IMPROVEMENTS IN THE MANUFACTURE OF SALTS OF MAGNESIA AND SALTS OF ZINC
Year: 1881

page_text: 55
LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of IMPROVEMENTS IN
THE MANUFACTURE OF SALTS OF MAGNESIA AND SALTS OF ZINC." A com-
munication from abroad by Adrien Lanquetin, of Paris, France.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 3rd September 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. IMPROVEMENTS IN THE MANUFACTURE OF SALTS OF
MAGNESIA AND SALTS OF ZINC." [A communication from abroad by Adrien
Lanquetin, of Paris, France.]
"
Many processes for the manufacture of magnesia are based on the replacement of
magnesium by calcium in chloride of magnesium. This latter salt is found in sea
water, in the residues of salt works, and in certain natural deposits, such as those of
Stassfurt in Germany. Various attempts have also been made to produce it
artificially by means of dolomite or carbonates of magnesia more or less pure, and
hydrochloric acid or various chlorides.
It is unnecessary here to describe these processes which produce either chloride
of magnesium or a double chloride (of magnesium and calcium for example.)
This Invention consists in the employment for producing chloride of magnesium
of chloride of calcium, a residue of various manufactures which has never hitherto
been employed for this purpose. If carbouate of magnesia be treated at the ordinary
temperature by a solution of chloride of calcium in water, carbonate of lime and
chloride of magnesium are formed. The preferable mode is to reduce the carbonate
of magnesia to powder, and treat it with a solution of chloride of calcium, either in
a vat provided with a stirrer, or by causing the solution of chloride to pass through
a sufficiently thick layer of carbonate of magnesia.
This sort of filter may be formed of lumps of carbonate of magnesia, or by
forming into balls or other shapes the pulverised magnesia.
For the purposes of this Invention I employ matters containing carbonate of
magnesia together with impurities which render them unsuited for producing
commercially pure magnesia by simple_calcination, such as, for example, natural
magnesites, magnesian limestones, and dolomites. The chloride of magnesium
obtained is itself commercially useful. It may also be used in another patented

page_text: process for the production of magnesia, in which case the residue of the manufacture
would be chloride of calcium. There would thus be a complete cycle of operations
for the manufacture of magnesia.
Using chloride of calcium, for example, we obtain with dolomite chloride of
magnesium, and a deposit of carbonate of lime resulting from the decomposition of
chloride of calcium and dolomite, and from this deposit lime may be obtained by
calcination, and if the chloride of magnesium be treated with this lime, a deposit of
magnesia and chloride of calcium is obtained, which serves for another operation.
Calcined dolomite may also be employed in this manufacture, which will double
the quantity of magnesia obtained, and facilitate filtration and washing. Instead
of employing chloride of calcium the double chloride of magnesium and calcium
may be employed, obtained in the manner previously described. If chloride of
calcium and carbonate of magnesia produce under the above conditions chloride of
magnesium and carbonate of lime, on the other hand by means of pressure, and at
from 150° to 200°, a mixture of carbonate of lime and chloride of magnesium will
produce carbonate of magnesia and chloride of calcium.
Thus with bodies containing carbonate of magnesia, there is also a continuous
cycle of operations for the obtainment of pure carbonate of magnesia, and by
calcination, magnesia.
The reactions above indicated which admit of readily obtaining chloride of
magnesium, and consequently of magnesia by means of chloride of calcium and
carbonate of magnesia, are also applicable when in lieu of chloride another salt of
calcium is employed. Thus, for example, with sulphate of lime and the various
magnesian limestones, sulphate of magnesia may be obtained, which, by means of
lime, will furnish magnesia and sulphate of lime. In this case weaker liquors
would be operated on.
In this manner also phosphate of magnesia may be obtained by means of
phosphate of lime, and the various magnesian limestones as above mentioned.
Instead of employing dolomite in its natural state, reduced to powder as before
mentioned, and in order to obtain a perfect reaction and arrive at a practical
result, the following precautions should be observed:-
The dolomite or impure carbonates of magnesia should be calcined at a
temperature below a red heat, at which carbonate of magnesia decomposes, the
dolomite thus calcined being then reduced to powder, and recarbonated by holding
it in suspension in water through which is passed-a-current-of-carbonic-acid-gas.
The dolomite thus recarbonated is employed in the reaction, which is assisted by
an excess of carbonic acid.
The carbonation may be effected either separately and the reaction then pro-
ceeded with, or the calcined dolomite may be placed in water containing chloride
of calcium in solution, and through which is passed a current of carbonic acid gas.
The dolomite may also be so calcined as to remove the whole of the carbonic acid.
Pulverization in this case takes place by slaking, and the recarbonation is effected
in the manner above described. The same chloride of calcium is used continuously,
compensation being made for waste, but as this chloride forms a very abundant
residue, only that need be retained which can be collected without washing, and
the loss can be made good by adding fresh chloride.
Among the chloride of calcium residues which may be employed may be
mentioned those of the manufacture of soda by the ammonia processes, of the
chlorine manufacture, of the treatment of phosphates by hydrochloric acid, of
chloride of lime, of the treatment of sea water or salt water by means of lime or of
lyes, such as those of Stassfurt, &c.
Exactly the same results are obtained if in lieu of magnesia, carbonate of
magnesia and dolomite, either oxide of zinc, carbonate of zinc, or calamine be
operated on, whereby I obtain a salt of zinc and chloride of calcium. The method
of procedure being the same, it is unnecessary to repeat the description.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on
the 3rd March 1882.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN THE MANUFACTURE OF SALTS OF
MAGNESIA AND SALTS OF ZINC." A communication from abroad by Adrien
Lanquetin, of Paris, France.
Many processes for the manufacture of magnesia are based on the replacement of
magnesium by calcium in chloride of magnesium. This latter salt is found in sea
water, in the residues of salt works, and in certain natural deposits, such as those of
Stassfurt in Germany. Various attempts have also been made to produce it
artificially by means of dolomite or carbonates of magnesia, more or less pure, and
hydrochloric acid or various chlorides. It is unnecessary to describe these processes,
which produce either chloride of magnesium or a double chloride (of magnesium
and calcium, for example).
This Invention consists in the einployment for producing chloride of magnesium
of chloride of calcium, a residue of various manufactures which has never hitherto
been employed for this purpose. If carbonate of magnesia be treated at the ordinary
temperature, or, better still, with the aid of heat, by a solution of chloride of calcium
in water, carbonate of lime and chloride of magnesium are formed. The preferable
mode is to reduce the carbonate of magnesia to powder, and treat it with a
solution of chloride of calcium, either in a vat provided with a stirrer, or by causing
the solution of chloride to pass through a sufficiently thick layer of carbonate of
magnesia. This sort of filter may be formed of lumps of carbonate of magnesia, or
by forming into balls or other shapes the pulverised magnesia.
For the purposes of this Invention I employ matters containing carbonate of..
magnesia together with impurities which render them unsuited for producing
commercially pure magnesia by simple calcination, such as, for example, natural
magnesites, magnesian limestones, and dolomites. The chloride of magnesium
obtained is itself commercially useful. It may also be used in a previously patented
process for the production of magnesia, in which case the residue of the manufacture.
would be chloride of calcium. There would thus be a complete cycle of operations
for the manufacture of magnesia. Using chloride of calcium, for example, we obtain
with dolomite chloride of magnesium and a deposit of carbonate of lime resulting
from the decomposition of chloride of calcium and dolomite, and from this deposit
lime may be obtained by calcination, and if the chloride of magnesium be treated
with this lime a deposit of magnesia and chloride of calcium is obtained, which
serves for another operation. Calcined dolomite may also be employed in this
manufacture, which will double the quantity of magnesia obtained, and facilitate
filtration and washing, as indicated in previous Patents. Instead of employing
chloride of calcium the double chloride of inagnesium and calcium may be employed;
obtained in the manner previously described. If chloride of calcium and carbonate
of magnesia produce under the above conditions chloride of magnesium and carbonate
of lime, on the other hand, by means of pressure, and at from 150° to 200°, a mixture
of carbonate of lime and chloride of magnesium will produce carbonate of magnesia
and chloride of calcium.
Thus with bodies containing carbonate of magnesia there is also a continuous cycle
of operations for the obtainment of pure carbonate of magnesia, and, by calcination,
magnesia.
The reactions above indicated, which admit of readily obtaining chloride of
magnesium (and consequently magnesia) by means of chloride of calcium and
carbonate of magnesia, are also applicable when in lieu of chloride another salt of

page_text: calcium is employed. Thus, for example, with sulphate of lime and the various
magnesian limestones sulphate of magnesia may be obtained, which by means of
lime will furnish magnesia and sulphate of lime; in this case weaker liquors would
be operated on. In this manner also phosphate of magnesia may be obtained by
means of phosphate of lime and the various magnesian limestones, as above
mentioned. Instead of employing dolomite in its natural state reduced to powder,
as before mentioned, and in order to obtain a perfect reaction and arrive at a practical
result, the following precautions should be observed:
:-
The dolomite or impure carbonates of magnesia should be calcined at a tempe-
rature below a red heat, at which carbonate of magnesia decomposes, the dolomite
thus calcined being then reduced to powder and recarbonated by holding it in
suspension in water through which is passed a current of carbonic acid gas. The
dolomite thus recarbonated is employed in the reaction, which is assisted by an excess
of carbonic acid.
The carbonation may be effected either separately, and the reaction then proceeded
with, or the calcined dolomite may be placed in water containing chloride of calcium
in solution, and through which is passed a current of carbonic acid gas. The
dolomite may also be so calcined as to remove the whole of the carbonic acid.
Pulverisation in this case takes place by slaking, and the recarbonation is effected
in the manner above described. The same chloride of calcium is used continuously,
compensation being made for waste, but as this chloride forms a very abundant
residue, only that need be retained which can be collected without washing, and the
loss can be made good.by adding fresh chloride.
Among the chloride of calcium. residues which may be employed may be
mentioned those of the manufacture of soda by the ammonia processes, of the
chlorine manufacture, of the treatment of phosphates by hydrochloric acid, of those
manufactures where chloride of lime is used, of the treatment of sea water or salt
water by means of lime or of lyes, such as those of Stassfurt, &c.
Exactly the same results are obtained if in lieu of magnesia, carbonate of magnesia,
and dolomite, either oxide of zinc, carbonate of zinc, or calamine be operated on,
whereby I obtain a salt of zinc and chloride of calcium, although in this case the
reaction is less easy and less complete. The method of procedure being the same, it
is unnecessary to repeat the description.
Having described the nature of the said Invention and the manner of performing
the same, I declare_that_what.I.claim-as-the-Invention-to-be-protected-by-the
herein before in part recited Letters Patent is,―
"
1st. The manufacture of chloride of magnesium, as herein specified, with dolomite
and chloride of calcium.
2nd. The process, consisting of the continuous cycle of operations herein described,
for the manufacture of the magnesia and the reconstitution of the raw materials
necessary for this manufacture.
3rd. The particular application, in the manner and for the purposes herein
specified, of the residues of the manufacture of soda by the ammonia processes, of the
manufacture of chlorine and of chloride of lime, and of the treatment of phosphates
by hydrochloric acid.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
me hand and l