Darcet, Jean

In the midst of the excitement, Leblanc told his former chemistry professor, Jean Darcet, the fabulous secret of his discovery. After running some tests and confirming Leblanc s discovery, Darcet recommended it to their patron, the Duke of Orleans. So far the process had worked only in laboratory crucibles, but Darcet declared optimistically, I the undersigned, professor of chemistry at the Royal College of France and at the Royal Academy of Sciences, etc., certify that. . . with this same process, it will be easy to establish a factory. As is often the case, reality proved to be a trifle more complicated. 

P.-J. Macquer has left us, in his Dictionary of Chemistry, a fine first-hand account of the scientific history of this gem (255). On July 26, 1771, Macquer and Godefroy de Villetaneuse, in presence of Jean Darcet (1725-1801), Hilaire-Marin Rouelle (Rouelle the Younger), and others, heated a flawless diamond in a refractory capsule in Macquer s wind furnace. When it reached the temperature of melting copper, a flame could be seen surrounding it, and in less than an hour the gem disappeared without leaving a trace (257, 258, 259). 

At about the same time, Lavoisier was preoccupied with the disappearance of diamonds, which had caused a sensation since Jean Darcet s (1725-1801) report to the Academy in May of 1768. Public demonstrations continued intermittently until April of 1772. Early in 1772, to settle the dispute among several contending interpretations for this phenomenon, the Academy set up a committee consisting of Macquer, Cadet, and Lavoisier. They examined three hypotheses—volatilization, combustion, and decrepitation—respectively favored by Darcet, Macquer, and Cadet. The answer hinged on the experimental control of air in the process. Volatilization or vaporization did not require the presence of air combustion and decrepitation would require the chemical or the mechanical role of air in the process, respectively. Darcet had... 

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