CHAPTER XI

ON THE DEVELOPMENT OF PHYSICAL CHEMISTRY SINCE 1850

Chemistry and physics are each complementary to the other: that region of inquiry in which they mutually overlap is known as _physical chemistry_. Its beginnings are practically contemporaneous with those of chemistry itself. Its main development has occurred, however, during the last twenty-five years. Certain of its leading features have been referred to already in connection with the establishment of the fundamental principles of chemistry, the explanation of the so-called gaseous laws, the constitution of gases, the relations of their volumes to heat and pressure, and the conditions affecting their transition to the liquid state.

As regards the molecular volumes of gases it has been shown that simple relations are obtained when quantities represented by their respective molecular weights are compared under identical conditions of temperature and pressure—that is, under circumstances in which equal numbers of molecules form the basis of comparison. The investigation of the molecular volumes of liquids is complicated by the uncertainty as to what constitutes in their case a valid condition of comparison. Kopp’s assumption that a comparable condition was the temperature at which the vapour pressures of the liquids are equal to the mean atmospheric pressure was justified by the fact that the boiling-points of liquids are approximately two thirds of their respective critical temperatures. His conclusions have been confirmed and extended by Lossen, Thorpe, and Schiff. It has been shown that the molecular volume of a liquid—that is, the product of its relative density at the boiling-point into its molecular weight—is in the main an additive function modified by constitutive influences. Definite values have thus been obtained for a number of the elements from a comparison of homologous or similarly constituted compounds; and in certain cases these are found to be practically identical with the values of the elements in the uncombined state.

Considerable light has been gained during the last two decades concerning the nature of _solution_. In its most comprehensive sense solution means the homogeneous mixture of two or more substances: thus the gases which exert no chemical action on each other are mutually soluble; gases, liquids, and solids may be soluble in liquids; and, lastly, solids maybe soluble in solids, forming what are known as _solid solutions_. The mutual solubility of gases was studied by Dalton who enunciated the _law of partial pressures_, which states that the total pressure of a mixture of gases is the sum of the pressures exerted by the individual components. This, like all the so-called gaseous laws, is necessarily not strictly accurate under ordinary conditions, but approximates to truth in proportion as the gases are rarefied. Van ’t Hoff pointed out that the true partial pressures of the components of a gaseous mixture might be experimentally ascertained by the use of a membrane capable of effecting their separation, and on this principle Ramsay measured the partial pressures of a mixture of hydrogen and nitrogen contained in a palladium vessel connected with a manometer. The palladium, at a sufficiently high temperature, is permeable to hydrogen to the exclusion of the nitrogen. The conditions affecting the solubility of gases in liquids were experimentally studied by Dalton and Henry, and what is known as Henry’s law implies that the volume of a gas dissolved by a definite volume of a liquid is independent of the pressure; or, in other words, the density (concentration) of the gas in solution is proportional to that in the space above the liquid. Gases are dissolved by liquids in very different amounts, but nothing definite is known as yet concerning the relation between the nature of the gas and its solubility, although certain broad generalisations are possible. Thus neutral gases—_e.g._, hydrogen and nitrogen—are sparingly soluble, whereas gases which show acidic or basic properties, such as the hydrogen halides, etc., ammonia, etc., are freely soluble. Easily liquefiable gases are also comparatively soluble as noted by Graham.

Comparatively little is known definitely concerning the conditions of solubility of liquids in liquids. Some liquids are wholly, others partially miscible; and temperature and pressure appear to affect the proportions in which the components form a homogeneous mixture. As regards the solubility of solids in liquids, our knowledge is more extensive, and a considerable body of literature exists on the subject, chiefly concerning solubility of solids in water. The solubility of a solid depends on the temperature of the solvent, and, as a rule, increases with the temperature until a certain amount of the solid has been dissolved, when the solution is said to be _saturated_. If the clear saturated solution be slowly cooled, say, to a particular temperature, it is frequently observed that more of the solid remains in solution than is normal to that temperature; such a solution is said to be _supersaturated_. On adding some of the solid to the supersaturated solution the excess of the _solute_ is precipitated. In certain cases of solubility of substances in water, increase of temperature appears to diminish the amount dissolved. In nearly all such cases the difference in solubility is due to differences in the hydration of the solute. The phenomena of solid solutions have been less perfectly investigated, but the facts appear to show that such solutions in general tend to obey the laws regulating the solution of liquids in liquids. Alloys may be looked upon as solid solutions; and Roberts-Austen has shown that metals are capable of intradiffusion, like liquids and gases respectively.

The general question of solution was greatly developed in 1885 by Van ’t Hoff, by specially considering the case of dilute solutions. The gaseous laws are capable of their simplest expression when the gases are rarefied to such an extent that their molecules exert no sensible mutual influence. The case of dilute solutions is analogous. If the solute is present only in very small amount, the mutual influence of its molecules is practically negligible. Under such conditions it obeys the laws hitherto supposed to be applicable only to matter in the gaseous state.

It may be desirable to explain how this fundamental fact was recognised. It has long been known to the physiologist that certain membranes are _semi-permeable_—that is, they allow of the passage of certain liquids, and of substances in solution, to the exclusion of others. This phenomenon is termed _osmosis_, and is of great biological significance. It was first studied by plant-physiologists, notably by Traube and Pfeffer. Many such semi-permeable membranes can be formed artificially, but the most generally convenient is found to be one consisting of copper ferrocyanide deposited on the walls of a porous vessel.

If a vessel so prepared be filled with a solution of sugar, and be then placed in water, the water is found to pass through the membrane, but the membrane is impermeable to the sugar. In consequence pressure, termed _osmotic pressure_, is found to occur within the pot, and may be measured by suitable means. These osmotic pressures may at times be very large: thus a 1 per cent. solution of sugar may exert a pressure of half an atmosphere, and in the case of a solution of potassium nitrate of the same concentration it may amount to a couple of atmospheres.

Pfeffer determined the relation of the osmotic pressures to the concentration of solutions of these substances, measuring the pressures in centimetres of mercury by a manometer attached to the closed porous vessel. His results in the case of sugar were as follows:

_Percentage _Pressure in cm. strength (C)._ of mercury (P)._ _P/C._

1 53.5 53.5 2 101.6 50.8 4 208.2 52.1 6 307.5 51.3

It will be seen from these numbers that the ratio P/C is practically constant—that is, _the osmotic pressure varies directly as the concentration_. It was further found that the osmotic pressure exerted by a solution of uniform strength increases with the temperature.

The importance, of these observations in relation to the general theory of solution was first recognised by Van ’t Hoff. Osmotic pressure was regarded by him as analogous to gaseous pressure. Since P/C is constant for any one substance, and since for a definite weight of the solute the concentration is inversely as the volume of the solution, we obtain an equation analogous to the statement of Boyle’s law, PV = constant. Van ’t Hoff also found that the _osmotic pressure is proportional to the absolute temperature_, like the gaseous pressure. From these results, in conjunction with Avogadro’s hypothesis, it follows that _the osmotic pressure exerted by any substance in solution is the same as it would exert if present as gas in the same volume as that occupied by the solution, provided that the solution is so dilute that the volume occupied by the solute is negligible in comparison with that occupied by the solvent_. Another important consequence is that _solutes, when present in the ratio of their molecular weights in equal volumes of the same solvent, exert the same osmotic pressure_. Such solutions are said to be _isomotic_ or _isotonic_. It can be proved by thermodynamical reasoning that depression of the vapour pressure and freezing-point of a solution is proportional to its osmotic pressure. The significance of this relation in connection with the determination of the molecular weight of a soluble substance has already been referred to.[6]

[6] See pp. 70–73.

Determinations of molecular freezing-point depressions by Raoult and others showed that certain substances exerted only about half the osmotic pressure calculated from their known formulæ, whereas others have abnormally high osmotic pressures. The explanation of the discrepancies in the latter case was given in 1887 by Arrhenius, who pointed out that _only those solutions which have abnormally high osmotic pressures are electrically conductive_. This pregnant observation proved to be very fruitful in suggestiveness; and the connection between conductivity and Van ’t Hoff’s theory of solution was developed by Arrhenius into the doctrine of _electrolytic dissociation_ or _ionisation_—one of the most important consequences of Faraday’s electrolytic laws, the work of Hittorf, and the kinetic conceptions of Williamson and Clausius to which the last quarter of a century has given rise. Arrhenius showed that not only were free ions present in an electrically conductive solution before electrolysis, as maintained by Clausius, but that the proportion of molecules dissociated into ions could be calculated from measurements of electrical conductivity, as well as from measurements of osmotic pressure. Both methods give concordant results—a strong confirmation of the validity of the theory. In a solution of common salt, containing a gramme equivalent of that substance in a litre, Arrhenius calculated that only about three tenths of the salt exists as NaCl, the remaining seven tenths being resolved into independent ions of chlorine (chloridion) and sodium (sodion): NaCl⇄[Na·] + Cl´, each moving freely in all directions, like gaseous molecules. On passing the current, electrodes placed in the solution exert a directive action on the free ions, these alone being concerned in determining the conductivity, the un-ionised molecules or the solvent itself exercising no influence. Methods of determining the migration velocity of the ions have been worked out by Hittorf, Kohlrausch, Lodge, and others.

The theory of ionisation affords a satisfactory explanation of many chemical phenomena. It accounts for the characteristic properties of acids, and explains why different acids have varying “strengths” and why a “weak” acid has the same “strength” as the “strong” acid at high equivalent dilutions: in each case the acid is nearly completely ionised—in other words, the “strength” of an acid depends on the concentration of its hydrogen ions. So, too, the “strength” of a base is related to the number of its hydroxyl ions. Aqueous ammonia is relatively a “weak” base—its solution contains few hydroxyl ions. On the other hand, caustic potash is a “strong” base—its solution, on moderate dilution, is almost completely ionised: KOH = K· + OH´, the positive ion being represented by one or more dots, and the negative ion by one or more dashes. The theory accounts, too, for many phenomena in analytical chemistry—such as why magnesia is precipitated by ammonia only in the absence of ammonium chloride, and why sulphuretted hydrogen throws down zinc sulphide in the absence of hydrochloric acid. It also serves to explain many thermo-chemical facts observed by Hess, Thomsen, and others, such as the fact that the heat of neutralisation of the “strong” acids and bases is independent of their nature, and has the uniform value of 13,700 calories, in agreement with the value, as calculated by Van ’t Hoff, for the reaction H· + OH´ = H2O, deduced from Kohlrausch’s measurements of the conductivity of water at varying temperatures.

Certain phenomena relative to the effect of concentration (mass action) in determining chemical change—many of which have been studied by Ostwald and his pupils, as, for example, why two dilute solutions can be mixed together without thermal disturbance; numerous hydrolytic actions; the alkalinity and acidity of salts on solution; the behaviour of the “indicators” in analysis; such phenomena as the precipitability of common salt in aqueous solution by hydrogen chloride; the influence of an excess of a precipitant; the varying behaviour of reagents; the varying colour of salt solutions; the reason why water is formed in so many reactions; why a potential difference occurs at the surface of two electrolytic solutions, etc.—phenomena for the most part otherwise unintelligible, are all capable of explanation by means of it.

Although, in the above statement, we have been mainly concerned with aqueous solutions, it should be said that the theory of ionisation is applicable to other solvents, organic and inorganic. Moreover, it should be added, the theory has not been universally accepted as accounting for all the phenomena of solution. Many substances form definite hydrates which can be isolated, and it is a moot point whether such hydrates are capable of existing in aqueous solution, as contended by Mendeléeff, Pickering, Kahlenberg, Armstrong, and others. Such hydrates are, however, unstable compounds, affected by temperature changes, and dissociable on dilution in accordance with the law of concentration (mass action). Further, there is evidence, largely based on the work of Kohlrausch, H. C. Jones, and Lowry, to show that the ions in aqueous solutions of electrolytes are themselves hydrated.

Limitations of space preclude further attempts to deal with the development of physical chemistry during the last half-century, and many important matters must remain practically unnoticed.

The subject of thermo-chemistry is mainly the creation of the last half-century, elaborated by the labours of Hess, Andrews, Thomsen, Favre and Silbermann, and Berthelot. The work of Wenzel and Berthollet on the influence of molecular concentration on chemical change has been greatly extended by Berthelot, Guldberg and Waage, Julius Thomsen, Van ’t Hoff, Harcourt and Esson, and Le Chatelier; and the theory of mass action and the nature of reversible processes are now capable of definite expression, and can be proved independently by thermo-dynamical and kinetic reasoning. The phenomena of catalysis and the action of enzymes and of fermentation in general have received attention from many investigators. The phenomena of gaseous transpiration have been studied by Graham, Maxwell, and O. E. Meyer. Thermal dissociation has been experimentally observed by Deville, Troost, and others, and mathematically investigated by Willard Gibbs and Van der Waals; and its analogy to electrolytic dissociation has been established. The nature of gaseous explosions has been investigated by Berthelot, Le Chatelier, Abel, and Dixon. Important work has been done by Gladstone, Lorentz, Landolt, Nasini, Brühl, and others, on the connection between the nature and constitution of substances and their optical characters. Similar work has been done by Sir William Perkin as regards their magnetic rotation, and by Thorpe and Rodger with reference to their viscosity. The theory of phases, originating with Gibbs and developed by Van der Waals and Roozeboom, has been greatly extended. Sir J. J. Thomson and Sir J. Larmor have elaborated an electrical theory of the atom. Barlow and Pope have traced the relation between valency and volume, and the accurate measurements of Groth and of Tutton have extended our knowledge of the crystallographic relations of correlated substances.

Lastly, the whole subject of photo-chemistry, although originating with the observations of Ingenhousz, Scheele, and Senebier, may be said to have been studied only within our own time, notably by Bunsen and Roscoe, Pringsheim, Pfeffer, Vogel, and Abney.

BIBLIOGRAPHY

RELATING TO THE PERIOD COVERED BY VOL II.

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Beilstein’s _Handbuch der Organischen Chemie_. Nine vols. Leopold Voss, Hamburg, 1901–1906.

Bischoff’s _Materialen der Stereochemie_. Vieweg and Son, Brunswick, 1904.

Bischoff and Walden’s _Handbuch der Stereochemie_. H. Beckhold, Frankfort-on-the-Main, 1894.

Cain, J. C., and Thorpe, J. F. _Synthetic Dyestuffs and Intermediate Products._ Griffin and Co., 1905.

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Chemical Society. _Memorial Lectures, 1893–1900._ Gurney and Jackson, 1901.

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Curie, Marie. _Radio-Active Substances._ “Chemical News,” London, 1903.

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Fischer, Emil. _Untersuchungen in der Puringruppe._ Julius Springer, Berlin, 1907.

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Freund, Ida. _Study of Chemical Composition._ Cambridge University Press, 1904.

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Maxwell, Clerk. _Theory of Heat._ With corrections and additions by Lord Rayleigh. Longmans.

Meldola, Raphael. _Chemical Synthesis of Vital Products._ Edward Arnold, 1904.

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Meyer, Lothar. _Modern Theories of Chemistry._ Translated by Bedson and Williams. Longmans, 1888.

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Meyer, O. E. _The Kinetic Theory of Gases._ Translated by R. E. Baynes. Longmans, 1899.

Muir, M. M. Pattison. _History of Chemical Theories and Laws._ John Wiley and Sons, New York, 1907.

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Richter’s _Lexikon der Kohlenstoff Verbindungen_. Leopold Voss, Hamburg and Leipzig.

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Rutherford, E. _Radio-Activity._ Cambridge University Press, 1904.

Schorlemmer, Carl. _Rise and Development of Organic Chemistry._ Edited by Arthur Smithells. Macmillan.

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Thorpe, T. E. _Dictionary of Applied Chemistry._ Three vols. Longmans.

Thorpe, T. E. _Essays in Historical Chemistry._ Macmillan, 1902.

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Van ’t Hoff, J. H. _Arrangement of Atoms in Space._ Translated by A. Eiloart. Longmans, 1898.

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INDEX

Abel, 184

Abney, 185

Absolute zero, 97

Acetanilide, 159

Aceto-acetic ester, 148

Actinium, 59

Adrenaline, 160

Agurin, 158

Alizarin, 162

Alkaloids, 132

Allyl alcohol, 4

Alyhine, 160

Ammonium chloride, dissociation of, 66

Ampère, 62

Anderson, 133

Andrews, 70, 95, 183

Aniline blue, 4

Aniline purple, 4

Antimony, origin of name, 28

Antipyrin, 159

Argon, 43, 45, 46

Argyrodite, 37

Armstrong, E. F., 151

Armstrong, H. E., 183

Aromatic compounds, 121, 123

Arrhenius, 179, 180

Arsine-dimethyl, 20

Artiads, 116

Asymmetry, 141

Atmolysis, 84

Atomic value, 114

Atomic weight, determination of, 75

Atomicity, 114

Atropine, 135, 162 its synthesis 135

Australene, 130

Autoracemisation, 144

Avogadro, 62 his hypothesis, 63

Baeyer, 125, 129, 161, 163

Balard, 139

Baly, 129, 151

Bamberger, 147

Barbier, 154

Barlow, 184

Basarow, 157

Basicity, 16

Becquerel, Henri, 52

Behrend, 157

Benzene, 123 its constitution, 123 _et seq._, 128

Benzidam, 3

Berberine, 136

Bernoulli, Daniel, 82

Berthelot, Daniel, 82, 183, 184

Berthollet, 183

Berzelius, 63

Biot, 138

Bitter almond oil, 7

Blagden, Sir Charles, 72

Boisbaudran, Lecoq de, 36, 38, 39

Boltzmann, 83

Bone oil, 133

Boron, specific heat of, 71

Boyle’s law, 84–87

Brauner, 33

Bredt, 129, 130

Brieger, 161

Brühl, 149, 151

Bunsen, Robert W., 18, 34, 43, 185

Bunsen burner, 22

Cacodyl, 20

Cadaverine, 161

Cæsium, 21, 34

Caffeine, 157

Cahours, 4, 132

Cailletet, 96

Camphene, 131

Camphor, 130, 131, 162

Cannizzaro, Stanislao, 64, 79

Carbon, atomic weight of, 75 specific heat of, 71 tetravalency of, 115

Carbon carbonyl, 155

Carbon suboxide, 155

Carnelley, 108

Carnolite, 58

Cavendish, 43, 45

Cayley, 120

de Chancourtois, 102

Chloral hydrate, 159

Choline, 161

Cinchonine, 137

Clausius, 83, 179

Cleve, 38, 47

Cleveite, 47

Cocaïne, 136, 162

Codeine, 137

Coindet, 8

Collie, 49, 128

Condensation, 152

Conine, 162

Conservation of mass, law of, 78

Coumarin, 132, 162

Critical point, 94

Critical pressure, 95

Crookes, Sir William, 35, 40, 75

Curie, Marie, 55

Cyanic acid, 7

Cyanuric acid, 7

Debierne, 59

Decipium, 40

Delafontaine, 49

Demarçay, 30

Desch, 151

Deville, 184

Dewar, 71, 96, 127

Dexter, 157

Didymium, 40

Digitalis, 10

Disintegration theory, 54

Dixon, 184

Dobbie, 151

Doebner, 134

Dumas, Jean B. A., 8, 9, 30, 31, 63, 75, 102, 130

Duppa, 148

Dysprosium, 38

Edestin, 169

Electrolysis, 179

Elements, nomenclature of, 27

Emanation from Radium, 58

Emanium, 60

Enantiomorphism, 140

Enzymes, 144

Ether, discovery of its constitution, 12, 17

Etherin theory, 10

Europium, 39

Favre, 183

Fenton’s reagent, 154

Findlay, 151

Fischer, Emil, 158, 165, _et seq._

Fittig, 153

Fluorine, 33, 34

Formulæ, chemical, significance of, 68

Frankland, 114, 116, 148

Fuchsine, 4

Fumaric acid, 146

Gadolinium, 39

Gallium, 36, 107

Gases, kinetic theory of, 83 law of diffusion of, 84, 89 liquefaction of, 94 molecular theory of, 79

Gas-mantles, 40

Gay Lussac, 63, 80

Geometrical isomerism, 146, 147

Gerhardt, 79, 113

Germanium, 37, 107

Geuther, 148

Gibbs, Willard, 184

Giesel, 60

Gladstone, 30, 102, 184

Gmelin, 7, 63, 102

Gore, 33

Graebe, 162

Graham, Thomas, 2, 14, 23, 29, 83

Grignard’s reagent, 154

Groth, 184

Guldberg, 183

Guye, 81

Haarmann, 132

Hæmoglobin, 168

Hantzsch, 147

Hartley, 151

Haüy, 139

Heliotropin, 132

Helium, 43, 47, 49

Helmholtz, 117

Henry’s law, 173

Hermann, 26

Herschel, 140

Hess, 181, 183

Heumann, 163

Heymann, 163

Hillebrand, 47

Hittorf, 179

Hofmann, August W., 3, 67, 133, 161

Holmium, 38

Hoogewerff, 133

Horbaczewski, 157

Hübner, 127

Hydrogenium, 16

Hyoscyamine, 135

Ilmenium, 26

Indigo, 162, 164

Indigo blue, 163

Indium, 36

Ingenhousz, 185

Ionisation, 178

Ionium, 58

Ionone, 132

Irone, 132

Isoborneol, 131

Isoconine, 134

Isoquinoline, 133

Isotonic solutions, 178

Jones, H. C., 183

Jones, H. O., 147

Kahlenberg, 183

Kammerlingh Onnes, 49, 97

Kekulé, Friedrich August, 23, 113, 114, 121, 123, 125, 153

Kiliani, 165

Kipping, 147

Kirchhoff, 21

Knorr, 128, 151, 159

Koenigs, 133

Kohlrausch, 182, 183

Komppa, 129

Kopp, 172

Körner, 127

Krüss, 40

Krypton, 43, 50

Krystallin, 3

Kundt, 46

Laar, 149

Lactic acid, spatial representation of, 141

Ladenburg, 127, 134, 147, 161

Lamy, 35

Landolt, 78, 184

Langlet, 49

Larmor, Sir J., 184

Lauder, 151

Laurent, 79

Le Bel, 143, 147, 148

Leduc, 80, 81

Le Royer, 8

Leucol, 133

Liebermann, 162

Liebig, Justus von, 5

Linnemann, 127

Liquid diffusion, 16

Liquids, molecular volumes of, 172

Lossen, 172

Lowry, 151, 183

Low temperature research, 97, 39

Lutecium, 89

Magenta, 4

Magnus, 79

Maleic acid, 146

Mansfield, 3

Marignac, 39, 75

Mauve, 4

Maxwell, 83

Medlock, 3

Mellitic acid, 7

Membranes, semi-permeable, 176

Mendeléeff, 30, 102, 109, 183

Mercury forms a monatomic gas, 71, 92

Metaphosphoric acid, 14

Meyer Lothar, 103

Meyer, Victor, 67, 147

Mitscherlich, 63, 138

Moissan, 33

Molecule, integral, 62

Molecules, their number, 93 their size, 93

Monium, 40

Morley, 80

Morphine, 137

Mosander, 39

Multirotation, 145

Muscarine, 161

Muspratt, 4

Mutarotation, 145

Naphthalene, 163

Narceïne, 136

Narcotine, 136

Nasini, 184

Natanson, 157

Neodymium, 39

Neon, 43, 50

Neoytterbium, 38

Neurine, 161

Newlands, 102

Nicotine, 135, 162

Nilson, 37, 40, 107

Nirvanine, 160

Nitrogen compounds, stereo-isomerism of, 147

Novocaïne, 160

Odling, 30, 114

Oil of wintergreen, 162

Olszewki, 96

Opianic acid, 136

Organic synthesis, 152

Orthoforms, 160

Osmotic pressure, 176

Ostwald, 182

Oxyhæmoglobin, 167

Ozone, 70 its symbol, 70

Papaverine, 136

Partial pressure, law of, 173

Pasteur, 139

Peachey, 148

Pelopium, 26

Penny, 75

Periodic law, 101

Perissads, 116

Perkin, Sir William, 3, 129, 131, 132, 162

Pettenkofer, 30

Pfeffer, 176, 185

Phenacetin, 159

Phenylglycin, 163

Phosphorous oxide, molecular weight of, 73

Phosphorus pentachloride, 66

Phosphorus pentafluoride, 67

Phthalic acid, 163

Pickering, 183

Pictet, 96, 135

Pinene, 130, 131

Pinner, 135

Piperine, 134, 162

Plattner, 35

Playfair, 20

Pollucite, 35

Pope, 147, 184

Posselt, 135

Praseodymium, 38

Pringsheim, 185

Protamines, 168

Proteins, 165

Prout’s law, an illusion, 76

Ptomaines, 161

Pyridine, 133

Quinine, 137

Quinoline, 133

Racemic acid, 140

Racemism, 143

Radio-thorium, 60

Radium, atomic weight of, 58 discovery of, 55 disintegration of, 58 emanation, 58 extraction of, 55

Radium chloride, 57

Ramsay, Sir William, 44, 47, 173

Raoult, 72, 178

Rayleigh, Lord, 44, 81

Regnault, 43, 79, 88, 157

Reich, 36

Reimann, 135

Richards, Theodore, 77

Richter, 36

Rodger, 184

Roosen, 157

Roozeboom, 184

Rosaniline, 4

Roscoe, 21, 30, 117, 185

Rose, 26

Rotatory power, 144

Rubidium, 21, 34

Runge, 133

Rutherford, 59

Salicylic acid, 162

Salmine, 168

Samarium, 40

Sarcine, 157

Sarcolactic acid, 140

Saturated solutions, 174

Saussure, 43

Scandium, 37, 107

Scheele, 33, 140, 185

Schiff, 172

Schischkoff, 21

Schmidt, 83

Schmiedeberg, 161

Scott, 80

Selmi, 161

Senebier, 185

Sesquiterpenes, 129

Silbermann, 183

Silicon, specific heat of, 71

Skraup, 133

Solute, 175 influence of, on boiling-point, 71 on freezing-point, 71 on vapour pressure, 73

Sonstadt, 153

Soret, 70

Spectrum analysis, 21

Stas, 75

Steric hindrance, 151

Stovaïne, 160

Strecker, 102, 158, 161

Sugars, 165

Sulphonal, 159

Supersaturated solutions, 174

Tait, 70

Tautomerism, 149

Terebenthene, 130

Terpenes, 129

Tetanine, 161

Tetronal, 159

Thallium, 35

Thebaine, 137

Thénard, 43

Theobromine, 157

Thioacetic acid, 127

Thomsen, Julius, 51, 108, 183

Thomson, Sir J. J., 184

Thomson, Thomas, 3

Thorium, 60

Thorpe, 172, 184

Thulium, 38

Thyreoglobulin, 169

Tiemann, 129, 132

Traube, 176

Travers, 50

Trional, 159

Triphenylrosaniline, 4

Troost, 184

Turner, Edward, 2, 14, 75

Turpentine, oil of, 129

Tutton, 184

Type theory, 18

Typhotoxine, 161

Unverdorben, 3

Uranium, 54

Uranium │x│, 54

Urbain, 40

Urea, synthesis of, 157, 158

Uric acid, 158

Valency, 112

Vanadium, 30

Van der Waals, 95, 184

Van Dorp, 133

Vanillin, 132, 162

Van ’t Hoff, 117, 141, 145, 147, 173, 177

Veronal, 159

Verquin, 4

Victorium, 40

“Vital force” doctrine, 169

Vogel, 185

Von Miller, 134

Waage, 183

Wallach, 129

Warburg, 46

Waterston, 83

Weber, 71

Weisbach, 37

Welsbach, Auer von, 38

Werner, 147

Williamson, Alexander W., 14, 16, 113

Winkler, 107

Wintergreen, oil of, 132

Wislicenus, 140

Wöhler, Friedrich, 5, 7

Wollaston, 63

Wroblewski, 96

Wurtz, 153

Xanthine, 157

Xenon, 43, 51

Zein, 169

Zinin, 3

A History of the Sciences

¶ Hitherto there have been few, if any, really popular works touching the historical growth of the various great branches of knowledge. The ordinary primer leaves unexploited the deep human interest which belongs to the sciences as contributing to progress and civilization, and calling into play the faculties of many of the finest minds. Something more attractive is wanted.

¶ The above need in literature has now been met. Each volume in _The History of Sciences_ is written by an expert in the given subject, and by one who has studied the history as well as the conclusions of his own branch of science. The monographs deal briefly with the myths or fallacies which preceded the development of the given science, or include biographical data of the great discoverers. Consideration is given to the social and political conditions and to the attitudes of rulers and statesmen in furthering or in hindering the progress of the given science. The volumes record the important practical application of the given science to the arts and life of civilized mankind, and also contain a carefully-edited bibliography of the subject. Each volume contains from twelve to sixteen carefully-prepared illustrations, including portraits of celebrated discoverers, many from originals not hitherto reproduced, and explanatory views and diagrams. The series as planned should cover in outline the whole sphere of human knowledge.

¶ Science is to be viewed as a product of human endeavor and mental discipline, rather than taken in its purely objective reference to facts. The essential purpose has been to present as far as practicable the historical origins of important discoveries, also to indicate the practical utility of the sciences to human life.

G. P. Putnam’s Sons New York London

A History of the Sciences

Each volume is adequately illustrated, attractively printed, and substantially bound.

_16mo. Each, net, 75 cents. By mail, 85 cents. 12 illustrations_

History of Astronomy

By George Forbes, M.A., F.R.S., M.Inst. C.E.

Formerly Professor of Natural Philosophy, Anderson’s College, Glasgow

I thank you for the copy of Forbes’s _History of Astronomy_ received. I have run it over, and think it very good indeed. The plan seems excellent, and I would say the same of your general plan of a series of brief histories of the various branches of science. The time appears to be ripe for such a series, and if all the contributions are as good as Prof. Forbes’s, the book will deserve a wide circulation, and will prove very useful to a large class of readers.—_Extract from a letter received from Garrett P. Serviss, B. S._

History of Chemistry

By Sir Edward Thorpe, C.B., LL.D., F.R.S.

Author of “Essays in Historical Chemistry,” “Humphry Davy: Poet and Philosopher,” “Joseph Priestley,” etc.

_12 illustrations. Two vols. Vol. I—circa 2000 B.C. to 1850 A.D. Vol. II—1850 A.D. to date_

The author traces the evolution of intellectual thought in the progress of chemical investigation, recognizing the various points of view of the different ages, giving due credit even to the ancients. It has been necessary to curtail many parts of the History, to lay before the reader in unlimited space enough about each age to illustrate its tone and spirit, the ideals of the workers, the gradual addition of new points of view and of new means of investigation.

The History of Old Testament Criticism

By Archibald Duff

Professor of Hebrew and Old Testament Theology in the United College, Bradford

The author sets forth the critical views of the Hebrews concerning their own literature, the early Christian treatment of the Old Testament, criticism by the Jewish rabbis, and criticism from Spinoza to Astruc, and from Astruc until the present.

_In Preparation_

The History of Geography.

By Dr. JOHN SCOTT KELTIE, F.R.G.S., F.S.A., Hon. Mem. Geographical Societies of Paris, Berlin, Rome, Brussels, Amsterdam, Geneva, etc.

The History of Geology.

By HORACE B. WOODWARD, F.R.S., F.G.S., Assistant Director of Geological Survey of England and Wales.

The History of Anthropology.

By A. C. HADDON, M.A., Sc.D., F.R.S., Lecturer in Ethnology, Cambridge and London.

The History of New Testament Criticism.

By F. C. CONYBEARE, M.A., late Fellow and Praelector of Univ. Coll., Oxford; Fellow of the British Academy; Doctor of Theology, _honoris causa_, of Giessen; Officer d’Academie.

_Further volumes are in plan on the following subjects_:

Mathematics and Mechanics—Molecular Physics, Heat, Light, and Electricity—Human Physiology, Embryology, and Heredity—Acoustics, Harmonics, and the Physiology of Hearing, together with Optics, Chromatics, and Physiology of Seeing—Psychology, Analytic, Comparative, and Experimental—Sociology and Economics—Ethics—Comparative Philology—Criticism, Historical Research, and Legends—Comparative Mythology and the Science of Religions—The Criticism of Ecclesiastical Institutions—Culture, Moral and Intellectual, as Reflected in Imaginative Literature and in the Fine Arts—Logic—Philosophy—Education.

New York G. P. Putnam’s Sons London

Transcriber’s Notes

Punctuation and spelling were made consistent when a predominant preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected; occasional unbalanced quotation marks retained.

Ambiguous hyphens at the ends of lines were retained; occurrences of inconsistent hyphenation have not been changed.

Index not checked for proper alphabetization or correct page references.

The table on page 105 has been split into three parts to keep it narrow.