Improvements in the Production of Carbonate of Soda.
Year: 1888

page_text: Date of Application, 25th Oct., 1888
Complete Specification Left, 25th July, 1889-Accepted, 21st Sept., 1889
PROVISIONAL SPECIFICATION.
Improvements in the Production of Carbonate of Soda.
I, HENRY WESTON WALLIS of 17 Holborn Viaduct in the City of London,
Analytical Chemist, do hereby declare the nature of this invention to be as
follows:-
In the process of extracting lead from its sulphur compounds by the use of an
alkali as the reducing agent, a sulphide of the alkali is formed as slag, which is
practically a waste product.
The object of my invention is to utilize this slag, or any alkaline-sulphide otherwise
obtained, for the purpose of precipitating as sulphides metals in solution as sulphates.
With this object dissolve the sulphide of the alkali in water and add to this solution
the metals in solution as sulphates. I then introduce carbonic acid into the solution,
the result being that the said metals, as well as any precipitable metals which may be
contained in the slag, are precipitated as sulphides while at the same time the alkali is
converted into carbonate of the alkali and sulphate of the alkali. Or I add the
carbonic acid first to the solution of the alkaline sulphide, by which addition
sulphuretted hydrogen is set free, which I then convey into a solution of metals
contained in another reservoir or vessel. The sulphide solution is thus converted into
a solution of commercially pure carbonate of the alkali, and the metals are precipitated
from their solution as sulphides in the other reservoir. If the solution of said metals
contain alkali, which is the case, when the ores of the metals previous to their solution
have been roasted with salt, then such solution, after the treatment with sulphuretted
hydrogen consists of sulphate of soda.
The carbonic acid employed as above described may be introduced either by adding
bicarbonate of soda to the solution, or by forcing carbonic acid as gas into the
solution. The solution of carbonate of soda obtained may then be causticized and
concentrated by the usual methods, or it may be directly concentrated for carbonate of
soda.
Dated this 25th d
1000
J. C. MEWBURN,
169, Fleet Street, London, Agent.
COMPLETE SPECIFICATION.
Improvements in the Production of Carbonate of Soda.
I, HENRY WESTON WALLIS, of 17, Holborn Viaduct, in the city of London,
Analytical 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 :-
My invention chiefly relates to the recovery of the alkali from the slag obtained in
extracting lead from its sulphur compounds by the use of an alkali as the reducing
agent, which slag is a sulphide of the alkali.
According to my invention I dissolve the sulphide of the alkali in water and then
introduce carbonic acid into the solution, the result being that sulphuretted hydrogen
is set free. The sulphide solution is thus converted into a solution of commercially
pure carbonate of the alkali which may be directly concentrated for the production
of the carbonate, or causticized and concentrated by any of the usual methods.
The carbonic acid above referred to may be introduced either by adding bi-
carbonate of soda to the solution or forcing carbonic acid gas into the solution.
The sulphuretted hydrogen set free as hereinbefore described may be used to
precipitate sulphides from solutions of metals, for instance sulphide of copper from a
[Price 4d.1

page_text: solution of copper, the sulphuretted hydrogen being conveyed into the solution; or
the sulphide solution may be mixed with the metal solution prior to the addition of the
carbonic acid. If the solution of metal thus treated contains alkali, which is the case
when the ores of the metal previous to their solution have been roasted with salt,
then such solution, after the treatment with sulphuretted hydrogen, is a solution of
sulphate of soda.
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:-
(1) The method of recovering soda from slags obtained as hereinbefore described,
substantially as set forth
day of July 1889.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.