Electro-deposition of Gold and Silver.
Year: 1895

page_text: Date of Application, 4th ept., 1895-Accepted, 4th Sept. 1896
Electro-deposition of Gold and Silver.
EMILE ANDREOLI, Journalist, of 18 Somerleyton Road, Brixton 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 :-
This invention relates to the electro deposition of gold or silver, from cyanide,
or cyanide compound solutions by means of insoluble anodes.
In my Specification No. 11752/1895, I have described how I can effect the
electro deposition of gold and silver from a cyanide solution by means of peroxidised
lead anodes in presence of mercurial cathodes combined with a layer of mercury
acting also as a cathode. I have since found that this layer of mercury is not very
efficient and that other metals than mercury may advantageously be used as a
substratum for gold, or silver. The great difficulty in the electrodeposition of
gold from a cyanide solution has, up to the present been to find an insoluble
anode, e. a metal or conducting material which resists the action of a cyanide
electrolyte.
In carrying out the electrodeposition of metals from their cyanide or cyanide
compounds solutions, I use peroxidised lead plates as anodes. Peroxide of lead is
not disintegrated or attacked in cyanide solutions, and such solutions are not
decomposed or spoilt in presence of anodes made of peroxidised lead.
My anodes and my cathodes may be perforated or not.
As an illustration, will describe the deposition of gold on zinc cathodes, but
I may deposit gold on other metals. There is no invention whatever, and conse-
quently there can be no patent, in depositing gold or silver on such and such a
metal unless this mode of electrodeposition itself is characterized by something new
and original, and the merit of my process as an invention is that to the best of
my knowledge I believe I am the first who has found and ascertained that a
cyanide of gold and potassium, or of silver and potassium solution is not contaminated
by metallic salts and remains limpid when electrolised with the aid of peroxidised
lead anodes.
I do not confine myself to any metal on which the previous metals may
be deposited. I may use any metal or alloy which I find suitable; I can also use
as cathodes, plates of metals or conducting materials galvanically coated with zinc
or another convenient metal in either a hard or pulverulent state.
When the anodes and the cathodes are perforated they are disposed transversely
in the tank, and the gold solution which enters at one end of the electrolyser passes
through the holes of the electrodes, and is in perfect contact with the surface of the
cathodes, on which the gold is deposited. The solution flows out through convenient
outlets at the other end of the tank. When the electrodes are not perforated, they
are arranged longitudinally.
Fig. 1 shows a tank "a" to which the gold solution is fed from a supply cistern
and passes through the perforated anodes bbbb and cathodes cccc and flows
out through convenient outlets.
Fig. 2 shows a cathode made of perforated zinc.
Fig. 3 shows a perforated peroxidised lead anode.
The peroxide of lead anodes are inserted in grooves cut in the sides of the
tank, and they are mounted on wooden or other frames to avoid short circuits.
1 preferably arrange them transversely because in this manner, the size of the

page_text: plates is not so large and they are more easily handled and manipulated than
when they are placed longitudinally.
The lead anodes can be peroxidised in diluted sulphuric acid, or according to
the Becquerel process in a hot alkaline solution, or according to any other efficient
process. The accompanying drawing shows that I have arranged in the vat "A"
more cathodes bbb than anodes c cc, but I may have in my electrolyser as many
anodes as cathodes. Each perforated zinc cathode is provided on top and bottom
and on each side with a thin wooden lath, which in two or three places is fixed to
the plate. This keeps the plates rigid and allows me to have them all parallel,
and placed at a very short distance from each other, say + inch.
When the thickness of the gold deposited on the cathodes is considered sufficient,
the zinc plates are withdrawn from the tank and brushed in a diluted acid
solution or other convenient solution, or they are scrubbed when dry with metallic
cloth and then brushed in a suitable solution. The scrapings and washings are
then collected, and treated according to the well-known metallurgical means for
recovering gold.
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 use of peroxide of lead plates as anodes in the electrodeposition of gold,
or silver, from a cyanide or cyanide compound solution.
2. The combination of perforated or plain anodes made of peroxidised lead with
perforated or plain cathodes made of convenient metal or metallic alloy.
3. The combination in an electrolytic tank for the deposition of gold from a
cyanide solution, of perforated or plain peroxide of lead anodes with metallic
cathodes so disposed as to allow of a rapid circulation of the gold cyanide or cyanide
compound solution, and of its good contact with the electrodes.
Dated this 4th day of September 1895.
EMILE ANDREOLI.