Improvements in Extracting Gold and Silver from Ores and the like.
Year: 1893

page_text: Date of Application, 10th Mar., 1893
Complete Specification Left. 9th Dec, 1893-Accepted, 10th Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements in Extracting Gold and Silver from Ores
and the like.
We, JOHN STEWART MACARTHUR, Managing Director of The Cassel Gold
Extracting Company, Limited, CHARLES JAMES ELLIS, Technical Chemist to
the said Company, and THE CASSEL GOLD EXTRACTING COMPANY, LIMITED,
all of 157 West George Street, Glasgow, in the County of Lanark, North Britain,
do hereby declare the nature of this invention to be as follows:-
"
Our said invention relates to what is known as the "MacArthur Forrest process
for extracting gold and silver from ores and the like by means of cyanides, and
has for its object to increase the efficiency and economy of that process, in cases
in which, from the nature of the ores treated, it is found that in the solution of
cyanide as heretofore used there is formed or becomes present a soluble sulphide,
which retards and objectionably affects the action of the cyanide on the precious
metals.
Our invention consists in removing or rendering inert such soluble sulphide by
adding to the solution a suitable salt or compound of a metal which will form with
the sulphur of the soluble sulphide a sulphide which is practically insoluble or
inert in the cyanide solution, or which will materially diminish the objectionable
action.
In carrying out our invention we may use any one or more of various metallic
salts or compounds of which the following may be mentioned, by way of example,
preference being given to them in the order in which they are noted, namely
Plumbates; carbonate, acetate, or sulphate of lead; sulphate or chloride of
manganese; zincates; oxide or chloride of mercury; and ferric hydrate or oxide.
The proportion to be used in any case will depend on the proportion of soluble
sulphide which has to be dealt with in the cyanide solution applied to the particular
ore; and is easily and most conveniently ascertained by trials of a few small
samples in each case.
Dated this 10th day of March 1893.
ALLISON BROS.,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in Extracting Gold and Silver from Ores
and the like.
We, JOHN STEWART MACARTHUR, Managing Director of The Cassel Gold
Extracting Company, Limited, CHARLES JAMES ELLIS, Technical Chemist to
the said Company, and The CASSEL GOLD EXTRACTING COMPANY, LIMITED,
all of 157 West George Street, Glasgow, in the County of Lanark, North Britain,
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:-
"
Our said invention relates to what is known as the "MacArthur-Forrest process
for extracting gold and silver from ores and the like by means of cyanides, and has
for its object to increase the efficiency and economy of that process, in cases in
which from the nature of the ores treated or other circumstances it is found that in

page_text: the solution of cyanide, as heretofore used, there is formed, or becomes present a
sulphide soluble therein which retards and objectionably affects the action of the
cyanide on the precious metals.
Our invention consists in removing or rendering inert such sulphide, by adding
to the solution of cyanide, or to the ore, or to the mixture of ore and cyanide
solution a suitable salt or compound of a metal which will form with the sulphur
of the sulphide a sulphide which is practically insoluble or inert in the cyanide
solution, or which will materially diminish the objectionable action.
In carrying out our invention we may use any one or more of various metallic
salts or compounds, of which the following may be mentioned, by way of example,
preference being given to them in the order in which they are noted :-namely,
salts or compounds of lead such as plumbates; carbonate, acetate, or sulphate of
lead; or salts or compounds of other metals such as sulphate or chloride of
manganese; zincates; oxide or chloride of mercury; and ferric hydrate or oxide.
The proportion to be used in any case will depend on the proportion of soluble
sulphide which has to be dealt with in the cyanide solution applied to the particular
ore; and is easily and most conveniently ascertained by trials of a few small samples
in each case. Any person versed in the art to which the invention relates will have
no difficulty in deciding as to the best and most economical quantities of the
various compounds to use, by applying a simple test to the material about to
undergo treatment. The test is made by carrying out the operation on the
laboratory scale, .e. adding the specific compound, for instance à lead salt, to a
mixture of the material to be treated and cyanide solution until the lead in the
salt ceases to be transformed into sulphide, such mixture being agitated for a
time.
The invention is carried into effect by adding the compound selected either to the
solution, to the ore, tailings etc., or to the mixture of solution and ore etc., in such
quantity as is found by the preliminary test to be most efficient and economical for
the material under treatment.
In the case of some ores containing sulphur we find that the addition of salts or
compounds, as and for the purpose hereinbefore referred to, and especially those of
lead and mercury, increases the percentage of precious metals obtained.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
1. In the MacArthur-Forrest process for extracting gold and silver from ores
and the like, the addition to the cyanide solution, or to the ore, or to the mixture of
ore and cyanide, of salts or compounds of lead, substantially as and for the
purposes hereinbefore described.
2. In the MacArthur-Forrest process for extracting gold and silver from ores
and the like, the addition to the cyanide solution, or to the ore, or to the mixture
of orc and cyanide, of any one or more of the metallic salts or compounds hereinbefore
indicated and capable of forming insoluble sulphides as and for the purposes
hereinbefore described.
Dated this 6th day of December 1893.
ALLISON BROS.,
Agents for the Applicants.