Process for Working Metallic Sulphides.
Year: 1896

page_text: Date of Application, 1st Apr., 1896-Accepted, 16th May, 1895
COMPLETE SPECIFICATION.
Process for Working Metallic Sulphides.
I, ARNOLD VON SIEMENS, of 94 Markgrafen-strasse, Berlin, in the Empire of
Germany,
Owner of Manufactory, 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:-
The existing electrolytic methods for working those metallic sulphides which
give soluble double salts with the sulphides and sulphhydrates of the alkalies, that
is to say principally the sulphides of antimony, arsenic and mercury, have been
carried out in two ways:
1. By electrolytic decomposition of these double salts without use of a diaphragm,.
in which case the extraction lye (alkali monosulphide) must always be made anew
and by-products (alkali hyposulphite) are produced, the sale of which is supposed
to pay wholly or partially for the raw materials required for making the lye
(Borcher's process).
2. By decomposing these double salts in the cathode compartment of an
electrolytical decomposing vessel provided with a diaphragm, whereby no doubt,
the extraction lyes (alkali sulphhydrate) are always regenerated, but on the
other hand, a separate oxidising process had to be effected in the anode compart-
ment, the products of which process are either entirely waste, or have to be used
for other processes which are quite foreign to the metallurgical process in view
(Siemens and Halske's process).
I have discovered that not only the sulphhydrates and sulphides of the alkalies
but also the analogous compounds of the alkaline earth metals (Ca, Ba, Sr, Mg,)
show the property of yielding, under certain conditions, soluble double sulphides of
antimony, arsenic and mercury. The employment of this group of the alkaline
earth sulphides has furthermore the advantage that the lyes, precipitated electro-
lytically without the use of a diaphragm can be regenerated without the use of
new raw materials and be led back into the process.
By way of example I will describe such a closed circuit process for antimony
sulphide as the ore to be worked, and calcium sulphhydrate as extraction lye,
observing at the same time that the working of the sulphides of antimony, arsenic
and mercury by means of the sulphides or sulphbydrates of calcium, barium,
strontium and magnesium is effected in an analogous manuer, care being taken,
in the case of mercury, that the lye shall contain an excess of alkaline
earth-hydrate.
In the example chosen the process is as follows:
The antimony sulphide is treated with calcium sulphhydrate lye in suitable
extraction apparatus (tanks with stirrers, percolation towers &c.).
As in the example given the whole of the sulphuretted hydrogen corresponding
to the sulphur contained in the ore does not pass off, there may be employed
simultaneously two processes in the extraction :-

page_text: If now the lye freed from the metal containing calcium sulphide be treated with
carbonic acid, the half of the sulphur contained therein escapes in the form of
sulphuretted hydrogen, while at the same time a mixture of carbonate of lime and
the remainder of the sulphur of the lye is precipitated :
The sulphuretted hydrogen is also collected, while the residue is converted into
caustic lime by heating to redness under exclusion of air, the sulphur contained in
the precipitate being distilled off while the carbonic acid is employed for the
precipitation of farther bisulphide lyes.
The caustic lime and the collected sulphuretted hydrogen are used for the
production of fresh calcium sulph-hydrate lye. Thus not only is the whole of the
extraction lye regenerated but also, the whole of the sulphur of the ore is obtained
in a useful form.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. Extraction of the sulphur compounds of antimony, arsenic and mercury by
means of the sulph-hydrates or sulpbides of the alkaline earths, with or without
addition of alkaline earth hydrates, and the electrolytic precipitation of the lyes
obtained for the purpose of obtaining antimony, arsenic and mercury, in which
process sulphuretted hydrogen escapes, substantially as described.
2. In the process referred to in the first claim, the introduction of carbonic acid
into the precipitated lyes, whereby the regeneration of the extraction-lye from the
sulphuretted hydrogen escaping in this operation and also from that obtained in
the extraction and precipitation is rendered possible by employing the same in
conjunction with the alkaline earth oxides obtained by heating to redness the
precipitated alkaline earth carbonates for the production of alkaline earth sulph-
hydrates or sulphides in using the alkaline earth oxides obtained by heating to
redness the separated alkaline earth carbonates, substantially as described.
Dated this 1st day of April 1896.
ABEL & IMRAY,
Agents for the Applicant.