with, for it
is found that by allowing the prepared cotton to lie about it becomes
covered with brown stains, and when such stained cotton is passed
through the developing bath stains and defective dyeing result.

It has been found that by adding a little tartar emetic to the
beta-naphthol bath this is largely if not entirely prevented, and the
prepared cloth may be kept for a reasonable length of time before
proceeding with the development without fear of stains being formed.

Various additions have been made from time to time to the naphthol bath.
Some of these take the form of special preparations of the colour
manufacturers, and are sold as naphthol D, naphthol X, red developer C,
etc., sometimes gum tragacanth has been added, at others in place of
Turkey-red oil there is used a soap made from castor oil with soda and
ammonia, but such complicated baths do not yield any better results than
the simple preparing liquor given above.

[Illustration: FIG. 28.--Padding Machine for Paranitroaniline Red.]

=Dyeing Paranitroaniline Red on Piece Goods.=

The dyeing of this red on to piece goods only differs from that on yarn
by reason of the difference in the form of material that is dealt with.

1. _Preparing or Grounding._--The same liquor may be used. This
operation is best done on a padding machine, a sketch of which is given
in Fig. 26, showing the course of the cloth through the liquor. This is
contained in the box of the machine, and this is kept full by a constant
stream flowing in from a store vat placed beside the machine. After
going through the liquor, the cloth passes between a pair of squeezing
rollers which squeeze out the surplus liquor. Fig. 28 shows a view of a
padding machine adapted for grounding paranitroaniline reds. After the
padding, the cloth is dried by being sent over a set of drying
cylinders, or through what is known as the hot flue.

2. _The Developing._--After being dried, the pieces are sent through a
padding machine charged with the developing liquor made as described
above, after which the cloth is rinsed, then soaped, and then washed.
Some dyers use a continuous machine for these operations, such as shown
in Fig. 29.

While the developing bath used for piece goods may be the same as that
used for yarns, some dyers prefer to use one made somewhat differently,
thus 6-1/4 lb. paranitroaniline are mixed with 7 gallons boiling-water
and 1-1/2 gallons hydrochloric acid; when dissolved 1