Improvements in and relating to the Extraction of Gold from Refractory and other Ores and in Apparatus Employed therein.
Year: 1888

page_text: Date of Application, 3rd Oct., 1888
Complete Specification Left, 3rd July, 1889-Accepted, 3rd Aug., 1889
PROVISIONAL SPECIFICATION.
Improvements in and relating to the Extraction of Gold from
Refractory and other Ores and in Apparatus Employed therein.
I, JAMES GREENWOOD, of 77, Queen Victoria Street, in the City of London,
Metallurgical Chemist, do hereby declare the nature of this invention to be as
follow's
My invention relates to improvements in what is generally known as the chlorination
method or process of extracting gold from refractory and other ores, and also in
recovering the chlorine used in the process.
In treating auriferous ore according to my invention and forming the gold
contained in such ore into chloride of gold, I proceed as follows:-
The ore having been previously pulverized, and if of a refractory nature also
roasted, is charged into the chlorinator from a hopper placed immediately above, and
which contains the exact weight or quantity required for each charge of ore.
arrangement obviates any weighing or handling of the ore.
This
The said chlorinator is in the form of a cylinder, and is constructed of steel or
wrought iron plates, and lined inside with pure sheet lead. A further lining of teak
or other suitable material is also added, and the outside of the cylinder is well coated
with pitch or tar.
The ore is fed into the chlorinator through a manhole, which is hermetically closed
after each charge of ore therein, and a chlorine solution is then pumped into the
chlorinator through a valve connected therewith, until a pressure of from 80 to 100 lbs.
per square inch is obtained. The chlorine solution I prefer employing is that obtained
by the process described in the Specification of an application for a Patent of even
date with this application.
To treat the ore more effectually with the chlorine solution, I expel the whole of
the air from the chlorinator by means of a small valve which is closed immediately
the air is exhausted therefrom.
The chlorinator is then slowly revolved for a short time until the whole of the gold
is effectually dissolved from the ore and forms chloride of gold.
The ore and solution is then discharged into a suitable filtering vessel placed beneath
the said chlorinator. The filtering vessel is a shallow vat substantially constructed of
oak or other suitable material, the lower part being cone-shaped, and of the same
capacity as the chlorinator already described.
This vat is closed by a cover bolted down, in the centre of which is a hopper shaped
inlet for receiving the ore and solution. A perforated wooden diaphragm covered
with asbestos cloth or other required filtering medium is fixed from 1 to 2 inches
below the top of the said vat, through which the auriferous solution filters and flows
through a filter of ground asbestos into a suitable receiver. The gold chloride is
washed out of the ore by a stream of water which enters the vat at the lowest part
thereof, and percolates upwards through the ore until the same is perfectly free from
any gold in solution. The treated ore is then discharged automatically by means of
the large outlet at the bottom of the filtering vessel.
The gold chloride is now conducted from the above mentioned receiver into the
outer or battery jar of an electrolytic cell constructed as follows:-
I take one or more large battery jars, in which I place a number of carbon
rods, and arrange them in a circle around the jar so as to form a suitable
electrode, which I connect with the negative pole or terminal of a dynamo or other
electrical generator.
Inside each battery jar, I place a porous cell of suitable dimensions in which I also
arrange a number of carbon rods to form a suitable électrode, which I connect with
the positive pole or terminal of the dynamo or other electrical generator.

page_text: The gold solution flows into, and enters the jar named at the bottom, and slowly
circulates upwards, and at the same time a current of electricity is passed through
the cell, which reduces and precipitates the gold from the solution in a perfectly pure
state, and the chlorine liberated at the same time at the electrode in the inner
or porous cell is absorbed by the water circulating. therein and forms a chlorine
solution.
The recovery of the chlorine by this method is an important and distinctive feature
of this process of gold extraction..
The solution may still retain a minute quantity of gold undecomposed after passing
through the electrolytic cell named, and I therefore pass the said solution through a
column of charcoal in which the gold remaining in solution is deposited, and from
which it is obtained by any of the well known methods.
If required, the whole of the water used in the process may be drawn from the
waste vat or tank and be used over again.
Dated the 3rd day of October 1888
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in and relating to the Extraction of Gold from
Refractory and other Ores and in Apparatus Employed therein.
I, JAMES GREENWOOD, of 77ª, Queen Victoria Street, in the city of London,
Metallurgical Chemist, 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 :-
My invention relates to improvements in and connected with what is generally
known as the chlorination method or process of extracting gold from refractory
and other ores, and also in recovering the chlorine used in the process, and
consists of:-
I. An improved process and apparatus for treating auriferous ores with a chlorine
solution, and forming the gold contained therein into chloride of gold.
II. An improved process and apparatus for filtering the gold chloride from the ore,
and automatically discharging the same after treatment.
III. An improved process and apparatus for reducing and precipitating the gold
from the gold chloride by electrolysis and also at the same time recovering the
chlorine contained in the said chloride and forming a chlorine solution therefrom.
In order to enable my invention to be fully understood I will proceed to describe
the same by reference to the accompanying drawing, which represents an elevation
(partly in section) of the arrangement and construction of the apparatus I employ
for carrying out my invention for extracting gold from refractory and other ores.
The receiver is charged with chlorine, which is advantageously and preferably
generated by the process and apparatus described in my Specification No. 14239 of
even date with this Specification, the said apparatus being now shown in the drawing
in connection with the apparatus for extracting the gold from its ores, but no separate
claim is made in this Specification to the generating apparatus, the parts of the same
being herein referred to by the same letters of reference as in my said Specification
No. 14239, videlicet, A is the battery; c¹ the conductor from the electrode in the
large battery jar to the negative pole of the electrical generator; e³ the conductor
from the electrode in the porous cell to the positive pole of the generator; d' is the
reservoir containing a saturated solution of chloride of sodium, which passes to the
battery A through the pipe e, and 9 is the reservoir containing water connected by
.the pipe with the porous cell of the battery.
g
The ore to be treated having been previously pulverized, and if of a refractory
nature, also roasted, is charged into a chlorinator from a hopper placed immediately
above and which is adapted to contain the exact weight or quantity required for each
charge of ore. This arrangement obviates any, weighing or handling of the ore. In

page_text: the drawing i represents the said chlorinator which as usual is in the form of a cylinder
and is constructed of steel or wrought iron plates and lined inside with pure sheet
lead. A further lining of teak or other suitable material is also added and the outside
of the cylinder is well coated with pitch or tar; j represents the hopper above the
chlorinator.
The ore is fed from the hopper j into the chlorinator i through the manbole k
which is then hermetically closed by hand, after each charge of ore is introduced
therein and the valves or cocks and z being opened, chlorine solution (generated
as hereinbefore described) from the receiver will flow through the pipe into
the chlorinator until it is full; the pipe is then disconnected from the chlorinator
and the pipe m of the pump in connected thereto and a small quantity of water from
the cistern m² is pumped into the chlorinator until a pressure of from 80 to 120 lbs.
per square inch is obtained therein.
t
To treat the ore more effectually with the chlorine solution I find it advantageous
to expel the whole of the air from the chlorinator; for this purpose I provide the
chlorinator with a small valve i¹ so that the air contained in the said chlorinator will
pass out as the chlorine solution passes in, the said valve being closed immediately
the air is expelled.
The chlorinator after being disconnected from the pipe m¹ is then slowly revolved
by means of the pulley and strap from an engine (or in any other suitable
manner) until the whole of the gold is effectually dissolved from the ore and, forms
chloride of gold. The time required for treatment of the ore in the chlorinator
varies from about one half hour to two hours, according to the nature of the ore
under treatment. The ore and solution are then discharged into a suitable filtering
vessel p placed beneath the chlorinator. The filtering vessel is a shallow vat P,
substantially constructed of oak or other suitable material, the lower part of which I
make cone-shaped, as shown, and of the same capacity as the chlorinator.
A
This vat is closed by a cover a bolted down; in the centre of the cover is a
hopper-shaped-inlet r for receiving the ore and solution from the chlorinator.
perforated diaphragm s, covered with asbestos cloth, over which is advantageously
placed a layer of other suitable filtering medium, such as ground asbestos is fixed
from 1 to 2 inches below the top of the said vat, through which asbestos cloth and
layer of ground asbestos the auriferous solution filters into a suitable receiver u. The
gold chloride is washed out of the ore by a stream of water from a tank v which
water enters the vat through the pipe at the lowest part thereof as shown and
percolates upwards through the ore until the same is perfectly free from any gold in
solution, which can be conveniently ascertained by drawing off a small sample of the
solution and testing it in the usual manner. A sliding door to in the hottom of the
vat p is then opened and the residue from the treated ore will be discharged
automatically by means of the large outlet thus opened into a truck placed
underneath.
The gold chloride as water descends through passes through the pipe v² into the
receiver u and is afterwards conducted from the receiver u by the pipe e¹ into the
outer or battery jar of the electrolytic cell B, which is similar to the one for
generating chlorine described and illustrated in my above named Specification
No. 14239 of 1888; the inner or porous cell of the battery B is connected by means
of the pipe with the reservoir g containing water which flows into and enters the
said cell d at the bottom part thereof. The gold solution flows into and enters the
jar at the bottom and slowly circulates upwards, and at the same time a current of
electricity is passed through the cell which reduces and precipitates the gold from the
solution, in a perfectly pure state upon the bottom of the jar and is afterwards
removed by hand, the interior of the jar B having been previously removed. The
chlorine which is liberated at the same time at the electrode in the inner or porous
cell d is absorbed by the water circulating therein and forms a chlorine solution which
passes up through the pipe h¹ to the receiver h. This operation being identical with
that described in my said Specification No. 14239 of 1888 for the generation of
chlorine needs no further description.

page_text: I would remark that the water employed for taking up or absorbing the chlorine in
the porous cell is advantageously made slightly alkaline.
The recovery of the chlorine by this method is an important and distinctive feature
of my process of gold extraction.
The electrolysed solution may still retain a minute quantity of gold undecomposed
after passing through the electrolytic cell; I therefore pass the said solution through
a column of charcoal y in which the gold remaining in solution is deposited and from
which it is obtained by any of the well known methods. Taps or cocks z are placed
on all the pipes so as to allow of regulating and shutting off the flow of the liquids
therein as desired.
If required, the water used in the process of treating the gold chloride may be
recovered for reuse by being pumped back into the reservoir.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is-
(1) The process of, and apparatus for treating auriferous ores with chlorine solution
and forming the gold contained therein into chloride of gold, in the manner, substan-
tially as described.
(2) The process of, and apparatus for filtering the chloride from the ore, whereby
the ore is automatically discharged after treatment in the manner described.
(3) The process herein described of reducing and precipitating the gold from the
chloride by electrolysis and also at the same time recovering the chlorine contained
in the said chloride and forming a chlorine solution therefrom, in the manner
described and set forth.
(4) The use of an electric battery such as that herein referred to for separating
gold from its chloride.
(5) The combination of parts forming the improved machinery or apparatus for the
treatment of auriferous ores as hereinbefore described and illustrated in the accom-
panying drawing.
Dated the 3rd day of July 1889
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.