Improved Means applicable for Use in Extracting Gold and Silver from Auriferous and Argentiferous Solutions.
Year: 1893

page_text: Date of Application, 5th Dec., 1893-Accepted, 6th Jan., 1894
COMIDDIN DIUIFICATION.
Improved Means applicable for Use in Extracting Gold and Silver
from Auriferous and Argentiferous Solutions.
I, CHARLES RALEIGH, of Johannesburg, in the South African Republic,
Milling Engineer, 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 :-
This invention relates to improved means applicable for use in extracting gold
and silver from auriferous and argentiferous solutions.
In the process of extracting gold (or silver) from ores or compounds by
cyanogen, it is usual to precipitate the gold (or silver) from the cyanide solution
by passing the latter through boxes or filters containing metallic zinc, on the
surface of which the gold or silver is deposited.
It is, however, found that by this method, not only is the gold or silver incom-
pletely extracted, but, owing to further chemical action between the zinc and the
cyanide solution, the latter is rendered inefficient for further use.
In the process of extracting gold (or silver) from ores or compounds by chlorine,
the usual precipitant is sulphate of iron; the employment of which renders the
chlorine solution unsuitable for further use.
The objects of my present invention are to provide a suitable and efficient method
of, and apparatus for, precipitating or depositing gold (or silver) from cyanide,
chlorine and other solutions without rendering the same inefficient for further use.
My improved method consists in filtering the solution through granular or
permeable electrodes which, while retaining the precious metal, do not deteriorate
the solution; the latter remaining available for utilization in the treatment of a
fresh charge of ore or compound.
In the accompanying drawings,
Fig. 1 is a vertical section of filtering or precipitating apparatus constructed
according to my invention; Figs. 2 and 3 showing modifications.
A is a box or casing of wood, porcelain or other material, containing divisions B,
Between
made of any suitable porous substance, such as earthenware or canvas.
these divisions, there are alternate layers C and D composed of particles or pieces
of carbon, charcoal or metal, suitable for forming "electrodes."
The metal may
be an amalgam; copper saturated with mercury being especially suitable.
The particles or pieces of carbon, charcoal or other substance, of which the
electrodes are composed may be in a loose granular form or may be compressed
into cakes of suitable shape; and both electrodes may be composed of the same
material, or of dissimilar materials. By preference, I use electrodes having both
anodes and cathodes of carbon, or anodes of carbon and cathodes of pieces of
copper saturated with mercury and sensitized by sodium or potassium amalgam.
The layers or electrodes C and D are coupled up or connected to a battery,
dynamo or other suitable source of electricity, and respectively form anodes and
cathodes.
The layers or electrodes may be arranged either in series or in parallel, or partly
in series and partly in parallel, with the conductors (shown in dotted lines)
connected to the source of electricity.
The cyanide or chlorine solution containing gold (or silver) enters by the pipe E
and is evenly spread over the top of the filter by the perforated piece F. As the
liquid or electrolyte filters through the layers or electrodes, the precious metals
become separated and deposited in the cathode layers D.

page_text: The liquid, after filtering through the last layer, can either run into a tank for
further use, or be led into another filter A' constructed similarly to A.
In Fig. 3, the layers or electrodes are vertical instead of horizontal.
In Fig. 4,
the electrodes are arranged in narrow porous pots G, each alternate porous pot
containing an anode or a cathode. H are the conductors, which lead the electric
current to the centres of the electrodes. The electrodes are composed of materials
or substances such as those previously enumerated.
In the recovery of gold (or silver) by means of my "electric filter," the action
may be expedited by raising the temperature of the apparatus by the application
of steam or otherwise. With the same object, oxygen or air may be supplied by
the pipe K. The operation may be carried out under pressure or in vacuo.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I claim :-
1. The improved method of extracting. gold and silver from auriferous and
argentiferous solutions, substantially as herein described, the same consisting in
filtering the solution through granular or permeable electrodes, and subsequently
recovering the precious metals therein deposited.
2. The improved method of extracting gold and silver from auriferous and
argentiferous solutions, substantially as herein described, and whereby after
filtering the auriferous or argentiferous solution through granular or permeable
electrodes, the solvent solution is yielded in a condition suitable for reuse with a
further charge of ore or compound.
3. The herein-described filtering or precipitating apparatus for use in the
extraction of gold and silver, the same comprising perforated, porous or permeable
material which, while permitting solutions containing gold and silver to filter
through them, act in conjunction with a current of electricity to decompose the
solution in its passage through the filter, the precious metals being precipitated
and deposited in the interstices of the said material.
4. The herein-described filtering or precipitating apparatus for use in the
extraction of gold and silver, the same comprising parts which form anodes and
cathodes respectively, the electrodes being composed of particles or pieces of loose
or compressed charcoal, carbon, metal, metallic alloys or amalgams.
5. A filtering or precipitating apparatus for use in the extraction of gold and
silver, constructed substantially as herein before described, and in which precipitation
is expedited by artificial heat and the introduction of air, oxygen or hydrogen.
6. A filtering or precipitating apparatus for use in the extraction of gold and
silver, constructed substantially as hereinbefore described and arranged to operate
under pressure or in vacuo.
Dated the 17th day of Novemba 1002
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.