Improvements relating to the Extraction of Gold, Silver, and Copper from Ores and other Substances or Products Containing such Metals.
Year: 1886

page_text: Date of Application, 18th June, 1886.
Specification Accepted, 22nd Mar., 1887.
COMPLETE SPECIFICATION.
Improvements relating to the Extraction of Gold, Silver, and Copper
from Ores and other Substances or Products Containing such
Metals.
I, JAMES NOAD, Engineer, of Hawthorn Cottage, East Ham, Essex, do hereby
declare the nature of the said 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 extraction of gold, silver and copper from ores, scoria,
slag, regulus and other substances, materials or metallurgical products containing such
metals.
The special objects of the Invention are to avoid the usual waste and loss of metal
consequent upon the partial extraction thereof as effected by existing methods and
means, and to obtain or recover all of the contained.metal sought in a metallic state
free from alloy, to attain this result by a simple and less costly method and means
and which will effect a very considerable saving in labor, and in time, and will
dispense with the costly apparatus and means hitherto used in the extraction of such
metals as effected by the process of smelting, and to enable the poorer classes of ores,
minerals and products containing but a very small percentage of such metals or any
of them and which could not be profitably treated by existing methods of manipulation
and are at present treated as waste, being treated according to the present improve-
ments to great advantage.
The Invention consists in an improved method or process and means of extracting
the metal or metals from the ore substance or product containing it or them, and such
improved process consists,-after the mechanical or other reduction of the ore, mineral,
product or substance to be operated upon to a finely pulverized condition, in the
concentration purification and reduction of such product substantially as hereinafter
described by a process in part chemical and in part by calcination, in the combination
of the material thus purified and concentrated with a suitable depositing solution and
in the use of this admixture as an electrolyte and in the extraction therefrom by
electrolysis of the contained metal sought, as a chloride in the case of silver and gold,
and in a metallic state in the case of copper, and in the subsequent chemical develop-

page_text: ment of the said chloride into a pure metallic state free from alloy with any baser
metal.
Such being the nature and object of the said invention, I will now proceed to
describe more in detail the manner in which the same is to be or may be performed
or carried into practical, effect, and will in the first instance describe its application to
the extraction of silver from lead-galena, as illustrative of the method of its application
to the extraction of this metal from other substances or materials containing it, and
for the sake of giving a definite example of the materials and respective proportions
thereof which may be used with great advantage in carrying out the said improved
process, I will describe the latter as applied to the extraction of silver from lead-galena
containing say about 300 ozs. of silver to the ton of galena, and I would remark that
the quantities of the chemical materials next firstly mentioned should vary approxi-
mately in accordance with the percentage of metal in the ore and should preferably be
of about the proportions herein mentioned.
I first proceed by pulverizing the ore to as fine a state of subdivision as can be
readily attained preferring to attain this result by what is known as pulverising and
floating the material under treatment.
For every 112 lbs. of such pulverized material, I take about 14 lbs. of chloride of
sodium, and about 28 lbs. of commercial sulphuric acid, and thoroughly mix these
latter materials together, and let the mixture stand for about 24 hours to allow of the
escape of the fumes given off so that all danger to the operatives will be avoided.
I next admix with such mixture the said pulverized material containing the metal
desired to be extracted, and let this admixture stand for about 24 hours.
The product thus obtained is next calcined in any convenient or suitable apparatus
at about a blood red heat for the purpose of desulphurising or eliminating therefrom
the contained sulphur and arsenic.
This process results in leaving the silver and lead in combination with the chloride
of sodium as chloride of silver and lead combined, and in setting free the contained
baser metals.
After calcination, the whole product is ground up, and when ground is washed in a
bath of water being suitably agitated therein, and by this means such baser metals
are dissolved out (the water becoming saturated therewith and from which they can
be recovered by any known means) and the silver and lead are left combined as a
chloride.
The said calcined and washed silver chloride and lead is next stirred into and allowed
to settle in a depositing bath consisting of a saturated solution of cyanide of potassium
containing about 1 per cent. each of carbonate of ammonia and of boracic acid.
This solution and precipitate are then used as an electrolyte from which the contained
silver is extracted by decomposition of the electrolyte by an electric current which
may be generated by means contained within the bath as hereinafter next described,
or may be derived from an external source as also hereinafter referred to.
To extract the contained silver from the said solution and material precipitated
therein there is placed in the solution and resting on the precipitate one or more
porous cells charged with a suitable exciting solution and each containing a positive
electrode or decomposing plate which is suitably connected with one or more negative
or stripping or depositing plates or electrodes which overhang the porous cell or cells
and depend into the solution in the bath but not so as to make contact, with the
sediment or precipitate therein. An electric current is thus generated and decom-
position of the electrolyte ensues and continues as long as the said cell or cells is or
are kept charged and excited as stated and as long as there is a trace of silver remaining
in the solution or precipitate, and the said contained silver is deposited on the negative
plates or cathodes as a chloride.
In order to obtain the silver thus deposited on the cathodes, in a pure metallic state,
the cathodes are occasionally removed from the solution and the silver chloride is
washed and brushed therefrom in a developing bath consisting of proto-Sulphate of
iron, about 40 grains, glacial acetic acid about 10 grains, rock alum about 40 grains
and water about 40 ounces, and the silver is thereupon and therein precipitated in a

page_text: metallic state as pure silver in very fine particles, and, which are collected, washed
and dried and may be then treated in the crucible in the ordinary way for casting into
ingots.
The solution remaining in the depositing tank after extraction of the silver there-
from as aforesaid is run off into a similar tank for re-use for the same purpose, leaving
in the depositing tank the bye-product of the work, which, in the case under con-
sideration, consists of lead in a state of oxide, and which is washed in water and is
then recoverable in the ordinary way by smelting, and the water is put back into the
depositing tank to keep up the quantity of the solution therein.
For the extraction of gold from gold bearing ores substances or products the treat-
ment is substantially the same as that hereinbefore described until the depositing tank
or bath is reached, which in the treatment of this metal consists of a saturated solution
of ferro-sulphate into which the gold chloride is stirred and allowed to settle, and in
which there is placed substantially in the manner hereinbefore referred to or in any
suitable equivalent manner one or more cells or porous pots charged with any suitable
exciting solution, the anodes and cathodes being arranged as described. In the
decomposition of this electrolyte, the gold combines with the iron of the bath and is
deposited together therewith upon the cathodes or stripping plates, and to obtain the
gold thus deposited in a pure metallic state, the cathodes are removed and steeped in
acidulated water to dissolve the iron, and the gold is thereby freed and precipitated,
and such precipitate can be collected washed and dried and run into ingots as herein-
before described with reference to the treatment of the silver precipitate.
The remaining solution in this bath is available for continued re-use and the said
acidulated water containing the dissolved iron is put thereinto.
For the extraction of copper from copper bearing ores substances or products the
treatment is also substantially the same as that herein before described with reference
to the silver bearing ores substances or products until the depositing tank or bath is
reached, which in the treatment of this metal consists of a saturated solution of sulphato
of copper into which the copper chloride is stirred and allowed to settle, and in which
there is also placed substantially in the manner hereinbefore referred to or in any
suitable equivalent manner one or more porous pots charged with any suitable exciting
solution, the anodes and cathodes being arranged as before mentioned, but being left
in position until the precipitated copper is deposited upon the cathodes in a chemically
pure state.
The remaining solution in this depositing bath is also available for continued
re-use.
In extracting any of the above metals, when a very large depositing tank is employed
and there is required a decomposing force which could not be obtained from a con-
venient number of cells, there may be used a dynamo-electric machine or other source
of generating a sufficient current externally of the bath, using a cell or cells therein
composed and arranged as aforesaid, the positive electrode of such cell forming the
anode of the bath, and a series of cathodes or depositing plates being suspended within
the bath at different parts thereof from wires or other suitable means of connection
stretched or arranged across, the said anode and series of cathodes being respectively
connected to the proper poles of the Dynamo.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is :-
1. The hereinbefore described improved method or process of extracting gold silver
and copper from ores and other substances or products containing such metals, the same
consisting, after the mechanical or other reduction of the ore, mineral, product or
substance to be operated upon to a finely pulverized condition, in the concentration
purification and reduction of such product substantially as hereinbefore described by a
process in part chemical and in part by calcination, in the combination of the material
thus purified and concentrated with a suitable depositing solution and in the use of
the admixture as an electrolyte and in the extraction therefrom by electrolysis of the
contained metal sought, as a chloride in the case of silver and gold, and in a metallic

page_text: state in the case of copper, and in the subsequent chemical development of the said
chloride into a pure metallic state free from alloy with any baser metal, all substantially
as hereinbefore set forth.
2. In the extraction of gold by such improved process, the use of a depositing bath
composed of a saturated solution of ferro-sulphate, and which may be continually
re-used, and into which the gold chloride is stirred and allowed to settle, and to which
an electric current is suitably applied in the manner hereinbefore described for the
purpose of causing the contained gold to combine with the iron of the bath and to be
deposited together therewith upon depending cathodes or stripping plates, substantially
as hereinbefore set forth.
3. In the extraction of silver by such improved process, the use of a depositing bath
composed of a saturated solution of cyanide of potassium containing about 14 per cent.
each of carbonate of ammonia and of boracic acid, and which may be continually
re-used, and into which the silver chloride is stirred and allowed to settle, and to
which an electric current is suitably applied in the manner hereinbefore described for
the purpose of causing the contained silver to be deposited upon depending stripping
plates, substantially as hereinbefore set forth.
4. In the extraction of silver by such improved process, the use of a developing bath
consisting of proto-sulphate of iron, glacial acetic acid, rock alam and water, for
precipitating in a pure metallic state the silver deposited as aforesaid upon the
depending cathodes.
5. In the extraction of copper by such improved process, the use of a depositing
bath composed of a saturated solution of sulphate of copper, and which may be
continually re-used, and into which the copper chloride is stirred and allowed to settle,
and to which an electric current is suitably applied in the manner hereinbefore described
for the purpose of causing the contained copper to be deposited in a chemically pure
metallic state upon depending stripping plates substantially as herein before set forth.
Dated this 17th day of June 1886.
DAY, DAVIES & HUNT,
321, High Holborn, London, W.C.,
Agents for the Applicant.