nd, will
yield tar, but tar of another kind, from which colour-generating
substances cannot be obtained practically, but instead, paraffin oil and
paraffin wax for making candles, etc. Coal-tar contains a very large
number of different substances, but only a few of them can be extracted
profitably for colour-making. All the useful sources of colours and dyes
from coal-tar are simply compounds of carbon and hydrogen--hydrocarbons,
as they are called, with the exception of one, namely, phenol, or
carbolic acid. I am not speaking here of those coal-tar constituents
useful for making dyes, but of those actually extracted from coal-tar
for that purpose, _i.e._ extracted to profit. For example, aniline is
contained in coal-tar, but if we depended on the aniline contained ready
made in coal-tar for our aniline dyes, the prices of these dyes would
place them beyond our reach, would place them amongst diamonds and
precious stones in rarity and cost, so difficult is it to extract the
small quantity of aniline from coal-tar. The valuable constituents
actually extracted are then these: benzene, toluene, xylene,
naphthalene, anthracene, and phenol or carbolic acid. One ton of
Lancashire coal, when distilled in gas retorts, yields about 12 gallons
of coal-tar. Let us now learn what those 12 gallons of tar will give us
in the shape of hydrocarbons and carbolic acid, mentioned as extracted
profitably from tar. This is shown very clearly in the following table
(Table A).

The 12 gallons of tar yield 1-1/10 lb. of benzene, 9/10 lb. of toluene,
1-1/2 lb. of carbolic acid, between 1/10 and 2/10 lb. of xylene, 6-1/2
lb. of naphthalene, and 1/2 lb. of anthracene, whilst the quantity of
pitch left behind is 69-1/2 lb. But our table shows us more; it
indicates to us what the steps are from each raw material to each
colouring matter, as well as showing us each colouring matter. We see
here that our benzene yields us an equal weight of aniline, and the
toluene (9/10 lb.) about 3/4 lb. of toluidine, the mixture giving, on
oxidation, between 1/2 and 3/4 lb of Magenta. From carbolic acid are
obtained both Aurin and picric acid, and here is the actual quantity of
Aurin obtainable (1-1/4 lb.). From naphthalene, either naphthylamine (a
body like aniline) or naphthol (resembling phenol) may be prepared. The
amounts obtainable you see in the table. There are two varieties of
naphthol, called alpha- and beta-naphthol, but only one phenol, namely,
carbol