As a discoverer, Berzelius first made known the existence of cerium (1803), of selenium (1818), and of thorium (1828); and he prepared and investigated a large number of their combinations. He isolated silicon (1823), zirconium (1824), tantalum (1824), and studied the compounds of vanadium, discovered by his countryman Sefström. He largely extended our knowledge of groups of substances in which sulphur replaces oxygen; investigated compounds of fluorine (1824), platinum (1828), and tellurium (1831–1833), and made many analyses of minerals, meteorites, and mineral-waters. He discovered racemic acid and investigated the ferrocyanides. It was his investigation of racemic acid—which has the same percentage composition as tartaric acid—that first enabled him to grasp the conception of isomerism, a term which we owe to him, and of metamerism and polymerism. He was the first to study the phenomena of contact-actions, which he comprehended under the term catalysis.
Jöns Jakob Berzelius.
From a painting by J. G. Sandberg.
As an author his literary activity was astonishing. His new system of mineralogy marks an epoch in the history of that branch of science. His text-book on chemistry was long the leading manual, and went through many editions, being constantly revised by him. His annual reports on the progress of physics and chemistry extended to twenty-seven volumes and constitute a monument to his industry, thoroughness, perspicacity, and critical ability.
Although holding no university appointment, and with a laboratory of the most modest dimensions and character, Berzelius, exercised great influence as a teacher. Some of the most notable chemists of the last century, such as Heinrich and Gustav Rose, Dulong, Mitscherlich, Wöhler, Chr. Gmelin, and Mosander, were among his pupils; and many of them have testified to his stimulating power as an investigator of nature, and to his merits as a worthy, genial man.
The reasonableness of Dalton’s conjecture received further support from the discovery by Gay Lussac in 1808, that gases always combine in simple proportions by volume, and that the volume of the gaseous product formed, when measured under comparable conditions of temperature and pressure, stands in a simple relation to the volumes of the constituents. The law of pressure discovered by Boyle, that of thermal expansion by Dalton, and of volumes by Gay Lussac (which, it ought to be stated, was previously and independently made by Dalton), are explained on the assumption that equal numbers of the particles—either as simple particles or as compound particles—are present in the same volume of the gas. This method of explanation was first clearly stated by the Italian physicist Avogadro in 1811, but its significance, as will be seen subsequently, was not appreciated until half a century later.
As the values for the atomic weights gradually became more exact, speculations arose as to the significance of the numerical relations which were observed to exist among them. In 1815 William Prout threw out the supposition that the atomic weights of the gaseous elements are multiples by whole numbers of that of hydrogen. Extended into a generalisation, this might be held to indicate that all kinds of matter are so many forms of a primordial substance. Subsequent inquiry showed that Prout’s “Law,” as it is sometimes called, was not tenable in its original form. Certain elements, it was conclusively proved, had atomic weights which were not whole numbers. Dumas subsequently modified the law, after a redetermination of a large number of atomic weights, by assuming that the substance common to the so-called elements had a lower atomic weight than unity. Although there are a considerable number of elements whose atomic weights, based upon the most accurate determinations, are remarkably close to whole numbers, the investigations of Stas and others afford no valid reason for believing that Prout’s hypothesis, and the underlying supposition to which it has been held to point, are justified by experimental evidence.
CHAPTER X
The Beginnings of Electro-Chemistry
The first year of the nineteenth century is further memorable on account of the invention of the voltaic pile, and by reason of its application by William Nicholson and Sir Anthony Carlisle to the electrolytic decomposition of water. This mode of resolving water into its constituents made a great sensation at the time, mainly because of the extraordinary method by which it was effected. It afforded an independent and unlooked-for proof of the compound nature of water by a method altogether differing in principle from that by which its composition had been previously ascertained. The formation of water by the combustion of hydrogen brought no conviction of its real nature to a confirmed phlogistian like Priestley; and it is even doubtful whether Cavendish ever fully realised the true significance of his great discovery. But the fact that the quantitative results of the analysis thus effected were identical with those of its synthesis, as made by Cavendish and Lavoisier, admitted of only one interpretation. This cardinal discovery may be said to have completed the downfall of phlogiston.