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

page_text: A com-
PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 3rd September 1881.
munication from abroad by Adrien Lanquetin, of Paris, France.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN THE MANUFACTURE OF SALTS OF
SODA AND MAGNESIA." [A communication from abroad by Adrien Lanquetin, of
Paris, France.]|
The process of making carbonate of soda by putting in suspension in a solution
of chloride of sodium magnesia or carbonate of magnesia in powder and passing
a current of carbonic acid through is known. Bicarbonate of soda is formed, which
is deposited, and chloride of magnesium, which is dissolved. It has been proposed
to decompose this chloride of magnesium by heat into magnesia, and hydrochloric
acid to reproduce carbonate of magnesia, &c. But this decomposition is
incomplete, and this has been the defect of the process. I am enabled to avoid it
by employing for the production of the magnesia or carbonate of magnesia from
chloride of magnesium one of the known processes. Thus, for example, I treat
with calcined dolomite and obtain chloride of calcium, and also the magnesia of
the chloride of magnesium and that of the dolomite, carbonate of soda and of
magnesia being thus produced at same time. I can recarbonate a portion of this
magnesia and recommence the operation; I can also proceed in a different manner.
Instead of carbonate of magnesia I take magnesian limestones, magnesites, more or
less pure, or dolomites. The carbonate of lime and the other impurities do not
matter, as I can recover by washing after calcination the carbonate of suda of the
bicarbonate which has deposited. I thus produce directly with dolomite and
chloride of sodium carbonate of soda and chloride of magnesium from which
magnesia can be obtained.
Instead of using dolomite reduced to powder I may, to facilitate the reaction, first
calcine the dolomite so as to expel the carbonic acid, and afterwards recarbonate
it. This operation may be performed separately. It may also be performed after
having added to the water containing the calcined dolomite reduced to powder, by
slaking or otherwise, the proper proportion of chloride of sodium. The operation
is better and more completely effected when the carbonate of magnesia is in excess

page_text: relatively to the chloride of sodium. It is easy to conform to this condition. A
good result is also obtained by calcining the dolomite at a temperature at which
the carbonate of magnesia is decomposed without the lime being decarbonated. In
any case the same result is obtained, viz., the production of carbonate of soda and
chloride of magnesium. The operations are all performed in the cold, which is a
great advantage. Different reactions to those here obtained being met with under
other conditions. The question of low temperature is however of less importance
in the present case than in making soda by means of ammonia.
1 operate with dilute liquids (15° Baume, for instance), and there is therefore no
danger of the deposit with the bi-carbonate of soda of chloride of magnesium
which is difficult of separation. The chloride of magnesium dissolved is separated
by simple washing. No chloride of calcium can be present, as I operate with an
excess of carbonate of magnesia, and under these conditions the carbonate of
magnesia and the chloride of calcium yield carbonate of lime and chloride of
magnesium. Since I employ an excess of carbonate of magnesia I entirely
decompose the chloride of sodium.
One of the advantages of the process is that no titrations or precise
measurements are required, and there are no losses as in the ammonia process.
The apparatus for recarbonating and for effecting the reaction is of the ordinary
construction, closed and provided with an agitator. I utilize the gas resulting
from the decomposition of the bicarbonate of soda. There is also bicarbonate of
magnesia in the water; this bicarbonate is decomposed at the time of decarbonating
and carbonate of magnesia is deposited.
The same reactions above described take place with chloride of sodium and
carbonate of zinc forming chloride of zinc and carbonate of soda, and therefore with
chloride of sodium and calamine. The novelty in the process is the employment of
a carbonate of magnesia (or a carbonate of zinc) of sufficiently low price to permit
of its being used in excess, whereby (whether it be employed either for producing
magnesia or for any other purpose) the regeneration of magnesia for the process
itself is in practice generally unnecessary unless desired in a special case.
My process is the substitution of the use of dolomite more or less modified in its
physical condition for carbonate of magnesia, in order to produce carbonate of soda
and a salt of magnesia. The Invention therefore consists in the production in the
manner above described of carbonate of soda and chloride of magnesium by means
_of_chloride of sodium and carbonate of magnesia, viz., (a), the carbonate of
magnesia produced by the regeneration of-the-maguesia-by-one-of-the-known
processes.
(b). The carbonate forming part of the dolomite or of a magnesian lime-
stone, and being employed mixed with carbonate of lime or other impurities.
The Invention also relates to the details of the operations above described. and
the conditions under which they are performed, viz., the employment of an excess
of carbonate of magnesia of magnesia necessary for the commercial working of the
reaction; the low price of dolomite permits of this excess being as much as double
the amount theoretically required which is suitable.
The Invention also relates to the means employed and described for causing the
dolomite to effect the reaction.
It also relates to the application of the same processes and the employment of
dolomite in the processes of making soda and potash already patented, such as those
patented by Mr. Engel for making carbonate of potash by means of carbonate of
imagnesia, carbonic acid, and a salt of potash.