An Improved Process and Apparatus for the Extraction of Gold.
Year: 1893

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by LOUIS CLÉMENT DAUMAS, of 70, Rue de Rivoli,
Paris, France, B.A., B.Sc., M.D.]
An Improved Process and Apparatus for the Extraction of Gold.
I, ERNEST DE PASS, of 78, Fleet Street, in the City of London, Fellow of the
Chartered Institute of Patent Agents, 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, reference being had
to the accompanying drawings and to the letters and figures marked thereon, that is
to say-
This invention relates to an improved process and apparatus for the extraction
of gold from its ores, and in carrying out the same I utilize the property possessed
by the protochloride of sulphur (S,Cl) saturated with dry chlorine, of dissolving
gold at a temperature of 130° centigrade. A double perchloride of gold and
sulphur is thus formed, the formula of which is Au,Cl, S₂C₁₁.
The ore may be treated directly when it does not contain any other metal than
gold, but if other métals be associated with it, these must be converted into the
oxides by a thorough roasting.
The dry ore having been pulverized and, if necessary, previously roasted, is
introduced with the protochloride of sulphur into an iron or steel receiver provided
with a protective coating of oxide of iron. This coating may be produced by
causing steam to act upon sheet iron at a red heat, as in Bower and Barff's process,
or by electrolysis, as in De Meritens's process, but any other substance unattackable
by chlorine at 130° C. can be used. This receiver is of cylindrical or other suitabe
shape, and is supported on legs, or it may be suspended by its upper part according
to local arrangements. Its lower end is conical, or is hopper shaped, and its
interior is provided throughout with a number of tubes of elliptical section for the
passage of steam, the elliptical or flattened section being in the direction of their
width so as to offer less impediment to the descent of the material than would the
circular section.
In the accompanying drawings
Fig. 1 shows, in vertical section, apparatus for carrying out the invention, and
Fig. 2 is a horizontal section through the receiver.
A is the receiver which is surrounded by a jacket D, between which and the
receiver, is arranged a steam worm B', forming a continuation of the tubes B, and
through this worm steam is caused to circulate. The steam admitted by the upper
pipe F, passes through the various tubes B and worm B' (see Fig. 2) and after
having heated the interior of the receiver passes out through the lower pipe E.
On the top of the receiver is a wide charging opening which may be closed by an
oiled rubber stopper, or one covered with asbestos card, or other substance
unattackable by chlorine at 130° C. This stopper is provided with two openings,
through one of which passes a pipe H of oxidised iron, or other suitable material,
also unattackable by chlorine at 130° C., and the lower end of which terminates
above the level of the material in the receiver. The chlorine passes off through
this pipe H, when the protochloride of sulphur is saturated, and is received into a
tank I containing protochloride of sulphur for absorbing it. Through the other
opening in the rubber stopper is inserted a glass pipette J, which dips into the
liquid mass contained in the receiver. This pipette is provided, at its outer end,
with a rubber bulb, which has its interior oiled, and it serves for making tests.
The receiver A is also furnished with an oxidised iron pipe K, through which
the chlorine is admitted, and said pipe extends to the bottom of the receiver and
projects into a layer of slag wool or mineral wool.

page_text: L is a registering thermometer provided with an oxidised iron casing.
At the bottom of the receiver is an outlet which may be closed by a cover
plate M, above which the slag wool or mineral wool is piled between two perforated
plates a and b.
This slag wool or mineral wool allows of the liquid being first filtered, when the
lower cover plate M is removed, then, when the stopper, formed by the slag
wool and the two plates, is removed, the ore may be discharged from the
receiver.
In addition to this receiver a funnel or hopper N is provided, the top of which
may be covered; the bottom is closed by a cock O. A third vessel P has at its
upper part, an opening R through which a vacuum may be created in said vessel P
by suction, so as to accelerate the filtration of the liquid in the funnel or
hopper.
To dissolve out the gold contained in the ore, steam is passed through the
worm B and tubes B, in order that the ore in the receiver may be heated up to
130° C. At the same time dry chlorine, under sufficient pressure, is sent through
the pipe K so as to saturate the liquid. The saturated protochloride of sulphur
then allows the chlorine to escape through the pipe H.
A test is then made by means of the pipette J, so as to ascertain whether the
liquid possesses the characteristic deep red color. If it be of a deep red, it indicates
that the gold is dissolved, and the operation is completed. The liquid from the
receiver is then rapidly filtered into the funnel N, by pressure, obtained by com-
pressed air conveyed through a pipe which is connected to the pipe H. This
funnel also contains at its lower part, a layer of slag wool or mineral wool. The
liquid is allowed to cool in the funnel, and is then filtered into the vessel P. This
cooling may however be more quickly effected by constructing the funnel with a
double wall and causing a stream of cold water to pass between these walls. Or if
desired the funnel may be provided with a conical worm through which cold water
may pass.
On the slag wool or mineral wool in the funnel, will be found the double
perchloride of gold and sulphur, which is separated as soon as the protochloride of
sulphur has been cooled. By exposing this salt to moisture the whole of the gold
will be precipitated in the form of powder. This powder may be washed with a
little bisulphide of carbon to dissolve out the sulphur which is mixed with the gold.
In the vessel P will be found the protochloride of sulphur which can be used over
again.
The duration of the operation, that is to say, the time during which the proto-
chloride of sulphur is to be kept at 130° C., will vary according to the size of the
grains of gold to be dissolved.
The chlorine which has been absorbed by the protochloride of sulphur in the
tank I, may be recovered by heating the tank to 130° C., and by connecting the
pipe H to the pipe K admitting the chlorine into the receiver A.
The following are the advantages resulting from this process :-
(a.) The operations by which the gold is extracted from its ore are very rapid
and easy.
(b.) The chlorine, after combining with the protochloride of sulphur, is again
liberated by reason of the elevation of the temperature, and attacks the gold in a
hot and nascent state, under pressure, and without the presence of water, thus
permitting a more rapid dissociation or dissolution of this metal.
(c.) The immediate precipitation of the gold, by a little water, or by moisture
alone.
(d.) The ebullition of the protochloride of sulphur allows of mechanical means
being dipensed with for obtaining agitation of the ore. The mixing of the material,
by means of ebullition, renews the surfaces in contact with the chlorine.
(e.) The mode of recovering the chlorine whereby a very great saving of the
same is effected.

page_text: Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I claim :—
1. The herein described process for extracting gold from its ores, consisting in
causing chlorine, in a dry state, to act at 130° C. under sufficient pressure so as to
saturate the protochloride of sulphur and enable it to dissolve out the gold from
the ore and to form a double perchloride of gold and sulphur.
2. The mode of absorption of the excess chlorine by the protochloride of
sulphur, and the recovery of the chlorine thus absorbed, by heating the proto-
chloride so that the chlorine may be returned again into the main receiver.
3. The mode whereby the same protochloride of sulphur, used for a previous
soaking of the ore, may be again employed for use in succeeding operations.
4. The arrangement, combination, and use of apparatus substantially as herein
described and as illustrated in the annexed drawings, and for the purposes set forth.
Dated this 24th day of March 1893.
ERNEST DE PASS.