Improvements in the Manufacture of Potassium Carbonate.
Year: 1891

page_text: Date of Application, 22nd June, 1891
Complete Specification Left, 21st Mar., 1892-4ccepted, 23rd Apr., 1892
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Potassium Carbonate.
I, AUGUST DUPRE Ph.D., F.R.S., F.C.S., of The Westminster Hospital
Medical School, in the County of Middlesex, (a communication to me from abroad
by Frederick Dupré, of Stassfurt, in the Empire of Germany,) do hereby declare
the nature of this invention to be as follows:-
I obtain potassium carbonate (acid or neutral) by acting on potassium sulphate
with sodium carbonate (acid or neutral) in the presence of water and regenerate
from the potassium and sodium sulphate thereby formed the pure potassium sulphate
by the action on it of a solution of potassium chloride.
The process may be conducted as follows:-
163 parts of water together with 53 parts of carbonate of sodium and 42 parts of
bicarbonate of sodium are put into a pan or boiler which can be heated by steam
and is provided with an effective stirrer. The temperature is raised to about 40° C.
after which 50 parts of sulphate of potassium are introduced, under constant stirring
and similar amounts are added at intervals of of an hour until from 6 to 8 such.
quantities have been used, the temperature having gradually been raised to 70
or 75° C. care being taken not to expel any carbon dioxide. The stirring is
continued for about 1 hour after the last addition of sulphate when the contents of
the pan are put upon a vacuum filter and rapidly drained. The filtrate, on cooling,
deposits some potassium sulphate and sodium bicarbonate which may be used for
subsequent operations, leaving a solution of nearly pure potassium carbonate which
can be obtained from it by evaporation. If more than the proportion of sodium
bicarbonate given above is employed some potassium bicarbonate is also deposited
during the cooling of the filtrate.
REGENERATION OF POTASSIUM SULPHATE.
The potassium sodium sulphate on the vacuum filter is, in the first place, washed
with successive small portions of water until, in all, about 160 parts have been so
used. This wash water is used for dissolving the carbonate of sodium in subsequent
operations. The remaining double sulphate, almost free from carbonates, is now
boiled with about 400 parts of water, sufficient only to dissolve about one half of the
salt, aud the solution is strained off from the undissolved portion. To the hot
solution potassium chloride is added in quantity equivalent to half the amount of
potassium carbonate obtained. Potassium sulphate begins to separate at once.
The mixture is allowed to cool the liquid strained from the crystals and once more
heated to boiling with the double sulphate left undissolved from the first operation
any portion of the salts which remains undissolved consists of potassium sulphate
and need not he separated. A second portion of potassium chloride is added to the
hot solution when, on cooling, a further crop of potassium sulphate is obtained.
The mother liquor from this may be concentrated by evaporation when a further
crop of salt is obtained which may be added to the double sulphate in any
subsequent regeneration. The final mother liquor now contains little else but sodium
chloride.
Dated this 22nd day of June 1891.
CARPMAEL & Co.,
Agents for the Applicant.,

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Potassium Carbonate.
I, AUGUST DUPRÉ, Ph.D., F.R.S., F.C.S., of The Westminster Hospital
Medical School, in the County of Middlesex, (a communication to me from abroad
by Frederick Dupré, of Stassfurt, in the Empire of Germany,) 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:-
I obtain potassium carbonate (acid or neutral) by acting on potassium sulphate
with sodium carbonate (acid or neutral) in the presence of water and regenerate
from the potassium and sodium sulphate thereby formed the potassium sulphate by
the action on it of a solution of potassium chloride.
The process may be conducted as follows:-
163 parts of water together with 53 parts of carbonate of sodium and 42 parts of
bicarbonate of sodium are put into a pan or boiler which can be heated by steam
and is provided with an effective stirrer. The temperature is raised to about 40° C.
after which 50 parts of sulphate of potassium are introduced under constant stirring
and similar amounts are added at intervals of of an hour until from 6 to 8 such
quantities have been used, the temperature having gradually been raised to 70
or 75° C. care being taken not to expel any carbon dioxide. The stirring is
continued for about 1 hour after the last addition of sulphate when the contents of
the pan are put upon a vacuum filter and rapidly drained. The filtrate, on cooling,
deposits some potassium sulphate and more sodium bicarbonate which may be used
for subsequent operations, leaving a solution of nearly pure potassium carbonate
which can be obtained from it by evaporation. If more than the proportion of
sodium bicarbonate given above is employed some potassium bicarbonate is also
deposited during the cooling of the filtrate."
Instead of using a solution containing both carbonate and. bicarbonate of sodium
a solution of carbonate of sodium only may be treated in the way described. The
solution of potassium carbonate so obtained is less pure, contains more sodium
carbonate (in the form of potassium sodium carbonate) than the liquor obtained by
using both sodium carbonate and bicarbonate. During the evaporation of the
liquor or by freezing the liquor this excess of sodium carbonate separates out.
A stirring apparatus or a so called Shank's battery may be used by working with
a solution of sodium carbonate only.
REGENERATION OF POTASSIUM SULPHATE.
The potassium sodium sulphate on the vacuum filter (or in Shank's apparatus) is,
in, the first place, washed with successive small quantities of water to free it entirely
of all and any of the mother liquor of the carbonate. This wash water is used for
dissolving the carbonate of sodium in subsequent operations. The washed sulphate
is now treated, direct on the vacuum filter or in Shank's apparatus or in a stirring
apparatus, with a cold solution of potassium chloride of about 26° Twaddle 19.15%
KCl and in quantity sufficient to contain somewhat more potassium chloride than
is, required for the conversion into potassium sulphate of the sodium sulphate
contained in the potassium sodium sulphate under operation. The pure potassium
sulphate thus obtained is washed with water, the water washings being used for
preparing the solution of potassium chloride for a subsequent operation..
The liquor separated from the potassium sulphate on evaporation to about to
its original bulk deposits some potassium sodium sulphate and some more on cooling
as well as some potassium chloride, these salts are added to a subsequent operation
of regeneration of potassium sulphate. The cold liquor contains little else but
sodium chloride.

page_text: 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 process for the production of potassium carbonate consisting in :-
a-The decomposition of potassium sulphate with sodium carbonate; acid or
neutral.
The separation of the resulting potassium carbonate acid or neutral and
potassium sodium sulphate.
The conversion by the addition of potassium chloride of the potassium sodium
sulphate into potassium sulphate wherewith the process may be recommenced.
2. The manufacture of potassium carbonate acid or neutral substantially in the
manner herein described.
Dated his olda
1040
A. DUPRÉ.