Improvements in or connected with Electrical Apparatus for Extracting Gold and Silver from Cyanide Solutions.
Year: 1895

page_text: Date of Application, 6th Sept., 1895
Complete Specification Left, 26th May, 1896-Accepted, 27th June, 1896
Improvements in or connected with Electrical Apparatus for
Extracting Gold and Silver from Cyanide Solutions.
I, JOHANNES PFLEGER of Kaiserslautern in the Empire of Germany, do hereby
declare the nature of this invention to be as follows:-
This invention relates to apparatus employed in the precipitation obtainment of
gold and silver from cyanide solutions by electricity.
Hitherto it has been usual to obtain the gold and silver from the cyanide
solutions by depositing it on electrodes of thin sheet metal, such as lead for example
but such electrodes require a very large and cumbersome apparatus to get a
practically sufficient area of electrode.
According to my invention I employ an electrode to receive the deposit in
a divided or equivalent form such as shavings, wires, powder or shot or like form
presenting a large surface in contact with the solution a very much smaller
apparatus is required than has hitherto been required and I thus effect great
economy and the separation of the gold and silver from the solution is also
effected more perfectly than hitherto.
When depositing gold or silver electrically only that portion of the solution
which actually comes in contact with the electrode which receives the deposit,
becomes exhausted of its metal. When therefore an electrode is used in the form
of a sheet or plate a large portion of the solution does not come into contact with
the electrode and is therefore not exhausted of its metal but an electrode in the
improved form herein before described acts as a sort of filter or gives such a large
surface in proportion to the quantity of solution that practically the whole of the
solution is brought into contact with the electrode without impeding the action of
the electric current, and thus nearly the whole of the gold and silver becomes
deposited.
The metal in the improved form described may be iron, lead, tin, copper or
other suitable metal. As however iron is but little attacked by the cyanide
solution I prefer to employ iron, ordinary commercial iron or steel answers very
well. I do not limit myself to any one particular construction of an electrode
according to my invention but a convenient way to make it is to form it of a large
number of wires, preferably in the form of woven gauze arranged for instance
vertically and horizontally and at a distance of 16 to of an inch apart the mesh
of the gauze being sufficiently open to allow the proper passage of the electric
current through it, a mesh of 10 to 30 wires per lincar inch is found to answer this
requirement.
The cyanide solution containing gold or silver may enter the electrolytic vessel
for instance at bottom and rise and escape at top and in its passage it passes
through the wire gauze practically every particle of the solution being thus
brought into contact with the electrode so that it is deprived of its metal very
efficiently and completely.
The deposited metal may be removed from the electrode by any known or
suitable means.
1
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.

page_text: Improvements in or connected with Electrical Apparatus for
Extracting Gold and Silver from Cyanide Solutions.
I, JOHANNES PFLEGER, of Kaiserslautern, in the Empire of Germany
Electrolytical and Mechanical Engineer, do hereby declare the nature of my
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 apparatus employed in the precipitation and obtainment
of gold and silver from cyanide solutions by electricity.
Hitherto it has been usual to obtain the gold and silver from the cyanide
solutions by deposition on electrodes of thin sheet metal such as lead for example,
but such electrodes require a very large and cumbersome apparatus to get a
practically sufficient area of electrode.
According to my invention I employ an electrode to receive the deposit in a
divided or equivalent form such as shavings, wires, powder or shot or like form,
presenting a large surface in contact with the solution a very much smaller
apparatus is required than has hitherto been required and thus effect great
economy and the separation of the gold and silver from the solution is also effected
more perfectly than hitherto. When depositing gold or silver electrically only
that portion of the solution which actually comes in contact with the electrode
which receives the deposit becomes exhausted of its metal. When therefore an
electrode is used in the form of a sheet or plate a large portion of the solution does
not come into contact with the electrode and is therefore not exhausted of its metal
but an electrode in the improved form herein before described acts as a sort of
filter or gives such a large surface in proportion to the quantity of solution that
practically the whole of the solution is brought into contact with the electrode
without impeding the action of the electric current, and thus nearly the whole of
the gold and silver becomes deposited.
The metal in the improved form described may be iron, lead tin copper or other
suitable metal. As however iron is but little attacked by the cyanide solution
I prefer to employ iron, ordinary commercial iron or steel answers very well. I do
not limit myself to any one particular construction of an electrode according to my
invention but a convenient way to make it is to form it of a large number of wires,
preferably in the form of woven gauze arranged for instance, vertically and
horizontally and at a distance of to of an inch apart the mesh of the gauze
being sufficiently open to allow the proper passage of the electric current through
it, a mesh of 10 to 30 wires per linear inch is found to answer this requirement.
The cyanide solution containing gold or silver may enter the electrolytic vessel
for instance at bottom and rise and escape at top and in its passage it passes
through the wire ganze practically every particle of the solution being thus brought
into contact with the electrode so that it is deprived of its metal very efficiently
and completely.
The deposited metal may be removed from the electrode by any known or
suitable means.
In the accompanying drawings I bave illustrated an apparatus arranged
according to my invention wherein wire work, or gauze is employed for the
depositing electrode.
It is shewn in transverse section in Figure 1 longitudinal section in Figure 2
and plan in Figure 3.
In the chamber or vessel A, a separate compartment is formed at B by the
insertion of partitions, or diaphragms, and this compartment receives the

page_text: depositing electrode C. of wire-work or gauze, and through this compartment,
thus partitioned off, the solution to be treated is caused to pass or circulate.
Outside the diaphragms bb the vessel A contains a dilute solution of soda (say a
1 to 5 per cent. solution) and in this latter solution zinc plates D and D¹ are placed
and there is thus formed a galvanic cell somewhat like a Daniells' cell. When
this cell is short-circuited that is to say, when the electrode C is connected with
the electrodes D D' by a suitable electrical conductor, such as copper wire, or the
like, an electrical circuit is formed which will rapidly and completely separate all
the precious metal, causing it to be deposited on the electrode C. and the zinc
plates D and D¹ to dissolve in the soda solution.
The bath is preferably divided into a number of compartments (say six as shewn)
by partitions 2 which are open alternately above and below within the space
partitioned off by the diaphragms, so that the solution in its passage through the
portion comprised between the diaphragms b is compelled to rise and descend
alteruately. This course of the solution is indicated by arrows in Figure 2 and in
taking this course, the said solution must necessarily come into very complete and
intimate contact with the wire-work or gauze contained in the compartment B.
In the first compartment the greatest proportion of precious metal will of course
be precipitated.
The following figures will give an idea of the relation of the different quantities
of gold collecting upon the six depositing electrodes assuming the amount of gold,-
settling on the last depositing electrode to be = 1.
Hence it follows that the precious metal has to be removed from the first
depositing electrode more often than from the remaining five depositing electrodes.
The precious metal may be removed from the depositing electrodes in various
ways, for example, it may be detached by means of mercury, the amalgam being
subsequently distilled. Or the wire-work, or gauze, covered with precious metal
can be immersed in a solution, containing from 8 to 10 per cent. of cyanide of
potassium, and facing such wire-work, or gauze is placed a plate of carbon, and by
electrically connecting outside the bath the wire-work, or gauze, and the carbon
plate, the precious metal will very quickly separate from the electrode and dissolve
so that a concentrated solution of the precious metal will be obtained from which
the said precious metal can be extracted in any convenient manner.
If the metal be used in the form of shavings powder or shot or the like it will
be placed and held by any suitable means in the position herein before explained
with regard to the wire gauze.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is.
1. In or for apparatus for precipitating gold and silver from cyanide solutions
thereof by electrolysis the employment of a depositing electrode consisting of
shavings, wire-work or gauze or metal in an equivalently divided form so as to
offer a very extensive surface to the action of the solution substantially as herein-
before explained.
2. In or for apparatus for precipitating gold and silver from cyanide solutions
thereof by electrolysis the employment of a depositing electrode consisting of iron
wire arranged substantially as herein before described.

page_text: 3. An electrolytical apparatus for extracting gold and silver from cyanide
solutions the said apparatus being constructed or arranged substantially as herein-
before described and illustrated by the accompanying drawings.
Dated this 23rd day of May 1896.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.