regardless
of expense, which, thanks to his inheritance, he could ignore. In this
process he found that a gas was given off which precipitated lime from
water, and proved to be carbonic acid. Observing this, and experimenting
with other substances known to give off carbonic acid in the same
manner, he was evidently impressed with the now well-known fact that
diamond and charcoal are chemically the same. But if he did really
believe it, he was cautious in expressing his belief fully. "We should
never have expected," he says, "to find any relation between charcoal
and diamond, and it would be unreasonable to push this analogy too far;
it only exists because both substances seem to be properly ranged in the
class of combustible bodies, and because they are of all these bodies
the most fixed when kept from contact with air."

As we have seen, Priestley, in 1774, had discovered oxygen, or
"dephlogisticated air." Four years later Lavoisier first advanced his
theory that this element discovered by Priestley was the universal
acidifying or oxygenating principle, which, when combined with charcoal
or carbon, formed carbonic acid; when combined with sulphur, formed
sulphuric (or vitriolic) acid; with nitrogen, formed nitric acid,
etc., and when combined with the metals formed oxides, or calcides.
Furthermore, he postulated the theory that combustion was not due to any
such illusive thing as "phlogiston," since this did not exist, and it
seemed to him that the phenomena of combustion heretofore attributed to
phlogiston could be explained by the action of the new element oxygen
and heat. This was the final blow to the phlogiston theory, which,
although it had been tottering for some time, had not been completely
overthrown.

In 1787 Lavoisier, in conjunction with Guyon de Morveau, Berthollet,
and Fourcroy, introduced the reform in chemical nomenclature which until
then had remained practically unchanged since alchemical days. Such
expressions as "dephlogisticated" and "phlogisticated" would obviously
have little meaning to a generation who were no longer to believe in
the existence of phlogiston. It was appropriate that a revolution in
chemical thought should be accompanied by a corresponding revolution in
chemical names, and to Lavoisier belongs chiefly the credit of bringing
about this revolution. In his Elements of Chemistry he made use of this
new nomenclature, and it seemed so clearly an improvement over the
old that the sci