Electro-deposition of Gold and Silver.
Year: 1895

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 18 of the Patents, &c. Act, 1883), as allowed by
the decision of the Comptroller General of the 22nd day of November 1895.
Date of Applica'ion, 17th June, 1895-Accepted, 20th July, 1895
COMPLETE SPECIFICATION (AMENDED).
Electro-deposition of Gold and Silver.
EMILE ANDREOLI _Journalist, of 18 Somerleyton Road, London S.W. 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 the usual electr. deposition of gold or silver, each anode or row of anodes is
opposite and near to a cathode or row of cathodes either in a single electrolyte or
in two liquids separated by porous cells, and the metal is only deposited on the
side of the cathode which faces the anode. According to this invention, I use
two anodes only in presence of numerous cathodes and deposit gold and silver from
their solution in less time and on a much larger surface of cathodes, although in
smaller tanks than by the ordinary process.
I will take as an illustration the treatment of a cyanide of gold and potassium
cyanide solution, but my process is applicable to other gold and silver solutions.
In carrying out this invention, I may use a tank without compartments, or a
tank divided in three compartments by porous diaphragms. When there are three
compartments in the tank, the central one contains the gold solution, say, a cyanide
of gold and potassium solution, and is the negative compartment between two
positive compartments.
The electrolyte in the positive compartments may be varied. I prefer however
to use a caustic potash or soda solution, or a cyanide of gold solution similar to the
one electrolysed in the negative compartment.
I may use iron auodes, but I preferably use peroxidised lead as a positive plate,
and to the best of my knowledge, such peroxidised lead anodes have never been
employed in a cyanide solution.
At the bottom of the central compartment is a thin layer of mercury, in which
a copper or other metal plate con ected with the negative pole of the generator of
electricity is immersed.
In this mercurial cathode dip the lower edges of as many perforated plates or
gauzes, or pieces of wire network of amalgamated copper, or other suitable metal
as the width of the central compartment allows me to put one against the other,
making good contact with the mercury in which they stand up and work each as a
cathode. Thus these amalgamated plates present the largest surface possible of
mercurial cathodes to the gold solution, which rises from the bottom of the tank
and passes through their interstices as through a filter which retains the gold.
When a sufficient quantity of gold has been absorbed by the amalgamated cathodes,
the plates are cleaned up and the mercury is retorted in the ordinary way.
..
The gold solution enters the tank at the bottom by means of a pipe, or several
pipes, conveniently disposed over the mercury cathode, and escapes through outlets'

page_text: in the upper part of the compartment after it has yielded its gold to the mercury
layer and to the amalgamated perforated plates, gauzes, wire network, or
the like.
When I have several tanks, the gold solution runs from one central compartment
to a second, etc., through suitable pipes. The diaphragms are preferably made of 5
porous asbestos, or Kieselguhr porcelain, mounted on suitable frames made of
paraffined wood or slate, or similar material, and fixed in grooves cut at the bottom
and on the walls of the tank where they make watertight compartments. The
advantage in employing asbestos or Kieselguhr porcelain, or their equivalent,
is that it does not allow the diffusion of the cyanide, and that this material is not 1
attacked by alkalies, or by cyanide of potassium.
When such porous porcelain cannot be procured, the compartments are formed
by finely woven tissues stretched on frames, and in such a case, the same gold
solution circulates in the three compartments, or, still better the electro deposition
of gold takes place in a tank without compartments, as hereinafter described and 1
illustrated.
A convenient arrangement according to my invention is represented in Fig. 1 in
longitudinal section, and Fig. 2 in cross section in the accompanying drawing:
A, A. is the tank.
BB are the positive compartments containing a caustic potash or cyanide of gold 2
and potassium solution.
CC are the iron or peroxide of lead anodes.
D is the central compartment containing the gold solution.
E is the layer of mercury, in which is immersed a copper or other metal F,
connected with the negative pole of the generator of electricity.
G G G are the amalgamated perforated plates which dip in the mercurial
cathodes.
His the pipe through which the solution enters.
K is the pipe through which the solution runs off.
2
Fig. 3 shows an installation of several tanks and the gold solution runs from 3
one central compartment to a second, etc. through suitable pipes.
In Fig. 3, A is the cistern containing the gold solution to be treated.
BBB is a series of electrolysers through which the solution passes and yields
its gold.
Cis the collecting tank in case the solution has to pass again through the 3
electrolysers to be thoroughly exhausted.
P is the pump which sends back the solution to the feeding cistern A.
The simplest apparatus for electro deposition of gold and the one which I prefer,
consists of tanks without partitions and which I will illustrate as follows
Fig. 4. A is the tank along the sides of which are suspended two peroxidised lead 4
anodes B B, which are perforated and do not reach the surface of the layer of
mercury C, in which a plate of copper, or other convenient metal, is immersed and
is connected with the negative pole of the generator of electricity. Proper means
are adopted to prevent any contact between the anodes B B and the numerous
amalgamated perforated plates, gauzes, network, which dip in the mercury, fill up 4
the tank, and work practically each as mercurial cathode. There is more
efficiency, conductivity, and economy in using this tank without compartments than
the two others I have herein before described and illustrated.
a
Instead of arranging lengthwise my anodes and cathodes in a tank, I may have
them disposed crosswise, and in such a case, I have one perforated anode for every
group of 12, or 15, cathodes.
The advantages of this last arrangement are that I can have a very long tank
without the trouble of using long, peroxidised lead plates and amalgamated plates,
which it is difficult to keep apart and parallel without the risk of short circuiting.
Fig. 5 shows a tank A in which B B B B are the perforated anodes, connected 5
outside on a bar C¹.
CCCC are the amalgamated perforated cathodes, dipping in a thin layer of

page_text: mercury D, connected by E to the generator of electricity. F are the inlet pipes ;:
G the outlet pipes.
Fig. 6 shows a cathode.
means.
Fig. 7 shows a perforated anode made of lead peroxidised by one of the known
The anodes are fixed in a slate or paraffined wood frame. The anodes
slide in grooves cut in the walls of the tank, so as to be straight between the
cathodes which are kept apart from each other by means of convenient separators,
so as to have their two faces in contact with the gold solution.
The frame prevents contact with the cathodes and its lower part is high enough
to render impossible the contact of the anode with the layer of mercury.
I am aware that gold has been deposited on layers of mercury or amalgamated
plates by aid of electricity, but to the best of my knowledge, no apparatus has ever
been constructed, such as the one I have described, in which in presence of
peroxidised lead anodes, which are perforated, the combination of a mercurial
cathode with numerous amalgamated perforated plates, or wire network etc., secures
an intimate and perfect contact of the gold solution with every particle of an
enormous amalgamated surface, which fills up the compartment and acts as cathode,.
thus helping in the recovery of the gold which the layer of mercury has not
completely effected.
The great advantages of this process are that the rate of circulation of the gold
solution can be much more rapid, that the installation of tanks is less costly, since
in a few tanks more surface of active cathode is available for the deposition of gold
than in the usual apparatuses for electro deposition, that it requires less mercury,
that the conductivity is at its maximum, that the perforated plates, etc., being in
contact with the mercury do not require terminals, connections, and that without
the slightest trouble, and without interfering with the operation, each of them can
be withdrawn from the tanks and replaced by other plates for the cleaning up.
Having now particularly described and ascertained the nature of my inven
tion, and in what manner the same is to be performed, I declare that what I
laim is:
1. The construction of an apparatus for the electro deposition of gold or silver
from their solution, which consists of the above described tank, without compart-
ments, or of a tank divided in three compartments by partitions made of porous
porcelain, or of convenient tissues.
2. The use of peroxidised lead anodes in a cyanide of gold and potassium
solution.
3. The use in a tank for the electro deposition of gold or silver of perforated
plates, gauzes, or network of amalgamated copper or other convenient metal, the
lower part of which dips in a mercurial cathode as herein before described and
illustrated.
4. The above described and illustrated process for the electro deposition of gold
and silver from a solution circulating on and through a very large surface of
catliode constituted by a layer of mercury and by numerous amalgamated perforated
plates, wire network, and the like, which fills up the tank in the vicinity of
perforated anodes made of peroxide of lead.
Dated this Seventeenth day of June 1895.
EMILE ANDREOLI.