A History of Hindu Chemistry from the Earliest Times to the Middle of the Sixteenth Century A.D. v1.c13.3

v1.c13.3

and Targioni, members of the Academia del Cimento, who, at the request of the Grand Duke Cosmo III., of Tuscany, placed a diamond in the focus of a large burning-glass and observed that it entirely disappeared. Francis I., who is said to have received from an alchemist an anonymous receipt for melting diamonds, exposed, in the year 1751, diamonds and rubies of the value of 6,000 gulden for twenty-four hours to the action of a powerful fire; the rubies were found unaltered, but the diamonds had altogether disappeared. The volatilization of the diamond by means of heat was from this time forwad made the subject of numerous experiments. Thus, Darcet observed in 1766 that diamonds disappear when they are heated in a cupel-furnace, even in closed crucibles, but, continuing his experiments at the request of the Paris Academy, he, together with Rouelle, found that when heated in perfectly hermetically-sealed vessels, the diamond did not disappear. Macquer, in the year 1771, was the first to observe that when the diamond undergoes volatilization it appears to be surrounded by a flame. In conjunction with Cadet and Lavoisier, he afterwards found that a true combustion takes place. In continuation of these experiments Lavoisier, together with Macquer, Cadet, Brisson, and Baumé,¹ placed a diamond in a glass vessel containing air collected over mercury, and on igniting the diamond by means of a burning-glass, they found that carbonic acid gas was produced."—Roscoe and schor. Vol 1. pp. 658-59.