Improvements in the Process and Apparatus for the Recovery from Sulphate Lyes or Liquor of Sulphuric Acid Free from Arsenic and Antimony.
Year: 1893

page_text: Date of Application, 9th Aug., 1893-Accepted, 21st Oct., 1893
COMPLETE SPECIFICATION.
Improvements in the Process and Apparatus for the Recovery from
Sulphate Lyes or Liquor of Sulphuric Acid Free from Arsenic
and Antimony.
I, CARL VON GRABOWSKI of 9, Bahnhofstrasse Eisleben, in the Empire of
Germany, Ironmaster, 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:-
In order to render sulphate lye or liquor which contains free sulphuric acid
suitable for being subsequently directly utilised, a series of processes requiring
much trouble and work has been hitherto necessary, and thus the process of
purifying the same rendered very difficult and expensive.
This invention has for its object the removal of these drawbacks, and is carried
out as follows:-
The sulphate lye is first subjected to a suitable concentrating process, and the
then concentrated liquid is exposed to the action of an electric current of high
strength, suitable anodes and cathodes being used, whereupon the arsenic and
antimony still remaining therein are deposited on the cathodes in a reguline form,
or in the form of a metallic sulphide, so completely that the freed sulphuric
acid contained in the sulphate lye, is again directly applicable for any suitable
purpose.
If it be a question, for instance, of the treatment of the active lye which is
gradually charged with impurities in the course of the process for the electrolytic
recovery of pure copper in the sulphate bath, such lye is converted, first by
evaporation, and subsequently crystallisation, into sulphate of copper. The mother
liquor remaining from the crystallisation of the sulphate of copper contained in the
lye contains, in addition to free sulphuric acid, and metallic sulphates, arsenic and
antimony in considerable quantities, and is unsuitable for being directly purified by
electrolysis. If this mother liquor, however, be suitably evaporated, the dehydrated
sulphates are separated from the other metals contained in the liquor, and the lyes
are then rendered suitable for electrolytical purification, or the separation of arsenic
and antimony which remain in solution.
The process of purification is carried out in the following manner :-
Sulphate lyes containing free sulphuric acid, which are rendered impure not
only by the metallic sulphates but also by arsenic and antimony, are brought by
evaporation, with a simultaneous deposition of the sulphates, to a specific gravity
of about 52 degrees Baumé, and are then subjected or exposed in cells or vessels of
about 1 cubic metre capacity, to the action of an electric current of high strength
(60-80 ampères per square metre of anode surface) using anodes and cathodes of
lead or copper.
These cells or vessels are shown on the accompanying drawing-
Figure 1 being a longitudinal section:
Figure 2, a cross section, and
Figure 3, a plan view thereof.
Arsenic and antimony are thereupon deposited in a reguline form on the cathodes
so that the lye entirely freed therefrom and purified is again directly available for
any suitable purpose.
If the concentration of the liquor attains more than 52 degrees Baumé, the
separation of arsenic and antimony takes place as metallic sulphides, because, under
the action of the electric current, the free sulphuric acid is decomposed, causing
the formation of sulphuretted hydrogen. Arsenic and antimony, or their metallic
sulphides, may then be obtained from the deposits on the cathodes by carefully
washing off and drying in the usual known manner. The vessels employed for

page_text: obtaining these metals electrolytically consist of a box a formed of wood, which is
lined inside with lead plates 6 and afterwards given a coat of asphalt. A wooden
frame c is placed on top on the sides of the box, the latter being provided on two
sides with metal rails p and p', the first of which, p, is connected with the positive
pole, and the second, p', with the negative pole of a source of an electrical current
of high strength.
A suitable number of cross bars d of wood rest on the frame c and project
beyond the two guide rails p and pl, and the electrodes A and K are suspended
from these bars by means of strips i and i¹ of sheet copper, in such a way, however,
that the strip of each clectrode is merely intended to carry the same, whilst the
strip of copper of each electrode serves both for carrying the same and also for
conveying or transferring the electric current from one or other of the guide
rails and p to the electrodes. Each conducting strip is, for this purpose,
connected at one end with its electrode, and the other end, which is wound several
times round the bar d, is brought into connection with the positive or negative poles
of the source of current, according as the electrode is used as anode or cathode.
In the case of anodes, the strips of copper are coated with lead so far as they
penetrate into the liquid.
On the accompanying drawing, each anode is marked A, and each cathode K...
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. An improved process for purifying or regenerating sulphate lyes or liquors
containing free sulphuric acid, and, in addition to metallic sulphates, contain also
arsenic, and antimony, which consists in the lye or liquor being brought, by
-evaporation and allowing the sulphates therein contained to crystallise out, to a
specific gravity of 52 degrees Baumé, and then being, exposed to the action of an
-electric current of high strength, using anodes and cathodes of lead or copper, with
the object of entirely separating out the arsenic and antimony, and recovering the
free sulphuric acid contained in the sulphate liquor, substantially as described.
2. For carrying out the process described in Claim 1, an apparatus consisting of
a box or case a, having a lining b, current conducting bars or rails p and p', and
bars d, from which bars clectrodes are suspended by means of metal strips and i,
such metal strips being so arranged that each anode A is in connection by means of
its strip with the positive pole, and each cathode K. by means of its strip i¹ with
the negative pole of the source of current, substantially as described.
Dated this 8th day of August 1893.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicant.