e a fair degree of affinity, while there are others which have but
little affinity, and while in the former case there is little dye left
in the bath, in the latter case there is a good deal. When dyeing plain
shades with single dye-stuffs this is not of much moment, because if the
bath be kept for further use, as will be spoken of presently, the bath
may be brought up to its original strength by adding a proportionate
amount of dye-stuff, but when compound shades are being dyed, using two
or more dyes, then this feature has some influence, for they will not be
absorbed by the fibre in the same proportion as they were put in the
bath, and so when making up the dye-bath for the second lot, and adding
the same proportion of dyes, the shade which is produced will not be
quite the same, for the first lot of cotton in taking up the dyes in
varying quantities has altered their relative proportions, and so the
bath for the second lot of cotton will actually contain more of one dye
than did the first bath, and the influence of this excess of the one
constituent will show itself in the shade ultimately dyed. The more lots
of cotton there are dyed in the bath the greater will this influence be.
The dyer must by practical experience find out for himself in what
direction this feature of the direct dyes exerts its influence on the
particular dyes he is working with and make due allowance.

It is found in practice that from one-fourth to one-half of the original
weight of dye-stuff is left in the bath, and in order to be as
economical as possible a custom has arisen of keeping the bath and using
it again for dyeing further lots of cotton. In thus making a continuous
use of dye-baths it is important in preparing the baths for the next lot
of cotton to add first the requisite quantities of dye-stuffs, how much
will depend upon the factors and conditions already detailed, but from
one-half to three-fourths of the original quantities are added.
Practical experience alone is the guide to be followed.

Having added the dye-stuff, then sufficient water must be added to bring
up the volume of the bath to the proper amount, for it will have lost
some. The loss of water arises from two sources: first there is the
evaporation, which always occurs when dye-baths are heated up, and,
second, there is the mechanical loss due to its absorption by the
material which is being dyed. When a piece of cotton or other textile
fabric is immersed in a dye l