magnificent blue was the final
result. But here also the dye was of a basic character, and being
insoluble in water had only a limited application, as a spirit bath had to
be used for dissolving the substance. In 1862, however, an English
technologist, the late E. C. Nicholson, found that by the action of strong
sulphuric acid the aniline blue could be rendered soluble in water or
alkali, and the value of the colouring-matter was enormously increased by
this discovery. The basic and slightly soluble spirit blue was by this
means converted into acid blues, which are now made in large quantities,
and sold under the names of Nicholson's blue, alkali blue, soluble blue,
and other trade designations. There is at the present time hardly any
other blue which for fastness, facility of dyeing, and beauty can compete
with this colouring-matter introduced by Nicholson as the outcome of the
work of Girard and De Laire.

Other transformations of rosaniline have yet to be chronicled. In 1862
Hofmann found that by acting upon this base--the base of magenta--with the
iodide of methyl, violet colouring-matters were produced, and these were
for some years extensively employed under the name of Hofmann's violets.
And still more remarkable, by the prolonged action of an excess of methyl
iodide upon rosaniline, Keisser found that a green colouring-matter was
formed. The latter was patented in 1866, and the dye was for some time in
use under the name of "iodine green." The statement that technology
profited by the introduction of magenta has therefore been justified.

It remains to add, that the tar obtained from one ton of Lancashire coal
furnishes an amount of aniline capable of giving a little over half a
pound of magenta. The colouring power of the latter will be inferred from
the fact, that this quantity would dye 375 square yards of white flannel
of a full red colour, and if converted into Hofmann violet by methylation,
would give enough colour to dye double this surface of flannel of a deep
violet shade. It should be stated also, that during the formation of
magenta by the arsenic acid process, there are formed small quantities of
other colouring-matters which are utilized by the manufacturer. Among
these by-products is a basic orange dye, which was isolated by Nicholson,
and investigated by Hofmann in 1862. Under the name of "phosphine" this
colouring-matter is still used, especially for the dyeing of leather. Even
the spent arsenic