Process and Apparatus for the Extraction of Gold and Silver from their Ores, and from other Auriferous and Argentiferous Substances.
Year: 1895

page_text: Date of Application, 28th Sept., 1895-Accepted, 4th Jan., 1896
COMPLETE SPECIFICATION.
Process and Apparatus for the Extraction of Gold and Silver from
their Ores, and from other Auriferous and Argentiferous
Substances.
1, HENRI AUGUSTE DE NEUFVILLE of 21 Boulevard Poissonnière Paris. in
the French Republic Banker 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:-
This invention has for object a novel process and improved apparatus for the
extraction of gold' and silver from their ores or from other substances containing
those metals.
The process hereinafter described in detail may be carried into practice by the
aid of electrolysis preferably by employing one or other of the apparatus shewn on
the accompanying drawings the first apparatus represented in Figures 1, 2, 3, 4, 5
and 6, being more particularly adapted to the treatment of substances' previously
reduced to a fine powder, and the other or automatic apparatus represented in
Figures 7, 8, 9, 10 and 11 adapted to the treatment of coarser material.
My improved process of extraction is based substantially upon the use in
combination of bromine, or one of its compounds (for instance bromide of
potassium), chlorine; or some combination thereof, (for example chloride of sodium)
and electricity; these agents producing bromine, chlorine and chloride' of bromine
in a nascent state together with complex bromo-chlorides, in which condition they
all attack gold and silver most energetically.
These reagents moreover possess the peculiar characteristic of partially
liberating the bromine from the various bromo-chlorides formed by the chlorine
which displaces it, the liberated bromine attacking fresh quantities of gold; by
which alternating action of the bromine the operation is rendered more economical
by requiring only a relatively small quantity of that agent.
Although the above mentioned agents may be employed without other chemical
compounds for the purposes of extraction, it is quite evident that they may also
be used in combination with any other known solvent of gold or silver (such as
hypochlorites; cyanides and the like); and in order to more fully explain my
invention I shall proceed to give a detailed description of the manner in which it
may be advantageously put into practice, referring to the accompanying drawings
illustrating two arrangements of my improved apparatus.
Figure 1 is a vertical section through the axis of the apparatus as arranged for
treating ores previously pulverised,
Figure 2. being a plan of the same.
Figure 3 is a part section drawn to an enlarged' scale of Figure 2 on line 1'-2,
shewing in detail the devices for suspending the electrodes in such a manner as to
make them readily removable.
Figure 4 shews details of the arrangements for supporting and retaining the
plates in position.
Figure 5-is-a-plan' of Figure 6.**
Figure 6, a part section drawn to an enlarged scale on line 3-4 of Fig. 2.
Figure 7 is a vertical section through the axis of an apparatus arranged for
treating ores-not reduced to a fine state,<
Figure 8 heinea plan of the sent

page_text: Figure 9 a part plan enlarged shewing the mechanism for adjusting the angular
aclination of the teeth of the agitator.
Figure 10 is an elevation on the same scale of a rotary arm carrying teeth for
gitating the solution, and.
Figure 11 is a transverse section of one of the arms of the agitator.
For treating substances previously pulverised I employ the apparatus shewn on
igures 1 to 6.
The materials to be operated upon-whether crude or calcined-having been
reviously reduced to fine powder and mixed with water in an ordinary agitator,
re introduced into the apparatus while it is in motion so as to keep them in
uspension. The reagents undermentioned are then added in the following
roportions:
(a) Bromine, or one of its compounds or one of its combinations, 0.10 to 0.50%
of the mineral.
(b) Chloride of sodium or hydrochloric acid 0.50 to 3%.
c) Cyanide of potassium 0.05 to 0.15 %.
(d) A plate of copper connected to the anode so as to ensure the solution of
a quantity of copper from 2 to 5 times as large as that of the precious
metals contained in the substances under treatment.
(e) Mercury either in a free state or as an amalgam applied upon metallic
plates electrically connected with the anode in such manner and proportion.
as to ensure the solution of a quantity of mercury from 5 to 20 times as
large as that of the precious metals contained in the substances under
treatment.
(Sufficient sulphuric acid to render the bath slightly acid and to stimulate
the production of hypochlorite solvents of gold.
(9) Sulphate of iron and sulphate of copper in sufficient quantities to assist
in the formation of complex salts and in the precipitation of gold and
silver.
The mixture above described is given as an example and is useful more especially
n the case of composite minerals containing gold in a refractory state; and it is
eedless to remark that the proportions of the reagents specified may be varied
ccording to the character of the minerals to be operated upon, their richness in
precious metals, and the ease or difficulty of attacking them. It would be feasible
o substitute for the copper and mercury used in the anodes soluble salts of those
metals added to the bath, but their action would then be much less energetic and
efficient than that obtained by the direct solution of those metals by means of
lectrolysis.
'
Electric connection is then established between a dynamo and the apparatus, a
difference in potential being given to the terminals of from 2 to 6 volts varying
according to the superficies of the electrodes used and the character of the minerals
to be treated. The contents of the bath are kept in movement for from 3 to
6 hours, and are then drawn off through suitably arranged discharge cocks into a
convenient receptacle in which the solid substances are allowed to settle, the liquid
being afterwards poured off and the exhausted mineral thrown away, whilst the
residual fluid may either be run off as waste, or reserved for subsequent treatment.
after it has been compensated with the several reagents in the requisite
proportions.
When the mercury at the bottom of the tank has been sufficiently enriched with
the precious metal, it is run off through stopcocks and submitted to the usual
treatment of gold or silver amalgams, whilst a fresh quantity of mercury is supplied
to the tank.
Similarly when the amalgamated plates of the cathodes are sufficiently enriched
or require a fresh coating of mercury, they are removed and treated by any
ordinary process, other amalgamated plates, previously prepared to avoid loss of
time in the operation of the apparatus being substituted. So also any amalgamated

page_text: plates used at the anode may be replaced, when they have been deprived of their
mercurial coating.
The gold and silver are extracted from the amalgam by the ordinary methods.
In action, the chemical changes produced are as follow:-Electrolysis of the
reagents a and b produces at the anodes chlorine, bromine and chloride of bromine
in a nascent state, which are very favorable to the activity of these agents, which
combine with the gold and silver to form soluble complex bromo-chlorides. The
simultaneous use of chlorine and bromine effects moreover the partial displacement
in the various bromo-chlorides produced of a certain quantity of bromine by the
chlorine, the bromine thus released acting upon fresh quantities of gold. The
sulphuric acid is used for the purpose of further facilitating the action upon
the gold by the production of hypo-chlorites, and the liberation of chlorine by.
electrolysis of the chloride of sodium. Assistance is rendered to the formation of
these complex salts by the copper and iron which cause a separate alternating
action conducing to the solution and precipitation of the precious metals.
The use of the cyanide of potassium is to scour the surface of the mercury so as
to increase the activity of amalgamation.
By means of the electrolytic transfer of mercury to the cathodes energetic aid is
afforded to the withdrawal precipitation and amalgamation of the precious metals
upon the mercurial cathodes; the re-amalgamation of the plates of the cathodes.
in a continuous manner is also effected in proportion as they are charged with
the precious metals, thereby stimulating their action and rendering it more
constant.
The same reagents are used in the second apparatus in which the mineral is
continuously introduced by a central funnel, the reagents being added as fast as
they are decomposed so as to keep them constantly in the desired proportions in
the bath. The mineral is pushed progressively by mixing-teeth towards the
circumference of the bath, from which it falls into an external basin whence it is
The
withdrawn by a chain with buckets or otherwise as hereinafter described.
rate of ejection of the mineral can be accelerated more or less according to the
position given to the teeth and if desired a simple mixing can be produced.
The apparatus I preferably use for carrying out the above described process, in
the case of substances previously reduced to a fine powder, consists of an electro-
lytic bath in which removable electrodes of large superficial area are arranged
concentrically above a cathode of mercury, and of a central and lower agitator for
mixing the materials under operation so as to prevent deposition. As shewn on
Figures 1 and 2 the apparatus is contained in a tank A of circular form, but it may
be made polygonal, or square, and of dimensions suitable for the quantity of
minerals it is intended to treat therein. I prefer a circular tank as allowing a
freer movement of the materials. This tank A is made of wood covered with tar
or lined with any other non-conductor of electricity, or it may be constructed of
iron or steel lined with non-conducting material. In the centre of the tank A is
arranged a vertical movable agitator axis B, electrically insulated at the points
where it is in contact with the tank, and at its points of contact with the arms H
and geared pinion K, and having an electric contact piece, D, at one point. Upon
this axis B, blades E are arranged crosswise and are set alternately at right-angles
to each other at intervals upon the axis. They are made of dimensions permitting
them to revolve within an arrangement of electrodes hereinafter to be described.
The lowermost blades E' are placed a few centimetres from the bottom of the tank A
and extend across nearly the entire diameter thereof so as to pass below the
plates P, N used as electrodes, and by their movement to prevent the deposition of
the substances in suspension in the bath. These blades E E' may be made of retort-
carbon or coke, platinum or any other suitable substance not liable to be affected
by chlorine or bromine, and are perforated with holes so as to offer less resistance
to their movement in the bath and at the same time to allow them to distribute
their electricity better.

page_text: Within the tank A and extending from near its circumference to within about
0.50 metre of its centre are suspended two sets of plates, positive P, and
negative N, concentrically arranged either in a circular or in a polygonal form
around the central axis B. As shewn in plan on Figure 2, I preferably adopt a
polygonal arrangement as offering comparatively slight resistance to the circular
movement of the substances in the bath when agitated by the blades E, while
presenting very large electrolytic surfaces and permitting of the ready cleaning of
the plates P and N which in this arrangement are perfectly flat.
•
Each set of plates is independently insulated and supported, so as to allow the
one set P, to be conneeted to the positive pole, and the other N, to the negative
pole of a dynamo. The supports shewn in detail in Figures 3, 4, 5 and 6, consist
of radially arranged rods T T¹, secured near the centre by separate collars C C¹
and supported at their outer ends in sockets F F¹ provided on the inner sides of
the tank A. The collars C C' are also independently supported by cross rods G G
arranged diametrically in the tank. The positive plates are supported at the top
by the rods T' and are held in position at the bottom by another set of radial
rods T. Similarly the negative_plates are supported and kept in position at top.
and bottom by the rods T T. To ensure this retention of the plates in position
I employ guides t t' corresponding respectively to each set of electrodes.
Each plate is so suspended as to be independently removable and therefore
readily replaceable. By the use of the guides tt' the plates are secured in such a
manner as to prevent any substantial movement and all contact between the two sets.
Between adjacent plates on the same polygon or circle a free space of 0.05 metre or
0.10 metre is left to allow of the proper circulation of the substances in the bath.
All the plates are provided at their upper ends with copper conducting rods P, and n,
for the positive and negative sets respectively, supported on conductors; and the
plates terminate short of the bottom of the tank A so as to leave a sufficient
free space, about 0.40 metre, for the revolution of the lowermost blades or
floats E¹.
As above mentioned two sets of plates are arranged concentrically and parallel
to each other, the negative plates alternating with the positive, a space between
each set being left of 0.04 m., to 0.06 m. according to the difference of potential
employed.
The plates P or anode connected with the positive pole of the dynamo are made
of retort-carbon or coke, platinum or any suitable substance not liable to be
affected by chlorine or bromine and are perforated with holes.
The other plates N forming the cathode are connected with the negative pole,
and are amalgamated with mercury; they are not perforated.
A thin covering or layer of mercury is placed over the bottom of the tank and
electrically connected with the negative pole of the dynamo.
The central agitator axis B and blades E E' of the agitator are connected with
the positive pole.
A certain number of plates amalgamated with mercury are substituted for a
corresponding number of the plates P forming the anode; and a smaller number
of copper plates are substituted for an equal number of plates P.
Two draw-off cocks V are provided near the bottom of the tank A. for emptying
the bath except as to the mercury, and two other cocks R at the bottom for drawing
off the mercury.
The entire apparatus is surrounded by a platform Q to facilitate manipulation and
conduct of the operation.
For the treatment of mineral substances not previously pulverised the apparatus
shewn on Figures 7, 8, 9, 10 and 11 is employed.
As shewn on Figs. 7 and 8, the tank A' in this arrangement is preferably
cylindrical, and may be made of wood or of metal internally lined with a non-
conducting substance and of sufficient size for the quantity of minerals to be
treated. Preferably it is made shallower than the tank used for the process

page_text: already described. Near its circumference this tank is provided with an
opening at the bottom communicating with a receiver Q extending below the
tank A but with its upper rim at the same level as the top of the tank A¹. For
the purpose of continuously withdrawing the substances expelled from the tank and
deposited in the receiver Q, the latter is furnished with a chain of cups S. At the
inner side of the opening O is provided a flange O¹ which projects slightly above the
bottom of the tank. Two discharge cocks Rare provided on the bottom of the tank
and a vertical shaft B' is arranged centrally within it for the purpose of operating an
agitator by means of geared tooth wheels K¹, electrical insulators being provided
for the shaft at its points of contact with the tank, with the arms H', and with
the geared wheels K', while an electrical contact is provided at one point D' of the
vertical shaft B. Upon this shaft are secured by means of a collar U radial
arms each consisting of two parallel rods Y Y joined together by suitable cross
pieces .
The radial arms are supported by means of tie-rods y' secured
at the top of the shaft B'. The lower rods Y of the arms are united together
by means of curved or straight cross-bars y, which besides keeping them in
fixed relative positions afford supports for the carbon or other plates referred
to below.
Upon the lower rods Y and cross-bars 2 of the arms are carried perforated
plates Z, see Fig. 11, formed of retort-carbon or coke, platinum or any other suitable
material not liable to be acted upon by chlorine or bromine, a certain number of
which plates are replaced by plates amalgamated with mercury and others by
copper plates. All these plates form anodes and are electrically connected
with the positive pole of a dynamo, as well as the central shaft and the teeth
described hereafter.
Above the plates Z and at a distance of about 0.04 m. to 0.06 m. are carried in
insulating supports y a set of mercurially amalgamated plates Z¹ (see Fig. 11)
arranged parallel to the plates Z and connected electrically with the negative pole,
both sets of plates being secured to their several supports by keys or screws y* or
equivalent devices.
The radial arms Y Y¹ carry teeth M in the form of triangular prisms set upon
vertical axes m passing through the radial arms, as shewn on Fig. 10, and fixed by
screws. By means of these axes m the teeth may be turned to any desired angle,
and electrical connection is formed between the arms and the teeth. An interval
of about G-15 m. is left between the axes of adjacent agitating teeth upon each arm,
and they are so arranged relatively to those upon successive arms, that the circular
paths of the teeth upon three consecutive arms intersect a radial line at intervals
of 0.05 m. as shewn on Fig. 9. Thus the teeth on the arms are arranged in
groups of three arms, and in each group the above described distribution of
teeth is repeated.
The teeth which may be made of iron steel or other suitable material are free to
move on their vertical axes. 1 may vary the intervals above specified in spacing
the teeth upon a single arm and also the number of arms in a group.
The teeth may alternatively be replaced by sets of flat plates arranged movable
around vertical axes.
All the teeth on a single arm are connected to a horizontal bar L furnished with
studs entering a mortise m¹ formed lengthwise in the upper part of the corre-
sponding tooth; see Figs. 9 and 10. This bar L is guided by means of bolts l
secured at several points in the arms Y, and passing through eyes provided
) in the bar. At its outer end the bar L is furnished with a projection
screwed to receive a screwed stem arranged at the extremity of the
The stem
arm Y, and loose between two bosses carried by the arm.
is furnished with a square head to allow of its being turned by a key
whereby the bar L is moved and imparts an angular movement to all the
teeth. By this mechanism or equivalent devices the angle at which cach
side of the teeth strikes the substances agitated during the rotation of the

page_text: -central shaft may be varied as desired. Each side of the teeth thus drives the
substances away to a greater or less extent from their axes, and according to their
adjustment effect either a simple agitation of the substances or their progressive
expulsion from the tank.
On the bottom of the tank is placed a thin layer of mercury which is connected
electrically with the negative pole of the dynamo.
Around the central motor shaft B¹ is arranged a conical hopper J for the purpose
of feeding in the substances to be treated; see Figure 7.
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 processes for the extraction of gold and silver from their ores or other
substances the use of bromine or one of its compounds, (such as bromide of
potassium) with chlorine or one of its combinations (as chloride of sodium) by the
aid of electrolysis as described.
2. In the extraction of gold and silver from their mineral ores or other substances
by electrolysis of bromine and chlorine compounds, the simultaneous use of one or
more known solvents of gold and silver, (as cyanides, hypochlorites, mercury and
others) as described.
3. In processes for the extraction of gold and silver the use of mercury at the
anode, or of a mercurial salt dissolved in an electrolytic bath, concurrently with
the use of metallic mercury at the cathode as described.
4. The combination in processes for the extraction of gold and silver in an
electrolytic bath containing the auriferous or argentiferous substances, of
bromine or one or more of its compounds (as bromide of potassium) chloride
(usually chloride of sodium), simple or complex cyanides (as cyanide of
potassium) mercury as the anode, or mercurial salt dissolved in the electrolytic
bath, concurrently with a cathode, of mercury; sulphuric acid sulphate of iron,
and copper connected with the anode, or a salt of copper (as chlorate or sulphate)
in solution.
5. For the extraction of gold and silver from their mineral ores or other
substances an apparatus essentially comprising a tank A groups of vertical
plates P N arranged in a circle or in polygonal form concentrically around a central
vertical shaft B carrying radial blades E, blades E' extending between the bottom
of the concentric plates and the bottom of the tank.
6. For the extraction of gold and silver from their mineral ores or other
substances, an apparatus consisting essentially of a tank groups of vertical
electrodes concentrically arranged either in a circular or polygonal form around a
central shaft carrying radial blades, such electrodes being connected alternately to
opposite poles of the source of electricity, and the shaft having its lower blades
extended between the base of the plates and the bottom of the tank, and being
.connected to the positive pole of the source of electricity.
7. In an apparatus for the extraction of gold and silver by electrolysis described
above, the mode of supporting and maintaining in position the plates or electrodes
so as to permit of their independent renoval as described with reference to
Figures 1 to 6 of accompanying drawings.
8. For the extraction of gold and silver from their mineral ores and other
substances an apparatus comprising essentially a tank A¹, a vertical shaft B',
capable of rotating centrally therein, furnished with arms Y Y₁ arranged radially;
said arms carrying teeth M of triangular section or with flat surfaces, united in
sets by a rod or bar L and arranged to be turned simultaneously to the same
angular extent around vertical axes m for the purpose specified and as described
with respect to Figures 7, 8, 9, 10 and 11 of the accompanying drawings.
9. In an apparatus for extraction of gold and silver from their ores comprising
a tank, a central shaft provided with radial arms adapted to rotate therein and

page_text: furnished with adjustable teeth, the use of electrodes supported between the radial.
arms for the purpose and as specified.
10. Apparatus for the extraction of gold and silver by electrolysis, constructed
combined and arranged as described with reference respectively to Figures 1, 2,
3, 4, 5, and 6; and to Figures 7, 8, 9, 10 and 11 of the accompanying drawings.
Dated this 28th day of September 1895.
кррисонид
GEDGE & FEENY,
Agents.