The
diamond is not acted upon by any acid, but is a combustible body,
becoming entirely consumed when exposed to a very strong degree of heat
(140 Wedgwood). Although Newton early surmised the fact of
its combustibility, the first record of its having really been burnt
was in 1694, at the Academy of Florence, under the dukedom of Cosmo
III., by means of powerful burning-glasses, when it first' split, then
emitted sparks, and at last disappeared, leaving no trace behind. The
Emperor Francis I. exposed diamonds and rubies together in an assayer's
furnace for twenty-four hours, when the diamonds had disappeared, and
the rubies remained in their normal state. Some French chemists also
burnt a fine diamond in the year 1771; but the point was still mooted
among the learned, whether diamonds were burnt, became vaporized, or
split into impalpable powder. A French jeweller named Mail-lard,
however, declared that he had frequently exposed diamonds to heat as
intense as that which had consumed the others without injury, and
offered to submit some to the test. He imbedded them in charcoal dust,
and sealed them hermetically in a clay pipe bowl, when, after leaving
them in the furnace for the same time, brought them forth uninjured;
thus solving the problem, and clearly proving that the diamond, like
other combustible bodies, only really burns when in connection with
the oxygen of the air. Lavoisier burnt a diamond in oxygen, and
obtained the same result as arises from the combustion of pure
carbon—carbonic
e 2
