Improvements in or appertaining to Dyeing with Indigo.
Year: 1890

page_text: Date of Application, 11th Feb., 1890
Complete Specification Left, 7th Oct., 1890-Accepted, 8th Nov., 1890
PROVISIONAL SPECIFICATION.
Improvements in or appertaining to Dyeing with Indigo.
1, ISAAC BRAITHWAITE of Kendal, in the County of Westmoreland, Engineer,
do hereby declare the nature of this invention to be as follows:-
In the well known process of Schutzenberger for dyeing with indigo, a hyposulphite,
together with an alkali were used to reduce and make the indigo soluble. Now,
previous to his time, however, indigo had been reduced in various ways, but in all
these old processes, the bath had to be kept alkaline, otherwise, indigo was
precipitated.
My process is designed to enable me to dye with indigo in a neutral or somewhat
acid bath, the said bath containing hyposulphurous acid. As, however, hyposulphurous
acid is very unstable, I form this acid or its salt as required for use.
My invention, therefore, consists essentially in the combination of indigo with the
materials requisite for forming hyposulphurous acid or hypophosphite. These materials
are preferably sulphurous acid or a bisulphite and metallic zinc powder. The indigo
and these materials can be mixed together dry and kept in this state for a long
period, but, on mixing with water, they begin to re-act upon each other, and the
indigo becomes soluble.
In carrying out my invention, I prefer to use one of the following receipts, but I
give these receipts, not as exhausting all the available ones for this purpose, but as
illustrations of my process :-
A. Indigo and zinc powder in about equal quantities are stirred together in warm
water, and bisulphite of soda is added, either before, contemporaneously with, or
after the other ingredients have been mixed.
B. The finely ground indigo and zinc powder, and dry alkaline bisulphite are well
mixed together. This mixture is kept dry and will keep for months and be ready
for use in a few minutes by simply mixing with warm water.
C. Powdered indigo, powdered zinc, and an alkaline sulphite are mixed together.
They can be dissolved as required in warm water containing one equivalent of a
strong acid such as sulphuric acid for each two equivalents of the alkaline
sulphite.
D. Powdered indigo, powdered zinc, and an alkaline bisulphite can be mixed in
warm water and, after the indigo is dissolved, sufficient lime added to make the liquid
alkaline; dyeing will then proceed as in the ordinary hydrosulphite vat.
By the words "alkaline bisulphite," I wish to include, not merely bisulphite of soda,
but other bisulphites which readily give up their sulphurous acid and do not interfere
with the particular dyeing operation employed, the main principle of the invention
being the combination of indigo with the materials requisite to form hyposulphurous
acid or a hyposulphite on the addition of water, and without requiring the addition
of a carbohydrate or an alkaline carbonate or other like salt; these, especially an
alkaline carbonate, having hitherto been thought necessary for this purpose.
Dated this 10th day of February 1900
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Patent Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in or appertaining to Dyeing with Indigo.
I, ISAAC BRAITHWAITE of Kendal in the County of Westmoreland, Engineer, do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
but
In the well known process of Schutzenberger for dyeing with indigo, a hypo-
sulphite together with an alkali were used to reduce and make the indigo soluble.
Previous to his time, however, indigo had been reduced in various
in all these old processes the bath had to be kept alkaline otherwise indigo was
ways,
precipitated.
My process is designed to enable me to dye with indigo in a neutral or somewhat
acid bath, the said bath containing hyposulphurous acid, also to supply a dry powder
or cake (compressed powder) or two or more dry constituent powders or cakes which
can be carried in small bulk, kept for an indefinite period and simply require dissolving
in warm water to at once form a bath. As, however, hyposulphurous acid is very
unstable, I form this acid or its salt as required for use.
My invention therefore consists essentially in the combination of indigo with the
materials requisite for forming hyposulphurous acid or a hyposulphite. These materials
are preferably a bisulphite and metallic zinc powder. The indigo and these materials
can be mixed together dry or kept separate in weighed packages or compressed or
agglutinated cakes of definite weight, so that one cake of each constituent mixed
together will form a bath with the constituents in the best proportions. These can be
kept in this state indefinitely or for a long period, but on mixing with water, they
begin to re-act upon each other, and the indigo becomes soluble.
In carrying out my invention, I prefer to use one of the following receipts, but I
give these receipts, not as exhausting all the available ones for this purpose, but as
illustrations of my process—
A. About 20 pounds of indigo and 10 pounds of zinc powder are stirred together
in warm water, and 45 pounds of bisulphite of soda added, either before, contempo-
raneously with, or after the other ingredients have been mixed.
B. The finely ground indigo and zinc powder, and dry alkaline bisulphite are
well mixed together in the proportions above stated. This mixture is kept dry and
will keep for months, and be ready for use in a few minutes, by simply mixing with
warm water.
C. Powdered indigo, powdered zinc and an alkaline sulphite are mixed together.
They can be dissolved, as required, in warm water containing one equivalent
of a strong acid, such as sulphuric acid for each two equivalents of the alkaline
sulphite.
D. Powdered indigo, powdered zinc and an alkaline bisulphite can be mixed in
warm water, and, after the indigo is dissolved, sufficient lime added to make the
liquid alkaline; dyeing will then proceed as in the ordinary hydrosulphite vat.
By the words "alkaline bisulphite "I wish to include, not merely bisulphite of soda,
but other bisulphites which readily give up their sulphurous acid and do not interfere
with the particular dyeing operation employed. The main principle of the invention
being the combination of indigo with the materials requisite to form hyposulphurous
acid or a hyposulphite on the addition of water, and without requiring the addition
of a carbohydrate. or an alkaline carbonate or other like salt. These, especially an
alkaline carbonate, having hitherto been thought necessary for this purpose.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. The improvement in the process of dyeing with indigo which consists in formino

page_text: the vat as required by dissolving in the warm water, indigo, powdered zinc, and an
alkaline bisulphite or mixture which will form an alkaline bisulphite.
2. As a new article of manufacture and commerce, the dry mixture or assemblage
of solid materials in definite proportions which, added to water, forms an indigo dyeing
5 vat substantially as described.
Dated this 6th day of October 1890.
WM. P. THOMPSON & Co.,
Of Liverpool, Manchester, Nottingham and London, Patent Agents.