Improvements in the Manufacture of Dis- and Poly-azo-dyes by Oxidation.
Year: 1895

page_text: Date of Application, 16th Sept., 1895
Complete Specification Left, 22nd May, 1896-Accepted, 27th June, 1896
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Dis- and Poly-azo-dyes by
Oxidation.
I BENJAMIN WILLCOX of 47 Lincoln's Inn Fields in the County of London,
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me by The Badische Anilin & Soda Fabrik, Ludwigshafen-,
on-Rhine, in the Empire of Germany) to be as follows:
This invention relates to the preparation of dis- and poly-azo-dyes by oxidation
which has hitherto been effected by means of a chemical oxidizing agent in.the
sulphuric acid solution of the mono- or other azo dye to be converted into dis- or
poly-azo-colouring matters.
The present invention consists in the employment of electricity to effect oxidation,
the electric current being passed through the sulphuric acid solution of azo-dye to
be oxidized, the said solution being situated at the positive electrode of an
electrolytic cell.
When chemical oxidizing agents are used, salts. (such for instance as manganic
salts if manganese peroxide be the oxidizing agent used) are formed in the solution.
and all such salts have to be removed when working up the dye but in the new
process according to this invention no salts are formed in the said solution, so that
the isolation, or working up, of the finished dye is simplified and facilitated.
The following example of the application of this invention in one case will serve
to further illustrate its nature but I do not limit myself to the details of this,
example as the conditions and proportions can be varied without departure: from
the nature of the invention.
by weight of ortho-toluidine-azo-
Example.-Dissolve about fifty parts
naphthionic acid (sodium salt) in about seven hundred and fifty parts, by weight,.
of concentrated sulphuric acid (containing about ninety-four per cent. real
acid H,SO) and pour the solution into a porous porcelain cell fitted with a positive
electrode of platinum or other suitable material. Place this porcelain cell in a
vessel containing concentrated sulphuric acid (containing about ninety-four per cent.
real acid H,SO) and fitted with the negative electrode. Pass a current of about
four ampères per square decimetre and about five to six volts tension through, the
cell and continue the current and consequently the electrolytic oxidation until, the
colour of the solution, or other test, shews that no further change of mono-azo-
dye to dis-azo-dye takes place. Then pour the solution onto ice, filter, wash and
convert into the sodium salt.
In an analogous manner the oxidation of other azo-dyes with a free para-position,
5 or of mixtures thereof, can be effected.
1
C Contember 1895.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents..

page_text: Oxidation.
I, BENJAMIN WILLCOX, of 47 Lincoln's Inn Fields, in the County of London,.
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me from abroad by The Badische Anilia & Soda Fabrik of
Ludwigshafen-on-Rhine in the Empire of Germany) and in what manner the
same. is to be performed, to be particularly described and ascertained in and by
the following statement :-
This invention relates to the preparation of dis- and poly-azo-dyes by oxidation
which has hitherto been effected by means of a chemical oxidizing agent in the
sulphuric acid solution of the mono- or other azo-dye to be converted into dis- or
poly-azo-colouring matters.
The present invention consists in the employment of electricity to effect
oxidation; an electric current being passed through the sulphuric acid solution of
azo-dye to be oxidized, the said solution being situated at the positive electrode of
an electrolytic cell.
When chemical oxidizing agents are used salts (such for instance as manganic
salts if manganese peroxide be the oxidizing agent used) are formed in the
solution and all such salts have to be removed when working up the dye but
in the new process according to this invention no salts are formed in the said
solution, so that the isolation, or working up, of the finished dye is simplified and
facilitated.
The following example of the application of this invention in one case will serve
to further illustrate its nature and the manner in which it can be carried into
practical effect but I do not limit myself to the details of this example as the
conditions and proportions can be varied without departure from the nature of the
invention. The parts are by weight.
Example. Dissolve about fifty parts of ortho-toluidine-azo-naphthionic acid
(sodium salt) in about seven hundred and fifty parts of concentrated sulphuric acid
(containing about ninety-four per cent. real acid H,SO) and pour the solution
into a porous porcelain cell, fitted with a positive electrode of platinum or other
suitable material. Place this porcelain cell in a vessel containing concentrated
sulphuric acid (containing about ninety four per cent. real acid H,SO) and fitted
with the negative electrode. Pass an electric current of about four ampères per
square decimeter and about five to six volts tension through the cell and continue
the current and consequently the electrolytic oxidation until the colour of the
solution, or other test shews that no further change of mono-azo-dye to dis-azo-dye
takes place. Then pour the solution onto ice, filter, wash and convert into the
sodium salt.
In an analogous manner the oxidation of other azo-dyes with a free para-position
or mixtures thereof can be effected.
Having now particularly described and ascertained the nature of this inven
tion, and in what manner the same is to be performed, I declare that what I
claim is:-
1. The manufacture and production of dis- and poly-azo-dyes by oxidation of

page_text: 2. The manufacture and production of dis- and poly-azo-dyes in the manner
described in the foregoing example.
and day of May 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents..