ratively clear, greenish yellow solution is obtained,
this will contain about 1 lb. of indigo per gallon.

This mother liquor may be used in setting the vat as follows. The vat
is filled with water which is heated to 120 deg. F., about 200 gallons
being used. To this is then added 1 gallon of either hydrosulphite or
bisulphite of soda to destroy the free oxygen it contains, and prevent
it from oxidising the indigo solution, which is next added. The
quantity of the latter is solely regulated by the depth of shade it is
desired to dye, and as soon as the requisite quantity has been added
the dyeing may be proceeded with at once, and the first portion of
goods put through will soon show the dyer whether too much or too
little of the mother indigo has been added.

Continued use and the consequent agitation of the vat thereby
generated causes it to become oxidised, and the vat acquires a
greenish colour, and does not give fast colours. When this is noticed
the use of the vat is stopped; it is heated to about 160 deg. F., and a
little lime and hydrosulphite added, when all the oxidised indigo in
the vat will speedily be reduced, and the vat put into a workable
condition again. By use this vat tends to become alkaline, and
consequently will spoil the wool, making it harsh and brittle. This is
remedied by adding a little hydrochloric acid.

#Holliday's Patent Indigo Vat.#--Messrs. Read Holliday & Sons have
patented an improved method of making an indigo solution and the
method of using it. They supply the indigo in the form of solution in
two strengths, ordinary and concentrated. Both are used in the same
way, only of the latter less, about one-fourth to one-third, is (p. 144)
required than of the former. For those who would wish to buy their
indigo ready prepared for use these are very convenient forms.

The best way of working the vat for wool is the following: 40 gallons
of water heated to about 50 deg. C., add 1/4 lb. of a mixture of 1-1/4
gallons bisulphite of soda, 52 deg. Tw., and 1 lb. zinc dust, and, say,
1/2 gallon to 2 gallons, of the patent indigo solution, according to
the depth of shade required. The boiled out wool is worked below the
surface of the liquor for about three minutes, then taken out, and the
excess of liquor squeezed back into the vat, the whole operation is
repeated until the shade is arrived at. After dyeing, rinse in an acid
bath of 1 deg. to 2 deg. Tw.

The advantages of this new vat are