A Process for the Production of a Substantive Cotton Colour.
Year: 1890

page_text: Date of Application, 13th Sept., 1890
Complete Specification Left, 11th Oct., 1890-Accepted, 15th Nov., 1890
PROVISIONAL SPECIFICATION.
A Process for the Production of a Substantive Cotton Colour.
We, JOHN DAWSON of Kirkheaton Color Works near Huddersfield and ROBERT
HIRSCH Ph. D. of Huddersfield do hereby declare the nature of this invention to be
as follows:-
In Patent 3803* 1885 a process is described, by which by the action of one
molecule of tetrazoditolyl, produced from orthonitrotoluol, on two molecules of
napthylamine-mono-sulpho-acid coloring matters are formed, soluble in water &
capable of dyeing unmordanted cotton in the soap- or alkaline-bath a yellowish red.
Our researches have shown that a different & very superior result is obtained, if
napthionic-acid is used in great excess and if the reaction is allowed to continue for
several days or a week. If the color obtained according to the instructions of
Patent 3803* 1885, be termed a red orange, the color obtained by our process is a
blueish red.
In order to carry out this invention, the excess necessary for the completion of the
process is at least two molecules of napthionic-acid. But we have found that still
better results will be obtained by using an excess of four molecules of napthionic-
acid (altogether six molecules), while a further increase of the quantity of napthionic-
acid does not essentially change the results.
The following gives a description of our process.
10 kilos. of orthotolidine are dissolved in 30 kilos. of bydrochloric-acid of 30%
and 200 litres of water, and diazotised by the addition of 6, 7 kilos. of nitrite of
soda dissolved in 75 kilos. of water, at a temperature not exceeding 10° Centigrade.
The solution thus obtained is mixed with a solution of 90 kilos. of the technical
sodium-salt of napthionic-acid (containing 4 molecules of water of crystallization) in
900 litres of water, and the mixture allowed to stand for about six days. The black
precipitate formed at the commencement gradually assumes a red yellow tint, which
on the addition of a drop of caustic-soda turns a brilliant scarlet. When no further
change of color is perceptible, the mixture is diluted with 1,000 litres of water, made
alkaline by the addition of 20 kilos. of caustic-soda 30%, heated to 80° Centigrade,
precipitated by the addition of 25 kilos. of salt, filtered pressed and dried. The
mother liquor contains the excess of napthionic-acid employed, which may be
recovered by precipitation with hydrochloric-acid.
Dated this 12th day of Santambor 1890
JOHN DAWSON.
ROBERT HIRSCH.
COMPLETE SPECIFICATION.
A Process for the Production of a Substantive Cotton Colour.
We, JOHN DAWSON of Kirkheaton Color Works near Huddersfield and ROBERT
HIRSCH Ph. D. of Huddersfield, 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 :-
:-
In Patent 3803* 1885, a process is described, by which by the action of one
molecule of tetrazo ditolyl, produced from orthonitrotoluol, on two molecules of
napthylamine-mono-sulpho-acid coloring matters are formed, soluble in water and
capable of dyeing unmordanted cotton, in the soap or alkaline bath, a yellowish red.
Our researches have shown that a different and very superior result is obtained if
napthionic acid is used in great excess and if the reaction is allowed to continue for

page_text: several days or a week. If the color obtained according to the instructions of
Patent 3803* 1885, be termed a red orange, the color obtained by our process is a
blueish red.
In order to carry out this invention the excess necessary for the completion of the
process is at least two molecules of napthionic acid. But we have found that still
better results will be obtained by using an excess of four molecules of napthionic-
acid (altogether six molecules), while a further increase of the quantity of napthionic-
acid does not essentially change the results.
The following gives a description of our process.
10 kilos. of orthotolidine are dissolved in 30 kilos. of hydrochloric acid of 30%
and 200 litres of water, and diazotised by the addition of 6, 7 kilos. of nitrite of soda
dissolved in 75 kilos. of water, at a temperature not exceeding 10° Centigrade.
The solution thus obtained is mixed with a solution of 90 kilos. of the technical
sodium salt of napthionic acid (containing 4 molecules of water of crystallization) in
900 litres of water, and the mixture allowed to stand for about six days. The black
precipitate, formed at the commencement, gradually assumes a red yellow tint, which,
on the addition of a drop of caustic soda, turns a brilliant scarlet. When no further
change of color is perceptible, the mixture is diluted with 1000 litres of water,
made alkaline by the addition of 20 kilos. of caustic soda 30%, heated to
80° Centigrade, precipitated by the addition of 100 kilos. of salt, filtered, pressed
and dried.
The mother liquor contains the excess of napthionic acid employed which may be
recovered by precipitation with hydrochloric-acid.
As is well known, the production of azo-colors consists in the reaction of one
molecule of a diazotised aromatic base on one molecule of a phenole or its sulpho-
acids, or in the case of a di-acid base on two molecules of one or even two different
phenoles or their sulpho-acids; in all these cases, with hardly any exception, as far as
any combination takes place, the combination is complete and the yield is quantitative.
In the case of the manufacture of amido azo compounds the formation, as a rule, will
also be complete by the action of one molecule of one diazo-group on one molecule of
an aromatic base, or its sulpho acid. But in some exceptions, especially in the case of
the manufacture of the so called substantive cotton colors a large excess of the base or
its sulpho acid will be required, which fact has hitherto been overlooked or is not
generally known and we wish it to be clearly understood that our process also holds
good in the manufacture of other substantive cotton colors, in which by the
employment of a large excess of base a different or superior result is obtained, in
distinction from the result obtained by the employment of two molecules of base or
such quantities as given in previous Specifications.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :
1. The process for the production of a substantive cotton color, which process
consists in the reaction of one molecule of diazotised orthotolidine on a large excess
(4 to 6 molecules) of napthionic acid, substantially as herein before described.
Dated this 10th dove of Antahan 1000
JOHN DAWSON.
ROBERT HIRSCH.