dye-stuff
used, but also upon other factors, that a certain assistant be used.
Some dyes work on the cotton better from a bath containing Glauber's
salt, while with others common salt works best, while a little soda
along with the salt facilitates the dyeing in some cases. It is
practically impossible to specify here the best assistant for all the
direct colours, on account of the great number of such dyes which are
known, but in the practical recipes given below much useful advice will
be found. Then the quantity of such assistants used is of much
importance; there is one proportion at which the best results are
obtained for each dye. The dyer should find out for himself by
experiment and the use of the dyes he employs in his work what assistant
and how much is best, and make his baths up to that strength. With some
dyes 10 per cent. of the assistant will be found sufficient, while with
others, 25 to 30 per cent. will not be too much. The percentage refers
to the weight of the cotton that is taken.

One function of the assistants must be pointed out here: it is that in
some cases they--especially the alkaline ones, soda, potash, borax,
phosphate of soda--help the dyeing by promoting the solubility of the
dye-stuff in the bath, thereby retarding the exhaustion of the bath and
ensuring the production of level shades.

The following formulas show the application of the foregoing principles
to the dyeing of numerous shades on to cotton and also the dyes which
are applicable, some of the combinations which are possible with these
direct dyes, and give some idea of the tints and shades of the colours
that can be got by their means. The best assistants to use are also
indicated in the formulae.

All the formulae here given and all that will be given in future chapters
are intended for 100 lb. weight of cotton fabrics in any condition,
whether of loose cotton, yarn in cops, hanks or wraps and woven fabrics
of every kind.

_Bright Red._--Dye with 3 lb. Benzo purpurine 4 B, 3 lb. soda and 15 lb.
Glauber's salt. This dye may also be used with 3 lb. soap and 10 lb.
soda in the bath with equally good results.

_Pale Salmon._--Prepare a dye-bath with 3 lb. salt, 5 lb. phosphate of
soda, 1 lb. soap, 1/2 oz. Benzo orange R. For a pale shade like this it
is not necessary to heat to the boil, a temperature of 170 deg. to 180 deg. F.
is sufficient.

_Dark Plum._--Prepare a dye-bath with 20 lb. of Glauber's salt, 2-1/2
lb. soap, 1