Improvements in the Wet Method of Extracting Gold from Finely Divided Auriferous Quartz Ores or other Auriferous Material, and in Apparatus therefor.
Year: 1890

page_text: Date of Application, 6th Jan., 1890-Accepted, 7th June, 1890
COMPLETE SPECIFICATION.
Improvements in the Wet Method of Extracting Gold from Finely
Divided Auriferous Quartz Ores or other Auriferous Material,
and in Apparatus therefor.
We, RICHARD BROWN of Haily Largs, Scotland at present residing in Brisbane in
the Colony of Queensland, a Member of the Iron and Steel Institute and GEORGE
HENRY IRVINE of Brisbane in the aforesaid Colony, Analytical Chemist and Assayer,
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 relates to improvements in the wet method of extracting gold from
finely divided auriferous quartz ores or other auriferous material, and in our process
we dispense with steam, gas, air and water pressure such as described by Toussaint
and Langlois, De Lacy, Mears, Newbery-Vantin and Pollok in their several
specifications.
Our invention consists in the extraction of gold from finely divided quartz ores
or material containing same in vacuo and the retention of the vacuum during the
process of chlorinating; the vacuum being obtained by a pump or other suitable
means in combination with a stationary vessel with a mechanical agitator, or a
revolving barrel; the admission into the chlorinating vessel or barrel, by suction, of
chlorine gas direct into the water or mixture of ore and water by which a better,
quicker and more effectual solution of chlorine is obtained; or the admission, by
suction, of chlorinated water, or of chlorinated water and chlorine gas direct into
the chlorinating vessel containing simply the ore, and in the use of a revolving barrel
having internally projecting staves or battens with means for producing a vacuum.
The chlorinating vessel may be stationary and fitted with a mechanical stirring
appliance or agitator; or a revolving barrel may be used, provided that either
arrangement is so designed that the chlorine gas or chlorinated water or chlorinated
water and gas may be admitted into the greatest amount of material to be treated.
In order that our invention may be clearly understood we give the following
description. The auriferous quartz ore or other auriferous material in the finely
divided state is roasted in the usual way to expel the sulphur, also to render it more
porous and thus allow the chlorine to act with greater effect; however, with certain
classes of auriferous quartz ores or other material roasting may be dispensed with.
The charge of finely divided roasted or other ore is placed in the vessel or barrel
with the necessary quantity of water for maintaining the whole in a perfectly fluid
condition (which quantity will vary according to the nature of the ore) until the
vessel is about half full of ore and water; the door of the vessel or barrel is then
securely closed, and the air inside is exhausted by means of a pump or other suitable
arrangement communicating therewith through a pipe, so as to form a vacuum (the
amount of vacuum being determined by means of an ordinary vacuum gauge) the
exhaust air pipe is then detached and the vessel or barrel is revolved a few turns so
as to thoroughly mix the ore and water, and the barrel is left in a position so that
the inlet pipe is brought to the lowest point.
This being accomplished, the necessary quantity of chlorine gas is admitted by
suction by means of a leaden or other suitable pipe (fitted with taps or valves)
leading from the gas holder to the vessel or barrel, inside of which is the inlet pipe
hereinafter described. The said gas is admitted slowly into that part of the vessel
or barrel which contains the greatest amount of ore, and in such manner that the
chlorine has to percolate through the mixture of ore and water. There being no
air in the vessel or barrel, the gas is in no way diluted and there being a vacuum,
the water more readily absorbs the gas. When sufficient chlorine has been admitted,

page_text: while vacuum still exists more or less in the vessel or barrel the connection is closed
by said taps or valves and the pipe is detached.
The contents of the vessel are then agitated either by a mechanical agitator in the
vessel or by revolving the barrel for from one to two hours according to the nature
of the ore being treated.
In some instances it may be necessary to admit a second charge of chlorine during
the process, which is done as hereinbefore described by means of the vacuum in the
chlorinating vessel or barrel.
After chlorination is completed the charging door may be removed at once (as in
this process the excess of chlorine gas in the upper part of the vessel or barrel should
be very small, if any, there ought to be no necessity for a chamber containing slaked
lime for drawing off the same) and the chlorinated batch is discharged into a vat
with a gravel false bottom or other suitable filtering material; the gold solution is
then drawn off and conducted into precipitating vats. The residue is next carefully
washed, the last washing being reserved for the first washing of the succeeding batch.
The gold is then precipitated with Ferrous Sulphate or it may be allowed to percolate
through charcoal filters direct from the filtering vats and the gold be subsequently
recovered by smelting, all of which methods are well known. As the liquors after
precipitation will contain a certain percentage of chlorine in solution it may be found
economical to reserve them for mixing with the ore in the vessel or barrel instead
of water previous to treatment by chlorination. The chlorine gas may be manufactured
by any of the known methods or obtained in the compressed or liquefied state and
conveyed direct in metallic cylinders and stored in a leaden or other suitable gas
holder or chamber; the gas may be measured by a scale on the gas holder or by any
other suitable means.
With regard to the chlorinating vessel, although various forms may be used, we
prefer the ordinary revolving barrel fitted with an inlet pipe in the charging door ;
the said door should be raised externally and is preferably flat; the inlet pipe may be
so designed that it can be used as a suction pipe for exhausting the air.
In order to prevent the inlet pipe from becoming choked, we cover it with a bonnet
pipe fitted to the vessel or barrel or charging door and the said pipe has holes drilled
in it, as has also the inlet pipe which neatly fits inside the bonnet pipe; these holes
are so arranged that on turning the cock or valve (which with the inlet pipe are in
one piece) open so as to admit chlorine (or exhaust air) the holes in the bonnet and
inlet pipes are opposite each other, but on closing the cock or valve the holes in the
inlet pipe come opposite the solid parts of the bonnet pipe and so prevent the mixture
of ore and water blocking up the inlet pipe. We also prefer to have on the inside
of the wooden lining of the barrel three or more of the staves, equidistant, to be of
increased thickness, such thickness extending inwardly; or three or more wooden
battens also equidistant and fastened to the lining and ends, parallel to its axis; this
prevents the mixture from merely sliding round as the barrel revolves, and ensures
the thorough mixing with the chlorine. In determining the size of the chlorinating
vessel or barrel, provision must be made for sufficient space for the vacuum and we
prefer that the vacuum space should be equal to that of the space occupied by the ore
and water combined.
Fig. 1 of the accompanying drawing shews a longitudinal section and Fig. 2 a
cross section of the above described barrel. A is the outer shell of iron or steel,
having circular rails R R that rest upon rollers to which rotary motion is imparted
so as to produce rotation of the barrel in the well known manner; C is the lead
lining, and B the wood lining, of which the three staves B¹ are made of increased
depth so as to project into the barrel as described. D is the manhole cover, also
consisting of the iron or steel outer part d, the lead lining d¹ and the wood lining d².
This is secured to the barrel by internal cross bars EE and screw bolts FF,
suitable packing being provided for rendering the joint between the barrel and the
cover air tight. G is the cock plug, having its outer end connected temporarily to the
pipe H, for exhausting the air or for introducing the chlorinated water and chlorine.
gas; this plug fits accurately into the bonnet I projecting into the barrel and

page_text: provided with holes, the plug having corresponding holes, so that when turned into
one position the two sets of holes are opposite each other, so as to open the
communication with the barrel while when the plug is turned into another position,
the communication is closed. The plug G is provided with handles G¹ for turning it.
In some cases it may be preferable instead of sucking in chlorine gas direct into
the chlorinating vessel or barrel, to suck in chlorinated water, or chlorinated water and
chlorine gas; in this case only ore is put into the vessel or barrel in the first instance,
after which the chlorinated water or chlorinated water and gas is sucked in by the
before mentioned vacuum and the same treatment adopted as that already described.
By the use of chlorine gas, or chlorinated water, or chlorinated water and gas direct,
a purer solution is obtained, thus materially facilitating the filtration and washing of
the chlorinated batch, whereas by the use of bleaching powder, and sulphuric acid in
the vessel or barrel sulphate of lime is formed which tends to make a bulky and
gelatinous mass, thus rendering filtration and washing slower and less effective. Care
must be taken in all cases to prevent the inlet of air into the said vessel or barrel so
as not to weaken the vacuum.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The method of extracting gold by means of the wet process from finely divided
ores or other auriferous material in vacuo in such manner that the vacuum is more or
less maintained during the process of chlorination, the vacuum being obtained by a
pump or other suitable means in combination with a stationary closed vessel with
mechanical agitator or with a revolving barrel in which the ore is treated, substantially
as and for the purposes herein set forth.
2. In the extraction of gold by means of the wet process such as is referred to in
the preceding claim, the admission by suction of chlorine gas direct into the water, or
mixture of ore and water in the vessel or barrel, substantially as and for the purposes
herein set forth.
3. In the extraction of gold by means of the wet process such as is referred to in
the first claim, the admission by suction of chlorinated water into the vessel or barrel
containing the ore substantially as and for the purpose set forth.
4. In the extraction of gold by means of the wet process such as is referred to
in the first claim, the admission by suction of both chlorinated water and chlorine
gas into the vessel or barrel containing the ore substantially as and for the purposes
herein set forth.
5. For use in the extraction of gold by means of the wet process from finely divided
ores or other auriferous material such as is referred to in the preceding claims, the
construction of a revolving barrel with internally projecting staves or battens, and
provided with means for exhausting the air and the introduction of chlorine gas or
chlorinated water, substantially as and for the purposes herein set forth.
Dated this 6th day of January 1890.
ABEL & IMRAY,
Agents for the Applicants.