MANUAL OF CHEMISTR Y. A GUIDE TO LECTURES AND LABORATORY-WORK FOR BEGINNERS IN CHEMISTRY. A TEXT-BOOK SPECIALLY ADAPTED FOR STUDENTS OF PHARMACY AND MEDICINE. BY \\r. Ph.D., M.D., PROFESSOR OF CHEMISTRY AND TOXICOLOGY~TnT!IE COLLEGE OF PHYSICIANS AND SURGEONS; PROFESSOR OF CHEMISTRY AND ANALYTICAL CHEMISTRY IN THE MARYLAND COLLEGE OF PHARMACY, BALTIMORE, JID. SECOND EDITION, THOROUGHLY REVISED AND GREATLY ENLARGED. WITH FORTY-FOUR ILLUSTRATIONS AND EVEN COLORED PLATES, REPRESENTING FIFTY-SIX CHEMICAL REACTIONS. PHILADELPHIA: LEA BROTHERS & CO. 1888. Entered according to Act of Congress in the year 1888, by LEA BROTHERS & CO., in the Office of the Librarian of Congress at Washington. All rights reserved. DORNAN, PRINTER. PREFACE. It has been the aim of the author to present a work on general chemistry which may be used to advantage as a text-book by beginners, and which, at the same time, covers the special needs of the medical and pharmaceutical student. While the general character of the second edition is the same as that of the first, many changes and numerous additions have been made with the view of rendering the work more complete and useful. As heretofore, the material has been divided into seven parts. In the first, the fundamental properties of matter are considered briefly and so far as is necessary for an understanding of chemical phenomena. 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 various 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. 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. iv PREFACE. 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 how 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 be readily 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. Having frequently noticed the difficulty experienced by beginners in becoming familiar with the variously shaded colors of chemicals and their reactions, the author decided to illustrate the work with a number of plates presenting the colors of those most important. While but a portion of the first edition contained these plates, the desirability of this feature became so apparent that the entire second edition has been supplied with them. w. s. Baltimore, August, 1888. CONTENTS. I. FUNDAMENTAL PROPERTIES OF MATTER. RESULTS OF THE ATTRACTION BETWEEN MASSES, SURFACES, AND MOLECULES. 1. Extension or figure. Matter — State of aggregation — Solids—Cohesion — Force — Crystallized, amorphous, polymorphous, isomorphous substances —Liquids—Gases—Law of Mariotte 17-21 2. Divisibility. Mechanical comminution—Action of heat on matter—Mo- lecular theory—Law of Avogadro—Motion of molecules, heat —Melting, boiling, 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—Capil- lary attraction—Absorption—Diffusion—Dialysis—Indestructi- bility 32-37 PAGE II. PRINCIPLES OF CHEMISTRY. RESULTS OF THE ATTRACTION BETWEEN ATOMS. 5. Chemical divisibility. Decomposition by heat—Elements—Compound substances— Chemical affinity—Atoms—Chemistry—Atomic and molecular weight—Chemical symbols and formulas 38-43 VI CONTENTS 6. Laws of chemical combination. Law of the constancy of composition—Law of multiple propor- tions—Law of chemical combination by volume—Law of equiva- lents—Quantivalence, valence 43-49 7. Determination of atomic weights. Determination of atomic weights by chemical decomposition, by means of specific weights of gases or vapors, by means of specific heat 50-53 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 54-60 9. General remarks regarding elements. Relative importance of different elements—Classification of elements—Metals and non-metals—Natural groups of elements —MendelejefF'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 .... 60-69 PAGE III. NON-METALS AND THEIR COMBINATIONS. Symbols, atomic weights, and derivation of names—Occur- rence in nature—Time of discovery—Valence .... 70-71 10. Oxygen. History—Occurrence in nature—Preparation—Physical and chemical properties—Combustion—Ozone .... 72-76 11. Hydrogen. History—Occurrence in nature—Preparation—Properties— Water—Mineral waters—Drinking water—Distilled water— Hydrogen dioxide . 76-82 12. Nitrogen. Occurrence in nature — Preparation — Properties — Atmos- pheric air—Ammonia—Compounds of nitrogen and oxygen— Nitrogen monoxide—Nitric acid, tests for it . . . 82-89 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 89-97 CONTENTS. vii 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—Thiosul- phuric acid—Hydrosulphuric acid; tests for it—Bisulphide of carbon—Selenium—Tellurium 97-106 15. Phosphorus. Occurrence in nature—Manufacture, properties, and modifi- cations—Poisonous properties and detection in cases of poi- soning—Oxides of phosphorus—Phosphorous acid; tests for it—Metaphosphoric, pyrophosphoric, ortliophosphoric acid; tests for them—Hypophospliorous acid ; tests for it—Phos- phoretted hydrogen ......... 106-114 16. Chlorine. Haloids or halogens—Preparation and properties of chlorine — Chlorine water — Hydrochloric acid; tests for it — Nitro- hydrochloric acid — Compounds of chlorine with oxygen — Hypochlorous acid—Chloric acid ; tests for it . . . . 114-120 17 Bromine. Iodine. Fluorine. Bromine—Hydrobromic acid—Tests for bromides—Iodine —Hydriodic acid—Tests for iodine and iodides—Fluorine— Hydrofluoric acid 120-124 PAGE 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 . 125-130 19. Potassium. General remarks regarding the alkali-metals—Occurrence in nature—Potassium hydroxide, carbonate, bicarbonate, nitrate, chlorate, sulphate, sulphite, hypophosphite, iodide, bromide— Analytical reactions . . 131-137 20. Sodium. Occurrence in nature—Sodium hydroxide, chloride, carbo- nate, bicarbonate, sulphate, sulphite, thiosulphate, phosphate, nitrate—Analytical reactions—Lithium 137-141 21. Ammonium. General remarks—Ammonium chloride, carbonate, sulphate, nitrate, phosphate, iodide, bromide, and sulphide—Analytical reactions ........... 142-145 viii CONTENTS. PAGE 22. Magnesium. General remarks—Occurrence in nature—Metallic magne- sium—Magnesium carbonate, oxide, sulphate, sulphite—Ana- lytical reactions. . 145-148 23. Calcium. General remarks regarding alkaline earths—Occurrence in nature—Calcium oxide, hydroxide, carbonate, sulphate, phos- phate, acid phosphate, and hypophosphite—Bone black and bone-ash—Chlorinated lime, calcium chloride and bromide— Sulphurated lime—Analytical reactions for calcium—Barium and strontium ; their salts and analytical reactions . . . 148-154 24. Aluminium. Occurrence in nature—Metallic aluminium—Alum—Alu- minium hydroxide, oxide, sulphate, and chloride—Clay—Glass —Ultramarine—Analytical reactions—Cerium . . . 154-159 25. Iron. General remarks regarding the metals of the iron group— Occurrence 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 160-169 26. Manganese. Chromium. Cobalt. Nickel. Manganese; its oxides and sulphate—Potassium permanga- nate—Manganese reactions—Chromium—Potassium dichro- mate—Chromium trioxide—Chromic oxide and hydroxide— Reactions for chromium compounds—Cobalt and nickel . . 170-176 27. Zinc. Occurrence in nature—Metallic zinc—Zinc oxide, chloride, bromide, iodide, carbonate, sulphate, and phosphide—Ana- lytical reactions—Antidotes—Cadmium 176-179 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—Poisonous properties and anti- dotes—Copper reactions—Bismuth—Bismuthyl nitrate, carbo- nate, and iodide—Bismuth reactions 180-188 29. Silver. Mercury. Silver—Silver nitrate, oxide, iodide—Antidotes—Silver reac- tions—Mercury—Mercurous and mercuric oxides, chlorides, iodides, sulphates, nitrates, sulphides—Ammoniated mercury —Antidotes—Mercurv reactions 189-199 CONTENTS. IX 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 treat- ment of organic matter for arsenic analysis—Antidotes . . 199-208 31. Antimony. Tin. Gold. Platinum. Molybdenum. Antimony—Trisulphide, oxysulphide, and pentasulphide of antimony—Antimonious chloride and oxide—Antidotes—An- timony reactions—Tin—Stannous and stannic chloride—Tin reactions—Gold—Platinum—Molybdenum .... 209-215 PAGE y. ANALYTICAL CHEMISTRY. 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—Physi- cal properties—Action on litmus—Heating on platinum-foil— Heating on charcoal alone and mixed with sodium carbonate —Flame-tests—Colored borax-beads—Liquefaction of solid substances—Table I.: Preliminary examination . . 216-226 33. Separation of metals in different groups. General remarks—Group reagents—Acidifying the solution —Addition of hydrosulphuric 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 227-232 34. Separation of the metals of each group. Table III.: Treatment of the precipitate formed by hydro- chloric acid—Treatment of the precipitate formed by hydro- sulphuric acid—Table IV.: Treatment of that portion of the hydrosulphuric acid precipitate w’hich is insoluble in ammo- nium sulphide—Table Y.: Treatment of that portion of the hydrosulphuric 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 carbonate—Table VIII.: Detection of the alkalies and of magnesium . . 233-236 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 x CONTENTS. PAGE their neutral or acid solution—Table X.: Detection of the more important acids by means of reagents added to the solution— Table XI.: Systematically arranged table, showing the solu- bility and insolubility of inorganic salts and oxides—Table XII.: Table of solubility ....... 237-243 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, mercury, arsenic, and antimony 244-251 37. Methods for quantitative determinations. General remarks — Gravimetric methods — Volumetric methods—Standard solutions—Different methods of volume- tric determination—Indicators—Titration—Acidimetry and alkalimetry—Normal acid and alkali solution—Neutralization equivalents—Oxidimetry—Potassium permanganate and di- chromate—Iodimetry—Solutions of iodine, sodium thiosul- phate, and silver nitrate—Gas—Analysis .... 252-268 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 sub- stances—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 anal- ysis—Empirical and molecular formulas—Rational, constitu- tional, structural, or graphic formulas ..... 269-278 39. Constitution, decomposition, and classification of organic compounds. Radicals or residue—Chains—Homologous series—Types — Substitution—Derivatives—Isomerism — Metamerism — Poly- merism—Various modes of decomposition—Action of heat upon organic substances—Dry or destructive distillation— Action of oxygen upon organic substances—Combustion— Decay—Fermentation and putrefaction—Antiseptics, disinfec- tants, and deodorizers—Action of chlorine, bromine, nitric acid, alkalies, dehydrating and reducing agents upon organic sub- stances—Classification of organic compounds .... 278-291 CONTENTS. XI PAGE 40. Hydrocarbons. Occurrence in nature—Formation of hydrocarbons—Proper- ties—Paraffin or methane series—Methane—Coal, coal-oil, petroleum — Illuminating gas —Coal-tar—Olefines — Benzene series or aromatic hydrocarbons—Volatile or essential oils . 291-300 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 — Phenol 301-309 42. Aldehydes. Haloid derivatives. Aldehydes—Acetic aldehyde—Paraldehyde—Trichloralde- hyde—Chloral hydrate—Chloroform—Iodoform—Sulphonal . 309-315 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 —Valerianic acid and its salts—Oleic acid . . 316-324 44 Dibasic and tribasic organic acids Oxalic acid, oxalates, and analytical reactions—Tartaric acid ; analytical 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 . 325-333 45. Ethers. Constitution—Formation of ethers—Occurrence in nature— General properties—Ethyl ether—Acetic ether—Ethyl nitrite —Amyl nitrite—Fats and fat oils—Soap—Lanolin . . 333-341 46. Carbohydrates Constitution—Properties—Occurrence in nature—Groups of carbohydrates—Grape-sugar; tests for it—Fruit-sugar—Ino- site —Cane-sugar — Milk-sugar — Starch — Dextrin —Gums— Cellulose — Nitro-cellulose—Glycogen—Glucosides—Digitalin —Myronic acid .......... 341-350 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—Hydrocy- anic acid—Potassium, silver, and mercuric cyanide—Reactions for cyanides—Antidotes—Cyanic acid—Sulphocyanic acid— Metallocyanides—Potassium ferrocyanide—Reactions forferro- cvanides—Potassium ferricyanide—Nitro-cvan-methane . 350-359 xii CONTENTS. PAGE 48 Benzene series. Aromatic compounds. General remarks—Benzene series of hydrocarbons—Benzene — Nitro-benzene — Benzene-derivatives — Phenols —Carbolic acid—Tests for it—Creasote—Sulphocarbolic acid — Picric acid — Resorcin —Cymene — Terpenes — Stearoptenes — Cam- phors—Resins—Menthol—Thymol—Benzoic acid—Oil of bit- ter almond—Salicylic acid—Phtalic acid—Gallic acid—Tannin —Naphthalene—Naphtol—Santonin 360-375 49. Benzene derivatives containing nitrogen Aniline—Aniline dyes—Antifebrine—Antipyrine—Saccha- rine—Pyrrole—Pyridine—Quinoline—Kairine—Thalline . 375-380 50. Alkaloids. General remarks—General properties of alkaloids—Mode of obtaining 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—Cinchonine—Cinchonidine—Quinidine— Strychnine and its reactions—Brucine—Atropine—Hyoscya- mine—Cocaine and its reactions—Aconitine—Yeratrine— Hydrastine—Berberine—Caffeine—Ptomaines . . . 380-396 51. Albuminous substances or proteids. Occurrence in nature—General properties—Analytical reac- tions—Classification — Serum-albumin—Egg-albumin—V ege- table albumin — Globulins — Blood-fibrin — Muscle-fibrin — Vegetable fibrin—Milk-casein—Legumin—Peptone— Haemo- globin—Animal crvptolites—Pepsin—Gelatinoids . . . 396-403 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—Decom- position of vegetable matter in the animal system—Animal food—Nutrition of animals, digestion—Absorption—Respira- tion—Waste products of animal life—Chemical changes after death 404-413 53. Animal fluids and tissues. Constituents of the animal body—Blood—Examination of blood stains—Chyle—Lymph—Saliva—Gastric juice—Bile— Biliary pigments—Biliary acids; tests for them—Cholesterin — Lecithin — Pancreatic juice — Feces —Bone—Teeth—Hair, nails, etc.—Mucus—Muscles—Brain ..... 413-425 CONTEXTS. xiii PAGE 54. Milk. Properties and composition—Changes in milk—Butter— Cheese—Adulteration of milk—Testing milk—Lactometer, creamometer, lactoscope—Analysis of milk .... 425-432 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 . . . . . . . 432-440 56. Examination of normal and abnormal urine. Points to be considered in the analysis of urine—Color— Odor—Keaction—Specific gravity—Determination of total solids, and of total organic and inorganic constituents—Detec- tion and estimation of albumin—Blood—Detection and esti- mation of sugar—Detection of bile—Urinary deposits—Uri- nary calculi—Microscopical examination of urinary sediments 440-460 APPENDIX. Table of weights and measures 461 Table of elements 463 Index 465 LIST OF ILLUSTRATIONS. FIG. PAGE 1-2. 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 73 7. Apparatus for generating hydrogen ....... 78 8. Apparatus for generating ammonia 85 9. Distillation of nitric acid ........ 87 10. Structure of flame 95 11. Apparatus for making sulphurous acid .... 100 12. Apparatus for detection of phosphorus ...... 109 13-16. Detection of arsenic 205-207 17-21. Apparatus for analytical operations .... 217-218 22. Heating of solids in bent glass tube ....... 222 23. Heating on charcoal by means of blowpipe ..... 222 24. Washing and decanting in agate mortar 223 25. Platinum wire for blowpipe experiments ...... 224 26-27. Apparatus for generating hydrosulphuric acid .... 229 28. Drying-oven 253 29. Desiccator 254 30. Watch-glasses for weighing filters . . . . 254 31. Litre-flask ............ 255 32. Pipettes 255 33. Mohr’s burette and clamp 256 34. Mohr’s burette and holder ......... 256 35. Gay Lussac’s burette 257 36. Titration .......... 261 37. Flask for dissolving iron ......... 263 38. Gas-furnace for organic analysis ... . . 274 39. Flasks for fractional distillation , 292 40. Liebig’s condenser, with flask ........ 304 41. Apparatus for estimation of urea . 437 42. Urinometer 443 43. Nitric acid test for urine . 446 44. Urinary sediments .......... 458 COLORED PLATES. FACING PAGE Plate I. Compounds of iron and zinc ....... 168 Plate II. Compounds of manganese and chromium .... 174 Plate III. Compounds of copper, lead, and bismuth .... 186 Plate IV. Compounds of silver and mercury 198 Plate V. Compounds of arsenic, antimony, and tin ... 204 Plate VI. Reactions of alkaloids 382 Plate VII. Urine and tests for its constituents 432 ABBREVIATIONS. cc. = 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 ATTRACTION 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 necessary 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? No 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 we 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. Generally speaking, we may also say force is the cause tending to produce, change, or destroy 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. 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 wdth 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 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. 1 It will be shown later that all matter is supposed to consist of smallest particles, which we call molecules. EXTENSION OR FIGURE. 19 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 substances—for instance, common salt and Glauber’s salt—be dissolved together in water, and the solution be allowed to crystallize, the attrac- tion 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 solid substances from mixtures by crystallization. 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 also be obtained in an amorphous state (carbon, sulphur). Other substances are capable of assuming different crystalline shapes under different 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 difference 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. 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. 20 INTRODUCTION. Brittleness is that property of solids which causes them to be easily broken 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. Grold is so malleable that it may be beaten into sheets so thin that it will 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. Whilst 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- 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 DIVISIBILITY. 21 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 besides 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 line 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 in an empty flask. The flask will be tilled completely by this water-gas (or steam) obtained by vaporizing that minute particle 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 state. 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. of ice-dust. This fact demonstrates that mechanical comminution does not carry us beyond a certain degree of subdivision of matter. That is to say, the smallest fragment of the finest pow- der 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—little mass, and means the smallest par- ticle 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 temperature above the boiling-point in close vessels of the same size are the DIVISIBILITY. 23 same, no matter whether the vessel was entirely empty or con- tains 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. This fact will undoubtedly prove that there must be small parti- cles 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 Fig. 2. matter 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 to 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. about -g o o o o og o o °f one inch, 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 importance for 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; hut 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, having also absorbed large quantities of heat, shows 100° C. (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 caused by 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 also noticed 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 molecules 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 of 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 pressure, 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 only been accom- plished quite recently and in very small quantities. Other substances, again, raa}7 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 an 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-point 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. While heat is one of the results of molecular motion, there are other phenomena also caused by it; as instances, may be cited those of light, actinism, electricity and magnetism. 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 not only gives out 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 28 INTRODUCTION. electricity and magnetism we know little, and the various theories which have 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 J. If we say the specific heat of mercury is -gV> 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 32°. 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 substance oflers on being moved, 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 Neivton’s law, may thus be stated : All bodies attract each other with a force directly propor- tional 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 is conse- quently 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 volumes 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 con- tained in it has been removed will weigh less than the same flask when filled with atmospheric air or with any other gas. Barometer. A second method, by which the fact that atmos- pheric air possesses weight may be demonstrated, 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 thickness, 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 tilling 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 tills 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 density of the atmosphere diminishes gradually from the level of the sea upward, the height of the mercury column will be lower in localities situated at an elevation. This diminu- tion of pressure is so regular 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 also learned 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°0. (807° F.), of 10 atmospheres at 180° C. (856° 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 disks of considerable thickness, that gases may 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 wliat 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. POROSITY. 33 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 conditions, 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 also be noticed 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. Every 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, wTe call this process absorption. This absorbing pow7er 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 filled 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 a 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 of one liquid into another, of a dissolved substance into another liquid, or of one gas into another gas, is called diffusion. 36 INTRODUCTION. Osmosis. 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 osmosis or dialysis. The apparatus used for dialysis is called a dialyzer (Fig. 4), and usually consists 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 then placed into another, and the two liquids are introduced into the two vessels. If the inner vessel be tilled with a salt solution and the outer one with pure water, it will be found that part of the salt solution passes through the membrane into the water, whilst at the same time water passes over to the salt solution. 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, erystallizable 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 phen- omena of osmosis, the surface of the diaphragm exercising an attraction upon the liquids. Fjg 4 Dialyzer' Diffusion of 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 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 POROSITY. 37 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. Hot only is matter indestructible, forces also partake of this property. Forces, when acting, manifest themselves in motion of either masses or particles of masses, and no change of any kind can take place without the action of a force or without motion. It has been shown before that heat is a manifestation of motion, and it may here be stated that light, electricity, magnetism, and also all varieties of chemical changes, depend on various kinds of motion. The nature of force and with it the nature of motion may be changed, but force itself cannot be destroyed, it is inde- structible like matter itself. 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 osmosis. 39. Which substances are most apt to dialyze, and which have no such tendency ? 40. What is meant by saying that matter and force 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, another effect may be frequently noticed which has not yet been 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 is so constructed that the escaping gases may be col- lected and cooled, we shall not find the red oxide in our receiver, but in its place a colorless gas, whilst at the same time globules CHEMICAL DIVISIBILITY. 39 of metallic mercury are found to be deposited in the cooler parts of the apparatus (Fig. 5). The action of heat has consequently 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 different from the oxide are liberated. 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 atmospheric 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 again into two or more new substances of different properties. 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 decompo- sition 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. We are, therefore, 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 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. 40 PRINCIPLES OF CHEMISTRY. 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 newT properties. This kind of attractive power is called chemical force, affinity, or chemism, 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. 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 of mercury must also consist of molecules. CHEMICAL DIVISIBILITY. 41 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, whilst 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, wffiilst 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 place in consequence of chemical affinity. "We may also say that chemistry is that branch of science which treats of the com- position of substances, their changes in 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: acting between General Force of Attraction Heavenly bodies or masses. Surfaces. Molecules. Atoms. is termed: Gravitation. Surf ace-action. Adhesion. Capillary attrac- tion, etc. Cohesion. Chemical affinity. The phenomena caused by these respective actions are con- sidered by: Astronomy or Mechanics. Physics. Physics. Crystallography. Chemistry. 42 PRINCIPLES OF CHEMISTRY. Atomic weight. All matter possesses weight; this is true of a mass as well as any part of it, and must consequently be also true of the atoms and molecules of which matter consists. It is, of course, impossible to weigh a single atom or a single molecule, 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 pro- ducts of decomposition (viz., the oxygen and the mercury) of a given, previously weighed quantity of oxide of mercury. In doing this, it will invariably be found 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 + 16 = 216. Chemical symbols. For reasons to be better understood here- after, chemists designate each element by a symbol, and the first or the first two letters of the Latin name of the element have generally been selected. Thus, the symbol of hydrogen is H, of LAWS OF CHEMICAL COMBINATION. 43 oxygen 0, of mercury Hg (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 Hg, 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 oxygen. 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 II20, whilst 2HO or 2(HO) 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 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, 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 molecule? 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 chem- ical symbols and formulas. 44 PRINCIPLES OF CHEMISTRY. 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 by 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 tbe 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 maybe 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 proportion only, 56 parts by weight of iron combining with 32 parts by weight of sulphur to form 88 parrs 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 3 B, etc. This law was discovered at the beginning of the present cen- tury, when it was found that the ratio of carbon to hydrogen in LAWS OF CHEMICAL COMBINATION. 45 olefiant gas, C2H4, is as 6 to 1, in marsh gas, CH4, 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 combine 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 N205, 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 also represent 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 Voliumes Hydrochlioric Acid W =;36.4 1 Volume Hydrogen W = 1 + 1 Volume Hydrogen W = 1 1 Volume Oxygen W = 16 + 2 Voliumes Water:-vapor W =jl8 1 Volume Hydrogen W = 1 + 1 Volume Hydrogen W = 1 1 Volume Hydrogen \V = 1 + + 1 Volume Nitrogen W = 14 2 Voliumes Amm jonia W = i 17 1 Volume Hydrogen W = 1 + 1 Volume Hydrogen W = 1 + 1 Volume Sulphur W = 32 1 Volume Oxygen W = 16 + + 2 Voliumes Sulphurjic acid Weight: = 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 stated heretofore, and which says that all gases under equal conditions contain the same number of molecules. The weighing of equal volumes of gases is consequently identical with the weighing of equal numbers of molecules. The molecular weight of a substance can therefore 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 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, and steam, we find weights in the proportion of 2, 70.8, 32, 36.4 and 18. These numbers at the same time express the molecular weights of these substances, but the numbers also show that atomic and molecular weights of elements are not identical, but that the latter weight is twice that LAWS OF CHEMICAL COMBINATION 47 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. Law of equivalents. (Juantivalence, or Valence. When one element replaces another element in a compound, the quantities of the two elements are said to be equivalent to each other, and according to the law of equivalents the replacement of elements one by another always takes place in definite proportions. For- merly it was believed that all atoms were equivalent amongst each other, and, accordingly, atomic weights were frequently designated as equivalent weights. This view, however, is not correct, as it is found that frequently one atom of one element 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 best understood by selecting a few compounds of different elements with hydrogen, for consideration. I. HC1 HBr HI II. h2o h2s H2Se III. H3N H„As H3P IV. H4C H4Si We see here, that Cl, Br, and I combine with II 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; H, As, P combine with 3; C and Si with 4 atoms of hydrogen. It has been, moreover, found that the compounds mentioned in column I. are the only ones which can possibly 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 NaCl or HaBr. Looking at columns II., III., and IV., we see that the elements mentioned there combine with 2, 3, and 4 atoms of hydrogen, 1 A few exceptions to this general rule will be mentioned at the proper places. 48 PRINCIPLES OF CHEMISTRY. respectively. It is evident, therefore, that there must be some peculiarity in the power of attraction of different elements to- ward other elements, and to this property of the atoms of ele- ments of holding in combination one, two, three, four, or more atoms of other elements the name atomicity, quantivalence, or simply valence, has 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, ISTa, K, Ag, etc. Those elements which combine with hydrogen 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. The elementary atoms are often named, according to their valence: monads, diads, triads tetrads, pentads, hexads, and heptads. To indicate the valence of the elements, dots or numbers are frequently placed above the chemical symbols, thus IT, 0“, N1U, Cmi or Civ. 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- LAWS OF CHEMICAL COMBINATION. 49 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 is correct. Thus chlorine, the valence of which is generally I., may also have a valence equal to III., V., or VII., while sulphur shows a valence of either 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 that valence will, in most cases, only be men- tioned which the element seems to possess predominantly. The doctrine of the valence of atoms has modified our views of the equivalence of atoms. We say the atoms of univalent, bivalent, or trivalent elements are equivalent among each other; 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 may now be better understood why the atoms do not exist as such in a free and uncombined state in an element, but combine with each other to form molecules. The atoms having the tendency of combining with, or attaching themselves to 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 mole- cules, 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 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 will an equal volume of oxygen and how much an equal volume of hydro- chloric acid gas weigh, provided pressure and temperature be the same? 50 PRINCIPLES OF CHEMISTRY. 7. DETERMINATION OF ATOMIC WEIGHTS.1 Determination of atomic weights by chemical decomposition. The great difficulties originally encountered in the determination of atomic weights cannot be described here, and the present methods only, of which there are principally three, will be con- sidered. 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 clew 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. Thus, in examining water, it was found that it contains 8 parts by weight of oxygen to every 1 part of hydrogen, and the con- clusion was drawn that the atomic weight of oxygen was 8, the molecule of water being 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 the molecule of water is composed of 2 atoms of hydrogen and 1 of oxygen. 1 The consideration of Chapter 7 should be postponed until the student has become familiar with chemical phenomena generally. 51 DEFINITION OF ATOMIC WEIGHTS 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 hydrochloric acid the hydrogen is replaced by some other ele- ment, for instance by sodium, we are enabled to determine the atomic weight of sodium by weighing its quantity and that of the liberated hydrogen. Suppose by the action of 36.4 grams of hydrochloric acid on sodium 1 gram of hydrogen be replaced by 23 grams of sodium, we would say that the atomic weight of sodium is equal to 23. The same difficulty exists in this mode of determination of atomic weights which was alluded to above, viz., not knowing whether it was actually one atom of sodium that replaced the one part of hydrogen, a doubt is left whether the determination is absolutely 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 small or large the number of atoms within the molecules may be), and that the molecules of elements con- tain (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 ele- ment is found to weigh 71 grams, then the atomic weight of the latter element must be 35.5, because 2 and 71 represent the rela- tive weights of the molecules of the two elements. Each mole- cule being composed of 2 atoms, these molecular weights have to be divided by 2 in order to find the atomic weights, which are, consequently, 1 and 35.5 respectively. In comparing oxygen by this method 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 be converted into them. There are, however, elements which cannot be volatilized, and in 52 PRINCIPLES OF CHEMISTRY. this case it becomes necessary to determine 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, which 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 heal 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, 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 heat. 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 DEFINITION OF ATOMIC WEIGHTS. 53 have the same capacity for heat, we will select three elements to illustrate this law. If we take of lithium T 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 tem- perature increases equally for all three substances—that is to say, the same 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 new means of determining 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 deter- mined 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. Questions.—61. What are the three principal methods used for the determi- nation of atomic weights? 62. Why are chemical means not always sufficient 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? 54 PRINCIPLES OF CHEMISTRY. 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 substance in consequence of greater affinity between them under given conditions. 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 causes the molecules to strike against one another with greater energy, thereby bringing the atoms of the different mole- cules into closer contact and facilitating chemical change. For instance: Mer- cury 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. The amount of heat required for decomposition differs widely according to the nature of the substance. Some substances can only be produced at a temperature below the freezing-point of water, a higher temperature causing their decomposition; other substances will 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- DECOMPOSITION OF COMPOUNDS. 55 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, electricity also 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. There is a certain relation between electrical and chemical action, as the amount 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. 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; electricity is the consequence of the motion of an assumed electric fluid. These motions, in being transferred to atoms, have, as shown above, frequently 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 contact to exchange their atoms. The free motion of the molecules in liquid or gaseous substances facilitates such a close contact, and conse- quently 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 fine powder and mixing them together thoroughly, chemical 56 PRINCIPLES OF CHEMISTRY. combination may follow, provided the affinity between them be sufficiently 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 + B = AB. 2. AB + C = AC + B. 3. AB + CD = AC + BD. 4. AB + 2C = AC + BC. As instances illustrating the above, may be mentioned the fol- lowing chemical reactions: 1. H 4- Cl = HC1. Hydrogen Chlorine. Hydrochloric acid. The formula here given for the formation of hj-drochloric 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: Or HH + C1C1 = ‘2HC1. 2H + 2C1 = 2HC1. 2. Hydrochloric acid and sodium form chloride of sodium and hydrogen: HC1 + Na = NaCl + H. The formula more correctly written would be : 2HC1 + 2Na = 2NaCl + 2H. 3. Hydrochloric acid. HC1 + AgNO, = AgCl + HNOs. Nitrate of silver. Chloride of silver. Nitric acid. This form of decomposition, known as double decomposition, is one of the most common kinds of chemical changes met with in chemical operations. 4. Hydrosulphuric acid. H2S + 30 = H20 + S02. Oxygen. Water. Sulphur dioxide. 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 must be explained by saying, that sodium has a greater affinity for chlorine than hydrogen, as the latter is expelled by the sodium. DECOMPOSITION OF COMPOUNDS. 57 No general rule can, however, be given for the amount 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, oxide of iron 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 that between oxygen and iron. Many similar instances are known and will be spoken of later. 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 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 in- soluble 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, iNa2C03, calcium carbonate is produced. 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 combination with other atoms of either the same kind (to form elementary molecules) or of another kind (to form com- 58 PRINCIPLES OF CHEMISTRY. 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, this 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, AsH3, and water, H20. Chemical reactions. This expression is used for any chemical change brought about with the intention of studying the nature of a substance. The expression reagent is applied to those sub- stances 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 elements are made to unite to produce compound substances. 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 easily be 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. DECOMPOSITION OF COMPOUNDS. 59 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, H2S04, is a dibasic, phosphoric acid, H3P04, is a tribasic acid. Bases or basic substances show properties which are opposite to those of acids. These properties are : 1. They have (when soluble in water) the taste of lye, or an alkaline taste. 2. They restore the color of organic substances when previously 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 the salt potassium chloride and water, KHO + HC1 = H20 + KC1. 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 b}T the action of an acid on a metal (usually with the liberation of hydrogen). 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, IvCl, potassium sulphate, K2S04, potassium phosphate, K3P04. (As monobasic acids have but one atom of hydrogen which can be replaced, they form normal salts only.) Acid salts are acids in which only a portion of tne replaceable hydrogen atoms has been replaced. For instance: KHS04, K2HP04, kh2po4. Double salts are salts formed by replacement of hydrogen in an acid by more than one metal. For instance: potassium-sodium sulphate, KNaS04. 60 PRINCIPLES OF CHEMISTRY. 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 II20, water. If we take from this II20 one atom of H, there is left the group of atoms HO, 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, HO, is a residue or radical, and is known to enter into many compounds ; it is, for instance, a constituent of all the different hydroxides or hydrates, such as potassium hydroxide, KIIO, calcium hydroxide, Ca2HO, 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 CH3', CH2", CH'", are formed. 9. GENERAL REMARKS REGARDING ELEMENTS. Relative importance of different elements. Of the total number of about sixty-seven elements, but few comparatively (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, of the water and atmosphere, and of all animal and vege- table matter. Another number of elements are of less importance, either Questions.—71. What physical actions have a tendency to decompose com- pound substances? 72. Explain the terms reaction and reagent. 73. Mention 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 dilferent 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. GENERAL REMARKS REGARDING ELEMENTS. 61 because 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 quan- tities in nature that they are almost exclusively of scientific in- terest. The existence of some elements, the discovery of which has been claimed, is even doubtful. The elements enumerated in column I. are those of great and general interest; in II. those claiming our interest on account of the use made of them; in III. those having scientific interest only. I. II. III. Aluminium Antimony Beryllium (Glucinium) Calcium Arsenic Csesium 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 Silicon Gold Osmium Sodium Iodine Palladium Sulphur Lead Rhodium Lithium Rubidium 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 very natural classification of all elements is the one dividing them into the two groups of metals and non-metals. 62 PRINCIPLES OF CHEMISTRY. 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 52 elements being metals. Natural groups of elements. Besides classifying all elements into metals and non-metals, certain members of both classes ex- hibit 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, 127 Sulphur, 32 Selenium, 78.8 Tellurium, 128 Lithium, 7 Sodium, 23 Potassium, 39 Calcium, 49 Strontium, 87 Barium, 136.8 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 _ R1 . 32 + 128 _fin. 7 + 39 _ 95. 40 + 136.8 _ 88 4 2 ’2 ’2 ’2 Mendelejeff’s 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 Mendelejeff may be selected as most suitable to show this relation. Looking at MendelejefFs table on page 64, it will be seen 1 The consideration of this law should be postponed until the student has become acquainted with the larger number of important elements. GENERAL REMARKS REGARDING ELEMENTS. 63 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 ths right to left, as may be shown by the following instances: I. II. III. IV. V. VI. VII. Nh20 MgO A1203 Si02 P205 S03 C1207 Hydrogen compounds unknown SiHA PH3 SH2 C1H The oxides on the left show strongly basic properties, as illustrated 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 little basic properties, which latter increase gradually in the fifth, sixth, and seventh groups. While some elements show an exception, it may also be stated that most of the elements of group I. are univalent, of II. bivalent, of III. trivalent, of IV. quadrivalent, of V. quinquiva- lent, 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 also 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). PRINCIPLES OF CHEMISTRY. Series. Group I. Ii/) Group II. R 0 Group III. R0O3 Group IV. R H4 R O2 Group Y. R H3 11 *j 0;j Group VI. R Ho R 03 Group VII. R II R207 Group VIII. R04? 1 2 H, 1 Li, 7 Be, 9 B, 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 Y, 51 Cr, 52 Mn, 54 Fe, 56. Ni, 58.6. Co, 59 5 (Cu, 63) Zn, 65 Ga, 69 Ge, 72 As, 75 Se, 79 Br, 80 6 Kb, 85 Sr, 87 Y, 89 Zr, 90 Nb, 94 Mo, 96 - Rh, 104. Ru, 104.5. Pd, 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, 144 — - — — — 9 — — — _ Er, 166 — — 10 - - Yb, 173 - Ta, 182 W, 184 - Os, 192. Ir, 193. Pt, 195 11 (Au, 196) Hg, 200 Tl, 204 Pb, 206 Bi, 209 - - 12 - -- Th, 231 - U, 240 — — — — 1 The decimals are generally omitted in giving the atomic weights. Periodic System.1 GENERAL REMARKS REGARDING ELEMENTS. 65 The 12 series or periods given in the preceding 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 closety 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 above table the elements belong- ing 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 formino- an intermediate series following the even periods 4, 6, and 10. 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 the}r now occupy. Physical properties of elements. Most elements are, at the ordi- nary temperature, solid substances, two are liquids (bromine and mercury), live are gases (oxygen, hydrogen, nitrogen, chlorine, 66 PRINCIPLES OF CHEMISTRY. 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 are also 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- 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 were 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 will be generally adopted. When two elements combine in one proportion only, little GENERAL REMARKS REGARDING ELEMENTS 67 difficulty is experienced in the formation of a name, as, for in- stance, in iodide of potassium or potassium iodide, KI, chloride of sodium or sodium chloride, Nad. When two elements combine in more than one proportion, the syllables mono, di, tri, teira, and penta are frequently used to designate the relative quantity of the elements. For instance: Carbon monoxide, CO, carbon rteoxide, C02, phosphorus tri- chloride, PC13, phosphorus PC15. In many cases the syllables ons 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 phosphonc chloride, PC15; ferrons oxide, FeO, feme oxide, Fe203. The syllables mono and sesqui are also occasionally used 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, P203, forms phosphorous acid; phosphonc oxide, P205, forms phosphonc acid. The salts formed by these acids are distinguished by using the sjdlables ite and ate. Phosph/te of sodium is derived from phos- phorous acid, phosphate of sodium from phosphoric acid. Sul- pffi'tes 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 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. Writing chemical equations. It has been shown that chemical changes are expressed by means of symbols in chemical equations. 68 PRINCIPLES OF CHEMISTRY. 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 -j-, 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 also correct mathematically —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 + CaCI2 = 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: 2Na =46 Ca = 40 Ca = 40 2Na = 46 C = 12 2C1 = 71 C = 12 2C1 = 71 30 = 48 30 = 48 106 + 111 = 217 100 + 117 = 217 Chemical equations are not only used for representing chemical changes, but they are also 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. GENERAL REMARKS REGARDING ELEMENTS. 69 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 maybe 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 also be noticed. 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 re- lationship 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 non-metals is fourteen : two of them, selenium and tellurium, are of so little importance that they will be but briefly considered in this hook. 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 ppupog (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 Greek (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 (genao), to generate. Iodine, I = 126.6. From the Greek iov (ion), violet, referring to the color of its vapors. Nitrogen, N = 14. From the Greek virpov (nitron), nitre, and yevvau (genao )> to generate. Oxygen, O = 16. From the Greek (oxus), acid, and yevvau (genao), to generate. Phosphorus, P = 31. From the Greek ug (phos), light, and tyepeiv (pherein) to bear. Silicium, Si — 28. From the Latin, silex, flint, or silica, the oxide of silicium. Sulphur S = 32. From sal, salt, and nvp (pur), fire, referring to the com- bustible properties of sulphur. THE NON-METALS. 71 State of aggregation. Under ordinary conditions the non-metals show the following states : Gases. Liquids. Solids. B. P. F. P. B. P. Hydrogen, ■ 1 Can scarcely be Bromine, 63° C. Phospho rus, 44° C. 280° C. Oxygen, v converted into Iodine, 107 175 Nitrogen, - ' liquids. Sulphur, 111 400 Chlorine, Easily liquetied. Carbon, ■ 1 Fluorine, ? Boron, }■ Infusible. Silicon, . ) Occurrence in nature. a. In a free or combined state. Carbon in coal, organic matter, carbon dioxide, carbonates. Nitrogen in air, ammonia, nitrates, organic matter. Oxygen in air, water, organic matter, most minerals. Sulphur chiefly as sulphates and sulphides. Boron in boric acid and borax. Bromine in saline springs and sea-water as bromide of magnesium, etc. Chlorine as chloride of sodium in sea-water, etc. Fluorine as fluoride of calcium, fluorspar. Hydrogen in water and organic matter. Iodine as iodides in sea-water. Phosphorus as phosphate of calcium, iron, etc., in bones. Silicon as silicic acid or silica, and in silicates. b. In combination only. Time of discovery. Sulphur, ) Long known in the elementary state; recognized as elements Carbon, / in the latter part of the eighteenth century. Phosphorus, 1669, by Brandt, of Germany. Chlorine, 1770, by Scheele, of Sweden. 1772, by Rutherford, of England. Oxygen, 1774, by Priestley, of England, and Scheele, of Sweden. Hydrogen, 1781, by Cavendish, of England. Boron, 1808, by Gay-Lussac, of France Fluorine, 1810, by Ampere, of France. Iodine, 1812, by Courtois, of France. Silicon, 1823, by Berzelius, of Sweden. Univalent. Bivalent Trivalent or quinquivalent. Quadrivalent. Hydrogen, Oxygen, Nitrogen, Carbon, Chlorine, Sulphur. Boron, Silicon. Bromine, Phosphorus. Iodine, Fluorine. Valence. 72 NON-METALS AND THEIR COMBINATIONS. 10. OXYGEN. History. Oxygen was discovered in the year 1774 by Priestley, in England, and Scheele, in Sweden, independently of each other; its true nature was soon afterward recognized by Lavoisier, of France, who gave it the name oxygen, from the two Greek words, <%• (oxus), acid, and yewdu (genao), to produce or generate. Oxygen means, consequently, generator of acids. 0>i = 16. Occurrence in nature. There is no other element on our earth present in so large a quantity as oxygen. It has been calculated that not less than about one-third, possibly as much as 45 per cent., of the total weight of our earth is made up of oxygen; it is found in a free or uncombined state in the atmosphere, of which it forms about one-fifth of the weight. Water contains eight- ninths of its weight of oxygen, and most of the rocks and different mineral constituents of our earth contain oxygen in quantities varying from 30 to 50 percent.; finally, it is found as one of the common constituents of most animal and vegetable matter. If the unknown interior of our earth should be similar in com- position to the solid crust of mineral constituents which have been analyzed, then the subjoined table will give approximately the proportions of those elements present in the largest quantity. Oxygen . .45 parts. Silicon . 28 “ Aluminium 8 “ Iron . . . 6 “ Calcium . . .4 parts. Magnesium . . 2 u Sodium . . . 2 “ Potassium . . 2 *• Preparation. The oxides of the so-called noble metals (gold, silver, mercury, platinum) are easily decomposed by heat into the metal and oxygen : HgO = Hg + 0; Ag20 = 2Ag + 0. A more economical method of obtaining oxygen is the decom- position of potassium chlorate, KC103, into potassium chloride, KCl, and oxygen by application of heat: KC103 = KC1 + 30. If the potassium chlorate is mixed with about 10-20 per cent, of manganese dioxide, and this mixture heated, the liberation of OXYGEN. 73 oxygen takes place with greater facility and at a lower tempera- ture than by heating potassium chlorate by itself. Apparently, the manganese dioxide takes no active part in the decomposition, as its total amount is found in an unaltered condition after all potassium chlorate has been decomposed by heat. A satisfactory explanation regarding this action of manganese dioxide is yet wanting. A third method is to heat to redness, in an iron vessel, the manganese dioxide (Mn02), which then suffers a partial decom- position : 8Mn02 as Mn304 -f- 20. In this case but one-third of the total amount of oxygen present is liberated, while two-thirds remain in combination with the manganese. Other methods of obtaining oxygen are decomposition of water by electricity, heating of chromates, nitrates, barium dioxide, sulphuric acid, and other substances, which evolve a portion of the oxygen present in the molecules. Experiment 1. Generate oxygen by heating a small quantity (about 5 grams) of potassium chlorate in a dry flask of about 100 c. c. capacity, to which, by means of a perforated cork, a bent glass tube has been attached, which leads under the surface of water contained in a dish. (Fig. 6.) Collect the gas by Fig. 6. Apparatus for generating oxygen. placing large test-tubes (or other suitable vessels) filled with water over the delivery-tube. Notice that a strip of wood, a wax candle, or any other substance 74 NON-METALS AND THEIR COMBINATIONS. which burns in air, burns with greater energy in the oxygen gas, and that an extinguished taper, on which a spark yet remains, is rekindled when placed in oxygen gas. Notice, also, the physical properties of the gas. How many c. c. of oxygen can be obtained from 5 grams of potassium chlorate? 1000 c. c. of oxygen weigh 1.43 gram. The quantity of oxygen liberated from a given quantity of a substance may easily be calculated from the atomic and molec- ular weights of the substance or substances suffering decomposi- tion. For instance : 100 pounds of oxygen may be obtained from how many pounds of potassium chlorate, or from how many pounds of manganese dioxide? The molecular weight of potassium chlorate is found by adding up the weights of 1 atom of potassium = 39 + 1 atom of chlorine = 35.4 + 3 atoms of oxygen = 48; total = 122.4. Every 122.4 parts by weight of potassium chlorate liberate the weight of 3 atoms, or 48 parts by weight of oxygen. If 48 are obtaiaed from 122.4, 100 are obtained from 255. 48 : 122.4 : : 100 : x x — 255. In a similar manner, it will be found that 806.2 pounds of man- ganese dioxide are necessary to produce 100 pounds of oxygen. Mn02 = 54 + 32 = 86. 3 Mn02 = 3 X 86 = 258. Every 258 parts furnish 2 X 16 = 32 parts of oxygen. 32 : 258 :: 100 : x x == 806.8. Physical properties. Oxygen is a colorless, inodorous, tasteless gas; up to a few years ago it was looked upon as a permanent or stable gas, as all attempts to liquefy or solidify it had failed. Lately, however, these efforts have been successful, and oxygen has been converted (though in very small quantities) into a color- less liquid by the application of a pressure of 470 atmospheres at a temperature of —130° C. (—202° F.). Oxygen is but sparingly soluble in water (about 3 volumes in 100 at common temperature). A litre of oxygen at the standard temperature and pressure weighs 1.4336 gram. Chemical properties. The principal feature of oxygen is its great affinity for almost all other elements, both metals and non- metals ; with nearly all these elements it combines in a direct manner. The more important elements with which oxygen does OXYGEN. 75 not combine directly are : Cl, Br, I, FI, Au, Ag, and Pt, but even with these it combines indirectly, excepting FI. The act of combination between other substances and oxygen is called oxidation, and the products formed, oxides. The large number of oxides are usually divided into three groups, and dis- tinguished as basic oxides (sodium oxide, Ha20, calcium oxide, CaO), peroxides (manganese peroxide, Mn02, lead peroxide, Pb02), and acid-forming or acid oxides (carbon dioxide, C02, sulphur trioxide, S03). Whenever the heat generated by oxidation (or by any other chemical action) is sufficiently high to cause the emission of light, the process is called combustion. Ox}Tgen is the chief supporter of all the ordinary phenomena of combustion. Substances which burn in atmospheric air burn with greater facility in pure oxygen. This property is taken advantage of to recognize and distinguish oxygen from most other gases. Pro- cesses of oxidation evolving no light are called slow combustion. An instance of slow combustion is the combustion of the different organic substances in the living animal, the oxygen being sup- plied during the process of respiration. It is not absolutely necessary for a process of oxidation that free oxygen be present, as many substances contain oxygen in such a form of combination that they part with it easily when brought in contact with substances having a greater affinity for it. Such substances are called oxidizing agents, as, for instance, nitric acid, potassium chlorate, potassium permanganate, etc. In all combustions we have at least two substances acting chemically upon one another, which are generally spoken of as combustible bodies and supporters of combustion. Illuminating gas is a combustible substance, and oxygen a sup- porter of combustion ; but these terms are only relatively correct, since oxygen may be caused to burn in illuminating gas, whereby it is made to assume the position of a combustible substance, whilst illuminating gas is the supporter of combustion. Ozone is an allotropic modification of oxygen, which is formed when non-luminous electric discharges pass through atmospheric air or through oxygen ; when phosphorus, partially covered with water, is exposed to air, and also during a number of chemical decompositions. Ozone differs from ordinary oxygen by pos- sessing a peculiar odor, by being an even stronger oxidizing agent than common oxygen, by liberating iodine from potassic iodide, etc. This latter action may be used for demonstrating the presence of ozone by suspending in the gas paper moist- 76 NON-METALS ANI) TIIEIR COMBINATIONS. ened with a solution of potassium iodide and starch. The iodine, liberated by the ozone, forms, with starch, a dark blue compound. Theoretically, we assume that ozone contains three, common oxygen but two, atoms in the molecule, which is substantiated by the fact that three volumes suffer a condensation to two vol- umes, when converted into ozone, which would indicate that three molecules of oxygen furnish two molecules of ozone, thus: 302 = 203 °=° A 0=0 = °~° °=° ol^o or 11. HYDROGEN. Hi = 1. History. Hydrogen was obtained by Paracelsus in the 16th century; its elementary nature was recognized by Cavendish, in 1781. The name is derived from Wup (hudor), water, and yswdu (genao), to generate, in allusion to the formation of water by the combustion of hydrogen. Occurrence in nature. Hydrogen is found chiefly as a compo- nent element of water; it enters into the composition of most animal and vegetable substances, and is a constituent of all acids. Small quantities of free hydrogen are found in the gases pro- duced by the decomposition of organic matters (as, for instance, in the intestinal gases), and also in the natural gas escaping from the interior of the earth. Preparation. Hj-drogen may be obtained by passing an electric current through water, by which it is decomposed into its ele- ments : H20 = 2H + 0. Questions.—91. By whom and at what time was oxygen discovered? 92. How is oxygen found in nature? 93. Mention three processes by which oxygen may be obtained? 94. How much oxygen may be obtained from 490 grains of potassium chlorate ? 95. State the physical and chemical properties of oxygen. 96. Explain the terms combustion, slow combustion, combustible substance, and supporter of combustion. 97. Mention some oxidizing agents. 98. What is ozone, and how does it differ from common oxygen ? 99. Under what circum- stances is ozone formed? 100. State the molecular weight of oxygen and ozone. HYDROGEN. 77 A second process is the decomposition of water by metals. Some metals, such as potassium and sodium, decompose water at the ordinary temperature, whilst others, iron, for instance, decom- pose it at a red heat: K + H20 = KHO + H ; Fe + H20 = FeO + 2H. A very convenient way of liberating hydrogen is the decompo- sition of dilute hydrochloric or sulphuric acid by zinc or iron : Zn + 2HC1 = ZnCl2 + 2H; Zinc chloride. Fe + H2S04 = FeS04 + 2H. Ferrous sulphate. Hydrogen may also be obtained by heating granulated zinc or aluminium with strong solutions of potassium or sodium hydroxide, in which case the decomposition is explained thus: Zn + 2KHO = K2Zn02 + 2H; Potassium zincate. A1 + 3NaHO = Na3A103 + 3H Sodium aluminate. Whenever hydrogen is generated, care should be taken to expel all atmospheric air from the vessel in which the generation takes place, before the hydrogen is ignited, as otherwise an explosion may result. Experiment 2. Place a few pieces of granulated zinc (about 10 grams) in a flask of about 200 c. c. capacity, which is arranged as shown in Fig. 7. Cover the zinc with water, and pour upon it through the funnel tube a little sulphuric acid, adding more when gas ceases to be evolved. Notice the effervescence around the zinc. Collect the gas in test-tubes over water and ignite it by taking the test tube with mouth downward to a flame near by. Notice that the first- portions of gas collected, which are a mixture of hydrogen and atmospheric air, explode when ignited in the test-tube, while the subsequent portions burn quietly. Pour the contents of one test-tube into another one by allowing the light hydrogen gas to rise into and replace the air in a test-tube held over the one filled with hydrogen. Take two test-tubes completely filled with the gas ; hold one mouth upward, the other one mouth downward : notice that from the first one the gas escapes after a few seconds, while it remains in the second tube a few minutes, as may be shown by holding the tubes near a flame to cause ignition. After having ascertained that all atmospheric air has been expelled from the flask, the gas may be ignited directly at the mouth of the delivery tube, after moving it out of the water. NON-METALS AND THEIR COMBINATIONS Fig. 7. Experiment 3. Pour into a test-tube of not less than 50 c. c. capacity 5 c. c. of hydrochloric acid, fill up with water, close the tube with the thumb and set it inverted into a porcelain dish partly filled with water. Weigh of metallic zinc 0.04 gram, and bring it quickly under the mouth of the test-tube, so that the generated hydrogen rises in the tube. Prepare a second tube in the same manner, and introduce 0.04 gram of metallic magnesium. In case the decomposition of the acid by the metals should proceed too slowly, a little more acid may be poured into the dishes. When the metals are completely dissolved it will be seen that the volumes of hydrogen in the two tubes bear a relation to each other of about 10 to 27. In order to measure the gas volumes as correctly as the simple apparatus per- mits, the tubes should be transferred to a large beaker filled with cold water, bringing tbe surface of the liquids in the test-tube and beaker on a level, and marking on the outside of the test-tubes with a file or paper the exact height of the gas. After having emptied the test-tubes, they may be filled with water from a pipette or from a burette to the point which has been marked, and thus the exact volume of gas generated is ascertained. Repeat the operation, using 0.065 gram of zinc and 0.024 gram of magnesium. Notice that in this case equal volumes of hydrogen are obtained. Calculate the weight of hydrogen from the cubic centimetres liberated, and compare this weight with the weights of zinc and magnesium used. What relation is there between the weights of the liberated hydrogen and the metals used, and the atomic weights of these three elements ? Apparatus for generating hydrogen. Properties. Hydrogen is a colorless, inodorous, tasteless gas ; it is the lightest of all known substances, having a specific gravity of 0.0602 as compared with atmospheric air=l. One litre of hydrogen at 0° C. (82° F.), and a barometric pressure of 760 mm., weighs 0.0896 gram, or one gram occupies a space of 11.163 litres; 100 cubic inches weigh about 2.265 grains. HYDROGEN. 79 In its chemical properties, hydrogen resembles the metals more than the non-metals; it easily burns in atmospheric air, or in pure oxygen, with a non-luminous, colorless, or slightly bluish flame, producing during this process of combustion a higher tem- perature than can be obtained by the combustion of an equal weight of any other substance : H2 + o = H,0. The formation of water by the combustion of hydrogen distin- guishes it from other gases. Two volumes of hydrogen combine with one volume of oxygen, forming two volumes of gaseous water. Water, 11,0 = 18. Hydrogen monoxide. Water is not found in nature in an absolutely pure state. The purest natural water is rain-water collected after the air has been purified from dust, etc., by previous rain. Comparatively pure water may be ob- tained by melting ice, since, when water containing impurities is partially frozen, these are mostly left in the uncongealed water. The waters of springs, wells, rivers, etc., differ widely from each other; they all contain more or less of substances dissolved by the water in its course through the atmosphere or through the soil and rocks. The constituents thus absorbed by the water are either solids or gases. Solids generally found in natural waters are common salt (sodium chloride), gypsum (calcium sulphate), and carbonate of lime (calcium carbonate); frequently found are chlorides and sulphates of potassium and magnesium, traces of silica and salts of iron. The gases absorbed by the water are chiefly constituents of the atmospheric air, oxygen, nitrogen, and carbon dioxide. One hundred volumes of water contain about two volumes of nitrogen, one volume of oxygen, and one volume of carbon dioxide. Mineral waters are spring waters containing one or more sub- stances in such quantities that they impart to the water a peculiar taste and generally a decided medicinal action. According to the predominating constituents we distinguish bitter waters, contain- ing larger quantities of magnesium salts; iron or chalybeate waters, containing carbonate or sulphate of iron; hepatic waters, containing sulphuretted hydrogen; acidulous waters, containing larger quantities of carbonic acid, etc. 80 NON-METALS AND THEIR COMBINATIONS. Drinking water. A good drinking water should neither be an absolutely pure water, nor a water containing too much of foreign matter. Water containing from 1 to 3 parts of total solids (chiefly carbonate of lime and common salt) in 10,000 parts of water and about 1 volume of carbon dioxide in 100 volumes of water, may be said to be a good drinking water. There are, however, good drinking waters which contain more of total solids than the amount mentioned above. Most objectionable in drinking water are organic substances, especially when derived from animal matter, and more especially when in a state of decomposition. The presence of organic matter in water may be demonstrated by evaporating about one litre of it in a small porcelain or platinum dish over a steam bath. The residue left represents the total solids, and is generally of a white color. If this residue, upon being further heated over a flame, turns black (by separation of carbon), the presence of organic matter is indicated. Another method to prove the presence of organic matter is the addition of a solution of potassium permanganate. On heating 100 c. c. of water, acidulated with 10 c. c. of diluted sulphuric acid, to the boiling-point, and adding enough of a dilute solution of potassium permanganate (1 in 1000) to impart to the liquid a decided rose-red tint, this tint should not be entirely destroyed by boiling for five minutes, as, otherwise, organic or other oxidizable matter is present. Water containing organic matter due to sewage or to other nitrogenous substances, yields ammonia when boiled with an alkaline solution of potassium permanganate; more than 0.10 gram per million of such ammonia is claimed to indicate an unwholesome water. Distilled water, Aqua destillata. The process for obtaining pure water is distillation in a suitable apparatus. From 1000 parts of water used for distillation, the first 50 parts distilling over should not be used, as they contain the gaseous constituents. The solids contained in the water are left in the undistilled portion. Properties of water. Water is a colorless, inodorous, tasteless liquid. It is perfectly neutral, yet it has a tendency to combine with both acid and basic substances. These compounds are usu- ally called hydroxides or hydrates, such as NaliO, Ca2HO, etc. HYDROGEN. 81 These compounds are often formed by direct union of an oxide with water, thus: CaO -f H20 = Ca2HO. Water is the most common solvent, both in nature and in artificial processes. As a general rule, solids are dissolved more quickly and in larger quantities by hot water than by cold, but to this there are many exceptions. For instance: Common salt is nearly as soluble in cold as in hot water; sulphate of sodium is most soluble in water of 33° C. (91° F.), and some calcium salts are less soluble in hot than in cold water. Many salts combine with water in crystallizing; crystallized sulphate of sodium, for instance, contains more than half its weight of water. This water is called water of crystallization, and is generally expelled at a temperature of 100° C. (212° F.). Some crystallized substances lose water of crystallization when exposed to the air; this property is known as efflorescence. Crystals of sodium carbonate, ferrous sulphate, etc., effloresce, as is shown by the formation of powder upon the crystalline surface. The term deliquescence is applied to the power of certain solid sub- stances to absorb moisture from the air, thereby becoming damp or even liquid, as, for instance, potassium hydroxide, calcium chloride, etc. Such substances are also spoken of as being hygro- scopic, and are used for drying gases. Hydrogen dioxide, Hydrogen peroxide, H202. This compound may be obtained by the action of carbonic acid or other acids on barium dioxide suspended in water, when carbonate of barium and hydrogen dioxide are formed : Ba02 + H20 + C02 = BaCOg + H202. The liquid, separated by decantation from the insoluble carbo- nate, may be concentrated under the receiver of an air-pump, and is, when thus obtained, a colorless liquid of a specific gravity 1.45, possessing remarkable bleaching properties. By higher tempera- tures, as well as by the action of many substances, it is readily decomposed into water and oxygen. Hydrogen peroxide is used in a diluted form as a powerful antiseptic. The commercial article is sold in various degrees of strength, rated by volumes of oxygen; a “ten volume” solution 82 NON-METALS AND THEIR COMBINATIONS. being one which will give off ten volumes of oxygen from every one volume of the solution. Such a ten volume solution con- tains 2.1 per cent, by weight of pure dioxide, whilst a “ two volume” solution contains 0.4 per cent. A little acid is generally added to the commercial dioxide, as it aids its stability. Glycozone is hydrogen dioxide dissolved in glycerine instead of in water. 12. NITROGEN. Niii = 14. Occurrence in nature. By far the larger quantity of nitrogen is found in the atmosphere in a free state. Compounds containing nitrogen are chiefly the nitrates, ammonia, and many organic substances. Preparation. Nitrogen is usually obtained from atmospheric air by the removal of oxygen. This may be accomplished by burning a piece of phosphorus in a confined portion of air, when phos- phoric oxide, a white solid substance, is formed, whilst nitrogen is left in an almost pure state. Other methods for obtaining nitrogen are by heating a mixture of potassium nitrite and ammonium chloride dissolved, in water : KN02 + NH4C1 = KC1 + 2H20 + 2N ; Potassium nitrite. Ammonium chloride. or by heating ammonium nitrite in a glass retort NH4NOj = 2H20 + 2N. Experiment 4. Use an apparatus as in Fig. 6, page 73. Place in the flask about 10 grams of potassium nitrite and nearly the same amount of ammonium Questions.—101. Mention two processes by which hydrogen may be obtained. 102. Show by symbols the decomposition of water by potassium and of sulphuric acid by iron. 103. State the chemical and physical properties of hydrogen. 104. How many pounds of zinc are required to liberate 100 pounds of hydro- gen ? 105. State the composition of water in parts by weight and volume. 106. Mention the most common solid and gaseous constituents of natural waters. 107. How does a mineral water differ from other waters? Mention some different kinds of mineral waters and their chief constituents. 108. What substances are most objectionable in drinking water, and how can they be recognized? 109. What are the characteristics of a good drinking water. 110. What are the purest natural waters, and by what process may chemically pure water be obtained? NITROGEN. 83 chloride ; add enough water to dissolve the salts and apply heat, which is to be carefully regulated from the time the decomposition begins, as the evolution of gas may otherwise become too rapid. Collect the gas, and notice its properties mentioned below. Properties. Nitrogen is a colorless, inodorous, tasteless gas; which at a temperature of —130° C. (—202° F.) and a pressure of 280 atmospheres, may be condensed to a colorless liquid. It is neither, like oxygen, a supporter of combustion, nor, like hydrogen, a combustible substance; in fact, nitrogen is distinguished by having very little affinity for any other element, and it scarcely enters directly into combination with any substance. Nitrogen is not poisonous, yet not being a supporter of combustion it cannot sustain animal life. Nitrogen is a trivalent in some compounds, quinquivalent in others. Atmospheric air is a mixture of about four-fifths of nitrogen and one-fifth of oxygen, with small quantities of aqueous vapor, carbon dioxide, and ammonia, containing frequently also traces of nitric acid and carburetted hydrogen, occasionally sulphuretted hydrogen and sulphur dioxide. Besides these gases there are frequently suspended in the air solid particles of dust and very minute cells of either animal or vegetable origin. 100 volumes of atmospheric air contain of Oxygen . . . 20.61 volumes. Nitrogen . 77.95 Carbon dioxide . 0.04 “ Aqueous vapor Ammonia, 1 . 1.40 “ Nitric acid, / . traces. An analysis of air may be made by the following method : A graduated glass tube, containing a measured volume of air, is placed with the open end downward into a dish containing mer- cury. A small piece of phosphorus is then introduced and allowed to remain in contact with the air for several hours, when it gradu- ally 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 (T-shaped glass tubes. One of these tubes has previously been filled with pieces of calcium chloride, the other tube with pieces of potassium hydrate, and 84 NON-METALS AND THEIR COMBINATIONS. both tubes have been weighed separately. In passing the meas- ured air through these tubes the first one will retain all the moist- ure, 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. Uitrogen is found uncombined, because it has so little affinity for other elements. Ammonia, NH3 = 17. This compound is constantly formed 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 illum- inating 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 and liberated as ammonia gas, which is condensed by passing the gases through water. Another method of obtaining ammonia is the decomposition of ammonium salts by the oxides or hydroxides of sodium, potas- sium, or calcium. Usually ammonium chloride is mixed with calcium hydroxide and heated, when calcium chloride, water, and ammonia are formed: 2(NH4C1) + Ca2H0 = CaCl2 + 2H20 + 2NH3. Experiment 5. Mix about equal weights (10 grams each) of ammonium chloride and calcium hydroxide (slaked lime) in a flask of about 200 c. c. capacity, and arranged as in Fig. 8 ; cover the mixture with water and apply heat. Gas bubbles will pass through the water contained in the cylinder as long as any atmospheric air remains in the apparatus ; 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. NITROGEN 85 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, forming ammonium hydroxide : nh3 + h2o = nh4ho. Water of ammonia, Aqua ammonise (Spirit of hartshorn). This is a solution of ammonia gas in water or hydroxide of ammonium in water. The common water of ammonia contains 10 per cent. 86 NON-METALS AND THEIR COMBINATIONS. by weight of ammonia, and has a specific gravity of 0.959; the stronger water of ammonia contains 28 per cent., and has a specific gravity of 0.900. Ammonia water has the same odor, taste, and reaction which characterize the gas. Compounds of nitrogen and oxygen. Five distinct compounds of nitrogen and oxygen are known. They are named and consti- tuted as follows: Composition. By weight. By volume. N 0 N 0 Nitrogen monoxide, N20 . 28 16 2 1 Nitrogen dioxide, N202 == 2(NO) . . 28 32 2 2 Nitrogen trioxide, N203 . . 28 48 2 3 Nitrogen tetroxide, N204 = 2(N02) . 28 64 2 4 Nitrogen pentoxide, N205 . 28 80 2 5 The first, third, and fifth of these compounds are capable of combining with water to form acids, known as hyponitrous, nitrous, and nitric acid, respectively. Nitrogen monoxide, N20 — 44. (Sometimes called nitrous oxide; also, laughing gas). This compound may be easily obtained by heating ammonium nitrate in a flask at a temperature not ex- ceeding 250° C. (482° F.), when the salt is decomposed into nitrogen monoxide and water: nh4no3 = 2H2o + n2o. Experiment 6. Use apparatus as represented in Fig. 6, page 73. Place in the dry flask about 10 grams of ammonium nitrate, apply heat, collect the gas in cylinders over water, and verify by experiments and observations the correctness of the statements below regarding the physical and chemical properties of nitro- gen monoxide. Nitrogen monoxide is a colorless, almost inodorous gas, of dis- tinctly sweet taste. It supports combustion almost as energeti- cally as oxygen, but differs from this element by its solubility in cold water, which absorbs nearly its own volume. Under a pressure of about 50 atmospheres it condenses to a colorless liquid, the boiling point of which is at about —80° C. (—112° F.) and freezing point at —100° C. (—148° F.). When inhaled it causes exhilaration, intoxication, anaesthesia, and finally asphyxia. The gas is used in dentistry as an an- aesthetic, the liquefied compound being sold for this purpose in wrought iron cylinders. NITROGEN. 87 Hyponitrous acid, HNO, is not known in a pure state, but some of its salts have been prepared. Nitrogen dioxide, NO = 30. This is a colorless gas which is generally formed when nitric acid acts upon metals or upon sub- stances which deoxidize it. It is capable of combining directly with one or more atoms of oxygen, thereby forming N02, nitrogen tetroxide, which is a gas of a deep red color and poisonous prop- erties. Nitrogen trioxide is of no practical interest. Experiment 7. Pour about 1 c. c. of nitric acid upon a few fragments of metallic copper, and apply heat. Notice that red fumes escape, which are nitro- gen tetroxide, and that a blue solution is formed which contains cupric nitrate. See explanation of the change below. Nitric acid, Acidum nitricum, HN03 = 63 (Hydric nitrate). Nitrogen pentoxide, a white, solid, unstable compound, is of scientific interest only. When brought in contact with water it readily combines with it, forming nitric acid: N205 + H20 = 2HN03. The usual method for obtaining nitric acid is the decomposi- tion of sodium nitrate by sulphuric acid: NaN03 + H.,S04 = HN03 + NaHS04; Bisulphate of sodium. or 2NaN03 + H2S04 = 2HN03 + Na2So4. Neutral sul- phate of sodium. Pig. 9. Distillation of nitric acid. 88 NON-METALS AND THEIR COMBINATIONS. 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? 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 HN03 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. 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 = Cu2N03 + 2H ; and the deoxidation of another portion of nitric acid by the liberated hydrogen while yet in the nascent state. Thus: HNOg + 3H = 2H20 + NO. The liberated nitrogen dioxide, which is colorless, readily absorbs oxygen from the air, forming red vapors of nitrogen tetroxide. Tests for nitric acid or nitrates. 1. Nitric acid when heated with copper tilings, or nitrates when heated with copper filings 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. (Nitrate of potassium, KN03, may be used as a nitrate.) CARBON. 89 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 carbonate of sodium, 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 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. 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 decomposition. 119. How does nitric acid act on animal matter, and what are its properties generally ? 120. Give tests and antidote for nitric acid. 90 NON-METALS AND THEIR COMBINATIONS. Diamond is the purest form of carbon ; it crystallizes in regular octahedrons, cubes, or in some figure geometrically connected with these. Diamond is the hardest substance known; it is in- fusible, 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 the organic substances. Tests for carbon. 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. Many carbonates are decomposed by heating into oxides of the metals and carbon dioxide. Lime-burning is such a process of decomposition : Calcium carbonate. CaC03 = CaO + C02 Calcium oxide. 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. CAEBON. 91 Experiment 9. Use apparatus represented in Fig. 7, page 78. Place about 20 grains 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 dis- places 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 converted 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 indi- rectly as a poison when inhaled, because it cannot support respir- ation, 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 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 92 NON-METALS AND THEIR COMBINATIONS. 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, which amounts to 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 per cent, 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. Many processes by which carbon dioxide is constantly produced in nature have been mentioned above, and we might assume that the amount of 0.04 per cent, of carbon dioxide contained in atmospheric air would gradually increase. This, however, is not the case, because the 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: C02 + H20 = h2co3. Carbonic acid, H2C03, is not known in a pure state, but always diluted with much water, as in all the different natural waters. CARBON. 93 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. (Sodium carbonate, Na2C03, may be used.) 1. Pass the gas through lime-water, which is rendered turbid by the formation of calcium carbonate: 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. Ca2H0 + C02 = ChC03 + H20. 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, by 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 also formed 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 also manufactured on the large scale by causing the decomposition of steam by coal heated to red heat. The decomposition takes place thus : H20 + C = 2H + CO. 94 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 in 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 carbon and hydrogen. Several hundred of these hydrocarbons are known, and their consideration 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 also frequently formed 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 there liberated giving rise to the explosions in coal mines. During these explosions of the methane (mixed generally with other gases), called fire-damp by the miners, the carbon is converted into carbon dioxide, which the miners speak of as choke-damp. Flame is a gas in the act of combustion. Of combustible gases, have been mentioned : hydrogen, carbon monoxide, marsh-gas, and oletiant gas. These four gases are actually those gases which are chiefly found in any of the common flames produced by the combustion of organic matter, such as paper, wood, oil, wax, or illuminating gas itself. These gases are generated by destructive distillation, the heat being either supplied by a separate process (manufacture of SILICON AND BORON. 95 illuminating gas by heating wood or coal in retorts), or generated during the combustion itself. In burning a candle, for instance, the fat is constantly decom- posed 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. Fig. 10. 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 carbon; only a limited amount of oxygen can pene- trate into the flame, and the hydrogen of the hydrocarbon will consume this oxygen, the carbon being liberated momentarily 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 no light, but a more intense heat is generated. Structure of flame. Silicon or Silicium, Si = 28, and Boron, B = 11, are elements which, in many respects, resemble carbon. Both, like carbon, are infusible, non-volatile, and insoluble in all common solvents. Like carbon, they are known in the amorphous state, and as crystals which resemble diamond or graphite. Silicium is, like carbon, quadrivalent; boron, however, is trivalent. Silicon is found in nature very abundantly 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 96 NON-METALS AND THEIR COMBINATIONS. mixture of them. Small quantities of silica are found in spring waters, and also enter into vegetable and animal bodies. Silicon forms with hydrogen, chlorine, and fluorine gaseous compounds of the composition SiH4, SiCl4, and SiF4. The latter compound is obtained by the action of hydrofluoric acid on silica or silicates, thus : Si02 + 4HF = SiF* + 2H20. This reaction is used in the analysis of silicates, which are decomposed and rendered soluble by the action of hydrofluoric acid. Several varieties of silicic acid are known, of which may be mentioned the normal silicic acid, H4Si04, and the ordinary silicic acid, H2Si03, from the latter of which, by heating, water may be expelled, when silicon dioxide, Si02, is left. Boron is found in but few localities, either as boric or boracic acid, or borate of sodium (borax). Formerly the total supply of boron was derived from Italy; lately large quantities of borax have been discovered in California. Boric acid, Acidium 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, FFa2B407 + 10H2O, is derived. At a white heat boric acid loses all water, and is converted into boron trioxide, B203. Boric acid boiled with glycerine forms boroglyceride, which is used as an antiseptic. Tests for silicic and boric acids or their salts. 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 portion of the silica separates as the gelatinous hydrate. Com- plete separation of the silica is accomplished by evaporating the mixture to complete dryness over a water hath, 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. SULPHUR. 97 3. Boric acid and borates color the flame green, especially when moistened with sulphuric acid; their solution, when acidi- fied by hydrochloric acid, turns turmeric paper brown (after being dried), and when neutral gives, with barium and silver salts, white precipitates of the borates of barium and silver. Con- centrated hot solutions of borates, when treated with hydro- chloric acid, form on cooling a crystalline deposit of boric acid. 14. SULPHUR. Sii = 32. Occurrence in nature. Sulphur is found in the uncombined state in volcanic districts, the chief supply being derived from Sicily. In combination sulphur is widely diffused in the form of sulphates (gypsum, CaS04.2H20), and frequently as sulphides (iron pyrites, FeS2, galena, PbS, cinnabar, HgS, etc.). Sulphur also enters 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, liquefied 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 111° C. (232° F.) to an amber-colored liquid, which is fluid as water ; increasing the heat gradually, it becomes 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. 98 NON-METALS AND THEIR COMBINATIONS. 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 H2S, C02 and CS2, CuO and CuS. Crude sulphur is the sulphur obtained from the localities where it is found. It generally contains from 2 to 4 per cent, of earthy impurities. 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 in suitable vessels to the boiling-point, 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. Precipitated sulphur, Sulphur prsecipitatum (Milk of sulphur). Made by boiling hydrate of calcium with sulphur and water, filtering the solution, adding to it dilute hydrochloric acid until nearly neutral, washing and drying the precipitated sulphur. By the action of sulphur on calcium hydrate are formed poly- sulphide of calcium, hyposulphite of calcium, and water: Calcium hydroxide 3(Ca2HO) + 12S = 2CaS5 + CaS203 + 3H20. Sulphur. Polysulphide of calcium. Hyposulphite of calcium. Water. On adding hydrochloric acid to the solution, both substances are decomposed and sulphur is liberated : 2CaS5 + CaS203 + 6HC1 = 3CaCl2 + 3H20 + 12S. Precipitated sulphur differs from sublimed sulphur by being in a more finely divided state, and by having a much paler yellow, almost white color. 99 SULPHUR. Sulphur dioxide, S02 = 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 always formed when sulphur or substances containing it in a combustible form (II2S, CS2, etc.) burn in air. It is also formed by the action of strong sulphuric acid on many metals (Cu, Hg, Ag, etc.), or on charcoal: 2H2S04 + Cu = CuS04 + 2H20 + S02. Sulphuric acid. Copper Cupric sulphate. Water. Sulphur dioxide. 2H,S04 + C = C02 -f 2H20 + 230, Sulphur dioxide is a colorless gas, having a suffocating, dis- agreeable odor; it liquefies 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 irritation of the air-passages and coughing. Sulphurous acid, Acidum sulphurosum, K,S03 = 82. One volume of cold water absorbs about 43 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 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 las the odor as well as the disinfecting and bleaching properties 100 NON-METALS AND THEIR COMBINATIONS Fig. 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 per- manganate of potassium, in consequence of the deoxidation of the latter. 2. Similarly to the above, an acid solution of bichromate of potassium 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 + 3H20. 4. Chloride of barium added to neutral solution of a sulphite produces a white precipitate of sulphite of barium, soluble in diluted hydrochloric acid; sulphate of barium is insoluble in hydrochloric acid: Na2S03 + BaC]2 = BaSOs + 2Na01. Sulphite of sodium. Chloride of barium. Sulphite of barium. Chloride of sodium SULPHUR. 101 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, S0:>> = 80 (Anhydrous sulphuric acid). This is a white, silk like solid substance, having a powerful affinity for water; it may be obtained by the action of phosphoric oxide on strong sulphuric acid; it is merely of scientific interest. Sulphuric acid, Acidum sulphuricum, H2S04 = 98 (Oil of vitriol, Hydrogen sulphate). 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 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 (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 being also provided for. The oxygen of the nitric acid oxidizes the sulphur dioxide, which, at the same time, takes up water: S02 + O 4- 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. 102 NON-METALS AND THEIR COMBINATIONS. By the action of nitric acid on sulphurous acid are formed sulphuric acid, water, and nitrogen dioxide: 3H2S03 + 2HN03 = 3H2S04 + H20 + 2N0 Nitrogen dioxide is capable of readily absorbing oxygen from atmospheric air, forming nitrogen tetroxide : 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: NO + O = N02. H2S03 + N02 = H2S04 + NO. The liquid sulphuric acid thus formed in the lead-chamber collects at the bottom of the chamber, whence it is drawn off. In this state it is known as chamber acid (specific gravity 1.6), 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 ob- tained. This acid contains about 96 per cent, of sulphuric acid; the remaining 4 per cent, of water cannot be expelled by heat. Properties of sulphuric acid. Pure acid has a specific gravity of 1.848; it is a colorless liquid, of oily consistence, boiling at 338° 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, hydrogen, and oxygen. Sulphuric acid added to such organic substances re- moves 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 pre- dominates. 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, SULPHUR. 103 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 he used.) 1. Barium chloride produces a white precipitate of barium sulphate, insoluble in all acids : Na2S04 + BaCl2 = BaS04 + 2NaCl 2. Soluble lead salts (acetate of lead) produce a white precipi- tate of sulphate of lead, soluble in hot concentrated acids and in ammonium 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. Antidotes. Magnesia, carbonate of sodium, 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, H2S2Or Thiosulphuric acid, H2S203. Dilhionic acid, H2S206 Trithionic acid, H2S306. Tetrathionic acid, H2S406. Pentathionic acid, H2S506. 104 NON-METALS AND THEIR COMBINATIONS. Thiosulphuric acid, formerly Hyposulphurous acid, H2S203, is of interest because some of its salts are used, as, for instance, sodium thiosulphate, Na2S203, 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: NaS203 + H2S04 = Na2S04 -f H20 + S02 + S. 2. Silver nitrate and barium chloride produce white precipitates 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 also formed 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. Experiment 11. Use apparatus shown in Fig. 11, page 100. Place about 20 grams of ferrous sulphide in the flask, cover the pieces with water, and add sul- phuric 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. IIow 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)2S. 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 SULPHUR. 105 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 compounds, the color of which is frequently very characteristic : CuS04 + H2S = CuS + H2SOr 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 solution of lead acetate, in the liberated gas, when the paper turns dark. Some sulphides, FeS2, for instance, are not decom- posed by the acids mentioned, unless zinc be added. Bisulphide of carbon, Carbonei bisulphidum, CS2 = 76. This compound is obtained by passing vapors of sulphur over heated 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 two latter 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 106 NON-METALS AND THEIR COMBINATIONS. and Te02, which combine with water, forming the acids H2Se03 and H2Te03, analogous to Id2S03. The acids Il2Se04 and H2Tc04, corresponding to H2S04, are also known. 15. PHOSPHORUS. Pm ==. 31. Occurrence in nature. Phosphorus is found in nature chiefly in the form of phosphates of calcium (apatite, phosphorite), iron, and aluminium, and occurs diffused, though generally in small quantities, through all soils upon which plants will grow, as phos- phorus is 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 chiefly eliminated by the urine. Manufacture of phosphorus. Phosphorus was first made and discovered 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 : Tricalcium phosphate. Ch32P04 + 2H2S04 = CaH42P04 + 2CaS04 Sulphuric acid. Acid phosphate of calcium. Calcium sulphate. The soluble acid phosphate of calcium is separated from the insoluble calcium sulphate, mixed with charcoal and sand, and 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. 107 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 metaphos- phate of calcium is formed : CaH42P04 = Ca2P03 + 2H20. The action of charcoal and sand upon the metaphosphate of calcium at red heat causes the formation of silicate of calcium and a deoxidation of the liberated phosphoric acid by the carbon: 2(Ca2P03) + 23i02 + IOC = 2CaSiOs + 10CO + 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 finally 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 when exposed to the air, the slow oxidation taking place upon the surface of the phosphorus soon raising it to 60° C. (140° 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. 108 NON-METALS AND THEIR COMBINATIONS. Phosphorus not onty 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 240° to 250° C. (4G4° to 482° 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 before it has been heated to about 280° C. (536° F.), when it is re- converted into common phosphorus, which latter inflames at 40° C. (104° 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 paraffine, 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 elementary state are phosphorated oil (oleum phosphoratum), and pills of phosphorus (pilulse phosphori). Phosphorus is also used for making phosphoric acid and other compounds. Poisonous properties of phosphorus, and antidotes. Common phosphorus is extremely poisonous, two kinds of phosphorus- poisoning being distinguished. They are the acute form, conse- quent upon the ingestion of a poisonous dose, and the chronic form affecting the workmen employed in the manufacture of phosphorus or of lucifer matches. PHOSPHO RUS. 109 There is no antidote to phosphorus which acts chemically. Oil of turpentine has been used successfully, though its action has not been sufficiently explained. Efforts should be made to elimi- nate 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 in detecting phosphorus (when in the elementary state) of its lumi- nous properties. Organic matter (contents of stomach, food, etc.) containing phosphorus will often show this luminosity when Fig. 12. Apparatus for detection of phosphorus in cases of poisoning. 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. 110 NON-METALS AND THEIR COMBINATIONS. 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 gradually raised to the boiling-point, the liquid kept boiling for some time, and the products of distillation col- lected 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 vapors is diminished, or even prevented, by vapors of essential oils (oil of turpentine, for instance), ether, olefiant gas, and a few other substances. Oxides of phosphorus. Two oxides of phosphorus are known in the separate state. They are phosphorous trioxide or phosphorous oxide, P203, and phosphorous 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, which combine readily with water, forming the corre- sponding acids. Phosphorous acid, H3P03 = 82. This acid is obtained by dis- solving phosphorous oxide in water: -f- 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. 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. PHOSPHORUS. 111 Phosphoric acids. Phosphoric oxide is capable of combining chemically with one, two, or three molecules of water, forming thereby three different acids : P203 -f- H20 == H2P206 = 2HP03 Metaphosphoric acid. P205 -f- 2H20 = H4P207 Pyrophosphoric acid. P205 + 3H20 = II6P208 = 2H3P04 Orthophosphoric acid. These three acids show 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-pbosphoric 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, H,P04 = 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- 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 it an inverted 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 portion of the solution 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 112 NON-METALS AND THEIR COMBINATIONS. 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 is finally volatilized at a low red heat. It is a tribasic acid forming three series of salts, namely: Na3P04 = Trisodium phosphate. Na2HP04 Disodium hydrogen phosphate. NaH2P04 = Dihydric sodium phosphate. If the metal is bivalent, the formulas are thus: Ca32P04 = Tricalcium phosphate. Ca2H22P04 = Dicalcium orthophosphate. CaH42P04 = Monocalcium orthophosphate. Tests for phosphoric acids and phosphates. 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: (Sodium phosphate, Na2HP04, may be used.) H3P04 + MgSO* + 3NH4HO = MgNH4P04 + (NH4)2S04 + 3H20; Na2HP04 + MgS04 + NH4HO = MgNH4P04 + Na2S04 + H20. 2. Add to a neutral solution of a phosphate, silver nitrate; a yellow precipitate of phosphate of silver is produced, which is soluble both in ammonia and nitric acid : Na3P04 + BAgNOj = Ag3P04 + 3NaNOs. 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, (!SriI4)3PO4.10MoO3.2II2O, 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 maybe recognized by it; moreover, it can be used in an acid solution, while the first two tests cannot. 113 PHOSPHORUS. 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 + Fe2Cl6 = Fe22POt + 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 hypopbos- 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. Tests for hypophosphites. (Sodium hypophosphite, NaH2P02, may be used.) 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. 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 phosphate, which alone gives a yellow precipitate with the reagent. 114 NON-METALS AND THEIR COMBINATIONS. Phosphoretted hydrogen. When phosphorus is heated with solution of potassium or calcium hydrate, 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 property is most likely due to the presence of small quantities of another compound of phosphorus and hydrogen which has the composi- tion P2TI4. 16. CHLORINE. Cli = 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 62). In many other respects a resemblance or relation can be discovered. For instance : All haloids are univ- alent elements, they combine with hydrogen, forming the acids IIF, HC1, HBr, 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, iodine 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 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 their 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. 115 gaseous state, have a disagreeable odor, and possess disinfecting properties. Occurrence in nature. Chlorine is chiefly found as sodium chloride or common salt, NaCl, 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, are also found in nature. As common salt, chlorine enters the animal system, taking there an active part in many of the physiologicaLand 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: MnOa + 4HC1 = MnCl2 + 2H20 + 2C1. Chlorine is also liberated by the action of acids on bleaching- powder, which is a mixture of calcium chloride and calcium hypochlorite: CaCl2.Ca2C10 + 2H2S04 = 2CaS04 +2H20 + 4C1. Experiment 13. Use apparatus as in Fig. 8, page 85. 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 left at the bottom of flask, apply heat, and collect the gas in dry 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. 116 NON-METALS AND THEIR COMBINATIONS. c. Moisten a paper with oil of turpentine, Ci„H16, 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 whilst 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, sutfocating 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 very great, 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 + 0. NH3 + 3C1 = 3HC1 + N. C10H16 4- 16C1 = 16HC1 + IOC: 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 117 CHLORINE. 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, Acidium 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 chlo- rides by sulphuric acid: NaCl + H2S04 = HC1 + NaHS04; or 2NaCl + H2S04 = 2HC1 + Na2S04. Experiment 14. Use apparatus as in Fig. 8, page 85. 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 sulphuric acid; mix well, apply heat, and pass the gas into water for absorption. If a pure acid shall be made, the gas has to be passed through water in a wash-bottle; apparatus shown in Fig. 11, page 100, 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 ? Hydrochloric acid is a colorless gas, having 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 also used for its 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 118 NON-METALS AND THEIR COMBINATIONS. 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 may 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: AgNOg 4- NaCl = NaNOs + AgCl; AgN03 + HC1 = HNOg + AgCl. 2. Add solution of mercurous salt (mercurous nitrate): a white precipitate is produced, which blackens on the addition of am- monia: Hg22N03 + 2NaCl = 2NaN03 + Hg2Cl2. 3. Add solution of lead acetate: a white precipitate of lead chloride is formed, which is soluble in much water. 4. To a dry chloride add strong sulphuric acid and heat: vapors of hydrochloric acid gas are evolved, which may be rec- ognized by the odor, or by their 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 + 3HC1 = N0C1 + 2H20 + 2C1 ; HNOs + 3HC1 = NOCl2 + 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 gas, both of which part easily with their 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 : CHLOKINE. 119 Hypochlorous oxide, C120 -j- 1I20 = 2HC10. Chlorous oxide, C1203 4- H20 = 2HC102. Chlorous tetroxide, C1204 does not combine with water to form an acid. Chloric oxide, C1205 + H20 '= 2HC103 Perchloric oxide, C1207 -j- H20 = 2HCl04 Not known in the separate state, but in combination with water. 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, HC1. 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 also formed: 2HgO + 4C1 + H20 = Hg2OCl2 + 2HC10. Hypochlorous acid is a colorless, monobasic acid possessing strong bleaching properties. Hypochlorites are formed by the action of chlorine on the hydrates of potassium, sodium, calcium, etc., at the ordinary temperature: Chloric acid, HC103, may be obtained from potassium chlorate by the action of hydrofluosilieic acid; it is, however, an unstable substance which decomposes frequently with a violent explosion. Chlorates are generally obtained by the action of chlorine on alkaline hydrates at a temperature of about 100° C. (212° F.) 2NaH0 + 2C1 = NaCl + NaCIO + H20. 6KHO -f 6C1 = 5KC1 + KC103 + 3H20. 120 NON-METALS AND THEIR COMBINATIONS. Mixtures of hypochlorites and chlorides are converted into chlorates by boiling their solution : 3KC1 +3KC10 = 5KC1 + KC103. Tests for chlorates and hypochlorites. 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 (hypochlorous 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 = Mg Cl 2 + 2Br. Bromine is at common temperature a dark, reddish-brown liquid, giving off brown fumes of an exceedingly suffocating and irritating odor; it is very volatile, and freezes at about —24° C. 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 manga- nese 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 hydrate 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? IODINE. 121 (—110° F); 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 + 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: PBr5 + 4H20 = 5HBr + H3P(\. In the form of solution this acid may also be prepared by treating bromine under water with hydrosulphuric acid until the brown color of bromine has entirely disappeared. The reaction is as follows: lOBr + 2H2S + 4H20 = lOHBr + H2SO, + 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, maybe 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. 3. Mucilage of starch added to the liberated bromine is colored yellow. 4. Strong sulphuric acid added to a dry bromide liberates 122 NON-METALS AND THEIR COMBINATIONS. 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 chiefly derived from the vitrified ashes of sea-weeds, known as kelp. By washing this kelp 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, but it is also volatilized at ordinary temperature in small quantities. 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 hydrosulphuric acid upon iodine in the presence of water is as follows: Whilst not of much importance itself, many of its salts, the iodides, are of great interest. H2S + 21 = 2HI + S. IODINE. 123 Tests for iodine and 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. Liberate from solution of an iodide the 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 in- soluble 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, IIgI2, 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 itself was, until quite 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 chemically 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, possess- ing affinities stronger than those of any other element. It combines spontaneously even in the dark and at low temperature with hydrogen; sulphur, phosphorus, and many metals also 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; organic substances such as oil of turpentine, alcohol, ether, and even cork ignite spontaneously when brought in contact with this remarkable element. 124 NON-METALS AND THEIR COMBINATIONS Hydrofluoric acid, HF (Hydrogen fluoride). A colorless gas, very irritating, soluble in water. It is obtained by the action of sulphuric acid on fluorspar: 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, SiF4 2HF. CaF2 + H2S04 = 2HF + CaS04. 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 aside for a few hours (heating slightly facilitates'the action); upon remov- ing 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 also serves 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, and how does it stain the skin? 168. Mention reactions by which iodine and iodides may be 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 ? IV. 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. From alum, a salt containing it. Antimony, (Stibium.) Sb 120. From the Greek avri (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, OTi(ii (stibi), the name for the native sulphide of antimony. Arsenicum, As = 74.9. From the Greek apcevuwv (arsenicon), the name for the native sulphide of arsenic. Barium, Ba 136.8. From the Greek flapvg (barys), heavy, in allusion to the high specific gravity of barium sulphate, or heavy-spar. Bismuth, Bi 210. 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 aadfida (kadmeia), the old name for calamine (zinc carbonate), with which cadmium is frequently associated. Calcium, Ca = 40. From the Latin calx, lime, the oxide of calcium. Chromium, Cr = 52.4. From the Greek xpo te%o 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 ail forms of rock, clay, sand, and earth; its presence in these being generally indicated by their color (red, reddish-brown, or yellowish-red), as iron is the most IRON 161 common of all natural, inorganic coloring agents. It is also found, 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 occasional^7 fall upon our earth from the universe. The chief compounds of iron found in nature are: Red hematite, ferric oxide, Fe203. Mag netic iron ore, ferrous-ferric oxide, Fe0.Fe203. Spathic iron ore, ferrous carbonate, FeC03. Iron pyrites, bisulphide of iron, FeS2. The carbonate and sulphate are sometimes found in spring waters, which, when containing considerable quantities of iron, are called chalybeate waters. Finally, iron is also a constituent of some organic substances which are of importance in the animal system. Manufacture of iron. There is no other metal that is manu- factured in such immense quantities as iron, the use of which in thousands of different tools, machines, and appliances is highly characteristic of our present age. Iron is manufactured from the above-named oxides or the carbonate by heating with coal, limestone, and sand in large blast furnaces, which have a somewhat cylindrical 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 from the side below. The chemical change taking place in the upper and less heated part of the furnace is a deoxidation of the ferric oxide or ferrous carbonate by the carbon : Fe303 + 3C = SCO + 2Fe ; FeCOg + C = CO + C03 + Fe. The heat necessary for this decomposition and fusion of the ore is produced by the combustion of the coal, maintained by the oxygen of the air blown into the furnace. The same air, however, would also burn (oxidize) the iron in the lower and hotter part of the furnace, were it not protected from coming in contact with it by a thin tilm of a fusible silicate (slag), formed by the combination of the sand and calcium of the limestone, which is added for that purpose. The iron and slag collect at the bottom of the furnace, and are allowed to run otf every few hours. 162 METALS AND THEIR COMBINATIONS. Iron thus obtained is known as cast-iron, or pig-iron, and is not pure, but always contains, besides traces of silicon (occasionally also sulphur, phosphorus, and various metals), a quantity of carbon varying from 2 to 5 per cent. It is the quantity of this carbon which imparts to the different kinds of iron different properties. Steel contains from 0.5 to 2 per cent., wrought- or bar- iron from 0.03 to 0.3 per cent, 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 blowing air through the molten mass. Steel is made either from cast- iron by partially removing the carbon, or from wrought-iron by recombining it with carbon—i.e., by melting together wrought- and cast-iron in proper proportions. 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 hydrate (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, Eerrum reductum. This is metallic iron, obtained as a very fine, grayish-black powder by passing hydrogen gas 163 IRON. (purified and dried by passing it through sulphuric acid) over ferric oxide, heated in a glass tube : Fe203 + 6H = 3H20 + 2Fe. The officinal article should have at least 80 per cent, of metallic iron. Ferrous oxide, FeO (.Monoxide or suboxide of iron). This compound 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, Fe2HO, 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 bluish- green, dark gray, black, and finally brown, in consequence of the absorption of oxygen (see Plate I., 2): FeS04 + 2NH4HO = (NH4)2S04 + Fe2H0; 2(Fe2HO) + O + H20 = Fe26HO. 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-brown powder, which may be obtained by heating ferric hydrate to expel water : Fe26HO = Fe203 + 3H20. It is a feeble base; its salts show usually a brown color. Ferric hydroxide, Ferric hydrate, Ferri oxidum hydratum, Fe^6H0 = 213.8 (Hydrated oxide of iron, Per- or sesqui-oxide, lied oxide of iron), is obtained by the precipitation of ferric sulphate or ferric chloride by ammonium or sodium hydroxide (see Plate I., 3) : Fe23S04 + 6NH4HO = 3[(NH4)2S04] + Fe26HO. The precipitation is complete, no iron remaining in solution as in the case of ferrous salts. Ferric hydroxide is a reddish-brown powder, frequently 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 with arsenious acid than the hydroxide 164 METALS AND THEIR COMBINATIONS. which has been kept some time, or which has been dried, and thereby assumed a more dense 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, Fe0.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 black color, and is produced 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. Trioxide of iron, Fe03. Not known in a separate state, but in combination with alkalies. In these compounds, called ferrates, FeOs acts as an acid oxide, analogous to chromic oxide, 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: Fe -f 2HC1 = FeCl2 + 2H. By evaporation of the solution, the dry salt may be obtained. The solution and salt absorb oxygen very readily: 3FeCl2 + O = FeO + Fe2Cl6. Ferric chloride, ferrous, and afterward ferric oxide, are formed. Ferric chloride, Ferri chloridum, Fe2Cl6.12H20 = 540.2 (Chloride, sesquichloride, 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 also formed : By sufficient evaporation of the solution, ferric chloride is obtained as a crystalline mass of an orange-yellow color; it is 6FeCl2 + 2HN03 -f 6HC1 = 3Fe2Cl6 + 4H20 + 2N0. IRON. 165 very deliquescent, has an acid reaction, and a strongly styptic taste. The water of crystallization cannot be expelled by heat, as decomposition of the salt takes place, 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 potas- sium 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 precipi- tate. The 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 Fe2Cl6.12H20 can be obtained from 1 gram of iron ? Solution of chloride of iron, Liquor ferri chloridi, TJ. 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 neutral salt is usually called 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 (fine wire is best) and iodine, the two elements combine directly, forming a pale green solution of the ferrous iodide, from which the salt may be obtained by evaporation. As it is easily oxidized and decomposed by the action of the air, 166 METALS AND THEIR COMBINATIONS. an officinal preparation, the saccharated iodide of iron, U. S. P., is made by adding about 30 parts of sugar of milk to 20 parts of the 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 gradually dissolved, 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 filings with sulphur, when the elements combine. It is chiefly used 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 (,Sulphate of iron, Green vitriol, Copperas). Obtained by dissolving iron in sulphuric acid, evaporating, and crystallizing: Fe + H2S04 = 2H + FeS04. Also obtained as a by-product in some branches of chemical industry, or by oxidation of the native sulphide of iron : FeS2 + 40 = FeS04 + S. Ferrous sulphate crystallizes in large, bluish-green prisms; it is soluble in water, insoluble in alcohol. Exposed to the air, it loses water of crystallization, and absorbs oxygen. The dried ferrous sulphate, U. S. P., is made by expelling 6 molecules of water by heating to 150° C. (302° F.); the precipitated ferrous sulphate is made by pouring a strong aqueous solution of ferrous sulphate, slightly acidulated with sulphuric acid, into alcohol, when ferrous sulphate separates as a crystalline powder, which is washed and dried. Ferric sulphate, Fe23S04. The solution of this salt, Liquor ferr i tersulphatis, Solution of tersulphate of iron, U. S. P., is made by adding sulphuric and nitric acids to a solution of ferrous sulphate, and heating : 6FeS04 -f 3H2S04 + 2HN03 = 3(Fe23S04) + 2N0 + 4H20 The action of nitric acid is similar to that described above under ferric chloride. The hydrogen of the sulphuric acid is 167 IRON. oxidized, and the liberated radical S04 unites with the ferrous sulphate, nitrogen dioxide being liberated. The solution of ferric sulphate is used in the preparation of Ammonio-ferric sulphate, Fernet ammonii sulpha#, (N H4)2S04.F e2-SS04. 2fH20. (iron alum or ammonio-ferric alum), which is made by mixing solution of ferric sulphate with ammonium sulphate and crystallizing. Solution of subsulphate of iron, Liquor ferri subsulphatis (MonseVs solution). This is a solution similar to the preceding, but con- tains less sulphuric acid, and is, therefore, looked upon as a basic ferric sulphate, of the doubtful composition Fe405S04. The color of the tersulphate of iron solution is reddish-brown; that of Monsel’s solution is ruby-red. Ferric nitrate, Fe26N03. A 6 per cent, solution of this salt is officinal, under the name Solution of nitrate of iron, Liquor ferri nitratis, U. 8. P., and is made by dissolving ferric hydroxide in nitric acid: Fe26HO + 6HN03 = 6H20 + Fe26N03. It is an amber-colored or reddish, acid liquid. Ferrous carbonate, FeC03. Occurs in nature; may be obtained by mixing solutions of ferrous sulphate and sodium carbonate or bicarbonate : FeS04 + Na2C03 == Na2S04 + FeC03. The precipitate is first nearly white, but soon assumes a gray color by oxidation. The saccharated carbonate of iron, U. S. P., is made by mixing the washed precipitate with sugar, and drying. The sugar prevents, to some extent, rapid oxidation. Ferric carbonate does not exist, the affinity between the feeble ferric oxide and the weak carbonic acid not being sufficient to unite them chemically. Ferrous phosphate, Fe32P04. Obtained as a slate-colored pre- cipitate, when sodium phosphate is added to ferrous sulphate. Like all ferrous salts, it absorbs oxygen from the air, becoming darker in color: 3FeS04 + 2Na2HP04 = Fe32P04 + 2Na2S04 + H2S04. As shown by this formula, some sulphuric acid is set free, which has a dissolving action on the ferrous phosphate; to prevent which, sodium acetate may be added forming sodium 168 METALS AND THEIR COMBINATIONS. sulphate and free acetic acid, which latter does not act as a, solvent. Ferric hypophosphite, Ferri hypophosphis, Fe26H2P02 = 501.8 (Hypophosphite of iron). Made by dissolving ferric hydrate in hypophosphoric acid, and evaporating. It is a grayish-white powder, insoluble in water, soluble in hydrochloric acid. Scale compounds of iron. Quite a number of officinal prepara- tions of iron are made by mixing solution of ferric citrate (obtained by dissolving ferric hydrate 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 tem- perature, 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 evaporation of a mixture of ferric citrate and sodium phosphate. The ferric pyrophosphate of the U. S. P. is a similar scale com- pound. 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, tartrate of iron and potassium, etc. Compounds of iron with organic acids will be more fully con- sidered in connection with the acids themselves. The object of these various organic scale compounds of iron is, doubtless, to present otherwise insoluble iron compounds in a soluble and convenient form for administration. 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 hydrates. 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. IRON. ZINC. IPH.-fi-TE I. Ferrous sulphide, precipitated from ferrous or ferric solutions by am- monium sulphide. [Page 16!l.] Ferrous hydroxide passing into ferric hydroxide. Ferrous solutions prec'pitated by alkaline hydroxides. [ Paves 163.169.] Ferric hydroxide, precipitated from ferric solutions by alkaline hy- droxides. [Pages 166,169.] Ferrous solutions, precipitated by potassium ferro-cyanide. [Page 169.] Ferric solutions, precipitated by potassium ferro-eyanide or Ferrous solutions precipitated by potassium ferri-cyanide. [Page 169.] Ferric solutions, precipitated by alkaline sulpho-cyanates. [Page 169.] Ferric solutions, precipitated by tannic acid. [Page 169.] Zinc solutions, precipitated by either ammonium sulphide or by alka- line hydrates, carbonates, phosphates, ’ferro-cyanides, etc. [Page 179.J IRON 169 Analytical reactions. Ferrous salts. (Use FeS04.) Ferric salts. (Use Fe2Cl6.) 1. Ammonium sul- phide. Black precipitate of ferrous sulphide (Plate I., 1). FeS04 + (NH4)2S = (NH4)2S04 + FeS. Black precipitate of ferrous sulphide mixed with sulphur Fe2Cl6 + 3[(NH4)2S] = 6NH4C1 + 2FeS + S. 2. Hydrosulphuric acid. No change. Ferric salts are converted into ferrous salts with precipita- tion of sulphur. Fe2Cl6 + II2S = 2FeCl2 + 2HC1 + S. 3. Ammonium, so- dium, or potas- sium hydroxide. White precipitate of ferrous hydroxide soon turning green, black, and brown. Precipitation not complete (Plate I., 2). FeCl2 + 2NaHO = 2NaCI + Fe2HO. Reddish-brown precipitate of ferric hydroxide. Precipi- tation is complete (Plate I., 3). Fe2Cl6 + 6(NII4HO) = 6NH4C1 + Fe26HO. 4. Ammonium, so- dium, or potas- sium carbonate. White precipitate of ferrous carbonate, soon turning darker. FeCl2 -f Na2C03 = 2NaCl + FeC03. Reddish-brown precipitate of ferric hydroxide, with libera- tion of carbon dioxide (Plate I., 3). Re„CL + 3Na2CO„ 4- 3H20 = 6NaCl + Fe26HO + 3C02. 5. Alkaline phos- phates or arseni- ates. Almost white precipitate, soon turning darker. A yellowish-white precipitate is produced. 6. Potassium ferro- cyanide. K4Fe(CN6). Almost white precipitate, soon turning blue by ab- sorption of oxygen (Plate I., 4). Dark blue precipitate of ferric ferrocyanide, or Prussian blue. Decomposed by alka- lies ; insoluble in acids (Plate I-, 5). 2Fe2Cl6 + 3(K4Fe6CN) = 12KC1 + Fe43Fe6CN. 7. Potassium ferri- cvanide. K6Fe2(CN)12. Blue precipitate of ferrous ferricyanide, or Turnbull’s blue. 3FeCL + K6Fe2(CN)12 = 6KC1 + Fe3Fe2(CN)12. No precipitate is produced, but the liquid is darkened to a greenish or olive hue. 8. Tannic acid. No change, provided oxida- tion of the ferrous salt has not taken place. A dark greenish-black precipi- tate of tannate of iron (ink) is produced (Plate I., 7). 9. Potassium sul- phocyanate. KCNS. As above. Deep blood-red precipitate of ferric sulphocyanate (Plate !•» 6). 170 METALS AND THEIR COMBINATIONS. 26. MANGANESE—CHROMIUM—COBALT—NICKEL. Manganese, Mn — 54. Manganese is found either as dioxide (black oxide of manganese, or pyrolusite), Mn02, 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 manga- nese with oxygen are known in the separate state, and two others only in combination with other elements. These oxides are: Manganous oxide (monoxide or protoxide), MnO. Manganous-manganic oxide, Mn0.Mn203= Mn304. Manganic oxide (sesquioxide), Mn203. Manganese dioxide (binoxide, peroxide, black oxide), Mn02. Manganic acid, Permanganic acid,. Not known in a separate state, - H20 + Mn03. H20 -+- Mn207. Manganous oxide is a greenish-gray powder, obtainable by heating the carbonate; or as a nearly white hydrate by precipi- tating a manganous salt by sodium hydrate. 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 + 2H20 + 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 Mn02. 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: Mn02 + H2S04 = M nS04 + H20 + O. MANGANESE. 171 As the manganese dioxide generally contains iron oxide, the solution 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 solu- tion evaporated 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. Potassium permanganate, Potassii permanganas, K2Mn208 = 314 (.Permanganate of potassium). Whenever a compound (any oxide or salt) of manganese is fused with alkaline carbonates (or hydrates) and alkaline nitrates (or chlorates) the manganese is converted into manganic acid, which combines with the alkali, forming potassium (or sodium) manganate : 3Mn02 + 3K2C03 + KC103 = 3K2Mn04 + 3C02 + KC1. 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. The green solution is easily decomposed by any acid (or even by water in large quantity) into a red solution of potassium permanganate and a precipitate of dioxide of manganese : By evaporation and crystallization the 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 affinity 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 : •3K2Mn04 + 2H2S04 = Mn02 + 2K2S04 -f K2Mn208 + 2H2G. K2Mn208 + 6HC1 + a; = 2KC1 + 2MnCl2 + 3H20 + x05. 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, 172 METALS AND THEIR COMBINATIONS. 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, MnS04, 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): M nS04 + (NH4)2S = (NH4)2S04 + MnS. 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. MnCl2 + 2NH4HO = 2NH4C1 + Mn2H0. 3. Sodium (or potassium) carbonate produces a nearly white precipitate of manganous carbonate : MnS04 + Na2C03 = Na2S04 + 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 wuth 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^pa (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, CHROMIUM. 173 Cr03, and the acid, II2Cr04, which are analogous to S03 and H2S04. Moreover, the barium and lead salts of chromic and sulphuric acids are equally 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 hydrate 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 formed, the latter combining with the potassium, forming neutral potassium chromate, Iv2Cr04. 2(Fe0Cr203) + 4K.C0, + 70 = Fe203 + 4C02 + 4(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(K2Cr04) +H2S04 = K2Cr207 + 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 -f- H20 = H2Cr04 = 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 : K2Cr207 + H2S04 = K2S04 + H20 + 2Cr03. 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 174 METALS AND THEIR COMBINATIONS. in water has strong acid properties; it combines with metallic oxides forming chromates and dichromates. Experiment 29. Dissolve a few grams of potassium dichromate 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 (Sesquioride of chromium), is obtained by heating potassium dichromate with sulphur, when potassium sulphate and chromic oxide are formed : K2Cr207 -f- S = K2SO, -j* Cr203. By washing the heated mass with water, the chromic acid 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 as a green color, especially in the manufacture of painted glass and porcelain. Chromic hydroxide, Cr26H0. 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: Cr28S04 + 6NH4HO = 3[(NH4)2S04] -f Cr26HO. 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 isomorphous with other alums. MANGANESE. CHROMIUM. PLATE IX. Potassium permanganate solu- tion, more or less saturated, Borax- bead colored by manganese. [Pages 171, 172.] Manganous sulphide precipi- tated from manganous solutions by ammonium sulphide. [Page 172.] Manganous hydroxide passing into the higher oxides. Manganous solutions precipitated by alkaline hy- droxides. [Page 172.] Potassium dichromate solution deoxidized by reducing agents. [Page 175.] Chromic hydroxide precipitated from chromic solutions by alkaline hydrates or by ammonium sulphide. [Pages 174, 175.] Lead Chromate precipitated from soluble chromates by lead acetate [Pages 175, 183.] Silver chromate precipitated from neutral chromates by silver ni- trate. [Pages 175,191.] Mercurous chromate precipi- tated from neutral chromates by mer- curous solutions. \Fage 175.] CHROMIUM. 175 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) : 3. Barium chloride produces a pale yellow precipitate of barium chromate, BaCr04: K2Cr04 + Pb2N03 = PbCr04 + 2KN03 K2Cr04 + BaCl2 = BaCrO, + 2KC1. 4. Silver nitrate produces a dark red precipitate of silver chromate, Ag2Cr04 (Plate II., 8): 2AgN08 + 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, Cr26HO, is precipitated (Plate II., 5): Cr2Cl6 + 3[(NH4)2S] + 6H20 = 6NH4C1 + 3H2S + Cr26HO. 7. Potassium or sodium hydrate causes a similar green pre- cipitate of chromic hydrate, which is soluble in an excess of the reagent, but is reprecipitated on boiling for a few minutes. 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. c. Of chromium in any form. 176 METALS AND THEIR COMBINATIONS. 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 precipitate 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 precipitates, which are insoluble in an excess. Cobalt is chiefly used 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.) 27. ZINC. Zn» = 64.9. Occurrence in nature. Zinc is chiefly found either as sulphide (zinc-blende), ZnS, or as carbonate (calamine), ZnC03; it also occurs in combination with silicic acid as silicate and as the red oxide. Metallic Zinc is obtained by heating the oxide or carbonate mixed with charcoal in retorts, 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, Questions.—251. How is manganese found in nature? 252. Mention the different oxides of manganese. What is the binoxide used for? 253. What is the color of manganese salts, of manganates, 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 pro- perties 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. ZINC. 177 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 frequently used in the metallic state by itself or fused together with other metals (German silver and brass contain it); galvanized iron is iron coated with metallic zinc. Zinc is a bivalent metal, forming but one oxide and one series of salts, which have all 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(Zn2H0).2ZnC03 == 5ZnO + 2C02 + 3H20. 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 reassumes the w’hite color on cooling. Zdnc hydroxide, Zn2IIO, is obtained by precipitating zinc salts with the hydrate 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 + 2HC1 = 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 178 METALS AND THEIR COMBINATIONS. 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(Zn2H0) = 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(ZnC03).3(Zn2H0). 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 diluted sul- phuric acid: H2S04 + a;H20 + Zn = ZnS04 + a;H20 + 2H 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 in 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 crystallized zinc sulphate which may be obtained. Zinc phosphide, Zinci phosphidum, Zn3P2 = 256.7 (.Phosphide of zinc). The two elements zinc and phosphorus combine readily when the latter is thrown upon melted zinc, forming a grayish- black powder, or minutely crytalline, friable fragments, having a metallic lustre on the fractured surface. Antidotes. Soluble zinc salts (sulphate, chloride) have a poisonous effect. If the poison have not produced vomiting, it CADMIUM. 179 should be induced. Milk, white of egg, or, still better, some substance containing tannic acid (with which zinc forms an insol- uble compound) should be given. Analytical reactions. (Zinc sulphate, ZnS04, may be 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 + (NH4]2S = (NH4)2S04 + ZnS. 2. Add ammonium, sodium, or potassium hydroxide: a white precipitate of zinc hydroxide, Zn2HO, 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. 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; the yellow sulphide is used as a pigment, the sulphate and iodide sometimes for medicinal purposes. 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 sulphate of zinc. 267. What is white vitriol ? 268. Explain the formation of precipi- tated zinc carbonate, and state its composition. 269. Mention tests for zinc compounds. 270. How many pounds of crystallized zinc sulphate may be obtained from 22.63 pounds of metallic zinc? 180 METALS AND THEIR COMBINATIONS. 28. LEAD—COPPER-BISMUTH. General remarks regarding the metals of the lead group. The six metals belonging to this group (Pb, Cu, Bi, Ag, Ilg, and Cd) are distinguished by forming sulphides which are insoluble in water, insoluble in diluted mineral acids, insoluble in ammonium sulphide; they are consequently precipitated from neutral, alka- line, or acid solutions by hydrosulphuric acid or ammonium sulphide. The metals themselves do not decompose water at any tem- perature, and are not acted upon by diluted 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, either by heating it with iron, when ferrous sulphide and lead are formed : PbS -j- Fe = FeS -f- Pb, or by roasting the sulphide until a portion of it is converted into oxide and sulphate: PbS + 30 = PbO + S02; PbS + 40 = PbS04, and heating the mixture of sulphide, sulphate, and oxide without access of air, when the following decompositions take place: PbS + 2PbO = 3Pb + S02; PbS + PbS04 = 2Pb + 2S02. 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 also a 181 LEAD constituent 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 slowly deposited 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 this crystallized lead is generally called a lead-tree. Lead oxide, Plumbi oxidum, PbO = 222.5 (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, and is then 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 is prob- ably a mixture (or combination) of oxide and peroxide of lead, PbO,2PbO. 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, Pb2N03 = 330.5 (Nitrate of lead). Obtained by dissolving the oxide in nitric acid: PbO + 2HN03 = H20 + Pb2N03 Lead nitrate is the only salt of lead (with a mineral acid) which is easily soluble in wTater; it has a white color, and a sweetish, astringent, and afterward metallic taste. Lead carbonate, Plumbi carbonas, 2(PbC03).Pb2H0 = 773.5 (Car- bonate of lead, White lead). This compound maybe obtained by precipitation of lead nitrate with sodium carbonate, but is manu- factured on a large scale directly from lead, by exposing it to 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. 182 METALS AND THEIR COMBINATIONS. The action of acetic acid on lead or lead oxide will be con- sidered in connection with acetic acid. Carbonate of lead is a heavy, white, insoluble, tasteless pow- der; the white-lead of commerce is frequently found adulterated with 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): Pb2N03 + 2KI = 2KN03 + Pbl2. 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. Poisonous properties and antidotes. Compounds of lead are directly poisonous, and it happens, not unfrequently, 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 water contains carbonates and sulphates, however, these will form insoluble compounds, producing a film or coating over the lead, preventing further contact with the water. 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 y or even -yiy of its original volume before applying the test. The constant handling of lead compounds is also one of the causes of lead-poisoning (painters’ colic). As an antidote, mag- nesium sulphate should be used, which forms with lead an insoluble sulphate; the purgative action of magnesia is also useful. Analytical reactions. (Lead acetate or lead nitrate, Pb2N03, may be used.) 1. To a solution of a lead salt add liydrosulphuric acid or am- monium sulphide: a black precipitate of lead sulphide is pro- duced (Plate III., 1): Pb2N03 + H2S = 2HN03 + PbS. COPPER. 2. Add sulphuric acid or soluble sulphate : a white precipitate of lead sulphate is formed: Pb2NOs + Na2S04 = 2NaN03 + PbS04 3. Add hydrochloric acid or soluble chlorides: 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 insoluble. For the same reason, the precipitate is not formed when the solutions used are highly diluted. 4. Other reagents which give precipitates with lead solutions are: Potassium chromate, producing 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, Cu“ = 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 hydrate of copper, CuC03.Cu2H0. The cupric and cuprous oxide are also occasionally found. Copper is obtained from the oxide by reducing it with charcoal; the sulphides are previously converted 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 film of green subcarbonate when exposed to moist air. Copper is frequently used in the manufacture of alloys, of which the more important are : Copper. Zinc. Tin. Nickel. Brass . . 64 36 ... German silver . . 51 31 18 Bell-metal . . 78 22 Bronze . 80 4 16 Gun-metal . . 90 10 184 METALS AND THEIR COMBINATIONS. Copper is also frequently 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 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 also obtained 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 hydrate to the solution of a cupric salt, when a bulky, pale blue pre- cipitate of cupric hydroxide, Cu2HO, is formed, which, upon boiling, is decomposed into water and cupric oxide, a heavy dark brown powder (Plate III., 2): CuS04 -f 2KH0 = K2S04 + Cu2H0 ; Cu2H0 = H20 + CuO. Cuprous oxide, Cu_,0 (Bed 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 -f- 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 vitriol, 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 copper in sulphuric acid, evaporating and crystallizing the solution : Cu + 2H2S04 = CuS04 + 2H20 + S02. 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° F.) all water of crystallization is expelled, and the anhydrous cupric sulphate formed, which is a nearly white powder. By further heating this is decomposed, sul- phuric 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 COPPER. 185 crystallization. State the exact quantities of copper and II2S04 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 hydrate (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: CuC]22HH3, CuC124JsTI3, and CuC126NII3. Cupric sulphate forms in like man- ner, cupro-diammonium sulphate, CuS042AII3, or (N2H6Cu)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 hydrate from precipitating cupric hydrate 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 adul- terations of food with compounds of copper have been detected. In cases of poisoning by copper the stomach-pump should be used, vomiting induced, and albumin (white of egg) adminis- tered, which forms an insoluble compound with copper. Re- duced iron or a very diluted solution of potassium ferrocyanide, may also be of use as antidotes. Analytical reactions. 1. Add to solution of copper, hydrosulphuric acid or ammo- nium sulphide: a black precipitate of cupric sulphide is formed (Plate III., 1): (Cupric sulphate, CuS04, may be used.) CuSO, + H2S = H2S04 + CuS. 186 METALS AND THEIR COMBINATIONS. 2. Add sodium or potassium hydroxide: a bluish precipitate of cupric hydroxide, Cu2HO, is formed, which is converted into dark brown cupric oxide, CuO, by boiling. (See equation above.) (Plate III., 2.) 3. Add ammonium hydroxide: a dark blue solution is pro- duced, containing an ammonio-copper compound. (See explana- tion above.) (Plate III., 3.) 4. Add potassium ferrocyanide: a reddish-brown precipitate of cupric ferrocyanide, Cu2Fe6Ci7, 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 + 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 anydrous) have mostly a blue or green color: sulphate, nitrate, chloride, and the ammonio- copper compounds are soluble, most other compounds are in- soluble. Bismuth, Bim = 210. Found in nature chiefly in the metallic state, disseminated, in veins, through various rocks. The extrac- 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. It is occa- sionally used in alloys 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 the decompo- sition of the concentrated solution of any of its normal salts by the addition of much water, with the formation and precipitation COPPER. LEAD. BISMUTH. rPXjJL-TE III. Cupric sulphide or lead sul- phide precipitated from solutions of copper or lead by hydrosulphuric acid. [Pages 182, 186.] Cupric hydroxide passing into cupric oxide. Cupric solutions pre cipitated by potassium hydroxide and boiling. [Pages 184,186.] Amnionic - cupric compounds obtained by adding ammonium hy- droxide to cupric solutions. [Page 186.] Cupric Carbonate precipitated from cupric solutions by sodium car- bonate. [Page 186.] Cupric ferro-eyamide precipi- tated from cupric solutions by potas- sium ferro-cyanide. [Page 186.] Bead iodide precipitated from lead solutions by soluble iodides. [ Pages 182,183.] Bead solutions with soluble chlorides, sulphates or carbonates Bismuth solutions with alkaline hy droxides or carbonates. [Pages 183 188.] Bismuth sulphide precipitatec' from solutions of bismuth by hydro sulphuric acid. [Page 188.] BISMUTH. 187 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, BiCl3. Bismuthyl chloride, (BiO)Cl. “ bromide, BiBr3. “ bromide, (BiO)Br. “ iodide, BiT3. “ iodide, (BiO)I. “ nitrate, Bi3N03. “ nitrate, (BiO)N03. “ sulphate, Bi23S04. “ sulphate, (Bi0)2S04, “ carbonate, Bi23COs, not known. “ carbonate, (Bi0)2C03 Bismuthyl nitrate, Subnitrate of bismuth, Bismuthi subnitras, Bi0N03.H20 = 306 (Oxynitrate of bismuth). By dissolving metallic bismuth in nitric acid, a solution of bismuth nitrate is obtained, nitrogen dioxide escaping: Bi + 4HN0S = Bi3N03 + NO + 2H20. Upon evaporation of the solution, colorless crystals of bismuth nitrate (Bi3N03.5H20) 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) + 8II20 = 4(Bi0N03.H20) + Bi3N03 + 8HN03 As bismuth frequently contains arsenic, tests should be applied for this metal before using the bismuth. 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 pre- cipitate 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 188 METALS AND THEIR COMBINATIONS. by adding sodium carbonate to solution of bismuth nitrate, when the subcarbonate is precipitated, some carbon dioxide escaping: 2(Bi3N03) + 3Na2C03 + H20 = 6NaN03 + 2C02 + (Bi0)2C03.II20. A white, or pale yellowish-white powder, resembling the sub- nitrate. It readily loses water and carbon dioxide on heating, while the yellow oxide, Bi203, is left. . Bismuthyl iodide, Subiodide of bismuth, BiOI, may be obtained by adding solution of hydriodic acid to freshly precipitated bismuth oxide: Bi203 + 2HI = 2BiOI + H20. 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 decom- position is this: 2Bi3N03 + 2H20 + 2KI + 4NaC2H302 = 2RiOI + 4NaN03 + 2KN03 + 4C2H402. (Bismuth nitrate, Bi3N03, or bismuth chloride, BiCl3, may be used.) Analytical reactions. 1. Add to solution of bismuth, hydrosulphuric acid or ammo- nium sulphide : a dark brown (almost black) precipitate of bismuth sulphide, Bi2S3, is produced (Plate III., 8): 2BiCl3 -f 3H2S = 6HC1 + Bi3S3. 2. Pour a concentrated solution of bismuth into water: a white precipitate of a bismuthyl salt is formed. (See explanation above.) 3. Add to bismuth solution ammonium or sodium hydroxide, or carbonate: a white precipitate of bismuth hydroxide, Bi3HO, or of bismuthyl carbonate is produced. (See explanation above.) 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 ivhat conditions are they formed? 277. What is “blue vit- riol how is it made, and what are its properties? 278. How does ammonium hydrate 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 consti- tution ? SILVER. 189 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. A second method, by which silver is obtained from ores con- taining it in the metallic state (or in such a form that the com- pounds are easily decomposed with liberation of metallic silver), is the so-called amalgamation process, which depends upon the solubility of silver in mercury; the ores are treated with this metal, and the silver-amalgam upon being distilled leaves silver behind, the mercury being, of course, condensed to be used over and over again. 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 hydrosulphurie 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 is, therefore, 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 sodium chloride is formed, carbon dioxide escapes, and a button of silver is found at the bottom of the crucible : 2AgCl + Ha2C03 = 2NaCl + 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 maybe treated with sodium carbonate, 190 METALS AND THEIR COMBINATIONS. 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 redissolving it in nitric acid, and evapora- tion of the solution to dryness. Use this solution for silver reactions. Silver nitrate, Argenti nitras, AgNO;i = 169.7 (Nitrate of silver). Pure silver is dissolved in nitric acid : BAg - 4HN03 = NO + 2H20 + 3AgNOs. The solution is evaporated to dryness with the view of expelling all free acid, the dry mass dissolved in hot water and crystal- lized. 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 usually 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 IT. 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- 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. MERCURY. 191 Silver oxide, Argenti oxidum, Ag.,0 = 231.4 (Oxide of silver). Made by the addition of an alkaline hydroxide to silver nitrate: 2AgN03 + 2KH0 = 2KN03 + H20 + Ag20. 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: AgNOs + KI = KN03 + Agl. A heavy, amorphous, light yellowish powder, insoluble in water, and but slightly soluble in ammonium hydrate. Antidotes. Sodium chloride, white of egg, or milk, followed by an emetic. Analytical reactions. 1. Add to solution of a silver salt, hydrosulphuric acid or ammonium sulphide: a black precipitate of silver sulphide is produced: (Silver nitrate, AgN03, may be used.) 2AgN03 + H2S = 2HN03 + Ag2S 2. Add hydrochloric acid, or any soluble chloride: a white, curdy precipitate of silver chloride is produced, which is insoluble in acids, but soluble in ammonium hydrate: 3. Add chromate or bichromate of potassium : 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 nitric acid. 5. Alkaline hydroxides precipitate dark brown silver oxide. (See above.) 6. Potassium iodide or bromide gives a pale yellow precipitate. (See above.) 7. Metallic copper, zinc, or iron precipitates metallic silver. Ag]Sr03 + NaCl = NalSTOg + AgCl. Mercury, Hydrargyrum, Hg = 199.7 (Quicksilver). Mercury is sometimes found in small globules in the metallic state, but 192 METALS AND THEIR COMBINATIONS. generally as mercuric sulphide or cinnabar, a dark red mineral. The chief supply was formerly obtained from Spain and Austria; lately, however, large quantities have been obtained from Cali- fornia; it is also 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 state 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 Hg< XC1 Mercuric chloride. Hg-Cl Hg-Cl 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 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 looking- 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 MERCURY. 193 blue pill, mercurial ointment, and mercurial plaster. In these prepa- rations, which are made by intimately mixing (triturating) metallic mercury with the different substances used (viz., chalk, pill-mass, fat, lead-plaster), mercury exists in a metallic, but highly subdivided state. It is most probable that the action of these agents upon the animal system is chiefly due to the conver- sion of small quantities of mercury into mercurous oxide, which, in contact with the acids of the gastric juice or perspiration, are converted into soluble compounds capable of absorption. Mercurous oxide, Hg20 [Black oxide or suboxide of mercury). An almost black, insoluble powder, made by adding an alkaline hydrate to a solution of mercurous nitrate: Hg22N03 + 2KH0 = 2KN03 + II20 4- Hg20. A similar decomposition takes place when alkaline hydrates are added to the 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 + Ca2H0 = 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° P.) (Plate IV., 3): HgCl2 + 2KH0 = 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 this has been intimately mixed with an amount of metallic mercury equal to the mercury in the nitrate used (Plate IV., 4). In the first case, nitrous fumes and oxygen are given off, mer- curic oxide remaining: Hg2N03 = HgO + 2N02 + 0. Iii the other case, no oxygen is evolved : Hg2N03 + Hg = 2HgO + 2N02. 194 METALS AND THEIR COMBINATIONS. 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: HgClj + Hg = Hg2Cl2; HgS04 + Hg + 2NaCl = Na2S04 + Hg2Cl2. Another method for making calomel is the precipitation of a soluble mercurous salt by any soluble chloride : Hg22N03 + 2NaCl = 2NaN03 + Hg2Cl2. 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, MERCURY. 195 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, hydrates, 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, w'hich are condensed in the cooler part of the apparatus, while sodium sulphate is left: 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. HgSQ4 + 2NaCl = Na2S04 + HgC!2. 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 = Hg2T2 The powder is finally 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). 196 METALS AND THEIR COMBINATIONS. Mercuric iodide, Hydrargyri iodidum rubrum, Hgl2 = 452.9 (Red iodide or hiniodide of mercury). Made by mixing solutions of potassium iodide and mercuric chloride, when a yellow precipi- tate is formed, turning red immediately (Plate IV., 6): 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. HgCl2 + 2KI = 2KC1 + Hgl2. 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-sulphaie). 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, IIgS04.2IIg0, 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 Nitrates of mercury. Mercurous nitrate, IIg22N03, and Mercuric nitrate, Hg2N03, 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 MERCURY. 197 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 + 8HN0S = 3Hg22N03 + 4H20 + 2N0; 3Hg22N03 + 8HNO3 = 6Hg 2N03 + 4H20 + 2N0. Mercuric sulphide, HgS = 231.7. This compound has been mentioned as the chief ore of mercury, occurring crystallized as cinnabar, and has a red color (Plate IV., 2). The same compound may, however, be obtained by passing hydrosulphuric acid gas through mercuric solutions, when at first a white precipitate is formed (a double compound of the sulphide of mercurj7 in com- bination with the mercuric salt), wdiich soon turns black (Plate IV., 1): HgCl2 + H2S = 2H01 + 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 sulphidum 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 nitrohydrochloric acid. Mercuric and mercurous sulphides may also be made by tritu- rating the elements mercury and sulphur in the proper propor- tions, when they combine directly. 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 198 METALS AND THEIR COMBINATIONS. washed with highly diluted ammonia water and dried at a low temperature : HgCl2 + 2NH4IIO = NH2HgiiCl + NH4C1 + 2H20 As shown by the composition of this compound, it may be regarded as ammonium chloride, NH4C1, 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.) Ammoniated mercury is a white, tasteless, insoluble powder. 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. Analytical reactions. Mercurous salts. (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: Hg,2NO„ + H„S = 2HN03 + 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 IV., 7): Hg2N03 + 2KI = 2KNO, + Hg2T2. Red precipitate of mercuric iodide. (See above.) (Plate IV., 6.) 3. Potassium or so- dium hydroxide. Dark-brown precipitate of mer- curous oxide, Hg20 (Plate IV., 5). Yellow piecipitate of mer- curic 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 mer- curic 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 ; un- stable. 6. Hydrochloric acid or soluble chlorides. White precipitate of mercurous chloride is produced: Hg22N03 -|- 2HC1 = 2HN03 + Hg2Cl2 No change. MERCURY. SILVER. PLATE ITT. Mercuric sulphide precipitated from mercuric solutions by hydrosnl- phuric acid. [Pages 197,198.] Mercuric sulphide. Cinnabar. [Page 197.] Yellow mercuric oxide precipi- tated from mercuric solutions hy po- tassium hydroxide. [Pages 193,198.] Pled mercuric oxide obtained by heating mercuric nitrate. [Page 193.] Mercurous oxide precipitated from mercurous solutions by potas- sium hydroxide. [Pages 193.198.] Silver sulphide precipitated from silver solutions by hydrosulphuric acid. [Page 191.] Mercuric iodide precipitated from mercuric solutions hy alkaline iodides. [Pages 196,198.] Mercurous iodide precipitated from mercurous solutions hy alkaline iodides. [Pages 195,198.] Mercuric solutions with ammo- nium hydroxide. [Page 198.] Mer- curous solutions with soluble chlor- ides. [Page 198.] Silver solutions with soluble chlorides. [Page 191.] ARSENIC. 199 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 reducing or deoxi- dizing 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: 2HgCJ2 + SnCl2 = Hg.,Cl2 + SnCl4; Hg2Cl2 + SnCI2 = 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. 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- Questions.—281. IIow 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 hydrate, calcium hydrate, potassium or sodium hydrate 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. 200 METALS AND THEIR COMBINATIONS. 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 only resem- blance which unites these metals is the insolubility of their sul- phides in diluted acids and the solubility of these sulphides in ammonium sulphide (or alkaline hydrates), 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 prop- erties in common, and resemble in many respects the non-metallic elements phosphorus and nitrogen, as may be shown by a com- parison of their hydrides, oxides, acids, and chlorides: NH3 N20s N205 NCI,. ph3 p2o3 p2o5 h3po4 PC13. AsH„ Af20, Ap20k H,AsO, AsCL. SbH3 Sb203 Sb205 SbCl3. 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 unfrequently met with in nature. Certain mineral waters contain traces of arsenic compounds. Arsenic may easily be obtained by heating arsenious oxide with charcoal, or by allowing vapors of arsenious oxide to pass over charcoal heated to redness: In both cases the arsenic, when liberated by the reducing action of the charcoal, exists in the form of vapors, which condense in the cooler part of the apparatus as a steel-gray metallic mass, which, when exposed to the atmospheric air, loses the metallic 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 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. As203 + 3C = 3C0 + 2As. ARSENIC. 201 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 trivalent in some compounds, quinquivalent in others. Arsenious oxides, Acidum arseniosum, As203 =197.8 (White arsenic, Arsenic trioxide, Arsenious anhydride, improperly Arsenious acid). This compound is frequently 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 oxide, which, at that temperature, is volatilized and 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 water, 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, II3ASO3, which compound, however, cannot be obtained in an isolated condition, but is only known in solution: 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 deoxidized, giving otf, at the same time, an odor resembling that of garlic. Arsenious oxide is frequently 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 A?203 + 3H20 = ‘2H3As03. 202 METALS AND THEIR COMBINATIONS 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, H3As04, from which the water may be expelled by further heating, when arsenic oxide is left: 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. 2H3As04 == As205 -(- 3H20. Arsenic oxide and arsenic acid are largely used as oxidizing agents in the manufacture of aniline colors. 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 : As203 + 2NaN03 -f Na2C03 = Na4As207 + 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: Na4As207 + 15H20 = 2(Na,HAs04.7H20). Arseniuretted hydrogen, AsH3 (Hydrogen arsenide). This com- pound is always formed when either arsenious or arsenic oxides or acids, or any of their salts, are brought in contact with nascent ARSENIC. 203 hydrogen, for instance, with zinc and diluted sulphuric acid, which evolve hydrogen: As203 -|- 12H == 2AsH3 + 3H20. A?205 + I6H = 2AsH3 + 5H20. AsCI3 -)- 6H = AsH3 -(- 3HU1. 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 = As203 + 6H20. 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 aflinity 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 decomposed 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 may also be obtained by fusing the elements, or by precipitating an arsenic solution by hvdrosul- phuric acid (Plate V., 1). Both sulphides of arsenic are sulphur- acids, uniting with other metallic sulphides to form sulphur-salts, as, for instance, K2S.As2S3, or (HH4)2S.As2S3. These compounds are known as sulph-arsenides. 204 METALS AND THEIR COMBINATIONS. 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 equal parts of arsenious iodide and mercuric iodide in 100 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): 4~ 3H2S = 3H20 -j- A?2S3. 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 : As203 + 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 formed at first) 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, both in alkalies and acids. 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 (CuHAs03), 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 ammonic salts, silver nitrate or cupric sulphate may be added to the acid (or neutral) solution of arsenic, then adding water of ammonia carefully in -V. ARSENIC. ANTIMONY. TIN. Arsenious sulphide,, precipi- tated f.om arsenious solutions by hy- drosulphuric acid. [Page 204.] Cupric arsenite, precipitated from arsenious solutions by ammonio- sulphate of copper. [Page 204.] Silver arsenite, precipitated from arsenious solntions"by silver nitrate. [Iage 20%.] Silver arseniate, precipitated from arsenic solutions ni- trate. [Page 204,] A ntimonious sulphide, precipi- tated from solutions of antimony by hydrosulphuric acid. [Pages 209,211.] Native or Crystallized antimo- nious sulphide. [Page 209.] Stannous sulphide, precipitated from stannous solutions by hydrosul- phuric acid. [Page 213.] Stannic sulphide, precipitated from stannic solutions by hydrosul- phuric acid. [Page 213.] ARSENI C. 205 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 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 tube. (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. lieinsch’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. 9. Fleitmarm’s test. Zinc and moderately strong solution of sodium hydrate evolve, upon heating, hydrogen gas: Zn + 2NaH0 = Na2Zn02 + 2H. 206 METALS AND THEIR COMBINATIONS. If arsenious or arsenic acid be present, arseniuretted hydrogen is evolved, which may he 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 hydrates.) (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 Woulfs 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 30 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 sometimes 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 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 cold piece of porcelain held in the flame Fig 14. ARSENIC. 207 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 re- liable 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 will generally answer for student’s tests. Fig. 16. Student’s apparatus for makiug arsenic spots. Preparatory treatment of organic matter for arsenic analysis. If organic matter is to be examined for arsenic (or for any other 208 METALS ANI) THEIR COMBINATIONS. metallic poison), it ought to be treated as follows: The sub- stance, 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 from some remaining solid matter by filtration. 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 sulphides, a little organic matter being also generally precipitated. The precipitate is collected upon a small filter and treated with warm ammonium 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 he present, in nitro-muriatic acid, and the solution tested by the methods mentioned for the respective metals. The ammonium sulphide solution is evaporated to dryness, this residue mixed with nitrate and carbonate of sodium and the mixture fused in a small porce- lain 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 treat- ing 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 anti- monv. Antidotes. Moist, recently prepared ferric hydrate or dialyzed iron are the best antidotes, insoluble ferric arsenite 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 composi- tion, mode of manufacture, appearance, solubility, and other properties. ANTIMONY. 209 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. Antimon}' 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, Sh2S3 — 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 liberation 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 sulphide 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 also be obtained 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 {Oxysulphide of antimony), chiefly antimonious sulphide with some antimonious 295. Which three solutions, containing arsenic, are officinal, and what is their com- position ? 296. How is arsenic acid obtained from arsenious oxide, and which arseniate 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. 210 METALS AND THEIR COMBINATIONS. oxide. This preparation is made by boiling purified antimonious sulphide with solution of sodium hydrate, 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, Na3SbS3, and the sodium antimonite, lSTa3Sb03, are formed when anti- monious sulphide is boiled with sodium hydrate: Sb2S3 + 6NaH0 = Na3SbS3 + Na3Sb03 + 3H20. By the addition of sulphuric acid, both salts are decomposed, sodium sulphate is formed, and antimonious sulphide and oxide are precipitated: 2Na3SbS3 +. 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 hydrate. 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 diluted 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 (Tercliloride of antimony, Butter of antimony). Obtained by boiling the native sulphide with hydro- chloric acid: Sb2S3 + 6HC1 = 3H2S + 2SbCl3. 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. Experiment 38. Boil about 2 grams of black antimony with 10 c. c. of hydrochloric acid until most of the sulphide is dissolved. Set aside for subsid- ANTIMONY. 211 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 : This white precipitate was formerly known as powder of Alga- roth. It is completely converted into oxide by treating it with sodium carbonate: 12SbCl3 + 15H20 3= 2SbCl3.5Sb203 + 30HC1. 2SbCl3.5Sb203 + 3Na2C03 == 6Sb203 + 6NaCl + 3C02. The precipitate, when washed and dried, is a heavy, grayish- white, tasteless powder, insoluble in water, soluble in acids. Antimonious oxide, while 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 the white precipitate of oxychloride thus obtained by decantation 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 hydrate, should be administered. Analytical reactions (A solution of tartar emetic, KSb0C4H406, 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). 212 METALS AND THEIR COMBINATIONS. 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 carbonate; in either case white antimonious hydroxide, Sb3HO, 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 + 20 = Sn + 2CO. Tin is an almost silver-white, very malleable metal, fusing at the comparatively low temperature of 228° C. (444° 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, SnCl2 (Protochloride of tin). Obtained by dis- solving tin in hydrochloric acid by the aid of heat: Sn + 2HC1 = SnCl2 -f 2H. Sufficiently evaporated, the solution yields crystals of the composition SnCl2.2II20. Stannous chloride is a strong deoxi- dizing agent, frequently used as a reagent for mercury and 213 TIN—GOLD. gold, which metals are precipitated from their solutions in the metallic state. It is also used 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. Analytical reactions. (Stannous chloride, SnCl2, and stannic chloride, SnCh, may be used.) 1. Add hydrosulphurie acid to solution of a stannous salt: brown stannous sulphide is precipitated (Plate V., 7): The precipitate is soluble in ammonium sulphide. 2. Add hydrosulphurie acid to solution of a stannic salt : yellow stannic sulphide is precipitated (Plate V., 8): SnCl2 + H2S = 2HC1 + SnS. SnCl4 + 2H2S = 4IIC1 + SnS2. The precipitate is soluble in ammonium sulphide. 3. Sodium or potassium hydrate added to a stannous salt, pro- duces a white precipitate of stannous hydrate, Sn2IIO. 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 in the free state, and is separated from adhering sand and rock by a me- chanical process of washing, in which advantage is taken of the high specific gravity of gold. Pure gold is too soft for general use, and is therefore 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. Gold is generally trivalent, as in auric chloride, AuC13, but most likely also univalent in some compounds, as in aurous chloride, AuCl. 214 METALS AND THEIR COMBINATIONS. 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 hvdrosulphuric 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, wffiich, 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 PtCl4.2KCl and PtCl4.21SriI4Cl. 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, MoOa, is obtained, The oxide, when dissolved in water, forms an acid which combines w7ith metals, forming a series of salts 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 hydrate. QUESTIONS. 215 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 hydrates act upon antimonious sulphide ? 304. What is the sulphurated antimony of the U. S. P. ? 305. Mention the two chlorides of antimony, 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. INTRODUC TORY 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 he either qualitative or quantita- tive, 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 chiefly he considered, 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 he devoted to analytical chemistry in this work. Some brief directions con- cerning quantitative determinations, especially by volumetric methods, are given in Chapter 37. Every one 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 by which substances are recognized when mixed with others, by analyzing various complex substances. Such a course of practical work in a chemical laboratory is of the greatest advantage to all studying chemistry, arid students cannot be too strongly advised to avail themselves of any facilities offered in performing chemical experiments, analytically or otherwise. INTRODUCTORY REMARKS. 217 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. 3. Test-tube stand and one dozen assorted test-tubes. (Fig. 18.) 4. Three small beakers from 100 to 150 cc. capacity. (Fig. 19, A.) 218 ANALYTICAL CHEMISTRY. 5. Two flasks of 100 to 150 cc. capacity. (Fig. 19, B.) 6. Wash-bottle of about 400 cc. capacity. (Fig. 20, A.) 7. Three small glass funnels, about one and a half to two in 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. 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, D.) INTRODUCTORY REMARKS. 219 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. a. Liquids. 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, HNOs. 6. Acetic acid, sp. gr. 1.048, C2H402. 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, (NH4i2C204; five per cent, solution. 13. Ammonium molybdate, (NH4)2Mo04. A five percent, solution of the salt in a mixture of equal parts of water and nitric acid. 14. Sodium hydroxide, NaHO. 15. Sodium carbonate, Na2C03. 16. Sodium phosphate, Na2HP04. 17. Sodium acetate, NaC2H302. 18. Potassium chromate, K2Cr04. 19. Potassium dichromate, K2Cr2Or - Ten per cent, solutions. 20. Potassium iodide, KI. 21. Potassium ferrocyanide, K4Fe6CN. 22. Potassium ferricyanide, K6Fe212CN. 23. Potassium sulphocyanate, KCNS. Five per cent, solutions. 24. Magnesium sulphate, MgS04. 25. Barium chloride, BaCl2. 26. Calcium chloride, CaCl2. Ten per cent, solutions. 27. Calcium hydroxide, Ca2HO (lime-water). 28 Calcium sulphate, CaS04. Saturated solutions. 29. Ferric chloride, Fe2Cl6. 30. Lead acetate, Pb.2C2H302. 31. Silver nitrate, AgN03. 32. Mercuric chloride, HgCl2. 33. Platinic chloride, PtCl4. Five per cent, solutions. 34. Solution of indigo. 35. Alcohol. 1. Litmus or blue and red paper. 2. Turmeric paper. 3. Sodium carbonate, dried, Na2C03. 4. Sodium biborate, borax, Na2Bo4Or10H2O. b. Solids. 220 ANALYTICAL CHEMISTRY. 5. Sodium-ammonium-bydrogen phosphate (microcosmic salt), Na(NH4)HP04.4H20. 6. Potassium carbonate, K2C03. 7. Potassium nitrate, KNOs. 8. Potassium chlorate, KC103. 9. Potassium permanganate, K2Mn208, 10. Potassium cyanide, KCN. 11. Calcium hydroxide,Ca2HO. 12. Perrous 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. AYhile 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 quantitative 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. Hot 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 PRELIMINARY EXAMINATION. 221 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 gram. A smaller amount may frequently answer, and a much larger quantity may occasionally be needed, as, for instance, in such 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; crystallized 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 is consequently 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 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, 222 ANALYTICAL CHEMISTRY. leaving in many cases a black residue of carbon, which, upon 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 225.) 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 examined on platinum foil. Fig. 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 glass tube, as shown in Fig. 22, instead of on platinum foil, be- cause volatile products evolved during the process of heating may become recondensed in the cooler part of the tube, and are thus saved for further examination. PRELIMINARY EXAMINATION. 223 The presence of water, sulphur, mercury, arsenic, etc., may often be readily demonstrated by this mode of operating. 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 glob- ules 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, due to the precipitation of some metallic oxide around the heated spot on the charcoal, is formed by some metals. If sulphur as such, or in any form of combination, be 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. 224 ANALYTICAL CHEMISTRY. 6. Flame tests. Many substances impart a characteristic color to a non-luminous flame. The best mode of performing this test is as follows : A platinum wire is cleaned by washing in hydro- chloric acid and water, and heated 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 as to form Fig. 25. 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 substance 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 strongly heated. The metallic compound is chemically acted upon by the boracic acid, a borate being formed which colors the bead more or less intensely, according to the quantity of the metallic com- pound 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 oxj’gen) 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 PRELIMINARY EXAMINATION. 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 223 ) 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 potas- sium 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 and strontium. Orange flame, compounds of calcium. Yellowish-green flame, compounds of barium and molybdenum. Green flame, compounds of copper, phosphoric and boric acids. Blue flame, compounds of arsenic, antimony, lead, and cupric chloride. Heat a colorless borax bead with very little of the substance. Green bead, compounds of chromium. Blue bead, compounds of cobalt and 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 bead, compounds of the light metals and those of the arsenic group ; also silver, bismuth lead, etc. Table I.—Preliminary examination. 226 ANALYTICAL CHEMISTRY. form. In some cases microcosmic salt, NaNH4IIP04 is used for making the bead. 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 destroyed during the process of dissolving, as, for instance, when calcium carbonate is dissolved in hydro- chloric acid; this solution now contains and leaves on evaporation calcium chloride. The solvents used are water, or for substances insoluble in that liquid the mineral acids, especially diluted, or, if necessary, strong hydrochloric acid. The dissolving action of the acid should be facilitated by the aid of heat. Nitric or even nitrohydrochloric acid may have to be used in some cases. Three mistakes are frequently made by beginners in dissolv- ing 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 solutions separately. Substances insoluble in water and 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 hj'drochloric acid. Insoluble silicates may be decomposed by the methods men- tioned on page 96. Questions.—311. What is analytical chemistry, and what is the object of qualitative and of quantitative analysis? 312. What properties of a substance should first be noticed in making a qualitative analysis? 313. By what tests SEPARATION OF METALS IN DIFFERENT GROUPS. 227 33. SEPARATION OF METALS IN 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., 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 the 55 known metals from each other, when all in one solution, would be to add successively 55 different reagents, each of which should form an insoluble compound with but one of the metals. By separating this in- soluble 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. Hgdrosulphuric 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 sidphide, added after supersaturating with am- monium 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 magne- sium. may organic compounds be distinguished from inorganic compounds? 314. Explain the terms decrepitation and deflagration. 315. Mention some sub- stances which are completely volatilized by heat, some which are fusible, and some 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 com- pounds 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. 228 ANALYTICAL CHEMISTRY. The order in which these group-reagents are added cannot be reversed or changed, because ammonium sulphide added first would precipitate not only the metals of the iron group and the earths, but also the metals of the lead group; ammonium car- bonate would also precipitate 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 bis- muth 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, is not 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 233. Hydrochloric acid added to a solution may, in a few cases (other than those just mentioned), cause a precipitate, as, for in- SEPARATION OF METALS IN DIFFERENT GROUPS. 229 stance, when added to solutions containing certain compounds of antimony or bismuth (the precipitated oxychlorides of these 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 solution 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 reagent 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 hydrosu lphuricacid, For generating hydrosulphuric acid the directions given on page 104 may be followed. In place of the apparatus there men- tioned 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 continuous preparation of the gas. It consists of three glass bulbs; the 230 ANALYTICAL CHEMISTRY. 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 the generated gas forces the liquid from the second bulb through the lower to the upper, thus pre- venting 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 tilled 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 may he formed. The yellow ammonium sulphide SEPARATION OF METALS IN DIFFERENT GROUPS. 231 is almost invariably a polysulphide of ammonium, that is, am- monium sulphide which has combined with one or more atoms of sulphur. If an acid be added to this compound, an ammo- nium salt is formed, hydrosulphuric acid is liberated, and sulphur precipitated: (NH4)2S2 + 2HC1 = 2NH4C1 + H2S + S. Ammoniun sulphide precipitates the metals of the iron group as sulphides, with the exception of chromium, which is precipitated as hydrate; aluminium is precipitated in the same form of com- bination. 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 235. 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. 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 hydrate, before adding the 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 ? ANALYTICAL CHEMISTRY. 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, it is generally 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: Hpdrosulphuric acid precipitate.-: Ammonium hy- droxide and sulph- ide 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- Soluble in ammo- nium sulphide. nium sulphide. Silver chloride, 1 Lead sulphide, ] Arsenious sulph- Ferrous sulphide, Calcium car- Magnesium. Mercurous 1 •- Mercuric sul- ide, yellow. black. bonate. Potassium. chloride, j phide, Antimonious sul- Cobaltous sulphide, Barium car- .■§ Sodium. Lead chloride, J Bismuth sul- «s phide, orange. black. bonate. £ Lithium. phide, 5 Stannous sulphide, Nickelous sulphide, Strontium Ammonium. A precipitate may he Cupric sul- brown. black. carbonate. caused by other sub- phide, Stannic sulphide, Manganous sulph- stances than those men- Cadmium sulphide, yellow. ide, flesh-colored. tioned. See page 228. yellow. Auric sulphide, Zinc sulphide, white. brown. Chromic hydrate, Platinic sulphide, green. brown. Aluminium hydrate, white. A precipitate may be caused by other sub- stances than those men- tioned. See page 231. See Table III. See Table IV. See Table V. See Table VI. See Table VII. See Table VIII. , Table II.—Separation of metals in different groups. 233 SEPARATION OF METALS OF EACH GROUP. 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 dilute sulphuric acid : a white Besidue may consist of mercurous and silver chlorides. Digest residue with ammonium hydrate. precipitate of lead sul- phate is produced. Solution may contain sil- ver. Neutralize with nitric acid, when silver chloride is reprecipitated. 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- 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 of sulphur only is white and milky, but fiocculent, and more or less colored in the presence of the metals of the arsenic group. 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 hvdrosulphuric 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- 234 ANALYTICAL CHEMISTRY. 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 sul- phide, which is black and easily dissolves in ni- trohydrochloric acid, which solu- tion, after suffi- cient evapora- tion, is tested by potassium iodide etc. Lead sulphate is white, pul- verulent, and soluble in am- monium tartrate Sulphur is yel- low and com- bustible. Filtrate may contain the nitrates of lead, copper, bismuth, and cadmium. Add to the solution a few drops of dilute sulphuric acid. Precipitated is lead as white lead sulphate, which is soluble in ammonium tartrate with ex- cess of ammo- nium hydrate. Solution may contain copper, bismuth, and cadmium. Supersaturate with ammonium hydroxide. Precipitated is white bismuth hydroxide. Dis- solve in hydro- chloric acid and apply tests for bismuth. Solution may contain cop- per and cadmium. Divide solution in two parts, and test for copper by po- tassium ferrocyanide in the acidified solution; a red precipitate indicates cop- per. To second part add potassium cyanide and hy- drosulphuric acid. A yel- low precipitate indicates cadmium. Table A".—Treatment of the hydrosulphuric acid precipitate which is soluble in ammonium sulphide. The precipitate may contain the sulphides of arsenic, antimony, tin, and of 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 is gradually evolved as antimoniuretted hydrogen, while tin remains with the undissolved zinc as a black metallic powder, which may be col- lected, Avashed, dissolved in hydrochloric acid, and the solution tested by the special tests for tin. uionium 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 dissolved 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 METALS OF EACH GROUP. 235 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 hydrate 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 wuh hydrochloric acid, and add ammonium car- bonate. A white gelatinous pre- cipitate indicates aluminium. Boil the (green) solution for some time. A green precipitate indicates 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 potas- sium hydroxide. The filtrate then contains the zinc, the black pre- cipitate 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 nitrohydrochlorie acid. 2 In the absence of a sufficient quantity of ammonium chloride some magnesium hydrate may also be precipitated. Table VI.—Treatment of the precipitate formed by ammonium hydroxide and ammonium sulphide. 236 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 hydrate, sulphide, and carbonate, may contain magnesium and the alkalies. Divide solution into two portions. To the first portion add sodium A white crystalline precipitate in- dicates magnesium.2 The second portion is evaporated to dryness, and further heated (or ignited) until all ammonium compounds are expelled. The residue is dissolved in water, and platinic chloride added. A yellow precipitate 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 treating 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. 237 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 by means of acids is attempted, 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 respective solubility of the substance, and the nature of the metal or metals present, will aid in point- ing out the acid or acids which are believed to be present. If, for instance, a solid substance be completely soluble in water, and if the only metal found were iron, it would become unnecessary 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 solids. 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 are either decomposed, with liberation of the acid (which may escape in 238 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 only be applied to a neutral or alkaline solution ; in attempting, how- ever, 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 important feature. It will also guide him in the analysis of inorganic sub- stances, as it gives directions for over 300 (positive or negative) 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 neutral solutions, one contain- ing the metal, the other containing the acid of the insoluble salt to be formed. For instance: Table XI. states that the car- bonates of most metals are insoluble in water. To produce, therefore, the carbonate of any of these metals (zinc, for in- stance) it becomes necessary to add to any solution of zinc (sul- phate, chloride, or nitrate of zinc) any soluble carbonate (sodium or potassium carbonate), when the insoluble zinc carbonate is produced. Soluble carbonates are consequently reagents for soluble zinc salts, while at the same time soluble zinc salts are reagents for soluble carbonates. DETECTION OF ACIDS. 239 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, j Arsenious acid, J Hydrochloric acid (silver test). Carbonic acid (the gas is also generated 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 ferrous sulphate). Nitrous acid (red vapors). Whenever one or more acids are suspected or indicated by the above tests, their presence is to be verified by the tests in Tables X. and XL, 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. 240 ANALYTICAL CHEMISTRY. Barium chloride pre- cipitates : Calcium chloride pre- cipitates from neutral or al- kaline solution: Ferric chloride pre- cipitates from neutral solu- tion : Magnesium sulphate precipitates in the pres- ence of ammonium hydrate and chlor- ide: Silver nitrate precipitates from neutral solution : from neutral or acid solution : Sulphuric acid, white. Sulphurous acid, white. Phosphoric acid, white. Phosphorous acid, white. Carbonic acid, white. Boric acid, white. Arsenic acid, white. Arsenious acid, white. Chromic acid, pale yel- low. Sulphuric acid, white. Sulphurous acid, white. Phosphoric acid, white. Hydrochloric acid, white. Hydrobromic acid, white. Hydriodic acid, white. Iodic acid, white. Hydrocyanic acid, white. Ferrocyanides, white. Ferricyanides, reddish brown. Sulphocyanides, white Hydrosulphuric acid black. Sulphurous acid, white Phosphoric acid, pale yellow. Phosphorous acid, white, then black. Carbonic acid, white. Boric acid, white. Arsenic acid, brownish- red. Arsenious acid, yellow. Chromic acid, red. Phosphoric acid, yel- lowish-white. Phosphoric acid, white. Carbonic acid, white. Boric acid, white. Arsenic acid, white. (Ferric hydroxide is precipi- tated and carbon dioxide escapes.) Boric acid, yellowish. Arsenic acid, yellowish- white. Ferrocyanides, blue. Sulphocyanides, red coloration. Hydrosulphuric acid, black. Oxalic acid, yellow. Tannic acid, black. Acetic acid, a reddish- brown coloration is pro- duced, and, on boiling a reddish-brown precipitate. Arsenic acid, white. Oxalic acid, white. Tartaric acid, white. Citric acid, white. All the above precipitates are soluble in hydrochloric and most other acids, with the exception of barium sul- phate. Oxalic acid, white. Tartaric acid, white. Citric acid, white. Tartaric acid, white; precipitate forms slowly. Oxalic acid, white. Tartaric acid, white. Citric acid, white. Not precipitated are: Nitric acid. Nitrous acid. Chloric acid. Hypochlorous acid. Acetic acid. Table X.—Detection of the more important acids by means of reagents added to the solution. 241 Table XI. DETECTION OF ACIDS. 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. I Arscnite. Oxide. Ilydi’ate. 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 Arsen ions Antimony Gold Platinum Arsenic Group. Copper Bismuth Cadmium Mercuric Mercurous Silver Lead Lead Group. 242 ANALYTICAL CHEMISTRY. w = soluble "in water, a = insoluble in water, soluble in acids (HC1, HN03). 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. 8* P 3 -< « Bismuth. 8 P i p o Calcium Chromium. Cobalt. Copper. p O OS w Ph Ferric. Lead. Magnesium. w W 5 O. If p o 8 o os M i«=i Mercuric. p V w o £ p < c Silver. Sodium. Strontium. Zinc. Acetate . w W vv vv w w VV VV vv w vv VV VV VV vv a vv vv VV vv VV w w Arseniate. a W a a a a a a a a a a a a a a a VV a w a Arsenite . W a a a a a a a a a a a a a vv a vv a Borate a W a a w a a a a a a a a w a a a vv a w a a Bromide . w W w a w w a w w vv t vv \v vv vv w t vv vv a t vv vv vv a vv vv w Carbonate a w a a a a a a a a a a a a a a vv a vv a a Chlorate . w w w VV w vv vv vv w vv vv VV vv vv vv vv vv w VV w w vv Chloride . vv w w a w vv a w w vv vv w w vv vv t w vv a t vv vv vv t vv VV w Chromate w a a a a vv a a a vv vv a t vv vv a vv a a vv a vv vv a vv Citrate w vv a a vv n vv vv w vv vv a vv a » vv a vv vv a vv a vv a Cyanide . w w a a vv a a t a a t a vv a vv a t w t vv vv a Ferricvanide . vv vv t t vv vv a vv t t vv t vv a Ferrocvanide . w vv a vv t t t t a vv a t vv t vv w a t Fluoride . w w w a t w w a a vv 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 vv a a a w a a a a a a a a a a vv vv vv a a Iodide w w w a w a vv w vv w w w vv vv a vv vv a a vv vv t vv w vv Nitrate w w vv vv vv VV vv w vv VV VV vv vv vv w w w vv vv w vv w Oxalate a w a a a a a vv a a a a a a a vv a 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 w a w vv a a Phosphate a w vv a vv or a a a w a a a a a a a a a a a a vv a w a a Silicate a t a a a a a a a a a a a a vv vv a a Sulphate . vv w a a VV VV t w a w VV VV w a t vv vv w a VV VV vv w a vv t w Sulphide . a w a vv a a \v a a t a a a a a a a a a a vv a vv vv a Tartrate . w w a a a vv a a VV VV w w a VV a w a vv a w a a a w a vv a a Table XII.—Table of solubility. 243 DETECTION OF ACIDS. For similar reasons soluble zinc salts are, according to Table XI., reagents for soluble phosphates, arseniates, arsenites, hy- drates, 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, there being some exceptions. For instance : Cupric hydroxide is insoluble in water; by adding solution of cupric sulphate to any soluble hydroxide, therefore, the insoluble cupric hydroxide should be precipitated, and is pre- cipitated 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 XL, aluminium carbonate and chromium carbonate are insoluble salts: actually, however, these compounds do not exist, the affinity between the weak carbonic acid and the feeble bases not being sufficient to unite them. It may be finally 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 compounds 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 may 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, phosphates, arseniates, sulphates, and sulphides respectively. 347. Which oxides or hydrates 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 impossible to render a substance soluble in order to test for the acid in the solution obtained? 244 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 work beyond the limits considered necessary for the beginner. Impurities present in chemical preparations are either 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 may possibly have been added, and for them a search has to be made, or, if necessary, a complete analysis, by which the absence of everything else but the constituents of the pure substance is proved. Impurities derived from the materials used in the manufacture of a substance (generally through an imperfect or incorrect process of manufacture), or from the vessels used in the manu- facture, 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 by which the impuri- ties can be detected. For one familiar with analytical chemistry it is an easy task to suggest, in most cases, the best and quickest method by which the presence or absence of an impurity can be demonstrated; for one unacquainted with these methods, it might be an impossibility to do so, 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- 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. Ill order to give the student, and especially the beginner, a DETECTION OF IMPURITIES. 245 guide in the 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. 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, 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 5 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 phosphorus, nitric, sul- phuric, hydrochloric, pyrophosphoric, and metaphosphoric 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. 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 246 ANALYTICAL CHEMISTRY. U. S. P. The amount of actual acid can either be determined by the specific gravity of the liquid acid, or by the quantity of an alkali required to neutralize a certain quantity of the acid. 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 the hydroxide, sulphide, carbonate, or phosphate of ammonium (absence of heavy metals, alkaline earths, and mag- nesium). The nitrates, hydroxides, carbonates, and bicarbonates (the three latter, 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 neutral car- bonate by adding a solution of 2 grams of the salt in 30 cc. of cold water to a solution made by dissolving 0.3 gram of mercuric chloride in 6 cc. 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 neutral carbonate is demonstrated. Iodides may contain an iodate, which is indicated by a blue color on the addition of gelatinized starch and some diluted sulphuric acid; chlorides and bromides may be detected by precipitating a solution of the iodide with an excess of silver nitrate, collect- ing and washing the precipitated iodide (bromide and chloride) of silver, and digesting it with ammonium hydrate, which dis- solves the chloride and bromide, but not (or only traces of) the iodide; the Altered ammonium solution, upon being supersatu- rated with nitric acid, will give a white precipitate if chlorides or bromides are present; a slight turbidity may be due to traces of dissolved iodide. Potassium salts should impart a violet color to a noil-luminous flame, a yellow color indicating sodium. All compounds of ammonium should be completely volatilized by heat without leaving a residue. DETECTION OF IMPURITIES. 247 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 hydrosulphurie acid or by ammonium hydrate (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). 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 diluted nitric acid and adding barium chloride and silver nitrate. Iron will be indicated in calcium phosphate by saturating its solution in hydrochloric acid with hydrosulphurie acid, and then adding an excess of ammonium hydrate; the precipitate should be white, a dark color indicating iron (or possibly other heavy metals). Calcium hypochlorite (bleaching-powder) has to be examined by quantitative methods to ascertain the amount of hypochlorous acid present. Examination of magnesium compounds. Magnesium sulphate, oxide, and carbonate, the two latter after being dissolved in diluted hydrochloric acid, should not be precipitated by hydrosulphurie 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 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 hydrosulphurie acid and show no blue color 248 ANALYTICAL CHEMISTRY. 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 hydrate 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 impart a blue color to the filtrate (absence of copper), and this filtrate 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 in order to expel the ammonium compounds (absence of zinc, manganese, alkalies, etc.). Solution of potassium hydroxide added in excess to ferric solu- tions and filtered, should not be precipitated by ammonium carbonate after the alkaline solution has been neutralized 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 should 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 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 in hydrochloric acid, should give no precipitate in the acidulated DETECTION OF IMPURITIES. 249 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 reagent (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 be 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 has, consequently, to be examined by quantitative analysis. A solution of manganese sulphate, acidulated with hydrochloric acid, should give no precipitate with hydrosulphuric acid (ab- sence 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 completely decolorized (deoxidized) bv oxalic acid and sulphuric acid. The colorless solution should be tested with ferrous sulphate for nitric acid, and with silver nitrate for hydrochloric acid. It should also be tested quantitatively. 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- phuric acid); both substances, when neutralized with potassium hydrate, 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 250 ANALYTICAL CHEMISTRY 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 ammo- nium hydroxide, sulphide, or carbonate. Ammonium hydroxide added to a cupric solution should form a dark blue solution 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 hydrate, 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 be completely dissolved by ammonium hydrate. 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 DETECTION OF IMPURITIES. 251 parts of diluted 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. 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 hydrate. 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 252 ANALYTICAL CHEMISTRY. 37. METHODS FOR 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 electricity 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. 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. If we then add a solution of sodium hydroxide of known strength to a weighed portion of cupric 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. Grive methods for detecting metallic impurities in compounds of lead, copper, bismuth, and silver. 359. What is the action of heat upon mercury compounds, and by what solvents may the various officinal mercur}7 preparations be dis- solved? 360. How is mercuric chloride detected in mercurous chloride, and how mercuric iodide in mercurous iodide ? 253 METHODS FOR QUANTITATIVE DETERMINATION. sulphate until all the copper is precipitated, we may calculate 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 emplo}7ed that a few remarks may be of advantage to the beginner. A small quan- tity (generall}7 from 0.5 to 1 gram) of the substance to be analyzed is very carefully and exactly weighed on a delicate balance, trans- ferred to a beaker, and dissolved in a suitable agent (water or acid). From this solution the constituent to be determined is precipitated 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 I>rying-oven. precipitate 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 254 ANALYTICAL CHEMISTRY. 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 por- celain) crucible, 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 particles of the precipitate mixed with it, is trans- ferred to the crucible, 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 determined by burning a few filters of same kind) deducted, and thus the amount of the precipitated substance determined. Fig. ‘29. Fig. 30. Desiccator. Watch glasses for weighing filters. As platinum-crucibles (like all other solid substances) absorb moisture, which is expelled by heating, it is well to allow the heated crucible to cool in a so-called desiccator, which is an air- tight vessel, containing calcium chloride or strong sulphuric acid on the bottom. Fig. 29 shows a convenient form of desiccator. 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 platinum chloride) cannot be ignited without suffering partial or complete decom- METHODS FOR QUANTITATIVE DETERMINATION. 255 position. It is for this reason that some precipitates are collected upon filters which have been previously dried at 100° C. (212° F.) and weighed carefully. The precipitate is then collected upon the weighed filter, well washed, again dried at 100° C. (212° F.) and weighed. The weighing and drying of 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. 32. Fig. 31. 10 CC T,if rp-flnslr. Pipettes. The above described methods may be employed for the de- termination of those substances which can be precipitated from their solutions in the form of some stable compound. Alu- minium, zinc, iron, bismuth, copper, etc., may, for instance, be 256 ANALYTICAL CHEMISTRY. precipitated as hydroxides and weighed as oxides, into which the precipitated 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 deter- mination. Fig. 33 Fig. 34. Mohr’s burette and clamp Mohr’s burette aud holder. Volumetric methods. The great advantage of volumetric over gravimetric analysis consists chiefly in the rapidity with which these determinations are performed. Unfortunately, volumetric methods cannot be employed to advantage for the estimation of all substances. METHODS FOR QUANTITATIVE DETERMINATION. 257 The special apparatus required for volumetric analysis consists of a few flasks, some pipettes, burettes, and burette holder. The flasks should have a mark on the neck, indicating a capacity of 100, 250, 500, and 1000 cc. 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 requirements, but its application is excluded whenever.the test solution is chemi- cally affected by rubber, as in the case of solutions of silver, per- manganate, and a few other substances. For such solutions Gay Lussac’s bu- rette (Fig. 35) is generally used. Standard solutions. The test solutions used in volumetric analysis are adjusted according to a uniform system, so that each solution contains within a litre (1000 cc.) the weight of one atom or one molecule of the active reagent ex- pressed in grams. This rule refers to all cases of univalent elements (Ag, Cl, I), or monobasic acids (HC1, HN03), or mon-acid bases (KHO, NH4HO). In case a bivalent element (O, S), or dibasic acids (H2S04, H2C204), or di-acid bases (Ca2HO), are used in volumetric solu- tions, 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 centimeters of monovalent and divalent 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 cc., the saturating power of 1 cc. of the diluted sulphuric acid would be equal to that of 2 cc. of hydrochloric acid solution, because 36.4 parts by weight Fig. 35. Gay Lussac’s burette. 258 ANALYTICAL CHEMISTRY. 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 cc. 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 furnish, when boiled with strong hydrochloric acid, free chlorine, which is not determined directly, but is caused to act upon potassium iodide, from which the iodine is liberated, and now 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 METHODS FOR QUANTITATIVE DETERMINATION. 259 normal acid is used for their decomposition, this excess being titrated afterward by the addition 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 termination 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 titre of a volumetric test-solution, when we refer to its strength per volume (per litre or per cubic centimeter). 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 reducing agents) and precipitation (silver nitrate by sodium chloride).. Acidimetry and alkalimetry. Preparing the volumetric test- solutions correctly is often more difficult than to make a volu- metric determination. '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 titre adjusted afterward by methods which will be spoken of later. Neither our common mineral acids, such as sulphuric, hydro- 260 ANALYTICAL CHEMISTRY. chloric, and nitric acids, nor many of our alkaline substances, such as sodium hydroxide or ammonium hydroxide, are suffi- ciently pure to permit of being used directly for volumetric solutions, because these substances contain water, and an ab- solutely correct determination 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 cc. normal alkali solution neutralize 7.6 cc. of the acid, then 24 cc. of water have to be added to every 76 cc. 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 weight) of pure sodium carbonate (obtainable by heating pure sodium dicarbonate 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 easily be 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 cc. of water, titrating this solution with normal acid, and METHODS FOR QUANTITATIVE DETERMINATION. 261 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 25 parts of alcohol and 75 parts of water). While litmus changes from red 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. 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 acid carbonate. Fig. 36. Titration 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 262 ANALYTICAL CHEMISTRY. case of salts of most of the organic acids with alkalies, which are first converted into carbonates by ignition). One cc. of normal oxalic acid is the equivalent of: Ammonia, NH3 ........ 0.0170 Ammonium carbonate, NH4HC03.NH4NH2C02 . . 0.0523 Lead acetate, crystallized, Pb2(C2H302).3H20 . . 0.1892 Lead subacetate, Pb202(C2H302) 0.1367 Potassium acetate, KCjHjOj.1 . . . . . . 0.0980 Potassium bicarbonate, KHC03 ..... 0.1000 Potassium bitartrate, KHC4H4061 ..... 0.1880 Potassium carbonate K2C03 ...... 0.0690 Potassium citrate, KgCgHjOj1 ...... 0.1020 Potassium hydroxide, KHO ...... 0.0560 Potassium permanganate, K2Mn208 .... 0.0314 Potassium sodium tartrate, KNaC4H406.4H201 . . 0.1410 Potassium tartrate, 2K2C4H406.H201 .... 0.1175 Sodium acetate, NaC2H302.2H201 ..... 0.1360 Sodium bicarbonate, NaHC03 0.0840 Sodium borate, Na2B4O7.10H2O ..... 0.1910 Sodium carbonate, crystallized, Na2CO3.10H2O . . 0.1430 Sodium carbonate, Na2C03 ...... 0.0530 Sodium hydroxide, NaHO ...... 0.0400 Gram. One cc. of normal sodium carbonate, or sodium hydroxide, is the equivalent of: Gram. Acetic acid, HC2H302 0.0600 Citric acid, H3C6H507.H20 0.0700 Hydrobromic acid, IIBr . . . . . . . 0.0808 Hydrochloric acid, HC1 ....... 0.0364 Hydriodic acid, HI 0.1276 Lactic acid, HC3H503 ....... 0.0900 Nitric acid, HN03 ........ 0.0630 Oxalic acid, H2C204.2II20 ...... 0.0630 Sulphuric acid, H2S04 ....... 0.0490 Tartaric acid, H2C4H406 0.0750 Oxidimetry. Potassium permanganate. The substances generally used as oxidizing agents are potassium permanganate and potas- sium dichromate, both of which salts can be obtained in a pure crystallized condition. Potassium permanganate, Iv2Mn208== 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: Iv2Mn208 + 5H2C204 + 3H2S04 = K2S04 + 2MnS04 + 10CO2 + 8H20. K2Mn208 + 10FeSO4 + 8H2S04 = K2S04 + 2MnS04 + 5Fe23S04 -f 8H20. 1 After ignition. 263 METHODS FOR QUANTITATIVE DETERMINATION. It follows that one-fifth the molecular weight of potassium permanganate, or 62.8 grams, is the equivalent of 1 oxygen atom. But as oxygen is diatomic and the volumetric normal is calculated 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 is not very stable, but is decomposed by dust and other agents, and its titre has, therefore, to be determined before use. This may be done by dissolving 0.2 gram of pure, thin iron wire in about 20 cc. of diluted sulphuric acid, 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 having a vertical slit about one inch long and closed at the upper end by a piece of glass rod; gas or steam generated in it may escape, while the atmospheric air cannot enter, the ferrous solution being thus prevented from oxidation The iron solution, obtained from the 0.2 gram of iron, is diluted with about 300 cc. of water, a few cc. of diluted sulphuric acid are added, and then deci-normal potas- sium permanganate solution, until the red color no longer disappears. As 1 cc. of deci-normal permanganate solution corresponds to 0.0056 gram of metallic iron, the 0.2 gram iron wire used will consume 35.7 cc. of the solution. 10 cc. 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 cc. should be decolorized.] The titration is accomplished by diluting the 10 cc. of oxalic acid solution with about 50 cc. of water, to which a few cc. of dilute sulphuric acid are added, heating moderately, and adding the permanganate solution until the red color no longer disap- pears. Permanganate is generally used in determinations of iron and iron compounds. Many of the latter contain iron in the ferric Fig. 37. Flask for dissolving iron for volumetric determination. 264 ANALYTICAL CHEMISTRY. state, and have to 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 cc. 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, Fe203 0.0080 Oxalic acid, H2C204.2H2G ...... 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 oxygen upon the deoxidizing agent, thus: K2Cr207 + 6FeS04 + 7H2S04 = K2S04 + Cr23S04 -f 7H20 + 3(Fe23SOJ. 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 cc. The disadvantage of this solution is, that the final point of 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 need an acid to combine with, as shown in the above equation. METHODS FOR QUANTITATIVE DETERMINATION. 265 One cc. potassium dichromate solution, containing of this salt 0.0147 gram, is the equivalent of: Gram. Iron in ferrous combinations, Fe 0.01677 Ferrous oxide, FeO 0.02156 Ferrous carbonate, FeCO.( ...... 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 : 21 + 2Na2S2()3 = 2NaI + Na2S406. A normal solution of one can be measured by an equal number of cc. of normal solution of the other substances. As indicator is used a freshly prepared gelatinized starch solution, which is colored blue by minute portions of free iodine. 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 this itself is determined by the thiosul- phate solution. In many cases the latter solution is also used for the determination of chlorine, which is caused to act upon potas- sium iodide, the liberated iodine being titrated. Deci-normal iodine solution is generally used and made by dis- solving 12.66 grams of pure iodine in a solution of 18 grams of potassium iodide in about 700 cc. of water, diluting the solution to 1000 cc. The article to be tested by this solution is treated with a little starch paste, and then the iodine solution is added until, on stir- ring, the blue color ceases to be discharged. One cc. of deci-normal iodine solution, containing of iodine 0.01266 gram, is the equivalent of: Gram. Arsenious oxide, As203 ....... 0.00494 Potassium sulphite, K2S03.2H20 ..... 0.0097 Sodium bisulphite, NaHS03 ...... 0.0052 Sodium thiosulphate, jSTa2S203.5H20 .... 0.0248 Sodium sulphite, Na2S03.7H20 ..... 0.0126 Sulphur dioxide, S02 0.0032 Sodium thiosulphate (Hyposulphite). The crystallized salt, Na2S203.5H20 = 248, is used for making the deci-normal solu- tion by dissolving 24.8 grams of the pure crystallized salt in 266 ANALYTICAL CHEMISTRY. water to make 1000 cc. If the salt should not be absolutely pure, a somewhat larger quantity (30-32 grams) should be dis- solved in 1000 cc. of water, 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 gelatinized starch is added, and the addition of the solution continued until the blue color has just disappeared. One cc. 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, AgN03 = 169.7, is used for this solution, which is made by dissolving 16.97 grams of the salt in water to make 1000 cc. Tiie titre of this solution may be tested 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 hydroxide, 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 dryness with pure hydrochloric acid, and heating to about 120° C. (248° F.). The chlorides thus obtained may be titrated with silver solution. In the case of chlorides, iodides, and bromides, neutral 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. In case free acids are determined by silver, these are neutralized before titration with sodium hydroxide. The operation is conducted as follows: The weighed quantity of the chloride is dissolved in 50-100 cc. of water, neutralized, METHODS FOR QUANTITATIVE DETERMINATION. 267 if necessary, mixed with a little potassium chromate, and silver solution added from the burette until a red coloration is 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 permanent 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 cc. of the standard silver solution em- ployed will indicate exactly one-half of the equivalent amount of cyanide present in the solution. One cc. of deci-normal silver nitrate solution, containing 0.01697 gram of AgiST03, is the equivalent of: Gram Ammonium bromide, NH4Br ..... 0.00978 Ammonium chloride, NH4C1 ..... 0.00534 Ammonium iodide, NH4I ...... 0.0155 Hydriodic acid, HI ....... 0.01276 Hydrobromic acid, HBr ...... 0.00808 Hydrochloric acid, HC1 ....... 0.00364 Hydrocyanic acid, HCN ...... 0.0054 Potassium bromide, KBr ...... 0.01198 Potassium chloride, KC1 ...... 0.00744 Potassium cyanide, KCN ...... 0.0130 Potassium iodide, KI ....... 0.01656 Sodium bromide, NaBr ....... 001028 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. 268 ANALYTICAL CHEMISTRY. 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 cc. of hydrogen, which, at the temperature of 0° C. (32° F.) and a pressure of 760 mm., is 0.0000896 gram. 1 cc- of any other gas weighs as many times more 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 cc. of carbon dioxide weighs 22 times heavier than 1 cc. 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 cc. of normal acid for neutralization, what are the per- centages 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 cc. 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 cc. 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 were formerly 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 combination of the elements. It was in consequence of this fact that the theory of the supposed “ vital force,” by which organic substances could be formed exclusively, had to be abandoned. An organic compound, according to modern views, is sim- ply a compound of carbon generally containing hydrogen, frequently also oxygen and nitrogen, and sometimes other elements. 270 CONSIDERATION OF CARBON COMPOUNDS. Organic chemistry may consequently be defined as the chemistry of 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 the greatest difficulty. Moreover, hydrogen is highly combus- tible, oxygen is a supporter of combustion, whilst nitrogen is perfectly indifferent. Finally, hydrogen is univalent, oxygen bivalent, nitrogen trivalent, and carbon quadrivalent. These elements are, therefore, 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 INTRODUCTORY REMARKS. 271 possessed by each atom, thus increasing the possibilities of the formation of complex 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 di- oxide, carbonic acid and its salts, be considered organic com- pounds, we have an exception to the rule, as they are not com- bustible.) 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 four other 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 1 Non-volatile organic substances are decomposed by heat with generation of volatile products. 272 CONSIDERATION OF CARBON COMPOUNDS. 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 artificially produced or how they are found in nature, how 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, is 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 is 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 may be recognized by them; these reactions will be mentioned in the proper places. ELEMENTARY ANALYSIS. 273 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, 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 somewhat 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 sub- stance with dry soda-lime (a mixture of two parts of calcium hydroxide and one part of sodium hydroxide), when the nitrogen is converted 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 method 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 quantity of the pure and dry substance is mixed with a large excess of dry cupric oxide, and this mixture 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 filled 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 filled. Upon 274 CONSIDERATION OF CARBON COMPOUNDS. heating the combustion-tube in a suitable furnace, the organic matter is burnt 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- sented in Fig. 38 shows the gas-furnace in which rests the com- bustion tube with calcium chloride tube and potash bulb attached. Gas-furnace for organic analysis. 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. 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. 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 ELEMENTARY ANALYSIS. 275 is, then, equal to 49.383 per cent, and the composition of the substance as follows: Carbon ........ 44.444 per cent. Hydrogen ........ 6.172 “ Oxygen . 49.384 “ 100.000 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 be passed through a measured volume of normal hydrochloric acid and the unsaturated 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 two latter acids combine with the sodium of the sodium carbonate, forming sulphate and phosphate 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 phosphate, 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 obtained : 276 CONSIDERATION OF CARBON COMPOUNDS 44 444 _ = 3.703 12 617_ = 6.172 1 4M8f = 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- 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 : 3.703 _ = 6 ; 0 6172 A172. _ 10; 0.6172 ’ 3.087 _ fi 0.6172 ~ The simplest numbers of atoms are, accordingly, carbon 6, hydrogen 10, oxygen 5, or the composition is C6II10O5. 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, he possible that this formula does 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 C18II30O15. 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 to determine 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 : The analysis of a liquid substance gave the follow- ing result: Carbon ........ 92.308 per cent. Hydrogen 7.692 “ 100.000 ELEMENTARY ANALYSIS. 277 From this result the empirical formula, CH, is deducted by applying the method stated above. If this formula were also 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 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. Hot 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 be 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 IIC2II302 is deducted for acetic acid. In man}7 cases, however, it is as yet absolutely impossible to give the molecular formula of a compound with certainty. Rational, constitutional, structural, or graphic formulas. These formulas are intended to represent the theories which have been formed in regard to the relative arrangement of the atoms within the molecule, or to represent the modes of formation and decomposition of a compound, or the relation which allied com- pounds bear to one another. The molecular formula of acetic acid, for instance, is C2II402, but different constitutional formulas have been used to represent the structure of the acetic acid molecule. Thus, H.C2II302 is a formula analogous to Ii.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. C2H3Oi.HOi 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 also indicates that acetic acid is analogous to 278 CONSIDERATION OF CARBON COMPOUNDS. hydroxides, the radical C2H30 having replaced one atom of hydrogen in II20. CIIi3.C02Hi is a formula indicating that acetic acid is com- posed of the two compound radicals, methyl and carboxyl. It may be finally said, that quite another number of rational formulas has been applied, or, at least, has been proposed by different scientists and at different times, to represent the struc- ture of acetic acid, but it should be remembered that these 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 already stated, 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 suf- cient to prove that the unsaturated group of atoms exists as such in a number of compounds, and that it can be transferred from one compound into another without suffering decomposition. Questions.—371. What is organic chemistry, according to modern views? 372. Mention the four chief 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? CONSTITUTION OF ORGANIC COMPOUNDS. 279 Radicals exist in organic and inorganic compounds; an inor- ganic radical spoken of heretofore is the water residue or hydroxyl, HO, 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 hydrates or hydroxides, as, for instance, of KIIO, Ca2II0, Fe26IIO, etc. If one atom of hydrogen he removed from the saturated hydro- carbon methane, CII4, the univalent residue methyl, CH3, is left, which is capable of combining with univalent elements, as in methyl chloride, CII3C1, or, with univalent residues, as in methyl hydrate, CH3HO. If two atoms of hydrogen be removed from CH4, the bivalent residue methylene, CH2, is left, capable of forming the compounds CII2C12, CH22HO, etc. If three atoms of hydrogen be removed from CII4, the triva- lent residue CH is left, capable of combining with three atoms of univalent elements, as in CHC13, 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—, —O—O—O—O—, 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, Hydrogen peroxide. H—O—O—O—Cl, Chloric acid. H—O—O—O—O—Cl. Perchloric acid. In a similar manner, carbon atoms unite, forming chains, as, for instance: I I —e—c—, I I I I I —C—C—C—, I I I I I I I —C—C—0—U—, etc. I I I 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 it is known, be continued indefinitely. This fact, in connection with the possibility of saturating the free affinities with various atoms 280 CONSIDERATION OF CARBON COMPOUNDS. 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 i3 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 by two or three affinities as indicated by the compounds C2H4 and C2H2, the graphic formulas of which may be represented by H H ;C=C( , H—C=C—H. HX \H It is finally assumed that the carbon atoms are united partially by double and partially by single union, as, for instance, in the so-called dosed chain of Ce, capable of forming the saturated hydrocarbon benzene, C6H6: I I II /ScxC\ I H I H. .CK .H W \C/ H/ %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, tilling 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 following each other, differ by CII2. 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 CII4, C2H6, C3H8, C4II10, etc. H H H I I l H—C—H, H—C—C—H, I I I II H H H H H I I I H—C—0—C—H, I I I II H H H H H H I I I I H—0—C—C—C—H, etc. I I I I H H H H CONSTITUTION OF ORGANIC COMPOUNDS. 281 Many homologous series of various organic compounds are known, as, for instance : CH3C1, ch4o, ch2o2, c2h5ci, c2h6o, C2H4 02, CoH7C1, C\,HsO, Co^Oj,, C4H9C1, C4H10O, c4h8 02) c5huci, c5h12o, c5h10o2, etc. etc. etc. Types. It has been proposed to select some substances in which the arrangement of atoms in the molecules may be taken as rep- 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—H, II. Water. H—O—H, III. Ammonia. /H N^H, IV. Methane. H [./H ]\H’ H Y. Phosphoric chloride. Cl I /Cl P—Cl. | \ci 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 types. The following five substances may, for instance, be said to have an atomic arrangement similar to the types above stated: I. Hydrochloric acid. H—Cl, II. Potassium hydrate. C—O—H, III. Arsenious chloride. C1 As—Cl, \ci TV. Ethane. CH3 kH I XH H V. Phosphoric oxychloride. o l/cl. | \ci Cl 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 theoreti- cal 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: K + H20 = KHO + H. Potassium. Water. Potassium hydroxide. Hydrogen. 282 CONSIDERATION OF CARBON COMPOUNDS. C2H402 + 2C1 = C2H3C102 + HC1. Acetic acid Chlorine. Monochloracetic acid. Hydrochloric acid. Benzene. C6H6 + HN03 = C6H5N02 + H20. 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, CIIC13, is a derivative of methane, CPI4, obtained from the latter by replacement of three atoms of hydrogen by the same number of atoms of chlorine. Isomerism. Two or more substances may have the same elements in the same proportion by weight (or the same cen- tesimal composition), and yet be different bodies, showing dif- ferent properties. 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 polarized light, etc. The only explanation which can be given regarding this difference of properties is, that the atoms are arranged differently wdthin 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 have both the composition C2H402, but the arrangement of the atoms (or the structure) is very different, as shown by the formulas: Acetic acid. c2h3o\ H/U’ Methyl formate. CHO\q ch3/u- As another instance, may be mentioned the compound dST2H40, which represents either ammonium cyanate or urea: Ammonium cyanate. nh4\0 CN/U- Urea. NH8/u- Polymerism. Substances are said to be polymeric when they have the same centesimal composition, but a different molecular DECOMPOSITION OF ORGANIC COMPOUNDS. 283 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, C6II6; acetic acid, C2Id402, is polymeric with grape-sugar, » 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, NH4CNO, is easily converted into urea, C02(NH2). b. A molecule may split up into two or more molecules. For instance : C6H1206 = 2C2H60 + 2C02. Grape-sugar. Alcohol. Carhon dioxide. c. Two molecules, either of the same kind, or of different sub- stances, may unite together directly : C2H4 -j- 2Br = C2H4Br2, Ethylene. Bromine. Ethylene bromide. d. Atoms maybe removed from a compound without replacing them by other atoms: c2h6o + o = c2h4o + h2o. Alcohol. Oxygen. Aldehyde. Water. e. Atoms may be removed and replaced by others at the same time (substitution): C2H402 + 2C1 = C2H3C102 + HC1. Acetic acid. Chlorine. Monochloracetic 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 de- composition or transformation. Heat acts differently upon organic substances, some of which may be volatilized without decomposition, whilst others are de- composed by heat with generation of volatile products. This process of heating non-volatile organic substances in such a 284 CONSIDERATION OF CARBON COMPOUNDS manner that the ox}Tgen 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 molecule, than the substance which suffered decomposition ; in other 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 de- structive 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 gen- erated 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, so little heat is produced at a time that it can scarcely be noticed. Ho 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 he 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. Daring the process of decay the compounds mentioned above are finally produced, although many intermediate products are also generated. For instance: If a piece of wood be burnt, complete oxidation takes place: intermediate products are also formed chiefly in consequence of the destructive distillation DECOMPOSITION OF ORGANIC COMPOUNDS. 285 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 produced during common combustion. Common alcohol has the composition C2H60 ; in burning, it requires six atoms of oxygen, when it is converted into carbon dioxide and water: C2H60 + 60 = 2C02 -f- 3H20. 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, C2H40, is formed: C2H60 + o = C2H40 + h2o. This aldehyde, when further acted upon by oxygen, takes up an atom of this element, thereby forming acetic acid : 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, wdiich takes place in the living animal; this process will be more fully considered in the physiological part of this book. Fermentation and putrefaction. These terras 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 286 CONSIDERATION OF CARBON COMPOUNDS. 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 lower 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 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 C6II1206, 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 eause or prevent decomposition, inasmuch as the atmosphere is tilled with millions of minute germs of organic nature, which germs may act as ferments when in contact with organic matter under otherwise favorable conditions. DECOMPOSITION OF ORGANIC COMPOUNDS. 287 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 jars, tin cans, etc.), which, when tilled, are heated sufficiently to destroy any germs which may have been present. 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 also generally antiseptics, but 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, but 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 in- stance, 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 288 CONSIDERATION OF CARBON COMPOUNDS. organic substance, or remove hydrogen, or replace hydrogen. The following equations illustrate this action: C2H4 + 2Br = C2H4Br2. Ethylene. Bromine. Ethylene bromide. C2HbO + 2C1 = C2H40 + 2HC1. Aldehyde. Hydrochloric Ethyl alcohol. Chlorine. Aldehyde. Hydrochloric acid. Acetic acid. C2H402 -f 2C1 = C2H3C102 + HC1. Chlorine. Monochloracetic 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. 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, H02, for oxygen. As instances of the latter action, may be mentioned the formation of nitro- benzene and nitro-cellulose: Benzene. c6h6 + HNOg = c6h5no2 + h2o. Nitric acid. Nitro-benzene. Water. C6H10O5 + 3HN03 = C6H73(N02)05 + 3H20. The additional quantity of oxygen thus introduced into the molecules, renders them highly combustible, or even explosive. Cellulose. Nitric acid. Trinitro-cellulose. Water. 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 mainly 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 + KHO = KCH02. Carbonic oxide. Potassium hydroxide. Potassium formate. CLASSIFICATION OF ORGANIC COMPOUNDS. 289 Salts are formed: C2H402 + NaHO = NaC2H302 + H20. Acetic acid. Sodium hydroxide. Sodium acetate. Water. Fats are decomposed with the formation of soap: C3H5B(C18H3302) + 3NaHO = CsH#3HO + 3(NaC18H3302). Oleate of glyceril. Sodium hydroxide. Glycerin. Sodium oleate. Oxidation takes place, while hydrogen is liberated C2H60 + KHO = KC2H302 + 4H. Ethyl alcohol. Potassium hydroxide. Potassium acetate. Hydrogen, From compounds containing nitrogen, ammonia is evolved : NH2C2H30 + KHO = KC2H302 + NH3. Acetamide. Potassium hydroxide. Potassium acetate. Ammonia. Action of reducing agents. Deoxidizing or reducing agents, especially hydrogen in the nascent state, act upon organic sub- stances either by direct combination : C2H40 + 2H = C2H60. Etliene oxide.. Ethyl alcohol. or by removing oxygen (and also chlorine or bromine) : C7H602 + 2H — C7HfiO + H20. Benzoic acid. Ben/oic aldehyde. In some cases hydrogen replaces oxygen: Nitrobenzene. C6H5N02 + 6H = C6H5NH2 + 2H20. 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, ®^C. 2. Alcohols. These are unsaturated hydrocarbons or hydro- carbon residues in combination with hydroxyl, HO. For in- stance, ethyl alcohol, CgHf/HO, glycerin, C3Hm53HO, etc. 290 CONSIDERATION OF CARBON COMPOUNDS. 3. Aldehydes. Unsaturated hydrocarbons in combination with the radical COII; they are compounds intermediate between alcohols and acids, or alcohols from which hydrogen has been removed. For instance : Ethyl alcohol. Aldehyde. Acetic acid c2h60, c2h4o, c2h4o, 4. Organic acids. ITnsaturated hydrocarbons in combination with carboxyl, a radical having the composition C02II, 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- carbons, or, what is the same, by other alcohol radicals. For instance: H/ CjUj/ ’ C H3/ 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. i CH3CO\q C2H5\ , H\ H/U H/u — CH3CU/U 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: CgH1206, C6H10O5, etc. 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 hydrogen in ammonia by alcohol or acid radicals. For instance : ethyl amine, UH2.C2H5, urea, N2II4.CO, etc. The alkaloids belong to this group. 9. Cyanogen and its compounds. Substances containing the radical cyanogen, CN\ For instance : potassium cyanide, IvdST. 291 HYDROCARBONS. 10. Proteuls 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, C1I4, or benzene, C61I6, 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- 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 wTater : IOC02 + 8H20 = O10H16 -f 280. 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 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. Gfive 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. 292 CONSIDERATION OF CARBON COMPOUNDS. 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. Other hydrocarbons are found in nature as products of the decomposition of organic matter. Thus methane, CII4, 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, 02H2, which is formed when electric sparks pass between electrodes of carbon in an atmosphere of hydrogen. Fig. 39. 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 Flasks arranged for fractional distillation HYDROCARBONS. 293 organic bodies, such as alcohols, acids, amines, etc., and from derivatives of these substances. 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 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 liquids, known as fractional distillation, is, however, not absolutely complete, because traces of substances having a higher boiling-point are simultaneously volatilized 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 of 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 CnH2Q + 2 are known as paraffins, the name being derived from the higher members of 294 CONSIDERATION OF CARBON COMPOUNDS. 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, ch4, , B. P. 1 Sp. gr. Ethyl hydride or ethane, c2h6, [• gases. Propyl hydride or propane, c3h8, J Butyl hydride or butane, 1 ° c. Amyl hydride or pentane, c5h12, 38 0.628 Hexyl hydride or hexane, C6Hm, 70 0.669 Heptyl hydride or heptane, c7hJ6, 99 0.690 Octyl hydride or octane, 125 0.726 Nonyl hydride or nonane, C9H2o* 148 0.741 Decyl hydride or decane, c10h22, 1R6 0.757 Undecyl hydride or undecane, C„Hm, 184 0.766 Dodecyl hydride or dodecane, Cj.2H26, 202 0.778 Tridecyl hydride or tridecane, Ci3H28, 218 0.796 Tetradecyl hydride or tetradecane, 236 0.809 Pentadecyl hydride or pentadecane, c15h32, 258 0.825 Hexadecyl hydride or hexadecane, 280 etc. 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 substauces 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, C2H6i and C3H8, not otherwise, then thus: C-H “g C=HS I c=h2 ! C=H. C"H3 I c=h3 HYDROCARBONS. 295 In the next compound butane, C4H10, we have two possibilities explaining the structure of the molecule, namely, those : csh3 I C=:H2 I C=H, I C=H:J c=h3 C—H3—(JH—C=H3. Both these compounds are known, and termed normal butane and isobutane, respectively. The next member, pentane, C5H]2, shows three possibilities of constitution, thus: c=h3 I c=h2 I C=H2 I C H2 I t=Hs C^H.j I C=H3—C—H I c=h.2 I C=Ha c=h3 C=H:j—C—C=H3 c=h3 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 : 6Cu + CS2 + 2H20 = 2Cu2S + 2CuO + CH4. 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. 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 296 CONSIDERATION OF CARBON COMPOUNDS. so-called “combustion tubingapply heat and collect the gas over water. The decomposition takes place thus: 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 cc. 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 and how many volumes of atmospheric air are needed for the complete com- bustion of one volume of methane? NaC2H302 + NaHO = Na2C03 + CH4. Coal, Coal-oil, Petroleum. The name coal-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 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 wdll 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 it 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- HYDROCARBONS. 297 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 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. The liquids formed during the formation of coal are water and that mixture of hydrocarbons known as crude coal-oil or petroleum, which finds it way to the surface either from natural causes or is lifted up by suitable pumps. 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 C6II14, 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 298 CONSIDERATION OF CARBON COMPOUNDS. 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 kerosene, 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 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 350° 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 destructive 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. Gases ' Nitrogen . N. Ammonia . . KH, Carbonic oxide . . CO. Carbon dioxide . . co2. Hydrosulphuric acid . . h2s. , Hydrocyanic acid . HCN. HYDROCARBONS. 299 f Benzene • • c6h6. B. P. 80° Toluene . c7h8. 110 f Liquids Aniline . c6h.nh2. 132 j Acetic acid . . . c2h4o2. 117 Coal-tar -j Water . . h2o. 100 | Carbolic acid . . C6H60. 188 l Solids Kresylic acid . . C7H80. 201 Naphthalene C10IIg. 220 Anthracene C14Hi0. 360 Paraffin ■ C16H34 280 Solid residue Coke, chiefly carbon and inorganic matter. The gases are purified by condensing ammonia (and some other gases) by means of water, carbon dioxide and hydrosul- phuric acid by calcium hydroxide. The following is the com- position of a purified 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 (most 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 B, 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 CnII2n are termed olefines. To this series belong : Ethene or ethylene . . C.2H4. Propene or propylene . • C3H8 Butene or butylene • • Pentene or amylene • • C5H1O Hexene or hexylene C6Hl2 etc. 300 CONSIDERATION OF CARBON COMPOUNDS. Methene, CII2, 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, elhene 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 CnII2n_6, and all the derivatives of this group, including the 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 in a similar manner as fats or fat oils, from which they differ, however, by the disap- pearance of the produced stain after some time, 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 shall be considered. 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 ? ALCOHOLS. 301 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, HO. Any hydrocarbon may be converted into an alcohol radical by removal of one or more hydrogen atoms; methane, CII4, for instance, is converted into methyl, CII3, which, upon combining with hydroxyl, forms methyl alcohol, CII3IIO. 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 these isomeres) we have homologous series of alcohols. The isomeric alcohols also show different properties, and yield dif- ferent 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 the 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.HO I OH,. If hydroxyl replaces 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, C2H42HO, while glycerin, C3H53HO, is a triatomic alcohol. Alcohols correspond in their composition to the hydroxides of inorganic substances; both classes of compounds containing hydroxyl, HO, 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, KHO. If we represent any unsaturated hydrocarbon by Al.R. (alco- hol radical), the general formula of the alcohols will be : Monatomic alcohol Diatomic alcohol. /HO Al.Rii(„X \H0 Triatomic alcohol. /HO Al.RiHO \HO Al.Ri—HO or Al.RiHO Al.R«2HO Al.Riii3HO corresponding to KiHO Caii2H0 Bi*»3H0. 302 CONSIDERATION OF CARBON COMPOUNDS. 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 compound ethers mixed with volatile oils. The triatomic alco- hol glycerin is a normal constituent of all fats or fatty oils, and is therefore found in some 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 enters into combination with the alkali, whilst the alcohols are liberated according to the general formula: AcB>° + KH0 = AcK>° + A,-EH0- 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: Ethane. C2H6 + 2C1 = C2H5C1 + HC1. Ethyl chloride. C2H5C1 + KHO = KC1 + C2H5HO. 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, CII3HO = methyl alcohol; CHglSTaO = sodium methyl oxide or sodium methylate. The oxygen of alcohols may be replaced by sulphur, when com- pounds are formed known as hydrosulphides or mercaptans\ these ALCOHOLS. 303 bodies may be obtained by treating the chlorides of hydrocarbon residues with potassium sulphydrate : C2H-C1 + KHS = KC1 + C,H3HS. 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+iHO or CnH2n - 2O. Methyl alcohol . . CHsHO, B. P. 67° C. Ethyl “ • c2h5ho, 78 Propyl “ . C3H.H0, 97 Butyl “ . c4h9ho, 115 Amyl “ • c6huho, 132 Hexyl “ • 06h13ho, 150 Heptyl “ • 0th16ho, 168 Octyl “ . c8h17ho, 186 Nonyl “ • C9H19HO, 204 Cetyl “ • C)6H33HO, 50) Fusing- point. Ceryl “ • 027H..HO, 79 Melissyl “ • C30H61HO, 851 Methyl alcohol, CH3HO (Methyl hydrate, Methylic 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. Methyl alcohol mixes in all proportions with water; it dissolves resins and volatile oils as freely 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, C3HsH0 — 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- 304 CONSIDERATION OF CARBON COMPOUNDS. tating ethene with strong sulphuric acid, when direct combination takes place and ethyl sulphuric acid is formed: c2h4 + h2so4 = c2h5hso4. Ethene. Sulphuric acid. Ethyl sulphuric acid. Ethyl sulphuric acid mixed with water and distilled yields sulphuric acid and ethyl alcohol: C2H5HS04 + H20 = H2S04 + C2H5HO. Ethyl alcohol may also be obtained, as already mentioned, by treating ethyl chloride with potassium hydroxide: C2H5C1 + KHO = KC1 + C2H5HO. While the above methods for obtaining alcohol are of scien- tific 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 of grape-sugar under the influence of certain ferments (yeast) suffers decomposition, yielding carbon dioxide and alcohol: C6H1206 = 2C02 + 2C2H5HO. Glucose. Carbon dioxide. Ethyl alcohol. Experiment 43. Add to a solution of 25 grams of commercial glucose (grape- sugar) in 1000 cc. of water 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 Fig. 40. Liebig’s condenser with distilling-flask. ALCOHOLS. 305 leading into clear lime-water, contained in a small flask. After standing (a warm place should be selected in winter for this operation) a few hours fermentation will commence, which can be noticed by the 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 cc. 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 water to flow into h, 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 diluted alcohol a second and a third time, collecting the first portions of the distilled liquid separately, an alcohol is obtained containing but little water. These last quantities of water, amounting to about 14 per cent., cannot he removed by simple distillation, but may be separated 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 pare, absolute, or real alcohol. The alcohol of the TJ. 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 dilated 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 containing 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 substances immersed in it; to this property are due its coagulat- ing action on albumin, and its preservative action on animal 1 It is claimed that perfectly anhydrous alcohol has no odor. 306 CONSIDERATION OF CARBON COMPOUNDS. substances. The solvent powers of alcohol are very extensive, both for inorganic and organic substances; of the latter it readily dissolves essential oils, resins, alkaloids, and many other bodies, for which reason it is used in the manufacture of the numerous officinal tinctures, extracts, and fluid extracts. Alcohol taken internally in a dilute form has intoxicating properties; pure alcohol acts poisonously ; it lowers the tempera- ture 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 cc. of alcohol; add to the cold solution potassium hydroxide until the brown color of the solution disappears : a yellow precipitate of iodoform, CI1I3, forms. Many other alcohols, aledhyde, acetone, ect., show the same reaction. 2. Add to about 1 cc. 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 cc. of potassium dichromate solution add 0.5 cc. of sulphuric acid and 1 cc. 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 con- tain 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 unde- composed, such wines are known as sweet wines. Effervescent wines, as champagne, are bottled before the fermentation is cotn- ALCOHOLS. 307 plete; the carbonic acid is disengaged under pressure and re- tained in solution 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 beers in so far as the latter are not distilled, and therefore contain also non-volatile organic and inorganic substances, as 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; ram, by fermenting and distilling molasses; arrack, from fermented rice; gin, from various grains flavored with juniper berries. Amyl alcohol, C5HnH0. 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. Glycerin, Glycerinum, C3H53H0 == 92. Glycerin is the triatomic or tri-acid alcohol of the residue glyceryl, C3II5, formed by re- moval of three atoms of hydrogen from the saturated hydrocarbon propane, C3I18, and by combination of the residue with three times HO. 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 308 CONSIDERATION OF CARBON COMPOUNDS. 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. sw7eet, and neutral in reaction, soluble in wrater 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 decotnposition, 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. 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. Nitroglycerin, C,H.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 N02 replaces hydrogen in the glycerin, forming either mono- or tri-nitro-gly- cerin, 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. 309 ALDEHYDES. 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. 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 : C2n60 — 2H = 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 tw'o 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 CII3.CO.IIO ; the radical of acetic acid or acetyl is the group CII3.CO, and the hydride of acetyl is acetic aldehyde, CH3.COH. It is the group COII which is characteristic of, and found in, all aldehydes. Only a few aldehydes are of practical interest, as, for instance, acetic aldehyde, paraldehyde, and benzoic aldehyde, which latter substance will be more fully considered in connection with the aromatic substances. 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 CJELn + iHO. 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, 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? 310 CONSIDERATION OF CARBON COMPOUNDS. Acetic aldehyde, C2H40 or CH:JC0H. 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 = c2h4o + h2o. Experiment 44. Place into a 500 cc. flask, provided with 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 cc. of sulphuric acid, 24 cc. of water, and 6 cc. of alcohol. Chemical action begins generally without application of heat, and often becomes so violent that the liquid boils up, for which reason so large a 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 maybe obtained by repeated distillation. Use the distillate for silvering a test-tube by 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. (—6° 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, CXjIIjO.lSi’lIg, a beautifully crystallizing substance, with hydrocyanic acid to form aldehyde hydrocyanide, C2II4O.ClSf, and with many other substances. In the absence of such other substances 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, CcH1203. When a few drops of concentrated sulphuric acid are added to aldehyde, this becomes hot and solidifies 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. ALDEHYDES. 311 (253° F.), and is reconverted into common aldehyde by boiling it with dilute sulphuric or hydrochloric acid. Metaldehyde, (C2H40)x. 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 CC13.C0H (Trichloracetyl hydride). This substance may be looked upon as acetic aldehyde, C2II40, 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 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: C2H60 + 2C1 = CzH40 + 2HCI, and by the subsequent replacement of hydrogen by chlorine : C2II40 + 6C1 = CZHC1S0 + 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.H,0 = 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 312 CONSIDERATION OF CARBON COMPOUNDS. 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 alkalies into chloroform and a formate of the alkali metal: C2HC130 + KHO = KCHO, + CHCU. 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. 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 Fehliug’s solution a red precipitate is formed. Chloroform, Chloroformnm, CHC13 = 119.2 (Trichlormetliane, Di- chlormethyl chloride). When chlorine, bromine, or iodine is allowed to act upon methane, CI14, a number of substitution products are formed. Thus, if methane is considered as methyl hydride, CH3II, the first product of substitution is methyl chlo- ride, CII3CI; the second is monochlormethyl chloride, CII2C1C1; the third is dichlormethyl chloride or chloroform, CIIC12C1; 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 practical purposes by the above process, but by the action of bleaching-powder and calcium hydroxide on alcohol. The three last named substances, 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; ALDEHYDES. 313 the upper layer of chloroform is removed and treated with sodium carbonate (to remove any acids) and distilled over calcium oxide (to remove water). 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 alkaline 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. If the various intermediate steps of the decomposition are not considered, the process may be represented by the following equation : 4C2H60 + 8CaCl202 == 2(CHC13) + 3(Ca2CH02) + 5CaCl2 + 8H20. Alcohol. 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 should not give a precipitate with silver nitrate; for aldehyde by heating with solution of potassium hydroxide, which should not be colored brown ; for empyreumatic 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 314 CONSIDERATION OF CARBON COMPOUNDS. 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 arc added to an alcoholic solution of potassium hydroxide, a peculiar, offensive odor of benzo-isonitril, C6II5HC, is noticed. In 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 chloroform is expelled and decomposed in the heated glass tube, as stated above. What has been said above regarding antidotes to chloral holds O O 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 alkaline 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 cc. of water ; add to this solution 1 cc. of alcohol, heat to about 70° C. (158° F.), and add gradually 1 gram of iodine. A yellow crystalline deposit of iodoform sepa- rates. Sulphonal, (CH3)2C(C2II6S02)2, Dimethyl-diethyIsulphonyl-methane. It has been stated before that mercaptans are alcohols in which ALDEHYDES. 315 the oxygen is replaced by sulphur. Alcohols 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, C2II5IIS, when treated with nitric acid is converted into ethyl-sulphonic acid, C2H5HS03. The radical of this acid, known as ethylsulphonyl, C2II5S02, may, by indirect process, be caused to replace hydrogen in methane, CII4, 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 chapter, may be shown graphically thus : H I H—C—H I H Cl I H—C—Cl I Cl Methane. I I II—C—I I CH, I CH3—0—C2H5S02 I g2h5so2 Chloroform. Iodoform. Sulphonal 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. 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. Hive 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? 316 CONSIDERATION OF CARBON COMPOUNDS. 43. MONOBASIC FATTY ACIDS. General constitution of organic acids. When hydroxyl, HO, replaces hydrogen in hydrocarbons, alcohols are formed; when the univalent group C02II, 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, dibasic, and tribasic acids are formed by substituting one, two, or three hydrogen atoms by carboxyl. For instance: Hydrocarbons. ch4 Monobasic acids. ch3.coh2 Bibasic acids. prr /'C02H u*\co2h Methane. Acetic acid. Malonic acid. C2H6 c2h..co2h C /C02h Ethane. Propionic acid. Succinic acid. I The constitution of carboxyl is represented by 0=C—0—H, which shows that of the four affinities of the carbon atom, two are saturated by an atom of oxygen, one by hydroxyl, whilst one is unprovided for; any univalent hydrocarbon residue may attach itself to this unprovided affinity, when an acid is formed. Acids may, therefore, be looked upon 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 iustance, the radical is CII3CO, 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 hydro- gen 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. MONOBASIC FATTY ACIDS. 317 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: Ethyl alcohol. c2h5ho + o = c2h3ho + h2o. Acetic aldehyde. C2H3HO + O = C2H3O.HO. Acids are obtained from compound ethers by boiling them with alkalies, when salts are formed, which may be decomposed by sulphuric or other acids. For instance : Acetic aldehyde, Acetic acid. + KHO = C2H30\0 _L C„H,HO. 02H5/ 1 5 Ethyl acetate. Potassium hydrate. Potassium acetate. Ethyl alcohol 2(C2H3K02) + H2S04 = 2(C2H402) + K2S04. Potassium acetate. Sulphuric acid. Acetic acid. Potassium sulphate. Acids are also formed 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 for inorganic acids, viz., when 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 CONSIDERATION OF CARBON COMPOUNDS. tribasic organic acids are known, the two latter being capable of forming neutral, 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 upon heating the salt suffi- ciently for combustion. 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 oxygen of the hydroxyl by sulphur. The acids formed by this last reaction are known as tliio acids, for instance, thio-acetic acid, C2II4OS. 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: HN03 or N02.H0 Nitric acid. C2H402 or C2H3O.HO. Acetic acid. -^^2X0 c2hso\() c2u3o/u- Nitric anhydride. Acetic anhydride. Amido-acids are compounds obtained by replacement of a hydrogen atom by NII2; these compounds will be spoken of later in connection with amides. Fatty acids of the general composition, CnH2n02 or CuH2a+1C02H. Fusinq- Boilinq- « point. point. Occurs m: Formic acid, H C02H 4° 100° Red ants and some plants, etc. Acetic acid, c h3 co2h -(-17 118 Vegetable and animal fluids. Propionic acid, c2h5 co2h —21 140 Sweat, fluids of the stomach, etc. Butyric acid, c3 h7 co2h —20 162 Butter. Valerianic acid, c4 h9 co2h —16 185 Valerian root. Caproic acid, c5 HnCOaH — 2 205 Butter. (Enanthylicaeid. ,c6h13co2h —10 224 Castor oil. Caprylic acid, c7 h15go2h -(-14 236 Butter; cocoanut oil. Pelargonic acid, c8 u17co2u 18 254 Leaves of geranium. Capric acid, C9 H19(J02H 30 270 Butter. Laurie acid, cuh23co2e 43 y Cocoanut oil. Myristic acid, Gi3H270O2H 54 ... J Palmitic acid, 62 Palm oil, butter. Margaric acid, c16h33co2h 60 (Obtained artificially.) Stearic acid, c17h35oo2h 70 Most solid animal fats. MONOBASIC FATTY ACIDS. 319 Fusing- Bom0- Ormrsin- Arachidic acid, 2H point. 75° point. ] i Bebenic acid, C91 HiaCO,,FI 76 l ► Oils of certain plants. Hysenic acid, C24H4gC02H 77 J 1 Cerotic acid, c26h53co2h 80 j- Beeswax. Melissic acid, C29H59C02H 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: First member. Is liquid. Volatilized at 100° C. Strongly acid. Strongly odoriferous. Easily soluble in water. Produces no grease spot. Porms salts easily soluble without decomposition. Last member. Is solid. Not volatilized without decomposition. Scarcely acid. Odorless. Insoluble in water. Produces a grease spot. Porms salts which are insoluble or de- composed by water. 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.CH02 or CHO.HO. 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: CH,0 + 02 = CH202 + H20, Methyl alcohol. Formic acid by the action of carbonic oxide on potassium hydroxide: KIIO + CO = KCH02, by the action of potassium hydroxide on chloroform : CHC)3 + 4KHO = 3KC1 + 2H20 + KCH02, Potassium formate. by heating equal parts of glycerin and oxalic acid, when the latter is split up iuto carbon dioxide and formic acid, which may be separated from the glycerin by distillation : c2h2o4 = co2 + ch2o2. Oxalic acid. Formic acid. 320 CONSIDERATION OF CARBON COMPOUNDS. 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 then converted into carbon dioxide and water: CH202 + O = C02” + H20 Acetic acid, H.C2H302, or C2H3O.HO, 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 chiefly formed 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 80° C. (75° to 86° F.), and the liquid having passed through the shavings is repeatedly poured back in 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. MONOBASIC FATTY ACIDS. 321 Experiment 46. Add to 54 grams 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 cc. 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 a diluted acetic acid (about six per cent.), con- taining often other substances, such as coloring matter, compound ethers, etc. Vinegar was formerly obtained exclusively by the oxidation of fermented fruit-juices (wine, cider, etc.), the various substances 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 a diluted acetic acid. Vinegar should be tested for sulphuric and hydrochloric acids, which are sometimes fraudulently added. Acidum aceticum, Acidum aceticum dilution, and Acidum aceticum glaciale are the three officinal forms of acetic acid. The first- 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 C2II402.1I20. The addition of either acetic acid or of water causes the liquid to become lighter, so that, for in- stance, 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 a diluted 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 be easily calculated. (See also volu- metric methods in Chapter 37.) 322 CONSIDERATION OF CARBON COMPOUNDS. Analytical reactions. (Sodium acetate, NaC2.H302, may be used.) 1. Any acetate heated with sulphuric acid evolves acetic acid, which may be recognized by its odor. 2. Acetic acid 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, Potassii acetas, KC2H302 = 98. Sodium acetate, Sodii acetas, NaC2H302.3H2Q = 136. Zinc acetate, Zinci acetas, Zn2(C2H:!02).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. 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(C2II302)+2Pb0, 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. MONOBASIC FATTY ACIDS. 323 Cupric acetate, Cupri acetas, Cu2(C2H302).H20 = 199.2 (Acetate of copper). The commercial verdigris is a basic acetate of copper, Cu2(C2II302).Cu0, made by the action of diluted 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 also be made directly 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(C2II302), 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. 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 : 8ijS88> - + c»co. Calcium acetate. Acetone. The above graphic formula of acetone shows this substance to be dimethyl carbonyl or carbon monoxide, whose two available affinities have been satisfied by 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 assumed to be , R representing in this case any uni- valent radical. R—C—R II O 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 albuminous substances. Butyric acid is a colorless liquid, having a characteristic, un- pleasant odor; it mixes with water in all proportions. 324 CONSIDERATION OF CARBON COMPOUNDS. Valerianic acid, HC5Hy02 (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 : C5HnHO + 20 = hc5h902 + II20. Amyl alcohol. Yalerianic 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 three last-named compounds are white salts, whilst the ferric valerianate has a dark-red color; the ammonium salt is easily soluble in water, the three other compounds are insoluble or nearly so. Oleic acid, Acidum oleicum, HC18H3302 = 282. As shown by its formula, oleic acid does not belong to the above-described series of fatty acids of the composition CnII2n02, but to a series having the general composition CnH2n-202. Oleic 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 oleic acid is liberated. Ole'ic 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 oleic acid. 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 325 DIBASIC AND TRIBASIC ORGANIC ACIDS. 44. DIBASIC AND TBIBASIC ORGANIC ACIDS. Dibasic acids of the general composition CnH2a-204. Oxalic acid H2C204 or (C02H)2. Malonic acid H203H204 or C H2(C02H)2. Succinic acid H2C4H404 or C2H4(C02H)2. Pyrotartaric acid .... H2C5Hfi04 or (J3H6(C02H)2. Adipic acid H2C6H804 or C4H8(C02H)2. etc. Of these acids, only the first member is of general interest. Oxalic acid, H2C2042H20. This acid may be looked upon as a direct combination of two carboxyl groups, C02II—C02H, both atoms of hydrogen being replaceable by metals. Oxalic acid is largely distributed in the vegetable kingdom in the form of potassium, sodium, or calcium salts. It may be ob- tained 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 cc. nitric acid and 35 cc. of water upon 10 grams of sugar contained in a 200 cc. 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 alkaline oxalate, insoluble calcium oxalate is formed which is decomposed by sulphuric acid. 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 acid from alcohol and from wood. 428. What is vinegar, and what is glacial acetic acid? Give 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. Where and in what form of com- bination is oleic acid found in nature, and what are its properties? 326 CONSIDERATION OF CARBON COMPOUNDS. 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 + 2H2C20, = Pt + 4C02 + 4HC1. Analytical reactions. (Sodium oxalate, Na2C2Ch, maY he 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, Ag2C204. 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. 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 alkaline oxalates are soluble. Oxalates. The acid 'potassium oxalate, IyHC204, or its combina- tion with oxalic acid, is known under the name of salt of sorrel. Calcium oxalate, CaC204, is, in small quantities, a normal constituent of urine. Ferrous oxalate, ferri oxalas, FeC204.II20, is made by adding potassium or ammonium oxalate to ferrous sulphate, when double decomposition takes place, and the ferrous oxalate is precipitated as a pale yellow, crystalline, nearly insoluble powder. DIBASIC AND TRIBASIC ORGANIC ACIDS. 327 Dibasic acids with alcoholic hydroxyl. .OH Malic acid = C4HeO- or C2H3AC02H \C02H .OH />°H Tartaric acid = C4H606 or C2H2 V-co2h xco2h 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, Acidnm tartaricum, H2C4H406 = 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, the sugar is converted into alcohol; potas- sium acid tartrate is less soluble in alcoholic fluids than in water, and is, therefore, gradually deposited, forming the crude tartar, or argot 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 acids 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(KH(J4H406) + CaC03 = CaC4H406 + K2C4H406 + H20 C02. Potassium acid tartrate. Calcium carbonate. Calcium tartrate. Potassium tartrate. Water. Carbon dioxide. K,C4H406 + CaCl2 = CaC4H406 + 2KC1. Potassium tartrate. Calcium chloride. Calcium tartrate. Potassium chloride. 328 CONSIDERATION OF CARBON COMPOUNDS. 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 + H.2S04 = 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. Analytical reactions. (Potassium sodium tartrate, KNaCJPtOg, may be used.) 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 hydrate; 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 addition of potassium acetate. (Precipitate forms slowly.) 3. A neutral solution of a tartrate gives with silver nitrate a 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 is 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, KHC4H40G = 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 DIBASIC AND TRIBASIC ORGANIC ACIDS. 329 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. Potassium 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) + K2COs = 2(K2C4H406) + H20 + 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, KIfaC4H406. 4H20 = 282 (Tartrate of potassium and sodium, Pochette 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 25 grams of potassium acid tartrate to a hot solution of 20 grams of crystallized sodium carbonate in 100 cc. 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- bonate, causing the formation of sodium tartrate, while the escaping carbon dioxide causes effervescence. Antimony potassium tartrate, Antimonii et potassii tartras, 2(KSb0.C4H406).H20 = 684 (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 = 2K.Sb0.C4H4O|. + H20. Potassium acid tartrate. Antimonious oxide. Tartar emetic. CONSIDERATION OF CARBON COMPOUNDS. The fact that not antimony itself, but the group SbO replaces the hydrogen, has led to the assumption of the hypothetical radical ShO, termed antimonyl. 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 previously added 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 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, H3C6H50rH20 = 210. Citric acid is a tribasic acid containing three atoms of hydrogen replaceable by metals; its constitution may be expressed by the graphic formula: DIBASIC AND TRIBASIC ORGANIC ACIDS. 331 . HO //C02H c3h4 VCOsH x CO„H Citric acid is found in the juices of many fruits (strawberry, raspberry, currant, cherry, etc.), and in other parts of plants. It is obtained from the juice of lemons by saturating it with calcium carbonate and decomposing the calcium citrate thus formed by sulphuric acid. (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 h}rdrate, 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, renders the red solution green or reddish-green, whilst tartrates decolorize it. Citrates. Potassium citrate, K3C6H507.II20, Lithium citrate, Li3C6H507, and Magnesium citrate, Mg3 2(C6H507).14H02, are color- less substances, easily soluble in water and obtained by dissolving the carbonates in citric acid. 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(CfT1.07)61120. Obtained in transparent, red scales, by dissolving ferric hydrate in citric acid and evaporating the solution as mentioned heretofore. By mixing 332 CONSIDERATION OF CARBON COMPOUNDS. 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 CnII2n03, 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, ITC2IT303, 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, C2II402, 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 enselage, sauer-kraut, etc. The formation of lactic acid from sugar may be expressed by the equation: Sugar. C6II1206 = 2(HC,H60,). 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 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. ETHERS. 333 Ferrous lactate, Ferri lactas, Fe2(C3H503)3H.,0 = 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 hydroxy], HO, 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 HO, and that the term acid rad- ical is applied to that group of atoms in acids which embraces the hydrocarbon residue + CO. If we represent an alcohol radical by AIR, and an acid radical by AcR, the general formula of an alcohol is A1R.HO, or and °f an acid, AcR.HO, or AcR\q Ethers are formed by replacement of the hydrogen of the 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: KHO = hx° K2° = K/° HN°3 = NH2>° KN°3 = Nli/° Hydroxides. Oxides. Acids. Sails. Potassium hydrate. Potassium oxide. Nitric acid. Potassium nitrate. C2H5\q c2h3o\0 c2h30\ 02H5/U C2Jd5/U Ethyl alcohol. Ethyl ether. Acetic acid. Ethyl acetate, or acetic ether. 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, liochelle 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 wdiat process is lactic acid obtained; what are its properties? CONSIDERATION OF CARBON COMPOUNDS AlR\n H/U AlR\n A1R/U AcR\n AcR\n A1R/U Alcohol. Ether. Acid. Compound ether. 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: CH,.C,HS 0 = t?g»)0 C,HrCsHu.O = 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 hydroxyl 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 : 4_ n H T 4- N«T Nh/U 02tl5L _ + JNai- Sodium ethylate. Ethyl iodide. Ethyl ether. Sodium iodide. 4- OH T C2H5\q , -vr T JSTa/U 1 '-'"s1 “ CH,/U + iNai- Sodium ethylate. Methyl iodide. Ethyl-methyl ether. Sodium iodide. Ethers are also formed by the action of sulphuric acid upon alcohols; the sulphuric acid removing water in this case, thus: 2(C2H5HO) = + H^°' Ethyl alcohol. Ethyl ether. Water. Compound ethers are formed by the combination of acids with alcohols and elimination of water. (Presence of sulphuric acid facilitates this action.) \(3 4- \q C2H30\q . TT Q H/u 1 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 : C3HuC1 + CH£)o = + KC1. Amyl chloride. Potassium formate. Amyl formate. Potassium chloride. E THERS. 335 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.C16H310.0. The most important group of com- pound ethers are the fats and fatty oils, which are widely dis- tributed 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 chiefly due to ethers or compound ethers, which are formed during (and after) the fermentation by the action of the acids present on 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 ethers, termed fats, will be considered further on.) Ethyl ether, JEther, (C2H5)20 = 74 (Ether, Sulphuric ether, Ethyl oxide). The name of the whole group of ethers is derived from this (ethyl-) ether, in a similar manner as 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 unknown, and for the reason that sulphuric acid was used in its manufacture. Ether is manufactured by heating to about 140° C. (284° E.) a mixture of about equal parts of alcohol and sulphuric 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, in order to con- dense the highly volatile product of the distillation. 336 CONSIDERATION" OF CARBON COMPOUNDS. 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 cc., 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, llepeat 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 stopcock. 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- vinie 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 : Alcohol. c2h5ho + h2so4 = c2h5hso4 + h2o. Sulphuric acid. Ethyl-sulphuric acid. Water. C2H5HSO, + C2H5HO = H2S04 + (C2H3)20, Ethyl-sulphuric acid. Alcohol. Sulphuric acid. Ether., The liberated sulphuric acid at once attacks another molecule of alcohol, again forming ethyl-sulphuric acid, which is again decomposed, etc. Theoretically, a given quantity of sulphuric acid should, therefore, be capable 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 337 ETHERS. 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, aether 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 : C2H5HO + NaC2H302 + H2S04 = C2H5C2H302 + NaIIS04. 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 sulphuric acid 60 grams of sodium acetate. Introduce this mixture into a boiling flask, connect it with a Liebig’s condenser and distil about 50 cc. Re- distil the liquid from a flask, as represented in Fig. 39, page 292, and collect the portion which passes over at a temperature of 77° C. (170° F.) ; it is nearly pure ethyl acetate. 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, IIN03, the 338 CONSIDERATION OF CARBON COMPOUNDS. latter is converted into nitrous acid, IIN02, which in its turn acts on alcohol, the two substances combining with elimination of water, which is absorbed by the sulphuric acid: 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. c2h5ho + hno2 = c2h5.no2 + h2o. Amyl nitrite, Amyli nitris, C5HnN02 = 117 (.Nitrite of amyl). Made b\7 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 purified by agitating it with a solution of potassium carbonate and hydrate, 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: .HO Glycerin = C3H-.3(HO) or CsH6<-HO Stearic acid = C18H35O.IIO or C18H350\q H/ /(C18H350).0 Stearin or trislearin == C3H5.3(C18H350).03 or C3H5 —(C18H350).0 (^18^35 Whilst all natural fats are glycerin in which the three hydrogen atoms are replaced, we may by artificial means intro- duce but one or two acid radicals, thus forming: /(C]8H350)0 Monostearin = CSH-—HU \HO /(C18h350)0 Distearin = C3H5—(C18H330)0 \ho ETHERS. 339 Fats are often termed glycerides; stearin being, for instance, the glyceride of stearic acid. The principal fats consist of mixtures of palmitin, C3H5. 3(C16II310).03, stearin, C3II5.3(C18H350).03, and olein, C3H5. 3(C18H330).O3. Stearin and palmitin are solids, ole'in 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 tasteless substances, which stain paper permanently; they are insoluble 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 disagreeable odor, as, for instance, acrolein, C3II40, an aldehyde which in composition is equal to glycerin minus two molecules of water: C3H53HO — 2H20 = C3H40. Some fats keep without change when pure; since they, how- ever, generally contain impurities, such as albuminous matter, etc., they suffer 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 oleic acid. Drying oils are prevented from drying by albuminous 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- 340 CONSIDERATION OF CARBON COMPOUNDS. doms. They exist in plants chiefly in the seeds, while in animals they are generally found 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 olein. Butter consists of the glycerides of butyric acid, caproic acid, caprylic acid, and capric acid, which are volatile with water vapors and of myristic, palmitic, and stearic acids, which are not volatile. The principal non-drying vegetable oils (consisting chiefly of olein) 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 : C'3-H53(C18HS302) -J- 3NaH0 = 3(NaC]8H3302) -|- C3H53HO Oleate of glyceryl (olive oil). Sodium hydroxide. Sodium oleate (hard soap). Glycerin. Experiment 51. Boil 50 grams of olive oil with 60 cc. 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 cc. 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, Linimentum ammonice, and lime liniment, Lini- mentum caleis, are obtained by mixing cottonseed oil with water of ammonia and lime-water, respectively. The oleate of am- monium or calcium is formed, and remains mixed with the liberated glycerine. Lead plaster, Emplastrum plumbi. Chiefly lead oleate, Pb2ClsH3302. Obtained by boiling lead oxide with olive oil and water for several hours, until a homogeneous mass is formed. CARBOHYDRATES. 341 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 C26H43HO and known as cholesterin and iso-cholesterin. 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 with 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. 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 46. CARBOHYDRATES. 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 spirits 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? 342 CONSIDERATION OF CARBON COMPOUNDS. 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, C6II14Ofi, the chief constituent of manna: C6Hu06 - 2H = C6H1206. Mannite itself is formed from the saturated hydrocarbon C6II14, by replacement of 6 atoms of hydrogen by 6IIO ; its con- stitutional formula is, therefore, (C6H8)vi.6(HO). 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. 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. Glucoses. c6h12o6. f Grape-sugar, Saccharoses. c12h22ou. Cane-sugar, Amylases. c6h10o5. Starch, Origin - Vegetable 1 Fruit-sugar, 1 Mannitose, Melitose, Maltose, Dextrin, Gums, Animal l Inosite. Milk-sugar. Cellulose, Glycogen Groups of carbohydrates. CARBOHYDRATES. Grape-sugar, CcH120(! (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 also found 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 diluted mineral (sulphuric) acids, which convert starch first into dextrin and then into grape-sugar. Cornstarch 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 cc- 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 cc. of the solution is no longer pre- cipitated on the addition of 6 cc. 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 sul- phate. Filter, evaporate the solution to a syrup and notice its sweet taste. Glucose is generally met with as a thick syrup which crystal- lizes with difficulty, combining during crystallization with one molecule of water, but anhydrous crystals, closely resembling those of cane-sugar, are also known. Glucose is soluble in its own weight of water and 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, C6TI10O5; by stronger heating it loses more water and forms caramel, a mixture of various substances; it turns the plane of polarization to the right. Grape-sugar combines with various metallic oxides (alkalies, 344 CONSIDERATION OF CARBON COMPOUNDS. 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 alkalies. 3. By easily fermenting when yeast is added to the solution, alcohol and carbon dioxide being formed: C6H1206 = 2C2H5HO + 2C02. Fruit-sugar, C6H1206 [Levulose), occurs with glucose in swreet fruits and honey; it resembles glucose in most chemical and physical properties, but does not crystallize from an aqueous solution; it may, however, be obtained in white, silky needles from an alcoholic solution; it is generally met with as a thick syrup, is about as sweet as cane-sugar, and turns the plane of polarization 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 : Cane-sugar. -f- H20 = C6H1206 + C6H1206. Dextrose. Levulose. Mannilose, C6H1206. 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, blit does not ferment with yeast. Inosite, CGH1206 (.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 CARBOHYDRATES. 345 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. All 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- sistence 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 also be obtained 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, which 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 dextrose, cane-sugar forms compounds with metals, metallic oxides, and salts, which compounds are known as sucrates. 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 cc. of the cane-sugar solution 5 drops of hydrochloric acid and heat on a water- bath for half an hour. Again examine the solution with Fehling’s solution : a precipitate of cuprous oxide is now formed, proving the conversion of cane- sugar into glucose. Maltose, C12H22Ou, 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, 346 CONSIDERATION OF CARBON COMPOUNDS. 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 : Starch. 3(C6Hi0O5) + H20 = C12H22On + C6H10O5. Maltose. Dextrin. 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 dextrose. Maltose crystallizes, reduces alkaline copper solutions, and ferments with yeast. Melitose, C12II22Ou, is the chief constituent of Australian manna. Milk-sugar, Saccharum lactis, C12H22Ou + 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 solution of copper, from which it precipitates cuprous oxide. Starch, Amylum, C6H10O. = 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- 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 slowly deposits from the washings, and is further purified by treating it with water. CARBOHYDRATES. 347 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 CgITglOji. Starch is an important article of food, especially when asso- ciated, as in ordinary flour, with albuminous substances. Dextrin, CGHlu05 (.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 now extensively used as a substitute for gum- arabic in mucilage. Gums. These are amorphous substances of vegetable origin, soluble in water or swelling up in it, forming thick, sticky masses; they are insoluble in alcohol, and are converted into glucose by boiling with diluted sulphuric acid. Gum-arabic consists chiefly of the calcium salt of arabic acid, C6II10O5.II2O. Other gums occur in the cherry tree, in linseed or flaxseed, in Irish moss, in marsh-mallow root, etc. Cellulose, C6H10O5, perhaps Cl8H30O15 (Plant-fibre, Lignine). Cellu- lose constitutes the fundamental material of which the cellular 348 CONSIDERATION OF CARBON COMPOUNDS. 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 graduall}7 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 cellulose, three different substitution products may be obtained, which are distinguished as mono-, di-, and trinitro-cellulose: C6H10O5 + HN03 = C6H9(N02)05 + H20 C6H10O5 + 2HN0„ = C6H8(N02)205 + 2H20 C6H10O5 + 3HN03 = 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 pyroxylin is soluble in a mixture of ether and alcohol; this solu- tion is known as collodion. Neither the mono- nor trinitro-cellulose is soluble in a mixture of ether and alcohol. 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 CARBOHYDRATES. 349 in muscular tissue. Pure glycogen is a white, starch-like, amor- phous substance, soluble in water, insoluble in alcohol; by the action of diluted 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 the composition and the source whence they are obtained : Amygdalin, C20H27NO11, Bitter almonds, etc. Arbutin, Arbutus uva ursa. Cathartic acid, ? , Senna. Carminic acid, ? Cochineal. Colocynthin, 9 Colocynthis. Digitalin, ? Digitalis. Gentiopicrin, Boot of gentiana. Glycyrrhizin, Liquorice root. Helleborin, 36^42^6) Boot of hellebore. Indican, ? Indigo plant. Jalapin, Jalap resin. Myronic acid, C10H19NS2O10, Seeds of black mustard. Salicin, c13h18o7, Bark of willow. Scammonin, Besin scammony. Solanin, ? Various specimens of solanum. Tannins, Ci4H10O9, 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 contained in the leaves; this substance forms, however, the greater part of the “ digitalin crystallise nativelle.” Chiefly used now are two preparations, viz., the German or Merck’s digitalin, which consists chiefly of digitalein and is soluble in water and the amorphous digitalin, which contains chiefly digitalin with some digitoxin, is but sparingly soluble in water and ether, 350 CONSIDERATION OF CARBON COMPOUNDS. 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 shown 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 acid or its salts, potassium myronate is converted into dextrose, allyl mustard oil, and potassium bisulphate : KC10H18NS2O10 = C6H1206 + c3h5ncs + khso4 Potassium myronate. Dextrose. Allyl mustard oil. Potassium bisulphate. The univalent radical allyl, Cgllg1, is isomeric, but not identical with the trivalent radical glyceryl, C3II5Ui. The triatomic alcohol glycerin, C3H53IIO, may., however, be converted into the mon- atomic allyl alcohol C3II5HO, by various processes. From allyl alcohol an artificial allyl mustard oil is manufactured. Allyl sulphide, (C3Hs)2S, is the chief constituent of the oil of garlic. 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 either he 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- 47. AMINES AND AMIDES. CYANOGEN COMPOUNDS. Questions.—451. To which group of substances is the term “carbo- hydrates” applied? 452. State the general properties of carbohydrates. 453. Mention the three groups of carbohydrates, and the composition and character- istics of the members of each group. 454. Mention some fruits in which grape-sugar, and some plants in which cane-sugar is found. 455. 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 ob- tained ? 457. What is starch, what are its properties, by what tests can it be recognized, and what substance is formed when diastase or diluted acids act upon it? 458. Where is cellulose found in nature, and what are its properties ? 459. What three compounds may be obtained by the action of nitric acid upon cellulose, and what are they used for? 460. What substances are termed glu- cosides ? Mention some of the more important glucosides. AMINES AND AMIDES. 351 cellulose, nitro-benzene, etc., clo 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-eompounds 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 N^H, \H /C2h5 , \H /C2II5 n£c2h5i \H /C2h5 n(-c2h5, xc2h5 /CH3 n^c2h3 \c4h9 Or NHS, N(C2H5)H2, N(C2H5)2H, n(C2h5)3, nch3.c2h5.c4h9. Amines resemble ammonia in their chemical properties; they are, like ammonia, basic substances ; they combine with acids directly and without elimination of water, thus: Ammonia. Ethylamine. Diethylamine. Triethylamine. Methyl-ethyl-butylamine. NH3 + HC1 = NH4C1; N(C2H5)3 + HC1 = N(C2H5)3HC1 Triethylamine. Triethylamine chloride. Amides are substances derived from ammonia by replacement of hydrogen atoms by acid radicals. Thus: /H n(-H, \H /C2h3o NfH , \H /C2H30 n(cJh*o. N=H„. & 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. Ammonia. Acetamide. Diacetamide. Amido-acids are acids in which hydrogen has been replaced by NH2. Thus, amido-acetic acid, also known as glycocoll or glycine, NET is represented by the formula C2II3(NII2)02 or CII2X qq2II ; it is a substance which has both acid and basic properties, and is a 352 CONSIDERATION OF CARBON COMPOUNDS. 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 commercial ammonium carbonate. It is formed by the direct action of carbon dioxide upon ammonia. C02 + 2NH3 = c.nh4.nh2.o2. 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: C2H5.I + NH3 = HI + NHS C2H5. Ethyl iodide. Ammonia. Hydriodic acid. Ethylamine. C2H30.C1 + 2NH3 = NH4C1 + nh2.c2h3o. Acetyl chloride. Ammonia. Ammonium chloride. Acetamide. Amines may also be formed by the action of nascent hydrogen upon the cyanides of the alcoholic radicals: Methyl cyanide. CH3CN + 4H = NH2.C2H5 Ethylamine. Amines may in some cases be formed by the action of nascent hydrogen upon nitro-compounds; the manufacture of aniline depends on this decomposition : Nitro-benzene. C6H5N02 + 6H = 2H20 + NH2.C6H, 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 (compounds containing, besides the three elements named, also oxygen). But a small number of organic bases is found in the animal system, 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 de- ferred until benzene and its derivatives are spoken of. CYANOGEN COMPOUNDS. 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 c}’anogen compounds. The univalent residue cyanogen, —CEEN, or GN”, or Cy, 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 Turn- bull’s blue) containing it. The symbol Cy, frequently used in place of CN, 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: C1C1, Chlorine. HC1, Hydrochloric acid KI, Potassium iodide. HCIO, Hypochlorous acid. 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 or Cy2. The unsaturated radical CH does not exist as such in a free state, but combines whenever liberated with another CN, forming dicyanogen. It may 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 or HCy = 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 destructive distillation of coal, and is formed by a great number of chemical decompositions. For instance: 354 CONSIDERATION OF CARBON COMPOUNDS. By passing ammonia over red-hot charcoal: 4NH3 + 3C = 2(NH4CN) + CH4. Ammonia. Carbon. Ammonium cyanide. Methane. the action of ammonia on chloroform CHC13 + NH3 = HCN + 3HC1. Chloroform. Hydrocyanic acid. Hydrochloric acid. By heating ammonium formate to 200° C. (392° F.): Ammonium formate. NH4CH02 = HCN + 2H20. Hydrocyanic acid. Water. By the action of hydrosulphuric acid upon mercuric cyanide: Hg2CN + H2S = HgS + 2HCN. By the decomposition of alkaline cyanides by diluted acids: KCN + HC1 = KC1 + HCN. By the action of hydrochloric acid upon silver cyanide : AgCN + HC1 = AgCl -i- HCN. By distilling potassium ferrocyanide with diluted sulphuric acid : Potassium ferrocyanide. 2(K4Fe6CN) + 6(H2S04) = K2Fe26CN + 6(KHS04) + 6HCN. Sulphuric acid. Potassium ferrous ferrocyanide. Potassium acid sulphate. Hydrocyanic acid. Experiment 55. Place 20 grains of potassium ferrocyanide and 40 cc. of water into a boiling flask of about 200 cc. capacity ; provide the flask with a funnel- tube and connect it with a suitable condenser, the exit of which should dip into 60 cc. 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 funnel-tube a previously prepared mixture of 15 grams of sulphuric acid and 20 cc. of water. Apply heat and slowly distil until there is but 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, Acidurn hydrocyanicum dilutum. CYANOGEN COMPOUNDS. 355 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 oft' 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 diluted 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- 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 + 2COa. Potassium cyanide. Potassium carbonate. Potassium cyanide. Potassium cyanate. Iron. Carbon dioxide. Potassium cyanide is a white, deliquescent salt, odorless when perfectly dry, but emitting the odor of hydrocyanic acid when moist. Potassium cyanides and other alkaline 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, HaCN’.AgGN’, etc. 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. CONSIDERATION OF CARBON COMPOUNDS. 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 alkaline cyanides or thiosulphates, but insoluble in diluted nitric acid. Concentrated nitric acid dis- solves it with decomposition: HCN + AgN03 = 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 sulphocyanate of iron. (Excess of ammonium sulphide must be avoided.) 3. Hydrocyanic acid, or soluble cyanides, give, when mixed with ferrous and ferric salts and potassium hydrate, a greenish precipitate, which, upon being dissolved in hydrochloric acid? forms a precipitate of Prussian blue, Fe48Fe6CN. This reaction depends on the formation of potassium ferrocyankle 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 diluted 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- 357 CYANOGEN COMPOUNDS. liminary examination should, therefore, decide whether or not ferro- or ferricyanides 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 alkaline 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 alkaline cyanide: KCN -f- O — KCNO == Potassium cyanate. KCN -)- S = KCNS = Potassium sulphocyanate, The acids themselves may be liberated from their salts by diluted mineral acids. Sulpliocyanates 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 pres- ence can only be demonstrated by these reagents after the organic 358 CONSIDERATION OF CARBON COMPOUNDS. 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 FeCy6ix,Eindferricyanogen [Fe2vi(CFT)12i]viorFe2Cy12vi. These two radicals contain iron in the ferrous and ferric state respectively, and form, upon combining with hydrogen, acids which are known as hydroferrocyanic acid, H4Fe(CN)6 (tetrabasic), and hydroferricyanic acid, H6Fe2(CN)12 (hexabasic); the salts of these acids are termed ferrocyanides 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 carbonate 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, w’hich 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. Analytical reactions: 1. Perrocyanides 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 diluted sulphuric acid liberate hydrocyanic acid; with concentrated hydrochloric acid liberate hydroferrocyanic acid. 3. Soluble ferrocyanides give a blue precipitate with ferric salts (Plate I., 5): Potassium ferrocyanide. 3(K4Fe6CN) + 2Fe2Cl6 = 12KC1 + Fe4.3(Fe6CN) Ferric chloride. Potassium chloride. Ferric ferro- cyauide. 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. CYANOGEN COMPOUNDS. 359 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 (Bed prussiate of potash). Obtained by passing chlorine through solution of potassium ferrocyanide : 2(K4Fe6CN) + 2C1 = 2KC1 + K6Fe2(CN)ls. Potassium ferrocyauide. Chlorine. Potassium chloride. Potassium ferricyanide While apparently this decomposition consists merely in a re- moval 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 ferricyanide of iron or Turnbull’s blue: With ferric solutions no precipitate is produced by potassium ferricyanide, but the color is changed to a dark olive green. K6Fe2(CN)12 + 3(FeS04) = 3(K2S04) + Fe3Fe2(CN)12. Nitro-cyan-methane, CH2.CN.N02 (Fulminic acid). This substance may be looked upon as a derivative of methane, CII4, in which two atoms of hydrogen are replaced by cyanogen and IST02 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. 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- nogen, 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 360 CONSIDERATION OF CARBON COMPOUNDS. 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, CII4, or benzene, C6II6, 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 decom- position of the molecule, and in most cases this transformation 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 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: 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. 361 1 6\c/kc/2 5'/C\c^>Cn'3 I 4 H H\c/V II I h/u\c^\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, one nitro-benzene, C6H5N02, 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 IIO replace hydrogen in different positions : HO H\cAc/H° II I H/C\CA\H I H HO %AC/H II I h/U\c^°\ho I H HO H\ /Cn\ /H \cx II I H/(J\c^C\h L Ortho-position. 1.2. Meta-position. 1.3. Para-position. 1.4. Designating the hydrogen atoms in benzene with numbers, thus the above 8 compounds show that in one case the hydrogen atoms 1 and 2, in the second 1 and 8, in the third 1 and 4 have been replaced by HO. The compounds formed in this way are distinguished as ortho-, meta-, and para- compounds. The molecular formula of the above three compounds is C6II602, apparently indicating benzene in combination with two atoms of oxygen or dioxybenzene, actually they are di- 1 2 3 4 5 6 : C6II H II II II II, 362 CONSIDERATION OF CARBON COMPOUNDS. 1 2 hydroxy benzene, O/Ao-di-hydroxy benzene, C6II4IIOIIO, is 1 3 known as pyro-catechin, raeAz-di-hydroxy benzene, C6II4IIOIIO, as 1 4 resorcin, and jsara-di-hydroxy benzene, C6H4HOIIO, as hydroqui- none. Benzene series of hydrocarbons. By replacing the hydrogen atoms in benzene by methyl, CII3, a series of hydrocarbons is formed having the general composition CnH2n_6. To this ben- zene series belong: Benzene c6 h6 B, P. 80° C. Toluene c7 h8 = c6h5ch3 no Xylene c8 HI0 = C6H42CH3 142 Cumene . c9 h12 — C6H33CH3 151 Cymene = (C6H24CH3?) 175 Pen ta-methy 1-benzene CuH« = C6H5CH3 188 Hexa-methy 1-benzene Ci2H18 = Cg6CH3 202 The first four members of this series are found in coal-tar; the fifth member, cymene, C10HU, 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-methyl-benzene, but the para-methyl- propyl-benzene, CgH4.CII3.C3H7. This compound is of interest on account of its close relation to the terpenes and camphors, which will be spoken of later. Benzene, CflH6 (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 : C6H5.C02H + Ca2H0 = CaCOg + H20 + C6H6. 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 dis- tilled 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 BENZENE SERIES. 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 carbonate of the decomposing hydroxide being formed in both cases. 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° O. (177° F.) and solidifies at 0° C. (32° F.); it is an excel- lent solvent for fats, oils, resins, and many other organic substances. Nitro-benzene, C6H..N02. 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 + H20. Experiment 57. Mix 50 cc. sulphuric acid with 25 cc. nitric acid ; allow to cool, place the vessel containing the mixture in water, and add gradually 6 cc. of benzene, waiting after the addition of a few drops each time until the reaction is over. Shake well until all benzene is dissolved and pour the liquid into 300 cc. 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 name of essence of mirbane. It is manufactured on the 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, CH;j Benzyl, 1 Phenyl, ( c6h5 Ethane, Methyl-methane, }ch:).ch3 Toluene, 1 Methyl-benzene, j • C6H5.CH3 Methyl-hydroxide, Methyl alcohol, 1 CH.J.HO Phenyl hydroxide, 1 Penol, J c6h5.ho Glycerin, .HO c,H5fHO \ho Pyrogallic acid, /HO C6H3fHO \ho Acetic acid, ch3.co2h Benzoic acid, c6h5.co2h. Acetic aldehyde, CH3.COH Benzoic aldehyde, c6h5.coh CONSIDERATION OF CARBON COMPOUNDS. Ethyl-sulphonic acid, S02(^ Benzene-sulphonic acid, yn £J 5 Malonic acid, C H2^^q2^ C6H4X^2|| II Phtalic acid, C6H4^^q Tartaric acid, Salicylic acid, Ethyl ether, {cHr/O Phenyl ether, / C6H5\q \c6h5/u Methyl-ethyl ether, | ysX0 Methyl-phenyl ether, anisol, f C H3\q \ C6H5/ The following graphic formulas may serve to illustrate the constitution of some compounds and derivatives of aromatic H H\cAc/H H/C\C^^XH I H Hydrocarbons. HO H 6 H X .a H X XH I H Alcohols. co2H Hs A /H II I II/C \h I H A cids. Benzene, C6H6. Phenol or carbolic acid, C6H5.HO Benzoic acid, C6H5. CCMT. no2 H\ L H \c/ %c/ H I H/C\c^C\h I H HO I H\ .C H H C XHO I H co2h I H C C02H XCX X'C/ X A H/ \(A \h I H Nitro-benzene, 06H5N02. Resorcin, C6H4(HO)2. Phtalic acid, C6H4(C02H;2. ch3 I h\c/c^c/H h/C\0^\h A HO HXC/HO I c3h7 COH l H. Ax H \c/ A /A I H Cymene, methyl-propyl benzene, c6h4.ch3.c3h7. Thymol, C6H3.CH3.C3H7.HO. Benzaldeliyde, oil of bitter almond, C6H5.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 in the hydrocarbon molecule, and in the third column chiefly aromatic acids, formed by introducing carboxyl, C02H, or carboxyl 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 alcohols. Phenols differ from common alcohols in not yielding aldehydes or acids by oxidation. Carbolic acid, Acidum carbolicum, C6H5H0 = 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, C7Ii7IIO, and other 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. 366 CONSIDERATION OF CARBON COMPOUNDS. 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 : C6H5HO + NaHO = C6H5NaO + H20. As antidotes may be used olive oil or castor oil, a mixture of both, or a mixture of magnesia and oil. 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, C6H2Br3HO. 4. A fresh-cut slip of pine wood moistened with carbolic acid, and then exposed to hydrochloric acid fumes, turns blue on ex- posure to sunlight. 5. On heating with nitric acid it turns yellow, picric acid being formed. Creasote, Creasotum [Creosote). This is a product of the dis- tillation 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, C7H80, the second member of the phenol series. 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-sidphonic acid). Formed by dissolving carbolic acid in strong sulphuric acid: C6H5HO + H2S04 = HC6H5S04 -f- H,0. Sulphocarbolate of sodium, Sodii sulphocarbolas, NaC6H5S04.2H20, is obtained as a white soluble salt by dissolving sodium carbonate in the above acid. BENZENE SERIES. 367 Sulphonic acid has been spoken of before, when it was shown that mereaptans are converted into compounds termed sulphonic acids. These acids may be looked upon as derivatives of sulphurous acid, 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, ro/HO tu\HO Sulphuric acid, S02 Formic acid, CO/H lu\ho Sulphurous acid, S02' Acetic acid, u\ho Metbyl-sulphonic acid, SO., Any compound carbonic acid, CO ou\HO Any sulphonic acid, S02 According to this view, the above sulphocarbolic acid is actually phenol- sulphonic acid, its constitution being represented by the formula, S02\ Picric acid, C6H2(N02)3H0 (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 manu- factured 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. Resorcin, (Meta-dihydroxy-benzene). 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. C.HA or CtH/™ 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. 368 CONSIDERATION OF CARBON COMPOUNDS. Cymene, C10H14 or C0H4.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 C10If16, 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- 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 white solid substance of the composition CioII16HC1 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 cc. 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 BENZENE SERIES. 369 156° 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 cymenebothin 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 Clt)H160. Camphor, Clt)II160 (.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 maybe 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, 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-resin of the conifers, contains besides the oil of turpentine a resin called colophony, rosin, or ordinary resin, consisting chiefly of sylvic acid, C44IIfi405. Copaiva balsam consists of a volatile oil and a resin, the latter being principally copaivic acid, C20H30O2. Caoutchouc, C8H14, and gutta-percha, C1()H1(P 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. 370 CONSIDERATION OF CARBON COMPOUNDS. 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 C3H6.CH3.C3H7.H0 (Methyl-propyl phenol). 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 Umbellifene), 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 comparative 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 chloroform a violet color, which on heating soon changes into a beautiful violet-red. Benzoic acid, Acidum benzoicum, HC7H502 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, NH4C7II502, and sodium benzoate, NaC7II602.H20, are obtained. Both salts are white, soluble in water, and have a slight odor of benzoin. BENZENE SERIES. Oil of bitter almond, Oleum amygdalae amarae, C7HfiO or C6H5COH (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., hut 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: Cj0H27NOu + 2H20 = 2C6H1206 + HCN + C7II60. 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 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 amarce, is made by dissolving 1 part of the oil in 999 parts of water. Salicylic acid, Acidum salicylicum, HC7H503 or C6H4H0.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: C6H5HO + NaHO = C6H.NaO + H20. Carbolic acid. Sodium hydroxide. Sodium carbolate. 2(C6H5NaO) + C02 = C6H4Na0C02Na + C6H.HO. Sodium carbolate. Carbon dioxide. Sodium salicylate. Carbolic acid. CONSIDERATION OF CARBON COMPOUNDS. Sodium salicylate, thus obtained, is decomposed by hydro- chloric acid : CcHiNa0C02Na + 2HC1 = C6H4H0C02H + 2NaCl Sodium salicylate. Hydroch loric 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. (302° F.); it is a valuable antiseptic. Salicylic acid assumes a fine 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(NaC7lI503).II20, and lithium, salicylate, 2(LiC7II503).II20, both of which are white, soluble salts. Phtalic acid, CflH4.2(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-phtale'in : 2(C6HbO) + C8H403 = H20 + c20h]4o4. Phenol. Phtalic anhydride. Phenol-phtale'in. A solution of phenol-phtale'in 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-phtale'in serves as an indicator. Gallic acid, Acidum gallicum, HC7H.05 or C6H2(H0)3.C02H — 188. Obtained by exposing moistened gall-nuts 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 has a white, solid substance, forming long, silky needles; it has an astringent and slightly acidulous taste, and an acid reaction; it gives a bluish- BENZENE SERIES. 373 black color with ferric salts, and does not coagulate albumin; by heating, it is decomposed into carbon dioxide and pyrogallic acid, C61I603, a substance which is actually a tri-atomic phenol, CflH3.(TIO)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, gall-nuts, 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, having a faint acid reaction and astringent properties; they all precipitate albumin, alka- loids, ferric sals (bluish-black), and form with animal substances compounds which 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 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. Ilaphtalene, C10H8. The constitution of all benzene-derivatives, considered so far, may be explained by the introduction of radicals in benzene. Uaphtalene 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 HXc/xoAc/H i, i] i, A A H HO I I H. .C. .CL U \ \ II I I H H Naphtalene, CioHg. Naphtol, CioH7.IIO. Naphtalene has been mentioned as a product of the destruc- tive distillation of coal, and is obtained from that portion of coal-tar which boils between 180° and 220° C. (356° and 428° F.). CONSIDERATION OF CARBON COMPOUNDS. This distillate is treated with caustic soda and then with sulphuric acid and distilled with water vapor. When pure, naphtalene 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 naphtalene assumes, when ex- posed to light, a reddish or brownish color. Naphtalene is con- verted into phtalic acid by oxidizing agents. Naphtol, C10H7HO. This compound bears to naphtalene the same relation as phenol to benzene—i. e., hydroxyl replaces hydrogen in the respective hydrocarbons. Two isomeric naph- tols are known, which differ in their physical properties and in their physiological action. The naphtol 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. (547° F.), is soluble in about 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 naphtol are used as dyes, as, for instance, dinitro-naphtol, C10H5(NO2)2.HO, 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 naphtalene, for which reason it is mentioned 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 instance, with sodium hydroxide, forming the officinal santoninate of sodium, 2(NaC15H1904).7II20. Santonin solutions give a white precipitate with silver, zinc, and mercurous salts; with an alcoholic solution of potassium BENZENE DERIVATIVES CONTAINING NITROGEN. 375 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. 49. BENZENE DERIVATIVES CONTAINING NITROGEN. Aniline, Phenyl-amine, C,;H.lSrH2. The constitution of amines, to which class aniline belongs, has been considered in chapter 47. Aniline is found in coal-tar and in bone-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 cc. 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: CflH5N02 + 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. 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 of amyg- dalin, to which class of substances does it belong, and what are the products of its decomposition under the influence of einulsine? 478. Explain the process for the manufacture of salicylic acid from phenol, and state its properties. 479. Give composition and properties of naphtalene and naphtol? 480. Give tests for tannin, state the source from which it is derived and for what it is used. 376 CONSIDERATION OF CARBON COMPOUNDS. 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, 06II6, and toluene, C7II8. This mixture is first converted into nitro-benzene, C6II5]ST02, and nitro-toluene, C7II7N02, and then into aniline, C6II5NII2, and toluidine, C7HrNH2. 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: C6HjN + 2C7H9N + 30 = C20H19N3 + 3H20. 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 potas- sium 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. Aniline. Toluidine. Rosaniline. Antifebrine, Acetanilid, CbH9NO 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 “acid anilids.” If the radical used for replacing the hydrogen in aniline is acetyl, C2II30, the radical of acetic acid, the resulting compound is acetanilid, the constitution of which is represented in the Q JJ formula NH'0Va It is obtained by boiling together lor 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 BENZENE DERIVATIVES CONTAINING NITROGEN. 377 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, CnH12N20 or C9H6(CH3)2N20 (Dimethyl-oxyqidnizine). Hydrazine compounds are substances derived from the hypothet- ical body N2II4 (or NII2—JSTH2) 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.NH2, because it furnishes when heated with diacetic ether, n2Twn xx \r\ /O, a substance known as methyl-oxyquinizine, C10H10N2O. (Quinizine is the name given to a hypothetical base of the composition C9II10N2.) In methyl-oxyquinizine a second hydrogen atom may be replaced 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, but only in 50 parts of ether. 2 cc. of a solution of 1 part of antipyrine in 100 parts of w’ater 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 cc. of a solution of 1 part of antipyrine in 1000 parts of water give with a drop of ferric chloride a deep red color. Saccharine, C7H5S03N or CeH4.C0.S02NH (Benzoic sulphnide, Anhydro ortho-sulphamine-benzoic acid). This substance, discovered by Ira Remsen (not by Fahlberg, who manufactures the compound), is a derivative of benzoic acid, C6II5.CO.IIO, obtained from it by introducing the two bivalent radicals S02 and Nil with elimination of water. The constitution is, therefore, rep- resented by the formula Practically, saccharine is not not made from benzoic acid, but from toluol, C6II5.CfI3, by a series of rather complicated syn- thetical processes. 7 7 1. n TT /CO \-VTTT 378 CONSIDERATION OF CARBON COMPOUNDS. 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 substances are treated with ether, which is filtered off’ and evaporated, when the saccharine may be recognized by its taste in the remaining residue. Pyrrole, C4H5N. During the destructive distillation of certain nitrogenous matters (chiefly bones), a liquid, known as bone-oilr 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. 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, C4III4H. This com- pound has been used lately 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, tasteless and odorless, and contains of iodine 88.97 per cent. Pyridine, C,H5N. This substance has been mentioned above as being a constituent of the bone-oil. Other substances have been isolated from this oil and have been found to form a homologous series: Pyridine, C5H5N Picoline, C6HTlSr Lutidine, C?H9 N Collidine, C8HltN 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 hear to pyridine the same relation that benzoic acid bears to benzene, or that acetic acid bears to methane. 379 BENZENE DERIVATIVES CONTAINING NITROGEN. Thus, when nicotine is treated with oxidizing agents, nicotinic acid, C6II5lSr02, is obtained, which, when distilled with lime, breaks up into pyridine and carbon dioxide, thus: c6h5no2 = C5H5N + C02. The relation of nicotinic acid to pyridine, of benzoic acid to benzene, acetic acid to methane, may be shown thus: ch3.h c6h5.h c5h4n.h Methane. Benzene. Pyridine. ch3.co2h Acetic acid. c6h5.co2h Benzoic acid. o5h4n.co2h Nicotinic acid. Pyridine is also obtained together with another basic substance, termed quinoline, C9II7N, by distilling quinine or cinchonine 'with potash. These observations, showing an intimate relation- ship between alkaloids and the pyridine and quinoline bases, have lead to numerous experiments made with the view of either solving the problem of making alkaloids synthetically, or of ob- taining 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 odor, strongly basic properties, and a boiling-point of 116° C. (241° F.). Quinoline, C9H7N, 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 properties are less marked than those of pyridine. Boiling-point 237° C. (458° F.). Kairine, CUH15.N0.HC1. 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, CHI0N.O.CH3 {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 380 CONSIDERATION OF CARBON COMPOUNDS. 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 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 elements, but by direct combination of these acids with the alka- loids. 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 of 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 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 con- stituents of bone-oil. 488. State the composition of iodol. 489. Explain the relation existing between methane, benzene, pyridine, and the compounds ob- tained from these three bodies by introducing carboxyl. 490. Mention two processes by which, and two sources from which pyridine may be obtained. ALKALOIDS. 381 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-volatilve 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 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. 382 CONSIDERATION OF CARBON COMPOUNDS. 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 cc. 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 accurate volumetric de- termination of alkaloids. (In most cases the alkaloid replaces the potassium in the potassium-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 cc. This solution is poured gradually into 100 cc. 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 re- dissolve 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 volatile, it is obtained frara this solution by distillation, after having been liberated by an alkali. Non-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, as is generally the case, in very small quantities, is one of the most difficult tasks of VI. ALKALOIDS. 3 Morphine with solution of ferric chloride, [Page 38('.] 2 Morphine, with nitric acid, [rage 38C.] O o Codeine with sulphuric acid con- taining one per cent, of molybdic acid. [Page 387.] Quinine treated with chlorine water and ammonium hydrate. [Page 389.] 4 5 Strychnine with sulphuric acid and potassium dichromate. [Page 891.] Brucine dissolved in nitric acid and treated with stannous chloride. {Fage 391.] C 7 Atrophic treated with sulphuric ■ acid find potassium dichromate. \Fage 392.] 8 Verntrine treated with sulphuric acid. [Page 394.] ALKALOIDS. 383 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 evapo- rated 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 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 of 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 (deducted from the symptoms before death, or from the results of the post-mortem exami- nation) pointing to a certain poison, which, of course, facilitate his work con- siderably. Important alkaloids. a. Liquid and volatile alkaloids. Coniine, C8 HJ5N, Conium maculatum. Nicotine, C10H14N2, Tobacco plant. 384 CONSIDERATION OF CARBON COMPOUNDS. b. Solid and fixed alkaloids. Morphine, C17H19N03, 10.00 per cent. Codeine, c18h21no3, 0.25 u Thebaine, c19h21no3, 0.15 u Papaverine, c21h21no4, 1 00 a Narcotine, c22h23no7, 1.30 u In opium. Narceine, Pseudo-morphine, c23h29no9, Ci7Hi9N04, 0.70 ll The percentages given are an average, but Protopine, Codamine, Laudamine, Meconidine, c20h19no5, C20H23NO4, c21h27no4, C21H23N04, . less than 0.1 per cent. vary widely. Cryptopine, C2iH23N 05, Laudanosine, c21h27no4, J Quinine, C20H24N2O2 + 3H20, 1 Cinchonine, Quinidine, c19h22n20. isomere to quinine, i f In cinchona bark. Cinchonidine, isomere to cinchonine > J } Strychnine, Brucine, c21h22n2o2, C23H26N2Q4 + 4H20, In nux vomica. Solanine, ) Atropine, c17h23no3, In solanacese. Hyoscy amine, c17h23no3, i Cocaine, c„h21no4, Erythroxylon coca. Veratrine, Veratrum officinale. Aconitine, Aconitum napellus. Colchicine, c17h19no5, Colchicum autumnale. Berberine, c20h17no4, Berberis vulgaris. Hydrastine, Hydrastis canadensis. Piperine, c17h19no3, Pepper. Emetine, c28h40n2o5, Ipecacuanha root. Sinapine, c16h23no6, White mustard seed. Eserine or Physostigmine, }c15h21n3o2, Calabar bean. Pilocarpine, cuh16n2o2, Pilocarpus. Caffeine, c8 h]0n4o2, + h2o, Coffee, tea. Theobromine, c7 h8 n4o2, Seeds of theobroma cacao. Coniine, C8H15N, 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, ALKALOIDS. 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 theU. S. P. method, which is as follows: Triturate in a mortar 7 grams of opium, 3 grams of freshly slaked lime, and 20 cc. of water, until a uniform mixture results; then add 50 ce. 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 cc. and marked at exactly 50 cc.) until the filtrate reaches this mark. To this liquid (representing 5 grams of opium) add 5 cc. of alcohol and 25 cc. 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 cc. 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 cc. 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 hydrate liberates the alkaloids, most of which are precipitated, while morphine is redissolved by the excess of calcium hydrate; 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, Morphina, C17H19N03.H20 = 303 [Morphia). A white, crystalline powder, or colorless, shining, prismatic crystals, odorless, of a bitter taste, and an alkaline reaction; almost in- soluble in ether and chloroform, very slightly in cold water, soluble in 100 parts of cold and 36 parts of boiling 386 CONSIDERATION OF CARBON COMPOUNDS. 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 apomorphine, C17II17N02, a crystalline, solid alkaloid, valuable as an emetic. The hydrochlorate of apomorphine, C17II17N02.1IC1, 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 crystallization. The crude morphine thus obtained is purified by crystallization. Morphine combines with acids, and of the salts are officinal: Acetate of morphine, morphine acetas, C17H19N03.HC2H302 3H20. Hydroehlorate of morphine, morphinse hydroehloras, C1TH19N03.HC1.3H20. Sulphate of morphine, morphinae sulphas, (C17H19N0g)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.) 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 hydrates; the precipitated morphine is soluble in potassium or sodium hydrate, but not in ammonium hydrate. ALKALOIDS. 387 7. Neutral solutions of morphine afford yellow precipitates with the chloride of gold or platinum, with potassium chromate or clichromate, and with picric acid, but not with mercuric chloride. Codeine, Codeina, ClsH2lN03.H.,0 = 317. A white or yellowish- white, crystalline powder, sparingly soluble in cold water, easily soluble in alcohol and chloroform. Analytical reactions: 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.) 2. Codeine, dissolved in sulphuric acid, forms a colorless liquid, which, upon being warmed with a trace of ferric chloride, becomes deep blue. 3. Codeirie 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 chiefly combined with the alkaloids. 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 diluted 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, CONSIDERATION OF CARBON COMPOUNDS. termed kinic acid. The quantity and relative proportion of the alkaloids vary widely in different barks, but the officinal bark should not contain 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 quanti- tative 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 alka- loids in an uncombined state, is dried at a temperature 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 hydrate. 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) diluted solution of sodium hydrate until exactly neutral, when the “effloresced sulphate of quinine,” (C20II24N2O2)2.TI2SO4.2H2O, 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 separa- tion 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. Quinine, Quinina, C20H24N2O2.3H2O = 378. This formula repre- sents tlie crystallized alkaloid, but it is also known as anhydrous, ALKALOIDS. 389 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, Quininse 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, Quininee bisulphas, (C20H24N'2O2)H2SO4.7H2O = 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, C20H24N2O2.HBr.2II2O == 440.8 Valerianate of quinine, C20H24N2O2.C5H10O2.H2O = 444. The above 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 dis- solving ferric hydrate and quinine in citric acid, evaporating, etc. Analytical reactions for quinine. 1. Quinine or its salts, dissolved in water or in diluted 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. 3. Solutions of quinine give with water of ammonia a white 390 CONSIDERATION OF CARBON COMPOUNDS. 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, C20H24N2O = 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 diluted acids. By dissolving the alkaloid in sulphuric acid is obtained : Cinchonine sulphate, Cinchonince sulphas, (C20H24I72O)2H2SO4.2H2O = 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 hark of different varieties of strychnos, and is generally obtained from nux ALKALOIDS. 391 vomica. Strychnine is a white, crystalline powTder, 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 diluted acids. By dissolving it in sulphuric acid the officinal strychnine sul- phate, Strychnince sulphas, (C21II22N202)2.H2S04.7II20 = 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 in nitric acid without 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, when collected, washed, and heated with concentrated sulphuric acid, shows the play of colors described in test 2. 5. ISTeutral solutions of strychnine give yellow precipitates with the chlorides of gold and platinum and with picric acid, a white precipitate with mercuric chloride. Brucine, C23H2rN204.4H20. 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 VL, 6); chlorine water colors brucine bright red, changed to yellowish- brown by ammonium hydrate. Atropine, Atropina, C17H23N03 = 289. Occurs in belladonna; it is a white, crystalline powder, having a bitter and acrid taste, 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, (C17II23N03)2.II2S04, 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 dicbromate (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 adding now 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 hydroxide, until supersaturated. Hyoscyamine, C17H23N03. 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 belong- ing to the sol an acese. Hyoscyamine resembles atropine closely in most of its chemical, 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 atropine 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. 393 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 wdth acids in sealed tubes is decomposed into methyl alcohol, benzoic acid, and ecgonine, showing it to be methyl-benzoyl-ecgonine : C„HnN04 + 2H20 = CH3IIO + C6H5C()2H + 09H15NO3. Cocaine. Methyl alcohol. Benzoic acid. Ecgonine. Ecgonine is found in the coca leaves as benzovl-ecgonine, C9H15(C7H50)N03 + 4II20; 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 Of the various salts of cocaine, the hydrochlorate, C17II21N04. HC1, has been chiefly used. 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 tem- perature of 100° C. (212° F.). The anhydrous salt fuses at 182° C. (360° F.) and is readily soluble in water; this salt solution 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, mer- curic 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.) 394 CONSIDERATION OF CARBON COMPOUNDS. 3. Boil a small quantity of cocaine solution for a few minutes with dilute sulphuric acid; neutralize carefully with potassium hydroxide and then add a few7 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 potassium permanganate (1 part salt in 330 parts of water); a beautiful violet, crystalline precipitate of cocaine per- manganate is produced. Aconitine, C33HwN012? 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, C37H53NOu. 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 varying ALKALOIDS. 395 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 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, C2uH17N04. Found in a number 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 water, 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 num- ber of other substances, as, for instance, with alcohol, ether, chloroform, etc. Some of these compounds crystallize well, as, for instance, berberine-chloroform, C2IH17H704.C[IC13. The al- coholic solution of a berberine salt treated with yellow ammonium sulphide forms crystals of berberine hydrogen polysulphide, having the composition (C2iri17X04) JI2S6. Caffeine, Caffeina, C8H]0N4O2.H2O = 212 (Theine), occurs in coffee, 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 396 CONSIDERATION OF CARBON COMPOUNDS. 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 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, C4I112X2, from cadavers ; parvoline, C9II13lSr, 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 ptomaines is intimately connected with or most likely due to the existence of certain forms of bacteria. 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? 397 ALBUMINOUS SUBSTANCES OR PROTEIDS. 51. ALBUMINOUS SUBSTANCES OB PTOTEIDS. 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 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 C144H224H736044S2, which represents 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 “ “ 17.4 “ Oxygen . 21.8 “ “ 24.0 “ Sulphur . 0.8 “ “ 1.5 “ Of other properties may be mentioned : 1. They are amorphous, colorless, odorless, and nearly tasteless substances, incapable of dialysis. 2. They easily undergo that decomposition known as putre- faction. 3. Some are soluble in water, others only in water containing alkalies, acids, or other substances, whilst some are insoluble. 4. They are not volatile without decomposition. 5. The soluble proteids are converted into insoluble modifica- tions either by heating to 60° or 70° C. (140° or 158° F.), or by the addition of mineral acids, alcohol, or certain metallic salts. This process of converting soluble into insoluble proteids is called coagulation ; and proteids when once coagulated will not return to their original soluble form without suffering some alteration. 6. They are converted into peptones by the action of gastric juice. (See later.) 398 CONSIDERATION OF CARBON COMPOUNDS. Analytical reactions. (Use a solution made by dissolving some of the white of an egg in about 10 parts of water, and filtering.) 1. Proteids are colored yellow by warm nitric acid, the color changing to orange with ammonia. 2. Milton’s reagent colors them purple-red on heating. This reagent is a solution of mercuric nitrate, containing some excess of nitric acid; it is best made by dissolving 1 part of mercury in 2 parts of nitric acid of a specific gravity of 1.42, and diluted with 2 volumes of water. 3. A few drops of cupric sulphate solution and then potassium hydroxide added, give a violet color. 4. A few drops of solution of 1 part of cane-sugar in 4 parts of water and then strong sulphuric acid added, produce a purple color. 5. They are often precipitated by highly diluted acids, but redissolved by boiling with strong hydrochloric acid, forming a violet-red solution. The precipitated proteids are also generally dissolved by caustic alkalies. 6. They are also precipitated by tannin, carbolic and picric acids, by potassium ferrocyanide and acetic acid, by lead acetate, mercuric chloride, and by most salts of heavy metals. (The use of egg-albumin in cases of poisoning by metallic compounds depends on this property.) Classification. Our present unsatisfactory state of knowledge regarding prote'ids, the close resemblance which they show in properties, and the difficulties which are met with in separating them in a pure state, make it difficult to arrange these bodies properly. Three principal groups may, however, be distin- guished ; they are: I. True albumins. II. Fibrins. III. Caseins. Serum-albumin. Blood-fibrin. Milk-casein. Egg-albumin. M uscle- fibrin. Serum-casein. Plant-albumin. Plant-fibrin or gluten. Plant-casein or legumin. Soluble in water and pre- Insoluble in water ; solu- Not coagulated by heat, cipitated (coagulated) ble in water containing but by diluted acids, by warming their rolu- certain neutral salts, al- and also by the mucous tion to 60° or 70° C. kalies or acids. They be- membrane of the stom- (140° or 158° F.). come generally insoluble as soon as they leave the living organism. ach of the calf (tennet). ALBUMINOUS SUBSTANCES OR PROTEIDS. 399 True albumins occur in the whites'of birds’ eggs, in milk, in the plasma of the blood, chyle, lymph, in the juices of muscles, in serous and nutritive liquids; they are also found in the juices of plants. Solutions of albumin become turbid at 60° C. (140° F.), and are coagulated at or below 75° C. (167° F.); the presence of a little free acid facilitates precipitation, whilst strongly alka- line solutions are not precipitated by heating. (The presence of too much acid may also prevent precipitation.) During the coagulation some sulphuretted hydrogen is generally liberated, indicating a decomposition. Coagulated albumin is dissolved by strong solutions of alka- line hydroxides; compounds of albumin with an alkali, so-called alkali-albumins, are found in vegetable and animal fluids. Albumin is also precipitated by picric acid, metaphosphoric acid, and by mercuric chloride. Serum-albumin is the most abundant albuminous substance in animal bodies, and may be obtained from blood (after having separated the fibrin) by heating to 70° C. (158° F.), when it coagulates. It is an almost white, or pale yellow, elastic sub- stance. Pathologically it occurs in urine. Egg-albumin differs but little from the former, but may be dis- tinguished from it by being coagulated by ether, which does not affect blood-albumin. It exists in solution in the white of eggs, where it is contained in a network of delicate membrane. The yolk of egg contains a substance in solution called vitellin, an albuminous substance containing also phosphorus; it is probably a mixture of albumin and casein; it is precipitated by heating to 75°-80° C. (167°-176° F.), or by alcohol, which latter decomposes it into albumin and lecithin, a peculiar glyceride containing phosphorus, but no sulphur. Vegetable albumin exists in nearly all vegetable juices, and is the most valuable constituent of vegetables used as food. It is coagulated at 61°-63° C. (142°-146° F.), and by nearly all acids. Globulins are proteids which are coagulated by heat, like true albumins, but differ from them by not being soluble in pure water. They are soluble in dilute solutions of sodium chloride (1 per cent.) and are precipitated from such solutions by passing 400 CONSIDERATION OF CARBON COMPOUNDS. a current of carbon dioxide through them. The above-mentioned vitellin belongs to this group, as also a substance found in the lens of the eye and termed crystalline. Blood-fibrin is found in the blood, chyle, lymph, and in many serous exudations; it coagulates (clots) as soon as the blood leaves the organism, and may be obtained from coagulated blood by whipping with a bundle of twigs, and washing the separated fibrin with water. It is, when recently obtained, a white, gelatinous, tenacious mass, consisting of numerous minute fibrils; when dried it becomes hard and brittle. It is insoluble in water, alcohol, and ether, but swells up and dissolves slowly in diluted acids. Whether or not fibrin exists as such in the blood, or is pro- duced by the decomposition of another substance when blood leaves the organism, is a question not yet decided; it is, however, highly probable that there exist in the blood two substances, known as paraglobulin and fibrinogen, which combine together (forming fibrin) as soon as the blood leaves the organism. Muscle-fibrin or muscle-protoplasm is a liquid contained in the muscles; after death this liquid coagulates, becomes solid (rigor mortis), and this insoluble body is termed myosin or flesh-jibrin. Vegetable fibrin or gluten exists in many parts of vegetables, and is best obtained from wheat-flour by kneading it on a sieve with water, when the starch passes through and gluten remains as a soft, elastic mass, insoluble in water, alcohol, and ether. It is probably a mixture of several proteids. Milk-casein, most likely an alkali-albumin, is the principal albuminous substance of milk, in which it occurs in solution. Casein is precipitated by acids, alcohol, many metallic salts, and by rennet; it is soluble in alkalies. Vegetable casein or legumin occurs in considerable quantities in the seeds of leguminosse, such as peas and beans, which contain nearly 25 per cent.; it is also found in almonds, various nuts, etc. It shows reactions very similar to milk-casein. Peptone is a term assigned to the products formed by the action of gastric and pancreatic juices upon proteids during the process ALBUMINOUS SUBSTANCES OR PROTEIDS. 401 of digestion. Peptones are soluble in water, insoluble in alcohol; the neutral aqueous solution is precipitated by alcohol, but not by heat, acids, or alkalies. Peptones are capable of dialysis, or of diffusion through membranes, whilst prote'ids are not. Whilst peptones are looked upon as but slightly altered albumins by some scientists, they are considered by others as mixtures of leucine, C6H13N02, tyrosine, C9HnH03, asparaginic acid, etc. Haemoglobin (Hemato-crystallin, Hosmato-globulin). This sub- stance is the coloring agent of the blood; it resembles the prote'ids in many respects, but differs from them in being crys- tallizable and in containing iron. Its composition has been found to correspond to the formula C600H960H154OmFeS3. The most characteristic feature of a solution of haemoglobin is its power of absorbing various gases; it absorbs oxygen in con- siderable quantities, thereby assuming a bright-red color, but gives up the oxygen again when treated with deoxidizing agents. Accordingly, we distinguish between common or reduced haemo- globin, and oxyhaemoglobin ; by means of oxidizing and reducing agents the one body can readily be converted into the other. Solutions of oxyhaemoglobin show a bright-red or scarlet color, those of haemoglobin are much darker and of a purple tint. Upon the absorption of oxygen by the haemoglobin of the blood in the lungs, and the deoxidation of the haemoglobin by the tissues, depends the process of respiration, which will be spoken of later. Haemoglobin absorbs certain other gases, for instance, carbonic oxide, nitrogen dioxide, and hydrocyanic acid more readily than oxygen, and the poisonous properties of these gases are, to some extent, due to their rendering haemoglobin incapable of taking up oxygen. Haemoglobin is soluble in water, dilute solutions of albumin, off the alkalies and their carbonates, and in sodium or ammonium phosphate. It is insoluble in strong alcohol, ether, and in the volatile and fatty oils. With the spectroscope both oxyhaemo- globin and reduced haemoglobin show characteristic absorption bands. Haemoglobin may be obtained in beautiful red crystals, which differ in shape, and solubility in water, according to the species of animal from whose blood they were obtained. Haemoglobin may be decomposed by boiling with alcohol (or 402 CONSIDERATION OF CARBON COMPOUNDS by other agents) into albumin and a substance called hcematin, C34H35lSr405Fe, which is soluble in acidified alcohol. Hsematin is a bluish-black powder, which forms with hydrochloric acid a crystalline compound, hcemine, which fact is made use of in a characteristic microscopical test for the presence of blood. Animal cryptolites. This term is applied to a number of animal substances of an unknown composition, but resembling somewhat the albuminoids in their properties. Their character- istic feature is the power of effecting changes in other organic substances, but the true cause of this action is unknown. The most important cryptolites are pepsin, ptyalin, and pancreatin. Pepsin is the active principle of gastric juice, capable of con- verting albumin readily into soluble peptones. Saccharated pepsin, Pepsinum saccharatum, is officinal. Pepsin, obtained from the mucous membrane of the stomach of the hog, is mixed with powdered sugar of milk; this mixture is a white powder, not completely soluble in water, but readily and completely dissolves on the addition of a small quantity of hydrochloric acid. One part of saccharated pepsin dissolved in 500 parts of water, acidu- lated with 7.5 parts of hydrochloric acid, should dissolve at least 50 parts of hard-boiled egg-albumin, in 5 or 6 hours, at a temperature of 38°-40° C. (100°-104° F.). Experiment 62. Boil an egg in water for 10 minutes. Rub the coagulated albumin through a No. 30 wire sieve ; place 10 grams of this albumin and 0.1 gram of pepsin in a 200 ce. flask. Add 100 cc. of a dilute hydrochloric acid (made by mixing 15 cc. of hydrochloric acid with 985 cc. of water), set the flask in a water bath and digest at a constant temperature of 38°-40° C- (100°- 104° F ), stirring occasionally. The pepsin will gradually dissolve the albumin. Should any portion of the latter remain undissolved after five hours’ digestion, it should be determined by collecting, washing with water, drying at the ordinary temperature and weighing it. As it is difficult, however, to bring the undissolved albumin in exactly the same condition in which it was originally used, it is a better plan to make a series of tests of the pepsin, with different proportions of albumin, until the maximum amount which the pepsin is capable of dissolving has been found. Ptyalin is a compound found in saliva, and having the property of converting starch into maltose. Pancreatin is the term applied to the active principles of the pancreatic secretion, which are capable of converting starch into sugar, albumins into peptones, neutral fats into emulsions, and also into glycerin and fatty acids. (For details, see next chapter.) ALBUMINOUS SUBSTANCES OR PROTEIDS. 403 Gelatinoids. To this group belong a number of substances occurring in bones, skins, horns, hair, nails, feathers, etc., and having generally the property of forming a jelly with water. The organic matter in bones, usually called ossein, contains, besides an albuminous substance, the two gelatinoids collagen and gelatin, an impure mixture of which forms common glue. Questions.—501. To which class of substances is the term prote'ids applied, and which elements enter into their composition ? 502. By what processes are albuminous substances formed in nature, and where do they occur? 503. State the general properties of albuminous substances. 504. How are prote'ids acted upon by heat, nitric acid, and Millon’s reagent? 505. Into which three groups may proteids be classified, and how do they differ from each other? 506. Men- tion some true albumins ; state where they are found, and by what tests they are characterized. 507. Which substance is the cause of the clotting of blood, and how may that substance be obtained? 508. Where is animal, and where is vegetable casein found? 509. What elements are found in haemoglobin, where does it exist, and what are its characteristic properties? 510. What is pepsin, and how does it act upon albuminous substances? VII. PHYSIOLOGICAL CHEMISTRY. 52. CHEMICAL CHANGES IN PLANTS AND ANIMALS. General remarks. Physiological chemistry is that part of chem- istry which has more especially for its object the various chemical changes which take place in the living organism of either plants or animals. It considers the chemical nature of the different substances used as “food,” follows up the changes which this food undergoes during its absorption and assimilation in the organism, and treats finally of the products which are eliminated by it. The chemical changes taking place in the organism are either normal (in health) or abnormal (in disease). The abnor- mal products formed under abnormal conditions are generally termed “pathological ” products. Difference between vegetable and animal life. As a general rule, it may be stated that the chemical changes in a plant are pro- gressive or constructive, in an animal regressive or destructive. That is to say, plants take up as food a small number of inorganic substances of a comparatively simple composition, convert them into organic substances of a more and more complicated composition with the simultaneous liberation of oxygen, whilst animals take up as food those organic vegetable substances of a complex composition, assimilating them in their system, where they are gradually used (burned up) and finally discharged as waste products, which are identical (or nearly so) with those sub- stances serving as plant food. Plant food. Carbon dioxide. Water. Ammonia, nh3. Nitrates, m*no3. Phosphates Sulphates Chlorides f Calcium. ) i Magnesium, j j Sodium. Potassium. Waste products of animal life. Carbon dioxide. W ater. Urea, CO(NH2)2. Urates, Ma;C5H2N403. f Calcium. Phosphates » i ,, r 1 Magnesium. Sulphates of -j godium Chlorides J 1 „ . 1 Potassium. 405 CHEMICAL CHANGES IN PLANTS AND ANIMALS. Formation of organic substances by the plant. As shown in the preceding table, plants take up the necessary elements for organic matter from a comparatively small number of compounds. All carbon is derived from carbon dioxide; hydrogen chiefly from water ; oxygen from either of the two substances named, as well as from the various salts; nitrogen either from ammonia, nitrates or nitrites; while sulphur and phosphorus are derived from sulphates and phosphates respectively. These substances are taken into the plant chiefly by the roots, the assimilation of the necessary mineral constituents being facilitated by an acid secre- tion (discharged from the roots) which has a tendency to render these salts, present in the soil and surrounding the roots, soluble. Water having absorbed more or less of carbon dioxide, of ammonia or ammonium salts, and of nitrates, phosphates, and sulphates of potassium, calcium, etc., enters the plant through the roots by a simple process of diffusion, and is carried to the various green parts of the plant (chiefly to the leaves), where, under the influence of sunlight, a chemical decomposition and the formation of new compounds take place, the liberated oxygen being discharged directly through the leaves into the atmosphere. It is difficult to explain fully the process of the formation of highly complex organic compounds in the plant, because we know so little in regard to the intermediate products which are formed. It is, however, fair to assume that the various com- pounds above mentioned as plant food are first decomposed (with liberation of oxygen) in such a manner that residues or unsaturated radicals are formed, which combine together. From these compounds, produced at first, more complicated ones will be gradually formed by replacement of more hydrogen, oxygen, or other atoms by other residues. The following equations, while not showing the various radicals and intermediate compounds formed, may illustrate some of the results obtained by the plant in forming organic compounds: co2 + h2 0= h2co3 H2C03 — 0 == H2C02 = Formic acid. 2C02 + H20 = H2C205 H2C205 — O == H2C204 = Oxalic acid. fiC02 + 6H20 = C6H12018 C6H12018 — 120 = C6H1206 = Glucose. 406 PHYSIOLOGICAL CHEMISTRY. 10CO2 + 8H20 = C]0H16O28 C10II16O28 — 280 = C10H16= Oil of turpentine. 10CO2 + 4H20 + 2NH3 = C10H14O24N2 C10Hi4O24N2—240 = C10H14N2= Nicotine. The above formulas show that the formation of organic com- pounds in the plant is always accompanied by the liberation of oxygen, and it may be stated, as a general rule, that no organic substance (produced in nature) contains a quantity of oxygen sufficient to convert all carbon into carbon dioxide and all hydro- gen into water, which fact also explains the combustibility of all organic substances. Why it is that the living plant has the power of forming organic substances in the manner above indicated, we know not, and we know very little even in regard to the means by which the living cell accomplishes this formation, but we do know that sunlight is that agent, the action of which is indispensable for the plant in the formation of more complicated organic sub- stances from simpler ones. Decomposition of vegetable matter in the animal system. It has been stated above, that the process of chemical decomposition taking place in the animal system is chiefly regressive or destruc- tive, that is to say: the substances formed in the plant are taken into the animal system, where they are assimilated, and then gradually oxidized by the inhaled atmospheric oxygen, thereby being converted into simpler forms of combination which are finally eliminated as waste products. It has been shown above how a molecule of glucose which is formed in the plant requires not less than 6 molecules of carbon dioxide, and the same number of molecules of water for its for- mation, 6 molecules of oxygen being eliminated. A molecule of glucose taken into the animal system undergoes the reverse process; by combining there with 6 molecules of oxygen it is converted into 6 molecules of carbon dioxide and the same number of molecules of water, thus : C8H1206 + 120 = 6C02 + 6H20. Animal food. The food taken by animals is (besides water and a few of its mineral constituents) all derived from vegetables, but it is taken from them either directly or indirectly ; in the latter case it has been previously taken into and assimilated by other animals, as in case of food taken in the form of meat, milk, CHEMICAL CHANGES IN PLANTS AND ANIMALS. 407 eggs, etc. While some animals (herbivora) feed upon vegetable, and some (carnivora) upon animal food exclusively, others are capable of taking and assimilating either. The fact that animal food is derived from vegetable matter, renders it superfluous to state that the elements taking an active part in the formation of either vegetable or animal matter are identical. Of the total number of 67 elements, only 14 are found as necessary constituents of the animal body. These elements are carbon, hydrogen, oxygen, nitrogen, sulphur, phosphorus, chlorine, fluorine, silicium, calcium, magnesium, sodium, potas- sium, and iron. A few other elements, such as aluminium, manganese, copper, etc., are sometimes found in the animal system, but they cannot be looked upon as normal or necessary constituents. The various kinds of animal food are derived chiefly from three groups of organic substances, viz., carbohydrates (sugars, starch, etc.), fats, and albuminous or nitrogenous substances, The inorganic substances, such as phosphates, chlorides, etc., required by the animal in the construction of bones, for the liberation of hydrochloric acid in the gastric juice, etc., are generally found as constituents of various kinds of food or are derived from drinking water. Milk contains all the necessary organic or inorganic constituents; bread is rich in phosphates, which latter are also found in smaller or larger quantities in nearly all kinds of vegetable and animal food. Food has a twofold office, viz., to build up or nourish the whole body, and to maintain the animal heat. Of the heat produced by the oxidation of the various foods, after they have been assimilated by the system, a certain amount escapes, whilst another quantity is employed in working the in- voluntary machinery of the body (motion of the heart, lungs, intestinal canal, etc.), and the rest is available for conversion into voluntary muscular actions. Whilst the nitrogenous substances have primarily the task of continuously replacing the wear and tear of the nitrogenous tissues, they also serve to keep up the animal heat and consequently the involuntary or voluntary motion. To some extent, the animal body may be regarded as a com- plicated machine, in which the potential energy, supplied by the food, is converted into actual energy of heat and mechanical labor. The main difference is that in our machines the fuel 408 PHYSIOLOGICAL CHEMISTRY. serves as the source of energy only, while in the body the food is first mainly changed into tissue (thus building up and renewing the body constantly), serving as fuel afterward. While in the best steam-engine only one-tenth of the fuel is utilized as mechanical work, over one-fifth of the energy of the food is real- ized in the human body. The relative proportions in which the two kinds of food are taken by animals depend upon the nature of the animal and upon its particular condition of existence. Below are given in column A the daily quantities of dry food required to maintain a grown person in good health, with neither loss nor gain in weight, while the figures in column B refer to the quantities of dry food for a working man of average height and weight: A. B. Albuminous substances . . 100 grams. 130 grams. Fats ..... . 100 “ 85 “ Carbohydrates . 240 « 400 “ Inorganic salts . 25 “ 30 *• Water . 2600 “ 2600 “ The table below shows that 900 grams (about 2 pounds) of bread, 340 grams (f pound) of lean meat, and 57 grams (2 ounces) of butter will supply the quantities of solid food required in a day by an active laborer: Albuminous substances, Bread (900 grams). 74 grams, Lean meat (340 grams). 66 grams. Butter (57 grams). Bread, meat, and butter. 140 grams, Fats . 14 “ 12 “ 50 grams. 76 “ Carbohydrates 460 “ 460 “ Inorganic salts 22 “ 17 “ 39 - In providing a diet, it must be borne in mind that the digesti- bility of a food is more a measure of its nutritive value than its elementary composition. Different foods show great differences in the rapidity and completeness with which they are absorbed. Thus eggs, fresh meat, white bread, and butter are absorbed and assimilated more readily than pork, rye bread, potatoes, green vegetables, and bacon. The relative proportions of nitrogenous and non-nitrogenous matter in various kinds of food are shown in the following table: CHEMICAL CHANGES IN PLANTS AND ANIMALS. 409 Sweet potatoes Nitro- genous. . 1 Non-nitro- genous. 17 Pork . Nitro- genous . 1 Non-nitro genous. 3 Rice. . 1 12 Fat mutton . 1 2.7 Carrots . 1 11 Peas (dried) . 1 2.5 Potatoes . . 1 10 White beans . 1 2.3 Bread . 1 5.0-6.8 Milk . . 1 2.2 Flour . 1 5.0-6.5 Beef . . 1 1.7 Turnips . . 1 6 Cheese . 1 0.7 Onions . 1 6 Meat . . 1 0.5-1.5 Oatmeal . . 1 5.5 Yeal . . 1 0.1 Cocoa . 1 5 White of egg . 1 0 Nutrition of animals—Digestion. In the process of nutrition four phases may be distinguished, viz.: Digestion, absorption (assimilation), respiration, and elimination of waste products. It has been stated before that foods are divided into two classes, inorganic and organic, and that the latter are subdivided into albuminoids, carbohydrates, and fats. As a rule, the in- organic foods are taken into the body without chemical change. Before the organic foods can be absorbed, they have to undergo digestion. This is the process by which organic compounds, capable of acting as foods, are so altered that they may be absorbed. The first part of the process of digestion is accomplished in the mouth and consists in the breaking up of the food by the teeth and mixing it with saliva, the process being known as mastica- tion. In addition, the saliva, to a limited extent, converts starch into maltose. This action of the saliva is due to its ferment ptyalin. Other functions of the saliva are to keep the mucous membrane of the mouth moist, and to lubricate the food bolus. After being masticated, the food is passed into the stomach, where it comes in contact with the gastric juice. The two active principles of the gastric juice are free hydrochloric acid, which is present in about 0.2 per cent., and a ferment, pepsin. The albu- minoids are the only compounds affected by the gastric juice. The free acid first converts them into syntonin, which is soluble in dilute acids, but is insoluble in water, or solutions of neutral salts. The pepsin converts the syntonin into peptones, which, as stated in Chapter 51, are dialyzable, and soluble in water, dilute acids, dilute alkalies, and neutral solutions. Starch cells and fat globules are set free by the gastric juice acting upon their albu- minous envelopes. After the food has been acted upon by the gastric juice it forms 410 PHYSIOLOGICAL CHEMISTRY. a very turbid mixture, chyme, which, by the contraction of the stomach, is forced through the pyloric orifice into the small in- testine. Here it soon comes in contact with the bile and pancreatic juice. So far as is known, the bile takes no part in the process of digestion. It has been thought to assist in the emulsification of fats, but there is much doubt as to whether it actually does do so; probably its principal function is to assist absorption. Pancreatic juice is alkaline in reaction and contains most likely four ferments, trypsin, steopsin, amylopsin, and one unnamed. Much the larger portion of fats are simply emulsified by the pancreatic juice. Under the influence of steopsin a small portion is broken up into fatty acids and glycerin. For example : C3H5.B(C18H350)03 + 3H20 = 3C18H3602 + C8H53HO. Stearin. Water. Stearic acid. Glycerin. A portion of the alkali present then unites with the fatty acid to form a dialyzable soap. Amylopsin acts upon starches, converting them into maltose. The change is one of hydration : Starch. 2C6H10O5 + H20 = C„HbOu. Maltose. Any albuminoids that may have escaped the action of the gastric juice are converted into peptones by trypsin. In this process, which is apparently one of hydration, the intermediate compound syntonin is not formed. The fourth, assumed and unnamed ferment of pancreatic juice, has the property of coagu- lating casein. In addition to the above considered digestive fluids, there are the intestinal juices. The}7, are, however, so small in quantity and so difficult of investigation that little is known of their action. They probably have properties similar to the pancreatic juice, though weaker than that secretion. By the combined action of the various digestive fluids, the chyme is gradually converted into chyle. It is a milky white, or occasionally a yellowish fluid, having an alkaline reaction, a faint smell, a saltish taste, and a specific gravity varying from 1007 to 1022. It is this chyle which is absorbed by the intestinal villi, and forms the material from which the blood is constantly renewed. Absorption. All forms of food that are dialyzable when taken into the stomach, or that are there converted into dialyzable com- CHEMICAL CHANGES IN PLANTS AND ANIMALS. 411 pounds, are, for the most part, taken directly into the radicles of the portal vein by osmosis. The products of intestinal digestion make their way partly into the bloodvessels and partly into the lacteals. It has been shown that the larger portion of fats which are not dialyzable get into the lacteals as fats, and not as dialyz- able soaps. At present wTe do not understand the process by which this absorption of emulsified fats takes place. All material absorbed by the lacteals is carried by the thoracic duct and poured into the left subclavian vein. All material taken up by the portal vein is first carried to the liver. In the liver the maltose undergoes dehydration, being thereby converted into an insoluble compound, isomeric with starch, and termed glycogen. This glycogen is stored up in the liver, and when wanted in the system is reconverted into soluble maltose. Respiration. The most important changes in respired air are the changes in the quantities of oxygen and carbon dioxide. Pure air, after being dried, contains by volume of oxygen 20.8 per cent., of nitrogen 79.2 per cent., and a quantity of carbon dioxide (0.04 per cent.) so small that it need not be considered. When 100 volumes of air have been breathed once, it gains a little more than four parts of carbon dioxide and loses a little more than five parts of oxygen; so that the composition of 100 volumes of inspired air, when inspired, is, after being dried, oxygen 15.4 parts, nitrogen 79.2 parts, and carbon dioxide 4.3 parts by volume. Much the greater portion of the oxygen lost from respired air enters into combination with the haemoglobin, a small portion is absorbed by the blood serum. The immediate source of the carbon dioxide is the blood, in which it exists partly in simple solution and partly in a loose combination with some unknown body. The blood is the common carrier of the body; from the ali- mentary canal it receives ultimately all the food material; from the lungs it receives oxygen, and carries them to tissues for their sustenance; from the tissues it receives the products of destruc- tive metamorphosis, and carries them to their proper organs of elimination. The bright red color of the arterial blood is due to oxyhsemo- globin. A large portion of this oxygen absorbed by the haemo- globin is given up to the tissues as the blood passes through the capillaries, and we have then the reduced haemoglobin to which 412 PHYSIOLOGICAL CHEMISTRY. is due the dark color of the venous blood. (The action of haemo- globin as a carrier of oxygen is not unlike that of nitrogen dioxide in the process of manufacturing sulphuric acid.) In some way, not understood, the blood plasma takes up the carbon dioxide from the tissues and carries it to the lung. It has been shown that the dark color of the venous blood is not due to the presence of carbon dioxide, but to a decrease of the oxygen. In suspension in the plasma are found the food materials on their way to different portions of the body. A small percentage of peptones is found, but the quantity is so insignificant in pro- portion to the total amount absorbed, that it is extremely probable that they are converted into the more common forms of albumin. Waste products of animal life. The changes which the food suffers after having been absorbed by the animal system are ex- tremely complicated, and far from being thoroughly understood. Numerous products and organs are formed and nourished from and by the blood; among them muscular-, nerve-, and brain- substance, excretions and secretions, such as milk, saliva, bile, gastric and pancreatic juice, etc., also bones, teeth, hair, and many others. Most of these substances (some excretions, such as milk and others, excepted) suffer a constant oxidation in the system, and are finally eliminated as waste products; in regard to the inter- mediate compounds formed in the tissues, we know little, but it is highly probable that the reduction of the complicated food material to the simple forms of the waste products is very gradual. There are three channels through which the waste products are given off; they are the lungs, the skin, and the kidneys. By the lungs are eliminated chiefly carbon dioxide and some water, by the kidneys urine (which is a weak aqueous solu- tion of urea, uric acid, urates, phosphates, chlorides, and sulphates of calcium, magnesium, sodium, potassium, etc.), and by the skin are constantly eliminated carbon dioxide and water, and during the process of sweating also more or less of the constituents of urine. Chemical changes after death. After the death of either a plant or animal, a chemical decomposition commences which finally results in the formation of those inorganic compounds from which the plant originally derived its food, viz., carbon dioxide, ANIMAL FLUIDS AND TISSUES. water, ammonia, sulphates, phosphates, etc. This decomposition of a dead body is generally a simultaneous fermentation or putrefaction, aided by decay or slow combustion. There are numerous intermediate products formed, which differ according to the nature of the decomposing substance, or according to the conditions (degree of temperature, amount of moisture and air present, etc.) under which the decomposition takes place. During the decomposition of dead vegetable matter (especially of moist wood) the intermediate products are frequently called humus, which substance (or better mixture of substances) forms the chief part of the organic matter in the soil. During the decomposition of dead animals, the sulphur is first eliminated as hydrosulphuric acid, and a number of other inter- mediate products have been shown to be formed; among them certain organic bases called ptomaines or cadaveric alkaloids, sub- stances which have been spoken of in Chapter 50. The de- composition of organic matter may be prevented under conditions which have been mentioned heretofore in connection with putre- faction. 53. ANIMAL FLUIDS AND TISSUES Constituents of the animal body. The animal body consists mainly of three kinds of matter, viz., water, organic and inor- ganic matter. It contains of water, about 70 per cent., of organic matter 25 per cent., and of inorganic matter about 5 per cent. The water may be determined by drying a weighed quantity in an air-bath at a temperature of 100° to 105° C. (212° to 221° F.); the inorganic matter is estimated by burning the dried substance, and the inorganic matter (ash) by weighing the residue. Some Questions.—511. What is the difference between vegetable and animal life in a chemical point of view? 512. Mention the chief substances serving as plant food. 513. Explain the formation of organic substances in the plant. 514. What elements enter into the animal system as necessary constituents? 515. The members of which three groups of organic substances are chiefly used as food by animals? 516. Give a full explanation of respiration. 517. Explain the chemical changes which food suffers during digestion. 518. Mention the principal fluids which are secreted by various organs of the animal body, in order to facilitate or cause digestion. 519. What are the waste products of animal life, and through which channel are they eliminated? 520. What is the final result of the decomposition of dead plants or animals? 414 PHYSIOLOGICAL CHEMISTRY. of the elements which are left in the inorganic residue have, however, been actually constituents of organic compounds; iron, for instance, which is left in the ash, has been chiefly a con- stituent of haemoglobin; sulphur left as a sulphate, may have been a constituent of albumin, etc. Tfce relative quantities of the three constituents in some of the animal fluids and tissues is shown in the following table: Water. Organic and •volatile matter. Inorganic resi due (ash). Saliva. . 99.50 0.32 0.18 Gastric juice . 99.43 0.33 0.24 Pancreatic juice. . 94. ? 4. ? 2. ? Bile .... . 85.92 13.30 0.78' Chyle. . 91.80 7.40 0.80 Lymph . 91.80 7.40 0.80 Pus .... . 87.00 12.20 0.80 Cows’ milk . 87.00 12.25 0.75 Human milk . 86.80 12 85 0.35 Blood .... . 79.50 19.70 0.80 Blood-corpuscles . 54.60 44 68 0.72 Blood-serum . 90.50 8.68 0.82 Urine. . 95.70 3.00 1.32 Bone (varies widely). . 22.00 26.00 52 00 Dentine . 10.00 25.00 65 00 Enamel . 0.4 3.60 96.00 The complex nature of the various organic matters has been referred to in the preceding chapter, and will be more fully con- sidered below; but it may be mentioned here, that some of these organic substances (or groups of substances) may be sepa- rated by a successive treatment of the animal matter with various solvents. Thus, by treating with ether or carbon disulphide, all fats may be extracted; by treating them with alcohol and water successively other substances (generally termed extractive matter or extractives) are dissolved, which may be obtained by evaporating the solution. Among the extractives are found kreatin and kreatinin, urea, uric acid, organic salts, etc. After the fatty matter and the extractives have been removed, there remains an elastic and somewhat horny mass, which consists chiefly of prote'ids (albu- min, fibrin, globulin, etc.). The complete separation of all substances is extremely diflicult on account of the great similarity in properties of many of these 1 The metals in combination with the biliary acids not included. ANIMAL FLUIDS AND TISSUES. 415 substances, and the rapid changes which they sutler when acted upon by solvents or chemical agents. As the nature or composition of many of the inorganic salts present in the animal tissues is changed during the burning off of the organic matter, it is necessary to determine them either in the aqueous solution (extract) or by subjecting the animal matter to dialysis, by which process they may be more or less completely separated from the organic matter, which is left in the dialyzer, whilst the salts pass through the membrane. Experiment 63. Cut a mouse (or some other small animal) into fragments, weigh and place them in a weighed dish; expel all water by heating the dish first over a water-bath, and then in an air-bath at a temperature of about 110° C. (230° F.) until there is no longer any loss in weight; this loss is the amount of water present in the animal. Disintegrate the dry pieces further by grind- ing in a mortar and cutting with a pair of scissors, mix well and ignite a few grams in a platinum crucible until all organic matter is burned off and a white or nearly white residue of inorganic matter is left. (Complete combustion is facilitated by cooling and heating alternately several times, since the animal charcoal, left after the first ignition, readily absorbs atmospheric oxygen, which aids in combustion when again heated.) From the results obtained by the ignition of the portion of dry animal matter calculate the organic and inorganic matter of the animal operated on. Digest the inorganic residue with water, filter and test in the filtrate for chlorides by silver nitrate. Dissolve the residue upon the filter in dilute hydro- chloric acid and test portions of this solution for phosphoric acid by means of ammonium molybdate ; for iron by potassium ferrocyanide ; for sulphuric acid by barium chloride and for calcium by adding an excess of sodium acetate and then ammonium oxalate. Weigh a few grams of the dried animal matter and digest it in a stoppered flask with about 10 parts of ether for an hour; filter and repeat the operation once or twice ; allow the ether to evaporate in a small dish, previously weighed; the residue left consists chiefly of fats, which may be recognized by their physi- cal properties. Digest the animal matter left from previous treatment twice with hot alcohol and twice writh boiling water; evaporate the alcoholic and aqueous solutions separately ; they contain the so-called extractives and soluble salts. Dry the exhausted animal matter completely as before and weigh it; it con- sists chiefly of insoluble salts and albuminous substances. Ignite and burn as stated above. The loss represents mainly albuminoids. Notice the difference between the percentage of inorganic matter left now and in the determination made before ; this difference represents the soluble inorganic compounds. Blood. Two kinds of blood are distinguished, the arterial or oxidized and the venous or deoxidized blood. Arterial blood as it is present in the system, or immediately after it has been drawn from the body, is a red liquid of an alkaline reaction and 416 PHYSIOLOGICAL CHEMISTRY. a specific gravity of about 1055. Upon examination under the microscope, blood is seen to consist of a colorless fluid, called plas?na, or serum, in which float small globules or corpuscles which make up about 40 per cent, of the whole volume of blood. These corpuscles are capable of transmitting red light only, thus imparting to the blood its red color; their shape is that of a biconcave disk, and their size about of an inch in diameter. Besides the red corpuscles, there are found some of a white color, but their number is very much smaller, the proportion of white to red corpuscles being about 1 to 350. The composition of normal human blood is about: Water . . . . . . . .79.50 per cent. Serum-albumin ...... 7.34 “ Fibrin 0.21 “ Haemoglobin ....... 11.64 “ Fatty matters ....... 0.18 “ Extractives 0.32 “ Ash 0.81 “ Wet red-blood corpuscles contain of water 54.63 per cent., haemoglobin 41.1 per cent., other proteids 3.9 per cent., fats (chiefly cholesterin and lecithin) 0.37 per cent. The quantity of water in corpuscles varies widely, and most likely ranges in healthy blood from 76 to 80 percent. Dried corpuscles contain of haemo- globin about 90 per cent. The white-blood corpuscle consists of a thin envelope filled with an albuminoid (or a mixture of them) called protoplasm. The blood plasma is a colored liquid of the average composi- tion as follows: Water. ......... 90.20 Albumin ......... 5.30 Fibrinoplastin ........ 2.20 Fibrinogen ......... 0.30 Fatty matters ........ 0.25 Crystallizable nitrogenous matter .... 0.40 Other organic ingredients ...... 0.60 Mineral salts ........ 0.85 The alkaline reaction of blood is due to the presence of acid sodium carbonate, NaHC03, and sodium phosphate, Ua2HP04, both of which have a weak alkaline reaction. Besides these alkaline salts, blood also contains others, among them chiefly sodium chloride, and also the chlorides, phosphates, and sulphates of calcium, magnesium, sodium, potassium, etc. ANIMAL FLUIDS AND TISSUES. 417 When blood leaves the body and is allowed to stand a while (or, quicker, on shaking or agitating it violently) it separates into a semisolid mass termed clot, and a pale, yellow liquid termed serum, which latter, however, also solidities after a time in con- sequence of the coagulation of the serum-albumin. Clot consists of tibrin, holding in its meshes the blood corpuscles; the latter may be removed by washing the clot in a stream of water. Another method for obtaining the corpuscles is to dilute mamma- lian blood with 10 volumes of a 2 per cent, sodium chloride solution, which prevents coagulation, but allows the corpuscles to settle at the bottom of the fluid. Fibrin is an albuminoid, which exists most likely not as such in the blood, but forms whenever the latter is taken from the body (or under some circumstances when within the living body). It is now assumed, that for the formation of tibrin four factors are necessary, viz., tibrinoplastin, fibrinogen, fibrin ferment, and a small portion of neutral salts. The origin of the fibrin ferment is not positively known, but it is supposed to come from the edges of the wounded bloodvessels. The other factors are all present in the blood. How these substances by their interaction produce fibrin is not known ; fibrinogen is the only one of which the total quantity is used. There is always an excess of tibrinoplastin. While the presence of fibrin ferment and neutral salts is necessary, their quantities do not seem to be diminished. The blood cor- puscles take no active part in the formation of the clot, but are simply entangled in its meshes. Ilcemoglobin is the chief constituent of the red corpuscles and the substance which carries oxygen to the various tissues, as described in connection with the consideration of the process of respiration in the previous chapter. Experiment 64. Pour some freshly drawn venous blood into four volumes of a saturated solution of sodium sulphate contained in a vessel which stands in ice ; mix and set aside for several hours ; no coagulation occurs and the corpus- cles settle to the bottom of the vessel. Pour off the supernatant liquid, collect the sediment on a filter, and wash it first with cold solution of sodium sulphate and then with water. Prepare haemoglobin from these corpuscles as follows : Agitate the collected mass violently with small quantities of ether until the corpuscles are nearly dis- solved ; allow the liquid to settle, filter, render the filtrate slightly acid with acetic acid, and add alcohol as long as the precipitate first formed continues to dissolve ; cool the red solution to 0° C. (32° F.) for several hours, when crystals of haemoglobin will form, which collect on a filter and wash with an n e-cold mixture of alcohol and water. 418 PHYSIOLOGICAL CHEMISTRY. Examination of blood-stains. Blood-stains may be recognized, after having been washed off with as little water as possible, by the following methods : 1. Examine the reddish fluid under the microscope for blood corpuscles. 2. Evaporate a drop of the fluid on a microscope slide with a fragment of sodium chloride, cover with a cover-glass, allow a drop of glacial acetic acid to enter from the side and warm gently: abundant crops of hremin crystals are seen under the microscope after cooling. 8. Add a drop of the fluid to some freshly prepared tincture of guaiacum in a test-tube and float on the surface of an ethereal solution of hydrogen dioxide: a blue ring forms at the junction of the ethereal solution and the guaiacum. (Blood is, however, not the only substance showing this reaction.) 4. The spectroscope shows bands characteristic of haemoglobin. Chyle is a white, creamy liquid, of a strongly alkaline reaction, having in common with blood the property of coagulating (upon leaving the organism) into white fibrin and turbid serum. The composition of chyle differs according to the state of digestion; it contains : Water During full digestion. . 91.8 per cent. During fasting. 96 8 per cent. Fibrin . 0.2 “ 0.09 “ Proteids . 3.5 “ 2.30 “ Fats . . 3.3 “ 0.04 “ Extractives . 0.4 “ 0.28 “ Salts . . 0.8 “ 0.49 “ Lymph is a clear, colorless, or slightly yellow liquid of a faint alkaline reaction; in composition it closely resembles chyle, but differs from it in containing smaller quantities of fibrin and fatty matters. Saliva is secreted by several glands situated in the mouth, and represents in its mixed condition a viscid, generally slightly alkaline liquid of a specific gravity 1.008. It contains of Water ......... 99.49 per cent. Ptyalin . . . . . . . . 0.12 “ Epithelium and mucin . . . . . 0.13 “ Fatty matters . . . . . . . 0.11 “ Salts 0.15 “ ANIMAL FLUIDS AND TISSUES. 419 Ptyalin, the active principle of saliva, is a ferment which has the power of converting starch into maltose; its composition is doubtful. Among the various salts of saliva is found potassium sulphocyanate, as may be shown by the addition of a drop of ferric chloride solution, which produces a deep red color, disap- pearing on the addition of mercuric chloride (difference from meconic acid). Experiment 65. To a few cc. of thin starch paste add an equal volume of saliva, mix well and digest at a temperature of 35°-40° C. (95°-104° F.) for about half an hour. Examine the liquid for sugar by Fehling’s solution. Gastric juice is a liquid secreted by the follicles of the stomach; it has always a decidedly acid reaction, due to free hydrochloric acid, which is most likely formed by the action of sodium phos- phate on calcium chloride: 2(Na2HP04) + 3CaCl2 = Ca32P04 + 4NaCl + 2HC1. Sodium phosphate. Calcium chloride. Calcium phosphate. Sodium chloride. Hydrochloric acid. According to others, the hydrochloric acid is liberated by the action of acid sodium carbonate on sodium chloride: NaHC03 + NaCl = Na2C03 + HC1. Sodium acid carbonate. Sodium chloride. Sodium carbonate. Hydrochloric acid The above formulas show the reverse action of that which these substances exert upon each other under common condi- tions, but it must be remembered that the living cell is capable of decomposing matter generally in a manner different from that which it suffers ordinarily. Gastric juice contains of: Water 99.260 per cent. Pepsin 0.304 “ Free hydrochloric acid ...... 0.220 “ Alkaline chlorides ...... 0.200 “ Phosphates of calcium, magnesium, and iron . 0.016 “ Pepsin, the most important constituent of gastric juice, has been spoken of heretofore; it has, in the presence of free hydro- chloric acid, the power of converting proteids into peptones. Experiment 66. Open the stomach of a pig, sheep, or calf, recently killed while fasting; wash it rapidly in cold water, spread it out and scrape off the mucous surface; digest it under frequent stirring with about 10 parts of water for six hours, and filter. The solution contains pepsin, which verify by its dis- solving action on coagulated albumin. 420 PHYSIOLOGICAL CHEMISTRY. The solution may also be evaporated to dryness with or without sugar at a temperature not exceeding 40° C. (104° F.), and the dry pepsiu tested by the directions given in Experiment 62. Bile, secreted by the liver, is a thin, transparent liquid of a golden-yellow color, and a specific gravity of 1.020; it has a very bitter taste and an alkaline reaction; it varies widely in com- position, the total solids ranging from 9 to 17 per cent., being always highest after a meal; its composition, moreover, is highly complex; the following is an average of five analyses of bile from subjects with healthy livers: Water ......... 91.68 per cent. Mucus pigment 1.29 “ Taurocholate of sodium ..... 0.87 v “ Glycocholate of sodium ..... 3.03 z‘ Fat 0.73 “ Soaps ......... 1.39 “ Cholesterin ........ 0.35 “ Lecithin . . ...... 0.53 “ The true physiological action of bile is yet doubtful; it is, however, known that it acts on fats, forming with them an emul- sion which renders their passage through animal membranes more easy; it also precipitates peptones, and it most likely serves as a disinfectant, preventing putrefaction of the organic matters during their passage through the intestines; it finally acts as a natural purgative by irritation of the muscular tissue of the intestines. Bile obtained after death is of a brownish-yellow color; freed from mucus it will remain undecomposed for an almost indefinite period. The mucus may be separated by the addition of diluted alcohol and subsequent filtration. The quantity of bile discharged daily by a grown person may be put at forty ounces, but a considerable quantity of this dis- charged bile is reabsorbed in a changed form by the intestines; only a small amount of bile matters (in a decomposed state, however) is discharged by the feces. Biliary pigments. Of these four are known, but it is probable that more exist. Bilirubin, C16II18N203, is, when amorphous, an orange-yellow powder; when crystalline, it forms red prisms. It is sparingly soluble in water, alcohol, and ether, readily soluble in hot chloroform and carbon disulphide. When treated ANIMAL FLUIDS AND TISSUES. 421 with a mixture of concentrated nitric acid and sulphuric acid it turns first green, then blue, violet, red, and finally yellow. This reaction, known as Gmelin’s test, is used for the detection of bile- pigments in urine and other fluids. (See Plate VII., 7.) Biliverdin, C32H36N408, is a green powder existing in green biles; it responds to Glmelin’s test. Biliary acids. Glycocholic acid, C26II43U06, and taurocholic acid, C26II45^07S, exist as sodium salts in the bile of man and most animals. Both salts may be obtained as colorless crystals, which dissolve in water, forming solutions of an acid reaction, and an intensely bitter taste. Both acids are easily decomposed by heating with alkalies or with diluted acids, also by the action of putrefying material or by the chemical changes taking place in the intestines. In all these cases is formed cholic acid, C24II40O5, and a second product, which in the case of glycocholic acid is glycocol, C2II.N02, and in the case of taurocholic acid taurine, c2h7uo3s. Pettenkofer's test. The biliary acids and their salts show a characteristic reaction known as Pettenkofer’s test. This reac- tion is shown by adding very little cane-sugar to the liquid sub- stance under examination, and adding concentrated sulphuric acid in such a manner that the temperature does not rise above 70° C. (158° F.). In the presence of biliary acids a beautiful cherry-red color is developed, which gradually changes to dark reddish-purple. (See Plate VII., 8.) The bile acids are, however, not the only substances which show this reaction, and it, therefore, becomes in many cases necessary to separate the bile acids from other organic matter. This separation is accomplished by evaporating the substance under examination (urine, for instance), after having been mixed with a small quantity of coarse animal charcoal, to dryness at 100° C. (212° F.). The residue is extracted with absolute alcohol, the filtered alcoholic solution is again partially evaporated, and mixed with 10 volumes of absolute ether. The biliary acids are soluble in alcohol, but not in ether, or in ether containing one- tenth of alcohol. After standing an hour or two, the biliary acids will form a deposit, which is collected on a small filter, dissolved in a little water, and mixed with a few drops of a strong solution of sugar. Upon the addition of sulphuric acid, with the pre- 422 PHYSIOLOGICAL CHEMISTRY. caution above mentioned, the characteristic colors will indicate the presence of the bile acids. Experiment 67. Evaporate ox bile to a thick syrup, digest it with 5 parts of pure, cold alcohol for two hours, and filter. Mix the filtrate, which contains glycocholate and taurocholate of soda, with freshly prepared animal charcoal, boil and filter; evaporate to dryness in a water-bath, redissolve in the smallest possible amount of pure alcohol, and add ether until the solution becomes markedly turbid. A white, crystalline mass is deposited in a few hours or days ; this is known as Plattner s crystallized bile, and is a mixture of the two sodium salts mentioned. Dissolve the mass in a small volume of water, adding a little ether and then dilute sulphuric acid ; glycocholic acid crystallizes out in shining needles. Cholesterin, C26H43.HO. This substance is classed by physiolo- gists among the fats, because it is greasy and soluble in ether, but its chemical constitution is that of an alcohol. It is found chiefly in bile, but also in blood, nerve-tissue, brain, contents of the intestines, feces, etc.; its presence in certain vegetables, as peas, beans, etc., has also been demonstrated. Cholesterin crystallizes in colorless, silky needles, which are insoluble in water, alkalies, and diluted acids, but soluble in ether. It sometimes forms in the organism solid masses, known as biliary calculi or gallstones, some of which are almost pure cholesterin. Tests for cholesterin : 1. Evaporated with nitric acid it gives a yellow mass, which turns brick-red on addition of ammonia. 2. Mixed in the dry state with strong sulphuric acid, it pro- duces a blue-red or violet color on the addition of chloroform, the color changing to green on exposure to air. 3. Evaporated with a mixture of 2 volumes of sulphuric acid and 1 volume of ferric chloride solution, it turns violet. Lecithins, C44H90NTO9 or C42H84NT09. Lecithin, one of the con- stituents of bile, is the member of a group of substances generally termed phosphorized fats or lecithins. These bodies are highly complex in composition, and may be looked upon as fats formed from glycerin, in which hydrogen atoms are replaced by the radicals of phosphoric and fatty acids. Pancreatic juice. There is no thoroughly reliable analysis of this highly complex liquid on record. It contains from 3 to 6 per cent, of solids, two-thirds of which are of organic, one-third ANIMAL FLUIDS AND TISSUES. 423 of inorganic nature. Amoug the organic constituents are a number (certainly two, probably four) of cryptolites or animal ferments, which manifest themselves: 1, by converting starch into sugar (this action is more energetic than that of ptyalin); 2, by converting albuminoids into peptones (this action takes place in alkaline, but not in acid solution, as in case of pepsin); 3, by emulsifying neutral fats; 4, by decomposing fats into glycerin and fatty acids. Feces consist of that portion of the food which has not been taken into the system by absorption, and is discharged from the body mixed with some of the products of the biliary and intes- tinal secretions. The odor depends largely on two substances, indol and skatol, and to a less degree on the valerianic and butyric acids and the sulphuretted hydrogen present. Indol, C8H belongs to the aromatic compounds, and is one of the products of the putrefaction of albumin. The quantity passed depends on the nature of the food taken, and on the energy of the digestive powers. A grown person, in normal condition, discharges from 7 to 9 ounces daily. An approximate analysis of the feces of a healthy adult shows: Water ......... 77.3 per cent. Mucin ......... 2.3 “ Prote'ids . 5.4 “ Extractives . . . . . . . 1.8 “ Fats . . 1.5 “ Salts ......... 1.8 “ Eesinous, biliary, and coloring matters . . . 5.2 “ Insoluble residue of food ...... 4.7 “ Bone is chemically distinguished from other tissues by the large quantity of inorganic salts which it contains. Bones con- tain about 31 per cent, of organic matter combined with 69 per cent, of mineral matter. Different bones (and even different parts of the same bone) of the same person differ somewhat in composition; moreover, the bones of a child contain somewhat more of organic matter than those of a grown person, as may be shown by the following analysis of the corresponding bone in children and a grown person : Child one year. Child five years. Man twenty-five years. Organic matter, 43.42 per cent. 32.29 per cent. 31.17 per cent. Tricalcium phosphate, 48.55 U 59.74 “ 58.95 “ Magnesium phosphate, 1.00 Lt 1,34 “ 1.30 “ Calcium carbonate, 5.79 l t 6.00 “ 7.08 “ Soluble salts, 1.24 11 0.63 “ 1.50 “ 424 P HYSIOLOGICAL CHEMISTRY. Frequently human bones contain calcium fluoride, which sub- stance, to the amount of 1 to 2 per cent., is a normal constituent of the bones of many animals. The organic matter of bone is called ossein, and is a mixture of collagen, elastin, and an albu- minoid existing in the bone-cells. Collagen is a nitrogenous substance, insoluble in water, but forming when treated with it under the influence of heat and pressure, gelatin, an amorphous, tasteless, translucent substance, which swells up in boiling water, forming on cooling a soft jelly; an impure form of gelatine is common glue. Teeth consist of three distinct tissues, viz., dentine, forming the chief mass, in its interior being the pulp cavity; enamel, investing the crown and extending some way down the neck; and cement, covering the fangs. The composition of cement is almost the same as that of bone, its organic and inorganic constituents having the relative proportions of 30 : 70. Dentine contains less water than bone and is also poorer in organic matter. The following table gives the composition of the dentine of an adult woman and man respectively : Organic matter—ossein and vessels Woman. . 27.61 Man. 20.42 Calcium phosphate . ... . . 66.72 67.54 Calcium carbonate . . 3.36 7.97 Magnesium phosphate . . . . . 1.08 2.49 Soluble salts, chiefly sodium chloride . 0.83 1.00 Fat . 0.40 0.58 Enamel is distinguished by the very small proportion of water and organic matter contained in it. Its average composition may be thus stated: Water and organic matter ....... 3.6 Calcium phosphate and fluoride ..... 86.9 Magnesium phosphate ....... 1.5 Calcium carbonate ........ 8.0 Hair, nails, horns, hoofs, feathers, epithelium, are nearly identical in composition. They all contain a nitrogenous substance, termed keratin, which is probably not a distinct chemical com- pound, but a mixture of several substances similar in composi- tion and properties. Mucus is secreted by the various mucous membranes, and is found in saliva, bile, connective tissues, feces, urine, etc. When MILK. 425 pure it forms a clear, translucent or viscid mass; it contains a substance termed mucin, which swells up in water, and readily dissolves in water containing an alkali; from these solutions it is precipitated by acetic acid. Muscles contain fibrin, albumin, myosin, kreatin, sarkin, C5H4N40, xanthin, C5II4K402, uric acid, glucose, inosite, lactates, and salts. Kreatin, sarkin, and xanthin are substances formed in the organism by oxidation of proteids, and may be looked upon as compound ureas or substances formed as intermediate products of the final conversion of proteids into urea, carbon dioxide, water, etc. These substances may indeed be decomposed arti- ficially in such a manner that urea is produced as one of the products of decomposition. Brain consists of so many individual parts that the analysis of it as a whole is of little value, and to separate these parts suc- cessfully is a task not yet accomplished. Brain, as a whole, contains cerebrin, lecithin, neurin, cholesterin, protagon, and many other substances, some of which are distinguished by the large quantity of phosphorus they contain. 54. MILK. Properties and composition. Milk is the secretion of the mam- mary glands, the presence of which is characteristic of the class of animals known as mammalia. The milk of different animals differs somewhat in composition, but it always contains all the constituents necessary for a normal development of the various Questions.—521. What three kinds of matter are found as constituents of the animal body, and how can they be determined quantitatively? 522. Men- tion the chief constituents of blood, and state those which predominate in serum and in the corpuscles respectively. 523. What substances cause the clotting of blood, and what explanation can be given? 524. How may blood-stains be recognized? 525. What is the active principle of saliva, and how does it act on starch? 526. State the composition of gastric juice, and explain its physio- logical action. 527. State the general properties of bile, and mention its chief constituents. 528. Give Gmelin’s test for biliary pigments, and Pettenkofer’s test for biliary acids. What precautions are necessary in using the latter test? 529. What is cholesterin ? State its properties and reactions. 530. Mention the principal constituents of muscles, bone, teeth, and hair. 426 PHYSIOLOGICAL CHEMISTRY. tissues, liquids, organs, etc., of the young mammal, which gener- ally feeds exclusively upon milk for a shorter or longer period of its early life. Milk is an opaque, aqueous solution of casein, albumin, lactose, and inorganic salts, holding in suspension small globules of fat invested, most likely, with coatings of casein or with some other albuminous envelope. The reaction of woman’s milk and that of the herbivora is normally alkaline, but that of carnivora is acid. Its specific gravity ranges from 1.029 to 1.033, but may in extreme cases vary between 1.018 and 1.045. The average composition of various kinds of milk is given below, but it must be remembered that milk not only differs in certain species, but also in the same animal at different times; for instance, the quality and quantity of food taken, as also various physiological changes, have decided influence upon the milk secreted. Human mlik. Cow’s milk. Variations. Average. Variations. Average. Water . 90.4 to 85.7 88 05 90.2 to 83.7 86.95 Casein and albumin 1.8 to 3.1 2.45 3.3 to 5 5 4.40 Fat (butter) . 3.0 to 3.8 3.40 2.8 to 4.5 3.65 Lactose. 4.5 to 7.0 5.75 3.0 to 5.5 4.25 Inorganic salts 0.3 to 0.4 0.35 0 7 to 0.8 0.75 Goat. Sheep Ass. Mare. Cream. Water . 86.0 83.3 90.6 90.6 50 to 70 Casein and albumin 3.8 5.4 2.7 2.2 5 to 4 Fat (butter) . 5.2 5.3 1.0 1.1 41 to 22 Lactose . 4.3 5.2 5.3 5.8 3 to 3 Inorganic salts 0.7 0.8 0.4 0.3 0.7 to 0.7 Skimmed milk. Condensed Bl.ttpr milk. nutter. Buttermilk. Curd. Whey. Water . 89.6 25 15.0 91 0 59.4 93 8 Casein and albumin 4.2 14 2.2 3.7 27.7 0.8 Fat (butter) . 1 0 10 82.0 0.8 6.4 0 3 Lactose . 4.4 491 0.3 3.8 5.0 4.5 Inorganic salts 0 8 2 0.5 0.7 1.5 0.6 The inorganic salts consist chiefly of calcium or sodium phos- phate and sodium and potassium chloride, but contain also some magnesium and iron. The proteids consist mainly of casein with some albumin, the proportion being about as 6 to 1. 1 Including cane-sugar added by the manufacturer. 427 MILK Beside the constituents mentioned in the above analyses, milk also contains a very small quantity of extractives, among which are found peptone, kreatin, leucin, etc. The principles which give to milk its peculiar odor have not yet been conclusively pointed out. The gaseous constituents of milk are mainly carbon dioxide, oxygen, and nitrogen. 100 volumes of milk contain of carbon dioxide 7.6, of oxygen 0.1, of nitrogen 0.7 volumes. Changes in milk. Soon after milk leaves the animal system changes take place which are either of a physical or chemical nature. The first change in milk, when allowed to stand for a few hours, is a separation of the suspended fat globules toward the upper part of the liquid, which gradually becomes loaded with fat, forming a distinct layer over the liquid. This upper layer having a slightly yellowish color (cream color) is cream, the watery liquid below having a bluish-white color is skimmed milk. Another change taking place in milk (rarely after a few hours, but generally after a day or a few days) is the coagulation of casein, which takes place both in the cream and in the skimmed milk, converting the whole into a thick, semi-liquid mass, which gradually separates into a solid white card, and a thin, transparent milk-serum or whey. The coagulation of the casein is caused by lactic acid, pro- duced by the so-called lactic fermentation of lactose. The ferments causing this fermentation are undoubtedly floating in the air, as it is possible to prevent the decomposition of milk- sugar for a considerable length of time by taking proper precau- tions for destroying and excluding them. Simultaneously with the coagulation of milk the alkaline reaction becomes acid and the sweet taste gradually more and more sour. These changes in milk can, to some extent, be artificially produced, hindered, and controlled. Thus, the casein may be precipitated by the addition of rennet or acetic acid (or any mineral acid) and heating. The decomposition of the milk-sugar and with it the “curdling” may be prevented—1, by chemical treatment with alkaline salts or antiseptics; 2, by physical treat- ment, such as cooling or icing, boiling and aeration; 3, by con- densation or evaporation, with or without the addition of a preservative agent. All these systems of preservation, however, 428 PHYSIOLOGICAL CHEMISTRY. are subject to serious disadvantages because they either interfere with the natural constitution and properties of the milk, or because they serve their purpose for too limited a time. The addition of alkalies such as lime-water, sodium carbonate or bicarbonate, does not prevent the lactic fermentation, but prevents the action of the liberated acid on the casein by forming a lactate of calcium or sodium. Of antiseptics, salicylic acid has been used with good results (2 grains to a pint), but it should be remembered that salicylic acid is not altogether harmless. Of all preservatives, cold is the most efficient and least objec- tionable, and milk when cooled to within a few degrees of the freezing-point may be kept for eight to twelve days sweet and without change. The condensation of milk is effected either simply by evapo- rating (generally in vacuum pans) a portion of the water, or by first dissolving in it a certain quantity of sugar (generally cane- sugar) and then evaporating to the consistence of a thick syrup, which is placed in suitable air-tight jars. The sugar which is added serves as an additional preventive of decomposition. The following gives the constituents of milk which may be obtained from it by mechanical processes after it has been changed as described above: Cream, 20 < f Butter . . . 3 5 parts. L Buttermilk . 16.5 “ Skimmed milk, 80s f Curd .... . 8 0 “ ’ 1 1 Whey . 72.0 “ Butter. Even in the thickest varieties of cream there is no cohesion between the fat globules, whilst in butter the fat has actually cohered. This change is accomplished by violently agitating (churning) the cream, when the fat particles gradually combine with each other, whilst the liquid (buttermilk) separates. Chemically, butter is a milk-fat, a mixture of different fats or glycerides of the fatty acids, chiefly palmitic and ole'ic acids, with small quantities of butyric, capronic, caprylic, and stearic acids; it always contains a certain proportion, 15 to 16 per cent,, of water, besides traces of casein, salts, coloring matter, etc. For curing butter, common salt is often used; the quantity added should not exceed 5 per cent. The composition of buttermilk has been given above; when 429 MILK . freshly obtained from sweet cream it is a pleasant drink and a wholesome food. Cheese consists mainly of casein, milk-fat, water, and inorganic salts; these constituents vary as follows : Water . . . . . . . . . 61 to 28 parts. Casein 15 to 35 “ Fat . . . . . . . . . 20 to 30 “ Salts . ' . . . . . . . 4 to 7 “ Cheese is made either from pure milk, from skimmed milk, or from a mixture of milk and cream, and accordingly varies highly in composition. Practically, cheese is made by causing milk to coagulate (either by allowing it to stand or by the addition of rennet, acids, or other substances), and separating the curd (casein and fat) from the whey by mechanical means, such as filtering and pressing. The curd is placed in suitable moulds and afterward allowed to stand or “ ripen ” for a shorter or longer period. The process of ripening is a partial decomposi- tion (decay and putrefaction) of the casein, and the value of cheese depends mainly upon the nature of the products formed during this decomposition. Adulterations of milk. Of these, the most commonly practised are removal of cream, addition of water, or both. Sometimes sodium carbonate, sugar, and even chalk are added, but these latter adulterations are fortunately but rarely practised by milk- dealers. The question whether or not milk has been tampered with is generally decided by ascertaining whether cream has been removed or water added. It is, therefore, chiefly the quantity of total solids which has to be determined in order to decide the purity of milk. But it has been shown by the above tables of milk analysis that the quantity of these solids varies considerably, and a minimum of total solids should, therefore, be adopted legally. While no such minimum quantity is offi- cially recognized in most States of this country, it is safe to say that milk containing less than 11 per cent, of total solids may be looked upon as adulterated. (The above given lowest quan- tity of 9.8 per cent, of total solids in cow’s milk is very abnor- mal.) The methods for detecting such fraud will now be con- sidered. 430 PHYSIOLOGICAL CHEMISTRY. Testing milk. There is, unfortunately, no instrument which will indicate the purity or quality of milk directly. An instru- ment heretofore used for that purpose (especially in France), and known as the lactometer, is simply a hydrometer which indi- cates the specific gravity of milk. There are, however, in milk substances which have a tendency to increase the specific gravity, such as lactose, salts, and casein, whilst there is at the same time one substance, the fat, which is specifically lighter than water. The specific gravity of milk ranges from 1.027 to 1.034, the average being about 1.030. If water be added to milk, the specific gravity will become lower, but the same effect may be obtained by adding fat or cream. Again, if cream be removed, the specific gravity will be higher, and in order to bring the milk back to the standard of 1.030, water may be added. In other words, cream may be removed from and water added to the same milk and the specific gravity will be unchanged; or a natural milk containing large quantities of fat has the same specific gravity as a poorer milk to which water has been added. These facts show that the lactometer alone is of no value whatever in milk analysis, although it is useful in determining the quantity of cream present. This is generally accomplished by the so-called crcamometer, a glass tube or glass cylinder about one foot long, half an inch in diameter, and graduated into 100 parts by volume, the 0 being about an inch from the top. The tube is filled with milk to the 0 and set aside for 12 or 13 hours, when the line of demarcation between the cream and the liquid below is well defined and may be easily read off. The quantity of cream varies from 8 to 20 per cent., but should not fall below 10 per cent. Milk which shows a larger quantity of cream (15 to 18 per cent.) may fall considerably below 1.030 in specific gravity, but if there is little cream (8 to 10 per cent.) and the milk shows a low specific gravity, there can be little doubt that it has been tampered with. There are a number of other instruments, the so-called “ lactoscopes," used for the determination of cream, the operations of which are based on the fact that milk rich in cream is a much more opaque (or more white) fluid than that from which cream has been taken or to which water has been added. One of the lactoscopes has been introduced under the name of pioshope, and consists of a round disk about two and a half inches in diameter, with a shallow disk-like depression in the centre, in which a few drops of milk are placed. This is then covered by a glass disk, transparent in the middle where it rests on MILK 431 the milk, the rim being covered by six radial strips of oil-paint, varying from white to dark gray, and marked with the quality corresponding to it, from “cream” to “ very poor milk.” The color of the thin layer of milk as seen through the transparent part of the glass plate corresponds with one of the six color strips, and its quality is thus readily, though not very accurately, determined. The above methods of determining the purity of milk, although answering for ordinary purposes, are absolutely insufficient for scientific purposes or as evidence upon which to base legal pro- ceedings. In such cases a complete analysis, including the exact determination of total solids and of the various constituents, is required. Analysis of milk. The total solids are determined by placing a weighed quantity (from 5 to 10 cc.) of the well-mixed milk in a weighed platinum dish and heating for several hours in a water- bath until no more weight is lost. The loss in weight represents the water, the weight of the residue the total solids. Tha fat is determined by extracting the solid residue repeatedly with warm ether, filtering this solution through a small filter, which is to be well washed with ether, and evaporating the ethereal solution in a weighed platinum dish. Milk-sugar is next determined by treating the residue (from which fat has been extracted) with hot diluted alcohol; lactose and a few soluble salts enter into solution; the liquid evaporated to dryness in a weighed dish gives the quantity of sugar plus some salts. Upon igniting the milk-sugar a residue of salts is left, which is also weighed and this weight deducted from the first one. Casein. The residue now left (after treatment with ether and alcohol) contains chiefly casein with some albumin and salts. If any casein should have been washed upon the filters accidentally, it has to be transferred back to the dish, the contents of which are dried and weighed. By burning off the casein and reweigh- ing the dish plus the salts, the quantity of the casein is deter- mined. The remaining salts added to those previously obtained from the alcoholic solution form the total ash or inorganic solids, an analysis of which may be made according to the methods given heretofore. 432 PHYSIOLOGICAL CHEMISTRY. Casein may also be determined directly by precipitating it from milk, by the addition of acetic acid and boiling. The pre- cipitated casein is filtered off, and has to be well washed, first with water, and then with ether, as it contains most of the fat. Experiment 68. Determine the constituents of milk quantitatively by using the directions given above. 55. URINE AND ITS NORMAL CONSTITUENTS. Secretion of urine. It has been explained in a former chapter how blood absorbs the digested food as chyle, how this is acted upon by the atmospheric oxygen in the lungs, and how this arterial blood, whilst passing through the system, deposits albuminous and other substances, receiving in exchange the products formed by the oxidation of the various tissues. These products are either gases (chiefly carbon dioxide), liquids (chiefly water), and solids held in solution by the water. These waste solids must necessarily be eliminated from the system, and the organs which accomplish this result are the kidneys. The process of separating the waste materials from the blood is chiefly of a physical nature, partly a transudation or filtration, and partly a diffusion or osmosis. The conditions essential for such an exchange are given in the kidneys. Blood is separated by delicate membranes from a thin, aqueous, saline solution; the interchange taking place is chiefly a passage of the waste crystalline products of the blood into the aqueous solution, which is thereby gradually converted into urine, that liquid, which is finally discharged, carrying oft" nearly the total quantity of all the nitrogen taken into the system in the form of nitroge- nous food. Questions—531. Mention the five principal constituents of milk. 532. Grive the average composition of human and of cow’s milk. 533. What com- pounds constitute milk-ashes? 534. What physical and what chemical changes does milk suffer on standing? 535. What acid is formed in milk on standing, and how does this acid act on the casein? 536. Describe the processes used for preventing the decomposition of milk. What are their advantages and their disadvantages? 537. Grive approximately the quantities of the chief com- ponents of cream, skimmed milk, butter, buttermilk, curd, whey, and cheese, and state how these substances are obtained. 538. Why does the specific gravity of milk not indicate its purity and richness? 539. Describe the advan- tages of the combined use of the lactometer and creamometer in testing milk. 540. Grive a process for the complete quantitative analysis of milk. URINE. ITrine tints—Pale yellow, light yellow, yello.v. 1 2 Urine tintr—Ueddish ye’.lcw, ye'lowiah rod, red. 3 ZTrine tints—Brownish red, re 1- dish brown, brownish black. 4 Murexul test for uric aci 1. 5 Troturner’s or Fehling’s test for sugar. liotr/er’s bismuth test for sugar. 6 7 Gmelin’s test for biliary color- ing matters. I'ettenltofer’s test for biliary acids. Albuminous substances show nearly the same reaction. 8 URINE AND ITS NORMAL CONSTITUENTS. 433 General properties. Normal human urine, when in a fresh state, is a clear, transparent aqueous liquid, of a lighter or deeper amber color, having a peculiar, faintly aromatic odor, a bitter, saline taste, a distinct acid reaction on blue litmus-paper, and a specific gravity heavier than water (average about 1.020). When urine is kept in a clean vessel it may remain unchanged for several days, provided the temperature be not too high, and the amount of total solid constituents not too small. In urine, shortly after cooling, especially if it be concentrated, a light, cloudy film of mucus is formed, which slowly sinks to the bottom; the acid reaction gradually increases, small yellowish- red crystals of acid urates, or uric acid, are deposited. In this condition the urine may often continue unchanged for sev- eral weeks, provided the temperature be low. If, however, the urine be very dilute, and the temperature above the mean, decomposition speedily takes place. The urine is then found to be covered with a thin, shining, and frequently iridescent membrane, fragments of which sink gradually to the bottom. The urine then becomes turbid, acquires a pale color, its reac- tion becomes alkaline, and it begins to develop a nauseous ammoniacal odor, due to the products formed during the decom- position of urea and other substances. Composition. Urine is chiefly an aqueous solution of urea and inorganic salts, containing, however, always some uric acid, mucus, coloring and other organic matters. The average com- position of normal human urine may be stated thus: Water. Urea . . 2.50 “ Uric acid . 0.04 “ Hippuric acid Kreatin Kreatinin . 0.40 per cent. Coloring matter . Mucus. Unknown organic matters . sodium 1 Phosphates 'j potassium Chlorides t of calcium - . . . 1.30 per cent. Sulphates J magnesium iron The above average composition of human urine varies con- siderably, and is influenced by the water and food taken, amount of work done, time of day, temperature of air, age, sex, etc. 434 PHYSIOLOGICAL CHEMISTRY. Urine also contains gaseous constituents, amounting to about 16 per cent, by volume; these gases are chiefly carbon dioxide (88 per cent.), and nitrogen (11 per cent.), with very little oxygen (1 per cent.). The quantity of urine passed in a day also varies widely, an adult discharging from 500 to 2300 cc. in twenty-four hours; a normal average quantity is about 1500 to 1700 cc. (about 52J to 59J ounces). The quantity of total solids contained in this urine varies from 55 to 60 grams (840 to 920 grains), and over one-half of this quantity is urea. NIL, CO Urea, Carbamide, C0H4N2, or or N=H2 or X a Urea is the most important constituent of urine, and is the substance which carries off by far the largest quan- tity of all nitrogen taken in the food. Urea has never yet been found as a product of vegetable life, but is found as a normal constituent of the urine of the mammalia, and in smaller quan- tity in the excrement of birds, fishes, and some reptiles. It occurs also in the blood, muscular tissue, chyle, lymph, bile, perspiration, and many other animal fluids. When pure, urea crystallizes from an aqueous solution in colorless prisms; it is odorless, and has a cooling, bitter taste; it easily dissolves in water, the solution having a neutral reaction : it fuses when heated to 130° C. (266° F.), but decomposes at a higher temperature, giving off ammonia gas and water, whilst a number of other substances are formed at the same time. A pure solution of urea does not decompose at ordinary tempera- ture, but on boiling, and especially under pressure, it takes up water, and is decomposed into ammonia and carbon dioxide, or into ammonium carbonate: CO(NH2\ + 2H20 == C02 + 2NH3 + H20 = (NH4)2C03. The same decomposition takes place in urine under the influ- ence of a ferment (most likely present in urine, or perhaps de- rived from the air), if the temperature be not too low. A solution of urea is decomposed by the action of chlorine or bromine with generation of hydrochloric (or hydrobromie) acid, carbon dioxide, and nitrogen : CO(NH2)a + 6C1 + H20 = 6HC1 + C02 + 2N. URINE AND ITS NORMAL CONSTITUENTS. 435 Alkaline hypochlorites or hypobromites cause a similar de- composition, upon which is based the quantitative estimation of urea. Urea forms with acids definite salts and with certain oxides and salts definite compounds. Urea is formed artificially by numerous decompositions, as, for instance: а. By a process similar to the one taking place in the animal system, viz., by limited oxidation of albuminous substances by potassium permanganate. б. By oxidation of uric acid in the presence of water: c5h4x4o3 + II20 + O = CO(NH2)2 + c4h2x2o4. Uric acid. Urea. Alloxan. c. By the action of caustic alkalies upon kreatin: c4h9x3o2 + H20 = CO(NH2)2 + C3H7X02. Kreatin. Urea. Sarcosine. d. By the molecular transformation of ammonium cyanate, which takes place when its solution is evaporated and allowed to crystallize: XII4.CXO = CO(NH2)2. e. By the action of ammonia on carbonyl chloride: Ammonium cyanate. Urea. COC)2 + 2XH3 = 2HC1 + CO(NH2)2. Carbonyl chloride. Ammonia Hydrochloric acid. Urea. f. By the action of ammonia on ethyl carbonate : (C2H5)2C03 + 2XH, = 2(C2H5HO) + CO(NH2)2. Ethyl carbonate. Ammonia. Ethyl alcohol. Urea. Urea may be obtained from urine by evaporating it to the con- sistency of a syrup and mixing the cooled residue with an equal volume of nitric acid, when crystals of urea nitrate,C0(NH2)2.HN03, form, which may be decomposed by barium carbonate into urea and barium nitrate: 2[C02(NH2).HN03] + BaC03 = C02XH, + Ba2N03 + C02 + H20. Urea nitrate. Barium carbonate. Urea. Barium nitrate. Experiment 69. Evaporate about 200 cc. of urine to a syrupy consistence, allow to cool, place the vessel containing the syrup in ice and add slowly with stirring a volume of nitric acid equal to that of the evaporated urine. Set aside for twenty-four hours, collect the crystalline mass of urea nitrate on a filter, wash with very little cold water, allow to drain well and dissolve in hot water. (If much colored, shake the solution with animal charcoal and filter.) 436 PHYSIOLOGICAL CHEMISTRY. To the hot solution add freshly precipitated barium carbonate as long as carbon dioxide escapes. Filter and evaporate the solution to dryness over a water-bath ; boil the mass with alcohol, which dissolves the urea, but does not act on the barium nitrate. Allow the urea to crystallize from the alcoholic solution. Reactions and determination of urea. There are no very char- acteristic reactions by which urea can be well recognized. From organic mixtures it is separated by digesting them with from 3 to 4 volumes of alcohol in the cold; the filtered liquid is evapo- rated to dryness and extracted with alcohol, which again is evaporated. The dry residue may be tested for urea as follows : 1. Dissolved in a few drops of water, the addition of an equal quantity of colorless nitric acid causes the formation of white, shining, crystalline plates or prisms of urea nitrate. 2. If a strong solution of oxalic acid is added, instead of nitric acid, rhombic plates of urea oxalate form. 3. The residue (or urea) heated in a test-tube to about 160° C. (320° F.) until no more vapors of ammonia are evolved, leaves a substance termed biuret, C2H6N302, which upon the addition of a few drops of potassium hydrate solution and a drop of cupric sulphate solution, causes the solution of the cupric hydrate with a reddish-violet color. The quantitative estimation of urea in urine may be effected by various methods, of which but one will be mentioned, because it requires less time and less skill in manipulation than most other methods. This determination is based upon the fact that urea is decomposed by alkaline hypobromites into carbon di- oxide, water, and nitrogen : CO(NH2)2 + 3(NaBrO) = 3NaBr + C02 + 2H20 + 2N. Urea. Sodium hypobromite. Sodium bromide. Carbon dioxide. Water. Nitrogen, The liberated nitrogen is collected, and from its volume its weight and that of the urea are calculated. Practically the operation is conducted as follows : 100 grams of sodium hydrate are dissolved in 250 cc.. of water, and to this cooled solution are added 25 cc. of pure bromine, when sodium hypobromite is formed, leaving, however, an excess (over one- half) of the sodium hydrate in an unaltered condition. (The solution easily decomposes, and should, therefore, be freshly pre- pared for analysis.) The apparatus required (Fig. 41) consists, in its most simple URINE AND ITS NORMAL CONSTITUENTS. 437 form, of a wide-mouth bottle A; a small test-tube B, of about 10 cc. capacity ; a glass cylinder C, and a graduated burette D. Fig. 41. Apparatus for the volumetric estimation of urea. Into the bottle is fitted a perforated cork, which is connected by means of tubing with the burette. 5 cc. of urine are intro- duced into the test-tube and 20 cc. of the alkaline hypobromite solution into the bottle, care being taken not to bring the liquids in contact with each other. The graduated burette is lowered in the cylinder, until the zero mark is on a level with the surface of the water in the cylinder and the connection between the burette and the bottle made. By now inclining the bottle so that the urine comes in contact with the hypobromite, decom- position of urea takes place energetically. The liberated carbon dioxide is absorbed by the sodium hydrate, while the nitrogen increases the volume of air present in the apparatus. The bu- rette is gradually raised as the nitrogen is evolved and the whole 438 PHYSIOLOGICAL CHEMISTRY. allowed to stand for half an hour. The cubic centimeters of nitrogen gas are read off (whilst the water in the burette and cylinder are on a level), and give, multiplied by 0.0027, the grams of urea in 5 cc. of urine. As the volume of gas depends upon temperature and pressure, corrections for these have to be made by using the following formula: ? _ 100 v b 760.370. a (1 -f- 0.003665£j. p = Weight, of urea for 100 cc. urine. a = Volume of urine used, expressed in cc. v = Volume of nitrogen read off. b = Barometric pressure in mm. t == Temperature during the measurement of nitrogen. 370 represents the cc. of nitrogen (at 0° and 760 mm. pressure) obtained from one gram of urea. The above described process for estimation of urea is, for various reasons, far from being perfect (uric acid and kreatinin, for instance, are also decomposed with liberation of nitrogen); but it has been found that the results obtained are quite sufficient for clinical purposes. Experiment 70. Determine urea in urine by the method described above. Uric acid, H2C5H2N403. Uric acid is found in small quantities in human urine, chiefly in combination with sodium, potassium, and ammonium, but also with calcium and magnesium. In larger proportions, uric acid is found in the excrement of birds, mollusks, insects, and chiefly of serpents, the solid urine of the latter consisting almost entirely of uric acid and urates. It is also found in Peruvian guano. Pure uric acid is a white, crystalline, tasteless, and odorless substance, almost insoluble in water, requiring 1900 parts of boiling and 15,000 parts of cold water for its solution; it is also insoluble, or nearly so, in alcohol and ether. The great insolu- bility of uric acid causes its separation in the solid state, both in the bladder and in the tissues. Reactions and determination of uric acid. Uric acid ma}7 be recognized by its crystalline form, and by the murexid test, which is made by placing a fragment of uric acid in a porcelain dish, adding a drop of nitric acid, and carefully evaporating over a flame. To the dry residue a drop of ammonia water is added, URINE AND ITS NORMAL CONSTITUENTS. 439 which produces a beautiful purplish-red color. (Plate VIL, 4.) This reaction occurs, however, also with a number of substances which are similar to, but more complex in composition than, uric acid. The quantitative estimation of uric acid in urine is best accom- plished by adding 10 cc. of hydrochloric acid to 250 cc. of urine, setting aside for 24 hours in a cool place, and collecting the crystals of uric acid on a small filter which has been previously weighed. The crystals are washed with a little water, and dried at 100° 0.(212° F.). As uric acid is not entirely insoluble, 0.0038 gram has to be added for every 100 cc. of urine employed for the analysis. If the urine (to be tested for uric acid) be very dilute, it should be evaporated to about one-half its bulk before adding hydro- chloric acid; if it contain albumin, this should be removed by adding a drop of acetic acid, boiling and filtering. Hippuric acid, C9H9N03 (Benzyl-glycocol, Benzyl-amido-acetic acid), is a normal constituent of human urine, but is found in much larger quantities in the urine of herbivora. Its constitution may be considered as ammonia in which two hydrogen atoms are replaced by the radicals of benzoic and acetic acid respec- /C7II50 tively, thus, F—C2H302. Hay, and especially aromatic herbs, \H contain benzoic acid, or compounds having a similar composition, and a portion of these compounds is eliminated in hippuric acid. Administration of benzoic acid also increases the amount of hippuric acid in urine. When pure, hippuric acid crystallizes in transparent, colorless, odorless prisms, which have a bitter taste, and are sparingly soluble in water. Analytically, hippuric acid is characterized : 1. By giving a sublimate of benzoic acid, and an odor of hydrocyanic acid, when heated in a dry test-tube. 2. By giving a brown precipitate with ferric chloride. 3. By giving off benzene and ammonia when heated with calcium hydrate. 4. By evolving an intense odor of nitro-benzene when evapo- rated to dryness with a few drops of nitric acid. Other organic substances, such as kreatin, kreatinin, xanthin, 440 PHYSIOLOGICAL CHEMISTRY. lactic acid, mucus, coloring matters, etc., occur in such small quantities in normal urine that their detection, separation, and quantitative estimation are very difficult, and almost exclusively attempted during scientific investigations. 56. EXAMINATION OF NORMAL AND ABNORMAL URINE. Points to be considered in the analysis of urine. They are : 1. Color, odor, general appearance—whether clear, smoky, cloudy, turbid, etc. 2. Reaction : whether acid, neutral, or alkaline to test-paper. 3. Specihc gravity. 4. Total amount of organic and inorganic solids. 5. Total amount of inorganic matter (ash). 6. Determination of urea. 7. Determination of uric acid. 8. Determination of inorganic acids and bases. (Hydrochloric, sulphuric, and phosphoric acids; sodium, potassium, calcium, magnesium, and iron.) 9. Determination of albumin. 10. Determination of sugar. 11. Examination for bile. 12. Examination of any organic or inorganic sediment, either by chemical means or by the microscope. Samples of urine should always be drawn from the well-mixed and exactly measured quantity of the total urine discharged in twenty-four hours. Color. Normal urine is generally pale yellow or reddish-yellow, but it may be as colorless as water, or as dark brownish-black as porter ; a reddish and smoky tint generally indicates the presence Questions.—541. What is urine, where and by what process is it formed in the animal body, and what is its function ? 542. Mention the general physical and chemical properties of urine. 543. Give the average composition of human urine, and state by what conditions the composition is influenced. 544. State the composition and properties of urea. 545. By what process is urea formed in the animal body, and how can it be obtained artificially ? 546. Describe a process by which urea may be estimated quantitatively in urine. 547. In what forms is uric acid found in urine, and what are its properties ? 548. Describe the murexid test. 549. How can uric acid be determined quantitatively in urine? 550. What is hippuric acid, and by what tests may it be recognized? EXAMINATION OF NORMAL AND ABNORMAL URINE. 441 of blood, and a brownish-green suggests the presence of the coloring matter of bile. (Plate VII., 1-3.) The true nature of the normal coloring matters of urine is as yet doubtful; the existence of at least two has, however, been demonstrated; they have been named urobilin and indican or uroxanthin, and are, most likely, products of the decomposition of biliary matters. Indican. Vormal urine contains but very little of this coloring matter, but its quantity is increased in a number of diseases. The most convenient test is made by mixing equal volumes of urine and hydrochloric acid in a test-tube and adding drop by drop a filtered solution of bleaching-powder until a green, violet, or blue color is noticed. Vormal urine shows a green color only, while a violet-red or intense blue color indicates the presence of indican. By shaking the contents of the test tube with a little chloroform, the indican is absorbed by the latter, imparting to it a distinct blue color. If the urine should contain albumin, this must be separated before applying the test. Abnormal coloring matters are chiefly those of blood, bile, and of certain vegetables; thus, rhubarb and senna leaves cause a reddish-yellow to deep red color, especially in alkaline urine; santonin produces a bright yellow color, changing to red or crimson on the addition of an alkali. Carbolic acid introduced into the system causes a dark, or even black discoloration of urine. The coloring matters of blood may be recognized by adding to a few drops of urine a drop of freshly prepared tincture of guaiacum, and agitating with a solution of ozonized ether (ethe- real solution of hydrogen dioxide); the latter is colored blue in case haemoglobin is present. In place of ozonized ether oil of turpentine, which has been in contact with atmospheric air for some weeks, may be used and the test made by allowing urine to flow down the test-tube containing a mixture of the oil and tincture; a blue coloration, slowly appearing at the juncture of the liquids, indicates the presence of blood. Detection of biliary coloring matter will be considered later. Odor. The normal odor of fresh urine is characteristic, and is sometimes spoken of as aromatic; it is not known by what sub- stance or substances this odor is caused. The ammoniacal and 442 PHYSIOLOGICAL CHEMISTRY. putrescent odor which urine acquires on standing, is due to the products of decomposition formed, chiefly ammonia. A number of substances taken internally and separated |by the kidneys from the blood, cause the urine to assume a charac- teristic odor; aromatic substances especially impart such odors; oil of turpentine gives an odor reminding of violets, and the odor of cubebs, copaiba, asparagus, garlic, valerian, and other substances is promptly transferred to the urine of persons using these drugs internally. A sweetish smell sometimes attends the presence of large quantities of sugar in urine. Keaction. This is generally acid in healthy urine which has been recently passed, but may become neutral or alkaline within a short period, by decomposition of urea and formation of am- monium carbonate. The acid reaction of urine is due chiefly to free uric and liip- puric acid, and also to the acid phosphates of sodium and potas- sium. The acidity may be determined volumetrically by the addition of deci-normal solution of sodium or potassium hydrox- ide to 100 cc. of urine. The acidity of urine is generally expressed as oxalic acid, of which 1 cc. of normal potash solution neutralizes 0.0063 gram. If, for instance, 100 cc. of urine require 15 cc. of deci-normal potash solution, then the acidity of the 100 cc. urine is 15 X 0.0063 = 0.0945; and for the total urine of the 24 hours—say 1800 cc.—the acidity expressed as oxalic acid is, therefore, equal to 1.701 gram. Experiment 71. Prepare normal soda solution as directed on page 259, dilute it with 9 parts of water, and titrate with this deci-norinal solution 100 cc. of urine, using litmus paper as an indicator. Specific gravity. The normal specific gravity of an average amount of 1500 cc. of urine passed in twenty-four hours is about 1.020, but it varies, even in health, from 1.012 to 1.025 or more. A specific gravity above 1.028 generally indicates the presence of sugar, larger quantities of which may cause the specific gravity to rise to 1.050. Albuminous urine is generally of 1owt specific gravity, 1.010 to 1.012. The determination of the specific gravity of urine is generally accomplished bj' the urinometer, which is a small hydrometer indicating specific gravities from zero (or 1000) to 60 (or 1060). As the temperature influences the density of liquids, a urinometer EXAMINATION OF NORMAL ANI) ABNORMAL URINE. can only give correct results at a certain degree of temperature, which is generally marked upon instrument. Many of the urinometers manufactured] and sold, even at the normal (or stated) tempera- ture, show incorrect gravities, and for this reason a urinometer should always be thoroughly tested before placing full confidence in the results obtained by it. (See Fig. 42.) Determination of total solids. An ap- proximate determination of total solids may be deducted from the specific gravity of the urine, as it has been found that the last two figures of the specific gravity of urine, multiplied by 2.2, correspond to the number of grams in 1000 cc. of urine. If, for instance, 1750 cc. of urine, of a specific gravity of 1.018, have been discharged in twenty- four hours, then the quantity of total solids in 1000 cc. will be 18 X 2.2, or 39.6grams; and in 1750 cc. 69.3 grams. A more exact method of determining the total solids in urine is the evapo- ration of about 10 cc. in a weighed platinum dish over a water-bath (or, better, under the receiver of an air- pump over sulphuric acid), until it is found that no more loss in weight ensues on continued exposure of the dish in the drying apparatus. By now reweighing the dish, plus contents, and deducting from the weight that of the empty dish, the weight of total solids is found. Fin. 42. Urinometer. Determination of inorganic constituents. The platinum dish con- taining the known quantity of total solids is exposed to the action of a non-luminous flame, and the heat continued until all organic matter has been destroyed and expelled. By reweighing now, and deducting the weight of the platinum dish, plus ash, from the weight of the dish, plus total solids, the quantity of 444 PHYSIOLOGICAL CHEMISTRY. total organic matter is determined; and by deducting weight of dish from weight of dish plus ash, the total quantity of inorganic matter is found. Experiment 72. Determine total solids, water, total organic and inorganic matters in a specimen of urine by following the directions given above. Use 10 or 20 cc. of urine for the analysis. The analysis of this ash is effected by the methods given in connection with the consideration of the various acid and basic constituents themselves. Chlorine is determined by precipitating the solution of the ash in nitric acid with silver nitrate, sulphuric acid by barium chloride, phosphoric acid by ammonium molyb- date, calcium by ammonium oxalate, potassium by platinic chloride, iron by potassium etc. For the determination of many of the inorganic constituents, it is not necessary to destroy the organic matter as described above, but this determination can be effected directly. Thus, chlorine may be precipitated directly from urine (slightly acidu- lated with nitric acid) by silver nitrate; the precipitated silver chloride is collected upon a small filter, well washed, dried, and weighed in a porcelain crucible, after the filter (to which par- ticles of silver chloride adhere) has been burned separately and its ash added to the contents of the crucible, which is moderately heated before weighing. Experiment 73. Prepare deci-normal solution of silver nitrate as directed on page 266, and use it for the quantitative estimation of chlorine as follows: Dilute 10 cc. of urine with about 100 cc. of water, add a few drops of potas- sium chromate solution and then the silver solution from a Gray Lussac burette until the appearance of a permanent reddish color indicates the end of the reac- tion. Each cc. of silver solution used represents 0.00354 gram of chlorine or 0.00584 gram of sodium chloride. If the urine should be highly colored, destroy the coloring matter by boiling the 10 cc. of urine previous to titration with a dilute solution of permanganate of potassium, which add drop by drop until a slight rose tint becomes permanent. Now add a trace of oxalic acid to destroy this excess of permanganate and filter off the precipitate of organic matter and oxide of manganese and use the clear neutralized solution for titration. Phosphoric acid is found in urine, in part (about two-thirds) combined with alkalies, and in part (about one-third) with lime and magnesia. These phosphates have in acid or neutral urine the composition NaH2P04, Na2HP04, CaHP04, CaH42P04, MgHP04; in alkaline urine compounds of the composition Na3P04, Ca32P04, Mg32P04, MgNH4P04 may be present. 445 EXAMINATION OF NORMAL AND ABNORMAL URINE. By adding any alkali the phosphates of calcium and magnesium (generally termed earthy phosphates) are precipitated, the phos- phates of sodium or possibly potassium remain dissolved. The so-called earthy phosphates (phosphates of calcium and magnesium) may be approximately determined by adding a few drops of an alkaline hydrate to about 50 cc. of urine, heating to the boiling-point, collecting on a filter, washing, igniting, and weighing in a platinum crucible. Experiment 74. Add to 50 cc. of urine a few drops of calcium chloride solu- tion and then water of ammonia. Phosphoric acid is completely precipitated, chiefly as tricalcium phosphate, Ca32P04, containing, however, a very small quantity of magnesium ammonium phosphate. Collect the precipitate on a filter, wash well, dry, ignite and weigh it. Calculate the phosphoric acid from the tricalcium phosphate, without reference to the small amount of magnesium phosphate. Experiment 75. Add to 100 cc. clear urine 5 cc. hydrochloric acid; boil, and then add barium chloride to complete precipitation. Set aside for one hour, filter, wash well, dry, ignite and weigh. Calculate from the weight of barium sulphate, thus obtained, the percentage of sulphuric acid present in the urine examined. The methods for estimating urea and uric acid have been de- scribed in the preceding chapter. Detection of albumin. Serum-albumin and serum-globulin are the forms most frequently present in urine, but peptones and other albuminoids are also met with. There are chiefly three methods by which the presence of albumin in urine may be demonstrated; they are based upon the coagulation of albumin by heat, by nitric acid, or by picric acid, but either metaphos- phoric acid or trichloracetic acid may also be used. The urine used for any of these tests must be perfectly clear; if it be not clear, it must be rendered so by processes which vary according to the nature of the substance [causing the tur- bidity. In most cases filtration through good filter-paper may be sufficient; but if this does not accomplish the desired result, it may become necessary to use other means. Thus, if earthy, amorphous phosphates be present (which, especially in alkaline urine, are apt to pass through the best filter-paper),, they may be removed by adding to the urine about a fourth part of potas- sium hydrate solution, warming the mixture, and filtering. If the turbidity be caused by urates, the urine will generally be- 446 PHYSIOLOGICAL CHEMISTRY. come clear by passing the test-tube once or twice through a flame. The clear urine is then tested by either (or all) of the following methods: a. Coagulation by heat. A test-tube is tilled about one-halt with the urine, to which, if not distinctly acid to test-paper, a few drops of acetic acid are added. (In case potassium hydrate has been added in order to precipitate the phosphates, enough of acetic acid must be added to cause a distinct acid reaction.) The test-tube is then held over the flame in such a manner that the heat acts upon the upper half of the urine only, heating this portion gradually to the boiling-point. By thus operating, two strata of fluid are obtained for comparison, and by holding the test-tube against the light, or against a black background, any difference in the appearance of the upper and lower strata may easily be noticed. Any cloudiness or opacity seen may be due to albumin, but may also be caused by phosphates. To decide this question a few drops (10 to 15) of nitric acid are allowed to flow gently down the side of the tube into the urine. The precipitate will readily disappear when caused by phosphates, but will be permanent when albumin is present. Fro. 43 Nitric acid test for urine. Instead of heating, as above described, merely the upper'half of the urine, the total quantity of the urine (acidulated by a few drops of acetic acid) may be heated, and the test-tube set aside 447 EXAMINATION OF NORMAL AND ABNORMAL URINE. for several hours (after having added 10 to 15 drops of nitric acid), in order to allow the albumin to subside, when it can be more distinctly seen and its quantity noticed. b. Nitric acid test. A test-tube is filled to the depth of about half an inch with colorless nitric acid, and an equal quantity of urine is allowed to flow down the side of the test-tube in such a manner that the specifically lighter urine forms a distinct and separate layer over the nitric acid. (If the urine be allowed to flow from a pipette, as shown in Fig. 43, the formation of the two strata is easily accomplished.) In case albumin is present, ii white band or zone of varying thickness (according to the quan- tity of albumin present) appears at the point of contact. If the urine be highly concentrated, a similar white zone is formed between the acid and urine, due to the separation of in- soluble acid urates; the difference between the separated urates and albumin is that the latter forms a sharply defined zone, whilst the urates diffuse into the urine above. Moreover, the urates dissolve on the application of heat. Finally, the separa- tion of acid urates may be avoided by diluting the urine with an equal volume of water and placing this diluted urine upon the nitric acid. c. Picric acid test for albumin. This test has the advantage that neither phosphates nor urates can be mistaken for albumin. It consists in slowly dropping urine into a test-tube filled to about one-fourth with a highly colored solution of picric acid in water. In the presence of albumin a white cloud or sharply defined white turbidity is formed, and on warming the liquid the albumin collects into balls which rise to the surface of the liquid. d. Metaphosphoric acid (glacial phosphoric acid) or trichlor-acetic acid may be used for the detection of albumin by dropping a fragment of either substance into a few cc. of urine contained in a test-tube. As the acids dissolve, a cloudy ring forms in the presence of albumin, which is not dissolved on warming. In the above methods the manipulations and precautions are minutely described, in order to detect small quantities or even traces of albumin. When albumin is abundantly present, there is no difficulty whatever in its determination, as heat will pre- cipitate it from an acid, neutral, or sometimes even alkaline urine; the precipitate should, however, always be tested by the addition of a few drops of nitric acid, and the previous addition of a few drops of acetic acid is also advisable. 448 PHYSIOLOGICAL CHEMISTRY. A neutral urine should never be acidified by nitric acid (instead of acetic acid), because a drop or two of nitric acid may in some cases prevent the coagulation of albumin by heat, though a larger quantity (10 to 20 drops) has no such effect. Quantitative estimation of albumin. The average amount of albumin present in acute cases of albuminuria is 0.1 to 0.5 per cent., rarely over 1 per cent., though it may rise to 4 per cent. An approximate method for the comparative estimation of albumin is to precipitate it (with the precautions above given) in a graduated test-tube by heat and setting aside for twelve (or better for twenty-four) hours. At the end of that time the pro- portion of the coagulated albumin which has collected at the bottom of the fluid is noticed. If the albumin occupy one-fourth, one-sixth, one-tenth of the height of the liquid, there is said to be one-fourth, one-sixth, or one-tenth of albumin in the urine. If, however, at the end of twelve or twenty-four hours scarcely any albumin has collected at the bottom, there is said to be a trace. A better method of exactly estimating the amount of albumin is its complete separation and weighing, as described below. Experiment 76. Acidify 100 cc. of clear albuminous urine with acetic acid ; heat to the boiling-point in a water-bath for half an hour, and filter through a small filter, previously dried at 110° 0. (230° F.) and weighed; wash with boiling water to which a little ammonia water has been added (to remove uric acid and urates), then with pure water until the filtrate is not rendered turbid any longer by silver nitrate, next with pure alcohol, and finally with ether. Dry filter and contents at 110° C. (230° F.) and weigh. As it may happen that the precipitated albumin encloses earthy phosphates, it is well to burn filter with contents in a platinum crucible, and to deduct the weight of the remaining inorganic residue (less the weight of the filter ash) from that of the albumin. Peptones may be recognized by first precipitating all albumin by means of boiling the urine acidified by acetic acid, filtering and pouring the cold filtrate carefully upon some Fehling’s solu- tion contained in a test-tube. At the junction of the two fluids a phosphatic cloud will appear, above which there will be seen a rosy-tinted layer in the presence of peptones. In case the albumin should not have been separated completely, the color will be more violet. Blood. The presence of blood in urine manifests itself gener- ally, unless the amount be too slight, by a blood-red or brownish EXAMINATION OF NORMAL AND ABNORMAL URINE. 449 color with a bluish, smoky, or greenish tint, and deposits a red or reddish-brown sediment after standing. As a general rule, all constituents of blood, including the corpuscles, are present, but in some cases haemoglobin alone has been found. The tests for blood depend either on the microscope or on chemical changes. By the microscope is examined the deposit which forms on standing; almost unaltered blood corpuscles may be found, or they may be much swollen, decolorized, and de- formed ; the corpuscles are generally accompanied by blood and fibrin casts. Whenever blood is present, there are necessarily also albu- minoids, which are precipitated by acidulating with acetic acid and boiling, when a brownish coagulum of albumin and haematin is precipitated. Haemoglobin is also tested for by means of adding to the urine a few drops of freshly prepared tincture of guaiacum, a little ozonized ether, and shaking well. If haemoglobin is present, the ether assumes a blue color. Detection of sugar. Traces of sugar, or as much as 0.01 per cent., are said to occur normally in urine, and are of no signifi- cance ; moreover, it is as yet doubtful whether these traces of sugar are actually present in normal urine. A large amount of sugar is often indicated by a high specific gravity of the urine, which then varies from 1.030 to 1.050; the quantities found vary from mere traces to 10 per cent., the latter quantity, how- ever, being a very rare occurrence, while 3 to 5 per cent, is often found in the urine of persons suffering from diabetes mellitus. Of the many tests by which sugar may be detected in urine four only will be mentioned; they are generally known as the copper tests (also termed Trommer’s or Fehling’s test, according to the manner in which the reaction is conducted), the bismuth test, the fermentation test, and the picric acid test. The copper tests, as well as the bismuth test, are based upon the deoxidizing or reducing power which grape-sugar possesses for many metallic oxides such as cupric, bismuthic, and silver oxide, which, in the presence of alkalies, are converted into the lower state of oxida- tion, or are reduced to metals. The tests for sugar should always be preceded by tests for 450 PHYSIOLOGICAL CHEMISTRY. albumin, which latter, if present, should be removed by coagula- tion and filtration. Trommer’s test. A few drops (2-4) of a 5 per cent, solution of cupric sulphate are added to about 5 to 8 cc. of urine in a test- tube and then an equal volume of potassium (or sodium) hydroxide solution is added. The alkaline hydroxide precipitates both earthy phosphates and cupric hydroxide, the latter, however, dis- solving (especially if sugar be present) in the excess of the alkali, producing a beautiful blue transparent liquid. (If no sugar is present, the color is less blue, but more of a greenish hue.) The liquid is now boiled for a fewr seconds, when, if sugar be present, a yellow precipitate of cuprous hydroxide is formed which sub- sequently loses its water and becomes the red cuprous oxide, which falls to the bottom or adheres to the sides of the test-tube. (Plate VII., 5.) As various organic substances (other than sugar) have a ten- dency to reduce cupric oxide at a temperature of 100° C. (212° F.), it is well to set aside a test-tube prepared as above (without heating it) for from six to twenty-four hours. If sugar be present, the formation of cuprous hydrate will gradually take place, whilst most other organic matters do not act upon cupric oxide at ordi- nary temperature. In drawing conclusions from the above test, it.should be re- membered that a change of color does not indicate sugar; that a precipitate of earthy phosphates must not be mistaken for cuprous oxide; and that substances other than sugar may de- oxidize cupric oxide at the temperature of 100° C. (212° F.). jFehling’s test differs from Trommer’s test merely in using a previously mixed reagent instead of producing this reagent, as it were, in the urine by adding to it cupric sulphate and an alkaline hydroxide successively. This reagent, known as Fehling’s solu- tion, is made as follows : Crystallized cupric sulphate ..... 34.65 grams. Dissolved in Pure water 200 “ This solution is poured gradually into a solution of Crystallized sodium potassium tartrate . . . 173 “ Dissolved in Solution of sodium hydroxide of sp. gr. 1.12 . . 500 “ The clear, well-mixed fluid is diluted to 1000 cc. The addition of sodium-potassium tartrate in Fehling’s solu- tion prevents the precipitation of cupric hydroxide by the alka- EXAMINATION OF NORMAL AND ABNORMAL URINE. 451 line hydroxide. This action is analogous to the formation of the soluble scale compounds of iron, where the precipitation of ferric hydroxide is also prevented by tartaric or other organic acids. Fehling’s solution is very apt to decompose, and if not recently made should be tested by boiling some of it alone and some of it mixed with about three volumes of water in test-tubes; if no precipitate occurs in either case, the fluid may safely be used. This is done by heating about 10 cc. of Fehling’s solution in a test-tube, and adding drop by drop the suspected urine; if the latter contains larger quantities of sugar a yellow or red precipi- tate of cuprous hydroxide and oxide will be produced very readily; if but small quantities are present, an equal volume of urine may be added to the solution, and the boiling repeated several times before the reaction takes place. Botger’s bismuth test consists in adding to a mixture of equal volumes of urine and potassium (or sodium) hydroxide solution a few grains of subnitrate of bismuth and boiling for half a minute. If sugar be present, a gray or dark-brown, finally black, precipitate of metallic bismuth is formed. If but very little sugar is present, the undecomposed excess of bismuthic nitrate mixes with the metallic bismuth, imparting to it a gray color; the test should then be repeated with a smaller amount of the bismuth salt. (Plate VII., 6.) If the urine contains hydrogen disulphide (sometimes pro- duced by decomposition of certain urinary constituents), black bismuthic sulphide will be formed, which may be mistaken for metallic bismuth; albumin itself may be the cause of the forma- tion of alkaline sulphides: the previous complete separation of albumin is therefore indispensable. The fermentation test is based upon the decomposition of sugar by the action of yeast with generation of carbon dioxide. The test is made by adding to about 50 or 75 cc. of urine (contained in a large test-tube or small flask) a few cc. of ordinary baker’s or brewrer’s yeast. The vessel containing the urine is provided with a perforated cork, through which is passed one limb of a bent glass tube, long enough to reach nearly to the bottom of the vessel, which should be completely filled with urine. If the urine be acid, it should be rendered slightly alkaline by a little sodium carbonate. Under the second limb of the bent glass tube is placed a beaker. 452 PHYSIOLOGICAL CHEMISTRY. The apparatus thus prepared, is placed in a room having a temperature of about 22°-28° C. (72°-82° F.). If sugar be present, fermentation will commence within twelve hours, and will manifest itself by the formation of carbon dioxide, which will force a portion of the fluid through the bent tube into the beaker placed there for its reception. The disadvantages of this process are the length of time re- quired for its performance, the unreliability of the ferment, and the fact that small quantities of sugar (less than 0.5 per cent.) evolve so little carbon dioxide that a doubt may be felt as to the presence of sugar at all. Picric acid test for sugar. It has been mentioned above that picric acid serves as an excellent reagent for albumin; in the presence of alkalies it may also be used to advantage as a reagent for sugar. Urine is mixed with an equal volume of an aqueous solution of picric acid, a little caustic potash is added and gently heated: a marked reddish or reddish-brown coloration indicates sugar. Quantitative estimation of sugar. Various methods for the de- termination of sugar in urine have been suggested, some of which depend on the loss in weight caused by the escape of carbon dioxide during fermentation. The disadvantages of the fermentation test for qualitative determination have been pointed out above, and apply also to quantitative estimations. By far the best method is the decomposition of a copper solu- tion of a known strength, and Fehling’s solution prepared as stated, above, answers this purpose well. 1000 cc. of Fehling’s solution, containing 34.65 grams of crystallized cupric sulphate, CuS04.5H2O, are exactly decom- posed by 5 grams of grape-sugar, or 1 cc. of solution by 0.005 of grape-sugar. To make the quantitative determination, operate as follows: 10 cc. of Fehling’s solution are poured into a porcelain dish of about 200 cc. capacity, placed over a flame. The copper solution is diluted with about 40 cc. of water, and heated to boiling; to the boiling liquid, urine (which has been previously diluted with 9 parts of water) is added from a burette very gradually, until the blue color of the solution has disappeared, and there remains, upon subsidence of the cuprous oxide, an almost color- less, clear liquid. A filtered portion of this liquid, acidified EXAMINATION OF NORMAL AND ABNORMAL URINE. 453 with hydrochloric acid, should not give a reddish-brown pre- cipitate with potassium ferrocyanide (a precipitate would show that all copper had not been precipitated, and that more urine was needed), whilst a second portion of the filtered fluid should not produce a red precipitate on boiling with a few drops of Fehling’s solution (a precipitate would indicate that too much urine has been added, in which case the operation has to be repeated). The calculation of the amount of sugar present is easily made. 10 cc. of Fehling’s solution are decomposed by 0.05 gram of sugar; this quantity must, therefore, be contained in the number of cc. of urine used. Suppose 30 cc. of urine, diluted with 9 parts of water, or 3 cc. of pure urine, have been required to decompose the 10 cc. of Fehling’s solution, then 3 cc. of urine contain of grape sugar 0.05 gram, or 100 cc. of urine 1.666 gram, according to the equation : 3 : 0.05 :: 100 : x x = 1 666. If the urine contains but very little sugar, it may be used di- rectly without diluting it, or instead of diluting it with 9 parts of water, it may be diluted with 4 volumes or with an equal volume of water. Experiment 77. Determine the amount of sugar in urine by the method de- scribed above. If no suitable urine is to be had, add some glucose to urine and use this solution. Detection of bile. The presence of bile in urine is generally indicated by a decided color, which varies from a deep brownish- red to a dark brown ; the foam of such urine (produced by shaking) has a distinct yellow color, and a piece of filtering- paper or a piece of linen dipped into the urine assumes a yellow color, which does not disappear on drying. The further detection of bile depends upon the reactions of the biliary coloring matters or biliary acids ; it frequently happens, however, that the pigments are present, whilst the acids are not. Grudin's test for biliary coloring matters has been already con- sidered, and may be applied to urine either by allowing a small quantity of nitric acid, containing some nitrous acid, to flow down the sides of a test-tube (containing the urine) in such a manner that the two fluids do not mix, or by placing upon a porcelain plate a few drops of the urine, near it a few drops of 454 PHYSIOLOGICAL CHEMISTRY. nitric acid, to which one drop of sulphuric acid has been added, and allowing the two liquids to approach gradually. In both cases (if bile pigment is present) a play of color is seen at the point of union between the two fluids, the colors changing from green to blue, violet-red, and yellow or yellowish-green; while the appearance of the green at the beginning is indispensable to prove the presence of bile, the presence of all the other colors is not essential. (Plate VII., 7.) The above test may be made in a somewhat modified form by mixing the urine with a concentrated solution of sodium nitrate, and pouring down the sides of the test-tube concentrated sul- phuric acid in such a manner as to form two distinct layers; the colors are seen at the point of contact as above. If the urine be very dark in color, it should be diluted with water before applying the above tests. Ultzmann’s test for bile pigment is made mixing 10 cc. of urine with 3 or 4 cc. of potassium hydroxide solution (1 in 3 of water), and supersaturating with hydrochloric acid; the mixture assumes a beautiful emerald-green color. Pettenkofer’s test for biliary acids is made by dissolving a few grains of cane-sugar in urine contained in a test-tube, and allow- ing some concentrated sulphuric acid to trickle down the side of the inclined test-tube; a purple band is seen at the upper margin of the acid and on slightly shaking the liquid becomes at first turbid, then clear and almost simultaneously turns yellow, then pale cherry-red, dark carmine-red, and finally a beautiful purple violet. The temperature must not be allowed to rise much above 38° C. (100° F.). (Plate VII-,, 8.) As many substances (other than biliary acids) show a similar reaction, it is often necessary to separate the bile acids by the process described in connection with the consideration of bile itself. Urinary deposits (sediments). Normal urine is always clear, but occasionally, and particularly in abnormal conditions, it is turbid. Urine may be turbid when passed, and this indicates an excess of mucus, or the presence of renal epithelium, pus, blood, chyle, semen, bile, or phosphate or urate of sodium in excess, etc. A turbidity subsequent to the passage of the urine is generally due to the precipitation of phosphates or urates, or it may result EXAMINATION OF NORMAL AND ABNORMAL URINE. 455 from fermentation or decomposition. Either of the substances named will form a deposit on standing. When such a deposit is to be examined, a few ounces of the urine should be set aside for several hours in a tall, narrow, cylindrical glass; wThen the sediment has collected at the bottom, the supernatant urine may be decanted, or the sediment may be taken out by means of a pipette for examination. Sediments are either organized or unorganized. To the first belong: mucus, blood, pus, urinary casts, epithelium, sperma- tozoids, fungi, infusorise, etc. ; to the second belong: uric acid, urates, calcium oxalate, phosphate, or carbonate, magnesium- ammonium phosphate, cystin, hippuric acid, etc. The chemical examination of any urinary sediment should always be preceded by a microscopical examination, which latter is in many cases the only way of determining the nature of the sediment, especially of the organized substances. Most of the unorganized and either crystalline or amorphous sediments may be easily recognized by chemical means. Urates of ammonium, calcium, and sodium dissolve on heating the urine, and are reprecipitated on cooling. The murexid test is used in addition. Phosphates of calcium or ammonium-magnesium dissolve in acetic acid, and ammonium molybdate dissolved in nitric acid produces a yellow precipitate on heating. Calcium oxalate is insoluble in acetic, but soluble in hydro- chloric acid, from which solution it is reprecipitated on neutraliz- ing with ammonia. Uric acid is not dissolved by heat, nor by acetic or hydro- chloric acid, but dissolves on the addition of caustic potash and burns on platinum foil without leaving a residue; it is recog- nized by the murexid test. Cystin is insoluble in water and alcohol, but soluble in mineral acids and in caustic alkalies; from either solution it is reprecipitated by neutralizing. Cystin contains 26 per cent, of sulphur, which causes the formation of black sulphide of lead when cystin is boiled with caustic potash to which a few drops of solution of lead acetate have been added. Urinary calculi are solid deposits of larger or smaller size formed from the urine within the tracts (kidneys, ureter, bladder, and urethra). The chemical composition of the calculi is gener- PHYSIOLOGICAL CHEMISTRY. ally that of either of the above-named unorganized sediments, and their nature can easily be determined by using the following method: Make a section through the centre of the calculus, scrape some of the substance off, powder it finely, and heat some of it on platinum foil. It may either burn away completely (uric acid, urate of ammonium, cystin, xanthin) or may be partially combus- tible (urates or oxalates), or may be incombustible (chiefly phos- phates). A slight blackening occurs generally, even in heating a calculus consisting of incombustible matter and is due to the presence of traces of organic urinary constituents. If completely combustible, digest a little of the powder with dilute hydrochloric acid; cystin and xanthin are dissolved, uric acid remains undissolved. Apply murexid test for uric acid, the above mentioned lead test for cystin, and for xanthin test by dissolving a little of the calculus in nitric acid and evaporating to dryness, when in the presence of xanthin a bright yellow residue will be left, which becomes violet-red, when treated with caustic potash. In case uric acid has been found, it may be in combination with ammonia, which may be verified by heating the powder with a little caustic potash, when ammonia gas is liberated, which may be recognized by its action on red litmus paper, odor, etc. If partially combustible or incombustible, digest some of the powder with dilute hydrochloric acid. If it dissolves completely, uric acid is not present. If a residue be left, apply the murexid test. To a portion of the solution add ammonium molybdate and heat; a yellow precipitate indicates phosphoric acid. To another portion add ammonia water and then excess of acetic acid; a white pulverulent residue indicates calcium oxalate, which can be verified by igniting some of the calculus and adding a drop of acid, when effervescence will be noticed, the oxalate having been converted into a carbonate by the ignition ; the solution thus obtained can be tested for calcium by the addi- tion of water of ammonia and ammonium oxalate. In case phosphoric acid has been found, this is present either as a calcium or magnesium-ammonium salt. To distinguish between them, neutralize the solution of the powder in hydrochloric acid with ammonia, add acetic acid and ammonium oxalate; a white pre- cipitate indicates calcium ; if no precipitate is produced, super- EXAMINATION OF NORMAL AND ABNORMAL URINE. 457 saturate with ammonia, when the crystalline magnesium-ammo- nium phosphate will gradually form. Most common are calculi of uric acid ; often met with are those of urates, phosphates, and oxalates; rarely, however, those of xanthin and cystin. Microscopical examination of urinary sediments. The chemical examination of any urinary sediment should always be preceded by a microscopical examination, which latter is in many cases the only way of determining the nature of the sediment, especi- ally of the organized substances. Fig. 44, A-O, shows the principal sediments found in, or produced from, urine, as seen with a magnifying power of 200 diameters. A. Uric acid occurs in many different forms, mostly in rhombic plates, with rounded obtuse angles, often joined into rosettes. Uric acid is found almost invariably colored red or reddish- brown, which generally distinguishes it from other sediments. The crystals or clusters of crystals are often large enough to be seen by the naked eye, and are then known by the terms “sand,” “ gravel,” or “ red-pepper grains.” B. Acid ammonium urate is found generally associated with amorphous or crystalline phosphates, in urine which has become alkaline. The crystalline globules are generally covered with spinous excrescences, which give them the characteristic “thorn- apple” appearance. C. Sodium urate forms generally a part in the pulverulent, heavy, variously tinted deposit of the mixed urates known as “ brickdust ” or “ lateritious ” sediment. It occurs either in fine amorphous granules which cannot be distinguished microscopi- cally from other amorphous sediments or in a crystalline form as shown in the figure. D. Urea nitrate crystallizes readily in large six-sided plates on the addition of nitric acid to urine. E. 1, Leucin, or amido-caproic acid, C6Hn(]^H2)02; and 2, Tyrosin, C9HlrNU3, are but rarely met with in urinary de- posits. Leucin is found either as rounded lumps, showing but little crystalline structure, or as spherical masses, exhibiting fine radial striation. Tyrosin appears generally in fine, long, silky needles, forming bundles or rosettes. F. Cystin occurs occasionally as a grayish, crystalline deposit, 458 PHYSIOLOGICAL CHEMISTRY. Fig. 44. Urinaiy sediments. 459 EXAMINATION OF NORMAL AND ABNORMAL URINE. forming transparent six-sided plates; it also occurs in calculi. The latter may be recognized by the above mentioned chemical properties or by dissolving a little in hydrochloric acid and neutralizing with ammonia, when cystin is reprecipitated and shows the characteristic six-sided plates under the microscope. G. Magnesium ammonium phosphate, or triple phosphate, MglSTH4P04.6II20, is found generally in triangular prisms with bevelled ends, as shown in 1, but sometimes also in star-shaped, feathery crystals, represented in 2. H. Calcium phosphate, Ca32P04, is most frequently found in amorphous globules, but also crystallized either in prisms, 1, or in “wedge-shaped ” crystals, 2. I. Calcium oxalate, CaC204 occurs either in quadratic octohedra with brilliant refraction, 1, or sometimes in the shape of “dumb- bells,” 2. J. Blood-corpuscles appear under the microscope as reddish, circular disks, sometimes laid together in strings. If seen in protile, they appear biconcave. 1 shows the corpuscles in a fresh condition; 2, as generally seen in urine. Iv. Mucus and pus are often difficult to distinguish from one another under the microscope, as they both appear as little granular globules, varying somewhat in appearance with the reaction of the urine. Pus is rendered slimy, ropy, viscid, and tenacious by the addition of caustic potash. 1 shows globules of mucus, 2 of pus, and 3 of pus treated with acetic acid, which, clears up the granular globules with the appearance of a nucleus L. Hcemin crystals. The formation of these crystals often serves to recognize blood and is accomplished by mixing the latter on a glass slide with a little sodium chloride and a drop of glacial acetic acid and warming gently, when the characteristic crystals will appear. By repeating the process several times larger and better developed crystals are obtained. M. 1, Hyaline casts ; 2, Granular casts. Urinary casts are tube- like cylinders, often found together with blood and pus cor- puscles, or holding in their substance or walls epithelial cells, mucous corpuscles, and fat globules. Hyaline casts are dis- tinguished by their transparent appearance, while granular casts show a more or less granular surface. H. Epithelial casts and cells. According to the origin (vagina, urethra, bladder, etc.) of these bodies, they differ somewhat, and 460 PHYSIOLOGICAL CHEMISTRY. it is difficult to recognize with certainty the source whence they are derived. 0.1, Waxy casts; 2, Casts with blood corpuscles; 3, Casts with fat globules. Waxy casts resemble hyaline casts, but are less transparent. Casts containing blood corpuscles or fat globules are generally easily recognized. In addition to the above mentioned urinary deposits may also be found various kinds of fungi, vibrionse, spermatozoids, hair, or even such foreign matters as fibres of cotton, wool, or silk, with the characteristic appearance of which the student should familiarize himself thoroughly. Questions.—551. What points are to be considered, and what substances determined in the analysis of normal and abnormal urine ? 552. What is the color of urine, and what are the chief causes influencing the color? 553. What is the specific gravity of healthy urine, how is it determined, and how is the total amount of solids approximately calculated from the specific gravity ? 554. De- scribe three tests by which albumin may be recognized, and state the precautions necessary in making these tests. 555. How may the quantity of albumin in urine approximately and how accurately be determined? 556. Describe Trommer’s, Fehling’s, the bismuth, and the fermentation test for sugar. On what principles are they based ? 557. How is sugar determined quantitatively ? 558. By what tests are biliary pigments and acids recognized in urine? 559. What is the nature of urinary sediments, and by what means are they recognized ? 560. What are urinary calculi generally composed of, and by what simple tests can their nature be determined ? APPEN DI X. TABLE OF WEIGHTS AND MEASURES. Measures of length. 1 millimeter = 0.001 meter = 0.0394 inch. 1 centimeter = 0.01 meter = 0.3937 inch. 1 decimeter = 0.1 meter = 3.9371 inches. 1 meter == 39.3708 inches. 1 decameter = 10 meters = 32.8089 feet. 1 hectometer == 100 meters = 328.089 feet. 1 kilometer = 1000 meters = 0.6214 mile. 1 yard or 36 inches = 0.9144 meter. Measures of capacity. 1 milliliter — 1 cc. = 0.001 liter = 0.0021 U. S. pint. 1 centiliter = 10 cc. = 0.01 liter = 0.0211 U. S. pint. 1 deciliter = 100 cc. = 0.1 liter = 0.2113 U. S. pint. 1 liter == 1000 cc. = = 1.0567 U. S. quart. 1 decaliter = 10 litres — 2.6418 TJ. S. gallons. 1 hectoliter = 100 litres = 26.418 TJ. S. gallons. 1 kiloliter = 1000 litres = 264 18 U.S. gallons. 1 TJ. S. gallon =3785.3 grams. Weights. 1 milligram = 0.001 gram = 0.015 grain Troy. 1 centigram = 0.01 gram = 0.154 grain Troy. 1 decigram = 0.1 gram = 1.543 grain Troy. 1 gram = 15.432 grains Troy. 1 decagram = 10 grams = 154.324 grains Troy. 1 hectogram = 100 grams = 0.268 pound Troy. 1 kilogram = 1000 grams = 2.679 pounds Troy. 1 grain Troy = 0.0648 gram. 1 drachm Troy == 3.888 grams. 1 ounce Troy = 31.103 grams 1 ounce avoirdupois = 28.350 grams 1 pound avoirdupois = 453 592 grams. 462 AP PEN DIX. Commercial weights and measures of the U. S. A. 1 pound avoirdupois = 16 ounces. 1 ounce = 437.5 grains. 1 gallon = 231 cubic inches. 1 gallon = 4 quarts = 8 pints. 1 pint of water weighs 7291.2 grains at a temperature of 16.6°. Troy Weight. 1 drachm = 60 grains. 1 ounce = 8 drachms = 480 grains. TABLE OF ELEMENTS. Aluminium . . A1 27 Antimony . . Sb 120 Arsenic . . As 74.9 Barium . . Ba 136.8 Beryllium . .Be 9 Bismuth . . Bi 210 Boron . . . Bo 11 Bromine . . Br 79.8 Cadmium . . Cd 111.8 Ceesium . . Cs 132.6 Calcium . . Ca 40 Carbon . . . C 12 Cerium. . - Ce 141 Chlorine . . Cl 35.4 Chromium . . Cr 52.4 Cobalt . . .Co 58.9 Copper . . . Cu 63.2 Didymium . . Di 144.6 Erbium. . . E 165.9 Fluorine . . F 19 Gallium . . G 68.8 Germanium . . Ge 72 Gold. . . . Au 196.2 Hydrogen . .11 1 Indium . . In 113.4 Iodine . . .1 126.6 Iridium. . . Ir 192.7 Iron . . . Fe 55.9 Lanthanum . . La 138.5 Lead . . . Pb 206.5 Lithium . .Li 7 Magnesium . . Mg 24 Manganese . . Mn 54 Mercury . . Hg 199.7 Symbol. Atomic weight. Molybdenum . Mo 95.5 Xickel . . . Xi 58 Xiobium . . Xb 94 Xitrogen . .X 14 Osmium . . Os 198.5 Oxygen . .0 16 Palladium . . Pd 105.7 Phosphorus . . P 31 Platinum . . Pt 194.4 Potassium . . K 39 Rhodium . . Rh 104.1 Rubidium . . Rb 85.3 Ruthenium . . Ru 104.2 Scandium . .Sc 44 Selenium . . Se 78.8 Silicon . . .Si 28 Silver . . . Ag 107.7 Sodium. . . Xa 23 Strontium . . Sr 87.4 Sulphur . . S 32 Tantalum . . Ta 182 Tellurium . . Te 128 Thallium . . T1 203.7 Thorium . . Th 233 Tin . . . Sn 117.7 Titanium . . Ti 48 Tungsten . . W 183.6 Uranium . . U 238.5 Vanadium . . V 51.3 Ytterbium . . Yb 172.7 Yttrium . . Y 89.8 Zinc . . . Zn 64.9 Zirconium . . Zr 90 Symbol. Atomic weight. INDEX. 4 BSORPTION, 35 A Acetanilid, 376 Acetic acid, 320 analytical reactions of, 322 Acetic ether, 337 Acetone, 323 Acetylene, 292 Acid, acetic, 320 adipic, 325 arabic, 347 arachidic, 319 arsenic, 202 arsenious, 201 behenic, 319 benzoic, 370 boric, 96 bromic, 121 butyric, 323 capric, 318 caproic, 318 caproylic, 318 carbamic, 352 carbazotic, 367 carbolic, 365 carbonic, 92 carminic, 349 cathartic, 349 cerotic, 319 chloric, 119 cholic, 361, 421 chromic, 173 citric, 330 copaivic, 369 cyanic, 357 dithionic, 103 fluoric, 124 formic, 319 fulminic, 359 gallic, 372 glacial acetic, 321 phosphoric, 111 glycocholic, 361, 421 glycolic, 332 hippuric, 439 byaenic, 319 hydriodic, 122 hvdrobromic, 121 hydrochloric, 117 hydrocyanic, 353 Acid, hydroferricyanic, 358 hydroferrocyanic, 358 hydrofluoric, 124 hvdrosulphuric, 104, 229 hypobromic, 121 hypochlorous, 119 hyponitrous, 87 liypophosphorous, 113 hyposulphurous, 104 lactic, 332 lauric, 318 malic, 327 malonic, 325 manganic, 170 margaric, 318 meconic, 387 melissic, 319 metaphosphoric, 111 muriatic. 117 myristic, 318 myronic, 350 nitric, 87 nitro-hydrochloric, 118 nitro-muriatic, 118 nitrous, 86 oenanthylic, 318 oleic, 324 orthophosphoric, 311 oxalic, 325 palmitic, 318 pelargonic, 318 pentathionic, 103 perchloric, 119 permanganic, 170 phenol-sulphonic, 366 phospho-molybdic, 382 phosphoric, 111 phosphorous, 110 phtalic, 372 picric, 367 propionic, 318 prussic, 353 pyrogallic, 373 pyrophosphoric, 111 pyrotartaric, 325 salicylic, 371 sarco-lactic, 332 silicic, 96 stannic, 213 466 INDEX. Acid, stearic, 318 succinic, 325 sulphocarbolic, 366 sulphocyanic, 357 sulphonic, 315, 367 sulphuric, 101 sulphurous, 99 sylvic, 369 tannic, 373 tartaric, 327 taurocholic, 421 tetrathionic, 103 thiosulphuric, 104 trithionic, 103 uric, 438 valerianic, 324 Acidimetry, 259 Acids, amido-, 318 aromatic, 370 biliary, 421 definitions of, 58 detection of, 237 fatty, 318 organic, 316 sulphonic, 315 thio-, 318 Aconitine, 384 Actinic waves, 27 Adhesion, 33 iEther, 335 Affinity, chemical, 46 Agate, 95 Air, composition of, 83 Alabaster, 148 Albumin, 399 in urine, 445. Albuminous substances, 397 analytical reactions of, 398 Alcohol, 303 absolute, 305 amyl, 307 analytical reactions of, 306 butyl, 270 diluted, 305 ethyl, 303 methyl, 303 real, 305 Alcoholic liquors, 306 Alcohols, 391 monatomic, 303 Aldehyde, acetic, 310 benz-, 371 par-, 310 Aldehydes, 309 Alkali metals, 131 Alkalimetry, 259 Alkaline earths, 148 Alkaloids, 380 antidotes to, 382 detection of, 382 Allotropic modification, 66 Alloy, definition of, 129 Allyl-mustard oil, 350 sulphide, 350 Alum, 155 Aluminium, 154 and ammonium sulphate, 155 analytical reactions of, 159 chloride, 157 hydroxide, 156 oxide, 157 sulphate, 157 Amalgam, 130 ammonium-, 142 tin-, 212 Amber, 369 Amides, 351 Amido-acetic acid, 351 -acids, 318, 351 -formic acid, 352 Amines, 351 Ammonia, 84 liniment, 340 water, 85 Ammoniated mercury, 197 Ammonio-copper compounds, 185 Ammonium, 142 amalgam, 142 analytical reactions of, 144 benzoate, 370 bromide, 143 carbamate, 143, 352 carbonate, 143 chloride, 142 hydroxide, 85, 142 iodide, 143 molybdate, 214 nitrate, 143 phosphate, 143 sulphate, 143 sulphide, 144 sulphydrate, 144 valerianate, 324 Amorphism, 19 Amorphous phosphorus, 108 Amygdalin, 349, 371 Amyl alcohol, 307 nitrite, 338 Amyloid, 348 Analysis, definition of, 58 gas-, 267 gravimetric, 253 organic, 273 qualitative, 216 quantitative, 252 ultimate, 273 urinary, 440 volumetric, 256 Analytical chemistry, 217 Analytical reactions of acetates, 322 alcohol, 306 albuminous substances, 398 467 INDEX. Analytical reactions of aluminium, 159 ammonium, 144 antimony, 211 arsenic, 204-207 atropine, 392 barium, 153 benzoates, 370 bile, 421 bismuth, 188 blood, 418 borates, 96 bromides, 121 calcium, 152 carbolic acid, 365 carbon, 90 carbonates, 93 chloral, 312 chlorates, 120 chlorides, 118 chloroform, 314 cholesterin, 422 chromates, 175 chromium, 175 citrates, 331 cocaine, 392 codeine, 387 copper, 185 cyanides, 353 ferric salts, 169 ferricyanides, 359 ferrocyanides, 358 ferrous salts, 169 fluorides, 124 glycerin, 308 gold, 214 grape sugar, 344 hippuric acid, 439 hydrocyanic acid, 353 hypochlorites, 120 hypophosphites, 113 iodides, 123 iron, 169 lead, 182 magnesium, 147 manganese, 172 mercury, 198 morphine, 386 nitrates, 88 oxalates, 326 phosphates, 112 phosphites, 110 potassium, 136 quinine, 389 santonin, 374 silicates, 96 silver, 191 sodium, 141 starch, 346 strontium, 153 strychnine, 391 sugar, 344 Analytical reactions of sulphates, 103 sulphides, 105 sulphites, 100 tannic acid, 373 tartrates, 328 thiosulphates, 104 tin, 213 urates, 438 urea, 436 veratrine, 394 zinc, 179 Anilid, 376 Aniline, 375 dyes, 376 Animal charcoal, 151 cryptolites, 402 fluids and tissues, 413 food, 406 Anthracite coal, 296 Antidotes to acids, 89 alkalies, 132 alkaloids, 382 antimony, 211 arsenic, 208 barium, 153 carbolic acid, 365 copper, 185 cyanides, 357 hydrocyanic acid, 357 lead, 182 mercury, 198 nitric acid, 98 oxalic acid, 326 phosphorus, 108 silver, 191 sulphuric acid, 103 zinc, 178 Antifebrine, 376 Antimonous chloride, 210 oxide, 211 Antimony, 209 analytical reactions of, 211 and potassium tartrate, 329 antidotes to, 211 black, 209 butter, 210 chloride, 210 crude, 209 oxide, 211 pentasulphide, 210 potassio-tartrate, 211, 329 sulphide, 209 sulphurated, 209 trisulphide, 209 Antipyrine, 377 Antiseptics, 287 Apomorphine, 386 Arbutin, 349 Argentum, 189 Argol, 327 Aromatic compounds, 360 468 IN DEX. Arrack, 307 Arsen iates, 202 Arsenic, 199 acid, 202 analytical reactions of, 204-208 antidotes to, 208 detection of,in case of poisoning,207 Fleitmann’s test for, 205 Marsh’s test for, 206 oxide, 202 red native sulphide, 200 Reinsch’s test for, 205 sulphides, 203 yellow native sulphide, 200 Arsenious acid, 201 anhydride, 201 iodide, 204 oxide, 201 Arsenites, 201 Arseniuretted hydrogen, 202 Artiads, 49 Asbestos, 145 Ash, black-, 138 bone-, 151 soda-, 138 Asphalt, 369 Atmospheric air, 83 pressure, 31 Atom, definition of, 41 Atomic theory, 41 Atomic weights, determination of, 42,50 Atoms, 40 quantivalence of, 47 Atropine, 391 analytical reactions of, 392 Auric chloride, 214 sulphide, 214 Auripigment, 200 Aurum, 213 Avogadro’s law, 24 BALSAM, copaiva, 369 Balsams, 369 Barium, 153 analytical reactions of, 153 antidotes to, 153 carbonate, 153 chloride, 153 chromate, 175 sulphate, 153 sulphide, 153 Barometer, 30 Basalt, 154 Bases, definition of, 59 Beer, 307 Beet-sugar, 344 Bell-metal, 183 Benzaldehyde, 371 Benzene, 362 Benzene-series, 362 Benzin, 297 Benzol, 362 Benzoic acid, 370 sulphinide, 377 Benzyl-glycocol, -139 Berberine, 395 Beryllium, 61 Bicarbonate of potassium, 133 sodium, 139 Bichloride of mercury, 195 Bichromate of potassium, 173 Bile, 420 detection of, in urine, 453 Biliary acids, 421 calculi, 422 pigments, 20 Bilirubin, 420 Biliverdin, 421 Bismuth, 186 analytical reactions of, 188 carbonate, 187 citrate, 331 hydroxide, 188 iodide, 188 nitrate, 187 oxide, 188 oxy-salts, 187 subcarbonate, 187 subnitrate, 187 sulphate, 187 sulphide, 188 Bismuthyl, 187 carbonate, 187 iodide, 188 nitrate, 187 Bisulphide of carbon, 105 Biuret, 436 Black antimony, 209 -ash, 138 -lead, 90 oxide of copper, 184 manganese, 170 mercury, 193 -wash, 193 Bleaching-powder, 152 Blood, 415 corpuscles, 416 detection of, 418, 448 -fibrin, 400 -serum, 416 -stains, examination of, 418 Blue mass, 192 pill, 193 Prussian, 169 -stone, 184 Turnbull’s, 169 vitriol, 184 Bone, 423 -ash, 151 -black, 151 Bone-oil, 378 INDEX. 469 Boric acid, 96 analytical reactions of, 96 Borax, 141 lead, 224 Boron, 95 Botger’s bismuth-test, 451 Brain, 425 Brandy, 307 Brass, 183 Brittleness, 20 Bromides, analytical reactions of, 121 Bromine, 120 Bronze, 183 Brucine, 391 Butter, 428 -milk, 428 of antimony, 210 CADAVERIC alkaloids, 395 Vj Cadaverine, 396 Cadmium, 179 iodide, 179 sulphate, 179 sulphide, 179 Caesium, 61 Caffeine, 395 Calamine, 176 Calcined magnesia, 146 Calcium, 148 analytical reactions of, 152 bromide, 152 carbonate, 150 chloride, 152 fluoride, 123 hydrate, 149 hydroxide, 149 hypophosphite, 151 oxalate, 326 oxide, 149 phosphate, 150 sulphate, 150 superphosphate, 151 tartrate, 327 Calc-spar, 148 Calculi, biliary, 422 urinary, 455 Calomel, 194 Camphor, 368 mint-, 370 monobromated, 369 Cane-sugar, 344 Caoutchouc, 369 Capillary attraction, 33 Caramel, 343 Carbamide, 352, 434 Carbazotic acid, 367 Carbohydrates, 342 Carbolic acid, 365 analytical reactions of, 365 Carbolic acid, antidotes to, 365 Carbon, 89 bisulphide, 105 dioxide, 90 disulphide, 105 monoxide, 93 Carbonate, analytical reactions of, 93 Carbonic acid, 92 oxide, 93 | Carboxyl, 316 I Casein, 396 vegetable, 400 i Cast-iron, 162 | Casts, urinary, 459 Caustic, 190 lunar, 190 potash, 132 ■ Celluloid, 348 Cellulose, 347 nitro-, 348 j Centigrade thermometer, 27 Cerebrin, 425 : Cerite, 159 Cerium, 159 oxalate, 159 i Chains, 279 Chalk, 148 Charcoal, 89 animal, 151 . Cheese, 429 Chemical action, definition of, 40 affinity, 40 formulas, 43 reactions, 58 symbol, definition of, 42 Chemism, 40 Chemistry, analytical, 216 definition of, 41 how to study it, 69 organic, 269 physiological, 404 Chili saltpetre, 141 Chinoidine, animal, 396 Chloral, 311 hydrate, 311 Chlorates, analytical reactions of, 120 Chloric acid, 119 oxides, 119 Chlorides, analytical reactions of, 118 Chlorinated lime, 152 Chlorine, 114 acids, 119 oxides, 118 -water, 117 Chloroform, 312 Chlorous oxide, 119 tetroxide, 119 Choke-damp, 94 Cholic acid, 421 Cholesterin, 341, 422 Chromates, analytical reactions of, 175 Chrome-alum, 174 470 INDEX. Chrome-iron ore, 172 -yellow, 185 Chromic acid, 173 hydroxide, 174 oxide, 174 Chromite, 172 Chromium, 172 chloride, 174 sulphate, 174 Chyle, 410, 418 Chyme, 410 Cinchona alkaloids, 387 Cinchonidine, 390 Cinchonine, 390 sulphate, 390 Cinnabar, 192, 197 Citrates, analytical reactions of, 331 Citric acid, 330 Clay, 157 Clot, 417 Coagulation, 397 Coal, 296 -oil, 296 -tar, 299 Cobalt, 176 Cocaine, 392 Codeine, 387 Cognac, 307 Cohesion, 18 Colchicine, 384 Collagen, 403, 424 Collidine, 378 Collodion, 348 Colloids, 36 Colocynthin, 349 Colophony, 369 Columbium, 61 Combustion, 75, 284 Compound radicals, 60 Compounds, decomposition of, 55 definition of, 39 Coniine, 384 Copaiva balsam, 369 Copper, 183 acetate, 323 ammonio-sulphate, 185 analytical reactions of, 185 antidotes to, 185 arsenite, 186 black oxide, 184 -glance, 183 hydroxide, 184 oxide, 184 pyrites, 183 sulphate, 184 sulphide, 183, 185 Corrosive chloride of mercury, 195 sublimate, 195 Corundum, 155 Cream, 427 of tartar, 328 Creamometer, 330 Creasote, 366 Crude antimony, 209 tartar, 327 Cryptolites, 402 Crystallization, 19 Crystalloids, 36 Cubic nitre, 141 Cumene, 362 Cupric acetate, 323 arsenite, 186 ferrocyanide, 188 hydroxide, 384 oxide, 185 sulphate, 184 sulphide, 183, 185 Cuprous oxide, 184 Cuprum, 183 Curd, 427 Cyanates, 355 Cyanhydric acid, 353 Cyanic acid, 357 Cyanides, analytical reactions of, 356 antidotes to, 357 Cyanogen, 353 Cymene, 368 Cystin, 457 DALTON’S atomic theory, 45 Daturine, 392 Decay, 284 Decomposition by electricity, 55 heat, 38, 54 light, 55 various modes of, 55 Decrepitation, 222 Deflagration, 223 Dentine, 424 Deodorizers, 287 Detection of impurities in officinal preparations, 244 Deposits, urinary, 454, 457 Derivatives, 282 Desiccator, 254 Destructive distillation, 284, 299 Dextrin, 347 Dextrose, 343 Diacetic ether, 377 Dialysis, 36 Dialyzed iron, 165 Diamond, 90 Diastase, 345 Dibasic acids, 59, 325 Dicyanogen, 353 Didymium, 61 Diffusion, 35 Digitalein, 349 Digitalin, 349 Digitin, 349 Digitonin, 349 1NDEX. 471 Digitoxin, 349 Digestion, 409 Dimorphism, 19 Disinfectants, 287 Distillation, 26 destructive, 284, 299 dry, 284 fractional, 293 Disulphide of carbon, 105 Divisibility, 21 chemical, 38 Dolomite, 145 Donovan’s solution, 204 Double salts, 59 Dried alum, 155 Drinking water, 80 Dry distillation, 284 Drying-oven, 253 Duboisine, 392 Ductility, 20 Dynamite, 308 Earths, 154 Alkaline, 148 Ecgonine, 393 Elasticity, 20 Electricity, 55 Elementary analysis, 273 Element, definition of, 39 Elements, 61 derivation of names of, 70, 125 natural groups of, 62 non-metallic, 70 metallic, 125 relative importance of, 60 time of discovery of, 71, 127 valence of, 71, 128 Emerald green, 323 Emery, 155 Emetine, 384 Empirical formulas, 276 Emulsine, 371 Enamel, 424 Epithelium, 424 Epsom salt, 147 Equations, chemical, 67 Equivalence, 47 Erbium, 61 Eserine, 384 Essential oils, 300 Esters, 333 Ethane, 294 Ethene, 94, 300 Ether, 335 acetic, 337 diacetic, 377 ethyl-, 336 nitrous, 337 sulphuric, 335 Ethers, 333 Ethyl, 303 acetate, 337 alcohol, 303 ether, 335 hydroxide, 303 hydride, 294 nitrite, 337 oxide, 335 Ethylene, 299 Ethylic alcohol, 303 Extension, 17 FAHRENHEIT’S thermometer, 27 * Fatty acids, 318 Fats, 338 Feathers, 424 Feces, 423 Fehling’s solution, 450 Feldspar, 154 Fermentation, 285, 320 Ferric acetate, 322 chloride, 164 citrate, 331 hydrate, 163 hydroxide, 163 hypophosphite, 168 nitrate, 167 oxide, 163 salts, analytical reactions of, 169 sulphate, 166 sulphocyanate, 169 tartrate, 330 valerianate, 324 Ferricyanogen, 358 Ferricyanides, analytical reactions, of, 358 Ferrocyanides, analytical reactions of, 358 Ferrocyanogen, 353 Ferrous bromide, 166 carbonate, 167 chloride, 164 hydroxide, 163 iodide, 165 lactate, 333 oxalate, 326 oxide, 163 phosphate, 167 salts, analytical reactions of, 169 sulphate, 166 sulphide, 166 Ferrum, 125 Fibrin, 400, 417 vegetable, 490 Fire-damp, 94, 295 Flame, structure of, 94 -tests, 224 Fleitmann’s test, 205 Flesh-fibrin, 400 Flowers of sulphur, 98 472 INDEX. Fluorine, 123 Fluorspar, 123 Food, absorption of, 410 animal, 406 nitrogenous, 408 plant, 404 Force, definition of, 18 Formic acid, 319 Formulas, chemical, 43 empirical, 276 graphic, 277 molecular, 276 rational, 277 Fowler’s solution, 202 Fractional distillation, 293 Fruit-sugar, 344 Fusel oil, 307 Fusibility of metals, 126 Galena, iso argentiferous, 189 Gallic acid, 372 Gallium, 61 Gall-stones, 422 Galvanized iron, 177 Gas-analysis, 267 definition of, 20 -furnace, 274 illuminating, 298 Gasoline, 297 Gastric juice, 409, 419 Gelatin, 403, 424 Gelatinized starch, 346 Gelatinoids, 403 Germanium, 61 German silver, 183 Gin, 307 Glacial acetic acid, 321 phosphoric acid, 111 Glass, 158 Glauber’s salt, 139 Globulin, 399 Glucinum, 61 Glucose, 343 Glucosides, 349 Glue, 403, 424 Gluten, 343 Glycerin, 307 Glycerites, 308 Glycine, 351 Glycocol, 351, 421 Glycocolic acid, 421 Glycogen, 348 Glycols, 301 Glycyrrhizin, 349 Gmelin’s test, 421, 453 Gold, 213 and sodium chloride, 214 analytical reactions of, 214 chloride, 214 Gold coin, 213 sulphide, 214 Golden sulphuret of antimony, 210 Goulard’s extract, 322 Granite, 95, 154 Grape-sugar, 243 Graphic formulas, 277 Graphite, 90 Gravitation, 23 Green vitriol, 166 Gum, 347 -arabic, 347 British, 347 • Gun-cotton, 348 -metal, 183 -powder, 134 Gutta-percha, 369 Gypsum, 150 Hair, 403,424 Hsematin, 402 Haemato-crystallin, 401 Hsemine, 402 crystals, 459 Haemoglobin, 401 Haloids, 114 Halogens, 114 Hardness, 19 Heat, 24 action upon compounds, 54 matter, 21 organic substances, 283 decomposition by, 38, 54 latent, 25 specific, 28 Heavy magnesia, 146 spar, 153 Helleborin, 349 Hippuric acid, 439 Homologous series, 280 Hoofs, 424 Hornblende, 154 Horns, 403, 424 Humus, 413 Hydrargyrum, 191 Hydrastine, 394 Hydrazine compounds, 377 Hydriodic acid, 122 Hydrobromic acid, 121 Hydrocarbons, 94, 291 Hydrochloric acid, 117 analytical reactions of, 118 Hydrocyanic acid, 353 analytical reactions of, 356 antidotes to, 357 Hydroferricyanic acid, 358 Hydroferrocyanic acid, 358 Hydrofluoric acid, 124 Hydrogen, 76 arseniuretted, 202 INDEX. Hydrogen dioxide, 81 peroxide, 81 sulphide, 104 sulphuretted, 104 Hydrometers, 30 Hydrosulphuric acid, 104, 229 Hydroxyl, 279 Hyoscine, 392 Hyoscyamine, 392 Hypobromites, 121 Hypochlorites, tests for, 120 Hypochlorous acid, 119 oxide, 119 Hyponitrous acid, 87 Hypophosphites, tests for, 113 Hypophosphorie acid, 113 Hyposulphurous acid, 104 ILLUMINATING gas, 298 1 oil, 297 Indestructibility, 37 Indican, 349, 441 Indicators, 259 Indium, 61 Indol, 423 Iodides, analytical reactions of, 123 Iodimetrv, 265 Iodine, 122 tests for it, 123 tincture of, 122 Iodized starch, 347 Iodoform, 314 lodol, 378 Iridium, 61 Iron, 160 acetate, 322 analytical reactions of, 169 bromide, 166 carbonate, 167 cast-, 162 chlorides, 164 citrate, 331 dialyzed, 165 galvanized, 177 hydroxides, 163 hypophosphite, 168 iodide, 165 lactate, 333 nitrate, 167 ores, 161 oxalate, 326 oxides, 163 phosphates, 167 pyrites, 161 reduced, 162 scale compounds of, 168 sulphates, 167 tannate, 169 tartrate, 330 trioxide, 164 Iron, wrought-, 162 Isomerism, 282 Isomorphism, 19 KAIRINE, 379 Kalium, 131 Kelp, 122 Keratin, 427 Ketones, 323 Kreatin, 425 T ACTIC acid, 332 Ju Lactometer, 430 Lactoscope, 430 Lactose, 346 Lanolin, 341 Lanthanum, 61 Lapis infernalis, 190 lazuli, 158 Latent heat, 25 Laughing-gas, 86 Laurinol, 369 Law, Avogadro’s, 24 Charles’s, 26 of chemical combination by volume, 45 by weight, 43 of constancy of composition, 43 of diffusion of gases, 37 Dulong and Petit, 52 of equivalents, 47 Gay Lussac’s, 45 Graham’s, 37 Mariotte’s, 20 Mendelejeff’s, 62 of multiple proportions, 44 periodic, 62 Lead, 180 acetate, 322 analytical reactions of, 182 antidotes to, 182 carbonate, 181 chloride, 183 chromate, 183 iodide, 182 nitrate, 181 oxide, 181 plaster, 340 phosphate, 183 sugar of, 322 -water, 322 white, 181 Lecithin, 399, 422 Legumin, 400 Leucin, 401,457 Levulose, 344 Light, decomposition by, 55 Light magnesia, 146 Lignine, 347 474 INDEX. Lignite, 296 Lime, acid phosphate of, 151 chloride of, 152 chlorinated, 152 -kiln, 149 liniment, 340 quick-, 149 slaked, 149 superphosphate of, 151 -water, 149 Limestone, 148 Liquefaction of solids, 226 Liquids, definition of, 20 Litharge, 181 Lithium, 141 bromide, 141 carbonate, 141 citrate, 331 salicylate, 372 Litmus, 58 Lunar caustic, 190 Lutidine, 378 Lymph, 418 Magnesia, 146 calcined, 146 Magnesite, 145 Magnesium, 145 analytical reactions of, 147 carbonate, 146 citrate, 331 oxide, 146 sulphate, 147 sulphite, 147 Magnetic iron ore, 161 Malachite, 183 Malic acid, 327 Malleability, 20 Maltose, 345 Manganates, 171 Manganese, 170 analytical reactions of, 172 black oxide of, 170 dioxide, 170 oxides of, 170 Manganous carbonate, 172 hydroxide, 172 oxide, 170 sulphate, 170 Mannitose, 344 Marble, 148 Mariotte’s law, 20 Marsh-gas, 94, 295 Marsh’s test for arsenic, 206 Mastication, 409 Matter, definition of, 17 Mass, 17 Mayer’s reagent, 382 Meconic acid, 387 Meerschaum, 145 Melissic acid, 319 Melitose, 346 Melting-points of metals, 126 Mendelejeff’s law, 63 Menthol, 370 Mercurial ointment, 193 plaster, 193 Mercuric chloride, 195 cyanide, 355 fulminate, 359 iodide, 196 nitrate, 196 oxide, 193 salts, analytical reactions of, 198 sulphate, 196 sulphide, 197 Mercurous chloride, 194 chromate, 175 iodide, 193 nitrate, 196 oxide, 193 salts, analytical reactions of, 198 sulphate, 196 sulphide, 197 Mercury, 191 ammoniated, 197 analytical reactions of, 198 antidotes to, 198 basic sulphate, 196 black oxide, 193 carbonates, 198 chlorides, 194, 195 iodides, 195, 196 nitrates, 196 oleate, 324 oxides, 193 red oxide, 193 sulphates, 196 sulphides, 197 with chalk, 192 Metaldehyde, 311 Metallic elements, 125 Metallo-cyanides, 357 Metalloids, 70 Metals, 125 classification of, 129 derivation of names, 125 melting-points, 126 separation of, 232 specific gravity, 127 valence, 128 Metamerism, 282 Metaphosphoric acid, 111 Methane, 94, 295 series, 293 Methyl alcohol, 303 hydroxide, 303 hydride, 294 Methylated spirit, 303 Mica, 154 Microcosmic salt, 220 INDEX. 475 Milk, 525 adulterations of, 429 analysis of, 431 -casein, 429 -sugar, 346 Millon’s reagent, 398 Mineral waters, 79 Minium, 181 Mint-camphor, 370 Mispickel, 200 Molasses, 345 Molecular motion, 25, 27 theory, 22 Molecule, definition of, 22 Molybdenum, 214 Molybdic acid, 214 oxide, 214 Monobasic acids, 59 Monsel’s solution, 167 Morphine, 385 acetate, 386 analytical reactions of, 386 hydrochlorate, 386 sulphate, 386 Muscle-fibrin, 400 -sugar, 344 Muscles, 425 Mucilage of starch,. 346 Mucin, 425 Mucus, 424 Murexid test, 438 Muriatic acid, 117 Myosin, 400 Myronic acid, 350 AT AILS, 424 Naphtalene, 373 Naphthol, 374 diniiro, 374 Narceine, 387 Narcotine, 387 Nascent state, 57 Natrium, 137 Neutral substances, 59 Neurin, 425 Nickel, 176 Nicotine, 384 Niobium, 61 Nitrates, analytical reactions of, 88 Nitre, 133 Nitric acid, 87 Nitro-benzene, 363 -cellulose, 348 -cyanmethane, 359 -glycerin, 308 Nitrogen, 82 determination, 275 oxides, 86 Nitro-hydrochloric acid, 118 -muriatic acid, 118 j Nitrous acid, 86 ether, 337 oxide, 86 Nomenclature, 66 ■ Non-metallic elements, 70 Nordhausen sulphuric acid, 101 Nutrition of animals, 409 OIL, almond, 340 bitter almond, 371 bone-, 378 castor, 340 cod-liver, 330 cotton-seed, 340 heavy, 362 illuminating, 297 juniper, 282 lemon, 282 light. 362 linseed, 340 olive, 340 turpentine, 368 vitriol, 101 wintergreen, 371 Oils, essential, 300 fat, 338 Olefiant gas, 300 Olefines, 299 Oleic acid, 324 Oleo-resins, 369 : Olive oil, 340 Opium, 384 -alkaloids, 384 denarcotized, 385 Organic analysis, 273 chemistry, 269 substances, classification of, 289 decomposition of, 283, 406 formation of, in plants, 405 Orpiment, 200 Orthophosphoric acid, 111 j Osmium, 61 Osmosis, 36 Ossein, 403, 424 ! Oxalates, analytical reactions of, 326 j Oxalic acid, 325 antidotes to, 326 • Oxide, definition of, 75 Oxidimetry, 262 Oxygen, 72 Ozone, 75 PALLADIUM, 61 I Palmitic acid, 318 ; Pancreatic juice, 422 Pancreatin, 402 | Papaverine, 384 Paper, 348 Paraffin, 298 476 INDEX. Paraldehyde, 310 Paris green, 322 Parvoline, 396 Pearl-white, 187 Peat, 296 Pentathionic acid, 103 Pepsin, 402, 419 saccharated, 402 Peptone, 400 Perchloric acid, 119 Periodic law, 62 Perissads, 49 Permanganates, 171 Petrolatum, 298 Petroleum, 296 -ether, 297 ointment, 298 Pettenkofer’s test, 421, 454 Phenol, 365 methyl-propyl, 370 phtalein, 372 -sulphonic acid, 366 trinitro, 367 Phenyl-amine, 375 -hydrazine, 377 Phosphates, analytical reactions of, 112 Phospho-molybdic acid, 382 Phosphites, analytical reactions of, 110 Phosphoretted hydrogen, 114 Phosphoric acid, 111 Phosphorous acid, 110 Phosphorus, 106 antidotes to, 108 detection of, 109 determination in organic com- pounds, 275 red or amorphous, 108 Phtalic acid, 372 Physiological chemistry, 404 Physostigmine, 384 Picoline, 378 Picric acid, 367 Pilocarpine, 384 Pioskop, 430 Piperine, 384 Pipettes, 255 Plant-fibre, 347 -food, 404 Plaster of Paris, 150 Platinic chloride, 214 Platinum, 214 and ammonium chloride, 214 and potassium chloride, 214 Plumbago, 90 Plumbum, 180 Polymerism, 282 Polymorphism, 19 Porcelain, 158 Porosity, 32 Potash, 132 caustic, 132 Potassium, 131 Potassium, acetate, 322 acid carbonate, 133 acid oxalate, 326 acid tartrate, 328 analytical reactions of, 136 bicarbonate, 133 bichromate, 173 bitartrate, 328 bromide, 136 carbonate, 133 chlorate, 134 chromate, 173 citrate, 331 cyanate, 355 cyanide, 355 dichromate, 173 ferricyanide, 359 ferrocyanide, 358 hydrate, 132 hydroxide, 132 hypophosphite, 135 iodide, 135 manganate, 171 nitrate, 133 oxalate, 326 permanganate, 171 prussiate, 358, 359 sodium tartrate, 329 sulphate, 134 sulphite, 135 sulphocyanate, 357 sulphurated, 135 tartrate, 329 Preliminary examination, 221 table for, 225 Proof-spirit, 305 Propionic acid, 318 Propyl alcohol, 303 Proteids, 397 Prussian blue, 358 Prussiate of potash, red, 359 yellow, 358 Prussic acid, 253 Ptomaines, 395 Ptyalin, 402, 419 Putrefaction, 285 Pyridine, 378 Pyrites, copper, 183 iron, 161 Pyrrole, 278 Pyrophosphoric acid, 111 Pyroxylin, 348 QUANTIYALENCE, 47 Quartz, 95 Quicksilver, 191 Quinidine, 390 Quinine, 388 acid sulphate, 389 INDEX. 477 Quinine, analytical reactions of, 389 citrate of iron and, 389 sulphate, 389 valerianate, 324 Quinizine, 377 Quinoline, 379 RADICAL, definition of, 60, 278 Reactions, 58 analytical, 58 synthetical, 58 Reagents, list of, 219 use of, 204 Realgar, 200 Red iodide of mercury, 196 oxide of copper, 184 oxide of mercury, 193 precipitate, 193 Reinsch’s test, 205 Residue, definition of, 60, 278 Resin, 369 Resorcin, 367 Respiration, 92, 411 Rhodium, 61 Rochelle salt, 329 Rock-crystal, 95 Rosaniline, 376 Rosin, 369 Rubber, 369 Rubidium, 61 Ruby, 155 Rum, 307 Ruthenium, 61 C ACCHARINE, 377 Salicin, 349, 371 Salicylic acid, 371 Saliva, 418 Sal sodse, 138 Salt-cake, 138 common, 137 Saltpetre, 233 Chili, 141 Salts, definition of, 59 tables of solubility, 241, 242 Sand, 95 Santonin, 374 Sapphire, 155 Sarkin, 425 Scale compounds of iron, 168, 330 Scamonium, 349 Scandium, 61 Scheele’s green, 204 Schweinfurth’s green, 204, 323 Seidlitz powder, 329 Selenium, 105 Serpentine, 145 Serum, 417 Sherry wine, 306 Silica, 95 Silicates, 95 Silicic acid, 95 Silicon, 95 Silicum, 95 Silver, 189 analytical reactions of, 191 antidotes to, 191 chloride, 191 chromate, 175, 191 cyanide, 355 fulminate, 359 German, 183 iodide, 191 nitrate, 190 oxide, 191 sulphide, 191 Sinapine, 384 Sinigrin, 350 Skatol, 423 Slaked lime, 149 Slate, 154 Soap, 340 Soapstone, 145 Soda, 138 -ash, 138 -lime, 273 Sodium, 137 acetate, 322 analytical reactions of, 141 arseniate, 202 benzoate, 370 bicarbonate, 139 bisulphite, 139 borate, 141 carbonate, 138 chloride, 137 hydrate, 137 hydroxide, 137 hyposulphite, 140 nitrate, 141 phosphate, 140 salicylate, 372 santoninate, 374 sulphate, 139 sulphite, 139 sulphocarbolate, 366 thiosulphate, 140 Solanine, 384 Solids, definition of, 18 Specific heat, 28 weight, 29 Spirit of hartshorn, 85 of wine, 305 proof, 305 rectified, 305 wood-, 303 Standard solutions, 257 Stannic acid, 213 chloride, 213 sulphide, 213 478 INDEX. Stannous chloride, 212 hydroxide, 213 sulphide, 213 Stannum, 212 Starch, 346 iodized, 347 Stearic acid, 318 Stearin, 338 Stearoptenes, 369 Steel, 162 Steopsin, 410 Stibnite, 209 Strontium, 153 analytical reactions of, 153 carbonate, 153 nitrate, 153 sulphate, 153 Structure of flame, 94 Strychnine, 396 analytical reactions of, 391 sulphate, 391 Sublimation, 26 Sublimed sulphur, 98 Substitution, 281 Sugar, 344 cane-, 344 detection of, in urine, 449 fruit-, 344 grape-, 344 of lead, 322 milk, 346, 431 Sulphates, analytical reactions of, 103 Sulphides, analytical reactions of, 105 Sulphites, analytical reactions of, 100 Sulphocarbolates, 366 Sulphocyanic acid, 357 Sulphonal, 314 Sulphonic acid, 315, 367 Sulphur, 97 dioxide, 99 determination in organic com pounds, 275 flowers of, 98 milk of, 98 precipitated, 98 sublimed, 98 trioxide, 101 Sulphurated antimony, 209 Sulphuretted hydrogen, 104, 227 Sulphuric acid, 101 antidotes to, 103 dilute, 103 fuming, 101 Nordhausen, 101 Sulphuric ether, 335 Sulphurous acid, 99 Superphosphate of lime, 151 Surface-action, 33 Sweet spirit of nitre, 338 Symbols, function of, 42 Synthesis, 58 TABLES of solubility, 241, 242 1 Talc, 145 Tannic acid, 373 Tannin, 373 Tantalum, 61 Tartar, cream of, 328 crude, 327 emetic, 329 Tartaric acid, 327 Tartrates, analytical reactions of, 328 Taurine, 421 Taurocholic acid, 421 Teeth, 424 Tellurium, 105 Tenacity, 20 Tension, 20 Terebene, 368 Terpenes, 368 Thalline, 379 Thallium, 61 Thebaine, 384 Theine, 395 Theobromine, 384 Thermometers, 27 Thorium, 61 Thymol, 370 Tin, 212 -amalgam, 212 analytical reactions of, 213 chlorides of, 213 -stone, 212 Titanium, 61 Titration, 259 Toluene, 362 Trichloraldehyde, 311 Triclilormethane, 312 Trinitro-cellulose, 348 -phenol, 367 Triple phosphate, 459 Trommer’s test, 450 Trypsin, 410 Tungsten, 61 Turpentine, 369 Turpeth mineral, 196 Type metal, 209 Types, chemical, 281 Tyrosin, 457 Tyrotoxine, 396 TTLTIMATE analysis, 273 U Ultramarine, 158 Ultzmann’s test, 454 Uranium, 61 Urates, 438, 455 Urea, 434 determination of, 436 nitrate, 435 Uric acid, 438 Urinary calculi, 455 deposits, 454, 457 INDEX. 479 Urinary sediments, 454, 457 Urine, 432 analysis, 440 color, 440 composition, 433 reaction, 442 secretion, 432 specific gravity, 442 Urinometer, 443 Urobilin, 441 Uroxanthin, 441 VALENCE, 47 ' Valerianates, 324 Valerianic acid, 324 Vanadium, 61 Vaseline, 298 Veratrine, 384 analytical reactions of, 394 oleate, 324 Verdigris, 323 Vermilion, 197 Vinegar, 321 Vitellin, 399 Vitriol, blue, 184 green, 166 oil of, 101 white, 178 Volatile oils, 300 Vulcanite, 369 WASTE products of animal life, 412 Water, 78 distilled, 80 drinking, 80 lime-, 149 mineral, 79 of ammonia, 85 of bitter almond, 371 Weight, 29 Weight, atomic, 42 specific, 29 Whey, 427 Whiskey, 307 White arsenic, 201 lead, 181 precipitate, 197 vitriol, 178 Wine, 306 Wood naphtha, 303 -spirit, 303 Wrought-iron, 162 V ANTHIN, 425 4V Xylene, 362 YELLOW oxide of mercury, 193 -wash, 194 Ytterbium, 68 Yttrium, 61 7 INC, 176 acetate, 322 analytical reactions of, 179 antidotes to, 178 -blende, 176 bromide, 177 carbonate, 178 chloride, 177 ferrocyanide, 179 hydroxide, 177 iodide, 178 oxide, 177 phosphide, 178 sulphate, 178 valerianate, 324 -white, 177 Zirconium, 61 i he American systems or uynecology and Obstetrics. 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THE MEDICAL NEWS PHYSICIANS9 LEDGER. Containing 400 pages of fine linen “ ledger ” paper, ruled so that all the accounts of a large practice may be conveniently kept in it, either by single or double entry, for a long period. Strongly bound in leather, with cloth sides, and with a patent flexible back, which permits it to lie perfectly flat when opened at any place. Price, $5.00. Also, a small special lot of same Ledger, with 300 pages. Price, $4.00. HA ms HORNE, HE NR Y, A. M., M. I)., LL. D., Lately Professor of Hygiene in the University of Pennsylvania. 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 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 every busy 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. JO., and SMITH, F. G., M. JO., Late Surgeon to the Penna. Hospital. Prof, of the Institutes of Med. in the Vniv. 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 12mo. 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. 4 Lea Brothers & Co.’s Publications—Dictionaries. DUNGLISON, ROBLEY, M. 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- Srudence and Dentistry, Notices of Climate and of Mineral Waters, Formulae for Officinal, Impirical 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 Richard J. Dungrison, M. D. In one very large and handsome royal octavo volume oi 1139 pages. Cloth, $6.50; leather, raised bands, $7.50; very handsome half Russia, raised bands, $8. The object of the author, from the outset, has not been to make the work a mere lexi- con or dictionary of terms, but to afford under each word a condensed view of its various medical relations, and thus to render the work an epitome of the existing condition of medical science. Starting with this view, the immense demand which has existed for the work has enabled him, in repeated revisions, to augment its completeness and usefulness, until at length it has attained the position of a recognized and standard authority wherever the language is spoken. Special pains have been taken in the preparation of the present edition to maintain this enviable reputation. The additions to the vocabulary are more numerous than in any previous revision, and particular attention has been bestowed on the accentuation, which will be found marked on every word. The typographical arrangement has been greatly improved, rendering reference much more easy, and every care has been taken with the mechanical execution. The volume now contains the matter of at least four ordinary octavos. About the first book purchased by the medical student is the Medical Dictionary. The lexicon explanatory of technical terms is simply a sine qua non. In a science so extensive and with such col- laterals as medicine, it is as much a necessity also to the practising physician. To meet the wants of students and most physicians the dictionary must be condensed while comprehensive, and practical while perspicacious. It was because Dunglison’s met these indications that it became at once the dictionary of general use wherever medicine was studied in the English language. In no former revision have the alterations and additions been so great. The chief terms have been set in black letter, while the derivatives follow in small caps; an arrangement which greatly facilitates reference. —Cincinnati Lancet and Clinic, Jan. 10,1874. A book of which every American ought to be proud. When the learned author of the work passed away, probably all of us feared lest the book should not maintain its place in the advancing science whose terms it defines. Fortunately, Dr. Richard J. Dunglison, having assisted his father in the revision of several editions of the work, and having been, therefore, trained in the methods and imbued with the spirit of the book, has been able to edit it as a work of the kind should be edited—to carry it on steadily, without jar or inter- ruption, along the grooves of thought it has trav- elled during its lifetime. To show the magnitude of the task which Dr. Dunglison has assumed and carried through, it is only necessary to state that more than six thousand new subjects have been added in the present edition.—Philadelphia Medical Times, Jan. 3,1874. It has the rare merit that it certainly has no rival in the English language for accuracy and extent of references.—London Medical Gazette. JIOBL YN, RICHARD D., M. D. 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 have, and ought always to be upon the student’s table.—Southern Medical and Surgical Journal. STUDENTS’ SERIES OF MANUALS. 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 vol- umes are now ready: Treves’ Manual of Surgery, by various writers, in three volumes, each, $2; Beer’s Comparative Physiology and Anatomy, $2; Gourd’s Surgical Diagno- sis, $2; Robertson’s Physiological Physics, $2; Bruce’s Materia Medica and Therapeu- tics (4th edition), $1.50; Power’s Human Physiology (2d edition), $1.50; Cearke and Lockwood’s Dissectors' Manual, $1.50; Rarfe’s Clinical Chemistry, $1.50; Treves’ Surgical Applied Anatomy, $2; Pepper’s Surgical Pathology, $2; and Krein’s Elements of Histology (3d edition), $1.50. The following are in press: Bereamy’s Operative Surgery, Pepper’s Forensic Medicine, and Curnow’s Medical Applied Anatomy. 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 woodcuts. The following volumes are now ready: Carter & Frost’s Ophthalmic Surgery, $2.25; Hutchinson on Syphilis, $2.25; Baer 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; Butrin on the Tongue, $3.50; Treves on Intestinal Obstruction, $2; and Savage on Insanity and Allied Neuroses, $2. The following are in active preparation: Broadbent on the Pulse, and Lucas on Diseases of the Urethra. For separate notices see index on last page. Lea Brothers & Co.’s Publications—Anatomy. 5 GRAY, HENRY, F. R. S., Anatomy, Descriptive and Surgical. The Drawings by H. Y. Carter, M. D., and Dr. Westmacott. The dissections jointly by the Author and Dr. Carter. With an Introduction on General Anatomy and Development by T. Holmes, M. A., Surgeon to St. George’s Hospital. Edited by T. Pickering Pick, F. R. C. 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 anil improved London edition, thoroughly revised and re-edited by William W. Keen, M. D., Professor of Anatomy in the Pennsylvania Academy of the Fine Arts, etc. To which is added the second American from the latest English edition of Landmarks, Medical and Surgi- cal, 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 to 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 in 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 will be published also in black alone, and main- tained in this style at the price of former editions, notwithstanding the largely increased size of the work. 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, it is believed, 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 all 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. Also fob sale separate— HOLDEN, LUTHER, F. R. C. S., Landmarks, Medical and Surgical. Second American from the latest revised English edition, with additions by W. WT Keen, M. D., Professor of Artistic Anatomy in the Pennsylvania Academy of the Fine Arts, formerly Lecturer on Anatomy in the Phila- delphia School of Anatomy. In one handsome 12mo. volume of 148 pages. Cloth, $1.00. Surgeon to St. Bartholomew's and the Foundling Hospitals, London. This little book is all that can be desired within its scope, and its contents will be found simply in- valuable to the young surgeon or physician, since they bring before him such data as he requires at every examination of a patient. It is written in language so clear and concise that one ought almost to learn it by heart. It teaches diagnosis by external examination, ocular and palpable, of the body, with such anatomical and physiological facts as directly bear on the subject. It is eminently the student’s and young practitioner’s book.—Phy- sician and Surgeon, Nov. 1881. The study of these Landmarks by both physi- cians and surgeons is much to be encouraged. It inevitably leads to a progressive education of both the eye and the touch, by which the recognition of disease or the localization of injuries is vastly as- sisted. One thoroughly familiar with the facts here taught is capable of a degree of accuracy and a confidence of certainty which is otherwise unat- tainable. We cordially recommend the Landmarks to the attention of every physician who has not yet provided himself with a copy of this useful, practical guide to the correct placing of all the anatomical parts and organs.—Canada Medical and Surgical Journal, Dec. 1881. 6 Lea Brothers & Co.’s Publications—Anatomy. ALLEN, HARRISON, M. D., 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 Fascije. 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 witn 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 Doints, 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 4. Messrs.Clarke and Lockwood have written abook that 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 fiven. With such a guide as this, accompanied y 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. 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 4. He has produced a work which will command a | larger circle of readers than the class for which it ! was written. This union of a thorough, practical I acquaintance with these fundamental branches, | quickened by daily use as a teacher and practi- tioner, has enabled our author to prepare a work which it would be a most difficult task to excel.— The American Practitioner, Feb. 1884. CURNOW, JOHN, M. 1)., F. R. C. F., Professor of Anatomy at King's College, Physician at King's College Hospital. Medical Applied Anatomy. In one pocket-size 12mo. volume. Shortly. See Students’ Series of Manuals, page 4. BELLAMY, EH WARE, F. R. C. S., 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. Senior Assistant-Surgeon to the Charing-Oross Hospital, London. 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, ERASM US, F. R. S. CLELAND, JOHN, M. D., F. 11. 8., Professor of Anatomy and Physiology in Queen's College, Oalway. A Directory for the Dissection of the Human Body. In one 12mo. volume of 178 pages. Cloth, $1.25. HARTSHORNE’S HANDBOOK OF ANATOMY AND PHYSIOLOGY. Second edition, revised. In one royal 12mo. volume of 310 pages, with 220 woodcuts. Cloth, 81.75. 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, JOHN C., M. D., LL. D., 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. 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. FROM THE PREFACE. This elegant and useful work bears ample testi- mony to tne learning and good judgment of the author. He has fitted his work admirably to the exigencies of the situation by presenting the reader with brief, clear and simple statements of sitch propositions as he is by necessity required to master. The subject matter is well arranged, liberally illustrated and carefully indexed. That it will take rank at once among the text-books is certain, and it is to be hoped that it will find a place upon the shelf of the practical physician, where, as a book of reference, it will be found useful and agreeable.—Louisville Medical News, September 26,1885. Certainly we have no textbook as full as the ex- cellent one he has prepared. It begins with a statement of the properties of matter and energy. After these the special departments of physics are explained, acoustics, optics, heat, electricity and magnetism, closing with a section on electro- biology. The applications of all these to physiology and medicine are kept constantly in view. The text is amply illustrated and the many difficult points of the subject are brought forward with re- markable clearness and ability.—Medical and Surg- ical Reporter, July 18,1885. That this work will greatly facilitate the study of medical physics is apparent upon even a mere cursory examination. It is marked by that scien- tific accuracy which always characterizes Dr. Draper’s writings. Its peculiar value lies in the fact that it is written from the standpoint of the medical man. Hence much is omitted that ap- pears in a mere treatise on physical science, while much is inserted of peculiar value to the physi- cian.—Medical Record, August 22,1885. ROBERTSON, J. McGREGOR, M. 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 4. 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- i 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 I Medical Association, Dec. 6, 1884. DALTON, JOHN €., M. I)., 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 one 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. ., E. B. C. P., Member of the Pathological Society, Senior Assistant Physician and Lecturer on Pathological Anat- omy, St. Thomas' Hospital, London. A Manual of General Pathology. Designed as an Introduction to the Prac- tice of Medicine. In one handsome octavo volume of about 600 pages, with 150 illustra- tions. In press. GBEFN, T. HENR Y, M. D., Pathology and Morbid Anatomy. New (sixth) American from the seventh revised and enlarged English edition. In one very handsome octavo volume of about 500 pages, with about 150 fine engravings. Preparing. Lecturer on Pathology and Morbid Anatomy at Charing-Oross Hospital Medical School, London. WOOD HEAD, G. SIMS, M. D., F. JR. C. P. E., Practical Pathology. A Manual for Students and Practitioners. In one beau- tiful octavo volume of 497 pages, with 136 exquisitely colored illustrations. Cloth, $6.00. Demonstrator of Pathology in the University of Edinburgh. It forms a real guide for the student and practi- tioner who is thoroughly In earnest in his en- deavor to see for himself and do for himself. To the laboratory student it will be a helpful com- panion, and all those who may wish to familiarize themselves with modern methods of examining morbid tissues are strongly urged to provide themselves with this manual. The numerous drawings are not fancied pictures, or merely schematic diagrams, but they represent faithfully the actual images seen under the microscope. The author merits all praise for having produced a valuable work.—Medical Record, May 31,1884. We would heartily recommend it to any student who desires to acquaint himself with the subject. In the matter we can find nothing to criticise. Every point is explained with perfect satisfaction, so that the merest tyro may understand.—Physician and Surgeon, December, 1883. SCHAFEB, ED WARD A., F. B. S., Assistant Professor of Physiology in University College, London. The Essentials of Histology. In one octavo volume of 246 pages, with 281 illustrations. Cloth, $2.25. This admirable work was greatly needed. To those who are familiar with the author’s former “Course of Practical Histology,” the book needs no recommendation. It has been written with the object of supplying the student with directions for the microscopical examination of the tissues, which are given in a clear and understandable way. Although especially adapted for laboratory work, at the same time it is intended to serve as an elementary text-book of histology, comprising all the essential facts of the science, but omitting unimportant details. The author has recom- mended only those methods upon which long ex- perience has proved that full dependence can be placed. The strict observance of this plan per- mits of no doubt, and makes the work eminently satisfactory.— The Physician and Surgeon, July, 1887. KLEIN, E., M. D., F. It. 8., Joint Lecturer on General Anat. and Phys. in the Med. School of St. Bartholomew's Hosp., London. Elements of Histology. Third edition. In one pocket-size 12mo. volume of 360 pages, with 181 illus. Limp cloth, $1.50. See aStudents? Series of Manuals, page 4. This little volume, originally intended by its able author as a manual for medical students, contains much valuable information, systematic- ally arranged, that will be acceptable to the general practitioner. It gives a graphic and lucid description of every tissue and organ in the hu- man body; and, while small in size, it is full to overflowing with important facts in regard to these multiform and complex structures. We know of no book of its size that will prove of greater value to medical students and practitioners of medi- cine.— The Southern Practitioner Nov. 1883. PEPPEB, A. J., M. B., M. S., F. B. C. 8., Surgeon and Lecturer at St. Mary's Hospital, London. 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 4. It is not pretentious, but it will serve exceed- ingly well as a book of reference. It embodies a treat deal of matter, extending over the whole eld of surgical pathology. Its form is practical, its language is clear, and the information set forth is well-arranged, well-indexed and well- illustrated. The student will find in it nothing that is unnecessary. The list of subjects covers the whole range of surgery. The book supplies a very manifest want and should meet with suc- cess.—New York Medical Journal, May 31,1884. 14 Lea Brothers & Co.’s Publications—Practice of Med. FLINT, AUSTIN, M. I)., LL. JO. 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; very handsome half Bussia, raised bands, $7.00. A new edition of a work of such established rep- utation as Flint’s Medicine needs but few words to commend it to notice. It may in truth be said to embody the fruit of his labors in clinical medicine, ripened by the experience of a longlife devoted to its pursuit. America may well be proud of having produced a man whose indefatigable industry and gifts of genius have done so much to advance med- icine; and all English-reading students must be ?rateful for the work which he has left behind him. t has few equals, either in point of literary excel- lence, or of scientific learning, and no one can study its pages without being struck by the lu- cidity and accuracy which characterize them. It is qualities such as these which render it so valu- able for its purpose, and give it a foremost place among the text-books of this generation.—The London Lancet, March 12,1887. 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. HABTSHOBNF, HEN BY, M. D., EE. JO., 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 textrbooks 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. BBISTOWE, JOHN STFB, M. JO., F. B. C. F., A Treatise on the Practice of Medicine. Second American edition, revised by the Author. Edited, with additions, by James H. Hutchinson, M.D., physician to the Pennsylvania Hospital. In one handsome octavo volume of 1085 pages, with illustrations. Cloth, $5.00; leather, $6.00; very handsome half Russia, raised bands, $6.50. Physician and Joint Lecturer on Medicine at St. Thomas' Hospital, London. The book is a model of conciseness, and com- bines, as successfully as one could conceive it to be possible, an encyclopaedic character with the smallest dimensions. It differs from other admi- rable text-books in the completeness with which it covers the whole field of medicine.—Michigan Medical News, May 10,1880. His accuracy in the portraiture of disease, his care in stating subtle points of diagnosis, and the faithfully given pathology of abnormal processes have seldom been surpassed. He embraces many diseases not usually considered to belong to theory and practice, as skin diseases, syphilis and insan- ity, but they will not be objected to by readers, as he has studied them conscientiously, and drawn from the life.—Medical and Surgical Reporter, De- cember 20, 1879. The reader will find every conceivable subject connected with the practice of medicine ably pre- sented, in a style at once clear, interesting and concise. The additions made by Dr. Hutchinson are appropriate and practical, and greatly add to its usefulness to American readers.—Buffalo Metr- ical and Surgical Journal, March, 1880. WATSON, SIB THOMAS, M. I)., 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. 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 Robert D. Lyons, K. C. C. In one 8vo. vol. of 354 pp. Cloth, $2.26. LA ROCHE ON YELLOW FEVER, considered in its Historical, Pathological, Etiological and Therapeutical Relations. In two large and hand- some octavo volumes of 1468 pp. Cloth, $7.00. A CENTURY OF AMERICAN MEDICINE, 1776—1876. By Drs. E. H. Clarke, H. J. Bigelow, S. D. Gross, T. G. Thomas, and J. S. Billings. In one 12mo. volume of 370 pages. Lea Brothers & Co.’s Publications—System of Med. 15 For Sale by Subscription Only. A System of Practical Medicine. BY 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 just 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 of 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 guidance, and authors will resort to for facts. From 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 suph 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 highest 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 Neios, 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 advanced views of the day.—North Carolina Medi- cal Journal, Sept. 1886. 16 Lea Brothers & Co.’s Publications—Clinical Med., etc. FOTHERGILL, J. 31., M. D., Edin., M. R. C. 1*., Land., 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. Physician to the City of London Hospital for Diseases of the Chest. 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.—New York Medical Journal, June 11,1887. This is a wonderful book. If there be such a thing as “medicine made easy,” this is the work to accomplish this result. The author deals with the “Principles of Therapeutics,” the study of which will give great vantage to the physician.— Virginia Medical Monthly, June, 1887. VAUGHAN, VICTOR C., Ph. />., M. D., Prof, of Phys. and Path. Chem. and Assoc. Prof, of Therap. and Mat. Med. in the Univ. of Mich. and NOVY, FR E DERICK G., 31. I), Ptomaines and Leucomaines, or Putrefactive and Physiological Alkaloids. In one handsome 12mo. volume of about 200 pages. Shortly. REYNOLDS, J. RUSSELL, M. D., Professor of the Principles and Practice of Medicine in University College, London. 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; leather, $18; half Russia, $19.50. Sold only by subscription. STILLE, ALFRED, M. D., LL. D., Professor Emeritus of the Theory and Practice of Med. and of Clinical Med. in the TJniv. 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. FINLAYSON, JAMES, M. J)., Editor, 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. Eobertson 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 sub- ject is treated is a most practical one. Symptoms alone and their diagnostic indications form the basis of discussion. The text explains clearly and thoroughly the methods of examination and the conclusions to be drawn from the physical signs.— The Medical News, April 23, 1887. This manual is one of the most complete and perfect of its kind. It goes thoroughly into the question of diagnosis from every possible point. It must lead to a thoroughness of observation, an examination in detail of every scientific appliance, and a study of means to the end which cannot fail in laying an excellent foundation for the student for future success as an able diagnostician. —Medical Record, August 13,1887. The second edition of this manual is a very considerable improvement upon the first. Much new matter has been introduced and the work has been brought up to the present time in all respects. As it stands it is one of the best manuals of diag- nosis in the English language for beginners. The whole work is so complete and so simply written, and yet contains such an amount of valuable information, that it should be a part of the library of every practitioner.—New York Medical Journal, July 23,1887. FENWICK, SAMUEL, M. D., The Student’s Guide to Medical Diagnosis. From the third revised and enlarged English edition. In one very handsome royal 12mo. volume of 328 pages, with 87 illustrations on wood. Cloth, $2.25. Assistant Physician to the London Hospital. HABERSHON, S. O., M. JO., Senior Physician to and late Lect. 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. TANNER, THOMAS HAWKES, M. I). A Manual of Clinical Medicine and Physical Diagnosis. Third American from the second London edition. Revised and enlarged by Tilbury Fox, M. D. In one small 12mo. volume of 362 pages, with illustrations. Cloth, $1.50. Lea Brothers & Co.’s Publications—Hygiene, Electr., Pract. 17 BARTHOLOW, ROBERTS, A. 31., M. D., LL. D., 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 News, May 14,1887. This “practical treatise on the applications of electricity to medicine and surgery” has grown to be so important a work that every practitioner should read it, especially when it is recalled what possibilities lie in the path of the further study of the therapeutics of electricity. Dr. Bartholow has here presented the profession with a concise work that, beginning with elementary descriptions and principles, gradually grows, page by page, into a magnificently practical treatise, describing opera- tions in detail, and giving records of successes that prove electricity to be marvellous as a curative agent in many forms of disease. The doctor can- not now do better than to possess himself of Dr. Bartholow’s treatise, just as it is.— Virginia Medi- cal Monthly, J une, 1887. RICHARDSON, B. W., M.D., LL. D., F.R.S., Preventive Medicine. In one octavo volume of 729 pages. Cloth, $4; leather, $5; very handsome half Russia, raised bands, $5.50. Fellow of the Royal College of Physicians, London. 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 that contains 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. HARTSHORNE, HENRY, M. D., LL. D., A Household Manual of Medicine, Surgery, Nursing and Hygiene: For Daily Use in the Preservation of Health and Care of the Sick and Injured, with an Introductory Outline of Anatomy and Physiology. In one large royal octavo volume of 946 pages, with 8 plates and 283 engravings. Cloth, $4.00; full red leather, $5.00. Formerly Professor of Hygiene in the University of Pennsylvania, and Professor of Physiology and Diseases of Children in the Woman’s Medical College of Pennsylvania. THE YEAR-BOOK OF TREATMENT FOR 1887. A Comprehensive and Critical Review for Practitioners of Medi- cine. In one 12mo. volume of 341 pages, bound in limp cloth, $1.25. Just ready. *** For special commutations with periodicals see page 3. This is one of the most valuable books for its price which is published in this or any coun- try. It contains a summary of the changes in medical practice, the new remedies introduced, and the experience with them and with others which have been longer in use, during the year 1887, made up from the reading and observation of a number of very capable men. The classifica- tion is according to diseases, so that one who con- sults these pages can obtain in a few minutes an excellent idea of the present status of therapeu- tics in regard to any given ailment. The book also has a good index, by means of which the reader may ascertain the different diseases for which any particular drug has been used during the year past.—Medical and Surgical Reporter, April 14, 1888. THE TEAR-BOOK OF TREATMENT FOR 1886. Similar to that of 1887 above. 12mo., 320 pages. Limp cloth, $1.25. SCHREIBER, DR. JOSEPH. 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. Just ready. Cloth, $2.75. This is a work abounding in common sense, a book that sweeps away a great deal of nonsense by which a simple matter has been made obscure, a volume that ought to be read by every one inter- ested in modern therapeutics. The work gives admirable directions for the employment of mas- sage, and capital descriptions of methodical exer- cise, after which there is a detailed account of the results of treatment of different diseases by these methods. A full bibliography adds to the value of the volume, which can be recommended as one of the best on the subjects with which it deals.— Edinburgh Medical Journal, April, 1888. STURGES’ INTRODUCTION TO THE STUDY OF CLINICAL MEDICINE. Being a Guide to the Investigation of Disease. In one handsome 12mo. volume of 127 pages. Cloth, $1.25. DAVIS’ CLINICAL LECTURES ON VARIOU8 IMPORTANT DISEASES. By N. 8. Davis. M. D. Edited by Frank H. Davis, M. D. Second edition. 12mo. 287 pages. Cloth, $1.75. TODD’S CLINICAL LECTURES ON CERTAIN ACUTE DISEA8ES. In one octavo volume of 320 pages. Cloth, $2.50. PAVY’S 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, 82.00. 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, 82.76. HOLLAND’S MEDICAL NOTES AND REFLEC- TIONS. 1 vol. 8vo., pp. 493. Cloth, 83.50. 18 Lea Brothers & Co.’s Publications—Throat, Lungs, Heart. FLINT, AUSTIN, M. I)., Professor of the Principles and Practice of Medicine in Bellevue Hospital Medical College, N. Y. A Manual of Auscultation and Percussion ; Of the Physical Diagnosis of Diseases of the Lungs and Heart, and of Thoracic Aneurism. Fourth edition. In one handsome royal 12mo. volume of 278 pages, with 14 illustrations. Cloth, $1.75. This admirable little book is too well known to require any extended notice. That a third and large edition has been exhausted in little more than two years, is evidence that the book is appre- ciated. We ourselves have used a former edition as a text-book in teaching the physical examina- tion of the chest, and can consequently speak from experience.—Boston Med. and Sur. Jour.,Feb. 11,’86. Physical Exploration of the Lungs by Means of Auscultation and Percussion. Three lectures delivered before the Philadelphia County Medical Society, 1882-83. In one handsome small 12mo. volume of 83 pages. Cloth, $1.00. B Y THE SAME A UTHOR. 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 handsome 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., A Practical Guide to Diseases of the Throat and Nose, including Associated Affections of the Ear. With 120 illustrations in color, and 200 en- gravings on wood designed and executed by the Author. New (second) and enlarged edition. In one imperial octavo volume of 628 pages. Cloth, $6. Just ready. Senior Physician to the Central London Throat and Ear Hospital. Mr. Browne’s book can be recommended to students and still more to practitioners as a clear, sound and practical guide to the diagnosis and treatment of diseases of the throat. His experi- ence is not only large, but ripe, and he gives his readers the full benefit of it. A particularly praise- worthy feature is that from beginning to end Mr. Browne, whilst giving due prominence to local measures, never fails to insist on the necessity of supplementing these by proper constitutional treatment.—London Medical Recorder, May, 1888. GROSS, S» D.j JyT. I)*, LL.JJ., I). C. L. Oxoii., LL.D. Cantab. A Practical Treatise on Foreign Bodies in the Air-passages. In one octavo volume of 452 pages, with 59 illustrations. Cloth, $2.75. COHEN, J. SOLIS, M. I)., 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. SEILER, CARL, M. 1)., A Handbook of Diagnosis and Treatment of Diseases of the Throat, Nose and Naso-Pharynx. New (third) edition. In one handsome royal 12mo. volume of 400 pages, with 100 illustrations and 2 colored plates. In press. Lecturer on Laryngoscopy in the University of Pennsylvania. BROAJDBENT, W. IT., M. D., F. 11. C. !>., Physician to and Lecturer on Medicine at St. Mary's Hospital. The Pulse. In one 12mo. volume. Preparing. See Series of Clinical Manuals, page 4. 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. 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.,pp. 158. Cloth, $1.25. WALSHE ON THE DISEASES OF THE HEART AND GREAT VESSELS. Third American edi- tion. In 1 vol. 8vo., 416 pp. Cloth, $3.00. SMITH ON CONSUMPTION; its Early and Reme- diable Stages. 1 vol. 8vo., pp. 253. 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. JONES’ CLINICAL OBSERVATIONS ON FUNC- TIONAL NERVOUS DISORDERS. Second Am- erican edition. In one handsome octavo volume of 340 pages. Cloth, $3.25. Lea Brothers & Co.’s Publications—Nerv. and Ment. Dis., etc. 19 BOSS, JAMES, M.H., F.B.C.P., LL.H., Senior Assistant Physician to the Manchester Royal Infirmary. A Handbook on Diseases of the Nervous System. In one octavo volume of 725 pages, with 184 illustrations. Cloth, $4.50; leather, $5.50. 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 materiaUat 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. MITCHELL, S. WE lit, M. 11., Physician to Orthopaedic Hospital and the Infirmary for Diseases of the Nervous System, Phila., etc. Lectures on Diseases of the Nervous System; Especially in Women. Second edition. In one 12mo. volume of 288 pages. Cloth, $1.75. No work in our language develops or displays more features of that many-sided affection, hys- teria, or gives clearer directions for its differen- tiation, or sounder suggestions relative to its general management ana treatment. The book is particularly valuable in that it represents in the main the author’s own clinical studies, which have been so extensive and fruitful as to give his teachings the stamp of authority all over the realm of medicine. The work, although written by a specialist, has no exclusive character, and the general practitioner above all others will find its perusal profitable, since it deals with diseases which he frequently encounters and must essay to treat.—American Practitioner, August, 1885. HAMILTON, ALLAN McLANE, M. 11., 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. Cloth, $4. When the first edition of this good book appeared we gave-it our emphatic endorsement, and the present edition enhances our appreciation of the book and its author as a safe guide to students of clinical neurology. One of the best and most critical of English neurologicaljournals, 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. H., 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 handsome octavo volume of 467 pages, with two colored plates. Cloth, $3.00. Joint Author of The Manual of Psychological Medicine, etc. 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. CLO US TO N, THOMAS S., M. 11., F. It. C. P., L. It. 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 nis 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 make it a desirable addition to every library. —American Psychological Journal, July, 1884. 4@“Dr. Folsom’s Abstract may also be obtained separately in one octavo volume of 108 pages. Cloth, $1.50. SAVAGE, GFOJEtGE H., M. 11., 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 4. PL A YFAIR, W. S., M. 1)., F. jB. C. P. 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 Treatment: Lectures on the Treatment, Medical and Legal, of Insane Patients. In one very handsome octavo volume. 20 Lea Brothers & Co.’s Publications—Surgery. ASHHURST, JOHN, Jr., M. D., The Principles and Practice of Surgery. New (fourth) edition, enlarged and revised. In one large and handsome octavo volume of 1114 pages, with 597 illustra- tions. Cloth, $6; leather, $7 ; half Russia, $7.50. Professor of Clinical Surgery, Umv. of Penna., Surgeon to the Episcopal Hospital, Philadelphia. As with Erichsen so with Ashhurst, its position in professional favor is established, and one has now but to notice the changes, if any, in theory and practice, that are apparent in the present as compared with the preceding edition, published three years ago. The work has been brought well up to date, and is larger and better illustrated than before, and its author may rest assured that it will certainly have a “continuance of the favor with which it has heretofore been received.”— The American Journal of the Medical Sciences, Jan. 1886. Every advance in surgery worth notice, chroni- cled in recent literature, has been suitably recog- nized noted in its proper place. Suffice it to say, we regard Ashhurst’s Surgerv, as now pre- sented in the fourth edition, as the best single volume on surgery published in the English lan- guage, valuable alike to the student and the prac- titioner, to the one as a text-book, to the other as a manual of practical surgery. With pleasure we give this volume our endorsement in full.—New Orleans Medical and Surgical Journal, Jan., 1886. GROSS, S. D., M. D., LL. D., D. 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; half Russia, raised bands, $16. Emeritus Professor of Surgery in the Jefferson Medical College of Philadelphia. Dr. Gross’ System of Surgery has long been the standard work on that subject for students and practitioners.—London Lancet, May 10,1884. The work as a whole needs no commendation. Many years ago it earned for itself the enviable reputation of the leading American work on sur- gery, and it is still capable of maintaining that standard. A considerable amount of new material has been introduced, and altogether the distin- fuished author has reason to be satisfied that he as placed the work fully abreast of the state of our knowledge.—Med. Record, Nov. 18,1882. His System of Surgery, which, since its first edi- tion in 1859, has been a standard work in this country as well as in America, in “the whole domain of surgery,” tells how earnest and labori- ous and wise a surgeon he was, how thoroughly he appreciated the work done by men in other countries, and how much he contributed to pro- mote the science and practice of surgery in his own. There has been no man to whom America is so much indebted in this respect as the Nestor of surgery.—British Medical Journal, May 10, 1884. 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 form ulfe 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 textbook 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. BALL, CHARLES B., M. Ch., Dub., F. R. C. S. E., Surgeon and Teacher at Sir P. Dun's Hospital, Dublin. Diseases of the Rectum and Anus. In one 12mo. volume of 417 pages, with 54 engravings and 4 colored plates. Cloth, $2.25. Just ready. See Series of Clinical Manuals, page 4. It is a pleasure to read an exhaustive and well- arranged book, such as the one before us. It covers all the ground, and yet is written in aterse and concise style that makes it exceedingly good reading. The work is far in advance of the ordi- nary text-book on this specialty. It is very com- plete, and the matter is all of practical importance and well arranged. The writer has done for rectal surgery what Treves in the companion volume has done for intestinal obstruction, and both works are alike creditable.—N. Y. Medical Journal, Jan. 28, 1888. GIBNEY, V. P., M. D., 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. ROBERTS, JOHN B., A. M., 31. D., Lecturer on Anatomy and on Operative Surgery at the Philadelphia School of Anatomy. 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 about 500 pages, with many illustrations. Preparing. BELLAMY, EDWARD, F. R. C. S., Surgeon and Lecturer on Surgery at Charing Cross Hospital, London. Operative Surgery. Shortly. See Students’ Series of Manuals, page 4. 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; half Russia, raised bands, $12. In noticing the eighth edition of this well- known work, it would appear superfluous to say more than that it has, like its predecessors, been brought fully up to the times, and is in conse- quence one of the best treatises upon surgery that has ever been penned by one man. We nave al- ways 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 read- ers.— The Medical News, April 11,1885. After being before the profession for thirty years and maintaining during that period a re- putation as a leading work on surgery, there is not much to be said in the way of comment or criti- cism. That it still holds its own goes without say- ing. The author infuses into it his large experi- ence and ripe judgment. Wedded to no school, committed to no theory, biassed by no hobby, he imparts an honest personality in his observations, and his teachings are the rulings of an impartial judge. Such men are always safe guides, and their works stand the tests of time and experience. Such an author is Erichsen, and such a work is his Surgery.—Medical Record, Feb. 21,1885. BRYANT, THOMAS, F. R. Surgeon and Lecturer on Surgery at Ghuy's Hospital, London. c. s., 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; half Russia, $8.00. 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. TREVES, FREDERICK, F. 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 4. We have here the opinions of thirty-three authors, in an encyclopaedic 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 ox 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. The hand of Mr. Treves is evident throughout in the choice, arrangement and logical sequence of the subjects. Every topic, as far as observed, is treated with a fulness of essential detail, which is som e what surprising. Another characteristic of the work is the well-nigh universal acceptance of mod- ern and progressive views of pathology and treat- ment. The entire work is conceived and executed in a scientific spirit. It contains the bone and mar- row of modern surgery.—Annals oj Surgery, Oct. 1886. BUTLIN, 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 4. The language of the text is clear and concise, j The author has aimed to state facts rather than to express opinions, and has compressed within the compass of this small volume the pathology, etiol- [ ogy, etc., of diseases of the tongue that are incon- | veniently scattered through general works on sur- gery and the practice of medicine. The physician and surgeon will appreciate its value as an aid and guide.—Physician and Surgeon, Sept. 1886. 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 Manuals, page 4. A standard work on a subject that has not been so comprehensively treated by any contemporary English writer. Its completeness renders a full review difficult, since every chapter deserves mi- nute attention, and it is impossible to do thorough justice to the author in a few paragraphs. Intes- tinal Obstruction is a work that will prove of equal value to the practitioner, the student, the pathologist, the physician and the operating sur- geon.—British Medical Journal, Jan. 31, 1885. GOULD, A. REARCE, M. S., M. B., F. II. 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 Manuals, page 4. 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 PRACTICE OF SURGERY. Fourth and revised American from the last Edinburgh edition. In one large 8vo. vol. of 682 pages, with 364 illustrations. Cloth, $3.78. SKEY’S OPERATIVE SURGERY. In one vol. 8vo. of 661 pages, with 81 woodcuts. Cloth* $3.25. 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. 22 Lea Brothers & Co.’s Publications—Surgery, Frac., Disloc. 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; half Russia, $22.50. Sold only by subscription. SMITH, STEPHEN, M. I)., 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. It can be truly said that as a hand- book for the student, a companion 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. STIMSON, LFWIS A., B. A., M. D., Surgeon to the Presbyterian and Bellevue Hospitals, Professor of Clinical Surgery in the Medical Faculty of the University of the City of New York, 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 342 illustrations. Cloth, $2.50. 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 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. the same Author. A Treatise on Fractures and Dislocations. In two handsome octavo vol- umes. Yol. I., Fractures, 582 pages, 360 beautiful illustrations. Yol. II., Disloca- tions, 540 pages, with 163 illustrations. Complete work just ready, 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. HAMILTON, FRANK II., M. 1)., LL. II., Surgeon to Bellevue Hospital, New York. A Practical Treatise on Fractures and Dislocations. Seventh edition thoroughly revised and much improved. In one very handsome octavo volume of 998 pages, with 379 illustrations. Cloth, $5.50 It is about twenty-five years ago since the first edition of this great work appeared. The edition now issued is the seventh, and this fact alone is enough to testify to the excellence of it in all par- ticulars. Books upon special subjects do not usually command extended sale, but this one is without a rival in any language. It is essentially a practical treatise, and it gathers within its covers almost everything valuable that has been written about fractures and dislocations. The principles and methods of treatment are very fully given. The book is so well known that it does not require leather, $6.50; half Russia, $7.00. any lengthened review. We can only say that it is still unapproached as a treatise, and that it is a proof of the zeal and industry and great ability of its distinguished author.—The Dublin Journal of Medical Science, Feb. 1886. His famous treatise on Fractures and Disloca- tions, published first in 1860, is justly regarded as the best book on that subject in existence. It has now run through seven editions, and has been translated into French and German.—Medical Record, Aug. 14, 1886. 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 Manuals, page 4. PICK, T. PICKERING, F. R. C. 8., 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 4. Lea Brothers & Co.’s Publications—Otol., Ophthal. 23 BURNETT, CHARLES II, A. 31, M. D., The Ear, Its Anatomy, Physiology and Diseases. A Practical Treatise for the use of Medical Students and Practitioners. New (second) edition. In one handsome octavo volume of 580 pages, with 107 illustrations. Cloth, $4.00; leather, $5.00. Professor of Otology in the Philadelphia Polyclinic; President of the American Otological Society. 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. FOLITZER, ADAM, Imperial-Royal Prof, of Aural Therap. in the Univ. of Vienna. A Text-Book of the Ear and its Diseases. Translated, at the Author’s re- quest, by James Patterson Cassells, M. D., M. R. C. S. In one handsome octavo vol- ume of 800 pages, with 257 original illustrations. Cloth, $5.50. The whole work can be recommended as a reli- able guide to the student, and an efficient aid to the practitioner in his treatment.—Boston Medical and Surgical Journal, June 7,1883. JVLER, HENRY E., E. R. C. S., A Handbook of Ophthalmic Science and Practice. In one handsome octavo volume of 460 pages, with 125 woodcuts, 27 colored plates, selections from the Test-types of Jaeger and Snellen, and Holmgren’s Color-blindness Test. Cloth, $4.50; leather, $5.50. Senior Ass't Surgeon, Royal Westminster Ophthalmic Hosp.; lade Clinical Ass't, Moorfields, London. It presents to the student concise descriptions and typical illustrations of all important eye affec- 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. NETTLE SHU, EDWARD, E. R. C. S., Ophthalmic Surg. and Led. on Ophth. Surg. at St. Thomas' Hospital, London. The Student’s Guide to Diseases of the Eye. New (third) edition, thor- oughly revised. With a chapter on the Detection of Color-Blindness, by William Thomson, M. D., Professor of Ophthalmology in the Jefferson Medical College. In one 12mo. volume of 479 pages, with 164 illust., test-types and formulae. Cloth, $2. Just ready. In the small work before us we have combined simplicity of description with thoroughness of instruction. It is such a book as any intelligent student can read with profit to himself.—St. Louis Medical and Surgical Journal, Oct. 1887. This excellent and trustworthy manual is ad- dressed to students, but is equally suited to the needs of practitioners, who will find in its pages much valuable instruction. The style of the au- thor is pleasant, and the matter of his book is admirable.—Medical and Surgical Reporter, Oct. 1, 1887. NORRIS, WM. F., 31 D., and OLIVER, CHAS. A., 31. D. Clin. Prof, of Ophthalmology in Univ. of Pa. A Text-Book of Ophthalmology. In one octavo volume of about 500 pages, with illustrations. Preparing. CARTER, R. BR UDFNFL L, & FROST, W. ADAMS, F. R. C. S., F. R. C. S., Ophthalmic Surgeon to and Lecturer on Oph- thalmic Surgery at St. George's Hospital, London. Assistant Ophthalmic Surgeon to and Joint Lecturer on Ophthalmic Surgery at St. George's Hospital, London. 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, page 4. WELLS, J. SOELBERG, F. R. C. S., A Treatise on Diseases of the Eye. New (fifth) American from the third London edition. In one large octavo volume. Preparing. Professor of Ophthalmology in King's College Hospital, London, etc. BROWNE, EDGAR A., Surgeon to the Liverpool Eye and Ear Infirmary and to the Dispensary for Skin Diseases. How to Use the Ophthalmoscope. Being Elementary Instructions in Oph- thalmoscopy, arranged for the use of Students. In one small royal 12mo. volume of 116 pages, with 35 illustrations. Cloth, $1.00. 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 illust. Cloth, $2.75. LAWSON ON INJURIES TO THE EYE, ORBIT AND EYELIDS: Their Immediate and Remote Effects. 8 vo., 404 pp., 92 illus. Cloth, $3.60. 24 EGBERTS, WILLIAM, M. JD., Lecturer on Medicine in the Manchester School of Medicine, etc. A Practical Treatise on Urinary and Renal 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. Lea Brothers & Co.’s Publications—Urin. Dis., Dentistry, etc. The previous editions of this book have made it so familiar to and so highly esteemed by the med- ical public, that little more is necessary than a mere announcement of the appearance of this, their successor. But it is pleasant to be able to say that, good as those were, this is still better. In fact, we think 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.—J an. 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. FURJDY, CHARLES W., M. D. 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., F. R. C. S., 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 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 4. 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 Ouy's Hospital, London. Diseases of the Urethra. In one 12mo. volume. Preparing. See Series of Clinical Manuals, page 4. THOMFSON, 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 Fistulse. 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 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- Jierior. It should form a part of every dentist’s ibrary, as the information it contains is of the greatest value to all engaged in the practice of dentistry.—American Jour. Dent. Sci., Sept., 1886. j A grand system, big enough and good enough! and handsome enough for a monument (whichi 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. JR. C. F., F. JR. C. 8., Exam. L. JD. 8., Senior Dent. Surg. and Led. 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 at 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 met, price should not be considered in purchasing such a work. If the money put into some of our so- called standard text-books could be converted into such publications as this, much good would result. —Southern Dental Journal, May, 1882. The author brings to his task a large experience acquired under the most favorable circumstances. There have been added to the volume a hundred pages by the American editor, embodying the views of the leading home teachers in dental sur- gery. The work, therefore, may be regarded as strictly abreast of the times, and as a very high authority on the subjects of which it treats.— American Practitioner, July, 1882. BASHAM ON RENAL DISEASES: A Clinical Guide to their Diagnosis and Treatment. In one 12mo. vol. of 304 pages, with 21 illustrations. Cloth, 82.00. Lea Brothers & Co.’s Publications—Venereal, Impotence. 25 GROSS, SAJHUFL W., A. JH., JH. H., LL. H., 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 (third) edition, thoroughly revised. In one very handsome octavo volume of 163 pages, with 16 illustrations. Cloth, $1.50. It must be gratifying to both author and pub- lishers that large first and second editions of this little work were so soon exhausted, while the fact that it has been translated into Russian may indi- cate that it filled a void even in foreign literature. His is a careful and physiological study of the sexual act, so far as concerns the male, and all his conclusions are scientifically reached. The book has a place by itself in our literature, and furnishes a large fund of information concerning important matters that are too often passed over in silence.—The Medical Press, June, 1887. This now classical work on the subject of impo- tence and sterility in the male needs no extended review, for it is already well known to the pro- fession. Dr. Gross has by his tireless labor done more towards clearing up the diagnosis and treat- mentof these obscure cases than any other Ameri- can physician. The fact that this book has rapidly run through two large editions, and that the author is now forced to issue a third, is good and sufficient evidence of its excellence.— Atlanta Medical and Surgical Journal, April, 1888. B U3ISTEA1), F. J., 31. L).f LL. L).f Late Professor of Venereal Diseases at the College of Physicians and Surgeons, New York, etc. and TAYLOR, R. W., A. M., 31. !>., Surgeon to Charity Hospital, New York, Prof, of Venereal and Skin Diseases in the University of Vermont, Pres, of the Am. Dermatological A«8’n. The Pathology and Treatment of Venereal Diseases. Including the results of recent investigations upon the subject. Fifth edition, revised and largely re- written, by Dr. Taylor. In one large and handsome octavo volume of 898 pages with 139 illustrations, and thirteen chromo-lithographic figures. Cloth, $4.75; leather, $5.75; very handsome half Russia, $6.25. 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. It is certainly the best single treatise on vene- real in our own, and probably the best in any lan- guage.—Boston Med. and Surg. Journal, April 3,1884. The character of this standard work is so well known that it would be superfluous here to pass in review its general or special points of excellence. The verdict of the profession has been passed; it has been accepted as the most thorough and com- plete exposition of the pathology and treatment of venereal diseases in the language. Admirable as a model of clear description, an exponent of sound pathological doctrine, and a guide for rational and successful treatment, it is an ornament to the medi- cal literature of this country. The additions made to the present edition are eminently judicious, from the standpoint of practical utility.—Journal of Cutaneous and Venereal Diseases, Jan. 1884. CORNIL, V., 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 University of Pennsylvania, and J. William: White, M. D., Lecturer on Venereal Diseases and Demonstrator of Surgery in the University of Pennsylvania. In one handsome octavo volume of 461 pages, with 84 very beautiful illustrations. Cloth, $3.75. Professor to the Faculty of Medicine of Paris, and Physician to the Lour cine Hospital. 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. 11. 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 4. 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. JO., JH. H., LL. H., H. C. L., 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 FRIER, A., & BUJHSTEAH, F. J., JH.JO., LL.JO., Surgeon to the Hdpital du Midi. Late Professor of Venereal Diseases in the College of Physicians and Surgeons, New York. An Atlas of Venereal Diseases, Translated and edited by Freeman J. Bum- stead, M. D, 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 DISORDERS. In one 8vo vol. of 479 p. Cloth, $3.25. 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, $2.25. 26 Lea Brothers & Co.’s Publications—Venereal, Skin. TAYLOR, ROBERT W., A. M., M.D., Surgeon to Charity Hospital, New York, and to the Department of Venereal and Skin Diseases 0 the New York Hospital. 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 192 figures, and 400 pages of text with 65 engravings. Price per part, $2.50. Parts I. and II. are just ready. For sale by subscrip- tion only. Specimen plates sent on receipt of 10 cents. A full prospectus is now ready for distribution on application. As we have often stated, American physicians have contributed very creditably to the advance in dermatology that has taken place within the past quarter of a century. Not the least important of their contributions have been graphical clinical descriptions and telling pictorial delineations. These are precisely the features needed in any atlas illustrating a department of medicine. We were glad, therefore, to meet with the an- nouncement, some time ago, that the preparation of such a work, to be issued by Messrs. Lea Brothers & Co., of Philadelphia, was in the hands of Dr. Robert W. Taylor, of New York, all of whose writings have been conspicuously marked by vividness and accuracy. We have lately bad the opportunity of examining impressions of a great part of the plates and cuts to be given in Dr. Taylor’s new Atlas, together with the system of its arrangement. Besides the beauty and fidelity of the illustrations, they have the great merit of portraying typical and instructive rather than startling appearances, and espe- cially of representing not only the acme but the various phases of the disease to which they appertain. Having those objects in view, whoever sets to work to produce an atlas of cutaneous and venereal diseases, finds his greatest difficulty to lie in the work of selec- tion, and the greater are his attainments as a clinician the more readily will he surmount it. Dr. Taylor’s well-known excellence in this respect might well have been taken as sufficient guarantee of the quality of his new work, and our inspection of the plates and letter-press has been only confirmatory. The work will be a most valuable guide in diagno- sis and treatment, and we have no doubt that it will shed new lustre on American medicine. EDITORIAL FROM THE NEW YORK MEDICAL JOURNAL, FEB. 4, 1888. HYDE, J. NFVINS, A. M., M. D., 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. Just ready. Professor of Dermatology and Venereal Diseases in Rush Medical College, Chicago. The United States can now boast of having the best and freshest literature on dermatology, sur- prising in the number of its volumes. Dr. Hyde now presents us with a revision of his book which shows faithful rewriting, making it in reality a new work. He has adopted the plan of inserting his formulae for remedies in the text. The illustra- tions are good. He has selected from his own cases to illustrate in colors, two rare diseases. The woodcuts are clear and instructive. The book is a faithful exposition of dermatology, and the printer’s art has been carefully bestowed upon it to make it a handsome volume, a delight to the eye, a welcome companion to the working outfit of the busy doctor.—N. C. Medical Journal, May, 1888. There is no clearer or more succinct teacher of dermatology in this country than Prof. Hyde, of Chi- cago, and the second edition of his treatise is like his clinical instruction, admirably arranged, attrac- tive 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.f M. B., F.R. C. F., and FOX, T. C., B.A., M.R. C.S., Physician to the Department for Skin Diseases, University College Hospital, London. Physician for Diseases of the Skin to the Westminster Hospital, London. An Epitome of Skin Diseases. With Formulae. For Students and Prac- titioners. Third edition, revised and enlarged. In one very handsome 12mo. volume of 238 pages. Cloth, $1.25. 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. It. 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; 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—Dis. 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 of about 800 pages each, fully illustrated by wood engravings and colored plates. Volume I. of the Gynecology, containing 784 pages, with 201 engravings on wood and 3 colored plates, is now ready. Volume I. of the Obstetrics, containing 812 pages, with 309 engrav- ings and a colored plate, is just ready. The subsequent volumes are to follow at short inter- vals. Per volume: Cloth, $5.00; leather, $6.00; half Russia, $7.00. For sale by subscrip- tion 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., E. C. DUDLEY, A. B., M. D., EDWARD S. DUNSTER, M. D., B. McE. EMMET, M. D., GEORGE J. ENGELMANN, M. D., HENRY J. GARRIGUES, A. M., M. D., WILLIAM GOODELL, A. M., M. D., EGBERT H. GRANDIN, A. M., M. D., CHARLES M. GREEN, 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. D., WILLIAM T. LUSK, M. D., LL. D., MATTHEW D. MANN, A. M., M. D., H. NEWELL MARTIN, F. R. S., M. D., D. Sc., M.A., 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., WILLIAM L. RICHARDSON, M. D., A. D. ROCKWELL, A. M., M. D., ALEXANDER J. C. SKENE, M. D., J. LEWIS SMITH, M. D., R. STANSBURY SUTTON, A. M., M. D., LL. D., T. GAILLARD THOMAS, M. D., LL. D., ELY VAN DE WARKER, M. D., In our notice of the “System of Practical Medi- cine by American Authors,” we made the follow- ing statement:—“It is a work of which the Dro- 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,” W. GILL WYLIE, M. D. which we desire now to bring to the attention of our readers. 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 practis- ing physician is called upon to treat diseases of females, and as they constitute a class to which the familly physician 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 gen- erally purchasing.—Cincinnati Med. News, July,1887. THOMAS, T. GAILLARH, M. H., Professor of Diseases of Women in the College of Physicians and Surgeons, N. Y. A Practical Treatise on the Diseases of Women. Fifth edition, thoroughly revised and rewritten. In one large and handsome octavo volume of 810 pages, with 266 illustrations. Cloth, $5.00; leather, $6.00; very handsome half Russia, raised bands, $6.50. The words which follow “fifth edition” are in this case no mere formal announcement. The alterations and additions which have been made are both numerous and important. The attraction and the permanent character of this book lie in the clearness and truth of the clinical descriptions of diseases; the fertility of the author in thera- peutic resources and the fulness with which the details of treatment are described; the definite character of the teaching; and last, but not least, the evident candor which pervades it.—London Medical Times and Gazette, July 30,1881. That the previous editions of the treatise of Dr. Thomas were thought worthy of translation into German, French, Italian and Spanish, is enough to give it the stamp of genuine merit. At home it has made its way into the library of every obstet- rician and gynaecologist as a safe guide to practice. No small number of additions have been made to the present edition to make it correspond to re- cent improvements in treatment.—Pacific Medical and Surgical Journal, Jan. 1881. E1JI8, ARTHUR W., M. I)., Lond., F.R. C.P., 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, $3.00; leather, $4.00. It is a pleasure to read a book so thoroughly good as this one. The special qualities which are conspicuous are thoroughness in covering the whole ground, clearness of description and con- ciseness of statement. 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 rtsumt of the whole subject. Specialists, too, will find many useful hints in its pages.—Boston Med. and Surg. Journ., March 2,1882. BARNES, ROBERT, M. 1)., E. R. C. 1\, Obstetric Physician to St. Thomas' Hospital, London, etc. A Clinical Exposition of the Medical and Surgical Diseases of Women. In one handsome octavo volume, with numerous illustrations. New edition. Preparing, 28 Lea Brothers & Co.’s Publications—Dis. of Women, Midwfy. EMMET, THOMAS ADDIS, M. D., 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 Eussia, 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 gynae- cological science and art.—British Medical Jour- nal, May 16, 1885. The time has passed when Emmet’s Gynaecology was to be regarded as a book for a single country or for a single generation. It has always been his aim to popularize gynaecology, to bring it within easy reach of the general practitioner. The orig- inality of the ideas compels our admiration and respect. We may well take an honest pride in Dr. Emmet’s work and feel that his book can hold its own against the criticism of two conti- nents. It represents all that is most earnest and most thoughtful in American gynsecology.—Amer- ican Journal of Obstetrics, May, 1885. TAIT, LAWSON, F.R. C. S., Fellow of the Royal Medico- Chirurgieal Society of London, Honorary Member of the Boston Gyne- cological Society, Surgeon to the Birmingham and ''Midland Hospital for Women. Diseases of Women and Abdominal Surgery. In one very handsome octavo volume of 600 pages, fully illustrated. In press. D UNCAN, J. MATTHEWS, M I)., EL. I)., F. B. 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; I 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. 31 AY, CHARLES H., M. D., Late Home Surgeon to Mount Sinai Hospital, New York. A Manual of the Diseases of Women. Being a concise and systematic expo- sition of the theory and practice of gynaecology. In one 12mo. volume of 342 pages. Cloth, $1.75. Medical students will find this work adapted to their wants. Also practitioners of medicine will find it exceedingly convenient to consult for the purpose of refreshing their minds upon the lead- ing points of a gynaecological subject. By syste- matic condensation, the omission of disputed ques- tions, and the presentation only of accepted views, it constitutes a very satisfactory exposition of the leading principles of gynaecology as they are un- derstood at the present time.—Cincinnati Medical News, Nov. 1885. HODGE, HUGH L., 31. D., Emeritus Professor of Obstetrics, etc., in the University of Pennsylvania. On Diseases Peculiar to Women; Including Displacements of the Uterus. Second edition, revised and enlarged. In one beautifully printed octavo volume of 519 pages, with original illustrations. Cloth, $4.50. the Same Author. The Principles and Practice of Obstetrics. Illustrated with large litho- graphic plates containing 159 figures from original photographs, and with numerous wood- cuts. In one large quarto volume of 542 double-columned pages. Strongly bound in cloth, $14.00. Specimens of the plates and letter-press will be forwarded to any address, free by mail, on receipt of six cents in postage stamps. RAMSBOTHAM, FRANCIS H., 31. I). The Principles and Practice of Obstetric Medicine and Surgery: In reference to the Process of Parturition. A new and enlarged edition, thoroughly revised by the Author. With additions by W. V. Keating, M. D., Professor of Obstetrics, etc., in the Jefferson Medical College of Philadelphia. In one large and handsome imperial octavo volume of 640 pages, with 64 full-page plates and 43 woodcuts in the text, contain- ing in all nearly 200 beautiful figures. Strongly bound in leather, with raised bands, $7. WINCKEE, 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. E. Chadwick, M. D. Octavo 484 pages. Cloth, $4.00. WEST, CHARLES, M. D. 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, $4.75. ASHWELL’S PRACTICAL TREATISE ON THE j DISEASES PECULIAR TO WOMEN. Third American from the third and revised London edition. In one 8vo. vol., pp. 520. Cloth, $3.50. 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. Lea Brothers & Co.’s Publications—Midwifery. 29 PARVIN, TIIEOPIIII US, 31. B., XX. JO., Prof, of Obstetrics and the Diseases of Women and Children in Jefferson Med. Coll., Phila. The Science and Art of Obstetrics. In one handsome 8vo. volume of 697 pages, with 214 engravings and a colored plate. Cloth, $4.25 ; leather, $5.25. It is a ripe harvest that Dr. Parvin offers to his readers. There is no book that can be more safely recommended to the student or that can be turned to in moments of doubt with greater assurance of aid, as it is a liberal digest of safe counsel that has been patiently gathered.—The American Journal of the Medical Sciences, July, 1887. There is not in the language a treatise on the subject which so completely and intelligently gleans the whole field of obstetric literature, giv- ing the reader the winnowed wheat in concise and well-jointed phrase, in language of exceptional purity and strength. The arrangement of the matter of this work is unique and exceedingly favorable for an agreeable unfolding of the science and art of obstetrics. This new book is the easy superior of any single work among its predeces- sors for the student or practitioner seeking the best thought of the day in this department of medicine.—The American Practitioner and News, April 2,1887. This treatise may be defined as exact, concise and scholarly. Parvin’s distinguished position as a teacher, his scholarly attainments, and his honest endeavor to do his best by both the student and the physician, will secure for his treatise favorable recognition.—American Journal of Obstet- rics, May, 1887. BARNES, ROBERT, M. 1)., and FANCOTJRT, M. JD., 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 contributed by Prof. Milnes Marshall. In one handsome octavo volume of 872 pages, with 231 illus- trations. Cloth, $5; leather, $6. This system will be eagerly sought for, not only on account of its intrinsic merit, but also because the reputation which the elder Barnes, in particu- lar, has secured, carries with it the conviction that any book emanating from him is necessarily sound in teaching and conservative in practice. It is in- deed eminently fitting that a man who has done so much towards systematizing the obstetric art, who for so many years has been widely known as a eapa- ble teacher and trusted accoucheur, should embody within a single treatise the system which he has taught and in practice tested, and which is the out- come of a lifetime of earnest labor, careful obser- vation and deep study. The result of this arrange- ment is the production oi a work which rises above criticism and which in no respect need yield the palm to any obstetrical treatise hitherto published. —American Journal of Obstetrics, Feb. 1886. PLAYFAIR, W. S., 31. />., F. R. C. P., Professor of Obstetric Medicine in King's College, London, etc. A Treatise on the Science and Practice of Midwifery. New (fourth) American, from the fifth English edition. Edited, with additions, by Robert P. Har- ris, M. D. In one handsome octavo volume of 654 pages, with 3 plates and 201 engrav- ings. Cloth, $4; leather, $5; half Russia, $5.50. This still remains a favorite in America, not only because the author is recognized as a safe guide and eminently progressive man, but also as sparing no effort to make each successive edition a faithful mirror of the latest and best practice. A work so frequently noticed as the present requires no further review. We believe that this edition is simply the forerunner of many others, and that the demand will keep pace with the supply.—American Journal of Obstetrics, Nov. 1885. Since its first publication, only eight years ago, it has rapidly become the favorite text-book, to the practical exclusion of all others. A large measure of its popularity is due to the clear and easy style in which it is written. Few text-books for students have very much to boast of in this respect.—Medical Record. KING, A. F. A., 31. I)., 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 (third) edition. In one very handsome 12mo. volume of 376 pages, with 102 illustrations. Cloth, $2.25. This little manual, certainly the best of its kind, fully deserves the popularity which has made a third edition necessary. Clear, practical, concise, its teachings are so fully abreast with recent ad- vances in obstetric science that but few points can be criticised.—American Journal of Obstetrics, March, 1887. This volume deserves commendation. It is not bulky—it is concise. The chapters are divided with sub-headings, which aid materially in the finding of any particular subject, and the definitions are clear and explicit. It fulfils its purpose admirably, and we know of no better work to place in the stu- dent’s hands. The illustrations are good.—Arch- ives of Gynecology, January, 1887. BARKER, EORBYCE, A. 31., 31. !>., XX. X). Edin., Clinical Professor of Midwifery and the Diseases of Women in the Bellevue Hospital Medical College, New York, honorary Fellow of the Obstetrical Societies of London and Edinburgh, etc., etc. Obstetrical and Clinical Essays. In one handsome 12mo. volume of about 300 pages. Preparing. BARNES, FAN COURT, 31. I)., Obstetric Physician to St. Thomas' Hospital, London. A Manual of Midwifery for Midwives and Medical Students. In one royal 12mo. volume of 197 pages, with 50 illustrations. Cloth, $1.25. PARRY, JOHn S., M. JO., Obstetrician to the Philadelphia Hospital, Vice-President of the Obstet. Society of Philadelphia. Extra-Uterine Pregnancy: Its Clinical History, Diagnosis, Prognosis and Treatment. In one handsome octavo volume of 272 pages. Cloth, $2.50. TANNER ON PREGNANCY. Octavo, 490 pages, 4 colored plates, 16 cuts. Cloth, $4.25. 30 Lea Brothers & Co.’s Publications—Midwfy., Dis. Childn. LEISHMAN, WILLIAM, M. D., Regius Professor of Midwifery in the University of Glasgow, etc. A System of Midwifery, Including the Diseases of Pregnancy and the Puerperal state. Third American edition, revised by the Author, with additions by John S. Parry, M. D., Obstetrician to the Philadelphia Hospital, etc. In one large and very handsome octavo volume of 740 pages, with 205 illustrations. Cloth, $4.50; leather, $5.50; very handsome half Russia, raised bands, $6.00. The author is broad in his teachings, and dis- cusses briefly the comparative anatomy of the pel- vis and the mobility of the pelvic articulations. The second chapter is devoted especially to the study of the pelvis, while in the third the female organs of generation are introduced. The structure and development of the ovum are admirably described. Then follow chapters upon the various subjects embraced in the study of mid- wifery. The descriptions throughout the work are plain and pleasing. It is sufficient to state that in this, the last edition of this well-known work, every recent advancement in this field has been brought forward.—Physician and Surgeon, Jan. 1880. To the American student the work before us must prove admirably adapted. Complete in all its parts, essentially modern in its teachings, and with demonstrations noted for clearness and precision, it will gain in favor and be recognized as a work of standard merit. The work cannot fail to be popular and is cordially recommended.—N. O. Med. and Surg. Journ., March, 1880. It has been well and carefully written. The views of the author are broad and liberal, and in- dicate a well-balanced judgment and matured mind. We observe no spirit of dogmatism, but the earnest teaching of the thoughtful observer and lover of true science. Take the volume as a whole, and it has few equals.—Maryland Medical Journal, Feb. 1880. LANDIS, HENRY 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. 5, Columbus, 0. 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 proceedures are safe and practical. Centralblatt fur Cynakologie, 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. SMITH, J. LEWIS, M. D., Clinical Professor of Diseases of Children in the Bellevue Hospital Medical College, N. f. A Treatise on the Diseases of Infancy and Childhood. New (sixth) edition, thoroughly revised and rewritten. In one handsome octavo volume of 867 pages, with 40 illustrations. Cloth, $4.50; leather, $5.50 ; half Russia, $6.00. Rarely does a pleasanter task fall to the lot of the bibliographer than to announce the appearance of a new edition of a medical classic like Prof. J. Lewis Smith’s Treatise on the Diseases of Infancy and Childhood. For years it has stood high in the confidence of the profession, and with the addi- tions and alterations now made it may be said to be the best book in the language on the subject of which it treats. An examination of the text fully sustains the claims made in the preface, that “in preparing the sixth edition the author has revised the text to such an extent that a considerable part of the book may be considered new.” If the young practitioner proposes to place in his library but one book on the diseases of children, we would unhesitatingly say, let that book be the one which is the subject of this notice.—The American Journal of the Medical Sciences, April, 1886. No better work on children’s diseases could be placed in the hands of the student, containing, as it does, a very complete account of the symptoms and pathology of the diseases of early life, and possessing the further advantage, in which it stands alone amongst other works on its subject, of recommending treatment in accordance with the most recent therapeutical views.—British and Foreign Medico-Chirurgical Review. It is a pleasure to the busy practitioner—inter- ested in the advancement of his profession—to meet, fresh from the hands of its author, a medi- cal classic such as Smith on Diseases of Children. Those familiar with former editions of the work will readily recognize the painstaking with which this revision has been made. Many of the articles have been entirely rewritten. The whole work is enriched with a research and reasoning which plainly show that the author has spared neither time nor labor in bringing it to its present ap- proach towards perfection. The extended table of contents and the well-prepared index will enable the busy practitioner to reach readily and quickly for reference the various subjects treated of in the body of the work, and even those who are familiar with former editions will find the improvements in the present richly worth the cost of the work.— Atlanta Medical and Surgical Journal, Dec. 1886. OWEN, EDMUND, M. B., E. R. C. S., Surgeon to the Children's Hospital, Oreat 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 4. 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. WEST, CHARLES, M. 1)., Physician to the Hospital for Sick Children, London, etc. On Some Disorders of the Nervous System in Childhood. In one small 12mo. volume of 127 pages. Cloth, $1.00. WEST’S LECTURES ON THE DISEASES OF IN- FANCY AND CHILDHOOD. In one octavo vol. 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. Lea Brothers & Co.’s Publications—Med. Juris., Miscel. 31 TIDY, CHARLES MEYMOTT, M. B., F. C. S., Professor of Chemistry and of Forensic Medicine and Public Health at the London Hospital, etc. 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. 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. J)., A Manual of Medical Jurisprudence. Eighth American from the tenth Lon- don edition, thoroughly revised and rewritten. Edited by John J. Eeese, M. D., Professor of Medical Jurisprudence and Toxicology in the University of Pennsylvania. In one large octavo volume of 937 pages, with 70 illustrations. Cloth, $5.00; leather, $6.00; half Russia, raised bands, $6.50. Lecturer on Medical Jurisprudence and Chemistry in Quy's Hospital, London. ■s-The American editions of this standard manual have for a long time laid claim to the attention of the profession in this country; and the eighth comes before us as embodying the latest thoughts and emendations of Dr. Taylor upon the subject to which he devoted his life with an assiduity and success which made him facile princeps among English writers on medical jurisprudence. Both the author and the book have made a mark too deep to be affected by criticism, whether it be censure or praise. In this case, however, we should only have to seek for laudatory terms.—American Journal of the Medical Sciences, Jan. 1881. This celebrated work has been the standard au- thority in its department for thirty-seven years, both in England and America, in both the profes- sions which it concerns, and it is improbable that it will be superseded in many years. The work is simply indispensable to every physician, and nearly so to every liberally-educated lawyer, and we heartily commend the present edition to both pro- fessions.—Albany Law Journal, March 26,1881. The Principles and Practice of Medical Jurisprudence. Third edition. In two handsome octavo volumes, containing 1416 pages, with 188 illustrations. Cloth, $10; leather, $12. the Same Author. For years Dr. Taylor was the highest authority in England upon the subject to which he gave especial attention. His experience was vast, his judgment excellent, and his skill beyond cavil. It is therefore well that the work of one who, as Dr. Stevenson says, had an “enormous grasp of all matters connected with the subject,” should be brought up to the present day and continued in its authoritative position. To accomplish this re- sult Dr. Stevenson has subjected it to most careful editing, bringing it well up to the times.—Ameri- can Journal of the Medical Sciences, Jan. 1884. the Same Author. 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. REEFER, AUGUSTUS J., M. S., M. B., E. R. 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, page 4. LEA, HENRY C. 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. Cloth, $2.50. This valuable work is in reality a history of civ- ilization as interpreted by the progress of jurispru- dence. . . In “Superstition and Force” we have a philosophic survey of the long period intervening between primitive barbarity and civilized enlight- enment. There is not a chapter in the work that should not be most carefully studied; and however well versed the reader may be in the science of jurisprudence, he will find much in Mr. Lea’s vol- ume of which he was previously ignorant. The book is a valuable addition to the literature of so- cial science.— Westminster Review, Jan. 1880. Studies in Church History. The Rise of the Temporal Power—Ben- efit of Clergy—Excommunication. New edition. In one very handsome royal octavo volume of 605 pages. Cloth, $2.50. the Same Author. The author is pre-eminently 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. In no other single volume is the development of the primitive church traced with so much clearness, and with so definite a perception of complex or conflicting sources. The fifty pages on the growth of the papacy, for instance, are admirable for con- ciseness and freedom from prejudice.—Boston Traveller, May 3,1883. Allen’s Anatomy .... 6 American Journal of the Medical Sciences . 3 American Systems of Gynecology . . .27 American System of Practical Medicine. . 15 An American System of Dentistry . . 24 ♦Ashhurst’s Surgery ..... 20 Ashwell on Diseases of Women . . .28 Attfield’s Chemistry ... . .9 Ball on the Rectum and Anus . . . 4, 20 Barker’s Obstetrical and Clinical Essays, . 29 Barlow's Practice of Medicine . . .17 Barnes’ Midwifery ..... 29 ♦Barnes on Diseases of Women . . .27 Barnes’ System of Obstetric Medicine . . 29 Bartholow on Electricity .... 17 Bartholow’s New Remedies and their Uses . 11 Basham on Renal Diseases .... 24 Bell’s Comparative Physiology and Anatomy . 4, 7 Bellamy’s Operative Surgery . . . 4,20 Bellamy’s Surgical Anatomy ... 6 Blandford on Insanity .... 19 Bloxam’s Chemistry ..... 9 ♦Bristowe’s Practice of Medicine . . . 14 Broadbent on the Pulse . . . . 4,18 Browne on the Ophthalmoscope . . . 23 Browne on the Throat, Nose and Ear . . 18 Bruce’s Materia Medica and Therapeutics . 11 Brunton's Materia Medica and Therapeutics . 11 ♦Bryant’s Practice of Surgery . . . 21 ♦Bumstead on Venereal Diseases . . . 25 ♦Burnett on the Ear . . . . .23 Butlin on the Tongue ..... 4,21 Carpenter on the Use and Abuse of Alcohol . 8 ♦Carpenter’s Human Physiology ... 8 Carter & Frost’s Ophthalmic Surgery . .4,23 Century of American Medicine . . .14 Chambers on Diet and Regimen . . .17 Chapman’s Human Physiology ... 8 Charles’ Physiological and Pathological Chem. 10 Churchill on Puerperal Fever . . .28 Clarke and Lockwood’s Dissectors’ Manual . 4, 6 Classen’s Quantitative Analysis . . .10 Cleland’s Dissector ..... 6 Clouston on Insanity . .... 19 Clowes’ Practical Chemistry . . .10 Coats’ Pathology . . , . .13 Cohen on the Throat . . . . .18 Coleman’s Dental Surgery .... 24 Condie on Diseases of Children . . .30 Cornil on Syphilis ..... 25 Cullerier’s Atlas of Venereal Diseases . . 25 Cnrnow’s Medical Anatomy . . . 4, 6 Dalton on the Circulation .... 7 ♦Dalton’s HumanPhysiology ... 8 Davis’ Clinical Lectures . . .17 Draper’s Medical Physics .... 7 Druitt’s Modern Surgery ... .20 Duncan on Diseases of Women . . .28 ♦Dunglison’s Medical Dictionary ... 4 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 Therapeucics and Mat. Med. . 12 Fenwick’s Medical Diagnosis . . .16 Finlayson’s Clinical Diagnosis . . .16 Flint on Auscultation and Percussion . . 18 Flint on Phthisis . . . . .18 Flint on Physical Exploration of the Lungs . 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 . . 18 Galloway’s Analysis . . . . 8 Gibney’s Orthopsedic Surgery . . .20 Gould’s Surgical Diagnosis . . . . 4, 21 ♦Gray’s Anatomy . . . . . .5 Greene’s Medical Chemistry .... 9 Green’s Pathology and Morbid Anatomy . 13 Griffith’s Universal Formulary ... 11 Gross on Foreign Bodies in Air-Passages . 18 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 Hartshorne’s Anatomy and Physiology . . 6 Hartshorne’s Conspectus of the Med. Sciences . 3 Hartshorne’s Essentials of Medicine . . 14 Hartshorne’s Household Medicine . . 17 Hermann’s Experimental Pharmacology . 11 Hill on Syphilis ...... 25 Hillier’s Handbook of Skin Diseases . . 26 Hoblyn’s Medical Dictionary ... 4 Hodge on Women ..... 28 Hodge’s Obstetrics ..... 28 Hoffmann and Power’s Chemical Analysis . 10 Holden’s Landmarks ..... 5 Holland’s Medical Notes and Reflections . 17 ♦Holmes’System of Surgery . . .22 Horner’s Anatomy and Histology ... 6 Hudson on Fever . ... 4 Hutchinson on Syphilis . . . .4,25 Hyde on the Diseases of the Skin ... 26 Joues (C. Handheld) on Nervous Disorders . 18 Juler’s Ophthalmic Science and Practice . 23 King’s Manual of Obstetrics .... 29 Klein’s Histology . . . . . 4,13 Landis on Labor ..... 30 La Roche on Pneumonia, Malaria, etc. . . 18 La Roche on Yellow Fever .... 14 Laurence and Moon’s Ophthalmic Surgery . 23 Lawson on the Eye, Orbit and Eyelid . . 23 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 . . . 4,24 Ludlow’s Manual of Examinations . . 3 Lyons on Feter ...... 14 Maisch’s Organic Materia Medica ... 11 Marsh on the Joints . . . 4,22 May on Diseases of Women .... 28 Medical News . ... 1 Medical News Visiting List .... 3 Medical News Physicians’ Ledger ... 3 Meigs on Childbed Fever . . . .28 Miller’s Practice of Surgery . . .21 Miller’s Principles of Surgery . . .21 Mitchell’s Nervous Diseases of Women . . 19 Morris on Diseases of the Kidney . . . 4,24 Neill and Smith’s Compendium of Med. Sci. . 3 Nettleship on Diseases of the Eye . . .23 Norris and Oliver on the Eye . . .23 Owen on Diseases of Children . . . 4, 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 . . . . 4, 31 Pepper’s Surgical Pathology . . . 4,13 Pick on Fractures and Dislocations . .4,22 Pirrie’s System of Surgery . ... 21 Playfair on Nerve Prostration and Hysteria . 19 ♦Playfair’s Midwifery . ... 29 Politzer on the Ear and its Diseases . . 23 Power’s Human Physiology . . . . 4, 8 Purdy on Bright’s Disease and Allied A flections 24 Ralfe’s Clinical Chemistry . . . 4,10 Ramsbotham on Parturition ... 28 Remsen’s Theoretical Chemistry . . .10 ♦Reynolds’ System of Medicine . . .16 Richardson’s Preventive Medicine . . 17 Roberts on Urinary Diseases . . .24 Roberts’ Compencf of Anatomy ... 7 Roberts’ Principles and Practice of Surgery . 20 Robertson’s Physiological Physics . . 4, 7 Ross on Nervous Diseases .... 19 Savage on Insanity, including Hysteria . . 4,19 Schafer’s Essentials of Histology, . . 13 Schreiber on Massage . ... 17 Seiler on the Throat, Nose and Naso-Pharynx 18 Series of Clinical Manuals .... 4 Simon’s Manual of Chemistry ... 9 Skey’s Operative Surgery .... 21 Slade on Diphtheria . . . . .18 Smith (Edward) on Consumption . . .18 ♦Smith (J. Lewis) on Children ... 30 Smith’s Operative Surgery .... 22 Stllle on Cholera ..... 16 *Still6 * Maisch’s National Dispensatory . 12 ♦Stilly’s Therapeutics and Materia Medica . 12 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 Poisons ..... 31 ♦Taylor’s Medical Jurisprudence . . .31 Taylor's Prin. and Prac. of Med. 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 Treves’ Surgical Applied Anatomy . . 4, 6 Treves on Intestinal Obstruction . . .4,21 Tuke on the Influence of Mind on the Body . 19 Vaughan