Improvements in the Separation of the Isomeric Substances Produced in the Manufacture of Dithiosalicylic Acid.
Year: 1889

page_text: Date of Application, 17th Aug., 1889
Complete Specification Left, 17th May, 1890-Accepted, 28th June, 1890
PROVISIONAL SPECIFICATION.
Improvements in the Separation of the Isomeric Substances Produced
in the Manufacture of Dithiosalicylic Acid.
I, ALEXANDER MELVILLE CLARK, of the firm of A. M. and Wm. Clark, of 53,
Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent Agents,
do hereby declare the nature of this invention (a communication to me from abroad
by the firm of Dr. F. von Heyden's successor, of Radebeul, near Dresden, Saxony,
Manufacturers of Chemicals) to be as follows:
This Invention has for its object the separation of the isomeric substances produced
in the manufacture of dithiosalicylic acid, and constitutes an improvement in, or an
addition to, the process_described in the specification of a previous application for
Letters Patent filed by Heinrich Baum dated the 8th day of October 1888 No. 14,443.
The dithiosalicylic acid produced according to the specification of the said former
Letters Patent is a mixture of two isomerides which can be easily separated in the
form of their salts, for instance sodium salts.
On precipitating with common salt, the greater part of the less soluble salt of the
dithiosalicylic acid No. I separates out whilst the salt of dithiosalicylic acid No. II
contaminated with a little dithio salt No. I remains in solution.
The separation is however, effected most perfectly by treating the dry sodium salt
of crude lithiosalicylic acid with boiling alcohol. The latter only dissolves the sodium
dithiosalicylate No. II whilst the more difficultly soluble sodium salt No. I remains
behind as a sulphur-yellow powder. On evaporating down the mother liquor, it yields
the salt No. II as a grey-white mass which is hygroscopic and extremely soluble in
water.
A. MELVILLE CLARK.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
Improvements in the Separation of the Isomeric Substances Produced
in the Manufacture of Dithiosalicylic Acid.
I, ALEXANDER MELVILLE CLARK of the firm of A. M. and Wm. Clark, of 53,
Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent Agents,
do hereby declare the nature of this invention (a communication to me from abroad
by the firm of Dr. F. von Heyden's successor, of Radebeul, near Dresden, Saxony,
Manufacturers of Chemicals) and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-
This Invention has for its object the separation of the isomeric substances produced
in the manufacture of dithiosalicylic acid, and constitutes an improvement in, or an
addition to, the process described in the specification of Letters Patent granted to
Heinrich Baum dated 8th October 1888, No. 14.443.
The dithiosalicylic acid produced according to the specification of the said former
Letters Patent is composed of two isomerides which can be easily separated in the
form of their alkali salts, for instance, sodium salts, that is to say the dithiosalicylic
acid is converted into its sodium salt by combination with soda in the well known way,
and the sodium salt thus produced may be separated into two isomeric salts either by
common salt or by alcohol.
If common salt is used the sodium salt is first to be dissolved in water and this
aqueous solution is then to be treated with common salt, whereby the greater part of
D

page_text: the less soluble of the two isomeric salts (salt I) is precipitated whilst the other
isomeric salt (salt II) contaminated with a little of the salt 1 remains in solution.
If, then, the mother liquor be decanted off, the isomeric salt No. II can be recovered
in any way, well known to chemists.
The other and most complete way of effecting the separation is to treat the dry
sodium salt of the crude dithiosalicylic acid with boiling alcohol, which dissolves only
the sodium dithiosalicylate No. Il. When the mother liquor is decanted off, the more
difficultly-soluble sodium salt No. I remains behind as a sulphur-yellow powder. By
then evaporating the mother liquor it yields the salt No. II as a grey-white mass
which is hygroscopic and extremely soluble in water.
It must of course be understood that the process is not limited to sodium salts,
which are only instanced by way of example, and that salts of other alkaline bases
(e.g. potassium or ammonium salts) may be used.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The herein-described processes of effecting the separation of the isomeric dithio-
salicylates, produced as above mentioned.
(1.) By precipitating the less-soluble dithiosalicylate No. I with common salt from.
the aqueous solution of an alkali salt of the crude acid.
(2.) By treating the alkali salt with boiling alcohol; substantially in the manner
set forth.
D
1000
A. MELVILLE CLARK.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
A. MELVILLE CLARK.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.