6 gallons of cold
water are added, then, after completely cooling, 3-1/2 lb. sodium
nitrite dissolved in 3 gallons cold water. After twenty minutes, when
the diazotisation is complete, water is added to make the whole up to 40
gallons. The acetate liquor is made from 13-1/4 lb. acetate of soda in
13-1/2 gallons of water.

Equal quantities of these two liquors are used in making the developing
bath.

[Illustration: FIG. 29--Developing Machine for Paranitroaniline Red.]

Of late years, under the names of Azophor red P N, Nitrazol C,
Nitrosamine, etc., there has been offered to dyers preparations of
diazotised paranitroaniline in the form of a powder or paste, readily
soluble in water, that will keep in a cool and dry place for any
reasonable length of time. These are prepared in various ways, and to
any dyer who does not want the trouble of diazotising the
paranitroaniline they offer some advantages. They produce a red equal in
every respect to that obtained from paranitroaniline. The following
details show the method to be followed with some of these products,
others are very similar to make the developing baths.

_Paranitroaniline Red with Nitrazol C._--Dissolve 25 lb. Nitrazol C in
12 gallons of cold water with constant stirring, then add sufficient
cold water to make 37 gallons. In another vessel dissolve 11 lb. of
acetate of soda in 5-1/2 gallons water, then add 1-1/2 gallons caustic
soda, 36 deg. Tw., mixed with 5-1/2 gallons water. The developing bath is
made by mixing both these solutions. It will suffice for both yarn and
piece goods.

_Paranitroaniline Red with Azophor Red P N._--Dissolve 5-1/2 lb. of
Azophor red P N in 4 gallons of water--it dissolves almost completely
but usually a few particles of a flocculent character remain
undissolved, these can be removed; 2-1/4 gallons of caustic soda lye of
36 deg. Tw. are diluted with water to 10 gallons, and this is added with
constant stirring to the azophor red P N solution. When all is mixed and
a clear solution obtained, the developing bath is ready for use, and is
used in the same way as the paranitroaniline bath.

_Metanitroaniline Orange._--This orange is produced in the same way as
the paranitroaniline red, using metanitroaniline or Azophor orange M N
in place of the paranitroaniline or the Azophor red P N given for the
red. The quantities of all the materials used are identical.

_Nitrosamine Red._--Dissolve 5 lb. Nitrosamine red in 5 gallons of wate