Martin Heinrich Klaproth, born in 1743 at Wernigerode, in the Hartz, began life, like Vauquelin, as an apothecary’s apprentice at Quedlinburg. Thence he went to Hanover, and ultimately to Berlin, where he studied under Pott and Marggraf and entered the pharmacy of Valentine Rose, father of Heinrich Rose, the distinguished chemist, and Gustav Rose, the mineralogist. In 1788 he became a member of the Berlin Academy, and, on the creation of the Berlin University in 1809, was made Professor of Chemistry. As already stated, he was the first chemist of eminence in Germany to adopt the antiphlogistic theory. He was distinguished as an analyst. He discovered tellurium, analysed pitchblende and uranit, and first made known the existence of uranium, zirconium, and cerium, which he termed “ochroita.” He analysed corundum, and was an independent discoverer of titanium and glucinum, termed by him beryllium. He made a large number of analyses of minerals, such as leucite, chrysoberyl, hyacinth, granite, olivin, wolfram, malachite, pyromorphite, etc. He continued actively at work until his death, in the seventy-fourth year of his age.
Analytical chemistry is under great obligations to Klaproth. He established a standard of accuracy never before approached; and much of his analytical work, both as regards processes and results, is of permanent value.
Joseph Louis Proust, the son of a pharmacist was born at Angers in 1761. He received his early training in chemistry from his father, and, after studying under Rouelle in Paris, obtained an appointment at the Salpetrière. Proust has the credit of being the first chemist to make a balloon ascent—in a Montgolfier balloon with Pilatre de Rozier. On the invitation of the King of Spain, he went to that country to superintend certain chemical manufacturing processes. He became Professor of Chemistry at the University of Salamanca, and subsequently went to Madrid, where he was installed in a well-equipped laboratory to enable him to examine the mineral riches of Spain. On the breaking out of war his work was interrupted, and he was obliged to leave Madrid. His laboratory was completely destroyed, and his valuable collection of apparatus and specimens dissipated. Through the good offices of Berthollet, Proust was offered a considerable sum of money by Napoleon in order to induce him to turn his discovery of grape sugar to practical account. Proust was, however, too broken in health to undertake the work of a factory manager, and he retired to Mayence. On the restoration of the Monarchy he was made a member of the French Academy, his honorarium as an Academician being augmented by a pension from Louis XVIII. He died in 1826, while on a visit to Angers, his native place.
Proust is the discoverer of what is now styled “the law of constant proportion,” which states that the same body is invariably composed of the same elements, united in the same proportion. He was a skilful analyst, and made numerous analyses of minerals; and he was one of the earliest to undertake a systematic study of metallic salts of organic acids.
CHAPTER IX
The Atomic Theory
The opening years of the nineteenth century were made memorable by the promulgation of the atomic theory by John Dalton. The enunciation of this theory, which affords a simple and adequate explanation of the fundamental laws of chemical combination, marks an epoch in the history of chemistry.
It may be desirable to trace, as briefly as possible, the successive steps which led up to the generalisation which more than any other has served to stamp chemistry as an exact science. That matter was discrete—that is, that it was not continuous, but was composed of ultimate particles—was, as already stated, imagined by the ancients, and was part of the philosophy of Leukippus, Demokritus, and Leucretius. But this supposition, although favoured by Newton and other thinkers, had little or no scientific basis prior to the middle of the eighteenth century. From that time onward a variety of chemical facts gradually accumulated, many of which at the time of their discovery had no obvious connection with pre-existing facts. It was reserved for Dalton to point out how an extension and more precise definition of the old doctrine would suffice to connect and explain them.
The first germ of an atomic theory based on chemical fact may be traced in the observation of Toburn Bergmann (b. 1735, d. 1784), Professor of Chemistry at Upsala, that neutral solutions of certain metals in contact with other metals gave a precipitate without the neutrality of the solution being disturbed, and without gas being evolved. One metal had simply replaced the other in solution. Bergmann thus incidentally discovered the fact of the chemical equivalence of metals. He was of opinion, however, that the phenomenon meant a transference of phlogiston from one metal to another, and that the process might be made a mode of determining the relative amount of phlogiston in various metals. Lavoisier extended Bergmann’s observations, and sought to show, in effect, that the process afforded a means of determining the amounts of the several metals which combined with one and the same quantity of oxygen. But neither Bergmann nor Lavoisier really grasped the idea of equivalence as we understand it to-day. It began to be appreciated as the result of the work of Jeremiah Benjamin Richter (b. 1762, d. 1807) and of G. E. Fischer on the mutual action of salts in solutions, and on the determinations of the amounts of acid and bases which respectively combine with one another. Methods of measurement of the proportions in which substances combine were grouped by Richter under the term Stochiometry.
However desirable it may be in the interests of history to indicate the sequence of the surmises and facts which preceded the formulation of the atomic theory, it is very doubtful whether Dalton was, to any material extent, influenced by them. A self-educated man of lowly origin, sturdily independent and highly original, he was accustomed to rely upon his own faculty of observation and experiment for his facts, and upon his own intellectual powers and mental energy for their interpretation.