Process for Separating Ortho-anhydro-sulphamine-benzoic Acid from Para-sulphamine-benzoic Acid.
Year: 1897

page_text: Date of Application, 21st June, 1897-Accepted, 31st July, 1897
COMPLETE SPECIFICATION.
Process for Separating Ortho-anhydro-sulphamine-benzoic Acid from
Para-sulphamine-benzoic Acid.
I, RUDOLF BARGE, of Stassfurt, in the Empire of Germany, Chemist, 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:-
In the preparation of ortho-anhydro-sulphamine benzoic acid (benzoic sulphinide).
is obtained as a by-product; since this has not the valuable properties of benzoic
sulphinide it must be regarded as an impurity.
The separation of parasulphamine-benzoic acid from the mixture of both acids
forms the object of the present invention; it depends on the fact that benzoic
sulphinide and para-sulphamine benzoic acid yield basic copper salts which differ from
each other in solubility.
The basic copper salt of parasulphamine-benzoic acid is more sparingly soluble than
that of benzoic sulphinide and is therefore precipitated first by a cupric compound
from a mixture of these ortho- and para-derivatives. The composition of the basic
cupric salt of para-sulphamine-benzoic acid, when certain conditions are observed,
corresponds with the formula:
The separation of parasulphamine benzoic acid from benzoic sulphinide by taking.
advantage of the different solubility of the copper salts is effected according to any of
the following methods, which are modifications of the application of the same
invention, a choice between them depending on the proportion in which the cupric
salt of the parasulphamine benzoic acid is to be precipitated, or remain undissolved,
while the orthosulphamine benzoic acid remains as a metallic salt in the solution or is
dissolved.

page_text: 1 PRECIPITATION FROM THE NEUTRAL AQUEOUS SOLUTION OF SALTS OF THE MIXTURE OF
ACIDS WITH A QUANTITY OF A CUPRIC SALT SOLUBLE IN WATER CORRESPONDING
WITH THE PARASULPHAMINE BENZOIC ACID PRESENT.
A neutral aqueous solution of salts of the acids is prepared and the quantity of
parasulphamine benzoic acid is ascertained by one of the known analytical methods;
a cupric salt, soluble in water, for example cupric sulphate, is added in quantity
sufficient to convert the whole of the parasulphamine benzoic acid present into the
cupric compound. For 3 molecules of parasulphamine-benzoic acid at least
2 inolecules of cupric oxide, that is, the equivalent quantity of a cupric salt, must be
present. For 603 parts by weight of parasulphamine-benzoic acid 159 parts by
weight of cupric oxide (CuO) must be used.
To make sure that the whole of the para-compound is separated, a slight excess of
cuprice salt may be employed with advantage. By mixing the solution of the
mixture of acids with that of the quantity of cupric salt corresponding with the
parasulphaminebenzoic acid present, the basic cupric salt of the parasulphamine
benzoic acid separates while pure ortho-anhydrosulphaminebenzoic acid remains in
the solution and may be separated therefrom by the addition of a mineral acid.
The separated basic cupric salt requires further treatment, as, owing to the use of
an excess of soluble cupric salt it always contains some of the cupric salt of the
orthosulphamine benzoic acid. The latter is separated from the mixture by prolonged
treatment with warm water, whereby the copper salt of the orthosulphamine benzoic
acid together with a small part of the para-copper salt, dissolves, while the larger part
of the para compound remains undissolved as basic copper salt. By filtering hot, the
residue consists of pure basic cupric parasulphamine benzoate, whilst by cooling the
filtrate a mixture of ortho and para-cupric salts crystallises.
By the foregoing separation of the mixture of ortho anhydrosulphamine benzoic
acid and parasulphamine benzoic acid, the mixture is.divided into 3 parts, namely:-
I, pure ortho-anhydrosulphamine-benzoic acid.
II, a mixture of basic cupric salts of both acids; this mixture may be termed the
"middle fraction."
III, pure basic cupric para-sulphamine benzoate.
Pure
The foregoing separation can be advantageously carried out in one operation by
mixing the hot neutral solution of the orthosulphamine benzoic acid and
parasulphamine benzoic acid salts with a hot solution of a cupric salt (corresponding in
quantity with the parasulphaminebenzoic acid present) and filtering while hot.
basic cupric parasulphamine benzoate then remains in the filter and the middle
fraction crystallises from the filtrate on cooling; if these crystals be filtered off, the
pure ortho sulphamine benzoic acid can be precipitated from the mother liquor by
addition of a mineral acid.
The method of working and the conditions to be observed in the application of the
foregoing process of separation will be best understood from the following example,
concerning which, however, it must be remarked that the process of separation can
also be accomplished by the use of other degrees of concentration, temperatures &c.
Example: 10 kilos. of a dry mixture of 62-65 parts of sodium ortho-anhydrosulpha-
mine benzoate and 38-35 parts of sodium para-sulphamine-benzoate (such a mixture
is obtained in the manufacturing process for obtaining benzoic sulphinide or its sodium
salt) are dissolved in 100 litres of water, heated to 60° C., and the solution is mixed
with a solution of 2.8 kilos. of crystalised cupric sulphate in 20 litres of water heated
to the same temperature. The separated copper salt is filtered off at 50-55° C. and
once covered with water; it is then free from ortho-anhydrosulphamine benzoic acid.
Its weight when dry is 2.3 kilos.
From the filtrate 2.5 kilos. of middle fraction crystallise after several days standing.
From the filtrate of this 3.5 kilos. of pure ortho-anhydro-sulphamine benzoic acid
(benzoic sulphinide) are precipitated by hydrochloric acid.
The middle-fraction obtained in the foregoing process is heated with excess of soda
solution, and the solution of the sodium salts of both acids thus obtained, is returned

page_text: to the process of manufacture. The middle-fraction can also be further treated by the
method of separation to be described under 2.
Instead of cupric sulphate used in the example given any soluble cupric salt can be used,
for example, cupric chloride, cupric nitrate, normal cupric acetate. The concentration
of the cupric solution can be stronger than is given in the example.
2. PRECIPITATION OF THE BASIC CUPRIC SALTS OF THE ORTHO-SULPHAMINE BENZOIC ACID
AND PARA-SULPHAMINE BENZOIC ACID TOGETHER AND DISSOLUTION OF THE SALT-OF-
THE ORTHO-SULPHAMINE-BENZOIC ACID IN ALKALI CARBONATE OR ALKALI-
HYDROXIDE SOLUTION.
The solution of the ortho-sulphamine benzoic acid and para sulphamine benzoic acid
is completely precipitated with a solution of a cupric salt and the basic cupric salts are
treated with a hot solution of sodium carbonate or hydroxide equivalent to the benzoic
sulphinide present this quantity having been ascertained by known analytical methods.
The undissolved residue consists of basic cupric para-sulphamine benzoate and pure
copper oxide, this latter having been formed in the decomposition of the cupric ortho
anhydrosulphamine benzoate by sodium carbonate or hydroxide; it is filtered off and
the filtrate is further treated as in the process described under 1.
The concentration of the sodium carbonate or sodium hydroxide solution used can
be varied within somewhat wide limits but for choice it should correspond substantially
with the example given in 1.
2 AnatmLAY

page_text: This acid affects the complete formation and separation of the basic cupric salt and
easily leads to the contamination of the ortho-sulphamine benzoic acid remaining in
solution with some para sulphamine benzoic acid which has remained dissolved.
This objection is overcome by adding a quantity of sodium hydroxide equivalent to
the liberated mineral acid to the neutral solution of the salts of the acids before the
cupric salt is added, thus, in the example given in 1, about 0-2 kilo of sodium
hydroxide (NaOH) corresponding with 1 part of NaOH for 14 parts of crystallised
cupric sulphate is added.
The reaction then takes place in accordance with the following equation :
[6 [C₁ H.
SO,NH,
COO
SO,NH,
insoluble
Cu +2 Cu 0] + 8 Na, SO, + 2 H₂ 0.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The herein described process for separating ortho-anhydro-sulphamine benzoic
acid (benzoic sulphinide) from para-sulphamine benzoic acid, by nixing the neutral
solution of salts of the mixture of acids with a soluble cupric salt thus causing the
ortho-compound to remain in solution while the para-compound is precipitated.
2. The modification of the process, above described by mixing the solution of the
salts of the ortho sulphamine benzoic and para sulphamine benzoic acids with a
quantity of a soluble cupric salt sufficient to precipitate the total acids and by treating
the separated mixture of the basic cupric salts, with a suitable quantity of sodium
carbonate or sodium hydroxide, thus causing the sodium salt of the ortho-sulphamine
benzoic acid to pass into solution, while the para-sulphamine benzoic acid remains as
copper salt.
3. The modification of the processes above described by mixing the neutral solution
of the salts of the mixed acids with a quantity of sodium hydroxide equivalent to the
mineral acids set free.
ABEL & IMRAY,
Agents for the Applicant.