Improvement in the Production of Pure Saccharine.
Year: 1891

page_text: Date of Application, 30th Dec., 1891
Complete Specification Left, 2nd Sept., 1892-Accepted, 8th Oct., 1892
PROVISIONAL SPECIFICATION.
Improvement in the Production of Pure Saccharine.
I, CONSTANTIN FAHLBERG, Doctor of Philosophy at Salbke near Magdeburg
in the Kingdom of Prussia German Empire Manufacturing Chemist, do hereby
declare the nature of this invention to be as follows:-
The crude saccharine produced according to the Specification of my British
Patent No. 6626 A.D. 1885, consists in a mixture of anhydro-orthosulphamine-
benzoic-acid (also called benzoic-acid-sulphinide) and parasulphamine-benzoic-acid
in the nearly constant proportion of 60 per cent. of the former and 40 per cent. of
the latter. The sweetening power of this mixture is about three-hundred times
as great as that of common sugar, while that of the pure anhydro-orthosulphamine-
benzoic-acid is still greater by about 40 per cent. The separation of the two acids
from each other has, however, heretofore presented considerable difficulties, because
the solubility of the acids themselves, as well as that of their salts, in water and
other solvents is nearly the same. The only available method of separating the
free acids has been that by means of sulphuric ether, but this method is expensive
and dangerous, and also imperfect, inasmuch as the purified saccharine produced
according to the same, still contains 10 per cent. and more of parasulphamine-
benzoic acid.
(For sake of simplicity of expression I shall, in the following part of this Speci-
fication, call the anhydro-orthosulphamine-benzoic-acid the "ortho-acid," and the
para-sulphamine-benzoic acid the "para-acid.")
The new method for attaining the said separation and whereby the inconveniencies
mentioned are obviated, is based on the property inherent to the two acids and
discovered by me, that the ortho-acid has greater affinity to alkalies and alkaline
earths than the para-acid. If therefore, to a solution of a mixture of the alkaline
salts of the two acids, an acid is added which is stronger than the para-acid, and
the quantity whereof is the chemical equivalent of the same, the acid that is
added will attack the para-salt only and combine with the alkaline base thereof,
while the para-acid is precipitated, the ortho-acid remaining unchanged in
solution.
If, on the other hand, a dry mixture of the ortho-acid and para-acid themselves
is introduced into an alkaline solution containing a quantity of alkali chemically
equivalent to the ortho-acid, the alkali will combine with the ortho-acid only to form
therewith the corresponding salt, which dissolves, while the para-acid remains
undissolved.
The acids to be employed according to the first mode of proceeding, may be
mineral acids, for instance hydrochloric and sulphuric acids, or organic acids such
as oxalic, tartaric, citric and acetic acids; but also the ortho-acid itself is available,
and even the mixture of ortho-acid and para-acid (or crude saccharine) may be
used. In the latter case the whole quantity of para-acid contained in the mixture
In the second mode of
of the salts and in the saccharine added, is separated out.
proceeding, caustic alkalies and alkaline earths and also the carbonates thereof may
be employed. As regards the quantity of acid or alkali, &c., to be added, it is
for practical reasons advantageous to take of either somewhat more than the exact
equivalent of the para-acid or the ortho-acid, as the case may be.
The solution of ortho-acid obtained by any one of the described methods of
operating, is filtered off from the para-acid, and the filtrate is acidulated by means
of a suitable acid with the effect of precipitating the ortho-acid or pure saccharine.
Dated the 30th day of December 1891.

page_text: COMPLETE SPECIFICATION.
Improvement in the Production of Pure Saccharine.
I, CONSTANTIN FAHLBERG, D.Ph., of Salbke near Magdeburg, Kingdom of
Prussia, Manufacturing 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 :-
The crude saccharine produced according to the Specification of my British
Patent No. 6626 A.D. 1885, consists in a mixture of anhydro-orthosulphamine-
benzoic-acid (also called benzoic-acid-sulphinide) and parasulphamine-benzoic-acid
in the nearly constant proportion of 60 per cent. of the former and 40 per cent.
of the latter. The sweetening power of this mixture is about three-hundred times
as great as that of common sugar, while that of the pure anhydro orthosulphamine-
benzoic-acid is still greater, by about 40 per cent. The separation of the two acids
from each other has, however, heretofore presented considerable difficulties, because
the solubility of the acids themselves, as well as that of their salts, in water and
other solvents is nearly the same. The only available method of separating the
free acids has been that by means of sulphuric ether, but this method is expensive
and dangerous, and also imperfect, inasmuch as the specified saccharine produced
according to the same, still contains 10 per cent. and more of parasulphamine-
benzoic acid.
For sake of simplicity of expression I shall, in the following part of this Speci-
fication, call the anhydro-orthosulphamine-benzoic-acid the "ortho-acid,” and the
parasulphamine-benzoic acid the "para-acid."
The new method for attaining the said separation and whereby the inconveniencies
mentioned are obviated, is based on the property inherent to the two acids and
discovered by me, that the ortho-acid has greater affinity to alkalies and alkaline
earths than the para-acid. If therefore, to a solution of a mixture of the alkaline
salts of the two acids, an acid is added which is stronger than the para-acid, and
the quantity whereof is the chemical equivalent of the same, the acid that is
added will attack the para-salt only and combine with the alkaline base thereof,
while the para-acid is precipitated, the ortho-acid remaining uncharged in
solution.
If, on the other hand, a dry mixture of the ortho-acid and para-acid themselves
is introduced into an alkaline solution containing a quantity of alkali chemically
equivalent to the ortho-acid, the alkali will combine with the ortho-acid, only to
form therewith the corresponding salt, which dissolves, while the para-acid remains
undissolved.
The acids to be employed according to the first mode of proceeding, may be
mineral acids, for instance hydrochloric and sulphuric acids, or organic acids such
as oxalic, tartaric, citric and acetic acids, but also the ortho-acid itself is available,
and even the mixture of ortho-acid and para-acid (or crude saccharine) may be
used. In the latter case the whole quantity of para-acid contained in the mixture
of the salts and in the saccharine added, is separated out. In the second mode of
proceeding, caustic alkalies and alkaline earths and also the carbonates thereof
may be employed. As regards the quantity of acid or alkali, &c., to be added,
it is for practical reasons advantageous to take of either somewhat more than the
exact equivalent of the para-acid or the ortho-acid, as the case may be.
The following are examples of the ways of carrying out the invention.
I take a cold, concentrated, nearly-saturated and neutral solution of the mixture
of the alkaline salts of ortho and para-acid, such as is obtained according to the
Specification of the aforesaid British Patent by neutralizing and evaporating down
the lyes of oxydation of toluol-sulphamide, and I add to the same a mineral acid
sufficient in quantity to separate out the para-acid. If, for instance hydrochloric
acid (HCl) is used, a suitable proportion thereof to the para-acid (C,H,O,SN)

page_text: is 40 parts by weight of the former to 200 parts of the latter. The liquid is heated
to about 100 degrees centigrade in order to promote the decomposition. When it
becomes cold again, nearly the whole amount of para-acid precipitates, while in
the solution there remains almost pure salt of ortho-acid together with the alkali-salt
of the acid added. This solution is then filtered off from the para-acid.
The process is the same if ortho-acid is used instead of the said mineral acid,
but the liquor remaining after the precipitation of the para-acid contains the
alkaline salt of the ortho-acid only. If the mixture of ortho and para-acids, or
crude saccharine, is employed, the operative agent will again be the ortho-acid,
while the para-acid added precipitates out together with the quantity of para-acid
obtained by decomposition from the para-salt.
If any mixture of the ortho and para-acids themselves, such as constitutes the
crude saccharine, is to be freed from the para-acid, the said mixture is brought in
solid state into a solution of an alkali, an alkaline earth, or a carbonate thereof,
containing a quantity of any of the said substances sufficient to neutralize and
dissolve the ortho acid present. Thus with caustic potash (KOH) about 55 parts
by weight thereof would have to be used to 185 parts by weight of the ortho-acid
(C,H,O,SN). Under these conditions the ortho-acid only is dissolved, while
the para-acid remains behind, so that it may again be separated from the former by
filtration.
For producing the ortho-acid from the filtrate obtained by any one of the
described modes of operating, the said filtrate is acidulated by means of a mineral
acid with the effect of precipitating the ortho-acid, or pure saccharine, which is
finally washed and, if desired, recrystallized, in order to be converted into a
marketable article.
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 process of separating out para-sulphamine-benzoic acid in solid state from a
mixture of the salts of anhydro-orthosulphamine-benzoic acid and parasulphamine-
benzoic acid, or from a mixture of the said acids themselves, which consists in treating
the dissolved mixture of the salts with an acid stronger than the para-sulphamine
benzoic acid, and the quantity whereof is only sufficient to separate the same from
its base, or in treating the mixture of the said acids in dry condition with a solution
of an alkali, an alkaline earth, or a carbonate of the alkalies or alkaline earths,
the quantity whereof is only sufficient to neutralize and dissolve the anhydro-
orthosulphamine-benzoic acid, and in filtering off the liquid from the parasulph-
amine-benzoic acid, which separates out in solid state or remains undissolved,
substantially as described.
Dated the 2nd day of September 1892.