ic and amidic derivatives of naphthalene,
_i.e._ the naphthols and naphthylamines, are of the greatest importance to
the colour industry. One of the first uses of alpha-naphthylamine has
already been mentioned, viz. for the production of the Manchester yellow,
which was afterwards made more advantageously from alpha-naphthol. A red
colouring-matter possessing a beautiful fluorescence was afterwards (1869)
made from this naphthylamine and introduced as "Magdala red." The latter
was discovered by Schiendl of Vienna in 1867. It was prepared in precisely
the same way as induline was prepared from aniline yellow. The latter,
which is amido-azobenzene, and which is prepared, broadly speaking, by the
action of nitrous acid on aniline, has its analogue in
amido-azonaphthalene, which is similarly prepared by the action of nitrous
acid on naphthylamine. Just as aniline yellow when heated with aniline and
an aniline salt gives induline, so amido-azonaphthalene when heated with
naphthylamine and a salt of this base gives Magdala red. The latter is,
therefore, a naphthalene analogue of induline, as was shown by Hofmann in
1869, and the knowledge of the constitution of the azines which has been
gained of late years, enables us to relegate the colouring-matter to this
group. This knowledge has also enabled the manufacture to be conducted on
more rational principles, viz. by the method employed for the production
of the saffranines, as previously sketched.

The introduction of azo-dyes, formed by the action of a diazotised
amido-compound on a phenol or another amido-compound, marks the period
from which the naphthols and naphthylamines rose to the first rank of
importance as raw materials for the colour manufacturer. The introduction
of chrysoidine in 1876 was immediately followed by the manufacture of acid
azo-dyes obtained by combining diazotised amido-sulpho-acids with phenols
of various kinds, or with bases, such as dimethylaniline and
diphenylamine. From what has been said in the foregoing portion of this
volume, it is evident that all such azo-compounds result from the
combination of two things, viz. (1) a diazotised amido-compound, and (2) a
phenolic or amidic compound. Either (1) or (2) or both may be a
sulpho-acid, and the resulting dye will then also be a sulpho-acid.

The first of these colouring-matters derived from the naphthols, was
introduced in 1876-77 by Roussin and Poirrier, and by O. N. Witt. They
were prepared by co