IMPROVEMENTS IN OBTAINING SULPHATES AND CARBONATES OF POTASH AND SODA
Year: 1865

page_text: LETTERS PATENT to Charles Frederick Claus, of Fearnhead, near
Warrington, in the County of Lancaster, Chemist, for the Invention
of "IMPROVEMENTS IN OBTAINING SULPHATES AND CARBONATES OF POTASH
AND SODA."
Sealed the 20th October 1865, and dated the 6th July 1865.
PROVISIONAL SPECIFICATION left by the said Charles Frederick Claus
at the Office of the Commissioners of Patents, with his Petition, on the
6th July 1865.
I, CHARLES FREDERICK CLAUS, of Fearnhead, near Warrington, in the
County of Lancaster, Chemist, do hereby declare tho nature of the said
Invention for "IMPROVEMENTS IN OBTAINING SULPHATES AND CARBONATES OF
POTASH AND SODA," to be as follows:-
Heretofore the only commercial source of sulphates and carbonates of
potash has been the ashes of vegetables and the crude potash derived
therefrom, for the supply of which English commerce is almost entirely
dependent upon America. Any process, therefore, which opens out the
manufacture of pearlash from less exhaustible sources is of importance.
This is the object of my Invention:-I take the rock salt of Strassfurt, in
Prussia, or similar rock salt containing a large per-centage of chloride of

page_text: potassium, or it may be the refined salt, in which the per-centage of chloride
of potassium has been increased by crystallization. I convert these mixed
chlorides into sulphates, and then separate the sulphates the one from the
other by washing, as herein-after described. In case the native rock salt is
used I grind the same into coarse powder, and decompose it with its equivalent
of sulphuric acid in the way in which it is done with common salt in the
manufacture of alkali; in case the refined salt is used I decompose the same
without previous grinding. The mixed sulphates (which I prefer to grind) I
treat repeatedly with water, by preference at a temperature of about 90° or 100°
Fahrenheit, at which temperature the water will dissolve out the maximum
of sulphate of soda, whilst but little of the sulphate of potash will be dissolved,
or if any be dissolved I allow the same to crystallize out of the solution of
sulphate of soda. The solution of sulphate of soda being very concentrated
requires very little boiling down to convert the same into dry sulphate. When
dry I (if required) convert the sulphate into carbonate by the process
generally known, and which is no part of my Invention. The sulphate of
potash when freed from all salts of soda by repeated washings with water (as it
can be almost perfectly), I, if required, convert into carbonate of potash by a
process analogous to the well-known alkali process (Le Blanc's). The crude
carbonate of potash thus obtained I lixiviate and carbonate and boil down
the solution, and afterwards calcine the residue. The product of this operation
may then be further refined in the manner now practised in the manufacture
of refined pearlash or the production of pearlash from the sulphate of potash
may be otherwise effected.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Frederick Claus, in the Great Seal Patent Office
on the 6th January 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
FREDERICK CLAUS, of Fearnhead, near Warrington, in the County of Lancaster,
Chemist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Sixth day of July, in the year of our Lord
One thousand eight hundred and sixty-five, in the twenty-ninth year of Her
reign did, for Herself, Her heirs and successors, give and grant unto me, the
said Charles Frederick Claus, Her special licence that I, the said Charles
Frederick Claus, my executors, administrators, and assigns, or such others as

page_text: I, the said Charles Frederick Claus, my executors, administrators, and assigns,
should at any time agree with, and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN OBTAINING SULPHATES AND CARBONATES OF POTASH AND SODA,"
upon the condition (amongst others) that I, the said Charles Frederick Claus,
my executors or administrators, by an instrument in writing under my, or their,
or one of their hands and seals, should particularly describe and ascertain
the nature of the said Invention, and in what manner the same was to be
performed, and cause the same to be filed in the Great Seal Patent Office
within six calendar months next and immediately after the date of the
said Letters Patent.
.
NOW KNOW YE, that I, the said Charles Frederick Claus, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say :-
Heretofore the only commercial source of sulphates and carbonates of
potash has been the ashes of vegetables and the crude potash derived
therefrom, for the supply of which English commerce is almost entirely
dependent upon America. Any process, therefore, which opens out the
manufacture of pearlash from less exhaustible sources is of importance.
This is the object of my Invention:-I take the rock salt of Stassfurt, in
Prussia, or similar rock salt containing a large per-centage of chloride of
potassium, or it may be the refined salt in which the per-centage of chloride of
potassium has been increased by crystallization. I convert these mixed
chlorides into sulphates, and then separate the sulphates the one from the other
by washing or bringing the sulphate of soda into a state of solution, whilst
the sulphate of potash is left solid, as herein-after described. In carrying
out my Invention I mix with about a ton of the salt (which I will
suppose now to be the refined salt), its equivalent of sulphuric acid or by
preference rather more than its equivalent, viz., 9 cwt. of sulphuric acid 'of
140° Twaddle in the apparatus known to alkali makers as a decomposing pot
or furnace; and I decompose the same by the application of heat in a similar
manner to that practised in the manufacture of soda from common salt, the
beat should, however, be somewhat greater. When the decomposition is
carried as far as it is practicable in the decomposing furnace, the mixture now
partly converted into sulphate of soda and potash is transferred into the
roasting furnace, where also a greater heat should be applied than is usual

page_text: in the manufacture of soda from common. salt. The heat should in fact be
carried to cherry red heat. Where the quality of the fuel and the construction
of the roaster will not admit of the application of such a heat it is desirable
to add to the usual roaster a small reverberatory furnace. One similar to an
"ash finishing furnace" will answer the purpose, and the waste heat from
it may be applied to the working of the ordinary roaster. The operation of
roasting may be considered complete when from the hot charge of the roasting
furnace fumes of muriatic acid cease to be emitted; this can be ascertained by
withdrawing a shovel full of the sulphates, and if the sample be found to be
odourless, the operation of roasting is complete. Upon the proper per-
formance of the operation of roasting rests the success of the subsequent
separation of the sulphates of potash and soda. The more incomplete the
roasting the more incomplete and difficult will be the separation of the
sulphates. This separation of the mixed sulphates can be effected con-
veniently either by completely dissolving them both together, and boiling down
the solution until the sulphate of potash is deposited, leaving the sulphate of
soda in solution, or by grinding the mixed salts into a fine powder, and adding
water to the powder to dissolve out the sulphate of soda, and leave the
sulphate of potash undissolved.
The
If the former course be pursued the mode of operating is as follows:-
The roasted sulphates are put into an iron pan and covered with water;
steam is turned on, and the water kept boiling for about an hour.
clear liquid is then drawn off and a fresh quantity of water is added and boiled
again; this is repeated until the whole of the salt is dissolved. The clear
solution obtained in this way is then run into an iron boiling-down pan in
which it is evaporated. This pan should either be heated by "dry steam" or
with a fire playing over the surface of the liquid, the bottom not being
exposed to the heat; and the evaporation should be carried on with as low a
temperature as possible to prevent a violent ebullition of the liquid. The
object of ovaporating without violent ebullition is to obtain well-formed and
large crystals of sulphate of potash rather than a crystalline powder. By
obtaining good-sized crystals, the separation from the mother-liquor is greatly
facilitated. The sulphate of potash deposited from the liquid in the pan is
fished out and separated whilst still hot from the adhering liquid by means of
a centrifugal machine. The mother-liquor is returned to the liquid in the
pan, and the whole is boiled down to a density of about 50° to 55° Twaddle
when it ceases to deposit any more crystals of sulphate of potash. The crystals
taken out of the centrifugal machine are macerated in water of about 90°
Fahrenheit, and dried again in the centrifugal machine; the wash water in

page_text: this case is used for dissolving a further quantity of mixed súlpbates. The
evaporation of the liquid in the boiling-down pan may. be either carried on in
this pan in one operation, as described above, or it may be interrupted, and
the partly evaporated liquid may be run into coolers. In these the liquid is
allowed to cool down to 90° or 100° Fahrenheit, when good-sized sulphate of
potash crystals will be deposited. The temperature of the liquid should not
be allowed to fall lower than 90° Fahrenheit, as otherwise sulphate of soda
would also crystallize out. The mother-liquor is now returned to the boiling-
down.pan and further evaporated until it begins again to form crystals on the
surface, when it is again run into coolers and allowed to cool down to about
90° Fahrenheit; another quantity of sulphate of potash being deposited, the
mother-liquor from these is returned again to the boiling-down pan, and this
is repeated until the mother-liquor assumes: a density of from 50° to 55°
Twaddle, when it will be found to contain little or no sulphate of potash.
The crystals of sulphate of potash are freed from the adhering mother-liquor
in the centrifugal machine, and (whether obtained by this or the former
plan) they are dried on a kiln. The mother-liquors (obtained by this or
the former plan) are boiled down to dryness, and may be used for the manu-
facture of soda or otherwise. If the other method mentioned above of
separating the mixed sulphates be adopted the mixed salt should first be
ground into a fine powder and sifted so as to have no lumps larger than a
grain of fine sand left in it. A pan supplied with a slowly rotating mechanical
agitator worked by an engine is now half filled with the same, and water
heated to 90° or 100° Fabreubeit is run on to it in quantity equal to the
weight of the sulphate of soda contained in the mixed sulphates; the agitator
is set in motion, and the powdered sulphates are washed by the water which
dissolves away from the sulphate of potash the greater portion of the sulphate
of soda. This solution is drawn off so soon as after repeated agitation the
strength of the same does not increase any further. Another quantity of
water is then poured on to the sulphate; it is again heated to 90° Fahrenheit,
the agitation is repeated, and when the wash water will no longer increase in
strength it also is run off. This operation is repeated so long as the wash
water attains a strength of more than 32° Twaddle. All the wash waters of
a strength of more than 45° Twaddle are boiled down, and treated as the
liquor in the other method already described; the weaker liquors are used
for washing the next quantity of mixed sulphates instead of water. The
undissolved sulphate of potash after being dried with a centrifugal machine
and on a kiln as before, will be ready for the further operations of manufac-
turing the same into carbonate. These operations are quite similar to those

page_text: called Leblanc's alkali process from common salt; they are well known,
and form no part of my Invention, and need not therefore be described.
When the native rock salt is used instead of the refined salt all the operations
are the same as in the process described, excepting that the rock salt will
have to be ground previous to decomposing it with sulphuric acid; and it
may be observed that although the native rock contains some chloride of
magnesium no sulphuric acid need be allowed in the calculation for the
decomposition of it, as in roasting the sulphates the sulphate of magnesia will
yield up its sulphuric acid for the decomposition of chloride of sodium or
potassium.
I claim as my Invention in the manufacture of sulphates of potash and
soda the separation of sulphate of potash from sulphate of soda (after the
said mixed sulphates have been obtained from mixed chlorides by the decom-
position thereof with sulphuric acid) by treating these mixed sulphates with
water so as to bring the sulphate of soda into a state of solution whilst the
sulphate of potash is in a solid state.
In witness whereof, I, the said Charles Frederick Claus, have hereunto set
my hand and seal, this Fifth day of January, in the year of our
Lord One thousand eight hundred and sixty-six.
C. F. CLAUS.
(L.S.)