Improvements in the Electrolytical Treatment of Ores for Facilitating the Extraction and Recovery therefrom of Gold, Silver, or Copper, and in Apparatus therefor.
Year: 1887

page_text: Improvements in the Electrolytical Treatment of Ores for Facilitating
the Extraction and Recovery therefrom of Gold, Silver, or
Copper, and in Apparatus therefor.
I, HENRY LIEPMANN, of 40, Lexham Gardens, Kensington in the County of
Middlesex, Doctor of Philosophy, F.C.S., do hereby declare the nature of this
Invention, to be as follows:
In the treatment of ores containing copper, silver or gold separately or when
present together, or in conjunction with other metals in such ores, it is advisable and
expedient-especially when the extraction of the precious metals is the chief aim-to
subject the mass to a lengthened treatment with chlorine.
By this means and in an enhanced degree when a simultaneous action of the
atmospheric air on the ore under treatment is provided for the necessity of furnacing
or roasting the ore is wholly or partially avoided; and as the chlorine can be easily
obtained from a solution of a soluble chloride by electrolytical means, it becomes of
great importance to so apply it to the mass or body of the ore that it shall be
generated under the most favourable conditions for liberating and dissolving the
metals, which it is desired to obtain.
According to my invention 1 therefore apply chlorine generated by electrolysis
from a solution of a soluble chloride, simultaneously with a free action of atmospheric
air, to large masses of ore for a certain period of time (according to the nature of
the ore) in order to obtain in an efficient manner solutions of the useful or previous
metals contained therein.
In carrying out my method or process, in practice I moisten the finely ground
ore with a solution of a soluble chloride, preferably chloride of sodium (common
salt.) The moistened mass, which is preferably of such consistency that a small
portion when balled together in the hands only just holds together, is placed in a
heap and preferably on slightly slanting boards with a gutter or pipe surrounding
the bottom, or with any equivalent arrangement such as an interposed perforated
false bottom in order to allow the liquor gradually to drain off. The whole mass
may be boarded in at the sides.

page_text: Into this mass I insert, at certain distances, electrodes of carbon of a suitable
hardness and electrical conductivity, such for instance as those electrodes patented
by me on 25th February 1885 No. 3884.
These carbons I couple up together by suitable means and connect with the positive
pole of a dynamo machine or other source of electricity. These carbons form
together the anode of an electrolytical arrangement, as is well understood. I also
place at a certain distance from the carbons a pipe or pipes of unglazed porcelain
or other porous material and place inside of this a conductor of electricity or I may
provide the latter with a porous envelope. The pipe which is preferably closed at
the end is filled with a solution of common salt, or a portion of the ore or some sand
is moistened with common salt and filled into the pipe around the aforesaid conductor.
These conductors are also coupled together, when more than one is used, and are
connected to the negative pole of the source of electricity. This forms the cathode of
an electrolytical arrangement, as is well understood. I furthermore allow by means
of a spray, or pipe, or by placing cloths kept constantly moist with salt water and
placed on the surface of the piled up ore (or by any other suitable means) a gradual
and finely divided stream of common salt solution to flow through and permeate
the mass.
In some instances I may make the mass of ore more conductive by mixing there-
with lumps, pieces or granules of conductive carbon. But it is necessary in every
instance to keep this mass so divided or porous as to admit of access of air. I for that
purpose provide special channels or spaces throughout the mass of the ore by any
suitable means to allow a simultaneous action of the atmospheric air and in some
cases I may even inject air by suitable means throughout the mass.
When now a current of electricity is sent through this arrangement by means of
the generator of electricity an evolution of chlorine takes place from the surface of
the carbons.
The electro-motive force must be great enough to overcome the resistance, but by
suitably arranging the anodes and cathodes this need not be very great. At an
expenditure of very little power currents of electricity may be passed for any required
period of time.
The constant and gradual change of solution removes the products of the chemical
and electrolytical action and supplies fresh quantities of chloride to continue the
decomposition and solution. The liquors flowing off and collecting at the bottom are
tested from time to time for any valuable constituent.
It is sometimes advisable to increase the stream of solution flowing through the
mass and sometimes to interrupt it for a certain period. For this purpose I provide
suitable means of regulation. The effluent liquors may be pumped back to a suitable
tank or reservoir and be allowed to flow through several times, either alone or mixed
with fresh common salt solution.
The various portions containing the metals in solution are collected either
separately or mixed and the metallic constituents thrown down by means of well
known chemical processes.
151 1
1+ T
1007

page_text: Improvements in the Electrolytical Treatment of Ores for Facilitating
the Extraction and Recovery therefrom of Gold, Silver, or
Copper, and in Apparatus therefor.
I, HENRY LIEPMANN of 40 Lexham Gardens Kensington in the County of Middlesex
Doctor of Philosophy, F.C.S. do hereby declare the nature of the said invention and
in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
In the treatment of ores containing copper silver or gold separately
or when
present together or in conjunction with other metals or metalloids in such ores, it is
advisable and expedient-especially when the extraction of the precious metals is the
chief aim to subject the mass to a lengthened treatment with chlorine.
By this means and in many instances in an enhanced degree, when a simultaneous
action of the atmospheric air on the ore under treatment is provided for, the necessity
of furnacing or roasting the ore is wholly or partially avoided; and as the chlorine
can be easily obtained from a solution of a soluble chloride by electrolytical means, it
becomes of great importance to so apply it to the mass or body of the ore that it shall
be generated under the most favourable conditions for liberating and dissolving the
metals, which it is desired to obtain.
According to my invention I therefore apply chlorine generated by electrolysis
from a solution of a soluble chloride or chlorides simultaneously with a free action of
atmospheric air to large masses of ore for a certain period of time (according to the
nature of the ore) in order to obtain in an efficient manner solutions of the useful or
precious metals contained therein.
In order that my method of carrying out the process may be readily understood, I
will now give a description of the entire operation as applied to one particular ore
It will however be
and indicate the apparatus which I find advantageous to use.
readily understood that in the treatment of other ores whatever their composition and
however great their refractoriness there will be modifications as regards the time
required for the treatment and strength of solutions.
The ore under treatment is say a "Pyrites" containing gold which is not in the
free state showing by assay 1 to 3 ounces of gold to the ton.
The quantity of iron or other pyrites in the mass may as an example be assumed to
be from 20 to 30 per cent of the whole mass. This material which preferably previous
to the treatment has been reduced to such a fineness as to pass through a sieve of
about 40 to 80 meshes to the linear inch though I can also treat coarser particles is
placed on a floor and is mixed with one of the following chlorides, sodiuin chloride

page_text: alone, or mixed with calcium chloride, or Aluminium chloride or iron chloride. A
suitable proportion is about 1 to 5 pounds of chloride to each hundred weight of ore;
sodium chloride and calcium chloride, being the cheapest and most readily obtainable,
I prefer to use, (though very quick results are obtained with sodium chloride mixed
with aluminium chloride). The chloride is well incorporated with the mass and being
hygroscopic especially the calcium chloride is allowed to diliquesce by the absorption
of moisture from the air. In very dry countries a suitable moistening of the mass
may be provided for. The proper consistency is ascertained by taking a sample and
forming it into a ball in the hands. It should then when well squeezed just hold
together. The reason for the admixture of these chlorides is this that, in the presence
of free chlorine as will be described they probably form unstable higher compounds
which readily giving off their chlorine to surrounding bodies enable the chlorine to
act in a more energetic way than was hitherto possible on the minutest individual
portion of the ore mass. The electrolytical generation of the chlorine may then be
carried out in one of the following ways and, for instance, by apparatus shewn in
Figure 1. in sectional elevation and in plan Figure 2.
The mass prepared as described is placed in heaps of 2 or 3 hundredweights each
(but might advantageously be much larger) on slightly slanting boards A with a
gutter or pipe B at the bottom or with any equivalent arrangement such as an inter-
posed perforated false bottom in order to allow the liquors gradually to drain off and
is in most cases also boarded in at the sides as shewn at C.
A suitable depth for the heap in connection with this apparatus would be about
two feet.
Into this mass I insert at certain distances electrodes of carbon D and E or such
for instance as those electrodes patented by me on. 25th February 1884 No. 3884 and
as it is of advantage that the relative position of each of the anode and cathode
carbons or carbon bundles to one another be nearly as possible alike and also that the
anode and cathode have approximately the same surface I arrange them as shewn in
the drawing. The carbons should be of a suitable hardness and conductivity and are
held in a wood frame F and connected to their respective terminals by wires which
are well insulated so as to protect them from the chlorine vapours generated when a
current of electricity is sent through this arrangement from a dynamo machine or
other source of electricity. This current of electricity must have the necessary
electromotive force to overcome the resistance. A current of 12 to 15 Ampères will
produce a liberal generation of chlorine gas. It is found of advantage in practice to
arrange in this manner a dozen or more heaps of ore. The current having for a
couple of hours been passed through one or a series of such heaps according to the
strength of dynamo available the heap or heaps are allowed to rest, so that the actions
of the chlorine on the mass may take effect. After a period of repose it is advantageous
to reverse the path of the current. These intervals of repose and reversals are repeated
some three or four times. There will be no difficulty in this as the acting surface of
the two sets of carbons was equal. The reversing may be done by means of a threeway
switch such as are used for electric lighting purposes.
After each rest, or at intervals while the current is passing as just described during
which time the liquors are gradually draining off by the gutter B. I allow by means
of a spray or pipe or by placing cloths kept constantly moist with salt water to which
may be added some chloride of calcium solution and placed on the top of the piled up
ore or by any other suitable means a gradual and finely divided stream of such salt
solution to flow through or permeate the mass. Or I may employ more frequently a
spray or shower of same. The ore mass being thus prepared again with a fresh
quantity of electrolyte the same course of operation as described is repeated four or
five times till the effluent liquors contain no more valuable metal. The liquors having
been deprived of their contents of valuable metal by means of precipitation by proto-
sulphate of iron or otherwise are pumped back to a suitable tank and may be used
over and over again for the percolating process above described.
It is necessary in all cases or modes of carrying out my invention to keep the mass

page_text: 30 divided or porous as to admit of access of air to all parts. The carbons D and E
in Figures 1 and 2 afford to a certain extent means for creating special channels or
spaces throughout the mass of the ore to allow a simultaneous action of the
atmospheric air. But I may in addition for this purpose and for making the mass of
ore more conductive mix therewith lumps pieces or granules of conductive carbon.
Or I may insert into the mass rods of carbon of a tubular or cruciform angular or
other suitable channelled form for promoting the penetration of the air into the interior
of the mass.
Or the anode and cathode carbons D and E or the former only may be
of such tubular cruciform or other channelled form for the purpose.
In some cases and notably where I treat the ore in closed up vessels or chambers I
inject or forcibly draw in air by suitable means throughout the mass. In the
arrangement just described I may also inject air and for this purpose place a coil or nest
of perforated pipe in the lower part of the ore heap and inject air into such pipes
thus permeating the ore with air. Figure 3 is a sectional elevation illustrative of
the mode of treating ore in closed up chambers or vessels air being injected. The
heap of ore is placed on a floor A. In the mass I insert one or more tanks G of the
following construction. They are made preferably of glazed earthenware and by a
diaphragm H parted in two compartments one for containing the positive carbon
electrode D and the other the negative carbon electrode E. The carbons may be
single rods as shown or carbon tubes or handles as described in my patent
specification 3884 of 1884. These electrodes are coupled to the poles of the dynamo
or other generator in the usual manner. The whole apparatus is enclosed in an
airtight chamber or box C with removable cover. The compartments being charged
with a solution of common salt and a current sent through chlorine gas is evolved at
the anode and penetrates the enclosed mass of ore. The liquors run off the sloping
floor A and escape by the gutter B and thence to a suitable precipitating tank. Air is
forced in by the pipe. I which terminates in a coil or nest of perforated piping within
the chamber C. Or the air instead of being forced in may be forcibly drawn in by a
pump or other suction appliance. A perforated pipe is also provided for occasionally
or continuously introducing a spray of a solution of common salt to which may be
added some chloride of calcium. Or the cover may be removed when the mass is to
be thus sprinkled. I observe in this method the same stages of repose as in the one
first described.
In the sectional elevation figure I have shown another arrangement of apparatus
where G is an earthenware cell with porous diaphragm H forming two compartments
the upper one for the carbon anode 1 and the lower one for the carbon cathode E.
The chlorine gas evolved at the former is by a descending pipe K connected to the
air injecting pipe I the current of which serves to induce the gas the combined stream
being forced into the space above the mass of the ore and thus permeating it. N is a
pipe from a tank O containing a solution of chloride of sodium and of calcium, this
pipe terminates in a perforated coil or nest of piping for sprinkling the mass of ore.
Lis a pipe for supplying at a slow rate salt solution from a tank M to the lower
compartment of the cell G, and P is an overflow pipe therefrom to a receptacle Q.
The pipes are furnished with cocks or valves for regulation. R is a pipe from the
highest point in the lower compartiment of the tank G for the escape of hydrogen gas
accumulating there by reason of the slanting position of the partition H.
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
First The process for treating powdered auriferous and other ores by means of
chlorine gas which is produced by electrolysing a suitable chloride solution mixed
with the ore, air being simultaneously admitted thereto all substantially in the manner
described.
Second-In the process for treating powdered auriferous and other ore by means
of chlorine gas which is produced by electrolysing a suitable chloride solution mixed

page_text: with the ore, the application of air under pressure or vacuum such air being forced or
drawn into the ore substantially in the manner described.
Third The combination of parts forming apparatus for treating powdered
auriferous and other ores for the purpose of extracting the valuable metals therefrom
substantially as described and shown."
HENRY
LIEPMANN.
By Jensen & Son,
77, Chancery Lane, London, W.C.,
Patent Agents. .