MANUAL OF CHEMISTRY. A GUIDE TO LECTURES AND LABORATORY WORK FOR BEGINNERS IN CHEMISTRY. A TEXT-BOOK SPECIALLY ADAPTED FOR STUDENTS OF PHARMACY AND MEDICINE. BY W. Ph.D., M.D., PROFESSOR OF CHEMISTRY AND TOXICOLOGY-TN I’IIeTcOLLEGE OF PHYSICIANS AND SURGEONS J PROFESSOR OF CHEMISTRY AND ANALYTICAL CHEMISTRY IN THE MARYLAND COLLEGE OF PHARMACY, BALTIMORE, Ml). THIRD EDITION, THOROUGHLY REVISED. WITH FORTY-FOUR ILLUSTRATIONS AND SEVEN COLORED PLATES, REPRESENTING FIFTY-SIX CHEMICAL REACTIONS. PHILADELPHIA: LEA BROTHERS & CO. 189 1. Entered according to Act of Congress in the year 1891, by LEA BROTHERS & CO., In the Office of the Librarian of Congress at Washington, D. C. All rights reserved. DORNANj PRINTER. PREFACE. A third edition of this manual having been called for, the author has gladly availed himself of the opportunity to make such alterations and additions as are necessitated by the progress of science, and it has been his aim to make the work more than ever useful as a text-book for the medical and pharmaceutical student. Although much new matter has been added, the size of the volume remains unchanged owing to the use of smaller type for those portions which are of minor importance. The plates showing the variously shaded colors of chemicals and their reactions, that have proved so useful in previous editions, have been reproduced for this one with great care and fidelity. As heretofore, the material has been divided into seven parts which include material selected to give a fundamental grasp of the whole science. In the first, the fundamental properties of matter are considered briefly and so far as is necessary for an understanding of chemical phe- nomena. The second part treats of those principles of chemistry which are the foundation of the science, and enters briefly into a discussion of theoretical views regarding the atomic constitution of matter. Though the author prefers to present these theories to his classes at the proper times during the course of lectures, he did not deem it desirable to have them scattered throughout the work, choosing rather to present them compactly in such a form that the student may be able to study them after having acquired some knowledge of chemical phenomena. The third and fourth parts are devoted to the consideration of the non-metallic and metallic elements and their compounds. The old classification of metals and non-metals, organic and inorganic compounds,, has been adhered to for the reason that the author believes it to be the best adapted for purposes of instructing beginners in chemistry. All our classifications of either natural objects or phenomena are imperfect, because Nature does not draw those distinct lines of demarcation which we adopt as necessary for our studies. The most simple and natural classi- fication is, therefore, always to be preferred, even if, as in the above case, the student might derive from it the impression that matter was thus separated into distinct groups. IV PREFACE. Of elements, those only are considered which have either intrinsically or in combination a practical interest, or which take an active part in the various chemical changes in nature. For the special benefit of pharmaceutical and medical students all chemicals mentioned in the United States Pharmacopoeia are included, and when of sufficient interest are fully considered. The fifth part is devoted to analytical chemistry and will serve the student as a guide in his laboratory work. While qualitative methods are chiefly considered, a chapter is also added giving the principal methods for volumetric determinations. The sixth treats of organic chemistry. It was with much hesitation that the author has so briefly considered this portion of his subject, but he felt that a more extended consideration of this highly developed branch of chemical science in a volume of so condensed a character would be out of place. The seventh and last part, giving some of the more important facts of physiological chemistry, was prepared for the benefit of the medical student, and in the hope that it may serve as a guide to others who extend their studies to this very interesting branch of the science. As an assistance in the laboratory, a number of experiments have been added, which may readily be performed by students with a comparatively small outfit of chemical apparatus. The decimal system has been strictly adhered to in all weights and measures; degrees of temperature are expressed in the same system, the corresponding degrees of Fahrenheit being also mentioned. Baltimore, October, 1891. w. s. C 0 N T E N T S . i. FUNDAMENTAL PROPERTIES OF MATTER. RESULTS OF THE ATTRACTION BETWEEN MASSES, SURFACES, AND MOLECULES. PAGE 1. Extension or figure. Matter—State of aggregation—Solids—Cohesion—Force—Crystal- lized, amorphous, polymorphous, isomorphous substances—Liquids— Gases—Law of Mariotte 17-21 2. Divisibility. Mechanical comminution—Action of heat on matter—Molecular theory—Law of Avogadro—Motion of molecules, heat—Melting, boil- ing, distillation, sublimation—Thermometers—Specific heat . . 21-28 3. Gravitation. Action of gravitation—Weight, specific weight-—Hydrometers— Weight of gases—Barometer—Changes in the atmospheric pressure- influence of pressure on state of aggregation 28-32 4. Porosity. Nature of porosity—Surface, surface-action—Adhesion—Capillary attraction—Absorption—Diffusion—Dialysis—Indestructibility . . 32-37 ir. PRINCIPLES OF CHEMISTRY. RESULTS OF THE ATTRACTION BETWEEN ATOMS. 5. Chemical divisibility. Decomposition by heat—Elements—Compound substances—Chem- ical affinity—Atoms—Chemistry—Atomic and molecular weight— Chemical symbols and formulas ........ 38-43 6. Laws of chemical combination. Law of the constancy of composition—Law of multiple proportions —Law of chemical combination by volume—Law of equivalents— Quantivalence, valence 43-49 CONTENTS. VI 7. Determination of atomic and molecular weights. Determination of atomic weights by chemical decomposition, by means of specific weights of gases or vapors, by means of specifi c heat—Determination of molecular weights 50-54 8. Decomposition of compounds. Groups of compounds. Decomposition by heat, light, and electricity—Mutual action of substances upon each other—The nascent state—Analysis and synthesis—Acid, basic, and neutral substances—Salts—Residues, radicals 55-62 9. General remarks regarding elements. Relative importance of different elements—Classification of ele- ments—Metals and non-metals—Natural groups of elements—Men- delejeff’s periodic law—Physical properties of elements—Allotropic modifications—Relationship between elements and the compounds formed by their union—Nomenclature—Writing chemical equations —How to study chemistry 63-73 PAGE III. NON-METALS AND THEIR COMBINATIONS. Symbols, atomic weights, and derivation of names—Occurrence in nature—Time of discovery—Yalence 74—75 10. Oxygen. History—Occurrence in nature—Preparation—Physical and chem- ical properties—Combustion—Ozone 76-80 11. Hydrogen. History—Occurrence in nature—Preparation—Properties—Water —Mineral waters—Drinking-water—Distilled water—Hydrogen di- oxide 80-86 12. Nitrogen. Occurrence in nature—Preparation—Properties—Atmospheric air —Ammonia—Compounds of nitrogen and oxygen—Nitrogen mon- oxide—Nitric acid; tests for it . . . . . . . 86-93 13. Carbon. Occurrence in nature—Properties—Diamond—Graphite—Tests for carbon—Carbon dioxide—Carbonic acid—Tests for carbonic acid —Carbon monoxide—Compounds of carbon and hydrogen—Flame —Silicon—Boron—Tests for silicic and boric acids .... 93-101 14. Sulphur. Occurrence in nature—Properties—Crude, sublimed, washed, and precipitated sulphur—Sulphur dioxide—Sulphurous acid; tests for it —Sulphur trioxide—Sulphuric acid, its manufacture and properties —Tests for sulphates—Sulpho-acids—Thiosulphuric acid—Hydro- sulphuric acid, tests for it—Bisulphide of carbon—Selenium—Tel- lurium 101-110 CONTENTS. vii PAGE 15. Phosphorus Occurrence in nature—Manufacture, properties, and modifications —Poisonous properties and detection in cases of poisoning—Oxides of phosphorus—Phosphorous acid ; tests for it—Metaphosphoric, pyrophosphoric, orthophosplioric acids; tests for them—Hypophos- phorous acid ; tests for it—Phosphoretted hydrogen . . . 110-118 16. Chlorine. Haloids or halogens—Preparation and properties of chlorine— Chlorine water—Hydrochloric acid; tests for it—Nitro-hydroehloric acid—Compounds of chlorine with oxygen—Ilypochlorous acid— Chloric acid; tests for it 118-124 17. Bromine. Iodine. Fluorine. Bromine—Hydrobromic acid—Tests for bromides—Iodine—Hy- driodic acid—Tests for iodine and iodides—Fluorine—Hydrofluoric acid 124-128 IV. METALS AND THEIR COMBINATIONS. 18. General remarks regarding metals. Derivation of names, symbols, and atomic weights—Melting- points, specific gravities, time of discovery, valence, occurrence in nature, classification, and general properties of metals . . . 129-134 19. Potassium. General remarks regarding the alkali-metals—Occurrence in nature—Potassium hydroxide, carbonate, bicarbonate, nitrate, chlo- rate, sulphate, sulphite, hypophosphite, iodide, bromide—Analytical reactions ............ 135-141 20. Sodium. Occurrence in nature—Sodium hydroxide, chloride, carbonate, bicarbonate, sulphate, sulphite, thiosulphate, phosphate, nitrate— Analytical reactions—Lithium 141-145 21. Ammonium. General remarks—Ammonium chloride, carbonate, sulphate, ni- trate, phosphate, iodide, bromide, and sulphide—Analytical reactions 145-148 22. Magnesium. General remarks—Occurrence in nature—Metallic magnesium— Magnesium carbonate, oxide, sulphate, sulphite—Analytical reactions 149-151 CONTENTS. PAGE 23. Calcium. General remarks regarding alkaline earths—Occurrence in nature —Calcium oxide, hydroxide, carbonate, sulphate, phosphate, acid phosphate, and hypophosphite—Bone-black and bone-ash—Chlorin- ated lime, calcium chloride and bromide—Sulphurated lime—Ana- lytical reactions for calcium—Barium and strontium ; their salts and analytical reactions .......... 151-157 24. Aluminium. Occurrence in nature—Metallic aluminium—Alum—Aluminium hydroxide, oxide, sulphate, and chloride—Clay—Glass—Ultrama- rine—Analytical reactions—Cerium 157-162 25. Iron. General remarks regarding the metals of the iron group—Occur- rence in nature—Manufacture of iron—Properties—Reduced iron— Ferrous and ferric oxides, hydroxides, and chlorides—Dialyzed iron —Ferrous iodide, bromide, sulphide, and sulphate—Ferric sulphate and nitrate—Ferrous carbonate, phosphate, and hypophosphite— Scale compounds of iron—Analytical reactions .... 162-172 26. Manganese. Chromium. Cobalt. Nickel. Manganese; its oxides and sulphate—Potassium permanganate— Manganese reactions—Chromium—Potassium dichromate—Chro- mium trioxide—Chromic oxide and hydroxide—Reactions for chro- mium compounds—Cobalt and nickel ...... 172-178 27. Zinc. Occurrence in nature—Metallic zinc—Zinc oxide, chloride, bro- mide, iodide, carbonate, sulphate, and phosphide—Analytical reac- tions—Antidotes—Cadmium 179-182 28. Lead. Copper. Bismuth. General remarks regarding the metals of the lead group—Lead— Lead oxides, nitrate, carbonate, iodide—Poisonous properties of lead —Antidotes—Lead reactions—Copper—Cupric and cuprous oxide— Cupric sulphate and carbonate—Ammonio-copper compounds—Poi- sonous properties and antidotes—Copper reactions—Bismuth—Bis- muthyl nitrate, carbonate, and iodide—Bismuth reactions . . 182-191 29. Silver. Mercury. Silver—Silver nitrate, oxide, iodide,—Antidotes—Silver reactions —Mercury—Mercurous and mercuric oxides, chlorides, iodides, sul- phates, nitrates, sulphides—Ammoniated mercury—Antidotes—Mer- cury reactions 191-201 30. Arsenic. General remarks regarding the metals of the arsenic group— Arsenic—Arsenious and arsenic oxides and acids—Sodium arseniate —Arseniuretted hydrogen—Sulphides of arsenic—Arsenious iodide —Analytical reactions—Preparatory treatment of organic matter for arsenic analysis—Antidotes . . . . • • • 202-210 CONTENTS. IX PAGE 31. Antimony. Tin. Gold. Platinum. Molybdenum. Antimony—Trisulphide, oxysulphide, and pentasulphide of anti- mony—Antimonious chloride and oxide—Antidotes—Antimony reactions—Tin—Stannous and stannic chloride—Tin reactions—Gold —Platinum—Molybdenum 211-217 V. AX A LYTICAL CH EM ISTRY. 32. Introductory remarks and preliminary examination. General remarks—Apparatus needed for qualitative analysis— Reagents needed—General mode of proceeding in qualitative analysis —Use of reagents—Preliminary examination—Physical properties —Action on litmus—Heating on platinum foil—Heating on char- coal alone and mixed with sodium carbonate—Flame-tests—Colored borax-beads—Liquefaction of solid substances—Table I.: Prelimi- nary examination 218-228 33. Separation of metals in different groups. General remarks — Group reagents—Acidifying the solution— Addition of bydrosulphuric acid—Separation of the metals of the arsenic group from those of the lead group—Addition of ammonium sulphide and ammonium carbonate—Table II.: Separation of metals in different groups 229-234 34. Separation of the metals of each group. Table III.: Treatment of the precipitate formed by hydrochloric acid—Treatment of the precipitate formed by bydrosulphuric acid— Table IV.: Treatment of that portion of the bydrosulphuric acid precipitate which is insoluble in ammonium sulphide—Table V.: Treatment of that portion of bydrosulphuric acid precipitate which is soluble in ammonium sulphide—Table VI.: Treatment of the precipitate formed by ammonium hydroxide and sulphide—Table VII.: Treatment of the precipitate formed by ammonium car- bonate—Table VIII.: Detection of the alkalies and of magnesium 234—238 35. Detection of acids. General remarks—Detection of acids by means of the action of strong sulphuric acid—Table IX.: Preliminary examination for acids—Detection of acids by means of reagents added to their neutral or acid solution—Table X.: Detection of the more important acids by means of reagents added to the solution —Table XI.: Systemati- cally arranged table, showing the solubility and insolubility of inor- ganic salts and oxides—Table XII.: Table of solubility . . . 239-245 36. Detection of impurities in officinal inorganic chemical preparations. General remarks—Examination of sulphuric, sulphurous, nitric, phosphoric, and hydrochloric acids -Examination of the compounds of potassium, sodium, ammonium, calcium, magnesium, aluminium, iron, zinc, manganese, chromium, lead, copper, bismuth, silver, mer- cury, arsenic, and antimony ........ 246-254 CONTENTS. PAGE 37. Methods for quantitative determinations. General remarks—Gravimetric methods—Volumetric methods— Standard solutions—Different methods of volumetric determination —Indicators—Titration—Acidimetry and alkalimetry—Normal acid and alkali solution—Neutralization equivalents—Oxidimetry—Po- tassium permanganate and dichromate — Iodimetry — Solutions of iodine, sodium thiosulphate, and silver nitrate—Gas—Analysis. . 254-271 VI. CONSIDERATION OF CARBON COMPOUNDS, OR ORGANIC CHEMISTRY. 38. Introductory remarks. Elementary analysis. Definition of organic chemistry—Elements entering into organic compounds—General properties of organic compounds—Difference in the analysis of organic and inorganic substances—Qualitative analysis of organic substances—Ultimate or elementary analysis— Determination of carbon, hydrogen, oxygen, nitrogen, sulphur, and phosphorus—Determination of atomic composition from results obtained by elementary analysis—Empirical and molecular formulas —Rational, constitutional, structural, or graphic formulas . . 272-281 39. Constitution, decomposition, and classification of organic compounds. Radicals or residues—Chains—Homologous series—Types—Sub- stitution —Derivatives — Isomerism — Metamerism—Polymerism — Various modes of decomposition—Action of heat upon organic sub- stances—Dry or destructive distillation—Action of oxygen upon or- ganic substances—Combustion—Decay—Fermentation and putrefac- tion—Antiseptics, disinfectants, and deodorizers—Action of chlorine, bromine, nitric acid, alkalies, dehydrating and reducing agents upon organic substances—Classification of organic compounds . . 281-294 40. Hydrocarbons. Occurrence in nature—Formation of hydrocarbons—Properties— Paraffin or methane series—Methane—Coal, coal-oil, petroleum— Illuminating gas—Coal-tar—Olefines—Benzene series or aromatic hydrocarbons—Volatile or essential oils 294-303 41. Alcohols. Constitution of alcohols—Occurrence in nature—Formation and properties of alcohols—Monatomic normal alcohols—Methyl alcohol —Ethyl alcohol—Alcoholic liquors—Wines, beer, spirits—Amyl alcohol—Glycerin—Nitro-glycerin—Phenols 303-311 42. Aldehydes. Haloid derivatives. Aldehydes—Acetic aldehyde—Paraldehyde—Trichloraldehvde— Chloral hydrate—Chloroform—Iodoform—Sulphonal . . . 312-318 CONTENTS. XI PAGE 43. Monobasic fatty acids. General constitution of organic acids—Occurrence in nature— Formation of acids—Properties —Fatty acids—Formic acid—Acetic acid — Vinegar — Reactions for acetates — Acetate of potassium, sodium, zinc, iron, lead, and copper—Acetone—Butyric acid—Vale- rianic acid and its salts—Oleic acid 318-327 44. Dibasic and tribasic organic acids. Oxalic acid, oxalates, and analytical reactions—Tartaric acid; ana- lytical reactions—Potassium tartrate—Potassium-sodium tartrate— Antimony-potassium tartrate—Action of certain organic acids upon certain metallic oxides—Scale compounds—Citric acid; analytical reactions—Citrates—Lactic acid 327-335 45 Ethers. Constitution—Formation of ethers—Occurrence in nature—Gen- eral properties—Ethyl ether—Acetic ether—Ethyl nitrite—Amyl nitrite—Fats and fat oils—Soap—Lanolin 335-343 46. Carbohydrates. Constitution—Properties—Occurrence in nature—Groups of car- bohydrates—Grape-sugar; tests for it—Fruit-sugar—Inosite—Cane- sugar — Milk-sugar — Starch — Dextrin—Gums—Cellulose—Nitro- cellulose—Glycogen—Glucosides—Digitalin— Myronic acid . . 344-352 47. Amines and amides. Cyanogen compounds. Forms of nitrogen in organic compounds—Amines—Amides— Amido-acids—Formation of amines and amides—Occurrence in nature—Cyanogen compounds—Dicyanogen—Hydrocyanic acid— Potassium, silver, and mercuric cyanides—Keactions for cyanides— Antidotes — Cyanic acid—Sulphocyanic acid — Metallocyanides — Potassium ferrocyanide — Eeactions for ferrocyanides—Potassium ferricyanide—Nitro-cyan-methane . . . . . . 353-362 48. Benzene series. Aromatic compounds. General remarks—Benzene series of hydrocarbons—Benzene— Nitro-benzene—Benzene-derivatives--Phenols—Carbolic acid ; tests for it—Creasote—Sulpliocarbolic acid — Picric acid — Kesorcin— Cymene—Terpenes—Stearoptenes—Camphors—Kesins—Menthol — Thymol—Benzoic acid—Oil of bitter almond—Salicylic acid— Phtalic acid — Gallic acid — Tannin — Naphthalene — Naphtol— Santonin ............ 362-377 49. Benzene-derivatives containing nitrogen. Aniline—Aniline dyes—Antifebrine—Antipyrine—Saccharine— Pyrrole—Pyridine—Quinoline—Kairine—Thalline . . . 378-382 50. Alkaloids. General remarks—General properties of alkaloids—Mode of ob- taining them—Antidotes—Detection in cases of poisoning—List of important alkaloids — Coniine — Nicotine—Opium—Morphine, its salts and reactions—Codeine—Narcotine and narceine—Meconic acid—Cinchona alkaloids—Quinine, its salts and reactions—Cincho- nine — Cinchonidine — Quinidine — Strychnine and its reactions— Brucine—Atropine—Hyoscvamine— Cocaine and its reactions—Aco- nitine—Veratrine—Hydrastine—Berberine—Cafleine—Ptomaines . 382-398 xii CONTENTS. PAGE 51. Albuminous substances or proteids Occurrence in nature—General properties—Analytical reactions— Classification—Serum-albumin—Egg-albumin—Y egetable albumin —Globulins—Blood-fibrin—Muscle-fibrin — Vegetable fibrin—Milk- casein—Legumin—Peptone — I hemoglobin — Animal cryptolites — Pepsin—Gelatinoids .......... 389-404 VII. PHYSIOLOGICAL CHEMISTRY. 52. Chemical changes in plants and animals. General remarks—Difference between vegetable and animal life— Formation of organic substance by the plant — Decomposition of vegetable matter in the animal system—Animal food—Nutrition of animals, digestion—Absorption—Respiration—Waste products of animal life - Chemical changes after death ..... 405-414 53. Animal fluids and tissues. Constituents of the animal body—Blood—Examination of blood stains—Chyle—Lymph—Saliva—Gastric juice—Bile—Biliary pig- ments—Biliary acids ; tests for them—Cholesterin—Lecithin—Pan- creatic juice—Feces—Bone—Teeth—Hair, nails, etc. — Mucus— Muscles—Brain 414-425 54. Milk. Properties and composition—Changes in milk—Butter—Cheese— Adulteration of milk—Testing milk—Lactometer, creamometer, lac- toscope—Analysis of milk 425-431 55. Urine and its normal constituents. Secretion of urine—General properties—Composition—Urea; its properties and determination—Uric acid; tests for it—Hippuric acid; tests for it 431-439 56. Examination of normal and abnormal urine. Points to be considered in the analysis of urine—Color—Odor— Reaction—Specific gravity—Determination of total solids, and of total organic and inorganic constituents — Detection and estimation of albumin—Blood—Detection and estimation of sugar—Detection of bile—Urinary deposits—Urinary calculi—Microscopical examina- tion of urinary sediments 439-458 APPENDIX. Table of weights and measures 461 Table of elements 463 Index 465 LIST OF ILLUSTRATIONS. FIG. PAGE I, 2. Structure of matter 22, 23 3. Thermometric scales 27 4. Dialyzer 36 5. Apparatus for the decomposition of mercuric oxide 38 6. Apparatus for generating oxygen 78 7. Apparatus for generating hydrogen ........ 82 8. Apparatus for generating ammonia ........ 89 9. Distillation of nitric acid .......... 92 10. Structure of flame 99 II. Apparatus for making sulphurous acid 104 12. Apparatus for detection of phosphorus 114 13-16. Detection of arsenic 207-209 17-21. Apparatus for analytical operations 219, 220 22. Heating of solids in bent glass tube 224 23. Heating on charcoal by means of blowpipe 224 24. Washing and decanting in agate mortar 225 25. Platinum wire for blowpipe experiments 226 26,27. Apparatus for generating hvdrosulphuric acid . . . ■ . 231 28. Drying-oven 255 29. Desiccator 256 30. Watch-glasses for weighing filters ........ 256 31. Litre-flask ............. 257 32. Pipettes 257 33. Mohr’s burette and clamp 258 34. Mohr’s burette and holder 258 35. Gay Lussac’s burette ........... 259 36. Titration ............. 263 37. Flask for dissolving iron 265 38. Gas-furnace for organic analysis 277 39. Flasks for fractional distillation 295 40. Liebig’s condenser, with flask 307 41. Apparatus for estimation of urea 436 42. Urinometer 442 43. Nitric acid test for urine 446 44. Urinary sediments 457 COLORED PLATES. FACING PAGE Plate I. Compounds of iron and zinc 170 “ II. Compounds of manganese and chromium . . ' . . .178 “ III. Compounds of copper, lead, and bismuth 188 “ IV. Compounds of silver and mercury 200 V. Compounds of arsenic, antimony, and tin ..... 206 “ VI. Reactions of alkaloids 384 “ VII. Urine and tests for its constituents ...... 432 ABBREVIATIONS. c. c. = Cubic centimeter. B. P. = Boiling-point. F. P. = Fusing-point. Sp. gr. = Specific gravity. U. S. P. = United States Pharmacopoeia. PRACTICAL CHEMISTRY, PHARMACEUTICAL AND MEDICAL. I. INTRODUCTION. FUNDAMENTAL PROPERTIES OF MATTER. RESULTS OF THE ATTRACTIONS BETWEEN MASSES, SURFACES, AND MOLECULES. As the science of chemistry has for its object the study of the nature of all substances, or of all varieties of matter, it is neces- sary first to consider some of the properties which belong to every kind of matter, and are known as essential or fundamental properties. The fundamental properties of matter having a special interest for those studying chemistry are : extension, divisibility, gravitation, porosity, and indestructibility 1. EXTENSION OR FIGURE. Matter is anything occupying space, and this property is known as extension. All bodies, without exception, fill a certain amount of space; they all have length, breadth, and thickness. That portion of matter lying within the surrounding surface of a body is called its mass. We distinguish three different conditions of matter, namely: Solids, Liquids, and Gases. These conditions of matter are known as the three states of aggregation, and we will now consider the peculiarities of matter when existing in either of these states. 18 INTRODUCTION. Solid state. Solids are distinguished by a self-subsistent figure. A solid substance forms for itself, as it were, a casing in which its smallest particles1 are enclosed. The question arises, By what means are these particles connected, how are they kept together ? Ho other answer can be given, than that the particles themselves attract each other to such an extent that force is necessary to make them alter their relative position. We see, consequently, that some form of attraction or attractive power is acting between the particles of a solid mass, and w7e call this kind of attraction cohesion, to distinguish it from other forms of attraction. The external appearance or the figure of solid bodies is various. It may be an irregular or a natural regular figure. Of these two forms, only the latter is here of interest, as it includes all the different crystallized substances. Force may be defined as the action of one body upon another body, or as the action of particles of matter upon other particles either of the same or of another body. Strictly speaking, we may say that force is the cause tending to produce, change, or arrest motion; or it is any action upon matter changing or tending to change its form or position. In many cases force manifests itself as an attractive power; for instance, in the case of cohesion mentioned above, but also in adhesion, gravitation, etc. Forces often give rise to motion (as in the case of heat and electricity), and also to a great variety of changes in matter. The three different states of aggregation are due to the relative intensity of two opposing forces, one—that of molecular attraction—which tends to draw the molecules together, and a second one—that of heat—which tends to separate the molecules from one another. Energy of a body is its capacity of doing work, and is measured by the pro- duct of the force acting and the distance through which it acts. Crystals are solid substances, bounded by plane surfaces sym- metrically arranged according to fixed laws. In explaining the formation of crystals we have to assume that the particles are endowed with the power of attracting one another in certain directions, thereby building themselves up into geometrical forms. The first condition essential to the formation of crystals is the possibility of free motion of the smallest particles of the matter to 1 It will be shown later that all matter is supposed to consist of smallest particles, which we call molecules. EXTENSION OR FIGURE. 19 be crystallized; in that case only will they be able to attract each other in such a way as to assume a regular shape or form crystals. Particles of a solid mass can move freely only after they have been transferred to the liquid or gaseous state. There are two different methods of liquefaction, viz., by means of heat (melting), or solution in some suitable agent (dissolving). In the liquid condition thus produced, the smallest particles can follow their own attraction, and unite to form crystals on removal of the cause of liquefaction (heat or solvent). If two or more (non-isomorphous) substances—for instance, common salt and Glauber’s salt—be dissolved together in water, and the solution be allowed to crystallize, the attraction of like particles for one another will be readily noticed by the formation of distinct crystals of common salt alongside of crystals of Glauber’s salt; neither do the particles of common salt help to build up a crystal of Glauber’s salt, nor the particles of the latter a crystal of common salt. Advantage is taken of this property in separating (by crystallization) solids from each other, when they are contained in the same solution. Not all matter can form crystals; some substances never have been obtained in a crystallized state, and these are known as amorphous bodies (starch, gum, glue). Some substances capable of crystallization may be obtained also in an amorphous state (carbon, sulphur). Other substances are capable of assuming different crystalline shapes under dif- ferent conditions. Thus sulphur, when liquefied by heat, assumes, on cooling, a shape different from the sulphur crystallized from a solution. One and the same substance under the same conditions always assumes the same shape. Substances capable of assuming two or more different forms of crystals are said to be dimorphous and polymorphous, respectively. When substances of different kinds crystallize in exactly the same form, we call them iso- morphous (sulphate of magnesia and sulphate of zinc). If two isomorphous substances be contained in one solution, they will crystallize together, and the crystals are made up of particles of both substances. Characteristic properties of solids. Solid substances show a great variety of properties caused by the differences in the cohe- sion of the particles (molecules) composing the substances, and accordingly we distinguish between hard and soft, brittle, tena- cious, malleable, and ductile substances. 20 INTRODUCTION. Hardness is that property in virtue of which some bodies resist attempts to force passage between their particles, or which enables solids to resist the dis- placement of their particles. Diamond and quartz are extremely hard, while wax and lead are comparatively soft. Brittleness is that property of solids which causes them to be broken easily when external force is applied to them. Glass, sulphur, coal, etc., are brittle. Tenacity is that property in virtue of which solids resist attempts to pull their particles asunder. Iron is one of the most tenacious substances. Malleability, possessed by some solids, is the property in virtue of which they may be hammered or rolled into sheets. Gold is so malleable that it may be beaten into sheets so thin that it would require about 300,000 laid upon one another to measure one inch. Ductility is the property in virtue of which some solids may be drawn into wire or thin sheets—as, for instance, copper, iron, and platinum. Liquid state. The characteristic features of liquids are, that they have no self-subsistent figure; that they consequently re- quire some vessel to hold them; and that they present a hori- zontal surface. While in a solid substance the smallest particles are held together by cohesion to such an extent that they cannot change their relative position without force, in a liquid this cohesion acts with much less energy and permits of a compara- tively free motion of the particles; the repellant and attractive forces nearly balance each other in a liquid. That cohesion is not altogether suspended in a liquid is shown by the formation of drops or round globules, which, of course, consist of a large number of smallest particles. If there were no cohesion at all between these particles of a liquid, drops could not be formed. The terms semi-solid and semi-liquid substances are used for bodies occupying a position intermediate between true solids and fluids; butter, asphalt, amorphous sulphur, are instances of this kind. Gaseous state. Matter in the gaseous state has absolutely no self-subsistent figure. Gases fill any vessel or room entirely; the smallest particles show the highest degree of mobility and move freely in every direction. Cohesion is entirely suspended in gases; indeed, the smallest particles exhibit toward each other an infinite repulsion, so that force is necessary to restrain them within any given bounds whatever. It, therefore, follows that gases set up and maintain a pressure against the walls of vessels enclosing them. This characteristic property, possessed by all gases, is known as elasticity, or, better, as tension, and is so un- DIVISIBILITY. 21 varying that a law has been established in relation to it. This law is known as the Law of Mariotte (though really discovered by Boyle, of England, in 1661), and may be expressed thus : The volume of a gas is inversely as the pressure; the density and elastic force are directly as the pressure and inversely as the volume. For instance : If a vessel contains one cubic foot of a gas under a pressure of ten pounds, the volume will be reduced to one-half, one-tenth, or one-hundredth of one cubic foot, if the pressure be increased to 20, 100, or 1000 pounds respectively. On the contrary, the gas will expand to 2, 10, or 100 cubic feet, if the pressure is reduced to 5,1, or one-tenth pound respectively. Vapors, produced by evaporation of liquids or solids, have the same properties as gases. 2. DIVISIBILITY. Mechanical comminution. All matter admits of being sub- divided into smaller particles, and this property is called divisi- bility. The processes by which we accomplish the comminution of a solid substance may be of a mechanical nature, such as cutting, crushing, grinding, but beside these modes of sub- division we have other agents or causes by which matter may be divided into smaller particles, and one of these agents is heat. Action of heat on matter. Let us take a piece of ice and con- vert it, by means of mortar and pestle, into a very fine powder. When the smallest particle of this finely powdered ice is placed under the microscope and heat applied, we shall observe that it becomes liquid, thus proving that it was capable of further sub- division, that it consisted of smaller particles, which have now by the action of heat become movable. By further applying heat to the liquid particle of water we may convert it into a gas or vapor, which will escape into the air, or which we may collect Questions.—1. What is matter and what is force? 2. Mention the prin- cipal fundamental properties of matter. 3. Mention the three states of aggre- gation. 4. Describe the characteristic properties of matter in the solid, liquid, and gaseous states. 5. What is cohesion ? 6. Grive a definition of a crystallized substance. 7. Under what circumstances will matter crystallize ? 8. State the difference between amorphous, polymorphous, and isomorphous substances. 9. What is meant by elasticity or tension of gases. 10. State the law of Mariotte. 22 INTRODUCTION. in an empty flask. The flask will be filled completely by this water-gas (or steam) obtained by vaporizing that minute particle of ice-dust. This fact demonstrates that mechanical comminution does not carry us beyond a certain degree of subdivision of mat- ter. That is to say, the smallest fragment of the finest powder still consists of a very large number of much smaller particles. To the smallest particles which compose matter the name mole- cules has been given. Molecular theory. The expression molecule is derived from the Latin word molecula—a little mass, and means the smallest particle of matter that can exist by itself, or into which matter is capable of being subdivided by physical actions. To explain more fully what is meant by the expression molecule, we will return to the conversion of water into steam. Fig. 1. When water boils at the ordinary atmospheric pressure it expands about 1800 times, or one cubic inch of water yields about 1800 cubic inches, equal to about one cubic foot of steam. In explaining this fact we have either to assume that the water, as well as the steam, is homogeneous matter (Fig. 1), or that the water consisted of small particles of a given size, which now exist in the steam again as such, with the only difference that they are more widely separated from each other (Fig. 2). Of the many proofs which we have of the fact that the latter assumption is correct, I will mention but one, viz., that the quan- tities of vapor formed by volatile liquids at any certain tempera- DIVISIBILITY. ture above the boiling-point, in close vessels of the same size, are the same, no matter whether the vessel was entirely empty or contains the vapors of one, two, or more other substances. For instance: If we place one cubic inch of water in a flask hold- ing one cubic foot, from which flask the air has been previously removed, and then heat the flask to the boiling-point, the cubic inch of water will evaporate, filling the vessel with steam. Upon now introducing into the flask a second and a third liquid—for instance, alcohol and ether—we find that of each of these liquids exactly the same quantity will evaporate which would have evap- orated if these liquids had been introduced into the empty flask.1 This fact is evidence that there must be small particles of steam which are not in close contact, that there are spaces between these particles which may be occupied by the particles of a second, third, or more substances. To these particles of matter Fig. 2. we give the name molecules, and the spaces between them we call intermolecular spaces. We have thus demonstrated the correctness, or, at least, the likelihood of the so-called molecular theory, but the proof given is but one of many. Of these molecules (though individually by far too small to make any impression whatever upon our senses), our conception is so perfect, that we have formed an idea of the actual size of these minute particles of matter. Very good rea- sons lead us to believe that the diameter of a molecule is equal 1 As each gas, in consequence of its tension, exerts a certain pressure, the pressure in the flask rises with the introduction of every additional gas. 24 INTRODUCTION. to about one and that one cubic inch of a gas under ordinary conditions contains about one hundred thousand million million millions of molecules. These figures at first glance appear to be beyond the limit of human conception, but in order to give some idea of the size of these molecules it may be mentioned that if a mass of water as large as a pea were to be magnified to the size of our earth, each molecule being magnified in the same proportion, these molecules would represent balls of about two inches in diameter. Whilst molecules consequently are exceedingly small particles, yet they are not entirely immeasurable; they are, as Sir W. Thomson says, pieces of matter of measurable dimensions, with shape, motion, and laws of action, intelligible subjects of scien- tific investigation. Before leaving the molecular theory, I will mention the Law (more correctly, the hypothesis) of Avogadro which may be stated as follows: All gases or vapors, without exception, contain, in the same volume, the same number of molecules, provided temperature and pressure are the same. Or, in other words: Equal volumes of different gases contain, under equal circumstances, the same number of molecules. The correctness of this law has good mathematical support deduced from the law of Mariotte, many other facts and considerations leading to the same assumption. We shall learn, hereafter, that the law of Avogadro is one of the greatest impor- tance to the science of chemistry. Motion of molecules. Heat. If we place over a gas-flame a vessel containing a lump of ice of the temperature of 0° C., or 32° F., the ice gradually melts and becomes converted into water; but if we measure with a thermometer the temperature of the water at the moment when the last particle of ice is melted, we still find it at the freezing-point, 0° C. or 32° F. From the position of the vessel over the flame, as well as from the fact that the ice has been liquefied, we know that the vessel and its contents have absorbed heat. Yet vessel and water show the same temperature as before. If the heat of the flame is allowed to continue its action on the ice-cold water, the thermometer will soon indicate a rapid absorption of heat until it reaches 100° C., or 212° F. Then the water begins to boil and escapes in the form of steam, but the temperature again remains stationary until the last particle of water has disappeared. DIVISIBILITY. 25 There must be, consequently, some relation between the state of aggregation of a substance and that agent which we call heat. It was the heat which liquefied the ice, it was the heat which converted the liquid water into steam or gaseous water. Yet the water, having absorbed considerable heat during the process of melting, shows a temperature of 0° C. (32 F.), and the steam also having absorbed large quantities of heat, shows 100° 0. (212° F.), the temperature of boiling water. A certain amount of heat has consequently been lost or at least hidden. What has become of it ? According to our present theory, heat is a result of the motion of molecules. All molecules of any substance are in a constant vibratory motion, and the velocity or amplitude of this molecular motion determines the degree of what we call heat. An increase of heat is equal to an increase of the vibratory motion of the molecules and a decrease in temperature is caused by slower motion. The transfer of heat is a transfer of the motion of some particles to other particles. One of the effects of increased heat is in nearly all cases an increase in volume, or, in other words, all substances expand when heated, and contract on cooling. Another effect of the application of heat is, as we have just learned, the conversion of solids into liquids, and of liquids into gases. We noticed also the apparent loss of heat during this conversion, and can easily account for it now by saying, that a certain amount of vibratory motion or a certain velocity of the molecules (more correctly speaking, perhaps, a certain amplitude of molecular motion) is required to convert solids into liquids and liquids into gases. The molecules of steam vibrate with a much greater velocity than those of water of the same tempera- ture, and the molecules of water move with greater velocity than those of ice of the same temperature. In other words, the dif- ferent states of aggregation depend on the rapidity of the motion of molecules; and the heat which is necessary to convert solids into liquids and liquids into gases, and which is not indicated by the thermometer, is called latent heat. This latent heat may again be converted into free heat (heat capable of being indicated by a thermometer), by reconverting the gas into a liquid, or this latter into a solid. In both cases a liberation of heat, which is a transfer of the motion of the mole- cules upon the surroundings, will be noticed. 26 INTRODUCTION. Increase of volume by heat. The increase of volume by heat is not alike for all matter. Gases expand more than liquids, liquids more than solids, and of the latter the metals more than most other solid substances. Whilst the expansion of any two or more different solids or liquids is not alike, gases show a fixed regu- larity in this respect, namely, all gases without exception expand or contract alike, when the temperature is raised or lowered an equal number of degrees. This expansion or contraction of gases is 0 3665 per cent., or °f their volume for every degree centigrade; thus 100 volumes of air become 100.3665 volumes when heated 1 degree C., or 136.65 when heated 100 degrees C. This regularity in the expansion and contraction of gases is expressed in the law of Charles, which says: If the pressure remain constant, the volume of a gas in- creases regularly as the temperature increases, and decreases as the temperature decreases. If heat be applied to a gas confined in a closed vessel and be thus prevented from expanding, the increase of heat will manifest itself as pressui-e, which rises with the same regularity as shown for expansion, viz., 0.3665 per cent, for every degree centigrade. Melting and boiling. The temperature at which a solid sub- stance is converted into a liquid and this into a gas, is of a certain fixed degree or point for every substance, and the temperatures at which this conversion takes place are known as melting- busing-) and boiling-points. Some forms of matter appear incapable of existing in the three states of aggregation, like water. As yet, we know carbon in the solid state only, and the conversion of some gases, as, for instance, oxygen and hydrogen, into liquids or solids, has been accomplished only quite recently and in very small quantities. Other substances, again, may assume two, but not the third state. Some substances pass from the solid directly into the gaseous state (ammonium chloride, calomel), and the process of converting a solid into a gas directly, and this back again into a solid, is called sublimation. Distillation is the conversion of a liquid into a gas, and the recondensation of the gas into a liquid. Many liquids, and even some solids, evaporate or assume the gaseous state at nearly all temperatures. Water and ice, mercury, camphor, and many other substances vaporize at temperatures which are far below their regular boiling- points. This fact is to be explained by the assumption that during the rapid vibratory motion of the particles of these masses, some particles are driven from the surface beyond the sphere to which the surrounding molecules exert au attraction, and thus intermingle with the molecules of the surrounding air. DIVISIBILITY. 27 This evaporation, which takes place at various temperatures and at the surface only, is not to be confounded with boiling, which is the rapid conversion of a liquid into a gas at a fixed temperature with the phenomena of ebullition, due to the formation of gas in the mass of liquid. Thermometers are instruments indicating different temperatures. Use is made in their construction of the change in volume of different substances by the action of heat. The most common thermometer is the mercury thermometer. This instru- ment may be easily constructed by partly filling with mercury a glass tube having a bulb at the lower end, and placing it into boiling water. The point to which the mercury rises is marked B. P. (boiling- point), and the tube sealed by fusion of the glass. It is then placed in melting ice, and the point to which the mercury sinks is marked F. P. (freezing-point). The distance between the boiling- and freezing-points is then divided into 100 degrees in the so-called centigrade ther- mometer, or into 180 degrees in the Fahrenheit thermometer. The inventor of the latter instrument, Fahrenheit, com- menced counting not from the freezing- point, but 32° below it, which causes the freezing-point to be at 32°, the boiling-point at 180° above it, or at 212°. (Fig. 3.) Fig. 3. Centigrade. Fahrenheit. Thermometric scales. Molecular motion. Heat is bat one of the results of molecular motion; other results are light, actinism, electricity and mag- netism. When a body is heated the molecules vibrate quicker, and this molecular motion gives rise to heat waves in the assumed surrounding and all-pervading medium called ether; if the heating be continued to a higher degree, the body begins to give out light, which is due to ether waves of shorter length ; and if heated yet higher, it gives out not only dark heat waves and light waves, but also waves of still shorter length, which make no direct impression on our senses, but which are capable of producing chemical changes in certain substances, and are known as actinic waves. Of the character of the molecular motion causing electricity and magnetism we know little, and the various theories which have 28 INTRODUCTION. been advanced in order to explain electrical phenomena are inadequate and insufficient to do so satisfactorily. Specific heat. Equal weights of different substances require different quantities of heat to raise them to the same temperature. For instance: The same quantity of heat which is sufficient to raise one pound of water from 60° to 70°, will raise the tempera- ture of one pound of olive oil from 60° to 80°, or two pounds of olive oil from 60° to 70°. Olive oil consequently requires only one-half of the heat necessary to raise an equal weight of water the same number of degrees. Specific heat is therefore the heat required to raise a certain weight of a substance a certain number of degrees, compared with the heat required to raise an equal weight of water the same number of degrees. The heat required to raise one pound of water one degree centigrade, is usually taken as the unit of comparison. On thus comparing olive oil, we find its specific heat to be If we say the specific heat of mercury is we indicate that equal quanti- ties of heat will be required to raise one pound of water or 32 pounds of mercury one degree centigrade, or that the heat which raises one pound of water one degree will raise one pound of mercury 82 degrees. 3. GRAVITATION Action of gravitation. Every particle of matter in the universe attracts every other particle; consequently, all masses attract each other, and this attraction is known as gravitation. The action of gravitation between the thousands of heavenly bodies moving in the universe is to be considered by astronomy, but some of the phenomena caused by the mutual attraction of the substances composing the earth are of importance for our present considera- tions. Questions.—11. What two kinds of divisibility of matter do we distinguish, and by what actions are they accomplished? 12. Explain the term molecule. 13. Mention one of the facts which prove that a gas consists of particles with intervals between them. 14. State the law of Avogadro. 15. Mention the effects produced by increased velocity of the molecules of a mass. 16. Give an explanation of the expressions—latent heat, free heat, and specific heat. 17. Explain the construction of a mercury thermometer. 18. How many degrees of Fahrenheit are equal to 50° C.? 19. How many degrees of centigrade are equal to 167° F.? 20. What is distillation, and what is sublimation? GRAVITATION. 29 Such phenomena caused by gravitation are the falling of substances, the flowing of rivers, the resistance which a sub- stance offers on being lifted or carried. A body thrown up into the air or deprived of its support will fall back upon the earth. In this case the mutual attraction between the earth and the substance has caused its fall. It might appear that in this case the attraction was not mutual, but exerted by the earth only; it has been proved, however, by most exact experiments, that there is also an attraction of the falling substance for the earth, but the amount or the force of this attraction is directly proportional to the mass of the bodies, and consequently too insignificant in the above case to be noticed. The law of gravitation, known as Newton’s law, may thus be stated: All bodies attract each other with a force directly pro- portional to their masses and inversely proportional to the squares of their distance apart. Weight is an expression used to denote the quantity of mutual attraction between the earth and the body weighed. Here, again, the attraction of the substance for the earth is not taken into consideration. All our weighing is a comparison with, or measurement by, some standard weight, such as pound/ounce, gram, etc. Specific weight or specific gravity denotes the weight of a body, as compared with the weight of an equal bulk or equal volume of another substance, which is taken as a standard or unit. The word density is frequently used for specific weight, as density means comparative mass. By the density of a body conse- quently is meant its mass (or quantity of matter) compared with the mass of an equal volume of some body arbitrarily chosen as a standard. The standard or unit adopted for all solids and liquids is water at a temperature of 15° C. = 59° F. Specific weight is generally expressed in numbers which denote how many times the weight of an equal bulk of water is contained in the weight of the substance in question. If we say that mercury has a specific gravity or density of 13.6, or that alcohol has a specific gravity of 0.79, we mean that equal vol- umes of water, mercury, and alcohol represent weights in the proportion of 1, 13.6, and 0.79, or 100, 1360, and 79. 30 INTRODUCTION. The standard or unit chosen for comparing the specific gravity of gases is either atmospheric air or hydrogen. In order to obtain the specific gravity of any liquid, it is only necessary to weigh equal volumes of water and the liquid to be examined, and then to divide the weight of the liquid by the weight of the water. A second method by which the specific gravity of liquids may be determined is by means of the instruments known as hydrom- eters, or, if made for some special purposes, as alcoholometers, urinometers, alkalimeters, lactometers, etc. Hydrometers are instruments usually made of glass tubes, having a weight at the lower end to maintain them in an upright position in the fluid to be tested as to specific gravity, and a stem above, bearing a scale. The principle upon which their con- struction depends is the fact that a solid substance when placed in a liquid heavier than itself displaces a volume of this liquid equal to the whole weight of the displacing substance. The hydrometer will consequently sink lower in liquids of lower specific gravity than in heavier ones, as the instrument has to displace’a larger bulk of liquid in the lighter than in the heavier liquid in order to displace its own weight. Weight of gases. We have so far considered the gravity of solids and liquids only, and the next question will be: Do gases also possess weight, are they also attracted by the earth ? The fact that a gas, when generated or liberated, expands in every direction, might indicate that the molecules of a gas have no weight, are not attracted by the earth. A few simple experi- ments will, however, show that gases, like all other substances, have weight. Thus a flask from which the atmospheric air has been removed will weigh less than the same flask when filled with atmospheric air or any other gas. Barometer. A second method, by which may be demonstrated the fact that atmospheric air possesses weight, is by means of the barometer. The atmosphere is that ocean of gas which encircles the earth with a layer some 50 or 100 miles in thick- ness, exerting a considerable pressure upon all substances by its weight. The instruments used for measuring that pressure are known as barometers, and the most common form of these is the GRAVITATION. 31 mercury barometer. It may be constructed by filling with mercury a glass tube closed at one end (and about three feet long) and then inverting it in a vessel containing mercury, when it will be found that the mercury no longer fills the tube to the top, but only to a height of about 30 inches, leaving a vacuum above. The column of mercury is maintained at this height by the pressure of the atmosphere upon the surface of the mercury in the vessel; a column of mercury about 30 inches high must consequently exert a pressure equal to the pressure of a column of the atmosphere of the same diameter as that of the mercury column. As the weight of a column of mercury, having a base of one square inch and a height of about 30 inches, is equal to about 15 pounds, a column of atmosphere having also a base of one square inch must also weigh 15 pounds. In other words, the atmospheric pressure is equal to about 15 pounds to the square inch, or about one ton to the square foot. This enormous pres- sure is borne without inconvenience by the animal frame in consequence of the perfect uniformity of the pressure in every direction. A barometer may be constructed of other liquids than mercury, but as the height of the column must always bear an inverse proportion to the density of the liquid used, the length of the tube required must be greater for lighter liquids. As water is 13.6 times lighter than mercury, the height of a water column to balance the atmospheric pressure is 13.6 times 30 inches, or about 34 feet, which would therefore be the height of the column of water required. Changes in the atmospheric pressure. The height of the mercury column in a barometer is not the same at all times, but varies within certain limits. These variations are due to a number of causes disturbing the density of the atmosphere, and are chiefly atmospheric currents, temperature, and the amount of moisture contained in the atmosphere. As the height and with it the density of the atmosphere dimin- ishes gradually from the level of the sea upward, the height of the mercury column will be lower in localities situated at an elevation. This diminution of pressure is so constant that the barometer is used for estimating elevations. 32 INTRODUCTION . Influence of pressure on state of aggregation. We have seen that the volume of a substance, and, more especially, of a gas, depends upon pressure and temperature, an increase of pressure or decrease of temperature causing the volume to become smaller. We learned also that liquids may be converted into gases, and that this conversion takes place at a certain fixed temperature called the boiling-point. This point, however, changes with the pressure. An increased pressure will raise, a decreased pressure will lower, the boiling-point. Thus water boils at the normal pressure of one atmosphere at 100° C. (212° F.), but it will boil at a lower temperature on mountains in consequence of the diminished atmospheric pres- sure. If the pressure be increased, as, for instance, in steam- boilers, the boiling-point will be raised. Thus the boiling-point of water under a pressure of 2 atmospheres is at 122° C. (251° F.), of 5 atmospheres at 153° C. (307° F.), of 10 atmospheres at 180° C. (356° F.). 4. POROSITY. Nature of porosity. We have seen that the molecules of any substance are not in absolute contact, but that there are spaces between them which we call intermolecular spaces, and the property of matter to have spaces between the particles composing it is known as 'porosity. In the case of solids, these spaces or pores are sometimes of considerable size, visible even to the naked eye, as, for instance, in charcoal, whilst in most cases these spaces cannot be discovered, even by the microscope. That even apparently very dense sub- stances are porous, can be demonstrated by the fact that liquids may be pressed through metallic discs of considerable thickness, that gases maj7 be caused to pass through plates of metal or stone, that solids dissolve in liquids without showing a corre- Questions.—21. What is gravitation ? 22. Mention some phenomena caused by gravitation. 23. Give a definition of weight. 24. What is specific weight? 25. Name the substances adopted as standards for the determination of specific gravities of solids, liquids, and gases. 26. What is the use made of hydrom- eters, and on what principle is their construction based? 27. Explain con- struction and use of the mercury barometer. 28. Mention some of the causes which have an influence upon the height of the mercury column in the barometer. 29. What is the atmospheric pressure upon a surface of five square feet? 30. State the relation between boiling-point, temperature, and pressure. 33 POROSITY. sponding increase in volume of the solution thus obtained, and, finally, also by the fact that substances suffer expansion or con- traction in consequence of increased or diminished heat, or in consequence of mechanical pressure. Surface. In every-day life the expression “surface” refers to that part of a substance which is open to our senses, visible and measurable; but from a more scientific point of view, we have also to take into consideration those surfaces which, in conse- quence of porosity, extend to the interior of matter and are invisible to our eyes and absolutely immeasurable by instruments. Surface-action. Attraction acts differently under different con- ditions, and, accordingly, we assign different names to it. We call it cohesion when it acts between molecules, gravitation when acting between masses, and surface-action or surface- attraction when the attraction is exerted either by the visible surface or by that surface which pervades the whole interior of matter. The phenomena caused by this surface-action are extremely manifold, and some are of sufficient interest to be taken into consideration. Adhesion. Most solid substances, when immersed in water, alcohol, or many other liquids, become moist; immersed in mer- cury, they remain dry. We explain this fact by saying that the surfaces of most solid substances exert an attraction for the par- ticles of such liquids as water and alcohol to such an extent that these particles adhere to the surface of the solids. Such an attraction, however, does not manifest itself for the particles of mercury. This form of surface-attraction by which liquids are caused to adhere to solids is called adhesion. This adhesion may be noticed also between two plates of even surface. A drop of water pressed between these plates will cause them to adhere to each other. The application and use of glue and mucilage, our methods of writing and painting, the welding together of pieces of metal, etc., depend on this kind of surface- action. Capillary attraction. Whilst it is the general rule, that liquids in a vessel present a horizontal surface, this rule does not hold good near the sides of the vessel. When the liquids wet the 34 INTRODUCTION. vessel, as in the case of water in a glass vessel, the surface is some- what concave in consequence of the attraction of the glass surface for the particles of water; on the contrary, when the liquids do not wet the vessel, as in the case of mercury in a glass vessel, the surface is somewhat convex. The smaller the diameter of the vessel holding the liquids, the more concave or convex will the surface be. If a narrow tube is placed in a liquid, this surface- action will be more striking, and it will be found that a liquid wetting the tube will not only have a completely concave surface, but the level of the liquid stands perceptibly higher in the tube than the level of the liquid outside. Substances not wetting the tube will show the reverse action, namely, the surface inside of the tube will be convex, and will be below the level of the liquid outside. The attraction of the surface of tubes for liquids, manifesting itself in the concave shape of the surface and in the elevation of the liquid near the tube, is known as capillary attraction. Capil- lary elevations and depressions depend upon the diameter of the tube, temperature, and the nature of the liquid. The narrower the tube, the higher the elevation or the lower the depression; both are diminished by increased temperature. Capillary eleva- tions and depressions, all other circumstances being equal, are inversely proportional to the diameters of the tubes. Surface-attraction of solids for gases. Any dry solid substance, carefully weighed, will, after having been exposed to a higher temperature, show a decrease in weight whilst yet warm. Upon cooling, the original weight will be restored. This fact cannot be explained otherwise than that some substance or substances must have been expelled by heat, and that this substance or these substances are reabsorbed on cooling. This is actually the case, and the substances expelled and reab- sorbed are the gaseous constituents of the atmospheric air, chiefly the aqueous vapor. Ever}7 solid substance upon our earth condenses upon its surface more or less of the gaseous constituents of the atmosphere. This condensation takes place upon the outer as well as upon the inner surface. The amount of gas absorbed depends upon the nature of the gas as well as upon the nature of the absorbing solid. Some of the so-called porous substances, such as charcoal, generally condense or absorb larger quantities than solids of a more dense POROSITY. 35 and compact structure. Heat, as stated above, counteracts this absorbing power. Surface-attraction of solids for liquids or for solids held in solution. When a mixture of different liquids, or a mixture of different solids dissolved in a liquid, is brought in contact with or filtered through a porous solid substance, such as charcoal or bone-black, it will be found that the surface of the solid substance retains a certain amount of the liquids or of the solids held in solution, and that it retains more of one kind than of another. It is this peculiarity of surface-attraction which is made use of in purifying drinking-water by allowing it to pass through char- coal. Bone-black is similarly used for decolorizing sugar-syrup and other liquids. Absorbing power of liquids. In a similar manner as in the case of solids, liquids also exert an attraction for gases. When a gas is condensed within the pores or upon the surface of a solid, or when it is taken up and condensed by a liquid, we call this process absorption. This absorbing power of different liquids for different gases varies greatly; it is facilitated by low temperature and high pressure, and counteracted by high temperature and removal of pressure. Thus: One volume of water absorbs at ordinary tem- perature and pressure about 0 03 volume of oxygen, 1 volume of carbon dioxide, 30 volumes of sulphur dioxide, and 800 volumes of ammonia. Diffusion. When a cylindrical glass vessel has been partially tilled with water, and alcohol, which is specifically lighter than water, is poured upon it, care being taken to prevent a mixing of the two liquids, so as to form two distinct layers, it will be found that after a certain lapse of time the two liquids have mixed with each other, particles of water having entered the alcohol and par- ticles of alcohol the water, until a uniform mixture of the two liquids has taken place. Upon repeating the experiment with a layer of water over a column of solution of common salt, it will again be found that the two liquids gradually enter one into the other until a uniform salt solution has been formed. In a similar manner, two or more gases introduced into a vessel or a room will readily mix with each other. This gradual passage INTRODUCTION. of one liquid into another, of a dissolved substance into another liquid, or of one gas into another gas, is called diffusion. Osmose. Dialysis. This diffusion takes place also when two liquids are separated by a porous diaphragm, such as bladder or parchment paper, and it is then called osmose or dialysis. The apparatus used for dialysis is called a dialyzer (Fig. 4), and consists usually of a glass cylin- der, open at one end and closed at the other by the membrane to be used as the separating medium. This vessel is placed into another, and the two liquids are introduced into the two ves- sels. If the inner vessel be filled with a salt solution and the outer one with pure water, it will be found that part of the salt solu- tion passes through the membrane into the water, whilst at the same time water passes over to the salt solution. Fig. 4. Dialyzer. On subjecting different substances to this process of dialysis, it has been found that some substances pass through the membrane with much greater facility or in larger quantities than others, and that some do not pass through at all. As a general rule, crystallizable substances pass through more freely than amor- phous substances. Those substances which do not pass through membranes in the process of dialysis are known as colloids, those which diffuse rapidly crystalloids. Capillary attraction, or, more generally speaking, surface- attraction, is undoubtedly to some extent the cause of the phe- nomena of osmose, the surface of the diaphragm exercising an attraction upon the liquids. Diffusion of gases. A diffusion similar to that of liquids takes place also when two different gases are separated from each other by some porous substance, such as burned clay, gypsum, and others. It has been found that specifically lighter gases diffuse with greater rapidity than the heavier ones. The quantities of two different gases which diffuse into one another in a given time are, as a general rule, inversely as the square roots of their 37 INDESTRUCTIBILITY. specific gravities. Oxygen is sixteen times as heavy as hydrogen ; when the two gases diffuse, it will be found that four times as much hydrogen has penetrated into the oxygen as of the latter gas into the hydrogen. This regularity in the diffusion of gases is expressed in the Law of Graham, thus: The velocity of the dif- fusion of any gas is inversely proportional to the square root of its density. Indestructibility. All matter is indestructible—i. e., cannot possibly be destroyed by any means whatever, and this property is known as indestructibility. Form, shape, appearance, properties, etc., of matter may be changed in many different ways, but the matter itself can never be annihilated. Apparently, matter often disappears, as for instance, when water evaporates or oil burns; but these apparent destructions indicate simply a change in the form of matter; in both cases gases are formed, which become invisible constituents of the atmospheric air, and can, therefore, not be seen for the time being, but may be recondensed or rendered visible in various ways. Not only is matter indestructible, energy also partakes of this property. Energy may be converted from one form into some other form. Motion may be converted into heat, and heat into motion, or this motion into electrical energy and chemical energy. In fact, all the different forms of energy are convertible one into the other without loss. This fact is spoken of as the Law of the conservation of energy. To repeat: The total quantity of matter in the universe is constant, and the same is true of energy. Questions.—31. What is porosity? 32. What two meanings may be assigned to the word surface? 33. Mention some phenomena caused by surface-action. 34. Explain the term adhesion. 35. Under what circumstances can capillary attraction be noticed, and how does it manifest itself? 36. Give an explanation of the word absorption, and mention some instances of the absorption of gases by solids or liquids. 37. What do we understand by diffusion of gases or liquids ? 38. Define the word osmose. 39. Which substances are most apt to dialyze, and which have no such tendency? 40. What is meant by saying that matter and energy are indestructible? II. PRINCIPLES OF CHEMISTRY. RESULTS OF THE ATTRACTION BETWEEN ATOMS. 5. CHEMICAL DIVISIBILITY. Decomposition by heat. The results of the action of heat upon matter have been stated to be: Increased velocity of the motion of molecules, increase in volume of the substance heated, and in many cases a conversion of solids into liquids and of these into gases. Besides these results there frequently may be noticed another, now to be mentioned. Decomposition of mercuric oxide in A; collection of mercury in B, and of oxygen in C. To illustrate this action of heat, we will select the red oxide of mercury, a solid substance which is insoluble in water, almost tasteless, and of a brick-red color. When this oxide of mercury is placed in a glass tube and heated, it will be found to disappear gradually, and we might assume that it has been converted into a gas from which, upon cooling, the red oxide of mercury would be re-obtained. If the apparatus for heating the oxide of mercury be so constructed that the escaping gases may be collected and CHEMICAL DIVISIBILITY. 39 cooled, we shall not find the red oxide in our receiver, but in its place a colorless gas, whilst at the same time globules of metallic mercury will be found deposited in the cooler parts of the appa- ratus (Fig. 5). The action of heat consequently has in this case produced an effect entirely different from the effects spoken of heretofore. There is no doubt that the first action of the heat upon the oxide of mercury is an increased velocity of the motion of its molecules and simultaneously an increase of its volume, but afterward a decomposition of the oxide takes place, and two substances are liberated, each different from the oxide. One of these substances is a silvery-white, heavy, liquid metal, the mercury; the other substance is a colorless, odorless gas, which supports combustion much more freely than does atmos- pheric air, and is known as oxygen. Elements. We have thus succeeded in proving that red oxide of mercury may be converted or decomposed by the mere action of heat into mercury and oxygen. It is but natural to inquire whether it would be possible further to subdivide the mercury or the oxygen into two or more new substances of different proper- ties. To this question, which has been experimentally pro- pounded to Nature over and over again, we have but one answer, viz.: Oxygen and mercury are substances incapable of decom- position by any method or means as yet known to us. They resist the powerful influences of electricity and heat, even when raised to the highest attainable degrees of intensity, and they issue unchanged from every variety of reaction hitherto devised with the view of resolving them into simpler forms of matter. Therefore we are justified in regarding oxygen and mercury as non-decomposable or simple substances, in contradistinction to compound or decomposable substances, such as the red oxide of mercury. All substances which cannot by any known means be resolved into simpler forms of matter, are called elements; all substances which may, by one process or another, be subdivided or decom- posed in such a manner that new substances with new properties are formed, are called compound substances or compounds. While the number of known compounds exceeds many thou- sands, the number of elements is comparatively small, but sixty- seven of these simple substances being known to exist on our 40 PRINCIPLES OF CHEMISTRY. earth. And yet this small number of elements, by combining with each other in many different proportions, form all that boundless variety of matter which we see in nature. Chemical affinity. There must be some cause which enables or even forces the different elements to unite with each other so as to form compound bodies. There must be, for instance, a cause which enables oxygen and mercury to combine and form a red powder. This cause is to be found in the existence of another form of the general attraction which causes the smallest particles of different elements to unite to form new substances with new properties. This kind of attractive power is called chemical force, or chemical affinity, and bodies possessing this capacity of uniting with each other are said to have an affinity for each other. There is a great difference between chemical attraction and the various forms of attraction spoken of heretofore. Cohesion simply holds together the molecules of the same substance, adhe- sion acts between the molecules of solid and liquid substances, gravitation acts between masses. But all these forces do not change the nature, the external and internal properties of matter; this is done when chemical force or affinity is operating, when a chemical change takes place. For instance: In a piece of yellow sulphur the molecules are held together by cohesion, and we can counteract this cohesion by mechanical subdivision, reducing the sulphur to a fine powder; or by the application of heat we can further subdivide the sulphur, melt, and finally volatilize it; or we can throw a piece of sulphur into the air, when it will fall back upon the earth in consequence of gravitation; or we can dip it into water, when it becomes moist in consequence of surface-action. Yet in all these cases sulphur remains sulphur. It is entirely different when sulphur enters into chemical com- bination exerting chemical attraction, for instance, when it burns; this means when it combines with the oxygen of the atmospheric air. In this case a new substance, a disagreeably smelling gas, a compound of oxygen and sulphur, is formed. It is consequently a complete change in the properties of matter which follows the action of true chemical attraction; we might define affinity to be a force by which elements unite and new substances are generated. CHEMICAL DIVISIBILITY. 41 Atoms. Molecules, as stated heretofore, are the smallest par- ticles of matter which can exist. All matter consists of mole- cules, consequently the red oxide ef mercury must also consist of molecules. By heating the oxide of mercury, oxygen and mercury are obtained, each of which also must consist of molecules. As the oxide of mercury consists of molecules, and as these molecules are neither pure oxygen nor pure mercury, we must come to the conclusion that a molecule of the oxide of mercury is composed of a small particle of oxygen and a small particle of mercury. We consequently learn that a molecule of a compound substance is composed of yet smaller particles of elements, and these smallest particles of elements capable of entering into combination are called atoms, while molecules are the smallest particles of matter which are capable of existing in a free state. Having now established the difference between atoms and molecules, we may give a better definition of elements and com- pounds by saying that an elementary substance is one in which the atoms composing its molecules are alike, whilst in a com- pound substance the molecules contain atoms of different kinds. Chemistry is the science of affinity, and affinity is the attraction acting between atoms and causing them to unite and form mole- cules. As every chemical change is due to the motion of atoms, chemistry may also be defined as the science of the motion of atoms taking glace in consequence of chemical affinity. Also, we may say that chemistry is that branch of science which treats of the com- position of substances, the changes in their composition, and the laws governing such changes. The scheme below may help to illustrate the relation of chem- istry to some other branches of physical science: General Force of Attraction acting between— Heavenly bodies masses. or Surfaces. Molecules. Atoms. is termed : Gravitation. Surf ace-action. Adhesion. Capillary attrac- tion, etc. Cohesion. Chemical affinity. 42 PRINCIPLES OF CHEMISTRY. The phenomena caused by these respective actions are con- sidered by: Astronomy Mechanics. or Physics. Physics. Crystallography. Chemistry. Atomic weight. All matter possesses weight; this is true of a mass as well as any part of it, and must consequently be true of the atoms also and of the molecules of which matter consists. It is, of course, impossible to weigh a single atom or a single mole- cule, yet science has formed an opinion in regard to the relative weights of these minute particles. The experiment referred to above may be so conducted as to ascertain the weight of the products of decomposition (viz., the oxygen and the mercury) of a given, previously weighed quantity of oxide of mercury. In doing this, it will be found invariably that every 13.5 parts by weight of the oxide of mercury yield upon heating 12.5 parts by weight of mercury and 1 part of oxygen, that we have conse- quently in 13.5 pounds of oxide 12.5 pounds of mercury and 1 pound of oxygen. If we assume that a molecule of the oxide is composed of one atom of mercury and one atom of oxygen, we are justified in saying that a mercury atom is 12.5 times heavier than an oxygen atom. In a manner similar to this, the weights of the atoms of all different elements have been compared with each other, and the element having the lightest atom has been selected as the unit of comparison. The element having the lightest atom is hydrogen, and we say the atomic weight of hydrogen is 1, and compare with this weight the weights of all other elements. In doing this, we find that the atom of oxygen weighs sixteen times as much as the atom of hydrogen, and we consequently say the atomic weight of oxygen is 16. We have learned before, from the decomposition of the red oxide of mercury, that the mercury atom is 12.5 times as heavy as that of oxygen. As the atomic weight of this element is 16, the atomic weight of mercury must be 12.5 times 16, or 200. Whilst atomic weight is the weight of the atom of any element as compared to the weight of an atom of hydrogen, molecular weight is the combined weight of the atoms forming the molecule. Thus the molecular weight of oxide of mercury is 200 + 1(3 = 216. 43 LAWS OF CHEMICAL COMBINATION. Chemical symbols. For reasons to be better understood here- after, chemists designate each element by a symbol, and the first or first two letters of the Latin name of the element have generally been selected. Thus, the symbol of hydrogen is H, of oxygen O, of mercury Ilg (from hydrargyrum), of sulphur S, etc. These symbols designate, moreover, not only the elements, but one atom of these elements. For instance : 0 not only signifies oxygen, but one atom or 16 parts by weight of oxygen; and Ilg, one atom or 200 parts by weight of mercury. Chemical formulas. In a similar manner as atoms of elements are represented by symbols, the molecules of a compound sub- stance are designated, and such a representation of a compound substance by symbols is called its formula. Thus, HgO is the formula of the red oxide of mercury, and it tells at once that it is a substance composed of one atom or 200 parts by weight of mercury, and one atom or 16 parts by weight of ox}7gen. In the molecule of a compound body there must be at least two atoms, each one of a different element, but there may be in a molecule of a compound more than two atoms belonging to two or more elements. For instance: The composition of water is H20 ; this means, a molecule of water contains 2 atoms of hydrogen and 1 atom of oxygen. When there is more than one atom of an element in a molecule, the number of these atoms is designated by placing the figure on the right of the symbol and a little below” it, as in H20, whilst 2HO or 20H would designate 2 molecules of a substance containing one atom of hydrogen and one atom of oxygen. 6. LAWS OF CHEMICAL COMBINATION. Law of the constancy of composition. This law, also known as the law of definite proportions, was the first ever recognized in Questions.—41. How does heat act upon the red oxide of mercury ? 42. State the difference between mechanical and chemical divisibility. 43. Define the terms element and compound. 44. How many elements and how many com- pound substances are known? 45. What is chemical affinity, and how does it differ from other forces? 46. What is an atom, and how does it differ from a mole- cule? 47. What is chemistry ? 48. Give a definition of atomic weight and of molecular weight. 49. The atom of which element has been selected as the unit for comparison of atomic weights? 50. Give an explanation of chemical symbols and formulas. 44 PRINCIPLES OF CHEMISTRY. chemical science; it was discovered toward the close of the last century, and may be stated thus : A definite compound always con- tains the same elements in the same proportion ; or, in other words, All chemical compounds are definite in their nature and in their compo- sition. To make this law perfectly understood, the difference between a mechanical mixture and a chemical compound must be pointed out. Two powders, for instance sugar and starch, may be mixed together very intimately in a mortar, so that it seems impossible for the eye to discover more than one body. But in looking at this powder with the aid of a microscope, the particles of sugar as well as those of starch may be easily distinguished. The mixture thus produced is a mechanical mixture of molecule clusters. It is somewhat different when two substances, for instance two metals, are fused together, or when two gases or two liquids (oxygen and nitrogen, water and alcohol) are mixed together, or when finally a solid is dissolved in a liquid (sugar in water). In these instances no separate particles can be discovered even by the microscope. The mixtures thus produced are mixtures of molecules. Such mixtures always exhibit properties intermediate between those of their constituents and in regular gradation according to the quantity of each one present. The proportions in which substances may thus be mixed are variable. In a true chemical compound the proportions of the constituent elements admit of no variation whatever; it is not formed by the mixing of molecules, but by the combination of atoms into mole- cules : the properties of a compound thus formed usually differ very widely from those of the combining elements. Powdered iron and powdered sulphur may be mixed together in many different proportions. If such a mixture be heated until the sulphur becomes liquid, the two elements, iron and sulphur, combine chemically, but they do so in one pro- portion only, 56 parts by weight of iron combining with 32 parts by weight of sulphur to form 88 parts of sulphide of iron. If the two substances had been mixed together in any other proportion than the one mentioned, and which cor- responds to the atomic weights of both elements, the excess of one will be left undisturbed and uncombined. Law of multiple proportions. If two elements, A and B, are capable of uniting in several proportions, the quantities of B which combine with a fixed quantity of A bear a simple ratio to each other. Thus A may combine with B, or A with 2 B, or A with B B, etc. LAWS OF CHEMICAL COMBINATION. 45 This law was discovered at the beginning of the present cen- tury, when it was found that the ratio of carbon to hydrogen in olefiant gas, C21I4, is as 6 to 1, in marsh gas, CII4, as 6 to 2, and that the ratio of carbon to oxygen in carbon monoxide, CO, is as 6 to 8, in carbon dioxide, C02, as 6 to 16. These and similar instances led to the discovery of the law of multiple proportions, and it was this law which led Dalton, in 1804, to the adoption of the atomic theory. In thinking and reasoning about this law, he could find no other explanation than that there must be small particles of definite weight which com- bine with each other, and to these small particles he gave the name atoms. As a very good example illustrating the law of multiple proportions may be mentioned the five compounds formed by the elements nitrogen and oxygen, which compounds have the composition N20, N202, N203, N204, and N.205. respectively. In these compounds we find 16, 2X16, 3X16, 4X16, and 5X16 parts by weight of oxygen in combination with 28 parts by weight of nitrogen. The law of chemical combination by volume, or the law of Gay- Lussac, may be stated as follows: When two or more gaseous con- stituents combine chemically to form a gaseous compound, the volumes of the individual constituents bear a simple relation to the volume of the product. The law may be divided into two laws, thus: 1. Gases combine by volume in a simple ratio. 2. The resulting volume of the compound, when in the form of a gas, bears a simple ratio to the volumes of the constituents. For instance: 1 volume of hydrogen combines with one volume of chlorine, forming 2 volumes of hydrochloric acid gas; 2 volumes of hydrogen com- bine with 1 volume of oxygen, forming 2 volumes of water-vapor; 3 volumes of hydrogen combine with 1 volume of nitrogen, form- ing 2 volumes of ammonia. If the different combining volumes of the gases mentioned are weighed, it will be found that there exists a simple relation be- tween these volumes and the atomic or molecular weights of the elements. For instance: Equal volumes of hydrogen and chlorine com- bine, and the weights of these volumes are as 1 : 35.4, which numbers represent also the atomic weights of the two elements. Two volumes of hydrogen combine with one volume of oxygen, and the weights of the volumes are as 1 : 8 or 2 : 16, the latter being the atomic weight of oxygen. 46 PRINCIPLES OF CHEMISTRY. 1 Volume Hydrogen Weight=l 1 Volume Chlorine Weight=35.4 2 Vol umes Hydrochl oric Acid gas. W =:36.4 + 1 Volume Hydrogen W = 1 1 Volume Hydrogen W = 1 1 Volume Oxygen W = 16 2 Voliumes Water-vapor W =118 + '+ 1 Volume Hydrogen W = 1 1 Volume Hydrogen W = 1 1 Volume Hydrogen W = 1 1 Volume Nitrogen W = 14 2 Vol umes Amm onia gas. \V = 17 + + + 1 Volume Hydrogen W = 1 + 1 Volume Hydrogen W = 1 1 Volume Sulphur W = 32 1 Volume Oxygen W = 16 + + + 2 Vol; umes Sulphuriic acid gas. Weightj= 98 1 Volume Oxygen W = 16 1 Volume Oxygen W = 16 1 Volume Oxygen W = 16 + + The above diagram shows the simple relation which exists between combining volumes, atomic and molecular weights; and that such a relation exists is not surprising, if we remember the law of Avogadro, which has been before stated, and which says that all gases under equal conditions contain the same number of molecules. The weighing of equal volumes of gases consequently is identical with the weighing of equal numbers of molecules. The molecular weight of a substance therefore can be found by weighing this substance in the gaseous state and comparing with it the weight of an equal volume of another gas, the molecular weight of of which is known. The gas usually adopted for this comparison is hydrogen. If, for instance, we weigh equal volumes of hydrogen, chlorine, oxygen, hydrochloric acid gas, and steam, we find weights in the proportion of 2, 70.8, 32, 36.4 and 18. These numbers express also the molecular weights of these substances; moreover they show that atomic and molecular weights of elements are not LAWS OF CHEMICAL COMBINATION. 47 identical, but that the latter weight is twice that of the atomic weight, or that the molecules of elements consist of two atoms} One litre of hydrogen at the freezing-point of water and under the ordinary pressure of 15 pounds to the square inch, weighs 0.0896 gram. This weight of one litre of hydrogen is taken as the unit or standard of comparison for gases, and is called one crith. A litre of oxygen weighs 16 criths, one of chlorine 35.4 criths, one of steam 9 criths, etc. Theory (Law) of equivalents, Quantivalence, or Valence. When one element replaces another element in a compound, the quan- tities of the two elements are said to be equivalent to each other, and according to the law of equivalents the replacement of ele- ments one by another takes place always in definite proportions. Formerly it was believed that all atoms were equivalent among each other, and, accordingly, atomic weights frequently were designated as equivalent weights. This view, however, is not correct, as it is found that one atom of one element frequently displaces two or more atoms of another element. This fact, as well as other considerations, has led to the assumption of the quantivalence of atoms. This property will be understood best by selecting for consideration a few com- pounds of different elements with hydrogen. I. II. III. iy. HC1 h2o h3n h4c HBr h2s H3 As H4Si HI H2Se h3p We see here that Cl, Br, and I combine with H in the propor- tion of atom for atom; 0, S, Se combine with II in the propor- tion of 2 atoms of hydrogen for 1 atom of the other element; N, As, P combine with 3; C and Si with four atoms of hydrogen. Moreover, it has been found that the compounds mentioned in column I. are the only ones which possibly can be formed by the union of the elements Cl,Br, and I with H. They invariably combine in this proportion only. Other elements show a similar behavior. For instance, the metal sodium combines with chlo- rine or bromine in one proportion only, forming the compound ISTaCl or NaBr. Looking at columns II., III., and IV., we see that the elements mentioned there combine with 2, 3, and 4 atoms of hydrogen, respectively. It is evident, therefore, that there must be some 1 A few exceptions to this general rule will be mentioned in the proper places. 48 PRINCIPLES OF CHEMISTRY. peculiarity in the power of attraction of different elements toward other elements, and to this property of the atoms of elements of holding in combination one, two, three, four, or more atoms of other elements the name atomicity, quantivalence, or simply valence, lias been given. According to this theory of the valence of atoms, we distin- guish univalent, bivalent, trivalent, quadrivalent, quinquivalent, sexivalent, and septivalent elements. All elements which com- bine with hydrogen in the proportion of one atom to one atom are univalent, as, for instance, Cl, Br, I, FI, and all elements which combine with these in but one proportion, that is, atom with atom, bear the same valence, or are also univalent, as for instance, iNa, K, Ag, etc. Those elements which combine with hydroden or other univa- lent elements in the proportion of one atom to two atoms are bivalent, such as O, S, Se. Trivalent and quadrivalent elements are those the atoms of which combine with 3 or 4 atoms of hydrogen, respectively. Figuratively speaking, we may say that the atoms of univalent elements have but one, those of bivalent elements two, of triva- lent elements three, of quadrivalent elements four bonds or points of attraction, by means of which they may attach themselves to other atoms. Elementary atoms are often named according to their valence: monads, diads, triads, tetrads, pentads, hexads, and heptads. To indicate the valence of the elements frequently dots or numbers are placed above the chemical symbols, thus H‘, Ou, NiU, CiiU or Civ. The bonds are often graphically represented by lines, thus : I I H— —0-, —N—, —C— I It is needless to say that such representations are merely sym- bolical, and express the view that atoms have a definite power to combine with others. When atoms combine with one another the bonds are said to be satisfied, and it is graphically expressed thus: H H .H | H—Cl, H—0—H or 0( , H—N—H or N—H Xh \h LAWS OF CHEMICAL COMBINATION 49 Whilst the valence of some elements is invariably the same under all circumstances, other elements show a different valence (this means a different combining power for other atoms) under different conditions. For instance: Phosphorus combines both with 3 and 5 atoms of chlorine, forming the compounds PC13 and PC15. As chlorine is a univalent element, we have to assume that phosphorus has in one case 3, in another case 5 points of attraction. Many similar instances are known, and will be spoken of later. The only explanation which we can furnish in regard to the variability of the valence of atoms is the assumption that sometimes one or more of the bonds of an atom unite with other bonds of the same atom. If, for instance, in the quin- quivalent phosphorus atom two bonds unite with one another a trivalent atom will remain. It is noticed invariably that the valence of atoms increases or diminishes by two, which could not be otherwise, if the explanation given be correct. Thus chlorine, the valence of which generally is I., may also have a valence equal to III., V., or YU., while sulphur shows a valence either of II., IV., or VI. Atoms whose valence is even, as in case of sulphur, are called artiads; those whose valence is expressed in uneven numbers, as chlorine and phosphorus, are called perissads. While it is now being assumed that most of the elements possess more than one valence, in consequence of the assumed power of bonds in the same atom to saturate one another, in this book will be mentioned chiefly that valence which the element seems to possess predominantly. The doctrine of the valence of atoms has modified our views of the equivalence of atoms. We now say that all atoms of a like valence are equivalent to each other. The atoms of each univalent element are equivalent to each other, and so of the atoms of any other valence, but two atoms of a univalent element are equivalent to one atom of a bivalent element, or two atoms of a bivalent element to one atom of a quadrivalent element, etc. After having explained this valence of atoms, it now may be better understood why the atoms in an element do not exist in a free but uncombined state, but combine with each other to form molecules. Atoms having the tendency of combining with, or attaching themselves to other atoms, are bound to exert that attraction, and if they are not combined with atoms of other elements, they combine with each other. For instance: Oxygen gas is not a mass of oxygen atoms, but of oxygen molecules, each molecule being formed by the union of two atoms. Questions.—51. State the law of the constancy of composition. 52. What is the difference between a mixture and a chemical compound ? 53. Mention some 4 50 PRINCIPLES OF CHEMISTRY. 7. DETERMINATION OF ATOMIC AND MOLECULAR WEIGHTS.1 Determination of atomic weights by chemical decomposition. The great difficulties originally encountered in the determination of atomic weights cannot well be described here. Consideration will be given alone to the three principal methods at present in use. These methods depend either on chemical action or on physical properties. One of the chemical methods used for the determination of atomic weights has been stated before in describing the decom- position of the red oxide of mercury by heat. The principle of this method is the determination of the proportions by weight in which the element, the atomic weight of which is unknown, combines with an element the atomic weight of which is known. For instance: If in decomposing a substance we find it to con- tain in 72 parts by weight 16 parts by weight of oxygen and 56 parts by weight of another element, we have a right to assume the atomic weight of this second element to be 56, provided, however, that the compound is actually formed by the union of one atom of oxygen and one atom of the other element. These 56 parts by weight might, however, represent 2 or 3 or more atoms. If 56 represented 2 atoms, the atomic weight would be but 28; if 4 atoms, 14. As this mode of determination gives no clue to the number of atoms present in the molecule, the results obtained are liable to be incorrect. In fact, the atomic weights of a number of ele- ments had originally been determined incorrectly by using the above or similar methods, and many of these old atomic weights had to be corrected (generally doubled) in order to obtain the correct numbers. instances of the production of molecular mixtures. 54. State the law of multiple proportions. 55. What considerations led Dalton to the adoption of the atomic theory? 56. What regularity regarding volume is noticed when gases combine chemically? 57. To what was the term equivalent quantities applied formerly, and what is to be understood by it to-day? 58. Explain the term quantivalence or atomicity. 59. Mention some univalent, bivalent, trivalent, and quadrivalent elements. 60. Suppose a certain volume of hydrogen to weigh 20 grains, how much yvill an equal volume of oxygen and how much an equal volume of hydro- chloric acid gas weigh, provided pressure and temperature be the same ? 1 The consideration of Chapter 7 should be postponed until the student has become familiar with chemical phenomena generally. DEFINITION OF ATOMIC WEIGHTS. 51 Thus, in examining water, it was found that it contained 8 parts by weight of oxygen to 1 part of hydrogen, and the conclusion was drawn that the atomic weight of oxygen was 8, and that the molecule of water was formed by the union of one atom of hydrogen and one atom of oxygen. It will be demonstrated below why we assume, to-day, that the atomic weight of oxygen is 16, and that the molecule of water is composed of 2 atoms of hydrogen and 1 of oxygen. Another chemical method of determining atomic weights is the replacement of hydrogen atoms in a known substance, by the element the atomic weight of which is to be determined. For instance: Hydrochloric acid is composed of one atom of chlorine weighing 35.4, and one atom of hydrogen weighing 1, the molecular weight of hydrochloric acid being 36.4. If in this acid the hydrogen be replaced by some other element, for instance by sodium, we are enabled to determine the atomic weight of sodium by weighing its quantity and that of the liber- ated hydrogen. Suppose that by the action of 36.4 grams of hydrochloric acid on sodium, 1 gram of hydrogen was replaced by 23 grams of sodium. In that case we would say that the atomic weight of sodium is equal to 23. The difficulty which was alluded to above exists also in this mode of determination of atomic weights, viz., not knowing whether actually it was one atom of sodium that replaced the one part of hydrogen, a doubt is left as to whether or not the determination is correct. Determination of atomic weights by means of specific weights of gases or vapors. It has been stated before that equal volumes of gases contain, under like conditions, the same number of mole- cules (no matter how few or many atoms within the molecules may be), and that the molecules of elements contain (in most cases) two atoms. These facts give in themselves the necessary data for the determination of atomic weights. For instance: If a certain volume of hydrogen is found to weigh 2 grams, and an equal volume of some other gaseous element is found to weigh 71 grams, then the atomic weight of the latter element must be 35.5, because 2 and 71 represent the relative weights of the molecules of the two elements. Each molecule being composed of 2 atoms, these molecular weights 52 PRINCIPLES OF CHEMISTRY. have to be divided by 2 in order to find the atomic weights, which are, consequently, 1 and 35.5 respective^. In comparing by this method oxygen with hydrogen.it is found that equal volumes of these gases weigh 32 and 2 respectively, that the atomic weight of oxygen is consequently 16, and not 8, as determined by chemical methods. This mode of determining atomic weights may be applied to all elements which are gases or which may without decomposition be converted into gas. There are, however, elements which can- not be volatilized, and in this case it becomes necessary to deter- mine the specific gravity of some gaseous compound of the element. The element carbon itself has never been volatilized, but we know many of its volatile compounds, and these may be used in the determination of its atomic weight. Determination of atomic weights by specific heat. Specific heat has been stated to be the quantity of heat required to raise the temperature of a given weight of any substance a given number of degrees, as compared with the quantity of heat required to raise the temperature of the same weight of water the same number of degrees. In comparing atomic weights with the numbers expressing the specific heats, it is found that the higher the atomic weight the lower the specific heat, and the lower the atomic weight the higher the specific heat. This simple relation may thus be expressed: Atomic weights are inversely proportional to the specific heats; or the product of the atomic weight multiplied by the specific heat is a constant quantity for the elements examined. Elements. Specific heats. (Water = 1 ) Atomic weights. Product of specific heat X atomic weight. Lithium, 0.9408 7 6.59 Sodium, 0.2934 23 6.75 Sulphur, 0.2026 32 6.48 Zinc, 0 0956 65.2 6.24 Bromine (solid),0.0843 80 6.75 Silver, 0.0570 108 6.16 Bismuth, 0.0308 210 6.48 An examination of this table will show this relation between atomic weight and specific heat, and also that the product of atomic weight multiplied by specific heat is equal to about 6.5. The variations noticed in this constant quantity of about 6.5 may be due to errors made in the determinations of the specific heats, DEFINITION OF ATOMIC WEIGHTS. 53 and subsequent determinations may cause a more absolute agree- ment. However, the agreement is sufficiently close to justify the deduction of a law which says: The atoms of all elements have exactly the same capacity for heal. This law was first recognized by Dulong and Petit in 1819, and is simply a generalization of the facts stated. To show more clearly what is meant by saying that all atoms have the same capacity for heat, we will select three elements to illustrate this law. If we take of lithium 7 grams, of sulphur 32 grams, of silver 108 grams, we have of course in these quantities equal numbers of atoms, because 7, 32, and 108 represent the atomic weights of these elements. If we expose these stated quantities of the three elements to the same action of heat, we shall find that the temperature increases equally for all three substances—that is to say, the same heat will be required to raise 7 grams of lithium 1°, which is necessary to raise either 32 grams of sulphur or 108 grams of silver 1°. The quantity of heat necessary to raise the atom of any element a certain number of degrees is, consequently, the same. As heat is the consequence of motion, the result of the facts stated may also be expressed by saying : It requires the same energy to cause different atoms to vibrate with such a velocity as to acquire the same temperature, no matter whether these atoms be light or heavy. It is evident that these facts give us another means of deter- mining atomic weights, by simply dividing 6.5 by the specific ■heat of the element. The specific heat of sulphur, for instance, has been found to be 0.2026. 6.5 divided by this number is 31.6, or nearly 32. Originally the atomic weight of sulphur had been determined by chemical methods to be 16, but its specific heat, as well as other properties, has shown this number to be but one- half of the weight, 32, now adopted. It may be mentioned that elements possess essentially the same specific heat whether they exist in a free state or are in combi- nation ; this fact will, in many cases, be of use in the determi- nation of atomic weights. Determination of molecular weights. From the statements made regarding the determination of atomic weights, it is evident that we 54 PRINCIPLES OF CHEMISTRY. may use a number of methods for determining molecular weights, these methods being to some extent analogous to the former. Thus we have methods which are based entirely on chemical analysis or on chemical changes generally. If, for instance, the analysis of a substance shows of calcium 40 per cent., of carbon 12 per cent., and of oxygen 48 per cent., we have a right to assume that the molecule is made up of 1 atom of calcium, 1 atom of carbon, and 3 atoms of oxygen, as the atomic weights of these elements are 40, 12, and 16, respectively. The molecular weight in this case is 100, and the composition is expressed by the formula CaC03, but the molecular weight might be 200 and the correct formula Ca2C206. There are actually substances which contain such multiples of atoms, as, for instance, the compounds C2II2 and C6I16, and as their percentage composition is identical, analytical methods are insufficient to indicate the number of atoms contained in these molecules. The second method, based on Avogadro’s law, is applicable to all substances which are or can be converted into gases or vapors without decomposition. Weighing of equal volumes of hydrogen and of some other substance in the gaseous state gives at once the data for calculating the molecular weight. (See page 46.) A third method, that of Raoult, is based upon the fact that the freezing-point of a liquid is lowered to the same extent, by dis- solving in it compounds in quantities proportional to their molec- ular weights. For example: Water begins to solidify at 32° F. (0° C.), but by dissolving in it say 4 per cent, of its weight of a salt (the molecular weight of which is known) the freezing-point is lowered, say 1° C. If, then, another salt(the molecular weight of which is not known) be dissolved in water, and it be found that to reduce the freezing-point 1° C. there must be dissolved a quantity equal to 7 per cent, of the weight of the water used— then are the molecular weights of the two salts to each other as is 4 to 7. In regard to this method of Raoult it should be stated that it is applicable only to such substances as do not act chemically upon the solvent used, and that the ratio of the lowering of the freezing-point is not the same for all substances, but only for members of the same class of substances. Questions.—61. What are the three principal methods used for the determi- nation of atomic weights? 62. Why are chemical means not alwajTs sufficient DECOMPOSITION OF COMPOUNDS. 55 8. DECOMPOSITION OF COMPOUNDS. GROUPS OF COMPOUNDS. Action of heat upon compounds. All phenomena taking place in nature are, without exception, due to motion. Chemistry con- siders the motion of atoms, without which no chemical change takes place. The causes for chemical changes are either physical actions (heat, electricity), or the decomposing influence of one substance upon another caused by the atoms rearranging them- selves into new bodies, so as to better satisfy their affinities. The decomposing action of heat upon compounds has been mentioned before in connection with the decomposition of red oxide of mercury into mercury and oxygen. Similarly to this process, many other compound substances are decomposed by heat either into elements, or, more frequently, into simpler forms of combination. This means that the molecule of a substance containing, for instance, 10 atoms, is split up into 2, 3, or more molecules, each one containing a portion of the 10 atoms. For instance : A piece of marble, which is carbonate of cal- cium, or CaC03, is decomposed by heat into oxide of calcium, CaO, and carbon dioxide, C02. That heat has such decomposing influence upon compounds is readily ac- counted for, if we bear in mind, that increase in heat means increased molecular vibration, which most likely weakens the stability of the molecule, and dimin- ishes the attractions of its component atoms. On the other hand, heat will in many cases facilitate chemical combination between two substances, because the increased molecular vibration brings the molecules closer within the sphere of each other’s attraction, thereby facilitating chemical union. For instance : Mercury and oxygen do not act upon each other at ordinary temperature, but when heated to a temperature somewhat below the boiling-point of mercury, they combine slowly, forming oxide of mercury. This compound, however, as shown before, readily decomposes into mercury and oxygen when heated to a low red heat. to determine atomic weights? 63. How can the specific gravity of elements in the gaseous state be used for the determination of atomic weight ? 64. Describe a method of the determination of atomic weight by chemical means. 65. State one of the reasons why the atomic weight of oxygen has been changed from 8 to 16. 66. What relation exists between atomic weight and specific heat? 67. State the law of Dulong and Petit. 68. Suppose the specific heat of an element to be 0.1138, what will its atomic weight be ? 69. Suppose the specific gravity of an elementary gas to be 14, what will its atomic weight be ? 70. Sup- pose 216 grams of an element replace 2 grams of hydrogen in 73 grams of HC1, what will the atomic weight of the element be ? 56 PRINCIPLES OF CHEMISTRY. The quantity of heat required for decomposition differs widely according to the nature of the substance. Some substances can be produced only at a temperature below the freezing-point of water, a higher temperature causing their decomposition; other substances may be decomposed at temperatures between the freezing- and boiling-points; others again, and to these belong the majority of compounds, may be raised to red or white heat before decomposition sets in ; and still another number of com- pounds have never yet been decomposed by heat. Theoretically however, we assume that all compounds may be decomposed by heat, should it be possible to raise it to a sufficiently high degree. Decomposition by electricity. Similarly to heat, also electricity decomposes many substances, provided they are in a liquid or gaseous state. These decompositions are usually accomplished by allowing an electric current to pass through the liquid, or electric sparks to pass through the gas. Thus hydrochloric acid, HC1, may be decomposed into hydrogen and chlorine; water, H20, into hydrogen and oxygen. The act of decomposing a compound by electricity is known as electrolysis, and the substance thus decomposed is termed electrolyte. During the decomposition of substances by electrolysis one of the products of decomposition appears at the negative, the other at the positive pole of the battery. Thus, when water is decomposed, the hydrogen is evolved from the negative, the oxygen from the positive pole. Or, when salts are decomposed, the metal is deposited at the negative pole, and the acid or its decomposition products at the positive pole. It was formerly believed that those elements which in electrolysis appear at the negative pole were charged with positive electricity, and were called electro- positive elements, while those appearing at the positive pole were charged with negative electricity and called electro-negative elements. According to this view the non-metals are electro-negative, while the metals are electro-positive. There is a certain relation between electrical and chemical action, as the quantity of electricity which, for instance, sets free 35.4 grams of chlorine, will also set free 80 grams of bromine or 127 grams of iodine. The figures 35.4, 80, and 127 represent the atomic weights of these elements. Decomposition by light. Another cause of decomposition is, in many cases, the action of light. The art of photography is based upon this kind of decomposition. Many substances, easily affected by light, have to be kept in the dark to prevent them from being decomposed. DECOMPOSITION OF COMPOUNDS. 57 The phenomena of heat, light, and electricity resemble each other in so far as they are phenomena of motion. Heat is the consequence of the motion of material particles (molecules) ; light is the consequence of the vibratory motion of the hypothetical medium ether ; probably the same is true of electricity. These motions, in being transferred to atoms, have, as shown above, fre- quently the tendency of splitting up the molecules of compound substances. Mutual action of substances upon each other. As a general rule, it may be said that no chemical action takes place between two substances, both of which are in the solid state, because the molecules do not come in sufficiently close proximity to exchange their atoms. The free motion of the molecules in liquid or gaseous substances facili'tates such a proximity, and consequently chemical action. It is often sufficient to have but one of the acting substances in the gaseous or liquid state, whilst the second one is a solid. By converting two solids into extremely tine powder and mixing them together thoroughly, chemical combi- nation may follow, provided the affinity between them be suffi- ciently strong. The action of substances upon each other may be represented by the following equations, in which the letters stand for elements or groups of elements : 1. A -f- B — x\B — direct combination. 2. AB -J- C = AC -f- B — direct decomposition. 3. AB -j- CD = AC -j- BD — doable decomposition. As instances illustrating the above, may be mentioned the fol- lowing chemical reactions: 1. H + Cl = HC1. Hydrogen. Chlorine. Hydrochloric acid, The formula here given for the formation of hydrochloric acid is not entirely correct, because the action between hydrogen and chlorine does not take place between free atoms, but between the molecules of the two elements, each molecule containing two atoms. The more correct way of writing the formula would therefore be : HH + C1C1 = 2HC1. Or 2H + 2C1 = 2HC1. 2. Hydrochloric acid and sodium form sodium chloride and hydrogen: HC1 + Na = NaCl + H. 58 PRINCIPLES OF CHEMISTRY. The formula more correctly written would be : 2HCI 4- 2N a = 2NaCl + 2H 3. HC1 + AgN03 = AgCl + HNOa Hydrochloric acid. Silver Nitrate Silver Chloride. Nitric acid, This form of decomposition, known as double decomposition or metathesis, is one of the most common kinds of chemical changes met with in chemical operations. All the decompositions mentioned above are caused by the affinity which the atoms of one substance have for atoms of another substance. For instance: The decomposition of the hydrochloric acid by sodium may be explained by saying that sodium has a greater affinity for chlorine than for hydrogen, as the latter is expelled by the sodium. ISTo general rule can, however, be given for the intensity of affinity with which the atoms of different elements attract each other, because this attraction differs under different conditions. For instance: Water passed in the form of steam over red-hot iron is decomposed, iron oxide and free hydrogen being formed : Fe + H20 = FeO + 2H. This decomposition would indicate that the attraction between iron and oxygen is greater than between hydrogen and oxygen. But in passing free hydrogen over heated oxide of iron the reverse action takes place, water and free iron being formed : FeO + 2H = Fe + H20. This reaction would indicate that the affinity between oxygen and hydrogen is greater than between oxygen and iron. As a general rule it may be stated that the quantity of a product formed by chemical action of two substances upon one another, is influenced by the relative proportions of the reacting substances. In the above instance iron decomposes water when the iron is in large excess, while a liberal supply of hydrogen causes the reverse action. As a second instance may be men- tioned the decomposition of sodium nitrate by sulphuric acid, with the formation of sodium acid sulphate and free nitric acid. On the other hand, sodium acid sulphate is decomposed by a large excess of nitric acid into sodium nitrate and free sulphuric acid. A consideration of this mass-action, as it is now termed, has DECOMPOSITION OF COMPOUNDS. 59 led to the establishment of the law, that Chemical action is propor- tional to the active mass of each substance taking part in the change. While the power of affinity possessed by atoms or compounds does not furnish us with data sufficient to predict all chemical changes, we may lay down a general rule which governs the decomposition of certain compounds and which may be stated thus: When two (or more) substances are brought together in solution, which substances by any rearrangement of the atoms may form a product insoluble in the liquid present, this product will form and separate as a precipitate. As instances of this kind of decomposition may be mentioned the formation of all the hundreds of insoluble metallic salts, which are produced by the action of one salt solution upon another salt solution, the first solution containing a metal which with the acid of the second solution may form an insoluble com- pound, which is then invariably produced as a precipitate. For instance: Calcium carbonate, CaC03, is insoluble; if we bring together two solutions containing a soluble calcium salt and a soluble carbonate, such as calcium chloride, CaCl2, and sodium carbonate, Ha2C03, calcium carbonate is precipitated. A second general rule may be stated thus: When two substances capable of forming a volatile product are brought together, the reaction generally takes place. As instances may be mentioned the libera- tion of carbon dioxide from any carbonate by the action of an acid, and the liberation of ammonia gas from ammonium com- pounds by calcium hydroxide. The nascent state. This expression is used of elements at the moment when their atoms leave molecules and have not yet had time to reenter into combination. When in this state the atoms have a much greater energy to combine than after having entered into a combination with other atoms of either the same kind (to form elementary molecules) or of another kind (to form com- pound molecules). White arsenic, As203, is a compound of the metal arsenic with oxygen; if through a solution of this com- pound hydrogen gas be allowed to pass, no chemical change takes place. If, however, hydrogen be generated or set free in a solution of white arsenic, then the hydrogen atoms, while in the nascent state, have sufficient energy to combine with both the elements arsenic and oxygen, forming arseniuretted hydrogen, AsII3, and water, H20. 60 PRINCIPLES OF CHEMISTRY. Chemical reaction in its broader sense refers to any chemical change, but is used more especially when the intention is to study the nature of the substances decomposed or formed. The expres- sion reagent is applied to those substances used for bringing about such changes. Analysis and synthesis. These expressions refer to two methods of research in chemistry, accomplished by two kinds of reaction, analytical and synthetical. Analysis is that mode of research by which compound sub- stances are broken up into their elements or into simpler forms of combination, and analytical reactions are all chemical processes by which the nature of an element, or of a group of elements, may be recognized. Synthesis is that method of research by which bodies are made to unite to produce substances more complex. Analytical and synthetical methods, or reactions, frequently blend into one another. This means: A reaction made with the intention of recognizing a substance may at the same time pro- duce some compound of interest from a synthetical point of view. Acids. The many compounds formed by the union of elements are so various in their nature, that no system of classification proposed up to the present time can be called perfect. There are, however, a few groups or classes of compounds, the properties of which are so well marked, that a substance belonging to either of them may be easily recognized. These, groups are the acids, bases, and neutral substances. Acids are characterized by the following properties: 1. They have (when soluble in water) an acid or sour taste. 2. They change the color of many organic substances, for instance of litmus, from blue to red. 3. They contain hydrogen, which can be replaced by metals, the compound thus formed being a salt. According to the number of hydrogen atoms replaceable by metals, we distinguish monobasic, dibasic, and tribasic acids. Hydrochloric acid, HC1, is a monobasic, sulphuric acid, II2S04, is a dibasic, phosphoric acid, H3P04, is a tribasic acid. Bases or basic substances show properties which are opposed to those of acids. These properties are : DECOMPOSITION OF COMPOUNDS. 61 1. They have (when soluble in water) the taste of lye, or an alkaline taste. 2. They restore the color of organic substances when pre- viously changed by acids, for instance that of litmus, from red to blue. 3. When acted upon by acids, they form salts. For instance : Potassium hydroxide is a base; when brought in contact with hydrochloric acid it forms water and the salt potassium chloride: IvOH + HC1 = H20 + IvCl Neutral substances. All substances having neither acid nor basic properties are neutral. Water, for instance, is a neutral substance, having no acid or alkaline taste, and no action on red or blue litmus. Many neutral substances, to some extent even water, appear to possess the characteristic properties of both classes, acids and bases; of neither class, however, to a very great extent. Salts. A salt is a compound formed by the union of an acid and a base (usually with the simultaneous formation of water), or by the action of an acid on a metal (usually with the liberation of hydrogen). For instance: NaOH + HN03 = NaN03 + H20 Sodium hydroxide. Nitric acid. Sodium nitrate. Water Iron. Fe + H2S04 = FeS04 + II2 Sulphuric acid. Ferrous sulphate. Hydrogen. The process of combining an acid with a base in such a pro- portion that the acid and alkaline reactions disappear, and a neutral salt is formed, is known as neutralization. According to the number of hydrogen atoms replaced in an acid, we distinguish normal and acid salts. A normal salt is one formed by the replacement of all the replaceable hydrogen atoms of an acid. For instance : Potassium chloride, KC1, potassium sulphate, K2S04, potassium phosphate, I\3P04. (As monobasic acids have but one atom of hydrogen which can be replaced, they form normal salts only.) Normal salts often have a neutral reaction to litmus, but the}7 may have an acid, or even an alkaline reaction. Acid salts are acids in which there has been replaced only a portion of their replaceable hydrogen atoms. For instance: khso4, k2hpo4, kh2po4. 62 PRINCIPLES OF CHEMISTRY. Basic salts are salts containing a higher proportion of a base than is necessary for the formation of a normal salt. Instances are basic mercuric sulphate, IIgS04.2Hg0, basic lead nitrate, Pb2X03.Pb20H. According to modern views basic salts are looked upon as derived from bases by neutralization of part of the hydrogen contained in them. In the base lead hydroxide, Pb20II, the hydrogen atoms may be replaced by the radical of nitric acid, when basic lead nitrate, Pb\Qjp is formed. In bismuth hydroxide, Bi(OH)3, one, two or three h}7drogen atoms may be replaced by nitric acid, when the salts Bi\OH^2 and Bi(H03)3 are formed. The first two compounds are basic salts, while the third one is the normal salt. Double salts are salts formed by replacement of hydrogen in an acid by more than one metal. For instance : potassium-sodium sulphate, KXaS04. Residue, radical, or compound radical, are expressions for unsatu- rated groups of atoms known to enter as a whole into different compounds, but having no separate existence. For instance: The bivalent oxygen combines with two atoms of the univalent hydrogen, forming the saturated compound H20, water. If we take from this Id20 one atom of H, there is left the group of atoms IIO (now generally written OH), consisting of an atom of oxygen in which but one point of attraction is actually saturated, the second one not being provided for. This group, OH, is a residue or radical, and is known to enter into many compounds; it is, for instance, a constituent of all the different hydroxides (formerly called hydrates), such as potassium hydroxide, KOH, calcium hydroxide, Ca20II, etc. According to the number of points of attraction left unprovided for in a radical, we distinguish univalent, bivalent, trivalent, and quadrivalent radicals. Carbon is a quadrivalent element forming with the univalent hydrogen the saturated compound CH4. By removal of one, two, or three hydrogen atoms the radicals CII3', CH2", CH'", are formed. Questions.—71. What physical actions have a tendency to decompose com- pound substances? 72. Explain the terms reaction and reagent. 73. Mention GENERAL REMARKS REGARDING ELEMENTS. 68 9. GENERAL REMARKS REGARDING ELEMENTS. Relative importance of different elements. Of the total number of about sixty-seven elements, comparatively but few (about one- fourth) are of great and general importance for the earth, and the phenomena taking place upon it. These important elements form the greater part of the mass of the solid portion of the earth, and of the water and atmosphere, and of all animal and vegetable matter. Another number of elements are of less importance, because either they are not found in any large quantity, or do not take any active or essential part in the formation of organic matter; yet they are of interest and importance on account of being used, in their elementary state or in the form of different compounds, in every-day life for various purposes. A third number of elements are found in such minute quanti- ties in nature that they are almost exclusively of scientific interest. Even the existence of some elements, the discovery of which has been claimed, is doubtful. The elements enumerated in column I. are those of great and general interest; in II. those claiming interest on account of the special use made of them ; in III. those having scientific interest only. I. II. III. Aluminium Antimony Beryllium (Glucinum) Calcium Arsenic Caesium Carbon Barium Cerium Chlorine Bismuth Columbium (Niobium Hydrogen Boron Didymium Iron Bromine Erbium Magnesium Cadmium Gallium Nitrogen Chromium Germanium Oxygen Cobalt Indium Phosphorus Copper Iridium Potassium Fluorine Lanthanum some instances of decomposition produced by the action of one substance upon another substance. 74. Why can no general rules be established in regard to the amount of attraction which different elements have for each other? 75. What is the difference between analytical and synthetical methods? 76. Define an acid, and state the general properties of basic and neutral substances. By what means can they be recognized? 77. Distinguish between mono-, di-, and tri-basic acids. 78. What are salts and how are they formed? 79. Define neutral, acid, and double salts. 80. Explain the term radical or residue. 64 PRINCIPLES OF CHEMISTRY. I. II. III. Silicon Gold Osmium Sodium Iodine Palladium Sulphur Lead Rhodium Lithium Kubidium Manganese Ruthenium Mercury Scandium Molybdenum Selenium Nickel Tantalum Platinum Tellurium Silver Thallium Strontium Thorium Tin Titanium Zinc Tungsten Uranium Vanadium Ytterbium Yttrium Zirconium Classification of elements may be based upon either physical or chemical properties, or upon a consideration of both. A natural classification of all elements is the one dividing them into two groups of metals and non-metals. Metals are all elements which have that peculiar lustre known as metallic lustre; which are good conductors of heat and elec- tricity ; which, in combination with oxygen, form compounds generally showing basic properties; and which are capable of replacing hydrogen in acids, thus forming salts. Non-metals or metalloids are all elements not having the above- mentioned properties. Their oxides in combination with water generally have acid properties. In all other respects the chemical and physical properties of non-metals differ widely. Their num- ber amounts to 14, the other 53 elements being metals. Natural groups of elements. Besides classifying all elements into metals and non-metals, certain members of both classes exhibit so much resemblance in their properties, that many of them have been arranged into natural groups. The members of such a natural group frequently show some connection between atomic weights and properties. Chlorine, 35.4 Bromine, 80 Iodine, 126.6 Sulphur, 32 Selenium, 78 8 Tellurium, 128 Lithium, 7 Sodium, 23 Potassium, 39 Calcium, 40 Strontium, 87 Barium, 136.8 GENERAL REMARKS REGARDING ELEMENTS. 65 Each three elements mentioned in the above four columns resemble each other in many respects, forming a natural group. The relation between the atomic weights will hardly be sus- pected by looking at the figures, but will be noticed at once by adding together the atomic weights of the first and last ele- ments and dividing this sum by 2, when the atomic weights (very nearly, at least) of the middle members of the series are obtained. Thus: 35 4 + 126.6 ~ 2 — = 81; 32 + 128 = 80; 40 + 136.8 „ — = 88.4. Mendelejeffs periodic law.1 The relationship between atomic ■weights and properties has been used for arranging all elements systematically, in such a manner that the existing relation is clearly pointed out. Of the various schemes proposed, the one arranged by Mendelejetf may be selected as most suitable to show this relation. Looking at MendelejefF’s table on page 67, it will be seen that all the elements are arranged in the order of their atomic weights, and that the latter increase gradually by only a unit or a few units. Moreover, the arrangement is such that eight groups and twelve series are formed. The remarkable features of this classification may thus be stated: Elements which are more or less closely allied in their physical and chemical properties are made to stand together in a group, as may be seen by pointing out a few of the more generally known instances as found in the groups I., II., and VII., the first one containing the alkali metals, the second, the metals of the alkaline earths, the last the halogens. There is, moreover, to be noticed a periodic repetition in the properties of the elements arranged in the horizontal lines from left to right. Leaving out group VIII. for the present, we find that the power of the elements to combine with oxygen atoms increases regularly from the left to the right, whilst the power of the elements to combine with hydrogen atoms increases from the right to left, as may be shown by the following instances: I. II. III. IV. V. VI. VII. Na20 MgO A1202 Si02 P205 S03 C1207 Hydrogen compounds unknown SiH4 PH3 SH2 C1II 1 The consideration of this law should he postponed until the student has become acquainted with the larger number of important elements. 66 PRINCIPLES OF CHEMISTRY. The oxides on the left show strongly basic properties, as illus- trated by sodium oxide ; these basic properties become weaker in the second, and still weaker in the third group; the oxides of the fourth group show either indifferent, or but slightly acid proper- ties, which latter increase gradually in the fifth, sixth, and seventh groups. While some elements show an exception, it may be stated that most of the elements of group I. are univalent, of II. bivalent, of III. trivalent, of IV. quadrivalent, of Ar. quinquivalent, of VI. sexivalent, and of VII. septivalent. Properties other than those above mentioned might be enumer- ated in order to show the regular gradation which exists between the members of the various series, but what has been pointed out will suffice to prove that there exists a regular gradation in the properties of the elements belonging to the same series, and that the same change is repeated in the other series, or that the changes in the 'properties of elements are periodic. It is for this reason that a series of elements is called a period (in reality a small period, in order to distinguish it from a large period, an explanation of which term will be given directly). The 12 series or periods given in the following table show another highly characteristic feature, which consists in the fact that the corresponding members of the even (2, 4, 6, etc.) periods and of the uneven (3, 5, 7, etc.) periods resemble each other more closely than the members of the even periods resemble those of the uneven periods. Thus the metals calcium, strontium, and barium, of the even periods, 4, 6, and 8, resemble each other more closely than they resemble the metals magnesium, zinc, and cadmium, of the uneven periods 3, 5, and 7, the latter metals again resembling each other greatly in many respects. It is for this reason that in the table the elements belonging to one group are not placed exactly underneath each other, but are divided into two lines containing the members of even and uneven periods separately, 'whereby the elements resembling each other most are made to stand together. In arranging the elements by the method indicated, it was found that the elements mentioned in group VIII. could not be placed in any of the 12 small periods, but that they had to be kept separately in a group by themselves, three of these metals always forming an intermediate series following the even periods 4, 6, and 10. GENERAL REMARKS REGARDING ELEMENTS. 67 Series 1 2 Group I. RoO H, 1 Li, 7 Group II. R 0 Group III. r2o3 Group IV. R H4 ROj Group V. RHj r.,o5 Group VI. R Ho r o: Group VII. R H Ro07 Group VIII. R 04? Be, 9 li, 11 C, 12 N, 14 _ 0, 16 F, 19 3 Na, 23 Mg, 24 Al, 27 Si, 28 P, 31 S, 32 Cl, 35 4 K, 39 Ca, 40 Sc, 44 Ti, 48 V, 51 Cr, 52 Mn, 54 Fe, 56. Ni, 58. Co, 59 5 (Cu, 03) Zn, 65 Ga, 69 Ge, 72 As, 75 Se, 79 Br, 80 6 Rb, 85 Sr, 87 Y, 89 Zr, 90 Cb, 94 Mo, 96 - Rn, 101. Rh, 103. I’d, 106 7 Ag, 108 Cd, 112 In, 114 Sn, 118 Sb, 120 Te, 125 I, 127 8 Cs, 133 Ba, 137 La, 139 Ce, 141 Di, 142 - - - - - 9 — — — — Er, 166 — — 10 - — Yb, 173 - Ta, 182 W, 184 - Os, 191. Ir, 193. Pt, 195 11 (Au, 196) Ilg, 200 T* o CM EH Pb, 206 Bi, 208 — — 12 - - - Th, 2ol - U, 240 ” ~ — — 1 The decimals are generally omitted in giving the atomic weights. Periodic System.1 PRINCIPLES OF CHEMISTRY. An uneven and even period, together with an intermediate series, form a large period, the number of elements contained in a complete, large period being, therefore, 7 + 7 + 3 = 17. An apparently objectionable feature is the incompleteness of the table, many places being left blank; but it is this very point which renders the table so highly interesting and valuable. Mendelejeff, in arranging his scheme, claimed that the places left blank belonged to elements not yet discovered, and he pre- dicted not only the existence of these as yet missing elements, but also described their properties. Fortunately his predictions have, in at least three cases, been verified, three of the missing elements having since been discovered, and named scandium, gal- lium, and germanium. These elements not only fitted in the pre- viously blank spaces by virtue of their atomic weights, but their general properties also assigned to them the places which they now occupy. Physical properties of elements. Most elements are, at the ordi- nary temperature, solid substances, two are liquids (bromine and mercury), five are gases (oxygen, hydrogen, nitrogen, chlorine, and fluorine). Most of the solid elements may be converted into liquids and gases by the action of heat. Some solid elements, however, have so far resisted all attempts to change their state of aggregation, as, for instance, carbon. Most, if not all, of the solid elements may be obtained in the crystallized state; a few are amorphous and crystallized, or poly- morphous. The physical properties of many elements in these different states differ widely. For instance: Carbon is known crystallized as diamond and graphite, or amorphous as charcoal. The property of elements to assume such different conditions is called allotropic modification. Some of the gaseous elements also are capable of existing in allotropic modifications. For instance : Oxygen is known as such and as ozone, the latter differing from the common oxygen both in its physical and chemical properties. The explanation given for this surprising fact, that one and the same element has dif- ferent properties in certain modifications, is, that either the mole- cules or the atoms within the molecules are arranged differently. Ozone, for instance, has three atoms of oxygen in the molecule, while the common oxygen molecule contains but two atoms. Most of the elements are tasteless and odorless; a few, how- GENERAL REMARKS REGARDING ELEMENTS. 69 ever, have a distinct odor and taste, as, for instance, iodine and bromine. Relationship between elements and the compounds formed by their union. The properties of the compounds formed by the com- bination of elements are so various that it is next to impossible to give any general rule by which they may be indicated. It may be said, however, that nearly all of the gaseous compounds contain at least one gaseous element, and that solid elements, when combining with each other, generally form solid substances, rarely liquids, and never compounds showing the gaseous state at the ordinary temperature. Nomenclature. The chemical nomenclature of compound sub- stances has undergone considerable changes within the last twenty years. These changes wrnre made in conformity with our present or modern views of the constitution of compounds, but many years may yet pass before a uniform system of nomencla- ture wrill be adopted generally. When two elements combine in one proportion only, little difficulty is experienced in the formation of a name, as, for in- stance, in iodide of potassium or potassium iodide, IvE, chloride of sodium or sodium chloride, ]STaCl. When two elements combine in more than one proportion, the syllables, mono, di, tri, tetra, and penta are frequently used to designate the relative quantity of the elements. For instance: Carbon monoxide, CO, carbon dioxide, C02, phosphorus tri- chloride, PC13, phosphorus prntachloride, PC15. In many cases the syllables ous and ic are used to distinguish the proportions in which two elements combine; the syllable ous being used for the simpler or lower, the syllable ic for the more complex or higher form of combination. For instance : Phos- phorous chloride, PC13, and phosphoric chloride, PC15; ferrous oxide, FeO, ferric oxide, Fe203. The syllables mono and sesqui also are used occasionally to mark this difference, as, for instance, monoxide of iron, FeO, sesqui- oxide of iron, Fe203. When two oxides of the same element ending in ous and ic form acids (by entering in combination with water), the same syllables are used to distinguish these acids. Phosphorous oxide, 70 PRINCIPLES OF CHEMISTRY. P203, forms phosphorous acid; phosphoric oxide, P205, fbrm8 phosphoric acid. The salts formed by these acids are distinguished by using the syllables ite and ate. Phosphite of sodium is derived from phos- phorous acid, phosphate of sodium from phosphoric acid. Sul- phites and sulphates are derived from sulphurous and sulphuric acid, respectively. According to the new nomenclature, the name of the metal precedes that of the acid or acid radical in an acid. For instance, sodic phosphite or sodium phosphite, instead of phosphite of sodium; potassic sulphate or potassium sulphate, instead of sul- phate of potassium. The acids themselves are looked upon as hydrogen salts, and are sometimes named accordingly: hydrogen nitrate for nitric acid, hydrogen chloride for hydrochloric acid, etc. When the number of elements and the number of atoms in- crease in the molecule, the names become in most cases more complicated. The rules applied to the formation of such com- plicated names will be spoken of later. Writing1 chemical equations. It has been shown that chemical changes are expressed in chemical equations by means of symbols. These equations are formed by placing the molecules which are to act upon one another, and which are called factors and are connected by the sign +, to the left of the sign of equality, and by placing the molecule or molecules which result from the de- composition, and are called product or products, to the right of the sign of equality, connecting them also by the + sign if more than one product be formed. Every correct chemical equation is correct mathematically also —i. e., the sum of the atoms as well as that of the molecular weights of the factors equals the sum of the atoms and that of the molecular weights of the products respectively. For instance : Sodium carbonate and calcium chloride form calcium carbonate and sodium chloride. Expressed in chemical equation we say: Na2C03 + CaCl2 = CaC03 + 2NaCl. Sodium carbonate and calcium chloride are the factors, calcium carbonate and sodium chloride the products. Adding together the molecular weights of the factors and those of the products we find equal quantities, as follows : GENERAL REMARKS REGARDING ELEMENTS 71 2 Nu = 46 Ca = 40 C = 12 2C1 = 71 30 = 48 106 + 111 = 217 Ca = 40 2Na = 46 C = 12 2C1 = 71 80 = 48 100 + H7 = 217 Chemical equations not only are used for representing chemical changes, but also are the starting-point in all the chemical calculations in which the quantities of substances entering into chemical actions, or the quantities of the product formed, are concerned. The above calculation teaches, for instance, that 106 parts by weight of sodium carbonate are acted upon by 111 parts by weight of calcium chloride, and that 100 parts by weight of cal- cium carbonate and 117 parts by weight of sodium chloride are formed by this action. These data may, of course, be utilized to find how much calcium chloride may be needed for the decompo- sition of one pound or of any other definite weight of sodium carbonate; or how much of these two substances may be required to produce one hundred pounds, or any other definite weight of calcium carbonate. While in many cases of chemical decomposition the change which is to take place cannot be foretold, but has to be studied experimentally, there are other chemical changes which can be predicted with certainty (see Chapter VIII, page 57). In the latter case especially there is no difficulty in writing out the change in the form of an equation. In doing this it must be borne in mind that equivalent quantities replace one another; that, for instance, two atoms of a univalent element are required to replace one atom of a bivalent element, as, for instance, in the case of the decomposi- tion taking place between potassium iodide and mercuric chlo- ride, when two molecules of the first are required to decompose one molecule of the second compound : K — I , „ /Cl XT /I , K — Cl K-I + HS\C1 = HS\I + K — Cl or 2KI + HgCl2 = Hgl2 + 2KC1. Whenever the exchange of atoms takes place between univa- lent and trivalent elements, three of the first are required for one of the second, as in the case of the action of sodium hydroxide on bismuth chloride: Na — OH /Cl /OH Na — Cl Na — OH + Bi—Cl = Bi—OH + Na — Cl Na — OH \C1 \OH Na — Cl or 3NaOH + Bid, = Bi30H + 3NaCl. 72 PRINCIPLES OF CHEMISTRY. In the following examples of double decomposition an ex- change takes place between the atoms of metallic elements, or between the metallic elements and the hydrogen. The student, in completing the equations, has also to select the correct quantity, i. e., the correct number of molecules of the factors required for the change. The interrogation marks indicate that more than one molecule of the substance is needed for the reaction. NV + H'Cl = H/so4 + K'(?) Ca" + H'Cl (?) = He" + H./SO, = H'Cl + Ag'NOg = Ca"Cl2 +Ag'N0j(?) = Bi'"C)3 + Ag'NOs (?) = Cu//S04 + H./S = Ba"CI2 + Nh,/S04 = Na/C03 -j- H,/S04 = BioNOj + K'OH (?) = A12///3S04 + K'OH (?) = A12///3S04 + Ca20H (?) = Fe2Cl6 + AgN03 (?) = How to study chemistry. In studying chemistry, the student is advised to impress upon his memory five points regarding every important element or compound. These points are : 1. Occurrence in nature. (Whether in free or combined state; whether in the air, water, or solid part of the earth.) 2. Mode of preparation by artificial means. 3. Physical properties. (State of aggregation and influence of heat upon it; color, odor, taste, solubility, etc.) 4. Chemical properties. (Atomic and molecular weight; valence; amount of attraction toward other elements or compounds; acid, alkaline, or neutral reaction ; reactions by which it may be recog- nized and distinguished from other substances.) 5. Application and use made of it in every-day life, in the arts, manufactures, or medicine. Of the most important elements and compounds, the history of their discovery, and, occasionally, some special points of interest, should be noticed also. All students having the facilities for working in a chemical laboratory are strongly advised to make all those experiments and reactions which will be mentioned in connection with the different substances to be considered in this book. By adopting this mode of studying chemistry the student will soon acquire a fair knowledge of chemical facts, yet he might know little of the science of chemistry. In order to acquire this latter knowledge he should study not only facts, but also the GENERAL REMARKS REGARDING ELEMENTS. 73 relationship existing between them and between the laws govern- ing the phenomena connected with these facts. It is by this method only that the science of chemistry may be successfully mastered. Questions.—81. Why are not all the elements of equal importance? 82. State the physical and chemical properties of metals. 83. How are metals dis- tinguished from non-metals? 84. What relation often exists between the atomic weights of elements belonging to the same group? 85. Explain the term allo- tropic modification. 86. Mention some elements capable of existing in allotropic modifications. 87. What relation exists between the properties of elements and the properties of the compounds formed by their union ? 88. In which cases are the syllables mono-, di-, tri-, tetra-, and penta- used in chemical nomencla- ture ? 89. What use is made of the syllables ous and ic, ite and ate, in distin- guishing compounds from each other? 90. What are the principal features of the periodic law? III. NON-METALS AND THEIR COMBINATIONS. Tiie total number of the 11011-metals is fourteen; two of them, selenium and tellurium, are of so little importance that they will be but briefly considered in this book. Symbols, atomic weights, and derivation of names. Boron, B = 11. From borax, the substance from which boron was first obtained. Bromine, Br= 79.8. From the Greek (ipupoq (bromos), stench, in allusion to the intolerable odor. Carbon, C = 12. From the Latin carbo, coal, which is chiefly carbon. Chlorine, Cl = 35.4. From the G-reek (chloros), green, in allusion to its green color. Fluorine, FI = 19. From fluorspar, the mineral fluoride of calcium, used as flux {fluo, to flow). Hydrogen, H = 1. From the Greek vdup (hudor), water, and yevvau (gennao), to generate. Iodine, I = 126.6. From the Greek lov (ion), violet, referring to the color of its vapors. Nitrogen, N = 14. From the Greek virpov (nitron), nitre, and yevvau (gen- nao), to generate. Oxygen, O = 16. From the Greek ogvg (oxus), acid, and yevvau (gennao), to generate. Phosphorus, P = 31. From the Greek traces Nitric acid J An analysis of air may be made b}7 the following method: A graduated glass tube, containing a measured volume of air, is 88 NON-METALS AND THEIR COMBINATIONS. placed with the open end downward into a dish containing mercury. A small piece of phosphorus is then introduced and allowed to remain in contact with the air for several hours, when it gradually combines with the oxygen. The remaining volume of air is chiefly nitrogen, the loss in volume represents oxygen. For the determination of carbon dioxide and water, a measured volume of air is passed through two U-shaped glass tubes. One of these tubes has previously been tilled with pieces of calcium chloride, the other tube with pieces of potassium hydroxide, and both tubes have been weighed separately. In passing the meas- ured air through these tubes the first one will retain all the moisture, the second one all the carbon dioxide; the increase in weight of the tubes at the end of the operation will give the amounts of the two constituents. That oxygen is found in the atmosphere in a free state is explained by the fact that all elements having affinity for oxygen have entered into combination with it, whilst the excess is left uncombined. Nitrogen is found uncombined, because it has so little affinity for other elements. Ammonia, NH3 = 17. This compound is constantly forming in nature by the decomposition of organic (chiefly animal) matter, such as meat, urine, blood, etc. It is also obtained during the process of destructive distillation, which is the heating of non- volatile organic substances in closed vessels to such an extent that decomposition takes place, the generated volatile products being collected in suitable receivers. The manufacture of illu- minating gas is such a process of destructive distillation ; coal is heated in retorts, and the large amount of nitrogen contained in the coal is converted into and liberated as ammonia gas, which is absorbed in water, through which the gas is made to pass. Another method of obtaining ammonia is through decomposi- tion of ammonium salts by the oxides or hydroxides of sodium, potassium, or calcium. Usually ammonium chloride is mixed with calcium hydroxide and heated, when calcium chloride, water, and ammonia are formed : 2(NH4C1) + Ca20H = CaCl2 + 2H20 + 2NHa Experiment 5. Mix about equal weights (10 grams of each) of ammonium chloride and calcium hydroxide (slaked lime) in a flask of about 200 c.c. capa- city, and arranged as in Fig. 8 ; cover the mixture with water and apply heat. As long as any atmospheric air remains in the apparatus, bubbles of it will NITROGEN. 89 pass through the water contained in the cylinder; afterward all gas will be readily and completely absorbed by the water. Notice the odor and alkaline reaction on litmus of the ammonia water thus obtained. When the gas is being freely liberated move the tube upward, as shown in B, and collect the gas by upward displacement in a cylinder or tube, which when filled with gas is held mouth downward into water, which will rapidly rise in the tube by absorption of the gas. Notice that ammonia is not readily combustible, by applying a flame to the gas escaping from the delivery tube. Fig. 8. Apparatus for generating ammonia. Ammonia is a colorless gas, of a very pungent odor, an alka- line taste, and a strong alkaline reaction. In pure oxygen it burns, forming water and free nitrogen. By the mere application of a pressure of seven atmospheres or by intense cold (—40° C., —40° F.), ammonia may be converted into a liquid, which at —80° C. (—112° F.) forms a solid crystal- line mass. Water dissolves about 700 times its volume of am- monia gas, forming ammonium hydroxide : nh3 + h2o = nh4oh. 90 NON-METALS AND THEIR COMBINATIONS. Water of ammonia, Aqua ammonise ('4. Sodium sulphate. Experiment 8. Prepare an apparatus as shown in Fig. 9. Heat in a retort of about 250 c.c. capacity a mixture of about 50 grams of potassium nitrate and nearly the same weight of sulphuric acid. Nitric acid is evolved and distils over into the receiver, which is to be kept cool during the operation by pouring cold water upon it or by surrounding it with pieces of ice. Examine the pro- perties of nitric acid thus made, and use it for the tests mentioned below. How much pure nitric acid can be obtained from 50 grams of potassium nitrate? 92 NON-METALS ANI) THEIR COMBINATIONS. Weigh the acid which you obtained in the experiment and compare this weight with the theoretical quantity. The acid thus obtained is an almost colorless, fuming, corrosive liquid, of a peculiar, somewhat suffocating odor, and a strongly acid reaction. Common nitric acid of a specific gravity 1.42, is composed of 69.4 per cent, of HlSTOg and 30.6 per cent, of water. The diluted nitric acid of the U. S. P. is made by mixing one part of the common acid with six parts of water. Fro. 9. Distillation of nitric acid. Nitric acid is completely volatilized by heat; it stains animal matter distinctly yellow; it is a monobasic acid forming salts called nitrates. These salts are all soluble in water, for which reason nitric acid cannot be precipitated by any reagent. Nitric acid is a strong oxidizing agent; this means it is capable of giving off part of its oxygen to substances having affinity for it. The action of nitric acid upon such metals as copper, silver, and many others involves two changes, viz.: displacement of the hydrogen of the acid by the metal: Cu + 2HN03 = Cu2X03 + 2H ; and the deoxidation of another portion of nitric acid by the liberated hydrogen while yet in the nascent state. Thus: IIN03 + 3II = 2H20 + NO. The liberated nitrogen dioxide, which is colorless, readily absorbs oxygen from the air, forming red vapors of nitrogen tetroxide. CARBON. 93 Tests for nitric acid or nitrates. (Potassium nitrate, KN03, may be used as a nitrate.) 1. Nitric acid when heated with copper tilings, or nitrates when heated with copper tilings and sulphuric acid, evolve red fumes of nitrogen tetroxide. (See explanation above.) On the addition of alcohol to the mixture, the odor of nitrous ether is noticed. 2. The solution of a nitrate, to which a few small pieces of ferrous sulphate have been added, will show a reddish-purple or black coloration upon pouring a few drops of strong sulphuric acid down the side of the test-tube, so that it may form a layer at the bottom of the tube. The black color is due to the formation of an unstable compound of the ferrous salt and nitric oxide. 3. Solution of indigo is decolorized by nitric acid. Solutions of nitrates mixed with dilute sulphuric acid do not bleach indigo in the cold, but do so on heating. 4. Nitrates give a red color with brucine in the presence of concentrated sulphuric acid. 5. Nitrates deflagrate when heated on charcoal by means of the blowpipe. As an antidote in cases of poisoning by nitric acid a solution of sodium carbonate, or a mixture of magnesia and water, may be administered with the view of neutralizing the acid. 13. CARBON. Civ = 12. Occurrence in nature. Carbon is a constituent of all organic matter. In a pure state it is found crystallized as diamond and graphite, amorphous in a more or less pure condition in the various kinds of coal, charcoal, boneblack, lampblack, etc. As Questions.—111. State the physical and chemical properties of nitrogen. 112. Mention the principal constituents of atmospheric air and the quantity in which they are present. 113. By what processes can the four chief constituents of atmospheric air be determined ? 114. Mention some decompositions by which ammonia is generated. 115. Explain the process of making water of ammonia. 116. State the physical and chemical properties of ammonia gas and ammonia water. 117. How is nitrogen monoxide obtained, and what are its properties? 118. Describe the process for making nitric acid, and give symbols for decompo- sition. 119. How does nitric acid act on animal matter, and what are its prop- erties generally? 120. Give tests and antidote for nitric acid. 94 NON-METALS AND THEIR COMBINATIONS. carbon dioxide, carbon is found in the air; as carbonic acid in water; as carbonates (marble, limestone, etc.) in the solid portion of our earth. Properties. The three different allotropic modifications of carbon differ widely from each other in their physical properties. Diamond is the purest form of carbon, in which it is crystal- lized in regular octahedrons, cubes, or in some figure geometri- cally connected with these. Diamond is the hardest substance known; it is infusible, but burns when heated intensely, forming carbon dioxide. Graphite, plumbago, or black-lead, is carbon crystallized in short six-sided prisms; it is a somewhat rare, dark-gray mineral, chiefly used for lead-pencils. Amorphous carbon is a soft, black, solid substance. Neither form of carbon is fusible, volatile, or soluble in any of the common solvents. Carbon is a quadrivalent element; it has little affinity for metals, but combines with many of the non-metals, chiefly with oxygen, hydrogen, and nitrogen, forming organic substances. 1. Most non-volatile (organic) substances containing carbon, blacken when heated on platinum foil. Starch or sugar may be used for this test. 2. The product of combustion of carbon (or of combustible matter containing it), C02, renders lime-water turbid, in conse- quence of the formation of insoluble calcium carbonate, CaC03. Carbon dioxide, C02 = 44. (Formerly named carbonic acid, or anhydrous carbonic acid.) This compound is always formed during the combustion of carbon or of organic matter ; also during the decay (slow combustion), fermentation, and putrefaction (pro- cesses of decomposition) of organic matter ; it is constantly pro- duced in the animal system, exhaled from the lungs, and given off through the skin. Many spring waters contain considerable quantities of the gas, one single spring, in Nauheim, Germany, liberating as much as 3000 pounds of carbon dioxide a day. By heating, many carbonates are decomposed into oxides of the metals and carbon dioxide. Tests for carbon. Lime-burning is such a process of decomposition : CaCO, = CaO + C02 Calcium carbonate. Calcium oxide. CARBON. 95 Another method for the generation of carbon dioxide is the decomposition of any carbonate by an acid: CaC03 + 2HC1 = CaCl2 + H20 + C02 Calcium carbonate. Hydrochloric acid. Calcium chloride. Experiment 9. Use apparatus represented in Fig. 7, page 82. Place about 20 grams of marble, CaC03, in small pieces (sodium carbonate or any other car- bonate may be used) in the flask, cover it with water, and add hydrochloric acid through the funnel-tube. The escaping gas may be collected over water, as in the case of hydrogen, or by downward displacement—i. e., by passing the delivery-tube to the bottom of a tube or other suitable vessel, when the carbon dioxide, on account of its being heavier than atmospheric air, gradually displaces the latter. This will be shown by examining the contents of the vessel with a burning taper, which is extinguished as soon as most of the air has been expelled. Examine the gas for its high specific gravity, by pouring it from one vessel into another; for its power of extinguishing flames, by mixing it with an equal volume of air, which mixture will be found not to support the combustion of a taper notwithstanding that oxygen is contained in it. Add to one portion of the collected gas some lime-water, shake it, and notice that it becomes turbid. Blow air exhaled from the lungs through a glass tube into lime-water, and notice that it also turns turbid. Carbon dioxide is a colorless, odorless gas, having a faintly acid taste. By a pressure of 38 atmospheres, at a temperature of 0° C. (32° F.), carbon dioxide is converted into a colorless liquid, which by intense cold (—79° C., —110° F.) may be con- verted into a white, solid, crystalline, snow-like substance. The specific gravity of carbon dioxide is 1.524; it is consequently about one-half heavier than atmospheric air. Cold water absorbs at the ordinary pressure about its own volume of carbon dioxide, and much larger quantities under an increased pressure (soda water). Carbon dioxide is not combustible, and not a supporter of com- bustion ; on the contrary, it has a decided tendency to extinguish flames, air containing one-tenth of its volume of carbon dioxide being unable to support the combustion of a candle. Whilst not poisonous when taken into the stomach, carbon dioxide acts indirectly as a poison when inhaled, because it cannot support respiration, and prevents, moreover, the proper exchange between the carbon dioxide of the blood and the oxygen of the atmos- pheric air. Common atmospheric air contains about 4 volumes of carbon dioxide in 10,000 of air, or 0.04 per cent. In the process of respiration this air is inhaled, and a portion of the oxygen is 96 NON-METALS AND THEIR COMBINATIONS. absorbed in the lungs by the blood, which conveys it to the different portions of the animal body, and receives in exchange for the oxygen a quantity of carbon dioxide, produced by the union of a former supply of oxygen with the carbon of the different organs to which the blood is supplied. The air issuing from the lungs contains this carbon dioxide, in quantity about 4 volumes in 100 of exhaled air, which is 100 times more than contained in fresh air. Exhaled air is, moreover, contaminated by other substances than carbon dioxide, such as ammonia, hydrocarbons, and most likely traces of other organic bodies, the true nature of which has not been fully recognized, but which seem to be directly poisonous. The bad effects experienced in breathing air which has become contaminated by the exhalations from the lungs, are most likely due to these unknown bodies. As we have as yet no methods of ascertaining the quan- tity of these poisonous substances present in exhaled air, the determination of the amount of exhaled carbon dioxide present must serve as an indicator of the fitness of an air for breathing purposes. As a general rule, it may be stated that it is not advisable to breathe, for any length of time, air containing more than 0.1 per cent, of exhaled carbon dioxide ; in air containing 0.5 per cent, most persons are attacked by headache, still larger quantities produce insensibility, and air containing 8 percent, of carbon dioxide causes death in a few minutes. As exhaled air contains from 3.5 to 4 per cent, of carbon dioxide, it is unfit to be breathed again. The total amount of carbon dioxide evolved by the lungs and skin of a grown person amounts to about 0.7 cubic foot per hour. Hence the necessity for a constant supply of fresh air by ventilation. This becomes the more necessary where an additional quantity of carbon dioxide is supplied by illuminating flames. Mentioned above are many processes by which carbon dioxide is constantly produced in nature, and we might assume that the amount of 0.04 per cent, of carbon dioxide contained in atmos- pheric air would gradually increase. This, however, is not the case, because plants, and more especially all their green parts, are capable of absorbing carbon dioxide from the air, whilst at the same time they liberate oxygen. This process of vegetable respiration (if we may so call it), which takes place under the influence of sunlight, is, conse- quently, the reverse of that of animal respiration. The animal uses oxygen and liberates carbon dioxide; the plant consumes this carbon dioxide and liberates oxygen. Carbon dioxide is an acid oxide, which combines with water, forming carbonic acid: O C02 + H20 - H2C03. 97 CARBON. Carbonic acid, H2C03, is not known in a pure state, but always diluted with much water, as in all the different natural waters. Carbonic acid is a bibasic, extremely weak acid, the salts of which are known as carbonates. Many of these carbonates (calcium carbonate, for instance) are abundantly found in nature. Tests for carbon dioxide, carbonic acid, and carbonates. 1. Pass carbon dioxide through lime-water, which is rendered turbid by the formation of calcium carbonate: (Sodium carbonate, Na2C03, may be used.) Ca20H + C02 = CaC03 + H20. 2. From carbonates, evolve the gas by the addition of some acid, and examine it by the same method. 3. The soluble carbonates of potassium and sodium give pre- cipitates with the solutions of most metallic salts; for instance, with the chlorides of Ba, Ca, Sr, Mg, Fe, Zn, Cu, etc. Carbon monoxide, Carbonic oxide, CO = 28. Carbon monoxide is a colorless, odorless, tasteless, neutral gas, almost insoluble in water; it burns with a pale-blue flame, forming carbon dioxide; it is very poisonous when inhaled, forming with the coloring matter of the blood a compound which prevents the absorption of oxygen. Carbon monoxide is formed when carbon dioxide is passed over red-hot coal. C02 + C = 2C0. The conditions necessary for the formation of carbon monoxide are, consequently, present in any stove or furnace where coal burns with an insufficient supply of air. The carbon dioxide formed in the lower parts of the furnace is decomposed by the coal above. The blue flames frequently playing over a coal fire are burning carbon monoxide. This gas is formed also by the decomposition of oxalic acid (and many other organic substances) by sulphuric acid: h2c2o4 + h2so4 = h2so4.h2o + C02 + CO. Oxalic acid. Sulphuric acid. Carbon monoxide is now manufactured on the large scale by causing the decomposition of steam by coal heated to red heat. The decomposition takes place thus : H20 + 0 = 2H + CO. 98 NON-METALS AND THEIR COMBINATIONS. The gas mixture, thus obtained and known as water-gas, may be used for heating purposes directly, but has to be mixed with hydrocarbons when used as an illuminating agent, for reasons which will be pointed out below when considering the nature of flames. Compounds of carbon and hydrogen. There are no other two elements which are capable of forming so large a number of different combinations as are carbon and hydrogen. Several hundred of these hydrocarbons are known, and their considera- tion belongs to the domain of organic chemistry. Two of these hydrocarbons, however, may be briefly men- tioned, as they are of importance in the consideration of common flames. These compounds are : methane (marsh-gas, fire-damp), CH4; and ethene (olefiant gas), C2H4. Both compounds are colorless, almost odorless gases, and both are products of the destructive distillation of organic substances. Destructive distillation is the heating of non-volatile organic sub- stances in such a manner that the oxygen of the atmospheric air has no access, and to such an extent that the molecules of the organic matter are split up into simpler compounds. Among the gaseous products formed by this operation, more or less of the two hydrocarbons mentioned above is found. Marsh-gas is formed frequently by the decomposition of organic matter in the presence of moisture (leaves, etc., in swamps), and during the formation of coal in the interior of the earth ; the gas often gives rise to explosion in coal mines. During these explo- sions of the methane (mixed with air and other gases), called fire-damp by the miners, carbon is converted into carbon dioxide, which the miners speak of as choke-damp, or after-damp. Flame is gas in the act of combustion. Of combustible gases, have been mentioned: hydrogen, carbon monoxide, marsh-gas, and olefiant gas. These four gases are actually those which are found chiefly in any of the common flames produced by the com- bustion of organic matter, such as paper, wood, oil, wax, or illu- minating gas itself. These gases are generated by destructive distillation, the heat being supplied either by a separate process (manufacture of illuminating gas by heating wood or coal in retorts), or generated during the combustion itself. CARBON. 99 In burning a candle, for instance, fat is constantly decomposed by the heat of the flame itself, the generated gases burn- ing continuously until all fat has been decom- posed, and the products of decomposition have been burned up or converted into carbon dioxide and water. An ordinary flame (Fig. 10) consists of three parts or cones. The inner or central portion is chiefly unburnt gas; the second is formed of partially burnt and burning gas; the outer cone, showing the highest temperature, but scarcely any light, is that part of the flame where complete combustion takes place. The light of a flame is caused by solid particles of carbon heated to a white heat. The separation of carbon in the flame is explained by the fact that hydrogen has a greater affinity for oxygen than has carbon; only a limited amount of oxygen can penetrate into the flame, and the hydrogen of the hydrocarbon will consume this oxygen, the carbon being liberated momen- tarily until it reaches the outer cone, where it finds sufficient oxygen with which to combine. If a sufficient amount of air be previously mixed with the illuminating gas, as is done in the Bunsen burner, no separation of carbon takes place, and, therefore, no light is produced, but a more intense heat is generated. Fig. 10. Structure of flame. Silicon, or Silicium, Si — 28, is found in nature very abun- dantly as silicon dioxide, or silica, Si02 (rock-crystal, quartz, agate, sand), and in the form of silicates, which are silicic acid in which the hydrogen has been replaced by metals. Most of our common rocks, such as granite, porphyry, basalt, feldspar, mica, etc., are such silicates, or a mixture of them. Small quantities of silica are found in spring waters, as well as in vegetable and animal bodies. Silicon resembles carbon both in its physical and chemical properties. Like carbon it is known in the amorphous state, and forms two kinds of crystals, which resemble graphite and diamond. Like carbon, silicon is quadrivalent, forming silicon dioxide, Si02, silicic acid, H2Si03, silicon hydride, SiH4, silicon 100 NON-METALS AND THEIR COMBINATIONS. chloride, SiCl4, which compounds are analogous to the correspond- ing carbon compounds, C02, II2C03, CII4 and CC14. The compounds formed by the union of silicon with hydrogen, chlorine, and fluorine are gases. The latter compound, silicon fluoride, SiF4, is obtained by the action of hydrofluoric acid on silica or silicates, thus : Si02 + 4IIF = SiF4 -f 2H20. This reaction is used in the analysis of silicates, which are decomposed and rendered soluble by the action of hydrofluoric acid. Silicon fluoride is decomposed by water into silicic acid and hydrofluosilicic acid, II2 SiF6, thus : 3SiF4 + 3H20 = H2Si03 + 2H2SiF6. Several varieties of silicic acid are known, of which may be mentioned the normal silicic acid, HiSiOi, and the ordinary silicic acid, U.,iSi03, from the latter of which, by heating, water may be expelled, when silicon dioxide, Si02, is left. Tests for silicic acid and silicates. (Soluble glass or flint may be used.) 1. Silicic acid and most silicates are insoluble in water and acids. By fusing silicates with about 5 parts of a mixture of the carbonates of sodium and potassium, the silicates of these metals (known as soluble glass) are formed. By dissolving this salt in water and acidifying the solution with hydrochloric acid a por- tion of the silica separates as the gelatinous hydrate. Complete separation of the silica is accomplished by evaporating the mix- ture to complete dryness over a water-bath, and redissolving the chlorides of the metals in water acidulated with hydro- chloric acid; silica remains undissolved as a white, amorphous powder. 2. Silica or silicates when added to a bead of microcosmic salt (see index) form on heating before the blowpipe the so-called silica-skeleton. Boron, W" — 11, is found in but few localities, either as boric (boracic) acid or sodium borate (borax). Formerly the total sup- ply of boron was derived from Italy; lately large quantities of borax have been discovered in California. Boric acid, Acidum boricum, H3B03 = 62, is a white, solid sub- stance, which is sparingly soluble in water, and has but weak acid properties. When heated to 100° C. (212° F.) it loses water, and is converted into metaboric acid, HB02, which when heated yet higher is converted into tetraboric acid, H2B407, from which borax, SULPHUR. 101 Na2B407 -f- 10II2O, is derived. At a white heat boric acid loses all water, and is converted into boron trioxide, B203. Boric acid boiled with glycerin forms boroglyceride, which is used as an antiseptic. (Sodium borate, Na2B4O7.10H2O, may be used.) Tests for boric acid and borates. 1. Heat some borax on the loop of a platinum wire. Notice that it swells up during the time that water is expelled, and then melts into a transparent, colorless bead of fused borax. 2. To a concentrated neutral solution of a borate add solution of either calcium, barium, or silver. In either case white pre- cipitates of borates are formed, having the composition CaB407, BaB407, or Ag2B407. 3. Mix in a porcelain dish some borax with a few drops of sul- phuric acid, pour upon the mixture some alcohol and ignite. The flame has a seam or mantle of a green color, which is best seen by repeatedly extinguishing and rekindling the alcohol. A borax bead moistened with sulphuric acid and heated in a flame also colors it green. 4. To a warm saturated solution of a borate add some sulphuric acid. On cooling, shining scales of boric acid separate. 5. A solution of borax, even when acidulated with hydrochloric acid, colors turmeric-paper brown, after this has been dried. 14. SULPHITE. S!i = 32. Occurrence in nature. Sulphur is found in the uncombined state in volcanic districts, the chief supply being derived from Questions.—121. How is carbon found in nature ? 122. State the physical and chemical properties of carbon in its three allotropic modifications. 123. Mention three different processes by which carbon dioxide is generated in nature, and some processes by which it is generated by artificial means. 124. State the physical and chemical properties of carbon dioxide. 125. Explain the process of respiration from a chemical point of view. 126. What is the percentage of carbon dioxide in atmospheric air, and why does its amount not increase? 127. State the composition of carbonic acid and of a carbonate. How can they be recognized by analytical methods? 128. Under what circumstances will carbon monoxide form, and how does it act when inhaled ? 129. What is de- structive distillation, and what gases are generally formed during that process? 130. Explain the structure and luminosity of flames. 102 NON-METALS AND THEIR COMBINATIONS. Sicily. In combination sulphur is widely diffused in the form of sulphates (gypsum, CaSo4.2H20), and frequently as sulphides (iron pyrites, FeS2, galena, PbS, cinnabar, IlgS, etc.). Sulphur enters also into organic compounds, during the decomposition of which sulphur is evolved as sulphuretted hydrogen, which gas is also a constituent of some waters. Properties. Sulphur is a yellow, brittle, solid substance, having neither taste nor odor. It is insoluble in water and alcohol, soluble in carbon disulphide, oil of turpentine, and fat oils. Sulphur is polymorphous; it crystallizes, from a solution in bi- sulphide of carbon, in octahedrons with a rhombic base; when, however, liquified by heat it crystallizes in six-sided prisms, and is obtained as a brown, amorphous substance by pouring melted sulphur into cold water. Sulphur melts at 1110 C. (232° F.) to an amber-colored liquid, which is fluid as water; increasing the heat gradually, it becomes brown and thick, and at about 200° C. (392° F.) it is so tena- cious that it scarcely flows; when heated still further the sulphur again becomes thin and liquid, and, finally, boils at a temperature of about 440° C. (824° F.). In its chemical properties sulphur resembles oxygen, being like this element bivalent, and supporting, when in the form of vapor, the combustion of many substances, especially of metals. Many compounds of oxygen and sulphur show an analogous composition, as, for instance, II20 and II2S, C02 and CS2, CuO and CuS. Crude sulphur is that obtained from the localities where it is found. It contains generally from 2 to 4 per cent, of earthy im- purities. Melted sulphur poured into round moulds is known as roll-sulphur or brimstone. Sublimed sulphur, Sulphur sublimatum (Flowers of sulphur). Ob- tained by heating sulphur to the boiling-point in suitable vessels, and passing the vapor into large chambers, where it deposits in the form of a powder, composed of small crystals. Washed sulphur, Sulphur lotum, is sublimed sulphur washed with a very dilute ammonia water, and then with pure water; the ob- ject of this treatment being to free the sulphur from all adhering sulphurous and sulphuric acid. SULPHUR. 103 Precipitated sulphur, Sulphur prsecipitatum (Milk of sulphur). Made by boiling calcium hydroxide with sulphur and water, fil- tering the solution, adding to it dilute hydrochloric acid until nearly neutral, washing and drying the precipitated sulphur. By the action of sulphur on calcium hydroxide are formed calcium polysulphide, calcium hyposulphite, and water : 3(Ca20H) + 12S = 2CaS5 + CaS203 + 3H20. Sulphur. Calcium Polysulphide. Calcium Hyposulphite. Water. Calcium hydroxide. On adding hydrochloric acid to the solution, both substances are decomposed and sulphur is liberated : 2CaS3 + CaS203 + 6HC1 = 3CaCl2 + 3H20 + 12 S. Precipitated sulphur differs from sublimed sulphur by being in a more finely divided state, and by having a much paler yellow, almost white color. Sulphur dioxide, SO., = 64 (Sulphurous anhydride, improperly also called sulphurous acid). Two combinations of sulphur and oxygen are known; they are sulphur dioxide, S02, and sulphur trioxide, S03. Sulphur dioxide is formed always when sulphur or substances containing it in a combustible form (H2S, CS2, etc.) burn in air. It is formed also by the action of strong sulphuric acid on many metals (Cu, Hg, Ag, etc.), or on charcoal: 2H2S04 + Cu = CuS04 + 2H,0 + S02. Sulphuric acid. Copper. Cupric sulphate. Water. Sulphur dioxide. 2H2S04 + C = C02 + 2H20 + 2S0 Sulphur dioxide is a colorless gas, having a suffocating, dis- agreeable odor; it liquifies at a temperature of—10° C. (14° F.), and solidifies at —60° C. (—76° F.); it is very soluble in water, forming sulphurous acid; it is a strong, deoxidizing, bleaching, and disinfecting agent; when inhaled in a pure state it is poison- ous, when diluted with air it produces coughing and irritation of the air-passages. Sulphurous acid, Acidum sulphurosum, H2S03 = 82. One volume of cold water absorbs about 48 volumes of sulphur dioxide, or 100 parts by weight of water absorb 3.5 parts by weight of sulphur dioxide. To make the officinal acid, the gas is to be generated by heating charcoal and sulphuric acid in a flask, and passing the 104 NON-METALS AND THEIR COMBINATIONS. gas through a wash-bottle containing water, into distilled water for absorption. Experiment 10. Use an apparatus as shown in Fig. 11. Place in the flask about 20 grams of charcoal in small pieces, cover it with sulphuric acid, apply heat, and pass the generated gas first through a small quantity of water con- tained in the wash-bottle, and then into pure water, contained in the cylinder. The solution, sulphurous acid, may be used for the tests mentioned below; when the neutral solution of a sulphite is required, make this by adding solution of sodium carbonate to a portion of the sulphurous acid until litmus-paper shows neutral reaction. Examine also the contents of the wash-bottle by means of the tests given below for sulphuric acid ; most likely some of the latter will be found. How much carbon and how much sulphuric acid are required to make 100 grams of a 3.5 per cent, sulphurous acid ? Thus obtained, sulphurous acid is a colorless acid liquid, which has the odor as well as the disinfecting and bleaching properties Fio. 11. Apparatus for making sulphurous acid. of sulphur dioxide ; it is completely volatilized by heat. Sulphur- ous acid is a bibasic acid, the salts of which are termed sulphites. Tests for sulphurous acid and sulphites. (Sodium sulphite, Na2S03, may be used.) 1. Sulphurous acid, or the gas liberated from sulphites by the addition of sulphuric acid, decolorizes an acidified solution of SULPHUR. 105 potassium permanganate, in consequence of the deoxidation of the latter. 2. Similarly to the above, an acid solution of potassium bichro- mate is turned green by conversion of chromic acid into chromic oxide. 3. When sulphurous acid or sulphites are added to diluted sulphuric acid and zinc (which evolve hydrogen), sulphuretted hydrogen gas is liberated: H2S03 + 6H = H2S + 8H20 4. Barium chloride added to a neutral solution of a sulphite produces a white precipitate of barium sulphite, soluble in diluted hydrochloric acid; barium sulphate is insoluble in hydrochloric acid: Na2S03 + BaCl2 = BaSo3 + 2NaCl. Sodium Sulphite. Barium chloride. Barium sulphite. Sodium chloride. 5. Silver nitrate produces a white precipitate of silver sulphite, which darkens when heated, metallic silver and sulphuric acid being formed : Ag2S03 + H20 = 2Ag + H2S04 Sulphur trioxide, S03 = 80 {Anhydrous sulphuric acid). This is a white, silk-like solid subtance, having a powerful affinity for water; it may be obtained by the action of phosphoric oxide on strong sulphuric acid ; it is of scientific interest only. Sulphuric acid, Acidum sulphuricum, H2S04 = 98 {Oil of vitriol, Hydrogen sidphate). There is no other acid, and perhaps no other substance, manufactured by chemical action which is so largely used in chemical operations, and in the manufacture of so many of the most important articles, as is sulphuric acid. Sulphuric acid was accidentally discovered in the fifteenth century by Basile Valentine, a very laborious monk, who ob- tained it by heating ferrous sulphate (green vitriol) in a retort. To the liquid distilling over he gave the name of oil of vitriol, in allusion to the thick or oily appearance, and the green vitriol from which it was obtained. The article of commerce called Nordhausen oil of vitriol, or fuming sulphuric acid, is yet made by this process of heating ferrous sulphate. The acid thus obtained is sulphuric acid containing some sulphur trioxide (II2S04.S03). Sulphuric acid is found in nature in combination with metals as sulphates. Thus calcium sulphate (gypsum), barium sulphate 106 NON-METALS AND THEIR COMBINATIONS. (heavy-spar), magnesium sulphate (Epsom salt), and others occur in nature. Manufacture of sulphuric acid. Sulphuric acid is manufactured on a very large scale by passing into large leaden chambers simultaneously, the vapors of sulphur dioxide (obtained by burning sulphur or pyrites in furnaces), nitric acid, and steam, a supply of atmospheric air also being provided for. The oxygen of the nitric acid oxidizes the sulphur dioxide, which, at the same time, takes up water : so2 + 0 + h2o = h2so4. Only a portion of the oxygen necessary for oxidation is derived from the nitric acid directly ; the larger quantity is obtained from the atmospheric air, the nitrogen dioxide serving as an agent for the transfer of the atmospheric oxygen. By the action of nitric acid on sulphurous acid are formed sulphuric acid, water, and nitrogen dioxide : 3H2SO;! + 2HN03 = 3H2S04 + H20 + 2N0 Nitrogen dioxide is capable of readily absorbing oxygen from atmospheric air, forming nitrogen tetroxide: NO + O = N02. The nitrogen tetroxide again transfers one atom of its oxygen to the sulphurous acid, and so on indefinitely, as long as sulphur- ous acid and oxygen are present: The liquid sulphuric acid thus formed in the lead-chamber collects at the bottom of the chamber, whence it is drawn oft. In this state it is known as chamber acid (specific gravity 1.48), and is not pure, but contains an excess of water, and frequently either sulphurous or nitric acid. By evaporation in shallow leaden pans it is further concentrated, until it shows a specific gravity of 1.72. When this point is reached the acid acts upon the lead, wherefore the further concentration is conducted in vessels of glass or platinum, until a specific gravity of 1.84 is obtained. This acid contains about 96 per cent, of sulphuric acid; the remaining 4 per cent, of water cannot be expelled by heat. H2S03 + N02 = H2S04 + NO. Properties of sulphuric acid. Pure acid has a specific gravity of 1.848; it is a colorless liquid, of oily consistence, boiling at SULPHUR. 107 388° C. (640° F.). It has a great tendency to combine with water, absorbing it readily from atmospheric air. Upon mixing sulphuric acid and water, heat is generated in consequence of the combination taking place between the two substances. To the same tendency of sulphuric acid to combine with water must be ascribed its property of destroying and blackening organic matter. Organic substances generally contain the elements carbon, hydro- gen and oxygen. Sulphuric acid added to such organic sub- stances removes the elements hydrogen and oxygen (or at least a portion of them), combines them into water, with which it unites, leaving behind compounds so rich in carbon that the black color predominates. It is due to this decomposing action of sulphuric acid upon organic matter that traces of the latter color sulphuric acid dark yellow, brown, and, when present in larger quantities, almost black. The poisonous caustic properties are due to the same action. Sulphuric acid is a very strong bibasic acid, which expels or displaces most other acids; its salts are known as sulphates. The sulphuric acid of the U. S. P. should contain not less than 96 per cent, of H2S04, corresponding to a specific gravity of not less than 1.84. The diluted sulphuric acid, Acidum sulphuricum dilutum, is a mix- ture of 1 part of acid and 9 parts of water. Tests for sulphuric acid and sulphates. (Sodium sulphate, Na2S04, may be used.) 1. Barium chloride produces a white precipitate of barium sulphate, insoluble in all acids : Na2S04 + BaC)2 = BaS04 + 2NaCl. 2. Soluble lead salts (lead acetate) produce a white precipitate of lead sulphate, soluble in hot concentrated acids and in ammo- nium acetate. 3. Sulphates, sulphur, or any compound containing it, fused on charcoal with sodium carbonate and potassium cyanide by means of a blowpipe, form hepar (chiefly sulphide of an alkali metal), which, when placed upon a silver coin and moistened with dilute hydrochloric acid, causes a black stain, due to the formation of silver sulphide. This test is of value in the case of insoluble sulphates, such as barium sulphate and others. 108 NON-METALS AND THEIR COMBINATIONS Antidotes. Magnesia, sodium carbonate, chalk, and soap, to neutralize the acid. Stomach-pump must not be used. Sulpho-acids. Whilst but two oxides of sulphur exist in the separate state, there are a large number of sulpho-acids known. They are: Hydrosulphuric acid, H2S. Hyposulphurous acid, H2S02. Sulphurous acid, H2S03. Sulphuric acid, H2S04- Fuming sulphuric acid, H2S207. Thiosulphuric acid, H2S203. Dithionic acid, H2S206. Trithionic acid, H2S306. Tetrathionic acid, H2S406. Pentathionic acid, H2S506. Thiosulphurie acid, formerly Hyposulphurous acid, H2S203, is of interest because some of its salts are used, as, for instance, sodium thiosulphate, Ha.aS203, the sodium hyposulphite of the U. S. P. The acid itself is not known in the separate state, since it decom- poses into sulphur and sulphurous acid when attempts are made to liberate it from its salts. Tests for thiosulphates. (A solution of sodium thiosulphate, Na2S203, may be used.) 1. Thiosulphates liberate with sulphuric or hydrochloric acid sulphur dioxide, while sulphur is set free : Na2S203 + H2S04 - Na2S04 + H,0 + S02 + S. 2. Silver nitrate and barium chloride produce white precipi- tates of silver thiosulphate and barium thiosulphate. The silver salt becomes dark on heating; the barium salt is soluble in much water and is decomposed by hydrochloric acid. Hydrosulphuric acid, H2S = 34 (Sulphuretted hydrogen, Hydrogen sulphide). This compound has been mentioned as being liberated by the decomposition of organic matter (putrefaction) and as a constituent of some spring waters. It is formed also during the destructive distillation of organic matter containing sulphur. The best mode of obtaining it is the decomposition of metallic sulphides by diluted sulphuric or hydrochloric acid. Ferrous sulphide is usually selected for decomposition : FeS + H2S04 = FeS04 + H2S. SULPHUR. 109 Experiment 11. Use apparatus shown in Pig. 11, page 104. Place about 20 grarus of ferrous sulphide in the flask, cover the pieces with water, and add sulphuric or hydrochloric acid. Pass a portion of the washed gas into water, another portion into ammonia water. Use the solutions for the tests mentioned below. Ignite the gas at the delivery tube and notice that sulphur is deposited upon the surface of a cold plate held in the flame. Place the apparatus in the fume chamber during the operation. How much ferrous sulphide is required to liberate a quantity of hydrosulphuric acid sufficient to convert 1000 grams of 10 per cent, ammonia water into ammonium sulphide solution? The reaction taking place is this : 2NH3 + H2S = (NH4\S. Hydrosulphuric acid is a colorless gas, having an exceedingly offensive odor and a disgusting taste. Water absorbs about three volumes of the gas, and this solution is feebly acid. It is highly combustible in air, burning with a blue flame, and forming sulphur dioxide and water. It is directly poisonous when inhaled, the sulphur entering into combination with the iron of the blood. Plenty of fresh air, or air containing a very little chlorine, should be used as an antidote. Hydrosulphuric acid gas and its solution in water are fre- quently used as reagents in analytical chemistry for precipitating and recognizing metals. This use depends on the property of the sulphur to combine with many metals to form insoluble com- pounds, the color of which frequently is very characteristic: CuS04 + H2S = CuS + h2so4. The salts of hydrosulphuric acid are known as sulphides. Tests for hydrosulphuric acid or sulphides. 1. Hydrosulphuric acid or soluble sulphides (ammonium sul- phide may be used), when added to soluble salts of lead, copper, mercury, etc., give black precipitates of the sulphides of those metals. 2. From insoluble sulphides (ferrous sulphide, FeS, may be used) liberate the gas by sulphuric or hydrochloric acid, and test as above, or suspend a piece of filter-paper, moistened with solu- tion of lead acetate, in the liberated gas, when the paper turns dark. Some sulphides, FeS2, for instance, are not decomposed by the acids mentioned, unless zinc be added. Bisulphide of carbon, Carbonii bisulphidum, CS2 = 76. This compound is obtained by passing vapors of sulphur over heated 110 NON-METALS AND THEIR COMBINATIONS. charcoal. It is a colorless, highly refractive, very volatile, and inflammable neutral liquid, having a characteristic odor, and a sharp, aromatic taste. It boils at 46° C. (115° F.); it is insoluble in water, soluble in alcohol, ether, chloroform, fixed and volatile oils; for the latter two it is an excellent solvent, but dissolves, also, many other substances, such as sulphur, phosphorus, iodine, many alkaloids, etc. Selenium, Se, and Tellurium, Te, are but rarely met with. Both elements show much resemblance to sulphur; both are polymorphous; both combine with hydrogen, forming H2Se and H2Te, gaseous compounds having an odor more disagreeable even than that of H2S. Like sulphur, they form dioxides, Se02 and Te02, which combine with water, forming the acids H2Se03 and H2Te03, analogous to 1I2S03. The acids H2Se04 and H2Te04, corresponding to H,S04, also are known. 15. PHOSPHORUS. P‘« = 31. Occurrence in nature. Phosphorus is found in nature chiefly in the form of phosphates of calcium (apatite, phosphorite), iron, and aluminium, which occur diffused, though generally in small quantities, through all soils upon which plants will grow, phos- phorus being an essential constituent of the food of most plants. Through the plants it enters the animal system, where it is found either in organic compounds, or—and this in by far the greater quantity—as tricalcium phosphate principally in the bones, which contain about 60 per cent, of it. From the animal system it is eliminated chiefly in the urine. Questions.—131. How is sulphur found in nature? 132. Mention of sul- phur: atomic weight, valence, color, odor, taste, solubility, behavior when heated, and allotropic modifications. 133. State the processes for obtaining sublimed, washed, and precipitated sulphur. 134. State composition and mode of preparing sulphur dioxide and sulphurous acid ; what are they used for, and what are their properties? 135. Explain the process for the manufacture of sulphuric acid on a large scale. 136. Mention of sulphuric acid: color, specific gravity, its action on water and organic substances. 137. Give tests for sul- phates and sulphites, sulphuric and sulphurous acids. 138. What is the differ- ence between sulphates, sulphites, and sulphides? 139. How is hydrosulphuric acid formed in nature, and by what process is it obtained artificially? What are its properties, and what is it used for? 140. Mention antidotes in case of poisoning by sulphuric and hydrosulphuric acids. PHOSPHORUS. Manufacture of phosphorus. Phosphorus was discovered and made first in 1669 by Brandt, of Hamburg, Germany, a bank- rupt merchant, who obtained it in small quantities by distilling urine previously evaporated and mixed with sand. The manufacture of phosphorus to-day depends on the con- version of common tricalcium phosphate into acid phosphate of calcium by the action of sulphuric acid: Ch32P04 + 2H2S04 = CaH42P04 + 2ChS04 Tricalcium phosphate. Sulphuric acid. Calcium acid phosphate. Calcium sulphate. The soluble acid phosphate of calcium is separated from the insoluble calcium sulphate, mixed with charcoal and sand, and evaporated to dryness; the mixture is then introduced into iron retorts and heated, when decomposition takes place. By heating the acid phosphate of calcium, water is expelled, and calcium metaphosphate is formed : CaH42P04 = Ca2P03 + 2H20. The action of charcoal and sand upon the calcium metaphos- phate at red heat, causes the formation of calcium silicate and a deoxidation of the liberated phosphoric acid by the carbon : 2(Ca2P03) + 2Si02 + IOC = 2CaSiOs + lO(CO) + 4P. The phosphorus is liberated in the form of vapor, which is con- densed by passing through water, carbonic oxide escaping at the same time. Properties of phosphorus. When recently prepared, phosphorus is a colorless, translucent, solid substance, which has somewhat the appearance and consistency of bleached wax. In the course of time, and especially on exposure to light, it becomes by degrees less translucent, opaque, white, yellow, and iinally yellowish-red. At the freezing-point phosphorus is brittle; as the temperature increases it gradually becomes softer, until it fuses at 44° C. (111° F.), forming a yellowish fluid, which at 290° C. (554° F.) (in the absence of oxygen) is converted into a colorless vapor. The most characteristic features of phosphorus are its great affinity for oxygen, and its luminosity, visible in the dark, from which latter property its name, signifying bearer of light, has been derived. In consequence of its affinity for oxygen, phos- phorus has to be kept under water, as it invariably takes fire 112 NON-METALS AND THEIR COMBINATIONS. when exposed to the air, the slow oxidation taking place upon the surface of the phosphorus soon raising it to 50° C. (122° F.) at which temperature it ignites, burning with a bright white flame, and giving off dense, white fumes of phosphoric oxide. The luminosity of phosphorus, due to this slow oxidation, is seen when a piece of it is exposed to the air, and whitish vapors are emitted which are luminous in the dark; at the same time an odor, resembling that of garlic, is noticed. Phosphorus is insoluble in water, sparingly soluble in alcohol, ether, fatty and essential oils, very soluble in bisulphide of carbon, from which solution it separates in the form of crystals. Phosphorus not only combines directly with oxygen, but also with chlorine, bromine, iodine, sulphur, and with many metals, the latter compounds being known as phosphides. Phosphorus is trivalent in some compounds, as in PC13, P203; quinquivalent in others, as in PC15, P205. The molecules of most elements contain two atoms; phos- phorus is an exception to this rule, its molecule containing four atoms. The molecular weight of phosphorus is consequently 4 X 31 = 124. Allotropic modifications. Several allotropic modifications of phosphorus are known, of which the red phosphorus (frequently called amorphous phosphorus) is the most important. This variety is obtained by exposing common phosphorus for about two days to a temperature of 260° C. (500° F.), in an atmosphere of carbon dioxide. Phosphorus is thereby gradually converted into a red powder, which differs widely from common phosphorus. It is not poisonous, not luminous, not soluble in the solvents above mentioned, not combustible until it has been heated to about 280° C. (536° F.), when it is reconverted into common phosphorus, which latter inflames at 50° C. (122° F.). Use of phosphorus. By far the largest quantity of all phos- phorus (both common and red) is used for matches, which are made by dipping wooden splints into some combustible sub- stance, as melted sulphur or paraffin, and then into a paste, made by thoroughly mixing phosphorus with glue in which some oxidizing agent (potassium nitrate or chlorate) has been dissolved. Pharmaceutical preparations. containing phosphorus in the PHOSPHORUS. 113 elementary state are phosphorated oil (oleum phosphoratum), and pills of phosphorus (pilulse phosphori). Phosphorus is used also for making phosphoric acid and other compounds. Poisonous properties of phosphorus; antidotes. Common phos- phorus is extremely poisonous, two kinds of phosphorus-poison- ing being distinguished. They are the acute form, consequent upon the ingestion of a poisonous dose, and the chronic form affecting the workmen employed in the manufacture of phos- phorus or of lucifer matches. There is no antidote (which acts chemically) to phosphorus. Oil of turpentine has been used successfully, though its action has not been sufficiently explained. Efforts should be made to eliminate the poison as rapidly as possible by means of a stomach- pump, emetics, or cathartics. Oil or fatty matter (milk) must not be given, as they act as solvents of the phosphorus, causing its more ready assimilation. Detection of phosphorus in cases of poisoning. Use is made of its luminous properties in detecting phosphorus, when in the ele- mentary state. Organic matter (contents of stomach, food, etc.) containing phosphorus will often show this luminosity when agitated in the dark. If this process fails, in consequence of too small a quantity of the poison, a portion of the matter to be examined is rendered fluid by the addition of water, slightly acidulated with sulphuric acid, and placed in a flask, which is connected with a bent-glass tube leading to a Liebig’s condenser. The apparatus (Fig. 12) is placed in the dark, and the flask is heated. If phosphorus be present, a luminous ring will be seen where the glass tube, leading from the flask, enters the condenser. The heat should be raised gradually to the boiling-point, the liquid kept boiling for some time, and the products of distillation collected in a glass vessel. Phosphorus volatilizes with the steam, and small globules of it may be found in the collected fluid. If, however, the quantity of phosphorus in the examined matter was very small, it may all have become oxidized during the distilla- tion, and the fluid will then contain phosphorous acid, the tests for which will be stated below. It should be mentioned that the luminosity of phosphorous 114 NON-METALS AND THEIR COMBINATIONS. vapors is diminished, or even prevented, by vapors of essential oils (oil ot turpentine, for instance), ether, oletiant gas, and a few other substances. Apparatus for detection of phosphorus in cases of poisoning. Oxides of phosphorus. Two oxides of phosphorus are known in the separate state. They are phosphorus trioxide or phosphorous oxide, P203, and phosphorus pentoxide or phosphoric oxide, P205. The first is obtained by slow oxidation of phosphorus, the second by burning phosphorus in dry air or oxygen. Both oxides are white solids, wdiich combine readily with water, forming the corre- sponding acids. Phosphorous acid, H3P03 = 82. This acid is obtained by dis- solving phosphorous oxide in water: P203 + 3H20 = 2H3P03. It is a colorless, acid liquid, which forms salts known as phos- phites; it is a strong deoxidizing agent, easily absorbing oxygen, forming phosphoric acid. PHOSPHORUS. 115 Tests for phosphorous acid. 1. Added to mercuric chloride, a white precipitate of mercur- ous chloride is formed. 2. Added to silver nitrate, a black precipitate of metallic silver is produced. 3. After being heated with nitric acid, it shows reactions of phosphoric acid. Phosphoric acids. Phosphoric oxide is capable of combining chemically with one, two, or three molecules of water, forming thereby three different acids: P205 -)- H20 = H2P206 = 2HP()g Metaphosphoric acid. P205 -f- 2H20 = H4P207 Pyrophosphoric acid. P205 -j- 3H2() = II6P208 = 2H3P04 Orthophosphoric acid. These three acids showT different reactions, act differently upon the animal system, and form different salts. Metaphosphoric acid, HP03= 80 (Glacial phosphoric acid). This acid is always formed when phosphoric oxide is dissolved in water; gradually, and more rapidly on heating with water, it absorbs the latter, forming orthophosphoric acid ; by evaporating the latter sufficiently, metaphosphoric acid is re-formed. Metaphosphoric acid is a monobasic acid which coagulates albumin (pyro- and ortho-phosphoric acids do not) and gives a white precipitate with ammonio-silver nitrate; it is not precipi- tated by magnesium sulphate in the presence of ammonia and ammonium chloride. It acts as a poison, whilst common phos- phoric acid is comparatively harmless. Pyrophosphoric acid, H4P207 = 178. This is a tetra-basic acid which gives a white precipitate with ammonio-silver nitrate, whilst orthophosphoric acid gives a yellowish precipitate; it is not precipitated by ammonium molybdate, and does not coagulate albumin. Phosphoric acid, Orthophosphoric acid, Acidum phosphoricum, H3P04 = 98 (Trihydric phosphate, Common or tribasic phosphoric acid). Nearly all phosphates found in nature are orthophos- phates. Phosphoric acid may be made by burning phosphorus, dis- 116 NON-METALS AND THEIR COMBINATIONS. solving the phosphoric oxide in water, and boiling for a sufficient length of time to convert the meta- into ortho-phosphoric acid. Experiment 12. Place a piece of phosphorus (about 0.5 gram), after having dried it quickly between filter paper, in a small porcelain dish, standing upon a glass plate ; ignite the phosphorus by touching it with a heated wire, and place over the dish an inverted large beaker. The white vapors of phosphoric oxide soon condense into flakes, which fall on the glass plate. Collect the white mass with a glass rod, and dissolve in a few c.c. of water. Use a portion of the solu- tion for tests of metaphosphoric acid ; evaporate the remaining quantity in a porcelain dish until it becomes syrupy, dilute with water and use it for making tests for orthophosphoric acid, either as such or after having neutralized with sodium carbonate. How much phosphorus is needed to make 490 grams of the U. S. P- 50 per cent, phosphoric acid ? For medicinal purposes, phosphoric acid is made by gently heating pieces of phosphorus with diluted nitric acid, when the phosphorus is oxidized, red fumes of nitrogen tetroxide escaping. The liquid is evaporated until the excess of nitric acid has been expelled, and enough of water added to obtain an acid which contains 50 per cent, of the pure acid, H3P04. Phosphoric acid is a colorless, odorless liquid, which, on heat- ing, loses water, and finally is volatilized at a low red heat. It is a tribasic acid, forming three series of salts, namely: ]STa3P04 = Trisodium phosphate. Na2HP04 = Disodium hydrogen phosphate. NaH2P04 — Dihydric sodium phosphate. If the metal be bivalent, the formulas are thus: Ca32P04 = Tricalcium phosphate. Ca2H22P04 = Dicalcium orthophosphate. CaH42P04 = Monocalcium orthophosphate. Tests for phosphoric acids and phosphates. (Sodium phosphate, Na2HP04, may be used.) 1. Add to phosphoric acid, or to an aqueous solution of a phos- phate, a mixture of magnesium sulphate, ammonium chloride, and ammonia water; a crystalline precipitate falls, which is dimagnesium ammonium phosphate: H3P04 + MgS04 + SNITCH = MgNH4P04 + (NH4)2S04 + 3H20 ; Na2HP04 + MgS04 + NH4OH = MgNH4P04 + Na2S04 + H20. 2. Add to a neutral solution of a phosphate, silver nitrate; a yellow precipitate of silver phosphate is produced, which is soluble both in ammonia and nitric acid: Na3P04 + 3AgN03 = Ag3P04 4- 3NaNOs. PHOSPHORUS. 117 3. Add to phosphoric acid, or to a phosphate dissolved in water or in nitric acid, an excess of a solution of ammonium molybdate in dilute nitric acid, and apply heat; a yellow precipitate of phos- phomolybdate of ammonium, (NH4)3PO4.10MoO3.2H2O, is pro- duced ; the precipitate is readily soluble in ammonia water. This test is by far the most delicate, and even traces of phosphoric acid may be recognized by it; moreover, it can be used in an acid solution, while the first two tests cannot. 4. Add to a neutral solution of a phosphate, calcium or barium chloride: a white precipitate of calcium or barium phosphate is produced, which is soluble in acids. 5. Ferric chloride produces in neutral solution a yellowish- white precipitate of ferric phosphate, Fe22P04, thus: 2Na2HP04 + Fe2C]6 = Fe22P04 + 4NaCl + 2HC1. The liberated hydrochloric acid dissolves some of the precipi- tate, which may be avoided by adding previously some sodium acetate ; the hydrochloric acid combines with the sodium of the acetate, and the acetic acid which is set free has no dissolving action upon the ferric phosphate. Hypophosphorous acid, H3P02, or HPH202. This acid is of little interest in the free state, but many of its salts, named hypophos- phites, are frequently used in medicine. The acid may be ob- tained by adding sulphuric acid to barium hypophosphite, or oxalic acid to solution of calcium hypophosphite, when barium sulphate or calcium oxalate is precipitated, the acid being left in solution. Although containing three atoms of hydrogen, hypophosphor- ous acid is a monobasic acid, only one of the hydrogen atoms being replaceable by metals. (Sodium hypophosphite, NaH2P02, may be used.) Tests for hypophosphites. 1. Heated over a flame they burn with a phosphorescent light, in consequence of their decomposition into inflammable hydrogen phosphide and a phosphate. 2. From solutions of mercuric chloride and silver nitrate they precipitate the metals in consequence of the deoxidizing action of hypophosphorous acid. 118 NON-METALS ANI) THEIR COMBINATIONS. 3. With zinc and diluted sulphuric acid they evolve hydrogen and phosphoretted hydrogen. 4. An acid solution of potassium permanganate is readily decolorized. 5. Ammonium molybdate solution produces a blue precipitate; a green color would indicate the presence of a phosphate also, which alone gives a yellow precipitate with the reagent. Phosphoretted hydrogen. When phosphorus is heated with solu- tion of potassium or calcium hydroxide, a number of products, chiefly hypophosphites, and phosphoretted hydrogen are formed. The latter compound has the composition PH3, and is a colorless, badly smelling, poisonous gas, which, when generated as directed above, is spontaneously inflammable. This last-named propert}’ is due to the presence of small quantities of another compound of phosphorus and hydrogen which has the composition P2II4, and is spontaneously inflammable, while the compound PH3 is not. 16. CHLORINE. Cl1 = 35 4. Haloids or Halogens. The four elements, fluorine, chlorine, bromine, and iodine, which form a natural group of elements, are known as haloids or halogens. The relation shown by the atomic weights of these four elements has been mentioned in connection with the consideration of natural groups of elements generally (see page 64). In man}’- other respects a resemblance or relation can be discovered. For instance : All haloids are uni- valent elements, they combine with hydrogen, forming the acids Questions.—141. In what forms of combination is phosphorus found in nature? 142. Give an outline of the process for manufacturing phosphorus. 143. What are the symbol, valence, atomic and molecular weights of phos- phorus? 144. State the chemical and physical properties both of common and red phosphorus. 145. By what methods may phosphorus be detected in cases of poisoning? 146. What two oxides of phosphorus are known ; what is then- composition, and what four acids do they form by combining with water? 147. State the officinal process for making phosphoric acid, and what are its proper- ties? 148. By what tests may the three phosphoric acids be recognized and distinguished from phosphorous acid? 149. What is a phosphide, phosphite, phosphate, and hypophosphite? 150. What is glacial phosphoric acid, and in what respect does its action upon the animal system differ from the action of common phosphoric acid ? CHLORINE. 119 HF, HC1, IIBr, HI; they combine directly with most metals, forming fluorides, chlorides, bromides, and iodides. The relative combining energy lessens as the atomic weight increases; fluorine with the lowest atomic weight having the greatest, iodiue with the highest atomic weight the smallest, affinity for other elements. The first two members of the group are gases, the third (bromine) is a liquid, the last (iodine) a solid at ordinary temperature. They show, with the exception of fluorine, a distinct color in the gaseous state, have a disagreeable odor, and possess disinfecting properties. Occurrence in nature. Chlorine is found chiefly as sodium chloride or common salt, aSTaCl, either dissolved in water (small quantities in almost every spring water, larger quantities in some mineral waters, and the principal amount in sea-water), or as solid deposits in the interior of the earth as rock salt. Other chlorides, such as those of potassium, magnesium, cal- cium, also are found in nature. As common salt, chlorine enters the animal system, taking there an active part in many of the physiological and chemical changes. Preparation of chlorine. Most methods of liberating chlorine depend on an oxidation of the hydrogen of hydrochloric acid by suitable oxidizing agents, the hydrogen being converted into water, whilst chlorine is set free. As oxidizing agents, may be used potassium chlorate, potas- sium bichromate, potassium permanganate, chromic acid, nitric acid, and many other substances. The most common and cheapest mode of obtaining chlorine is to heat manganese dioxide, usually called black oxide of man- ganese, with hydrochloric acid, or a mixture of manganese di- oxide and sodium chloride with sulphuric acid: Mn02 + 4HC1 = MnCl2 + 2H20 + 201. Chlorine is liberated also by the action of acids on bleaeliing- powder, which is a mixture of calcium chloride and calcium hypochlorite: Ca(Jl2 Ca2C10 + 2H2S04 = 2CaS04 + 2H20 + 4C1. Experiment 13. Use apparatus as in Fig. 8, page 89. Conduct operation in a fume-chamber. Place about 50 grams of manganese dioxide in coarse powder in the flask, cover it with hydrochloric acid, shake up well to insure that no dry powder be lefc at the bottom of flask, apply heat, and collect the gas in dry 120 ON-METALS AND THEIR COMBINATIONS. bottles by downward displacement. Keep the bottles loosely covered with pieces of stiff’ paper while filling them. Use the gas for the following experiments: a. Fill a test-tube with chlorine, a second test-tube of same size with hydro- gen ; place them over one another so that the gases mix by diffusion, then hold them near a flame; a rapid combustion or explosion ensues. b. Hold in one of the bottles filled with chlorine a lighted wax candle, and notice that it continues to burn with liberation of carbon. The hydrogen contained in the wax is in this case the only constituent of the wax which burns, i. e., combines with chlorine. c. Moisten a paper with oil of turpentine, C10H16, and drop it into another bottle filled with the gas ; combustion ensues spontaneously, a black smoke of carbon being liberated. d. Drop some finely powdered antimony into another bottle, and notice that each particle of the metal burns while passing through the gas, forming white antimonious chloride, SbCl3. e. Pass some chlorine gas into water, and suspend in the chlorine water thus formed colored flowers or pieces of dyed cotton, and notice that the color fades and in many cases disappears completely in a few hours. Properties. Chlorine is a greenish-yellow gas, having a dis- agreeable taste and an extremely penetrating, suffocating odor, acting energetically upon the air-passages, producing violent coughing and inflammation. It is about two and a half times heavier than air, soluble in water, and convertible into a greenish- yellow liquid by a pressure of about four atmospheres. Chemically, the properties of chlorine are well marked, and there are but few elements which have as strong an affinity for other elements as chlorine; it unites with all of them directly, except with oxygen, nitrogen, and carbon, but even with these it may be made to combine indirectly. The act of combination between chlorine and other elements is frequently attended by the evolution of so much heat that light is produced, or, in other words, combustion takes place. Thus, hydrogen, phosphorus, and many metals burn easily in chlorine. The affinity between chlorine and hydrogen is intense, a mixture of the two gases being highly explosive. Such a mixture, kept in the dark, will not undergo chemical change, but when ignited, or when exposed to direct sunlight, the combination occurs instantly with an explosion. The affinity of chlorine for hydrogen is also demon- strated by its property of decomposing water, ammonia, and many hydrocarbons (compounds of carbon with hydrogen), such as oil of turpentine, C10H16, and others: H20 + 2C1 = 2HC1 + O. NH3 + 3C1 = 3HC1 + N. C10H16 + 1601 = IfiHOl + IOC. CHLORINE. 121 As shown by these formulas, hydrochloric acid is formed, whilst the other elements are set free. Chlorine is a strong disinfecting, deodorizing and bleaching agent; it acts as such either directly by combining with certain elements of the coloring or odoriferous matter, or, indirectly, by decomposing water with liberation of oxygen, which in the nascent state—that is, at the moment of liberation—has a strong tendency to oxidize other substances. Chlorine water, Aqua chlori, is water saturated with pure chlorine at a temperature of about 10° C. (50° F.). One volume of water absorbs at that temperature about two volumes of chlorine, which is equal to 0.4 per cent, by weight. Chlorine water is a greenish- yellow liquid, having the odor and taste of chlorine. It must be kept in the dark, as otherwise decomposition takes place. Hydrochloric acid, Acidum hydrochloricum, HC1 —36.4 (Chlor- hydric acid, Muriatic acid, Hydrogen chloride). One volume of hydrogen combines with one volume of chlorine to form two volumes of hydrochloric acid. Another method for obtaining it is the decomposition of a chlo- ride by sulphuric acid : or ISTaCl + H2S04 = HC1 + NaHS04; Experiment 14. Use apparatus as in Fig. 8, page 89. Place about 20 grams of sodium chloride into the flask (which should be provided with a funnel-tube) and add about 30 c.c. of concentrated sulphuric acid ; mix well, apply heat, and pass the gas into water for absorption. If a pure acid be desired, the gas has to be passed through water contained in a wash-bottle; apparatus shown in Fig. 11, page 104, may then be used. Use the acid made for tests mentioned below. How much of the U. S. P. 31.9 per cent, hydrochloric acid can be made from 117 pounds of sodium chloride? 2NaCl + H2S04 = 2HC1 + Na2S04. Hydrochloric acid is a colorless gas, has a sharp, penetrating odor, and is very irritating when inhaled. It is not combustible, not a supporter of combustion, and has great affinity for water, which property is the cause of the formation of white clouds whenever the gas comes in contact with the vapors of water, or with moist air; the white clouds being formed of minute particles of liquid hydrochloric acid. Whilst hydrochloric acid is a gas, this name is used also for its 122 NON-METALS AND THEIR COMBINATIONS. solution in water, one volume of which at ordinary temperature takes up over 400 volumes of the gas. The hydrochloric acid of the U. S. P. is an acid containing 31.9 per cent, of HC1. It is a colorless, fuming liquid, having the odor of the gas, strong acid properties, and a specific gravity of 1.16. The officinal diluted hydrochloric acid is made by mixing 6 parts of the above acid with 13 parts of water. The same antidotes maj7 be used as for nitric acid. Tests for hydrochloric acid and chlorides. (Sodium chloride, NaCl, may be used.) 1. To hydrochloric acid, or to solution of chlorides, add silver nitrate; a white, curdy precipitate is produced, which is soluble in ammonia water, but insoluble in nitric acid : AgN03 + NaCI = ISTaNOj + AgCl; AgN03 -f HC1 = HN03 + AgCl. 2. Add solution of mercurous salt (mercurous nitrate): a white precipitate is produced, which blackens on the addition of am- monia : H?22N03 + 2NaCl = 2NaN03 + Hg2CI2. 3. Add solution of lead acetate: a white precipitate of lead chloride is formed, which is soluble in much water, and is, there- fore, not formed in dilute solutions. 4. To a dry chloride add strong sulphuric acid and heat: hydrochloric acid gas is evolved, which may be recognized by the odor, or by its action on silver nitrate. 5. Chlorides treated with sulphuric acid and manganese dioxide evolve chlorine. Aqua regia, Nitro-hydrochloric acid (Acidum nitro-hydrochloricum, Nitro-muriatic acid). Obtained by mixing 4 parts of nitric acid with 15 parts of hydrochloric acid. The two acids act chemically upon each other, forming chloronitrous or chloronitric gas, chlo- rine, and water: HN03 + BHCl = N0C1 + 2H20 + 2C1 ; HX03 + 3HC1 = NOCI2 + 2H20 + Cl. The dissolving power of this acid upon gold and platinum depends on the action of the free chlorine and the action of the chloronitrous and chloronitric gases, both of which part easily with their chlorine. CHLORINE. Compounds of chlorine with oxygen. There is no method known to combine chlorine and oxygen directly, all the compounds formed by the union of these elements being obtained by indirect processes. The oxides of chlorine are the following: Hypochlorous oxide, C120 -f- H20 = 2HC10. Chlorous oxide, C1202 -f- H20 = 2HC102. Chlorous tetroxide, Cl204 does not combine with water to form an acid. C1205 + H20 = 2HC103 C1207 + H20 = 2HC10, Hot known in the separate state, but in combination with water. Chloric oxide, Perchloric oxide, All these oxides, as well as the corresponding acids formed by their union with water, are distinguished by the great facility with which they decompose, frequently with violent explosion, for which reason many of their compounds are used in the manu- facture of explosive mixtures. Chlorine acids. Hydrochloric acid, HOI. Hypochlorous acid, HCIO. Chlorous acid, HC102. Chloric acid, HC103. Perchloric acid, HC104. "With the exception of hydrochloric acid, which has been con- sidered, none of these five acids is of practical interest as such, but many of the salts of hypochlorous and chloric acids, known as hypochlorites and chlorates respectively, are of great and general importance. Hypochlorous acid, HC10, may be obtained by the action of chlorine water on mercuric oxide, insoluble mercuric oxychloride being formed also: Hypochlorous acid is a colorless, monobasic acid possessing strong bleaching properties. Hypochlorites are formed by the action of chlorine on the hydroxides of potassium, sodium, calcium, etc., at the ordinary temperature : 2HgO + 4C1 + Ha0 = HgaOOI, + 2HC10. 2HaOH + 2C1 = NaCl + NaClO + H20. Chloric acid, HC103, may be obtained from potassium chlorate by the action of hydrofluosilicic acid; it is, however, an unstable substance which will decompose, frequently with a violent explo- 124 NON-METALS AND THEIR COMBINATIONS. sion. Chlorates are generally obtained by the action of chlorine on alkaline hydroxides at a temperature of about 100° C. (212° F.) 6K0II + 6CI = 5KC1 + KC103 + 3H20. Mixtures of hypochlorites and chlorides are converted into chlorates by boiling their solution : 3KC1 + 3KC10 = 5KC1 + KC103. Tests for chlorates and hypochlorites. (Potass, chlorate, KC10:), and bleaching powder, Ca2C10.CaCl2, may be used.) 1. Chlorates liberate oxygen when heated by themselves. 2. Chlorates liberate chlorous tetroxide, C1204, a deep-yellow explosive gas, on the addition of strong sulphuric acid. 3. Chlorates deflagrate when sprinkled on red-hot charcoal. 4. Hypochlorites evolve a peculiarly smelling gas (hypoehlorous acid) on the addition of acids, and are strong bleaching agents. 17. BROMINE—IODINE—FLUORINE. Bromine, Bromum, Br = 79.8. This element is found in sea- water and many mineral waters, chiefly as magnesium bromide, which compound, however, represents in all these waters a com- paratively small percentage of the total quantity of the different salts present. Most of these salts are separated from the water by evaporation and crystallization, and the remaining mother- liquor, containing the magnesium bromide, is treated with chlorine, which liberates bromine, the vapors of which are con- densed in cooled receivers : MgBr2 + 2C1 = M^C12 + 2Br. Questions.—151. State the names and general physical and chemical prop- erties of the four halogens. 152. How is chlorine found in nature, and why does it not occur in a free state? 153. State the general principle for liberating chlorine from hydrochloric acid, and explain the action of the latter on mangan- ese dioxide. 154. Mention of chlorine: its atomic weight, molecular weight, valence, color, odor, action when inhaled, and solubility in water. 155. How does chlorine act chemically upon metals, hydrogen, phosphorus, water, ammonia, hydrocarbons, and coloring matters? 156. Mention two processes for making hydrochloric acid ; state its composition, properties, and tests by which it may be recognized. 157. What is aqua regia? 158. State the composition of hypochlorous and chloric acids. 159. What is the difference in the action of chlorine upon a solution of potassium hydroxide at ordinary temperature and at the boiling-point? 160. How many pounds of manganese dioxide, and how many of hydrochloric acid gas are required to liberate 142 pounds of chlorine? BROMINE — IODINE—FLUORIN E. 125 Bromine is at common temperature a heavy, dark reddish- brown liquid, giving off brown fumes of an exceedingly suffo- cating and irritating odor; it is very volatile, freezes at about —24° C. (—11° F.), and has a specific gravity of 2.99; it is but sparingly soluble in water, more freely in alcohol, abundantly in ether and bisulphide of carbon; it is a strong disinfectant, and its aqueous solution is also a bleaching agent. Hydrobromic acid, Acidum hydrobromicum, HBr = 80.8. This acid cannot well be obtained by the action of sulphuric acid upon bromides, since the hydrobromic acid first formed becomes readily decomposed with the formation of sulphur dioxide and free bromine. Thus: 2NaBr -f H2S04 = 2HBr + Na2S04; 2HBr + H2S04 = 2Br + S02 + 2H20 It may be obtained by the formation of bromide of phosphorus, PBr5 (the two elements combine directly), and its decomposition by water: In the form of solution this acid may be prepared also by treating bromine under water with hydrosulphuric acid until the brown color of bromine has entirely disappeared. The reaction is as follows: PBr5 + 4H20 = 5HBr + H3P04. lOBr + 2H2S + 4H20 = lOHBr + H2S04 + S. The liquid is filtered from the sulphur and separated from the sulphuric acid by distillation. Hydrobromic acid is, like hydrochloric acid, a colorless gas, of strong acid properties, easily soluble in water. A 10 per cent, solution is the officinal acid. Hypobromic acid, HBrO; Bromic acid, HBr03, and their salts, the hypobromites and bromates, are analogous to the corresponding chlorine compounds. Tests for bromides. (Potassium bromide, KBr, may be used.) 1. Silver nitrate produces in solutions of bromides a slightly yellowish-white precipitate of silver bromide, insoluble in nitric acid, sparingly soluble in ammonium hydroxide. 2. Addition of chlorine water liberates bromine, which may be dissolved by shaking with chloroform or ether. 126 NON-METALS AND THEIR COMBINATIONS. 3. Mucilage of starch added to the liberated bromine is colored yellow. 4. Strong sulphuric acid added to a dry bromide liberates hydrobromic acid, HBr, a portion of which decomposes with liberation of yellowish-red vapors of bromine. See explanation above. Iodine, Iodum, I —126.6. Iodine is found in nature in com- bination with sodium and potassium, in some spring waters and in sea-water, from which latter it is taken up by sea-plants and many aquatic animals. Iodine is derived chiefly from the ashes of sea-weeds known as kelp. By washing these ashes with water, the soluble constituents are dissolved, the larger quantities of sodium chloride, sodium and potassium carbonates are removed by evaporation and crystallization, and from the remaining mother-liquor iodine is obtained by treating the liquor with manganese dioxide and hydrochloric (or sulphuric) acid. The liberated iodine distils, and is collected in cooled receivers. Sodium nitrate found in Chili contains a small quantity of sodium iodate, and the mother-liquors, from which the nitrate has been crystallized, contain enough iodate to be employed for the prep- aration of iodine. Iodine is a heavy, bluish-black, crystalline substance of a somewhat metallic lustre, a distinctive odor, a sharp and acrid taste, and a neutral reaction. It fuses at 114° C. (237° F.), and boils at 180° C. (356° F.), being converted into beautiful purple- violet vapors; also, it volatilizes in small quantities at ordinary temperature. It is sparingly soluble in water, more soluble in water containing certain salts, for instance potassium iodide; it is soluble in 11 parts of alcohol (tincture of iodine), very soluble in ether, bisulphide of carbon, and chloroform. The solution of iodine in alcohol or ether has a brown, the solution in bisulphide of carbon or in chloroform a violet color. Iodine stains the skin brown, and when taken internally acts as an irritant poison. Hydriodic acid, Hydrogen iodide, HI. This is a colorless gas, readily soluble in water; the solution is unstable, being easily decomposed with liberation of iodine. It may be obtained by processes analogous to those mentioned for the preparation of hydrobromic acid. The action of hydrosulphurie acid upon iodine in the presence of water is as follows: H2S + 21 = 2HI + S. BROMINE — IODINE—FLUORINE. 127 Whilst not of much importance itself, many of its salts, the iodides, are of great interest. Tests for iodine ancl iodides. (Potassium iodide, KI, may be used.) 1. Add to free iodine (or to an iodide, after it has been de- composed by a few drops of chlorine water) mucilage of starch: a dark-blue color is produced, due to the formation of “ blue iodized starch.” 2. From solution of an iodide liberate iodine by chlorine water, and shake the solution with bisulphide of carbon or chloroform. After standing a few minutes the liquids form a layer of a beautiful violet color. 3. Add to solution of an iodide, solution of silver nitrate: a pale yellow precipitate of silver iodide, Agl, falls, which is insolu- ble in nitric acid, and sparingly soluble in dilute ammonium hydroxide. 4. Add lead acetate to a neutral solution of an iodide: a yellow precipitate of lead iodide, Pbl2, is produced. 5. Add mercuric chloride to a neutral solution of an iodide: a red precipitate of mercuric iodide, Hgl2, is produced. Fluorine, F —19. This element is found in nature, chiefly as fluorspar, calcium fluoride, CaF2; traces of fluorine occur in many minerals, in some waters, and also in the enamel of teeth, and in the bones of mammals. Fluorine was, until recently, scarcely known in the elementary state, because all attempts to isolate it were frustrated by the powerful affinities which this element possesses, and which render it difficult to obtain any material (from which a vessel may be made) which is not chemi- cally acted upon, and, therefore, destroyed, by fluorine. Lately the element has been obtained in quantities sufficient to study its properties, and it has been found that fluorine is a colorless gas of a highly irritating and suffocating odor, possessing affini- ties stronger than those of any other element. It combines spontaneously even in the dark and at low temperature with hydrogen; sulphur, phosphorus, and also many metals ignite readily in fluorine; even the noble metals, gold, platinum, and mercury, are converted into fluorides; from sodium chloride the chlorine is liberated with the formation of sodium fluoride; 128 NON-METALS AND THEIR COMBINATIONS. organic substances, such as oil of turpentine, alcohol, ether, and even cork ignite spontaneously when brought in contact with this remarkable element. Hydrofluoric acid, HF (Hydrogen fluoride). A colorless gas, very irritating, soluble in water. It is obtained by the action of sul- phuric acid on fluorspar: CaF2 + H2S04 = 2HF + CaS04. Hydrofluoric acid, either in the gaseous state or its solution in water, is used for etching on glass. This effect is due to the action of the acid upon the silica of the glass, which is converted into either silicon fluoride, SiF4; or into hydrofluosilicic acid, H2SiF6. Experiment 15. Prepare a glass plate by heating it slightly and covering its surface with a thin layer of wax or paraffin ; after cooling, scratch some letters or figures through the wax, thus exposing the glass. Set the plate over a dish (one made of lead or platinum answers best), in which a few grams of powdered fluorspar have been mixed with about an equal weight of sulphuric acid, and set in the open air for a few hours (heating slightly facilitates the action); upon removing the wax or paraffin, the glass will be found to be etched where its surface was exposed to the vapors of the acid. This experiment serves also as the best test for fluorides. Questions.—161. How is bromine found in nature ? 162. State the physical and chemical properties of bromine. 163. What is hydrobromic acid, and how can it be made? 164. By what tests may bromine and bromides be recognized? 165. What is the chief source of iodine ? 166. What are the chemical and physical properties of iodine? 167. What is tincture of iodine, what is its color, aud how does it stain the skin ? 168. Mention reactions by which iodine and iodides maybe recognized. 169. By what element may bromine and iodine be liberated from their compounds? 170. How is hydrofluoric acid made, and what is it used for? IY. METALS AND THEIR COMBINATIONS. 18. GENERAL REMARKS REGARDING METALS. Of the total number of fifty-four metallic elements only twenty-six are of sufficient general interest and importance to deserve consideration in this book. Derivation of names, symbols, and atomic weights. Aluminium^ A1 = 27 0. From alum, a salt containing it. Antimony, (Stibium.) Sb = 120.0. From the Greek avrl (anti), against, and moine, a French word for monk, from the fact that some monks were poisoned by compounds of antimony. Stibium, from the Greek, artfh (stibi), the name for the native sulphide of antimony. Arsenicum, As = 74.9. From the Greek apaeviKov (arsenicon), the name for the native sulphide of arsenic. Barium, Ba = 136.8. From the Greek fiapvs (barys), heavy, in allusion to the high specific gravity of barium sulphate, or heavy-spar. Bismuth, Bi = 210.0. From the German wismuth, an expression used long ago by the miners in allusion to the variegated tints of the metal when freshly broken. Cadmium, Cd = 111.8. From the Greek nad/uda (kadmeia), the old name for calamine (zinc carbonate), with which cadmium is frequently associated. Calcium, Ca = 40.0. From the Latin cake, lime, the oxide of calcium. Chromium, Cr — 52.4. From the Greek XP&Pa (chroma), color, in allusion to the beautiful colors of all its compounds. Cobalt, Co = 58.9. From the German Kobold, which means a demon inhabiting the mines. Copper, Cu = 63.2 From the Latin cuprum, copper, and this from the Island of Cyprus, where copper was first obtained by the ancients. Gold, (Aurum.) Au = 196.2. Gold means bright yellow in several old languages. The Latin aurum signifies the color of fire. Iron, Fe = 55.9. Iron probably means metal ; the derivation of the Latin ferrum is not definitely known. 130 METALS AND THEIR COMBINATIONS. Lead, Pb = 206.5. Both words signify something heavy. (Plumbum.) Lithium, Li = 7.0. Prom the Greek kideiog (litheios), stony. Magnesium, Mg = 24.0. From Magnesia, a town in Asia Minor, where mag- nesium carbonate was found as a mineral. Manganese, Mn = 54.0. Probably from magnesium, with the compounds of which it was long confounded. Mercury, Hg == 199.7. From Mercury, the messenger of the Greek gods. (Hydrargyrum.) Hydrargyrum means liquid silver. Molybdenum, Mo — 95.5. From the Greek fi6?u[i6og (molybdos), lead. Nickel, Ni = 58.0. From the old German word nickel, which means worthless. Platinum, Pt = 1944. Platina is the diminutive of the Spanish word plata, silver. Potassium, K = 39.0. From pot-ash ; potassium carbonate being the chief (Kalium.) constituent of the lye of wood-ashes. Kali is the Arabic word for ashes. Silver, Ag = 107.7. Both words signify white. (Argentum.) Sodium, Na= 23.0. From soda-ash, or sod-ash, the ashes of marine plants (Natrium.) which are rich in sodium carbonate. Natron is an old name for natural deposits of sodium carbonate. Strontium, Sr = 87.4. From Strontian, a village in Scotland, where stron- tium carbonate is found. Tin, Sn = 117.7. Both words most likely signify stone. (Stannum.) Zinc, Zn — 64.9. Most likely from the German zinn or tin, the metals having been confounded with each other. Melting-points of metals. C. F. Mercury ..... —40° — 40° Potassium .... +62 +144 Sodium ..... 97 207 Fusible below the boiling-point of water, Lithium ..... 180 356 Tin 228 443 Bismuth ..... 260 500 Cadmium .... 300 572 Lead 325 617 Zinc ..... 412 773 Aluminium .... 425? 796 Antimony .... 450? 842 Fusible below red heat, ' Barium. Calcium. Strontium. Arsenic. Magnesium—red heat. Unknown, 131 TIME OF DISCOVERY OF THE METALS. Silver ..... 1020 1868 Copper ..... 1100 2012 Gold 1200 2192 Cast-iron 1800 3272 Infusible below a red heat, Pure iron, Nickel, Cobalt, Manganese, *■ Highest heat of forge. Molybdenum, Chromium, Agglomerate, but do not melt in forge Fusible in the oxyhydrogen blowpipe flame. Platinum, Specific gravities of metals at 15.5° C. Lithium . . . 0.593 Potassium . . . 0.865 Sodium . . . 0.972 Calcium . . . 1.57 Magnesium . . 1.75 Stron'.ium . . .2.54 Aluminium . . 2.60 Barium . . . 4.00 Arsenic . . .5.88 Antimony . . . 6.80 Zinc .... 6.90 Tin . . . . 7.29 Iron . . . .7.79 Manganese . . . 8.00 Cobalt . . . .8.54 Molybdenum . . . 8.63 Cadmium . . . 8.70 Nickel .... 8.80 Copper . . . .8.96 Bismuth .... 9.90 Silver .... 10.50 Lead .... 11.45 Mercury .... 13.59 Gold .... 19.50 Platinum . . . 21.50 Time of discovery of the metals. Gold, Silver, Mercury, Copper, Zinc, Tin, Iron, Lead, These metals were known to the ancients, because either they are found in a metallic state, or can be obtained by comparatively simple processes from the oxides. Antimony, Bismuth, Latter part of the fifteenth century. Arsenic, 1694, by Schroder. Cobalt, 1733, by Brandt. Platinum, 1741, by Wood. Nickel, 1751, by Cronstedt. Manganese, 1774, by Galm. Molybdenum, 1782, by Hjelm. Chromium, 1797, by Vauquelin. 132 METALS AND THEIR COMBINATIONS. Potassium, Sodium, Barium, Calcium, Strontium, Magnesium, 1807-1808 H. Davy discovered methods for the separation of these metals from their oxides. Cadmium, 1817, by Stromeyer. Lithium, 1817, by Arfvedson. Aluminium, 1828, by Wohler. Valence of metals. Univalent. Lithium, Potassium, Sodium, Silver. Bivalent. Barium, Calcium, Strontium, Magnesium, Cadmium, Zinc, Copper, Mercury. Trivalent. Aluminium, Bismuth, Gold. Bi- and sexivalent. Chromium, Cobalt, Iron, Manganese, Nickel. Bi- and quadrivalent. Lead, Platinum, Tin. Tri- and quinquivalent. Antimony, Arsenic. Sexivalent. Molybdenum. Occurrence in nature. a. In a free or combined state. Gold, Platinum, Silver, Mercury, Almost exclusively in the metallic state. As metals or sulphides. Bismuth, generally metallic, also as oxide and sulphide. Copper, rarely metallic ; chiefly as sulphide, oxide, and carbonate b. In combination only. Potassium, Sodium, Lithium, Chiefly as chlorides or silicates. CLASSIFICATION OF METALS. 133 Barium, as sulphate. Calcium, Strontium, Magnesium, As carbonates, sulphates, silicates. Aluminium, in silicates. Iron, Zinc, Cadmium, As oxides, carbonates, sulphides. Arsenic, Antimony, Lead, Cobalt, ]Si iekel, Molybdenum, Chiefly as sulphides. Chromium, Manganese, Tin, Chiefly as oxides. Classification of Metals. Light metals. Sp. gr. from 0.6 to 4. Sulphides soluble in water. Heavy metals. Sp. gr. from 6 to 21.5. Sulphides insoluble in water. Light metals. Earth metals. Al, and many rare metals. Oxides insoluble. Alkaline earth metals. Ba, Ca, Sr, (Mg). Oxides soluble ; Carbonates insoluble. Alkali-metal. K, Na, Li, (NH4). Oxides, carbonates, and most salts soluble. Arsenic group. As, Sb, Sn, Au, Pt, Mo. Lead group. Pb, Cu, Bi, Ag, Hg, Cd, Heavy metals. Iron group. Fe, Co, Ni, Mn, Zn, Cr. Sulphides insoluble in dilute acids. Sulphides soluble in dilute acids. Sulphides soluble in am- Sulphides insoluble in monium sulphide. ammonium sulphide. Properties of metals. All metals have a peculiar lustre known as metallic lustre, and all are good conductors of heat and elec- tricity. The color of most metals is white, grayish, or bluish- white, or dark gray ; a few metals show a distinct color, as, for instance, gold and calcium (yellow), copper (red). At ordinary temperatures metals are solids with the exception of mercury, all are fusible, and some are so volatile that they may be distilled. Most, probably all, metals may be obtained in a crystallized condition. The combinations of metals among themselves are called alloys, 134 METALS AND THEIR COMBINATIONS. or, when mercury is one of the constituents, amalgams. These combinations, which usually may be obtained by fusing the metals together, must be looked upon as molecular mixtures, not as definite chemical compounds. All alloys still exhibit the metallic nature in their general physical characters. It is different, however, when metals combine with non-metals; in this case the metallic characters are lost almost invariably. All metals combine with chlorine, fluorine, and oxygen ; most metals also with sulphur, bromine, and iodine, forming the respective chlorides, fluorides, oxides, sulphides, bromides, and iodides. Metals replace hydrogen in acids, forming salts. Most metals may be obtained from their oxides by heating the latter with charcoal, the carbon combining with the oxygen of the oxide, whilst the metal is liberated: or MO + C = CO + M ; 2M0 + C = C02 + 2M Also hydrogen may be used in some cases as the deoxidizing agent: MO + 2H = H20 + M. Some metals are found in nature chiefly as sulphides, which usually are converted into oxides (before the metal can be obtained) by roasting. The term roasting, when used in metal- lurgy, means heating strongly in an oxidizing atmosphere, when the sulphides are converted into sulphates or oxides, thus: or MS + 40 = MS04; MS + 30 = MO + S02. Questions.—171. How many metals are known, and about bow many are of general interest? 172. Mention some metals having very low, and some having very high fusing-points. 173. What range of specific gravities do we find among the metals? 174. Mention some univalent and some bivalent metals; also some which show a different valence under different conditions. 175. Men- tion some metals which are found in nature in an uncombined state; some which are found as oxides, sulphides, chlorides, and carbonates, respectively. 176. Into what two groups are the metals divided? 177. State the three groups of light metals. 178. What is a metal? 179. What is an alloy, and what an amalgam? 180. By what process can most metals be obtained from their oxides ? POTASSIUM. 135 19. POTASSIUM (KALIUM). Ki = 39. General remarks regarding alkali-metals. The metals potassium, sodium, lithium (rubidium and c?esium) form the group of the alkali-metals, which, in many respects, show to each other a great resemblance in chemical and physical properties. For reasons to be explained hereafter, the compound radical ammonium usually is classed among the alkali-metals. The alkali-metals are all univalent; they decompose water at the ordinary temperature, with liberation of hydrogen; they combine spontaneously with oxygen and chlorine; their oxides, hydroxides, sulphates, nitrates, phosphates, carbonates, sulphides, chlorides, iodides, and nearly all other of their salts are soluble in water; all these compounds are white, solid substances, many of which are fusible at a red heat. Of all metals, those of the alkalies are the only ones forming hydroxides and carbonates which are not decomposed by heat. The metals themselves are of a silver-white color, and extremely soft; on account of their tendency to combine with oxygen they must be kept in a liquid not containing that element (coal-oil) or in an atmosphere of hydrogen. The metals may be obtained by heating their carbonates with carbon in iron retorts, the escaping vapors being passed under coal-oil for condensation of the metal: Occurrence in nature. Potassium is found in nature chiefly as a double silicate of potassium and aluminium (granite rocks, feld- spar, and other minerals), or as chloride and nitrate. By the gradual disintegration of the different granite rocks containing potassium silicate, this has entered into the soil, whence it is taken up by plants as one of the necessary constituents of their food. In the plant potassium enters largely into combination with organic acids (tartaric acid, citric acid, etc.), and when the plant is burned, ashes are left containing the potassium, now in the form of carbonate. By washing such ashes (chiefly wood-ashes) with water and filtering, the insoluble matter (carbonates, phos- phates, and sulphates of calcium and magnesium, silica, etc.) is left behind, whilst a lye is obtained containing the soluble con- K2C03 + 2C = 3C0 + 2K. METALS AND THEIR COMBINATIONS. stituents, of which potassium carbonate is the principal one, chlo- rides and sulphates of potassium and sodium also being present in small quantities. By evaporation to dryness of this lye an impure potassium carbonate is obtained, which is sold as crude potash. Up to within twenty years ago the chief supply of potash was obtained by this process, and the trees of thousands of acres were burned with the view of obtaining potash. To-day this mode of manufacturing potash is very limited, and is rapidly decreasing, as, fortunately, a new supply of soluble potassium salts has been discovered in the salt-mines of Stassfurt, Germany, where large quantities of potassium chloride (and some sulphate) are found, from which the carbonate and other salts are manufactured. Potassium hydroxide, Potassium hydrate, Potassa, KOH = 56 [Caustic potash), may be obtained by the action of the metal on water: The usual process for making potassium hydroxide is to boil together a dilute solution of potassium carbonate or bicarbonate and calcium hydroxide: K + H20 = H + KOH. K2C03 + Ca20H = CaC03 + 2K0H. Experiment 16. Add gradually 5 grams of calcium hydroxide (slaked lime) to a boiling solution of about 5 grams of potassium carbonate in 50 c.c. of water, and continue to boil until the conversion of potassium carbonate into hydroxide is complete. This can be shown by filtering off a few drops of the liquid, and supersaturating with dilute hydrochloric acid, which should not cause effer- vescence. Set aside to cool, and when all solids have subsided, pour off the clear solution of potassium hydroxide, which may be used for Experiment 17. What quantities of K2C03 and Ca20H are required to make one litre of a 5 per cent, solution of potassium hydroxide? Potassium hydroxide is a white, hard, solid substance, soluble in 0 5 part of water and 2 parts of alcohol; it fuses at a low red heat, forming an oily liquid, which may be poured into suitable moulds to form pencils; at a strong red heat it is slowly vola- tilized without decomposition; it is a very strong base, readily combining with all acids; when taken internally it acts as a powerful corrosive, and most likely otherwise as a poison. Antidotes: dilute acids, vinegar, to form salts; or fat, oil, or milk, to form soap. Liquor potassce is a 5 per cent, solution of potassium hydroxide in water. POTASSIUM. 137 Potassium bicarbonate, K2C03 = 138, Potassii carbonas, U. S. P., (K2C03)23H20 = 330 (Carbonate of potassium), is obtained from ashes in an impure state as described above, or from the native chloride by the so-called Leblanc process, which will be described in con- nection with sodium carbonate. Crude potash when calcined in a furnace until white is known as pearlash. Pure potassium carbonate is obtained by heating the bicar- bonate, which is decomposed as follows : 2KHC03 = k2co3 + h2o + co2. Potassium carbonate is deliquescent, is soluble in an equal weight of water, and has strong basic and alkaline properties. Potassium bicarbonate, Potassii bicarbonas, KHC03 — 100 (Bicar- bonate of potassium). Obtained by passing carbon dioxide through a strong solution of potassium carbonate, when the less soluble bicarbonate forms and separates in crystals : k2co3 + H20 + C02 = 2KHCO3. Potassium nitrate, Potassii nitras, KN03=101 (Nitre, Saltpetre). Potassium and sodium nitrate are found as an incrustation upon and throughout the soil of certain localities in dry and hot coun- tries, as, for instance, in Peru, Chili, and India. The formation of these nitrates is to be explained by the absorption of ammonia (present in the atmosphere) by the soil, where it gradually is oxi- dized and converted into nitric acid, which then combines with the strongest base present in the soil. If this base be potash, potassium nitrate will be formed; if soda, sodium nitrate; if lime, calcium nitrate. Upon the same principle is based the manufacture of nitre on a large scale, which is accomplished by mixing animal refuse matter with earth and lime, and placing the mixture in heaps under a roof, to prevent lixiviation by rain. By decomposition (putrefaction) of the animal matter, ammonia is formed, which, by oxidation, is converted into nitric acid, which then combines with the calcium of the lime, forming calcium nitrate. This is dissolved in water, and to the solution potassium carbonate (or chloride) is added, when calcium carbonate (or chloride) and potassium nitrate are formed : Ca2N03 + K2C03 = 2KN03 + CaC03. 138 METALS AMD THEIR COMBINATIONS. Large quantities of potassium nitrate are made also by decom- posing sodium nitrate (Chili saltpetre) by potassium chloride : Potassium nitrate crystallizes in six-sided prisms ; it is soluble in about 5 parts of cold, and 0.5 part of boiling water. It has a cooling, saline, and pungent taste, and a neutral reaction. When heated with deoxidizing agents or combustible substances, these are readily oxidized. It is this oxidizing power which is made use of in the manu- facture of gunpowder—an intimate mixture of potassium nitrate, sulphur, and carbon. Upon heating or igniting the gunpowder, the sulphur and carbon are oxidized, a considerable quantity of various gases (CO, C02, N, S02, etc.) being formed, the sudden generation and expansion of which cause the explosion. NaNOg + KC1 = KN03 + NaCl. Potassium chlorate, Potassii chloras, KC103 = 122.4 (Chlorate of potassium), may be obtained by the action of chlorine on a boiling solution of potassium hydroxide : 6C1 + 6K0H = 5KC1 + KC103 + 3H20. A cheaper process for the manufacture of potassium chlorate is the action of chlorine upon a boiling solution of potassium carbonate, to which calcium hydroxide has been added : K2C03 + 6(Ctt20H) + 12C1 = 2KC10S + CaC03 + 5CaCl2 + 6U20. Potassium chlorate crystallizes in plates of a pearly lustre; it is soluble in 17 parts of cold, and 2 parts of boiling water. It is even a stronger oxidizing agent than potassium nitrate, for which reason care must be taken in mixing it with organic or other deoxidizing agents, or with strong acids, which will liberate chloric acid. When heated by itself, it is decomposed into potas- sium chloride and oxygen. Potassium sulphate, Potassii sulphas, K2S04 = 174. Obtained by the decomposition of potassium chloride, nitrate, or carbonate, by sulphuric acid : 2KC1 + H2S04 = 2HC1 + K2S04; k2co3 + h2so4 = h2o + co2 + k2so4. Potassium sulphate exists in small quantities in plants, and in nearly all animal tissues and fluids, more abundantly in urine. Potassium hydrogen sulphate, bisulphate, or potassium acid sulphate, POTASSIUM. 139 may be obtained by the action of one molecule of potassium chloride upon one molecule of sulphuric acid: Potassium sulphite, Potassii sulphis, K,S032H20 = 194. Obtained by the decomposition of potassium carbonate by sulphurous acid : KC1 + H2S04 = HC1 + KHS04. “1“ H2S03 — H20 -j- C02 -f- k2so3. Potassa sulphurata, TJ. S. P. (Sulphurated potassa, Sulphuret of potash, Hepar sulphuris). A mixture of potassium sulphide, polysulphide, and thio- sulphate. It is made by heating a mixture of sulphur and potassium carbonate in a covered crucible, and pouring the fused mass on a marble slab: 3K2COg + 8S = K2S203 + 2K2S3 + 3C02. The freshly prepared substance has a liver-brown color, turning gradually to greenish yellow ; it is very apt to absorb oxygen, both the sulphide and hypo- sulphite becoming oxidized, and finally converted into sulphates. Potassium hypophosphite, Potassii hypophosphis, KH2P02 = 104, may be obtained by decomposing a solution of calcium hypo- phosphite by potassium carbonate : Ca2PH202 + K2C03 = 2KPH202 + CaC03. The filtered solution is evaporated at a very gentle heat, stirring constantly from the time it begins to thicken until a dry, granular salt is obtained. Potassium iodide, Potassii iodidum, KI = 165.6 (Iodide of 'potas- sium), is made by the addition of iodine to a solution of potassium hydroxide until the dark-brown color no longer disappears: 6K0II + 61 = 5KI + KIOs + 3H20. Iodide and iodate of potassium are formed, and may be separ- ated by crystallization. A better method, however, is to boil to dryness the liquid containing both salts, and to heat the mass after having mixed it with some charcoal, in a crucible, when the iodate is converted into iodide: Experiment 17. Add to a solution of about 3 grams of potassium hydroxide in about 25 c.c. of water (or to the solution obtained by making Experiment 16) iodine until the brown color no longer disappears. (How much iodine will be needed for 3 grams of KOII ?) Evaporate the resulting solution (What does this solution contain now?) to dryness, mix the powdered mass with about 10 per cent, of powdered charcoal and heat the mixture in a crucible until slight deflagration takes place. Dissolve the fluid mass in hot water, filter and set aside for crystallization; if too much water has been used for dissolving, the liquid must be concentrated by evaporation. KI03 + 3C = KI + 3C0. 140 METALS AND THEIR COMBINATIONS. Potassium iodide forms colorless, cubical crystals, which are soluble in 0.5 part of boiling and 0.8 part of cold water, also soluble in 18 parts of alcohol. Potassium bromide, Potassii bromidum, KBr = 118.8 (Bromide of potassium.), may be obtained in a manner analogous to that given for potassium iodide, by the action of bromine upon potassium hydroxide, etc. Or it may be made by the decomposition of a solution of ferrous bromide by potassium carbonate : Ferrous carbonate is precipitated, whilst potassium bromide remains in solution, from which it is obtained by crystallization. FeB-2 + K2C08 = 2KBr + FeCOs. Potassium salts of interest, which have not yet been mentioned, will be con- sidered under the head of their respective acids. Some of these salts are potas- sium chromate and permanganate, and the salts formed from organic acids, such as potassium tartrate, acetate, etc. Analytical reactions. (Potassium chloride, KC1, or nitrate, KN03, may be used.) 1. To a solution of potassium chloride, or to any salt of potas- sium, after a few drops of hydrochloric acid have been mixed with it, add platinic chloride and some alcohol: a yellow crystal- line precipitate falls, which is a double chloride of platinum and potassium, PtCl42KCl. 2KC1 + PtCl4 = PtCl4 2KC1; 2KN03 + 2HC1 + PtCl4 = PtCI42KCl + 2HN03. The last formula shows the necessity of adding hydrochloric acid, which is not required in case potassium chloride is used. The addition of alcohol facilitates the precipitation of the double chloride of potassium and platinum, because it is less soluble in alcohol than in water. 2. Add to a concentrated solution of a neutral potassium salt a strong solution of tartaric acid: a white precipitate of potassium acid tartrate is slowly formed. Addition of alcohol facilitates precipitation. 3. Potassium compounds color violet the flame of a Bunsen burner or of alcohol. The presence of sodium, which colors the flame intensely yellow, interferes with this test, as it masks the violet caused by potassium. The difficulty may be overcome by observing the flame through a blue glass or through a thin vessel SODIUM. 141 filled with a solution of indigo. The yellow light is absorbed by the blue medium, while the violet light passes through and can be recognized. 4. All compounds of potassium are white (unless the acid has a coloring effect), soluble in water, and not volatile at a low red heat. 20. SODIUM (NATRIUM) Occurrence in nature. Sodium is found very widely diffused in small quantities through all soils. It occurs in large quanti- ties in combination with chlorine, as rock-salt, or common salt, which forms considerable deposits in some regions, or is dissolved in spring waters, and is by them carried to the rivers, and finally to the ocean, which contains immense quantities of sodium chlo- ride. It is found, also, as nitrate, silicate, etc. Nui = 23. Sodium hydroxide, Sodium hydrate, Soda, NaOH — 40, may be obtained by the processes mentioned for potassium hydroxide. Sodium chloride, Sodii chloridum, NaCl = 58.4 (Chloride of sodium, Common salt). This is the most important of all sodium com- pounds, and also is the material from which the other compounds are directly or indirectly obtained. Common table-salt frequently contains small quandtes of calcium and magnesium chlorides, the presence of which causes absorption ol moisture, as these compounds are hygroscopic, whilst pure sodium chloride is not. In the animal system, sodium chloride is found in all parts, it being of great importance in aiding the absorption of albumi- noid substances and the phenomena of osmose; also by furnish- Questions.—181. How is potassium found in nature, and from what sources is the chief supply of potassium salts obtained? 182. What color have the salts of the alkali metals, and which are insoluble? 183. Mention two pro- cesses for making potassium hydroxide, aud what are its properties? 184. Show by symbols the conversion of carbonate into bicarbonate of potassium. 185. Explain the principle of the manufacture of' potassium nitrate, and what is the office of the latter in gunpowder? 186. How is potassium chlorate made, and what are its properties? 187. Give the processes for manufacturing iodide and bromide of potassium, both in words and symbols. 188. State the composition of potassium sulphate and sulphite. How can they be obtained? 189. What is sulphuret of potash ? 190. Mention tests for potassium compounds. 142 METALS AND THEIR COMBINATIONS. ing, through decomposition, the hydrochloric acid of the gastric juice. Sodium chloride is soluble in about 2.8 parts of water, at all temperatures; it crystallizes in cubes. Sodium carbonate, Sodii carbonas, Na2C03.10H20 = 286 (Carbonate of sodium., Washing soda, Sal sodce). This compound is, of all alkaline substances, the one manufactured in the largest quanti- ties, being used in the fabrication of many highly important articles, as, for instance, soap, glass, etc. Sodium carbonate is made, according to Leblanc’s process, from the chloride by first converting it into sulphate (salt-cake) by the action of sulphuric acid : 2NaCl + H2S04 = 2HC1 + Na2S04. The escaping vapors of hydrochloric acid are absorbed in water, and this liquid acid is used largely in the manufacture of bleaehing-powder. The sodium sulphate is mixed with coal and limestone (calcium carbonate) and the mixture heated in furnaces, when decomposition takes place, calcium sulphide, sodium car- bonate, and carbonic oxide being formed : Na2S04 + 4C + CaC03 = CaS + Na2C03 + 4C0. The resulting mass, known as black-ash, is washed with water, which dissolves the sodium carbonate, whilst calcium sulphide enters into combination with calcium oxide, thus forming an insoluble double compound of oxy-sulphide of calcium. The liquid obtained by washing the black-ash, when evaporated to dryness, yields crude sodium carbonate, or “ soda ash;” when this is dissolved and crystallized it takes up ten molecules of water, forming the ordinary u soda ” Sodium carbonate is manufactured also by a process which depends on the decomposition of sodium chloride by ammonium bicarbonate under pressure, when sodium bicarbonate and ammo- nium chloride are formed, thus : NaCl + NH,HC03 = JSH.Cl + NaHC03. The sodium acid carbonate, thus obtained, is converted into carbonate by heating: 2NaHC03 = NtijCOg + H20 + C02 The carbon dioxide obtained by this action is caused to act upon ammonia, liberated from the ammonium chloride, obtained SODIUM. 143 as one of the products in the first reaction. Ammonium car- bonate is thus regenerated and used in a subsequent operation for the decomposition of common salt. Sodium carbonate has strong alkaline properties; it is soluble in 1.6 parts of water at ordinary temperature, and in much less water at higher temperatures; the crystals lose water on exposure to the air, falling into a white powder; heat facilitates the expul- sion of the water of crystallization, and is applied in making the dried sodium carbonate, Sodii carbonas ezsiccata of the U. S. P. Sodium bicarbonate, Sodii bicarbonas, NaHC03 = 84 (.Bicarbonate of sodium). Made by passing carbon dioxide over sodium car- bonate from which the larger portion of water of crystallization has been expelled : Na2C02 + H20 + C02 = 2NaHC03. It is a white powder, having a cooling, mildly saline taste, and a slightly alkaline reaction. Soluble in 12 parts of cold water, and insoluble in alcohol. It is decomposed by heat or by hot water into sodium carbonate, water, and carbon dioxide. Sodium sulphate, Sodii sulphas, Na2S04.10H20 = 322 (Sulphate of sodium, Glauber’s salt). Made, as mentioned above, by the action of sulphuric acid on sodium chloride, dissolving the salt thus obtained in water, and crystallizing. Large, colorless, trans- parent crystals, rapidly efflorescing on exposure to air. Soluble in 2.8 parts of wrater at 15° C. (59° F.), in 0.25 part at 33° C. (91° F.), and in 0.4 part of boiling water. Experiment 18. Dissolve about 10 grams of crystallized sodium carbonate in lOc-c. of hot water, add to this solution dilute sulphuric acid until all efferves- cence ceases, and the reaction on litmus-paper is exactly neutral. Evaporate to about 20c.c., and set aside for crystallization. Explain the action taking place, and state how much H2S04, and how much of the diluted sulphuric acid, U. S. P., are needed for the decomposition of 10 grams of crystallized sodium carbonate. Sodium sulphite, Sodii sulphis, Na2S03.7H20 = 252. Sodium bisul- phite, Sodii bisulphis, NaHS03 = 104. By saturating a cold solu- tion of sodium carbonate with sulphur dioxide, the sodium bisulphite is formed, and separates in opaque crystals : Nh2C03 + 2S0j + H20 = 2NuHS03 + C02. 144 METALS AND THEIR COMBINATIONS. If to the sodium bisulphite thus obtained a quantity of sodium carbonate be added, equal to that first employed, the normal salt is formed: 2NaIlS03 + Na2C03 = 2Na2S03 + H20 + C02. Sodium thiosulphate, Sodium hyposulphite, Sodii hyposulphis, Na2S203.5H20 = 248. Made by digesting a mixture of solution of sodium sulphite with powdered sulphur, when combination slowly takes place: It is used under the name of “ hypo,” in photography to dis- solve chloride, bromide, or iodide of silver. Na2S03 + S = Nh2S203. Disodium hydrogen phosphate, Sodii phosphas, Na2HP04.12H20 = 358 (Phosphate of sodium), is made from calcium phosphate by the action of sulphuric acid, which removes two-thirds of the calcium, forming calcium sulphate, while acid phosphate of calcium is formed and remains in solution: Cas2P04 + 2H2S04 = 2CaS04 + CaH42P04. The solution is filtered and sodium carbonate added, when calcium phosphate is precipitated, phosphate of sodium, carbon dioxide, and water being formed: ChH42P04 + Nh2C03 = CaHP04 + H20 + C02 + N»2HP04. The filtered and evaporated solution yields crystals of phos- phate of sodium, which have a slightly alkaline reaction. Experiment 19. Mix thoroughly 30 grams of bone-ash with 10 c.c. of sul- phuric acid, let stand for some hours, add 20 c.c. of water, and again set aside for some hours. Mix with 40 c.c. of water, heat to the boiling point, and filter. The residue on the filter is chiefly calcium sulphate. To the hot filtrate of calcium acid phosphate add concentrated solution of sodium carbonate until a precipitate ceases to form and the liquid is faintly alkaline, filter, evaporate, and let crystallize. When sodium phosphate is heated to a low red heat it loses water, and is converted into pyrophosphate, which, dissolved in hot water, and crystallized, forms the sodium 'pyrophosphate, Na4P2O7.10H2O, of the U. S. P. The normal sodium phosphate, Na3P04, is known also, but it is not a very stable compound, being acted upon even by the moisture and carbon dioxide of the air, with the formation of sodium carbonate and disodiutn hydrogen phos- phate, thus: 2Na3P04 + H20 + C02 = 2Nh2HP04 + Nh2C03 145 AMMONIUM. Sodium nitrate, Sodii nitras, NaN03 = 85 (Nitrate of sodium, Chili saltpetre, Cubic nitre). Found in nature, and is purified by crys- tallization. Other sodium salts which are officinal are sodium borate (borax), Aa2B4Or10H2O; bromide, ISTaBr; iodide, ISTal; chlorate, AaC103. The latter three salts may be obtained by processes analogous to those given for the corresponding potassium compounds. Tests for sodium. 1. As all salts of sodium are soluble in water, we cannot pre- cipitate this metal in the form of a compound by any of the common reagents. (Potassium antimoniate precipitates neutral solution of sodium salts, but this test is not reliable.) 2. The chief reaction for sodium is the flame-test, compounds of sodium imparting to a colorless flame an intensely yellow color. (The spectroscope shows a characteristic yellow line.) 3. Sodium compounds are white and are not volatile at or below a red heat. Lithium, Li = 7. Found in nature in combination with silicic acid in a few rare minerals or as a chloride in some spring waters. Of inorganic salts, the bromide and carbonate are officinal. Hydroxide, carbonate, and phosphate of lithium are much less soluble than the corresponding compounds of potassium and sodium. Sodium phosphate added to a strong solution of a lithium salt produces, on boiling, a white precipitate of lithium phosphate, Li3P04. Lithium compounds color the flame a beautiful crimson or carmine-red. 21. AMMONIUM. NH4i = 18. General remarks. The salts of ammonium show so much re- semblance, both in their physical and chemical properties, to Questions.—191. What is the composition of common salt; how is it found in nature, and what is it used for? 192. Describe Leblanc’s process for manu- facturing sodium carbonate on a large scale. 193. How much water is in 100 pounds of the crystallized sodium carbonate? 194. What is Glauber’s salt, and how is it made? 195. State the composition of disodium hydrogen phos- phate, and how is it prepared from calcium phosphate? 196. What difference exists between sodium carbonate and bicarbonate, both in regard to physical and chemical properties? 197. (rive the composition of sodium hyposulphite ; what is it used for? 198. Which sodium salts are soluble, and which are insoluble? 199. How does sodium and how does lithium color the flame? 200. Which lithium salts are officinal ? 146 METALS AND THEIR COMBINATIONS. those of the alkali-metals, that they may be studied most conve- niently at this place. The compound radical NH4 acts in these ammonium salts very much like one atom of an alkali-metal, and, therefore, frequently has been looked upon as a compound metal. The physical metallic properties (lustre, etc.) of ammonium cannot be fully demonstrated, as it is not capable of existing in a separate or free state. There is known, however, an alloy of ammonium and mercury, which may be obtained by dissolving potassium in mercury and adding to the potassium-amalgam thus formed, a strong solution of ammonium chloride, when potassium chloride and ammonium-amalgam are formed. The latter is a soft, spongy, metallic-looking substance, which readily decomposes into mer- cury, ammonia, and hydrogen: HgK + NH4C1 = KC1 + NH4Hg; NH4Hg = NH3 + H + Hg. The source of all ammonium compounds is ammonia, jSTI3, or ammonium hydroxide, NH4OII, both of which have been con- sidered heretofore. Ammonium chloride, Ammonii chloridum, NH4C1 = 53.4 (Chloride of ammonium, Sal-ammoniac). Obtained by saturating the “ am- moniacal liquor” of the gas-works with hydrochloric acid, evaporating to dryness, and purifying the crude article by sub- limation. Pure ammonium chloride either is a white, crystalline powder, or presents itself in the form of long, fibrous crystals, which are tough and flexible; it has a cooling, saline taste; is soluble in 3 parts of cold, and 1.5 parts of boiling-water; and, like all ammo- nium compounds, is completely volatilized by heat. Experiment 20. To 10 c.c. of water of ammonia add hydrochloric acid until the solution is neutral to test paper. Evaporate to dryness and use the salt for the analytical reactions mentioned below. How many c.c. of 32 per cent, hydrochloric acid are required to saturate 10 c.c. of 10 per cent, ammonia water ? Ammonium carbonate, Ammonii carbonas, NH4HC03.NH4NH.,C02 = 157 (Carbonate of ammonium). Commercial ammonium carbonate is not the pure salt, but, as shown by the above formula, a com- bination of acid ammonium carbonate with ammonium carbamate. It is obtained by sublimation of a mixture of ammonium chloride AMMONIUM. 147 and calcium carbonate, when calcium chloride is formed, am- monia gas and water escape, and ammonium carbonate condenses in the cooler part of the apparatus: 2CaC03 + 4NH4C1 = NH4HC03.NII4NH2C02 + 2CaCl2 + H20 + NH3. Ammonium carbonate thus obtained forms white, translucent masses, losing both ammonia and carbon dioxide on exposure to the air, becoming opaque, and finally converted into a white powder of acid ammonium carbonate: NH4HC03.NH4NH2C02 = NH4HC03 + 2N H3 + C02. When commercial ammonium carbonate is dissolved in water, the carbamate unites with one molecule of water, forming normal ammonium carbonate : NH4NH2C02 + H20 = (NH4)2C03. A solution of the common ammonium carbonate in water is, consequently, a liquid containing both acid and normal carbonate of ammonium ; by the addi- tion of some ammonia water the acid carbonate is converted into the normal salt. The solution thus obtained is used frequently as a reagent. The Aromatic spirit of ammonia (sal volatile) is a solution of normal ammo- nium carbonate in diluted alcohol to which some essential oils have been added. Ammonium sulphate, (NH4)2S04, Ammonium nitrate, NH4N03, and Ammonium phosphate, (NH4)2HP04, may be obtained by the addi- tion of the respective acids to ammonia water or ammonium carbonate: H2S04 + 2NPL0H = (NH4)2S04 + 2H20. hno3; + nh4oh = nh4no3 h2o. H3P04 + 2NH4OH = (NH4)2HP04+ 2H,0. h2so4 + (NH4)2COs= (Nh4)2so4 + h'o + co2 Ammonium iodide, Ammonii iodidum, NH4I, and Ammonium bro- mide, Ammonii bromidum, NH4Br, may be obtained by mixing together strong solutions of potassium iodide (or bromide) and ammonium sulphate, and adding alcohol, which precipitates the potassium sulphate formed; by evaporation of the solution the ammonium iodide (or bromide) is obtained : 2KI + (NH4)jS04 = 2NH4[ + K2S04; 2KBr + (NH4)2S04 = 2NH4Br + K2S04. Another mode of preparing these compounds is by decom- position of ferrous bromide (or iodide) by ammonium hydroxide : FeBr2 + 2NH4OH — 2NH4Br + Fe20H. Ammonium iodide is the principal constituent of the Decolorized tincture of iodine. 148 METALS AND THEIR COMBINATIONS. Ammonium hydrogen sulphide, NH4SH (.Ammonium hydro sulphide, Ammonium sulphydrale). Obtained by passing sulphuretted hydro- gen gas through water of ammonia until this is saturated: h2s + nh4oh = nh4sh + h2o. The solution thus obtained is, when recently prepared, a colorless liquid, having the odor of both ammonia and of sul- phuretted hydrogen; when exposed to the air it soon assumes a yellow color. By the addition of ammonia wTater it is converted into ammonium sulphide, (AH4)2S : Both substances, the ammonium hydrogen sulphide and ammonium sulphide, are valuable reagents, frequently used for precipitation of certain heavy metals, or for dissolving certain metallic sulphides. NH4SH + NH4OH = (KH4)2S + h2o. Analytical reactions. 1. All compounds of ammonium are volatilized by heating to a low red heat. (Ammonium chloride, NH4CL, may be used.) 2. All compounds of ammonium evolve ammonia gas when heated with hydroxide of calcium, potassium, or sodium. The ammonia may be recognized by its odor, or by its action on paper moistened with solution of cupric sulphate, which is thereby colored dark-blue. 3. Add to solution of ammonium salt some platinic chloride, a few drops of hydrochloric acid, and some alcohol; a yellow precipitate of ammonium platinic chloride, (XII4Cl)2PtCl4, is pro- duced. See explanation of the corresponding potassium reaction on page 140. 4. Ammonium salts are colorless, and (almost all) soluble in water. Questions.—201. What is ammonium, and why is it classed with the alkali- metals? 202. Is ammonium known in a separate state? 203. What is am- monium-amalgam, how is it obtained, and what are its properties? 204. What is the source of ammonium compounds? 205. State tlie composition, mode of preparation, and properties of sal-ammoniac? 206. How is ammonium carbon- ate manufactured, and what difference exists between the solid article and its solution ? 207. State the composition of ammonium sulphide and of ammonium hydrogen sulphide ; how are they made, and what are they used for? 208. By what process may ammonium sulphate, nitrate, and phosphate be obtained from ammonium hydroxide or ammonium carbonate, and what chemical change takes place? 209. How does heat act upon ammonium compounds? 210. Give analytical reactions for ammonium salts. MAGNESIUM. 149 22. MAGNESIUM. Mgii = 24. General remarks. Magnesium occupies a position intermediate between the alkali metals and the alkaline earths, with which latter it was formerly classed as a member. To some extent it resembles also the heavy metal zinc, with which it has in com- mon, the volatility of the chloride, the solubility of the sulphate, and the isomorphism of several of its compounds with the analo- gously constituted compounds of zinc. Occurrence in nature. Magnesium is widely diffused in nature, and several of its compounds are found in large quantities. It occurs as chloride and sulphate in many spring waters and in the salt-mines of Stassfurt; as carbonate in the mineral mag- nesite ; as double carbonate of magnesium and calcium in the mineral dolomite (magnesian-limestone), which forms entire mountains; as silicate of magnesium in the minerals serpentine, meerschaum, talc, asbestos, soapstone, etc. Metallic magnesium may be obtained by the decomposition of magnesium chloride by sodium : MgCl2 + 2Na = 2NaCl + Mg. Magnesium is an almost silver-white metal, losing its lustre rapidly in moist air by oxidation of the surface. It decomposes hot water with liberation of hydrogen: Mg + 2H20 = 2H + Mg20H. When heated to a red heat it burns with a brilliant bluish- white light forming magnesium oxide. Magnesium carbonate, Magnesii carbonas, 4(MgC03).Mg20H.5H20 = 484 (Carbonate of magnesium, Magnesia alba, Light magnesia). The normal magnesium carbonate, MgCOa, is found in nature, but the officinal preparation is a mixture of carbonate, hydrox- ide, and water. It is obtained by boiling a solution of mag- nesium sulphate with solution of sodium carbonate, when the carbonate is precipitated, some carbon dioxide evolved, and sodium sulphate remains in solution : 5MgS04 + 5Na2C03 + 6H20 = 4(MgC03).Mg20H.5H20 -f 5Na2S04 + CO.. By filtering, washing, and drying the precipitate, it is obtained in the form of a white, light powder; if, however, the above- 150 METALS AND THEIR COMBINATIONS. mentioned solutions are mixed, evaporated to dryness, and the sodium sulphate removed by washing, the magnesium carbonate is left in a more dense condition, and is then known as heavy magnesia. Experiment 21. Dissolve 10 grams of magnesium sulphate in hot water and add a concentrated solution of sodium carbonate until no more precipitate is formed. Collect the precipitated magnesium carbonate on a filter and dry it at a low temperature. (How much crystallized sodium carbonate is needed for the decomposition of 10 grams of crystallized magnesium sulphate?) Notice that the dried precipitate evolves carbon dioxide when heated with acids. Magnesium oxide, Magnesia, MgO = 40 (Calcined magnesia, Light magnesia), is obtained by heating light magnesium carbonate in a crucible to a full red heat, when all carbon dioxide and water are expelled: 4(MgC03).Mg20H.5H20 = 5MgO + 4C02 + 6H20. It is a very light, amorphous, white, almost tasteless powder, which absorbs moisture and carbon dioxide gradually from the air; in contact with water it forms the hydroxide Mg20H, which is very sparingly soluble in water. Milk of magnesia is the hydroxide suspended in water (1 part in about 15). The heavy magnesia of the U. S. P. differs from the common or light magnesia, not in its chemical composition, but merely in its physical condition, being a white, dense powder obtained by heating the heavy magnesium carbonate. Experiment 22. Place 1 gram of magnesium carbonate, obtained in perform- ing Experiment 21, into a weighed crucible and heat to redness, or until by further heating no more loss in weight ensues. Treat the residue with dilute hydrochloric acid and notice that no evolution of carbon dioxide takes place. What is the calculated loss in weight of magnesium carbonate when converted into oxide, and how does this correspond with the actual loss determined by the experiment ? Magnesium sulphate, Magnesii sulphas, MgS04.7H20 = 246 {Sulphate of Magnesium, Epsom salt), is obtained from spring waters, from the mineral Kieserite, MgS04.H2(), and by decom- position of the native carbonate by sulphuric acid : MgC03 + H2S04 = MgS04 + C02 + H20. . It forms colorless crystals, which have a cooling, saline, and bitter taste, a neutral reaction, and are easily soluble in water. magnesium. 151 Magnesium sulphite, Magnesii sulphis, MgS036H20 = 212, may be obtained by adding sulphurous acid to magnesium carbonate: MgC03 + H.2S03 = MgS03 + C02 + H,0. Analytical reactions. (Magnesium sulphate, MgS04, may be used.) 1. Add to a magnesium solution potassium or sodium carbon- ate and heat: a white precipitate of basic magnesium carbonate, 4MgC03.Mg20H, is produced. 2. Add to a magnesium solution ammonium carbonate (or ammonium hydroxide): part of the magnesium will be precipi- tated as carbonate (or hydroxide). These precipitates, however, are soluble in ammonium chloride and many other ammonium salts; if these latter had been added previously to the magnesium solution, ammonium carbonate (or hydroxide) would cause no precipitation. (The dissolving action of the ammonium chloride is due to the tendency of magnesium to form double salts with ammonium salts.) 3. To solution of magnesium add a solution containing sodium phosphate, ammonium chloride, and ammonia: a white crystal- line precipitate of magnesium-ammonium phosphate, MglSriI4P04, is produced, which is somewhat soluble in water, but almost insoluble in water containing some ammonia. 4. Salts of magnesium are white and soluble, except the car- bonate, phosphate, and arseniate; the oxide and hydroxide also are insoluble; the latter is precipitated by sodium or potassium hydroxide. 23. CALCIUM Ca« = 40. General remarks regarding the metals of the alkaline earths. The three metals, calcium, barium, and strontium, form the second group of light metals. Similar to the alkali-metals, they Questions.—211. How is magnesium found in nature? 212. By what pro- cess is metallic magnesium obtained? 213. Grive the physical and chemical properties of magnesium. 214. State two methods by which magnesium oxide can be obtained. 215. What is calcined magnesia? 216. State the composition and properties of the officinal magnesium carbonate, and how it is made. 217. What is Epsom salt, and how is it obtained? 218. Which compounds of mag- nesium are insoluble? 219. Grive tests for magnesium compounds. 220. How can the presence of magnesium be demonstrated in a mixture of magnesium sulphate and sodium sulphate? 152 METALS AND THEIR COMBINATIONS. decompose water at the ordinary temperature with liberation of hydrogen ; their separation in the elementary state is even more difficult than that of the alkali-metals. They differ from the latter by forming insoluble carbonates and phosphates (those of the alkalies are soluble), from the earths by their soluble hydroxides (those of the earths are insoluble), and from all heavy metals by the solubility of their sulphides (those of heavy metals are insoluble). The sulphates are either insoluble (barium) or sparingly soluble (strontium and calcium). The hydroxides and carbonates are decomposed by heat, water or carbon dioxide being expelled and the oxides formed. They are bivalent elements. Occurrence in nature. Calcium is one of the most abundantly oecuring elements. As carbonate (CaC03) it is found in the form of calc-spar, limestone, chalk, marble, shells of eggs and mol- lusca, etc.; or, as acid carbonate, dissolved in water. The sul- phate is found as gypsum or alabaster (CaS042H20); the phos- phate (Ca32P04) in the different phosphatic rocks (apatite, etc.); the fluoride (CaF2) as fluorspar; the chloride (CaCl2) in some waters, and the silicate in many rocks. It enters the vegetable and animal system in various forms of combination, chiefly, how- ever, as phosphate and sulphate. Calcium oxide, Lime, Calx, CaO — 56 (Oxide of Calcium, Quick- lime, Burned lime), is obtained on a large scale by the common process of lime-burning, which is the heating of limestone or any other calcium carbonate to about 800° C. (1472° F.), in the so-called lime-kilns. On a small scale decomposition may be accomplished in a suitable crucible over a blowpipe flame: CaC03 = CaO + C02. The pieces of oxide thus formed retain the shape and size of the carbonate used for decomposition. Lime is a white, odorless, amorphous, infusible substance, of alkaline taste and reaction; exposed to the air it gradually ab- sorbs moisture and carbon dioxide, the mixture thus formed being known as air-slaked lime. Lime occupies among bases a position similar to that of sul- phuric acid among acids, and is used directly or indirectly in many branches of chemical manufacture. CALCIUM. 153 Calcium hydroxide, Calcium hydrate, Ca20H {Slaked lime). AV hen water is sprinkled upon pieces of calcium oxide, the two sub- stances combine chemically, liberating much heat; the pieces swell up, and are converted gradually into a dry, white powder, which is the slaked lime. When this is mixed with water, the so- called milk of lime is formed. Lime-water, Liquor ealcis. This is a saturated solution ot cal- cium hydroxide in water: 10,000 parts of the latter dissolving about 15 parts of hydroxide. In making lime-water, 1 part of calcium oxide is slaked and stirred for about half an hour with 30 parts of water. The mixture is then allowed to settle, and the liquid, containing besides calcium hydroxide the salts of the alkali-metals which may have been present in the lime, is decanted and thrown away. To the calcium hydroxide left, and thus purified, 300 parts of water are added and occasionally shaken in a well-stoppered bottle, from which the clear liquid may be poured off for use. Lime-water is a colorless, odorless liquid, having a feebly caustic taste, and an alkaline reaction. When heated to boiling it becomes turbid by precipitation of calcium hydroxide (or per- haps dioxide). Carbon dioxide causes a precipitation of calcium carbonate. Experiment 23. Make lime-water according to directions given above. Calcium carbonate, Calcii carbonas praecipitatus, CaC03=100 {Carbonate of calcium). Precipitated calcium carbonate is obtained as a white, tasteless, neutral, impalpable powder by mixing solu- tions of calcium chloride and sodium carbonate : CaCl2 + Na2C03 = 2NaCl + CaC03. Experiment 24. Add to about 10 grams of marble (calcium carbonate) in small pieces, hydrochloric acid as long as effervescence takes place ; filter the solution of calcium chloride thus obtained and add to it solution of sodium carbonate as long as a precipitate is formed, collect the precipitate on a filter, wash and dry it. Calcium sulphate, CaS04 = 136 (Anhydrous sulphate of calcium,, Plaster-of-Paris, Calcined plaster). It has been mentioned above, that the mineral gypsum is native calcium sulphate in combination with 2 molecules of water of crystallization. By heating to about 115° C. (239° F.) this water is expelled, and the anhydrous sul- phate formed. It readily recombines with water, becoming a hard mass, for which reason it is used for making moulds and 154 METALS AND THEIR COMBINATIONS. casts, and in surgery. For the latter purpose plaster is often mixed with alum and gelatine before adding the water, this mix- ture being preferred on account of forming a harder, less porous mass, with a smooth surface that can be washed with water con- taining disinfecting agents. Tricalcium phosphate, Calcii phosphas praecipitatus, Ca32P04 = 310 (Precipitated phosphate of calcium, Phosphate of lime, Bone-phosphate). By dissolving bone-ash (bones from which all organic matter has been expelled by heat) in hydrochloric acid, and precipitating the solution with ammonia water there is obtained calcium phosphate, which contains traces of calcium fluoride aud magnesium phos- phate. A pure article is made by precipitating a solution of calcium chloride by sodium phosphate and ammonia : It is a white, tasteless, amorphous powder, insoluble in water, soluble in all acids. 2Na2HP04 + 3CaCl2 + 2NH4OH = Ca32P04 + 4NaCl + 2NH4C1 + 211,0. Superphosphate, or acid phosphate of lime. Among the inorganic substances which serve as plant-food, calcium phosphate is a highly important one. As this compound is found usually in very small quantities as a constituent of the soil, and as this small quantity is soon removed by the various crops taken from a cultivated soil, it becomes necessary to replace it in order to enable the plant to grow and to form seeds. For this purpose the various phosphatic rocks (chiefly calcium phosphate) are converted into commercial fertilizers, which is accomplished by the addition of sulphuric acid to the ground rock. The sulphuric acid removes from the tri- calcium phosphate one or two atoms of calcium, forming mono- or dicalcium phosphate and calcium sulphate. The mixture of these substances, containing also more or less of the impurities originally present in the phosphatic rocks, is sold as acid phosphate or superphosphate. Bone-black and bone-ash. Phosphates enter the animal system in the various kinds of food, and are to be found in every tissue and fluid, but most abundantly in the bones and teeth. Bones contain about 30 per cent, of organic and 70 per cent, of inor- ganic matter, most of which is tricalcium phosphate. When bones are burned until all the organic matter has been destroyed and volatilized, the resulting product is known as bone-ash. If, however, the bones are subjected to the process of destructive distillation (heating with exclusion of air), the organic matter suffers decomposition, many volatile products escape, and most CALCIUM. 155 of the non-volatile carbon remains mixed with the inorganic portion of the bones, which substance is known as bone-black or animal charcoal. Calcium hypophosphite, Calcii hypophosphis, Ca2(PH202) = 170. Obtained by heating pieces of phosphorus with milk of lime until phosphoretted hydrogen ceases to escape. From the filtered liquid the excess of lime is removed by carbon dioxide, and the clear liquid evaporated to dryness. (Great care must be taken during the whole of the operation, which is somewhat dangerous on account of the inflammable and explosive nature of the compounds.) Calcium chloride, Calcii chloridum, CaCl2= 110.8, and Calcium bromide, Calcii bromidum, CaBr2 = 199.6, may both be obtained by dissolving calcium carbonate in hydrochloric acid or hydro- bromic acid, until the acids are neutralized. Both salts are highly deliquescent. 8P + 6H,0 -f 8(Ca20H) = 3(Ca2PH202) + 2PHS. Chlorinated lime, Calx chlorata (Bleaching-'powder, incorrectly called Chloride of lime). This is chiefly a mixture (according to some, a compound) of calcium chloride with calcium hypo- chlorite, and is manufactured on a very large scale by the action of chlorine upon calcium hydroxide: 2(Ca20H) + 4C1 = 2H20 + Ca2C10 + CaCl2. Bleaching-powder is a white powder, having a feeble chlorine- like odor; exposed to the air it becomes damp from absorption of moisture, undergoing decomposition at the same time; with dilute acids it evolves chlorine gas; it is a powerful disinfecting and bleaching agent. Calcium hydroxide. Chlorinated lime. Sulphuretted lime, Calx sulphurata, is a mixture of calcium sulphide and sulphate, obtained by heating in a crucible a mix- ture of equal parts of sulphur and calcium oxide. Analytical reactions. (Calcium chloride, CaCl2, may be used.) 1. Add to solution of a calcium salt, the carbonate of either potassium, sodium, or ammonium : a white precipitate of calcium corbonate, CaC03, is produced. 156 METALS AND THEIR COMBINATIONS. 2. Add sodium phosphate to neutral solution of calcium: a white precipitate of calcium phosphate is produced. 3. Add ammonium (or potassium) oxalate to a calcium solu- tion : a white precipitate of calcium oxalate, CaC204,is produced, which is insoluble in acetic, soluble in hydrochloric acid. 4. Sulphuric acid or soluble sulphates produce a white pre- cipitate of calcium sulphate, CaS04, in concentrated, but not in dilute solutions of calcium. 5. Calcium compounds impart a reddish-yellow color to the flame. Barium, Bau = 136.8. Strontium, Sr11 = 87.4. Both metals are but rarely met with in nature. Barium occurs chiefly as sulphate or heavy-spar, BaS04, and strontium as sulphate or carbonate. From the native sulphates the other salts may be made by first converting them into sulphides, by heating with charcoal in crucibles: BaS04 + 4C = BaS + 4C0. When the sulphide is dissolved in hydrochloric acid, barium chloride is formed and sulphuretted hydrogen liberated: BaS + 211 Cl = H2S + BaCl2. By precipitating the barium chloride solution with sodium carbonate, barium carbonate is obtained : BaCl2 + Na2C03 = 2NaCl + BaC03. By dissolving barium carbonate in the various acids the cor- responding salts are obtained. For instance : Strontium compounds may be made by an analogous process. Neither barium nor strontium enters into any officinal prepara- tion. Strontium is chiefly used in the form of nitrate for pyro- technical purposes, as it imparts a beautiful red or crimson color to the flame. Barium is chiefly used as sulphate for adulterating white-lead and other colors, or as chloride or nitrate as reagents for sul- phuric acid and soluble sulphates. Barium salts are poisonous; antidotes are sodium and magne- sium sulphates. BaC03 = 2HN03 = H20 + C02 + Ba2N03. ALUMINIUM. 157 Analytical reactions of barium and strontium. (The chloride or nitrate may be used.) 1. Like calcium solutions, those of barium and strontium give a white precipitate with soluble carbonates, phosphates, and oxa- lates. 2. Barium gives with potassium chromate, or with potassium dichromate, a pale yellow precipitate of barium chromate, BaCr04,which is insoluble in acetic acid; calcium is not precipi- tated by this agent, strontium is precipitated slowly by the normal chromate, but not by the dichromate. 3. Barium and strontium solutions are precipitated by solution of calcium sulphate; calcium solutions are not. 4. Barium gives with sulphuric acid, or with soluble sulphates, an immediate white precipitate of barium sulphate, BaS04, which is entirely insoluble in all acids; strontium sulphate is less insol- uble, and calcium sulphate may be completely dissolved in water or in dilute hydrochloric acid. 5. Barium colors the flame pale-green, strontium crimson, cal- cium reddish-yellow. 6. Barium, strontium, and calcium compounds are colorless, unless the acid has a coloring effect. 24. ALUMINIUM. Aliii 27.4. Aluminium is the representative of the metals of the earths proper; all other members of this class are found in nature in very small quantities, and are chiefly of scientific interest only. Questions.—221. Which metals form the group of the alkaline earths, and in what respect do their compounds differ from those of the alkali-metals? 222. How is calcium found in nature? 223. What is burned lime; from what, and by what process is it made, and how does water act on it? 224. What is lime- water ; how is it made, and what are its properties? 225. Mention some varie- ties of calcium carbonate as found in nature, and how is it obtained by an artificial process from the chloride? 226. What is plaster-of-Paris, and what is gypsum; what are they used for? 227. State composition and mode of manufacturing bleaching-powder; what are its properties, and how do acids act upon it? 228. What is bone-black, bone-ash, acid phosphate, and precipi- tated tricalcium phosphate? How are they made? 229. Give tests for barium, calcium, and strontium ; how can they be distinguished from each other? 230. Which compounds of barium and strontium are of interest, and what are they u sed for ? 158 METALS AND THEIR COMBINATIONS. Occurrence in nature. Aluminium is found almost exclusively in the solid mineral portion of the earth ; rarely more than traces of aluminium compounds are found dissolved in water, and the occurrence of aluminium in either the vegetable or animal organism seems to be purely accidental. By far the largest quantity of aluminium is found in combina- tion with silicic acid in the various silicated rocks forming the greater mass of our earth, such as feldspar, slate, basalt, granite, mica, hornblende, etc., or in the various modifications of clay formed by their decomposition. The minerals known as corundum, ruby, sapphire, and emery, are aluminium oxide in a crystallized state, and more or less colored by traces of other substances. Metallic aluminium may be obtained by the decomposition of aluminium chloride by metallic sodium: A12C]6 + 6Na = 6NaCl + '2A1 It is now manufactured by the electrolysis of aluminium and sodium fluoride. Aluminium is an almost silver-white metal of a very low specific gravity (2.6); it is capable of assuming a high polish, and for this reason is used for ornamental articles; it is very strong, yet malleable, and does not change in dry or moist air. Some of the alloys of aluminium are now used in the arts, as, for instance, aluminium-bronze, an alloy resembling gold, and composed of 10 parts of aluminium with 90 of copper. Aluminium is trivalent, and shows, like a number of other ele- ments (iron, chromium, etc.), the peculiarity that the double atom Al2vi acts as a single sexivalent atom. Alum is the general name for a group of isomorphous salts, composed of one molecule of the sulphate of a univalent metal in combination with one molecule of the sulphate of a trivalent metal, combined in crystallizing with 24 molecules of water. The general formula of an alum is consequently Mi2S04,M2iii3S04,24H20, M* represents in this case a univalent, MiU a trivalent metal. Alums known are, for instance : Potassium-aluminium sulphate, Iv2S04, A123S04, 24H20. Ammonium-aluminium sulphate, (NH4)2S04, A123S07, 24H20, Potassium-chromium sulphate, K2S04, Cr23S04, 24H20. Ammonium-ferric sulphate, (NH4)2S04, Fe23S04, 24H20. ALUMINIUM. 159 The officinal alum is the 'potassium-aluminium alum, a white sub- stance crystallizing in large octahedrons, soluble in 10 parts of cold and 0.3 part of boiling water; this solution has an acid reaction and a sweetish astringent taste. Alum is manufactured on a large scale by decomposing certain kinds of aluminium silicates by sulphuric acid, when aluminium sulphate is formed, to the solution of which potassium or ammo- nium sulphate is added, when, on evaporation, potassium or ammonium alum crystallizes. Dried alum, Alumen exsiccatum, K2S04,A123S04 = 516. This is common alum, from which the water of crystallization has been expelled by heating it for several days to a temperature of about 80° C. (176° F.). Aluminium hydroxide, Aluminium hydrate, Aluminii hydras, A1260H = 156. Obtained by adding water of ammonia or solu- tion of sodium carbonate to solution of alum, when aluminium hydroxide is precipitated in the form of a highly gelatinous sub- stance, which, after being well washed, is dried at a temperature not exceeding 40° C. (104° F.). K2S04.A123S04 -f- 6iNH4OH = K2S04 + 3[(NH4)2S04] + A1260H ; K2S04A123S04 + 3Na2COs + 3H20 = K2S04 + 3Aa2S04 + 3C02 + A1260H. The usual decomposition between a soluble carbonate and any soluble salt (provided decomposition takes place at all) is the formation of an insoluble car- bonate ; according to this rule, the addition of a soluble carbonate to alum should produce aluminium carbonate. The basic properties of aluminium oxide, however, are so weak that it is not capable of uniting with so weak an acid as carbonic acid, and it is for this reason that the decomposition takes place as shown by the above formula, with liberation of carbon dioxide, whilst the hydroxide is formed. (Other metals, the oxides of which have weak basic properties, show similar reactions, as, for instance, chromium, and iron in the ferric salts.) The weak basic properties of aluminium are shown also by the fact that alu- minium sulphate, chloride, and nitrate, and even alum itself, have an acid reaction, while the corresponding salts of the alkalies or alkaline earths are neutral. Aluminium hydroxide shows considerable surface-attraction toward many substances, which property is made use of in the art of dyeing, where the hydroxide is used for retaining coloring matter upon the cotton-fibre. Practi- cally this is accomplished by precipitating aluminium hydroxide from solutions containing coloring matter, which latter is carried down and precipitated upon the fibre by the aluminium hydroxide; or by impregnating the articles to be dyed with this compound and placing them in the colored solutions. 160 METALS AND THEIR COMBINATIONS. Experiment 25. Dissolve 10 grams of sodium carbonate in 150 c. c. of water, heat it to boiling, and add to it, with constant stirring, a hot solution, made by dissolving 11 grams of alum in 150 c. c. of water. Wash the precipitate first by decantation, and then upon a filter, until the washings are not rendered turbid by barium chloride. Dry a portion of the precipitate at a low tempera- ture, and use as aluminium hydroxide. Mix a small quantity of the wet pre- cipitate with a decoction of logwood (made by boiling about 0.2 gram of logwood with 50 c. c. of water), agitate for a few minutes, and filter. Notice that the red color of the solution has entirely disappeared, or nearly so, in consequence of the great surface-attraction of the aluminium hydroxide for coloring matter. Aluminium oxide, A1203 —102, is obtained as a white, tasteless powder either by burning the metal or by expelling the water from the hydroxide by heat : Aluminium sulphate, Aluminii sulphas, A123S0418H20 = 666. A white, crystalline powder, soluble in about its weight of water; obtained by dissolving the oxide or hydroxide in sulphuric acid. A1260H = A1203 + 3H20. A1260H + 3H2S04 = A123S04 + 6H20. Aluminium chloride, A12C16 = 267. This compound is of interest on account of being the salt from which the metal was formerly obtained. Most chlorides may be obtained by dissolving the metal, its oxide, hydroxide, or carbonate in hydrochloric acid. Accordingly, aluminium chloride may be obtained in solution : A1260H + 6HC1 = A12C16 + 6H20. On evaporating the solution to dryness, however, and heating the dry mass further with the view of expelling all water, de- composition takes place, hydrochloric acid escapes, and alu- minium oxide is left: A12C)6 + 3H20 = A1203 + 6HC1. Aluminium chloride, consequently, cannot be obtained in a pure state (free from water) by this process, but it may be made by exposing to the action of chlorine a heated mixture of alu- minium oxide and carbon. Neither carbon nor chlorine alone causes any decomposition of the aluminium oxide, but by the united efforts of these two substances decomposition is accom- plished : A1203 + 3C + 6C1 — 3C0 + A12C16. Clay is the name applied to a large class of mineral substances, differing considerably in composition, but possessing in common ALUMINIUM. 161 the two characteristic features of plasticity and the predominance of aluminium silicate in combination with water. The various kinds of clay have been formed in the course of time from such double silicates as feldspar and others, by a process which is partly of a mechan- ical, partly of a chemical nature, and consists chiefly in the disintegration of rocks and a removal of potassium and sodium by the chemical action of carbonic acid, water, and other agents. The various kinds of clay are used in the manufacture of bricks, earthenware, stoneware, porcelain, etc. The process of burning these substances accomplishes the hardening by expelling water which is present in the clay. Pure clay is white ; the red color of the common varieties is due to the presence of ferric oxide. For china or porcelain, clay is used containing silicates of the alkalies which, in burning, melt, causing the production of a more homogeneous mass, while in common earthenware the pores, produced by expelling the moisture, remain unfilled. Glass is similar in composition to the better varieties of porce- lain. All varieties of glass are mixtures of fusible, insoluble silicates, made by fusing silicic acid (white sand) with different metallic oxides or carbonates, the silicic acid combining chemi- cally with the metals. Sodium and calcium are the chief metals in common glass, though potassium, lead, and others also are frequently used. Color is imparted to the glass by the addition of certain metallic oxides, which have a coloring effect, as, for instance, manganese violet, cobalt blue, chromium, green, etc. Ultramarine is a beautiful blue substance, found in nature as the mineral “lapis lazuliwhich was highly valued by artists as a color before the discovery of the artificial process for manufacturing it. Ultramarine is now manufactured on a very large scale by heating a mixture of clay, sodium sulphate and carbonate, sulphur, and charcoal in large crucibles, when decomposition takes place and the beautiful blue compound is obtained. As neither of the substances used in the manufacture has a tendency to form colored compounds, the formation of this blue ultramarine is rather surprising, and the true chemical constitution of it is yet unknown. Ultramarine is insoluble in water and is decomposed by acids with liberation of sulphuretted hydrogen, which shows the presence of sulphide of sodium. A green ultramarine is now also manufactured. Analytical reactions (A solution of alum or of aluminium sulphate, A123S04, may be used.) 1. To solution of an aluminium salt add potassium or sodium hydroxide: a white gelatinous precipitate of aluminium hy- droxide, A1260H, is produced, which is soluble in excess of the alkali. 162 METALS AND THEIR COMBINATIONS. 2. To aluminium solution add ammonium hydroxide: the same precipitate as above is obtained, but it is insoluble in an excess of the reagent. 3. The carbonates of ammonium, sodium, or potassium pro- duce the same precipitate with liberation of carbon dioxide. (See explanation above.) 4. Ammonium sulphide produces the same precipitate with liberation of sulphuretted hydrogen: A12C16 + 3(NH4)2S + 6H20 = A1260H + 6NH4C1 + 3H2S. 5. Sodium phosphate produces a precipitate of aluminium phosphate, soluble in acids. Cerium, Ce = 141. This element occurs in nature chiefly as cerite, but sparingly in a few rare minerals. In its general deportment cerium resembles aluminium. Cerium solutions give with either ammonium sulphide, or ammo- nium and sodium hydroxide, white precipitate of cerium hydroxide, Ce20H. Ammonium oxalate forms a white precipitate of cerous oxalate, CeC2H4, which is the only officinal cerium preparation. Cerium oxalate is a white, granular powder, insoluble in water and alcohol, but soluble in hydrochloric acid. Ex- posed to a red heat it is converted into yellow oxide of cerium. 25. IRON. Fe» = 55.9. Fe.vi = 111.8. General remarks regarding the metals of the iron group. The six metals (Fe, Co, M, Mn, Cr, Zn) belonging to this group are distinguished by forming sulphides (chromium excepted) which are insoluble in water, but soluble in dilute mineral acids; they are, consequently, not precipitated from their neutral or acid solutions by hydrosulphuric acid, but by ammonium sulphide as sulphides (chromium as hydroxide); their oxides, hydroxides, Questions.—231. Mention some varieties of crystallized aluminium oxide found in nature and some silicates containing it. 232. Give the general formula of an alum, and mention some alums. 233. Which alum is officinal, how is it made, what are its properties, and what is it used for? 234. What is dried alum, and how does it differ from common alum? 235. How is aluminium chloride made, and how is the metal obtained from it? 236. State the pro- perties of aluminium. 237. What change takes place when ammonium hy- droxide, and what change when sodium carbonate is added to a solution of alum? 238. What is the composition of earthenware, porcelain, and glass; how and from what materials are they manufactured ? 239. What is ultra- marine? 240. Give tests for aluminium compounds. IRON 163 carbonates, phosphates, and sulphides are insoluble; their chlo- rides, iodides, bromides, sulphates, and nitrates are soluble in water. With the exception of zinc, these metals are magnetic; they decompose water at a red heat, the oxide being formed and hydrogen liberated; in dilute hydrochloric or sulphuric acid, they dissolve with formation of chlorides or sulphates, respectively, and liberation of hydrogen. With the exception of zinc, which is bivalent, the metals of the iron group are bivalent in some compounds, trivalent in others, and form a number of oxides, the higher of which show, in some cases, decided by acid properties, as, for instance, chromic or manganic oxides. The trivalence of the elements mentioned is now assumed to be due to the combining of two quadrivalent atoms of these elements. It is for this reason that we find in ferric, manganic, or chromic compounds always a double atom of these elements exerting a valence of six. The constitution of ferric chloride, Fe2Cl6 and ferric oxide, Fe2Oa, may be graphically represented thus: /Cl Fef Cl I XC1 I /Cl Fe—Cl \C1 /O Fef J>° Fef Occurrence in nature. Among all the heavy metals, iron is both the most useful and the most widely and abundantly dif- fused in nature. It is found, though usually in but small quantities, in nearly all forms of rock, clay, sand, and earth; its presence in these being indicated generally by their color (red, reddish-brown, or yellowish-red), as iron is the most common of all natural, inorganic coloring agents. It is found also, though in small quantities, in plants, and in somewhat larger proportions in the animal system, chiefly in the blood. In the metallic state iron is scarcely ever found, except in the meteorites or metallic masses which fall occasionally upon our earth out of space. The chief compounds of iron found in nature are: Hematite, ferric oxide, Fe203. Magnetic iron ore, ferrous-ferric oxide, Fe0.Fe203. Spathic iron ore, ferrous carbonate, FeC03. Iron pyrites, bisulphide of iron, FeS2. 164 METALS AND THEIR COMBINATIONS. The carbonate and sulphate are found sometimes in spring waters, which, when containing considerable quantities of iron, are called chalybeate waters. Finally, iron is a constituent of some organic substances which are of importance in the animal system. Manufacture of iron. There is no other metal manufactured in such immense quantities as iron, the use of which in thousands of different tools, machines, and appliances is highly character- istic of our present age. Iron is manufactured from the above- named oxides or the carbonate by heating them with coke and limestone in large blast furnaces, which have a somewhat cylin- drical shape, and are constantly fed from above with a mixture of the substances named, while hot air is forced into the furnace through suitable apertures near its hearth. The chemical change which takes place in the upper and less heated part of the furnace is a deoxidation of the iron oxide by the carbon: Fe203 + 3C = 3C0 + 2Fe. The heat necessary for this decomposition and fusion of the reduced iron is produced by the combustion of the fuel, main- tained by the oxygen of the air blown into the furnace. At the same time the lime and other bases combine with the silica con- tained in the ore, forming a fusible glass, called cinder or slag. The iron and slag collect at the bottom of the furnace, where they separate by gravity, and are run off every few hours. Iron thus obtained is known as cast-iron, or gig-iron, and is not pure, but always contains, besides silicon (also sulphur, phos- phorus, and various metals), a quantity of carbon varying from 2 to 5 per cent. It is the quantity of this carbon and its condi- tion which imparts to the different kinds of iron different properties. Steel contains from 0.16 to 2 per cent., wrought- or bar-iron but very small quantities, of carbon. Wrought-iron is made from cast-iron by the process known as puddling, which is a burning-out of the carbon by oxidation, accomplished by agitating the molten mass in the presence of an oxidizing flame. Steel is made either from cast-iron by partially removing the carbon, or from wrought-iron by recombining it with carbon— i.e., by agitating together molten wrought- and cast-iron in proper proportions. IRON 165 Properties. The high position which iron occupies among the useful metals is due to a combination of valuable properties not found in any other metal. Although possessing nearly twice as great a tenacity or strength as any of the other metals commonly used in the metallic state, it is yet one of the lightest, its specific gravity being about 7.7. Though being when cold the least yielding or malleable of the metals in common use, its ductility when heated is such that it admits of being rolled into the thin- nest sheets and drawn into the finest wire, the strength of which is so great that a wire of one-tenth of an inch in diameter is capable of sustaining 700 pounds. Finally, iron is, with the exception of platinum, the least fusible of all the useful metals. Iron is little affected by dry air, but is readily acted upon by moist air, when ferric oxide and ferric hydroxide (rust) are formed. Iron forms two series of compounds, distinguished as ferrous and ferric compounds; in the former, iron is bivalent, in the latter, apparently trivalent, because, as shown above, the double atom exerts a valence of six. Almost all ferrous compounds show a tendency to pass into ferric compounds when exposed to the air, or more readily when treated with oxidizing agents, such as nitric acid, chlorine, etc. As the reactions of iron in ferrous and ferric compounds differ considerably, they must be studied separately. Reduced iron, Ferrum reductum. This is metallic iron, obtained as a very fine, grayish-black powder by passing hydrogen gas (purified and dried by passing it through sulphuric acid) over ferric oxide, heated in a glass tube: Fe203 -f- 6H = 8H20 -(- 2Fe, The officinal article should have at least 80 per cent, of metallic iron. Ferrous oxide, FeO (Monoxide or suboxide of iron). This com- pound is little known in the separate state, as it has (like most ferrous compounds) a great tendency to absorb oxygen from the air. The ferrous hydroxide, Fe20H, may be obtained by the addition of any alkaline hydroxide to the solution of any ferrous salt, when a white precipitate is produced which rapidly turns 166 METALS AND THEIR COMBINATIONS. bluish-green, dark gray, black, and finally brown, in consequence of absorption of oxygen (see Plate I., 2): FeS04 + 2NH4OH = (NH4)2S04 + Fe20H ; 2(Fe20H) + O + H20 = Fe260H. The precipitation of ferrous hydroxide is not complete, some iron always remaining in solution. Ferrous oxide is a strong base, uniting with acids to form salts, which have usually a pale-green color. Ferric oxide, Fe203. A reddish-browm powder, which may be obtained by heating ferric hydroxide to expel water: Fe260H = Fe203 + 3H20. It is a feeble base; its salts show’ usually a brown color. Ferric hydroxide, Ferric hydrate, Ferri oxidum hydratum, Fe260H = 213.8 (.Hydrated oxide of iron, Per- or sesqui-oxide, Red oxide of iron), is obtained by precipitation of ferric sulphate or ferric chloride by ammonium or sodium hydroxide (see Plate I., 3): Fe23S04 + 6NH4OH = 3[(NH4)2S04] + Fe./.OH. Precipitation is complete, no iron remaining in solution as in the case of ferrous salts. Ferric hydroxide is a reddish-brown powder, sometimes used as an antidote in arsenic poisoning; for this purpose it is not used in the dry state, but after having been freshly precipitated and washed, it is mixed with water, and this mixture used. Recently precipitated and consequently highly divided ferric hydroxide combines more readily w7ith arsenious acid than the hydroxide which has been kept some time, or which has been dried, and thereby assumed a denser condition. Hydrated oxide of iron with magnesia, U. S. P., is a mixture made by adding magnesia to a solution of ferric sulphate, when magnesium sulphate and ferric hydroxide are formed; the two substances are not separated from each other, the mixture being intended for immediate administration as an antidote in cases of arsenic poisoning. Ferrous-ferric oxide, FeO.Fe203 (Magnetic oxide). This compound, which shows strong magnetic properties, has been mentioned above as one of the iron ores, and is known as loadstone. It has a metallic lustre and iron-black color, and is produced artificially IRON 167 by the combustion of iron in oxygen, or in the hydrated state by the addition of ammonium hydroxide to a mixture of solutions of ferrous and ferric salts. Iron trioxide, Fe03. Xot known in a separate state, but in combination with alkalies. In these compounds, called ferrates, FeOa acts as an acid oxide, analogous to chromium trioxide, Cr03, in chromates. The composition of potassium ferrate is K2Fe04. Ferrous Chloride, FeCl2 (Protochloride of iron), is obtained as a pale-green solution by dissolving iron in hydrochloric acid: B}r evaporation of the solution, the dry salt may be obtained. The solution and salt absorb oxygen very readily: Fe + 2HC1 = FeCl2 + 2H. 3FeC!2 + O = FeO + Fe2Cl6. Ferric chloride, ferrous, and afterward ferric oxide, are formed. Ferric chloride, Ferri chloridum, Fe2Cl6.12H20 = 540.2 (Chloride, sesqui-chloride, or perchloride of iron), is obtained by adding to the solution of ferrous chloride (obtained as mentioned above) hydro- chloric and nitric acids in sufficient quantities, and applying heat until complete oxidation has taken place. The nitric acid oxidizes the hydrogen of the hydrochloric acid to water, while the chlorine combines with the ferrous chloride, nitrogen dioxide being formed also: 6FeCI2 + 2HN03 + 6HC1 = 3Fe2Cl6 + 4H20 + 2^0, By sufficient evaporation of the solution, ferric chloride is obtained as a crystalline mass of an orange-yellow color; it is very deliquescent, has an acid reaction, and a strongly styptic taste. The water of crystallization cannot be expelled by heat, because heat decomposes the salt, free hydrochloric acid and ferric oxide being formed. Experiment 26. Dissolve by the aid of heat 1 gram of fine iron wire in about 4 c.c. of hydrochloric acid, previously diluted with 2 c.c. of water. Filter the warm solution of ferrous chloride, mix it with 2 c.c. of hydrochloric acid and add to it slowly and gradually about 0.6 c.c. of nitric acid. Evaporate in a fume chamber as long as red vapors escape; then test a few drops with potassium ferricyanide, which should not give a blue precipitate ; if it does, the solution has to be heated with a little more nitric acid until the conversion into ferric chloride is complete and the potassium ferricyanide produces no precipitate. 168 METALS AND THEIR COMBINATIONS. Ferric chloride thus obtained may be mixed with 4 c.c. of hot water and set aside, when it forms a solid mass of Fe2Cl6.12H20. How much FeCl2, how much Fe2Cl6, and how much Fe2Cl6.12lI20 can be obtained from 1 gram of iron ? Solution of chloride of iron, Liquor ferri chloridi, U. S. P. This is a solution in water, containing 37.8 per cent, of the anhydrous ferric chloride. It is a reddish-brown liquid of specific gravity 1.405, having the taste and reaction of the dry salt. This solu- tion, mixed with about 2 parts of alcohol and left standing in a closed vessel for several months, forms the tincture of chloride of iron, Tinctura ferri chloridi, U. S. P. Dialyzed iron is an aqueous solution of about 5 per cent, of ferric hydroxide with some ferric chloride. It is made by slowly adding to a solution of ferric chloride, ammonium hydroxide as long as the precipitate of ferric hydroxide formed is redissolved in the ferric chloride solution, on shaking violently. The clear solution thus obtained is placed in a dialyzer floating in water, which latter is renewed every day until it shows no reaction with silver nitrate. The ammonium chloride passes through the membrane of the dialyzer into the water, while all iron as hydroxide with some chloride is left in solution. The combination of an oxide or hydroxide with a normal salt is called usually a basic salt or oxy-salt; dialyzed iron is a highly basic oxychloride of iron. Ferrous iodide, Fel2. When water is poured upon a mixture of metallic iron (tine wire is best) and iodine, the two elements com- bine directly, forming a pale-green solution of ferrous iodide, from which the salt may be obtained by evaporation. As it is oxidized and decomposed easily by the action of the air, an officinal prep- aration, the saccharated iodide of iron, IT. S. P., is made by adding about 30 parts of sugar of milk to 20 parts of ferrous iodide; the sugar prevents, to some extent, rapid oxidation. Experiment 27. Cover some fine iron wire with water, heat gently and add iodine in fragments as long as the red color of iodine disappears. Notice that the iron is dissolved gradually, the result of the reaction being the formation of a pale-green solution of ferrous iodide. Ferrous bromide, FeBr2. Made analogously to ferrous iodide, by the action of bromine on metallic iron. Ferrous sulphide, FeS. Easily obtained as a black, brittle mass, by heating iron tilings with sulphur, when the elements combine. IRON 169 It is used chiefly for liberating hydrosulphuric acid, by the addi- tion of sulphuric acid. Iron combines with sulphur in several proportions; some of these iron sulphides are found in nature. Ferrous sulphate, Ferri sulphas, FeS04.7H20 = 277.9 ( 6). 172 METALS AND THEIR COMBINATIONS. Scale compounds of iron. Quite a number of officinal preparations of iron are made by mixing solution of ferric citrate (obtained by dissolving ferric hydroxide in citric acid) with solutions of other salts, evaporating them to the consistence of thick syrup, spreading this on glass plates, and drying at a low temperature, when the compounds are obtained in the form of thin, translucent scales. While the Ferri phosphas of the U. S. P. of 1870 was the above-mentioned ferrous phosphate, Fe32P04, the Ferri phosphas, phosphate of iron, of the U. S. P. of 1880 is a mixture (or, most likely, double compound) obtained by evapor- ation of a mixture of ferric citrate and sodium phosphate. The ferric pyrophosphate of the U. S. P. is a similar scale compound. Of others may be mentioned : Citrate of iron and ammonium, citrate of iron and quinine, citrate of iron and strychnine, etc. In some cases, tartaric acid is used in place of citric acid, as, for instance, in tartrate of iron and ammonium, tar- trate of iron and potassium, etc. Compounds of iron with organic acids will be more fully considered in connec- tion with the acids themselves. The object of these various scale compounds of iron is, doubtless, to present otherwise insoluble iron compounds in a soluble and convenient form for admin- istration. 26. MANGANESE—CHROMIUM—COBALT—NICKEL. Manganese, Mn = 54. Manganese is found either as dioxide (Black oxide of manganese, pyrolusite), Mu02, or as sesquioxide, Mn203. In small quantities it is a constituent of many minerals. Metallic manganese resembles iron in its physical and chemical properties, and may be obtained by reducing the carbonate with charcoal. Manganese is darker in color than iron, considerably harder, and somewhat more easily oxidized. Oxides of manganese. Four well-defined compounds of man- ganese with oxygen are known in the separate state, and two Questions.—241. Which metals belong to the “ iron group,” and what are their general properties ? 242. How is iron found in nature, and what com- pounds are used in its manufacture? 243. Describe the process for manufac- turing iron on a large scale, and state the difference between cast-iron, wrought-iron, steel, and reduced iron. 244. State the composition and mode of preparation of ferrous and ferric hydroxides. What are their properties ? 245. Describe in words and chemical symbols the process for making ferric chloride. What is tincture of chloride of iron? 246. How are ferrous iodide and bromide made? 247. State the properties of ferrous sulphate. Under what other names is it known, and how is it made? 248. What change takes place when soluble carbonates are added to soluble ferrous and ferric salts? 249. What is the composition of ferrous phosphate, and what is the phosphate of iron, U. S. P. ? 250. Mention tests for ferrous and ferric compounds. MANGANESE — CHROMIUM — COBALT — NICKEL 173 others only in combination with other elements. These oxides are: Manganous oxide (monoxide or protoxide), MnO. Manganous-manganic oxide, MnO.Mn2 03 = Mn304. Manganic oxide (sesquioxide), Mn203. Manganese dioxide (binoxide, peroxide, black oxide), Mn02. Manganic acid, Permanganic acid, Not known in a separate state, Ha0 + Mn03. - H20 + Mn2Or Manganous oxide is a greenish-gray powder, obtainable by heating the carbonate; or as a nearly white hydroxide by precipi- tating a manganous salt by sodium hydroxide. It is a strong base, saturating acids completely, and forming salts which have gener- ally a rose color or a pale reddish tint. Manganese dioxide, Mangani oxidum nigrum, Mn02 = 86. This is by far the most important compound of manganese, as it is largely used for generating chlorine : Mn02 + 4HC1 = MnCl2 + 2H,0 + 2C1. It is a heavy, grayish-black, crystalline mineral, liberating oxygen when heated to redness: 3Mn02 = Mn304 + 20 The officinal article should contain at least 66 per cent, of MnOr Manganous sulphate, Mangani sulphas, MnS04.4H20 = 222, may be obtained by dissolving the oxide or dioxide in sulphuric acid; in the latter case oxygen is evolved: As manganese dioxide generally contains iron oxide, the solu- tion contains sulphates of both metals. By evaporating to dryness and strongly igniting, the iron salt is decomposed. The ignited mass is now lixiviated with water, and the filtered solution evap- orated for crystallization. It is an almost colorless, or pale rose-colored substance, iso- morphous with the sulphates of magnesium and zinc; it is easily soluble in water. Mn02 + H2S04 = MnS04 + H20 + O. Potassium permanganate, Potassii permanganas, K2Mn208 = 314 (.Permanganate of 'potassium). Whenever a compound (any oxide or salt) of manganese is fused with alkaline carbonates (or hydroxides) and alkaline nitrates (or chlorates) the manganese is 174 METALS AND THEIR COMBINATIONS. converted into manganic acid, which combines with the alkali, forming potassium (or sodium) manganate: The fused mass has a dark-green color, and when dissolved in water gives a dark emerald-green solution, from which, by evaporation, green crystals of potassium manganate may be ob- tained. 3Mn02 + 3K2C03 + KC103 = 3K2Mn04 + 3C02 + KC1. The green solution is decomposed easily by any acid (or even by water in large quantity) into a red solution of potassium permanganate and a precipitate of dioxide of manganese: 3K2Mn04 + 2H2S04 = Mn02 + 2K2S04 + K2Mp208 + 2H20, By evaporation and crystallization potassium permanganate is obtained in slender, prismatic crystals, of a deep purple-violet color, and a somewhat metallic lustre. The solution in water has a deep purple, or, when highly diluted, a pink color (Plate II., 1). It is a powerful oxidizing agent, and an excellent dis- infectant, both properties being due to the facility with which a portion of the oxygen is given off to any substance which has aflinity for it. If the oxidation takes place in the absence of an acid, a lower oxide of manganese is formed, which separates as an insoluble substance. If an acid is present, both the potassium and manganese combine with it, forming salts, thus: K2Mn208 + 6HC1 + * = 2KC1 + 2MnCI2 + 3H20 + .r03. x represents here any substance capable of combining with oxygen while in solution. Experiment 28. Heat in a porcelain crucible a mixture of 2 grams manga- nese dioxide, 2 grams potassium hydroxide, and 1 gram potassium chlorate, until the fused mass has turned dark-green. Dissolve the cooled mass with water, filter the green solution of potassium manganate, and pass carbon dioxide through it until it has assumed a purple color, showing that the conversion into permanganate is complete. Notice that the acidified solution is readily decolor- ized by ferrous salts and other deoxidizing agents. Analytical reactions. (Manganese sulphate, MnSO*, may be used.) 1. Ammonium sulphide produces, with manganous salts, a yellowish-pink or flesh-colored precipitate of manganous sulphide, soluble in acetic and in mineral acids (Plate II., 2): MnS04 + (NH4)2S = (NH4)2S04 + MnS. 175 MANGANESE — CHROMIUM — COBALT — NICKEL. 2. Ammonium (or sodium) hydroxide produces a white precipi- tate of manganous hydroxide, which soon darkens by absorption of oxygen (Plate II., 3) and dissolves in oxalic acid with a rose-red color. MnClj, + 2NH4OH = 2NH4C1 + Mn20H. 3. Sodium (or potassium) carbonate produces a nearly white precipitate of manganous carbonate : MnS04 + N»2C03 = i^a2S04 + MnC03 4. Any compound of manganese heated on platinum foil with a mixture of sodium carbonate and nitrate forms a green mass, giving a green solution in water, which turns red on addition of an acid. (See explanation above.) 5. Manganese compounds fused with borax on a platinum wire give a violet coloration to the borax bead. 6. Traces of manganese may be detected by boiling with dilute nitric acid and red lead, when the solution acquires a violet color due to the formation of permanganic acid. Chromium, Cr = 52.4. Found in nature almost exclusively as chromite, or chrome-iron ore, Fe0.Cr203, a mineral analogous in composition to magnetic iron ore, Fe0.Fe203. The name chro- mium, from the Greek xp&w (chroma), color, was given to this metal on account of the beautiful colors of its different com- pounds, none of which is colorless. Chromium forms two basic oxides, CrO and Cr203, and an acid oxide, Cr03, the combina- tions and reactions of which have to be studied separately. While chromium is closely allied to aluminium and iron on one side, it also shows a resemblance to sulphur, as indicated by the trioxide, CrOs, and the acid, II2Cr04, which are analogous to S03 and H2S04. Moreover, the barium and lead salts of chromic and sulphuric acids are both insoluble. Potassium dichromate, Potassii bichromas, K2Cr207 = 294.8 (Bi- chromate or red chromate of 'potassium). This salt is by far the most important of all combinations of chromium, and is the source from which they are obtained. Potassium dichromate is manufactured on a large scale by exposing a mixture of the finely ground chrome-iron ore with potassium carbonate and calcium hydroxide to the heat of an oxi- dizing flame in a reverberatory furnace, when both constituents of the ore become oxidized, ferric oxide and chromic acid being 176 METALS AND THEIR COMBINATIONS. formed, the latter combining with the potassium, forming normal potassium chromate, K2Cr04. By treating the heated mass with water a yellow solution of potassium chromate is obtained, which, upon the addition of sul- phuric acid is decomposed into potassium dichromate and potas- sium sulphate : 2(Fe0Cr203) + 4K2C03 -f 70 = Fe203 + 4C02 + 4(K2Cr04). 2(K2Cr04) + H2S04 = K2Cr20T + K2S04 + H20. The two salts may be separated by crystallization. Potassium dichromate forms large, orange-red, transparent crystals, which are easily soluble in water; heated by itself oxygen is evolved, heated with hydrochloric acid chlorine is liberated, heated with organic matter or reducing agents these are oxidized. To explain the constitution of dichromates we have to assume that chromic anhydride, Cr03, is capable of forming two acids: Cr03 -{- H20 = H2Cr 04 = Chromic acid. 2Cr03 -|~ H20 = H2Cr207 = Dichromic acid. Chromium trioxide, Acidum Chromicum, Cr03 = 100.4 (Chromic acid, Chromic anhydride), is prepared by adding sulphuric acid to a saturated solution of potassium dichromate, when chromium trioxide separates in crystals : Thus prepared, it forms crimson, needle-shaped crystals, which are deliquescent, and very soluble in water; it is powerfully corrosive, and one of the strongest oxidizing agents; the solution in water has strong acid properties; it combines with metallic oxides, forming chromates and dichromates. K2Cr207 + H2S04 = K2S04 + H20 + 2Cr03. Experiment 29. Dissolve a few grams of potassium dicliromate in water and add to 4 volumes of the cold saturated solution 5 volumes of strong sulphuric acid; chromium trioxide separates on cooling. Collect the crystals on asbestos, wash them with a little nitric acid, and dry them by passing warm dry air through a tube in which they have been placed for this purpose. Chromic oxide, Cr203 (Sesquioxide of chromium), is obtained by heating potassium dichromate with sulphur, when potassium sulphate and chromic oxide are formed: By washing the heated mass with water, the chromic oxide is left as a green powder, which is insoluble in water and in acids; it is a basic oxide combining with acids to form salts; it is used K2Cr207 + S = K2S04 + Cr203. fiate IX. MANGANESE. CHROMIUM. Potassium permanganate solu- tion, more or less saturated. Borax, bead colored by manganese. [Page* 174, 175. 1 2 Manganous sulphide precipi- tated from manganous solutions by ammonium sulphide. [PageYH.\ Manganous hydroxide passing into the higher oxides. Manganous solutions precipitated by alkaline hy- droxides. [Page 175.] 3 4 Potassium dichromate solution deoxidized by reducing agents. [Page 177] 5 Chromic hydroxide precipitated from chromic solutions by alkaline hydrates or by ammonium sulphide. [Pages 177, 178.] Lead chromate precipitated from soluble chromates by lead ace- tate. [Pages 177,185,] 6 7 Silver chromate precipitated from neutral chromates by silver ni- trate. [ Pages 178,193 ] 8 Mercurous chromate precipi- tated from neutral chromates by mer- curous solutions. [ Page 178.] MANGANESE — CHROMIUM — COBALT — NICKEL. 177 as a green color, especially in the manufacture of painted glass and porcelain. Chromic hydroxide, Cr260H. A solution of potassium dichro- mate may be deoxidized by the action of hydrosulphuric acid, sulphurous acid, alcohol, or any other deoxidizing agent, in the presence of sulphuric or hydrochloric acid: K2Cr207 + 4H2S04 + 3H2S = K2S04 + 7H20 + 3S + Cr23S04. As shown by this formula, the sulphates of potassium and chromium are formed and remain in solution, while sulphur is precipitated, the hydrogen of the hydrosulphuric acid having been oxidized and converted into water. By adding ammonium hydroxide to the solution thus obtained, chromic hydroxide is precipitated as a bluish-green gelatinous substance : Cr23S04 + 6 N- H4OH = 3[(NH4)2S04] + Gr260H. By dissolving this hydroxide in the different acids, the various salts, such as chloride, Cr2Cl6, sulphate, etc., are obtained. Chromic sulphate, similar to aluminium sulphate, combines with potassium or ammonium sulphate and water, forming chrome alum, K2S04.Cr23S04.24H20; it is a purple salt, and is isomorph- ous with other alums. Analytical reactions a. Of chromic acid or chromates. (Use potassium chromate, K2Cr04 ) 1. Hydrosulphuric acid added to an acidified solution of a chromate, changes the red color into green with precipitation of sulphur. The solution now contains chromium in the basic form. (See explanation above.) (Plate II., 4.) The conversion of chromic acid into oxide is more readily accomplished by heating the chromic solution with alcohol and hydrochloric acid; the alcohol is partly oxidized, being converted into aldehyde. 2. Soluble lead salts produce a yellow precipitate of lead chromate (chrome yellow), PbCr04, insoluble in acetic, soluble in hydrochloric acid (Plate II., 6): K2Cr04 + Pb2N03 = PbCr04 + 2K]ST03, 12 178 METALS AND THEIR COMBINATIONS. 3. Barium chloride produces a pale-yellow precipitate of barium chromate, BaCr04: 4. Silver nitrate produces a dark-red precipitate of silver chromate, Ag2Cr04 (Plate II., 8): K2Cr04 + BaCl2 = BaCrO, + 2KC1 2AgNOs + K2Cr04 = 2KN03 + Ag2Cr04. 5. Mercurous nitrate produces a red precipitate of mercurous chromate, Hg2Cr04. b. Of salts of chromium. (Use chrome-alum or chromic chloride, Cr2Cl6.) 6. To chromic chloride or sulphate add ammonium hydroxide or ammonium sulphide: in both cases the green hydroxide of chromium, Cr260H, is precipitated (Plate II., 5): 7. Potassium or sodium hydroxide causes a similar green pre- cipitate of chromic hydroxide, which is soluble in an excess of the reagent, but is reprecipitated on boiling for a few minutes. Cr2Cl6 + 8[(NH4)2S] + 6H20 = 6NH4C1 + 3H2S + Cr60H. c. Of chromium in any form. 8. Compounds of chromium, when mixed with sodium (or potassium) carbonate and nitrate, give, when heated upon plati- num foil, a yellow mass of the alkaline chromate. 9. Compounds of chromium impart a green color to the borax bead. Cobalt and Nickel, Co — 59.1, Ni == 58.5. These two metals show much resemblance to each other in their chemical and physical properties, and occur in nature associated with each other as sulphides or arsenides. Both metals are nearly silver-white ; the salts of cobalt show generally a red, those of nickel a green color. The solutions of both metals give a black pre- cipitate of the respective sulphides on the addition of ammonium sulphide. Ammonium hydroxide produces in solutions of cobalt a blue, in solutions of nickel a green precipitate of the hydroxides, both of which are soluble in an excess of the reagent; potassium or sodium hydroxide produces similar precipi- tates, which are insoluble in an excess. Cobalt is used chiefly when in a state of combination (for coloring glass blue); nickel when in the metallic state. (German silver is an alloy of nickel, copper, and zinc.) Questions.—251. How is manganese found in nature? 252. Mention the different oxides of manganese. What is the binoxide used for? 253. What ZINC 179 27. ZINC. Znii = 64.9. Occurrence in nature. Zinc chiefly is found either as sulphide (zinc-blende), ZnS, or as carbonate (calamine), ZnC03; also it occurs in combination with silicic acid as silicate and with oxygen as the red oxide. Metallic Zinc is obtained by heating in retorts the oxide or car- bonate mixed with charcoal, when decomposition takes place. The liberated metal is vaporized, and distils into suitable re- ceivers, where it solidifies. Zinc is a bluish-white metal, which slowly tarnishes in the air, becoming coated with a film of oxide and carbonate; it has a crystalline structure and is, under ordinary circumstances, brittle; when heated to about 130°-150° C. (260°-302° F.) it is malleable, and may be rolled or hammered without fracture. Zinc thus treated retains this malleability when cold; the sheet-zinc of commerce is thus made. When zinc is further heated to about 200° C. (392° F.), it loses its malleability and becomes so brittle that it may be powdered; at 410° C. (760° F.) it fuses, and at a bright red heat it boils, volatilizes, and, if air be not excluded, burns with a splendid greenish-white light, generating the oxide. Zinc is used by itself in the metallic state or fused together with other metals (German silver and brass contain it); galvan- ized iron is iron coated with metallic zinc. Zinc is a bivalent metal, forming but one oxide and one series of salts, all of which have a white color. Zinc oxide, Zinci oxidum, ZnO = 80.9 (Oxide of zinc, Flores zinci, Zinc-white), may be obtained by burning the metal, but if made for medicinal purposes by heating the carbonate, when carbon dioxide and water escape and the oxide is left: 3(Zn20H).2ZnC03 = 5ZnO + 2C02 + 3H20. is the color of manganese salts, of mangauates, and of permanganates ? 254. How is potassium permanganate made; what are its properties, and what is it used for? 255. Give tests for manganese. 256. State composition and prop- erties of potassium dichromate. 257. How is chromium trioxide made; what are its properties; what is it used for; and under what other name is it known ? 258. By what process may chromium sesquioxide be converted into chromates? 259. What is the composition of the oxide and hydroxide of chromium, and how are they made? 260. Mention tests for chromates and chromium salts. 180 METALS AND THEIR COMBINATIONS. It is a soft, pale-yellowish or nearly white, tasteless powder, in- soluble in water, soluble in acids; when strongly heated it turns yellow, but on cooling resumes the white color. Zinc hydroxide, Zn20H, is obtained by precipitating zinc salts with the hydroxide of sodium or ammonium; the precipitate, however, is soluble in an excess of either of the alkaline hydroxides. Zinc chloride, Zinci chloridum, ZnCl2=135.7 (Chloride of zinc). Made by dissolving zinc or zinc carbonate in hydrochloric acid and evaporating the solution to dryness : Zn + 2H01 = ZnCl2 + 2H. It is met with either as a white, crystalline powder, or in white opaque pieces; it is very deliquescent and easily soluble in water and alcohol; it combines readily with albuminoid substances; it fuses at about 115° C. (239° F.), and is volatilized, with partial decomposition, at a higher temperature. Zinc bromide, Zinci bromidum, ZnBr2 = 224.5 (.Bromide of zinc). Obtained analogously to the chloride by dissolving zinc in hydro- bromic acid: Zn + 2HBr = ZnBr2 + 2H. A white powder, resembling the chloride in its properties. Zinc iodide, Zinci iodidum, Znl2 = 318.1 (.Iodide of zinc). The two elements zinc and iodine combine readily when heated with water; the colorless solution when evaporated to dryness yields a powder whose physical properties resemble those of the chloride. Zinc carbonate, Zinci carbonas prsecipitatus, 2(ZnC03).3(Zn20H) — 546.5 (.Precipitated Carbonate of zinc). Solutions of equal quan- tities of zinc sulphate and sodium carbonate are mixed and boiled, when a white precipitate is formed, which is a mixture of the carbonate and hydroxide of zinc, while carbon dioxide escapes and sodium sulphate remains in solution : 5ZnS04 + 5Na2C03 + 3H20 = 3C02 + 5Na2S04 +2(ZnC08).3(Zn20H). Precipitated zinc carbonate is a white, impalpable powder, odorless and tasteless, insoluble in water, soluble in acids. Zinc sulphate, Zinci sulphas, ZnS04.7H20=286.9 (Sulphate of zinc, White vitriol), is obtained by dissolving zinc in dilute sulphuric acid : H2S04 + a;H20 + Zn = ZaS04 + xR.fi + 2H. ZINC. 181 If zinc be added to strong sulphuric acid, no decomposition takes place : no sufficient explanation has as yet been given for this fact. Zinc sulphate forms small, colorless crystals, which are iso- morphous with magnesium sulphate; it is easily soluble iu water. Experiment 30. Use the liquid obtained when performing Experiment 2, or, if not left, dissolve a few grams of metallic zinc in dilute sulphuric acid, filter the solution, evaporate sufficiently, and set aside for crystallization. Use the zinc sulphate thus obtained for the analytical reactions. State the quantity of dilute sulphuric acid required for dissolving 5 grams of zinc, and the quantity of crys- tallized zinc sulphate which may be obtained. Zinc phosphide, Zinci phosphidum, Zn3P2 = 256.7 (Phosphide of zinc). The twTo elements zinc and phosphorus combine readily when the latter is thrown upon melted zinc, forming a grayish- black powder, or minutely crystalline, friable fragments, having a metallic lustre on the fractured surface. Antidotes. Soluble zinc salts (sulphate, chloride) have a poi- sonous effect. If the poison have not produced vomiting, that should be induced. Milk, white of egg, or, still better, some sub- stance containing tannic acid (with which zinc forms an insoluble compound) should be given. Analytical reactions. (Zinc sulphate, ZnS04, may he used.) 1. Add to solution of a zinc salt ammonium sulphide: a white precipitate of zinc sulphide, ZnS, is produced. (Zinc sulphide is the only white insoluble sulphide.) ZnS04 -f (NH4)2S = (NH4)2S04 + ZnS. 2. Add ammonium, sodium, or potassium hydroxide : a white precipitate of zinc hydroxide, Zn20H, is produced, soluble in excess of the reagent. 3. Soluble carbonates and phosphates give white precipitates in neutral solutions of zinc. 4. Potassium ferrocyanide gives a white precipitate of zinc ferrocyanide. (This test may be used to distinguish compounds of zinc from those of magnesium or aluminium.) 5. Zinc is the only heavy metal whose compounds are all color- less. The oxide, carbonate, phosphate, and ferrocyanide are insoluble; the chloride, nitrate, and sulphate soluble. 182 METALS AND THEIR COMBINATIONS. Cadmium, Cd = 111.8. Found in nature associated (though in very small quantities) with the various ores of zinc, with which metal it has in common a number of physical and chemical properties. Cadmium differs from zinc by forming a yellow sulphide (with hydrosulphuric acid), soluble in diluted acids. Cadmium and its compounds are of little interest here ; the yellow sulphide is used as a pigment, the sulphate and iodide sometimes for medicinal purposes. 28. LEAD-COPPER-BISMUTH. General remarks regarding the metals of the lead group. The six metals belonging to this group (Pb, Cu, Bi, Ag, Hg, and Cd) are distinguished by forming sulphides which are insoluble in water, insoluble in dilute mineral acids, insoluble in ammonium sulphide; consequently they are precipitated from neutral, alka- line, or acid solutions by hydrosulpburic acid or ammonium sulphide. The metals themselves do not decompose water at any tem- perature, and are not acted upon by dilute sulphuric acid; heated with strong sulphuric acid, most of these metals are con- verted into sulphates with liberation of sulphur dioxide; nitric acid converts all of them into nitrates with liberation of nitrogen dioxide. The oxides, iodides, sulphides, carbonates, phosphates, and a few of the chlorides and sulphates of these metals are insoluble ; all the nitrates, and most of the chlorides and sulphates are soluble. In regard to valence, they show no uniformity whatever, silver being univalent, copper, cadmium, and mercury bivalent, bismuth trivalent, and lead either bivalent or quadrivalent. Lead, Pb" = 206.5 [Plumbum). This metal is obtained almost exclusively from the native sulphide of lead, called galena, PbS, by roasting until it is converted into oxide, and smelting this with coke in a blast furnace. Questions.—261. How is zinc found in nature, and by what process is it obtained ? 262. Mention the properties of metallic zinc, and what is it used for ? 263. Mention two processes for making zinc oxide. 264. How does heat act on zinc oxide ? 265. Show by chemical symbols the action of hydrochloric and sulphuric acids on zinc. 266. State the properties of chloride and of sulphate of zinc. 267. What is white vitriol ? 268. Explain the formation of precipitated zinc carbonate, and state its composition. 269. Mention tests for zinc com- pounds. 270. How many pounds of crystallized zinc sulphate may be obtained from 22.63 pounds of metallic zinc ? LEAD — COPPER—BISMUTH. 183 Lead owes its usefulness in the metallic state chiefly to its softness, fusibility, and resistance to acids, which properties are of advantage in using it for tubes or pipes, or in constructing vessels to hold or manufacture sulphuric acid. Lead is a con- stituent of many alloys, as, for instance, of type-metal, solder, britannia metal, shot, etc. Experiment 31. Dissolve 1 gram of lead acetate or lead nitrate in about 200 c.c. of water, suspend in the centre of the solution a piece of metallic zinc and set aside. Notice that metallic lead is deposited slowly upon the zinc in a crys- talline condition, whilst zinc passes into solution, which may be verified by analytical methods. The chemical change taking place is this: Pb2N03 + Zn = Zn2N03 + Pb. The formation of the crystallized lead is called generally a lead-tree Lead oxide, Plumbi oxidum, PbO = 2.22.5 [Oxide of lead, Litharge). Obtained by exposing melted lead to a current of air, when the metal is gradually oxidized with the formation of a yellow powder, known as massicot; at a higher temperature this fuses, forming reddish-yellow crystalline scales, known as litharge; by heating still further in contact with air, a portion of the oxide is converted into dioxide (or peroxide), Pb02, and a red powder is formed, known as red lead (or minium), which probably is a mixture (or combination) of oxide and peroxide of lead, Pb022Pb0. Oxide of lead is used in the manufacture of lead salts, lead plaster, glass, paints, etc. Nitric acid when heated with red lead combines with the oxide, while the dioxide is left as a dark-brown powder, which, on heating with hydrochloric acid, evolves chlorine (similar to manganese dioxide). Lead nitrate, Plumbi nitras, Pb2No3 = 330.5 (Nitrate of lead). Obtained by dissolving the oxide in nitric acid: PbO + 2HN03 — H20 + Pb2NOa Lead nitrate is the only salt of lead (with a mineral acid) which is easily soluble in water; it has a white color, and a sweetish, astringent, and afterward metallic taste. Lead carbonate, Plumbi carbonas, 2(PbC03).Pb20H = 773.5 [Car- bonate of lead, White lead). This compound may be obtained by precipitation of lead nitrate with sodium carbonate, but is manu- factured on a large scale directly from lead, by exposing it to 184 METALS AND THEIR COMBINATIONS. the simultaneous action of air, carbon dioxide, and vapors of acetic acid. The latter combines with the lead, forming a basic acetate, which is converted into the carbonate (almost as soon as produced) by the carbon dioxide present. The action of acetic acid on lead or lead oxide will be con- sidered in connection with acetic acid. Lead carbonate is a heavy, white, insoluble, tasteless powTder; the white-lead of commerce frequently is found adulterated wdth barium sulphate. Lead iodide, Plumbi iodidum, Pbl2 = 459.7 {Iodide of lead). Made by adding solution of potassium iodide to lead nitrate (Plate III., 6): It is a heavy, bright citron-yellow, almost insoluble powder, which may be distinguished from lead chromate by its solubility in ammonium chloride solution on boiling, lead chromate being insoluble in this solution. Pb2NOs + 2KI = 2K]ST()3 + Pbl2. Poisonous properties and antidotes. Compounds of lead are directly poisonous, and it happens, not infrequently, that water passing through leaden pipes or collected in leaden tanks becomes contaminated with lead. Water free from air and salts scarcely acts on lead; but if it contain air, oxide of lead is formed, which is either dissolved by the water or is decomposed by the nitrates or chlorides present in the water, the soluble nitrate or chloride of lead being formed. If the wTater contains carbonates and sulphates, however, these will form insoluble compounds, producing a him or coating over the lead, preventing further contact with the water. Rain water, in consequence of its containing atmospheric constituents, and no sulphates, acts as a solvent on lead pipe; spring and river waters generally do not. Water containing lead will show a dark color on passing hydro- sulphuric acid through it; if the quantity present be very small, the water should be evaporated to or even of its original volume before applying the test. The constant handling of lead compounds is one of the causes of lead poisoning (painters’ colic). As an antidote, magnesium sulphate should be used, which forms with lead an insoluble sul- phate; the purgative action of magnesia is also useful. (In lead LEAD—COPPER—BISMUTH. 185 works workmen often drink water containing a little sulphuric acid. Analytical reactions. (Lead acetate or lead nitrate, Pb2N03, may be used.) 1. To a solution of a lead salt add hydrosulphuric acid or am- monium sulphide: a black precipitate of lead sulphide is pro- duced (Plate III., 1): Pb2NOs + H2S = 2HN03 + PbS. 2. Add sulphuric acid or soluble sulphate : a white precipitate of lead sulphate is formed: 3. Add hydrochloric acid or a soluble chloride : a white pre- cipitate of lead chloride, PbCl2, is produced, which dissolves on heating or on the addition of much water, as lead chloride is not entirely soluble. For the same reason, the' precipitate is not formed when the solutions used are highly dilute. Pb2NOs + Ns2S04 = 2NaN03 + PbS04. 4. Other reagents which give precipitates with lead solutions are: Potassium chromate, j>roducing yellow lead chromate (chrome yellow). (Plate II., 6.) Potassium iodide, producing yellow lead iodide. (Plate III., 6.) Alkaline carbonates, producing white basic lead carbonate. Alkaline phosphates, producing white lead phosphate. Copper, Cu11 = 63.2 (Cuprum). Found in nature sometimes in the metallic state, generally, however, combined with sulphur or oxygen. The commonest copper-ore is Copper pyrites, a double sulphide of copper and iron, CuFeS2 or Cu2S.Fe2S3, having the color and lustre of brass or gold. Other ores are : Copper glance, cuprous sulphide, having a dark-gray color and the composition Cu2S; malachite, a beautiful green mineral, being a carbonate and hydroxide of copper, CuC03.Cu20H. Cuprous and cupric oxide also are found occasionally. Copper is obtained from the oxide by reducing it with coke; sulphides previously are con- verted into oxide by roasting. Copper is the only metal showing a distinct red color; it is so malleable that, of the metals in common use, only gold and silver surpass it in that respect; it is one of the best conductors of heat and electricity, it does not change in dry air, but becomes covered with a him of green subcarbonate when exposed to moist air. 186 METALS AND THEIR COMBINATIONS. Copper frequently is used in the manufacture of alloys, of which the more important are : Brass . Copper. . 64 Zinc. 36 Tin. Nickel. German silver . 51 31 18 Bell-metal . . 78 22 Bronze . 80 4 16 Gun-metal . . 90 10 Copper frequently is alloyed with gold and silver. Copper is a bivalent element, forming two oxides and two series of salts, distinguished as cuprous and cupric compounds; the cuprous salts are here of but little interest. Cupric oxide, CuO (Oxide or monoxide of copper). Heated to red- ness, copper becomes covered with a black scale, which is cupric oxide ; it is obtained also by heating cupric nitrate or carbonate, both compounds being decomposed with formation of the oxide; finally, it may be made by adding sodium or potassium hydroxide to the solution of a cupric salt, when a bulky, pale-blue pre- cipitate of cupric hydroxide, Cu20II,is formed, which, upon boiling, is decomposed into water and cupric oxide, a heavy dark-brown powder (Plate III., 2): CuS04 + 2K0H = K2S04 + CV20H; Cu20H = H20 + CuO. Cuprous oxide, Cu,0 (Red oxide or suboxide of copper). When cupric oxide is heated with metallic copper, charcoal, or organic matter containing this element, the cupric oxide is decomposed, and cuprous oxide is formed. (Excess of carbon or organic matter reduces the oxide to metallic copper.) CuO + Cu = Cu20 ; 2CuO + C = Cu20 + CO. Some organic substances, especially grape-sugar, decompose strong alkaline solutions of cupric sulphate with precipitation of cuprous oxide, which is a red, insoluble powder. Cupric sulphate, Cupri sulphas, CuS04.5H20 = 249.2 (Sulphate of copper, Blue vitrol, Blue-stone). This is the most important com- pound of copper. It is manufactured on a large scale, either from copper pyrites, or by dissolving cupric oxide in sulphuric acid, evaporating and crystallizing the solution : CuO + H2S04 = CuS04 + h2o. LEAD—COPPER — BISMUTH . 187 Cupric sulphate forms large, deep-blue crystals, which are easily soluble in water, and have a nauseous, metallic taste. By heating it to about 230° C. (446° P.) all water of crystallization is expelled, and the anhydrous cupric sulphate formed, which is a nearly white powder. By further heating this is decomposed? sulphuric and sulphurous oxides are evolved, and cupric oxide is left. Experiment 32. Boil about 5 grams of fine copper wire with 15 c.c. of con- centrated sulphuric acid until the action ceases and most of the copper is dissolved. Dilute with about 15 c.c. of hot water, filter, and set aside for crystallization. State the exact quantities of copper and H.2S04 required to make 100 pounds of crystallized cupric sulphate. Cupric carbonate is obtained by the addition of sodium carbonate to solution of cupric sulphate, when a bluish-green precipitate is formed, which is cupric carbonate with hydroxide (Plate III., 4); by dissolving this in the various acids, the different cupric salts are obtained. Ammonio-copper compounds. A number of compounds are known which are either double salts of ammonia and copper, or are derived from ammonium salts and contain copper. Thus, cupric chloride forms with ammonia the compounds : CuG122NTE3, CuC124NH3, and CuCl26iIH3. Cupric sulphate forms in like man- ner, cupro-diammonium sulphate, CuS042NH3, or (N2I16Cu)S04, which is a deep-blue compound capable of forming large crystals (Plate III., 3). It is this formation of soluble ammonio-copper compounds which prevents ammonium hydroxide from precipitating cupric hydroxide from its salts. Poisonous properties and antidotes. The use of copper for culi- nary vessels is frequently the cause of poisoning by this metal. A perfectly clean surface of metallic copper is not affected by any of the substances used in the preparation of food, but as the metal is very apt to become covered with a film of oxide when exposed to the air, and as the oxide is easily dissolved by the combined action of water, carbonic or other acids, such as are found in vinegar, the juice of fruits, or rancid fats, the use of copper for culinary vessels is always dangerous. Actual adultera- tions of food with compounds of copper have been detected. In cases of poisoning by copper the stomach-pump should be 188 METALS AND THEIR COMBINATIONS. used, vomiting induced, and albumin (white of egg) adminis- tered, which forms an insoluble compound with copper. Re- duced iron, or a very dilute solution of potassium ferrocyanide, may be of use as antidotes. Analytical reactions. (Cupric sulphate, CuS04, may be used.) 1. Add to solution of copper, hydrosulphuric acid or ammo- nium sulphide: a black precipitate of cupric sulphide is formed. (Plate III., 1) : 2. Add sodium or potassium hydroxide: a bluish precipitate of cupric hydroxide, Cu20II, is formed, which is converted into dark-brown cupric oxide, CuO, by boiling. (See equation above.) (Plate III., 2.) 3. Add ammonium hydroxide in excess: a dark-blue solution is produced, containing an ammonio-copper compound. (See explanation above.) (Plate III., 3.) 4. Add potassium ferrocyanide: a reddish-brown precipitate of cupric ferrocyanide, Cu2Fe6C]Sr, is obtained. (Plate III., 5.) 5. Add solution of arsenious acid and carefully neutralize with sodium hydroxide: green cupric arsenite is precipitated. (Plate V, 2.) 6. Add sodium or potassium carbonate: green cupric carbonate with hydroxide is precipitated. (Plate III., 4.) 7. Immerse a piece of iron or steel, showing a bright surface, in an acidified solution of copper : the latter is precipitated upon the iron, an equivalent amount of iron passing into solution: CuS04 + H2S = H2S04 + CuS. CuS04 + Fe = FeS04 + Cu. 8. Most compounds of copper color the flame green, cupric chloride blue. 9. Cupric compounds give a blue, cuprous compounds a red borax bead. 10. Cupric salts (when not anhydrous) have mostly a blue or green color: sulphate, nitrate, chloride, and the ammonio- copper compounds are soluble, most other compounds are in- soluble. Bismuth, BiiU = 208. Found in nature chiefly in the metallic state, disseminated, in veins, through various rocks. The extrac- XXX i COPPER. LEAD. BISMUTH. Cuvric sulphide or lead sul- phide precipitated from solutions of copper or lead by hydrosulphuric acid. [ Pages 185,188.] 1 2 Cupric hydroxide passing into cupric oxide. Cupric solutions pre- cipitated by potassium hydroxide and boiling. [Pages 186, 188.] Amnionic - cupric compounds obtained by adding ammonium hy- droxide to cupric solutions. [Pages 187,188.] 3 4 Cupric Carbonate precipitated from cupric solutions by sodium car- bonate. [Page 188.] Cupric ferro-cyanide precipi- tated from cupric solutions by potas- sium ferro-cyanide. [Page 188.] 5 6 head iodide precipitated from lead solutions by soluble iodides. [Pages 184, 185 ] head solutions with soluble chlorides, sulphates or carbonates bismuth solutions with alkaline hy- droxides or carbonates. [Pages 185, 190.] 7 8 Sismuth sulphide precipitated irom solutions of bismuth by hydro- sulphuric acid. [Page 190.] LEAD—COPPER — BISMUTH. 189 tion of the metal is a mere mechanical process, the earthy matter containing it being heated in iron cylinders, and the melted bis- muth collected in suitable receivers. Bismuth is grayish-white, with a pinkish tinge, very brittle, generally showing a distinct crystalline structure. Occasion- ally it is used in alloj’S and in the manufacture of a few medicinal preparations. Bismuth is trivalent, as shown in the chloride, BiCl3, or oxide, Bi203. A characteristic property of this metal is decomposition of the concentrated solution of any of its normal salts by the addition of much water, with the formation and precipitation of so-called oxy-salts or subsalts of bismuth, while some bismuth with a large quantity of acid remains in solution. The true constitution of these subsalts is as yet doubtful, but a comparison of them has led to the assumption of a radical Bis- muthyl, BiO, which behaves like an atom of a univalent metal. The relation between the normal or bismuth salts, and the subsalts or bismuthyl salts, will be shown by the composition of the following compounds: Bismuth chloride, BiOI3. “ bromide, BiBr3. “ iodide, Bil3. ‘l nitrate, Bi3N03. sulphate, Bi23S04. “ carbonate, Bi23C03,) not known. J Bismuthyl chloride, (BiO)Cl. “ bromide, (BiO)Br. “ iodide, (BiO)I. “ nitrate, (BiO)N03, “ sulphate, (Bi0)2S04. “ carbonate, (Bi0)2C03. Bismuthyl nitrate, Subnitrate of bismuth, Bismuthi subnitras, Bi0N03.H.,0 = 304 (Oxynitrate of bismuth). By dissolving metallic bismuth in nitric acid, a solution of bismuth nitrate is obtained, nitrogen dioxide escaping: Bi + 4HN03 = Bi3N03 + NO -(- 2H20. Upon evaporation of the solution, colorless crystals of bismuth nitrate (Bi3]ST03.5II20) are obtained. If, however, the solution (or the dissolved crystals) be poured into a large quantity of water, the salt is decomposed with the formation of bismuthyl nitrate, some bismuth and the larger quantity of nitric acid remaining in solution : 5(Bi3N03) + 8H20 = 4(Bi0N03.H20) + Bi3N03 + 8HN03. As bismuth frequently contains arsenic, tests should be applied for this metal before using the bismuth. 190 METALS AND THEIR COMBINATIONS. Subnitrate of bismuth is a heavy, white, tasteless powder, insoluble in water, soluble in most acids. Experiment 33. Dissolve by the aid of heat about 1 gram of metallic bismuth in a mixture of 2 c.c. of nitric acid and 1 c.c. of water. Evaporate the clear solution to about one-half its volume, in order to remove excess of acid, and pour this solution of normal bismuth nitrate into 100 c.c. of water. Collect the precipitate of bismuthyl nitrate on a filter, wash and dry it. Prove the presence of bismuth in the filtrate by tests mentioned below. Bismuthyl carbonate, Subcarbonate of bismuth, Bismuthi subcar- bonas, (Bi02)C03.H20 (Oxycarbonate of bismuth, Pearl-white). Made by adding sodium carbonate to solution of bismuth nitrate, when the subcarbonate is precipitated, some carbon dioxide escaping: 2(Bi3NO„) + 3Na2C03 -f H20 = 6NaN03 + 2C02 + (Bi0)2C03.H30. A white, or pale yellowish-white powder, resembling the sub- nitrate. It readily loses water and carbon dioxide on heating, when the yellow oxide, Bi203, is left. Bismuthyl iodide, Subiodide of bismuth, BiOf, may be obtained by adding solution of hydriodic acid to freshly precipitated bismuth oxide: Bi203 + 2III = 2BiOI + 1I20. A better method for making the compound is to pour gradu- ally a solution, made by dissolving 95 grams of crystallized normal bismuth nitrate in 125 c.c. of glacial acetic acid, into a solution of 40 grams of potassium iodide and 55 grams of sodium acetate in 2500 c.c. of water. The precipitate, which has a brick-red color, is well washed and dried at 100° (212° F.). The decomposition is this: 2(Bi3N03) + 2H20 + 2KI + 4]STaC2H302 = 2(BiOI) + 4NaN0, + 2KN03 + 4C2H402. Analytical reactions. (Bismuth nitrate, Bi3N03, or bismuth chloride, BiCl3, may be used.) 1. Add to solution of bismuth, hydrosulphuric acid or ammo- nium sulphide: a dark-brown (almost black) precipitate of bis- muth sulphide, Bi2S3, is produced (Plate III., 8): 2BiCl3 + 3H2S = 6HC1 + Bi2S3. 2. Pour a concentrated solution of bismuth into water: a white precipitate of a bismuthyl salt is formed. (See explanation above.) SILVER—MERCURY. 191 3. Add to bismuth solution ammonium or sodium hydroxide, or carbonate : a white precipitate of bismuth hydroxide, Bi30H, or of bismuthyl carbonate is produced. (See explanation above.) 29. SILVER,—MERCURY. Silver, Ag = 107.7 {Argentum). This metal is found sometimes in the metallic state, but generally as a sulphide, which is nearly always in combination with large quantities of lead sulphide, such ore being known as argentiferous galena. The lead manu- factured from this ore contains the silver, and is separated from it by roasting the alloy in a current of air, whereby lead is oxi- dized and converted into litharge, while pure silver is left. Silver is the whitest of all metals, and takes the highest polish; it is the best conductor of heat and electricity, and melts at about 1000° C. (1873° F.); it is univalent, and forms but one series of salts; it is not affected by the oxygen of the air at any tempera- ture, but is readily acted upon by traces of hydrosulphuric acid, which forms a black film of sulphide upon the surface of metallic silver. Hydrochloric acid scarcely acts on silver, nitric and sul- phuric acids dissolve it. Silver is too soft for use as coin or silverware, and, therefore, is alloyed with from 5 to 25 per cent, of copper, which causes it to become harder, and consequently gives it more resistance to the wear and tear by friction. Pure silver may be obtained by dissolving silver coin in nitric acid, when a blue solution, containing the nitrates of copper and silver, is formed. By the addition of sodium chloride to the solu- tion a white precipitate of silver chloride forms, while cupric nitrate remains in solution. The silver chloride is washed, dried, mixed with sodium carbonate, and heated in a crucible, when Questions.—271. What are the properties of lead, and from what ore is it obtained? 272. What is litharge, and how does it differ from red lead? 273. Give the composition of nitrate, carbonate, and iodide of lead; how are they made? 274. State the analytical reactions for lead. 275. How is copper found in nature? 276. How many oxides of copper are known ; what is their compo- sition, and under what conditions are they formed? 277. What is “blue vit- riol how is it made, and what are its properties? 278. How does ammonium hydroxide act on cupric solutions? 279. Mention tests for copper. 280. What is the composition of subnitrate and subcarbonate of bismuth ; how are they made from metallic bismuth, and what explanation is given in regard to their constitution ? 192 METALS AND THEIR COMBINATIONS. sodium chloride is formed, carbon dioxide escapes, and a button of silver is found at the bottom of the crucible : 2AgCl + Na2C03 = 2Na01 + C02 + 2Ag + O. Experiment 34. Dissolve a small silver coin in nitric acid, dilute with water and precipitate the clear liquid with an excess of solution of sodium chloride. The washed precipitate of silver chloride may be treated with sodium carbonate, as stated above, or may be converted into metallic silver by the following method. Place the dry chloride in a small porcelain crucible and apply a gentle heat until the chloride has fused; when cold place a piece of sheet zinc upon the chlo- ride, cover with water, to which a few drops of sulphuric acid have been added, and set aside for a day, when the silver chloride will be found to have been decomposed with liberation of metallic silver and formation of zinc chloride: 2AgCl + Zn = ZnCl, + 2Ag. Wash the spongy silver with dilute sulphuric acid and then with water. Use this silver for making silver nitrate by dissolving it in nitric acid, and evapora- tion of the solution to dryness. Use this solution for silver reactions. Silver nitrate, Argenti nitras, AgN03 = 169.7 {Nitrate of silver). Pure silver is dissolved in nitric acid: 3Ag + 4HN03 = NO + 2H20 + 3AgN03. The solution is evaporated to dryness with the view of expelling all free acid, the dry mass dissolved in hot water and crystallized. If the silver used should contain copper, the latter may be eliminated from the mixture of silver and cupric nitrate by evapo- rating to dryness and fusing, when the latter salt is decomposed, insoluble cupric oxide being formed. The fused mass is dissolved in water, filtered, and again evaporated for crystallization. When fused and poured into suitable moulds it yields the white cylindrical sticks which are usualty known as caustic, lunar caustic, or lapis infernalis. When fused with an equal weight of potassium nitrate and formed into similar rods, it represents the diluted nitrate of silver of the U. S. P. Silver nitrate forms colorless, transparent, tabular, rhombic crystals, or, when fused, a white, hard substance; it is soluble in less than its own weight of water, the solution having a neutral reaction. Exposed to the light, especially in the presence of organic matter, silver nitrate blackens in consequence of decom- position; when brought in contact with animal matter, it is readily decomposed into free nitric acid and metallic silver, which produces the characteristic black stain; it is this decom- SILVER— MERCURY. 193 position, and the action of the free nitric acid, to which the strongly caustic properties of silver nitrate are due. Nitrate of silver is used largely in photography, and also in the manufacture of various kinds of indelible inks and hair-dyes. Silver oxide, Argenti oxidum, Ag20 = 231.4 (Oxide of silver). Made by the addition of an alkaline hydroxide to silver nitrate: 2AgNOs + 2K0H = 2KN0S + H20 + AgaO. A dark-brown, almost black powder, but very sparingly solu- ble in water, imparting to the solution a weak alkaline reaction. It is a strong base, and easily decomposed into silver and oxygen. Silver iodide, Argenti iodidum, Agl = 234.3 (Iodide of silver). Made by the addition of potassium iodide to silver nitrate: AgK03 + KI = KN03 + Agl. A heavy, amorphous, light-yellowish powder, insoluble in water, and but slightly soluble in ammonium hydroxide. Antidotes. Sodium chloride, white of egg, or milk, followed by an emetic. Analytical reactions. (Silver nitrate. AgN03, may be used.) 1. Add to solution of a silver salt, hydrosulphuric acid or ammonium sulphide: a black precipitate of silver sulphide is produced: 2AgN03 + H2S = 2HN03 + Ag2S. 2. Add hydrochloric acid, or any soluble chloride: a white, curdy precipitate of silver chloride is produced, which is insolu- ble in acids, but soluble in ammonium hydroxide: AgN03 + NaCI = NaN03 + AgCl. 3. Add potassium chromate or dichromate: a red precipitate of silver chromate, Ag2Cr04, is formed (Plate II., 7). 4. Add sodium phosphate: a pale-yellow precipitate of silver phosphate, Ag3P04, is formed, which is soluble in ammonia and in nitric acid. 5. Alkaline hydroxides precipitate dark-brown silver oxide. (See above.) 194 METALS AND THEIR COMBINATIONS. 6. Potassium iodide or bromide gives a pale-yellow precipitate. (See above.) 7. Metallic copper, zinc, or iron precipitates metallic silver. Mercury, Hydrargyrum, Hg = 199.7 (Quicksilver). Mercury is found sometimes in small globules in the metallic state, but generally as mercuric sulphide or cinnabar, a dark-red mineral. The chief supply was formerly obtained from Spain and Austria; now, however, large quantities are obtained from California; it also is imported from Peru and Japan. Mercury is obtained from cinnabar either by roasting it, whereby the sulphur is converted into sulphur dioxide, or by heating it with lime, which combines with the sulphur, while the metal volatilizes, and is condensed by passing the vapors through suitable coolers. Mercury is the only metal showing the liquid state at the ordi- nary temperature; it solidifies at —40° C. (—40° F.), and boils at 357° C. (662° F.); but is slightly volatile at all temperatures; it is almost silver-white, and has a bright metallic lustre; its specific gravity is 13.59. Mercury is peculiar in that its molecule contains but one atom, at least when in the state of a gas; in the liquid and solid states it may contain two atoms, like most other elements, but we have as yet no means of proving this fact. Mercury is bivalent, and forms, like copper, two series of com- pounds, distinguished as mercuric and mercurous compounds. In the former, one atom of mercury exerts its bivalence, as in HgO, HgCl2; in the mercurous compounds two atoms of mercury exert the same valence, as in Hg20,Hg2Cl2. We have to explain this fact by assuming that of the four points of attraction, repre- sented by the two atoms of mercury, two are required to hold together or unite these two atoms, so as to leave but two for other elements. Cl XC1 Hg-Cl Hg-Cl Mercuric chloride. Mercurous chloride Mercury is not affected by the oxygen of the air, nor by hydro- chloric acid, while chlorine, bromine, and iodine combine with it directly, and warm sulphuric and nitric acids dissolve it. Mercury is used in the metallic state for many scientific instru- ments (thermometer, barometer, etc.); in the silvering of lookiug- SILVER MERCURY. 195 glasses, which is effected by means of an amalgam of tin (amalgams are alloys in which mercury is one of the constituents); for manufacturing from it all of the various mercury compounds, and those officinal preparations in which mercury exists in the metallic state. These latter preparations are: Mercury with chalk, blue mass or blue pill, mercurial ointment, and mercurial plaster. Mercury exists in a metallic, but highly subdivided state in these preparations, which are made by intimately mixing (triturating) metallic mercury with the different substances used (viz., chalk, pill-mass, fat, lead-plaster). It is most probable that the action of these agents upon the animal system is chiefly due to the conversion of small quantities of mercury into mercurous oxide, which, in contact with the acids of the gastric juice or with perspiration, are converted into soluble compounds capable of being absorbed. Mercurous oxide, Hg20 (Black oxide or suboxide of mercury). An almost black, insoluble powder, made by adding an alkaline hydroxide to a solution of mercurous nitrate: Hg22N03 + 2K0H = 2KN03 + H20 + Hg20. A similar decomposition takes place when alkaline hydroxides are added to insoluble mercurous chloride. A mixture of lime- water and mercurous chloride (calomel) is known as black-wash; when the two substances are mixed, calomel is converted into mercurous oxide, while calcium chloride is formed : Hg2Cl2 + Ca20H = CaCl2 + H20 + Hg20. Mercuric oxide, Oxide of mercury, HgO = 215.7 There are two mercuric oxides which are officinal; they do not differ in their chemical composition, but in their molecular structure. The yellow oxide of mercury, Hydrargyri oxidum flavum, is made by pouring a solution of mercuric chloride into a solution of potassium hydroxide, when an orange-yellow, heavy precipitate is produced, which is washed and dried at a temperature not exceeding 40° C. (104° F.) (Plate IV., 3): HgCl2 + 2K0H = HgO + 2KC1 + H20. The red oxide of mercury, Hydrargyri oxidum rubrum, or red pre- cipitate, is made by heating mercuric nitrate, either by itself or after it has been intimately mixed with an amount of metallic mercury equal to the mercury in the nitrate used (Plate IV., 4). 196 METALS AND THEIR COMBINATIONS. In the first case, nitrous fumes and oxygen are given off, mer- curic oxide remaining : Hg2N03 = HgO + 2N02 + O. In the other case, no oxygen is evolved : Hg2N03 + Hg = 2HgO + 2NOr The red oxide of mercury differs from the yellow oxide in being more compact, and of a crystalline structure; while yellow oxide is in a more finely divided state, and consequently acts more energetically when used in medicine. Yellow oxide, when digested on a water-bath with a strong solution of oxalic acid, is converted into white mercuric oxalate within 15 minutes, while red oxide is not acted upon by oxalic acid under the same conditions. When mercuric chloride is added to lime-water, a mixture is formed holding in suspension a yellow oxychloride of mercury; this mixture is known as yellow-wash. Experiment 35. Heat some mercuric nitrate in a porcelain dish, placed in a fume chamber, until red fumes no longer escape. The remaining red powder is mercuric oxide, which, by further heating, may be decomposed into its elements. Mercurous chloride, Hydrargyrum chloridum mite, Hg2Cl2 = 470.2 (Calomel, Mild chloride of mercury, Subchloride or protochloride of mer- cury). Mercurous chloride, like mercurous oxide, may be made by different processes, but the U. S. P. does not state by which method calomel shall be made, though the precipitated salt is in a finer state of subdivision, and consequently more energetic in its action than the sublimed article. The latter is made either by subliming a mixture of mercuric chloride and mercury : or by thoroughly mixing with mercuric sulphate a quantity of mercury equal to that contained in the sulphate; by this opera- tion mercurous sulphate is obtained, which is mixed with sodium chloride, and sublimed from a suitable apparatus into a large chamber, so that the sublimate may fall in powder to the floor: HgC12 + Hg = Hg2Cl2, HgS04 + Hg + 2NaCl = Na2S04 + Hg2Cl2. Another method for making calomel is precipitation of a solu- ble mercurous salt by any soluble chloride : Hg22N03 + 2NaCl = 2NaN03 + Hg2Cl2. SILVER—MERCURY. 197 Mercurous chloride, made by either process, generally contains traces of mercuric chloride, and should, therefore, be washed with hot water until the washings are no longer acted upon by ammonium sulphide or silver nitrate. Mercurous chloride is a white, impalpable, tasteless powder, insoluble in water and alcohol; it volatilizes without fusing pre- viously; when given internally, it should not be mixed with either mineral acids, alkaline bromides, iodides, hydroxides, or carbonates, all of which have a decomposing action upon this salt. Mercuric chloride, Hydrargyri chloridum corrosivum, HgCl2 = 270.5 (Corrosive chloride of mercury, Corrosive sublimate, Perchloride or bichloride of mercury). Made by thoroughly mixing mercuric sulphate with sodium chloride, and subliming the mixture, when mercuric chloride is formed, and passes off in white fumes, which are condensed in the cooler part of the apparatus, while sodium sulphate is left: HgS04 + 2NaCl = Na2S04 + HgCl2. Mercuric chloride is a heavy, white powder, or occurs in heavy, colorless, rhombic crystals or crystalline masses; it is soluble in 16 parts of cold and 2 parts of boiling water, in about 2 parts of alcohol, and in 4 parts of ether; when heated, it fuses and is volatilized; it has an acrid, metallic taste, an acid reac- tion, and strongly poisonous and antiseptic properties. Mercurous iodide, Hydrargyri iodidum viride, Hg2I2 = 652.6 (Green iodide or protiodide of mercury). Both iodides of mercury may be obtained either by rubbing together mercury and iodine in the proportions represented by the respective atomic weights, or by precipitation of soluble mercurous or mercuric salts by potassium iodide. According to the U. S. P., mercurous iodide is made by triturating 8 parts of mercury with 5 of iodine (and a little alcohol) until all globules of mercury have disappeared and a green powder has been formed, which is washed with alcohol in order to eliminate small quantities of mercuric iodide which may have been formed : 2Hg + 21 = Hg2I2. 198 METALS AND THEIR COMBINATIONS. The powder finally is collected and dried between paper at a low temperature. During the whole operation light should be excluded as much as possible, as it decomposes the compound. Mercurous iodide is a dull-green to greenish-yellow, tasteless powder, insoluble in water, alcohol, and ether. It is easily de- composed into mercuric iodide and mercury (Plate IV., 5). Mercuric iodide, Hydrargyri iodidum rubrum, Hgl2 = 452.9 (.Red iodide or biniodide of mercury). Made by mixing solutions of po- tassium iodide and mercuric chloride, when a yellow precipi- tate is formed, turning red immediately (Plate IV., 6): HgCl2 + 2KI = 2KC1 + HgT2. Mercuric iodide is soluble both in solution of potassium iodide and mercuric chloride, for which reason an excess of either substance will cause a loss of the salt when prepared. It is a scarlet-red, crystalline, tasteless powder, almost insoluble in water and but slightly soluble in alcohol; on heating or subliming it turns yellow in consequence of a molecular change which takes place; on cooling, and, more quickly, on pressing or rubbing the yellow powder, it reassumes the original condition and the red color. Mercuric sulphate, HgS04. When mercury is heated with strong sulphuric acid (the presence of nitric acid facilitates the forma- tion) chemical action takes place between the two substances, sulphur dioxide being liberated and mercuric sulphate formed, which is obtained as a heavy, white, crystalline powder : Hg + 2H2S04 = HgS04 + 2H20 + S02. Yellow subsulphate of mercury, Hydrargyri subsulphas flavus, HgS04.2Hg0 = 727.1 (Basic mercuric sulphate, Turpeth mineral, Mer- curic oxy-sulphate). When mercuric sulphate, prepared as directed above, is thrown into boiling water, it is decomposed into an acid salt which remains in solution, and a basic salt which is precipitated. As shown by its composition, HgS04.2Hg0, it may be looked upon as mercuric sulphate in combination with mercuric oxide. It is a heavy, lemon-yellow, tasteless, insoluble powder. Mercurous sulphate, IIg2S04. When mercuric sulphate is trit- urated with a sufficient quantity of mercury, direct combination takes place, and the mercurous salt is formed : IIgS04 + Hg = Hg2S04. SILVER— MERCURY. 199 Nitrates of mercury. Mercurous nitrate, IIg22H03, and Mercuric nitrate, IIg2V03, may both be obtained as white salts by dis- solving mercury in nitric acid. The relative quantities of the two substances present determine whether mercurous or mercuric nitrate be formed. If mercury is present in excess the mercurous salt, if nitric acid is present in excess the mercuric salt is formed, the latter especially on heating. Both salts are white and soluble in water. Experiment 36. Heat gently a small globule (about 1 gram) of mercury with 2 c.c. of nitric acid until red fumes cease to escape. If some of the mercury remains undissolved, the solution will deposit crystals of mercurous nitrate on cooling. Use some of the solution, after being diluted with much water, for mercurous tests. Use another portion as follows: Heat the solution, or some of the crystals, with about an equal weight of nitric acid until no more red fumes escape. Add to a few drops of the diluted liquid a little hydrochloric acid, which, if the conversion of the mercurous into mercuric salt has been complete, will give no precipitate. If, however, one should be formed, the solution has to be heated with more nitric acid until no longer a precipitate is formed by hydrochloric acid, when the solution is evaporated and set aside for crystal- lization. The respective changes may be represented by the following equations: 6Hg + 8HN03 = 3Hg22NOs + 4H20 + 2N0; 3Hg22N 03 + 8HNO3 = 6Hg2N03 + 4H20 + 2N0. Mercuric sulphide, HgS = 231.7. This compound has been mentioned as the chief ore of mercury, occurring crystallized as cinnabar, which has a red color (Plate IV., 2). The same com- pound may,however, be obtained bypassing hydrosulphuric acid gas through mercuric solutions, when at first a white precipitate is formed (a double compound of the sulphide of mercury in combination with the mercuric salt), which soon turns black (Plate IV., 1): HgCl2 + H2S = 2HC1 + HgS. The black, amorphous, mercuric sulphide may be converted into the red, crystallized variety by sublimation, and is then the officinal preparation known as red sulphide of mercury, Hydrargyri sidphidum rubrum, cinnabar, or vermilion. It forms brilliant, dark- red, crystalline masses, or a fine, bright, scarlet powder, which is insoluble in water, hydrochloric or nitric acid, but soluble in nitro-hydrochloric acid. Mercuric and mercurous sulphides may be made also by tritu- rating the elements mercury and sulphur in the proper propor- tions, when they combine directly. 200 METALS AND THEIR COMBINATIONS. Ammoniated mercury, Hydrargyrum ammoniatum, NH2HgCl = 251.1 (White precipitate, Mercur ammonium chloride). This com- pound is made by pouring solution of mercuric chloride into water of ammonia, when a white precipitate falls, which is washed with highly diluted ammonia water and dried at a low temperature: As shown by the composition of this compound, it may be regarded as ammonium chloride, ETI4C], in which two atoms of hydrogen have been replaced by one atom of the bivalent mercury. (There are many compounds known in which metallic atoms replace hydrogen in salts of ammonium; the ammonium copper compounds belong to this group of substances.) HgCl2 + 2NH4OH = NH2HgCl + NH4CI + 2H20. Ammoniated mercury is a white, tasteless, insoluble powder. Analytical reactions. Mercurous sails. (Mercurous nitrate, Hg22N03, may be used.) Mercuric salts. (Mercuric chloride, HgCl2, may be used.) 1. Hydrosulphuric acid, or ammo- nium sulphide. Black precipitate of mercurous sulphide: IIg22N03 + H„S = 2HK03 + Hg2S. Black precipitate of mercuric sulphide. (Precipitate may be white or gray, with an insufficient quantity of the reagent.) (See above.) (Plate IV., 1.) 2. Potassium iodide Green precipitate of mercurous iodide (Plate I.V, 7) : Hg22N03 + 2KI = 2KN03 + Hg2T2. Red precipitate of [mercuric iodide. ((See above.) (Plate IV, 6.)' 3. Potassium or so- dium hydroxide. Dark-brown precipitate of mer- curous exide, Hg20 (Plate IV., 5). Yellow precipitate of mercuric oxide, HgO. (See above.) (Plate IV, 3.) 4. Ammonium hy- droxide. Black precipitate of mercurous ammonium salt is formed. (The insoluble white calomel is converted into a black pow- der.) White precipitate of a mercuric ammonium salt is formed. (See explanation above.) 5. Potassium or so- dium carbonate. Yellowish precipitate of mer- curous carbonate, which is ! unstable. Brownish-red precipitate of mercuric carbonate; unstable 6. Hydrochloric acid or soluble chlorides. White precipitate of mercurous chloride is produced: Hg22N03 + 2HC1 = 2HN03 + Hg2Cl2 No change. MERCURY. SILVER. zFXjjs-TiE x^r. Mercuric sulphide precipitated from mercuric solutions by hydrosul- phuric acid [Pages 199, 200.] 1 2 Mercuric sulphide, Cinnabar. [Page 199.1 Yellow mercuric oxide precipi- tated from mercuric solutions by po- tassium hydroxide. {Pages 195, 200.] 3 4 Red mercuric oxide obtained by heating mercuric nitrate. [Page 195.] Mercurous oxide precipitated from mercurous solutions by potas- sium hydroxide. [Pages 195, 200.] Silver Sulph ide precipitated from silver solutions by hydrosulphuric acid. [Page 193 ] 5 6 Mercuric iodide precipitated from mercuric solutions by alkali iodides. [Pages 198, 200.] Mercurous iodide precipitated from mercurous solutions by alkali iodides. [Pages 198, 200.] 7 8 Mercuric solutions with ammo- nium hydroxide. [Page 200.] Mer- curous solutions with soluble chlor- ides. [Page 200.] Silver solutions with soluble chlorides. [Page 193.] SILVER—MERCURY. 201 7. Stannous chloride produces, in solutions of mercury, a white precipitate, which turns dark-gray on heating with an excess of the reagent. The reaction is due to the strong reduc- ing or deoxidizing property of the stannous chloride, which itself is converted into stannic chloride, while the mercury salt is first converted into a mercurous salt and afterward into metallic mercury: 2HgCl, + SnCl, = Hg„CL + SnCl4; Hg2Cl2 + SnC)2 - 2Hg + SnCl4. 8. Dry mercury compounds, when mixed with sodium car- bonate and potassium cyanide, and heated in a narrow test-tube, are decomposed with liberation of metallic mercury, which con- denses in small globules in the cooler part of the tube. 9. A piece of bright metallic copper, when placed in a slightly acid mercury solution (which must not contain any free nitric acid) becomes coated with a dark film of metallic mercury in a fine state of division. The mercury may be separated by placing the copper (after having been washed with water and dried at a very gentle heat) in a narrow test-tube and heating to redness, when the mercury is volatilized and deposited in the cooler part of the tube. 10. All compounds of mercury are completely volatilized by heat, either with or without decomposition. Antidotes. Albumin (white of egg), of which, however, not too much should be given at one time, lest the precipitate formed by the mercuric salt and albumin be redissolved. The antidote should be followed by an emetic to remove the albu- minous mercury compound. Questions.—281. How is silver obtained from the native ores, and how may it be prepared from silver coin ? 282. State of silver nitrate: its composition, mode of preparation, properties, and names by which it is known. 283. Give analytical reactions for silver. 284. How is mercury found in nature; how is it obtained from the native ore; what are its physical and chemical properties ? 285. Mention the three oxides of mercury; how are they made, what is their composition, what is their color and solubility? 286. State of the two chlorides of mercury: their names, composition, mode of preparation, solubility, color, and other properties. 287. Mention the same of the two iodides, as above, for the chlorides. 288. State the difference between mercuric sulphate, basic mer- curic sulphate, and mercurous sulphate. 289. What is formed when ammonium hydroxide, calcium hydroxide, potassium or sodium hydroxide is added to either mercurous or mercuric chloride ? 290. Give tests answering for any mercury compound, and tests by which mercuric compounds may be distinguished from mercurous compounds. 202 METALS AND THEIR COMBINATIONS. 30. ARSENIC. As = 74.9. General remarks regarding the metals of the arsenic group. The metals belonging to either of the five groups considered hereto- fore, show much resemblance to each other in their chemical properties, and consequently in their combinations. This is much less the case among the six metals (As, Sb, Sn, Au.Pt, Mo) which are classed together in this group. In fact, the onty re- semblance which unites these metals is the insolubility of their sulphides in dilute acids and the solubility of these sulphides in ammonium sulphide (or alkaline hydroxides), with which they form soluble double compounds; the oxides have also a tendency to form acids. In all other respects no general resemblance exists between these metals. Arsenic and antimony have many properties in common, and resemble in many respects the non- metal lie elements phosphorus and nitrogen, as may be shown by a comparison of their hydrides, oxides, acids, and chlorides: NH„ PHg AsHg SbHg N2Og P203 AS.O. Sb.Og N,0, PA As205 Sb205 HgPO, Hs A.s04 ]STCL. PC13. AsClg. SbClg. Arsenic. Found in nature sometimes in the native state, but generally as sulphide or arsenide. One of the most common arsenic ores is the arsenio-sulphide of iron, or mispickel, FeSAs. Realgar is the native red sulphide, As2S2, and orpiment or auripig- ment, the native yellow sulphide, As2S3. Arsenides of cobalt, nickel, and other metals are not infrequently met with in nature. Certain mineral waters contain traces of arsenic compounds. Arsenic may be obtained easily b}7 heating arsenious oxide with charcoal, or by allowing vapors of arsenious oxide to pass over charcoal heated to redness : A?203 -f 8C = 3C0 + 2As. In both cases the arsenic, when liberated by the reducing action of the charcoal, exists in the form of vapor, which con- denses in the cooler part of the apparatus as a steel-gray metallic mass, which when exposed to the atmospheric air, loses the me- tallic lustre in consequence of the formation of a film of oxide. When pure, arsenic is odorless and tasteless; it is very brittle, and volatilizes unchanged and without melting when heated to ARSENIC. 203 180° C. (356° F.), without access of air. Heated in air, it burns with a bluish-white light, forming arsenious oxide. Although insoluble in water, yet water digested with arsenic soon contains some arsenious acid in solution, the oxide of arsenic being formed by oxidation of the metal by the oxygen absorbed in the water. Arsenic is used in the metallic state as fly-poison, and in some alloys, chiefly in shot, an alloy of lead and arsenic. The molecule of arsenic contains four atoms, and not two, like most elements. It is trivalentin some compounds, quinquivalent in others. Arsenious oxide, Acidum arseniosum, As203 = 197.8 (White arsenic, Arsenic trioxide, Arsenious anhydride, improperly Arsenious acid). This compound frequently is obtained as a by-product in metal- lurgical operations during the manufacture of metals from ores containing arsenic. Such ores are roasted (heated in a current of air), when arsenic is converted into arsenious oxid«, which, at that temperature, is volatilized and afterward condensed in chambers or long flues. Arsenious oxide is a heavy, white solid, occurring either as an opaque, slightly crystalline powder, or in transparent, or semi- transparent amorphous masses which frequently show a stratified appearance; recently sublimed, arsenious oxide exists as the semi-transparent glassy mass known as vitreous arsenious oxide, which gradually becomes opaque and ultimately resembles porce- lain. These two modifications of arsenious oxide differ in their solu- bility in w-ater, the amorphous or glassy variety dissolving more freely than the crystallized. One part of arsenious oxide dis- solves in from 30 to 100 parts of cold and in 15 parts of boiling water, the solution having at first a faint acrid and metallic, and afterward a sweetish taste. This solution contains the arsenious oxide not as such, but as arsenious acid, II3As03, which compound, however, cannot be obtained in an isolated condition, but is known in solution only: As203 -{- 3H20 = 2H3As03. The salts of arsenious acid are known as arsenites. When heated to about 220° C. (428° F.) arsenious oxide is vola- tilized without fusion; the vapors, when condensed, form small, shining, eight-sided crystals; when heated on charcoal, it is 204 METALS ANT) THEIR COMBINATIONS. deoxidized, giving off, at the same time, an odor resembling that of garlic. Arsenious oxide frequently is used in the arts and for manu- facturing purposes, as, for instance, in the manufacture of green colors, of opaque white glass, in calico-printing, as a powerful antiseptic for the preservation of organic objects of natural history, and, finally, as the substance from which all arsenic compounds are obtained. The officinal solution of arsenious acid, Liquor acidi arseniosi, is a 1 per cent, solution of arsenious oxide in water to which 2 per cent, of hydrochloric acid has been added. The officinal solution of arsenite of potassium, Liquor potassii arsenitis, or Fowler’s solution, is made by dissolving 1 part of arsenious oxide and 1 part of potassium bicarbonate in 95 parts of water and adding 3 parts of compound tincture of lavender; the solution contains the arsenic as potassium arsenite. Arsenic oxide, As205 [Arsenic pentoxide, Anhydrous arsenic acid). When arsenious oxide is heated with nitric acid, it becomes oxidized and is converted into arsenic acid, IT3As04, from which the water may be expelled by further heating, when arsenic oxide is left: 2H3 A.s04 = A.=205 + 3H20. Arsenic oxide is a heavy, white, solid substance which, in con- tact with water, is converted into arsenic acid. This acid resem- bles phosphoric acid not only in composition, but also in forming metarsenic and pyroarsenic acids under the same conditions under which the corresponding phosphoric acids are formed. The salts of arsenic acid, the arseniates, also resemble in their constitution the corresponding phosphates. Arsenic oxide and arsenic acid are used largely as oxidizing agents in the manufacture of aniline colors. o Disodium hydrogen arseniate, Sodii arsenias, Na2HAs04.7H20 = 311.9 (Arseniate of sodium). This salt is made by fusing arsenious oxide with carbonate and nitrate of sodium: Ap203 + 2 N alST 03 + Na2C03 = Na4A?207 + N203 + C02. Sodium pyroarseniate is formed, nitrogen trioxide and carbon dioxide escaping. By dissolving in water and crystallizing, the officinal salt is obtained in colorless, transparent crystals: Na4As307 + 15H20 = 2(Na3HAs04.7H30). 205 ARSENIC. Arseniuretted hydrogen, AsH3 (Hydrogen arsenide). This com- pound is formed always when either arsenious or arsenic oxides or acids, or any of their salts, are brought in contact with nascent hydrogen, for instance, with zinc and diluted sulphuric acid, which evolve hydrogen: As203 + 12H = 2AsH;j + 3H.20. As205 -f- 16H — 2AsH3 A- 5H2U. AsCI3 + 6H = AsH3 + 3HC1. Arseniuretted hydrogen is a colorless, highly poisonous gas, having a strong garlic odor. Ignited, it burns with a bluish flame, giving off white clouds of arsenious oxide: 2AsH3 + 60 = As=203 + 3H20. When a cold plate (porcelain answers best) is held in the flame of arseniuretted hydrogen, a dark deposit of metallic arsenic (arsenic spots) is produced upon the plate (in a similar manner as a deposit of carbon is produced by a common luminous flame). The formation of this metallic deposit may be explained by the fact that the heat of the flame decomposes the gas, and that, furthermore, of the two liberated elements, arsenic and hydrogen, the latter has the greater affinity for oxygen. In the centre of the flame, to which but a limited amount of oxygen penetrates, the latter is taken up by the hydrogen, arsenic being present in the metallic state until it burns in the outer cone of the flame. It is this liberated arsenic which is deposited upon a cold sub- stance held in the flame. Arseniuretted hydrogen, when heated to redness, is decom- posed into its elements; by passing the gas through a glass tube heated to redness, the liberated arsenic is deposited in the cooler part of the tube, forming a bright metallic ring. Sulphides of arsenic. Two sulphides of arsenic are known and have been mentioned above as the native disulphide or realgar, As2S2, and the trisulphide or orpiment, As2S3. Disulphide of arsenic is an orange-red, fusible, and volatile substance, used as a pigment; it may be made by fusing together the elements in the proper proportions. Trisulphide is a golden-yellow, fusible, and volatile substance, which also may be obtained by fusing the elements, or by precipitating an arsenic solution by hydrosul- phuric acid (Plate V., 1). Both sulphides of arsenic are sulpho- aeids, uniting with other metallic sulphides to form sulpho-salts, 206 METALS AND THEIR COMBINATIONS as, for instance, Iv2S.As2S3, or (OTT4)2S.As2S3. . These compounds are known as sulph-arsenides. Arsenious iodide, Arsenii iodidum, Asl3 = 454.7 {Iodide of arsenic), may be obtained by direct combination of the elements, and forms orange-red crystalline masses, soluble in water and alcohol, but decomposed by boiling with either of these liquids. . It is used in the officinal preparation, Solution of iodide of arsenic and mercury, Donovan s solution, which is made by dissolving one part each of arsenious iodide and mercuric iodide in 98 parts of water. Analytical reactions. (Use arsenious oxide, As203, and sodium arseniate, Na2HAs04, respectively.) 1. Add hydrosulphuric acid to a slightly acid solution of arsenic: a yellow precipitate of arsenious sulphide is produced (Plate V., 1): -^■s H- 3H2S — 3H20 -f-A-SjSg. If arsenic is present as arsenic acid, this compound is reduced to arsenious acid previous to its precipitation; heating of the liquid facilitates this reaction: As205 + 2H2S = As203 + 2H20 + 2S. 2. Add ammonium sulphide or any alkaline hydroxide to the yellow precipitate of arsenious sulphide: the latter is readily dissolved, but may be reprecipitated by neutralizing with an acid. 3. Ammonio-nitrate of silver (silver nitrate to which enough of water of ammonia has been added to redissolve the precipitate at first formed) produces in neutral solutions of arsenious acid a yellow precipitate of arsenite of silver (Ag3As03) (Plate V., 3), in arsenic acid solutions a chocolate-colored precipitate of arseniate of silver (Ag3As04) (Plate V., 4). The two precipitates are soluble in alkalies and acids both. 4. Ammonio-sulphate of copper (made similarly to ammonio- nitrate of silver from cupric sulphate) added to neutral arsenious solutions produces a green precipitate of cupric arsenite (CuIIAsOg) known as Scheele s green (Plate V., 2). (Arsenite of copper mixed with cupric acetate is known as Schweinfurth green.) The same reagent produces in neutral arsenic acid solutions a similar green precipitate of cupric arseniate. Instead of using for the above tests the ammonio salts, silver PLATE ~XT ARSENIC. ANTIMONY. TIN. 1 Arsenious sulphide, precipi- tated from arsenious solutions by hy- drosulphuric acid. [Page 206.] 2 Cupric arsenite, precipitated from arsenious solutions by ammonio- sulphate of copper. [Page 206.] 3 Stiver arsenite, precipitated from arsenious solutions by silver nitrate. [Page 206.] Silver arseniate, precipitated from arsenic solutions by silver ni- trate. {Page 206.] 4 5 Antimonious sulphide, precipi- tated from solutions of antimony by hydrosulphuric acid. {Pages 211,214.] 6 Native or Crystallized ant itno- nious sulphide. [Page 211.] 7 Stannons sulphide, precipitated from stannous solutions by hydrosul- phuric acid. [Page 215.] Stannic sulphide, precipitated from stannic solutions by hydrosul- phuric acid. [Page 215.] 8 ARSENIC. 207 nitrate or cupric sulphate may be added to the acid (or neutral) solution of arsenic, then adding water of ammonia carefully in small quantities until a neutral reaction has been obtained, when the precipitate is formed. 5. Soluble arseniates give white precipitates with soluble salts of barium, calcium, magnesium, zinc, and some other metals; soluble arsenites do not. 6. Heat any dry arsenic compound, after being mixed with some charcoal and dry potassium carbonate in a very narrow test-tube (or, better, in a drawn-out glass tube having a small bulb on the end): the arsenic compound is decomposed and the metallic arsenic deposited as a metallic ring in the upper part of the contraction. (Fig. 18.) Fig. 13. 7. Heat arsenious or arsenic oxide upon a piece of charcoal by means of a blowpipe; a characteristic odor of garlic is per- ceptible. 8. Beinsch’s test. A thin piece of copper, having a bright metallic surface, placed in a slightly acidified solution of arsenic (nitric acid should not be present) becomes, upon heating the solution, coated with a film of metallic arsenic; the latter may be sublimed from the copper by placing it in a dry narrow test- tube and heating. During this operation most of the arsenic is converted into arsenious oxide, which forms a deposit of small, octahedral crystals. 208 METALS AND THEIR COMBINATIONS. 9. Fleitmann’s test. Zinc and moderately strong solution of sodium hydroxide evolve, upon heating, hydrogen gas : Zn + 2NaOH = Na2Zn02 + 2H. If arsenious or arsenic acid be present, arseniuretted hydrogen is evolved, which may be recognized by placing over the mouth of the flask in which the reaction takes place a piece of paper, moistened by a drop of silver nitrate solu- tion, which latter is decomposed by the arseniuretted hydrogen with liberation of free silver, which im- parts to the paper a purplish-black color. (Anti- mony compounds do not evolve antimoniuretted hydrogen, when treated with zinc and alkaline hydroxides.) (Fig. 14.) 10. Marsh's test. This test is, especially for the detection of traces of arsenic, by far the best and most reliable, and should never be omitted in testing for arsenic in cases of poisoning. The apparatus used for performing this test consists of a glass vessel (flask or Woulf s bottle) provided with a funnel-tube and de- livery-tube (bent at right angles), which is connected with a wider tube, filled with pieces of calcium chlo- ride or plugs of asbestos; this drying tube is again connected with a piece of hard glass tube, about one foot long, having a diameter of J inch, drawn out at intervals of about 3 inches, so as to reduce its diam- eter to | inch. Hydrogen is generated in the flask by the action of sulphuric acid on zinc, and examined for its purity by heating the glass tube to redness at one of its wide parts for at least 80 minutes; if no trace of a metallic mirror is formed at the constriction beyond the heated point, the gas and the substances used for its generation may be pronounced free from arsenic. (Both zinc and sulphuric acid often contain arsenic.) After having thus demonstrated the purity of the hydrogen, the suspected liquid, which must contain the arsenic either as oxide or chloride (not as sulphide), is poured into the flask through the funnel-tube. If arsenic is present in not too small quantities, the gas ignited at the end of the glass tube shows a flame decid- edly different from that of burning hydrogen. The flame becomes larger, assumes a bluish tint, and emits an odor of garlic, while above it a white cloud appears which is more or less dense; a Fig. 14. ARSENIC. 209 cold test-tube held inverted over the flame will be covered upon its walls with a white deposit of minute octahedral crystals of arsenious oxide; a piece of cold porcelain held in the flame becomes coated with a brown stain (arsenic spot) of metallic arsenic. (See explanation above in connection with arseniuretted hydrogen.) Fig. 15. Marsh’s apparatus for detection of arsenic. The glass tube heated, as above mentioned, at one of its wide parts, will show a bluish-black metallic mirror at the constriction beyond. The only element which, under the same con- ditions, forms spots and mirrors similar to arsenic, is antimony; there are, however, sufficiently reli- able tests to distinguish arsenic spots from those of antimony. Arsenic spots treated with solution of hypo- chlorites (solution of bleaching-powder) dissolve readily; antimony spots are not affected. When nitric acid is added to an arsenic spot, evaporated to dryness and moistened with a drop of silver nitrate, it turns brick-red; antimony spots treated in like manner remain white. Arsenic spots dis- solved in ammonium sulphide and evaporated to dryness show a bright yellow, antimony spots an orange-red residue. Fig. 16 represents a simpler form of Marsh’s apparatus, which generally will answer for student’s tests. Fig. 16 Student’s apparatus for making arsenic spots. 210 METALS AND THEIR COMBINATIONS. Preparatory treatment of organic matter for arsenic analysis. If organic matter is to be examined for arsenic (or for any other metallic poison) it ought to be treated as follows: The subtance, if not liquid, is cut into pieces, well mashed and mixed with water ; the liquid or semiliquid substance is heated in a porcelain dish over a steam bath with hydrochloric acid and potassium chlorate until the mass has a uniform light-yellow color and has no longer an odor of chlorine. By this operation all poisonous metals (lead and silver excepted, because insoluble silver chloride and possibly insoluble lead sulphate are formed) are rendered soluble even when present as sulphides, and may now be separated by filtration from some remaining solid matter. The clear solution is heated and treated with hydrosulphuric acid gas for several hours, when arsenic and all metals of the arsenic and lead groups are precipitated as sul- phides, a little organic matter also being precipitated generally. The precipitate is collected upon a small filter and treated with warm ammo- nium sulphide, which dissolves the sulphides of arsenic and antimony, leaving behind the sulphides of the lead group, which may be dissolved in nitric, or, if mercury be present, in nitro-muriatic acid, and the solution tested by the methods mentioned for the respective metals. The ammonium sulphide solu- tion is evaporated to dryness, this residue mixed with nitrate and carbonate of sodium and the mixture fused in a small porcelain crucible. By the oxidizing action of the nitrate, both sulphides are converted into the higher oxides, arsenic forming sodium arseniate, antimony forming antimonic oxide. By treating the mass with warm water, sodium arseniate is dissolved and may be filtered off, while antimonic oxide remains undissolved, and may be dissolved in hydrochloric acid. Both solutions may now be used for making the respective tests for arsenic or antimony. Antidotes. Moist, recently prepared ferric hydroxide or dialyzed iron are the best antidotes, insoluble ferric arseriite or arseniate being formed. Vomiting should be induced by tickling the fauces or by administering zinc sulphate, but not tartar emetic. Questions.—291. Which metals belong to the arsenic group, and what are their characteristics? 292. Which non-metallic elements does arsenic resemble ? Mention some of the compounds showing this analogy. 293. How is arsenic obtained in the metallic state ; what are its physical and chemical properties; how does heat act upon it ? 294. What is white arsenic ? State its compo- sition, mode of manufacture, appearance, solubility, and other properties. 295. Which three solutions, containing arsenic, are officinal, and what is their composition? 296. How is arsenic acid obtained from arsenious oxide, and which arsenate is officinal ? 297. State composition and properties of arseniuretted hydrogen, and explain its formation. What use is made of it in testing for arsenic? 298. State the composition of realgar, orpiment, Scheele’s green, and Schweinfurth green. 299. Give a detailed description of the process by which arsenic can be detected in organic matter. 300. Describe Marsh’s test and other tests for arsenic, and state the difference between arsenic and antimony spots. ANTIMONY. 211 31. ANTIMONY—TIN—GOLD—PLATINUM—MOLYBDENUM. Antimony, Sb = 120 {Stibium). This metal is found in nature chiefly as the trisulphide, Sb2S3, an ore which is known as black antimony, crude antimony, or stibnite. The metal is obtained from the sulphide by roasting, when it is converted into oxide, which is reduced by charcoal. Antimony is a brittle, bluish-white metal, having a crystalline structure; it fuses at 450° C. (842° F.), and may at a higher temperature be distilled without change, provided air is excluded ; heated in air it burns brilliantly. Antimony is used in a number of important alloys, for in- stance, in type-metal, an alloy of lead, tin, and antimony. Antimony trisulphide, Antimonii sulphidum, Sb2S3 = 336 (Anti- monious sulphide, Sulphide of antimony). The above-mentioned native sulphide, the black antimony, is purified by fusion; it forms steel-gray masses of a metallic lustre, and a striated, crys- talline fracture, forming a grayish-black, lustreless powder, which is insoluble in water, but soluble in hydrochloric acid with libera- tion of hydrosulphuric acid. When finely powdered antimonious sulphide is treated with water of ammonia to remove any traces of arsenic (which is fre- quently found in this ore) and the washed sulphide dried, the purified sidphide of antimony of the U. S. P. is obtained. Antimonious sulphide found in nature is crystallized and steel- gray (Plate V., 6), but it may be obtained also in an amorphous condition as an orange-red (Plate V., 5) powder, by passing hydro- sulphuric acid gas through an antimonious solution. By heating the orange-red sulphide, it is converted into the black variety. Sulphurated antimony, Antimonium sulphuratum [Oxy sulphide of antimony), chiefly antimonious sulphide with some antimonious oxide. This preparation is made by boiling purified antimonious sulphide with solution of sodium hydroxide, and adding to the hot solution sulphuric acid as long as a precipitate is formed, which is collected and dried. The sulphides and oxides of antimony, like those of arsenic, combine with many metallic sulphides or oxides to form sulpho- salts or oxy-salts. Thus the sodium sulph-antimonite, NTa3SbS3, 212 METALS AND THEIR COMBINATIONS and the sodium antimonite, Ha3Sb03, are formed when anti- monious sulphide is boiled with sodium hydroxide. Sb2S3 + 6NaOH = Na3SbS3 + Na3SbOs + 3H20 By the addition of sulphuric acid, both salts are decomposed, sodium sulphate is formed, and antimonious sulphide and oxide are precipitated : 2NasSbS3 + 3H2S04 = 3Na2S04 + Sb2S3 + 3H2S; 2Na3Sb03 + 3H2S04 = 3Na2S04 + Sb203 + 3H20. It is a reddish-brown, amorphous powder, insoluble in water, soluble in hydrochloric acid or sodium hydroxide. Experiment 37. Boil about 2 grams of finely powdered black antimony with a solution of 2 grams of sodium hydroxide in 80 c.c. of water for about one hour, stirring frequently and occasionally adding water to preserve the same volume. Filter the warm liquid through paper or muslin and add dilute sulphuric acid so long as it produces a precipitate. Collect, wash, and dry the precipitated red powder, which is chiefly amorphous antimonious sulphide with oxide. Antimony pentasulphide, Sb2S5 (Golden sulphuret of antimony). A red powder, which, like antimonious sulphide, forms sulpho- salts. It may be obtained by precipitation of acid solutions of antimonic acid by hydrosulphuric acid. Antimonious chloride, SbCl3 (Ter chloride of antimony, Batter of antimony). Obtained by boiling the native sulphide with hydro- chloric acid: The clear solution is evaporated and the remaining chloride distilled, when it is obtained as a white, crystalline, semi-trans- parent mass. By passing chlorine over antimonious chloride it is converted into antimonic chloride, SbCl5, which is a fuming liquid. Sb2S3 + GHC1 = 3H2S + 2SbCl3. Experiment 38. Boil about 2 grams of black autimony with 10 c.c. of hydrochloric acid until most of the sulphide is dissolved. Set aside for subsid- ence, pour off the clear solution of antimonious chloride, evaporate to about half its volume and use solution for next experiment. Antimonious oxide, Antimonii oxidum, Sb203 = 288 (Oxide of antimony). When antimonious chloride is added to water, de- composition takes place, and an oxychloride of antimony, 2SbCl3.5Sb203, is precipitated : 12SbCl3 + 15H.,0 = 2SbCl3.5Sb203 + 30HC1. ANTIMONY. 213 This white precipitate was formerly known as powder of Alga- roth. It is completely converted into oxide by treating it with sodium carbonate: 2SbCl3.5Sb203 + 3Na2C03 = 6Sb203 + 6NaCl + 3C02. The precipitate, when wrnshed and dried, is a heavy, grayish- white, tasteless powder, insoluble in wrater, soluble in acids. Antimonious oxide, tvhile yet moist, dissolves readily in potas- sium acid tartrate, forming the double tartrate of potassium and antimony, or tartar emetic, which salt will be more fully considered hereafter. Experiment 39. Pour the solution of antimonious chloride obtained by Experiment 37 into 100 c.c. of water, wash by decantation the white precipitate of oxychloride thus obtained, and add to it an aqueous solution of about 1 gram of sodium carbonate. After effervescence ceases, collect the precipitate on a filter, wash well and treat some of the precipitate, while yet moist, with a solution of potassium acid tartrate, which dissolves it readily, forming tartar emetic. (For the latter compound see index.) Antidotes. Poisonous doses of any preparation of antimony are generally quickly followed by vomiting: if this, however, have not occurred, the stomach-pump must be applied. Tannic acid in any form, or recently precipitated ferric hydroxide, should be administered. Analytical reactions. (A solution of tartar emetic, KSb0C4Ht06, may be used, to which enough hydrochloric acid has been added to redissolve the white, antimonious oxychlo- ride, SbOCl, which is formed when the acid is first added.) 1. Add hydrosulphuric acid to an acidified solution of anti- mony : an orange-red precipitate of antimonious or antimonic sulphide (Sb2S3 or Sb2S5) is produced (Plate V., 5). 2. Add ammonium sulphide to the precipitated sulphide of antimony : this is dissolved and may be reprecipitated by neu- tralizing with an acid. 3. Produce a concentrated solution of antimonious chloride by dissolving the sulphide in hydrochloric acid, and pour it into water: a white precipitate of oxychloride is formed. (See explanation above.) 4. Add sodium hydroxide, ammonium hydroxide, or sodium 214 METALS AND THEIR COMBINATIONS. carbonate; in either case white antimonious hydroxide, Sb30II, is produced, which is soluble in sodium hydroxide. 5. Boil a piece of metallic copper in the solution of anti- monious chloride : a black deposit of antimony is formed upon the copper. By heating the latter in a narrow test-tube, the antimony is volatilized and deposited as a white incrustation of antimonious oxide upon the glass. 6. Use “ Marsh’s test ” as described under analytical reactions for arsenic, and apply tests mentioned there for distinguishing spots of arsenic from those of antimony. Tin, Sn = 117.7 (Stannum). This metal is found in nature chiefly as stannic oxide or tin-stone, Sn02, from which the metal is easily obtained by heating with coal: Sn02 + 2C = Sn + 2CO. Tin is an almost silver-white, very malleable metal, fusing at the comparatively low temperature of 228° C. (440° F.). It is used in many alloys, in the silvering of looking-glasses by tin- amalgam, and chiefly in the manufacture of tin-plate, which is sheet-iron covered with a thin layer of tin. Tin is bivalent in some compounds, quadrivalent in others. These combinations are distinguished as stannous and stannic compounds. Stannous chloride, SnCl,2 (Protochloride of tin). Obtained by dis- solving tin in h}Tdrochloric acid by the aid of heat: Sn + 2HC1 = SnCl2 + 2H. Sufficiently evaporated, the solution yields crystals of the composition SnCl2.2H20. Stannous chloride is a stroug deoxi- dizing agent, frequently used as a reagent for mercury and gold, which metals are precipitated from their solutions in the metallic state. It is used also in calico-printing. Stannic chloride, SnCl4 (Perchloride, of tin). Stannous chloride may be converted into stannic chloride either by passing chlo- rine through its solution or by heating with hydrochloric and nitric acids. 215 GOLD. Analytical reactions. (Stannous chloride, SnCl2, and stannic chloride, SnCl4. may be used.) 1. Add hydrosulpliuric acid to solution of a stannous salt: brown stannous sulphide is precipitated (Plate V., 7) : SnCI2 + H2S = 2HC1 + SnS. The precipitate is soluble in ammonium sulphide. 2. Add hydrosulphuric acid to a solution of a stannic salt : yellow stannic sulphide is precipitated (Plate V., 8): SnC)4 + 2H2S = 4HC1 + SnS2. The precipitate is soluble in ammonium sulphide. 3. Sodium or potassium hydroxide added to a stannous salt, produces a white precipitate of stannous hydroxide, Sn20H. The same reagents added to a stannic salt produce white stannic acid, H2Sn03. Both precipitates are soluble in excess of the alkali. Gold, Au = 196.2 (Aurum). Gold occurs in nature chiefly in the free state, often associated with silver, copper, and possibly with other metals. This impure gold is separated from most of the adhering sand and rock by a mechanical process of washing, in which advantage is taken of the high specific gravity of the metallic masses. The remaining mixture of heavy material is treated with mercury, which dissolves gold and silver, leaving behind most other impurities. The gold amalgam is placed in a retort and heated, when the mercury distils over, while the gold is left behind. If this should contain silver, the metals may be separated by treating the alloy with hot sulphuric acid, which dissolves silver, leaving gold behind. Pure gold is too soft for general use, and therefore is alloyed with various proportions of silver and copper. American coin is an alloy of 90 parts of gold and 10 parts of copper; jeweler’s gold contains generally 75 per cent. (18 carat) of gold, the other 25 per cent, being copper and silver ; the varying proportions are well indicated by the color. Gold is not affected by either hydrochloric, nitric, or sul- phuric acid, but is dissolved by nitrohydrochloric acid, by free chlorine or bromine, and by mercury, with which it forms an amalgam. 216 METALS AND THEIR COMBINATIONS. Gold is trivalent generally, as in auric chloride, AuC13, but most likely also univalent in some compounds, as in aurous chloride, AuCl. Auric chloride, AuC13. Obtained by dissolving pure gold in nitrohydrochloric acid and evaporating the solution. A mixture of equal parts of auric chloride and sodium chloride is officinal under the name of chloride of gold and sodium. It is an orange- yellow, very soluble powder. Analytical reactions. (Auric chloride, AuC13, may be used.) 1. Add hydrosulphuric acid to solution of gold: brown auric sulphide, Au2S3, is precipitated, which is soluble in ammonium sulphide. 2. Add ferrous sulphate to solution of gold and set aside for a few hours; metallic gold is precipitated as a dark powder, which, by fusion, is converted into a metallic mass. Platinum, Pt = 194.4. Platinum, like gold, is found in nature in the free state, the chief supply being derived from the Ural mountains, where it is found associated with a number of metals (iridium, ruthenium, osmium, palladium, rhodium) resembling platinum in their properties. Platinum is of great importance and value on account of its high fusing-point and its resistance to the action of most chemical agents, for which reason it is used in the manufacture of vessels serving in chemical operations. Platinum, when dissolved in nitrohydrochloric acid, forms platinic chloride, PtCl4, a salt frequently used as a reagent for potassium or ammonium salts, with which it forms insoluble double chlorides of the composition PtCl4.2KCland PtCl4.2NH4Cl. By heating the latter salt sufficiently it is decomposed and metallic platinum is left as a gray spongy mass. Molybdenum, Mo =95.5. This metal is found in nature chiefly as sulphide, MoS2, from which, by roasting, molybdic oxide, Mo03, is obtained. The oxide, when dissolved in water, forms an acid which combines with metals, forming a series of salts MOLYBDENUM. 217 termed molybdates. Of interest is ammonium molybdate, a solution of which in nitric acid is an excellent reagent for phosphoric acid, with which it forms a yellow precipitate, insoluble in acids, soluble in ammonium hydroxide. Questions.—301. How is antimony found in nature, and what are the prop- erties of this metal? 302. State the composition of antimonious sulphide, and its color when crystallized and amorphous. 303. How do hydrochloric acid and alkaline hydroxides act upon antimonious sulphide? 304. What is the sul- phurated antimony of the U. S. P. ? 305. Mention the two chlorides of anti- mony and state their properties. 306. How is antimonious oxide made, and what is it used for ? 307. Give tests for antimony. 308. State the use made of tin in the metallic state ; mention the two chlorides of tin, and what stannous chloride is used for. 309. How are gold and platinum found in nature ; by what acid may they be dissolved, and what is the composition of the compounds formed? 310. Which is the most important compound of molybdenum, and what is it used for? V. ANALYTICAL CHEMISTRY. 32. INTRODUCTORY REMARKS AND PRELIMINARY EXAMINATION. General remarks. Analytical chemistry is that part of chemistry which treats of the different analytical methods by which sub- stances are recognized and their chemical composition deter- mined. This determination may be either qualitative or quanti- tative, and, accordingly, a distinction is made between a qualitative analysis, by which simply the nature of the elements (or groups of elements) present in the substance under examination is de- termined, and a quantitative analysis, by which also the exact amount of these elements is ascertained. In this book qualitative analysis will be considered chiefly, as the methods for quantitative determinations of the different elements are so numerous and so varied that a detailed descrip- tion of them would occupy more space than can be devoted to analytical chemistry in this work. Some brief directions con- cerning quantitative determinations, especially by volumetric methods, are given in Chapter 37. Everyone studying analytical chemistry should do it practically, that is, should perform for himself in a laboratory all those reactions which have been men- tioned heretofore as characteristic of the different elements and their compounds, and, furthermore, should make himself ac- quainted with the methods b}7 which substances are recognized when mixed with others, by analyzing various complex sub- stances. Such a course of practical work in a chemical laboratory is of the greatest advantage to all studying chemistry, and students cannot be too strongly advised to avail themselves of any facilities offered in performing chemical experiments, analytically or otherwise. INTRODUCTORY REMARKS. 219 Apparatus needed for qualitative analysis. 1. Iron stand. (Fig. 17.) 2. Bunsen lamp with flexible tube (Fig. 17), or (where without gas-supply) spirit- lamp and alcohol. Fig. 17. Fig. 18. Fig. 19. 8. Test-tube stand and one dozen assorted test-tubes. (Fig. 18.) 4. Three small beakers from 100 to 150 c.c. capacity. (Fig. 19, A.) 220 ANALYTICAL CHEMISTRY. 5. Two flasks of 100 to 150 c.c. capacity. (Fig. 19, B.) 6. Wash-bottle of about 400 c.c. capacity. (Fig. 20, A.) 7. Three small glass funnels, about one and a half to two inches in diameter. (Fig. 20, B.) Fig. 20. 8. A few pieces of glass tubing about ten inches long, and some India-rubber tubing to fit the tubing. 9. Three glass rods. 10. Three small porcelain evaporating dishes, about two inches in diameter. (Fig. 21, A.) 11. Blowpipe. (Fig. 21, B.) 12. Crucible tongs. (Fig. 21, C.) Fig. 21. 13. Round and triangular file. 14. Wire gauze, about six inches square, or sand tray. 15. One square inch of platinum foil (not too light), and six inches of platinum wire. 16. Filter-paper. 17. Pair of scissors. 18. One or two dozen assorted corks. 19. Sponge and towel. 20. Two watch-glasses. 21. Small pestle and mortar. (Fig. 21, I).) INTRODUCTORY REMARKS. 221 22. Small porcelain crucible. 23. Small platinum crucible. (Fig. 21, E.) 24. Wire triangle to support the crucible. (Fig. 21, F.) Reagents needed in qualitative analysis. 1. Sulphuric acid, sp. gr. 1.84, H2S04. 2. Sulphuric acid diluted, sp. gr. 1.068 (1 part sulphuric acid, 9 parts water). 3. Hydrochloric acid, sp. gr. 1.16, HC1. 4. Hydrochloric acid diluted, sp. gr. 1.049 (6 parts hydrochloric acid, 13 parts water). 5. Nitric acid, sp. gr. 1.42 HN03. 6. Acetic acid, sp. gr. 1.048, C2II402. 7. Hydrosulphuric acid, either the gas or its solution in water, H2S. 8. Ammonium sulphide, (NH4)2S. 9. Ammonium hydroxide (water of ammonia), NH4HO. 10. Ammonium carbonate (NH4)2C03. A solution of one part of the salt in a mixture of four parts of water and one part of water of ammonia. 11. Ammonium chloride, NH4C1; ten per cent, solution. 12. Ammonium oxalate, (NH4)2C204; five per cent, solution. 13. Ammonium molybdate, (NH4)2Mo04. A five per cent, solution of the salt in a mixture of equal parts of water and nitric acid. a. Liquids. 14. Sodium hydroxide, NaOH. 15. Sodium carbonate, Na2C03. 16. Sodium phosphate, Na2HP04. 17. Sodium acetate, NaC2H302. 18. Potassium chromate, K2Cr()4. 19. Potassium dichromate, K2Cr207. I }- Ten per cent, solutions. 20 Potassium iodide, KI. 21. Potassium ferrocyanide, K4Fe6CN. 22. Potassium ferricyanide, K6Fe212oN\ 23. Potassium sulphocyanate, KCNS. 1 I }- Five per cent, solutions. I J 24. Magnesium sulphate, MgS04. 25. Barium chloride, BaCl2. 26. Calcium chloride, CaCl2. j Ten per cent, solutions. 27. Calcium hydroxide, Ca20H (lime-water). 28. Calcium sulphate, CaS04. } Saturated solutions. 29. Ferric chloride, Fe2Cl6. 30. Lead acetate, Pb.2C2H302. 31. Silver nitrate, AgN03. 32. Mercuric chloride, HgC!2. 33. Platinic chloride, PtCl4. 34. Solution of indigo. 35. Alcohol. 1 I [- Five per cent, solutions. ! j b. Solids. 1. Litmus or blue and red paper. 2. Turmeric paper. 3. Sodium carbonate, dried, Na2C03. 4. Sodium biborate, borax, Na2Bo4O-.10H2O. 222 ANALYTICAL CHEMISTRY. 5. Sodium-ammonium-hydrogen phosphate (microcosmic salt), Na(NH4)HP04.4H20. 6. Potassium carbonate, K2C03. 7. Potassium nitrate, KJ703. 8. Potassium chlorate, KC103. 9. Potassium permanganate, K2Mn208. 10. Potassium cyanide, KCN. 11. Calcium hydroxide, Ca20H. 12. Ferrous sulphide, FeS. 13. Ferrous sulphate, FeS04.7H20. 14. Manganese dioxide, Mn02. 15. Zinc, granulated, Zn. 16. Copper, Cu. 17. Cupric oxide, CuO. 18. Cupric sulphate, CuS04.5H20. 19. Tartaric acid, H2C4H406. 20. Starch, C6H10O5. While the apparatus and reagents here enumerated are the more important ones, the analyst will occasionally require others not mentioned in the above lists. General mode of proceeding- in qualitative analysis. Every step taken in analysis should be properly written down in a note-book, and these remarks should be made directly after a reaction has been performed, and not after the nature of the substance has been revealed by perhaps numerous reactions. Not only the reactions by which positive results have been obtained should be noted, but also those tests and reagents men- tioned which have been applied with negative results—that is, which have been applied without revealing the presence of any substance, or any group of substances. Such negative results are, however, positive in so far as they prove the absence of a certain substance, or certain substances, for which reason they are of direct value, and should be noted. In comparing, finally, the result obtained by the analysis with the notes taken during the examination, none of them should be contradictory to the conclusions drawn. If, for instance, the preliminary examination showed the substance to have been volatilized by heating upon platinum foil with the exception of a very slight residue, and if, afterward, other tests show the presence of ammonia and hydrochloric acid and the absence of everything else, and if, then, the conclusion be drawn that the substance is pure ammonium chloride, this conclusion must be incorrect, because pure ammonium chloride is wholly volatile, and does not INTRODUCTORY REMARKS. 223 leave a residue. It will then be the task of the operator to find where the mistake occurred, and to correct it. Use of reagents. A mistake made by most beginners in ana- lyzing is the use of too large quantities both of the substance applied for testing and of the reagents added. This excessive use of material is not only a waste of money, but, what is of greater importance, a waste of time. Some experience in analyzing will soon convince the student of the truth contained in this remark, and will also enable him to select the correct quantities of mate- rials to be used, which rarely exceed 0.5-1.0 gram. A smaller amount frequently may answer, and a much larger quantity may occasionally be needed, as, for instance, in cases where highly diluted reagents, such as calcium sulphate solution, lime-water, hydrosulphuric acid water, etc., are applied. Preliminary examination. This examination includes the fol- lowing points : 1. Physical properties. Solid or liquid; metallized or amor- phous ; color, odor, hardness, gravity, etc. (On account of pos- sible poisonous properties, the greatest care should be exercised in tasting a substance.) 2. Action on litmus. Examined by holding litmus-paper in the liquid, or by placing the powdered solid upon red and blue litmus- paper, moistened with water. (It should be remembered that many normal salts, as, for instance, aluminium sulphate, ferrous sulphate, etc., have an acid reaction to litmus-paper, and that such a reaction consequently is not conclusive of the presence of a free acid, nor even of an acid salt.) 3. Heating on platinum foil or in a dry glass tube, open at both ends. (If the substance to be examined be a liquid, it should be evaporated in a small porcelain dish to see whether a solid residue be left or not. If a residue be left, it should be treated like a solid.) The heating of a small quantity of a solid substance upon platinum foil held over the flame of a Bunsen burner or of an alcohol lamp, is a test which should never be omitted, as it dis- closes in most cases the fact whether the substance is of an organic or inorganic nature. Most organic (non-volatile) sub- stances, when thus heated, will burn with a luminous flame, leaving in many cases a black residue of carbon, which, upon 224 ANALYTICAL CHEMISTRY. further heating, disappears. In cases where the organic nature of a compound is not clearly demonstrated by heating on platinum foil, the substance is heated with an excess of cupric oxide in a test-tube or other glass tube, provided with a delivery- tube, which passes into lime-water. Upon heating the mixture, the carbon of the organic matter is converted into carbon dioxide, which renders lime-water turbid. The analytical processes by which the nature of an organic substance is determined, are not considered in this part of the book, but will be mentioned when considering the carbon compounds. An inorganic substance, heated on platinum foil, may either be volatilized, fused, change color, become oxidized, suffer decom- position, or remain unchanged. (See Table I., page 227.) Some substances, containing small quantities of water enclosed between the crystals (common salt, for instance), decrepitate when heated, the small fragments being thrown from the foil; such substances should be heated in a test-tube to expel the water and then be examined on platinum foil. Fir. 22. Fig. 23. Heating of solids in bent glass tube. Heating on charcoal by means of blowpipe. In many cases it is preferable to heat the substance in a bent o;lass tube, as shown in Fig. 22, instead of on platinum foil, because volatile products evolved during the process of heating may become recondensed in the cooler part of the tube, and thus saved for further examination. The presence of water, sulphur, mercury, arsenic, etc., may often be readily demonstrated by this mode of operating. INTRODUCTORY REMARKS. 225 4. Heating on charcoal by means of the blowpipe. This test reveals the presence of chlorates and nitrates by the vivid com- bustion of the charcoal (known as deflagration), which takes place in consequence of the oxidizing action of these substances. Arsenic is indicated by a characteristic odor of garlic. 5. Heating on charcoal with sodium carbonate and potassium cyanide. A small quantity of the finely powdered substance is mixed with twice its weight of potassium cyanide and dry sodium carbonate. This mixture is placed in a small hole made in a piece of charcoal, and heat applied by means of the blowpipe (see Fig. 23). Many metallic compounds may be recognized by this test, the metals being liberated and found as metallic globules or shining particles in the fused mass after this has been removed from the charcoal and washed with water in a small mortar. (See Fig. 24.) Fig. 24. A characteristic incrustation is formed by some metals, due to the precipitation of a metallic oxide around the heated spot on the charcoal. If sulphur as such, or in any form of combination, he present in the substance examined by this test, the fused mass contains a sulphide of the alkali (hepar), which may be recognized by placing it on a piece of bright silver (coin) moistened with a drop of water, when the silver will be stained black in consequence of the formation of silver sulphide. The presence of the alkaline sulphide may also be demonstrated by the addition of a few drops of hydrochloric acid to the fused mass, when hydrosulphuric acid is evolved and may be recognized by its odor. 6. Flame tests. Many substances impart a characteristic color to a non-luminous flame. The best mode of performing this 226 ANALYTICAL CHEMISTRY. test is as follows: A platinum wire is cleaned by washing in hydrochloric acid and water, and heating it in the flame until the latter is no longer colored. One end of the wire is fused in a short piece of glass tubing (see Fig. 25), the other end is bent so Fig. 25. as to form a small loop, which is heated, dipped into the substance to be examined, and again held in the lower part of the flame, which then becomes colored. Some substances show the color-test after being moistened with hydrochloric or sulphuric acid. A second method of showing flame reactions is to mix the sub- stance with alcohol in a small dish; the alcohol, upon being ignited, shows a colored flame, especially in the dark. 7. Colored borax beads. The compounds of some metals when fused with glass, impart to it characteristic colors. For analytical purposes not the silica-glass, but borax-glass is generally used. This latter is made by dipping the loop of a platinum wire in powdered borax and heating it in the flame (directly, or by means of the blowpipe) until all water has been expelled and a color- less, transparent bead has been formed. To this colorless bead a little of the finely powdered substance is added and the bead strongly heated. The metallic compound is chemically acted upon by the boric acid, a borate being formed which colors the bead more or less intensely, according to the quantity of the metallic compound used. Some metals'(copper, for instance) forming two series of com- pounds, give different colors to the bead when present in either the higher or lower state of oxidation. By modifying the blowpipe flame so as either to oxidize (by supplying an excess of atmospheric oxygen) or deoxidize (by allowing some unburnt carbon to remain in the flame), the metallic compound in the bead may be made to assume the higher or lower state of oxidation. A copper bead may thus be changed from blue to red or red to blue, the blue bead con- taining the copper in the cupric, the red bead in the cuprous form. In some cases microcosmic salt, NaKH4HP04, is used for making the bead. INTRODUCTORY REMARKS. 227 Heat the solid sub- stance upon plati- num foil, or in a dry, narrow glass tube open at both ends. Combustible are: All organic compounds, carbon, sulphur, phosphorus, etc. Easily volatilized are: All compounds of ammonium and mercury, most of arsenic, some of antimony, etc. (Heat in a glass tube as directed on page 224.) Fusible are: Most of the salts of the alkalies, and some of those of the alkaline earths, many metals, etc. Infusible are: Salts of the earths, and most salts of the alkaline earths and heavy metals, most silicates, etc. Assume a darker color: Many oxides of the heavy metals and their salts (oxides of zinc, antimony, lead, etc.). Evolve water: Many salts containing water of crystallization, some hydroxides, etc. Decrepitate: Some salts, sodium chloride, for instance. Heat the solid sub- stance on charcoal. Deflagrate: Nitrates, chlorates, iodates, bromates, etc. Give garlic odor: Most compounds of arsenic. Heat the substance, mixed with sodium carbonate and po- tassium cyanide, on charcoal. Give hepar: Sulphur and all its compounds. Give bright metallic grains without incrustation: Compounds of gold, silver, copper, tin. Give bright metallic grains with incrustation : Compounds of lead, bismuth, antimony. Give gray infusible powder: Compounds of iron, cobalt, nickel, platinum. Heat the substance on platinum wire in a non-luminous flame. Yellow flame, compounds of sodium. Violet flame, compounds of potassium. Crimson flame, compounds of lithium or strontium. Orange flame, compounds of calcium. Yellowish-green flame, compounds of barium or molybdenum. Oreen flame, compounds of copper, phosphoric or boric acids. Blue flame, compounds of arsenic,antimony, lead, or cupric chloride. Heat a colorless borax bead with very little of the substance. Green bead, compounds of chromium. Blue bead, compounds of cobalt or copper in the oxidizing flame. Red bead, compounds of copper in the reducing flame. Violet bead, compounds of manganese. Yellow to brown bead, compounds of iron. Colorless head, compounds of the light metals and those of the arsenic group; also silver, bismuth, lead, etc. Table L — Preliminary examination. 228 ANALYTICAL CHEMISTRY. 8. Liquefaction of solid substances. Most solid substances have to be dissolved for analysis. The solution obtained may be either a simple or chemical solution. In a simple solution the dissolved body retains all of its original properties, with the exception of its shape, and may be reobtained by evaporation. Sodium chloride and sugar dissolved in water form simple solutions. A chemical solution is one in which the chemical composition of the substance has been changed during the process of dissolving, as, for instance, when calcium carbonate is dissolved in hydrochloric acid; this solution now contains and leaves on evaporation cal- cium chloride. The solvents used are water, or the mineral acids for substances insoluble in water, especially dilute, or, if neces- sary, strong hydrochloric acid. The dissolving action of the acid should be facilitated by the aid of heat. Nitric or even nitro- hydrochloric acid may have to be used in some cases. Three mistakes are frequently made by beginners in dissolving substances in acids, viz.: The substance is not powdered as finely as it should be; sufficient time is not given for the acid to act; too large an excess of the acid is used. If a substance is partly dissolved by water and partly by one or more other solvents, it may be well to examine the different solu- tions separately. Substances insoluble in water and in acids have to be rendered soluble by fusion with a mixture of potassium and sodium car- bonate, or with potassium acid sulphate, or by the action of hydrofluoric acid. The insoluble sulphates of the alkaline earths, when fused with the alkaline carbonates, are converted into carbonates, while the sulphates of the alkalies are formed. The latter com- pounds may be eliminated by washing the fused mass with water and filtering : the solid residue upon the filter contains the carbonates of the alkaline earths, which may be dissolved in hydrochloric acid. Insoluble silicates may be decomposed by the methods men- tioned on page 100. Questions.—311. What is analytical chemistry, and what is the object of qualitative and of quantitative analysis ? 312. What properties of a substance should be noticed first in making a qualitative analysis? 313. By what tests may organic compounds be distinguished from inorganic compounds? 314. Ex- plain the terms decrepitation and deflagration. 315. Mention some substances which are completely volatilized by heat, some which are fusible, and some SEPARATION OF METALS INTO DIFFERENT GROUPS. 229 33. SEPARATION OF METALS INTO DIFFERENT GROUPS. General remarks. The preliminary examination will, in most cases, decide whether or not a metal or metals are present in the substance to be examined. If there be metals, the solution should be treated according to Table II., page 233, in order to find the group or groups to which these metals belong, and also to separate them into these groups, the individual nature of the metals themselves being afterward demonstrated by special methods. The simplest method of separating from each other the 55 metals known, when all in one solution, would be to add succes- sively 55 different reagents, each of which should form an insol- uble compound with but one of the metals. By separating this insoluble compound from the metals remaining in solution (by filtration), and by thus precipitating one metal after the other, they all could be easily separated. We have, however, no such 55 reagents, and are, consequently, compelled to precipitate a number of metals together, and the reagents used for this pur- pose are known as group-reagents. They are: 1. Hydrosulphuric acid, added to the solution previously acidi- fied by hydrochloric acid. Precipitated are : the metals of the arsenic and lead groups as sulphides. 2. Ammonium sulphide, added after supersaturating with ammo- nium hydroxide. Precipitated are : the metals of the iron group and of the earths as sulphides or hydroxides. 3. Ammonium, carbonate. Precipitated are: the metals of the alkaline earths as carbonates. 4. In solution are left: the metals of the alkalies and magnesium. The order in which these group-reagents are added cannot be reversed or changed, because ammonium sulphide added first which are not changed by heating them. 316. What is meant by “hepar,” and which element is indicated by the formation of hepar? 317. Mention some metals which may be liberated from their compounds by heating on charcoal with potassium cyanide and carbonate. 318. Which metallic compounds and which acids are capable of coloring a non-luminous flame? Name the colors imparted. 319. State the metals which impart characteristic colors to a borax bead. 320. Which solvents are used for liquefying solids, and what precautions should be observed in this operation? 230 ANALYTICAL CHEMISTRY. would precipitate not only the metals of the iron group and the earths, but also the metals of the lead group; ammonium carbo- nate would precipitate also most of the heavy metals. For the same reasons, in separating metals of the different groups, the group-reagents must be added in excess, that is, enough of them must be added to precipitate the total quantity of the metals of one group, before it is possible to test for metals of the next group. Suppose, for instance, a solution to contain a salt of bismuth only. Upon the addition of hydrosulphuric acid to the acidified solution, a dark-brown precipitate (of bismuth sulphide) is produced, indicating the presence of a metal of the lead group. Suppose, further, that hydrosulphuric acid has not been added in sufficient quantity to precipitate the whole of the bismuth, then ammonium sulphide, as the next group-reagent, would produce a further precipitation in the filtrate, which fact would lead to the assumption that a metal of the iron group was present, which, however, would not be the case. If the solution contain but one metal, the group-reagents are added successively in small quantities to the same solution, until the reagent is found which causes a precipitation, which reagent is then added in somewhat larger quantity in order to produce a sufficient amount of the precipitate for further examination. Acidifying the solution. Hydrosulphuric acid has to be added to the acidified solution for two reasons, viz.: In a neutral or alkaline solution some metals of the arsenic group (which are to be precipitated) would not be precipitated by hydrosulphuric acid; some of the metals of the iron group (which are not to be precipitated) would be thrown down. The best acid to be used in acidifying is dilute hydrochloric acid; but this acid forms insoluble compounds with a few of the metals of the lead group, causing them to be precipitated. Com- pletely precipitated by hydrochloric acid are mercurous and silver compounds; partially precipitated are compounds of lead, chloride of lead being somewhat soluble in water. The precipi- tate formed by hydrochloric acid may be examined by Table III., page 234. Hydrochloric acid added to a solution may, in a few cases (other than those just mentioned), cause a precipitate, as, for instance, when added to solutions containing certain compounds of antimony or bismuth (the precipitated oxychlorides of these SEPARATION OF METALS INTO DIFFERENT GROUPS. 231 metals are soluble in excess of the acid), to metallic oxides or hydroxides which have been dissolved by alkaline hydroxides (for instance, hydroxide of zinc dissolved in potassium or ammo- nium hydroxide), to solutions of alkaline silicates, when silica separates, etc. Addition of hydrosulphuric acid. This reagent is employed either in the gaseous state (by passing it through the heated solu- tion) or as sulphuretted hydrogen water. The latter reag6nt answers in those cases where but one metal is present; if, how- ever, metals of the arsenic and lead groups are to be separated from metals of other groups, the gas must be used. Fig. 26. Fig. 27. Apparatus for generating hydrosulphuric acid, Apparatus for generating hydrosulphuric acid. For generating hydrosulphuric acid the directions given on page 109 may be followed. In place of the apparatus there mentioned for generating the gas, others may be used which have the advantage to the analyst that the supply of gas may be better regulated. Fig. 26 shows such an apparatus for the con- tinuous preparation of the gas. It consists of three glass bulbs ; the upper bulb, prolonged by a tube reaching to the bottom of the lowest one, is ground air- tight into the neck of the second. Ferrous sulphide is introduced into the middle bulb through the tubulure, which is then closed by a perforated cork through which connection is made with the wash bottle. Acid poured in through the safety tube, runs into the bottom globe and rises to the ferrous sulphide in the second bulb. Upon closing the delivery tube, the pressure of 232 ANALYTICAL CHEMISTRY. the generated gas forces the liquid from the second bulb through the lower to the upper, thus preventing contact of acid and ferrous sulphide until the gas is used again. A convenient and cheaper apparatus is shown in Fig. 27. A glass tube, drawn at its lower end to a small point and partly filled with pieces of ferrous sulphide, is suspended through a cork (not air-tight) in a cylinder containing the acid. The gas supply is regulated by closing or opening the stop-cock, and also by raising or lowering the tube in the acid. In some cases sulphur is precipitated on the addition of hydro- sulphuric acid, while a change in color may take place. This change is due to the deoxidizing action of hydrosulphuric acid, the hydrogen of this reagent becoming oxidized and converted into water, while sulphur is liberated. Thus, brown ferric com- pounds are converted into pale-green ferrous compounds ; red solutions of acid chromates become green; and red permanga- nates or green manganates are decolorized. The same deoxidizing action of hydrosulphuric acid is the reason why this reagent cannot be employed in a solution con- taining free nitric acid, which latter compound oxidizes the hydrosulphuric acid. Separation of the metals of the arsenic from those of the lead group. The precipitate produced by hydrosulphuric acid in acid solution contains the metals of the arsenic and lead groups. They are separated by means of ammonium sulphide, which dissolves the sulphides of the arsenic group, but does not act on those of the lead group. Addition of ammonium sulphide. This reagent should never be added to the acid solution, but the solution should be previously supersaturated by ammonium hydroxide, as, otherwise, a precipi- tate of sulphur maybe formed. The yellow ammonium sulphide is almost invariably a polysulphide of ammonium, that is, ammo- nium sulphide which has combined with one or more atoms of sulphur. If an acid be added to this compound, an ammonium salt is formed, hydrosulphuric acid is liberated, and sulphur pre- cipitated : (NH4)2S2 + 2HC1 = 2NH4C1 + H2S + S. Ammonium sulphide precipitates the metals of the iron group as sulphides, with the exception of chromium, which is precipitated as hydroxide; aluminium is precipitated in the same form of combination. SEPARATION OF METALS INTO DIFFERENT GROUPS. Add the following reagents successively to the same solution. Every time a precipitate is formed an excess of the precipitant is to be used ; the precipitate is collected upon a filter, well washed, and treated by the tables mentioned. To the clear filtrate the next group-reagent is added. If the solution contains but one metal, generally it is sufficient to find by means of this table the group to which it belongs, and then to use the original solution for testing according to Tables III.-VIII. Dilute hydrochloric acid precipitates : Hydrosulphuric acid prepipitates: Ammonium hydrox- ide and sulphide precipitate: Ammonium car- bonate precipitates: In solution are left: Metals of the lead group. Arsenic group. Iron group and earths. Alkaline earths. Alkalies and mag- nesium. Insoluble in ammo- nium sulphide. Soluble in ammo- nium sulphide. Silver chloride, "| Mercurous [_ •- chloride, | Lead chloride, J l"' A precipitate may be caused by other sub- stances than those men- tioned. See page 230. Lead sulphide, ~] Mercuric sul- 1 pliide, 1 Bismuth sul- j- J phide, 1 pq Cupric sul- | phide, J Cadmium sulphide, yellow. Arsenious sulph- ide, yellow. Antimonious sul- phide, orange. Stannous sulphide, brown. Stannic sulphide, yellow. Auric sulphide, brown. Platinic sulphide, brown. Ferrous sulphide, black. Cobaltous sulphide, black. Nickelous sulphide, black. Manganous sulphide, flesh-colored. Zinc sulphide, white. Chromic hydroxide, green. Aluminium hydroxide, white. A precipitate may be caused by other sub- stances than those men- tioned. See page 234. Calcium car- bonate, | Barium car- | bonate, f Strontium | carbonate, J Magnesium. Potassium. Sodium. Lithium Ammonium. See Table III. See Table IV. See Table Y. See Table VI. See Table VII. See Table.VIII. Table IT.—Separation of metals into different groups. 234 ANALYTICAL CHEMISTRY. Ammonium sulphide (or ammonium hydroxide) causes also the precipitation of metallic salts which have been dissolved in acids, as, for instance, of the phosphates, borates, silicates, or oxalates of the alkaline earths, magnesium, and others. The processes by which the nature of some of these precipitates is to be recog- nized are found in Table VI., page 237. Addition of ammonium carbonate. The reagent used is the com- mercial salt, dissolved in water, to which some ammonium hydroxide has been added. Heating facilitates complete precipi- tation of the carbonates of the alkaline earths. 34. SEPARATION OF THE METALS OF EACH GROUP. Table III.—Treatment of the precipitate formed by hydrochloric acid. The precipitate may contain silver, mercurous, and lead chlorides. Boil the washed precipitate with much water, and filter while hot. Filtrate may contain lead chloride. Add dilate sulphuric acid: a white Residue may consist of mercurous and silver chlor- ides. Digest residue with ammonium hydroxide. precipitate of lead sul- phate is produced. Solution may contain sil- ver. Neutralize with nitric acid, when silver chloride is reprecipi- tated. A dark gray residue indi- cates mercury, the white mercurous chloride hav- ing been converted into dimercurous ammonium chloride. Treatment of the precipitate formed by hydrosulphuric acid in warm acid solution. The precipitate is collected upon a small filter, well washed with water, and then examined for its solu- bility in ammonium sulphide. This is done by placing a por- Questions.—321. State the three groups of heavy, and the three groups of light metals. 322. By which two reagents may all heavy metals be precipi- tated? 323. Why is a solution acidified before the addition of hydrosulphuric acid, when testing for metals? 324. Which metals are precipitated by hydro- chloric acid? 325. Which two groups of metals are precipitated by hydrosul- phuric acid in acid solution? 326. How are the sulphides of the arsenic group separated from those of the lead group? 327. Why is an acid solution neutralized or supersaturated by ammonium hydroxide, before adding am- monium sulphide? 328. Which two groups of metals are precipitated by ammonium sulphide, and in what forms of combination? 329. Name the group-reagent for the alkaline earths. 330. Which metals may be left in solu- tion after hydrosulphuric acid, ammonium sulphide, and ammonium carbonate have been added? SEPARATION OF THE METALS OF EACH GROUP. 235 tion of the washed precipitate in a test-tube, adding ammonium sulphide, and warming gently. It is either wholly insoluble (metals of the lead group), and treated according to Table IV., or fully soluble (metals of the arsenic group), and treated ac- cording to Table V., or it is partly soluble and partly insoluble (metals of both groups). In the latter case, the total quantity of the washed precipitate is to be treated with warm ammonium sulphide; upon filtering, an insoluble residue is left, which is treated according to Table IV.; to the filtrate, diluted sulphuric acid is added as long as a precipitate is formed, which precipitate contains the metals of the arsenic group as sulphides, generally with some sulphur from the ammonium sulphide. The precipitation of sulphur, in the absence of metals of the arsenic group, frequently leads beginners to the assumption that metals of this group are present. The precipitate consisting only of sulphur is white and milky, but flocculent, and more or less colored in the presence of the metals of the arsenic group. Table IV.—Treatment of that portion of the hydrosulphuric acid preci- pitate which is insoluble in ammonium sulphide. The precipitate may contain the sulphides of lead, copper, mercury, bismuth, and cadmium. Heat the well-washed precipitate with nitric acid in a test-tube, and filter. Residue may con- sist of: Mercuric sulph- ide which is Filtrate may contain the nitrates of lead, copper, bis- muth, and cadmium. Add to the solution a few drop* of dilute sulphuric acid. black and easily dissolves in ni- Precipitated is Solution may contain copper, bismuth, trohydrochloric lead,as white and cadmium. Supersaturate with am- acid, which solu- lead sulphate, monium hydroxide. tion, after suffi- cient evaporation, which is sol- uble in ammo- is tested by potas- nium tartrate Precipitated is Solution may contain copper sium iodide, etc. with excess of white bis- and cadmium. Lead sulphate ammonium muth hy- Divide solution in two parts, is white, pulveru- hydroxide. droxide. Dis- and test for copper by potas- lent, and soluble solve in hy- sium ferrocyanide in the in ammonium drochloric acidified solution ; a red pre- tartrate. acid and ap- cipitate indicates copper. Sulphur is yellow ply tests for To second part add potas- and combustible. bismuth. sium cyanide and hydro- sulphuric acid. A yellow precipitate indicates cad- mium. 236 ANALYTICAL CHEMISTRY. Table V.—Treatment of the hydrosulphuric acid precipitate which is soluble in ammonium sulphide. The precipitate may contain the sulphides of arsenic, antimony, tin, and a few of those metals which are but rarely met with in qualitative analysis, such as gold, platinum, molybdenum, and others, which latter metals, if suspected, may be detected by special tests. Boil the washed precipitate with strong hydrochloric acid. An insoluble yellow residue con- sists of arsenious sulphide. The residue is dissolved by boiling with hydrochloric acid and a little potassium chlorate, and the solution examined by Marsh’s test. A dark-colored residue may indi- cate gold or platinum for which use special tests. The solution may contain the chlorides of antimony and tin. The solution is introduced into Marsh’s apparatus when all antimony is gradually evolved as antimoniuretted hydrogen, while tin remains with the undissolved zinc as a black metallic powder, which may be col- lected, washed, dissolved in hydrochloric acid, and the solution tested by the special tests for tin. Questions.—331. By what tests can mercurous chloride be distinguished from the chloride of silver or lead? 332. How can it be proved that a pre- cipitate produced by hydrosulphuric acid in an acid solution contains a metal or metals of either the arsenic or lead group ? 333. How can mercuric sulphide be separated from the sulphides of copper and bismuth ? 334. How does am- monium hydroxide act on a solution containing bismuth and copper? 335. State the action of strong, hot hydrochloric acid on the sulphides of arsenic and antimony. 336. Suppose a solution to contain salts of iron, aluminium, zinc, and manganese ; by what process could these four metals be separated and recog- nized? 337. How can barium, calcium, and strontium be recognized when dis- solved together? 338. By what tests is magnesium recognized? 339. State a method of separating potassium when mixed with other metallic compounds. 340. How are ammonium compounds recognized when in solution with other metals ? SEPARATION OF THE METALS OF EACH GROUP. The precipitate may contain the sulphides of iron, manganese, and zinc (cobalt and nickel),1 the hydroxides of chromium and aluminium, and possibly the phosphates of barium, calcium, strontium, and magnesium.2 Dissolve the washed precipitate in the smallest possible quantity of warm, dilute hydrochloric acid, and heat the solution with a few drops of nitric acid. To the clear solution add ammonium chloride, and supersaturate it with ammonium hydroxide. The precipitate may contain the hydroxides of iron, aluminium, and chromium, and the phosphates of the alkaline earths or of magnesium. Dissolve the precipitate in a little hydrochloric acid, and supersaturate with potassium hydroxide. The solution may contain zinc, manganese, cobalt, and nickel. Acidulate the ammonia solution with acetic acid, and add hydrosulphuric acid. Precipitated is ferric hydrox- ide, reddish-brown. Dissolve in dilute hydrochloric acid, and add potassium ferrocyanide. A blue precipitate indicates iron. Precipitate may also contain the phosphates of the alkaline earths or magnesium To the solution of the precipitate in hydrochloric acid add ammonium hydroxide until a precip- itate is formed which does not redissolve on stirring. Add a few drops of acetic acid to dissolve the precipitate, and then ammo- nium oxalate. A white precipitate indicates calcium. Barium and strontium are indicated by the addition of calcium sulphate, and distin- guished by flame reaction. Test for phosphoric acid by ammonium molybdate. Solution may contain alumin- ium, and, if green, chromium. Supersaturate the alkaline solu- tion slightly with hydrochloric acid, and add ammonium carbon- ate. A white gelatinous precipi- tate indicates aluminium. Boil the (green) solution for some time. A green precipitate indi- cates chromium. Precipitate may contain the sulphides of zinc, cobalt, and nickel. If the precipitate be white, it is zinc sulphide only; if black, it may contain cobalt and nickel. If the latter be present, the precipi- tate is dissolved in hydrochloric acid with little nitric acid, and the solution supersaturated with po- tassium hydroxide. The filtrate then contains the zinc, the black precipitate cobalt and nickel. Solution may contain man- ganese, which is verified by adding ammonium hydroxide and sulphide, which produce a flesh-colored precipitate. 1 The sulphides of cobalt and nickel are but sparingly soluble in hydrochloric acid, but dissolve readily in nitrohydrochloric acid. 2 In the absence of a sufficient quantity of ammonium chloride some magnesium hydroxide may also be precipitated. Table VI.—Treatment of the precipitate formed by ammonium hydroxide and ammonium sulphide. 238 ANALYTICAL CHEMISTRY. Table VII.—Treatment of the precipitate formed by ammonium carbonate. The precipitate may contain the carbonates of barium, calcium, and strontium.1 Dissolve the precipitate in acetic acid, and add potassium chromate. Precipitated is barium, as pale yellow barium chromate. Solution may contain calcium and strontium. Add very dilute sulphuric acid, and let stand for fifteen minutes. Precipitated is stron- tium, as white stron- tium sulphate. Solution may contain cal- cium. Supersaturate with ammonium hydrox- ide and add ammonium oxalate. A white pre- cipitate indicates cal- cium. Table VIII.—Detection of the alkalies and of magnesium. The fluid which has been treated with hydrochloric acid, hydrosulphuric acid, ammonium hydroxide, sulphide, and carbonate, may contain magnesium and the alkalies. Divide solution into two portions. To the first portion add sodium phosphate. A white crystalline precipitate indicates magnesium.2 The second portion is evaporated to dryness, further heated (or ignited) until all ammonium compounds are expelled, and white fumes are no longer given off. The residue is dissolved in water, and platinic chloride added. A yellow precipi- tate indicates potassium. The residue is also examined by flame test: a yellow color indicating sodium, a red color lithium. Ammonium compounds have to be tested for in the original fluid by treat- ing it with calcium hydroxide, when ammonia gas is liberated. 1 If an insufficient quantity of ammonium chloride should have been present, some magnesia may also be contained in this precipitate, and may be redissolved by treating it with ammonium chloride solution. 2 If an insufficient quantity of ammonium chloride has been produced in the original solution by the addition of hydrochloric acid and ammonium hydroxide, a portion of the magnesia may have been precipitated by the ammonium hydroxide or carbonate. DETECTION OF ACIDS. 239 35. DETECTION OF ACIDS. General remarks. There are no general methods (similar to those for the separation of metals) by which all acids can be separated, first into different groups, and afterward into the individual acids. It is, moreover, impossible to render all acids soluble (when in combination with certain metals) without de- composition, as, for instance, in the case of carbonic acid when in combination with calcium; calcium carbonate is insoluble in water, and when the solution is attempted by means of acids, decomposition takes place with liberation of carbon dioxide. Many other acids suffer decomposition, in a similar manner, when attempts are made to render soluble the substances in which they occur. It is due to these facts that a complete separation of all acids is not so easily accomplished as the separation of metals. There is, however, for each acid a sufficient number of characteristic tests by which it may be recognized; moreover, the preliminary examination, as well as the solubility of the substance, and the nature of the metal or metals present, will aid in pointing out the acid or acids which are present. If, for instance, a solid substance be completely soluble in water, and if the only metal found were iron, it would be un- necessary to test for carbonic, phosphoric, and hydrosulphuric acids, because the combinations of these acids with iron are insoluble in water; there might, however, be present sulphuric, hydrochloric, nitric, and many other acids, which form soluble salts with iron. Detection of acids by means of the action of strong sulphuric acid upon the dry substance. The action of sulphuric acid upon a dry powdered substance often furnishes such characteristic indications of the presence or absence of certain acids, that this treatment should never be omitted when a search for acids is made. When the substance under examination is liquid, a portion should be evaporated to dryness, and, if a solid residue remains, it should be treated in the same manner as a solid. Most non-volatile, organic substances (including most organic acids) color sulphuric acid dark when heated with it. Dry inorganic salts when heated with sulphuric acid either are decomposed, with liberation of the acid (which may escape in 240 ANALYTICAL CHEMISTRY. the gaseous state), or with liberation of volatile products (pro- duced by the decomposition of the acid itself), or no apparent action takes place. See Table IX. Detection of acids by means of reagents added to their neutral or acid solution. Whenever a substance is soluble in water, there is little difficulty of finding the acid by means of Table X.; but if the substance is insoluble in water, and has to be rendered soluble by the action of acids, this table may, in some cases, be of no use, because the acid originally present in the substance may have been liberated, and escaped in a gaseous state (as, for instance, when dissolving insoluble carbonates in acids), or the tests mentioned in the table may refer to neutral solutions, while it is impossible to render the solution neutral without re- precipitating the dissolved acid. If calcium phosphate, for instance, be dissolved by hydrochloric acid, the magnesium test for phosphoric acid cannot be used, because this test can be applied to a neutral or an alkaline solution only; in attempting, however, to neutralize the hydrochloric acid solution, calcium phosphate itself is reprecipitated. Table XI., showing the solubility or insolubility (in water) of over 300 of the most important inorganic salts, oxides, and hydroxides, will greatly aid the student in studying this impor- tant feature. It will also guide him in the analysis of inorganic substances, as it gives directions for over 300 (positive or nega- tive) tests for metals, and an equal number for acids. To understand this, it must be remembered that any salt (or oxide or hydroxide) which is insoluble in water may be produced and precipitated by mixing two solutions, one containing the metal, the other containing the acid of the insoluble salt to be formed. For instance: Table XI. states that the carbonates of most metals are insoluble in water. To produce, therefore, the carbonate of any of these metals (zinc, for instance) it becomes necesssary to add to any solution of zinc (sulphate, chloride, or nitrate of zinc) any soluble carbonate (sodium or potassium car- bonate), when the insoluble zinc carbonate is produced. Soluble carbonates consequently are reagents for soluble zinc salts, while at the same time soluble zinc salts are reagents for soluble carbonates. DETECTION OF ACIDS. 241 A small quantity of the finely powdered substance is treated with about four times its weight of concentrated sulphuric acid, in a test-tube, care being taken not to heat to the boiling-point of sulphuric acid. No apparent change takes place. No gas is evolved. A colorless gas is evolved. A colored gas is evolved. Sulphuric acid (hepar and barium test). Phosphoric acid (molybdate of ammonium test). Boric acid (green flame after moistening with sulphuric acid). Arsenic acid, Silicic acid, Molybdic acid, Special tests. Phosphorous acid, Arsenious acid, Hydrochloric acid (silver test). Carbonic acid (the gas is generated also by diluted acids in the cold, and renders lime-water turbid). Nitric acid (the vapors turn red on the addition of ferrous sulphate). Sulphurous acid (odor). Hydrosulphuric acid (odor). Hydrofluoric acid (corrodes glass). Acetic acid (odor of acetic ether on the addition of alcohol). Many organic acids are decomposed with liberation of colorless gases. Hydriodic acid (violet vapors of iodine). Hydrobromic acid (brown vapors of bro- mine). Bromic acid (brown vapors ; deflagration on charcoal). Chloric acid (the greenish-yellow gas ex- plodes readily). Nitric acid (vapors more red on adding fer- rous sulphate). Nitrous acid (red vapors). Whenever one or more acids are suspected or are indicated by the above tests, their presence is to be verified by the tests in Tables X. and XI., or by the reactions given in connection with the considerations of the acids themselves. For latter tests see Index. Table IX.—Preliminary examination for inorganic acids. 242 ANALYTICAL CHEMISTRY. Magnesium sulphate Silver nitrate precipitates Calcium chloride pre- Barium Chloride pre- | cipitates from neutral or precipitates in the pres- ence of ammonium Ferric chloride precipi- cipitates : alkaline solution : tates from neutral solution : hydroxide and chlo- ride : from neutral solution: from neutral or acid solution Sulphuric acid, white. Sulphuric acid, white. Hydrochloric acid, Sulphurous acid, white. white. Hydrobromie acid, Sulphurous acid, white. Sulphurous acid, white. white. Phosphoric acid, white, j Phosphoric acid, white- Phosphoric acid, yel- Phosphoric acid, white. Phosphoric acid, pale Hydriodic acid, white. lowish-white. yellow. Phosphorous acid, Phosphorous acid, white, then black. Iodic acid, white. white. Carbonic acid, white. Carbonic acid, white. (Ferric hydroxide is precipi- Carbonic acid, white. Hydrocyanic acid, tated and carbon dioxide escapes). white. Boric acid, white. Boric acid, white. Boric acid, yellowish. Boric ae d, white. Ferrocyanides, white. Arsenic acid, white. Arsenic acid, white. Arsenic acid, yellowish- Arsenic acid, white. Arsenic acid, brownish- Ferricyanides, reddish white. red. brown. Ferrocyanides, blue. Sulphocyanides, red coloration. Arsenious acid, yellow. Chromic acid, red. Sulphocyanides, white Hydrosulphuric acid, black. low. Hydrosulphuric acid, black. Oxalic acid, white. Oxalic acid, white. Oxalic acid, yellow. Oxalic acid, white. Tartaric acid, white. Tartaric acid, white. Tannic acid, black Tartaric acid, white; Tartaric acid, white. Not precipitated are: precipitate forms slowly. Citric acid, white. Nitric acid. Citric acid, white. Citric acid, white. Acetic acid, a reddish- brown coloration is pro- Nitrous acid. All the above precipitates duced, and, on boiling, a Chloric acid. are soluble in hydrochloric j and most other acids, with 1 the exception of barium sul- reddish-brown precipitate. Hypochlorous acid. pliate. Acetic acid. ! - • _____ Table X — Detection of the more important acids by means of reagents added to the solution. DETECTION OF ACIDS. 243 Table XI Systematically arranged table showing the solubility and insolubility of inorganic salts and oxides in water. The dark squares represent insoluble, the white soluble compounds. .Carbonate. Phosphate Arseniate. Arsenite. Oxide. Hydroxide. Sulphide. Iodide. Chloride. Sulphate. Nitrate. Chlorate. Potassium Sodium Ammonium Alkalies. Calcium Barium Strontium Alkaline Earths. Magnesium Aluminium Ferric Ferrous Zinc Chromium Nickel Cobalt Manganese Iron Group. Stannic Stannous Arsenic Arsenious Antimony Gold Platinum Arsenic Group. Copper Bismuth Cadmium Mercuric Mercurous Silver Lead- Lead Group. 244 ANALYTICAL CHEMISTRY Table XII.—Table of solubility. w = soluble in water, a = insoluble in water, soluble in acids (HC1, HNOs). t = insoluble in water and acids, w a = sparingly soluble in water, but soluble in acids. wt = sparingly soluble in water and acids, a t = insoluble in water, sparingly soluble in acids. Aluminium. Ammonium. Antimony. £ Bismuth. Cadmium. Calcium. Chromium. Cobalt. Copper. Ferrous. d £ w Eh Lead. Magnesium. Manganese. Mercurous. Mercuric. W o yA Potassium. Silver. Sodium. Strontium. Zinc. Acetate w w vv vv vv w w VV VV VV W w w w w a W w w w vv vv VV Arseniate . a w a a a a a a a a a a a a a a a a vv a vv a Arseni te . w a a a a a a a a a a a a a vv a vv a Borate a w a a vv a a a a a a a a vv a a a vv a vv a a Bromide . w w w a VV vv a VV vv vv t w w vv w vv t VV vv a t VV w vv a vv vv w Carbonate a w a a a a •a a a a a a a a a a vv a w a a Chlorate . w vv w w VV VV VV w w vv w VV VV vv VV VV VV vv w vv vv w Chloride . w w vv a vv vv a w w w vv w w VV w t vv vv a t w VV w t \v vv w Chromate . vv a a a a w a a a vv vv a t w vv a vv a a vv a vv vv a w Citrate w vv a a vv a w w w w w a vv a a w a vv vv a w a w a Cyanide . vv vv a a w a a t a a t a vv a vv a t vv t vv w a Ferricyanide w vv t t w w a w t t vv t w a Ferrocyanide . vv w a vv t t t t a vv a t vv t vv VV a t Fluoride . w vv VV a t w w a a w vv a a vv a w a a t a vv a w a vv w vv a t w a Hydroxide a vv a w a a a w a a a a a a a a a a vv vv vv a a Iodide w vv vv a vv a w vv w VV w w w vv a vv w a a VV vv t vv w VV Nitrate vv vv vv vv w w w vv w w w w vv vv w vv vv vv vv vv vv w Oxalate a vv a a a a a vv a a a a a a a VV it a a a vv a w a a Oxide a or t a vv a a a w a a t a a a a a a a a a a vv a vv vv a a Phosphate a w w a w or a a a w a a a a a a a a a a a a w a w a a Silicate . a t a a a a a a a a a a a a vv w a a Sulphate . w w a a vv VV t vv a w w w w a t w w W it vv \v vv w a vv t VV Sulphide . a w a vv a a vv a a t a a a a a a a a a a vv a w vv a Tartrate . w vv a a a vv a a w w vv w a w a w a w a w H a a vv a w a a 245 DETECTION OF ACIDS. For similar reasons soluble zinc salts are, according to Table XI., reagents for soluble phosphates, arSeniates, arsenites, hy- droxides, and sulphides, but not for iodides, chlorides, sulphates, nitrates, or chlorates. The insolubility of a compound in water is not an absolute guide for preparing this compound according to the general rule given above for the precipitation of insoluble compounds, there being some exceptions. For instance: Cupric hydroxide is insoluble in water; there- fore, by adding solution of cupric sulphate to any soluble hy- droxide, the insoluble cupric hydroxide should be precipitated, and is precipitated by the soluble hydroxides of potassium and sodium, but not by the soluble hydroxide of ammonium, on account of the formation of the soluble ammonium cupric sulphate. There are not many such exceptions, and to mention them in the table would have greatly interfered with its simplicity, for which reason they have been omitted. For the same reason some compounds, which are not known at all, have not been specially mentioned. For instance, accord- ing to Table XI., aluminium carbonate and chromium carbonate are insoluble salts: actually, however, these compounds can scarcely be formed, the affinity between the weak carbonic acid and the feeble bases not being sufficient to unite them. Finally, it may be stated that no well-defined line can be drawn between soluble and insoluble substances. There is scarcely any substance which is not slightly soluble in water, and many of the so-called soluble substances are but very sparingly soluble, as, for instance, the hydroxide and sulphate of calcium. Table XII. shows the solubility of a large number of com- pounds more accurately than Table XI.; it may be used for reference. Questions.—341. Why is sulphuric acid added to a solid substance when it is to be examined for acids? 342. Mention some acids which cause the libera- tion of colorless, and some which cause the liberation of colored gases when the salts of these acids are heated with sulphuric acid. 343. Mention an acid which is precipitated by barium chloride in acid solution, and some acids which are precipitated by the same reagent in neutral solution. 344. Which acids inay be precipitated by silver nitrate from neutral solutions, and which from either neutral or acid solutions? 345. Mention some acids which form soluble salts only. 346. Mention three soluble, and three insoluble carbonates, phos- phates, arseniates, sulphates, and sulphides respectively. 347. Which oxides 246 ANALYTICAL CHEMISTRY. 36. DETECTION OF IMPURITIES IN OFFICINAL INORGANIC CHEMICAL PREPARATIONS. General remarks. Very little has been said, heretofore, about impurities which may be present in the various chemical prepa- rations, and this omission has been intentional, because it would have increased the bulk of this book beyond the limits considered necessary for the beginner. Impurities present in chemical preparations either are derived from the materials used in their manufacture, or they have been intentionally added as adulterations. In regard to the last, no general rule for detecting them can be given, the nature of the adulterating article varying with the nature of the substance adulterated; the general properties of the substance to be ex- amined for purity will, in most cases, suggest the nature of those substances which possibly may have been added, and for them a search has to be made, or, if necessary, a complete analysis, by which is proved the absence of everything else but the constitu- ents of the pure substance. Impurities derived from the materials used in the manufacture of a substance (generally through an imperfect or incorrect pro- cess of manufacture), or from the vessels used in the manufacture, are usually but few in number (in any one substance), and their nature can, in most cases, be anticipated by one familiar with the process of manufacture itself. For one not acquainted with the mode of preparation, it would be a rather difficult task to study the nature of the impurities which might possibly be present. The same remarks apply to the methods bjr which the impuri- ties can be detected. One familiar with analytical chemistry can easily find, in most cases, a good method by which the presence or absence of an impurity can be demonstrated; but to one un- acquainted with chemistry, it might be an impossibility to detect impurities, even if a method were given. For these reasons little stress has been laid upon the occur- rence of impurities in the various chemical preparations hereto- or hydroxides are soluble, and which are insoluble in water? 348. Mention some metals, the solutions of which are precipitated by soluble chlorides, iodides, and sulphides. 349. State a general rule according to which most insoluble salts may be formed from two other compounds. 350. Why is it sometimes impossi- ble to render a substance soluble in order to test for the acid in the solution obtained? DETECTION OF IMPURITIES. fore considered; moreover, the U. S. P. itself gives, in most cases, directions for the detection of impurities, and, finally, the analyst may avail himself of books specially treating of the examination of chemicals. In order to give the student, and especially the beginner, a guide to examination for impurities, the following pages furnish a few directions in regard to the impurities which may be present in the more important chemical preparations, and also some of the tests used for recognizing them. O O Examination of sulphuric, sulphurous, nitric, phosphoric, and hydrochloric acids. The pure acids should be colorless, and upon evaporation leave no residue whatever (phosphoric acid requires a red heat for complete evaporation). After being neutralized with an alkali, and then slightly acidulated with hydrochloric acid, they should give no precipitate with hydrosulphuric acid, ammonium hydroxide, or sulphide, or carbonate. Sulphuric, phosphoric, and hydrochloric acids sometimes (nitric acid very rarely) contain arsenic, and should, therefore, be ex- amined by Marsh’s test. Sulphuric acid may contain sulphurous or nitric acid; the former may be recognized by potassium permanganate, which is decolorized by sulphurous acid; the latter is detected by care- fully pouring solution of ferrous sulphate upon the acid, when, if nitric acid be present, a brownish zone appears at the line of contact. Sulphurous acid frequently contains sulphuric acid; it should not give more than a very slight turbidity with barium chloride (limit of sulphuric acid). Nitric acid diluted with o parts of water should afford no pre- cipitate with either barium chloride or silver nitrate (absence of sulphuric and hydrochloric acids). Phosphoric acid should be tested for phosphorous, nitric, sul- phuric, hydrochloric, pyrophosphoric, and metapliosphoric acids. Phosphorous acid is indicated by the formation of a dark color when silver nitrate is added to the diluted acid; sulphuric and hydrochloric acids by the formation of white precipitates on the addition of barium chloride or silver nitrate, respectively, to the diluted acid; pyrophosphoric and metaphosphoric acids, by the formation of a precipitate upon adding to the acid an equal volume of tincture of chloride of iron. 248 ANALYTICAL CHEMISTRY. Hydrochloric acid, after being diluted, should not give a pre- cipitate with barium chloride (absence of sulphuric acid), and should not liberate iodine from potassium iodide (absence of free chlorine). The officinal acids should have the strength required by the U. S. P. The amount of actual acid can be determined either by the specific gravity of the liquid acid, or by the quantity of an alkali required to neutralize a certain quantity of the acid (See next chapter, on volumetric analysis.) Examination of potassium, sodium, and ammonium compounds. The acidulated solution of the hydroxides, carbonates, bicar- bonates, sulphates, nitrates, and phosphates of potassium, sodium, and ammonium should afford no precipitate with hydrosulphuric acid, or with hydroxide, sulphide, carbonate, or phosphate of ammonium (absence of heavy metals, alkaline earths, and mag- nesium). The nitrates, hydroxides, carbonates, and bicarbonates (the latter three, after being supersaturated with nitric acid), should be tested with solution of barium chloride and silver nitrate for sulphates and chlorides. Bicarbonates may contain carbonates; the latter are indicated by a white precipitate formed with magnesium sulphate in the cold solution; bicarbonates are not precipitated by this reagent in the cold. Sodium bicarbonate may also be tested for normal carbonate by adding a solution of 2 grams of the salt in 30 c.c. of cold water to a solution made by dissolving 0.3 gram of mercuric chloride in 6 c.c. of water. If within three minutes only a white cloud, but neither a red precipitate nor a red color has appeared, the absence of more than three per cent, of normal carbonate is demonstrated. Iodides may contain an iodate, which is indicated by a bine color on the addition of gelatinized starch and some diluted sulphuric acid; chlorides and bromides maybe detected by precipitating a solution of the iodide with an excess of silver nitrate, collecting and washing the precipitated iodide (bromide and chloride) of silver, and digesting it with ammonium hydroxide, which dis- solves the chloride and bromide, but not (or only traces of) the iodide; the filtered ammonium solution, upon being supersatu- rated with nitric acid, will give a white precipitate if chlorides DETECTION OF IMPURITIES or bromides are present; a slight turbidity may be due to traces of dissolved iodide. Potassium salts should impart a violet color to a non-luminous flame, a yellow color indicating sodium. All compounds of ammonium should be completely volatilized by heat, leaving no residue. Examination of compounds of calcium. Calcium chloride and calcium carbonate, the latter after having been converted into chloride by neutralizing with hydrochloric acid, should not be precipitated by hydrosulphuric acid or by ammonium hydroxide (absence of heavy metals and of aluminium); the solution, after adding ammonium hydroxide, ammonium chloride, and an excess of ammonium carbonate, and filtering off the precipitated calcium carbonate, should not be precipitated by sodium phos- phate (absence of magnesium). Distilled water digested with calcium carbonate or with tricalcium phosphate, should leave no residue upon evaporation. Calcium carbonate and phosphate should be tested for sulphates and chlorides by dissolving the salts in dilute nitric acid and adding barium chloride and silver nitrate. Iron will be indicated in calcium phosphate by saturating its solution in hydrochloric acid with hydrosulphuric acid, and then adding an excess of ammonium hydroxide ; the precipitate should be white, a dark color indicating iron (or possibly other heavy metals). Calcium hypochlorite (bleaehing-powder) has to be examined by quantitative (volumetric) methods to ascertain the amount of hypochlorous acid present. Examination of magnesium compounds. Magnesium sulphate, oxide, and carbonate, the latter two after being dissolved in dilute hydrochloric acid, should not be precipitated by hydrosulphuric acid, nor by ammonium hydroxide, sulphide, or carbonate after a sufficient amount of ammonium chloride has been added (absence of heavy metals and alkaline earths). Magnesium sulphate should be tested for chlorides by the addi- tion of silver nitrate. Water digested with the oxide or carbonate should leave no residue upon evaporation. The same compounds dissolved in nitric acid should not be precipitated by either barium chloride 250 ANALYTICAL CHEMISTRY. or silver nitrate. The oxide should not effervesce with acids (absence of carbonic acid). Examination of aluminium compounds. Aluminium sulphate and aluminium-potassium sulphate (alum) when dissolved in water, or aluminium hydroxide when dissolved in sulphuric acid, should not be precipitated by hydrosulphuric acid and should show no blue color on the addition of potassium ferrocyanide (absence of iron). Potassium or sodium hydroxide, added to the above solutions, should cause a white gelatinous precipitate, which is com- pletely dissolved by an excess of the reagent. Water digested with aluminium hydroxide should leave no residue upon evapo- ration. Examination of compounds of iron. The solution of ferrous salts, acidulated with hydrochloric acid, should not be precipi- tated by hydrosulphuric acid; solutions of ferric salts give with the same reagent an almost white precipitate of sulphur; a more or less colored precipitate would indicate the presence of metals of the arsenic or lead group. Solutions of ferric salts (or of ferrous salts after they have been converted into ferric salts by heating with hydrochloric and nitric acids), after having been precipitated by an excess of ammonium hydroxide and filtered,should not impartablue color to the tiltrate (absence of copper), and this tiltrate should not be precipitated by ammonium carbonate or phosphate (absence of alkaline earths and magnesium) and should not leave a residue on evaporation and gentle ignition (absence of zinc, manganese, alkalies, etc.). When solution of potassium hydroxide is added in excess to ferric solutions, the tiltrate should not be precipitated by am- monium carbonate after the alkaline solution has been neutral- ized by hydrochloric acid (absence of aluminium). Compounds of iron may contain arsenic, and should, therefore, be examined by Marsh’s test. Ferrous salts (sulphate) should give no immediate blue precipi- tate with potassium ferrocyanide (absence of ferric compounds). Ferric salts shovld give no blue color with potassium ferricyanide (absence of ferrous compounds). Ferric chloride should also be tested for nitric acid by placing a crystal of ferrous sulphate into the solution to which sulphuric DETECTION OF IMPURITIES 251 acid has been added (a brown color indicating nitric acid), and for sulphuric acid by barium chloride. Examination of compounds of zinc. Chloride or sulphate of zinc when dissolved in water, oxide or carbonate of zinc when dissolved i?i dilute hydrochloric acid, should give no precipitate, in the acidulated solution, with hydrosulphuric acid (absence of the metals of the arsenic and lead groups). Ammonium hydroxide added to zinc solutions should cause a white precipitate, which is completely dissolved by an excess of the reagents (absence of iron, aluminium, etc.). The filtrate of zinc solutions from which the metal has been precipitated by an excess of ammonium sulphide, should not he precipitated by ammonium carbonate or phosphate (absence of alkaline earths and magnesium), nor should it leave a residue on evaporation and gentle ignition (absence of alkalies). Water digested with zinc oxide or carbonate should leave no residue on evaporation. Zinc sulphate should be tested for chlorides by silver nitrate, and zinc chloride for sulphates by barium chloride. Examination of compounds of manganese. The native manganese dioxide invariably contains other mineral matter; according to the U. S. P., it should contain not less than 66 per cent, of the dioxide, and should, consequently, be examined by quantitative analysis. A solution of manganese sidphate, acidulated with hydrochloric acid, should give no precipitate with hydrosulphuric acid (absence of copper, etc.); the aqueous solution of the salt from which the manganese has been precipitated by ammonium sulphide should leave no residue on evaporation and gentle ignition (absence of magnesium, alkalies, etc.). Potassium. permanganate is complete^7 decolorized (deoxidized) by oxalic acid or sulphurous acid. The colorless solution should be tested with ferrous sulphate for nitric acid, and with silver nitrate for hydrochloric acid. It should also he tested quan- titatively. Examination of compounds of chromium. Solution of 'potassium dichromate and chromium trioxide, acidulated with nitric acid, should not be precipitated by barium chloride (absence of sul- 252 ANALYTICAL CHEMISTRY. phuric acid); both substances, when neutralized with potassium hydroxide, should give an immediate red precipitate with silver nitrate, a white precipitate indicating chlorides. Examination of compounds of lead. Solutions of compounds of lead, when completely precipitated with either sulphuric acid or with hydrosulphuric acid, should yield a filtrate which leaves no residue on evaporation and gentle ignition (absence of most other metals). Lead oxide (litharge) and lead carbonate should dissolve com- pletely in nitric acid. Lead iodide should be tested for lead chromate by triturating it with 2 parts of ammonium chloride and water, which dissolve the iodide, but not the chromate. Examination of compounds of copper. Solutions of cupric salts (sulphate), when completely precipitated by hydrosulphuric acid, should yield a filtrate which gives no precipitate with ammonium hydroxide, sulphide, or carbonate. Excess of ammonium hy- droxide added to a cupric solution should form a dark-blue solu- tion without leaving a residue. Examination of compounds of bismuth. Subnitrate and subcar- bonate of bismuth should be completely soluble in about 8 parts of a mixture of equal parts of nitric acid and water. When this solution is poured into 50 parts of water a white precipitate falls; the filtrate from this precipitate may be used to test for lead by sulphuric acid, for silver by hydrochloric acid, for sul- phates by barium chloride, for chlorides by silver nitrate (all of which reagents give white precipitates if the impurities named are present), and for copper by an excess of ammonium hydroxide, which precipitates the bismuth yet in solution, while copper would be indicated by the blue color of the filtrate. Another portion of the bismuth salt is dissolved in hydro- chloric acid and all bismuth precipitated by hydrosulphuric acid; the filtrate should leave no residue (absence of metals of the iron group and of the light metals). Examination of compounds of silver. A solution of silver nitrate in water, or of silver oxide in nitric acid, should give a white precipitate with hydrochloric acid, which precipitate should DETECTION OF IMPURITIES. 253 be completely dissolved by ammonium hydroxide. The filtrate from a solution from which all silver has been precipitated by hydrochloric acid, should leave no residue on evaporation. Silver oxide is readily dissolved by ammonia water. Examination of compounds of mercury. All compounds of mercury are completely volatilized on heating. The oxides of mercury are dissolved by heating with about 10 parts of dilute nitric acid; mercuric oxide, when heated in a tube, should evolve no red fumes (absence of nitric acid). Mercuric chloride should be soluble in water and in alcohol; it should be tested for arsenic by Marsh’s test. Mercurous chloride, when digested with water, should yield a filtrate which, on evaporation, leaves no residue, and which is not changed by either hydrosulphuric acid, silver nitrate, or potassium iodide (absence of mercuric chloride). Mercurous chloride is soluble in warm hydrochloric acid to which a little nitric acid is gradually added. Mercuric iodide should be dissolved by 25 parts of boiling alcohol, or by digesting it with potassium iodide and water. Mercurous iodide should be tested for mercuric iodide by digesting it with alcohol, which, upon evaporation, should leave no residue. Ammoniated mercury should be wholly soluble, without effer- vescence, in warm hydrochloric, nitric, or acetic acid; when digested with diluted alcohol, the filtrate should not be acted upon by hydrosulphuric acid or potassium iodide (absence of mercuric chloride). The basic mercuric sulphate is almost insoluble in cold water, but soluble in diluted hydrochloric or nitric acid. Examination of compounds of arsenic. Arsenious and arsenic oxides, arsenious bromide and iodide are completely volatilized by heating (a residue indicating non-volatile impurities). The four compounds are also soluble in water, the bromide and iodide with decomposition. Examination of compounds of antimony. Antimonious oxide should be completely soluble in tartaric acid; the solution should be tested for chlorides and sulphates by means of silver nitrate and barium chloride ; also for iron, by potassium ferrocyanide. 254 ANALYTICAL CHEMISTRY. Antimonious and antimonic sulphides are soluble in concentrated hydrochloric acid, with liberation of hydrosulphuric acid and formation of the trichloride. Antimonic oxide, as well as antimonious oxychloride, is dissolved by boiling with sodium or potassium hydroxide. 37. METHODS FOB QUANTITATIVE DETERMINATIONS. General remarks. Quantitative determination of the different elements or groups of elements may be accomplished by various methods, which differ generally with the nature of the substance to be examined. But even one and the same substance may often be analyzed quantitatively by entirely different methods, of which the two principal ones are the gravimetric and volumetric methods. In the gravimetric method, the quantities of the constituents of a substance are determined by separating and weighing them either as such, or in the form of some compound, the exact com- position of which is known. For instance: From cupric sul- phate, the copper may be precipitated as such by electrolysis and weighed as metallic copper, or it may be precipitated by sodium hydroxide as cupric oxide, CuO, and weighed as such. Knowing that every 79.2 parts by weight of cupric oxide contain of oxygen 16 parts and of copper 63.2 parts, the weight of copper contained in the cupric oxide found may be readily calculated. Questions.—351. Give some general methods by which the mineral acids may be examined for metallic impurities and their strength determined. 352. How is sulphuric acid to be tested for sulphurous and nitric acids, and how is nitric acid tested for sulphuric and hydrochloric acids? 353. What impurities are sometimes present in phosphoric acid? How is their presence demonstrated? 354. By what tests is sodium carbonate detected in sodium bicarbonate, and potassium iodate in potassium iodide? 355. How can the presence of ferrous sulphate be demonstrated in either ammonium chloride, calcium phosphate, magnesium carbonate, aluminium sulphate, or cupric sulphate? 356. State the various methods by which preparations of iron are examined for metallic im- purities, and how ferric chloride can also be tested for ferrous chloride, nitric and sulphuric acids. 357. By what methods can zinc oxide be tested for any other metal, and for carbonic, sulphuric, or hydrochloric acid? 358. Give methods for detecting metallic impurities in compounds of lead, copper, bismuth, and silver. 359. What is the action of heat upon mercury com- pounds, and by what solvents may the various officinal mercury preparations be dissolved? 360. How is mercuric chloride detected in mercurous chloride, and how mercuric iodide in mercurous iodide ? METHODS FOR QUANTITATIVE DETERMINATION. 255 In the volumetric methods, the determination is accomplished by adding to a weighed quantity of the substance to be examined, a solution of a reagent of a known strength until the reaction is just completed, no excess being allowed. For instance: We know that every 80 parts by weight of sodium hydroxide pre- cipitate 79.2 parts by weight of cupric oxide, containing 63.2 parts by weight of copper. Therefore, if we add a solution of sodium hydroxide of known strength to a weighed portion of cupric sulphate until all the copper is precipitated, we may cal- culate from the volume of soda solution used the weight of sodium hydroxide, and from this the weight of copper which has been precipitated. The operation of volumetric analysis is termed titration. Gravimetric methods. While the quantitative determinations by these methods differ widely in some cases, there are a number of operations so often and so generally employed that a few Fig. 28. Drying-oven. remarks may be of advantage to the beginner. A small quan- tity (generally from O.Djto 1 gram) of the substance to be analyzed is very exactly weighed on a delicate balance, transferred to a beaker, and dissolved in a suitable agent (water or acid). From this solution the constituent to be determined is precipitated 256 ANALYTICAL CHEMISTRY. completely, which is ascertained by allowing the precipitate to subside and adding to the clear liquid a few drops more of the agent used for precipitation. The precipitate is next collected upon a small filter of good filter paper containing as little of inorganic constituents (ash) as possible ; the particles of precipi- tate which may adhere to the beaker are carefully washed off by means of a camel’s-hair brush. The precipitate is well washed (generally with pure water) until free from adhering solution, and dried by placing funnel and contents in a drying-oven, Fig. 28, in which a constant temperature of about 100° C. (212° F.) is maintained. The dried filter is then taken from the funnel and its contents are transferred to a platinum (or porcelain) crucible, Fig. 20. Fig. 30. Desiccator. Watch glasses for weighing filters. which has been previously weighed and stands on a piece of glazed, colored paper in order to collect any particle of the dried precipitate which may happen to fall beside the crucible. The filter from which the precipitate has been removed as completely as possible, by slightly rubbing it, is now folded, placed upon the lid of the crucible, which rests on a triangle over a gas burner, and completely incinerated. The remaining filter-ash, with par- ticles of the precipitate mixed with it, is transferred to the cru- cible, which is now placed over the burner and heated until all water (or possibly other substances) is completely expelled. After cooling, the crucible is weighed, the weight of the empty crucible and that of the filter-ash (the latter having been previously deter- mined by burning a few filters of the same kind) deducted, and thus the quantity of the precipitate determined. METHODS FOR QUANTITATIVE DETERMINATION. 257 As platinum crucibles and many precipitates, after ignition, absorb moisture from the air, it is well to allow the heated cru- cible to cool in a desiccator. This is a closed vessel in which the air contained in it is kept dry by means of concentrated sulphuric acid. Fig. 29 shows a convenient form of desiccator. Fig. 32 Fig. 31. Litre flask. Pipettes. The empty crucibles should be weighed under the same condi- tions—i. e., after having been heated and cooled in a desiccator. Some precipitates (as, for instance, potassium platinic chloride), cannot be ignited without suffering partial or complete decompo- sition. It is for this reason that some precipitates are collected upon filters which have been previously dried at 100° C. (212° F.) 258 ANALYTICAL CHEMISTRY. and weighed carefully. The precipitate is then collected upon the weighed filter, well wmshed, dried at 100° C. (212° F.) and weighed. The weighing of dried filters is best accomplished by placing them between two watch-glasses held together by means of a brass or nickel clamp, as shown in Fig. 30. Fig. 33. Fig. 34. Mohr's burette and clamp, Mohr’s burette and holder. The above-described methods may be employed for the deter- mination of those substances which can be precipitated from their solutions in the forrn'of some stable compound. Aluminium, zinc, iron, bismuth, copper, etc., nmy, for instance, be precipi- tated as hydroxides and weighed as oxides, into which the pre- METHODS FOR QUANTITATIVE DETERMINATION. 259 cipitated compound is converted by ignition. Sulphuric acid may be precipitated and weighed as barium sulphate, phosphoric acid may be precipitated by magnesia mixture and weighed as magnesium pyrophosphate, etc. Some substances, like nitric acid, chloric acid, etc., cannot be precipitated from their solutions, for which reason other methods have to be employed for their determination. Volumetric methods. The great ad- vantage of volumetric over gravimetric analysis consists chiefly in the rapidity with which these determinations are performed. Unfortunately, volumetric methods cannot be employed to advan- tage for the estimation of all substances. The special apparatus required for volumetric analysis consists of a few flasks, some pipettes, burettes, and a burette holder. The flasks should have a mark on the neck, indicating a capacity of 100, 250, 500, and 1000 c.c. respectively. (See Fig. 31.) Of pipettes (Fig. 32) are mostly used those having a capacity of 5,10, 25, and 50 cubic centimetres. Of burettes many different forms are used; in most cases Mohr’s burette (Figs. 33 and 34) answers all require- ments, but its application is excluded whenever the test solution is chemically affected by rubber, as in the case of solutions of silver, permanganate, and a few other substances. For such solu- tions Mohr’s burette with glass stop- cock, or Gay Lussac’s burette (Fig. 35) is generally used. Standard solutions. The test solutions used in volumetric anal- ysis are adjusted according to a uniform system, so that each solution contains in a litre (1000 c.c.) the weight of one atom or one molecule of the active reagent expressed in grams. This Fig. 35. Gay Lussac’s burette. 260 ANALYTICAL CHEMISTRY. rule refers to all cases of univalent elements (Ag, Cl, I), or mono- basic acids (HC1, IIN03), or monacid bases (KOH, iSTI4OH). In case a bivalent element (0, S), or dibasic acids (1I2S04, H2C204), or di-acid bases (Ca20H), are used in volumetric solutions, only one-half of the atomic or molecular weight in grams is used per litre, in order to have the saturating or neutralizing power the same for an equal number of cubic centimetres of univalent and bivalent substances. To illustrate why this is done, if we were to take the molecular weight of hydrochloric acid, 36.4, and of sulphuric acid, 98, in grams, diluted to 1000 c.c., the saturating power of 1 c.c. of the diluted sulphuric acid would be equal to that of 2 c.c. of hydro- chloric acid solution, because 36.4 parts by weight of hydrochloric acid saturate 40 parts by weight of sodium hydroxide, and 98 parts by weight of sulphuric acid saturate 80 parts by weight of sodium hydroxide. The solutions thus obtained are known as normal solutions. For some operations these normal solutions are too concentrated, and are diluted to one-tenth of their strength, and are then called deci-normal solutions. In some instances volumetric solutions are prepared which do not belong to the above system of normal solutions, but are adjusted to correspond to a certain unit of the special substance they are to act upon. Such solutions are called empirical solutions, and, as an instance, may be mentioned Fehling’s solution, used for the determination of sugar. This solution is so adjusted that 1 c.c. decomposes or indicates 0.005 gram of grape-sugar. Different methods of volumetric determination. Of these we have at least three, which may be called the direct, the indirect, and the method of rest or residue. The direct methods are used in all cases in which the quantities of volumetric solutions can be added until the reaction is com- plete ; for instance, until an alkaline substance has been neutral- ized by an acid, or a ferrous salt has been converted into a ferric salt by potassium permanganate, etc. In the indirect methods one substance, which cannot well be deter- mined volumetrically, is made to act upon a second substance, with the result that, by this action, an equivalent amount of a substance is generated or liberated, which may be titrated. For instance : Peroxides, chromic and chloric acids, when boiled with METHODS FOR QUANTITATIVE DETERMINATION. 261 strong hydrochloric acid, liberate chlorine, which is not deter- mined directly, but is caused to act upon potassium iodide, from which it liberates the iodine, which may be titrated with sodium thiosulphate. The methods of residue are based upon the fact that while it is impossible or extremely difficult to obtain complete decompo- sition between certain substances and reagents, when equivalent quantities are added to one another, such a complete decompo- sition is accomplished by adding an excess of the reagent, which excess is afterward determined by a second volumetric solution. For instance: Carbonate of calcium, magnesium, zinc, etc., can- not well be determined directly, for which reason an excess of normal acid is used for their decomposition, this excess being titrated afterward by means of an alkali. Indicators. In all cases of volumetric determination it is of the greatest importance to observe accurately the completion of the reaction. In some cases the final point is indicated by a change in color, as, for instance, in the case of potassium permanganate, which changes from a red to a colorless solution, or chromic acid, which changes from orange to green under the influence of deoxi- dizing agents. In other cases the determination is indicated by the formation or cessation of a precipitate, and in yet others the final point could not be noticed with precision unless rendered visible by a third substance added for that purpose. Such substances are termed indicators. Litmus may be used as an indicator in the determination of acid and alkaline substances, as it changes from red to blue or from blue to red according to the presence of free alkali or free acid. Starch paste is an indicator for iodine, potassium chromate for silver, etc. Titration. This term is used for the process of adding the volumetric solution from the burette to the solution of the weighed substance until the reaction is completed. We also speak of the standard or titre of a volumetric test-solution, when we refer to its strength per volume (per litre or per cubic centi- metre). Of the principal processes of titration, or of volumetric methods used, may be mentioned those based upon neutralization (acidi- metry and alkalimetry), oxidation and reduction (permanganates and chromates as oxidizing, oxalic acid and ferrous salts as 262 ANALYTICAL CHEMISTRY. reducing agents) and 'precipitation (silver nitrate by sodium chloride). Acidimetry and alkalimetry. Preparing the volumetric test- solutions is often more difficult than to make a volumetric deter- mination. Whenever the reagents employed can be obtained in a chemically pure condition it is an easy task to prepare the solution, because a definite weight of the reagent is dissolved in a definite volume of water. In many instances, however, the reagent cannot be obtained absolutely pure, and in such cases a solution is made and its standard adjusted afterward by methods which will be spoken of later. Neither the common mineral acids, such as sulphuric, hydro- chloric, and nitric acids, nor the alkaline substances, such as sodium hydroxide or ammonium hydroxide, are sufficiently pure to permit of being used directly for volumetric solutions, because these substances contain water, and an absolutely correct deter- mination of the amount of this water is an operation which involves a knowledge of gravimetric methods. It is for this reason that the basis in preparing a volumetric normal acid solution is oxalic acid, a substance which can be readily obtained in a pure crystallized condition. Normal acid solution. Crystallized oxalic acid has the com- position H2C204.2II20 and a molecular weight of 126. Being dibasic, only half of its weight is taken for the normal solu- tion, which is made by placing 63 grams of pure crystallized oxalic acid in a litre flask, dissolving it in pure water, filling up to the mark at the temperature of 15° C. (59° F.) and mixing thoroughly. Normal solutions of sulphuric or hydrochloric acid are, for various reasons, often preferred to oxalic acid. These solutions are best made by diluting approximately the acids named, titrat- ing the solution with normal sodium hydroxide and adding water until equal volumes saturate one another. For instance, if it should be found that 10 c.c. normal alkali solution neutralize 7.6 c.c. of the acid, then 24 c.c. of water have to be added to every 76 c.c. of the acid in order to obtain a normal solution. Normal sulphuric acid contains 49 grams of H2S04, and normal hydrochloric acid 36.4 grams of HC1 per litre. Normal alkali solution. A normal solution of sodium carbonate may be made by dissolving 53 grams (one-half the molecular METHODS FOR QUANTITATIVE DETERMINATION. 263 weight) of pure sodium carbonate (obtainable by heating pure sodium bicarbonate to a low red-heat) in water, and diluting to one litre. This solution, however, is not often used, but may serve for standardizing acid solutions, as it has the advantage of being prepared from a substance that can be easily obtained in a pure condition, which is not the case in preparing the otherwise more useful normal solutions of potassium or sodium hydroxide, both of which substances contain and absorb water. The solutions are made by dissolving about 60 grams of potassium hydroxide or 50 grams of sodium hydroxide in about 1000 c.c. of water, titrating this solution with normal acid, and diluting it with water, until equal volumes of both solutions neutralize one another exactly. The indicators used in alkalimetry are either solutions of litmus (1 part of litmus macerated with 10 parts of water), or of phenol-phthalein (1 part dissolved in a mixture of 250 parts of alcohol and 750 parts of water). While litmus changes from red Fig. 36. Titration. to blue and vice versa, phenol-phthalein is colorless in neutral or acid solutions, but changes intensely red with even traces of alkalies. Only a few drops of the phenol-phthalein solution are needed for a determination. This indicator acts extremely well with potassium and sodium hydroxide, but is not suitable for use with ammonia, with which the change occurs too slowly. ANALYTICAL CHEMISTRY. Whenever carbonates are titrated with acids or vice versa, the solution has to be boiled toward the end of the reaction in order to drive off the carbon dioxide, as neither of the two indicators mentioned gives reliable results in the presence of carbonic acid or an acid carbonate. The proper mode of performing the operation of titration is shown in Fig. 36. Neutralization equivalents. The normal solutions of acid and alkali may be used for the determination of a large number of substances, either directly (as in the case of free acids, caustic and alkaline carbonates and bicarbonates) or indirectly (as in the case of salts of most of the organic acids, with alkalies, which are first converted into carbonates by ignition). One c.c. of normal oxalic acid is the equivalent of: Gram. Ammonia, NH3 ........ 0.0170 Ammonium carbonate, NH4HC03.lSrH4NH2C02 . . 0.0523 Lead acetate, crystallized, Pb2((J2H302).3H2G . . 0.1892 Lead subacetate, Pb202(C2H302) 0.1367 Potassium acetate, KCgHgCq1 ...... 0.0980 Potassium bicarbonate, KHC03 ..... 0.1000 Potassium bitartrate, KHC4H4061 ..... 0.1880 Potassium carbonate, K2C03 .0 0690 Potassium citrate, ...... 0.1020 Potassium hydroxide, KOH 0.0560 Potassium permanganate, K2Mn208 .... 0.0314 Potassium sodium tartrate, KNaC4Il406.4H201 . . 0.1410 Potassium tartrate, 2K2C4H406.H201 .... 0.1175 Sodium acetate, NaC2H302.2Hs01 ..... 0.1360 Sodium bicarbonate, NaH0O3 0.0840 Sodium borate, Na2B4O7.10H2O ..... 0.1910 Sodium carbonate, crystallized, Na2CO3.10H2O . . 0.1430 Sodium carbonate, Na2C03 0.0530 Sodium hydroxide, NaOH ...... 0.0400 One c.c. of normal sodium carbonate, or sodium hydroxide, is the equivalent of: Gram. Acetic acid, HC2H30.2 ....... 0.0600 Citric acid, H3CeH507.H2U ...... 0.0700 Hydrobromic acid, HBr ....... 0.0808 Hydrochloric acid, HC1 ....... 0.0364 Hydriodic acid, HI . . . . . . . . 0.1276 Lactic acid, HC3H5Q3 ....... 0.0900 Nitric acid, HN03 ........ 0.0630 Oxalic acid, H2C204.2H20 0.0630 Sulphuric acid, H2S04 ....... 0.0490 Tartaric acid, H2C4H4Q6 ....... 0.0750 1 After ignition. METHODS FOR QUANTITATIVE DETERMINATION. 265 Oxidimetry. Potassium permanganate. The substances gener- ally used as oxidizing agents are potassium permanganate and potassium dichromate, both of which salts can be obtained in a pure crystallized condition. Potassium permanganate, K2Mn208 = 314, acts generally in the presence of free acids, upon deoxidizing substances, by losing 5 atoms of oxygen of the 8 atoms present, as is shown in the following equations: K2Mn2Og + 5H2C204 + 3H2S04 = K2S04 + 2MnS04 +10CO2 + 8H20 K2Mn2Og +10FeS04 + SH2S04 = K2S04 + 2MnS04 + 5Fe23S04 + 8H20. It follows that one-fifth the molecular weight of potassium per- manganate, or 62.8 grams, is the equivalent of 1 oxygen atom. But as oxygen is diatomic and the volumetric normal is calcu- lated for monatomic values, this number must be divided by 2, and 31.4 grams of pure crystallized potassium permanganate is therefore the amount to furnish 1 litre of normal solution, but as this is too concentrated for most determinations, a deci-normal solution containing 3.14 grams to the litre is generally employed. Permanganate solution, when made with pure water, does not alter its standard, if contained in a tight (glass-stoppered) bottle, kept in a dark closet. If the water used contain organic matter, the standard will alter until all that matter is oxidized. The standardizing of permanganate solution may be done by dissolving 0.2 gram of pure, thin iron wire in about 20 q.c. of dilute sulphuric acid (1 acid, 5 water) by the aid of heat, and in a flask arranged as in Fig. 37. The flask is provided, by means of a perforated cork, with a piece of glass tubing, to which is attached a piece of rubber tubing in which is cut a vertical slit about one inch long and which is closed at the upper end by a piece of glass rod; gas or steam generated in the flask may escape, while atmospheric air cannot enter, the ferrous solution being thus protected from oxidation. The iron solution, obtained from the 0.2 gram of iron, is cooled and diluted with about 300 c.c. of water, and then deci-normal potasssium permanganate solution is added with constant stirring until the solution is tinged pinkish. As 1 c.c. of deci-normal permanganate solution corresponds to Fig. 37. Flask for dissolving iron for volumetric determination. 266 ANALYTICAL CHEMISTRY. 0.0056 gram of metallic iron, the 0.2 gram iron wire used will consume 35.7 c c. of the solution. 10 c.c. of the normal oxalic acid solution, or 0.63 gram of pure crystallized oxalic acid, may also be used for titrating the per- manganate solution, of which 100 c.c. should be decolorized. The titration is accomplished by diluting the 10 c.c. of oxalic acid solution with about 50 c.c. of water, to which a few c.c. of dilute sulphuric acid are added, heating moderately, and adding the permanganate solution as in the above instance. Permanganate is generally used in determinations of iron and iron compounds. Many of the latter contain iron in the ferric state, which must be converted into ferrous compounds before titration. This conversion is accomplished by heating the solu- tion of a weighed quantity of the ferric compound with nascent hydrogen—i. e., with metallic zinc and dilute sulphuric acid—in a flask arranged as the one spoken of above, and shown in Fig. 37. A very much quicker reduction of the ferric into a ferrous com- pound may be accomplished by adding very slowly with constant stirring a saturated solution of sodium sulphite to the boiling, acidified iron solution contained in the flask until the liquid becomes colorless. All excess of sulphur dioxide is expelled before titrating by boiling the solution for about ten minutes in a flask, arranged as the one mentioned above. One c.c. of deci-normal potassium permanganate is the equiva- lent of: Gram. Iron in ferrous compounds, Fe 0.0056 Ferrous oxide, FeO ........ 0.0072 Ferric oxide, Fe2Os 0.0080 Oxalic acid, H2C204.2H20 ...... 0 0063 Potassium dichromate, K2Cr207 = 294.8. Whenever this salt acts in the presence of free acid, as an oxidizing agent, it transfers 3 atoms of ox}Tgen upon the deoxidizing agent, thus : K2Cr207 + 6FeS04 + 7H2S04 = K2S04 + Cr23804 + 7II20 + 3(Fe23S04). A normal solution should, therefore, contain one-sixth of the molecular weight, or 49.1 grams per litre. The U. S. P., how- ever, considers potassium dichromate as a dibasic salt, using, therefore, one-half the molecular weight, 147.4, and prepares a deci-normal solution, which is obtained by dissolving 14.74 grams of pure potassium dichromate in water, and diluting to 1000 c.c. The disadvantage of this solution is, that the final point of METHODS FOR QUANTITATIVE DETERMINATION. 267 titration cannot be well seen, for which reason, in the determina- tion of iron, for which it is chiefly used, the end of the reaction is determined by taking out a drop of the solution and testing it on a white porcelain plate with a drop of potassium ferricyanide solution; when this no longer gives a blue color, the reaction is at an end. In all determinations by this solution dilute sulphuric acid has to be added, because both the potassium and chromium require an acid to combine with, as shown in the above equation. One c.c. potassium dichromate solution, containing of this salt 0.01-17 gram, is the equivalent of: Gram. Iron in ferrous combinations, Fe . . . . . 0.01677 Ferrous oxide, FeO ....... 0.02156 Ferrous carbonate, FeC03 0.03477 Ferrous sulphate, FeS04.7H20 0.08337 Iodimetry. Solutions of iodine and of sodium thiosulphate (hyposulphite) act upon one another with the formation of sodium iodide and sodium tetrathionate : A. normal solution of one can be standardized by a normal solution of the other. As indicator is used a freshly prepared boiled starch solution, which is colored blue by minute portions of free iodine. 21 + 2Nh2S203 = 2NaI + Na2S406. Many other substances, such as sulphurous acid, hydrosulphuric acid, arsenious oxide, act upon iodine with the formation of color- less compounds, and may, therefore, be estimated by normal solution of iodine, while the iodine may be standardized by the thiosulphate solution. In many cases the latter solution is also used for the determination of chlorine, which is caused to act upon potassium iodide, the liberated iodine being titrated. Deci-normal iodine solution is the one generally used, and is made by dissolving 12.66 grams of pure iodine, in a solution of 18 grams of potassium iodide in about 700 c.c. of water, diluting the solution to 1000 c.c. To the article to be estimated by this solution is added a little starch paste, and then the iodine solution is added until, on stir- ring, the blue color ceases to be discharged. One c.c. of cleci-normal iodine solution, containing of iodine 0.011266 gram, is the equivalent of: 268 ANALYTICAL CHEMISTRY Gram. Arsenious oxide, A=203 ....... 0.00494 Potassium sulphite, K2S03.2H20 ..... 0.0097 Sodium bisulphite, ]STaHS03 ...... 0.0052 Sodium thiosulphate, Na2S203.5H20 . . . 0.0248 Sodium sulphite, Na2S03.7H2G ..... 0.0126 Sulphur dioxide, S02 ....... 0.0032 Sodium thiosulphate (Hyposulphite). The crystallized salt, Na2S2O3.5H20 = 248, is used for making the deci-normal solu- tion by dissolving 24.8 grams of the pure crystallized salt in water to make 1000 c.c. If the salt should not be absolutely pure, a somewhat larger quantity (30-32 grams) should be dis- solved in 1000 c.c. of w'ater, and this solution titrated with deci- normal solution of iodine and diluted with a sufficient quantity of water to obtain the deci-normal solution. The article to be tested, containing free iodine, either in itself or after the addition of potassium iodide, is treated with this solution until the color of iodine is nearly discharged, when a little starch liquor is added, and the addition of the solution con- tinued until the blue color has just disappeared. One c.c. of deci-normal solution of sodium thiosulphate, con- taining of the crystallized salt 0.0248 gram, is the equivalent of: Gram. Bromine, Br ........ 0.00798 Chlorine, Cl ........ 0.00354 Iodine, I ......... 0.01266 Deci-normal solution of silver. The pure, dry crystallized silver nitrate, AgV03 = 169.7, is used for this solution, which is made by dissolving 16.97 grams of the salt in water to make 1000 c.c. The standard of this solution may be found by means of a deci- normal solution of sodium chloride, containing of this salt 5.84 grams in one litre. Volumetric silver solution is used directly for the estimation of most chlorides, iodides, bromides, and cyanides, including the free acids of these salts. Insoluble chlorides must first be con- verted into a soluble form by fusing them with sodium In-droxide, dissolving the fused mass (containing sodium chloride) in water, filtering and neutralizing with nitric acid. The hydroxides and carbonates of alkali metals and of alkaline earths may be converted into chlorides by evaporation to dry- ness with pure hydrochloric acid, and heating to about 120° C. METHODS FOR QUANTITATIVE DETERMINATION. 269 (248° F.). The chlorides thus obtained may be titrated with silver solution. In the case of chlorides, iodides, and bromides, normal potas- sium chromate is used as an indicator. This salt forms with silver nitrate a red precipitate of silver chromate, but not before the silver chloride (bromide or iodide) has been precipitated entirely. In case free acids are determined by silver, these are neutralized with sodium hydroxide before titration. The operation is conducted as follows: The weighed quantity of the chloride is dissolved in 50-100 c.c. of water, neutralized if necessary, mixed with a little potassium chromate, and silver solution added from the burette until a red coloration is just produced, which does not disappear on shaking. In estimating cyanides, the method has to be modified, because the silver cyanide produced is soluble in an equivalent quantity of potassium or sodium cyanide, a soluble double cyanide of silver and the alkali metal being formed, thus: 2KCN + AgN03 = AgK2CN + KN03. If to this soluble double compound more silver nitrate be added, it is decomposed with the formation of a precipitate of silver cyanide: AgK2CN + AgN03 = 2AgCN + KN03. The estimation of hydrocyanic acid or of simple cyanides is accomplished by first rendering slightly alkaline the solution of the substance to be examined by the addition of sodium hydroxide, and then adding the silver solution until a perma- nent cloudiness is produced in the liquid, which shows that all cyanogen present has been converted into the soluble double salt. As but one-half of the silver solution has been added, which is needed for the complete conversion of the cyanogen present into silver cyanide, the number of c.c. of the standard silver solution employed will indicate exactly one-half of the equivalent amount of cyanide present in the solution. One c.c. of deci-normal silver nitrate solution, containing 0.01697 gram of AgJ703, is the equivalent of: Gram. Ammonium bromide, NH4Br ..... 0.00978 Ammonium chloride, NH4C1 0.00534 Ammonium iodide, NHJ ...... 0.0155 Hydriodic acid, HI 0.01276 Hydrobromic acid, HBr ...... 0.00808 270 ANALYTICAL CHEMISTRY. Gram. Hydrochloric acid, HC1 ...... 0.00364 Hydrocyanic acid, HCN" ...... 0.0054 Potassium bromide, KBr . . . . . . 0.01198 Potassium chloride, KCI ...... 0.00744 Potassium cyanide, KCN ...... 0.0130 Potassium iodide, KI . . . . . . . 0 01656 Sodium bromide, NaBr ....... 0.01028 Sodium chloride, NaCl ....... 0.00584 Sodium iodide, Nal ....... 0.01028 Gas-analysis. The analysis of gases is generally accomplished by measuring gas volumes in graduated glass tubes (eudiometers) over mercury (in some cases over water), noting carefully the pressure and temperature at which the volume is determined. From gas mixtures, the various constituents present may often be eliminated by causing them to be absorbed one after another by suitable agents. For in- stance : From a measured volume of a mixture of nitrogen, oxygen, and carbon dioxide, the latter compound may be removed by allowing the gas to remain in contact for a few hours with potassium hydroxide, which will absorb all carbon dioxide, the diminution in volume indicating the quantity of carbon dioxide originally present. The volume of oxygen may next be determined by intro- ducing a piece of phosphorus, which will gradually absorb the oxygen, the remaining volume being pure nitrogen. In some cases gaseous constituents of liquids or solids are eliminated and measured as gases. Thus, the carbon dioxide of carbonates, the nitrogen dioxide evolved from nitrates, the nitrogen of urea and other nitrogenous bodies are instances of substances which are eliminated from solids in the gaseous state and determined by direct measurement. The gas volume thus found is, in most cases, converted into parts by weight. The basis of this calculation is the weight of 1 c.c. of hydrogen, which, at the temperature of 0° C. (32° F.) and a pressure of 760 mm., is 0.0000896 gram. 1 c.c. of any other gas weighs as many more times as the molecule of this sub- stance is heavier than that of hydrogen. Thus, the molecular weight of carbon dioxide is 22 times greater than that of hydrogen, consequently 1 c.c. of carbon dioxide weighs 22 times heavier than 1 c.c. of hydrogen, or 0.0019712 gram. It has been shown on pages 21 and 26 that heat and pressure cause a regular increase or decrease in volume. The data there given are used in calculating the volume of the measured gas for the temperature of 0° C. (32° F.) and a pressure of 760 mm. Questions.—361. Explain the principles which are made use of in gravi- metric and volumetric determinations. 362. Give an outline of the operations to be performed in the gravimetric determination of copper in cupric sulphate. 363. What are normal and deci-normal solutions, and how are they made? 364. What is the use of indicators in volumetric analysis ? Mention some in- dicators and explain their action. 365. Why is oxalic acid preferred in pre- paring normal acid solution? What quantity of oxalic acid is contained in a litre, and why is this quantity used? 366. Suppose 2 grams of crystallized sodium carbonate require 14 c.c. of normal acid for neutralization, what are the METHODS FOR QUANTITATIVE DETERMINATION. 271 percentages of crystallized sodium carbonate and of pure sodium carbonate con- tained in the specimen examined ? 367. Ten grams of dilute hydrochloric acid require 33.5 c.c. of normal sodium hydroxide solution for neutralization. What is the strength of this acid? 368. Explain the action of potassium perman- ganate and of potassium dichromate when used for volumetric purposes. 369. Which substances may be determined volumetrically by solutions of iodine and sodium thiosulphate? Explain the mode in which the determinations by these agents are accomplished. 370. Suppose 1 gram of potassium iodide requires for titration 60 c.c. of deci-normal solution of silver nitrate : What quantity of pure potassium iodide is indicated by this determination? YI. CONSIDERATION OF CARBON COMPOUNDS, OR ORGANIC CHEMISTRY. 38. INTRODUCTORY REMARKS. ELEMENTARY ANALYSIS. Definition of organic chemistry. The term organic chemistry was originally applied to the consideration of compounds formed in plants and in the bodies of animals, and these compounds were believed to be created by a mysterious power, called “ vital force,” supposed to reside in the living organism. This assumption was partly justified by the failure of the earlier attempts to produce these compounds by artificial means, and also by the fact that the peculiar character of the compounds, and the numerous changes which they constantly undergo in nature, could not be sufficiently explained by the experimental methods then known, and the laws then established. It was in accordance with these views that a strict distinction was made between inorganic and organic compounds, and accord- ingly between inorganic and organic chemistry, the latter branch of the science considering the substances formed in the living organism, and those compounds which were produced by their decomposition. Since that time, it has been shown that many substances which formerly were believed to be exclusively produced in the living organism, under the influence of the so-called vital force, can be formed artificially from inorganic matter, or by direct combina- tion of the elements. It was in consequence of this fact that the theory of the supposed “ vital force,” by which organic sub- stances could be formed exclusively, had to be abandoned. An organic compound, according to modern views, is simply a compound of carbon generally containing hydrogen, frequently also oxygen and nitrogen, and sometimes other elements. Organic chemistry may consequently he defined as the chemistry of INTRODUCTORY REMARKS. 273 carbon compounds. The old familiar terms, organic compounds and organic chemistry, are, however, still in general use. In a strictly systematically arranged text-book of chemistry organic compounds should be considered in connection with the element carbon itself, but as these carbon compounds are so numerous, their composition often so complicated, and the decompositions which they suffer under the influence of heat or other agents so varied, it has been found best for purposes of instruction to defer the consideration of these compounds until the other elements and their combinations have been studied. Elements entering into organic compounds. Organic compounds contain generally but a small number of elements. These are, besides carbon, chiefly hydrogen, oxygen, and nitrogen, some- times sulphur and phosphorus. Other elements, however, enter occasionally into organic compounds, and by artificial means all metallic and non-metallic elements may be made to enter into organic combinations. Here the question presents itself: Why is it that the four ele- ments carbon, hydrogen, oxygen, and nitrogen are capable of producing such an immense number (in fact, millions) of different combinations ? To this question but one answer can be given, which is that these four elements differ more widely from each other, in their chemical and physical properties, than perhaps any other four elements. Carbon is a black, solid substance, which has never yet been fused or volatilized, while hydrogen, oxygen, and nitrogen are colorless gases which can only be converted into liquids with difficulty. Moreover, hydrogen is highly combustible, oxygen is a supporter of combustion, whilst nitrogen is perfectly indiffer- ent. Finally, hydrogen is univalent, oxygen bivalent, nitrogen trivalent, and carbon quadrivalent. These elements are, there- fore, capable of forming a greater number, and a greater variety of compounds than would be the case if they were elements of equal valence and of similar properties. It will be shown later that carbon atoms have, to a higher degree than the atoms of any other element, the power of com- bining with one another by means of a portion of the affinities possessed by each atom, thus increasing the possibilities of the formation of complex compounds. 274 CONSIDERATION OF CARBON COMPOUNDS. General properties of organic compounds. The substances formed by the union of the four elements just mentioned have properties in some respects intermediate to those of their com- ponents. Thus, no organic substance is either permanently solid1 like carbon, nor an almost permanent gas like hydrogen, oxygen, and nitrogen. Some organic substances are solids, others liquids, others gases; they are generally solids when the carbon atoms pre- dominate; they are liquids or gases when the gaseous elements, and especially hydrogen, predominate; likewise, it may also be said that compounds containing a small number of atoms in the molecule are gases or liquids which are easily volatilized; they are liquids of high boiling-points, or solids, when the number of atoms forming the molecules is large. The combustible property of carbon and hydrogen is trans- ferred to all organic substances, every one of which will burn when sufficiently heated in atmospheric air. (If carbon dioxide, carbonic acid and its salts, be considered organic compounds, we have an exception to the rule, as they are not combustible) The properties possessed by organic compounds are many and widely different. There are organic acids, organic bases, and organic neutral substances; there are some organic compounds which are perfectly colorless, tasteless, and odorless, whilst others show every possible variety of color, taste, and odor; many serve as food, whilst others are most poisonous; in short, organic substances show a greater variety of properties than the com- binations formed by any other four elements. And yet, the cause of all the boundless variety of organic matter is that peculiar attraction called chemical affinity, acting between the atoms of a comparatively small number of elements and uniting them in many thousand different proportions. It would, of course, be entirely inconsistent with the object of this book, if all the thousands of organic substances already known (the number of which is continually being increased by new discoveries) were to be considered or even mentioned. It must be sufficient to state the general properties of the various groups of organic substances, to show by what processes they are produced artificially or how they are found in nature, how 1 Non-volatile organic substances are decomposed by heat with generation of volatile products. 275 INTRODUCTORY REMARKS. they may be recognized and separated, and, finally, to point out those members of each group which claim a special attention for one reason or another. Difference in the analysis of organic and inorganic substances. The analysis of organic substances differs from that of inorganic substances, in so far as the qualitative examination of an organic substance furnishes in many cases but little proof of the true nature of the substance (except that it be organic), whilst the qualitative analysis of an inorganic substance discloses in most cases the true nature of the substance at once. For instance: If a white, solid substance, upon examination, be found to contain potassium and iodine, and nothing else, the conclusion may at once be drawn that the compound is potassium iodide, containing 39 parts by weight of potassium, and 126.6 parts by weight of iodine. Or, if another substance be examined, and found to be composed of mercury and chlorine, the con- clusion may be drawn that the compound is either mercurous or mercuric chloride, as no other compounds containing these two elements are known, and whether the examined substance be the lower or higher chloride of mercury, or a mixture of both, can easily be determined by a few simple tests. Whilst thus the qualitative examination discloses the nature of the substance, it is different with organic compounds. Many thousand times the analysis might show carbon, hydrogen, and oxygen to be present, and yet every one of the compounds ex- amined might be entirely different; it is consequently not only the quality of the elements, but chiefly the quantity present which determines the nature of an organic substance, and in order to identify an organic substance with certainty, it frequently becomes necessary to make a quantitative determination of the various elements present, and this quantitative analysis by which the elements in organic substances are determined is generally called ultimate or elementary analysis. There are, however, for many organic substances such charac- teristic tests that these substances maybe recognized by them; these reactions will be mentioned in the proper places. An analysis by which different organic substances, when mixed together, are separated from each other is frequently termed 'proximate analysis. Such an analysis includes the separa- tion and determination of essential oils, fats, alcohols, sugars, 276 CONSIDERATION OF CARBON COMPOUNDS. resins, organic acids, albuminous substances, etc., and is one of the most difficult branches of analytical chemistry. Qualitative analysis of organic substances. The presence of carbon in a combustible form is decisive in regard to the organic nature of a compound. If, consequently, a substance burns with generation of carbon dioxide (which may be identified by passing the gas through lime-water), the organic nature of this substance is established. The presence of hydrogen can be proven by allowing the gaseous products of the combustion to pass through a cool glass tube, when drops of water will be deposited. It is difficult to show by qualitative analysis the presence or absence of oxygen in an organic compound, and its determination is therefore generally omitted. The presence of nitrogen is determined by heating the substance with dry soda-lime (a mixture of two parts of calcium hydroxide and one part of sodium hydroxide), when the nitrogen is con- verted into ammonia gas, which may be recognized by its odor or by its action on paper moistened with solution of cupric sulphate, a dark-blue color indicating ammonia. Ultimate or elementary analysis. While the student must be referred to books on analytical chemistry for a detailed descrip- tion of the apparatus required and the methods employed for ele- mentary analysis, it may here be stated that the quantitative determination of carbon and hydrogen is generally accomplished by the following process : A weighed of the pure and dry substance is mixed with a large excess of dry cupric oxide, and this mixture is introduced into a glass tube, the open end of which is connected by means of a perforated cork and tubing with two glass vessels, the first one of which (generally a U-shaped tube) is tilled with pieces of calcium chloride, the other (usually a tube provided with several bulbs) with solution of potassium hydroxide. The two glass vessels, containing the substances named, are weighed separately after having been tilled. Upon heating the combustion-tube in a suitable furnace, the organic matter is burned by the oxygen of the cupric oxide, the hydrogen is converted into water (steam), which is absorbed by the calcium chloride, and the carbon is converted into carbon dioxide, which is absorbed by the potassium hydroxide. The apparatus repre- ELEMENTARY ANALYSIS. 277 sented in Fig. 38 shows the gas-furnace in which rests the com- bustion-tube with calcium chloride tube and potash bulb attached. Upon re-weighing the two absorbing vessels at the end of the operation, the increase in weight will indicate the quantity of water and carbon dioxide formed during the combustion, and from these figures the amount of carbon and hydrogen present in the organic matter may easily be calculated. Fig. 38. Gas-furnace for organic analysis. For instance : 0.81 gram of a substance having been analyzed, furnishes, of carbon dioxide 1.32 gram, and of water 0.45 gram. As every 44 parts by weight of carbon dioxide contain 12 parts by weight of carbon, the above 1.32 gram contains of carbon 0.36 gram, or 44.444 per cent. As every 18 parts of water contain 2 parts of hydrogen, the above 0.45 gram consequently contains 0.05 gram, or 6.172 per cent. Oxygen is scarcely ever determined directly, but generally indirectly, by determining the quantity of all other elements and deducting their weight, calculated to percentages from 100. The difference is oxygen. If, in the above instance, 44.444 per cent, of carbon and 6.172 per cent, of hydrogen were found to be present, and all other elements, except oxygen, to be absent, the quantity of oxygen is, then, equal to 49.383 per cent, and the composition of the sub- stance is as follows: Carbon ........ 44.444 per cent. Hydrogen ........ 6.172 “ Oxygen 49.384 “ 100.000 278 CONSIDERATION OF CARBON COMPOUNDS. Determination of nitrogen. Nitrogen is generally determined by heating the substance with soda-lime and passing the gen- erated ammonia gas through hydrochloric acid, contained in a suitable glass vessel. Upon evaporation of the acid solution in a weighed platinum dish over a water-bath, ammonium chloride is left, from the weight of which compound the quantity of nitrogen may be calculated. Or the ammonia gas may he passed through a measured volume of normal hydrochloric acid and the unsatu- rated portion of the acid determined volumetrically. Determination of sulphur and phosphorus. These elements are determined by mixing the organic substance with sodium car- bonate and nitrate, and heating the mixture in a crucible. The oxidizing action of the nitrate converts all carbon into carbon dioxide, hydrogen into water, sulphur into sulphuric acid, phos- phorus into phosphoric acid. The latter two acids combine with the sodium of the sodium carbonate, forming sulphate and phos- phate of sodium. The fused mass is dissolved in water, and sulphuric acid precipitated by barium chloride, phosphoric acid by magnesium sulphate and ammonium hydroxide and chloride. From the weight of barium sulphate and magnesium pyrophos- phate the weight of sulphur and phosphorus is calculated. Determination of atomic composition from results obtained by elementary analysis. The elementary analysis gives the quantity of the various elements present in percentages, and from these figures the relative number of atoms may be found by dividing .the figures by the respective atomic weights. For instance: The analysis above mentioned gave the composition of a com- pound, as carbon 44.444 per cent., hydrogen 6.172 per cent., and oxygen 49.384 per cent. By dividing each quantity by the atomic weight of the respective element, the following results are ob- tained : 4 = 3 703 12 = 6.172 49'384 = 3.087 16 The figures 3.703, 6.172, and 3.087, represent the relative number of atoms present in a molecule of the compound ex- amined. In order to obtain the most simple proportion express- ELEMENTARY ANALYSIS. 279 ing this relation, the greatest divisor common to the whole has to be found, a task which is sometimes rather difficult on account of slight errors made in the quantitative determination itself. In the above case, 0.6172 is the greatest divisor, which gives the following results: 3 708 _ . . 0.6172 — ’ 0.6172 3.087 _ , 0.6172 — The simplest numbers of atoms are, accordingly, carbon 6, hydrogen 10, oxygen 5, or the composition is C6H10O5. Empirical and molecular formulas. A chemical formula is termed empirical when it merely gives the simplest possible expression of the composition of a substance. In the above case, the formula C6H10O5 would be the empirical formula. It might, however, be possible that this formula did not represent the actual number of atoms in the molecule, which might contain, for instance, twice or three times the number of atoms given, in which case the true composition would be expressed by the formula C12H20O10 or C18H30O15. If it could be proven that one of the latter formulas is the correct one, it would be termed the molecular formula, because it expresses not only the numerical relations existing between the atoms, but also the absolute number of atoms of each element contained in the molecule. The best method for determining the actual number of atoms contained in the molecule is the determination of the specific weight of the gaseous compound, taking hydrogen as the unit. For instance: Assume the analysis of a liquid substance gave the following result: Carbon ........ 92.308 per cent. Hydrogen ........ 7.692 “ 100.000 From this result the empirical formula, CH, is deducted by applying the method stated above. If this formula were the molecular formula, the density of the vapors of the substance would, when compared with hydrogen (according to the law of Avogadro), be equal to 6.5, because a molecule of hydrogen weighs 2 and a molecule of the compound CH weighs 13. Suppose, however, the density of the gaseous substance is found to be 39, then the molecular formula would be expressed 280 CONSIDERATION OF CARBON COMPOUNDS. by C6H6, because its molecular weight (6 X 12 + 6 X 1) is equal to 78, which weight, when compared with the molecular weight of hydrogen = 2, gives the proportions 78 : 2, or 39 : 1. Not all organic compounds can be converted into gases or vapors without undergoing decomposition, and the determination of the molecular formulas of such compounds has to he accom- plished by other methods. If the substance, for instance, is an acid or a base, the molecular formula may be determined by the analysis of a salt formed by these substances. For instance: The empirical formula of acetic acid is CH20; the analysis of the potassium acetate, however, shows the composition KC2H302, from which the molecular formula HC2H302 is deducted for acetic acid. In many cases, however, it is as yet absolutely impossible to give with certainty the molecular formula of some compounds. Rational, constitutional, structural, or graphic formulas. These formulas are intended to represent the theories which have been formed in regard to the arrangement of the atoms within the molecule, or to represent the modes of the formation and decom- position of a compound, or the relation which allied compounds bear to one another. The molecular formula of acetic acid, for instance, is C2H402, hut different constitutional formulas have been used to represent the structure of the acetic acid molecule. Thus, H.C2H302 is a formula analogous to H.N03, indicating that acetic acid (analogous to nitric acid), is a monobasic acid, containing one atom of hydrogen, which can be replaced by metallic atoms. C2H30\0H is a formula indicating that acetic acid is com- posed of two univalent radicals which may be taken out of the molecule and replaced by other atoms or groups of atoms. This formula indicates also that acetic acid is analogous to hydroxides, the radical C2H30 having replaced one atom of hydrogen in II20. CH'3.C02Hi is a formula indicating that acetic acid is com- posed of the two compound radicals, methyl and carboxyl. It may be said finally, that quite a number of other rational formulas have been applied, or, at least, have been proposed by different chemists and at different times, to represent the struc- ture of acetic acid, but it should be remembered that these 281 CONSTITUTION OF ORGANIC COMPOUNDS. formulas are not intended to represent the actual arrangement of the atoms in space, but only, as it were, their relative mode of combination, showing which atoms are combined directly and which only indirectly, that is, through the medium of others. 39. CONSTITUTION, DECOMPOSITION AND CLASSIFICATION OF ORGANIC COMPOUNDS. Radicals or residues. The nature of a radical or residue has been stated already in Chapter 8, but the important part played by radicals in organic compounds renders it necessary to consider them more fully. A radical is an unsaturated group of atoms obtained by removal of one or more atoms from a saturated compound. It is not necessary that this removal of atoms should be practically accom- plished in order to call a group of atoms a radical, but it is suffi- cient to prove that the unsaturated groups of atoms exists as such in a number of compounds, and that it can be transferred from one compound into another without suffering decomposition. Radicals exist in organic and inorganic compounds; an inor- ganic radical spoken of heretofore is the water residue or hydroxyl, OH, obtained by removal of one atom of hydrogen from one molecule of water. Hydroxyl does not exist in the separate state, but it exists in hydrogen dioxide, H202, or HO—OH, and is also a constituent of the various hydroxides, as, for instance, of KOH, Ca20H, Fe260H, etc. Questions.—371. What is organic chemistry, according to modern views? 372. Mention the chief four elements entering into organic compounds, and name the elements which may be made to enter into organic compounds by artificial processes. 373. State the reason why the four elements, carbon, hydrogen, oxygen, and nitrogen, are more apt to form a larger number of com- pounds than most other elements. 374. State the general properties of organic compounds. 375. Why does a qualitative analysis of an organic compound, in most cases, not disclose its true nature? 376. By what test may the organic nature of a compound be established ? 377. By what tests may the presence of carbon, hydrogen, and nitrogen be demonstrated in organic compounds? 378. State the methods by which the elements carbon, hydrogen, oxygen, sulphur, and phosphorus are determined quantitatively. 379. By what general method may a formula be deducted from the results of a quantitative analysis ? 380. What is meant by an empirical, molecular, and constitutional formula ; how are they determined, and what is the difference between them ? 282 CONSIDERATION OF CARBON COMPOUNDS. If one atom of hydrogen be removed from the saturated hydro- carbon methane, CH4, the univalent residue methyl, CH3, is left, which is capable of combining with univalent elements, as in methyl chloride, CH3C1, or, with univalent residues, as in methyl hydroxide, CH3OH. If two atoms of hydrogen be removed from CH4, the bivalent residue methylene, CH2, is left, capable of forming the compounds 0H2C12, CH220H, etc. If three atoms of hydrogen be removed from CH4, the triva- lent residue CH is left, capable of combining with three atoms of univalent elements, as in CIIC13, or with another trivalent radical, etc. Chains. The expression, chain, designates a series of multiva- lent atoms (generally, but not necessarily of the same element), held together in such a manner that affinities are left unsaturated. For instance: _0—0—, —0—0—0—, _0—0—0—0—, are oxygen chains, each one of which has two free affinities which may be saturated, for instance, with the following results : H—O—O—H, H—0—O—0—Cl, H—0—0—0—0—Cl. Hydrogen peroxide. Chloric acid. Perchloric acid. In a similar manner, carbon atoms unite, forming chains, as, for instance: I I -—C—C—, I I i i i —C—C—C—, I I I I 1 II —C—C—C—C—, etc. i m i The above carbon chains have 6, 8, and 10 free affinities, respectively, which may be saturated by the greatest variety of atoms or radicals. The chain combination of carbon, above indi- cated by the first three members of a series, may, as far as is known, be continued indefinitely. This fact, in connection with the possibility of saturating the free affinities with various atoms or radicals, indicates the almost unlimited number of possible combinations to be formed in this way. In fact, the existence of such an enormous number of carbon compounds is greatly due to the property of carbon to form these chains. It is not always the case that the atoms when forming a chain are united by one affinity only, as above, but they may be united CONSTITUTION OF ORGANIC COMPOUNDS. 283 by two or three affinities, as indicated by the compounds C2II4 and C2H2, the graphic formulas of which may be represented by H\ /H \C=C< , \H H—C=C—H. Finally it is assumed that the carbon atoms are united partially by double and partially by single union, as for instance, in the so-called closed chain of C6, capable of forming the saturated hydrocarbon benzene, C6H6: I, I I! I H H\c^C\c/H I II H/C^C/C\h I H • A chain has also been termed a skeleton, because it is that part of an organic compound around which the other elements or radicals arrange themselves, filling up, as it were, the unsaturated affinities. Homologous series. This term is applied to any series of organic compounds the terms or members of which, preceding or follow- ing each other, differ by CH2. Moreover, the general character, the constitution, and the general properties of the members of an homologous series are similar. The explanation regarding the formation of an homologous series is to be found in the above-described property of carbon to form chains. By saturating, for instance, the affinities in the open carbon chains mentioned above, we obtain the compounds 0H4, C2H6, C3H8, C4H10, etc. H H—i—II, I H H H I I H—C—C—H, I I H H H H H J I I H—C—C—C—H, Ui H H H H I I I I II—C—C—0—C—H, I I I I H H H H etc. Many homologous series of various organic compounds are known, as, for instance: C HSC1, C2H5OI, c3h7ci, c4h9 Cl, etc. C H40, c2h6o, csh8o, c;h10o, c5h12o, etc. C H2 02. C2H4 02. c3h6o2. c4h8 o2. etc. Types. It has been proposed to select some substances in which the arrangement of atoms in the molecules may be taken as rep- 284 CONSIDERATION OF CARBON COMPOUNDS. resentative of whole classes of other substances, the molecules of which have a similar arrangement, and these normal substances have been termed types. Most substances may be classified under the following five types : I. Hydrogen. II. Water. III. Ammonia. IY. Methane. Y. Phosphoric chloride. H—H, H—0—H, /H N/H, \H H | H C( , | XH H Cl | .Cl P/Cl I \C1 Cl By replacing the constituents of these types by other elements or radicals of equal valence, most of the compounds known (both organic and inorganic) may be classed in one of these t}7pes. The following live substances may, for instance, be said to have an atomic arrangement similar to the types above stated: I. Hydrochloric acid. II. Potassium. hydroxide. III. Arsenious. chloride. IV. Ethane. V. Phosphoric oxychloride. ch3 kH I XH H o II/Cl p\ I XC1 Cl H—Cl, K—O—H, /Cl As^-Cl, \ci The graphic representation of the constitution of compounds according to types has greatly aided in disclosing their structure, and is frequently used to give a picture, as it were, of the theo- retical views held regarding the atomic arrangement. Substitution is a term used for those reactions or chemical changes which depend on the replacement of an atom or a group of atoms by other atoms or groups of atoms. Substitution takes place in organic or inorganic substances, and its nature may be illustrated by the following instances : Potassium. K + H20 = KOH + H. Water. Potassium hydroxide. Hydrogen. C2H402 + 2C1 = C2H3C102 + HC1. Acetic acid. Chlorine. Monochloracetic acid. Hydrochloric acid. Benzene. c6h6 + hno3 = c6h5no2 + h2o. Nitric acid. Nitro-benzene. Water. Derivatives. This term is applied to bodies derived from others by some kind of decomposition, generally by substitution. Thus, nitro-benzene is a derivative of benzene ; chloroform, CHC13, is a derivative of methane, CH4, obtained from the latter by replace- CONSTITUTION OF ORGANIC COMPOUNDS 285 ment of three atoms of hydrogen by the same number of atoms of chlorine. Isomerism. Two or more substances may have the same ele- ments in the same proportion by weight (or the same centesimal composition), and yet be different bodies, showing different prop- erties. Such substances are called isomeric bodies. Two kinds of isomerism are distinguished, viz., metamerism and polymerism. Metamerism. Substances are metameric when their molecules contain equal numbers of atoms of the same elements. Thus, the oils of juniper, turpentine, lemon, etc., all have the molecular formula C10H16, and yet they have different physical properties, and may be distinguished by their odor, by their action on polar- ized light, etc. The explanation given regarding this difference of properties is, that the atoms are arranged differently within the molecule. In some cases this arrangement is as yet unknown, in other cases structural or graphic formulas showing this atomic arrangement may be given. For instance : Acetic acid and methyl formate both have the composition C2H402, but the arrangement of the atoms (or the structure) is very different, as shown by the formulas: Acetic acid. Methyl formate. C'S^sOXq CHO\0 ch3/u- As another instance may be mentioned the compound CFT2H40, which represents either ammonium cyanate or urea: Ammonium cyanate. ■NH4\0 CN/U- nh2\ nh2/u- Urea. Polymerism. Substances are said to be polymeric when they have the same centesimal composition, but a different molecular weight, or, in other words, when one substance contains some multiple of the number of each of the atoms contained in the molecule of the other. For instance, some volatile oils have the composition C20H32, which is double the number of atoms contained in oil of tur- pentine, C10H16; acetylene, C2H2, is polymeric with benzene, C6H6; acetic acid, C2FI402, is polymeric with grape-sugar, 6^12^6? 286 CONSIDERATION OF CARBON COMPOUNDS. Various modes of decomposition. The principal changes which a molecule may suffer are as follows : a. The atoms may arrange themselves differently within the molecule. Ammonium cyanate, HII4CjSTO, is easily converted into urea, C02(NH2). b. A molecule may split up into two or more molecules. For instance: Grape-sugar. C6H1206 = 2C2H60 + 2C02 Alcohol. Carbon dioxide. c. Two molecules, either of the same kind, or of different sub- stances, may unite together directly : C2H4 + 2Br = C2H4Br2. Ethylene. Bromine. Ethylene bromide. d. Atoms may be removed from a compound without replacing them by other atoms : C2H60 + O = 02H40 + h2o. e. Atoms may be removed and replaced by others at the same time (substitution): Alcohol. Oxygen. Aldehyde. Water. C2H402 + 2C1 = C2H3C102 + HC1. Acetic acid. Chlorine. Mo nochloracetic acid. Hydrochloric acid. Action of heat upon organic substances. As a general rule, organic bodies are distinguished by the facility with which they decompose under the influence of heat or chemical agents; the more complex the body is, the more easily does it undergo decom- position or transformation. Heat acts differently upon organic substances, some of which may be volatilized without decomposition, whilst others are decomposed by heat with generation of volatile products. This process of heating non-volatile organic substances in such a manner that the oxygen of the atmospheric air has no access, and to such an extent that decomposition takes place, is called dry or destructive distillation. The nature of the products formed during this process varies not only with the nature of the substance heated, but also with the temperature applied during the operation. The products formed by destructive distillation are invariably less complex in composition, that is, have a smaller number of atoms in the mole- cule, than the substance which suffered decomposition; in other DECOMPOSITION OF ORGANIC COMPOUNDS. 287 words, a complex molecule is split up into two or more molecules less complex in composition. Otherwise, the products formed show a great variety of prop- erties ; some are gases, others volatile liquids or solids, some are neutral, others basic or acid substances. In most cases of destruc- tive distillation a non-volatile residue is left, which is nearly pure carbon. Action of oxygen upon organic substances. Combustion. Decay. All organic substances are capable of oxidation, which takes place either rapidly with the evolution of heat and light and is called combustion, or it takes place slowly without the emission of light, and is called slow combustion or decay. The heat generated during the decay of a substance is the same as that generated by burning the substance; but as this heat is liberated in the first instance during weeks, months, or perhaps years, its generation is so slow that it can scarcely be noticed. iSTo organic substance found or formed in nature contains a sufficient quantity of oxygen to cause the complete combustion of the combustible elements (carbon and hydrogen) present; by artificial processes such substances may, however, be produced, and are then either highly combustible or even explosive. During common combustion, provided an excess of atmospheric oxygen be present, the total quantity of carbon is converted into carbon dioxide, hydrogen into water, sulphur and phosphorus into sulphuric and phosphoric acids, while nitrogen is generally liberated in the elementary state. During the process of decay the compounds mentioned above are produced finally, although many intermediate products are generated. For instance : If a piece of wood be burnt, complete oxidation takes place: intermediate products also are formed chiefly in consequence of the destructive distillation of a portion of the wood, but they are consumed almost as fast as they are produced, as was mentioned in connection with the consideration of flame. Again, when a piece of wood is exposed to the action of the atmosphere, it slowly burns or decays. The intermediate products formed in this case are entirely different from those pro- duced during common combustion. Common alcohol has the composition C2II60; in burning, it requires six atoms of oxygen, when it is converted into carbon dioxide and water: C2H60 + 60 = 2C02 + 3H20. 288 CONSIDERATION OF CARBON COMPOUNDS. But alcohol may also undergo slow oxidation, in which case oxygen first removes hydrogen, with which it combines to form water, whilst at the same time a compound known as acetic alde- hyde, C2II40,is formed: This aldehyde, when further acted upon by oxygen, takes up an atom of this element, thereby forming acetic acid: c2h6o + O = C2H40 + H20. c2h4o + o = c2h4o2 The three instances given above illustrate the action of oxygen upon organic substances, which action may consist in a mere removal of hydrogen, in a replacement of hydrogen by oxygen, or in an oxidation of both the carbon and hydrogen, and also of sulphur and phosphorus, if they be present. An organic substance, when perfectly dry and exposed to dry air only, may not suffer decay for a long time (not even for cen- turies), but in the presence of moisture and air this oxidizing action takes place almost invariably. Besides the slow oxidation or decay which all dead organic matter undergoes in the presence of moisture, there is another kind of slow oxidation, called respiration, which takes place in the living animal; this process will be more fully considered in the physiological part of this book. Fermentation and putrefaction. These terms are applied to pecu- liar kinds of decomposition, by which the molecules of certain organic substances are split up into two or more molecules of a less complicated composition. These decompositions take place when three factors are simultaneously acting upon the organic substance. These factors are: presence of moisture, favorable temperature, and presence of a substance generally termed fer- ment. The most favorable temperature for these decompositions lies between 25° and 40° C. (77° and 104° F.), but they may take place at lowrer or higher temperatures. No substance, however, will either ferment or putrefy at or below the freezing-point, or at or above the boiling-point. The nature of the various ferments differs widely, and their true action cannot, in many cases, be explained; what we do know is, that the presence of comparatively small (often minute) quantities of one substance (the ferment) is sufficient to cause the CONSTITUTION OF OEGANIC COMPOUNDS. 289 decomposition of large quantities of certain organic substances, the ferment itself suffering often no apparent change during this decomposition. The ferments are, in a few cases, organic sub- stances, but generally living organisms of either vegetable or animal origin. The nature of the ferment generally determines the nature of the decomposition which a substance suffers, or, in other words, one and the same substance will under the influence of one fer- ment decompose with liberation of certain products, while a second ferment causes other products to be evolved. Sugar, for instance, under the influence of yeast, is converted into alcohol and carbon dioxide, while under the influence of certain other ferments it is converted into lactic acid. The difference between fermentation and putrefaction is, that the first term is used in those cases where the decomposing sub- stance contains carbon, hydrogen, and oxygen only, while sub- stances containing, in addition to these three elements, either nitrogen or sulphur (or both) undergo putrefaction. The two last-named elements are generally evolved as ammonia and hydrosulphuric acid, which gases give rise to an offensive odor. Sugar, having the composition C6Hl206, undergoes fermenta- tion, whilst albuminous substances which contain nitrogen and sulphur putrefy. The oxygen of the air takes no part in either fermentation or putrefaction, but the presence or absence of atmospheric air may cause or prevent decomposition, inasmuch as the atmosphere is filled with millions of minute germs of organic nature, which germs may act as ferments when in contact with organic matter under favorable conditions. Whenever organic bodies (a dead animal, for instance) undergo decomposition in nature, the processes of fermentation and putre- faction are generally accompanied by oxidation or decay. The conditions under which a substance will ferment or putrefy have been stated above, and the non-fulfilment of these conditions enables us to prevent decomposition artificially. Thus, we freeze substances (meat); or expel all water from or dry them (fruit, etc.), in order to prevent decomposition. The action of the ferments is counteracted either by the so-called anti- septic agents (salt, carbolic or salicylic acid, etc.) which are incom- patible with organic life, or by excluding the air, and with it the ferments, by enclosing the substances in air-tight vessels (glass 290 CONSIDERATION OF CARBON COMPOUNDS. jars, tin cans, etc.), which, when filled, are heated sufficiently to destroy any germs which may have been present, and are then sealed. Antiseptics and disinfectants. While the term antiseptics is applied to those substances which retard or prevent fermentation and putrefaction, the term disinfectants refers to those agents actually destroying the organisms which are the causes of these decompositions. If we assume that all infectious diseases are due to microorganisms, or germs of various kinds, disinfectants may be considered as equivalent to germicides. Disinfectants are generally antiseptics also, hut the latter are not in all cases dis- infectants. The solution of a substance of certain strength may act as a disinfectant and antiseptic, while the same solution diluted further may act as an antiseptic only, hut not as a disin- fectant. Deodorizers are those substances which convert the strongly smelling products of decomposition into inodorous compounds. Strong oxidizing agents are generally good deodorizers, as, for instance, chlorine, potassium permanganate, hydrogen dioxide, etc. Among the best antiseptics and disinfectants are chlorine (gener- ally used in the form of a 4 per cent, solution of hypochlorite of calcium), mercuric chloride (a solution of 1: 500 or 1:1000), carbolic acid (a 5 per cent, solution), and some other substances. Action of chlorine and bromine. These two elements act upon organic substances (similarly to oxygen) in three different ways, viz., they either (rarely, however) combine directly with the organic substance, or remove hydrogen, or replace hydrogen. The following equations illustrate this action: Ethylene. C2H4 + ‘2Br = C2H4Br2. Bromine. Ethylene Bromide. C2H60 + 2C1 = C2H40 + 2HC1. Ethyl alcohol. C2H402 + 2C1 = C2H3C102 + HC1 Chlorine. Aldehyde. Hydrochloric acid. Acetic acid. Chlorine. Mo noch loracetic acid. Hydrochloric acid. In the presence of water, chlorine and bromine often act as oxidizing agents by combining with the hydrogen of the water and liberating oxygen; iodine may act in a similar manner as an oxidizing agent, but it rarely acts directly by substitution. CONSTITUTION OF ORGANIC COMPOUNDS. 291 Action of nitric acid. This substance acts either by direct combination with organic bases forming salts, or as an oxidizing agent, or by substitution of nitryl, N02, for As instances of the latter action, may be mentioned the formation of nitro- benzene and nitro-cellulose: C6H6 + HN03 = C6H5N02 + H20. Benzene. Nitric acid. Nitrobenzene. Water. C6H10O5 + 3HN0S = C6H73(N02)05 + 3H20. Cellulose. Nitric acid. Trinitro-cellulose. Water The additional quantity of oxygen thus introduced into the molecules, renders them highly combustible, or even explosive. Action of dehydrating agents. Substances having a great affinity for water, such as strong sulphuric acid, phosphoric oxide, and others, act upon many organic substances by removing from them the elements of hydrogen and oxygen, and combining with the water formed, while, at the same time, frequently dark or even black compounds are formed, which consist largely of carbon. The black color imparted to sulphuric acid by organic matter depends on this action. Action of alkalies. The hydroxides of potassium and sodium act in various ways on organic substances. In some cases direct combination takes place: CO + KOH = KCH02. Carbonic acid. Potassium hydroxide. Potassium formate. Salts are formed: C2H402 + NaOH = NaC2H302 + H20. Acetic. acid. Sodium hydroxide. Sodium acetate. Water, Fats are decomposed with the formation of soap C3H53(C18H3302) + 3NaOH — C3II53HO -j- 3(NaC18H3302). Oleate of glyceril. Sodium hydroxide. Glycerin. Sodium oleate. Oxidation takes place, while hydrogen is liberated: C2H60 + KOH = KC2Hs02 + 4H. Ethyl. alcohol. Potassium hydroxide. Potassium acetate. Hydrogen. From compounds containing nitrogen, ammonia is evolved : NH2C2H30 + KOH = KC2H302 + NH3. Acetamide. Potassium hydroxide. Potassium acetate. Ammonia. 292 CONSIDERATION OF CARBON COMPOUNDS. Action of reducing agents. Deoxidizing or reducing agents, especially hydrogen in the nascent state, act upon organic sub- stances either by direct combination : Ethene oxide. C2H40 + 2H = C2H60 Ethyl alcohol. or by removing oxygen (and also chlorine or bromine): C7H602 + 2H = C7H60 + H20. In some cases hydrogen replaces oxygen : Benzoic acid. Benzoic aldehyde. C6H5N02 + 6H = C6H5NH2 + 2H20. Nitro-benzene. Aniline. Classification of organic compounds. There are great difficulties in arranging the immense number of organic substances prop- erly, and in such a manner that natural groups are formed the members of which are similar in composition and possess like properties. Various modes of classification have been proposed, some of which, however, are so complicated that the beginner will find it difficult to make use of them. The grouping of organic sub- stances here adopted, while far from being perfect, has the ad- vantages of being simple, easily understood, and remembered. 1. Hydrocarbons. All compounds containing the two ele- ments carbon and hydrogen only. For instance, CH4, C6H6, GtC- 2. Alcohols. These are unsaturated hydrocarbons or hydro- carbon residues in combination with hydroxyl, OH. For in- stance, ethyl alcohol, glycerin, C3Hm530H, etc. 3. Aldehydes. Unsaturated hydrocarbons in combination with the radical COH; they are compounds intermediate between alcohols and acids, or alcohols from which hydrogen has been removed. For instance: c2h6o, Ethyl alcohol. c2h4o, Aldehyde. c2h402. Acetic acid. 4. Organic acids. Unsaturated hydrocarbons in combination with carboxyl, a radical having the composition C02H, or com- pounds formed by replacement of hydrogen in hydrocarbons by carboxyl. Otherwise, organic acids have the general properties of inorganic acids. 5. Ethers. Compounds formed from alcohols by replacement of the hydrogen of the hydroxyl by other unsaturated hydro- CONSTITUTION OF ORGANIC COMPOUNDS. 293 carbons, or, what is the same, by other alcohol radicals. For instance: c^>0, c2H5/°> c2h5\0 C Hs/U- 6. Compound ethers or esters. Formed from alcohols by re- placement of the hydrogen of the hydroxyl by acid radicals, or from acids by replacement of the hydrogen of carboxyl by alcohol radicals. For instance: Ethyl alcohol. Ethyl ether. Ethyl-methyl ether. c2ha0 , CH3co\0 = c2H5\0 H\0 H/u ' H/u — CH3CO/u h H/u Ethyl alcohol. Acetic acid. Acetic ether. Water. The various fats belong to this group of compound ethers. 7. Carbohydrates. (Sugars, starch, gum, etc.) These com- pounds contain 6 atoms of carbon (or a multiple of 6) in the molecule, and hydrogen and oxygen in the proportion of 2 atoms of hydrogen to 1 atom of oxygen, or in the proportion to form water. Most carbohydrates are capable of fermentation, or of being easily converted into fermentable bodies. Instances: Glucosides are substances the molecules of which may be split up in such a manner that several new bodies are formed, one of which is sugar. 8. Amines and amides. Substances formed by replacement of hodrogen in ammonia by alcohol or acid radicals. For instance : ethyl amine, NH2.C2H5, urea, H2H4.CO, etc. The alkaloids belong to this group. 9. Cyanogen and its compounds. Substances containing the radical cyanogen, CH. For instance: potassium cyanide, KCFT. 10. Proteids or albuminous substances. These contain, besides carbon, hydrogen, and oxygen, always nitrogen and sulphur, sometimes also other elements. Instances: albumin, casein, fibrin, etc. In connection with each of these groups have to be considered the derivatives obtained from them directly or indirectly. As all those organic compounds, the constitution of which has been explained, may be looked upon as derivatives of either methane, CH4, or benzene, C6H6, a separation of organic com- pounds is made into two large classes, each one embodying all the derivatives of one of the two hydrocarbons named. The derivatives of methane are termed fatty compounds, those of benzene aromatic compounds. Fatty compounds have representa- 294 CONSIDERATION OF CARBON COMPOUNDS. tives in each one of the above ten groups: aromatic compounds are missing in a few. As far as practicable, the two classes will be considered separately, because the properties of fatty and aromatic compounds differ so widely, in some respects, that this method of studying the nature of carbon compounds is to be preferred. 40. HYDROCARBONS. Occurrence in nature. Hydrocarbons are seldom derived from animal sources, being generally products of vegetable life; thus, the various essential oils (oil of turpentine and others) of the composition C10H16 or C20H32 are frequently found in plants, where they are formed from carbon dioxide and water: This equation, whilst showing the possibility of the formation of an essential oil in the plant, must not be taken to mean that 10 molecules of carbon dioxide and 8 molecules of water are simultaneously decomposed, with the production of an essential oil; on the contrary, we know that many intermediate substances are formed, and the formula simply gives the final result, not the intermediate stages of the process. 10CO2 + 8H20 = C10H16 4- 280. Other hydrocarbons are found in nature as products of the decomposition of organic matter. Thus methane, CH4, is gen- erally formed during the decay of organic matter in the presence of moisture; the higher members of the methane series are found in crude coal-oil. Formation of hydrocarbons. It is difficult to combine the two elements carbon and hydrogen directly; as an instance of such direct combination, may be mentioned acetylene, C2H2, which is Questions.—381. Explain the term residue or radical. 382. What is under- stood by the expression chain, when used in chemistry? 383. What are the characteristics of an homologous series? 384. Give an explanation of the terms isomerism, metamerism, and polymerism. 385. How does heat act upon organic compounds? 386. What is destructive distillation? 387. State the difference between combustion, decay, fermentation, and putrefaction; what is the nature of these processes, and under what conditions do they take place? 388. How do chlorine, nitric acid, and alkalies act upon organic substances? 389. What is the action of hydrogen, and of dehydrating agents, upon organic substances? 390. Mention the chief groups of organic compounds. HYDROCARBONS. 295 formed when electric sparks pass between electrodes of carbon in an atmosphere of hydrogen. Many hydrocarbons are obtained by destructive distillation of organic matter, and their nature depends on the composition of the material used and upon the degree of heat applied for the decomposition. Hydrocarbons may also be obtained by the decomposition (other than destructive distillation) of numerous organic bodies, such as alcohols, acids, amines, etc., and from derivatives of these substances. Fig. 39. Flasks arranged for fractional distillation The hydrocarbons found in nature are generally separated from other matter, as well as from each other, by the process known as fractional distillation. As the boiling-points of the various compounds differ more or less, they may be separated by carefully distilling off the compounds of lower boiling-points, while noting the temperature of the vapors above the boiling liquid by means of an inserted thermometer, and changing the receiver every time an increase of the boiling-point is noticed. This separation of volatile liquid, known as fractional distillation, is, however, not absolutely complete, because traces of sub- 296 CONSIDERATION OF CARBON COMPOUNDS. stances having a higher boiling-point are simultaneously volatil- ized with the distilling substance. For fractional distillation of small quantities of liquids as well as for the determination of boiling-points, flasks arranged like those shown in Fig. 39 may be used. Properties of hydrocarbons. There are no other two elements which combine together in so many proportions as carbon and hydrogen. Several hundred hydrocarbons are known, many ot which form either homologous series or are metameric or poly- meric. Hydrocarbons occur either as gases, liquids, or solids. If the molecule contains not over 4 atoms of carbon, the compound is generally a gas at the ordinary temperature; if it contains from 4 to 10 or 12 atoms of carbon, it is a liquid; and if it contains a yet higher number of carbon atoms, it is generally a solid. All hydrocarbons may be volatilized without decomposition, all are colorless substances, and many have a peculiar and often characteristic odor; they are generally insoluble in water but soluble in alcohol, ether, bisulphide of carbon, etc. In regard to chemical properties, it may be said that hydro- carbons are neutral substances, behaving rather indifferently toward most other chemical agents. Most of them are, however, oxidized by the oxygen of the air, by which process liquid hydro- carbons are often converted into solids. Hydrocarbons of the paraffin or methane series. The hydrocar- bons having the general composition CnH2n+2 are known as paraffins, the name being derived from the higher members of the series which form the paraffin of commerce. The following table gives the composition, boiling-points, etc., of the first sixteen members of this series: Methyl hydride or methane, Ethyl hydride or ethane, C H0 C2 H6 B. P. gases. Sp. gr. Propyl hydride or propane, Butyl hydride or butane, 03h8J c4h10 1° c. Amyl hydride or pentane, c5h12 38 0.628 Hexyl hydride or hexane, 70 0.669 Heptyl hydride or heptane, o7h16 99 0.690 Octyl hydride or octane, c8h18 125 0.726 Nonyl hydride or nonane, c9h20 148 0.741 Decyl hydride or decane, 166 0.757 Undecyl hydride or undecane, cuh24 184 0.766 HYDROCARBONS. 297 Dodecyl hydride or dodecane, c12h26 P. B. 202 Sp. gr. 0.778 Tridecyl hydride or tridecane, c13h28 218 0.796 Tetradecyl hydride or tetradecane, 236 0.809 Pentadecyl hydride or pendadecane, c15h32 258 0.825 Hexadecyl hydride or hexadecane, etc. c16h34 280 The above table shows that the paraffins form an homologous series; the first four members are gases, most of the others liquids, regularly increasing in specific gravity, boiling-point, viscidity, and vapor density, as their molecular weight becomes greater. The paraffins are saturated hydrocarbons, the constitution of which has been already explained; they are incapable of uniting directly with monatomic elements or residues, but they easily yield substitution-derivatives when subjected to the action of chlorine or bromine. Most of the paraffins are known in two (or even more) modifications; there are, therefore, other homologous series of hydrocarbons of the same composition as the above normal paraffins, which show some difference from the normal paraffins in boiling-points and other properties. In these isomeric paraffins the atoms are arranged differently from those in the normal hydrocarbons, which fact may be proven by the difference in decomposition which these substances suffer when acted upon by chemical agents. No isomeric hydrocarbons of the first three members of the paraffin series are known, which fact is in accordance with our present theories. Assuming that the quadrivalent carbon atoms exert their full valence, and that they are held together by one atomicity only, we can arrange the atoms in the compounds, CH4, C2H6, and C3H8, not otherwise than thus: /H C-H \H o=H3 C—h2 i=H3 c=h3 CEEH3 In the next compound, butane, C4H10, we have two possibilities explaining the structure of the molecule, namely, these : C=H3 i=H2 c=h2 c~h3 CSH3 ! C=H3—CH—CEEHg. Both these compounds are known, and termed normal butane and isobutane, respectively. The next member, pentane, C5H12, shows three possibilities of constitution, thus: 298 CONSIDERATION OF CARBON COMPOUNDS. c=h3 I C=T H2 c=h2 d=Hs I c=h3 0=h3 I C=HS—c-h Lh. ceeh3 C=Ho I c=h3—c—c=h3 I ceeh3. These compounds also are known. With the higher members of the paraffins the number of possible isomeres rises rapidly according to the law of permuta- tion, so that we have of the seventh member 9, of the tenth 75, and of the thirteenth member 799, possible isomeric hydrocarbons. Methane, CH4 (Marsh-gas, Fire-damp). This hydrocarbon has been spoken of in Chapter 13, where it was stated that it is a color- less, combustible gas, which is formed by the decay of organic matter in the presence of moisture, during the formation of coal in the interior of the earth, and by the destructive distillation of various organic matters. Methane is of special interest, because it is the compound from which thousands of other substances are derived. It may be made by the action of inorganic substances upon one another; for instance, by passing a mixture of steam and carbon disulphide over copper heated to red heat, when the following change takes place: Bearing in mind that carbon disulphide, as well as water, may be obtained by direct union of the elements, it is evident that methane may be formed indirectly, by means of the above method, from the elements carbon and hydrogen. 6Cu + CS2 + 2H20 = 2CujS + 2CuO + CH4. Experiment 40. Use apparatus shown in Fig. 5, page 38, omitting the bent tube B. Mix in a mortar 20 grams of sodium acetate with 20 grams of potas- sium (or sodium) hydroxide and 30 grams of calcium hydroxide ; fill with this mixture the tube A, which should be made of glass fusing with difficulty, or of so-called “ combustion tubing; ” apply heat and collect the gas over water. The decomposition takes place thus: NaC.2H302 + NaOH = Na.2COs + CH4. Ignite the gas, and notice that its flame is but slightly luminous. Mix some of the gas in a wide-mouth cylinder, of not more than about 200 c.c. capacity, with an equal volume of air and ignite. Repeat this experiment with mixtures of one volume of methane with 2, 5, 7, 5, and 10 volumes of atmospheric air. Which mixture is most explosive, and why ? How many volumes of oxygen aud how many volumes of atmospheric air are needed for the complete com- bustion of one volume of methane ? HYDROCARBONS. 299 Coal, Coal-oil, Petroleum. The name eoal-oil is applied to a mixture of the various liquid paraffins, containing often in solu- tion the gaseous and solid members of the group, and also hydro- carbons belonging to other series. Coal-oil is produced in nature most likely by the decomposition of organic matter, possibly during the formation of coal. The various substances classed together under the name of coal consist principally of carbon, associated with smaller quantities of hydrogen, oxygen, nitrogen, sulphur, and certain inorganic mineral matters which compose the ash. Coal is formed from buried vegetable matter by a process of decomposition which is partly a fermentation, partly a decay, and chiefly a slow destruc- tive distillation, the heat for this latter process being derived from the interior of the earth, or by the decomposition itself. The principal constituent of the organic matter furnishing coal is wood (or woody fibre, cellulose), and a comparison of the com- position of this substance with the various kinds of coal gradu- ally formed will help to illustrate the chemical change taking place: Carbon. Hydrogen. Oxygen. Wood .... . 100 12.18 83.07 Peat .... . 100 9.85 55.67 Lignite . . . . . 100 8.37 42.42 Bituminous coal . 100 6.12 21.23 Anthracite coal . 100 2.84 1.74 This table shows a progressive diminution in the proportions of hydrogen and oxygen during the passage from wood to anthra- cite. These two elements must, therefore, be eliminated in some form of combination which allows them to move, viz., as gases or liquids. The gases formed are chiefly carbon dioxide (which finds its way through the rocks and soils to the surface either in the gaseous state, or after having been absorbed by water in the form of carbonic acid springs) and methane, known to coal- miners as fire-damp, frequently causing the formation of explo- sive gas mixtures in the coal mines, or escaping, like carbon dioxide, through fissures to the surface of the earth, where it may be ignited. While methane and other combustible gases are undoubtedly formed during the formation of coal, the gas mixture now generally termed natural gas (a mixture of methane, ethane, propane, hydrogen and a few other gases), and used largely for heating and illuminating purposes, is most likely a product of the complete decomposition of vegetable and animal matter which has been 300 CONSIDERATION OF CARBON COMPOUNDS. precipitated from water, simultaneously with inorganic matter, during the forma- tion of certain rocks, chiefly slate and limestone. The decomposition of this organic matter has been so complete that the gaseous decomposition-products only are left, but no solid residue similar to coal. A theory has been advanced explaining the formation of natural gas and of petroleum by the action of water on red-hot carboniferous metals in the interior of the earth, but there are as yet no facts beyond laboratory experiments to justify this assumption. Petroleum, as has been stated, is chiefly a mixture of various hydrocarbons, the boiling-points of which lie between 0° and 300° C. (32° and 572° F.), or even higher. The crude oil is purified, by treating it with sulphuric acid, followed by other processes of refining, and finally by fractional distillation, in order to separate the members of low boiling-points from those of higher boiling-points. The hydrocarbons of low boiling-points, chiefly a mixture of C5H12 and C6H14, are officinal, under the name of petroleum-ether or benzin, which name must not be confounded with benzene or benzol, C6H6. According to the U. S. P., benzin should have a specific gravity from 0.67 to 0.675, and a boiling-point of 50° to 60° C. (122° to 140° F.). Other similar liquids are sold in the market under the name of rhigoline (B. P. about 21° C. (70° F.)) and gasoline (B. P. about 75° C. (167° F.)); they are highly inflammable. The paraffins distilling between 150° and 250° C. (302° and 408° F.) constitute the common illuminating oil, various kinds of which are sold as kerosene, paraffin oil, astral-oil, mineral sperm- oil, etc. The danger which arises in the use of coal-oil as an illuminating agent is caused by the use of oils which have not been sufficiently freed from the more volatile members of the series, which, when but slightly heated (or even at ordinary temperature), will vaporize, and, upon mixing with atmospheric air, form explosive mixtures. An oil to be safely used for illuminating purposes in common lamps should not give off inflammable vapors (or flash) below 49° C. (120° F.). Experiment 41. Various forms of apparatus are used for the exact determi- nation of the flashing-point; students may determine it approximately by operating as follows: Fill a cylinder (about one inch in diameter and six inches high) two-thirds with keroseue, suspend in the oil a thermometer, place the cylinder in a vessel with water (water-bath), keeping the level of the oil even with that of the water, and heat the latter slowly. Cover the cylinder loosely with a piece of pasteboard, and when the thermometer indicates a rise HYDROCARBONS. 301 in temperature pass a small flame quickly over the mouth of the cylinder after having removed the pasteboard. Repeat this operation, from degree to degree, until a bluish flame is noticed running down to the surface of the oil. The temperature at which this takes place indicates the flashing-point. After the illuminating oil has been distilled off", a mixture of substances passes over, which is used for lubricating purposes or furnishes, after having been purified by treatment with bone- black, the officinal article known as petrolatum, petroleum ointment, or vaseline. A mixture of the highest and solid members of the paraffin series distilling at a temperature about 850° C. (662° F.) is known as paraffin, a white, crystalline substance used for candles, etc.; it fuses at about 75° C. (167° F.). Illuminating gas is a mixture of gases obtained by the destruc- tive distillation of coal (or wood) in iron retorts, with subsequent purification of the gases generated. The constituents of coal have been mentioned above. The products formed from it during its destructive distillation are very numerous; the follow- ing are the most important: Hydrogen . . . . H. Methane .... CH4. Ethene .... C2H4 Acetylene .... C2H2 Nitrogen . . . . N. Ammonia .... NH3. Carbonic acid . . . CO. Carbon dioxide . . . C02. Hydrosulphuric acid . . H2S. . Hydrocyanic acid . . HCN Gases B. P. Benzene .... C6H6 80° Toluene .... C7H8 110 Aniline .... C6H3NH2 132 Acetic acid .... C2H402 117 Water . . . . E20 100 ' Liquids Coal-tar Carbolic acid . . . C6H60 188 Kresylic acid . . . C7H80 201 Naphthalene . . . C10H8 220 Anthracene . . . C14H]0 360 Paraffin .... C16H34 ' 280 Solids Solid residue : Coke, chiefly carbon and inorganic matter. The gases are purified by condensing ammonia (and some other gases) in water, carbon dioxide and hydrosulphuric acid in 302 CONSI DERATION OF CARBON COMPOUNDS. calcium hydroxide. The following is the composition of a puri- fied illuminating gas obtained from cannel-coal: Hydrogen ...... 46 volumes. Methane 41 “ Ethene ...... 6 “ Carbonic oxide ..... 4 “ Carbon dioxide ..... 2 “ Nitrogen ...... 1 volume. Experiment 42. Use apparatus shown in Fig. 5, page 38. Fill the combus- tion-tube A with sawdust (almost any other non-volatile organic matter may be used), apply heat and continue it as long as gases are evolved. Notice that by this process of destructive distillation are formed a gas (or gas mixture), which may be ignited, a dark, almost black liquid (tar), which condenses in the tube 13, and that a residue is left which is chiefly carbon. The tarry liquid shows an acid reaction, due to acetic and other acids present. Coal-tar, obtained as a by-product in the manufacture of illu- minating gas, contains, as shown by the above table, many valuable substances, such as benzene, aniline, carbolic acid, paraffin, etc., which are separated from each other by making use of the difference in their boiling-points and specific gravities, or of their solubility or insolubility in various liquids, or, finally, of their basic, acid, or neutral properties. Olefines. The hydrocarbons of the general formula CnH2D are termed olefines. To this series belong: Ethene or ethylene .... C2H4 Propene or propylene .... C3H6 Butene or butylene .... C4H8 Pentene or amylene . . . . C5H10 Hexene or hexylene .... C6H12 Methene, CH2, the lowest terms of this series is not known. The hydrocarbons of this series are not only homologous, but also polymeric with one another. Of special interest is the first known member of the series, ethene or olefiant gas, on account of its normal occurrence in illu- minating gas, as well as in most common flames, the luminosity of which depends greatly on the quantity of this compound present in the burning gas. Benzene series or aromatic hydrocarbons. The members of a series of hydrocarbons having the general composition CnH2n_6, and all the derivatives of this group, including the alcohols, ALCOHOLS. acids, etc., are the substances spoken of before as aromatic com- pounds, and will be considered later. Volatile or essential oils. The term essential oil is more a phar- maceutical than chemical term, and is used for a large number of liquids obtained from plants, and having in common the prop- erties of being volatile, soluble in ether and alcohol, almost insol- uble in water, and having a distinct and in most cases even highly characteristic odor. They stain paper as do fats or fat oils, from which they differ, however, by the disappearance after some time of the stain produced, while fats leave a permanent stain. In their chemical composition essential oils differ widely; some are compound ethers, others aldehydes, but most of them are hydrocarbons or oxidized hydrocarbons, belonging to the benzene- derivatives, where they will be considered. 41. ALCOHOLS. Constitution of alcohols. The old term “ alcohol ” originally indicated but one substance (ethyl alcohol), but is now applied to a large group of substances which may be looked upon as being derived from hydrocarbons by replacement of one, two or more hydrogen atoms by hydroxyl, OH. Any hydrocarbon may be converted into an alcohol radical by removal of one or more hydrogen atoms; methane, CH4, for instance, is converted into methyl, CH3, which, upon combining with hydroxyl, forms methyl alcohol, CH3OH. It has been shown before that the higher members of the paraffin series are capable of forming a number of isomeric compounds. Running parallel to the various series of hydrocarbons (and their isomeres) we have homologous series Questions.—391. How do hydrocarbons occur in nature, and by what pro- cesses are they formed in nature or artificially ? 392. State the general physical and chemical properties of hydrocarbons? 393. What is the general composition of the paraffins? 394. State the composition and properties of methane, and also the conditions under which it is formed in nature. 395. What is coal, what are its constituents, from what is it derived, and by what process has it been formed ? 396. What is crude coal-oil, what is petroleum ether, and what is petrolatum? 397. How is illuminating gas manufactured, and what are its chief constituents? 398. Mention some of the important substances found in coal-tar. 399. Explain a method by which the flashing-point of coal-oil can be determined. 400. Which substances are termed volatile oils, and what are their properties? 304 CONSIDERATION OF CARBON COMPOUNDS. of alcohols. The isomeric alcohols also show properties different from one another, and yield different decomposition products. The isomeric alcohols are distinguished as normal or primary, secondary and tertiary alcohols; a normal alcohol is derived from a normal paraffin, and contains hydroxyl in the place of a hydrogen atom in a methyl group, the constitution of normal ethyl alcohol being, for instance, represented by the formula CH2.OH ch3. If hydroxyl replace but one atom of hydrogen in a hydro- carbon, the alcohol is termed monatomic; diatomic and triatomic alcohols are formed by replacement of two or three hydrogen atoms respectively. (Diatomic alcohols are also termed glycols.) As an instance of a diatomic alcohol may be mentioned ethylene alcohol, C2H420H, while glycerin, C3H530H, is a triatomic alcohol. Alcohols correspond in their composition to the hydroxides of inorganic substances; both classes of compounds containing hydroxyl, OH, which, in the case of alcohols, is in combination with residues containing carbon and hydrogen, in the case of inorganic hydroxides with metals, as, for instance, in potassium hydroxide, KOH. If we represent any unsaturated hydrocarbon by Al.R. (alcohol radical), the general formula of the alcohols will be: Monotomic alcohol. Diatomic alcohol. Triatomic alcohol. Al.Ri—OH a 1 /OH A1K \OH /OH Al.Kiii—OH \OH or Al.R'OH Al.Rii20H Al.Riii30H corresponding to KOH Ca»20H Biiii30H. Occurrence in nature. Alcohols are not found in nature in a free or uncombined state, but generally in combination with acids as compound ethers. Some plants, for instance, contain com- pound ethers mixed with volatile oils. The triatomic alcohol glycerin is a normal constituent of all fats or fatty oils, and is therefore found in many plants and in most animals. Formation of alcohols. Alcohols are often produced by fer- mentation (ethyl alcohol from sugar), sometimes by destructive distillation (methyl alcohol from wood): they are obtained from compound ethers (which are compounds of acids and alcohols) by treating them with the alkaline hydroxides, when the acid ALCOHOLS. 305 enters into combination with the alkali, whilst the alcohols are liberated according to the general formula: f' S V> + KOH = . ?\o + Al.R.OH. Ac.R./ 1 Ac.R./ 1 Alcohols may be obtained artificially by various processes, as, for instance, by treating hydrocarbons with chlorine, when the chloride of a hydrocarbon residue is formed, which may be de- composed by alkaline hydroxides in order to replace the chlorine by hydroxyl, when an alcohol is formed. For instance: C2H6 + 20 = C2H5C1 + HO. Ethane. Ethyl chloride. C2H5C1 + KOH = KC1 + C2H5OH. Ethyl chloride. Potassium hydroxide. Potassium chloride. Ethyl alcohol. Properties of alcohols. Alcohols are generally colorless, neutral liquids; some of the higher members are solids, none is gaseous at the ordinary temperature. Most alcohols are specifically lighter than water; the lower members are soluble in or mix with water in all proportions; the higher members are less soluble, and, finally, insoluble. Most alcohols are volatile with- out decomposition; some of the highest members, however, decompose before being volatilized. Although alcohols are neutral substances, it is possible to replace the hydrogen of the hydroxyl by metals, as, for instance, CH3OH = methyl alcohol; CH3(XNa = sodium methyl oxide or sodium methylate. The oxygen of alcohols maybe replaced by sulphur, when com- pounds are formed known as hydro sulphides or mercaptans ; these bodies may be obtained by treating the chlorides of hydrocarbon residues with potassium sulphydrate : C2H3C1 + KSH = KC1 + C2H5SH. By replacement of the hydrogen of the hydroxyl in alcohols by alcohol radicals ethers are formed; by replacing the same hydrogen with acid radicals compound ethers are produced. Monatomic normal alcohols of the general composition CnH2n+1OH or C H2n +20. Methyl alcohol . C H3 OH B. P. 67° C. Ethyl u . c2h5oii 78 Propyl u . c3h,oh 97 Butyl u . C4H9OH 115 Amyl u • C5HuOH 132 306 CONSIDERATION OF CARBON COMPOUNDS. Hexyl *• • C6H13OH B. P. 150 Heptyl “ • (.',h15oh 168 Octyl “ . c8h17oh 186 Nonyl “ • C9H19OH 204 Cetyl “ Ceryl “ • Cl6H33OH • c27h55oh | Fusing- slt point- Melissyl “ Methyl alcohol, CH:J0H (Methyl hydroxide, Methyl alcohol, Wood- spirit, Wood-naphtha). Methyl alcohol is one of the many pro- ducts obtained by the destructive distillation of wood. When pure it is a thin, colorless liquid, similar in smell and taste to ethyl alcohol; crude wood-spirit, which contains many impuri- ties, has an offensive odor and a nauseous, burning taste. Metbyl alcohol mixes in all proportions with water; it dissolves resins and volatile oils as freety as ethyl alcohol, and is often substituted for the latter for various purposes in the arts and manufactures. A mixture of 90 per cent, of ethyl alcohol and 10 per cent, of partially purified wood-spirit is sold in England by licensed dealers under the name of methylated spirit; no internal revenue tax is paid on this mixture, which is unfit for human consump- tion, but answers well for most purposes for which common alcohol is otherwise used. Ethyl alcohol, C,H5OH = 46 (Common alcohol, Ethyl hydroxide, Ethylic alcohol), may be obtained from ethene, C2H4, by addition of the elements of water, which may be accomplished by agi- tating ethene with strong sulphuric acid, when direct combination takes place and ethyl sulphuric acid is formed: C2H4 + H2S04 = C2H.HS04 Ethyl sulphuric acid mixed with water and distilled yields sulphuric acid and ethyl alcohol: Ethene. Sulphuric acid. Ethyl sulphuric acid. c2h5hso4 + h2o = h2so4 + C2H5OH. Ethyl alcohol may also be obtained, as already mentioned, by treating ethyl chloride with potassium hydroxide : C2H5C1 + KOH = KC1 + C2H5OH. While the above methods for obtaining alcohol are of scientific interest, there is but one mode of manufacturing it on a large scale, namely, by the fermentation of certain kinds of sugar, especially grape-sugar or glucose, C6H1206. A diluted solution ALCOHOLS. 307 of grape-sugar under the influence of certain ferments (yeast) suffers decomposition, yielding carbon dioxide and alcohol: C6H1206 = 2C02 + 2C2H5OH. Glucose. Carbon dioxide. Ethyl alcohol. Experiment 43. To a solution of 25 grams of commercial glucose (grape- sugar) in 1000 c.c. of water add a little brewer’s yeast and introduce this mixture into a flask. Attach to the flask, by means of a perforated cork, a bent glass tube leading into clear lime water, contained in a small flask. After standing Fig. 40. Liebig’s condenser with distilling-flask. (a warm place should be selected in winter for this operation) a few hours fer- mentation will commence, which can be noticed by tbe evolution of carbon dioxide, which, in passing through the lime-water, causes the precipitation of calcium carbonate. After fermentation ceases connect the flask with a condenser and distil over 50 to 100 c.c. of the liquid. Verify in the distilled portion the presence of alcohol by applying the tests mentioned below. For condensation of the distill- ing vapors a Liebig’s condenser, represented in Fig. 40, may be used. This apparatus consists of a wide glass tube through which passes the narrow con- densing tube, connected with the boiling-flask a. A constant current of cold water is obtained by allowing w'ater to flow into b, and to escape by c. A small flask is placed under d for collecting the distillate. By distilling the fermented liquid an alcohol is obtained con- taining large quantities of water; on distilling this dilute alcohol a second and a third time, collecting the first portions of the dis- tilled liquid separately, an alcohol is obtained containing but little water. These last quantities of water, amounting to about 14 per 308 CONSIDERATION OF CARBON COMPOUNDS. cent., cannot be removed by simple distillation, but may be sepa- rated by mixing the alcohol with half its weight of calcium oxide, which combines with the water to form calcium hydroxide, from which the alcohol may now be separated by distillation. The alcohol thus obtained is known as, pure, absolute, or real alcohol. The alcohol of the U. S. P. contains 91 per cent, by weight, or 94 per cent, by volume of real alcohol, and has a specific gravity of 0.820 at 15.6° C. (60° F.). The diluted alcohol is made by mixing equal weights of water and alcohol, and has a specific gravity of 0.928. What is generally known as spirit of wine or rectified spirit is an alcohol containing 84 per cent., and proof-spirit one con- taining 49 per cent, by weight of pure alcohol. Pure alcohol is a transparent, colorless, mobile, and volatile liquid, of a characteristic, pungent, and agreeable odor,1 and a burning taste; it boils at 78.3° C. (173° F.), has a specific gravity of 0.794, is of a neutral reaction, becomes syrupy at —110° C. (—166° F.), and solidifies at —130° C. (—202° F.); it burns with a non-luminous flame; when mixed with water a contraction of volume occurs, and heat is liberated; the attraction of alcohol for water is so great that strong alcohol absorbs moisture from the air or abstracts it from membranes, tissues, and other similar sub- stances immersed in it; to this property are due its coagulating action on albumin and its preservative action on animal sub- stances. The solvent powers of alcohol are very extensive, both for inorganic and organic substances; of the latter it readily dis- solves essential oils, resins, alkaloids, and many other bodies, for which reason it is used in the manufacture of the numerous offi- cinal tinctures, extracts, and fluid extracts. Alcohol taken internally in a dilute form has intoxicating properties; pure alcohol acts poisouously; it lowers the temper- ature of the body from 0.5° to 2° C. (0.9° to 3.6° F.), although the sensation of warmth is experienced. Analytical reactions for ethyl alcohol. 1. Dissolve a small crystal of iodine in about 2 c.c. of alcohol; add to the cold solution potassium hydroxide until the brown color of the solution disappears : a yellow precipitate of iodoform, CHI3, forms. Many other alcohols, aldehyde, acetone, etc., show the same reaction. 1 It is stated that perfectly anhydrous alcohol has no odor. ALCOHOLS. 309 2. Add to about 1 c.c. of alcohol the same volume of sulphuric acid; heat to' boiling and add gradually a little more alcohol : the odor of ethyl ether will be noticed distinctly on further heating. 3. Add to a mixture of equal volumes of alcohol and sulphuric acid, a crystal (or strong solution) of sodium acetate : acetic ether is formed and recognized by its odor. 4. To about 2 c.c. of potassium dichromate solution add 0.5 c.c. of sulphuric acid and 1 c.c. of alcohol : upon heating gently the liquid becomes green from the formation of chromic sulphate, while aldehyde is formed and may be recognized by its odor. Alcoholic liquors. Numerous substances containing sugar or starch (which may be converted into sugar) are used in the manufacture of the various alcoholic liquors, all of which contain more or less of ethyl alcohol, besides coloring matter, ethers, compound ethers, and many other substances. White and red wines are obtained by the fermentation of the grape-juice; the so-called light wines contain from 10 to 12, the strong wines, such as port and sherry, from 19 to 25 per cent, of alcohol; if the grapes contain much sugar, only a portion of it is converted into alcohol, whilst another portion is left undecom- posed, such wines are known as sweet wines. Effervescent wines, as champagne, are bottled before the fermentation is complete; the carbonic acid is disengaged under pressure and retained in solu- tion in the liquid. Beer is prepared by fermentation of germinated grain (gener- ally barley) to which much water and some hops have been added; the active principle of hops is lupulin, which confers on the beer a pleasant, bitter flavor, and the property of keeping without injury. Light beers have from 2 to 4, strong beers, as porter or stout, from 4 to 6 per cent, of alcohol. Spirits differ from either wines or beersin so far as the latter are not distilled, and therefore contain also non-volatile organic and inorganic substances, such a3 salts, etc., not found in the spirits, which are distilled liquids containing volatile compounds only. Moreover, the quantity of alcohol in spirits is very much larger, and varies from 45 to 55 per cent. Of distilled spirits may be mentioned : American whiskey, made from fermented rye or Indian corn ; Irish whiskey, from potatoes ; Scotch whiskey, from barley ; brandy or cognac, by distilling French wines; rum, by fermenting 310 CONSIDERATION OF CARBON COMPOUNDS. and distilling molasses; arrack, from fermented rice; gin, from various grains flavored with juniper berries. Amyl alcohol, CsHu0H. This alcohol is frequently formed in small quantities during the fermentation of corn, potatoes, and other substances. When the alcoholic liquids are distilled, amyl alcohol passes over toward the end of the distillation, generally accompanied by propyl, butyl, and other alcohols, and by certain ethers and compound ethers. A mixture of these substances is known as fusel oil, and, from this liquid, amyl alcohol may be obtained in a pure state. It is an oily, colorless liquid, having a peculiar odor, and a burning, acrid taste; it is soluble in alcohol, but not in water. By oxidation of amyl alcohol, valerianic acid is obtained. Amylene hydrate, Ethyl-dimethyl-carhinol, Cb HVI 0, is an alcohol isomeric with the above amyl alcohol, but yielding only acetic acid on oxidation. It is a colorless liquid, having a pungent, ethereal odor, aud a boiling-point of 100° C. (212° F.). Glycerin, Glycerinum, C3H530H = 92. Glycerin is the triatomic or tri-acid alcohol of the residue glyceryl, C3H5, formed by removal of the three atoms of hydrogen from the saturated hydro- carbon propane, C3II8, and by combination of the residue with 30H. Glycerin is a normal constituent of all fats, which are glycerin in which the three atoms of hydrogen of the hydroxyl have been replaced by residues of fat acids. When fats are treated with alkalies, these latter combine with the fat acids, whilst glycerin is liberated. Upon this decomposition, carried out on a large scale in the manufacture of soap, depends the mode of obtaining glycerin. Pure glycerin is a clear, colorless, odorless liquid of a syrupy consistence, oily to the touch, hygroscopic, very sweet, and neutral in reaction, soluble in water and alcohol in all propor- tions, but insoluble in ether, chloroform, benzol, and fixed oils; its specific gravity is 1.255; it cannot be distilled by itself without decomposition, but is volatilized in the presence of water, or when hot steam is allowed to pass through it. Glycerin is a good solvent for a large number of organic and inorganic substances, the solutions thereby obtained are often termed glycerites; frequently used are the glycerites of starch, carbolic acid, tannic acid, sodium biborate, etc. ALCOHOLS. 311 Analytical reactions. 1. A borax bead immersed for a few minutes in a solution of glycerin (made slightly alkaline with potassium hydroxide) imparts a green color to a non-luminous flame, owing to the liberation of boric acid. 2. Glycerin slightly warmed with an equal volume of sulphuric acid should not turn dark, but on further heating the character- istic, irritating odor of acrolein is noticed. 3. Fehling’s solution (see index) should not cause a red pre- cipitation on heating, indicating the absence of glucose and dextrin. Nitro-glycerin, C3H.3(N020), (Glyceryl tri-nitrate). When gly- cerin is treated with nitric acid, or, better, with a mixture of concentrated sulphuric and nitric acids, the radical jST02 replaces hydrogen in the glycerin, forming either mono- or tri-nitro- glycerin, substances which belong to the compound ethers, the constitution of which will be explained later. The tri-nitro- glycerin is the common nitro-glycerin, a pale-yellow oily liquid, which is nearly insoluble in water, soluble in alcohol, crystallizes at —20° C. (—4° F.) in long needles, and explodes very violently by concussion ; it may be burned in an open vessel, but explodes when heated over 250° C. (482° F.). Dynamite is infusorial earth impregnated with nitro-glycerin. Phenols. The substances termed phenols are formed by re- placement of hydrogen by hydroxyl in the aromatic hydrocar- bons of the benzene series; they have the constitution of alcohols but are not alcohols in the sense in which this term is used. The more important substances belonging to this group will be con- sidered later. Questions.—401. What is the general constitution of alcohols, and what is the difference between monatomic, diatomic, and triatomic alcohols? 402. How do alcohols occur in nature? 403. By what processes may alcohols be formed artificially, and how may they be separated from their combinations? 404. State the general properties of alcohols. 405. Mention names and composition of the first five members of alcohols of the general composition CnH2n+iOH. 406. By what process is methyl alcohol obtained, under what other names is it known, and what are its properties? 407. Describe the manufacture of pure alcohol from sugar. 408. Give the alcoholic strength of the alcohol and diluted alcohol of the U. S. P., and also of spirit of wine, proof-spirit, light wines, 312 CONSIDERATION OF CARBON COMPOUNDS. 42. ALDEHYDES. HALOID DERIVATIVES. Aldehydes. The name aldehyde is derived from alcohol de- hydrogenatum, referring to its method of formation, viz , by the removal of hydrogen from alcohols, as, for instance: cya6o — 2 h = c2h4o. Ethyl alcohol. Acetic aldehyde. This removal of hydrogen may be accomplished by various methods, as, for instance, by oxidation of alcohols, when one atom of oxygen combines with two atoms of hydrogen, forming water, whilst an aldehyde is formed at the same time. Alde- hydes, when further oxidized, are converted into acids; aldehydes are, consequently, the intermediate products between alcohols and acids, and are frequently looked upon as the hydrides of the acid radicals. The constitution of acetic acid may be represented by the formula CH3.CO.OH; the radical of acetic acid or acetyl is the group CH3.CO, and the hydride of acetyl is acetic aldehyde, CH3.COH. It is the group COH which is characteristic of, and found in, all aldehydes. Only a few aldehydes are of practical interest, as, for instance, acetic aldehyde, paraldehyde, and ben- zoic aldehyde, which latter substance will be more fully considered in connection with the aromatic substances. Acetic aldehyde, C2H40 or CH3C0H. Alcohol may be converted into aldehyde by the action of various oxidizing agents; the one generally used is potassium dichromate, which oxidizes two hydrogen atoms of the alcohol molecule, converting it into aldehyde: c2h60 + O = C2H40 + H20. Experiment 44. Place in a 500 c.c. flask, provided with a funnel-tube and connected with a Liebig’s condenser, 6 grams of potassium dichromate. Pour upon this salt through the funnel-tube, very slowly, a previously prepared and cooled mixture of 5 c.c. of sulphuric acid, 24 c.c. of water and 6 c.c. of alcohol. Chemical action begins generally without application of heat, and often becomes so violent that the liquid boils up, for which reason a large flask is used. The escaping vapors, which are a mixture of aldehyde, alcohol, and water, are col- lected in a receiver kept cold by ice. From this mixture pure aldehyde may be obtained by repeated distillation. Use the distillate for silvering a test-tube by heavy wines, beers, and spirits. 409. What are the general properties of com- mon alcohol? 410. What is glycerin, how is it found in nature, how is it obtained, and what are its properties? ALDEHYDES. HALOID DERIVATIVES. 313 adding some ammoniated silver nitrate. How much potassium dichromate is needed for the conversion of 5 grams of pure alcohol into aldehyde? Aldehyde is a neutral, colorless liquid, having a strong and characteristic odor; it mixes with water and alcohol in all pro- portions and boils at 21° C. (69.8° F.). The most character- istic chemical property of aldehyde is its tendency to combine directly with a great number of substances; thus it combines with hydrogen to form alcohol, with oxygen to form acetic acid, with ammonia to form aldehyde-ammonia, C2H4O.NH3, a beautifully crystallizing substance, with hydrocyanic acid to form aldehyde hydrocyanide, C2H4O.C]Sr, and with many other substances. In the absence of such other substance it unites often with itself, forming polymeric modifications, such as paraldehyde and met- aldehyde. Aldehyde is a strong reducing agent, which property is used in the silvering of glass, which is done by adding aldehyde to an ammoniacal solution of silver nitrate, when metallic silver is deposited on the walls of the vessel or upon substances immersed in the solution. Paraldehyde, C6H1203. When a few drops of concentrated sulphuric acid are added to aldehyde, this becomes hot and solidities on cooling to 0° C. (32° F.). This solid crystalline mass of paraldehyde, which liquefies at 10.5° C. (51° F.), has been formed by the direct union of three molecules of common alde- hyde. Paraldehyde is soluble in 8 parts of water, boils at 124° C. (253° F.), and is reconverted into common aldehyde by boiling it with dilute sulphuric or hydrochloric acid. Metaldehyde, (C2H40)*, is another polymeric modification of aldehyde, ob- tained by a process similar to the one mentioned for paraldehyde, but at a lower temperature. It is a solid crystalline substance, insoluble in water, but slightly soluble in alcohol, ether, and chloroform. Trichloraldehyde, Chloral, C2HC130 or CCl3.COH (Trichlor acetyl hydride). This substance may be looked upon as acetic aldehyde, C2H40, in which three atoms of hydrogen have been replaced by chlorine. It is made by passing a rapid stream of dry chlorine into pure alcohol to saturation, keeping the alcohol cool during the first few hours, and warming it gradually until the boiling- point is reached. According to the quantity of alcohol operated on, the conversion requires several hours or even days. The 314 CONSIDERATION OF CARBON COMPOUNDS. crude liquid product separates into two layers; the lower is removed and shaken with three times its volume of strong sul- phuric acid and distilled, the distillate is mixed with calcium oxide and again distilled; the portion passing over between 94° and 99° C. (201° and 210° F.) is collected. The decomposition taking place between alcohol and chlorine may be explained by the formation of aldehyde : and by the subsequent replacement of hydrogen by chlorine : C2H6Q + 201 = C2H40 + 2HC1 C2H40 + 6C1 = C2HC130 + 3HC1. The actual decomposition is, however, somewhat more compli- cated, numerous other products being formed at the same time. By treatment with sulphuric acid these other substances are removed. Chloral is a colorless, oily liquid, having a penetrating odor and an acrid, caustic taste; its specific gravity is 1.5, and its B. P. 95° C. (203° F.). Chloral hydrate, Chloral, U. S. P., C2HC130.H20 = 165.2. When water is added to chloral the two substances combine, heat is disengaged, and the hydrate of chloral is formed, which is a crystalline, colorless substance, having an aromatic, penetrating odor, a bitter, caustic taste, and a neutral reaction; it is freely soluble in water, alcohol, and ether, also soluble in chloroform, carbon disulphide, benzene, fatty and essential oils, etc.; it liquefies when mixed with carbolic acid or with camphor; it melts at 58° C. (136° F.) and boils at 95° C. (203° F.), and also volatilizes slowly at ordinary temperature. Chloral, and its hydrate, are decomposed by weak alkalies into chloroform and a formate of the alkali metal: C2HC130 + KIIO = KCH02 + CHC13. Chloral. Potassium hydroxide. Potassium formate. Chloroform, This decomposition was believed to take place in the animal body, and especially in the blood, whenever chloral was given internally, but recent investigations seem to contradict this assumption. There is no chemical antidote which may be used in cases of poisoning by chloral, and the treatment is, therefore, confined to the use of the stomach-pump and to the maintenance of respiration. ALDEHYDES. HALOID DERIVATIVES. 315 Analytical reactions. 1. Chloral or chloral hydrate heated with potassium hydroxide is converted into potassium formate and chloroform, which latter may be recognized by its odor. (See explanation above.) 2. Heated with silver nitrate and ammonium hydroxide a silver-mirror is formed on the glass. 3. Heated with Fehlitig’s solution a red precipitate is formed. Chloroform, Chloroformum, CHC13—119.2. Triehlormethane, Di- chlormethyl chloride.’). When either chlorine, bromine, or iodine is allowed to act upon methane, CII4, a number of substitution products are formed. Thus, if methane is considered as methyl hydride, CH3H, the first product of substitution is methyl chlo- ride, CH3C1; the second is monochlormethyl chloride, CH2C1C1; the third is dichlormethyl chloride or chloroform, CHC12C1; and the fourth is carbon tetrachloride, CC14. Similar products are formed by the action of iodine or bromine upon methane, or, in fact, upon any of the paraffins. Chloroform is, however, not obtained for commerce by the above process,but by the action of bleaching-pow’der and calcium hydroxide on alcohol. The last three substances named, after being mixed with a considerable quantity of water, are heated in a retort until distillation commences; the crude product of distillation is an impure chloroform, which is purified by mixing it with sulphuric acid and allowing the mixture to stand ; the upper layer of chloroform is removed and treated with sodium carbonate (to remove any acids) and distilled over calcium oxide (to remove wTater). The explanation of the formation of chloroform by the above process has indirectly been given in connection with the con- sideration of chloral, where it has been shown that alcohol is converted by the action of chlorine first into aldehyde and sub- sequently into chloral, which, upon being treated with alkalies, is decomposed into an alkali formate and chloroform. The action of the chlorine of the calcium hypochlorite (which is the active principle in bleaching-powder) upon the alcohol is similar to that of free chlorine upon alcohol; in both cases alde- hyde, and afterward chloral, are formed, which latter, in the manufacture of chloroform, is decomposed by the calcium hydroxide into calcium formate and chloroform. 316 CONSIDERATION OF CARBON COMPOUNDS. If the various intermediate steps of the decomposition are not considered, the process may be represented by the following equation : Alcohol. 4C2H60 + 8CaCl202 = 2(CHC13) + 3(Ca2CH02) + 5CaC)2 + 8H20. Calcium hypochlorite. Chloroform. Calcium formate. Calcium chloride. Water, Pure chloroform is a heavy, colorless liquid, of a characteristic ethereal odor, a burning, sweet taste, and a neutral reaction ; it is but very sparingly soluble in water, but miscible with alcohol and ether in all proportions; the specific gravity of pure chloro- form is 1.50, but a small quantity of alcohol (from one-half to one per cent.), allowed to be present by the U. S. P., causes the specific gravity to be about 1.488; boiling-point 62°C. (143° F.), but rapid evaporation takes place at all temperatures. Chloroform should be tested for excess of alcohol by specific gravity; for hydrochloric acid and chlorine by shaking it with water, which afterward should not give a precipitate with silver nitrate; for aldehyde by heating with solution of potassium hydroxide, which should not be colored brown; for empyreu- mat.ic and other organic compounds by shaking with an equal volume of pure sulphuric acid, which should remain colorless; or by evaporation, when no residue should be left and no odor should be perceptible after the chloroform has been volatilized. The only characteristic test for chloroform consists in passing its vapors through a glass tube heated to redness, when chloro- form is decomposed, a deposit of carbon being formed, whilst chlorine and hydrochloric acid escape, and may be recognized by their action on silver nitrate (white precipitate of silver chloride) and mucilage of starch, to which potassium iodide has been added (free chlorine liberates iodine, which forms with the starch blue iodized starch). In applying this chloroform test to an acid mix- ture (possibly containing chlorides), this should be neutralized previous to the expelling of the vapors, as otherwise the acid might decompose chlorides with liberation of hydrochloric acid. Fehling’s solution is readily reduced on heating it with chloro- form. When a drop of aniline and then a drop of chloroform are added to an alcoholic solution of potassium hydroxide, a peculiar, offensive odor of benzo-isonitril, C6H5iIC, is noticed. Iii cases of poisoning, chloroform is generally to be sought for in the lungs and blood, which are placed in a flask connected with a tube of difficultly fusible glass. By heating the flask the ALDEHYDES. HALOID DERIVATIVES. 317 chloroform is expelled and decomposed in the heated glass tube, as stated above. What has been said above regarding antidotes to chloral holds good for chloroform also. Iodoform, Iodoformum, CHI3=: 392.8 (Diiodomethyl iodide). This compound is analogous in its constitution to chloroform. It is made by heating together an aqueous solution of an alkali car- bonate, iodine, and alcohol until the brown color of iodine has disappeared; on cooling, iodoform is deposited in yellow scales, which are well washed with water and dried between filtering paper. Iodoform occurs in small, lemon-yellow, lustrous crystals, having a peculiar, penetrating odor, and an unpleasant, sweetish taste; it is nearly insoluble in water and acids, soluble in alcohol, ether, fatty and essential oils. Iodoform digested with an alcoholic solution of potassium hydroxide imparts, after acidulation with nitric acid, a blue color to starch solution. Experiment 45. Dissolve 4 grams of crystallized sodium carbonate in 6 c.c. of water ; add to this solution 1 c.c. of alcohol; heat to about 70° C. (158° F.), and add gradually 1 gram of iodine. A yellow crystalline deposit of iodoform separates. Sulphonal, (CH3)2C(C2H5S02)2, Dimethyl-diethylsulphonyl-methane. It has been stated before that mercaptans are alcohols in which the oxygen is replaced by sulphur. Alcohol treated with oxi- dizing agents are converted into acids by exchanging two atoms of hydrogen for one atom of oxygen. Mercaptans behave dif- ferently; they combine directly with three atoms of oxygen, forming compounds known as sulphonic acids. Thus, ethyl mer- captan, C2H5HS, when treated with nitric acid is converted into ethyl-sulphonic acid, C2H5HS03. The radical of this acid, known as ethylsulphonyl, C2H5S02, may, by indirect process, be caused to replace hydrogen in methane, CH4, twice, while the two remaining methane hydrogen atoms can be replaced by methyl. The compound thus obtained is the dimethyl-diethylsulphonyl- methane, or sulphonal. The relations between methane and some of its derivatives, which have been considered in this chap- ter, may be shown graphically thus : 318 CONSIDERATION OF CARBON COMPOUNDS. H II—C—H I H Cl I H—C—Cl I Cl Methane. Chloroform. I H—C—I I I ch3 CH3—(J—C2H5S02 I c2h5so2 Sulphonal is a white crystalline substance, having neither odor nor taste ; it is soluble in 20 parts of boiling and 100 parts of cold water, soluble with difficulty in alcohol, but easily soluble in ether, benzene, and chloroform; it fuses at 130° C. (266° F.), and volatilizes at about 300° C. (572° F.), with partial decompo- sition. Iodoform. Sulphonal. 43. MONOBASIC FATTY ACIDS. General constitution of organic acids. When hydroxy], OH, replaces hydrogen in hydrocarbons, alcohols are formed; when the univalent group, C02H, known as carboxyl, replaces hydrogen in hydrocarbons, acids are formed. Monatomic, diatomic, and triatomic alcohols are formed by introducing hydroxyl once, twice, or three times respectively into hydrocarbon molecules; mono- basic, diabasic and triabasic acids are formed by substituting one, two, or three hydrogen atoms by carboxyl. For instance: Hydrocarbons. ch4 Monobasic acids. ch3.co2h Bibasic acids. ch2\co;S- Methane. Acetic acid. Malonic acid. c,h6 C2H5.C02H c H /CO,H fl4\C02H' The constitution of carboxyl is represented by 0=0—0—H, which shows that of the four affinities of the carbon atom, two Ethane. Propionic acid. Succinic acid. Questions.—411. What is an aldehyde, and what are its relations to alcohols and acids? 412. State the composition of acetic aldehyde. 413. Explain the action of chlorine upon alcohol. 414. Give the composition and properties of chloral and chloral hydrate. 415. What decomposition takes place when alka- lies act upon chloral? 416. Describe the process of preparing and purifying chloroform? 417. What is the composition of chloroform and what are its properties? 418. How is chloroform tested for impurities? 419. By what test may chloroform be recognized? 420. How is iodoform made, and what are its properties ? MONOBASIC FATTY ACIDS. 319 are saturated by an atom of oxygen, one by hydroxy], whilst one is unprovided for; any univalent hydrocarbon residue may attach itself to this unprovided affinity, when an acid is formed. Acids may be looked upon, therefore, as being composed of hydrocarbon residues and hydroxyl, united by the bivalent radical CO, termed carbonyl. By replacement of the hydrogen of the hydroxyl (or of the carboxyl, which is the same) by metals the various salts are formed. What is termed the acid radical is the group of the total number of atoms present in the molecule, with the exception of the hydroxyl. In acetic acid, C2H402, for instance, the radical is CH3CO, or C2H30, which group of atoms, known as acetyl, is characteristic of acetic acid, and of all acetates, and may often be transferred from one compound into another without decomposi- tion. The difference between alcohol radicals and acid radicals may also be stated, by saying that the first contain carbon and hy- drogen only, while acid radicals contain carbon, hydrogen, and oxygen. In a similar manner, as there are homologous series of alcohols corresponding to the various series of hydrocarbons, there are also homologous series of organic acids running parallel with the corresponding series of hydrocarbons or alcohols. Occurrence in nature. Organic acids are found and formed both in vegetables and animals, and are present either in the free state, or (and more generally) in combination with bases as salts, or with alcohols as compound ethers. Uncombined or as salts are found, for instance, citric, tartaric, and oxalic acids in plants, formic acid in some insects, uric acid in urine, etc.: as compound ethers, are found many of the fatty acids in the various fats. Some organic acids are also found as products of the decompo- sition of organic matters in nature. Formation of acids. Many acids are produced by oxidation of alcohols. As intermediate products are formed aldehydes, which may be looked upon (as stated in the last chapter) as alcohols from which two atoms of hydrogen have been removed. For instance: c2h5oh + o = c2h3oh + h2o. Ethyl alcohol. Acetic aldehyde. C2H3OH + O = C2H3O.OH. Acetic aldehyde. Acetic acid. 320 CONSIDERATION OF CARBON COMPOUNDS. Acids are obtained from compound ethers b}7 boiling them with alkalies, when salts are formed, which may be decomposed by sulphuric or other acids. For instance : + K0H “ + C2tr5OH- Ethyl acetate. Potassium hydroxide. Potassium acetate. Ethyl alcohol, Potassium acetate. 2(02H3K02) + H2S04 = 2(C2H402) + K2S04. Sulphuric acid. Acetic acid. Potassium sulphate. Acids are formed also by destructive distillation (acetic acid); by fermentation (lactic acid); by putrefaction (butyric acid); by oxidation of many organic substances (formic acid by oxidation of starch), etc. Properties. Organic acids show the characteristics mentioned of inorganic acids, viz., wdien soluble, have an acid or sour taste, redden litmus, and contain hydrogen replaceable by metals, with the formation of salts. Most organic acids, and especially the higher members, show these acid properties in a less marked degree than inorganic acids; in fact, they become so weak that the acid properties can often scarcely be recognized. As stated above, mono-, di-, and tri-basic organic acids are known, the latter two being capable of forming normal, acid, or double salts. Most organic acids are colorless, some of the lower and volatile acids have a characteristic odor, but most of them are odorless; most organic acids are solids, some liquids, scarcely any gaseous at the ordinary temperature. Any salt formed by the union of an organic acid and a non-volatile metal (especially alkali metal) leaves the carbonate of this metal after the salt has suffered com- bustion. It is for this reason that ashes contain most metals in the form of carbonates. Whilst the hydrogen of the hydroxyl may be replaced by metals or by other residues, the hydrogen of the acid radical may often be replaced by chlorine, and the ox}7gen of the hydroxyl by sulphur. The acids formed by this last reaction are known as thio acids, for instance, tliio-acetic acid, C2H4OS. When the hydrogen of the hydroxyl is replaced by a second acid radical (of the same kind as the one forming the acid) the so-called anhydrides are produced, which correspond to the inor- ganic anhydrides. For instance : MONOBASIC FATTY ACIDS. UNO, or NO...OH C2H402 or C2H3O.OH. Nitric acid, no2\0 NO,/u Acetic acid. c2h3o\0 c2h30/u- Nitric anhydride. Acetic anhydride. Amido-acids are compounds obtained by replacement of a hydrogen atom by JSTH2; these compounds will be spoken of later in connection with amides. Fatty acids of the general composition, C„H2„02 or CnE^n+iCOoH. Fusing- point. Boiling- point. Occurs in : Formic acid, H C02H + 4° C. 100° c . Bed ants and some plants, etc. Acetic acid, c h3 co2h + 17 118 Vegetable and animal fluids. Propionic acid, c2 h5 C02I1 —21 140 Sweat, fluids of the stomach,etc. Butyric acid, C3 H. (J02H —20 162 Butter. Valerianic acid, c4 h9 co2h —16 185 Valerian root. Caproic acid, c5 huco2h 2 205 Butter. (Enanthylic acid , C6 H1sC()2H —10 224 Castor oil. Caprylic acid, C7 H15C02H +14 236 Butter; cocoanut oil. Pelargonic acid, C8 h17co2h 18 254 Leaves of geranium. Capric acid, c9 h19co2h 30 270 Butter. Laurie acid, CuH23C02H 43 j Cocoanut oil. Myristic acid, c13h27co2h 54 J Palmitic acid, c15h31co2h 62 Palm oil, butter. Margaric acid, c13h33co2h 60 (Obtained artificially.) Stearic acid, c17h35co2h 70 Most solid animal fats. Arachidic acid, c19h39co2h 75 | Behenic acid, c21h43co2h 76 Oils of certain plants. Hyaenic acid, c24h49co2h 77 ) Cerotic acid, c26h53co2h 80 1 Beeswax. Melissic acid, 90 ) The name fatty acids has been given to these acids on account of their frequent occurrence in fats, and also in allusion to the somewhat fatty appearance of the higher members of the series. The gradual change of properties which the members of an homologous series show, is well marked in the series of fatty acids, thus: jFirst member. Is liquid. Volatilized at 100° C. Strongly acid. Strongly odoriferous. Easily soluble in water. Produces no grease spot. Forms salts easily soluble without decomposition. Last member. Is solid. Not volatilized without decomposition. Scarcely acid. Odorless. Insoluble in water. Produces a grease spot. Forms salts which are insoluble or de- composed by water. 322 CONSIDERATION OF CARBON COMPOUNDS. The intermediate members of the series show intermediate properties, and this change in properties is in proportion to the gradual change in molecular weight. Formic acid, H.C02H or CHO.OH. This acid is found in the red ant and in other insects, which eject it when irritated. It is also contained in some plants, as, for instance, in the leaves of the stinging-nettle. It is formed by the oxidation of methyl alcohol: Methyl alcohol. CH30 + 02 - ORA + H20,’ Formic acid. by the action of carbonic oxide on potassium hydroxide : KOH + CO = KCH02, Potassium formate. by the action of potassium hydroxide on chloroform: CHC13 + 4K0H = 3KC1 + 2H20 + KCH02, by heating equal parts of glycerin and oxalic acid, when the latter is split up into carbon dioxide and formic acid, which may be separated from the glycerin by distillation : C2H204 — C02 -|- ch2o2. It is also a product of the decomposition of sugar, starch, etc. Formic acid is a colorless liquid having a penetrating odor, and a strongly acid taste; it produces blisters on the skin; it is a powerful deoxidizer, being, when thus acting, converted into carbon dioxide and water : Oxalic acid. Formic acid. ch2o2 + o = co2 + h2o. Acetic acid, H.C2H302, or C2H3O.OH, or CH3.C02H = 60. The most important alcohol is ethyl alcohol, and the most largely used organic acid is acetic acid, obtained from ethyl alcohol by oxida- tion. Acetic acid is found in combination with alkali metals in the juices of many plants, also in the secretions of the glands, etc. Acetic acid is formed chiefly either by the oxidation of alcohol (and aldehyde) or by the destructive distillation of wood. It is produced commercially on a large scale as follows : A diluted alcohol (8 to 10 per cent.) is allowed to trickle down slowly through wood-shavings contained in high casks having perforated sides in order to allow a free circulation of the air; the tempera- ture is kept at about 24° to 30° C. (75° to 86° F ), and the liquid having passed through the shavings is repeatedly poured back in MONOBASIC FATTY ACIDS. 323 order to cause complete oxidation. When the latter object has been accomplished the liquid is a diluted acetic acid. It appears that the conversion of alcohol into acetic acid is greatly facilitated by the presence of a microscopic organism (mycoderma aceti) commonly termed “ mother of vinegar.” This serves in some unexplained way to convey the atmospheric oxygen to the alcohol. The term “ acetic fermentation ” is often applied to this conversion, although it is not a true fermentation, since no splitting up of the alcohol molecule into other less complex compounds, but a process of slow oxidation, takes place. The second process for manufacturing acetic acid is the heating of wood to a red heat in iron retorts, when numerous products (gases, aqueous and tarry substances) are formed. The aqueous products contain, besides other substances, methyl alcohol and acetic acid. The liquid is neutralized with calcium hydroxide and distilled, when methyl alcohol, water, etc., evaporate and a solid residue is left, which is an impure calcium acetate. From this latter, acetic acid is obtained by distilling with sulphuric (or hydrochloric) acid, calcium sulphate (or chloride) being formed and left in the retort, whilst acetic acid distils over. Experiment 46. Add to 54 grains of sodium acetate contained in a small flask which is connected with a Liebig’s condenser, 40 grams of sulphuric acid. Apply heat and distil over about 35 c.c. Determine volumetrically the amount of pure acetic acid in this liquid. Pure acetic acid or glacial acetic acid is solid at or below 16° C. (61° F.); at higher temperatures it is a colorless liquid having a characteristic, penetrating odor, boiling at 118° C. (244° F.), and causing blisters on the skin; its specific gravity is 1.056; it is miscible with water, alcohol, and ether, is strongly acid, forming salts known as acetates, which are all soluble in water. Vinegar is dilute acetic acid (about six per cent.), containing often other substances, such as coloring matter, compound ethers, etc. Vinegar was formerly obtained exclusively by the oxida- tion of fermented fruit-juices (wine, cider, etc.), the various sub- stances present in them imparting a pleasant taste and odor to the vinegar ; to-day vinegar is often made artificially by adding various coloring and odoriferous substances to dilute acetic acid. Vinegar should be tested for sulphuric and hydrochloric acids, which are sometimes fraudulently added. Acidum aceticum, Acidum aceticum dilutum, and Acidum aceticum glaciale are the three officinal forms of acetic acid. The first- 324 CONSIDERATION OF CARBON COMPOUNDS. named acid contains 36 per cent., the second 6 per cent., the third at least 99 per cent, of pure acetic acid. Acetic acid shows an exceptional behavior in regard to the specific gravity of its aqueous solutions. The highest specific gravity of 1.0748 belongs to an acid of 77 per cent., which is equal to an acid containing one molecule of water and one of acetic acid, or C2H402.II20. The addition of either acetic acid or of water causes the liquid to become lighter. For instance, the specific gravity of an acid containing 95 per cent, is equal to that containing 56 per cent, of pure acid, both solutions having a specific gravity of 1.066. The specific gravity of dilute acetic acid cannot, therefore, be used as a means of determining the amount of pure acid; this is done by exactly neutralizing a weighed portion of the acid with an alkali; from the quantity of the latter used, the quantity of actual acid present may he easily calculated. (See also volu- metric methods in Chapter 37.) Analytical reactions. (Sodium acetate, NaC2H302, maybe used.) 1. Any acetate heated with sulphuric acid evolves acetic acid, which may be recognized by its odor. 2. Acetic acids or acetates heated with sulphuric acid and alcohol give a characteristic odor of acetic ether. 3. A solution containing acetic acid, or an acetate carefully neutralized, turns deep red on the addition of solution of ferric chloride, and forms, on boiling, a reddish-brown precipitate of an oxyacetate of iron. Potassium acetate, Potassi acetas, KC2H302 = 98. Sodium acetate, Sodii acetas, NaC2H302.3H20 = 136. Zinc acetate, Zinci acetas, Zn2(C2H302).3H20 = 236.9. These three salts may be obtained by neutralizing the respective carbonates with acetic acid and evap- orating the solution; they are white salts, easily soluble in water. Ferric acetate, Fe26(C2H302). A 33 per cent, solution of this salt is the Liquor ferri acetatis of the U. S. P. It is made by dis- solving freshly precipitated ferric hydroxide in acetic acid ; it is a dark, red-brown, transparent liquid of a specific gravity of 1.16. MONOBASIC FATTY ACIDS. 325 Lead acetate, Plumbi acetas, Pb2(C2H302).3H20 = 378.5 {Sugar of lead), is made by dissolving lead oxide in diluted acetic acid. It forms colorless, shining, transparent crystals, easily soluble in water; on heating, it melts and then loses water of crystalliza- tion ; at yet higher temperatures it is decomposed; it has a sweetish, astringent, afterward metallic taste. Commercial sugar of lead contains often an excess of lead oxide in the form of basic salts; such an article when dissolved in spring water gives generally a turbid solution, in consequence of the formation of lead carbonate ; the addition of a few drops of acetic acid renders the liquid clear by dissolving the precipitate. When a mixture of lead acetate and lead oxide is digested or boiled with water, the acetate combines with the oxide, forming a basic lead acetate, Pb.2(C2H302) + 2PbO, a 25 per cent, solution of which is the Liquor plumbi subacetatis, or Goulard’s extract, whilst a solution containing about 1 per cent, is the Liquor plumbi sub- acetatis dilutus, or lead-water. Cupric acetate, Cupri acetas, Cu2(C2H302).H20 = 199.2 {Acetate of copper). The commercial verdigris is a basic acetate of copper, Cu2(C2H302).Cu0, made by the action of dilute acetic acid and atmospheric air on metallic copper. By adding to this basic acetate more acetic acid, the neutral acetate is obtained, but this may be made directly also by dissolving cupric hydroxide - or carbonate in acetic acid. It forms deep green, prismatic crystals, which are soluble in water. By boiling verdigris with arsenious oxide, cupric aceto-arsenite, 3CuAs204 -f- Cu2(C2H302), is formed, which is the chief constituent of emerald green or Schweinfurt green, a substance often used as a coloring matter. Paris green is of a similar composition, but less pure. Chlor-acetic acids. By treating acetic acid with chlorine, either one, two, or three hydrogen atoms may be replaced by this element, when either mono-, di-, or tri-chlor acetic acid is formed. Trichlor-acetic acid, C2CI3H02, is a color* less, crystalline substance, which fuses at 55° C. (131° F.), and boils at 195° C. (383° F.) Acetone, C3H60. This compound is obtained by the destructive distillation of acetates (and of a number of other substances). The decomposition which calcium acetate suffers may be shown by the equation : CH3COO\r, _ CHs\rn , r, rn CII3C00xC ~ CHS/C0 + OftCOg. Calcium acetate. Acetone. 326 CONSIDERATION OF CARBON COMPOUNDS. The above graphic formula of acetone shows this substance to be dimethyl carbonyl, or carbon manoxide whose two available affinities have been satisfied two methyl groups. Acetone is the representative of a series of compounds known as acetones or generally as ketones, the general composition of which may be R—C—R assumed to be || , R representing in this case anv uni- O valent radical. Acetone is a colorless liquid, boiling at 58° C. (136° F.), miscible with water, alcohol, and ether in all proportions. Butyric acid, HC4H702. Among the glycerides of butter those of butyric acid are found; they exist also in cod-liver oil, croton oil, and a few other fatty oils; some volatile oils contain com- pound ethers of butyric acid ; free butyric acid occurs in sweat and in cheese. It may be obtained by a peculiar fermentation of lactic acid (which itself is a product of fermentation), and is also generated during the putrefaction of albuminious substances. Butyric acid is a colorless liquid, having a characteristic, un- pleasant odor: it mixes with water in all proportions. Valerianic acid, HC5H902 (Valeric acid). This acid occurs in valerian root and angelica root, from which it may be separated; it is, however, generally obtained by oxidation of amyl alcohol by potassium dichromate and sulphuric acid. After oxidation has taken place the mixture is distilled, when valerianic acid with some valerianate of amyl distils over. The change of amyl alcohol into valerianic acid is analogous to the conversion of ethyl alcohol into acetic acid : 05HuOH + 20 = HC5H902 + H20 Amyl alcohol. Valerianic acid Pure valerianic acid is an oily, colorless liquid, having a pene- trating, highly characteristic odor; it is slightly soluble in water, but soluble in alcohol; it boils at 185° C. (365° F.). Several of the salts of valerianic acid are officinal; they are the valerianate of iron, of ammonium, of zinc, and of quinine. The last named three compounds are white salts, while the ferric valeriante has a dark-red color; the ammonium salt is easily soluble in water, the other three compounds are insoluble or nearly so. DIBASIC AND TRIBASIC ORGANIC ACIDS. 327 Oleic acid, Acidum oleicum, HC13H3302 = 282. As shown by its formula, oleic acid does not belong to the above-described series of fatty acids of the composition CnH2n02, but to a series having the general composition CnH2n_202. Ole'ic acid is a constituent of most fats, especially of fat oils. Thus, olive oil is mainly oleate of glyceril. By boiling olive oil with potassium hydroxide, potassium oleate is formed, which may be decomposed by tartaric acid, when ole'ic acid is liberated. Oleic acid is a nearly colorless or yellowish, odorless, tasteless, neutral liquid, insoluble in water, soluble in alcohol, chloroform, oil of turpentine, and fat oils, crystallizing near the freezing- point of water; exposed to the air it decomposes and shows then an acid reaction. Lead oleate is soluble in ether, lead palmitate and lead stearate are not. The officinal oleate of mercury and oleate of veratrine are obtained by dissolving the yellow mercuric oxide or veratrine in ole'ic acid. 44. DIBASIC AND TKIBASIC ORGANIC ACIDS. Dibasic acids of the general composition CnH2n-204. Oxalic acid H2C204 or (C02H)2. Malonic acid H2C3H204 or C H2(C02H)a. Succinic acid H2C4H404 or C2H4(C02H)2. Pyrotartaric acid .... H2C5£f604 or C3H6(C02H)2. Adipic acid ..... H2C6H804 or C4H8(C02H)2. etc. Oxalic acid, H2C2042H20. This acid may be looked upon as a direct combination of two carboxyl groups, C02li—C02II, both atoms of hydrogen being replaceable by metals. Of these acids, only the first member is of general interest. Questions.—421. What is the constitution of organic acids, which group of atoms is found in all of them, and how does an alcohol radical differ from an acid radical ? 422. Give some processes by which organic acids are formed in nature or artificially ? 423. Mention the general properties of organic acids. 424. Which series of acids is known as fatty acids, and why has this name been given to them ? 425. Mention names, composition, and occurrence in nature of the first five members of the series of fatty acids. 426. By what processes may formic acid be obtained, and what are its properties? 427. Describe the pro- cesses of manufacturing acetic acids from alcohol and from wood. 428. What is vinegar, and what is glacial acetic acid ? Grive tests for acetic acid and for acetates. 429. Describe the processes for making the acetates of potassium, zinc, iron, lead, and copper, and also of Goulard’s extract and lead-water; state their composition and properties. 430. When and in what form of com- bination is oleic acid found in nature, and what are its properties? 328 CONSIDERATION OF CARBON COMPOUNDS. Oxalic acid is distributed largely in the vegetable kingdom in the form of potassium, sodium, or calcium salts. It may be obtained from vegetables, or by the oxidation of many organic substances, chiefly fats, sugars, starch, etc., by nitric acid or other strong oxidizing agents. Experiment 47. Pour a mixture of 15 c.c. nitric acid and 35 c.c. of water upon 10 grams of sugar contained in a 200 c.c. flask. Apply heat gently until the reaction begins. When red fumes cease to escape pour the solution into a porce- lain dish and evaporate to about one-half its volume. Crystals of oxalic acid separate on cooling ; use them for making the analytical reactions mentioned below. Oxalic acid is manufactured on a large scale by heating saw- dust with potassium or sodium hydroxide to about 250° C. (482° F.), when the oxalate of these metals is formed; by the addition of calcium hydroxide to the dissolved alkali oxalate, insoluble calcium oxalate is formed which is decomposed by sulphuric acid. Oxalic acid crystallizes in large, transparent, colorless prisms, containing two molecules of water; it is soluble in water and alcohol, and has poisonous properties. When heated slowly, it sublimes at a temperature of about 155° C. (311° F.); but if heated higher or with sulphuric acid it is decomposed into water, carbonic oxide, and carbon dioxide : H2c204 = H20 + CO + C02. Oxalic acid acts as a reducing agent, decolorizing solutions of the permanganates, and precipitating gold and platinum from their solutions: PtCl4 + 2H2C204 = Pt + 4C02 + 4HC1. Analytical reactions. (Sodium oxalate, Na2C204, may be used.) 1. Oxalic acid or oxalates when heated with strong sulphuric acid evolve carbonic oxide and carbon dioxide (see above). 2. Neutral solutions of oxalic acid give with calcium chloride a white precipitate of calcium oxalate, CaC204, which is insoluble in acetic, soluble in hydrochloric acid. 3. Silver nitrate produces a white precipitate of silver oxalate, Ag2C20, 4. A dry oxalate (containing a non-volatile metal) heated in a test-tube evolves carbonic oxide, whilst a carbonate is left which shows effervescence with acids. DIBASIC AND TRIBASIC ORGANIC ACIDS. 329 Antidotes to oxalic acid. Calcium carbonate or lime-water should be administered, but no alkalies as in cases of poisoning by mineral acids, because the alkali oxalates are soluble. Oxalates. The acid potassium oxalate, KIIC204, or its combina- tion with oxalic acid, is known under the name of salt of sorrel. Calcium oxalate, Ca0204, is,in small quantities, a normal constituent of urine. Ferrous oxalate, ferri oxalas, FeC204.H20, is made by adding potassium or ammonium oxalate to ferrous sulphate, when double decomposition takes place, and the ferrous oxalate is pre- cipitated as a pale-yellow, crystalline, nearly insoluble powder. Dibasic acids with alcoholic hydroxyl. .HO Malic acid = C4H605 or 02H3<-C02H \C02H „ HO /ho Tartaric acid = C4H606 or C2H2 Vs C02H \ C02II In the various acids heretofore considered, the hydrogen is derived either from the unsaturated hydrocarbon residue, or from the hydroxyl in the carboxyl. As shown by the graphic formulas of the above two acids, they contain also hydrogen in the hydroxyl form not in combination with CO. This hydrogen, whilst not replaceable by metals, may be replaced by alcohol radicals; in other words, it behaves like the hydroxyl hydrogen in alcohols. In order to indicate this difference in the function of the hydrogen, malic acid is said to be dibasic, but triatomic; tartaric acid is dibasic and tetratomic. A few other acids behave in a similar manner, as, for instance, lactic acid. Malic acid, II2C4II405, occurs in the juices of many fruits, as apples, currants, etc. Tartaric acid, Acidum tartaricum, H2C4H40G = 150. Frequently found in vegetables, and especially in fruits, sometimes free, gen- erally as the potassium or calcium salt; grapes contain it chiefly as potassium acid tartrate, which is obtained in an impure state as a by-product in the manufacture of wine. During the fermen- tation of grape-juice, its sugar is converted into alcohol; potas- sium acid tartrate is less soluble in alcoholic fluids than in water, and therefore is deposited gradually, forming the crude tartar, or 330 CONSIDERATION OF CARBON COMPOUNDS. argol of commerce, a substance containing chiefly potassium acid tartrate, but also calcium tartrate, some coloring matter, and often traces of other substances. Crude tartar is the source of tartaric acid and its salts. Tartaric acid is obtained from potassium acid tartrate by neu- tralizing with calcium carbonate, and decomposing the remaining neutral potassium tartrate by calcium chloride: 2(KHC4H406) + CaC03 = CaC4H406 + K2C4H406 + H20 + C02. Potassium acid tartrate. Calcium carbonate. Calcium tartrate. Potassium tartrate. Water. Carbon dioxide. Potassium tartrate. K2C4H406 + CaCl2 = CaC4H406 + 2K01. Calcium chloride. Calcium tartrate. Potassium chloride. The whole of the tartaric acid is thus converted into calcium tartrate, which is precipitated as an insoluble powder; this is collected, well washed, and decomposed by boiling with sulphuric acid, when calcium sulphate is formed as an almost insoluble residue, while tartaric acid is left in solution, from which it is obtained by evaporation and crystallization : Calcium tartrate. CaC4H406 + H2S04 = H2C4H406 + CaS04. Sulphuric acid. Tartaric acid. Calcium. sulphate. Tartaric acid crystallizes in colorless, transparent prisms; it has a strongly acid, but not disagreeable taste; it is readily soluble in water and alcohol, and fuses at 135° C. (275° F.). There are three acids which are isomeric with common tartaric acid, differing from it in physical, but not in chemical properties. These acids are known as inactive tartaric acid, levotartaric acid, and racemic acid, whilst the common tartaric acid is termed dex- trotartaric acid. Crude tartar sometimes contains racemic acid. (Potassium sodium tartrate, KNaC4H406, may be used.) Analytical reactions. 1. Neutral solutions of tartaric acid give with calcium chloride a white precipitate of calcium tartrate, which, after being quickly collected on a filter and washed, is soluble in potassium hydroxide; from this solution calcium tartrate is precipitated on boiling. (Calcium citrate is insoluble in potassium hydroxide.) 2. A strong solution of a tartrate, acidulated with acetic acid, gives a white precipitate of potassium acid tartrate on the addi- tion of potassium acetate. (Precipitate forms slowl}7.) 3. A neutral solution of a tartrate gives with silver nitrate a DIBASIC AND TRIBASIC ORGANIC ACIDS. white precipitate of silver tartrate, Ag2C4II406, which blackens on boiling, in consequence of the decomposition of the salt, with separation of silver. If, before boiling, a drop of ammonia water be added, a mirror of metallic silver will form upon the glass. 4. Sulphuric acid heated with tartrates chars them readily. 5. Tartrates, when heated, are decomposed (blacken), and evolve a somewhat characteristic odor resembling that of burnt sugar. Potassium acid tartrate, Potassii bitartras, KHC4H406 = 188 [Bi- tartrate of potassium, Cream of tartar). The formation of this salt in the .crude state (argol) has been explained above. It is purified by dissolving in hot water and crystallizing, when it is obtained in colorless crystals, or as a white, somewhat gritty powder of a pleasant, acidulous taste; it is sparingly soluble in cold, easily soluble in hot water. Potasssium tartrate, Potassii tartras, 2(K2C4H406)H20 = 470 (Tar- trate of potassium). Obtained by saturating a solution of potassium acid tartrate with potassium carbonate : 2(KHC4H406) + K2C03 = 2(K2C4H406) + II20 + C02. Potassium acid tartrate. Potassium carbonate. Potassium tartrate. Small, transparent or white crystals, or a white neutral powder, soluble in less than its own weight of water. Potassium sodium tartrate, Potassii et sodii tartras, KNaC4H406. 4H20 =282 (Tartrate of potassium and sodium, Rochelle salt). If in the above-described process for making neutral potassium tar- trate, sodium carbonate is substituted for potassium carbonate, the double tartrate of potassium and sodium is formed. It is a white powder, or occurs in colorless, transparent crystals which are easily soluble in water. Experiment 48. Add gradually 24 grams of potassium acid tartrate to a hot solution of 20 grams of crystallized sodium carbonate in 100 c.c. of water. Heat until complete solution has taken place, filter, evaporate to about one-half the volume, and set aside for the potassium sodium tartrate to crystallize. How much crystallized sodium tartrate is required for the conversion of 25 grams of potassium acid tartrate into Rochelle salt? Seidlitz powders consist of a mixture of 120 grains of Rochelle salt with 40 grains of sodium bicarbonate (wrapped in blue paper), and 35 grains of tartaric acid (wrapped in white paper). When dissolved in water, the tartaric acid acts upon the sodium bicar- 332 CONSIDERATION OF CARBON COMPOUNDS. bonate, causing the formation of sodium tartrate, while the escaping carbon dioxide causes etfervescence. Antimony potassium tartrate, Antimonii et potassii tartras, 2(KSbO.C4H400).H2O = 664 (Tartrate of antimony and potassium, Po- tassium antimonyl tartrate, Tartar emetic). This salt is made by dissolving freshly prepared antimonious oxide (while yet moist) in a solution of potassium acid tartrate. From the solution some- what evaporated, tartar emetic separates in colorless, transparent rhombic crystals: 2(KHC4H406) + Sb203 = 2(K Sb0.C4H406) + 1I20. The fact that not antimony itself, but the group SbO replaces the hydrogen, has led to the assumption of the hypothetical radical SbO, termed antimonyl. Potassium acid tartrate. Antimonious oxide. Tartar emetic. Tartar emetic is soluble in water, insoluble in alcohol; it has a sweet, afterward disagreeable metallic taste. Action of certain organic acids upon certain metallic oxides. The solution of a ferric salt (or certain other metallic salts) is pre- cipitated by alkaline hydroxides, a salt of the alkali and ferric hydroxide being formed. When a sufficient quantity of either tartaric, citric, oxalic, or various other organic acids has been added previously to the iron solution (or to certain other metallic solutions) no such precipitate is produced by the alkaline hydrox- ides, because organic salts or double salts are formed which are soluble, and from which the metallic hydroxides are not precipi- tated by alkaline hydroxides. Upon evaporation no crystals (of the organic salt) form, and in order to obtain the compounds in a dry state, the liquid, after being evaporated to the consistence of a syrup, is spread on glass plates which are exposed to a tem- perature not exceeding 60° C. (140° F.), when brown, green, or yellowish-green, amorphous, shining, transparent scales are formed, which are the scale compounds of the U. S. P. Instead of obtaining these compounds, as stated above, by adding the organic acids (or their salts) to the inorganic salts, they are more generally obtained by dissolving the freshly pre- cipitated metallic hydroxide in the organic acid. The true chemical constitution of many of these scale com- pounds has as yet not been determined with certainty. Of officinal scale compounds containing tartaric acid may be DIBASIC AND TRIBASIC ORGANIC ACIDS. 333 mentioned the tartrate of iron and ammonium, and the tartrate of iron and potassium. The first compound is obtained by dissolving freshly precipitated ferric hydroxide in a solution of ammonium acid tartrate, the second by dissolving ferric hydroxide in potas- sium acid tartrate. The clear solutions, after having been suf- ficiently evaporated, are dried, as mentioned above, on glass plates. Citric acid, Acidum citricum, H3CGH.07.H20 = 210. Citric acid is a tribasic acid containing three atoms of hydrogen replaclable by metals; its constitution may be expressed by the graphic formula : /OH > oojf c3h4 \N co2h \CO„H Citric acid is found in the juices of many fruits (strawberry, raspberry, currant, cherrj’, etc.), and in other parts of plants. It is obtained from the juice of lemons by saturating it with calcium carbonate and decomposing by sulphuric acid the calcium citrate thus formed. (100 parts of lemons yield about 5 parts of the acid.) It forms colorless crystals, easily soluble in water. Analytical reactions. (Potassium citrate, K3C6H507, may be used.) 1. Neutral solutions of citrates yield with calcium chloride on boiling (not in the cold) a white precipitate of calcium citrate, which is insoluble in potassium hydroxide, but soluble in cupric chloride. 2. Neutral solutions of citrates are precipitated white by silver nitrate. The precipitate does not blacken on boiling, as in the case of tartrates. 3. A neutral or alkaline solution of a citrate to which a few drops of a solution of potassium permanganate have been added, becomes green or reddish-green. Tartrates decolorize perman- ganate. Citrates. Potassium citrate, K3C6H507.1I20, Lithium citrate, Li3C6H507, and Magnesium citrate, Mg32(CGII507).14II02, are color- less substances, easily soluble in water and obtained by dissolving the carbonates in citric acid. 334 CONSIDERATION OP CARBON COMPOUNDS. Bismuth citrate, BiC6H507, is obtained by boiling a solution of citric acid with bismuth nitrate, when the latter is gradually converted into citrate whilst nitric acid is set free; the insoluble bismuth citrate is collected, washed, and dried; it forms a white, amorphous powder, which is insoluble in water, but soluble in water of ammonia. Bismuth ammonium citrate is a scale compound obtained by dis- solving bismuth citrate in water of ammonia and evaporating the solution at a low temperature. Ferric citrate, Ferri citras, Fe22(C6H507)6H20. Obtained in transparent, red scales, by dissolving ferric hydroxide in citric acid and evaporating the solution as mentioned heretofore. By mixing solution of ferric citrate with either water of ammonia, or quinine, or strychnine, evaporating to the consistence of syrup and drying on glass plates, the following three scale compounds are obtained respectively: Citrate of iron and ammonia, citrate of iron and quinine, citrate of iron and strychnine. Lactic acid, Acidum lacticum, HC3H503 = 90. This acid is the second member of a group of monobasic, diatomic acids which have the general composition CnH2U03, and which contain two hydroxyl groups, the hydrogen of one being capable of replace- ment by metals, the other by alcohols. The first member of this series is glycolic acid, HC2H303, a white, deliquescent, crystalline substance which is found in unripe grapes and in the leaves of the wild grape. Glycolic acid has been shown to be acetic acid, C2H402, in which one atom of hydrogen has been replaced by hydroxyl. The name hydroxy-acetic acid, has, therefore, been given to this compound. Lactic acid occurs in many plant-juices; it is formed from sugar by a peculiar fermentation known as “lactic fermentation,” which causes the presence of this acid in sour milk and in many sour, fermented substances, as in ensilage, sauer-kraut, etc. The formation of lactic acid from sugar may be expressed by the equation: C6H1206.= 2(HC3n503). Sugar. Lactic acid. For practical purposes lactic acid is made by mixing a solution of sugar with milk, putrid cheese, and chalk, and digesting this mixture for several weeks at a temperature of about 30° C. (86° F.). The cheese acts as a ferment, and the chalk neutralizes ETHERS. 335 the acid generated during the fermentation. The calcium lactate thus obtained is purified by crystallization and decomposed by oxalic acid, which forms insoluble calcium oxalate. Lactic acid is a colorless, syrupy liquid, of strongly acid prop- erties : it mixes in all proportions with water and alcohol. A lactic acid called sarco-lactic acid is found in meat-juice, and, therefore, as a constituent of meat-extract. This acid has the composition and all the properties of the above ordinary lactic acid, with the exception that it acts differently on polarized light. Ferrous lactate, Ferri lactas, Fe2(C3H503)3H20 = 287.9. Made by dissolving iron filings in diluted lactic acid; hydrogen is liberated and the salt formed. It is a pale, greenish-white, crystalline substance, soluble in water. 45. ETHERS. Constitution. It has been shown that alcohols are hydrocarbon residues in combination with hydroxyl, OH, and that acids are hydrocarbon residues in combination with carboxyl, CO.OH; it has further been shown that carboxyl may be considered as being composed of CO, and hydroxyl, OH, and that the term acid rad- ical is applied to that group of atoms in acids which embraces the hydrocarbon residue -f CO. If we represent an alcohol radical by AIR, and an acid radical by AcR, the general formula of an alcohol is A1R.OH, or and of an acid, AcR.OII, or A1R\q II /u AcR\q H Ethers are formed by replacement of the hydrogen of the Questions.—431. Name the more common organic acids found in vegetables and especially in sour fruits. 432. What is the composition of oxalic acid, how is it manufactured, and what are its properties? 433. Explain the formation of crude tartar during the fermentation of grape-juice, and how is tartaric acid obtained from it? 434. Give properties of and tests for tartaric acid. 435. State the composition and formation of cream of tartar, Rochelle salt, and tartar emetic. 436. What are Seidlitz powders, and what changes take place when they are dissolved? 437. Mention some officinal scale compounds of iron, and give a general outline of the mode of preparing them. 438. From what and by what process is citric acid obtained ? 439. Mention tests by which citric acid may be distinguished from tartaric acid. 440. From what, and by what process is lactic acid obtained ; what are its properties? 336 CONSIDERATION OF CARBON COMPOUNDS. hydroxyl in alcohols by hydrocarbon residues (or alcohol radicals), and compound ethers or esters are formed by replacement of the hydrogen of the hydroxyl (or carboxyl) in acids by hydrocarbon residues. While alcohols correspond in their constitution to hydroxides, ethers correspond to oxides, and compound ethers to salts. For instance: Hydroxides. KOI! = J^)0 k2o=f yo Oxides. hno3 = N(^\o Acids. kno3 = n^\0 Salts. Potassium hydroxide. Potassium oxide. Nitric acid. Potassium nitrate. c^)o c2h5\0 C2H5/U CjHgO \ Q H/u C2H30 \ q c2h5/u Ethyl alcohol. Ethyl ether. Acetic acid. Ethyl acetate, or acetic ether. AIR \o H/U A1R\0 AIR/ u AcR\ n H/U AcR\n A1R/U‘ It is not necessary that the two hydrocarbon residues in an ether should be alike, as in the above ethyl ether, but they may be different, in which case the ethers are termed mixed ethers. For instance : Alcohol. Ether. Acid. Compound ether. CH C! H O = C ®3\n 3o2n5u C2H6/u C,Ht.06Hu.0 = lrr \0. Methyl-ethyl ether. Propyl-amyl ether. In diatomic or triatomic alcohols, or in dibasic or tribasic acids, containing more than one atom of hydrogen derived from h}7droxyl or carboxyl, these hydrogen atoms may be replaced by various other univalent, bivalent, or trivalent residues. This fact shows that the number of ethers or compound ethers which are capable of being formed is very large. Formation of ethers. Ethers may be formed by the action of the chloride or iodide of a hydrocarbon residue upon an alcohol, in which the hydroxyl hydrogen has been replaced by a metal. For instance: _i_ n H T = 1 tu-„t Na/U ' C2H5/U * xNaA* Sodium ethylate. Ethyl iodide. Ethyl ether. Sodium iodide. | nw t _ C2H6\(-v , -vr r Na/U 1 sL CH,/U + iNa1' Sodium ethylate. Methyl iodide. Ethyl-methyl ether. Sodium iodide. Ethers are also formed by the action of sulphuric acid upo alcohols; the sulphuric acid removing water in this case, thus: 2(C2h5oh) = + h2o. Ethyl alcohol. Ethyl ether. Water. ETHERS. 337 Compound ethers are formed by the combination of acids with alcohols and elimination of water. (Presence of sulphuric acid facilitates this action.) 4- C2H30\q — C2H30\0 I jj q H/U H/U C2H5/U + Ethyl alcohol. Acetic acid. Ethyl acetate. Water. They are also formed by the action of hydrocarbon chlorides (or iodides) on salts. For instance : C5HuC1 + CH£)o = + KOI Amyl chloride. Potassium formate. Amyl formate. Potassium chloride.J Occurrence in nature. Many ethers are products of vegetable life and occur in some essential oils; wax contains the compound ether palmitate of melissyl, C30H61.C16H31O.O, and spermaceti, a solid substance found in the head of the whale, is the palmitate of cethyl, C16H33.016H310.O. The most important group of com- pound ethers are the fats and fatty oils, which are distributed widely in the vegetable, but even more so in the animal kingdom. General properties. The ethers and compound ethers of the lower members of the monatomic alcohols and fatty acids have generally a characteristic and pleasant odor. Fruit essences consist mainly of such compound ethers, and what is generally known as the “ bouquet” or “ flavor ” of wine and other alco- holic liquors is due chiefly to ethers or compound ethers, which are formed during (and after) the fermentation by the action of the acids present upon the alcohol or the alcohols formed. The improvement which such alcoholic liquids undergo “ by age” is caused by a continued chemical action between the substances named. All ethers are neutral substances; those formed by the lower alcohols and acids are generally volatile liquids, those of the higher members are non-volatile solids. When compound ethers are heated with alkalies, the acid combines with the latter, whilst the alcohol is liberated. (The properties of the compound ettiers, termed fats, will be considered further on.) Ethyl ether, iEther, (C2H5)20 = 74 (.Ether, Sulphuric ether, Ethyl oxide). The name of the whole group of ethers is derived from this (ethyl-) ether, in the same way that common (ethyl-) alcohol has given its name to the group of alcohols. The name sulphuric ether was given at a time when its true composition was yet 338 CONSIDERATION OF CARBON COMPOUNDS. unknown, and for the reason that sulphuric acid was used iu its manufacture. Ether is manufactured by heating to about 140° C. (284° F.) a mixture of 1 part of alcohol and 1.8 parts of concentrated sul- phuric acid in a retort, which is so arranged that additional quantities of alcohol may be allowed to flow into it, while the open end is connected with a tube, leading through a suitable cooler, iu order to condense the highly volatile product of the distillation. Experiment 49. Mix 100 grams of alcohol with 180 grams of ordinary sul- phuric acid, allow to stand and pour the cooled mixture into a flask which is provided with a perforated cork through which pass a thermometer and a bent glass tube leading to a Liebig’s condenser. Apply heat and notice that the liquid commences to boil at about 140° C. (284° F.). Distil about 50 c.c., pour this liquid into a stoppered bottle and add an equal volume of water. Ethyl ether will separate in a distinct layer over the water, and may be removed by means of a pipette. Repeat the washing with water, add to the ether thus freed from alcohol a little calcium chloride and distil it from a dry flask, standing in a water-bath. The greatest care should be exercised and the neighborhood of flames avoided in working with ether on account of its volatility and the inflammability of its vapors. The apparatus described above for etherification can be constructed so as to make the process continuous- This may be done by using with the boiling-flask a cork with a third aperture through which a glass tube passes into the liquid. The other end of the tube is connected by means of rubber tubing with a vessel filled with alcohol and standing somewhat above the flask. As soon as distil- lation commences alcohol is allowed to flow into the flask at a rate equal to that of the distillation, keeping the temperature at about 140° C. (284° F.). The flow of alcohol is regulated by a stop-cock. The action of sulphuric acid upon alcohol is not quite so simple as described above in connection with the general methods for obtaining ethers, where the final result only was given. An intermediate product, known as ethyl-sulphuric acid or sulpho- vinic acid, is formed, which, by acting upon another molecule of alcohol, forms sulphuric acid and ether, which latter is volatilized as soon as formed. The decomposition is shown by the equa- tions : c2h5oh + h2so4 = c2h5hso4 + h2o. Alcohol. Sulphuric acid. Ethyl-sulphuric acid. Water, Etliyl-sulphurio acid c2h5hso4 + C2H5OH = H2S04 + (C2h5)2o. Alcohol. Sulphuric acid. Ether, The liberated sulphuric acid at once attacks another molecule of alcohol, again forming ethyl-sulphuric acid, which is again ETHERS. 339 decomposed, etc. Theoretically, a given quantity of sulphuric acid should be capable, therefore, of converting any quantity of alcohol into ether; practically, however, this is not the case, because secondary reactions take place simultaneously, and because the water which is constantly formed does not all distil with the ether, and, therefore, dilutes the acid to such an extent that it no longer acts upon the alcohol. Ether thus obtained is not pure, but contains water, alcohol, sulphurous and sulphuric acids, etc.; it is purified by mixing it with chloride and oxide of calcium, pouring off the clear liquid and distilling it. Pure ether is a very mobile, colorless, highly volatile liquid, of a refreshing, characteristic odor, a burning and sweetish taste, and a neutral reaction; it is soluble in alcohol, chloroform, liquid hydrocarbons, fixed and volatile oils, and dissolves in eight volumes of water. Specific gravity at 0° C. (32° F., is 0.720; boiling-point 35° C. (95° F.) It is easily combustible and burns with a lumi- nous flame. When inhaled, it causes intoxication and then loss of consciousness and sensation. The great volatility and com- bustibility of ether necessitate special care in the handling of this substance near fire or light. Stronger ether, JEther fortior of the U. S. P., contains about 94 per cent, of pure ether and 6 per cent, of alcohol, with a little water, while ether, cether of the U. S. P., contains 74 per cent, of pure ether and 26 per cent, of alcohol, with some water. Spiritus cetheris and Spiritus cetheris compositus are mixtures of about one part of ether and two parts of alcohol, three per cent, of certain ethereal oils being added to the second preparation. Acetic ether, iEther aceticus, C2H5C2H302 = 88 [Ethyl acetate). Made by mixing dried sodium acetate with alcohol and sulphuric acid, distilling and purifying the crude product by shaking with calcium chloride and rectifying : C2H5OH + NaC2H302 + H2S04 = C2H5C2H302 + NaHSO,. Ethyl alcohol. Sodium acetate. Acetic ether. Sodium acid sulphate. Experiment 50. Add to a mixture of 40 grams of pure alcohol and 100 grams of concentrated sulphuric acid 60 grams of sodium acetate. Introduce this mix- ture into a boiling-flask, connect it with a Liebig’s condenser and distil about 50 c.c. Redistil the liquid from a flask, as represented in Fig. 39, page 295, and collect the portion which passes over at a temperature of 77° C. (170° F.); it is nearly pure ethyl acetate. 340 CONSIDERATION OF CARBON COMPOUNDS. Acetic ether is a colorless, neutral, and mobile liquid, of a strong ethereal and somewhat acetous odor, soluble in alcohol, ether, chloroform, etc., in all proportions, and in 17 parts of water. Specific gravity 0.889. Boiling-point 76° C. (169° F.). Ethyl nitrite, C2H5N02 (Nitrous ether). Made by distilling a mixture of alcohol, sulphuric and nitric acids at a temperature of 80° C. (176° F.). By the deoxidizing action of alcohol on nitric acid, HH03, the latter is converted into nitrous acid, IFSr02, which in its turn acts on alcohol, the two substances combining with elimination of water, which is absorbed by the sulphuric acid : c2h5oh + hno2 = o2h5.no2 + h2o. Spirit of nitrous ether, Spiritus cetheris nitrosi, Sweet spirit of nitre. This is a mixture of 5 parts of the crude ethyl nitrite with 95 parts of alcohol. It is a clear, mobile, volatile, and inflammable liquid, of a pale straw color inclining slightly to green, a fragrant, ethereal odor, and a sharp, burning taste. It slightly reddens litmus paper, but evolves no carbon dioxide with carbonates. Amyl nitrite, Amyli nitris, C5HuN02 = 117 {Nitrite of amyl). Made by distilling equal volumes of pure amyl alcohol and nitric acid from a retort until an inserted thermometer shows a tem- perature of 100° C. (212° F.). The crude distillate is puritied by agitating it with a solution of potassium carbonate and hy- droxide, separating the upper layer of the liquid and redistilling it; the liquid passing over between 96° C. and 100° C. (205° F. and 212° F.) is the amyl nitrite. It is a clear, pale-yellowish liquid, of an ethereal, fruity odor, an aromatic taste, and a neutral or slightly acid reaction. Specific gravity 0.872. Boiling-point 96° C. (205° F.). Fats and fat oils. All true fats are compound ethers of the triatomic alcohol glycerin, in which the three replaceable hydrogen atoms of the hydroxyl are replaced by three univalent radicals of the higher members of the fatty acids. For instance: Glycerin = C3H5.3(OH) /OH or C3H3VOH xOH Stearic acid = C18H35O.OH or C18H35 0\n /(C18H35°)'° C3H5—(018H35O).O (^18^35^)-^ Stearin or tristearin = C3H5.3(C18H350).03 or ETHERS. 341 While all natural fats are glycerin in which the three hydrogen atoms are replaced, we may by artificial means introduce but one or two acid radicals, thus forming: /(C18H330)0 Monostearin = C3H5—OH \qh /(C18H350)0 Distearin = C3H5^-(C18H350)0 X0H Fats are often termed glycerides; stearin being, for instance, the glyceride of stearic acid. The principal fats consist of mixtures of palmitin, C3H5. 3(C16H310).03, stearin, C3II5.3(C18H350).03, and olein, C3H5. 8(C18H330).03. Stearin and palmitin are solids, olein is a liquid at ordinary temperature; the relative quantity of the three fats mentioned determines its solid or liquid condition. The liquid fats, containing generally olein as their chief constituent, are called fatty oils or fixed oils in contradistinction to volatile or essential oils. All fats, when in a pure state, are colorless, odorless, and taste- less substances, which stain paper permanently; they are insolu- ble in water, difficultly soluble in cold alcohol, easily soluble in ether, bisulphide of carbon, benzene, etc. The taste and color of fats are due to foreign substances, often produced by a slight decomposition which has taken place in some of the fat. All fats are lighter than water, and all solid fats fuse below 100° C. (212° F.); fats can be distilled without change at about 300° C. (572° F.), but are decomposed at a higher temperature with the forma- tion of numerous products, some of which have an extremely diagreeable odor, as, for instance, acrolein, C3H40, an aldehyde which in composition is equal to glycerin minus two molecules of water: C3H53HO — 2H,0 = C3H40. Some fats keep without change when pure; since they con- tain, however, impurities generally, such as albuminous matter, etc., they sutler decomposition (a kind of fermentation aided by oxidation), which results in a liberation of the fatty acids, which impart their odor and taste to the fats, causing them to become what is generally termed rancid. Some fats, especially some oils, suffer oxidation, which renders them hard. These drying oils differ from other oils in being mix- tures of olein with another class of glycerides, containing un- saturated acids with less hydrogen in relation to carbon than ole'ic acid. Drying oils are prevented from drying by albuminous 342 CONSIDERATION OF CARBON COMPOUNDS. impurities, which may be removed by treating the oil with 4 per cent, of concentrated sulphuric acid; the acid does not act on the fat, but quickly destroys the albuminous matters, which, with the sulphuric acid, sink to the bottom, whilst the “refined” oil may be removed by decantation. Fats are largely distributed in the animal and vegetable king- doms. They exist in plants chiefly in the seeds, while in animals they are found generally under the skin, around the intestines, and on the muscles. Human fat, beef tallow, mutton tallow, and lard, are mixtures of palmitin and stearin with some ole'in. Butter consists of the glycerides of butyric acid, capro'ic acid, caprylic acid, and capric acid, which are volatile with water vapors, and of myristic, pal- mitic, and stearic acids, which are not volatile. The principal non-drying vegetable oils (consisting chiefly of ole'in) are olive oil, cottonseed oil, cocoanut oil, palm oil, almond oil. Among the drying oils are of importance: linseed oil, castor oil, croton oil, hemp oil, cod-liver oil. Whenever fats are treated with alkaline hydroxides, or with a number of other metallic oxides, decomposition takes place, the fatty acids combining with the metals, whilst glycerin is set free. Some of the substances thus formed are of great importance, as, for instance, the various kinds of soap. Soap. Any fat boiled with sodium or potassium hydroxide will form soap. Soft soap is potassium soap, hard soap is sodium soap. The better kinds of hard soap are made by boiling olive oil with sodium hydroxide : Oleate of glyceryl (olive oil). C3H53(018H3302) + 3NaOH = 3(NaC18H3302 + C3H530H. Sodium hydroxide. Sodium oleate (hard soap). Glycerin, Experiment 51. Boil 50 grams of olive oil with 60 c.c. of a 15 per cent, sodium hydroxide solution for about one hour. The soap which is thereby formed remains dissolved in or mixed with water and glycerin. Cause separation by adding a solution of 15 grams of sodium chloride in 40 c.c. of water and boiling for a short while, when the soap, which is insoluble in the salt solution, rises to the surface and solidifies on cooling. Soaps are soluble in water and alcohol; they contain rarely less than 30 per cent., but sometimes as much as 70-80 per cent, of water. Ammonia liniment, Linimenlum ammonite, and lime liniment, Lini- mentum calm, are obtained by mixing cottonseed oil with water ETHERS. 343 of ammonia and lime-water, respectively. The oleate of ammo- nium or calcium is formed, and remains mixed with the liberated glycerin. Lead plaster, Emplastrum plumbi. Chiefly lead oleate, Pb2C18H3302. Obtained by boiling lead oxide with olive oil and water for several hours, until a homogeneous mass is formed. Lead oleate differs from the oleates of the alkalies by its complete insolubility in water. Lanolin. This name has been given to the fat or fats which are found in sheep’s wool and are obtained by treating the wool with soap-water, and acidifying the wash liquor, when the fats separate unchanged. These fats differ from the fats spoken of above in so far as the alcohol present is not glycerin, but an alcohol, or rather two isomeric alcohols of the composition C26H43OH and known as cholesterin and iso-cholesierin. These alcohols, which are white, crystalline, fusible substances, when in combination with fatty acids form the compound ethers known as lanolin. Lanolin is a yellowish-white (or, when not sufficiently purified, a more or less brownish), fat-like substance, having the peculiar odor of sheep’s wool and fusing at a moderate temperature, forming an oily liquid. Unlike true fats, lanolin is capable of mixing wdth upward of 30 per cent, of water or aqueous solutions and yet retaining its fatty consistency; it is, moreover, much less liable to decompose than fats, and it is this property and its power to mix with aqueous solutions which have rendered lanolin a valuable agent in certain pharmaceutical preparations. Questions.—441. Explain the constitution of simple, mixed, and compound ethers. To what inorganic compounds are they analogous? 442. State the general processes for the formation of ethers and compound ethers. 443. What is the composition of ethyl ether? Explain the process of its manufacture in words and symbols, and state its properties. 444. How is acetic ether made, and what are its properties? 445. What is sweet spirit of nitre, and how is it made? 446. State the general composition of fats and the chief constituents of tallow, butter, and olive oil. 447. What is the solubility of fats in water, alcohol, and ether; how do heat and oxygen act upon them ; what is the cause of their becoming rancid ? 448. Explain the composition and manufacture of soap, and state the difference between hard and soft soap. 449. How are am- monia liniment, lime liniment, and lead plaster made, and what is their com- position ? 450. What is the source of lanolin; what are its constituents and properties? 344 CONSIDERATION OF CARBON COMPOUNDS. 46. CARBOHYDRATES. Constitution. The term carbohydrates or carbhydrates is not well chosen, because it implies that these substances are carbon in combination with water. Carbohydrates do contain hydrogen and oxygen in the proportion of two atoms of hydrogen to one atom of oxygen, or in the proportion to form water, but this does not exist as such in the carbohydrates. The true atomic structure of carbohydrates is as yet but little known. The compounds of the composition C6H1206 are now looked upon as the aldehyde of the hexatomic alcohol mannite, C6H1406, the chief constituent of manna: C6Hu06 - 2H = C6H1206. Mannite itself is formed from the saturated hydrocarbon C6H14, by replacement of 6 atoms of hydrogen by 60H; its con- stitutional formula is, therefore, (C6H8)vi.6(OIT). Carbohydrates generally contain 6 atoms of carbon or a mul- tiple of 6. Properties. Carbohydrates are either fermentable, or can, in most cases, be converted into substances which are capable of fermentation. They are not volatile, but suffer decomposition when sufficiently heated; they have neither acid nor basic pro- perties, but are of a neutral reaction. Oxidizing agents convert them into saccharic and mucic acids and finally into oxalic acid. (Soluble carbohydrates have the property of bending the plane of polarized light.) Most carbohydrates are white, solid substances, and, with the exception of a few, soluble in water. The members of the first two groups (glucoses and saccharoses) have a more or less sweet taste. Many of them, especially glucoses, are good reducing agents, as is shown by the fact that they deoxidize in alkaline solution salts (or oxides) of copper, bismuth, mercury, gold, etc., either to a lower state of oxidation or to the metallic state. Occurrence in nature. No other organic substances are found in such immense quantities in the vegetable kingdom as the members of this group, cellulose being a chief constituent of all, starch and various kinds of sugar of most plants. Carbohydrates are also found as products of animal life, as, for instance, the sugar in milk, in bees’ honey, etc. CARBOHYDRATES. 345 Groups of carbohydrates. f Glucoses. Grape-sugar, Saccharoses. Ci2H22Ou. Cane-sugar, Amylases. c6h10o5. Starch, Origin - Vegetable - Fruit-sugar, Mannitose, Melitose, Maltose, Dextrin, Gums, Animal Inosite. Milk-sugar. Cellulose, Glycogen Grape-sugar, CeH1206 (Ordinary glucose, Dextrose). This substance is very abundantly diffused throughout the vegetable kingdom, and is generally accompanied by fruit-sugar. It is contained in large quantities in the juice of many fruits; the percentage of grape-sugar in the dried fig is about 65, in grape 10-20, in cherry 11, in mulberry 9, in strawberry 6, etc. Grape-sugar is found also in honey and in minute quantities in the normal blood (0.1 per cent, or less), and traces occur, perhaps, in normal urine, the quantity in both liquids rising, however, during certain diseases, as high as five per cent, or higher. Grape-sugar is produced in the plant from starch by the action of the vegetable acids present; it may be obtained artificially from starch (and from many other carbohydrates) by heating with dilute mineral (sulphuric) acids, which convert starch first into dextrin and then into grape-sugar. Corn-starch is now largely used for that purpose, the excess of sulphuric acid being removed by treating the solution with chalk; the filtered solution is either evaporated to a syrup and sold as “ glucose,” or evaporated to dryness, when the commercial “ grape-sugar” is obtained. Experiment 52. Heat to boiling 100 c.c. of a one per cent, sulphuric acid and add to it very gradually and under constant stirring a mixture made by rubbing together 25 grams of starch and 25 grams of water. Continue to boil until iodine no longer causes a blue color (which shows complete conversion of starch into either dextrin or glucose), and until 1 c.c. of the solution is no longer pre- cipitated on the addition of 6 c.c. of alcohol (which shows the conversion of dextrin into sugar, dextrin being precipitated by alcohol). Apply to a portion of the glucose solution thus obtained, and neutralized by sodium carbonate, the tests mentioned below. To the remaining solution add a quantity of pre- cipitated calcium carbonate sufficient to convert all sulphuric acid into calcium sulphate. Filter, evaporate the solution to a syrup and notice its sweet taste. Glucose is met with generally as a thick syrup which crystal- lizes with difficulty, combining during crystallization with one molecule of water; but anhydrous crystals, closely resembling 346 CONSIDERATION OF CARBON COMPOUNDS. those of cane-sugar, are also known. Glucose is soluble in its own weight of water and is less sweet than cane-sugar, the sweet- ness of glucose compared to that of cane-sugar being about 3 to 5; when heated to 170° C. (338° F.) it loses water, and is con- verted into glucosan, C6II10O5; by stronger heating it loses more water and forms caramel, a mixture of various substances; it turns the plane of polarized light to the right. Grape-sugar combines with various metallic oxides (alkalies, alkaline earths, etc.), and also with a number of other substances forming a series of compounds known as glucosides. Grape-sugar may be recognized analytically : 1. By causing a bright-red precipitate of cuprous oxide, when boiled with a solution of cupric sulphate in sodium hydroxide, to which tartaric acid has been added. (A solution containing these three substances in definite proportions is known as Fehling’s solution. See index.) 2. By precipitating metallic silver, bismuth, and mercury, when compounds of these metals are heated with it in the presence of caustic alkalies. 3. By easily fermenting when yeast is added to the solution, alcohol and carbon dioxide being formed: C6H1206 = 2C2H5OH + 2C02. Fruit-sugar, C6H1206 (Levulose), occurs with glucose in sweet fruits and honey; it resembles glucose in most chemical and physical properties, hut does not crystallize from an aqueous solution; it may, however, be obtained in white, silky needles from an alcoholic solution; it is met with generally as a thick syrup, is about as sweet as cane-sugar, and turns the plane of polarized light to the left; it is formed by the action of dilute mineral acids or ferments on cane-sugar, which latter takes up water and breaks up thus : Ci2H22On -|~ H20 — C6Hi206 -f- Cane-sugar. Dextrose. Levulose. Mannitose, C6H]206. Obtained by the oxidation of mannite; it does not crystallize and resembles grape-sugar. Galactose, C6H1206, is formed together with dextrose when either milk-sugar or gum-arabic is boiled with dilute sulphuric acid. Galactose crystallizes, reduces an alkaline copper solution, but does not ferment with yeast. CARBOHYDRATES. 347 Inosite, C6H1206 (Muscle-sugar), occurs in various muscular tissues, in the lungs, kidneys, liver, spleen, brain, and blood. Although identical in composition with grape-sugar, inosite differs from the latter in not being fermentable and by not pre- cipitating cuprous oxide from alkaline copper-solutions. Cane-sugar, Saccharum, C12H22On = 342 (Ordinary saccharose, Common sugar, Beet-sugar). Cane-sugar is found in the juices of many plants, especially in that of the different grasses (sugar- cane), and also in the sap of several forest trees (maple), in the roots, stems, and other parts of various plants (sugar-beet), etc. Plants containing cane-sugar do not contain free organic acids, which latter would convert it into grape-sugar. Cane-sugar is manufactured from various plants containing it by crushing them between rollers, expressing the juice, heating and adding to it milk of lime, which precipitates vegetable albuminous matter. The clear liquid is evaporated to the con- sistency of a syrup, which is further purified (refined) by filtering it through bone-black and evaporating the solution in “vacuum pans” to the crystallizing-point; the mother-liquors are further evaporated, and yield lower grades of sugar; finally a syrup is left which is known as molasses. Cane-sugar forms white, hard, distinctly crystalline granules, but may be obtained also in well-formed, large, monoclinic prisms. It dissolves in 0.2 part of boiling, in 0.5 part of cold water, and in 175 parts of alcohol; when heated to 160° C. (320° F.) it fuses, and the liquid, on cooling, forms an amorphous, transparent mass, known as barley-sugar; at a higher temperature cane-sugar is decomposed, water is evolved, and a brown, almost tasteless substance is formed, wrhich is known as caramel or burnt sugar. Oxidizing agents act energetically upon cane-sugar, which is a strong reducing agent. A mixture of cane-sugar and potassium chlorate will deflagrate when moistened with sulphuric acid; potassium permanganate is readily deoxidized in acid solution; cane-sugar, however, does not affect an alkaline copper-solution, and does not ferment itself; but when heated with dilute acids or left in contact with yeast for some time, it is decomposed into dextrose and levulose, both of which are fermentable. Like dex- trose, cane-sugar forms compounds with metals, metallic oxides, and salts, which compounds are known as sucrates. 348 CONSIDERATION OF CARBON COMPOUNDS. Experiment 53. Make a one per cent, cane-sugar solution; test it with Fehling’s solution and notice that no cuprous oxide is precipitated. Add to 50 c.c. of the cane-sugar solution 5 drops of hydrochloric acid and heat on a water- bath for half an hour. Again examine the liquid with Fehling’s solution : a precipitate of cuprous oxide is now formed, proving the conversion of cane- sugar into glucose. Maltose, CJ2H220n, is obtained by the action of diastase on starch. Diastase is a substance formed during the germination of various seeds (rye, wheat, barley, etc.), and it is for this reason that grain, used for alcoholic liquors, is allowed to germinate, during which process diastase is formed, which, acting upon the starch present, converts it into maltose and dextrin: 3(O6H10O5) + h2o - c12h22ou + C6H10O5. Maltose is also formed by the action of dilute sulphuric acid upon starch, and is hence often present in commercial glucose; by further treatment with sulphuric acid it is converted into dex- trose. Maltose crystallizes, reduces alkaline copper solutions, and ferments with yeast. Starch. Maltose. Dextrin. Melitose, C12II22On, is the chief constituent of Australian manna. Milk-sugar, Saccharum lactis, C12H22On + H20 = 360 {Lactose). Found almost exclusively in the milk of the mammalia. Ob- tained by freeing milk from casein and fat and evaporating the remaining liquid (whey) to a small bulk, when the milk-sugar crystallizes on cooling. It forms white, hard, crystalline masses; it is soluble in 7 parts of water (at 15° C., 59° F.) and in 1 part of boiling water, insoluble in alcohol and ether; it is much harder than cane-sugar, and but faintly sweet; it is not easily brought into alcoholic fer- mentation by the action of yeast, but easily undergoes “ lactic fermentation” when cheese is added. During this process milk- sugar is converted into lactic acid. Milk-sugar resembles grape-sugar in its action on alkaline solu- tion of copper, from which it precipitates cuprous oxide. Starch, Amylum, C6H10O5 = 162. Starch is very widely distributed in the vegetable kingdom, and found chiefly in the seed of cereals and leguminosse, but also in the roots, stems, and seeds of nearly all plants. It is prepared from wheat, potatoes, rice, beans, sago, arrow- CARBOHYDRATES. 349 root, etc., by a mechanical operation. The vegetable matter containing the starch is comminuted by rasping or grinding, in order to open the cells in which it is deposited, and then steeped in water; the softened mass is then rubbed on a sieve under a current of water which washes out the starch, while cellular fibrous matter remains on the sieve; the starch deposits slowly from the washings, and is further purified by treating it with water. Starch forms white, amorphous, tasteless masses, which are peculiarly slippery to the touch, and easily converted into a powder; it is insoluble in cold water, alcohol, and ether; when boiled with water, it yields a white jelly (mucilage of starch, starch-paste) which cannot be looked upon as a true solution, but is a suspension of the swollen starch particles in water; by con- tinued boiling with much water some starch passes into solution. Starch, when examined under the microscope, is seen to consist of granules differing in size, shape, and appearance, according to the plant from which the starch was obtained. Concentric layers, which are more or less characteristic of starch-granules, show that they are formed in the plant by a gradual deposition of starch matter. The most characteristic test for starch is the dark-blue color which iodine imparts to it (or better to the mucilage). This color is due to the formation of iodized starch, Amylum iodatum, U. S. P., an unstable dark-blue compound of the doubtful com- position C6H9I05I. Starch is an important article of food, especially when asso- ciated, as in ordinary flour, with albuminous substances. Dextrin, C6H10O5 [British gum). Obtained by boiling starch with diluted acids, or by subjecting starch to a dry heat of 175° C. (347° F.) or by the action of diastase (infusion of malt) upon hydrated starch. Malt is made by steeping barley in water until it germinates and then drying it. Dextrin is a colorless or slightly yellowish, amorphous powder, resembling gum-arabic in some respects: it is soluble in water, reduces alkaline copper solutions, and is colored light wine-red by iodine. It is extensively used in mucilage as a substitute for gum-arabic. Gums. These are amorphous substances of vegetable origin, soluble in water or swelling up in it, forming thick, sticky 350 CONSIDERATION OF CARBON COMPOUNDS. masses; they are insoluble in alcohol, and are converted into glucose by boiling with dilute sulphuric acid. Gum-arabic consists chiefly of the calcium salt of arabic acid, C6H10O5.H2O. Other gums occur in the cherry tree, in linseed or flaxseed, in Irish moss, in marsh-mallow root, etc. Cellulose, C6H10O5, perhaps C18H30O13 (Plant-fibre, Lignine). Cellu- lose constitutes the fundamental material of which the cellular membrane of vegetables is built up, and forms, therefore, the largest portion of the solid parts of every plant; it is well adapted to this purpose on account of its insolubility in water and most other solvents, its resistance to either alkaline or acid liquids, and its tough and flexible nature. Some parts of vegetables (cotton, hemp, and flax, for instance) are nearly pure cellulose. Pure cellulose is a white, translucent mass, insoluble in all the common solvents, but soluble in an ammoniacal solution of basic cupric carbonate; it is not colored blue by iodine. Treated with concentrated sulphuric acid it swells up, and gradually dissolves; water precipitates from such solutions a substance known as amyloid, which is an altered cellulose giving a blue color with iodine. Upon diluting the sulphuric acid solu- tion with water and boiling it, the cellulose is gradually converted into dextrin and dextrose. Unsized paper (which is chiefly cellulose) dipped into a mixture of two volumes of sulphuric acid and one volume of water, forms, after being washed and dried, the so-called “parchment paper,” which possesses all the valuable properties of parchment. Pyroxylin, Pyroxylinum, C6H8(N02)205 (.Dinitro-cellulose, Soluble gun- cotton). By the action of nitric acid of various strengths on cellu- lose, three different substitution products may be obtained, which are distinguished as mono-, di-, and trinitro-cellulose : c6h10o5 + hno3 = C6H9(N02)05 + H20. C6H10O5 + 2HNO3 = C6H8(N02)205 + 2H20. C6H70O5 + 3HNOs = C6H7(N02)305 + 3H20. The trinitro-cellulose is the highly explosive gun-cotton ; an in- timate mixture of gun-cotton and camphor is now extensively used under the name of celluloid. The dinitro-cellulose or pyrox- ylin is soluble in a mixture of ether and alcohol; this solution is known as collodion. Neither the mono- nor trinitro-cellulose is soluble in a mixture of ether and alcohol. CARBOHYDRATES. 351 Experiment 54. Immerse 2 grams of dry cotton for ten hours in a previously cooled mixture of 20 grams of nitric acid and 24 grams of sulphuric acid. Wash the pyroxylin thus obtained with cold water until the washings have no longer an acid reaction. Dissolve 1 part of the dry pyroxylin in a mixture of 18 parts of ether and 6 parts of alcohol. The solution obtained is collodion. Glycogen, C6H10O5. Found exclusively in animals; it occurs in the liver, the white blood-corpuscles, in many embryonic tissues, and in muscular tissue. Pure glycogen is a white, starch-like, amor- phous substance, soluble in water, insoluble in alcohol; by the action of dilute acids it is converted into glucose. Glucosides. This term is applied to a group of substances (chiefly of vegetable origin) which, by the action of acids, alka- lies, or ferments, suffer decomposition in such a manner that one of the products formed is grape-sugar. Glucosides may, there- fore, be looked upon as compound sugars, or sugar in combina- tion with various other substances. The following is a list of the more important glucosides, giving also their composition and the sources whence they are obtained : Amygdalin, c20h27nou Bitter almonds, etc. Arbutin, 14 Arbutus uva ursi. Cathartic acid, N4SO 82? Senna. Carminic acid, ? Cochineal. Colocynthin, Colocynthis. Digitalin, • Digitalis. Gentiopicrin, Boot of gentiana. Glycyrrhizin, Liquorice root. Helleborin, Boot of hellebore. Indican, ? Indigo plant. Jalapin, Jalap resin. Myronic acid, Seeds of black mustard. Salicin, Bark of willow. Scam monin, Besin scammony. Solanin, ? Various specimens of solanum Tannins, In many barks, leaves, etc. Digitalin. The leaves of digitalis purpurea contain digitalein, an amorphous glucoside, soluble in water; Schmiedeberg’s digitalin, a crystalline glucoside, insoluble in water; digitoxin, digitonin, and digitin. The various preparations now used as “ digitalin ” are mixtures of the substances named, containing more or less of the glucosides, which alone seem to possess the characteristic physi- ological action of digitalis. The most poisonous of the constituents of digitalin is digitoxin, a crystalline substance, of which only 0.01 to 0.02 per cent, is 352 CONSIDERATION OF CARBON COMPOUNDS. contained in the leaves; this substance forms, however, the greater part of the “ digitalin nativelle.” Chiefly used now are two preparations, viz., the German or Merck’s digi- talin, which consists chiefly of digitalein and is soluble in water, and the amorphous digitalin, which contains chiefly digitalin with some digitoxin and is but sparingly soluble in water and ether, soluble in chloroform and alcohol, and forms, by warming it with concentrated hydrochloric or phosphoric acid, a beautiful green solution. Myronic acid, C10H19NS2O10, is found as the potassium salt, which is known as sinigrin, in black mustard seed. When treated with solution of myrosin, a substance also contained in mustard seed and acting as a ferment upon myronic acid or its salts, potassium myronate is converted into dextrose, allyl mustard oil, and potassium bisulphate: KC10H18NS2O10 = C6H1206 + C,H5NCS + KHSCV Potassium myronate. Dextrose. Allyl mustard oil. Potassium bisulphate. The univalent radical allyl, CgH/, is isomeric, but not identical with the trivalent radical glyceryl, C3H5m. The triatomic alcohol glycerin, C3H530H, may, however, be converted into the mon- atomic allyl alcohol C3H5OH, by various processes. From allyl alcohol an artificial allyl mustard oil is manufactured. Allyl sulphide, (C3H5)2S, is the chief constituent of the oil of garlic. Questions.—451. To which group of substances is the term “carbohydrates” applied? 452. State the general properties of carbohydrates. 453. Mention the three groups of carbohydrates, and the composition and characteristics of the members of each group. 454. Mention some fruits in which grape-sugar, and some plants in which cane-sugar is found. 555. What is the difference between grape-sugar and cane-sugar, and by what tests can they be distinguished ? 456. From what source, and by what process is milk-sugar obtained? 457. What is starch, what are its properties, by what tests can it be recognized, and what substance is formed when diastase or dilute acids act upon it? 458. Where is cellulose found in nature, and what are its properties? 459. What three com- pounds may be obtained by the action of nitric acid upon cellulose, and what are they used for? 460. What substances are termed glucosides? Mention some of the more important glucosides. AMINES AND AMIDES. CYANOGEN COMPOUNDS. 353 47. AMINES AND AMIDES. CYANOGEN COMPOUNDS. Forms of nitrogen in organic compounds. Nitrogen may be present in organic compounds in three forms, viz., ammonia, cyanogen, nitric acid, or derivatives of these compounds. Sub- stances containing nitrogen in the nitric acid form may be either organic salts of this acid (nitrates), or may have been formed by replacement of hydrogen atoms by the nitric acid radical N02. These latter compounds, termed nitro-compounds, such as nitro- cellulose, nitro-benzene, etc., do not occur in nature, but are obtained exclusively by artificial means, generally by treatment of the organic substance with concentrated nitric acid; all these nitro-compounds are more or less explosive. Cyanogen compounds contain nitrogen in the form of cya- nogen, CN, a radical the compounds of which will be considered hereafter. Organic compounds containing nitrogen in the ammonia form are known as amines or amides, organic bases or alkaloids. (Albuminous substances also contain nitrogen in the ammonia form.) Amines. Whenever the hydrogen of ammonia is replaced by alcoholic radicals (or hydrocarbon residues) compounds are formed which are termed amines. For instance : /H /C2H5 /C2n5 /C2H5 /C h3 N H, N —H , N^-C2H5, NvC2H5, x(-C2H5. XH \h xC2H. XC4H9 Or nh3) N(C2H5)H„ N(02h5)2h, N(c2H5)3t nch3 c2h5 c4h9. Ammonia. Ethylamine. Diethylamine. Triethylamine. Methyl-ethyl-buty lamina, Amines resemble ammonia in their chemical properties; they are, like ammonia, basic substances; they combine with acids directly and without elimination of water, thus : NH, + HC1 = NH4C1; N(C2H5)3 + HC1 = N(C2H5)3HC1 Triethylamine. Triethylamine chloride. Methylamine, N(CH3)H2, is a colorless, inflammable gas, has a fishy, animo- niacal odor, and is the most soluble gas known, 1 volume of water dissolving over 1100 volumes of the gas at the ordinary temperature. Trimethylamine, N(CH3)3, is found in small quantities in cod-liver oil, ergot, yeast, different plants, urine, the blood of the calf, and in many other substances. It is produced during the putrefaction of fish, brain-tissue, muscular tissue, and 354 CONSIDERATION OF CARBON COMPOUNDS. other albuminous substances. It is an oily liquid, of a disagreeable, fishy odor, boils at 8° C. (46.4° F.) and combines with acids to form crystallizable salts. Amides are substances derived from ammonia by replacement of hydrogen atoms by acid radicals. Thus : /H n( H, Ml /C2h3o N^-H \H /C2h3o n^c2h3o, \fl n=h2. %h2 Ammonia. Acetamide. Diacetamide. Carbamide or urea. Amides also resemble ammonia in their chemical properties ; to a less extent, however, than amines, because the acid radicals have a tendency to neutralize the basic properties of ammonia. Formamide, N(CHO)H2, is a colorless liquid, obtained by heating ethyl foriniate with an alcoholic solution of ammonia. This compound is of interest because it combines with chloral, forming Chloralformamide (Chloralamide), N(CHO)H2. C2HC130, a substance recently used as a hypnotic. It is a colorless, odorless, crystalline substance, having a faintly bitter taste. It is soluble in 20 parts of cold water and in 1.5 parts of alcohol. By heating the aqueous solution to 60° C. (140° F.) it is decomposed into chloral and formamide or ammonium formate. Caustic alkalies liberate iodoform and ammonia. Amido-acids are acids in which hydrogen has been replaced by NIT2. Thus, amido-acetic acid, also known as glycocoll or glycine, /JJJT is represented by the formula C2H3(NH2)02 or CH2\qq2jj; it is a substance wThich has both acid and basic properties, and is a product of the decomposition of either glycocholic or hippuric acid by hydrochloric acid. Amido-formic acid or carbamic acid, CII.NH2.02, is the acid which, in the form of the ammonium salt, is a constituent of the com- mercial ammonium carbonate. It is formed by the direct action of carbon dioxide upon ammonia: Formation of amines and amides. These substances are found as products of animal life (urea), of vegetable life (alkaloids), of destructive distillation (aniline, pyridine), of putrefaction (pto- maines), and may also be produced synthetically, for instance, by the action of ammonia upon the chloride or iodide of an alcohol or acid radical: C02 + 2NH3 = c.nh4.nh2.o2. Ethyl iodide. C2H5.I + NH3 = HI + NHjOjHj. Ammonia. Hydriodic acid. Ethylamine. C2H30.C1 + 2NH3 = NH4C1 + nh2.c2h3o. Acetyl chloride. Ammonia. Ammonium chloride. Acetamide, AMINES AND AMIDES. CYANOGEN COMPOUNDS. 355 Amines may also be formed by the action of nascent hydrogen upon the cyanides of the alcoholic radicals : CHgCN + 4H = NH2.C2H5. Amines may in some cases be formed by the action of nascent hydrogen upon nitro-compounds; the manufacture of aniline depends on this decomposition : Methyl cyanide. Ethylamine. C6H5N0.2 + 6H = 2H20 + NH,C6H5. Nitro-benzene. Hydrogen. Water. Phenylamine, or aniline. Occurrence of organic bases in nature. The various organic basic substances found in nature are either amines (compounds containing carbon, hydrogen, and nitrogen only), or amides (com- pounds containing,besides the three elements named, also oxygen). But a small number of organic bases is found in the animal sys- tem, urea being the most important one. In plants organic bases are more frequently met with, and are grouped together under the name of alkaloids. While the constitution of many alkaloids has not yet been sufficiently explained, we know that many of them are derivations of aromatic compounds, for which reason the consideration of the whole group will be deferred until ben- zene and its derivatives are spoken of. Cyanogen compounds. Cyanogen itself does not occur in nature, but compounds of it are found in a few plants (amygdalin), and also in some animal fluids (saliva contains sodium sulphocyanate). Gases issuing from volcanoes (or from iron furnaces) sometimes contain cyanogen compounds. The univalent residue cyanogen, — or CH, was the first compound radical distinctly proved to exist, and isolated by Gay- Lussac in 1814. The name cyanogen signifies “ generating blue/’ in allusion to the various blue colors (Prussian and Turnbull’s blue) containing it. (The symbol Cy, sometimes used in place of OUST, has been adopted merely to simplify the writing of formulas of cyanogen compounds). Cyanogen and its compounds show much resemblance to the halogens and their compounds, as indicated by the composition of the following substances : C1CI, HC1, Kf, HCIO, Chlorine. Hydrochloric acid. Potassium iodide. Hypochlorous acid 356 CONSIDERATION OF CARBON COMPOUNDS. CNCN, Cyanogen. HBr, Hydrobromic acid. KCN, Potassium cyanide. HCNO, Cyanic acid. CNC1, Cyanogen chloride. HCN, Hydrocyanic acid. AgCN, Silver cyanide. HCNS. Sulphocyanic acid. Dicyanogen, (CN)2. The unsaturated radical CIST does not exist as such in a free state, but combines whenever liberated with another Chf, forming dicyanogen. It ma}7 be obtained by heating mercuric cyanide: Hg2CN = Hg + 2CN. It is a colorless gas, having an odor of bitter almonds, and burning with a purple flame, forming carbon dioxide and nitro- gen ; it is soluble in water, and may be converted into a color- less liquid by pressure; it acts as a poison, both to animal and vegetable life, even when present in but small proportions in the air. Hydrocyanic acid, HCN — 27 (Cyanhydric acid, Hydrogen cyanide, Prussic acid). This compound is found in the water distilled from the disintegrated seeds or leaves of amygdalus, prunus, laurus, etc. It is also found among the products of the destruc- tive distillation of coal, and is formed by a great number of chemical decompositions. For instance : passing ammonia over red-hot charcoal : 4NH3 + 3C = 2(NH4CN') + CH4. Ammonia. Carbon. Ammonium cjanide. Methane. the action of ammonia on chloroform : Chloroform. CHClg + NH3 = HCJf + 3HC1. Hydrocyanic acid. Hydrochloric acid. By heating ammonium formate to 200° C. (392° F.): NH4CH02 = HCN + 2H20. Ammonium formate. Hydrocyanic acid. Water, By the action of hyclrosulphuric acid upon mercuric cyanide: Hg2CN + H2S = HgS + 2HCN. By the decomposition of alkali cyanides by diluted acids : KCN + HC1 = KC1 + HCN. By the action of hydrochloric acid upon silver cyanide: AgCN + HC1 = AgOl + HCN. AMINES AND AMIDES. CYANOGEN COMPOUNDS. 357 By distilling potassium ferrocyanide with diluted sulphuric acid: 2(K4Fe6CN) + 6(H2S04) = K2Fe26CN + 6(KHS04) + 6HCN. Potassium ferrocyanide. Sulphuric acid. Potassium ferrous ferrocyanide. Potassium acid sulphate. Hydrocyanic acid. Experiment 55. Place 20 grams of potassium ferrocyanide and 40 c.c. of water into a boiling-flask of about 200 c.c. capacity; provide the flask with a funnel- tube and connect it with a suitable condenser, the exit of which should dip into 60 c.c. of diluted alcohol, contained in a receiver, which latter should be kept cold by ice during the operation. After having ascertained that all the joints are tight, add through the fuunel tube a previously prepared mixture of 15 grams of sulphuric acid and 20 c.c. of water. Apply heat and slowly distil until there is little liquid left with the salts remaining in the flask. Determine the strength of the alcoholic solution of hydrocyanic acid thus prepared volumetrically and dilute it with water until it contains exactly two per cent, of HCN. Pure hydrocyanic acid is (at a temperature below 26° C. (78.8° F.) a colorless, mobile liquid, of a penetrating, characteristic odor resembling that of bitter almonds; it boils at 26.5° C. (80° F.) and crystallizes at —15° C. (5°F.). It is readily soluble in water, and a 2 per cent, solution is the diluted hydrocyanic acid, Acidum hydrocyanicum dilutum. According to the U. S. P., this diluted acid is made either by the decomposition of potassium ferrocyanide by diluted sulphuric acid in a retort, the delivery tube of which passes into a receiver containing a mixture of water and alcohol, by which the liberated gas is absorbed, this liquid being afterward diluted with a sufficient quantity of water to make a 2 per cent, solution, or it is made extemporaneously by the decomposition of 6 parts of silver cyanide by 5 parts of hydrochloric acid, diluted with 55 parts of water, allowing the silver chloride to subside and pouring off the clear liquid. The diluted acid has the characteristic odor of bitter almonds, a slightly acid reaction, and is completely volatilized by heating. Whilst the pure acid is very readily decomposed by exposure to light, etc., the dilute acid is very stable, and is rendered more so by a trace of mineral acids. Potassium cyanide, Potassii cyanidum, KCN = 65 (Cyanide of potassium). The pure salt may be obtained by passing hydro- cyanic acid into an alcoholic solution of potassium hydroxide. The commercial article, however, is a mixture of potassium cyanide with potassium cyanate. It is obtained by fusing potas- 358 CONSIDERATION OF CARBON COMPOUNDS. sium ferrocyanide with potassium carbonate in a crucible, when potassium cyanide and cyanate are formed, whilst carbon dioxide escapes, and metallic iron is set free and collects on the bottom of the crucible. The decomposition is as follows : 2(K4Fe6CN) + 2(K2C03) = 10KCN + 2KCNO + 2Fe + 2COr Potassium ferrocyanide. Potassium cyanide is a white, deliquescent salt, odorless when perfectly dry, but emitting the odor of hydrocyanic acid when moist. Potassium cyanides and other alkali cyanides show a tendency to combine with the cyanides of heavy metals, forming a number of double cyanides, such as the cyanides of sodium and silver, NaCH.AgCH, etc. Potassium carbonate. Potassium cyanide. Potassium cyanate. Iron. Carbon dioxide. Silver cyanide, Argenti cyanidum, AgCn = 133.7 (Cyanide of silver). A white powder, obtained by precipitating solution of potassium cyanide with silver nitrate. It is insoluble in water, slightly soluble in water of ammonia; evolves cyanogen when heated. Mercuric cyanide, Hydrargyri cyanidum Hg(CN)2 (Cyanide of mercury). A white, crystalline salt, obtained by dissolving mer- curic oxide in hydrocyanic acid ; it is soluble in water and alcohol and evolves cyanogen when heated. Analytical reactions for hydrocyanic acid. (Potassium cyanide, KCN, may be used.) 1. Hydrocyanic acid, or soluble cyanides, give with silver nitrate a white precipitate of silver cyanide, which is sparingly soluble in ammonia, soluble in alkali cyanides or thiosulphates, but insoluble in diluted nitric acid. Concentrated nitric acid dis- solves it with decomposition : IICN + AgN"03 = AgCN + HN03. 2. Hydrocyanic acid mixed with ammonium hydric sulphide and evaporated to dryness forms sulphocyanic acid, which upon being slightly acidulated with hydrochloric acid gives with ferric chloride a blood-red color of ferric sulphocyanate. (Excess of ammonium sulphide must he avoided.) 3. Hydrocyanic acid, or soluble cyanides, give, when mixed with ferrous and ferric salts and potassium hydroxide, a greenish precipitate, which, upon being dissolved in hydrochloric acid, AMINES AND AMIDES. CYANOGEN COMPOUNDS. 359 forms a precipitate of Prussian blue, Fe43Fe6CiSr. This reaction depends on the formation of potassium ferrocyanide by the action of the cyanogen upon both the potassium of the potassium hydroxide and the iron of the ferrous salt. In alkaline solutions, the blue precipitate does not form, for which reason hydrochloric acid is added. 4. Hydrocyanic acid heated with dilute solution of picric acid gives a deep-red color on cooling. 5. In cases of poisoning, the matter under examination is dis- tilled (if necessary after the addition of water) from a retort connected with a cooler. To the distilled liquid the above tests are applied. If the substance under examination should have an alkaline or neutral reaction, the addition of some sulphuric acid may be necessary in order to liberate the hydrocyanic acid. The objectionable feature to this acidifying is the fact that non- poisonous potassium ferrocyanide might be present, which upon the addition of sulphuric acid would liberate hydrocyanic acid. In cases where the addition of an acid becomes necessary, a pre- liminary examination should, therefore, decide whether or not ferro- or ferricyanide are present. Antidotes. Hydrocyanic acid is a powerful poison both when inhaled or swallowed in the form of the acid or of soluble cyanides. As an antidote is recommended a mixture of ferrous sulphate and ferric chloride with either sodium carbonate or magnesia. The action of this mixture is explained in the above reaction 3, the object being to convert the soluble cyanide into an insoluble ferrocyanide of iron. In most cases of poisoning by hydrocyanic acid there is, however, no time for the action of such an antidote, in consequence of the rapidity of the action of the poison, and the treatment is chiefly directed to the main- tenance of respiration by artificial means. Cyanic acid, HCNO, and Sulphocyanic acid, HCNS, are both color- less acid liquids, the salts of which are known as cyanates and sulphocyanates. These salts are obtained from alkali cyanides by treating them with oxidizing agents or by boiling their solu- tions with sulphur, when either oxygen or sulphur is taken up by the alkali cyanide : KCN -|- O = KCNO = Potassium cyanate. KCN -j- S = KCNS = Potassium sulphocyanate. 360 CONSIDERATION OF CARBON COMPOUNDS. The acids themselves may be liberated from their salts by dilute mineral acids. Sulphocyanates give with ferric salts a deep-red color, which is not affected by hydrochloric acid, but disappears on the addition of mercuric chloride. Metallocyanides. Cyanogen not only combines with metals to form the true cyanides, which may be looked upon as derivatives of hydrocyanic acid, but cyanogen also enters into combination with certain metals (chiefly iron), forming a number of complex radicals, which upon combining with hydrogen form acids, or with basic elements form salts. It is a characteristic feature of the compound cyanogen radicals, thus formed, that the analytical characters of the metals (iron, etc.) entering into the radical are completely hidden. Thus, the iron in ferro- or ferricyanides is not precipitated by either alkalies, soluble carbonates, ammonium sulphide, or any of the common reagents for iron, and its presence can only be demonstrated by these reagents after the organic nature of the compound has been destroyed by burning it (or otherwise), when ferric oxide is left, which may be dissolved in hydrochloric acid and tested for in the usual manner. The principal iron-cyanogen radicals are ferrocyanogen [Feii(CN)61]"r, and ferricyanogen [Fe2vi(CN)12i]vi. These two radicals contain iron in the ferrous and ferric state respectively, and form, upon combining with hydrogen, acids which are known as hydro- ferrocyanic acid, H4Fe(CN)6 (tetrabasic), and hydroferricyanic acid, H6Fe2(CN)12 (hexabasic); the salts of these acids are termed ferro- cyanides and ferricyanides. Potassium ferrocyanide, Potassii ferrocyanidum, K4Fe(CN)6.3H20 = 421.9 (.Ferrocyanide of 'potassium,, Yellow prussiate of potash). This salt is manufactured on a large scale by heating refuse animal matter (scrapings of horns, hoofs, hides, etc.) with potassium car- bonate and waste iron (filings, etc.). The fused mass is boiled with water, and from the solution thus formed the crystals Separate on cooling. The nitrogen and carbon of the organic matter (heated as above stated) combine, forming cyanogen, which enters into combination first with potassium and afterward with iron. Potassium ferrocyanide forms large, translucent, pale lemon- yellow, soft., odorless, non-poisonous, neutral crystals, easily dissolving in water. AMINES AND AMIDES. CYANOGEN COMPOUNDS. 361 Analytical reactions: 1. Ferrocyanides heated on platinum foil burn and leave a residue of (or containing) ferric oxide. 2. Ferrocyanides heated with concentrated sulphuric acid evolve carbonic oxide; with dilute sulphuric acid liberate hydro- cyanic acid; with concentrated hydrochloric acid liberate hydro- ferrocyanic acid. 3. Soluble ferrocyanides give a blue precipitate with ferric salts (Plate I., 5) : 3(K4Fe6CN) + 2F.*2C16 = 12KC1 + Fe4.3(Fe6CN). Potassium ferrocyanide. Ferric chloride. Potassium chloride. Ferric fen- cyanide The blue precipitate of ferric ferrocyanide, or Prussian blue, is insoluble in water and diluted acids, soluble in oxalic acid (blue ink), and is decomposed by alkalies with separation of brown ferric hydroxide and formation of potassium ferrocyanide. The addition of an acid restores the blue precipitate. 4. Soluble ferrocyanides give with cupric solutions a brownish- red precipitate of cupric ferrocyanide. (Plate III., 5.) 5. Soluble ferrocyanides produce, with solutions of silver, lead, and zinc, white precipitates of the respective ferrocyanides. 6. Ferrocyanides give with ferrous salts a white precipitate of ferrous ferrocyanide, soon turning blue by absorption of oxygen. (Plate I., 4.) Potassium ferricyanide, K6Fe2(CN)12 (Red prussiate of potash). Obtained by passing chlorine through solution of potassium ferrocyanide: 2(K4Fe6CN) + 2C1 = 2KC1 + K6Fe2(CN),2. Potassium ferrocyanide. Chlorine. Potassium chloride. Potassium ferrocyanide. While apparently this decomposition consists merely in a removal of two atoms of potassium from two molecules of potas- sium ferrocyanide, the change is actually more complete, as the atoms arrange themselves differently, the iron passing also from the ferrous to the ferric state. Potassium ferricyanide crystallizes in red prisms, soluble in water. It forms, with ferrous solutions, a blue precipitate of ferrous ferricyanide, or Turnbull'1 s blue: K6Fe2(CN)12 + 3(FeS0J = 3(K2S04) + Fe3Fe2(CN)12 With ferric solutions no precipitate is produced by potassium ferricyanide, but the color is changed to a dark olive-green. 362 CONSIDERATION OF CARBON COMPOUNDS. Nitro-cyan-methane, CH2.CN.N02 (Fulminic acid). This substance may be looked upon as a derivative of methane, CH4, in which two atoms of hydrogen are replaced by cyanogen and H02 respectively. It is not known in the separate state, but its com- binations with metals are well known, especially mercuric fulmi- nate, which is manufactured and used as an explosive in per- cussion caps, etc. It is made by adding alcohol to a solution of mercury in nitric acid. Silver fulminate can be obtained by a similar process. 48. BENZENE SERIES. AROMATIC COMPOUNDS. General remarks. It has been stated before, that all organic compounds may be looked upon as derivatives of either methane, CH4, or benzene, C6H6, these derivatives being often spoken of as fatty and aromatic compounds respectively. The term aromatic compounds was given to these substances on account of the peculiar and fragrant odor possessed by many, though not by all of them. Benzene and methane derivatives differ consider- ably in many respects, and, as a general rule, aromatic com- pounds cannot be converted into fatty compounds, or the latter into aromatic compounds without suffering the most vital de- composition of the molecule, and in most cases this transforma- tion cannot be accomplished at all. On the average, aromatic compounds are richer in carbon than fatty compounds, containing of this element at least 6 atoms; when decomposed by various methods, aromatic compounds, in many cases, yield benzene as one of the products; most aromatic Questions.—461. What are the three chief forms in which nitrogen enters into organic compounds? 462. What are amines and amides ; in what respects do they resemble ammonia compounds? 463. What is cyanogen, what is dicya- uogen, and how is the latter obtained? 464. How does cyanogen occur in nature, and which non-metallic elements does it resemble in the constitution of various compounds? 465. Mention some reactions by which hydrocyanic acid is formed, and state the two processes by which the officinal diluted acid is obtained. What strength and what properties has this acid? 466. State the composition of pure potassium cyanide and of the commercial article. How is the latter made ? 467. Give reactions for hydrocyanic acid and cyanides. 468. Explain the constitution and give the composition of ferro- and ferri- cyanides. 469. Give composition, mode of manufacture, and tests of potassium ferrocyanide. 470. What is red prussiate of potash, how is it obtained, and by what reactions can it be distinguished from the yellow prussiate? BENZENE SERIES. AROMATIC COMPOUNDS. substances have antiseptic properties, and none of them serves as animal food, although quite a number are taken into the system in small quantities, as, for instance, some essential oils, caffeine, etc. While some aromatic compounds are products of vegetable life, many of them (like benzene itself) are obtained by destruc- tive distillation, and are, therefore, contained in coal-tar, from which quite a number are separated by fractional distillation. The constitution of benzene is best explained by assuming that of the 4 X 6 = 24 affinities of the 6 carbon atoms, 18 affinities are lost by uniting the carbon atoms into a closed chain, while but 6 affinities are left unprovided for and may be saturated by other elements or groups of elements. The carbon chain of aromatic compounds and benzene may be graphically represented thus: 1 II I, 5XC\c^'C\3 I 4 H H\c/V II I H/ W \h H It has been found that whenever one atom or one radical replaces hydrogen in benzene, the product obtained is the same, no matter by what method the change was brought about. Thus we know but one mono-brom-benzene, C6II5Br, one nitro-benzene, C6H5H02, etc. It is different when two or more atoms or radicals (of the same kind) replace hydrogen in benzene, since it has been found that in this case often isomeric compounds are formed. For instance, we know three different substances which have been obtained’ by replacement of two hydrogen atoms in benzene by two hydroxyl groups. This would indicate that it makes a difference, as far as the properties of a compound are concerned, in which relative position the introduced radicals stand to one another, and while we have no proof whatever in regard to this position, yet we often represent it graphically, as, for instance, in the following three cases, where the two groups OH replace hydrogen in different positions : 364 CONSIDERATION OF CARBON COMPOUNDS. OH H\cAc/0H II I h/cwc\h I H OH 0 \c/ II I H \0H I H OH H\ L ,H \cx II I h/C\c^°\h I OH Ortho-position. 1.2. Meta-position 1.3. Para-position. 1.4. Designating the hydrogen atoms in benzene with numbers, 1 2 3 4 5 6 thus: C6 H H H II H H, the above 3 compounds show that in one case the hydrogen atoms 1 and 2, in the second 1 and 3, in the third 1 an 4 have been replaced by OH. The compounds formed in this way are distinguished as ortho-, meta-, and para- compounds. The molecular formula of the above three compounds is C6H602, apparently indicating benzene in combination with two atoms of oxygen or dioxybenzene, actually they are dihydroxy 1 2 benzene. benzene, C6H4OHOH, is known as 1 3 pyro-catechin, me/a-di-hydroxy benzene, C6H4OHOH, as resorcin, 1 4 andy>ara-di-hydroxy benzene, C6II4OHOH, as hydroquinone. Benzene series of hydrocarbons. By replacing the hydrogen atoms in benzene by methyl, CH3, a series of hydrocarbons is formed having the general composition CnH2n_6. To this benzene series belong: Benzene c6h6 B. P. 80° C. Toluene c7h8 = c6h5ch3 110 Xylene c8 H10 = C6H42CH3 142 Cumene Cg Hu = C6H33CH3 151 Cymene C10HU = (C6H24CH3?) 175 Penta-methyl-benzerie c„h16 = C6tl5CH3 188 Hexa-methyl-benzene c12h18 = C66C H3 202 The first four members of this series are found in coal-tar; the fifth member, cymene, C10II14, occurs in the oil of thyme; the last two have been obtained by synthetical processes. While but one toluene is known, the higher members form quite a number of isomeric compounds. Cymene, found in the oil of thyme, is, for instance, not the tetra-methy 1-benzene, but the para-methyl- propyl-benzene, C6II4.CH3.C3II7. This compound is of interest on BENZENE SERIES. AROMATIC COMPOUNDS. 365 account of its close relation to the terpenes and camphors, which will be spoken of later. Benzene, CGH6 {Benzol). When coal-tar is distilled, products are obtained which are either lighter or heavier than water, and by collecting the distillate in water a separation into so-called light oil (floating on the water) and heavy oil (sinking beneath the water) is accomplished. Benzene is found in the light oil and obtained from it by distillation after phenol has been removed by treatment with caustic soda and some basic substances by means of sulphuric acid. Pure benzene may be obtained by heating benzoic acid with calcium hydroxide : Experiment 56. Mix 25 grams of benzoic acid with 40 grams of slaked lime and distil from a dry flask, connected with a condenser. Add to the distilled fluid a little chloride of calcium and redistil from a small flask. The product obtained is pure benzene. Notice that it solidifies when placed in a freezing mixture of ice and common salt. Observe the analogy between Experiments 56 and 40. In one case a fatty acid is decomposed by an alkali with liberation of methane, in the other an aromatic acid with liberation of benzene, the car- bonate of the decomposing hydroxide being formed in both cases. C6H5.C02H + Ca20H = CaC03 + H20 + C'6H6 Pure benzene is a colorless, highly volatile liquid, having a peculiar, pleasant odor and a specific gravity of 0.884; it boils at 80.5° C. (177° F.) and solidities at 0° C. (32° F.); it is an excellent solvent for fats, oils, resins, and many other organic substances. Nitro-benzene, C6H-.N03. When benzene is treated with con- centrated nitric acid, or with a mixture of nitric and sulphuric acids, nitro-benzene is formed: c6h6 + hno3 = c6h5no2 + h2o Experiment 57. Mix 50 c.c. sulphuric acid with 25 c.c. nitric acid ; allow to cool, place the vessel containing the mixture in water, and add gradually 5 c.c. of benzene, waiting after the addition of a few drops each time until the reac- tion is over. Shake well until all benzene is dissolved and pour the liquid into 300 c.o. of water. The yellow oil which sinks to the bottom is nitro-benzene. It may be purified by washing with water and redistilling, after removal of water and shaking with calcium chloride. Nitro-benzene is an almost colorless or yellowish oily liquid, which is insoluble in water, has a specific gravity of 1.2, a boiling-point of 205° C. (401° F.), a sweetish taste, highly poison- ous properties, even when inhaled, and an odor resembling that of oil of bitter almond, for which it is substituted under the 366 CONSIDERATION OF CARBON COMPOUNDS. narne of essence of mirbane. It is manufactured on a large scale and used chiefly in the preparation of aniline, for which see Index. Benzene-derivatives. The relation existing between methane- and benzene-derivatives may be shown by comparing the compo- sition of a few derivatives: Methane, ch4 Benzene c6h6 Methyl, CH3 Benzyl, l CLH- Phenyl, 1 5 Ethane, I0H3.CH3 Toluene, |c6h5.ch3 Methyl-methane, Methyl-benzene, Methyl-hydroxide, IciEOH Phenyl-hydroxide \ „ qti Methyl alcohol, J 3 Penol, j 0 a OH /OH Glycerin, C3H5 OH xOH Pyrogallic acid, C6H3-OH xOH Acetic acid, ch3.co2h Benzoic acid, c6h3.co2h Acetic aldehyde, CH3.COH Benzoic aldehyde, , c6h5.coh /n Ethyl-sulphonic acid, S02^q2jj5 Benzene-sulphonic Qn ,/C6H5 acid, bU2\OH Malonic acid, rH /C02H otl2\C02H Phtalic acid, rA4\Co2H Tartaric acid, r h -/2°H tl2\2002H Salicylic acid, c H /OH 6 4\002H Ethyl ether, /c2h5\0 \c2h5/u Phenyl ether, -j f c6h5\0 ic6h5xu Methyl-ethyl ether, /ch»\0 \C2H5/U Methyl-phenyl ether, anisol, 1 rCH3\ ic6h5/u The following graphic formulas may serve to illustrate the constitution of some aromatic compounds: Hydrocarbons. Alcohols. Acids. H h\0Ac/H II I A A H/ \h 1 H OH h\cAc/h II I /C\ Hy C XH I H C02H h\cA«/h II I A c Hx XH l II Benzene, C8H6. Phenol or carbolic acid, C8H5.OH. Benzoic acid, C8H5.C02H. NO. I H. .CvX .H II I /Cx A\ H/ \GS \h i OH I H CL H II I /c\ //c\ H' 'oh i C02H I H CL C02H II I /c\ A\ H< xh A Nitrobenzene, C8H5N02. Resorcin, 06H4(0H)2. Phtalic acid, C8H4(C02H)2. BENZENE SERIES. AROMATIC COMPOUNDS. 367 CH3 H .CL H II I H XH I H OH H, O .OH \c/ \C/ 11 1 . H C\c^C\0H I H OH OH. .CL CO..II \c/ C/ A A R/ \qS \0H I H Toluene, methyl-benzene, c6h5ch3. Pyrogallol, pyrogallic acid, C6H3(HO)3. Gallic acid, C6H2.C02H.(H0)a. CH3 h\cA0/0H* II I .Cv /C, H X XH I H OH I H v .CL CH., \cy %cy II 1 A .c Hx X XH I H OH I Hx ,C. .CO„H II I /C\ SsK H II I H Xylene, di-methyl-benzene, C6H5.(CH3)o. Cresol, C5H4.CH3.OH. Salicylic acid, C5H4.CO2H.OH. ch3 h\ A R II I /Cv \h c3h7 CH3 I H C H \C/ II I H/C\c^C\OH I c3h7 COH I H, ,C s H \c/ II I h/€\c^C\h I H 3ymene, methyl-propyl benzene, C6H4.CH3.C3H7. Thymol, C6H3CH3.C3H7.OH. Benzaldehyde, oil of bitter almond, C5H5.COH. The preceding graphic formulas show in the first column (besides nitro-benzene) a number of hydrocarbons, in the second column alcohols (or phenols), obtained by introducing hydroxyl into the hydrocarbon molecule, and in the third column chiefly aromatic acids, formed by introducing carboxyl, C02H, or car- boxyl and hydroxyl. Phenols. While the term phenol is generally used for carbolic acid, it also belongs to that class of substances which we may call aromatic alcohols. According to the number of hydrogen atoms replaced by hydroxyl, we find mon-atomic, di-atomic, and tri- atomic phenols, corresponding to the similarly constituted alco- hols. Phenols differ from common alcohols in not yielding alde- hydes or acids by oxidation. Carbolic acid, Acidum carbolicum, C6H5OH = 94 [Phenol). Crude carbolic acid is a liquid obtained during the distillation of coal- tar between the temperatures of 170°-190° C. (338°-374° F.), and containing chiefly phenol, besides cresol, C7H7OH, and other 368 CONSIDERATION OF CARBON COMPOUNDS. substances. It is a reddish-brown neutral liquid of a strongly empyreumatic and disagreeable odor. By fractional distillation of the crude carbolic acid, the pure acid is obtained, which forms colorless, interlaced, needle-shaped crystals, sometimes acquiring a pinkish tint; it has a character- istic, slightly aromatic odor, is deliquescent in moist air, soluble in 20 parts of water, and very soluble in alcohol, ether, chloro- form, glycerin, fat and volatile oils, etc.; it has, when diluted, a sweetish and afterward burning, caustic taste; it produces a benumbing and caustic effect, and even blisters on the skin ; it is strongly poisonous, and a powerful antiseptic agent, preventing fermentation and putrefaction to a marked degree; fusing-point 42° C. (108° F.), boiling-point 182° C. (360° F.), specific gravity 1.065. Phenol, though generally called carbolic acid, has a neutral reaction, and the constitution of an alcohol, but it readily combines with strong bases, for instance, with sodium, forming sodium phenoxide or sodium phenolate : As antidotes may be used olive oil or castor oil, a mixture of both, or a mixture of magnesia and oil. C6H3OH + jSTiiOH = 06H50Xa + II20. Tests for carbolic acid. (Use an aqueous solution.) 1. It coagulates albumin. 2. It colors solutions of neutral ferric chloride intensely and permanently blue or violet. 3. Bromine water produces, even in dilute solutions, a white precipitate of tribrom-phenol, C6H2Br3OII. 4. A fresh-cut slip of pinewood moistened with carbolic acid, and then exposed to hydrochloric acid fumes, turns blue on exposure to sunlight. 5. On heating with nitric acid it turns yellow, picric acid being formed. Creasote, Creasotum (Creasote). This is a product of the distil- lation of wood-tar, and resembles carbolic acid in many respects, especially in its antiseptic properties and its action on the skin. It is a mixture of substances, but consists chiefly of creasol, C8H10O2, and cresol, C7II80, the second member of the phenol series. BENZENE SERIES. AROMATIC COMPOUNDS. 369 From carbolic acid creasote may be distinguished by not coag- ulating albumin, by not being solidified on cooling, by not coloring ferric chloride permanently, and by its boiling-point, which should not be below 200° C. (392° F.). Sulphocarbolic acid, HC6H5S04, [Phenol-sulphonic acid). Formed by dissolving carbolic acid in strong sulphuric acid: c6h5oh + h2so4 = hc6h5so4 + h2o. Sulphocarbolate of sodium , Sodii sulphocarbolas, jSTa06H5S04.2H20, is obtained as a white soluble salt by dissolving sodium carbonate in the above acid. Sulphonic acid has been spoken of before, when it was shown that mercaptans are converted into compounds termed sulphonic acids. These acids may be looked upon as derivatives of sulphurous acids, obtained from it by replacement of hydrogen by radicals. The relation existing between carbonic and sulphonic acids may be represented by the following formulas : Carbonic acid, C0/°H CU\OH Sulphuric acid, SO /°H b°*\OH Formic acid, CO/H LU\OH Sulphurous acid, SO bU2\OH C0/CH3 lu\OH Methyl-sulphonic acid, S02^^||3 Acetic acid, Any compound carbonic acid, C J\OH Any sulphonic acid, so nUj\OH According to this view, the above sulphocarbolic acid is actually phenol- sulphonic acid, its constitution being represented by the formula, SO /CeH50 fcU2\0H • Picric acid, CrH2(N02)30H (Trinitro-phenol, Carbazotic acid). This substance is formed by the action of nitric acid on various matters (silk, wool, indigo, Peruvian balsam, etc.), and is manufactured on a large scale by slowly dropping carbolic acid into fuming nitric acid. Picric acid forms yellow crystals, which are sparingly soluble in water; it has a very bitter taste, strongly poisonous properties, and is used as a yellow dye for silk and wool, and as a reagent for albumin. While carbolic acid has but slight acid properties, picric acid behaves like a strong acid, forming salts known as picrates, most of which are explosive. Para-acetphenetidin, Phenacetine, C6H4.0(C2H5).NH(C2H30). When mononitrophenol, C6H4.N02.0H, is treated with reducing agents, the oxygen of N02 is replaced by hydrogen, and amido-phenol, C6H4OH.NH2, is formed. The methyl ether of this compound, C6H4.0(CH3).NH2, is known as anisidin, and the ethyl ether, C6H4.0(C21I5).NH2, asphenetidin. By the action of glacial acetic 370 CONSIDERATION OF CARBON COMPOUNDS. acid upon para-phenetidin one hydrogen atom in NET, is replaced by acetyl, C2H30, when para-acetphenetidin is formed. The compound is used as an anti- pyretic under the name of phenacetine. It is a colorless, odorless, tasteless powder, sparingly soluble in water, readily soluble in alcohol; it fuses at 134.5° C. (274° F.). Fresh chlorine water colors a hot aqueous solution first violet, then ruby-red. The same color is obtained by boiling 0.1 gram of phenacetine with 1 c.c. of hydrochloric acid for one minute, diluting with 10 c.c. of water, filtering when cold, and adding 3 drops of solution of chromic acid. Resorcin, C6H602 The formula indicates that this compound is a di-atomic phenol. It is formed by fusing different resins, such as galbanum, asafoetida, etc., with caustic alkalies, but it is also obtained synthetically from benzene. or r H (Meta-dihydroxy-benzene). Resorcin is a white, crystalline powder, having a somewhat sweetish taste and a slightly aromatic odor; it fuses at 118° C. (244° F.), boils at 276° C. (529° F.), and is soluble in about its own weight of water. This solution gives with ferric chloride a dark-purple color. Resorcin, when heated for a few minutes with phtalic acid in a test-tube, forms a yellowish-red mass, which, when added to a dilute solution of caustic soda, forms a highly fluorescent solution. Other fluorescent compounds are obtained by heating resorcin with very little sulphuric and either citric, oxalic, or tartaric acid, dissolving in a mixture of water and alcohol and supersaturating the solution with ammonia. Resorcin is largely used in the manufacture of certain dyes. Cymene, C10H14 or C6H4.CH3.C3H7 (Para-methyl-propyl-benzene). This hydrocarbon occurs in the oil of thyme and in the volatile oils of a few other plants; it has also been made synthetically ; it is a liquid of a pleasant odor, boiling at 175° C. (347° F.). Cymene is of special interest, because it is closely related to the terpenes and camphors, from all of which it may be obtained by comparatively simple processes. Terpenes, C10H16. This term is applied to the various isomeric hydrocarbons of the composition C10H16, which are often looked upon as compounds formed by direct addition of hydrogen to cymene. Terpenes are the chief constituents of a large number of essential oils, such as oil of turpentine, juniper, lemon, rose- mary, bergamot, lavender, etc. Terpenes are readily acted upon by many agents, and hence undergo numerous changes. One of these changes is polymerization—i. e., conversion into compounds of the composition C15H24 and C20H32, which may be effected by heating a terpene in a sealed tube, or by shaking it with concen- BENZENE SERIES. AROMATIC COMPOUNDS. 371 trated sulphuric acid or with certain other substances. Oxygen and hydrochloric acid combine directly with terpenes; dilute nitric acid oxidizes them readily with the formation of a number of organic acids; bromine and iodine convert them into cymene. Oil of turpentine, C10H16, is the terpene most largely used. It is a thin, colorless liquid of a characteristic aromatic odor, and an acrid, caustic taste; it is insoluble in water, soluble in alcohol, and an excellent solvent for resins and many other substances. When treated with hydrochloric acid gas direct combination takes place and a wrhite solid substance of the composition C10II16HC1 is formed, which is known as terpene hydrochloride, or artificial camphor, on account of its similarity to camphor both in appearance and odor. Experiment 58. Through 10 or 20 c.c. of oil of turpentine pass a current of hydrochloric acid gas for some time, or until a quantity of a solid substance has separated. Collect this substance, which is artificial camphor, upon a filter: notice its characteristic odor. Heat some of it: hydrochloric acid is set free. Terebene, C10H16, is the optically inactive modification of terpene, obtained from oil of turpentine by mixing it with sulphuric acid, distilling, washing the distilled oil with soda solution, redistilling and collecting the portions which pass over at a temperature of 156° to ,160° C. (313° to 320° F.). Terebene resembles oil of turpentine in most respects, but has not the unpleasant odor of this oil. Stearoptenes or Camphors are substances closely related to the terpenes and to cymene both in physical and chemical properties; while terpenes are liquids, camphors are crystalline solids. Borneo camphor has the composition C10H18O, while the camphor found in the camphor-trees of China and Japan has the com- position C10H16O. Camphor, C10H16O (Laurinol), forms white, translucent masses of a tough consistence and a crystalline structure; it has a characteristic, penetrating odor and poisonous properties; in the presence of a little alcohol or ether it may be pulverized; it is nearly insoluble in water, but soluble in alcohol, ether, chloroform, etc.; boiled with bromine it forms the monobromated camphor, C10H15BrO, of the U. S. P., a white crystalline substance having a mild camphoraceous odor and taste. Resins are obtained, together with the essential oils, from plants. Mixtures of a resin and a volatile oil are known as oleo-resins, 372 CONSIDERATION OF CARBON COMPOUNDS. while mixtures of a resin or oleo-resins and gum are known as gum-resins. The name balsam is also used for a certain group of oleo-resins. The resins are mostly amorphous, brittle bodies, insoluble in water, but soluble in alcohol, ether, fatty and essential oils; they are fusible, but decompose before being volatilized; they all contain oxygen and exhibit somewhat acid properties. Turpentine, the oleo-resiirof the conifers, contains besides the oil of turpentine a resin called colophony, rosin, or ordinary resin, consisting chiefly of sylvic acid, C44H6405. Copaiva balsam consists of a volatile oil aud a resin, the latter being principally copaivic acid, C20H30O2. Caoutchouc, C8H14, and gutta-percha, C10H16, are intimately re- lated to the essential oils and resins. Caoutchouc heated with sulphur combines with it (becomes “ vulcanized ”), and is then more elastic and does not become brittle when cold. Vulcanite or hard rubber is made by heating caoutchouc to a certain temperature. Of fossil resins may be mentioned amber and asphalt, the latter having most likely been formed from petroleum. Menthol, C10H20O (Mint-camphor). Found together with a terpene in oil of peppermint, and separates in crystals on cooling the oil. Menthol is insoluble in water, fuses at 36° C. (96.8° F.) and boils at *213° C. (415.4° F.). It has the characteristic odor of peppermint. Thymol, C10H14O or C3Hg.CH3.C3H..OH (Methyl-propylphenol). Thymol is found in small quantities as a constituent of the volatile oils of wild thyme, horse-mint, and a few other plants; in larger proportions it occurs in the oil of Ptychotis Ajovan (order Umbelliferse), an East-Indian plant from which thymol is now manufactured in large quantities. Thymol crystallizes in large transparent plates, has a mild odor, a peppery taste, melts at 44° C. (111° F.) and boils at 230° C. (446° F.). It is now largely used as an excellent and very valu- able antiseptic, preference being given to it on account of its com- parative harmlessness when compared with the strongly poison- ous carbolic acid. Thymol dissolved in moderately concentrated warm solution of potassium hydroxide, gives on the addition of a few drops of BENZENE SEKIES. AROMATIC COMPOUNDS. 373 chloroform a violet color, which on heating soon changes into a beautiful violet-red. Benzoic acid, Acidnm benzoicum HCrH502 or C6H5C02H — 122. Found in benzoin and some other resins; also in combination with other substances in the urine of herbivorous animals; it is obtained from benzoin by heating it carefully, when the volatile benzoic acid sublimes. It forms white, lustrous scales or friable needles, having a slight aromatic odor of benzoin, and an acid reaction; it is but slightly soluble in cold water, but easily soluble in alcohol, ether, oils, etc. Benzoic acid, when neutralized with an alkali, gives a flesh- colored or reddish precipitate of ferric benzoate on the addition of a neutral solution of ferric chloride. By neutralizing benzoic acid with either ammonium hydroxide or sodium hydroxide, the two officinal salts ammonium benzoate, iIII4C7II502, and sodium benzoate, NaC7H502.H20, are obtained. Both salts are white, soluble in water, and have a slight odor of benzoin. Oil of bitter almond, Oleum amygdalse amarae, C7H0O or C6H5C0H (.Benzalhehyde). As shown by the formula, oil of bitter almond differs from benzoic acid in containing one atom less of oxygen; in all its reactions it behaves like a true aldehyde, being, for instance, easily converted into benzoic acid by oxidation. It does not occur in a free state in nature, but is formed by a peculiar fermentation of a glucoside, amygdalin, existing in bitter almonds, in cherry-laurel, and in the kernels of peaches, cherries, etc., but not in sweet almonds. The ferment causing the de- composition of amygdalin is a substance termed emulsine, which is found in both bitter and sweet almonds. As water is required for the decomposition, the emulsine does not act upon the amygdalin contained in the same seed until water is added, when the decomposition takes place as follows : C20H27NOn + 2H20 = 2C6H1206 + HCN + C7H60. Amygdalin. Water. Glucose. Hydrocyanic acid. Oil of bitter almond.. The oil is obtained by distilling bitter almonds with water, when it distils over with hydrocyanic acid and steam, and sepa- rates as a heavy oil in the distillate. It is an almost colorless, thin liquid of a characteristic aromatic odor, a bitter and burning taste, and a neutral reaction. The 374 CONSIDERATION OF CARBON COMPOUNDS. pure oil is not poisonous, but the crude oil of bitter almond is poisonous on account of its containing hydrocyanic acid. Bitter almond water, Aqua amygdalae amaroe, is made by dissolving 1 part of the oil in 999 parts of water. Salicylic acid, Acidum salicylicum, HC7H503 or C6H40H.C02H = 138. Derived from benzene by introducing one hydroxyl and one carboxyl radical. It is found in several species of violet, and in the form of methyl salicylate in the wintergreen oil (oil of Gaultheria procumbens). May be obtained by fusing potas- sium hydroxide with salicin, a glucoside found in the bark of willow. Salicylic acid is manufactured from carbolic acid by passing carbon dioxide through sodium acid carbolate (sodium phen- oxide), when sodium salicylate remains and carbolic acid distils over: Carbolic acid. C6H5OH + NaOH = C6H5ONa + H20. Sodium hydroxide. Sodium carbolate. 2(C6H5ONa) + C02 = C6H4N aO C 02 N a + CBH5OH. Sodium carbolate. Carbon dioxide. Sodium salicylate. Carbolic acid. Sodium salicylate, thus obtained, is decomposed by hydro- chloric acid : C6H40NaC02Na + 2HCI = C6H40HC02H + NaCl. Sodium salicylate. Hydrochloric acid. Salicylic acid. Sodium chloride. Salicylic acid is a white, solid substance, odorless or of a slight aromatic odor, having a sweetish, slightly acrid taste, and an acid reaction ; it is but sparingly soluble in cold water, but readily soluble in alcohol, ether, etc.; it fuses at about 175° C. (347° F.), and sublimes at 200° C. (392° F.); it is a valuable antiseptic. Salicylic acid assumes a tine violet color with ferric chloride; this reaction is so delicate that the color may be noticed in a solution containing 1 part of salicylic acid in 500,000 parts of water. Salicylic acid, heated with sulphuric acid and resorcin, forms a green mass, which diluted with water is fluorescent. By dissolving the alkaline hydroxides in salicylic acid, the various salts may be obtained, as, for instance, sodium salicylate, 2(NaC7H603).H20, and lithium salicylate, 2(LiC7H503).H20, both of which are white, soluble salts. Phenyl salicylate, Salol, C6H4.OH.CO2.C0H5. This compound ether is a white, crystalline, tasteless powder, which is soluble in water, BENZENE SERIES. AROMATIC COMPOUNDS. 375 alcohol, ether, and benzol, and fuses at 42° C. (107.4° F.). It is used as an antiseptic and antipyretic. Phtalic acid, C,;H4.2(C02H), is a dibasic acid, which, when heated, loses water, and is converted into phtalic anhydride : C6H4.2^C02H) = H20 + C6H4C203. The latter compound, when treated with phenol in the presence of sulphuric acid, forms phenol-phtalem : 2(C6H60) + c8h4o3 = H20 + C20HuO4. Phenol. Phtalic anhydride. Phenol-phtalein. A solution of phenol-phtalem shows a red or violet color in the presence of alkalies; this color is destroyed by acids. This property is made use of in alkalimetry, where phenol-phtalem serves as an indicator. Gallic acid, Acidum gallicum, HC7H505, or C6H2(H0)3.C02H = 188 (.Pyrogallol). Obtained by exposing moistened nut-galls to the air for about six weeks, when a peculiar fermentation takes place, during which tannic acid is converted into gallic acid, which is purified by crystallization. The crystals contain one molecule of water, which may be expelled at 100° C. (212° F.). It is a white, solid substance, forming long, silky needles; it has an astringent and slightly acidulous taste, and an acid reaction; it gives a bluish-black color with ferric salts, and does not coagulate albumin; by heating it is decomposed into carbon dioxide and pyrogallic acid, C6H603, a substance which is actually a tri-atomic phenol, C6H3.(HO)3. Tannic acid, Acidum tannicum, C14H10O9 = 322. There are a number of tannic acids, or tannins, found in various parts of dif- ferent plants (oak-bark, nut-galls, cinchona, coffee, tea, etc.), the composition of which is not identical with the above formula; in fact, some tannins have been shown to be glucosides. All tannins, however, are amorphous, have a faint acid reaction and astringent properties; they all precipitate albumin, alkaloids, ferric salts (bluish-black), and form with animal substances com- pounds wffiich do not putrefy. Use is made of this property in the process of tanning—i. e., converting hides into leather. The officinal tannic acid is obtained by extracting nut-galls with ether and alcohol, and evaporating the solution. Tannic acid forms light-yellowish, amorphous scales, having a 376 CONSIDERATION OF CARBON COMPOUNDS. faint and characteristic odor, a strongly astringent taste, and an acid reaction ; it is easily soluble in water and diluted alcohol. Analytical reactions ; Tannic acid forms with ferric salts a bluish- black precipitate (ink), and also precipitates gelatine, alkaloids, albumin, gelatinized starch, and solution of tartar emetic. Naphthalene, C10H8. The constitution of all benzene-derivatives considered so far, may be explained by the introduction of radicals in benzene. Naphthalene and its derivatives must be assumed to be formed by the union of two benzene residues in such a way that they have two carbon atoms in common, as represented in these formulas : H H I I H 0 XH X XCX I II I H/C'^C'/ \cx>C'xH I I H H H OH I I X XCT I II I, H/'C'^C'/CNsC^C!\h I I H H Naphthalene has been mentioned as a product of the destructive distillation of coal, and is obtained from that portion of coal- tar which boils between 180° and 220° C. (856° and 428° F.). This distillate is treated with caustic soda and then with sulphuric acid and distilled with water vapor. Naphthalene, Ci0H3. Naphthol, C10H7.OH. When pure, naphthalene forms colorless, lustrous crystalline plates, having a penetrating but not unpleasant odor and a burn- ing, aromatic taste. It fuses at 80° C. (176° F.), and boils at 216° C. (421° F.), but volatilizes readily with water vapor. It is only sparingly soluble in water, but easily soluble in alcohol, ether, chloroform, etc. Impure naphthalene assumes, when ex- posed to light, a reddish or brownish color. Naphthalene is con- verted into phtalic acid by oxidizing agents. Naphthol, C10H-OH. This compound bears to naphthalene the same relation as phenol to benzene—i. e., hydroxyl replaces hydro- gen in the respective hydrocarbons. Two isomeric naphthols are known, which differ in their physical properties and in their physiological action. The naphthol which is used medicinally is a solid compound crystallizing in thin, shining plates, having an odor similar to phenol and a burning, acrid taste. It fuses at 125° C. (257° F.), boils at 286° C. (517° F.), is soluble in about BENZENE SERIES. AROMATIC COMPOUNDS. 377 1000 parts of cold or 75 parts of boiling water; and readily soluble in alcohol, ether, chloroform, and fatty oils. The aqueous solution is colored green by ferric chloride. Some of the substitution-products of naphthol are used as dyes, as, for instance, dinitro-naphthol, C10H5(XO2)2.OH, which is known as Martin’s yellow. Santonin, C15H1803. Although many efforts have been made to disclose the constitution of santonin, and though many deriva- tives of it have been formed, we know as yet but little of its structure; several reactions, however, point to a relationship between santonin and naphthalene, for which reason it is men- tioned in this place. Santonin is the active principle of wormseed, the unexpanded flower-heads of Artemisia. It crystallizes in colorless prisms, which turn yellow on exposure to light; it is but sparingly soluble in water, more soluble in alcohol and ether; it has dis- tinct acid properties, combining with strong bases, as, for in- stance, with sodium hydroxide, forming the officinal santoninate of sodium, 2(NaC15H1904).7H30. Santonin solutions give a white precipitate with silver, zinc, and mercurous salts; with an alcoholic solution of potassium hydroxide they yield a scarlet-red liquid, which gradually becomes colorless. Santonin taken internally confers upon the urine a dark color resembling the color of urine containing bile; upon heating such urine it turns cherry-red or crimson, the color dis- appearing on the addition of an acid, and reappearing on neutralization. Questions.—471. What is the difference between fatty and aromatic com- pounds, and from which two hydrocarbons are they derived? 472. From what source is benzene obtained, how can it be made from benzoic acid, and what are its properties? 473. Give the graphic formulas of benzene, nitro-benzene, cymene, phenol, thymol, benzoic acid, and salicylic acid. Mention methane- derivatives which have a constitution analogous to that of the substances mentioned. 474. Give composition, properties, and mode of manufacture of, and tests for carbolic acid. What relation exists between this acid and creasote? 475. What substances are known as terpenes, where are they found in nature, and how are they related to camphors? 476. What relation exists between benzoic acid and oil of bitter almond? 477. What is the source of amyg- dalin, to which class of substances does it belong, and what are the products of its decomposition under the influence of emulsine ? 478. Explain the process for the manufacture of salicylic acid from phenol, and state its properties. 479. Give composition and properties of naphthalene and naphthol? 480. Give tests for tannin, state the source from which it is derived, and for what it is used. 378 CONSIDERATION OF CARBON COMPOUNDS. 49. BENZENE DERIVATIVES CONTAINING NITROGEN. Aniline, Phenyl-amine, C6H.NH2. The constitution of amines, to which class aniline belongs, has been considered in chapter 47. Aniline is found in coal-tar and in hone-oil; it is manufactured on a large scale by the action of nascent hydrogen upon nitro- benzene, iron and hydrochloric acid being generally used for generating the hydrogen. Experiment 59. Dissolve 20 c.c. of nitro-benzene (this may be obtained according to the directions given in Experiment 57, using larger quantities of the material) in alcoholic ammonia and pass through this solution sulphuretted hydrogen as long as a precipitate of sulphur is produced; the reaction takes place thus: C6H.N02 + 3H2S = C6H5NH2 + 2H20 + 3S. Evaporate on a water-bath to expel ammonium sulphide and alcohol; add to the residue dilute hydrochloric acid, which dissolves the aniline, but leaves any unchanged nitro-benzene undissolved. Separate the nitro-benzene from the aniline chloride solution, evaporate this to dryness, mix with some lime, in order to liberate the aniline, which may be obtained by distillation from a dry flask. Pure aniline is a colorless, slightly alkaline liquid, having a peculiar, aromatic odor, a bitter taste, and strongly poisonous properties. It boils at 184.5°C. (364° F.). Like all true amines, it combines with acids to form well-defined salts. Aniline dyes. The crude benzene used in the manufacture of aniline dyes is generally a mixture of benzene, C6H6, and toluene, C7II8. This mixture is first converted into nitro-benzene, C6H5lSr02, and nitro-toluene, C7H71N02, and then into aniline, C6H5NH2, and toluidine, C7H7NH2. When these substances are treated with oxidizing agents, such as arsenious and arsenic oxides, hypo- chlorites, chromic or nitric acid, etc., various substances are obtained which are either themselves distinguished by beautiful colors or may be converted into numerous derivatives showing all the various shades of red, blue, violet, green, etc. As an instance of the formation of an aniline dye may be mentioned that of rosaniline, which takes place thus: C6H7N + 2C7egN + 30 = C20H19N3 + 3H20. Auiline. Toluidine. Kosaniline. Experiment 60. To some of the aniline obtained by performing Experiment 59 add a little solution of bleaching powder: a beautiful purple color is obtained. Treat another portion with sulphuric acid to which an aqueous solution of BENZENE DERIVATIVES CONTAINING NITROGEN. 379 potassium dichromate has been added: a blue color is produced. A third quantity treat with solution of cupric sulphate and potassium chlorate : a dark color is the result. Antifebrine, Acetanilid, C8H9NO or C6H5.NH.C2H30. The term anilid is used for derivatives of aniline obtained from this com- pound by replacement of the ammonia hydrogen (or amido hydrogen) by radicals, and according to the introduction of an alcohol radical or acid radical a distinction is made between “alcohol anilids” and u acid anilids.” If the radical used for replacing the hydrogen in aniline is acetyl, C2H30, the radical of acetic acid, the resulting compound is acetanilid, the constitution of which is represented in the /Q JJ formula NII\q6jj5q It is obtained by boiling together for one or two days equal weights of pure aniline and glacial acetic acid, distilling and collecting the portion which passes over at a temperature of about 295°C. (563° F.). The distillate solidifies on cooling and may be purified by recrystallization from solu- tion in water. Pure acetanilid forms white, odorless crystals of a silken lustre and a greasy feeling to the touch. It fuses at 112° C. (234° F.) and boils at 295° C. (563° F.); it is but slightly soluble in cold, much more soluble in hot water, readily soluble in alcohol and ether; the solutions have a neutral reaction. Antipyrine, CuH12N20 or C9H6N0(CH3)2N20 (Dimethyl-oxyquinizme). Hydrazine compounds are substances derived from the hypo- thetical body H2II4 (or IsII2—NH2) by replacement of hydrogen atoms by alcohol radicals. They possess strong basic properties and unite directly with acids, like amines or amides. Of interest is phenyl-hydrazine, C6H5.NH.JSTH2, because it furnishes when heated with diacetie ether, pj a 8U^stance known as methyl-oxyquinizine, C10H10H2O. (Quinizine is the name given to a hypothetical base of the composition C9II10N2.) In methyl-oxyquinizine a second hydrogen atom may be re- placed by methyl, when dimethyl-oxyquinizine is formed, which is the substance to which the name antipyrine has been given. Antipyrine is a white, crystalline, odorless powder, having a slightly bitter taste; it fuses at 110° to 113° C. (230° to 235° F.), is soluble in less than its own weight of water, in one part of alcohol, in one part of chloroform, hut only in 50 parts of ether. 380 CONSIDERATION OF CARBON COMPOUNDS. 2 c.c. of a solution of 1 part of antipyrine in 100 parts of water is colored green by 2 drops of fuming nitric acid; this solution heated to boiling is colored red on the addition of one drop more of fuming nitric acid. 2 c.c. of a solution of 1 part of antipyrine in 1000 parts of water give with a drop of ferric chloride a deep- red color. Solution of sodium nitrite produces in solution of antipyrine a green color, or causes the formation of green crys- tals when both solutions are concentrated. Saccharine, C7H5S03N or C6H4.CO.SOJTH (.Benzoic sulphinide, Anhy- dro ortho-sulphamine-benzoic acid). This substance, discovered by Ira Kemsen (not by Fahlberg, who manufactures the compound), is a derivative of benzoic acid, C6H5.C02H, obtained from it by introducing the two bivalent radicals S02 and NEL with elimina- tion of water. The constitution is, therefore, represented by the formula n TT () \\|[ L(iU<\S02/iNJ1- Practically, saccharine is not made from benzoic acid, but from toluol, CgHg.CIIg, by a series of rather complicated synthetical processes. Saccharine is a white, amorphous or somewhat crystalline powder, having a very slight odor of oil of bitter almond, which becomes more perceptible on heating the substance. It is but sparingly soluble in water, requiring about 230 parts for solution ; this solution is slightly acid and has an extremely sweet taste, which is yet perceptible when saccharine is dissolved in 70,000 parts of water, which shows that it is about 280 times sweeter than cane-sugar, a solution of which in 250 parts of water is yet perceptibly sweet. Saccharine is soluble in alcohol and ether, and it is this latter property which is made use of in testing sugar (or other substances insoluble in ether) for saccharine. The sub- stances are treated with ether, which is filtered off and evaporated, when the saccharine may be recognized by its taste in the remain- ing residue. Pyrrole, C4H5N. Daring the destructive distillation of certain nitrogenous matters (chiefly bones), a liquid known as bone-oil is obtained, which contains a number of nitrogenous basic sub- stances, among which pyridine and pyrrole are found. Pyrrole has but weak basic properties, is insoluble in water and has an odor like chloroform. BENZENE DERIVATIVES CONTAINING NITROGEN. 381 A solution of pyrrole in alcohol, treated with iodine in the presence of oxidizing agents, such as ferric chloride, deposits after some time crystals of tetra-iodo pyrrole, C4HI4N. This compound is used under the name of iodol. It is a pale-yellow, crystalline powder, almost insoluble in water, soluble in 3 parts of alcohol, 1 part of ether, and 15 parts of fatty oils; it is, when pure, taste- less and odorless, and contains of iodine 88.97 per cent. Pyridine, C5H.N. This substance has been mentioned above as being a constituent of bone-oil. Other substances have been isolated from this oil and have been found to form a homologous series: Pyridine, C5H5N Picolino, C6H7N Lutidine, C7H9 Collidine, C8HulSr Pyridine is of special interest, because it has been found that several of the alkaloids, such as quinine, cinchonine, etc., when oxidized, yield acids containing nitrogen, which bear to pyridine the same relation that benzoic acid bears to benzene, or that acetic acid bears to methane. Thus, when nicotine is treated with oxidizing agents, nicotinic acid, C6H5N02, is obtained, which, when distilled with lime, breaks up into pyridine and carbon dioxide, thus: c5h3no2 = C5H5N + C02. The relation of nicotinic acid to pyridine, of benzoic acid to benzene, acetic acid to methane, may be shown thus : CH.S II c6h5.h Benzene. c5h4n.h ch3 co2h Methane. c6h..co2h Pyridine. c5h4n.co2h. Acetic acid. Benzoic acid. Nicotinic acid. Pyridine is also obtained together with another basic substance, termed quinoline, C9II7X, by distilling quinine or cinchonine with potash. These observations, showing an intimate relationship between alkaloids and the pyridine and quinoline bases, have led to numerous experiments made with the view of either solving the problem of making alkaloids synthetically, or of obtaining substances which might have physiological actions similar to those of the alkaloids. The result of these efforts has been the introduction into the materia medica of quite a number of new remedies. Pyridine is a colorless liquid, having a sharp, characteristic 382 CONSIDERATION OF CARBON COMPOUNDS. odor, strongly basic properties, and a boiling-point of 116° C. (241° F.). Quinoline, C9H7N (Chinoline), has been mentioned above as a product of the distillation of quinine with potash; it may also be obtained by the action of sulphuric acid upon a mixture of aniline, nitro-benzene, and glycerin. It is, like pyridine, a colorless liquid, but its aromatic odor is less pleasant and its basic proper- ties are less marked than those of pyridine. Boiling-point 237° C. (458° F.). Kairine, CnH15.N0.HCl. The name kairine has been given to the hydrochloride of oxy-quinoline-ethyl-hydride. It is a white, crystalline, odorless powder, soluble in 6 parts of water or in 20 parts of alcohol. Thalline, CH10N.O.OH3 (Tetra - hydro - paramethyl- oxyquinoline). Quinoline serves in the manufacture of thalline, a white, crystal- line substance, which has an aromatic odor, fuses at 40° C. (104° F.) and is soluble in water, alcohol, and ether. The most char- acteristic feature of the substance is, that it is colored intensely green by various oxidizing agents, such as ferric chloride and others. Some of the salts of thalline, chiefly the sulphate, tar- trate, and tannate, have been used medicinally. 50. ALKALOIDS. General remarks. The basic substances found in plants are grouped together under the name of alkaloids, this term signi- fying alkali-like, in allusion to the alkaline or basic properties of these substances. They belong either to the amines (compounds containing carbon, hydrogen, and nitrogen only), or to the amides (compounds containing, besides the three elements named, also Questions.—481 - From what, and by what process is aniline obtained ; what is its composition and what its constitution? 482. How are aniline dyes manu- factured from aniline? 483. What is the difference between an amide and an anilid? 484. What is the composition of antifebrine, and how is it made? 485. State the properties and some reactions characteristic of antipyrine. 486. What is saccharine, and what are its properties? 487. Mention some constituents of bone-oil. 488. State the composition of iodol. 489. Explain the relation exist- ing between methane, benzene, pyridine, and the compounds obtained from these three bodies by introducing carboxyl. 490. Mention two processes by which, and two sources from which pyridine may be obtained. ALKALOIDS. 383 oxygen), and show their derivation from ammonia to a more or less marked degree, as, for instance, in their power to combine with acids without elimination of water, to combine with platinic chloride to form insoluble double compounds, etc. The compounds formed by the direct combination of alkaloids with acids are, in the case of oxygen acids, named like other salts of these acids, for instance, sulphates, nitrates, acetates, etc. In the case of halogen acids, however, a different method has been adopted, because it would be incorrect to apply the terms chlo- rides and bromides to substances formed not by the combination of chlorine or bromine with other substances, nor by the replace- ment of hydrogen in the respective hydrogen acids of these ele- ments, but by direct combination of these acids with the alkaloids. The terms hydrochloride and hydrobromide would have been very appropriate, but the terms hydrochlorate and hydrobromate have been adopted for the compounds obtained by direct union to alkaloids with hydrochloric and hydrobromic acids. Alkaloids are found in the leaves, stems, roots, barks, and seeds of various plants; it often happens that a certain alkaloid is found in the different species of one family, and it is also often the case that various alkaloids of a similar composition are found in the same plant. General properties of alkaloids : 1. They combine with acids (without elimination of water (to form well-defined salts, and are set free from the solutions of these salts by alkalies and alkaline carbonates. 2. Those containing no oxygen (amines) are (in most cases) volatile liquids, those containing oxygen (amides) are non-volatile solids. 3. The volatile alkaloids have a peculiar, disagreeable odor re- minding of ammonia; the non-volatile alkaloids are odorless. 4. Most solid alkaloids fuse at a temperature above 100° C. (212° F.) without decomposition, but are decomposed when the heat is raised much beyond the fusing-point. 5. Most alkaloids are insoluble, or nearly so, in water, but soluble in alcohol, chloroform, benzene, acetic ether, and many also in ether. 6. The chlorides, sulphates, nitrates, acetates (and most other salts) of alkaloids are either soluble in water, or in water which has been slightly acidulated, and also in alcohol; but they are 384 CONSIDERATION OF CARBON COMPOUNDS. insoluble, or nearly so, in ether, acetic ether, chloroform (except veratrine and narcotine), amyl alcohol (except veratrine and quinine), benzene, and benzin. 7. The solid alkaloids, as well as their salts, may be obtained in a crystalline state. 8. Most alkaloids are white. 9. Most alkaloids have a very strong, generally bitter taste. 10. Most alkaloids act very energetically upon the animal system. 11. From the aqueous solutions of alkaloid salts, the solid alkaloids are precipitated by alkaline hydroxides, in an excess of which reagents some alkaloids (morphine, for instance) are soluble. Alkaline carbonates and bicarbonates liberate all, and precipitate most alkaloids; not precipitated by bicarbonates are strychnine, brucine, veratrine, atropine, and a few rare alkaloids. Most alkaloids give precipitates with tannic acid, picric acid, phospho-molybdic acid, potassium-mercuric iodide; and the higher chlorides of platinum, gold, and mercury. 12. Most alkaloids give beautiful color reactions when treated with oxidizing agents, such as nitric acid, chloric acid, chromic acid, ferric chloride, chlorine water, etc. A solution of potassium-mercuric iodide (KI)2.HgI2, made by dissolving 13.546 grams mercuric chloride and 49.8 grams potassium iodide in 1000 c.c. of water, is known as Mayer's reagent. This precipitates all alkaloids, forming with them white or yellowish-white, generally crystalline compounds of definite composition, for which reason this solution is used for volumetric determination of alkaloids. (In most cases the alkaloid replaces the potassium in the potas- sium-mercuric iodide.) Phospho molybdic acid, mentioned above as a reagent for alkaloids, is prepared as follows: 15 grams ammonium molybdate are dissolved in a little ammonia water and diluted with water to 100 c.c. This solution is poured gradually into 100 c.c. of nitric acid, specific gravity 1.185, and to this mixture is added a warm 6 per cent, solution of sodium phosphate as long as a precipitate is pro- duced. This precipitate is collected on a filter, washed and dissolved in very little sodium hydroxide solution ; the solution is evaporated to dryness, further heated until all ammonia has been expelled and the residue dissolved in 10 parts of water. To this solution is added a quantity of nitric acid sufficient to redis- solve the precipitate which is formed at first. This reagent gives precipitates not only with the alkaloids, but also with the salts of potassium and ammonium. General mode of obtaining alkaloids. The disintegrated vege- table substance (bark, seeds, etc.) is extracted with acidified water, which dissolves the alkaloids. When the alkaloid is PLATE VI. ALKALOIDS Morphine with solution of ferric chloride. 1 2 Morphine with nitric acid. Codeine with sulphuric acid con- taining one per cent, of molybdic acid. 3 4 Quinine treated with chlorine water and ammonium hydroxide. 5 Strychnine with sulphuric acid and potassium dichromate. 6 Brucine dissolved in nitric acid and treated with stannous chloride. 7 Atropine treated with sulphuric acid and potassium dichromate. 8 Veratrine treated with sulphuric acid. ALKALOIDS. 385 volatile, it is obtained from this solution by distillation, after having been liberated by an alkali. Hon-volatile alkaloids are precipitated from the acid solution by the addition of an alkali, and the impure alkaloid thus obtained is purified by again dissolving in an acid and reprecipi- tating, or by dissolving in alcohol and evaporating the solution. Antidotes. In cases of poisoning by alkaloids the stomach- pump and emetics (zinc sulphate) should be applied as soon as possible; astringent liquids may be given, because tannic acid forms insoluble compounds with most of the alkaloids. In some cases special physiological antidotes exist, and should be used. Detection of alkaloids in cases of poisoning. The separation and detection of poisonous alkaloids in organic matter (food, contents of stomach, etc.), especially when present in very small quanti- ties, as is generally the case, is one of the most difficult tasks of the toxicologist, and none but an expert who has made himself thoroughly familiar with the methods of discovering minute quantities of organic poisons in the animal system should undertake to make such an analysis in case legal proceedings depend on the result of the chemist’s report. Of the various methods applied for the separation of alkaloids from organic matter, the following may be mentioned: The substance to be examined is properly comminuted (if this be necessary) and repeatedly digested at 40° to 50° C. (104° to 122° F.) with water slightly acidulated with sulphuric acid. The filtered liquids (containing the sulphates of the alkaloids) are evaporated over a water-bath to a thin syrup, which is mixed with three or four times its own volume of alcohol; this mixture is digested at about 35° C. (95° F.) for several hours, cooled, filtered, and again evaporated nearly to dryness. (By this treatment with alcohol many substances soluble in the acidified water, but insoluble in diluted alcohol, are eliminated and left on the filter, whilst the alkaloids remain in solution as sulphates.) A little water is now added to the residue, and this solution, which should yet have a slight acid reaction, is shaken with about three times its own volume of acetic ether, which dissolves some coloring and extractive matters, but does not act upon the alkaloid salts. The two strata of liquids which form on standing in a tube are separated by means of a pipette and the operation is repeated, if necessary, i. e., if the ether should have been strongly colored. The remaining acid aqueous solution is next slightly supersaturated with sodium carbonate, which liberates the alkaloids. Upon now shaking the solu- tion with acetic ether, all alkaloids are dissolved in this liquid, which, after being separated from the aqueous solution, leaves upon evaporation, at a low tem- perature, the alkaloids generally in a sufficiently pure state for recognition by 386 CONSIDERATION OF CARBON COMPOUNDS. t special tests. It may, however, be necessary to purify the residue further by neutralizing with an acid, allowing to crystallize in a watch-glass, and separating the small crystals from adhering mother-liquor. The above method for detecting alkaloids in the presence of organic matter, generally answers the requirements of students. The practical toxicologist has in most cases of poisoning some data (deduced from the symptoms before death, or from the results of the post-mortem exam- ination) pointing to a certain poison, which, of course, facilitate his work con- siderably. Important alkaloids. a. Liquid and volatile alkaloids. Coniine, c8h17n Conium maculatum. Nicotine, c10hun2 Tobacco plant. b. Solid and fixed alkaloids. Morphine, C17H19N03 10.00 per cent. Codeine, c18h,1no3 0.25 “ Thebaine, C19H2iN03 0.15 “ Papaverine, c21h21no4 1.00 “ Narcotine, Narceine, c22h23no7 c23h29no9 Ci7H19N04 c20h19no5 c20h23no4 1.30 “ 0.70 “ In opium. Pseudo-morphine, Protopine, Codamine, less than 0.1 r>er cent. The percentages given are an average, but vary widely. Laudamine, c21h27no4 Meconidine, c21h23no4 Cryptopine, Laudanosine, c21h27no4 . Quinine, C20e24N2O2 + 3H20 ] Cinchonine, CtoHooNoO 19 22 2 i- In cinchona bark. Quinidine, isomere to quinine Cinchonidine, isomere to cinchonine Strychnine, c21h22n2o2 Brucine, + (4H20) _ >- In nux vomica. Solanine, c43h71no16 ] Atropine, ■ In solanaceae. Hyoscyamine, c17h23no3 J Cocaine, c17h21no4 Erythroxylon coca. Yeratrine, c32h49no9 Veratrum officinale. Aconitine, 12 Aconitum napellus. Colchicine, c17h19no6 Colchicum autumnale. Berberine, c20h17no4 Berberis vulgaris. Hydrastine, C2iH21N06 Hydrastis canadensis. Piperine, c17h19no3 Pepper. Emetine, C2sH40N2O5 Ipecacuanha root. Sinapine, Ci6h23no6 White mustard seed. Eserine or Physostigmine, C15H21N302 Calabar bean. Pilocarpine, ChH16N202 Pilocarpus. Caffeine, H10 4^2 -f H20 Coffee, tea. Theobromine, c7 h8n4o2 Seeds of theobroma cacao. ALKALOIDS. 387 Coniine, C8H17N, occurs in conium maculatum (hemlock), ac- companied by two other alkaloids. It is a colorless, oily liquid, having a disagreeable, penetrating odor. Nicotine, C10H14N2. Tobacco leaves contain from 2 to 8 per cent, of nicotine, which is a colorless, oily liquid, having a caustic taste and a disagreeable, penetrating odor. It gives with hydrochloric acid a violet, with nitric acid an orange color. Opium is the concrete, milky exudation obtained, in Asia Minor, by incising the unripe capsules of papaver somniferum, poppy. Chemically, opium is a mixture of a large number of substances, containing besides gum, albumin, wax, volatile and coloring matter, meconic acid, meconin, etc., not less than sixteen or eighteen different alkaloids, many of which are, however, present in minute quantities. Ordinary opium should contain not less than 9 per cent., and when dried at 85° C. (185° F.) from 12 to 16 per cent, of morphine. Dried and powdered opium, after having been exhausted with ten times its weight of stronger ether (which dissolves chiefly the narcotine, but not the morphine salts), the ethereal solution filtered off’, and the weight of the opium restored by sugar of milk, forms the denarcotized opium of the U. S. P. Experiment 61. Determine quantitatively the amount of morphine in a sample of opium by using the U. S. P. method, which is as follows: Triturate in a mortar 7 grams of opium, 3 grams of freshly slaked lime, and 20 c.c. of water, until a uniform mixture results; then add 50 c.c. of water, and stir occasionally, during half an hour- Filter the mixture through a plaited filter, 3£ inches in diameter, into a stoppered flask (having a capacity of about 120 c.c. and marked at exactly 50 c.c.) until the filtrate reaches this mark. To this liquid (representing 5 grams of opium) add 5 c.c. of alcohol and 25 c.c. of stronger ether, and shake the mixture ; then add 3 grams of ammonium chloride, shake well and frequently during half an hour, and set it aside for 12 hours. Counterbalance two small filters, place one within the other in a small funnel, and decant the ethereal layer upon the filter, and afterward wash the latter with 5 c.c. of stronger ether, added slowly and in portions. Now let the filter dry in the air, and pour upon it the liquid in the bottle in such a way as to transfer the greater portion of the crystals to the filter. Wash the bottle and transfer the remaining crystals to the filter, with small portions of water, using not much more than 10 c.c. in all. After draining well, dry the filter at a temperature of about 55° C. (131° F.). Weigh the crystals in the inner filter ; counterbalancing by the outer filter. The weight of the crystals, multiplied by 20, equals the percentage of morphine. The explanation of the above process is as follows: Calcium hydroxide liber- ates the alkaloids, most of which are precipitated, while morphine is redissolved 388 CONSIDERATION OF CARBON COMPOUNDS. by the excess of calcium hydroxide; by the addition of ammonium chloride, calcium chloride and ammonia are formed, which latter causes the dissolved alkaloids to be precipitated ; ether is added in order to dissolve and eliminate traces of other alkaloids, especially narcotine, which it dissolves, whilst it does not act as a solvent of the morphine. Morphine determinations made by this method are not correct, the results obtained being invariably too low. The loss of morphine is caused by the dis- solving action of the ammonia upon the alkaloid. If, instead of 3 grams of slaked lime and 3 grams of ammonium chloride, 1.5 grams of lime and 1 gram of ammonium chloride are used, the results are higher and more correct. Morphine, Morphina, C17H19N03.H20 = 303 (.Morphia). A white crystalline powder, or colorless, shining, prismatic crystals, odor- less, of a bitter taste, and an alkaline reaction ; almost insoluble in ether and chloroform, very slightly soluble in cold water, sol- uble in 100 parts of cold and 36 parts of boiling alcohol; it fuses at 120°, losing its water; heated with excess of hydrochloric acid for some hours, under pressure, to 150° C. (302° F.), it loses water, and is converted into apmorphine, Cl7H17N02, a crystalline, solid alkaloid, valuable as an emetic. The hydrochlorate of apomorphine, C17HirN’02.HCl, is officinal; it is a white salt, which turns green when exposed to the air, especially in the presence of moisture. The above-mentioned process for the quantitative estimation of morphine in opium may be used for its manufacture, or it may be made by adding to infusion of opium an equal bulk of alcohol, then slight excess of ammonia, and setting aside for crystalliza- tion. The crude morphine thus obtained is purified by crystal- ization. Morphine combines with acids, and of the salts are officinal : Acetate of morphine, morphings acetas, CnH19N03 HC2H302.3H20 Hydrochlorate of morphine, morphinse hydrochloras, C17H19N03.HC1.3H20. Sulphate of morphine, morphings sulphas, (C17H19N03)2H2S04.5H20. The above three salts are white, and soluble in water. Analytical reactions for morphine 1. Nitric acid first reddens morphine, and then renders it yellow. (Plate VI., 2.) 2. Strong neutral solution of ferric chloride causes a blue color with morphine or with neutral solutions of morphine salts; the color is changed to green by an excess of the reagent, and is destroyed by free acids or alcohol, but not by alkalies. (Plate VI., 1.) ALKALOIDS. 389 3. A fragment of iodic acid added to a strong solution of a morphine salt is decomposed, with liberation of iodine, which imparts a violet color to chloroform upon shaking the latter with the mixture. 4. A mixture of 1 part of morphine and 4 parts of cane-sugar added to concentrated sulphuric acid gives a dark-red color, which is intensified by a drop of bromine water. 5. Morphine dissolves in cold, concentrated sulphuric acid, forming a colorless solution, which, after standing for several hours, turns pink on the addition of a trace of nitric acid. 6. Aqueous or acid solutions of morphine salts are precipitated by alkaline hydroxides; the precipitated morphine is soluble in potassium or sodium hydroxide, but not in ammonium hydroxide. 7. Neutral solutions of morphine afford yellow precipitates with the chloride of gold or platinum, with potassium chromate or dichromate, and with picric acid, but not with mercuric chloride. Codeine, Codeina, C18H21N03.H20 = 317. A white or yellowish- white, crystalline powder, sparingly soluble in cold water, easily soluble in alcohol and chloroform. 1. Codeine, dissolved in sulphuric acid containing 1 per cent, of sodium molybdate, forms at first a dirty-green solution, which after a while becomes pure blue, and gradually fades within a few hours to pale yellow. (Plate VI., 3.) Analytical reactions : 2. Codeine, dissolved in sulphuric acid, forms a colorless liquid, which, upon being warmed with a trace of ferric chloride, becomes deep blue. 3. Codeine forms with chlorine water a colorless solution, which turns yellowish-red with ammonium hydroxide. Narcotine, C22H23N07, and Narceine, C23H29N09.2H20, are white, crystalline opium alkaloids, which are almost insoluble in water, soluble in alcohol. Concentrated sulphuric acid forms with narcotine a solution which is at first colorless, but turns yellow in a few minutes, and purple on heating. Narceine dissolves in concentrated sulphuric acid with a gray-brown color, which changes to red when heated. Meconic acid, C7H407.3H20. A tribasic acid, characteristic of opium, in which it exists most likely combined with the alkaloids. 390 CONSIDERATION OF CARBON COMPOUNDS. It is a white, crystalline substance, soluble in water and alcohol. Meconic acid forms with ferric chloride a blood-red color, which is not affected by dilute acids or by mercuric chloride (different from ferric sulphocyanate), but disappears on the addi- tion of stannous chloride and of the alkaline hypochlorites. This test may be used in cases of poisoning to decide whether opium or morphine is present. Cinchona alkaloids. The bark of various species of cinchona contains a number of alkaloids, of which the most important are quinine, cinchonine, quinidine, and cinchonidine. These alkaloids exist in the bark in combination with a peculiar acid, termed kinic acid. The quantity and relative proportion of the alkaloids vary widely in different barks, but the officinal bark should contain not less than 3 per cent, of alkaloids. Determination of the total alkaloids and of quinine in Cinchona. The U. S. P. has adopted the following method for the quantitative estimation of the cinchona alkaloids : Powdered cinchona bark is thoroughly mixed with milk of lime, containing of calcium oxide about one-fourth of the weight of cinchona used. This mixture, which now contains the alkaloids in an uncombined state, is dried at a temper- ature not above 80° C. (176° F.), and then exhausted by hot alcohol, which dis- solves the alkaloids. The filtered alcoholic solution is slightly acidulated with sulphuric acid, and then evaporated to expel the alcohol. The residue is mixed with a little water, and the clear solution, containing the alkaloids as sulphates, is precipitated by sodium hydroxide. The precipitated alkaloids are collected on a small filter, washed and dried at 100° C. (212° F.). From the total alkaloids the quinine is separated by dissolving them in water acidulated with sulphuric acid, and adding to this solution (which should be just distinctly acid to test-paper, and should weigh seventy times as much as the alkaloids used) dilute solution of sodium hydroxide until exactly neutral, when the “effloresced sulphate of quinine,” (C20H24N2O2)2.H2SO4.2EI.,O, separates; this is collected on a small filter, dried at 60° C. (140° F.), and weighed. The precipitation of the salt is facilitated by heating the mixture to about 60° C. (140° F.) for five minutes, and subsequent cooling to 15° C. (59° F.) for half an hour. As sulphate of quinine is soluble in water of 15° C. (59° F.) to the extent of 0.12 per cent., the filtered liquid has to be weighed, and for every 100 grams of the filtrate 0.12 gram has to be added to the weight of the quinine sulphate collected on the filter. If the quantity of quinine in the alkaloids be too small, or the quantity of the filtered liquid too large, no separation of the salt may take place. In order to calculate from the precipitated “ effloresced sulphate of quinine” the quantity of “ crystallized sulphate of quinine,” 11.5 per cent, of its weight has to be added for water of crystallization. ALKALOIDS. 391 Quinine, Quinina, C2l)H24N202.3H20 = 378. This formula repre- sents the crystallized alkaloid, but it is also known as anhydrous, and in combination with either one or two molecules of water. The anhydrous quinine is a resinous substance, whilst the crys- tallized quinine is a white powder, having a bitter taste and an alkaline reaction. It is nearly insoluble in water, but soluble in alcohol, ether, and chloroform. Quinine sulphate, Quininae sulphas, (C20H24N2O2)2H2SO4.7H2O = 872 (Sulphate of quinine). This salt, containing two molecules of the alkaloid in combination with one of sulphuric acid and seven of water, is the common form of sulphate of quinine. It forms snow-white, loose, filiform crystals, fragile and somewhat flexible, making a very light and easily compressible mass; it has a very bitter taste and a neutral reaction; it is soluble in 740 parts of cold and in 30 parts of boiling water, soluble in 65 parts of alcohol, but nearly insoluble in ether and chloroform; it readily dissolves in diluted sulphuric or hydrochloric acid. Quinine acid sulphate, Quininae bisulphas, (C20H24N2O2)H2SO4.7H,JO = 548 (Bisulphate of quinine). This salt is formed when the common sulphate is dissolved in an excess of diluted sulphuric acid. It crystallizes in colorless, silky needles, has a strongly acid reaction, and is soluble in 10 parts of water. Hydrochlorate of quinine, C20H24N2O2.HC1.2H2O = 396.4 Hydrobromate of quinine, C20H21h[2O2.HBr.2H2O = 440.8 Yalerianate of quinine, (J20H24 N2O2.C5H10O2.H2O = 444. The abo.ve three salts are obtained by dissolving quinine in the respective acids; they are white, crystalline substances ; the first two are easily, the valerianate is sparingly soluble in water. Citrate of iron and quinine is a scale compound obtained by dissolving ferric hydroxide and quinine in citric acid, evapor- ating, etc. Analytical reactions for quinine. 1. Quinine or its salts, dissolved in water or in dilute acids, give, after having been shaken with fresh chlorine water, an emerald-green color on the addition of ammonium hydroxide. (Plate VI., 4.) 2. Solutions of quinine, treated with chlorine water, then with fragments of potassium ferrocyanide, turn pink, then red on the addition of ammonium hydroxide not in excess. 392 CONSIDERATION OF CARBON COMPOUNDS. 3. Solutions of quinine give with water of ammonia a white precipitate of quinine, which is readily dissolved in an excess of ammonia. The precipitate is also soluble in about twenty times its own weight of ether (the other cinchona alkaloids requiring larger proportions of ether for solution). 4. Most solutions of quinine, especially when acidulated with sulphuric acid, show a vivid blue fluorescence. 5. Chlorine, passed through water holding quinine in sus- pension, forms a red solution. 6. Neutral solutions of quinine are precipitated by alkaline oxalates. 7. Quinine and its salts, when heated on platinum foil, burn entirely away. 8. Quinine and its salts form colorless solutions with concen- trated sulphuric acid. A dark or red color indicates the presence of other organic substances. Cinchonine, Cinchonina, C19H22N20 = 308. This alkaloid is found in cinchona bark in quantities varying from 0.5 to 3 per cent. It crystallizes without water, forming white needles; it is almost insoluble in water, soluble in 110 parts of alcohol or in 370 parts of ether, readily soluble in dilute acids. By dissolving the alkaloid in sulphuric acid is obtained: Cinchonine sulphate, Cinchonince sulphas, (C19H22N20)2H2S04.2H20 = 750. It is a white, crystalline substance. Cinchonine differs from quinine by its greater insolubility in ether, by its insolu- bility in ammonia water, by not forming fluorescent solutions, and by not giving a green color with chlorine water and am- monia. Cinchonidine, C20H24N2O. An alkaloid isomeric with cincho- nine; soluble in 75 times its weight in ether. The sulphate is officinal. duinidine, C24H24N202. Isomeric with quinine; it gives, like the latter, a green color with chlorine water and ammonia, and forms fluorescent solutions. Unlike quinine, it is not precipi- tated from neutral solutions by alkaline oxalates. Strychnine, Strychnina, C21H22N202 = 334. This alkaloid is found, together with brucine, in the seeds and bark of different varieties of strychnos, and is generally obtained from nux ALKALOIDS. 393 vomica. Strychnine is a white, crystalline powder, having an intensely bitter taste, which is still perceptible in solutions con- taining 1 in 700,000. It is nearly insoluble in water and in ether, soluble in chloroform and in dilute acids. By dissolving it in sulphuric acid the officinal strychnine sul- phate, Strychninaz sulphas, (C21H22N2O2)2.H2S04.7H20 = 892, is ob- tained. Strychnine has strong basic properties and is one of the most powerful poisons known, one-quarter of a grain having caused death within a few hours. Analytical reactions of strychnine. 1. Strychnine dissolves in sulphuric acid and nitric acid with- out color. 2. A fragment of potassium dichromate, drawn through a solution of strychnine in concentrated sulphuric acid, produces momentarily a blue, then brilliant violet color, which slowly passes to cherry-red, then to rose-pink, and finally to yellow. This reaction may yet be noticed with grain of strychnine (Plate VI., 5.) 3. Strychnine, when moistened with a solution of iodic acid in sulphuric acid, produces a yellow color, changing to brick-red and then to violet-red. 4. Solutions of strychnine give with diluted solution of potas- sium dichromate a yellow, crystalline precipitate, which, w7hen collected, washed, and heated with concentrated sulphuric acid, shows the play of colors described in test 2. 5. Neutral solutions of strychnine give yellow precipitates with the chlorides of gold and platinum and with picric acid, a white precipitate with mercuric chloride. Brucine, C23H26N204.4H20. This alkaloid acts similarly to strych- nine, but less energetically, upon the animal system. It is distinguished from strychnine by giving a bright-red color with concentrated nitric acid, soon changing into yellow, whilst stan- nous chloride changes the red color to violet (Plate VI., 6); chlorine water colors brucine bright-red, changed to yellowish- brown by ammonium hydroxide. Atropine, Atropina, C17H23N03 = 289. Occurs in belladonna; it is a white, crystalline powder, having a bitter and acrid taste, 394 CONSIDERATION OF CARBON COMPOUNDS. and an alkaline reaction ; it is nearly insoluble in water, but very soluble in alcohol and chloroform. The sulphate of atropine, Atropince sulphas, (C17H23FT03)2.H2S04, is a white, crystalline pow- der, easily soluble in water. Analytical reactions: 1. Atropine dissolves in concentrated sulphuric acid without color. 2. The above solution is not colored by nitric acid (difference from morphine), and not at once by potassium dichromate (difference from strychnine). Prolonged contact with potassium dichromate causes the solution to turn green. (Plate VI., 7.) 3. The green solution obtained by the action of potassium dichromate upon atropine which has been dissolved in sulphuric acid, evolves on the addition of a few drops of water and warm- ing, a pleasant odor reminding of roses and orange flowers. A similar odor may be noticed when a fragment of atropine is heated slowly in a dry test-tube until it fuses and white fumes begin to appear, heating this mass with a few drops of concen- trated sulphuric acid until it commences to turn brown, and then adding at once, but carefully, about two volumes of water. 4. Solutions of atropine dilate the pupil of the eye to a marked extent. 5. One milligram of atropine, mixed well with an equal weight of sodium nitrate and 3 drops of sulphuric acid, gives a yellowish- red mixture, which turns violet on adding, carefully, an aqueous solution of sodium lrydroxide, until supersaturated. Hyoscyamine, Cl7H23N03. This alkaloid is isomeric with atropine and hyoscine, and identical with daturine and duboisine. It is found in small quantities together with atropine in belladonna, in the seeds of hyoscyamus niger and albus, and in some other plants belonging to the solanacese. Hyoscyamine resembles atropine closely in most of its chemi- cal, physical, and physiological properties. Atropine fuses at 115° C. (239° F.); hyoscyamine at 108° C. (226° F.). The corre- sponding salts of the two alkaloids crystallize in different forms. Hyoscine is an amorphous alkaloid found associated with atro- pine and hyoscyamine, which alkaloids it resembles closely. Cocaine, C17H21N04. This alkaloid is found in the leaves of Erythroxylon coca in quantities varying from 0.15 to 0.65 per cent. It is a white, crystalline powder, soluble in about 1300 ALKALOIDS. 395 parts of cold and 700 parts of boiling water, easily soluble in alcohol, ether, and chloroform ; it fuses at 98° C. (208° F.). A fragment of cocaine placed on the tongue causes the sensation of numbness without acrid or bitter taste; the solution in water is faintly bitter. Cocaine heated with acids in sealed tubes is decomposed into methyl alcohol, benzoic acid, and ecgonine, showing it to be methyl-benzoyl-eegonine: C1TH21N04 + 2H20 = CH3HO + C6H5C02H + c9h13no3. Ecgonine is found in the coca leaves as benzoyl-ecgonine, C9Hl5(C7H50)N03 + 4H20; this is a white, crystalline substance from which cocaine may be obtained by heating it with methyl- iodide. The mother-liquors obtained in the manufacture of cocaine from the leaves contain the alkaloid in an amorphous state and possibly one or two other alkaloids, one of which has been named hygrine. Whether these alkaloids are contained in the coca-plant, or are products of the decomposition of cocaine, are questions not yet decided. Cocaine. Methyl alcohol. Benzoic acid. Ecgonine. Of the various salts of cocaine, the hydrochlorate, C17II2rNf)4. HC1, has been used chiefly. This salt crystallizes from alcohol in short, anhydrous prisms, from an aqueous solution, however, with two molecules of water, which are completely expelled at a temperature of 100° C. (212° F.). The anhydrous salt fuses at 182° C. (360° F.) and is readily soluble in water; this salt solu- tion has a somewhat more bitter taste than the alkaloid itself. Analytical reactions: 1. Cocaine salts are precipitated from an aqueous solution as follows : Platinum chloride produces a yellowish-white, mercuric chloride a white flocculent, picric acid a yellow pulverulent, the alkaline carbonates and hydroxides a white precipitate, which latter is soluble in ammonia. 2. To a freshly prepared solution of potassium ferricyanide add an equivalent amount of ferric chloride; with this solution of ferric ferricyanide moisten a slip of filter-paper and place on this a drop of cocaine solution. A deep-blue spot of ferric ferro- cyanide will appear shortly in consequence of the deoxidizing action of the alkaloid upon the ferricyanide. (Morphine, a few other alkaloids, and many reducing agents show the same reaction.) 3. Boil a small quantity of cocaine solution for a few minutes 396 CONSIDERATION OF CARBON COMPOUNDS. with dilute sulphuric acid; neutralize carefully with potassium hydroxide and then add a few drops of ferric chloride solution. A pale brownish-yellow precipitate of basic ferric benzoate will form. 4. To a few drops of a dilute solution add one drop of a solu- tion of potasium permanganate (1 part salt in 330 parts of water); a beautiful violet, crystalline precipitate of cocaine per- manganate is produced. Aconitine, This alkaloid is found in various species of aconitum to the amount of about 0.2 per cent. The com- mercial article is most likely a mixture of aconitine with other substances, as it is extremely difficult to obtain the alkaloid in an entirely pure form; the composition given above corresponds to the analysis of the purest obtainable article. Aconitine is one of the most poisonous substances known; there are no reliable chemical tests by which it may be readily distinguished from other alkaloids; the aqueous solution is precipitated by alkalies, tannic acid, Mayer’s reagent, and solution of iodine in potassium iodide, but not by platinic chloride, mercuric chloride, and picric acid. Characteristic is the intensely acrid taste of the alkaloid and the numbness and tingling caused by it in the mouth and throat. The greatest care should be exercised in examining aconitine for these properties. Veratrine, Veratrina, C32H49N09. An alkaloid, or a mixture of alkaloids, obtained from veratrum officinale. It is a white, amorphous, rarely crystalline powder, highly irritating to the nostrils; nearly insoluble in water, readily soluble in alcohol. Analytical reactions: 1. Concentrated sulphuric acid causes with veratrine first a yellow, then reddish-yellow, intense scarlet, and, finally, violet- red color. (Plate VI., 8.) 2. Veratrine when heated with concentrated hydrochloric acid, dissolves with a blood-red color. 3. Bromine water colors veratrine violet. 4. Veratrine forms with nitric acid a yellow solution. Hydrastine, C21H21N06. Found together with berberine in the rhizome of hydrastis Canadensis (golden seal) in quantities vary- ing from 0.1 to 0.2 per cent. Hydrastine crystallizes in four-sided, colorless prisms; it fuses at 132° C. (270° F.), is insoluble in ALKALOIDS. 397 water and benzin, soluble in about 2 parts of chloroform, 15 parts of benzene, 83 parts of ether, and 120 parts of alcohol at the ordinary temperature. Hydrastine answers to all the general tests for alkaloids: treated with concentrated sulphuric acid it shows a yellow color, turning red, then purple on heating. Concentrated nitric acid produces a yellow color, changing to orange. The fluorescence noticed in solutions of hydrastine or its salts is due to products formed from it by oxidation. While hydrastine itself crystallizes very readily, especially from solutions in acetic ether, its salts can scarcely be obtained in crystals. Berberine, C20H17NO4. Found in a nu'mber of plants (berberis vulgaris, hydrastis Canadensis, etc.) belonging to entirely different families. It is a yellow, crystalline substance, soluble in 7 parts of alcohol, 18 parts of wTater, insoluble in ether, chloroform, and benzene. Berberine not only forms well-defined, readily crystallizing salts with acids, but it also enters into combination with a number of other substances, as, for instance, with alcohol, ether, chloro- form, etc. Some of these compounds crystallize well, as, for instance, berberine-chloroform, C20H17NO4.CHCl3. The alcoholic solution of a berberine salt treated with yellow ammonium sul- phide forms crystals of berberine hydrogen polysulphide, having the composition (C20HlrN’O4)2H2S6. Caffeine, Caffeina, C8H10N4O2.H2O = 212 (Theine), occurs in coffee, tea, Paraguay tea, and a few other plants. It forms long, silky needles, which are soluble in 75 parts of water and in 35 parts of alcohol; it has a slightly bitter taste and a neutral reaction. Caffeine is dissolved by sulphuric acid without color; when treated with strong nitric acid it forms a yellow liquid which, after evaporation, assumes a purplish color when moistened with water of ammonia. Ptomaines (Cadaveric alkaloids). Basic substances (amines and amides) are also found as constituents of normal animal tissues and are formed as intermediate products of the oxidation of albuminous matter taken into the system as food. In certain pathological conditions of the body, albuminous substances (or tissues) suffer an abnormal decomposition, pro- ducing abnormal basic substances. These latter compounds, as 398 CONSIDERATION OF CARBON COMPOUNDS. well as a number of basic substances, which are products of the decomposition (putrefaction) of nitrogenous matter, are known as ptomaines. Some ptomaines are not poisonous, but most of them possess strongly toxic properties. Ptomaines show so much resemblance to vegetable alkaloids, that they have been mistaken for the latter in several cases of forensic examinations. Ptomaines not only possess the general characters of true alkaloids, but even the often highly character- istic color-tests of the latter are in some cases almost identical with those of ptomaines. Thus, ptomaines have been found which resemble in their chemical properties as well as in their physiological action upon the animal system, the alkaloids mor- phine, atropine, strychnine, coniine, digitaline, etc. Of ptomaines which have been isolated may be mentioned cadaverine, C41II2N2, from cadavers; parvoline, C9H13N, from putre- fying mackerel; animal chinoidine, from human and animal livers; tyrotoxine, from cheese and decomposing milk. It appears from recent researches that the formation of pto- maines is intimately connected with or most likely due to the existence of certain forms of bacteria. 51. ALBUMINOUS SUBSTANCES OR PROTEIDS. Occurrence in nature. Albuminous substances form the chief part of the solid and liquid constituents of the animal body; they occur in blood, tissues, muscles, nerves, glands, and all other organs; they are also found in small quantities in nearly every part of plants, and in larger quantities in many seeds. They have never yet been formed by artificial means, but are Questions.—491. State the general physical and chemical properties of alkaloids. 492. Give a general method for the extraction and separation of alkaloids from vegetables. 493. Mention the chief constituents of opium, and explain the process for determining the percentage of morphine in opium. 494. Mention the properties of morphine and its salts; give tests for them. 495. Mention the principal alkaloids found in cinchona bark, and give a process by which the total quantity of these alkaloids and of quinine may be determined. 496. State the physical and chemical properties of quinine and cinchonine. Which of their salts are officinal, and by what tests may these alkaloids be recognized and distinguished from each other? 497. Give tests for strychnine, brucine, atropine, and veratrine. 498. Into which substances is cocaine decom- posed when heated with acids in sealed tubes? 499. Mention properties of and give tests for cocaine. 500. Which two alkaloids are found in golden seal ? ALBUMINOUS SUBSTANCES OR PROTEIDS. 399 almost exclusively products of vegetable life, and undergo but little change when consumed as food and assimilated by animals. General properties. The various proteids resemble one another closely in their properties. Their composition is so complex that, as yet, no chemical formula has been assigned to them with any certainty. The percentage composition and other reasons have led to a formula represented by C144H224N36044S2, which rep- resents about the average composition of the proteids. The percentage composition is shown in the following figures: Carbon . 51.5 per cent, to 53.6 per cent. Hydrogen . . 6.7 “ “ 7.1 “ Nitrogen . 15.6 K cienceg Published Monthly, at Four Dollars Per Annum Enters upon its seventy-second year (1891) with assurances of increased usefulness. 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A Conspectus of the Medical Sciences; Containing Handbooks on Anatomy, Physiology, Chemistry, Materia Medica, Practice of Medicine, Surgery and Obstetrics. Second edition, thoroughly revised and greatly improved. In one large royal 12mo. volume of 1028 pages, with 477 illustrations. Cloth, $4.25; leather, $5.00. The object of this manual is to afford a conven- ient work of reference to students during the brief moments at their command while in attendance upon medical lectures. It is a favorable sign that it has been found necessary, in a short space of time, to issue a new and carefully revised edition. The illustrations are very numerous and unusu- ally clear, and each part seems to have received its due share of attention. We can conceive such j a work to be useful, not only to students, but to | practitioners as well. It reflects credit upon the | industry and energy of its able editor.—Boston Medical and Surgical Journal, Sept. 3,1874. We can say with the strictest truth that it is the best work of the kind with which we are ac- quainted. It embodies in a condensed form all recent contributions to practical medicine, and is therefore useful to everybusy practitioner through- out our country, besides being admirably adapted to the use of students of medicine. The book is faithfully and ably executed.—Charleston Medical Journal, April, 1875. NEILL, JOHN, M. D., and SMITH, F. G., M. D., Late Surgeon to the Penna. Hospital. Prof, of the Institutes of Med. in the TJniv. of Penna. An Analytical Compendium of the Various Branches of Medical Science, for the use and examination of Students. A new edition, revised and improved. In one large royal 12mo. volume of 974 pages, with 374 woodcuts. Cloth, $4; leather, $4.75. LUDLOW, J.L.,M.D., Consulting Physician to the Philadelphia Hospital, etc. A Manual of Examinations upon Anatomy, Physiology, Surgery, Practice of Medicine, Obstetrics, Materia Medica, Chemistry, Pharmacy and Therapeutics. To which is added a Medical Formulary. Third edition, thoroughly revised, and greatly enlarged. In one l‘2mo. volume of 816 pages, with 370 illustrations. Cloth, $3.25; leather, $3.75. The arrangement of this volume in the form of question and answer renders it espe- cially suitable for the office examination of students, and for those preparing for graduation. HOBLYN, RICHARD D., M. I). A Dictionary of the Terms Used in Medicine and the Collateral Sciences. Revised, with numerous additions, by Isaac Hays, M. D., late editor of The American Journal of the Medical Sciences. In one large royal 12mo. volume of 520 double-columned pages. Cloth, $1.50; leather, $2.00. It is the best book of definitions we hare, and ought always to be upon the student’s table .—Southern Medical and Surgical Journal. 4 Lea Brothers & Co.’s Publications—Dictionaries. THE STANDARD. THE rtaioim IUgdkjal DienonARY INCLUDING English, French, German, Italian and Latin Technical Terms used in Medicine and the Collateral Sciences, and a Series of Tables of Useful Data. John Billing, ftJ.D., LL.D., Ediij. and HadV., D.G.L, Oyoi), BY Member of the National Academy of Sciences, Surgeon U. S. A., etc. WITH THE COLLABORATION OF Prop. W. O. ATWATER. FRANK BAKER, M. D., S. M. BURNETT, M. D., W. T. COUNCILMAN, M. D., JAMES M. FLINT, M. D., J. H. KIDDER, M. D., WILLIAM LEE, M.D., R. LORINI, M. D., WASHINGTON MATTHEWS, M.D.,, C. S. MINOT, M.D. H. C. YARROW, M. D., In two very handsome royal octavo volumes containing 1574 pages,, with two colored plates. Per Volume—Cloth, $6; heather, $7; Half Morocco, Marbled Edges, $8.50. For Sale by Subscription, only. Specimen pages on application. A.ddress the Publishers. The publishers have great pleasure in presenting to the profession a new practical working dictionary embracing in one alphabet all current terms used in every depart- ment of medicine in the five great languages constituting modern medical literature. For the vast and complex labor involved in such an undertaking no one better quali- fied than Dr. Billings could have been selected. He has planned the work, chosen the most accomplished men to assist him in special departments, and personally supervised and combined their work into a consistent and uniform whole. Special care has been taken to render the definitions clear, sharp and concise. They are given in English, with synonyms in French, German and Italian of the more important words in English and Latin. Regarded as a dictionary, therefore, this standard work supplies the physician, surgeon and specialist with all information concerning medical words, simple and com- pound, found in English, giving correct spelling, clear, sharp definitions and accentua- tion, and furthermore it enables him to consult foreign works and to understand the large and increasing number of foreign words used in medical English. It is especially full in phrases comprising two, three or more words used in special senses in the various departments of medicine. The work is, however, far more than a dictionary, and partakes of the nature of an encyclopaedia, as it gives in its body a large amount of valuable therapeutical and chemi- cal information, and gftmps in its tables, in a condensed and convenient form, a vast, amount of important data which will be consulted daily by all in active practice. The completeness of the work is made evident by the fact that it defines 84,844 separate words and phrases. The type has been most carefully selected for boldness and clearness, and everything, has been done to secure ease, rapidity and durability in use. Its scope is one which will at once satisfy the student and meet all the requirements of the med- ical practitioner. Clear and comprehensive defi- nitions of words should form the prime feature of any dictionary, and in this one the chief aim seems to be to give the exact signification and the different meanings of terms in use in medicine and the collateral sciences in language as terse as is compatible with lucidity. The utmost brevity and conciseness have been kept in view. The work is remarkable, too, for its fulness. The enumera- tions and subdivisions under each word heading are strikingly complete, as regards alike the Eng- lish tongue and the languages chiefly employed by ancient and modern science. It is impossible to do justice to the dictionary by any casual illus tration. It presents to the English reader a thoroughly scientific mode of acquiring a rich vocabulary and offers an accurate an d ready means of reference in consulting works in any of the three modern continental languages which are- richest in medical literature. To add to its use- fulness as a work of reference some valuable tables are given. Another feature of the work is the accuracy of its definitions, all of which have been checked by comparison with many other standard works in the different languages it deals with. Apart from tne boundless stores of informa- tion which may be gained by the study of a good dictionary, one is enabled by the work under notice to read intelligently any technical treatise in any of the four chief modern languages. There can- not be two opinions as to the great value and use- fulness of this dictionary as a book of ready refer- ence for all sorts and conditions of medical men. So far as we have been able to see, no subject has been omitted, and in respect of completeness it will be found distinctly superior to any medical lexicon yet published.— The London Lancet, April 5,1890. Lea Brothers & Co.’s Publications—Anatomy. 5 GRAY, HENRY, F. R. S., Anatomy, Descriptive and Surgical. Edited by T. Pickering Pick, F. R. (J. S., Surgeon to and Lecturer on Anatomy at St. George’s Hospital, London, Examiner in Anatomy, Royal College of Surgeons of England. A new American from the eleventh enlarged and improved London edition, thoroughly revised and re-edited by William W. Keen, M. D., Professor of Surgery in the Jefferson Medical College of Philadelphia. To which is added the second American from the latest English edition of Landmarks, Medical and Surgical, by Luther Holden, F. R. C. S. In one imperial octavo volume of 1098 pages, with 685 large and elaborate engravings on wood. Price of edition in black: Cloth, $6; leather, $7; half Russia, $7.50. Price of edition in colors (see below): Cloth, $7.25; leather, $8.25; half Russia, $8.75. This work covers a more extended range of subjects than is customary in the ordinary text-books, giving not only the details necessary for the student, but also the application of those details to the practice of medicine and surgery. It thus forms both a guide for the learner and an admirable work of reference for the active practitioner. The engravings form a special feature of the work, many of them being the size of nature, nearly all original, and having the names of the various parts printed on the body of the cut, in place of figures of reference with descriptions at the foot. In this edition a new departure has been taken by the issue of the work with the arteries, veins and nerves distinguished by different colors. The engravings thus form a complete and splendid series, which will greatly assist the student in forming a clear idea of Anatomy, and will also serve to refresh the memory of those who may find in the exigencies of practice the necessity of recall- ing the details of the dissecting-room. Combining, as it does, a complete Atlas of Anatomy with a thorough treatise on systematic, descriptive and applied Anatomy, the work will be found of great service to all physicians who receive students in their offices, relieving both preceptor and pupil of much labor in laying the groundwork of a thorough medical education. For the convenience of those who prefer not to pay the slight increase in cost necessi- tated by the use of colors, the volume is published also in black alone, and maintained in this style at the price of former editions, notwithstanding its largely increased size. Landmarks, Medical and Surgical, by the distinguished Anatomist, Mr. Luther Holden, has been appended to the present edition as it was to the previous one. This work gives in a clear, condensed and systematic way all the information by which the practitioner can determine from the external surface of the body the position of internal parts. Thus complete, the work will furnish all the assistance that can be rendered by type and illustration in anatomical study. Lecturer on Anatomy at St. George's Hospital, London. The most popular work on anatomy ever written. It is sufficient to say of it that this edition, thanks to its American editor, surpasses all other edi- tions —Jour, of the Amer. Med. Ass'n, Dec. 31, 1887. A work which for more than twenty years has had the lead of ali other text-books on anatomy throughout the civilized world comes to hand in such beauty of execution and accuracy of text and illustration as more than to make good the large promise of the prospectus. It would be in- deed difficult to name a feature wherein the pres- ent American edition of Gray could be mended or bettered, and it needs no prophet to see that the royal work is destined for many years to come to hold the first place among anatomical text- books. The work is published with black and colored plates. It is a marvel of book-making.— American Practitioner and News, Jan. 21,1888. Gray’s Anatomy is the most magnificent work upon anatomy which has ever been published in the English or any other language.—Cincinnati Medical News, Nov. 1887. As the book now goes to the purchaser he is re- ceiving the best work on anatomy that is published in any language.— Virginia Med. Monthly, Dec. 1887. Gray’s standard Anatomy has been and will be for years the text-book for students. The book needs only to be examined to be perfectly under- stood.—Medical Press of Western New York, Jan. 1888. HOLDEN, LUTHEIt, F„ R. C. S., Surgeon to St. Bartholomew's and the Foundling Hospitals, London. Landmarks, Medical and Surgical. Second American from the latest revised English edition, with additions by W. W. Keen, M. D., Professor of Artistic Anatomy in the Penna. Academy of Fine Arts. In one 12mo. volume of 148 pages. Cloth, $L.OO. Also for sale separate— DUNGLISON, MOBLEY, JL D., Late Professor of Institutes of Medicine in the Jefferson Medical College of Philadelphia. MEDICAL LEXICON; A Dictionary of Medical Science: Containing a concise Explanation of the various Subjects and Terms of Anatomy, Physiology, Pathol- ogy, Hygiene, Therapeutics, Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Juris- prudence and Dentistry, Notices of Climate and of Mineral Waters, Formulae for Officinal, Empirical and Dietetic Preparations, with the Accentuation and Etymology of the Terms, and the French and other Synonymes, so as to constitute a French as well as an English Medical Lexicon. Edited by RrcHARD J. Dunglison, M. D. In one very large and handsome royal octavo volume of 1139 pages. Cloth, $6.50; leather, raised bands, $7.50; very handsome half Russia, raised bands, $8.00. It has the rare merit that it certainly has no rival in the English language for accuracy and extent of references.—London Medical Gazette. 6 Lea Brothers & Co.’s Publications—Anatomy. ALLEN, HARRISON, M. IX, Professor of Physiology in the University of Pennsylvania. A System of Human Anatomy, Including Its Medical and Surgical Relations. For the use of Practitioners and Students of Medicine. With an Intro- ductory Section on Histology. By E. O. Shakespeare, M. D., Ophthalmologist to the Philadelphia Hospital. Comprising 813 double-columned quarto pages, with 380 illustrations on 109 full page lithographic plates, many of which are in colors, and 241 engravings in the text. In six Sections, each in a portfolio. Section I. Histology. Section II. Bones and Joints. Section III. Muscles and Fascia. Section IV. Arteries, Veins and Lymphatics. Section V. Nervous System. Section VI. Organs of Sense, of Digestion and Genito-Urinary Organs, Embryology, Development, Teratology, Superficial Anatomy, Post-Mortem Examinations, and General and Clinical Indexes. Price per Section, $3.50; also bound in one volume, cloth, $23.00; very handsome half Russia, raised bands and open back, $25.00. For sale by subscription only. Apply to the Publishers. It is to be considered a study of applied anatomy in its widest sense—a systematic presentation of such anatomical facts as can be applied to the practice of medicine as well as of surgery. Our author is concise, accurate and practical in his statements, and succeeds admirably in infusing an interest into the study of what is generally con- sidered a dry subject. The department of Histol- ogy is treated in a masterly manner, and the ground is travelled over by one thoroughly famil- iar with it. The illustrations are made with great care, and are simply superb. There is as much of practical application of anatomical points to the every-day wants of the medical clinician as to those of the operating surgeon. In fact few general practitioners will read the work without a feeling of surprised gratification that so many points, concerning which they may never have thought before are so well presented for their con- sideration. It is a work which is destined to be the best of its kind in any language.—Medical Record, Nov. 25,1882. CLARKE, W. B., F.R. C.S. & LOCKWOOD, C. B., F.R. C.S. Demonstrators of Anatomy at St. Bartholomew's Hospital Medical School, London. The Dissector’s Manual. In one pocket-size 12mo. volume of 396 pages, with 49 illustrations. Limp cloth, red edges, $1.50. See Students’ Series of Manuals, page 31. Messrs.Clarke and Lockwood have written abook tint can hardly be rivalled as a practical aid to the dissector. Their purpose, which is “how to de- scribe the best way to display the anatomical structure,” has been fully attained. They excel in a lucidity of demonstration and graphic terseness of expression, which only a long training and intimate association with students could have given. With such a guide as this, accompanied by so attractive a commentary as Treves’ Surgical Applied Anatomy (same series), no student could fail to be deeply and absorbingly interested in the study of anatomy.—New Orleans Medical and Sur- gical Journal, April, 1884. HIRST, BARTON C., 31.1)., & FIERSOL, GEO. A., M IX Professor of Obstetrics in the University of Pennsylvania. Professor of Anatomy and Embryology in the University of Pennsylvania. Human Monstrosities. Magnificent folio, containing about 120 pages of text, illustrated with engravings, and many photographic plates from nature. In four parts, price, each, $5. Limited edition, for sale by subscription only. Address the Publishers. TREVES, FREDERICK, F. R. C. S., Senior Demonstrator of Anatomy and Assistant Surgeon at the London Hospital. Surgical Applied Anatomy. In one pocket-size 12mo. volume of 540 pages, with 61 illustrations. Limp cloth, red edges, $2.00. See Students’ Series of Manuals, page 31. BELLAMY, EJDWARJD, F. R. C. S., Senior Assistant-Surgeon to the Charing-Cross Hospital, London. The Student’s Guide to Surgical Anatomy: Being a Description of the most Important Surgical Regions of the Human Body, and intended as an Introduction to operative Surgery. In one 12mo. volume of 300 pages, with 50 illustrations. Cloth, $2.25. A System of Human Anatomy, General and Special. Edited by W. H. Gobrecht, M. D., Professor of General and Surgical Anatomy in the Medical College of Ohio. In one large and handsome octavo volume of 616 pages, with 397 illustrations. Cloth, $4.00; leather, $5.00. WILSON, ERASMUS, F. R. S. CLELAND, JOHN, M. IX, F. R. S., A Directory for the Dissection of the Human Body. In one 12mo. volume of 178 pages. Cloth, $1.25. Professor of Anatomy and Physiology in Queen's College, Qalway. HARTSHORNE’S HANDBOOK OF ANATOMY AND PHYSIOLOGY. Second edition, revised. In one royal 12mo. volume of 310 pages, with 220 woodcuts. Cloth, $1.75. HORNER’S SPECIAL ANATOMY AND HISTOL- OGY. Eighth edition, extensively revised and modified. In two octavo volumes of 1007 pages, with 320 woodcuts. Cloth, $6.00. Lea Brothers & Co.’s Publications—Physics, Physiol., Anat. 7 DRAPER, JO MX G., M. M., LL. JD., Professor of Chemistry in the University of the City of New York. Medical Physics. A Text-book for Students and Practitioners of Medicine. In one octavo volume of 734 pages, with 376 woodcuts, mostly original. Cloth, $4. FROM THE PREFACE. The fact that a knowledge of Physics is indispensable to a thorough understanding of Medicine has not been as fully realized in this country as in Europe, where the admirable works of Desplats and Gariel, of Robertson and of numerous German writers constitute a branch of educational literature to which we can show no parallel. A full appreciation of this the author trusts will be sufficient justification for placing in book form the sub- stance of his lectures on this department of science, delivered during many years at the University of the City of New York. Broadly speaking, this work aims to impart a knowledge of the relations existing between Physics and Medicine in their latest state of development, and to embody in the pursuit of this object whatever experience the author has gained during a long period of teaching this special branch of applied science. While all enlightened physicians will agree that a knowledge of physics is desirable for the medi- cal student, only those actually engaged in the teaching of the primary subjects can be fully aware of the difficulties encountered by students who attempt the study of these subjects without a knowledge of either physics or chemistry. These are especially felt by the teacher of physi- ology. It is, however, impossible for him to impart a knowledge of the main facts of his subject and establish them by reasons and experimental dem- onstration, and at the same time undertake to teach ab initio the principles of chemistry or phys- ics. Hence the desirability, we may say the necessity, for some such work as the present one. No man in America was better fitted than Dr. Draper for the task he undertook, and he has pro- vided the student and practitioner of medicine with a volume at once readable and thorough. Even to the student who has some knowledge of physics this book is useful, as it shows him its applications to the profession that he has chosen. Dr. Draper, as an old teacher, knew well the diffi- culties to be encountered in bringing his subject within the grasp of the average student, and that he has succeeded so well proves once more that the man to write for and examine students is the one who has taught and is teaching them. The book is well printed and fully illustrated, and in every way deserves grateful recognition.—The Montreal Medical Journal, July, 1890. ROBERTSOX, J. McGREGOR, 31. A., M. B., Muirhead Demonstrator of Physiology, University of Glasgow. Physiological Physics. In one 12mo. volume of 537 pages, with 219 illustra- tions. Limp cloth, $2.00. See Students’ Series of Manuals, page 31. The title of this work sufficiently explains the nature of its contents. It is designed as a man- ual for the student of medicine, an auxiliary to his text-book in physiology, and it would be particu- larly useful as a guide to his laboratory experi- ments. It will be found of great value to the practitioner. It is a carefully prepared book of reference, concise and accurate, and as such we heartily recommend it.—Journal of the American Medical Association, Dec. 6, 1884. I) ALTO X, JO MX €., M. JO., Professor Emeritus of Physiology in the College of Physicians and Surgeons, New York. Doctrines of the Circulation of the Blood. A History of Physiological Opinion and Discovery in regard to the Circulation of the Blood. In one handsome 12mo. volume of 293 pages. Cloth, $2. Dr. Dalton’s work is the fruit of the deep research of a cultured mind, and to the busy practitioner it cannot fail to be a source of instruction. It will inspire him with a feeling of gratitude and admir- ation for those plodding workers of olden times, who laid the foundation of the magnificent temple of medical science as it now stands.—New Orleans Medical and Surgical Journal, Aug. 1885. In the progress of physiological study no fact was of greater moment, none more completely revolutionized the theories of teachers, than the discovery of the circulation of the blood. This explains the extraordinary interest it has to all medical historians. The volume before us is cne of three or four which have been written within a few years by American physicians. It is in several respects the most complete. The volume, though small in size, is one of the most creditable con- tributions from an American pen to medical history that has appeared.—Med. & Surg. Rep., Dec. 6,1884. BELL, F. JEFFREY, M. A., Professor of Comparative Anatomy at King’s College, London. Comparative Physiology and Anatomy. In one 12mo. volume of 561 pages, with 229 illustrations. Limp cloth, $2.00. See Students’ Series of Manuals, page 31. The manual is preeminently a student’s book— clear and simple in language and arrangement, It is well and abundantly illustrated, and is read- able and interesting. On the whole we consider it the best work in existence in the English language to place in the hands of the medical student.—Bristol Medico-Chirurgical Journal, Mar. 1886. ELLIS, GEORGE VINER, Emeritus Professor of Anatomy in University College, London. Demonstrations of Anatomy. Being a Guide to the Knowledge of the Human Body by Dissection. From the eighth and revised London edition. In one very handsome octavo volume of 716 pages, with 249 illustrations. Cloth, $4.25; leather, $5.25. ROBERTS, JOHN B., A. M., M. JO., The Compend of Anatomy. For use in the dissecting-room and in preparing for examinations. In one 16mo. volume of 196 pages. Limp cloth, 75 cents. Lecturer in Anatomy in the University of Pennsylvania. 8 Lea Brothers & Co.’s Publications—Physiology, Chemistry. CHAPMAN, HE NET C., M. IK, Professor of Institutes of Medicine and Medical Juris, in the Jefferson Med. Coll, of Philadelphia. A Treatise on Human Physiology. In one handsome octavo volume of 925 pages, with 605 fine engravings. Cloth, $5.50; leather, $6.50. It represents very fully the existing state of physiology. The present work has a special value to the student and practitioner as devoted more to the practical application of well-known truths which the advance of science has given to the profession in this department, which may be con- sidered the foundation of rational medicine.—Buf- falo Medical and Surgical Journal, Dec. 1887. Matters which have a practical bearing on the practice of medicine are lucidly expressed; tech- nical matters are given in minute detail; elabo- rate directions are stated for the guidance of stu- dents in the laboratory. In every respect the work fulfils its promise, whether as a complete treatise for the student or for the physician ; for the former it is so complete that he need look no farther, and the latter will find entertainment and instruction in an admirable book of reference.— North Carolina Medical Journal, Nov. 1887. The work certainly commends itself to both student and practitioner. What is most demanded by the progressive physician of to-day is an adap- tation of physiology to practical therapeutics, and this work is a decided improvement in this respect over other works in the market. It will certainly take place among the most valuable text-books.— Medical Age, Nov. 25, 1887. It is the production of an author delighted with his work, and able to inspire students with an en- thusiasm akin to his own.—American Practitioner and News, Nov. 12,1887. B ALTON, JOHN C., M. Professor of Physiology in the College of Physicians and Surgeons, New York, etc. A Treatise on Human Physiology. Designed for the use of Students and Practitioners of Medicine. Seventh edition, thoroughly revised and rewritten. In one very handsome octavo volume of 722 pages, with 252 beautiful engravings on wood. Cloth, $5.00; leather, $6.00. From the first appearance of the book it has been a favorite, owing as well to the author’s renown as an oral teacher as to the charm of simplicity with which, as a writer, he always succeeds in investing even intricate subjects. Ii must be gratifying to him to observe the fre- quency with which his work, written for students and practitioners, is quoted by other writers on physiology. This fact attests its value, and, in great measure, its originality. It now needs no such seal of approbation, however, for the thou- sands who have studied it in its various editions have never been in any doubt as to its sterling worth.—N. Y. Medical Journal, Oct. 1882. Professor Dalton’s well-known and deservedly- appreciated work has long passed the stage at w hich it could be reviewed in the ordinary sense. The work is eminently one for the medical prac- titioner, since it treats most fully of those branches of physiology which have a direct bearing on the diagnosis and treatment of disease. The work is one which we can highly recommend to all our readers.—Dublin Journal of Medical Science, Feb.’83. EOSTEB, MICHAEL, 31. D., E. B. S., Prelector in Physiology and Fellow of Trinity College, Cambridge, England. Text-Book of Physiology. Hew (fourth) and enlarged American from the fifth and revised English edition, with notes and additions. In one handsome octavo vol- ume of about 900 pages, with about 300 illustrations. Beady in a few days. It is delightful to meet a book which deserves j only unqualified praise. Such a book is now before us. It is in all respects an ideal text-book. With a complete, accurate and detailed knowledge of his subject, the author has succeeded in giving a thoroughly consecutive and philosophic account of the science. A student’s attention is kept throughout fixed on the great and salient ques- A REVIEW OF THE FIFTH ENGLISH EDITION IS APPENDED. tions, and his energies are not frittered away and degenerated on petty and trivial details. Review- ing this volume as a whole we are justified in say- ing that it is the only thoroughly good text-book of physiology in the English language, and that it is probably the best text-book in any language, —Edinburgh Medical Journal. POWEB, HENBT, M. B., F. B. C. Examiner in Physiology, Royal College of Surgeons of England. Human Physiology. Second edition. In one handsome pocket-size 12mo. vol- ume of 509 pp., with 68 illustrations. Cloth, $1.50. See Students' Series of Manuals, p. 31. SIMON, W., Ph. />., M. I)., Professor of Chemistry and Toxicology in the College of Physicians and Surgeons, Baltimore, and Professor of Chemistry m the Maryland College of Pharmacy. Manual of Chemistry. A Guide to Lectures and Laboratory work for Beginners in Chemistry. A Text-book, specially adapted for Students of Pharmacy and Medicine. Hew (second) edition. In one 8vo. vol. of 478 pp., with 44 woodcuts and 7 colored plates illustrating 56 of the most important chemical tests. Cloth, $3.25. In this book the author has endeavored to meet the wants of the student of medicine or pharmacy in regard to his chemical studies, and he has suc- ceeded in presenting his subject so clearly that no one who really wishes to acquire a fair knowledge of chemistry can fail to do so with the help of this work. The largest section of the book is naturally that devoted to the consideration of the carbon compounds, or organic chemistry. An excellent feature is the introduction of a number of plates showing the various colors of the most important chemical reactions of the metallic salts, of some of the alkaloids, and of the urinary tests. In the part treating of physiological chemistry the section on analysis of the urine will be found very practi- cal, and well suited to the needs of the practitioner of medicine.— The Medical Record, May 25, 1889. Wohler’s Outlines of Organic Chemistry. Edited by Fittig. Translated by Ira Remsen, M. D., Ph. D. In one 12mo. volume of 550 pages. Cloth, $3. LEHMANN’S MANUAL OF CHEMICAL PHYS- IOLOGY. In one octavo volume of 327 pages, with 41 illustrations. Cloth, 82.25. CARPENTER’S HUMAN PHYSIOLOGY. Edited by Henry Power. In one octavo volume. CARPENTER’S PRIZE ESSAY ON THE USE AND Abuse of Alcoholic Liquors in Health and Dis- ease. With explanations of scientific words. Small 12mo. 178 pages. Cloth, 60 cents. Lea Brothers & Co.’s Publications—Chemistry. 9 FRANKLAND, E., D. C. L., F. R.S., &JAFF, F. 11., F. I. G, Professor of Chemistry in the Normal School of Science, London. Assist. Prof, of Chemistry in the Normal School of Science, London. Inorganic Chemistry. In one handsome octavo volume of 677 pages with 51 woodcuts and 2 plates. Cloth, $3.75 ; leather, $4.75. This work should supersede other works of its class in the medical colleges. Itis certainly better adapted than any work upon chemistry,with which we are acquainted, to impart that clear and full knowledge of the science which students of med- icine should have. Physicians who feel that their chemical knowledge is behind the times, would do well to study this work. The descriptions and demonstrations are made so plain that there is no difficulty in understanding them.—Cincinnati Medical News, January, 1886. This excellent treatise will not fail to take its place as one of the very best on the subject of which it treats. We have been much pleased with the comprehensive and lucid manner in which the difficulties of chemical notation and nomenclature have been cleared up by the writers. It shows on every page that the problem of rendering the obscurities of this science easy of comprehension has long and successfully engaged the attention of the authors.—Medical and Surgical Reporter, October 31, 1885. FOWNES, GEORGE, Fix. D. A Manual of Elementary Chemistry; Theoretical and Practical. Em- bodying Watts’ Physical and Inorganic Chemistry. New American, from the twelfth English edition. In one large royal 12mo. volume of 1061 pages, with 168 illustrations on wood and a colored plate. Cloth, $2.75; leather, $3.25. Fownes’ Chemistry has been a standard text- book upon chemistry for many years. Its merits are very fully known by chemists and physicians everywhere in this country and in England. As the science has advanced by the making of new discoveries, the work has been revised so as to keep it abreast of the times. It has steadily maintained its position as a text-book with medi- cal students. In this work are treated fully: Heat, Light and Electricity, including Magnetism. The influence exerted by these forces in chemical action upon health and disease, etc., is of the most important kind, and should be familiar to every medical practitioner. We can commend the work as one of the very best text-books upon chemistry extant.—Cincinnati Med. News, Oct. ’85. Of all the works on chemistry intended for the use of medical students, Fownes’ Chemistry is perhaps the most widely used. Its popularity is based upon its excellence. This last edition con- tains all of the material found in the previous, and it is also enriched by the addition of Watts’ Physical and Inorganic Chemistry. All of the mat- ter is brought to the present standpoint of chemi- cal knowledge. We may safely predict for this work a continuance of the fame and favor it enjoys among medical students.—New Orleans Medical and Surgical Journal, March, 1886. ATTFIELD, JOHX, M. A., Fit. D., F. I. CF. R. S„ Etc. Professor of Practical Chemistry to the Pharmaceutical Society of Great Britain, etc. Chemistry, General, Medical and Pharmaceutical; Including the Chem- istry of the U. S. Pharmacopoeia. A Manual of the General Principles of the Science, and their Application to Medicine and Pharmacy. A new American, from the twelfth English edition, specially revised by the Author for America. In one handsome royal 12mo. volume of 782 pages, with 88 illustrations. Cloth, $2.75; leather, $3.25. Attfield’s Chemistry is the most popular book among students ot medicine and phaimacy. This popularity has a good, substantial basis. It rests upon real merits. Attfield’s work combines in the happiest manner a clear exposition of the theory of chemistry with the practical application of this knowledge to the everyday dealings of the phy- sician and pharmacist. His discernment is shown not only in what he puts into his work, but also in what he leaves out. His book is precisely what the title claims for it. The admirable arrangement of the text enables a reader to get a good idea of chemistry without the aid of experiments, and again it is a good laboratory guide, and finally it contains such a mass of well-arranged information that it will always serve as a handy book of refer- ence. He does not allow any unutilizable knowl- edge to slip into his book; his long years of experience have produced a work which is both scientific and practical, and which shuts out everything in the nature of a superfluity, and therein lies the secret of its success. This last edition shows the marks of the latest progress made in chemistry and chemical teaching.—New> Orleans Medical and Surgical Journal, Nov. 1889. BLOXAM, CHARLES L., Chemistry, Inorganic and Organic. New American from the fifth Lon- don edition, thoroughly revised and much improved. In one very handsome octavo volume of 727 pages, with 292 illustrations. Cloth, $2.00; leather, $3.00. Professor of Chemistry in King's College, London. Comment from us on this standard work is al- most superfluous. It differs widely in scope and aim from that of Attfield, and in its way is equally beyond criticism. It adopts the most direct meth- ods in stating the principles, hypotheses and facts of the science. Its language is so terse and lucid, and its arrangement of matter so logical in se- quence that the student never has occasion to complain that chemistry is a hard study. Much attention is paid to experimental illustrations of chemical principles and phenomena, and the mode of conducting these experiments. The book maintains the position it has always held as one of the best manuals of general chemistry In the Eng- lish language.—Detroit Lancet, Feb. 1884. We know of no treatise on chemistry which contains so much practical information in the same number of pages. The book can be readily adapted not only to the needs of those who desire a tolerably complete course of chemistry, but also to the needs of those who desire only a general knowledge of the subject. It is both a satisfactory text-book, and a useful book of reference.—Boston- Medical and Surgical Journal, June 19, 1884. GREENE, WILLIAM 11., M 1)., Demonstrator of Chemistry in the Medical Department of the University of Pennsylvania. A Manual of Medical Chemistry. For the use of Students. Based upon Bow- man’s Medical Chemistry. In one 12mo. volume of 310 pages, with 74 illus. Cloth, $1.75. It is a concise manual of three hundred pages, giving an excellent summary of the best methods of analyzing the liquids and solids of the body, both for the estimation of their normal constituent and the recognition of compounds due to pathological conditions. The detection of poisons is treated with sufficient fulness for the purpose of the stu- dent or practitioner.—Boston Jl. of Chem. June,’80. 10 Lea Brothers & Co.’s Publications—Chemistry. REMSEN, IRA, M. D., Eh. Jh, Professor of Chemistry in the Johns Hopkins University, Baltimore. Principles of Theoretical Chemistry, with special reference to the Constitu- tion of Chemical Compounds. New (third) and thoroughly revised edition. In one hand- some royal 12mo. volume of 316 pages. Cloth, $2.00 This work of Dr. Remsen is the very text-book needed, and the medical student who has it at his fingers’ ends, so to speak, can, if he chooses, make himself familiar with any branch of chem- istry which he may desire to pursue. It would be difficult indeed to find a more lucid, full, and at the same time compact explication of the philos- ophy of chemistry, than the book before us, and we recommend it to the careful and impartial examination of college faculties as the text-book of chemical instruction.—St. Louis Medical and Sur- gical Journal, January, 1888. It is a healthful sign when we see a demand for a third edition of such a book as this. This edi- tion is larger than the last by about seventy-five pages, ana much of it has been rewritten, thus bringing it fully abreast of the latest investiga- tions.—N. Y. Medical Journal, Dec. 31, 1887. CHARLES, T. CRANSTO UN, M. D., F. C. S., M. S., Formerly Asst. Prof, and Demonst. of Chemistry and Chemical Physics, Queen's College, Belfast. The Elements of Physiological and Pathological Chemistry. A Handbook for Medical Students and Practitioners. Containing a general account of Nutrition, Foods and Digestion, and the Chemistry of the Tissues, Organs, Secretions and Excretions of the Body in Health and in Disease. Together with the methods for pre- paring or separating their chief constituents, as also for their examination in detail, and an outline syllabus of a practical course of instruction for students. In one handsome octavo volume of 463 pages, with 38 woodcuts and 1 colored plate. Cloth, $3.50. Dr. Charles is fully impressed with the impor- tance and practical reach of his subject, and he has treated it in a competent and instructive man- ner. We cannot recommend a better book than the present. In fact, it fills a gap in medical text- books, and that is a thing which can rarely be said nowadays. Dr. Charles has devoted much space to the elucidation of urinary mysteries. He does this with much detail, and yet in a practical and intelligible manner. In fact, the author has filled his book with many practical hints.—Medical Rec- ord, December 20, 1884. HOFFMANN, F., A.M., Fh.D., & ROWER, F.B., Rh.D., A Manual of Chemical Analysis, as applied to the Examination of Medicinal Chemicals and their Preparations. Being a Guide for the Determination of their Identity and Quality, and for the Detection of Impurities and Adulterations. For the use of Pharmacists, Physicians, Druggists and Manufacturing Chemists, and Pharmaceutical and Medical Students. Third edition, entirely rewritten and much enlarged. In one very handsome octavo volume of 621 pages, with 179 illustrations. Cloth, $4.25. Public Analyst to the State of New York. Prof, of Anal. Chem. in the Phil. Coll, of Pharmacy. We congratulate the author on the appearance of the third edition of this work, published for the first time in this country also. It is admirable and the information it undertakes to supply is both extensive and trustworthy. The selection t>f pro- cesses for determining the purity of the substan- ces of which it treats is excellent and the descrip- tion of them singularly explicit. Moreover, it is exceptionally free from typographical errors. We have no hesitation in recommending it to those who are engaged either in the manufacture or the testing of medicinal chemicals.—London Pharma- ceutical Journal and Transactions, 1883. CLOWES, FRANK, D. Sc., London, Senior Science-Master at the High School, Newcastle-under-Lyme, etc. An Elementary Treatise on Practical Chemistry and Qualitative Inorganic Analysis. Specially adapted for use in the Laboratories of Schools and Colleges and by Beginners. Third American from the fourth and revised English edition. In one 12mo. volume of 387 pages, with 55 illustrations. Cloth, $2.50. This work has long been a favorite with labora- tory instructors on account of its systematic plan, carrying the student step by step from the simplest questions of chemical analysis, to the. more recon- dite problems. Features quite as commendable are the regularity and system demanded of the student in the performance of each analysis, These characteristics are preserved in the present edition, which we can heartily recommend as asat- isfactory guide for the student of inorganic chem- ical analysis.—New York Medical Journal, Oct. 9, 1886. RALFE, CHARLES H., M. D., F. R. C. 1\, Clinical Chemistry. In one pocket-size 12mo. volume of 314 pages, with 16 illustrations. Limp cloth, red edges, $1.50. See Students’ Series of Manuals, page 31. Assistant Physician at the London Hospital. This is one of the most instructive little works that we have met with in a long time. The author is a physician and physiologist, as well as a chem- ist, consequently the book is unqualifiedly prac- tical, telling the physician just what he ought to know, of the applications of chemistry in medi- cine. Dr. Ralfe is thoroughly acquainted with the latest contributions to his science, and it is quite refreshing to find the subject dealt with so clearly and simply, yet in such evident harmony with the modern scientific methods and spirit.—Medical Record, February 2,1884. CLASSEN, ALEXANDER, Elementary Quantitative Analysis. Translated, with notes and additions, by Edgar F. Smith, Pli. D., Assistant Professor of Chemistry in the Towne Scientific School, University of Penna. In one 12mo. volume of 324 pages, with 36 illus. Cloth, $2.00. Professor in the Royal Polytechnic School, Aix-larChapelle. It is probably the best manual of an elementary nature extant, insomuch as its methods are the best. It teaches by examples, commencing with single determinations, followed by separations, I and then advancing to the analysis of minerals and such products as are met with in applied chemis- try. It is an indispensable book for students in chemistry.—Boston Journal of Chemistry, Oct. 1878 Lea Brothers & Co.’s Publications—Pharm., Mat. Med., Therap. 11 HARE, HOBART AMORY, B. Sc., M. H., Professor of Materia Mediea and Therapeutics in the Jefferson Medical College of Philadelphia; Secretary of the Convention for the Revision of the United States Pharmacopceai of 1890. A Text-Book of Practical Therapeutics; With Especial Reference to the Application of Remedial Measures to Disease and their Employment upon a Rational Basis. With special chapters by Drs. G. E. de Schweinitz, Edward Martin, J. Howard Reeves and Barton C. Hirst. New (2d) and revised edition. In one handsome octavo volume of 650 pages. Cloth, $3.75; leather, $4.75. Just ready. This work has received the rare distinction among medical works of reaching a second edition six months after its first appearance. We note among the important new features characterizing the second edition, additional information regard- ing the remedies recently added to the Materia Mediea; the method of employing the rest cure; the use of suspension in the treatment of locomo- tor ataxia and allied affections. Many new pre- scriptions have also been inserted to illustrate the best modes of applying remedies. Among other features of this practically helpful treatise which will make reference to it convenient and profitable, are the arrangement of titles of drugs and diseases in alphabetical order, according to their English names; the introduction of the preparations of the British Pharmacopceia; a dose list of drugs officinal and unoflficinal. In addition to the general index, a copious and explanatory index of diseases an ' remedies has been appended which will render the contents easily accessible. —The Medical Age, July 10,1891. HARE, HOBART AMORY, B. Sc., II. F>., Editor. A System of Practical Therapeutics; By American and Foreign Authors. In a series of contributions by seventy-seven eminent physicians. In three large octavo volumes of about 1000 pages each, with illustrations. For sale by subscription only. In press. BR UNTON, T. LAUDER, M.D., D.Sc., F.R.S., F.R.C.P., Lecturer on Materia Mediea and Therapeutics at St. Bartholomew's Hospital, London, etc. A Text-Book of Pharmacology, Therapeutics and Materia Mediea; Including the Pharmacy, the Physiological Action and the Therapeutical Uses of Drugs. Third edition. Octavo, 1305 pages, 230 illustrations. Cloth, $5.50; leather, $6.50. No words of praise are needed for this work, for it has already spoken for itself in former editions. It was by unanimous consent placed among the foremost books on the subject ever published in any language, and the better it is known and studied the more highly it is appreciated. The present edition contains much new matter, the insertion of which has been necessitated by the advances made in various directions in the art of therapeu- tics, and it now stands unrivalled in its thoroughly scientific presentation of the modes of drug action. No one who wishes to be fully up to the times in this science can afford to neglect the study of Dr. Brunton’s work. The indexes are excellent, and add not a little to the practical value of the book. —Medical Record, May 25,1889. MAISCH, JOHN M., Phar. D., Professor of Materia Medica and Botany in the Philadelphia College of Pharmacy. A Manual of Organic Materia Medica; Being a Guide to Materia Medica of the Vegetable and Animal Kingdoms. For the use of Students, Druggists, Pharmacists and Physicians. New (4th) edition, thoroughly revised. In one handsome royal 12mo. volume of 529 pages, with 258 illustrations. Cloth, $3.00. For everyone interested in materia medica, Maisch’s Manual, first published in 1882, and now in its fourth edition, is an indispensable book. For the American pharmaceutical student it is the work which will give him the necessary knowl- edge in the easiest way, partly because the text is brief, concise, and free from unnecessary matter, and partly because of the numerous illustrations, which bring facts worth knowing immediately be- fore his eyes. That it answers its purposes in this respect the rapid succession of editions is the best evidence. It is the favorite book of the American student even outside of Maisch’s several hundred personal students. The arrangement of its con- tents shows the practical tendency of the book. Maisch’s system of classification is easy and com- prehensive.—Pharmaceutisclie Zeitung, Germany, 1890. PARRISH, EDWARD, Late Professor of the Theory and Practice of Pharmacy in the Philadelphia College of Pharmacy. A Treatise on Pharmacy: Designed as a Text-book for the Student, and as a Guide for the Physician and Pharmaceutist. With many Formulae and Prescriptions. Fifth edition, thoroughly revised, by Thomas S. Wiegand, Ph. G. In one handsome octavo volume of 1093 pages, with 256 illustrations. Cloth, $5.00; leather, $6.00. No thorough-going pharmacist will fail to possess himself of so useful a guide to practice, and no physician who properly estimates the value of an accurate knowledge of the remedial agents em- ployed by him in daily practice, so far as their miscibility, compatibility and most effective meth- ods of combination are concerned, can afford to leave this work out of the list of their works of reference. The country practitioner, who must always be in a measure his own pharmacist, will find it indispensable.—Louisville Medical News, March 29, 1884. HERMANN, Dr. L., Professor of Physiology in the University of Zurich. Experimental Pharmacology. A Handbook of Methods for Determining the Physiological Actions of Drugs. Translated, with the Author’s permission, and with extensive additions, by Robert Meade Smith, M. D., Demonstrator of Physiology in the University of Pennsylvania. 12mo., 199 pages, with 32 illustrations Cloth, $1.50. STIFLE, ALFRED, M. D., LL. I)., Professor of Theory and Practice of Med. and of Clinical Med. in the Univ. of Penna. Therapeutics and Materia Mediea. A Systematic Treatise on the Action and Uses of Medicinal Agents, including their Description and History. Fourth edition, revised and enlarged. In two large and handsome octavo volumes, containing 1936 pages. Cloth, $10.00; leather, $12.00. 12 Lea Brothers & Co.’s Publications—Mat. Med., Therap. STILLE, A., M.D.,LL.D., & MAISCH, J. M.,Fliar.D., Professor Emeritus of the Theory and Prac- tice of Medicine and of Clinical Medicine in the University of Pennsylvania. Prof, of Mat. Med. and Botany in Phila. College of Pharmacy, Sec'y to the Ameri- can Pharmaceutical Association. The National Dispensatory CONTAINING THE NATURAL HISTORY, CHEMISTRY, PHARMACY, ACTIONS AND USES OF MEDICINES, INCLUDING THOSE RECOGNIZED IN THE PHARMACOPdIAS OF THE UNITED STATES, GREAT BRITAIN AND GERMANY, WITH NUMEROUS REFERENCES TO THE FRENCH CODEX. Fourth edition revised, and covering the new British Pharmacopoeia. In one mag- nificent imperial octavo volume of 1794 pages, with 311 elaborate engravings. Price in cloth, $7.25 ; leather, raised bands, $8.00. * A This work will be furnished with Patent Ready Reference Thumb-letter Index for $1.00 in addition to the price in any style of binding. It is with much pleasure that the fourth edition of this magnificent work is received. The authors and publishers have reason to feel proud of this, the most comprehensive, elaborate and accurate work of the kind ever printed in this country. It is no wonder that it has become the standard au- thority for both the medical and pharmaceutical profession, and that four editions have been re- quired to supply the constant and increasing demand since its first appearance in 1879. The entire field has been gone over and the various articles revised in accordance with the latest developments regarding the attributes and thera- peutical action of drugs. The remedies of recent discovery have received due attention.—Kansas City Medical Index, Nov. 1887. We think it a matter for congratulation that the profession of medicine and that of pharmacy have shown such appreciation of this great work as to call for four editions within the comparatively brief period of eight years. The matters with which it deals are of Si practical a nature that neither the physician nor the pharmacist can do without the latest text-books on them, especially those that are so accurate and comprehensive as this one. The book is in every way creditable both to the authors and to the publishers.—New York Medical Journal, May 21, 1887. COHEN, SOLOMON SOLIS, 31. D., Professor of Clinical Medicine and Applied Therapeutics in the Philadelphia Polyclinic. A Handbook of Applied Therapeutics. Being a Study of Principles, Applicable and an Exposition of Methods Employed in the Management of the Sick. In one large 12mo. volume, with illustrations. Preparing. FARQ UIIARSON, ROBERT, M. D., F. R. C. P., LL. I)., Lecturer on Materia Medica at St. Mary's Hospital Medical School, London. A Guide to Therapeutics and Materia Mediea. New (fourth) American, from the fourth English edition. Enlarged and adapted to the U. S. Pharmacopoeia. By Frank Woodbury, M. D., Professor of Materia Mediea and Therapeutics and Clinical Medicine in the Medico-Chirurgical College of Philadelphia. In one handsome 12mo. volume of 581 pages. Cloth, $2.50. , —j • It may correctly be regarded as the most modern work of its kina. It is concise, yet complete. Containing an account of all remedies that have a place in the British and United States Pharma copoeias, as well as considering all non-official but important new drugs, it becomes in fact a min iature dispensatory.—Pacific Medical Journal, June, 1889. An especially attractive feature is an arrange ment by which the physiological and therapeutical actions of various remedies are shown in parallel columns. This aids greatly in fixing attention and facilitates study. The American editor has en- larged the work so as to make it include all the remedies and preparations in the U. S. Pharma- copoeia. The book is a most valuable addition to the list of treatises on this most important subject. —American Practitioner and News, Nov. 9,1889. EDES, ROBERT T, M. D., Jackson Professor of Clinical Medicine in Harvard University, Medical Department, A Text-Book of Therapeutics and Materia Mediea. Intended for the Use of Students and Practitioners. Octavo, 544 pages. Cloth, $3.50; leather, $4.50. The present work seems destined to take a prom i- nent place as a text-book on the subjects of which it treats. It possesses all the essentials which we expect in a book of its kind, such as conciseness, clearness, a judicious classification, and a reason- able degree of dogmatism. All the newest drugs of promise are treated of. The clinical index at the end will be found very useful. We heartily commend the book and congratulate the author on having produced so good a one.—IV. F. Medical Journal, Feb. 18, 1888. Dr. Edes’ book represents better than any older book the practical therapeutics of the present day. The book is a thoroughly practical one. The classification of remedies has reference to their therapeutic action.—Pharmaceutical Era, Jan. 1888. BBUCF, J. MITCHELL, M. I)., F. B. C. P., Physician and Lecturer on Materia Mediea and Therapeutics at Charing Cross Hospital, London. Materia Mediea and Therapeutics. An Introduction to Rational Treatment. Fourth edition. 12mo., 591 pages. Cloth, $1.50. See Students’ Series of Manuals, page 31. GRIFFITH, ROBERT EG LESFIELD, M. I). A Universal Formulary, containing the Methods of Preparing and Adminis- tering Officinal and other Medicines. The whole adapted to Physicians and Pharmaceut- ists. Third edition, thoroughly revised, with numerous by John M. Maisch, Phar. D., Professor of Materia Medica and Botany in the Philadelphia College of Pharmacy. In one octavo volume of 775 pages, with 38 illustrations, Cloth, $4.50; leather, liLML— Lea Brothers & Co.’s Publications—Pathol., HistoL 13 UrlBBES, HENEAGE, 31. D., Practical Pathology and Morbid Histology. In one very handsome octavo volume of 314 pages, with 60 illustrations, mostly photographic. Cloth, $2.75. Just ready. Professor of Pathology in the University of Michigan, Medical Department. Dr. Gibbes’ established reputation as a master of the technique of microscopy would lead us to anticipate a work of great value, and in this we are not disappointed. The chapters devoted to this subject are models of completeness, con- densed in such a manner as to render them of the greatest possible value to the laboratory worker. The author’s methods of hardening, section-cutting and staining are given in detail, and are accompanied by valuable formulae for reagents, etc.— The Medical News, July 4, 1891. SENN, NICHOLAS, 31.D., Ph.D., Professor of Surgery in Rush Medical College, Chicago. Surgical Bacteriology. New (second) edition. In one handsome octavo of 268 pages, with 13 plates, of which 10 are colored, and 9 engravings. Cloth, $2. Just ready. A very thorough and exhaustive review of cur- rent literature of that part of bacteriology relating to surgery. Such books as this are of incalcula- ble benefit to the general practitioner, as they bring before him in a condensed and orderly man- ner all the literature of a subject, thus saving much time. We cordially commend this book to all physicians desirous of keeping pace with mod ern investigations.—Cincinnati Lancet-Clinic, May 30, 1891. GREEN, T. HENRY, 31. D Lecturer on Pathology and Morbid Anatomy at Charing-Cross Hospital Medical School, London. Pathology and Morbid Anatomy. New (sixth) American from the seventh revised English edition. Octavo, 539 pp., with 167 engravings. Cloth, $2.75. The Pathology and Morbid Anatomy of Dr. Green is too well known by members of the medi- cal profession to need any commendation. There is scarcely an intelligent physician anywhere who has not the work in his library, for it is almost an essential. In fact it is better adapted to the wants of general practitioners than any work of the kind with which we are acquainted. The works of German authors upon pathology, which have been translated into English, are too abstruse for the physician. Dr. Green’s work precisely meets his wishes. The cuts exhibit the appearances of pathological structures just as they are seen through the microscope. The fact that it is so generally employed as a text-book by medical stu- dents is evidence that we have not spoken too much in its favor.—Cincinnati Medical News, Oct. 1889. PAYNE, JOSEPH F., 31. D., F. R. C. P., Senior Assistant Physician and Lecturer on Pathological Anatomy, St. Thomas' Hospital, London. A Manual of General Pathology. Designed as an Introduction to the Prac- tice of Medicine. Octavo of 524 pages, with 152 illus. and a colored plate. Cloth, $3.50. Knowing, as a teacher and examiner, the exact needs of medical students, the author has in the work before us prepared for their especial use what we do not hesitate to say is the best introduc- tion to general pathology that we have yet ex- amined. A departure which our author has taken is the greater attention paid to the causa- tion of disease, and more especially to the etiologi- cal factors in those diseases now with reasonable certainty ascribed to pathogenetic microbes. In this department he has been very full and explicit, not only in a descriptive manner, but in the tech- nique of investigation. The Appendix, giving methods of research, is alone worth the price of the book, several times over, to every student of pathology.—St. Louis Med. and Surg. Jour., Jan.’89. COATS, JOSEPH, M. D., F. F. F. S., Pathologist to the Glasgow Western Infirmary. A Treatise on Pathology. In one very handsome octavo volume of 829 pages, with 339 beautiful illustrations. Cloth, $5.50; leather, $6.50. Medical students as well as physicians, who desire a work for study or reference, that treats the subjects in the various departments in a very thorough manner, but without prolixity, will cer- tainly give this one the preference to any with which we are acquainted. It sets forth the most recent discoveries, exhibits, in an interesting manner, the changes from a normal condition effected in structures by disease, and points out the characteristics of various morbid agencies, so that they can be easily recognized. But, not limited to morbid anatomy, it explains fully how the functions of organs are disturbed by abnormal conditions.—Cincinnati Medical News, Oct. 1883. SCHAFER, EDWARD A., F. R. S., Jodrell Professor of Physiology in University College, London. The Essentials of Histology. In one octavo volume of 246 pages, with 281 illustrations. Cloth, $2.25. KLEIN, E., M. D., F. R. S., Joint Lecturer on General Anat. and Phys. in the Med. School of St. Bartholomew's Bosp., London. Elements of Histology. Fourth edition. In one 12mo. volume of 376 pages, with 194 illus. Limp cloth, $1.75. See Students’ Series of Manuals, page 31. WOODHEAD’S PRACTICAL PATHOLOGY. A Manual for Students and Practitioners. In one beautiful octavo volume of 497 pages, with 136 exquisitely colored illustrations. Cloth, $6.00. PEPPER’S SURGICAL PATHOLOGY. In one pocket-size 12mo. volume of 511 pages, with 81 illustrations. Limp cloth, red edges, $2.00. See Students' Series of Manuals, page 31. 14 Lea Brothers & Co.’s Publications—Practice of Med. FLINT, AUSTIN, M. I)., II. D., Prof, of the Principles and Practice of Med. and of Clin. Med. in Bellevue Hospital Medical College, N. Y. A Treatise on the Principles and Practice of Medicine. Designed for the use of Students and Practitioners of Medicine. New (sixth) edition, thoroughly re- vised and rewritten by the Author, assisted by William H. Welch, M. D., Professor of Pathology, Johns Hopkins University, Baltimore, and Austin Flint, Jr., M. D., LL. D., Professor of Physiology, Bellevue Hospital Medical College, N. Y. In one very handsome octavo volume of 1160 pages, with illustrations. Cloth, $5.50; leather, $6.50. No text-book on the principles and practice of medicine has ever met in this country with such general approval by medical students and practi- tioners as the work of Professor Flint. In all the medical colleges of the United States it is the fa- vorite work upon Practice; and, as we have stated before in alluding to it, there is no other medical work that can be so generally found in the libra- ries of physicians. In every state and territory of this vast country the book that will be most likely to be found in the office of a medical man, whether in city, town, village, or at some cross-roads, is Flint’s Practice. We make this statement to a considerable extent from personal observation, and it is the testimony also of others. An examina- tion shows that very considerable changes have been made in the sixth edition. The work may un- doubtedly be regarded as fairly representing the present state of the science of medicine, and as reflecting the views of those who exemplify in their practice the present stage of progress of med- ical art.—Cincinnati Medical News, Oct. 1886. Bill STOWE, JOHW SYEB, M. 1)., LL. I)., F. It. S., Senior Physician to and Lecturer on Medicine at St. Thomas' Hospital, London. A Treatise on the Science and Practice of Medicine. Seventh edi- tion. In one large octavo volume of 1325 pages. Cloth, $6.50; leather, $7.50. Just ready. The remarkable regularity with which new edi- tions of this text-book make their appearance is striking testimony to its excellence and value. This, too, in spite of the numerous rivals for the favor of the student which have been put forth within the sixteen years since Bristowe’s “ Medi- cine” first appeared. Nor can it be said that the author himself has failed to keep his manual abreast of advancing knowledge, arduous as that task must prove. So long as there is shown such care and circumspection in the inclusion of all new matter that has stood the test of criticism, so long will this work retain the favor which it has always met. For it is a work that is built on a stable foundation, systematic, scientific and prac- tical, containing the matured experience of a physician who has every claim to be considered an authority, and composed in a style which at- tracts the practitioner as much as the student. No one can say that this book has obtained a success which was undeserved, and we trust that its author will long continue to supervise the production of fresh editions for the advantage of the coming generation of medical students.— The Lancet, July 12,1890. Dr. Bristowe’s now famous treatise appears in its seventh edition. It has long passed the stage in which it requires critical examination or com- mendation, and has thoroughly established itself as among the most complete and useful of text- books.—British Medical Journal,September 27,1890. HARTSHORNE, HENRY, M. H., II. H., Lately Professor of Hygiene in the University of Pennsylvania. Essentials of the Principles and Practice of Medicine. A Handbook for Students and Practitioners. Fifth edition, thoroughly revised and rewritten. In one royal 12mo. volume of 669 pages, with 144 illustrations. Cloth, $2.75; half bound, $3.00. Within the compass of 600 pages it treats of the history of medicine, general pathology, general symptomatology, and physical diagnosis (including laryngoscope, ophthalmoscope, etc.), general ther- apeutics, nosology, and special pathology and prac- tice. There is a wonderful amount of information contained in this work, and it is one of the best of its kind that we have seen.—Glasgow Medical Journal, Nov. 1882. An indispensable book. No work ever exhibited a better average of actual practical treatment than this one; and probably not one writer in our day had a better opportunity than Dr. Hartshorne for condensing all the views of eminent practitioners into a 12mo. The numerous illustrations will be very useful to students especially. These essen- tials, as the name suggests, are not intended to supersede the text-books of Flint and Bartholow, but they are the most valuable in affording the means to see at a glance the whole literature of any disease, and the most valuable treatment.—Chicago Medical Journal and Examiner, April, 1882. REYNOLDS, J. RUSSELL, M. I)., A System of Medicine. With notes and additions by Henry Hartshorne, A. M., M. D., late Professor of Hygiene in the University of Pennsylvania. In three large and handsome octavo volumes, containing 3056 double-columned pages, with 317 illustra- tions. Price per volume, cloth, $5.00; sheep, $6.00; very handsome half Russia, raised bands, $6 .50. Per set, cloth, $15.00; leather, $18.00. Sold only by subscription. Professor of the Principles and Practice of Medicine in University College, London. STILLE, A LEBED, M. /)., LL. D., Professor Emeritus of the Theory and Practice of Med. and of Clinical Med. in the Univ. of Penna. Cholera: Its Origin, History, Causation, Symptoms, Lesions, Prevention and Treat- ment. In one handsome 12mo. volume of 163 pages, with a chart. Cloth, $1.25. WATSONSin THOMAS, M. J)., Late Physician in Ordinary to the Queen. Lectures on the Principles and Practice of Physic. A new American from the fifth English edition. Edited, with additions, and 190 illustrations, by Henry Hartshorne, A. M., M. D., late Professor of Hygiene in the University of Pennsylvania. In two large octavo volumes of 1840 pages. Cloth, $9.00 ; leather, $11.00. Lea Brothers & Co.’s Publications—System of Med. 15 For Sale by Subscription Only. A System of Practical Medicine. AMERICAN AUTHORS. Edited by WILLIAM PEPPER, M. D., LL. D., PROVOST AND PROFESSOR OF THE THEORY AND PRACTICE OF MEDICINE AND OF CLINICAL MEDICINE IN THE UNIVERSITY OF PENNSYLVANIA, Assisted by Louis Starr, M. D., Clinical Professor of the Diseases of Children in the Hospital of the University of Pennsylvania. The complete work, in five volumes, containing 5573 pages, with 198 illustrations, is now ready. Price per volume, cloth, $5; leather, $6; half Russia, raised bands and open back, $7. In this great work American medicine is for the first time reflected by its worthiest teachers, and presented in the full development of the practical utility which is its pre- eminent characteristic. The most able men—from the East and the West, from the North and the South, from all the prominent centres of education, and from all the hospitals which afford special opportunities for study and practice—have united in generous rivalry to bring together this vast aggregate of specialized experience. The distinguished editor has so apportioned the work that to each author has been assigned the subject which he is peculiarly fitted to discuss, and in which his views will be accepted as the latest expression of scientific and practical knowledge. The practitioner will therefore find these volumes a complete, authoritative and unfailing work of reference, to which he may at all times turn with full certainty of finding what he needs in its most recent aspect, whether he seeks information on the general principles of medi- cine, or minute guidance in the treatment of special disease. So wide is the scope of the work that, with the exception of midwifery and matters strictly surgical, it embraces the whole domain of medicine, including the departments for which the physician is accustomed to rely on special treatises, such as diseases of women and children, of the genito-urinary organs, of the skin, of the nerves, hygiene and sanitary science, and medical ophthalmology and otology. Moreover, authors have inserted the formulas which they have found most efficient in the treatment of the various affections. It may thus be truly regarded as a Complete Library op Practical Medicine, and the general practitioner possessing it may feel secure that he will require little else in the daily round of professional duties. In spite of every effort to condense the vast amount of practical information fur- nished, it has been impossible to present it in less than 5 large octavo volumes, containing about 5600 beautifully printed pages, and embodying the matter of about 15 ordinary octavos. Illustrations are introduced wherever requisite to elucidate the text. A detailed prospectus will be sent to any address on application to the publishers. These two volumes bring this admirable work to a close, and fully sustain the high standard reached by the earlier volumes; we have only therefore to echo the eulogium pronounced upon them. We would warmly congratulate the editor and his collaborators at the conclusion of their laborious task on the admirable manner in which, from first to last, they have performed their several duties. They have succeeded in producing a work which will long remain a standard work of reference, to which practitioners will look for fuidance, and authors will resort for facts. 'rom a literary point of view, the work is without any serious blemish, and in respect of production, it has the beautiful finish that Americans always give their works.—Edinburgh Medical Journal, Jan. 1887. * * The greatest distinctively American work on the practice of medicine, and, indeed, the super- lative adjective would not be inappropriate were even all other productions placed in comparison. An examination of the five volumes is sufficient to convince one of the magnitude of the enter- prise, and of the success which has attended its fulfilment.—The Medical Age, July 26,1886. This huge volume forms a fitting close to the great system of medicine which in so short a time has won so high a place in medical literature, and has done such credit to the profession in this country. Among the twenty-three contributors are the names of the leading neurologists in America, and most of the work in the volume is of the hightH order.—Boston Medical and Surgical Journal, July 21,1887. We consider it one of the grandest works on Practical Medicine in the English language. It is a work of which the profession of this country can feel proud. Written exclusively by American physicians who are acquainted with all the varie- ties of climate in the United States, the character of the soil, the manners and customs of the peo- ple, etc., it is peculiarly adapted to the wants of American practitioners of medicine, and it seems to us that every one of them would desire to have it. It has been truly called a “ Complete Library of Practical Medicine,” and the general practitioner will require little else in his round of professional duties.—Cincinnati Medical News, March, 1886. Each of the volumes is provided with a most copious index, and the work altogether promises to be one which will add much to the medical literature of the present century, and reflect great credit upon the scholarship and practical acumen of its authors.— The London Lancet, Oct. 3, 1885. The feeling of proud satisfaction with which the American profession sees this, its representative system of practical medicine issued to the medi- cal world, is fully justified by the character of the work. The entire caste of the system is in keep- ing with the best thoughts of the leaders and fol- lowers of our home school of medicine, and the combination of the scientific study of disease and the practical application of exact and experimen- tal knowledge to the treatment of human mal- adies, makes every one of us share in the pride that has welcomed Dr. Pepper’s labors. Sheared of the prolixity that wearies the readers of the German school, the articles glean these same fields for all that is valuable, it is the outcome of American brains, and is marked throughout by much of the sturdy independence of thought and originality that is a national characteristic. Yet nowhere is there lack of study of the most advanced views of the day.—North Carolina Medi- cal Journal, Sept. 1886. 16 Lea Brothers & Co.’s Publications—Clinical Med., etc. EOTHERGILL, J. 31., 31. I)., Edin., M. R. C. E., Loud., Physician to the City of London Hospital for Diseases of the Chest. The Practitioner’s Handbook of Treatment; Or, The Principles of Thera- peutics. New (third) edition. In one 8vo. vol. of 661 pages. Cloth, $3.75; leather, $4.75. To have a description of the normal physiologi- cal processes of an organ and of the methods of treatment of its morbid conditions brought together in a single chapter, and the relations between the two clearly stated, cannot fail to prove a great convenience to many thoughtful but busy physicians. The practical value of the volume is greatly increased by the introduction of many prescriptions. That the profession appreciates that the author has undertaken an important work and has accomplished it is shown by the demand for this third edition.—N. Y. Med. Jour., June 11,’87. This is a wonderful book. If there be such a thing as “medicine made easy,” this is the work to accomplish this result.— Va. Med. Month., June,’87. It is an excellent, practical work on therapeutics, well arranged and clearly expressed, useful to the student and young practitioner, perhaps even to the old.—Dublin Journal of Medical Science, March, 1888. We do not know a more readable, practical and useful work on the treatment of disease than the one we have now before us.—Pacific Medical and Surgical Journal, October, 1887. VAUGHAN, VICTOB C., Ph. JJ., 31.1)., Prof, of Phys. and Path. Chem. and Assoc. Prof, of Therap. and Mat. Med. in the Univ. of Mich. and NO VY, FREDERICK (I., M. 1). Instructor in Hygiene and Phys. Chem. in the Univ. of Mich. Ptomaines and Leucomaines, or Putrefactive and Physiological Alkaloids. New edition. In one handsome 12mo. volume of 400 pages. Cloth,$2,25. Ready shortly. FINLAYSON, JA3IES, M. 1)., Editor, i Physician and Lecturer on Clinical Medicine in the Glasgow Western Infirmary, etc. Clinical Manual for the Study of Medical Cases. With Chapters by Prof. Gairdner on the Physiognomy of Disease; Prof. Stephenson on Diseases of the Female Organs; Dr. Robertson on Insanity; Dr. Gemmell on Physical Diagnosis; Dr. Coats on Laryngoscopy and Post-Mortem Examinations, and by the Editor on Case- taking, Family History and Symptoms of Disorder in the Various Systems. New edition. In one 12mo. volume of 682 pages, with 158 illustrations. Cloth, $2.50. The profession cannot but welcome the second edition of this very valuable work of Finlayson and his collaborators. The size of the book has been increased and the number of illustrations nearly doubled. The manner in which the subject is treated is a most practical one. Symptoms alone and their diagnostic indications form the basis of discussion. The text explains clearly and fully the methods of examinations and the con- clusions to be drawn from the physical signs.— The Medical News, April 23, 1887. We are pleased to see a second edition of this admirable book. It is essentially a practical treatise on medical diagnosis, in which every sign and symptom of disease is carefully analyzed, and their relative significance in the different affec- tions in which they occur pointed out. From their synthesis the student can accurately determine tire disease with which he has to deal. The book has no competitor, nor is it likely to have as long as future editions maintain its present standard of excellence. The general practitioner will find many practical hints in its pages, while a careful study of the work will save him from many pitfalls in diagnosis.—Liverpool Medico-Chirurgical Jour- nal, January, 1887. BROADBENT, W. H., 31. D., F. B. C. P., Physician to and Lecturer on Medicine at St. Mary's Hospital, London. The Pulse. In one 12mo. volume of 312 pages. Cloth, $1.75. See Series of Clin- ical Manuals, page 31. This little book probably represents the best practical thought on this subject in the English language. A correct interpretation of the pulse, with its almost infinite modifications, brought about by almost unlimited bodily variations, can only be achieved by experience, and, as an aid toward attaining this goal, nothing will be of more service than this brochure on the study of the pulse.— The American Journal of Medical Sciences, September, 1890. • BLABEBSHON, S. O., 31. I)., Senior Physician to and late Led. on Principles and Practice of Med. at Guy's Hospital, London. On the Diseases of the Abdomen; Comprising those of the Stomach, and other parts of the Alimentary Canal, (Esophagus, Caecum, Intestines and Peritoneum. Second American from third enlarged and revised English edition. In one handsome octavo volume of 554 pages, with illustrations. Cloth, $3.50. This valuable treatise on diseases of the stomach and abdomen will be found a cyclopaedia of infor- mation, systematically arranged, on all diseases of the alimentary tract, from the mouth to the rectum A fair proportion of each chapter is devoted to symptoms, pathology, and therapeutics. The present edition is fuller than former ones in many particulars, and has been thoroughly revised and amended by the author. Several new chap- ters have been added, bringing the work fully up to the times, and making it a volume of interest to the practitioner in every field of medicine and surgery. Perverted nutrition is in some form associated with all diseases we have to combat, and we need all the light that can be obtained on a subject so broad ana general. Dr. Habershon’s work is one that every practitioner should read and study for himself.—N. Y. Medical Journal, April, 1879. TANNER, THOMAS HA WKES, M. I). A Manual of Clinical Medicine and Physical Diagnosis. Third American from the second London edition. Revised and enlarged by Tilbury Fox, M. I). In one small 12mo. volume of 362 pages, with illustrations. Cloth, $1.50. LECTURES ON THE STUDY OF FEVER. By A. Hudson, M. D., M. R. I. A. In one octavo volume of 308 pages. Cloth, $2.50. / A TREATISE ON FEVER. By Robebt D. Lyons,' K. C. C. In one 8vo. vol. of 354 pp. Cloth, $2.25. LA ROCHE ON YELLOW FEVER, considered in Historical, Pathological, Etiological and . 6 , , . Therapeutical Relations. In two large and hand- some octavo volumes of 1468 pp. Cloth, $7.00. Lea Brothers & Co.’s Publications—Hygiene, Electr., Pract. 17 BARTHOLO W, ROBERTS, A. 31., 31.1)., LL. I)., Prof, of Materia Medica and General Therapeutics in the Jefferson Med. Coll, of Phila., etc. Medical Electricity. A Practical Treatise on the Applications of Electricity to Medicine and Surgery. New (third) edition. In one very handsome octavo volume of 308 pages, with 110 illustrations. Cloth, $2.50. The fact that this work has reached its third edi- tion in six years, and that it has been kept fully abreast with the increasing use and knowledge of electricity,demonstrates its claim to be considered a practical treatise of tried value to the profession. The matter added to the present edition embraces the most recent advances in electrical treatment. The illustrations are abundant and clear, and the work constitutes a full, clear and concise manual well adapted to the needs of both student and practitioner.— The Medical JSews, May 14, 1887. YEO, I. BURNEY, 31. J)., F. JR. C. F., Professor of Clinical Therapeutics in King's College, London, and Physician to King's College Hospital. Pood in Health and Disease. In one 12mo. volume of 590 pages. Cloth, $2. See Series of Clinical Manuals, page 31. Dr.Y*eo supplies in a compact form nearly all that the practitioner requires to know on the subject of diet. The work is divided into two parts—food in health and food in disease. Dr. Yeo has gathered together from all quarters an immense amount of useful information within a comparatively small compass, and he has arranged and digested his materials with skill for the use of the practitioner. We have seldom seen a book which more thor- oughly realizes the object for which it was written than this little work of Dr. Yeo.—British Medical Journal, Feb. 8, 1890. RIC HARD SON, B. W., 31. I)., LL. ])., F. R. S., Fellow of the Royal College of Physicians, London. Preventive Medicine. In one octavo volume of 729 pages. Cloth, $4; leathei $5. Dr. Richardson has succeeded in producing a work which is elevated in conception, comprehen- sive in scope, scientific in character, systematic in arrangement, and which is written in a clear, con- cise and pleasant manner. He evinces the happy faculty of extracting the pith of what is known on the subject, and of presenting it in a most simple, intelligent and practical form. There is perhaps no similar work written for the general public thatcontains such a complete, reliable and instruc- tive collection of data upon the diseases common to the race, their origins, causes, and the measures for their prevention. The descriptions of diseases are clear, chaste and scholarly; the discussion of the question of disease is comprehensive, masterly and fully abreast with the latest and best knowl- edge on the subject, and the preventive measures advised are accurate, explicit and reliable.— The American Journal of the Medical Sciences, April, 1884. THE YEAR-BOOK OF TREATMENT FOR 1891. A Comprehensive and Critical Review for Practitioners of Medi- cine. In one 12mo. volume of 485 pages. Cloth, $1.50. Just ready. *** For special commutations with periodicals see pages 1 and 2. The present issue, the seventh, has been in- creased by more than one hundred and fifty pages, but the original plan of the book is not altered. It still remains a concise epitome of the chief articles of the past year—articles selected and epitomised by a staff of contributors which in- cludes many of the best-known and ablest spe- cialists, and these gentlemen have wisely kept in mind that the Year Book is for practitioners, and they have given what actual practice requires— useful, workable information. We have no hesi- tancy in recommending the present volume, which we consider to be superior to any of its predeces- sors; more practical, more generally useful to- practitioners. The sectional editors have confined their attention to fulfilling the object of the book’s existence—the providing of an epitome of the most practical and useful of the medical articles,, of the past year, for the use of men whose prac- tice does not allow time for the study of a large number of home and foreign medical journals.— The Dublin Journal of Medical Science, May, 1891. THE YEAR-BOOKS of THE A TMENTfor >86,987 and 990 Similar to above. 12mo., 320-341 pages. Limp cloth, $1.25 each. S CURE IB ER, JOSEPH, M. I). A Manual of Treatment by Massage and Methodical Muscle Ex- ercise. Translated by Walter Mendelson, M. D., of New York. In one handsome octavo volume of 274 pages, with 117 fine engravings. Cloth, $2.75. STURGES’ INTRODUCTION TO THE STUDY OF CLINICAL MEDICINE. Being a Guide to the Investigation of Disease. In one handsome l2mo. volume of 127 pages. Cloth, $1.25. DAVIS’ CLINICAL LECTURES ON VARIOUS IMPORTANT DISEASES. By N. S. Davis. M. D. Edited by Frank H. Davis, M. D. Second edition. 12mo. 287 pages. Cloth, $1.76. TODD’S CLINICAL LECTURES ON CERTAIN ACUTE DISEASES. In one octavo volume of 320 pages. Cloth, $2.50. PAVY’3 TREATISE ON THE FUNCTION OF DI- GESTION ; its Disorders and their Treatment. From the second London edition. In one octavo volume of 238 pages. Cloth, $2.00. BARLOW’S MANUAL OF THE PRACTICE OF MEDICINE. With additions by D. F. Condie, M. D. 1 vol. 8vo., pp. 603. Cloth, $2.50. CHAMBERS’ MANUAL OF DIET AND REGIMEN IN HEALTH AND SICKNESS. In one hand some octavo volume of 302 pp. Cloth, $2.75 HOLLAND’S MEDICAL NOTES AND REFLEC- TIONS. 1 vol. 8vo., pp. 493. Cloth, $3.50. FULLER ON DISEASES OF THE LUNGS AND AIR-PASSAGES. Their Pathology, Physical Di- agnosis, Symptoms and Treatment. From the second and revised English edition. In one octavo volume of 475 pages. Cloth, $3.50. WALSHE ON THE DISEASES OF THE HEART AND GREAT VESSELS. Third American edi- tion. In 1 vol. 8vo., 416 pp. Cloth, $3.00. SLADE ON DIPHTHERIA; its Nature and Treat- ment, with an account of the History of its Pre- valence in various Countries. Second and revised edition. In one 12mo. vol., 158 pp. Cloth, $1.25. SMITH ON CONSUMPTION; its Early and Reme- diable Stages. 1 vol. 8vo., 253 pp. Cloth, $2.25. LA ROCHE ON PNEUMONIA. 1 vol. 8vo. of 490 pages. Cloth, $3.00. WILLIAMS ON PULMONARY CONSUMPTION; its Nature, Varieties and Treatment. With an analysis of one thousand cases to exemplify its duration. In one 8vo. vol. of 303 pp. Cloth, $2.50 18 Lea Brothers & Co.’s Publications—Throat, Dungs, Heart, Nerves. FLINT, AUSTIN, M. J)., LI. I)., A Manual of Auscultation and Percussion; Of the Physical Diagnosis of Diseases of the Lungs and Heart, and of Thoracic Aneurism. New (fifth) edition. Edited by James C. Wilson, M. D., Lecturer on Physical Diagnosis in the Jefferson Medical College, Philadelphia. In one handsome royal 12mo. volume of 274 pages, with 12 illustrations. Cloth, $1.75. Professor of the Principles and Practice of Medicine in Bellevue Hospital Medical College, N. Y. This little book through its various editions has probably done more to advance the science of physical exploration of the chest than any other dissertation upon the subject, and now in its fifth edition it is as near perfect as it can be. The rapidity with which previous editions were sold shows how the profession appreciated the thor- oughness of Prof. Flint’s investigations. For stu- dents it is excellent. Its value is shown both in the arrangement of the material and in the clear, concise style of expression. For the practitioner it is a ready manual for reference.—North Ameri- can Practitioner, January, 1891. THE SAME AUTHOR. A Practical Treatise on the Physical Exploration of the Chest and the Diagnosis of Diseases Affecting the Respiratory Organs. Second and revised edition. In one handsome octavo volume of 591 pages. Cloth, $4.50. Phthisis: Its Morbid Anatomy, Etiology, Symptomatic Events and Complications, Fatality and Prognosis, Treatment and Physical Diag- nosis ; In a series of Clinical Studies. In one octavo volume of 442 pages. Cloth, $3.50. A Practical Treatise on the Diagnosis, Pathology and Treatment of Diseases of the Heart. Second revised and enlarged edition. In one octavo volume of 550 pages, with a plate. Cloth, $4. Essays on Conservative Medicine and Kindred Topics. In one very hand- some royal 12mo. volume of 210 pages. Cloth, $1.38. BROWNE, LENNOX, F. R. C. S., E., Senior Physician to the Central London Throat and Ear Hospital. A Practical Guide to Diseases of the Throat and Nose, including Associated Affections of the Ear. New (third) and enlarged edition. In one imperial octavo volume of 734 pages, with 120 illustrations in color, and 235 engravings on wood. Cloth, $6.50. The third edition of Mr. Lennox Browne’s in- structive and artistic work on “ The Throat and Its Diseases” appears under the title of “The Throat and Nose and Their Diseases.” This change has been rendered desirable by the ad- vances made during the last decade in rhinology. The nasal sections, which extend to upwards of 100 pages, give in a short space the best account of the present position of rhinology with which we are acquainted. The engravings in this hand- some volume are of the same high order as here- tofore, and more numerous than ever; they can- not fail to be of the greatest assistance to senior stu- dents and practitioners. The instruments, either figured or described, are those which, as the result of experience, Mr. Browne has found to be of the greatestutility in diagnosis and treatment; they are most simple, inexpensive and easily kept aseptic- points of much importance. We have on a former occasion eulogised the beautiful and typical col- ored plates drawn on stone by the author-artist himself, and forming in themselves a valuable and instructive atlas, the equal of which is not to be found in any modern work, treating of these subjects. Mr. Lennox Browne is to congratulated on having produced the best practical text-book on diseases of the throat and nose extant. We are glad to learn that it is being translated into French and German.— The Provincial Medical Journal, August 1,1890. Koch’s Remedy in Relation to Throat Consumption. In one octavo volume of 121 pages, with 45 illustrations, 4 of which are colored, and 17 charts. Cloth, $1.50. Just ready. THE SAME A UTHOR. SEILER, CAUL, 31. I)., Lecturer on Laryngoscopy in the University of Pennsylvania. A Handbook of Diagnosis and Treatment of Diseases of the Throat, Nose and Naso-Pharynx. Third edition. In one handsome royal 12mo. volume of 373 pages, with 101 illustrations and 2 colored plates. Cloth, $2.25. Few medical writers surpass this author in ability to make his meaning perfectly clear in a few words, and in discrimination in selection, both of topics and methods. The book deserves a large sale, especially among general practitioners—Chi- cago Medical Journal and Examiner, April, 1889. COHEN, J. SOLIS, M. J)., Lecturer on Laryngoscopy and Diseases of the Throat and Chest in the Jefferson Medical College. Diseases of the Throat and Nasal Passages. A Guide to the Diagnosis and Treatment of Affections of the Pharynx, (Esophagus, Trachea, Larynx and Nares. Third edition, thoroughly revised and rewritten, with a large number of new illustrations. In one very handsome octavo volume. Preparing. GROSS, S. JD., 31. H., LL.H., H.C.L. Oxon., LL.H. Cantab. A Practical Treatise on Foreign Bodies in the Air-passages. In one octavo volume of 452 pages, with 59 illustrations. Cloth, $2.75. Lea Brothers & Co.’s Publications—Nerv. andMent. Dis.,ete. 19 ROSS, JAMES, M.L>., F.R. C.F., LL.JD., A Handbook on Diseases of the Nervous System. In one octavo volume of 725 pages, with 184 illustrations. Cloth, $4.50; leather, $5.50. Senior Assistant Physician to the Manchester Royal Infirmary. The book before us is entitled to the highest consideration; it is painstaking, scientific and exceedingly comprehensive.—New York Medical Journal, July 10, 1886. The author has rendered a great service to the profession by condensing into one volume the principal facts pertaining to neurology and nerv- ous diseases as understood at the present time, and he has succeeded in producing a work at once brief and practical yet scientific, without entering into the discussion of theorists, or burdening the mind with mooted questions.—Pacific Medical and Suraical Journal and Western Lancet, May, 1886. This admirable work is intended for students of medicine and for such medical men as have no time for lengthy treatises. In the present instance the duty of arranging the vast store of material at the disposal of the author, and of abridging the de- scription of the different aspects of nervous dis- eases, has been performed with singular skill, and the result is a concise and philosophical guide to the department of medicine of which it treats. Dr. Ross holds such a high scientific position that any writings which bear his name are naturally expected to have the impress of a powerful intel- lect. In every part this handbook merits the highest praise, and will no doubt be found of the greatest value to the student as well as to the prac- titioner.—Edinburgh Medical Journal, Jan. 1887. HAMILTON, ALLAN McLANE, M. 1)., Attending Physician at the Hospital for Epileptics and Paralytics, Blackwell's Island, N. Y Nervous Diseases; Their Description and Treatment. Second edition, thoroughly revised and rewritten. In one octavo volume of 598 pages, with 72 illustrations. Clotli, $4. When the first edition of this good book appeared we gave it our emphatic endorsement, and the Csent edition enhances our appreciation of the k and its author as a safe guide to students of clinical neurology. One of the best and most critical of English neurological journals, Brain, has characterized this book as the best of its kind in any language, which is a handsome endorsement from an exalted source. The improvements in the new edition, and the additions to it, will justify its purchase even by those who possess the old.— Alienist and Neurologist, April, 1882. TUKE, DANIEL HACK, M. JO., Joint Author of The Manual of Psychological Medicine, etc. Illustrations of the Influence of the Mind upon the Body in Health and Disease. Designed to elucidate the Action of the Imagination. New edition. Thoroughly revised and rewritten. In one 8vo. vol. of 467 pp., with 2 col. plates. Cloth, $3. It is impossible to peruse these interesting chap- ters without being convinced of the author’s per- fect sincerity, impartiality, and thorough mental grasp. Dr. Tuke has exhibited the requisite amount of scientific address on all occasions, and the more intricate the phenomena the more firmly has he adhered to a physiological and rational method of interpretation. Guided by an enlight- ened deduction, the author has reclaimed for science a most interesting domain in psychology, previously abandoned to charlatans and empirics. This book, well conceived and well written, must commend itself to every thoughtful understand- ing.—New York Medical Journal, September 6,1884. GRAY, LANHON CARTER, M.I)., Professor of Diseases of the Mind and Nervous System in the New York Polyclinic. A Practical Treatise on Diseases of the Nervous System. Preparing. CLO USTON, THOMAS S., M. I)., E. R. C. I\, L. R. C. S., Lecturer on Mental Diseases in the University of Edinburgh. Clinical Lectures on Mental Diseases. With an Appendix, containing an Abstract of the Statutes of the United States and of the Several States and Territories re- lating to the Custody of the Insane. By Charles F. Folsom, M. D., Assistant Professor of Mental Diseases, Med. Dep. of Harvard Univ. In one handsome octavo volume of 541 pages, with eight lithographic plates, four of which are beautifully colored. Cloth, $4. The practitioner as well as the student will ac- cept the plain, practical teaching of the author as a forward step in the literature of insanity. It is refreshing to find a physician of Dr. Clouston’s experience and high reputation giving the bed- side notes upon which his experience has been founded and his mature judgment established. Such clinical observations cannot but be useful to the general practitioner in guiding him to a diag- nosis and indicating the treatment, especially In many obscure and doubtful cases of mental dis- ease. To the American reader Dr. Folsom’s Ap- pendix adds greatly to the value of the work, and will mike it a desirable addition to every library. —American Psychological Journal, July, 1884. ®gg?“Dr. Folsom’s Abstract may also be obtained separately in one octavo volume of 108 pages. Cloth, $1.50. SAVAGE, GEORGE H, M. I)., Lecturer on Mental Diseases at Guy's Hospital, London. Insanity and Allied Neuroses, Practical and Clinical. In one 12mo. vol. of 551 pages, with 18 illus. Cloth, $2.00. See Series of Clinical Manuals, page 31. As a handbook, a guide to the practitioner and student, the book fulfils an admirable purpose. The many forms of insanity, are described with characteristic clearness, the illustrative cases are carefully selected, and as regards treatment sound common sense is everywhere apparent. Dr. Sav- age has written an excellent manual for the prac- titioner and student.—Amer. Jour, oflnsan., Apr.’85. PLA YFAIR, W. S., M. 1)., F. R. C. F. The Systematic Treatment of Nerve Prostration and Hysteria. In one handsome small 12mo. volume of 97 pages. Cloth, $1.00. BLANDFORD ON INSANITY AND ITS TREAT- MENT. Lectures ou the Treatment, Medical and Legal, of Insane Patients. In one very hand- some octavo volume. JONES’ CLINICAL OBSERVATIONS ON FUNC- TIONAL NERVOUS DISORDERS. Second American Edition. In one handsome octavo volume of 340 pages. Cloth, $3.25. 20 Lea Brothers & Co.’s Publications—Surgery. ROBERTS, JOHN B., M.B., Professor of Anatomy and Surgery in the Philadelphia Polyclinic. Professor of the Principles and Practice of Surgery in the Woman's Medical College of Pennsylvania. Lecturer in Anatomy in the Univer- sity of Pennsylvania. The Principles and Practice of Modern Surgery. For the use of Students and Practitioners of Medicine and Surgery. In one very handsome octavo volume of 780 pages, with 501 illustrations. Cloth, $4.50; leather, $5.50. Just ready. In this work the author has endeavored to give to the profession in a condensed form the doctrines and procedures of Modern Surgery. He has made it a work devoted more especially to the practice than to the theory of surgery. His own large experience has added many valuable features to ■the work. It contains many practical points in diagnosis, which render it the more valuable to the practitioner; and the systematization which pervades the whole work, together with its perspicuity, enhance its value as a student’s manual. The fact that this work is eminently practical cannot be too strongly emphasized. It is modern, and as its teaching is that generally accepted and such that affords little opportunity for discussion, it will be lasting. It is clear and concise, yet full. The book is entitled to a place in modern surgical literature.—Annals of Surgery, Jan. 1891. This work is a very comprehensive manual upon general surgery, and will* doubtless meet with a favorab’e reception by the profession. It has a thoroughly practical character, the subjects are treated with rare judgment, its conclusions are in accord with those of the leading practitioners of the art, and its literature is fully up to all the ad- vanced doctrines and methods of practice of the present day. Its general arrangement follows this rule, and the author in his desire to be con- cise and practical is at times almost dogmatic, but this is entirely excusable consideringthe admira- ble manner in which he has thus increased the usefulness of his work.—Medical Record, Jan. 17, 1891. ASHHURST, JOHN, Jr., M. D., Barton Prof, of Surgery and Clin. Surgery in TJniu. of Penna., Surgeon to the Penna. Hosp., etc. The Principles and Practice of Surgery. New (fifth) edition, enlarged and thoroughly revised. In one large and handsome octavo volume of 1144 pages, with ■642 illustrations. Cloth, $6; leather, $7. A complete and most excellent work on surgery. It is only necessary to examine it to see at once its excellence and real merit either as text-book for the student or a guide for the general practi- tioner. It fully considers in detail every surgical injury and disease to which the body is liable, and every advance in surgery worth noting is to be found in its proper place. It is unquestionably the best and most complete single volume on surgery, in the English language, and cannot but receive that continued appreciation which its merits justly demand.—Southern Practitioner, Feb. 1890. This is one of the most popular and useful of the many well-known treatises on general surgery. It furnishes in a concise manner a clear and comprehensive description of the modes of prac- tice now generally employed in the treatment of surgical affections, with a plain exposition of the principles on which those modes of practice are based. The entire work has been carefully revised, and a number of new illustrations introduced that greatly enhance the value of the book.— Cincinnati Lancet-Clinic, Dec. 14, 1889. DRUITT, ROBERT, M. R. C. S., etc. Manual of Modern Surgery. Twelfth edition, thoroughly revised by Stan- ley Boyd, M. B., B. S., F. R. C. S. In one 8vo. volume of 965 pages, with 373 illustra- tions. Cloth, $4; leather, $5. It is essentially a new book, rewritten from be- ginning to end. The editor has brought his work up to the latest date, and nearly every subject on which the student and practitioner would desire to consult a surgical volume, has found its place here. The volume closes with about twenty pages of formulse covering a broad range of practical therapeutics. The student will find that the new Druitt is to this generation what the old one was to the former, and no higher praise need be accorded to any volume.—North Carolina Medical Journal, October, 1887. Druitt’s Surgery has been an exceedingly popu- lar work in the profession. It is stated that 50,000 copies have been sold in England, while in the United States, ever since its first issue, it has been used as a text-book to a very large extent. Dur- ing the late war in this country it was so highly appreciated that a copy was issued by the Govern- ment to each surgeon. The present edition, while it has the same features peculiar to the work at first, embodies all recent discoveries in surgery, and is fully up to the times.—Cincinnati Medical News, September, 1887. GANT, FREDERICK JAMBS, F. R. C. S., Senior Surgeon to the Royal Free Hospital, London. The Student’s Surgery. A Maltum in Parvo. In one square octavo volume of 848 pages, with 159 engravings. Cloth, $3.75. GBOSS, S. />., M. B., LL. B., I). C. L. Oxon., LL. D. Cantab., A System of Surgery: Pathological, Diagnostic, Therapeutic and Operative. Sixth edition, thoroughly revised and greatly improved. In two large and beautifully printed imperial octavo volumes containing 2382 pages, illustrated by 1623 engravings. Strongly bound in leather, raised bands, $15. Emeritus Professor of Surgery in the Jefferson Medical College of Philadelphia. BALL, CHARLES B., M. Ch., l)ub., F. R. C. S., F., Surgeon and Teacher at Sir P. Dun's Hospital, Dublin. Diseases of the Rectum and Anus. In one 12mo. volume of 417 pp., with 54 cuts, and 4 colored plates Cloth, $2.25. See Series of Clinical Manuals 31. GIBNEY, V. 1\, M. I)., Surgeon to the Orthopaedic Hospital, New York, etc. Orthopaedic Surgery. For the use of Practitioners and Students. In one hand- some octavo volume, profusely illustrated. Preparing. Lea Brothers & Co.’s Publications—Surgery. 21 ERICHSEN, JOHN E., F. R. S., F. R. C. S., Professor of Surgery in University College, London, etc. The Science and Art of Surgery; Being a Treatise on Surgical Injuries, Dis- eases and Operations. From the eighth and enlarged English edition. In two large and beautiful octavo volumes of 2316 pages, illustrated with 984 engravings on wood. Cloth, $9; leather, raised bands, $11. We have always regarded “The Science and Art of Surgery” as one of the best surgical text- books in the English language, and this eighth edition only confirms our previous opinion. We take great pleasure in cordially commending it to our readers.— The Medical News, April 11,1885. For many years this classic work has been made by preference of teachers the principal text-book on surgery for medical students, while through translations into the leading continental languages it may be said to guide the surgical teachings of the civilized world. No excellence of the former edition has been dropped and no discovery, device or improvement which has marked the progress of surgery during the last decade has been omitted. The illustrations are many and executed in the highest style of art. —Louisville Medical News, Feb. 14,1835. BRYANT, THOMAS, F. R. C. S., Surgeon and Lecturer on Surgery at Guy's Hospital, London. The Practice of Surgery. Fourth American from the fourth and revised Eng- lish edition. In one large and very handsome imperial octavo volume of 1040 pages, with 727 illustrations. Cloth, $6.50; leather, $7.50. The fourth edition Of this work is fully abreast of the times. The author handles his subjects with that degree of judgment and skill which is attained by years of patient toil and varied ex- perience. The present edition is a thorough re- vision of those which preceded it, with much new matter added. His diction is so graceful and logical, and his explanations are so lucid, as to place the work among the highest order of text- books for the medical student. Almost every topic in surgery is presented in such a form as to enable the busy practitioner to review any subject in every-day practice in a short time. No time is lost with useless theories or superfluous verbiage, In short, the work is eminently clear, logical and practical.—Chicago Medical Journal and Examiner, April, 1886. This book is essentially what it purports to be, viz.: a manual for the practice of surgery. It is peculiarly well fitted for the student or busy general practitioner.—The Medical News, August 15, 1885. TREVES, FREDERICK, I. R. C. S., Hunterian Professor at the Royal College of Surgeons of England. A Manual of Surgery. In Treatises by Various Authors. In three 12mo. volumes, containing 1866 pages, with 213 engravings. Price per volume, cloth, $2. See Students’ Series of Manuals, page 31. We have here the opinions of thirty-three authors, in an encyclopedic form for easy and ready reference. The three volumes embrace every variety of surgical affections likely to be met with, the paragraphs are short and pithy, and the salient points and the beginnings of new sub- jects are always printed in extra-heavy type, so that a person may find whatever information he may be in need of at a moment’s glance.—Cin- cinnati Lancet-Clinic, August 21, 1886. HOLMES, TIMOTHY, M. A., Surgeon and Lecturer on Surgery at St. George's Hospital, London. A System of Surgery; Theoretical and Practical. IN TREATISES BY VARIOUS AUTHORS. American edition, thoroughly revised and re-edited by John H. Packard, M. D., Surgeon to the Episcopal and St. Joseph’s Hospitals, Philadelphia, assisted by a corps of thirty-three of the most eminent American surgeons. In three large imperial octavo volumes containing 3137 double-columned pages, with 979 illustrations on wood and 13 lithographic plates, beautifully colored. Price per set, cloth, $18.00; leather, $21.00. Sold only by subscription. WHARTON, HENRY R., M. D., Demonstrator of Surgery and Lecturer on Surgical Diseases of Children in the Un v. of Penna. Minor Surgery and Bandaging. In one very handsome 12mo. volume of 498 pages, with 403 engravings, many being photographic. Cloth, $3.00. Just ready. MARSH, HOWARD, F. R. C. 8., Senior Assistant Surgeon to and Lecturer on Anatomy at St. Bartholomew's Hospital, London. Diseases of the Joints. In one 12mo. volume of 468 pages, with 64 woodcuts and a colored plate. Cloth, $2.00. See Series of Clinical Munuals, page 31. BUT UN, HENRY T., F. R. C. S., Assistant Surgeon to St. Bartholomew's Hospital, London. Diseases of the Tongue. In one 12mo. volume of 456 pages, with 8 colored plates and 3 woodcuts. Cloth, $3.50. See Series of Clinical Manuals, page 31. TREVES, FREDERICK, F. R. C. S., Surgeon to and Lecturer on Surgery at the London Hospital. Intestinal Obstruction. In one pocket-size 12mo. volume of 522 pages, with 60 illustrations. Limp cloth, blue edges, $2.00. See Series of Clinical Ifanuals, page 31. GOULD, A. PEARCE, 31. S., 31. B., I. R. C. S„ Assistant Surgeon to Middlesex Hospital. Elements of Surgical Diagnosis. In one pocket-size 12mo. volume of 589 pages. Cloth, $2.00. See Students’ Series of 3Ianuals, page 31. PIRRIE’S PRINCIPLES AND PRACTICE OF SURGERY. Edited by John Neill, M. D. In one 8vo. vol. of 784 pp. with 316 illus. Cloth, *3.75. MILLER’S PRINCIPLES OF SURGERY. Fourth American from the third Edinburgh edition. In one 8vo. vol. of 638 pages, with 340 illustrations. Cloth, *3.75. MILLER’S PRACTICE OF SURGERY. Fourth and revised American edition. In one large 8vo. vol. of 682 pp., with 364 illustrations. Cloth ,*3.75. 22 Lea Brothers & Co.’s Publications—Surgery, Frac., Disloe. SMITH, STEPHEN, M. D., Professor of Clinical Surgery in the University of the City of New York. The Principles and Practice of Operative Surgery. New (second) and thoroughly revised edition. In one very handsome octavo volume of 892 pages, with 1005 illustrations. Cloth, $4.00; leather, $5.00. This excellent and very valuable book.is one of the most satisfactory works on modern operative surgery yet published. Its author and publisher have spared no pains to make it as far as possible an ideal, and their efforts have given it a position prominent among the recent works in this depart- ment of surgery. The book is a compendium for the modern surgeon. The present, the only revised edition since 1879, presents many changes from the original manual. The volume is much en- larged, and the text has been thoroughly revised, so as to give the most improved methods in asep- tic surgery, and the latest instruments known for operative work. Itcau be truly said that as ahand- book for the student, aeompanion for the surgeon, and even as a book of reference for the physician not especially engaged in the practice of surgery, this volume will long hold a most conspicuous place, and seldom will its readers, no matter how unusual the subject, consult its pages in vain. Its compact form, excellent print, numerous illustra- tions, and especially its decidedly practical char- acter, all combine to commend it.—Boston Medical and Surgical Journal, May 10,1888. HOLMES, TIMOTHY, M. A., Surgeon and Lecturer on Surgery at St. George's Hospital, London. A Treatise on Surgery; Its Principles and Practice. New American from the fifth English edition, edited by T. Pickering Pick, F. R. C. S. In one octavo volume of 997 pages, with 428 illustrations. Cloth, $6.00; leather, $7.00. To the younger members of the profession and to others not acquainted with the book and its merits, we take pleasure in recommending it as a surgery complete, thorough, well-written, fully illustrated, modern, a work sufficiently volumi- nous for the surgeon specialist, adequately concise for the general practitioner, teaching those things that are necessary to be known for the successful prosecution of the physician’s career, imparting nothing that in our present knowledge is consid- ered unsafe, unscientific or inexpedient.—Pacific Medical Journal, July, 1889. HAMILTON, FRANK II., M. I)., LL. I)., Surgeon to Bellevue Hospital, New York. A Practical Treatise on Fractures and Dislocations. New (8th) edi- tion, revised and edited by Stephen Smith, A. M., M. D., Professor of Clinical Surgery in the University of the City of New York. In one very handsome octavo volume of 832 pages, with 507 illustrations. Cloth, $5.50; leather, $6.50. It has received the highest endorsement that a work upon a department of surgery can possibly receive. It is used as a text-book in every medi- cal college of this country, and the publishers have been called upon to print eight editions of it. What more can be said in commendation of it? It has been said with truth that it is doubtful if any surgical work has appeared during the last half century which more completely filled the place for which it was designed. As Dr. Smith says, its great merits appear most conspicuously in its clear, concise, and yet comprehensive state- ment of principles, which renders it an admirable text-book for teacher and pupil, and in its wealth of clinical materials, which adapts it to the daily necessities of the practitioner. Fractures and dislocations are injuries which the general practi- tioner, in his character as a surgeon, is most called upon to treat. They form a part of surgery that he cannot avoid taking charge of. Under the circumstances, therefore, he needs all the aid he can secure. But what better assistance can he seek than a work that is devoted exclusively to treating fractures and dislocations, and conse- quently contains full information, in plain lan- guage, for the management of every emergency that is likely to be met with in such injuries? The country is filled with railroads and manufac- tories where accidents are constantly occurring, and to which general practitioners, and not dis- tinguished surgeons, are constantly liable to be called. We consider that the work before us should be in the library of every practitioner.— Cincinnati Medical News, February, 1891. STIMSON, LEWIS A., li. A., M. I)., Surgeon to the Presbyterian and Bellevue Hospitals, Professor of Clinical Surgery in the Medical Faculty of Univ. of City of N. Y., Corresponding Member of the Societe de Chirurgie of Paris. A Manual of Operative Surgery. New (second) edition. In one very hand- some royal 12mo. volume of 503 pages, with There is always room for a good book, so that while many works on operative surgery must be considered superfluous, that of Dr. Stimson has held its own. The author knows the difficult art of condensation. Thus the manual serves as a work of reference, and at the same time as a handy guide. It teaches what it professes, the steps of operations. In this edition Dr. Stimson has sought to indicate the changes that have been 342 illustrations. Cloth, $2.50. effected in operative methods and procedures by the antiseptic system, and has added an account of many new operations and variations in the steps of older operations. We do not desire to extol this manual above many excellent standard British publications of the same class, still we be- lieve that it contains much that is worthy of imi- tation.—British Medical Journal, Jan. 22, 1887. A Treatise on Fractures and Dislocations. In two handsome octavo vol- the same Author. umes. Vol. I., Fractures, 582 pages, 360 beautiful illustrations. Vol. II., Disloca- tions, 540 pages, with 163 illustrations. Complete work, cloth, $5.50; leather, $7.50. Either volume separately, cloth, $3.00; leather, $4.00. The appearance of the second volume marks the completion of the author’s original plan of prepar- ing a work which should present in the fullest manner all that is known on the cognate subjects of Fractures and Dislocations. The volume on Fractures assumed at once the position of authority on the subject, and its companion on Dislocations will no doubt be similarly received. The closing volume of Dr. Stimson’s work exhibits the surgery of Dislocations as it is taught and practised by the most eminent surgeons of the present time. Con- taining the results of such extended researches it must for a long time be regarded as an authority on all subjects pertaining to dislocations. Every practitioner of surgery will feel it incumbent on him to have it for constant reference.—Cincinnati Medical News, May, 1888. HICK, T. PICKERING, 1\ R. C. S., Surgeon to and Lecturer on Surgery at St. George's Hospital, London. Fractures and Dislocations. In one 12mo. volume of 530 pages, with 93 illustrations. Limp cloth, $2.00. See Series of Clinical Manuals, page 31. Lea Brothers & Co.’s Publications—Otol., Ophthal. 23 BURNETT, CHARLES H, A. M., M. D., Professor of Otology in the Philadelphia Polyclinic; President of the American Otological Society. The Ear, Its Anatomy, Physiology and Diseases. A Practical Treatise for the use of Medical Students and Practitioners. Second edition. In one handsome octavo volume of 580 pages, with 107 illustrations. Cloth, $4.00; leather, $5.00. We note with pleasure the appearance of a second edition of this valuable work. When it first came out it was accepted by the profession as one of the standard works on modern aural surgery in the English language; and in his second edition Dr. Burnett has fully maintained his reputation, for the book is replete with valuable information and suggestions. The revision has been carefully carried out, and much new matter added. Dr. Burnett’s work must be regarded as a very valua- ble contribution to aural surgery, not only on account of its comprehensiveness, but because it contains the results of the careful personal observa- tion and experience of this eminent aural surgeon. —London Lancet, Feb. 21, 1885. BERRY, GEORGE A., M. B., F. R. C. 8., Ed., Diseases of the Eye. A Practical Treatise for Students of Ophthalmology. In one octavo volume of 683 pages, with 144 illustrations, 62 of which are beautifully colored. Cloth, $7.50. Ophthalmic Surgeon, Edinburgh Royal Infirmary. novice—with a mass of details with no key to their unravelling. It is apparent that the literature of each subject has been gone over in a very thor- ough manner. The fact that he was writing a clinical treatise for beginners and not an encyclo- pedia has always been present with the author. The number and excellence of the colored illus- trations in the text deserve more than a passing notice.—Archives of Ophthalmology, Sept. 1889. This newest candidate for favor among ophthal- mological students is designed to be purely clinical in character and the plan is well adhered to. We have been forcibly struck by the rare good taste in the selection of what is essential which per- vades the book. The author seems to have the uncommon faculty of viewing his subject as a whole and seizing the salient points and not con- fusing his reader—presumably a student and a NETTLE SHIP, EDWARD, E. R. C. 8., Ophthalmic Surgeon at St. Thomas' Hospital, London. Surgeon to the Royal London (Moorfields) Ophthalmic Hospital. Diseases of the Eye. New (fourth) American from the fifth English edition, thoroughly revised. With a Supplement on the Detection of Color Blindness, by Wil- liam Thomson, M. D., Professor of Ophthalmology in the Jefierson Medical College. In one 12mo. volume of 500 pages, with 164 illustrations, selections from Snellen’s test- types and formulae, and a colored plate. Cloth, $2.00. This is a well-known and a valuable work. It was primarily intended for the use of students, and supplies their needs admirably, but it is as useful lor the practitioner, or indeed more so. It does not presuppose the large amount of recondite knowledge to be present which seems to be as- sumed in some of our larger works, is not tedious from over-conciseness, and yet covers the more important parts of clinical ophthalmology. A supplement is made to the present edition on the practical examination of railroad employes as to color-blindness and acuteness of vision and hear- ing. This is well written, and contains good suggestions for those who may be called on to make such examinations.—New York Medical Journal, December 13,1890. JJJLER, HENRY E., F. R. C. 8., Senior Ass't Surgeon, Royal Westminster Ophthalmic Hosp.; late Clinical Ass't, Moorfields, London. A Handbook of Ophthalmic Science and Practice. Handsome 8vo. vol- ume of 460 pages, with 125 woodcuts, 27 colored plates, selections from Test-types of Jaeger and Snellen, and Holmgren’s Color-blindness Test. Cloth, $4.50; leather, $5.50. It presents to the student concise descriptions and typical illustrations of all important eyeafl'ec- tions, placed in juxtaposition, so as to be grasped at a glance. Beyond a doubt it is the best illus- trated handbook'of ophthalmic science which has ever appeared. Then, what is still better, these illustrations are nearly all original. We have ex- amined this entire work with great care, and it represents the commonly accepted views of ad- vanced ophthalmologists. We can most heartily commend this book to all medical students, prac- titioners and specialists.—Detroit Lancet, Jan. ’85. NORRIS, JVM. F., M. I)., and OLIVER, C'HAS. A., M. I). A Text-Book of Ophthalmology. In one octavo volume of about 500 pages, with illustrations. Preparing. Clin. Prof, of Ophthalmology in Univ. of Pa. CARTER, R. BRUDENELL, & FROST, W. ADAMS, F. R. C. S., E. R. C. 8., Ophthalmic Surgery. In one 12mo. volume of 559 pages, with 91 woodcuts, color-blindness test, test-types and dots and appendix of formulae. Cloth, $2.25. See Series of Clinical Manuals, 31. Ophthalmic Surgeon to and Led. on Ophthal- mic Surgery at St. George's Hospital, London. Ass't Ophthalmic Surgeon and Joint Led. on Oph. Sur., St. George's Hosp., London. WELLS ON THE EYE. In one octavo volume. LAURENCE AND MOON’S HANDY BOOK OF OPHTHALMIC SURGERY, for the use of Prac- titioners. Second edition. In one octavo vol- ume of 227 pages, with 65 illus. Cloth, $2.75. LAWSON ON INJURIES TO THE EYE, ORBIT AND EYELIDS: Their Immediate and Remote Effects. In one octavo volume of 404 pages, with 92 illustrations. Cloth, $3.50. 24 Lea Brothers & Co.’s Publications—Urin. Dis., Dentistry, etc. ROBERTS, SIR WILLIAM, M. I)., Lecturer on Medicine in the Manchester School of Medicine, etc. A Practical Treatise on Urinary and Kenal Diseases, including Uri- nary Deposits. Fourth American from the fourth London edition, in one hand- some octavo volume of 609 pages, with 81 illustrations. Cloth, $3.50. It may be said to be the best book in print on the subject of which it treats.—The American Journal of the Medical Sciences, Jan. 1886. The peculiar value and finish of the book are in a measure derived from its resolute maintenance of a clinical and practical character. It is an un- rivalled exposition of everything which relates directly or indirectly to the diagnosis, prognosis and treatment of urinary diseases, and possesses a completeness not found elsewhere in our lan- guage in its account of the different affections.— The Manchester Medical Chronicle, July, 1885. The value of this treatise as a guide book to the physician in daily practice can hardly be over- estimated. That it is fully up to the level of our present knowledge is a fact reflecting great credit upon Dr. Roberts, who has a wide reputation as a busy practitioner.—Medical Record, July 31, 1886. By the Same Author. Diet and Digestion. In one 12mo. volume of 270 pp. Cloth, $1.50. Just ready. PUR BY, CHARLES W., M. D., Chicago. Bright’s Disease and Allied Affections of the Kidneys. In one octavo volume of 288 pages, with illustrations. Cloth, $2. The object of this work is to “furnish a system- atic, practical and concise description of the pathology and treatment of the chief organic diseases of the kidney associated with albuminu- ria, which shall represent the most recent ad- vances in our knowledge on these subjects and this definition of the object is a fair description of the book. The work is a useful one, giving in a short space the theories, facts and treatments, and going more fully into their later developments. On treatment the writer is particularly strong, steering clear of generalities, and seldom omit- ting, what text-books usually do, the unimportant items which are all important to the general prac- titioner.—The Manchester Medical Chronicle, Oct. 1886. MORRIS, HENRY, M. B., E. R. C. S., Surgical Diseases of the Kidney. In one 12mo. volume of 554 pages, with 40 woodcuts, and 6 colored plates. Limp cloth, $2.25. See Series of Clinical Manuals, page 31. Surgeon to and Lecturer on Surgery at Middlesex Hospital, London. In this manual we have a distinct addition to surgical literature, which gives information not elsewhere to be met with in a single work. Such a book was distinctly required, and Mr. Morris has very diligently and ably performed the task he took in hand. It is a full and trustworthy book of reference, both for students and prac- titioners in search of guidance. The illustrations in the text and the chromo-lithographs are beau- tifully executed.— The London Lancet, Feb. 26,1886. LUCAS, CLEMENT, M. B., B. S., F. R. C. S., Senior Assistant Surgeon to Guy's Hospital, London. Diseases of the Urethra. In one 12mo. volume. Preparing. See Series of Clinical Manuals, page 4. THOMPSON, SIR HENRY, Surgeon and Professor of Clinical Surgery to University College Hospital, London. Lectures on Diseases of the Urinary Organs. Second American from the third English edition. In one 8vo. volume of 203 pp., with 25 illustrations. Cloth, $2.25. By the Same Author. On the Pathology and Treatment of Stricture of the Urethra and Urinary Pistulae. From the third English edition. In one octavo volume of 359 pages, with 47 cuts and 3 plates. Cloth, $3.50. THE AMERICAN SYSTEM OF DENTISTRY. In Treatises b; In Treatises by Various Authors. Edited by Wilbur F. Litch, M. D., D. D. S., Professor of Prosthetic Dentistry, Materia Medica and Therapeutics in the Pennsylvania College of Dental Surgery. In three very handsome octavo volumes con- taining 3160 pages, with 1863 illustrations and 9 full-page plates. Per volume, cloth, $6; leather, $7 ; half Morocco, gilt top, $8. The complete work is now ready. For sale by subscription only. As an encyclopaedia of Dentistry it has no su- perior. It should form a part of every dentist’s library, as the information it contains is of the freatest value to all engaged in the practice of entistry.—American Jour. Dent. Sci., Sept. 1886. A grand system, big enough and good enough and handsome enough for a monument (which doubtless it is), to mark an epoch in the history of dentistry. Dentists will be satisfied with it and proud of it—they must. It is sure to be precisely what the student needs to put him and keep him in the right track, while the profession at large will receive incalculable benefit from it.—Odonto- graphic Journal, Jan. 1887. COLEMAN, A., L. R. C. P., E. It. C. S., Exam. L. 1). S., Senior Dent. Surg. and Lect. on Dent. Surg. at St. Bartholomew's Hosp. and the Dent. Hosp., London. A Manual of Dental Surgery and Pathology. Thoroughly revised and adapted to the use of American Students, by Thomas C. Stellwagen, M. A., M. D., D. D. S., Prof, of Physiology in the Philadelphia Dental College. In one handsome octavo volume of 412 pages, with 331 illustrations. Cloth, $3.25. It should be in the possession of every practi- tioner in this country. The part devoted to first and second dentition and irregularities in the per- manent teeth is fully worth the price. In fact, price should not be considered in purchasing such a work. If the money put into some of oiy so- called standard text-books could be converted into such publications as this, much good would result. —Southern Dental Journal, May, 1882. BASHAM ON RENAL DISEASES: A (Clinical Guide to their Diagnosis and Treatment. In one 12mo. vol. of 304 pages, with 21 Illustrations. Cloth, $2.00. Lea Brothers & Co.’s Publications—Venereal, Impotence. 25 GROSS, SAMUEL W.9 A. M.9 M. D.9 LL. D., Professor of the Principles of Surgery and of Clinical Surgery in the Jefferson Medical College of Phila. A Practical Treatise on Impotence, Sterility, and Allied Disorders of the Male Sexual Organs. New (4th) edition, thoroughly revised by F. R. Sturgis, M. D., Prof, of-Diseases of the Genito-Urinary Organs and of Venereal Diseases, N. Y. Post Grad. Med. School. In one very handsome octavo volume of 165 pages, with 18 illustrations. Cloth, $1.50. Three editions of Professor Gross’ valuable book have been exhausted, and still the demand is unsupplied. Dr. Sturgis has revised and added to the previous editions, and the new one appears more complete and more valuable than before. Four important and generally misunderstood sub- jects are treated—impotence, sterility, spermator- rhoea, and prostatorrhoea. The book is a practical one and in addition to the scientific and very in- teresting discussions on etiology, symptoms, etc., there are lines of treatment laid down that any practitioner can follow and which have met with success in the hands of author and editor.—Medi- cal Record, Feb. 25, 1891. It has been the aim of the author to supply in a compact form, practical and strictly scientific information especially adapted to the wants of the general practitioner in regard to a class of common and grave disoriers. The work contains very many facts in regard to the sexual disorders of men, of the most interesting character. We com- mend the study of it to every professional man, and especially to those engaged in the general practice of medicine.—Cin. Med. News, Jan. 1891. The work before us has become a standard text- book on the subjects of which it treats. In the present edition the author’s work has been con- siderably augmented by Dr. Sturgis, whose con- tributions and views are to be feen everywhere. They contain many valuable suggestions and are the fruit of a ripe experience which cannot but enhance the original text. The profession is quick to appreciate succinct treatises which are full and complete, more especially when the authors are known to be worthy of respect and confidence.—St. Louis Med. and Swg. Jour., Feb.’91. TAYLOR, R. TV., A. M., M. I)., Clinical Profeswr of Cenito- Urinary Diseases in the College of Physicians and Surgeons, New York, Prof, of Venereal and Skin Diseases in the University of Vermont, The Pathology and Treatment of Venereal Diseases. Including the results of recent investigations upon the subject. Being the sixth edition of Bumstead and Taylor. Entirely rewritten by Dr. Taylor. Large 8vo. volume, about 900 pages, with about 150 engravings, as well as numerous chromo-lithographs. In active preparation. A notice of the previous edition is appended. It is a splendid record of honest labor, wide research, just comparison, careful scrutiny and original experience, which will always be held as a high credit to American medical literature. This is not only the best work in the English language upon the subjects of which it treats, but also one which has no equal in other tongues for its clear, comprehensive and practical handling of its themes.—Am. Jour, of the Med. Sciences, Jan. 1884. CULVFR, F. M.. M.I).. and HAYDEN. J. R.. M. D. Pathologist and Assistant Attending Surgeon, Manhattan Hospital, N. Y. Chief of Clinic Venereal Department, Van- derbilt Clinic,Coll, of Phys. andSurgs., N. Y. A Manual of Venereal Diseases. In one 12mo. volume of about 250 pages, with illustrations. Ready shortly. CO It NIL, V., Professor to the Faculty of Medicine of Paris, and Physician to the Lourcine Hospital. Syphilis, its Morbid Anatomy, Diagnosis and Treatment. Specially revised by the Author, and translated with notes and additions by J. Henry C. Simes, M. D., Demonstrator of Pathological Histology in the Univ. of Pa., and J. William White, M. D., Lecturer on Venereal Diseases, Univ. of Pa. In one handsome octavo volume of 461 pages, with 84 very beautiful illustrations. Cloth, $3.75. The anatomy, the histology, the pathology and the clinical features of syphilis are represented in this work in their best, most practical and most instructive form, and no one will rise from its perusal without the feeling that his grasp of the wide and important subject on which it treats is a stronger and surer one.—The London Practi- tioner, Jan. 1882. HUTCHINSON, JONATHAN, F. It. S., F. It. C. S., Consulting Surgeon to the London Hospital. Syphilis. In one 12mo. volume of 542 pages, with 8 chromo-lithographs. Cloth, $2.25. See Series of Clinical Manuals, page 31. Those who have seen most of the disease and those who have felt the real difficulties of diagno- sis and treatment will most highly appreciate the facts and suggestions which abound in these pages. It is a worthy and valuable record, not only of Mr. Hutchinson’s very large experience | and power of observation, but of his patience and assiduity in taking notes of his cases and keep- ing them in a form available for such excellent use as he has put them to in this volume.—London Medical Record, Nov. 12, 1887. GROSS, S. D.9 M. D.9 LL. D.9 JD. C. L.9 etc. A Practical Treatise on the Diseases, Injuries and Malformations of the Urinary Bladder, the Prostate Gland and the Urethra. Third edition, thoroughly revised by Samuel W. Gross, M. D. In one octavo volume of 574 pages, with 170 illustrations. Cloth, $4.50. CULL ER IE R, A& B UMSTEA D9 F. J.9 M.I)., LL.I)., Sturgeon to the H&pital du Midi. Late Prof, of Ven. Dis. Coll. Phys. and Surg., N. Y. An Atlas of Venereal Diseases. Translated and edited by Freeman J. Bum- stead, M. I). In one imperial 4to. volume of 328 pages, double-columns, with 26 plates, containing about 150 figures, beautifully colored, many of them the size of life. Strongly bound in cloth, $17.00. A specimen of the plates and text sent by mail, on receipt of 25 cts. HILL ON SYPHILIS AND LOCAL CONTAGIOUS I DISORDERS. In one 8vovol. of479 p. Cloth, 83.25. ! LEE’S LECTURES ON SYPHILIS AND SOME ! FORMS OF LOCAL DISEASE AFFECTING PRINCIPALLY THE ORGANS OF GENERA- TION. In one 8vo. vol. of 246 pages. Cloth, 82.25, 26 Lea Brothers & Co.’s Publications—Venereal, Skin. TA YLOR, ROBERT W., A. M., M. 1)., Clinical Professor of Oenilo Urinary Diseases in the College of Physicians and Surgeons, New York; Surgeon to the Department of Venereal and Skin Diseases of the New York Hospital; Presi- dent of the American Dermatological Association. A Clinical Atlas of Venereal and Skin Diseases: Including Diagnosis, Prognosis and Treatment. In eight large folio parts, measuring 14 x 18 inches, and comprising 58 beautifully colored plates with 213 figures, and 431 pages of text with 85 engravings. Complete work just ready. Price per part, $2.50. Bound in one volume, half Russia, $27 ; half Turkey Morocco, $28 For sale by subscription only. Specimen plates sent on receipt of 10 cents. A full prospectus sent to any address on application. The completion of this monumental work is a subject of congratulation, not only to the author ana publishers, but to the profession at large; indeed it is to the latter that it directly appeals as a wonderfully clear exposition of a confessedly difficult branch of medicine. Good literature has joined hands with good art with highly satisfac- tory results for botn. There are altogether 213 figures, many of which are life size, and represent the highest perfection of the chromo-litho- graphic art, and scattered throughout the text are innumerable engravings. Quite a proportion of these illustrations are from the author’s own collection, while on the other hand the best atlases of the world have been drawn upon for the most typical and successful pictures of the many different types of venereal and skin dis ease. We think we may say without undue exaggeration that the reproductions, both in color and in black and white, are almost invariably successful. The text is practical, full of thera- peutical suggestions, and the clinical accounts of disease are clear and incisive. Dr. Taylor is, happily, an eminent authority in both departments, and we find as a consequence that the two divis- ions of this work possess an equal scientific and literary merit. We have already passed the limits allotted to a notice of this kind, and while we have nothing but praise for this admirable atlas, it must be said in justification that it is more than warranted by the merits of the work itself.— The Medical News, Dec. 14,1889. It would be hard to use words which would per- spicuously enough convey to the reader the great value of this Clinical Atlas. This Atlas is more complete even than an ordinary course of clinical lectures, for in no one college or hospital course is it at all probable that all of the diseases herein represented would be seen. It is also more ser- viceable to the majority of students than attend- ance upon clinical lectures, for most of the students who sit on remote seats in the lecture hall cannot see the subject as well as the office studentcan examine these true to-life chromo-lith- ographs. Comparing the text to a lecturer.it is more satisfactory in exactness and fulness than he would be likely to be in lecturing over a single case. Indeed, this Atlas is invaluable to the gen- eral practitioner, for it enables the eye of the physician to make diagnosis of a given case of skin manifestation by comparing the case with the picture in the Atlas, where will be found also the text of diagnosis, pathology, and full sections on treatment.— Virginia Medical Monthly, Dec. 1889. HYDE, J. NEVINS, A. M., M. I)., Professor of Dermatology and Venereal Diseases in Rush Medical College, Chicago. A Practical Treatise on Diseases of the Skin. For the use of Students and Practitioners. New (second) edition. In one handsome octavo volume of 676 pages, with 2 colored plates and 85 beautiful and elaborate illustrations. Cloth, $4.50; leather, $5.50. We can heartily commend it, not only as an admirable text-book for teacher and student, but in its clear and comprehensive rules for diagnosis, its sound and independent doctrines in pathology, and its minute and judicious directions for tne treatment of disease, as a most satisfactory and complete practical guide for the physician.—Ameri- can Journal of the Medical Sciences, July, 1888. A useful glossary descriptive of terms is given. The descriptive portions of this work are plain and easily understood, and above all are very accurate. The therapeutical part is abundantly supplied with excellent recommendations. The picture part is well done. The value of the work to practitioners is great because of the excellence of the descriptions, the suggestiveness of the advice, and the correctness of the details and the principles of therapeutics impressed upon the reader.— Virginia Med. Monthly, May, 1888. The second edition of his treatise is like his clinical instruction, admirably arranged, attractive in diction, and strikingly practical throughout. The chapter on general symptomatology is a model in its way; no clearer description of the various primary and consecutive lesions of the skin is to be met with anywhere. Those on general diagno- sis and therapeutics are also worthy of careful study. Dr. Hyde has shown himself a compre- hensive reader of the latest literature, and has in- corporated into his book all the best of that which the past years have brought forth. The prescrip- tions and formulae are given in both common and metric systems. Text and illustrations are good, and colored plates of rare cases lend additional attractions. Altogether it is a work exactly fitted to the needs of a general practitioner, and no one will make a mistake in purchasing it.—Medical Press of Western New York, June, 1888. FOX, T., M. 1)., F. R. C. F., and FOX, T. C., B.A., 31.It. C.S., Physician to the Department for Skin Diseases, University College Hospital, London. An Epitome of Skin Diseases. With Formulae. For Students and Prac- titioners. Third edition, revised and enlarged. In one 12mo. vol. of 238 pp. Cloth, $1.25. Physician for Diseases of the Skin to the Westminster Hospital, London. The third edition of this convenient handbook calls for notice owing to the revision and expansion which it has undergone. The arrangement of skin diseases in alphabetical order, which is the method of classification adopted in this work, becomes a positive advantage to the student. The book is one which we can strongly recommend, not only to students but also to practitioners who require a compendious summary of the present state of dermatology.—British Medical Journal, July 2,1883. We cordially recommend Fox’s Epitome to those whose time is limited and who wish a handy manual to lie upon the table for instant reference. Its alphabetical arrangement is suited to this use, for all one has to know is the name of the disease, and here are its description and the appropriate treatment at hand and ready for instant applica- tion. The present edition has been very carefully revised and a number of new diseases are de- scribed, while most of the recent additions to dermal therapeutics find mention, and the formu lary at the end of the book has been considerably augmented.— The Medical News, December, 1883. WILSON, ERASMUS, F. R. S. The Student’s Book of Cutaneous Medicine and Diseases of the Skin. In one handsome small octavo volume of 535 pages. Cloth, $3.50. HILLIER’S HANDBOOK OF SKIN DISEASES; I for Students and Practitioners. Second Ameri- | can edition. In one 12mo. volume of 353 pages, with plates. Cloth, $2.25. Lea Brothers & Co.’s Publications—I>is. of Women. 27 The American Systems of Gynecology and Obstetrics. Systems of Gynecology and Obstetrics, in Treatises by American Authors. Gynecology edited by Matthew D. Mann, A. M., M. D., Professor of Obstetrics and Gynecology in the Medical Department of the University of Buffalo; and Obstet- rics edited by Barton Cooke Hirst, M. D., Associate Professor of Obstetrics in the University of Pennsylvania, Philadelphia. In four very handsome octavo volumes, con- taining 3612 pages, 1092 engravings and 8 plates. Complete work now ready. Per vol- ume: Cloth, $5.00; leather, $6.00; half Russia, $7.00. For sale by subscription only. Address the Publishers. Full descriptive circular free on application. LIST OF CONTRIBUTORS. WILLIAM H. BAKER, M. D., ROBERT BATTEY, M. D., SAMUEL C. BUSEY, M. D., JAMES C. CAMERON, M. D., HENRY C. COE, A. M., M. D., EDWARD P. DAVIS, M. D., G. E. De SCHWEINITZ, M. D., E. C. DUDLEY, A. B., M. D., B. McE. EMMET, M. D., GEORGE J. ENGELMANN, M. D., HENRY J. GARR1GUES, A. M., M. D., WILLIAM GOODELL, A. M., M. D., EGBERT H. GRANDIN, A. M., M. D., SAMUEL W. GROSS, M. D., ROBERT P. HARRIS, M. D.. GEORGE T. HARRISON, M. D., BARTON C. HIRST, M. D. STEPHEN Y. HOWELL, M. D., A. REEVES JACKSON, A. M., M. D., W. W. JAGGARD, M. D., EDWARD W. JENKS, M. D., LL. D., HOWARD A. KELLY, M. D., CHARLES CARROLL LEE, M. T>., WILLIAM T. LUSK, M. D., LL. D., J. HENDRIE LLOYD, M. D., MATTHEW D. MANN, A. M., M. D.. H. NEWELL MARTIN, F. R. S., M. D., RICHARD B. MAURY, M. D., C. D. PALMER, M. D., ROSWELL PARK, M. D., THEOPHILUS PARVIN, M. D., LL. D., R. A. F. PENROSE, M. D., LL. D., THADDEUS A. REAMY, A. M., M. D., J. C. REEVE, M. D., A. D. ROCKWELL, A. M., M. D., ALEXANDER J. C. SKENE, M. D., J. LEWIS SMITH, M. I)., STEPHEN SMITH, M. D., R. STANSBURY SUTTON, M. D.. LL. D., T. GAILLARD THOMAS, M. D., LL. D., ELY VAN DE WARKER, M. D., W. GILL WYLIE, M. D. These volumes are the contributions of the most eminent gentlemen of this country in these de- partments of the profession. Each contributor pre- sents a monograph upon his special topic, so that everything in the way of history, theory,methods, and results is presented to our fullest need. As a work of general reference, it will be found remarka- bly full and instructive in every direction of inquiry.—The Obstetric Gazette, September, 1889. There can be but little doubt that this work will find the same favor with the profession that has been accorded to the “System of Medicine by American Authors,” and the “System of Gynecol- ogy byAmerican Authors.” One is at a loss to know wnat to say of this volume, for fear that just and merited praise maybe mistaken for flattery. The papers of Drs. Engelmann, Martin, Hirst, Jaggard and Reeve are incomparably beyond anything that can be found in obstetrical works. Certainly the Editor may be congratulated for having made such a wise selection of his contributors.—Journal of theAmericar Medical Association, Sept. 8, 1888. In our notice of the “System of Practical Medi- cine by American Authors,” we made the follow- ing statementIt is a work of which the pro- fession in this country can feel proud. Written exclusively by American physicians who are ac- quainted with all the varieties of climate in the United States, the character of the soil, the man- ners and customs of the people, etc., it is pecul- iarly adapted to the wants of American practition- ers of medicine, and it seems to us that every one of them would desire to have it.” Every word thus expressed in regard to the “American Sys- tem of Practical Medicine” is applicable to the “ System of Gynecology by American Authors.” It, like the other, has "been written exclusively by American physicians who are acquainted with all the characteristics of American people, who are well informed in regard to the peculiarities of American women, their manners, customs, modes of living, etc. As every practising physician is called upon to treat diseases of females, and as they constitute a class to which the family phy- sician must give attention, and cannot pass over to a specialist, we do not know of a work in any department of medicine that we should so strongly recommend medical men generally purchasing.— Cincinnati Med. News, July,1887. THOMAS, T. GAILLARD, and HINDU, RAUL F., M. D.,LL. D., M.D., A Practical Treatise on the Diseases of Women. New (sixth) edition, thoroughly revised and rewritten by Dr. Munde. In one large and handsome octavo volume of about 900 pages, with over 300 illustrations. Ready shortly. Dr. Thomas’ standard work in the original text and by its translations into other languages is everywhere regarded as the best representative of the peculiarly American science of gynecology. In this revision the joint authors have undertaken to preserve the practical nature of the work which has rendered it so useful to students and physicians, and also to bring it abreast with the best gynecological views and practice of the present day. The thorough character of the revision can be understood from the fact that of the illustrations one hundred and seventy-five are new. Professor of Diseases of Women in the College of Physicians and Surgeons, N. Y. Professor of Gynecology in the Hew York Polyclinic. ED IS, ART HU It W., M. D., Rond., If. It. C.R., M.R. C.S., Assist. Obstetric Physician to Middlesex Hospital, late Physician to British Lying-in Hospital. The Diseases of Women. Including their Pathology, Causation, Symptoms, Diagnosis and Treatment. A Manual for Students and Practitioners. In one handsome octavo volume of 576 pages, with 148 illustrations. Cloth, $8.00; leather, $4.00. The special qualities which are conspicuous are thoroughness in covering the whole ground, clearness of description and conciseness of state- ment. Another marked feature of the book is the attention paid to the details of many minor surgical operations and procedures, as, for instance, the use of tents, application of leeches, and use of hot water injections. These are among the more common methods of treat- ment, and yet very little is said about them in many of the text-books. The book is one to be warmly recommended especially to students and general practitioners, who need a concise but com- plete rZsumi of the whole subject. Specialists, too, will find many useful hints in its pages.—Boston Med. and Surg. Journ., March 2, 1882. 28 Lea Brothers & Co.’s Publications—Dis. of Women, Midwfy. EMMET, THOMAS ADDIS, M. I)., EL. D., Surgeon to the Woman's Hospital, New York, etc. The Principles and Practice of Gynaecology; For the use of Students and Practitioners of Medicine. New (third) edition, thoroughly revised. In one large and very handsome octavo volume of 880 pages, with 150 illustrations. Cloth, $5; leather, $6; very handsome half Russia, raised bands, $6.50. We are in doubt whether to congratulate the author more than the profession upon the appear- ance of the third edition of this well-known work. Embodying, as it does, the life-long experience of one who has conspicuously distinguished himself as a bold and successful operator, and who has devoted so much attention to the specialty, we feel sure the profession will not fail to appreciate the privilege thus offered them of perusing the views and practice of the author. His earnestness, of purpose and conscientiousness are manifest. He gives not only his individual experience but- endeavors to represent the actual state of gyne- cological science and art.—British Medical Jour- nal, May 16, 1885. TAIT, LAWSON, F.R. C. S., Professor of Gynaecology in Queen's College, Birmingham; late President of the British Gyne- cological Society; Fellow American Gynecological Society. Diseases of Women and Abdominal Surgery. In two very handsome octavo volumes. Volume I., 554 pages, 62 engravings and 3 plates. Cloth, $3. Nou> ready. Volume II., preparing. The plan of the work does not indicate the regu- lar system of a text book, and yet nearly every- thing of disease pertaining to the various organs receives a fair consideration. The description of diseased conditions is exceedingly clear, and the treatment, medical or surgical, is very satisfactory. Much of the text is abundantly illustrated with cases, which add value in showing the results of the suggested plans of treatment. We feel con- fident that few gynecologists of the country will fail to place the work in their libraries.—The Obstetric Gazette, March, 1890. DAVENPORT, F. II., M. T)., Assistant in Gynaecology in the Medical Department of Harvard University, Boston. Diseases of Women, a Manual of Non-Surgical Gynaecology. De- signed especially for the Use of Students and General Practitioners. In one handsome 12mo. volume of 317 pages, with 105 illustrations. Cloth, $1.50. We agree with the many reviewers whose no- tices we have read in other journals congratulating Dr. Davenport on the success which he has attained. He has tried to write a book for the student and general practitioner which would tell them just what they ought to know without distracting their attention with a lot of compila- tions for which they could have no possible use. In this he has been eminently successful. There is not even a paragraph of useless matter. Everything is of the newest, freshest and most practical, so much so that we have recommended it to our class of gynecology students. What the author advises in the way of treatment has all been practically tested by himself, and each method receives only so much commendation as he has found that it deserves. We are sure that these good qualities will command for it a large sale.—Canada Medical Record, Dec. 1889. MAY, CHARLES II.. M. j Late House Surgeon to Mount Sinai Hospital, il, New York. A Manual of theDiseases of Women. Being a concise and systematic expo- sition of the theory and practice of gynecology. New (2d) edition, edited by L. S. Rau,. M. D., Attending Gynecologist at the Harlem Hospital, N. Y. In one 12mo. volume of 360 pages, with 31 illustrations. Cloth, $1.75. Just ready. _ This is a manual of gynecology in a very con- densed form, and the fact that a second edition has been called for indicates that it has met with a favorable reception. It is intended, the author tells us, to aid the student who after having care- fully perused larger works desires to review the subject, and he adds that it may be useful to the practitioner who wishes to refresh his memory rapidly but has not the time to consult larger works. We are much struck with the readiness- and convenience with which one can refer to any subject contained in this volume. Carefully com- piled indexes and ample illustrations also enrich the work. This manual will be found to fulfil its purposes very satisfactorily.— The Physician and Surgeon, June, 1890. I) VNCA N, J. MATTHEWS, MI)., EE. I)., F. JR. S. E., etc* Clinical Lectures on the Diseases of Women; Delivered in Saint Bar- tholomew’s Hospital. In one handsome octavo volume of 175 pages. Cloth, $1.50. They are in every way worthy of their author ; indeed, we look upon them as among the most valuable of his contributions. They are all upon matters of great interest to the general practitioner. Some of them deal with subjects that are not, as a rule, adequately handled in the text-books; others of them, while bearing upon topics that are usually treated of at length in such works, yet bear such a stamp of individuality that they deserve to be widely read.—N. Y. Medical Journal, March, 1880. HODGE ON DISEASES PECULIAR TO WOMEN. Including Displacements of the Uterus. Second edition, revised and enlarged. In one beauti- fully printed octavo volume of 519 pages, with original illustrations. Cloth, $4.50. RAMSBOTHAM’S PRINCIPLES AND PRAC- TICE OF OBSTETRIC MEDICINE AND SURGERY. In reference to the Process of Parturition. A new and enlarged edition, thor- oughly revised by the Author. With additions by W. V. Keating, M. D., Professor of Obstetrics, etc., in the Jefferson Medical College of Phila- delphia. In one large and handsome imperial octaro volume of 640 pages, with 64 full page plates aud 43 woodcuts in the text, containing in all nearly 200 beautiful figures. Strongly bound in leather, with raised bands, $7. WEST’S LECTURES ON THE DISEASES OF WOMEN Third American from the third Lon- don edition. In one octavo volume of 543 pages. Cloth, $3.75; leather, $-1.75. Lea Brothers & Co.’s Publications—Midwifery. 29 PARVIN, THEOP HILLS, M. I)., LL. I)., Prof, of Obstetrics and the Diseases of Women and Children m Jefferson Med. Coll., Phila. The Science and Art of Obstetrics. New (2d) edition In one handsome- 8vo. volume of 7 01 pages, with 239 engravings and a colored plate. Cloth, $ 1.25; leather,. $5.25. The second edition of this work is fully up to the present state of advancement of the obstetric art. The author has succeeded exceedingly well in incorporating new matter without apparently in- creasing the size of his work or interfering with the smoothness and grace of its literary construc- tion. He is very felicitous in his descriptions of conditions, and proves himself in this respect a scholar and a master. Rarely in the range of obstetric literature can be found a work which is so comprehensive and yet compact and practical. In such respect it is essentially a text book of the first merit. The treatment of the subjects gives a. real value to the work—the individualities of a. practical teacher, a skilful obstetrician, a close thinker and a ripe scholar.—Medical Record, Jar- 17, 1891. PLAYFAIR, W. S., M. I)., F. R. C. P., A Treatise on the Science and Practice of Midwifery. New (fifth) American, from the seventh English edition. Edited, with additions, by Robert P. Har- ris, M. D. In one handsome octavo volume of 664 pages, with 207 engravings and 5 plates. Cloth, $4.00; leather, $5.00. Professor of Obstetric Medicine in King's College, London, etc. Truly a wonderful book; an epitome of all ob stetrical knowledge, full, clear and concise. In thirteen years it has reached seven editions. It is perhaps the most popular work of its kind ever presented to the profession. Beginning with the anatomy and physiology of the organs concerned, nothing is left unwritten that the practical ac- coucheur should know. It seems that every conceivable physiological or pathological condi- tion from the moment of conception to the time of complete involution has had the author’s- patient attention. The plates and illustrations* carefully studied, will teach the science of mid- wifery. The reader of this book will have before him the very latest and best of obstetric practice* and also of all the coincident troubles connected therewith.—Southern Practitioner, Dec. 1889. KING, A. F. A., M. J)., Professor of Obstetrics and Diseases of Women in the Medical Department of the Columbian Univer- sity, Washington, D. C., and in the University of Vermont, etc. A Manual of Obstetrics. New (fourth) edition. In one very handsome 12nKk volume of 432 pages, with 140 illustrations. Cloth, $2.50. Dr. King, in the preface to the first edition of this manual, modestly states that “its purpose is to furnish a good groundwork to the student at the beginning of his obstetric studies.” Its pur- pose is attained; it will furnish a good ground- work to the student who carefully reads it; and further, the busy practitioner should not scorn the volume because written for students, as it con- tains much valuable obstetric knowledge, some of which is not found in more elaborate text- books. The chapters on the anatomy of the female generative organs, menstruation, fecunda- tion, the signs of pregnancy, and the diseases of pregnancy, are all excellent and clear; but it is in the description of labor, both normal and abnor- mal, that Dr. King is at his best. Here his style is so concise, and the illustrations are so good, that the veriest tyro could not fail to receive a clear conception of labor, its complications and treat- ment. Of the 141 illustrations it may be safely said that they all illustrate, and that the engraver’s work is excellent. The name of the publishers is a sufficient guarantee that the work is pre- sented in an attractive form, and from every standpoint we can most heartily recommend the book both to practitioner and student.— The Medi- cal News, Dec. 7, 1889. BARNES, ROBERT, M. D., and FAN COURT, M. I)., Phys. to the General Lying-in Hosp., Lond. Obstetric Phys. to St. Thomas' Hosp., Lond. A System of Obstetric Medicine and Surgery, Theoretical and Clin- ical. For the Student and the Practitioner. The Section on Embryology by Prof. Milnes Marshall. In one 8vo. volume of 872 pp., with 231 illustrations. Cloth, $5; leather, $6. The immediate purpose of the work is to furnish a handbook of obstetric medicine and surgery for the use of the student and practitioner. It is not an exaggeration to say of the book that it is the best treatise in the English language yet published, and this will not be a surprise to those who are acquainted with the work of the elder Barnes. Every practitioner who desires to have the best obstetrical opinions of the time in a readily accessible and condensed form, ought to own a copy of the book.—Journal of the American Medical Association, June 12, 1886. The Authors have made a text-book which is in every way quite worthy to take a place beside the best treatises of the period.—New York Medical Journal, July 2, 1887. WINCKEL, F. A Complete Treatise on the Pathology and Treatment of Childbed, For Students and Practitioners. Translated, with the consent of the Author, from the second German edition, by J. K. Chadwick, M. D. Octavo 484 pages. Cloth, $4.00. ASHWELL’S PRACTICAL TREATISE ON THE DISEASES PECULIAR TO WOMEN. Third American from the third and revised London edition. In one 8vo. vol., pp. 520. Cloth, $3.50. PARRY ON EXTRA-UTERINE PREGNANCY: Its Clinical History, Diagnosis, Prognosis and Treatment. Octavo, 272 pages. Cloth, $2.50. TANNER ON PREGNANCY. Octavo, 490 pages, colored plates. 16 cuts. Cloth, $4.25 CHURCHILL ON THE PUERPERAL FEVER AND OTHER DISEASES PECULIAR TO WO- MEN. In one 8vo. vol. of 464 pages. Cloth, $2.60 MEIGS ON THE NATURE, SIGNS AND TREAT- MENT OF CHILDBED FEVER. In one 8vo. volume of 346 pages. Cloth, $2.00. 30 Lea Brothers & Co.’s Publications—Midwly., I>is. Childn. SMITH, J. LEWIS, M. D., Clinical Professor of Diseases of Children in the Bellevue Hospital Medical College, N. Y. A Treatise on the Diseases of Infancy and Childhood. New (seventh) edition, thoroughly revised and rewritten. In one handsome octavo volume of 881 pages, with 51 illustrations. Cloth, $4.50; leather, $5.50. Just ready. Every department shows that it has been thor- oughly revised, and that every advantage has been taken of recent advance in knowledge to bring it completely up to the times What makes the work of Dr. Smith of especial value is the attention paid to diagnosis and the careful detail of treatment, Iris undoubtedly one of the best treatises on children’s diseases, and asa text book for students and guide for young practitioners it is unsurpassed, —Buffalo Medical and Surgical Journal, Jan. 1891. Already in previous editions the work of Dr. Smith held position undisputed at the head of its class. No book in any language could dispute with it the title lo pre-eminence. A list of works on diseases of children, made up in any country, would have this work at its head, and for the pur- poses of the great majority of practitioners the list would be complete with this one alone.— Ameri- can Practitioner and News, May 9,1891. Notwithstanding the many excellent volumes that have been issued recently on diseases of children, the work of Dr. J. Lewis Smith easily holds a front Its several editions have all been thoroughly revised. In the present one we notice that many of the chapters have been en- tirely rewritten. Full notice is taken of all the recent advances that have been made. As its author states in the preface, the necessary revision has virtually produced anew work. Inthe amount of information presented the work may properly be considered to have doubled in size, but by condensation and the exclusion of all obsolete material the volume has not been rendered incon- veniently large. Many diseases not previously treated of have received special chapters. The work is a very practical one. Especial care has been taken that the directions for treatment shall be particular and full. In no other work are such careful instructions given inthe details of infant hygiene and the artificial feeding of infants.— Montreal Medical Journal, Feb. 1891. LEISHMAN, WILLIAM, M. JD., Regius Professor of Midwifery in the University of Glasgow, «tc. A System of Midwifery, Including the Diseases of Pregnancy and the Puerperal state. Fourth edition. Octavo. LANDIS, TIENRY G., A. M., M. D., Professor of Obstetrics and the Diseases of Women in Starling Medical College, Columbus, O. The Management of Labor, and of the Lying-in Period. In one handsome 12mo. volume of 334 pages, with 28 illustrations. Cloth, $1.75. The author has designed to place in the hands of the young practitioner a book in which he can find necessary information in an instant. As far as we can see, nothing is omitted. The advice is sound, and the procedures are safe and practical. Centralblatt fur Gynakologie, December 4, 1886. This is a book we can heartily recommend. The author goes much more practically into the details of the management of labor than most text-books, and is so readable throughout as to tempt any one who should happen to commence the book to read it through. The author pre- supposes a theoretical knowledge of obstetrics, and has consistently excluded from this, little work everything that is not of practical use in the lying-in room. We think that if it is as widely read as it deserves, it will do much to improve obstetric practice in general.—New Orleans Medi- cal and Surgical Journal, Mar. 1886. OWFN, EDMUND, M. B., F. R. C. S., Surgeon to the Children’s Hospital, Great Ormond St., London. Surgical Diseases of Children. In one 12mo. volume of 525 pages, with 4 chromo-lithographic plates and 85 woodcuts. Cloth, $2. See Series of Clinical Manuals, page 31. One is immediately struck on reading this book with its agreeable style and the evidence it every- where presents of the practical familiarity of its author with his subject. The book may be honestly recommended to both students and practitioners. It is full of sound information, pleasantly given.—Annals of Surgery, May, 1886. STUDENTS’ SERIES OF MANLALS. A Series of Fifteen Manuals, for the use of Students and Practitioners of Medicine and Surgery, written by eminent Teachers or Examiners, and issued in pocket-size 12mo volumes of 300-540 pages, richly illustrated and at a low price. The following volumes are now ready: Treves’ Manual of Sur- gery, by various writers, in three volumes, each, $2; Bell’s Comparative Physiology and Anatomy, $2; Gould’s Surgical Diagnosis. $2; Robertson’s Physiological Physics, $2; Bruce’s Materia Medica and Thera- peutics (4th' edition), $1.50; Power’s Human Physiology (2d edition), $1.50; Clarke and Lockwood’s Dissectors' Manual, $1.50; Ralfe’s Clinical Chemistry, $1.50; Treves’ Surgical Applied Anatomy, $2; Pepper’s Surgical Pathology, $2; and Klein’s Elements Of Histology (4th edition), $1.75. The following is in press: Pepper’s Forensic Medicine. For separate notices see index on last page. SERIES OF CLINICAL MANUALS. In arranging for this Series it has been the design of the publishers to provide the profession with a collection of authoritative monographs on important clinical subjects in a cheap and portable form. The volumes will contain about 550 pages and will be freely illustrated by chromo-lithographs and wood- cuts. The following volumes are now ready: Yeo on Foodin Health and Disease, $2; Broadbent on the Pulse, $1-75; Carter & Frost’s Ophthalmic Surgery, $2 25; Hutchinson on Syphilis, $2.25; Ball on the Rectum and Anus, $2.25; Marsh on the Joints, $2; Owen on Surgical Diseases of Children, $2; Morris on Surgical Diseases of the Kidney, $2.25; Pick on Fractures and Dislocations, $2; Butlin on the Tongue, $1-50; Trevf.s on Intestinal Obstruction, $2; and Savage on Insanity and Allied Neuroses, $2. The following is in active preparation: Lucas on uiseases of the Urethra. For separate notices see index on last page. CONDIE’S PRACTICAL TREATISE ON THE DISEASES OF CHILDREN. Sixth edition, re- vised and augmented. In one octavo volume of 779 pages. Cloth, $5.25; leather, $6.25. WEST ON SOME DISORDERS OF THE NERV- OUS SYSTEM IN CHILDHOOD. In one small 12mo. volume of 127 pages. Cioth,$1.00. Lea Brothers & Co.’s Publications—Med. Juris., Miscel. 31 TIDY, CHARLES MEYMOTT, JX B., F. C. S., Legal Medicine. Volume II. Legitimacy and Paternity, Pregnancy, Abor- tion, Rape, Indecent Exposure, Sodomy, Bestiality, Live Birth, Infanticide, Asphyxia, Drowning, Hanging, Strangulation, Suffocation. Making a very handsome imperial oc- tavo volume of 529 pages. Cloth, $6.00; leather, $7.00. Professor of Chemistry and of Forensic Medicine and Public Health at the London Hospital, etc. Volume I. Containing 664 imperial octavo pages, with two beautiful colored plates. Cloth, $6.00; leather, $7.00. The satisfaction expressed with the first portion of this work is in no wise lessened by a perusal of the second volume. We find it characterized by the same fulness of detail and clearness of ex- pression which we had occasion so highly to com- mend in our former notice, and which render it so valuable to the medical jurist. The copious tables of cases appended to each division of the subject must have cost the author a prodigious amount of labor and research, but they constitute one of the most valuable features of the book, especially for reference in medico-legal trials.— American Journal of the Medical Sciences, April, 1884. TAYLOR, ALFRED S., M. D., Lecturer on Medical Jurisprudence and Chemistry m Guy 's Hospital, London. Poisons in Relation to Medical Jurisprudence and Medicine. Third American, from the third and revised English edition. In one large octavo volume of 788 pages. Cloth, $5.50; leather, $6.50. A Manual of Medical Jurisprudence. Eighth American from the tenth Lon- don edition, thoroughly revised and rewritten. Edited by John J. Reese, M. D. In one large octavo volume. the Same Author. PEPPER, AUGUSTUS J., M. S., M. B., F. It. C. S., Examiner in Forensic Medicine at the University of London. Forensic Medicine. In one pocket-size 12mo. volume. Preparing. See Students’ Series of Manuals, below. LEA, HENRY C., XX. X. Chapters from the Religious History of Spain.—Censorship of the Press.—Mystics and Illuminati.—The Endemoniadas.—El Santo Hino de la Guardia.—Brianda de Bardaxi. In one 12mo. volume of 522 pages. Cloth, $2.50. Just ready. The width, depth and thoroughness of research which have earned Dr. Lea a high European place as the ablest historian the Inquisition has yet found are here applied to some side-issues of that great subject. We have only to say of this volume hat it worthily complements the author’s earlier tudies in ecclesiastical history. His extensive and minute learning, much of it from inedited manuscripts in Mexico, appears on every page.— ondon Antiquaiy, Jan. 1891. After attentively reading the work one does not know whether the author is a Catholic, a Protestant or a free-thinker. This moderation deprives the indictment of none of its force. The facts and the documents, of which the number and novelty attest a patient erudition, are grouped in luminous order and produce on the reader an effect all the more powerful in that it seems the less designed. When we add that the style is in every way excel- lent, that it is clear, sober and precise, we do full justice to a work which reflects the highest honor on the talents of the writer and on the method of the modern school of history.—Revue Critique d’Histoire et de Litterature, Paris, Jan. 1891. By the same Author. Superstition and Force: Essays on The Wager of Law, The Wager of Battle, The Ordeal and Torture. Third revised and enlarged edition. In one handsome royal 12mo. volume of 552 pages. Mr. Lea’s curious historical monographs, of hich one of the most important is here produced in an enlarged form, have given him a unique position among English and American scholars. He is distinguished for his recondite and affluent learning, his power of exhaustive historical analy- Cloth, $2.50. sis, the breadth and accuracy of his researches among the rarer sources of knowledge, the gravity and temperance of his statements, combined with singular earnestness of conviction, and his warm attachment to the cause of freedom and intellect- ual progress.—N. Y. Tribune, August 9,1878. Studies in Church History. The Rise of the Temporal Power—Ben- efit of Clergy—Excommunication—The Early Church and Slavery. Sec- ond and revised edition. In one royal octavo volume of 605 pages. Cloth, $2.50. the Same Author. The author is preeminently a scholar; he takes up every topic allied with the leading theme and traces it out to the minutest detail with a wealth of knowledge and impartiality of treatment that compel admiration. The amount of information compressed into the book is extraordinary, and the profuse citation of authorities and references makes the work particularly valuable to the student who desires an exhaustive review from original sources. In no other single volume is the develop- ment of the primitive church traced with so much clearness and with so definite a perception of complex or conflicting forces.—Boston Traveller. Mr. Lea is facile princeps among American scholars in the history of the Middle Ages, and, indeed, we know of no European writer who has shown such research, accuracy and grasp in investigating important and out-of the-way topics connected with the history of Europe in the Mid- dle Ages.—N. Y. Times. It is some years since we read the first edition of this work by Mr. Lea, and the impression made by it on us at the time is confirmed by reperusal of it in this enlarged and improved form; namely, that it is a book of great research and accuracy, full of varied information on very interesting phases of church life and history. It discusses each subject with a rare fulness of dates and in- stances, and a curious conscientiousness of veri- fication and citation of authorities.—Edinburgh Scotsman. Allen’s Anatomy ..... 6 American Journal of the Medical Sciences . 3 American Systems of Gynecology and Obstetrics 27 American System of Practical Medicine . . 15 American System of Dentistry - .24 Ashhurst’s Surgery . . . . .20 Ashwell on Diseases of Women . . .29 Attfi eld’s Chemistry . ... 9 Ball on the Rectum and Anus . . . 20, 30 Barlow’s Practice of Medicine . . .17 Barnes’System of Obstetric Medicine . . 29 Bartholow on Electricity .... 17 Basham on Renal Diseases .... 24 Bell’s Comparative Physiology and Anatomy . 7, 30 Bellamy’s Surgical Anatomy ... 6 Berry on the Eye ..... 23 Billings’ National Medical Dictionary . . 4 Blandford on Insanity . . . . 19 Bloxam’s Chemistry . . ... 9 Bristowe’s Practice of Medicine . . 14 Broadbent on the Pulse . . . . 16,30 Browne on Koch’s Remedy . ... 18 Browne on the Throat, Nose and Ear . . 18 Bruce’s Materia Medica and Therapeutics . 12,30 Brunton’s Materia Medica and Therapeutics . 11 Bryant’s Practice of Surgery . . . .21 Bumstead and Taylor on Venereal. See Taylor. 25 Burnett on the Ear . 23 Butlin on the Tongue . . .21,30 Carpenter on the Use and Abuse of Alcohol . 8 Carpenter’s Human Physiology ... 8 Carter & Frost’s Ophthalmic Surgery . . 23,30 Chambers on Diet and Regimen ... 17 Chapman’s Human Physiology ... 8 Charles’ Physiological and Pathological Chem. 10 Churchill on Puerperal Fever . . .29 Clarke and Lockwood’s Dissectors’ Manual . 6,30 Classen’s Quantitative Analysis ... 10 Cleland’s D ssector . .... 6 Clouston on Insanity . ... 19 Clowes’ Practical Chemistry . . .10 Coats’ Pathology .... 13 Cohen on the Throat . . . .18 Cohen’s Applied Therapeutics ... 12 Coleman’s Dental Surgery .... 24 Condie on Diseases of Children . . .30 Cornil on Syphilis ..... 25 Culver & Hayden on Venereal Diseases . . 25 Dalton on the Circulation .... 7 Dalton’s Human Physiology ... 8 Davenport on Diseases of Women . . . 28 Davis’ Clinical Lectures . . .17 Draper’s Medical Physics .... 7 Druitt’s Modern Surgery .... 20 Duncan on Diseases of Women . . .28 Dungllson’s Medical Dictionary ... 5 Edes’ Materia Medica and Therapeutics . 12 Edis on Diseases of Women . . . . . 27 Ellis’ Demonstrations of Anatomy . . 7 Emmet’s Gynaecology . . , 28 Erichsen’s System of Surgery . . .21 Farquharson’s Therapeutics and Mat. Med. . 12 Finlayson’s Clinical Diagnosis ... 16 Flint on Auscultation and Percussion . . 18 Flint on Phthisis ..... 18 Flint on Respiratory Organs ... 18 Flint on the Heart . ... 18 Flint’s Essays . . .... 18 Flint’s Practice of Medicine . . .14 Folsom’s Laws of U. S. on Custody of Insane . 19 Foster’s Physiology ..... 8 Fothergill’s Handbook of Treatment . . 16 Fownes’ Elementary Chemistry ... 9 Fox on Diseases of the Skin . ... 26 Frankland and Japp’s Inorganic Chemistry . 9 Fuller on the Lungs and Air Passages . . 17 Gant’s Student’s Surgery . . . .20 Gibbes* Practical Pathology ... 13 Gibney’s Orthopaedic Surgery . . .20 Gould’s Surgical Diagnosis . . . . 21, 30 Gray’s Anatomy . . . . . .5 Gray on Nervous Diseases ... .19 Greene’s Medical Chemistry .... 9 Green’s Pathology and Morbid Anatomy . 13 Griffith’s Universal Formulary ... 12 Gross on Foreign Bodies in Air-Passages . IS Gross on Impotence and Sterility ... 25 Gross on Urinary Organs . . 25 Gross System of Surgery . . 20 Habershon on the Abdomen . . 16 Hamilton on Fractures and Dislocations . 22 Hamilton on Nervous Diseases . . .19 Hare’s Practical Therapeutics . . .11 Hare’s System of Practical Therapeutics . 11 Hartshorne’s Anatomy and Physiology . . 6 Hartshorne’s Conspectus of the "Med. Sciences . 3 Hartshorne’s Essentials of Medicine . . 14 Hermann’s Experimental Pharmacology . 11 Hill on Syphilis ...... 25 Hillier’s Handbook of Skin Diseases . , 26 Hirst & Piersol on Human Monstrosities . 6 Hoblyn’s Medical Dictionary ... 3 Hodge on Women . . . .28 Hoflmann and Power’s Chemical Analysis . 10 Holden’s Landmarks ..... 5 Holland’s Medical Notes and Reflections . 17 Holmes’ Principles and Practice of Surgery . 22 Holmes’ System ofSurgery . . .21 Horner’s Anatomy and Histology . . 6 Hudson on Fever . ... 16 Hutchinson on Syphilis . . . . 25,30 Hyde on the Diseases of the Skin . . .26 Jones (C. Handheld) on Nervous Disorders . 19 Juler’s Ophthalmic Science and Practice . 23 King’s Manual of Obstetrics .... 29 Klein’s Histology ... 13,30 Dandis on Labor ... 30 La Roche on Pneumonia, Malaria, etc. . . 17 La Roche on Yellow Fever .... 16 Laurence and Moon’s Ophthalmic Surgery . 23 Lawson on the Eye, Orbit and Eyelid . . 23 Lea’s Chapters from Religious History ot Spain 31 Lea’s Studies in Church History . .31 Lea’s Superstition and Force . .31 Lee on Syphilis . . ... 25 Lehmann's Chemical Physiology ... 8 Leishman’s Midwifery .... 30 Lucas on Diseases of the Urethra . . .24,30 Ludlow’s Manual of Examinations . . 3 Lyons on Fever ...... 16 Maisch’s Organic Materia Medica . . .11 Marsh on the Joints . . .21,30 May on Diseases of Women .... 28 Medical News ...... 1 Medical News Visiting List .... 3 Medical News Physicians’ Ledger ... 3 Meigs on Childbed Fever .... 29 Miller’s Practice of Surgery ... .21 Miller’s Principles of Surgery . . .21 Morrison Diseases of the Kidney . . .24,30 National Dispensatory . . . 12 National Medical Dictionary . . 4 Neill and Smith's Compendium of Med. Sci. . 3 Nettleshlp on Diseases of the Eye . . .23 Norris and Oliver on the Eye . . .23 Owen on Diseases of Children . . .30 Parrish’s Practical Pharmacy . . .11 Parry on Extra-Uterine Pregnancy . . 29 Parvin’s Midwifery . .... 29 Pavy on Digestion and its Disorders . . 17 Payne’s General Pathology .... 13 Pepper’s System of Medicine . . .15 Pepper’s Forensic Medicine . . . . 30,31 Pepper's Surgical Pathology . .13,30 Pick on Fractures and Dislocations . . 22,30 Pirrie’s System of Surgery . ... 21 Playfair on Nerve Prostration and Hysteria . 19 Playfair’s Midwifery ..... 29 Power’s Human Physiology . . . .8.30 Purdy on Bright’s Disease and Allied A Sections 24 Ralfe’s Clinical Chemistry . . . 10,30 Ramsbotham on Parturition . . .28 Remsen’s Theoretical Chemistry . . .10 Reynolds’System of Medicine . . .14 Richardson’s Preventive Medicine . . 17 Roberts on Diet and Digestion . . .24 Roberts on Urinary Diseases . . .24 Roberts’ Compend of Anatomy ... 7 Roberts’ Surgery . ... 20 Robertson’s Physiological Physics . .7,30 Ross on Nervous Diseases .... 19 Savage on Insanity, including Hysteria . . 19,30 Schafer’s Essentials of Histology, . . 13 Schreiber on Massage . ... 17 Seiler on the Throat, Nose and Naso-Pharynx 18 Senn’s Surgical Bacteriology . . 13 Series of Clinical Manuals .... 4 Simon’s Manual of Chemistry ... 8 Slade on Diphtheria . . ' . . .17 Smith (Edward) on Consumption . . .17 Smith (J. Lewis) on Children . . .30 Smith’s Operative Surgery . . .22 Stille on Cholera . ... 14 Still6 & Maisch’s National Dispensatory . 12 StilK’s Therapeutics and Materia Medica . 11 Stimson on Fractures and Dislocations . 22 Stimson’s Operative Surgery . . .22 Students’ Series of Manuals .... 4 Sturges’ Clinical Medicine .... 17 Tait’s Diseases of Women and Abdom. Surgery 28 Tanner on Signs and Diseases of Pregnancy . 29 Tanner’s Manual of Clinical Medicine . . 16 Taylor’s Atlas of Venereal and Skin Diseases 26 Taylor on Venereal Diseases . . . 25 Taylor on Poisons . ... .31 Taylor’s Medical Jurisprudence . .31 Thomas on Diseases of Women . .27 Thompson on Stricture . ... 24 Thompson on Urinary Organs . . .24 Tidy’s Legal Medicine. .... 31 Todd on Acute Diseases . ... 17 Treves’Manual of Surgery . . . .21,30 Treves’Surgical Applied Anatomy . .6,30 Treves on Intestinal Obstruction . . .21,30 Tuke on the Influence of Mind on the Body . 19 Vaughan & Novy’s Ptomaines and Leucomaines 16 Visiting List, The Medical News ... 3 Walshe on the Heart . .... 17 Watson’s Practice of Physic .... 14 Wells on the Eye .... 23 Weston Diseases of Women . .28 West on Nervous Disorders in Childhood . 30 Wharton’s Minor Surgery and Bandaging . 21 Williams on Consumption .... 17 Wilson’s Handbook of Cutaneous Medicine . 26 Wilson’s Human Anatomy .... 6 Winckel on Pathol, and Treatment of Childbed 29 Wohler's Organic Chemistry ... 8 Woodhead’s Practical Pathology . . .13 Year-Books of Treatment for 1886, ’87, ’89 and ’90 17 Yeo on Food in Health and Disease . .17,30 IiEA BROTHERS & CO., Philadelphia.