Improvements in the Extraction of Gold and Silver from Ores or Compounds containing the same.
Year: 1891

page_text: Date of Application, 3rd July, 1891
Complete Specification Left. 4th Apr., 1892-Accepted, 3rd Aug.. 1892
PROVISIONAL SPECIFICATION.
Improvements in the Extraction of Gold and Silver from Ores or
Compounds containing the same.
We, HENRY PARKES, of 237, Friern Road, Dulwich, in the County of Surrey,
Chemist, and 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; the same being specially adapted for use with ores of a
refractory character.
The ore or other material having been reduced by preference to a finely
triturated state (capable of passing through a sieve having sixty meshes to the
linear inch), it is subjected to an oxidizing or chloridizing process prior to
submitting it to the action of solvents or to treatment by amalgamation. Should
any gold or silver be found in suspension in the solution, it is precipitated by
sulphate of iron or other precipitant, and the supernatant liquid containing base
metals and other impurities is then discharged. The ore is further washed and
filtered, and if found acid is neutralized. The residual product is then treated with
cyanide of potassium for the purpose of dissolving the precious metals; a solution
of cyanide of gold and silver resulting. This solution is then decanted and if
necessary filtered, the ore is further washed for the purpose of recovering all the
precious metals which may remain (in solution) with the ore, and the gold and
silver are then precipitated by any known method.
Instead of discharging the supernatant liquid and washing the orė as above
described, the chloridized mass, after dilution with a little water, may be neutralized
with an alkali or an alkaline earth, and the solvent may then be added without
removing either the solid or the fluid portion of the charge from the barrel or other
vessel employed.
We are aware that the process of chlorination is well known in connection with
the extraction of the precious metals from ores or compounds containing the same,
and we are also aware that cyanide of potassium, amongst other solvents, has been
employed in treating such ores or compounds with a similar object.
It will,
however, be observed that our invention in its primary form consists in the
combination and use in special manner of these two processes, either or both
being subjected to certain modifications. For example, the chloridizing or
oxidizing treatment, carried to the extent to which we apply it, renders the
precious metals readily soluble in the cyanide or other solvent."
According to one of the simplest modes of carrying out our invention, we add to
1 ton of ore 12 gals. of hydrochloric acid (or its equivalent of a chloride salt and
sulphuric acid), together with sufficient water, preferably warm (say about
180° Fahrenheit) to reduce the mass to the consistency of thin mortar. In some
cases, when employing hydrochloric acid, we find it useful to combine a little
common salt or other chloride therewith. The charge is placed in any suitable
vessel to which oxygen gas at a pressure of from 50 to 100 lbs. per square inch is
admitted. The vessel is well agitated for from four to six hours, the temperature
being maintained at about 180° Fahrenheit. A barrel is most convenient for this
purpose, and is kept in rotation the whole time the action is going on. The time
will, however, vary according to the quantity of the metal to be dissolved, the
strength of the solvent, the temperature and the pressure of the oxygen employed.
In certain cases, the oxygen is not required. The barrel is then discharged and a

page_text: quantity of water added to its contents. Should any gold or silver be found in
solution, it is precipitated by means of any of the known agents; the whole being
then allowed to remain until the earthy matter subsides, whereupon the liquid part
is drawn off. The remainder, containing the ore and a little water, is then
neutralized and treated with solvent as hereinafter described. Instead of waiting
for the earthy matter to subside, the charge may, after dilution with a little water,
be forthwith filtered.
Or to the same quantity of ore, we add (instead of hydrochloric acid) 12 gals. of
sulphuric acid, 64 lbs. of peroxide of manganese, 48 lbs. of common salt and sufficient
water as before described.
Amongst other chloridizing and oxidizing agents adapted for use in our improved
process, the following may be inentioned; a sufficient quantity of water being in
each instance added:
:
We have sometimes found it useful to employ common salt, or a solution thereof
saturated with chlorine or bromine, as a chloridizing or brominating agent; or the
same may be added to the chloridizing solution. A solution of common salt with

page_text: In either of these cases, after calcining the ore or other material at a red heat,
we add the saltpetre and the salt, or the green vitriol and salt, and continue the
calcination at a low red heat until the precious metals in the ore are sufficiently
chloridized.
In the further treatment of the ore with the aid of what is known as the "barrel"
system, the solid material resulting from the processes above described is placed in
a barrel together with a solvent composed of say 18 lbs. of cyanide of potassium
and 30 gals. of water or a sufficient quantity to convert the ore to the consistency
of thin mortar. We have found a solvent of the above description particularly
appropriate for use with an ore containing from 40 ozs. to 60 ozs. of silver and
from 1 oz. to 2 ozs. of gold. per ton. The barrel, having been closed, is kept in
rotation for a period of four or five hours; a temperature of about 150° Fahrenheit
being maintained at this stage of the process. The time will, however, vary
according to the quantity of the metal to be dissolved, the strength of the solvent,
the temperature and the pressure employed. The mixture of ore and solvent is
then filtered and further washed with water until the ore is free from the precious
metals dissolved. The liquor containing the precious metals in solution is then
treated in any known manner for the recovery of the said metals; as, for example,
by precipitation with metallic zinc.
Other solvents, such as hyposulphites, may be substituted with certain varieties
of ore; as, for example, by hyposulphite of soda. Or a mixture of hyposulphite
of soda or of ammonia or of sulphite of soda with cyanide of potassium may be
employed; or sulphocyanide of ammonium or of potassium may be used.
According to a modification of the two-stage process hereinbefore described,
certain ores may be treated at a single operation in the following manner :- -To
one ton of ore, moistened as previously described, we add about 18 lbs. of cyanide
of potassium or other cyanide and subject same to agitation in the presence of
oxygen under pressure for four to five hours. A pressure of from 50 lbs. to 100 lbs.
per square inch will usually be found convenient. The oxygen is then drawn off*
for further use, and the contents of the barrel filtered and washed as before
described. We have found this process well adapted for employment with ore of
the particular description above specified. To obtain the full effect of the oxygen,
the air in the barrel should first be exhausted before applying the oxygen.
Or according to another modification, we saturate the liquid mass in the barrel
with chlorine and apply the oxygen as above described.
The treatment with cyanide of potassium and with oxygen under pressure may
also be employed in substitution for either of the modes of treatment hereinbefore
described as the second stage of the two-stage process first above referred to.

page_text: In conjunction with cyanide of potassium or other cyanide with or without oxygen
under pressure, peroxide of hydrogen may be employed; or there may be substituted
for peroxide of hydrogen, hypochlorite of lime, of soda, of potash or of magnesia
or other suitable hypochlorite.
It will sometimes be found advantageous to separate some of the earth or silicious
matters from the ores by a concentrating or winnowing process, or by means of a
centrifugal or other concentrating machine.
In many cases, after chloridizing or oxidizing the ores or other materials to be
treated by the employment of any of the means herein before described, the precious
metals may, if preferred, be extracted by the amalgamation process..
Dated this 3rd day of July 1891
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Agent for the Applicants.
COMPLETE SPECIFICATION.
Improvements in the Extraction of Gold and Silver from Ores or
Compounds containing the same.
We, HENRY PARKES, of 237, Friern Road, Dulwich, in the County of Surrey,
Chemist, and 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 con-
tained therein; the same being specially adapted for use with ores of a refractory
character.
The ore or other material having been reduced by preference to a finely-
triturated state (capable of passing through a sieve having sixty meshes to the
linear inch), is subjected to an oxidizing or chloridizing process prior to submitting
it to the action of solvents or to treatment by amalgamation. When using the
chloridizing or oxidizing method, the treatment is of a modified character as
compared with that ordinarily employed; that is to say, it is carried to an extent
adapted to render the precious metals peculiarly susceptible to the influence of
solvents, but not to the extent of dissolving the gold to any considerable degree;
whilst the silver, in the form of chloride of silver, is left with the gold in the ore.
(The chloride of silver may, if required, be reduced to the metallic state by means
of metallic iron, copper or zinc; especially if it be desired to extract the precious
metals by amalgamation.) Should any gold or silver be found in suspension in the
solution, it is precipitated by sulphate of iron or other precipitant, and the super-
natant liquid containing base metals and other impurities is then discharged. The
ore is further washed and filtered, and if found acid is neutralized. The residual
product is then treated with cyanide of potassium for the purpose of dissolving the
precious metals; a solution of cyanide of gold and silver resulting. This solution
is then filtered from the ore, and the ore is further washed for the purpose of
recovering all the precious metals which may remain (in solution) with the ore,
and the gold and silver are then precipitated from the solution by any known
method.
Instead of discharging the supernatant liquid and washing the ore as above
described, the chloridized mass, after dilution with a little water, may be neutralized
with an alkali or an alkaline earth, and the solvent may then be added without
removing either the solid or the fluid portion of the charge from the barrel or other
vessel employed.
We are aware that the process of chlorination is well known in connection with
the extraction of the precious metals from ores or compounds containing the same,

page_text: and we are also aware that cyanide of potassium, amongst other solvents, has been
employed in treating such ores or compounds with a similar object. It will,.
however, be observed that our invention in its primary form consists in the com-
bination and use in a special manner of these two processes, either or both being
subjected to certain modifications. For example, the chloridizing or oxidizing
treatment, carried to the extent to which we apply it, renders the precious metals
readily soluble in the cyanide or other solvent.
According to one of the simplest modes of carrying out our invention, we add.
to 1 ton of ore 9 gals. of hydrochloric acid, sp. gr.12 (or its equivalent of a
chloride salt and sulphuric acid), together with sufficient water, preferably warm
(say about 180° Fahrenheit), to reduce the mass to the .consistency of thin mortar.
In some cases, when employing hydrochloric acid, we find it useful to combine a
little common salt or other chloride therewith. The charge is placed in any
suitable vessel to which oxygen gas at a pressure of from 50 to 100 lbs. per square.
inch is admitted. The vessel is well agitated for from two to six hours; the
temperature being maintained at about 180° Fahrenheit. A barrel is most con-
venient for this purpose, and is kept in rotation the whole time the action.is going
on. The time will, however, vary according to the refractory character of the ore
under treatment, the quantity of the metal to be acted on, the strength of the
chemical agent used, the temperature employed and the pressure of the oxygen..
In certain cases, neither the application of heat nor of oxygen is required. The
barrel is then discharged and a quantity of water added to its contents. Should
any gold or silver be found in solution, it is separated by any of the known means,
or may be precipitated by the addition of metallic copper or iron, the whole being-
then allowed to remain until the solid matters subside, whereupon the liquid part is
drawn off. The remainder, containing the ore and a little water, is then neutralized.
and treated with the solvent as hereinafter described. Instead of waiting for the
solid matters to subside, the charge may, after dilution with a little water, be.
forthwith filtered and the solid portion washed for the removal of acid.
.
Or, to the same quantity of ore, we add (instead of hydrochloric acid) 9 gals. of
sulphuric acid, 42 lbs. of peroxide of manganese, 50 lbs. of common salt and sufficient.
water, as before described.
Amongst the chloridizing and oxidizing agents adapted for use in our improved
process, the following may be mentioned; a sufficient quantity of water being in.
cach instance added

page_text: with other agents and under different degrees of pressure-we regard as highly
advantageous in all oxidizing processes for the preliminary treatment of ores or
other compounds, or for at once extracting the precious metals according to the
nature of the material operated on.

page_text: In the further treatment of the ore with the aid of what is known as the " barrel "
system, the solid material resulting from the processes above described is placed in
a barrel together with a solvent composed of say 18 lbs. of cyanide of potassium and
30 gals. of water, or a sufficient quantity to convert the ore to the consistency of
thin mortar. We have found a solvent of the above description particularly
appropriate for use with an ore containing from 40 ozs. to 60 ozs. of silver, and
from 1 oz. to 2 ozs. of gold per ton; but where the quantity of silver is com-
paratively small in proportion to that of the gold, a considerably smaller proportion
of cyanide will suffice. The barrel, having been closed, is kept in rotation for a
period of four or five hours; a temperature of about 150° Fahrenheit being main-
tained at this stage of the process when very refractory ores are under treatment.
The time will, however, vary according to the quantity of the metal to be dissolved,
the strength of the solvent, the temperature and the pressure employed. The
mixture of orc and solvent is then filtered and further washed with water until the
ore is free from the precious metals dissolved. The liquor containing the precious
metals in solution is then treated in any known manner for the recovery of the said
metals; as, for example, by precipitation with metallic zinc.
In carrying out our improved mode of treatment with chloridizing and solvent
agents successively, other solvents, such as salt, or salt with cyanide of potassium,
or hyposulphites, may be substituted with certain varieties of ore; as, for example,
hyposulphite of soda. Or, a mixture of hyposulphite of soda or of ammonia, or of
sulphite of soda, with cyanide of potassium may be employed; or sulphocyanide of
ammonium or of potassium may be used.
According to a modification of the two-stage process herein before described,
certain ores may be treated at a single operation in the following manner :-To
one ton of ore, moistened as previously described, we add (according to the
character of the ore to be treated and the quantities of the gold and silver present)
from 5 lbs. to 25 lbs. of cyanide of potassium or other cyanide, and subject the same
to agitation in the presence of oxygen (in any of its various conditions, as passive,
or active as ozone) or of peroxide of hydrogen under pressure for from four to six
hours. A pressure of from 50 lbs. to 100 lbs. per square inch will usually be found
convenient. The oxygen is then drawn off for further use, and the contents of the
barrel filtered and washed as before described. We have found this process well
adapted for employment with ore of the argentiferous character above specified,
and with which 18lbs. of cyanide of potassium is used. To obtain the full effect
of the oxygen, the air in the barrel should first be exhausted before applying the
oxygen.
Or, according to another modification, we saturate the liquid mass in the barrel
with chlorine and apply the oxygen as above described.
The treatment with cyanide of potassium and with oxygen under pressure may
also be employed in substitution for either of the modes of treatment herein before
described as the second stage of the two-stage process first above referred to..
In conjunction with cyanide of potassium or other cyanide with or without
oxygen under pressure, peroxide of hydrogen may be employed; or there may be
substituted for peroxide of hydrogen, hypochlorite of lime, of soda, of potash, or of
magnesia or other suitable hypochlorite.
It will sometimes be found advantageous to separate some of the earth or silicious
matters from the ores by a concentrating or winnowing process, or by means of a
centrifugal or other concentrating machine.
In many cases, after chloridizing or oxidizing the ores or other materials to be
treated by the employment of any of the means herein before described, the precious
metals may, if preferred, be extracted by the amalgamation process.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, we claim :-
1. The herein-described process for extracting gold and silver from ores or
compounds containing the same, consisting in subjecting the crushed ore to oxidation

page_text: or chlorination to an extent adapted to render it readily susceptible to the influence
of a solvent, neutralising the same (if acid), treating it with cyanide of potassium or
other solvent of gold and silver, and finally recovering the precious metals by
precipitation or other known means.
2. In carrying out the process referred to in the preceding claiming clause,
effecting the treatment of the ore with a chloridizing agent in the presence of
oxygen or peroxide of hydrogen under pressure, such treament being specially
appropriate for use with ores which are rich in gold.
3. In carrying out the process referred to in the first of the preceding claiming
clauses, effecting the treatment of the ore with cyanide of potassium or other
solvent of gold and silver in the presence of oxygen, or peroxide of hydrogen under
pressure, or of bypochlorite of lime or other suitable hypochlorite, such treatment
being appropriate for use with ores of a refractory or other character and which
are rich in both gold and silver.
4. In the extraction of gold and silver from ores or compounds containing the
same, the employment, as a chloridizing and oxidizing agent, of chromic or chloro-
chromic acid with dilute hydrochloric acid (or its equivalent), substantially as
herein described.
5. In the extraction of gold and silver from ores or compounds containing the
same, the employment, as a chloridizing and oxidizing agent, of chloride of lead
mixed with about twice its weight of common salt and saturated with chlorine,
substantially as herein described.
6. In the treatment of ore or other material with cyanide of potassium.or other
solvent in the presence of oxygen or peroxide of hydrogen, the employment, as a
chloridizing and brominating agent, of common salt or a solution thereof saturated
with chlorine or bromine, or in conjunction with chloride or sulphate of copper,
substantially as herein described.
7. The hercin-described process for extracting gold and silver from ores or
compounds containing the same by an uninterrupted operation consisting in treating
the ore with cyanide of potassium, or other cyanide, in the presence of oxygen
under pressure and subjecting the same to agitation, the ore being subsequently
filtered and washed. and the precious metals recovered from the liquor by pre-
cipitation or other known means.
8. The herein-described modification of the process referred to in the last
preceding claiming clause, according to which saturation of the mass with chlorine
is substituted for the treatment with cyanide.
Dated this 4th day of April 1892.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.