Improvements in and in connection with the Extraction of Gold and Silver from Ores or Compounds containing the same.
Year: 1893

page_text: Date of Application, 27th Oct., 1893
Complete Specification Left, 27th July, 1894-Accepted, 1st Sept., 1894
PROVISIONAL SPECIFICATION.
Improvements in and in connection with the Extraction of Gold and
Silver from Ores or Compounds containing the same.
I, JOHN CUNINGHAME MONTGOMERIE, of Dalmore, Stair, in the County of
Ayr, Justice of the Peace, 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, and to means for regenerating or recovering certain of the agents
employed during the process of extraction; the objects of the invention being to
secure expedition, a high rate of efficiency and economy in the cost of working.
In applying my invention to the treatment of ores containing gold or silver or
gold and silver, I crush or grind the ore sufficiently fine to admit of its passing
through a sieve of from 40 to 60 meshes to the lineal inch, according to the nature
of the ore. The pulverised ore is subsequently treated in a barrel along with water
in sufficient quantity to render the mixture of the consistency of cream or very
thin mud. For a ton of sandy ore, about 140 gallons of water would be
appropriate; whilst for a muddy ore, about 180 gallons of water might be required.
The water is first put into the barrel or other vessel employed and the following
chemicals added thereto :-Cyanide of potassium or of sodium or other cyanide,
sodium oxide (caustic soda) or other alkaline oxide and nitrate of soda or of potash
or of ammonia or other nitrate or nitrite. To the ore, I add from half a pound to
two pounds or more, as circumstances demand, of sodium dioxide or other dioxide
of the alkalies, and immediately charge the same into the barrel and close the inlet.
The barrel is put in motion for a short time in order to thoroughly dissolve the
chemicals and mix its contents. I prefer however to have the chemicals dissolved
before introducing them to the barrel, with the exception of the sodium dioxide,
which is mixed with the ore. The barrel is then charged with air or oxygen to a
pressure of from 50 to 100 lbs. per square inch. When oxygen is used, the sodium
dioxide may be withheld from the ore. Some ores may not require either air or
oxygen under pressure when sodium dioxide is used. By way of example, an ore
containing 8 ozs. of gold and 50 ozs. of silver per ton may be treated with
10 lbs. of cyanide of potassium; 10 lbs. caustic soda and 10 lbs. nitrate of soda,
with one pound of sodium dioxide added to the ore; but these proportions will
vary considerably with different descriptions of ore. The most suitable proportions
may be readily determined by experiment. Should the other chemicals mentioned
be employed, the same proportions may be used. The barrel is now revolved and
maintained in motion for the requisite time for dissolving the precious metals;
average ores occupying from four to six hours. The barrel is then emptied, the
contents filtered and the solution treated in any known manner for the recovery of
the precious metals.
"
In treating the liquor received from the filters and containing the precious metals
in solution, I nevertheless prefer to proceed in the following manner :-
I pass the
liquid through a series of wood charcoal filters (the construction of which is
hereinafter more particularly described); but instead of burning the wood charcoal
on its failing to precipitate more metal (as is at present done when used with a
chlorine solution), I place the wood charcoal in a retort and distil off any moisture
or volatilisable matter the wood charcoal may contain, bringing it to a red heat or
nearly so. After having cooled, it may be returned to the filter and reused for the
precipitation of the precious metals.

page_text: Instead of removing the charcoal from the filters and charging the same into
retorts, superheated air, carbonic acid gas, nitrogen or other gas, may be passed
through the filters at such a temperature as to drive off the water and other
volatilisable matter, the precipitating power of the charcoal being thus regenerated.
In order to cool the charcoal quickly for use, I pass air or the gases before
mentioned in a cold state through the filters. When air or other gas capable of
supporting combustion is employed, care must be taken not to raise the charcoal to
a red heat, or to apply the same whilst the charcoal is at such a heat as would
result in its combustion. This process of regeneration in retorts or by superheated
air, carbonic acid gas, nitrogen or other gas, is repeated whenever the charcoal
fails to perform its function, and until the charcoal is so charged with the precious
metals that it fails to work satisfactorily. It is then finally discharged, and may be
used for heating the retorts, or the air carbonic acid gas or nitrogen heaters; and
the carbonic acid gas yielded at this stage may be applied to the purpose herein-
before referred to. Finally, the ashes of the charcoal are collected and the gold
and silver recovered therefrom by smelting or by amalgamation.
According to my improved method of constructing and working a charcoal filter,
the wood charcoal is in a powdered or granulated state (capable of passing through
a quarter-inch-mesh sieve), about 2 feet thick, is placed in a properly-constructed
iron filter provided with a false bottom covered with asbestos or other non-
combustible filtering material and is lightly rammed. A sheet of asbestos cloth or
perforated iron is also placed upon the top of the charcoal to prevent it floating
and to protect it from disturbance. If it be desired to extract substantially the
whole of the cyanide as well as the precious metals, percolation should be allowed
to take place slowly, through a dense mass of the filtering material. Under such
circumstances, the effluent is rendered fit for discharge to a water-course. If it be
desired to save the cyanide, a less dense filter is employed, and more rapid action
permitted; the liquid yielded being subsequently re-employed in washing tailings,
or, after fortification with cyanide solvent, in the treatment of ore.
Filters of the kind herein before described may be used for purifying the water
when it becomes unfit for further use in consequence of having deleterious matter
in solution.
By the herein-described method of treatment, the contamination of the precious
metals which takes place when a zinc percolator is employed is avoided, the action
is more expeditious, and the cyanide can be either removed altogether from the
liquid or to a large extent saved for further use.
Dated the 25th day of October 1893.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.
COMPLETE SPECIFICATION.
Improvements in and in connection with the Extraction of Gold and
Silver from Ores or Compounds containing the same.
I, JOHN CUNINGHAME MONTGOMERIE, of Dalmore, Stair, in the County of
Ayr, Scotland, Justice of the Peace, 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, and to means for regenerating or recovering certain of the agents
employed during the process of extraction; the objects of the invention being to
secure expedition, a high rate of efficiency and economy in the cost of working.
In applying my invention to the treatment of ores containing gold or silver or
gold and silver, 1 crush or grind the ore sufficiently fine to admit of its passing

page_text: through a sieve of from 40 to 60 meshes to the lineal inch, according to the nature
of the ore.
The pulverised ore is subsequently treated in a barrel or vessel along
with water in sufficient quantity to render the mixture of the consistency of cream
or very thin mud. For a ton of sandy ore, about 80 gallons of water would,
I find, be appropriate; whilst for a muddy ore, about 90 gallons of water might be
required. The water is put into the barrel or other vessel employed, and the
following chemicals added thereto :-Cyanide of potassium or of sodium or other
cyanide, sodium oxide or its hydrate (caustic soda) or other alkaline oxide or a
hydrate of an alkaline oxide, and nitrate of soda or of potash or of ammonia or
other suitable nitrate or a nitrite. To the ore, I add from lb. to 2 lbs. or more,
as circumstances demand, of sodium dioxide or other alkaline dioxide, and
immediately charge the same into the barrel and close the inlet. The barrel is
then revolved for a short time in order to thoroughly mix its contents. I prefer
to let the chemicals dissolve before introducing them to the barrel; the sodium
dioxide being however mixed in a solid state with the ore. The sodium dioxide
may nevertheless be placed in a receptacle on the top of the barrel and allowed to
run into the barrel after the manhole door has been closed. The barrel is then
charged with air, oxygenated air or oxygen to a pressure of from 50 to 100 lbs.
per square inch. When oxygenated air or oxygen is used, sodium dioxide is not
required. With some ores, air or oxygen under pressure is not needed when
sodium dioxide is employed; the ore being in such cases treated in tanks with or
without agitation. When there is no agitation, it is preferable to allow the solvent
liquid to percolate through the mass of ore repeatedly; the liquid as it passes
away being fed back to the surface of the ore until the precious metals are
sufficiently dissolved. Under such procedure, the sodium dioxide, instead of being
mixed with the ore, may be dissolved in the solvent solution in very small quantities
at a time so as to prevent, any violent action or great loss of oxygen occurring.
By way of example, a refractory ore of a muddy character containing 8 ozs.
of gold and 50 ozs. of silver per ton may be treated with 10 lbs. of cyanide of
potassium, 10 lbs. of caustic soda and 7 lbs. of nitrate of soda, with 14 lbs. of
sodium dioxide added to the ore. These proportions will, however, be subject to
considerable variation with different descriptions of ore; the most suitable
proportions being readily determined by experiment. Should the other chemicals
mentioned as equivalents for potassium cyanide, sodium oxide, nitrate of soda and
Bodium dioxide be employed, the same proportions may be used, with the
exception that when the dioxides of barium, strontium and calcium are used, a larger
proportion of them is required, and when the weight of the carbonate of soda and
of potash combined (commonly occurring as impurities in the cyanide of potassium
and alkali employed) is not about double that of the dioxide used, the deficiency.
of the former must be added. These act as liberating agents of the oxygen.
Bicarbonates may also be used for this purpose. The barrel is then again revolved
and maintained in motion until the precious metals are dissolved; the time occupied
with average ores being from four to six hours. The barrel is thereupon emptied,
the contents filtered and washed and the solution treated in any known manner for
the separation of the precious metals. I prefer however to filter and to proceed,
as regards the re-use of the liquid, in the manner set forth in the Specification
filed in pursuance of my application for Letters Patent No. 12641 of 1892.
If the cyanide liquid hold sulphur in solution, the well-known precipitant lead
carbonate may be added either to the liquid after it has been drawn from the
tailings or to the contents of the barrel, when the ore is run in, in such quantity as
may be required to precipitate the sulphur in the form of sulphide of lead.
Peroxide of lead or red lead or oxide of lead may also be employed for this
The requisite
purpose, same being placed in the barrel along with the ore.
quantity for any ore may be determimed by experiment.
An important advantage resulting from the use of a nitrate or nitrite as herein-
before described is that the liquid filtered from the tailings is tolerably free from.
muddy particles, any matter left in suspension settling quickly, so that charcoal

page_text: employed as a precipitant is not liable to become choked by sediment. I have
found with many ores that, when cyanide alone is used, the liquid is very muddy,
and takes weeks or even months to settle; whereas a solvent solution containing &
nitrate or nitrite becomes fairly clear in a day or so after filtration from the
tailings.
In treating the liquid received from the filters and containing the precious metals
in solution, as also the unused solvent and other chemical agents employed, I pass
the said liquid through a filter containing charcoal, preferably wood charcoal, or
through a series of such filters the construction of which is hereinafter more
particularly referred to. When dealing with a chlorine gold solution, it has
hitherto been the practice to burn the charcoal when it fails in its precipitating
action and forthwith to proceed with the recovery of the precious metals therefrom.
Instead of following this course I place the wood charcoal in a retort and distil
off any moisture or volatilisable matter it may contain, bringing it if necessary to a
red heat or nearly so. After having been allowed to cool, the charcoal, still
containing the precious metals, is returned to the filter and reused for the
precipitation of a further quantity of the precious metals.
Instead of removing the charcoal from the filter and charging the same into
retorts, for the purpose of regeneration it may be treated in situ by passing
therethrough superheated steam, air, carbonic acid gas or nitrogen or other
suitable gas at such a temperature as to drive off the water and other volatilisable
matter. In order to cool the charcoal quickly for reuse, I pass air or other gas in
a cold state through the filter. When air or other gas capable of supporting
combustion is employed, care must be taken not to apply the same at such a
temperature, or whilst the charcoal is at such a temperature, as would result in
combustion.
The above described process of regeneration in retorts or by superheated steam,
air or other gas, is repeated whenever the charcoal fails to perform its functions,
aud until it becomes so charged with the precious metals that it is no longer
capable of acting satisfactorily as a precipitant; whereupon it is discharged, and
may be used as fuel for heating the retorts, or the steam, air or gas heaters, or it
may be burned in a reverberatory furnace with as much draught as will suffice to
effect its slow combustion. The carbonic acid gas yielded at this stage may be
applied to the purpose herein before referred to. Finally, the ashes are collected,
and the gold and silver recovered therefrom by smelting or by amalgamation with
mercury.
In constructing a charcoal filter adapted for use in my.improved process, I
employ an iron vessel containing wood charcoal in a powdered or granulated state
(capable of passing through a ths inch-mesh sieve), about 2 feet thick, and lightly
rammed. The vessel is provided with a false bottom covered with asbestos or other
non-combustible fabric or material. A sheet of asbestos cloth or perforated iron is
also placed upon the top of the charcoal to prevent it floating and to protect it
against disturbance. The filter is closed with a removable top and is furnished
with pipe connections for the liquid and for the gas admitted for regenerative
purposes.
Another mode of charging the filter is to grind the charcoal to a powder, mix it
with a little water to form a paste and then to press it evenly into the filter;
suction being at the same time applied from below. In this case, a thickness of
six inches will suffice, but in working pressure must be used or suction applied to
force or draw the liquid through the comparatively dense mass of filtering material.
Where, owing to the presence of much fine ore in the solution, there is a tendency
for the filter to clog, the solution may, prior to its arrival in the charcoal filter, be
passed through a mechanical filter of any suitable description; or the solution may
be ran into tanks and allowed to stand till the matter in suspension is precipitated.
If it be desired to extract substantially the whole of the cyanide as well as the
precious metals, percolation should be allowed to take place slowly, through a dense
mass of the charcoal newly charred or regenerated. Under such circumstances, the

page_text: effluent is rendered fit for discharge to a water-course. Two or more filters may be
used in succession. If it be desired to save the cyanide; a' less dense and less active
filter is employed, and more rapid action permitted, in which case the water escaping
from the filter contains cyanide in solution. Charcoal which, after charring, has for
Some while been exposed to the atmosphere is most suitable for saving the cyanide.
Such cyanide solution may be re-used in washing tailings, or, after fortification with
cyanide, in the treatment of ore.
By the hereinbefore described method of: dealing with auriferous and
argentiferous solutions in charcoal filters, and by the repeated regeneration of the
charcoal without extracting the precious metals contained therein, the contamination
of the said metals which takes place when a zinc percolator is employed is avoided,
the action is more expeditious and the cyanide can be either removed altogether
from the liquid or to a large extent saved for further use.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I would have it known
that I do not claim any exclusive right to the employment, in the extraction of the
precious metals, of cyanide of potassium or other cyanogen-yielding agent, or alkali
or alkaline oxide, or nitrate or nitrite; 'neither do I claim the exclusive use of
charcoal as a precipitating agent; nor do I claim the treatment of the mixture of
ore and solvent in the presence of oxygen or of air under pressure; but I declare
that what I claim is :-
1. The improved process of extracting gold and silver from ores or compounds
containing the same substantially as herein described, and consisting in mixing with
the pulverised ore or compound sodium dioxide or other alkaline dioxide, and
charging this mixture into a barrel or vessel containing water holding in solution
cyanide of potassium or other cyanide together with sodium oxide or other alkaline
oxide or a hydrate of an alkaline oxide, and nitrate of soda or other nitrate or
a nitrite, and allowing the chemicals to act on the ore until the precious metals are
sufficiently dissolved.
2. The improved process of extracting gold and silver from ores or compounds
containing the same substantially as herein described, and consisting in charging the
pulverized ore or compound into a barrel or vessel containing water holding in
solution cyanide of potassium or other cyanide, sodium dioxide or other alkaline
dioxide, sodium oxide or other alkaline oxide or a hydrate of an alkaline oxide, and
nitrate of soda or other nitrate or a nitrite, and allowing the chemicals to act on the
ore until the precious metals are sufficiently dissolved.
3. The improved process of extracting gold and silver from ores or compounds
containing the same substantially as herein described, and consisting in mixing with
the pulverized ore or compound sodium dioxide or other alkaline dioxide, charging
the mixture into a barrel or vessel containing water holding in solution cyanide of
potassium or other cyanide, sodium oxide or other alkaline oxide or a hydrate of an
alkaline oxide and nitrate of soda or other nitrate or a nitrite, closing the barrel or
vessel and forcing in air, oxygenated air or oxygen, the contents being then
agitated until the precious metals are sufficiently dissolved.
4. The improved process of extracting gold and silver from ores or compounds
containing the same substantially as herein described, and consisting in charging
the pulverized ore or compound into a barrel or vessel containing water holding in
solution cyanide of potassium or other cyanide, sodium oxide or other alkaline oxide
or a hydrate of an alkaline oxide and nitrate of soda or other nitrate or a nitrite,
closing the barrel or vessel and forcing in air, oxygenated air or oxygen, the
contents being then agitated until the precious metals are sufficiently dissolved.
5. The improved method of working a charcoal filter employed for separating
precious metals from a solution, the same consisting in regenerating the charcoal,
without removing the precious metals therefrom, by heating the charcoal in sitú
or otherwise in order to drive off volatilisable matter, substantially as herein
described.

page_text: 6. In the extraction from auriferous and argentiferous solutions of the precious
metals contained therein, repeatedly employing the same body of charcoal for
filtering successive. charges of solution and until that body becomes saturated with
the precious metals, the active properties of the charcoal being occasionally restored
or regenerated by subjecting it to a suitably high temperature.
7. In the treatment of auriferous and argentiferous cyanide solutions for the
extraction of the precious metals and of the cyanide contained therein, the
employment of a charcoal filter or series of charcoal filters, substantially as herein
described, and whereby the said metals and the cyanide may be either simultaneously
or successively extracted from the solution, the active properties of the charcoal
being occasionally restored or regenerated as herein set forth.
Doted this 97th do T1 1904