IMPROVEMENTS IN EXTRACTING GOLD AND OTHER PRECIOUS METAL FROM ORES AND OTHER SUB- STANCES, AND IN THE APPARATUS EMPLOYED THEREIN.
Year: 1880

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for the Invention of "IMPROVEMENTS IN
EXTRACTING GOLD AND OTHER PRECIOUS METAL FROM ORES AND OTHER SUB-
STANCES, AND IN THE APPARATUS EMPLOYED THEREIN.' "
A communication
from abroad by Paul Gustave Louis Gabriel Designolle, of Paris, in the
Republic of France.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 5th February 1880.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN EXTRACTING GOLD AND OTHER PRECIOUS METAL
FROM ORES AND OTHER SUBSTANCES, AND IN THE APPARATUS EMPLOYED THEREIN.”
A communication from abroad by Paul Gustave Louis Gabriel Designolle, of Paris,
in the Republic of France.
This Invention relates to a process for extracting the whole of the precious metal,
and more particularly the gold, contained in ores of all descriptions, goldsmiths'
ashes, and the like, the said process comprising a mode of effecting the electro
chemical and mechanical amalgamation of such metals, as well as a mechanical
treatment for enabling the amalgam so obtained to be collected and completely
separated from the gangues and other impurities in which it is desimated.
The Invention relates more particularly to the treatment of auriferous ores or
minerals in which a portion of the gold escapes the process of extraction heretofore
employed, either by reason of the extremely fine state of division in which it exists,
or in consequence of peculiar chemical conditions which prevent the dissolving action
of the quicksilver, as heretofore employed.
Among such ores may be instanced auriferous schists and the pyritous ores con-
taining gold known as sulphurets.
The improved process is however equally applicable to the treatment of all ores
containing amalgamable gold or silver.
By the aid of an electro chemical process combined with a powerful mechanical
action the amalgamation is effected of the whole of the gold contained in the ores

page_text: herein before referred to, which ores could not heretofore be advantageously worked
except when they were of extreme richness sufficient to compensate for the great
waste involved by the treatment. The operation is completed by the employment
of a very simple rotary apparatus, which enables the whole of the extremely finely
divided amalgam obtained to be separated from the refuse.
The improved process of amalgamation is based upon the following principles,
viz. =
(1.) When an acid solution of any salt of mercury is exposed to the action of an
electric current the salt will be decomposed and the mercury will be deposited in a
metallic state at the negative pole.
When the negative pole is formed by a blade or strip of gold amalgamation will
take place.
(2.) When strips of scoured or cleansed iron are in contact with a slightly acid
solution of a salt of mercury, if these strips are touched with a gold wire or leaf an
electro chemical action takes place, in consequence of which the salt of mercury is
instantaneously decomposed, and metallic mercury passes to the gold wire or leaf
and amalgamates with it.
In certain cases the reaction is accelerated by slightly elevating the temperature.
(3.) Taking into consideration the natural combinations of gold with antimony or
tellurium, and the great affinity of chlorine for these two latter metals, then by
employing-
(A.) Bichloride of mercury in solution in water containing chloride of sodium,
(B.) The electro chemical reaction causing the decomposition of the bichloride of
mercury on contact with gold and iron, the antimonial gold and telluride of gold
will be decomposed, the chlorine uniting with the tellurium or antimony to form
chlorides, whilst the mercury unites with the gold and forms an amalgam.
When gold is present in the finest imaginable condition of tenuity preliminary
amalgamation has the effect of increasing the volume of each particle of gold, which
increase of volume is highly favourable to their separation from their gangues. The
preliminary amalgamation has the effect of modifying the condition of the auriferous
slimes which are formed during the pulverization; in fact these slimes after amal-
gamation lose their stiffness and assume under certain conditions a spherical form,
which is the form most favorable to their precipitation. Bichloride in solution
in water containing a certain quantity of chloride of sodium is preferably employed
as a salt of mercury in order to avoid the formation of protochloride of mercury,
which would be precipitated.
'
In order to effect the amalgamation of the whole of the gold present in the ore
the weight of the mercury contained in the salt employed should be at least five
times greater than the weight of the gold contained in the ore.
The difficulty in obtaining a practical result from the reaction which takes place
consists in the necessity for bringing all the extremely fine particles of gold which
are contained in finely pulverized ore held in suspension in water containing a
salt of mercury in solution into intimate contact with iron within a relatively short
time.
According to this Invention this result is obtained with great simplicity by
effecting the amalgamation simultaneously with a perfect pulverization in a special
apparatus constructed wholly of wrought and cast iron, in which the coarsely pul-
verized ore is placed together with the salt of mercury in solution in water, the said
apparatus being constructed in such a manner as to present a large amount of surface
of contact with the iron.
This apparatus consists of an iron cylinder containing spheres of the same metal
of different sizes, and effects the complete pulverization of the ore, at the same time
bringing all the particles of gold contained in the ore into forcible contact with
iron, which ensures the electro chemical action requisite for effecting the amalga-
mation. This cylinder performs a double function; it acts as a mechanical agent
for effecting the pulverization, and as a chemical agent, owing to its being con-
structed of a metal which effects the electro-chemical reaction. Thus the particles

page_text: of gold, instead of being reduced by a simple grinding action into very fine lamina
or flakes, which float in the liquid and so escape from amalgamation, as in the appa-
ratus heretofore employed, are immediately amalgamated, thereby increasing their
weight and volume, and facilitating their deposition, at the same time that the
influence of the movement causes the diminutive masses of semifluid amalgam to
rapidly assume a spherical form more favorable to their precipitation.
It is of the greatest importance in treating the various minerals herein before
referred to that the amalgamation of the particles of gold should be absolutely com-
plete in the apparatus appropriated for this process before the substances pass on to
the plates provided for collecting the amalgam.
It is found that the very fine and light particles of gold are carried away without
adhering to the plates, but that this is not the case with the globules of amalgam
previously formed, which are precipitated on to the plate and remain fixed thereto,
the refuse alone being carried away by the current of water.
The special apparatus constructed according to this Invention enables the whole
of the amalgam produced to be collected, and is composed essentially of a series of
alternate revolving and stationary amalgamated discs or plates, upon which the
liquid is caused to fall on leaving the grinding apparatus in which the amalgamation
is effected.
Moreover, as the apparatus is completely closed in, there is no risk of loss of the
precious metal from the dishonesty of the work people; and as the whole of the
amalgam is retained, the water carrying the refuse containing no trace of mercury
may be allowed to flow off into any stream or river without polluting the same or
involving any waste of the precious metal.
Two apparatus are required for carrying out the system in practice, viz. :--
(1.) An apparatus for effecting the amalgamation.
(2.) An apparatus for fixing or collecting the amalgam.
The apparatus for effecting the amalgamation consists of a horizontal cylinder of
sheet iron capable of rotating in either direction on a horizontal axis; the said
cylinder is terminated at each extremity in the form of truncated cones, and contains
a quantity of cast iron balls of different sizes. The coarsely pulverized ore is intro-
duced at one end of the cylinder through a suitable hopper together with water
containing a salt of mercury in solution, and the amalgamation of the gold is
effected at the same time as the grinding during the rotation of the apparatus under
the electro chemical action which is produced, and when the whole of the salt of
mercury is decomposed, which is known to be the case when the liquid ceases to
yield a reddish orange precipitate with iodide of potassium, the motion of the
cylinder is arrested, and immediately recommenced in the opposite direction, where-
upon the materials treated are discharged automatically through an opening at the
end of the cylinder furthest from the hopper, the said end being provided internally
with blades in the form of a conical helix. This arrangement may however be
modified, provided that the apparatus is constructed entirely of iron; for example,
the water containing the ore in suspension may be caused to circulate in vessels
provided with perforated iron plates or metallic gratings or gauze, or grinding mills
of wrought or cast iron may be employed, having a horizontal or vertical axis or
balls rolling in a circular trough, and the like.
The apparatus for collecting the amalgam consists of a series of copper or silver
discs or plates fast on a vertical rotating shaft, and enclosed in a cylindrical case,
the latter being provided internally with a series of concave plates forming annular
shelves of copper or silver sloping towards the centre, and arranged alternately with
the discs on the shaft. These shelves are formed in segments, and are attached to
the sides of the cylindrical case, which are likewise formed in segments, being also
mounted on hinges so as to be capable of opening when required. The revolving
discs and stationary shelves being amalgamated, and the segments of the case
closed, the finely pulverized ore in suspension in water, which has been treated in
the grinding and amalgamating apparatus hereinbefore described, is introduced

page_text: through a hopper at the upper part of the apparatus near the axis, and the vertical
shaft is rotated. The liquid falls onto the uppermost rotating disc, upon which it
spreads out laterally under the centrifugal action and flows over the edge of the
disc, whence it falls onto the uppermost stationary shelf, which causes it to flow
back towards the centre of the apparatus, where it falls onto the next rotating disc,
which again causes it to flow to the sides of the apparatus, and so on in succession,
the refuse, from which the whole of the gold will have been abstracted, being dis-
charged at the lower part of the apparatus.
The amalgam accumulated upon the discs and shelves may be readily collected
and removed by opening the sides of the case and scraping it off with an india
rubber scraper.
The amalgamation of the discs and shelves of copper or silver for fixing the
amalgam is effected preferably, according to this Invention, by means of bichloride
of mercury with the addition of chloride of sodium.
The reactions and apparatus herein before described for the treatment of gold are
also applicable to native silver, chloride of silver, and to the extraction of the silver
contained in ores in any state of combination, provided that the said silver has
been previously brought to the condition of native silver or chloride.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Henry Johnson in the Great Seal Patent Office on the 10th
April 1880.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN EXTRACTING GOLD AND OTHER PRECIOUS METAL
FROM ORES AND OTHER SUBSTANCES, AND IN THE APPARATUS EMPLOYED THEREIN."
A communication from abroad by Paul Gustave Louis Gabriel Designolle, of Paris,
in the Republic of France.
The said Invention relates to a process for extracting the whole of the precious
metal, and more particularly the gold, contained in ores of all descriptions, gold-
smith's ashes, and the like, the said process comprising a mode of effecting the
electro chemical and mechanical amalgamation of such metals, as well as a
mechanical treatment for enabling the amalgam so obtained to be collected and
completely separated from the gangues and other impurities in which it is
distributed.
The Invention relates more particularly to the treatment of auriferous ores or
minerals in which a portion of the gold escapes the process of extraction heretofore
employed, either by reason of the extremely fine state of division in which it exists,
or in consequence of peculiar chemical conditions which prevent the dissolving
action of the quicksilver as heretofore employed. Among such ores may be instanced
auriferous schists and the pyritous ores containing gold known as sulphurets. The
improved process is however equally applicable to the treatment of all ores con-
taining amalgamable gold or silver, and in all cases it presents the advantage of
ensuring the extraction of at least ninety nine per cent. of the precious metal,
whereas the maximum obtained by the processes heretofore employed does not
exceed eighty per cent.
It is well known that in the case of auriferous schists the precious metal is in
such a fine state of division that it escapes amalgamation by means of quicksilver
as heretofore employed. It is also well known that the schist divides the quick-
silver to such an extent that this metal is held in suspension in the mass, and is
ultimately carried away with the refuse by the water employed in washing.
With regard to auriferous pyrites or sulphurets it has been heretofore erroneously
conjectured that the gold is contained in them in a state of combination. It
is however more frequently found in such pyrites in a native state, but in an
extremely fine state of division, and uniformly distributed in the mass. Moreover
the metallic sulphurets with which it is intimately mixed act as an insulating
substance which opposes the dissolving action of the quicksilver.
When the sulphurets are tested or assayed by a dry process, and the yield of gold
is found to be less than the quantity actually present, this result is owing to the
formation of volatile combinations of the gold during the assaying process, which
combinations are engendered under the action of the temperature.
Gold is only found in nature in three distinct conditions, videlicet:-
1. In the condition of free gold or amalgamable gold.
2. In the condition of telluride of gold.
3. In the condition of antimonial gold; and it has never been observed in com-
bination with sulphur, arsenic, selenium, and the like.
The improved method of amalgamation, according to the present Invention, by
the employment of an electro chemical process combined with a powerful mechanical
action, renders it possible to effect the amalgamation of the whole of the gold
contained in the ores hereinbefore referred to, which ores could not heretofore be
advantageously worked except when they were of extreme richness sufficient to
compensate for the great waste involved by the treatment.

page_text: The improved system of treatment, according to this Invention, is completed by
the employment of a very simple rotary apparatus, which enables the whole of the
amalgam obtained in an extremely fine state of division to be separated from the
refuse.
The improved process of amalgamation is based upon the following principles,
videlicet :-
With regard to the chemical action,―
1. When an acid solution of any salt of mercury is exposed to the action of an
electric current the salt will be decomposed, and the mercury will be deposited in a
metallic state at the negative pole.
When the negative pole is formed by a blade or strip of gold amalgamation will
take place.
2. When strips of scoured or cleansed iron are in contact with a slightly acid
solution of a salt of mercury, if these strips are touched with a gold wire or leaf
an electric chemical action takes place, in consequence of which the salt of mercury
is instantaneously decomposed, and metallic mercury passes to the gold wire or leaf
and amalgamates with it.
In certain cases the reaction is accelerated by slightly elevating the temperature.
3. Taking into consideration the natural combinations of gold with antimony or
tellurium, and the great difficulty of chlorine for these two latter metals, then by
employing,
A. Bichloride of mercury in solution in water containing chloride of sodium,
B. The electro chemical reaction causing the decomposition of the bichloride of
mercury on contact with gold and iron, the antimonial gold and telluride of gold
will be decomposed, the chlorine uniting with the tellurium or antimony to form
chlorides, whilst the mercury unites with the gold and forms an analgam.
With regard to the physical action,―
1. The mercury or amalgamated metal plates powerfully attract the globules of
mercury however finely divided.
2. The attraction of the mercury or amalgamated metal plates is greater for gold
amalgam than for native gold.
3. The water containing particles of gold in suspension is a positive obstacle to
the adherence of this metal to the amalgamated metal plates.
4. This phenomenon does not take place when the particles of gold have been
previously amalgamated, because by reason of the attraction hereinbefore referred
to the particles of gold amalgam become instantaneously attached to the mercury of
the plates with which they unite.
5. When gold is present in the finest imaginable condition of tenceity preliminary
amalgamation has the effect of increasing the volume of each particle of gold, which
increase of volume is highly favorable to the separation of these particles from
their gangues.
6. The preliminary amalgamation has the effect of modifying the condition of the
auriferous slimes which are formed during the pulverization; in fact these slimes
after amalgamation lose their stiffness and assume under certain conditions a
spherical form, which is the form most favorable to their precipitation.
Bichloride in solution in water containing a certain quantity of chloride of sodium
is preferably employed as a salt of mercury in order to avoid the formation of proto
chloride of mercury which would be precipitated.
In order to effect the amalgamation of the whole of the gold present in the ore,
the weight of the mercury contained in the salt employed should be at least five
times the weight of the gold contained in the ore.
The difficulty in obtaining a practical result from the reaction which takes place
consists in the necessity for bringing all the extremely fine particles of gold which
are contained in finely pulverized ore held in suspension in water containing a salt
of mercury in solution, into intimate contact with iron within a relatively short
time.

page_text: According to this Invention this result is obtained with great simplicity by
effecting the amalgamation simultaneously with a perfect pulverization in a special
apparatus constructed wholly of wrought and cast iron, in which the coarsely
pulverized ore is placed together with the salt of mercury in solution in water, the
said apparatus being constructed in such a manner as to prevent a large amount of
surface of contact with the iron.
This apparatus consists of an iron cylinder containing spheres of the same metal
of different sizes, and effects the complete pulverization of the ore, at the same
time bringing all the particles of gold contained in the ore into forcible contact
with iron, which ensures the electro chemical action requisite for effecting the
amalgamation. This cylinder performs a double function; it acts as a mechanical
agent for effecting the pulverization, and as a chemical agent, owing to its being
constructed of a metal which effects the electro chemical reaction. Thus the
particles of gold instead of being reduced by a simple grinding action to or into
very fine laminæ or flakes, which float in the liquid and so escape from amalga-
mation, as in the apparatus heretofore employed, are immediately amalgamated,
thereby increasing their weight and volume and facilitating their deposition, at the
same time that the influence of the movement causes the diminutive masses of
semifluid amalgam to rapidly assume a spherical form more favorable to their
precipitation.
It is of the greatest importance in treating the various minerals hereinbefore
referred to that the amalgamation of the particles of gold should be absolutely
complete in the apparatus appropriated for this process before the substances pass
on to the plates provided for collecting the amalgam.
It is found that the very fine and light particles of gold are carried away without
adhering to the plates, but that this is not the case with the globules of amalgam
previously formed, which are precipitated on to the plate and remain fixed thereto,
the refuse alone being carried away by the current of water.
The special apparatus constructed according to this Invention, which enables the
whole of the amalgam produced to be collected, is composed essentially of a series of
alternate revolving and stationary discs or plates of amalgamated metal, upon
which the liquid caused to fall on leaving the grinding apparatus in which the
amalgamation is effected.
Moreover as the apparatus is completely closed in, there is no risk of loss of the
precious metal from the dishonesty of the work people, and as the whole of the
amalgam is retained, the water carrying the refuse containing no trace of mercury
may be allowed to flow off into any stream or river without polluting the same or
involving any waste of the precious metal.
In carrying the said Invention into practice two apparatus are employed,
videlicit, (1) an apparatus for effecting the amalgamation, and (2) an apparatus for
fixing or collecting the amalgam as hereinafter described.
Figure 1 of the accompanying Drawings represents a side elevation, partly in
section, of an apparatus for collecting the amalgam, and Figure 2 is a plan, also
partly in section, corresponding to Figure 1. Figure 3 is a side elevation, partly
in section, of an apparatus for effecting the amalgamation, and Figure 4 is a
corresponding transverse section of the same.
The apparatus for effecting the amalgamation, which is illustrated in Figures 3
and 4, consist of a horizontal cylinder a of sheet iron capable of rotating in either
direction on a horizontal axis f supported in suitable bearings g; the said cylinder
is terminated at its opposite extremities in the form of truncated cones b, 6¹, and
containing a quantity of cast iron balls h of different sizes. The coarsely pulverized
ore is introduced at the end b of the cylinder through a hopper c together with
water containing a salt of mercury in solution, and the amalgamation of the gold is
effected at the same time as the grinding during the rotation of the apparatus
under the electro chemical action which is produced. When the whole of the
salt of mercury is decomposed, which is known to be the case when the liquid

page_text: ceases to yield a reddish orange precipitate with iodide of potassium, the motion
of the cylinder is arrested and immediately recommenced in the opposite direction,
whereupon the materials treated are discharged automatically through an opening
at the end b¹, the said end being provided internally with blades d in the form of
a conical helix.
The arrangement of apparatus hereinbefore described may however be somewhat
modified provided that the apparatus is constructed entirely of iron, as for example
the water containing the ore in suspension may be caused to circulate in vessels
provided with perforated iron plates, or metallic gratings, or gauze; or grinding
mills of wrought or cast iron may be employed having a horizontal or vertical axis
or balls rolling in a circular trough, and the like.
The apparatus for collecting the amalgam, which is illustrated in Figures 1 and 2,
is constructed and arranged in the following manner :-A is a series of copper or
silver discs or plates fast on a vertical rotating shaft D and enclosed in a cylindrical
case K, the latter being provided with a hopper E for the introduction of the
materials to be treated, and a suitable outlet at the lower part for the escape of the
refuse. The cylinder K is also provided internally with a series of concave plates
forming annular shelves C of copper or silver sloping towards the centre and
arranged alternately with the discs A on the shaft D. These shelves are formed
in segments and are attached to the sides of the cylindrical case K, which are
likewise formed in segments, being also mounted on hinges so as to be capable of
opening outwards when required. In Figure 1 one of these segments on the right
is represented in the open position, and in Figure 2 all the segments are represented
as being open.
In operating with this apparatus the discs A having been amalgamated, as also
the stationary shelves C, and the segments of the case having been closed, the
finely pulverised ore in suspension in water, after having been treated in the
the grinding and amalgamating apparatus bereinbefore described, is introduced
through the hopper E, and the shaft D is set in motion.
The liquid falls on to the central part of the uppermost rotating disc, upon which
it is distributed laterally under the centrifugal action and flows over the edge of
the disc; the liquid thence falls on to the uppermost stationary shelf, which causes
it to flow back towards the centre of the apparatus, where it falls on to the next
rotating disc, which again causes it to flow to the sides of the apparatus, and so on
in succession, the refuse, from which the whole of the gold will have been abstracted,
being discharged at the lower part of the apparatus.
The number of discs and shelves, their dimensions, and the speed of rotation
will vary according to the nature of the gangue, the degree of tenuity of the particles
of amalgam, and the richness of the ore under treatment.
The amalgam accumulated upon the discs and shelves may be readily collected
and removed by opening the sides of the case and scraping it off with an india-
rubber scraper.
The amalgamation of the discs and shelves of copper or silver for fixing the
amalgam is effected preferably, according to this Invention, by means of bichloride
of mercury with the addition of chloride of sodium.
The reactions and apparatus hereinbefore described for the treatment of gold are
also applicable to native silver, chloride of silver, and to the extraction of silver
contained in ores in any state of combination, provided that the said silver has
been previously brought to the condition of native silver or chloride.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,-
First. The system or mode of electro chemical amalgamation obtained and

page_text: carried out by means of combined mechanical and chemical action, substantially as
herein before described.
Secondly. The application and use of bichloride of mercury in solution in
conjunction with chloride of sodium, substantially as and for the purpose herein-
before described.
Thirdly. The peculiar construction and arrangement of grinding and amalga-
mating apparatus constructed entirely of iron, and consisting of a cylinder and
balls, with provision for the admission and discharge of the materials under
treatment, substantially as hereinbefore described and illustrated in Figures 3 and 4
of the accompanying Drawings.
Fourthly. The peculiar construction and arrangement of apparatus for fixing
the amalgam, the said apparatus consisting essentially of a series of revolving
discs of amalgamated metal alternating with stationary concave plates also of
amalgamated metal arranged so as to act in succession upon the substances under
treatment, and contained in a case capable of being entirely closed in on all sides,
substantially as hereinbefore described and illustrated in the accompanying
Drawings.
In witness whereof, I, the said John Henry Johnson, have to this my Specifi-
cation set my hand and seal, this Ninth day of April, One thousand eight
hundred and eighty.
J. HENRY JOHNSON. (L.S.)