Improvements in Obtaining Gold, Silver, and Copper from Ores.
Year: 1891

page_text: Date of Application, 24th Feb., 1891;
Complete Specification Left, 23rd Nov., 1891-Accepted, 24th Dec., 1891
PROVISIONAL SPECIFICATION.
Improvements in Obtaining Gold, Silver, and Copper from Ores.
We, ANDREW FRENCH, of Willowbank, Larbert, in the County of Stirling,
North Britain, Metallurgist, and WILLIAM STEWART, of Craigmuir, Lenzie, in
the County of Dumbarton, North Britain, Gentleman, do hereby declare the nature
of this invention to be as follows, that is to say :—
This invention has for its object the obtaining of gold, silver, and copper from
ores by an improved combination of processes which is of special advantage in
treating complex and refractory ores containing sulphur, and is applicable to ores
containing also arsenic, antimony, tellurium, zinc, or other ingredients found to
interfere seriously with wet extraction processes hitherto in use.
In carrying out the invention in the case for example of an ore containing 2
to 6 per centum of copper and some gold and silver the ore after being simply
roasted or calcined to drive off as much of the sulphur as can be conveniently got
rid of in that way, if it contains more than 10 per centum of sulphur, is pulverised
and mixed with from 2 to 3 per centum of "nitre-cake or bisulphate of soda and
from 1 to 2 per centum of common salt. The mixture put into a suitable furnace is
brought to and maintained at a red heat with a limited supply of air, for about an
hour. With this treatment all the copper almost all the silver and a part of the
gold will have been brought to the condition of salts soluble in slightly acidulated
water. The furnaced materials are withdrawn from the furnace, allowed to cool
and then leached or lixiviated in the manner ordinarily practised in the wet processes
for extracting copper and silver. After the soluble metallic salts have been washed
out chlorine gas is introduced beneath the false bottom of the leaching vessel and
passed through the as yet undissolved materials until its odour is distinctly perceived
above them. After from 1 to 2 hours when all the gold will have become soluble,
water slightly impregnated with chlorine is passed through the materials and is led
away with the gold in solution into vats or apparatus to be treated in any suitable
known way for precipitating or separating the precious metal.
It
In ores containing principally gold and silver the same process may be adopted.
may however be desirable to extract any silver not washed out by the acid water,
by using a dilute solution of hyposulphite of soda or aqueous ammonia. When alĺ
the silver has been washed out, the gold may be attacked with chlorine as herein-
before described. Or cyanide of potassium may be used instead of chlorine to
extract the gold, after roasting the ore with "nitre-cake" or bisulphate of soda and
salt and washing out the soluble salts thereby formed. -
The improved combination of processes is very economical in plant, labor, and
time; and is well adapted for treating the refractory form of copper ore containing
monosulphide of iron and known as pyrrhotite. Ores which do not yield, or only
with difficulty to ordinary chlorination or treatment with cyanide of potassium,
readily give up their gold and silver to the improved combination of processes. In
all cases, of course, the proportions of "nitre-cake" or bisulphate of soda (which
may in some cases be used alone) and of the common salt, must be modified to suit
the ores treated.
Dated this Twenty-third day of February 1891.
EDMUND HUNT,
Applicants' Agent.

page_text: :
COMPLETE SPECIFICATION.
Improvements in Obtaining Gold, Silver, and Copper from Ores.
We, ANDREW FRENCH, of Willowbank, Larbert, in the County of Stirling,
North Britain, Metallurgist, and WILLIAM STEWART, of Craigmuir, Lenzie, in
the County of Dumbarton, North Britain, Gentleman, 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, that is to say :-
This invention has for its object the obtaining of gold, silver, and copper, from
ores by improved combinations of processes, which are of special advantage in
treating complex and refractory ores containing sulphur, and are applicable to ores
containing also arsenic, antimony, tellurium, zinc, or other ingredients found to
interfere seriously with wet extraction processes hitherto in use.
The distinguishing part of the processes to be used in carrying out the invention
is what may be termed a preparatory process or combination of processes. when
applied to some ores, and one which has to be followed, for the more complete obtain-
ment of the precious metals, by processes which have heretofore been applied
without such preparatory process and without obtaining good results in the case of.
complex and refractory ores. At the same time the so-called preparatory process
will in most cases obtain in solution some of the metal or metals of the ores treated
by it.
In the so-called preparatory process the ore having intimately mixed, with it
small percentages of bisulphate of soda and common salt is furnaced at a
red heat
and is afterwards leached or lixiviated. Metals rendered soluble by furnacing with
the salts mentioned are washed out, whilst precious or other metals not thus separable
are by the furnacing put into a condition in which they are very amenable to
subsequent treatment.
In carrying out the invention, in the case, for example, of an ore containing 21
to 6 per centum of copper and some gold and silver, the ore after being simply
roasted or calcined to drive off as much of the sulphur as can be conveniently got
rid of in that way, if it contains more than 10 per centum of sulphur, is pulverised and
mixed with from 2 to 3 per rentum of "mitre-cake" or bisulphate of soda, and, from.
1 to 2 per centum of common salt. The mixture put into a reverberatory or other
suitable furnace is brought to a red heat, and maintained thereat, with a limited
supply of air, for about an hour. With this treatment, all the copper, almost all
the silver and a part of the gold will have been brought to the condition of salts
soluble in slightly acidulated water. The furnaced materials are withdrawn from:
the furnace, allowed to cool, and then leached or lixiviated in the manner ordinarily
practised in the wet processes for extracting copper and silver. After the soluble
metallic salts have been washed out, the well known chlorination process is applied, in
which chlorine gas is introduced beneath the false bottom of the leaching, vessel
and passed through the as. yet undissolved materials until its odour is distinctly.
perceived above them. After 1 to 2 hours when all the gold, will have, become
soluble, water slightly impregnated with chlorine is passed, through the materials,
and is led into vats or apparatus to be treated in any suitable, known way fo
precipitating or separating the precious metal. Any other suitable known variation
of the chlorination process may be used if preferred.
As affording another example, of the application of the invention an ore may be
taken containing little or no copper but principally silver and gold. In such a case
we mix, with the pulverised ore from 1 to 2 per centum of nitre-cake and from
1 to 2 per centum of common salt, and furnace the mixture at a red heat for from
40 to 70 minutes. When the chlorine or hydrochloric acid is evolved the furnacing
is continued until such evolution ceases or nearly ceases. The furnaced materials
are leached and the bulk of the base metals rendered soluble in the furnacing
operation are washed out.

page_text: In the case of ores containing principally gold and silver, the materials left after
furnacing and leaching may be treated by chlorination as hereinbefore described.
It may however be desirable to first extract any silver not washed out by the acid
water, by using a dilute solution of hyposulphite of soda or aqueous ammonia. Or
cyanide of potassium may be used instead of chlorine to extract the gold. Any
suitable known variety of the amalgamation process may also be used for completing
the extraction of the precious metals. As with the chlorination and cyanide
processes amalgamation effects a more complete extraction of the gold and silver,
and along with them any platinum present, than when such processes are applied
to refractory ores without the preparatory furnacing with nitre-cake and common
salt.
Our improved combinations of processes are very economical in plant, labor, and
time; and they are well adapted for treating the refractory form of copper ore
containing monesulphide of iron and known as pyrrhotite. Ores which do not
yield, or only with difficulty to ordinary chlorination, or treatment with cyanide of
potassium, or amalgamation, readily give up their gold and silver to the improved
combination of processes. In all cases of course, the proportions of nitre-cake or
bisulphate of soda, and of the common salt must be modified to suit the ores treated;
but in no case will the aggregate quantity of these salts require to be greater than
10 per centum of the ores; and in most cases 5 per centum will suffice.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, we declare that
what we claim is:
In processes for obtaining gold, silver, and copper from ores, the treatment or
preparatory treatment of the ores by pulverising, mixing therewith small percentages
of nitre-cake or bisulphate of soda and common salt, furnacing at a red heat, and
leaching substantially as hereinbefore described.
Dated this Twenty-first day of November 1891.
EDMUND HUNT,
Applicants' Agent.