A NEW METHOD OF MANUFACTURING MAGNESIA AND SULPHATE OF POTASSIUM OR OF SODIUM
Year: 1881

page_text: LETTERS PATENT to Carl Pieper, Civil Engineer and Patent Agent, of
109-110, Gneisenaustrasse, Berlin, S.W., Prussia, for an Invention of "A
NEW METHOD OF MANUFACTURING MAGNESIA AND SULPHATE OF POTASSIUM
OR OF SODIUM." A communication from Max Sprenger, Doctor of Philosophy
of Berlin, Prussia.
COMPLETE SPECIFICATION filed by the said Carl Pieper at the Office of the
Commissioners of Patents on the 19th February 1881.
56
CARL PIEPER, Civil Engineer and Patent Agent, of 109-110, Gneisenaustrasse,
Berlin, S.W., Prussia. A NEW METHOD OF MANUFACTURING MAGNESIA AND
SULPHATE OF POTASSIUM OR OF SODIUM." A communication from Max Sprenger,
Doctor of Philosophy, of Berlin, Prussia.
This Invention relates to a new method of manufacturing magnesia and sulphate
of potassium or of sodium from certain materials consisting of or containing, for
one part, sulphate of magnesium, and for the other part chloride of potassium or
of sodium, the process consisting in mixing in the requisite proportions the
pulverized materials, in heating the mixture, and in exposing it at the same time to
the action of steam.
The materials which the inventor uses for his process are, for one part, kiserite
(Mg SO. + H. O), schoenite (Mg SO. + к₂ SO₁ + 6 H, O), or kainite
(Mg SO, + K. Cl + 3 H, O); and, for the other part, chloride of potassium
(K Cl), chloride of sodium (Na Cl), and carnallite (K Cl + Mg Cl₂ + 6 H₂ O).
The process constituting the Invention in its simplest form is carried out as
follows:-
A mixture of one chemical equivalent of sulphate of magnesium (Mg SO₁), and
of two equivalents of chloride of sodium (Na Cl) is heated to a dark red heat,
while at the same time steam, which may be mixed with air, is conducted over the
same. An interchange of the components of the said substances thereby takes
place, muriatic acid being evolved, while a mixture of magnesia (Mg O) with
sulphate of sodium (Na, SO) is obtained as solid product, from which the said
sulphate may easily be extracted by hot water, so that magnesia remains as residue.
It may be presumed on the base of a chemical hypothesis that by the process first
ID

page_text: of all sulphate of sodium and chloride of magnesium are formed, and that the
latter salt is at the moment of its formation decomposed by the steam.
Expressed in chemical formulae, the process will be thus:-
Mg SO +2 Na Cl + H, O
-
Mg O+ Na, SO, + 2 H Cl. Instead of chloride
of sodium, chloride of potassium may be used, without in other respects altering
the process.
The final products are in this case magnesia and sulphate of
potassium.
The process as explained will ordinarily not find any direct application in
practice, as the pure sulphate of magnesium is too expensive therefor, but the
mineral called kiserite (Mg SO + Ì₂ O), and which substantially consists of
sulphate of magnesia, may with advantage be employed for the purpose, together
with chloride of potassium, or chloride of sodium, or any mixture of these salts.
The impurities contained in the kiserite will however all or partly be found again
in the magnesia together with those which may be contained in the chloride of
potassium or of sodium.
When minerals are used which comprise other salts besides sulphate of magnesium
the quantity of chloride of potassium or of sodium which is added must be so
determined by calculation relatively to the sulphate of magnesium found by
analysis in the mineral, that always two equivalents of the chloride will be brought
together with one equivalent of sulphate of magnesium. A mineral of this kind
is the schoenite (Mg SO, + K₁ SO, + 6 H₂‍O). The sulphate of potassium
contained in the same does not affect the process, and only increases the quantity
of sulphate finally obtained.
Another mineral suitable for the purpose kainite (Mg SO₁ + KCl + 3 H₂ O)
in which already half the requisite quantity of the alcaline chloride is comprised,
and to which therefore but one equivalent of chloride of potassium or of sodium is
to be added.
Instead of the said chlorides, minerals may be used which contain either of these
salts or both of them, on condition that the other substances forming part thereof
are not prejudicial to the process. A mineral of this kind is carnallite (K CI +
Mg Cl, +6 H, O), the chloride of magnesium which it contains being decomposed
into magnesia (Mg O) and muriatic acid during the treatment. The due proportions
of the materials to be used have, in this case, as in the former ones, to be determined
by analysis and calculation.
When minerals or substances are used from which, for one part, sulphate of
sodium (without sulphate of potassium) is obtained, the final product may be
employed with advantage for the manufacture of carbonate of soda according to
the Le Blanc process. For this purpose either the whole mass obtained may be
submitted to the known treatment by carbonate of calcium and coal, or the sulphate
of sodium is first extracted and then used.
I am aware that several methods have heretofore been made known of producing
sulphates of alkalies from sulphate of magnesium, or from minerals containing the
same, by treatment with chloride of potassium or sodium, or with certain minerals
of which they form a component part; but these are all different from my process,
as I will proceed to show.
1. According to the German Patent No. 2173, dated September 25, 1877, to
G. Borsche, the inventor first produces from solutions of chloride of potassium, and
of sulphate of magnesium or of kiserite, a compound sulphate of potassium
and magnesium, which is subsequently decomposed by a renewed treatment with
chloride of potassium. The process is rendered by the formulae :—
=
1.) 2 K CI+ 2 Mg SO = (K, SO, Mg SO₁) + Mg Cl₂.
II.) K, SO, Mg SO, + 4 K CI: 2 K, SO, + (Mg Cl, 2 K. Cl).
2. The process described in the Specification of the German Patent No. 4933, of
the 12th April 1878, to R. Grüneberg, is similar to the foregoing, as it also requires
a solution of sulphate of magnesium to be treated by chloride of potassium,
whereby a substance of the same composition as schoenite (K, SO, Mg SO +
6 H, O) is obtained, which is thereafter transformed by means of several successive

page_text: macerations with chloride of potassium into sulphate of potassium, together with
the compound chloride of magnesium and potassium (Mg Cl, 2 K CI).
3. H Grüneberg, according to the Specification of the German Patent No. 5607,
dated 19th November 1878, mixes carnallite (K Cl + Mg Cl₂ + 6 H₂O) with
5 kiserite (Mg SO. + H, O) in proportion to their respective chemical equivalents,
and grinds them with water to a uniform and liquid pulp. After a certain time
chloride of magnesium in solution may be drawn off from the compound sulphate
of potassium and magnesium, which is thereupon lixivated with water.
formula for the process is given thus:-
The
2 (K Cl + Mg C₁₂ + 6 H₂ O) + 2 Mg SO, = (K, SO, Mg SO + 6 H₂ O) +
2 Mg Cl₂.
4. Fr. W. Dupré and Cécil N. Hake (German Patent Specification No. 8021,
dated 21st January 1879), describe a process for obtaining sulphate of potassium
directly from schoenite (K, SO, Mg SO. + 6 H, O). The mineral after having
been ground to a fine powder is mixed with slaked or unslaked lime, calcined, and
allowed to stand for several days.
The water of crystallization of the schoenite promoting the decomposition by
the lime, a very hard mass is in either case obtained, from which the sulphate of
potassium may be extracted by means of water. The process is explained by the
formula:-
=
(K, SO, Mg SO + 6 H, O) + Ca O K. SO, + Ca SO. + Mg O.
The resulting magnesia is mixed with the sulphate of calcium, a part of which
however also enters into the solution of sulphate of potassium.
5. C. N. Hake, according to the German Patent Specification No. 9108, dated
October 13th, 1878, obtains sulphate of potassium froin carnallite by adding to a
concentrated solution of this substance a finely powdered mixture of kiserite and
gypsum. The exchange of ingredients which in consequence takes place is shown
as follows:-
4. (K Cl Mg C₁₂) + Mg SO4 + Ca SO₁ = (K, SO, Ca SO. + H, O) + 2 (K Cl
Mg Cl₂) + 3 Mg Cl..
The compound sulphate of potassium and calcium (K. SO, Ca SO + H₂O) is
calcined, whereupon sulphate of potassium may be extracted by lixivation.
In all these cases the process is carried out by means of solutions of the various
substances, or at least by aid of the water of crystallization contained therein and
at a low temperature, and moreover magnesia is either not obtained at all in the
process, or when obtained it is mixed with sulphate of calcium (gypsum) so as to
be worthless.
6. In Wagner's annual report on the progress in chemical technology (Wagner's
Fahresberichte über die Leistungen der Chemischen Technologie) of the year
1855, p. 853, a note by Roman de Luna is contained about the decomposition of
chloride of sodium by means of sulphate of magnesium. The author heats two
equivalents of the sulphate with one equivalent of the chloride, this proportion
being however given according to the former chemical system of equivalents, so
that the proportion according to the modern system will be two equivalents of
sulphate to two equivalents of chloride. He thus produces muriatic acid together
with a residue consisting, as the author alleges, of magnesia (Mg O) and sulphate
of sodium (Na, SO), the latter salt being thereafter extracted by hot water and
freed from a small quantity of sulphate of magnesium by addition of some milk
of lime.
Considering that in this case two equivalents of sulphate of magnesium are
caused to act upon two equivalents of chloride of sodium, the product finally
obtained must contain in addition to the other substances half the quantity of
sulphate of magnesia Mg SO, employed, and not only, as the author states, a small
amount of this salt, as will be seen from the following formula:-
2 Mg SO. + 2 Na Cl + H, O = Mg O + Mg SO, + Na, SO. + 2 H Cl.
The water shown herein is the water of crystallization of the salts, without which
the process would be altogether impossible.

page_text: The difference between the process of de Luna and the one forming the subject
matter of the present Invention is as follows:-
-:
In the former, half the quantity of sulphate of magnesia remaining undecomposed
is to be considered as lost, as it cannot be separated from the chloride of sodium by
crystallization, and because when treated according to the author's prescription by
lime, the precipitated magnesia is mixed with gypsum, and is therefore of no value.
In my correspondent's process, on the other hand, in which one equivalent of
sulphate of magnesia is decomposed by two equivalents of chloride of sodium or
potassium, there is no loss of material, and the final products contain no other
impurities than those which accompany the substances originally employed. The
more important difference lies, however, in the means by which the decomposition
is effected. In de Luna's process (in which no steam is used) the reaction of
the substances upon each other ceases as soon as the water of crystallization is
expelled, and this expulsion takes place at a temperature insufficient for terminating
the decomposition, whereas in my correspondent's process the complete operation
upon each other of the substances mixed in the proper proportions is ensured by a
continuous supply of water in the form of steam, while at the same time the
temperature is raised to about 700° centigr.
Having thus described this Invention, and the manner in which it is to be
carried out in practice. (as communicated to me by my correspondent) I hereby
claim as new and important features of the same,-
The method of producing magnesia and sulphate of potassium or of sodium from
sulphate of magnesium (Mg SO₁), or kiserite (Mg SO, + H, O), or schoenite
(Mg SO, + K, SO, + 6 H. O), or kainite (Mg SO, + KCl + 3 H₂O) for one part,
and from chloride of potassium (K CI), or chloride of sodium (Na Cl), or carnallite
(K CIMg Cl. + 6 H, O) for the other part, by mixing one or more of the
substances of the first part with one or more of the substances of the second part,
in such proportion that one chemical equivalent of sulphate of magnesia will be
brought together with two equivalents, or thereabout, of chloride of potassium or of
sodium (or of both chlorides combined) by heating such mixture in pulverized state
to a dark red heat, and by exposing it at the same time to the action of steam,
substantially as hereinbefore specified.
In witness whereof, I, the said Carl Pieper, have hereunto set my hand and
seal, this Sixteenth day of February, in the year of our Lord One thousand
eight hundred and eighty one.
CARL PIEPER. (L.S.)