A Process for the Preparation of a Yellow Sulphur-containing Dye from Sulphocyanide Salts.
Year: 1898

page_text: Date of Application, 25th July, 1898-Accepted, 27th Aug., 1898
COMPLETE SPECIFICATION.
A Process for the Preparation of a Yellow Sulphur-containing Dye
from Sulphocyanide Salts.
Dr.
We, ALWIN GOLDBERG, Dr. Phil., of 3, Inselstrasse, Chemnitz, Professor,
WILHELM SIEPERMANN, of 116, Konigstrasse, Elberfeld, Chemist, and
Dr. HUGO FLEMMING, of 165, Hauptstrasse, Kalk, near Cologne on the Rhine, all
in the German Empire, do hereby declare the nature of this invention and in
what manner the same is to be performed, to be particularly described and ascer
tained in and by the following statement:-
This invention relates to a process for the preparation of a yellow sulphur-
containing dye from sulphocyanide salts.
As far back as the year 1829 Liebig published papers (see Poggendorf's
Annalen XV 548) upon the action of dry chlorine gas upon fused sulphocyanides,
the results of which may be shortly summed up as follows, that is to say, that
Liebig worked at a suitable temperature and with unlimited quantities of chlorine
gas and that sulphur chloride and cyanogen chloride escaped in the form of
gases, whilst a sublimate and a solid residue remained behind. Analyses of these
latter bodies did not shew the presence of cyanogen sulphide which Liebig expected
to obtain and it is obvious that the resulting substances were not of the same
composition as Liebig, according to another paper published in Poggendorf's
Annalen XV 559, succeeded with a sufficiently long reaction of the chlorine and at
suitable temperatures in completely driving off the sulphur and in obtaining
the body mellon which is free from sulphur.
Now we have discovered by experiment that a technically valuable, very inten-
sive yellow dye which dyes cotton, linen, paper, etc., directly and is light and
soap fast, can be efficiently obtained by altering the Liebig process in essential
points as follows, that is to say:
1. By confining the operation within certain temperatures.
2. By employing the dry gas (chlorine or bromine) which is passed over the
sulphocyanide salt in equivalent quantities only that is to say, one atom of the
halogen to one C N S of the sulphocyanide salt, and,
3. By maintaining the mass constantly in movement during the reaction.
If the operation is so conducted that the temperature of the sulphocyanide salt
does not exceed 200° Centigrade, but remains between 100° and 200° C and if
only equivalent quantities of dry chlorine or bromine are employed for the
reaction, that is to say, one atom of chlorine to 1 molecule of the alkaline sulpho-
cyanide and two atoms of chlorine to 1 molecule of the sulphocyanide of the
alkaline earth, for example calcium sulphocyanide, then neither sulphur chloride
nor cyanogen chloride escapes, but the chlorine or bromine which is employed
is completely absorbed by the sulphocyanide salt if care be taken that the
reaction mixture is maintained in constant movement so that a fresh surface is
always offered to the inflowing gases. We have obtained this result by the
employment of a rotating ball-mill heated by gas.
When the reaction is finished, which can be recognized by measuring or weigh-
ing the sulphocyanide salt and the quantity of gas used or by observing when the
sulphur chloride and the cyanogen first begin to escape, a reddish brown coloured
product remains behind, which product can, after being cooled by washing, be
freed from the halogen-alkali or alkaline earth formed. The residue is a yellow
dye which, for the purpose of convenient use, is either converted to its sodium

page_text: combination in the following described manner or it is obtained from this in the
most concentrated form by decomposition with hydrochloric acid as is also
described in the following example.
EXAMPLE.
If 8 kilogrammes of sodium sulphocyanide be heated in a ball-mill to a tem-
perature of from 160° to 180°, and if 35 kilogrammes of dry chlorine gas be
passed over it, then a brownish red powder is obtained. This powder is washed
with water whereby sodium chloride is removed and the residue is then heated
with 5 kilogrammes of caustic soda in from 50 to 100 litres of water to a tem-
perature of about 60° C. The residue is then allowed to cool and is filtered and
washed with 1 to 2% soda solution. A pale yellow substance goes into solution
and the residue is the sodium compound of the yellow dye from which the dye' can
be separated, by decomposition with acid and washing, as a brownish yellow pre-
cipitate which becomes darker on drying.
If calcium sulphocyanide be employed, the proportions are as follows, that is
to say, 71 kilogrammes of chlorine to 15'6 kilogrammes of calcium sulphocyanide,
as in this case a molecule of chlorine is necessary to separate a molecule of calcium
from its sulphocyanide combination.
Sulphuric anhydride acts upon sulphocyanide salts in the same manner as
chlorine and bromine and forms a brownish body of the nature of a dye. The
requirements with regard to temperature and stirring of the mass are the same as
those above described; one molecule of the sulphocyanide salt requires, however,
one molecule of SO3, as SO, first combines with the metal of the sulphocyanide
salt, for example in the case of potassium to form K₂SO, and this is then decom-
posed with further SO, according to the equation,
EXAMPLE.
97 kilogrammes of potassium sulphocyanide are heated in a ball-mill to
about 1600 and 8 kilogrammes of sulphuric anhydride are passed over the same.
Sulphurous acid escapes and a brown powder remains behind which, after being
washed in the above described manner, yields the same yellow dye as is obtained
by the action of chlorine or bromine.
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. A process for the preparation of a yellow sulphur-containing dye, such pro-
cess consisting in causing chlorine or bromine to react under heat upon sulpho-
cyanide salts in the proportions of one atom of the halogen to one CNS of the
sulphocyanide salt in such a manner that no compounds of sulphur or cyanogen
and the halogen escapes, substantially as hereinbefore described.
2. The modification of the process described in Claim 1 wherein the halogen
is replaced by sulphuric anhydride in such a manner that instead of one atom
of the halogen, one molecule of the SO, is caused to react upon the sulphocyanide
salt under heat, sulphurous acid being developed.
3. As a new commercial product, the yellow dye obtained by the processes
described in Claims 1 and and having the properties specified.
Dated the 25th day of T、1., 1900
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicants.