Coloring Matters.
Year: 1885

page_text: Coloring Matters.
I EMIL ELSAESSER of Brogler Strasse Barmen in the Kingdom of Prussia,
Chemist to the firm of Dahl and Company in Barmen in the Kingdom of Prussia,
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:-
My invention refers to the production of new azo dyes, which are obtained by
the action of the diazo-compound of Thioparatoluidin (the so-called Tetrazothio-
paratoluol) on sulpho acids of naphtol- and naphtylamin.
Thioparatolindin has been known for some time. It was discovered in 1871 by
Messrs Merz and Weith and is described in the reports of the German Chemical
Society Vol 4. p. 393.
The method of production which I employ is exactly the same as that described
by the discoverers.
I dissolve, for example, (in an iron retort provided with a condensing coil)
11 kilogrammes of Sulphur in 40 kilogrammes of melted paratoluidin, heat to
150° Centigrade and add gradually 42 kilogrammes of monoxide of lead (litharge).
The reaction is complete when any further addition of litharge is unaccompanied
by effervescence. I then remove the superfluous paratoluidin by blowing in Steam,
and extract the remaining mass by means of dilute hydrochloric acid.
.
The Thioparatoluidin which has passed into solution is precipitated by means of
a solution of soda, and can then be used directly in the production of dyes, or it
may be first purified by crystallization from a strong hydrochloric-acid solution in
the manner given by Messrs Merz and Weith.
The Thioparatoluidin is transformed into a diazo-compound (Tetrazothio-para-
toluol) readily soluble in water by the action of nitrous acid in a bydrochloric
acid solution.
With sulpho-acids of naphtol and naphtylamin this diazo-compound (Tetrazo-
thioparatoluol) furnishes red, orange, and brown tetrazo dyes. The mode of
producing the dye is that generally used for the production of azo-dyes.
The following descriptions of the modes of obtaining the two Tetrazo dyes,
which are produced by the action of the diazo-compound of Thioparatoluidin on
beta-naphtol disulpho-acid and piria's naphtion acid, are given as a typical
examples of the method I employ. At the same time I would specially remark

page_text: that both Amido groups of the Thioparatoluidin are transformed into diazo groups
by means of nitrous acid, and each of the two diazo groups combines with one
molecule of naphtol respectively naphtylamin sulpho-acid so that for one molecule
of the diazodized Thioparatoluidin (Tetrazothioparatoluol) there are two molecules
of naphtol or naphtylamin sulpho acid, and the calculations of the proportions to
be used are to be made on this basis, in the manner well known to chemists.
I. The production of a tetrazo dye from Tetrazothioparatoluol and beta-
naphtoldisulpho acid.
30 kilogrammes of Thioparatoluidin are dissolved with 90 kilogrammes of
30% Hydrochloric acid in 500 litres of water, and are transformed into the diazo-
compound by the gradual adding (under a constant temperature of from 0° to
5° Centigrade) of a solution of 19 kilogrammes of Nitrite of Soda in 50 litres of
water. After several hours stirring this diazo-compound is allowed to flow slowly
into an alkaline solution of 85.5 kilogrammes of the sodium salt of beta-naphtoldi-
sulpho acid in 1500 litres of water kept cooled to a temperature of 5° Centigrade.
The solution is rendered alkaline by 50 kilogrammes of soda.
The resulting red azo dye is separated in the well known way by the addition
of common salt, and purified by redissolving, filtering and a further precipitation
with salt, and brought into a dry condition in known manner. This dye stuff in
an acid bath colours wool red.
As the proportions to be adhered to in the production of the azo dye from the
naphtolmono and trisulpho acid can be easily calculated by chemists, it will
probably suffice for naphtolsulpho acid to limit myself to the above example.
II. The production of a Tetrazo dye from Tetrazothioparatoluol and piria's
napthion acid.
30 kilogrammes of Thioparatoluidin are transferred into the diazo compound
exactly in the manner stated above in example. I. Since an excess of nitrous acid
would act injuriously on the further stages of the process, this excess is removed at
the end of the diazodizing by the addition of the necessary quantity of sulphurous
acid.
The diazo compound thus obtained is allowed after being cooled down to
5° Centigrade to flow into a solution of 60 kilogrammes of sodium salt and
naphtionic acid and 70 kilogrammes of acetate of soda in 600 litres of water, and
to stand for 24 hours with repeated stirring. The dye stuff separates out from the
solution, which is filtered off, and the dye is pressed and brought into a soluble
form by neutralizing with soda.
This dye in an acid bath colours wool bluish-red.
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
I. The application of the diazo-compound of the Thioparatoluidin, discovered by
Messrs Merz and Weith (Tetrazothioparatoluol) for the production of azo-dye stuffs
by combination with sulpho acids of naphtol and naphtylamin as above described.
II. The use of the azo-dye stuffs produced by the action of Tetrazothioparatoluol
on sulpho acids of naphtol and naphtylamin (as above described) for dyeing and
printing.