Year: 1887

page_text: Date of Application, 6th June, 1887
Complete Left, 6th Mar., 1888
Complete Accepted, 13th Apr., 1888
I, LEONHARD ADOLF STAUB D.Sc., of Northwich, in the County of Chester,
Chemist, do hereby declare the nature of this invention to be as follows:-
Hitherto it has been found necessary for the manufacture of certain carbonates of
soda, such as the monohydrated carbonate of soda to evaporate the whole of the
surplus water used for dissolving the carbonate of soda, thus requiring a large
expenditure of fuel. I have however, found, that if a high strength solution of
sodium carbonate be saturated with ammonia at a temperature and pressure varying
with the desired amount of hydration of the carbonate, the carbonate of soda is directly
precipitated in the desired form. For instance, the monohydrated carbonate of soda
is formed by saturating the sodium carbonate solution with ammonia at a temperature
of 55-60 degrees Centigrade, and under a pressure of not less than 5 pounds per
square inch. Saturation may however be effected at any other suitable temperature,
provided this temperature is kept so high as to prevent the formation of higher
hydrated carbonates of soda. As the sodium carbonate gets less soluble, the more
free ammonia such a solution contains, and as the solubility of the ammonia in such
solutions at the same temperature increases in the same proportion as the pressure,
it may be of advantage to use much higher pressures. Instead of having pressure on
the top of liquor, a high vessel may be used, in which the height of liquor produces
the necessary pressure.
The higher hydrated crystallised carbonates may be obtained by saturation with
ammonia at correspondingly lower temperatures.
In carrying out this invention a convenient way of operating is as follows:
A solution of sodium carbonate of high strength, which has been previously freed
from any organic and insoluble matters or other impurities by well known means, is
saturated with caustic ammonia in a closed vessel, provided with suitable agitating
and circulating arrangement. Sodium carbonate being very much less soluble in a
solution of free or caustic ammonia a carbonate of soda is precipitated in crystalline
form, and may be separated from the mother liquor by any known means.
pressure and temperatures at which such saturation is effected, vary as above stated
according to the form of the carbonate of soda it is desired to make. The crystallised
The

page_text: carbonate thus obtained may be first washed with a concentrated solution of sodium
carbonate, but this is not necessary. It may then be put under vacuum in any closed
apparatus, at a convenient temperature in order to volatilise any ammonia, which may
have been retained. Instead of putting it under vacuum, an inert gas may be passed
over it. The ammonia thus volatilised may be used for the same process over again,
or for any other useful purpose. The mother liquor containing the caustic ammonia
and some of the sodium carbonate which may have been kept in solution, separated
from the crystals is heated up by any suitable well known means in order to drive out
all or part of the ammonia.
Vacuum greatly hastens the evolution of ammonia. The ammonia thus evolved
may, after such treatment as required by the circumstances, such as cooling to
condense the water, be used again with advantage, for saturating another solution of
sodium carbonate. Thus no fresh ammonia would be required except to make up for
losses which may occur. The mother liquor' thus partly or completely freed from
ammonia, may be used for dissolving a fresh quantity of sodium carbonate, or if still
sufficiently rich in sodium carbonate it may be allowed to cool down for the manufacture
of ordinary crystal soda as is well understood.
Instead of using a high strength solution of sodium carbonate alone, such a solution
mixed with the bicarbonate of soda of the ammonia soda process may be employed.
In this case however, I treat such a mixture with ammonia under high pressure at a
temperature somewhat below the boiling point. The bicarbonate contained in the
mixture is by this treatment, decomposed into monocarbonate, which is precipitated as
above described, and carbonic acid which escapes, the ammonia acting partly as a
carrier of the carbonic acid.
The carbonic acid thus evolved, may after passing through suitable cooling apparatus
be used for the manufacture of pure bicarbonate of soda, or for any other useful
purpose. The precipitated monocarbonate, and the mother liquor may be treated as
above described. The mother liquor may also be used for mixing with a fresh
quantity of bicarbonate of soda, either direct or after all, or part of the ammonia has
been driven out. Thus solid monocarbonate can be obtained direct from bicarbonate
of soda by this process.
All the operations above described have to be carried on in one or more closed
vessels or apparatus, which may be conveniently arranged in such a way as to make
the process continuous. These vessels have however, to be made strong enough to
allow the use of vacuum or pressure as the case may be, and must be provided with
suitable appliances for regulating or altering the temperature to any required extent,
and for the distillation of ammonia from the mother liquor, and with agitators for
causing more uniform precipitation of the crystals.
73
11
1
1
1000

page_text: I, LEONHARD ADOLF STAUB, D.Sc. of Northwich, in the County of Chester,
Chemist, 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:—
Hitherto it has been found necessary for the manufacture of certain carbonates of
soda, such as the monohydrated carbonate of soda to evaporate the whole of the
surplus water used for dissolving the carbonate of soda, thus requiring a large
expenditure of fuel. I have, however, found that if a high strength solution of
sodium carbonate be saturated with ammonia at a temperature and pressure varying
with the desired amount of hydration of the carbonate, the carbonate of soda is
directly precipitated. in the desired form. For instance, the monohydrated carbonate
of soda is formed by saturating the sodium carbonate solution with ammonia at a
temperature of 55-60 degrees Centigrade, and under a pressure of not less than
5 pounds per square inch. Saturation may, however, be effected at any other suitable
temperature, provided this temperature is kept so high as to prevent the formation
of higher hydrated carbonates of soda. As the sodium carbonate gets less soluble, the
more free ammonia such a solution contains, and as the solubility of the ammonia in
such solutions at the same temperature increases in the same proportion as the
pressure, it may be of advantage to use much higher pressures. Instead of having
pressure on the top of liquor, a high vessel may be used, in which the height of liquor
produces the necessary pressure.
The higher hydrated crystallised carbonates may be obtained by saturation with
ammonia at correspondingly lower temperatures, but I have not yet by experiment
ascertained at exactly what temperature the various hydrates crystallise out, such
precise information being of little value.
In carrying out this invention a convenient way of operating is as follows:
'is
A solution of sodium carbonate of high strength, which has been previously freed
from any organic and insoluble matters or other impurities by well known means,"
saturated with caustic ammonia in a closed vessel, provided with suitable agitating
and circulating arrangement. Sodium carbonate being very much less soluble in a
solution of free or caustic ammonia, a hydrated carbonate of soda is precipitated in
crystalline form, and may be separated from the mother liquor by any known means.
The pressure and temperatures at which such saturation is effected, vary as above
stated according to the form of the hydrated carbonate of soda it is desired to make.
The crystallised hydrated carbonate thus obtained may be first washed with a con-
centrated solution of sodium carbonate, but this is not necessary. It may then be
put under vacuum in any closed apparatus, at a convenient temperature in order to
volatilise any ammonia, which may have been retained. Instead of putting it under
vacuum, an inert gas may be passed over it. The ammonia thus volatilised may be
used for the same process over again, or for any other useful purpose. The mother

page_text: liquor containing the caustic ammonia and some of the sodium carbonate which may
have been kept in solution, separated from the crystals is heated up by any suitable
well known means in order to drive out all or part of the ammonia.
Vacuum greatly hastens the evolution of ammonia. The ammonia thus evolved
may, after such treatment as required by the circumstances, such as cooling to
condense the water, be used again with advantage, for saturating another solution of
sodium carbonate. Thus no fresh ammonia would be required except to make up for
losses which may occur. The mother liquor thus partly or completely freed from
ammonia, may be used for dissolving a fresh quantity of sodium carbonate.
Instead of using a high strength solution of sodium carbonate, such a solution
mixed with the bicarbonate of soda of the ammonia soda process, or even water mixed
with bicarbonate of soda may be employed. In this case, however, I treat such a
mixture with ammonia under high pressure at a temperature somewhat below.the
boiling point. The bicarbonate contained in the mixture is by this treatment, lecom-
posed into monocarbonate, which is obtained as a precipitate, and carbonic acid which
escapes, the ammonia acting, first, as a carrier of the carbonic acid then by its
presence in the solution or liquor, rendering the monocarlionate of soda less soluble.
The carbonic acid thus evolved, may, after passing through suitable cooling
apparatus be used for the manufacture of pure bicarbonate of soda, or for any other
useful purpose. The precipitate of hydrated mono-carbonate, and the mother liquor
may be treated as above described. The mother liquor may also be used for mixing
with a fresh quantity of bicarbonate of soda, either direct or after all, or part of the
ammonia has been driven out. Thus solid monocarbonate can be obtained direct from
bicarbonate of soda by this process.
No special form of apparatus need be employed for this process, and I have not yet
decided in my mind which to prefer, but ani rather in favour of an apparatus such as
the following, for general use.
A strong vertical, cylindrical chamber of wrought iron or steel of any convenient
dimensions is provided in its interior, with a heating coil of large diameter, a per-
forated false bottom or serrated bell at bottom covering the orifice of the pipe, by
which the ammonia (preferably in the gaseous form) enters, and a suitable agitator
driven by a central vertical shaft and outside gearing. It is also provided with a
pressure gauge and adjustable safety valve, and an entrance near the top also for the
alkaline solutions or mixtures. If bicarbonate of soda be used, there is also an exit
at the top controlled by a valve for the carbonic acid.
A blow off pipe at the bottom, connects the chamber with a closed filter having
preferably a sloping bed, where the crystalline precipitates are separated from the
mother liquor. By means of a pump; this latter is drawn from the filter, and sent
into an ordinary ammonia still, where the ammonia is driven off and obtained in the
form of gas.
It is then returned again to the chamber, and used for saturating fresh
liquors. The remaining mother liquor from the still, (still containing sodium-
carbonate) can be used for dissolving or mixing with fresh quantities of carbonate or
bicarbonate of soda. After the crystals are sufficiently drained, and after the valve
on the pipe, carrying off the mother liquor, has been closed, the crystals are elevated
by means of any convenient elevating apparatus to a dryer, preferably consisting of a
long inclined or nearly. horizontal tube or trough, along the bottom of which runs a
worm or creeper, and through which, in the opposite direction to the action of the
worm, passes a current of hot or cold air, or other gas. The crystals passing through
this dryer are deprived of their moisture and residual free ammonia, which latter is
collected from the effluent air in any convenient manner.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what
claim is :-
1st. The process of separating carbonate of soda as a crystalline mono or other
hydrate from a solution of carbonate of soda, by means of ammonia, substantially as
- described

page_text: 2nd. In combination with the above claimed process, regulating the degree of
hydration of the solid product by varying the temperature and pressure at which the
solution of sodium carbonate stands, while treated with the ammonia, substantially as
described.
3rd. The process of manufacturing solid monohydrated monocarbonate (or other
carbonates of soda) and carbonic acid from a mixture of bicarbonate of soda in
water, or in a solution of mono-carbonate of soda, substantially as hereinbefore
described.