Ores or other Finely Divided Auriferous Material.
Year: 1887

page_text: Ores or other Finely Divided Auriferous Material.
I, JAMES HOLMS POLLOK of the University of Glasgow, in the County of Lanark,
North Britain, Assistant to the Professor of Chemistry in the said University do hereby
declare the nature of this invention to be as follows:-
This Invention, which relates to improvements in the wet method of extracting
gold from crushed ores or other finely divided auriferous material, has for its object
to dispense with the necessity of forcing compressed air by means of a pump or the
mechanical equivalent thereof into the vessel containing the auriferous material and
the source of chlorine and acid used for liberating it.
The Invention consists in closing up the vessel in which the wet process is conducted
so soon as the auriferous material the source of chlorine and the acid or other reagent
or reagents have been placed therein. So soon as the vessel is thus closed water
under the pressure of a sufficient head is admitted until the air in the vessel is com-
pressed to such an extent as will cause the whole or nearly the whole of the chlorine
to remain in solution.
ST. JOHN V. DAY,
115, St. Vincent Street, Glasgow,
Petitioner's Agent.

page_text: Improvements in the Wet Method of Extracting Gold from Crushed
Ores or other Finely Divided Auriferous Material.
1. JAMES HOLMS POLLOK of the University of Glasgow, in the County of Lanark,
North Britain, Assistant to the Professor of Chemistry in the said University 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:
My Invention relates to improvements in the wet method or process for the
extraction of gold by chlorine from crushed ores, such as quartz or from other finely
divided auriferous material and more particularly from refractory ores or tailings.
My Invention greatly facilitates the production of a high pressure and thus shortens
the time taken for extracting gold from ore or other auriferous material by chlorina-
tion under pressure and makes the extraction thereof more economical and complete
than has hitherto been effected.
It has long been known that pressure in the vessels wherein the extraction of gold
from auriferous material takes place greatly assists that extraction and several processos
have been devised for the extraction of gold by chlorination under pressure. Amongst
these processes are those known as the De Lacy process, Mear's process, and the
Newberry Vantin process. In the De Lacy process, pressure is developed by
generating a considerable excess of chlorine in the vessel in which the extraction is
conducted. In Mear's process, pressure is obtained by pumping chlorine gas into the
cylinders, whilst in the Newberry Vantin process, pressure is obtained by pumping
atmospheric air into the vessels. Each of these processes has been more or less
successful and the success has varied according to the pressure produced and the cost
of producing it.
According to my Invention I extract gold from the ores or other auriferous material
by chlorination under pressure produced by hydraulic means. In using hydraulic
pressure, I am enabled to produce any desired degree thereof in a short time and at
a small cost.
While the production of pressure in the vessels by hydraulic means is the essential
feature of my improvements on the wet chlorination process, I give the following
description of working the process so that my improvements may be more readily
understood and its advantages distinctly seen. The entire process may be considered
as divided into four stages as follows:-
First. The crushed ore is roasted to expel the sulphur. The pyrites or other
metallic sulphides which envelope the gold and thus make the ore refractory are by
roasting rendered porous or spongy by the removal of the sulphur which if allowed
to remain would have taken up a large quantity of the chlorine-in-the-vessel and
therefore rendered that.chlorine useless for the purpose of extracting the gold. Where
no sulphur or only a small quantity exists, it is unnecessary to roast the ore.

page_text: After
Secondly. The ore is then placed in a cylinder A, shewn in end elevation at Figure 1,
and in longitudinal section at Figure 2. This cylinder has a lead lining a', within
the cast-iron exterior and a lining of wood 61, within that again as shewn at Figure 1,
and in longitudinal section at Figure 2. Bleaching powder as the source of chlorine
and sulphuric acid or other reagent for liberating the chlorine from the bleaching
powder are also charged into the cylinder. The cylinder is provided with a charging
hole B, and a covering door C, as shewn at Figures 1 and 2, through which the
charge is placed in the cylinder, the door C, being removed for charging it by
unscrewing the nuts which retain it on the studs as shewn at Figures 1 and 2.
the ore, bleaching powder and sulphuric acid or other reagent used are charged into
the cylinder, the cylinder is closed by replacing the door C, and tightening the nuts
by which it is pressed against and held over the charging hole B. So soon as this is
one water under pressure is admitted into the cylinder through the cock D, a pipe
being coupled to the screwed end of the cock connected to a pump, accumulator or
other source of supply. The admission of water under pressure is continued until
the pressure within the cylinder reaches to at least 100 lbs. per square inch, when
the cock D, is closed and the pipe connected to the said cock is disconnected. The
cylinder A, as shewn at Figures 1 and 2, is carried upon roilers E, and is rotated by
means of a spur pinion gearing into a circle of spur teeth around the cylinder (not
shewn in the drawings) such an arrangement being well understood and used in
connection with various rotating vessels in chemical works. The rotation of the
vessel A, is continued for from half an hour to one hour when the whole of the gold
will be found to have been dissolved; the pressure having forced the chlorinating
liquid into the pores of the ore.
The proportions of water and ore are regulated by the amount of ore placed in the
cylinder. I find it convenient to use cylinders A, of about 42 cubic feet capacity
and to introduce about 1 ton of ore at each charge. With a vessel of this capacity
and with the aforesaid charge of ore, about 25 cubic feet of water will have been
forced into the vessel when the pressure reaches 100 lbs. per square inch and I find
as a general rule that this is a good proportion to adopt for successful chlorination.
When it is desirable from the light and spongy character of the ore or otherwise
to use less water, this is easily effected by introducing more ore into the cylinder.
Thirdly. When the chlorination of the charge is completed the rotation of the
vessel A, is stopped, care being taken that the vessel A, is stopped in such position
that the cock D, is at its highest point. The cock D, has then a pipe connected to it
leading to chambers containing slaked lime. The cock D, is then opened and the
excess of chlorine flowing out therethrough into the chambers containing the slaked
lime is reconverted into bleaching powder, the last portions of chlorine being drawn
out of the chamber A, by the action of an exhaust pump connected to the slaked
lime chambers.
At Figure 3, is shewn in side elevation and at Figure 4, in plan, a series of three
rotating cylinders A, in which the chlorination process under hydraulic pressure is
conducted in accordance with my improvements. The three cylinders A, are placed
in proximity to an inclined trough F, and after the chlorine has been exhausted from
cach cylinder A, the cover of the charging door is removed and the cylinder is rotated
until the charging door at its lowest position, when the water with the ore and
solution of gold pours out into the inclined trough F, at the lower end of which
there is a filter of any suitable material contained in the division or receptacle G.
A material suitable for such filter is gravel. By this means the solution containing
the gold is rapidly drained off, the last portions being washed out with washings from
the last preceding chlorination and finally washed with pure water, these last washings
being reserved by themselves to be in their turn used for washing the next charge.
The solution as filters through the gravel bed G, flows into the trough H, by any
suitable conduit not shewn in the drawings. The trough H, is placed alongside a
series of tanks I, J, K, L, M, and N. The sides of the trough H, are fitted with
sluices a, by lifting any one of which the solution from the filter is run off into
any one of the tanks I, J, K, L, M, and N. The washings from the ore left on

page_text: the trough F, and in the filter G, are collected in the two last tanks O, and P.
As will be more particularly seen at Figure 4, and in transverse section at Figure 5,
rails are laid parallel with the trough F, on which trucks or wagons are run for
the purpose of receiving the ore, which collects in the trough F, after having
been treated in the cylinders A.
Fourthly. The solution which passes through the filter G, and which is run into
the collecting tanks I, J, K, L, M, and N, contains practically the whole of the
gold. Ferrous sulphate is then added to the solution in these tanks. This
precipitates the gold in the metallic state and after the precipitate has sunk to the
bottom of each tank the liquid is syphoned off, more gold solution run in, more
ferrous sulphate added and therefore more gold precipitated when the liquid is
again syphoned off. This treatment is repeated in succession until a sufficient
quantity of gold is deposited to admit of its being conveniently removed. The
deposit of gold being wet and in a state of extremely fine division, is, on being
removed from the tanks, dried and fused into ingots.
Although I have on the annexel drawings shewn, and in the preceding parts of
the specification described, apparatus of a construction suitable for advantageously
working my Invention, yet I wish it to be understood that my Invention is not
necessarily practised in apparatus constructed like that hereinbefore described as other
forms of apparatus may be adopted.
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:
The production of pressure in the vessel wherein the wet process or method of
extracting gold by chlorination is conducted by forcing water into the said vessel by
means of a hydraulic pump, accumulator, or other water forcing apparatus substantially
as herein before described.