d browns, Amidazol blacks,
browns and olives, Sulfaniline black and brown, Katigen blacks, greens
and browns, etc., have been added, and the group is likely to become a
very numerous one in the future.

All these colours are dyed on to the cotton or linen from baths
containing soda and salt, while some require the addition of sodium
sulphide or caustic soda in order to have the dye-stuff properly
dissolved. They are very weak dyes compared with the direct colours, and
require from 20 to 60 per cent. to produce full shades, although of this
fully one-third remains in the bath unabsorbed by the cotton. It is,
therefore, important in order to work as economically as possible to
retain the bath, bringing it up to strength by the addition of fresh
dye-stuffs, etc.

Most of the dyes require the dyed goods to pass through a second bath of
some reagent, bichromate of potash, sulphate of copper, etc., in order
to fully develop and fix the dye on the fabric.

The best method of using the various dyes of this group will be given in
the form of formulae. Two points of importance are to use as strong a dye
liquor as possible, and to expose the cotton as little as possible to
the air during the dyeing operation. The dye-stuffs when exposed to the
air readily become oxidised, and are thereby converted into insoluble
products which become fixed on the fibre in a loose form, and in that
case the dyed fibre rubs rather badly.

_Pale Brown._--Prepare a dye-bath with 15 lb. Cachou de laval, 10 lb. of
soda, and 10 lb. salt. The bath is not exhausted of colouring matter,
and by adding one-half of the above quantities of dye-stuff and salt may
be used again for another lot of cotton. After the dyeing the cotton is
passed into a fixing bath of 2 lb. bichromate of potash and 1 lb. acetic
acid, working at 180 deg. F. ten to fifteen minutes.

_Black._--Prepare the dye-bath with 200 gallons of water, 10 lb. soda,
10 lb. sulphide of sodium, 60 lb. salt and 16 lb. Immedial black V
extra. Work at the boil for one hour, keeping the cotton well under the
surface during the operation, in the case of yarns this is effected by
using bent iron rods on which to hang the hanks in the vat, in the case
of pieces by working with vats the guide rollers of which are below the
surface of the dye liquor. After the dyeing the yarn or pieces are
squeezed, well rinsed in water, then passed into the fixing bath, which
contains 2 lb. sulphate of copper, 2 lb. bichr