Improvements in Obtaining Partly in the Free State and Partly as Vapour of Hydrochloric Acid, the Chlorine of the Chloride of Magnesium, of Aqueous Solutions of Chloride of Magnesium THE OFTIONS OR OF MIXED SOLUTIONS OFIDE OF ANDLORIDE OF SODI
Year: 1884

page_text: Improvements in Obtaining Partly in the Free State and Partly
as Vapour of Hydrochloric Acid, the Chlorine of the Chloride
of Magnesium, of Aqueous Solutions of Chloride of Magnesium,
[Communicated in part from abroad by Messieurs A. R. Pechiney et. Cie., of
Salindres, in the Department of Gard, in the Republic of France.]
PROVISIONAL SPECIFICATION.
I, WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey Fellow
of the Royal Society, President of the Society of Chemical Industry, do hereby
declare the nature of the said Invention for IMPROVEMENTS IN OBTAINING PARTLY
IN THE FREE STATE AND PARTLY AS VAPOUR OF HYDROCHLORIC ACID THE
CHLORINE of THE CHLORIDE OF MAGNESIUM OF AQUEOUS SOLUTIONS OF
CHLORIDE OF MAGNESIUM OR OF MIXED SOLUTIONS OF CHLORIDE OF
MAGNESIUM AND CHLORIDE OF SODIUM, to be as follows:-
The application of this invention may commence either with an aqueous solution
of chloride of magnesium only, or with a mixed solution of chloride of magnesium
and chloride of sodium such as is obtained by decomposing by magnesia the
chloride of ammonium contained in certain residual liquors of the manufacture of
soda by what is known as the Ammonia Process.
I first evaporate the said solution to or nearly to the point at which if its
evaporation were carried further vapour of hydrochloric acid would begin to be
evolved. If the solution operated upon be a mixed solution of magnesium chloride
and sodium chloride the latter will "salt out" as the evaporation proceeds, and
I then fish out or otherwise separate such sodium chloride, and so eventually obtain
a solution of magnesium chloride free from or but slightly contaminated with
sodium chloride.
To the solution of magnesium chloride concentrated to or nearly to the point
I have indicated I add a quantity of magnesia, preferably regenerated magnesia,
obtained in a subsequent operation which will be described below. I thus convert
the solution of chloride of magnesium into solid oxychloride of magnesium.
I prefer to add this magnesia while the solution is boiling or nearly so, and to
incorporate it by mechanical means intimately therewith.
The proportion of magnesia used may vary within wide limits, but it should be
such that the resulting oxychloride will not soften appreciably during the
succeeding operations of the process. I prefer to use from half an equivalent to
an equivalent and a half of magnesia per equivalent of chloride of magnesium; but
very much larger proportions of magnesia may be employed with no disadvantage
beyond that of rendering the bulk of material to be treated in the subsequent
operations of the process greater than it would otherwise be

page_text: I next submit the oxychloride of magnesium obtained as above set forth to an
operation the object of which is to drive off as much of its water as possible while
driving off from it as little as possible of its chlorine. To this end I heat it to a
low temperature, in any convenient kind of furnace or stove, or by means of hot
air or hot gases. During this operation the oxychloride gives off a large part of
its water, and a small part of its chlorine is at the same time driven off as vapour
of hydrochloric acid. The proportion of its chlorine which is thus driven off as
vapour of hydrochloric acid is the smaller the lower the temperature employed.
I do not confine myself to the use of any particular temperature, but a temperature
which I have found to give good results is one between 150 degrees and
200 degrees Centigrade. This operation of desiccation may be performed in stoves
or other apparatus so disposed that the vapour of hydrochloric acid evolved in them
may be collected and utilized.
The oxychloride which has been so desiccated I next treat by heating it in
contact with a current of air. Its chlorine is thereby driven off, partly in the free
state, and partly as vapour of hydrochloric acid, the residual product consisting
for the most part of magnesia. Some of the magnesia thus obtained may be used
as above described to convert solution of chloride of magnesium into solid oxy-
chloride of magnesium.
The operation of heating the desiccated oxychloride of magnesium in contact
with air may be performed in any one of many kinds of apparatus, such apparatus
being either of the nature of a muffle furnace, or of a series of muffle furnaces
connected together, and either cold or previously heated air being admitted there-
into during the operation, or apparatus which is not heated externally, but the
contents of which are heated by highly heated air being sent among and through
them; but I believe that it may be performed to most advantage in and by means
of a new apparatus and application for a patent for which will be deposited at the
Patent Office on the same day as the present application, the said other application
being for a patent for an invention of: "Improvements in Furnaces for Heating
Solid Substances out of Contact with the products of Combustion of the Fuel
Employed."
What will pass off from the apparatus in which desiccated oxychloride of
magnesium is heated in contact with air will be a mixture of free chlorine and
other gases with vapour of hydrochloric acid. From this mixture vapour of
hydrochloric acid must first be condensed out, as will be well understood, and the
chlorine of the remaining mixture of chlorine and other gases can then be absorbed
and utilized in known ways.
What is new in the present invention consists:
Firstly, in submitting oxychloride of magnesium, obtained by adding magnesia
to a concentrated aqueous solution of chloride of magnesium, to an operation of
desiccation, substantially as and for the purpose above described, before submitting
such oxychloride of magnesium to the operation of heating it in contact with air.
Secondly, in separating chloride of sodium from a mixed solution of chloride of
magnesium and chloride of sodium, substantially as is above described, before
treating that chloride of magnesium for the obtainment from it of chlorine and
vapour of hydrochloric acid; and,
Thirdly, obtaining the chlorine of a concentrated solution of chloride of
magnesium by adding magnesia to that solution and so converting the chloride
of magnesium into oxychloride of magnesium, desiccating that oxychloride of
magnesium by heating it to a low temperature, and then heating the desiccated
oxychloride of magnesium in contact with atmospheric or other oxygen.
.
T
1004

page_text: Improvements in Obtaining Partly in the Free State and Partly
as Vapour of Hydrochloric Acid, the Chlorine of the Chloride
I, WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, Fellow
of the Royal Society, do hereby declare the nature of the said Invention for
IMPROVEMENTS IN OBTAINING PARTLY IN THE FREE STATE AND PARTLY AS VAPOUR
OF HYDROCHLORIC ACID THE CHLORINE OF THE CHLORIDE OF MAGNESIUM OF
AQUEOUS SOLUTIONS OF CHLORIDE OF MAGNESIUM OR OF MIXED SOLUTIONS OF
CHLORIDE OF MAGNESIUM AND CHLORIDE OF SODIUM, and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement:—
The application of this invention may commence either with an aqueous solution
of chloride of magnesium only, or with a mixed solution of chloride of magnesium
and chloride of sodium such as is obtained by decomposing by magnesia the
chloride of ammonia contained in certain residual liquors of the manufacture of
soda-by what is known as the ammonia process.
I first evaporate the said solution to or nearly to the point at which if its
evaporation were carried further vapour of hydrochloric acid would begin to be
evolved. If the solution operated upon be a mixed solution of magnesium chloride
and sodium chloride, the latter will "salt out" as the evaporation proceeds, and in
such case I fish out or otherwise separate such sodium chloride, and so eventually
obtain a solution of magnesium chloride free from or but slightly contaminated with
Bodium chloride.
To the solution of magnesium chloride concentrated to or nearly to the point I
have indicated I add a quantity of magnesia, preferably regenerated magnesia, such
as is obtained in a subsequent operation which will be described below. I thus
convert the solution of chloride of magnesium into solid oxychloride of magnesium.
I prefer to add this magnesia while the solution is boiling or nearly so, and to
incorporate it by mechanical means intimately therewith. I thus obtain a soliḍ
hydrated oxychloride of magnesium.
The proportion of magnesia used as just said may vary within wide limits, but it
should be such that the resulting oxychloride will not soften appreciably during
the succeeding operations of the process. I prefer to use from half an equivalent
to an equivalent and a half of magnesia per equivalent of chloride of magnesium;
but very much larger proportions of magnesia may be employed with
disadvantage beyond that of rendering the bulk of material to be treated in the
subsequent operations of the process greater than it would otherwise be.
no
I next submit the oxychloride of magnesium obtained as above set forth to an
operation of desiccation. To this end I heat it to a low temperature, in any
convenient kind of furnace or stove, or by means of hot air or hot gases. During
this operation the oxychloride gives off a large part of its water, and a small part
of its chlorine is usually at the same time driven off as vapour of hydrochloric

page_text: acid. The proportion of its chlorine which is thus driven off as vapour of hydro-
chloric acid is the smaller the lower the temperature employed. I do not confine
myself to the use of any particular temperature, but a temperature which I have
found to give good results is one between 150 degrees and 300 degrees Centigrade.
This operation of desiccation may be performed in stoves or other apparatus so
disposed that any vapour of hydrochloric acid evolved in them may be collected and
utilized, as will be well understood.
The oxychloride which has been so desiccated I next treat by heating it in
contact with a current of air. Its chlorine is thereby driven off, partly inthe free
state, and partly as vapour of hydrochloric acid, the residual product consisting for
the most part of magnesia. Some of the magnesia thus obtained may be used as
above described to convert the next quantity of solution of chloride of magnesium
into solid oxychloride of magnesium.
The operation of heating the desiccated oxychloride of magnesium in contact
with air may be performed in any one of many kinds of apparatus, such apparatus
being either of the nature of a muffle furnace or of a series of muffle furnaces
connected together, and either cold or previously heated air being admitted
thereinto during the operation, or apparatus which is not heated externally, but the
contents of which are heated by highly heated air being sent among and through
them; but I believe that it may be performed to most advantage in and by means
of a new apparatus, invented by Messieurs Pechiney et Compagnie, of Salindres,
for which the patent No 9304, of 23rd. June, 1884, has been granted to me, under
the title of: "Improvements in Furnaces for Heating Solid Substances out of
Contact with the Products of Combustion of the Fuel Employed."
What will pass off from the apparatus in which desiccated oxychloride of
magnesium is heated in contact with air will be a mixture of free chlorine and
other gases with vapour of hydrochloric acid. From this mixture vapour of
hydrochloric acid must first be condensed out, as will be well understood, and the
chlorine of the remaining mixture of chlorine and other gases can then be absorbed
and utilized in known ways.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
Firstly, submitting oxychloride of magnesium, obtained by adding magnesia to a
concentrated aqueous solution of chloride of magnesium, to an operation of
desiccation, substantially as and for the purpose above described, before submitting
Buch oxychloride of magnesium to the operation of heating it in contact with air.
Secondly, separating chloride of sodium from a mixed solution of chloride of
magnésium and chloride of sodium, substantially as is above described, before
treating that chloride of magnesium for the obtainment from it of chlorine and
vapour of hydrochloric acid by means of the present invention; and,
Thirdly, obtaining the chlorine of a concentrated solution of chloride of
magnesium by adding magnesia to that solution and so converting the chloride
of magnesium into oxychloride of magnesium, desiccating that oxychloride of
magnesium by heating it to a low temperature, and then heating the dessicated
oxychloride of magnesium, in contact with atmospheric or other oxygen, to such
higher temperature that the said oxygen shall react upon it, wholly or partially,
driving off from it chlorine in the free state.