A. NEW METHOD OF DYEING COTTON AND OTHER VEGETABLE FIBRES WITH INSOLUBLE AZO COLOURING MATTERS
Year: 1884

page_text: I, DAN DAWSON of Hofmann Street Milnsbridge, near Huddersfield, Yorkshire
Chemist, do hereby declare the nature of my invention for "A. NEW METHOD OF
DYEING COTTON AND OTHER VEGETABLE FIBRES WITH INSOLUBLE AZO COLOURING
MATTERS," to be as follows:-
The object of my Invention is to fix insoluble azo colors upon vegetable fibre at
one operation.
Hitherto such colors have been fixed by two well known methods, both of which
methods required two operations to fix the color.
According to one of these methods the cotton is impregnated with an alkaline
solution of phenol or naphtol, or other similar body, and then passed into a
neutral solution of a diazo-compound when the colors thereby produced precipitate
instantaneously upon the fibre.
According to the other method, the cotton is worked in an acid solution, con-
taining both the diazo-body and the naphtol or similar body (the acid therein
contained preventing the formation and precipitation of the color) and afterwards
passed into an alkaline solution, the acid which prevented the formation of the
color being thus neutralized, the color forms immediately upon the fibre.
Now I have discovered that the diazo colors can be fixed upon cotton and other
fibre at one operation, which I accomplish by bringing the materials composing the
bath into such a condition that there is a tendency to a slow and gradual com-
bination between the naphtol or naphtol like bodies and the diazo-compound.
Cotton immersed into such a bath acts catalytically and induces the gradual
formation of the color upon its surface or within the fibre, thereby becoming
gradually and effectively dyed. This condition of the bath is brought about by
ensuring that the bath contains no free mineral acid, or only a slight excess of a
weak organic acid, such for instance as acetic acid.
As an example of preparing such a bath I proceed as follows;
I azotize a body, say for example zylidine, by adding in the usual way nitrite of
soda to a weak solution containing say point one per cent of the hydrochlorate of
this base, together with a somewhat large excess of hydrochloric acid until the
base becomes thoroughly azotized, then an emulsion of pure chalk is added until
complete neutralization is attained, after which naphtol is added in a finely

page_text: precipitated state in at least equivalent proportions to the zylidine employed along
with the acetate of soda, and a slight quantity of acetic acid. The finely
precipitated naphtol, and acetate of soda are obtained together by precipitating
naphtol from naphtolate of soda by means of acetic acid, the acid being added
slightly in excess.
Cotton immersed into a bath prepared as mentioned above will gradually fix
upon itself the coloring matter as it forms and thereby become effectively dyed, the
rate of formation being regulated by introducing into the bath a larger or smaller
quantity of acetic acid.
The following are some of the bodies which may be azotized and employed in
the same manner as the example previously cited-viz-aniline, toluidine, zylidine,
naphtylamine, amidoazobenzole, and roseaniline, all of which give colors by the same
treatment, but doubtless there are many other compounds containing amidogen
which will act in the same way.
The quantity of materials used for the purposes herein mentioned will vary
according to depth of shade required as will be well understood by chemists and
Dyers.

page_text: I, DAN DAWSON, Hofmann Street Milnsbridge, near Huddersfield, Yorkshire,
Chemist do hereby declare the nature of my invention for "A NEW METHOD OF
DYEING COTTON, AND OTHER VEGETABLE FIBRES WITH INSOLUBLE AZO COLOURING
MATTERS," and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
The object of my Invention is to fix insoluble azo colors upon vegetable fibre at
one operation.
Hitherto such colors have been fixed by two well known methods, both of which
methods required two operations to fix the color.
According to one of these methods the cotton is impregnated with an alkaline
solution of phenol or napthol, or other similar body, and then passed into a
neutral solution of a diazo-compound when the colors thereby produced precipitate
instantaneously upon the fibra.
According to the other method the cotton is worked in an acid solution
containing both the diazo body and the napthol or similar body (the acid therein
contained preventing the formation and precipitation of the color) and afterwards
passed into an alkaline solution, the acid which prevented the formation of the
color being thus neutralized the color forms immediately upon the fibre.
Now I have discovered that the diazo colors can be fixed upon cotton and other
fibre at one operation, which I accomplish by bringing the materials composing the
bath into such a condition that there is a tendency to a slow and gradual com-
bination between the napthol or napthol like bodies and the diazo compound.
Cotton immersed into such a bath acts catalytically and induces the gradual
formation of the color upon its surface or within the fibre, thereby becoming
gradually and effectively dyed.
This condition of the bath is brought about by ensuring that the bath contains
no free mineral acid, or only a slight excess of a weak organic acid, such for
instance as acetic acid.
As an example of preparing such a bath I proceed as follows; I azotize a body,
say for example naphtylamine by adding in the usual way nitrite of soda to a
weak solution containing, say-point one per cent of the hydrochlorate of this base,
together with a somewhat large excess of hydrochloric acid until the base becomes
thoroughly azotized, then an emulsion of pure chalk is added until complete
neutralization is attained after which napthol is added in a finely precipitated state
in at least equivalent proportion to the naphtylamine employed along with acetate
of soda, and a slight quantity of acetic acid.
The finely precipitated napthol and acetate of soda are obtained together by
precipitating napthol from naphtolate of soda by means of acetic acid, the acid
being added slightly in excess.
Cotton immersed into a bath prepared as mentioned above will gradually fix
upon itself the coloring matter as it forms, and thereby become effectually dyed, the
rate of formation being regulated by introducing into the bath a larger or smaller
quantity of acetic acid,

page_text: The following are some of the bodies which may be azotized and employed in
the same manner as the example previously cited-viz-aniline, toluidine, zylidine,
naphtylamine, amidoazobenzole, and roseaniline, all of which give colors by the
same treatment, but doubtless there are many other compounds containing amidogen
which will act in the same way.
The quantity of materials used for the purposes herein mentioned will vary
according to depth of shade required as will be well understood by Chemists and
Dyers.
I find that by fixing an insoluble soap upon cotton or other vegetable fibre before
dyeing, that the said dyeing process is more quickly performed and deeper shades
obtained thereby.
The kind of color produced by this process depends upon the kind of base made
use of to be azotized.
For instance-Aniline yields orange, zylidine scarlet, and naphtylamine red
with naphtol, yellower shades are obtained by substituting phenol for naphtol, but
the colors obtained by means of phenol are not so fast as those produced by
naphtol.
1
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
Fixing on vegetable fibre at one operation insoluble azo coloring matters, in
which the bodies employed are so balanced as to cause the dyeing process to
proceed in one bath slowly and gradually, according to the rate of formation of
the coloring matter.