sometimes set on fire. A clever 
 blacksmith can hammer a nail till it is red-hot, and so 
 emits light as well as heat. During the boring of cannon 
 the shavings are too hot to be touched, and, lastly, some 
 savages are able to procure a light by rubbing two dry 
 sticks together. 
 
 In all these cases there is a direct conversion of motion 
 caused by force into heat, and even, in some cases, into 
 light. Friction is but arrested motion — motion hindered 
 or reduced by an opposing force. If the sand-paper had 
 not pressed on the wire, the same amount of energy em- 
 ployed by the arms would have given rise to a much 
 greater motion than that actually produced. The diifer- 
 ence, though lost as motion, takes the new form of heat. 
 When a pound weight falls to the earth from a height of 
 772 feet, its motion is lost, but the weight and the earth 
 receive heat enough to raise the temperature of one pound 
 of water one degree Fahrenheit. 
 
 We have already seen that friction may, under certain 
 circumstances, produce electricity, so that we have gained 
 illustrations of the conversion of motion into heat, light, 
 and electricity. Let us now start from heat. The 
 steam-engine affords the best possible illustration of the 
 conversion of heat into motion. The work done by the 
 engine is done by the heat expended, and so ultimately 
 by the coals burnt. When heat becomes sufficiently 
 intense, it is always accompanied by light, and Tyndall 
 has devised a direct experiment in which invisible heat 
 becomes visible light. In fact, heat and light only differ 
 from one another as low and high notes in music do. 
 The conversion of heat into electricity requires for its 
 demonstration a delicate galvanometer, a somewhat ex- 
 pensive piece of apparatus. Heat is seldom directly 
 converted into chemical energy, though the converse is one 
 of the commonest of phenomena ; but the development 
 of the force of cohesion during the disappearance of heat 
 can be readily demonstrated, as the following experiment 
 j will show. 
 
 Experiment 2. — Take a tumbler full of powdered 
 crystals of sodium sulphate, and drench it with common 
 hydrochloric acid. The salt will rapidly dissolve and 
 
 I 
 f, 
 
 i 
 
10 
 
 EXPERIMENTAL CHEMISTRY. 
 
 become liquid, and the force of cohesion will come into 
 operation. But at the same time heat will be taken so 
 rapidly from the materials in the tumbler that the out- 
 side will be covered with hoar frost, and if a little water 
 in a test tube be plunged into the mixture it will freeze 
 in a minute or two. The so-called freezing mixtures 
 depend upon this principle. 
 
 Experiment 3. — Now try the reverse of this experiment. 
 Take a clean Florence oil flask, nearly fill it with hot 
 water, dissolve as much sodium sulphate in it as the 
 water will dissolve (filtering the solution while hot if it 
 appears dirty) and then, while the solution is nearly 
 boiling, cork the flask tightly and allow it to get quite 
 cold. There is now a great deal more of the solid in the 
 solution than cold water could dissolve, but for some 
 curious reason the excess does not immediately separate 
 out. But take out the cork, and in a minute beautiful 
 feathery crystals appear at the upper surface and pass 
 downwards until the whole mass is solid. If the crystalli- 
 zation does not begin at once, drop in a small crystal of 
 the sulphate, which will immediately produce the desired 
 effect. As soon as the liquid has changed to solid, feel 
 the outside of the flask with your hand. It is sensibly 
 warm, showing that during the exertion and disap- 
 pearance of the cohesive force heat has been given out. 
 The experiment is even more easily made with the salt 
 commonly called hyposulphite of soda. 
 
 The conversion of electricity into other forms of energy 
 has already been illustrated to some extent in the battery. 
 When the platinum becomes red-hot, it emits heat and 
 light. When the poles of a powerful battery are connected 
 with pieces of coke shaped like lead pencils, and the coke 
 points after touching one another are separated by a short 
 distance, a most intense light, called the "electric arc," 
 passes between them. The rays given out by it are 
 similar to those of the sun, and, like the sun's rays, they 
 consist of three kinds : 
 
 1. Invisible heat rays. 
 
 2. Light rays. 
 
 3. Invisible actinic or chemical rays. 
 
 The invisible chemical rays are only to be recognised 
 
MATTER AND FORCE. 
 
 11 
 
 by tiieir effect in producing chemical changes. The 
 interesting art of photography entirely depends on the 
 power of rays to produce alterations of composition in 
 certain chemical substances, and particularly the com- 
 pounds of silver. The following experiment will illus- 
 trate this curious property. 
 
 Experiment 4. — In a room from which daylight is 
 entirely excluded, but which may be lighted by a 
 candle, dissolve sixty grains of silver nitrate (lunar 
 caustic) in an ounce of cold distilled water. Pin a sheet 
 of smooth white paper on to a flat board, and, by means 
 of a flat camel's hair brush, paint it all over uniformly 
 with the colourless silver solution. Allow it to dry in 
 the dark ; repeat the painting, and again allow it to 
 dry. Paper so prepared is called " sensitive " paper. To 
 show its properties, place upon it a piece of lace, a few 
 fine feathers, or a sprig of fern, cover it with a sheet of 
 window glass, and press the glass down with weights at 
 the corners. The board may now be brought out of the 
 dark room and exposed to sunlight, or to the strong 
 diffused light of a bright day. The paper will soon 
 begin to change colour, and after a time it will assume a 
 rich brown tint. The whole arrangement must then be 
 taken back to the dark room, the glass, ferns, &c., 
 removed, and the paper immersed in clean rain or 
 distilled water and well soaked, the water being changed 
 a good many times. A beautiful image, in white on a 
 dark ground, of the object employed will remain on the 
 paper, which may now be dried and exposed freely to light, 
 for the water will have washed away all the silver salt that 
 has not been affected, and the picture will be permanent. 
 
 The waves of light consist of waves analogous to those 
 of water, and the three kinds of waves just referred to 
 differ from one another only in length, the length being 
 measured from the crest of one to the crest of the next. 
 The average wave-length for white light is about 
 1-50000 of an inch, and the eye perceives those only 
 which, in round numbers, are between the 1-40000 and 
 1-60000 of an inch in length. Longer waves possess 
 the energy of heat, and shorter waves of chemical action, 
 but they do not affect the eye. 
 
12 
 
 EXPERIMENTAL CHEMISTRY. 
 
 It has already been mentioned that the action of the 
 sun's rays can also be produced by the rays from the 
 electric light, and we have therefore an instance, to 
 which many others might be added, of the production of 
 chemical energy from electricity. Even with the single 
 cell described in Experiment 2, page 4, some striking 
 illustrations may be obtained, as will be seen from the 
 experiments which follow. 
 
 Experiment 5. — Attach a small strip of platinum foil 
 to the end of each wire. Cut a card so that it will 
 stand upright in a wine-glass, and divide it in two. 
 Then fill the glass with the card in it with a solution of 
 the salt called potassium iodide, and bring one of the 
 platinum poles into each of the two divisions which the 
 card makes. The pole which is connected with the 
 copper plate immediately produces a brown colour on 
 that side of the card. The electricity breaks up, or 
 decomposes the salt into two substances : potassium, which 
 owing to its action on water is not seen, and iodine, the 
 substance which gives the brown colour in this ex- 
 periment. Pour into the brown liquid on one side of the 
 card a little of the smooth, pasty liquid obtained by 
 adding a good deal of boiling water to starch, stirring 
 and cooling. The starch will combine with the iodine 
 and form a beautiful blue colour. 
 
 Experiment 6. — Dissolve in some cold water as much 
 copper sulphate (blue vitriol) as the water will take up, 
 and substitute this solution for the potassium iodide used 
 in the last experiment. The card is unnecessary. The 
 salt will be decomposed, and copper will be deposited on 
 the platinum pole which proceeds from the zinc plate. If 
 the poles are reversed the copper will soon dissolve off the 
 one platinum plate and appear on the other. This experi- 
 ment is an example of the process called electroplating. 
 Other metals, such as gold and silver, may by analogous 
 means be deposited from solutions. The decomposition of 
 liquids by electricity is called electrolysis. 
 
 Experiment 7. — Decomposition of Water hy Electricity. — 
 With the assistance of a more powerful battery, and the 
 little piece of apparatus shown in Fig. 1, water may be 
 decomposed into the two gases of which it consists. Thick 
 
MATTER AND FORCE. 
 
 13 
 
 platinum wires pass through the sides of a glass and 
 terminate inside in flat plates (stout platinum wires 
 hammered flat at the ends do very well). The holes in 
 the glass can easily be made by a bradawl filed to a square 
 point and constantly moistened with a mixture 
 of turpentine and camphor, and the wires may 
 be cemented in the holes with sealing-wax. 
 The glass is filled with water to which a drop 
 or two of sulphuric acid has been added, and 
 over each of the plates a test tube filled with 
 the same acidulated water is inverted. The 
 two ends of the wires are now connected with 
 the poles of the battery. In an instant bubbles 
 of gas rise from the two plates into the test 
 tubes. The gas which comes from the pole connected with 
 the zinc is called hydrogen, that from the other oxygen ; and 
 it will be observed that the volume of the former is twice 
 as great as of the latter. When a little gas has been collected, 
 the mouths of the tubes may be closed with the thumb, 
 the tubes removed, and the gas examined with a taper in 
 the manner described under their respective names. 
 
 This is the most important instance of the production 
 of chemical energy at the expense of electricity that we 
 possess. Electricity disappears during the experiment, 
 but the hydrogen and oxygen which are produced are 
 able, as we shall find hereafter, to exert an enormous force 
 when they once more combine together. 
 
 Lastly, let us study the forces which are called into 
 existence during the exertion and consequent disappear- 
 ance of chemical energy. We have, in point of fact, just 
 been considering one of the most interesting cases of this 
 kind in the voltaic battery. In the battery, the electricity 
 which is called into being proceeds directly from, and is 
 proportionate in amount to, the chemical energy which is 
 destroyed in the cell. The zinc is constantly being 
 dissolved by the sulphuric acid, and the force which is 
 thereby exerted immediately takes the new form of 
 electricity. From this electricity we can, as we have 
 seen, produce heat, light, ^and finally, chemical force, so 
 that we can ultimately recover the very same form of 
 force that we lost in the battery. One of Faraday's 
 
14 
 
 EXPERIMENTAL CHEMISTRY. 
 
 greatest discoveries proved that there is no loss of force 
 throughout these changes, but that, provided we can 
 prevent the force from assuming other forms, the chemical 
 energy produced by the decomposition of the water is 
 exactly equal to the energy lost in the battery. 
 
 One or two simple experiments will illustrate the direct 
 production of other forces from the chemical, but it is 
 unnecessary to multiply them, because the whole study of 
 chemistry is full of such illustrations. 
 
 Ex;periment 8. — Take a piece of phosphorus, about the 
 size of a small pea, and about an equal quantity of iodine. 
 Place them side by side on a slate or a piece of tin-plate, 
 and push the phosphorus with a knife till it touches the 
 iodine. Chemical action is instantly exerted, and the 
 mass bursts into flame, producing thereby light and heat, 
 
 Experiment 9. — Warm two tumblers : put into one a few 
 drops of strong ammonia, and into the other a few drops 
 of hydrochloric acid. Each will give out a gas, and when 
 the mouths of the tumblers are held together these gases 
 will combine, and a dense white smoke will be produced, 
 which will before long settle down on the inside of the 
 glasses in the form of a white, solid powder (sal-ammoniac). 
 The chemical action is in this case accompanied by the 
 development of the force of cohesion. The lost force takes 
 the form of heat, which, however, can only be perceived 
 by the thermometer. 
 
 When gunpowder or any other explosive substance is 
 burnt, it is converted into gas ; very energetic chemical 
 action takes place, and a great deal of force is exerted. 
 But the force is entirely reproduced, for the cohesion of 
 the solid is destroyed, a great expansion, which is nothing 
 but a motion of the particles, takes place, and heat and 
 light are evolved. Every one knows what powerful work 
 the expansion may be made to do. Heavy shot can be 
 thrown from a gun to an enormous distance, and solid 
 rocks torn in fragments by the burning even of a small 
 weight of the powder. 
 
 The result of the researches of the present century has 
 been to convince scientific men that, various as are its 
 manifestations, there is in na^iire but one force, namely. 
 Motion : motion of masses, motion of particles, motion in 
 
OBJECTS OF CHEMICAL INQUIRY. 
 
 15 
 
 lines, motions of rotation and vibration, and motion in 
 other modes. As regards heat and light this strange 
 doctrine may be said to be already demonstrated, for these 
 remarkable forces have been proved to be merely peculiar 
 modes of motion in tlie particles of matter. And the 
 close connection of heat with the other forms of force 
 forbids ns to doubt that its nature is essentially similar to 
 theirs, and that they also are modes of motion. Science 
 has still a great work before her in the investigation of 
 force, but enough has already been accomplished to enable 
 us to take a far wider view of the kingdom of nature than 
 was possible to our fathers, and to reveal to us something 
 of the unity and simplicity that underlies the marvellous 
 complexity of the universe. 
 
 OBJECTS OF CHEMICAL INQUIRY. 
 
 It has already been mentioned that the science of chem- 
 istry is concerned with the operations of chemical force. 
 Tiiere eixe four chief points to which the attention of the 
 chemist is mainly directed in his study of the solid, liquid, 
 and gaseous substances which are met with in nature. 
 
 1. Their composition, — Take a piece of bone. How is it 
 affected when strongly heated in a furnace ? It becomes 
 whiter, lighter, and less solid than before (bone-ash). 
 But how is it affected when heated in a covered vessel ? 
 It becomes lighter, and black (bone-black). If exposed 
 to boiling water, or to steam, how is it affected ? It 
 becomes lighter, and remains white ; but in the water is 
 dissolved gelatine. How in hydrochloric acid ? It 
 becomes transparent ; the bone earth is dissolved, and a 
 gristly ijiass remains, which, when boiled with water, 
 turns to gelatine. What is the action of fire upon the 
 gelatine? In a covered vessel it is converted into 
 charcoal, in an open one it burns and disappears. These 
 few experiments show that the bone contains gelatine 
 which is combustible, and an earth which is not so ; they 
 show at the same time that it is the carbonized gelatine 
 which, in the second experiment, colours the bone-earth 
 black, and makes it bogie-black ; that this gelatine 
 dissolves in water, but not in hydrochloric acid, &c. 
 Gelatine and bone-earth are called the proximate constituents 
 
16 
 
 EXPERIMENTAL CHEMISTRY. 
 
 of bone, but by continued chemical processes these can be 
 resolved still further, that is, separated into simpler 
 constituents. In bone-earth are found phosphorus, a 
 metal (calcium), and oxygen; in the gelatine, besides 
 carbon, three other bodies — oxygen, hydrogen, and nitro- 
 gen. These bodies can be decomposed no further by any 
 known method of analysis, and are therefore called simple 
 bodies, or elements. There are now about seventy known 
 elements, and almost every year adds to their number. 
 This separating of compound bodies into simple ones is 
 designated by the name of decomposition, and the process 
 of ascertaining the composition of any substance is called 
 analysis. 
 
 When a substance contains two or more elements, held 
 together by chemical force, it is called a compound. Com- 
 pounds are always quite different in properties from their 
 constituents. 
 
 When a substance contains two or more other substances 
 (elements or compounds), not held together by chemical 
 force, but present as it were accidentally together, it is 
 called a mixture. In a mixture the properties of the 
 separate ingredients are still perceptible. 
 
 This distinction between element, compound, and mix- 
 ture is very important. The following illustrations will 
 assist to fix it in the memory. Water is a compound of 
 the elements hydrogen and oxygen, which are held together 
 by chemical force. Air is a mixture of the elements 
 oxygen and" nitrogen, which are not in chemical combina- 
 tion with one another. Gunpowder is a mixture, contain- 
 ing the elements carbon and sulphur and the compound 
 saltpetre. The compound saltpetre contains the elements 
 potassium, nitrogen, and oxygen. 
 
 2. The changes which they undergo hy the action of other 
 bodies and of the various forces upon f^em.— Phosphorus, 
 which is obtained from bones, is luminous in the air, and 
 is gradually converted into an acid liquid ; it unites with 
 the oxygen of the air and with water, as iron does when 
 exposed to moist air. If the phosphorus is gently heated, 
 this union is attended with a vivid combustion, and there 
 is formed a body which is different from the former ; to 
 which, if water and lime be added, a new body is formed. 
 
OBJECTS OF CHEMICAL INQUIRY. 
 
 17 
 
 very similar to bone-ash ; it is, in fact, artificial bone-ash. 
 The number of new bodies which may be produced by the 
 union of the elements with each other, or with compound 
 bodies, is infinite ; and entirely different substances are 
 often formed, according as the combination takes place 
 under the influence of cold or heat, in water or in air, in 
 greater or smaller quantities. This is combination or 
 synthesis, 
 
 3. The causes of chemical changes and the laws according to 
 udhich they take place, — If chemical experiments are per- 
 formed as they should be, with the balance at hand, it 
 will soon be observed, that when two different bodies 
 which can unite with each other are brought together, 
 sometimes a part of the one, sometimes a part of the 
 other, remains free. Further experiments will show how 
 much of one body, in weight, can be united with the 
 other. If all bodies are tested in the same manner, the 
 certainty is finally attained, that all chemical combinations 
 take place only in fixed, unchangeable proportions, and 
 that to every individual body is assigned a definite 
 weight, with which it always enters into any combination 
 whatever. (Chap. III.) This certainty is called a natural 
 law. Many such laws of nature have already been 
 ascertained, and they serve as a certain guide to the 
 chemist in his labours, since they cannot, like human 
 laws, be arbitrarily evaded or changed. By them alone 
 we attain to a scientific insight into chemical processes, 
 and to the capability of putting direct questions to bodies 
 by experiment, and of testing the truth of the answers 
 received. An explanation of chemical processes based on 
 natural laws, which presents a clear idea of the subject to 
 the mind, is called a Theory, 
 
 4. The extent to which the facts which have been discovered 
 may be made useful to man, — When the chemist discovers a 
 new body, or a new property in one already known, or a 
 new method of synthesis or analysis, he imparts bis 
 discovery to the apothecary, the physician, the farmer, 
 the manufacturer, and the tradesman, that experiments 
 may be instituted for the purpose of ascertaining whether 
 any advantage, facility, or improvement can be derived 
 for pharmacy, medicine, agriculture, or the arts. Phos- 
 
 C 
 
18 
 
 EXPERIMENTAL CHEMISTRY, 
 
 phoriis ignites spontaneously at a gentle heat ; it is used 
 in lucifer matches. Taken into the stomach, it acts as a 
 violent poison ; it is at present one of the most common 
 means for the destruction of vermin. The constituents of 
 bone-earth and those of gelatine have been found to be 
 universally present in the seeds of different kinds of corn ; 
 the chemist concludes from this that pulverised bones 
 should yield an excellent manure; the agriculturist 
 demonstrates this by experiments on a large scale. In 
 bone-black the property has been discovered of attracting 
 many substances held in solution in liquids, and of 
 condensing them in itself ; on account of this property it 
 is used for making impure water potable ; the sugar- 
 refiner employs it to make brown syrup colourless. This 
 is applied or practical chemistry. 
 
 Nothing is better calculated to excite an interest in 
 chemical knowledge than a consideration of the useful 
 application which can be made of it in every-day life. 
 Chemistry teaches the apothecary how to compound and 
 prepare his medicines ; it teaches the physician how to 
 cure maladies by means of these medicines; it not only 
 shows the miner the metals concealed in rocks, but aids 
 him also in smelting and working them. Chemistry, in 
 connection with physics, has been the principal lever by 
 which so many arts and trades have been brought to such 
 a degree of perfection within the last few decades, and by 
 its means we have been supplied with numberless con- 
 veniences of life that were not enjoyed by our fathers. 
 It is obvious that the farmer must regard chemistry as his 
 indispensable friend, for it is this alone which acquaints 
 him with the constituent parts of his soil, with the proper 
 nutriment of the plants he wishes to cultivate, and with 
 the means whereby he can enchance the fruitfulness of his 
 fields. 
 
 The ancient so-called Elements. — The dogma of the 
 ancient philosophers, that there are four elements, earth, 
 air, water, and fire, has long been known to be erroneous, 
 although the words are still repeated very often. We now 
 know that three of them are either mixtures or compounds 
 of the true elements, and that fire is but a peculiar 
 operation of heat and light. 
 
( 1^ ) 
 
 CHAPTEE IT. 
 
 GRAVITY, HEAT, PRESSURE. 
 GEAVITY. 
 
 The force of gravity is chiefly interesting • to chemists 
 because it confers upon all kinds of matter the property 
 called weight. 
 
 weighing and measuring. 
 
 Weighing, — The balance is the plumb-line, as well as the 
 touchstone in chemical experiments ; it teaches us how to 
 ascertain the true composition of bodies, and shows us 
 whether the questions put, the answers received, or the 
 conclusions drawn from them, are correct or false. Hence 
 it cannot be too strongly recommended to those com- 
 mencing the study of chemistry to use the balance even in 
 simple experiments. For the experiments described in 
 this book, a common apothecaries' balance is all that is 
 requisite. 
 
 Avoirdupois weight is most frequently used in England. 
 The only numbers required in chemistry are the follow- 
 ing :— 
 
 Pound. Ounces. Grains. 
 
 1 = 16 = 7000 
 1 = 437-5 
 
 Apothecaries' weight is somewhat different, but the 
 grain is the same. 
 
 Pound. Ounces. Drachms. Scruples. Grains. 
 
 1 = 12 = 96 = 288 = 5760 
 1 = 8 = 24 = 480 
 1 = 3 = 60 
 
 1 = 20 
 
 The French system of weights and measures, which is 
 now almost universally adopted by chemists, is charac- 
 
 c 2 
 
20 
 
 EXPERIMENTAL CHEMISTRY. 
 
 terised by great simplicity, all its divisions being made by 
 ten ; hence the name decimal weight and measure. Its 
 unit is derived from the size of our globe. 
 
 In order to define the different localities on this globe, 
 imaginary circles, as is well known, have been drawn 
 around it. Those which pass round the earth from east to 
 west, the largest of which is the equator, are called 
 parallels of latitude ; those which pass round the earth 
 lengthwise, intersecting at the 
 poles, meridians. The parallels 
 of latitude gradually become 
 smaller towards the poles; the 
 meridians, on the contrary, are 
 all of equal size. The circle 
 N E S W represents a meridian 
 or circle of longitude. The 
 fourth part of this circle, or, 
 what is the same thing, the 
 fourth part of the circumference 
 of our earth, as N E, is the 
 basis of the French system. 
 This quadrant was divided into ten million parts, one of 
 which was taken as the unit, under the name of metre, A 
 metre is nearly forty, or about 39f inches in length. The 
 smaller measures are produced by dividing by ten, and 
 are designated by Latin prefixes ; the larger ones by 
 multiplying by ten, and are designated by Greek prefixes. 
 
 Smaller Measures. Larger Measures. 
 
 Metre. Metre. 
 
 Decimetre = '1 or j^,, metre. Decametre = 10 metres. 
 Centimetre = -01 or jjg „ Hectometre = 100 „ 
 Millimetre = 001 or j^'g^ „ Kilometre = 1,000 „ 
 
 Myriametre = 10,000 „ 
 The niillimeti e is nearly r}^ of an inch. 
 
 The system of weights are derived from the measure of 
 length, in the following manner. A cube of water at its 
 greatest density (at the temperature 39^ F.) (4° C.) was 
 taken as unit, which would measure one centimetre in 
 each direction, and the weight of this quantity of 
 water was called a gramme. This is taken as the unit of 
 the decimal weights, and is multiplied or divided l)y ten. 
 
WEIGHING AND MEASURING. 
 
 2t 
 
 Smaller Weights. Larger Weights. 
 
 Gramme =1*0 Gramme = 1 
 
 Decigramme = -1 or gramme. Decagramme = 10 grammes 
 Centigramme = -01 or „ Hectogramme = 100 „ 
 
 Milligramme = -001 or y-Jgj „ Kilogramme = 1 , 000 „ 
 
 Myriagramme = 10,000 „ 
 One gramme is equal to 15 4321 grains. 
 One kilogramme is equal to 2*204 lbs. Av. 
 
 It is well enough known that the body whose weight is 
 to be ascertained must be put into one scale, and in the 
 other, weights sufficient to restore the index to its original 
 perpendicular position. The weight of a body thus 
 determined is called its absolute weight. Thus, a piece of 
 sugar weighing two ounces has an absolute weight of two 
 ounces. 
 
 Measuring of Liquids and Gases, — The English system 
 for liquids is as follows : — 
 
 Gallon. i 
 
 Quarts. 
 
 Pints. 
 
 Fluid Ounces. 
 
 Fluid Drachms. 
 
 Minims. 
 
 C. 
 
 
 0. 
 
 fl..^. 
 
 fl. 5- 
 
 m. 
 
 1 = 
 
 4 
 
 = 8 
 
 = 160 = 
 
 1,280 = 
 
 76,800 
 
 
 1 
 
 = 2 
 
 = 40 = 
 
 320 = 
 
 19,200 
 
 
 
 1 
 
 = 20 = 
 1 - 
 
 160 = 
 8 = 
 1 = 
 
 9,600 
 480 
 60 
 
 1 gallon of water at 60° Fah. = 277*276 cubic inches, weighs 10 lbs. 
 Av. = 70,000 grains. 
 
 1 fluid ounce of water weighs 1 ounce Av. = 437*5 grains. 
 
 Grains of water are likewise frequently employed as a measure for 
 liquids. 1,000 grain measures = of a gallon. 
 
 Gases are generally measured in cubic inches. 
 
 The standard of measure in the French system is the 
 litre, which is the same as one cubic decimetre, or a cube 
 of nearly 4 inches on each side. The same prefixes are 
 used for the fractions and multiples as for the metre and 
 gramme, but it will be seen that the litre is also equal to 
 1000 cubic centimetres. Cubic centimetres are generally 
 used in chemistry for the measurement both of liquids 
 and gases. As one cubic centimetre of water weighs one 
 gramme, a litre of water weighs 1 kilogramme. It is 
 almost exactly equal to If pint. 
 
 The student will find it advantageous to use the French 
 weights and measures. They are now generally employed 
 by scientific men. 
 
22 
 
 EXPERIMENTAL CHEMISTRY. 
 
 SPECIFIC GRA.VITY. 
 
 Ice floats in water, iron sinks in it, because the former is 
 lighter, the latter heavier, than water. But if we put a 
 piece of ice in spirit it sinks, or if we put a piece of iron 
 upon mercury (quicksilver), it floats ; consequently, ice is 
 heavier than spirit, iron lighter than mercury. It also 
 follows that spirit is lighter than water, since it can 
 support less weight, and mercury heavier than water, as it 
 can bear a greater weight. The terms heavier and lighter, 
 in this sense, correspond to what in scientific language is 
 called specifically heavier or specifically lighter, and equal 
 hulks are always to be understood in speaking of the 
 comparative weights of bodies. The expression, ice is 
 lighter than iron, means, therefore, that, taking equal bulks 
 of each, the former weighs less than the latter ; and when 
 we say that mercury is heavier than water, we mean that 
 in equal volumes, as a pint, for instance, the mercury has 
 a greater weight than the water. But in absolute weight, 
 no regard is paid to the volume of substances. 
 
 In order to ascertain how many times heavier mercury is 
 than water, or iron than ice, it is only necessary to weigh 
 equal volumes or portions of each, and to compare their 
 weights at the same temperature. If, for example, we take 
 five vessels, each of which would contain exactly 100 grains 
 of water, and fill them respectively with spirit, ice, water, 
 iron, and mercury, the following differences in weight will 
 be found : the vessel with spirit would weigh 80 grains ; 
 with ice, 90 grains ; with water, 1 00 grains ; with iron 
 (if quite pure), 780 grains; with mercury, 1360 grains. 
 
 To facilitate the comparison of the numbers which denote 
 how much greater the specific gravity of one body is than 
 that of another, water has been fixed upon as the standard 
 or unit. Therefore, in the above case, the question is, how 
 much lighter than water are spirit and ice, and how much 
 heavier are iron and mercury? or, in other words, how 
 many times is 100 contained in 80, 90, 780, and 1360? 
 The other numbers, then, are to be divided by 100, the 
 weight of water, and there is found for 
 Spirit, or, in decimals, 0*80 ; it is therefore ^ lighter 
 
 than water. 
 
SPECIFIC GRAVITY. 
 
 23 
 
 Ice, ^Vo9 ^1'' decimals, 0*90 ; it is therefore j\ lighter 
 than water. 
 
 Iron, If^, or, in decimals, 7*80 ; it is therefore times 
 
 heavier than water. 
 Mercury, ^-^-^jj, or, in decimals, 13*60; it is therefore 13.;^ 
 
 times heavier than water. 
 
 These numbers represent the specific weights (sp. gr.). 
 Thus, according to calculation, sjoirit having a specific 
 gravity of 0*80, 80 parts of it would occupy the same space 
 as 100 parts of water; therefore it is only four-fifths as 
 heavy as water, or, what is the same thing, one-fifth lighter 
 than water. The specific gravity of mercury being 13*6, 
 that is, 13^ parts of mercury do not take up any more space 
 than one part of water ; since it is about 13^ times heavier 
 than water. 
 
 ^ Determination of Specific Gravity. — Experiment. — To deter- 
 mine the specific gravity (the density) of a fluid, a bottle 
 is weighed, then filled with water, and again weighed. 
 This gives the weight of the water. Now pour out the 
 water, and refill the bottle either with spirit, syrup, lye, 
 beer, or some other liquid, and ascertain by the balance the 
 weight of each. Then divide the weight of each of these 
 fluids by the weight of the water, and the quotient indicates 
 the specific weight. It is very convenient to use a bottle 
 made to contain exactly 100 grammes of water. As bodies 
 expand by heat, and so become specifically lighter, they 
 must be compared at a constant temperature. 
 
 Experiment. — Weigh a bottle filled with water ; then 
 place a 20-gramme weight on the pan which holds the 
 weights, and by the side of the bottle nails enough to 
 adjust the beam. Kemove both the nails and the bottle 
 from the pan, and put the nails into the bottle. A bulk of 
 water will be displaced equal to that of the nails ; to deter- 
 mine its amount, replace the bottle, after it has been 
 thoroughly wiped on the outside, upon the pan, and remove 
 weights from the other pan until the equipoise is restored. 
 The weights taken away (about 2*6 grammes) form the 
 divisor, and the 20 grammes the dividend ; the quotient, 
 \^=7'7, is the specific gravity of iron of which the nails 
 were made. English weights may, of course, be used. 
 
 The specific gravity of gases is determined by a process 
 
24 
 
 EXPERIMENTAL CHEMISTRY. 
 
 whicli is similar in principle to the above, but is mucb more 
 difficult. The standard of specific gravity for gases now 
 generally used is hydrogen, which is the lightest gas known. 
 When we say that the specific gravity of oxygen is 16, we 
 mean that it is 16 times heavier than hydrogen. Air is 
 sometimes taken as the standard. It is 14*5 times heavier 
 than hydrogen, so that, knowing the specific gravity of a 
 gas in relation to hydrogen, it is easy to find it in relation 
 to air by dividing by 14*5. Thus the specific gravity of 
 oxygen as compared with air is y^^^^ = 1*1. 
 
 Experiment — If we have to determine the specific gravity 
 of a piece of iron, or of any other body which cannot be put 
 into a bottle, it must be fastened by a piece of fine thread 
 to the pan of a common balance (Fig. 3, &), the cords of 
 Fig. 3. this pan having been 
 
 o previously shortened. 
 
 Weigh 'the body first 
 in air,^ and then in 
 water, immersing it 
 an inch deep. When 
 it is immersed, the 
 opposite pan falls ; 
 consequently iron must 
 be lighter in the water 
 than in the air. If 
 the iron in the air 
 weighed 240 grains 
 then, in order to re- 
 store the equilibrium, it will be necessaiy, as in the 
 former experiment, to remove from the pan a 32 grains, 
 equal to the weight of the bulk of water displaced by the 
 iron. The loss of weight is the same, whether the water 
 be removed from the vessel or merely displaced within it. 
 This forms the divisor, and 240, the weight of the iron in 
 the air, the dividend, giving the quotient = 7*5. 
 
 Every substance becomes as much lighter in water as 
 the quantity of water displaced weighs. If it displaces 
 less water than its weight in the air, it sinks ; if more, it 
 floats. Even very heavy bodies can be made to float by 
 increasing their volume ; ships are constructed of iron, 
 although it is eight times heavier than water ; a tumbler 
 
SPECIFIC GRAVITY. 
 
 25 
 
 floats upon water, and yet the specific gravity of glass is 
 three or four times greater than that of water. A thick 
 piece of iron, weighing half an ounce, loses in water nearly 
 one-eighth of its weight ; but if it is hammered out into a 
 plate or vessel of such a size that it occupies eight times as 
 much space as before, it then loses its whole weight in 
 water, and will float, sinking just to the brim. If made 
 twice as large, it will displace one ounce of water — conse- 
 quently twice its own weight. It will then sink to the 
 middle, and can be loaded with half an ounce weight before 
 sinking entirely. 
 
 Hydrometer or Areometer, — The same floating body will 
 sink to a greater or less depth in different liquids — deeper 
 in the lighter ones, and not so deep in those which are 
 denser. This has suggested a very convenient instrument 
 for determining the specific gravity of liquids — the hydro- 
 meter^ or areometer. This instrument consists of a hollow 
 glass tube, made as represented in Fig. 4. 
 The interior is hollow, and blown out into a 
 bulb at the lower end, to cause it to float; 
 the under part is loaded with quicksilver or 
 shot, to give it a vertical position. The 
 narrow tube serves to denote the depth to 
 which it sinks in any liquid, by means of a 
 scale of degrees, vdth which it is furnished. 
 There are various instruments of this kind, 
 especially adapted for determining the density 
 of spirits, brandy, oil, soda, syrup, &c. If a 
 hydrometer for weighing spirits is put into 
 water, it sinks only to the lowest point on the scale, (f 
 (Fig. 4, a) ; but in the strongest alcohol, which is 
 much lighter than water, it sinks to the highest point, 
 100"^. A scale for testing soda (Fig. 4, h) must, on the 
 contrary, have the 0° point at the top of the scale, to which 
 it would sink in pure water ; for soda being heavier than 
 water, the instrument would be more or less buoyed up in 
 it, according to its strength. In hydrometers for lighter 
 liquids, the degrees proceed from the bottom to the top ; in 
 those for heavier liquids, from the top downwards. In 
 some of these scales the degrees are ai-bitrary, and in order 
 to convert them into the corresponding specific numbers, 
 
26 
 
 EXPERIMENTAL CHEMISTRY. 
 
 tables, constructed for the purpose, must be refeiTed 
 
 Experiment. — Pour brandy into a cylindrical jar, and 
 observe the degree which it marks on the hydrometer; 
 then put it in a warm place, and when lukewarm, again 
 note the degree, which will be higher than before, as the 
 heat has expanded the liquid, made it lighter, and conse- 
 quently apparently stronger than it really is. The specific 
 gravity of all bodies, when warmed, is less than when 
 cold. On this account, in determining the density of 
 bodies, regard should be paid to their temperature, and 
 it is usual to consider 60"^ F. (15*5° C.) as the mean tem- 
 perature. 
 
 In some hydrometers the mercury serving as the counter- 
 poise has been ingeniously contrived also to indicate the 
 degree of heat of the liquid, by connecting with it a 
 Fig. 5. graduated tube. The small scale, a (Fig. 5), 
 denotes the temparature, the long scale, h, the 
 I density. The small scale is frequently so con- 
 [ structed that the degrees correspond to those on 
 H. the long scale, and in order to guard against error 
 -r it is only necessary to add the degrees below the 
 ' mean temperature to the density, or to subtract 
 from the density those above. 
 
 Gold is nineteen times, and silver ten times, 
 heavier than water ; gold alloyed with silver must, 
 therefore, have a less specific weight than pure 
 gold. The specific weight of brass is only = 8. 
 Alcohol and ether are lighter in proportion to 
 their purity and strength, while lye, syrup, the 
 acids, &c., increase in density according to their 
 purity. Hence it is evident how important it is, in many 
 cases, to know the specific gravity of a body in order to 
 judge of its quality. 
 
 HEAT. 
 
 We have already seen that heat is often given out 
 during chemical action. When chemical force is exerted, 
 heal is generally, if not always, produced ; and, on the 
 other hand, many chemical changes will not take place 
 without the assistance of heat. 
 
HEAT. 
 
 27 
 
 The artificial heat which is employed in chemical 
 operations and in ordinary life is obtained from chemical 
 action. Coal, wood, spirit, oils, and all the other kinds of 
 fuel undergo a chemical change when they burn, which 
 will be fully explained hereafter. They combine with 
 the oxygen of the air, and in doing Yig. 6. 
 
 so chemical force is consumed and 
 changed into heat. 
 
 Sources of heat for chemical opera- 
 tions. — If the student is fortunate 
 enough to have gas at his command, 
 he will seldom need any other fuel. 
 The gas may be brought from the nearest burner, from 
 which the jet has been screwed off, by means of an india- 
 rubber tube. For most purposes, the burner known as the 
 Bunsen burner (Fig. 6) is convenient. The gas becomes 
 mixed with air in this burner before burning, and burns 
 therefore with a smokeless flame, which gives very little 
 light, but an intense heat. Little Fig. 7. 
 
 iron caps, a (Fig. 6), are sold with 
 each burner, which fit on it, and 
 convert the single flame into a ring 
 of smaller jets. Some of the burners 
 made by Fletcher of Warrington 
 are exceedingly useful in chemistry, 
 and they are very cheap. 
 
 If gas cannot be obtained, a small 
 spirit-lamp, such as shown in Fig. 7, 
 may be used for ordinary purposes, 
 and methylated spirit, which is very 
 cheap, may be burned in it. More powerful spirit-lamps 
 are, however, sold, and small oil-lamps may sometimes be 
 employed for the sake of economy when the heat has to 
 be employed for a long time. Furnaces are scarcely 
 necessary to the beginner in chemistry. The few crucible 
 operations he has to perform may be done in a common fire. 
 
 EFFECTS OF HEAT. 
 
 Expansion of Liquids. — Experiment 1. — Counterpoise a 
 flask — that is, place it on one of the pans of a balance, 
 and equipoise it by weights or shot put into the opposite 
 
28 
 
 EXPERIMENTAL CHEMISTRY. 
 
 pan; then fill it to the brim with water, and note the 
 weight of the latter. Warm the flask on a tripod over a 
 spirit-lamp or gas-burner. The water will expand, and 
 part of it will run over, and may be carried away by a 
 gutter of tin plate just under the neck of the flask. When 
 it begins to boil, remove the lamp, and let the vessel cool, 
 and the water will then sink below the neck. How much 
 has been displaced is found by its loss in weight ; it will 
 amount to about of the first weight. 
 
 The lamp heats the bottom of the glass vessel, which 
 in its turn communicates heat to the water. The heat 
 expands the water, consequently it occupies a greater 
 space than before, and part of it must run over. Hence 
 it follows that warm water must be lighter than cold 
 water. If a pitcher filled with two pounds of ice-cold 
 water be afterwards filled with boiling water, it will 
 weigh about an ounce and a half less. 
 Fig. 8. The same occurs with all other liquids, and, 
 ^ indeed, also with solids and gases ; hence, it may 
 ^1 be stated as a natural law, ihat all bodies exjpand 
 
 by heat, and contract on cooling. But the amount 
 of expansion is very different in different bodies 
 at the same temperature ; alcohol, for example, 
 ^'l expands much more, mercury much less, than 
 
 i water. When fluids are to be bought and sold 
 by measure, an advantageous application may be 
 made of this principle. If a hundred measures 
 of brandy or alcohol were purchased in hot, and 
 sold in cold weather, there would be a loss of 
 four or five measures ; therefore we should gain 
 by buying in winter and selling in summer. 
 Experiment 2. — In order to observe more accurately the 
 expansion of water by heat, adapt to a flask a cork, rendered 
 so soft by gently striking it with a piece of wood that it 
 may be exactly fitted to the opening by mere pressure ; 
 perforate the cork with a round file or cork-borer, and make 
 the hole just large enough to admit a glass tube tightly. 
 Fill the flask with water, so that, when the cork is firmly 
 pushed in, the water shall stand at about a (Fig. 8), and 
 heat it as in the former experiment. 
 
 The water, which in the former experiment was displaced 
 
EFFECTS OF HEAT. 
 
 29 
 
 from tlie flask, now rises in the tube, and this higher in 
 proportion to the smallness of its bore. By this means 
 very slight changes of space are rendered visible, and 
 these deviations may be applied to the measurement of 
 heat. This is done by particular instruments called 
 thermometers. 
 
 Thermometer. — Water might be employed for measuring 
 heat, by marking the boiling and freezing points, and 
 graduating the intervening space ; but mercury is far 
 better adapted to the purpose, as it boils and freezes at 
 greater extremes of temperature, and becomes hot and cold 
 more quickly ; hence it more quickly denotes the variations 
 of heat and cold : moreover it expands more uniformly 
 than water. 
 
 The vessel containing the mercury may also be regarded 
 as consisting of a flask and tube, but which, instead of 
 being joined by a cork, are composed of one entire piece. 
 Having introduced into it a suffi- 9. 
 cient quantity of mercury, and 
 sealed the open end by fusion, it is 
 immersed in melting ice, and the 
 point to which the quicksilver falls 
 is marked freezing point; that to 
 which it rises in boiling water, 
 boiling point. The space between 
 these two points can now be divided 
 into degrees, to form the scale. 
 The degrees below the freezing 
 point must be of the same dimen- 
 sions as those above. There are 
 several scales in use, though it is to 
 be regretted that more than one 
 has been adopted. The most common are the three 
 following : — Beaumur's (B.), divided into eighty degrees ; 
 the Centigrade of Celsius (C), into one hundred; and 
 Fahrenheit's (F.), into one hundred and eighty degrees. 
 The difference between these can be easily seen in the 
 annexed figure. 
 
 According to K. water freezes at 0"^ and boils at 80° ; 
 according to C. it freezes at' 0°, and boils at 100^ ; accord- 
 ing to F. it freezes at +32°, and boils at 212°. 
 
30 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Fahrenheit, a philosophical-instrument maker, commenced 
 reckoning very strangely, not at the freezing point, but at 
 32^ below it. His scale is still in common use in England, 
 and the high numbers found in English works are thus 
 accounted for. In Germany, Beaumur's thermometer is 
 used, except for scientific purposes, when the Centigrade, in 
 common use in France also, is employed. In order to com- 
 pare these thermometers with each other, it need only be 
 remembered that 4° E. are equal to 5° C. or 9° F. In re- 
 ducing the degrees of Fahrenheit's scale above 32° to those 
 of the Centigrade, the number of degrees above or below 
 32° must be multiplied by 5 and the product divided by 9. 
 And to reduce those of Fahrenheit to Eeaumur, the number 
 of degrees above or below 32° must be multiplied by 4 and 
 divided by 9. To the degrees above 0°, the sign -f- is pre- 
 fixed or understood ; to those below, the sign — is invariably 
 added. 
 
 A cylindrical thermometer, graduated to about 600° F. 
 Fig. 10. (315° C), is best suited for chemical experiments, 
 as shown in the annexed fi.gure, because it can be 
 easily adapted to a perforated cork, and then 
 fitted to a flask, in which liquids are to be heated 
 to a certain temperature. The degrees above 
 the boiling point are to be divided off at distances 
 equal to those below. 
 
 Mercury freezes at -38° F. (-39° C). In the 
 northern regions of the earth a degree of cold of 
 -58° F. -50° C.) has been observed, and by 
 artificial means the temperature can be lowered 
 to temperature lower than -148° F. (-100° C). 
 When great degrees of cold are to be measured, 
 alcohol is used in the construction of this instrument, as 
 it does not congeal at -148° F. (-100° C). 
 
 Mercury boils at 675° F. (357° C.) ; therefore its use 
 must be limited to temperatures below this point. The 
 high temperatures attending ignition are sometimes 
 measured by the expansion of bars of platinum, a metal 
 which does not melt in any ordinary furnace. Such an 
 instrument is called a pyrometer. The determination of 
 very high temperatures is, however, obtained by other 
 means. 
 
EFFECTS OF HEAT. 
 
 31 
 
 Expansion of Solids. — If an iron vessel, when cold, is jnst 
 large enough to pass through the door of a furnace, it 
 cannot be removed from it when heated. The iron bands 
 or tires of carriage wheels are applied while hot to the 
 frame, and on cooling they contract and bind the wood- 
 work together with great force. A metallic disk, which, 
 when red-hot, fits exactly into a circular box, will, on cool- 
 ing, become loose, and shake in it. The tire and the disk 
 both become smaller on cooling. These examples show 
 that solids also are expanded by heat and contracted by 
 cold, and explain many of the phenomena of common life. 
 Clocks are apt to go faster in winter, and slower in summer, 
 because the pendulums elongate in summer, and, conse- 
 quently vibrate slower ; while in winter they becorde 
 shorter, and vibrate more rapidly. A piano gives a higher 
 tone in a cold than in a warm room, on account of the con- 
 traction of the strings. A nail driven into the wall becomes 
 loose after a time, because the iron expands in summer and 
 contracts in winter more than the stone or the wood, and 
 thus the opening is gradually enlarged. For this reason, 
 in the construction of railroads, the rails must not be laid 
 too close together ; in the arrangement of steam-pipes, 
 these must not be too fi.rmly inclosed ; in roofing, the zinc 
 plates, instead of being nailed together, must overlap each 
 other, that they may neither tear nor warp on alternate 
 contraction and expansion. 
 
 Brittle bodies, as glass and porcelain, expand or contract 
 so rapidly, by sudden heating or cooling, that they break. 
 
 Experiment 3. — Wind round a bottle two bands of paper, a 
 and h, Fig. 11, and secure them firmly with -p. 
 thread ; pass a piece of string round the 
 bottle, between these folds of paper, and move 
 the bottle quickly to and fro on the string 
 until the latter breaks. Then immediately 
 pour cold water upon the place, and the 
 glass will break as evenly as if cut. The 
 sharp edges can be removed with a file. In 
 this manner, common white or green glass 
 bottles may be converted into vessels adapted 
 to chemical and other purposes. 
 
 It is well known that heat is produced by the friction of 
 
32 
 
 EXPERIMENTAL CHEMISTRY. 
 
 two bodies upon each other ; that by sliding quickly down 
 a line or a pole by the hands, these will be burnt ; and that 
 rapid motion will ignite the axles of a carriage, unless they 
 are well greased. Thus, in the above experiment, the 
 friction produced great heat in the glass, the string emitted 
 a burnt odour and broke, and great expansion of the glass 
 was produced. When the outer surface was suddenly 
 cooled by the cold water, the expanded particles at once 
 contracted, and more rapidly in the external particles than 
 in those of the inner surface, causing the fracture of the 
 glass, and the more easily the greater its thickness. If the 
 temperature had been slowly reduced, it would not have 
 broken. 
 
 Thus it is obvious (a) that glass and porcelain vessels 
 intended for sustaining high temperatures, such as flasks, 
 alembics, retorts, capsules, &c., should be thin, particularly 
 at the bottom ; and (h) that, when used, they should always 
 be gradually heated and cooled. 
 
 The above method of heating glass by a piece of string 
 furnishes the chemist with a simple expedient for removing 
 stoppers which are too firmly fixed in 
 the bottles to be taken out by turning 
 or tapping them. All that is necessary 
 is to wind a piece of thick string round 
 the neck of the bottle, and move it 
 quickly until sufficient heat has been 
 produced to loosen the stopper. 
 
 No two solids expand alike ; the 
 metals expand the most, and all solids 
 less than fluids. 
 
 Expansion hy Cold, — A remarkable 
 exception to this law of expansion by 
 heat and contraction by cold occurs in 
 the case of water. 
 
 Experiment 4. — A large flask is ar- 
 ranged as directed in Experiment 2, 
 page 28, but inserting a cylindrical 
 thermometer, a, through a second hole made in the cork. 
 The flask is filled with water to the top of the tube h, and 
 placed in a vessel filled with ice. A strip of paper may be 
 pasted on this tube, upon which the level of the water may 
 
 Fis:. 12. 
 
EFFECTS OF HEAT. 
 
 33 
 
 be marked as the thermometer falls. The water as it cools 
 will sink in the tube until the mercury stands at 39° F. 
 (4° C.) ; yet, on cooling still more, it does not fall any 
 further, as we should expect it would, but, on the contrary, 
 it begins to rise again, and continues to do so till it reaches 
 the freezing point. At 32° F. (0° C.) it stands at the same 
 point as when its temperature was at 46° F. (8° C). Water 
 is accordingly most dense at 39° F. (4° G.) ; all other liquids 
 continue to increase in density as they cool. 
 
 However unimportant this exception may appear at first, 
 our admiration must be excited when we reflect upon 
 its consequences. Were it not for this, our country would 
 have the climate of Greenland. The freezing of our waters, 
 as the winter sets in, is principally owing to the coldness 
 of the atmosphere. Consequently, the upper part of the 
 water is colder and heavier, and sinks to the bottom ; the 
 warmer water ascends, becomes cold, and also sinks. If 
 the water continually became denser, to its freezing point, 
 this circulation would continue till the whole mass of water 
 to its greatest depth reached freezing point, and a few cold 
 days would suffice to convert all our 
 ponds, lakes and rivers into ice. This Fig. 13. 
 does not happen, because the circulation 
 ceases when its temperature has fallen 
 to 39° F. (4° C), when the water, though 
 yet colder, becomes lighter, and floats on 
 the surface. Thus, freezing can only 
 take place at the surface, and the ice be 
 but gradually formed. At a small depth 
 below the ice the water generally retains 
 the temperature of 39° F. (4° C). 
 
 Expansion of Gases. — Experiment 5. — 
 Dip a glass tube, provided with a bulb, 
 into water, and heat the bulb gently ; a 
 part of the air is expelled, and escapes in 
 bubbles through the water ; consequently, 
 there is not room enough in the bulb for the heated air ; 
 but it requires a larger space than it did in its cold con- 
 dition. It follows from this, also, that the warm air is 
 lighter than cold. If the lamp be removed, the air remain- 
 ing in the bulb will co^tract on cooling, and water will be 
 
34 
 
 EXPERIMENTAL CHEMISTRY. 
 
 pressed up into the bulb, replacing the air which has 
 been expelled. Such an apparatus, when the tube is 
 small, may be used as an air thermometer. When the 
 bulb is heated, the liquid descends in the tube, and vice 
 versa. 
 
 All gases expand alike when equally heated, differing in 
 this respect from solids and liquids. The extent to which 
 they expand is moreover much greater than with either of 
 the other forms of matter. A gas at freezing point expands 
 of its volume for every degree Fahrenheit of its 
 volume for every degree Centigrade) that is added to its 
 temperature, so that it is very easy, knowing the volume 
 that a certain weight of gas occupies at one temperature, 
 to calculate what its volume would be at some given 
 standard temperature. In experiments on gases their 
 volume is always given (unless otherwise stated) at 0° C. 
 or 32^ F., which is therefore said to be the standard of 
 temperature. 
 
 Example. — A certain weight of gas measures 23 cubic inches 
 at 65° F. : what would he its volume at 32° F. f 
 
 491 volumes at 32° become 492 at 33°, 493 at 34° and so 
 on, increasing 1 volume for every 1° F. Therefore, at 65°, 
 the 491 volumes would become 491 + 33 = 524 volumes. 
 Hence the calculation is a mere rule of three sum :— 
 
 Vols, at 65°. Vols, at 32°. 
 
 524 : 491 : : 23 : a; = 21-5 cubic inches. 
 
 Similar calculations may of course be made in the Centi- 
 grade scale, as the following example will show. 
 
 We have 100 measures of a gas at 50° G. : what would he 
 its volume at 0° C. f 
 
 273 vols, of gas at 0° C. = 274 vols, at 1°, 275 at 2°, and 
 so on. Heated from 0° to 50°, 273 vols, would become 
 323 vols. Therefore— 
 
 323 : 273 : : 100 : a; = 84-5 measures. 
 
 We can in this way find the volume that a gas would 
 occupy at any given temperature, although it most fre- 
 quently happens that we want to find its volume at 
 freezing point. 
 
 We have 100 volumes of gas at 17° C. : what would he its 
 volume at 193° C.f 
 
EFFECTS OF HEAT* 
 
 35 
 
 273 vols, at 0° C. = 290 vols, at 17°, and 466 vols, at 
 193°. Therefore— 
 
 290 : 466 : : 100 : a; = 160-7 volumes. 
 
 These calculations are generally spoken of as " correc- 
 tions for temperature." 
 
 Change of State as produced hy Heat, 
 
 (1) From Solid to Liquid. — Melting of Solids, — Expansion 
 is the first general effect of heat ; but in many solid 
 bodies another effect is observed ; they change their state 
 of aggregation, they become liquid, they melt. Many of 
 them become soft before melting, so that they can be 
 kneaded ; for instance, butter, glass, and iron ; in this 
 condition, glass can be bent and moulded like wax, and 
 iron can be forged. 
 
 Experiment 1. — Hold a piece of a small glass tube in the 
 upper part of the flame of a spirit-lamp, revolving it 
 slowty between the fingers ; when red-hot, it will be so 
 soft that it can be bent into any shape desired. Thus are 
 easily formed any of the numerous bent tubes required 
 in chemical experiments. For softening larger tubes, a 
 flame with a current of air passing through it, or a Bun- 
 sen burner must be us6d, as either gives a much stronger 
 heat than the simple lamp. To break a glass tube, a 
 scratch is made upon it with a three-cornered file, at the 
 place to be broken, and then it can be parted by gently 
 bending it with both hands. 
 
 Most solid bodies become suddenly fluid, as ice, lead, &c. 
 
 Experiment 2. — Place one vessel containing snow or ice, 
 and another containing a piece of a tallow-candle, on a 
 warm stove, dipping a thermometer from time to time into 
 the melting substances; the temperature will remain 
 stationary in the first vessel at 32° F. (0° C), in the other 
 at about 100° F. (38° C), so long as any ice or tallow 
 remains unmelted, but when the melting is complete it 
 will commence rising. The degree of heat at which a 
 body melts is called its melting point. Every substance 
 has its own melting point, sometimes above and sometimes 
 below the freezing point of water ; for example, lead melts 
 at 620° F. (327° C), silver at above 1800° F. (1000° C), 
 
 D 2 
 
36 
 
 EXPERIMENTAL CHEMISTRY. 
 
 solid mercury at -38° F. (-39° C). If the two vessels 
 containing the melted ice and the melted tallow are placed 
 in the cold, it will be observed that the tallow soon 
 hardens at about 95° F. (35° C), but the water does not 
 until the mercury has fallen to 32° F. (0° C). Thus the 
 congelation of fluids takes place at about the same tem- 
 perature as that at which they pass from the solid to the 
 fluid state. 
 
 Many substances, charcoal for instance, have never yet 
 been melted, and others have never been frozen, as, for 
 instance, alcohol ; but it is very probable that, when some 
 method of producing still greater degrees of cold and heat 
 is discovered, we shall succeed in rendering all solid 
 bodies liquid, and all liquids solid. 
 
 Latent Heat. — Experiment 3. — Put two vessels of equal 
 size on the top of a warm oven, one of them containing a 
 pound of ice at 32° F. (0° C), and the other a pound of 
 water at 32° F. (0° C.) ; when the snow is melted, remove 
 them both. By the touch merely it will be perceived that 
 the snow-water is still cold, while the water in the other 
 vessel has become warm ; and the thermometer will in- 
 dicate that in the former the temperature is at 32° F. 
 (0° C), in the latter at 176° F. (80° C). As both vessels 
 have received equal degrees of heat, and when placed upon 
 the oven were of the same temperature ; the question 
 suggests itself. What has become of the 144° of heat im- 
 parted to the vessel filled with ice ? The reply is, This 
 heat has been absorbed by the ice, thus converting it into 
 a fluid, — melting it. 
 
 Experiment 4. — Put one pound of ice at 32° F. (0° C.) 
 * into the vessel containing the water heated at 176° F. 
 (80° C), and then examine it with the thermometer ; as 
 soon as all the ice has disappeared, the quicksilver will 
 have fallen to the freezing point. Consequently, the ice 
 has taken from the hot water 144° F. (80° C.) of heat, and 
 has thus become liquid. 
 
 The heat which is lost in the melting of ice and other 
 solids is employed in overcoming the cohesion of the solid. 
 The force of cohesion is overcome in the manner described 
 in the previous chapter, and when the liquid again be- 
 comes solid the heat is reproduced ; the exertion of the 
 
EFFECTS OF HEAT. 
 
 37 
 
 cohesive force being attended with the evolution of heat. 
 Heat lost during liquefaction is often called latent heat, 
 because it was formerly supposed to lie hidden, or stored 
 up in the liquid. In a limited sense the term may still be 
 retained, for although we now know that heat is nothing 
 but motion, there can be no doubt that the molecules 
 (particles) of the liquid are in incessant motion, which 
 motion they lose to a great extent when the substance 
 becomes solid. 
 
 (2) From Liquid to Gas. — Boiling of Liquids. — Most 
 liquids, when heated to a certain temperature, different 
 for every liquid, boil and become converted into vapour or 
 gas. It must be understood that there is no real differ- 
 ence between the condition of a gas and of a true vapour, 
 except in regard to the temperature at which they are 
 formed. All the so-called gases can by great cold and 
 pressure be converted into liquids ; and, on the other 
 hand, when a liquid is converted by heat into vapour, the 
 vapour has all the properties of a true gas. In fact, some 
 substances are known which are liquid in cold weather 
 and gaseous in hof. Gases which become liquid at 
 ordinary temperatures are generally called vapours. 
 
 The phenomena of boiling are most conveniently studied 
 in the case of water. 
 
 Experiment 1. — Two-thirds fill a flask with spring water, 
 and heat it gently over a lamp (Fig. 14). 
 In a short time numerous little bubbles will 
 appear on the walls of the flask, which will 
 gradually increase in size, and rise towards 
 the surface. These bubbles consist of the gases 
 of air, which are exp3,nded by the heat and 
 expelled from the water. All spring-water 
 contains gases in solution, and to these is 
 chiefly due its refreshing taste, which is not 
 found in boiled water or in that which has 
 been standing for some time. Afterwards, 
 when the water has become quite hot, larger 
 bubbles appear on the hotter part of the flask, 
 which also ascending, become smaller, and 
 entirely disappear before reaching the surface of the 
 water ; they consist of gaseous water (steam), which con- 
 
38 
 
 EXPERIMENTAL CHEMISTRY. 
 
 denses as it comes in contact with the cooler liquid above. 
 The collapsing of the particles of water at the places 
 where these steam-bubbles disappear occasions that pecu- 
 liar noise which precedes boiling, and which is comm only- 
 called the singing of the water. When the whole mass of 
 water is heated to 212° F. (100° C), these bubbles no 
 longer condense, but rise to the surface, where, surrounded 
 by a thin film of water, they remain quiescent for a few 
 seconds, and then, their watery mantle again sinking, 
 they finally burst. This is the boiling of water. It boils 
 at 212° F. (100° C); other liquids boil more readily— 
 alcohol, for instance, at 176° F. (80° C.) ; others again with 
 greater difficulty — mercury, for instance, at675°F. (357° C). 
 
 Latent Heat of Steam, — The space above the boiling 
 water in the interior of the flask appears empty, but it is 
 in fact filled with aeriform water, which has displaced the 
 air that was in it. This aeriform water is called steam. 
 It is almost 1700 times lighter than water, because a 
 measure of water yields nearly 1700 measures of steam at 
 212° F. (100° C). Within the flask the steam is trans- 
 parent and invisible, but in the open air it ascends in the 
 form of white clouds, which greatly increase if cold air is 
 blown into the flask by means of a glass tube; for on 
 cooling the transparency of the vapour is disturbed, on 
 account of the formation of drops of water, so small and 
 li<iht as to float in the air. Clouds also consist of this 
 partly-condensed vapour. As the condensation increases, 
 the drops become so large and heavy, that they descend 
 as rain. A thermometer immersed in boiling water in- 
 dicates 212° F. (100° C.) ; if placed in the steam imme- 
 diately above, it shows the same ; and this temperature 
 will not rise higher, however long the boiling be con- 
 tinued, or however strongly the flame of the lamp be 
 urged. This is similar to what occurs in the melting of 
 snow; heat disappears, and its disappearance proceeds 
 from the same cause in both cases ; steam requires heat 
 for its production, and this heat disappears, or becomes 
 latent during its formation, and reappears, or becomes 
 sensible during its condensation. We have, in fact, to study 
 the latent heat of steam as well as the latent heat of water. 
 
 Experiment 2. — Adapt the shorter limb of a bent glass 
 
EFFECTS OF HEAT. 
 
 39 
 
 tube, by means of a perforated cork, to the neck of a 
 flask, and pass the longer limb to the bottom of a beaker- 
 glass or common tumbler. Pour into each of these two 
 vessels five ounces 
 of ice-cold water, 
 and gradually heat 
 the flask upon a 
 tripod until it boils. 
 Note the time re- 
 quired for this opera- 
 tion. Continue the 
 process until the 
 water in the beaker- 
 glass begins to 
 bubble, and note also 
 the time, which will 
 be found the same 
 as that required for 
 boiling the water in the flask. The steam formed in the flask 
 has no other outlet than through the tube into the water, 
 where it condenses, until the contents of the second glass 
 reach the temperature of 212° F. (100° C), and boil. 
 
 Both of the vessels must now be weighed ; and it will 
 be found that the flask weighs about one ounce less, and 
 the beaker-glass about one ounce more, than before ; 
 consequently, one ounce has passed from the former as 
 steam, and has been condensed again in the latter; and 
 yet this ounce of steam has raised five ounces of water 
 from 32° to 212° F. (0° to 100° C), that is, through 180° 
 F. (100° C). Now five ounces raised 180° is the same as 
 one ounce raised 180 x 5 = 900°, so that the ounce of steam 
 in condensing gave out 900° F. (500° C.) of heat. This 
 is expressed by saying that the latent heat of steam is 
 900° F. (500° C). More exact experiments give as the true 
 number 965° F. (536° C). The property of steam to give out 
 a large quantity of heat during condensation peculiarly 
 adapts it for the heating of other bodies, the burning of 
 them being thus guarded against, as the heat of steam in 
 open vessels can never exceed 212° F. (100° C). Apothe- 
 caries avail themselves of steam in the preparation of in- 
 fusions, decoctions, and extracts ; it serves for many of the 
 
40 
 
 EXPERIMENTAL CHEMISTRY. 
 
 processes of cookery, and for the distillation of spirits and 
 other liquids; it is employed in dyeing and bleaching 
 establishments, and is often resorted to for heating apart- 
 ments, buildings, laundries, &c. 
 
 All gases give out heat when they condense into liquids, 
 but the amount of heat so evolved is not known in every 
 case. Steam gives more than any other known gas. 
 
 Evaporation. — Aqueous Vapour, — Water exposed in a 
 vessel to the open air disappears in summer more rapidly 
 than in winter ; the heat of the air converts it into gas 
 — it evaporates. The same happens as in evaporation 
 over the fire, only in the former case evaporation takes 
 place without any visible motion of the water, owing to 
 its becoming aeriform, not throughout the whole mass at 
 once, but upon the surface only. The vapour rises in an 
 invisible form in the air. Warm air, indeed, takes up 
 more of it than cold, but a fixed quantity of it only for 
 each temperature. Thus one hundred measures of air at 
 32^ F. (0^ C.) absorb two-thirds of a measure of vapour ; 
 at 50° F. (10° C), one measure and a quarter ; at 
 68° F. (20° C), two and an eighth measures, &c. If the 
 air has not absorbed all the vapour which it can, it eagerly 
 takes up more, as, for example, when one hundred measures 
 of air at 68° F. (20^ C.) contain only one or one and a half 
 measures of vapour ; it is then called dry air, and wet 
 articles are soon dried in it by rapid evaporation. But if it 
 be already saturated with vapour it is called moist air ; and 
 damp articles cannot be dried in it, or at least but slowly. 
 If yet more vapour be added to this saturated atmosphere, 
 or if it be cooled, then the excess separates in visible 
 particles, called mist or fog when they lie near the surface 
 of the earth, and clouds when they float in the higher regions 
 of the atmosphere. The white smoke which in winter is 
 seen rising from steampipes, the visibility of the breath in 
 frosty weather, and the smoking of rivers in winter and 
 after a storm, are phenomena of the same kind. 
 
 If the cooling of the air is occasioned by a cold solid 
 body, the vapour is then condensed in small drops of water, 
 as may be observed on the outside of a cold glass when 
 brought into a warm room, and the deposit of moisture on 
 the inside of our window-panes, when cooled by the ex- 
 
EFFECTS OF HEAT. 
 
 41 
 
 ternal cold air. The temperature at which this occurs is 
 called the dew-point, signifying the temperature at which 
 the air is saturated with vapour. 
 
 Experiment 3. — Fill a tumbler one quarter full with cool 
 water, place in it a thermometer, and at short 
 intervals gradually add ice or cold water, until 
 moisture begins to deposit on the outside of the 
 glass. Then observe the degree indicated by the 
 thermometer, which is the dew-point. If much 
 cold water must be added before the glass clouds 
 over, that is, if the dew-point is much lower than 
 the temperature of the air, fair weather may be 
 expected ; while, on the contrary, if the difference between 
 the dew-point and the temperature of the air be but slight, 
 rain may soon be expected, as then the air requires but a 
 slight addition of moisture or increase of cold to become 
 saturated. Instruments by means of which the amount of 
 moisture in the air is ascertained are called hygrometers. 
 Many substances readily imbibe moisture from the air, and 
 become damp ; such bodies, for instance, as catgut, car- 
 bonate of potassium, sulphuric acid, fresh barley-sugar, 
 &c., are called hygroscopic. 
 
 Evaporation may be accelerated, not only by heat, but 
 also by a current of air, because by this means the air 
 above the surface of the fluid, which is charged with 
 vapour, is removed and replaced by a drier, and, as it 
 were, more thirsty air, which takes up the vapour more 
 rapidly and abundantly than the former. For this reason, 
 the earth dries rapidly after rain, when followed by a high 
 wind, and hence it is necessary in kilns, laundries, drying- 
 rooms, &c., to arrange them in such a manner that the 
 air, when saturated with moisture, may be constantly 
 replaced by dry air. 
 
 That heat disappears during slow as well as rapid evapora- 
 tion may be readily illustrated by the following experiment. 
 
 Experiment 4. — Fill a tube half full of water, and fasten 
 securely round the bulb of it a piece of wadding ; saturate 
 the wadding with cold water, and then twirl the tube 
 rapidly between the hands ; presently the water in the 
 tube will become sensibly colder, and the degree of cold 
 may be accurately determined by the thermometer. 
 
 I 
 
42 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Moisten the wadding with ether, a veiy volatile liquid, 
 and twirl it again in the same manner as before ; by which 
 Fig 17. ^^^^^ contents, even in summer, may be con- 
 verted into ice. Water evaporates slowly, ether 
 rapidly ; and both require heat for their conversion 
 into vapour, and in the above experiment they obtain 
 this heat from the water in the bulb, which is of 
 course the reason of the water becoming cold. On 
 this principal, one feels cool on just leaving the 
 bath, when invested in damp garments, or when 
 the floor of a hot apartment is sprinkled with water. 
 It explains, also, how man is enabled to support 
 the scorching sun of the hottest climates, and even 
 to endure a heat of 212° F. (100° C), without his 
 blood exceeding the temperature of from 100° F. (38° C.) 
 to 104° F. (40° C.) ; it is owing to the more copious per- 
 spiration, which, by evaporation, renders all the heat above 
 104° F. (40° C.) latent. If we blow on hot soup, it is also 
 the increased evaporation which cools it more rapidly ; but 
 if we blow on the cold hands in winter, they become moist 
 and warm, because the latent heat contained in the vapour 
 of the breath is set free, as the vapour is condensed into water. 
 
 Distillation. — If the condensation of wateiy vapour be 
 earned on in a closed vessel, the water may be collected as 
 it forms. 
 
 Experiment 5. — A small glass retort is half filled with 
 •p. jg water, and heated ; the 
 
 steam, as it forms, passes 
 through the neck of the 
 retort into a glass re- 
 ceiver, contained in a 
 vessel filled with cold 
 water, and is there con- 
 densed. That the re- 
 frigeration may take 
 place more rapidly, the 
 receiver is covered with 
 coarse blotting- paper which is frequently moistened with 
 cold water. This operation is called distillation^ and the 
 pure water obtained is said to be distilled. It is purer 
 than sprii:g-water, for this reason, that the non-vo- 
 
DIFFUSION OF HEAT. 
 
 43 
 
 latile, earthy and saline portions contained in all spring- 
 water do not evaporate, but remain in the retort. By this 
 means also very volatile bodies can easily be separated 
 from less volatile ones ; as in the distillation of brandy, 
 v^here the more volatile spirit is partially separated from 
 the less volatile water. Copper stills are usually employed 
 for distillation on a large scale, and for condensors vats are 
 constructed, holding serpentine pipes, or worms, which 
 present a greater condensing surface than if the pipe had 
 passed straight through the vat. The cold water with 
 which the vats must be filled is very soon warmed by the 
 heat liberated in the condensation of the steam, and must 
 be renewed by leading off the hot water from above, and 
 letting in a fresh supply of cold water beneath. 
 
 DIFFUSION OF HEAT. 
 
 Conduction of Heat. — Experiment 1. — A test-tube, nearly 
 filled with water, is held over a spirit- 
 lamp, in such a manner as to direct 
 the flame against the upper layers of 
 the water ; the water will boil at the 
 top, but remain quite cold below. If 
 mercury is treated in a similar way, 
 its lower layers will gradually become 
 heated. The particles of mercury 
 will communicate the heat to each other, but not so the 
 particles of water. Substances through which, as in 
 mercury, heat rapidly passes, are called good conductors; 
 but bodies which comport themselves like water are called 
 had conductors of heat. In the former class are included 
 principally the metals, and in the latter, stone, glass, wood, 
 snow, water, and especially soft bodies, as cloth, fur, linen, 
 straw, paper, ashes, &c., and also the gases. 
 
 The good conductors are readily heated, and soon become 
 cold again, as is well known to be the case with iron 
 stoves. A piece of iron feels hotter in the sun and colder 
 in the shade than a piece of wood at the same temperature. 
 The explanation of this delusion of the sense of touch, is 
 that the warm iron conducts the heat more rapidly to the 
 hand, while the cold iron withdraws it more rapidly than 
 the wood is capable of doing. 
 
44 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The bad conductors of heat become only slowly heated, 
 and also slowly cooled ; for this reason, stoves constructed 
 of brick (the Russian stove) and those made of Dutch tiles, 
 a preparation of clay, retain their heat longer than iron 
 stoves. Bad conductors are frequently employed both for 
 preventing the quick heating and the quick cooling of bodies. 
 Vessels of glass and porcelain are placed on sand (a sand bath) 
 or asbestos, to heat them gradually, and thus guard against 
 their breaking. If a hot liquid is to be poured into them, 
 it must be done by small portions at a time, twirling the 
 vessels round for some minutes before adding more. 
 
 On removing vessels from the fire, the precaution should 
 be taken never to place them while hot on metal or stone, 
 but always on some bad conductor, such as straw, wood, 
 paper, cloth, &c. ; as they are often cracked by sudden 
 cooling and contraction, which is frequently produced even 
 by a current of cold air. Doors of furnaces, ladles, &c., are 
 provided with wooden handles, to prevent those using 
 them from being burnt. Should a person desire to hold a 
 flask or a test-tube while liquids are boiling in them, he 
 must wrap round them several folds of paper, or tie round 
 them a piece of twine, in order that they may serve as a 
 bad conductor between the glass and his fingers. By 
 inclosing substances in bad conductors, the entrance of 
 cold, or, more correctly, the departure of heat, may be 
 prevented ; this principle is illustrated in our method of 
 clothing, in the protection given to 
 our wells and trees by covering them 
 with straw, in the preservation of plants 
 by snow, and in numerous other pheno- 
 mena of daily occurrence. Hence bad 
 conductors are frequently called pre- 
 servers of heat. 
 
 Convection of Heat. — Liquids and 
 gases, though very bad conductors, 
 readily become heated by a process 
 called convection, which is a necessary consequence of the 
 expansion produced in them by heat. 
 
 Experiment 2. — Water, to which some sawdust has been 
 added, is heated in a test-tube over a spirit-lamp. The 
 tube is held by the upper part, and rotated for some 
 
DIFFUSION OF HEAT. 
 
 45 
 
 minutes between the fingers, that the flame may have 
 equal access to all the lower parts of the tube. If the 
 water be carefully observed, it will be seen that the saw- 
 dust ascends on the upper surface of the liquid, and 
 descends in the lower strata ; the warm water expands, 
 and, becoming lighter, rises upwards, while the colder, 
 and consequently heavier, water Fig. 21. 
 
 sinks; the water circulates. In 
 consequence of this circulation, 
 the heating of fluids takes place 
 more rapidly when the heat is 
 applied beneath. If the wpper part 
 of a test-tube full of water is 
 heated by the lamp, the water 
 will boil at the top while it 
 remains quite cold, and may even 
 contain ice, held down by a wire, at the bottom. Test- 
 tubes are cylindrical glass vessels with rounded bottoms. 
 To prevent their breaking on the application of heat, the 
 bottom must be thin, and blown of a uniform shape. A 
 simple wooden rack, as in the annexed figure, serves as a 
 convenient stand for them. 
 
 Convection in Gases. — Currents of Air. — A great many 
 phenomena of daily occurrence may be explained by the 
 difference in lightness between warm and cold air. When 
 a fire is lighted in a stove for the heating of an apartment, 
 the air immediately in contact with the stove is first 
 heated, becomes lighter, and ascends ; colder air rushes in 
 to supply its place, and this likewise becomes heated and 
 ascends ; consequently a constant circulation of air is kept 
 up. By a similar circulation, the whole atmosphere of the 
 earth is kept in continual motion. At the equator, the 
 strongly heated air ascends and moves in the upper regions 
 of^ the atmosphere towards the poles, while in the lower 
 regions the current of cold air flows from the arctic zone 
 towards the equator, in order here to restore again the equi- 
 librium, disturbed every moment by the ascent of the warm 
 air. These regular currents of air, the direction of which 
 is somewhat diverted by the revolution of the earth on its 
 axis, are called trade-winds. 
 
 In every heated apartment, a difference between the heat 
 
 t 
 
46 
 
 EXPERIMENTAL CHEMISTRY. 
 
 of the air near the ceiling and that near the floor is veiy 
 perceptible. If a door or window in such a room be opened, 
 a current of air is produced, the direction of which may 
 
 Fig. 22. 
 
 easily be perceived by holding a 
 lighted candle in the opening ; the 
 flame, when held above, at c (Fig. 
 22), is blown from the room ; when 
 placed below at a, it is blown into it ; 
 consequently, the light warm air 
 above rushes out of the room, and is 
 replaced by heavier and colder air 
 from below. A draught of air is 
 also noticed in passing from the sun- 
 shine into the shade ; where the sun 
 shines, the warmer air ascends, and 
 the colder air from the shade sup- 
 plies its place. For the same reason, 
 a current of air is produced wherever 
 a fire is burning, in every stove, and 
 round every lamp. To ventilate a room properly, the hot 
 and foul air should be allowed to escape from some aperture 
 near the ceiling, while cool and fresh air is admitted near 
 the ground. 
 
 The air-balloons, first constructed by Montgolfier, strik- 
 ingly show how buoyant air may be rendered by heat ; 
 these are caused to ascend merely by filling them with air, 
 kept continually hot by a fire beneath. 
 
 Radiation of Heat. — By conduction, bodies can communi- 
 cate or abstract heat only when in contact. But heat is 
 felt even at some distance from a fire or from a heated 
 stove, and the earth is warmed by the sun, although a 
 space of millions of miles is between them. This sort of 
 heating is called radiation of heat. 
 
 Experiment 3. — Envelop three tumblers with paper, one 
 with silver paper, another with white, and a third with 
 dull black paper, and place them in the sun; a thermo- 
 meter will indicate that the tumbler with the black paper 
 is heated the most, and that with the silver paper the least, 
 and yet all these vessels have been equally exposed to the 
 rays of the sun. This difference is explained on the 
 principle, that some substances have the power of absorb- 
 
DIFFUSION OF HEAT. 
 
 47 
 
 ing the rays of heat, while others throw them off again, or 
 reflect them. Good reflectors of heat, such as bright metals, 
 are the worst absorbers, for a thing cannot absorb the heat 
 and also reject it. 
 
 If hot water is poured into the tumblers enveloped with 
 paper, and the cooling of it noted by the thermometer, the 
 contrary effect will be observed ; the glass covered with 
 black paper will first become cold, and that wrapped in 
 silver paper the last; because bodies with dull surfaces 
 radiate the heat more rapidly than those with polished 
 surfaces. Good absorbers of heat are therefore seen to be 
 good radiators, and good reflectors bad radiators. For this 
 reason, coffee retains heat longer in a bright than in a 
 tarnished pot ; a stove of glazed Dutch tiles remains hot 
 longer than another of unglazed tiles ; a smooth sheet-iron 
 stove, longer than a similar one of rough cast-iron, &c. 
 
 The radiation of heat enables us to explain some of those 
 common natural phenomena which otherwise would remain 
 obscure. Why do not the rays of the sun, even in the 
 hottest summers, melt the snow upon the tops of high 
 mountains, which are nearer than the level portions of the 
 earth to the sun? Because they only heat those bodies 
 which can absorb their warmth, as the rough surface of 
 the earth. The snow is indeed struck by the rays of the 
 sun, but being a white and shining body it reflects them 
 and remains cold. 
 
 Formation of Dew. — When the surface of the earth has 
 become warm, the air is heated by it ; hence, during the 
 day the lower strata will always be warmer than the 
 upper. But a change takes place after the sun has gone 
 down. The earth continues to radiate heat without 
 receiving any in exchange, and its temperature con- 
 sequently diminishes. On the other hand, the air does 
 not so readily part with its heat, and therefore it retains 
 during the night a higher temperature than the surface of 
 the earth ; it is only cooled where it comes in contact with 
 the colder earth. If this cooling should reach the dew- 
 point of the air, then the vapours are condensed, on the 
 soil or on the plants growing upon it, in the form of small 
 drops, just as a tumbler is covered with vapour when 
 brought from a cold into a warm room — dew forms. If 
 
48 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the temperature of the earth sinks in the night to the 
 freezing point, or below it, the aqueous vapour is de- 
 posited in a solid form, and is called hoar-frost 
 
 The radiation of heat from the earth is greatest when 
 the weather is clear and serene, but it is obstructed by 
 clouds and wind. Hence the most copious deposit of dew 
 takes place only in clear and quiet nights. The clouds 
 serve as a screen in reflecting back the rays of heat to the 
 earth, so that it is but slightly cooled. The same effect is 
 produced by the mats, straw, and boards with which the 
 gardener covers his young plants, to protect them from 
 the late frosts of spring, or from freezing. The annexed 
 figure, in which arrows denote the direction of the rays of 
 heat, will serve to render this process more intelligible. 
 
 Sunbeams. 
 
 Fig. 23. 
 
 59° Surface of 
 the earth. 
 
 41° 
 Dew. 
 
 32° 
 Frost. 
 
 54° 
 
 No dew or frost. 
 
 41° 
 
 No dew or frost. 
 
 In the day- 
 time. 
 
 In clear and serene Cloudy or windy 
 nights. nights. 
 
 Clear nights. 
 Soil protected. 
 
 SOLUTION AND CRYSTALLIZATION. 
 
 These subjects are so closely connected with that of heat 
 that they may conveniently be studied in this place. 
 
 Solution. — Water can dissolve many bodies, and unite 
 intimately with them, without losing its transparency. 
 Such combinations are called solutions. If rain-water 
 meets with soluble substances, either in the earth or in the 
 rocks through which it oozes, it dissolves them ; and this 
 explains why all spring-water, on evaporation, yiehls an 
 
SOLUTION AND CRYSTALLIZATION. 
 
 49 
 
 earthy or saline residue. Frequently this residue, par- 
 ticularly when it contains lime, is so altered during 
 evaporation, that it can no longer be dissolved in water, 
 and forms a hard incrustation round the inner sides of the 
 vessels used in cookery. The springs of Carlsbad deposit 
 so much residue, that articles immersed in them apj)ear in 
 a short time to be externally petrified or incrusted. If 
 water is unusually rich in soluble substances, especially 
 such as possess medicinal properties, as, for example, iron, 
 sulphur, &c., it is called mineral water ^ and the springs 
 from which it issues are called mineral springs. A pound 
 of sea water contains about half an ounce of substances in 
 solution. 
 
 Experiment 1. — Pour a teaspoonful of slaked lime into 
 a bottle, and fill it with water; cork it up, and, after 
 shaking it for some minutes, let it stand until the water 
 has become perfectly clear. By carefully inclining the 
 bottle, most of the liquid may be poured off free from the 
 sediment. This operation is called decantation, and the 
 clear liquid is lime-water. Lime is but slightly soluble, 
 about 600 parts of cold water being required to dissolve 
 one part of it; the excess remains undissolved, and as 
 lime is heavier than water, it settles at the bottom. That 
 a portion of it has been dissolved is known by the peculiar 
 taste imparted to the liquid. This taste is called alkaline. 
 
 Keep a part of the lime-water in a well-stopped bottle 
 for future use ; it will remain transparent and clear. 
 Pour the remainder into a tumbler, and expose it to the 
 air ; the water soon becomes turbid, and covered with a 
 film, which gradually grows thicker, and settles at the 
 bottom. When, after some days, the water has become 
 clear again, it will have lost its alkaline taste ; the lime 
 dissolved in it, having been chemically changed by the air 
 and rendered insoluble, will be found as a powder at the 
 bottom of the tumbler. 
 
 Experiment 2. — Put into a flask half an ounce of litmus ; 
 pour over it three ounces of water, and let it remain in a 
 warm place until the liquid has obtained a dark-blue 
 colour. Litmus consists of a blue colouring-matter, which 
 is soluble in water, and is hence taken up by it ; it also 
 contains some earthy matter which is insoluble, and is 
 
 E 
 
50 EXPERIMENTAL CHEMISTRY. 
 
 deposited as a slimy mass. These two substances might 
 be separated from each other, as in the former experiment, 
 by decantation, but it can be done more readily by filtra- 
 tion. For this purpose cut a piece of blotting-paper into 
 a circular shape, fold it together 
 Fig. 24. Fig. 25. twice, and then place this filter into 
 a glass funnel. That the paper 
 and the glass may not come into 
 too close contact, place between 
 them thin pieces of wood or glass ; 
 a piece of string must also be 
 inserted between the funnel and 
 the neck of the flask into which 
 the liquid is to be filtered, to allow 
 an opening for the escape of the 
 air from the flask, as otherwise the 
 fluid could not flow in. The filter, which must never be 
 higher than the top of the funnel, is first moistened with 
 water before the fluid is poured upon it. Blotting-paper 
 consists of fine linen or cotton-fibres matted together, between 
 which are small interstices or pores, through which 
 liquids, but no fine solid particles, can pass ; these remain 
 on the filter. Writing-paper cannot be used for filtration, 
 as its pores are filled up by size or starch. 
 
 Experiment 3. — Pour a part of the solution obtained into 
 a saucer, and pass strips of fine blotting- or of letter-paper 
 one or more times through it, until they have acquired a 
 distinct blue colour. Preserve these strips, after being 
 dried in a box ; they are called blue litmus, or test-paper ; 
 they are reddened by vinegar, lemon-juice, and all acid 
 fluids, and serve to test a liquid, to ascertain whether it is 
 acid (has an acid reaction). 
 
 Experiment 4. — Mix cautiously another portion of the 
 solution with lemon-juice or vinegar, until the blue colour 
 appears distinctly red ; this also serves to colour paper. 
 The red test-paper is used for the purpose of recognising a 
 class of substances opposed to acids — that is, alkaline or 
 basic bodies ; these restore the original blue colour of the 
 paper, as can be seen by bringing it into contact with 
 lime-water or solution of caustic potash. 
 
 Experiment 5. — Add gradually, with constant agitation. 
 
SOLUTION AND CRYSTALLIZATION. 
 
 51 
 
 to one ounce of cold water, powdered saltpetre (potassium 
 nitrate), as long as it continues to be dissolved — perhaps 
 about a quarter of an ounce : if more is added than is 
 necessaiy, it will remain undissolved at the bottom of the 
 vessel. This solution is called a cold saturated solution. 
 If this mixture be boiled, and saltpetre again be added, 
 then about three ounces more will be required to saturate 
 the water. A thermometer held in this boiling saturated 
 solution will indicate about 240° F. (115-5'' C), while 
 simple boiling water indicates only 212° F. (100° C). All 
 saline solutions hoil and freeze ivith more difficulty than water. 
 All bodies soluble in water behave in a similar manner — 
 that is, they are soluble in it only in definite quantities, 
 and in most cases hot water dissolves more of them than 
 cold. 
 
 Experiment 6. — If the solution obtained in the last experi-. 
 ment be poured into a porcelain dish and be suffered to 
 remain quiet until cold, then the three ounces of saltpetre 
 which were last added separate again, not as a 
 powder, but as regularly formed prisms. These 
 prisms are six-sided, and are surmounted by 
 faces similar to a roof; they are called crystals of 
 saltpetre (Fig. 26.). All crystals are characterized 
 by having planes, edges and angles, constructed, 
 as it were, of simple triangular or quadrangular 
 pieces, with polished surfaces. This symmetry is found 
 even in the interior of them, as can easily be seen 
 by holding a transparent crystal towards the light, and 
 turning it slowly round; or breaking it, when the 
 fragments will often exhibit the same regular form which 
 characterized the whole crystal. Thus, in inanimate 
 nature, a mysterious power exists, similar to that which 
 compels the bees to construct six-cornered cells, and the 
 potato to produce its five-angled corolla and five stamens, 
 and by which the smallest particles of bodies, called 
 molecules^ are forced to arrange themselves in a fixed order, 
 assuming a regular shape. But this can in general only 
 be accomplished by a body in its fluid or aeriform state, 
 since free motion of the molecules is essential. Time also 
 is required for this operation ; hence crystals are always 
 more regular the more slowly they are formed. Many o£ 
 
 E 2 
 
52 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the splendid crystals which are dug from the depths of 
 the earth, were, perhaps, very many years in forming. 
 
 Experiment 7. — Evaporate the liquid remaining above 
 the crystals in the former experiment at a gentle heat, 
 until a scum is formed on the surface, then remove it from 
 the fire and let the solution cool, stirring it constantly with 
 a wooden stick. In this way, instead of crystals, a 
 'powder of saltpetre will be obtained consisting of minute 
 crystals. ♦ 
 
 The liquid just alluded to may be regarded as a cold 
 saturated solution, containing about a quarter of an ounce 
 of saltpetre. If, by evaporation only, so much water is 
 left as is sufficient when hot to keep in solution but a 
 quarter of an ounce of the saltpetre, then crystals begin to 
 appear in the form of a film on the cooler surface, 
 indicating the saturation of the liquid. If this again is 
 allowed to cool quietly, a second crop of crystals will be 
 obtained ; but, by continual stirring, they are broken at 
 the moment of their formation — by slow movement into a 
 coarse, and by rapid movement into a fine powder. This 
 may be called interrupted crystallization. Sugar presents a 
 similar example ; the same syrup, which, if cooled quietly, 
 yields sugar-candy, when stirred, yields common loaf- 
 sugar. 
 
 Experiment 8. — Put into boiling water as much common 
 salt as will dissolve, and let the solution cool ; very few 
 crystals will form, because salt is nearly as soluble in cold 
 as in hot water. Now evaporate one half of the solution 
 over a spirit-lamp, and set aside the other half in a warm 
 place ; in the first case, mere irregular grains of salt will 
 be obtained, but in the latter case, after some days, regular 
 cubes of salt will be deposited. 
 
 Experiment 9. — Dissolve a spoonful of salt and one of 
 saltpetre in lukewarm water, and put the solution in a 
 warm place, that the water may gradually evaporate ; the 
 two salts, which are intimately mixed in the solution, will 
 upon crystallization separate completely from each other. 
 The saltpetre separates into long prisms, containing no 
 trace of the common salt, and the latter separates into 
 cubes, entirely free from saltpetre. Thus the particles of 
 salt and saltpetre did not attract each other j but, upon 
 
PRESSURE. 
 
 53 
 
 crystallizing out of the solution, the homogeneous saltB 
 assumed separately a regular form, precisely as if one 
 only of these two substances had been dissolved. 
 
 PRESSUKE. 
 
 The earth is surrounded by air, as by a mantle ; this 
 mantle is called the atmosphere, and extends to an inde- 
 finite height above the solid earth. The air possesses no 
 colour, and is transparent ; hence it is invisible, and its 
 particles are so easily movable upon each other 27. 
 that it cannot be grasped by the hand. But it 
 is rendered obvious that the air is material, and 
 • fills every space commonly called empty, by 
 wrapping strips of moistened paper round a 
 funnel, so that it may fit exactly into the mouth 
 of a bottle; if the funnel be now filled with 
 water, the fluid will not run into the bottle, as 
 the air contained in the latter will not let it 
 enter ; but if the funnel be raised a little, the 
 air escapes, and the water immediately rushes 
 into the bottle. We learn also by the balance that 
 a vessel apparently empty, i.e., containing atmospheric 
 air, weighs more than one which is really empty, as when 
 the air has been exhausted from it. But air is so light 
 that 800 measures of it weigh rather less than one measure 
 of water, yet the atmosphere presses with great weight 
 on the earth, and upon everything thereon. But this 
 pressure is only noticed when the air in removed from a 
 place, thus leaving it withont counter-pressure. The 
 total weight of the atmosphere has been estimated to be 
 equal to that of a globe of solid lead sixty miles in diameter. 
 When a solid is immersed in a fluid (either a liquid or 
 gas), it is pressed upon equally on all sides by the fluid 
 with a force which depends partly upon the weight of 
 the fluid and partly upon the depth to which the solid is 
 immersed. A stone suspended one foot from the surface 
 of water is only pressed upon with half the force that it 
 would experience if sunk two feet ; a stone sunk one foot 
 in mercury would receive 13^ times as much pressure as 
 
54 
 
 EXPERIMENTAL CHEMISTRY. 
 
 it would if sunk one foot in water, because mercury is 13^ 
 times as heavy as water. The same thing is true in 
 regard to air and other gases, and bodies near the surface 
 Fio". 28. ^1^^ earth are pressed upon equally on 
 
 all sides by the whole forty-five miles of 
 air above. 
 
 Pressure of the Atmosphere, — Experiment 
 1. — Wrap some tow round one end of a 
 stick and grease it with tallow, thus form- 
 ing a plug, which must fit tightly into a 
 strong test-tube. Boil some water in the 
 test-tube, and when the air has been ex- 
 pelled by the steam, insert the plug ; as 
 the water cools the steam condenses, a 
 vacuum is produced, and the plug will 
 be pressed down upon the surface of the 
 water ; by heating, it is again forced up by 
 the steam thus generated, and by immersing in cold water 
 it is again forced down. In consequence of the cooling 
 and condensation of the steam a vacuum is formed, and, 
 therefore, the counter-pressure against the weight of the 
 exterior air is removed ; the pressure of the latter, ac- 
 cordingly, forces down the plug. On this principle the 
 
 piston is forced up 
 and dowu in the 
 cylinder of many 
 steam-engines. 
 
 This one - sided 
 pressure often causes 
 the ascent and re- 
 flux of liquids in 
 tubes. 
 
 Experiment 2. — If 
 water is boiled as 
 was directed at page 
 39, by means of 
 steam, and during 
 the boiling the lamp 
 is removed, then the pressure of the air acting on the 
 surface of the water in the beaker-glass will very soon 
 force the water contained in it through the tube back 
 
PRESSURE. 
 
 55 
 
 into the flask, which in a short time becomes quite filled 
 with water. The counter-pressure of the steam must 
 naturally decrease as it cools and condenses. Fig. 30. 
 As long as the lamp is under the flask, the 
 pressure of the steam is stronger than that of 
 the air, and the steam, being continually gene- 
 rated, forces the air previously contained in 
 the flask into the water of the beaker-glass. 
 This reflux of liquids is particularly to be 
 feared, when such kinds of gases are conducted 
 into water as are absorbed b}^ it readily, and 
 in large quantities. This is prevented by 
 passing through the cork a second glass tube 
 open at both ends, and letting it reach nearly to the bottom 
 of the flask, by which tube air can penetrate into the flask 
 as the pressure of the steam diminishes. This contrivance 
 is called a safety- tube. 
 
 Barometer, — It can be proved by experiment that the 
 atmosphere presses upon the earth with a force equal to 
 that of a layer of mercury 30 inches deep, or a layer of 
 water 13 J times deeper (34 feet), water being 13 J times 
 lighter than mercury. The instrument by which the 
 amount of atmospheric pressure can be observed and 
 measured is called the barometer. Fill a glass tube, 32 
 inches in length, one end of -p.^ 
 which is closed, with mer-. 
 cury ; close it with the finger, _ 
 
 and invert it into a vessel of, - 
 
 mercury; onremoving the fin-, 
 ger, the mercury will not run 
 out, but will fall some inches, ^ 
 perhaps to s (Fig. 32). The 
 height of the column of mer- 
 cury, from a 6 to s, amounts to about 30 inches. The 
 mercury does not fall lower, on account of the external 
 pressure of the atmosphere, which is exerted on the 
 mercury at a h, and not at s, since this end is closed. 
 The column of mercury in the tube may be regarded 
 as the counterpoise to the atmospheric pressure, and 
 it is hence concluded that the latter exerts just as 
 much pressure upon the earth as a column of mercury 
 30 inches high. If the tube be opened at the top, the 
 
 Air. 
 
 "Wa ter, 34 feet j jghT 
 "Mer ^ry> 30 inche shTghT 
 
 Surface of the earth. 
 
56 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Fig. 32. 
 
 pressure of the air on both extremities being then made 
 equal, the mercury will flow from the tube. The space 
 above the mercury, at s, is a vacuum, and is called the 
 Torricellian vacuum, because it was first ob- 
 served by Torricelli. In some barometers the 
 tube is curved at the bottom, and provided 
 with a bulb. This bulb is open at the top, 
 and supplies the place of the vessel filled with 
 mercury in the preceding figure. Here also 
 the pressure is only exerted at one end, for 
 tho atmosphere can only press on the mercury 
 contained in the bulb. The height from o 
 (Fig. 33) to the top of the mercury amounts 
 to about 30 inches. 
 
 If weights be placed in one pan of a balance, 
 the opposite one will rise, but on their re- 
 moval it will sink. The same thing happens 
 with the barometer. Any increase in the 
 weight or density of the air presses the 
 mercury up, and the barometer rises ; but any 
 diminution of weight will make it fall. The 
 height of the mercury may be read off by 
 fixing to the upper part of the tube a 
 scale divided into inches and tenths of an inch. The 
 mean state of the barometer is at 30 inches, equal to 760 
 Fig. 33. Mdillimetres, and 31 is called a very high, and 
 29 a very low, state of the barometer. In this 
 country, as a general rule, the north and east 
 winds cause the barometer to rise, and the south 
 and west winds cause it to fall. The former 
 winds, blowing chiefly from the land, are cooler, 
 and at the same time drier, than the latter, 
 which pass over the ocean, there becoming satu- 
 rated with moisture ; the former likewise come 
 from colder into warmer, while the latter, on 
 the contrary, proceed from warmer into colder 
 regions ; by which the capacity of saturation for 
 vapour is increased in one case and diminished 
 in the other. Hence it is natural that, when 
 north and east winds prevail, it should rain less 
 frequently than during south and west winds ; and that 
 the former winds are dry, while the latter are damp. 
 
PRESSURE. 
 
 57 
 
 Why water does not flow from a jar inverted over the 
 pneumatic trough, why it continues to flow through a 
 syphon after the air has been exhausted, why liquids will 
 not run into a vessel when the air is confined, or why 
 water will only rise to the height of 34 feet in a suction 
 pump, are questions that scarcely require further ex- 
 planation. 
 
 Elasticity of Gases. — All gases are perfectly elastic ; they 
 all contract equally under an increase of pressure, and 
 expand when it is diminished. When a gas is collected 
 in a bottle or other vessel the weight of it that the bottle 
 will hold depends upon the pressure of the air at the 
 time, which, as we have seen, is measured by the 
 barometer. It is therefore of the utmost importance in 
 measuring a gas to take account of the state of the 
 barometer at the time. One hundred grains of air, for 
 example, will occupy 333 cubic inches when the barometer 
 is at 29, 322 when it is at 30, and only 311 when it is at 
 31 inches. As the alterations in volume are exactly in 
 inverse proportion to the alterations of pressure, it is 
 easy, after noting the volume of the gas and observing 
 the height of the mercury in the barometer, to calculate 
 what the volume would be at some standard pressure. 
 The standard pressure at which gases are always measured 
 is represented by 30 inches (or 760 millimetres) of 
 mercury. The calculation required for this purpose is 
 called the " correction for pressure." It must be applied, 
 in addition to the correction for temperature (page 34), 
 whenever gas is t > be measured. It can always be made 
 by the formula V P = V^ P\ in which V is observed 
 volume, and P observed pressure. Hence 
 
 Vol. at observed pressure x Observed pressure _ j Volume of gas at 
 Standard pressure. (standard pressure. 
 
 For example, we have 333 cubic inches of air when the 
 barometer stands at 29 inches. How many cubic inches 
 would there be if the barometer stood at 30 inches ? 
 
 Here we must multiply by the observed pressure 29, 
 and divide by the standard pressure 30 : 
 
 on cubic inches (nearly). 
 
58 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The corrections for pressure and temperature may be 
 made separately, in either order, or may be combined into 
 one, as in the following example : — 
 
 100 c.c. (cubic centimetres) of gas at pressure 700 m.m. 
 and temperature 10^ C. What would be volume at 
 standard pressure and temperature ? 
 
 For pressure, — 
 
 yi ^ 100 X 700 
 760 
 
 For pressure and temperature, — 
 
 100 X 700 X 273 . , . 
 
 The ordinary air pump depends for its action in pro- 
 ducing a vacuum upon the elasticity and pressure of the 
 air. 
 
 If the pressure or tension of a confined quantity of air 
 be increased, by compressing it either directly or by the 
 addition of more air, it can be forced to stream out from a 
 small openirjg with great rapidity, as is shown on a small 
 Fig. 34. ^^^1^ common bellows, and on a larger scale 
 
 in the blacksmith's bellows. Should there be 
 water before this opening, the air will press it out 
 in a jet or stream. 
 
 Experiment 3. — Take a piece of a fine glass 
 tube, draw out to a point, and adapt it, by 
 means of a perforated cork, to a bottle. Fill the 
 bottle half full of water, and blow into it through 
 the point of the tube; when the blowing ceases, 
 the air will escape in a stream. But if the bottle 
 be inverted as soon as the air is blown in, then 
 the water will be spurted out by the compressed 
 air above. Such an apparatus (the washing- 
 bottle) was at one time employed for washing 
 residues or precipitates remaining on filters, in 
 order to free them from soluble matter. The 
 washing-bottles now used have besides the jet, which is 
 curved, a second tube by which air can be blown in and 
 the water thereby forced out. 
 
 The pressure of the atmosphere exerts a great influence 
 
PRESSURE. 
 
 59 
 
 on the boiling of water, and of other liquids. If water is 
 made to boil when the mercury in the barometer is very 
 low (in foul weather), brisk ebullition will take place at 
 about 210° F. (99° C.) ; when the mercury is very high 
 (in clear weather), boiling will not occur under 214° F. 
 (101° C). 
 
 Experiment 4. — Heat a flask half filled with water till 
 the water boils briskly ; then remove it from the fire and 
 quickly cork it ; the boiling immediately ceases, but will 
 commence again if cold water be poured 
 over the upper part of the flask. In this 
 manner it can be made to bubble or boil, 
 even though it be only lukewarm. There 
 is no air in the flask, it having been ex- 
 pelled by the steam, and it could nut re- 
 enter it, on the cooling and condensation 
 of the steam, on account of its having 
 been closed. Consequently there is no 
 pressure of air on the water, and it will boil even at a 
 temperature of 68° F. (20° C). The boiling ceased on 
 account of the pressure of the steam upon the water ; but 
 the steam being condensed by the cold water, the pressure 
 was so much diminished, that a portion of water again 
 became aeriform with a boiling motion. In many manu- 
 factories, an appropriate apparatus (vacuum-pan) has been 
 contrived for boiling and evaporating in a vacuum, as, 
 for instance, in sugar-houses. 
 
 The air is densest at the level of the sea, and thinner 
 in proportion to its distance from the earth, as there is 
 less air above it. Hence the mercury will stand lower, 
 and water boil more easily, on the top of a mountain than 
 in the valley below. On the top of Mont Blanc mercury 
 rises only to the height of 1 6 inches in the barometer, and 
 water boils at 183° F. (84° C). Hence the barometer and 
 the boiling point of water may be employed for calculating 
 the heights of mountains. 
 
 As water boils more easily under diminished pressure, 
 so it boils with more difficulty when the pressure is increased. 
 An increase of pressure can he produced, not only by the 
 air, but by the steam of the water itself, if new steam be 
 constantly generated, while the escape of that already 
 
60 
 
 EXPERIMENTAL CHEMISTRY. 
 
 formed is prevented. This is best done by heating water 
 confined in a strong and firmly closed vessel. For this 
 purpose a Papin's Digester may be used, in which water 
 may be heated to the temperature of 392° F. (200^^ C), 
 and, indeed, still higher, whilst in open vessels it cannot 
 be heated above 212° F. (100° C). If the amount of 
 steam in it is twice as much as in an uncovered vessel, 
 the pressure is said to amount to two atmospheres ; if 
 there is 3, 4, 5, 10, 20 times the quantity, there is said to 
 be a pressure of 3, 4, 5, 10, 20 atmospheres. Vessels of 
 this kind are often employed to effect a complete penetra- 
 tion of the water into solid and hard substances. Thus, 
 for example, water at 212° F. (100° C.) dissolves the 
 gelatinous matter only on the surface of the bones, whilst 
 water at a temperature ranging from 230° F. (110° C.) to 
 248° F. (120° C.) entirely penetrates the bones, and 
 extracts the gelatine also from the iDterior of them. 
 
( 61 ) 
 
 CHAPTER III. 
 
 FUNDAMENTAL LAWS OF CHEMISTRY. 
 
 We have already, in Chapter I., seen something of the 
 operations of that form of force which is known as chemical 
 force. We have seen that by its operation compounds are 
 produced by the nnion of elements, the compounds being in 
 all cases different from the elements which compose them. 
 And we have seen that the science of chemistry is mainly 
 concerned with the changes which are brought about by 
 chemical force. It is now necessary, before entering on 
 the systematic study of chemical facts, to consider the 
 theories of chemistry — the laws of constitution and the laws 
 according to which chemical actions take place. These 
 laws have been discovered by thousands of difficult and 
 laborious investigations. For the most paii: it will not be 
 possible for the student to prove them to himself experi- 
 mentally : the processes necessary for this are too difficult, 
 and require apparatus of too expensive a kind. He must 
 be content in the outset of his study to take the laws upon 
 trusts 
 
 MODES IN WHICH CHEMICAL ACTION TAKES PLACE. 
 
 Combination, — Experiment 1 . — The simplest way in which 
 chemical action can take place is when two substances, 
 elements or compounds, combine directly together and 
 produce a single new compound. Examples of this have 
 already been given at page 13, but another may be added 
 here. Take a globule of mercury about the size of a veiy 
 small pea, heat it in a test-tube until it boils, and then 
 throw in about an equal weight of iodine. Shake the tube 
 slightly, so as to bring the two into contact. They will 
 combine, and a beautiful scarlet compound called mercuric 
 iodide will be found on the sides of the glass. 
 
62 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Decomposition, — Experiment 2. — Another kind of chemical 
 change is called decomposition. It consists in a separation, 
 either partial or complete, of the constituents of a compound 
 from one another. The following experiment will illustrate 
 it. Introduce into a somewhat tall, but not too thin, test- 
 tube of hard glass, 
 108 grains of mer- 
 curic oxide. One 
 end of a bent glass 
 tube is adapted to 
 it by means of a 
 perforated cork, and 
 the other end is 
 conducted into a 
 vessel filled with 
 water. Either sus - 
 pend the tube by 
 means of a piece of 
 string or wire, or 
 support it by a 
 retort - holder. A 
 retort-holder is a 
 wooden stand, pro- 
 vided with a movable vice, by which glass vessels can be 
 held in the most convenient manner, as shown in the 
 annexed figure. Then heat the test-tube carefully until 
 all the mercuric oxide has disappeared. The red powder 
 becomes black as the heat increases, and bubbles of gas 
 escape, which are collected in a pint bottle held over 
 the end of the tube, this bottle having been previously 
 filled with water and then inverted into the bowl, after 
 closing the mouth of it with the finger or a glass plate. 
 No water will escape until bubbles of gas from the 
 tube are passed into it, which, on account of their 
 greater lightness, ascend and displace the water. When 
 the evolution of gas ceases, cork the bottle and remove 
 it. The first bubbles that pass over consist of the 
 atmospheric air contained in the test-tube, and expanded 
 by the heat, but oxygen gas quickly succeeds. This is one 
 of the component parts of mercuric oxide, and can easily 
 be recognized by the vivid combustion in it of a glowing 
 
MODES IN WHICH CHEMICAL ACTION TAKES PLi^ 
 
 shaving. At the same time there is formed on the 
 part of the test-tube a brilliant metallic mirror, which con- 
 sists of mercury, the second element of the red oxide. 
 When the latter has entirely disappeared, immediately 
 withdraw the tube from the water, let the test-tube cool, 
 and unite the mercury adhering to its sides into a single 
 globule, by means of a feather. It should amount in 
 weight to 100 grains ; this, subtracted from the original 
 weight, 108 grains, leaves 8 grains, the amount of the 
 oxygen. The red powder consists of a brilliant heavy 
 etal and of a gas, two entirely dissimilar bodies, and it 
 ,s been decomposed by the heat. If these are chemically 
 mbined together by proper means, they will unite again 
 d form the red oxide, a body in which the peculiar pro- 
 erties of the mercuiy as well as of the oxygen are entirely 
 
 St. 
 
 Double Decomposition, — Experiment 3. — It very often 
 appens that two compounds are capable of decomposing 
 ne another, thus producing two new compounds. This 
 ind of chemical action is called double decomposition, 
 eigh out 27 grains of mercuric chloride (corrosive subli- 
 ate) and 33 of potassium iodide. Dissolve them separately 
 n water and then mix the solutions. A yellow precipitate 
 vill appear, which will quickly change to a beautiful scarlet 
 powder, which will soon subside and leave the liquid colour- 
 The red powder is mercuric iodide, the same compound 
 which was formed in Experiment 1. The clear liquid on 
 evaporation will yield cubical crystals of potassium chloride. 
 Mercuric chloride consists of the elements mercuiy and 
 chlorine ; potassium iodide, of potassium and iodine. When 
 mixed, the mercury of the one unites with the iodine of 
 the other, and the chlorine of the one with the potassium 
 of the other. 
 
 Substitution, or Displacement. — Experiment 4. — Take a cold 
 saturated solution (see page 51) of mercuric chloride, and 
 immerse in it a strip of bright copper. Very soon the 
 surface of the copper will become covered with a film of 
 mercuiy, and in the course of a few hours the whole of the 
 mercuiy will be separated in this way, and some of it may 
 be collected into a globule at the bottom of the liquid. 
 But in the meantime a portion of the copper will have been 
 
EXPERIMENTAL CHEMISTRY. 
 
 solved, and has now taken tlie place formerly occupied 
 y tlie mercury, and tlie solution is found to be green. 
 The copper has, in fact, displaced, or been substituted for 
 the mercury in the original compound, so that we have 
 now in solution copper chloride instead of mercuric chloride. 
 For every 100 grains of mercury which are separated in 
 the metallic form, 31 grains of copper are dissolved, so 
 that we learn that 31 parts of copper will displace 100 of 
 mercury. 
 
 When the whole of the mercury has been separated, the 
 clear green solution may be poured into another glass a]ad. 
 the bright blade of a knife immersed in it. The iron will 
 displace the copper, just as the copper displaced the mercury, 
 an iron chloride (called ferrous chloride) remains in solution, 
 and the copper is precipitated on the unaltered iron, giving 
 it at first the appearance of being converted into copper. 
 The 31 parts of copper which displaced 100 of mercury are 
 themselves displaced by 28 of iron. Examples of this kind 
 are very common in chemistry. 
 
 QUANTITIES CONCERNED IN CHEMICAL CHANGES. 
 
 It will readily be understood from the foregoing illustrfis. 
 tions that it is of the utmost importance in studyiniTs 
 chemistry to attend to the relative quantities of different \ 
 substances which enter into chemical changes. It is to 1 
 the careful study of these quantities that the dignity of | 
 chemistry as an exact science is due. ' 
 
 Law of constant composition. — This, the fundamental law 
 of chemistry, may be stated in these words : ' 
 
 A given chemical compound always contains the same elements^ 
 in the same proportions. | 
 
 The law scarcely requires explanation. Water always, 
 contains, in 9 parts by weight, 8 of oxygen and 1 of*, 
 hydrogen ; mercuric oxide always contains 8 of oxygen to 
 100 of mercury ; mercuric iodide, 100 of mercury to 127 ' 
 of iodine, and so on. If 100 grains of mercuiy are heated 
 with 130 grains of iodine, 227 grains only of mercuric 
 iodide are produced, and 3 grains of iodine remain un- 
 changed. 
 
 Difference hetwei n combination by weight, and by volume, — 
 
CONSTITUTION OF GASES. 
 
 65 
 
 Combination by volume means combination by measure, 
 and it will be obvious to every one that, as bodies dififer 
 very much in weight, there will generally be a great 
 difference between the proportions by measure and the 
 proportions by weight in which two bodies combine. Take 
 the case of the two gases hydrogen and chlorine (both 
 elements). One volume or measure of hydrogen will 
 combine with one volume of chlorine ; but, as chlorine is 
 35 i times heavier than hydrogen, one part by weight 
 of hydrogen really combines with 35^ parts by weight of 
 chlorine. 
 
 In the cases of solids, and to a great extent of liquids 
 also, we are compelled to trust almost entirely to the 
 evidence of weight, for solids are very difficult to measure, 
 and both solids and liquids exhibit such irregularities in 
 regard to the volume that they occupy, that it has not 
 been found possible to frame general laws for them. But 
 with ga^es it is not so. They are very much easier to 
 measure than to weigh ; and as they exhibit a remarkable 
 simplicity in the proportions by volume in which they act 
 on one another ; as moreover they are all equally affected 
 in volume by alterations of temperature and pressure 
 (Chap. IL), they are always measured for the purposes of 
 experiment. Their weight (or specific gravity) is deter- 
 mined once for all with the utmost care, and it is then easy 
 to calculate in a few minutes the weight of any given 
 volume of any one of them. 
 
 CHEMICAL ACTION BETWEEN GASES. — CONSTITUTION 
 OF GASES. 
 
 Wlien chemical action tahes place betiveen two gases, the 
 volumes of those gases ivhich are concerned in the change are 
 found to hear a definite and generally a very simple proportion 
 to one another, and also to the volume of the resulting gas, if 
 the resulting compound he a gas.^ 
 
 This fundamental law, which is sometimes called the 
 
 * It will be understood hereafter that the apparent exceptions to 
 this rule are in perfect accordance with it. They only occur when a 
 compound gas of complex structure is decomposed during a chemical 
 change. 
 
 F 
 
66 
 
 EXPERIMENTAL CHEMISTRY. 
 
 " law of gaseous volumes," will be better understood with 
 the aid of a few illustrations. In studying them it is 
 necessary to bear in mind the fact mentioned before, that 
 all true vapours are gases. In considering the laws of 
 gases, we have to include water-gas (steam), sulphur-gas, 
 and even zinc-gas, for zinc is a gas at a high temperature, 
 as well as oxygen and hydrogen, which are gases at ordinary 
 temperatures. We deal in fact with matter in the gaseous 
 state. For the sake of exact comparison all gases and 
 vapours are assumed to be measured at a temperature of 
 32° F. (0° C.) and a pressure of 30 inches (760 millimetres) 
 of mercury. Even if, as is the case with steam, the gas can- 
 not really be cooled to 32° without condensing, it is easy 
 to calculate by the formula already given (page 34) what 
 its volume would be if it could. 
 
 1 volume of chlorine gas combines with 1 volume of 
 hydrogen gas to form 2 volumes of hydrochloric acid gas. 
 This is the simplest case. « 
 
 2 volumes of hydrogen combine with 1 volume of oxy- 
 gen to form 2 volumes of water-gas, or steam. Here 3 
 volumes condense, during the act of combination, into 2. 
 
 1 volume of arsenic vapour combines with 3 volumes of 
 oxygen to form 1 volume of the vapour of white arsenic 
 (arsenious anhydride). Here 4 volumes become condensed 
 into 1. 
 
 These three cases will serve to illustrate the great 
 simplicity that exists in the proportions in which gases 
 unite by measure. Any given measure, pints, cubic inches, 
 or litres, may of course be substituted for volumes in the 
 above examples, and we may, for instance, say that every 
 2 pints of steam contain 2 pints of hydrogen and 1 pint of 
 oxygen condensed into 2. 
 
 But this is not all. "When a gas is decomposed into 
 other gases, the volumes of its separated constituents are 
 all found to bear simple and definite proportions to that 
 of the original gas. 
 
 The gas called nitrous oxide, or laughing gas, is com- 
 posed of nitrogen and oxygen, but it cannot be formed by 
 the direct combination of these two elements. Neverthe- 
 less it is found, that when it is decomposed every 2 volumes 
 yield 2 volumes of nitrogen and 1 volume of oxygen, so 
 
CONSTITUTION OF GASES. G7 
 
 that there can be no doubt that its constitution is similar 
 to that of steam. 
 
 Ammonia-gas, again, is composed of nitrogen and 
 hydrogen. When it is decomposed by electric sparks every 
 2 volumes yield 1 volume of nitrogen and 3 of hydrogen. 
 The gases when separated from one another occupy in fact 
 twice the volume that they did in a state of combination. 
 
 Standard of Volume for Gases, — The next point that we 
 have to determine is, how best to represent the constitution 
 of the numerous gases which are known to us ; or in other 
 words, how to represent the kind and the quantity of the 
 elements which are present in equal volumes of them. 
 It is obviously necessary, if we would compare them, to 
 deal with equal volumes. It would appear at first sight 
 that the best and simplest plan would be to state in all 
 cases the composition of one volume of each gas. It is quite 
 possible to do so, and indeed it does not very much matter 
 what volume we take as the standard. But if we select 
 one volume we are compelled to make constant use of 
 fractions in representing the composition of gases, and it 
 is therefore usual to take two volumes as the standard of 
 comparison. A single example will make this plain. 
 
 We have already seen that 1 volume of chlorine com- 
 bines with 1 volume of hydrogen to form 2 volumes of 
 hydrochloric acid. If we wish to state the composition of 
 
 1 volume of hydrochloric acid, we must do so by saying 
 that it contains ^ a volume of chlorine and J a volume of 
 hydrogen. But on the 2-volume system the fi actions are 
 avoided. 2 volumes of chlorine are said to combine with 
 
 2 of hydrogen to form 4 of hydrochloric acid; and 2 
 volumes of hydrochloric acid contain 1 of chlorine and 1 
 of hydrogen. 
 
 Let us therefore agree to state in every case the com- 
 position of 2 volumes of gas. If we do so, we must never 
 represent less than 2 volumes as taking part in any 
 chemical process. We must, in fact, assign arbitrarily to 
 the smallest quantity of any gas that is ever concerned in 
 any chemical change a volume of 2. It is almost needless 
 to add that our facts will then be equally true if we apply 
 them to 2 millionths of a cubic inch or to 2 gallons. 
 
 Illustrations by Absolute Weights and Measures. — It will 
 
 F 2 
 
68 
 
 EXPERIMENTAL CHEMISTRY. 
 
 occasionally be convenient in this study to supply illus- 
 trations in absolute weights and measures. We may do 
 this in simple numbers in the following manner. 
 
 11*2 litres of hydrogen (11*16 more exactly) weigh 1 
 gramme. 11*2 litres may therefore be taken as 1 volume, 
 and 22-4 litres as 2 volumes. As the specific gravity of a 
 gas is the number of times it is heavier than hydrogen, 
 tlie specific gravity of every gas, tahen in grammes, has a 
 volume of 11*2 litres. For example, as 11*2 litres of 
 hydrogen weigh 1 gramme, 11*2 litres of oxygen weigh 
 16 grammes, since oxygen is 16 times as heavy as 
 hydrogen. This is a very useful fact to remember, and it 
 may be stated in another way. 1 litre of hydsogen weighs 
 0*09 gramme (0*0896 more exactly). Therefore, to find 
 the weight of 1 litre of any gas, multiply its specific 
 gravity by 0*09. 
 
 Chemical Symbols and Formulse, — Each one of the elements 
 is denoted in the system of modern chemistry by a symbol, 
 which is either the first letter, or the first and some other 
 characteristic letter, of its Latin name. Thus, oxygen is 
 denoted by 0 ; hydrogen by H ; carbon by C ; chlorine, 
 which begins with the same letter, by CI ; calcium by Ca, 
 and so on. In most cases the Latin name is the same as 
 the English, but in a few instances it is difterent and the 
 symbol must be remembered carefully. The following 
 are the exceptions : Antimony is Sb, from stibium ; 
 copper, Cu, from cuprum ; gold, Au, from aurum ; iron, 
 Fe, from ferrum ; lead, Pb, from plumbum ; mercury, 
 Hg, from hydrargyrum ; potassium, K, from kalium ; 
 silver, Ag, from argentum ; sodium, Na, from natrium ; 
 tin, Sn, from stannum ; and tungsten, W, from wolfram. 
 / Compounds are described by formulse, which consist of the 
 / symbols of the elements composing them. Thus the 
 formula for hydrochloric acid is HCl, for mercuric oxide, 
 HgO, and so on. 
 
 Syml3ols then are employed to denote the elements, but 
 they are also employed, by a very useful extension, to 
 denote definite weights of them. What these weights are we 
 have now to consider, confining ourselves for the present 
 exclusively to elements in the state of gas. 
 
 To begin with, let us represent the standard 2 volumes 
 
SYMBOLS AND FORMULA. 
 
 69 
 
 of hydrogen by the symbol H, and 2 volumes of chlorine 
 by the symbol CI. How are we in this case to represent 
 hydrochloric acid, which, as we have already seen, contains 
 in 2 volumes, 1 of hydrogen and 1 of chlorine ? 2 volumes 
 of this compound must evidently be represented by such a 
 formula as this : CIJ. This is inconvenient, and yet 
 such cases will be of incessant occurrence, unless we alter 
 our representation of the elements. Accordingly we describe 
 the 2 volumes of hydrogen as H2 and the 2 volumes of 
 chlorine as CI2, and the formula for hydrochloric acid, 
 which contains ^ of each, then becomes HCl. 
 
 To take another instance. The symbol N might be 
 applied to 2 volumes of nitrogen, if we did not know that 
 2 volumes of ammonia contain only 1 volume of nitrogen 
 united to 3 volumes of hydrogen. If we use the symbol 
 N for 2 volumes of nitrogen and H for 2 volumes of 
 hydrogen, ammonia must be described by the inconvenient 
 formula Hl^. But calling nitrogen N2, and hydrogen 
 H2, both of these are doubled, and the formula for ammonia 
 becomes NH3. 
 
 Again, with phosphorus : we might apply the symbol 
 P to 2 volumes of phosphorus-vapour if it were not for 
 such compounds as phosphine gas, 2 volumes of which 
 contain only one quarter as much phosphorus as is 
 present in 2 volumes of phosphorus-vapour. But by 
 describing phosphorus as P, and phosphine as PH3, we get 
 over the difficulty ; for the formulao show plainly, and in 
 whole numbers, that one contains four times as much 
 phosphorus in 2 volumes as the other. 
 
 The symbol therefore denotes the least weight of the 
 element formed in 2 volumes of gas. 
 
 Belative Weight of Gases, — It has already been shown 
 that the specific gravity of a body means its weight as 
 compared with the weight of an equal volume of some 
 other body which is taken as a standard. The standard 
 for gases is hydrogen, 1 volume of which is said to 
 weigh 1. We have therefore only to double the specific 
 gravities of the gases (which have been carefully de- 
 termined by experiment) to find the relative weights of 
 the standard 2 volumes of each gas. If 2 volumes of 
 hydrogen weigh 2 (2 grains, 2 grammes, or 2 hundred- 
 
70 
 
 EXPERIMENTAL CHEMISTRY. 
 
 weight), 2 volumes of clalorine will weigh 71, 2 volumes 
 of oxygen, 32, and so on with the rest. We must now 
 study the relative weights of the different elements which 
 go to make up the weight of 2 volumes of each of the more 
 important gases, elementary and compound. It will be 
 best to take the elementary gases first. 
 
 Constitution of Elementary Gases. — It has already been 
 seen that the formula for 2 volumes of any elementary 
 gas is determined by the compounds which contain that 
 gas. The formula for hydrogen is H2, because compounds 
 are known which contain in 2 volumes only half as much 
 hydrogen as is contained in 2 volumes of the pure element. 
 Now what is true of a large volume must also be true of 
 any volume, however minute, and we are therefore led to 
 the conclusion that even the smallest conceivable volume 
 of hydrogen gas that exists in a separate state must be 
 capable of division into two parts, and as the weight of 2 
 x^olumes of hydrogen has already been defined to be 2 
 (hydrogen being the standard), each of these constituent 
 parts must have a weight of 1. 
 
 Atoms.* — The name atom is, for reasons that will be 
 explained hereafter, applied to the quantity of each 
 element that is denoted by its symbol. 2 volumes of 
 hydrogen denoted by the formula Hg, weigh 2, and consist 
 of 2 atoms, each denoted by the symbol H, and each 
 weighing 1. In like manner, 2 volumes of phosphorus- 
 vapour are said to consist of 4 atoms ; the formula for 
 2 volumes being P4 and the symbol for each atom P. The 
 atom in this case weighs 31. In the case of mercury and 
 a few other elements the 2 volumes of gas are said to 
 contain but 1 atom (weighing, in the case of mercury, 
 200), because no gas is known which contains in 2 
 volumes less than 200 of mercury. 
 
 The atom is therefore the smallest weight of each 
 
 * I use this word in its present connection with regret. It would 
 certainly be better to exclude it altogether from an account of gases 
 which is independent of the truth or untruth of the atomic theory. 
 But there is no word in use wliicli exactly answers to the conditions, 
 and I hold the coinage of a word to bo far too serious an experiment 
 to be undertaken in an elementary treatise. Might not tlie word 
 " prime,'* originally employed by WoUaston, be conveniently revived 
 for this purpose ? 
 
ELEMENTARY GASES — ATOMS. 
 
 71 
 
 element ever found in 2 volumes, of any gas, the smallest 
 weight of hydrogen so found being taken as 1. The 
 weights of the atoms are, of course, relative weights. By 
 the use of small index figures any number of atoms may 
 be represented. Thus Sg means 6 atoms of sulphur each 
 weighing 32. 
 
 These remarks will sufficiently explain the following 
 table which exhibits the composition of all the more 
 important elementary gases. It is only necessary to point 
 out that three of them, oxygen, sulphur, and iodine, occur 
 in two places. Two different modifications of each of 
 these gases are known, which differ from one another 
 in weight. The atoms are, however, the same in each case. 
 
 To translate the numbers in the three following tables 
 into absolute weights and measures, the system described 
 on page may be adopted. For 2 volumes, read 22*4 
 litres. Then all the weights will be grammes. Thus in 
 the first table 22*4 litres of hydrogen weigh 2 grammes, 
 of oxygen, 32 grammes, of ozone, 48 grammes, and 
 so on. 
 
 Constitution of Compound Gases. — It will now be obvious 
 that two volumes of every compound gas must contain 
 two or more atoms of two or more kinds. The formula 
 for a compound gas must denote the number and kind of 
 atoms that there are in two volumes of it. Hydrochloric 
 acid is an example of the simplest kind of gaseous com- 
 pound, two volumes of it containing, as we have already 
 seen, one atom of hydrogen and one of chlorine. Other 
 gases contain atoms of three and even four difierent 
 elements, and there are sometimes as many as twenty, 
 thirty, or even more atoms in two volumes. In fact, we 
 know no limit to the number of atoms which may enter 
 into the composition of a compound gas. 
 
 The following table shows the constitution and formulae 
 of a few of the more important compound gases. The 
 rules according to which they are named will be explained 
 hereafter. 
 
 Compound Gases containing non-volatile Elements. — Many 
 gases contain atoms of elements which have not as yet 
 been converted into the condition of gas, or which, even 
 if they do exist as gas, have never had their specific 
 
72 
 
 EXPERIMENTAL CHEMISTRY. 
 
 ELEMENTARY GASES. 
 
 Name of Gas. 
 
 Sp. Gr. or 
 weight of 
 1 volume. 
 
 Weight of 
 2 volumes. 
 
 No. of 
 atoms in 2 
 volumes. 
 
 Symbol 
 for each 
 atom. 
 
 Weight of 
 each atom. 
 
 Formula 
 
 for 
 2 volumes. 
 
 
 100 
 
 200 
 
 1 
 
 
 209 
 
 
 '7ir»/% 
 
 32-5 
 
 65 
 
 1 
 
 Zn 
 
 65 
 
 Zn 
 
 Cadmium .... 
 
 56 
 
 112 
 
 1 
 
 Cd 
 
 112 
 
 Cd 
 
 
 63-5 
 
 127 
 
 1 
 
 I 
 
 127 
 
 I 
 
 Hydrogen .... 
 
 1 
 
 2 
 
 2 
 
 H 
 
 1 
 
 H. 
 
 
 35-5 
 
 71 
 
 2 
 
 CI 
 
 35-5 
 
 CI2 
 
 
 80 
 
 160 
 
 2 
 
 Br 
 
 80 
 
 Br, 
 
 
 127 
 
 254 
 
 2 
 
 I 
 
 127 
 
 I2 
 
 
 16 
 
 32 
 
 2 
 
 0 
 
 16 
 
 
 Sulphur (above 1000° C.) 
 
 32 
 
 64 
 
 2 
 
 s 
 
 32 
 
 s. 
 
 
 14 
 
 28 
 
 2 
 
 N 
 
 14 
 
 
 Oxygen (as ozone) . 
 
 24 
 
 48 
 
 3 
 
 0 
 
 16 
 
 O3 
 
 Phosphorus .... 
 
 62 
 
 124 
 
 4 
 
 P 
 
 31 
 
 P4 
 
 
 150 
 
 300 
 
 4 
 
 As 
 
 75 
 
 AS4 
 
 Sulphur (below 1000^ C.) 
 
 96 
 
 192 
 
 6 
 
 S 
 
 32 
 
 
 gravities accnrately determined in that condition. In 
 these cases the atomic weight (weight of the atom) of 
 the non- volatile element can be found by exactly the 
 same rule as that given before, namely, by observing the 
 smallest weight of the element that ever enters into the 
 composition of 2 volumes of a compound gas. 
 
 Take the case of carbon, an element which has never 
 been converted into vapour. Many gases containing 
 carbon are known, but not one of them contains in 2 
 volumes less than 12 of carbon. The atomic weight of 
 carbon is therefore taken to be 12 and the atom is denoted 
 by the symbol C, but not knowing the weight of 2 volumes 
 of carbon- vapour we cannot tell what fraction 12 is of 
 that weight ; or, in other words, how many atoms of 
 carbon there are in 2 volumes of carbon-gas. 
 
 It is obvious that we cannot have a formula for a non- 
 volatile element, and that even in the case of volatile 
 elements it is incorrect to apply the formula belonging to 
 
.OMPOUND GASES. 
 
 73 
 
 the gas to the liquid or solid element. For liquid and 
 solid elements we must be content to use the symbol which 
 denotes the atom. 
 
 COMPOUND GASES. 
 
 Name of Gas. 
 
 Specific 
 gravity. 
 
 vv tigut 
 
 ot 2 
 volumes 
 
 Mercuric Chloride . 
 
 135 '5 
 
 271 
 
 Hydrochloric Acid . 
 
 18-25 
 
 36-5 
 
 Hypochlorous An-I 
 hydride . . / 
 
 43-5 
 
 87 
 
 Water, (Steam) 
 
 9 
 
 18 
 
 Hydrofiren Sulphide . 
 
 17 
 
 34 
 
 Sulphurous Anhy-l 
 dride . . . j 
 
 32 
 
 64 
 
 Ammonia 
 
 8-5 
 
 17 
 
 Nitrous Oxide . . 
 
 22 
 
 44 
 
 Nitric Oxide 
 
 15 
 
 30 
 
 Phosphine . . 
 
 17 
 
 34 
 
 PhosphorousChloride 
 
 68-75 
 
 137-5 
 
 Arsine .... 
 
 39 
 
 78 
 
 Kind, number, and weight of 
 the atoms in 2 volumes. 
 
 J Mercury 1 
 \ Chlorine 2 
 
 r Hydrogen 1 
 \ Chlorine 1 
 
 /Oxygen 1 
 \Chlorine 2 
 
 (Hydrogen 2 
 t Oxygen 1 
 
 /Hydrogen 2 
 \ Sulphur 1 
 
 /Oxygen 2 
 \Sulphur 1 
 
 /Hydrogen 3 
 \ Nitrogen 1 
 
 /Nitrogen 2 
 \Oxygen 1 
 
 /Nitrogen 1 
 \ Oxygen 1 
 
 /Hydrogen 3 
 \Phosphorusl 
 
 /Chlorine 3 
 (Phosphorusl 
 
 /Hydrogen 3 
 \ Arsenic 1 
 
 200 \ 
 71 / 
 
 5-5} 
 
 } 
 ) 
 
 35 
 
 16 
 71 
 
 2 
 16 
 
 2 ^ 
 32 
 
 32 
 32 
 
 3 
 14 
 
 28 ^ 
 
 14 ^ 
 16 
 
 3 ] 
 31 J 
 
 106-51 
 31 J 
 
 3 1 
 75 j 
 
 HgCI 
 
 HCl 
 
 CI2O 
 
 H2O 
 
 H^S 
 
 SO2 
 
 H3N 
 
 N2O 
 
 NO 
 
 H3P 
 
 CI3P 
 
 H,As 
 
 The following table will show the constitution of a few 
 important gases of the kind here specified and also the 
 way in which the atomic weights of their non- volatile 
 constituents can be determined from them. 
 
 The atomic weight of iron, as deduced from the com- 
 position of the vapour of ferric chloride, is 112. But 
 
74 
 
 EXPERIMENTAL CHEMl.'^RY. 
 
 ferric chloride is so similar to chromic chloride that the 
 atomic weight of iron is held to be 56. The formula 
 for ferric chloride is then Fe2 Clg ; 2 atoms of iron, each 
 56, united with 6 atoms of chlorine, each 35*5. This 
 brings it into analogy with chromic chloride Cr2 Clg. 
 
 COMPOUND GASES CONTAININO NON-VOLATILE ELEMENTS. 
 
 KAME 
 • OF 
 GAS. 
 
 
 
 Specific 
 gravity. 
 
 Weight 
 
 of 2 
 volumes 
 
 Kind, weight, and number 
 of the atoms in 2 
 volumes. 
 
 Formula. 
 
 Symbol and 
 atomic weight 
 
 of the 
 non-volatile 
 constituent. 
 
 Methane . 
 
 8 
 
 16 
 
 r Hydrogen 
 \ Carbon 
 
 4= 4 \ 
 1= 12 / 
 
 CH, \ 
 
 
 Ethylene . 
 
 14 
 
 28 
 
 1 Hydrogen 
 \ Carbon 
 
 4= 4 \ 
 2= 24 j 
 
 
 
 Ethane 
 
 15 
 
 30 
 
 1 Hydrogen 
 \ Carbon 
 
 6= 6 \ 
 2= 24 j 
 
 
 
 Carbonic ) 
 oxide / 
 
 14 
 
 28 
 
 (Oxygen 
 \ Carbon 
 
 1= 16 \ 
 1= 12 j 
 
 CO 1 
 
 C = 12 
 
 Carbonic \ 
 anhydride/ 
 
 22 
 
 44 
 
 J Oxygen 
 (Carbon 
 
 2= 32 \ 
 1= 12 j 
 
 C02 
 
 
 Cyanogen . 
 
 26 
 
 52 
 
 (Nitrogen 
 (Carbon 
 
 2= 28 \ 
 2= 24 / 
 
 C2N2 
 
 
 Chloroform 
 
 59-75 
 
 119'5 
 
 j Hydrogen 
 < Chlorine 
 (Carbon 
 
 1= 1 I 
 3 = 106-5 
 1= 12 ) 
 
 CHC13 / 
 
 
 Silicon ) 
 chloride / 
 
 85 
 
 170 
 
 (Chlorine 
 \ Silicon 
 
 4 = 142 \ 
 1= 28 / 
 
 Sici4 ^ 
 
 
 Methyl | 
 siUcate / 
 
 76 
 
 152 
 
 f Carbon 
 1 Hydrogen 
 j Silicon 
 (Oxygen 
 
 4= 48 ] 
 12= 12 1 
 1= 28 ( 
 4= 64 j 
 
 C.HioSiO, j 
 
 Si = 28 
 
 Chrorajd \) 
 chloride j 
 
 Chromic ) 
 chloride J 
 
 77-75 
 159 
 
 155-5 
 318 
 
 (Oxygen 2= 32 1 
 Clilorine 2= 71 [ 
 (Chromium 1= 52-5) 
 
 (Chlorine 6 = 213 \ 
 (Chromium 2 = 105 / 
 
 CrO.Cl^ 1 
 Cr^Cle ! 
 
 Cr = 52-5 
 
 Ferric \ 
 chloride / 
 
 162-5 
 
 325 
 
 (Chlorine 
 (Iron 
 
 6 = 213 \ 
 1 = 112 / 
 
 FeCl^ 
 
 Fe = 112 
 
COMBINATION BY WEIGHT. 
 
 75 
 
 The composition and properties of other iron compounds 
 confirm this view. 
 
 Calculation of the Specific Gravities of Gases from their 
 Formulae, — If the formula for any gas be accurate ; that 
 is, if it truly represents 2 volumes of the gas, the specific 
 gravity of the gas may be calculated from the formula. 
 This may be illustrated by an example. 
 
 The formula for carbonic anhydride gas is CO2. What is 
 its specific gravity ^ 
 
 The formula tells us that 2 volumes of the gas contain 
 
 1 atom of carbon, the weight of which we know to be 12, 
 and 2 atoms of oxygen, each of which weighs 16, total 44. 
 
 2 volumes of carbonic anhydride therefore weigh 44, 
 whereas 2 volumes of hydrogen weigh 2 ; which shows 
 that carbonic anhydride is 22 times heavier than hydrogen ; 
 or, in other words, that its specific gravity is 22. 
 
 To find the specific gravity of any gas, elementary or 
 compound, we have therefore only to find the weight of 
 2 volumes of it, by adding together the weights of the 
 constituent atoms, and then to divide the number so 
 obtained by 2. 
 
 COMPOSITION AS DETERMINED BY WEIGHT. — LAWS OF COM- 
 BINATION BY WEIGHT. 
 
 We must now leave on one side for the present all 
 considerations of volume and confine ourselves to the 
 examination of the weights of different substances which 
 are concerned in chemical changes, and the constitution 
 of compounds as determined by weight. This method of 
 study is of universal application, and it is used in- 
 differently for solids, liquids, and gases, whereas we have 
 already seen that the study of volumes only gives satisfac- 
 tory results when applied to gases. 
 
 Percentage Composition, — The most obvious w^ay of 
 stating the composition of a compound is as parts in 100. 
 The results of an analysis are always calculated in this 
 way first of all, the figures being usually carried to the 
 second or third decimal place. Thus, if 20 grammes of lime 
 are analysed they are found to contain 14*286 grammes of 
 
76 
 
 EXPERIMENTAL CHEMISTRY. 
 
 calcium, 5-7 14 of oxygen. By a simple proportion sum 
 it is then found that the percentage composition is : 
 
 Calcium 71-43 
 Oxygen 28-57 
 
 100-00 
 
 For 20 : 100 
 And 20 : 100 
 
 14-286 : 71-43 
 5-714 : 28-57 
 
 The percentage composition of a few important hydrogen 
 compounds is shown in the following table. 
 
 Simplest numerical Proportion of the Constituents. — From 
 the percentage composition, it is easy to calculate the pro- 
 
 Name of Compound. 
 
 Hydrochloric acid 
 Water 
 Ammonia 
 Methane . 
 Ethylene 
 Acetylene 
 Hydrogen sulphide 
 
 Compositiou of 100 
 parts. 
 
 Hydrogen 
 Chlorine 
 
 2 
 97 
 
 74 
 
 26 
 
 1 
 
 35-5 
 
 Hydrogen 
 Oxygen 
 
 11 
 
 88 
 
 1 
 
 8 
 
 1 
 
 8 
 
 Hydrogen 
 Nitrogen 
 
 17 
 
 82 
 
 65 
 35 
 
 1 
 
 4-6 
 
 Hydrogen 
 Carbon 
 
 25 
 75 
 
 
 1 
 
 3 
 
 Hydrogen 
 Carbon 
 
 14 
 
 85 
 
 29 
 71 
 
 1 
 6 
 
 Hydrogen 
 Carbon 
 
 7 
 92 
 
 69 
 31 
 
 1 
 
 12 
 
 Hydrogen 
 Sulphur 
 
 5 
 91 
 
 88 
 12 
 
 I 
 
 16 
 
 Composition. 
 H-1. 
 
 portion that the weight of each constituent bears to that 
 of some one which is taken as unity. In the preceding, 
 table the last column shows the weights of various 
 elements which are combined with 1 of hydrogen in a few 
 important compounds, the proportion being of course the 
 same as in the percentage composition. Any other element 
 might be taken instead of hydrogen as the standard. It 
 
COMBINATION BY WEIGHT. 
 
 77 
 
 was indeed common at one time to take oxygen as the 
 standard, calling it 100, but hydrogen is more convenient 
 and is now generally employed. 
 
 When the composition of hydrogen compounds is repre- 
 sented in this way, very simple numbers are for the most 
 pai-t obtained, and some numerical relations are observed 
 which are hidden in the mere percentage compositions. 
 Thus in the three carbon compounds (which are examples 
 of a large number actually known) we obseiwe that 1 of 
 hydrogen unites with 3, 6, and 12 of carbon. 3 is the 
 smallest proportion ever found. 
 
 By extending the above table we can easily obtain a 
 series of numbers which represent the proportions in 
 which a good many of the most important elements 
 combine with one part of hydrogen. It is now necessary 
 to extend our study to those compounds which do not 
 contain hydrogen. 
 
 And here there are two courses open to us. We ma}^ 
 begin by choosing some other element as a standard, 
 calling its quantity 1, and calculating the weight of other 
 elements which combine with it. But this method, 
 though it serves to exhibit some interesting relations, does 
 not bring out the simple general law towards which we 
 are tending. We must make the comparison in another 
 way. 
 
 Knowing the weight of any element which unites with 
 1 of hydrogen, let us calculate the weight of other 
 .elements which unite with that weight. For example : 35*5 
 of chlorine unite with 1 of hydrogen. Instead therefore 
 of calculating how much of each other element will unite 
 with 1 of chlorine, let us calculate how much will combine 
 with 35*5 of chlorine. And inasmuch as 8 of oxygen 
 combine with 1 of hydrogen, let us see what weight of 
 each other element unites with 8 of oxygen. In ex- 
 amining the results so obtained, it must be remembered 
 that two elements often unite in several different pro- 
 portions. 
 
 Confining ourselves to the elements mentioned on the 
 preceding table, we can obtain, from the analyses of well- 
 known compounds, the following figures, which are merel}' 
 samples of an immense number at our disposal : 
 
78 
 
 EXPERIMENTAL CHEMISTRY. 
 
 35'5 parts by weight of clilorine unite with 1 of 
 hydrogen ; with 8, 24, and 32, of oxygen ; with 3, 4, 6, 
 and 12, of carbon, and with 32 of snlphur. 
 
 8 parts of oxygen unite with 1 and with 0*5 parts of 
 hydrogen; with 8*875, 11*83, and 35*5 parts of chlorine; 
 with 2*8, 3*5, 4*6, 7 and 14 parts of nitrogen ; with 3 and 
 6 parts of carbon, and with 5*3 and 8 parts of sulphur. 
 
 4*6 parts of nitrogen unite with 1 of hydrogen ; with 
 2*6, 5*3, 8, 10*6, and 13*3 parts of oxygen, and with 4 
 parts of carbon. 
 
 3 parts of carbon (the smallest quantity that unites 
 with' 1 of hydrogen) unite with 0*25, 0*5 and 1 part of 
 hydrogen; with 8*875, 17*75, 26*625, and 35-5 of chlorme ; 
 with 4 and 8 parts of oxygen ; with 7 of nitrogen, and 16 
 of sulphur. 
 
 16 parts of sulphur unite with 16 and 24 of oxygen ; 
 with 17*75 of chlorine and with 3 of carbon. 
 
 A careful study of these figures will elucidate two of 
 the most important laws of chemistry. It will be seen : — 
 
 1. That in some cases the proportions in which tico elements 
 combine with one of hydrogen are exactly the proportions in 
 which they unite with one another. 35*5 parts of chlorine 
 and 8 parts of oxygen will respectively combine with 1 of 
 hydrogen, and a compound is known which contains in 
 every 43*5 parts, 35*5 of chlorine and 8 of oxygen. 
 
 2. That even when two elements unite in proportions different 
 from those in which they unite with one of hydrogen, the numbers 
 representing the two proportions bear a simple relation to one 
 another. — Chlorine forms three compounds with oxygen. 
 The one mentioned above contains 35*5 of chlorine to 8 of 
 oxygen ; the other two, 35*5 chlorine to 24 and 33 of 
 oxygen. In these two latter the proportion of oxygen is 
 exactly three and four times as great as is found combined 
 with hydrogen in water. The five oxides of nitrogen 
 afford a still more striking example, although some 
 thought is required to make it apparent. We already 
 know that 1 of hydrogen unites with 4*6 of nitrogen. In 
 the following table the columns next to the names of the 
 compounds show the quantities of oxygen which are 
 combined with 4*6 of nitrogen in each of the oxides. 
 Those quantities of oxygon are rei)resented by somewhat 
 
ATOMIC WEIGHTS. 
 
 79 
 
 awkward fractions. But if we multiply the 4*6 by 3, and 
 note tlie quantities of oxygen which unite with 14 of 
 nitrogen, as in the middle columns of the table, we find 
 that the proportions of oxygen can be expressed by whole 
 numbers, and furthermore that these numbers are simple 
 multiples of 8, which we already know is the proportion 
 in which oxygen unites with 1 of hydrogen. For the 
 sake of comparison the percentage compositions are given 
 in the last columns. 
 
 OXIDES OF NITROGEN. Parts in 100. 
 
 A ^ 
 
 Nitrogen. Oxygen. Nitrogen. Oxygen. Nitrogen. Oxygen, 
 Nitrous oxide • 4-6 : 2-6 \ / 14 : 8\ / 63-6 : 36-4 
 Nitric oxide • • 4*6 : 5'3 14 : 16 46-7 : 53-3 
 Nitrous aiihydride4' 6 : 8-0 } = { 14 : 24 ={ 36-8 : 63-2 
 Nitric peroxide • 4*6 : 10-6 14 : 32 30-4 : 69 6 
 
 Nitric anhydride 4*6 : 13-3 J I 14 : 40 j • I 25*9 : 74-1 
 
 Units of Combining Weight. — Combining Weights. — Atomic 
 Weights. — By an extension of the above methods of com- 
 parison, it is at last made out that a number may be found 
 for each element which is variously known as its " com- 
 bining weight," "proportional number," or, for reasons 
 which will be explained hereafter, its " atomic weight." 
 This number denotes the smallest quantity which is ever 
 found united with one of hydrogen, or with an analogous 
 quantity of any other elenient. For shortness it may be 
 spoken of as the atom of the substance. When we have 
 once fixed upon the numbers which shall stand for the 
 atoms of the elements, it is easy to represent the composi- 
 tion of all compounds by stating the number and kind of 
 atoms which they contain. Thus with the oxides of 
 nitrogen. If we agree that the atom of nitrogen is 14 and 
 that of oxygen 8, we see by the above table that in the 5 
 oxides, one atom of nitrogen is united with 1, 2, 3, 4 and 
 5 atoms of oxygen. 
 
 Use of Symbols. — The symbols which have already been 
 used to denote volumes of gas, may be applied with equal 
 exactness of meaning to the atoms of elements as found by 
 weight. Thus, H may denote 1 atom, or 1 part by weight 
 of hydrogen. N, 1 atom, or 14 parts of nitrogen. O, 1 
 atom, or 8 parts of oxygen, and so on. With these 
 symbols, formulse, perfectly analogous to those already 
 
80 
 
 EXPERIMENTAL CHEMISTRY. 
 
 explained, may be constructed and applied to compounds. 
 The formulae for the 5 oxides of nitrogen are, if the above 
 mentioned atomic weights be adopted : NO, NO2, NO3, 
 NO4, and NO5. ^ 
 
 Modes of fixing the Atomic Weights of Elements, — The 
 numbers found for the combining or atomic weights of the 
 elements from the study of the percentage composition of 
 their compounds are liable to one serious drawback. We 
 can never be certain that the number adopted represents 
 the weight of any real unit of the element. We cannot 
 indeed by fair reasoning conclude that there is any con- 
 stant unit of combining weight for each element. All that 
 we can say is, that if there be such a unit, it must either 
 have the weight we have assigned to it or bear some 
 simple numerical relation to that weight. Looking at the 
 carbon compounds, for example, in the table on page 76, 
 we come to the conclusion that the atomic weight of 
 carbon is either 3, 6, or 12, for carbon unites with 1 of 
 hydrogen in all those proportions. The atomic weight of 
 nitrogen indicated by its hydrogen compound is 4*6, but 
 the oxygen compounds of the same element seem to require 
 it to be 14. In the same way the atomic weight of 
 oxygen may be 4, 8, 16, or even some less simple number, 
 and in all these cases analysis is powerless to tell us with 
 any certainty which of the different numbers should be 
 adopted. In fact, to speak accurately, analysis would 
 appear to indicate that each element has more than one, 
 or indeed many combining weights, but that these weights 
 all bear a simple relation to one another. 
 
 Fortunately, however, there are other facts at our 
 disposal with regard to the elements of their compounds 
 which give clear evidence upon this point, and which not 
 only indicate that there is a single unit of combination for 
 each element, but enable us to fix its weight with a near 
 approach to certainty. The chief of these exterior sources 
 of evidence may be briefly mentioned in this place. 
 
 1. The Law of Gaseous Volumes, with the extensions of 
 it that have already been considered. This method can 
 of course only be applied where gases are concerned, but 
 its evidence when it can bo obtained is exceedingly 
 valuable. The weights of the atoms of a great many of 
 
EQUIVALENTS. 
 
 81 
 
 the elements are fixed in this way, and the method has 
 been so fully explained that it is unnecessary to do more 
 than refer to it here. We have seen, to take a single 
 example, that the atomic weight of oxygen is taken as 16, 
 because 16 is the smallest weight of oxygen that occurs in 
 2 volumes of any gas. 
 
 2. Substitution, — Equivalents. — This is merely a modifi- 
 cation of the method by weight which has already been 
 described. It has been seen (page 63) that one of the 
 commonest modes in which chemical action takes place is 
 by the substitution of a certain weight of one substance for 
 another. In a series of substitutions we have only to 
 ascertain the weight of different substances, which will 
 displace one another to obtain a series of numbers which 
 are called the equivalents of those substances. Starting 
 from hydrochloric acid, for instance, which contains 1 of 
 hydrogen to 35*5 of chlorine, we find we can replace the 1 
 of hydrogen by 23 of sodium, 39 of potassium, 20 of cal- 
 cium, and ^o on. And in the same way the 35*5 of 
 chlorine may be replaced (either directly or indirectly) 
 by 8 of oxygen, 4*6 of nitrogen, 80 of bromine, 16 of 
 sulphur, and so on. These various numbers are the 
 equivalents of the elements, and it is found that the quan- 
 tities they represent are not only equivalent to 1 of 
 hydrogen, or 35*5 of chlorine, but also to one another. 16 
 of sulphur may take the place of 8 of oxygen or 80 of 
 bromine, and 20 of calcium are always equivalent to 39 of 
 potassium. 
 
 All this is simple enough, and it would seem as if the 
 equivalents so found might be adopted as the most con- 
 venient of "combining weights." They were in fact 
 adopted, and for years were pretty generally employed 
 for this purpose. But certain difficulties and incon- 
 veniences attend their use and have at last occasioned 
 their abandonment. For, in the first place, the equi- 
 valents of some elements do not agree with the numbers 
 indicated by the law of volumes. The equivalent of 
 oxygen, for instance, is 8, but its atom, as deduced from 
 the composition of compound gases, is 16. A still graver 
 objection lies in the fact that as elements often combine 
 in more than one proportion, it then follows that there 
 
 G 
 
82 
 
 EXPERIMENTAL CHEMISTRY. 
 
 are several equivalents for the same element. The case 
 of the oxides of nitrogen, already cited, will make this 
 plain. On page 76, it is stated that 8 parts of oxygen 
 will combine with 1 of hydrogen, and with 2*8, 3-5, 4*6, 7 
 and 14, of nitrogen ; it is therefore evident that these five 
 quantities of nitrogen are all, in different compounds, 
 equivalent to 1 of hydrogen, and that, in fact, nitrogen 
 has five equivalents. This difficulty is indeed only 
 another form of that which was pointed out at the begin- 
 ning of this section. 
 
 But although the equivalent values of the elements are 
 no longer thought sufficient to fix their atomic weights, 
 this method of study is still of immense importance in 
 chemistry, for two reasons : 
 
 First, because, as we have seen, the true atomic weight, 
 when not identical with the equivalent, always bears a 
 simple relation to it. 
 
 And secondly, because it often enables to fix the exact 
 constitution of a compound, as will be seen from the 
 following simple illustration. The formula deduced from 
 the analysis of acetic acid is CHgO (0 = 12, H = l, C = 16). 
 But we find by experiment that one quarter of the hy- 
 drogen of acetic acid may be replaced by a metal — by 
 sodium, for instance, or silver. Now it is evident that, 
 if the above formula were correct, the metal must displace 
 half an atom of hydrogen, which, as the atom is defined to 
 be the smallest possible quantity, is absurd. We must, 
 therefore, double the formula and make it C2H4O2. It is 
 then seen to consist of 2 atoms of carbon, 4 of hydrogen, 
 and 2 of oxygen. Sodium displaces one atom of hydrogen, 
 and the formula for the compound so obtained is CaHaNaOg. 
 This view is completely confirmed by the law of volumes. 
 By the rule given on page 75, the specific gravity of the 
 vapour of acetic acid ought, if the formula CH2O were 
 correct, to be 15, whereas experiment shows it to be 30. 
 
 3. Specific Heat. — Atomic Seat. — This method gives very 
 good results with elements in the solid state, and is of the 
 utmost importance. Equal weights of different substances 
 heated to an equal extent, require veiy different times for 
 cooling down to the same point. If one pound of water 
 and one pound of mercury, at a temperature of 100° C. 
 
SPECIFIC HEAT. 
 
 83 
 
 (boiling point), be allowed to cool down to 50^, it will be 
 found that the water is 30 times as long in doing so as the 
 mercury, and gives out 30 times as much heat. Water at 
 any one temperature contains 30 times as much heat as an 
 equal weight of mercury at the same temperature, and 
 analogous differences are observed with all other substances. 
 The quantities of heat which equal weights of different 
 bodies contain at the same temperature (measured by the 
 time required for their cooling, or in some other way) are 
 called their specific heats. The specific heat of water is 
 greater than that of any other known substance (except 
 hydrogen), and it is therefore taken as the standard, and 
 called 1. The specific heat of liquid mercury is therefore 
 0-033. 
 
 Now if we compare together the specific heat of different 
 elements in the solid state, we find, as the following table 
 will show, that no relation can be observed between them. 
 But if we compare together the specific heats, not of equal 
 weights, but of atomic weights^ which we can easily do by 
 multiplying the specific heats of the first column by the 
 atomic weights, we find that the numbers are very similar 
 to one another, and approximate to 6*3. It is therefore 
 inferred that if we could compare all elements in the solid 
 state and at equal temperatures, in quantities proportionate 
 to their atomic weights, and could avoid all errors of ex- 
 periment, they would all contain the same quantity of heat. 
 This quantity, found by multiplying the specific heat by 
 the atomic weight, is called the atomic heat of the element. 
 
 It is easy to understand the assistance which this theory, 
 discovered by Dulong and Petit (we must remember that 
 it is only a theory, for its truth cannot be demonstrated), 
 affords in fixing the atomic weights of elements. Let us 
 take the case of zinc to illustrate it. The equivalent of 
 zinc, as compared with hydrogen, is 32-5, and that number 
 was formerly taken as the atomic weight of the metal. 
 But the specific heat of zinc is 0*0955, and this number 
 multiplied by 32*5 only gives 3*1, so that the atomic heat 
 of zinc must be regarded as exceptional, and only half of 
 the usual quantity. But if we take 65 as the atomic 
 weight of zinc, the anomaly vanishes, and the atomic 
 heat becomes 6*2. The atomic weights of many other 
 
 G 2 
 
84 
 
 EXPERIMENTAL CHEMISTRY. 
 
 elements liave of late years been doubled for tbe same 
 reason. 
 
 Some few exceptions to this rule of atomic heat are 
 known, of which carbon, boron and silicon are the 
 most important, but at high temperatures these dis- 
 appear. 
 
 it will be seen that if we wish to find the atomic weight 
 of an element from its specific heat, we must divide the 
 average atomic heat 6*3 by the specific heat. The atomic 
 weight so obtained will not be exact, but it will serve to 
 indicate whether a particular number or a fraction or 
 multiple of it is to be chosen as the true atomic 
 weight. 
 
 6*3 
 
 E.g, Atomic weight of tin is ———=112, which suffi- 
 
 SPECIFIC AND ATOMIC HEATS. 
 
 Element. 
 
 Specific Heat. 
 
 Atomic 
 Weight. 
 
 Atomic Heat. 
 
 Bromine (solid) . . 
 
 0-0843 
 
 80- 
 
 6-7440 
 
 Iodine 
 
 0 0541 
 
 127- 
 
 6-8707 
 
 Potassium . 
 
 0-1696 
 
 39- 
 
 6-6144 
 
 Sodium .... 
 
 0-2934 
 
 23- 
 
 6-7482 
 
 Silver .... 
 
 0-0570 
 
 108- 
 
 6-1560 
 
 Gold 
 
 0-0324 
 
 196- 
 
 6-3504 
 
 Phosphorus . 
 
 0-1887 
 
 31- 
 
 5-8497 
 
 Arsenic .... 
 
 0-0814 
 
 75- 
 
 6-1050 
 
 Antimony 
 
 0-0508 
 
 120- 
 
 6-0960 
 
 Bismuth .... 
 
 0-0308 
 
 208- 
 
 6-3064 
 
 Sulphur 
 
 0-1776 
 
 32- 
 
 5-6832 
 
 Magnesium . 
 
 0-2499 
 
 24- 
 
 5-9976 
 
 Zinc 
 
 0-0955 
 
 65- 
 
 6-2075 
 
 Mercury (solid) . 
 
 0-0319 
 
 200- 
 
 6-3800 
 
 Copper .... 
 
 0-0951 
 
 63-5 
 
 6-0389 
 
 Lead 
 
 0-0314 
 
 207- 
 
 6-4998 
 
 Iron 
 
 0-1138 
 
 56- 
 
 6-3728 
 
 Aluminium . 
 
 0-2143 
 
 27- 
 
 5-7861 
 
 Tin 
 
 0-0562 
 
 118- 
 
 6-6316 
 
 Platinum 
 
 0-0324 
 
 197- 
 
 6-3828 
 
 ciently indicates that 118, and not 59, should be taken as 
 the atomic weight of tin. 
 
 4. JsomorpMsm. — It was discovered by Mitscherlich, 
 
ISOMORPHISM. 
 
 85 
 
 that compounds which might be supposed to have a similar 
 chemical structure, very cctoimoiily crystallized in the 
 same form, even though quite different in properties. 
 Similar compounds of calcium, strontium, barium, and 
 lead ; similar sulphates, selenates, and chromates, and 
 similar phosphates and arsenates, are examples of this law, 
 and many others might be quoted. Compounds which 
 exhibit this peculiarity are said to be isomorphous with one 
 another (from to-os, like, and fiopcfyrj, form). Mitscher- 
 lich's law, though not universal, is yet so frequently true, 
 that when two analogous substances yield crystals having 
 the same angular measurement, there is a great a priori 
 probability that their constituents are arranged in a 
 similar manner, and this probability is sometimes of great 
 use in fixing the atomic weight of an element. For 
 example, the metal aluminium has only one oxide, alumina, 
 which contains 18 of the metal to 16 of oxygen. As 16 
 is the atomic weight of oxygen, it would be natural to 
 suppose that that of aluminium was 18, in which case the 
 formula of alumina would be AlO. But alumina is iso- 
 morphous with red oxide of iron (ferric oxide), which is 
 known to have the formula Fe203, and it is therefore 
 concluded that the formula of alumina must be AI2O3, in 
 which case the atomic weight of aluminium must be 27. 
 Of course either formula agrees equally well with the 
 result deduced from analysis. For if : — 
 
 Al = 18, then AlO =18 Aluminium : 16 Oxygen. 
 Al = 27, then AI2O3 = 54 „ : 48 
 
 the proportion being the same in both cases. The number 
 27 is confirmed by the specific heat of aluminium, 
 for — 
 
 =29.4 
 
 •2143 
 
 which is tolerably near. 
 
 The atomic weights of the principal elements, deter- 
 mined by the collation of all these various facts and 
 theories, are given in the table at the commencement of 
 this volume, to which is prefixed a definition of the 
 terms. 
 
86 
 
 EXPERIMENTAL CHEMISTRY. 
 
 EQUIVALENT VALUE OF ATOMS. — VALENCY, ATOMICITY, OE 
 gUANTIVALENCE. 
 
 The above remarks will have made it evident that the 
 quantity which is known as the atom of an element is not 
 always the same as its equivalent. The equivalent of 
 oxygen is 8, because 8 parts of oxygen will replace 85-5 
 of chlorine, or 1 of hydrogen, but the atomic weight of 
 oxygen is held to be 16 : the equivalent of nitrogen is 
 4*6, but its atomic weight is 14 : and lastly, in its simplest 
 compound, the equivalent of carbon is 3, whereas its 
 atomic weight is 12. It follows from this, that an atom 
 of oxygen is equivalent to two, an atom of nitrogen to 
 three, and an atom of carbon to four atoms of hydrogen. 
 For if 8 of oxygen be equivalent to 1 of hydrogen, 16 
 must evidently be equivalent to 2. The atom of each 
 element has therefore its own equivalent value, represented 
 by the number of atoms of hydrogen to which it is equi- 
 valent. This equivalent value, as compared with that of 
 the atom of hydrogen, is often spoken of as the valency^ or 
 atomicity^ or quantivalence of the element, and its amount 
 is described by the words nomad, diad, triad, tetrad, pentad, 
 &c., according as the atom is equivalent to one, two, three, 
 four, or five atoms of hydrogen. 
 
 Classification of Elements hy their Valency, — All those 
 elements of which one atom is equivalent to one atom of 
 hydrogen, either in replacing it or combining with it, are 
 classed together as monads. The most important monad 
 elements are, hydrogen, chlorine, bromine, iodine, and 
 fluorine among the non-metals, and potassium, sodium, 
 and silver, among the metals. 
 
 The chief diad elements are oxygen and sulphur among 
 the non-metals, and barium, strontium, calcium, mag- 
 nesium, zinc, copper, mercury, and lead among the metals. 
 
 As examples of triads may be mentioned nitrogen, 
 phosphorus, arsenic, and boron, and the metals antimony, 
 bismuth and gold. 
 
 Carbon, silicon, and many of the other metals are tetrads. 
 
 Mode of marking Valency. — As the symbol denotes one 
 atom, some chemists mar k the equivalent value, or valency, 
 of that atom by dashes or Eoman figures placed above 
 
VARIATIONS OF VALENCY. 
 
 87 
 
 and to the right of the symbol, in the following manner : — 
 H' 0" N'" C"" or The monad atoms, however, are 
 
 seldom marked at all. 
 
 Let it be understood distinctly that a diad atom may 
 take the place of or may combine with any two monad 
 atoms. One atom, or 16 parts of oxygen, for instance, 
 may very often, by mere substitution, be made to displace 
 and take the place of two atoms (2 parts) of hydrogen, 
 and we already know that 16 parts of oxygen will combine 
 with 2 of hydrogen. The formulae for a few important 
 compounds will illustrate the different values of the atoms 
 more clearly than words. 
 
 HCl, H2O", H3N'", KCl, K2O", Zn"Cl2, Bi'Tlg. 
 
 Mode of fixing Valency. — When an element combines 
 -vN^ith hydrogen, the hydrogen compound decides the 
 valency, as with chlorine, oxygen, nitrogen, and carbon. 
 In other cases the chlorine compound, or any other com- 
 pound that the element may form with a monad, may be 
 used instead. Thus platinum is reckoned a tetrad because 
 it forms the chloride, Pt'''Cl4, in which the atom of 
 platinum is united with four of the monad atoms of 
 chlorine. 
 
 Perissiad and Artiad Atoms, — Dr. Odling proposed to 
 name those elements whose valency is an uneven number 
 jperissiads (776/9 to-cros, odd), and those in which it is even, 
 artiads (aprtos, even). There is great convenience in the 
 use of these words, but they are not often used. 
 
 Variations of Valency, — Many elements have different 
 valencies in different compounds. For example, a second 
 compound of platinum and chlorine is known, which has 
 the formula Pt"Cl 2, and here the metal is clearly a diad. 
 So carbon, which is tetrad in C'^'H^ and C'''0"2 (tw^o diad 
 atoms act, of course, like four monad ones), is diad in C"0". 
 And nitrogen, which is triad in N"'H3, is monad in N'20", 
 and pentad in N^'H^Cr. But these variations are subject 
 to one rule, which is of very general application. Peris- 
 siads are seldom artiads, or artiads perissiads, A pentad, for 
 example, which of course is a perissiad, may sometimes act 
 as a triad, or a monad, but not as a tetrad, or diad. Two 
 of the oxides of nitrogen, NO and NO2, are almost the only 
 
88 
 
 EXPERIMENTAL CHEMISTRY. 
 
 certain exceptions of this important rule, which must be 
 borne carefully in mind in constructing formulae. 
 
 Badicals. — The formula for nitric acid is HNO3. Now a 
 large number of compounds called nitrates are known, 
 which differ from nitric acid only in containing some metal 
 in place of hydrogen. Thus we have sodium nitrate 
 ]SI'aN03, silver nitrate AgNOg. In all these nitrates, 
 however, the common quantity NO3 is found, and NO3 is 
 therefore called the radical of the nitrates. In the same 
 way the formula for sulphuric acid is H2SO4, and the 
 sulphates all contain the radical SO4. Neither NO3 nor 
 SO4 exist in a separate state. It is probably impossible 
 for them to do so. We do not even know that they exist 
 in the compounds, but we do know that their elements are 
 present in the same proportions in a large number of com- 
 pounds, and that all these compounds are linked together 
 by a cei-tain similarity of properties ; and therefore, with- 
 out troubling ourselves either to affirm or deny their 
 existence as separate entities, it is convenient to assume 
 their presence in certain compounds. We shall meet with 
 many radicals as we go on, many of them very unlike one 
 another in function ; but for the present we have to regard 
 them only in one point of view. In the compounds which 
 contain them, radicals play the part of elements, and, like 
 elements, every radical has its own proper valency. The 
 acids which contain radicals afford good examples of this. 
 
 Nitric Acid H N O3 is like Hydrochloric Acid H CI. 
 Sulphuric Acid H2 S ,, Water O. 
 Phosphoric Acid H3 P O4 ,, Ammonia H3N. 
 
 As CI is united with one of H, so NO3 is united with 
 one of H. NO3 is therefore called a monad radical. And 
 as SO4 is united with two of H, it may be compared to 
 oxygen, and is called a diad radical. Their valency may be 
 marked as that of elements is marked (NO3)', (SO4)", and 
 (PO4)'", and lastly it must be remembered that in all 
 nitrates NO3 is monad, and in all sulphates SO4 is diad. 
 
 Measure of the Valency of Badicals. — The equivalent 
 value of a radical is measured, just as that of an element 
 is, by the number of atoms of hydrogen or other monad 
 element with which it combines. NO3, for instance, is a 
 
RADICALS — NOMENCLATURE. 89 
 
 monad radical, because in HNO3 combined with one 
 atom of hydrogen. A radical is in fact an incomplete 
 compound, and it is monad, diad, or triad according as it 
 lacks one, two, or three monads to complete it. The 
 following table includes some of the most important 
 radicals of chemistry. Only a few of them have individual 
 names. 
 
 MONAD RADICALS, 
 ^drate'^'''^^^^'''.^^^^ C^"(OH),. Br(0H)3. 
 
 ^Amidlt'^!'^''^'''^ " ^^3. KNH,. 
 
 CI O in Hypochlorites'. , , H CI O. K CI O. 
 CI O2 in Chlorites . . , , H CI O2. K CI O2. 
 CI O3 in Chlorates. . HCIO3. KCIO3. 
 
 CI O, in Perchlorates . , , H CI O4. K CI O,. 
 N O2 in Nitrites . . , , H N O2. K N O2. 
 N Oo in Nitro-com-) r< xj xr 
 
 pounds ..../" C56H5NO2. 
 N O3 in Nitrates . . , , H N O3. K N O3. 
 P O3 in Metaphosphates , , HP O3. K P O3. 
 
 N H4 (Ammonium) in Ammonium Compounds, as in NH4 CI. N H4 NO3. 
 C H3 (Methyl) in Methyl Compounds. . . , , C H3 CI. 
 C2H5 (Ethyl) in Ethyl Compounds . . . , , C2H5CI. 
 
 DIADS. 
 
 S O3 in Sulphites . asinH2S03. K2SO3. Ca'SOs. 
 
 S O4 in Sulphates . ,, H2SO4. K2SO,. KHSO4. 
 
 C O3 in Carbonates . , , K2 C O3. K H C O3. Ca"C O3. 
 
 Si O3 in Metasilicates , , H2Si O3. Mg"Si O3. 
 
 C H2 (Methylene) in Methylene Compounds, as in C H2 CI2. 
 TRIADS. 
 
 P O4 in Phosphates, as in H3PO4. K3PO4. KH2PO4. K2HPO4. 
 As O4 in Arseniates , , H3 As G4. Ag3 As O4. 
 
 C H in such compounds as Chloroform, C H CI3. 
 TETRADS. 
 
 Si O4 in Silicates . . as in H4 Si O4. M Si O4. 
 
 P2 O7 in Pyrophosphates , , H4 P2 O7. Na4 P2 O7. Mg"2 P2 O;. 
 
 NOMENCLATURE. 
 
 Names are given to chemical compounds, according to 
 rules which, though not perfect, are better than those 
 
90 
 
 EXPERIMENTAL CHEMISTRY. 
 
 employed in any other science. Only a few of the simplest 
 need be indicated in this place. 
 
 1. Compounds of two elements only are distinguished by 
 the termination ide. Thus the compound of zinc and 
 oxygen is called oxide of zinc, or zinc oxide ; zinc and 
 chlorine, zinc chloride; sodium and chlorine, sodium 
 chloride ; and so on. This rule is invariable, though for 
 special reasons a different name is more often used for 
 many simple compounds. 
 
 2. When there are two compounds of the same two 
 elements, the lower — that which contains the least oxygen, 
 chlorine, &c. — is distinguished by the termination ous, and 
 the higher by the termination ^c. The lower chloride of 
 tin SnCl2, for instance, is called stannous chloride, and the 
 higher, SnCl4, stannic chloride. The same rule is applied 
 to acids. HNO2 is called nitrous acid, and HNO3 nitric 
 acid. 
 
 3. The substances called salts which are derived from 
 an acid which ends in ous have the termination ite. All 
 the salts, for instance, which contain the radial NO2, and 
 which therefore correspond to nitrous acid, are called 
 nitrites. Salts which correspond to acids ending in ^c, 
 have the termination ate. Nitric acid, for instance, forms 
 nitrates, sulphuric acid, sulphates, and acetic acid, acetates. 
 Almost the only exception to this rule is in the compounds 
 called hydrates or hydroxides, which contain the radial HO, 
 and which, instead of corresponding in composition to an 
 acid, correspond to water. 
 
 Other rules will be more conveniently given as instances 
 occur. 
 
 ATOMIC AND MOLECULAR HYPOTHESES. 
 
 Atoms — Atomic Weights. — Dalton, to whom we are in- 
 debted for the first clear enunciation of the laws of com- 
 bination by weight, contrived a beautiful hyj)othesis to 
 account for them. In its simplest form it is known as 
 Dalton's atomic hypothesis. According to this view, 
 matter is composed of ultimate indivisible particles called 
 atom^ (dTo/jLo<;, indivisible). Every element has its own 
 atom, peculiar in properties and in weight. All com- 
 pounds are formed by the union together of elementary 
 
ATOMIC AND MOLECULAR HYPOTHESES. 
 
 91 
 
 atoms. The relative weights of the atoms are expressed 
 by their combining weights, and afford a simple reason for 
 those combining weights. Thus (taking the modern 
 numbers), 3,5 '5 parts of chlorine combine with 1 of 
 hydrogen, because every atom of chlorine is attracted by 
 and combines with one atom of hydrogen. In the same 
 way, every one atom of oxygen, weighing 16, combines 
 with two atoms of hydrogen, weighing 2. In fact, the 
 combining weights of the elements show the relative 
 weights of the atoms, hydrogen being taken as unity, and 
 this is the reason why the combining weights are generally 
 called atomic weights. It follows from this that the 
 ultimate particle — the smallest possible quantity — of any 
 compound must contain at least two different elementary 
 atoms. Compounds are groups of atoms of two or more 
 kinds. 
 
 Molecules, — Molecular Weights, — The ultimate particles 
 of compounds, consisting, as we have seen, of groups of 
 atoms, are called molecules (moleculus, small mass). Their 
 weight is, of course, the sum of the weights of their con- 
 stituent atoms. Thus the molecular weight of hydro- 
 chloric acid, HCl, is 36*5, and of water, 18. Keasons have 
 already been given for believing that the ultimate 
 particles of most elements, in the gaseous state, consist of 
 two or more similar atoms. The view adopted for com- 
 pounds must therefore be extended to elements, and we 
 must admit that in the gaseous state elements consist of 
 molecules incapable of division, which molecules them- 
 selves consist of atoms of similar kind, sometimes of only 
 one (mercury, zinc, and cadmium gases), sometimes of 
 two (hydrogen, oxygen, &c.), and sometimes of more 
 than two (ozone, phosphorus, arsenic, and sulphur gases). 
 
 By an extension of this view, the symbols and formuli^ 
 which are used to denote two volumes of any gas, 
 elementary or compound, can also be applied with equal 
 accuracy to denote respectively one atom and one molecule of 
 it. The atom of hydrogen may be denoted by H, the 
 molecule by H2 ; the atom of arsenic by As, the molecule 
 (as gas) by As^ ; ancl single molecules of hydrochloric 
 acid, steam, and ammonia may be represented by the 
 formulae HCl, H2O, and H3N. This leads us to another 
 
92 
 
 EXPERIMENTAL CHEMISTRY. 
 
 important hypothesis, wMcIl of late years has been very 
 generally adopted. It refers only to gases. 
 
 Hypothesis of Avogadro and Ampere, — This hypothesis, 
 suggested by Avogadro in 1811, and further developed by 
 Ampere in 1814, may be stated in the following terms : 
 
 Equal volumes of different gases, at equal pressure and 
 temperature, contain equal numbers of molecules. 
 
 This hypothesis explains two things. 
 
 1. The fact already mentioned (pages 34 and 57), that 
 all gases are equally affected in volume by variations of 
 pressure and temperature. Physical agencies, such as heat 
 and pressure, do not affect the nature of molecules, but 
 only their distance from one another, and this being the 
 same in all gases under similar conditions, the effect 
 produced by those agencies must naturally be the same in 
 all cases. 
 
 2. The law of gaseous volumes. If one molecule of 
 chlorine enters into chemical action with one molecule of 
 hydrogen, the same will be true of one thousand, or one 
 million, mokcules of each. Now by the hypothesis one 
 thousand, or one million, molecules of chlorine occupy a 
 space equal to that occupied by one thousand, or one 
 million, molecules of hydrogen, and it therefore follows 
 that the two elements should react together in the pro- 
 portion of equal volumes, which experiment proves to be 
 the fact. In like manner, two volumes of hydrogen react 
 with one volume of oxygen, because one volume of oxygen 
 contains and two volumes of hydrogen 2n molecules, and 
 every molecule of oxygen reacts with two molecules of 
 hydrogen. 
 
 Structure of Gases. — Summary of hypotheses. — The modem 
 doctrine may be summed up in these words. 
 
 1. Equal volumes of gases, at equal pressure and temperature, 
 cxmtain equal numbers of molecules. 
 
 2. Every molecule consists of one or more atoms, either 
 similar in hind (^elementary molecules^ or dissimilar in kind 
 (compound molecules).* 
 
 * The molecular hypothesis is sometimes ^referred to so loosely, that 
 a few further remarks upon it may not be out of {)lace. 
 
 1. The hypotliesis asserts nothing of the relative bulk of molecules, 
 or atoms. It does not assert that one molecule of hydrogen has the 
 
ATOMIC AND MOLECULAR HYPOTHESES 
 
 93 
 
 Molecules of Solids and Liquids. — The formulae applied to 
 gases are generally extended for convenience sake, but by 
 imperfect reasoning, to the same substances in the liquid 
 and solid state. But it is right to point out that neither 
 hypothesis nor experiment tell us anything of the number 
 of atoms contained in the molecules of solids and liquids. 
 We have good reason for believing that a molecule of 
 phosphorus- vapour contains four atoms ; but we do not 
 know how many a molecule of solid phosphorus may contain. 
 The formula for common salt, which is non-volatile, is 
 written NaCl, on account of its analogy, not with solid, 
 but with gaseous HCl. 
 
 Hypothesis to account for Valency. — The different equiva- 
 lent value of different elementary atoms can be accounted 
 for by supposing that each atom has the power of fixing 
 to itself a certain number of other atoms. It is as though 
 a carbon atom, for example, had four arms by which it 
 could grasp and be grasped by four hydrogen, or chlorine 
 atoms, or two oxygen, or sulphur atoms, each of the latter 
 having two arms of its own. It must, of course, be under- 
 stood that this is a mere illustration, for no one believes 
 that the atoms have real arms projecting from them. But 
 the illustration gives a lively idea of the hypothesis ; and 
 symbols are sometimes written with arms (called bonds) 
 proceeding from them. The following figures represent a 
 few of these atoms and their compounds : 
 
 Monad atoms H 
 Diad , , O 
 
 Triad , , N 
 
 same bulk as one molecule of chlorine, but only that n molecules of 
 hydrogen occupy, by their molecular movements, the same space as 
 n molecules of chlorine. 
 
 2. Similarly, the hypothesis does not assert that the bulk of an 
 atom of hydrogen is equal to the bulk of an atom of chlorine, but only 
 that two atoms of hydrogen and two atoms of chlorine occupy, respec- 
 
 Hydrochloric Acid H — CL 
 Water ^ — H 
 
 _H. 
 
 Ammonia N — H. 
 
 — H. 
 
 Methane C 
 
94 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The hypotliesis put in this form, appears somewliat 
 fanciful, but it harmonizes well with known facts, and has 
 the merit of assisting wonderfully in the comprehension of 
 the complex compounds of organic chemistry. 
 
 EQUATIONS, OR FORMULA OF CHEMICAL CHANGE. 
 
 Chemical changes of all kinds can be very conveniently 
 represented in the form of equations, the formulae for the 
 substances concerned being written in the first half, and 
 the formulae for the new substances produced in the other. 
 Thus the combination of zinc and chlorine is thus ex- 
 pressed : 
 
 Zinc. Chlorine. Zinc Chloride. 
 
 Zn" + CI2 = Zn" CI2; 
 
 which may be read in the following manner. One 
 molecule of zinc added to one molecule (two atoms) of 
 chlorine is equal to, or rather produces one molecule of 
 zinc chloride. 
 
 In making out an equation of this kind, it is necessary, 
 as with algebraical equations, to take care that eveiy 
 atom which appears in the first half shall duly appear and 
 be accounted for in the second. The following equation, 
 which expresses the oxidation of ethylene-gas, illustrates 
 this : 
 
 Ethylene. Carbonic Anhydride. Water. 
 
 C^H, + 3 O2 = 2 C + 2 0. 
 
 Two atoms of carbon, four of hydrogen, and six of oxygen 
 are concerned in the change, and it will be seen that 
 though differently arranged, they are all accounted for in 
 the second half of the equation. The large figures in the 
 above and in similar equations refer, it must be re- 
 membered, to the whole molecule. 2CO2, for instance, 
 means two molecules of carbonic anhydride, containing 
 together two atoms of carbon and four of oxygen. A few 
 more equations, one or two of them rather complex ones, 
 
 lively, by their atomic movements, the space of one molecule. The 
 atoms of matter may be almost infinitely small, as compared with the 
 molecules, and now tliat we know approximately the size of the mole- 
 cules we are no nearer to knowing that of the atoms. 
 
 A molecule of hydrogen may, for aught we know, be comparable to 
 an inflated bladder, with two peas rotating in it. 
 
EQUATIONS, OR FORMULAE OF CHEMICAL CHANGE. 
 
 95 
 
 may, with advantage, be studied in this place. They 
 represent chemical changes of several kinds. 
 
 Decomposition of water : 
 
 2 H2 0 = 2 H2 + O2. 
 Synthesis of water : 
 
 2 H2 + O2 = 2 H2 0. 
 
 Substitutions : 
 
 Sulphuric Acid. Zinc Sulphate. 
 
 Hj S O4 + Zn = Zn S O4 4- 
 
 Water. Potassium Hydrate. 
 
 2H2O + 2K = 2K0H + Hj. 
 
 Copper Chloride. Ferrous Chloride. 
 
 Cu CI2 + Fe = Fe CI2 + Cu. 
 Double decompositions : 
 
 Mercuric Potassium Mercuric Potassium 
 
 Chloride. Iodide. Iodide. Chloride. 
 
 Hg CI2 + 2 K I = Hg I2 + 2 K CI. 
 
 Potassium Hydrochloric Potassium 
 Hydrate. Acid. Water. Chloride. 
 
 KHO + HCl = H2O + KCl. 
 
 Copper Oxide. Nitric Acid. Water. Copper Nitrate. 
 
 CuO + 2HNO3 = H2O + Cu(N03)2. 
 
 Calcium Phosphoric Hydrochloric Calcium 
 
 Chloride. Acid. Acid. Phosphate 
 
 3CaCl2 + 2H3PO4 = 6HC1 + Ca3(P04)2. 
 The brackets in the two last examples will readily be 
 understood. Cu (N03)2 expresses that one atom of the 
 diad metal copper is united with two units of the monad 
 radical NO3. 
 
 One great advantage of these equations is that they 
 afford us the means of calculating the respective quantities 
 by weight in which bodies act on one another. Take, for 
 example, the above -described action of mercuric chloride 
 and potassium iodide. HgCl2 means one atom of mercury- 
 weighing 200 combined with two atoms of chlorine 
 weighing 35*5 x 2 = 71, total 271. KI means one atom 
 of patassium 39 and one atom of iodine 127, total 166 ; or, 
 as 2KI is employed, 332. We therefore know that 271 
 parts (pounds, grammes, or tons) of mercuric chloride will 
 act upon 332 parts of potassium iodide, and in a similar 
 
96 
 
 EXPERIMENTAL CHEMISTRY. 
 
 manner we can calculate that 454 parts of mercuric iodide 
 (Hgl2 = mercury, 200 + iodine, 127 X 2 = 254), and 
 149 parts of potassium chloride will be produced during 
 the change. Now suppose that a chemist has 100 grains 
 of mercuric chloride, and wishes to know how much 
 potassium iodide he must add to convert all the mercury 
 into iodide. He knows that 271 parts of the chloride will 
 require 332 of the iodide, and he has therefore only to 
 perform a simple proportion sum. 
 
 271 : 332 : : 100 : x = 122J grains. 
 
 In like manner he can readily find out that he ought to 
 obtain as the result of the action 167^ grains of mercuric 
 iodide and 55 grains of potassium chloride, for as 271 parts 
 of mercuric chloride yield 454 parts of mercuric iodide and 
 149 parts of potassium chloride, 
 
 271 : 454 : : 100 : a: = 1671 grains 
 and 271 : 149 : : 100 : a; = 55 
 
 In short, to sum up the whole reaction, 100 grains of 
 mercuric chloride, with 122^ grains of potassium iodide, 
 will yield 167^ grains of mercuric iodide and 55 grains of 
 potassium chloride. It is of course equally easy to find 
 out how much mercuric chloride and potassium iodide 
 must be employed to yield a certain weight, say 100 grains 
 of mercuric iodide. 
 
 When the equations refer to gases they have another 
 advantage. As every single formula for an element or 
 compound denotes two volumes of gas, the volumes of 
 different gases concerned in a reaction can at once be in- 
 ferred from the equation. In the equation given above 
 
 C2H,-f3 0^ = 2 0 0^ + 2 0, 
 
 C2 H4 means 2 volumes of ethylene, and 3O2 means 3x2 = 6 
 volumes of oxygen ; so that 2 volumes of ethylene require 
 6 volumes of oxygen for their complete oxidation. There 
 will be produced during the action, 2CO2, that is, 4 
 volumes of carbonic anhydride and 211^0, that is, 4 volumes 
 of steam. For if CO2 represents 2 volumes, 2CO2 must 
 evidently represent 4 volumes. It must not, however, be 
 forgotten that these relations of volume are only correct if 
 the pressure and temperature remain unaltered. If other- 
 
ACIDS, BASES, SALTS. 
 
 97 
 
 wise, a correction must be made by the methods already 
 given. 
 
 Taking the data already given, it is easy to calculate on 
 the metrical system the absolute volume of any gas yielded 
 by a certain weight of material, or the weight required to 
 produce a certain volume of gas at standard pressure and 
 temperature. 
 
 Examples, — 1. What weight of carbonic anhydride gas 
 can be obtained from 100 grammes of sodium carbonate ? 
 The equation is this — 
 
 Na2 C O3 + H2 S O4 = Na2 S O4 4- H2 0 + C O2. 
 106 44 
 106 grammes of the carbonate yield 44 grammes of the 
 gas. But as the formula for a gas always denotes 2 
 volumes, 44 grammes measure 22*4 litres. Hence 
 106 : 100 : : 22-4 : x = 21-1. 
 2. What weight of potassium chlorate must be decom- 
 posed if we wish to obtain 100 litres of oxygen ? 
 Equation — 
 
 2KC103 = 2KCl + 302. 
 Here 2KCIO3 = 245 grammes, and 3O2 = 96 grammes = 67*2 
 litres. Hence — 
 
 67-2 : 100 : : 245 : = 364-6. 
 
 ACIDS, BASES, SALTS. 
 
 Allusion has already been made in Chapter II. to certain 
 substances which have long been known under the respective 
 names of acids and bases. Acids are sour and redden litmus, 
 and bases, when soluble, have what is called an alkaline 
 taste, and turn the colour of reddened litmus back again to 
 blue. They have a kind of antagonistic function, and will 
 neutralize one another. When an acid acts on a base, a new 
 compound called a salt is produced, which commonly has 
 no action on either blue or red litmus. 
 
 But although in well-marked cases acids, bases, and salt 
 are so different from one another in properties, modem 
 chemistry has taught us that the compounds usually 
 known by those names bear so much resemblance to one 
 another and to other compounds in structure, that it is im- 
 possible to frame accurate definitions for them. If possible 
 
 H 
 
98 
 
 EXPERIMENTAL CHEMISTRY. 
 
 it would perhaps be as well to banish the terms altogether ; 
 but as that would produce great inconvenience, it is better 
 to take such imperfect definitions as we can get. 
 
 1. Acids, — An acid is composed of hydrogen with one of 
 those atoms, or groups of atoms, which are called acid radicals. 
 The hydrogen can he replaced hy metals, in v^hich case one of 
 the compounds called salts is formed. Acids redden litmus, 
 and are commonly sour. 
 
 The following are important examples: — Hydrochloric 
 Acid, HCl ; Nitric Acid, HNO3 ; Sulphuiic Acid, H2SO4 ; 
 Phosphoric Acid, H3PO4. In the first of these hydrogen 
 is united with the elementary acid radical CI, in the others, 
 with the compound radicals NO3, SO4, and PO4. 
 
 The imperfection of the definition will be apparent if we 
 remember that we can only define an acid radical as a 
 radical which, united with hydrogen, forms an acid. 
 
 Basity of Acids. — Acids are said to be monobasic, dibasic, 
 or tribasic, according as they contain one, two, or three 
 atoms of hydrogen which can be replaced by acids. In 
 the previous examples HCl and HNO3 are monobasic, 
 H2SO4 is dibasic, and H3PO4 is tribasic. Of course this is 
 equivalent to saying that the radicals of those acids are 
 monad, diad, or triad. PO4 is a triad radical, and its acid 
 may be written in this way, H3(P04)'". Acids which 
 contain more than one atom of replaceable hydrogen are 
 said to be polybasic. 
 
 Oxygen Acids, or Oxy-acids, — Most acids contain oxygen 
 as a part of their radical, and these are related in a very 
 simple manner to a particular series of oxides, which, for 
 that reason, are called acid oxides or anhydrides. When 
 one of these anhydrides combines with water, an acid is 
 formed, and when, on the other hand, water is removed 
 from an acid, the corresponding anhydride is obtained. 
 
 Nitilc 
 Anhydride. 
 
 Nitric Acid. 
 
 + H^O 
 
 2 H N O3. 
 
 Sulphuric 
 Anhydride. 
 
 Sulphuric 
 
 Acid. 
 
 S O3 + H, 0 
 
 Anhydride. 
 
 Phosphoric 
 
 Phosphoric 
 Acid. 
 
 P,0, + 3H,0 
 
 2H3PO4. 
 
ACIDS, BASES, SALTS. 
 
 99 
 
 One molecule of nitric anhydride, uniting with one of 
 water, forms two molecules of nitric acid. In a similar 
 manner, if from one molecule of sulphuric acid one mole- 
 cule of water be taken, one molecule of sulphuric anhydride 
 will remain. 
 
 It must not, however, be supposed the acids are always, 
 or even generally, prepared in practice from the anhydrides. 
 One anhydride, indeed, silicic anhydride, Si02, will not 
 combine directly with water, although its acid can be 
 obtained by indirect means. The anhydrides of many 
 acids have not yet been obtained, and a few, such as car- 
 bonic anhydride, CO2, are known to which no corresponding 
 acids can be proved to exist. The formula for carbonic 
 acid should be H2CO3. 
 
 The acid anhydrides are now very commonly named as 
 oxides. Thus SO3 is called sulphuric trioxide, and COg 
 carbon dioxide. 
 
 2. Salts. — A salt is a compound containing a metal and an 
 elementary or compound acid radical, 
 
 A salt only differs from an acid by containing a metal in 
 place of hydrogen. Taking, for example, the salts of sodium, 
 those corresponding to the acids already mentioned are — 
 
 Na CI Sodium chloride ; corresponding to H CI. 
 NaNOg „ nitrate „ HNO3. 
 
 Nag S O4 „ sulphate „ S O4. 
 
 Na3P04 „ phosphate „ H3PO4. 
 
 The proportion which the metal and radical bear to one 
 another depends of course on the valency of each. Thus 
 the chloride, nitrate, sulphate, and phosphate of the diad 
 metal calcium, and of the triad metal bismuth, are formu- 
 lated in this way : 
 
 Ca" CI2 Ca" (N 03)2 Ca" (S OJ Cei\ (P 0J\. 
 Bi'" CI3 Bi'" (N 03)3 Bi'"2(S 0,)\ Bi'"(P O4)'". ^ 
 
 In many salts of polybasic acids the hydrogen is only 
 partially replaced by metals. Thus we have — 
 
 Phosphoric Sodium-dihydrogen Disodium-hydrogen Sodium phcsphate. 
 Acid. Phosphate. Phosphate. Trisodiuai Phosphate. 
 
 H3 P O4. Na Ho P O4. Na2 H P O4. ^ ao P O4. 
 
 It will be seen from the above remarks that acids are 
 
 H 2 
 
100 
 
 EXPERIMENTAL CHEMISTRY. 
 
 really hydrogen salts. Some chemists indeed name them 
 accordingly, and call H2SO4 " hydrogen sulphate," instead 
 of sulphuric acid. The term acid is applied by them to 
 the anhydrides, so that the formula for sulphuric acid 
 becomes SO3. Many salts are known which are more or 
 less irregular in their composition, but modern chemical 
 theory enables us to give a tolerably satisfactory account 
 of all of them. 
 
 3. Bases. — A base is a metallic hydrate or hydroxide (that 
 is, a compound of a metal with the radical OH) which is 
 capable of reacting with acids to form salts. 
 
 As OH is a monad radical, the constitution of hydrates 
 is closely analogous to that of chlorides, nitrates, &c. For 
 example : 
 
 Sodium Hydrate. 
 
 Ka 0 H is like Na CI and Na N O3. 
 
 Calcium Hydrate. 
 
 Ca" (0 H)2 is like Ca" CI2 and Ca" (N Oa)^. 
 
 Bismuth Hydrate. 
 
 Bi'" (0 H)3 is like Bi'" CI3 and Bi'" (N 03)3. 
 Bases, like acids, are related to a particular series of 
 oxides called basic oxides. These oxides are sometimes 
 called bases. They differ from the true bases by the 
 elemejits of water. 
 
 Sodium Oxide. Sodium Hydrate. 
 
 Aa2 0 + H2O = 2NaH0. 
 
 Calcium Oxide. Calcium Hydrate. 
 
 Ca"0 + H2O = Ca"(H0)2. 
 
 Bismuth Oxide. Bismuth Hydrate. 
 
 Bi'"2 0''3 + 3H2O = 2Bi'"(HO)3. 
 Some basic oxides, however (bismuth oxide, for instance), 
 will not combine directly with water ; and, on the other 
 hand, some basic hydrates (sodium hydrate, for instance, 
 cannot be dehydrated by heat. Calcium oxide and hydrate 
 are examples of compounds which experience both changes 
 with ease. The oxide (quick lime) combines eagerly with 
 water, great heat is produced, and calcium hydrate (slaked 
 lime) is formed. When slaked lime is heated, water is 
 expelled, and quick lime once more obtained. 
 
 Ca"0 + H2 0 = Ca"(OH)2; 
 and Ca" (0 H)^ - II2 0 ^ Ca" 0. 
 
ACIDS, BASES, SALTS. 101 
 
 Formation of Salts, — Salts can be formed by a variety of 
 processes, a few of which may be specified here, with one 
 or two examples of each. It must not be supposed that 
 every process is practicable in all cases. 
 
 1. By the action of metals on acids : 
 
 H2 S O4 + Zn = Zn S O4 + K^. 
 
 2. By the action of metallic oxides on acids : 
 
 CaO + 2HC1 = CaCl2 + H2 0. 
 
 3. By the action of bases on acids : 
 
 NaOH + HCl = NaCl + H2 0; 
 Ca (0 H)2 + 2 H CI = Ca CI2 + 2 H2 0. 
 This is the case before referred to. 
 
 4. By the action of anhydrides on bases : 
 
 CO2 + 2NaH0 = Na2C03 + H2 0. 
 
 5. By the action of anhydrides on metallic oxides : 
 
 S O3 + Na2 0 = Na2 S O4. 
 
 It will be seen that in most of these reactions water is 
 formed simultaneously with the salt. 
 
 THE LAW OF NEWLANDS, OR THE PERIODIC LAW. 
 
 If the elements are arranged in the numerical order of 
 their atomic weights, it will be seen that, omitting hy- 
 drogen, the lower members arrange themselves in octaves 
 or groups of seven, and that starting from any one of 
 these elements, the eighth is in many physical and 
 chemical respects analogous to it. 
 
 H 1. Li 7. Be 9. B 11. C 12. N 14. 0 16. F 19. 
 Na 23. Mg 24. Al 27. Si 28. P 31. S 32. CI 35-5. 
 K 39. Ca 40. So 44. Ti 48. V 51. 
 
 Allowing for unknown elements, the table may be made 
 comprehensive, and the law is of daily increasing impor- 
 tance in chemistry. 
 
( 102 ) 
 
 PAET IL 
 NON-METALLIC ELEMENTS. 
 
 INTRODUCTION. 
 
 The old distinction between organic and inorganic chemistry 
 has faded away. It was formerly believed that vegetables 
 and animals had the power of producing in their organisms 
 chemical compounds which could not be formed artificially 
 in the laboratory. Vast numbers of compounds were 
 known which owed their origin directly or indirectly to 
 the animal or vegetable kingdom, and which could not be 
 obtained from any other source. To the department of 
 chemistry which dealt with such compounds, the name 
 " Organic Chemistry " was very properly applied. But 
 the progress of scientific research has taught us to manu- 
 facture a great number of these compounds from inorganic 
 materials, and there is therefore no longer any reason why 
 they should be separated from other compounds in a general 
 system of classification. 
 
 The so-called organic compounds have, however, one 
 feature in common. They all contain carbon, and it is 
 therefore convenient for purposes of study to retain them 
 in a separate department of chemistiy. Moreover, although 
 some few carbon compounds enter into the composition of 
 important minerals, a very large number of them bear 
 some direct or indirect relation to the processes of life, and 
 the term " organic " may therefore, in this limited sense, 
 still be applied to them. It is only necessary ^;o bear in 
 mind that what is still generally called organic chemistry 
 is but the chemistry of carbon compounds. In the present 
 division of the book we shall say as little about it as 
 possible. 
 
INTRODUCTION. 
 
 103 
 
 A less important distinction is that which is commonly 
 made between metallic and non-metallic elements. No 
 exact definition can be attached to the word metal, no one 
 property can be connected exclusively with it, and there is 
 no line of demarcation that can be drawn between the two 
 classes. We shall trouble ourselves very little with the 
 precise meaning of the word metal, but shall use it in its 
 current sense, and shall introduce the elements in the order 
 which appears most simple, and convenient, grouping them 
 according to their valencies. The present part contains an 
 account of the elements generally classed as non-metallic. 
 Part III. is devoted to the metals, and Part IV. to organic 
 chemis'try. 
 
( 104 ) 
 
 CHAPTEE I. 
 
 NON-METALLIC MONADS. 
 
 (Hydrogen, Chlorine, Bromine, Iodine, Fluorine.) 
 HYDKOGEN. 
 Symbol, H = 1. Formula, Hg. 
 This element in its chemical relations resembles the monad 
 metals. It stands alone among the non-metals, and it 
 must, for convenience, be studied first. 
 
 PREPARATION. 
 
 Hydrogen is a gas which can only be liquefied by intense 
 cold. It occurs in nature almost exclusively in a state of 
 combination, but various means are known by which it 
 can be set free and obtained in a state of purity. We 
 have already seen (p. 12) that when a current of electricity 
 from a tolerably powerful battery is transmitted through 
 water, acidulated with sulphuric acid, the water is de- 
 composed, oxygen goes to one pole of the battery and 
 hydrogen to the other; and both gases can easily be 
 collected. 
 
 Electrolysis of Water, — Other compounds containing hy- 
 drogen yield it up under similar treatment. 
 
 The ordinary processes for preparing hydrogen almost 
 all involve the use of some metal. A certain number of 
 the metals have the power of displacing hydrogen from 
 its combinations, either easily or with difficulty. For 
 common purposes zinc or iron is used. 
 
 Experiment 1. — Boil some water for fifteen minutes, that 
 all the air contained in it may be expelled ; let it cool, 
 and fill a bowl and a test-tube with it ; close the latter 
 with the finger, and invert the mouth of it under the 
 
HYDROGEN. 
 
 105 
 
 water in the bowl. Now wrap in a scrap of blotting-paper, 
 a piece of sodium of the size of a small pea, and thrust it 
 quickly under the mouth of the test-tube ; the metal being 
 lighter than water, ascends into the tube, floating there 
 with a rotatory motion ; a gas is evolved from the water, 
 and collects in the upper part of the tube. This gas is 
 hydrogen. The metal sodium displaces one half of the 
 hydrogen from water, in the manner shown in the follow- 
 ing formula : 
 
 2H2O -f 2Na = 2NaOH + H2. 
 
 The compound NaOH is called sodium hydrate. It 
 remains dissolved in the water, and may be obtained in a 
 pure state if the water is evaporated off. Close the tube 
 again with the finger, remove it from the bowl, and apply 
 a light to the mouth, the gas will burn with a flash of 
 light. This experiment proves hydrogen to be a combustible 
 gas. Pour into the bowl some solution of litmus, which 
 has been reddened with a drop of vinegar or other acid, 
 the litmus will be immediately changed to blue, showing 
 that sodium hydrate is one of the substances called 
 bases. 
 
 Experiment 2. — Lay a piece of blotting-paper on the 
 surface of some water contained in a saucer, and throw 
 upon it a small piece of sodium ; an energetic decomposition 
 of the water will take place, and in a few moments the 
 sodium will apparently burst into flame, and burn for 
 some time with an intense yellow colour. Tljis apparent 
 combustion of the sodium is really due to the burning of 
 the hydrogen, set free by that metal, which is inflamed by 
 the intense heat which accompanies its evolution. This 
 experiment differs only from the preceding one inasmuch 
 as in the former case the hydrogen is collected, while in 
 the latter it is burnt as it is liberated. The sodium hydrate 
 may be rendered evident as before by the addition of red 
 litmus solution to the water. 
 
 Experiment 3. — Throw a piece of potassium on some 
 water (the blotting-paper may be dispensed with in this 
 case), the same effect as in the preceding experiment will 
 occur, the water will be more violently decomposed, and 
 the hydrogen — but apparently the potassium — will burn 
 
106 
 
 EXPERIMENTAL CHEMISTRY. 
 
 instantaneously with a beautiful violet flame. Potassium 
 hydrate, KOH, remains in solution in the water. It is a 
 base like sodium hydrate. 
 
 Experiment 4. — What sodium and potassium accomplish 
 at ordinary temperatures, iron can do if it be heated to 
 redness. Pass water in the form of steam, obtained by 
 boiling the water in a flask, or a retort, through a red-hot 
 iron pipe, as a gun or gas barrel, containing small iron 
 nails or wire. At this high temperature the iron in the 
 pipe unites with the oxygen in the water, forming a black 
 oxide of iron, and the hydrogen is set free and may be 
 collected in the manner described below. The reaction is 
 as follows: 4H,0 + 3 Fe = FejO, + 4H3. 
 
 The best means, however, for obtaining hydrogen is by 
 the decomposition of an acid by iron or some other metal, 
 zinc being generally chosen for the purpose. 
 
 Collection of Gases. — For collecting con.siderable quantities 
 of gases the following contrivance, called a ^pneumatic trough, 
 may be used. Make a shelf out of slate or a piece of lead, 
 from three to four inches broad, and so long that it will 
 rest about half-way up the sloping sides of a pan or wash- 
 hand basin; cut a hole about half 
 ^^_^?_J_^ an inch in diameter through the 
 centre of the shelf, and having 
 placed the latter in position, pour 
 into the pan sufficient water to cover 
 it an inch deep. The shelf is for 
 the purpose of supporting the vessel 
 intended for the reception of the 
 gas, which, filled with water, is placed with its mouth 
 exactly over the hole. The gas to be collected is then 
 delivered from a tube, the extremity of which is placed 
 directly under the mouth of the inverted vessel. The 
 accompanying figure conveys an idea of the kind of 
 apparatus required. A rectangular box with a shelf at 
 one end, about two inches from the top, is more con- 
 venient. 
 
 Experiment 5. — Put half an ounce of granulated zinc * in 
 
 * Zinc is granulated by being melted in an iron ladle, and poured 
 from the height of a few feet into cold water. , 
 
HYDROGEN. 
 
 107 
 
 a bottle or flask, and pour over it a little water. No 
 action takes place, but if a small quantity of sulphuric 
 acid be gradually added, effervescence, and heating of the 
 mixture will ensue. The effervescence is caused by the 
 escape of hydrogen gas. Insert into the mouth of the 
 bottle a cork, which has previously been perforated and 
 fitted with a tube bent so that the mouth of it may be 
 conveniently placed beneath the hole in the shelf of the 
 pneumatic trough.* Allow time for the hydrogen to dis- 
 place the air contained in the flask and bent tube (two 
 or three minutes is sufficient if the effervescence is toler- 
 ably brisk). While the air is being expelled, preparation 
 may be made for collecting the gas by filling several 
 bottles quite full of water. One of the bottles is then 
 closed with a smooth card or glass plate, and rapidly in- 
 verted in the pneumatic trough with its mouth directly 
 over the hole in the shelf. The tube being then placed 
 beneath, the gas will ascend and displace the water in the 
 bottle. When the entire displacement is effected the 
 bottle is corked or stoppered while still in the trough, 
 removed and replaced by another bottle, inverted in the 
 same manner, and so on until the evolution of gas ceases. 
 
 There is one indispensable caution to be observed in 
 experimenting with hydrogen, which is, not to begin to 
 collect the gas until all the atmospheric air 
 existing in the flash has been expelled, as other- ^^S- ^8. 
 wise an explosion might take place. To be 
 quite safe, it is as well to reject the first 
 bottleful of hydrogen collected. 
 
 PROPERTIES. 
 
 Experiment 6. — Inflame hydrogen contained 
 in a bottle, and immediately pour in some 
 water. The water does not extinguish the 
 flame, but rather increases it, since it rapidly 
 forces the gas out of the flask. The gas does not burn in 
 
 * Instead of a rigid glass tube, it is more convenient for tins and 
 similar purposes to carry the gas to the pneumatic trough by means of 
 a piece of india-rubber tubing, of about one-eighth of an inch internal 
 diameter. It may be slipped over a short piece of glass tubing which 
 passes through the cork. 
 
108 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the interior of the vessel, but only on the outside, where 
 it is surrounded by atmospheric air. 
 
 Experiment 7. — Open a bottle of hydrogen under an 
 inverted tumbler, and, after a minute or two, apply a 
 lighted taper to the mouth of the tumbler. A flame will 
 burst forth from the tumbler with a slight report. The 
 gas has ascended from the bottle into the tumbler, and is 
 consequently lighter than common air. In this experiment 
 the lower vessel must not be immediately exposed to the 
 lighted taper, because, if all the hydrogen is not displaced, 
 an explosion might ensue that might break the bottle ; 
 but if the taper be applied after a few minutes have 
 elapsed, the bottle will be found no longer to contain any 
 combustible gas, the gas having entirely escaped. 
 
 Hydrogen is the lightest of all gases. Its specific gravity 
 is 1, and 14^ measures of it weigh only as much as one 
 measure of atmospheric air. On account of this lightness, 
 it may be used for filling balloons. 
 
 Experiment 8. — If, instead of the glass tube, a piece of 
 tobacco-pipe or a short piece of glass tube drawn out at 
 one end to a jet be adapted to the cork of the 
 flask from which hydrogen was evolved, and 
 the gas then lighted, it will burn like a taper. 
 To kindle the gas, instead of a match or a 
 taper, very finely divided platinum may be 
 employed. This can be prepared in a few 
 minutes by dropping a solution of platinum 
 chloride on blotting-paper, attaching it to a 
 wire, and igniting it over a spirit-lamp, till 
 nothing but a grey coherent ash remains. The 
 platinum is thus reduced to an extremely 
 minute state of subdivision, and in this state 
 it exhibits the remarkable property of igniting in hydrogen 
 and inflaming it. It is called spongy platinum, and is 
 employed as tinder in the well-known Dohhereiner's lamp. 
 A sheet of "platinum leaf," prepared like gold leaf, is 
 excellent for the experiment. It is well to heat it to 
 redness first. 
 
 Experiment 9. — To observe the remarkable lightness of 
 hydrogen, a small balloon of gold-beater's skin may be 
 filled with hydrogen by means of the apparatus used in 
 
HYDROGEN. 
 
 109 
 
 Experiment 5. The balloon is squeezed flat to expel the 
 air, and the tube delivering the gas is passed a short way 
 into its orifice, and secured there with a piece of thread. 
 When the inflation is complete, the tube is withdrawn, 
 and the twine tightened simultaneously, thus preventing 
 any escape of gas. The balloon, if unimpeded, will then 
 ascend to a great height. It may be made captive with a 
 piece of thread. 
 
 Experiment 10. — Pour the contents of the flask in which 
 the hydrogen was generated (Experiment 5) into a porce- 
 lain dish, boil until they are reduced in bulk to one-half 
 or thereabouts, and filter them. A black residue will 
 remain on the filter, which consists of the impurities con- 
 tained in the zinc ; the zinc itself has been dissolved, and 
 has been converted into a salt called zinc sulphate, which, 
 on the cooling of the solution, is deposited in colourless 
 crystals. The reaction which takes place between zinc 
 and sulphuric acid is represented by the following 
 equation : 
 
 Sulphuric Acid. Zinc. Zinc Sulphate. Hydrogen. 
 
 H2SO4 + Zn = ZnSO^ + H2. 
 
 CHLOEINE. 
 Symbol, CI = 35*5. Formula, CI2. 
 
 Chlorine is one of a group, the members of which are 
 characterized by a remarkable similarity of chemical 
 properties. It consists of the elements chlorine, bromine, 
 iodine, and fluorine, the three first of which are often 
 termed halogens (from aAs, sea-salt), in allusion to their 
 marine origin. 
 
 Chlorine is a greenish-yellow gas, 2^ times heavier 
 than air, suffocating and irrespirable unless very much 
 diluted with air. Its odour, when very dilute, is some- 
 what like that of sea-weed, a peculiarity which it shares 
 with the other halogens. Chlorine occurs only in com- 
 bination ; chiefly with sodium as common salt (sodium 
 chloride, NaCl), which forms immense deposits in England 
 and elsewhere, and is the chief solid ingredient of sea- 
 water. 
 
110 
 
 EXPERIMENTAL CHEMISTRY. 
 
 PREPARATION. 
 
 Experiment 1. — Pour one ounce and a half of hydrocUoric 
 acid upon a quarter of an ounce of finely-powdered black 
 oxide of manganese, and heat it gradually in a flask, to 
 which is adapted a bent glass tube ; a yellowish-green gas 
 
 is disengaged, which is col- 
 lected by the process already 
 described. The pneumatic 
 trough is, however, filled with 
 warm water instead of cold. 
 This gas is chlorine (from 
 xA.wpo?, green). Fill with it 
 several six-ounce bottles of 
 white glass, and cork them 
 up. Fill, likewise, a bottle 
 with two-thirds of chlorine 
 and one-third of water, and 
 shake it up ; suction is exerted 
 upon a finger which closes 
 the mouth of it, — a proof that a vacuum has been pro- 
 duced. If the finger be removed, the air immediately 
 rushes in. This vacuum was caused by the chlorine 
 having dissolved in the water, which might be inferred 
 also from the disappearance of the yellow colour from the 
 upper part of the bottle. One measure of cold water 
 dissolves two measures of chlorine. This solution is 
 called chlorine water. 
 
 The mode in which chlorine is formed in this experiment 
 is shown in the following formula : 
 
 Manganese Manganese 
 Peroxide. Chloride. 
 
 Mn02 + 4HC1 = MnCl2 + 2H2O -f CI2. 
 
 When the evolution of gas has quite ceased the liquid 
 in the flask may be filtered and evaporated, when it will 
 yield on cooling pink crystals of MnCl2. 
 
 Experiment 2. — Chlorine may also be prepared from 
 common salt by mixing three quarters of an ounce of it 
 with half an ounce of black oxide of manganese, two 
 ounces of sulphuric acid, and one ounce of water, and 
 heating the mixture : 
 
 2NaCl+Mn02+3H2S04 = 2NaHS04-t-MnS04 4-2H20+Cl2 
 
CHLORINE. 
 
 Ill 
 
 Chlorine acts as a poison on being inhaled ; hence, care 
 must he taken not to inhale it while preparing it. For greater 
 security, pour some drops of alcohol and ammonia upon a 
 cloth and wave it frequently in the air ; the chlorine con- 
 tained in the air will then be so altered that it will lose 
 its injurious properties. 
 
 PROPERTIES. 
 
 Experiment 3. — In order to recognise the odour of chlo- 
 rine, smell chlorine water (but not the gas) cautiously ; 
 the chlorine water may be tasted also without danger. 
 
 Experiment 4. — If a flask containing chlorine gas be 
 exposed to the air for a short time, no diminution of the 
 chlorine will be perceptible ; but if the flask be inverted 
 it will soon contain only atmospheric air. Chlorine is 
 two and a half times heavier than common air, and may be 
 easily poured from one vessel to another like water with- 
 out material waste ; its specific gravity is 35*5 (H = 1). 
 
 Experiment 5. — Introduce a piece of litmus-paper into 
 chlorine gas, and it becomes white ; pour chlorine water 
 upon red wine, and ink, and both the liquids will lose 
 their colour. Chlorine bleaches and destroys most colours 
 derived from the animal or vegetable kingdom. In consequence 
 .of this property, chlorine has become a most important 
 agent in bleaching; and linen, cotton, paper, and other 
 materials, may be rendered perfectly white by it in a few 
 hours ; while, by the old method of laying them on the 
 grass in the sun, weeks, and even months, were required 
 for effecting it. Substances called antichlors are some- 
 times used to remove the last traces of chlorine. Sodium 
 thiosulphate is the most powerful. The modern method 
 of bleaching is very excellent, and does not injure the 
 strength of the fabric, provided all the chlorine be com- 
 pletely removed after the bleaching is finished, which is 
 not so easily done as might be supposed. If this precau- 
 tion be not observed, or if the chlorine water be too strong 
 or in excess, then, indeed, after the colour is destroyed, the 
 fibres of the yarn or fabric itself will be attacked. The 
 substance commonly called chloride of lime is now used 
 instead of chlorine. It is a salt from which chlorine is 
 easily disengaged, even by mere exposure to the air. 
 
112 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 6. — Apply chlorine water to decaying and 
 nauseous substances (water in which flowers have been 
 kept, manure, rotten eggs, &c.) ; the bad odour will at 
 once entirely vanish. Thus it not only decomposes colours, 
 but also the volatile combinations formed during putrefac- 
 tion, and which occasion disagreeable odours. It acts in 
 a similar manner also upon morbific matter (matters of 
 contagion, miasmata), which, being diffused in the air or 
 attached to clothes and beds, may communicate disease. 
 Chlorine is, therefore, a powerful disinfecting agent, and is 
 used for purifying putrefying matter and infected atmo- 
 spheres. Musty casks may also be purified by washing them 
 first with chlorine water, and then with some milk of lime. 
 Mouldy cellars, in which milk or beer cannot be kept 
 without turning sour, are again rendered serviceable for a 
 long time by fumigating them with chlorine-gas, or by 
 washing them with chlorine water, or a solution of chloride 
 of lime. 
 
 Experiment 7. — Fill a small bottle with chlorine water, 
 and invert it in a vessel filled with water ; if this is put 
 away in a dark place, it remains unchanged ; but if it is 
 exposed to the sun, a colourless gas will collect in the 
 upper part of the flask, in which a glowing taper will 
 inflame; this gas is oxygen. After some days the water, 
 will entirely lose its odour of chlorine, and will have 
 acquired a sour taste, and instead of bleaching blue litmus- 
 paper, it will redden it. Three elements only were present, 
 the constituents of water and chlorine ; thus it is obvious 
 that the chlorine must have united with the hydrogen of 
 the water to form hydrochloric acid, the oxygen being set 
 
 H^O + CI2-2HCI + 0. 
 
 Bottles in which chlorine water is kept should, there- 
 fore, be protected from the light, and this can be most 
 conveniently done by pasting black paper round them. 
 
 The bleaching and disinfecting power of chlorine is 
 now easily explained by its strong affinity for hydrogen. 
 All animal and vegetable substances contain hydrogen, 
 which is taken from them by chlorine. By the abstraction 
 of the hydrogen, the colouring matter becomes colourless, 
 the odorojis principles scentless, the morbific matter in- 
 
CHLORINE. 
 
 113 
 
 noxious, insoluble substances are very frequently rendered 
 soluble, &c. 
 
 Experiment 8. — Provide two bottles of chlorine, and 
 place in one of them some dry calcium chloride. This 
 salt eagerly absorbs water, and will thoroughly dry any 
 gas in contact with it. In a few hours introduce a piece 
 of blue litmus-paper into the dry chlorine ; no change in 
 the litmus will be apparent, or, at most, it will be but 
 slightly reddened. Perform the same operation in the 
 other bottle, and the litmus-paper will be rapidly bleached ; 
 proving that the presence of water is necessary to enable 
 chlorine to exert its power in this respect. 
 
 Experiment 9. — Put into clilorine water some gold-leaf ; 
 it will soon disappear, as the element chlorine combines 
 with the element gold. The combination is called auric 
 chloride; it is soluble in water. Chlorine has a very great 
 tendency to combine with the metals. These combinations 
 comport themselves as salts ; they are called metallic 
 chlorides, and most of them are soluble in water. 
 
 Experiment 10. — Pour into a vessel filled with chlorine- 
 gas a little metallic antimony, in fine powder ; it wdll fall 
 in a red-hot state to the bottom, as though it were a 
 shower of fire. The red heat is caused by the violent 
 combination of the chlorine with the antimony. The 
 white smoke which fills the flask is the new combination 
 formed, viz., antimonic chloride. If a fine brass wire, on 
 which a piece of tinsel (Dutch gold) has been fastened, be 
 introduced into chlorine-gas, both will burn with vivid 
 combustion, and with the emission of fumes. Here com- 
 bustion is another name for combination with chlorine. 
 Brass consists of zinc and copper : accordingly, chlorides 
 of zinc and copper are formed. Both dissolve in water, 
 and the copper chloride imparts to the solution a green 
 tinge. 
 
 Experiment 11. — If a piece of sodium of the size of a pea 
 is thrown into a cup containing chlorine water, it will 
 move rapidly round, just as in common water, with a 
 hissing noise, and finally disappear ; but if a sufficient 
 quantity of the chlorine was present, the liquid will not 
 afterwards give a basic reaction, as in Experiments 1 and 
 2, Hydrogen ; neither will it have an alkaline, but a saline 
 
 I 
 
114 
 
 EXPERIMENTAL CHEMISTRY. 
 
 taste. If allowed to evaporate gradually over a warm 
 stove, small cubic crystals remain behind, the constituents 
 of which are chlorine and sodium. Thus, from these two 
 elements a salt has been formed, familiarly known as 
 common salt, NaCl. 
 
 Chlorine, like oxygen and sulphur, often unites in 
 several proportions with a substance. Thus, there are 
 two different chlorides of mercury. 
 
 HYDROCHLORIC ACID, HCl. 
 
 Experiment 1. — Put into a porcelain capsule a few grains 
 of common salt, and pour a little sulphuric acid upon it ; 
 there escapes, with effervescence, a gas, which has an acid 
 taste, fumes in the air, and reddens moistened blue test 
 paper ; this gas is muriatic acid, or hydrochloric acid. If 
 you pour some ammonia upon a shaving, or slip of paper, 
 and wave the latter to and fro over the capsule, a thick 
 white smoke is formed ; and the odour of both the hydro- 
 chloric acid, and also the pungent fumes of the ammonia, 
 vanish. The two gases combine and form solid ammonium 
 chloride : 
 
 NH34-HCI = NH.Cl. 
 Experiment 2. — Mix carefully in a flask a quarter of an 
 Fig. 41. 
 
 ounce of water with three-quarters of an ounce of sulphuric 
 acid, and after the mixture has become cold, add to it half 
 an ounce of common salt. Adapt to the neck of the flask 
 
HYDROCHLORIC ACID. 
 
 115 
 
 a cork provided with a glass tube, the long limb of which 
 passes into a phial, containing one ounce of water. It' you 
 heat the flask in a sand-bath, the hydrochloric acid escapes, 
 but more quietly than in the former experiment, because 
 the sulphuric acid has been somewhat diluted. The tube 
 must only just dip into the water ; for should it reach to 
 the bottom of the phial, the whole liquid might suddenly 
 flow back into the flask, if the heat should chance to 
 slacken, as it might, for instance, from the flickering of 
 the lamp by an accidental current of air. The hydro- 
 chloric acid is so eagerly absorbed by the water, that, 
 when the evolution of the gas diminishes, a vacuum is 
 formed in the tube and flask ; the pressure of the exterior 
 air then forces the water up into the flask. When a 
 gaseous body condenses into a liquid, it no longer requires 
 the latent heat by which it became gas or vapour, and 
 therefore this heat is set free. From this it follows that 
 the water in which the acid condenses or dissolves must 
 soon become warm. But warm water takes up much less 
 gas than cold; accordingly, in order to obtain a concen- 
 trated solution of hydrochloric acid gas, we must place 
 the phial in a basin of cold water. When the liquid in 
 the receiver has sufliciently increased, one of the blocks 
 must be withdrawn from beneath, so as to keep the end of 
 the tube near the surface of the liquid. The solution thus 
 obtained has an intensely acid taste and reaction ; it is 
 called hydrochloric acid, but is often known by the name of 
 muriatic acid. One measure of cold water absorbs more 
 than four hundred measures of hydrochloric acid gas ; the 
 strong hydrochloric acid thus obtained fumes in the air, 
 because a part of the gas escapes. If you heat it to boiling 
 then half of it escapes, and an acid only half as strong 
 remains behind ; but this is always somewhat heavier than 
 water. 
 
 The hydrochloric acid of commerce is commonly 
 yellow, and contaminated with sulphurous acid, sulphuric 
 acid, chlorine, iron, and arsenic. It is manufactured from 
 common salt and sulphuric acid ; but, instead of glass 
 vessels, large iron retorts are employed, capable of con- 
 taining some hundredweights of common salt. The gas 
 is conducted into several bottles or jars filled with water, 
 
 I 2 
 
116 
 
 EXPERIMENTAL CHEMISTRY. 
 
 and connected with each, other. When the water in the 
 first vessel becomes saturated with the hydrochloric acid 
 Fi^. 42. gas, the gas passes over 
 
 into the second, then into 
 the third vessel, and so on, 
 saturating each succes- 
 sively. This is a very con- 
 venient method of conduct- 
 ing gases through liquids. 
 Such vessels, which are 
 commonly provided with 
 two or three necks, are called Woulf^s bottles. The upright 
 tube in the middle neck serves as a safety tube, that is, it 
 prevents the liquid from being forced back ; if a vacuum 
 is formed in one of the bottles, the air enters through this 
 tube. 
 
 Experiment 3. — If instead of dipping into water, the 
 delivery-tube is passed to the bottom of a dry bottle, the 
 heavy gas will displace the air, and fill the bottle. Its 
 solubility may then be shown by inverting the bottle 
 quickly in water. The water will rush up and fill the 
 bottle. 
 
 Common salt consists of chlorine and sodium. 
 
 With 
 
 sulphuric acid the following change takes place : 
 
 Sodium 
 Chloride. 
 
 NaCl 
 
 Sulphuric 
 Acid. 
 
 Acid Sodium 
 Sulphate. 
 
 = NaHSO, 
 
 Hydrochloric 
 Acid. 
 
 HCl. 
 
 4- H2SO4 = NaHSO^ + 
 
 The constituents of hydrochloric acid gas are equal 
 atoms of chlorine and hydrogen, and it is represented by 
 the formula HCl. 
 
 If you fill a glass vessel half with chlorine and half with 
 hydrogen, and put it in a dark place, no union ensues ; 
 but it takes place instantaneously when a light is applied 
 or when the vessel is exposed to the direct rays of the sun. 
 The union is accompanied by a violent detonation, which 
 often breaks the vessel, so that it is not advisable to 
 perform this experiment except on a very small scale. In 
 the diffused light of day the combination takes place 
 slowly. 
 
 Experiment 4. — Put some iron nails into a phial, and pour 
 upon them some hydrochloric acid ; brisk effervescence 
 
HYDROCHLORIC ACID. 
 
 117 
 
 will ensue. When tliis has continued some minutes, hold 
 a burning taper over the mouth of the phial ; the gas 
 which escapes takes fire ; it is hydrogen. The acid is 
 decomposed, and its second constituent, chlorine, combines 
 with the iron. The iron disappears, and is dissolved; 
 that is, it combines with the chlorine, forming a soluble 
 compound. When the effervescence has ceased, heat the 
 phial by placing it in hot water, and afterwards pour its 
 contents upon a filter of white blotting-paper. Put the 
 liquid which passes through (the filtrate) in a cool place ; 
 a salt is deposited from it in greenish crystals, called 
 ferrous cJiloride, reCl2. 
 
 Many other metals are also dissolved, like iron, by hy- 
 drochloric acid, and converted into chlorides. 
 
 Experiment 5. — Pour some hydrochloric acid upon iron- 
 rust that has been put into a test-tube ; it dissolves, but 
 without evolution of gas. In this case, the hydrogen of 
 the hydrochloric acid meets with a body with which it 
 can combine, namely, the oxygen of the oxide or rust of 
 iron ; and it does combine with it, forming water. The 
 yellowish-brown solution, which is difficult to crj^stallize, 
 yields, upon evaporation, a brown mass called ferric 
 chloride, re2Clg. This salt contains one half more chlorine 
 than the former. Hydrochloric acid is very often used 
 for dissolving metallic oxides. 
 
 Experiment 6. — Dissolve some of the ferrous chloride, 
 obtained according to Experiment 4, in a little cold water, 
 and then add some chlorine water ; the greenish colour 
 is converted into a yellow colour, and the solution 
 yields, on evaporation, brown ferric chloride. The chlorine 
 converts the ferrous chloride into ferric chloride. 
 
 Experiment 7. — Dissolve some carbonate of soda (sodium 
 carbonate) in water ; the solution turns red test-paper 
 blue; it has a basic reaction. Drop carefully into the 
 solution some hydrochloric acid, until neither the red nor 
 the blue paper is affected by it. If you put the liquid in 
 a warm place a salt will be deposited in small cubes ; you 
 readily perceive, both by the shape of the crystals and by 
 the taste, that it is common salt. Carbonic anhydride 
 escapes with effervescence. 
 
 Experiment 8. — To a little water in a test-tube add a 
 
118' 
 
 EXPERIMENTAL CHEMISTRY. 
 
 drop of hydrochloric acid or a grain of a soluble chloride, 
 such as common salt, and then a few drops of a solution 
 of silver nitrate (lunar caustic) ; a white cloudiness is 
 formed which does not happen in pure water. This 
 cloudiness or precipitate is due to the formation of silver 
 chloride, which is insoluble in water, but it may be dis- 
 solved by adding some solution of ammonia. Nitrate of 
 silver is a most accurate test for hydrochloric acid or for 
 chlorides : 
 
 Ag N O3 + Na CI = Ag CI + Na N O3. 
 BKOMINE. 
 Symbol, Br = 80. Formula, Br2. 
 
 Bromine is a deep brownish-red, heavy, and very 
 volatile liquid. Its name is derived from the Greek word 
 PpCjfjios, signifying a disagreeable odour. Bromine, at 
 common temperatures, emits yellowish-red fumes, which 
 have a penetrating and offensive odour, resembling that 
 of chlorine. It produces a yellow colour with starch, is 
 sparingly soluble in w^ater, but very soluble in ether. 
 Its specific gravity is 3. 
 
 Bromine occurs in many mineral waters, some of which, 
 as the Kreutznach spring, are comparatively rich in it, 
 and form the source from whence much of it is obtained 
 on the Continent. A very considerable supply is also 
 derived from sea-water. A large quantity of common 
 salt is obtained by evaporating sea-water, and it is from 
 the residual liquid, which is technically called bittern, 
 that bromine is obtained. The bittern is mixed in a re- 
 tort with manganese peroxide, and hydrochloric acid. 
 On the application of heat the chlorine liberated from the 
 acid decomposes the magnesium bromide contained in the 
 bittern, and bromine, mixed with water, distils over : 
 
 MgBr2 + Cl2 = MgCl2-f Br^. 
 
 The bromine may be separated from the water by shaking 
 it with ether or chloroform. The ethereal solution, which 
 has a brown colour, floats on the water and can be drawn 
 off. The bromine is then extracted by a somewhat 
 complex process. 
 
 Experiment 1. — The processes for the preparation of 
 
BKOMINES — IODINE. 
 
 119 
 
 bromine may be imitated by the student by dissolving a 
 few grains of potassium bromide in a little water contained 
 in a long test-tube ; this may represent the bittern. A 
 little chlorine water will liberate the bromine, and the 
 solution will become brown. If a drachm or two of ether 
 is then added and the mixture violently shaken for a 
 minute, the ether will remove all the bromine, and on 
 standing a little while will float as a dark layer on the 
 surface of the water. Pour ofi' the dark-coloured ether into 
 a porcelain basin, and add a few drops of potassium 
 hydrate (caustic potash) ; it will become colourless. Heat 
 it gently until all the liquid is driven off and a white 
 substance will remain behind, which on cooling may be 
 mixed with a few grains of manganese peroxide, and two 
 or three drops of sulphuric acid, and again heated. Free 
 bromine will then be evolved as brown vapours, very 
 readily seen against the white sides of the basin. 
 
 Experiment 2. — Pour a few drops of bromine into a small 
 phial with some distilled water, and shake the mixture 
 well. The bromine will partly dissolve and form a brown 
 solution. This may be preserved and labelled " Bromine 
 solution." 
 
 Experiment 3. — Add a few drops of the above solution to 
 a little very weak mucilage of starch, made by mixing a 
 few grains of starch with a little cold, and then adding a 
 considerable quantity of boiling water, with continual 
 stirring. A pale yellow colour will be produced, owing 
 to the formation of bromide of starch. 
 
 Experiment 4. — To a drop of bromine contained in a 
 wine-glass add a minute fragment of phosphorus, which 
 must be cut off under water, as it is very inflammable, 
 and carefully and quickly dried in a piece of blotting- 
 paper. The best plan is to drop the phosphorus from the 
 point of a knife on to the bromine. The phosphorus will 
 be immediately inflamed, and a smart explosion will occur. 
 
 IODINE. 
 
 Symbol, I = 127. Formula, 1^, 
 Iodine is a black solid of metallic lustre ; it smells some- 
 what like chlorine, has a pungent taste, and stains the 
 skin brown. 
 
120 
 
 EXPERIMENTAL CHEMISTRY. 
 
 It occurs in small quantity in sea-water, from which it 
 is separated and assimilated by the various sea-weeds, 
 which thus accumulate a considerable quantity ; and it is 
 from the ashes of certain kinds of sea- weeds that iodine is 
 always obtained, for sea-water contains much too small a 
 quantity to render its extraction profitable. The sea- weed 
 is burnt and the ash, or help^ as it is called, contains the 
 iodine in the forms of magnesium iodide, Mgl2, and 
 sodium iodide, Nal, and also corresponding bromides. 
 The kelp, after some preliminary treatment, is heated 
 with black oxide of manganese and sulphuric acid, and 
 yields iodine and bromine, just as the chlorides yield 
 chlorine when treated in the same way. 
 
 Experiment 1. — To a few grains of potassium iodide, or 
 some other iodide, in a test-tube, add an equal weight of 
 black oxide of manganese, and a drop or two of sulphuric 
 acid, and heat gently. Beautiful violet vapours of iodine 
 will be produced, and will condense on the sides of the 
 test-tube as black, shining spangles. The following 
 change occurs : 
 
 2KI + Mn02 + 2H2SO4 = K2SO4 + MnSO^ + 2H2O + \. 
 
 Experiment 2. — Dissolve a grain or two of potassium 
 iodide in a little distilled water in a test-tube, and add a 
 little solution of silver nitrate. A light yellow precipitate 
 (silver iodide) will be thrown down, which will not be re- 
 dissolved on the addition of solution of ammonia, thus 
 clearly distinguishing it from the similar white precipitate 
 obtained with chlorides. 
 
 Experiment 3. — Put 24 grains of iodine into a flask, and 
 pour over them half an ounce of strong alcohol ; if the 
 iodine is pure it will entirely dissolve. This dark brown 
 solution is called tincture of iodine. Water dissolves only 
 a trace of iodine, iait yet is rendered yellow by it. 
 
 Experiment 4. — I'ut a little iodine upon a knife, and 
 hold it over the flame of a lamp ; the iodine melts, and is 
 afterwards converted into a violet- coloured gas — vapour of 
 iodine. As the iodine fumes are nearly nine times heavier 
 than common air, they sink in it. Iodine owes its name 
 to the colour of its vapour, the Greek word twSr;? meaning 
 violet coloured. The vapour appears more beautiful 
 
FLUORINE. 
 
 121 
 
 when the iodine is heated in a small flask. After cooling, 
 the walls of the flask become lined with small brilliant 
 crystals of solid iodine, affording an example that re- 
 gular crystals may be formed when bodies pass from the 
 aeriform into the solid state. 
 
 Experiment 5. — Boil one grain of starch in a test-tube 
 with one drachm of water, and after cooling add to the 
 thin paste thus obtained a few drops of tincture of iodine ; 
 the iodine combines with the starch ; the combination is of a 
 deep blue colour. The blue colour disappears on careli 1 
 heating, but returns again on cooling. If one drop of the 
 starch paste is mixed with one quart of water, even at 
 this extreme dilution, the iodine tincture will impart to it 
 a violet tinge. Consequently it is an exceedingly delicate 
 test for starch, and starch, on the other hand, for iodine. 
 If a little tincture of iodine is dropped upon flour, bread, 
 potatoes, &c., the presence of starch in these substances 
 will at once be indicated. 
 
 COMPOUNDS OF BROMINE AND IODINE WITH HYDROGEN. 
 
 Hydrobromic Acid, HBr, and Hydriodic Acid, HI. — Both 
 of these acids closely resemble hydrochloric acid. They 
 are colourless gases, which fume strongly in air, and are 
 readily soluble in water, forming acid solutions. With 
 bases they form iodides and bromides : 
 
 KOH +HBr = + KBr, 
 KOH + HI =H20+ RI. 
 
 Both bromine and iodine are faithful companions of 
 chlorine ; wherever common salt occurs, whether in the 
 earth, the sea, or mineral springs, small quantities of 
 them are present, not in a free state, however, but com- 
 bined with metals. The different sea-weeds attract these 
 combinations from the sea- water, and from these sea- weeds 
 iodine and bromine are extracted. Both have poisonous 
 properties. 
 
 FLUORINE. 
 Symbol, F = 19. Formula unknown. 
 
 Fluorine is unknown in its isolated state. When 
 liberated from its compounds it acts energetically on all 
 
122 
 
 EXPERIMENTAL CHEMISTRY. 
 
 substances of which vessels are ordinarily made. The 
 mineral known as fluor-spar consists of fluorine and 
 calcium. 
 
 Hydrofluoric Acid, HF. 
 
 Experiment 1. — Fashion a small basin out of a piece of 
 thin sheet lead, place in it about a quarter of an ounce of 
 powdered fluor-spar, and half an ounce of strono: sulphuric 
 acid, and apply a gentle heat. Fumes of hydrofluoric acid 
 gas will arise, which are ex^tremely irritating to the eyes, 
 and which resemble those of hydrochloric acid. Fluor-spar 
 (calcium fluoride) is decomposed by sulphuric acid just as 
 common salt is : 
 
 Ca F2 + H2 S O4 = Ca S O4 -f 2 H F. 
 
 Hydrofluoric acid is intensely corrosive, and it attacks 
 and destroys glass and earthenware and most other 
 materials. But it does not act upon lead ; therefore 
 vessels made of that material must be used to prepare it 
 in. The most interesting property of hydrofluoric acid is 
 its power of corroding glass, and it is often used in the 
 arts to etch designs upon glass, which is done in the 
 following manner. 
 
 Experiment 2. — Thoroughly warm a small square of 
 window glass, and then rub over one side of it with a 
 piece of wax, so as to make a smooth coating. When the 
 glass has become cold and the wax hard, scratch any 
 design with a pointed instrument on the coated side of 
 the plate, taking care to cut quite throuiih the wax. The 
 glass plate thus prepared is then laid with the waxed side 
 doA\Ti wards, so as to covor the leaden basin in which the 
 hydrofluoric acid is being prepared as directed in Experi- 
 ment 1. 
 
 If, after being exposed to the acid fumes for a few 
 minutes, the plate is removed and cleaned from the wax 
 with a rag and a little turpentine, it will be found 
 corroded wherever the marks have been made, and the 
 design will remain engraved on the glass. 
 
C 123 ) 
 
 CHAPTEE II. 
 
 NON-METALLIC DIADS. 
 
 (Oxygen, Siilpliur, Selenium, Tellurium.) 
 
 OXYGEN. 
 Symbol, 0 = 16. Formula, O2. 
 
 Oxygen is the most abundant of the elements, for it is 
 probable that not less than two-thirds of all that portion of 
 our globe of which we know anything consists of it. About 
 one two-billionth part of this oxygen exists in the atmo- 
 sphere in a free, or uncombined state ; the remainder occurs 
 in combination with various other elements. It constitutes 
 eight-ninths of the weight of water, and about one-half of 
 the weight of the chief rocks, and it is an important con- 
 stituent of all animals and vegetables. 
 
 In the pure state it is a gas of specific gravity 16, that is, 
 about one-tenth heavier than common air. By extreme 
 cold it is liquefied. It is colourless, tasteless, and inodorous, 
 and is very slightly soluble in water, one hundred volumes 
 of water dissolving about three volumes of the gas at a 
 temperature of 15° C. Its compounds are called oxides, 
 and oxides of all the elements, except fluorine, are known. 
 The gas is magnetic ; for a balloon filled with it is 
 attracted by the poles of a powerful magnet. 
 
 Oxygen cannot readily be prepared from air, and in the 
 great majority of its most abundant compounds it is held 
 in combination by a force too strong to be easily overcome ; 
 but a certain number of oxygen-compounds are knoT^ro, 
 which are so unstable, that either by heat, or by some 
 other agency, the element may be displaced and collected 
 in a pure state. 
 
124 
 
 EXPERIMENTAL CHEMISTRY. 
 
 PREPARATION. 
 
 Oxygen was first prepared by Dr. Priestley, in 1774, 
 from mercuric oxide, by the process already described 
 (page 62). It is also obtained when water is decomposed 
 by electricity (page 12). 
 
 Experiment 1. — Into the same apparatus that was used 
 for heating mercuric oxide, introduce 100 grains of 
 potassium chlorate, and heat it carefully with the spirit- 
 lamp, or gas-lamp. The salt will soon melt, and after- 
 wards boil. As soon as the boiling commences the flame 
 must be lowered, to prevent the mass from frothing over. 
 When the liquid thickens, if some of the substance should 
 be found adherent to the colder parts of the tube, approach 
 it with the flame of the lamp until it is again melted 
 down. The gas may be collected over the pneumatic 
 trough, just like hydrogen ; but when it ceases to cume off 
 after strong heating, the delivery tube must immediately 
 be removed from the water. 
 
 Instead of using pure potassium chlorate, it is much 
 better to mix the salt with about one-tenth of its weight 
 of carefully -dried manganese peroxide. The oxygen is 
 then given ofl" at a lower temperature and more easily, but 
 the manganese peroxide remains unaltered after the experi- 
 ment. 
 
 The following equation shows the change which takes 
 place in this important reaction : 
 
 Potassium Potassium 
 Chlorate. Chloride. 
 
 2KCIO3 = 2KCI + 3O2. 
 
 Potassium chlorate contains for every one hundred 
 grains nearly forty grains of oxygen chemically combined ; 
 by the apx^lication of heat, these become free and escape. 
 Mercuric oxide contains nearly eight per cent, of oxygen ; 
 therefore the former will yield five times more oxygen 
 than the latter. If phials of twelve ounces' capacity are 
 selected for receiving the gas, we shall be able to fill five of 
 them, and shall have in each about eight grains, or nearly 
 twenty cubic inches, of oxygen. 
 
 Potassium chlorate may, under some circumstances, 
 particularly when treated with sulphuric acid, occasion 
 
OXYGEN. 
 
 125 
 
 very dangerous explosions; but no danger is to be appre- 
 hended from the application of it in the manner above 
 directed. 
 
 Experiment 2. — Add warm water to the salt remaining 
 in the test-tube after the expulsion of the oxygen, and 
 place the tube in a warm place until the salt is dissolved; 
 evaporate the solution gradually, when small cubic crystals 
 of potassium chloride will be deposited. The potassium 
 chlorate crystallizes in thin tables or plates, the heated 
 mass in cubes ; this difference in the form of the crystals 
 indicates that, by the heating of the former, an entirely 
 new salt is formed. It is indeed one which no longer con- 
 tains oxygen. 
 
 Oxygen may also be prepared by the following pro- 
 cesses, which, however, are less convenient on the small 
 scale than the foregoing : 
 
 1. By heating manganese peroxide to redness in an iron 
 tube closed at one end : 
 
 3 Mn O2 = Mug O4 + O2. 
 
 2. By passing the vapour of sulphuric acid through a 
 red-hot tube : 
 
 Sulphurous 
 
 Sulphuric Acid. Anhydride. 
 
 2 H2 S O4 = 2 H2 0+ 2 S O2 -t- O2. 
 The sulphurous anhydride may be absorbed by passing 
 the gas through lime. This, on the large scale, is a cheap 
 process for preparing oxygen. 
 
 PROPERTIES. 
 
 Experiment 3. — Introduce a glowing shaving into a 
 bottle of oxygen ; it will kindle and burn for some time 
 with great brilliancy and with a very dazzling flame, and 
 then be extinguished. The same takes place when a 
 piece of lighted tinder is fastened to a wire and suspended 
 in the oxygen ; the tinder burns with a lively flame, 
 while, as is well known, it merely smoulders away in the 
 open air. Oxygen, at a hi<;h temperature, combines eagerl}^ 
 with the component parts of wood and tinder, and heat 
 and light are developed. "When the combination is ended, 
 and the oxygen is consumed, the combustion ceases. The 
 product of the combustion, that is, the combination of the 
 
126 
 
 EXPERIMENTAL CHEMISTRY. 
 
 wood with the oxygen, is also aeriform ; but burning sub- 
 stances are extinguished in the newly- formed gas. If the 
 bottle be rapidly whirled round, the gas formed by the com- 
 bustion will escape, and atmospheric air will supply its 
 place. Air contains free oxygen ; and a kindled shaving 
 will burn in it for some time, but far more slowly and less 
 briskly than in pure oxygen ; because common air con- 
 tains only one-fifth part of oxygen. Accordingly, com- 
 bustion proceeds much more rapidly and violently in 
 oxyiijen than in atmospheric air. 
 
 Experiment 4. — Fasten a piece of charcoal to a wire, and 
 kindle it in the flame of a lamp, and then introduce it 
 into a bottle of oxygen ; it will burn very vividly, and, 
 if the charcoal had much bark on it, with beautiful sparks. 
 If a piece of moistened blue litmus-paper be introduced 
 into the bottle, after the combustion, it will be reddened ; 
 consequently an acid oxide has been formed from the 
 charcoal and the oxygen ; it is called carbonic anhydride 
 or dicarhon oxide. Pour into the bottle a little lime-water 
 (which is prepared by shaking slaked lime 
 with water for a short time and filtering). 
 The clear lime-water becomes milky from the 
 formation of the insoluble calcium carbonate. 
 This is a good test for carbonic anhydride. 
 
 Experiment 5. — If some pieces of sulphur are 
 fastened to a longer wire, kindled and sus- 
 pended in a second bottle, they will burn 
 with a beautiful blue flame. The gas formed 
 from this union of sulphur and oxygen has a very irritat- 
 ing odour; when dissolved in water, it likewise turns 
 litmus-paper red, and consequently it is of an 
 acid nature. It is called sulphurous anhydride. 
 
 Experiment 6. — Take a small piece of phos- 
 phorus, which, on account of its inflamma- 
 bility, must be cut off under water from the 
 stick, and place it, after it has been ivell dried 
 between blotting-paper, iu a scooped - out 
 piece of chalk. Fasten the latter to a wire, 
 and introduce it into a third bottle of oxygen. 
 Affix the wire to a cross-piece of wood, so that the chalk 
 may hang a little below the centre of the bottle. If the 
 
OXYGEN. 
 
 127 
 
 phosphorus be now touched with a hot wire, it will 
 kindle and burn with a dazzling brilliancy, filling the 
 bottle with a thick white smoke. This SQioke consists 
 of a chemical compound of oxygen and phosphorus; it 
 reddens the blue test-paper, and consequently is also an 
 acid oxide ; it is called phosphoric anhydride. If the bottle 
 be allowed to stand for a time, the smoke will sink to the 
 bottom and dissolve in the water which remains there, 
 v\^hich thus acquires an acid taste. 
 
 The two last experiments, and many others, can be 
 more conveniently performed in deflagrating spoons, which 
 are merely little ladles of iron or brass fastened at right 
 angles on the end of iron wires, which pass through a 
 cork and a piece of tin plate. The tin plate rests on the 
 mouth of the bottle. 
 
 Experiment 7. — Heat a small piece of sodium in a 
 deflagrating spoon till it begins to burn, and then plunge 
 it in a bottle of oxygen. It will burn with great 
 brilliancy, and with a yellow flame. A white oxide is 
 formed, which, when dissolved in water, turns red 
 litmus-paper to blue. Oxides of this kind are called 
 basic oxides (page 100). Potassium yields a similar com- 
 pound. 
 
 Experiment 8. — A piece of fine iron wire is so wound 
 round a slate- or common lead-pencil, that, 
 on the withdrawal of the latter, the wire may 
 have a spiral form. Fasten the upper part of 
 this wire, as in Experiment 6, to a cross-piece 
 of wood, and place on the lower end of it a 
 bit of tinder dipped in sulphur. When this is 
 kindled, introduce the wire into the oxygen ; 
 the burning tinder heats the iron to redness, 
 which then burns brilliantly, throwing out 
 sparks. The iron, when red-hot, combines with the oxygen. 
 The burnt or oxidized iron (iron scales) melts, and falls 
 to the bottom in black globules, which are so hot that 
 they are apt to melt into the glass, though it be partly 
 filled with water. This black oxide of iron, re304, 
 is the same that is formed when steam is passed over red- 
 hot iron in a tube. The inside of the bottle becomes 
 covered during the experiment with a brick-red oxide, 
 
128 
 
 EXPERIMENTAL CHEMISTRY. 
 
 re203, which is called ferric oxide. Common iron-rust is 
 ferric oxide. Ferric oxide is a basic oxide, although, 
 being insoluble in water, it cannot be tested with litmus- 
 paper. The black oxide is a neutral oxide. It is neither 
 acid, nor basic. 
 
 These experiments show that there are three kinds of 
 oxides : 
 
 1. Acid oxides, or anhydrides, which by combination 
 with water yield acids. 
 
 2. Basic oxides, which by combination with water 
 yield bases. 
 
 3. Neutral oxides. 
 
 The connection that these oxides have with the acids 
 and bases has already been described (page 98). 
 
 Combustion. — The process which we call combustion, or 
 burning, is nothing but rapid combination with oxygen, 
 with evolution of light and intense heat. It is in fact 
 only a particular case of oxidation. In all ordinary cases 
 oxidation is attended with the production of heat, which 
 we have before seen is a frequent result of the exertion 
 and consequent loss of chemical force. But the oxidation 
 of a certain weight of substance may take place rapidly 
 or slowly, and the intensify of the heat will, of course, 
 vary in like proportion, although the total quantity 
 remains the same. The term combustion is generally 
 limited to those cases of oxidation where light as well 
 as intense heat is evolved. But the term may also be 
 applied to similar combinations between other elements, 
 as, for instance, between chlorine and hydrogen or metals. 
 
 Experiment 9. — Invert a tumbler over a small piece of 
 lighted candle standing on a plate. In a short time the 
 candle will go out, having removed a j)ortion of the 
 oxygen from the air of the tumbler. The inside of the 
 tumbler will be seen to be covered with moisture, and if it 
 is rapidly removed, and a little lime-water shaken in it, 
 the latter will become milky, showing the formation of 
 carbonic anhydride. 
 
 All ordinary kinds of fuel — coal, wood, gas, oil, ike. — 
 contain carbon and h^Mlrogcn. This experiment shows 
 the important fact that, when they hum, the carbon becomes 
 carbonic anhydride, and the hydrogen loater. 
 
RESPIRATION — DEFLAGRATION. 
 
 129 
 
 The phenomena of slow oxidation are very interesting 
 and important. 
 
 Experiment 10. — Throw some iron filings, which have 
 been moistened with water, into a bottle, so that they 
 may adhere to its bottom. Invert the bottle with its 
 month in a basin of water, and leave it in a warm place 
 for a few days. The water will gradually ascend in the 
 bottle, for the air becomes diminished in bulk to the 
 extent of one- fifth ; in fact, the whole of the oxygen is 
 slowly absorbed by the iron and combines with it, forming 
 ferric oxide, Fe203. The gas remaining in the bottle is 
 nitrogen, as is shown by plunging a lighted taper into 
 the gas; the taper will be extinguished (p. 155). The 
 rusting of iron is here seen to be its slow oxidation. 
 
 Experiment 11. — Bruise a little hay with water, stuff it 
 in the bottom of another small phial, and proceed as in 
 the former experiment. The same effect will be produced 
 as with the iron filings; that is to say, the oxygen will 
 be absorbed by the hay, and nitrogen will remain, mixed 
 in this case with a little carbonic anhydride from the 
 oxidation of the hay. The hay undergoes the process of 
 decay, which is thus shown to be a slow oxidation. In 
 both of these cases, heat is evolved, though it possesses 
 but slight intensity. The heat of a hot-hed is due to the 
 slow oxidation of the manure, 
 
 Bespiration. — Experiment 12. — The heat of the animal 
 body is maintained by a process of slow oxidation, 
 analogous to that of the hay. Blow through a glass 
 tube into a tumbler half full of lime-water. In a few 
 minutes it will become turbid, showing that carhonic 
 anhydride is contained in the expired air. Breathe into 
 a cold and dry tumbler. It will become covered with 
 moisture. Animals consume the oxygen of the air, and 
 return carbonic anhydride and water to it. Fishes also 
 require oxygen for respiration. They cannot decompose 
 water, but they abstract the oxygen which it constantly 
 absorbs from the air, returning carbonic anhydride in 
 exchange. In water from which the oxygen has been 
 expelled by boiling, fishes soon die of asphyxia. 
 
 Substances are more easily burnt when they are in a 
 finely divided state than if they are solid ; shavings are 
 
 K 
 
130 
 
 EXPERIiMENTAL CHEMISTRY. 
 
 easier to burn than billets of wood, and iron is easily 
 combustible when in the form of filings. 
 
 Experiment 13. — Hold a small bar of iron in the flame 
 of a spirit lamp ; it will not burn ; but file it and let 
 the filings fall into the flame ; they will be immediately 
 ignited. Iron filings when sprinkled in a flame bum 
 brilliantly. 
 
 Deflagration, — The term deflagration is applied to those 
 cases of combustion where the body is burnt, not by the 
 agency of free oxygen as that of the air, but by the aid 
 of combined oxygen as it exists in substances which are 
 easily decomposed, such as potassium chlorate, KCIO3, 
 and potassium nitrate, KNO3. Deflagration may be 
 exemplified as follows : 
 
 Experiment 14. — Heat 20 or 30 grains of nitre in a 
 test-tube with a spirit lamp, and when it is melted throw 
 in some powdered charcoal or a fragment of sulphur ; it 
 will burn violently, being oxidized at the expense of the 
 nitre. 
 
 OZONE, O3. 
 
 When certain kinds of electrical discharge occur in an 
 atmosphere of pure oxygen, or even of air, a contraction of 
 volume takes place, and some of the oxygen is converted 
 into the curious gas called ozone (Gr., 6Xw, to smell), on 
 account of its peculiar odour. This odour can be perceived 
 in the neighbourhood of an electrical machine during its 
 action. The specific gravity of ozone is found to be 24 
 (H = l), that of oxygen being 16; so that ozone is half 
 as heavy again as oxygen. This fact is explained by the 
 more than probable theory that every molecule of ozone 
 contains three atoms of oxygen instead of two, as in 
 ordinary oxygen gas. 
 
 Ozone has been obtained in the pure state as a blue 
 liquid which yields a sky-blue vapour, but it is generally 
 met with diluted greatly with oxygen or air. It is an 
 amazingly powerful oxidizing, bleaching, and disinfecting 
 agent, a property which is due to the ease with which it 
 gives out its third atom of oxygen. At a temperature of 
 about 250*^ C. (482"^ F.), it is reconverted into common 
 oxygen, 2O3 = 3O2. It can be formed by several methods 
 besides the one above mentioned. 
 
OZONE. 
 
 131 
 
 Experiment 1. — Take a stick of phosphorus, about an 
 inch long, and scrape it with a knife, under water, so as 
 to expose a new surface ; then lay it in the bottom of a 
 large wide-mouth bottle, pour in enough water to half 
 cover it, and having loosely stoppered the bottle, set it 
 aside in a warm place for about half an hour. White 
 fumes of phosphorous acid will arise from the phosphorus, 
 but will soon be absorbed by the water, and, simultaneously, 
 ozone will be formed. The phosphorus combines gradually 
 with part of the oxygen of the air in the bottle, while 
 some of the remainder is converted into ozone, SOg, 
 becoming 2O3. Its presence may be shown by the use of 
 what is called the " ozone test," which is made by 
 dissolving a few grains of potassium iodide in a table- 
 spoonful of starch jelly, such as is prepared for use in the 
 laundry, and smearing the latter on strips of paper. 
 Introduce one of these test-papers in the bottle of ozone, 
 and it will immediately become dark blue or violet, the 
 colour being more or less intense according to the quantity 
 of ozone. The iodine is liberated from the potassium 
 iodide by the ozone, and it combines with the starch to 
 form iodide of starch (Experiment 5, page 121). 
 
 Experiment 2. — Lay a piece of the test-paper in the 
 bottom of a tumbler and gradually invert a bottle of 
 ozone, prepared as in Experiment 1, as though in the act of 
 pouring from the one vessel to the other. The ozone will 
 stream out and occupy the tumbler, and come in contact 
 with the test-paper, which will be immediately affected. 
 This experiment shows that ozone is heavier than air. 
 
 Experiment 3. — Suspend a moist silver coin in a bottle 
 of ozone. In a few minutes it will be covered with a 
 grey deposit of silver oxide, thus showing the remarkable 
 oxidizing power of ozone. 
 
 Experiment 4. — Place a few fragments of sulphide of 
 iron in a glass or jar, and pour upon them a little water 
 and a few drops of sulphuric acid ; hydrogen sulphide, a 
 gas of an extremely disagreeable odour, will be evolved. 
 Moisten a strip of paper with a solution of lead acetate, 
 and bring it in contact with the escaping sulphuretted 
 hydrogen, and the paper will become dark brown or 
 black, from the formation of lead sulphide, PbS. If the 
 
132 
 
 EXPERIMENTAL CHEMISTRY. 
 
 paper be then plunged into a bottle containing ozone it will 
 again become colourless. The ozone oxidizes lead sulphide, 
 which is black, into lead suJ/phate, which is white : 
 
 PbS +4O3 = PbS04 + 402. 
 
 Experiment 5,- — Moisten a glass rod with a strong 
 solution of ammonia, and introduce it into a bottle of 
 ozone. White fumes will be abundantly formed, which 
 consist of ammonium nitrite, NH4,!N02. 
 
 Experiment 6. — Moistened litmus-paper is immediately 
 bleached when introduced into a bottle of ozonized air. 
 The bleaching and disinfecting of bodies by ozone are 
 owing to their oxidation. Ozone is very commonly found 
 in the atmosphere, formed perhaps by the action of 
 electricity. It cannot be doubted that this atmospheric 
 ozone has important functions to fulfil in the economy 
 of nature. 
 
 Experiment 7. — Strips of paper moistened with ozone 
 test may be exposed to the air for a few hours. They 
 will frequently be found to have turned blue, especially in 
 country places. 
 
 WATER, H2O. 
 
 Water does not exibt in nature in a perfectly pure con- 
 dition. Even fresh water contains small quantities of solid 
 impurities, of which the carbonates and sulphates of calcium 
 and magnesium are among the most important and general. 
 Natural water also holds in solution small quantities 
 of oxygen, nitrogen, and carbonic acid ; but besides these 
 general impurities, there are others which occur only in 
 particular instances, such as iron, sulphuretted hydrogen, 
 iodine, &c., which are present in certain springs, and 
 which give to them a medicinal value, as is the case with 
 the waters of Harrogate, of Cheltenham, and of Tunbridge 
 Wells. Eain-water, collected in a vessel placed in a 
 large open space, such as a field, is the purest kind of 
 natural water that can be obtained, and may be used by 
 the student, for most purposes, in lieu of distilled water, 
 in cases where the latter cannot easily be obtained. 
 
 The composition of water was first determined by 
 Cavendish ; he proved that it is the sole product of the 
 combustion of hydrogen. 
 
WATER. 
 
 133 
 
 Experiment 1. — That water is really formed by the 
 burning of hydrogen can easily be shown by inverting 
 a clear glass bottle over the hydrogen flame ; Fig. 46. 
 the glass soon becomes clouded over, because 
 the water, which in consequence of the heat is ' 
 generated in the form of steam, condenses in 
 small globules on the cold sides of the bottle. 
 
 Experiment 2. — The extraordinary degree of 
 heat developed by the chemical union of oxygen 
 and hydrogen may be shown by the following 
 experiments. Insert into the opening of a large 
 pig's bladder, which has been softened by soak- 
 ing in water, the broken-off neck of a flask, ^ 
 and bind it firmly round with a string. Then 
 select two perforated corks, fitting this neck. 
 One cork is connected with a bent glass tube, 
 conducting the oxygen from the apparatus in 
 which it is evolved into the bladder, which 
 soon becomes filled with it. When this operation is finished, 
 replace the first cork by the second, having a glass tube 
 adapted to it only a few inches long, and drawn Fi^^. 47 
 out to a point at its outer end, and provided with 
 a wax plug pressed upon the opening. A glass 
 tube may be formed into a jet by heating it in the 
 flame of a spirit lamp, constantly turning it round 
 at the same time, till it becomes so soft at the 
 desired place as to be easily drawn 
 slender part, and hold it in 
 
 out. Break it at the 
 Fig. 48. 
 
 the flame for some moments, 
 until the sharp edges are 
 rounded off by incipient 
 melting. It would be more 
 convenient, though some- 
 what more expensive, to 
 substitute for the above 
 contrivance a small brass 
 stop-cock, provided with a 
 jet. 
 
 The bladder thus ar- 
 ranged and filled with oxygen is now placed upon a 
 block, at such a height that the point of the glass tube 
 
134 
 
 EXPERIMENTAL CHEMISTRY. 
 
 shall be on a level with the hydrogen flame, produced 
 as explained in a former experiment. Press upon the 
 bladder with the hand, and the oxygen will escape, 
 blowing into the hydrogen flame, which then takes a 
 horizontal direction. This flame has but little brilliancy, 
 less than the hydrogen flame alone, notwithstanding 
 which it afibrds the greatest heat yet known, except the 
 heat produced by electricity. Hold in it a platinum 
 wire, a metal which cannot be melted in the hottest 
 furnace, and it will melt like wax ; hold in it a piece of 
 lime scraped to a fine point, and it will emit light of the 
 most dazzling splendour. This is called the lime light A 
 watch-spring or a fine iron wire burns in it, throwing out 
 sparks as in oxygen. 
 
 Exact experiments have shown that two measures of 
 hydrogen unite with one measure of oxygen, the same 
 proportion as that in which the gases are obtained 
 when water is decomposed by electricity (page 12). The 
 result of the combination is steam, which condenses into 
 water. But two measures of hydrogen and one of oxygen 
 do not yield three measures of steam ; they afford two 
 measures only : 
 
 (4 Vols.) (2 Vols.) (4 Vols.) 
 
 + O2 = 2H2O. 
 
 Thus the two gases condense one-third by chemical 
 union. 
 
 If the hydrogen and oxygen were mixed together and 
 then ignited, the whole mass would combine together at 
 once, producing a most violent report, and bursting the 
 vessel to pieces. The explosion is due to the concussion 
 of the air, caused by the sudden and violent expansion of 
 the steam by the heat evolved. No danger is to be appre- 
 hended from the apparatus described, as the explosive 
 gas is formed at the point where the oxygen meets the 
 hydrogen flame, and only in small quantities at once. 
 The apparatus is an oxyhydrogen blowpipe on a small scale. 
 
 Experiment 3. — Procure a soda-water bottle fitted with a 
 good cork, and having filled it with water, invert it in the 
 pneumatic trough, and fill it two-thirds full of hydrogen, 
 and one-third with oxygen ; cork it securely, and allow 
 it to remain with its mouth immersed in the water 
 
WATER. 
 
 135 
 
 for five minutes, or sLake it so that the phases shall inter- 
 mix. If the bottle be then uncorked, and a light quickly 
 applied to the mouth, the gases will combine with a loud 
 explosion. Owing to the small quantity of the gaseous 
 mixture employed there is little danger in this experi- 
 ment ; but to prevent a chance of accident it is advisable, 
 before applying the light, to fold the bottle in a cloth, 
 so as to secure the fragments of glass, should the bottle 
 be broken by the explosion. 
 
 The composition of water by volume is thus easily 
 illustrated ; but to show directly the relative weight of its 
 constituents, the following rather complicated arrange- 
 ment may be used : 
 
 Fig. 49. 
 
 A is a hydrogen apparatus, and it is connected by a 
 bent tube with the bottle B, containing .sulphuric acid. 
 B is connected in turn to the two wide tubes C and D. C 
 contains a small heap of black copper oxide, CuO, heated 
 with a spirit or gas lamp, and D is filled with frag- 
 ments of calcium chloride. 
 
 Some granulated zinc having been placed in the bottle 
 A, a mixture of sulphuric acid and water is poured down 
 the long funnel called a thistle funnel. Hydrogen is 
 evolved and passes by the bent tube through the sulphuric 
 acid in the bottle B, and is thus dried, for sulphuric acid 
 eagerly combines with and retains any watery vapour that 
 may be carried over by the hydrogen. The dry gas, after 
 bubbling through the sulphuric acid, passes through the 
 wide tube C, and comes in contact with the copper oxide. 
 When the common air is expelled, the tube C is heated. The 
 hydrogen then combines with the oxygen of the copper 
 oxide and forms water : CuO-t-H2 = CU + H2O. The latter, 
 as fast as it is formed, is driven forward and absorbed by 
 the calcium chloride — a substance already mentioned as a 
 
136 
 
 EXPERIMENTAL CHEMISTRY. 
 
 powerful absorbent of water — in the tube D. Now if the 
 tube D be weighed before and after the experiment, any- 
 additional weight it may have gained will of course be 
 owing to the water formed during the experiment, and 
 thus its amount may be readily determined ; but if the 
 tube C containing the oxide of copper be also weighed, 
 any decrease in weight will represent the quantity of 
 oxygen which has been required to form the water 
 obtained. In this way it may be determined that for 
 every nine grains of water produced, the oxide of copper 
 loses eight grains of oxygen : the difference is of course due 
 to the hydrogen, and represents the relative weight with 
 which it combines with oxygen to form water. At the 
 end of the experiment the tube C contains metallic copper, 
 in fine powder. 
 
 Hydrogen Peroxide, H2O2. — Hydrogen may be made by 
 indirect means to combine with, an additional atom of 
 oxygen than that required to form water. This compound 
 is an oily liquid, easily decomposed, and of extreme oxi- , 
 dizing powers, rivalling those of ozone. 
 
 COMPOUNDS OF OXYGEN AND CHLORINE. 
 Oxides of Chlorine. Corresponding Acids. 
 
 '^gch^oSlntdri^e!' ^'-} Hypochlorous Acid, HCIO. 
 
 CI O2 Chlorine Tetroxide, or^ 
 Chlorine Peroxide. / 
 
 It is not necessary for the beginner to study all the 
 above compounds. Many of them are highly dangerous 
 substances, and all are difficult to prepare. Chlorine 
 peroxide is not an acid oxide. 
 
 Hypochlorous Anhydride^ CI2O, is a colourless gas easily 
 condensable to a red explosive liquid by cold. Combined 
 with water it yields hypochlorous acid : 
 
 CI2O + H2O == 2HC10. 
 
 This acid corresponds to the series of salts called 
 hypochlorites : 
 
 HCIO, Hypochlorous Acid. 
 NaClO, Sodium Hypochlorite. 
 Ca(ClO);^, Calcium Hypochlorite. 
 
COMPOUNDS OF OXYGEN AND CHLORINE. 
 
 137 
 
 The substance commonly called chloride of lime, or 
 bleaching powder, is intermediate in composition between 
 the chloride and hypochlorite of calcium (CaCl2 and Ca 
 (010)2). Its composition may be represented by the 
 formula 0aO0l2 or Oa 01(010), or as a compound of calcium 
 chloride and hypochlorite, — Ca OI2 + Oa (01 0)2- Bleach- 
 ing powder is prepared by acting on slaked lime (calcium 
 hydrate) with chlorine. 
 
 Experiment 1. — Throw a little slaked lime into a bottle 
 of chlorine, stoppered loosely. In a short time the 
 chlorine will disappear, the lime will absorb it, and be 
 converted into bleaching powder : 
 
 Calcium Hydrate. Bleaching Powder. 
 
 Ca (0 H)2 + OI2 = Oa 01 (01 0) + H2 0. 
 
 The manufacture of bleaching powder on a large scale 
 is carried on by passing chlorine through chambers in 
 which layers of slaked lime are spread. The process is 
 complete when the lime ceases to absorb chlorine. 
 
 Experiment 2. — Pour a few drops of very dilute hydro- 
 chlv:>ric acid on a little bleaching powder. Effervescence 
 will be produced by the escape of gaseous hypochlorous 
 acid, which has an odour somewhat resembling that of 
 chlorine. A piece of moistened litmus-paper, if it be 
 immersed in the jar, will be bleached. If sulphuric acid 
 is added in excess, chlorine is set free : 
 
 Oa 0 OI2 + H2 S O4 = Oa S O4 4- H2 0 + OI2. 
 
 This is a simple and effectual way of preparing chlorine 
 for disinfecting purposes. 
 
 In the ordinary process of bleaching, the materials to 
 be bleached are dipped into a solution of bleaching 
 powder, and then passed through a dilute acid (" soured"), 
 which liberates the hypochlorous acid. The acid is an 
 even more powerful bleaching agent than chlorine. 
 
 The peculiar odour which bleaching powder apparently 
 possesses is due to hypochlorous acid, which is slowly and 
 continuously formed from it by the carbonic acid of the 
 air, so easily is the compound decomposed. 
 
 Chlorine peroxide, OIO2 or OI2O4, is a dark yellow, easily 
 decomposed gas, formed by the action of sulphuric acid on 
 
138 
 
 EXPERIMENTAL CHEMISTRY. 
 
 potassium chlorate. It may be prepared, and its explosive 
 character safely observed, in the following way : 
 
 Experiment 3. — To two or three grains (not more) of 
 potassium chlorate in a test-tube add a few drops of 
 strong sulphuric acid, and gently warm. A peculiar 
 crackling noise will be heard, while a coloured gas is 
 slowly evolved. This gas is chlorine peroxide. If the 
 tube be more strongly heated a loud explosion will often 
 be produced from the sudden decomposition of the gas. 
 
 Chloric acid, HCIO3, an oily liquid, easily decomposed, 
 and of little utility. Its salts, especially the potassium 
 salt, are of great importance. Chloric acid can only be 
 prepared from its compounds, which are themselves readily 
 obtained. By acting upon barium chlorate with dilute 
 sulphuric acid, chloric acid is formed, together with the 
 insoluble substance, barium sulphate : 
 
 Barium Chlorate. Sulphuric Acid. Barium Sulphate. Chloric Acid. 
 
 Ba (0103)2 + H2SO4 = BaSO^ + 2HOIO3. 
 
 Potassium chlorate is formed by a process analogous to 
 that used for the preparation of bleaching powder. By 
 passing chlorine through a cold dilute solution of 
 potassium hydrate, a mixture of potassium chloride and 
 hypochlorite is obtained ; but if a hot solution be used, 
 chlorate instead of hypochlorite is formed : 
 
 6K0H + 30l2 = 5K01 + K0103 + 3H2O. 
 
 Experiment 4. — Pour a few drops of a strong and warm 
 solution of potassium hydrate into a bottle of chlorine 
 loosely stoppered. The chlorine will be absorbed, just as 
 it was by calcium hydrate, while a white crystalline 
 powder is abundantly formed which mainly consists of 
 potassium chlorate, the chloride being very soluble. The 
 chlorates are unstable bodies, and readily yield up their 
 oxygen when heated ; they therefore furnish convenient 
 sources of that gas. It will be remembered that potassium 
 chlorate is the salt commonly employed for the prepara- 
 tion of oxygen. 
 
 Experiment 5. — Powder a few grains of potassium 
 chlorate ; mix it gently with an equal quantity of 
 powdered sugar, and touch the mixture with a rod dipped 
 
SULPHUR. 
 
 139 
 
 in strong sulphuric acid. A brilliant combustion will 
 ensue, owing to the CIO2 set free from the chlorate. 
 
 Experiment 6. — If one grain of potassium chlorate is 
 triturated in a mortar with one grain of sulphur, a sharp 
 detonation will follow, the sulphur being oxidized at the 
 expense of the salt. 
 
 SULPHUK. 
 
 Symbol, S = 32. Formula of Vapour, S2 and S^. 
 The well-known element sulphur, which, on account 
 of its easy combustibility, is employed in the manufacture 
 of matches, &c., has neither taste nor smell. It is found 
 in nature in considerable quantity, mostly in a state of 
 combination. 
 
 Experiment 1. — Sulphur is fusible. Heat two ounces of 
 sulphur in small pieces in a small stone- ware crucible or 
 Florence flask, over a lamp at a gentle heat ; it is con- 
 verted, at a temperature a little above that Yig. 50. 
 of boiling water, into a thin yellow fluid. If 
 you pour some of it into cold water, you obtain 
 again solid sulphur. If this, after being pre- 
 viously dried, is returned to the crucible, it 
 will sink in the fluid mass, showing that solid 
 is heavier than melted sulphur. 
 
 Experiment 2. — Sulphur may be crystallized. 
 Let the crucible containing the melted sulphur 
 stand till a crust has formed over the surface ; 
 break this quickly, and pour out the portion 
 remaining fluid. Upon afterwards breaking the 
 crucible, the cavity of the sulphur will be found 
 lined with fine transparent crystals, in the form of length- 
 ened pillars (Fig. 50), which are called monoclinic, yio- 51 
 or oblique rhojnbic prisms. 
 
 In different parts of the world, particularly in 
 volcanic countries, such as Sicily and Iceland, large 
 beds of sulphur (native sulphur) are not unfre- 
 quently found, and, in these beds, fissures and * 
 cavities studded with the most beautiful crystals. 
 These native crystals have a very different form 
 from those prepared by fusion. They appease like two 
 pointed four-sided pyramids, applied base to ba§e (Fig. ol) ; 
 
140 
 
 EXPERIMENTAL CHEMISTRY. 
 
 such a form is called an acute octahedron, because contained 
 under eight acute triangles. Thus sulphur, like carbon in 
 the diamond and graphite, assumes two different crystal- 
 line forms ; it is dimorphous. 
 
 Experiment 3. — Although sulphur is insoluble in water, 
 many liquids are known which dissolve it ; the one most 
 convenient for this purpose is carbon disulphide. Pour a 
 little of this liquid into a small clean bottle, and add a few 
 pieces of sulphur. Close the bottle, and shake it at 
 intervals for an hour or two. Then filter the liquid from 
 the undissolved sulphur into a small basin, and allow it to 
 evaporate ; as it does so crystals of sulphur of the form 
 shown in Fig. 51 will appear. Their shape differs from 
 those obtained by fusion, but is similar to the native 
 crystals. 
 
 Experiment 4. — Put about two ounces of fragments of 
 roll-sulphur into a dry Florence flask, and place the latter 
 on a retort stand. Heat it gently at first, but afterwards 
 over a Bunsen's gas flame. The sulphur will first melt to 
 a thin yellowish liquid. When it is all melted, and when 
 the heat is increased, the character of the liquefied sulphur 
 is remarkably altered ; it loses its mobility, and becomes 
 thick and pasty, and dark in colour like treacle ; so much 
 so that the flask may be quite inverted without danger of 
 the contents running out. As the heat continues, this 
 condition is likewise changed, and soon the sulphur be- 
 comes again a thin liquid, which retains, however, its dark 
 colour, and thus it continues until the boiling-point is 
 reached. If the sulphur be thrown into water while in 
 this condition, a substance entirely different in appearance 
 from ordinary sulphur is obtained in the form of a reddish- 
 brown, soft, elastic mass, which serves admirably as a 
 medium for taking impressions of seals, medals, &c. But 
 this change is not a permanent one ; in a short time the 
 mass becomes hard and brittle, and is soon reconverted into 
 ordinary sulphur. This plastic form of sulphur is said to 
 be amorphous^ a term applied to other bodies having no 
 regular form, such as gum, pitch, glue, &c. 
 
 Experiment 5. — If, instead of pouring out the sulphur as 
 in the last experiment, the heat be further applied, the 
 sulphur will soon give out a rich dark-red vapour, which 
 
SULPHUR. 
 
 141 
 
 gradually occupies the whole of the upper part of the 
 flask : thus sulphur is volatile, and may, like water, assume 
 all the three states of aggregation (solid, fluid, and aeri- 
 form). Solid sulphur has a specific gravity of about 2 ; 
 that is, twice as heavy as water. Sulphur vapour has a 
 specific gravity of 96 (H = 1), but at a very high temper- 
 ature (1000° C.) it trebles its volume, and has a specific 
 gravity of only 32. The formula for the ordinary vapour 
 is, therefore, Sg, and for the vapour at high temperatures, 
 S2. Within the flask the vapour of the sulphur is trans- 
 parent, and has a reddish-brown colour ; but after escaping 
 it appears as a yellowish smoke, being condensed by the 
 cold air into a dust of solid sulphur. If this vapour be 
 conducted into a glass jar, immersed in cold water, the 
 sulphur condenses in it in the form of a soft yellow powder, 
 known in commerce by the name of flowers of sulphur. 
 The process by which a volatile substance is evaporated 
 and condensed again into a solid is called sublimation. In 
 distillation, the vapour is condensed into liquid (the dis- 
 tillate) ; in sublimation, into a solid (the sublimate). 
 
 The flowers of sulphur of commerce are obtained by 
 vaporizing the impure native sulphur in iron or earthen 
 retorts, and conducting the vapour into large chambers 
 built of brick or stone, where it condenses as a crystalline 
 powder, and lodges on the walls of the chambers. The 
 interior of the chamber is sometimes allowed to become 
 sufficiently hot to melt the deposited sulphur, which there- 
 fore runs down in the melted condition, and collects on the 
 floor. While still liquid it is drawn off and solidified in 
 wooden moulds, and so forms roll-sulphur, or hrimstone. 
 
 Experiment 6. — Fill a test-tube one-third full of solution 
 of caustic soda ; add to it as much flowers of sulphur as 
 can be taken up on the point of a knife, and boil the 
 mixture for some time ; a part of the sulphur will be dis- 
 solved, imparting to the liquid a yellowish-brown colour. 
 The clear liquid is now decanted, diluted with water, and 
 hydrochloric acid added to it ; it will immediately assume 
 a milky appearance, owing to the separation of the sulphur 
 in the form of an exceedingly fine powder, which is so 
 light that a considerable time must elapse before it will 
 subside. Collect the powder on a filter, wash it with 
 
142 
 
 EXPERIMENTAL CHEMISTRY. 
 
 water, and dry it at a gentle heat. It is called milk of 
 sulphur, or precipitated sulphur, and is sulphur in its finest 
 state of subdivision. Precipitated sul[)hur has a pale 
 yellowish tint, but on being melted it becomes distinctly 
 yellow, owing to the union of the individual particles into 
 a larger mass. 
 
 Experiment 7. — If sulphur be heated in a vessel with 
 free access of air, as in an iron spoon, or be touched by 
 some red-hot body, it hums with a blue flame ; that is, it 
 unites with the oxygen of the air, under the phenomenon 
 of fire, and forms with the oxygen, as has been previously 
 shown, a suffocating gas, sulphurous anhydride (SO2). 
 
 This property, which belongs to sulphur, of igniting at 
 a very moderate heat, is the reason of its being so com- 
 monly used for kindling purposes. By means of it, other 
 bodies more difficult of combustion may be heated to the 
 temperature at which they can continue to burn (matches, 
 gunpowder, fireworks, &c.). The kindling of a simple 
 coal-fire well illustrates how, by gradual transition from 
 easily inflammable materials to those of more difiicult 
 ignition, the latter are finally brought to that degree of 
 heat at which they will ignite and continue to burn. 
 
 Sulphur is an energetic element, and has, like oxygen, a 
 powerful affinity for other elements. 
 
 Experiment 8. — Boil some sulphur in a flask, and expose 
 
 very thin copper-plate to the brownish vapour ; the 
 copper will glow vividly for some moments, lose its red 
 colour and flexibility, become grey and brittle, and weigh 
 more than before. The newly-formed grey crystalline 
 body is copper sulphide, CuS. Both elements have inti- 
 mately combined, and in fixed proportions. The proper- 
 ties of the sulphur, as well as of the copper, have entirely 
 disappeared. The great heat produced is a consequence of 
 the chemical combination. 
 
 In a similar manner many other metals may be con- 
 verted into sulphides. We find many, however, already 
 formed in the earth, and miners call them glance, blende, 
 or pyrites. The pyrites having the lustre of brass, and 
 found in almost all coal, is sulphide of iron ; red cinnabar 
 is a sulphide of mercury, &c. The sulphide of copper, 
 artificially prepared as above, occurs also as an ore. 
 
HYDROGEN SULPHIDE. 
 
 143 
 
 Experiment 9. — Mix three-fourths of an ounce of iron- 
 filings, half an ounce of flowers of sulphur, and one-fourth 
 of an ounce of water, in a small vessel, and put it in a 
 warm place ; the mass becomes heated, the water evapo- 
 rates, and in half an hour a black powder will be obtained, 
 in which no particles of iron or of sulphur will be per- 
 ceived ; a chemical compound, ferrous sulphide^ is formed. 
 If the two substances be mixed together without water, 
 no combination will take place, unless they be heated to 
 redness. 
 
 Experiment 10. — Melt an ounce of sulphur in a covered 
 earthen crucible, and then gradually throw in rather more 
 than half an ounce of iron filings, closing the crucible 
 after each addition. The iron will glow and combine 
 with the sulphur just as the copper did in Experiment 8. 
 The compound formed is the same as that obtained in 
 Experiment 9, namely, ferrous sulphide, FeS. When larger 
 quantities are required it is better to buy than to make it. 
 
 HYDROGEN SULPHIDE, OR SULPHURETTED HYDROGEN, H2S. 
 
 Experiment 1. — Put half an ounce of ferrous sulphide 
 (FeS) and half an ounce of diluted sul- ji- ^2 
 phuric acid into a small bottle, and quickly 
 stop the bottle with a cork, to which a 
 bent glass tube is adapted. Introduce the 
 longer limb of the tube into a bottle filled 
 with cold water. The atmospheric air 
 contained in the flask and tube first passes 
 over, followed by a very ofiensive gas, 
 which dissolves in the water, to which it likewise imparts 
 its fetid odour of rotten eggs. This gas is called hydrogen 
 sulphide or sulphuretted hydrogen. The following change 
 takes place : 
 
 FeS -f-H^SO^ = FeSO^ + H^S. 
 
 When the disengagement of the gas ceases, add some 
 diluted sulphuric acid, that the gas may again be generated. 
 The water is known to be saturated with the gas when, on 
 shaking the bottle, the finger by which the opening is closed 
 is no longer sucked in, or, more correctly speaking, pressed 
 in. One measure of water contains about two and a half 
 
144 
 
 EXPERIMENTAL CHEMISTRY. 
 
 measures of gas in a saturated solution. It is put up in 
 small well-stoppered bottles. If the air be admitted, the 
 solution becomes turbid, owing to the oxygen of the air 
 uniting with the hydrogen of the sulphuretted hydrogen, 
 forming water, and the consequent liberation of the sulphur 
 as a fine powder. 
 
 If, during the evolution of the gas, the bottle of water 
 be removed, the gas issuing from the tube can be ignited 
 by a match ; it burns with a blue flame, and its nauseous 
 odour is no longer perceptible, but is replaced by the well- 
 known odour of burning sulphur. Both constituents unite 
 with the oxygen of the air, the sulphur forming sulphurous 
 anhydi ide, and the hydrogen, water. 
 
 The inhalation of sulphuretted hydrogen is detrimental 
 to health ; hence care should be taken to avoid it. When 
 experimenting with it, it is best to do so where there is a 
 free circulation of air. 
 
 Hydrogen sulphide turns blue litmus-paper red ; it also 
 combines with bases, and hence it may be regarded as an 
 acid. 
 
 Experiment 2. — Drop some hydrogen sulphide water 
 upon a bright silver or copper coin, and upon a piece of 
 lead and iron. The first three metals tarnish quickly, and 
 finally become black ; they combine with the bulphur, 
 forming dark metallic sulphides ; the iron, on the contrary, 
 undergoes no change. 
 
 Experiment 3. — Put into one test-tube a small portion of 
 litharge, into another some ignited iron-rust, and pour 
 upon them a solution of this gas. The yellow litharge, 
 oxide of lead, becomes immediately black, an exchange of 
 elements takes place, the hydrogen sulphide gives its 
 sulphur to the lead of the litharge, and receives in return 
 the oxygen of the latter. Accordingly, lead sulphide and 
 water are formed, and the offensive odour disap23ears. In 
 the vessel containing the iron-rust, neither the colour nor 
 the smell is changed — a proof that no chemical change has 
 taken place. 
 
 Experiment 4. — Eepeat the same experiment with a small 
 crystal of sugar of lead instead of the litharge, and some 
 green vitriol instead of the iron-rnst, together with a few 
 drops of acetic acid, these salts having been j^reviously 
 
HYDROGEN SULPHIDE. 
 
 145 
 
 dissolved in a large quantity of water ; the result will be the 
 same as in the former experiment. Sugar of lead is lead 
 acetate ; the salt of lead is converted into sulphide, which 
 subsides sooner or later as a black precijDitate. When 
 this solution is extremely diluted it is only rendered 
 brown. Acetic acid is set free, and remains in solution. 
 
 Most of the metallic sulphides are insoluble in water; 
 hence hydrogen sulphide is peculiarly adapted for pre- 
 cipitating metals from their solution, so that they can be 
 separated and collected by filtration. If hydrogen sulphide 
 is passed through a solution of acetate or sulphate of copper, 
 sulphide of copper will be precipitated, and can be separated 
 by filtration from the acid. Some of the sulphides do not 
 possess a black colour ; sulphide of antimony has an orange - 
 red, sulphide of arsenic a yellow, and sulphide %^ zinc 
 a white colour. On this is partly based the application 
 of hydrogen sulphide as a test; that is, as a means of 
 detecting many metals. Wine containing lead is blackened 
 by hydrogen sulphide. 
 
 Many metals are precipitated from their acidified solu- 
 tions as sulphides by the addition only of sulphuretted 
 hydrogen ; for example, copper, silver, gold, lead, mercury, 
 tin, antimony, and arsenic ; and others are not precipitated 
 until a base is added ; for example, iron, zinc, manganese, 
 cobalt, and nickel. Hydrogen sulphide may accordingly 
 be used to separate one metal from another ; it is, therefore, 
 an important means of separation in analytical chemistry. 
 Lead paper is used for the detection of hydrogen sulphide, 
 by which it is coloured brown or black. It is made by 
 passing strips of paper through a weak solution of sugar 
 of lead in water. 
 
 Finally, it remains to be stated that this gas occurs also 
 in some mineral waters^ as may be recognised by the smell 
 and taste. Many of these springs — for instance, the cele- 
 brated springs of Harrogate and Aix-la-Chapelle — are 
 resorted to by invalids, and are called sulphur springs, A 
 rotten wooden water-pipe may convert an otherwise potable 
 water, if it should contain calcium sulphate, into a nauseous 
 sulphuretted water ; but by clearing out the well, and 
 laying down new pipes, the water may be rendered com- 
 pletely odourless and good. 
 
 L 
 
146 
 
 EXPERIMENTAL CHEMISTRY. 
 
 COMPOUNDS OF SULPHUR AND OXYGEN. 
 
 Sulpliiir combines with, oxygen in two proportions, form- 
 ing tlie oxides SO2 and SO3 ; they both unite with water 
 to form acids. 8O2 is hence called sulphur dioxide, or 
 sulphurous anhydride, and SO3 sulphur trioxide, or sul- 
 phuric anhydride. The latter substance can onl}'' be pre 
 pared indirectly, whereas sulphurous anhydride is formed 
 by the direct union of its constituents whenever sulphur 
 is burnt in air or oxygen, as has been already 
 mentioned. 
 
 SidpJiurous Anhydride, SO2, and Sulphurous Acid, H2SO3. 
 — Sulphurous anhydride is a colourless gas of a pungent 
 suffocating odour, well known as the smell of sulphur. 
 One of its most characteristic properties is its power of 
 bleaching animal and vegetable colours. 
 
 Experiment 1. — Suspend a red flower, such as a rose or 
 peony, in an inverted glass jar, or other similar vessel, 
 and introduce a piece of ignited sulphur. It will be found 
 that tbe colour of the flower is slowly changed to 
 white. Sulphurous anhydride, unlike chlorine, does not 
 actually destroy the colouring matter, for by dipping the 
 flower into dilute sulphuric acid the original colour is 
 slowly restored. Straw, wool, silk, &c., are very commonly 
 bleached with sulphurous anhydride, but the result of its 
 action on these materials is far from permanent ; for on 
 exposing a bleached straw hat in the sunshine it again 
 becomes yellow, or " sun-burnt," as the eff'ect is popularly 
 termed ; and on washing whitened flannel it resumes its 
 original appearance. 
 
 Sulphurous anhydride can be formed in a variety of ways: 
 one of* the most convenient, when a quantity is required 
 in a tolerable state of purity, is the following : 
 
 Experiment 2. — Select a thin-bottomed, well-made Flor- 
 ence flask, fit it with a delivery tube, and place in it half 
 an ounce of thin copper, sheet or turnings, and two ounces 
 of strong sulphuric acid. Apply a gentle but gradually 
 increasing heat, and after a time sulphurous anhydride 
 will be evolved, according to the equation : 
 
 CU + 2II2SO4 = CuS04-|-2H20-f-S02. 
 
 Sulphurous anhydride is more than twice as heavy as 
 
COMPOUNDS OF SULPHUR AND OXYGEN. 
 
 147 
 
 air, SO it may be collected in dry bottles by displacement ; 
 that is, by allowing the gas to pass to the bottom of a dry 
 bottle. It will gradually displace the lighter air, just as 
 water does when poured into a bottle, and as it is very 
 soluble in water this mode is the most convenient. 
 
 Experiment 3. — Pour a little blue litmus solution into 
 a bottle of sulphurous anhydride; it will be reddened^ 
 showing the acid character of the gas. 
 
 Experiment 4. — Dip the end of the delivery tube from 
 which the gas is issuing into a little water ; the gas is 
 absorbed in large quantities and imparts to the water its 
 characteristic taste and smell. One measure of water dis- 
 solves about forty measures of the gas. The solution 
 obtained is one of sulphurous acid : 
 
 SO, + H,0 = H2SO3. 
 
 The salts corresponding to sulphurous acid are called 
 mlpMtes : g Sulphurous acid. 
 
 Na2 S O3, Sodium sulphite. 
 Ca S O3, Calcium sulphite. 
 
 Experiment 5. — When the gas ceases to be absorbed by 
 the water, substitute for the latter a solution of sodium 
 carbonate ; this likewise absorbs the gas and forms with it 
 sodium sulphite, while the carbonic acid is liberated with 
 effervescence. If a sulphite be treated with a strong acid 
 it is decomposed and sulphurous anhydride is evolved. 
 
 Experiment 6. — Place a few grains of sodium sulphite in 
 a test-tube, pour upon it a little slightly diluted sulphuric 
 acid, and gently warm. Sulphurous anhydride is given 
 off and is readily identified by its odour : 
 
 Na^SOs-t-H^SO^ = Na2S04-f H20-f SO2. 
 Experiment 7. — When the residue in the flask, in which 
 the sulphurous anhydride was generated, has become cold, 
 add water to it, and heat it gently to boiling until most 
 of the residual mass is dissolved. The solution is dark 
 and turbid, but after filtering it is of a beautiful blue 
 colour, and transparent. If allowed to cool slowly, blue 
 crystals of copper sulphate, CUSO45H2O (blue vitriol), 
 of considerable size will be formed. Silver and mercury 
 comport themselves like copper and may be used instead. 
 
 L 2 
 
148 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Sulphuric Anhydride, SO3, and Suljphuric Acid, H2SO4. 
 
 Sulphuric Anhydride, — Experiment 8. — Pour into a small 
 flask, placed in a sand-bath over a tripod, half an ounce 
 
 of fuming, or Naud- 
 hausen sulphuric 
 acid, and heat it 
 gently till it boils 
 moderately. Conduct 
 the vapour through 
 a tolerably wide glass 
 tube into an empty 
 flask, not shown in 
 the cut, which is 
 placed in a vessel 
 filled with cold water. 
 If the vapour be 
 suffered to escape into 
 the air, it appears in 
 thick white fumes, having a pungent acid smell ; but if con- 
 ducted into the flask, it is condensed into a liquid which 
 solidifies into a glistening white solid mass. This is sul- 
 phuric anhydride. The distillation is stopped as soon as 
 the boiling ceases, and the glass tube becomes too hot for 
 the hand to bear. What remains in the flask no longer 
 fumes ; it has become common sulphuric acid. To cause 
 this to boil, you must apply a much stronger heat than 
 before, for it does not begin to boil till 640° F. (338° C), 
 while the anhydride boils at 115°r. (46° C). This is the 
 reason why the boiling ceases when the latter has escaped. 
 
 Experiment 9. — Take out some of the anhydride by 
 means of a glass rod, and introduce it into a dry test-tube ; 
 it will fume violently, and after a time become fluid ; that 
 is, it attracts water from the air, and is thereby converted 
 into Nordhausen sulphuric acid. On longer standing, it 
 absorbs still more water, and ceases to fume ; it thus 
 })ecomes common sulphuric acid. By evaporation this 
 water cannot again be removed. 
 
 Experiment 10. — If anhydrous sulphuric acid be thrown 
 into water, it is dissolved with a hissing noise and the 
 violent evolution of heat. 
 
SULPHURIC ACID. 
 
 149 
 
 Experiment 11. — It is likewise dissolved by common sul- 
 phuric acid, converting this into the fuming acid. Fuming 
 sulphuric acid may therefore be regarded as a compound 
 of the anhydride with ordinary sulphuric acid, £[2804,803. 
 
 Fuming, or Nordhausen sulphuric acid, is obtained by the 
 distillation of green vitriol, or ferrous sulphate. 
 
 Experiment 12. — Put a crystal of green vitriol into a hard 
 glass tube, and heat it ; aqueous Fig. 54. 
 
 vapour escapes, and the green 
 
 crystal becomes white (anhy- ■ 
 drous). On further heating, the 
 white colour passes into reddish- 
 brown, and sulphurous and sul- 
 phuric anhydrides are evolved, 
 while the iron remains as ferric oxide : 
 
 2FeS04 = S02 + S03-f Fe2 03. 
 
 In preparing the fuming acid on a large scale, earthen 
 retorts are used, and the anhydride is conducted into 
 common sulphuric acid, which dissolves the sulphuric 
 anhydride, and is thereby converted into the fuming acid, 
 while the sulphurous anhydride escapes. It is a thick 
 liquid, like oil, and is called Nordhausen sulphuric acid, 
 because this city supplied Germany with it for centuries. 
 It has the specific gravity of 1 • 9. 
 
 As long as the process of manufacturing sulphuric acid 
 from green vitriol was the only one known, it was a very 
 expensive article. A hundredweight is now obtained for 
 the same sum that was formerly paid for two pounds. 
 
 Common Sulphuric Acid, H2SO4. — Sulphur by burning is 
 converted into sulphurous anhydride, 8O2, and this com- 
 bined with water gives sulphurous acid, H2SO3. To con- 
 vert this into sulphuric acid, H2SO4, an additional atom of 
 oxygen is necessary, and this additional oxygen is generally 
 supplied at the expense of nitric acid. 
 
 Experiment 13. — Fasten some pieces of sulphur to an 
 iron wire, inflame, and hold them in a capacious botrle 
 containing a little water, until the blue sulphur flame is 
 extinguished ; the bottle becomes filled with a white 
 smoke, which is recognised by its odour to be sulphurous 
 acid. If you now introduce a shaving moistened with 
 
150 
 
 EXPERIMENTAL CHEMISTRY. 
 
 nitric acid into the vessel, reddish-yellow fumes will im- 
 mediately form around the wood, gradually filling the 
 whole bottle. These fumes are nitric peroxide, 
 and their evolution indicates that the sul- 
 phurous acid has withdrawn oxygen from the 
 nitric acid, and has been oxidized and con- 
 verted into sulphuric acid. After some time 
 the bottle becomes clear again, because the 
 vapour of the sulphuric acid formed sinks to 
 the bottom, and dissolves in the water, and 
 we can now again burn sulphur in the bottle. 
 If we repeat this operation several times, we can soon 
 prepare a few ounces of dilute sulphuric acid. 
 
 Experiment 14. — Add some drops of a solution of barium 
 chloride to a portion of the acid liquid just obtained ; a 
 copious white precipitate is formed, which disappears 
 neither by boiling, nor by the addition of water or nitric 
 acid. This precipitate is barium suljphate^ a salt quite 
 insoluble in water and acids. Add one drop of the diluted 
 acid to a wine-glassful of water, and add to this a little 
 more of the solution of barium chloride ; even at this 
 great dilution a perceptible cloudiness will be produced. 
 A solution of barium chloride, or nitrate, is the most 
 certain test for detecting sulphuric acid and sulphates. 
 
 TJie manufacture of common sulphuric acid on a large scale 
 is conducted on the same principle as in the last experi- 
 ment but one. The sulphur is burnt on a sort of hearth, 
 and the sulphurous anhydride thus formed is carried by 
 the draught of air into an immense leaden chamber, the 
 atmosphere of which is kept moist by jets of steam. The 
 sulphurous anhydride thus becomes sulphurous acid. A 
 little nitric acid (or sodium nitrate and sulphuric acid, 
 which yield nitric acid) is placed in a basin, supported 
 above the burning sulphur, and the heat drives it in 
 vapour into the chamber. In the leaden chamber this 
 nitric acid immediately oxidizes a portion of sulphurous 
 acid into sulphuric acid, and is itself reduced to nitric 
 oxide, NO : 
 
 2HNO3 + 3H2S03= H,0 -f 2N0-f- 3H2SO4. 
 Now we shall hereafter learn that nitric oxide is a 
 
SULPHURIC ACID. 
 
 151 
 
 colourless gas which, on contact with air, takes up oxygen 
 and forms the brown gas, nitric peroxide, NO2. NO + 
 0 = NO2. This change immediately takes place in the 
 leaden chamber, and as fast as the NO2 i« formed it is 
 again reduced to NO by another portion of sulphurous 
 
 ^"^'^ • N O2 + H2 S O3 = N 0 + H2 S O4. 
 
 Again the NO takes oxygen from the air of the chamber, 
 and becomes NO2, and again a new portion of sulphurous 
 acid is oxidized into sulphuric acid, so that the process, 
 after the first stage, is continuous. The nitric oxide acts 
 as a carrier^ taking oxygen from the air, and giving it out 
 again to the sulphurous acid, which is unable to take 
 oxygen direct from the air (except very slowly ), «o that 
 theoretically there is no limit to the quantity of sulphurous 
 acid which may be oxidized by a given weight of nitric 
 acid. As fast as the sulphuric acid forms, it condenses 
 and settles down on the floor of the leaden chamber. 
 From time to time it is drawn off and concentrated by 
 evaporation, first in leaden, and afterwards in glass or 
 platinum vessels. The acid thus obtained has almost 
 exactly the composition of true sulphuric acid, H2SO4. 
 
 The above account of the sulphuric acid manufacture 
 must only be regarded as an approximation to the truth, 
 for the process is in fact extremely complex. If the 
 quantity of steam be deficient, white ciystals of complex 
 composition are apt to form. On the addition of water, 
 however, they are decomposed, and sulphuric acid formed 
 from them. 
 
 Experiment 15. — Let some sulphuric acid remain in an 
 open flask exposed to the air ; it will increase every day 
 in weight, /or it very eagerly attracts water from the air. 
 After standing for some months in a damp place it will 
 become two or three times heavier than before. Some 
 substances, especially gases, are dried by means of sulphuric 
 acid. 
 
 Experiment 16. — A piece of wood introduced into sul- 
 phuric acid becomes black, and is charred just as when it is 
 exposed to the flame of a candle. The sulphuric acid seizes 
 upon its hydrogen and oxygen, which combine to form 
 water, and the cai'bon is left behind. Wood may be charred 
 
152 
 
 EXPEEIMENTAL CHEMISTRY. 
 
 in tbis way, in order to protect it from decay in moist 
 situations. In tiie refining of lamp-oil, the mucilage of 
 the oil is charred by sulphuric acid. Sulphuric acid chars 
 and destroys many vegetable and animal substances. If 
 figures are inscribed on paper with very dilute sulphuric 
 acid, and the paper warmed, the figures will come out 
 black. As the acid becomes concentrated, it acts upon 
 and chars the paper. 
 
 Experiment 17. — Pour a drop of oil of vitriol upon paper ; 
 decomposition takes place slowly, but it will take place 
 instantaneously if a drop of water is added, because water 
 and sulphuric acid unite together with the evolution of strong 
 heat. For this reason, when sulphuric acid comes in 
 contact with the skin, it should first be wiped off with dry 
 paper or cloth, and then be immediately washed with a 
 great quantity of water. 
 
 Experiment 18. — Pulverise a small quantity of indigo, and 
 form a thin paste of it with fuming sulphuric acid. After 
 a few days add to it some water, and you obtain a deep 
 blue liquid — solution of indigo. With this solution wool 
 may be dyed of a fine blue colour (Saxon-blue). Common 
 sulphuric acid dissolves indigo only imperfectly. Indigo, 
 although a vegetable substance, is not carbonised by 
 sulphuric acid, thus forming an exception to the general 
 rule. 
 
 Experiment 19. — To half an ounce of copper oxide add two 
 ounces of water, and then gradually two-thirds of an ounce 
 of sulphuric acid, and put it in a warm place ; you obtain 
 a blue solution, from which afterwards blue crystals 
 will be deposited. The edges of these crystals are usually 
 obtuse, giving to the narrow sides a roof-like appearance. 
 Copper oxide combines with the acid, forming copper 
 sulphate (blue vitriol), a soluble salt. The following 
 metallic sulphates are commonly called vitriols : ferrous 
 sulphate (green vitriol) ; zinc sulphate (white vitriol) ; and 
 copper sulphate (blue vitriol). Copper or iron vessels are 
 cleaned more rapidly and made brighter by water to which 
 some sulphuric acid has been added, than by simple water 
 alone, because the oxide, which tarnished the vessels, is 
 dissolved by the acid. 
 
 Experiment 20. — Put a small iron nail into a test-tube. 
 
SELENIUM AND TELLURIUM. 
 
 153 
 
 and drencli it with twenty drops of common sulphuric acid ; 
 it is not acted upon. But if you add a little water, about 
 four or five times more than the acid, a brisk effervescence 
 will ensue, and the iron will be dissolved. The strong 
 acid may be heated to boiling in iron vessels without 
 acting upon them, which is by no means the case with the 
 diluted acid. In this experiment, hydrogen escapes, and 
 iron sulphate remains in solution. Zinc behaves in a 
 similar manner. Consequently, the diluted acid must be 
 employed for dissolving such metals. But there are also 
 metals which dissolve only in the stronger acid, with the 
 aid of heat ; for instance, copper, silver, &c. This has 
 been treated of under sulphurous acid. 
 
 SELENIUM, Se = 79, AND TELLURIUM, Te = 128. 
 These elements are very scarce and unimportant ; they 
 occur combined with certain metals in some rare minerals. 
 They both resemble sulphur in their properties, but 
 partake more of the character of metals in appearance. 
 Their compounds with hydrogen and oxygen correspond 
 perfectly to those of sulphur. 
 
154 
 
 EXPERIMENTAL CHEMISTRY. 
 
 CHAPTEE III. 
 
 NON-METALLIC TRIADS. 
 
 (Nitrogen, Phosphorus, Boron.) 
 NITROGEN. 
 
 Symbol, N = 14. Formtila, N2. 
 In the free state as gas nitrogen constitutes about four- 
 fifths of the atmosphere, the remaining one-fifth being 
 oxygen. In a state of combination it is an important 
 constituent of organic structures. It is also found in the 
 mineral kingdom, as in saltpetre or nitre, a salt occurring 
 as an incrustation on the earth in India and elsewhere ; 
 from this salt the name nitrogen (generator of nitre) is 
 derived. 
 
 The most convenient and simple method for the pre- 
 paration of nitrogen consists in removing the oxygen from 
 a confined portion of air by the ordinary process of com- 
 bustion. 
 
 Experiment 1. — Fasten a piece of sponge to a wire, drop 
 some alcohol upon it, and hold the wire 
 in a vessel containing water so that the 
 sponge may be some inches above the 
 water. Then kindle the spirit, and im- 
 mediately place an empty bottle over it, 
 so that the mouth of it may dip into the 
 water ; the flame will soon cease burning, 
 and some of the water will rise into the 
 bottle, in proportion to the amount of air 
 disappearing during the combustion. The 
 consumed air was oxygen, which united 
 with the constituents of the alcohol. Close the bottle 
 tightly with the finger, shake it briskly, and again open 
 it below the water, iV-hen a little more water will enter. 
 
NITROGEN. 
 
 155 
 
 The air which remains in the bottle is nitrogen ; it is some- 
 times called azote (a, privative, and ^077, life), from its 
 inability to support respiration. 
 
 Other combustibles may be used for the purpose of ab- 
 stracting the oxygen from air, such as sulphur, charcoal, 
 &c., but phosphorus is the best ; for the products of 
 combustion of the other substances, being gaseous, are 
 not easily got rid of, and ccmsequently contaminate the 
 nitrogen, whereas the phosphorus compound produced 
 is solid, and moreover very soluble in .water. Moreover 
 phosphorus burns till all the oxygen is removed, which 
 is not the case with many combustibles. 
 
 Experiment 2. — Place a small piece of dry phosphorus 
 in a little basin floating in water. Ignite the phosphorus 
 and place over it a bell-jar or the mouth of a wide-necked 
 bottle. The phosphorus will burn until the whole of the 
 oxygen is consumed. Dense white clouds of phosphoric 
 anhydride (P2O5) are formed and fill the jar, but these 
 after a time are precipitated in snowy flakes, and are 
 rapidly dissolved by the water. The water will rise in 
 the bottle, partly from the removal of oxygen and partly 
 from some air having been expelled at the beginning of 
 the experiment in consequence of the expansion produced 
 by the heat. When the white fumes have entirely dis- 
 appeared the bottle may be shaken so as to cause the 
 basin to fill and sink, and the nitrogen transferred in the 
 pneumatic trough to a series of smaller bottles. 
 
 Nitrogen is incombustible, except at a very high tem- 
 perature. It will not support combustion, for a lighted 
 taper immersed in a jar of it is extinguished. It has 
 neither colour, smell, nor taste, and in a chemical point 
 of view it must be regarded as a very inert body, since 
 it does not combine directly with any other substance 
 except with great difficulty. 
 
 Nitrogen gas is erroneously called azote, as we are 
 continually breathing it without perceiving any injurious 
 effects from it. The human body is so coustructed, that 
 it will not thrive on substances intended as nourishment 
 if they are presented to it in their purest form. Strong 
 alcohol acts as a poison, but when diluted with four or five 
 times its quantity of water, as in -wine, it is invigorating. 
 
156 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Even the respiration of oxygen would soon destroy life, 
 were it not diluted with four times its volume of nitro- 
 gen, as in atmospheric air. 
 
 Besides oxygen and nitrogen, air contains vapour of 
 water and carbonic anhydride. The presence of the former 
 is rendered obvious by the fall of rain, snow, dew, &c. ; 
 and that of carbonic anhydride can easily be shown by 
 letting lime-water remain exposed to the air, or by 
 shaking it in a flask containing air. This occasions a 
 cloudiness in the liquid. If you ask, What is the source 
 of this carbonic anhydride? the reply is, It is formed 
 wherever substances are burning, wherever men and 
 animals are breathing, and wherever decay and putrefac- 
 tion are taking place. (Page 129.) 
 
 The following is a close approximation to the average 
 composition of the air : 
 
 By Volume. By Weight. 
 
 Nitrogen 79 77 
 Oxygen 21 23 
 
 100 100 
 
 The carbonic anhydride amounts in pure country air 
 to about three volumes in 10,000. In towns it is more 
 abundant. 
 
 The air is not a compound, but only a mixture. It varies 
 slightly in composition, which compounds never do, and 
 its properties are intermediate between those of its con- 
 stituents, whereas those of a compound are entirely dif- 
 ferent. 
 
 In crowded rooms, and other confined places, the air 
 becomes deteriorated ; that is, poorer in oxygen and richer 
 in carbonic anhydride. 
 
 That the air also contains other foreign ingredients is 
 not strange, since it is the constant receptacle of volatile 
 substances and dust. Tbe air coming from the Spice 
 Islands, even at the distance of eight or ten miles, is 
 impregnated with the odour of cinnamon and cloves. 
 The dust contained in the air can be discerned in the sun- 
 beam, &c. Minute quantities of ammonia and nitric acid 
 are also found in the air. The presence of ozone has 
 
AMMONIA. 
 
 157 
 
 already been noticed. The specific gravity of dry air, at 
 standard pressure and temperature, is 14*47, that is, it is 
 about 14 J times heavier than hydrogen. 
 
 AMMONIA, NH3. 
 
 This important gas cannot be prepared by the direct 
 union of its elements. It is frequently formed during the 
 putrefaction of organic bodies, but its most convenient 
 source is in the " ammoniacal liquor " of gas-works. From 
 this a white substance called sal-ammoniac — the ammonium 
 chloride of chemists — is manufactured. 
 
 Experiment 1. — Mix about half an ounce of powdered 
 sal-ammoniac with about one ounce of slaked lime. A 
 pungent odour of hartshorn is perceived. Introduce the 
 mixture into a dry Florence flask fitted with a cork and 
 a short tube which communicates by an india-rubber tube 
 with a long straight tube. Apply a gentle heat, and 
 ammonia-gas will come off in abundance. It is very 
 soluble in water, but being lighter than air it may be 
 collected by upward displacement^ that is, by holding a 
 bottle mouth downwards over the tube and allowing the 
 light gas to displace the heavier air. The reaction by 
 which the gas is prepared is as follows : — 
 
 Ammonium Tirr.^ ArY^»v^^r^^„ Calcium 
 
 Chloride. Ammonia, chloride. 
 
 2NH4Cl+Ca(OH)2 = 2NH3-fCaCl2-)-2H20. 
 
 ^2^ 
 
 Calcium chloride remains in the flask, together with the 
 excess of lime. 
 
 Experiment 2. — Plunge a taper into a bottle of ammonia 
 held with its mouth downwards. The taper will be ex- 
 tinguished and will not ignite the gas. 
 
 Experiment 8. — We must not too hastily conclude from 
 the preceding experiment that ammonia cannot be made 
 to burn. Hold the end of the tube from which the gas is 
 issuing in a flame. You will perceive that the gas burns 
 with a greenish flame as long as the jet is heated, but that 
 it goes out when the lamp is removed. Ammonia icill hum 
 when strongly heated. During its combustion its hydrogen 
 is oxidized to water, and its nitrogen escapes free. 
 
 Experiment 4. — Eemove the stopper downwards from a 
 bottle of ammonia, and afterwards immerse the mouth of 
 
158 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the bottle in water. The water will rise rapidly, and if 
 the bottle was quite full of gas, will fill it. If a piece of 
 red litmus-paper is dipped in the water of the bottle its 
 blue colour will return. Ammonia is soluble in water, and 
 its solution is a base. 
 
 One volume of water at freezing-point will dissolve 
 1149, and at ordinary temperatures about 800 volumes of 
 the gas, so that it is even more soluble than hydrochloric 
 acid. A concentrated solution of it may be prepared like 
 that of hydrochloric acid. It is sold under the name of 
 solution of ammonia, or "liquor ammonias," and lias a 
 specific gravity of 0*88. Weaker solutions are sometimes 
 called hartshorn," or " spirits of hartshorn," because they 
 were formerly obtained by the distillation of horn. 
 
 Experiment 5. — Ammonia-gas, like hydrochloric acid, can 
 easily be prepared by gently heating its concentrated 
 solution. By prolonged boiling all trace of ammonia may 
 be removed from water. 
 
 Experiment 6. — The direct combination of ammonia and 
 hydrochloric acid gases has already been noticed (page 14 ). 
 The experiment may be repeated with equal volumes of the 
 pure gases. Sal-ammoniac or ammonium chloride is formed : 
 NHg-l-HCl = NH^Cl. 
 
 Experiment 7. — Carefully neutralize a dilute solution of 
 ammonia with nitric acid, so that it has no effect on either 
 blue or red litmus. The solution will contain a salt 
 called ammonium nitrate, which may be obtained in the 
 dry state by evaporation : 
 
 NH3 + HNO3 = NH4NO3. 
 
 Ammonium compounds, — The compounds of ammonia are 
 so similar in many of their properties to those of po- 
 tassium and sodium, that they are generally supposed to 
 be analogous in structure, and to contain a sort of com- 
 pound metal called ammonium, NH4, which has not been 
 isolated. When the gas dissolves in water it is assumed 
 that the hydrate of this quasi metal is formed : NH3-f-H20 
 = NH4H0. The theoiy is convenient, but is inconsistent 
 with some known facts. 'I'he following table shows the ana- 
 logy which on this view exists between potassium and am- 
 monium salts : — 
 
AMMONIUM COMPOUNDS. 
 
 159 
 
 K O H Potassium Hydrate. 
 
 KCl „ Chloride. 
 
 K N O3 „ Nitrate. 
 
 KgS O4 „ Sulphate. 
 
 N H4 O H Ammonium Hydrate (?). 
 NH4CI „ Chloride. 
 
 N H4 N O3 „ Nitrate, 
 (N S O4 „ Sulphate. 
 
 It will be seen that to represent the composition of any 
 ammonium salt we need only take the formula of the 
 corresponding potassium or sodium compound and write 
 NH4 instead of K or Na. 
 
 Experiment 8. — Put about an ounce of mercury into a 
 mortar and press into it with the pestle a few fragments 
 of clean dry sodium. The two metals will combine with 
 a flash of light, and a semi-fluid mass called sodium 
 amalgam will be obtained. When cold, throw this into a 
 tumbler about one-quarter full of a cold saturated solution 
 of sal-ammoniac. The amalgam will immediately begin 
 to swell, and will soon assume such an enormous volume 
 as to float in the liquid as a metallic mass, which feels 
 like butter. From the moment of its formation, however, 
 this curious substance begins to change into ammonia, 
 hydrogen and mercury. It is called ammonium amalgam, 
 and it is believed to be formed by the temporary com- 
 bination of the ammonium, which has lost its chlorine, 
 with mercury. The following formula, in which n denotes 
 an unknown number of atoms, explains its formation : 
 
 N H4 CI + Na Hg, = N H4 Hg„-f- Na CI. 
 
 By washing with water the mercury is afterwards 
 recovered without loss. 
 
 The specific gravity of ammonia-gas is 8*5, a little 
 more than half that of air (U-47); at -84° C. (-29° F.) 
 it becomes liquid, and at — 75° C. ( — 103° F.) it freezes to 
 a transparent, ice-like solid. 
 
 It must be born'e in mind that the name ammonia is 
 often given to the solution, which is commonly called 
 ammonium hydrate. 
 
 COMPOUNDS OF NITROGEN AND OXYGE^^. 
 Oxides. Corresponding Acids. 
 
 N,0 Nitrogen monoxide, or! ^ q .^^^^^^^^^ 
 Nitrous oxide J ^ 
 
 N2 O2 or N 0 itrogen dioxide, ) 
 or Nitric oxide j 
 
160 
 
 EXPERIMENTAL CHEMISTRY. 
 
 COMPOUNDS OF NITROGEN AND OXYGEN — Continued, 
 Oxides. Corresponding Acids. 
 
 N,03 Nitrogen trioxide, or J jj ^ j^j^^^^^ 
 
 Nitrous anhydride j ^ 
 
 N2 O4 orN O2 Nitrogen tetroxide, 1 
 or Nitric peroxide j 
 
 ^Mtriflnhydridr''*''^'^^^ ] H N O3 Nitric acid. 
 
 Of these compounds nitric acid is undoubtedly the most 
 important, and as, moreover, it is the source from whence 
 the other oxides are obtained, it claims our first attention. 
 
 The oxide N2O5, nitric anhydride, corresponding to 
 nitric acid, is prepared with difficulty. Tt is a white 
 crystalline solid, which combines eagerly with water : 
 
 N2O5 + H2O = 2HNO3. 
 
 Nitric Acid or Aquafortis^ H N O3. 
 
 Experiment 1. — Introduce into a small retort half an 
 
 ounce of powdered salt- 
 * petre and add, by means 
 
 of a thistle-headed 
 funnel, about an equal 
 weight of sulphuric acid. 
 If a tubulated, i.e., 
 stoppered, retort is used, 
 the thistle funnel is not 
 required. Then adapt 
 the beak of the retort to 
 a flask or bottle, and 
 apply a gentle heat. In a short time a yellowish fuming 
 fluid passes over into the receiver, which is placed in a 
 vessel filled with water, and must frequently be sprinkled 
 with cold water ; this fluid is heavier than water, and is 
 called nitric acid. 
 
 Saltpetre is potassium nitrate, KNO3. When it is 
 acted upon by sulphuric acid the metal and part of the 
 hydrogen change places; we get nitric acid and a salt 
 called hydrogen potassium sul})hate, HKSO4, in which 
 half the hydrogen of the acid is replaced by potassium ; 
 KNO3 + H2SO4 = HNO3 + HKSO,. 
 
NITRIC ACID. 
 
 IGl 
 
 At a higher temperature the hydrogen potassium sul- 
 phate will decompose another molecule of potassium nitrate : 
 
 KNO3 + HKSO4 = HNO3 + K2SO4; 
 
 but on the small scale it is better not to push the action 
 so far, or the retort will be apt to break. K2SO4 is called 
 neutral, or di-potassium sulphate. 
 
 By using perfectly dry potassium nitrate and con- 
 centrated sulphuric, acid, true nitric acid, HNO3, 
 obtained as a yellowish liquid, which fumes strongly 
 when exposed to the air. It is hence called fuming nitric 
 acid, and is the strongest that can be prepared. It is one 
 and a half times heavier than water, its specific gravity 
 being 1 • 52. A weaker kind is commonly met with in 
 commerce as ordinary nitric acid, or aquafortis. It con- 
 sists of 60 parts of true nitric acid and 40 of water, and 
 has a specific gravity of 1-42. This acid is colourless 
 when pure, but usually^ possesses a yellowish tint. When 
 very strong or very weak nitric acid is heated, acid of 
 this strength is obtained. It can be distilled unchanged. 
 
 Experiment 2. — A drop of nitric acid is sufficient to 
 acidify several spoonfuls of water, and even at a greater 
 dilution it will redden blue litmus-paper ; nitric acid is 
 accordingly distinctly characterized as an acid. 
 
 Experiment 3. — If lead be heated for a long time in the 
 air it abstracts oxygen from it, and becomes converted 
 into a reddish-yellow powder, called lead oxide, or 
 litharge. Take up a small portion of this litharge on the 
 point of a knife, put it into a test-tube, and add some 
 dilute nitric acid. The greater part will be dissolved by 
 gentle heating. Filter the solution while warm, and put 
 it in a cold place ; a salt will be deposited from it in white 
 brilliant crystals ; this is lead nitrate. This shows that 
 lead oxide is a basic oxide, as it combines with acids 
 forming salts. 
 
 Nitric acid dissolves most of the metallic oxides, and 
 forms with them salts, all of which are soluble in water. 
 For this reason, nitric acid is often used for cleaning 
 metals, for instance, copper and brass instruments, which, 
 during the process of annealing, soldering, &c., have 
 become covered with a coating of oxide. 
 
 •M 
 
162 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 4. — Pour over some shot, common nitric 
 acid, slightly diluted with water ; a solution is also 
 effected in this instance, but it is accompanied by the 
 evolution of a yellowish-red vapour of a suffocating smell. 
 This vapour is nitric peroxide. Part of the nitric acid is 
 decomposed, while another part of it combines with the 
 lead, and forms the same salt, as in the former experiment. 
 This likewise crystallizes from its solution, if it is evapo- 
 rated until a film forms on its surface. 
 
 In this case the lead is apparently dissolved, but it is 
 obvious that this is quite a different kind of solution from 
 that of common salt or sugar in water. The salt and 
 sugar are unchanged in the solution, while the lead is not 
 contained in the liquid as a metal, but as a salt, a nitrate. 
 The same thing occurs with all other metals which are 
 soluble in nitric acid ; as, for example, with silver, 
 mercury, copper, iron, &c. Gold is not dissolved by it ; 
 hence gold may be separated from silver by means of 
 nitric acid. 
 
 Nitric acid readily parts with a portion of its oxygen. 
 It is therefore a powerful oxidizing agent. 
 
 Experiment 5. — Place a few fragments of tin in a glass, 
 and pour over them nitric acid with a few drops of water. 
 A violent action is set up, and red suffocating fumes are 
 copiously evolved. The tin is not dissolved and converted 
 into nitrate as the lead was, but becomes a white insoluble 
 powder, an oxide of tin called meta-stannic acid. 
 
 Experiment 6. — Some of the non-metallic elements, as 
 well as of the metals, are oxidized by nitric acid ; charcoal, 
 on being boiled in it, becomes carbonic acid ; sulphur, 
 sulphuric acid ; phosphorus, phosphoric acid, &c. In all 
 these cases yellowish-red fumes are evolved. 
 
 Experiment 7. — Organic substances also, as wool, feathers, 
 wood, indigo, (fee, are oxidized and decomposed by heating 
 them with nitric acid. This sort of decomposition may 
 be regarded as combustion in the moist way. If sub- 
 stances of animal origin are allowed to remain for a short 
 time only in contact witli this acid, they will assume a 
 yellow colour. In this manner wood may be stained, and 
 silk may be dyed yellow ; the hands and clothes are also 
 stained yellow by nitric acid. Cotton undergoes a most 
 
NITROUS OXIDE. 
 
 163 
 
 remarkable change if soaked for a short time in the 
 strongest nitric acid ; it will then detonate and explode 
 like gunpowder, only far more violently (gun-cotton). 
 Strong nitric acid is partially decomposed, and coloured 
 yellow, by the rays of the sun. 
 
 If you colour some water blue in a test-tube with one 
 drop of solution of sulphate of indigo, and add to it on 
 boiling one drop of nitric acid, the blue colour will 
 disappear. This reaction often serves for the detection of 
 nitric acid. 
 
 Experiment 8. — The nitrates are easily decomposed by 
 heat, being in most cases converted into metallic oxides or 
 metals. Having powdered some of the lead nitrate, 
 obtained in Experiment 3 or 4, throw it upon a red-hot 
 coal ; active combustion of the coal will ensue, at the 
 expense pf the nitrate, and globules of metallic lead will 
 remain beyond. If the lead nitrate is heated alone on a 
 crucible cover or fragment of a broken Florence flask, yellow 
 lead oxide will remain. 
 
 Nitric acid is monobasic; that is, it contains but one 
 atom of hydrogen which can be replaced by metals. Its 
 salts are called nitrates, and it must be remembered that 
 they all contain the monad radical, NO3. 
 
 HNO3 Nitric acid. 
 KNO3 Potassium nitrate. 
 NH4NO3 Ammonium nitrate. 
 Cu(N03)2 Copper nitrate. 
 Bi(N03)3 Bismuth nitrate. 
 
 The nitrates are less easily decomposed than the 
 chlorates, but they resemble the latter salts in the readi- 
 ness with which they part with their oxygen to com- 
 bustibles. In consequence of this property, potassium 
 nitrate is a constituent of some inflammable and explosive 
 mixtures, such as gunpowder, fuses, coloured fires, &c. 
 
 Nitrogen Monoxide, or Nitrous Oxide, N2O. 
 
 Experiment 1. — Cautiously heat the ammonium nitrate, 
 made by Experiment 7 (page 158), in a Florence flask to 
 which a gas delivery tube is connected. The salt will 
 gradually melt and soon effervesce briskly, as a gas — 
 
 M 2 
 
164 
 
 EXPERIMENTAL CHEMISTRY. 
 
 nitrous oxide — is evolved. When the air has been ex- 
 pelled from the flask the issuing gas may be collected at 
 the pneumatic trough, which must be filled with warm 
 water instead of cold, as the gas is soluble in the latter. 
 
 The change which occurs is simple. Heat decomposes 
 ammonium nitrate NH4NO3 entirely into water and nitrous 
 oxide : 
 
 NH4NO3 = 2H2O +N2O. 
 
 Nitrous oxide is seen to be a colourless gas. It can, 
 however, be condensed to the liquid state by great cold. 
 
 It is respirable in moderate quantity, and its effecst 
 when inhaled are peculiar. At first it produces a pleasur- 
 able kind of intoxication — whence its name of laughing gas ; 
 but after a time it causes complete insensibility to pain. 
 It is now much used as a substitute for chloroform in 
 minor surgical operations. 
 
 Nitrous oxide is a good supporter of combustion, its 
 power in this respect being little inferior to that of oxygen. 
 
 The experiments which were performed with the latter 
 gas may be repeated with nitrous oxide, with little 
 difi'erence in their results. Phosphorus, for example, will 
 burn in it with brilliancy, combining with the oxygen and 
 leaving nitrogen behind, which is equal in volume to the 
 original gas. 
 
 N2O - 0 = N2. 
 
 Nitrogen Dioxide, or Nitric Oxide, NO, or N2O2. 
 Experiment 1 . — Pour over a few scraps of copper, placed 
 ■picr^ 58. in a wide-mouthed bottle, a 
 
 little water, and then add by 
 degrees some nitric acid, until 
 a brisk efiervescence ensues. 
 This efiervescence is caused by 
 the evolution of nitric oxide, 
 which must be collected in a 
 jar of white glass over the 
 pneumatic trough. Close the 
 mouth of the jar under water ; 
 it seems to be empty, for the nitric oxide is colour- 
 less ; but if the jar be oi)ened, and air be carefully blown 
 
PHOSPnoRua. 
 
 165 
 
 in, then the jar becomes filled from above downwards 
 with, yellowish-red vapours. The nitric oxide takes 
 thereby from the air one atom of oxygen, and is converted 
 into nitric peroxide. NO becomes NO2. On account of 
 this property, it has an important application in the 
 preparation of sulphuric acid. 
 
 The following is the somewhat complicated equation 
 which describes the formation of nitric oxide : 
 
 Nitric Acid. Copper Nitrate. 
 
 8HNO3 + 3Cu = 3Cu(N03)2 +4H2O + 2N0. 
 The copper nitrate remains as a blue solution in the 
 bottle, and it may be obtained in crystals by evaporation. 
 Nitric oxide supports combustion, although not with the 
 readiness of nitrous oxide. If a piece of phosphorus be 
 ignited and plunged into nitric oxide while feebly burning, 
 it will be extinguished, but if the phosphorus burns briskly 
 when immersed in the gas the combustion proceeds with 
 energy. As in the previous case, the oxygen is removed by 
 the phosphorus ; the nitrogen which remains having half 
 the volume of the original gas. 
 
 2 N 0 - 2 0 = N2. 
 
 4 Vols. 2 Vols. 
 
 Nitrogen trioxide or nitrous anhydride, N2O3, is a red gas, 
 easily condensed to a blue liquid by cold. With water it 
 forms the very unstable nitrous acid, HNO2. 
 
 Nitrogen tetroxide, or nitric peroxide, NO2, or N2O4, is the 
 red gas formed when nitrous oxide comes in contact with 
 excess of oxygen. It is absorbed by water and converted 
 into a mixture of nitrous and nitric acids : 
 
 2NO2 + H2O = HNO2 + HNO3. 
 
 PHOSPHORUS. 
 Symbol, P = 31. Formula for vapour, P4. 
 Great care is required in experimenting with phosphorus 
 that it does not take fire at an unseasonable moment, as it 
 continues burning with the greatest violence, and might 
 occasion dangerous wounds. It may catch fire even when 
 lying upon blotting-paper, particularly in summer-time, 
 or by the heat of the finger. Hence it must be kept, and 
 also cut, under water. On being taken from the water, 
 it should be held by a pair of forceps, or be stuck on the 
 
166 
 
 EXPERIMENTAL CHEMISTRY. 
 
 point of a knife. Prudence also would dictate to experi- 
 ment with, small quantities only at a time, and to have a 
 vessel of water in readiness, in which it may be quenched 
 in case it should catch fire. 
 
 Phosj)horus, like sulphur, melts, boils, evaporates, and 
 burns, but far more easily and rapidly. In winter it is 
 brittle, in summer flexible as wax. When pure and 
 freshly prepared it is colourless, transparent, and amorphous 
 (non-crystalline), but after a time it becomes yellow, and 
 coated over with a white crust. 
 
 Phosphorus is insoluble in water, but soluble in ether, 
 carbon disulphide, and oils. 
 
 Phosphorus is an exceedingly violent poison, and is, for 
 this reason, frequently employed for the extirpation of rats 
 and other vermin. The rat paste, as it is called (phosphorus 
 paste), is composed of one drachm of phosphorus, 8 ounces 
 of hot water, and 8 ounces of flour. 
 
 Preparation of Phosphorus. — Phosphorus was formerly 
 obtained from urine, but is now prepared from bone-ash. 
 Bones consist chiefly of gelatin (or rather ossein) and 
 calcium phosphate, Ca3(P04)2. When the bones are cal- 
 cined the gelatin bums away and the phosphate remains. 
 The ash is treated with sulphuric acid, which converts the 
 greater part of the calcium into the insoluble calcium 
 sulphate, CaS04, while impure phosphoric acid remains in 
 solution. This is dried with charcoal powder and intensely 
 heated in a clay retort. The carbon takes oxygen from 
 the acid, forming carbonic oxide gas, CO, which escapes. 
 The phosphorus also comes over as gas, but is condensed 
 by passing through cold water. 
 
 The changes which occur in the above processes are 
 somewhat more complicated than the description, which is 
 only intended as an approximation, would imply. 
 
 Experiments with Phosphorus, 
 
 Experiment 1. — Put into a small flask first a quarter of an 
 ounce of ether, then a piece of phosphorus, of the size of a 
 pea. Cork the flask and let it stand some days, frequently 
 shaking it. Decant the liquid ; it contains in solution a 
 small quantity of phosphorus, and will serve for the 
 following experiments. 
 
PHOSPHORUS. 
 
 167 
 
 Experiment 2. — Pour some drops of this solution upon 
 tlie hand, and rub them quickly together ; the ether will 
 evaporate in a few moments, but the phosphorus will 
 remain upon the hands in a state of minutest division. 
 The more finely it is divided, so much the more easily does 
 it combine with the oxygen of the air. During this 
 combination it diffuses a white smoke and a faint light (it 
 phosphoresces), causing the hands to shine in the dark ; 
 hence its name, phospJiorus, from c^w?, light, and (/)epa>, to 
 carry. It undergoes slow combustion and is converted 
 into phosphorous anhydride, P2O3, which rapidly takes up 
 water from the air and becomes phosphorous acid : 
 
 P203 + 3H20 = 2H3P03. 
 
 Experiment 3. — Moisten a lump of sugar with the 
 solution of phosphorus in ether and throw it into hot 
 water. The surface of the water will glow prettily in a 
 dark room. 
 
 Experiment 4. — Instead of ether use a few drops of 
 carbon disulphide to dissolve the phosphorus. This liquid 
 takes up more phosphorus than ether does, and the solution 
 is highly dangerous. It is the basis of the modern "Greek 
 fire." Its inflammability may be observed in the following- 
 way : 
 
 Experiment 5. — Pour some of the solution upon fine 
 blotting-paper : the latter ignites spontaneously after the 
 li:][uid has evaporated. The more minutely the phos- 
 phorus is divided, so much the more readily it begins to 
 brrn. 
 
 Experiment 6. — Put a piece of phosphorus of the size of 
 a pea on blotting-paper, and sprinkle over it some soot or 
 pulverized charcoal : it melts after a while, and spon- 
 taneously inflames. The finely pulverized charcoal causes 
 this combustion, owing to its porosity. It eagerly absorbs 
 oxygen from the air, imparts it again to the phosphorus, 
 and, being a bad conductor of heat, the cooling of the 
 latter is prevented. 
 
 Phosphorus is also easily ignited hy friction, and is, for 
 this reason, employed in the manufacture of lucifer- 
 matches. The combustible mass is prepared from hot 
 mucilage, at 158° F. (70^^ C), to which small pieces of 
 
168 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Fig. 59. 
 
 phosphorus are added, being thoroughly incorporated 
 with it by constant rubbing till cold. But as the mass, 
 by becoming hard on drying, prevents the access of air to 
 the phosphorus, there must be added 
 some substance rich in oxygen, as blact 
 oxide of manganese, nitre, or red-lead, 
 from which the phosphorus can abstract 
 the oxygen necessary for its ignition. 
 If part of phosphorus, 4 of gum 
 arable, 4 of water, 2 of nitre, and 2 of 
 red-lead, form a good inflammable 
 mass. A temperature of 149° F. (GS'' C.) 
 to 158° F. (70° C.) is requisite for 
 kindling such matches ; in this case 
 the temperature is caused by friction. 
 The coating of the match is thus broken 
 and kindled, and the continued burning 
 is now maintained by the oxygen of the air. 
 
 Experiment 7.— Put a piece of phosphorus, of the size of 
 a pea, into a wine-glass, and pour hot water upon it until 
 the glass is half filled ; the phosphorus melts, but does not 
 isnite, as access of air is prevented by the water. But if 
 air be carefully blown by the mouth through a long glass 
 tube upon the bottom of the wine-glass, combustion will 
 ensue, which is visible, especially in the dark. 
 
 Experiment 8. — Heat gently a piece of phosphorus of the 
 size of a pea, placed in the middle of a glass tube, about 
 twelve inches long. When ignition commences, remove 
 the lamp. While the tube is held horizontally, the 
 combustion is feeble and im- 
 perfect, because the heavy smoke, 
 consisting of phosphoric and 
 phosphorous anhydrides, pass- 
 ing off slowly, allows the ad- 
 mission of only a small quantity 
 of air. But the combustion im- 
 mediately becomes more vivid 
 on inclining the tube, and when the tube is held per- 
 pendicularly it is complete, as then the draught of air is 
 most powerful. In this way phosphorus may be oxidized 
 to either degree required; it may be slowly burnt to 
 
 Fig. 60. 
 A 
 
PHOSPHINE. 
 
 169 
 
 form phosphorous anhydride, or completely, to form 
 phosphoric anhydride. 
 
 Phosphorus, like sulphur, is capable of existing in 
 several different states (allotropic states). Besides the 
 ordinary kind the most interesting is that called red, or 
 amorphous phosphorus. This is prepared by heating 
 ordinary phosphorus to a temperature of about 240"^ C. 
 (464^ F.) for some time, in a vessel filled with carbonic 
 anhydride or nitrogen to prevent it from burning. Red 
 phosphorus is curiously different in properties from the 
 ordinary kind, being insoluble in carbon disulphide, not 
 poisonous, and only inflammable at a high temperature. 
 It is now used extensively in the manufacture of " safety 
 matches." The tips of these matches do not contain phos- 
 phorus, but when rubbed on the outside of the box they 
 take up a little of the red phosphorus with which the side 
 is covered, and combustion ensues. 
 
 PHOSPHINE, PH3. 
 Experiment 1. — Put into an ounce flask a quarter of an 
 ounce of slaked lime, and a piece of phosphorus the size of 
 a pea, fill it up to the neck with water, and place it in a 
 sm^iU vessel containing a strong solution of salt, prepared 
 
 Fig. 61. 
 
 by adding half an ounce of common salt to an ounce and 
 a half of water. Fit to the flask a bent glass tube, one 
 end of which is made to dip into a basin of water ; heat 
 the salt water to boiling, and a gas will be evolved, 
 which, as it issues from the tube and comes in contact 
 with the air, talzes fire spontaneously. This gas consists 
 chiefly of phosphine, or phosphuretted hydrogen. If you 
 collect it in a small jar filled with water, it immediately 
 
170 
 
 EXPERIMENTAL CHEMISTRY. 
 
 takes fire upon the admission of air. Both the phosphorus 
 and the hydrogen combine with the oxygen of the air, and 
 there results phosphoric anhydride, P2O5, and water, H2O. 
 The first appears as a white smoke, which, when it issues 
 in separate bubbles from the water, rises in rings. 
 
 Phosphine, when unburnt, emits the smell of garlic. 
 
 In this experiment, the flask is placed in salt water, in 
 order to guard against the ignition of the phosphorus, in 
 case the flask should accidentally break. Salt water, at 
 the strength specified, will not boil under 228° F. (109° C.) ; 
 C(>nsequently, the boiling in the flask is more active than 
 if it had been placed in pure water, the temperature of 
 which, under ordinary pressure, can only be raised to 212° 
 F. (100° C). The apparatus for heating substances by 
 means of hot water or saline solutions is called a water or 
 saline hath. By such contrivances extracts are evaporated, 
 and substances dried, which, at a stronger heat, would 
 easily burn, or otherwise be decomposed. 
 
 Phosphine, when pure, is inflammable, but not spon- 
 taneously inflammable. When prepared as above it contains 
 a little of the vapour of another compound of phosphorus 
 and hydrogen — a liquid — which has the formula P2H4. 
 It is the latter compound which is spontaneously inflam- 
 mable. 
 
 COMPOUNDS OF PHOSPHORUS AND OXYGEN. 
 
 P2O3, Phosphorus trioxide, or Phosphorous anhydride. 
 
 P2O5, Phosphorus pentoxide, or Phosphoric anhydride. 
 
 It has been already stated that these oxides can be 
 formed by the direct union of oxygen and phosphorus. 
 The lower oxide and its corresponding acid are un- 
 important. Both oxides are white, snow-like powders, 
 and they greedily combine with water to form acids. 
 
 Phosphoric Anhydride, 
 
 Experiment 1. — Ignite a small piece of phosphorus on a 
 plate and cover it with a dry bottle or bell-jar. Phosphoric 
 anhydride will be abundantly formed, as a white cloud, 
 which settles on the sides of the bottle and on the plate. 
 Shake the powder into a saucer, and pour a little water on 
 it. A sharp hissing noise will be heard, testifying to the 
 
PHOSPHORIC ACID. 
 
 171 
 
 energy with which combination ensues. A solution of 
 phosphoric acid is produced. 
 
 Phosphoric Acid, H3PO4. 
 
 Experiment 2. — Place a piece of phosphorus and a little 
 water in a flask, and carefully heat them until the water 
 boils ; then add a little nitric acid and continue the heat. 
 The phosphorus slowly dissolves, and is oxidized into 
 phosphoric acid. Phosphoric acid prepared in this way 
 is of course contaminated with the excess of nitric acid 
 left undecomposed. This can be removed by evaporating 
 to dryness and boiling the residue with water. 
 
 Phosphoric acid is tribasic, containing three replaceable 
 atoms of hydrogen ; and inasmuch as one, two, or all three 
 of these atoms may be replaced by metals, its salts are 
 very numerous. With sodium, for instance, the three 
 foil wing salts may be obtained : 
 
 NaIl2P04, Sodium di-hydrogen phosphate. 
 Na2HP04, Di-sodium hydrogen phosphate. 
 Na3P04, Tri-sodium phosphate. 
 
 A very great variety of compound salts may be formed 
 by substituting part of the hydrogen with one metal, and 
 part with another. As, for instance, in ammonium magne- 
 sium phosphate, NH4MgP04, in which one atom of hydro- 
 gen is replaced by the monad group of atoms, or compound 
 radical, NH4, and the remaining two atoms by the diad 
 metal magnesium, Mg. 
 
 Experiment 3. — Add ammonia to a solution of sodium 
 phosphate, and then a little solution of magnesium 
 sulphate, MgS04 (Epsom salts). A white precipitate 
 will be produced, consisting of the above-mentioned 
 ammonium magnesium phosphate : 
 
 MgS04-f-Na2HP04 + NH4HO = Na.S04 + 
 NH4MgP04-fH2 0. 
 
 Phosphoric acid or any other soluble phosphate would 
 produce the same effect. Ammonium hydrate and mag- 
 nesium sulphate therefore serve as a test for phosphoric 
 acid and its salts. 
 
172 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The body of an adult contains 
 from 9 to 12 pounds of bones, containing 
 ,, 6 „ 8 pounds of bone ashes, containing 
 „ 5 „ 7 pounds of calcium phosphate, containing 
 „ 1 „ If pounds of phosphorus. 
 
 Phosphates are also contained in the blood, flesh and 
 other portions of the body. Whence does it obtain this 
 phosphorus ? The answer is, from the meat and vegetables 
 which it consumes. The phosphates occur in bread, in 
 all kinds of grain, in leguminous and many other plants, 
 particularly in their seeds. But how do the plants obtain 
 these salts ? By means of the soil. If arable land con- 
 tained no such salts, no seeds could be produced. If we 
 increase their quantity by mixing ground bones with the 
 soil, we place the latter in a situation to produce a larger 
 quantity of grain ; consequently, bones furnish us with a 
 powerful manure. The tri-calcium phosphate present in 
 bones is however insoluble in water, and is absorbed but 
 slowly by soils. It is therefore generally treated with 
 sulphuric acid, by which a mixture of calcium sulphate and 
 acid calcium phosphate, both soluble in water, is obtained, 
 
 C2^3(PO,\+2-R^SO, = CaH4(P04)2+2CaS04. 
 
 The mixture is largely used as manure, and is known 
 as superphosphate of lime. 
 
 Besides ordinary phosphoric acid, two other varieties of 
 phosphoric acid are known, differing in constitution from 
 ordinary phosphoric acid by the relative quantities of 
 water combined with the anhydride. These compounds 
 are distinguished by the prefixes " pyro " and " meta " 
 from ordinary or or^y^o-phosphoric acid. To form ortho- 
 phosphoric acid three molecules of water are necessary, 
 while for pyro-phosphoric acid two are required, and for 
 meta-phosphoric acid only one : 
 
 P2O5 + ^H^O = 2H3PO4, Ortho-phosphoric acid. 
 P.P5 + 2H.p = ll^l\0^, Pyro-phosphoric acid. 
 P.Ps + H2O = 211P03, Meta-phosphoric acid. 
 
 These three acids form salts which correspond to them 
 in constitution. The common or ortho-phosphates contain 
 the triad radical l^O^, the pyro-phosphates, the tetrad 
 
BORON. 
 
 173 
 
 radical V^O^, and the meta-phospliates, which resemble 
 the nitrates in constitution, the monad radical, PO3. 
 
 Experiment 4. — Heat conimon sodium phosphate to red- 
 ness in a crucible for some time. Water is driven off, and 
 sodium pyro-phosphate remains : 
 
 2 Na2 H P O4 = Na^ P2 0^ + H2 0. 
 
 Sodium meta-phosphate may be prepared by heating 
 microcosmic salt, NaNH4HP04 (sodium ammonium hydro- 
 gen phosphate). Ammonia and water are expelled, and 
 the meta-phosphate remains : 
 
 Na N H4 H P O4 = Na P O3 -f N H3 + H2 0. 
 
 These pyro- and meta-phosphates may be dissolved in 
 cold water without change, but if the solutions are boiled 
 water is taken up and common phosphates obtained. 
 
 When common phosphoric acid is evaporated to dryness, 
 meta-phosphoric, or " glacial " phosphoric acid is obtained. 
 This, when -boiled with water, is reconverted to ortho- 
 phosphoric acid : 
 
 HP03-f-H20 = H3P04. 
 
 Experiment 5. — To solutions of sodium ortho-, pyro-, and 
 meta-phosphate add a little solution of silver nitrate. 
 With the ortho-phosphate, a yellow precipitate, and with 
 the others white precipitates are produced. This test 
 distinguishes the ortho-phosphate from the other two. 
 To distinguish between these, add to each of the salts, 
 first some acetic acid, and then a little white of egg beaten 
 np with water. A white precipitate is produced with the 
 meta-phosphate ; none at all with the pyro-phosphate, or 
 ortho-phosphate. 
 
 BORON. 
 B = 11. 
 
 Boron is a triad element, but it resembles carbon in its 
 physical characters. Like carbon it can be obtained as an 
 amorphous powder, and also in the form of octahedi-al 
 crystals which are nearly as hard as diamonds. Boron is 
 chiefly found combined as boric acid in the steam which 
 issues from fissures in the earth in some parts of Tuscany, and 
 bubbles up through small lakes or basins of water. The 
 
174 
 
 EXPERIMENTAL CHEMISTRY. 
 
 acid is obtained by evaporating tbe water of these lakes 
 by an ingenious arrangement, whereby the heat required 
 for the purpose is supplied by the hot springs themselves. 
 
 A sodium salt of boric acid called tincal is imported from 
 Thibet; when purifiedby recrystallization,it is sold as horax. 
 
 Boron is capable of combining directly with many 
 elements, as sulphur, oxygen, and nitrogen. 
 
 The oxygen compound of boron is the most important, 
 the others are of little interest. 
 
 Boric anhydride, B2O3, and Boric acid, H3BO3, sometimes 
 called Boracic acid. 
 
 Experiment 1. — Add powdered borax to boiling water 
 until it ceases to be dissolved, pour off the solution from 
 any undissolved borax, and mix it with about half its bulk 
 of strong hydrochloric acid. Flaky crystals are immedi- 
 ately formed, and deposit abundantly as the mixture 
 cools. Collect the crystals in a filter, wash them with a 
 little cold water, preserve, and label them boric acid, H3BO3. 
 
 Experiment 2. — Pour alcohol on some boric acid, or on 
 borax which has been moistened with oil of vitriol. 
 Inflame the spirit, and in either case it will burn with a 
 greenish flame, from the presence of boric acid. Curiously 
 enough, dry boric acid may be heated to redness without 
 volatilizing, but if it be boiled with water or alcohol it 
 readily passes off in the vapour of those substances. 
 
 Experiment 3. — Heat boric acid in a crucible with a 
 Bunsen's burner. Below a red heat it fuses, and on 
 cooling appears as a colourless glassy mass consisting of 
 boric anhydride, B2O3 : 
 
 2H3BO3 - 3H2O3 = B2O3. 
 
 Experiment 4. — If boric acid is heated at a temperature 
 of about 120'^ C. (248° F.) part only of the water is driven 
 off, and a substance remains called meta-boric acid, IIBOg. 
 
 Borax is an irregular substance, having the formula 
 Na2B407. It may bo regarded as a compound of sodium 
 metaborate with boi ic anhydride, 2NaB02,B203. Borax is 
 often employed in metallurgical operations as a flux. It ' 
 is also used in blowpipe experiments, because some me- 
 tallic oxides give coloured beads when fused with it on a 
 loop of platinum wire. 
 
( ) 
 
 CHAPTER IV. 
 
 NON-METALLIC TETRADS. 
 
 (Carbon, Silicon.) 
 CAKBON. 
 C = 12. Formula unknown. 
 
 If a piece of wood be placed on the hot hearth of a stove, 
 it becomes brown, and finally black — it is charred or 
 carbonized. If water be poured upon a burning chip, the 
 latter is extinguished — it is seen to be also carbonized. A 
 piece of linen, when inflamed and immediately smothered, 
 becomes tinder. Tinder is carbonized linen. In the first 
 case, the heat was not sufficiently strong entirely to burn 
 the wood ; in the second, the complete combustion was 
 prevented by cooling ; and in the third, by the exclusion 
 of air. Many animal and vegetable substances if only partially 
 burnt yield charcoal. As charcoal, on exclusion of the air 
 cannot be melted, even in the strongest heat, so its 
 external appearance is very different, according to the 
 nature and structure of the substance from which it was 
 prepared ; indeed, this difierence often extends to the 
 properties of charcoal, as in wood-charcoal, soot, coke, 
 bone-black, &c. The black matter of the different kinds 
 of charcoal consists of the element carbon. Organic 
 bodies always contain carbon. When they are charred, a 
 great part of the other constituents is driven off, together 
 with a portion of the carbon, as is shown by the fact that 
 the carbonized body weighs much less than the original 
 substance. 
 
 Carbon also exists in the mineral kingdom. It forms 
 the principal element of common coal, brown coal, &c., 
 which have all been formed from the vegetation of an 
 earlier period, and also of the mineral oil and tar which 
 occur in such large quantities in America and other 
 
176 
 
 EXPERIMENTAL CHEMISTRY. 
 
 parts of the world. It is found almost pure as diamond 
 and graphite (black lead), and, combined with oxygen, is 
 contained in limestone, marble, chalk, and various other 
 minerals. 
 
 Charcoal, — Experiment 1. — Gradually introduce a burn- 
 Fig. 62. ing splinter of wood into a test- 
 tube. The part outside of the tube 
 only will burn with a flame, while 
 that within merely carbonizes, be- 
 cause the air is excluded. On the 
 same principle, wood-charcoal is 
 prepared on a large scale. Piles 
 of wood (charcoal kilns) are erected, 
 which are covered with turf and 
 moist earth, and the wood is 
 then kindled. This would be 
 extinguished, however, for want of air, if holes were not 
 made, by wooden pokers, at different parts of the kiln, 
 through which fresh air may be admitted, and the burnt 
 air may escape. Only so much air should be admitted 
 as is necessary for carbonizing or half-bnrning the wood. 
 One pound of wood commonly yields about one quarter 
 of a pound of chaicoal. The quantity, however, varies 
 much with the temperature and the nature of the wood. 
 
 Experiment 2. — Weigh a piece of freshly-burnt charcoal, 
 and let it remain for a day in a moist place ; it will now 
 weigh more than before, owing to its having imbibed air 
 and moisture. If the charcoal be now put into hot water, 
 the air will escape from it in numerous bubbles, being 
 expelled by the heavier water, which replaces the air in 
 the small interstices or pores of the charcoal. 
 
 Experiment 3. — Cover a dead rat to a depth of about an 
 inch with coarsely-powdered wood-charcoal. The animal 
 will soon putrefy, but the vessel will not give out any 
 disagreeable odour even if kept for years. All the noxious 
 gases which are given out are absorbed and destroyed by 
 the charcoal. 
 
 Experiment 4. — Foul stagnant water ig deprived of its 
 bad taste, and is rendered clear and colourless, by being 
 filtered through charcoal. In some large cities, where 
 there is a scarcity of potable water, it is not unusual to 
 
CARBON. 
 
 177 
 
 filter throngli cliarcoal. Charcoal renders ordinary 
 brandy pleasanter in taste and smell, by absorbing into 
 its pores an acrid volatile oil, fusel oil, with Fig. 63. 
 which crude brandy is contaminated. It also 
 deprives beer of its bitterness, by absorbing 
 certain component parts of the hops. 
 
 The cause of these remarkable properties of 
 charcoal is to be found in the number of pores 
 with which it is permeated. Into these pores, 
 gases are absorbed, sometimes in enormous 
 quantity. Cocoa-nut charcoal introduced into 
 ammonia-gas standing over mercury, will absorb 
 
 171 times its volume of the gas. Now under 
 
 ordinary circumstances charcoal, being exposed to the air, 
 contains a great deal of absorbed oxygen, and it is this 
 oxygen which destroys the noxious matters with which 
 the charcoal comes in contact. 
 
 In addition to wood-charcoal, the following other kinds 
 of charcoal have many different applications. 
 
 Soot^ or lamp'hlach, is charcoal in a state of minute 
 division, which is deposited from carbonaceous gases, 
 commonly from illuminating gas ; for instance, from the 
 flame of common coal, wood, oil, rosin, &c., when during 
 the combustion there is an insufficient supply Fig. 64. 
 of air. One variety of superior quality is called 
 lamp-black. The soot must be freed from empy- 
 reumatic substances, by igniting it thoroughly 
 in a well-closed vessel. Soot, as is well known, 
 is our most important black colouring substance 
 (Indian ink, printing-ink). 
 
 Coke, or carbonized coal, has a grey colour, 
 is more or less porous, is very hard and has a 
 metallic lustre ; it burns without forming soot, 
 and gives out an intense heat ; hence it is an 
 excellent fuel, and especially adapted for the 
 smelting of iron, and for the heating of locomotive 
 boilers. Coke is obtained as a secondary product in the 
 preparation of illuminating gas from coal. 
 
 Bone-hlaclc, or animal cliarcoal, is obtained by heating 
 bones in close vessels. The carbon contained in it amounts 
 to little more than one-tenth part of the whole, the rest 
 
 N 
 
178 
 
 EXPERIMENTAL CHEMISTRY. 
 
 being bone-ash ; but, notwithstanding this, its decoloriz- 
 ing power is so strong, that it is preferred to all other 
 kinds of charcoal as a means of abstracting colour from the 
 syrup of brown sugar, or from other dark liquids. 
 
 Two sorts of carbon found in the mineral kingdom, viz., 
 graphite and the diamond, possess very remarkable, yet 
 different, properties. 
 
 Graphite, or plumbago, a grey substance, having a 
 metallic lustre, imparts its colour so readily to other bodies, 
 that it is used for making pencils, and for giving a black 
 polish to iron articles, such as stoves,- &c.; it is so soft 
 and lubricating, that it is added to grease for the purpose 
 of preventing friction in wheels and machinery ; it is also 
 so nearly incombustible, that it is sometimes used in the 
 manufacture of crucibles. 
 
 Diamond is the hardest of all bodies. In external ap- 
 pearance it has not, indeed, the slightest resemblance to 
 charcoal, yet it can be entirely burnt up in oxygen, and 
 carbonic anhydride is the only product obtained from it ; 
 and exactly so much is obtained as would have resulted 
 from the combustion of an equally heavy piece of 
 purified wood- charcoal or coke. At a high temperature 
 and under great pressure minute diamonds can be obtained 
 artificially. 
 
 Carbon shows very clearly how one and the same body 
 can have quite difi'erent forms and different properties. 
 In wood-charcoal, soot, coke, and animal charcoal, it is 
 black, without any determinate shape (amorphous), and very 
 combustible ; in graphite it is black, with a crystalline 
 foliated structure, and is nearly incombustible ; in the 
 diamond it is colourless, and is crystallized as a double 
 four-sided pyramid (octahedron), and is likewise almost 
 incombustible. Hence carbon is said to be dimorphous, 
 having two different crystalline forms. If a body can 
 assume more than two crystalline forms it is said to be 
 polymorphous (having many forms). 
 
 Charcoal undergoes no change on exposure to the air, 
 or when imbedded in the ground. It is not changed 
 at common temperatures, that is, it does not enter into 
 combination with the oxygen of the air or of water. But 
 this, as is well known, takes place very readily, when 
 
CARBON AND OXYGEN. 
 
 179 
 
 heated to redness. It then burns and disappears, with 
 the exception of a small quantity of ash. The heat thus 
 developed is the result of its chemical combination with 
 the oxygen of the air. The gas generated is called 
 carbonic anhydride, which forms, with lime-water, a white 
 precipitate (calcium carbonate), as has been stated pre- 
 viously. 
 
 COMPOUNDS OF CARBON AND OXYGEN. 
 
 Carbonic anhydride, or carbon dioxide, CO2. Carbonic 
 acid H2CO3 (?). 
 
 Carbonic oxide, or Carbon monoxide, CO. 
 
 Carbonic anhydride, CO2, sometimes called carbonic 
 acid gas. — It has already been shown (page 128) that 
 all ordinary kinds of fuel contain carbon, and there- 
 fore yield, during their combustion, carbonic anhy- 
 dride, and that this gas may be detected by lime-water, 
 which is thereby rendered turbid, owing to the formation 
 of calcium carbonate. 
 
 Calcium carbonate occurs in nature in immense quan- 
 tities, as chalk, marble, limestone, calc spar, &c. 
 
 By treating calcium carbonate with almost any acid it 
 is decomposed, and carbonic anhydride is liberated, which 
 is thus procured more conveniently than by burning 
 carbon. 
 
 Experiment 1. — Place some fragments of white marble 
 with a little water in the apparatus used for preparing 
 hydrogen, and then add small quantities of hydrochloric 
 acid until a brisk ejBfervescence is produced. Carbonic 
 anhydride is rapidly evolved, and as it is a heavy gas, it 
 may be collected in dry bottles by downward displace- 
 ment (page 116). The reaction is as follows : 
 
 Ca C O3 + 2 H CI = Ca CI2 + H2 0 + C O2. 
 
 Solution of calcium chloride remains in the bottle when 
 all the marble has disappeared, and it may be obtained 
 solid by evaporation. 
 
 Experiment 2. — A burning taper is extinguished when 
 held in carbonic anhydride, and it is fatal to men and 
 animals if they inhale it. The gas can neither support 
 combustion nor life. 
 
 N 2 
 
180 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 3. — Invert a jar filled with carbonic an- 
 hydride over one containing only atmospheric air ; if 
 Fig. 65. after some moments you introduce into each of 
 these jars a burning taper, that in the upper 
 vessel will continue to burn, while that in the 
 lower one will be extinguished. Carbonic acid 
 is heavier than common air ; it has sunk into the 
 lower jar, while the atmospheric air has ascended 
 into the upper one. If a bottle, filled with car- 
 bonic anhydride, be held with its mouth obliquely 
 over the flame of a lamp, so that the gas can flow 
 out, the light will be extinguished. 
 
 Experiment 4. — Eepeat the experiment with the 
 two jars, filling, instead of the upper one, the 
 lower one with carbonic anhydride. If, after some 
 hours, you add lime-water to both of the jars, 
 and shake them, you will obtain in both of them a 
 precipitate of calcium carbonate — a proof that the car- 
 bonic anhydride has partly ascended into the upper 
 jar. Both gases have become intimately mixed, or the 
 carbonic anhydride, though heavier, has ascended, and 
 the common air, though lighter, has difiused itself down- 
 wards. This voluntary mixing of the different kinds 
 of gases together is called diffusion of gases. This 
 diffusion of gaseous bodies, since it maintains a constant 
 equality and balance of the constituents of the atmosphere, 
 is of great importance in the economy of nature, and 
 accounts for the fact that the constitution of the air is 
 everywhere nearly uniform, although in one place free 
 oxygen is withdrawn from it, and in another place car- 
 bonic acid is added to it. 
 
 Experiment 5. — Fill a bottle containing carbonic anhy- 
 dride half full of pure water, close it with the finger, and 
 shake it ; the water takes up the carbonic anhydride, and, 
 as a vacuum is formed, the finger is pressed into the 
 mouth of the bottle by the external air. Carbonic 
 anhydride is soluble in water ; and the solution is supposed 
 to be one of carbonic acid : 
 
 One volume of water will absorb about one volume 
 
CARBON AND OXYGEN. 
 
 181 
 
 of carbonic anhydride at the ordinary temperature of the 
 air. If the gas be condensed by pressure, water will still 
 absorb the same volume, but of course a much greater 
 weight. The water thereby acquires an acid taste, and 
 the property of effervescing. 
 
 Experiment 6. — Throw a piece of chalk into vinegar ; 
 vinegar is one of the weakest of common acids, yet it is 
 able to expel carbonic anhydride. 
 
 Carbonic anhydride can be converted into a liquid by 
 strong compression at a low temperature. This liquid 
 boils at a temperature of 108° F. ( — 78° C.) ; when allowed 
 to escape from a jet, intense cold is produced by the rapid 
 evaporation (page 41), and a portion is frozen into a white 
 snow-like solid. The solid, mixed with ether, will freeze 
 mercury instantly. 
 
 Experiment 7. — To prove that carbon is contained in the 
 colourless carbonic anhydride, 
 take a test-tube, break the bottom 
 of it, and adapt to it, by means 
 of a perforated cork, a glass 
 tube, and connect it with a bottle 
 in which carbonic anhydride is 
 evolved. Introduce into the test- 
 tube a piece of potassium of the 
 size of a pea, previously dried 
 between blotting-paper, and heat 
 the place where it lies with a lamp. The potassium will 
 remove the oxygen from the CO2 and black carbon will 
 remain in the tube. 
 
 Carbonates, — Although we must regard carbonic acid, 
 H2CO3, as hypothetical, its salts are well-known and 
 stable compounds. The following are examples of im- 
 portant carbonates : 
 
 NaHCOg, Sodium hydrogen carbonate. 
 Na2C03, Sodium carbonate. 
 CaC03, Calcium carbonate. 
 
 Carhonic oxide, CO. — When charcoal during combustion 
 has a sufficient supply of oxygen, carbonic anhydride, CO2, 
 is formed ; but if there is a deficiency of oxygen, the 
 lower oxide, CO, is produced. 
 
182 
 
 EXPERIMENTAL CHEMISTRY. 
 
 This gas, which is a deadly poison, is formed when 
 charcoal burns slowly, for example, in a chafing-dish, and 
 it is also formed when the damper of a stove is closed, 
 before the coal is burnt out, since in this case the draught 
 of air, and consequently the supply of sufficient oxygen, 
 is prevented. Carbonic oxide burns when kindled, with 
 a blue flame ; it takes up the deficiency of oxygen not 
 supplied to it by the air while forming, and is converted 
 into carbonic anhydride; that is, it takes up as much 
 oxygen again, and CO becomes COg. The blue flame 
 which is often perceived in large masses of glowing coals 
 is burning carbonic oxide gas. 
 
 Carbonic oxide can be prepared by passing carbonic 
 anhydride through a red-hot tube containing fragments 
 of charcoal : one molecule of carbonic anhydride combines 
 with one atom of carbon, and forms two molecules of car- 
 bonic oxide : 
 
 C02 + C = 2CO. 
 
 The gas can be collected at the pneumatic trough. 
 
 Experiment, — Fill about half an inch of a test-tube with 
 crystals of oxalic acid. Cover them with strong sulphuric 
 acid and apply heat — effervescence will take place, and a 
 mixture of carbonic anhydride and carbonic oxide will be 
 evolved. On applying a light the latter will burn with 
 its characteristic blue flame, in spite of the presence of 
 carbonic anhydride. If the gases are passed through a 
 strong solution of caustic soda the CO2 will be absorbed 
 and the CO obtained in a pure state. The sulphuric acid 
 acts by removing water : 
 
 H2C2O4 -H2O = CO2 + CO. 
 
 A great number of compounds of carbon and hydrogen 
 are known, but most of them belong to the department 
 of organic chemistry. A classification of them will be 
 found in Part III., Chap. I. It will, however, be con- 
 venient to study two or three of them in this place. 
 
 Methane or Marsh Gas, CH4. — If the mud at the bottom 
 of a pond is stirred up with a stick, bubbles of gas rise 
 which consist chiefly of marsh gas, mixed with carbonic 
 anhydride. 
 
 Experiment 1. — Fill a wide-mouthed bottle with water, 
 
CARBON AND HYDROGEN. 
 
 183 
 
 invert it in a pond and collect the bubbles which rise on 
 stirring. The bottle can then be removed with a saucer. 
 If a piece of moist potash is then passed up into the 
 bottle, the carbonic anhydride ^11 soon be absorbed. 
 The remaining gas will burn when a fiame is applied to 
 its mouth. 
 
 This experiment proves, 1, that methane is formed dur- 
 ing vegetable decay, and, 2, that it is an inflammable gas. 
 
 Experiment 2. — Dry some sodium acetate thoroughly at 
 a gentle heat, and weigh out half an ounce of it. Then 
 add half an ounce of dry caustic soda and three-quarters of 
 an ounce of quicklime. Grind them together quickly in 
 a mortar, and introduce the mixture into a dry Florence 
 flask fitted with a somewhat wide delivery tube. On the 
 application of heat methane is given off, and can be col- 
 lected at the pneumatic trough : 
 
 Sodium Acetate. Sodium Carbonate. 
 
 Na02H302 + NaOH = Na2C03+ CH^. 
 
 The lime is only used to prevent the action of the alkali 
 on the glass. 
 
 Experiment 3. — Next to hydrogen, methane is the 
 lightest of all known gases. Its specific gravity is only 
 8 (eight times heavier than hydrogen). 
 
 Balloons may be filled with it as with hydrogen, and 
 the gas be transferred from one vessel to another by the 
 method of inverted pouring used in the case of hydrogen. 
 
 Experiment 4. — We have already seen that methane is 
 iDflammable. In burning it is converted into carbonic 
 anhydride and water : 
 
 CH4 + 2O2 = CO2 + 2H2O. 
 
 Fill a soda-water bottle one-third with methane, and 
 two-thirds with oxygen. On the application of a light a 
 loud explosion will be produced. We see therefore that, 
 like hydrogen, methane will burn either quietly or with 
 explosion, according to circumstances. 
 
 The dsLngerovis fire-damp, as the miners call it, which is 
 given out from the beds of coal in coal-mines, is almost 
 pure methane. The disastrous explosions we so often 
 hear of are caused by the accidental contact of a light 
 with a mixture of fire-damp and air. 
 
184 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Methane is not poisonous. Miners can work in an 
 atmosphere largely charged with it, but its combustion 
 produces the deadly poison carbonic anhydride. This 
 hangs about the passafges of a mine after an explosion, and 
 often suffocates the poor creatures who have escaped from 
 the explosion. The miners call it chohe-damp, or after- 
 damp. 
 
 Methane is sometimes called "light carburetted hy- 
 drogen." 
 
 Ethylene^ or Olefiant gas, C2H4. — Sometimes called 
 " heavy carburetted hydrogen." 
 
 Experiment!, — Mix one volume (half an ounce hy 
 measure^ of strong alcohol, or methylated spirit, with 
 four volumes of strong sulphuric acid. Heat the mixture 
 in a flask and collect over warm water the gas that is 
 given off. It is ethylene. The sulphuric acid acts by 
 removing the elements of water from the alcohol : 
 
 Alcohol. 
 
 C^HeO-H^O = C,H,. 
 
 Experiment 2. — Ethylene may be burned at a jet, or at 
 the mouth of a bottle, like methane. To explode it, it 
 must be mixed with three volumes of oxygen : 
 
 C2 H4 + 3 O2 = 2 C O2 + 2 H2 O. 
 (2 vols.) (6 vols.) (4 vols.) (4 vols.) 
 
 This will be apparent from the above equation, since the 
 formula for every gas denotes two volumes of it. 
 
 Experiment 3. — Mix equal volumes of ethylene and 
 chlorine in a bottle over water. Allow the bottle to 
 remain for a short time with its mouth under water. The 
 two gases will combine, and an oily liquid, called ethylene 
 chloride, or Butch liquid, will be produced, and will float 
 on the water : 
 
 ^2 + CI2 = C2 H4 Clg. 
 
 Experiment 4. — Mix one volume of ethylene with two 
 volumes of chlorine in a tall bottle or jar, and apply a 
 light. A very curious combustion, attended with the 
 formation of thick black smoke, will take place. The 
 chlorine combines with hydrogen, and carbon is separated : 
 
 C2ll4 + 2Cl2= 4 II CI + 2 C. 
 
CAEBON DISULPHIDE. 
 
 185 
 
 Acetylene, C2H2. — This interesting gas is formed by the 
 direct union of its elements when the electric light passes 
 between two charcoal points in an atmosphere of hydrogen. 
 
 All the processes for preparing it are difficult. Methane, 
 Ethylene and Acetylene are all constituents of coal-gas. 
 The two last have remarkable illuminating power. 
 
 CARBON DISULPHIDE, CS2. 
 
 Just as charcoal at a red heat will combine with oxygen, 
 so it will with sulphur. The compound so produced is 
 called carbon disulphide, or " bisulphide of carbon." It 
 is a heavy liquid (specific gravity 1*27), which boils at 
 46° C. (109° F.), has a disgusting odour, and is extremely 
 inflammable. 
 
 Experiment 1. — Boil a little oil in a test-tube, and bring 
 the end of the tube in contact with a few drops of carbon 
 disulphide in an egg-cup. The liquid will ignite and 
 burn with a blue flame. It is therefore evident that 
 carbon disulphide ignites at a very low temperature. 
 
 Experiment 2. — Shake a few drops of the disulphide in 
 a wide-mouthed bottle, and apply a light. The vapour 
 will burn with a blue flame, or if the quantity of liquid 
 was very small, a slight explosion will be produced. A 
 portion of the sulphur escapes oxidation and remains on 
 the sides of the bottle. When, however, the liquid or 
 vapour burns in an open vessel or at a jet, both the sulphur 
 and carbon are oxidized, carbonic and sulphurous anhy- 
 dride being formed : 
 
 CS2+ 302 = C02 + 2S02. 
 
 Experiment 3. — Repeat the last experiment with a half- 
 pint wide-mouthed bottle of oxygen. A very loud 
 explosion will be produced. 
 
 Experiment 4. — Very fine iron wires may be burned in 
 the flame of carbon disulphide, the iron combining with 
 the sulphur to form ferrous sulphide, FeS. 
 
 In consequence of its remarkable volatility and inflam- 
 mability, carbon disulphide is a dangerous liquid to work 
 with. All the above experiments must be made with 
 small quantities, and with the greatest caution. 
 
 Carbon disulphide is a very useful solvent. Iodine, 
 
186 
 
 EXPERIMENTAL CHEMISTRY. 
 
 sulphur, phosphorus, and fixed oils are among the sub- 
 stances which can be dissolved in it. 
 
 CYANOGEN, C2N2 Or (CN)2. 
 
 Carbon and nitrogen do not unite directly with one 
 another, but by various indirect processes a series of 
 important salts called cyanides can be prepared. When, 
 for instance, a mixture of potassium carbonate and charcoal 
 is heated in a tube, and nitrogen gas is passed through it, 
 the following change takes place : 
 
 Potassium Potassium 
 Carbonate. Cyanide. 
 
 K2C03 + 4C + N2 = 2KCN + 3CO. 
 
 Potassium cyanide is in practice prepared from the salt 
 called potas.^ium ferrocyanide, or yellow prussiate of 
 potash. The last-named salt, which is a very important 
 article of commerce, is prepared by heating strongly a 
 mixture of potassium carbonate, iron filings, and refuse 
 animal matters, such as cuttings of horn and leather, 
 woollen rags, dried blood, and the like. From potassium 
 cyanide other cyanides can readily be prepared. 
 
 The cyanides all contain the monad radical CN, which 
 is often denoted by the symbol Cy, just as if it were an 
 elementary atom. The cyanides are, in fact, closely 
 analogous to the chlorides. 
 
 Cyanogen itself, and many of the cyanides, are deadly 
 poisons. 
 
 Experiment 1, — Heat a small quantity of mercuric 
 cyanide in a hard glass test-tube fitted with a short jet. 
 The white crystals decompose into mercury, which con- 
 denses on the upper part of the tube, and cyanogen gas, 
 which escapes, and can be burned at the jet. It burns 
 with a beautiful peach-coloured flame : 
 
 Hg(CN)2 = Hg+C2N,. 
 
 A brown substance, called paracyanogen, is formed at the 
 same time. 
 
 It will be seen that cyanogen gas is the radical CN 
 doubled. Its formula is therefore often written as (GN)2, 
 or Cy2. The resemblance of cyanogen and the cyanides 
 to chlorine and the chlorides is then perfect : 
 
CYANOGEN. 
 
 187 
 
 Cyanogen . . . (CN)2 or Cy2 like CI2. 
 
 Hydrocyanic Acid. HClSjr „ HCy „ HCl. 
 
 Potassium Cyanide KCJS" „ KCy „ KCl. 
 
 Mercuric Cyanide Hg(CN)2 „ HgCy2 „ HgCl2. 
 
 Cyanogen is soluble in water. To obtain it pure it 
 must be collected over mercury, for it would not be safe 
 to collect it by displacement. 
 
 Hydrocyanic Acid^ HCN, or HCy. — Often called prussic 
 acid. This deadly poison is obtained by tlie action of 
 sulphuric acid on cyanides. It is an exceedingly volatile 
 liquid, soluble in water in all proportions. 
 
 Experiment 2. — Put a feio grains of potassium cyanide 
 into a small beaker, and moisten the salt with dilute 
 sulphuric acid. Hydrocyanic acid will be set free with 
 effervescence, and its peculiar odour — that of bitter 
 almonds— will be recognised. It must, however, be 
 remembered that the acid is most deadly as vapour. 
 
 Experiment 3. — Eepeat the last experiment, covering the 
 beaker with a piece of glass moistened with a drop of 
 silver nitrate. The hydrocyanic acid vapour will decom- 
 pose the silver salt, and the white insoluble silver cyanide^ 
 AgCy, will be formed. This substance is very like silver 
 chloride, except that it does not turn purple on exposure 
 to light, and is soluble in hot nitric acid. Like the 
 chloride, it dissolves in ammonia. 
 
 Experiment 4. — Moisten the glass plate with a drop of 
 solution of potassium hydrate (potash) and expose it for 
 some minutes to the vapour. No change will be perceived, 
 but the potash will be partly converted to potassium 
 cyanide. Add a drop of ferrous sulphate (green vitriol) to 
 the liquid on the plate, and then, after standing for ten 
 minutes, a few drops of hydrochloric acid. A beautiful 
 blue precipitate (Prussian blue) will be formed. 
 
 This is a most delicate test for cyanogen. 
 
 Experiment 5. — The salt called potassium ferrocyanide 
 has the formula K^CygFe. It is regarded as containing a 
 tetrad radical (CygFe), the iron being a part of the radical. 
 Many other ferrocyanides can be formed from this one by 
 double decomposition. Add solution of potassium ferro- 
 cyanide to solutions of the following salts. In each case a 
 ferrocyanide of the metal will be precipitated : 
 
188 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Copper Sulphate . — Purple brown. 
 Lead Acetate. — White. 
 
 Ferrous Sulphate. — White, or pale blue, soon changing 
 to dark blue. 
 
 Ferric Sulphate or Chloride. — Dark blue (Prussian 
 blue). If the ferrous salt be absolutely free from ferric 
 salt, a white precipitate is obtained, but this is rarely the 
 case. 
 
 DESTRUCTIYE DISTILLATION.— FLAME. 
 When wood, coal, and many other substances are heated 
 in close vessels, an entire rearrangement of their con- 
 stituent elements takes place. A portion of the carbon 
 remains behind as charcoal, or coke, the rest distils over 
 in combination with the other constituents, in the form of 
 a number of volatile compounds, some of which readily 
 condense into liquids or solids, while others are permanent 
 gases. The nature of these volatile products cannot be 
 fully discussed in this place. Many of them are com- 
 bustible — these are for the most part compounds of 
 carbon and hydrogen. Most can be applied to some useful 
 purpose. 
 
 Processes of this kind, in which substances are destroyed 
 in the retort, and volatile compounds formed and distilled 
 from them, are called processes of destructive distillation. 
 The preparation of gas from coal is the most important 
 example. 
 
 Distillation of Coal. — Experiment 1. — Take a piece of hard 
 tube about half an inch in external diameter, and a foot in 
 length. Convert it into a long test-tube by drawing off a 
 short piece from one end, and then bend it twice at right 
 angles thus : N. Fit the open end with a small cork and 
 short jet. This is a very useful piece of apparatus for 
 experiments of this kind, acting at once as retort and 
 receiver. Introduce some fragments of dry coal into the 
 closed end and apply a strong heat (a Bunsen's burner 
 does very well). Water and tar will distil over and 
 condense in the bend, while coal gas will pass over and 
 may be ignited at the jet. When no more gas is evolved, 
 colce will remain in the retort. 
 
 Gas Manufacture. — On the large scale, the coal is 
 
DESTRUCTIVE DISTILLATION. — FLAME. 
 
 189 
 
 distilled in iron or clay retorts. The vajoours pass first 
 into the hydraulic main, a broad iron pipe placed horizon- 
 tally in front of the retorts. From this it passes through 
 a series of pipes called the condensers. In the hydraulic 
 main and condensers the gas is cooled, and the greater 
 part of the tar and water, which are the chief liquid 
 products, are condensed and separated. It then passes 
 first through a box filled with perforated trays containing 
 slaked lime, and afterwards through a similar box con- 
 taining ferric hydrate. The lime removes CO2 and other 
 acid impurities and the ferric oxide hydrogen sulphide, 
 from which the sulphur can afterwards be removed. The 
 gas is then carried to immense reservoirs called gas-holders, 
 from which it is distributed for use. 
 
 The products of the distillation of coal may be roughly 
 classified as follows. The list is not complete : 
 
 1. Coke (carbon). 
 
 2. Tar and water. 
 
 3. Gases and va- 
 pours injurious 
 to the gas. 
 
 4. Diluents. 
 
 5. Useful. 
 
 Kemains in the retort. 
 Mostly removed when the gas is cooled. 
 
 ( Chiefly remains 
 
 Ammonia. 
 
 Carbonic anhydride. 
 Sulphurous „ 
 Sulphuretted hydro- 
 gen. 
 Cyanogen. 
 Carbon disulphide. 
 Hydrogen. 
 Methane. 
 Acetylene. 
 Ethylene. 
 
 Vapours of liquid and 
 solid hydro-carbons 
 
 in the 
 
 water in combination 
 witli the following : 
 
 Partly remain in the 
 water as ammonium 
 salts. Partly absorbed 
 by the lime. 
 
 Very difficult to separate. 
 Do not contribute to lumi- 
 nosity. 
 
 Contribute luminosity. 
 
 Ditto. Also cause the 
 smell of the gas. 
 
 Flame. — What we ordinarily call a flame is the space in 
 which gases are combining with oxygen. Flame is only 
 produced by the union of gases. This at first sight appears 
 startling. It is natural to ask whether the burning of a 
 coal or a candle is not the burning of a solid, and the 
 burning of spirit or oil, of a liquid. But, in reality, we 
 do not burn these substances, but the gases or vapours 
 which they give off when heated. Charcoal burns A^dth- 
 out flame, because it gives out no vapour. In burning 
 phosphorus, sulphur, or spirits of wine, we really burn 
 
190 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the vapours of tliese substances, and in burning coal, wax, 
 wood, oil, or paper, we burn the gases which are produced 
 by a destructive distillation of those substances. 
 
 A candle is a miniature gas factory. In it wax or tallow 
 is distilled, and the gas so obtained is burned. Blow out a 
 candle and apply a light to the white smoke which ascends 
 from the wick. It will ignite, and the flame will run 
 down and settle on the wick. 
 
 It has been previously stated that hydrogen burns 
 very easily, and with a flame, while carbon burns more 
 difiicultly, and without flame ; this explains why fuel 
 burns with a flame at the commencement of the combus- 
 tion, but finally only glows ; it is the gases which first 
 burn with flame, and afterwards the carbon, with a mere 
 glow, without flame. All combustible substances that 
 contain hydrogen and carbon burn in a similar manner. 
 Burning wood presents a simple illustration of this fact. 
 
 The flame of alcohol consists of two parts ; the dark 
 central part is alcohol vapour, and the bright envelope 
 Fig. 67. around this is alcohol Vapour uniting chemically 
 with the oxygen of the air. The tapering 
 _iL form of the flame is owing to the ascent of the 
 hot gases, and the rushing in of cold air from 
 below. The alcohol is drawn up from the lamp 
 by the capillarity of the wick ; it burns with 
 little light, but if a twisted wire or some other 
 solid body be introduced into it, it will then emit 
 light. If a thin wire is placed across the flame, it will 
 be heated to redness near the margins of the flame, while 
 in the interior it will remain dark ; consequently, the 
 external part is much hotter than the central part of the 
 flame. The point of greatest heat is indicated by the 
 mark in the figure, and vessels to be heated over the 
 spirit-lamp should never be placed below this point. This 
 may be rendered very evident by applying a lucifer-match 
 to this part of the flame, when it will take fire at once ; 
 but not so quickly if thrust into the centre of the flame. 
 The flame of hydrogen is similar to that of alcohol. 
 
 In the flame of a candle or lamp, three parts can be 
 distinguished ; in the middle (a, Fig. 68), the dark centre, 
 consisting of illuminating gas (decomposed tallow) ; 
 
DESTRUCTIVE DISTILLATION. — FLAME. 
 
 191 
 
 around this (6), the luminous cone, consisting of burning 
 hydrogen, intimately mixed with carbon or heavy hydro- 
 carbons at a white heat ; and on the very outside (c), j,. 
 a thin, scarcely perceptible veil, in which carbon is 
 burning. If we imagine the flame to be cut hori f, 
 zontally through the centre, it would present nearly 
 the same appearance as in Fig. 69. The middle 
 circle is illuminating gas, the hydrogen of which 
 burns first, and the great heat thus evolved brings 
 the carbon or hydrocarbons to a white heat (this is 
 indicated by the second circle) ; and finally, in the 
 exterior circle, the carbon is burnt. The heated 
 matter in the second ring imparts to the flame its 
 illuminating power, just as the glowing wire ren- 
 dered the alcohol flame luminous. If a cold knife 
 be introduced into the flame, a portion of 
 the carbon will be so much cooled that it 
 cannot burn, and will be deposited upon 
 the knife in the form of soot. If a wire 
 be held through the flame, the glowing 
 part at the hot margins will remain clear, 
 while soot will be deposited upon that part 
 of it which is in the interior of the flame. 
 
 The brightness of a flame depends, either upon the 
 presence of a solid body, which glows in the flame, or of 
 dense hydrocarbons undergoing combustion in it ; if these 
 be only heated to redness, the flame will give out a smoky 
 red light, but, on the contrary, a brilliant light when 
 heated to a white heat. 
 
 The hlowpijpe. — In its simplest form, this valuable little 
 instrument consists of a tapering metal tube bent at a 
 right angle near its end, and terminating in a fine jet. 
 With it a current of air can be forced through a small 
 flame, sending it down horizontally, increasing its tem- 
 perature very much and altering its character. The 
 blowpipe flame consists of two cones : an inner one, which 
 is blue, and has the power of removing oxygen from many 
 metallic oxides, and an outer one, which is pale yellow, 
 and has the opposite power of promoting oxidation. The 
 inner cone, w^hich is much hotter than the other, is called 
 the reducing flame ; the outer, the oxidizing flame, Tho 
 
192 EXPERIMENTAL CHEMISTRY. 
 
 flame of tlie oxy hydrogen blowpipe (page 133) is similar to 
 tlie ordinary blowpipe flame in structure. 
 
 Tem^perature necessary for flame, — A certain definite tem- 
 perature is necessary for the combustion of each com- 
 bustible substance, and if the temperature be reduced 
 below that point the combustion ceases. A piece of cold 
 metal will extinguish a candle flame, because the metal, 
 being a good conductor, reduces the temperature of the 
 flame. When we " blow out a flame, the sudden current 
 of cold air exerts a similar cooling action. It is im- 
 possible to blow out the flame of phosphorus or carbon 
 disulphide, because those substances enter into combus- 
 tion at a very low temperature. 
 
 Sir Humphry Davy made the important discovery that 
 the fire-damp (methane) of coal-mines requires a very 
 high temperature for its combustion. From this know- 
 ledge he was led to invent the " safety-lamp," which has 
 done so much to mitigate the horrors of coal-mining. It 
 is simply an oil lamp in which the flame is entirely 
 surrounded by fine wire gauze. If this lamp is burned 
 in an atmosphere containing fire-damp, or even ordinary 
 coal-gas, the gas will enter and burn inside the lamp, 
 often extinguishing the oil flame, hut the flame cannot pass 
 through the wire gauze, and an explosion is therefore im- 
 possible, unless the lamp is out of order, or improperly used. 
 The wire gauze acts by cooling the flame below the 
 Flo-. 70. point required for combustion. Its 
 
 efiect can be shown by pressing a 
 piece down on an ordinary gas or 
 candle flame. The flame is, as it 
 were, crushed down by the gauze, 
 though the gas passes freely 
 through, and can be burned on 
 the other side. 
 
 SmoJcy flames. — When the supply 
 of air to a flame is insufficient, it smokes ; that is, a part 
 of the carbon escapes oxidation. A chimney often ob- 
 viates this ; the heat produces an upward current in it, 
 whereby more air is drawn in. In the argand burner the 
 flame is ring-shaped, and air enters through the centre, 
 as well as outside the flame. 
 
SILICON. 
 
 193 
 
 SILICON. 
 Si = 28. Formula unknown. 
 
 Silicon is the most abundant solid element. It is 
 always found in combination, and is only isolated with 
 great difficulty. It enters into the composition of so 
 many minerals that the greater part of the science of 
 mineralogy is occupied with the history of the silicon 
 compounds. Silicon, like carbon and boron, may be 
 obtained in two, and possibly in three conditions : amor- 
 phous, graphitoid and the so-called adamantine silicon. 
 In the free state the element is too expensive to be of 
 any practical importance. Like carbon and boron, it is 
 insoluble in all agents that do not change it, and non- 
 volatile. 
 
 Silicic anhydride, Si02, also called silica and silex, is 
 the only known oxide of silicon. It occurs native and 
 tolerably pure, as quartz, sand, flint, and almost perfectly 
 pure as rock crystal, which is found beautifully crystal- 
 lized in transparent six-sided prisms. Carnelian, agate, 
 jasper, opal, calcedony, and some other well-known 
 precious stones, consist likewise of silica ; their colour.s 
 are chiefly owing to the presence of minute quantities of 
 metallic silicates. 
 
 Three varieties of silicic acid analogous to the three 
 phosphoric acids are recognised. They must be prepared 
 by indirect means, for silicic anhydride will not combine 
 directly with water. The normal, or ortho-silicic acid, 
 H4Si04, has not been obtained free from water. 
 
 All silicates are insoluble in water except certain alka- 
 line silicates. 
 
 Soluble Glass. — Experiment 1. — Heat a common flint stone 
 in a fire, and when it is red-hot quench it in cold water. 
 The sudden cooling so influences and diminishes the in- 
 ternal cohesion, that now the flint can easily be reduced 
 to a fine white powder. Boil in a clean iron ladle two 
 drachms of tlie powder with four drachms of caustic 
 potash (potassium hydrate) and two ounces of water, for 
 some hours, supplying fresh water occasionally as the 
 other evaporates ; then let the mixture stand in a corked 
 bottle to settle. The silica dissolves in the potash solution 
 
194 
 
 EXPERIMENTAL CHEMISTRY. 
 
 and forms with it a thick fluid, potassium silicate. Or one 
 part of the powdered flint may be fused with four parts of 
 dry sodium carbonate (common washing soda), in a 
 crucible over the fire. The soda soon commences to 
 eflervesce, from the escape of carbonic anhydride, which 
 is replaced by tbe silicic anhydride. The mass on being 
 boiled with water and filtered furnishes a solution of 
 sodium silicate. These soluble silicates are often called 
 soluble glass, and their solutions, liquor silicum. 
 
 Liquor silicum has of late years been largely employed 
 for the hardening of soft building stone, and the artificial 
 preparation of hard stone from sand. 
 
 Experiment 2. — Add some hydrochloric acid to a strong 
 solution of sodium or potassium silicate. A white 
 gelatinous mass of silicic acid (probably H4Si04) is thrown 
 down. If this jelly is collected on a filter, washed well 
 with water and dried, a white powder, consisting of pure 
 silica in the amorphous state, is obtained. 
 
 Experiment 3. — If, on the contrary, the silicate solution 
 be diluted with ten or twelve times its bulk of water, 
 and then the alkali be removed with hydrochloric acid, 
 no precipitate is produced, the silicic acid remaining in 
 solution. This solubility is but a temporary state, as 
 after the lapse of a certain time, depending on the pro- 
 portion of silica present, the solution suddenly undergoes 
 a remarkable conversion into a transparent jelly-like 
 mass, the silicic acid passing into the insoluble modifi- 
 cation. By the addition of more alkali it may be again 
 re-dissolved and the experiment repeated. 
 
 Almost all our springs, as well as our plants, contain 
 small quantities of soluble silicates. If we evaporate 
 spring- water, we find silica in the insoluble residue ; and 
 if we burn a plant, we obtain it in the ashes. Grasses, 
 and the difierent kinds of grain, are particularly rich in 
 silica, and for this reason they have been called silicious 
 plants. Silica is to these plants what bones are to men, — 
 the substance to which the stalk owes its firmness and 
 stifi'ness. If tbe soil is deficient in soluble silica (or if 
 there is not enough potassa, which renders the silica 
 solul)le), these properties will be wanting in the stalk, 
 and it will bend. The horse-tail plant (Equisetum) 
 
SILICON. 
 
 195 
 
 contains so much silica that it may be used for polishing 
 wood. Silica is found even in the animal kingdom, 
 particularly in the class of Infusoria, which are only 
 visible under the microscope ; the shells of many Infusoria 
 are composed of silicic anhydride. 
 
 In its natural state, silica is so hard as to produce sparks 
 with steel, and is quite insoluble in water and acids, 
 except hydrofluoric acid. 
 
 Silicates, — The silicates are the most numerous and 
 complicated of all salts. Their study, however, belongs 
 to the science of mineralogy. Among important silicates 
 may be mentioned felspar, mica, horneblende, serpentine 
 and meerschaum. The differ-ent varieties of clay are 
 silicates of aluminium. Glass is a mixture of various 
 silicates, with excess of silica. 
 
 Silicon Fluoride, SiF^. — This interesting gas is obtained 
 by the action of hydrofluoric acid on silica, or any silicate. 
 To its formation the power which hydrofluoric acid 
 possesses of etching glass (p. 122) is due : 
 
 Si02 + 4Hr = SiF4 + 2H2 0. 
 
 It is immediately decomposed by water, with formation 
 of silica and an acid called hydrofluosilicic acid, 2HF, SiF^. 
 
 Experiment 4. — Heat powdered glass, fluor-spar and 
 sulphuric acid in a flask, and carry the gas produced to 
 the bottom of a glass of water, in which some mercury 
 has been placed. As the gas rises from the mercury it is 
 decomposed by the water, and beautiful tubes of silica are 
 built up. If it were not for the mercury, the mouth of 
 the tube would soon be choked up by the silica, and the 
 flask would then be apt to burst. 
 
 0 2 
 
( 196 ) 
 
 PAET III. 
 METALS. / 
 
 CHAPTEE 1. 
 
 METALLIC MONADS. 
 
 (Potassium, Sodium (Ammonium), Silver.) 
 POTASSIUM. 
 K - 39. 
 
 This interesting metal was discovered by Davy, who 
 obtained it by decomposing caustic potash (potassium 
 hydrate) by means of a powerful galvanic battery. 
 
 Potassium is now prepared by putting potassium carbon- 
 ate and finely divided carbon into an iron bottle, provided 
 with an iron exit-tube, and exposing them to a white heat. 
 At this high temperature the carbon combines with the 
 oxygen of the carbonate, forming carbonic oxide gas, 
 which escapes. The liberated potassium is also converted 
 into a green vapour, which is conducted into naphtha, 
 where it condenses into a solid mass. 
 
 K2C03 4-2C = 3CO + K2. 
 It has been shown, under Carbonic acid, that potassium, 
 at a moderate heat, can withdraw the oxygen from the 
 carbon ; while here, at a higher temperature, a contrary 
 action takes place. Similar incongruities in chemical 
 actions are not unfrequent ; they show that the affinities 
 of bodies for each other are greatly altered by the 
 temperature. 
 
 Exjperiment, — If a piece of potassium is cut with a knife, 
 it j)resents a blue metallic lustre ; but it immediately 
 tarnishes on exposure to air, and soon becomes converted 
 into solid ^[jotassium oxide. This experiment shows the 
 softness of the metal, and also its great affinity for oxygen. 
 
 Consequently, to preserve potassium from oxidation, it 
 is necessary to keep it in mineral naphtha, or some other 
 
POTASSIUM. 
 
 197 
 
 liquid which contains no oxygen. Its symbol, K, is 
 derived from the Latin name Kalium. 
 
 Potassium oxide, K.^O. — A small piece of potassium, 
 when exposed to dry air, is converted into a white mass 
 of potassium oxide. This substance combines eagerly 
 with water, and forms potassium hydrate : 
 
 K2O + H2O = 2K0H. 
 
 Potassium hydrate or hydroxide, KOH. — Caustic potash — 
 Potassa, — This important substance is obtained when 
 potassium acts on water (p. 105), but is more economically 
 prepared as follows : — 
 
 Experiment 1. — Place half ounce of quick lime in a 
 plate, sprinkle it with warm water, and let it stand until 
 it is slaked, that is, until it becomes 
 a fine dusty powder. Then put half 
 an ounce of potassium carbonate 
 into an iron basin with six ounces 
 of water, boil it, and, during the 
 boiling, gradually add half of the 
 slaked lime by teaspoonfuls, stir- 
 ring it at the same time. After 
 the mixture has boiled for some 
 time, put a teaspoonful of it upon a paper filter, and pour 
 the filtrate into vinegar. If it effervesces, still more lime 
 must be added ; but if no effervescence ensues, pour the 
 whole into a bottle, close it up, and let it remain quiet 
 for some hours, that the sediment may subside. Decant 
 the clear liquor, and preserve it in a well-stoppered bottle. 
 It is a solution of potassium hydrate. 
 
 Slaked lime is calcium hydrate : when it is boiled with 
 potassium carbonate, calcium carbonate and potassium 
 hydrate are formed by double decomposition, and the 
 former, being insoluble, is precipitated : 
 
 Calcium Potassium Calcium Potassium 
 
 hydrate. carbonate. carbonate. hydrate. 
 
 Ca (0 H)2 + K2 C O3 = Ca C O3 + 2 K 0 H. 
 Experiment 2. — Evaporate a portion of the potash solution 
 in a clean iron vessel (glass and porcelain are attacked by 
 it) , all the water is expelled and a white mass finally 
 remains behind, dry potassium hydrate. This may be 
 melted at a stronger heat, and cast into sticks or plates. 
 
198 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 3. — Expose some dry potash to the air ; it 
 will soon become moist ; it will deliquesce, and on longer 
 exposure will effervesce upon the addition of an acid. 
 Potash absorbs both water and carbonic anhydride from 
 the air, and is then converted into potassium carbonate. 
 
 Experiment 4. — Heat in one test-tube some white, and 
 in another some brown blotting-paper, with some solution 
 of potassium hydrate ; both papers will be decomposed and 
 dissolved, the vegetable fibres of the white paper (linen 
 or cotton) more slowly than the animal fibres of the 
 brown paper (wool). Potash exerts a very corrosive 
 action, esjDCcially on animal substances. The slippery 
 feeling caused by rubbing lye between the fingers is 
 owing to a gradual solution of the skin. 
 
 Experiment 5. — Boil in a test-tube a little tallow or fat 
 with a solution of potassium hydrate ; a union gradually 
 takes place ; soap is formed. The soap prepared from 
 potash remains soft, and is called soft-soap. 
 
 Experiment 6. — Dissolve a piece of blue vitriol (copper 
 sulphate) in water, and add to it some solution of potash. 
 The copper is precipitated as a blue hydrate, and 
 potassium sulphate remains in solution : 
 
 CuSO^-f- 2K0H = K2SO4 + Cu (0 H)2. 
 
 Potassium hydrate being a strong base precipitates 
 many other metals from their salts as hydrates, by an 
 interchange of the respective radicals. 
 
 Potassium Carbonate, K2CO3. 
 
 Experiment 1. — Fit into a funnel a filter of blotting- 
 paper, and place upon it a handful of wood 
 ashes, and gradually pour hot water over them. 
 The liquid filtered through has an alkaline 
 taste, and turns red test-paper blue. If you 
 evaporate it to dryness in a porcelain dish, a 
 grey mass finally remains behind, which be- 
 comes white after being heated to redness in a 
 porcelain crucible; it is pearlash, or impure 
 potassium carbonate. In those countries where 
 wood is abundant — in America, Eussia, &g, — it 
 is prepared in a similar manner on a large scale, 
 and is an article of great demand in commerce. 
 
POTASSIUM. 
 
 199 
 
 It can be purified by recry stall ization. 
 
 Experiment 2. — Put one portion of potassium carbonate 
 in a vessel, and let it stand in a dry apartment, and put 
 another portion in a cellar. The former becomes moist ; 
 the latter deliquesces. Both attract water from the air, 
 but that in the dry atmosphere of the room less than that 
 in the damp air of the cellar. Potassium carbonate is 
 a very deliquescent salt. 
 
 Experiment 3. — Boil for some time, in a vessel con- 
 taining a quarter of an ounce of potassium carbonate and 
 two ounces of water, a piece of grey linen, and some dirty 
 or greasy linen or cotton rags ; the liquid will become of 
 a dark colour, while the rags ai e made white and clean. 
 Dirt, as it is commonly called, is dust, which adheres to 
 the skin, garments, &c., particularly after they have 
 become moistened by perspiration, or have come in 
 contact with greasy or other adhesive substances. These 
 last-mentioned substances may be dissolved and removed 
 by pearlash ; on this depends the various application of 
 this substance in cleaning and washing. 
 
 Hydrogen potassium carbonate, HKCO3. — This salt, which 
 is commonly termed bicarbonate of potash, differs from the 
 preceding compound in having but one atom of the 
 hydrogen in carbonic acid replaced by potassium. It 
 consequently belongs to the class called acid salts, and is 
 prepared by passing a current of carbonic anhydride 
 through a solution of ordinary potassium carbonate until 
 no more is absorbed : 
 
 K2CO3 + H2O + CO2 = 2KHCO3. 
 
 Potassium sulphate, K2SO4. — Dissolve half-an-ounce of 
 potassium carbonate in two ounces of warm water, and 
 then add diluted sulphuric acid in very small quantities 
 until no more effervescence is produced on 
 stirring. 
 
 Filter and evaporate the liquid until a film 
 of crystals appears on the surface, then set it 
 aside. The hard crytals obtained (six-sided 
 double pyramids) are potassium sulphate ; 
 they are sparingly soluble in water, and have 
 a somewhat bitter taste. 
 
 Hydrogen, potassium sulphate, HKSO^, sometimes called 
 
200 
 
 EXPERIMENTAL CHEMISTRY. 
 
 bisulphate of potash, is obtained as a secondary produd 
 in the preparation of nitric acid from saltpetre. It i^ 
 an extreinely acid salt, and much more soluble than the 
 neutral sulphate. 
 
 Potassium Nitrate, KNO3. 
 
 Experiment 1. — Dissolve half an ounce of potassium car- . 
 bonate in one ounce of hot water, and neutralise with 
 nitric acid ; afterwards boil and filter the liquid, and set 
 it aside to cool ; prismatic crystals of potassium nitrate 
 will be deposited from it, which have a cooling taste, 
 and undergo no alteration in the air. 
 
 This salt is known as niti^e and saltpetre ; after fusion, it 
 solidifies to a crystalline mass, sometimes called sal- 
 prunella. 
 
 Experiment 2. — Throw a little nitre on a red-hot coal, 
 it will cause a brisk sparkling ; it deflagrates. The nitre 
 is decomposed and gives up its oxygen to the coal, and 
 thus causes it to burn more energetically. The hard 
 saline mass, congealed from its melted state, remaining 
 on the coal, has a basic reaction, and effervesces with 
 acids; it is potassium carbonate. In order to render 
 substances more inflammable, they are often soaked in 
 a solution of nitre ; as for example, tinder, touch-paper, 
 &c. 
 
 Experiment 3. — Mix thoroughly in a mortar fifteen 
 drachms of powdered nitre, three drachms of charcoal- 
 powder, and two drachms of sulphur; this mixture 
 contains the constituents of gunpowder. Take a little 
 on the point of a knife, put it on a stone, and ignite it 
 with a match ; a brisk deflagration will ensue. Knead 
 the rest of the powder, with some drops of water, into 
 a paste, and squeeze it through a tin colander or a sieve. 
 The thread-like mass thus obtained is, when partly dry, 
 divided into small grains by gently rubbing with the 
 fingers ; this is gunpowder. 
 
 Experiment 4. — Place some gunpowder upon an iron 
 plate, and ignite it ; the deflagration takes place more 
 rapidly, because the materials are more intimately mixed. 
 In this deflagration there are evolved from the charcoal 
 and the nitre carbonic anhydride and nitrogen^ two gases 
 
POTASSIUM. 
 
 201 
 
 whicli instantly occupy a mncli greater space than before. 
 Snlphnr not only causes an easier ignition of the gun- 
 powder, but it causes a stronger evolution of gas ; since 
 it combines with the potassium of the nitre, forming 
 potassium sulphide, and liberates carbonic anhydride. 
 The change which occurs is somewhat complex. 
 
 If the deflagration of the gunpowder takes place in a 
 confined space, as in a gun-barrel, the explosive violence 
 with which the two gases are suddenly expanded is strong 
 enough either to project the ball or to burst the gun. 
 The potassium sulphide remaining soon becomes moist 
 in the air, and then emits the odour of sulphuretted 
 hydrogen ; at the same time, the iron is blackened by the 
 formation of sulphide of iron upon the surface. 
 
 If nitre be heated with sulphuric acid, nitric acid escapes. 
 
 Animal substances are preserved from putrefying by 
 nitre ; it is therefore used in salting meat. 
 
 The manufacture of nitre was formerly conducted in a 
 very peculiar manner. Animal substances, for instance, 
 pieces of flesh, hides, hair, &c., are mixed with wood- 
 ashes and lime, and then moistened with water or urine, 
 and suffered to putrefy slowly. Animal substances are 
 rich in nitrogen, which, during putrefaction, is set free 
 in the form of ammonia (NH3) ; this, after a time, unites 
 with the oxygen of the air, forming nitric acid, which 
 acid is immediately neutralised by the potassium of the 
 wood-ashes. This process is called nitrification. If animal 
 substances decay without the presence of potash, or some 
 other strong base, no nitric acid, but only ammonia, will 
 be produced. 
 
 After the completion of the putrefaction, water is 
 added to extract the nitre, and the solution being evapo- 
 rated it is deposited ia crystals. Nitre beds, so called, 
 are prepared in this way. We formerly obtained nitre 
 from the East Indies, where it is found as an incrustation 
 on the surface of the soil. 
 
 Potassium chlorate, KCIO3. — This salt is very similar to 
 nitre, but it is more easily decomposed. By mere heat it 
 is resolved into oxygen and potassium chloride ; there- 
 fore it is used for the preparation of oxygen. Its pre- 
 paration has already been described (p. 138), 
 
202 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 1. — When thrown on glowing coals, it 
 deflagrates still more briskly than nitre; the oxygen, 
 as it is liberated, occasions a very energetic combustion 
 of the coal. This salt cannot be employed in the pre- 
 paration of gunpowder, as the rapidity with which it 
 explodes would be too much for the guns ; yet, on this 
 very account, it is extremely serviceable in fireworks, 
 especially for producing variegated fires. The greatest 
 caution must be observed in pulverising and mixing it 
 with combustible materials, as it may explode by merely 
 rubbing or pounding it. The mixing of it with other 
 substances must always be done with the fingers. 
 
 Experiment 2. — Introduce a crystal of potassium chlorate 
 into a beaker-glass, and add a few drops of alcohol, and 
 afterwards a drop of sulphuiic acid ; the sulphuric acid 
 expels chloric acid, which is immediately decomposed, 
 and there is so great an evolution of heat as to set fire 
 to the alcohol. 
 
 Experiment 3. — Mix a very little potassium chlorate be- 
 tween the fingers with about half as much fiowers of sulphur 
 and throw the mixture into sulphuric acid, contained in 
 a beaker-glass ; a brisk crackling ensues, and the sulphur 
 takes fire. 
 
 Potassium Chloride^ KCl. 
 
 This salt is found in very large quantity at Stassfiirth 
 in Germany and is now the most important source of 
 potassium compounds. 
 
 Experiment 1. — Dissolve half an ounce of potassium 
 carbonate in water, and neutralise with hydrochloric 
 acid ; upon concentrating the solution, cubic crystals will 
 be obtained, having a taste similar to that of common 
 salt. 
 
 Potassium Iodide, KI. 
 
 This salt likewise crystallizes in cubes, is easily soluble 
 in water, and is employed in medicine as a valuable 
 remedy. 
 
 Experiment 1. — To prove that iodine is really contained 
 in this white salt, heat a small portion of it in a test-tubo 
 with a little black oxide of manganese and some drops of 
 sulphuric acid, when violet fumes will be evolved. If 
 
SODIUM. 
 
 203 
 
 common salt is treated in the same manner, chlorine, as 
 is known, will be given off. The chemical action is the 
 same in both cases. 
 
 Potassium TersulpMde, K2S3. 
 
 Sulphur combines with potassium in five different 
 proportions, forming ill-defined compounds. One of the 
 most important of them is prepared as follows : 
 
 Experiment 1. — Put a mixture of one drachm of sulphur 
 and two drachms of dry potassium carbonate into an iron 
 ladle, cover it with a strip of sheet iron, and heat it until 
 the effervescence has ceased and the mass flows quietly. 
 The fused mass has the colour of liver, and on this account 
 has received the name liver of sulphur : pour it upon 
 a stone, and if it should inflame, cover it with a vessel to 
 extinguish it. On exposure for some time to the air it 
 becomes greenish and moist, and evolves an odour like 
 that of rotten eggs. It consists chiefly of potassium 
 tersulphide. A similar preparation has already been 
 described (p. 141). 
 
 Experiment 2. — Pour water into a test-tube containing 
 some liver of sulphur; you obtain a yellowish-green 
 solution. If to this you add diluted sulphuric acid, a 
 strong evolution of hydrogen sulphide takes place, and the 
 liquid becomes milky from the precipitation of two -thirds 
 of the sulphur (milk of sulphur) : 
 
 K,S3+H2SO,=K,SO,+H,S+2S. 
 
 The same thing is effected, though far more slowly, by 
 the carbonic anhydride of the air, and thus is explained 
 why the liver of sulphur (as well as the residue left on 
 the combustion of gunpowder) emits a smell like that of 
 rotten eggs when it is left exposed to the air. 
 
 The other sulphides of potassium can be formed by 
 varying the proportions of the potassium carbonate and 
 sulphur. 
 
 SODIUM. 
 Na = 23. 
 
 Sodium was discovered by Davy soon after the isolation 
 of potassium. Like potassium, it is obtained by reducing 
 
204 
 
 EXPERIMENTAL CHEMISTRY. 
 
 its carbonate with carbon. It is much easier to prepare 
 than potassium. 
 
 Sodium is a soft, white, and easily fusible metal, lighter 
 than water, and very similar to potassium in chemical 
 characters. 
 
 Experiment 1. — The action of sodium on water has 
 already been described (p. 104). It is closely analogous 
 to that of potassium. 
 
 Sodium oxide, Na20, and Sodium hydrate, NaOH, are 
 obtained in the same way as the potassium compounds, 
 and are so analogous to them that the descriptions given 
 of the latter are applicable, with few exceptions to either. 
 
 Sodium chloride, or common salt, 'NaCl. — Salt has twice 
 previously been artificially prepared ; namely, once from 
 sodium and chlorine (page 113 and again from soda and 
 hydrochloric acid (page 117) ; its constituents are accord- 
 ingly already known. It has the formula NaCl. 
 
 The earth and sea abound in common salt ; it may there- 
 fore be easily procured in large quantities. In many places 
 it is found in the interior of the earth, in immense beds, from 
 which it is broken up and dug out. This salt looks like a 
 transparent stone, and is, therefore, called rock-salt. In 
 those places where the rock-salt is mixed with atones and 
 earth, a hole is bored in the middle of the bed, and water 
 is let into it. The water is pumped out again as soon as 
 it has become saturated with the salt, and is again 
 expelled by evaporation. In some places springs are 
 found containing salt in solution — the so-called natural 
 brine springs. These are always occasioned by the water 
 permeating the earth over a bed of rock-salt, and appear- 
 ing as a spring at some lower leveL 
 
 In hot countries, salt is also prepared from sea-water, 
 which is evaporated in shallow tanks by the heat of the 
 sun. It is called hay-salt, and has a bitterish taste, owing 
 to the presence of salts of magnesium. Sea- water contains 
 rather more than 3 per cent of common salt. 
 
 Salt is indisjien sable to the life of animals, and is there- 
 fore a constant and necessary ingredient of food. It is 
 also used for preserving animal and vegetable substances, 
 because it has the power of preventing putrefaction or 
 decay. Meat and fish are salted down, and wood for the 
 
SODIUM. 
 
 205 
 
 purpose of building is rendered more durable by being 
 impregnated with salt. Sucb substances are called 
 antiseptics. 
 
 Experiment 1. — Dissolve one ounce of salt in two ounces 
 and three-fourths of cold water ; the water will dissolve no 
 more. Eepeat the experiment, using hot instead of cold 
 water ; the result is almost exactly the same. Common salt 
 has the remarkable property of being nearly as soluble in 
 cold as it is in hot water, A larger quantity of almost all 
 other salts is dissolved by hot than by cold water. Put one 
 of these solutions in a warm place ; by the gradual evapora- 
 tion, regular transparent cubical crystals of common salt 
 are formed. Boil down the other solution, quickly stirring 
 it all the while ; it yields a granular, opaque, saline powder. 
 Salt is prepared as last described on a large scale, and 
 hence the granular state of common salt. 
 
 Experiment 2. — If you expose a solution of salt in an open 
 place during the extreme cold of winter (~10°C.or + 14°F.), 
 transparent prismatic crystals will be formed, which 
 contain more than one-third of water of crystallization, 
 NaCl,2H20. When placed on the hand they quickly become 
 opaque and deliquesce into a syrupy mass, in which 
 numerous small cubic crystals may be perceived. 
 
 Experiment 3. — Heat some common salt on platinum 
 foil or a knife, it will crackle briskly, and part of it will 
 be thrown off the foil ; that which remains melts when the 
 foil becomes red hot. The crackling (decrepitation) 
 proceeds from a trace of water, which has remained in the 
 interstices of the crystals ; on being heated it expands and 
 bursts the crystals asunder. 
 
 Sodium sulphate, Na2S04. — As most of the potassium salts 
 and potassium are prepared from potassium pio-. 74. 
 chloride, or carbonate, so most of the sodium 
 salts are prepared from common salt. In the {Th 
 latter case, however, an indirect process must j : 
 often be resorted to, since chlorine is not so I 1 
 easily removed from sodium as carbonic acid is I i 
 from potassium. The sodium chloride must first I | 
 be converted into sodium sulphate. We are [_ ; 
 already acquainted with this salt, as it remains ^^Lu 
 in the retort after the preparation of hydrochlaric acid, 
 
206 
 
 EXPBRIMENTAL CHEMISTRY. 
 
 when common salt is heated with sulphuric acid. It was 
 formerly taken as a popular medicine, under the name of 
 Glauber's salts, so called from its discoverer, the physician 
 Glauber. We find it also in many mineral waters ; for 
 instance, in the Cheltenham, Plillna and Hunjadi Janos 
 waters. It is readily soluble, crystallizes in prisms, and 
 has a saline, bitter taste. 
 
 Experiment 1. — Place half an ounce of crystals of sodium 
 sulphate in a warm place ; they soon become covered with 
 an opaque white coating ; they effloresce. The powder 
 obtained weighs hardly a quarter of an ounce. That 
 which was lost was water. Crystals of sodium sulphate 
 contain more than half their weight of water of crystalli- 
 zation. Their composition is expressed by the formula 
 Na2SO4.10H2O. The transparency of the salt is lost when 
 chemically combined water is separated, but reappears 
 when the anhydrous salt is dissolved in water and re- 
 crystallized. Salts which effloresce must be kept well- 
 corked up. 
 
 Experiment 2. — If a crystal of sodium sulphate is heated 
 on charcoal before the blowpipe, it soon melts, because it 
 dissolves in its water of crystallization (watery fusion) ; 
 it becomes dry as soon as the water is expelled ; but finally 
 it melts for the second time when heated to redness (igneous 
 fusion). Those salts which contain no water of crystalli- 
 zation can undergo only the latter kind of fusion. 
 
 Experiment 3. — Heat in a small flask half an ounce of 
 water to 91° F.(33° C), and keep it at this temperature, 
 gradually adding crystallized sodium sulphate, as long as 
 they are dissolved, amounting to about an ounce and a 
 half. If a stronger heat be now applied to the saturated 
 solution, a salt will separate (anhydrous crystals, Na2S04) ; 
 if you let it cool, a salt will likewise separate (hydrated 
 crystals, Na2S04, IOH2O) ; — furnishing another example 
 of the great influence exerted by temperature on the 
 affinity of water for other substances. Sodium sulphate 
 has the peculiar property of being most soluble in water, 
 not at the boiling point, but at a lower temperature. 
 
 The curious manner in which a hot saturated solution of 
 the salt can be cooled without immediate crystallization 
 taking place, has already been noticed (p. 10, Exp. 3), 
 
SODIUM. 
 
 207 
 
 Experiment 4. — If you dissolve crystallized sodium 
 sulphate in water, cold is produced ; but if, on the contrary, 
 you dissolve the anhydrous salt in water, then heat is 
 produced. You will observe exactly the same phenomena 
 if you perform this experiment with sodium carbonate, 
 taking first the crystallized and then the calcined salt. 
 Whence the source of this heat ? It is due to a part of the 
 water combining with the anhydrous sulphate, or car- 
 bonate, as water of crystallization. 
 
 Sodium sulphide, NaaS. — Experiment 1. — Mix a small 
 portion of anhydrous sodium ^ig. 75. 
 
 sulphate with a little charcoal 
 powder, and heat the mixture 
 on charcoal before the blow- 
 pipe ; they will melt with brisk 
 effervescence into a brown 
 mass, which dissolves in 
 water, forming a yellovvi«h 
 liquid. The charcoal, when 
 heated to redness, abstracts the 
 oxygen, and forms with it 
 carbonic oxide gas, which 
 escapes with effervescence ; sodium and sulphur remain 
 behind, combined with each other. That is, the charcoal 
 deoxidizes the sodium sulphate, or reduces it to sodium 
 sulphide. 
 
 If you drop hydrochloric or diluted sulphuric acid into 
 the solution, the disagreeable smell of sulphretted hydro- 
 gen will be given off. 
 
 Sodium Ca'}'honate, Carhonate of soda, NagCOg. 
 
 Experiment 1. — Prepare some more sodium sulphide in 
 the manner just described, rub it in a mortar with the 
 adhering particles of charcoal and with about its own 
 weight of chalk, and ignite it again before the blow-pipe. 
 Warm the baked saline mass in water, and then filter the 
 liquid. A grey powder remains behind, which, when 
 drenched with hydrochloric acid, evolves sulphuretted 
 hydrogen ; it is calcium sulphide. The liquid, after being 
 evaporated on a shallow glass dish, leaves behind a white 
 powder, which has an alkaline reaction and effervesces 
 
208 
 
 EXPERIMENTAL CHEMISTRY. 
 
 with hydrochloric acid, but yet without emitting any dis- 
 agreeable odour ; it is sodium carbonate. The sulphur has 
 thus passed to the calcium of the chalk, while the carbonic 
 acid radicle of the chalk has passed to the sodium. 
 
 As sodium carbonate possesses almost exactly the same 
 properties as potassium carbonate, and can be advan- 
 
 large oven-shaped furnaces, 
 represented in the figure ; a is the grate, h the ash-pit, p the 
 chimney, d d the hearth for receiving the mixture, i the 
 aperture for throwing in the mixture, and g an opening 
 for stirring it and scooping it out. They are called 
 reverberatory-furnaces, because the heating is effected, not 
 by the fuel itself, but by the flame, which is reverberated 
 after passing over the bridge c ; they possess this 
 important advantage, that the ashes of the coal or peat do 
 not become mixed with the substance to be heated. In 
 some countries sodium carbonate is also obtained from the 
 ashes of marine plants (kelp). 
 
 Sodium carbonate occurs in commerce, either crystallized 
 — it then contains more than half its weight of water of 
 crystallization. Na.^CO3,10H2O, and effloresces very 
 readily — or calcined, consequently anhydrous. The latter, 
 accordingly, when it occurs pure, is of more than twice 
 the strength of the crystallized. Sodium carbonate is 
 
 Fig. 76. 
 
 tageously employed instead 
 of the latter in washing and 
 bleaching, and also in the 
 manufacture of glass and 
 soap, it is now manufactured 
 on an enormously large scale 
 in chemical works. The pro- 
 cess pursued is essentially 
 the same as that already 
 described, except that the two 
 operations, described sepa- 
 rately above, are united into 
 one; the chalk or limestone 
 is added, in the first place to 
 the sodium sulphate and 
 charcoal, and the who ie mass 
 is heated. This is done in 
 
SODIUM. 
 
 209 
 
 easily soluble in water. Many mineral waters contain 
 great quantities of it in solution. 
 
 Hydrogen sodium carhonate^ HNaCOg, is chiefly used for 
 preparing effervescing powders. It is prepared like the 
 similar potassium salt (p. 199), and is commonly called 
 bicarbonate of soda. 
 
 Sodium nitrate^ NaNOg. — Dissolve some sodium carbonat 
 in water, neutralize with nitric acid, evaporate Yi^. 11. 
 the solution, when crystals will separate, 
 having the form of an oblique rhombic prism ; 
 they are nitrate of soda. They deflagrate on 
 charcoal like potassium nitrate, and have 
 the greatest similarity to it in other respects. Extensive 
 beds of this salt are found in America, whence large 
 quantities are exported, under the name of Chili salt- 
 petre ; and it is substituted for the more costly nitre in 
 the manufacture of nitric acid and some of its salts. 
 But it does not answer for making gunpowder, as it is 
 deliquescent. Saltpetre is prepared from it by the 
 addition of the Stassfurth potassium chloride and sub- 
 sequent crystallization. 
 
 NaN03+KCl = NaCl+KNOg. 
 
 Sodium Phosphate, Na2HP04. 
 
 Experiment — Neutralise sodium carbonate, dissolved in 
 water, with phosphoric acid ; filter the liquid, and 
 evaporate the filtrate until a film forms on the surface ; 
 on cooling, transparent crystals will be deposited, which 
 Contain more than half their weight of water of crystalli- 
 zation : Na2HP04,12H20. They easily effloresce, and 
 yield a yellow precipitate with a solution of silver nitrate. 
 
 Other phosphates of sodium of less importance are 
 known. 
 
 Sodium di-horate, or Borax, l^Si2Bfi^» — The hard colour- 
 less crystals commonly called borax are an irregular 
 sodium salt of boric acid (p. 174). Tincal is a native 
 borax found in China and Thibet. Borax contain ten 
 molecules of water of crystallization : Na2B4O7,10H2O. 
 
 Experiment 1. — Heat some powdered borax upon a small 
 loop of platinum wire before the blow-pipe; it will puff 
 up and swell in its water of crystallization, and be con- 
 
 p 
 
210 
 
 EXPERIMENTAL CHEMISTRY. 
 
 verted into a porous spongy mass; on being farther 
 heated, it fuses to a transparent head. Moisten this bead 
 with the tongue, apply it to litharge so that some of the 
 latter may adhere to it, and again hold it in the outer 
 flame of the blow-pipe ; the litharge is dissolved ; the 
 bead remains colourless and transparent. If you now 
 substitute for the litharge other metallic oxides, you will 
 likewise observe that the oxides will dissolve, but that at 
 the same time the bead will be coloured by them ; namely, 
 yellowish-red, by sesquioxide of iron and oxide of antimony ; 
 green, by the oxide of chromium ; blue, by oxides of copper 
 and cobalt ; violet, by a small portion of oxide of man- 
 ganese ; and hrownish-hlack, by an excess of manganese. 
 
 On account of this property which borax has of 
 dissolving metallic oxides, it is used in chemistry as a 
 blow-pipe test for the detection of metallic oxides, and 
 in the trades for soldering, or joining one metal with 
 another. 
 
 Sodium Silicates (^Glass, dc.). 
 
 Experiment, — Melt some potassium or sodium carbonate 
 in a small loop of platinum wire before the blow-pipe, 
 and then add a little finely pulverised sand ; upon placing 
 it again in the blow-pipe flame, effervescence will ensue, 
 and afterwards a clear bead will be formed. If the 
 proj)ortion of sand used be small, the glass formed will 
 dissolve in water on long-continued boiling ; it is then 
 called soluble glass (p. 194). If more sand is taken, a glass 
 is obtained which is very difficult to dissolve in water. 
 To make a glass which shall be entirely insoluble, not 
 only in water but also in acids, beside alkalies, some 
 other earth or metallic base — for instance, lime or litharge 
 — must be added. Common glass is thus manufactured 
 in glass-houses : 
 
 The materials which are chiefly employed in the manu- 
 facture of glass are quartz, flint, or sand, potassium car- 
 bonate or wood-ashes, sodium carbonate, lime or chalk 
 and litharge or lead oxide. These substances, after 
 being pulverised, are mixed together, thrown into earthen 
 pots, and heated in a furnace until the mass forms 
 a uniform fluid. In this state it may be moulded like 
 
AMMONIUM, 
 
 211 
 
 wax, cut and bent, pressed into moulds, and blown, and 
 may accordingly be manufactured into all possible shapes 
 and forms ; on cooling, it becomes hard and brittle. In 
 order to diminish in a measure the brittleness, the glass 
 must be cooled very slowly (annealed). Glass vessels that 
 are rapidly cooled often crack when they are carried from 
 a warm into a cold room ; this defect may, to a certain 
 degree, be corrected, by gradually heating the vessels in 
 water till it boils, and then allowing it to cool very slowly. 
 
 For colouring and painting glass various metallic oxides 
 are employed. The milk-white colour which we observe 
 in the opaque glass of the lamp-screens, and in the enamel 
 of the dial-plate of watches, is produced by finely-ground 
 bone-earth or meta-stannic acid — neither of which sub- 
 stances is dissolved by the vitreous mass, but only mixes 
 with it mechanically, and renders it opaque, as chalk 
 does water. Glass is ground by sand and emery, polished 
 by ferric oxide and tripoli, etched by hydrofluoric acid, 
 and very easily perforated by the point of a three- 
 cornered file, which should be frequently moistened with 
 oil of turpentine. 
 
 The two principal kinds of glass are — 
 
 Crown or Bohemian glass, consisting of sodium and 
 calcium silicates. 
 
 Flint or crystal glass, consisting of potassium and lead 
 silicates. 
 
 Common bottle-glass contains the same ingredients as 
 crown glass, with the addition of ferric oxide, which 
 imparts to it a brownish-yellow colour ; of ferrous oxide, 
 which gives it a green tinge ; of alumina, &g. The iron 
 is contained in the impure materials (yellow sand and 
 wood-ashes) used in the preparation of the ordinary sorts 
 of glass. 
 
 AMMONIUM. 
 NH4 = 18. 
 
 Although ammonium is a compound radical and not an 
 element, its compounds, which are often called ammonia- 
 salts, are so similar to tho^^e of potassium and sodium, 
 that they are generally placed among the metals. Their 
 constitution has already been explained (p. 158 J. 
 
 p 2 
 
212 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Avfimonium hydrate, NH^OH. — The solution of ammonia 
 gas in water has been supposed to contain this compound. 
 The solution is strongly alkaline and caustic, like that of 
 potassium, or sodium hydrate. 
 
 Ammonium chloride, NH4CI. Sal-ammoniac, — Formed by 
 the direct union of ammonia and hydrochloric acid 
 (p. 158). It is generally prepared from the "ammoniacal 
 liquor" of gas-works (p. 157). It is a tough, fibrous 
 solid, which may be purified either by crystallization 
 from water or by sublimation, 
 
 Experiment 1. — Heat some impure sal-ammoniac in a 
 dry test-tube. It will volatilize, and the colourless 
 vapour will condense on the sides of the tube as a white 
 mass, which however, is still apt to contain iron. 
 
 Experiment 2. — Dissolve some crude sal-ammoniac in 
 water, and add a few drops of ammonium sulphide. If iron 
 be present, a black precipitate will appear, and will subside 
 after a time. The filtered liquid may then be evaporated to 
 dryness, the mass dissolved in water, the solution filtered 
 and evaporated until it crystallizes. The crystals will 
 consist of pure ammonium chloride. 
 
 Ammonium sulphide, ('N11^\S, and Sulphydrate, NH4SH. 
 — These compounds correspond to the hypothetical oxide 
 and hydrate of ammonium, (]SrH4)20, and NH4OH. 
 
 Experiment 1. — Pass sulphuretted hydrogen gas, prepared 
 as described on page 143, first through a bottle containing 
 a little water to remove impurities, and then into some 
 dilute ammonia. The gas will be absorbed in large 
 quantity. When the ammonia is saturated, there will 
 remain a solution of ammonium sulphydrate : 
 
 NH40H-I-H2S = NH^SH-l-H^O. 
 
 If this solution is mixed with a quantity of ammonia 
 equal to that first employed, the sulphydrate becomes 
 sulphide : 
 
 NH^SH + NH^OH = (N H^)^ S 4- 0. 
 This sulphide precipitates many metals, and is therefore 
 a valuable test. When freshly prepared it is colourless, 
 Viut soon turns 3 ellow from the formation of a higher 
 sulphide. The change does not often hinder its usefulness 
 as a lest. 
 
SILVER. 
 
 213 
 
 Ammonium carbonate. — Experiments, — Mix an ounce of 
 chalk (calcium carbonate) and half an ounce of ammonium 
 chloride in powder. Heat the mixture in a dry Florence 
 flask with the neck broken off, over which is inverted a 
 small beaker. Double decomposition takes place ; calcium 
 chloride remains in the flask, and the volatile ammonium 
 carbonate sublimes and condenses in the beaker. 
 
 This is the well-known smelling salts. It has, as its 
 common name implies, a strongly ammoniacal odour. In 
 reality the salt has a complex constitution, but the student 
 may safely regard it as ammonium carbonate (NH4)2C03. 
 
 Ammonium nitrate, NH4NO3, has already been described 
 (p. 158). 
 
 All ammonium salts, when warmed with solution of 
 potash or milk of lime, give off ammonia gas. They may 
 readily be identified by this means : 
 
 Ammonium Potassium 
 Nitrate. Nitrate. 
 
 NH^^Oa + KOH = KNO3 + NH3 +H2O. 
 
 SILVER. 
 Ag = 108. 
 
 Silver, though a monad, has but little analogy with the 
 others metals of this group. It sometimes occurs native 
 (uncombined), but more frequently as sulphide, either pure 
 or associated with the sulphide of lead or copper. It is 
 also found as chloride (horn-silver). Several processes are 
 adopted for its extraction. From galena (lead sulphide) 
 it is obtained by reducing both metals to the metallic state 
 by roasting and smelting the ore with charcoal. The 
 silver is then separated by a process called cupellation. 
 The alloy is placed on a hearth or cupel, made of bone ash, 
 and strongly heated in a current of air. The lead is 
 rapidly converted into oxide, which, fusing, is partly 
 volatilized, and partly absorbed by the porous hearth, 
 leaving the silver in the metallic state. If the lead be 
 poor in silver, the alloy is melted, and allowed to cool 
 slowly in iron pots. The portions which solidify first 
 consist chiefly of lead, and being removed TNdth a per- 
 forated ladle, the remaining lead becomes gradually much 
 richer in silver. Complete separation is finally effected by 
 
214 
 
 EXPERIMENTAL CHEMISTRY. 
 
 cupellation. This method, known as Pattinson's process, 
 can be used economically, even when the lead contains 
 less than ^^Vo" weight of silver. Zinc is sometimes 
 used instead of lead. Silver is obtained from the copper 
 ores by reducing them to the metallic condition. The 
 copper containing the silver is fused with lead, and the 
 alloy, after solidifying, is gradually heated. The lead 
 and silver melt first, and run off, leaving the copper. The 
 silver is finally isolated by cupellation. 
 
 Silver is often extracted by means of mercury from the 
 ores containing pure silver or silver sulphide, but no lead. 
 But in the case of silver-glance (silver-sulphide) the 
 metallic silver must first be separated from the sulphur. 
 This is done by two operations. In the first, the stamped 
 ore is roasted with common salt, by which process silver 
 chloride and sodium sulphate are formed ; in the second, 
 the roasted ore is mixed with water, iron, and mercury, 
 and kept in constant agitation for some time in closed 
 casks. Chloride of iron and metallic silver are thereby 
 formed, the latter of which is dissolved in the mercury. 
 The excess of mercury is then filtered off, and a solid silver 
 amalgam is obtained by subjecting it to pressure, and the 
 mercury is at last completely removed from the amalgam 
 by distillation. Several other methods for the separation 
 of silver are, or have been used. 
 
 As pure silver is very soft, and would quickly wear out 
 in using, it is generally alloyed with copper, whereby it 
 is rendered harder, without losing its ductility. If the 
 proportion of copper is only one-fourth, the silver still 
 retains its beautiful white colour ; but if more copper is 
 added, the alloy becomes yellow, and finally red, by use. 
 The standard silver, used in England for coinage, consists 
 of 9^ parts of pure silver and f of copper. 
 
 Silver nitrate, Ag NO3. — Experiment 1. — Heat a sixpence 
 in some dilute nitric acid until it is dissolved. Silver 
 nitrate is formed, but is contaminated with copper, as the 
 blue colour of the solution betokens. 
 
 Experiment 2. — Place a bright sheet of copper in the 
 silver solution, and let it stand for a few hours. The 
 copper immediately becomes covered with a black powder, 
 which soon increases to a mass of brilliant metallic crystals 
 
SILVER. 215 
 
 of silver. The copper decomposes the silver nitrate, 
 forming copper nitrate and free silver : 
 
 2 AgN03 + Cu = CuN03)2 + 2Ag. 
 
 By washing the crystals well with water in a filtei*, and 
 drying them, pure silver is obtained, which, by being 
 again dissolved in nitric acid, and evaporated to dryness 
 at a gentle heat, furnish a white mass of pure silver nitrate. 
 This may be dissolved in water, and crystallized, or fused 
 and formed into sticks, when it constitutes lunar caustic. 
 The crystals are anhydrous. 
 
 Experiment 3. — Place a small piece of silver nitrate upon 
 charcoal, and heat it before the blow-pipe ; it deflagrates 
 and yields metallic silver, which may be easily fused at a 
 stronger heat. 
 
 Experiment 4. — Add some ammonia to a solution of silver 
 nitrate ; the dark-grey precipitate is silver hydrate, AgOH. 
 If more ammonia is added, it is redissolved. 
 
 Silver chloride^ AgCl. — Experiment 5. — To a solution of 
 silver nitrate add hydrochloric acid or a solution of com- 
 mon salt ; you obtain a white curdy precipitate of silver 
 chloride^ This precipitate is so insoluble in water that it 
 will impart a cloudiness to a solution of silver diluted a 
 millionfold ; it is, however, easily dissolved by ammonia. 
 
 Experiment 6. — After having decanted the supernatant 
 liquid, rub the silver chloride with a cork upon a sheet of 
 paper, and let it dry in a dark place — in a drawer, for 
 instance ; it remains white. Now place the sheet partly 
 in a book, so that one-half may be exposed to the light ; 
 this part soon acquires a violet, and finally a black colour, 
 while that protected from the light remains white. Thus 
 light is capable of decomposing this salt. On this action 
 of the solar light on certain substances is founded the art 
 of photography, in which light acting upon the salts of 
 silver (especially the chloride, bromide, and iodide) may 
 be made to yield faithful representations of any objects. 
 
 Silver sulphide, Ag2S. — If you add sulphuretted hydrogen 
 to a solution of silver you obtain a black precipitate of 
 silver sulphide. This compound occurs in nature as the 
 most important silver ore ; it is called silver- glance. 
 
( 216 ) 
 
 CHAPTEE II. 
 
 METALLIC DIADS. 
 
 Group i. — Calcinm, Strontinm, Barium, Magnesiiim, 
 Zinc. 
 
 CALCIUM. 
 Ca = 40. 
 
 This metal never occurs pure, but many of its compounds, 
 such as chalk, marble, limestone, and gypsum, are found 
 in enormous quantities. Calcium is a yellow metal of no 
 practical value. It can only be separated with the 
 greatest difficulty. It is very light (Sp. Gr. 1-6), and 
 decomposes water at ordinary temperatures, though with 
 less energy than potassium and sodium exhibit. 
 
 Calcium oxide (Lime), CaO. — Experiment 1. — Heat a 
 small piece of chalk on charcoal before the blow-pipe for 
 several minutes. It will be converted into calcium oxide, 
 or quicldime, by losing carbonic anhydride : 
 
 CaC03 = CaO+C02. 
 
 Lime is obtained by burning a mixture of coal and 
 chalk, or limestone, in chambers called lime Jcilns, 
 
 Calcium hydrate (SlaJced lime), Ca(0II)2. — Experiment 2. 
 — Lime combines eagerly with water to form the hydrate. 
 Put some lime in a saucer, and sprinkle it with water. 
 In a few minutes, it cracks in various places, and becomes 
 very hot ; steam is copiously evolved, while the lime 
 crumbles to a white powder, called slaked lime. This is 
 calcium hydrate. It is alkaline and caustic, and slightly 
 soluble in water. Put a little in a bottleful of water, and 
 shake for a few minutes. A portion will dissolve. Allow 
 the remainder to subside, and pour the clear solution into 
 a fresh bottle, and label it lime-water. It becomes milky 
 
CALCIUM. 
 
 217 
 
 on exposure to the air, from the formation of calcium car- 
 bonate by the absorption of carbonic anhydride, hence it 
 is often used as a test for that gas (p. 40). 
 
 Calcium carbonate, CaCOj, exists in nature as chalk, 
 marble, and limestone, and as the beautiful, transparent 
 crystals of Iceland spar. Calcium carbonate is insoluble 
 in pure water, but soluble, to a small extent, in water im- 
 pregnated with carbonic acid. It is therefore found in 
 most natural waters, and is a frequent cause of what is 
 termed the hardness of water. 
 
 Experiment 3. — Pass a current of carbonic anhydride gas 
 through a little lime-water in a wine-glass. The lime- 
 water at first becomes milky, from the formation of car- 
 bonate : but after a time, the precipitate dissolves in the 
 dissolved gas, and the liquid becomes clear. The car- 
 bonates of magnesium, iron, lead, and zinc, behave in the 
 same way. 
 
 Experiment 4. — Boil a little of the above solution in a 
 test-tube. The CO2 which held the carbonate in solution 
 is expelled, and the calcium carbonate is once more pre- 
 cipitated. This explains why water which owes its hard- 
 ness to carbonates is softened by boiling. The white 
 deposit which collects inside tea-kettles and boilers is 
 formed in this way. For this reason hardness due to 
 carbonates is called temporary hardness. 
 
 Experiment 5. — Temporary hardness may be removed 
 from water without boiling. Take a little of the solution 
 prepared in Experiment 3, and add lime-water to it. The 
 lime-water will neutralise the carbonic acid which held 
 the carbonate in solution, and the whole of the calcium 
 will then be precipitated as carbonate. This process for 
 softening water is called " Clark's process." It has been 
 found very useful on the large scale. 
 
 Experiment 6. — Sodium carbonate may be used instead 
 of lime-water in the preceding experiment. The sodium 
 carbonate combines with the carbonic acid, forming 
 hydrogen sodium carbonate, Na2C03-fH2C03 = 2HNaC03. 
 We have already seen that carbonic anhydride can be ex- 
 pelled from calcium carbonate by strong heat, and also 
 (p. 179) by the action of acids. 
 
 Calcium sulphate, CaSO^, is found native as gypsum. 
 
218 
 
 EXPERIMENTAL CHEMISTRY. 
 
 alabaster, &c. It then contains two molecules of water. 
 By heating gyj5sum to about 120°C. (248° F.) the water is 
 driven off, and a white powder, the so-called plaster of 
 Paris, is left. This, on being mixed to a paste . with 
 water, again unites with it, and the mass expands and 
 becomes solid. Calcium sulphate is slightly soluble in 
 cold water; and even less in hot, and is a frequent cause of 
 hardness in spring water. The hard fur which accumu- 
 lates in kettles and boilers is mainly composed of this salt. 
 Hardness due to sulphates is not removed by boiling, and 
 is therefore called permanent hardness. 
 
 Calcium chloride CaCl2. — This salt is formed when 
 marble is dissolved in hydrochloric acid, as in the prepar- 
 ation of carbonic anhydride. The solution, if very much 
 concentrated by evaporation, deposits colourless crystals 
 (CaCl26H20) ; or, if evaporated to dryness, furnishes a 
 spongy mass of the anhydrous chloride, which, in this 
 state, is much used for drying gases, as it absorbs water 
 with great avidity. 
 
 Calcium fluoride, CaF2, commonly known as fluor-spar, 
 occurs crystallized in Derbyshire and elsewhere, and is 
 interesting as the source of fluorine. 
 
 The remaining compounds of calcium are of little im- 
 portance, with the exception of calcium chloro-hypo- 
 chlorite, CaCl(ClO), or bleaching-powder, which has 
 already been described under chlorine, and calcium phos- 
 phate, Ca3(P04)2 or bone earth, which was discussed 
 under phosphorus. Calcium phosphate occurs native as 
 apatite and phosphorite. 
 
 STRONTIUM. 
 Sr = 87-5. 
 
 The compounds of this metal are similar to those of cal- 
 cium. Their chief sources are the carbonate called stron- 
 tianite, and the sulphate known as celestine by mineralo- 
 gists. 1 he metal resembles calcium, both in appearance 
 and the difficulty which attends its extraction. Strontium 
 oxide, SrO, or strontia, like lime, combines with water to 
 form a hydrate. It is most easily prepared by heating the 
 nitrate. By dissolving the carbonate in different acids, 
 the other salts of strontium can be prepared. The most 
 
BARIUM — MAGNESIUM. 
 
 219 
 
 remarkable characteristic of the strontium salts is that of 
 communicating a crimson colour to the flame of burning 
 substances. Strontium nitrate, like the other nitrates, 
 deflagrates upon burning charcoal, and is used for produ- 
 cing a crimson flame in fireworks. Strontium chloride 
 is soluble in alcohol, and imparts a crimson tint to its 
 flame. 
 
 BARIUM. 
 Ba = 137. 
 
 Barium* compounds are more extensively distributed 
 than those of strontium. It chiefly occurs as heavy-spar 
 (sulphate) and witherite (carbonate). The metal can only 
 be obtained with difiiculty. Barium oxide, BaO, or 
 baryta, is best obtained by heating the nitrate : it forms a 
 hydrate with water which is much more soluble than the 
 hydrates of calcium and strontium. By passing air or 
 oxygen over the heated oxide the curious compound, 
 barium peroxide, Ba02, is obtained. This substance is 
 used for preparing hydrogen peroxide. Barium carbonate 
 is insoluble in water. Barium sulphate is insoluble in 
 everything, and is obtained whenever a soluble barium 
 salt is added to sulphuric acid or a sulphate. For this 
 reason harium chloride, BaCl2, and barium nitrate, Ba(N03)2, 
 which are soluble salts, are much employed as tests for the 
 presence of sulphuric acid and sulphates (p. 150). 
 
 Barium j?alts communicate a green colour to flame : 
 unlike the strontium compounds, they are very poisonous. 
 
 MAGNESIUM. 
 Mg = 24. 
 
 The chief sources of magnesium are Magnesite MgCOg 
 and dolomite, or magnesian limestone, which is a carbonate 
 of calcium and magnesium. The element occurs also in 
 sea- and spring-water as sulphate and chloride. The 
 metal is now prepared in somewhat large quantities, by 
 decomposing heated magnesium chloride with sodium : 
 
 MgCl2-hNa2 = 2NaCl+Mg. 
 
 Magnesium is a silver- white metal, which does not 
 
220 
 
 EXPERIMENTAL CHEMISTRY. 
 
 tarnish in dry air. Its specific gravity is 1*75. It is 
 malleable, and may be rolled into ribbon or drawn into 
 wire. The most notable property of magnesium is the 
 dazzling brilliancy with which it burns when held in a 
 flame. This fact has led to its adoption as an illumina- 
 ting agent in certain cases where a strong light is required. 
 For this purpose it is used in the form of ribbon or 
 powder, and burnt in specially contrived lamps. The 
 light of burning magnesium forms a valuable substitute 
 for sun-light in photography, owing to its extreme rich- 
 ness in rays of chemical power. Magnesium rapidly 
 dissolves in most acids, with the evolution of hydro- 
 gen. 
 
 Magnesium oxide (^Magnesia), MgO. — Experiment, — Set 
 fire to a piece of magnesium wire the flame of a spirit- 
 lamp, or Bunsen's burner. It will burn rapidly, and be 
 converted into a pure white powder. This is magnesium 
 oxide, or magnesia (sometimes sold as calcined magnesia)^ 
 formed by the direct union of its constituents. It is pre- 
 pared in quantity by strongly heating the carbonate, 
 which, like chalk, loses carbonic anhydride and yields the 
 oxide. When treated with water, the oxide yields a 
 hydrate analogous to that of calcium, but much less soluble 
 in water. 
 
 Magnesium carbonate, MgCOg, occurs crystallized as 
 magnesite, and is the chief constituent of the magnesia 
 alba of the shops. It is soluble, with effervescence, in 
 acids. 
 
 Magnesium sulphate (Epsom salts) MgS04,7H20, is the 
 chief salt of magnesium, owing to its extensive use in 
 medicine as a purgative. It is largely prepared by dis- 
 solving dolomite in sulphuric acid, and from its superior 
 solubility is easily separated from the very sparingly 
 soluble calcium sulphate which is formed simultaneously 
 with it. To the chemist magnesium sulphate is valuable 
 as a test for phosphates (p. 171). 
 
 Magnesium chloride, MgCl2, is a very soluble salt, pre- 
 pared by neutralizing hydrochloric acid with magnesium 
 carbonate or oxide. It can only be obtained in the solid 
 state by indirect means, as the solution decomposes on 
 evaporation into magnesia and hydrochloric acid. 
 
ZINC. 
 
 221 
 
 ZINC. 
 Zn = 65. 
 
 Zinc resembles magnesium closely, but is more easily 
 extracted from its ores, the chief of which are zinc blende 
 (sulphide) and calamine (carbonate). Zinc is obtained by 
 converting the ore into oxide by roasting in a current of 
 air. The oxide being mixed with coal dust is then intro- 
 duced into an iron retort and subjected to distillation. 
 The carbon removes the oxygen as carbonic oxide, while 
 the liberated zinc being converted into vapour, is carried 
 over and condensed in a vessel below. Zinc readily dis- 
 solves in acids, with evolution of hydrogen ; hence it is 
 much employed for the preparation of that gas. 
 
 Not very long ago, zinc was hardly used except for 
 making brass and pinchbeck ; but since the art of rolling 
 it out into sheets, of forging it, and of drawing it out into 
 wire, has been acquired, it is used also for the manufacture 
 of many articles which were formerly made of lead, copper, 
 and iron ; for instance, for making nails, gasometers, gas- 
 pipes, gutters, and for roofs of houses, for lining refriger- 
 ators, as it is harder, and yet lighter than lead, cheaper 
 than copper, and less liable than iron to be destroyed by 
 air and water. It usually occurs in commerce in the form 
 of plates, which are so biittle that they may be broken by 
 the hammer into small pieces ; the fresh fracture exhibits 
 a crystalline structure, and a bluish- white colour. 
 
 Experiment 1. — If a piece of polished sheet zinc be ex- 
 posed to the action of water and air, it will become 
 gradually covered with a white film ; it rusts like iron, 
 but the rust of zinc has a white colour. In iron the 
 oxidation proceeds rapidly towards the interior, but not 
 in zinc, or only very slowly; therefore articles made of 
 zinc, when exposed to the wind and weather, last much 
 better than those made of iron, and for this reason, also, 
 iron articles are frequently coated with zinc (galvanised 
 iron). Zinc attracts not only oxygen, but also some 
 carbonic acid, from the air, and this may be recognised by 
 the effervescence which follows when some acid is dropped 
 upon the tarnished metal. 
 
 Experiment 2, — Hold a rod of zinc by means of a pair 
 
222 
 
 EXPERIMENTAir CHEMISTRY. 
 
 of tongs or pincers in the alcohol-flame, until it hisses 
 if you touch it with a piece of moist wood; if you now 
 quickly hammer it upon a stone or anvil previously 
 heated, it does not bre^k, but spreads out like lead into a 
 thin, coherent sheet. Zinc has the singular property of 
 being ductile hetween 212° F. (100° C.) and 302° F. (i50° 
 C), but below or above this temperature is brittle. Ever 
 since it has been known that zinc is thus affected by heat, 
 it has been found easy to overcome the difficulties which 
 formerly opposed the conversion of this metal (which is 
 unpliant when cold) into sheets and wire. 
 
 Experiment 3.— Zinc, when heated to 433° C. (811° F.) 
 melts, as may easily be seen by holding a small piece of it 
 in an iron spoon over an alcohol flame. In this case a 
 grey film is formed ; but this after a time assumes a 
 yellow colour, and is converted into pure oxide (ZnO). 
 On cooling, the yellow colour passes to white ; the oxide 
 of zinc belongs to those substances which present a 
 colour in the heat diffei ent from the colour at the ordinary 
 temperature. 
 
 Experiment 4. — At a still stronger heat (1040° C. = 
 1904° F.), zinc evaporates and burns at the same time 
 with a blue flame, as may be seen by heating a thin strip 
 in the blow-pipe flame. The product of the combustion is 
 zinc oxide, ZnO, portions of which are carried up, and 
 being very light, float in the air in flocks. 
 
 Zinc oxide, ZnO, is a white light powder prepared by 
 heating the metal strongly in air. It is insoluble in 
 water, but dissolves in acids, forming the zinc salts. 
 
 Zinc hydrate, Zn (0H)2. — Experiment 5. — Add potassium 
 or soilium hydrate to a soluble zinc salt, such as the 
 sulphate. A white precipitate of zinc hydrate will be 
 produced : 
 
 ZnSO^ + 2K0H = K^SO^ + Zn(0H)2. 
 
 Zinc hydrate is soluble in the alkaline hydrates, there- 
 fore care must be taken not to add too great an excess, or 
 the precipitate will disappear. By heating the hydrate, 
 water is driven off and the oxide is obtained. 
 
 Zinc sulphate ( White vitriol), ZnS04,7H.^O, is one of the 
 most important salts of zinc. It is easily soluble and 
 
COPPER. 
 
 223 
 
 crystallizes in colourless prisms, containing nearly half 
 their weight of water. It may easily be obtained by 
 evaporating the waste liquors left after generating hydro- 
 gen from zinc and sulphuric acid. In commerce the 
 sulphate is prepared by gently roasting the native sulphide 
 (zinc-blende) in a current of air. The sulphide takes up 
 oxygen and is converted into sulphate. 
 
 The other salts of zinc are of little interest. The car- 
 honate may be prepared by adding sodium carbonate to 
 zinc bulphate ; the sulphide, by adding ammonium sul- 
 phide. They are both white, insoluble substances. The 
 native sulphide possesses a reddish colour, owing to im- 
 purities. The chloride is used as a disinfectant under the 
 name of " Burnett's disinfecting fluid." 
 
 Cadmium is a somewhat scarce metal, often found in zinc 
 ores. It is very similar to zinc, but yields a beautiful 
 yellow sulphide when its nitrate is treated with ammonium 
 sulphide. Artists call the sulphide cadmium yellow. 
 
 Group ii. — Copper, Mercury, Lead. 
 COPPEK. 
 Cu = 63-5. 
 
 Copper is often met with in the free state (native 
 cop per \ but seldom in any quantity. The following are 
 some 01 the more important ores of the metal : — 
 
 1. Hed oxide, Cu2 0. j 
 
 2. Black oxide, Cu 0. vr x j x 
 on ^ n a > JNot very abundant. 
 
 3. Copper-glance, Cu2 b. [ 
 
 4. Indigo Copper, Cu S. 1 
 Malachite, Cu C O3, Cu (H 0)2. 1 
 6. Azurite, 2 Cu C O3, Cu (H 0)2. 
 
 I: Sp^:ci'jrS.F:t S Theol.i,fE„glisho,es. 
 
 The processes by which the metal is smelted from these 
 ores differ very much. The ores which do not contain 
 sulphur are sometimes reduced by fusion (after previous 
 roasting) with coke and lime. The roasting converts the 
 metal to oxide ; this when heated with carbon loses its 
 oxygen, while the silica, which would otherwise combine 
 
 The chief Australian 
 ore. 
 
224 
 
 EXPERIMENTAL CHEMISTRY. 
 
 with some of the copper, is removed by the lime. The 
 ores which contain isulphur, and especially the English 
 ores, require an extremely complex series of processes for 
 their reduction. 
 
 In ancient times copper was chiefly obtained from the 
 island of Cyprus, whence its Latin name cuprum. The red 
 colour and other physical characters of the metal are well 
 known. Its specific gravity is 8*9 ; rather higher than 
 that of iron (7*8). It is very tough and ductile, that is, it 
 can be drawn into fine wire. It melts at a bright red heat. 
 
 Copper is not easily altered by exposure to the air. In 
 pure air or water it undergoes no change. In moist air 
 it takes up CO2, and acquires a green film of basic carbon 
 ate. At a red heat it takes up oxygen, and yields black 
 scales of oxide, CuO. It combines easily with chlorine, 
 bromide and iodine, and at a red heat, with sulphur and 
 phosphorus. It is not acted on b}^ dijute hydrochloric or 
 sulphuric acid. Boiled with strong sulphuric acid, it 
 yields copper sulphate and sulphurous anhydride (p. 146). 
 Dilute nitric acid dissolves it easily, with liberation of 
 nitric oxide (p. 164). 
 
 Alloys of Copj)er, — Copper forms very important alloys 
 with several other metals. 
 
 Gold and copper form the common gold, silver and copper 
 the common silver, from which gold and silver articles 
 and coins are made. 
 
 The well-known brass, and other metallic compounds 
 having the appearance of gold, such as tombac, similor, 
 prince's metal, red brass, &c., are composed of zinc and 
 copper. Spurious gold-leaf is made by hammering out 
 tombac into exceedingly thin leaves, which, when finely 
 pulverised, constitutes the so-called gold bronze. Yellow 
 metal contains 2 of zinc to 3 of copper. It is used for 
 sheathing ships' bottoms. Purple or copper bronze is pre- 
 pared by gently heating the gold-coloured bronze till it 
 turns to a purple-red colour. 
 
 Zinc, nickel, and copper constitute the ingredients of 
 German silver (pacJcfong, white copper). 
 
 Tin and copper form a very hard grey alloy, from which 
 statues, cannons, bells, mirrors, &c., are cast (bronze, gun- 
 metal, bell-metal, speculum-metal). 
 
COPPER. 
 
 225 
 
 Oopper, like mercury, forms two distinct classes of salts, 
 one denominated cuprous^ the other cupric. Thus we have 
 cuprous oxide, CugO, and cupric oxide, CuO ; cuprous 
 chloride, Cu^Clg, and cupric chloride, CuOlg. 
 
 In the cuprous compounds, two atoms of metal behave 
 as a single diad atom (O'ug). The cuprous compounds are, 
 for the most part, unimportant. 
 
 Cuprous oxide, CU2O. — Experiment 1. — On heating a piece 
 of bright copper in a smokeless flame, it passes through 
 various shades of colour — crimson, violet, blue, and finally 
 to grey. On speedily quenching the metal in water it 
 becomes brownish-red ; this red coating is cuprous oxide. 
 
 Cuprous oxide, when thrown into melting glass, colours 
 it hlood-red ; in this manner a beautiful red colour is 
 flashed on glass in the glass factories. This accounts, 
 also, for the red colour of the slag which forms during the 
 calcination and fusion of copper. 
 
 Experiment 2. — Cuprous oxide may easily be prepared 
 by boiling a solution of copper sulphate and grape or 
 starch sugar, to which an excess of an alkaline hydrate 
 has been added. This will be further noticed under 
 sugar. 
 
 Cupric oxide, CuO. — If the copper is heated for a longer 
 time in the air it becomes coated with a black substance. 
 This is cupric oxide ; it contains a larger proportion of 
 oxygen. By long-continued ignition, the whole mass of 
 the copper may be converted first into cuprous and ulti- 
 mately into cupric oxide. The glowing cinders which fall 
 in the workshops of the copper-smiths (copper-scales) con- 
 sist of a mixture of the two oxides. 
 
 Cupric oxide is extensively used 
 as an agent for effecting the 
 combustion of organic substances, 
 with a view to their ultimate 
 analysis. For this purpose it is 
 usually prepared by heating cu- 
 pric nitrate. 
 
 Experiment 3. — Introduce some 
 cupric oxide into a hard glass 
 tube, heat it, and then pass over it a stream of hydrogen, 
 which is evolved by zinc and diluted sulphuric acid, 
 
 Q 
 
226 
 
 e'xperimental chemistry. 
 
 and then heat the tube. In the heat, the hydrogen 
 abstracts from the oxide of copper its oxygen, a ad forms 
 with it water, which escapes. A process by which 
 this reaction has been utilized as a means of determining 
 the composition of water has already been described 
 (p. 135). 
 
 Ciipic hydrate, Gii (0H)2.— Ex]periment 4. — Most of the 
 metallic hydrates can be formed by adding an alkaline 
 hydrate to a salt of the metal. Thus, on adding potassium 
 hydrate to cupric sulphate there are obtained potassium 
 sulphate and cupric hydrate. The latter substance is 
 precipitated as a light-blue powder. Boil the liquid in 
 which it is contained, and it will become black, for it is 
 resolved into black cupric oxide and water : Cu(0H)2 = 
 CUO + H2O. This furnishes another example of chemical 
 decomposition effected by mere elevation of tempera- 
 ture. 
 
 Experiment 5. — Eepeat the former experiment, but 
 instead of potash take ammonia ; here also the copper 
 hydrate is first precipitated, but this is redissolved by 
 adding more ammonia, forming a splendid hlue liquid. 
 Ammonia is therefore a test for salts of copper. Pour 
 upon the blue liquid an equal quantity of strong alcohol, 
 and direct the stream against the side of the glass, so that 
 the alcohol may float on the surface ; after the lapse of 
 twenty-four hours, a mass of dark-blue acicular crystals is 
 perceptible, which consist of a compound of copper 
 sulphate with ammonia, and are called cupric ammonio- 
 sulphate. By dissolving them in water, the hlue liquid of 
 the apothecaries* show-bottles is prepared. 
 
 Cuprous chloride, CU2CI2, is an unimportant compound, 
 obtained by digesting cupric chloride with copper, out of 
 contact with air. It is colourless, but rapidly changes 
 to green cupric chloride when its acid solution is exposed 
 to the air. 
 
 Cupric chloride, CUCI2. — By boiling hydrochloric acid 
 with copper oxide, a green solution is obtained, and, b}^ 
 evaporation, a green salt — cupric chloride. It is soluble 
 in spiiit, and the solution, if ignited, burns with a beauti- 
 ful green flame. 
 
 Cupric nitrate, Cu(N03)2,3Il20. — Beautiful blue de- 
 
COPPER. 
 
 227 
 
 liquescent crystals, prepared, as already described, by 
 dissolving copper in dilute nitric acid. 
 
 Cupric sulphate {Blue vitriol)^ CuS04,5H20. — This im- 
 portant salt is prepared in large quantities by roasting 
 native or artificial sulphide : 
 
 CuS + 2O2 - CuSO,. 
 
 It is also formed by boiling copper with sulphuric acid, 
 sulphurous anhydride being evolved (p. 146). 
 
 Experiment 1. — If half an ounce of copper sulphate is 
 heated to boiling with an ounce and a half of water in a 
 porcelain basin, and then boiled a few minutes with some 
 granulated zinc, metallic copper separates as a powder, 
 and zinc sulphate is formed. The powder obtained is 
 washed, and then boiled with water and a few drops of 
 sulphuric acid, in order to remove all the zinc. It must 
 be dried quickly, but not at a high heaf, for copper in 
 this state of minute subdivision attracts oxygen with 
 more avidity than when it is in a compact mass. 
 
 Experiment 2. — Push an iron rod into a good-sized, 
 large-mouthed phial, forcibly enough to break 
 out the bottom, file off the sharp edges of the 
 fractured part, and bind some moistened bladder 
 over the mouth of the phial. Then twist a wire 
 firmly round the phial, in such a manner as to 
 form two or three supports, by means of which 
 it may be suspended in a tumbler. 
 
 Let a strip of strong sheet zinc, of the width 
 of the finger, and five inches long, be soldered to a strip 
 of thin copper plate, ten inches long, and bend 
 the strip of copper as represented in the annexed 
 figure. Put a coin upon the lower horizontal 
 part of a copper strip, — for instance, a bright 
 half-crown, — or some other metallic object, the 
 impression of which you wish to take. Now fill 
 the phial three-quarters full with very diluted 
 sulphuric acid (one drachm of sulphuric acid 
 to two ounces of water), introduce the zinc, and 
 suspend the apparatus in a tumbler, in wdiich a saturaled 
 solution of copper sulphate, and also a few whole crystals 
 of copper sulphate, have been put. In the course of a few 
 
 Q 
 
228 
 
 EXPERIMENTAL CHEMISTRY. 
 
 minutes tlie coin will be covered with a thin film of metallic 
 copper, and after some time, with a layer several lines in 
 thickness, which may be removed as a coherent mass. 
 
 Tallow or wax must be smeared over those 
 parts of the coin and plate on which the 
 copper is not to be deposited. The sunk im- 
 pression thns obtained may be used in the 
 same way again, iritead of the coin, as a 
 mouldy for obtaining a raised impression. 
 When the evolution of the gas in the 
 phial has ceased, a few drops of strong 
 sulphuric acid may be stirred in, or the 
 liquid, which contains zinc sulphate in 
 solution, may be replaced by a fresh supply of diluted 
 sulphuric acid. Salt water may also be used instead of 
 sulphuric acid, but then the separation of the copper 
 takes place more slowly. 
 
 The decomposition of salt has, in this case, been effected 
 by the voltaic current, which is always generated when 
 different kinds of metals, in contact, are introduced into 
 liquids capable of being decomposed. The bladder is a 
 porous subtance, which allows the voltaic current to 
 pass, but prevents the liquids from mixing. 
 
 This experiment is a modification of Experiment 6, 
 page 12. It affords an illustration of the art of electro- 
 typing. Solutions of gold, silver, &c., may be decomposed 
 in the same manner (e/ec/ro-plating and gilding). 
 
 MERCUEY. 
 Hg = 200. 
 
 This metal exists at ordinary temperatures as a liquid. 
 From it s appearance it is commonly called quicksilver, and 
 in pharmacy hydragyrum. It often occurs native ; but the 
 chief supply is obtained from the native sulphide 
 (cinnabar). The most celebrated mine is that of 
 Almaden in Spain. From cinnabar it is easily obtained 
 by heating the ore in a free current of air ; the sulphur 
 burns to sulphurous anhydride and escapes, while the 
 mercury volatilizes and can readily be condensed. In 
 the northern regions of the earth mercury becomes solid 
 
MERCURY. 
 
 229 
 
 in winter, at a temperature of— 38"^ F. ( — 39° C.) ; but in 
 our climate it can only be solidified by artificial frigorific 
 mixtures. Mercury boils at 357'' C. (675'' F.), and yields 
 a colourless vapour, the specific gravity of which is 100. 
 Hence it is easy to purify the metal by distillation. 
 
 Experiment 1. — Fasten to the cork of a phial containing 
 mercury a piece of wood, affixing to the bottom of the 
 latter some genuine gold-leaf; the gold, after some days, 
 will have assumed a white colour, and be converted into 
 an alloy of gold and mercury. It is obvious from this, 
 that fumes of mercury must be contained in the air of the 
 phial, and that mercury, like water, evaporates sloidy even at 
 ordinary temperatures. The vapour of mercury, and the 
 preparations of mercury, are very injurious ; they first 
 produce involuntary salivation, and afterwards lingering, 
 dangerous maladies ; therefore, in experimenting with 
 mercury, not only the inhalation of the fumes should be 
 avoided, but it must be weighed and decantered over a 
 bowl, so that, if any portion of it should happen to be 
 spilt, it may not fall upon the floor. As, in comparison 
 with water, mercury boils at a very high, and freezes at a 
 very low temperature, and as it has a great specific 
 gravity (13*6), it is excellently adapted to the construc- 
 tion of thermometers, barometers, areometers, &c. 
 
 Mercury, if quite pure, retains its metallic lustre in the 
 air and water, and it is therefore ranked among the noble 
 metals; but if it is mixed or adulterated with other 
 metals, as lead, tin, or zinc, a grey film will gradually 
 form upon its surface. 
 
 When mercury is long heated in contact with air, at a 
 temperature near its boiling point, it absorbs oxygen, and 
 is converted into the scarlet mercuric oxide, HgO, from 
 which oxygen gas was first prepared by Priestley. 
 Mercury is not acted on by hydrochloric acid, nor by cold 
 sulphuric acid. "When it is boiled with strong sulphuric 
 acid, mercuric sulphate, HgS04, is formed, and sulphurous 
 anhydride expelled. Nitric acid, even when cold, 
 dissolves it easily. Heated in chlorine it takes fire, and 
 mercuric chloride, HgCl2, is formed. 
 
 Mercury, like copper, forms two series of com- 
 pounds, the mercurous and mercuric. In the former two 
 
230 
 
 EXPERIMENTAL CHEMISTRY. 
 
 diad atoms of the metal play the part of a single diad 
 atom, as the following comparison of a few important 
 compounds will show. 
 
 OXIDES. 
 
 MercuTous Oxide — Mercury Suboxide — Hg20. 
 
 Experiment 1. — Dissolve a globule of mercury in a slight 
 excess of cold rather dilute nitric acid. Mercurous nitrate 
 is formed, and nitric oxide set free. To the solution add 
 caustic potash. A black precipitate of mercurous oxide is 
 formed. It is very unstable. 
 
 Mercuric oxide, — Mercury peroxide, — HgO. — Dissolve a 
 globule of mercury in excess of boiling nitric acid. Mer- 
 curic nitrate is thus obtained. On adding potash solution 
 a yellow precipitate will be produced : it is mercuric oxide. 
 Wash and dry it. This substance may also be obtained 
 by heating solid mercuric nitrate, and by the direct union 
 of its constituents with the aid of heat. 
 
 Mercurous nitrate^ or mercury sub-nitrate, IIg2(N03)2. — 
 This salt, it has already been stated, is formed \yj acting 
 on mercury with cold dilute nitric acid. It may be 
 obtained crystallized by pouring half an ounce of nitric 
 acid and a little water on an ounce of mercury in a 
 porcelain basin. In a few days the mercury will be 
 covered with white crystals of the salt in question. They 
 may be preserved and dissolved in water, with the aid of a 
 drop of nitric acid as required. 
 
 Experiment 1. — If a drop of the solution of mercurous 
 nitrate be rubbed upon a copper coin, the mercury separates 
 as metal, and effects a false silvering of the copper. 
 
 Experiment 2. — Make a stroke across a thin brass plate 
 with a wooden stick that has been dipped in the solution 
 of mercury ; if sometime afterwards the plate is bent at 
 this place it will break, as though it had been cut ; 
 because the reduced mercury penetrates the brass with 
 great quickness, and renders it brittle. Tims the brazier 
 can make use of this solution instead of shears. 
 
 Mercurous. 
 
 Mercuric. 
 
 Chloride 
 Oxide . 
 Nitrate . 
 
 (Hg,) (NO3V 
 
 HgCl^. 
 
 HgO. 
 
 Hg(N03),. 
 
CHLORIDES. 
 
 231 
 
 Mercuric nitrate, Hg(N03)2. — Formed in the manner 
 already described : when heated, red fumes escape, and 
 mercuric oxide is formed. 
 
 CHLORIDES. 
 
 Mercurous Chloride, or Mercury Subchloride (^Calomel), 
 
 Experiment 1. — Add some hydrochloric acid, or a 
 solution of common salt, to a diluted solution of mer- 
 curous nitrate ; a heavy white precipitate of mercurous 
 chloride is produced, which is insoluble in water. When 
 well washed and dried, this salt of mercury forms the 
 highly important medicine known as calomel (precipitated). 
 If some of it is moistened with an alkaline hydrate 
 it becomes black, from the formation of mercurous oxide ; 
 thus is explained the Greek name calomel (KaXo?, beauti- 
 ful, /xeXa^r, black). Calomel is now almost exclusively 
 obtained by a process which will be described presently. 
 
 Mercuric Chloride (^Corrosive Sublimate), HgCl2. 
 
 Experiment 1. — Heat some mercuric oxide with hydro- 
 chloric acid, and continue adding the latter till a complete 
 solution is obtained ; the white prismatic crystals which 
 separate on cooling are mercuric chloride, or mercury bi- 
 or perchloride— one of the most violent poisons. The same 
 compound is obtained on a large scale, in white, trans- 
 parent, heavy masses, by the following process : 
 
 Experiment 2. — Grind sixt}^ grains of mercuric sulphate 
 in a mortar, with an equal quantity of common salt. Heat 
 half the mixture thus obtained in a test-tube. A white 
 crystalline crust will condense on the upper and cooler 
 part of the tube, and may be removed and dissolved in 
 boiling water. It consists of mercuric chloride : 
 
 HgSO^ + 2 NaCl = Na^SO^ -f HgGl2. 
 Experiment 3. — Add twenty grains of mercury to the 
 other half of the mixture, and grind them together until 
 the mercury loses its fluidity and becomes incorporated 
 with the other materials to a grey powder. Heat this 
 mixture in a tube as before. A similar white crust is 
 
232 
 
 EXPERIMENTAL CHEMISTRY. 
 
 produced ; but it cannot be dissolved. It is mercurous 
 chloride, or calomel : 
 
 2NaCl+HgS04 + Hg = 2Na2S04+Hg2Cl2. 
 
 The same result would be produced by heating the 
 proper proportion of mercury directly with mercuric 
 chloride instead of the materials for preparing it. 
 
 Experiment 4. — Add ammonia to a solution of mercuric 
 chloride ; a white and not a yellow precipitate is formed. 
 
 This is called white precipitate or mercuric amido- 
 chloride. It contains the monad radical NH2, derived 
 from ammonia. 
 
 HgCl2 + 2NH3 = HgClNH2 + NH4CI. 
 
 Mercuric iodide, Hgl2. — This deadly poison is chiefly 
 interesting from its brilliant red colour, and the change 
 which the latter undergoes under the influence of heat. 
 It is very volatile, and its vapour is remarkable as being 
 more than fifteen times heavier than air (Sp. Gr. 227, 
 H = 1). It may be prepared by the direct union of its 
 constituents. 
 
 Experiment 1.- — Triturate a few grains of iodine in a 
 mortar with a small globule of mercury and a drop of 
 alcohol. The formation of the iodide will become apparent 
 by its red colour. 
 
 Experiment 2. — By far the best method of forming this 
 body is by the addition of an iodide to a soluble mercuric 
 salt. Add potassium iodide slowly to mercuric chloride. 
 Each drop of the iodide as it falls and mixes with the 
 other solution presents the most beautiful appearance. 
 Festoons of a canary-yellow precipitate are formed, and 
 soon change their colour to a brilliant red. The colour 
 disappears on stirring if the mercuric chloride be in excess, 
 but is reproduced by the addition of more iodide. The 
 red precipitate is also soluble in excess of potassium iodide. 
 
 Experiment 3. — Collect some of the red precipitate, wash 
 and dry it. Smear a little on a sheet of white paper, and 
 warm the latter over a lamp. The red colour will be 
 changed to yellow. Kub the changed colour with a hard 
 body as a stirring-rod ; wherever the rod touches the red 
 colour will reappear. The original colour also returns 
 spontaneously in a few days. The difference in colour is 
 
AMALGAMS. 
 
 233 
 
 not owing to altered composition, but to a change in mole- 
 cular arrangement. 
 
 Mercuric sulphate, HgS04. — This salt is obtained by 
 boiling mercury with sulphuric acid in a Florence flask 
 until a white mass is left. It is chiefly used for prepar- 
 ing calomel and corrosive sublimate. It is decomposed 
 by water. 
 
 Mercuric Sulphide, HgS. 
 
 Experiment, — If a solution of mercuric chloride be 
 agitated with a little sulphuretted hydrogen water, or 
 ammonium sulphide, a white precipitate is formed, which, 
 on adding more of the precipitated body, becomes yellow, 
 brown, and finally black ; the black substance is mercuric 
 sulphide. This compound is also obtained by mixing 
 mercury with melted sulphur, or indeed by rubbing it for 
 a day with flowers of sulphur (Ethiops mineral). If this 
 black sulphide is sublimed in a glass tube, then a blackish- 
 red crystalline mass is obtained, the colour of which, by 
 friction, passes into the most magnificent scarlet red. 
 The sulphide in this state is called vermilion, or cinnabar. 
 The red and the black sulphide have precisely the same 
 composition, and yet a very great difierence in appearance. 
 Vermilion is also frequently prepared in factories in the 
 moist way, by triturating together for a day mercury, 
 sulphur, and a solution of potassa. When vermilion is 
 pure, it volatilises completely on a glowing coal, emitting, 
 at the same time, a blue sulphurous flame ; but if 
 adulterated with red lead, beads of metallic lead remain 
 behind. On account of its insolubility, it is less pre- 
 judicial to health than many of the other compounds of 
 mercury. 
 
 Cinnabar also occurs in nature, and we have it in the 
 most important ore, from which we obtain mercury on a 
 large scale. Small globules of pure mercury are also found 
 in many porous stones. 
 
 AMALGAMS. 
 
 Experiment, — Introduce a globule of mercury into a 
 porcelain dish, put upon it a piece of lead, and let them 
 remain for some time in contact ; both metals will in- 
 
234 
 
 EXPERIMENTAL CHEMISTRY. 
 
 timately combine together. If the proportion of mercury 
 is small, a friable mass is produced ; bnt by increasing the 
 quantity, a paste, and, if still more is added, a liquid 
 solution, is obtained. Mercury will combine in a similar 
 manner with many other metals, forming what are called 
 amalgams. The amalgam of tin is especially important 
 for silvering glass. 
 
 LEAD. 
 Pb = 207. 
 
 Lead does not occur free in nature, but chiefly as 
 sulphide, PbS, called by mineralogists galena. In smelting 
 galena, the ore is first roasted in a current of air. During 
 the process part of the sulphide combines with oxygen, 
 and there are formed lead oxide and sulphurous anhydride, 
 whicii last escapes as gas. The air being then excluded 
 and the heat raised, the sulphide which remains reacting 
 with the oxide, forms sulphurous anhydride and metallic 
 lead : 
 
 2PbO + PbS=:S02 + 3Pb. 
 
 Galena generally contains silver in varying quantities. 
 The silver is economically extracted by the process already 
 described (page 213). 
 
 The physical properties of lead, its blue lustre, its easy 
 fusibility, softness and pliability, its high specific gravity 
 (11-4), &c., are well known. It contracts during solidi- 
 fication, and it is therefore impossible to obtain sharp casts 
 with it. 
 
 Lead-shot, — Lead may be granulated, like zinc, by being 
 melted and poured into water. In the manufacture of 
 sliot^ the drops of lead are let fall from such a height that 
 they solidify before reaching the water. For making the 
 largest-sized shot, a tower of at least 150 feet high is 
 required. A small quantity of arsenic is usually added to 
 the lead, to render the drops perfectly globular. As lead 
 and arsenic are both poisonous, shot should be used with 
 caution in washing out bottles. 
 
 Lead is not changed by exposure to air which is perfectly 
 free from vmtcr, or water perfectly free from dissolved air. 
 But in ordinary air it tarnishes rapidly, and in ordinary 
 
LEAD. 
 
 235 
 
 water its surface is soon converted into lead hydrate, 
 Pb(0H)2, which dissolves in the water, and commnnicateB 
 to it poisonous properties. This corrosion is, however, 
 almost immediately arrested in many cases by the action 
 of the carbonates and sulphates so often found in drinking 
 water. Carbonates convert the soluble lead hydrate into 
 an insoluble double salt (Pb(OH)2,PbC03), and sulphates 
 into an equally insoluble lead sulphate (PbS04), either of 
 which soon covers the metal with a coating which prevents 
 the further action of the water. New lead pipes and 
 cisterns are, therefore, more dangerous than old ones. 
 Neither should in any case be used for water which does 
 not contain notable quantities of carbonates, sulphates (or 
 phosphates, which have a similar effect). Chlorides and 
 nitrates have a contrary effect, and increase the corrosive 
 action of the water. 
 
 Experiment 1. — To detect the presence of minute traces 
 of lead in water, evaporate half a pint of the water to 
 dryness, add a little nitric acid, evaporate again, very 
 gently, till the residue is pasty, add half an ounce of 
 distilled water, warm and filter. Through the cold 
 filtered liquid pass sulphuretted hydrogen gas for some 
 minutes. A very minute trace of lead would in this case 
 yield a brown coloration ; a larger quantity of the metal 
 would cause a black precipitate (PbS). 
 
 Experiment 2. — The action of water on lead may be tried 
 by placing bright slips of lead in two glasses, one filled 
 with rain, the other with hard spring water, and allowing 
 them to remain for some days. The water in each glass 
 may then be carefully filtered and tested in the manner 
 above described. It will generally be found that the 
 spring water does not hold any lead, or only a very small 
 trace, in solution, while the rain water has dissolved a 
 good deal. 
 
 COMPOUNDS. 
 
 Lead oxide, PbO. — Experiment 1. — If lead is heated before 
 the blow-pipe in the outer flame, it melts at 617° F. 
 (325^^ C), and is thereby coated with a grey film ; indeed, 
 it is finally entirely converted into a grey powder. This 
 may be regarded as a mixture of oxide of lead with metallic 
 
236 
 
 EXPERIMENTAL CHEMISTRY. 
 
 lead. By contimied blowing, this grey colour is changed 
 to yellow ; the yellow body is lead oxide (PbO). At a 
 stronger heat the oxide melts, and solidifies on cooling 
 into a red dish -yellow mass, composed of brilliant scales, 
 the well-known litharge. By directing npon it the inner 
 blow-pipe, metallic lead will again be obtained. This 
 easy reducibleness, which is peculiar to almost all salts of 
 lead, together with the incrustation of yellow oxide, deposited 
 upon the charcoal, is a certain test for the presence of lead. 
 
 Litharge has many applications in the arts and trades. 
 Lead-glass (flint-glass), lead-glase, and sugar of lead are 
 prepared from it; the manufacturing chemist likewise 
 prepares from it red lead, white lead, and other lead 
 colours, and lead salts; the apothecary compounds lead 
 plaster, by boiling it with olive-oil; the cabinet-maker 
 makes a varnish that dries rapidly, by boiling it with 
 linseed oil, &c. 
 
 Lead di-oxide, Pb O2. — Experiment 2. — If you heat some 
 red lead gently in nitric acid for a few minutes, it is con- 
 verted partly into nitrate, which dissolves, and partly into 
 di-oxide, which remains undissolved as a dark-brown 
 powder. 
 
 Bed oxide of lead, — Experiment 3. — Heat in a ladle one 
 drachm of litharge and a quarter of a drachm of potassium 
 chlorate ; the yellowish mixture smoulders to a red powder, 
 which must be well washed with water. The same thing 
 happens on heating the litharge for a day, a little below 
 melting point ; and at the same time frequently stirring 
 it. By both methods the litharge receives one-third more 
 of oxygen ; in the former case from the chlorate, in the 
 second case from the air ; and is thereby converted into 
 ^^^3^4 ; this compound is called 7'ed lead, or minium, and is 
 much used as a scarlet pigment. 
 
 It may be regarded as a compound of 2PbO, and PbO.^. 
 
 Lead hydrate, Pb(0H)2. — This substance is obtained as 
 a white precipitate when potassium or sodium hydrate is 
 added to a soluble lead salt, as the nitrate. It is soluble 
 in excess of the alkali, and in most acids. 
 
 Lead nitrate, Vh(^N0-^).2' — The best solvent of lead is warm 
 nitric acid, diluted with w^ater ; the product is lead nitrate. 
 It may be obtained in crystals, by evaporating and cooling 
 
LEAD. 
 
 237 
 
 the solution. Litharge may be used instead of metallic 
 lead. 
 
 When dry lead nitrate is heated in a test tube, nitric 
 peroxide, NO2, escapes and PbO remains. 
 
 Lead cliloride, PbCl2. — JExperiment 4. — Heat to boiling a 
 little litharge, with hydrochloric acid and water, and 
 decant the clear liquid from the sediment into a glass 
 vessel ; you obtain, on cooling, lustrous white acicular 
 crystals of lead chloride (horn-lead). This salt is but very 
 sparingly soluble in water. 
 
 Experiment 5. — If two grains of litharge and fifteen 
 grains of sal ammoniac are fused together in an iron spoon, 
 there is obtained a combination of a small quantity of lead 
 chloride, with a large proportion of lead oxide, in the 
 form of a brilliant, yellow, laminated mass, which when 
 triturated yields a beautiful yellow powder. This powder is 
 used by painters under the name of Cassel or mineral yellow. 
 
 Lead acetate, Pb (0211302)2 3H2O, which contains one- 
 seventh of its weight of water of crystallization, -p.^ 
 forms, the most important soluble salt of lead, 
 sugar of lead, which commonly crystallizes in 
 four-sided prisms. 
 
 Basic lead acetate is prepared by digesting a 
 solution of sugar of lead with oxide of lead, 
 whereby part of the oxide of lead is dissolved. 
 This combination is kept in the apothecaries' 
 shops in a liquid form, under the name of 
 solution of suhacetate of lead, or Goulard's extract. When 
 mixed with water it forms the so-called Goulard ivater, 
 which has often a milky appearance, because some lead 
 carbonate is formed and separated by the carbonic acid of 
 the water or air. 
 
 Lead sulphate, PbSO^. — This salt is easily formed when 
 dilute sulphuric acid or a soluble sulphate is added to a 
 solution of lead. Even in a solution of lead more than a 
 thousand times diluted, a white turbidity is produced, 
 since the lead sulphate is a very insoluble salt ; we have, 
 accordingly, in sulphuric acid, a very delicate test for salts 
 of lead. 
 
 Lead carbonate, PbOOg. — Experiment 6. — Add to a solu- 
 tion of sugar of lead a solution of sodium carbonate as 
 
238 
 
 EXPERIMENTAL CHEMISTRY. 
 
 long as a precipitate is formed ; the precipitate is lead 
 carbonate. The pigment known under the name of ichite 
 lead is likewise carbonate of lead, but mixed with variable 
 quantities of lead hydrate. This is prepared on a large 
 scale in different ways. By the oldest, the Dutch method, 
 a large number of jars, in which some acetic acid has been 
 poured, are arranged in a building upon a layer of spent 
 tan, and rolls of sheet-lead are then suspended in the jars 
 above the acid, and the whole covered with another layer 
 of tan. After the lapse of several months the rolls of lead are 
 found'to be mostly, if not entirely, converted into white lead. 
 
 Lead carbonate is extensively used as a white paint, and 
 for this purpose it is very valuable, but from its poisonous 
 nature is often productive of serious disease to those who 
 work with it. Many less dangerous substitutes have con- 
 sequently been proposed, but none have been found to 
 equal it in opacity, or " body." 
 
 Powdered barium sulphate (heavy spar) is commonly 
 used to adulterate inferior kinds. This impurity may be 
 detected by dissolving the white lead in dilute nitric acid, 
 when the barium sulphate, being quite insoluble, remains 
 behind. 
 
 On heating white lead, carbonate anhydride is evolved 
 and lead oxide remains. 
 
 Lead Tree. — Experiment 7. — Dissolve half an ounce of 
 Fig 83. acetate of lead in six ounces of water, filter the 
 liquid, pour it into a phial, and then suspend in 
 the latter a zinc rod, by attaching it to a cork ; 
 the zinc is soon covered with a grey coating, 
 from which brilliant metallic spangles will 
 gradually shoot forth, finally filling up the 
 interior of the phial. They consist of pure lead 
 (the lead-tree). After twenty-four hours, no trace 
 of lead can be found in the solution ; it has 
 been replaced by zinc ; the stronger zinc has forced the 
 weaker lead from its combination. 
 
 This experiment might be made to illustrate not only 
 the relative combining powers of the two metals, but also 
 their ecjuivalents. It would only be nect ssary to weigh 
 the lead foinied, and the zinc beiore and afier the experi- 
 ment, to acertain tl at the weight of the precipitated lead 
 
LEAD. 
 
 239 
 
 is to the loss of zinc as 207 is to 65. An atom of lead is 
 therefore replaced by an atom of zinc. A similar experi- 
 ment, in which silver is precipitated by means of copper, 
 forming the silver-tree, was described in page 214. 
 
 Lead tartrate, FIoGJI^^Oq. — Experiment 8. — Make a strong 
 solution of lead acetate, and add fo it a solution of tartaric 
 acid. The white precipitate of lead tartrate formed is 
 collected on a- filter, washed well with water and dried. 
 It is interesting from the fact, that on being heated 
 strongly in a close vessel it is decomposed, and furnishes 
 a mixture of finely divided metallic lead and carbon which, 
 on exposure to air, spontaneously ignites. Such a substance 
 is termed a pyrophorus. Lead pyrophorus is prepared as 
 follows : Select a glass tube, as thick as a lead pencil, and 
 seal one end with the blow-pipe. Introduce sufficient dry 
 lead tartrate to fill it for about an inch and a half; then at 
 three inches from the closed end soften a part of the tube 
 in the blow-pipe flame, and draw it out so as to constrict 
 the tube to a narrow channel. When the tube is cold, hold 
 it horizontally and shake the tartrate, so that it occupies 
 the whole space to the constriction, and leaves a clear 
 channel above the substance. The tube must then be 
 heated, gradually and progressively, from the sealed end to 
 the constriction, with a lamp. As soon as the tartrate is 
 heated it begins to decompose and blacken, coloured drops 
 of moisture are formed and driven along the tube, and a 
 thick smoke is evolved which smells like burning sugar. 
 When the evolution of fumes ceases, the heating is dis- 
 continued and the tube allowed to cool ; the black sub- 
 stance obtained is the pyrophorus, and when shaken out 
 into the air it takes fire, and burns with a great glow and 
 much yellow smoke. By applying the blow-pipe flame, 
 the tube may be sealed at the constriction, and the 
 contents will then retain their pyrophoric powers for an 
 indefinite time. The yellow powder produced by the 
 ignition is lead oxide. 
 
 Lead sulphide, PbS. — This is a black powder, obtained 
 whenever a lead salt is precipitated with sulphuretted 
 hydrogen. It occurs native as galena, and is easily recog- 
 nised by its greyish-black colour, its shining metallic lustre, 
 and its high specific gravity. 
 
240 
 
 EXPERIMENTAL CHEMISTRY. 
 
 CHAPTEE III. 
 
 METALLIC DIADS, OR TETRADS. 
 
 Group i. — Iron, Chromium, Manganese, Aluminium, 
 Cobalt, Nickel. 
 
 The first three metals of this group yield two well- 
 defined series of compounds, analogous to those of copper 
 and mercury. In one series the metal is a simple diad. 
 Such compounds are sometimes called proto-com^ounds, but 
 are more frequently designated by the termination ous. 
 Ferrous chloride, or iron protochloride, Fe"Cl2, is an 
 example. In the other series two atoms of the metal are 
 generally supposed to play together the part of a single 
 Jiexad atom, e,g, (Fe2)'''. This is perfectly consistent with 
 the tetra valency of the metal, as will be fully explained 
 in the introduction to organic chemistry (Part III., 
 Chap. I.). Compounds of this kind have the termination 
 ^c, but are also known as per, or sesqui compounds. 
 Ferric chloride (iron perchloride, or iron sesquichloride), 
 (Fe2)'''Cl6, illustrates their composition. They may, 
 however, be regarded as compounds in which the metal is 
 a triad. Ferric chloride, then becomes Fe"'Cl3, and ferric 
 hydrate Fe"'(0H)3. The following table of a few 
 important iron compounds will explain the constitution of 
 the two series more clearly than words : 
 
 Ferrous. Ferric. 
 
 FeCl2 Fe2Cl6 Chloride. 
 
 FeO Fe203 Oxide. 
 
 Fe(0H)2 Fe2(6H)6 Hydrate. 
 
 Fe(N03)2 Fe2(N03)6 Nitrate. 
 
 FeSO^ ^62(804)3 Sulphate. 
 
 Besides these compounds, in which the metal is basic, 
 several of the metals of this group (notably chromium 
 
IRON. 
 
 241 
 
 and manganese) yield interesting and important acid 
 radicals. With the exception of aluminium, neutral 
 oxides of all of them are known. No aluminious and no 
 nichelic compounds (except nickelic oxide^ ^1303) are 
 known. 
 
 IRON. 
 
 Fe = 56. 
 
 This most important metal is rarely found native. The 
 meteorites which sometimes fall from the sky often contain 
 more than 90 per cent, of iron, together with nickel, 
 cobalt, and other elements. The following are the most 
 important ores of iron : 
 
 Fe304, Magnetite^ Loadstone, — Found in Norway, 
 Sweden, the United States, &c. The most valuable ore 
 of iron. 
 
 Fe203, Med hsematite. — Found in England and elsewhere. 
 The same oxide occurs in combination with water, as 
 brown Jisematite, 2Fe2033H20. 
 
 FeCOg (Ferrous carbonate). — Nearly pure as spathic ore, 
 found in Styria, &c. Clay-iron ore, the great English ore, 
 is ferrous carbonate, with clay and other impurities. It 
 occurs in Staffordshire, &c., in grey nodules. Black 
 hand, the chief Scotch ore, is clay-iron, with bituminous 
 matter. 
 
 FeS2, Iron pyrites. — Very abundant. It yields bad iron, 
 but is valuable as a source of sulphur. It is often used as 
 a substitute for sulphur in making sulphuric acid. 
 
 METALLURGY OF IRON. — CAST IRON — SMELTING. 
 
 The methods adopted for the separation of iron from its 
 ores vary a good deal, according to the nature of the ores. 
 The most important is that used in England for clay iron. 
 
 1. The ore is roasted at a dull red heat. This is effected 
 by piling it in heaps, with alternate layers of coal, and 
 burning the coal with free access of air. The ferrous 
 carbonate loses CO2, just as chalk does in a lime kiln, and 
 at the same time takes up oxygen : 
 
 2FeC02 + 0 = Fe203 + CO2. 
 The water of the ores is expelled at the same time. 
 
 2. The smelting is effected in a blast furnace (Fig. 84), 
 
 R 
 
242 
 
 EXPERIMENTAL CHEMISTRY. 
 
 whicli is from 50 to 90 feet in heiglit. The furnace is 
 charged with alternate layers of coal, roasted ore, and 
 limestone (CaCOs), fresh charges of each are added 
 every few hours, as the mass sinks in the furnace. In 
 this way tbe action of the furnace is rendered continuous, 
 and it can be worked for years without cessation. As the 
 ore sinks down, the ferric oxide is reduced to metallic 
 iron, which, in the lower and hotter part of the furnace, 
 is melted. Melted iron accumulates on the hearth of the 
 furnace, and is drawn off from time to time into rough 
 
 Fig. 84. 
 
 Mouth. 
 
 Shaft. 
 
 Bosnes. 
 
 Hearth. 
 
 Reducing. 
 
 Meltinar. 
 
 moulds printed in sand. When the iron is cold it is 
 broken up into bars, which are called pigs. The combus- 
 tion of the fuel is maintained by air forced in through 
 conical apertures, called tuyeres, just above the hearth. 
 To avoid waste of heat this air is now generally heated to 
 from 350^ to 700^ C. (662° to 1292° F.), by the waste gases 
 from the upper part of the furnace before it is blown in. 
 (Hot blast.) 
 
 Chemistry of the blast-furnace, — The accompanying wood- 
 cut represents one form of the blast-furnace, and the 
 
IRON. 
 
 243 
 
 teclinical names of the different parts of it. In the lower 
 part of the furnace, where the air comes in contact with 
 the fuel, the heat is most intense. Combining with the 
 oxygen of the air, the carbon of the fuel is here converted 
 to carbonic anhydride, which passes upward through the 
 hot mass above. But we have already seen (p. 182) that 
 when carbonic anhydride passes over red-hot carbon it is 
 reduced to carbonic oxide: C02 + C = 2CO. The latter 
 gas is, therefore, formed in large quantity. In the upper 
 and cooler part of the furnace this carbonic oxide comes 
 in contact with the heated ferric oxide, and at once 
 reduces it to a porous mass of metallic iron : 
 
 FeA + SCO = 2Fe + 3CO2. 
 
 As this porous iron descends into the intensely hot portion 
 of the furnace (the boshes), in which the temperature rises 
 to 1400° C. (2552° F.), it combines with carbon, and 
 melts, and the liquid compound accumulates on the 
 hearth, whence from time to time it is drawn off into the 
 moulds. (Cast iron.) 
 
 The use of the lime in this operation is very interesting. 
 It combines with the silica and the other foreign matters 
 of the ore and fuel, forming with them a kind of rough 
 glass (the slag), which melts at a lower temperature than 
 iron. The melted metal is always covered with a layer 
 of this liquid slag, which is constantly flowing off through 
 apertures arranged for the purpose. 
 
 The slag from the blast-furnaces has generally a green 
 or blue colour, owing to the oxides of iron and of man- 
 ganese dissolved in it. It is sometimes formed into square 
 blocks, and used for building stones. 
 
 Cast or Crude Iron. — The metal obtained by the above 
 process is by no means pure iron, but contains 5 or 6 per 
 cent, of carbon and other impurities, of which silicon, 
 snlphur and phosphorus are the most important. Cast- 
 iron, thus obtained, is characterised by the following 
 properties : 
 
 a.) It is fusible at a much lower temperature than pare 
 iron; therefore it is especially adapted for those iron 
 articles which are made by casting. For remelting iron 
 on a small scale, crucibles are made use of ; but on a 
 
 R 2 
 
244 
 
 EXPERIMENTAL CHEMISTRY. 
 
 large scale shaft-furnaces, or the so-called cupola-fur 
 naces. 
 
 h.) Cast-iron is brittle, and can neither he forged nor 
 welded (bar-iron and steel may be bent, forged, and 
 welded). The application of cast-iron nmst, therefore, be 
 limited to the manufacture of such articles as are not 
 exposed to being bent, or to strong concussions. 
 
 There are two kinds of cast-iron in commerce, known 
 as grey and white iron. The grey iron is almost black, 
 has a granular texture, and admits of being filed, bored, 
 &c. ; the white iron, on the contrary, is of a silvery white- 
 ness, possesses a lamellar-crystalline texture, and is 
 exceedingly hard. Crude white iron, by remelting and 
 very slow cooling, is changed to grey ; on the other hand, 
 the grey is changed to white iron by being heated and 
 suddenly cooled. Grey iron is best adapted lor castings ; 
 white iron is the most suitable for the manufacture of 
 bar iron and steel. When grey iron is dissolved in dilute 
 acids a mass of graphitic carbon remains, whereas in 
 white iron almost all the carbon is in a state of combina- 
 tion. Mottled iron is intermediate between white and grey. 
 
 Malleable, Wrought, or Bar Iron. — Cast-iron, by being 
 deprived of its carbon, is converted into malleable iron, and 
 acquires the lollowing very important properties : 
 
 a.) Bar-iron possesses great ductility and tenacity, and 
 may be hammered or rolled into sheets, and drawn out 
 into fine wire, which is not the case with cast-iron. 
 
 fc.) At a less degree of heat than that of fusion it 
 becomes soft, like wax or glass, so that two glowing pieces 
 may be welded into one. Upon this property depends its 
 capacity of being welded. 
 
 c. ) Wrought-iron is sufficiently soft to be worked by 
 steel instruments, and it does not become harder if, when 
 heated to redness, it is suddenly quenched in water (steel 
 is thereby rendered brittle). 
 
 d. ) Wrought-iron is distinguished, moreover, from cast- 
 iron by its fibrous texture, composed, as it were, of threads 
 incorporated together ; while cast-iron has the appearance 
 of being a baked granular muss. But it is a very striking 
 fact that fibrous wrought-iron, by repeated jolts or blows, 
 becomes gradually granular and brittle, as, for example, 
 
IRON. 
 
 245 
 
 in the axletrees of carriages. By thoroughly heating and 
 reworking, the former strength and flexibility, as well as 
 the fibrous texture, is restored to the iron. 
 
 Wrought-iron is not entirely free from carbon ; it 
 contains, however, only 0*1 to 0*5 per cent of it. Iron 
 entirely free from carbon is softer and more tenacious 
 than bar-iron. Thus we see that it is the chemical 
 combination of the carbon with the iron, as in cast-iron, 
 which destroys these two properties of softness and 
 tenacity. 
 
 Bejinery of Iron. — The method which is employed for 
 separating carbon from the cast-iron is very simple. The 
 carbon is burnt out by heating the iron to fusion, and 
 constantly stirring it (puddling) while exposed to a 
 current of air (or, as in the famous Bessemer process, by 
 forcing air through the melted metal), the oxygen of 
 which combines with the carbon, forming carbonic oxide 
 gas. During the operation, a considerable portion of the 
 iron is converted by oxidation into oxide, which fuses 
 with the sand, that is purposely strewed upon the hearth, 
 and forms with it a heavy black slag of iron silicate. 
 The iron mass becomes gradually more tenacious, since 
 the iron melts with more difficulty the less carbon it 
 contains ; and finally, in the form of a loosely coherent 
 mass (the hloorri), is placed under a steam hammer, by a 
 few blows of which the remaining slag is pressed out, 
 and the iron particles are formed into a compact mass. 
 The latter is afterwards usually hammered or rolled into 
 bars or bands. This method of converting brittle cast- 
 iron into ductile and malleable iron is called puddling. 
 It is sometimes preceded by a separate process called 
 refining. 
 
 Steel. — Steel holds a middle place between cast and 
 wrought iron, both as to the quantity of carbon it con- 
 tains, and other properties. 
 
 a.) If quenched when heated to redness, it is rendered 
 hard and brittle (like cast-iron) ; if cooled somewhat more 
 slowly, it is rendered elastic ; and if cooled very slowly, 
 it is soft, ductile, and malleable (like bar-iron). 
 
 &.) It is less fusible than cast-iron, and more so than 
 bar-iron. 
 
246 
 
 EXPERIMENTAL CHEMISTRY. 
 
 c.) It contains combined carbon generally less than 
 1 per cent. 
 
 To these properties steel owes its importance as a 
 material for thousands of articles, especially for cutting 
 instruments, since it may be made soft or hard, elastic or 
 brittle, at pleasure. The article manufactured is usually 
 first heated to redness, then suddenly cooled by quenching 
 it in water, and afterwards temjpered^ in order to diminish 
 its hardness and brittleness. 
 
 Experiment. — Hold a steel knitting-needle in the flame 
 of a spirit-lamp till it is red-hot, and then quickly plunge 
 it in cold water ; it thereby becomes so brittle as to break 
 on any attempt to bend it. Again hold the needle in the 
 fire, and observe the changes of colour which it passes 
 through ; it will first become yellow, then orange, 
 crimson, violet, blue, and finally dark-grey. The change 
 of colour is owing to the formation of a film of oxide, 
 which at first is thin, and has a yellow appearance, but 
 gradually it becomes thicker and also darker, as the heat 
 increases. A definite degree of hardness and elasticity 
 of the steel corresponds to each of these tints, the needle 
 when covered with the yellow film being the hardest and 
 most brittle, and when presenting a blue aspect being in 
 its softest and most elastic condition. The workmen in 
 steel impart to their articles various degrees of hardness 
 and elasticity by tempering ; files and razors are made 
 very hard and brittle, — saws, watchsprings, &c., soft and 
 elastic. 
 
 Steel may be prepared in various ways : — 
 
 1. By the process of cementation, which consists in 
 filling an iron box with bar-iron and powdered charcoal, 
 and then maintaining the whole for several days at a red 
 heat. The carbon gradually penetrates into the iron, 
 thus converting it into steel (blistered steel), 
 
 2. In the Bessemer process, by blowing air through 
 melted cast-iron until the impurities are oxidised and 
 then adding a definite quantity of melted white cast-iron 
 (spiegeleiseii). The cast-iron supplies exactly the quantity 
 of carbon necessary for the formation of steel. 
 
 Ii on, nickel, and cobalt, are the only metals which are 
 attracted by the magnet in a sensible degree. Magnetism 
 
COMPOUNDS OF IRON. 
 
 247 
 
 immediately vanishes from bar-iron when it is removed 
 from the magnet ; while steel, on the contrary, retains 
 the magnetic power, but loses it on being heated to 
 redness. 
 
 Absolutely pure iron can only be prepared with 
 difficulty. Its specific gravity is 7*8. When treated 
 with acids, pure hydrogen is evolved, whereas ordinary 
 iron yields impure hydrogen, as is sufficiently proved by 
 its disagreeable smell. 
 
 COMPOUNDS OF IRON. 
 
 Ferrous oxide. — Protoxide of iron, FeO, is prepared with 
 difficulty, so readily does it take up oxygen and pass to a 
 higher oxide. 
 
 Black, or magnetic oxide Ye^O^^, — Experiment 1. — Place a 
 few grains of iron filing 
 upon a piece of charcoal, 
 and heat it for some minutes 
 in the outer flame of the 
 blow-pipe, directed upon one 
 spot; it becomes red-hot, 
 and the heat spreads through- 
 out the whole mass, as is 
 apparent 'from the iridescent 
 tints which precede the red 
 heat. The iron on cooling 
 acquires a darker, almost a 
 black colour, and bakes into a coherent mass of this inter- 
 mediate oxide. It is the same compound as is formed 
 when iron bums in oxygen or air (p. 127). 
 
 Ferric oxide. — Peroxide of iron, re203. — Experiment 2. — 
 Iron cinders (Fe304) when exposed for a long time to the 
 outer or oxidising blow-pipe flame, become covered with 
 a red pulverulent coating; they take yet more oxygen 
 from the air, and become peroxide of iron. 
 
 It may be prepared more easily in the following 
 manner : Place a crystal of green vitriol upon charcoal, 
 and heat it until it has become of a brownish red colour. 
 The salt is decomposed and the peroxide remains. The 
 red colour of the latter is more clearly brought out by 
 rubbing it on paper with the nail. In the same manner, 
 
248 
 
 EXPERIMENTAL CHEMISTRY. 
 
 peroxide of iron remains behind when green vitriol is 
 heated in the preparation of Js' ordhausen sulphuric acid ; 
 this forms an article of commerce under the name of 
 colcotJiar, or rouge, and is a favourite and cheap pigment 
 for varnish, and is also used in the polishing of glass and 
 metals. 
 
 Ferrous hydrate, re(0H)2. — Experiment 3. — Add potas- 
 sium hydrate to a freshly prepared solution of green 
 vitriol (ferrous sulphate). A green precipitate of impure 
 ferrous hydrate will be produced by double decomposition : 
 
 FeCSO^) + 2K0H = K^CSO^) + re(0H)2. 
 
 If it were pure ferrous hydrate the precipitate would be 
 white, but is never obtained so except when oxygen is 
 completely excluded. The green precipitate, on exposure 
 to air, becomes brown by conversion into ferric hydrate. 
 
 Ferric hydrate, Fe2(0H)g. — Ferrous salts, when kept for 
 any length of time in contact with air and water, take 
 up oxygen, and become ferric salts. The former are 
 green, the latter brownish-red. 
 
 Experiment 4. — Make a solution of ferrous sulphate, 
 filter, and set it aside. The solution will gradually 
 become turbid, and a brown precipitate will settle on the 
 sides of the vessel, while in a few days the bright green 
 colour of the solution will give place to a decided brown. 
 The change of colour indicates the conversion of the 
 ferrous into the ferric salts. 
 
 Experiment 5. — To a fresh and dilute solution of ferrous 
 sulphate in a test-tube add a few drops of sulphuric and 
 nitric acids, and heat. The mixture will become of a 
 dark brown, almost black colour, which, as the heat 
 approaches boiling-point, suddenly vanishes and leaves 
 the reddish colour of the per-salt. The conversion of the 
 ferrous into ferric sulphate, which in the former experiment 
 requires an inconvenient length of time, is in this way 
 completed almost instantaneously by the oxygen supplied 
 by the nitric acid : 
 
 6FeS04 + 3H2SO4 + 2H NO3 = SFeaCSO^a + 4H2O + 2N0. 
 
 The dark substance first formed is a compound of ferrous 
 sulphate with nitric oxide, 2FeSO4.NO. 
 
COMPOUNDS OF IRON. 
 
 249 
 
 Experiment 6. — Add ammonia or potasli to the solution 
 of ferric sulphate obtained in the last experiment. 
 Instead of a green, a red precipitate will be obtained, 
 indicating the change which has taken place. The red 
 precipitate is ferric hydrate, Fe2(0H)g. The precipitate 
 may be washed on a filter. Any ferric salt may readily 
 be prepared by dissolving the moist hydrate in the acid. 
 When the hydrate is heated ferric oxide is obtained. 
 
 Ferrous chloride, FeClg, is a green salt obtained in 
 crystals by dissolving iron in hydrochloric acid and 
 evaporating the solution. 
 
 Ferric chloride^ Fe^GlQ. — This is one of the most im- 
 portant of the per-salts of iron. It may be obtained by 
 dissolving ferric hydrate or ferric oxide in hydrochloric 
 acid, or by converting the proto-chloride by boiling with 
 nitric and hydrochloric acids. 
 
 The salt cannot be obtained crystallised, but only as a 
 brown mass by evaporation to dryness. 
 
 Ferrous sulphate. — Green vitriol. — Copperas, FeSO^. — 
 This most important salt may be obtained in a variety of 
 ways. (1) By dissolving iron in sulphuric acid. (2) It 
 remains in solution in the bottle in which sulphuretted 
 hydrogen is generated by the action of sulphuric acid on 
 ferrous sulphide (p. 143). It is manufactured on the 
 large scale by the gradual oxidation of iron pyrites by 
 the action of moist air, and subsequent solution and 
 crystallization. This salt is largely used in dyeing for 
 the production of black colours, and also in the manu- 
 facture of writing-ink. The crystals of ferrous sulphate 
 have the formula FeS04,7H20. 
 
 Ferric sulphate. Fe2(S04)3. — The preparation of this 
 salt, b}^ boiling ferrous sulphate with nitric acid, has 
 already been described. It may also be formed by 
 dissolving ferric oxide, or hydrate, in sulphuric acid. 
 
 Ferric* nitrate, Fe2(N03)g, is obtained by adding iron 
 filings to warm dilute nitric acid as long as they continue 
 to dissolve in it. This solution is of a brown colour, and 
 is used in dyeing. If some nitric acid is dropped upon 
 cast-iron, steel, or bar-iron, black spots are produced, 
 becaiise the iron, but not the carbon, is dissolved. These 
 spots are darker in cast-iron and lighter in bar-iron. 
 
250 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Ferric acetate, Fe2(C2H302)6, inay be prepared directly, 
 by dissolving freshly precipitated and still moist ferric 
 hydrate in acetic acid. When the shoemaker pours beer 
 upon iron nails to prepare the iron-black with which he 
 blackens his leather, he obtains this salt, for, on exposure 
 to the air, the beer is changed into vinegar. 
 
 FeiTous sulphide, FeS. — On adding some sulphuretted 
 hydrogen water to a slightly acidified solution of ferrous 
 sulphate, no precipitate is produced ; but if ammonium 
 sulphide is added to the neutral solution, a deep black 
 precipitate is formed ; this precipitate is ferrous sulphide. 
 
 Ferrous sulphide is largely used by the chemist for 
 the preparation of sulphuretted hydrogen (p. 143). It 
 is best prepared in the following manner : 
 
 Experiment 7. — Heat a clay crucible to redness in a clear 
 fire and throw in, in small portions at a time, a mixture of 
 four parts of iron filings and 2^ parts of flowers of sulphur. 
 The moment the mixture is thrown in, the cover should 
 be placed on the crucible, to prevent, as far as possible 
 the access of air. The black mass so obtained is very 
 like cast-iron. It may be broken from the crucible, when 
 cold, with a chisel. A compound of ferrous and ferric 
 sulphides occurs native, and is called magnetic pyrites, 
 Fe3S4 = FeS,Fe2S3. 
 
 If you moisten ferrous sulphide with water, and let it 
 remain exposed to the air in a warm place, small green 
 crystals will be found disseminated throughout the mass, 
 the sulphur having gradually attracted oxygen from the 
 air. FeS thus becomes FeS04. 
 
 Iron disulphide. — Iron pyrites, TeS^- — Iron combined 
 with twice as much sulphur as in the proto-sulphide, 
 occurs native in many ores, and frequently in common 
 coal, and is called iron pyrites. It has the appearance of 
 brass, and usually occurs in cubic crystals. If heated in 
 a retort, a portion of the sulphur distils over, and is 
 collected, and magnetic pyrites remains behind. Green 
 vitriol is prepared from the residue, by piling it in heaps, 
 and leaving it for several months exposed to the air. The 
 green vitriol thus formed is freed from earthy impurities 
 by lixiviation and evaporation. When iron pyrites is 
 heated in the air, both its elements are oxidized : 
 
CHROMIUM. 
 
 251 
 
 2FeS2 + 110 = re203 + 4SO2. 
 
 The mineral is therefore often used instead of sulphur 
 in the manufacture of sulphuric acid. 
 
 lests for Iron. — The best test for iron is potassium 
 ferro-cyanide (p. 187), which gives, with ferrous salts, a 
 white or pale blue, and with ferric salts, a dark blue 
 precipitate. 
 
 CHROMIUM. 
 Cr = 52. 
 
 Chromium in the pure state is little known ; from the 
 difficulty attending its isolation it can only be obtained in 
 small quantities. It is remarkable for its hardness, and 
 for its infusibility, which even exceeds that of platinum. 
 
 The chief ore of chromium contains chromic oxide and 
 ferrous oxide (FeOjCrgOg), and is called chrome-iron-stone, 
 or chrome-iron-ore. Chromium likewise occurs in a mineral 
 crocoisite, which is a lead salt of chromic acid, PbCr04, 
 and in small quantities in many other minerals, but its 
 distribution is by no means abundant. 
 
 Experiment 1. — Grind a few grains of chrome-iron-ore to 
 fine powder, and mix them with equal quantities of 
 powdered nitre and potassium* carbonate. Place the 
 mixture in a small iron spoon and heat strongly with the 
 blow-pipe or in a fire for several minutes. When the 
 ignited mass is cold, detach it from the spoon and boil 
 with a little water in a test-tube, and filter the solution. 
 It will be of a bright yellow colour from the presence of a 
 salt called potassium chromate, K2Cr04 ; a compound which 
 will be described further on. Add dilute sulphuric acid 
 in minute quantities to the yellow solution. Effervescence 
 will be produced by the unaltered potassium carbonate. 
 The addition of acid is stopped the instant the colour of 
 the liquid changes to orange-red. The acid removes half 
 the potassium, and a new salt, called potassium dichromate, 
 KoCi fl^, is formed. This salt may be obtained by the 
 evaporation of its solution in beautiful prismatic orange- 
 red crystals. Immense quantities of j)otassium dichromate 
 are prepared from chrome-iron-ore by a method very 
 similar to the one just described. From this salt, directly 
 or indirectly, all other chromium compounds are formed. 
 
252 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The constitution of the chromium compounds has 
 already been indicated. The chromous compounds are dif- 
 ficult to prepare, and are of no interest. Of the chro- 
 mic compounds the following are the most important : 
 
 Chromic oxide, CrgOg. — Experiment 2. — Mix a few grains 
 of powdered potassium dichromate with a quarter of its 
 weight of starch, and ignite the mixture in the iron 
 spoon. After the ignition, boil the mass with some 
 w^ater. This will dissolve out the potassium carbonate 
 formed during the reaction, and will leave chromic oxide 
 as a green powder. Wash the powder once or twice, and 
 dry it. This substance is employed as a pigment, and is 
 valued for its permanence. It likewise produces a fine 
 green on glass and porcelain, and is accordingly esteemed 
 as a valuable vitrifiable pigment. It may be prepared in 
 many ways, and of various shades of brilliancy. It is 
 obtained in a beautiful form by strongly heating potassium 
 dichromate alone. 
 
 Chromic hydrate, Gt2(01I)q, — Experiment 3. — Mix some 
 sulphuric acid with a solution of potassium bichromate, 
 heat the mixture and gradually add methylated spirit. 
 The brown colour of the^solution will soon be changed to 
 bright green. The sulphuric acid, as we shall afterwards 
 find, decomposes the bichromate and sets free chromic acid. 
 This is in tuin decomposed by the spirit and reduced to 
 chromic oxide, which is instantly dissolved by the excess 
 of sulphuric acid present to form chromic sulphate. Org 
 (804)3, ^0 which the green colour is due. Add ammonia 
 in excess to the green solution, a bulky green precipitate 
 is produced. It is chromic hydrate : 
 
 Cr,(80,\ + 6NH40H = 3(NH4),S04 + Cr,(OH)e. 
 
 From chromic hydrate any of the per-salts of chromium 
 may be prepared by solution in acids ; thus, with hydro- 
 chloric acid, chromic chloride is obtained, with sulphuric 
 acid chromic sulphate, &c. These salts are green. A 
 corresponding series of violet chromic salts, of similar 
 constitution to the green, is likewise known. 
 
 Chromic anhydride, CrO^. — Experiment 4. — Add powdered 
 potassium dichromate to water until it ceases to dissolve, 
 and filter or pour off the clear saturated solution so 
 
CHROMIUM. 
 
 253 
 
 obtained. Measure four draclims of the solution, and add 
 to it gradually five drachms of strong sulphuric acid, and 
 allow the mixture to stand. When the solution is cold, a 
 mass of red needle-like crystals will be found at the 
 bottom of the vessel. Pour off the solution and scrape 
 out the crystals with a glass rod on a new brick or tile, 
 cover with a tumbler and leave them to drain. These 
 crystals consist of chromic anhydride. Chromic anhydride 
 is a powerful oxidising agent ; its action on combustible 
 bodies may be exemplified by the following experiments : 
 
 Experiment 5. — Einse out a tumbler with strong alcohol, 
 then throw into it a few grains of chromic anhydride ; 
 the alcohol which remains adhering to the tumbler will 
 combine with half the oxygen of the chromic anhydride, 
 with such energy, that it ignites and instantaneously 
 bursts into flame. The respective odours of acetic acid and 
 aldehyde may be detected as the products of the oxidation 
 of the alcohol, while the chromic anhydride is reduced to 
 chromic oxide. 
 
 Experiment 6. — Mix in a small mortar as much chromic 
 anhydride as can be taken up on the point of a knife with 
 about one quarter as much of powdered camphor (without 
 pressing upon it strongly), and then let some drops of 
 alcohol fall from a considerable height into the mortar ; 
 instantaneous ignition and deflagration ensue, almost as 
 if you were burning gunpowder. The residue in the 
 mortar presents, after the decomposition, the appearance 
 of a beautiful green mossy vegetation; it consists of 
 chromic oxide, which at the moment of its formation was 
 scattered by the burning camphor fumes, and was thereby 
 most delicately subdivided. 
 
 Chromic anhydride dissolves in water to form a solution 
 of a strongly acid character, and it is hence assumed to be 
 a solution of chromic acid, H2Cr04. 
 
 Potassium chromate, KoCr04. — Experiment 7. — Add potas- 
 sium carbonate to solution of chromic acid until efferves- 
 cence ceases : potassium chromate is thereby formed, as 
 shown by the change of colour, from brown to yellow, of 
 the solution. By evaporation the salt may be obtained in 
 lemon-yellow crystals. 
 
 Experiment 8. — Add a solution of potassium chromate to 
 
254 
 
 EXPERIMENTAL CHEMISTRY. 
 
 solutions of barium nitrate, lead acetate and silver nitrate, 
 or to any other soluble salts of these metals. With the 
 two former, light yellow precipitates of the chromates of 
 the respective metals, with the latter a dark red one, will 
 be produced. The lead chromate is used as a pigment, 
 under the name of chrome yellow. If chrome yellow is 
 digested with a cold solution of caustic soda, chrome red 
 PbCr04,PbO, is obtained. 
 
 Besides the chromates, a second series of salts, called 
 dichromates, is known. The potassium member of this 
 series we are already familiar with. It is by far the most 
 important of the chromium compounds. The process 
 employed for its preparation has already been given, and 
 during the preceding experiments many of its properties 
 will have been examined. The formula for potassium 
 dichromate is KaCraO^. It may be regarded as a com- 
 pound of potassium chromate with chromic anhydride 
 (K2Cr04,Cr03) and is therefore sometimes called an 
 anhydro-chromate. The rest of the dichromates are of 
 analogous constitution. As a rule, the dichromates are 
 orange-red, while the chromates are light yellow. 
 
 Ammonium dichromate, (NK^)2(jT20^, — Experiment 9. — 
 This compound is interesting from the curious way it is 
 decomposed on being heated. Divide a solution of 
 chromic acid into two equal parts, and cautiously add 
 ammonia to one of them until the brown colour changes 
 to yellow. If now the solution were evaporated, yellow 
 crystals of neutral ammonium chromate would be obtained, 
 but on adding the second part of the chromic acid, and 
 setting aside in a warm place to evaporate, red crystals of 
 ammonium dichromate will be formed. Collect some of 
 the crystals, dry in a fold of filtering paper, and heat 
 them in a dry test-tube or on a piece of tinned-plate. 
 The salt will decompose energetically, pure nitrogen will 
 be evolved, and the crystals will lose their shape and 
 colour, and be converted into an irregular green mass of 
 chromic oxide, bearing some resemblance to a heap of 
 green tea. 
 
 Experiment 10. — Another pretty experiment, founded 
 on the same decomposition, may be made by soaking 
 filtering-paper first in tincture of benzoin, and then in a 
 
MANGANESE. 
 
 255 
 
 strong solution of ammonium dichromate, and drying it. 
 On folding the paper in the shape of a fan, and applying 
 a light to one corner, it gradually smoulders away, and a 
 dark green residue is left, having the appearance of fern 
 leaves. 
 
 Ghloro-chromic anhydride, Cr02Cl2. — Experiment 11. — This 
 interesting compound may be prepared by mixing one 
 ounce of powdered potassium dichromate with an equal 
 amount of common salt, putting the mixture in an 
 earthen crucible, and heating strongly in a fire. The 
 contents will soon melt, and must then be poured on a 
 flat stone or metal surface to solidify. The hard cake so 
 obtained is broken into small pieces, and introduced with 
 three ounces of strong sulphuric acid into a retort of 
 moderate size. On applying heat, brown vapours soon fill 
 the vessel and condense to a dark-red liquid, which may 
 be received in a flask or bottle. This liquid is chloro- 
 ohromic anhydride, which may be regarded as chromic 
 anhydride, GrO^, having one atom of oxygen replaced by 
 two of chlorine. It is not, however, miscible with, or 
 soluble in water, but in contact with that liquid is soon 
 decomposed into chromic acid and hydrochloric acid. Its 
 action on combustible substances resembles that of 
 chromic anhydride, but is more violent. This may be 
 shown by pouring a drop of the liquid on a little alcohol, 
 benzol, or turpentine. In either case, the action which 
 ensues is sufficiently intense to inflame the mixture. A 
 minute fragment of phosphorus thrown on a drop of 
 the liquid produces a violent explosion. By the same 
 substance many other combustible bodies, sulphur, sugar, 
 &c., may be inflamed by mere contact. 
 
 MANGANESE. 
 Mn = 54. 
 
 Like chromium and many other metals, manganese is 
 so difficult to separate from its ores that it has not hither- 
 to been applied to any useful purpose, although some of 
 its compounds are of great importance. Manganese is an 
 exceedingly hard, brittle, reddish-white metal, which 
 rapidly oxidises when exposed to the air, and decomposes 
 water slowly, even at ordinary temperatures. Several 
 
256 
 
 EXPERIMENTAL CHEMISTRY. 
 
 compounds of manganese occur native, chiefly oxides, the 
 principal one being black oxide or manganese peroxide, 
 MnOg, which is found in great abundance as the mineral 
 pyrolusite, from which the metal may be obtained by 
 intense ignition with charcoal. The compounds of 
 manganese are analogous to those of chromium, but, 
 unlike the latter, the manganous compounds are more 
 stable than the manganic. 
 
 Oxides of Manganese. — Several oxides of manganese are 
 known. Manganous oxide, MnO, manganic oxide, MugOa, 
 both unimportant ; a red oxide, M]i304, analogous to the 
 magnetic oxide of iron, which is met with as the mineral 
 hausmannite ; and finally, the most important of all 
 manganese compounds, the peroxide, hinoxide, or black 
 oxide as it is often called MnOg. Many of the properties 
 of this oxide are already familiar to the student. When 
 heated to redness it loses part of its oxygen, and the red 
 oxide remains : 
 
 SMnOs^MnaO^+Os. 
 
 This fact, as well as its use in the preparation of 
 chlorine, iodine, and bromine, has already been treated of 
 in the description of those substances. 
 
 Glass-makers often add manganese binoxide to green 
 bottle glass, which contains iron in the ferrous condition, 
 to change its colour to brown, which it effects by con- 
 verting the iron from the ferrous to the ferric state. 
 When fused with white glass it communicates a violet 
 colour to it. In this way imitation amethysts are made. 
 From manganese binoxide the other compounds of the 
 metal may he obtained, either directly or indirectly. 
 
 Manganous sulphate, MnS04. — Experiment 1. — Mix in a 
 porcelain crucible a quarter of an ounce of manganese 
 peroxide with one-eighth of an ounce of sulphuric acid, 
 and expose the mixture to a gentle heat for fifteen 
 minutes, and then to a strong heat for an hour. After 
 cooling, boil the black mass in water, filter and evaporate 
 the solution to dryness, constantly stirring it when nearly 
 dry; the reddish- white powder is manganous sulphate, 
 generally accompanied with iron derived from the ore. 
 
 The effervescence with which the action of the sulphate 
 
MANGANESE. 
 
 257 
 
 acid is attended is due to the escape of oxygen, which 
 might easily be collected if the experiment were per- 
 formed in a suitable apparatus. This explains why a 
 mixture of sulphuric acid and manganese peroxide is 
 frequently used for oxidising purposes. The action 
 which occurs is thus represented : 
 
 MnO^+H^SO^ = MnSO^+H^O+O. 
 
 Manganous chloride, MnCl2. — JExperiment 2. — Heat strong 
 hydrochloric acid with pure manganese peroxide for half 
 an hour, filter the solution and evaporate to a small bulk. 
 On cooling, pink crystals of manganous chloride will be 
 obtained. 
 
 During the heating efferyescence will occur, owing, in 
 in this case, to the escape of chlorine. In fact, it will be 
 remembered, chlorine is most easily prepared by these 
 very materials, and accordingly manganous chloride is 
 obtained as a bye-product when they are employed : 
 
 4HC1 + Mn02 = MnCl2 + 2H2 0 +CI2. 
 
 Dissolve a portion of manganous sulphate or chloride 
 free from iron in water, and use it for the following 
 experiments : 
 
 Experiment 3. — Add ammonia or potash to a portion of 
 the solution. A white precipitate of manganous hydrate 
 will be thrown down. It rapidly turns brown and 
 becomes manganic hydrate. 
 
 Experiment 4. — Add ammonium sulphide to another 
 portion of the solution. A buff-coloured precipitate of 
 manganous sulphide is produced. 
 
 Manganic and Permanganic Acids, — Two very interesting 
 series of salts are known, the acid radicals of which are 
 derived from oxides of manganese, one of which is known. 
 They are called the manganates and permanganates. The 
 potassium salts are the most important : 
 
 Anhydride. Acid. Potassium Salt. 
 
 Manganic MnOg? H2Mn04? K2 Mn 0^. 
 Permanganic Mn2 07 H Mn O4 KMnO^. 
 
 Potassium manganate, K2Mn04. — Experiment 5. — Mix in- 
 timately in a mortar one drachm of potassium carbonate, 
 one drachm of manganese peroxide, and half a drachm of 
 
258 
 
 EXPERIMENTAL CHEMISTRY. 
 
 potassium nitrate ; put the mixture in a crucible and heat 
 strongly in a fire for half an hour. When cold add a little 
 water to a small portion of the mass, and allow it to stand 
 and settle. A dark-green solution will be obtained of 
 potassium manganate, analogous to potassium chromate, 
 K2Cr04, which is similarly obtained. Potassium manga- 
 nate is known as Chameleon mineral, a name conferred on 
 it on account of the change of colour from green to red 
 that it undergoes on its solution being diluted with water. 
 
 Experiment 6. — Pour a little of the potassium manga- 
 nate solution into a tumbler of water. The dark-green 
 colour of the salt instantly begins to change, passing 
 through various shades of green and violet until it 
 becomes crimson-red. This remarkable change is owing 
 to the conversion of the salt into permanganate and 
 is effected more easily by dilute acids. A hydrate of man- 
 ganese peroxide is formed at the same time : 
 
 SKaMn O4+3H2O = 2KMn 04+4K0H + Mn O2, H2O. 
 
 Potassium permanganate, KMn04, often written K2Mn208. 
 — This salt,l ike the manganate, is remarkable for the 
 facility with which it parts with its oxygen to oxidisable 
 substances. 
 
 Experiment 7. — To some of the potassium permanganate 
 prepared in the previous experiment add a few drops of 
 sulphurous acid. The red solution instantly becomes 
 colourless. The sulphurous acid takes the oxygen from the 
 permanganate, and a colourless manganous salt is formed. 
 
 Perform the same experiment with the green potassium 
 manganate, a like result will ensue. Even a piece of 
 wood, paper, or any other organic substance, thrown into 
 the green or red solutions, decomposes and removes their 
 colour, and for this reason they should not be filtered 
 through paper. 
 
 On account of the ready oxidation of organic matter 
 effected by these salts, they are often used as disinfectants, 
 and they are now prepared in largo quantities and sold as 
 " Condy's fluids," from the name of the manufacturer. 
 They rapidly oxidise and destroy noxious gases or putrefy- 
 ing substances, and indeed, almost any kind of organic 
 matter. 
 
ALUMINIUM. 
 
 259 
 
 Experiment 8. — The tinwholesome gas, hydrogen sulphide, 
 is often evolved from decomposing animal matters. Mix 
 a little of the green or red salt with a solution of hy- 
 drogen sulphide. The bad odour of the gas is instantly 
 destroyed. 
 
 Experiment 9. — Procure some water known to be of bad 
 quality, as from a stagnant ditch, acidulate it with sul- 
 phuric acid, and add some permanganate to it gradually. 
 A large quantity of the salt will be decolourized. Eepeat 
 the experiment with good drinking water ; the colour of 
 permanganate will remain, even though very little be 
 added. In fact, a sort of rough estimation of the amount 
 of impurity present may be made by observing the relative 
 quantities of permanganate which different waters de- 
 colourize. 
 
 ALUMINIUM. 
 Al = 27. 
 
 Aluminium, which derives its name from one of its 
 most important compounds — alum, exists in greater 
 abundance than any other metal. It is only separated 
 from the compounds which contain it with great difficulty, 
 and at one time was only obtainable in the smallest 
 quantities. New processes, however, have materially 
 facilitated its extraction, and it is now applied to many 
 useful purposes. It occurs in nuinerous minerals of 
 complex constitution, in shales, slates, clays, and in all 
 other older rocks. As oxide it forms the valuable 
 minerals corundum or emery, and the gems sapphire and 
 ruby, the two latter being coloured respectively, with cobalt 
 and chromium. A great number of silicates containing 
 aluminium are known, of which felspar, one of the con- 
 stituents of granite, is among the most important. 
 Aluminium is most easily obtained by the action of 
 sodium, at a high temperature, on a peculiar compound of 
 the chlorides of aluminium and sodium : 
 
 2 (Na CI, Al CI3) + 6 Na = 8NaCl-h 2 Al. 
 A double sodium and aluminium fluoride, 3NaF,AlF3, 
 found native, and known to mineralogists as cryolite, is 
 sometimes used instead of or with the double chloride. 
 
 s 2 
 
260 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Aluminium is a bluish white metal, somewhat resembling 
 zinc in appearance. It does not tarnish on exposure to 
 air, and from this property, and the fact that it is only 
 about one-fourth the weight of silver (Sp. Gr. 2*56), it is 
 applied to many useful and ornamental purposes. The 
 beautiful alloy called " aluminium gold " is an alloy of 
 one part of aluminium with nine parts of copper. 
 
 COMPOUNDS OF ALUMINIUM. 
 
 Aluminium oxide, AI2O3, Alumina, — This substance, it 
 has already been mentioned, is found native as corundum, 
 &c. When pure it is white. It may be formed artificially 
 by heating the hydrate. At a very high temperature rubies 
 and sapphires, identical with those found in Nature, have 
 been prepared. 
 
 Aluminium hydrate, Al2(0H)g. — Experiment 1. — Dissolve a 
 little alum in water, and add sodium carbonate in excess ; 
 a bulky white precipitate of aluminium hydrate wili be 
 thrown down. Carbonic anhydride escapes as gas, for 
 aluminium carbonate does not appear to exist. 
 
 Experiment 2. — Add potassium hydrate to a little of the 
 white precipitate ; it instantly dissolves. Potassium alumi- 
 nate, K2AI2O4, is formed. Aluminic hydrate plays in this 
 case the part of an acid. 
 
 Experiment 3. — Add potassium hydrate cautiously to the 
 alum solution ; aluminium hydrate is precipitated, but on 
 adding excess is again dissolved, as in the last experiment. 
 If ammonia is used instead of potash, the same precipitate 
 is formed, but does not dissolve in excess. 
 
 Experiment 4. — Put a piece of thin sneet aluminium into 
 potassium hydrate solution. It dissolves slowly with 
 effervescence, but more rapidly if heated. The efferve- 
 scence is due to the escape of hydrogen. Potassium 
 uluminate is formed. Aluminium dissolves in hydro- 
 chloric, and in dilute sulphuric acids, with production 
 respectively of chloride and sulphate, and escape of 
 hydrogen. Nitric acid does not act (m it when cold, and 
 only with difficulty when boiled with it. 
 
 Aluminium sulphate, Al2(S04)3. — Experiment 5. — Dry 
 thoroughly a piece of white clay, and expose it for some 
 hours to heat, which is most easily done on the plate of a 
 
COMPOUNDS OF ALUMINIUM. 
 
 261 
 
 heated oven ; then rub two ounces of it to a powder in a 
 porcelain bowl with one ounce of sulphuric acid ; pour 
 upon the mixture one ounce of water, and let it remain 
 some weeks in a warm place. Frequently stir the mass 
 during this time with a glass rod. Finally, dilute it 
 with six ounces of boiling water, and strain it through 
 linen. The residue on the latter consists principally of 
 silica, but aluminium sulphate is found dissolved in the 
 liquid. 
 
 Clay is an insoluble aluminium silicate, which, on being 
 treated with sulphuric acid in the manner described, is 
 decomposed, aluminium sulphate being formed and silica 
 set free. Evaporate the liquid so obtained till only one 
 and a half or two ounces of it remain, and then put it in 
 a cool place ; it will crystallize ^in thin silky plates of a 
 pearly lustre, which are very deliquescent. Pour off the 
 liquor remaining behind, which always contains free 
 sulphuric acid, and again dissolve the crystals in a little 
 water. In factories the solution is frequently evapo- 
 rated to dryness, and a solid mass is thereby obtained, 
 which is employed in calico-printing and dyeing. 
 
 Alum, K2Al2(S04)4.- — Experiment 6. — Saturate two ounces 
 of boiling water with potassium sul- 
 phate, and add to it the solution of 
 aluminium sulphate obtained in the 
 last experiment. Stir the mixture 
 till it is cold, and decant the clear 
 liquor from the white sediment. The 
 sediment is alum in a state of powder. 
 If dissolved in boiling water and slowly 
 cooled, you obtain from it crystallized 
 alum in beautiful, transparent, four- 
 sided double pyramids (octahedrons). 
 
 Alum is a double potassium and aluminium sulphate, 
 K2S04,Al2( 804)3, and is one of the most important of 
 aluminium compounds. It is obtained from various 
 sources ; in the country it is prepared from a kind of 
 shale, called alum shale, or alum ore, an aluminous mineral, 
 which contains an abundance of iron pyrites, FeS2. When 
 th^ shale is slowly roasted, the pyrites becomes ferrous 
 sulphate, FeS04, while the second atom of sulphur takes 
 
262 
 
 EXPERIMENTAL CHEMISTRY. 
 
 oxygen, and becomes sulpliiiric acid, wMcli decomposes 
 the aluminium silicate and forms aluminium sulphate. 
 On the addition of potassium sulphate, alum is. formed, 
 and may be purified by recrystallization. 
 
 At Tolfa, in Italy, native alum is found, in conjunction 
 with aluminium hydrate, called alum-stone. From this 
 it is prepared by gently heating to decompose the hydrate, 
 and then extracting the alum with water. It is sold as 
 Eoman alum, and is valued on account of its freedom from 
 iron, which always contaminates ordinary kinds. 
 
 Experiment 7. — Heat a small crystal of alum before the 
 blow-pipe ; it foams and melts, and ultimately yields a 
 white porous mass (burnt alum). The foaming is owing 
 to the evaporation of the water of crystallization, which 
 constitutes nearly one-half of the weight of the alum. 
 
 The formula for crystallized alum is 
 
 K^SO^Al^ (S0,)3 24H2O. 
 
 Experiment 8. — Boil half an ounce of Brazil-wood for 
 fifteen minutes in six ounces of water, decant the 
 decoction, and dissolve in it half an ounce of alum ; it 
 thereby acquires a more brilliant red colour. Now add 
 to it a solution of sodium or potassium carbonatCj as long 
 as any precipitate is produced ; this precipitate is of a fine 
 red colour, and, when dried, constitutes the Brazil-wood 
 lake of commerce. In a similar manner, coloured pre- 
 cipitates (lakes) are obtained from other vegetable colour- 
 ing substances. This example accounts for the great 
 importance of the aluminium salts in dyeing and calico- 
 printing. For these purposes aluminium acetate is very 
 frequently substituted for alum. It is obtained by mixing 
 together a solution of lead acetate and aluminium sulphate 
 (or alum), whereby soluble aluminium acetate (alum mor- 
 dant) and insoluble lead sulphate are formed. 
 
 Experiment 9. — Moisten a very small piece of alum with 
 a drop of a solution of cobalt nitrate, and heat it before 
 the blow-pipe ; the oxide of cobalt, which remains behind, 
 imparts a beautiful blue colour to the compound of alumi- 
 nium. This fact is frequently taken advantage of, as a 
 very accurate means of detecting ahimini]itu. 
 
 Another splendid blue pigment, artificial ultramarine, can 
 
COBALT AND NICKEL. 
 
 263 
 
 be prepared by heating to redness a mixture of white clay, 
 sand, sulphur and resin. Its nature is not known. This 
 pigment must be carefully kept from contact with acids, 
 as they would evolve from it sulphuretted hydrogen, and 
 destroy the colour. 
 
 Alum affords a fine example of isomorphism (p. 84). We 
 are able to replace the potassium in the alum by another 
 monad metal, as sodium or ammonium ; or to replace the 
 aluminium by a similar metal, as chromium or iron, 
 without thereby changing the octahedral crystalline form. 
 We thus obtain alums of which the following are 
 examples : 
 
 K2 (S O4) AI2 (S 04)3 24 H2 0 Potassium alum. 
 Na2 (S O4) AI2 (S 04)3 24 H2 0 Sodium 
 (N (S O4) AI2 (S 0 4)3 24 H2 0 Ammonium „ 
 K2 (S 04)01-2(8 04)3 24 H2O Ohromium „ 
 K2 (S O4) Fe2 (S 04)3 24 H2 0 Iron 
 
 The first three of the above alums have a white colour ; 
 chromium alum, a deep red; and iron alum, a pale 
 violet colour. They may be prepared by dissolving 
 together in water their constituent salts, in proper 
 proportions, and allowing the solution to crystallize. 
 
 Isomorphous compounds cannot be separated by crystal- 
 lization. If a crystal of common alum is hung in a cold 
 saturated solution of iron alum, a layer of the new salt 
 will form over the first, and this process may be repeated 
 with other alums. 
 
 COBALT AND NICKEL. 
 Co = 59. Ni = 58. 
 
 During the Middle Ages, when the miner believed in 
 the existence of earth-spirits and goblins in the solitary 
 depths of his mines, ores were occasionally found, par- 
 ticularly in the mines of Schneeberg, in Saxony, re- 
 sembling in brilliancy and weight the finest silver ores, 
 which, however, yielded in the smelting furnaces no 
 silver, but crumbled away to a grey ash, a disagreeable 
 odour of garlic being at the same time emitted. In 
 accordance with the superstitious notions of those times, 
 the miner attributed the disappearance of the supposed 
 
264 
 
 EXPERIMENTAL CHEMISTRY. 
 
 silver to the malicious jests of the earth-spirits, and 
 eontemptuoTisly rejected these ores, which he baptized by 
 the names — cobalt and nickel, which they still bear. 
 But now they are held in high estimation, cobalt being 
 used for imparting a beautiful blue colour to glass and 
 porcelain, and nickel for giving to brass the appearance of 
 silver. As these metals are melted only with great 
 difficulty, the heat of the old furnaces was not sufficient 
 to fuse them. The odour of garlic was occasioned by the 
 arsenic, which always accompanies the ores of cobalt and 
 nickel. 
 
 The ores (speiss-cobalt, cobalt glance, &c.), containing 
 arsenical cobalt and nickel, are now worked by a some- 
 what complicated process. The ore, after roasting, is 
 dissolved in sulphuric or hydrochloric acid and after 
 separation of other metals the cobalt is thrown down as 
 peroxide by bleaching powder and the nickel as hydrate 
 by soda, or lime. 
 
 Smalt is a potash glass coloured blue by cobalt silicate. 
 
 As pure metals, cobalt and nickel have a great similarity 
 to iron, both in their external appearance and in their 
 combinations ; but they do not attract oxygen with such 
 avidity. The three metals, iron, cobalt, and nickel, 
 constitute, as has been already mentioned, the magnetic 
 trio; they alone, of all the metals, are attracted by the 
 magnet to any appreciable extent. It is, moreover, 
 remarkable, that just these three metals always occur in 
 meteorites, which occasionally fall to the earth, we know 
 not whence, in a glowing state (meteoric iron, meteoric 
 stones). Nickel is largely used for plating iron (nickel 
 plating). The operation is conducted as with copper 
 (p. 227), except that the solution used is nickel- 
 ammonium sulphate, NiS04(NH4)2S04, and the positive 
 pole is a sheet of pure nickel. 
 
 Cobalt oxide, CoO, is of an olive-green colour, and its 
 hydrate is pink ; cobalt peroxide, C02O3, is black. The 
 oxide is frequently employed in staining glass. 
 
 Nickel oxide, NiO, is of a greenish-grey, and its hydrate 
 of a beautiful apple-green colour ; the joeroxide, Ni^Og, is 
 black. Chrysoprase, known as an ornamental stone, is 
 q^uartz, coloured green by nickel. 
 
TIN. 
 
 265 
 
 The iproto-salts of cobalt are of a pink colour. A solu- 
 tion of cobalt nitrate is often used in blow-pipe experi- 
 ments ; a solution of cobalt chloride is employed as a 
 sympathetic ink, as it possesses the property of becoming 
 blue when the water evaporates, and again pink on 
 absorbing water. Cobalt forms, with phosphoric and 
 arsenious acids, red insoluble compounds, which are now 
 employed as vitrifiable pigments in glass and porcelain 
 painting. The salts of nickel have a light-green colour. 
 
 The salts of cobalt and nickel, like those of iron, are 
 not precipitated in acid solutions by H2S, but are thrown 
 down as black sulphides by ammonium sulphide. 
 
 Group ii. — Tin, Platinum. 
 
 The members of this group form two series of com- 
 pounds, a diad series, represented by SnCl2, SnO, &c., and 
 a tetrad series, represented by SnCl4, SnOa, &c. The 
 former is analogous to the diad series, but the latter is 
 not analogous to the tetrad series in Group i. In fact, the 
 metals of the iron group do not yield simple tetra-com- 
 pounds, but only compounds in which two atoms of metal 
 act as a single hexad atom. The formulae for the chlorides 
 of iron and tin sufficiently illustrate the difference : 
 Fe CI2. Sn CI2. 
 
 Fe2Cl6. SnCl^. 
 TIN. 
 Sn = 118. 
 
 Tin is one of the few metals which were known in the 
 most ancient times. It becomes fluid at a very moderate 
 heat, namely, at 446° F. (230° C), and in many countries 
 its ores are found in the sand with which the surface of 
 the soil is covered; therefore it is easily obtained and 
 easily smelted. Formerly it was obtained principally 
 from the British Islands, which were, therefore, calJed 
 the tin islands, and even at the present time they, together 
 with Malacca in the East Indies, furnish the purest tin. 
 
 Tin almost exclusively occurs as an oxide, SnOo, called 
 tin-stone. The distribution of this ore in England is chiefly 
 confined to C^omwall. Largo quantities are also obtained 
 from the Malay Peninsula, Australia and elsewhere. 
 
266 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Tin is prepared in a very simple manner from tin-stone. 
 The finely ground and washed ore is first roasted, by 
 which process the arsenic and sulphur are volatilized and 
 the iron oxidized. The iron and copper are then in a 
 great measure removed by washing. Finally, the ore is 
 reduced with charcoal or anthracite (highly carbonaceous 
 ooal). 
 
 The properties which especially characterize tin, and 
 render it a very valuable metal, are its beautiful lustre, 
 and its great softness and flexibility, — its slight affinity 
 for oxygen, in consequence of which it long retains its 
 brightne^^s in the air and in water, — its easy fusibility — 
 it melts at 235° C. (455° F.), — which renders it peculiarly 
 well adapted for casting, and for coating other metals 
 {tinning). Most of the tin of commerce contains traces of 
 arsenic and other metals. A bar of tin emits a grating 
 sound on being bent, and by repeating the operation 
 several times in succession it becomes very hot ; the tin, 
 on hardening, assuming a crystalline texture. These 
 crystals may be very beautifully produced upon tinned- 
 iron sheets. 
 
 Experiment 1. — Heat a piece of tin-plate (tinned-iron 
 i^rj plate) upon a tripod, over a lamp, till the 
 tin is melted ; then quench it with water, 
 that the tin may harden quickly. The 
 surface of the plate has a dull grey aspect, 
 for it is covered with a film of oxide ; 
 but the most beautiful crystalline figures 
 will very soon appear upon it by rub- 
 bing it alternately with balls of paper, 
 one of which is moistened with diluted aqua regia, and 
 the other with potash. Both these liquids dissolve the 
 coating of oxide, and lay bare the pure metallic tin 
 surface (moire metallique). 
 
 Alloys of tin and lead are generally used by workers in 
 metal, under the name of solder, for joining metals to- 
 gether (soft soldering). Solder is to the tinman what 
 glue is to the carpenter. An alloy of two parts of tin and 
 one part of lead is the most easily fusible, and is called 
 fine solder. Another alloy, used in the soldering of 
 coarser articles, such as gutters, is composed of two parts 
 
TIN. 
 
 267 
 
 of lead and one part of tin, and is called coarse solder ; it 
 is so thick that it does not spread itself, but must be 
 applied by smearing. For soldering those metallic 
 articles which are to be subjected to a stronger heat, 
 brass, or some other alloy of difficult fusibility, is made 
 use of (hard solder or brazing). 
 
 Some lead is added even to the tin of which the tinman 
 makes his articles, because pure tin is somewhat brittle, 
 and does not adapt itself well to the moulds. The 
 quantity of lead which can be added to tin is in many 
 countries regulated by law (i to Such an alloy is 
 
 called proof tin, to distinguish it from refined or grain tin, 
 which is tin in its greatest purity. 
 
 Gun-metal contains copper 9 and tin 1 ; Speculum-metal, 
 copper 2, tin 1 ; Bell-metal, copper 5, tin 1 ; Bronze varies 
 much, consisting generally of copper, tin, and lead, or 
 zinc. 
 
 Tin is very malleable : sheets of tin-foil may be ob- 
 tained not more than xoV o^^ inch thick. Spurious 
 silver-leaf is an alloy of tin and zinc hammered out into 
 extremely thin leaves. 
 
 An alloy of tin and mercury, or tin- amalgam, forms the 
 silvering of looking-glasses. Tin does not readily tarnish 
 in air, and on this account is frequently employed as a 
 coating for the more oxidisable metals copper and iron. 
 For coating the latter, as in the manufacture of tin-plate, 
 clean sheets of the best iron are first immersed in melted 
 fat, and then in melted tin for some time, and drained. 
 For coating copper, melted tin is poured on the clean 
 surface of the metal, and rubbed over it with a wisp of 
 tow. 
 
 Experiment 2. — The tinning of brass or copper may also 
 be done in what is called the moist way, by heating to 
 the boiling point finely cut up tin-foil or tin scrapings in 
 a pot with cream of tartar and water, and then boiling 
 in this liquid for half an hour brightly polished copper 
 or brass articles ; as, for instance, farthings and brass 
 nails. In this manner, pins, which consist of brass wire, 
 can be tinned or whitened. 
 
 The symbol Sn for tin is derived from its Latin name, 
 stannum. 
 
268 
 
 EXPERIMENTAL CHEMISTRY. 
 
 COMPOUNDS OF TIN. 
 
 Stannous oxide, SnO. — Experiment 1. — Pour some am- 
 monia upon a solution of stannous chloride ; the white 
 precipitate which is formed is stannous hydrate. By- 
 boiling the liquid, the hydrate is decomposed into water 
 and stannous oxide, which has a black, or dark-green 
 colour, and must be quickly washed with boiled water 
 and dried, as it easily attracts more oxygen from the air. 
 If you heat the dried oxide before the blow-pipe, it burns 
 with great briskness, like tinder, forming stannic oxide. 
 
 Stannic oxide, or Stannic anhydride, SnO.^- — Experiment 2. 
 — Heat a piece of tin upon charcoal in the outer blow-pipe 
 flame ; it will soon become covered with a powder, of a 
 yellow colour when hot, but white when cold ; this is 
 stannic oxide. Tin peroxide thus obtained is not soluble 
 in any acid, and can only be fused with great difficulty. 
 It is so fine a powder, that it is often used for polishing 
 glass and metals. For this purpose it is sold as putty- 
 powder. 
 
 Experiment 3. — Mix a grain or so of stannic oxide with 
 a few grains of charcoal, and heat the mixture on a piece 
 of charcoal with the blow-pipe. The oxide will be 
 reduced and a bead of metallic tin will be formed. This 
 experiment serves to iJlustrate the process used for the 
 extraction of tin. 
 
 Stannic oxide resembles silica in its structure, and in 
 its relation to water. Although insoluble in water, it is a 
 true anhydride and two distinct acids, known respectively 
 as stannic and metastannic acids, can be prepared by in- 
 direct means. They are both compounds of SnOa with 
 water. 
 
 Stannic acid, TL^^jiO^, — Experiment 4. — Add ammonia in 
 excess to solution of stannic chloride. A white precipi- 
 tate falls, which, when dried in the air, has the formula 
 H2Sn03. It dissolves in potash and soda, forming salts 
 called stannates. Sodium stannate is largely used as a 
 mordant in calico-printing. 
 
 Metastannic acid. — Experiment 5. — Metallic tin is rapidly 
 oxidised by strong nitric acid; red fumes are given off 
 and a white powder remains. This is metastannic acid. 
 
COMPOUNDS OF TIN. 
 
 269 
 
 Dried in the air, its composition corresponds with the 
 formula H4Sn04, but when heated to 100° C. (212° F.), it 
 loses water, and its composition is then represented by the 
 formula H.^SnO^. The metastannates are ill-defined salts, 
 and their constitution is still uncertain. 
 
 Both the above acids are converted by heat into stannic 
 anhydride and water. 
 
 Stannous chloride, SnCl2. — Experiment 6. — Boil some 
 fragments of pure granulated tin (the tin of commerce 
 often contains lead) with strong hydrochloric acid. 
 Hydrogen escapes, and stannous chloride is formed, and 
 may be obtained in colourless crystals (SnCl2,2H20) by 
 evaporation : 
 
 Sn+2HC1= SnCl2 + H2. 
 
 The solution of stannous chloride on exposure to air 
 becomes milky, and changes in part to stannic chloride. 
 
 Stannic chloride, SnCl4. — Experiment 7. — Add chlorine 
 water to a solution of stannous chloride, until the odour of 
 chlorine is no longer destroyed. SnCl2 is thereby con- 
 verted into SnCl4. This combination can also be obtained 
 by dissolving tin in aqua regia (nitric and hydrochloric 
 acids). The dyers call this liquid tin mordant, or red 
 spirits. By the addition of ammonia, stannic acid is 
 obtained. 
 
 When pure, stannic chloride is a volatile liquid. 
 
 Stannous sulphide,SiiS. — Experiment 8. — Add sulphuretted 
 hydrogen to an acid solution of stannous chloride. A 
 reddish-brown precipitate of stannous sulphide is produced. 
 It may also be obtained by the direct combination of tin 
 and sulphur. 
 
 Experiment 9. — Envelop twelve grains of flowers of 
 sulphur in a piece of tin-foil, weighing twenty-four grains, 
 then roll up the packet so that it may be introduced into 
 a test-tube, and heat it ; half of the sulphur burns, but the 
 other half combines with the tin, forming a brownish-black 
 mass of a metallic lustre (SnS). If you sprinkle the tube, 
 while still hot, with water, it is rendered friable, and can 
 easily be separated from the fused sulphide. The weight 
 of the latter amounts to nearly thirty grains. 
 
 Stannic sulphide, SnSg. — Experiment 10. — Add sulphu- 
 
270 
 
 EXPERIMENTAL CHEMISTRY. 
 
 retted hydrogen to solution of stannic chloride. In this 
 case a bright yellow precipitate of stannic sulphide is pro- 
 duced. It may be prepared of a beautiful metallic 
 appearance as follows : 
 
 Experiment 11. — Pulverise thirty grains of stannous 
 sulphide obtained by a former experiment, 
 Fig. 88. and mix the powder intimately with six 
 
 4 grains of sulphur and twelve grains of 
 sal-ammoniac ; put the mixture into a 
 thin-bottomed glass flask of an ounce 
 capacity, and heat it strongly for an hour 
 and a half in a sand-bath. You obtain 
 stannic sulphide; but in this case, as a 
 mass which has a golden lustre, and to 
 which the name aurum musivum, or mosaic 
 , gold, has been given. It may be used for 
 ' giving a gold-like coating to wood, plaster 
 of Paris, clay, &c. (bronzing). The sal- 
 ammoniac is found again as a sublimate in the upper 
 portion of the flask ; it prevents by its volatilization the 
 mixture getting hot enough to destroy the colour of the 
 stannic sulphide. 
 
 PLATINUM. 
 Pt = 195. 
 
 Platinum, one of the heaviest of the elements (Sp.Gr. 
 21*5), was brought in the last century from America, 
 where it was found, in the form of small flattened grains, 
 mixed with the sand from which the gold was washed. 
 It received the name of platinum, derived from the Spanish 
 word plata, silver, on account of its resemblance to silver 
 in colour and ductility. It was afterwards found also in 
 the sand of the Ural Mountains, in compact lumps, from 
 the size of a lentil to that of a ujan's fist. Its occurrence 
 in large masses is, however, very rare. The native 
 platinum is not pure, but contains several other rarer 
 metals in small quantities, namely, palladium, rhodium, 
 ruthenium, iridium, and osmium. These metals can only 
 be removed by a difficult process. Platinum, like gold, is 
 a ruMe metal, and, like iron, is tenacious, ductile, and can he 
 welded, and is, moreover, infusible at the strongest furnace 
 
PLATINUM. 
 
 271 
 
 heat. These properties have rendered platinum an 
 invaluable metal to the chemist. Sulphuric and hydro- 
 fluoric acids can be distilled in platinum retorts, nitric acid 
 can be boiled in platinum capsules, and substances can be 
 subjected to the strongest white heat in platinum crucibles, 
 or on platinum foil or wire, without the platinum articles 
 being injured or melted. Great difficulties were at first 
 experienced in working platinum. It was for a long time 
 effected in the following manner : the platinum was first 
 converted into a double chloride of platinum and ammonium 
 by dissolving it in a mixture of nitric and hydrochloric 
 acids, and then adding ammonium chloride. A yellow pre- 
 cipitate is thus produced, which on being heated strongly 
 yields metallic platinum in a finely divided state (spongy 
 platinum). The powder on being hammered in moulds, 
 and then strongly heated and hammered again, becomes a 
 compact block capable of being beaten into any shape. 
 Although platinum is infusible by the heat from ordinary 
 fuel, it can be melted at a temperature of 2,000°C.(3,632° F.) 
 by the oxy-hydrogen blow-pipe, and at the present time 
 furnaces made of quicklime are used, in which very large 
 quantities of platinum can be fused by the aid of several 
 jets of the burning gases. Platinum, like tin, forms a diad 
 and a tetrad series of compounds. 
 
 Platinic chloride, PtCl4. — Experiment 1. — Heat some pieces 
 of thin platinum foil or wire in a mixture of nitric and 
 hydrochloric acids (aqua regia). The metal will gradually 
 dissolve and form a brownish-yellow solution, which by 
 evaporation on a water-bath yields a brown mass of 
 platinum hydrogen chloride H2PtCls =2HCl,PtCl4. This 
 is the chief salt of platinum, and from it the true chloride 
 and other compounds are prepared. The above acid 
 mixture forms the only available solvent of pure platinum, 
 and neither will dissolve it separately. An alloy of 
 platinum with much silver will however dissolve in nitric 
 acid, platinic and silver nitrates being thereby formed. 
 Platinum chloride combines with alkaline chlorides to form 
 double salts on their solutions being mixed. The sodium 
 salt is soluble, the rest are not. 
 
 Potassium-platinic chloride, 2KCl,PtCl4. — Experiment 2. — 
 Mix solutions of platinic chloride and potassium chloride. 
 
272 
 
 EXPERIMENTAL CHEMISTRY. 
 
 A yellow crystalline precipitate of the double chloride is 
 produced, which is rendered more abundant by adding 
 alcohol. Any other potassium salt may be employed if a 
 few drops of hydrochloric acid be likewise added. The 
 reaction thus affords a test for potassium. 
 
 Ammonium-platinic chloride, 2NH4Cl,PtCl4. — Experiment 
 3. — Eepeat the last experiment with solution of ammonium 
 chloride. A yellow precipitate, similar in appearance to 
 the preceding one, will be produced. It contains ammonium 
 instead of potassium. Consequently, before testing for 
 potassium it is necessary to prove the absence of ammonium. 
 
 Experiment 4. — Collect some of the yellow precipitate 
 obtained in the last experiment, dry it in a basin and then 
 heat it gently until it is quite grey. The compound will 
 be decomposed, and metallic platinum only will be left as 
 a grey, loosely coherent, porous mass — the so-called spongy 
 platinum. 
 
 Spongy platinum, like charcoal, has a remarkable power 
 of absorbing gases. On being introduced into a mixture 
 of hydrogen and oxygen it absorbs those gases, and by 
 thus bringing them into close contact causes them to unite, 
 and an explosion is produced. A jet of hydrogen may be 
 ignited in air by spongy platinum or platinum leaf by 
 reason of this property. The apparatus for this experi- 
 ment has already been described (page 108). Clean 
 sheet platinum itself possesses this property, but in a 
 less degree. 
 
 By proper chemical means, platinum may be dividd 
 still more minutely than in spongy platinum ; it is then 
 obtained in the form of a fine black powder, which pos- 
 sesses, in a still higher degree than spongy platinum, the 
 power of condensing gases ; it is called platinum hlaclc. If 
 some alcohol be dropped upon this platinum black, ignition 
 takes place, with an almost instantaneous oxidation of 
 the alcohol. The reason of this change is to be sought 
 for in a combination of the alcohol with the oxygen of 
 the air, which is effected by 'means of the porous platinum 
 black. 
 
 In many other cases oxidation may be promoted by 
 platinum in these states of division. 
 
( 273 ) 
 
 CHAPTEE IV. 
 
 METALLIC TRIADS, OR PENTADS. 
 
 Group i. — Gold. 
 
 Group ii. — Arsenic, Antimony, Bismuth. 
 
 Gold forms two chlorides, A11CI3 and AuCl. It is, there- 
 fore, triad and monad. The metals of Group ii. are some- 
 times triad and sometimes pentad. They may, therefore, 
 be classed with nitrogen and phosphorus ; and indeed 
 arsenic and antimony present so many points of analogy 
 with those non-metallic elements that they are often ex- 
 cluded from the class of metals. This analogy is sufficiently 
 indicated by the parallelism of the formulae for the hydrides 
 chlorides, oxides, and acids of the four elements. Bismuth 
 also is triad and pentad, but, as it does not yield a hydride, 
 its resemblance to the nitrogen group is less perfect than 
 that of the other two. 
 
 Group i. — Gold. 
 GOLD. 
 Au = 196. 
 
 Gold, like platinum, is always found in the metallic 
 state. It is found in most countries, yet it is disseminated 
 so sparingly, and the separation of it from the rocks or the 
 river-sand in which traces of it occur is attended with so 
 much labour, that it is rendered the most costly of our 
 common metals. At present it is obtained most abundantly 
 in Australia and California, and always contains silver, 
 and frequently small quantities of other metals. It occurs 
 in small grains, masses, or veins, in the older rocks and in 
 their detritus, and in minute quantities in the sands of 
 many rivers. To separate the gold from the sand or 
 
 T 
 
274 
 
 EXPERIMENTAL CHEMISTRY. 
 
 detritus the latter is mixed or stirred up with water, when 
 the gold, from its greater weight, sinks to the bottom, and 
 the impurities which remain suspended are poured off 
 with the water. Eocks containing gold are first finely- 
 crushed, and then shaken or mixed with mercury. The 
 latter dissolves the gold. The mercury is then, in a great 
 measure, removed by pressure in leathern bags, and finally 
 and completely, from the resulting almost-solid gold 
 amalgam, by distillation. In California the rocks are 
 disintegrated by enormously powerful jets of water. 
 
 Gold is more malleable than any other metal, and is also 
 very ductile. In making gold-leaf a single grain of the 
 metal is hammered out until it covers the space of more 
 than fifty square inches, or it may be drawn into a wire 
 seven hundred feet long. The wire does not, however, 
 possess much tenacity. It is far inferior to iron wire in 
 this respect. 
 
 Gold-leaf is often so thin as to be translucent ; that is, it 
 transmits light without being transparent. This may be 
 observed by carefully laying a gold-leaf on a plate of glass, 
 and looking through it at a bright light. The film of gold 
 transmits a green light. The colour becomes red if the 
 lustre of the metal is destroyed by heat. Gold is not 
 oxidised or tarnished by exposure to air or water, either 
 at high or low temperatures, nor is it acted on by any 
 common acid or alkali ; consequently it is highly esteemed 
 for ornamental purposes, and above all for coinage. Its 
 specific gravity is 19*3, so that it is rather lighter than 
 platinum. Its melting point is higher than that of silver 
 but lower than that of copper. 
 
 Pure gold, like pure silver, is somewhat soft, and quickly 
 wears out in using ; therefore, when it is to be manufactured 
 into coins or articles of luxury, it is alloyed with other 
 metals, usually silver and copper, to render it harder. The 
 quantity of pure gold contained in a mass is sometimes 
 expressed by the word carat, the standard number 
 not being 8, as in silver, but 24. A mark of gold (8 
 ounces) is divided into 24 parts, or caratw. If gold is said 
 to be 18 carats fine, it is understood that the mass consists 
 of three-fourths (18 parts) of gold, and one-fourth (6 parts) 
 of alloy ; if 6 carats fine, of one-fourth (6 parts) of gold. 
 
GOLD. 
 
 275 
 
 and three-fourths (18 parts) of alloy, &c. The gold used 
 for coinage in England contains 22 parts gold to 2 of 
 copper (22 carats). 
 
 Parting of gold, — In order to obtain fine gold from 
 alloyed gold, or to separate it from silver containing gold, 
 the alloy, which must not contain more than 25 per cent, 
 of gold, is boiled with concentrated sulphuric acid in iron 
 vessels ; the concentrated sulphuric acid does not dissolve 
 the iron. The silver and copper are dissolved with the 
 formation of sulphurous anhydride, while the gold remains 
 behind undissolved, as a brown powder. From the 
 solution of silver and copper, the silver is precipitated by 
 copper, and blue vitriol is obtained as a secondary 
 product. This operation is called refining. 
 
 Sometimes, with the same view, silver containing gold 
 is dissolved in nitric acid, which does not dissolve the 
 gold, though it does silver. In this case the remarkable 
 fact is observed, that the silver is completely dissolved 
 only when three-fourths of silver are present to one-fourth 
 of gold (two-thirds of silver, however, is an adequate 
 proportion) ; hence the term quartation. If more than 
 one-fourth or one-third of gold is contained in the alloy, 
 the gold exerts a protecting influence upon the silver, so 
 that the latter is not attacked and dissolved by the nitric 
 acid ; then it is necessary to add the proper quantity of 
 silver to the alloy. 
 
 The most simple mode of testing gold is to rub some of 
 it off upon a black flint slate (touchstone), and apply to 
 the mark a drop of nitric acid. If the gold is pure, the 
 yellow stroke remains unchanged, but if alloyed, it partly 
 disappears ; if it is only an imitation of gold, for instance, 
 tombac, it entirely dissolves. 
 
 Gold is represented by the symbol Au, from its Latin 
 name Aurum. It forms two classes of salts, typified by 
 aureus chloride, AuCl, and auric chloride, AuClg. 
 
 In contact with air, gold is dissolved by solution of 
 potassium cyanide, which converts it to a soluble double 
 cyanide, KAuCy4. It is also dissolved by solution of 
 chlorine, usually replaced in practice by aqua regia, which 
 acts by virtue of the free chlorine it contains. 
 
 Experiment 1. — Put a gold-leaf into a test-tube, and 
 
 T 2 
 
276 
 
 EXPERIMENTAL CHEMISTRY. 
 
 pour some chlorine solution on it. The gold will soon 
 disappear. 
 
 Experiment 2. — Put pieces of gold-leaf into two beakers ; 
 pour nitric acid into one, and hydrochloric acid into the 
 other. If the hydrochloric acid contains no free chlorine 
 the gold remains unacted upon in each case. Now mix 
 the contents of the beakers, and a rapid solution of the 
 metal will take place. 
 
 Auric chloride, AUCI3. — This compound combined with 
 hydrochloric acid, as AuCl3,HCl, is formed in both the 
 above experiments, and is the most important of the gold 
 salts. The rest are obtained from it. 
 
 Experiment 3.— Heat a few drops of solution of auric 
 chloride on a porcelain-crucible cover, or in a basin. The 
 salt will decompose, and the space it occupied will be 
 covered with a film of metallic gold. All the compounds 
 of gold may be decomposed by mere heating. If the 
 temperature does not exceed 185° C. (365° F.), only part 
 of the chloride is driven off, and aurous chloride, AuCl, is 
 formed. 
 
 Experiment 4. — Saturate filter-paper with auric chloride 
 solution, dry and burn it completely. Finely divided 
 gold mixed with the ashes of the paper is thus obtained. 
 Eub some on a bright silver spoon with a soft cork, which 
 has been moistened with salt water, and the silver will 
 become gilt (cold gilding). There are other methods of 
 gilding, such as the moist gilding, in which the copper, 
 brass, or silver articles are boiled with a diluted solution 
 of gold mixed with sodium hydrogen carbonate ; the hot, 
 or mercury gilding, by which metals are coated with a 
 solution of gold in mercury, and afterwards heated, and 
 the eZec^ro-gilding, in which the metal is deposited by a 
 galvanic current. 
 
 Experiment 5. — Add solution of ferrous sulphate to an 
 acid solution of auric chloride. The mixture immediately 
 assumes a changeable dark and brownish colour, but it 
 appears of a beautiful blue colour on looking through it. 
 On standing, a brown substance is deposited, which is 
 gold in the minutest state of division. The ferrous salt 
 at the same time becomes a ferric salt. The finely 
 divided gold is used in the arts for many purposes. 
 
ARSENIC. 
 
 277 
 
 Glass containing it has a ruby colour, and it is used for 
 gilding porcelain, &c., by being mixed with oil of lavender 
 and painted on the surface. 
 
 Experiment 6. — To a solution of gold add some stannous 
 chloride which has been partially converted into stannic 
 chloride by long standing. A purple precipitate of 
 unascertained composition will be produced, which is 
 called purple of Cassius. This substance produces the 
 most beautiful purple to glass with which it is fused. 
 
 Most of the other compounds of gold are unimportant. 
 Gold forms double salts with those of the alkali metals, 
 the most important of which are the double cyanides, 
 from their application in electro-gilding. Two oxides 
 exist ; a blue-brown aurous, and brown auric oxide 
 (AU2O+AU2O3). Hydrogen precipitates a sulphide of 
 gold from an* acid solution of auric chloride. 
 
 Group ii. — Arsenic, Antimony, Bismuth. 
 AKSENIC. 
 As = 75. Formula as gas, AS4. 
 
 Metallic arsenic is not unfrequently found in the earth, 
 as a lead-grey ore, of strong metallic lustre. It is 
 obtained on a large scale, — a.) as a secondary product in 
 the roasting of tin, silver, and cobalt ores ; 6.) as a 
 principal product, by heating arsenical ores with access of 
 air, by which the arsenic becomes oxidised. In both 
 cases the arsenious oxide passes off as vapour, with the 
 smoke, which is conducted through long chambers, and 
 the arsenious oxide condenses as a powder (white arsenic, 
 the arsenic of the shops). White arsenic is often 
 resublimed in some appropriate apparatus, and is then 
 obtained as amorphous arsenious oxide, in solid trans- 
 parent pieces. These after a time become opaque and 
 milk-white, like porcelain, without changing their con- 
 stitution. 
 
 The oxide may then be reduced by charcoal, or the 
 metal is obtained directly by heating mispickel, a native 
 compound of iron, with sulphur and arsenic (FeSAs), 
 when the arsenic, being volatile, is driven off in vapour 
 and suitably condensed, 4FeSAs = 4FeS-|- As^. 
 
278 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Metallic arsenic, which possesses a steel-grey lustre at 
 first, soon tarnishes and assumes motley colours in moist 
 air, and finally falls into a coarse grey powder, which is 
 kept on hand in the apothecaries' shops, under the name 
 of fly-poison. If boiled with water, the film of oxidised 
 arsenic dissolves, and a very poisonous liquid is obtained 
 (fly-water). A fresh film of oxide is produced upon the 
 metal which remains, and thus is very easily explained 
 why, after a time, a new poisonous solution can again be 
 j)repared from it, without any perceptible decrease of the 
 original powder. 
 
 Experiment 1. — Put a small piece of arsenic into a glass 
 
 Arsenious oxide, or anhydride, AS2O3. — Experiment 2. — 
 Let the arsenical mirror obtained in the above experiment 
 be heated once more, but in an open tube ; it is converted 
 into a vapour, which condenses on the colder parts of the 
 tube, partly in small white crystals, partly as powder. 
 Before the magnifying-glass the crystals appear as four- 
 sided double pyramids (octahedrons). They consist of 
 arsenious oxide, or white arsenic. When arsenic is spoken 
 of in a popular sense this compound is always meant. 
 The preparation of arsenious oxide on the large scale has 
 just been described. The ore most frequently employed 
 is mispickel, all the elements of which are oxidised when 
 the ore is roasted : 
 
 Arsenious oxide is soluble in water, but not to a great 
 extent, but it is sufiiciently soluble to render these 
 solutions exceedingly dangerous poisons. White arsenic 
 is generally employed for killing rats, moles, and other 
 troublesome house or field animals; for this purpose 
 coloured arsenic only should be purchased, as the white 
 
 Fig. 89. 
 
 tube closed at one end, and 
 heat it ; the arsenic volatilises, 
 and deposits itself on the upper 
 portion of the tube as a bril- 
 liant black mirror; the smell of 
 garlic, peculiar to the fumes of 
 arsenic, being at the same time 
 oiven ofiL 
 
 2reS As + 5O2 = FcaOs + 280^ + As^O^ 
 
ARSENIC. 
 
 279 
 
 arsenic looks very much like sugar or flour, and might 
 easily be mistaken for them. 
 
 Arsenious oxide prevents the decay of organic sub- 
 stances ; therefore the skins of animals intended for 
 shipping are sometimes rubbed with it upon the flesh 
 side. 
 
 Arsenious oxide when heated readily gives up its oxygen 
 to other bodies; for this reason it is added by glass- 
 makers to melted bottle-glass, to convert its black or green 
 colour into yellow. It acts like black oxide of manganese ; 
 namely, it converts the iron from ferrous into ferric salt. 
 On the other hand, it may be made to take up more 
 oxygen and pass into arsenic anhydride. 
 
 Experiment 3. — Heat a little arsenious oxide in the 
 bottom of a dry test-tube. It will volatilize and condense 
 as a ring of minute brilliant crystals on the upper part of 
 the tube. It may be noticed that the oxide will volatilize 
 entirely without previously melting. 
 
 Experiment 4. — Mix the arsenious oxide with dry 
 powdered charcoal, and then heat in a test-tube. Instead 
 of transparent crystals a brownish mirror of metallic 
 arsenic will be produced, the reduction being effected by 
 the charcoal. 
 
 Experiment 5. — If ten grains of arsenious oxide and 
 twenty grains of potassium carbonate are heated with half 
 an ounce of water, the oxide very readily dissolves, and a 
 solution of hydrogen potassium arsenite, KHgAsOg, is 
 obtained. 
 
 Arsenious oxide is therefore the anhydride of the 
 tribasic arsenious acid, H3ASO3 : it is hence often called 
 arsenious anhydride, and its solution in water is regarded 
 as one of arsenious acid : 
 
 AS2O3 -I- 3 HoO = 2 H3ASO3. 
 
 In the last experiment a salt is formed, in which one 
 atom of the hydrogen in this acid is replaced by one of 
 potassium. Its solution is known in medicine as Fowler's 
 solution. 
 
 Experiment 6. — Add some of the hydrogen potassium 
 arsenite to a dilute solution of copper sulphate. A bright 
 g reen precipitate is produced. When dried it forms the 
 
280 
 
 EXPERIMENTAL CHEMISTRY. 
 
 pigment known as Scheele's green, often employed for 
 colouring vvall-paper. It consists of hj^drogen copper 
 arsenite, HCuAsOg, a compound in which two of the 
 hydrogen of arsenious acid are replaced by one of the 
 diad copper. 
 
 Experiment 7. — Add some silver nitrate solution to 
 another portion of arsenite. A pale yellow precipitate of 
 silver arsenite, AggAsOg, is produced; all three of the 
 hydrogen atoms being replaced by silver. 
 
 Arsenic oxide, or anhydride, AsgOg. — Experiment 8. — Boil 
 some arsenious oxide with strong nitric acid in a basin. 
 A violent evolution of red fumes takes place. By evapo- 
 ration a white deliquescent mass is obtained, which on 
 being heated strongly furnishes arsenic oxide. The 
 deliquescent mass is arsenic acid, H3ASO4 ; but on being 
 heated it loses its water and becomes the anhydride : 
 
 2 H3ASO4 = 3 H2O + AsA- 
 
 The latter is again converted into arsenic acid by the 
 addition of water. Arsenic acid forms numerous com- 
 pounds, some of them being found native. It possesses 
 a strong sour taste, and dissolves zinc and iron with 
 liberation of hydrogen, and is in other respects a powerful 
 acid. 
 
 Arsenious sulphide, AS2S3. — Experiment 9. — Dissolve some 
 grains of arsenious oxide in dilute hydrochloric acid, and 
 add to the solution hydrogen sulphide; a precipitate of 
 yellow arsenious sulphide is formed, three atoms of sulphur 
 replacing three atoms of oxygen. In this way arsenic 
 may easily be detected in liquids, and separated from 
 them. The salts of cadmium and tin are the only ones, 
 except arsenic, which give a yellow precipitate with 
 sulphuretted hydrogen. The yellow precipitate of arsenic 
 is dissolved by the addition of ammonium sulphide, but is 
 insoluble even in boiling hydrochloric acid. 
 
 Arsenious sulphide also occurs native, and is called orpi- 
 ment, or king's yellow, and is used as a yellow pigment. 
 
 Experiment 10. — Add hydrogen sulphide to a solution of 
 arsenic acid. No immediate eftect is produced, but on 
 heating the mixture, adding more hydrogen sulphide, and 
 allowing it to stand, a yellow precipitate of a lighter colour 
 
ARSENIC. 
 
 281 
 
 than in the preceding experiment is formed. This is a 
 mixture of arsenious sulphide and free sulphur. 
 
 Arsine^ or Arseniuretted hydrogen, As Hg. — This gas, which 
 is similar in constitution to ammonia and pbosphine, cannot 
 easily be obtained pure, but mixed with hydrogen it is 
 evolved in the following experiment : 
 
 Experiment 11. — Introduce into a small flask diluted 
 sulphuric acid and some pieces of zinc, and let the hydrogen 
 which is evolved escape through a tube drawn out to a jet, 
 and after some time ignite it ; you obtain in this manner a 
 hydrogen-lamp. If you hold a glazed por- 
 celain capsule for a few moments in the 
 flame, you will perceive upon it only a 
 circle of small drops of water, which form 
 during the combustion of the hydrogen, 
 and condense on the cold portion. If you 
 now introduce a little arsenious oxide into 
 the flask, the flame, after the gas has been 
 rekindled, will present a bluish-white ap- 
 pearance, and will deposit on the porcelain 
 held in it a black or brown shining spot 
 (mirror) ; this mirror is metallic arsenic. 
 The flame is cooled by a cold body below 
 the temperature which arsenic requires 
 for burning; hence the latter condenses 
 on the porcelain, just in the same way as 
 carbon or soot is deposited on it when held in the 
 flame of a candle. The carbon separates as a light, 
 pulverulent body, arsenic as a coherent mirror. This 
 extremely sensitive test is called, after its inventor, 
 Marsh's arsenic test. Care should be taken not to inhale the 
 escaping gas, particularly the unburnt gas ; and more 
 than ordinary caution is necessary, as arseniuretted 
 hydrogen is a most poisonous gas, and one to which some 
 chemists have already fallen victims. 
 
 If a grain or two of arsenious oxide has been introduced 
 into the flask, a white smoke will be seen issuing from the 
 hydrogen flame when it burns freely. This is arsenious 
 oxide, which has been formed by the combination of the 
 arsenic with the oxygen of the air. If a dry test-tube be 
 held with its mouth a little above the flame, so that the 
 
282 
 
 EXPERIMENTAL CHEMISTRY. 
 
 smoke may enter, a white sublimate condenses on the 
 interior of the tube. It may be dissolved off with boiling 
 water, and if hydrochloric acid and hydrogen sulphide 
 are then added to the i^olution, the production of yellow 
 arsenious sulphide will prove the presence of arsenic. 
 
 Experiment 12. — Repeat the former experiment, substi- 
 tuting tartar emetic for arsenious oxide ; black spots are 
 in this case also deposited on the porcelain, but they are 
 darker, and often have a sooty appearance ; they consist 
 of metallic antimony. To distinguish spots of antimony 
 with certainty from spots of arsenic, drop upon them a 
 solution of bleaching powder ; the spots of antimony 
 remain unchanged, while the arsenical mirrors dissolve 
 immediately. 
 
 Experiment 13. — Another excellent test for arsenic is 
 known as Beinsch's test. Add a like solution of white 
 arsenic to a little porter or a cup of coffee. Boil some of 
 the liquid for ten minutes with a few drops of pure hydro- 
 chloric acid and a small slip of bright copper. The copper 
 will become grey from the deposition of arsenic. Eemove 
 it from the liquid, dry it carefully, and heat it gently in 
 a small and perfectly dry test-tube. The arsenic will 
 oxidize and sublime in the cool part of the t^be in brilliant 
 ootohedral crystals easily visible with a lens. 
 
 ANTIMONY. 
 Sb = 120. 
 
 Antimony exists native in small quantities, but chiefly 
 in the sulphide, SbsSg, which constitutes the mineral called 
 stihnite, or black antimony ore. This ore is generally 
 called antimony " in commerce, the metal being known 
 as " regulus of antimony." To obtain the antimony from 
 this ore the ore is melted with pieces of iron, or is roasted 
 to oxide and reduced with carbon. In the former case the 
 iron combines with the sulphur, forming ferrous sulphide, 
 and the antimony is set free. 
 
 Antimony has a lamellar crystalline textuiie, and a 
 white metallic lustre like bismuth, but without the red 
 tint of the latter ; it is brittle and may be easily rubbed 
 to powder in a mortar. The sp. gr. of antimony is 6*8. 
 It melts at 425^0. (797°r.) 
 
ANTIMONY. 
 
 283 
 
 Of the alloys which antimony forms with other metals, 
 that with lead, with which types are cast, deserves 
 especial notice. Lead alone is much too soft to be em- 
 ployed for this purpose, but if from a fifth to a sixth part 
 of antimony is mixed with it, it acquires such a degree of 
 hardness, that types cast from it may be used for printing 
 many thousand times without losing their sharp edges. 
 A sample of English type metal contains 50 of lead, 25 of 
 of antimony, and 25 of copper. Fjom the property 
 possessed by the alloy of expanding as it solidifies, it 
 reproduces the most minute patterns with perfect fidelity. 
 The metal itself, in the free state, is not applied to any 
 important purposes. Its Latin name is stibium, whence its 
 symbol Sb. 
 
 Antimonious oxide, SbgOg. — Experiment 1. — Antimony 
 does not alter in the air, but if a piece of it is heated on 
 charcoal before the blow-pipe, it soon melts, and burns 
 with a white flame, forming this oxide, which partly 
 escapes as a white vapour, and is partly deposited as a 
 coating on the charcoal. If you let the melted metallic 
 globule slowly cool, the oxide condenses into crystals, 
 which form around the metal an espalier of white points. 
 When thrown into a paper capsule, the white glowing 
 globule will burst into a multitude of small grains, which 
 skip about for some time, leaving in their trail a pul- 
 verulent oxide. In the presence of a free supply of air 
 the oxide formed is, however, not SbgOg, but a higher 
 intermediate oxide, Sb204. Antimony generally contains 
 traces of arsenic ; hence the smell, like that of garlic, 
 which almost always accompanies its fusion. 
 
 Antimonious oxide may be prepared in a pure state by 
 throwing the corresponding chloride into boiling solution 
 of sodium carbonate, and washing and drying the pre- 
 cipitate. 
 
 Antimonic oxide, SbgOg. — Experiment 2. — Pour a little 
 strong nitric acid containing a little hydrochloric acid on 
 some fragments of antimony. An action similar to that 
 with tin takes place, and the antimony is converted into 
 a white powder. On being dried and gently heated it 
 furnishes antimonic oxide. Combined with water it forms 
 antimonic acid, HSbOg ; it is therefore properly antimonic 
 
284 
 
 ^EXPERIMENTAL CHEMISTRY. 
 
 anhydride. The white powder obtained by the nitric acid 
 and antimony is, indeed, antimonic acid, but this is 
 decomposed by the subsequent heating into water and the 
 oxide. 
 
 Experiment 3. — Mix some powdered antimony with nitre 
 and throw it into a porcelain crucible which is made red- 
 hot with a Bunsen's burner. Potassium antimoniate, KSbOg, 
 is thus formed, and may be dissolved out from the fused 
 mass with boiling water. 
 
 Antimonious chloride, SbClg. — Experiment 4. — Put half an 
 ounce of antimonious sulphide into a capacious flask ; pour 
 over it two ounces and a half of strong hydrochloric acid, 
 and heat it in a sand-bath, at first moderately, but after- 
 wards to boiling. Sulphuretted hydrogen escapes, and the 
 chloride is formed : 
 
 ShSs + 6 HCl = 3 H^S -}- 2 SbCla- 
 
 By filtering and evaporating the liquid, antimonious 
 chloride is obtained as a soft yellow solid, which was 
 formerly known as butter of antimony. It may be dissolved 
 in a little water and hydrochloric acid, and on then being 
 thrown in a large quantity of water it is converted into a 
 white powder, an oxy-chloride of antimony, SbOCl, similar 
 in constitution to the oxy-chloride of bismuth. 
 
 It has already been shown that powdered antimony takes 
 fire if thrown into chlorine gas, and antimonious chloride 
 is formed as a white powder. If more than sufficient 
 chlorine is present to form this compound, antimonic chloride 
 SbCls, is produced. It is a yellow fuming liquid, which 
 is decomposed by heat into antimonious chloride and free 
 chlorine. 
 
 Fotassio-antimonious tartrate, K(SbO)C4H406. — This is the 
 best known and most important antimony salt. It is 
 called tartar emetic, and may be regarded as a tartrate of 
 potassium and the monad radical SbO. Oxy-chloride of 
 antimony, SbOCl, is a chloride of the same radical. 
 
 Experiment 5. — Boil in a porcelain dish two ounces of 
 distilled water, and during the boiling stir in a mixture 
 of one drachm of antimonious oxide, and one drachm of 
 cream of tartar (hydrogen potassium tartrate, KHC4H40(j). 
 When the liquid is half boiled away, filter it while boiling. 
 
BISMUTH. 
 
 285 
 
 and pour one half of it into one ounce of strong alcohol, 
 but set the other half aside. In both cases you obt;\in 
 tartar emetic ; in the latter case in the form of crystals, 
 but in the former as a fine powder, because tartar emetic 
 is insoluble in alcohol, and consequently is precipitated 
 by it instantly from its solutions. The following reaction 
 occurs : 
 
 Sb^Os + 2 KHC^H^Oe = H^O + 2 K(SbO)C4H40e. 
 
 We shall learn hereafter that the organic acid tartaric 
 acid, C4H6O6, is most simply regarded as containing the 
 diad radical C4H4O6 combined with hydrogen, for two of 
 its atoms of hydrogen can be replaced by metals. The 
 name, tartar emetic, indicates the medicinal application 
 of this double salt ; it is a very usual means of inducing 
 vomiting. Dissolved in sherry, it forms the well-known 
 wine of antimony. It is sparingly soluble in cold water. 
 In large doses it is very poisonous. 
 
 Stihine, or Antimoniuretted hydrogen, SbHg, has already 
 been noticed under arsenic. 
 
 Antimonious sulphide, SbgSg. — Experiment 6. — Add some 
 sulphuretted hydrogen to a solution of antimonious 
 chloride, or tartar emetic, in dilute hydrochloric acid ; an 
 orange coloured precipitate of antimonious sulphide is 
 obtained, which becomes darker on dryirjg. Thus the 
 compounds of antimony may be recognised, as no other 
 metal yields a sulphide of this colour. 
 
 The native sulphide, generally known as " black 
 antimony," or " antimony," has already been noticed. It 
 is identical in composition with, though so different in 
 appearance from, the sulphide obtained by precipitation. 
 
 Many other antimonious and antimonic compounds are 
 known, but few of them are of any interest. 
 
 BISMUTH. 
 Bi = 208. 
 
 Bismuth chiefly occurs in the metallic state imbedded 
 in quartz, and in less abundance as sulphide and oxide. 
 
 It is also frequently present in cobalt ore, and, in 
 the smelting of this ore for smalt, it separates as cobalt 
 speiss, nickel also being generally present. The metal is 
 
286 
 
 EXPERIMENTAL CHEMISTRY. 
 
 procured from the native ore by a very simple process. 
 It occurs both in the ores and in the speiss in a nearly 
 pure state, and as it melts at a low temperature (270° C. = 
 578° F.), it is only necessary to heat the ores moderately 
 in inclined tubes, when the bismuth melts and flows off 
 below, while the other metals or ores, together with the 
 gangue, remain behind unmelted. , This method of 
 working the metal is called eliquation. Bismuth is brittle, 
 has a crystalline laminated texture, and a reddish- white 
 colour. Its specific gravity is 9*8. 
 
 On allowing melted bismuth to cool till it is covered 
 with a crust, piercing the crust, and then pouring off the 
 fluid portion, the remainder will be found beautifully 
 crystallized in hollow cr3^stals nearly cubical in form. 
 
 Experiment 1. — Melt together in a ladle two drachms of 
 bismuth, one drachm of lead, and one drachm of tin. The 
 alloy formed has the very remarkable property of becoming 
 completely liquid when thrown into boiling water. It melts 
 at 94° C. = (201° P.). By increasing the quantity of lead, 
 alloys may be prepared which readily become liquid at any 
 temperature desired above 212° F. (100° C). They are some 
 times employed as safety-plates in steam-boilers. The heat 
 of the steam increases with the tension of the steam in the 
 boiler ; therefore the alloy to be used has only to be so 
 selected, that, in case of a too great increase of steam, the 
 plate may be melted by the heat of the steam before an 
 explosion of the boiler itself can take place. As this 
 alloy, in its melted state, does not burn the wood, and as 
 it expands during solidification, it is also very well 
 adapted for making metallic copies of engraved wooden 
 moulds for calico-printing and block impressions. This 
 alloy is called Boss's meted, after the discoverer. 
 
 Bismuth is easily dissolved by dilute nitric acid, but 
 not in hydrochloric acid. It dissolves in heated sulphuric 
 acid. 
 
 Bismuthous oxide, or Bismuth tri-oxide Bi203. — Experiment 
 2. — Heat a piece of bismuth upon charcoal before the blow- 
 pipe ; it melts with the ejection of sparks, and volatilizes 
 at a high temperature with brisk ebullition. A portion 
 of the fumes condense on the charcoal, coating it with a 
 yellow powder; this is bismuth oxide (BigOa). If you 
 
BISMUTH. 
 
 287 
 
 throw the glowing metallic bead into a small paper box, 
 it divides into small globules, which, while still glowing, 
 will skip about for some moments. An odour like that of 
 garlic, which is frequently emitted during the ignition, 
 proceeds from arsenic, small quantities of which occur in 
 almost all commercial bismuth. 
 
 Bismuth tri-nitrate, or Bismuthous nitrate, Bi (N03)3. — 
 Experiment 3. — Dissolve some bismuth in dilute nitric acid 
 at a moderate heat, evaporate the solution and set aside to 
 crystallize. The salt will be deposited in large colourless 
 prisms. 
 
 Experiment 4. — Eedissolve some of the crystals in water 
 to which a little nitric acid is added. Without the 
 addition of acid, solution cannot be effected ; but as little 
 as possible must be used. Pour some of the solution into 
 a tumbler of water : an opaque white precipitate of 
 bismuth oxy-nitrate, BiONOg, will be produced. 
 
 The rest of the bismuth compounds are of little 
 importance. 
 
 Bismuthous chloride, BiClg, can be formed by dissolving 
 the oxide in hydrochloric acid and evaporating to dryness, 
 it is a volatile solid and can be easily distilled ; on its 
 solution being mixed with water a white precipitate of 
 bismuth oxy-chloride, BiOClg, is produced, similar in con- 
 stitution to the oxy-nitrate. It is sometimes used as a 
 pigment under the name of pearl white. 
 
 Another series of bismuth compounds, in which the 
 metal is a pentad, exists. The chief member is bismuth 
 pent-oxide, or bismuthic oxide, BigOg ; the rest are little 
 known. 
 
 Sulphuretted hydrogen produces a black precipitate of 
 tri-sulphide, BigSg, in bismuth solutions. This sulphide 
 occurs native sls bismuthite. 
 
288 
 
 EXPERIMENTAL CHEMISTRY. 
 
 PAET IV. 
 
 ORGANIC CHEMISTRY, OR THE CHEMISTRY OF CARBON 
 COMPOUNDS. 
 
 CHAPTEE L 
 
 INTRODUCTION. 
 
 It has already been pointed out that the compounds of 
 carbon are analogous to those of other elements, and that 
 the term "organic," as applied to the former, has no 
 longer the definite meaning it once possessed. It is 
 indeed convenient to retain the old distinction, at least for 
 the present, partly on account of the enormous number 
 and frequent complexity of the carbon compounds, and 
 partly because the constitution of many of them is still 
 unknown to us ; but this does not preclude us from 
 adopting in their study the same principles which have 
 guided us through the domain of inorganic chemistry. 
 Carbon itself and a few of its compounds have already 
 been described. 
 
 Structure of the simpler carbon compounds, — Let it be 
 remembered that, except in one or two compounds, it is 
 always possible to consider carbon as a tetrad. This is 
 seen plainly in the compounds which have already been 
 noticed, and in a few others of equal simplicity ; for 
 example, in carbonic anhydride, CO2 ; carbon disulphide, 
 CSg ; carbon tetrachloride, CCI4 ; and methane, CH4. This 
 is the fundamental principle in the classification of carbon 
 compounds. 
 
 Structure of the Hydrocarbons, or compounds of carbon and 
 hydrogen. — The study of the very numerous compounds of 
 carbon and hydrogen throws a most important light on 
 
ORGANIC CHEMISTRY. 
 
 289 
 
 the constitution of the more complex carbon compounds 
 and is therefore taken as the starting point in modern 
 organic chemistry. One of these compounds, methane, or 
 marsh-gas (CH4), contains but one atom, the rest from 
 two to sixteen or more atoms of carbon. The quantity of 
 hydrogen varies from two atoms in acetylene (CoHg), up 
 to thirty-four atoms, or even more. Now in examining 
 the formulae of these hydrocarbons, we are struck with 
 two peculiarities : 
 
 1. The number of hydrogen atoms in a molecule is always an 
 even number, — We are acquainted, for example, with CgH , 
 C2H4, and C2H2, but not with CoH^, C2H3, or C2H. 
 
 2. The number of hydrogen atoms in a molecule is never 
 greater than twice plus two the number of carbon atoms, — For 
 example, no compound containing two atoms of carbon is 
 known which contains more than six atoms (that is 2 x 2 
 + 2) of hydrogen. And no compound containing seven 
 atoms of carbon is ever found to contain more than 
 sixteen atoms (7 x 2-|-2) of hydrogen. 
 
 Saturated Hydrocarbons, — Hydrocarbons which contain 
 the utmost possible quantity of hydrogen, as indicated by 
 the above rule, are called saturated hydrocarbons. Their 
 constitution can be expressed by the following very 
 important general formula : 
 
 in which n may stand for any number from 1 upwards. 
 Methane, CH^, is the type of the class. They are stable 
 compounds, and are, by their nature, incapable of com- 
 bining directly with chlorine, or any other monad 
 element. This is readily seen in the case of methane, 
 for if CH4, could combine with CI and form CH^Cl, it is 
 evident that carbon in the new compound must be a 
 pentad. 
 
 Unsaturated Hydrocarbons, — All hydrocarbons which con- 
 tain less than the maximum quantity of hydrogen may be 
 described as unsaturated. Ethylene, C2H4, and acetylene, 
 C2H2, for instance, are unsaturated, because one contains 
 two and the other four atoms of hydrogen short of the 
 maximum. 
 
 Homologues, — Homologous Series, — The general formula, 
 
 u 
 
290 
 
 EXPERIMENTAL CHEMISTRY. 
 
 C„H2„+2» for saturated hydrocarbons will, if studied, bring 
 to light the curious fact that all the members of this series 
 must differ from one another by CH2, or by some multiple 
 of CH2. The following table, which contains the names 
 and formulae of a few of the simpler hydrocarbons, shows 
 that this is true not only of this particular series, but also 
 of other series of similar hydrocarbons : 
 
 Saturated. Unsaturated. 
 (Methane Series.) (Ethylene Series.) (Acetylene Series.) 
 
 CwH2n + 2' CnH2n. C»H2n-2' 
 
 CH4 Methane. CHg Methylene 
 (unknown). 
 
 C2 Hg Ethane. C2 H4 Ethylene. ^2 Acetylene. 
 
 C3 Hg Propane. C3 Hg Propylene. C3 H4 AUylene. 
 
 C4 Butane. C4 Hg Butylene. C4 Hq Crotonylene. 
 
 C5 Pentane. C5 Hjo Amylene. C5 Hg Yalerylene. 
 
 Series of this kind are called homologous series, and the 
 members of them are said to be homologues of one another. 
 Amylene, for instance, is a homologue of butylene and of 
 ethylene. The phenomenon is not confined to hydro- 
 carbons. Many analogous series are known of compounds 
 which contain oxygen, nitrogen, and other elements in 
 addition to carbon and hydrogen. The arrangement of 
 carbon compounds in series of this kind facilitates their 
 study to an amazing extent, for the members of each 
 series generally resemble one another so closely as to 
 make it unnecessary to study more than one or two of 
 them. 
 
 Hypothetical explanation of the foregoing fact. — By a slight 
 extension, the doctrine of valency affords an intelligible 
 explanation of these peculiarities of carbon compounds. 
 Let us revert to the illustration employed before, and 
 suppose that every elementary atom has one or more bonds 
 or arms by which it can grasp and be grasped by other 
 atoms. The monads have one bond, the diads two, the 
 triads three, and the tetrads four. We can then conceive 
 how the carbon atom with its four bonds can attach to 
 itself four atoms of hydrogen. And we can understand 
 further that when there are two atoms of carbon, these 
 two must be linked together by at least one bond of each, 
 so that there will remain only six free bonds by which 
 hydrogen atoms can be attached. In like manner, three 
 
ORGANIC CHEMISTRY. 
 
 291 
 
 carbon atoms can only combine with eight hydrogen 
 atoms, because, for three atoms to be linked together one 
 of them must use two of its bonds. The following 
 diagram will show how simply this conjecture explains 
 the constitution of the saturated hydrocarbons : 
 
 The unsaturated hydrocarbons, and indeed all chemical 
 compounds the nature of which is understood, can be 
 represented by formulae analogous to these " glyptic " 
 formulae. But their use is quite unnecessary, for it is 
 sufficient to write against each carbon atom the symbols 
 for the elements or radicals which are attached to it. 
 Thus the above compounds are generally represented by 
 the following, which are are called structural formulas : 
 
 CH^ 
 
 CH3 CH3 
 CH3 CH2 CH3 
 CH3 CH2 OH2 CH3 
 
 It is well to repeat that no one supposes that the 
 
 u 2 
 
292 
 
 EXPERIMENTAL CHEMISTRY, 
 
 atoms really have anything like arms projecting from 
 them. The way in which atoms are held together is 
 unknown to us, and the hypothesis only pretends to 
 supply one conceivable mode of accounting for the 
 structure of compounds. 
 
 Hydrocarbon Badicals. — It has already been explained 
 that the name radical is given to a group of atoms which 
 is found in a number of different compounds, and which 
 plays in each of them the part of an elementary atom. 
 The group OH, for instance, is called a radical, because 
 it is found in all the hydrates, and plays in each of them 
 the part of one monad atom. A radical is necessarily 
 an incomplete body, and is very often, as in the case of 
 OH, incapable of separate existence. OH is called a 
 monad radical because it only requires one monad atom 
 to complete it. The compounds H2O, KOH, ClOH, are 
 complete, and cannot act as radicals. The radical SO4 is a 
 diad radical because it is short of the complete compound 
 H2SO4 by two atoms of hydrogen. The valency of a 
 radical is, in fact, measured by the number of hydrogen 
 or other monad atoms required to complete it. 
 
 The hydrocarbons, from their complexity, yield a great 
 many radicals. The saturated hydrocarbons, such as 
 CH4, being already complete, are not radicals; but any 
 hydrocarbon which contains less than the full number 
 2n-\-2 of hydrogen atoms may act as one, and its possible 
 valency may be measured by the number of hydrogen 
 atoms which it lacks. Thus we have the following 
 radicals derived from methane. The chlorine compound is 
 written after each to illustrate the kind of compound into 
 which it enters. 
 
 CH3CI Methyl chloride. 
 C H2 CI2 Methylene dichloride. 
 C H CI3 Methenyl trichloride. 
 
 (Chloroform.) 
 C CI4 Carbon tetrachloride. 
 
 In the same way, related to ethane, C2Hg, we have the 
 radicals (C2H,)' ethyl, (C2H4r ethylene, (C2H3)'" ethenyl, 
 (CaH^)'^ acetylene, and (G.J^j. The greater the number 
 
 C H4 Methane. 
 (CH3)' Methyl. 
 (CH2)" Methylene, 
 (CHf Methenyl. 
 
 C'" Carbon. 
 
ORGANIC CHEMISTRY. 
 
 293 
 
 of carbon atoms, the greater of course, will be the possible 
 number of hydrocarbon radicals in the series. 
 
 Any hydrocarbon radical which contains an even 
 number of hydrogen atoms is capable of separate exis- 
 tence but the others are not, and are therefore to be 
 compared with OH, NH4, &c. In the series last named, 
 CaHg, C2H4, and C2H2 are well known. 
 
 Valency of Hydrocarbon Badicals, — The rule just given, 
 namely, that the valency of the radical may be inferred 
 from the number of hydrogen atoms which it requires to 
 bring it to the formula C,,H2^+25 ^® universally true. 
 The radical phenyl, CgHg, for instance, should by this 
 rule have a valency equal to nine, whereas it is only 
 found to be a monad ; and oil of turpentine, G-^qBliq, which 
 should be a hexad, is only a tetrad. Many hydrocarbons 
 which should by their formula3 be radicals do not fulfil 
 this function, and seem to be complete, or saturated. It 
 is easy by the hypothesis before described to give an 
 explanation of these peculiarities, but it is only necessary 
 in this place to note the fact. 
 
 Compounds containing Hydrocarbon Badicals. — Hydro- 
 carbon radicals generally play in compounds the part of 
 metals. Compounds are known which correspond closely 
 to the hydrates, oxides, salts, &c., of the metals, differing 
 from them in composition only by containing some hydro- 
 carbon radical in place of the metal. Many of these 
 compounds are among the most important in chemistry. 
 It is essentially necessary to understand and remember 
 their formulae, and this will be done with ease if their 
 resemblance to the metallic compounds is carefully borne 
 in mind. 
 
 To begin with the monad radicals, such as methyl, CH3, 
 ethyl, C2H5, &c. They are strictly comparable to atoms 
 of potassium. Take the formula of any potassium com- 
 pound, replace the symbol K by the group CH3, and you 
 will have the formula for a methyl compound — oxide, 
 chloride, hydrate, or oxy-salt — which shall resemble the 
 potassium compound in many particulars. 
 
 So again with the compounds of diad radicals. The 
 diad radical ethylene, C2H4, is like an atom of zinc, and 
 the ethylene compounds are curiously similar to those 
 
294 
 
 EXPERIMENTAL CHEMISTRY. 
 
 of zinc. The following table will supply a few illus- 
 trations of this interesting resemblance : 
 
 CH3 CI 
 CH3OH 
 
 (CH3XO 
 
 CH3NO3 
 CH3HSO4 
 (CH3),S0, 
 C2 H4 CI2 
 
 C3 H5 CI3 
 C3H,(OH)3 
 
 Methyl chloride like 
 hydrate „ 
 (Methyl-alcohol.) 
 oxide „ 
 (Methyl-ether.) 
 nitrate „ 
 I hydrogen "1 
 (sulphate. / " 
 sulphate „ 
 
 Ethylene chloride 
 hydrate 
 (Glycol.) 
 oxide 
 
 Propenyl chloride, 
 
 hydrate 
 (Glycerine) 
 C5 Hg Valerylene bromide „ 
 
 KCl 
 KOH 
 
 KNO3 
 
 KHSO4 
 
 K2SO4 
 
 Zn CI2 
 Zn(0H)2 
 
 ZnO 
 
 Bi CI3 
 Bi(0H)3 
 
 Potassium chloride. 
 „ hydrate. 
 
 „ oxide. 
 
 „ nitrate. 
 
 J hydrogen 
 " (sulphate. 
 „ sulphate. 
 
 Zinc chloride. 
 „ hydrate. 
 
 „ oxide. 
 
 Bismuth chloride. 
 „ hydrate. 
 
 Sn Br4 Stannic bromide. 
 
 Nomenclature of the above compounds, — Besides the sys- 
 tematic names, founded on their analogy with metallic 
 compounds, many of these compounds are known by 
 other names, which were given to them before their 
 nature was understood. Thus the hydrates are generally 
 called alcohols, common alcohol, C2H5OH, being a member 
 of the class. Alcohols are sometimes said to be monatomic, 
 diatomic, or triatomic, according as they are the hydrates 
 of monad, diad, or triad radicals. Diatomic alcohols are 
 also known as glycols, from the old name of ethylene 
 hydrate, C2H4(OH)2, and triatomic alcohols, as glycerols or 
 glycerines ; common glycerine, €3115(011)3, being the only 
 important member of the class. 
 
 The oxides of the radicals are called ethers, from 
 common ether, which is the oxide of ethyl, (02115)20. 
 The salts — chlorides, sulphates, &c. — are sometimes, but 
 very improperly, called compound ethers. 
 
 Modes in which the above compounds are formed, — These 
 compounds are produced by a great variety of processes. 
 Some of them are formed by the processes of animal or 
 vegetal life ; as, for instance, the natural fats and oils, 
 which are salts of the triad radical propenyl : some by 
 artificial processes, the nature of which is as yet im- 
 perfectly understood, such as fermentation and destructive 
 
ORGANIC CHEMISTRY. 
 
 295 
 
 distillation. Very many can be prepared artificially, 
 either from hydrocarbons or from other carbon compounds, 
 and in these cases a satisfactory account can generally be 
 given of their mode of formation. The processes in fact 
 often bear a close resemblance to those of mineral 
 chemistry. By way of illustration, let us take a few of 
 the derivatives which may be obtained from marsh-gas, 
 or methane. 
 
 (1.) Methane mixed with chlorine and exposed to 
 sunlight yields methyl chloride and hydrochloric acid : 
 CH4+Cl2 = CH3Cl+HCl. 
 
 (2.) Methyl chloride with silver acetate yields methyl 
 acetate and silver chloride : 
 
 CH3CI+ AgC2H302 = CH3C2H3O2+ AgCl. 
 
 (3.) Methyl acetate with potassium hydrate yields 
 methyl hydrate (methyl alcohol) and potassium acetate. 
 This is a common way of producing alcohols : 
 
 CH3C2H3O2 + KOH = CH3OH + KC2H3O2. 
 
 (4.) Methyl hydrate, dehydrated by sulphuric acid, 
 yields methyl oxide (methyl ether). This is a common 
 way of producing ethers : 
 
 2CH3OH - H2O = (CH3)20. 
 
 Isomerism, Metamerism, Polymerism. — It often happens 
 that two or more compounds contain the same elements 
 in the same proportions, and even contain in each mole- 
 cule the same number of atoms, the difference between 
 them consisting entirely in the arrangement of the 
 atoms. If in such compounds all the carbon atoms are 
 united directly together, the compounds are said to be 
 isomeric. Thus CH2CI. CH2CI2 and CH3.CHCI2 are isomeric 
 though not identical. But if two or more carbon radicals 
 are linked together by a dissimilar atom, such as 0, S, or 
 N, the compounds are said to be metameric. Thus CH3. 
 CH2OH (ethyl alcohol) and CH3.O. CH3 (methyl ether) are 
 metameric, because in the second compound the two 
 carbon atoms are separated and yet united by an oxygen 
 atom. 
 
 Polymeric bodies are those in which the molecular 
 weights are multiples of one another, as, for example, 
 ethylene, C2H4, and butylene, C^Hg. 
 
296 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Analysis of Carbon compounds. — The analysis of organic 
 substances is of two kinds — proximate and ultimate. 
 Proximate analysis is applicable in the first place to 
 mixtures. It teaches us what compounds are mixed 
 together in any given substance. Coal tar, for instance, 
 is a highly complex mixture. Subjecting this to a variety 
 of processes of proximate analysis we find out that it 
 contains water, various basic and acid bodies, neutral 
 hydrocarbons, &c. The same term is sometimes applied 
 to many of the processes by which the arrangement of 
 the atoms in a compound is determined. The substance 
 called methyl acetate, for example, is found, by ultimate 
 or elementary analysis, to have the formula C3H6O2. But 
 when it is distilled with KOH it is found to divide into 
 two portions, of which one, CH3, combines with the OH, 
 and the other, C2H3O2, with the K. We therefore ascribe 
 to the compound the formula CH3,C2H302. By ultimate, 
 or elementary, analysis we ascertain the nature and 
 proportion of the elements of which any compound 
 consists. Almost all carbon compounds are analysed 
 by mixing a known weight of them with cupric oxide 
 in a hard glass tube, called a combustion tube, closed 
 at one end, and heating the tube to redness in a charcoal 
 or gas furnace. The carbon, taking oxygen from the 
 cupric oxide, becomes CO2, and the hydrogen H2O. The 
 water is absorbed in a tube filled with calcium chloride, 
 the carbonic anhydride in a series of bulbs partly filled 
 with solution of caustic potash. The calcium chloride 
 tube and the potash bulbs are weighed before and after 
 the experiment; the increase of weight showing the 
 quantity of water and carbonic anhydride formed by 
 the combustion of the substance. From these quantities, 
 that of the carbon and hydrogen can easily be calculated. 
 If nitrogen is present it is given ofi* as gas during the 
 combustion, and can be collected and measured. Other 
 elements, such as chlorine, sulphur, metals, &c., can 
 be estimated by appropriate methods. After all other 
 elements have been estimated and calculated as parts 
 per cent., the quantity required to make up 100 must 
 be oxygen, which is always determined in this way. 
 
( 297 ) 
 
 CHAPTEE II. 
 
 CLASSIFICATION OF THE SIMPLER CARBON COMPOUNDS. 
 
 Before commencing the experimental study of organic 
 chemistry, the student will find it well to master the 
 outlines of the system by which organic compounds are 
 classed. The following are a few of the most important 
 classes : 
 
 1. Hydrocarbons; many of which are radicals. 
 
 2. Alcohols, or hydrates of hydrocarbon radicals. These 
 radicals are sometimes called alcohol radicals. 
 
 3. Ethers, or oxides of hydrocarbon radicals. 
 
 4. Salts of hydrocarbon radicals; sometimes called com- 
 pound ethers, 
 
 5. Organic acids, or hydrates of acid radicals. Acid 
 radicals are, for the most part, hydrocarbon radicals, in 
 which a portion, or the whole of the hydrogen is replaced 
 
 oxygen. 
 
 6. Ammonia derivatives, in which a portion, or the whole 
 of the hydrogen of ammonia is replaced by alcohol 
 radicals or acid radicals. The alkaloids or organic bases 
 belong to this class. 
 
 7. Substitution compounds, in which hydrogen is partly, 
 or wholly replaced by CI, Br, I, NO2, &c. 
 
 All the above compounds can be arranged in homo- 
 logous series, each of which can be represented by a 
 general formula, in which n may stand for any number. 
 
 Many compounds are still too imperfectly known to be 
 referred with certainty to any of the classes. 
 
 HYDROCARBONS. 
 
 A few of the simplest compounds of carbon and 
 hydrogen have already been described, and the others 
 will be more conveniently considered in subsequent 
 chapters. A short classification of the most important of 
 them is all that is necessary here. 
 
298 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Series C^H2„+2 > sometimes called the Paraffins. — Me- 
 thane, or marsh-gas, CH^ is the lowest member of this, 
 which is par excellence the saturated series. The solid 
 substance called paraffin is a mixture of several of the 
 higher members of the series. The petroleum oils which 
 issue from the earth in America and other places, and the 
 so-called paraffin oils, obtained by destructive distillation 
 from some kind of coal, are very complex mixtures of 
 hydrocarbons, belonging to this series. Many of them 
 also can be formed in the laboratory by artificial 
 processes. 
 
 Series C„H2^ ; sometimes called the Olefines. — Ethylene, 
 C2H4, described before, is the lowest known member. 
 Many of them can be obtained by dehydratino; some 
 alcohol by means of sulphuric acid or zinc chloride. 
 They are also frequently formed during destructive 
 distillation, a process to which a subsequent chapter is 
 devoted. The true olefines are all diad radicals, inasmuch 
 as each of them will combine with two atoms of chlorine. 
 
 Series C„H2„_2. — Acetylene, C2H2 (p. 185), is the only 
 important member. 
 
 Series C^H2^.4. — Oil of turpentine, and many other of 
 the volatile oils described in a later chapter, have the 
 formula CioHig, or the polymeric formulae C15H24, or 
 C20H32, and therefore belong to this series. As the 
 saturated hydrocarbon would have the formula C10H22, it 
 is evident that these oils might act as hexad radicals. In 
 practice they only unite with four monad atoms, and are 
 therefore reckoned as tetrads. 
 
 Series C„H2„.6. — Benzene, CgHg, which is found in the 
 most volatile portion of coal tar, is the most important 
 member, but several higher homologues are known. 
 
 Series C„H2„.^2- — Naphthalene, G^^Hg, also found in coal 
 tar, is the only example of any importance. 
 
 Series CJl2n-iH' — Anthracene, C14H10, is found in the 
 least volatile portion of coal tar. 
 
 ALCOHOLS. 
 
 Methyl series, C„H2„+iOII. — This, which contains common 
 alcohol, is by far the most important. The following are 
 members of it : 
 
ALCOHOLS. 
 
 299 
 
 Methyl alcohol, CH3OH. Formed in the destruc- 
 tive distillation of wood. 
 
 Ethyl, or common alcohol, C2H5OH. 
 Trityl, or propyl „ GJEl^OIl. 
 Tetryl, or butyl „ C4H9OH. 
 Pentyl, or amyl „ C5H11OH. 
 Hexyl „ C6H13OH. 
 
 Heptyl „ C.Hi^OH. 
 
 The last six are all formed during the fermenta- 
 tion of sugar, but common alcohol in greatest 
 quantity. 
 
 Cetyl alcohol, CigHggOH, from spermaceti. 
 Myricyl alcohol, C^qUq^OH, from bee's-wax. 
 
 Allyl series, C„H2„.iOH. — Allyl alcohol, C3H5OH, an 
 unsaturated alcohol. 
 
 Benzyl series, CJEL^n-^OH. — Benzyl alcohol, C^H^OH, 
 which can be prepared from oil of bitter almonds, is the 
 lowest and most important of this series. 
 
 Phenols, — A few curious substances are known, of which 
 ordinary phenol (called also phenyl alcohol, and more 
 frequently carbolic or phenic acid) is the type. They 
 exhibit, to a certain extent, the nature both of alcohols 
 and of acids, and are yet different from either. Common 
 phenol, which, under the name of carbolic acid, is largely 
 used as an antiseptic, is formed during many processes of 
 destructive distillation. Its formula is CgHgOH, and it is 
 a hydrate of the monad radical phenyl, CgHg. 
 
 Diatomic Alcohols, or Glycols. — Very few are known, and 
 those have no practical importance. Common glycol is 
 C2H4(OH)2 ; it is therefore the hydrate of the diad radical 
 ethylene, C2H4. 
 
 Triatomic Alcohols, Glycerols, or Glycerines, — Common 
 glycerine, obtained from most fixed oils and fats, is the 
 only important member of the series. It has the formula 
 C3H5( 011)3, and is therefore the hydrate of the triad 
 radical propenyl or glyceryl, C3H5. 
 
 ETHERS. 
 
 Common ether may be taken as an example of com- 
 pounds of this class. It is an oxide of the monad radical 
 
300 
 
 EXPERIMENTAL CHEMISTRY. 
 
 ethyl C2H5, the radical of common alcohol, and its formula 
 is (02115)20 or GJI^qO. The relations of the alcohols and 
 ethers to one another and to metallic hydrates and oxides 
 have already been pointed out. Ethyl oxide, or ether, is 
 prepared by dehydrating alcohol by sulphuric acid>: 
 
 SALTS. 
 
 The salts of hydrocarbon radicals can be prepared by 
 various processes, but the simplest and one of the 
 commonest consists in treating the corresponding hydrate, 
 or alcohol, with the acid. Ethyl chloride, for example, 
 may be prepared by treating alcohol with hydrochloric 
 acid gas : 
 
 O2H5HO+HCU O2H5OI+H2O. 
 
 In other cases the alcohol is treated with the materials 
 from which the acid is made. Thus common alcohol 
 with sodium acetate and sulphuric acid gives ethyl 
 acetate (acetic ether) and sodium sulphate. 
 
 These compounds are sometimes called " compound 
 ethers." 
 
 ACIDS. 
 
 Oxygen-containing acids have hitherto been regarded 
 as compounds of hydrogen with radicals analogous in 
 function to chlorine. But it is equally easy and often 
 more convenient to regard them as hydrates, that is, as 
 containing the radical OH instead of H. The acid 
 radical will then of course contain less oxygen. The 
 difference between the two views will be readily under- 
 stood by the following formula for three of the commonest 
 mineral acids : 
 
 Nitric acid HNO3 or NO2OH. 
 
 Sulphuric acid H2SO4 or S02(OH)2. 
 
 Phosphoric acidHgPO^ or PO (0H)3. 
 
 The student will find no difficulty in applying these 
 formul96 to all known oxy-acids. The radicals of this 
 kind aie distinguished by the termination yl ; thus NO2 
 is called nitryl, SO 2 sulplmryl, and PO phosphoryL It will 
 be seen at a glance that they are respectively monad, diad, 
 and triad. 
 
ACIDS. 
 
 301 
 
 This view renders the structure of the simpler organic 
 acids easy to understand. Every organic acid may be 
 regarded as the hydrate of an acid radical analogous to 
 the above-named mineral radicals. And this radical is, 
 in all the simpler acids, a hydrocarbon in which part or 
 all of the hydrogen is replaced by oxygen, one atom of 
 oxygen replacing two atoms of hydrogen. Acids and 
 alcohols are therefore related very simply to one another, 
 as the following examples will show : 
 
 Methyl alcohol, CH3OH. Formic acid, CHOOH. 
 
 Ethyl alcohol, C2H5OH. Acetic acid, C2H3OOH.. 
 
 In these and in many other cases the acids can actually 
 be formed from the alcohols by direct oxidation. Thus 
 when dilute alcohol absorbs oxygen from the air it is 
 converted to vinegar, that is, to acetic acid : 
 
 Alcohol. Acetic Acid. 
 
 Similar relations can be observed between diatomic 
 alcohols and certain dibasic acids, as is shown by the 
 following comparison : 
 
 Ethylene Oxalic 
 Glycol. Acid. 
 
 It must, however, be remembered that many acids are 
 known to which no corresponding alcohol has been dis- 
 covered. 
 
 Let it be distinctly understood that either way of 
 writing the formula of an acid may with correctness be 
 employed. It does not much matter for ordinary purposes 
 whether we call acetic acid HC2H3O2 or C2H3OOH. 
 
 The following are a few of the most important classes 
 of organic acids. For the sake of comparison with the 
 alcohols, the acids are here formulated as hydrates. 
 
 Formic Series — Fattij Acids, C„H2„.iOOH. 
 
 This important series is related in the manner above 
 described to the first series of alcohols. The acids 
 belonging to it are often called the fatty acids, because 
 several of the higher members (palmitic, stearic) are 
 
302 
 
 EXPERIMENTAL CHEMISTRY. 
 
 derived from fats and oils, which are indeed glyceryl salts 
 of those acids. The most important acids are given in 
 the following table : 
 
 Fatty Acid. 
 
 Formic 
 
 Acetic 
 
 Propionic 
 
 Butyric 
 
 Valeric 
 
 Caproic 
 
 Palmitic 
 
 Stearic 
 
 CHOOH. 
 
 C2H3OOH. 
 
 C3H5OOH. 
 
 C^H^OOH. 
 
 C5H9OOH. 
 
 CgHiiOOH. 
 
 C16H31OOH. 
 
 C,«H,,OOH. 
 
 Corresponding 
 Alcohol. 
 
 Methyl CH3OH. 
 Ethyl C2H5OH 
 Trityl C3H^0H. 
 Tetryl 
 Amyl 
 Hexyl 
 Cetyl 
 
 C^H.^OH. 
 C6H13OH. 
 C16H33OH. 
 
 olive and other 
 
 Acrylic Series^ C„H2„.300H, 
 
 Acrylic acid, C3H3OOH, prepared from glycerin. 
 Oleic acid, C18II33OOH, „ 
 oils. 
 
 Benzoic Series, GJ1^,^.^0Q>Sl. 
 
 Benzoic acid, C-7H5OOH, prepared from gum benzoin 
 and in other ways, is the lowest and most important of 
 the series. It is related to benzyl alcohol, 0^11^011, 
 
 Other acids. — It is not necessary in this place to describe 
 the constitution of the less simple acids. The names and 
 formulae of a few of the more important are appended ; 
 the formulae being written on the older and, in some 
 respects, simpler plan : 
 
 Monohasic, 
 
 Lactic acid, IIC3H5O3 
 the juice of flesh. 
 
 Gallic acid, HC^H^Os. 
 Dibasic 
 
 Oxalic acid, H2C2O4. 
 
 Found in sour milk and in 
 In gall nuts. 
 
 In wood sorrel and other 
 plants, also by the oxidation of starch, sugar, &c., 
 by nitric acid. 
 Succinic acid, H2C4H4O4. By the distillation of 
 
 amber (succinum), and in other ways. 
 Malic acid, H2C4H4O5. In apples and other fruits. 
 Tartaric acid, H2C4H4O6. In grapes and other fruits. 
 Trihasic, 
 
 Citric acid, HaCgHgO^. In lemons and other fruits. 
 
AMMONIA DERIVATIVES. 
 
 303 
 
 AMMONIA DERIVATIVES, 
 
 We have seen that a portion, OH, of water is found in 
 a large class of compounds, and is therefore called a 
 radical. And we have also seen that three several portions 
 of methane, CH4, may act as radicals, namely, CH3, CH2, 
 and CH. In like manner, two portions of ammonia gas, 
 NH3, namely, NH2 and NH, both probably incapable of 
 separate existence, are found to play, in certain compounds, 
 the part of radicals. NH2, sometimes called amidogen, is of 
 course a monad, like OH and CH3 ; and NH, sometimes 
 called imidogen, a diad. They are formed by replacing 
 one or two atoms of the hydrogen of ammonia by metals, 
 by alcohol radicals, or by the acid radicals of which the 
 acids are hydrates. And it is possible, in many cases, to 
 replace the third atom of hydrogen by a metal or radical. 
 The metal or radical is then combined with nitrogen only. 
 
 Thus, starting from ammonia, we have — 
 
 H3 N, analogous to H2 0. 
 K H2 N, analogous to K O H. 
 K2 H N, not known. 
 K3 N, analogous to Kg 0. 
 
 In the same way, with the radical methyl,we have — 
 
 C H3 H2 N, (C H3)2 H N, and (C H3)3 N. 
 
 The metallic derivatives of ammonia are, for the most 
 part, unimportant, but those which contain alcohol or acid 
 radicals are very interesting. In the nomenclature which 
 is most frequently employed the former are called amines, 
 whether they contain NH2, NH, or N, and the latter 
 amides, and both are known as primary, secondary, or tertiary, 
 according as one, two or three atoms of hydrogen are 
 replaced. 
 
 Amines. 
 
 1. Of monad radicals. 
 
 C H3 H2 N Methylamine (Primary). 
 (C 113)2 H N Dimethylamine (Secondary). 
 (C 1X3)3 N Trimethylamine (Tertiary). 
 
 Which may serve as examples. Amines containing other 
 alcohol radicals are formed and named in the same way. 
 
304 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Two or three different alcohol radicals may be present in 
 an amine, as, for example : 
 
 C H3 C2 H5 C5 N, Methyl-ethyl-amylamine. 
 2. Of diad radicals. Generally called diamines. 
 C2H4 (H2N)2, called ethylene diamine, is a sufficient ex- 
 ample. 
 
 Compound ammoniums, — Amines are similar to ammonia 
 in constitution and generally in properties. Now we 
 know that ammonia combines with hydrochloric and 
 similar acids, and forms compounds which are called 
 ammonium salts : 
 
 H3N + HCI = H4NCI. 
 
 And it is usual to assume that the solution of ammonia 
 in water contains a definite hydrate of the same radical, 
 ammonium : 
 
 H3N + H2O = H4N,0H. 
 
 The amines are found to be capable of forming precisely 
 similar compounds, which are called compound ammonium 
 salts, because they are ammonium salts in which a portion 
 or the whole of the hydrogen is replaced by alcohol radicals. 
 To take the simplest instance — methylamine, CH3H2N, is 
 a gas, very similar to ammonia in properties, and even 
 more soluble in water. It combines with hydrochloric 
 acid, forming a white solid salt, methyl-ammonium chloride : 
 
 (CH3)H2N + HC1 - (CH3)H3NC1. 
 
 Its solution in water contains the hydrate : 
 
 (CH3)H2N + H20 = (CH3)H3N,OH. 
 
 Ammonium salts have been prepared in which all four 
 of the atoms of hydrogen are replaced by the same or by 
 different radicals. For example, 
 
 CH3C2H5C5HiiC,H5NCl; 
 
 a compound which bears the cumbrous name methyl-ethyl- 
 amyl-phenyl-ammonium chloride ! 
 
 The most important of the amines is phenylamine, 
 generally called aniline. It contains the radical phenyl, 
 and has the formula CgHsHaN. 
 
SUBSriTUTION COMPOUNDS. 
 
 305 
 
 Amides. 
 
 1. Of monad radicals. 
 
 C2H3OH2N, Acetamide, is a good example. It con- 
 tains acetyl, C2H3O, the hydrate of which is acetic 
 acid. The analogy between the amide and acid is 
 seen at a glance. 
 
 C2 H3 0 N II2, Acetyl amide, or acetamide. 
 C2 H3 0 0 H, Acetyl hydrate, or acetic acid. 
 
 2. Of diad radicals. 
 
 CO (NH2)2, Carbonyl diamide, commonly called 
 urea, is an extremely important example. It contains 
 the radical CO of carbonic acid. 
 
 C 0 (0 H)2 Carbonic acid ( = H2 C O3). 
 CO(NH2)2,Urea. 
 
 Amides are commonly neutral substances. 
 
 Natural bases, or alkaloids, — It cannot be doubted that 
 these very important compounds are derivatives of 
 ammonia, but their exact structure is not yet ascertained. 
 A chapter will be devoted to their study. 
 
 SUBSTITUTION COMPOUNDS CONTAINING CI, NO2 &C. 
 
 In many compounds a portion of the hydrogen may be 
 replaced by chlorine, by the radical NO2, or similar 
 bodies, without the character of the compound being 
 entirely lost. 
 
 ChlorO', Bromo-, and lodo- compounds, — We have already 
 seen that chlorine may displace the hydrogen in hydro- 
 carbons. The following compounds, obtained from acetic 
 acid, will explain themselves. Many analogous bodies 
 are known. 
 
 C2 H4 O2, Acetic acid. 
 C2 H3 CI O2, Chloracetic acid. 
 C2 H2 CI2 O2, Dichloracetic acid. 
 C2 H CI3 O2, Trichloracetic acid. 
 
 All of these are monobasic acids, like acetic. 
 Nitro-compounds, — Many substances, when treated with 
 nitric acid, exchange one or more atoms of hydrogen for 
 
 X 
 
306 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the radical NO2. Compounds so formed are called nitro- 
 compounds. Examples : 
 
 Gq Hg, Benzene. 
 
 Cg H5 N O2, Nitrobenzene. 
 
 Gq H4 (N 02)25 Dinitrobenzene. 
 Many important explosive agents, for example gun-cotton 
 and nitro-glycerine, are either nitro-compounds or nitrates 
 isomeric with them. The mode in which they are formed 
 is seen very clearly in the case of nitrobenzene : 
 
 Benzene Nitric Acid. Nitrobenzene. 
 
 Ce He + N O2 0 H = Ce H5 N O2 + H2 0. 
 
 The modern system of classification has not been em- 
 ployed in the following pages. Great as are the advantages 
 it presents, it does not appear so well fitted for the purposes 
 of a simple experimental study as the older and more 
 arbitrary arrangement here adopted. The student will 
 lind it wise, while investigating the properties of each 
 substance he deals with, to mark its formula and endeavour 
 to ascertain its true position among carbon compounds. 
 This will not always be possible, but in very many cases 
 a reference to this chapter will enable him to succeed. 
 
( 307 ) 
 
 CHAPTEE III. 
 
 CELLULIN, STARCH, GUM, AND SUGAR GROUP. 
 
 The members of this highly important group of com- 
 pounds have a complex structure which is as yet but im- 
 perfectly understood. They have not been prepared 
 artificially, but are formed by the subtle processes which 
 are connected with the functions of vegetable and animal 
 life. Some of them are peculiar to vegetables, a few to ani- 
 mals, and all are connected together by a great similarity 
 of composition and properties. Some of them, as, for 
 instance, starch and sugar, are highly important con- 
 stituents of food. 
 
 It will be seen, in the following table, that they all 
 consist of carbon, hydrogen, and oxygen, and that the two 
 latter elements are in almost every case present in the 
 same proportions as in water. They are therefore called 
 carbo-hydrates. Cellulin and starch are distinguished from 
 the rest, in that they have a definite structure — fibres and 
 granules. They are therefore said to be organized com- 
 pounds. 
 
 Cellulin, or vegetable fibre. 
 Starch, in the seeds and other 
 
 parts of plants. 
 Glycogen, in the tissues of animals 
 
 and in certain vegetables. 
 Dextrin, formed by the alteration 
 
 of starch, &c. 
 Arabin, in gum arable. ) 
 Glucose, or grape-sugar, found in 
 
 honey, fruits, &c., also in the 
 
 animal body. Can also be ) C^R-^^^q 
 
 formed from cellulin, starch, 
 
 dextrin, &c. 
 
 All of which have 
 the formula 
 
^08 
 
 EXPERIMENTAL CHEMISTRY. 
 
 \2^220ll' 
 
 Sucrose, or cane-sugar, found in\ 
 
 the sugar-cane, maple, beet-root, I 
 
 and other plants. 
 Lactose, or milk-sugar, in the milk j 
 
 of animals. 
 Maltose, in malt and wort. 
 The true formulae of many or all of these compounds 
 are probably multiples of those here given. 
 
 CELLULIN OR CELLULOSE. 
 
 All the cells and vessels of plants are composed of 
 cellulin. This substance is to plants what bones, flesh, 
 and skin are to the animal body ; it forms the solid mass 
 of all vegetable organs, and consequently imparts to 
 plants their shape and firmness; it forms the ducts or 
 veins of the plants, through which the sap circulates. 
 We find it very finely ramified, tender, soft, and easily 
 digestible in the young leaves, flowers, and stems, and 
 in the so-called pulp of fruits and roots, as apples, plums, 
 carrots, &c. ; hard and indigestible in straw, wood (woody 
 tissue), and in the husks of grain (hran) ; hardened like 
 stone in the stones of plums, cherries, and peaches, and 
 in the shells of nuts ; light, porous, and elastic in the pith 
 of the elder, and in the cork ; lengthened and pliant in 
 hemp, flax, and cotton. 
 
 The transverse section of the stem of a tree illustrates 
 the influence which age exerts upon the vegetable tissue 
 and how this tissue varies in one 
 and the same tree. Inside the harh 
 (a) lies the inner fibrous harh (6), 
 which consists of lengthened tubes, 
 and is peculiarly adapted to supply 
 the place of veins in the tree. Here 
 the sap principally circulates, and 
 therefore a tree will die when the 
 inner bark is girdled, whilst (as seen 
 in many hollow trees) the tree will 
 live on if only the inner and outer 
 bark remain, though the wood itself is entirely rotten and 
 gone. From the innei' bark towards the exterior is deposited 
 
 Fig. 91. 
 
CELLULIN. 
 
 309 
 
 every year a new layer of bark, and towards the centre a 
 new layer of wood (annual circles). The light and whiter 
 wood, lying next the inner bark, is 
 called sap wood (c) ; but this by the Fig. 92. 
 
 annually increasing compressure, 
 becomes denser and more solid, and 
 then it is called heart-wood (d). The ^ 
 latter is usually darker, and is fre- 
 quently impregnated with colouring 
 matter. The annexed figure will give 
 an idea of the internal structure, 
 which is manifest even in apparently ^ 
 simple dense wood, when viewed 
 under a strong magnifying glass. 
 It represents the transverse section 
 of a pine bough, the portion marked 
 a representing young ligneous cells, those marked h the 
 matured cells. 
 
 Most plants contain in the inner and outer bark a sub- 
 stance which has an astringent taste, is soluble in water, 
 and which is known by the name of tannin. 
 
 Linen is the inner bark of the flax plant. During the 
 process of retting, the outer bark, by the long-continued 
 influence of moisture and air, passes into decay, and then, 
 after rapid drying, may be rubbed off by bending it back- 
 wards and forwards (hreahing) ; but the filaments of the 
 inner bark, which do not so readily decay, remain behind, 
 and after being parted into their finest fibrils, and arranged 
 parallel by the so-called heckling, form the well-known 
 flax. The tow, which falls off during this process, consists 
 of tangled fibres of the inner bark. 
 
 Flax has a grey colour, because it contains a grey 
 colouring matter, which is not soluble in water and lye, 
 though it becomes soluble in lye by exposing the flax, the 
 thread spun, or the linen woven from it, during a long 
 time, to the action of light, water, and air. This is done 
 in the bleaching-yard by spreading it on the grass (grass 
 bleaching). Bleaching may be accomplished more rapidly 
 by the use of chloride of lime. 
 
 Bast. — Soak the bark of the lime-tree in water till the 
 outer bark is decomposed, and has become brittle ; when 
 
310 
 
 EXPERIMENTAL CHEMISTRY. 
 
 it is dry, the inner fibrous part of the hark can he peeled from 
 it, and it then forms the lime hast, used for tying np plants. 
 The outer covering of the trees, which is commonly, but 
 erroneously, called bark, consists by no means of the 
 proper bark only, but of two essentially different parts, 
 which have grown very closely together ; the external 
 layer is the true bark, the inner is the bast. 
 
 Cotton consists of delicate hollow hairs, which form in 
 the cotton-plant in considerable quantities around the 
 seeds. As it exists in nature it is beautifully white. It 
 is nearly pure cellulin, whereas most kinds of vegetable 
 tissue contain other compounds in considerable quantity. 
 
 Paper, which is made by beating vegetable fibres, such 
 as those of linen and cotton, with water, and straining the 
 pulp with wire sieves, is of course nearly pure cellulin. 
 
 Vegetable Tissue and Water. — Experiment 1. — Pour some 
 lukewarm water over sawdust, and let it stand for a day ; 
 then squeeze out the liquid through a cloth and boil it ; a 
 slight turbidity will appear, and on longer standing a 
 loose sediment will be deposited. Water does not dissolve 
 the woody fibre, though it does the sap contained in it ; in 
 this sap, as in that of all other plants, there is always 
 found a substance in solution, which is very analogous to 
 the white of eggs, and which, like it, coagulates in boil- 
 ing ; it is called vegetable albumin (see next chapter). 
 There are also contained in the liquid, separated from the 
 albumin, various other substances in solution (mucus, gum, 
 tannin, &c.), which are not precipitated by boiling. If 
 the sawdust, after it has been dried, is treated with 
 alcohol, this will also dissolve some substances (resin, 
 &c.) ; and so also will ether, lye, and other liquids. 
 Therefore, in the preparation of perfectly pure woody 
 tissue, it must be treated with various solvents in order to 
 remove all the constituents of the sap. 
 
 Properties of Cellulin. — Cellulin is insoluble in all 
 ordinary solvents, except those which alter it, but is 
 dissolved by ammonio-hydrate of copper, from which it 
 can be reprecipitated by the addition of hydrochloric acid. 
 Strong sulphuric and nitric acids act upon it in a very 
 remarkable manner. 
 
 Vegetable Parchment, — Experiment 2. — If a sheet of white 
 
CELLULIN. 
 
 311 
 
 blotting-paper is immersed for a few seconds in a cold 
 mixture of two measures of sulphuric acid with one mea- 
 sure of water, and is then washed very thoroughly (for 
 the last time with very dilute ammonia) and dried, it is 
 changed into a tough substance very like parchment, 
 which does not appear to differ from the original paper 
 in composition. It is now much used for industrial 
 purposes. 
 
 Experiment 3. — If cellulin is beaten for some time in a 
 mortar with strong sulphuric acid, it becomes liquid, and 
 is converted into dextrin and after adding water and boil- 
 ing into glucose. The excess of acid may be removed 
 by chalk, and the filtered liquid on evaporation will yield 
 both compounds. 
 
 Gun-cotton. — Experiment 4. — Mix one ounce of the strong- 
 est nitric acid (sp. gr. 1*5) with three ounces of strong sul- 
 phuric acid ; pour the mixture into a porcelain mortar, or 
 a cup, and press into it with the pestle as much cotton 
 (cotton- wool, calico, printing-paper, &c.) as can be 
 moistened by the acid. When the cotton has soaked for 
 twenty-four hours, it is taken out with a glass rod, put 
 into a vessel containing water, and washed repeatedly with 
 fresh quantities of water, until it no longer reddens blue 
 test-paper. The cotton is then squeezed out with the 
 hand, spread upon a sheet of paper, and dried in an airy 
 place. It is dangerous to dry it upon a stove, as it easily 
 takes fire. 
 
 If the gun-cotton thus prepared is struck smartly with 
 a hammer upon an iron anvil, it detonates violently. 
 This is a dangerous experiment. When touched with a 
 hot wire or a lighted match, it burns instantaneously, 
 without leaving any residue ; when fire-arms are loaded 
 with it, it acts like gunpowder, but its explosive power 
 is much greater than that of the latter. Gun-cotton being, 
 therefore, an exceedingly dangerous substance, the 
 greatest caution is indispensable in conducting experiments 
 with it, and only very small quantities should be used at 
 once. Another kind of gun-cotton dissolves in a mixture 
 of alcohol and ether into a syrupy liquid, which on 
 spontaneous evaporation leaves the cotton behind in the 
 form of a transparent film. This solution is called collodion. 
 
312 EXPERIMENTAL CHEMISTRY, 
 
 It is used instead of court-plaster, and for making small 
 air-balloons, &c. 
 
 The chemical change which takes place in the manu- 
 facture of gun-cotton has already been described (page 305). 
 It is described by the formula : 
 
 Ce H,o 0 5 + 3 N O2 0 H = Ce H, (N 0^3 O5 + 3 H^O. 
 
 It appears to be a nitrate and not a nitro-compound. 
 
 The use of the sulphuric acid is to absorb the water which 
 is formed in the reaction, and thus keep the nitric acid at 
 its maximum strength. The explosive force of gun-cotton 
 is due to the large quantity of oxygen which it contains, 
 and to the fact that when burnt it is entirely converted 
 into gases, which occupy an enormously larger volume 
 than the substance itself. 
 
 Experiment 5. — Scraps of well-prepared gun-cotton may 
 be ignited on the palm of the hand without danger, in 
 consequence of the suddenness with which the change to 
 gas is effected. Spread a little gunpowder on a plate, 
 and rest a few grains of gun-cotton on it. The gun-cotton 
 can be inflamed without igniting the gunpowder. 
 
 STARCH. 
 
 A mealy substance, which is known under the name of 
 starch, or fecula, is deposited in most vegetables, particu- 
 larly at the period of ripening, from the juices with which 
 the cells of the plants are filled. 
 
 It appears to the naked eye like particles of meal, but 
 
 Fig. 93. 
 
 under a powerful microscope it is found to 
 consist of small, generally regular grains 
 or globules. Their position in the plant 
 is shown in the annexed figure, which re- 
 presents a section of some of the cells of a 
 potato. Potatoes, grain, and leguminous 
 plants are very rich in starch. 
 
 Potatoes. — Experiment 1 . — Easp some 
 potatoes on a grater, knead the pulp thus 
 obtained with water, and squeeze it in a 
 linen cloth ; the fibrous particles of the cells remain 
 behind, but the juice, together with a large portion of the 
 starch, runs through. If you let the turbid liquid remain 
 
STARCH. 
 
 313 
 
 quiet for some hours, it becomes clear, because the heavier 
 starch settles at the bottom. Now decant the liquid, wash 
 the starch several times with fresh water, allowing it to 
 settle each time, and then dry it in a moderately warm 
 place. 
 
 Experiment 2. — Heat in a flask the clear liquid decanted 
 from the starch ; it becomes turbid when the heat 
 approaches the boiling point, and, after boiling for a few 
 moments, deposits a flaky, greyish-white substance, which 
 is to be collected on a filter. It is the same substance 
 already referred to (page 310), vegetable albumin, character- 
 ised by its property of dissolving in cold and warm water, 
 but of coagulating in boiling water. It contains nitrogen, 
 which the starch does not. 
 
 Experiment 3. — Put some of the coagulated albumin 
 upon a piece of plat mum foil, and heat it over a lamp ; it 
 will burn and emit a very disagreeable empyreumatic 
 odour. When starch is treated in the same manner, it 
 also gives off an empyreumatic, but far less unpleasant 
 smell. Many nitrogenous substances comport themselves 
 in this respect like albumin ; many non-nitrogenous 
 substances, like starch ; therefore, when a piece of woollen 
 cloth is singed, it diffuses a far more disagreeable odour 
 than a piece of cotton or linen, because nitrogen is 
 contained in the wool, but not in the cotton or linen. 
 
 Experiment 4. — Mix twenty drops of sulphuric acid with 
 three ounces of water, and pour this acid water upon a 
 potato cut in thin slices ; after standing twenty-four hours 
 the slices are to be taken out, washed w ith water till they 
 no longer redden litmus and then dried. During this 
 process the potatoes lose their juices, and also their albumin 
 and colouring matter, and after drying, form a solid, 
 mealy, white, and tasteless substance, which swells up 
 and becomes soft when boiling water is poured upon it. 
 Potatoes dried without this treatment become grey and 
 horn -like, and acquire an unpleasant smell. 
 
 Peas, — Experiment 5 — Pour a handful of split peas into 
 a capacious vessel containing water, and let it stand for 
 some days in a warm room ; a great deal of water is 
 absorbed by the peas, causing them to swell up, and finally 
 to become so soft that they can easily be mashed between 
 
3U 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the fingers. When in this state, bruise them in a mortar, 
 and add sufficient water to form with them a thin paste, 
 which may be squeezed out by means of a linen cloth. 
 Here, also, we obtain, as from potatoes — 1, a fibrous substance, 
 which remains on the cloth ; 2, starch, which is deposited, 
 after standing, from the turbid liquid ; 3, vegetable albumin, 
 when the decanted liquid is heated to boiling. 
 
 Experiment 6. — When you have separated the vegetable 
 albumin, by boiling and filtering, from the above-mentioned 
 liquid, add to the latter a few drops of any acid ; a flaky 
 white body will again be deposited ; this is called legumin, 
 or vegetable casein (cheesy matter), on account of its great 
 similarity to the cheese contained in milk (animal casein) 
 in its composition and also in its properties. Vegetable 
 casein, like vegetable albumin, contains nitrogen ; but it is 
 distinguished from the latter by this, namely, that it is 
 not coagulated by boiling, though it is by acids. It occurs 
 in the juice of many plants, but it is most abundant in the 
 seeds of leguminous plants ; potatoes, likewise, contain 
 small quantities of it. 
 
 Wheat-flour, — Experiment 7. — Moisten a handful of wheat- 
 flour with sufficient water to form a stiff paste when 
 triturated in a mortar ; enclose it in a piece of thick linen, 
 and knead it frequently under water as long as the liquid 
 which runs through continues to have a milky appear- 
 ance. After standing some time, a white powder will 
 settle from the turbid water ; this is wheat starch. 
 
 Starch is one of the principal constituents of flour, as, 
 indeed, of all sorts of meal ; the second constituent re^ 
 mains behind in the cloth, mixed with vegetable fibre, and 
 is a viscous, tough, grey substance, which has received 
 the name gluten. The gluten only swells up in water, with- 
 out being completely dissolved ; in its constitution it 
 corresponds exactly with albumin, and, like this, con- 
 tains nitrogen. 
 
 When the water decanted from the starch is boiled, it 
 becomes turbid, and when partially evaporated, yields a 
 flocculent precipitate ; thus wheat-flour contains also some 
 vegetable albumin. 
 
 If the results of these experiments are grouped together, 
 we shall find that there are always present in potatoes and 
 
STARCH. 
 
 315 
 
 peas, and also in wheat-flour, the two non-nitrogenons 
 substances, vegetable tissue and starch, and also one or 
 several of the nitrogenous compounds, vegetable albumin, 
 casein, and fibrin. 
 
 These nitrogenous substances are often known as 
 albuminoid compounds. Small quantities of them occur in 
 the sap of every plant. We shall learn more of them in 
 the next chapter. 
 
 Potato starch exhibits, under the microscope, 
 the form of egg-shaped grains, consisting of 
 many scales overlapping each other ; it glistens 
 in the sun, is hard to the touch, and has 
 always more of a pulverulent than of a con- 
 crete character. 
 
 In the starch of peas many of the grains 
 are concave longitudinally, while others seem 
 to be formed by the growing together of 
 several globules. 
 
 Wheat starch consists of dull, flattened, len- 
 ticular, grains, which, when moist, readily 
 adhere to each other, on which account the 
 wheat starch of commerce always comes in 
 loose lumps. 
 
 Arrowroot is a starchy meal, which is prepared in the 
 East and West Indies from the roots of some marsh plants. 
 
 Experiment 8. — Heat in a vessel half a drachm of starch, 
 with an ounce or an ounce and a half of water, constantly 
 stirring it till it boils ; the mixture first becomes slimy, 
 and finally as thick as a jelly. The grains of starch 
 absorb water, and swell up, so that the single membranes 
 break open, though starch is not soluble in water. This 
 swollen starch is well known for its adhesive properties, 
 and is variously employed as a means of thickening print- 
 ing colours. When linen and other woven fabrics are 
 passed through a thin paste of starch, they acquire, after 
 
 Fig. 94. 
 
316 
 
 EXPERIMENTAL CHEMISTRY. 
 
 drying, a degree of stiffness, and by ironing or strong 
 rubbing and pressing, a bright gloss (starching). The 
 swelling of many of our most common articles of food, 
 such as rice, groats, barley, beans, peas, lentils, &c., when 
 boiled with water, is now readily explained by their 
 containing a large quantity of starch. 
 
 Experiment 9. — Dilute some starch paste with a large 
 proportion of water, and add to it a few drops of tincture 
 of iodine ; an intensely deep blue liquid (iodide of starcJi) 
 is produced. The same colour may be perceived by drop- 
 ping some tincture of iodine upon flour, potatoes, carrots, 
 &c. We have in iodine an extremely delicate test for 
 starch. Iodine compounds do not give this reaction, until 
 the iodine is liberated. When the blue compound is gently 
 heated, the colour is discharged, but reappears on cooling. 
 The reason of this is unknown. 
 
 DEXTRIN, OR BRITISH GUM. 
 
 Experiment 1. — If starch is heated in a ladle over a 
 gentle flame, and during the heating (roasting) is con- 
 stantly stirred to prevent its burning and baking on the 
 bottom of the ladle, it acquires after a while a yellow 
 colour, and then possesses the new property of dissolving, 
 both in cold and in hot water, into a mucilaginous liquid. 
 (Common starch is entirely insoluble in cold water, and 
 only swells up in hot water.) Starch thus transformed 
 is called dextrin, starch gum, or British gum. It is well 
 adapted for the thickening of colours and mordants in 
 calico-printing, and therefore is now prepared on an ex- 
 tensive scale, usually by roasting starch. It is not turned 
 blue by iodine as starch is. 
 
 Experiment 2.. — Mix thoroughly, in a small dish, half an 
 ounce of starch with one drachm of water and four drops 
 of nitric acid ; let the mixture dry in the air, and then 
 place it on the plate of a heated oven, which is just hot 
 enough to hiss feebly when touched with the moistened 
 finger. After some hours, all the nitric acid will be 
 expelled, and the starch will dissolve almost entirely in 
 cold water, and completely in hot water. Dextrin thus 
 made is white, or has ouly a slight yellowish tinge. 
 
 JiJxperiment 3. — Make a paste of potato starch by boiling 
 
DEXTRIN, OR BRITISH GUM. 
 
 317 
 
 starch with v ater, and while still hot, add to it in a saucer, 
 some drops of sulphuric acid with constant stirring. That 
 this acid effects a change is evident, for the viscid mass 
 very soon becomes a thin liquid. Now place 
 the saucer on a jar, in which some water is 
 simmering (steam-bath), and let it remain 
 over the hot steam (the contents of the saucer 
 not being heated quite to the boiling point) 
 until the liquid has become semi-transparent. 
 When this is the case, add prepared chalk by 
 small portions at a time to the liquid, until 
 it ceases to give an acid reaction, and after having 
 filtered it from the gypsum, leave it to evaporate in a 
 warm place. The dry residue has an amorphous, vitreous 
 appearance and little taste, and dissolves in water, forming 
 a transparent viscid fluid. It consists of dextrin and 
 sugar ; and if strong alcohol be added the dextrin is 
 thrown down. 
 
 Glucose, or Starch-sugar. — Experiment 4. — Eepeat the for- 
 mer experiment, with the following deviation. Bring to 
 brisk boiling two ounces and a half of water, to which 
 twenty drops of sulphuric acid have been added, and then 
 add one ounce of starch mixed with a little water, forming 
 a paste, but only in small quantities at once, that the 
 boiling may not be interrupted. When all the starch has 
 disappeared, let the mixture boil for some time, then 
 neutralise the acid with chalk, and evaporate the filtered 
 liquid to the consistency of a thick syrup. It possesses a 
 very sweet taste, and consists mainly of a solution of sugar 
 in water. The starch-syrup thus made, as well as the 
 white, solid starch-sugar, easily prepared from it, are new 
 both articles of commerce. 
 
 Starch, as shown by these experiments, is converted by 
 sulphuric acid, or moderate heating, into dextrin and 
 sugar ; on more prolonged heating, into sugar. In the latter 
 case, also, dextrin is first formed, but this soon passes 
 into sugar. 
 
 It has not yet been explained how this effect is pro- 
 duced. 
 
 Malt and Diastase. — Experiment 5. — Pour two ounces of 
 lukewarm water upon a quarter of an ounce of coarsely 
 
318 
 
 EXPERIMENTAL CHEMISTRY. 
 
 pulverised barley-malt; let the mixture remain some 
 hours near a fire or stove, or in the sun, and then strain it 
 through a linen cloth; there is found in the filtrate a 
 substance not yet well known, called diastase, by means 
 of which the starch may be converted into dextrin and 
 sugar in the same way as by sulphuric acid. 
 
 Experiment 6. — Eub a quarter part of the diastase with 
 some hot starch paste, made of a quarter of an ounce of 
 potato starch and two ounces of water ; heat the mixture 
 moderately, but not above 149° F. (65"^ C), until the paste 
 is formed into a thin, transparent liquid. Now strain 
 through a cloth, and let the liquid evaporate in a warm 
 place. The mass remaining behind contains a soluble 
 variety of starch, dextrin and maltose, the latter a kind of 
 sugar. 
 
 Experiment 7. — Treat the other three-quarters of the 
 diastase in the same way, but prolong the heating for 
 several hours, which may be most conveniently done 
 on the hearth of a stove or fireplace, applying to the 
 liquid a heat not above 158° F. (70° C.) or 167° F. 
 (75° C). Here dextrin and maltose are first formed ; but 
 the dextrin is converted on further heating into maltose, 
 as may easily be perceived by its taste. 
 
 The remarkable change which malt causes in starch 
 is to be ascribed to the diastase contained in the malt. 
 The mode in which the diastase acts is, however, un- 
 known. At 212° F. (100° C), consequently, on boiling 
 the liquid, the effect of the malt (diastase) is destroyed. 
 The process of forming sugar by means of the diastase 
 of malt is of great importance to the brewer and distiller, 
 aB in the manufacture of beer from barley or wheat, 
 or spirit from rye and potatoes, the starch of these 
 substances must always be previously converted into 
 sugar and dextrin, before fermentation and the consequent 
 formation of alcohol can take place. Beer always contains 
 dextrin, as will be seen if strong alcohol is added to it. 
 
 The taste of malt is sweet and mucilaginous, because 
 the conversion of the starch into dextrin and sugar 
 commences during germination, the further progress of 
 which is arrested in this case by drying. If the germi- 
 nated barley is allowed to continue growing, as it does 
 
GUMS. 
 
 319 
 
 in the open fields, all the starch gradually vanishes from 
 the grain, and passes, in the form of dextrin and sngar, 
 into the juice of the young plant, as is obyious from the 
 sweet taste of the latter, and from its mucilaginous feeling 
 when rubbed between the fingers. 
 
 A similar metamorphosis is also clearly to be perceived 
 in potatoes, and in fruits during their ripening. 
 
 GUMS. 
 
 From the stem and branches of some trees, such as the 
 cherry and plum trees, and some species of acacia, a 
 transparent viscid liquid exudes, which hardens into 
 globular masses. These exudations are called natural 
 gums. There are several kinds ; but the most important 
 are gum arable, gum Senegal, and gum tragacanth. The 
 characteristic ingredients of these gums are closely re- 
 lated in composition and properties to the starches and 
 sugars. 
 
 Gum Arabic, — The best known of these gums is gum 
 arabic, which exudes spotaneously from several species 
 of acacia in Africa. The finer sorts of it are white ; the 
 more common kinds have a yellow or brown colour. 
 When well dried, it is so hard and brittle that it may be 
 reduced to a powder by pounding. It is soluble in water. 
 
 Experiment 1. — Pour two drachms of cold water on one 
 drachm of gum arabic, and occasionally stir the mixture ; 
 the gum will, after a few days, entirely dissolve in the 
 water, forming a viscid transparent mucilage, which may 
 be diluted at pleasure with more water. This mucilage 
 has great adhesiveness, for which reason it is often used, 
 instead of paste or glue, for joining together paper, &c., 
 or for converting a pulverulent substance into a coherent 
 mass (crayons, pastilles, &c.) ; it has, moreover, a thick 
 consistency, and hence is variously employed in calico- 
 printing as a thickening material for colours and mordants, 
 and in finishing and dressing operations. A variety of 
 gum obtained from the shores of the Senegal, whence it 
 has been called gum Senegal, is peculiarly well adapted 
 for the latter purpose, as it yields a thicker mucilage 
 than the common gum arabic. 
 
 Experiment 2. — Pour some drops of mucilage of gum 
 
820 
 
 EXPERIMENTAL CHEMISTRY. 
 
 arabic into alcoliol ; they will not mix with each other, 
 as the gum is insoluble in alcohol. If the mucilage is 
 previously mixed with water and a little dilute hydro- 
 chloric acid, and is then added to the alcohol, a turbidity 
 ensues, and afterwards a flaky precipitate will subside ; 
 accordingly, alcohol may be used for removing gum from 
 those liquids which contain it. The precipitate consists 
 of the substance called arahin, or arabic acid, which in the 
 gum is combined with lime, magnesia, and potash. 
 
 Gum tragacanth is also a vegetable exudation, well- 
 known as a stiffening material, and as forming with 
 water an adhesive paste ; it exudes from a shrub which 
 grows in Greece and Turkey, and it occurs in commerce 
 in the form of white, tortuous filaments, or bands. It 
 contains arabin and another compound called hassorin, 
 
 SUGARS. 
 
 Glucose. — We have already seen how cellulin, starch, 
 and dextrin may be converted into a kind of sugar. We 
 shall afterwards find that ordinary sugar, or sucrose, can 
 be changed into glucose with even greater ease. There 
 are two varieties of glucose, which, from the direction in 
 which their solutions deflect a ray of polarised light, are 
 called dextro- glucose and levo-glucose. They are, however, 
 identical in composition, and nearly identical in chemical 
 properties, so that their separate study need not occupy 
 us. 
 
 Glucose is formed also in many vegetables, and is 
 especially abundant in fruits ; as, for example, in plums, 
 cherries, pears, figs, grapes, &c. Honey and the white, 
 sweet grains in raisins, consist of it. On account of this 
 origin, glucose is sometimes called grape-sugar. 
 
 If you taste a dried granule of sugar from a raisin, and 
 then a little common sugar, you will at once perceive 
 that the former is much less sweet than the latter; one 
 ounce of common sugar has the same sweetening power 
 as two ounces and a lialf of grape-sugar. The solubility 
 of these two varieties of sugar in water is likewise very 
 different, grape-sugar dissolving in it much less readily 
 and more slowly than common sugar. 
 
 Sucrose or Cane-sugar, — Is found naturally in the sugar- 
 
SUGARS. 
 
 321 
 
 cane, beet-root, maple, and many fruits. It has not as 
 yet been prepared by any artificial process. 
 
 The operations whereby cane-sugar is obtained on a 
 large scale are the following : 
 
 1. Expressing the juice from the sugar-cane or the 
 rasped bulb of the beet, either by strongly squeezing, or 
 by hydi ostatic pressure. 
 
 2. Boiling down the juice with the addition of lime, by 
 which several foreign substances are precipitated, until 
 it acquires the consistency of a thick syrup ; on cooling, 
 the crude sugar is deposited from it, in brownish-yellow 
 crystalline grains (raw sugar, or Muscovado sugar). 
 The liquid sugar which does not crystallize is allowed 
 to drain off, and forms the well-known treacle (mo- 
 lasses). 
 
 3. Befining the raw sugar — that is, the removal of the 
 brown syrup still adhering to it. This is done — a), by 
 redissolving the raw sugar in a little water and filtering ; 
 h), by a second filtration through coarsely-ground animal 
 charcoal, which retains the colouring matter ; c), by 
 evaporating the clarified solution in vacuum pans. The 
 concentrated syrup is then allowed to cool in moulds of a 
 conical shape, stirring it frequently to disturb the crystal- 
 lization. A solid mass, consisting of small fragmentary 
 qrystals, the common loaf-sugar, is obtained, from which 
 the remaining liquid sugar is removed by causing a 
 concentrated solution of crystallizable sugar to percolate 
 gradually through. The thoroughly purified and glisten- 
 ing white sugar is called refined loaf-sugar ; that which 
 is not so completely clarified, and has a yellowish tinge, 
 is the common loaf-sugar. 
 
 Experiment 1. — Dissolve half an ounce of sugar in a 
 quarter of an ounce of hot water ; the viscous solution is 
 called ivhite {simple^ syrup. If this solution is put in a 
 cup, and set aside in a warm place, and evaporated slowly, 
 the sugar will separate from it, crystallizing in oblique 
 prisms. In a similar manner white sugar candy is pre- 
 j)ared on a large scale from refined sugar, brown candy 
 from raw sugar. As the crystals deposit more readily on 
 substances having a rough than on those having a smooth 
 surface, fine threads or pieces of wood are stretched 
 
 Y 
 
322 
 
 EXPERIMENTAL CHEMISTRY. 
 
 across the vessels containing the syrup, and they soon 
 become coated with crystals. 
 
 Cane-sugar, as already stated, has a much sweeter taste 
 than grape-sugar; therefore, when used as a sweetening 
 agent, it possesses a far greater value than the latter. 
 
 Experiment 2. — Put two or three lumps of sugar in a 
 breakfast cup standing in a basin, moisten them with 
 boiling water, and then add about twice the bulk of strong 
 sulphuric acid. The acid removes the elements of water 
 from the sugar, the mixture swells up enormously, and a 
 black mass of charcoal remains : 
 
 Ci2H2Ai-llH20 = 12C. 
 
 Experiment 3. — The two sorts of sugar may be accu- 
 rately distinguished from each other by the copper test. 
 First add, in test-tubes, to very dilute solutions of each 
 kind of sugar, some drops of a solution of copper sulphate 
 then excess of solution of potash. No turbidity occurs 
 in either case, as sugar prevents the precipitation of 
 copper as cupric hydrate. Place both tubes in boiling 
 water; the liquid containing the grape-sugar assumes in 
 a few minutes a reddish-yellow colour, while that con- 
 taining the cane-sugar remains blue. The grape-sugar 
 is able to abstract oxygen from the cupric salt, whereby 
 reddish-yellow cuprous oxide is formed. Cane-sugar, 
 when long boiled with the copper test, will also reduce 
 the copper, but only because it first passes into glucose. 
 Grape-sugar may be distinctly recognised by this test, 
 even in an extremely diluted solution. 
 
 FeJding's test. Experiment 4. — Dissolve 30 grains of 
 crystallised cupric sulphate in a little water. In another 
 portion of water dissolve 3J ounces of Eochelle salt 
 (tartrate of potassium and sodium) and 2i ounces of 
 caustic 1 otash. Mix the solutions and dilute with water 
 to one pint. 
 
 Tiie br ght blue solution so obtained is excellent for 
 sugar testiug. It may be boiled without change, but on 
 the addition to the boiling liquid of a dilute solution of 
 glucose, maltose, or lactose a red precipitate of CU2O is 
 at once formed. One-third ounce of the solution would 
 be decolorized by about 2 grains of glucose. 
 
SUGARS. 
 
 323 
 
 Experiment 5. — Boil in a dish half an ounce of sugar 
 with one drachm of water, until the viscous solution 
 begins to assume a yellowish tinge ; then pour it upon a 
 plate previously smeared with a little olive oil. The 
 transparent brittle mass is melted sugar in an amorphous 
 state (barley-sugar). The sugar is first dissolved by the 
 water ; on boiling, the water is again evaporated, and 
 the sugar passes gradually from the dissolved to the 
 melted state. The yellowish colour indicates that all the 
 water has passed off and that the sugar is on the point 
 of becoming burnt. 
 
 If the transparent sugar is kept for some weeks, it 
 becomes opaque and crystalline, returning to its original 
 condition. 
 
 Experiment 6. — Repeat the former experiment, but 
 without stopping the heating on the appearance of the 
 yellow colour ; the sugar will grow darker, until it finally 
 attains a brownish-black colour, and exhales, at the 
 same time, a peculiar empyreumatic odour. On cooling, 
 it is obtained as a hard, almost black mass, which soon 
 deliquesces in the air, forming a dark syrup, which is 
 called caramel or burnt sugar, A couple of drops of it 
 impart to a large vessel filled with water the appearance 
 of Jamaica rum. On account of its strong colouring 
 properties, burnt sugar is much used for imparting to 
 liquors — vinegar, alcohol, &c. — a yellow or brown colour. 
 
 Experiment 7. — When exposed to a still stronger heat, 
 the sugar becomes charred, and finally burns like wood, 
 as may easily be seen by holding a piece of it on platinum 
 foil over an alcohol flame. The flame indicates also that 
 inflammable gases are evolved. Pure sugar leaves scarcely 
 any residue. If it contains lime, white ashes remain 
 behind upon the foil, which do not volatilise even at the 
 strongest heat. 
 
 Experiment 8. — If you add a few drops of dilute sul- 
 phuric acid to a dilute boiling solution of sugar, and 
 continue to boil for some time, a liquid is obtained which 
 does not crystallize on evaporation. If you now apply 
 the copper test, you will find that it contains grape- 
 sugar ; cane-sugar is therefore converted by boiling with 
 sulphuric acid into grape-sugar. This metamorphosis is 
 
324 EXPERIMENTAL CHEMISTRY. 
 
 produced also by fermentation. If sugar is boiled for a 
 long time with diluted sulphuric acid, it finally passes 
 into a brown substance, resembling humus. When boiled 
 with nitric or other acids, which yield oxygen, it oxidises 
 first into saccharic acid, then into oxalic acid, and finally 
 into carbonic acid and water. 
 
 Sugar, as though it were an acid, can combine in fixed 
 proportions with oxide of lead, lime, and many other 
 bases ; but it thereby loses its sweet taste. 
 
 Lactose^ or Milk-sugar^ is that particular kind of sugar 
 which occurs in milk, and imparts to it its agreeable 
 sweetish taste. It is obtained in hard, white, crystalline 
 masses, by evaporating the sweet whey. Sugar of milk 
 is much less sweet to the taste than grape-sugar, and 
 requires six parts of cold water for its solution. Like 
 glucose it reduces copper. It is well known that milk 
 becomes sour by standing for some days ; this is owing 
 to the sugar of milk being gradually converted into a 
 peculiar acid, called lactic acid. 
 
 C12H22OH + H2O = 4 C3H6O3. 
 
 Mannite, CgH^^Oe, is a substance resembling sugar, 
 constituting the principal part of manna (the concrete 
 sweet juice of some species of the ash, growing principally 
 in Italy). 
 
 Although the composition of the preceding compounds 
 cannot yet be said to be established, it appears highly 
 probable that they are closely related to alcohols of high 
 valency. It is indeed known that mannite, CeHj^Oe, is a 
 true hexatomic alcohol, and that its formula should be 
 written CoH8(OH),3. The fact that glucose, by combining 
 with hydrogen, yields mannite, would seem to indicate 
 that it stands to the latter compound in the same relation 
 that aldehyde does to alcohol : 
 
 Alcohol C^H^O. 
 Aldehyde G^H^O. 
 
 Mannite C0H14O6. 
 Glucose CGHi20t5- 
 
( 325 ) 
 
 CHAPTER lY. 
 
 ALBUMINOID GROUP. 
 
 The members belonging to this group are among the 
 most complex and least understood of compounds. They 
 are found both in the animal and vegetal kingdoms, and 
 are essentially necessary to the processes of life. No 
 animal can live unless its food contains one or more of 
 them, and they are, therefore, sometimes spoken of as the 
 nitrogenous, or fiesh- forming elements of food. They 
 contain five, or even six elements, and they resemble one 
 another so closely in composition as to suggest tbe idea 
 that they are all modifications of some one substance. 
 But no satisfactory formulsB can be deduced for them, and 
 their composition must, therefore, be expressed in parts 
 per cent. The following analysis of albumin may be 
 given as an example. The simplest formula which can be 
 deduced from it is Cy2Hii2^i8S022. 
 
 Carbon . 
 
 . 53 
 
 3 
 
 Hydrogen . 
 
 7' 
 
 1 
 
 Nitrogen . 
 
 . 15' 
 
 7 
 
 Sulphur 
 
 1 
 
 8 
 
 Oxygen 
 
 . 22 
 
 1 
 
 
 100 
 
 0 
 
 The following are the m 
 group : 
 
 Albumin 
 Fibrin 
 
 Casein, or Legumin 
 Ossein, or bone cartilage 
 Gelatin 
 
 5t important members ot this 
 
 Derived both from animals 
 and vegetables. 
 
 Derived only from 
 animals. 
 
326 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The first three, as found in the vegetable kingdom, have 
 been described to some extent in the last chapter. Gluten, 
 obtained by washing wheat flour (page 314), appears to 
 be a mixture of substances like casein and fibrin. When 
 it is boiled with alcohol the former dissolves, and can be 
 obtained by evaporation. 
 
 Albumin. — The icliite of eggs consists of cells, in which 
 is contained a colourless alkaline liquid, the albumin. On 
 evaporation, we obtain from it one-eighth of solid albumin, 
 the rest is water. When burnt, it leaves behind common 
 salt, carbonate, phosphate and sulphate of sodium, and 
 phosphate of calcium. That albumin, when briskly beaten 
 up, yields a porous light froth, that it becomes insoluble 
 and coagulates by heating, &c., are well-known facts. 
 On account of the latter property, it is used for clarifying 
 turbid liquids, » especially saccharine juices. 
 
 Experiment 1. — Stir up some honey in warm water, add 
 a little albumin to the turbid solution obtained, and heat 
 the mixture to boiling. The albumin seizes upon the 
 foreign substances floating in the liquid, bears them to 
 the surface, and incloses them within itself as it coagulates ; 
 the liquid thereby becomes clear and transparent, and 
 may be separated by a strainer from the coagulated 
 albumin. 
 
 Experiment 2. — Add water to the white of a fresh egg, 
 and stir. As the cells break up a solution of albumin is 
 obtained, which after standing may be poured off from the 
 fibrous residue. With this solution several experiments 
 may be made. 
 
 1. Boil a little in a test-tube, and observe that it 
 becomes opaque (coagulates). 
 
 2. Add to fresh portions of the solution small quantities 
 of dilute nitric acid, strong alcohol and solution of mer- 
 curic chloride (corrosive sublimate). In each case the 
 albumin will become insoluble. 
 
 3. Other portions may be treated with acetic acid, with 
 common salt, and with many other substances, without 
 any precipitate being produced. It is therefore seen that 
 some acids and salts coagulate albumin while others do not. 
 
 The yolJc of eggs consists of albumin holding in suspension 
 yellow drops of oil. On account of the albumin contained 
 
ALBUMINOID GROUP. 
 
 327 
 
 in if, it coagulates when heated, and the fat {oil of the yolk 
 of eggs) may be extracted from it by strong pressure, or 
 by agitation with ether. Phosphorus is contained in the 
 oil of yolk of eggs. 
 
 We shall soon see that albumin is contained in the 
 blood. It is also an important constituent of the juice of 
 flesh. 
 
 Fibrin. — The solid substance of muscular tissue (flesh) 
 consists of this compound, which is also present (or a 
 substance similar to it) in a soluble condition in the blood. 
 From the latter it can readily be obtained, though only in 
 the insoluble form. The blood consists of a clear pale- 
 yellow liquid, the plasma, or liquor sanguinis, in which 
 float innumerable red discs like pieces of money, which 
 are called the red corpuscles. To these the colour of the 
 blood is due. 
 
 Experiment 1. — If you let the freshly-drawn blood of an 
 animal remain standing quietly in a vessel, it will, in a 
 short time, undergo a change ; it coagulates, forming a 
 dark-red jelly (clot, coaguluin), which contracts on longer 
 standing, and a yellowish liquid is separated (serum). 
 When the latter is heated to boiling, it coagulates to a 
 white jelly ; the serum consists mainly of a solution of 
 albumin. There are two substances in the coaguJum, one 
 of which called haemoglobin dissolves by washing in water, 
 yielding a red solution (colouring matter of the blood, the 
 principal constituent of the blood corpuscles), while the 
 other remains behind as a white fibrous mass (blood fibrin). 
 Accordingly, the most important proximate constituents 
 of the blood are water, albumin, blood corpuscles, and 
 animal fibrin, which, on the standing of the blood, are 
 transposed in the following manner : 
 
 From Water, Albumin, Blood Corpuscles, Fibrin, 
 are formed Serum and Coagulum. 
 It is a distinguishing peculiarity of the colouring matter 
 of the blood, that it always contains iron. 
 
 Experiment 2. — If the blood freshly drawn from the 
 veins is beaten up during cooling, it does not coagulate ; 
 the fibrin certainly becomes insoluble, but it separates as 
 a thread-like coherent mass, which, when kneaded for 
 
328 
 
 EXPERIMENTAL CHEMISTRY. 
 
 some time with water, "becomes finally grey, and, after 
 drying, resembles the muscular fibre. Indeed, it may be 
 regarded as half-formed flesh, since it has the same 
 composition, and the flesh of the animal body is formed 
 from it. The blood remaining behind {wJiipped blood) 
 retains, after the separation of the fibrin, its red colour, 
 and coagulates on boiling to a jelly of a dark-red colour, 
 as may be perceived in the so-called hlach-puddings. The 
 metamorphosis of the blood just treated of is, accordingly, 
 as follows : 
 
 Water, Albumin, Blood Corpuscles Fibrin 
 
 remain liquid. becomes solid. 
 
 Casein, — This substance, which constitutes the curd of 
 milk, resembles one variety of albumin which is obtained 
 by the action of dilute alkali on ordinary albumin. It 
 has already been mentioned that it agrees in composition 
 and properties with the legumin which is obtained from 
 peas and beans. The following short account of milk 
 includes a sufficient study of casein. 
 
 Milk. — Milk consists of a solution of casein and sugar of 
 milk, in which solution small globules of oil are held sus- 
 pended. The latter render the milk opaque, and give it 
 the appearance of an emulsion. The casein appears to 
 exist in the milk in the form of a soluble sodium com- 
 pound, and is therefore thrown down when the sodium is 
 removed by means of an acid. 
 
 Ex]periment 1. — The oil globules cannot be separated 
 from the milk by filtration alone, as they are so small 
 that they pass with it through the pores of the finest 
 paper ; but it may be accomplished in the following 
 manner : Dissolve an ounce of sodium sulphate and a 
 couple of grains of sodium carbonate in half an ounce of 
 lukewarm water, and agitate the solution with half an 
 ounce of fresh milk. If you now transfer this mixture to 
 a filter, the fatty portions (cream) remain behind, while a 
 liquid, only slightly opalescent, passes through. The 
 saline solution added does not act chemically upon the 
 constituents of the milk, but it only acts mechanically, 
 causing the globules to form a more compact mass, and to 
 be more readily separated from the watery liquid. 
 
ALBUMINOID GROUP. 
 
 329 
 
 Experiment 2. — If you add to the filtered liquor a few 
 drops of hydrochloric acid, the casein separates from it as 
 a white flaky mass ; accordingly, the animal casein is 
 coagulated and rendered insoluble by acid, in the same 
 manner as vegetable casein. Pure casein is insoluble in 
 water, but it dissolves in it when alkalies are present. 
 
 Experiment 8. — If you filter the casein from the liquid, 
 and then boil the latter, it again becomes turbid, although 
 less so than before. It is the albumin which separates, 
 small quantities of it being present in all milk. 
 
 Experiment 4. — Let a small piece of the dried membrane 
 of the stomach of a calf (^rennet) remain standing one night 
 in a small quantity of water, and afterwards mix this 
 water with a quart of new milk ; the milk, after having 
 stood for some hours in a warm place, will coagulate into 
 a gelatinous mass, which is to be put upon a filter. What 
 remains behind consists of an intimate mixture of the 
 curdled casein with globules of fat. By pressing and drying, 
 we obtain from it the so-called cream- or neio milk-cheese. 
 
 Experiment 5. — Separate the filtered liquid (siveet ivhey) 
 from its albumin by boiling, and, having again filtered 
 it, evaporate until only a few ounces of it remain. If left 
 in a warm place, hard, prismatic white crystals of sugar of 
 milk will be deposited (page 324). By this method sugar 
 of milk is procured on a large scale. Consequently the 
 sweet whey is to be regarded principally as a solution of 
 sugar of milk (together with some albumin and some 
 salts) in water. 
 
 Experiment 6. — Dissolve again in water the sugar of 
 milk obtained, and put a piece of rennet in the solution ; 
 the liquid will soon iDecome sour in a warm place, because 
 the sugar of milk is converted into lactic acid. 
 
 Experiment 7. — The coagulation of the milk, which was 
 produced by the rennet in a few hours, is effected 
 instantaneously by the addition of acids^ as is rendered 
 obvious by adding a few drops of some acid to warm milk. 
 In this curdled mas?s are contained all the casein and 
 fatty particles of the milk (cheese and butter). 
 
 Experiment 8. — Fill a bottle with fresh milk, close it, 
 and keep it inverted, from twenty-four to thirty-six 
 hours, in a cool place ; then loosen the stopper a little, so 
 
330 
 
 EXPERIMENTAL CHEMISTRY. 
 
 that the lower, thinner portion of the milk (blue or shim 
 milk) may run off, but the upper, thicker part (cream) 
 remain behind. On standing, the lighter oil-globules of 
 the milk ascend, and form on the surface the well-known 
 fatty, thick cream. If this is shaken for some time, the 
 membranes of the oil-globules are torn, and the latter 
 then unite together, forming masses of butter. The thin 
 milk which passes off from beneath may be separated, in 
 the way already described, into casein, albumin, and 
 sugar of milk. 
 
 Experiment 9. — If you let milk stand for some time in 
 open vessels, its sugar of milk is gradually converted into 
 lactic acid (p. 824), and this, like every other acid, causes 
 a curdling of the milk, and, at the same time, its well- 
 known sour taste. But the curdling first commences 
 after most of the oil-globules have collected on the surface 
 (sour crenm). From this cream butter is often prepared, 
 and therefore the buttermilk remaining (a mixture of 
 curdled casein, lactic acid, and water, with some particles 
 of butter remaining behind) has an acid taste. The so- 
 called curd beneath the cream now contains only traces 
 of fat, and consists accordingly of water, lactic acid, 
 and coagulated casein. By pressing we obtain from it 
 the sour ivJiey, and, as a residuum, the coagulated casein, 
 from which common sJcim-milk cheese is made. When kept 
 damp this undergoes a kind of putrefaction, and a soft 
 saponaceous mass is produced. If the putrefaction ad- 
 vances still farther, there will be finally generated also 
 volatile compounds of strong smell (ordinary cheese). 
 
 Gelatin. — The organic matter (about one- third) of bones 
 consists of a compound called ossein, or hone cartilage, which 
 is insoluble in water, but which, after prolonged boiling, 
 changes into the well-known substance gelatin, which, 
 though scarcely soluble in cold water, dissolves easily in 
 hot. The skin and some other parts of the animal body 
 experience the same change when long boiled with water. 
 If the water is made to boil at a higher temperature 
 (about 220° F., or 105° C), by enclosing it in a strong 
 iron vessel, the conversion is effected much more rapidly, 
 as it is also by superheated steam. Isinglass, which is pre- 
 pared from the air-bladder of the sturgeon, is nearly pure 
 
ALBUMINOID GROUP. 
 
 331 
 
 gelatin. Glue and size^ prepared from the hides, carti- 
 lages, &c., of animals, are impure gelatin. 
 
 Experiment 10. — Immerse a bone in a large jar of hydro- 
 chloric acid diluted with nine parts of water, and allow it 
 to remain for a day or two. The acid will dissolve out 
 the mineral jDortion of the bone, consisting chiefly of 
 tricalcium phosphate, CagPgOg, and a tough, cartilaginous 
 and semi-transparent mass of ossein^ having the form of the 
 bone, will remain. The calcium phosphate can be precipi- 
 tated from the acid solution by the addition of ammonia. 
 The ossein can, after thorough washing, be converted to 
 gelatin by boiling it for some hours. 
 
 The average composition of bone may be stated roughly 
 as follows : 
 
 Ossein .... 
 Tricalcium phosphate 
 Calcium carbonate . 
 Calcium fluoride 
 Magnesium phosphate 
 
 57 
 8 
 1 
 1 
 
 100 
 
332 
 
 EXPERIMENTAL CHEMISTRY. 
 
 CHAPTER V. 
 
 FERMENTATION. — ETHYL COMPOUNDS. 
 
 The compounds described in the last chapter, when 
 exposed to the air in a moist state and between certain 
 limits of temperature, experience a peculiar change, whict 
 is called joutrefaction. They decompose and are converted 
 into simpler compounds, some of which are gaseous, and 
 possess a foetid odour. This change, which is an example 
 of many similar ones which are known, is due to the 
 absorption from the air of minute germs — seeds, or eggs — 
 of low forms of life. If air be entirely excluded, the 
 change cannot take place, because the germs cannot 
 enter ; but when once commenced it will continue with- 
 out any assistance from the air. The organisms develope 
 and reproduce themselves; they feed on the compounds 
 with which they are in contact, and throw out as 
 excretions the compounds which we know as products of 
 putrefaction. 
 
 It is certain that very minute organised germs of many 
 kinds float constantly in the atmosphere, ready to develope 
 and increase whenever they meet with suitable food and 
 suitable conditions of temperature, moisture, &c. Some 
 have been detected, and their developments studied with 
 great care, but even the existence of many of them can 
 only be inferred from their effects. 
 
 FERMENTATION. 
 
 The albuminoid substances, when in a state of incipient 
 putrefaction, have a remarkable power of causing decom- 
 positions in solutions of sugar. These changes, which are 
 akin to putrefaction in their nature, are effected by peculiar 
 organisms, the germs of which are derived from the air. 
 
FERMENTATION. 
 
 333 
 
 The organisms feed on the albuminoid substances and 
 sugar jointly, and thereby convert them into new and 
 simpler compounds, which are distinguished from the 
 products of putrefaction by being, for the most part, 
 destitute of offensive odour. Changes of this kind are 
 called fermentations^ and the substances which produce 
 them ferments. There are several kinds of fermentation, 
 but the most important is that known as vinous^ or alcoholic 
 fermentation. 
 
 Experiment 1. — Half an ounce of honey (nearly pure 
 glucose) is dissolved in four ounces of water and some 
 gluten or flour, which has been kept in a warm room for 
 about a week till it has begun to putrefy, is added to it ; 
 the liquid is then put in a moderately warm place, from 
 64° F. (18° C.) to 75° F. (24° C), when it soon eaters 
 into fermentation, with the 
 evolution of a large quantity 
 of gas. If you perform the 
 experiment in a bottle fur- 
 nished with • a bent glass 
 tube, one end of which is 
 passed under. a second bottle, 
 filled with water, which is 
 inverted over the pneumatic 
 trough, the gas may easily 
 be collected ; it consists of carbonic anhydride. If the 
 liquid still retains a sweet taste after the evolution of the 
 gas has ceased, add another portion of the gluten to it, 
 whereby the fermentation is again renewed. Finally, all 
 the saccharine taste will have disappeared, and the liquid 
 will have acquired a spirituous flavour. The fermented 
 liquor is called mead ; instead of grape-sugar it contains 
 alcohol, and this is the cause of its intoxicating effect. 
 A portion of the gluten is found at the bottom of the 
 vessel, converted into a brownish residue. 
 
 Yeast. — While the foregoiog process is going on, the 
 liquid contains a multitude of minute egg-shaped bodies 
 called yeast-cells, because yeast is mainly composed of 
 them, which are the agents by which the sugar is con- 
 verted into alcohol and carbonic anhydride. Yeast is, of 
 course, the most powerful of ferments. 
 
334 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The change whicli grape-sugar undergoes in fermenta- 
 tion is represented in the following formula : 
 
 Glucose. Alcohol. Carb. Anhydride. 
 
 CgHi^Oe = 2C2H6O + 2CO2. 
 
 But some other compounds are also formed in small 
 quantity during the fermentation. Of these the higher 
 alcohols, glycerin, and succinic acid, may be mentioned. 
 
 Experiment 2. — Kepeat the former experiment, adding, 
 instead of the gluten, a teaspoonful of yeast, or a few- 
 fragments of the German dried yeast ; the fermentation 
 will now proceed more rapidly and regularly. 
 
 Experiment 3. — Instead of honey, take a solution of cane- 
 sugar and add some yeast to it. In this case the fermen- 
 tation will not begin so soon, for the cane-sugar has 
 first to take up the elements of water and change to 
 grape-sugar : 
 
 C12 Oil + H2 0 = 2 Cg Og. 
 
 WINE. 
 
 All sweet vegetable juices pass spontaneously into fer- 
 mentation without the necessity of adding to them a fer- 
 ment, because they always contain sugar and albuminous 
 substances, in which yeast cells will soon develope. 
 
 Experiment 1 . — Submit freshly expressed beet-juice to a 
 temperature of from 20° to 25° C. (68° to 77° F.) ; the 
 juice will soon effervesce, deposit a sediment, and be con- 
 verted into a spirituous liquid (beet-wine). 
 
 In the same manner currant and gooseberry wines are 
 prepared from currants and gooseberries, cider from 
 apples, the so-called cherry-water by fermenting and 
 afterwards distilling cherry-juice, rum by fermenting and 
 afterwards distilling the juice of the sugar-cane, &c. 
 
 The most common of all the fermentations of this kind 
 is the fermentation of grape-juice, wine being the result. 
 In order to prepare white wine, the grapes are pressed, the 
 juice (must) is poured into vats and allowed to remain in 
 them in the cellar, where, as the temperature is tolerably 
 low, the fermentation proceeds so slowly that it is not com- 
 pleted until after some months. The new wine is racJ^ed 
 off from the lees, and poured into fresh vats ; it still con- 
 
WINE. 
 
 335 
 
 tains a small quantity of sugar and albuminous matter, 
 which are both gradually converted, the former into 
 alcohol and carbonic anhydride, the latter into lees 
 (^secondary fermentation). In the manufacture of red luine^ 
 the purple grapes ar e bruised, and then fermented, together 
 with their skins and stalks ; by which means a red 
 colouring matter is extracted from the skins, and tannin 
 from the stalks and seeds, the tannin imparting to this 
 kind of wine its astringent taste. SparTcling wine (Cham- 
 pagne) is made' by allowing the secondary fermentation 
 to take place in corked-up bottles, whereby the carbonic 
 anhydride formed is retained in the wine. 
 
 The acidity of most wines is due to tartar or argol (acid 
 potassium tartrate, KHC^H^O^), which is contained in 
 grapes. A good deal of this subsides when the wine is 
 kept. Minute crystals of it are often seen on the corks of 
 claret bottles. 
 
 Many wines, champagne for instance, are sweetened by 
 the addition of sugar, and some (port and sherry) are 
 fortified, or rendered stronger, by the addition of spirit. 
 
 Experiment 2. — If some wine is put into a retort, and 
 subjected to distillation to 
 a moderate heat, at first 
 the more volatile alcohol, 
 together with certain frag- 
 rant ethers, will pass over. 
 A very agreeably smelling 
 spirit is thus obtained, 
 known in commerce under 
 the name of Cognac, or 
 French brandy. In the wine 
 countries, the lees remain- 
 ing after the wine is racked off, are generally used 
 for this- purpose, since, in the swollen, pap-like state in 
 which they settle in the vats, they retain mechanically a 
 large quantity of wine. 
 
 BEER. 
 
 The manufacture of beer differs essentially from that of 
 wine in this respect : that materials are employed which 
 contain very little sugar already formed, but instead of it 
 
336 
 
 EXPERIMENTAL CHEMISTRY. 
 
 starchy such as barley, wheat, rye, potatoes, &c. Starch 
 cannot, like sugar, be resolved directly into alcohol and 
 carbonic acid ; and, when employed in the manufacture of 
 alcohol, it must previously be converted into sugar. This 
 conversion is effected by the diastase of the barley-malt in 
 the so-called mashing process of the brewers and distillei s 
 (page 318). 
 
 Experiment 1. — Pour a mixture of an ounce and a half of 
 cold water and two ounces of boiling water upon half an 
 ounce of bruised malt, and set it aside for some hours in a 
 warm 23lace, where it will keep a temperature of from 
 65° to 75° C. (149° to 167° F.) ; a sweet liquid is thus 
 obtained, composed not only of dextrin and maltose, but 
 containing also the altered gluten, thereby rendered 
 soluble, which was present in the malt. The brewer calls 
 this liquid the wort. Strain it with pressure through a 
 cloth, and boil the liquid for some time until it becomes 
 clear and transparent ; then let it cool to 86° F. (30° C), 
 and add to it a teaspoonful of yeast ; it will soon begin to 
 ferment, and after some days will clarify again ; the clear 
 fermented liquor is beer. This is the mode of making the 
 Berlin ivJiite or pale beer, which is not bitter. If during 
 the boiling some hops (flowers of the hop-plant) are added 
 to the wort, an aromatic bitter substance is dissolved from 
 them, which not only imparts to the beer a pleasant and 
 bitter taste, but also makes it keep better. ; 
 
 What is particularly remarkable in the above fermenta- 
 tion (^surface fermentation) is the great quantity of yeast 
 that is formed. It is called surface yeast, it being raised 
 to the surface in consequence of the great evolution of 
 carbonic anhydride, and if the casks are full, it is forced 
 out of the bunghole ; it is the best yeast, and the quantity 
 obtained in the last experiment is sufficient to bring to 
 complete fermentation the wort of a whole pound of malt. 
 
 Its power of exciting fermentation is destroyed 
 when it is rendered quite dry, or when it is 
 boiled, or very finely triturated ; and likewise 
 by mixing antiseptic substances with it, as, for 
 instance, alcohol, carbolic acid, sulphurous acid, 
 volatile oils, &c. I'his yeast, when examined 
 through the microscope, has the form of simple cells (a) ; 
 
SPIRITS. 
 
 337 
 
 and their increase in the wort takes place in the same 
 manner as in the most simple plants, new cells or buds 
 developing themselves on each globule of the old yeast. 
 
 New beer contains, also, some sugar and gluten in solu- 
 tion ; therefore, like wine, it undergoes, when kept, a 
 second slight fermentation (secondary fermentation). If 
 this is allowed to take place in well-stopped bottles, so 
 that the carbonic anhydride cannot escape, a foaming beer 
 (bottled beer) is obtained, in the same way as in the manu- 
 facture of sparkling Champagne. 
 
 But all the gluten is not separated, even by the second 
 fermentation, and hence the beer undergoes a still further 
 change on being exposed to the air ; it is the alcohol, how- 
 ever, which is now altered by the albuminous matter 
 undergoing decomposition ; it passes into vinegar, and the 
 beer becomes acid (acetous fermentation). 
 
 Experiment 2. — Eepeat the former experiment, but cool 
 the wort below 50° F. (10° C.) before adding the yeast, 
 and then let the liquid remain in a cool place ; a very slow 
 fermentation takes place, which will not be completed 
 for several weeks, perhaps even months. During this pro- 
 cess, the carbonic acid is evolved in very small bubbles, and 
 the yeast settles at the bottom of the vessel (bottom fermenta- 
 tion, bottom yeast), German beer is made in this way. 
 
 SPIRITS. 
 
 The preparation of spirit is similar to that of beer, 
 inasmuch as the substances containing starch are employed 
 in the preparation of it, and as the starch must first be 
 converted into sugar before the fermentation can proceed. 
 This is done, as in the case of beer, by the mashing process 
 — that is, by the operation of the diastase of the malt upon 
 the starch. To this end either boiled and mashed 
 potatoes or rye, or rice, or barley, is mixed with bruised 
 barley-malt and hot water, so as to form a paste, which is 
 to be kept at a temperature of 158° F. (70° C.) until a 
 complete formation of sugar is effected ; then brewers' 
 yeast (surface yeast) is added to the sweet mash or wort 
 previously cooled, whereby fermentation is induced. 
 When this fermentation is concluded, the mass is put into 
 a copper still, and the volatile alcohol distilled from the 
 
 z 
 
338 
 
 EXPERIMENTAL CHEMISTRY. 
 
 non-Yolatile parts (husks, gluten, fibrous matter, &c.). 
 The residue is used as a nourishing food for the fattening 
 of cattle. Formerly simple retorts were used for this dis- 
 tillation, and a weak spirit was obtained, which consisted 
 of about one-third of alcohol and two-thirds of water ; but 
 now a more complicated apparatus is employed, by means 
 of which a spirit of double the strength is obtained (recti- 
 fied spirit). The principle upon which this apparatus 
 depends will be explained in the following experiments. 
 
 Beatification or strengthening of Spirit, — Experiment 1. — 
 Pour three ounces of common spirit of wine into a capa- 
 cious flask, and carefully distil half of it into a vessel, which 
 is cooled by means of very cold water, or what is still 
 
 better, by ice. If the spirit contained thirty per cent, of 
 alcohol, then the ounce and a half of alcohol first passing 
 over will contain at least fifty per cent. Alcohol is more 
 volatile than water ; therefore it passes over first, in com- 
 pany with a smaller quantity of the latter, while the greater 
 part of the water, together with the fusel oil (amyl 
 alcohol, &c.), which might have been contained in the 
 spirit, remains behind in the flask (pJilegm). 
 
 Experiment 2. — If you connect with the flask and the 
 receiver an intermediate vessel, a wide-mouthed bottle, 
 for instance, which is easily done by means of two glass 
 tubes bent at right angles, and a cork perforated with 
 two holes, and then repeat the above experiment of dis- 
 
 Fig. 101, 
 
SPIRITS. 
 
 33y 
 
 tillation, the alcoholic vapours passing over will first 
 condense in the middle vessel. But as this vessel is not 
 cooled down the liquid condensed in it will finally also 
 
 Fig. 102. • 
 
 boil, and the vapours thus formed will pass over into the 
 receiver surrounded with cold water, and will there be 
 condensed for the second time. In this manner a double 
 distillation (rectification) is effected. The flask contains 
 boiling spirit (at 30"^ Tralles*) ; the intermediate vessel, 
 boiling rectified alcohol (at about 50^ Tralles). After the 
 termination of the experiment, the first vessel will con- 
 tain phlegm ; the second, weak spirit ; and the third, very 
 strong, highly-rectified spirit (of 70° to 80° Tralles). 
 Common gas-pipe may be used with advantage instead of 
 glass in these experiments. 
 
 If you adapt to the corks of the first two vessels a 
 couple of thermometers, which shall dip into the liquid, 
 you will find that the liquid in the flask boiled at the 
 commencement of the experiment at 185° F. (85° C), and 
 at the end of the experiment at from 203° F. (95° C.) to 
 212° F. (100° C), while that contained in the second 
 vessel commenced boiling at 176° F. (80 C), and ended 
 with boiling at from 185° F. (85° C.) to 194° F. (90° C). 
 It is obvious from this that strong spirit boils at a much 
 lower temperature than that at which weaker spirits 
 
 * The alcoholometer of Tralles floats to a figure on the stem, which 
 indicates the percentage of alcohol, by volume, at 60° F. (15-5° C), 
 in the liquor in which it is placed. 
 
 z 2 
 
340 
 
 EXPERIMENTAL CHEMISTRY. 
 
 boil. The strongest alcohol (absolute) boils at 173^ F. 
 (78° C). 
 
 Exjoeriment 3. — Connect with, a flask a tolerably large 
 glass tube, which is so bent that its middle part has a 
 slight inclination upwards, as is shown in the annexed 
 figure : from 6, this tube is wound round with moistened 
 calico, or wick-yarn, the end of which hangs down at a. 
 
 Fig. 103. 
 
 At a, bind a strip of cloth (several times folded together 
 and smeared with a few drops of olive-oil) round the tube, 
 so that water from the wick may not run down upon the 
 flask. Now distil as before three ounces of spirit, but 
 during the distillation continually drop cold water upon 
 the wick-yarn, at h, in order to cool the vapour of the 
 spirit as it passes over. Catch the water running down 
 the outside of the tube in a vessel placed below the end 
 of the wick-yarn. If the distillation is arrested when 
 about one ounce of the spirit has passed over, we shall 
 have a stronger spirit in the receiver than was obtained 
 in Experiment 1, because, by the partial cooling of the 
 vapour of the spirit, the principal part of the steam was 
 condensed, and, therefore, a vapour richer in alcohol passed 
 into the receiver, while the water condensed in the tube 
 flowed back into the flask. 
 
 BREAD. 
 
 Exjoeriment 1. — Mix some flour with lukewarm water to 
 
BREAD. 
 
 341 
 
 a thick paste, cover it with a board, and let it remain for 
 eight or ten days in a warm place. The paste is gradually 
 altered, and two distinct periods may be observed during 
 the change. In the first place, on the third or fourth day 
 bubbles of air are evolved from it, having a sour, unplea- 
 sant smell, and the dough now possesses the capacity of 
 converting sugar into lactic acid, as may be readily per- 
 ceived by adding a little of it to some sugared water, and 
 letting it stand in a warm place. After six or eight days 
 the dough acquires a pleasant smell, and it now acts, when 
 added to a solution of sugar, like yeast ; that is, it effects 
 a decomposition of the sugar into alcohol and carhonic 
 anhydride. If the dough is allowed to stand still longer, it 
 again acquires an acid taste, but which now proceeds from 
 the acetic acid into which the alcohol previously generated 
 is gradually converted (leaven). In this state also it 
 excites a spirituous fermentation in sugared water ; but 
 this spirituous fermentation is immediately changed into 
 the acid — into the formation of vinegar. It is obvious, from 
 what has previously been stated, that the different actions 
 of the flour, when in "process of decomposition, upon the 
 sugar, depend upon the albuminous matter, the gluten, 
 contained in the flour ; consequently, we might call the 
 slightly altered gluten a lactic acid ferment, that which 
 is more altered an alcohol ferment, and that which is still 
 further altered a vinegar ferment. 
 
 Bread. — What thus takes place slowly, proceeds rapidly 
 in the making of bread, since a ferment is purposely 
 added to the flour, which has been stirred up with water. 
 
 In the making of white bread, the surface-yeast of 
 beer is used as a ferment. The sugar contained in the 
 flour is thereby resolved into alcohol and carbonic an- 
 hydride, which struggle to escape, whereby the tough 
 mass of dough is disintegrated, and rendered light and 
 porous (rising of the dough). These substances, together 
 with about half the water employed, volatilise by the 
 rapid heating in an oven having a temperature of from 
 320° F. (160° C.)to 356° F. (180° C), and the cellular 
 partitions of the baked bread acquire such solidity, that 
 they retain their form and place even after cooling. But 
 if the heat of the oven is not sufficient, or the dough i^ 
 
342 
 
 EXPERIMENTAL CHEMISTRY. 
 
 too watery, then the partitions harden too slowly, and, 
 on the escape of the carbonic acid, collapse, or run 
 into each other (^slack halting). This happens most 
 frequently with dark bread, since, in consequence of its 
 greater amount of gluten, it retains the water more ob- 
 stinately, and accordingly dries and hardens more slowly 
 than white bread, in which the starch is more abundant. 
 
 Leaven is commonly used as a ferment in the prepara- 
 tion of black bread. There is formed, during the process, 
 besides alcohol and carbonic anhydride, a little acetic 
 and lactic acids (perhaps also some butyric acid), which 
 communicate to the bread an acid taste. From three 
 pounds of flour we obtain about four pounds or more of 
 bread : consequently, at least a quarter of the bread con- 
 sists of water. The light, porous bread dissolves easily 
 in the stomach, we say that it is easily digestible, and 
 that the compact heavy bread is difficultly digestible. 
 
 It is known (p. 316) that starch is converted by roast- 
 ing, into gum (dextrin) ; a part of the starch undergoes, 
 also, this change in the oven, particularly on the surface 
 of the baked bread, which receives the strongest heat 
 from the roof of the oven. If the crust of the hot bread 
 is rubbed over with water, and the bread is then replaced 
 for a few minutes in the oven, some of the dextrin is 
 dissolved, and forms, after the evaporation of the water, 
 the shiny coating which we see on loaves of bread and 
 rolls. 
 
 Carbonic anhydride, as applied to the rising of bread, 
 may be more or less advantageously generated in other 
 ways than by the fermentation of sugar ; indeed, entirely 
 different substances, which become aeriform on the appli- 
 cation of heat, may be used for the purpose. 
 
 Experiment 2. — Mix intimately together two grains of 
 finely powdered hydrogen sodium carbonate (bicarbonate 
 of soda), and a drachm and a half of flour, and knead the 
 mixture into a dough with one drachm of water, to which 
 four drops of hydrochloric acid have previously been 
 added. Let the dough remain for some time in a warm 
 place, and then bake it. A porous mass of bread is ob- 
 tained, because the carbonic anhydride of the sodium salt 
 is expelled by the hydrochloric acid, and raises the dough 
 
ALCOHOL. — ETHYL HYDRATE. 
 
 343 
 
 while it is still soft. The common salt which is formed 
 remains behind in the bread, and imparts to it a faint 
 saline taste. This method has been introduced in 
 many places for making bread, cakes, &c., on a large 
 scale. 
 
 Experiment 3. — Eub a drachm and a half of flour with a 
 few grains of ammonium carbonate, and then knead it 
 with a drachm of lukewarm water into a dough, and treat 
 it as in the last experiment. In this case, also, the mass 
 will become light and porous after the rising and baking, 
 because the salt is rendered aeriform by the heat, and 
 during its escape the particles of the dough are forced 
 asunder. In this way bakers prepare light and spongy 
 cakes, as, for instance, gingerbread, &c. Aerated bread is 
 prepared by forcing carbonic anhydride into the dough by 
 powerful pumps. When the pressure is removed, the gas 
 escapes and the dough rises. 
 
 ALCOHOL. — ETHYL HYDRATE. 
 
 Although alcohol can be prepared by other processes, it 
 is always in practice obtained by the fermentation of 
 sugar. In the preceding pages we have shown how 
 alcohol is formed, how it is rendered stronger, and how it 
 is purified. This is done by partial distillation, or by 
 partial condensation, since the alcohol is more easy to 
 volatilise than water, whilst its vapour is more difficult to 
 condense than steam. But all the water cannot be se- 
 parated in this way from the alcohol, as the alcohol retains 
 one- tenth part of the water so firmly that it can neither 
 be withdrawn from it by distillation nor by cooling. In 
 order to procure it absolutely anhydrous, a body must be 
 presented to it which has a greater affinity for water, and 
 fixes it so firmly, that it cannot evaporate with the alcohol 
 at the boiling point of the latter. 8uch a body is quick- 
 lime. 
 
 Experiment, — Put into a flask one ounce of quicklime 
 that has been broken into small pieces, and pour upon it 
 one ounce of very strong alcohol ; connect a receiver with 
 the flask, as in Experiment 1 (p. 338), and let the mix 
 
344 
 
 EXPERIMENTAL CHEMISTRY. 
 
 ture remain in repose for one day. The lime gradually 
 combines with the water of the alcohol (it slakes), and 
 the latter is procured anhydrous by distilling it off at a 
 moderate heat. The best method of distilling in this case 
 is over the water-bath. Anhydrous alcohol is also called 
 absolute alcohol. In this experiment, the vessels used 
 must be previously rinsed out, not with water, but with 
 strong alcohol, because the moisture adhering to the 
 vessel would again impart water to the anhydrous alcohol. 
 
 Froperties of Alcohol, — Alcohol is the hydrate of the 
 monad radical ethyl, CgHg, and has accordingly the 
 formula C2H5OH (p. 297). It has a burning taste, and a 
 penetrating, agreeable odour. Strong alcohol, especially 
 absolute alcohol, acts as a poison when swallowed ; but 
 when diluted, it is, as is well known, stimulating and 
 intoxicating. 
 
 Absolute alcohol oiily freezes at a very low temperature 
 ( — 130° C.) ; it is therefore well adapted for use in ther- 
 mometers which are to measure low temperatures. Its 
 specific gravity is 0*8. When exposed to tbe air it 
 evaporates, and at the same time absorbs water, and so 
 becomes weaker. It may be mixed with water in all 
 proportions. If equal volumes of alcohol and water are 
 mixed, a slight contraction takes place. Alcohol is a 
 very valuable solvent, for it dissolves many substances, 
 resins, for instance, which are insoluble in water. On the 
 other hand, some substances which are soluble in water 
 are insoluble in alcohol. 
 
 Alcohol, from the small proportion of carbon it contains, 
 burns with a smokeless flame. In burning it is converted 
 into water and carbonic anhydride. 
 
 Methylated Spirit, — The Excise permits the sale, duty 
 free, of strong alcohol mixed with ten per cent, of the 
 wood spirit (methyl alcohol, see p. 299) which is obtained 
 in the destructive distillation of wood. This mixed spirit 
 is equal to pure alcohol as a solvent, and it cannot be used 
 for drinking purposes on account of the burning taste of 
 the wood spirit. Moreover, the latter cannot be separated 
 by any economical process. Methylated spirit is a treasure 
 to the chemist. 
 
 Other Alcohols, — The term alcohol is applied in chemistry 
 
ETHER. — ETHYL OXIDE. 
 
 345 
 
 to all hydrates of hydrocarbon radicals (page 297). The 
 other alcohols are for tlje most part of no great practical 
 importance. 
 
 ETHER. — ETHYL OXIDE, 
 
 It has already been shown (page 297) that the term 
 ether is applied to the oxides of hydrocarbon radicals. 
 Common ether, sometimes called sulphuric ether, because 
 sulphuric acid is used in its preparation, is the most im- 
 portant member of the class, and the only one that needs 
 description here. It differs from alcohol just as potassium 
 oxide differs from potassium hydrate : 
 
 KOH Potassium hydrate C2H5OH Ethyl hydrate 
 (Alcohol). 
 
 K2O Potassium oxide (02X15)20 Ethyl oxide (Ether). 
 
 Like the other ethers, it is obtained by removing the 
 elements of water from alcohol. This is generally effected 
 by sulphuric acid. 
 
 Preparation of Ether, — Experiment 1. — Put two fluid 
 ounces of strong alcohol (or methylated spirit) into a good- 
 sized flask, and add slowly one fluid ounce of strong 
 sulphuric acid. Connect the flask with a receiver by 
 means of a glass tube, close the opening remaining 
 between the neck of the receiver and the glass tube by 
 binding round it a piece of moistened bladder, in which 
 some fine holes are pierced, and heat the flask carefully in a 
 sand-bath till the contents of it assume a bubbling motion. 
 Maintain the boiling of the liquid till about one ounce of 
 the liquid is distilled over. In this experiment the liquor, 
 as it is distilled, must be carefully cooled, because it is 
 extremely volatile ; it is therefore advisable, if possible, 
 to surround the receiver with snow or ice. Care must also 
 be taken not to bring any burning substance too near the 
 vapours of the liquid which pass over, as they are ex- 
 ceedingly inflammable. The distilled, colourless liquid 
 possesses a penetrating pleasant smell ; it is called crude 
 ether. 
 
 In order to purify it, shake it up in a bottle with half an 
 ounce of water, and a little strong solution of potash ; close 
 
346 
 
 EXPERIMENTAL CHEMISTRY. 
 
 the bottle, and let it remain standing for an hour with 
 the bottom upwards. Crude ether contains a mixture of 
 water, alcohol, sulphuric acid and other impurities ; these 
 substances combine with the water and the potash added, 
 and form with them the heavier liquid layer, which 
 settles at the bottom of the phial. The very thin and 
 mobile liquid floating above is ether ^ which separates, 
 because it comports itself towards water in the same 
 manner as oil does, and is dissolved by it only in very small 
 quantity. If you now loosen the stopper of the inverted 
 phial, the aqueous liquid will run out, while the ether 
 remains behind. If the latter is required entirely pure it 
 must be again distilled or rectified. 
 
 The most profitable way of preparing ether on a large 
 scale is the following : Ten fluid ounces of sulphuric acid 
 and twelve fluid ounces of alcohol are mixed together, 
 and heated to the boiling point. While the mixture is 
 still boiling, just so much alcohol is allowed gradually to 
 drop in as there is ether distilled over. This is called the 
 continuous process for the manufacture of ether. 
 
 It will be seen that the materials used for the pre- 
 paration of ether are the same as for ethylene gas (page 
 184). But the proportion of sulphuric acid is smaller, 
 and the dehydration of the alcohol is therefore not carried 
 so far : 
 
 C2H5OH - H2O = C2H4, Ethylene. 
 2C2H5OH - H2O = (C2H5)2 0, Ether. 
 The curious fact that sulphuric acid will convert an in- 
 definite quantity of alcohol into ether and water is 
 explained by supposing that hydrogen ethyl sulphate, 
 HC2H5SO4, a salt of ethyl analogous to hydrogen- 
 potassium sulphate, HKSO4, first formed and then 
 decomposed by another molecule of alcohol : 
 
 C2H5OH + H2SO4 = H2O + HC2H5SO4, 
 and HC2H5SO4 + C2H5OH = {C^TL,)^ 0 -f H2SO4. 
 
 The water distils over with the ether, while the 
 sulphuric acid remains to act on a fresh quantity of 
 alcohol. 
 
 Experiment 2. — Pour some drops of ether upon the 
 
SALTS OF ETHYL. 347 
 
 hand ; it will evaporate in a few moments, imparting to 
 the hand a perceptible feeling of coldness. Ether is so 
 verij volatile that it boils at 95° F. (35° C.) ; therefore it 
 must always be kept in tightly-closed bottles, and in a 
 cool place. 
 
 Experiment 3. — Dip one piece of wood into ether, 
 another into alcohol, and hold both to the flame of a 
 candle ; the ether hums with far greater briskness, and 
 also with a much more luminous and a somewhat smoky 
 flame. Its stronger illuminating power is simply ex- 
 plained by its containing a larger amount of carbon. 
 The process in burning is the same as with alcohol ; the 
 ether being also converted into carbonic anhydride and 
 water. 
 
 Experiment 4. — If you pour some drops of ether into a 
 tumbler, and after some seconds, when the ether is con- 
 verted into vapour, apply to it a burning taper, a sudden 
 ignition ensues, accompanied by a small explosion. The 
 vapour of ether forms, like hydrogen or marsh gas, when 
 mixed with atmospheric air, a kind of explosive gas^ and 
 violent explosions have been occasioned by carrying 
 lighted candles or lamps into those places where, owing 
 to the breaking of a bottle filled with ether, its vapour 
 has become diffused in the air. 
 
 Put a piece of tallow, or a few drops of olive oil, into a 
 test-tube with some ether ; both will entirely dissolve in 
 it. But they are not soluble in alcohol or water. There- 
 fore either may be advantageously employed for dissolving 
 and separating such substances as will dissolve in it, but 
 not in other liquids. Besides the fixed oils and fats, 
 ether dissolves many resins, caoutchouc (india-rubber), 
 gutta-percha, &c. 
 
 Ether is sparingly soluble in water, but may be mixed 
 with alcohol in any proportion. It is very light (Sp. Gr. 
 at 0°C. 0.736). 
 
 Other Ethers. — Ethers corresponding to many of the 
 other alcohols are known, but few have any importance. 
 
 SALTS OF ETHYL. 
 
 It has been shown (page 300) that salts, sometimes called 
 compound ethers, of the alcohol radicals can be prepared 
 
348 
 
 EXPERIMENTAL CHEMISTRY. 
 
 wMcli are in all respects comparable to metallic salts. 
 Those of ethyl, which is the most important of alcohol 
 radicals, are very numerous and interesting, but, as they 
 do not possess much practical importance, we may pass 
 them by in the simple practical study which we have in 
 hand. 
 
( 349 ) 
 
 CHAPTER VI. 
 
 ORGANIC ACIDS, 
 
 The constitution of the simpler organic acids and their 
 relation to the alcohols have already been explained 
 (page 300). The student will find it well to read that 
 section again before commencing the practical work of 
 this chapter. 
 
 MONOBASIC ACIDS. 
 ACETIC ACID. 
 
 C2H,02 = HC2H3O2 or C2H3OOH. 
 This acid, which is contained in vinegar, is by far the 
 most important member of the series called the " fatty 
 acids" (page 301). It is often obtained by the oxidation 
 of alcohol, two atoms of hydrogen being replaced by one 
 atom of oxygen : 
 
 C2HeO +02 = C2H,02 + H2O, 
 but it is also formed during the destructive distillation of 
 wood, and by other means. 
 
 Acetous fermentation. — Vinegar, — When weak wine or 
 beer is exposed to the air, a peculiar organised ferment 
 (page 341) soon appears in it, which has the remarkable 
 power of effecting the oxidation of the alcohol into acetic 
 acid. These "vinegar cells" differ from yeast cells in 
 that they cannot develop except in the presence of 
 oxygen, but that they are organised cells, capable of 
 transplantation- and increase, there is no doubt. Like 
 yeast cells, they can only develop in presence of their 
 appropriate food, and at a suitable temperature. 
 
 Experiment 1. — Mix in a glass vessel half an ounce of 
 brandy with three ounces of water, and put in the liquid 
 a slice of leavened bread, which has been previously 
 
350 
 
 EXPERIMENTAL CHEMISTRY. 
 
 soaked in strong vinegar, or instead of it a little leaven 
 (page 341) ; cover the vessel with a piece of perforated 
 pasteboard, and put it in a place where the temperature 
 is between 86° F. (30° C.) and 104 F. (40° C.) ; the 
 spirituous liquor will, after some weeks, be converted 
 into vinegar. This conversion does not take place in a 
 closed vessel, as the oxygen of the air is indispensable to 
 the process. Neither is any vinegar formed if you do not 
 add the bread or the leaven. As a solution of sugar does 
 not of itself pass into alcohol, neither does the alcohol of 
 itself pass into vinegar. 
 
 In the same manner as with pure diluted alcohol, all 
 other alcoholic liquids^ as beer, wine, cider, &c., may, by 
 receiving oxygen, be converted into vinegar, aud it is 
 well known that vinegar is frequently prepared from 
 them. If, as is ordinarily the case, they contain gluten 
 or lees in solution, then these substances afford food for 
 the vinegar ferment, and the acidification ensues spon- 
 taneously, when the liquid is exposed in loosely covered 
 vessels to a temperature of from 86° F. (30° C.) to 104° (40° 
 C). This acidification most readily occurs immediately 
 after a spirituous fermentation, which has taken place at too 
 high a temperature ; for this reason, in the hot months of 
 summer, the brewers and distillers find difficulty in 
 keeping their fermenting wort and mash from turning 
 sour, which can only be prevented by rapid cooling. 
 
 Experiment 2. — Fill two tumblers loosely with the stalks 
 of grapes, and fill one entirely and the other only half 
 full with wine, beer, or a mixture consisting of one part 
 of brandy, one part of beer, and six parts of water. Put 
 both vessels in a warm place, and once or twice every day 
 pour the mixture from one vessel into the other, so that 
 each may be alternately full and only half full of the 
 liquid. The alcohol contained in the brandy will, in this 
 manner, be much more rapidly oxidised into vinegar, 
 because the liquid adhering to the grape-stalk is, in this 
 state of fine division, surrounded by air, and thus has a 
 far better opportunity of attracting oxygen from the 
 latter. The effervescence taking place at the commence- 
 ment is owing to the sugar contained in the beer and the 
 grape-stalks, and which was first converted into alcohol 
 
ACETIC ACID. 
 
 351 
 
 and carbonic anhydride. The alcohol thus formed is 
 likewise afterwards changed into vinegar, and this is the 
 reason why the vinegar thus produced is more acid, that 
 is, richer in acetic acid, than that obtained by the former 
 experiment. 
 
 Quick Method of making Vinegar, — The transition of 
 alcohol into acetic acid takes place still more rapidly by 
 subdividing the alcohol still further, or by exposing a 
 still greater surface of the liquid to the air than in the 
 way just described. This is effected in the following 
 manner : 
 
 A tub four or five yards high is filled with shavings of 
 beechwood, and is furnished with a perforated shelf, 
 which is placed somewhat below the upper opening. 
 Through each of the small holes a straw or a piece of 
 packthread is passed, prevented from falling through by 
 a knot at the upper end. 
 By this means an extreme 
 division of the alcohol is 
 effected, as when it is poured 
 in at the top, it only trickles 
 slowly down through the 
 holes by means of the straw 
 or packthread, and then 
 diffuses itself over the shav- 
 ings, forming a very thin 
 liquid layer, which presents 
 to the air a surface many 
 thousand times more extensive 
 than was produced by any 
 former method. Several large 
 holes are bored round the 
 lower part of the tub, and 
 likewise in the perforated 
 shelf ; glass tubes are fitted 
 into the^ holes made in the latter, in such a manner that 
 the liquid, when poured into the top, may not run off 
 through them. A free circulation of air is hereby 
 produced, the cooler air enters by the openings in 
 the tub, gives up its oxygen to the alcohol diffused 
 over the shavings, and, in consequence of this oxidation. 
 
EXPERIMENTAL "CHEMISTRY. 
 
 or slow combustion, SO much heat is evolved in the 
 interior of the tub that the temperature rises to 104° 
 r. (40^^ C). The air hereby becoming warmer, and 
 consequently lighter, passes out of the tub through the 
 glass tubes in the shelf, from an eighth to a fourth 
 poorer in oxygen than when it entered. Strong vinegar 
 is used to assist the fermentation in this process, the 
 tub and shavings having previously been moistened with 
 it, and a certain quantity being also added to the mix- 
 ture of spirit which is to be converted into vinegar. In 
 such a tub (vinegar generator^, warmed spirit, beer, wine, 
 &c., may be converted into vinegar in a few hours, by 
 being passed through the cask three or four times ; hence 
 this is called the quich method of malcing vinegar. 
 
 Aldehyde. — During this oxidation of alcohol, an inter- 
 mediate compound called aldehyde is first formed, and 
 then oxidised to acetic acid. It is regarded as hydride of 
 acetyl, (C2H3OH,) acetic acid being the hydrate (page 300) : 
 
 Alcohol. Aldehyde. Acetic acid. 
 
 C2H6O. C2H4O. C2H4O2. 
 
 Its peculiar and suffocating odour can often be per- 
 ceived in vinegar chambers. 
 
 Wood Vinegar. — When wood is distilled in close vessels 
 (page 188), besides charcoal, tar and gas, a certain 
 quantity of acetic acid is always formed. This impure 
 acid is sometimes called pyroligneous acid. When 
 neutralised by sodium carbonate, sodium acetate, NaC2H302, 
 is formed, and can be purified by crystallization. From 
 this salt it is easy to obtain pure acetic acid. 
 
 Experiment 3. — Mix some dry sodium acetate with 
 strong sulphuric acid in a flask connected with a cool re- 
 ceiver, and apply a gentle heat. Acetic acid will distil 
 over, and may be collected in a state of purity : 
 
 NaC2H302 + H2SO4 = HC2H3O2 + NaHSO^. 
 Pure acetic acid is an ice-like solid below 63° F. 
 (17° C), and is therefore sometimes called glacial acetic 
 acid. It boils at 244° F. (118° C). The strongest 
 English vinegar contains about 5 per cent, of the true 
 acid. 
 
 Acetic anhydride, or Acetyl oxide, (021130)20, can only bo 
 
LACTIC ACID. 
 
 353 
 
 prepared with difficulty. In constitution it is analogous 
 to nitric anhydride : 
 
 (C,H30),0, is like (N0,),0 or N^O^. 
 
 Acetates, — Those of lead (sugar of lead) and sodium are 
 among the most important. Acetates can be recognised 
 by warming them with sulphuric acid, when the odour of 
 vinegar will be apparent. 
 
 LACTIC ACID. 
 
 CsHgOg = HC3H5O3. 
 
 Lactic fermentation. — When milk is kept for some hours 
 in a warm place, the milk-sugar undergoes a fermentation 
 analogous to those already described. It is converted 
 entirely into lactic acid, which renders the milk sour, and 
 precipitates the casein as curd (page 328). The nature of 
 the change is shown by the following formula : 
 
 Milk Sugar. Lactic Acid. 
 
 C6Hi20(j = 20311^03. 
 
 Lactic acid can only be purified with difficulty. It is a 
 colourless, oily liquid, which is decomposed by heat. A 
 variety of lactic acid known as sarcolactic acid is found in 
 the juice of flesh. 
 
 Butyric fermentation, — If the fermentation of milk is 
 pushed past the stage in which lactic acid is formed, 
 butyric acid is produced by a distinct organised ft-rment. 
 The odour and taste of rancid butter and putrid cheese 
 are partly due to this acid. It is one of the fatty acids. 
 
 BENZOIC ACID. ( V g-^ 
 
 Experiment 1. — Put some powdered gum benzoin into a 
 saucer, cover it with a sheet of white filtering-paper on 
 which rests a cone of writing-paper. Apply a very gentle 
 heat to the saucer by means of a sand bath, and after an 
 hour or so the inside of the cone will be found to be 
 covered with beautiful white crystals of benzoic acid. 
 Good gum contains about 14 per cent, of the acid, and the 
 acid being volatile passes in vapour through the porous 
 
354 
 
 EXPERIMENTAL CHEMISTRY. 
 
 paper, and condenses on the cone. The filter paper ab- 
 sorbs some volatile oil which is given off with the acid. 
 
 Experiment 2. — Add benzoic acid to a solution of sodium 
 carbonate until it no longer dissolves. Effervescence will 
 take place from the escape of CO2, and sodium henzoate, 
 Na CYH5O2, will remain in solution, and may be obtained 
 in the solid state by crystallization. From this salt other 
 benzoates may be prepared by double decomposition. 
 
 Experiment 3. — Add solution of ferric chloride (rendered 
 neutral by ammonia) to solution of sodium benzoate. A 
 buff-coloured precipitate of ferric henzoate wWl be produced. 
 
 Experiment 4. — To a tolerably strong solution of sodium 
 benzoate add hydrochloric acid. Pearly crystals of ben- 
 zoic acid will be thrown down. Benzoates can be decom- 
 posed in this manner by very many acids. The preci- 
 pitation of the acid is due to its sparing solubility. It 
 requires 200 times its weight of cold water for solution. 
 
 OXALIC ACID. 
 
 This important dibasic acid corresponds to an oxide of 
 carbon, C2O3, intermediate between carbonic oxide 
 Fig. 105. ^j^^ carbonic anhydride. This oxide is however 
 unknown. The relation of oxalic acid to ethyleue 
 /Mi alcohol has already been shown (page 301). 
 
 i Experiment 1. — Heat with free access of air, in 
 i a porcelain dish, one-fourth of an ounce of sugar, 
 1 mixed with one and a half ounce of concentrated 
 i nitric acid, and one ounce of water. In a short 
 i time a strong evolution of yellowish-red fumes 
 (N2O3) will commence. Continue boiling until 
 these vapours cease, and then put the liquid in a 
 cool place ; colourless crystals (oblique rhombic 
 prisms) of oxalic acid will separate, which must 
 be purified by recrystallization. They have a 
 strong acid j eaction, and are poisonous. Starch, or even 
 saw-dust (impure cellulin), may be substituted for sugar 
 in this experiment. The crystals contain H2C204,2H20. 
 
 Experiment 2. — L^it about lialf an inch of crystallized 
 oxalic acid into a test tube. Moisten with strong 
 
OXALIC ACID. 
 
 355 
 
 sulpliurlc acid, and carefully heat the mixture ; a gas 
 will be evolved. Let this pass through solutioa of 
 ])otash contained in another test-tube. One half of the 
 escaping gas is absorbed by the potash ; this is carbonic 
 anhydride (CO.^). 'I'he other half escapes through the 
 open tube, and iDurns, when kindled, with a bluish flame ; 
 this is carbonic oxide (CO). The carbonic oxide will 
 even burn at the mouth of the tube if the carbonic 
 anhydride remains with it. When the evolution of gas 
 ceases, there will be found in the first test-tube common 
 sulphuric acid ; ccmsequently, the sulphuric acid has 
 removed water from tlie oxalic acid. The oxalic acid, 
 when it loses its water, is resolved into the two gases just 
 mentioned, in the following manner : 
 
 H^CA^H^O + CO-l-CO^. 
 
 Exjperiment 3, — Place some crystals of oxalic acid upon 
 a 2)iece of platinum foil, and hold them in the flamu of 
 a spirit-lamp. They melt, take fire, and burn without 
 becoming black or leaving any residue. The product of the 
 combustion is carbonic acid ; H2C2O4 and 0 (from the air) 
 are converted into 2CO2 + H2O. 
 
 Experiment 4. — Neutralise a strong solution of oxalic acid 
 with a strong solution of potassium carbonate or hydrate ; 
 neutral potassium oxalate (K2C2O4), an easily soluble salt, 
 is formed. It you now add as much more oxalic acid, 
 hard crystals will be deposited on cooling, which have an 
 acid reaction ; they are called acid oxalate of potassium, 
 or hydrogen potassium oxalate, HKC2O4. The acid oxalate 
 is likewise lormed by the vital jDrocess in many plants, 
 and it is found abundantly in the leaves of the wood-sorrel 
 (Oxalis), from which it may be obtained. The acid salt 
 is far less soluble than the neutral. 
 
 Experiment 5. — Heat some potassium oxalate upon 
 platinum foil ; it will be converted into potassium 
 carbonate. The oxalate loses carbonic oxide: K2C204 = 
 K2CO3 + CO. Many other oxalates are converted into 
 carbonates when treated in this way. 
 
 Experiment 6 — Agitate a little calcium sulphate with 
 water and let the liquid settle ; the decanted water 
 contains a small quantity (about 4^0) of the sulphate in 
 
 2 A 2 
 
356 
 
 EXPERIMENTAL CHEMISTRY. 
 
 solution. If a solution of oxalic acid is poured upon this 
 solution, you will soon obtain a precipitate of calcium 
 oxalate. The decomposition takes place more rapidly and 
 perfectly when the oxalic acid has been previously 
 neutralised by ammonia. Oxalic acid, or ammonium 
 oxalate, is the best test for calcium salts. 
 
 Experiment 7. — Pour a solution of ferrous sulphate on a 
 piece of white blotting-paper ; when this has imbibed the 
 liquid, spread it over some ammonia. The ammonia 
 precipitates green ferrous hydrate on the paper, which 
 soon absorbs oxygen, and is converted to the brown feiric 
 hydrate. In a similar manner, cotton, and other fabrics, 
 are often dyed brown or yellow. When it is dry, mix 
 some oxalic acid with water into a thin paste, and dot the 
 paper with it in several places; the colour will soon 
 disappear from these spots, and you obtain a white 
 pattern on a yellow ground. Oxalic acid dissolves ferric 
 oxide, and both are removed by washing. UjDon this is 
 founded an important use of this acid in calico-printing, 
 as likewise its application for the removal of ink-spots 
 from linen or paper. One of the principal constituents of 
 ink is an iron salt, which being dissolved by the oxalic 
 acid, the black colour of the ink disappears also. This 
 explains why, on removing ink-spots by oxalic acid or 
 salt of sorrel (which acts in the same manner as the free 
 acid) from yellow and brown articles of dress, the colour 
 of which often depends upon iron, the colour of the stuff 
 also disappears. 
 
 TARTARIC ACID. 
 
 C4H606 = H2C4H406. 
 
 Tartaric acid is dibasic. It is generally prepared from 
 tartar or argol, which is obtained in large quantities from 
 the wine countries, where it is deposited from wines in 
 the casks, as a white or reddish crust of impure hydrogen 
 potassium tartrate. Tartaric acid might be very easily 
 obtained from this salt by means of sulphuric acid; but 
 then two soluble substances would be obtained, which 
 could not well be separated from each other. Therefore 
 the tartar is first converted into calcium tartrate, and this 
 when treated with sulphuric acid yields tartaric acid, 
 
TARTARIC ACID. 
 
 357 
 
 wliicli can be purified by crystallization. The calcium 
 remains as the nearly insoluble sulphate. 
 
 Tartaric acid has very much the appearance of a salt ; 
 it crystallizes in colourless oblique prisms, which are 
 permanent in the air, and have a very acid taste. 
 
 Experiment 1. — Place a small crystal of tartaric acid 
 upon a piece of platinum foil, and heat it over the flame 
 of a lamp ; it will first melt, then 
 become brown, and finally black, and 
 emit at the same time a smell some- 
 what like that of burnt sugar. If, 
 during the process of charring, you 
 hold over the acid a dry, cold glass 
 vessel, it will become lined with 
 globules of water ; consequently the 
 acid contains oxygen and hydrogen. The dark residue 
 resembles charcoal, but it is more certainly recognised as 
 such by its burning completely at a higher heat. Accord- 
 ingly tartaric acid, when heated, behaves like sugar. 
 
 Experiment 2. — Pour a little warm water over some 
 tartaric acid ; it will dissolve therein, for it is readily 
 soluble in water. If you dilute the solution with more 
 water, and put it aside in a moderately warm place, slimy 
 flakes will be deposited, and the acid taste will gradually 
 be lost — it decom[)oses. Many other organic compounds, 
 when they are diluted with water, decompose after a time. 
 
 Experiment 3. — Neutralise a solution of potassium 
 carbonate with a solution of tartaric acid ; carbonic 
 anhydride escapes ; the liquid, however, remains clear, 
 because the neutral potassium tartrate (K2C4H^06) formed 
 is an easily soluble salt. But by adding yet more tartaric 
 acid, the liquid becomes turbid, especially on stirring, and 
 deposits a quantity of small transparent crystals, which 
 are difficultly soluble in water, have an acid taste, and 
 contain less potassium than the neutral salt. These 
 crystals are called acid tartrate of potassium, or hydrogen 
 potassium tartrate, HKC4H4O6 ; commonly, tartar, or 
 when pulverised, cream of tartar. The salts of potassium 
 may accordingly be used as tests for tartaric acid. 
 
 Experiment 4. — If you heat the crystalline powder of 
 tartar, obtained in the last experiment, on platinum foil, 
 
358 
 
 EXPERIMENTAL CHEMISTRY. 
 
 it will, like the taxtaric acid, become black, and burns 
 with an empyreumatic odour ; but there will, however, 
 finally remain a white powder, which has an alkaline 
 taste, a basic reaction, and which, on the addition of an 
 acid, will effervesce. It is potassium carbonate. 
 
 CITRIC ACID. 
 
 This is the characteristic acid of lemons, but it is also 
 found in many other fruits. It is tribasic, as is shown by 
 its forming three potassium salts. 
 
 Experiment 1. — Add chalk in small portions to some 
 lemon juice, until no further effervescence occurs. The 
 white seriiment consists of impure calcium citrate. It may 
 be carefully decomposed by sulphuric a- id (avoiding 
 excess), the free citric acid filtered from the insoluble 
 calcium sulphate, and crystallized. It is however some- 
 what difiicult to obtain it pure by this process. 
 
 Experiment 2. — Citric acid resembles tartaric acid in its 
 appearance and many of its properties. The effect of heat 
 on the crystals may be tried. 
 
 Experiment 3. — Add some lime water to a solution of 
 citric acid. No precipitate, or only a very slight one, is 
 formed. Boil the liquid and an abundant precipitate will 
 appear, but will again disappear as the liquid cools. 
 Calcium citrate is more soluble in cold water than in hot; a 
 remarkable exception to the general rule. 
 
 GALLIC ACID. — TANNIN. 
 
 Gallic Acid, O5. Tannin, C^^ H,, O9. 
 
 Closely allied monobasic acids. 
 Tanniny Tannic Acid, Gallotannic Acid. 
 
 Experiment 1. — Take a large test-tube with a small hole 
 in its end, l)lug the hole with cotton wool, and fill the 
 tube half lull of the best Aleppo gall nuts in fine powder. 
 The gall nuts found on Engli^>h oaks are very inferior. 
 Support the tube upright, and pour in some common 
 ether. Commercial ether always contains some water and 
 alcohol, both of which in small quantity are necessary for 
 
GALLIC ACID. — TANNIN. 
 
 359 
 
 the success of the operation. The ether soon percolates 
 through the gall nuts, and may be received in a small 
 buttle. Eepeat the addition of ether several times, and 
 then cork up the bottle and allow it to remain at rest for 
 some time. The liquid will separate into two layers, the 
 upper one of which consists mainly of ether, which may 
 be drawn off wiih a pipette,* and the ether purified by 
 distillation. The lower layer consists chiefly of an 
 aqueous solution of tannin, or tannic acid, a peculiar astrin- 
 gent substance which is contained in gall nuts, and in 
 less quantity in a great many vegetable products. Oak- 
 bark contains a good deal of it. 
 
 The aqueous solution may be evaporated to dryness at 
 a gentle heat, when the tannin is obtained as an amor- 
 phous mass of strong astringent taste. It is very soluble 
 in water and alcohol, but insoluble in pure ether. 
 
 The chief importance of tannin arises from its power of 
 combining with gelatin and gelatigenous substances, and 
 forming with them a substance, leather, which does not 
 putrefy. The process of tanning may be illustrated in the 
 following manner : 
 
 Experiment 2. — Add a solution of gelatin to a dilute 
 solution of tannin, or to a decoction of oak bark or gall 
 nuts ; a white flocculent precipitate will be formed. 
 
 Experiment 3. — Take a clean, dry piece of skin, weigh 
 it, and suspend it for some days in a solution of tannin, or 
 a decoction of bark. It will gradually remove the whole of 
 the tannin, and be converted to an imperfect leather. 
 When dried and weighed it will be found to have gained 
 in weight, the increase affording a rough measure of the 
 amount of tannin that the solution contained. 
 
 For the tanning of thick hides many months are often 
 required. 
 
 ^Experiment 4. — A solution of tannin gives with ferric 
 salt a blue-black precipitate, which is the colouring matter 
 of ordinary ink. Pure ferrous salts give a white precipi- 
 tate with tannin, which absorbs oxygen from the air and 
 turns black. The reason why so many inks become 
 
 * Pipettes are tubes drawn out to a fine jet at one end. They are 
 very useful for sucking up small quantities of liquid. They are often 
 made with a bulb in the middle. 
 
360 
 
 EXPERIMENTAL CHEMISTRY. 
 
 darker when the writing is exposed to air is that a ferrous 
 hSilt has been used in their manufacture. 
 
 Experiment 5. — Writing Ink, — Take one pound of bruised 
 Aleppo gall nuts, six ounces of green vitriol (ferrous sul- 
 johate), six ounces of gum arable, a few drops of carbolic 
 acid (or creosote), and one gallon of cold water. Mix 
 them in a stone jar, and stir at intervals for three weeks ; 
 then let the ink settle and decant it for use. The gum 
 gives thickness to the ink, the carbolic acid keeps it from 
 turning mouldy. 
 
 Experiment 6. — Tea contains a good deal of tannin. 
 Experiments 2, 3, and 4 may be repeated wit h a decoction 
 of tea. Tea made with waters which contain iron has an 
 inky appearance. 
 
 Gallic Acid. 
 
 Experiment 7. — To prepare gallic acid, moisten some 
 powdered gall nuts with water, and keep them for a 
 month in a warm place (about 20° C, or 68° F.), replacing 
 the water as it evaporates, and removing the mould which 
 forms. Press the mass in a calico bag, and afterwards 
 boil it with water and filter while hot. As the solution 
 cools, silky crystals of gallic acid will deposit. 
 
 Gallic acid is distinguished from tannin by its power of 
 crystallizing and by the fact that it does not precipitate 
 gelatin. It is useless in tanning. 
 
 Experiment 8. — Gallic acid gives with ferric salts an 
 even more intense blue-black colour than tannin does. Its 
 solution affords a most delicate test for those compounds. 
 
 Pyrogallic Acid, or Pyrogallol, Cg Hg O3. 
 
 Experiment 9. — Heat some gallic acid, very gently, in 
 the apjiaratus used for preparing benzoic acid (page 353). 
 After some time beautiful silky crystals of pyrogallic acid 
 are found in the paper cone : 
 
 C,H,05 = C«He03 + C0,. 
 Pyrogallic acid is used in jihotography. Its alkaline 
 solution absorbs oxygen rajiidly and turns brown ; it is 
 therefore much used in gas analysis. In constitution it is 
 allied to phenol. 
 
( 361 ) 
 
 CHAPTER VII. 
 
 FATS AND FIXED OILS, SOAP, &C. 
 
 Group i. — Non-dryinc^ Fats and Oils (Glycerides). 
 
 Group ii. — Drying Oils (also Glycerides). 
 
 Group iii. — Wax, Spermaceti, &c. (not Gtycerides). 
 
 Group i. — Non-drying Fats and Oils. 
 
 Throughout the vegetable and animal kingdoms a class of 
 oily substances is distributed which is of very great 
 interest and importance. The members of this class are 
 generally called fats when solid, and oils when liquid at 
 ordinary temperatures. They are almost invariably 
 mixtures in various proportions of two or more definite 
 compounds. They possess in common certain well-marked 
 peculiarities, which may be shortly enumerated. 
 
 1. They are all compounds of carbon^ hydrogen and oxygen 
 only, 
 
 2. They are lighter than water, 
 
 3. They are non-volatile^ being destroyed and converted 
 into gases when heated above a certain point. 
 
 4. They are insoluble in water, scarcely soluble in alcohol, 
 very soluble in ether, benzene and carbon disulphide. 
 
 5. They are fusible at a temperature much below that 
 of boiling water. 
 
 6. When boiled loith caustic alkali they all yield glycerine, 
 and peculiar salts of the alkaline metal {soaios : the change 
 is called saponification). 
 
 Proximate constituents of the members of this group. — The 
 most important of these are : stearin, Cs^H^ioO^j, a white 
 solid, the chief constituent of suet, tallow, and lard, con- 
 tained also in some vegetable oils ; palmitin, C51 H^sO^j, solid, 
 not so hard as stearin, found in palm oil, and in many 
 animal and vegetable fats ; and olein, G^^Hiq^O^^, liquid, the 
 
 I 
 
362 
 
 EXPERIMENTAL CHEMISTRY. 
 
 chief constituent of olive and many other oils, and also 
 present in most fats. 
 
 These three substances are called glycerides, because 
 they are salts of the triad radical glyceryl or propenyl, G^^^ 
 (page 294), of which glycerin is the hydrate, 03Hj^(OH)3. 
 Each of them contains the monad radical of a distinct 
 acid ; stearin, of stearic acid, HC18H35O2 ; palmitin, of pal- 
 mitic acid, E[CigH3i02 ; and olein, of oleic acid, HC18H33O2. 
 Their constitution may be represented in the following- 
 manner : 
 
 Stearin. 
 
 C^57 Oe = C3 H5 (C18 H35 02)3, cr Propenyl tri^tearate. 
 
 Palmiiin. 
 
 C51 H 98 = C3 H5 (C16 H31 02)3, or „ tripalmitrate. 
 
 Olein. 
 
 C57 H104 Oe = C3 H5 (C18 H33 03)3, or „ trioleate. 
 
 Palmitic and stearic acids are members of the formic 
 or fatty acid " series ; oleic acid, of the acrylic series 
 (page 302). 
 
 ANIMAL FATS AND OILS. 
 
 Experiment 1. — Boil some fat pork, cut up into small 
 pieces, for some time in a little water, and while the ^oft 
 mass is still hot, press it in a linen cloth ; a fat oil will 
 float on the surface, but it is fluid only at a temperature of 
 about 86° P. (30° C.) ; below this temperature it congeals 
 into a solid, yet soft, white substance. This is lubricating 
 to the touch, and produces greasy spots on paper. Tho.se 
 kinds of fat, whicli, at the common temperature, have a 
 soft unctuous consistency, are called lard ; and the cellular 
 membrane and skin remaining in the cloth, and saturated 
 with fat, are called scraps. 
 
 The suet of mutton, when treated in the same way, 
 yields a fat which, when hot, is also fluid, like oil, but 
 which, when cooled only to about 97° P. (36° C), congeals, 
 and then forms talloio, a harder substance than lard. By 
 boiling and roasting, we can melt out fat from many 
 animal ti>sues, especially froui those of the domestic 
 animals, in which we are able to produce a great quantity 
 of fat T)y keeping them confined, and giving them a 
 plentiful supply of food. The fats obtained by boiling 
 
ANIMAL FATS AND OILS. 
 
 363 
 
 with water are white, as thereby they do not become 
 heated above 242° F. (100° C.) ; while those obtained by 
 roasting- have a yellow or brown colour (brown butter, 
 gravy of roast meat, &c.), because in this case a portion 
 of the fat becomes burnt by being subjected to a stronger 
 heat — to a heat, perhaps, even above 572° F. (300° C). 
 
 These substances consist mainly of stearin, palmitin and 
 olein, the first predominating. When lard is strongly 
 pressed, olein is obtained from it (lard oil). 
 
 Train, or tvhale oil, is obtained from the blubber of the 
 whale. Sperm oil, from cavities in the skull of the sperm 
 whale. 
 
 Cod liver oil, obtained from the liver of the cod, contains 
 minute quantities of bromine, iodine, sulphur, phosphorus, 
 and free acids, in addition to stearin, palmitin, and olein. 
 To the bromine and iodine the value of the oil in medicine 
 is often ascribed. 
 
 Cream. — Butter. — That singularly complex and im- 
 portant liquid milk owes its opacity to myriads of minute 
 globules of oil which float in it. Under the microscope 
 these are seen to be perfectly transparent, for milk is 
 opaque, just as powdered or ground glass is opaque, only 
 because the rays of light which fall on it are scattered by 
 the irregularity of the globules or fragments. When 
 milk is kept for a time, most of the oil globules rise to the 
 surface and constitute cream. They do not run together, 
 because each is enclosed in a delicate membrane ; but 
 when the cream is violently agitated (churned), the mem- 
 branes are broken and a solid mass — hutter — is obtained. 
 Skim-milk is milk from which the greater part of the 
 cream has been skimmed. Butter-milk is the liquid residue 
 left after butter has been made from cream. Both consist 
 chiefly of milk-sugar and casein (page 328) and mineral 
 salts, with much water. In the modern cream separator, 
 the milk, rotating in drums with great velocity, is 
 divided in a few minutes into cream, which goes to the 
 outer edge and is skimmed off by a sharp-edged pipe, and 
 skim-milk which is separately received. 
 
 Fresh butter consists chiefly of olein, palmitin and 
 stearin, with small quantities of other glycerides, and of 
 albuminoid bodies (casein, &c.). When kept, the albu- 
 
364 
 
 EXPERIMENTAL CHEMISTRY. 
 
 minoids begin to putrefy, and a kind of fermentation 
 takes place, which produces soluble fatty acids. To some 
 of these fatty acids (butyric, caprylic, capric, &c.) the 
 disagreeable taste and smell of rancid butter is due. The 
 change can be to a great extent prevented by salt, which 
 acts as an antiseptic, or by purifying the butter by 
 melting it in hot water, and removing the solid mass 
 when cold. The latter process, however, injures the 
 delicate flavour of the butter. 
 
 VEGETABLE FATS AND OILS. 
 
 Almond oil, — Experiment 1. — Break open an almond, and 
 squeeze the white meat together by means of the finger- 
 nail ; small drops of fluid will be expressed, which are 
 slippery to the touch, and render blotting-paper greasy 
 and transparent. This liquid is called siveet oil of almonds. 
 If the almonds are first pounded, and then subjected in a 
 cloth to strong pressure, we shall obtain more than one- 
 fourth of their weight of oil of almonds. A great many 
 plants contain a similar oily juice, especially in their 
 seeds, and from many of the latter, oils are obtained by 
 pounding and expressing. They occur in small quantity 
 in almost all plants, even in those where we should not 
 expect to find any ; for instance, in different kinds of corn, 
 grasses, &c. 
 
 Palm oil is obtained from the fruit of certain kinds of 
 palm. It is yellow and has the consistence of butter. It 
 consists chiefly of palmitin, with olein, &c. It is largely 
 used in the manufacture of soap and candles, and also, 
 with tallow and a little soda, for greasing the wheels of 
 railway carriages. For the two tormer purposes it is 
 bleached by exposure to air in a melted state for ten or 
 fifteen hours. 
 
 Cocoa-nut oil is a soft white solid, somewhat like palm 
 oil. 
 
 Olive oil, expressed from the fruit of the olive tree, is 
 too well known to require description. A simple experi- 
 ment shows that it is a mixture. 
 
 Experiment 2. — Expose some olive oil to the cold of a 
 winter's night, or surround it fur some time with ice. It 
 will become semi-solid, and will be full of granules. 
 
SAPONIKICATION. — SOAP. 
 
 8G5 
 
 These granules consist of palmitin. Subject the mass to 
 gentle pressure in calico without allowing the temperature 
 to rise ; a clear oil will be expressed, which does not 
 solidify at 32"^ F. (0° C). This consists almost entirely 
 of olein. 
 
 Colza oil and Bape oil are obtained from the seeds of 
 several species of hrassica, to which genus the cabbage, 
 turnip, and rape belong. They are said to contain the 
 glyceride of a peculiar acid, hrassic acid. 
 
 The following experiment illustrates the mode in which 
 rape oil is refined or purified. 
 
 Experiment 3. — Mix one ounce of crude rape oil with 
 eight drops of common sulphuric acid, and shake it 
 frequently ; in half an hour add half an ounce of water ; 
 again shake the mixture briskly, and set it aside for some 
 day.s, when the oil floating on the surface will be freed 
 from mucilage (purified). The slimy paits, charred by 
 the sulphuric acid, and rendered insoluble, are found 
 settled in the water at the bottom of the vessel. The 
 sulphuric acid still adhering to the oil is removed by 
 repeated washing with water. Sulphuric acid chars, as is 
 known, all organic substances, some (for instance, muci- 
 lage) easily, others (tor instance, oil) with difficulty; if 
 just enough sulphuric acid, therefore, is added to the oil 
 to char the mucilage, then the mucilage only is destroyed, 
 and the oil l emains undecomposed. A larger quantity of 
 sulphuric acid would also attack the oil. 
 
 Castor oil, from the seeds of Bicinus communis, consists 
 chiefly of the glyceride of a peculiar acid, ricinoleic acid. 
 It also contains small quantities of a peculiar alkaloid, 
 ricinine, discovered by Tuson. The oil is remarkable for 
 being easily boluble in alcohol. 
 
 SAPONIFICATION. — SOAP, 
 
 When any one of the preceding fats and oils — in fact, 
 any glyceride, or mixture of glycerides — is exposed at a 
 suitable temperature, different with different oils, to the 
 action of a strong solution of caustic soda or potash 
 (alkaline lye), a double decomposition takes place, glycerine 
 is formed, and with it a sodium or potassium salt of the 
 acid, or acids of the oil. These salts are called soaps, 
 
366 
 
 EXPERIMENTAL CHEMISTRY. 
 
 and the change is called saponification. The following 
 formulae will show how similar the action is to some of 
 the changes of mineral chemistry : 
 
 Stearin, or Glycerine, or Stearin Soap, or 
 
 Propenyl Stearate. Propenyl Hydrate. Soiiium Stearate. 
 
 Bismuth Nitrate. Bismuth Hydrate. Sodium Nitrate. 
 
 Bi'" (1^03)3 +3NaOH= Bi"'(0'H)3+3NaN03. 
 
 Soaps are in fact salts of the higher fatty acids. The 
 ordinary hard soaps are sodium salts. Soft soaps are 
 potassium salts. These soaps are soluble in water, alcohol, 
 &c., but others, such as lead soap (lead plaster), calcium 
 soap^ &c., can be prepared which are insoluble in water. 
 It will readily be understood that ordinary washing soaps 
 are mixtuTcs of stearate, palmitate and oleate of sodium. 
 
 Hard soap. — Experiment 1. — Make first a strong lye with 
 one drachm of caustic soda and one ounce of water, and 
 next, a weak lye, with one drachm of caustic soda and 
 two ounces of water. Boil the latter gently with an 
 ounce and a half of beef-suet, for half an hour, in a vessel 
 only half filled with the mixture, and then add the strong 
 lye gradually while the boiling continues. The fat and 
 lye gradually unite and form a uniform mass, of a gluey 
 consistency, which after a time becomes thick and frothy. 
 If a drop of this, when pressed between the fingers, 
 presents firm white flakes, then add half an ounce of 
 common salt, boil for some minutes, and let the whole 
 mass cool quietly. We obtain a firm mass (soap) and a 
 watery liquid, in which the common salt and some free 
 soda remain dissolved. If tlie soap, when boiled with 
 distilled water, forms a turbid solution, it still contains 
 some unsaponified fat, in which case add to it some weak 
 lye, and continue boiling until the sample gives a clear 
 solution in water ; add again some common salt, and let 
 it cool. The soap prepared in this manner has the same 
 composition as common house-soap. Palm oil oi* cocoa-nut 
 oil is often used partly or entirely to supply the place of 
 .tallow; the palm oil because it is cheaper than tallow, 
 and the co(;oa-nut oil because it communicates to the soaj) 
 the property of forming a very strong lather. 
 
 Experiment 2. — Eepeat the former experiment, using 
 
SAPONIFICATION. — SOAP. 3 G 7 
 
 olive oil instead of tallow ; hard soap is likewise obtained 
 (o^7- or Marseilles soap). 
 
 Soft soap. — Experiment 3. — Prepare a(z;ain some oil-soap, 
 as above described, but instead of soda, use potash-lye, 
 which is prepared from caustic potash and water, and omit 
 the addition of common salt ; the glutinous mass does not 
 then pass by boiling into a hard soap, but. after sufficient 
 evaporation of the water, yields a soft mass. This kind 
 of soap is frequently employed in print-works for the 
 cleansing of coloured fabrics. If train oil, hemp-seed oil, 
 or linseed oil is used instead of olive oil, a darker-coloured 
 soft soap is obtained. 
 
 Ammonia acts far more feebly than potash and soda upon 
 fats. If .^ome oils are shaken up with ammonia, thick 
 white mixtures, called liniments, are obtained, which are 
 often applied by friction to the skin. 
 
 Experiment 4. — The action of common salt in soap- 
 making may be seen by trying to dissolve hard soap in 
 salt water ; no solution takes place, not even on boiling, 
 for soap is insoluble in salt water, and likewise in strong 
 lye ; therefore soap may be precipitated from a solution 
 in water by the addition of common salt. This method of 
 separation is sometimes employed on the large scale, since 
 it yields a purer isoap than when the water is removed by 
 evaporation ; f< )r, in the latter case, glycerine, surplus of 
 lye, and the impurities contained in the lye or fat, remain 
 mixed with the, soap, while by the former method they 
 are retained in the liquid. 
 
 Experiment 5. — Dissolve some hard soap in hot soft 
 water, and add white vinegar, a drop at a time, till the 
 liquid is thoroughly turbid. The acetic acid liberates the 
 t fatty acids of the s ap, which after a time rise to the 
 surface of the liquid and float there, being insoluble in 
 water. The liquid now contains sodium acetate. 
 
 Washing with soaps. — Soaps have two important pro- 
 perties : — 1st, they dissolve fat and oils ; 2nd, they are 
 very easily resolved, merely by mixing with much water, 
 into an acid salt and free alkali ; the latter dissolves, as 
 is well known, many organic substances, while the former 
 effects by its lubricity an easy washing away of the dis- 
 solved matter from other substances. On these two pro- 
 
368 
 
 EXPERIMENTAL CHEMISTRY. 
 
 perties depends the application of soap in washing. The 
 separated acid salt of the fatty acids both diminishes the 
 action of the free alkali, and keeps the articles pliant 
 which are washed with soap, while they would become 
 rigid if they were cleansed with caustic alkalies alone. 
 To prevent the shrinking of woollen articles, wash them 
 with a weak solution of sodium carbonate instead of with 
 soap. 
 
 Soap and Alcohol. — Experiment 6. — Pour one ounce of 
 alcohol upon one ounce of the shavings of soap ; the soap 
 is completely dissolved on heating in the water-bath, but 
 the solution congeals on cooling to a transparent jelly. 
 This jelly-like soap, mixed with camphor and ammonia, is 
 called opodeldoc. The white stars separating from this 
 consist of crystallized sodium stearate. All soaps pre- 
 pared from solid fats (rich in stearin) behave like tallow 
 soap. 
 
 Experiment 7. — Dissolve one drachm of Naples soap in 
 half an ounce of alcohol ; this solution does not coagulate 
 on cooling ; it forms a tincture of soap. By evaporation, a 
 diaphanous soap is obtained {transparent soapy All the 
 soaps made from the fluid fats (rich in oleinj act like the 
 Naples soap. 
 
 Experiment 8. —If some lime-water is added to a solution 
 of soap in water, a precipitate of insoluble calcium soap is 
 formed ; this explains why spring- water, which generally 
 contains calcium and magnesium salts (hard water), 
 neither dissolves soap nor lathers with it, and accordingly 
 cannot economically be used for washing. Hard water 
 may, however, be softened by the addition of sodinm 
 carbonate (common washing soda), which precipitates the 
 calcium and magnesium as insoluble carbonates. Of 
 course the metals can also be removed by soap, if enough 
 is used, but washer- women use soda instead because it is 
 chear^er. 
 
 Yellow soap. — The tallow and palm oil used in soap- 
 making is often mixed with common rosin, which at a 
 high temperature combines with alkalies even more easily 
 than the fats. The soap so obtained is called yellow soap. 
 It is cheap, but has a disagreeable odour. 
 
 3Iarine soap is made from cocoa-nut oil. It is soluble in 
 
SAPONIFICATION. * 3G0 
 
 somewhat dilute brine, and is therefore used for washing 
 in sea-water. 
 
 Glycerine. — Experiment 9. — In a deep basin, heat together 
 9 parts of olive oil (or any other glyceride), 5 parts of 
 finely-powdered litharge and a little water. A little more 
 water must be added from time to time to replace the loss 
 from evaporation. After a time the oil disappears, and a 
 firm mass insoluble in water is obtained and a watery 
 liquid. The mass is the insoluble lead soap generally 
 known as lead plaster. It consists, if olive oil has beer, 
 used, chiefly of lead oleate. The watery liquid is a solution 
 of glycerine containing some dissolved lead. It must be 
 separated from the liquid, and the latter thoroughly 
 saturated with sulphuretted hydrogen by j)assing a stream 
 of the gas through it. This throws down the lead as 
 sulphide, and the filtered liquid, evaporated to a syrup on 
 the water bath, yields glycerine. It generally retains, 
 however, a small quantity of lead. 
 
 A much better process for the preparation of glycerine 
 is generally adopted on the large scale. It depends on 
 the fact that superheated steam decomposes glycerides 
 into glycerine and the fatty acids, both of which are 
 carried over with the steam and readily condense in 
 separate layers. The process is usually applied to solid 
 fat (tallow, palm oil, &c.), and the solid fatty acids, 
 stearic and palmitic, are used for the manufacture of the 
 so-called stearin^ palm, or composite candles, now so largely 
 used. 
 
 Properties of Glycerine, — Pure glycerine is a colourless 
 syrupy liquid of sp. gr. 1*28. It mixes with water and 
 alcohol in all proportions, but is insoluble in ether. It 
 has a very sweet taste, whence its name (from yXvKog, 
 sweet). Distilled with steam, or at a reduced pressure, it 
 passes over unchanged, but under ordinary circumstances 
 the greater part is decomposed, and a substance of 
 pungent and irritating odour, called acrolein, CgH^O, is 
 produced. 
 
 Experiment 10. — Boil a little glycerine in a test-tube, 
 the irritating odour of acrolein will soon be perceived. If 
 some hydrogen potassium sulphate is mixed with the 
 glycerine, acrolein is produced in much larger quantities, 
 
 2 B 
 
370 ' EXPERIMENTAL CHEMISTRY. 
 
 but, unless elaborate precautions are taken, it is impossible 
 to remain in the laboratory while the experiment is in 
 progress, as the Yaponr, even in very minute quantity, 
 irritates the eyes insupportably. Acrolein, treated with 
 silver oxide, yields the silver salt of acrylic acid, AgC3H302 
 (page 302), of which acid acrolein is the aldehyde. 
 
 When glycerine is heated with fatty acids under pres- 
 sure, oils or fats identical with the proximate constituents 
 of the natural fats and oils (page 361) are obtained, water 
 being formed at the same time. 
 
 Group ii. — Drying or Varnish Oils. 
 
 We have seen that many seeds, when submitted to 
 pressure, yield fixed oils analogous in their nature to the 
 animal fats and oils. A certain number of these oils 
 possess the property of drying, that is, of becoming solid 
 and hard when exposed to the air. The change is attended 
 with the absorption of oxygen, but is not well understood. 
 It renders them very valuable in the manufacture of 
 paints and varnishes. The oils of linseed, hemp-seed, and 
 poppy- seed, and the oil of walnut kernels (nut oil), are 
 among the most important of this class. Linseed oil, 
 which is more largely used tthan the others, is the only 
 one which need be studied here. 
 
 All the drying oils are mixtures of glycerides. Linseed 
 oil contains the glyceride of a peculiar acid, linoleic acid. 
 They are, of course, all capable of saponification. 
 
 Linseed oil, — The well-known linseed, the seed of com- 
 mon flax, yields, on being subjected to pressure, a yellow 
 oil, equal to one-fourth of its own weight, which is 
 gradually bleached by long exposure to the sunlight. It 
 is most frequently used in oil varnishes. 
 
 Experiment 1. — Add to an ounce of linseed oil a quarter 
 of a drachm of litharge, and half a drachm of acetate of 
 lead ; put the mixture in a warm place, and frequently 
 shake it. The liquid, clarified by settling, now dries 
 much quicker than it would have done before ; it is used 
 in the manufacture of the common linseed oil varnish, 
 which, mixed with colours, is generally used for im- 
 parting a gloss to wood, metal, &c. The so-called oil- 
 cloth is cotton cloth smeared with coloured linseed oil ; 
 
WAXES AND SPERMACETI. 
 
 371 
 
 oil-silk is varnished silk. The oil is commonly prepared, 
 on a large scale, by heating one hundred pounds of linseed 
 oil with three pounds of litharge, and maintaining the 
 mixture for an hour at a temperature of 212'' F. (100'^ C). 
 A stronger heat renders the varnish darker and thicker, 
 and, besides, might easily cause it to boil over and take 
 fire. The slimy, dingy white sediment which remains 
 after both processes is a combination of mucilaginous 
 substances with oxide of lead. All oils contain, in the 
 unpurified state, mucilaginous (gummy and albuminous) 
 substances, which retard the drying ; these are rendered 
 insoluble by oxide of lead. Varnish is, accordingly, 
 linseed oil free from mucilage. 
 
 Experiment 2. — The difference between the drying and 
 non-drj^Dg oils may be shown by smearing two pennies, 
 one with olive, the other with linseed oil, and allowing 
 them to remain for several days in a warm place. The 
 linseed oil will dry up into a thin transparent solid layer. 
 
 Experiment 3. — Heat some linseed oil over a lamp, and 
 test the temperature of it occasionally by a thermometer. 
 At first the heat rapidly rises to 212° F. (100^ C), and 
 remains for some time at that temperature, during which 
 time the oil boils moderately ; this behaviour is occasioned 
 by all crude oil containing watery particles, which 
 evaporate at 212° F. (100° C). As soon as these have 
 volatilised, the temperature soon rises to 300° C. (572° F.), 
 or even higher, when the oil begins to boil for the second 
 time, but emits now a white smoke having a very dis- 
 agreeable odour. This vapour consists principally of 
 illuminating gas, from the decomposed oil, and burns, 
 when kindled, with a brisk flame. The oil at last ac- 
 quires a treacle-like consistence and a brown colour. It 
 is Called boiled oil. Printing inh is made with boiled oil, 
 lamp-black, and a little yellow soap. Putty is a mixture 
 of linseed oil and whiting. 
 
 Group iii. — The Waxes and Spermaceti. 
 
 These substances differ from the glycerides inasmuch as 
 their essential constituents are salts, not of the triad radical 
 propenyl, but of some of the monad alcohol radicals homo- 
 logous with methvl and ethyl (page 299). The acid radicals 
 
 2 B 2 
 
372 
 
 EXPERIMENTAL CHEMISTRY. 
 
 are those of the fatty acids, therefore they are homologues 
 of the radicals of formic and acetic acids, so that the 
 proximate constituents of these substances are true homo- 
 logues of the formate or acetate of methyl or ethyl. 
 
 Spermaceti, found in cavities in the head of the sperm 
 whale, consists chiefly of cetin ; Chinese wax, obtained from 
 the branches of certain trees in China, contains cerin, or 
 ceryl cerotate ; and hees-wax contains cerin and myricin, with 
 two or more other constituents. Other vegetable waxes 
 are known. 
 
 The following table will show the constitution of these 
 proximate constituents, and their relationship to the 
 simplest series of alcohols and fatty acids. Methyl 
 formate, the lowest possible member of the series, is 
 placed at the head for comparison : 
 
 Methyl Formate. 
 C2 H4 O2 = CH3, CHO2. 
 
 Cetyl Palmitate. 
 
 Cetin C30 O2 = C^g H33, C^g Hg^ O2. 
 
 Ceryl Cerotate. 
 
 Chinese wax C54 Hiog O2 = C2Y H55, C2Y H53 O2. 
 
 Myricyl Palmitate. 
 
 Myricin C46 H92 O2 = C30 H^i, G^q H31 O2. 
 
 These compounds are decomposed by caustic alkalies 
 just as the glycerides are, the products being an alcohol, 
 or hydrate of the basic radical, and a compound of the 
 acid radical with potassium, or sodium : 
 
 Myricin. Myricyl Alcohol. Potassium Palmitate. 
 
 ^30 1^61' H31 02 + K 0 H = C30 Hgi, 0 H + K Cig H31 02. 
 This is, in truth, a process of saponification. 
 
( 373 ) 
 
 CHAPTEE VIII. 
 
 VOLATILE OILS, RESINS, AND ALLIED BODIES. 
 
 The compounds enumerated in this chapter are closely 
 allied to one another. Many of them (the pure volatile 
 oils, caoutchouc, &c.) are hydrocarbons ; the rest are 
 compounds of carbon, hydrogen, and oxygen. The con- 
 stitution is not thoroughly understood, even of the best 
 known members of the different groups. The phenomenon 
 of isomerism (p. 295) is very common among them, many 
 of the volatile oils having the same formula as that of oil 
 of turpentine, CigHie- ^ derived from the animal 
 
 kingdom (ambergris, castoreum, civet), but the great 
 majority are the produce of plants. The following classi- 
 fication will be found useful. 
 
 Group I. Volatile, or Essential Oils, — Exist in several 
 parts of many plants, either alone or mixed with resin, &c. 
 They often separate by cold into two portions, one solid 
 and camphor-like, which contains oxygen, and is called 
 the stearopten ; the other liquid, and free from oxygen, 
 called the elseopten. They are commonly obtained by 
 distilling the plant, or portion of the plant, with water. 
 The oil comes over with the water and floats on its sur- 
 face when it condenses. The liquid oils of lemon and 
 orange peel, anise, cloves, lavender, thyme, and wormwood, 
 are among those isomeric with oil of turpentine. 
 
 Whenever we perceive an odour in a plant, it is pro- 
 bable that a volatile oil is present, which gradually 
 evaporates. But how incredibly diffused and diluted this 
 must be in many plants may be inferred from the fact 
 that scarcely a quarter of an ounce of volatile oil is con- 
 tained in one hundred pounds of fresh roses, or orange- 
 flowers. We most frequently find the volatile oils in the 
 flowers and seeds, sometimes in the stalks and leaves, and 
 
374 
 
 EXPERIMENTAL CHEMISTRY. 
 
 more rarely in the roots. The oils procured from the peel 
 of certain fruits, as the lemon, citron, bergamot-pear, &c., 
 are obtained by expression from the fresh rind. 
 
 An immense number of volatile oils are known. The 
 following are among the most important, 
 
 a.) From the flower : 
 
 Oil of roses, a yellowish, thick fluid, with flakes re- 
 sembling tallow floating in it. 
 
 Oil of orangeflowers (oil of neroli), colourless ; becomes 
 reddish on exposure to the light. 
 
 Oil of chamomile, a dark blue, thick liquid ; becomes 
 green, and finally brown, by age and light. 
 
 Oil of lavender, a yellowish, thin liquid. 
 
 Oil of cloves, yellowish, soon becomes brown; a some- 
 what thick fluid, heavier than water. 
 
 Oil of hops, greenish yellow. 
 
 Z>.) From seeds and fruits : 
 
 Oil of cumin, colourless ; becomes yellowish, and finally 
 brown, by age. 
 
 Oil of anise-seed, yellowish. 
 
 Oil of fennel, colourless or yellowish. 
 
 Oil of dill, yellow ; becomes brown in the light. 
 
 Oil of nutmeg, a pale yellow, thin liquid ; has the smell 
 of nutmegs. 
 
 Oil of hitter almonds, yellow ; heavier than water ; consists 
 chiefly of henzoyl-hydride, 0^11^,0,11, but contains hydro- 
 cyanic acid, and consequently is very poisonous. 
 
 Oil of mustard, yellowish, of an extremely pungent smell, 
 causing lachrymation ; contains sulphur. 
 
 Oil of juniper, colourless. 
 
 Oil of savin, colourless, or yellowish ; a thin fluid. 
 Oil of parsley, pale yellow ; yields much stearopten. 
 Oil of lemons, from lemon-peel. 
 Oil of orange-peel, very like oil of lemons. 
 Oil of hergamot, from the rind of the bergamot orange, 
 a pale yellow, very thin liquid. 
 c.) From the leaves and branches : 
 
 Oil of peppermint, colourless or yellowish, a very thin 
 liquid. 
 
 Oil of halm, pale yellow, has an odour like that of lemons. 
 Gil of marjoram, yellowish or brownish. 
 
VOLATILE OILS. 375 
 
 ■ Oil of thyme, when fresh, yellowish or greenish ; when 
 old, brownish-red. 
 
 Oil of sage, when fresh, yellowish or greenish ; when 
 old, brownish-red. 
 
 Oil of wormwood, dark green ; soon becomes brown or 
 yellow, and viscous in the light. 
 
 Oil of rosemary, colourless and very thin. 
 
 Cajeput oil, from the leaves of a tree growing in the 
 Moluccas ; the oil, when pure, is colourless ; the crude 
 oil is commonly green, and often contains camphor ; it has 
 a camphorated odour. 
 
 Oil of rue, pale yellow or greenish. 
 
 Oil of cinnamon, yellow ; soon becomes brown in the air ; 
 heavier than water. 
 
 Oil of turpentine, the most common of the volatile oils, 
 is contained in all our fir-trees, and exudes from them, 
 mixed with resin, as turpentine. When purified, it is 
 colourless and thin, and has an agreeable, penetrating 
 odour. An ordinary sort, possessing a disagreeable, 
 empyreumatio odour, obtained in the preparation of pitch 
 from pine resin, is crude oil of turpentine. 
 
 d.) From roots : 
 
 Oil of acorns, yellow or brownish. 
 
 Oil of valerian, pale yellow or greenish ; becomes rapidly 
 brown and viscous on exposure to the air. 
 
 It is very remarkable, that we sometimes find several 
 sorts of oil in one and the same plant. Thus, for example, 
 we find in the orange-tree three difi'erent kinds of oil ; one 
 in the leaves, another in the blossom, and a third in the 
 rind of the fruit. 
 
 Group II. Besins. — Solid bodies containing oxygen. 
 They have faint acid properties. Common colophony, or 
 rosin, which accompanies oil of turpentine, is a good 
 example. 
 
 Other resins are anime, copal, lac, and mastic. Amber is 
 a fossil resin. 
 
 Group III. Balsams. — Semi -solid masses. Some are 
 mixtures of resins and volatile oils. Of these the most 
 important are the difi'erent varieties of turpentine, in- 
 cluding Canada balsam ; Burgundy pitch ; balsam of Copa iba, 
 used in medicine, and balsam of Mecca, or balm of Liilead, 
 
376 
 
 EXPERIMENTAL CHEMISTRY. 
 
 of which the finest kind is hardly known in this country ; 
 others contain cinnamic acid (balsam of Peru, storax, tolu), 
 or benzoic acid (gu7n benzoin, dragon's bloody A few curious 
 and highly valuable animal substances, remarkable for 
 their odour, may be included among the balsams ; namely, 
 ambergris, found in the head of certain whales ; castor eum, 
 obtained from the beaver ; and civet, from the civet cat. 
 
 Group IV. Gum Besins are mixtures containing resin 
 gum and other ingredients. The most important are — 
 
 Asafoetida. from the root of a plant growing in Persia. 
 Its disgusting odour is due to the presence of about three 
 per cent, of a sulphuretted oil. 
 
 Gamboge, from the leaves and branches of a tree which 
 grows in Cambogia and Ceylon. 
 
 Myrrh, from Arabia and Abyssinia. Imported in the 
 form of reddish tears. 
 
 Olibanum, or incense. Burnt in religious ceremonies. 
 Brought from Arabia. 
 
 Scammony, from Syria and Asia Minor. Aleppo scam- 
 mony is the best. It has a strong odour and is used in 
 medicine. 
 
 Group V. Camphors. — Solid volatile bodies of peculiar 
 pungent odour. They contain carbon, hydrogen and 
 oxygen. Common, or laurel camphor, CioH^gO, obtained 
 from Laurus camphor a, a tree which grows in the East 
 Indian islands, is the most important. Borneo camphor^ 
 C^oHigO, is similar to common camphor. The stearoptens 
 of some volatile oils are closely allied to the camphors. 
 
 Group VI. Caoutchouc and Gutta percha, — These sub- 
 stances, though so different in properties, are allied in 
 composition to oil of turpentine. When pure they contain 
 no oxygen, and are said to have the formula CiqHiq. 
 
 VOLATILE OILS. 
 
 Preparation of Volatile Oils. — Experiment 1. — Put one 
 ounce of turpentine in a dish in a warm place, and when 
 it has become liquid transfer it to a capacious flask ; pour 
 upon it four ounces of water, and distil until about 
 three-fourths of the water have passed over. Pour the 
 residue, whilst stiil hot, into cold water, in which the non- 
 volatile portion of the turpentine will soon congeal into a 
 
VOLATILE OILS. 
 
 377 
 
 solid mass (resin), A strongly smelling, colourless liquid 
 — a volatile oil, commonly known under the name of oil of 
 turpentine — floats on the surface of the water. Turpentine 
 is the juice which exudes from pines and some other trees 
 when the inner bark is cut through. We see from this 
 experiment that it is a mixture of resin and volatile oil, 
 which latter is carried over as vapour with the water and 
 afterwards condensed. 
 
 If the distilled liquid is received in a pipette (p. 359), 
 the lower end of which dips in water, the oil will collect 
 in it and may easily be separated from the water. 
 
 Experiment 2. — Distil in the same manner half an ounce 
 of cumin-seeds (which have been previously bruised in a 
 mortar) in a retort containing four ounces of water-, until 
 two ounces of water have passed over. The drops floating 
 upon the water consist of a volatile oil, oil of cumin; they 
 have the smell and taste of the cumin- seeds, but in a 
 stronger degree, while the residue remaining in the retort 
 has scarcely the least smell or taste of them. All volatile 
 oils possess a burning taste, and are somewhat rough to 
 the touch; but the fat oils have a mild taste and an 
 unctuous feel. 
 
 Experiment 3. — Pour a drop of some volatile oil upon a 
 sheet of paper, and let it remain exposed to the air ; the 
 paper at first receives an apparent grease-spot, but this dis- 
 appears after a time, because the oil gradually evaporates. 
 
 If the oiled paper is placed upon a warm stove, evapo- 
 ration takes place much more rapidly. Aromatic oils are 
 employed in this way for perfuming apartments. Usually 
 a quantity of flowers, woods, and barks, finely cut up, are 
 moistened with the oils, and scattered as a fumigating 
 powder upon the stove. 
 
 Experiment 4. — Heat a quarter of an ounce of oil of 
 turpentine in a vessel to boiling. A thermometer in- 
 troduced into the liquid will indicate a temperature of 
 about 328° F. (160° C). Other oils boil with even more 
 difficulty. The vapour may be inflamed by a taper, when 
 it will burn with an intense sooty flame. It is easily 
 extinguished by covering the vessel with a board; but 
 ivater must on no account he employed for extinguishing burning 
 oils. Then remove the oil from the fire. After it is cold. 
 
878 
 
 EXPERIMENTAL CHEMISTRY. 
 
 mix it with some water, and again heat it; as long as 
 any water is present the temperature of the fluid will not 
 rise above 212^ F. (100° C). The ascending vapour is a 
 mixture of the vapours of water and oil. The same thing 
 occurs here as previously mentioned ; the less volatile oil 
 evaporates with the more easily volatile water. The oils 
 remain unchanged at the boiling point of water, but at 
 their own boiling point, between from 284° F. (140° C.) 
 and 392° F. (200° C), they become not unfrequently 
 somewhat empyreumatic : this is the reason why water 
 is always added in the preparation of oils, and also in the 
 redistillation of them (rectification). 
 
 Experiment 5. — Inflame some drops of oil of turpentine 
 put upon a shaving, and also a piece of camphor laid upon 
 water ; both bodies will ignite, and burn with a highly 
 luminous and sooty flame. The volatile oils are far more 
 easily combustible than the fat oils, which in order to 
 burn with a flame must be heated to 662° F. (350° C). 
 We have consequently in oil of turpentine a convenient 
 means for speedily lighting oil-lamps ; it being merely 
 necessary to smear the wick with a few drops of it. 
 
 Experiment 6. — Pour a mixture of half an ounce of 
 absolute alcohol with half a drachm of oil of turpentine 
 into a spirit-lamp ; the mixture gives, when lighted, a 
 strongly illuminating, but no longer a sooty flame, since 
 all the carbon of the oil of turpentine is converted by the 
 heat of the burning alcohol, rich in hydrogen, into 
 illuminating gas, and then into carbonic anhydride and 
 water. This mixture has sometimes been used in lamps 
 constructed for the purpose, and which are so made that 
 the liquid evaporates in them, and the vapour ignites as 
 it issues from several small openings. 
 
 Volatile Oils and Water, — Experiment 7. — Drop some oil 
 of cumin upon water ; the oil floats on the surface without 
 mixing with the water, for most of the volatile oils are 
 ligJiter than water ; but there are some, such as oil of 
 cinnamon, oil of cloves, and oil of bitter almonds, which 
 are heavier than water, and sink in it. 
 
 If the mixture is briskly shaken, the water becomes 
 turbid, because the oil is thus divided into small, invisible 
 globules, which are kept suspended in the water. The 
 
VOLATILE OILS. 
 
 379 
 
 water may be again clarified by filtration, but it retains 
 the smell and taste of the oil, since a small quantity of it 
 remains dissolved. Many such solutions are kept in the 
 apothecaries' shops, under the name of medicated or distilled 
 ivaters. It is well to keep them protected from the light, 
 and in full vessels, — both light and air having a decom- 
 posing action on the volatile oils. They are commonly 
 prepared by distilling with water the vegetable substance 
 containing the oil, as thereby a more intimate combination 
 of the water with the oil is effected than by merely 
 shaking it up. 
 
 Volatile Oils and Alcohol, — Experiment 8. — Add a drop of 
 oil of cumin to a little strong alcohol. It dissolves 
 readily and entirely. All the volatile oils are soluble in 
 alcohol, most of them even in alcohol of eighty per cent. ; 
 but the non-oxygenated oils, such as oil of turpentine, oil 
 of lemons, &c., only in very strong alcohol. It an ounce 
 of water, in which half an ounce of sugar has previously 
 been dissolved, is added to the solution, we obtain cumin- 
 cordial. In this manner, by the aid of various aromatic 
 oils, the innumerable cordials or liqueurs occurring in 
 commerce can be prepared. They were formerly manu- 
 factured from aromatic seeds, flowers, herbs, &c., by 
 pouring brandy over them, the brandy being afterwards 
 distilled or drawn off, whereby a spirituous solution of 
 the volatile oils was likewise obtained. 
 
 Experiment 9. — If some drops of oil of bergamot, orange- 
 flower, lavender, or rosemary, are dissolved in half an 
 ounce of strong alcohol, we obtain a spirit of a very 
 pleasant odour. In a similar way the innumerable kinds 
 of perfumed waters are prepared, at the head of which 
 stands the well-known eau de Cologne. The fumigating 
 spirit also, which, instead of the fumigating powder, 
 is often sprinkled on a warm stove, has a similar composi- 
 tion. Camphorated spirit, much used in medicine, is a 
 solution of camphor in alcohol. 
 
 The volatile oils are not only dissolved by alcohol, but 
 also by ether and concentrated acetic acid. A solution of 
 oil of cloves, cinnamon, bergamot, and thyme, in acetic 
 acid, is used as aromatic vinegar, on account of its refresh- 
 ing odour. 
 
380 
 
 EXPERIMENTAL CHEMISTRY. 
 
 The volatile oils may also be mixed with fat oils, and 
 with some kinds of tallow and lard ; hence by means of 
 them an agreeable odour may be imparted to the latter, as, 
 for instance, in hair oils, pomatum, &c., or grease-spots be 
 dissolved and removed by them from various articles. 
 Volatile oils mixed with alcohol yield, when shaken up 
 with olive oil, a turbid, milky liquid, because the alcohol 
 does not dissolve the olive oil; this behaviour may be 
 ta,ken advantage of for testing the purity of commercial 
 oils. 
 
 Conversion of the Volatile Oils into Besins. — Experiment 10. 
 — Let some oil of turpentine remain exposed to the air for 
 some weeks, in a cup covered with paper, and afterwards 
 put the cup in a warm place to evaporate the oil ; it will 
 not entirely volatilise, but will leave at first a viscous, and 
 afterwards a vitreous residue. This residue is a kind of 
 resin, obtained by the absorption of oxygen. Eesins are 
 often produced by the spontaneous oxidation of volatile 
 oils. For this reason, old oil of turpentine is not suitable 
 for removing grease spots, paint, &c., from clothing. 
 
 RESINS. 
 
 Preparation of the Besins. — Experiment 1. — Spread a little 
 turpentine upon a board, and put the board for some time 
 near a heated stove ; the oil of turpentine evaporates, but the 
 resin remains behind as an amorphous brittle mass. In some 
 countries, incisions are made through the bark of fir-trees, 
 and the turpentine which exudes is distilled with water, 
 when the volatile oil passes over, the resin remains behind. 
 Large quantities of such resin are now exported from the 
 forests of America. 
 
 KesinoTis juices, which harden in the air, forming solid 
 resins exude, either spontaneously or through incisions made 
 for the purposes, not only from our fir-trees, but also from 
 many other trees and shrubs, particularly those of hot 
 climates. Almost all the resins occurring in commerce are 
 procured in this manner. 
 
 Experiment 2. — Eesin is deposited most abundantly in 
 those parts of the trees where the branches join the trunk ; 
 wood impregnated with such resin is called resinous wood. 
 If a piece of resinous wood is lighted at the upper end, 
 
VOLATILE OILS. 
 
 381 
 
 and held by a wire in an oblique position over a basin of 
 water, one portion of the resin burns up ji^g 107. 
 with a sooty flame, while another part is 
 melted by the heat, and runs down into 
 the vessel beneath. Besin is not soluble in 
 water; hence it hardens in the latter 
 without mixing with it. 
 
 Experiment 3. — Pour strong alcohol upon 
 some resinous wood, and let it remain 
 for a day in a warm place ; the resin is 
 dissolved, and the woody fibre remains 
 behind. The solution is poured into eight 
 times its quantity of water, which is thereby rendered 
 milky, because the resin is precipitated, but in such a 
 state of fine division, that it floats about in the form of 
 small globules. If this milky fluid is heated to the boiling 
 point, the resinous particles soften and unite with each 
 other in small lumps, which may be taken out and pressed 
 together in larger masses. This is a third method of 
 extracting resin from vegetable substances. 
 
 Besin and Water. — The resins as a general rule are inso- 
 luble in water, and therefore tasteless ; but some of them 
 in very small quantities may be dissolved, and these 
 usually have a bitter taste. But many of the resins 
 which occur in commerce contain some water in a state of 
 minute division, and are thereby rendered dull and opaque ; 
 common pine-resin and boiled turpentine furnish examples 
 of this. 
 
 Colophony or Bosin, — Experiment 4. — Heat a piece of 
 solid turpentine, or else some pine-resin, in a spoon, till 
 all the water is evaporated ; the anhydrous resin will now 
 appear perfectly transparent. In this state it is called 
 colophony, or rosin, being white when it is moderately 
 heated, but brown when the heat is so strong as to convert 
 a part of the resin into black pitch. Colophony is so brittle, 
 that it may easily be reduced to a powder. When the 
 bow of a violin is rubbed with it, the rosin powder formed 
 remains adherent to the hairs, and these then again adhere 
 better to the strings of the violin. A similar effect is 
 produced on the cords which sustain the weights in 
 clocks when they are rubbed with rosin to prevent their 
 
382 
 
 EXPERIMENTAL CHEMISTRY. 
 
 slipping. The resins, accordingly, exert an effect con- 
 trary to tliat of oil ; by resin, a rough, uneven surface is 
 produced ; by oil, a smooth, slippery surface. 
 
 Action of Heat on Besins. — The experiment first j)er- 
 formed reveals at the same time another property of resin ; 
 namely, its easy fusibility. Most of the resins require, in 
 order to become fluid, a heat which is somewhat higher 
 than that of boiling water. If melted rosin is poured 
 upon a board, it spreads, and forms after hardening a solid, 
 brilliant coating on the wood. The resins are hereby well 
 adapted for protecting wood or metal from the penetra- 
 tion of air or water. For this reason, iron rails and iron orna- 
 ments are covered with a coating of pitch, to prevent them 
 from being so quickly oxidised by the oxygen of the air ; 
 for the same reason, also, wine-casks and beer-barrels are 
 smeared with pitch, that no air may penetrate into the 
 casks, and that no beer may penetrate into the staves. 
 The wood- work of ships, the hatches, &c., are covered 
 with tar to keep out the sea- water and rain ; and finally, also 
 the solid and tenacious resin, shell-lac, which is formed by 
 insects on the twigs of certain trees growing in the East 
 Indies, is employed in the form of sealing-wax. 
 
 Sealing-wax. — Experiment 5. — Melt together in a small 
 ladle one-fourth of an ounce of pale shell-lac, one drachm of 
 turpentine, one drachm of cinnabar, and three- fourths of a 
 drachm of prepared chalk; scrape out the mass w^hile yet 
 soft, and roll it out into sticks by the hands, moistened 
 with water. The turpentine renders the sealing-wax 
 more imflammable, and the cinnabar imparts to it the 
 favourite red colour. V arious other colours are given to 
 it by chrome-yellow, ultramarine, Brunswick-green, lamp- 
 black, bronze-powder, &c. 
 
 Bosin-gas. — Experiment 6. — When rosin is heated above 
 its melting point, it kindles and hums with a luminous and 
 sooty flame, leaving ])eliind some charcoal. Therefore 
 powdered rosin, when blown into a flame of the lamp, burns 
 vividly. 
 
 Burnt Pitch. — If the rosin, after it has burnt for some 
 time, is extinguished by putting aboard over it, we fcliall 
 have as a residuum a black, burnt resin, ship-pitch, and 
 cobbler's loax, possessing great tenacity. 
 
RESINS. 
 
 383 
 
 Lamp hlack. — Experiment 7. — If you hold a cone made of 
 blotting-paper over burning pine-wood, it will soon 
 become lined with soot. The well-known lamp-hlack 
 is prepared on a large scale by a similar method. 
 Eesinous wood, or the resin itself, is burnt with an in- 
 sufficient supply of air in a stove furnished with long 
 flues, or with a chamber in which the smoke deposits its 
 carbon on its passage through. 
 
 Experiment 8. — If some amber is scattered on glowing 
 charcoal, a vapour having a pleasant balsamic odour is 
 emitted from it as it smoulders away. Amber, frank- 
 incense, benzoin, and mastic are on this account fre- 
 quently used for fumigating purposes. 
 
 Besin and Alcohol. — Experiment 9. — Wrap half an ounce 
 of sandarach (a resin which comes from Barbary) in paper, 
 and break it with a hammer into smaller pieces ; then 
 mix it with a drachm of sand, which has been previously 
 freed from its finer particles by washing and afterwards 
 thoroughly dried, and pour the mixture into a glass vessel, 
 with two ounces of strong alcohol. Tie a piece of bladder 
 over the vessel, or cork it, and let it remain for several 
 days in a warm place, frequently stirring it round. The 
 clear solution of resin thus obtained is called lac-varnish, 
 because, when smeared over metal, wood, or paper, it 
 leaves behind, after the alcohol has evaporated, a 
 varnished, shining coat. If alcohol is poured upon the 
 sandarach, unmixed with sand, resinous powder will cake 
 together on the bottom of the vessel, forming a tenacious 
 mass of resin, which dissolves much more slowly. To 
 lacquer or varnish, then, is to coat the surface of anything 
 with resin. By this coat of varnish, articles not only 
 acquire a beautiful brilliancy, but are rendered at the same 
 time impervious to air and water. When paper articles, 
 as drawings, maps, &c., are to receive a coat of varnish, 
 size or a solution of gum must previously be spread over 
 them several times, as the solution of resin would other- 
 wise penetrate into the fibres of the paper, and render it 
 grey and transparent. This imbibition is usually prevented 
 in wooden articles by smearing them with linseed oil 
 before putting on the varnish. When the varnish is 
 applied on places that are wet, white opaque spots are 
 
384 
 
 EXPERIMENTAL CHEMISTRY. 
 
 formed, because the resin is separated by tbe water as a 
 dull white powder. 
 
 Experiment 10. — Dissolve half an ounce of shell-lac in 
 strong alcohol; a turbid liquid is obtained, as the shell- 
 lac contains, besides the resin, small quantities of wax and 
 mucilaginous substances, which float about undissolved in 
 the solution of resin. This solution is also employed as a 
 lac- varnish, but much more frequently as the so-called 
 French polish of the cabinet-makers ; that is, as a solution 
 of resin, which they rub continuously upon the wood with 
 a ball of linen, until the alcohol has evaporated. By this 
 means a still smoother and finer polish is obtained than 
 by merely applying the resinous solution with a brush, the 
 marks of which frequently remain visible. The finer 
 articles of furniture are usually French polished, the more 
 common ones varnished. 
 
 Besins and Oils. — Experiment 11. — Mix half an ounce of 
 dammara resin with some sand, and pour over the mixture 
 two ounces of oil of turpentine ; after a few days you will 
 obtain an almost complete solution, for all the resins are 
 soluble in the volatile oils. These solutions are also 
 frequently employed as lac-varnishes ; they dry, indeed, 
 more slowly, but form a more tenacious coating, which is 
 less liable to crack. The paler and finer varieties of varnish 
 are principally prepared from amber, copal, dammara, 
 shell-lac, sandarach, and mastic ; the inferior and darker 
 kinds, from amber-colophony, common colophony, turpen- 
 tine, asph^iltum, &c. A yellow colour is sometimes given 
 to the pale varnishes by the addition of dragon's-blood, or 
 gamboge. 
 
 The resins are likewise soluble in fat oils. Many of 
 the ointments and plasters of the apothecaries consist of 
 mixtures of fats and resins, and it is the latter which 
 communicate to the former the property of adhering to 
 the skin. Turpentine is sometimes employed for this 
 purpose. 
 
 The use of resins in soap-making has already been 
 noticed. They are also used by paper-makers, to prevent 
 the porosity of the paper and the consequent running of 
 the ink. 
 
CAOUTCHOUC AND GUTTA-PEKCHA . 
 
 385 
 
 3) 
 
 CAOUTCHOUC AND GUTTA-PERCHA. 
 
 Caoutchouc^ or India-rubber. — When incisions are made 
 in the bark of certain large trees, of which the Siplionia of 
 South America and Java, and the Ficus elastica of Assam, 
 are the most important, a milky juice exudes, which dries 
 in the air to ordinary caoutchouc. It is often imported in 
 the form of bottles, which are made by spreading the 
 milky juice on clay moulds and drying it over a fire. 
 
 Experiment 1 . — Caoutchouc at the ordinary temperature is 
 hard and stiff, but it becomes soft when 
 it is put into hot water or held near 
 
 the fire. Cut from a piece of thin sheet 
 
 caoutchouc, softened by heat, a square / j 
 piece, apply it evenly round the ends 
 •of two glass tubes, and then clip off with a pair of scissors 
 the ends of the strip in the direction marked out in the 
 annexed figure : the fresh surfaces of the caoutchouc adhere 
 firmly to each other (but still more p.^ 
 closely when they are pressed together 
 with the nail, yet without touching 
 the freshly cut surfaces), and thus is 
 formed a tube, which firmly tied at both ends, connects 
 the two glass tubes air-tight to each other. 
 
 To the chemist, tubes made of caoutchouc are of the 
 utmost value. They are sold of all sizes, and at a very 
 moderate price. Caoutchouc corks also have been intro- 
 duced into all laboratories. They are very useful, and 
 may readily be bored with ordinary brass-tube cork- 
 borers. 
 
 Caoutchouc is perfectly insoluble in water and alcohol, 
 but pure ether, benzene (the lightest portion of coal-tar 
 naphtha), and some volatile oils, including turpentine, 
 dissolve it more or less perfectly. The best solvents are 
 caoutchoucine {vide infra) and a mixture of carbon di- 
 sulphide, with about 8 per cent, of absolute alcohol. 
 When the solvent evaporates, the caoutchouc is left un- 
 altered, and solutions of this kind are therefore largely 
 used to render fabrics water-proof (the Mackintosh 
 process). The gas bags used by chemists are made in 
 this way. 
 
 2 c 
 
386 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 2. — Digest some india rubber in a stoppered 
 bottle with one of the solvents named above. The solu- 
 tion so obtained may be used for waterproofing, and in 
 the laboratory for a variety of useful purposes. 
 
 Caustic alkalies, cold or hot, have no action on 
 caoutchouc. It is affected by strong nitiic and sulphuric 
 acids and by chlorine, but not by the majority of acids. 
 
 The whole of the caoutchouc does not dissolve in the 
 above experiment, for caoutchouc appears to be a mixture of 
 two substances, one of which is sparingly soluble. 
 
 Experiment 3. — Allow a little of the solution obtained 
 in Experiment 2 to evaporate on a slip of grass. The 
 residue will be seen to be perfectly transparent and colour- 
 less (pure caoutchouc), for the colour of ordinary india- 
 rubber is due entirely to impurities. 
 
 Experiment 4. — Heat a little caoutchouc in an iron spoon 
 over a lamp, very gently. It will melt to a viscid mass, 
 which does not recover its elasticity on cooling. 
 
 Experiment 5. — Marine Glue. — Dissolve half-an-ounce of 
 caoutchouc in two ounces of coal-tar with the assistance 
 of heat, then add one ounce of sb ell-lac and heat the whole 
 till it is homogeneous. A very powerful cement is obtained, 
 which is readily melted by heat. 
 
 Experiment 6. — CaoutcJioucine. — Distil a little caoutchouc 
 very cautiously in a Florence flask with a large bent tube, 
 keeping the receiver as cool as possible. A volatile oil of 
 strong empyreumatic odour comes over, and can be ren- 
 dered colourless by redistillation. This is called caoutchou- 
 cine. It is a mixture of two or more hydrocarbons, 
 which are isomeric with one another and perhaps with 
 caoutchouc itself. It is an excellent solvent for caoutchouc 
 and resins. 
 
 Vulcanized Caoutchouc. — When caoutchonc is mixed with 
 flowers of sulphur, or red antimonious sulphide, and the 
 mixture kneaded in an iron vessel at a temperature of 
 about 250° F.(121°C.), the mineral substance is taken up 
 in a very curious manner. The caoutchouc acquires 
 additional elasticity ; it no lor ger hardens with cold, and 
 may be heated to a much higher temperature than 
 ordinal y caoutchouc without becoming sticky. This is 
 the so-called vulcanized caoutchouc, which is applied to so 
 
GUTTA-PERCHA. 
 
 387 
 
 many useful purposes. The kind made with antimony is 
 called red ruhher. 
 
 Ebonite, — When the mixture of caoutchouc and sulphur 
 is heated for four hours to 302° F. (150° C), a further 
 change takes place, and the beautiful black substance 
 called ebonite is obtained. At the temperature named it is 
 soft, and can be moulded, but when cold it is as hard 
 as horn, and can readily be cut and polished. Combs, 
 beads, and many other articles are now made of it. It is 
 of great value to the electrician, as it develops an amaz- 
 ing quantity of electricity when rubbed. It is insoluble, 
 even in carbon disulphide. 
 
 Gutta-percha, — The juice of the Isonandra gutta, a tree 
 which grows in Malacca and the islands of the Indian 
 archipelago, is obtained like caoutchouc, which it resembles 
 in many respects. It is imported in rough masses. 
 
 Gutta-percha dissolves easily, with the aid of heat, in 
 benzene, oil of turpentine, carbon disul})hide and chloro- 
 form. On allowing the solution to evaporate, the gutta 
 remains as a brownish-red porous film. 
 
 Gutta differs in several important particulars from 
 caoutchouc, with which however it appears to be identical 
 in composition. At ordinary temperature, it is tough and 
 flexible, but not elastic. At low temperature it is very 
 hard and brittle, but at about 100° F.(38° C.) it becomes 
 so soft that it can readily be welded or pressed into any 
 desired form. It is a non-conductor of electricity, and is 
 therefore largely used for coating telegraph wires. 
 
 When exposed to the air, gutta-percha undergoes slow 
 oxidation and becomes brittle. A resin is formed. Vul- 
 canized caoutchouc often undergoes a similar change. 
 
 Gutta-percha is attacked by strong nitric and sulphuric 
 acids. Hydrofluoric acid has no action on it, and it is 
 therefore used for making bottles to contain that acid. 
 
388 
 
 EXPERIMENTAL CHEMISTRY. 
 
 CHAPTER IX. 
 
 DERIVATIVES OF AMMONIA. ALKALOIDS. 
 
 We have already seen (p. 303) tliat a large number of 
 compounds can be formed, which may be regarded as 
 ammonia, in which the hydrogen is partly or entirely 
 replaced by alcohol radicals (amines), or acid radicals 
 (amides). The amines are true analogues of ammonia, and, 
 like ammonia, combine with acids to form salts, which are 
 called compound ammonium salts. The great majority of 
 these artificial ammonia derivatives can only be prepared 
 by difficult processes, and their description is therefore 
 left to more advanced manuals of chemistry. The very 
 important and interesting body called aniline will serve as 
 a type of the amines. 
 
 aniline, or phenylamine. 
 
 Experiment 1. — Take some powdered indigo ; add to it 
 about an equal quantity of very strong solution of potash, 
 and distil in a retort as long as any brown oil comes over. 
 Separate the oil from the ammoniacal water which accom- 
 panies it, and distil it again at as low a temperature as 
 possible. The distillate is now colourless, and consists of 
 aniline. This process is expensive, as it involves the loss 
 of a good deal of indigo. 
 
 Experiment 2. — The hydro-carbon called benzol, or benzene, 
 CgHg, is now prepared in very large quantities from coal- 
 tar. Take half an ounce of fuming nitric acid in a small 
 beaker glass, or large test-tube, warm it slightly, and 
 add, in very small quantities at a time, about an equal 
 quantity of benzene. A curious change takes place, 
 whereby the benzene is converted to nitrobenzene, C6H5NO2 
 
ANILINE, OR PHENYL AMINE. 
 
 389 
 
 (p. 306). On adding a little water, the nitrobenzene falls 
 to the bottom as a heavy yellow oil, insoluble in water, 
 which possesses a smell closely resembling that of bitter 
 almond oil. Wash the oil with water containing a little 
 caustic soda and separate it by a pipette. Cover some 
 granulated tin with strong hydrochloric acid and add the 
 nitrobenzene a little at a time. Towards the end of the 
 reaction the mixture should be heated, a new and peculiar 
 smell is now observed. The liquid contains aniline 
 combined with hydrochloric acid. Add excess of caustic 
 soda which liberates aniline. Then shake the liquid with 
 ether and decant the etherial solution of aniline. If this 
 is allowed to evaporate in a shallow basin, aniline is 
 obtained. 
 
 The action consists in the replacement of oxygen by 
 hydrogen. 
 
 Nitrobenzene. Aniline. 
 
 [Ce H5 N O2 + 6 H = Ce N + 4 0. 
 
 Aniline is very little heavier than water (sp. gr. 1 -03). 
 It is sparingly soluble in water, readily in alcohol and 
 ether. It boils at 363° F. (184° C). Its aqueous solution 
 is feebly alkaline. When exposed to the action of oxidiz- 
 ing agents, aniline yields a series of colours, which for 
 brilliancy and variety are unrivalled. The manufacture 
 of these so-called aniline, or coal-tar colours is now an 
 important branch of industry. Their discovery is a 
 remarkable example of the benefits which science confers 
 on civilization and commerce. 
 
 Experiment 3. — Add a little solution of bleaching powder 
 to a few drops of aniline on a white plate. A beautiful, 
 though evanescent, violet colour will be produced. This 
 is an excellent test for aniline. 
 
 Experiment 4. — When sulphuric acid is added to aniline, 
 a crystalline mass of sulphate of aniline, (CgH^N)2H2S04, is 
 formed, which is very soluble in water, and may be purified 
 by recrystallization. 
 
 Take a cold and somewhat dilute solution of this salt, and 
 add to it a cold solution, also somewhat dilute, of potassium 
 dichromate. Stir at intervals for ten or twelve hours. At 
 the end of that time a black mass will have formed, which 
 may be washed, first with water, and afterwards with 
 
390 
 
 EXPERIMENTAL CHEMISTRY. 
 
 boiling benzene, which last dissolves out a tarry substance. 
 The residue is the beautiful aniline purple, or mauve. It 
 dissolves easily in alcohol, and the solution may be used 
 for dyeing silk or woollen goods. Vegetable fabrics, such 
 as cotton, do not hold the colour, but require the assistance 
 of some mordant. 
 
 Exjperiment 5. — Add to a little aniline, in a test-tube, 
 several grains of dry mercuric chloride, and boil the 
 mixture for a few minutes. The liquid gradually becomes 
 almost black; allow it to cool, and pour it into a large 
 quantity of strong alcohol, which immediately acquires a 
 magnificent crimson colour, and may be used for dyeing 
 silk and wood. This is the colour generally knowD as 
 roseine, or magenta. It is the hydrochlorate of a colourless 
 base called rosaniline^ CaoH^gNgjIICl. The base may be 
 thrown down by potash. 
 
 Many salts of aniline besides the sulphate can be 
 prepared. Most of them can easily be purified by 
 crystallization. 
 
 UREA. 
 
 Carbamide, or Carhonyl diamide, COH4N2 = CO(NH2)2. 
 
 This important body maybe viewed as an amide, although 
 it differs from most amides in that it combines with acids. 
 Its constitution has already been explained (p. 305). 
 
 Experiment 1. — Evaporate a pint of fresh urine on a 
 water bath* to about one-eighth of its bulk ; allow it to 
 cool. Reserve a small portion, and mix the rest with about 
 an equal volume of a saturated solution of oxalic acid. A 
 crystalline precipitate of oxalate of urea, (COH4N2)2H2C204, 
 will form before long. When it has stood for a few hours, 
 the liquid may be poured off, and the crystals pressed 
 with blotting-paper, and dissolved in the smallest possible 
 quantity of warm water. Chalk is now added in excess, 
 when the oxalic acid is thrown down as the insoluble 
 calcium oxalate (p. 356), and, together with the excess of 
 chalk, may be removed by filtration. The clear liquid is 
 
 * A common saucepan without the cover makes a most excellent 
 \vat(3r-bath. It should be two-thircls filled with water, and the basin 
 containing the substance to be heated rested on its mouth, the basin 
 being of course somewhat wider than the saucei^an. 
 
NATURAL ALKALOIDS. 
 
 391 
 
 now to be concentrated to a small bulk on the water-bath, 
 when it will yield on cooling beautiful crystals of urea, 
 slightly coloured, however, by the pigment of the urine. 
 
 Experiment 2. — The other portion of the concentrated 
 urine may be mixed with strong nitric acid. Beautiful 
 pearly crystals of nitrate of urea, COH^N2HN03, will 
 separate. 
 
 Experiment 3. — When urine putrefies, a kind of fermen- 
 tation takes place, and the urea is converted to ammonium 
 carbonate : 
 
 GOH,N2 + 2H,0 = (NH.XCOj. 
 
 The smell of ammonia in putrid urine is well known. 
 
 Experiment 4. — Synthesis of urea. — Melt some potassium 
 cyanide in a porcelain crucible, and add red lead, or 
 litharge, in small portions at a time until it ceases to 
 be reduced by the cyanide, and a little remains unchanged. 
 Allow the crucible to cool, dissolve the mass in water, 
 and add dry ammonium sulphate equal to twice the 
 weight of the original cyanide. Evaporate to dryness 
 on a water-bath, boil the dry mass with strong alcohol 
 (methylated spirit), and filter. The filtered liquid will, 
 on evaporation, yield colourless crystals of pure urea. 
 
 This process, discovered by Wohler, in 1828, is of great 
 interest, because it afforded the first example of the 
 synthesis of an organic compound (p. 102). Its details 
 may be explained as follows : — The cyanide is first con- 
 verted into cyanate by the oxygen of the lead-oxide : 
 
 Potassium Potassium 
 Cyanide. Cyanate. 
 
 KCN-fPbO = KCNO-fPb. 
 When ammonium sulphate is added, ammonium cyanate 
 and potassium sulphate are formed by double decom- 
 position. But ammonium cyanate is instantly changed 
 by heat into urea, which is isomeric with it : 
 
 Ammonium 
 Cyanate. Urea. 
 
 NH.CNO = C0H,N2. 
 
 NATURAL ALKALOIDS. 
 A large and important class of compounds containing 
 nitrogen exists in different plants, to which the name 
 of alkaloids, or natural bases, is applied. They are 
 
392 
 
 EXPERIMENTAL CHEMISTRY. 
 
 commonly bitter in taste, and exceedingly active in 
 properties, some of them being among the most virulent 
 of known poisons. A few of them (nicotine, conine) are 
 volatile liquids, containing only carbon, hydrogen and 
 nitrogen, but the majority are crystallme solids, which 
 contain oxygen as well. Many of them have an alkaline 
 reaction, and all are capable of combining with acids and 
 forming definite salts. There can be no doubt that the al- 
 kaloids belong to the class of ammonia derivatives, although 
 few if any of them have as yet been prepared synthetically. 
 
 TOBACCO —NICOTINE. 
 
 Experiment. — Boil a quarter of a pound of common 
 shag tobacco for a short time with a pint of water. Pour 
 off the brown extract, and press the tobacco in calico. 
 The liquid contains nicotine in combination with malic 
 and citric acids. Evaporate it down on the water-bath 
 until it has the consistence of oil ; put it into a small 
 stoppered bottle with about an equal quantity of strong 
 potash solution and some ether or benzene, shaking the 
 bottle at intervals for an hour. The potash liberates the 
 nicotine from its combination, and the ether dissolves it. 
 The ethereal solution may then be drawn off into a basin, 
 and the ether allowed to vaporate, when nicotine in a 
 somewhat impure state will remain. It may be purified 
 by distillation, but as the boiling point is high (247^ C. 
 ~ 4:1 T F.), a portion is destroyed by the heat. This may 
 be avoided by distilling in a current of hydrogen, when 
 the alkaloid is obtained as a colourless oil, of sp. gr- 
 1-011. 
 
 Nicotine has the formula C1QH14N2. It is a deadly 
 poison, and possesses a terribly acrid and burning taste. 
 It is strongly alkaline, and forms a definite series of tsalts. 
 It is very soluble in water, alcohol, ether, and benzene. 
 
 Tobacco smoke is a complex and imperfectly known 
 mixture. It contains some permanent gases, CO2, &c., 
 and some empyreumatic oils, &c., in a state of vapour. 
 The tobacco oil which collects in pipes, and which is often 
 mistaken for nicotine, is an acid, tarry oil, analogous to 
 that formed during the imperfect combustion of wood, &c. 
 It contains some nicotine, but only a small quantity. 
 
PERUVIAN BARK — QUININE. 
 
 393 
 
 During the burning of tobacco, a slight deflagration is 
 often noticed. This is due to nitre, which is always 
 present in tobacco. 
 
 Conine is a volatile alkaloid, analogous in nicotine. It 
 is contained in hemlock, and has the formula CgHi-^N. 
 
 PERUVIAN BARK QUININE. 
 
 This celebrated bark, from which one of the most 
 valuable of medicines is obtained, has sometimes been 
 called Jesuits' bark, because its medicinal value was 
 believed to have been first made known to Europeans by 
 the Jesuits. It occurs on several species of the cinchona- 
 tree, which flourishes in Peru, but is now cultivated with 
 great success in India. It contains several alkaloids, of 
 which quinine, C20II24N2O2, and cinchonine, C20H24N2O, 
 are the most important, in combination with a peculiar 
 acid, called quinic, or Jcinic acid, C^11i20q. 
 
 Experiment 1. — Into the percolating apparatus used in 
 preparing tannin (p. 358), introduce some yellow cinchona 
 bark (the yellow is the best kind) in fine powder, and 
 pour on it some very dilute hydrochloric acid (1 of acid 
 to 24 water). As the acid passes through, it combines 
 with the alkaloids, and the liquid so obtained contains the 
 hydrochlorates of quinine and cinchonine, together with 
 a good deal of the colouring matter of the bark. The 
 addition of acid may be repeated three or four times. To 
 the acid solution, sodium carbonate is now added to 
 alkaline reaction, which throws down the alkaloids, 
 together with some colouring matter. After standing for 
 some time, pour off the greater part of the liquid and 
 evaporate the remainder, containing the alkaloids, to dry- 
 ness on a water-bath. The dry mass may now be shaken 
 up with ether in a small stoppered bottle. This takes up 
 the quinine, which can be obtained as a resinous mass by 
 evaporating the ether. After pouring off the ethereal 
 solution of quinine, the residue may be digested with 
 warm and strong alcohol. This takes up the cinchonine, 
 and on allowing the alcohol to evaporate spontaneously, 
 cinchonine separates in colourless anhydrous prisms. 
 Neither alkaloid is quite pure when prepared by this 
 process. 
 
394 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiment 2. — Both alkaloids dissolve very easily in 
 dilute sulphuric and other acids. The substance generally 
 sold as quinine is the neutral sulphate. Dilute sulphuric 
 acid dissolves it easily. From all acid solutions the 
 alkaloid may be precipitated by the addition of an alkali. 
 
 Experiment 3. — V\ hen quinine or any of its salts (acid 
 solution of the sulphate auswers well) is treated with 
 chlorine water, and afterwards with solution of ammonia, 
 a beautiful green colour is produced. This is the best 
 test for quinine. 
 
 Experiment 4. — Commercial sulphate of quinine is some- 
 times adulterated with salicin (the bitter principle of 
 willow bark). This may be detected by rubbing the dry 
 salt with a drop of strong sulphuric acid. If salicin bo 
 present in any quantity, a bright red colour will be 
 produced. 
 
 OPIUM — MORPHINE. 
 
 Opium is the dried juice of the unripe capsules of the 
 white poppy, a plant which is extensively cultivated in 
 the East. It contains many different alkaloids, together 
 with a peculiar acid, meconic acid, 0^1140^. The most 
 important of the alkaloids is morphine, CiYH^gNOg. The 
 complete separation of the opium alkaloids is a matter of 
 great difficulty, but the following experiment will illus- 
 trate the method. 
 
 Experiment 1. — Digest some opium, cut in thin slices, in 
 lukewarm water for some time till a strong decoction is 
 obtained ; pour off the solution, and add just enough 
 dilute ammonia to neutralize free acid. Evaporate on a 
 water-bath to a small bulk, and then add excess of calcium 
 chloride. Calcium meconate is preci^utated while the 
 alkaloids reniain in solution as hydrochlorates. Filter 
 and again concentrate, when more of the mecf)nate will 
 separate; after it has been filtered off, the hot solution 
 will, on cooling, de2)osit crystals of the hydrochlorates of 
 morphine and codeine. The first crystals may be dissolved 
 in a little water and treated with ammonia, which throws 
 down morphine. It is slightly coloured, but its solution 
 may be purified by agitation \N ith animal charcoal, which 
 removes the colour. 
 
OTHER ALKALOIDS. 
 
 395 
 
 Experiment 2. — From the calcium meconate formed in 
 the above process, meconic acid may he prepared as 
 follows : wash the calcium meconate and dissolve it in 
 the smallest possible quantity of warm and very dilute 
 hydrochloric acid. Add potash until a faint cloudiness 
 appears, filter and concentrate to a small bulk. Some- 
 what coloured crystals of meconic acid will separate. 
 
 Experiment 8. — An aqueous solution of morphine or any 
 of its salts gives, with neutral ferric chloride, a blue colour. 
 
 Experiment 4. — Put a minute particle of morphine, or 
 one of its salts, on a white plate, and touch it with a drop 
 of solution of iodic acid. Iodine will at once be liberated, 
 and its presence is shown by its br.own colour and the 
 violet compound formed on the addition of starch paste. 
 This is an excellent test for morphine. 
 
 Experiment 5. — Solution of meconic acid gives, with 
 ferric salts, a hlood-red colour. This test is so delicate that 
 meconic acid can sometimes be detected where the quantity 
 of opium present is too small to allow of the detection of 
 morphine. The red colour is much like that given by 
 iron salts with sulphocyanates, but the latter is instantly 
 destroyed by solution of corrosive sublimate. 
 
 NUX VOMICA STRYCHNINE. 
 
 The beans of nux vomica and St. Ignatius, and some 
 other products of the order strycJinos, contain two alkaloids, 
 strychnine and hrucine, both of which, especially the former, 
 are deadly poisons. They cannot easily be prepared on a 
 small scale. 
 
 Experiment — Dissolve a minute crystal of strychnine on 
 a white plate with a drop of strong sulphuric acid. Then 
 rub with it an equally minute quantity of potassium 
 dichromate. A beautiful blue colour, quickly fading to 
 brick-red, is produced. Other oxidizing agents added to 
 the sulphuric solution produce the same effect. This is 
 an exceedingly delicate test for strychnine. 
 
 OTHER ALKALOIDS. 
 
 The following are some of the more important vegetable 
 alkaloids, which have not been noticed in the preceding 
 sections : 
 
396 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Aconitine, found in monkshood (Aconitum napellus). Said 
 to be the most intensely poisonous of all the alkaloids. 
 Asparagine^ in asparagus. 
 
 Atropine, in deadly nightshade (Atropa belladonna) and 
 thorn-apple (^Datura stramonium) 
 Berherine, in the barberry. 
 Caffeine, or Theine, in coffee and tea. 
 Colchicine, in colchicum. 
 
 Hijoscyamine, in henbane (Hyoscyamus niger). 
 Piper ine, in pepper. 
 
 Bicinine, in castor seed {Bicinus communis), 
 
 Solanine, in the potatoe, &c. 
 
 Theobromine, in cacao beans. 
 
 Veratrine, in white hellebore (Veratrmn album). 
 
( 397 ) 
 
 CHAPTER X. 
 
 COLOURING MATTERS. 
 
 Of the pigments used in painting, dyeing and colour- 
 printing, a good many have already been described. Of 
 mineral pigments the following are a few of the most 
 important : 
 
 Beds. — Vermilion (HgS) ; red lead (PbgO^) ; Venetian 
 red (FeA)- 
 
 Yellows. — Chrome yellow (PbCr04) ; orpiment, or king's 
 yellow (AS2S3) ; yellow ochre (clay coloured by FegOg). 
 
 Greens. — Chrome green (Cr203) ; Schweinfurt, or im- 
 perial green (cupric aceto-arsenite). 
 
 Blues. — Ultramarine (a complex double silicate, contain- 
 ing a polysulphide of sodium) ; Prussian blue (ferric 
 ferrocyanide) ; cobalt blue (a compound of cobalt oxide 
 and alumina). 
 
 Among organic colours, some can only be prepared by 
 artificial methods. To this class belong the splendid 
 colours of almost every conceivable shade which are 
 prepared from aniline and its congeners (p. 389). A 
 beautiful crimson colour, called murexide, can be prepared 
 from uric acid, which in its turn is obtained from urine 
 or guano. 
 
 The term colouring matter is generally restricted to 
 those colours which are obtained directly from animals 
 and vegetables. To those we shall confine our attention 
 here. 
 
 COLOURING MATTERS OF FLOWERS. 
 
 The beautiful and various tints of colour that we see in 
 flowers are due to colouring matters which are very 
 imperfectly understood. The reds and blues are generally 
 soluble in water, the yellows only in alcohol. They are 
 very evanescent, fading rapidly when exposed to light. 
 
398 
 
 EXPERIMENTAL CHJCMISTRY. 
 
 Experiment 1. — Digest some of the flowers of the blue 
 iris, lobelia, or almost any blue flower, with a small 
 quantity of warm alcohol. Pour off the alcohol and press 
 the flowers in muslin. A blue solution will be obtained, 
 which will yield a blue pigment when evaporated on the 
 water-bath. Flowers of other colours will yield their 
 colouring matters in the same way. 
 
 Experiment 2. — The colouring matter obtained in an 
 impure state in the last experiment is called cyanin. 
 Dissolve a little in water, and add to one portion of the 
 solution a drop of acid. The blue colour changes to red. 
 To another portion add a drop of soda. The blue changes 
 to green. The red may be changed to green, and the 
 green to red, by the addition of alkali or acid. Such a 
 solution may therefore be used as a substitute for litmus. 
 Tincture of roses is sometimes used for this purpose. 
 
 Experiment 3. — On adding a drop of solution of sulphu- 
 rous acid to the aqueous solution the colour will first 
 change to red, and then disappear. On standing, how- 
 ever, the acid will pass away and the colour return. 
 
 It is believed by some that the colour of most red 
 flowers is due to cyanin reddened by an acid. 
 
 Experiment 4. — The red cabbage yields to water a 
 colouring matter similar to, if not identical with, cyanin. 
 The aqueous decoction yields a red with acids, a green 
 with alkalies, and a purple with solution of alum ; so that 
 four different colours may be produced from the same 
 solution. 
 
 Experiment 5. — Take the flowers of the orange-coloured 
 tropseolum majus, or the brown calceolaria, and digest them 
 with boiling water. A purple colouring matter will be 
 dissolved out. Pour off the water, press the flowers, and 
 digest them again with alcohol. A yellow colour will 
 now be obtained and both may be separated from their so- 
 lutions by evaporation. The flower is thus rendered white. 
 
 Some flowers therefore contain more than one colouring 
 matter. 
 
 COLOUR OF LEAVES — CHLOROPHYLL. 
 
 Experiment 1. — Digest some fresh grass or other leaves 
 with alcohol. A beautiful green solution is obtained, 
 
INDIGO. 
 
 399 
 
 I which contains chlorophyll. In. the solid state it is a dark 
 green powder, which is insoluble in water, but soluble in 
 
 I alcohol and ether. Neither acids nor alkalies change its 
 colour. 
 
 INDIGO. 
 
 A number of plants which grow in the East and West 
 Indies contain an almost colourless substance called 
 indican. When the leaves are macerated with water and 
 allowed to ferment, the indican is decomposed and indigo 
 blue, CgHgNO, is formed. 
 
 Indigo usually occurs in commerce in deep blue, friable 
 cakes, which exhibit, when rubbed by the nail, a coppery 
 colour and lustre. Its brilliant blue colouring matter is 
 called indigo-blue; but besides this, the crude indigo 
 contains other foreign substances, such as indigo-gluten, 
 indigo-brown, indigo-red. 
 
 Indigo is quite insoluble in water, alcohol, ether, &c. ; 
 there is only one liquid known which can dissolve it, 
 except in minute quantities, namely, concentrated 
 sulphuric acid. The Nordhausen, t)r fuming acid, is the 
 kind generally used, as six parts of it will dissolve as 
 much as fifteen parts of the common acid. The indigo- 
 blue chemically combines with the sulphuric acid, 
 forming a blue compound soluble in water, which is 
 called sulphindigotic acid. What we call tincture of 
 indigo is principally a mixture of water, sulphindigotic 
 acid, and free sulphuric acid. 
 
 The sulphindigotic acid combines with bases like a 
 simple acid, forming salts. The best known of these 
 salts is suljphindigotate of potassium (blue carmine), which 
 is obtained as a deep blue precipitate when the sulphin- 
 digotic acid is neutralised by potassa. The blue carmine 
 is indeed soluble in pure water, but not in water 
 containing a salt in solution. 
 
 Indigo-white. — We can also, but in a very dilBTerent w^ay, 
 render indigo soluble, by mixing it with bodies which, by 
 taking oxygen from water, will impart hydrogen to it ; 
 for instance, with ferrous or stannous salts. 
 
 Experiment 1. — Triturate half a drachm of finely- 
 powdered indigo with one and a half drachm of green 
 
400 
 
 EXPERIMENTAL CHEMISTRY. 
 
 • vitriol and two drachms of slaked lime ; shake up the 
 mixture in a four ounce bottle ; then, having filled the 
 bottle with water and closed it tightly, let it stand for 
 several days ; the indigo gradually loses its blue colour, 
 and dissolves into a clean yellowish liquid. The body 
 which effects the decolouration is the ferrous hydrate, 
 which is separated by means of the lime from the green 
 vitriol. The solution now contains the so-called white, or 
 reduced indigo, CgHgNO. As soon as the clear liquid is 
 exposed to the air, the extra atom of hydrogen is oxidised, 
 and it again becomes blue. If you saturate a piece of 
 blotting-paper or linen with the liquid, and then dry it 
 in the air, it first becomes green, and then blue, and the 
 blue colour formed adheres quite firmly, since it has not 
 only settled wpo^^ but in the fibres of the paper. In 
 dyeing establishments, such a solution of indigo is called 
 the cold vat. A third method of rendering indigo soluble 
 is by adding it, together with hot water, to a mixture of 
 bran, woad, madder, &c., which (potassium and calcium 
 carbonates being prese^nt) passes into fermentation. The 
 fermentation^ is partly acid, and partly putrefactive; in 
 both processes hydrogen is liberated and combines with 
 the indigo. The colourless indigo dissolves in the 
 alkaline liquid (ivarm vat^. 
 
 By treating indigo with powerful reagents, such as 
 nitric acid, chlorine, potash, &c., many interesting com- 
 pounds can be obtained. 
 
 Experiment 2. — Heat a little indigo carefully in a watch- 
 glass over which another watch-glass in inverted. A 
 portion of the indigo will sublime in beautiful crystals. 
 
 Woad is a European plant, which likewise contains 
 indican and yields indigo, but in far less quantities than 
 the foreign indigo plants. 
 
 MADDER. 
 
 This important dye-stuff is the root of the Buhia 
 tinctorum, a plant which is extensively cultivated in many 
 parts of Europe. 
 
 In its natural state, the root appears to contain a 
 glucoside, that is, a substance which is readily de- 
 composed into glucose and something else. This com- 
 
MADDER. 
 
 401 
 
 pound is called ruhian. It is analogous to the indican of 
 the indigo plant. It readily yields two colouring matters, 
 alizarin and purpurin, the former of which is much the 
 most valuable of the constituents of madder. 
 
 Experiment 1. — Digest some ground madder with warm 
 water. A dark brown muddy liquid is obtained. This 
 with dilute sulphuric acid yields a brown precipitate con- 
 sisting of alizarin and purpurin with foreign bodies. The 
 clear yellow liquid which remains contains nothing of 
 importance. It may be removed by filtration, and the 
 colouring matter washed with water. The precipitate is 
 then to be boiled with concentrated solution of aluminium 
 chloride (prepared by saturating strong hydrochloric acid 
 with aluminium hydrate), which dissolves alizarin and 
 purpurin but leaves a brown residue of impurities. On 
 adding hydrochloric acid to the filtered liquid a red pre- 
 cipitate of the two colouring matters is obtained. 
 
 If it be desired to separate them, dissolve them, while 
 moist, in dilute ammonia, and digest for some time with 
 moist aluminium hydrate. They both combine with the 
 metal, forming compounds called kthes (vide infra). The 
 mixed lakes are then boiled with sodium carbonate, which 
 dissolves out the purpurin. The residue is then boiled with 
 hydrochloric acid, which leaves the yellowish-red alizarin. 
 
 When pure, alizarin and purpurin resemble one another 
 closely. Both form yellowish-red crystals, which may to 
 a great extent be sublimed unchanged. Both are sparingly 
 soluble in water, more soluble in alcohol. Both are in- 
 soluble in acids, but easily soluble in alkalies, being 
 thrown down unchanged when the alkali is neutralized. 
 Both combine with the oxides of many metals (aluminium, 
 iron, tin, lead &c.), forming insoluble compounds called 
 lakes. It appears, however, that the colours produced by 
 dyeing fabrics with madder are mainly compounds of 
 alizarin. 
 
 Alizarin has the formula Ci4Hg04. It is now pre- 
 pared synthetically from anthracene (p. 410), and it 
 appears probable that the artificial compound will super- 
 sede the root altogether. The formula for purpurin is 
 C,,H,0,. 
 
 Madder lake. — A beautiful pigment bearing this name 
 
 2 D 
 
402 
 
 EXPERIMENTAL CHEMISTRY. 
 
 is used by artists. The following is said to be the best 
 receipt for it : 
 
 Experiment 2. — Enclose two ounces of the best ground 
 madder in. a strong calico bag capable of holding three 
 times as much. Macerate the bag with one pint of cold 
 soft water in a basin or mortar, pressing and twisting the 
 bag as much as possible. Pour off the coloured liquid, 
 and repeat the process until five pints of liquid are 
 obtained. Nearly boil the liquid in an earthen vessel or 
 large beaker, and pour it into another vessel containing 1 
 ounce of alum dissolved in 1 pint of boiling soft water. 
 Stir and add 1^ ounce of a saturated solution of potassium 
 carbonate. When cool, pour off the liquid and add to the 
 precipitated lake 1 quart of boiling soft water. When 
 cold, pour off the waskings and collect the lake, which 
 should weigh half an ounce, on a filter. If required for 
 water-colour painting it may be dried at a gentle heat 
 and mixed with a little glycerine. Paints so prepared 
 are called moist colours. 
 
 Dyeing with Madder, — Madder is a good example of what 
 is sometimes called an adjective, as distinguished from a 
 substantive colour. Substantive colours adhere to, or 
 combine with the fibre of a fabric, and do not require any 
 separate process to fix them. Adjective colours, on the 
 contrary, have no power of fixing themselves to a fabric, 
 but require the aid of some other substance, which, either 
 by rendering them insoluble or by some other means, fixes 
 them to the fabric. Such substances are called mordants. 
 The following simple experiments illustrate their use in 
 the case of madder : 
 
 Experiment 3. — Madder red, — Soak a piece of calico in 
 the solution of impure aluminium acetate, which is 
 obtained by mixing equal weights of alum and lead 
 acetate (both in solution) and filtering from the insoluble 
 lead sulphate. Let it hang in the air for a couple of days, 
 and then soak it for two or three hours in a strong 
 decoction of madder. It may then be removed and 
 thoroughly washed, when it will be found to be dyed a 
 fast and very permanent red. 
 
 Instead of soaking the calico in the mordant, the latter 
 may be printed on in any required pattern (calico-printing). 
 
COCHINEAL. 
 
 403 
 
 The red dye will only appear on the parts where the 
 mordant has been applied. 
 
 The action of the mordant here is obvious. The alizarin 
 combines with the aluminium and forms the insoluble red 
 madder lake. Aluminium acetate is called by dyers red 
 liquor, 
 
 Experiment 4. — Various shades of violet and purple can 
 be produced by using the mordant called iron liquor instead 
 of red liquor. Iron liquor is prepared like red liquor, by 
 mixing equal weights of green vitriol (FeS047 Aq) and lead 
 acetate. It consists, of course, of ferrous acetate. 
 
 Experiment 5. — Mixtures of the above two mordants 
 yield various shades of brown. 
 
 COCHINEAL. 
 
 A curious little insect, called the cochineal insect (Coccus 
 cacti), is known, which lives exclusively on certain species 
 of cactus. It was first discovered in Mexico in 1578, but 
 is now cultivated in many tropical places. I'his insect 
 contains about half its weight of a beautiful red colouring 
 matter called carmine, or carminic acid. The female insects 
 only are used. They are imported in the dry state. 
 
 Experiment 1. — Boil some powdered cochineal insects 
 with soft water for a quarter of an hour. A splendid red 
 solution will be obtained, for carminic acid is very soluble 
 in water. It is equally soluble in alcohol, but almost 
 insoluble in ether. 
 
 Experiment 2. — Add some moist aluminium hydrate to 
 the above solution (cold). The alumina will combine 
 with the colouring matter, and a beautiful crimson lake 
 will be obtained. 
 
 Experiment 3. — To other portions of the solution add 
 very small quantities of alum and stannic chloride re- 
 spectively. The former will yield a crimson, the latter a 
 fine scarlet colour. If these liquids are allowed to stand 
 for a time, beautiful precipitates are deposited which are 
 used by artists under the name of carmine. The pre- 
 cipitation appears to be due to the coagulation of the 
 albuminoid matters of the cochineal. 
 
 Experiment 4. — The two liquids from which, in the 
 last experiment, carmine was obtained may be cautiously 
 
 2 D 2 
 
404 
 
 EXPERIMENTAL CHEMISTRY. 
 
 treated with sodium carbonate. The whole of the colour 
 will now be thrown down as lakes, and, if excess of base 
 has been avoided, they will possess brilliant colours. 
 
 Experiment 5. — Silk and wool may be dyed by im- 
 mersing them in the solutions of Experiment 3. The 
 colour adheres very strongly to the fabrics, but it slowly 
 fades when exposed to light. 
 
 OTHER COLOURING MATTERS. 
 
 Brazil-wood, from the heart- wood of several trees growing 
 in South America, imparts to different materials a beautiful 
 but not very permanent red colour. It is employed also 
 in the preparation of red ink, of drop-lake, &c. Peach- 
 wood, Nicaragua wood, Sapan-wood, &c., differ but slightly 
 from Brazil-wood. ( Colouring matter, Brazilin, crystallizes 
 in orange-coloured needles, easily soluble in water.) 
 
 Safflower, the flowers of the dyer's saffron, is used for 
 obtaining a brilliant rose-colour (for pink-saucers). 
 (Colouring matter, Garthamin, soluble in water.) 
 
 The alkanet-root contains in its bark a resinous colouring 
 matter, which is not soluble in water ; silk is dyed violet 
 with it, but alcohol, oils (as petroleum), and fats (as lip- 
 salve), are coloured pink with it. 
 
 Sandal-wood (red sanders-wood), the rasped blood-red 
 wood of a tree growing in the East Indies, contains like- 
 wise red, resinous colouring matter (Santalin^, 
 
 The red dyes occurring in many fruits, as, for instance, 
 cherries, raspberries, &c., are but slightly durable, and 
 only used for colouring confectionery, cordials, &c. 
 
 Lac-dye is a red colouring matter very similar to 
 cochineal, which is deposited with shell-lac (page 382) on 
 the twigs of certain East Indian trees. The twigs with 
 their coating are known as stick-lac. 
 
 Fustic is the rasped trunk- wood of a mulberry-tree 
 which grows in the West Indies. It yields a yellow 
 
 Quercitron, a nankeen-yellow powder, mixed with fibrous 
 fragments, is obtained from the bark of the black oak, a 
 tree of North America. {Quercitron, a yellow powder, 
 soluble in water.) 
 
 Buckthorn, Persian, ' or yellow berries, the fruit of the 
 
OTHER COLOURING MATTERS. 
 
 405 
 
 buckthorn and other species of BJiamnus, growing in warm 
 countries. (^Bhamnin, little known.) 
 
 Weld and dyers weed are the names given to the Eeseda 
 luteola, dried after it has done blooming. Luteolin, 
 crystallizes in yellow needles, soluble in water.) 
 
 The four last-mentioned colouring substances are prin- 
 cipally used for dyeing silk, wool, cotton, and other 
 materials, yellow. 
 
 Annotto occurs as a brownish-red paste, which is pre- 
 pared from the pulp surrounding the seeds of the Bixa 
 Orellana, and contains two colouring principles, a yellow 
 and a red. The former is dissolved when the annotto is 
 boiled with water, the latter on boiling it with a weak 
 
 lye. 
 
 Turmeric, the root of a plant growing in the East Indies, 
 is very rich in a resinous yellow dye, which is coloured 
 brownish-red by alkalies. Paper stained with it may 
 therefore be used like red litmus-paper for detecting 
 alkalies. (^Cur cumin, an amorphous yellow mass.) 
 
 Saffron consists of the dried stigmas of the flowers of 
 the Crocus sativus. Its application, in colouring articles 
 of food and cordials yellow, is well known. 
 
 Logwood or Campeachy-wood, the reddish-brown interior 
 wood of a tree of tropical America, is one of the most com- 
 mon colouring matters for dyeing blue, violet, and black. 
 {Roematoxylin, in colourless crystals, which become speedily 
 violet and blue in the air, owing to the ammonia always 
 contained in the latter.) 
 
 Archil. — Several species of lichens, growing on the 
 rocks in England and France, containing peculiar sub- 
 stances, which, although in themselves colourless, acquire 
 a beautiful purple-red colour when they are acted upon 
 by ammonia and air. It is common to putrefy the bruised 
 lichen with urine, and th^n a red or ^'iolet-coloured paste 
 is obtained (cudbear, orchil). By the addition of lime or 
 potash, this red is changed into blue (litmus). We have 
 examples of both these colouring matters in red and blue 
 test-paper. 
 
406 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Experiments with the above Substances. 
 
 Experiment 1. — Take up some sandal- wood on the point 
 of a knife and put it on a filter, and pour over it some 
 alcohol ; the alcohol which passes through has a red 
 colour, and when poured upon a piece of wood, imparts 
 to it an intense blood-red colour. Cabinet-makers fre- 
 quently employ this solution for staining furniture. 
 Alcohol acquires a pink colour when a small piece of 
 alJmnet-root is put into it. "Water will not extract a red 
 dye from either of these substances. Those colouring 
 matters which are uncrystallizable, and soluble only in 
 alcohol, are called resinous. 
 
 Experiment 2. — Boil for some time in a jar, — 1st, either 
 fustic, or yellow berries ; 2nd, Brazil-wood ; and 3rd, log- 
 wood ; each separately, with twelve times its amount of 
 water; the decanted decoction of the first is yellow, of 
 the second reddish-yellow, and of the third brownish-red ; 
 a safficient proof that the colouring matters contained in 
 these substances have been dissolved in the water. Dyers 
 call these coloured decoctions baths. 
 
 Experiment 3. — Divide these colouring decoctions into 
 two equal parts. Dissolve a quarter of an ounce of alum 
 in one part of each, and then add to these a solution of 
 potassium carbonate, as long as any precipitate subsides. 
 Aluminium hydrate is precipitated ; but with it the 
 colouring matter, and hence the precipitates are coloured. 
 These precipitates are called lakes. The lake obtained 
 from the yellow berries occurs in commerce under the 
 name of yellow lake, and that from Brazil-wood as drop- 
 lake. 
 
 Experiment 4. — Prepare a solution of alum (a), another 
 of stannous chloride (b), a third of ferrous sulphate (c), 
 a fourth of potassium carbonate (d), a fifth of tartaric 
 acid (e), and saturate a sheet of white blotting-paper with 
 each solution. When dry, cut each sheet into three strips, 
 smear one of the strips from each sheet, with the fustic, 
 another of them with the Brazil-wood, and the third set 
 with the logwood decoction, and again dry them. You 
 will find that one and the same colouring matter produces 
 a different colour, or shade of colour, upon each of the five 
 
OTHER COLOURING MATTERS. 
 
 407 
 
 sheets. This colour will be very slight when the 
 coloured decoctions are applied to mere blotting-paper 
 (/). If yoTi now immerse the coloured and dried slips in 
 warm water, the colours will be for the most part dis- 
 solved from the three last tests (d, e, /), but not from 
 the former (a, b, c), on which the metallic bases act as 
 mordants. 
 
 These simple experiments give some idea of the interest- 
 ing and complex arts of dyeing and calico-printing. 
 
408 
 
 EXPERIMENTAL CHEMISTRY. 
 
 CHAPTEE XL 
 
 PRODUCTS OF DESTRUCTIVE DISTILLATION. 
 
 The general nature of tlie interesting and important pro- 
 cess of destructive distillation has already been explained 
 (p. 188). We have seen that coal and many other non- 
 volatile carbon compounds when heated in close vessels 
 are decomposed ; a portion of their carbon remains in the 
 retort (coke, charcoal, bone-V)lack, &c.), whilst a number 
 of new and volatile bodies are formed which can be 
 distilled over and collected. Of these, some at ordinary 
 temperatures are gases, some liquids, and some solids. 
 The manufacture of coal gas is a typical, and by far the 
 most important example of destructive distillation. A 
 reference to the table on page 189 will show how the 
 products of the distillation of coal divide themselves into 
 gases of various kinds which can be purified and collected, 
 ammoniacal water, the chief source of the ammonium salts 
 (p. 212), and tar, which collects below the water, and can 
 easily be removed from it. 
 
 It is with the very complex and valuable liquid tar, and 
 a class of substances allied to it, that we have to deal in 
 this chapter. 
 
 COAL TAR. 
 
 A gallon of coal-tar may be procured for a mere trifle 
 at any gas-works. It is black, viscid, like treacle, and 
 has a very disagreeable smell. A portion of the ammonia- 
 cal liquor often floats on it and may be poured off and 
 tested for ammonia, ammonium sulphide, carbonate, &c. 
 
 Distillation of Tar. — Experiment 1. — Introduce a pint of 
 the tar into a retort made from a tin oil-can capable of 
 holding a quart. The can must be fitted with a cork and 
 bent tube similar to those shown on page 333. The tube 
 should have an internal diameter of about half an inch, 
 
COAL TAR. 
 
 409 
 
 and a length of about eighteen inches. Carry the end of 
 the tube into a bottle to act as receiver, which at first 
 must be kept very cold. Then apply a gentle heat to the 
 retort. As soon as an ounce of liquid (naphtha) has dis- 
 tilled over, remove the receiver and replace it by another, 
 which is no longer necessary to cool artificially. The 
 heat must now be increased and the distillation continued 
 until yellow scales begin to solidify in the long neck of 
 the retort. A heavy oily liquid (dead oils) is obtained in 
 this stage of the distillation. The receiver is now again 
 changed and the temperature raised. The distillation 
 may now be continued very carefully until rather more 
 than one-fourth of the tar has been distilled off. In this 
 last stage the distillate solidifies into a yellow, butter-like 
 mass as it drops into the receiver. The neck of the 
 retort may be warmed with a spirit-lamp from time to 
 time to melt the solid that accumulates in it, and cause it 
 to drop into the receiver. The black residue left in the 
 retort must be poured out while still hot on to a stone or 
 iron slab. When cold it appears as a hard, shining 
 brittle mass ; the pitch, or asphalt, now so largely usijed for 
 coating woodwork and making pavements. 
 
 By this mode of conducting the distillation (fractional 
 distillation) the tar is separated into four portions, namely, 
 naphtha, or light oils, dead, or heavy oils, a solid portion, 
 ^nd pitch. Each of these is a very complex, mixture. 
 The constituents of these mixtures can only be separated 
 on the large scale, and with great difficulty. 
 
 1. Naphtha. — Coal-tar Naphtha. — The portion which first 
 comes over in the distillation of tar is very volatile, and 
 is lighter than water. It consists chiefly of the hydro- 
 carbon benzene, with its homologues. It contains also in 
 minute quantity aniline and some other bases, and an acid 
 portion, consisting of phenol or carbolic acid (p. 299), and 
 its homologues. Coal-tar naphtha also contains a little 
 naphthalene (p. 298). 
 
 The bases are first removed by agitating the naphtha 
 with dilute sulphuric acid ; the phenols are then removed 
 by agitating with caustic soda, and finally the hydrocar- 
 bons, chiefly benzene and toluene, are removed by rectifi- 
 cation nearly in the same manner as alcohol. 
 
410 
 
 EXPERIMENTAL CHEMISTRY. 
 
 2. Heavy oils, — Bead oils, — ^The heavy oils of coal tar 
 contain many hydrocarbons, some of which (notably 
 naphthalene) are, when pure, solid at ordinary tempera- 
 tures. But they are also valuable as containing the 
 imperfectly acid bodies called phenols in considerable 
 quantity. Ordinary phenol, or carbolic acid, is now pre- 
 pared on a very large scale from this portion of coal-tar. 
 
 3. Solid portion. — This often amounts to a very large 
 proportion of the whole products of distillation. The 
 most important of its constituents are naphthalene and 
 anthracene. From anthracene, alizarin, the chief colouring 
 matter of madder, can be prepared. 
 
 4. Pitch, — Gas-tar Asphalt. — The nature of pitch is not 
 yet well known. At a bright red heat, anthracene and 
 other solid hydrocarbons can be distilled from it, and a 
 coke remains which consists mainly of carbon. 
 
 PROXIMATE CONSTITUENTS OF COAL TAR. 
 
 Several of the constituents of coal tar are now im- 
 portant articles of commerce, and the student can there- 
 fore undertake a simple experimental study of them 
 although he may not be able to prepare them from the 
 tar. 
 
 Benzol or Benzene, C^Hg. — Experiment 1. — Distil a mix 
 ture of one part benzoic acid and three parts slaked lime. 
 Benzene and water pass over. The former has a specific 
 gravity of only 0*88, and therefore floats on the water. 
 Add some pieces of caustic potash to the mixture to 
 absorb traces of acid. After standing some time, decant 
 the benzene into a small flask containing solid calcium 
 chloride. Cork and allow the mixture to stand twenty- 
 four hours ; then distil off the perfectly pure benzene by 
 means of a water 'bath and bent tube, taking care to keep 
 the receiver very cold and to prevent the vapour from 
 coming near a light. The formula which describes the 
 formation of benzene in this experiment is as follows : 
 CvH6 02 -I- CaO = CaCOg-fCgHe. 
 
 Commercial benzene is obtained as above described 
 from gas tar. It is never pure, but contains higher 
 hydrocarbons, of which the most important is toluene, 
 C7H8> the homologue next above benzene, and also 
 
COAL TAR. 
 
 411 
 
 a curious compound called thiophene C4H4S. Neverthe- 
 less, when carefully rectified from a water bath, the less 
 volatile portions being rejected, it will do very well for 
 the following experiments : 
 
 Pure benzene boils at 80° C. (176° F.). It has a 
 peculiar but not unpleasant odour. 
 
 Experiment 2. — Benzene ignites very easily when alight 
 is applied, and burns with a bright smoky flame. 
 
 Experiment 3. — Benzene evaporates very easily at ordi- 
 nary temperatures, and the vapour is very inflammable. 
 Shake a few drops of the liquid in a small bottle of 
 oxygen and apply a light. An explosion will be pro- 
 duced. 
 
 Experiment 4. — Put some cotton wool into a tube drawn 
 to a jet at one end. Pour a few drops of benzene on 
 the cotton, blow gently through the tube, and apply a 
 light to the jet. The mixture of air and vapour will 
 burn with a luminous flame. 
 
 Experiment 5. — Benzene is a powerful solvent of oils 
 and fats. Shake a known weight of oil with benzene in 
 a test tube. It will dissolve in considerable quantity. 
 On allowing the solvent to evaporate on a basin the oil 
 will be recovered unchanged. If the basin is heated on 
 a water bath for some time and again weighed, the 
 increase of weight will correspond with that of the oil 
 employed. This experiment shows how benzene may be 
 employed in estimating the quantity of oil or fat present 
 in any substance. It also illustrates the use of benzene, 
 in removing grease-stains from articles of clothing. 
 
 Experiment 6. — Immerse a beaker or tumbler containing 
 benzene in a mixture of snow or crushed ice and salt. 
 The benzene crystallizes and may be separated from other 
 substances bv pressing it rapidly in a cloth. Toluene 
 does not solidify at- 20° C. (-4° F.). At 5° C. (41° F.), 
 the benzene, now very pure, once more becomes liquid. 
 
 The conversions of benzene into nitrobenzene, and of 
 nitrobenzene into aniline, have already been explained 
 (p. 389). Pure aniline does not yield the beautiful 
 aniline colours, but only a mixture of aniline and toluidine. 
 Toluidine, is a homologue of aniline, prepared 
 
 from toluene as aniline is from benzene. 
 
412 
 
 EXPERIMENTAL CHEMISTRY. 
 
 Phenol, or Carbolic Acid, C6HgO = C6H50H. — This valu- 
 able and interesting compound is now prepared on a large 
 scale from coal tar, and may be purchased in the pure 
 state at a cheap rate. When pure it crystallizes in 
 colourless deliquescent needles, which melt at 41° C. 
 (106^ F.) and boil at 180° C. (356° F.). It has a peculiar 
 tar-like odour, has a specific gravity of 1*056 and is very 
 poisonous. 
 
 Experiment 1. — If the heavy oil of coal tar is distilled 
 by itself, and the portion which comes over between 150° 
 and 200° C. (302° and 392° F.) is collected by itself, this 
 portion will contain the great bulk of the phenol of the 
 tar. When a concentrated solution of potash and a little 
 solid potash in powder is added to it, the liquid becomes 
 semi-solid from the formation of the white crystalline 
 potassium carholate. This is dissolved in hot water, the 
 neutral oil removed from the surface, and the salt neu- 
 tralised with hydrochloric acid. Impure phenol rises to 
 the surface as an oil, and may be washed, dried by agi- 
 tation with calcium chloride, and purified by repeated 
 distillations and crystallizations. The purification is, 
 however, a difficult process, and for many purposes is not 
 necessary 
 
 Experiment 2. — Dissolve some pure phenol in water, and 
 observe that it is sparingly soluble in cold, but somewhat 
 more in hot water. It dissolves easily in alcohol and 
 ether. The solutions, when pure, have a neutral reaction, 
 although phenol combines with bases, and so far has an 
 acid character. The salts are, however, somewhat in- 
 definite. With bromine water, even very weak solutions 
 of phenol give a white precipitate of trihromophenol CqH^ 
 Bt,0. 
 
 Experiment 3. — Phenol and its homologues are among 
 the most powerful of antiseptics. Suspend a piece of fresh 
 meat above a little phenol in a bottle. The vapour of 
 the phenol will entirely prevent the putrefaction of the 
 meat, which will in time dry up into a horny mass. For 
 this reason phenol is often used in preserving anatomical 
 specimens. Its action in disinfecting, which is its most 
 important use, is probably due to its power of destroying 
 the organized germs which appear to be the active agents 
 
PARAFFIN — PARAFFIN OIL — PETROLEUM. 413 
 
 of contagion in some zymotic diseases. It lias, however, 
 very little power as a deodorizer. 
 
 Trinitrophenol ; Picric, or Carhazotic Acid, CgH3(N02)30. 
 — Experiment 1. — Add fuming nitric acid, a drop^at a time, 
 to a small quantity of phenol in a large test tube. 
 Yiolent action takes place. When this begins to diminish, 
 the mixture must be warmed and ultimately boiled, for 
 otherwise mono- and dinitro[»henic acid will be formed. 
 On concentrating the acid liquid, beautifal yellow 
 crystals of trinitrophenic, or, as it is more often called, 
 picric acid are obtained, and may be purified by recrys- 
 tallization from water : 
 
 CeHgO + 3HNO3 = CeH3(N 02)30 + SH^O. 
 
 The same compound may be formed by the action of 
 nitric acid on indigo, silk, and other substances. The 
 dyeing of animal substances by nitric acid (p. 162) is 
 probably due to the formation of this compound. 
 
 Experiment 2. — Picric acid is sparingly soluble in cold 
 water, but the solution, even when it contains only 1 part 
 acid in 10,000 of water, has an intense yellow colour. It 
 is very soluble in alcohol. The solutions are used for 
 imparting a beautiful and permanent colour to silk. 
 
 Experiment 3. — Neutralize a warm and moderately con- 
 centrated solution of sodium carbonate with picric acid. 
 Sodium pier ate separates in yellow crystals as the solution 
 cools. Other picrates may be formed by double decom- 
 position with the sodium salt. Potassium pier ate requires 
 260 parts of cold water (15° C. = 59° F.) for solution, 
 and for this reason sodium picrate, which is very soluble 
 in water, is sometimes used as a test for potassium. 
 
 Experiment 4. — Heat a little potassium picrate on a 
 knife blade. It burns with explosion. In a close vessel 
 the explosion is violent, and the sodium salt has even been 
 proposed as a substitute for gunpowder. 
 
 PARAFFIN — PARAFFIN OIL — PETROLEUM. 
 
 When coal, peat, lignite, bituminous shales, &c., are 
 exposed to destructive distillation at a temperature which 
 is not allowed to rise above low redness, very little gas is 
 obtained, but instead, a considerable quantity of tar or 
 oil, which differs in composition from the tar obtained in 
 
414 
 
 EXPERIMENTAL CHEMISTRY. 
 
 manufacture of gas. This tar is called crude paraffin oil, 
 because it contains in solution the solid hydrocarbons 
 which are grouped together under the name of paraffin 
 (p. 298). A kind of coal, called boghead coal, found at 
 Bathgate near Edinburgh, is a good material for the 
 preparation of paraffin oil. It is said to yield as much as 
 100 gallons of crude oil per ton. 
 
 The crude oil is purified in much the same manner as 
 gas tar. It is freed from basic and acid constituents by 
 treatment with sulphuric acid and caustic soda. The 
 remaining oil consists entirely of hydrocarbons, and it is 
 separated by distillation into a light and very volatile 
 spirit, or naphtha, sometimes called henzoline, a burning oil, 
 and a heavy, or lubricating oil. The heavier portions of 
 the oil deposit solid paraffin on cooling, and this paraffin 
 is purified and applied to the manufacture of candles and 
 other useful purposes. After the paraffin has been 
 separated, the oil is again distilled with other portions 
 of the oil, and a large proportion of oil, suitable for 
 burning in lamps, is thereby obtained. The lighter 
 portions of the oil cannot be used with safety in ordinary 
 lamps, as the vapour, mixed with air, is very explosive. 
 Terrible accidents often occur from the use in lamps of 
 oil which contains too large a proportion of the lighter 
 constituents. The safety of paraffin or petroleum oil 
 may be tested in the following manner : 
 
 Experiment. — Fill a beaker two-thirds full of the oil 
 and cover it with a card, and immerse it in boiling water 
 till the temperature of the oil rises to 100° F. (38° C), 
 taking care to avoid draughts of air, which might blow 
 away the vapour. Then bring a taper very near to the 
 surface of the oil. If a flash of flame appears the oil is 
 unsafe, and ought on no account to be used. In short, 
 the flash point of the oil ought to be above 100° F. 
 
 Pure paraffin oil is a very complex mixture of hydro- 
 carbons, the greater number of which belong to the 
 saturated, or marsh gas series, 0„H2„+2- 
 
 Petroleum. — In many parts of the world, as, for instance 
 in North America, Burmah, Persia, and the West Indies, 
 hydrocarbon oils, known variously as petroleum, roch oil, 
 mineral tar, or naphtha, &c., are found in great abundance 
 
PARAFFIN PARAFFIN OIL — PETROLEUM. 
 
 415 
 
 below the soil, and can be obtained by sinking wells. 
 These oils are very similar to paraffin oil, and some of 
 them yield a great deal of solid paraffin. Kangoon tar 
 yields as much as eleven per cent, of this substance. 
 The petroleum of Pennsylvania has been found to yield 
 at least twelve homologous liquid hydrocarbons, besides 
 gases and solid paraffins. They all appear to belong to 
 the C„H2„+2 series. 
 
 Asphalt. — Compact Bitumen. — A solid black substance, 
 between coal and petroleum in composition and properties. 
 It melts at about 100° C, and burns with a smoky flame. 
 It is found in considerable quantities in some parts of 
 the world, notably on the shores of the Dead Sea and 
 in the celebrated bitumen lake — one mile and a half in 
 circumference — of Trinidad. There are also small deposits 
 of asphalt in Cornwall, Derbyshire, and other parts of 
 England. 
 
( 416 ) 
 
 INDEX. 
 
 Acetic acid, 349 
 Acetylene, 185, 298 
 Acids, 97 
 
 basity of, 98 
 
 organic, 301 
 
 Aconitine, 396 
 Acrolein, 369 
 Acrylic acid, 370 
 Adhesion, 3 
 
 Affinity, chemical, 5 * 
 
 Air-balloons, 46 
 
 Air, composition of, 156 
 
 currents of, 45 
 
 Air-pump, 58 
 Albumin, 326 
 
 Albuminoid substances, 315, 325 
 
 Alcohol, 343 
 
 Alcohols, 297 
 
 Aldehyde, 352 
 
 Alizarin, 401 
 
 Alkaloids, 388 
 
 Alkanet, 404 
 
 AUotropic states, 169 
 
 Alum, 261 
 
 Aluminium, 259 
 
 compounds of, 260 
 
 Amalgams, 233 
 Amides, 305 
 Amines, 303 
 Ammonia, 157 
 
 derivatives of, 303 
 
 Ammonium amalf?:am, 159 
 
 carbonate, 213 
 
 chloride, 212 
 
 sulphide, 212 
 
 Ammoniums, compound, 301 
 Analysis, 17 
 
 Analysis of carbon compounds, 296 
 Aniline, 388 
 Annotto, 405 
 Anthracene, 298, 410 
 Antichlor, 111 
 Antimony, 282 
 
 compounds of, 283 
 
 Antiseptics, 202, 412 
 Aqua fortis, 160 
 
 regia, 275 
 
 Archil, 405 
 Argand burner, 192 
 Argol, 356 
 Arrowroot, 315 
 Arsenic, 277 
 
 compounds of, 278 
 
 white, 277 
 
 Arsine, or arseniuretted hvdrogen, 
 
 281 
 Artiad, 87 
 Asafoetida, 376 
 Asparagine, 396 
 Asphalt, 410, 415 
 Atmosphere, pressure of, 53 
 Atomic theory, 90 
 
 weights, 79 
 
 modes of fixing, 80 
 
 Atomicity, 86 
 
 hypothesis to account for, 93 
 
 modes of fixing, 87 
 
 explains homology, 290 
 
 Atoms, 70 
 Atropine, 396 
 
 Aureus and auric salts, 275 
 Avogadro and Ampere's hypo- 
 thesis, 92 
 Azote, or nitrogen, 155 
 
INDEX. 
 
 417 
 
 Balance, 19 
 Balsams, 375 
 Barium, 219 
 
 salts of, 219 
 
 Barometer, 55 
 Bases, 97 
 Bassorin, 320 
 Bast, 309 
 Batterv, voltaic, 5 
 Beer, 335 
 
 Bell-metal, 224, 267 
 Benzoic acid, 353 . 
 Benzene or Benzol, 298, 410 
 Benzoline, 414 
 Berberine, 396 
 Bessemer process, 245 
 Bismuth, 285 
 
 compounds of, 286 
 
 glance, 287 
 
 Bittern, 118 
 Bitumen, 415 
 Blast furnace, 241 
 Bleaching, 309 
 
 by chlorine, 111 
 
 powder, 137 
 
 by sulphur, 146 
 
 Blood, 327 
 Blowpipe, 191 
 Boghead coal, 414 
 Boiling, 37 
 Bone, 330 
 Bone-black, 177 
 Boracic acid, 174 
 Borax, 174, 209 
 Boric acid, 174 
 
 anhydride, 174 
 
 Boron, 173 
 
 Brandy, 335 
 
 Brass, 224 
 
 Brassic acid, 365 
 
 Brazil-wood, 404 
 
 Brazilin, 404 
 
 Bread, 340 
 
 Brimstone, 141 
 
 Bromine, 118 
 
 Bronze, 224 
 
 Brucine, 395 
 
 Buckthorn, 404 
 
 Bunsen-burner, 27 
 
 Burgundy pitch, 375 
 
 Burnett's disinfecting fluid, 223 
 
 Butane, 290 
 Butter, '330, 363 
 Butylene, 290 
 
 Cadmium, 223 
 Caffeine, 396 
 Calcium, 216 
 
 carbonate, 217 
 
 chloride, 218 
 
 fluoride, 218 
 
 oxide, 216 
 
 sulphate, 217 
 
 Calomel, 231 
 Camphor, 376 
 Caoutchouc, 385 
 Caramel, 323 
 Carbazotic acid, 413 
 Carbohydrates, 307 
 Carbolic acid, 412 
 Carbon, 175 
 
 compounds, structure of, 238 
 
 disulphide, 185 
 
 oxides of, 179 
 
 Carbonates, 181 
 Carbonic anhydride, 179 
 
 oxide, 181 
 
 Carmine, 403 
 Case-hardening, 246 
 Casein, 328 
 Castor oil, 365 
 Celestine, 218 
 Cellulin or Callulose, 307 
 Cetin, 372 
 Chalk, 216 
 
 Chameleon mineral, 258 
 Changes of state by heat, 35 
 Charcoal, 175 
 
 absorption of gases by, 176 
 
 animal, 177 
 
 Cheese, 329 
 Chemistry, applied, 18 
 
 uses of, 18 
 
 Chloric acid, 138 
 Chlorides, test for, 118 
 Chlorine, 109 
 
 oxides of, 136 
 
 peroxide, 136 
 
 Chloro compounds, 305 
 Chlorophyll, 398 
 Choke damp, 184 
 Chrome iron ore, 251 
 
 2 E 
 
418 
 
 INDEX. 
 
 Chrome yellow, 254 
 Chromium, 251 
 
 compounds of, 252 
 
 Oinchonine, 393 
 Citric acid, 358 
 Clark's process, 217 
 Classification of carbon com- 
 pounds, 297 
 Clay, 259 
 Clouds, 40 
 
 Coal, distillation of, 188 
 Cobalt, 263 
 Cociiineal, 403 
 Cohesion, 3 
 Coke, 177 
 Colchicine, 396 
 Collodion, 311 
 Colophony, 381 
 
 Colouring matter of flowers, 397 
 
 of leaves, 398 
 
 matters, mineral, 397 
 
 Colours, coal tar, 389 
 Combination, 61 
 
 by weight and volume, 64 
 
 Combining weights, 79 
 Combustion, 128 
 Composition, per centage, 75 
 Condy's fluids, 258 
 Conine, 393 
 Copper, 223 
 
 ores of, 223 
 
 oxides of, 225 
 
 salts of, 226 
 
 smelting of, 223 
 
 Copperas, 249 
 Cordials, 379 
 Corrosive sublimate, 231 
 Corundum, 259 
 Cotton, 310 
 Cream, 330, 363 
 Crystallization, 52 
 Cudbear, 405 
 Cumin-seeds, 377 
 Cupellation, 213 
 Curcumin, 405 
 Cyanides, 186 
 Cyanin, 398 
 Cyanogen, 186 
 
 Dalton's atomic theory, 90 
 Davy lamp, 192 
 
 Decantation, 50 
 Decomposition, 62 
 
 double, 63 
 
 D(^flagration, 130 
 Destructive distillation, 183 
 Dew, 47 
 Dextrin, 316 
 Diamond, 178 
 Diastase, 318 
 Diff'usion of gases, 180 
 Dimorphism, 140 
 Disinfection by chlorine, 112 
 Distillation, 42 
 
 destructive, 408 
 
 Dohbereiner's lamp, 108 
 Dragon's blood, 376 
 Drying oils, 370 
 Dutch liquid, 184 
 
 Eau de Cologne, 379 
 Ebonite, 387 
 Eggs, 326 
 Electricity, 4 
 
 decomposition by, 12 
 
 Electro-plating, 12 
 Electrotypin^, 228 
 Elements and compounds, 16 
 classification of, by atom- 
 icity, 86 
 
 the ancient, 18 
 
 Eliquation, 286 
 Emery, 259 
 Energy, 2 
 Equations, 94 
 Equivalents, 81 
 Ethenyl, 292 
 Ether, 346 
 Ethers, 298 
 
 compound, 299 
 
 Ethylene, 184 
 
 chloride, 184 
 
 Evaporation, 40 
 Expansion by heat, 28 
 
 Fatty acids, 301 
 Fehling's test, 322 
 Fermentation, 332 
 
 acetous, 849 
 
 butyric, 353 
 
 lactic, 353 
 
 Ferrous and ferric salts, 248 
 Fibrin, 327 
 
INDEX, 
 
 419 
 
 Filtration, 50 
 
 Fire-damp, 183 
 
 Fishes. Respiration of, 129 
 
 Flamei 189 
 
 Flax, 309 
 
 Flour, wheat, 314 
 
 Fluor spar, 218 
 
 Fluorine, 121 
 
 Force, chemical, 5 
 
 conservation of, 8 
 
 forms of, 2 
 
 rays of, 10 
 
 Forces, correlation of, 8 
 
 relation to one another, 8 
 
 Formulae, 68 
 
 glyptic, 291 
 
 French polish, 384 
 Fusible metal, 286 
 Fustic, 404 
 
 Galena, 234 
 Gall-nuts, 358 
 Gallic acid, 302, 358 
 Galvanic battery, 5 
 Gamboge, 376 
 Gas manufacture, 188 
 
 resin, 382 
 
 Gases, collection of, 106 
 
 constitution of, 65, 71 
 
 correction for pressure, 58 
 
 correction for t -mperature, 35 
 
 elasticity of, 57 
 
 standard of volume for, 67 
 
 structure of, 92 
 
 Gelatin, 330 
 G(-rman silver, 224 
 Glass, 210 
 
 etching on, 122 
 
 soluble, 193 
 
 Glauber's salt, 206 
 Glucose, 320 
 Glue, 331 
 
 marine, 386 
 
 Gluten, 326 
 Glyeerides, 361 
 Glycerin, 369 
 Glycerins, 299 
 Glycerols, 294, 297 
 Glycols, 299 
 Gold, 273 
 
 compounds of, 274 
 
 Goulard water, 237 
 Graphite, 176 
 Gravity, 2-19 
 
 specific, 22 
 
 Gum Arabic, 319 
 
 British, 316 
 
 Senegal, 319 
 
 tragacantli, 320 
 
 resins, 376 
 
 Gun metal, 224, 267 
 Gun cotton, 311 
 Gunpowder, 200 
 Gutta-percha, 387 
 Gypsum, 216 
 
 Hsematoxylin, 405 
 Haloo:ens, 109 
 Hartshorn, 157 
 Heat, 27 
 
 conduction of, 43 
 
 convection of, 44 
 
 latent, 36, 38 
 
 radiation of, 46 
 
 specific, 82 
 
 Hoemoglobin, 327 
 Homologues, 289 
 Hydriodic acid, 121 
 Hydrobromic acid, 121 
 Hydrocarbons, 297 
 
 structure of, 288 
 
 saturated and unsaturated, 
 
 289 
 
 Hydrochloric acid, 114 
 Hydrocyanic acid, 187 
 Hydrofluoric acid, 122 
 Hydrofluosilicic acid, 195 
 Hydrogen, 104 
 
 peroxide, 134 
 
 sulphide, 143 
 
 Hydrometer, 25 
 Hydrosulphuric acid, 143 
 Hygrometers, 41 
 Hygroscopic b;)dies, 41 
 Hyoscyamine, 396 
 Hypochlorous anhydride, 136 
 
 India-rubber, 385 
 Indigo, 399 
 Ink, 360 
 
 printing, 371 
 
 Iodine, 119 
 
420 
 
 INDEX. 
 
 Iron, 241 
 
 cast, 243 
 
 compounds of, 247 
 
 ores of, 241 
 
 pyrites, 250 
 
 refining, 245 
 
 slag, 243 
 
 smelting of, 241 
 
 wrought, 244 
 
 Isinglass, 330 
 Isomerism, 295 
 Isomorphism, 84, 263 
 
 King's yellow, 280 
 
 Lac-dye, 404 
 
 Lactic acid, 330, 353 
 
 Lacquering, 383 
 
 Lactose, 308, 324 
 
 Lakes, 262, 401 
 
 Lamp-black, 177, 383 
 
 Lard, 362 
 
 Laughing gas, 164 
 
 Law of combination by weight, 78 
 
 of constant composition, 64 
 
 of gaseous volumes, 65 
 
 Lead, 234 
 
 chromate, 254 
 
 compounds of, 235 
 
 tree, 238 
 
 Leather, 359 
 Leaven, 342 
 Legumin, 328 
 
 Light, its chemical effects, 4, 
 
 116 
 Lime, 216 
 
 chloride of, 137 
 
 light, 134 
 
 water, 49 
 
 Linen, 309 
 Liniments, 367 
 Linoleic acid, 370 
 Linseed oil, 370 
 Litharge, 236 
 Litmus, 405 
 
 paper, 50 
 
 Liver of sulphur, 203 
 Logwood, 405 
 Lunar caustic, 215 
 
 Madder, 400 
 
 Magnesium, 219 
 - — salts of, 220 
 Magnetism, 5 
 Malt, 317 
 Maltose, 308, 318 
 Manganese, 255 
 
 compounds of, 256 
 
 Mannite, 324 
 
 March's test for arsenic, 281 
 
 Mashing, 318 
 
 Matter, 1 
 
 Mauve, 390 
 
 Mead, 333 
 
 Measures, 21 
 
 Meconic acid, 394 
 
 Melting, 35 
 
 Mercury, 228 
 
 oxides of, 230 
 
 salts of, 230 
 
 Meta-phosphoric acid, 172 
 
 Metamerism, 295 
 
 Methane, or marsh-gas, 182 
 
 Methenyl, 292 
 
 Metrical system, 20 
 
 Milk, 328 
 
 Minium, 236 
 
 Mispickel, 277 
 
 Mixture and compound, 16 
 
 Moire metallique, 266 
 
 Molecules, 91, 93 
 
 Mordants, 261, 402 
 
 Morphine, 394 
 
 Mosaic gold, 270 
 
 Motion, 3 
 
 Muroxide, 397 
 
 Myricin, 372 
 
 Myrrh, 376 
 
 Naphtha, coal tar, 409 
 Naphthalene, 298, 410 
 Newlands Law, 101 
 Nickel, 263 
 Nicotine, 392 
 Nitrates, 163 
 Nitre, 200 
 Nitric oxide, 164 
 
 acid, 160 
 
 peroxide, 165 
 
 Nitrogen, 154 
 
 oxides of, 160 
 
 Nitro-benzene, 389 
 
INDEX. 
 
 421 
 
 Nitro-compounds, 306 
 Nitrous anhydride, 165 
 
 oxide, 163 
 
 Nomenclature, 89, 294 
 Nordhausen sulphuric acid, 149 
 Nux vomica, 395 
 
 Oak-bark, 359 
 Oil, almond, 364 
 
 cocoa-nut, 364 
 
 cod-liver, 363 
 
 colza and rape, 365 
 
 olive, 364 
 
 palm, 364 
 
 rock, 414 
 
 train, 363 
 
 Oils, volatile, 373 
 Olefiant gas, 184 
 Oleic acid, 362 
 Olein, 361 
 Olibanum, 376 
 Opium, 394 
 
 Organic compounds, 102 
 Orpiment, 280 
 Ossein, 380 
 Oxalic acid, 354 
 Oxides, 127 
 Oxygen, 123 
 
 Oxy-hydrogen blowpipe, 134 
 Ozone, 130 
 
 Palmitic acid, 362 
 Palmitin, 361 
 Paper, 310 
 Papin's digester, 60 
 Paracyanogen, 186 
 Paraffin, 413 
 
 Parchment, vegetable, 310 
 Pattinson's process, 214 
 Pearl white, 287 
 Pearlash, 198 
 Pentane, 290 
 Periodic Law, 101 
 Perissiad, 87 
 Persian berries, 404 
 Peruvian bark, 393 
 Petroleum, 413 
 Phenol, 410 
 Phenols, 299 
 Phenylamine, 388 
 
 Phosphates, 170 
 
 Phosphine, or phosphuretted hy- 
 drogen, 169 
 Phosphoric acid, 171 
 
 anhydride, 170 
 
 Phosphorus, 165 
 
 oxides of, 170 
 
 Photography, 11 
 Picric acid, 413 
 Pipeline, 396 
 Pipettes, 359 
 Pitch, 410 
 
 Plaster of Paris, 218 
 Platinum, 270 
 
 black, 272 
 
 compounds of, 271 
 
 Platinum, oxidation by, 108 
 
 spongy, 272 
 
 Plumbago, 173 
 Pneumatic trough, 1 06 
 Polymerism, 295 
 Potash, caustic, 197 
 Potassium, 196 
 
 carbonate, 198 
 
 chlorate, 201 
 
 chloride, 202 
 
 hydrate 197 
 
 iodide, 202 
 
 nitrate, 200 
 
 oxide, 197 
 
 sulphate, 199 
 
 sulphide, 203 
 
 Pressure, 54 
 
 eifect of, on boiling, 59 
 
 Propane, 290 
 Propenyl, 294, 362 
 Propylene, 290 
 Prussic acid, 187 
 Puddling of iron, 245 
 Purple of Cassius, 277 
 Purpurin, 401 
 Putrefaction, 332 
 Putty, 371 
 
 powder, 268 
 
 Pyrogallic acid or Pyrogallol, 
 360 
 
 Pyroligiieous acid, 352 
 Pyrolusite, 256 
 Pyrophorus, lead, 239 
 Pyro-phosphoric acid, 172 
 Pyroxylin, 311 
 
422 
 
 INDEX. 
 
 Quanti valence, 86 
 Quartation, 275 
 Quercitron, 404 
 Quicksilver, 228 
 Quinic acid, 393 
 Quinine, 393 
 
 Radicals, 88 
 
 atomicity of, 88 
 
 hydrocarbon, 291 
 
 table of, 89 
 
 Rats, poison for, 166 
 Rennet, 329 
 Resins, 375 
 Respiration, 129 
 Reverberatory furnace, 208 
 Ricinine, 396 
 Rosaniline, 390 
 Roseine, 390 
 Rose's metal, 286 
 Rubian, 401 
 Ruby, 259 
 
 Safety tube, 55 
 Safflower, 404 
 Saffron, 405 
 Sal ammoniac, 212 
 Salicin, 394 
 Salt, common, 204 
 Saltpetre, 200 
 
 Chili, 209 
 
 Salts, 97 
 
 formation of, 101 
 
 of hydrocarbon radicals, 300 
 
 Snndal wood, 404 
 Sandarach. 384 
 Sapphire, 259 
 Scammony, 376 
 Sclieele's green, 280 
 Sealing-wax, 382 
 Selenium, 153 
 Serum, 327 
 Shellac, 404 
 Silica, 193 
 Silicates, 195 
 Silicic anhydride, 193 
 Silicon, 193 
 
 fluoride, 195 
 
 Silver, 213 
 
 chloride, 215 
 
 fulminating, 215 
 
 Silver, glance, 215 
 
 nitrate, 214 
 
 sulphide, 215 
 
 Smalt, 264 
 Smellino:-salts, 2 1 3 
 Soap, 365 
 Soda, caustic, 204 
 Sodium, 203 
 
 borate, 209 
 
 carbonate, 207 
 
 chloride, 204 
 
 hydrate, 204 
 
 nitrate, 209 
 
 phosphate, 209 
 
 silicates, 210 
 
 sulphate, 205 
 
 sulphide, 207 
 
 Solanine, 396 
 Solder, 266 
 Solution, 48 
 
 saturated, 51 
 
 Suot, 177 
 
 Specific gravity, 22 
 
 calculation of, 75 
 
 Speculum metal, 224, 267 
 Speiss, 264 
 Spermaceti, 371 
 Spirits, 337 
 
 methylated, 344 
 
 Stannous and stannic salts, 268 
 Starch, 312 
 Stearic acid, 362 
 Stearin, 361 
 Steel, 245 
 
 Stibine, or antimoniuretted hydro- 
 gen, 285 
 Strontium, 216 
 
 salts of, 216 
 
 Strychnin^, 395 
 Structural formulsB, 291 
 Sublimation, 141 
 Substitution, 63 
 Sugar-candy, 321 
 Sugar, cane, 321 
 
 grape, 320 
 
 milk, 324 
 
 Sulphindigotic acid, 399 
 Sulphides, 143 
 Sulphites, 147 
 Sulphur, 139 
 Sulphur, oxides of, 146 
 
INDEX. 
 
 423 
 
 Sulphuretted hydrogen, 143 
 Sulphureous waters, 145 
 Sulphuric acid, 146 
 
 ' anhydride, 146 
 
 Sulphurous acid, 146 
 
 ' anhydride, 146 
 
 Symbols,* 68 
 
 use of, 79 
 
 Synthesis, 17 
 
 Tallow, 362 
 Tannin, 358 
 Tar, coal, 408 
 Tartar, cream of, 357 
 
 emetic, 285 
 
 Tartaric acid, 356 
 Tellurium, 153 
 Test-tubes, 45 
 Theobromine, 396 
 Theory, 17 
 Thermometer, 29 
 Thiophene, 411 
 Tin, 265 
 
 compounds of, 268 
 
 plate, 266 
 
 stone, 265 
 
 Tincal, 174 
 Tobacco, 392 
 Toluidine, 411 
 Toluene, 408, 411 
 Turmeric, 405 
 Turpentine, 375 
 
 oil of, 298 
 
 Type metal, 283 
 
 Ultramarine, 262 
 Urea, 390 
 
 Vacuum, Torricellian, 56 
 Valency, 86, 93, 290 
 Vapour, aqueous, 40 
 Varnish, 383 
 Ventilation, 46 
 Veratrine, 396 
 Vinegar, 349 
 
 aromatic, 379 
 
 wood, 352 
 
 Vitriol, blue, 227 
 green, 249 
 
 oil of, or sulphuric acid, 148 
 
 white, 222 
 
 Wasliing-bottle, 58 
 Washing with soap, 367 
 Water, 132 
 
 composition of, 135 
 
 expansion of, 33 
 
 hardness of, 217 
 
 of crystallization, 205 
 
 Wax, 371 
 
 Weighing, 19 ^ 
 Weights and measures, 20 
 Weld, 405 
 White lead, 238 
 
 precipitate, 232 
 
 Wine, 334 
 Woad, 400 
 Wood, 308 
 
 Woulfe's bottles, 116 
 Yeast, 333 
 Zinc, 221 
 
 granulated, 106 
 
 salts of 222 
 
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