Improvements in the Wet Method of Extracting Gold, and in Apparatus to be used therewith.
Year: 1889

page_text: Date of Application, 25th June, 1889
Complete Specification Left, 20th Mar., 1890-Accepted, 26th Apr., 1890
PROVISIONAL SPECIFICATION.
Improvements in the Wet Method of Extracting Gold, and in
Apparatus to be used therewith.
I, JAMES HOLMS POLLOK, B. Sc. of the University of Glasgow, in the County of
Lanark, North Britain, Assistant to the Professor of Chemistry in the said University
do hereby declare the nature of this invention to be as follows:-
My Invention which relates to the wet method of extracting gold from crushed
ore or other finely divided auriferous material by chlorination, preferably by chlori-
nation under hydraulic pressure, has for its object to remove or absorb the excess
of chlorine in the vessel in which the operation of chlorination has been performed
prior to the opening of the said vessel, or prior to the discharging of the ore and
solution from the said vessel to the filter or other receptacle into which it may be
discharged. Thereby the deleterious fumes which hitherto have been a great draw-
back to the process of chlorination are completely removed, and the gold may be
more easily precipitated from the liquor, more particularly when charcoal is used as
the recipient; also in certain ways of operating these improvements the chlorine may
be very readily absorbed in such a way as to be capable of re-use, whereby is effected.
a great saving in bleaching powder, and the amount of liquor necessary for carrying
out the operation is minimised.
In practising this invention the process of chlorination is conducted in a suitable
vessel, having two stop-cocks with suitable connecting pipes. This vessel is preferably
in the form of a revolving iron cylinder, suitably lined to preserve it from the
corrosive action of the chlorine, having a charging aperture at the centre of the
circumference of the machine, with a pipe passing through the centre of rotation of
one end of the machine, to which end this pipe is kept fast by a suitable packing-box,.
which, while it keeps the pipe tight, leaves the cylinder free to revolve, and having
an escape valve placed on the circumference of the machine on the same side as the
charging aperture. After the operation of chlorination is completed the escape
valve is connected to a pipe leading to an exhaust pump, lime recoverers, or
other means of disposing of the chlorine. The valve is then opened, and part
of the chlorine escapes; steam is then injected through the aforementioned pipe.
through the centre of rotation of the machine, which steam rapidly raises the
temperature of the water and drives out the remainder of the chlorine; then, after
the steam is shut off, the escape valve is disconnected from the pipe, and the ore and
solution discharged from the machine to be afterward filtered in the usual manner.
Another method of effecting my object is, after the operation of chlorination is com-
pleted, to inject a quantity of slaked lime into the chlorinating cylinder, whereby the
whole of the excess of chlorine, or the larger part of the said excess of chlorine, as
may be desired, is absorbed by the lime, but the gold is not precipitated from solution;
so that when the machine is opened, and the ore and solution are discharged on the
filter, no injurious fumes come off, nor is there any disagreeable smell, yet the whole
of the gold is in solution and may be filtered off and recovered in the usual manner;
moreover the precipitation of the gold is greatly assisted, especially when charcoal is
the precipitant employed.
In place of slaked lime, I also employ for the purposes afore-mentioned car-
bonate of lime, or any other alkali, or alkaline earth, or carbonate of an alkali or
alkaline earth, or reducing agent, or any other substance which will absorb the excess
of chlorine without precipitating the gold, or which if introduced in proper quantity
will absorb the chlorine or the greater part thereof, but will leave the gold or the
greater part thereof in solution.
Another feature of this improvement is to inject slaked lime, carbonate of lime, or

page_text: any other alkali or alkaline earth, or carbonate of an alkali or alkaline earth, or any
other substance which, while it absorbs the chlorine, is capable of yielding the chlorine
again on treatment with another substance, such as an acid or acid salt. These
reagents being injected as aforesaid for the purposes afore-mentioned, and thereafter
the ore and solution are discharged on a suitable filter, and the liquors filtered off;
but in place of the gold being precipitated as formerly from these liquors, which now
contain the gold from the previous charge together with the whole, or the greater
part of the chlorine absorbed in a manner capable of being yielded again by treat-
ment with a suitable reagent, such as an acid or acid salt, the liquors are re-injected
into the same or another machine in which has been placed a new charge of ore
together with a fresh portion of acid, or other chlorine liberating agent, and to which
a small additional proportion of bleaching powder or other chlorine yielding agent
has been added to make up for the chlorine that may have been consumed, by the
gold or otherwise. Thereafter the process is continued and repeated as hereinbefore
described until the liquors contain such quantity of gold that it is thought desirable
to precipitate it, or otherwise recover it. In this mode of operation, not only is the
process healthful and convenient, but it is exceedingly economical, for the same
bleaching powder, or other chlorine yielding agent is made to perform the operation
of extraction many times over, without any practical loss of gold, and in a corre-
sponding degree the amount of ferrous sulphate or other precipitant used is also
reduced, thereby effecting great saving.
It is to be distinctly understood that these improvements are not only applicable
when chlorine or chlorine generating agents are employed, but also when bromine,
or iodine, or bromine or iodine generating agents are employed.
Dated this 24th day of June 1889.
J. HOLMS POLLOK,
Applicant.
COMPLETE SPECIFICATION.
Improvements in the Wet Method of Extracting Gold, and in
Apparatus to be used therewith.
I JAMES HOLMS POLLOK, B. Sc., of the University of Glasgow in the County of
Lanark, North Britain, Assistant to the Professor of Chemistry in the said University,
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 :-
used
My invention, which relates to the wet method of extracting gold from crushed
ore or other finely divided auriferous material by chlorination, preferably by
chlorination under hydraulic pressure, has for its object to remove or absorb the
excess of chlorine in the vessel in which the operation of chlorination has been
performed, prior to the opening of the said vessel, or prior to the discharging of the
ore and solution from the said vessel to the filter or other receptacle into which it
may be discharged. Thereby the deleterious fumes which hitherto have been a great
drawback to the process of chlorination, are completely removed, and the gold may
be more easily precipitated from the liquor, more particularly when charcoal
as the recipient; also, in certain ways of operating these improvements, the chlorine
may be very readily absorbed in such a way as to be capable of re-use, whereby a
great saving in bleaching powder is effected, and the amount of liquor necessary for
carrying out the operation is minimised. In practising this invention, the process
of chlorination is conducted in a suitable vessel having two stop cocks, with suitable
connecting pipes. This vessel is preferably in the form of a rotating iron sphere,
suitably lined to preserve it from the corrosive action of the chlorine, having a
charging aperture and a pipe passing through the centre of rotation at one side of
the machine, where the pipe is kept fast by a suitable packing box, which, while it
keeps the pipe tight, leaves the chlorinator free to rotate. An escape valve is
preferably placed on the circumference of the chlorinator on the same side as the

page_text: charging aperture, after the operation of chlorination is completed, a quantity of
slaked lime is injected into the chlorinating vessel, whereby the whole of the excess
of chlorine, or the larger part of the said excess of chlorine, as may be desired, is
absorbed, but the gold is not precipitated from solution, so that when the machine is
opened, and the ore and solution are discharged on the filter, no injurious fumes
come off, nor is there any disagreeable smell, yet the whole of the gold is in solution,
and may be filtered off and recovered in the usual manner; moreover, the precipi-
tation of the gold is greatly assisted, especially when charcoal is the precipitant
employed.
In place of slaked lime, I also employ, for the purposes afore mentioned, carbonate
of lime, or any other alkali or alkali earth, carbonate of an alkali, or alkaline earth,
or reducing agent, or any other substance which will absorb the excess of chlorine,
without precipitating the gold, or which, if introduced in proper quantity, will
absorb the chlorine, or the greater part thereof, but will leave the gold, or the greater
part thereof, in solution.
Another feature of the invention is the reuse of the liquors in which the chlorine
has been absorbed, by slaked lime, carbonate of lime, or any other alkali or alkaline
earth, or carbonate of an alkali or alkaline earth, or other substance which, while it
absorbs the chlorine, is capable of yielding the chlorine again on treatment with
another substance, such as an acid or acid salt, these reagents being injected as
aforesaid for the purposes aforementioned, and thereafter the ore and solution are
discharged on a suitable filter and the liquors filtered off, but in the place of the gold
being precipitated as formerly from these liquors, which now contain the gold from
the previous charge, together with the whole or the greater part of the chlorine
absorbed, in a manner capable of being yielded again by treatment with a suitable
reagent, such as an acid or acid salt, the liquors are reinjected into the same or another
machine, in which has been placed a new charge of ore, together with a fresh portion
of acid or other chlorine liberating agent, and to which a small additional proportion
of bleaching powder, or other chlorine-yielding agent, has been added, to make up for
the chlorine that may have been consumed by the gold or otherwise. Thereafter, the
process is continued and repeated, as hereinbefore described, until the liquors contain
such quantity of gold that it is thought desirable to precipitate it, or otherwise recover
it. In this mode of operation, not only is the process healthful and convenient, but
it is exceedingly economical, for the same bleaching powder or other chlorine-yielding
agent is made to perform the operation of extraction many times over without any
practical loss of gold; in a corresponding degree the amount of ferrous sulphate or
other precipitant used is also reduced, thereby effecting great saving.
It is to be distinctly understood that these improvements are not only applicable
when chlorine or chlorine-generating agents are employed, but also when bromine or
iodine, or bromine or iodine-generating agents are employed. The process may be
advantageously carried out in apparatus such as is illustrated in the accompanying
drawings, Fig. 1 of which is a sectional front, and Fig. 2 an end view. The vessel A
is made in hemispheres of in. steel lined with in. lead, and bolted together; it is
supported by two hollow axles cd, resting on journals, and inade to rotate by gearing B.
The vessel has a suitable charging aperture a, and two stop cocks, from which come
two pipes C and D respectively, which pass along the outside of the machine into
two hollow axles, at the extremities of which are suitable packing boxes, which allow
of the continuation of these pipes being made perfectly tight, yet leaving the machine
free to rotate.
Under the machine is placed a filter made of light steel or iron, lined with lead,
or of enamelled iron without lead, and from the lowest point of this filter comes a
pipe L.
The filter has a grating, on the top of which is placed asbestos cloth, then roughly
broken quartz, then finely crushed and washed quartz, with a light grating upon the
top: The filter has a trap N at the side, to lift up with a short sluice going into the
main sluice O, which passes along the building, delivering the ore over amalgamated

page_text: copper plates, which serve to arrest any coarse gold, and the final tailings from these,
pass to the waste heap.
On the side of one of the supports of the machine is an iron shelf, on which is
placed two small drums. One, K, is air tight, and through it passes the pipe D,
having a valve, before and after leaving the tank, as shewn in the drawing. At the
bottom of this tank is a tank for running out liquor, not shewn in the drawing. The.
other drum H is open at the top, and has a stirring arrangement. Near the shelf are:
placed three steam injectors worked by steam from the steam pipe E. The first
injector sucks the air out of machine by the pipe D after the ore & reagents are placed
in the cylinder, and sends it by pipe I into the open air. The second injector 1 draws
the liquor from the previous charge, which is in the vat P, by the pipe G, & delivers.
it into the chlorinator by the pipe C, until the requisite pressure is reached on the
gauge Z. The same injector, by use of a double stop cock, draws through the pipe F
the lione which is placed in the vessel H, and made into a cream by the stirrer, and
injects it likewise into the machine at the end of the operation, it being enabled to do
this by opening the cock on the pipe D between the chlorinator and the vessel K,
whereby the liquor can flow from the chlorinator, allowing room for the injection of
the lime from H. The third injector I draws the liquors or washings from the filter
by the pipe L, and delivers them by the pipe M, which ends in a flexible rubber hose,
so that it can be carried to any of the tanks P, Q, or R, as required.
The strong liquors from the filter are delivered to the vat P, to be rëinjected, for
the economy of the bleaching powder, then the washings from the previous charge
in the vat are run upon the filter by the pipe S, and sent through the injector by
the pipe M, to the vat R; thereafter, water is allowed to run upon the filter by the
pipe T, and this second & weak washing is then sent through the injector by the
pipe M to the vat Q, to be in its turn reused.
Thus, while the strong liquors are kept in the vat P, the strong washings from
each charge accumulate in R, and at the end of the day's operation, the strong liquor
in P is likewise run into R, and the gold precipitated.
When the gold is settled, the liquor is run away into a sluice U, which passes into
a filter of sawdust and charcoal contained in a suitable vessel, which arrests any gold
not completely settled, and thence the liquors pass away. W is a flexible pipe with
a float which keeps it just under the level of the liquor. The bottom of R is concave
in shape, and from the lowest point passes a pipe by which the gold precipitate can
be washed into stoneware jars V, to be subsequently fused.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, 1 declare that what I
claim is :-
1. In the extraction of gold by the wet method, the employment, after chlorination,
of a reagent, which, introduced in proper quantity into the chlorinator, will absorb
the chlorine or other solvent without precipitating the gold, substantially as herein-
before set forth.
2. In the process of gold extraction in which the chlorine, bromine, or iodine have
been absorbed by slaked lime, carbonate of lime, or any other alkali or alkaline earth,
or carbonate of an alkali or alkaline earth, the reuso of the liquors substantially as
herein before described and explained.
3. The apparatus for use in the extraction of gold by the wet method, constructed,
arranged, & operating substantially as herein before shewn & described.
Dated this 20th day of March 1890.
NEWTON & SON,
Agents for the Applicant.