Improvements in the Extraction of Copper and Zinc from their Ores, as also of the Precious Metals contained therein by Electrolysis, and Apparatus therefor.
Year: 1889

page_text: Date of Application, 27th Feb., 1889
Complete Specification Left, 27th Nov., 1889-Accepted, 18th Jan., 1890
PROVISIONAL SPECIFICATION.
[Communicated from abroad by the Firm of SIEMENS & HALSKE, of No. 94, Mark-
grafen Strasse, Berlin, in the Empire of Germany, Electrical Engineers.]
Improvements in the Extraction of Copper and Zinc from their Ores,
as also of the Precious Metals contained therein by Electrolysis,
and Apparatus therefor.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane,
in the County of Middlesex, Consulting Engineer and Patent Agent, do hereby
declare the nature of this invention to be as follows:-
According to previously patented processes for the electrolytic extraction of
copper or zinc from their ores, the electrolyte consisting of a solution of copper
sulphate and ferrous sulphate is led through cells which are divided by con-
ducting diaphragms into separate cathode and anode compartments, this being
effected in such a manner that the liquid is first made to flow consecutively through
all the cathode compartments (whereby a large proportion of the copper sulphate
is decomposed by the current, the copper being deposited on the cathode plates)
and then consecutively through all the anode compartments whereby the ferrous
oxide is oxidized into ferric oxide at the insoluble anode surfaces.
The liquid deprived of its copper and now containing ferric instead of ferrous
sulphate, is then again mixed with powdered roasted or unroasted ores, and can
then be again used for dissolving copper from the sulphurated ores, with forma-
tion of copper sulphate and simultaneous reconversion of the ferric sulphate into
ferrous sulphate.
The present invention relates to improvements both in the arrangements for
dissolving the copper or zinc from the powdered ores, as also in the decomposing
cells whereby the interdependent chemical and electrolytic processes are accele-
rated and rendered more certain; and it also relates to the application of the said
processes and of the apparatus employed therein, to the extraction of the precious
inetals contained in the ores treated.
The solution of the metal by means of the decopperized oxidized liquid was here-
tofore effected either in filtering vessels that were filled with the powdered ore and
through which the liquid containing ferric sulphate was made to pass repeatedly,
or in reservoirs or vats with stirring apparatus or in rotating drums in which the
liquid together with the powdered ore was kept in motion for a lengthened period.
In place of these inconvenient arrangements which do not operate continuously,
there are employed according to this invention narrow and shallow but long
channels or troughs of wood or other suitable material which are provided along
their entire length with two revolving shafts or rollers having radial arms or
vanes which are made to rotate in contrary directions so as to put the whole body
of liquid in the channel in rotatory motion in a transverse direction. The pow-
dered ore introduced together with the liquid is thus kept suspended without being
thereby moved in the longitudinal direction, such longitudinal motion being only
effected by the continuous introduction of liquid at one end of the channel and a
corresponding discharge at the other end, so that the duration of the action of the
oxidised lye upon the ore can be regulated at will by the regulation of the supply
of liquid.
As, for the perfect solution of the metal, a heating of the liquid is sometimes
required, this can be effected by means of one or more copper or lead pipes heated
by steam or other hot fluid which extend through the whole or part of the channel.
The said channel can either be straight, or, for economising space, it may be
arranged in zigzag form; if made of wood it may be covered externally with lead.
The shafts or rollers with radial arms or vanes, two of which are arranged parallel

page_text: in each straight length of the zigzag channel, receive rotary motion in contrary
directions (turning towards cach other) by means of pulleys on overhead shafts
and crossed waterproof bands or cords. A copper steam pipe of corresponding
zigzag form passes centrally down the channel.
The shafts or. rollers being situated at the bottom of the channel and having a
layer of liquid of a certain depth above them, the lower part of such liquid has a
rapid rotary motion imparted to it without disturbing the liquid at the surface,
so that no splashing takes place. If the powdered ore is reduced sufficiently in
size, it will by, this meanst be maintained, entirely suspended even when it has a
specific gravity four or five times that of the liquid.
If the said apparatus is to be employed for copper extraction by the so called
sulphate process, the steam pipe may be of lead as this metal is appreciably
attacked neither by sulphate of copper nor by sulphates of iron. The process of
the solution of the copper from the powdered ore is then effected in such a manner,
that on the discharge from the end of the trough of the lye that keeps the ore in
suspension, the whole of the ferric oxide of the liquid will have become reduced
to ferric oxide by the solution of copper from the ore, which will thus have become
almost entirely deprived of copper. The regenerated solution separated from such
ore by filtration or settling is then introduced into the decomposing cells in which
the copper is mostly separated in metallic form by means of the electric current,
the ferrous oxide salt formed in the dissolving trough being reconverted into ferric
oxide salt which is then again led to the dissolving trough.
If the chlorine process is employed in place of the sulphate process, the steam
pipe will have to be maile of burnt clay or similar material that is not acted upon,
instead of lead.
If the powdered ore' to be acted upon contains gold or silver, the lead heating
pipe is replaced by a cylinder of copper the lower side of which is made to di
along, its whole length in mercury contained in the lower part of the trough or.
channel: The surface of the cylinder is well' amalgamated and it receives a slow
rotary motion during the whole time of the operation. If the ore contains free
gold, the current of liquid passing continuously downward between the rollers,
in impinging upon the amalgamated surface of the copper cylinder, causes this
to take up the particles of goid and silver, and, in revolving, to carry them into
the mercury below: A's the amalgamated surface of the cylinder is renewed' and
freed from oxide every time it dips into the mercury, and as by the rapid rotation
of the liquid all particles thereof are brought in contact with the cylinder a very
great number of times, the latter will take up the whole of the free particles of
gold and silver contained in the charge and will deliver it into the mercury.
In the ore contains precious metals so combined as not be directly taken up by
mercury, there is added to the liquid a salt which will dissolve the precious metals
from such finely divided' ores, such as potassium cyanide and the like, 'and' there
is, introduced between the mercury at the bottom of the trough and' the revolving
cylinder in conducting contact therewith, on the one hand, and a carbon or iron
plate serving as anode, suitably placed in the trough, on the other hand, a gal-
vanic battery or dynamo machine..
By means of the continuously circulating galvanic current thus produced, the
dissolved precious metal will be deposited upon the surface' of the amalgamated
cylinder which acts as a cathode and which gives it up to the mercury. The pro-
cess is also in this case so regulated, that the finely divided ore is always kept
suspended in the liquid- and that on being discharged from the trough it shall
have given up all it's precious metal:
The electrolytic decomposing cells heretofore employed, which are divided' by
a diaphragm into a positive and negative compartment, are subject to the well
known disadvantages attendant on the use' of such diaphragms in' electrolytic pro
cesses. The diaphragms either offer too great a resistance to conduction, or they 5
are not sufficiently durable, expanding and permitting the passage of liquid by
diffusion or owing to their not being watertiglit!

page_text: According to the present invention such cells are constructed as follows:--A
shallow receptacle of wood, covered externally with lead or of other suitable
material, is provided with a perforated false bottom on which is laid an anode
which may either consist of suitably connected plates of retort carbon, or of per-
forated lead plates, covered with retort carbon in small pieces, or of a deeply cor-
rugated lead plate, with holes for the discharge of liquid. Over the horizontal
anode thus formed, which is provided with insulated conductors, is placed a filter-
ing layer with the object of preventing currents in the liquid in contact with the
anode. This filter may be of felt or any other suitable organic or inorganic material.
As cathode serve the surfaces of a number of horizontal cylinders situated above
the said filter bed which are entirely covered by the electrolyte and have a con-
tinuous slow rotary motion imparted to them from an overhead shaft by means of
waterproof bands.
These cylinders can consist of a wooden core coated with wax, cement, or the
like, on which is laid conducting covering to which the current is led from the
copper trunnions of the cylinders by suitable conductors.
The regenerated electrolyte consisting of solution of copper sulphate and ferrous
sulphate is introduced in continuous finely divided streams into the liquid covering
the cylinders.
The rotation of the cylinders effects the continuous mixture of the whole liquid
until it reaches the filter bed covering the anode.
As exactly the same quantity of liquid is discharged by a pipe from the space
below the false bottom as is introduced at top, a continuous slow current of the
electrolyte will take place through the filter to the anode.
At this latter the ferrous oxide of the ferrous sulphate is again oxidised to ferric
oxide by the inerated oxygen, whereby the oxidized parts will fall to the bottom
owing to the increased specific gravity, and are first led away, so that with a proper
regulation of the supply, the strength of current, and the percentage of copper and
iron in the solution, the result of the process will be that the electrolyte will lose
about two thirds of its copper in the upper part of the cell while in the anode
compartment the entire ferrous sulphate is converted into ferric sulphate.
This latter, as it flows off, is led continuously back to the above described trough
apparatus with stirrers, with addition of the necessary powdered ore, and after
taking up the copper from the latter, it then passes back to the decomposing cells
again, and so on continuously.
Dated this 27th day of February 1889.
ABEL & IMRAY,
Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements in the Extraction of Copper and Zinc from their Ores,
as also of the Precious Metals contained therein, by Electrolysis,
and Apparatus therefor.
I, CHARLES DENTON ABEL of No. 28 Southampton Buildings, Chancery Lane,
in the County of London, Consulting Engineer and Patent Agent, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement: —
According to previously patented processes for the electrolytic extraction of
copper or zinc from their ores, the electrolyte consisting of a solution of copper
sulphate, and ferrous sulphate is led through cells which are divided by con-
ducting diaphragms into separate cathode and anode compartments, this being
effected in such a manner that the liquid is first made to flow consecutively through
all the cathode compartments (whereby a large proportion of the copper sulphate
is decomposed by the current, the copper being deposited on the cathode plates)
and then consecutively through all the anode compartments, whereby the ferrous
oxide is oxidized into ferric oxide at the insoluble anode surfaces. .

page_text: The liquid deprived of its copper and now containing ferric instead of ferrous
sulphate is then again mixed with powdered roasted or unroasted ores, and can
then be again used for dissolving copper from the sulphurated ores, with forma-
tion of copper sulphate and simultaneous reconversion of the ferric sulphate into
ferrous sulphate.
The present invention relates to improvements both in the arrangements for
dissolving the copper or zinc from the powdered ores, as also in the decomposing
cells, whereby the interdependent chemical and electrolytic processes are accele-
rated and rendered more certain; and it also relates to the application of the said
processes and of the apparatus employed therein, to the extraction of the precious
metals contained in the ores treated.
The solution of the metal by means of the decopperized oxidized liquid was here-
tofore effected either in filtering vessels that were filled with the powdered ore and
through which the liquid containin ferric sulphate was made to pass repeatedly,
or in reservoirs or vats with stirring apparatus, or in rotating drums in which the
liquid, together with the powdered ore, was kept in motion for a lengthened period.
In place of these inconvenient arrangements which do not operate continuously,
there are employed, according to this invention, narrow and long channels or
troughs of wood or other suitable material which are provided along their entire
length with two revolving shafts or rollers having radial arms or blades which are
made to rotate in contrary directions so as to put the whole body of liquid in the
channel in rotatory motion in a transverse direction. The powdered ore introduced
together with the liquid is thus kept suspended without being thereby moved in
the longitudinal direction, such longitudinal motion being only effceted by the
continuous introduction of liquid at one end of the channel and a corresponding
discharge at the other end, so that the duration of the action of the oxidised lye
upon the ore can be regulated at will by the regulation of the supply of liquid.
As, for the perfect solution of the metal, a heating of the liquid is sometimes
required, this can be effected by means of one or more copper or lead pipes heated
by steam or other hot fluid which extend through the whole or part of the channel.
On the accompanying drawings Fig. 1 represents the cross section of such a
channel or trough shapped apparatus for extracting ore. The sides T T can be of
wood, made perfectly tight by an outside casing of lead, or they may consist of
concrete or stone. A A are the shafts carrying blades or paddles S S, and
rotated in opposite directions by means of rubber belting or other suitable mechani-
cal connections.
Dis the heating pipe by which the temperature of the solution can be raised to
any desirable point. Fig. 2 represents the plan of the apparatus to a smaller scale
showing the channel or channels arranged in a zigzag line in order to save space.
It will be easily understood that owing to the depth of liquid in the channels the
. lower part of the solution can be kept in a quick whirling motion, whereas its
surface remains comparatively quiet, and all splashing is thus avoided. The ore
sufficiently pulverised is thus kept completely suspended in the liquid, even if its
specific weight be four or five times greater than that of the solution."
Furthermore it will be seen that the rotating shafts and paddles do not in any
way propel the liquid in a direction parallel to the axis of the channel and that the
flow of the solution together with the suspended pulverised ore from one end M
to the other end N of the channel can only be effected by the amount of solution
introduced at one end and allowed to flow off at the other end of the channel.
As the suspended ore follows the longitudinal motion of the liquid in the channel
completely it will depend entirely upon the extent of the supply of liquid at the
one end and the discharge thereof at the other end as to the length of time which
the powdered ore is subjected to the dissolving action of the liquid.
When this apparatus is used for the extraction of copper by means of the so
called "
sulphate" process, the heating pipes D, can be made of lead, as this
metal is not materially affected by a solution containing copper sulphate, ferric
or ferrous sulphates and sulphuric acid. In this process the solution entering the

page_text: channel contains ferric sulphate and takes up nearly all the copper of the pul-
verised ore on its passage through the whole length of the channel, thereby con-
verting its ferrie sulphate into ferrous sulphate. On leaving the channel, the solu-
tion is finally separated from the ore by deposition or filtration and is thus ready
to be again passed through the electrolytic decomposing cells.
If the chlorine process is employed in place of the sulphate process, the steam
pipe will have to be made of earthenware or other suitable material that is not
acted upon by the chloride lye.
If the pulverised ore to be treated consists of minerals containing gold or silver,
the heating pipe must be replaced by a copper cylinder B as shewn in Fig. 3 which
by means of suitable mechanical arrangements such as that shewn is kept in con-
tinual rotation. This cylinder is so arranged that throughout its length its lower
part dips into a recess of the channel T filled with mercury, whereby its surface is
continuously amalgamated. As it is also placed just in the middle below the two
rotating shafts A A carrying sweeps or paddles S S, a continual stream of the
liquid and the pulverised ore suspended therein is made to impinge upon it. lu
case the pulverised ore contains free gold or silver, the particles of gold or silver
coming in contact with the amalgamated surface of the cylinder are taken up by
it and carried down into the mercury bath. Through the quick continual motion
of the liquid all its parts are exposed a great many times to the absorbing effect
of the amalgamated surface of the cylinder, and all free particles of gold or lvér
are necessarily taken up by it, and transferred to the mercury bath below, where,
at the same time, the amalgamation of the cylinder surface is renewed by each
rotation.
If the ore contains gold or silver in a state not directly affected by the contact
with mercury, a salt, such as potassium cyanide &c., capable of dissolving precious
metals, must be added to the liquid, and an electrical current from a galvanic
battery or a dynamo machine must be used. For this purpose an anode of carbon
or of another suitable substance must be placed conveniently in the channel and
electrically connected with the positive pole of a battery or dynamo, the rotating
cylinder B being made to serve as a cathode which can be easily connected with
the negative pole by means of the mercury bath.
A continuous galvanic current can now be applied for precipitating the precious
metal, already dissolved in a solution of cyanide of potassium or other suitable
dissolving substance, at the surface of the upper part of the rotating cylinder B,
whence it is transferred into the mercury bath below. In this process the fine
pulverised ore is also kept suspended in the solution by the rapid rotating motion
of the latter, and the flow of the liquid along the channel can be regulated in
such a manner that only liquid deprived of its contents of gold or silver, leaves
the apparatus.
It will be easily perceived that this apparatus is capable of somewhat extensive
application; it can be used, firstly, for precipitating free gold and silver from the
ore by amalgamation alone; secondly, for extracting the free gold and silver from
the ore by amalgamation, and the combined metal by using a salt capable of dis-
solving precious metals without employing an electric current, the precipitation
of the dissolved metals being effected in separate electrolytic apparatus and,
thirdly for precipitating and amalgamating gold and silver from the ore or
from an already prepared solution by means of an electric current.
In the arrangements shewn at Figs. 1, 2 and 3, the rotary motion of the paddles
SS is effected by an overhead shaft B through caoutchouc belts and pulleys within
the channels; Figs. 4 and 5 shew respectively a part cross section and sectional
plan of a modification in which the shafts pass through the walls of the channels
an carry external pullies by which they are driven.
The chambers are in this case made of masonry with an internal lining of lead.
The paddles A. A are made of hard lead with a central iron shaft of rectangular
section; DD are lead pipes for heating the liquid. For carrying the shafts
through the walls of the passages, these are formed with gaps into which are built

page_text: frames E of hard lead, with tapering sides, as shewn, and into these are accurately
fitted correspondingly tapered hard-lead castings F, which are held down by levers
G hinged to the masonry at one end and tied down by screws at the other. On
removing the levers the castings can be drawn out vertically by means of the
eyes F. The castings are formed with long tubular necks F2 forming stuffing
boxes through which pass the shafts of A, a water tight joint being insured by a
packing composed of caoutchouc discs and asbestos lagging. The charge to be
treated consisting of an intimate mixture of finely powdered ore and liquid is
introduced at a and is caused to flow through all the compartments of the apparatus
in the direction of the arrows at such a velocity that on flowing off at the dis-
charge end of the last compartment the lye no longer contains oxide of iron, and
is consequently regenerated, while the ore has the metal only partially extracted
from it. This regenerated lye is then separated from the ore and the latter is
mixed with lye strongly charged with oxide of iron, and is then passed through
another apparatus similar to that above described. After the mixture of lye and
ore has passed through this second apparatus, the metal must have been com-
pletely extracted from the ore, while the lye still contains oxide of iron, and is
consequently partially regenerated.
After separating the ore from the lye, the latter is mixed with a fresh quantity
of ore, and this mixture is then fed into the first described apparatus, from which
the lye passes in a perfectly regenerated state.
By the above described mode of proceeding a perfectly continuous separating
process is obtained.
The speed of the padale shafts A should be as great as possible (about 100 revo-
lutions per minute) in order that the ore and lye may be maintained in intimate
admixture, so that the ore shall not collect between and over the lead heating pipes.
The stuffing boxes of the shafts must be kept well lubricated. The number of
compartments of each apparatus will depend upon the quantity of ore to be
operated upon at one time.
The electrolytic cells hitherto used for the decomposition process, divided by
diaphragms into positive and negative compartments are subject to the well known
disadvantages attendant on the use of all such separating diaphragms in electro-
lytic operations. Either the resistance of the diaphragms to the electric current is
too great; or, if it has a suitable value, the diaphragms are of no durability, and
soon allow the mixing of the liquids, which they ought to keep separated, some-
times by diffusion and sometimes through direct leaks. The decomposition cells
forming the subject of the present invention show none of these faults. I will
proceed to describe them with reference to Figs. 6, 7, 8, 9, 10 and 11 of the draw-
ings in which Fig. 6 shows a cross section of one arrangement, Fig. 7 a cross sec-
tion of a somewhat modified form and Fig. 8 a plan partly in section. Figs. 9, 10
and 11 shew respectively a cross section, a part longitudinal section and a part
plan of another construction. The vessel H Figs. 6, 7 and 8 made of wood and
covered on the outside with a casing of lead, or constructed of any other suitable
material, is provided with a perforated second bottom I over which the anode K
is placed. The latter may consist of pieces or plates of retort-carbon conveniently
shaped and in electric connection with each other, or of perforated lead plates
covered with small pieces of retort-carbon as at Fig. 7, or else of lead plates with
rather deep corrugations, likewise perforated to allow the liquid to pass through
as at Fig. 6. Over the horizontal anode just described a filtering layer L is spread,
forming the only separation between the lower anode, compartment, and the upper,
cathode, compartment, and preventing the liquid surrounding the anode from
taking part in the motion of the liquid surrounding the cathode. The latter con-
sists of a number of cylindrical or prismatic bodies M M which are located in the
upper part of the vessel resting on the bearings N N and completely immersed in
the electrolyte. By means of suitable mechanical arrangements these cylinders can
be kept in slow and continual rotating motion. They can be made of wood with
a coating of wax or of similar material and with an outer coating capable of con-
ducting the galvanic current which must be conducted to the cylinders through the

page_text: gudgeons of the cylinders or more directly by means of sliding pieces or contact
brushes.
The regenerated solution to be subjected to electrolysis coming from the extract-
ing channels above described and containing sulphate of copper, ferrous sulphate
and free sulphuric acid, enters in a continual stream through the pipe O into the
upper or cathode partition of the cell. The liquid, after having been freed of the
greater part of its copper, which is precipitated at the rotating cathodes M passes
slowly and continuously through the filter L into the anode compartment. Here,
on the anodes, the solution gradually absorbs oxygen and, becoming heavier,
thereby sinks gradually down to the bottom of the cell from whence it is drawn off
by means of the pipe U in the same proportion as the inflow near the top of the cell.
If the influx of the regenerated solution, the galvanic current and the discharge of
the reoxidized solution are properly adjusted, the result of this process is, that the
solution to be subjected electrolysis loses about rds of its percentage of copper in
the upper compartment of the cell whereas in the lower compartment (below the
filter) it converts its ferrous sulphate into ferric sulphate, being thereby rendered
fit for extracting copper ore anew.
In the construction shown at Figures 9, 10 and 11 the vessel H is formed of
masonry with an internal lining of sheet lead. The cathode M in this case con-
sists of a cylinder of large diameter covered with copper and' running with trun-
nions of hard wood in bearings of hard lead.
On the cylinder bear copper contact springs P for conveying the current thereto
from a copper conductor P running along the top of the vessel and to which the
springs are secured. Surrounding the cylinder M is a diaphragm Q of gray
canvas attached to a wood framing and serving to separate the lye surrounding
the cylinder, which is free of oxide of iron, from the lye at the anode, which
contains oxide of iron. Surrounding the diaphragm on the outer side is the
anode K, consisting of a series of troughs placed end to end, formed of cylindrical
bars of carbon, which are secured together at their ends by a hoop of lead cast
round the same, so as to maintain them in conducting connection.
The lead hoops, which are coated with paraffin, are separated from the lead
coating of the vessel by strips of wood; they have soldered to them strips of lead
which are connected to the copper positive conductors R of the electric circuit*.
situated on the walls of the vessels.
The regenerated lye is fed in at the one end through a lead pipe S, and after
giving up its copper at the cathode M, the lye passes to the anode K where the
ferrous oxide is converted into ferric oxide, after which it is led off through a pipe
at the other end.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what I
claim is:
i. Effecting the solution of the metals from their ores by causing the same to
pass in a pulverised condition together with a suitable solvent liquid along a trough
or channel in which the mixture is agitated in a transverse direction by revolving
stirring apparatus so as to keep the ore suspended in the liquid during the whole
of its travel, such travel being caused solely by the inflow of the mixture at the
one end and a corresponding outflow at the other end substantially as herein
described.
2. In apparatus for extracting metals from their ores, the use for effecting the
solution of the metal from the pulverised ore of channels or troughs containing
stirring blades or paddles revolving in a transverse direction by means of which
the ore is kept suspended in the liquid so as to flow together with the same slowly
through the whole length of the channel such flow being produced solely by the
inflow at the one end and the outflow at the other end substantially as herein
described with reference to Figures 1 to 5 of the drawings.
3. In combination with extracting apparatus such as is referred to in the pre-

page_text: ceding claim, the use of heating pipes passing along the channels or troughs for
maintaining the liquid in a heated condition.
4. In apparatus for separating metals by electrolysis, the combination of a
cathode consisting of a revolving cylinder or cylinders with an anode consisting of
retort carbon or of lead plates, either arranged flat and near the bottom of the
electrolytic vessel, or made of trough shape so as to more or less surround the
cathode cylinder, the cathode being separated from the anode by a suitable filtering
medium, substantially as herein described with reference to Figures 6 to 11 of
the drawings.
5. In apparatus for separating metals from their ores, the use of separating
channels or troughs containing revolving stirring blades and a revolving amal-
gamated cylinder dipping at bottom into a mercury, bath for taking up the free
gold and silver of the pulverised ore passing through the channel and transferring
it to the mercury bath at bottom, substantially as described with reference to
Figure 3 of the drawings.
6. In apparatus for separating metals directly from their ores the use of separat-
ing channels or troughs containing revolving stirring blades and a revolving amal-
gamated cylinder dipping at bottom into a mercury bath, such cylinder being
included in an electrical circuit so as to act as cathode for both taking up the free
gold and silver of the pulverised ore passing through the channel, and for the
electrolytic deposit thereon of the metals dissolved by solvents such as potassium
cyanide mixed with the ore, substantially as herein described.
Dated this 27th day of November 1889.