CHAPTER XII

THE RISE OF PHYSICAL CHEMISTRY

Physics and Chemistry are twin sisters—daughters of Natural Philosophy; like Juno’s swans, coupled and inseparable. Physics is concerned with the forms of energy which affect matter; chemistry with the study of matter so affected. Each, then, is complementary to the other. Philosophers of old drew no practical distinction between them, at least as regards their own studies. Men like Boyle, Black, Cavendish, Lavoisier, Dalton, Faraday, Graham, Bunsen, were pioneers “on a very broad gauge,” pushing their inquiries into territories common to the two branches as their genius or inclinations directed them. Accordingly, it has happened that many so-called physical laws have been discovered by men who were professed chemists. It has also happened that men who began their scientific career as chemists, like Dalton, Regnault, and Magnus, eventually gave the whole of their energies to physical measurements; or, like Black, Faraday, and Graham, devoted themselves to the elucidation of physical problems. As certain of these physical laws and problems have greatly influenced the progress of chemistry, it becomes necessary, in any historical treatment of the subject, to give some account of their origin, and to show how they affected the development of chemical theory.

The relations of heat to chemical phenomena are so obvious and so intimate that the study of their connection necessarily attracted attention in very early times. But it was only when this study became quantitative that any important generalisations became possible. Most quantitative estimations of heat depend eventually upon the thermometer; and thermometry is indebted to Englishmen in the first instance for attempts to render the instrument trustworthy.

In this connection may be mentioned the names of Newton and Shuckburgh. Brooke Taylor, in 1723, made a special study of the mercurial thermometer as a measurer of temperature. In other words, he sought to discover whether equal differences of expansion or contraction of mercury corresponded to equal additions or abstractions of heat. The results showed that the principle of the mercurial thermometer is valid within at least the limits of temperature between the boiling and freezing-points of water. These experiments were subsequently repeated and confirmed by Cavendish, and, independently, by Black.

The discovery of the phenomenon of _latent heat_ by Black some time prior to 1760 marks an epoch in the history of science. It was then for the first time clearly recognised that the state of aggregation of a substance is associated with a definite thermal quantity, and that, in order to effect a change, a definite amount of energy, in the form of heat, must be employed. The quantitative connection that exists between work and energy was thus foreshadowed.

The doctrine of _specific heat_ was taught by Black in his lectures at Glasgow between 1761 and 1765. The subject was subsequently investigated experimentally by Irvine between 1765 and 1770, and by Crawford in 1779. A series of determinations was published in 1781 by Wilcke, in the _Transactions_ of the Swedish Academy. In these the term _specific caloric_, since changed to _specific heat_, was first used. About this time the determination of the amount of heat required to raise substances through a definite interval of temperature was made the subject of experiment by many observers, notably by Lavoisier and Laplace, who greatly improved the calorimetric arrangements. The values they obtained long remained the most trustworthy estimations of the specific heats of substances. Their joint research had a further influence on the development of thermo-chemistry by indicating the general experimental conditions which were needed to ensure accuracy in such determinations. Lavoisier and Laplace also measured, in 1782–1783, the heat disengaged by the combustion of substances, and that evolved during respiration. In 1819 Dulong and Petit pointed out that the specific heat of a number of substances, more particularly the metals, were inversely proportional to their atomic weights; or, in other words, the product of the specific heat into the atomic weight was a constant. The nature of the relation will be seen from the following table of certain of the results obtained by Dulong and Petit:—

Element. At. wt. Spec. heat. Atomic heat.

Bismuth 208 0.0288 6.0 Lead 207 0.0293 6.0 Gold 197 0.0298 5.8 Platinum 195 0.0314 6.1 Silver 108 0.0570 6.1 Copper 63 0.0952 6.0 Iron 56 0.1138 6.4

It will be seen that these various elements have an uniform, or nearly uniform, atomic heat—approximately 6.2 on the average.

This would appear to prove that, as Dulong and Petit expressed it, “the atoms of simple substances have equal capacities for heat.” The variations from a constant value are due partly to errors of observation, but more particularly to the circumstance that the substances compared are not all in a strictly comparable condition—_e.g._, they are not all equally remote from their melting points. It was shown, moreover, that the amount of heat needed to raise a substance through a definite interval of temperature increased with the temperature. The range of temperature through which a determination was made in a particular instance affected, therefore, the value of the specific heat. The most noteworthy departures from a uniform value were observed to occur among the metalloids—_e.g._, carbon, the various modifications of which had different specific heats—and generally among elements of low atomic weight, in which the variation of specific heat with temperature was particularly rapid.

Nevertheless, the significance of the generalisation discovered by Dulong and Petit, in spite of its limitations, was quickly appreciated, as it was perceived that a knowledge of the specific heat of an element might be of great value in determining its atomic weight. The immediate effect was that a certain number of the atomic weights fixed by Berzelius mainly on chemical considerations were required to be halved. Although subsequent experience has proved that the law of Dulong and Petit is not capable of the simple mathematical expression they gave it, it has shown itself to be of great value in fixing doubtful atomic weights.

=Pierre Louis Dulong= was born in 1785 at Rouen, and, after studying chemistry and physics at the Polytechnic School at Paris, became its Professor of Chemistry and subsequently its Professor of Physics. In 1830 he was made its Director of Studies; and in 1832 he became permanent Secretary of the Academy of Sciences. As a young man he worked with Berzelius, with whom he made the first approximately accurate determination of the gravimetric composition of water. In 1811 he discovered the highly explosive _nitrogen chloride_, in the investigation of which he was severely injured, losing an eye and several fingers. He died in 1838. His collaborator, =Alexis Therese Petit=, was born in 1791 at Vesoul, and died, when holding the position of Professor of Physics at the Lycée Bonaparte, in 1820.

The attempt made by Neumann to extend Dulong and Petit’s “law” to compound substances was only partially successful. Nor has any important generalisation followed from our knowledge of the specific heat of liquids. Almost simultaneously with the publication of Dulong and Petit’s “law,” Mitscherlich made known the fact that similarity in chemical constitution is frequently accompanied by identity of crystalline form. Boyle, as far back as the middle of the seventeenth century, had insisted upon the importance of the forms of crystals in throwing light upon the internal structure of bodies. Romé de l’Isle and Hauy had remarked that many different substances had the same crystalline form. It had been observed that a crystal of potash alum would continue to grow and preserve its shape in a solution of ammonia alum; and similar observations had been shown to occur in the case of vitriols. The invention of the reflecting goniometer by Wollaston greatly facilitated the investigation of such phenomena. Mitscherlich showed that the phosphates and arseniates of analogous composition had the same crystalline shape, or, in other words, were isomorphous. The same fact was observed to occur in the case of the analogously constituted sulphates and selenates, and in that of the oxides of magnesium and zinc, etc. The value of isomorphous relations in determining the group-relationships of the elements and in deducing the composition of salts was at once recognised by Berzelius, who styled the discovery of isomorphism by his pupil Mitscherlich as “the most important since the establishment of the doctrine of chemical proportions.” The quantities of the isomorphously replacing elements in a compound were regarded by him as a measure of their atomic weights; and the principle was subsequently constantly employed by him, whenever possible, as a criterion in fixing their values. Other investigators have followed his example in this respect; and isomorphism is still regarded as an important consideration in establishing the genetic relations of an element.

=Eilhard Mitscherlich=, the son of a minister, was born in 1794 at Neu Ende, near Jever, in Oldenburg, and, after studying philology and oriental languages at Heidelberg, went to Paris, and thence to Göttingen, where he occupied himself with natural science. In 1818 he repaired to Berlin and commenced to work on the arseniates and phosphates, the similarity in the crystal-forms of which he was the first to detect. His friend Gustav Rose, the mineralogist, thereupon instructed him in the methods of crystallography; to enable him to verify his discovery and to establish it by goniometric measurements. In 1821 he joined Berzelius at Stockholm, where he pursued his inquiries on the connection between crystal-form and chemical composition. It was at the suggestion of Berzelius that he adopted the term “isomorphy” to express this connection—the mechanical consequence of identity of atomic constitution. In the same year he was appointed Klaproth’s successor in Berlin, where he died in 1863.

Mitscherlich also worked on the manganates and permanganates, on selenic acid, on benzene and its derivatives, and on the artificial production of minerals.

The study of the physical phenomena of gases, initiated in 1660 by Boyle’s discovery of the law of gaseous pressure, has greatly contributed to our knowledge of their intrinsic nature. Boyle himself only proved his law in the case of atmospheric air; but the observation was subsequently (1676) generalised by Marriotte. Charles, Dalton, and Gay Lussac independently showed that gases have the same rate of thermal expansion.

That gases are made up of particles possessing an internal movement was surmised by the Greeks; but experimental evidence for such a view of their constitution was first presented by Thomas Graham in 1829–1831, when he discovered that gases move, or are diffused, at rates inversely proportional to the square roots of their densities. Observations of a like character, which found their explanation in Graham’s discovery, had previously been made by Priestley, Döbereiner, and Saussure. This interchange in the position of their particles is a property inherent in gases. Inequality of density is not essential to diffusion. Graham proved this by connecting together two vessels, one containing nitrogen and the other carbonic oxide, which have the same density. After the expiration of a certain time both gases were found to be uniformly diffused through the vessels.

How these laws were found to be interdependent and mutually connected, and how they led up to a molecular theory of gases which serves to explain them, as well as certain other gaseous phenomena to be subsequently noted, will be shown in the second part of this work.

By the end of the period with which we are concerned—that is, the middle of the nineteenth century—a considerable body of information had been accumulated as to the conditions which determine the different states of aggregation of matter—that is, the conditions which allow of the passage of the gaseous state into that of the liquid, and of the liquid into that of the solid. That the same substance was capable of existence in the three states of gas, liquid, and solid was of course evident from the case of water. Even the most primitive races must have realised that steam, dew, rain, snow, hail, and ice were only modifications of one and the same substance. As knowledge increased, other substances came to be known which resembled water in their capacity for existence in various physical states. It was but natural to assume that this was a general attribute, and that all substances would, sooner or later, be found capable of existence in each of the different conditions of aggregation.

Attempts were made during the first quarter of the last century to prove that all the æriform bodies then known were simply vapours more or less remote from their point of liquefaction, and still further removed from their point of congelation. Monge and Clouet condensed sulphur dioxide some time before 1800; and Northmore, in 1805, liquefied chlorine. But these observations attracted little attention until Faraday, in 1823, independently effected the liquefaction of chlorine, and Davy that of hydrochloric acid. Faraday almost immediately afterwards liquefied sulphur dioxide, sulphuretted hydrogen, carbon dioxide, euchlorine, nitrous oxide, cyanogen, and ammonia.

Other experimenters, among whom may be mentioned Thilorier and Natterer, greatly improved the mechanical appliances for liquefying these gases; liquid carbonic acid and nitrous oxide were obtained in considerable quantities, and employed in the production of cold. Certain of the gases—hydrogen, oxygen, nitrogen, nitric oxide, carbonic oxide, etc.—resisted all attempts to liquefy them; and hence gaseous substances came to be classified as _permanent_ and _non-permanent_, depending upon whether they could or could not be liquefied. The division was felt to be irrational even at the time it was made. There seemed no _à priori_ reason why carbon dioxide and nitrous oxide should be liquefiable, while carbonic oxide and nitric oxide should resist all attempts to coerce them into changing their state. The real clue to the conditions required to effect the liquefaction of a gas was not discovered until nearly half a century later, when, as will be shown subsequently, the arbitrary division of gases into permanent and non-permanent was swept away.

The discovery of the law of gaseous combination by Gay Lussac, and the recognition by Ampère and Avogadro of the relation between the density of a gas or a vapour and its atomic weight, early led to improvements in the methods of determining the absolute weights of gases and vapours, especially by French chemists. Both Gay Lussac and Dumas devised processes for determining vapour densities which were in use until late in the century, and which, although now superseded by more convenient and more rapid modifications afforded valuable information concerning the molecular weights of substances and the phenomena of gaseous dissociation.

During the first decade of the nineteenth century Dalton and Henry discovered the simple law which connects pressure with the solubility of a gas in any solvent upon which it exerts no specific action. Dalton further developed the law so as to include the absorption by a solvent of the several constituents of a gaseous mixture.

Attempts were made by Schröder, Kopp, and others, to discover relations between the weights of unit volumes of liquids and solids and their chemical nature; but such attempts were only partially successful, owing to the difficulty of finding valid conditions of comparison. By comparing the specific gravities of liquids at their boiling-points Kopp succeeded in detecting a number of regularities among their specific volumes which seem to indicate that a comprehensive generalisation connecting them may yet be discovered. Kopp has also shown that regularities exist among the boiling-points of correlated substances, and that there is an interdependence between the temperature of their ebullition and the chemical characters of compounds.

This short summary will suffice to show that attempts to discover relations between the physical attributes of substances and their chemical nature were made more or less sporadically from the time that chemistry was pursued in the spirit of science. But it is only in recent times that any great accession to knowledge has resulted from such efforts. The science of physical chemistry is practically a creation of our own period. Its systematic study may be said to date only from the last quarter of the nineteenth century, since which time it has made extraordinary progress. Its broad features will be dealt with in the second volume of this work.

BIBLIOGRAPHY

RELATING TO THE PERIOD COVERED BY VOL. I.

Agricola, Georg. _De Re Metallica._

Agricola, Georg. _Vom Bergwerck XII. Bücher darinn mit schöner Figuren_, etc.

Alembic Club, Publications of the. W. Clay, Edinburgh.

Beddoes, Thomas. _Chemical Essays of Scheele._ Murray, London, 1786.

Berthelot, Marcellin. _La Chimie des Anciens et du Moyenâge._ Steinheil, Paris, 1889.

Berthelot, Marcellin. _La Révolution Chimique._ Félix Alcan, Paris, 1890.

Berthollet, C. L. _Essai de Statique Chimique._ Firmin Didot, Paris, 1803.

Birch, Thomas. _Life of Boyle._ Millar, London, 1744.

Boerhaave, Hermann. _New Method of Chemistry._ Shaw and Chambers, London, 1727.

Boulton, Richard. _Boyle’s Works Epitomised._ Phillips and Taylor, London, 1699.

Burton, W. _Life of Boerhaave._ Lintot, London, 1746.

Dalton, John. _A New System of Chemical Philosophy._ Two Vols. Bickerstaff, London, 1807–1810.

Davy, John. _Life of Sir Humphry Davy._ Longmans, London, 1836.

Davy, Humphry. _Collected Works._ Edited by John Davy. Smith, Elder, and Co., London, 1839.

Figuier, Louis. _L’Alchimie et les Alchimistes._ Victor Lecon, Paris, 1855.

Gay Lussac and Thénard. _Recherches Physico-Chimiques._ Deterville, Paris, 1811.

Gerding, Th. _Geschichte der Chemie. Zweite Ausgabe._ Grunow, Leipzig, 1869.

Grimaux, Edouard. _Lavoisier, 1743–1794._ Félix Alcan, Paris, 1888.

Henry, William Charles. _Life of Dalton._ Cavendish Society, London, 1854.

Hoefer, Ferdinand. _Histoire de la Chimie._ Two vols., Deuxième édition. Firmin Didot Frères, Paris, 1866.

Jones, Bence. _Life and Letters of Faraday._ Longmans, London, 1870.

Kopp, Hermann. _Geschichte der Chemie._ Four vols. Braunschweig, 1843–47.

Kopp, Hermann. _Die Alchemie in älterer und neuerer Zeit._ Heidelberg, 1886.

Ladenberg, Albert. _History of Chemistry Since the Time of Lavoisier._ Translated by Leonard Dobbin. Alembic Club, Edinburgh, 1900.

Lavoisier. _Complete Works._ Edited by Dumas. Four vols. Paris, 1864.

Lemery, Nicolas. _Cours de Chimie._ Paris, 1675.

Meyer, Ernst v. _History of Chemistry._ Translated by George M’Gowan. Macmillian and Co., London, 1891.

Nordenskiöld, A. E. _Carl Wilhelm Scheele._ Norsledt and Söner, Stockholm.

Ostwald’s _Klassiker der Exakten Wissenschaften_.

Paris, John Ayrton. _Life of Sir Humphry Davy._ Colbourne and Bentley, London, 1831.

Priestley, Joseph. _Experiments and Observations on Different Kinds of Air._ Six vols. J. Johnson, London, 1775 _et seq._

Roscoe, H. E., and Harden, A. _A New View of the Origin of Dalton’s Atomic Theory._ Macmillian and Co., London.

Schmieder. _Geschichte der Alchimie._ Halle, 1832.

Schubert, E., und Sudhoff, K. _Paracelsus’s Forschungen._ Frankfurt, 1887–89.

Shaw, Peter. _Stahl’s Chemistry._ Osborn and Longman, London.

Stahl, G. E. _Cheimia Rationalis_ (1720).

Stahl, G. E. _Zymotechnia Fundamentalis_, etc. (1697).

Stange, Albert. _Zeitalter der Chemie._ Otto Wigand, Leipzig, 1908.

Thomson, Thomas. _History of Chemistry._ Two vols. Colbourne and Bentley, London, 1830.

Thorpe, T. E. _Essays in Historical Chemistry._ Second edition. Macmillian and Co., London, 1902.

Thorpe, T. E. _Humphry Davy, Poet and Philosopher._ Cassells, London, 1895.

Thorpe, T. E. _Joseph Priestley._ Dent and Co., London, 1906.

Wilson, George. _Life of Cavendish._ Cavendish Society, London, 1851.

INDEX

Æneas Garæus, 35

Agricola, Georg, 66

Aidoneous, god of earth, 22

Albertus Magnus, 40, 47

Alchemy, 28 and astrology, 36 its character, 39

Alkahest, 51

Anastatius the Sinaite, 35

Anaxagoras, 26

Anaximenes, 21

_Aqua regia_, 39

Arabian learning, influence on Western Europe, 25

Archæus, 59

_Argentarium_, 10

_Argentum vivum_, 11

Aristotle, his doctrine of “elements”, 23 his character as a man of science, 24

Arnoldus Villanovanus (Arnaud de Villeneuve), 42, 47, 48, 51

Arvidson, 155

_Arrenichon_, 13

_Ars Transmutatoria_, 46

Artephius, 49

Astrology and alchemy, 36

Atoms, ancient theories of, 26

_Atramentum_, 14

_Aurichalcum_, 9

_Auri pigmentum_ (orpiment), 13

Averroes, 25, 38

Avicenna, 38

Avogadro, 181

Bacon, Roger, 40, 41

Bacon, Lord, 55

Baldwin’s phosphorus, 80

Bartoletti, Fabrizio, 155

Basil Valentine, 43, 47, 49, 156

Bathurst, Ralph, 74

Becher, John Joachim, 81, 156

Benther, David, alchemist, 53

Bergman, 94, 107, 124, 158, 160

Berigard de Pisa, 48

Berthollet, Claude-Louis, 116 _et seq._, 156, 160, 164

Berthelot, 37

Berzelius, Jöns Jakob, 133, 156, 159, 160, 164

Black, Joseph, 98 _et seq._, 171

Bochart, 4

Boerhaave, 3–20, 35, 42, 49, 51, 106 his life and work, 84 _et seq._

Bolim, 160

Borri, 53

_Botryitis_, 12

Bouillon-Lagrange, 158

Boullay, 162, 167

Boyle, Robert 20, 72 _et seq._, 107, 113, 155, 157, 159, 175, 177

Bragadino, alchemist, 53

Brooke Taylor, 171

Brugnatelli, 158, 161

_Cadmia_, 12

_Cœruleum_, 12

Caligula, 34

_Carbunculus_, 48

Cardan, 110

Cavendish, 94, 102 _et seq._, 107, 171

Caventou, 162

Cerium, its discovery, 121

_Cerussa_, 10 _usta_, 12

_Chalcantum_ (copper sulphate), 12

Charles, 178

Chalybes, smelters of iron, 11

Chemistry of the ancients, 1

Chenevix, 157

Chevreul, 54, 162

Chlorine, discovery of, 107

Chromium, discovery of, 120

_Chrysocolla_, 12

Cinnabar, use as pigment, 13

Clouet, 180

Clytemius, John, 54

Cobalt, discovered by Brandt, 107

Combining proportion, 129

Conservation of matter, 113

Conringius, Hermann, 51

Copper, Egyptian, 8 Roman, 9

Cordus Valerius, 69

Crawford, 107, 172

Croll, Oswald, 65

Cronstedt, 107

Cyanogen, discovery of, 151

Dalton, 125 _et seq._, 178, 181

Davy, 29, 141

Dee, John, 53

Delambre, 116

Demokritos, 26

_De Re Metallica_, 66

Derosne, 157

Dickinson, 50

Diodorus Siculus, 7

Dioscorides, 156, 160

Döbereiner, 155, 162, 167

Dorn, 60

Duchesne, 61

Duhamel, 98, 157

Dumas, 162, 167, 168, 181

Dulong, 158, 173, 174

Dyeing by the Egyptians, 14

Egypt, birthplace of chemistry, 1

_Electrum_, 8

_Elementa Chemia_, 87

“Elements,” Aristotelian, qualities of, 23

_Elephantinum_, 14

Elixir, 32

Eller, 94

Empedokles, 23

Erastius, Thomas, 51

Equivalent, 129

_Fæx vini_, 137

Fischer, G. E., 124

Flos æris, 12

Fourcroy, 112, 118, 155, 158, 161, 162

Frankland, 168

Gahn, 108

_Gas sylvestre_, 63

Gay Lussac, 150, 155, 161, 164, 167, 178, 181

Geber, 36 theory of metals, 37, 156

Generation of metals, 33

Geoffroy, 106

Gerhardt, 168

Glass, known to the ancients, 15

Glauber, Johann Rudolf, 68

Glucinum, its discovery, 120

Gmelin, L. 161

Gold, extraction by ancients, 7

Goulard, 157

Gomes, 161

Göttling, 156

Graham, Thomas, 178

Gresham College, 74

Gualdo, 49

Guyton de Morveau, 112, 160

_Hæmatinon_, 15

Hales, Stephen, 89

“Harmonics,” Paracelsian, 61

Hauy, 176

Hellot, 108

Helmont, John Baptist van, 63

Helvetius, 48

Hennel, 155

Henry, 181

Herakleitos, 21

Here, god of air, 22

Hermbstädt, 158

Hermes Trismegistus, 4, 33

“Hermes of Germany, the”, 52

Hoffmann, 106

Homberg, William, 84

Houton-Labillardière, 158

Howard, 161

_Hyalos_, use of, for kindling fire, 15

_Hydrargyrum_, 11

Iatro-chemistry, 57

Ink of the ancients, 14

Ingenhousz, 21

Invisible College, the, 74

Iron, use of, by the ancients, 10

Irvine, 172

Isaac of Holland, 49

Isomerism, 165

Isomorphism, discovery of, 176

“Kalid,” his philosopher’s stone, 48

_Key of Wisdom_, 53

Kircher, 51

Kirchhoff, 162

Kirwan, 113

Klaproth, 120, 160

Klettenberg, Hector de, 54

Kopp, 181

Krohnemann, William de, 53

Kunkel, John, 51, 79

_Laboratorium Chymicum_, 80

_Lac Virginis_, 157

Lagrange, 116

Laplace, 172

Latent heat, 99, 172

Lauraquais, 155

Laurent, 168

Lavoisier, 20, 22, 109 antiphlogistic theory, 112, 116, 156, 164, 166, 173

Law of Dulong and Petit, 173, 174

Law of electrolytic action, 153

Lead, known to the ancients, 10

Leblanc, 108

Lehmann, 159

Lemery, Nicolas, 83, 154, 156

Leo Africanus, 36

Leukippos, 26

Libavius, Andreas (Libau), 62, 155, 157

Lieber, Thomas, 65

Liebig, 155, 156, 159, 164, 167

Löwiz, 156

Lucretius, 26, 27

Lully, Raymund, 41, 47, 49

Macquer, 98

Magistery, grand, 48 small, 48

_Magnesia alba_, nature of, 107

Manganese, discovery of, 107

Marggraf, 95, 107, 108, 157

Marie Ziglerin burnt, 53

Martian preparations, 37

Marriotte, 178

Maternus, Julius Firmicus, 35

Mayerne, Turquet de, 65

Mayow, John, 82 _et seq._

Medicine and Astrology, 58

_Melinum_, 13–14

Menethes Sibonita, 3

“Mercury,” as “element”, 31

Mercury, receipt for fixing, 50

Metallurgy of the ancients, 7

Metals of the phlogistians, 104

Minderer, Raymond, 157

_Minium_, 12

Mitscherlich, 159, 175, 176, 177

_Molybdena_, 12

Monge, 180

Monro, Donald, 159

Mordants, Egyptian, 15

Mundamus, 43

Mynsicht, Adrian van, 65, 158

Narcotine, 161

_Natron_, used as a detergent, 16

Natterer, 180

Nestis, god of water, 22

Neumann, 94, 175

_New System of Chemical Philosophy_, Dalton’s, 129

Nickel, discovery of, 107

Nitrogen, discovery of, 107

Northmore, 180

_Œrugo_, 12

Oil of wine, 155

_Okeanos_, 19

Oleus Borrichius, 33

Olimpiodorus, 35

_Onychitis_, 12

Operinus, 60

_Ostracitis_, 12

Oxides, metallic, used by ancients to colour glass 15

Oxygen, its discovery, 105 influence of, on chemistry, 105

Palissy, Bernard, 67

Paracelsus, 40, 48, 57

_Paratonium_, 13

Pelletier, 162

Peligot, 162

Peripatetic philosophy, influence on science, 24

Petit, Alexis Therese, 173, 175

Pherekides, 21

_Philosophia Orientalis_, 38

Philosopher’s Stone, 32, 46, 49

Philosophical egg, 33

Phlogistonism, 95 _et seq._

Phosphorus, discovery of, 80, 107

_Placitis_, 12

Platinum, discovery of, 107

Plato’s doctrine of “elements”, 23

Pliny, 156

_Plumbum album_, 10 _nigrum_, 10

Pope John XXII., alchemist, 46

Porret, 160

Pott, 94, 95, 159

Price, James of Guildford, 54

Priestley, Joseph, 20, 22 his life and work, 99 _et seq._

Proust, Joseph Louis, 121

Purple of Cassius, 81

_Purpurissum_, 13

Quintessence of philosophers, 32

Raquetaillade, Jean de, 43

Realgar, 13

Reaumur, 108

Rey, 110

Rhazes, 38

Richter, Jeremiah Benjamin, 124

Ripley, George, 43

Robiquet, 161, 167

Roebuck, 108

Romé de L’Isle, 176

Rose, Gustav, 177

Rosenkreutz, Christian, 55

Rouelle, 94, 106, 159

Royal Society, foundation of, 74

_Rubrica_, 13

Rupecissa, Johannes de, 43

_Saccharum plumbi quintessentiale_, 157

Sala, Angelus, 65

_Sal Armoniacum_, 44

_Sal Duplicatum_, 81

_Sal mirabile_, 68

_Sandarach_, 13

Saturnine solutions, 37

Savary, 155

Sceptical Chemist, The, 70

Scheele, 96 _et seq._, 107, 155, 158, 159, 160, 166

Schroeder, 181

_Scoria æris_, 12

Sefström, 135

Seguin, 159

Seignette, Peter, 157

Selenium, its discovery, 135

Sennert, Daniel, 65

Sertürner, 161

Severinus, 61

Silver, known to the ancients, 7

_Sinopis_, 13

Soap, manufacture by Gauls, 15

Specific heat, discovery of, 99

_Spiritus igno-aëreus_, 82

Stahl, George Ernst, 92, 156

_Stannum_, 10

_Statical Essays_ of Hales, 89

_Statique Chimique_, 117

Stephanus, 35

_Stibium_, 13 _Stimmi_, 13

Strontia, discovery of, 107

Suidas, 34

“Sulphur,” as “element”, 31

Sulzbach, 110

Sun worship, 22

Sylvius, Francis de le Boë, 64

Syncellus, 35

Tachenius, 69

Tartarus, doctrine of, 59, 157

Tellurium, discovery of, 121

_Terra pinguis_ of Becher, 92

_Tertiarium_, 10

Tertullian, 19

Thales of Miletus, 19

Thénard, 152, 164

Theophrastus, 156

The Tincture, 32

Thilorier, 180

Thomson, Thomas, 129

Thorium, its discovery, 135

Thurneysser, Leonard, 53, 60

Tin, known to the Egyptians, 9

Transmutation, 28, 30

Trommsdorff, 157

Tubal Cain (Tuval-Cain), 7

Turquet de Mayerne, 158

Tyrian purple, 14

Valentine, Basil, 43, 47, 49, 156

Van Helmont, 20, 48, 63

_Vasa murrhina_, 15

Vauquelin, 119, 155, 158, 161, 162

Verdigris, 56

Vincent de Beauvais, 50

Von Ittner, 160

Wallis, John, 74

Ward, Seth, 74

“White” gold, 7

Wilcke, 172

Willis, Thomas, 64, 74

Wöhler, 161, 163, 167

Wollaston, 144, 176

Woodward, 160

Wray, 159

Wren, Christopher, 74

Zacharias, Daniel, 49

Zozimus the Panopolite, 4

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.

Page 16: “_jeunesse d’oreé_” was printed that way, but should be “_jeunesse dorée_”.

Page 183: “Moyenâge” was printed that way, but should be “Moyen Âge”.