I. INORGANIC AND PHYSICAL CHEMISTRY.
H Davy Pres RS.
The three propositions established by Lavoisier, which serve as the foundation for inorganic and physical chemistry, are the following:—
1. Bodies burn only in contact with pure air.
2. The air is consumed in the combustion, and the increase in weight of the burnt body is equal to the decrease in weight of the air.
3. In combustion the body is generally changed, by its combination with the pure air, into an acid, and metals are changed into metal calx.
The total number of elementary bodies known at the beginning of the century was probably less than thirty. Many had been recognized as such since remote antiquity, but none of the non-metallic elements, except oxygen and sulphur, was known, and even their properties were not established with any degree of precision.
Not only did Lavoisier establish the fundamental principles of modern chemistry, but in connection with Fourcroy (1755–1809), Berthollet (1748–1822), and Guyton de Morveau (1737–1816), laid the foundation of modern chemical nomenclature.
The contributions to chemical knowledge at this time were greatly increased by the works of the Swedish chemist, Scheele (1742–1786), and in the beginning years of the century the great work which was accomplished by Sir Humphry Davy advanced very rapidly the general knowledge of chemical science.
Davy’s first works served to elucidate the connection between electricity and chemical processes, and it was through the classical experiment with an electric current that he isolated (1807) the metals sodium and potassium, and described their properties.
This achievement of Sir Humphry Davy’s was the second great step in the progress of chemistry, after the one taken by Lavoisier. By means of the metals sodium and potassium other metallic elements were separated, notably aluminium by Wöhler (1845). Basing his work upon the above experiment, Sainte Claire Deville developed the metallurgy of aluminium (1854), and Bussy isolated magnesium (1830).
In 1811 iodine was discovered by Courtois, and its properties examined simultaneously (1814) by Davy and Gay-Lussac.
The contributions made by Berzelius (1779–1848), who was a contemporary of Davy and Gay-Lussac (1778–1850), were of the most important character. Berzelius not only added to the knowledge of inorganic chemistry but also established many of the important theories on which chemical action depends. His elaboration of the employment of the blowpipe in chemical analysis was of the greatest practical value.
In 1807 Dalton published a work entitled “New System of Chemical Philosophy,” in which was announced for the first time the law of the definite proportions of bodies forming a definite union. The atomic theory of matter was also developed by Dalton, who gave it a definite form and expression. Chemists now began to consider the elements as definite indestructible particles of matter, forming unions among themselves and with different kinds of atoms to form molecules, which were considered as the units of substances. As a result of this supposition, the development of the principle of the relative weight with which bodies combine was the logical consequence.
Now for the first time the elements began to assume not only names and descriptions of properties but also numbers, showing the relative weight of their atoms or final conditions of existence. It was only necessary, therefore, to assume the standard of comparison for any one element, in order to determine the relative weights with which it combined with others. Thus the system of atomic weights was developed.
As a result of the law of chemical action, that most elementary bodies exist in a condition where two atoms are joined together to form a molecule, it follows, that in most instances the molecular weights of the elements are double their atomic weight. There are, however, many notable exceptions to this rule.
The supposition of the existence of atoms was followed soon by another theoretical proposition, advanced by Prout (1815). Assuming that the atomic weight of hydrogen was one, Prout’s hypothesis asserted that the atomic weights of all other elementary bodies were multiples of that of hydrogen. The most rigid investigations of recent years have shown that Prout’s hypothesis is untenable; but the remarkable fact still remains, that in a great many cases the atomic weights of the elements are almost whole numbers, or differ from whole numbers by almost a half unit.
The determination of the atomic weights of the various elements during the past one hundred years has been worked on by hundreds of chemists whose names it would be impracticable to mention. The most important of them are Berzelius, Cooke, Cleve, Delafontaine, Dumas, Hermann, Marchand, Marignac (1817), Morley, Noyes, Pelouse (1807–1867), Richards, Schneider, Stas (1813–1891), and Thompson. Of all these workers Stas, a Belgian chemist, is perhaps the most renowned. Among those mentioned, Cooke, Morley, Noyes, Delafontaine, and Richards are citizens of the United States.
From the less than thirty elements which were known at the beginning of the century, there are known to-day seventy-two with certainty, and perhaps one or two more whose identity has not yet been fully established. The chemists who have become most renowned by the discovery of elementary bodies are: Cavendish, Scheele, Berzelius, Wöhler (1800–1882), Davy, Gay-Lussac, Priestly, Bunsen (b. 1811), Crookes (b. 1832), and Ramsay.
The following elements, twenty-eight in number, were known before 1800:
| ELEMENTS KNOWN BEFORE 1800. | |
|---|---|
| 1. Copper | Known to Ancients. |
| 2. Gold | ” ” ” |
| 3. Iron | ” ” ” |
| 4. Lead | ” ” ” |
| 5. Silver | ” ” ” |
| 6. Tin | ” ” ” |
| 7. Carbon | ” ” ” |
| (But three forms not identified until 1786–1800.) | |
| 8. Mercury | Known to Ancients. |
| 9. Antimony | Fifteenth Century. |
| 10. Bismuth | ” ” |
| 11. Zinc | ” ” |
| 12. Phosphorus | 1669 |
| 13. Arsenic (Isolated) | 1697 |
| ” (Studied) | 1733 |
| 14. Cobalt | 1733 |
| 15. Platinum | 1735–1748 |
| 16. Nickel | 1751 |
| 17. Hydrogen | 1766 |
| 18. Nitrogen | 1772 |
| 19. Oxygen | 1774 |
| 20. Manganese (Studied in compounds, isolated at unknown date) | 1774 |
| 21. Barium | 1774 |
| 22. Tungsten | 1781–1785 |
| 23. Molybdenum | 1782 |
| 24. Tellurium | 1782–1798 |
| 25. Strontium | 1790 |
| 26. Yttrium | 1794 |
| 27. Chromium | 1797 |
| 28. Beryllium | 1798 |
Four additional elements were known to exist before that date, but they had not been isolated and identified. These are:—
| ELEMENTS KNOWN BUT NOT ISOLATED OR EXAMINED BEFORE 1800. | ||
|---|---|---|
| Chlorine | {Compound known | 1774 |
| {Isolated and studied | 1810 | |
| Titanium | {Known in compounds | 1791 |
| {Isolated | 1824 | |
| Uranium | {Known in compounds | 1789 |
| {Isolated | 1824 | |
| Zirconium | {Known in compounds | 1789 |
| {Isolated | 1824 | |
The following elements, forty-nine in number, have been discovered since 1800:—
The date in each case is that of the discovery. Numbers 49, 50, and 51 are not yet sufficiently well known to justify being considered elements, and are therefore properly followed by an interrogation point.