Improvements in Precipitating Precious Metals from Cyanide or similar Solutions.
Year: 1894

page_text: Date of Application, 25th Apr., 1894
Complete Specification Left, 23rd Jan., 1895-Accepted, 2nd Mar.. 1895
PROVISIONAL SPECIFICATION.
Improvements in Precipitating Precious Metals from Cyanide or
similar Solutions.
I, JOHN STEWART MAC ARTHUR, of 12 Knowe Terrace, Pollokshields, in the
County of Renfrew, North Britain, Technical Chemist, do hereby declare the
nature of this invention to be as follows:-
My said invention has for its object to obtain increased economy in precipitating
precious metals from cyanide or similar solutions, and to obviate injurious or
impeding actions due to the presence of certain metals in the solutions.
In carrying out my invention I employ zinc to some extent as described in Patent
Specification No. 10,223 of 1888. When copper is present in the solution along
with gold or silver or both it is precipitated first on the zine in a manner to interfere
with the precipitation of the other metals. The copper seems to be precipitated
on the zinc in a dense continuous form and greatly impedes the contact between
the liquid and the zinc. To overcome this difficulty 1 coat the zinc with a porous
precipitate of metallic lead which prevents the impeding action of the copper.
The porous lead may be deposited. on the zinc either before or during the precipi-
tation of the other metals. It may be conveniently done by immersing the zinc
for about a minute in a solution containing about one per cent. of lead as an acetate
of lead, or as a plumbate or other suitable salt; or if done during the precipitation
of the other metals a small quantity of the lead salt is added to the solution.
In cases in which the cyanide solution contains mercury along with gold or silver
or both, the mercury is precipitated with the other metals, and although not
impeding the chemical action is inconvenient physically as it forms an amalgam
rendering it difficult to separate the gold and silver from the precipitating metal
by chemical or mechanical means. To remove the mercury from the solution I
apply metallic lead, preferably in the form of shot or finely divided. The
mercury and possibly a little silver become precipitated on the lead, and the
precipitation of the gold and remainder of the silver proceeds without
inconvenience.
In ordinary solutions containing little else than gold and silver the zinc is
economised and the action facilitated by means of lead, preferably in the form
of shot or finely divided, the gold and silver being deposited on the lead as well
as on the zinc. It is the action of the lead when in direct or indirect contact or
connection with the zine which is advantageous, the action of lead alone being
unsatisfactory.
Instead of lead any suitable chemically inert substance which is a good conductor
and negative to zinc may be used, such for example as tin, iron, or carbon; I
believe however, that lead will be found most convenient in practice.
Dated this 25th day of April 1894.
ALLISON BROS.,
Agents for the Applicant.

page_text: Improvements in Precipitating Precious Metals from Cyanide or
similar Solutions.
I, JOHN STEWART MAC ARTHUR, of 12 Knowe Terrace, Pollokshields, in the
County of Renfrew, North Britain, Technical Chemist, 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 :-
My said invention has for its object to obtain increased economy in precipitating
precious metals from cyanide or similar solutions, and to obviate injurious or
impeding actions due to the presence of certain metals in the solution.
In carrying out my invention zinc is employed as the precipitant for the precious
metals, but when copper is present in the solution along with gold or silver or
both it is precipitated first on the zinc in a manner to interfere with the precipi-
tation of the other metals. The copper seems to be precipitated on the zinc in
a dense continuous form and greatly impedes the contact between the liquid and
the zinc. To overcome this difficulty I coat the zinc with a porous precipitate
of metallic lead which prevents the impeding action of the copper. The porous
lead may be deposited on the zinc either before or during the precipitation of the
other metals. It may be conveniently done by immersing the zinc for about a
minute in a solution containing about one per cent. of lead as an acetate of lead, or
as a plumbate or other suitable salt; or if done during the precipitation of
the other metals a small quantity of the lead salt is added to the solution.
In cases in which the cyanide solution contains mercury along with gold or silver
or both, the mercury is precipitated with the other metals, and although not
impeding the chemical action is inconvenient physically as it forms an amalgam
rendering it difficult to separate the gold and silver from the precipitating metal
by chemical or mechanical means. To remove the mercury from the solution
I apply metallic lead, preferably in the form of shot or finely divided. The
mercury and possibly a little silver become precipitated on the lead, and the
precipitation of the gold and remainder of the silver proceeds without
inconvenience.
In ordinary solutions containing little else than gold and silver the zinc is
economized and the action facilitated by means of lead, preferably in the form
of shot or finely divided, the gold and silver being deposited on the lead as
well as on the zinc. It is the action of the lead when in direct or indirect
contact or connection with the zinc which is advantageous, the action of lead
alone being unsatisfactory.
⚫ Instead of lead any suitable chemically inert substance which is a good
conductor and negative to zinc may be used, such for example as tin, iron, or
carbon; I believe however, that lead will be found most convenient in practice.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, I declare that what I
claim is:
-
1. In precipitating precious metals from cyanide or similar solutions by means of
zine, applying lead or a specified substitute therefor substantially in any of the
modes and for the purposes hereinbefore described.
2. In precipitating precious metals from cyanide or similar solutions containing
mercury in addition to such precious metals, the use of lead for precipitating the

page_text: mercury prior to the precipitation of the precious metals, substantially as herein-
before described. .
T
1805
ALLISON BROS.,
Agents for the Applicant.