Improvements in the Manufacture or Preparation of the Imide of Orthosulphobenzoic Acid.
Year: 1896

page_text: Date of Application, 28th Jan., 1896
Complete Specification Left, 13th Aug., 1896-Accepted, 26th Sept., 1896
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture or Preparation of the Imide of
Orthosulphobenzoic Acid.
I, GEORGE WILLIAM JOHNSON of 47 Lincoln's Inn Fields, in the County of
London Patent Agent (a communication from Chemische Fabrik vormals
Goldenberg, Geromont & Company of Winkel-on-the-Rhine Germany) do hereby
declare the nature of this invention to be as follows:-
A brownish red condensation product (which probably consists of azoxytolane-
disulphonic acid) arises from the action of concentrated caustic soda on paranitro-
toluene orthosulphonic acid. By reducing this product in alkaline solution with
zinc dust, F. Bender & G. Schultz (Reports of the German Chemical Society
1886 XIX 3234) have converted it into diamidostilbenedisulphonic acid.
This new disulphonic acid serves as the starting material for the preparation of
substantive azo-dyes German State Patent Nos. 38735 & 40575.
My foreign correspondents have discovered a new technical application of
diamidostilbenedisulphonic acid by using it as the starting material for the
preparation of the imide of orthosulphobenzoic acid the sweetening principle known
as saccharin.
According to Bender & Schultz (Reports of the German Chemical Society
1886 XIX 3236) on replacing the amido-groups of diamidostilbenedisulphonic
acid by hydrogen there is formed a stilbenedisulphonic acid which however has
not been submitted to closer investigation or description. In consideration of the
manner in which this stilbenedisulphonic acid is prepared, the sulpho-groups must
be in the ortho-position with regard to the carbon side-chain and it would therefore
appear suited to the manufacture of saccharin. This anticipation has been
completely fulfilled by experimental investigation since the diamide of this stilbene-
disulphonic acid may be easily and completely oxidised to pure saccharin by alkali
permanganate.
In the year one thousand eight hundred and sixty eight Limpricht and
Schwanert described a stilbenedisulphonic acid (Annals of Chemistry and Pharmacy
vol. 145 page 335) which they obtained by the action of concentrated sulphuric
acid on stilbene. A fuller investigation of the stilbenedisulphonic acid of
Limpricht and Schwanert has shown that this disulphonic acid is not a chemical
individual but consists of a mixture which probably contains the three isomeric
acids stilbene-ortho-ortho-disulphonic acid, stilbene-ortho-paradisulphonic acid
and stilbene-para-paradisulphonic acid of which the last named is in large
preponderance. By converting the stilbenedisulphonic acid of Limpricht aud
Schwanert into the disulphonamide and oxidising the latter with alkali perman-
ganate the chief product is parasulphonamidobenzoic acid together with an
extremely small quantity of saccharin. Under these circumstances the technical
application of the acid of Limpricht and Schwanert for the production of saccharin
must be regarded as entirely out of the question and especial emphasis is laid on
the fact that only the stilbeneorthodisulphonic acid obtained by Bender and Schultz
from diamido-stilbenedisulphonic acid can be used with advantage for the
preparation of saccharin.

page_text: A detailed description of the method of my foreign correspondents for the
preparation of saccharin is given below.
4 kilograms of paradihydrazidostilbene ortho-disulphonic acid (easily obtained
by known methods from diamidostilbenedisulphonic acid in the form of short
lustrous, brownish yellow needles, almost insoluble in water) is finely ground with
a small quantity of water and mixed in a suitable vessel with 5 kilograms of
crystallized copper sulphate dissolved in 50 litres of water, the liquid being boiled
until evolution of nitrogen ceases, metallic copper sinks to the bottom of the
vessel, and the clear, supernatant liquid consists solely of an aqueous solution of
stilbene-orthodisulphonic acid and sulphuric acid.
The reaction proceeds according to the equation
NH-NH,
CH-SO,H
H
CH-SOH
CH
+ 2CuSO,=
+ 2 N2+2 Cu + 2 H₂SO.
CH
CH
CH
C.H-SO,H
`NH – NH,
CH-SO,H
H
The liquid is decanted or filtered from copper and neutralised with milk of lime
which causes the separation of gypsum.
The solution of calcium stilbene-orthodisulphonate-after separating the
gypsum is evaporated to about 10 litres again separated from gypsum, and
treated with 11 kilogram of ammonia, soda, the calcium carbonate thus produced
is removed by filtration, and the solution of sodium salt evaporated to complete
dryness.
The dry, and very finely divided sodium salt of stilbene-ortho-disulphonic acid
obtained in this manner is stirred to a thin paste with phosphorus oxychloride
and treated with 4.2 kilograms of finely powdered phosphorus pentachloride which
is added gradually. The reaction begins at ordinary temperatures and is completed
on the application of heat. The phosphorus oxychloride produced in the reaction
is distilled off together with that which was added at first. There remains in the
distilling vessel, when cold, a pulverulent mixture of sodium chloride and stilbene
ortho-disulpho-chloride. The latter may be removed by ether, which, on
evaporation, deposits it in the crystalline form.
It is not necessary to the subsequent operations however, to remove the
disulpho chloride from the sodium chloride.
The residue in the distilling vessel is then gradually stirred into 6 kilograms
of 25 per cent. aqueous ammonia and by this means the stilbene-ortho-disulpho-
chloride is converted into stilbene-ortho-disulphonamide.
In order to separate and recover the excess of ammonia the liquid is reduced to
small bulk by distillation, when stilbene ortho disulphon amide crystallizes out in
aggregates of needles. The stilbene-ortho-disulphonamide is then washed with
water in order to free it from sodium chloride and ammonium chloride, and is
then dissolved in 22-4 kilograms of a cold, 5 per cent. solution of caustic potash.
To this liquid is added a solution of 4-3 kilograms of potassium permanganate iu
70 litres of water. The mixture being heated at 40-60° C., until the clear
liquid above the manganese peroxide assumes a yellow colour.
The solution is then filtered from the precipitate neutralized with hydrochloric

page_text: acid and evaporated to about 5 litres, again filtered and treated with concentrated
hydrochloric acid, which causes precipitation of the imide of orthosulphobenzoic
acid (saccharin) the product being then purified by recrystallization.
Dated this 28th day of January 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture or Preparation of the Imide of
Orthosulphobenzoic Acid.
1, GEORGE WILLIAM JOHNSON 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 Chemische Fabrik vormals
Goldenberg, Geromont, & Company of Winkel-on-the-Rhine, Germany) and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
on
A brownish-red condensation product (which probably consists of azoxytolane-
disulphonic acid) arises from the action of concentrated caustic soda
paranitrotoluene-ortho-sulphonic acid. By reducing this product in alkaline
solution with zinc dust, F. Bender and G. Schultz (Reports of the German
Chemical Society, 1886, XIX, 3234) have converted it into diamidostilbene-
disulphonic acid.
This new disulphonic acid serves as the starting material for the preparation of
substantive azo-dyes: German State Patent Nos. 38735, and 40575.
My foreign correspondents have discovered a new technical application of
diamidostilbenedisulphonic acid, by using it as the starting material for the
preparation of the imide of orthosul obenzoic acid the sweetening principle
known as saccharin.
According to Bender and Schultz (Reports of the German Chemical Society,
1886, XIX, 3236) on replacing the amido-groups of diamidostilbenedisulphonic
acid by hydrogen there is formed a stilbenedisulphonic acid which, however, has
not been submitted to closer investigation or description.
In consideration of the manner in which this stilbene-disulphonic acid is prepared,
the sulpho-groups must be in the ortho-position with regard to the carbon side-
chain, and it would therefore appear suited to the manufacture of saccharin. This
anticipation has been completely fulfilled by experimental investigation, since the
diamide of this stilbenedisulphonic acid may be easily and completely oxidised to
pure saccharin by alkali permanganate.
In the year 1868, Limpricht & Schwanert described a stilbenedisulphonic acid
(Annals of Chemistry and Pharmacy, vol. 145, page 335) which they obtained by
the action of concentrated sulphuric acid on stilbene. A fuller investigation of
the stilbenedisulphonic acid of Limpricht & Schwanert has shown that this
disulphonic acid is not a chemical individual, but consists of a mixture which
probably contains the three isomeric acids stilbene-ortho-disulphonic acid, stilbene-
ortho-paradisulphonic acid, and stilbene-para-paradisulphonic acid, of which the last
named is in large preponderance. By converting the stilbenedisulphonic acid of
Limpricht & Schwanert into the disulphonamide and oxidising the latter with alkali
permanganate, the chief product is parasulphonamidobenzoic acid, together with an
extremely small quantity of saccharin. Under these circumstances, the technical
application of the acid of Limpricht & Schwanert for the production of saccharin
must be regarded as entirely out of the question, and especial emphasis is laid on
the fact that only the stilbene-orthodisulphonic acid obtained by Bender & Schultz

page_text: from diamido-stilbenedi-sulphonic acid can be used with advantage for the
preparation of saccharin.
A detailed description of the method of my foreign correspondents for the
preparation of saccharin is given below.
4 kilograms of paradihydrazidostilbene-ortho-disulphonic acid (easily obtained
by known methods from diamidostilbenedisulphonic acid in the form of short,
lustrous, brownish-yellow needles, almost insoluble in water) is finely ground with
a small quantity of water and mixed in a suitable vessel with 5 kilograms of
crystallized copper sulphate dissolved in 50 litres of water, the liquid being boiled
until evolution of nitrogen ceases. Metallic copper sinks to the bottom of the
vessel, and the clear, supernatant liquid, consists solely of an aqueous solution of
stilbene-orthodisulphonic acid and sulphuric acid.
The reaction proceeds according to the equation
NH – NH,
CH-SO₂H
CH
H
CH 3-SOH
CH
11
+ 2 Cu SO₁ =
CH
CH, SO3H
NH.NH.
CH
+ 2 N, +2 Cu + 2 H₂SO.
CH-SO,H
H
The liquid is decanted or filtered from copper and neutralised with milk of lime,
which causes the separation of gypsum.
The solution of calcium stilbene-ortho-disulphonate, after separating the
gypsum, is evaporated to about 10 litres, again separated from gypsum, and
treated with 11 kilogram of ammonia-sode. The calcium carbonate thus
produced is removed by filtration, and the solution of sodium salt, evaporated to
complete dryness.
The dry, and very finely divided sodium salt of stilbene-orthodisulphonic acid
obtained in this manner is stirred to a thin paste with phosphorous oxychloride,
and treated with 42 kilograms of finely powdered phosphorus pentachloride,
which is added gradually. The reaction begins at ordinary temperatures, and is
completed on the application of heat. The phosphorus oxychloride produced in
the reaction is distilled off together with that which was added at first. There
remains in the distilling vessel, when cold, a pulverulent, mixture of sodium
chloride and stilbene-ortho-disulpho-chloride. The latter may be removed by
ether, which, on evaporation, deposits it in the crystalline form.
It is not necessary to the subsequent operations however, to remove the
disulphochloride from the sodium chloride.
The residue in the distilling vessel is then gradually stirred into 6 kilograms of
25 per cent. aqueous ammonia and by this means the stilbene-orthodisulphochloride
is converted into stilbene-orthodisulphonamide.
In order to separate and recover the excess of ammonia the liquid is reduced to
small bulk by distillation, when stilbene-orthodisulphonamide crystallizes out in
aggregates of needles. The stilbene-orthodisulphonamide is then washed with
water in order to free it from sodium chloride and ammonium chloride, and is then
dissolved in 22-4 kilograms of a cold, 5 per cent. solution of caustic potash. To
this liquid is added a solution of 4-3 kilograms of potassium permanganate in
70 litres of water, the mixture being heated at 40-60° C., until the clear liquid
above the manganese peroxide assumes a yellow colour.

page_text: The solution is then filtered from the precipitate, neutralised with hydrochloric
acid, and evaporated to about 5 litres, again filtered, and treated with concentrated
hydrochloric acid, which causes precipitation of the imide of orthosulphobenzoic
acid (saccharin), the product being then purified by recrystallization.
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:
The manufacture or preparation of the imide of orthosulphobenzoic acid,.
(saccharin) by converting stilbene-orthodisulphonic acid obtained from para-
diamidostilbene-orthodisulphonic acid, into stilbene-orthodisulphochloride by the
action of phosphorous pentachloride, transforming the stilbene-orthodisulphochloride
by means of ammonia or ammonium carbonate into stilbene-orthodisulphonamide
and oxidizing the latter with alkali permanganate.
Dated this 12th day of August 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.