Improvements in and relating to the Production of Potash from Potassium and Magnesium Carbonate.
Year: 1890

page_text: Date of Application, 22nd Mar., 1890
Complete Specification Left, 19th Dec., 1890-Accepted, 14th Feb., 1891
PROVISIONAL SPECIFICATION.
Improvements in and relating to the Production of Potash from
Potassium and Magnesium Carbonate.
I, HEINRICH PRECHT, of Lüderburg, near Stassfurt, in the Empire of Germany,
Doctor of Philosophy, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the production of potash from the double carbonate of
magnesium and potassium and it consists in decomposing the double salt by means
of water in a covered apparatus under a pressure of at least half an atmosphere and
a temperature above 115 degrees Centigrade which also causes a rapid and complete
decomposition of the bi-carbonates of potassium and magnesium which may have
become dissolved and the separation of the carbonate of magnesium in a condensed
state allowing the settlement to be easily separated from the liquid.
The carbonic acid set free is allowed to leave the decomposing vessel preferably
at a pressure higher than the expansive pressure of the steam from the potash
solution whereby obtain nearly pure carbonic acid with but little water in
admixture.
Dated the 22nd day of March 1890
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in and relating to the Production of Potash from
Potassium and Magnesium Carbonate.
1. HEINRICH PRECHT, of Lüderburg, near Stassfurt, in the Empire of Germany,
Doctor of Philosophy, 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:-
My invention relates to the production of potash (carbonate of potassium) and
other products from the double carbonate of magnesium and potassium.
The decomposition of the double salt of carbonate of magnesium-potassium KH CO³
Mg CO³ + 4 H2O for the production of potash (carbonate of potassium) can be
effected in various ways for instance by the following methods.
1. By heating the double salt in a muffle-furnace or flaming-kiln till all the
water and the greater part of the carbonic acid is driven off. The dry mass is then
treated either with cold or hot water.
2. By treating the double salt, without previously heating it, with warm or
boiling water whereby it is formed into insoluble carbonate of magnesium and
soluble carbonate of potassium (potash).
The first mentioned method which produces a pure and concentrated solution of
carbonate of potassium is very costly owing to the necessity of heating the double
salt and then macerating the dry mass. The second method produces a diluted
solution of potash (carbonate of potassium) which is mixed with bi-carbonate of
potassium as well as bi-carbonate of magnesium and is with difficulty separated
from the carbonate of magnesium.
The disadvantages of these two methods are obviated by the process forming the
subject of this invention which consists in decomposing the double salt by means of
water in a covered apparatus under a pressure of at least half an atmosphere and a
temperature above 115° C.

page_text: The res
1. A quick and complete decomposition of the double salt of carbonate of
magnesium-potassium and of the bi-carbonates of potassium and magnesium which at
the beginning of the decomposition may have become dissolved.
2. The separation of the carbonate of magnesium in a condensed state allowing
the settlement to be easily separated from the liquid.
The said reaction is effected during the decomposition at a temperature of about
10° C. above the boiling point of the so formed potash solution. It is advantageous
to use a higher temperature for the decomposition and I have found by experiment
that the most suitable temperature is that of 25 to 40° C. above the ordinary
boiling point of the solution."
The pressure should at least correspond to the expansive pressure of the steam
from the potash solution.
It is preferable to allow the carbonic acid set free during the decomposition of
the double salt to leave the decomposing vessel at a pressure higher than the
expansive pressure of the steam from the potash solution whereby obtain nearly
pure carbonic acid with but little water in admixture.
A suitable method of carrying out the invention and one which I have found to
answer well in practice is as follows:-
Heat is applied during the decomposition of the double salt at 140° C. and the
freed carbonic acid is allowed to leave the vessel by passing through a safety valve
at a pressure of five atmospheres above atmospheric pressure.
As the expansion of the steam from the pobash solution of 140° C. is about one
and a half atmospheres above atmospheric pressure the solution has not been heated
to its boiling point and consequently pure carbonic acid mixed with a little steam is
obtained.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed declare that what I
claim is:
(1.) A process for producing potash (carbonate of potassium) which consists in
decomposing the double salt of carbonate of magnesium-potassium by treating it
with water in a covered apparatus under a pressure of at least half an atmosphere
and a temperature of over 115° C., for the purpose of effecting the complete
decomposition of the bi-carbonates of potassium and magnesium which may have
become dissolved and of separating the carbonate of magnesium in a condensed
state, substantially as hereinbefore described.
(2.) The employment of the process referred to in Claim 1 for obtaining nearly
pure carbonic acid with but little water in admixture by allowing the carbonic acid
to escape from the decomposing vessel under a higher pressure than the expansive
pressure of the steam from the potash solution, the decomposing temperature of
which is above 115° C., substantially as hereinbefore described.
Dated the 19th day of December 1890.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.