Improvements in the Extraction of Gold and Silver from Ores or Compounds containing the same.
Year: 1892

page_text: Date of Application, 21st Sept., 1892
Complete Specification Left, 21st June, 1893-Accepted, 22nd July, 1893
PROVISIONAL SPECIFICATION.
Improvements in the Extraction of Gold and Silver from Ores or
Compounds containing the same.
I, JOHN CUNINGHAME MONTGOMERIE, of the "Water of Ayr" and "Tam
o'Shanter" Hone Works, Dalmore, Stair, in the County of Ayr, Manufacturer, do
hereby declare the nature of this invention to be as follows:-
This invention relates to the treatment of auriferous and argentiferous ores or
compounds for the purpose of separating and collecting the gold and silver
contained therein by means of solvent agents-as, for example, cyanide of
potassium.
According to a method commonly employed in the recovery of gold and silver by
means of cyanide of potassium, the ore or other material, having been reduced to a
finely-triturated state, is placed, along with the solvent, in a barrel or other vessel,
and is there subjected to agitation. After the lapse of a few hours, the contents of
the barrel are removed to a filter, where the liquid portion of the charge
The latter
(containing the precious metals in solution) is separated from the ore.
is further washed for the removal of any gold or silver remaining, in solution,
therewith. The cyanide solution of gold and silver, as also the wash water, is then
treated for the recovery of the precious metals by precipitation.
Where, in a process of the kind above referred to, cyanide of potassium is
employed as the solvent agent, it is necessary for the ore to be neutralised before
treatment; and in some cases, it is advantageous to render it more or less alkaline
according to the nature of the ore; especially so where its treatment is effected in
the presence of oxygen under pressure. With this object, sodium oxide (caustic
soda) may be added, either before or with the solvent agent; the quantity best
suited to the character of the ore being determined by experiment.
Instead however of treating the mixture of ore, cyanide solution and sodium
oxide in the presence of oxygen under pressure, I have found that equally satis-
factory results may be obtained with atmospheric air instead of oxygen if sodium
dioxide be added to the mixture of ore and cyanide solution. The proportion most
suitable will be best determined by experiment. For dioxide of sodium, dioxide of
potash or equivalent alkali may be substituted; the same being applied under
pressure of air, or of oxygen if preferred.
When sodium dioxide is employed in the manner hereinbefore described, the
mixture of ore and cyanide solution is not only neutralised or rendered alkaline;
but, by reason of the action of the dioxide upon the base metals and other impurities,
a larger proportion of the cyanide is left free to act on the gold and silver,
considerable economy resulting.
1
1000
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.

page_text: COMPLETE SPECIFICATION.
Improvements in the Extraction of Gold and Silver from Ores or
Compounds containing the same.
I, JOHN CUNINGHAME MONTGOMERIE, of the "Water of Ayr" and "Tam
o'Shanter" Hone Works, Dalmore, Stair, in the County of Ayr, Manufacturer, 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 the treatment of auriferous and argentiferous ores or
compounds for the purpose of separating and collecting the gold and silver
contained therein by means of solvent agents-as, for example, cyanide of
potassium.
According to a method commonly employed in the recovery of gold and silver by
means of cyanide of potassium, the ore or other material, having been reduced to a
finely-triturated state, is placed, along with the solvent, in a barrel or other vessel,
and is there subjected to agitation. After the lapse of a few hours, the contents of
the barrel are removed to a filter, where the liquid portion of the charge
(containing the precious metals in solution) is separated from the cre.
The latter
is further washed for the removal of any gold or silver remaining, in solution,
therewith. The cyanide solution of gold and silver, as also the wash-water, is then
treated for the recovery of the precious metals by precipitation in a zinc filter or
percolator.
Where, in a process of the kind above referred to, cyanide of potassium is
employed as the solvent agent, it is necessary for the ore to be neutralized before
treatment; and in some cases, it is advantageous to render it more or less alkaline
according to the nature of the ore, especially so where its treatment is effected in
the presence of oxygen under pressure. With this object, sodium oxide (Na,O) or
caustic soda (NaOH) may be added, either before or with the solvent agent; the
quantity best suited to the character of the ore being determined by experiment.
Instead however of treating the mixture of ore, cyanide solution and sodium
oxide in the presence of oxygen under pressure, I have found that equally satis-
factory results may be obtained with atmospheric air instead of oxygen if sodium
dioxide (Na,O,) be added to the mixture of ore and cyanide solution. In carrying
out this operation, I take of cyanide of potassium a quantity proportionate to the
ore to be treated and dissolve the same in a little water. then take a small
quantity of sodium oxide or caustic soda (say, three-fourths by weight of the
cyanide), and, having dissolved this also in a little water, 1 add the two solutions to
the quantity of water appropriate for the charge of ore about to be treated.
Before adding the ore to the mixture, I mix with the former the required quantity
of sodium dioxide. This may be one-third by weight of the sodium oxide. The
compound is then added to the mixture before referred to and subjected to
agitation, preferably in a closed vessel, in which case the oxygen gas evolved
generates pressure. Additional air may also be forced in. By way of illustration,
an ore containing, say, 4 ozs. of gold and 12 ozs. of silver to the ton may be treated
with 12 pounds of cyanide, 3 pounds of sodium dioxide and 9 pounds of sodium
oxide.
I find that by adding a certain proportion of sodium oxide or caustic soda to the
cyanide prior to the ore being added, the proportion of cyanide or other solvent, as
also that of the sodium dioxide to be subsequently added, may be largely economised.
In this way, moreover, I am enabled to mix the sodium dioxide with the ore; and,
without any violent action taking place, it gradually becomes dissolved as the ore
gets saturated with the water. I do not however confine myself to the precise
sequence of operations or to the particular proportions hereinbefore mentioned, as
these may be varied to a considerable extent for different kinds of ores and will be

page_text: best determined by experiment. For dioxide of sodium, dioxide of potash or
equivalent alkali may be substituted; the same being applied under pressure of air
or of oxygen, if preferred.
When sodium dioxide is employed in the manner hereinbefore described, the
mixture of ore and cyanide solution is not only rendered alkaline, but, by reason of
the action of the dioxide upon the base metals and other impurities, a larger
proportion of the cyanide is left free to act on the gold and silver, considerable
economy resulting.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim :-
1. In the extraction of the precious metals by a solvent process of the kind herein
referred to, the employment of dioxide of sodium (potash or equivalent) as an
oxidising and alkaline agent, substantially as herein described.
2. In the extraction of the precious metals by a solvent process of the kind herein
referred to, the employment of dioxide of sodium (potash or equivalent) in the
presence of oxygen, or atmospheric air, under pressure, substantially as and for the
purposes set forth.
Dated the 15th day of June 1893.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.