Gold yellow.
Resorcine Orange.
Naphthylamine ether Blue.
Blue developer A N Green.

As regards the dyeing operation, it no way differs from that described
for simple direct colours. It should, however, be noted that if good
results are required full shades must be dyed. The cotton must be
rinsed in cold water, and be quite cold before it is subjected to the
diazotising operation. _Diazotising_ is a simple operation, yet it must
be carried out with care if good results are desired. It consists
essentially in the use of an acidulated bath of sodium nitrite.

To make the bath for diazotising there is taken (for each 100 lb. of
goods) sufficient water to handle them in comfortably, 8 lb. of sodium
nitrite and 6 lb. hydrochloric acid. This bath must be quite cold
otherwise it does not work well. The goods are handled in this for from
fifteen to twenty minutes, when they are ready for the next operation.
The bath is not exhausted of nitrite, etc., hence it can be kept
standing, and for each succeeding lot of cotton it is strengthened up by
adding one-third of the quantities of nitrite and acid originally used.
Of course the bath cannot be kept for ever, sooner or later it will get
dirty, and then it must be thrown away and a new bath be made up.

The diazo compounds formed on the fibre are not very stable bodies. They
decompose on being exposed for any great length of time to the air,
while light has a strong action on most, if not all of them; hence it
follows that the diazotising process should not be carried out in a room
where direct, strong sunlight can enter or fall upon the goods. Then
again, after diazotising, the treated goods should not be allowed to lie
about exposed to air and light, but the operation of developing should
be proceeded with at once, otherwise the diazo body will decompose, and
weak and defective colours are liable to be obtained on subsequent
development.

For _developing_, quite a large number of substances are used. Some of
these are regular articles of commerce, others are the special
productions of certain firms, who advise their use with the dyes that
they also manufacture. These latter are sent out under such designations
as Developer B, Developer A N, or Fast-blue developer. Those most in use
are beta-naphthol for red from Primuline, and for bluish blacks from
Diamine blacks, Diazo blacks, Zambes