to allow ½ lb., or 5 gallons of this stock bath to each pound of dye-stuff used in dyeing the ground colour to be developed up.
To prepare the coupling bath there is taken 5 gallons of the stock bath, 1 lb. sodium acetate with sufficient water for each 1 lb. of dye that has been used.
This bath is used cold, and the cotton is worked in it for half an hour, then it is taken out, washed well and dried.
Nitrazol C is a ready prepared diazotised paranitroaniline in a powder form which keeps well if stored in a dry place. The method of using is to take 8 lb. Nitrazol C, stir into a paste with water and then add this paste to the coupling bath, together with 2 lb. soda and ¾ lb. acetate of soda. This bath is used cold and the dyed cotton is immersed in it for half an hour, then taken out, well washed and dried.
The quantity of Nitrazol C given will suffice for all shades dyed with from 2 to 4 per cent, of dye-stuff, but when paler shades are dyed, using less than say ½ per cent. of dye-stuff, about 4 lb. Nitrazol C, with the soda and acetate of soda in proportionate quantities, may be used.
Azophor red P N is also a preparation of diazotised paranitroaniline in the form of a dry powder which keeps well.
To prepare the coupling bath there is taken 2 lb. of Azophor red P N, which is dissolved in water and added to the bath along with 1 lb. acetate of soda. The dyed goods are worked in the cold bath for half an hour, then taken out, well washed and dried.
The quantities given are sufficient for shades dyed with 2 to 4 per cent. of dye-stuff; for weaker shades half the quantities may be taken.
Benzo-nitrol developer is sold in the form of a yellow paste. To use it take 5 lb., stir into a smooth paste with water, then add to the coupling bath. There is then added
3 pints of hydrochloric acid, with some stirring. Allow to stand for half an hour, add 1½ lb. acetate of soda and 6½ oz. soda, when the bath is ready for use. The cotton is entered and worked for half an hour, then lifted out, washed and dried.