ls, whereas there is only one phenol. The naphthols--known as
alpha- and beta-naphthol, respectively--are now made on a large scale from
naphthalene, by heating the latter with sulphuric acid; at a low
temperature the alpha sulpho-acid is produced, and at a higher temperature
the beta sulpho-acid, and these acids on fusion with caustic soda furnish
the corresponding naphthols. Similarly there are two amidonaphthalenes,
known as alpha- and beta-naphthylamine respectively. As aniline is to
benzene, so are the naphthylamines to naphthalene. The alpha-compound is
made in precisely the same way as aniline, viz. by acting upon naphthalene
with nitric acid so as to form nitronaphthalene, and then reducing the
latter with iron dust and acid. Beta-napthylamine cannot be made in this
way; it is prepared from beta-naphthol by heating the latter in presence
of ammonia, when the hydroxyl becomes replaced by the amido-group in
accordance with a process patented in 1880 by the Baden Aniline Company.
The principle thus utilized is the outcome of the scientific work of two
Austrian chemists, Merz and Weith. Setting out from the naphthols and
naphthylamines we shall be led into industrial developments of the
greatest importance.

The first naphthalene colour was a yellow dye, discovered by Martius in
1864, and manufactured under the name of "Manchester yellow." It is,
chemically speaking, dinitro-alpha-naphthol; but it was not at first made
from naphthol, as the latter was not at the time a technical product. It
was made from alpha-naphthylamine by the action of nitrous and nitric
acids. When a good method for making the naphthol was discovered in 1869,
the dye was made from this. The process is just the same as that employed
in making picric acid; the naphthol is converted into a sulpho-acid, and
this when acted upon by nitric acid, gives the colouring-matter.
Manchester yellow is now largely used for colouring soap, but as a
dye-stuff it has been improved upon in a manner that will be readily
understood. The original colouring-matter being somewhat fugitive, it was
found that its sulpho-acid was much faster. This sulpho-acid cannot be
made by the direct action of sulphuric acid upon the colouring-matter--as
in the case of acid yellow or acid magenta--but by acting upon the
naphthol with very strong sulphuric acid, three sulphuric acid residues or
sulpho-groups enter the molecule, and then on nitration only two of these
are replaced by n