IMPROVEMENTS IN THE MANUFACTURE OF 93 PROVISIONAL SPECIFICATION
Year: 1883

page_text: LETTERS PATENT to Walter Weldon, of Rede Hall, Burstow, in the County
of Surrey, for an Invention of "IMPROVEMENTS IN THE MANUFACTURE OF
93
PROVISIONAL SPECIFICATION left by the said Walter Weldon at the
Office of the Commissioners of Patents on the 3rd December 1883.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey, "IMPROVE-
MENTS IN THE MANUFACTURE OF SODA"
This invention consists in the manufacture of soda in such wise as to combine
the advantages of what is known as the Leblanc process with those of what is
known as the Ammonia process.
The Ammonia process yields soda very much more cheaply than the Leblanc
process, but the Leblanc process yields not only soda but also hydrochloric acid,
whereas the Aminonia process yields soda only.
:
The Ammonia process is based on the decomposition of chloride of sodium by
bicarbonate of ammonia. Obviously, if sodium sulphate could be decomposed by
bicarbonate of ammonia, the production of soda from sodium sulphate would be
immensely cheapened, while hydrochloric acid would at the same time be obtained
from the sodium chloride commenced with, just as in the Leblanc process.
It has hitherto been supposed, however, that it was not possible to obtain
bicarbonate of soda by the reaction of bicarbonate of ammonia on sodium sulphate,
by reason of sodium sulphate being so much less soluble than sodium chloride.
I have, however, discovered a means by which bicarbonate of soda can be obtained
industrially from sodium sulphate by the reaction thereupon of bicarbonate of
ammonia.
.
In the Ammonia process as at present practised, a saturated solution of sodium
chloride and free ammonia is treated by carbonic acid gas, with the result that
bicarbonate of soda and ammonium chloride are formed. The said saturated
solution contains, per hundred parts of water in it, about thirty-five parts of
sodium chloride and about eleven parts of ammonia. There are produced about
sixty parts of bicarbonate of soda and about forty-three parts of ammonium
chloride. The whole of the ammonium chloride produced dissolves, and with-it
about nine parts of bicarbonate of soda, the other fifty-one parts being precipitated
in the solid state. Of the theoretical yield of bicarbonate of soda, about 80 per
cept. is thus actually obtained,

page_text: If sodium sulphate were treated as sodium chloride is now treated in the
Ammonia process, per hundred parts of water used only eleven parts of sodium
sulphate could be dissolved, producing about thirteen parts of bicarbonate of soda,
of which nine parts would remain dissolved in the mother-liquor, leaving only four
parts to precipitate. Thus seventy per cent. of the bicarbonate of soda produced
would be lost, and only four parts by weight would be obtained per unit of volume
of liquor treated instead of the fifty-one parts by weight which are obtained when
the sodium salt used is the chloride as at present.
By my present invention, however, I am enabled to decompose sodium sulphate
by bicarbonate of ammonia, and to obtain absolutely the full quantity of
bicarbonate of soda which it is theoretically capable of yielding.
effect this
important object by using the sulphate of soda, or the greater part of it, in the
solid state.
in
There are several ways in which this method of working can be carried into
practice.
By one method, I begin with a solution of ammonia and sodium sulphate, the
quantity of the latter being as large as the quantity of water used will dissolve,
and the quantity of the former being such as corresponds to as much ammonium
sulphate as will form a saturated solution with the quantity af water used. I then
treat the mixed solution by carbonic acid gas. As the reactions which are thereby
caused to take place proceed, the water present becomes capable of dissolving more
sodium sulphate, and therefore I keep adding solid sodium sulphate as those
reactions go on, until I have at length obtained a mother-liquor saturated with
ammonium sulphate and bicarbonate of soda or ammonia as the case may be.
A modification of this method consists in adding to an aqueous solution of
ammonia as much sodium sulphate as is capable of yielding as much ammonium
sulphate as the quantity of water used will dissolve, and then treating the mixture
by carbonic acid gas. In such case, the greater part of the sodium sulphate will
at first remain undissolved, but it will gradually dissolve completely as the
. operation proceeds.
Another modification consists in treating together sodium sulphate and previously
formed bicarbonate of ammonia by such a quantity of water as will just dissolve
all the ammonium sulphate capable of being produced.
My new method of manufacturing soda thus consists of the following series of
operations:
1st. Decomposition of chloride of sodium by sulphuric acid, with production of
sodium sulphate and hydrochloric acid.
2nd. Decomposition of sulphate of soda by bicarbonate of ammonia, by one of
the methods above set forth.
3rd. Separation of the products of the second operation by filtration and
washing.
4th. Calcination of the filtered and washed solid product of the second operation,
to reduce it to the state of normal sodium carbonate, when it is not desired to use
or sell it as bicarbonate.
5th. Regeneration of ammonia for use again in the second operation, or for the
manufacture of bicarbonate of ammonia to be used in that operation, by distilling
the filtrate from the third operation with lime or magnesia.
6th. Filtering the residual liquor left after the performance of the 5th. operation,
and using it for the solution of more ammonia and sodium sulphate for a repetition
of the second operation.
I do not confine myself to the exact proportions of water, ammonia, and sodium
sulphate which are above prescribed, though I believe those proportions to be the
best

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Walter Weldon in the Patent Office on the 3rd June 1884.
WALTER WELDON, of Rede Hall, Burstow, in the County of Surrey,
MENTS IN THE MANUFACTURE OF SODA,"
"IMPROVE-
The present invention relates to the manufacture of soda from sulphate of soda.
by what is known as the ammonia process, and consists in using the sulphate of
soda, or a part of it, in the solid state.
There are several ways in which this manner of working may be carried into
practice.
By one method, I begin with a solution of ammonia and sodium sulphate, the
quantity of the latter being as large as the quantity of water used will dissolve,
and the quantity of the former being such as corresponds to as much ammonium
sulphate as will form a saturated solution with the quantity of water used. I then
treat the mixed solution by carbonic acid gas. As the reactions which are thereby
caused to take place proceed, the water present becomes capable of dissolving more
sodium sulphate, and therefore I keep adding solid sodium sulphate as those
reactions go on, until I have at length obtained a mother-liquor saturated with
ammonium sulphate and bicarbonate of soda or of ammonia as the case may be.
A modification of this method consists in adding to an aqueous solution of
ammonia as much sodium sulphate as is capable of yielding as much ammonium
sulphate as the quantity of water used will dissolve, and then treating the mixture.
by carbonic acid gas. In such case, the greater part of the sodium sulphate will at
first remain undissolved, but it will gradually dissolve completely as the operation
proceeds.
Another modification consists in treating together sodium sulphate and previously
formed bicarbonate of ammonia by such a quantity of water as will just dissolve
all the ammonium sulphate capable of being produced.
What I claim as the invention to be secured to me by the hereinbefore in part
recited Letters Patent is the treatment of sulphate of soda by ammonia and
carbonic acid, or by bicarbonate of ammonia, substantially as is above described.
In witness whereof I, the said Walter Weldon, have hereunto set my band and
seal this second day of June in the year of Our Lord one thousand eight hundred
and eighty four.