A New Improved Process for the Manufacture of Anhydro-ortho- sulphamine Benzoic Acid (Orthobenzoic Sulphinide) or of its Salts from Commercial Saccharin.
Year: 1893

page_text: Date of Application, 10th Nov., 1893
Complete Specification Left, 24th May, 1894-Accepted, 16th June, 1894
PROVISIONAL SPECIFICATION.
A New Improved Process for the Manufacture of Anhydro-ortho-
sulphamine Benzoic Acid (Orthobenzoic Sulphinide) or of its
Salts from Commercial Saccharin.
I, ARTHUR ROBERT LING of 45 Lambton Road, Cottenham Park, Wimbledon,
in the County of Surrey, Analytical Chemist, Fellow of the Institute of Chemistry
of Great Britain and Ireland do hereby declare the nature of this invention to be
as follows:-
Commercial saccharin which consists of a mixture of anhydro-orthosulphamine
benzoic acid (also called orthobenzoic sulphinide) and parasulphamine benzoic acid,
is treated with either a hot or cold solution containing the requisite amount or an
excess thereof, of any one of certain neutral salts which the said anhydro-ortho-
sulphamine benzoic acid is capable of decomposing, and among which may be
mentioned alkali acetates, and alkali salts of parsulphamine benzoic acid. Under
these circumstances, the anhydro-orthosulphamine benzoic acid decomposes the
neutral salt, combining with the alkali base thereof, and passes into solution as
soluble salt, leaving the parasulphamine benzoic acid unaltered and undissolved.
The last named acid may then be filtered off, washed and pressed, the filtrate and
washings being a solution of pure alkali salt of anhydro-orthosulphamine benzoic
acid, together with an equivalent quantity of the acid originally combined with the
said neutral salt. The anhydro-orthosulphamine benzoic acid may be isolated from
this solution in any appropriate manner, and when the acid, originally in combina-
tion with the said neutral salt, is volatile, it may be recovered by distillation.
For the sake of brevity anhydro-orthosulphamine benzoic acid will hereinafter
be referred to as the "ortho-acid," and parasulphamine benzoic acid as the "para
acid."
"
ortho
In the process thus briefly described, it is preferable to employ approximately
the exact amount of neutral salt i.e. the amount necessary to convert the
acid" into soluble salt. But this is not essential, and an excess of the neutral salt
may be employed, the fact on which my invention rests being that whereas the
"ortho-acid is a strong acid, capable of decomposing in aqueous solution alkali
acetates, oxalates, tartrates, citrates &c. .or the alkali salts of the "para acid,"
the "
para acid
is quite indifferent towards them and remains undissolved.
As previously stated, however, it is preferable to use the exact proportion of any
one of the salts. It is therefore desirable to ascertain the percentage of the two
proximate constituents in the sample by a preliminary test experiment:-The
sample is treated with a solution of say sodium acetate in excess, and the
undissolved 66 para-acid collected on a filter, washed, dried, and its weight
determined as in ordinary methods of gravimetric analysis. The percentage of
"ortho-acid " may then be calculated by difference.
.
دو
I may here cite the following example of the manner in which the process may
be carried out with ordinary 60 per cent. saccharin of commerce and sodium
acetate, but I do not limit myself to exact proportions or to the use of the salt
just named-10 kilogrms. of commercial 60 per cent. saccharin are treated with
either a hot or cold solution containing 5 kilogrms. of crystallised commercial
sodium acetate, dissolved in 50 kilogrms. of water. If the experiment be conducted
at the ordinary temperature, it is advisable to allow the mixture to remain for one
or two hours, and if the mixture be heated, it is allowed to cool; in either case
the cold liquid is filtered from the undissolved "para-acid" which latter is pressed
and washed until the washings are no longer sweet to the taste. The filtrate
a

page_text: solution of the pure sodium salt of the ortho acid together with an
equivalent
quantity of acetic acid. The "ortho acid " may be isolated from this solution in
any appropriate or convenient way, but it will generally be necessary, as a pre-
liminary step in the operation, to concentrate the solution.. This may be accomplished
in a distilling apparatus, so that when acetates or salts of volatile acids have been
made use of in the process, these acids may be condensed and recovered.
I am aware that a process has been patented by C. Fahlberg, British Patent
No. 22,787 of 1891 for purifying commercial saccharin, which consists; 1) in
treating commercial saccharin salt (soluble saccharin) in aqueous solution with an
acid stronger than the "para-acid" and in amount sufficient only to decompose the
salt of this acid; and 2) in treating dry commercial saccharin with a solution of
alkali or alkaline earth, the quantity whereof is only sufficient to neutralise and
dissolve the "ortho-acid." I would point out, however, that this process pre-
supposes a knowledge of the relative amounts of "ortho- and para-acid" present in
the sample. For, if, in the acid treatment, the exact proportions of acid be not
rigidly adhered to, but excess used, the ortho acid may be precipitated together
with the "para acid," when the acid used is also stronger than the "ortho acid ";
the same argument applies to the alkaline treatment, and if an excess of alkali be
used, the "para acid "will be dissolved along with the "ortho acid." To obviate
these, the patentee limits himself to exact proportions of acid and alkali.
Now, in my process, a solution containing excess of a neutral salt which is
decomposable by the "ortho acid " may be used, and the resulting solution of the
pure salt of the "ortho acid" is only vitiated by the presence of the excess of this
neutral salt; the presence of the latter may be altogether avoided by previously
ascertaining the requisite amount of neutral salt necessary by means of a preliminary
test experiment, as I have indicated. I contend therefore that my process is by
far the simpler one, since by its means, a solution of pure salt of the ortho acid is
obtained in one operation. Furthermore, the process is not limited to 60 per cent.
saccharin, but may be employed for refining saccharin containing any proportion of
" ortho acid."
•
Dated 10th day of November 1893.
ARTHUR R. LING.
COMPLETE SPECIFICATION.
A. New Improved Process for the Manufacture of Anhydro-ortho-
sulphamine Benzoic Acid (Orthobenzoic Sulphinide) or of its
Salts from Commercial Saccharin.
I, ARTHUR ROBERT LING of 45 Lambton Road Cottenham Park, Wimbledon,
in the County of Surrey, Analytical Chemist, Fellow of the Institute of Chemistry
of Great Britain and Ireland 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 :-
Commercial saccharin which consists of a mixture of anhydro orthosulphamine
benzoic acid (also called orthobenzoic sulphinide) and parasulphamine benzoic
acid is treated with either a hot or cold solution containing the requisite amount
or an excess thereof of any one of certain neutral salts among which may be
mentioned acetates of the alkali metals. Under these circumstances the anhydro-
orthosulphamine benzoic acid decomposes the said neutral salt combining with the
alkali base thereof and passes into solution as soluble salt leaving the para
sulphamine benzoic acid unaltered and undissolved. The last-named acid may
then be filtered off, washed and pressed, the filtrate and washings being a solution
of pure alkali salt of anhydro-orthosulphamine benzoic acid together with an equi-
valent quantity of the acid originally combined with the said neutral salt. The

page_text: anhydro-orthosulphamine benzoic acid may be isolated from the solution in any
appropriate manner, and when the acid separated from the neutral salt is volatile it
may be recovered by distillation.
For the sake of brevity anhydro-orthosulphamine benzoic acid will hereinafter be
spoken of as the "ortho acid " and parasulphamine benzoic acid as the "para acid."
In the process thus briefly described it is preferable to employ approximately the
exact amount of neutral salt, that is the amount necessary to convert the "ortho-
acid" into soluble salt. But this is not essential, and an excess of the neutral
salt may be employed, the fact on which my invention rests being that, whereas the
"ortho acid" is a strong acid, capable of decomposing in aqueous solution, alkali
acetates, oxalates, tartrates, citrates &c., or the alkali salts of the "para acid," the
para acid is quite indifferent towards them, and remains undissolved.
As previously stated, however, it is preferable to use the exact proportion
needful of any one of the salts. It is therefore desirable to ascertain the percentage
of the proximate constituents by a preliminary test experiment :-The sample is
treated with a solution of say sodium acetate in excess, and the undissolved ". para
acid" collected on a filter, dried, and its weight determined as in ordinary methods.
of gravimetric analysis. The percentage of "ortho acid " may then be calculated
by difference.
I may here cite the following example of the manner in which the process may
be carried out with ordinary 60 per cent. saccharin of commerce and sodium acetate,
but I do not limit myself to exact proportions:-10 kilogrammes of commercial
60 per cent. saccharin are treated with either a hot or cold solution of 5 kilogrammes
of crystallised commercial sodium acetate, dissolved in 50 kilogrammes of water.
If the experiment be conducted at the ordinary temperature it is advisable to allow
the mixture to remain for one or two hours, and if the mixture be heated it is
allowed to cool; in either case the cold liquid is filtered from the undissolved
para acid" which latter is pressed and washed with cold water until the washings
are no longer sweet to the taste. The filtrate is a solution of the pure sodium salt of
the "ortho acid" together with an equivalent quantity of acetic acid. The "ortho
acid" may be isolated from this solution in any appropriate or convenient way, but
it will generally be necessary as a preliminary step in the operation to concentrate
the solution. This may be accomplished in a distilling apparatus, so that when
acetates or salts of volatile acids have been made use of in the process, the acids may
be condensed and recovered.
66
I am aware that a process has been patented by C. Fahlberg British Patent
No. 22,787 of 1891 for purifying commercial saccharin, which consists, 1) in treating
commercial saccharin salt (soluble saccharin) in aqueous solution with an acid
stronger than the "para acid" and in amount sufficient only to decompose the salt
of this acid; and 2) in treating dry commercial saccharin with a solution of alkali
or alkaline earth, the quantity whereof is only sufficient to neutralise and dissolve
the ortho-acid. I would point out, however, that this process presupposes a
knowledge of the relative amounts of ortho and para acid present in the sample.
For if in the acid treatment the exact proportions of acid be not rigidly adhered to
but an excess used the "ortho-acid" will be precipitated along with the "para
acid "at least this will be the case when the acid employed is stronger also than
the "ortho acid." The same applies to the alkaline treatinent, and if an excess of
alkali be used not only will the para acid be dissolved but likewise the "ortho
acid." To obviate this the Patentee limits himself to exact proportions of acid and
alkali. Now in my process, an excess of a solution of a neutral salt which is
decomposable by the ortho acid may be used and the resulting solution of the salt
of the "ortho acid" is only vitiated by the presence of the excess of this neutral
salt;
the presence of the latter may be altogether avoided by previously ascertaining
the requisite amount of neutral salt necessary by means of a preliminary test as
have indicated. I contend therefore that my process is by far the simpler one
since by its means a solution of the salt of the pure "ortho-acid" is obtained in
one operation. Furthermore the process is not limited to 60 per cent. saccharin,

page_text: but may be employed for refining saccharin containing any proportion of "ortho
acid."
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 process of purifying commercial saccharin consisting in separating from it
parasulphamine benzoic acid by treatment with a solution of a neutral salt such that
the other constituent of commercial saccharin, which it is desired to isolate in the
pure state, rianhydro-orthosulphamine benzoic acid, is capable of decomposing
and of combining with the base thereof, the amount of neutral salt being preferably,
but not of necessity, employed in quantity equivalent to the amount of anhydro-
orthosulphamine benzoic acid present in the sample, removing the unaltered,
undissolved para sulphamine benzoic acid by filtration, pressing the latter and
washing it until the washings are no longer sweet to the taste, and isolating the
anhydro-orthosulphamine benzoic acid from the filtrate in which it occurs as soluble
salt either as such or otherwise in any convenient way, substantially as described.
II. In the process described in the first claim, when the neutral salt of a volatile
acid is used, and evaporation of the solution of the salt of anhydro-orthosulphamine
benzoic acid, obtained in the process, is resorted to as a preliminary step in the
isolation of pure anhydro-orthosulphamine benzoic acid, of recovering the said volatile
acid which is present in the solution in amount equivalent to that of the anhydro-
orthosulphamine benzoic salt, by distillation, substantially as described.
Dated this 24th day of May 1894.