, and the coal-tar industry
may thus be brought into relationship with another branch of applied
science. Aniline black is seldom used as a direct colouring-matter; it is
generally produced in the fibre by printing on the mixture of aniline salt
and oxidizing compounds thickened with starch, &c., and then allowing the
oxidation to take place spontaneously in a moist and slightly heated
atmosphere. By a similar process, using a dye-bath containing the aniline
salt and oxidizing mixture, cotton fibre is easily dyed. The black cannot
be used for silk or wool, as the oxidizing materials attack these fibres,
but for cotton dyeing and calico printing this colouring-matter has come
seriously into competition with the black dyes obtained from logwood and
madder. The use of aniline for this purpose, first rendered practicable by
Lightfoot, is among the most important of the many wonderful applications
of coal-tar products in the tinctorial industry.

The year 1863 witnessed the introduction of the first of a new series of
colouring-matters which have had an enormous influence both on the art of
the dyer as well as in the utilization of tar-products which were formerly
of but little value. We can consider the history of some of these colours
now, because the earliest of them was produced from aniline. The formation
of a yellow compound when nitrous acid acts upon aniline was observed by
several chemists prior to the date mentioned. In 1863 the firm of Simpson,
Maule and Nicholson manufactured a yellow dye by passing nitrous gas into
a solution of aniline in alcohol, and this had a limited application under
the name of "aniline yellow." Soon afterwards, viz. in 1866, the firm of
Roberts, Dale & Co. of Manchester introduced a brown dye under the name of
"Manchester brown"--this compound, which was discovered by Dr. Martius in
1865, having been produced by the action of nitrous acid on one of the
diamidobenzenes. Ten years later Caro and Witt discovered an orange
colouring-matter belonging to the same class, and the latter introduced
the compound into commerce as "chrysoidine." These three compounds are
basic, and the first of them is no longer used as a direct dye because it
is fugitive. Chrysoidine is still used to a large extent, and the
brown--now known as "Bismarck brown"--is one of the staple products of the
colour manufacturer at the present time. From this fragment of
technological history let us now turn to chemical science.