Improvements in the Extraction of Gold and Silver from Ores or Compounds containing the same and in Apparatus applicable for use in the Treatment of such Materials by means of Solvents.
Year: 1892

page_text: he decision of the Comptroller-General, of the 19th day of April 1895, allowed,
| under Section 18 of the Patents, &c. Act, 1883, an Amendment of this
Specification.
Date of Application, 8th July, 1892
Complete Specification Le!t, 10th Apr., 1893-4ccepted, 8th July 1893
PROVISIONAL SPECIFICATION.
Improvements in the Extraction of Gold and Silver from Ores or
Compounds containing the same, and in Apparatus applicable
for use in the Treatment of such Materials by means of
Solvents.
1, 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 con-
tained therein, by means of solvent agents-as, for example, cyanide of potassium-
and to apparatus applicable for use in processes of this description.
According to the method usually 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 ore.
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.
When a cyanide solvent is employed as herein before described, the proportion of
cyanide is necessarily considerably in excess of that required for chemical com-
bination with the gold and silver present in the ore. This excess remains with the
liquor after the precious metals have been precipitated therefrom, and is either
run to waste or is subjected to a separate process for the recovery of the cyanide.
My improvement in the process of extraction by the method herein before referred
to consists in applying the cyanide solution of gold and silver, after having been
separated from the ore by filtration, to a subsequent charge or to subsequent
charges of fresh ore prior to treating the solution for the separation of the precious
metals by precipitation; care being taken that the original quantity of water is
made good. With this object, the requisite quantity of water is preferably added
as soon as the surface of the ore contained in the filter presents a dry appearance ;
the added water displacing the liquid remaining in the ore and permitting the same
(which is highly charged with the solvent and with the precious metals in solution)
to be discharged.. The solution is then tested for cyanide of potassium (or such
other solvent agent as may be employed), and the deficiency supplied by the
addition of a suitable quantity of cyanide of potassium (or other solvent agent);

page_text: thereby restoring the solvent solution to its original strength before adding the
same to the fresh charge of ore. Before being added to the fresh charge of ore,
the solution is made slightly alkaline by the addition of an alkali, preferably
caustic soda.
Where cyanide is employed, it is necessary for the ore to be thoroughly
neutralized before treatment; and in some cases it is advantageous to have it
slightly alkaline, especially where oxygen is used under pressure. The tailings
are then further washed to remove the last trace of gold and silver remaining in
solution, and the resultant wash-water is treated in the usual way for the recovery
of the precious metals contained therein.
By this mode of procedure, considerable economy is effected, both in the quantity
of cyanide or other solvent used, and in the cost of working, the quantity of liquid
subjected to treatment for the recovery of the gold and silver by precipitation
being at the same time greatly reduced.
My invention relates secondly to the construction of the barrel or other vessel in
which the ore is subjected to the action of the solvent.
If this barrel or vessel be formed of metal, its internal surface is rapidly acted
upon by cyanide of potassium or other solvent of the precious metals; and if a
lining of wood or similar material be employed, the latter is incapable of with-
standing the chemical action of the solvent and the abrasive action of the ore for
any length of time.
With a view to overcoming these difficulties, I line the barrel or vessel with
tiles or segments composed of glass or glazed porcelain or similar solvent- and acid-
resisting material; the same being set in cement adapted to withstand the chemical
action of the cyanide or other solvent employed.
My invention relates thirdly to the construction of the filter or leaching vat
employed for separating the ore from the cyanide or other solution of gold and
silver or from the wash-water.
A filter constructed according to my improved method comprises an upper vessel
for the reception of the mixture of ore and solvent, and a lower vessel in which the
solution is received after passing through the filter-bed. The latter is formed of
filter cloth carried on wire gauze coated with an acid-proof enamel and supported
on wooden laths. The upper vessel is attached to the lower vessel by means of
bolts, and is so arranged that the bottom edge of the former rests upon the
periphery of the filter cloth and grips the same in a recess formed in the upper
edge of the lower vessel, thereby securing a water-tight joint between the two
vessels and at the same time holding the filter cloth securely in position.
The filter or leaching vat may be lined with segments or tiles in the manner
herein before described with reference to the barrel or other vessel in which the ore
is subjected to the action of the solvent.
Dated the 6th day of July 1892.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.
COMPLETE SPECIFICATION (AMENDED).
Improvements in the Extraction of Gold and Silver from Ores or 45
Compounds containing the same, and in Apparatus applicable
in the Treatment of such Materials by means of
for use
Solvents.
I, JOHN CUNINGHAME MONTGOMERIE, of the "Water of Ayr" and "Tam
Q'Shanter" Hone Works, Dalmore, Stair, in the County of Ayr, Scotland, 50
Manufacturer, do hereby declare the nature of this invention and in what manner

page_text: 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-and to
apparatus applicable for use in processes of this description.
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 ore. 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.
When a cyanide solvent is employed as hereinbefore described, a certain portion
thereof is taken up by base metals and other impurities invariably present in greater
or less proportions in the ore. The solvent is also contaminated by the zine
dissolved whilst the mixture of ore and solvent is under treatment in the zinc
percolator; both of these causes resulting in a considerable waste of the cyanide,
and in its contamination with deleterious matter.
My improvement in the process of extraction by means of the kind hereinbefore
referred to consists in adding sodium oxide (caustic soda), or other suitable oxide
of the alkalies, to the cyanide solution before (or whilst) mixing the same with the
ore, thereupon agitating or otherwise treating the resultant mass for the time
requisite for enabling the gold and silver to be dissolved by such a solution, then
discharging the same into a filter and drawing off the or ginal quantity of water
employed; the same being highly charged with the unconsumed cyanide and sodium
oxide, and with the precious metals in solution.
By the employment of sodium oxide in the manner herein before described,
particularly where the alkali is in excess, I have found that the proportion of
cyanide or other solvent may be considerably reduced and an important economy in
the cost of working effected.
In carrying out this stage of the process, a sufficient quantity of water is added
to the surface of the ore in the filter as soon as it becomes dry, the added water
displacing the liquid remaining in the ore and permitting the latter to be discharged.
The liquid obtained is then tested for cyanide of potassium and sodium oxide, and
the deficiency supplied by the addition of the necessary quantity of these agents so
as to restore the solvent solution to its original character and strength. This
solution is now applied to a fresh charge of ore and the same operation is repeated.
with successive charges till it is found necessary to discharge the solution, with a
view to precipitating the gold and silver in the usual manner. Experiment alone
can determine the quantity of solvent and of sodium oxide appropriate, and the
period of time requisite to ensure the greatest extraction of the precious metals
with the least consumption of the solvent, as these will vary according to the nature
of the ore operated upon. (It may be mentioned by way of illustration that for an
ore containing about 4 ozs. of gold and 12 ozs. of silver per ton, 12 lbs. of cyanide
of potassium and 3 lbs. of sodium oxide would be suitable.) The tailings are then
further washed to remove the last trace of gold and silver remaining in solution,
and the resultant wash-water is treated in the usual way for the recovery of the
precious metals contained therein.
By this mode of procedure, the quantity of liquid subjected to treatment for the
recovery of the goid and silver by precipitation is greatly reduced.
My invention relates secondly to the construction of the barrel or other vessel ia
which the ore is subjected to the action of the solvent.

page_text: If this barrel or vessel be formed of metal, its internal surface is rapidly acted
upon by cyanide of potassium or other solvent of the precious metals; and if a
lining of wood or similar material be employed, the latter is incapable of
withstanding the chemical action of the solvent and the abrasive action of the ore
for any length of time.
.
With a view to overcoming these difficulties, I line the barrel or vessel with tiles
or segments composed of glass or glazed porcelain or similar solvent- and acid-
resisting material; the same being set in cement adapted to withstand the chemical
action of the cyanide or other solvent employed.
My invention relates thirdly to the construction of the filter or leaching vat
employed for separating the ore from the cyanide or other solution of gold and
silver or from the wash-water.
Apparatus constructed according to my invention is illustrated in the accom-
panying drawings, whereof Fig. 1 is a vertical section, and Fig. 2 a plan. The
apparatus comprises an upper vessel A for the reception of the mixture of ore
and solvent, and a lower vessel B in which the solution is received after passing
through the filter-bed. The latter is formed of filter-cloth C carried on wire
gauze D coated with an acid-proof enamel and supported on wooden laths E on the
top of the vessel B. The vessel A is attached to the vessel B by means of bolts F
and nuts F, and is so arranged that its bottom edge rests upon the circular margin of
the filter-cloth C, which it presses against the bottom of a recess or socket formed
in the upper edge of the vessel B, thereby securing a water-tight joint between the
two vessels and at the same time holding the filter-cloth securely in position. G is
a draw-off cock; H being the exhaust cock. The vessels A and B are lined with
segments or tiles K composed of glass, glazed porcelain or similar solvent- and
acid-resisting material, set in cement adapted to withstand the chemical action of
the cyanide or other solvent employed. When a barrel is used, it may be lined
with segments or tiles set in a similar manner.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I wish it known that
I am acquainted with the Specifications to J. H. Rae's United States Patent,
dated 5th February, 1867, No. 61,866; J. F. Sanders' United States Patent,
dated 12th July, 1881, No. 244,080; J. W. Simpson's United States Patent dated
28th July, 1885, No. 323,222; J. B. Hannay's British Patent, dated 2nd November,
1886, No. 14,061; Mac Arthur, Forrest and Forrest's British Patent, dated
19th October, 1887, No. 14,174; C. D. Abel's British Application, dated
22nd March, 1888, No. 4,418; and Mac Arthur, Forrest and Forrest's British
Patent, dated 14th July, 1888, No. 10,223; and that I make no claim to the use,
in the cyanide process for extracting gold and silver, of caustic soda or its
equivalent otherwise than in the manner hereinafter specified; but what I claim
is :-
1. The improved process of extracting gold and silver from ores or compounds
containing the same, substantially as herein described; the same consisting in
mixing the ore with a solution of cyanide of potassium or other cyanide solvent
rendered alkaline by the addition of sodium oxide or an equivalent alkaline oxide,
filtering or otherwise separating the liquid (containing the gold and silver in
solution) from the ore, and treating the former, by precipitation or other known
mode, for the recovery of the precious metals.
2. In the extraction of the precious metals by a solvent process of the general
character herein referred to, applying the solvent solution, after separation from the
first charge of ore, but without removal of the precious metals therefrom to a subsequent
charge or successively to subsequent charges of fresh ore, the solution being
fortified at each operation by the addition of a suitable quantity of the chemical
agents employed, and ultimately treating the liquid (consisting of a more-or-less
saturated solution of gold and silver)-by any known means for the-separation-and
recovery of the precious metals substantially as herein described.

page_text: 3. In the process of extracting gold and silver by means of cyanide of potassium
cr other cyanide solvent, the addition of sodium oxide or other suitable alkaline
oxide to the solvent, either prior to or during its admixture with the ore, for the
purpose of economizing the solvent and expediting its action.
4. In the extraction of the precious metals by a solvent process of the general
character herein referred to, discharging the solvent remaining with the ore
after filtration by adding water to the surface of the ore and thereby displacing
the such remaining solvent containing the precious metals in solution, substantially
as herein described.
5. In apparatus adapted for use in the treatment of ores or compounds-con-
taining gold or silver, a barrel, filter or leaching vessel such as-A-or B-lined
with tiles K set in an acid or solvent-resisting cement, substantially as herein
described.
6. The herein-described apparatus for use in the treatment of ores or compounds
containing gold and silver by means of solvents, the same comprising an upper
vessel A for the reception of the ore and solvent, a lower vessel B in which the
solution is received, a filter-cloth C held between the lower part of the vessel A
and a socket in the upper part of the vessel B, wire gauze Don which the filter-
cloth lies, and bars E for supporting the wire gauze.
7. The herein described apparatus for use in the treatment of ores or compounds
containing gold and silver by means of solvents, the same comprising an upper
vessel A lined with tiles K, a lower vessel -B-also lined with tiles K, a filter-cloth C.
held between the vessels A and B, wire gauze D, under the filter-cloth, bars E for
supporting the wire gauze, a draw off cock G, and an exhaust-cock-H.
Dated the 8th day of April 1893.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.