IMPROVEMENTS IN THE MANUFACTURE OF THE SULPHATE OR MAGNESIA
Year: 1859

page_text: LETTERS PATENT to Isaac Lowthian Bell, of the Washington Chemical
Works, Newcastle-upon-Tyne, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF THE SULPHATE OR MAGNESIA"
PROVISIONAL SPECIFICATION left by the said Isaac Lowthian Bell
at the Office of the Commissioners of Patents, with his Petition, on the
10th December 1859.
I, ISAAC LOWTHIAN BELL, of the Washington Chemical Works, Newcastle-
upon-Tyne, do hereby declare the nature of the Invention for "IMPROVEMENTS
IN THE MANUFACTURE OF THE SULPHATE OF MAGNESIA," to be as follows:-
This Invention has for its object improvements in the manufacture of the
sulphate of magnesia, and consists in exposing magnesian limestone to the
action of sulphurous acid, by which means a salt or salts of magnesia are
produced, which can afterwards be oxidized so as to produce the sulphate.
The magnesian limestone operated on may either be in its natural or in a
calcined state, or if it is deemed advisable, in order to economize the use of
the sulphurous acid, I take the magnesian limestone, previously heated so as
to expel its carbonic acid, and then by repeated washings I remove the lime,
or a greater portion thereof.
In treating the magnesian limestone either in its natural state, or pre.
viously prepared as already described, I prefer adopting the following plan :-
In either case I reduce the mineral to fine powder, and mix it with sufficient
water to enable it to be easily lifted by means of a pump, taking care to add
water enough, so that the magnesia when dissolved by the sulphurous acid
has no tendency to crystallize. I then pump up the magnesia or magnesian
limestone to the top of one or more condensers, resembling in principle those

page_text: employed for the condensation of muriatic acid. These condensers are placed
in communication with burners in which sulphurous acid is given off by any
of the well known means of obtaining that substance, when it, meeting the
water containing the magnesia in suspension, rapidly combines with this earth,
forming a soluble salt of magnesia. This operation is continued until all or
nearly all the magnesia is dissolved. To secure the conversion of the salts
of magnesia.so obtained in a perfect sulphate, I expose them to the action of
atmospheric air, preferring to do so by boiling down the solution, & heating
the salt to redness, which salt I dissolve in water to separate any impurity,
and then crystallize in the ordinary way.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Isaac Lowthian Bell, in the Great Seal Patent Office on the
9th June 1860.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ISAAC
LOWTHIAN BELL, of the Washington Chemical Works, Newcastle-upon-Tyne,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Tenth day of December, in the year of our Lord
One thousand eight hundred and fifty-nine, in the twenty-third year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
ine, the said Isaac Lowthian Bell, Her special licence that I, the said
Isaac Lowthian Bell, my executors, administrators, and assigns, or such
others as I, the said Isaac Lowthian Bell, 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 THE MANUFACTURE OF THE SULPHATE OF MAG-
NESIA," upon the condition (amongst others) that I, the said Isaac Lowthian
Bell, 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 Isaac Lowthian Bell, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-

page_text: formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say:-
This Invention has for its object improvements in the manufacture of the
sulphate of magnesia, and consists in exposing magnesian limestone to the
action of sulphurous acid, by which means a salt or salts of magnesia are
produced, which can afterwards be oxidized so as to produce the sulphate.
The magnesian limestone operated on may either be in its natural or in a
calcined state, or if it is deemed advisable, in order to economize the use of
the sulphurous acid, I take the magnesian limestone, previously heated so as
to expel its carbonic acid, and then by repeated washings I remove the line,
or a greater portion thereof.
The following is the manner in which I prefer to conduct the process:-
The magnesian limestone is calcined in the ordinary manner of lime burning,
and it is then washed repeatedly with water. For this purpose it is thoroughly
mixed with water, and the mixture is allowed to settle. The water is then
run off, and replaced by fresh, and the operation is repeated; this is usually
done three or four times. The washed mineral is then again stirred up with
water, which should be sufficient in quantity both to allow of the mixture.
being readily lifted by a pump, and to prevent the solution of sulphite of
magnesia formed showing any tendency to crystallize during the process. A
chemist knowing the quantity of magnesia the mineral he is working contains,
will readily determine the quantity of water which should be used with it.
The mixture of the powdered mineral with water is lifted by a pump (which
should be of a material which is not injuriously acted on by sulphurous acid)
to the top of a condenser. This condenser may be similar to these ordinarily
employed for condensing muriatic acid gas, that is to say, it may consist of a
tower of brick or stone filled from top to bottom with some material, such as
coke or pebbles, exposing considerable surface, and not acted on by the acid.
The mixture poured in at the top of the tower trickles down over the
materials within it until it reaches the bottom, and during this time it is
exposed to an ascending current of sulphurous acid gas, which it absorbs and
combines with. Usually several condensers are employed, and the mixture of
mineral and water is introduced at the top of the first of the series, and from
the bottom of this coudenser it is lifted to the top of the second, and so on.
The gas is caused to enter at the bottom of the last condenser of the series.
It ascends this, and passes from the top thereof to the bottom of the next,
and thus it circulates till it reaches the top of the first condenser, by which
time, if sufficient surface is exposed in the condensers, the sulphurous acid gas
will be entirely absorbed. The sulphurous acid gas may be produced by

page_text: burning pyrites in burners, such as are used when producing this gas for the
manufacture of sulphuric acid. The liquid running from the last condenser
should contain a considerable excess of sulphurous acid; if it is not found to
do so, it should be passed again through the condensers or some of them.
The presence of an excess of sulphurous acid greatly increases the solubility
of the sulphite of magnesia formed. The liquid will then contain sulphite of
magnesia, together with some sulphate of magnesia, a trace of sulphite of iron,
and free sulphurous acid, all in solution, also some insoluble sulphite of lime
suspended in it. This latter is first separated; it is allowed to deposit, and the
clear liquid is run off. Magnesia, by preference in the form of magnesian
limestone, calcined and washed as above described, is then added to the liquid;
thus the free sulphurous acid is neutrallized, and the iron precipitated as oxide.
The liquid is now again allowed to stand until it becomes clear, and the clear
liquid is run off, and evaporated in open pans to crystalline strength. During
the evaporation the sulphite of magnesia passes into sulphate by the absorption
of oxygen from the air; the sulphate of magnesia is run into leaden pans to
crystallize, as in the manufacture of Epsom salts by the processes ordinarily
resorted to. When magnesian limestone is employed in the process without
previous calcination and washing, it is reduced to powder, mixed with water,
and at once passed through the condensers; in other respects the process is
identical with that already described.
I would remark, that although I have described the use of condensers to
cause the gas to be taken up by the mixture of magnesian mineral and water,
the gas may be forced by a pump, or otherwise, to bubble through the liquid;
but the process which I have described is that which I prefer. Sulphate of
magnesia may also be obtained by passing a current of sulphurous acid gas
over magnesian limestone, (either calcined and washed, or otherwise,) and
subsequently lixiviating the mass, and treating the solution obtained in
the same manner as if it were obtained from the condensers, as already
described.
In witness whereof, I, the said Isaac Lowthian Bell, have hereunto
set my hand and seal, this Seventh day of June, in the year of our
Lord One thousand eight hundred and sixty.
ISAAC LOWTHIAN BELL. (L.S.)