From Alchemy to Chemistry:
Five Hundred Years of Rare and Interesting Books

University of Illinois at Urbana-Champaign
Rare Book Room Exhibit

STAHL, GEORG (1659 - 1734). Opusculum Chymico-Physico-Medicum. Nuremberg, 1715.

Stahl was the originator of the phlogiston theory, which dominated chemistry until the end of the eighteenth century. Stahl took the structure of his theory from the Austrian chemist Johann Becher. Stahl elaborated from Becher's "second earth" a new chemical principle, phlogiston, a substance representing the principle of combustibility that combined with other chemical substances to form compounds. Stahl's phlogiston, although introduced mainly to explain combustion, became the center of his whole system of chemistry. He taught that it is the cause of solidity and particularly of color. Phlogiston is a descendent of a very old idea of the dismembering escape of fire, whether fire itself or its equivalent in a sulfureous, oily, or combustible principle. It is also a descendent of the alchemical principle sulfur. Experimental evidence for the existence of phlogiston came largely from metals and minerals, particularly from the reversible relationship of metals and their calces: when a metal was heated intensely, its phlogiston was driven off and a calx appeared, but when phlogiston was reintroduced to the calx (by heating it with carbon, oil, pitch or other phlogiston-rich materials), the metal reappeared. Air did not combine with phlogiston but received it when it was liberated during combustion; air could absorb only a limited amount of phlogiston, and when that limit was reached, combustion could no longer take place. The flaws in the phlogiston theory are obvious, and it did not survive the eighteenth century; however, it served as an important link between the older chemical concepts and the new, an attempt to modify the existing intellectual framework in order to account for new experimental observations. Stahl was proud, morose, and atrabilious; he rarely answered letters; he showed contempt for all who differed from his views and reacted violently to criticism. These qualities, as T. Thomson said, greatly enhanced his reputation.

DSB; Norman Library of Science, 2005; Partington II, p654, 666-667.

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