Manufacture of a Grey Basic Colouring Matter Soluble in Water.
Year: 1889

page_text: Date of Application, 18th Oct., 1889
Complete Specification Left, 5th July, 1890-Accepted, 9th Aug., 1890
PROVISIONAL SPECIFICATION.
Manufacture of a Grey Basic Colouring Matter Soluble in Water.
JOHN DAWSON, Kirkheaton Colour Works, Huddersfield, Manufacturing Chemis t
do hereby declare the nature of this invention to be as follows:-
As is well known, amido dimethylaniline when treated cold with oxydising agents,
is converted into a red rather instable compound. If however the action of the
oxydising agents is increased by boiling, the result is a basic blueish grey colour,
soluble in water, and suitable for dyeing mordanted cotton.
In carrying out this invention, I proceed as follows:
10 lbs. dimethylaniline are converted into nitroso-dimethylaniline, and the latter
reduced by 20 lbs. of zinedust. The filtered solution is diluted with 2000 lbs. of
water, mixed with 10 lbs. of chlorzink, heated to boiling and oxydised by the
successive addition of a solution of 9-10 lbs. of bichromate of soda or potash.
The reaction is complete, when a filtered sample of the solution, treated with
bichromate solution, does not show any more formation of the red colour. After
boiling for one hour the liquor is filtered, the color precipitated by the addition of
salt, filtered and dried.
It is a black powder easily soluble in water, with a violet grey, in concentrated
sulfuric acid with a dullish green, colour.
By diluting the sulfuric acid solution with water it changes through black into
red-violet. It dyes mordanted cotton a blueish grey, while from the mother liquor
by addition of an excess of chlorzink another colour may be precipitated dyeing on
mordanted cotton, an olive green.
Similar colors are obtained by the oxydation of amido diaethylaniline and similar
bases.
Dated this 10th day of October 1809.
COMPLETE SPECIFICATION.
Manufacture of a Grey Basic Colouring Matter Soluble in Water.
I, JOHN DAWSON of Kirkheaton Color Works near Huddersfield do hereby declare
the nature of this invertion and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement :-
It is well known that amido dimethylaniline when treated cold with oxydising
agents, particularly with iron chloride or chromic acid, is converted into a red some-
what instable compound, (Heber, Berichte der Deutschen Chemische Gesellschaft X.
762, C Hurster, ibid. XII. 526. 1803.) which hitherto has not been put to any
practical use. The oxydation of amido dimethylaniline in alkaline solutions yields
another, also instable product, which can easily be obtained by forcing a continuous
current of air through an aqueous solution of amidodimethylaniline; a brown
precipitate is formed, whose chief characteristic is that, an intense green is formed by
dissolving it in acetic acid, which however turns to yellow if water is added to the
solution. The solution of the product of the oxydation in hydrochloric acid has the
same color. If the hydrochloric acid solution be allowed to stand, it gradually
oxydises to the grey violet coloring matter described below. The same result is
obtained if free amidodimethylaniline in aqueous solution is treated with a diluted
solution of chromic acid, or a solution of bichromate which has been mixed with an
equivalent quantity of hydrochloric or sulphuric acid.
·
The reaction is quite different if in the oxydation of the amidodimethylaniline
(1.) for each molecule amidodimethylaniline, one molecule hydrochloric acid, or half.

page_text: a molecule sulphuric acid, is present and free chromic acid is used, or if (2.) free
amidodimethylaniline is oxydised with a solution of chromic acid and an adequate
quantity of hydrochloric or sulphuric acid or if (3.) a bichromate solution reacts on
amidodimethylaniline with 2 molecules of hydrochloric acid or 1 molecule sulphuric
acid present.
Under these circumstances, the chief result of the reaction consists of two basic
coloring matters, one blue and easily soluble, the other grey violet and less soluble
in water. If less than the above mentioned quantities of acid are used, the result will
be partly the same as above described product of oxydation in alkaline solution;
should more acid be used decomposition sets in and quinine is formed. Instead of
hydrochloric, sulphuric or other acids; their combinations with zinc, iron or other
metals may also be used.
To carry out this invention I proceed as follows:-
10 kilo hydrochlorate of nitrosodimethylaniline are suspended in 700 litres of water
and reduced with 10 kilo zinedust @ 40°. When the solution has become colorless
it is neutralised with a sufficient quantity of soda ash to show slightly alkaline if tested
with tropacoline, then filtered off from the precipitated zinc and mixed with 7 kilo
hydrochloric acid of 30 % or 5, 8 kilo sulphuric acid or 4 kilo chlorzine. To the
boiling solution 5 kilo bichromate of potash and 4, 5 kilo hydrochloric acid, or
3, 6 kilo sulphuric acid or 2, 5 kilo chlorzine, in 100 litres of water, is added in one
hour. It is not so advisible to treat the amidodimethylaniline solution, which has
been mixed with 11, 5 kilo hydrochloric acid, or 9, 2 kilo sulphuric acid or 6, 5 kilo
chlorzine, with bichromate solution; or to oxydise the free amidodimethylaniline
solution with a bichromate solution mixed with the same quantities of acid or
chlorzinc.
The completion of the reaction may be recognised when a drop of the solution shows
colorless instead of red on filter paper. Should this not be the case a small quantity
of bichromate solution must carefully be added. Then filter off boiling hot, precipitate
the blue coloring matter in the cold solution by adding 2, 5 kilo chlorzine and 100 kilo
salt, filter, press and dry.
The residue, containing chrome, left after filtering the hot solution, is suspended in
The grey
400 litres of water and extracted after adding 5 kilo hydrochloric acid.
violet coloring matter is then precipitated with chlorzine and salt as above described.
Should a shade between the two mentioned be desired, the preliminary filtering of the
liquor after the reaction must be omitted and instead boil up at once with 5 kilo
hydrochloric acid and precipitate as above.
The blue coloring matter obtained by this process is a dark blue powder, which
dissolves green in concentrated sulphuric acid. It is easily soluble in water and
alcohol and dyes cotton, mordanted with tannin, a very dark blue, but if mordanted
with iron a deep black.
It still contains small quantities of red coloring matter which may be removed by
putting unmordanted cotton in the solution of the blue coloring matter. The colorings
obtainable from the remaining solution are greenish blue.
The base is difficult to dissolve in water but easy to dissolve in alcohol or ether,
giving a purple red color. It probably corresponds with the formula

page_text: in concentrated sulphuric acid is a dirty brown and its solution in water a grey
violet.
It dies cotton, mordanted with tannin, grey violet and will also work on unmordanted
cotton.
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 :-
I. A process for the manufacture of a basic blue and a basic grey violet coloring
matter consisting in the oxydation of amido dimethylaniline with chromic acid in the
presence of about 1 molecule hydrochloric acid or the equivalent quantities of other
acids or the salts of heavy metals of those acids to 1 molecule of amido dimethyl-
aniline.
II. The process for the separation of the coloring matters obtainable according to
Claim I. consisting in extracting the mixture of the said coloring matters with a
quantity of acid not sufficient for the complete solution.
III. The substitution of the homologues & analogues of amido dimethylaniline for
amido dimethylaniline in Claims I. and II.
1000