Improvements in or relating to the Precipitation of Precious Metals from their Cyanide Solutions.
Year: 1896

page_text: Date of Application, 4th June, 1896
Complete Specification Left, 4th Mar., 1897-Accepted, 17th Apr., 1897
PROVISIONAL SPECIFICATION.
Improvements in or relating to the Precipitation of Precious Metals
from their Cyanide Solutions.
I, MARTIN BERNHARD ZERENER of 15 Bernard Street, Russell Square, in the
County of Middlesex, Metallurgist, do hereby declare the nature of this invention to
be as follows:-
This invention consists in a new method of precipitating gold and silver from
solutions containing these metals chemically combined with cyanogen, commonly
called cyanide-solutions.
The precipitating agent 1 prefer to employ is the amalgam of one or several of
the alkaline or alkaline earth metals which is brought into contact with the gold
bearing solution in a novel manner; and it is necessary that the said amalgam
should contain only so small a percentage of the alkaline metal as to be liquid like
mercury.
As is well known the alkaline metals and their amalgams have a very strong
affinity for cyanogen, and therefore are able to replace and liberate other metals
such as gold and silver from their combinations with cyanogen. But on the other
hand these alkaline metals when coming into contact with water or chemical
solutions, instantly react with the constituents of the water, oxidising themselves
and liberating hydrogen gas. Therefore, if the amalgam of an alkaline metal be
brought in contact in the ordinary way with a solution containing gold, the quantity
of which is exceedingly small in comparison to the quantity of water present, only
a small percentage of the alkaline metal will serve to precipitate gold, the greater
part being consumed for the decomposition of water, consequently, the quantity of
alkaline metal required to precipitate a given quantity of gold will be very large
and render such a method of precipitation too expensive for practical purposes.
To overcome this disadvantage I employ the said amalgams in a state of very
fine division and I cause every fine particle of the amalgam to pass rapidly through
the gold-solution, thereby bringing continually fresh parts of the solution into
contact with the amalgam. The quicker the alkaline metal passes through the
solution, the more opportunities will it find to precipitate gold, and the useless
decomposition of water will be greatly reduced.
To carry this out practically the cyanide-solution is contained in a vessel of any
convenient form and size; the liquid amalgam, kept in another vessel, is caused by a
simple mechanical arrangement to pass into and through the cyanide-solution in a
multitude of fine streams, or in a quick succession of fine drops, or in a number of fine
films, in all of which ways, the exposed surface of the amalgam is very large in
comparison to its bulk.
After thus quickly passing through the solution the amalgam (or rather the
mercury) is separated from the solution, charged again with alkaline metal and can
then be re-used for precipitating gold from the cyanide solution.
To still more clearly explain how I propose to employ the amalgam, I give the
following description as one way of carrying out this invention.
The gold-bearing solution is contained in a reservoir and passes through a pipe
controlled by a cock into the precipitating vessel; the solution slowly rises and then
passes through another pipe, into a reservoir. The precipitation of the gold and silver
takes place in the vessel and is effected in the following manner: Above this vessel is
another vessel of preferably the same diameter, containing a liquid alkaline amalgam.
-

page_text: The bottom of this vessel is provided with a number of fine openings holes or slots,
through which the amalgam passos in fine streams or drops into the precipitating
vessel and through the gold-solution. The alkaline metal replaces the gold, forming
an alkaline cyanide, the precipitated gold being taken up by the mercury. The fine
globules of amalgam and mercury collecting in the lower pirt quickly unite again in
one body of mercury which is delivered preferably through a syphou into a reservoir.
Thence the mercury is lifted by means of a pump or an elevator to another reservoir
where it is charged again, chemically or mechanically with an alkaline metal, to be
used for further precipitating purposes.
Thus the process is continued as long as there is cyanide-solution to treat.
The gold has to be separated from the mercury which can be done in any suitable
manner such for example as by straining filters; this may be done from time to time
as often as the mercury has taken up a certain amount of gold; or it may be done
continually, by putting one or more straining filters in any convenient position, when
the mercury will be freed from the gold-amalgam continually and the latter may be
collected from the straining filters without interrupting the precipitating process.
It is not necessary that the amalgam should fall vertically downwards as in the
case of this example; it might, for instance pass through holes in the sides of the
véssel, and it would then full in a curved line, or might be forced upwards under
pressure through holes in the bottom.
It will be understood that modifications may be made without departing from the
spirit of the invention.
Dated this 4th day of June 1896.
BOULT & WADE,
Agents for the Applicant.
Improvements in or relating to the Precipitation of Precious Metals
from their Cyanide Solutions.
I, MARTIN BERNHARD ZERENER of 17 Chelsea Gardens in the County of Middlesex,
Metallurgist, formerly of 15 Bernard Street, Russell Square, 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 consists in a new method of precipitating gold and silver from
solutions containing those metals chemically combined with cyanogen, commonly
called cyanide solutions.
The precipitating agent I prefer to employ is the amalgam of one or several of
the alkaline or alkaline earth metals which is brought into contact with the gold
bearing solution in a novel manner; and it is necessary that the said amalgam should
contain only so small a percentage of the alkaline metal as to be liquid like mercury.
As is well known the alkaline metals and their amalgans have a very strong affinity
for cyanogen, and therefore are able to replace and liberate other metals such as gold
and silver from their combinations with cyanogen. Bat on the other hand these
alkaline metals when coming into contact with water or chemical solutions, instantly
react with the constituents of the water, oxidising themselves and liberating
hydrogen gas.
These two reactions may be represented by the following eanations:

page_text: very small percentages of gold, the proportion of gold to water being frequently as
1 to 100000 or less. If the amalgam of an alkaline metal be brought in contact with
such a dilute solution in the ordinary way, that is, by simply immersing it, evidently
the second of the above reactions will prevail, while only a small part of the alkaline
metal could serve to precipitate gold, and the quantity of alkaline metal required to
precipitate a given quantity of gold would be very large and render such a method
too expensive for practical purposes.
I have, however, found that it is possible, even with small quantities of an alkaline
metal, to obtain complete precipitation of the precious metals if the following
conditions are observed:
1. The alkaline metal, preferably sodium, must be dissolved in a large excess of
mercury. In practical working I usually employ mercury containing about 5 parts
of sodium in 10000 parts of mercury; but, if all other arrangements are made
accordingly, good results may be obtained if the percentage of sodium is considerably
below this limit. The advantage derived from this is that the sodium dispersed
throughout a large quantity of mercury, is not so quickly and violently oxidised by
the water, and consequently, has more opportunity to react with the gold-compound
and to reduce the gold.
2. The alkaline amalgam must be employed in a state of fine division so as to
present a large surface to the gold-bearing solution. It is well known that other
metals when employed for the precipitation of gold from solutions, act most
satisfactorily if used in a state of very fine division. In the case of mercury, the
ordinary means of subdividing metals not being available, I find it the best plan to
employ the sodium-bearing mercury in the form of a great number of fine streams or
drops or films or as a shower or spray or in such form that the exposed surface of the
mercury is very large in proportion to its bulk. It is obvious that a certain quantity
of amalgam subdivided into a great number of the finest drops, and presenting a
surface many thousand times larger than the same quantity of amalgam spread out in
a thin layer, must necessarily give increased opportunities to the alkaline metal to
come in contact with and reduce the gold.
3. To increase still more the contact between the amalgam and the solution it
is important that the former should rapidly pass through the latter, thereby coming
continually into contact with fresh portions of the solution. The quicker the
amalgam changes its place the more completely will it be used for the desired
purpose, while the useless decomposition of water will be reduced in proportion.
4. The gold taken up by the mercury should be removed as far as possible continuously
so as to prevent any over-charging of the mercury.
To practically carry out these conditions I arrange the precipitating process on
the following general principles:
The gold-bearing solution is contained in a vessel of convenient size, and form; the
liquid amalgaın kept in another vessel is caused by means hereinafter described to
pass into and through the cyanide solution in a multitude of fine streams or a quick
succession of fine drops or in a number of fine films. After thus quickly passing
through the vessel the mercury is separated from the solution, transported back to
the starting point, freed from the gold or part of the gold or not, as may be desired,
charged again with alkaline metal and reused in the same manner. This circulation
of the amalgam or mercury is continuous and uninterrupted as long as desired.
To still more clearly explain the nature of this invention I give the following
illustration as one way of carrying out the process.
The gold-bearing solution contained in the reservoir A passes through the pipe a
controlled by cock b into the precipitating vessel B, slowly passing through it in an
upward direction escaping through pipe c into a reservoir C. The precipitation of
the precious metals is effected in B in the following manner. Above B is another
vessel D preferably of the same diameter and cross section as B, containing the
mercury charged with alkaline metal. The bottom of this vessel is provided with
fine openings such as holes or slots through which the amalgam passes in fine
streams or drops into the precipitating vessel and through the gold-solution. The

page_text: fine globules of mercury collecting in the lower part E, which now contain gold,
quickly unite again to one body of mercury which is separated from the solution
and delivered, preferably through a pipe e which acts as a seal into the strainer F
and in the reservoir G. Thence the mercury is lifted by means of a pump or an
elevator H into another vessel I where it is charged again with alkaline metal and
used for further precipitating purposes. Thus the process is continued without
interruption as long as there is cyanide solution to treat and the gold-amalgam
remaining in the strainer F may be taken out at frequent intervals without
interfering with the circulation.
It is obvious that the straining filter represented by F may be put in any
convenient position or that it may be replaced by another arrangement, for separating
out the precious metals. As the mercury is continually in circulation the straining
need not necessarily be perfect; in practical working the mercury will always retain
a small percentage of gold, but after being saturated to a certain degree depending
upon the nature of the process by which the gold is separated from the mercury,
it will deposit continually the whole of the precipitated gold and silver.
The charging of the mercury with alkaline metal may be effected in different ways
either mechanically or electrolytically.
Various ways may also be adopted to divide the amalgam into fine particles, but
in all cases the division is effected by forcing the amalgam through a number of
fine apertures, either by its own gravity or by external pressure. I find it a
practical way to employ a vessel such as D with a perforated bottom, the number,
size and shape of the perforations to be chosen according to requirements. Good
results are obtained with round holes of the smallest diameter that can be punched
in metal plates but oblong or square holes or long slots might be used with equally
good effect. Instead of a perforated metal-plate a bottom of other material may be
used, and if it is not possible to make fine and smooth perforations in such material,
fine pipes of metal or glass or other material might be fixed into it. Or a material
may be used the nature of which obviates artificial perforations, such as any woven
fabric as canvas or linen, or some naturally porous material like wood, through
which mercury can be passed under pressure.
All these appliances may be further modified by giving a slow motion to the
openings from which the amalgam issues; this may be effected in the above example
by causing the vessel D to revolve or the reaction of the issuing streams of mercury
may be utilized to create the revolution.
Furthermore, it is not essential that the mercury should fall vertically downwards
as in the example given above; it might describe a number of curved lines, or
traverse under sufficient pressure, the solution in a horizontal or upward direction.
Likewise the cyanide-solution may be either let into the precipitating vessel at
intervals or pass through it in an even flow in any direction; for instance upwards
as in the drawing, or downwards, or if several cylinders of different sizes are
arranged so as to form annular spaces, the solution may flow upwards, in the inner-
most cylinder, downwards in the next, then upwards again and so on. I can also
provide simple means for varying the speed of the falling mercury by altering the
head of mercury in D; if, for instance, the speed of the pump or elevator H is
increased and an increased quantity of mercury passes into 1 per unit of time,
the level of the mercury will rise; if, on the other hand, the total quantity of"
mercury in circulation is increased, the level of the mercury in D also rises and
the speed of the issuing streams or drops increases. Although this is the best
means of regulating the circulation of the mercury, it might also be effected by
applying external pressure regulated according to requirements.
It is obvious that the size and form of the various vessels can be varied to a great
extent.
.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I wish to state that I 5
am aware that the amalgams of the alkaline metals have been previously used for the

page_text: purpose set forth herein, and that I do not claim their exclusive use; nor do I claim
any method of continuously preparing these amalgams; but what I claim is :-
1. The process herein described of precipitating gold and silver from cyanide
solutions consisting in passing through them mercury charged with alkaline metal in
the form of a shower or spray or a number of fine streams or films.
2. For the precipitation of gold and silver from cyanide solutions the continuous
process of passing mercury charged with alkaline metal through the solution in the
form of a shower or spray; returning the mercury to the tank, recharging it
with alkaline metal and again passing it through the solution substantially as
described.
3. The apparatus for precipitating gold and silver from cyanide solutions
substantially as described and illustrated in the accompanying drawing.
Dated this 4th day of March 107.
M. B. ZERENER.
Boult & Wade,
Agents for the Applicant.
M. B. ZERENER.
Boult & Wade,
Agents for the Applicant.