IMPROVEMENTS IN. AND APPERTAINING TO THE MANUFACTURE OF SODIUM BICARBONATE
Year: 1884

page_text: We LUDWIG MOND and GUSTAV JÁRMAY, both of Winnington in the county of
Chester, Manufacturing Chemists do hereby declare the nature of our said invention
for "IMPROVEMENTS IN. AND APPERTAINING TO THE MANUFACTURE OF SODIUM
BICARBONATE," to be as follows:-
Bicarbonate of soda as obtained in the manufacture of soda by the ammonia-soda
process contains besides some minor impurities a certain quantity of ammonia
(probably in chemical combination with the bicarbonate of soda), which make this
product unfit for most of the purposes for which bicarbonate of soda of the market
is used. Moreover the drying of this crude bicarbonate of soda made by the
ammonia-soda process is a very tedious operation on account of its sludgy nature.
Washing with water does not free this crude bicarbonate of soda from the ammonia
it contains, nor have many attempts to obtain this end by washing it with caustic
ammonia (see James Richards' British Patent No 376 of 1874) or other chemicals
led to the desired result.
.
We have however discovered that if the crude bicarbonate of soda of the
ammonia-soda process be dissolved in warm water and the resulting solution
allowed to cool, pure bicarbonate of soda separates and all the ammonia remains in
solution. If a very pure article be required all the other impurities can be got rid
of by letting the warm solution clear itself either by settling or filtering it before
it is allowed to cool.
In carrying out our invention we dissolve the crude bicarbonate of soda in
water of about 60 degrees centigrade and separate the insoluble matter preferably
by filtration.
The clear solution is treated in different ways according to the quality or grain
of bicarbonate of soda that it is desired to obtain.
It is either run warm into pans and allowed to cool slowly, or it is first cooled
as far as practicable without separation of bicarbonate by means of cooling pipes or
other arrangements, and is then run into pans to cool further and deposit the
bicarbonate of soda, or the liquor may be run through a series of troughs or long
pans communicating one with the other so as to continually deposit bicarbonate of
soda as it cools in running slowly along, or other means may be employed for

page_text: keeping the liquor slightly agitated while it is cooling so as to expedite this
operation and to prevent the formation of crusts sticking to the sides of the pans.
The bicarbonate obtained by either of these opérations being of a crystalline
texture can easily be freed from mother liquor by a hydro-extractor or other means
and then dried, ground and dressed if necessary.
The solutions of the crude bicarbonate in water may be advantageously effected
under pressure and preferably in an atmosphere of carbonic acid. Under these
circumstances the temperature at which a solution of bicarbonate of soda
commences to decompose is much higher than under the ordinary pressure of the
atmosphere and consequently the solution can be effected at a higher temperature
and a larger amount of bicarbonate can be dissolved in water.
It is however necessary to cool this solution to 65 degrees centigrade before the
pressure is taken off.
The mother liquor of this operation can be used over several times for dissolving
fresh quantities of crude sodium bicarbonate to be treated in the same way till
ammonium or other salts accumulate to too great an extent, when the ammonia can
be boiled out and the liquor evaporated to dryness to save the chlorides and other
salts contained therein, or preferably it can be used without previous boiling to
replace the water or a part of the water used for washing out of the crude sodium
bicarbonate as it comes out of the carbonators the chlorides of sodium and
ammonium which it contains. The advantage which the mother liquor possesses
over pure water for this purpose is that being already saturated or nearly
saturated with sodium bicarbonate, it obviates or greatly reduces the loss now
sustained by the solution of a portion of sodium bicarbonate.
Dated
Dated 041 1
1004

page_text: We, LUDWIG MOND and GUSTAV JÁRMAY, both of Winnington, in the county of
Chester, Manufacturing Chemists do hereby declare the nature of our said invention
for "
IMPROVEMENTS IN AND APPERTAINING TO THE MANUFACTURE OF SODIUM
BICARBONATE" and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
Bicarbonate of soda as obtained in the manufacture of soda by the ammonia-soda
process contains besides some minor impurities a certain quantity of ammonia
(probably in chemical combination with the bicarbonate of soda), which makes
this product unfit for most of the purposes for which bicarbonate of soda of the
market is used. Moreover the drying of this crude bicarbonate of soda made by
the ammonia-soda process is a very tedious operation on account of its sludgy
nature. Washing with water does not free this crude bicarbonate of soda from the
ammonia it contains, nor have many attempts to obtain this end, by washing it
with caustic ammonia (see James Richards' British Patent N° 376 of 1874), or
other chemicals led to the desired result.
Wo have however discovered that if the crude bicarbonate of soda of the
ammonia soda process be dissolved, in warm water, and the resulting solution
allowed to cool, pure bicarbonate of soda separates, and all the ammonia remains in
solution. If a very pure article be required, all the other impurities can be got rid
of by letting the warm solution clear itself, either by settling or filtering it before
it is allowed to cool.
In carrying out our invention, we dissolve the crude bicarbonate of soda in
water of about 60 degrees centigrade, and separate the insoluble matter preferably
by filtration.
The clear solution is treated in different ways according to the quality or grain
of bicarbonate of soda, that it is desired to obtain.
It is either run warm into pans, and allowed to cool slowly, or it is first cooled
as far as practicable without separation of bicarbonate by means of cooling pipes
or other arrangements, and is then run into pans to cool further and deposit the
bicarbonate of soda, or the liquor may be run through a series of troughs or long
pans communicating one with the other, so as to continually deposit bicarbonate of
soda as it cools in running slowly along (we prefer this plan), or other means may
be employed for keeping the liquor slightly agitated while it is cooling, so as to
expedite this operation and to prevent the formation of crusts sticking to the sides
of the pans. The bicarbonate obtained by either of these operations being of a
crystalline texture can easily be freed from mother liquor by a hydro-extractor or
other means, and then dried, ground, and dressed if necessary.
The solutions of the crude bicarbonate in water may be advantageously effected
under pressure, and preferably in an atmosphere of carbonic acid. Under these
circumstances the temperature at which a solution of bicarbonate of soda commences
to decompose is much higher than under the ordinary pressure of the atmosphere,
and consequently the solution can be effected at a higher temperature, and a larger
amount of bicarbonate can be dissolved in water.
It is however necessary to cool this solution to 65 degrees centigrade before the
pressure is taken off,
The mother liquor of this operation can be used over several times for dissolving.
fresh quantities of crude sodium bicarbonate to be treated in the same way till
ammonium or other salts accumulate to too great an extent, when the ammonia can
c

page_text: be boiled out and the liquor evaporated to dryness to save the chlorides and other
Balts contained therein; or preferably it can be used without previous boiling to
replace the water, or a part of the water used for washing out of the crude sodium
bicarbonate, as it comes out of the carbonators, the chlorides of sodium and
ammonium which it contains. The advantage which the mother liquor possesses
over pure water for this purpose is that being already saturated or nearly saturated
with sodium bicarbonate, it obviates or greatly reduces the loss now sustained by
the solution of a portion of sodium bicarbonate.
Having now particularly described and ascertained the nature of our said
Invention, and in what manner the same is to be performed, we declare that what
we claim is:
1st The process substantially as herein described of manufacturing pure sodium
bicarbonate free from ammonia from crude impure sodium bicarbonate such as that
made by the ammonia-soda process.
2nd The following separate points, steps, or parts of the process of manufacturing
purified sodium bicarbonate from comparatively impure salt, such as that made at.
the present time by the ammonia-soda process, each substantially as described.
(a) Dissolving the crude salt in warm water at a temperature below the point at
which sodium bicarbonate decomposes, separating the insoluble matters, and
afterwards cooling the solution.
(b) Dissolving the crude salt in water under pressure at a temperature a little
below the point at which sodium bicarbonate decomposes at the pressure used,
separating the insoluble matters, cooling to about 65 degrees centigrade before
taking off the pressure, and then cooling further as far as practicable and removing
the sodium bicarbonate that solidifies out.
(c) Passing the warm saturated solution of sodium bicarbonate through a series
of cooling pans or troughs in a continuous current, whereby the salt is obtained of
the desired grain.
(d) Taking the mother liquor obtained after cooling a warm saturated solution
of the crude salt, heating it and dissolving therein a fresh batch of crude bicarbonate
of soda, and repeating the operation till the foreign salts accumulate to an injurious
extent, utilizing the final cooled mother liquor if desirable to wash the crude salt
as it comes from the carbonators, or by boiling it to dryness after boiling out, and
recovering the ammonia it contains.
Dated this 00
1
7000