Improvements in the Manufacture of Soda and Mono Calcic Phosphate.
Year: 1893

page_text: Date of Application, 6th Apr., 1893
Complete Specification Left, 6th Jan., 1894-Accepted, 10th Feb., 1894
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Soda and Mono Calcic
Phosphate.
I, FERDINAND HURTER Ph.D. of Widnes in the County of Lancaster
Analytical Chemist do hereby declare the nature of this invention which has
been communicated to me from abroad by Johannes Omholt of Christiania
(Kristian 4 Gade No. 12 III) in the Kingdom of Norway Chemist to be as
follows:-
This invention relates to the manufacture of soda by what is known as the
ammonia soda process from sulphate of soda and has for its principal object to
recover ammonia from the residual sulphate of ammonia produced in that process.
According to this invention the residual solution of sulphate of ammonia is
evaporated to dryness and the dry salt is mixed with ground or divided tri-calcic-
phosphate and the mixture is heated to an elevated temperature preferably in the
presence of steam. Ammonia gas is given off and this is removed as it is generated
and can be condensed in fresh solutions of sulphate of soda to be submitted to the
ammonia-soda process. The sulphuric acid of the said residual sulphate of ammonia
combines with some of the lime contained in the tri-calcic phosphate producing
mono-calcic phosphate (mixed with sulphate of lime) which may be used as a
manure. If any of the phosphate should remain as tri-calcic-phosphate it may be
converted into mono-calcic phosphate by the addition of a suitable proportion of
sulphuric acid.
Dated this 6th day of April 1893.
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, Agents:
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Soda and Mono Calcic
Phosphate..
I, FERDINAND HURTER Ph.D. of Widnes in the County of Lancaster
Analytical Chemist, do hereby declare the nature of this invention (which has
been communicated to me from abroad by Johannes Omholt of Christiania
(Kristian 4 Gade No. 12 III) in the Kingdom of Norway Chemist) and in
what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This invention relates to the manufacture of soda by what is known as the
ammonia soda process from sulphate of soda and has for its principal object to
recover ammonia from the residual sulphate of ammonia produced in that process..
In the manufacture of soda from sulphate of soda by the ammonia-soda process,.
sulphate of soda is dissolved in water and the solution is purified from any iron or.
lime it may contain by the addition of a small quantity of carbonate of soda. Into.
the purified solution of sulphate of soda ammonia gas is forced and is: absorbed
therein, and the ammoniacal solution is further treated with carbonic acid gas
obtained from a lime kiln. By these means the sulphate of soda is decomposed,
bicarbonate of soda and sulphate of ammonia being formed. The bicarbonate, by.
reason of its insolubility, is precipitated, whilst the sulphate of ammonia, being
readily soluble, remains in solution.

page_text: The bicarbonate of soda is separated from the solution of sulphate of ammonia
which can be done by filtration.
The process of manufacturing soda, and the apparatus therefor form no part of
this invention and are described in the Specifications of Letters Patent No. 571288
and No. 880484.
According to this present invention the residual solution of sulphate of ammonia
is evaporated to dryness preferably in pans known as "boat pans" made of steel.
The salt separating out during evaporation is fished out, drained and dried. The
dry salt consisting of sulphate of ammonia and a small quantity of sulphate of soda
is mixed with ground or finely divided tri-calcic phosphate, and the mixture is
heated to an elevated temperature preferably in the presence of steam. Ammonia.
gas is given off and this is removed as fast as it is generated, and condensed in
fresh solutions of sulphate of soda to be submitted to the ammonia soda process.
The sulphuric acid of the said residual sulphate of ammonia combines with some
of the lime contained in the tricalcic phosphate producing mono-calcic phosphate
(mixed with sulphate of lime) which may be used as a manure. If any of the
phosphate should remain as tricalcic phosphate it may be converted into monocalcic
phosphate by the addition of a suitable proportion of sulphuric acid.
The process may be represented by the following chemical equation:
CajPgO + 2 (NH,),SO,= CaH,P,O + 2CaSO,+ANH,
In practice I use native mineral phosphates and I prefer high grade phosphates.
The relative amounts of phosphate and of sulphate of ammonia to be used depend
upon the richness of the phosphates, and upon the composition of the residual
salts of sulphate of ammonia. For every one part of pure tricalcic phosphate
which the mineral contains, I add to, and intimately mix with it so much of
the sulphate of ammonia as corresponds to about 0.85 parts of pure sulphate
of ammonia, but I prefer to use the phosphate in excess.
The mixture is placed in a retort or equivalent vessel, preferably a horizontal
cast iron cylinder, set in brickwork and capable of being heated externally by
direct fire. The retort or vessel may be provided with a mechanical stirrer.
The mixture is introduced through a door which can be hermetically closed.
The retort or vessel has an exit pipe connected to it, for the exit of ammonia
gas, and is also provided with an inlet pipe through which steam can be admitted.
In this retort or vessel the mixture of tricalcic phosphate and sulphate of
ammonia is heated to a temperature of from 550° to 650° Fahrenheit or thereabouts,
and a slow current of steam, preferably previously superheated, is passed through
the retort or vessel. Ammonia gas is evolved and passes through the exit pipe to
suitable cooling apparatus, where the steam is condensed together with a small
amount of volatised sulphate of ammonia in the form of a dilute solution of sulphate
of ammonia. This solution may be used to dissolve the sulphate of soda to be sub-
mitted to the ammonia-soda process. The comparatively dry ammonia gas,
obtained by these means, is then conducted into absorbing apparatus where it meets
with fresh sulphate of soda solution and is absorbed therein, when these solutions
are treated as above described.
When it has been ascertained, by testing, that the evolution of ammonia gas in
the retort has ceased, the solid residue may be withdrawn, but I prefer to allow it
to cool either within the retort or vessel or in a special apparatus, in an atmosphere
of steam until the temperature has fallen to about 220° Fahrenheit. The process
of cooling when carried out in the retort or vessel may be accelerated by using
ordinary steam instead of superheated steam in which case two inlet pipes should be
provided, one for superheated steam and the other for ordinary steam.
During this process of cooling in an atmosphere of steam the monocalcic
phosphate reabsorbs to a great extent any water which it may have lost at the
higher temperature.
The residue is then withdrawn and, if necessary, ground to powder, when it
constitutes a valuable manure, It consists of a mixture of mono-calcic phosphate,

page_text: sulphate of lime and small quantities of sulphate of ammonia and soda, and of
unaltered tricalcic phosphate. In order to render the residual tricalcic phosphate
soluble in water, I add to the calcined residue a small quantity of sulphuric acid,
say about 10 to 15 per cent. of the weight of the said residue of sulphuric acid of a
specific gravity of 120° Twaddle. If the mass become too damp I dry it at a
temperature which should not exceed 212° Fahrenheit.
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 I
claim is :-
1. In the manufacture of soda from sulphate of soda by the ammonia soda process
heating the residual sulphate of ammonia with tricalcic phosphate so as to recover
the ammonia for reuse in the said process substantially as herein before described.
2. In the manufacture of soda from sulphate of soda by the ammonia soda
process, heating the residual sulphate of ammonia with tricalcic phosphate in an
atmosphere of steam so as to recover the ammonia and the reuse of the said
ammonia in the said process substantially as hereinbefore described.
3. In the manufacture of soda from sulphate of soda by the ammonia soda process
the production of mono-calcic phosphate by heating the residual sulphate of
ammonia with tri-calcic phosphate substantially as hereinbefore described.
4. In the manufacture of soda from sulphate of soda by the ammonia soda process,
the production of mono-calcic phosphate by heating the residual sulphate of
ammonia with tri-calcic phosphate in an atmosphere of steam substantially as
hereinbefore explained.
5. In the manufacture of soda from sulphate of soda by the ammonia soda process
heating the residual sulphate of ammonia with tri-calcic phosphate (either with
steam or without steam) and the production of mono-calcic phosphate and of
ammonia and the reuse of the said ammonia in obtaining soda by the said process
substantially as hereinbefore described.
Dated this 6th day of January 1894.
JOHNSONS & WILLCOX.