uring-matter. In fact, the aniline oil used
by the manufacturer had from the beginning consisted of a mixture of
aniline and toluidine, and at the present time "aniline for red" is made
by nitrating a mixture of benzene and toluene and reducing the
nitro-compounds.

From this work of Hofmann's suggestions naturally arose concerning the
"constitution" of rosaniline, and new and fruitful lines of work were
opened up. Large numbers of chemists of the greatest eminence pursued the
inquiry, but the details of their work, although of absorbing interest to
the chemist, cannot be discussed in the present volume. The final touch to
a long series of investigations was given by two German chemists, Emil and
Otto Fischer, who in 1878 proved the constitution of rosaniline by
obtaining from it a hydrocarbon, the parent hydrocarbon from which the
colouring-matter is derived. The purely scientific discovery of the
Fischers threw a flood of light on the chemistry of magenta, and enabled a
large number of colouring-matters related to the latter to be classed
under one group, having the parent hydrocarbon as a central type. This
hydrocarbon, it may be remarked, is known as triphenylmethane, as it is a
derivative of methane, or marsh gas. The blues and violets obtained from
rosaniline belong to this group, and so also do certain other
colouring-matters which had been manufactured before the Fischers'
discovery. In order to carry on the story of the utilisation of aniline,
it is necessary to know something about these other colouring-matters
which are obtained from it.

It has been explained that by the methylation of rosaniline Hofmann
obtained violet colouring-matters. Now as rosaniline is obtained by the
oxidation of a mixture of aniline and toluidine, it seems but natural that
if these bases were methylated first and then oxidized a violet dye would
be produced. The French chemist Lauth first obtained a violet
colouring-matter by this method in 1861. In 1866 this violet dye was
manufactured in France by Poirrier, and it is still made in large
quantities, being known under the name of "methyl violet." This
colouring-matter, and a bluer derivative of it discovered in 1868,
gradually displaced the Hofmann violets, chiefly owing to their greater
cheapness of production. We are thus introduced to methylated aniline as a
source of colouring-matters, and as the compound in question has many
different uses in the coal-tar industry, a few words