Improvements in the Manufacture of Caustic Soda.
Year: 1890

page_text: Date of Application, 12th June, 1890
Complete Specification Left, 25th Feb., 1891-Accepted. 2nd May, 1891
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Caustic Soda.
1, FRANCIS ELLERSHAUSEN, of Hebburn-on-Tyne, in the County of Durham,
Gentleman, do hereby declare the nature of this invention to be as follows:-
:-
My invention relates to the manufacture of caustic soda from sulphide of sodiun
by treating solutions of such sulphide with hydroxide of iron.
Many processes have heretofore been proposed for obtaining caustic soda from
sulphide of sodium by means of hydroxide of iron, but all such processes have
possessed defects which prevented them from being commercially adopted.
My invention has for its object to provide process which can be worked
commercially.
According to my invention the sulphide of sodium solution instead of having the
hydroxide of iron mixed therewith and being boiled as has heretofore been proposed
is caused to pass through a filter or bed of hydroxide of iron by which the sulphur
is taken up, the liquor passing through the filter or bed being a solution of caustic
soda. After a sulphide of sodium solution has been passed through the said filter
or bed, a quantity of water (preferably in a heated condition) is advantageously
passed through the said filter or bed, whereby a proportion of the soda remaining
in the bed after the previous filtering operation is removed and a solution of caustic
soda obtained.
In practice I prefer to pass solutions of sulphide of sodium and water through
the filter or bed alternately.
It is obvious that the hydroxide of iron will ultimately be converted into sulphide
of iron and so have no action upon the sulphide of sodium. It is then removed and
a fresh charge substituted therefor.
I prefer to employ hydroxide of iron in a porous condition which is advan
tageously obtained by heating peroxide of iron with carbonate of soda and then
lixiviating the same...---
::
"Dated the 19th dex of June 1890
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Caustic Soda.
J, FRANCIS ELLERSHAUSEN, of Hebburn-on-Tyne, in the County of Durham,
Gentleman, 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 relates to the manufacture of caustic soda from sulphide of
sodium.
According to my invention the sulphide of sodium solution is caused to pass
through a filter or bed of material capable of taking up sulphur, and thereby
transforming the sulphide of sodium into caustic soda and an insoluble double
sulphuret of iron and sodium, the liquor passing through the filter or bed being a
solution of caustic soda.
In my Provisional Specification I described this filter or bed as being composed
of hydroxide of iron and preferably such as is obtained by lixiviating the compound
obtained by heating peroxide of iron with carbonate of soda (such compound being
known as ferrate of soda) with water.

page_text: During the course of my experiments I have found that the best results are
obtained by lixiviating the compound, known as ferrate of soda, by means of the
solution of sulphide of sodium which is to be treated, and I therefore form the
filter or bed of ferrate of soda, and pass the said solution of sulphide of sodium
therethrough. A double reaction then takes place in the filter or bed, that is to
say, as the lixiviation proceeds the iron of the ferrate for the moment I believe
takes the form of hydroxide of iron, which, immediately it is formed, combines
with the sulphur of the sulphide of sodium, being thereby converted into a double
sulphide of iron and sodium which remains in the filter or bed together with caustic
soda, which latter passes through the filter.
I prefer to form the filter or bed in an open metal or other tank, the filtering
material lying therein, to a depth, say, of four fect; and in order that the sulphide
of sodium solution shall not injure the walls of the tank I introduce the said
solution into the filter at, say, the centre of its surface or in such other position,
that before it reaches the said walls it has come into contact with sufficient of
the filtering material to causticize it, in which condition it has no effect upon
the tank.
In practice I advantageously introduce the filtering material or ferrate of soda
into the tank in the hot condition in which it comes from the furnace wherein
it is formed and immediately pass the solution therethrough, as I believe I
thereby obtain the best results as regards the strength of solution obtained, but
the ferrate of soda may be in a cold condition, the solution itself being hot, and
sometimes both the filtering material and the solution may be cold, as heat is
produced spontaneously in the filter or bed owing to the reactions.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. The improvement in the manufacture of caustic soda from sulphide of
sodium, consisting in passing a solution of such sulphide of sodium through_a
filter or bed of ferrate of soda wherein the said solution is desulphurized, sub-
stantially as described.
2. The use in the manufacture of caustic soda from sulphide of sodium of a
filter or bed, substantially as hereinbefore described for the purpose specified.
Dated the 25th day of February 1891.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.