--was introduced as a substitute for bitter almond oil
under the name of "essence of mirbane." Nitrobenzene has an odour
resembling that of bitter almond oil, and it is still used for certain
purposes where the latter can be replaced by its cheaper substitute, such
as for the scenting of soap. Although the isolation of benzene from
coal-tar gave an impetus to the manufacture of nitrobenzene, no use
existed for the latter beyond its very limited application as "essence of
mirbane," and the production of this compound was at that time too
insignificant to take rank as an important branch of chemical industry.

The year 1856 marks an epoch in the history of the utilization of coal-tar
products with which the name of Perkin will ever be associated. In the
course of some experiments, having for their object the artificial
production of quinine, this investigator was led to try the action of
oxidizing agents upon a base known as aniline, and he thus obtained a
violet colouring matter--the first dye from coal-tar--which was
manufactured under a patent granted in 1858, and introduced into commerce
under the name of mauve. A brief sketch of the history of aniline will
serve to show how Perkin's discovery gave a new value to the light oils
from coal-tar and raised the manufacture of nitrobenzene into an important
branch of industry.

Thirty years before Perkin's experiments the Dutch chemist Unverdorben
obtained (1826) a liquid base by the distillation of indigo, which had the
property of forming beautifully crystalline salts, and which he named for
this reason "crystallin." In 1834 Runge discovered the same base in
coal-tar, although its identity was not known to him at the time, and
because it gave a bluish colour when acted upon by bleaching-powder, he
called it "kyanol." Again in 1840, by distilling a product obtained by the
action of caustic alkalies upon indigo, Fritzsche prepared the same base,
and gave it the name of aniline, from the Spanish designation of the
indigo plant, "anil," derived from the native Indian word, by which
name the base is known at the present time. That aniline could be obtained
by the reduction of nitrobenzene was shown by Zinin in 1842, who used
sulphide of ammonium for reducing the nitrobenzene, and named the
resulting base "benzidam." The following year Hofmann showed that
crystallin, kyanol, aniline, and benzidam were all one and the same base.
Thus when the discovery of mauve opened up a deman