B N, 10 lb. Glauber's salt, 2 lb.
oxalate of ammonia and 5 lb. acetic acid, after dyeing, and the
dye-bath, is exhausted of colour, add 1-1/2 lb. bichromate of potash
and 3 lb. hydrochloric acid, and boil again for half an hour. Finish
in the usual way.

One of the reasons for adding the oxalate of ammonia, is to
precipitate out any lime which may be in the water in such a form that
it will not react with the dye-stuff.

_Fast Black_.--Mordant the yarn with copperas (sulphate of iron). Dye
in a bath with 5 lb. Gambine Y, 2 lb. Acid Mauve, 2 lb. bisulphate of
soda. Proceed as described for full green.

_Blue Black_.--3-1/2 lb. Naphthylamine Black S, 10 lb. Glauber's salt,
and 5 lb. acetic acid; to fully exhaust the dye-bath add 8 lb.
bisulphate of soda.

_Jet Black_.--5 lb. Naphthylamine Black S, 1/4 lb. Fast Acid
Green B N, 10 lb. Glauber's salt, and 5 lb. acetic acid, adding 8 lb.
bisulphate of soda to exhaust the bath.

_Blue Black_.--Give a deep blue bottom in the indigo vat and dye with
2 lb. Anthracite Black B, 10 lb. Glauber's salt and 2 lb. acetic acid.

#Greys on Wool.#--The dyeing of greys follows very naturally after (p. 097)
the dyeing of blacks, for from a broad point of view greys are simply
light blacks, and any dye-stuffs that will dye black will if used in
smaller proportions give greys. There is a great variety of tone among
greys: reddish greys, bluish greys, greenish greys, and so on. They
may be dyed in a considerable variety of ways from a large number of
dye-stuffs, both natural and artificial. Of these two classes the
latter gives the best result as far as regards brightness of tone, and
as regards other properties the greys obtained from the artificial
coal-tar colours are fully equal to those from natural dyes.

A large number of recipes are in use by dyers for the production of
greys, so many that it becomes almost an impossibility to do more than
give a mere fraction of them here. However, a number of representative
recipes will be given, covering all classes of dye-stuffs capable of
being used for the purpose, and thus forming a guide to the methods of
dyeing and the proportions of dye-stuffs to be used.

_Light Grey_.--Dye at the boil for three-quarters of an hour, in a
bath containing 1 lb. perchloride of tin, 3 lb. alum, 3 oz. indigo
extract, and 2 oz. cochineal.

_Slate Grey_.--Mordant by boiling with 4 lb. alum and 1 lb. argol,
then dye with 6 lb. logwood, 6 oz. cudbear and 3