Improvements in or relating to the Extraction of Precious Metals from their Ores.
Year: 1895

page_text: Date of Application, 7th Dec., 1895
Complete Specification Left, 7th Oct., 1896-Accepted, 5th Dec., 1896
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Extraction of Precious Metals
from their Ores.
We, WALTER HAWEIS JAMES of 5 Lexham Gardens, Kensington, in the
County of London, Captain in the Reserve late Royal Engineers, and CHARLES
JAMES NORRIS of 24 Ravenscourt Gardens, Hammersmith, in the County of
London, Chemist, do hereby declare the nature of this invention to be as
follows:
This invention relates to an improved process for the treatment of auriferous
and argentiferous ores and the ores of other precious metals slimes tailings and
other compounds for the purpose of separating and collecting the gold or silver or
other metals contained therein by means of a solution that will act as a solvent on
the gold or silver or other precious metals.
When a solution of potassium cyanide is employed in the usual manner for
extracting gold the reaction that takes place is, according to Elsner's equation, as
follows:-
In the above equation the requisite oxygen is obtained from the air and the absolute
extraction of all the gold is therefore a long process.
According to our invention we propose to greatly hasten the process by the use
with the cyanide or solvent, solution of a substance or substances hereinafter
mentioned by which the requisite quantity of oxygen is obtained without depending
upon the oxygen of the air.
The substances we employ for this purpose are as follows:-
(a) The substance formed by the action of any one of the oxides of nitrogen on
a halogen, to wit, chlorine, bromine, iodine, fluorine, whether alone or in the presence
of water, or other substance; for instance the compound formed by saturating
bromine at the ordinary temperature of the air with nitric oxide gas and to which
the formula NOBr, has been assigned.
(b) Hypobromous acid or a hypobromite or a mixture of hypobromous acid and
a hypobromite.
(c) Hypochlorous acid or a mixture of hypochlorous acid and a hypochlorite.
(d) The substance commercially known as bleaching powder, the formula of
which is approximately Ca,(OH), (OCL), CL, either alone or mixed with hypo-
chlorous acid.
The solution for the extraction of the gold or other precious metals is rendered
much more rapid and efficient by the addition of one or more of the above named
substances in the proper proportion to a solution of cyanide of potassium, or the
cyanide of any other metals or non-metals, moreover, so long as the solution is kept
alkaline (and for this purpose we add if necessary an alkali) the action of the solvent
on the baser metals which may be present in the ore or other substance under
treatment is reduced to a minimum. We proceed to carry out our invention in any
of the following manners :-
We form any one of the substances named by any known and suitable method
and add the requisite proportion thereof to the required proportion of a solution
ED.

page_text: of cyanide of potassium of a proper strength, and the solution is then applied
to the substance to be treated in any suitable tank or vessel, open or closed.
When the solution of the gold or other precious metal is effected, which is
done very rapidly, the gold bearing solution is drawn off and the gold or other
precious metal recovered therefrom by means of any suitable precipitating or
depositing method. The substance added to the cyanide solution may also be
applied after the last-named solution has been mixed with the substance to be
treated.
The proportion in which the substances which form the subject of this patent
may be added to the potassium cyanide or other suitable cyanide vary with the
substance to be treated and the strength of the cyanide solution employed, and
will also vary in accordance with the substance to be treated and we do not bind
ourselves to any of these proportions and may use any mixture of the above
substances or compounds in any convenient manner or proportion either at the
ordinary or at increased or reduced temperatures and pressures and upon greater
or less proportions of ore or other substance treated, and we claim the use of all
the substances named herein either alone or in combination with cyanide of
potassium or other suitable cyanide of the metals or non-metals.
Dated this 7th day of December 1895.
BOULT & WADE,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements in or relating to the Extraction of Precious Metals
from their Ores.
We, WALTER HAWEIS JAMES of 5 Lexham Gardens, Kensington, in the
County of London, Captain in the Reserve late Royal Engineers, and CHARLES
JAMES NORRIS of 24 Ravenscourt Gardens, Hammersmith, in the County of
London, 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:-
This invention relates to an improved process for the treatment of auriferous
and argentiferous ores and the ores of other metals, slimes, tailings and other
compounds for the purpose of separating and collecting the gold or silver or other
metals contained therein by means of a solution that will act as a solvent on the
gold or silver or other metals.
To take the case of the treatment of gold; when a solution of potassium cyanide
is employed in the usual manner for extracting gold the reaction that takes place
is, according to Elsner's equation, as follows:-
ZON
+O+H,O=2AuK(ON), + 2 KOH.
ATZOUT
و
In the above equation the requisite oxygen is obtained from the air and the absolute
extraction of all the gold is therefore a long process.
According to our invention we propose to greatly hasten the process by the
use with the cyanide or solvent solution of a substance or substances hereinafter
mentioned by which the requisite quantity of oxygen is obtained without depending
upon the oxygen of the air.
The substances we employ for this purpose are as follows:-
on
(a) The substance formed by the action of any one of the oxides of nitrogen
a halogen, to wit, chlorine, bromine, iodine, fluorine, whether alone or in the
presence of water, or other substance; for instance the compound formed by

page_text: saturating bromine at the ordinary temperature of the air with nitric oxide gas.
and to which the formula NOBr, has been assigned.
(b) Hypobromous acid or a hypobromite or a mixture of hypobromous acid an
a hypobromite.
(c) Hypochlorous acid or a mixture of hypochlorous acid and a hypochlorite.
(d) The substance cominercially known as bleaching powder, the formula of
which is approximately Ca,(OH), (OCL), CL, either alone or mixed with hypo-
chlorous acid.
(e) Any or all of the oxides of chlorine or solutions of the oxyacids of chlorine.
The solution for the extraction of the gold or other precious metals is rendered
much more rapid and efficient by the addition of one or more of the above named
substances in the proper proportion to a solution of cyanide of potassium, or the
cyanide of any other of the metals or non-metals, moreover, so long as in certain
cases the solution is kept alkaline (and for this purpose we add if necessary an
alkali) the action of the solvent on the baser metals which may be present in the
ore or other substance under treatment is reduced to a minimum. We proceed to
carry out our invention in any of the following manners:-We find that the
substance obtained when bromine is saturated with the oxides of nitrogen possesses
greater power of oxydization than bromine alone, and on this depends its solvent
action on gold when used in conjunction with a cyanide.
To avoid confusion we call this substance, the composition of which is uncertain
"Nitrobromine."
The compounds of nitrogen with oxygen can be obtained by acting on excess of
zinc (or tin) with concentrated nitric acid. Nitric per-oxide is first evolved, but
later, when the acid becomes diluted, nitrous-anhydride, nitric-oxide, and finally
nitrous oxide are evolved.
These gaseous products are passed into bromine which is thereby converted into
"nitrobromine," a liquid, darker, redder and heavier than pure bromine. We
find that a weight of nitrobromine equal in weight to the potassium cyanide
employed added to the latter in small quantities from time to time, gives satisfac-
tory results, but we do not confine ourselves to the proportion of nitrobromine
used, and in dealing with large quantities of ore it may be found advisable to add
the nitrobromine either entirely to the first treatment with potassium cyanide, or
pro rata to the several treatments with cyanide. The weight of "nitrobromine
to be added also depends upon the nature of the ore under treatment but in all
cases care should be taken to employ as little nitrobromine as possible so as to
avoid oxidation to soluble salts of the sulphides, etc., of the baser metals, to. prevent
a too great oxidation of the potassium cyanide to potassium cyanate, and to prevent
the formation of gold bromine.
"
We also find that when the oxides of nitrogen either separately or together are
passed into chlorine or bromine water, substances different from nitrobromine
are obtained, but which resemble the latter in its oxidizing property-though
feebler-and on this account may yield more satisfactory results on the large
scale as there would result less soluble oxidation products from the baser metals
while there would be no danger of the formation of a chloride or bromide of
gold.
When using the above-mentioned substances we find that the amounts to be used
vary with the degree of saturation of the chlorine or bromine water, but as with
nitrobromine, the less that can be used consistent with the rapid dissolution of the
gold the better.
With regard to the use of hypochlorites we find that when three parts of potassium
bypochlorite are added to two parts of potassium cyanide the solvent action of the
latter is increased.
We find also that by heating approximately equal weights of bleaching powder
and potassium cyanide to a temperature not exceeding dull redness a substance is
obtained which acts as a more powerful solvent of gold than the mixture of potassium
cyanide and potassium hypochlorite.

page_text: In certain cases it is advisable to add a solution of hypochlorous acid, and should
a hypobromite be used, the solvent action is increased by the addition of hypo-
bromous acid.
Sulphuretted ores may also be treated with nitrobromine as experiments lead us
to believe that small quantities of nitrobromine will oxidize the sulphur to sulphuric
acid and that the gold can subsequently be extracted with cyanide.
The above mentioned substances can be employed either alone, or combined with
a cyanide for extracting metals from or treating metallic ores containing copper,
arsenic etc.
When the solution of the gold or other precious metal is effected, which is done
very rapidly, the gold bearing solution is drawn off and the gold or other precious
metal recovered therefrom by means of any suitable precipitating or depositing
method. The substance added to the cyanide solution may also be applied after
the last named solution has been mixed with the substance to be treated.
The proportion in which the substances which form the subject of this patent
may be added to the potassium cyanide or other suitable cyanide varies with the
substance to be treated and the strength of the cyanide solution employed, and we
do not bind ourselves to any of these proportions and may use any mixture of the
above substances or compounds in any convenient manner or proportion either at
the ordinary or at increased or reduced temperatures and pressures and upon
greater or less proportions of ore or other substance treated, and we claim the use
of all the substances named herein either alone or in combination with cyanide of
potassium or other suitable cyanide of the metals or non-metals, except a haloid
cyanide.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is :-
1. A solvent for precious metals formed by the action of any or all of the oxides
of nitrogen on a halogen compound in combination with cyanide of potassium or
other cyanide of the alkalis or alkaline earths or other metals.
2. A solvent for precious metals formed by saturating bromine with an oxide of
nitrogen in combination with cyanide of potassium or other cyanide of the alkalis
or alkaline earths or other metals.
3. A solvent for precious metals formed by fusing bleaching powder with
potassium cyanide, or other cyanide of the alkalis or alkaline earths, or other
metals.
4. A solvent for precious metals formed of hypobromous acid or a hypobromite
or a mixture of the two in combination with cyanide of potassium or other cyanide
of the alkalis or alkaline earths or other metals.
5. A solvent for precious metals formed of hypochlorous acid or a mixture of
hypochlorous acid and a hypochlorite in combination with cyanide of potassium or
other cyanide of the alkalis or alkaline earths or other metals.
6. A solvent for precious or other metals formed of a soluble cyanide to which
is added any or all of the oxides of chlorine or solutions of the oxyacids of
chlorine.
7. The use of any of the substances above mentioned either alone or in combina-
tion with a cyanide in the treatment of metallic ores.
Dated this 7th day of October 1896
WALTER H. JAMES.
Boult & Wade,
Agents for the Applicants.