a basic salt. Instead of ageing the cotton may be subjected to a
process of steaming with the same results. After this the cotton is
ready for dyeing, which is done by the method described in the last
section.

There is still another method to be noticed here, that is, one in which
a bath is prepared containing both the mordant and the dye-stuff. In
this case the character of the mordant must be such that, under the
conditions that prevail, it will not form a colour lake with the
dye-stuff. Such substances are the bisulphites, if used with the
bisulphite compounds of the dye-stuffs; the acetates, if mixed with some
acetic acid, may also be used. The process consists in preparing the
dye-bath containing both the mordant and the dye-stuff, entering the
cotton, steeping for some time, then wringing and steaming. During the
latter operation the acid combined with the mordant, being volatile,
passes away, and the colouring matter and mordant enter into combination
to form the colour lake, which is firmly fixed upon the fibre. Very good
results may be obtained by this method.

Lastly, in connection with the mordant colours, attention may be
directed to the process of using some of them, which consists in making
a solution of the dye-stuff in ammonia, impregnating the cotton with
this alkaline solution, and subjecting it to a steaming operation,
during which the alkali, being volatile, passes away, leaving the
colouring matter behind in an insoluble form. The cotton is next passed
into a weak bath of the mordant (preferably the acetates of iron,
etc.)., this being used first cold and then gradually heated up. The dye
on the fibre and the mordant combine to form the desired colour, which
is fixed on the fibre.

The chrome mordants are those which are most commonly applied by the
methods here sketched out, and with the large and increasing number of
mordant dyes available, the processes should be worth attention from the
cotton dyer.

The following recipes give fuller details than the outline sketches of
the methods given above for the use of the various dyes produced with
the mordant dyes and metallic mordants. In some cases as will be seen
other dyes may be added to produce special shades:--

_Dark Olive._--Prepare a bath from 8 lb. cutch, 4 lb. logwood extract, 7
lb. fustic extract, 2 lb. copper sulphate. Work in this for one to one
and a half hours at the boil. This bath may be kept standing, adding new
ingredients fr