Improvements in the Manufacture of Soda and Potasn.
Year: 1890

page_text: Date of Application, 20th Jan., 1890
Complete Specification Left, 20th Oct., 1890-Accepted, 14th Mar., 1891
Improvements in the Manufacture of Soda and Potasn.
I, FRANCIS ELLERSHAUSEN, of Hebburn-on-Tyne, in the County of Northum-
berland, Gentleman, do hereby declare the nature of this invention to be as
follows:-
:-
My invention chiefly relates to the manufacture of caustic soda from sulphide of
sodium.
According to my invention I treat a solution of sulphide of sodium with ferrate
of soda, the result of which is that during the subsequent chemical reaction the iron
of the ferrate of soda combines with the sulphur of the sulphide of sodium and
precipitates in the form of sulphide of iron.
The remaining liquor which is a solution of caustic soda can be concentrated in
the usual manner.
In practice I find it advantageous to utilize the sulphide of iron obtained as
before mentioned and the carbonate of soda (known as fished salts) obtained during
the concentration of the caustic liquor, for the production of ferrate of soda. For
this purpose the sulphide of iron is roasted so as to drive off the sulphur and
produce peroxide of iron, which latter is then combined with the fished salts under
the action of heat whereby ferrate of soda is produced.
A great advantage of thus utilizing the fished salts is that there is not the necessity
which usually exists of disposing of them, or of causticizing them in large quantities
of water which has subsequently to be evaporated.
Although I have only referred to the manufacture of caustic soda it is
to be understood that my invention is equally applicable for the manufacture of
caustic potash.
L
001 1
T
1000
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Soda and Potash.
I, 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 chiefly relates to the manufacture of caustic soda from sulphide of
sodium by means of ferrate of soda (sometimes called ferrite of soda and herein-
after referred to as ferrate).
It is known that if ferrate of soda be lixiviated with water a solution of caustic
soda is obtained and hydroxide of iron is deposited. It is also known that if a
solution of sulphide of sodium be treated with hydroxide of iron (either in the
natural state or produced as above described or in any other suitable manner) the
said solution is causticized and sulphide of iron is formed. The equation which
represents this reaction is probably as follows:-
:-

page_text: The chief drawbacks to the use of hydroxide of iron are its moist nature and its finely
divided condition which cause it when in contact with the solution treated to assume
a muddy form through which it is impossible for the liquid to percolate, so that
there is very little contact between the solution and the hydroxide and consequently
an imperfect reaction. If, in order to obviate this imperfectre-action the sulphide
of sodium solution is agitated after the introduction of the hydroxide of iron, it
is found that a large proportion of the soda gees with the sulphide of iron unless
the solution is diluted to such an extent as to render the cost of concentration a bar to
the commercial working of the process, and in addition to this the quantity of free
water given off by the hydroxide of iron, during the reaction, tends still further to
reduce the strength of the caustic solution. For these and other reasons such a
process has not been commercially successful although many attempts have been
made to use it.
The chief object of my invention is to obviate the defects heretofore experienced
in the direct use of hydroxide of iron in the manufacture of caustic soda from
sulphide of sodium and to this end I treat the sulphide of sodium with ferrate
directly. I believe that the reaction which occurs may be expressed as follows:-
FеОNa₂O + 4 H₂O + 4 Na,S = Fe, Na,S, + 8 NaOH.
I sometimes treat the solution of sulphide of sodium with the ferrate by stirring
up the ferrate in the solid form with the solution in a suitable tank. The liquor
resulting, when the precipitate is thrown down, is a solution of caustic soda which
can be concentrated in the usual manner.
Another mode of treatment which I find advantageous is as follows. I roast
carbonate of soda and peroxide of iron and obtain the ferrate in a granular form.
The use of ferrate in the granular condition gives the best results. I form a
filter-bed of the ferrate which may be of considerable thickness, say about four
feet deep, through which the solution of sodium sulphide of a strength of say
40 Twaddle can freely percolate, and in the course of this percolation nearly all the
soda in the ferrate and the sodium in the sulphide solution are converted into a
solution of caustic soda whilst another portion of the soda forms with the iron a
double compound, videlicet, sulphuret of iron and sodium which is insoluble. The
strength of the said solution is considerably increased by the presence of the soda
originally contained in the ferrate. By reason of the fact that ferrate is anhydrous
and in its conversion into caustic soda absorbs a considerable quantity of water
from the solution, the concentration of the solution is considerably increased.
The use of the filter-bed in the treatment above described is a modification of
that to which reference has been first made and is the subject of the Letters Patent
applied for on June 12th 1890 No. 9112 and will be more fully described in the
Complete Specification of that Patent.
The double sulphuret of iron and sodium, when the filter-bed is exhausted, may
be treated for the production of either sulphate or sulphite or hyposulphite of soda,
but this treatment forms no part of the present process and is also the subject of a
separate Application for a Patent numbered 16676 of 1890.
In the foregoing descriptions I have referred to the manufacture of caustic soda
and my invention is equally applicable for the manufacture of caustic potash, car-
bonate of potash being used instead of carbonate of soda in the preparation of the
ferrate.
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 manufacture of caustic soda and potash from their respective sulphides

page_text: (2.) In the manufacture of caustic soda and potash from their respective sulphides
by the use of ferrate, the use of the ferrate in a granular form, substantially as
described.
Dated the 20th day of October 1890.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.