Improvements in the Manufacture, Purification, or Separation of Sodium Bicarbonate.
Year: 1886

page_text: Date of Application, 27th Aug., 1886.
Complete Left, 26th May, 1887.
Complete Accepted, 28th June, 1887.
RESERVE
Improvements in the Manufacture, Purification, or Separation of
Sodium Bicarbonate.
We, JOHN ISAAO WATTS, of Sandbach in the County of Chester, Chemist, and
WILLIAM ARMSTRONG RICHARDS of the same place, Engineer do hereby declare the
nature of this invention to be as follows:-
The ammonium compounds and tarry matters existing in sodium bicarbonate as
it is obtained in the ammonia soda process, render it unsuitable for use in many
manufactures. In order to obtain a purer product Mond and Jarmay (Patent
No. 2996, 1884) dissolve the crude bicarbonate in water of a suitable temperature,
and re-crystallize from the solution so obtained. As the solubility of bicarbonate
varies little with alterations of temperature, the yield of crystals is sinall. In order
to increase the yield, we propose to dissolve salt either by agitation, or any other well
known means by which bicarbonate of soda is salted down. The quantity of salt
dissolved in these liquors may be varied as desired, either to salt down all the
bicarbonate, or only so far as is necessary to increase the yield. In the latter case,
the bicarbonate precipitated has a more crystalline form, and is therefore more
easily washed and dried. The bicarbonate crystals so obtained can be separated from
the liquor by vacuum filters, centrifugal machines, filter presses or any other well
known means, and the mother liquor can either be used instead of brine in the
ammonia soda process, or can be again used for dissolving fresh quantities of crude
bicarbonate, and then treated as above.
If bicarbonate of great purity is required the crystals separated may be washed with
cold water, or a strong saturated solution of pure bicarbonate, and then dried and
dressed in the usual way.
n
WM. P. THOMPSON & Co.,
323, High Holborn, London,
Patent Agents for the Applicants.

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Sodium Bicarbonate.
We, JOHN ISAAO WATTS of Sandbach in the County of Chester, Chemist and
WILLIAM ARMSTRONG RICHARDS of the same place, Engineer, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statenient :-
The ammonium compounds and tarry matters existing in sodium bicarbonate as
it is obtained in the ammonia-soda process, render it unsuitable for use in many
manufactures. In order to obtain a purer product Mond and Jarmay, (English
Patent No. 2996 of 1884) dissolve the crude bicarbonate in water of a suitable
temperature and separate from the solution so obtained a pure product by refri-
geration. As the solubility of bicarbonate varies little with alterations of temperature,
the yield of crystals is small. In order to increase the yield, we propose to add to
the warm saturated solution of bicarbonate of soda, or to the cold saturated solution,
which remains after having separated a quantity of bicarbonate by refrigerating the
warm solution, a quantity of common salt, and to dissolve this by agitation or any
other well known means, when bicarbonate of soda will separate out. The remaining
mother liquor can be used afterwards for the ammonia-soda process. The quantity
of salt dissolved in these liquors may be varied so as to obtain a larger or smaller
quantity of bicarbonate from the liquor. In the latter case the bicarbonate preci-
pitated has a more crystalline form and is therefore more easily washed and dried.
The chloride of sodium can be added all at once or gradually and during the separation
of the bicarbonate, or in a series of charges, each in succession being added after the
previous one has dissolved. The bicarbonate crystals thus obtained can be separated
from the liquor by vacuum filters, centrifugal machines, filter presses, or any other
well known means and the mother liquor can either be used instead of brine in the
ammonia-soda process, or can be again used for dissolving fresh quantities of crude
bicarbonate and then treated as above.
If bicarbonate of great purity is required, the crystals separated may be washed
with cold water, or a strong saturated solution of pure bicarbonate, and then dried
and dressed in the usual way.
Having now particularly described and ascertained the nature of the snid
invention, and in what manner the same is to be performed, we declare that what
wo claim is :-
The improvement in the manufacture of sodium bicarbonate, which consists in
adding sodium chloride to the aqueous solution of crude sodium bicarbonate, obtained
by the ammonia-soda process and agitating with or without artificial cooling, till the
sodium chloride is dissolved and sodium bicarbonate is separated out.
Dated this Twenty fifth day of M. 1007