Boerhaave was of a robust frame and healthy constitution, early inured to constant exercise and the inclemencies of weather. His stature was rather tall, and his habit corpulent. He had a large head, short neck, florid complexion, light brown curled hair (for he did not wear a wig), an open countenance, and resembled Socrates in the flatness of his nose and his natural urbanity. He died at Leyden on September 23rd, 1738, in the seventieth year of his age.
As a chemist Boerhaave is chiefly known by his Elementa Chemia, published in 1732—the most complete and most luminous chemical treatise of its time, translations of which appeared in the chief European languages. The work is divided into three main parts. The first is concerned with the origin and progress of the art, and with the personal history of its most distinguished cultivators. The second and largest part deals with the attempt to form a system of chemistry based on such observational matter as seemed well established. The third consists of a collection of chemical processes relating to the analysis or decomposition of bodies, grouped under the heads of “vegetables,” “animals,” and “fossils”—the beginnings, in fact, of subdivision of the science into organic and inorganic chemistry.
As regards his belief in alchemy, Boerhaave was an agnostic: he neither affirmed nor denied the possibility of transmutation. In this respect he resembled Newton and Boyle. Boyle, indeed, was singularly cautious and reticent in his references to alchemistic matters. As was said of him by Shaw, he was too wise to set any bounds to nature: he was not prone to say that every strange thing must needs be impossible, for he saw strange things every day, and was well aware that there are powerful forces in the world of whose laws and modes of action he knew nothing. With that wariness which was habitual to him, he was wont to say that “those who had seen them might better believe them than those who had not”; and he was modest enough to suppose that Paracelsus or Helmont might conceivably know of agents of which he was ignorant.
Boerhaave unquestionably spent much time in the study of alchemical works, particularly those of Paracelsus and Helmont, which he repeatedly read. The Philosophical Transactions of the Royal Society contain the results of a laborious but fruitless investigation by him on quicksilver, which he undertook in the hope of discovering the seminal or engendering matter which, on the old theory of the generation of metals, was supposed to be contained in mercury. But although, as he relates, he tortured it by “conquassation, trituration, digestion, and by distillation, either alone or amalgamated with lead, tin, or gold, repeating this operation to 511 or even to 877 distillations,” the mercury appeared only “rather more bright and liquid, without any other variation in its form or virtues, and acquired very little, if any, increase of its specific gravity.”
Stephen Hales (1677–1761), an ingenious divine—he held the perpetual curacy of Teddington, and lived practically the greater part of his life there—distinguished as a physiologist and inventor, occupied himself in chemical pursuits, and made a number of observations on the production of gaseous substances. His results were communicated to the Royal Society and subsequently republished, in a collected form, under the title of Statical Essays. In these experiments he used methods very similar in principle to those subsequently employed by Priestley. It is evident from his description of his experiments that he must have prepared a considerable number of gaseous substances—hydrogen, carbonic acid, carbonic oxide, sulphur dioxide, marsh gas, etc.—but he seems to have made no systematic attempt to study their properties, as he considered that they were simply air, modified or “tinctured” by the presence of substances which he regarded as more or less fortuitous. Prior to the time of Black all forms of gaseous substance were regarded as substantially identical—in fact, as being air, as understood by the Ancients—a simple elementary substance. It was Black’s study of carbonic acid which first clearly established that there were essentially distinct varieties of gaseous matter.
CHAPTER VII
Phlogistonism
Even before the appearance of The Sceptical Chemist there was a growing conviction that the old hypotheses as to the essential nature of matter were inadequate and misleading. We have seen how the four “elements” of the Peripatetics had become merged into the tria prima—the “salt,” “sulphur,” and “mercury”—of the Paracelsians. As the phenomena of chemical action became better known, the latter iatro-chemists—or, rather, that section of them which recognised that chemistry had wider aims than to minister merely to medicine—felt that the conception of the tria prima, as understood by Paracelsus and his followers, was incapable of being generalised into a theory of chemistry. Becher, while clinging to the conception of three primordial substances as making up all forms of matter, changed the qualities hitherto associated with them. According to the new theory, all matter was composed of a mercurial, a vitreous, and a combustible substance or principle, in varying proportions, depending upon the nature of the particular form of matter. When a body was burnt or a metal calcined, the combustible substance—the terra pinguis of Becher—escaped.
This attempt to connect the phenomena of combustion and calcination with the general phenomena of chemistry was still further developed by Stahl, and was eventually extended into a comprehensive theory of chemistry, which was fairly satisfactory so long as no effort was made to test its sufficiency by an appeal to the balance.
George Ernest Stahl, who developed Becher’s notion into the theory of phlogiston (φλογιοτός—burnt), and thereby created a generalisation which first made chemistry a science, was born at Anspach in 1660, became Professor of Medicine and Chemistry at Halle in 1693, physician to the King of Prussia in 1716, and died in Berlin in 1734.