Improvements in or relating to the Manufacture or Treatment of Bicarbonate of Soda.
Year: 1894

page_text: Date of Application, 4th Aug., 1894
Complete Specification Left, 3rd May, 1896-Accepted, 8th June, 1895
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Manufacture or Treatment of
Bicarbonate of Soda.
A communication from SOLVAY & Co., of 25, Rue du Prince Albert, Brussels,
Belgium.
I, WILLIAM LLOYD WISE, of No. 46 Lincoln's Inn Fields, in the County of
London, Consulting Engineer and Chartered Patent Agent, do hereby declare the
nature of this invention to be as follows:-
The bicarbonate of soda produced by the ammonia soda process is, at the time of
its formation, in a state of suspension in a liquid composed mainly of chloride of
ammonia from which it must be separated for use. Separation of the bicarbonate
of soda by filtration, or by centrifugal action, yields a product which is still
impregnated with the mother liquor, and if it be desired to obtain the bicarbonate
in some degree of purity, recourse must be had to washing operations which
are very tedious when the relatively great solubility of the bicarbonate is
considered.
Now an object of this invention is to effect the washing of bicarbonate of soda
with a minimum quantity of water by employing in a novel manner the method of
displacement by density.
For this purpose the mass of bicarbonate of soda with intermixed mother liquor
is placed in an apparatus of suitable form, for instance in a cylinder provided with
a pervious false-bottom, and deposition of the bicarbonate allowed to take place,
the mother liquid being gradually drained off as far as possible whilst deposition is
taking place.
Above the mass of bicarbonate of soda is then introduced a quantity of water, or
preferably a saturated solution of bicarbonate of sola,-obtained it may be from
a previous operation-approximately equal in volume to that of the ammoniacal
mother liquor with which the deposited bicarbonate of soda is still impregnated.
When this superposition has been effected with the necessary precautions to prevent
mixing, or agitation, it is sufficient to allow the denser impregnating mother liquor
to flow off slowly under the sole influence of the pressure due to the head of the
water or solution added, in order that the displacement of such mother liquor
shall be effected molecularly so to speak, and in the order of the densities of the
liquids present.
Under these conditions, the displacement takes place practically in horizontal
strata or layers without interference or places of easiest flow. The replacing of
the impregnating liquid by the washing liquid is nearly perfect, so that a practically
pure product can be obtained without loss due to dissolving action. This result,
which cannot be obtained either by means of a filter, or of a centrifugal
apparatus, constitutes therefore an important improvement in the manufacture or
treatinent of bicarbonate of soda obtained by the ammonia soda process.
But the washing operation, if arrested at this point, is not complete, because the
bicarbonate in the form of thin mud, which remains in the apparatus after the
natural flowing off of the washing water, contains too much water to be capable of
being directly utilized.
In order to free the said washed bicarbonate from the greater part of this
impregnating water, it is allowed to flow into a trough in which is immersed the

page_text: lower portion of a hollow cylinder mounted to revolve about a horizontal axis.
This cylinder is formed with two full or solid ends, and a periphery consisting of
perforated or reticulated sheet metal provided externally with material such as
metallic cloth covered with flannel, to act as a filter. Inside the cylinder a partial
vacuum is set up equal to a suction of from about 25 to 30 centimetres of mercury.
The trough containing the mass of bicarbonate is provided with an agitator which
keeps the solid contents in suspension. As a result of the suction and of the motion
of the cylinder, the bicarbonate of soda becomes attached to the said cylinder in
the form of a bomogeneous crust which is in an almost dry condition, of a perfectly
uniform nature and of uniform thickness.
The pure and almost dry bicarbonate of soda thus obtained, can be readily
removed from the cylinder by a knife or scraper and transferred to a suitable
receptacle.
Dated this 4th day of August 1894.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Pateut Agent.
Improvements in or relating to the Manufacture or Treatment of
Bicarbonate of Soda.
A communication from SOLVAY & Co., of 25, Rue du Prince Albert, Brussels,
Belgium.
I, WILLIAM LLOYD WISE, of No. 46 Lincoln's Inn Fields, in the County of
London, Consulting Engineer, and Chartered Patent Agent, 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 statement :-
The bicarbonate of soda produced by the animonia soda process is, at the time
of its formation, in a state of suspension in a liquid composed mainly of chloride of
ammonia from which it must be separated for use. Separation of the bicarbonate
of soda by filtration, or by centrifugal action, yields a product which is still
impregnated with the mother liquor, and if it be desired to obtain the bicarbonate
in some degree of purity, recourse must be had to washing operations which
are very tedious when the relatively great solubility of the bicarbonate is
considered.
Now an object of this invention is to effect the washing of bicarbonate of soda
with a minimum quantity of water by employing in a novel manner the method of
displacement by density.
For this purpose the mass of bicarbonate of soda with intermixed mother
liquor is placed in an apparatus ef suitable form, for instance in a cylinder provided
with a pervious false-bottom, and deposition of the bicarbonate allowed to take
place, the mother liquid being gradually drained off as far as possible whilst
deposition is taking place.
Above the mass of bicarbonate of soda is then introduced a quantity of water, or
preferably a saturated solution of bicarbonate of soda, obtained it may be from
a previous operation-approximately equal in volume to that of the ammoniacal
mother liquor with which the deposited bicarbonate of soda is still impregnated.
When this superposition has been effected with the necessary precautions to prevent
mixing, or agitation, it is sufficient to allow the deuser impregnating mother liquor
to flow off slowly under the sole influence of the pressure due to the head of the
water or solution added, in order that the displacement of such mother liquor shall
be effected molecularly so to speak, and in the order of the densities of the liquids
present.

page_text: Under these conditions, the displacement takes place practically in horizontal
strata or layers without interference or places of easiest flow. The replacing of
the impregnating liquid by the washing liquid is nearly perfect, so that a
practically pure product can be obtained without loss due to dissolving action.
This result, which cannot be obtained either by means of a filter, or of a
centrifugal apparatus, constitutes therefore an important improvement in the
manufacture or treatment of bicarbonate of soda obtained by the ammonia-soda
process. But the washing operation, if arrested at this point, is not complete,
because the bicarbonate in the form of thin mud, which remains in the apparatus
after the natural flowing off of the washing water, contains too much water to
be capable of being directly utilized.
In order to free the said washed bicarbonate from the greater part of this
impregnating water, it is allowed to flow into a trough in which is immersed the
lower portion of a hollow cylinder mounted to revolve about a horizontal axis.
This cylinder is formed with two full or solid ends, and a periphery consisting of
perforated or reticulated sheet metal provided externally with material such as
metallic cloth covered with flannel, to act as a filter. Inside the cylinder a partial
vacuum is set up equal to a suction of from about 25 to 30 centimetres of mercury.
The trough containing the mass of bicarbonate is provided with an agitator which
keeps the solid contents in suspension. As a result of the suction and of the
motion of the cylinder, the bicarbonate of soda becomes attached to the said cylinder
in the form of a homogeneous crust which is in an almost dry condition, of
a perfectly uniform nature, and of uniform thickness.
The pure and almost dry bicarbonate of soda thus obtained, can be readily
removed from the cylinder by a knife or scraper and transferred to a suitable
receptacle.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. In the manufacture or treatment of bicarbonate of soda obtained by the
ammonia-soda process, washing the bicarbonate of soda by displacement of the
mother liquor therein by the washing liquid in the manner herein set forth, and
removing the water of impregnation from the washed product by means of vacuum
apparatus consisting of a horizontal rotary vacuum or exhausting cylinder having
its periphery adapted to act as a filter and arranged to rotate partly within the
mass of washed bicarbonate of soda, whereby the latter is obtained in a practically
pure and almost dry condition, substantially as herein described.
Dated this 3rd day of May 1895.
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.